This study investigated the permeation behaviors of n-hexane and 2-methylpentane through two-types of silicalite-1 membranes that have different pore-connectivity. The permeation mechanisms of these hydrocarbons were able to be explained by the adsorption-diffusion model. In addition, the fluxes through silicalite-1 membranes could be expressed by the modified Fick's first law. The hydrocarbon fluxes through S-1S with better pore-connectivity were ca. 3-20 times larger than those through S-1M with poor pore-connectivity. For these membranes with different pore-connectivity, the activation energy of diffusion of n-hexane was 17.5 kJ mol-1 for the membrane with better pore-connectivity and 18.0 kJ mol-1 for the membrane with poorer pore-connectivity, whereas for 2-methylpentane it was 17.9 and 33.0 kJ mol-1, respectively. We concluded that the pore-connectivity in silicalite-1 membrane significantly influences the molecular diffusivities.

The micropore volumes and effective pore sizes of two types of silicalite-1 membranes were compared with those of a typical silicalite-1 powder. The silicalite-1 membrane with fewer grain boundaries in the membrane layer showed similar micropore volume and effective pores size to those of the silicalite-1 powder. In contrast, when the silicalite-1 membrane contained many grain boundaries, relatively small micropore volume and effective pore size were observed, suggesting that narrowing and obstruction of the micropore would occur along grain boundaries due to the disconnection of the zeolite pore. The silicalite-1 membrane with fewer grain boundaries exhibited relatively high permeation properties for C6-C8 hydrocarbons. There was an over 50-fold difference in benzene permeance between these two types of membranes. We concluded that it is important to reduce grain boundaries and improve pore-connectivity to develop an effective preparation method for obtaining a highly permeable membrane.

Alkaline treatment with surfactant was applied to silicalite-1 membrane for defect healing. By immersion of silicalite-1 membrane into an aqueous solution of sodium hydroxide and cetyltrimethylammonium bromide (CTAB), defects among crystals were sealed, with amorphous silica leached from the membrane itself. During the treatment, the zeolite pores in the membrane were protected by CTAB from excess alkaline etching. As a result, the separation performance of silicalite-1 membrane was successfully improved by this post-treatment without a decrease in permeability due to the collaborative effect of NaOH and CTAB. The separation factor for n-hexane/2,3-dimethylbutane mixture increased from 86.5 to 559 after only a 15 min treatment. In addition, the separation performances of other zeolite membranes (Na-*BEA, Na-ZSM-5, and Na-MOR) were also improved by the treatment. This novel defect-healing technique breaks the trade-off line of permeation and separation performance observed with previous post-treatments.

Y-type zeolite membranes were prepared on a porous tubular α-alumina support by a secondary growth process. Various experimental conditions such as seed size, pH of seed solution, and degassing of support were examined for understanding their influence on the membrane deposition process. The experimental results showed that the potential of alumina support surface and the USY seed slurry plays a significant role in controlling the electrostatic interaction between seed particles and support surface and also the aggregation of USY seed particles in the slurry. In addition, we also noted the significance of the capillary forces working at the three-phase interface on the support surface and is a key factor that governs the seeding behavior onto the tubular support surface. Optimization of these parameters resulted in crack-free compact membranes that were able to effectively separate a mixture of isopropyl alcohol and water in a vapor-phase separation process.

Silicalite-1 membrane was prepared on an outer surface of a tubular α-alumina support by a secondary growth method. Changes of defect amount and crystallinity during secondary growth were carefully observed. The defect-less well-crystallized silicalite-1 membrane was obtained after 7-days crystallization at 373 K. The silicalite-1 membrane became (h0l)-orientation with increasing membrane thickness, possibly because the orientation was attributable to “evolutionally selection”. The (h0l)-oriented silicalite-1 membrane showed high p-xylene separation performance for a xylene isomer mixture (o-/m-/p-xylene = 0.4/0.4/0.4 kPa). The p-xylene permeance through the membrane was 6.52 × 10−8 mol m−2 s−1 Pa−1 with separation factors αp/o, αp/m of more than 100 at 373 K. As a result of microscopic analysis, it was suggested that a very thin part in the vicinity of surface played as effective separation layer and could contribute to high permeation performance.

We investigated the adsorption properties of propylene and propane on an olefin-selective Ag-X membrane and discussed the contribution of adsorption selectivity to propylene/propane separation performance through this membrane. The isotherms of propylene and propane on Ag-X membranes were measured in unary systems at 313 K. The amount of propylene adsorbed on the Ag-X membrane at a lower pressure increased remarkably compared with that on the Na-X membrane. Such a change of adsorption property could induce excellent separation property for the Ag-X membrane. We compared the adsorption properties in a binary system calculated based on the Markham-Benton approach with the results of a permeation test. The molar fractions of propylene in the adsorbed phase in the binary system provided good agreement with propylene purity on the permeation side of the Ag-X membrane. These results clearly show that permeation selectivity of the Ag-X membrane for the propylene/propane mixture is mainly governed by adsorption selectivity.

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. T. Developing a novel ammonia synthesis process from N2 and H2 is of interest to the catalysis and hydrogen research communities. γ-Alumina-supported nickel was determined capable of serving as an efficient catalyst for ammonia synthesis using nonthermal plasma under atmospheric pressure without heating. The catalytic activity was almost unrelated to the crystal structure and the surface area of the alumina carrier. The activity of Ni/Al2O3 was quantitatively compared with that of Fe/Al2O3 and Ru/Al2O3, which contained active metals for the conventional Haber–Bosch process. The activity sequence was Ni/Al2O3 > Al2O3 > Fe/Al2O3 > no additive > Ru/Al2O3, surprisingly indicating that the loading of Fe and Ru decreased the activity of Al2O3. The catalytic activity of Ni/Al2O3 was dependent on the amount of loaded Ni, the calcination temperature, and the reaction time. XRD, visual, and XPS observations of the catalysts before the plasma reaction indicated the generation of NiO and NiAl2O4 on Al2O3, the latter of which was generated upon high-temperature calcination. The NiO species was readily reduced to Ni metal in the plasma reaction, whereas the NiAl2O4 species was difficult to reduce. The catalytic behavior could be attributed to the production of fine Ni metal particles that served as active sites. The PN2/PH2 ratio dependence and rate constants of formation and decomposition of ammonia were finally determined for 5.0 wt % Ni/Al2O3 calcined at 773 K. The ammonia yield was 6.3% at an applied voltage of 6.0 kV, a residence time of reactant gases of 0.12 min, and PH2/PN2 = 1.

© 2020 Journal of Visualized Experiments. Membrane separation has drawn attention as a novel-energy saving separation process. Zeolite membranes have great potential for hydrocarbon separation in petroleum and petrochemical fields because of their high thermal, chemical, and mechanical strength. A *BEA-type zeolite is an interesting membrane material because of its large pore size and wide Si/Al range. This manuscript presents a protocol for *BEA membrane preparation by a secondary growth method that does not use an organic structure-directing agent (OSDA). The preparation protocol consists of four steps: pretreatment of support, seed preparation, dip-coating, and membrane crystallization. First, the *BEA seed crystal is prepared by conventional hydrothermal synthesis using OSDA. The synthesized seed crystal is loaded on the outer surface of a 3 cm long tubular α-Al2O3 support by a dip-coating method. The loaded seed layer is prepared with the secondary growth method using a hydrothermal treatment at 393 K for 7 days without using OSDA. A *BEA membrane having very few defects is successfully obtained. The seed preparation and dip-coating steps strongly affect the membrane quality.

© 2019 The Authors A potential of zeolite membrane in forward osmosis operation was investigated for the first time. A hydrophilic zeolite, ZSM-5, membrane was prepared on an α-alumina tubular support by a secondary growth method. NaCl aqueous solution and distilled water were used as draw and feed solutions, respectively. The membrane exhibited a water flux of 2.2 L m−2 h−1 with a salt flux of 0.69 g m−2 h−1 at 313 K by using 9.0 wt% draw solution. ZSM-5 membrane showed a quite small reverse salt flux based on a molecular sieving effect in the relatively wide temperature ranges of 298–333 K. ZSM-5 membrane also kept its performance under acidic conditions. In addition, obvious deterioration of the membrane performance was not observed after intermittent use of our membrane for more than one month.

© 2019 The Authors Tubular zeolite *BEA membrane was prepared by a hydrothermal secondary growth method in the absence of an organic structure directing agent (OSDA). Membrane formation process was carefully observed by using FE-SEM, XRD, and N2 adsorption, and the role of seed crystals on the support surface was discussed. Seed crystals loaded on the outer surface of a tubular porous alumina support partially dissolved and a small amount of seeds remained in an amorphous layer formed on the support surface in the early stage of secondary growth step. Subsequently, crystal growth of remaining crystals occurred, and a continuous *BEA layer was obtained following crystallization for 7 days at 393 K. In the secondary growth step, the supported seed layer played an important role in inducing the formation of a high local concentration in the vicinity of the support surface. The prepared OSDA-free *BEA membrane was then applied in the separation of hydrocarbons. We found that this membrane contained very few defects, and exhibited a high ideal selectivity for cyclohexane/1,3,5-trimethylbenzene mixture of 100, with cyclohexane permeance of 1.0 × 10−7 mol m−2 s−1 Pa−1 based on molecular sieving effect at 623 K.

© 2019 American Chemical Society. Propylene/propane and ethylene/ethane separation was examined with Ag-exchanged X-type zeolite membrane (Ag-X membrane). The Na-X membrane was prepared on a porous tubular α-alumina support by a secondary growth method. The resulting Na-X membrane was ion-exchanged by using AgNO 3 aq. Olefin selectivities in both mixtures were markedly improved after the ion exchange from Na to Ag cation. The Ag-X membrane exhibited a maximum propylene selectivity of 55.4 with a permeance of 4.13 × 10 -8 mol m -2 s -1 Pa -1 at 353 K for a propylene/propane (50:50) mixture. This membrane also exhibited a maximum ethylene selectivity of 15.9 with a permeance of 9.04 × 10 -8 mol m -2 s -1 Pa -1 at 303 K for an ethylene/ethane (50:50) mixture. We consider that the strong interaction between olefin and Ag cation plays an important role for the appearance of such high selectivity of olefin.

© 2018 Hydrogen Energy Publications LLC The plasma decomposition of ammonia was studied as a function of applied voltage/power, residence time including length of an inner electrode and flow rate of reactant gases, partial pressure of ammonia, and amount and the metal species of the inner electrodes. The ammonia decomposition rates were in excellent agreement with the hydrogen production rates and no hydrazine production was detected, indicating the clean decomposition of ammonia in the current system. The decomposition rates were dependent on the applied power and the residence time and independent of metal species of the inner electrodes, in contrast to the strong dependence of the ammonia synthesis reaction on the metal species. A hydrogen yield of 100% was achieved with an applied power of approximately 50 W and a residence time of 1.2 s at ambient temperature and atmospheric pressure, with an applied voltage of 5 kV and a frequency of 50 kHz.

© 2018 American Chemical Society. A superheated steam (SHS) treatment was found to be effective for conversion of cellulose to levoglucosan (LG) and other organic compounds. Yields of water-soluble organic compounds (TOC) and LG reached 88% and 41%, respectively, with the SHS treatment at 300 °C for 30 min. The reaction temperature was far lower than temperatures employed in conventional pyrolysis treatments (≥500 °C), and the TOC and LG yields were comparable to values reported for pyrolysis. Product distributions were significantly altered by sodium content in the parent cellulose. Sodium at 0.05 wt % or more in cellulose lowered the LG yield to almost zero, giving approximately constant TOC values other than LG, and increased solid residue, which indicated that sodium greatly reduced the reactivity of cellulose to form LG. In the absence of sodium, the reactivity of the crystalline phase of cellulose was much higher than the amorphous phase, indicating that the widely reported phenomena in which amorphous cellulose has higher reactivity than crystalline cellulose might result from a sodium impurity. In addition, the effect of ball-milling treatment was investigated to reveal the reactivity of crystalline and amorphous phases of cellulose with or without sodium contamination. The crystalline phase was converted to an amorphous phase distinct from the original amorphous phase, which could be distinguished by XRD patterns. The reactivity of the new amorphous phase was higher than that of the original crystalline phase. The obstruction of the LG formation by sodium was suggested to be due to its coordination onto a terminal glucose unit of a cellulose nanocrystal, based on the cellulose structure and amounts of sodium.

Zeolites demonstrating better SCR of NOx performance due to wide temperature activity, hydrothermal stability and N-2 selectivity have been identified under a joint research initiative by the Research Association of Automotive Internal Combustion Engines (AICE), Japan. Based on the AICE's standards, over 25 zeolites with different structures and pore dimensions were investigated and their SCR efficiency and durability have been compared. While the performances of the top contenders cannot be related to a single parameter, the results suggest that the SAR, Cu quality/quantity, pore dimensions, diffusivity and acidity play a combined role in deciding the SCR activity and selectivity.

We have successfully investigated nitrogen adsorption measurement using ZSM–5 type zeolite membrane prepared by seed assisted hydrothermal synthesis with various crystallization periods under non–destructive condition. Micro– and meso–pores derived from zeolitic and non–zeolitic structures were analyzed using nitrogen adsorption isotherm with the Saito–Foley model and the Kelvin equation. ZSM–5 membranes synthesized for various crystallization periods were characterized and evaluated by SEM, XRD, nanopermporometry and permeation tests. In this study, it could be considered that ZSM–5 membrane formation process had two–step as follows. First, ZSM–5 seed crystal was grown up in/onα–alumina support, and ZSM–5 micro–crystals generated in pore ofα–alumina support until 6 hours synthesis. After that, ZSM–5 crystals on theα–alumina support surface were predominantly grown up, and these crystals covered the support surface. After synthesis of 12 hours, the membrane had hardly defects.

Highly stable FAU-type zeolite membrane for the separation of isopropanol (IPA)-water mixture by pervaporation is described. FAU membrane showed high water permselectivity and permeance. Comparison of FAU membrane with a conventional LTA-type zeolite membrane revealed superior stability of FAU zeolite membrane in a mixture containing a large water content.

Structures of platinum and chromium supported on zeolite beta were investigated by XAFS, XPS, UV-vis, NH3-TPD, XRD, CO chemisorption, and molecular dynamics simulation. Both platinum and chromium were uniformly dispersed in the micropore of zeolite beta. Loading of chromium helped platinum to disperse highly and stabilized in the micropore of beta. Major species of platinum on PtCr/beta after calcination at 773 K was Pt2+ forming a Pt-O bond. The Pt-O bond disappeared, and a Pt-Pt bond did not appear by reducing PtCr/beta in hydrogen, accompanying formation of Pt-0. Chromium was loaded as chromate anion in the micropore of zeolite. Results of molecular dynamics simulation showed that Pt2+ associated with CrO42- in the micropore of zeolite beta was more stable than those in the absence of chromium species. We concluded that CrO42- electrostatically stabilizes Pt2+ and inhibits migration and aggregation of platinum.

Silicalite-1, a pure silica MFI-type zeolite, membrane was prepared on a tubular a-alumina support by a secondary growth method. Separation of n-alkane from a mixture of hydrocarbons was carried out by using silicalite-1 membrane. We report the permeation and separation properties for n-alkanes having different carbon numbers.  

Catalysis of Pt/beta zeolite catalyst modified via the addition of various elements (Ca, Cr, Mn, Fe, Co, Ni or Cu) for n-heptane skeletal isomerization was investigated at 513 K in a conventional flow reactor with a fixed catalyst bed. It was found that, among the catalysts tested, PtCr/beta was the most promising, since its use resulted in relatively high yields of multi-branched alkanes in conjunction with a very low selectivity for cracking products. Ion exchange was found to be an effective method for the addition of chromium to zeolite, compared to the evaporation to dryness process. Platinum particle sizes were observed using STEM. While particles similar to 10-30 nm in size were evident on the surface of Pt/beta, they were rarely observed on the PtCr/beta catalyst. It was concluded that platinum homogeneously dispersed within beta zeolite micropores resulted in the observed decreased cracking activity during n-heptane isomerization and that the addition of chromium had been effective in increasing degree of platinum dispersion.

Reduction of energy consumption in the industry sector, especially chemical industry, is strong demand. In chemical industry about 40% of the total energy consumption is for distillation. Thus, reduction of the energy used in distillation by introducing membrane technology would have strong impact. Zeolites, a class of microporous ceramic materials, have superior physicochemical properties, such as molecular sieving and preferential adsorption, in addition to high thermal, chemical, and structural stability. In this report, development of zeolite membranes will be emphasized to be attractive as a strong candidate enabling us to reduce energy consumption in chemical industry. In particular, we have started operation of a bench-scale test plant for the separation of water and isopropyl alcohol (IPA) at the production site of IPA, Kawasaki, Japan. This is the first on-site test plant using ceramic membrane in petrochemical industry. Also, acid-resistant zeolite membrane has been developed for the dehydration of acetic acid.

Separation property of silicalite-1 membrane for C₁₀ hydrocarbons was investigated. Silicalite-1 membrane was prepared on a tubular support (pore size = 0.15 μm, i.d. = 7 mm, o.d. = 10mm) by secondary-growth method. n-Decane, n-butylbenzene and tetralin were used for model substance of C₁₀ hydrocarbons. n-Decane and n-butylbenzene could penetrate through the membrane but tetralin permeation was not observed. Thus permeance ratio of n-decane to tetralin was over 100. As a result, it was shown that C₁₀ hydrocarbons can be separated with silicalite-1 membrane by molecular sieving effect.

Oxidation of carbon particles by lattice oxygen on/in catalysts was investigated with and without electrical discharge at 673 K in a fluidized bed reactor. Application of dielectric barrier discharge promoted the evolution of lattice oxygen in the oxide catalyst, and oxidation of carbon by the evolved lattice oxygen was accelerated by application of the discharge. The total amount of consumed lattice oxygen in/on the catalyst was not changed by the application of the discharge due to the low diffusion rate of bulk oxygen at low temperature. Metal-loaded catalysts such as Ni/CeO2 evolved larger amounts of lattice oxygen because of interaction between the supported Ni particle and ceria support. (C) 2011 Elsevier Ltd. All rights reserved.

DGC-H-beta zeolite catalyst has higher activity and selectivity for the alkylation of isobutane with 1-butene in a CSTR. The cause of the deactivation of the catalyst and the optimum reaction conditions were investigated. Deactivation of the catalyst was caused not by adsorbed carbon species but by hydrocarbons formed by multiple alkylation or oligomerization of olefin. Optimized conditions to avoid these reactions achieved stable selective alkylation.

The effects of zeolite structures on alkylation of isobutane with 1-butene were investigated in a batch reactor and in a continuously stirred tank reactor (CSTR) using the proton-form zeolites, H-ZSM-5, H-L, H-Y, and H-*BEA (beta). H-ZSM-5 and H-L zeolite catalysts were deactivated rapidly, whereas H-Y and H-*BEA zeolites retained catalytic activity for a long time in the CSTR, implying that zeolites with three-dimensional large pore systems are useful for preventing deactivation of the catalyst during alkylation of isobutane with 1-butene. H-*BEA synthesized using a dried-gel method (DGC-H-*BEA) showed the most stable activity among the various H-*BEA zeolites. The effects of the synthesis methods and zeolite characteristics were investigated using H-*BEA zeolite. Characterization using NH3-TPD and pyridine-sorption monitored by FT-IR showed that high acid density and high Bronsted acid ratio promoted alkylation of isobutane with 1-butene over H-*BEA zeolite.

Oxidative coupling of methane (OCM) on La2O3 semiconductor catalysts at 423 K external temperature was investigated. DC power supplied from two electrodes in a catalyst bed enabled stable and selective production of C2H6 and C2H4 over Sr-La2O3 (Sr/La = 1/200 and 1/20), but plasma reactions proceeded over other catalysts. The electrical conductivity of the semiconductor catalyst was important for controlling this reaction. A high yield of C2 (49% selectivity, 51.3% O-2 conversion) was obtained using 2.7 W of electricity at a lower external temperature (423 K).

We found that LalnO(3) perovskite catalyst showed high activity for oxidative coupling of methane (OCM). Partial substitution of La3+ site in the LalnO(3) catalyst with Ba2+ increased its catalytic activity and selectivity to C2 hydrocarbons drastically. The partial substitution of La3+ site in LalnO(3) with Ba2+ increased oxygen vacancies in the stable cubic phase, and then contributed to the production of active oxygen species on its surface for selective C2 formation.

Catalytic steam reforming of methane in an electric field (named "electreforming") was conducted over metal catalysts supported on CeO2 or CexZr1-xO2 at low temperatures such as 423 K where conventional catalytic reactions hardly proceeded. The conversion of methane was greatly increased by weak and effective application of an electric field to the catalyst bed. Use of CexZr1-xO2 as a catalyst support promoted electreforming, the lattice oxygen of CexZr1-xO2 playing an important role. Energy efficiency of electreforming, reaction mechanism, and the role of lattice oxygen were investigated and are discussed in this paper. (C) 2011 Elsevier B. V. All rights reserved.

Dry reforming of diesel fuel, an endothermic reaction, is an attractive process for on-board hydrogen/syngas production to increase energy efficiency. For operating this dry reforming process in a vehicle, we can use the exhaust gas from an exhaust gas recirculation (EGR) system as a source of carbon dioxide. Catalytic dry reforming of heavy hydrocarbon is a very difficult reaction due to the high accumulation of carbon on the catalyst. Therefore, we attempted to use a non-equilibrium pulsed plasma for the dry reforming of model diesel fuel without a catalyst. We investigated dry reforming of model diesel fuel (n-dodecane) with a low-energy pulsed spark plasma, which is a kind of non-equilibrium plasma at a low temperature of 523 K. Through the reaction, we were able to obtain syngas (hydrogen and carbon monoxide) and a small amount of C(2) hydrocarbon without coke formation at a ratio of CO(2)/C(fuel) = 1.5 or higher. The reaction can be conducted at very low temperatures such as 523 K. Therefore, it is anticipated as a novel and effective process for on-board syngas production from diesel fuel using an EGR system.

Previously we reported that La(0.8)Ba(0.2)Fe(0.4)Mn(0.6)O(3-delta) (LBFMO) perovskite oxide catalyst showed extremely high activity for dehydrogenation of ethylbenzene to produce styrene. The reaction mechanism of dehydrogenation of ethylbenzene over LBFMO catalyst and the role of A/B site cation in the perovskite were investigated using transient response experiments and thermogravimetric analyses in a H(2)O/H(2) atmosphere. Results showed that the dehydrogenation of ethylbenzene over LBFMO perovskite catalyst proceeded via reduction-oxidation (redox) of the perovskite oxide in this temperature range (800-900 K). Thereby, oxidative dehydrogenation of ethylbenzene consumed lattice oxygen in the perovskite; the consumed lattice oxygen was regenerated by H(2)O. We measured the lattice oxygen release rate and regenerating rate over LBFMO perovskite catalyst. The regeneration rate of lattice oxygen was almost equal to the formation rate of styrene in the steady state of the dehydrogenation reaction. Substituting the B site of perovskite with Fe has a stabilizing effect for the lattice oxygen in the perovskite, and enhanced the regeneration rate of lattice vacancy drastically using steam. We concluded that the better stability of LBFMO than that of other catalysts was derived from enhanced lattice oxygen regeneration in the perovskite. (C) 2011 Elsevier B.V. All rights reserved.

This review describes prospects for energy saving in the chemical and petroleum industries and recommends that increasing efforts be exerted on the development of membrane-based separation systems. A preliminary estimate suggests that the simple addition of a membrane separation unit to an existing separation system or distillation unit can drastically reduce energy consumption by more than 70%. This review also describes state-of-the-art of zeolite-based separation membranes, which is the one of the most promising technologies among emerging separation methods. © 2011 Elsevier B.V.

This article discusses the directions for energy systems based on an urgent proposal to counter the energy crisis in eastern Japan, published from the Society of Chemical Engineers, Japan. We first illustrate the situation Japan faces, highlighting the urgency and seriousness of the consequences of power outages in industry and daily life. Then, we elaborate on the necessity for policy support to trigger collective actions to temporarily practice countermeasures that would not necessarily save resources or that could disrupt society's established routines. In this way, Japan can choose technologies without regret based on society-wide discussions on the future energy supply. Finally, we warn of the drawbacks induced by shortsighted decisions e. g., avoiding power outages by depending on less-efficient gas turbines. We conclude that Japan should commence a transition of its energy systems rather than compromising resource efficiency and grid robustness over the next decades.

We investigated the effect of loading potassium over iron-based catalysts for water-gas shift (WGS) reaction at 573 K. The iron-based water-gas shift catalyst has been known as a redox-mechanism catalyst. Therefore, to promote the redox reaction over iron oxide, we impregnated a small amount of Pd on various iron oxides. Results revealed that coexisting potassium and palladium accelerated the WGS reaction over iron-oxide catalyst. We examined the optimum amount of potassium over Pd/iron catalyst, and we found that the optimum molar ratio was about 2 (K/Pd molar ratio). From the viewpoint of reducibility of the catalyst, the addition of small amount of Pd onto iron oxide promotes reduction from Fe(2)O(3) to Fe(3)O(4). However, impregnation of potassium on iron oxide makes the catalyst structure robust. The promotion effect of Pd and potassium was not observed on SiO(2) support. We therefore concluded that the synergetic effect among Pd, K, and iron oxide, was important for the WGS reaction.

We examined the promotion effect of loading small amounts of Fe onto various Co catalysts for steam reforming of ethanol. Among these catalysts, catalysts supported on SrTiO3 and alpha-Al2O3 showed remarkable effects of iron loading onto cobalt catalyst. The Fe-loaded Co/alpha-Al2O3 showed higher yield of hydrogen, low coke deposition on the catalysts, and high activity for steam reforming of acetaldehyde, which was an intermediate of the steam reforming of ethanol. Characterization of the catalyst revealed that Fe and Co metal coexisted on the catalyst support. Synergetic effects of these two metals were observed. (C) 2010 Elsevier B.V. All rights reserved.

Catalytic properties of Pd and/or Pt supported/incorporated on/in perovskite-type oxides for water gas shift (WGS) reaction have been investigated. We found that the dominant reaction mechanism over these catalysts was redox mechanism by CO and steam, and their redox properties were controllable by the bulk structure of perovskite.

We investigated four catalytic reactions assisted with in electric field to promote catalytic activity, and we could achieve an effective process for hydrogen production at low temperatures. Such as 423 K. In the presence of the electric field, four reactions of steam reforming of ethanol, decomposition of ethanol, water gas shift, and steam reforming of methane proceeded at very low temperature, Such as 423 K, where a conventional catalytic reaction hardly proceeded. Conversion of reactant was greatly increased by the electric field, Zinc apparent activation energies for these four reactions were lowered by the application of the electric field. This process cart produce hydrogen and syngas by using a considerably small energy demand and has quick response.

We conducted steam reforming of methane at very low temperature like as 423 K in an electric field. Application of the electric field enabled to conduct low temperature steam reforming of methane. The promotion effect of catalytic reaction in the electric field was not derived from plasma activation, electrolysis, and it was not a faradic reaction, but a non-faradic reaction. The distribution of products was 4 to 1 for hydrogen and carbon dioxide. We found that some noble metals, and supports which had redox ability with its lattice oxygen, were effective for the low temperature steam reforming of methane with an aid of the electric field.

We investigated two types of electrical discharges for converting. biomethane into syngas at ambient temperature and atmospheric pressure. Low energy pulsed discharge (LEP) has a good property for this reaction and it could convert biomethane into syngas and also H(2)S was converted into solid sulfur simultaneously. This is due to the high electron energy of LEP, and the electron has enough energy to dissociate C-C bond and C-S bond. On the other hand, dielectric barrier discharge could convert H(2)S into solid sulfur, but methane and CO(2) in the biomethane were not reacted at lower input power. Our investigation showed that proper choice of electric discharge could bring selective reaction for dry reforming of biomethane and desulfurization, and this was due to the correlation between the bond dissociation energy of each molecule and electron energy level of each discharge. (C) 2009 Elsevier Ltd. All rights reserved.

We have studied the effect of steam in the steam-assisted crystallization (SAC) of *BEA-type zeolite. It was found that after an aluminosilicate dry gel with SiO2/Al2O3 = 100 was treated with steam in an autoclave at 130 degrees C and autogenous pressure, the thermal treatment of a resulting product at 130 degrees C in an autoclave without the addition of water gave *BEA nanoparticles with a high crystallinity. It was presumed that pseudo-*BEA structures as intermediates were formed during the SAC treatment, and the dehydration of silanols in the pseudo-*BEA solids during the thermal treatment in the presence of a minimum amount of water possibly promoted the transformation of the pseudo-*BEA phase into *BEA crystalline phase with a periodicity in long-range order.

Steam reforming of ethanol was examined over Co/SrTiO(3) with addition of another metal-Pt, Pd, Rh, Cr, Cu, or Fe-for promotion of the catalytic activity. Ethanol conversion and H(2) yield were improved greatly by adding Fe or Rh at 823 K. Although Rh addition promoted CH(4) formation, Fe addition enhanced steam reforming of ethanol selectively. A suitable amount of Fe loading was in the window of 0.33-1.3 mol%. A comparative study of the reaction over a catalyst supported on SiO(2) was conducted, but no additional effect of Fe was observed on the Co/SiO(2) catalyst. High activity of Fe/Co/SrTiO(3) catalyst came from interaction among Fe, Co, and SrTiO(3).

We investigated novel catalytic reaction systems which were activated by an electric field. This is the first report for the synergetic effect of catalyst and electric field. These catalytic systems showed very high activity compared to conventional catalytic reaction systems. Although Pt supported on CeO(2) catalyst without an electric field showed no activity at 473 K, the addition of an electric field to the catalyst promoted the degradation of ethanol. Pt/CeO(2) catalyst was activated by the electric field and synergetic effect of Pt catalyst and electric field was observed. Thermal analyses showed that about 5-10% of input electrical power was wasted as a heat and about 90-95% was consumed for the endothermic reaction. Catalytic reactions in an electric field proceed under mild conditions and show a quick response. (C) 2009 Elsevier B.V. All rights reserved.

We investigated novel LaMnOx perovskite-oxide (ABO(3)) catalysts for effective catalytic dehydrogenation of ethylbenzene to produce styrene monomer. Comparison with industrial Fe-K catalyst, our La(0.8)Ba(0.2)Mn(0.6)Fe(0.4)O(3-delta) catalyst showed higher activity. Results show that the A-site in perovskite-type oxides affected catalytic dehydrogenation activities and that the B-site affected stability of the activities.

Low temperature catalytic oxidation of solid carbon was conducted in a fluidized bed reactor with/without a non-equilibrium discharge. Solid carbons like as soot, PM, and char cause many operational problems and have lower reactivity. We tried to oxidize such carbon particles to carbon oxide and/or carbon dioxide by lattice oxygen in/on the oxide catalysts at lower temperature. To maintain high contact frequency between the catalyst and carbon particles, we applied a fluidized-bed reaction apparatus for this reaction. As a result, we found that carbon particles are oxidized at 673K by the lattice oxygen in/on the catalyst. Among various oxide catalysts, Fe/CeO_2 and some other catalysts showed higher activity for the oxidation of carbon particles.

Low temperature catalytic oxidation of solid carbon was conducted in a fluidized bed reactor with a non-equilibrium discharge. Solid carbons like as soot, PM, and char cause many operational problems and have lower reactivity. We tried to oxidize such carbon particles to carbon dioxide by oxide catalysts with DBD discharge at lower temperature. Also to maintain high contact frequency between the catalyst and carbon particles, we applied a fluidized-bed reaction apparatus for this reaction. As a result, we found that carbon particles are oxidized at 673 K by the plasma-catalytic reaction with some oxide catalysts. Among various oxide catalysts, Pt/BaCeMnOx showed higher activity for the oxidation of carbon particles in the hybrid process of catalyst and plasma.

Direct decomposition of nitric oxide (NO) was carried out with a plasma-assisted catalytic reaction system. As NO decomposition catalysts for the conversion of NO into N_2 and O_2, Ba/Ce-Mn-Ox and perovskite oxide were used as catalysts in this experiment. The combination of catalytic reaction and non-equilibrium electric discharge allows higher N_2 yield at low temperatures than catalytic reaction without plasma or non-equilibrium electric discharge without catalyst. And it was found that Ba/Ce-Mn-Ox is effective as a catalyst in this plasma-assisted catalytic reaction for direct decomposition of NO. Coexistence of oxygen or steam decreased N_2 yield drastically in this reaction. However, the synergistic effect of catalytic reaction and non-equilibrium electric discharge existed even though coexistence of oxygen or steam.

To achieve lower reaction temperature and higher conversion than existing catalytic processes for hydrogen production, catalytic reaction of methane steam reforming in an electric field was conducted. Conversion of methane increased on catalytic reaction in the electric field by the interaction of electric field and catalyst. In the presence of the electric field, reaction proceeded in considerably low temperature where conventional catalytic reaction hardly proceeded. Then, to investigate response of catalytic reaction in the electric field, transient experiment was conducted. As a result, conversion of methane quickly increased with impressing of the electric field.

We found that catalytic steam reforming of methane was drastically promoted in an electric field. In the presence of the electric field, reaction proceeded in considerably low temperature region like as 423 K where conventional catalytic steam reforming of methane hardly proceeded. Conversion was greatly increased by impressing the electric field to the catalyst bed. This process can produce hydrogen and syngas by using considerably small energy demand and has a property of quick response.

Water-gas-shift (WGS) reaction is important for hydrogen production process and synthesis gas production process. In the industrial process, high-temperature-shift (HTS) reaction is carried out at 593-723 K using iron-chromium catalyst, and low-temperature-shift (LTS) reaction is carried out below 573 K using copper-zinc catalyst, respectively. There are some problems that the iron-chromium catalyst has low activity at low temperature, and the copper-zinc catalyst is deactivated by cyclic operation like as DSS. Recently we reported that the activity of Pd/Pt/LaCoO3 was higher than the activity of the copper-zinc catalyst and the catalyst did not require reductive pretreatment. The noble metal catalyst is comparatively stable, but the cost of the noble metal catalyst is higher than the iron-chromium catalyst and the copper-zinc catalyst. Therefore it is important to reduce the amount of noble metal.The purpose of this study is to develop the novel catalyst for the WGS reaction in order to decrease the reaction temperature, and we examined the iron oxide catalyst and perovskite type oxide catalyst, expecting to improve the activity and the heat stability with redox properties.

Reverse-selective membranes, through which bigger molecules selectively permeate, are attractive for developing chemical processes utilizing hydrogen because they can maintain the high partial pressure of hydrogen required for their further downstream utilization. Although several of these chemical processes are operated above 473 K, membranes with outstanding reverse-selective separation performance at these temperatures are still to be reported. Herein, we propose a new adsorption-based reverse-selective membrane that utilizes a Na cation occluded in a zeolitic framework. The membrane developed in this work, a compact Na(+)-exchanged ZSM-5 (NaZSM-5) type zeolite membrane. enables us to selectively permeate and separate bigger polar molecules, such as methanol and water, from a stream containing hydrogen, above 473 K. On the other hand, a Na(+)-free, H(+)-exchanged ZSM-5 (HZSM-5) type zeolite membrane did not show separation properties at these temperatures. The microporous zeolite membrane developed in this study can be applied to a variety of chemical reaction systems to minimize energy consumption.

The water gas shift (WGS) reaction over Pt and Pd catalysts supported on various perovskite oxides has been investigated at 573 K without catalyst pretreatment. The Pt and Pd catalysts on LaCoO(3) support showed high catalytic activity. Interaction between Pt or Pd and the support is considered to promote the WGS reaction: Pt/LaCoO(3) had high initial activity but deactivated immediately: Pd/LaCoO(3) was less active than Pt/LaCoO(3), but had superior stability. Catalysts were characterized using XRD, STEM, XPS, and H(2)-temperature programmed reduction (TPR). Results of this study showed that reduction of the support decreased the CO conversion on Pt/LaCoO(3). On the other hand, Pd/LaCoO(3) showed stable activity for the WGS reaction. Therefore, Pd was added to Pt/LaCoO(3) for stabilizing the catalyst activity, and 0.5 wt.% Pd/1 wt.% Pt/LaCoO(3) catalyst showed higher activity and stability. (C) 2008 Elsevier B.V. All rights reserved.

Various La2O3-based catalysts are well-known to be useful for the oxidative coupling of methane (OCM reaction). We examined the catalytic activities of various La2O3-based OCM catalysts for the OCM reaction in the kinetic region (i.e., lower O-2 conversion). Our investigation revealed that the Fe-doped La2O3 catalyst is a good candidate for the OCM reaction. The La/Fe ratio of the Fe-doped La2O3 catalyst is an important factor for OCM activity. Especially, the O-2-based C-2 yield of the Fe-doped La2O3 catalyst was higher than that of La2O3 in the case of La/Fe > 5. The Fe-doped La2O3 catalyst modified with Na2O and Na4P2O7 showed high C-2 Selectivity (83%). Moreover, modification with Bi compounds also enhanced C-2 selectivity of the Fe-doped La2O3 catalyst. This catalyst showed higher C-2 yield than the Fe-doped La2O3 catalyst.

We investigated a novel oxidation reaction with surface-oxygen and lattice-oxygen induced using a non-equilibrium electric discharge at ambient temperature. We employed MgO, ZrO2, and TiO2 for this novel reaction. Methane was oxidized easily and converted into H2, CO, and CO2 by the surface-oxygen and lattice-oxygen of oxide with activation of discharge at ambient temperature without gas-phase oxygen. The oxide itself was stable after the reaction. Among these oxides, the tetragonal phase and amorphous phase of ZrO2 showed remarkably high activity for methane oxidation. Consequently, up to 8% of surface and lattice oxygen of the oxide was consumed by methane oxidation induced by electric discharge. The non-equilibrium electric discharge activated both the surface-oxygen and the lattice-oxygen of the oxides and methane molecules in the gas phase. After these reactions, the oxide surface vacant sites were recovered partially through steam post-treatment. Hydrogen formed simultaneously with steam decomposition. Other reactions were also studied by changing the reaction gas: methane into carbon monoxide, carbon monoxide with oxygen, and carbon monoxide with steam. Furthermore, the correlation of reactivity between the feed gas and surface oxygen was studied. Emission spectra under a CH4 atmosphere with electric discharge showed complex peaks caused by carbon monoxide formation at 280-500 nm at 0-4 min, suggesting that surface oxygen on oxides was probably consumed within 4 min from the start of the reaction. © 2007 Elsevier Ltd. All rights reserved.

Styrene is manufactured industrially through catalytic dehydrogenation of ethylbenzene on Fe-K oxide-based catalysts. It was invented by Sud-Chemie Group that the activity of the industrial ethylbenzene dehydrogenation catalysts (Styromax) based on the oxides of Fe and K is highly promoted by the addition of small amount (hundreds ppm-order) of precious metals such as Pd. The present work is intended to elucidate the role of Pd on the Fe-K catalyst empirically by use of a periodical pulse technique from a mechanistic point of view. The oxidative dehydrogenation was faster than the simple dehydrogenation, and it proceeded by consuming the surface lattice oxygen in the catalyst. The lattice oxygen was subsequently supplied from steam. Palladium added to the Fe-K oxide catalysts was found to enhance the rate of regeneration (supplying) of the lattice oxygen, although it hardly changed the rate of dehydrogenation of ethylbenzene or consumption of surface lattice O(2-) anions. This study demonstrated that steam works not only as a diluent but also as a reactant to form hydrogen and lattice oxygen.

A mordenite membrane was prepared on the outer surface of a porous a-alumina tubular support by a secondary-growth method. Permeation tests for water/methanol/hydrogen mixtures were performed at 423 and 473 K. A mordenite membrane free from non-zeolitic pores allowed us selective permeation of steam and blocked the permeation of hydrogen and methanol. In order to elucidate the mechanism of such selective permeation behavior, adsorption, permeation, and structural properties of the mordenite membrane were discussed. As a result, it was considered that selective permeation of steam against hydrogen was based on its preferential adsorption of steam, while boundaries between mordenite crystals in the membrane may play a key role for inhibiting the permeation of methanol.

Controlling the growth of zeolite crystals on a porous alumina support is essential for preparing a compact zeolite membarne. First, mordenite seed crystals applied on a nonporous a-alumina disk were grown and morphological change of mordenite crystals were observed in the course of growth. Then, mordenite membranes were synthesized on a porous a-alumina tube under the same conditions employed in the study using the alumina disks. We found that seed crystal growth was widely controllable by changing water content in reaction solution, which resulted in better control of the morphology of mordenite crystals for synthesizing a thin compact mordenite membrane. Separation properties for mordenite membranes were studied in water-hydrogen binary system at 473 K with 10 kPa of water partial pressure, where no capillary condensation was expected in non-zeolitic pores. Separation factor for a mordenite membrane with a few defects was poor; however, a defect-free mordenite membrane prepared under a suitable condition highly separated steam from hydrogen. (C) 2007 Elsevier B.V. All rights reserved.

The steam reforming of ethanol was performed over Co and Ni catalysts supported on perovskite-type oxides (LaAlO3, SrTiO3 and BaTiO3). Co and Ni catalysts supported on LaAlO3 and SrTiO3 showed high catalytic activities and long-term stabilities and suppressed coke formation while Co/BaTiO3 showed lower catalytic activities and poorer coking resistance. The average particle size of Co oil BaTiO3 was larger than that on SrTiO3. Lattice oxygen in perovskites may play positive roles in hindering coking and Co/SrTiO3 has more frequent participation of lattice oxygen in the oxidation of intermediates or precursor of coke in comparison with Co/BaTiO3. (c) 2007 Elsevier B.V. All rights reserved.

The steam reforming of ethanol for producing hydrogen was evaluated over 5 wt% Co catalysts supported on perovskite-type oxides, La1-xSrxBO3 (B = Al, Cr, Mn, Fe, x = 0-0.2) at 823 K with a molar H2O/C2H5OH ratio of 6. Co/LaAlO3 showed higher catalytic activity and stability than Co catalysts supported on LaCrO3, LaFeO3 and LaMnO3. The molar La/Al ratio markedly affected the stability of Co/LaAlO3 catalyst and a molar La/Al ratio of I was the most suitable, suggesting that the properties of the perovskite structure are important in the catalytic activity and stability. Partial substitution of Sr2+ for La 31 in LaAlO3 resulted in further remarkable improvement of catalytic activity and hydrogen yield. We consider that enhanced mobility of lattice oxygen in La1-xSrxAlO3-delta allows more frequent participation in the oxidation of intermediates over metallic cobalt, leading to both high catalytic activity and stability of Co/La1-xSrxAlO3-delta,5 in comparison with Co/LaAlO3.

Separation properties of a mordenite membrane for water-methanol-hydrogen mixtures were studied in the temperature range from 423 to 523 K under pressurized conditions. The mordenite membrane was prepared on the outer surface of a porous alumina tubular support by a secondary-growth method. It was found that water was selectively permeated through the membrane. The separation factor of water/hydrogen and water/methanol were 49-156 and 73-101, respectively. Even when only hydrogen was fed at 0.5 MPa, its permeance was as low as 10(-9) mol m(-2) s(-1) Pa-1 up to 493 K, possibly suggesting that water pre-adsorbed in the micropores of mordenite hindered the permeation of hydrogen. The hydrogen permeance dramatically increased to 6.5 x 10(-7) mol m(-2) s(-1) Pa-1 at 503 K and reached to 1.4 x 10(-6) mol m(-2) s(-1) Pa-1 at 523 K because of the formation of cracks in the membrane. However, the membrane was thermally stabilized in the presence of steam and/or methanol. (C) 2007 Elsevier B.V. All rights reserved.

We investigated effective catalysts for converting biomass-tar derived from the gasification/combustion of cellulose. Experiments were conducted with a sequential combined reactor with a fluidized bed gasifier/combustor and a fixed bed reactor for removing tar. Several kinds of Co or Ni supported catalysts were investigated. As a result, we found that Ni/CeO_2 and Ni/CaO catalysts showed higher activities for removing biomass-tar.

High-temperature coal utilization processes (combustion, gasification and pyrolysis) emit toxic trace elements into the atmosphere, where they affect the environment and human health. We carried out coal combustion and gasification experiments using several kinds of coals at various temperatures and atmospheric conditions to examine the release behavior of trace elements. Results showed that Group 1 and 2 metals such as Fig, Se, Sb, and Zn were partly released from coal during combustion, gasification and pyrolysis. Oxygen or steam in the operating atmosphere affected the behavior of Fig, Se, Sb, and Zn release from coal. (C) 2007 Elsevier B.V. All rights reserved.

Tubular FAU-type zeolite membrane was synthesized on porous alumina substrate with 80 cm long by a seeded growth method. Pervaporation experiments using a mixture of water (10 wt%)/ethanol (90 wt%) at 75 degrees C demonstrated superior permeation properties of this type of membrane showing the total flux of 4-10 (kg m(-2) h(-1)) with the separation factor of 110-300. A part of the synthesized membrane with 10 cm long was applied to gas separation at high pressures of 1-5 MPa and high temperatures of 130 and 180 degrees C. Ternary mixtures of water, methanol and hydrogen were used for evaluating the permselectivities of FAU-type membrane. It was found that hydrogen permeation was strongly depressed in the presence of water and methanol. Preferential adsorption of water and methanol in the micropores of FAU-type zeolite possibly played an important role for the appearance of permselectivity. (c) 2006 Elsevier Inc. All rights reserved.

We investigated the alkylation of toluene with methanol at 250 degrees C over MCM-22 and ITQ-2 zeolites possessing an MWW structure. Whereas ITQ-2, produced by the delamination of MCM-22 precursor, showed a poor p-xylene selectivity of 23% at 1.7% of the level of toluene conversion, a high p-xylene selectivity of 80% at 0.6% of the level of toluene conversion was obtained by poisoning the external surface of ITQ-2 with collidine. Similarly, MCM-22 treated with collidine showed a high p-xylene selectivity of 74% at 3.8% of the level of toluene conversion. We concluded that both interlayer and intralayer 10-membered ring (10MR) micropores in the MWW structure caused the shape-selective formation of p-xylene in the alkylation of toluene with methanol. (c) 2006 Elsevier B.V. All rights reserved.

We investigated the alkylation of toluene with methanol at 250 degrees C over MCM-22 and ITQ-2 zeolites possessing an MWW structure. Whereas ITQ-2, produced by the delamination of MCM-22 precursor, showed a poor p-xylene selectivity of 23% at 1.7% of the level of toluene conversion, a high p-xylene selectivity of 80% at 0.6% of the level of toluene conversion was obtained by poisoning the external surface of ITQ-2 with collidine. Similarly, MCM-22 treated with collidine showed a high p-xylene selectivity of 74% at 3.8% of the level of toluene conversion. We concluded that both interlayer and intralayer 10-membered ring (10MR) micropores in the MWW structure caused the shape-selective formation of p-xylene in the alkylation of toluene with methanol. (c) 2006 Elsevier B.V. All rights reserved.

Novel catalytic reaction with high voltage electric field was conducted with a pyloritic reaction of ethanol as a model reaction. As a catalyst, Pt was supported on some of oxides, and high voltage electric field was applied on the catalyst. Pt supported ceria catalyst showed very high activity among these catalysts at lower temperature as 300 degree centigrade. Compare to conventional catalytic process, this novel system can be achieved at lower temperature with a high energy efficiency.

On the steam reforming of methane, coke formation on the catalyst was severe problem which causes the deactivation of catalyst. So, suppressing the coke formation was expected for the fuel cell application. Up to now, we employed perovskite oxides as a support of catalyst which has mobile oxygen on/in the support, and conducted redox type steam reforming reaction with this catalyst. In this presentation, we tried to examine the effect of support on this reforming reaction.

Biogas is one of important energy which could be obtained from the anaerobic fermentation of organic materials. There are several problems in the catalytic reforming of biomethane due to the higher concentration of H2S in biogas. Therefore, we examined direct reforming of biogas at ambient temperature, atmospheric pressure without catalyst by electric discharge (esp. LEP, DBD), and influence of type of discharge on the chemical reactions in this study.

Tetraethylammonium (TEA(+))-containing silicate dry gels exhibiting a maximum in the reflection peak at 2 theta = 28 degrees in an XRD pattern using Cu K alpha radiation are always transformed into *BEA-type zeolite with steam-assisted crystallization.

Tetraethylammonium (TEA(+))-containing silicate dry gels exhibiting a maximum in the reflection peak at 2 theta = 28 degrees in an XRD pattern using Cu K alpha radiation are always transformed into *BEA-type zeolite with steam-assisted crystallization.

A novel organic-inorganic hybrid mesoporous iron oxophenyl phosphate has been synthesized by using supramolecular assembly of sodium dodecyl sulfate molecules. X-ray diffraction, transmission electron microscopic studies, and N-2 adsorption data indicated the wormhole-like disordered mesostructure in this sample. The C-13 and P-31 MAS NMR, FT IR, UV-visible spectroscopic data, and chemical analysis results indicated that all P atoms are attached to phenyl groups directly and combined with Fe atoms through O atoms. Calcination of this hybrid material produced organic-free mesoporous iron oxophosphate material, whereas sulfonation of the mesoporous iron oxophenyl phosphate resulted in sulfonated oxophenyl phosphate. The latter showed outstanding proton conductivity, which could be utilized in membrane or supports of anode and cathode materials in fuel cells.

A novel organic-inorganic hybrid mesoporous iron oxophenyl phosphate has been synthesized by using supramolecular assembly of sodium dodecyl sulfate molecules. X-ray diffraction, transmission electron microscopic studies, and N-2 adsorption data indicated the wormhole-like disordered mesostructure in this sample. The C-13 and P-31 MAS NMR, FT IR, UV-visible spectroscopic data, and chemical analysis results indicated that all P atoms are attached to phenyl groups directly and combined with Fe atoms through O atoms. Calcination of this hybrid material produced organic-free mesoporous iron oxophosphate material, whereas sulfonation of the mesoporous iron oxophenyl phosphate resulted in sulfonated oxophenyl phosphate. The latter showed outstanding proton conductivity, which could be utilized in membrane or supports of anode and cathode materials in fuel cells.

Ferrierite zeolite membranes were prepared for the first time in the absence of organic structure-directing agents (SDA) on the surface of a porous a-alumina support. These membranes were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and pervaporation tests.

A novel organic-inorganic hybrid mesoporous niobium oxophenylphosphate was synthesized by using supramolecular assembly of sodium dodecylsulfate molecules. X-ray diffraction, transmission electron microscopic image and NZ adsorption data indicated the formation of a wormhole-like disordered mesostructure in the sample. The C-13 and P-31 MAS NMR, FTIR, UV-visible spectroscopic data and chemical analysis results indicated that all P atoms are attached to phenyl groups directly and these are combined with Nb atoms through O atoms. Calcination of this hybrid material yielded an organic-free mesoporous niobium oxophosphate material. (c) 2006 Elsevier Inc. All rights reserved.

A novel organic-inorganic hybrid mesoporous niobium oxophenylphosphate was synthesized by using supramolecular assembly of sodium dodecylsulfate molecules. X-ray diffraction, transmission electron microscopic image and NZ adsorption data indicated the formation of a wormhole-like disordered mesostructure in the sample. The C-13 and P-31 MAS NMR, FTIR, UV-visible spectroscopic data and chemical analysis results indicated that all P atoms are attached to phenyl groups directly and these are combined with Nb atoms through O atoms. Calcination of this hybrid material yielded an organic-free mesoporous niobium oxophosphate material. (c) 2006 Elsevier Inc. All rights reserved.

This study is intended to clarify the relationship among the reactivity of coal char with steam, structural change in residual carbon, and ash behavior. Steam gasification of various coal chars and demineralized chars was carried out in a fixed-bed reactor. After gasification, the reacted char was analyzed using laser raman spectroscope (LRS), and scanning electron microscope, energy dispersive X-ray spectroscope (SEM/EDX) mapping. Results of SEM images and EDX-mappings revealed that novel parallel analysis of cross correlation between EDX-mapping and LRS-mapping was found to be very effective for the comprehensive evaluation of ash behavior and carbonaceous structure. As the gasification reaction proceeds, the reactivity of the char was varied; existence of Si and Al seemed to suffocate the char reactivity. (c) 2005 Elsevier Ltd. All rights reserved.

A disk-type SM0.4Ba0.6Co0.2Fe0.8O3 (- delta) perovskite-type mixed-conducting membrane was applied to a membrane reactor for the partial oxidation of methane to syngas (CO + H-2). The reaction was carried out using Rh (1 wt%)/MgO catalyst by feeding CH4 diluted with Ar. While CH4 conversion increased and CO selectivity slightly decreased with increasing temperature, a high level of CH4 conversion (90 %) and a high selectivity to CO (98 %) were observed at 1173 K. The oxygen flux was increased under the conditions for the catalytic partial oxidation of CH4 compared with that measured when Ar was fed to the permeation side. We investigated the reaction pathways in the membrane reactor using different membrane reactor configurations and different kinds of gas. In the membrane reactor without the catalyst, the oxygen flux was not improved even when CH4 was fed to the permeation side, whereas the oxygen flux was enhanced when CO or H-2 was fed. It is implied that the oxidation of CO and H-2 with the surface oxygen on the permeation side improves the oxygen flux through the membrane, and that CO2 and H2O react with CH4 by reforming reactions to form syngas. (c) 2005 Elsevier B.V. All rights reserved.

SrFeCo_0.5O_x asymmetric membranes for oxygen permeation consisting of a thin dense layer and a porous support layer were prepared using a simple method. A given amount of SrFeCo_0.5O_x powder was placed in a die, and then a mixture of SrFeCo_0.5O_x powder and ethyl cellulose powder was added on top of the SrFeCo_0.5O_x powder. The layered powders were pressed into a 13 mm-diameter disk, and calcined at 1423 K. This produced a membrane with a thin dense layer and, through the elimination of the ethyl cellulose, a porous support layer. Oxygen flux through membranes thus produced increased with decreasing dense-layer thickness. The maximum oxygen flux through an asymmetric membrane at 1173 K observed was 0.23 cm³ (STP) cm^–2 min^–1, which was 2.8 times larger than that through a 0.95 mm-thick symmetric membrane. Oxygen permeation was primarily limited by bulk diffusion in the thin dense layer, although the porous support layer acted to resist oxygen permeation.

The steam reforming of ethanol over Co and Ni catalysts supported on SrTiO3 was carried out at 823 K and atmospheric pressure. It was found that Co/SrTiO3 showed a high catalytic activity and long-term stability and remarkably inhibited carbon deposition. Copyright © 2005 The Chemical Society of Japan.

The steam reforming of ethanol over Co and Ni catalysts supported on SrTiO3 was carried out at 823 K and atmospheric pressure. It was found that Co/SrTiO3 showed a high catalytic activity and long-term stability and remarkably inhibited carbon deposition. Copyright © 2005 The Chemical Society of Japan.

Disk-type SrFeCo0.50Ox, asymmetric membranes were prepared for high-temperature oxygen separation using both a previously reported solid state technique in which ethyl cellulose is introduced and then removed by calcination to produce a porous support layer and a modified technique in which carbon fiber is added to the ethyl cellulose. The oxygen permeabilities of the resulting SrFeCo0.50Ox asymmetric membranes were measured at 973-1173 K. The addition of carbon fiber to ethyl cellulose resulted in the improvement of gas diffusivity in the porous support layer, which increased the flux of oxygen through the modified asymmetric membrane. (c) 2005 Elsevier B.V. All rights reserved.

Steam reforming of methane for the purpose of hydrogen production was performed using nickel catalysts supported on a variety of perovskites, including LaAlO3, LaFeO3, SrTiO3, BaTiO3, La0.4Ba0.6Co0.2Fe0.8O3-delta, to compare the catalytic activity and resistance to coking of these catalysts to those of the conventional Ni/alpha-Al2O3 catalyst. Ni/LaAlO3 and Ni/SrTiO3 showed high catalytic activities among the Ni/perovskites and longer-term stabilities than the conventional catalyst. Temperature programmed oxidation of carbon deposited on used catalysts revealed that inactive carbon species detected on Ni/alpha-Al2O3 were not formed in the case of Ni/LaAlO3. The results of temperature programmed reduction confirmed that consumption and recovery of the lattice oxygen in perovskites occurred during the reaction, and that the reducibility of perovskites had a great impact on the steam reforming activity. The lattice oxygen in perovskites is considered to play important roles in promoting the oxidation of CH, fragments adsorbed on metallic nickel. (c) 2005 Published by Elsevier B.V.

Disk-type SrFeCo0.50Ox, asymmetric membranes were prepared for high-temperature oxygen separation using both a previously reported solid state technique in which ethyl cellulose is introduced and then removed by calcination to produce a porous support layer and a modified technique in which carbon fiber is added to the ethyl cellulose. The oxygen permeabilities of the resulting SrFeCo0.50Ox asymmetric membranes were measured at 973-1173 K. The addition of carbon fiber to ethyl cellulose resulted in the improvement of gas diffusivity in the porous support layer, which increased the flux of oxygen through the modified asymmetric membrane. (c) 2005 Elsevier B.V. All rights reserved.

Steam reforming of methane for the purpose of hydrogen production was performed using nickel catalysts supported on a variety of perovskites, including LaAlO3, LaFeO3, SrTiO3, BaTiO3, La0.4Ba0.6Co0.2Fe0.8O3-delta, to compare the catalytic activity and resistance to coking of these catalysts to those of the conventional Ni/alpha-Al2O3 catalyst. Ni/LaAlO3 and Ni/SrTiO3 showed high catalytic activities among the Ni/perovskites and longer-term stabilities than the conventional catalyst. Temperature programmed oxidation of carbon deposited on used catalysts revealed that inactive carbon species detected on Ni/alpha-Al2O3 were not formed in the case of Ni/LaAlO3. The results of temperature programmed reduction confirmed that consumption and recovery of the lattice oxygen in perovskites occurred during the reaction, and that the reducibility of perovskites had a great impact on the steam reforming activity. The lattice oxygen in perovskites is considered to play important roles in promoting the oxidation of CH, fragments adsorbed on metallic nickel. (c) 2005 Published by Elsevier B.V.

The undesired structural change of mordenite with Si/Al-2 = 15 during the ion exchange and during calcination from the sodium form into proton form, especially the dealumination after the calcination, was studied. The Si-29 NMR results clarified that calcination of the NH4-form mordenite with Si/Al-2 = 15 at > ca. 800 K, followed by the contact of proton-form sample with the atmosphere containing humidity, induced the dealumination. However, the samples carefully kept free from humidity after the heat treatment showed no dealumination or only a low degree of it. The Al-27 NMR and ammonia TPD results agreed with these findings. The origin of dealumination is thus considered to be the contact of the proton-form sample with humidity after the calcination. On the other hand, the dealumination was not observed after calcination at < 673 K. The H-1 NMR indicated that the ca. 1/3 of the ion-exchange sites were blocked by the ammonium cations after calcination at 673 K, suggesting that the dealumination was prevented by the ammonium cations. On the basis of these findings, a standard set of conditions in which one can safely prepare the proton-form zeolite with high quality is proposed. The recommended temperature for the ion exchange is room temperature, because it is high enough to exchange the ions in this case. The most important variable is the calcination temperature; it should be lower than 673 K in order to avoid the dealumination. These conditions were confirmed to yield zeolites with a high framework aluminum content and ordinary catalytic performance. (c) 2005 Elsevier B.V. All rights reserved.

A joint study was organized to establish a standard set of conditions for the ion exchange of zeolite from sodium into proton-form. The sodium-form mordenite with Si/Al-2 = ca. 15 was ion exchanged into an NH4-form, followed by calcination according to various recipes. Then various advanced techniques for characterization (ICP, TG, XPS, SEM, XRD, N-2 adsorption Si-29 and Al-27 NMR, benzene diffusion, IR of OH and adsorbed pyridine and CO, ammonia TPD) were applied. and some test reactions (cracking of cumene, isopropylation of biphenyl, oligomerization of propene and chichibabin condensation of acetaldehyde and ammonia into picoline) were conducted. The ion exchange (removal of sodium) proceeded as expected, but remarkable differences were observed in physicochemical and catalytic properties of the thus-prepared proton-form samples. Exceptionally high temperature (383 K) for the ion exchange resulted in the structural degradation, while most samples exchanged at 333-353 K maintained the crystallinity and pore volume. The use of NH4Cl slightly changed the crystal morphology. Extra-framework aluminum species was formed on most samples after calcination above 773 K. In contrast, calcination at 673 K maintained the framework aluminum. Therefore, the dealumination is considered to proceed after complete removal of ammonia from the ammonium-form zeolite. However, the proton-form zeolite was stable under dry conditions, so it is speculated that the dealumination was induced by the contact of the proton-form zeolite to atmosphere with humidity. The total and Bronsted acidity decreased with the dealumination, while Lewis acidity increased. On the other hand, rapid heating of the ammonium type zeolite caused narrowing of the micropores. These structural changes seriously affected the catalytic activities for various reactions. (c) 2005 Elsevier B.V. All rights reserved.

The undesired structural change of mordenite with Si/Al-2 = 15 during the ion exchange and during calcination from the sodium form into proton form, especially the dealumination after the calcination, was studied. The Si-29 NMR results clarified that calcination of the NH4-form mordenite with Si/Al-2 = 15 at > ca. 800 K, followed by the contact of proton-form sample with the atmosphere containing humidity, induced the dealumination. However, the samples carefully kept free from humidity after the heat treatment showed no dealumination or only a low degree of it. The Al-27 NMR and ammonia TPD results agreed with these findings. The origin of dealumination is thus considered to be the contact of the proton-form sample with humidity after the calcination. On the other hand, the dealumination was not observed after calcination at < 673 K. The H-1 NMR indicated that the ca. 1/3 of the ion-exchange sites were blocked by the ammonium cations after calcination at 673 K, suggesting that the dealumination was prevented by the ammonium cations. On the basis of these findings, a standard set of conditions in which one can safely prepare the proton-form zeolite with high quality is proposed. The recommended temperature for the ion exchange is room temperature, because it is high enough to exchange the ions in this case. The most important variable is the calcination temperature; it should be lower than 673 K in order to avoid the dealumination. These conditions were confirmed to yield zeolites with a high framework aluminum content and ordinary catalytic performance. (c) 2005 Elsevier B.V. All rights reserved.

A joint study was organized to establish a standard set of conditions for the ion exchange of zeolite from sodium into proton-form. The sodium-form mordenite with Si/Al-2 = ca. 15 was ion exchanged into an NH4-form, followed by calcination according to various recipes. Then various advanced techniques for characterization (ICP, TG, XPS, SEM, XRD, N-2 adsorption Si-29 and Al-27 NMR, benzene diffusion, IR of OH and adsorbed pyridine and CO, ammonia TPD) were applied. and some test reactions (cracking of cumene, isopropylation of biphenyl, oligomerization of propene and chichibabin condensation of acetaldehyde and ammonia into picoline) were conducted. The ion exchange (removal of sodium) proceeded as expected, but remarkable differences were observed in physicochemical and catalytic properties of the thus-prepared proton-form samples. Exceptionally high temperature (383 K) for the ion exchange resulted in the structural degradation, while most samples exchanged at 333-353 K maintained the crystallinity and pore volume. The use of NH4Cl slightly changed the crystal morphology. Extra-framework aluminum species was formed on most samples after calcination above 773 K. In contrast, calcination at 673 K maintained the framework aluminum. Therefore, the dealumination is considered to proceed after complete removal of ammonia from the ammonium-form zeolite. However, the proton-form zeolite was stable under dry conditions, so it is speculated that the dealumination was induced by the contact of the proton-form zeolite to atmosphere with humidity. The total and Bronsted acidity decreased with the dealumination, while Lewis acidity increased. On the other hand, rapid heating of the ammonium type zeolite caused narrowing of the micropores. These structural changes seriously affected the catalytic activities for various reactions. (c) 2005 Elsevier B.V. All rights reserved.

Addition of an exceedingly small amount of zirconia onto iron oxide enhanced the activity for hydrogen production by the oxidation of partially reduced iron oxide. Sintering of iron oxide was also suppressed.

We examined the influence of carbonaceous structural change and ash behavior affecting reactivity. We developed a novel analysis method using LRS (Laser Raman Spectroscopy) and EDX (Energy Dispersive X-ray diffraction) for this examination. From these observations, Si and Al existence accorded with the rate of non-graphitic carbon at higher conversion of carbonaceous material. On the other hand, our previous results have shown that the ratio of graphitic carbon increases regardless of ash as gasification reactions proceed. Based on these results we inferred that Si and Al existence suppressed char conversion, so the reaction gas was unable to contact with the carbon. The effect of Fe for catalyst was also investigated and it showed catalytic activity for gasification in some cases.

Synthesis of novel mesoporous hybrid tin oxophosphate is reported from phenylphosphonic acid as the only precursor of phosphorus in the presence of anionic surfactant (SDS), which possesses a wormhole mesoporous structure and is stable even after calcination at 550 degrees C.

Rapid synthesis of Si-MCM-41 was accomplished in successive two steps; (1) aging of a Mixture of silica, hexadecylammonium bromide and water with ail aqueous ammonia solution for a short period of 30 min, and (2) successive evaporation-to-dryness of the resultant mixture at 80 degrees C in about 2 h. The yield of Si-MCM-41 reached 99% after calcination at 550 degrees C. The product obtained by this method gave a well-ordered 2d-hexagonal structure with high thermal stability and water-resistance. It was noteworthy that the d(100) value of calcined Si-MCM-41 was almost the same as that of as-made Si-MCM-41, suggesting that pore wall of as-made product was dense and rigid.

The role of steam oil the crystallization of zeolite beta by the steam-assisted crystallization (SAC) method was studied. It was found that after an aluminosilicate dry gel with SiO2/Al2O3 molar ratio = 100 was treated with steam in an autoclave at 130 degrees C and autogenous pressure, thermal treatment of a resultant product at 130 degrees C without the addition of water in an autoclave gave zeolite beta with a high crystallinity. Zeolite beta obtained by this method consisted of nano-particles with a diameter of ca. 30 nm. It was presumed that intermediates of zeolite beta was formed during steam treatment, and the dehydration between silanols in the intermediates during the thermal treatment in the absence of steam possibly caused the transformation from ill-ordered structures to zeolite beta crystals with a periodicity in long-range order.

A preferentially oriented mordenite membrane was successfully prepared on a seeded porous α-alumina support. Characterization results of XRD (X-ray diffractometer) and FE-SEM (field emission scanning electron microscope) revealed that evolutionary selection might predominantly contribute to the formation of the sharply oriented mordenite membrane. The necessary conditions under which evolutionary selection occurs are: (a) the number density of nuclei on the support surface should be high enough at the early stage
(b) the crystals should grow fastest along one direction
and (c) the zeolite layer should proceed via the successive growth of the crystals nucleated on the support surface instead of the accumulation of the crystals formed in the bulk solution.

We demonstrated that non-catalytic ethanol steam reforming proceeds efficiently and selectively without coking at the conditions of room temperature and atmospheric pressure using low-energy pulsed (LEP) discharge in combination with carbon fiber electrodes.

Synthesis of novel mesoporous hybrid tin oxophosphate is reported from phenylphosphonic acid as the only precursor of phosphorus in the presence of anionic surfactant (SDS), which possesses a wormhole mesoporous structure and is stable even after calcination at 550 degrees C.

Rapid synthesis of Si-MCM-41 was accomplished in successive two steps; (1) aging of a Mixture of silica, hexadecylammonium bromide and water with ail aqueous ammonia solution for a short period of 30 min, and (2) successive evaporation-to-dryness of the resultant mixture at 80 degrees C in about 2 h. The yield of Si-MCM-41 reached 99% after calcination at 550 degrees C. The product obtained by this method gave a well-ordered 2d-hexagonal structure with high thermal stability and water-resistance. It was noteworthy that the d(100) value of calcined Si-MCM-41 was almost the same as that of as-made Si-MCM-41, suggesting that pore wall of as-made product was dense and rigid.

The role of steam oil the crystallization of zeolite beta by the steam-assisted crystallization (SAC) method was studied. It was found that after an aluminosilicate dry gel with SiO2/Al2O3 molar ratio = 100 was treated with steam in an autoclave at 130 degrees C and autogenous pressure, thermal treatment of a resultant product at 130 degrees C without the addition of water in an autoclave gave zeolite beta with a high crystallinity. Zeolite beta obtained by this method consisted of nano-particles with a diameter of ca. 30 nm. It was presumed that intermediates of zeolite beta was formed during steam treatment, and the dehydration between silanols in the intermediates during the thermal treatment in the absence of steam possibly caused the transformation from ill-ordered structures to zeolite beta crystals with a periodicity in long-range order.

A preferentially oriented mordenite membrane was successfully prepared on a seeded porous α-alumina support. Characterization results of XRD (X-ray diffractometer) and FE-SEM (field emission scanning electron microscope) revealed that evolutionary selection might predominantly contribute to the formation of the sharply oriented mordenite membrane. The necessary conditions under which evolutionary selection occurs are: (a) the number density of nuclei on the support surface should be high enough at the early stage
(b) the crystals should grow fastest along one direction
and (c) the zeolite layer should proceed via the successive growth of the crystals nucleated on the support surface instead of the accumulation of the crystals formed in the bulk solution.

We demonstrated that non-catalytic ethanol steam reforming proceeds efficiently and selectively without coking at the conditions of room temperature and atmospheric pressure using low-energy pulsed (LEP) discharge in combination with carbon fiber electrodes.

Fuel cell is attracting attention, especially polymer electrolyte membrane fuel cell. However, hydrogen production and transportation processes have many problems with the present technology so innovative technological methods to produce hydrogen are needed. Low energy pulse discharge was used for this goal. The energy efficiency was improved because the liquid phase reactor did not require a heater which is needed to vaporize the mixture of water and ethanol. Any pump supplying the liquid into the reactor was not required. So the liquid phase reactor made the process scale reduced, and also made the device size compact without spoiling its function. This process would be very useful for room temperature hydrogen formation system.

MCM-41-type mesoporous materials possessing strong Bronsted acidity originated from ZSM-5 zeolite were synthesized by using soluble aluminosilicate species containing the fragments of the structure of ZSM-5 zeolite. The thermal stability of the mesoporous structure of the obtained mesoporous material was enhanced by the post-treatment with an ammonium aqueous solution. These results suggest an important role of alkalinity of slurries on the following two processes; (1) alkaline dissolution of ZSM-5 zeolite and (2) formation of mesoporous structure. These successive processes were efficiently improved by use of a continuous-flow reactor. The mesoporous material synthesized in the continuous-flow reactor catalyzed the cracking of cumene at 523 K, while a conventional Al-MCM-41 hardly catalyzed. The mesoporous material synthesized by using the filtrate of alkaline dissolution of ZSM-5 possessed a stronger Bronsted acidity than a conventional Al-MCM-41. (C) 2004 Elsevier Inc. All rights reserved.

MCM-41-type mesoporous materials possessing strong Bronsted acidity originated from ZSM-5 zeolite were synthesized by using soluble aluminosilicate species containing the fragments of the structure of ZSM-5 zeolite. The thermal stability of the mesoporous structure of the obtained mesoporous material was enhanced by the post-treatment with an ammonium aqueous solution. These results suggest an important role of alkalinity of slurries on the following two processes; (1) alkaline dissolution of ZSM-5 zeolite and (2) formation of mesoporous structure. These successive processes were efficiently improved by use of a continuous-flow reactor. The mesoporous material synthesized in the continuous-flow reactor catalyzed the cracking of cumene at 523 K, while a conventional Al-MCM-41 hardly catalyzed. The mesoporous material synthesized by using the filtrate of alkaline dissolution of ZSM-5 possessed a stronger Bronsted acidity than a conventional Al-MCM-41. (C) 2004 Elsevier Inc. All rights reserved.

MCM-41-type mesoporous materials possessing strong Bronsted acidity originated from ZSM-5 zeolite were synthesized by using soluble aluminosilicate species containing the fragments of the structure of ZSM-5 zeolite. The thermal stability of the mesoporous structure of the obtained mesoporous material was enhanced by the post-treatment with an ammonium aqueous solution. These results suggest an important role of alkalinity of slurries on the following two processes; (1) alkaline dissolution of ZSM-5 zeolite and (2) formation of mesoporous structure. These successive processes were efficiently improved by use of a continuous-flow reactor. The mesoporous material synthesized in the continuous-flow reactor catalyzed the cracking of cumene at 523 K, while a conventional Al-MCM-41 hardly catalyzed. The mesoporous material synthesized by using the filtrate of alkaline dissolution of ZSM-5 possessed a stronger Bronsted acidity than a conventional Al-MCM-41. (C) 2004 Elsevier Inc. All rights reserved.

MCM-22 zeolite crystallized by the vapor-phase transport (VPT) method showed a higher shape-selectivity to p-xylene in the alkylation of toluene with methanol, compared with MCM-22 crystallized by the hydrothermally synthetic (HTS) method, because VPT-MCM-22 has a smaller external surface area and a smaller number of acid sites thereon than HTS-MCM-22. Such textural properties of VPT-MCM-22 are caused by the fact that the spherical particles of VPT-MCM-22 are composed of hexagonal plates as thin as 55 nm; they are larger than those of HTS-MCM-22, which are 30 nm thick. The acidic properties, characterized by NH3-TPD and FT-IR using a pyridine adsorption technique, showed no significant difference between VPT- and HTS-MCM-22, except for the acidity on the external surface.

MCM-22 zeolite crystallized by the vapor-phase transport (VPT) method showed a higher shape-selectivity to p-xylene in the alkylation of toluene with methanol, compared with MCM-22 crystallized by the hydrothermally synthetic (HTS) method, because VPT-MCM-22 has a smaller external surface area and a smaller number of acid sites thereon than HTS-MCM-22. Such textural properties of VPT-MCM-22 are caused by the fact that the spherical particles of VPT-MCM-22 are composed of hexagonal plates as thin as 55 nm; they are larger than those of HTS-MCM-22, which are 30 nm thick. The acidic properties, characterized by NH3-TPD and FT-IR using a pyridine adsorption technique, showed no significant difference between VPT- and HTS-MCM-22, except for the acidity on the external surface.

Zeolite membrane has been fabricated on porous alumina substrate in a single continuous process of gelation and subsequent crystallization while suppressing nucleation of zeolite powder in the bulk.

Zeolite membrane has been fabricated on porous alumina substrate in a single continuous process of gelation and subsequent crystallization while suppressing nucleation of zeolite powder in the bulk.

Steam reforming of methane, propane, hexane, cyclohexane, methanol, and ethanol using a nonequilibrium pulsed discharge was investigated under the conditions of atmospheric pressure and low temperature (393 K) without the use of catalyst. In each case, steam reforming proceeded efficiently and selectively and hydrogen was formed as a main product. Although the steam/ carbon ratio was 1, there were trace amounts of carbon deposition or wax formation. The energy injection for the discharge region calculated by current and voltage waveforms measured by a digital signal oscilloscope was very small. As compared with the conventional catalytic steam reforming process, this method has some advantages such as fast start-up, quick response, and miniaturization and simplification of a hydrogen production system. Therefore we consider that the hydrogen production system employing a nonequilibrium pulsed discharge has a potential for being an effective way for supplying hydrogen or syngas.

In this study, a compact MFI-type zeolite membrane was prepared by a secondary growth method. Seed crystals of MFI-type zeolite were hydrothermally synthesized at 135°C and recovered by centrifugation. A porous alumina tube was used as a support and seeded by dip coating using a slurry of the seeds. Hydrothermal treatment was carried out at 125°C for 24 h to grow a thin layer of MFI-type zeolite on the support. The separation of an equimolar mixtures of C₆ hydrocarbon isomers, n-hexane, 2-methylpentane and 2,2-dimethylbutane, was carried out by a vapor permeation method. As a result of separation tests, the membrane showed a high n-Hex selectivity at 100°C. The permeation tests using the binary mixtures of n-Hex/2,2-DMB and n-Hex/2-MP and using the unary systems of these three kinds of molecules were carried out to explain that the appearance of the permselectivity to n-Hex. Molecular sieving effect caused the appearance of the permselectivity to n-Hex against 2,2-DMB and preferential adsorption of n-Hex enhanced its permselectivity. In the case of the selectivity of n-Hex against 2-MP, both differences in the amounts of adsorption and diffusion coefficients of C₆ isomers may contribute to determining the permeances of C₆ isomers.

Hydrothermal synthesis of faujasite-type (FAU) zeolite using a coal fly ash was investigated while rotating. We discussed that the formation of FAU from coal fly ash was influenced by four synthetic factors as follows; 1) the addition of FAU seeds, 2) the addition of an aluminum source, 3) alkalinity of synthetic mixture and 4) crystallization temperature in the temperature range of 90 to 120°C. The addition of FAU seeds in the synthetic mixture was essential for the formation of FAU, otherwise GIS-type zeolite (GIS), an undesired by-product, was simultaneously formed. Higher alkaline conditions using aqueous NaOH solution (3 N) gave a higher yield of FAU (45.4 wt%). The highest yield of FAU (56.7 wt%) was obtained with the addition of 1.4 mmol (g-coal)^-1 of aluminum in 3N-aqueous NaOH solution. A further increasing amount of the addition of aluminum resulted in increasing yields of sodalite (SOD) and LTA-type zeolite (LTA). The induction period of the formation of GIS was longer at the lower crystallization temperature of 90°C.

Separation properties of mordenite membrane for water-methanol-hydrogen mixtures were studied in the temperature range from 150 to 250°C under pressurized conditions. Mordenite is a kind of large pore zeolites with a pore diameter of 0.65 x 0.70 nm. Mordenite membrane was prepared on the outer surface of a porous alumina tubular support by a secondary-growth method. We found that water was selectively permeated through the membrane. The separation factors of water/hydrogen and water/methanol were 49 and 73, respectively, at 250°C. When only hydrogen was fed at 5 atm, its permeance was as low as 10^-9 mol m^-2 s^-1 Pa^-1 up to about 220°C, possibly suggesting that water pre-adsorbed in the micropores of mordenite hindered the permeation of hydrogen. The hydrogen permeance, however, dramatically increased to 6.5 x 10^-7 mol m^-2 s^-1 Pa^-1 at 230°C and reached to 1.4 x 10^-6 mol m^-2 s^-1 Pa^-1 at 250°C owing to the formation of cracks in the membrane. It was, however, found that the membrane was thermally stabilized in the presence of steam and/or methanol.

We studied steam reforming of ethanol at room temperature and atmospheric pressure using low energy pulse (LEP) discharge. In this study, we employed characteristic novel reformer, one electrode was made of carbon fibers (o.d. 7.0µm) bundle. So fuel was supplied to discharge region by capillary action of the fibers and reformed directly by LEP plasma without any pump or heater. When using this reformer, at first, the fuel was evaporated by heat emission from electrode, and then the vaporized reactants were reacted. Produced gaseous compounds were collected from upper part of the reactor, and analyzed by gas chromatography. H₂ and other compounds: CO, CH₄, CO₂, C₂H₄, and C₂H₆ were produced, and the formation rates were increased in proportion to the increase of the gap distance and input power. And compared to the former conventional reformer, the results were equivalent to the rates of gas phase reactor. The effects of ethanol concentration and of energy efficiency were studied, and the efficiency has reached 41.7 % at the ethanol concentration of 50 %, the discharge gap of 3.0 mm.

In this study, the reaction mechanism of limestone and Cl compounds was investigated by using fixed bed plug flow reactor. Trichloroethane(TCE) was identified as one of the Cl compounds emitting during the pyrolysis of model-RDF at 500°C ¹⁾, so TCE was chosen as the model compound of organic Cl compounds, and HCl was used as that of inorganic Cl compounds. Under any the partial pressure of steam, TCE and HCl were reacted with both CaO and Ca(OH)₂. Products of each reaction were identified by X-ray diffraction. Moreover by changing the injection volume of Cl compounds, the Cl absorption mechanisms of CaO and Ca(OH)₂ were investigated. The reaction of TCE with CaO was not observed. On the other hand, the product of TCE with Ca(OH)₂ was identified as CaClOH. And when the volume of TCE injection was increased, only CaClOH was identified. So, no further dechlorination was occurred. The products of HCl reaction with CaO were identified as CaCl₂ and CaCl₂·2H₂O. When the steam was added, the HCl reaction with Ca(OH)₂ was occurred, the product was identified as CaClOH and when the injection volume of HCl was increased, identified as CaCl₂, CaCl₂·2H₂O. That is to say, more dechlorination was occurred differently from TCE reactions with both CaO and Ca(OH)₂. CaClOH was also proposed as a product of HCl reaction with CaO, because the reaction of CaO with H₂O resulting from HCl reaction with CaO was occurred and the same time, HCl reaction with Ca(OH)₂ was also occurred. At high temperature(800°C), the reaction of TCE with limestone was considered as the reaction of HCl generated from decomposition of TCE with limestone, and it was considered that both the reaction of TCE with Ca(OH)₂ and that of HCl with CaO or Ca(OH)₂ were occurred at 650°C.

In order to clarify the influence among ash behavior, carbonaceous structural change and char reactivity, the analysis method from a microscopic viewpoint was proposed. This novel method utilized overlaying both the distribution mapping of carbonaceous structure by LRS and the distribution mapping of elements by SEM/EDX. Consequently, the function of ash content on carbonaceous structure was clarified by this novel method.

Four kinds of coal samples whose Cl-contents vary from 30ppm to 300ppm were pyrolyzed and burned, and the release behavior of Zn was examined. In the coal pyrolysis step, as the increase of Cl contents in coal, the release amounts of Zn also increased. It was considered that the generation of ZnCl2 was one reason for Zn emission. In the coal combustion, a part of Zn was released as ZnCl2 and the other part was remained in the ash as non-volatile ZnO, because some of Zn in the coal was reacted with Cl and others were oxidized during volatilization.

Microporous layered zirconium phenylphosphonate, Zr(O3P-C6H5)(2) was prepared in presence of sodium dodecylsulfate (SDS), for the first time. Interplanar spacing (d(001)) and surface area of microporous zirconium phenylphosphonate are 1.47 nm and 198 m(2)g(-1), respectively. FT-IR spectrum indicates absence or negligible amount of hydroxyls groups ill zirconium phenylphosphonate sample. P-31 solid MAS NMR also confirms the presence of trace amount of hydroxyl groups in zirconium phenylphosphonate. The presence of tetra-coordinated phosphorous ions and hexa-coordinated zirconium ions were realized by the P-31 solid MAS NMR and UV-visible, respectively. Sulfonated derivative of zirconium phenylphosphonate, Zr(O3PC6H4SO3H)(1.9) (O3PC6H5)(0.1)center dot 3.7H(2)O were also prepared.

The catalytic behavior of Pt supported on non-acidic silicalite-1 (MFI structure) and on the stannosilicate, Sn-sil-1 molecular sieves in the aromatization of n-hexane is investigated. The influence of Pt content, temperature, space velocity, H-2/n-hexane ratio and time on stream (TOS) on the n-hexane conversion, aromatic selectivity and aromatic yield are presented. Aromatics are the main products and this suggests that the aromatization proceeds via dehydrocyclization and/or hydrogenolysis, dehydrogenation to C-2-C-4 olefins followed by oligomerization inside the pores of the molecular sieve into cyclic intermediates in presence of hydrogen. The incorporation of Pt during the synthesis of the stannosilicate (Sn-sil-1) yields a more active catalyst (42 wt% aromatic selectivity) without any deactivation than when Pt is loaded by impregnation on Sn-sil-1 because catalyst deactivation associate with platinum outside the zeolite pores. A formation mechanism is proposed.

A new method of modification of TS-1 by weak base (aqueous NH3) treatment leads to formation of bigger crystals and generation of internal hydroxyl groups as evident by SEM and IR (hydroxyl region). All the catalysts were characterized using, XRD, N-2-sorption, UV-VIS, FT-IR and SEM. Activity of the modified and unmodified TS-1 were compare in the hydroxylation of phenol to hydroquinone and catechol in presence of aqueous H2O2. A ratio of hydroquinone to catechol over modified,(TS-1 (33)/OH1 and unmodified, TS-1(33) catalysts were 1.40 and 1.15, respectively, using H2O as solvent, and 2.01 and 1.68, respectively, using MeOH as solvent. Modification of TS-1 with strong base (e.g. NaOH) causes decrease in crystallinity, and hence decreases the conversion of phenol and selectivity of hydroquinone. A new mechanism controlling the product selectivity is proposed.

Compact ZSM-5 zeolite membranes have been prepared on the outer surface of a porous alpha-alumina tub without structure-directing agents (SDAs) by the seed-assisted crystallization method. An SDA-free gel and an SDA-free clear solution were used for the membrane preparation, respectively. ZSM-5 membrane prepared from the SDA-free gel showed the H-2/i-C4H10 ideal selectivity of 13.8 at 200 degrees C, but it decreased to be 2.1 after the pretreatment at 300 degrees C, indicating the limited thermal stability of this kind of ZSM-5 membrane. On the other hand, ZSM-5 membranes prepared from the SDA-free clear solution showed high thermal stability and good separation properties. After the pretreatment at 400 degrees C, the H-2/i-C4H10 idea selectivity was as high as 61 at 270 degrees C. The maximum of the n/i-C4H10 ideal selectivity was 36 at 300 degrees C and the separation factor was as high as 12.7 at 400 degrees C for a 50/50 n/i-C4H10 mixture.

Microporous layered zirconium phenylphosphonate, Zr(O3P-C6H5)(2) was prepared in presence of sodium dodecylsulfate (SDS), for the first time. Interplanar spacing (d(001)) and surface area of microporous zirconium phenylphosphonate are 1.47 nm and 198 m(2)g(-1), respectively. FT-IR spectrum indicates absence or negligible amount of hydroxyls groups ill zirconium phenylphosphonate sample. P-31 solid MAS NMR also confirms the presence of trace amount of hydroxyl groups in zirconium phenylphosphonate. The presence of tetra-coordinated phosphorous ions and hexa-coordinated zirconium ions were realized by the P-31 solid MAS NMR and UV-visible, respectively. Sulfonated derivative of zirconium phenylphosphonate, Zr(O3PC6H4SO3H)(1.9) (O3PC6H5)(0.1)center dot 3.7H(2)O were also prepared.

The catalytic behavior of Pt supported on non-acidic silicalite-1 (MFI structure) and on the stannosilicate, Sn-sil-1 molecular sieves in the aromatization of n-hexane is investigated. The influence of Pt content, temperature, space velocity, H-2/n-hexane ratio and time on stream (TOS) on the n-hexane conversion, aromatic selectivity and aromatic yield are presented. Aromatics are the main products and this suggests that the aromatization proceeds via dehydrocyclization and/or hydrogenolysis, dehydrogenation to C-2-C-4 olefins followed by oligomerization inside the pores of the molecular sieve into cyclic intermediates in presence of hydrogen. The incorporation of Pt during the synthesis of the stannosilicate (Sn-sil-1) yields a more active catalyst (42 wt% aromatic selectivity) without any deactivation than when Pt is loaded by impregnation on Sn-sil-1 because catalyst deactivation associate with platinum outside the zeolite pores. A formation mechanism is proposed.

A new method of modification of TS-1 by weak base (aqueous NH3) treatment leads to formation of bigger crystals and generation of internal hydroxyl groups as evident by SEM and IR (hydroxyl region). All the catalysts were characterized using, XRD, N-2-sorption, UV-VIS, FT-IR and SEM. Activity of the modified and unmodified TS-1 were compare in the hydroxylation of phenol to hydroquinone and catechol in presence of aqueous H2O2. A ratio of hydroquinone to catechol over modified,(TS-1 (33)/OH1 and unmodified, TS-1(33) catalysts were 1.40 and 1.15, respectively, using H2O as solvent, and 2.01 and 1.68, respectively, using MeOH as solvent. Modification of TS-1 with strong base (e.g. NaOH) causes decrease in crystallinity, and hence decreases the conversion of phenol and selectivity of hydroquinone. A new mechanism controlling the product selectivity is proposed.

Compact ZSM-5 zeolite membranes have been prepared on the outer surface of a porous alpha-alumina tub without structure-directing agents (SDAs) by the seed-assisted crystallization method. An SDA-free gel and an SDA-free clear solution were used for the membrane preparation, respectively. ZSM-5 membrane prepared from the SDA-free gel showed the H-2/i-C4H10 ideal selectivity of 13.8 at 200 degrees C, but it decreased to be 2.1 after the pretreatment at 300 degrees C, indicating the limited thermal stability of this kind of ZSM-5 membrane. On the other hand, ZSM-5 membranes prepared from the SDA-free clear solution showed high thermal stability and good separation properties. After the pretreatment at 400 degrees C, the H-2/i-C4H10 idea selectivity was as high as 61 at 270 degrees C. The maximum of the n/i-C4H10 ideal selectivity was 36 at 300 degrees C and the separation factor was as high as 12.7 at 400 degrees C for a 50/50 n/i-C4H10 mixture.

Microporous layered zirconium phenylphosphonate, Zr(O3P-C6H5)(2) was prepared in presence of sodium dodecylsulfate (SDS), for the first time. Interplanar spacing (d(001)) and surface area of microporous zirconium phenylphosphonate are 1.47 nm and 198 m(2)g(-1), respectively. FT-IR spectrum indicates absence or negligible amount of hydroxyls groups ill zirconium phenylphosphonate sample. P-31 solid MAS NMR also confirms the presence of trace amount of hydroxyl groups in zirconium phenylphosphonate. The presence of tetra-coordinated phosphorous ions and hexa-coordinated zirconium ions were realized by the P-31 solid MAS NMR and UV-visible, respectively. Sulfonated derivative of zirconium phenylphosphonate, Zr(O3PC6H4SO3H)(1.9) (O3PC6H5)(0.1)center dot 3.7H(2)O were also prepared.

The catalytic behavior of Pt supported on non-acidic silicalite-1 (MFI structure) and on the stannosilicate, Sn-sil-1 molecular sieves in the aromatization of n-hexane is investigated. The influence of Pt content, temperature, space velocity, H-2/n-hexane ratio and time on stream (TOS) on the n-hexane conversion, aromatic selectivity and aromatic yield are presented. Aromatics are the main products and this suggests that the aromatization proceeds via dehydrocyclization and/or hydrogenolysis, dehydrogenation to C-2-C-4 olefins followed by oligomerization inside the pores of the molecular sieve into cyclic intermediates in presence of hydrogen. The incorporation of Pt during the synthesis of the stannosilicate (Sn-sil-1) yields a more active catalyst (42 wt% aromatic selectivity) without any deactivation than when Pt is loaded by impregnation on Sn-sil-1 because catalyst deactivation associate with platinum outside the zeolite pores. A formation mechanism is proposed.

A new method of modification of TS-1 by weak base (aqueous NH3) treatment leads to formation of bigger crystals and generation of internal hydroxyl groups as evident by SEM and IR (hydroxyl region). All the catalysts were characterized using, XRD, N-2-sorption, UV-VIS, FT-IR and SEM. Activity of the modified and unmodified TS-1 were compare in the hydroxylation of phenol to hydroquinone and catechol in presence of aqueous H2O2. A ratio of hydroquinone to catechol over modified,(TS-1 (33)/OH1 and unmodified, TS-1(33) catalysts were 1.40 and 1.15, respectively, using H2O as solvent, and 2.01 and 1.68, respectively, using MeOH as solvent. Modification of TS-1 with strong base (e.g. NaOH) causes decrease in crystallinity, and hence decreases the conversion of phenol and selectivity of hydroquinone. A new mechanism controlling the product selectivity is proposed.

Compact ZSM-5 zeolite membranes have been prepared on the outer surface of a porous alpha-alumina tub without structure-directing agents (SDAs) by the seed-assisted crystallization method. An SDA-free gel and an SDA-free clear solution were used for the membrane preparation, respectively. ZSM-5 membrane prepared from the SDA-free gel showed the H-2/i-C4H10 ideal selectivity of 13.8 at 200 degrees C, but it decreased to be 2.1 after the pretreatment at 300 degrees C, indicating the limited thermal stability of this kind of ZSM-5 membrane. On the other hand, ZSM-5 membranes prepared from the SDA-free clear solution showed high thermal stability and good separation properties. After the pretreatment at 400 degrees C, the H-2/i-C4H10 idea selectivity was as high as 61 at 270 degrees C. The maximum of the n/i-C4H10 ideal selectivity was 36 at 300 degrees C and the separation factor was as high as 12.7 at 400 degrees C for a 50/50 n/i-C4H10 mixture.

Microporous layered zirconium phenylphosphonate, Zr(O3P-C6H5)(2) was prepared in presence of sodium dodecylsulfate (SDS), for the first time. Interplanar spacing (d(001)) and surface area of microporous zirconium phenylphosphonate are 1.47 nm and 198 m(2)g(-1), respectively. FT-IR spectrum indicates absence or negligible amount of hydroxyls groups ill zirconium phenylphosphonate sample. P-31 solid MAS NMR also confirms the presence of trace amount of hydroxyl groups in zirconium phenylphosphonate. The presence of tetra-coordinated phosphorous ions and hexa-coordinated zirconium ions were realized by the P-31 solid MAS NMR and UV-visible, respectively. Sulfonated derivative of zirconium phenylphosphonate, Zr(O3PC6H4SO3H)(1.9) (O3PC6H5)(0.1)center dot 3.7H(2)O were also prepared.

The catalytic behavior of Pt supported on non-acidic silicalite-1 (MFI structure) and on the stannosilicate, Sn-sil-1 molecular sieves in the aromatization of n-hexane is investigated. The influence of Pt content, temperature, space velocity, H-2/n-hexane ratio and time on stream (TOS) on the n-hexane conversion, aromatic selectivity and aromatic yield are presented. Aromatics are the main products and this suggests that the aromatization proceeds via dehydrocyclization and/or hydrogenolysis, dehydrogenation to C-2-C-4 olefins followed by oligomerization inside the pores of the molecular sieve into cyclic intermediates in presence of hydrogen. The incorporation of Pt during the synthesis of the stannosilicate (Sn-sil-1) yields a more active catalyst (42 wt% aromatic selectivity) without any deactivation than when Pt is loaded by impregnation on Sn-sil-1 because catalyst deactivation associate with platinum outside the zeolite pores. A formation mechanism is proposed.

A new method of modification of TS-1 by weak base (aqueous NH3) treatment leads to formation of bigger crystals and generation of internal hydroxyl groups as evident by SEM and IR (hydroxyl region). All the catalysts were characterized using, XRD, N-2-sorption, UV-VIS, FT-IR and SEM. Activity of the modified and unmodified TS-1 were compare in the hydroxylation of phenol to hydroquinone and catechol in presence of aqueous H2O2. A ratio of hydroquinone to catechol over modified,(TS-1 (33)/OH1 and unmodified, TS-1(33) catalysts were 1.40 and 1.15, respectively, using H2O as solvent, and 2.01 and 1.68, respectively, using MeOH as solvent. Modification of TS-1 with strong base (e.g. NaOH) causes decrease in crystallinity, and hence decreases the conversion of phenol and selectivity of hydroquinone. A new mechanism controlling the product selectivity is proposed.

Beta zeolite catalysts with different crystal sizes and similar acid strengths were synthesized in a "Steam-Assisted conversion (SAC)" technique. Pt loaded H-beta with an optimized crystal size of 600 nm showed high activity for hydrotreatment of tetralin by producing alkylbenzenes through area and low coke deposition. Isomerization reaction, which was expected to occur on the zeolite surface, was reduced considerably since tetralin interacted with strong Brönsted acid sites as soon as it penetrated the pore of the zeolite and underwent cracking to form linear hydrocarbons, C6 and C7 aromatics products. The method of supporting platinum on the zeolite had a significant effect on the activity of catalyst. For loading platinum of beta zeolite, ion exchange was a suitable method as it helped in well dispersion of platinum on the zeolite surface and inside the micropore.

Mordenite and ZSM-5 seeds could grow on the surface of an asymmetric α-Al2O3 support using an identical organic-free aluminosilicate solution under the same hydrothermal conditions. It suggests that the phase of zeolite can be controlled by varying the type of seed. Continuous mordenite and ZSM-5 membranes were prepared by the secondary growth method using corresponding seeds under appropriate conditions. The water content in the secondary growth mixture strongly influenced the growth of zeolite crystals. ZSM-5 seeds grew at a smaller rate and showed a habit of thin hexagonal plate in a concentrated mixture, while the crystals with a habit of rectangular parallelepiped were formed from a diluted secondary growth mixture. ZSM-5 crystals had poor intergrowth in the former case, whereas the crystals were highly intergrown in the latter case. ZSM-5 crystals in either membrane have a random orientation. In contrast to ZSM-5 zeolite, the crystal orientation in the secondary grown mordenite membranes strongly depended on the water content in the secondary growth mixture. The crystals in the mordenite membrane developed in a diluted secondary growth mixture were oriented with the (1 5 0) face parallel to the support surface, whereas the crystals in the membrane grown in a concentrated mixture were oriented with the (0 0 2) face parallel to the support surface. These results suggest that the crystal orientation in mordenite membranes can be manipulated only by changing the water content in a secondary growth mixture. The formation of the preferred crystal orientation in the secondary grown mordenite membrane is discussed in terms of an "evolutionary selection" process. © 2003 Elsevier Inc. All rights reserved.

A photoresponsive coumarin derivative was grafted on the pore outlet of Si-MCM-41. Irradiation of UV light longer than 310-nm wavelength to this coumarin-modified MCM-41 induced the photodimerization of coumarin to close the pore outlet with cyclobutane dimer. Guest molecules such as phenanthrene neither can enter nor escape from the one-dimensional, isolated, individual pores of MCM-41. On the other hand, the irradiation to the dimerized-coumarin-modified MCM-41 with shorter wavelength UV light around 250 nm regenerates the coumarin monomer derivative by the photocleavage of cyclobutane dimer, and guest molecules included inside are released from the pore void. For the first time, this intermolecular reversible photodimerization-cleavage cycle realized photo-switched storage and release of guest molecules from coumarin-modified MCM-41. Coumarin-modified MCM-41 prepared using tetradecyltrimethylammonium bromide as surfactant was able to store 21.6 wt % of phenanthrene as guest molecule after photodimerization and washing with n-hexane. Among the four different methods studied for the modification by the coumarin derivative, a grafting procedure with as-synthesized MCM-41 for short reaction time was found to be the most effective for the dense attachment of coumarin-derived monomer at the pore outlets of MCM-41, which is essential for effective storage-release controlled release.

Mordenite and ZSM-5 seeds could grow on the surface of an asymmetric alpha-Al2O3 support using an identical organic-free aluminosilicate solution under the same hydrothermal conditions. It suggests that the phase of zeolite can be controlled by varying the type of seed. Continuous mordenite and ZSM-5 membranes were prepared by the secondary growth method using corresponding seeds under appropriate conditions. The water content in the secondary growth mixture strongly influenced the growth of zeolite crystals. ZSM-5 seeds grew at a smaller rate and showed a habit of thin hexagonal plate in a concentrated mixture, while the crystals with a habit of rectangular parallelepiped were formed from a diluted secondary growth mixture. ZSM-5 crystals had poor intergrowth in the former case, whereas the crystals were highly intergrown in the latter case. ZSM-5 crystals in either membrane have a random orientation. In contrast to ZSM-5 zeolite, the crystal orientation in the secondary grown mordenite membranes strongly depended on the water content in the secondary growth mixture. The crystals in the mordenite membrane developed in a diluted secondary growth mixture were oriented with the (1 5 0) face parallel to the support surface, whereas the crystals in the membrane grown in a concentrated mixture were oriented with the (0 0 2) face parallel to the support surface. These results suggest that the crystal orientation in mordenite membranes can be manipulated only by changing the water content in a secondary growth mixture. The formation of the preferred crystal orientation in the secondary grown mordenite membrane is discussed in terms of an "evolutionary selection" process. (C) 2003 Elsevier Inc. All rights reserved.

A photoresponsive coumarin derivative was grafted on the pore outlet of Si-MCM-41. Irradiation of UV light longer than 310-nm wavelength to this coumarin-modified MCM-41 induced the photodimerization of coumarin to close the pore outlet with cyclobutane dimer. Guest molecules such as phenanthrene neither can enter nor escape from the one-dimensional, isolated, individual pores of MCM-41. On the other hand, the irradiation to the dimerized-coumarin-modified MCM-41 with shorter wavelength UV light around 250 nm regenerates the coumarin monomer derivative by the photocleavage of cyclobutane dimer, and guest molecules included inside are released from the pore void. For the first time, this intermolecular reversible photodimerization-cleavage cycle realized photo-switched storage and release of guest molecules from coumarin-modified MCM-41. Coumarin-modified MCM-41 prepared using tetradecyltrimethylammonium bromide as surfactant was able to store 21.6 wt % of phenanthrene as guest molecule after photodimerization and washing with n-hexane. Among the four different methods studied for the modification by the coumarin derivative, a grafting procedure with as-synthesized MCM-41 for short reaction time was found to be the most effective for the dense attachment of coumarin-derived monomer at the pore outlets of MCM-41, which is essential for effective storage-release controlled release.

It was investigated that the effects of preparation methods and conditions for SrFeCo0.5Ox dense membrane on their oxygen permeability. Three different methods, a solid-state reaction method, an evaporation-to-dryness method, and a combined citrate and EDTA complexing method, were applied for the preparation of parent powder. The oxygen flux through membrane at 900 degreesC was increased in the order listed above. The oxygen flux could be greatly improved by repeated calcination and grinding of parent powder. The membrane sintered at a temperature as high as 1200 degreesC showed a higher oxygen flux (0.22 cm(3) (STP)/cm(2) min). (C) 2003 Elsevier Science B.V. All rights reserved.

A study was carried out on the pervaporation of water from water-acetic acid mixtures through tubular ZSM-5 zeolite membranes. ZSM-5 zeolite membranes were prepared on the outer surface of a porous a-alumina tube by the seed-assisted crystallization method in the absence of organic templates. It was observed that water preferentially permeated with selectivities higher than the selectivity based on the vapor-liquid equilibrium in the entire range of acetic acid concentration. The separation mechanism of water through ZSM-5 zeolite membranes was discussed and compared with that through mordenite membranes. It was found that the permeability coefficients of both water and acetic acid decreased with increasing temperature, although the pervaporation fluxes of both water and acetic acid increased. As a result, it was concluded that the increase in the pervaporation flux with temperature was due to the increase in the driving force in terms of transmembrane partial vapor pressure difference with temperature. According to the mechanism proposed herein, a study was also directed to modify as-synthesized membranes for the improvement in their pervaporation performance. It was observed that both the water flux and the separation factor were increased through a membrane treated in alkaline solution under appropriate conditions. (C) 2003 Elsevier Science B.V. All rights reserved.

Mordenite membranes have been prepared on the outer surface of a porous a-alumina tube by seed-assisted crystallization. The kind of silica source was found to have significant influence on the microstructure of the membrane grown on the seeded support. Highly water-selective mordenite membranes were prepared with crystallization time as short as 2-4 h at 180 degreesC. The dehydration of acetic acid by pervaporation was investigated using these thin membranes as functions of temperature and feed concentration. The separation mechanism is discussed. (C) 2003 Published by Elsevier Science B.V.

It was investigated that the effects of preparation methods and conditions for SrFeCo0.5Ox dense membrane on their oxygen permeability. Three different methods, a solid-state reaction method, an evaporation-to-dryness method, and a combined citrate and EDTA complexing method, were applied for the preparation of parent powder. The oxygen flux through membrane at 900 degreesC was increased in the order listed above. The oxygen flux could be greatly improved by repeated calcination and grinding of parent powder. The membrane sintered at a temperature as high as 1200 degreesC showed a higher oxygen flux (0.22 cm(3) (STP)/cm(2) min). (C) 2003 Elsevier Science B.V. All rights reserved.

A study was carried out on the pervaporation of water from water-acetic acid mixtures through tubular ZSM-5 zeolite membranes. ZSM-5 zeolite membranes were prepared on the outer surface of a porous a-alumina tube by the seed-assisted crystallization method in the absence of organic templates. It was observed that water preferentially permeated with selectivities higher than the selectivity based on the vapor-liquid equilibrium in the entire range of acetic acid concentration. The separation mechanism of water through ZSM-5 zeolite membranes was discussed and compared with that through mordenite membranes. It was found that the permeability coefficients of both water and acetic acid decreased with increasing temperature, although the pervaporation fluxes of both water and acetic acid increased. As a result, it was concluded that the increase in the pervaporation flux with temperature was due to the increase in the driving force in terms of transmembrane partial vapor pressure difference with temperature. According to the mechanism proposed herein, a study was also directed to modify as-synthesized membranes for the improvement in their pervaporation performance. It was observed that both the water flux and the separation factor were increased through a membrane treated in alkaline solution under appropriate conditions. (C) 2003 Elsevier Science B.V. All rights reserved.

Template-free nanosized ZSM-5 seeds were prepared from commercially available ZSM-5 powder. By use of these seeds, thin and hydrophilic ZSM-5 zeolite membranes were prepared on the outer surface of a porous a-alumina tube in a clear solution free from organic template. The membranes showed high thermal stability to withstand pretreatment at 400 degreesC, At 270 degreesC, the ideal selectivities for H-2/i-butane and N-2/SF6 were 61 and 20, respectively. The membrane was effective to separate butane isomers at high temperatures. The maximum of the n/i-butane ideal selectivity was 36 at 300 degreesC. The separation factors for a 50/50 n/i-butane mixture were as high as 13 in the temperature range from 300 to 400 degreesC. (C) 2003 Elsevier Science Inc. All rights reserved.

Microporous layered titanium phenylphosphonate, Ti(O3PC6H5)(2) and sulfonated titanium phenylphosphonate, Ti(O3PC6H4SO3H)(0.89) (O3PC6H5)(1.1).1.8H(2)O were prepared in the presence of sodium dodecylsulfate (SDS). Interplanar spacing (d(001)) of titanium phenylphosphonate is 1.43 nm and after sulfonation it increased to 1.64 nm. The surface area of titanium phenylphosphonate is 264 m(2) g(-1).

Microporous layered titanium phenylphosphonate, Ti(O3PC6H5)(2) and sulfonated titanium phenylphosphonate, Ti(O3PC6H4SO3H)(0.89) (O3PC6H5)(1.1).1.8H(2)O were prepared in the presence of sodium dodecylsulfate (SDS). Interplanar spacing (d(001)) of titanium phenylphosphonate is 1.43 nm and after sulfonation it increased to 1.64 nm. The surface area of titanium phenylphosphonate is 264 m(2) g(-1).

The application of the membrane reactor to steam reforming of methanol was studied as a hydrogen producing reaction. The activities, stabilities and selectivities of Cu/ZnO, Ni/Al2O3 and Ru/Al2O3 catalysts were tested using a conventional fixed-bed flow reactor. Ni/Al2O3 catalyst showed the most stable activity at 723 K but relatively low hydrogen yield because of methanation. However, the hydrogen-permeable membrane reactor suppressed methanation and hydrogen yield was enhanced compared with the conventional reactor. The membrane reactor was more effective at higher temperatures and higher W/F.

The application of the membrane reactor to steam reforming of methanol was studied as a hydrogen producing reaction. The activities, stabilities and selectivities of Cu/ZnO, Ni/Al2O3 and Ru/Al2O3 catalysts were tested using a conventional fixed-bed flow reactor. Ni/Al2O3 catalyst showed the most stable activity at 723 K but relatively low hydrogen yield because of methanation. However, the hydrogen-permeable membrane reactor suppressed methanation and hydrogen yield was enhanced compared with the conventional reactor. The membrane reactor was more effective at higher temperatures and higher W/F.

Microporous layered titanium phenylphosphonate, Ti(O3PC6H5)2 and sulfonated titanium phenylphosphonate, Ti(O3PC6H4SO3H)0.89 (O3PC6H5)1.1 · 1.8H2O were prepared in the presence of sodium dodecylsulfate (SDS). Interplanar spacing (d001) of titanium phenylphosphonate is 1.43 nm and after sulfonation it increased to 1.64 nm. The surface area of titanium phenylphosphonate is 264 m2 g-1.

A Pd/alpha-Al2O3 composite membrane was prepared on a porous alpha-Al2O3 disk via the thermal decomposition of bis(hexafluoroacetylacetonato)Pd(II), Pd(hfac)(2). Pd(hfac)(2) was dissolved in supercritical CO2 at 303 K, supplied to the substrate, and thermally decomposed at 403 and 443 K. The decomposition of Pd(hfac)(2) at 443 K resulted in a sufficient pore filling of substrate with Pd as well as the formation of a thin Pd top layer. The hydrogen flux through this membrane was about 1.7 times than that of a electro-less plating Pd membrane with about 20 mum thick. Hydrogen permeation was governed by the solution-diffusion mechanism which gave a high separation selectivity.

Though light cycle oils (LCO) obtained in the fluid catalytic cracking (FCC) are rich in aromatics and sulphur but are insufficient to diesel fuels due to the low cetane number. It is worthwhile to produce alkylbenzenes from LCO without producing small olefinic hydrocarbons through hydrotreating polyaromatic compounds present in the LCO. In the present study tetralin was used as a model compound. Reactions such as ring opening, dealkylation, transalkylation, hydrogen transfer and coke formation were studied using Platinum-supported beta as catalyst. The objective of this study was to investigate the relationship between the crystal size of beta zeolite and catalytic properties for hydrotreatment of tetralin.

Though light cycle oils (LCO) obtained in the fluid catalytic cracking (FCC) are rich in aromatics and sulphur but are insufficient to diesel fuels due to the low cetane number. It is worthwhile to produce alkylbenzenes from LCO without producing small olefinic hydrocarbons through hydrotreating polyaromatic compounds present in the LCO. In the present study tetralin was used as a model compound. Reactions such as ring opening, dealkylation, transalkylation, hydrogen transfer and coke formation were studied using Platinum-supported beta as catalyst. The objective of this study was to investigate the relationship between the crystal size of beta zeolite and catalytic properties for hydrotreatment of tetralin.

A Pd/alpha-Al2O3 composite membrane was prepared on a porous alpha-Al2O3 disk via the thermal decomposition of bis(hexafluoroacetylacetonato)Pd(II), Pd(hfac)(2). Pd(hfac)(2) was dissolved in supercritical CO2 at 303 K, supplied to the substrate, and thermally decomposed at 403 and 443 K. The decomposition of Pd(hfac)(2) at 443 K resulted in a sufficient pore filling of substrate with Pd as well as the formation of a thin Pd top layer. The hydrogen flux through this membrane was about 1.7 times than that of a electro-less plating Pd membrane with about 20 mum thick. Hydrogen permeation was governed by the solution-diffusion mechanism which gave a high separation selectivity.

Though light cycle oils (LCO) obtained in the fluid catalytic cracking (FCC) are rich in aromatics and sulphur but are insufficient to diesel fuels due to the low cetane number. It is worthwhile to produce alkylbenzenes from LCO without producing small olefinic hydrocarbons through hydrotreating polyaromatic compounds present in the LCO. In the present study tetralin was used as a model compound. Reactions such as ring opening, dealkylation, transalkylation, hydrogen transfer and coke formation were studied using Platinum-supported beta as catalyst. The objective of this study was to investigate the relationship between the crystal size of beta zeolite and catalytic properties for hydrotreatment of tetralin.

Zeolite beta with SiO2/Al2O3 ratios from 30 to 730 was synthesized by a steam-assisted crystallization method, and the crystallized products obtained within 24 h were characterized by means of chemical analyses, XRD, FE-SEM, Si-29- MAS NMR, N-2 adsorption, and temperature-programmed decomposition of tetraethylammonium cation occluded in the micropores of zeolite beta. Based on these results, the crystallization mechanism is discussed herein. It was found that agglomerates of nano-particles were formed from a dry gel before the development of a periodical structure in a long-range order, which can be detected by XRD. After several hours of crystallization, morphological changes in nano-particle agglomerates proceeded to give highly crystalline zeolite beta. (C) 2002 Elsevier Science Inc. All rights reserved.

Palladium ion-exchanged zeolites (ZSM-5, mordenite, ferrierite, Y, beta) were tested to evaluate catalytic activity for selective reduction of nitric oxide with methane (CH4-SCR) and stability in the presence of 10% water vapor at a relatively high temperature of 500degreesC. Deactivation of the catalytic activity was inevitable on Pd/HZSM-5 with a Si/Al ratio of 19.8 under the reaction conditions. When the Si/Al ratio decreased, the durability was slightly enhanced. Among the zeolites tested, palladium supported on mordenite showed stable NO conversions. The addition of cobalt effectively stabilized the activity of Pd-H-zeolites, particularly with the addition of 3.3 wt% cobalt onto Pd/HZSM-5, of which no deactivation was noticeable for at least 50 h. Isolated Pd2+ cations on HZSM-5 were the active and selective sites for CH4-SCR. The isolated Pd2+ cations could not be exchanged by Na+ cations in NaCl titration test after the addition of 3.3 wt% cobalt, while NH4NO3 titration revealed that the isolated Pd2+ existed in the sample. This means that Co2+ changes the ion-exchange property of the isolated Pd2+, leading to a much higher stability than Pd/HZSM-5 with regard to durability. The effect of Co2+ on the stability of the isolated Pd2+ cations and their sitings in zeolite cavities is discussed. (C) 2002 Elsevier Science (USA).

Zeolite beta with SiO2/Al2O3 ratios from 30 to 730 was synthesized by a steam-assisted crystallization method, and the crystallized products obtained within 24 h were characterized by means of chemical analyses, XRD, FE-SEM, Si-29- MAS NMR, N-2 adsorption, and temperature-programmed decomposition of tetraethylammonium cation occluded in the micropores of zeolite beta. Based on these results, the crystallization mechanism is discussed herein. It was found that agglomerates of nano-particles were formed from a dry gel before the development of a periodical structure in a long-range order, which can be detected by XRD. After several hours of crystallization, morphological changes in nano-particle agglomerates proceeded to give highly crystalline zeolite beta. (C) 2002 Elsevier Science Inc. All rights reserved.

Palladium ion-exchanged zeolites (ZSM-5, mordenite, ferrierite, Y, beta) were tested to evaluate catalytic activity for selective reduction of nitric oxide with methane (CH4-SCR) and stability in the presence of 10% water vapor at a relatively high temperature of 500degreesC. Deactivation of the catalytic activity was inevitable on Pd/HZSM-5 with a Si/Al ratio of 19.8 under the reaction conditions. When the Si/Al ratio decreased, the durability was slightly enhanced. Among the zeolites tested, palladium supported on mordenite showed stable NO conversions. The addition of cobalt effectively stabilized the activity of Pd-H-zeolites, particularly with the addition of 3.3 wt% cobalt onto Pd/HZSM-5, of which no deactivation was noticeable for at least 50 h. Isolated Pd2+ cations on HZSM-5 were the active and selective sites for CH4-SCR. The isolated Pd2+ cations could not be exchanged by Na+ cations in NaCl titration test after the addition of 3.3 wt% cobalt, while NH4NO3 titration revealed that the isolated Pd2+ existed in the sample. This means that Co2+ changes the ion-exchange property of the isolated Pd2+, leading to a much higher stability than Pd/HZSM-5 with regard to durability. The effect of Co2+ on the stability of the isolated Pd2+ cations and their sitings in zeolite cavities is discussed. (C) 2002 Elsevier Science (USA).

Zeolite/mesoporous molecular sieve composites (ZMC) are made using zeolites as silica-alumina source. XRD patterns of the ZMC show the peaks for both zeolite and mesoporous molecular sieve with hexagonal symmetry. Morphology of the ZMC is different from that of a physical mixture of the two components. Unlike Al-containing mesoporous molecular sieves, the ZMC shows a strong acidity like zeolites. The activity of cracking of n-hexane for ZMC was higher than that of the zeolite. These products are expected to be useful for catalysts and adsorbents for their acidity and pore size.

Zeolite/mesoporous molecular sieve composites (ZMC) are made using zeolites as silica-alumina source. XRD patterns of the ZMC show the peaks for both zeolite and mesoporous molecular sieve with hexagonal symmetry. Morphology of the ZMC is different from that of a physical mixture of the two components. Unlike Al-containing mesoporous molecular sieves, the ZMC shows a strong acidity like zeolites. The activity of cracking of n-hexane for ZMC was higher than that of the zeolite. These products are expected to be useful for catalysts and adsorbents for their acidity and pore size.

The release of trace elements from coal combustion at high temperature was investigated in this study. About 0.1g of Wallarah coal smaller than 150μm was held in a platinum basket, inserted into an electronic furnace predetermined 573〜1573K and burned for 10min to release trace elements. The quantities of trace elements in the coal or ash in the platinum basket after coal combustion were determined by ICP-AES. It was found that initially, trace elements such as Zn and Pb released from a coal above 1173K in the absence of additional steam. Se, Sb and Hg released during 573〜773K and steam influenced the releasing behavior of these elements. Whereas Se and Sb enhanced, that of Hg depressed in the presence of steam.

Whereas the optimization of apparatus and the development of flotation results have been extensively reported in the research of column flotation of coal, there have been few studies on the relation of flotation results with the characteristics of coal. The changes in the distributions of particle size and inorganic elements involved in cleaned coal and tail refuse were studied in the course of column flotation. Demineralization mechanisms in a column flotation system were investigated.

We conducted steam gasification of various coal char under atomospheric pressure on pressurized conditions. Raw lank coal showed high hydrogen producibility at low temperature. And also alkaline metals catalyzed water gas shift reaction. From these results, we optimized the conditions for production of syngas from coal char and steam.

It is reported that the first synthesis of MCM-22 zeolite by the vapor-phase transport (VPT) method and the comparison in the morphologies of MCM-22 synthesized by the VPT and hydrothermal synthetic (HTS) methods. In the VPT method, pure MCM-22 zeolite was crystallized at 150degreesC for 5 days and at 175degreesC for 3 days. The morphology of MCM-22 zeolite crystallized by the VPT method was sphere which is an agglomerate of hexagonal thin plates having about 3similar to5 mum in width with less than 100 nm thick. Such morphology was similar to MCM-22 zeolite synthesized by the HTS method under static condition. The crystallization by the VPT method with the addition of HMI onto dry gel gave smaller MCM-22 crystals consisting of thin plates with 1similar to2 mum in width.

It is reported that the first synthesis of MCM-22 zeolite by the vapor-phase transport (VPT) method and the comparison in the morphologies of MCM-22 synthesized by the VPT and hydrothermal synthetic (HTS) methods. In the VPT method, pure MCM-22 zeolite was crystallized at 150degreesC for 5 days and at 175degreesC for 3 days. The morphology of MCM-22 zeolite crystallized by the VPT method was sphere which is an agglomerate of hexagonal thin plates having about 3similar to5 mum in width with less than 100 nm thick. Such morphology was similar to MCM-22 zeolite synthesized by the HTS method under static condition. The crystallization by the VPT method with the addition of HMI onto dry gel gave smaller MCM-22 crystals consisting of thin plates with 1similar to2 mum in width.

It is reported that the first synthesis of MCM-22 zeolite by the vapor-phase transport (VPT) method and the comparison in the morphologies of MCM-22 synthesized by the VPT and hydrothermal synthetic (HTS) methods. In the VPT method, pure MCM-22 zeolite was crystallized at 150degreesC for 5 days and at 175degreesC for 3 days. The morphology of MCM-22 zeolite crystallized by the VPT method was sphere which is an agglomerate of hexagonal thin plates having about 3similar to5 mum in width with less than 100 nm thick. Such morphology was similar to MCM-22 zeolite synthesized by the HTS method under static condition. The crystallization by the VPT method with the addition of HMI onto dry gel gave smaller MCM-22 crystals consisting of thin plates with 1similar to2 mum in width.

It is reported that the first synthesis of MCM-22 zeolite by the vapor-phase transport (VPT) method and the comparison in the morphologies of MCM-22 synthesized by the VPT and hydrothermal synthetic (HTS) methods. In the VPT method, pure MCM-22 zeolite was crystallized at 150degreesC for 5 days and at 175degreesC for 3 days. The morphology of MCM-22 zeolite crystallized by the VPT method was sphere which is an agglomerate of hexagonal thin plates having about 3similar to5 mum in width with less than 100 nm thick. Such morphology was similar to MCM-22 zeolite synthesized by the HTS method under static condition. The crystallization by the VPT method with the addition of HMI onto dry gel gave smaller MCM-22 crystals consisting of thin plates with 1similar to2 mum in width.

A high-silica hexagonal faujasite EMT was crystallized by a steam-assisted crystallization (SAC) method using a crown ether of 1,4,7,10,13,16-hexaoxacyclooctadecane, 18-crown-6, as a structure-directing agent. The growth mechanism of EMT by SAC is quite different from that of EMT by the conventional hydrothermal synthetic method, in which layer-by-layer growth occurs. Another characteristic of SAC is that nanoparticles fuse and the surface of the dry gel is rearranged, resulting in a distinct hexagonal shape for the EMT crystals. Sodium content must be strictly defined when the SAC method is used, and the crystallization temperature must be kept below 408 K to keep the crown ether in the dry gel to obtain a pure phase of EMT.

Beta zeolites with a wide range of Si/2Al ratios from 7 to infinity were synthesized by steam-assisted crystallization method. X-ray diffraction, FE-SEM, and MASNMR studies confirmed the formation of highly crystalline zeolite beta and Al incorporation in the framework under various conditions by the SAC method at temperatures ranging from 373 to 438 K. Na+ and TEA(+) contents occluded in micropores of beta zeolite were determined. Quantitative knowledge on such occluded cations gave great insight on understanding crystallization mechanism of beta. (C) 2001 Published by Elsevier Science B.V.

A high-silica hexagonal faujasite EMT was crystallized by a steam-assisted crystallization (SAC) method using a crown ether of 1,4,7,10,13,16-hexaoxacyclooctadecane, 18-crown-6, as a structure-directing agent. The growth mechanism of EMT by SAC is quite different from that of EMT by the conventional hydrothermal synthetic method, in which layer-by-layer growth occurs. Another characteristic of SAC is that nanoparticles fuse and the surface of the dry gel is rearranged, resulting in a distinct hexagonal shape for the EMT crystals. Sodium content must be strictly defined when the SAC method is used, and the crystallization temperature must be kept below 408 K to keep the crown ether in the dry gel to obtain a pure phase of EMT.

Beta zeolites with a wide range of Si/2Al ratios from 7 to infinity were synthesized by steam-assisted crystallization method. X-ray diffraction, FE-SEM, and MASNMR studies confirmed the formation of highly crystalline zeolite beta and Al incorporation in the framework under various conditions by the SAC method at temperatures ranging from 373 to 438 K. Na+ and TEA(+) contents occluded in micropores of beta zeolite were determined. Quantitative knowledge on such occluded cations gave great insight on understanding crystallization mechanism of beta. (C) 2001 Published by Elsevier Science B.V.

ZSM-5 zeolite having a SiO2/Al2O3 molar ratio of 39.4 was treated in a NaOH alkali solution and the changes in structural and acidic properties were investigated. A siliceous species was selectively dissolved from the framework of zeolite, although a lower amount of Al was also eluted. In this procedure, mesopores with a uniform size were formed on the zeolite, while the microporous structure remained. The acidic property was changed very little quantitatively or qualitatively, even though the catalytic activity for cracking of cumene was enhanced by the alkali-treatment. This can be explained by the facts that adsorptive and diffusive properties of cumene through micropores of the ZSM-5 are increased by the creation of mesopores. (C) 2001 Elsevier Science B.V. All rights reserved.

ZSM-5 zeolite having a SiO2/Al2O3 molar ratio of 39.4 was treated in a NaOH alkali solution and the changes in structural and acidic properties were investigated. A siliceous species was selectively dissolved from the framework of zeolite, although a lower amount of Al was also eluted. In this procedure, mesopores with a uniform size were formed on the zeolite, while the microporous structure remained. The acidic property was changed very little quantitatively or qualitatively, even though the catalytic activity for cracking of cumene was enhanced by the alkali-treatment. This can be explained by the facts that adsorptive and diffusive properties of cumene through micropores of the ZSM-5 are increased by the creation of mesopores. (C) 2001 Elsevier Science B.V. All rights reserved.

A novel organic-ceramic membrane having stable Si-C bonds was developed for separation of high temperature organic solutions. Porous vycor glass was employed for a substrate which was modified by a series of chemical vapor deposition (CVD) and hydrosilylation. 1,3,5,7-Tetramethylcyclotetrasiloxane (1-14) was used as a CVD source in order to introduce Si-H bonds on the surface of porous vycor glass. The Si-H bonds were then catalytically hydrosilylated with olefins. As a result, organic functional groups were introduced via Si-C bonds. A compact membrane was obtained when CVD treatment was carried out at 343 K. The membrane that was modified by the hydrosilylation of styrene showed benzene permselectivity in benzene/cyclohexane vapor permeation test at 373 K. The separation factor of benzene over cyclohexane was 2.9 and benzene flux was 1.2 x 10(-8) mol m(-2)s(-1)Pa(-1), and the permeation properties are stable for more than 1000 min at 373 K.

A novel organic-ceramic membrane having stable Si-C bonds was developed for separation of high temperature organic solutions. Porous vycor glass was employed for a substrate which was modified by a series of chemical vapor deposition (CVD) and hydrosilylation. 1,3,5,7-Tetramethylcyclotetrasiloxane (1-14) was used as a CVD source in order to introduce Si-H bonds on the surface of porous vycor glass. The Si-H bonds were then catalytically hydrosilylated with olefins. As a result, organic functional groups were introduced via Si-C bonds. A compact membrane was obtained when CVD treatment was carried out at 343 K. The membrane that was modified by the hydrosilylation of styrene showed benzene permselectivity in benzene/cyclohexane vapor permeation test at 373 K. The separation factor of benzene over cyclohexane was 2.9 and benzene flux was 1.2 x 10(-8) mol m(-2)s(-1)Pa(-1), and the permeation properties are stable for more than 1000 min at 373 K.

Al-free Ti-Si-beta was synthesized by a steam-assisted crystallization (SAC) method using tetraethylammonium hydroxide as a structure-directing agent. It was noted that Na in a parent gel was essential for synthesizing highly crystalline Ti-Si-beta by means of the SAC method. An absorption band at 225 nm, assigned to isolated Ti species, and another band at around 270 nm appeared in the UV spectra of the Ti-Si-beta. The latter absorption band decreased upon ion exchange of as-synthesized materials with 1 M aqueous NH4NO3 solution, and this treatment did not change the SiO2/TiO2 molar ratio in Ti-Si-beta. The Q(3) signal in the Si-29-NMR spectrum almost disappeared and the amount of H2O adsorbed decreased due to the NH4+ exchange of Ti-Si-beta. The NH4+ exchange resulted in a higher catalytic activity of the zeolite far cyclohexene epoxidation with H2O2 and a high selectivity toward epoxide compared with the H2SO4-treated Ti-Si-beta and AI-containing Ti-beta samples prepared in this study. Summarizing these results, the NH4+ exchange of Ti-Si-beta zeolite is found to induce a hydrophobic environment around Ti sites without detitanation from the zeolite framework. (C) 2001 Academic Press.

It is important to estimate the distribution of hydrophilic/hydrophobic sites on coal in a coal-cleaning process. The relationship between the distribution of hydrophilic/hydrophobic sites on coal and the carbonaceous materials recovery in a continuous column flotation was investigated. The amount of adsorbed methylene blue was determined to estimate the fraction of hydrophilic surface on coal surface. As a result, it turned out that the hydrophilic nature estimated by using methylene blue adsorption was closely related to the carbonaceous materials recovery.

We conducted steam gasification of various coal char under atomospheric pressure or pressurized conditions. Raw coal such as Adaro (SS-013) showed high hydrogen producibility at low temperature. And also alkaline metals catalyzed water gas shift reaction. From these results, we optimized the conditions for production of syngas from coal char and steam.

The elution behavior of inorganic matters from SS013, SS015, SS020, SS027, SS029 and SS045 was investigated. In particular, the amount of elution and time course were estimated by using ion chromatography. The time course of elution indicates that soluble minerals on the surface of coal was rapidly eluted within 5 minutes. The elution rate from SS027 was higher than those from SS020 or SS029. The amount of soluble minerals determines elution rate. We concluded that there was little relation between the amount of elution and ash content.

The distribution of hydrophilic/hydrophobic sites on coal is one of the essential factors in a column flotation process. In this study, methylene blue adsorption on coal was conducted to estimate the area of hydrophilic surface. The experimental results successfully suggested that methylene blue was adsorbed on the hydrophilic surface sites on minerals and oxygen-containing functional groups.

Microstructures of spherical and coffin-shaped MFI zeolite and its effect on the catalytic activity for cumene cracking were studied. While spherical MFI was composed of nanoparticles, coffin-shaped one has a layered structure where nanoparticles with ~ 30 nm in size were accumulated on the dense core. Both the thickness of nano-particles layer and mesopore volume linearly correlated with the activity for cumene cracking, suggesting that the mesopores in MFI particles formed during nanoparticles agglomeration, and that the reaction rate of cumene cracking was significantly affected by the diffusion of cumene molecule in the nanoparticles agglomerating layer. This is an abstract of a paper presented at the 13th International Zeolite Conference (Montpellier, France 7/8-13/2001).

A highly oriented mordenite membrane with c-axis of crystals perpendicular to the support surface was successfully prepared on a porous α-alumina support. Seeding was necessary to form a compact layer of mordenite. The "evolutionary selection" mechanism significantly contributed to the formation of a sharply oriented mordenite layer. Pervaporation results for separation of a water/iso-propanol mixture exhibited highly preferential permeation of water through the oriented mordenite membrane. This is an abstract of a paper presented at the 13th International Zeolite Conference (Montpellier, France 7/8-13/2001).

Microstructures of spherical and coffin-shaped MFI zeolite and its effect on the catalytic activity for cumene cracking were studied. While spherical MFI was composed of nanoparticles, coffin-shaped one has a layered structure where nanoparticles with ~ 30 nm in size were accumulated on the dense core. Both the thickness of nano-particles layer and mesopore volume linearly correlated with the activity for cumene cracking, suggesting that the mesopores in MFI particles formed during nanoparticles agglomeration, and that the reaction rate of cumene cracking was significantly affected by the diffusion of cumene molecule in the nanoparticles agglomerating layer. This is an abstract of a paper presented at the 13th International Zeolite Conference (Montpellier, France 7/8-13/2001).

A highly oriented mordenite membrane with c-axis of crystals perpendicular to the support surface was successfully prepared on a porous α-alumina support. Seeding was necessary to form a compact layer of mordenite. The "evolutionary selection" mechanism significantly contributed to the formation of a sharply oriented mordenite layer. Pervaporation results for separation of a water/iso-propanol mixture exhibited highly preferential permeation of water through the oriented mordenite membrane. This is an abstract of a paper presented at the 13th International Zeolite Conference (Montpellier, France 7/8-13/2001).

MFI-type zeolitic membranes were prepared by a vapor-phase transport (VPT) method on porous alpha-alumina flat disks. Single- and mixed-gas permeation measurements of butane isomers were performed in the temperature range of 300-375 K. The separation factor was always greater than the ideal selectivity. This result is explained by the preferential adsorption of n-butane on MFI in the binary system.
The pervaporation tests for xylene isomers were performed at 303 K. p-Xylene was the most permeable component in the unary system. In the permeation measurements of a binary mixture of p-xylene/m-xylene and a ternary mixture of p-xylene/m-xylene/o-xylene, p-xylene predominantly permeated in the early stage, and then, the Aux of p-xylene decreased gradually and finally became lower than that of the other xylene isomers. The adsorption of m-xylene in the pores of MFI seemed to block the permeation of p-xylene. (C) 2000 Elsevier Science B.V. All rights reserved.

MFI-type zeolitic membranes were prepared by a vapor-phase transport (VPT) method on porous alpha-alumina flat disks. Single- and mixed-gas permeation measurements of butane isomers were performed in the temperature range of 300-375 K. The separation factor was always greater than the ideal selectivity. This result is explained by the preferential adsorption of n-butane on MFI in the binary system.
The pervaporation tests for xylene isomers were performed at 303 K. p-Xylene was the most permeable component in the unary system. In the permeation measurements of a binary mixture of p-xylene/m-xylene and a ternary mixture of p-xylene/m-xylene/o-xylene, p-xylene predominantly permeated in the early stage, and then, the Aux of p-xylene decreased gradually and finally became lower than that of the other xylene isomers. The adsorption of m-xylene in the pores of MFI seemed to block the permeation of p-xylene. (C) 2000 Elsevier Science B.V. All rights reserved.

Treatment of ZSM-5 in alkaline solution dramatically changes morphology of the ZSM-5, leading to the formation of mesopores whose size is almost uniform without destruction of microporous structure.

Polycrystalline ferrierite/alumina composite membranes were prepared by a vapor-phase transport method. Pervaporation of m-xylene and 1,3,5-triisopropylbenzene was then used to evaluate the compactness of the membranes.
Permeation measurements were carried out for hydrogen, helium, methane, n-butane, i-butane and sulfur hexafluoride at 300-375 K. Ideal selectivities and the mixed gas separation factors were compared. The separation factor of butane isomers depended on the compactness of the membrane. The separation factor of n-butane/i-butane was as high as 40-70 at 375 K, and no detectable permeation flux of m-xylene was observed at 303 K.
Separation of a 25/75 p-xylene/m-xylene mixture was also performed at 303 K using pervaporation. The permeation of p-xylene was detectable, whereas that of m-xylene was below the detection limit of the experiment. The separation factor of p-xylene to m-xylene was greater than 16, which is much higher than the value of 1.0 expected from the vapor-liquid equilibrium. (C) 2000 Elsevier Science B.V. All rights reserved.

Polycrystalline ferrierite/alumina composite membranes were prepared by a vapor-phase transport method. Pervaporation of m-xylene and 1,3,5-triisopropylbenzene was then used to evaluate the compactness of the membranes.
Permeation measurements were carried out for hydrogen, helium, methane, n-butane, i-butane and sulfur hexafluoride at 300-375 K. Ideal selectivities and the mixed gas separation factors were compared. The separation factor of butane isomers depended on the compactness of the membrane. The separation factor of n-butane/i-butane was as high as 40-70 at 375 K, and no detectable permeation flux of m-xylene was observed at 303 K.
Separation of a 25/75 p-xylene/m-xylene mixture was also performed at 303 K using pervaporation. The permeation of p-xylene was detectable, whereas that of m-xylene was below the detection limit of the experiment. The separation factor of p-xylene to m-xylene was greater than 16, which is much higher than the value of 1.0 expected from the vapor-liquid equilibrium. (C) 2000 Elsevier Science B.V. All rights reserved.

MFI-type lozenge zeolitic membranes were prepared by a vapor-phase transport method on porous or-alumina flat disks. Pure or mixed gas permeation measurements of butane isomers were performed at 375 K using two methods: pressure gradient (PG) and concentration gradient (CG) methods. Pure gas permeation measurements of H-2, He, CH4, N-2, O-2, CO2 and SF6 were also carried out using PG method. Counter-diffusion of helium as a sweep gas was evaluated by determining the gas composition at the outlet of the feed side. It was confirmed that the counter-diffusion of helium occurs only when the total pressure of the feed side was <80 kPa.
In the mixed gas permeation measurements, the value of separation factor depended on the method of gas permeation. The separation factors of n-butane to i-butane were ca. 10 in the PG method and 30-60 in the CG method. (C) 2000 Elsevier Science B.V. All rights reserved.

Catalytic performance of Ir catalysts for reduction of nitric oxide with carbon monoxide in the presence of SO, and excess oxygen was investigated. NO was selectively reduced with CO on Ir/silicalite in an oxidizing atmosphere containing 1% to 10% O-2 in the temperature range of 300-500 degrees C. The catalytic activity was scarcely influenced by 150 ppm SO2.

MFI-type lozenge zeolitic membranes were prepared by a vapor-phase transport method on porous or-alumina flat disks. Pure or mixed gas permeation measurements of butane isomers were performed at 375 K using two methods: pressure gradient (PG) and concentration gradient (CG) methods. Pure gas permeation measurements of H-2, He, CH4, N-2, O-2, CO2 and SF6 were also carried out using PG method. Counter-diffusion of helium as a sweep gas was evaluated by determining the gas composition at the outlet of the feed side. It was confirmed that the counter-diffusion of helium occurs only when the total pressure of the feed side was <80 kPa.
In the mixed gas permeation measurements, the value of separation factor depended on the method of gas permeation. The separation factors of n-butane to i-butane were ca. 10 in the PG method and 30-60 in the CG method. (C) 2000 Elsevier Science B.V. All rights reserved.

Catalytic performance of Ir catalysts for reduction of nitric oxide with carbon monoxide in the presence of SO, and excess oxygen was investigated. NO was selectively reduced with CO on Ir/silicalite in an oxidizing atmosphere containing 1% to 10% O-2 in the temperature range of 300-500 degrees C. The catalytic activity was scarcely influenced by 150 ppm SO2.

Inorganic matters behavior during column flotation which is a good candidate for preparing clean coal, was fundamentally studied. A column with 180cm high was continuously operated for 5 kinds of coal. The samples obtained from the top and bottom of column and aqueous phase were analyzed for the contents of inorganic elements. Inorganic elements were classified into three groups: (1) Those included in clean coal, (2) those rejected from the bottom of column, and (3) those soluble in aqueous phase. Alkali and alkaline elements were suggested to be extracted partly into aqueous phase. Predominant distribution of other elements like Al and Fe in clean coal or drain were observed in some types of coal, implying possible control of ash composition.

The release of inorganic matters from coal combustion as volatile matters and aerosols at high temperatures and their deposition on lower temperature surfaces were investigated fundamentally. About 100mg of coal (SS027) smaller than 100μm held in a platinum basket was inserted into an electronic furnace and burned at 1080℃ to release vapor and aerosols of inorganic matters. A packed bed of ZrO_2 beads of 2mm was placed in the downstream of the reactor. The temperature of the bed was controlled at about 100℃ so that inorganic matters would be cauyht on the ZrO_2 beads. The quantities of inorganic matters ccaught on the ZrO_2 beads after 1, 10, 30, 60 and 180min of coal combustion were determined by use of inductively coupled plasma (ICP). It was found that initially, inorganic matters such as alkali, alkaline earth metals and iron release during volatilization followed by the release from char burning process. Inorganic matters further continued to be released from ash.

The preparation of model particles having controlled hydrophobic/hydrophilic surfaces was attempted to investigate flotation behavior of coal in a column flotation process quantitatively. The surface properties of glass beads with ca. 50μm diameter were modified by chemical vapor deposition of 1, 3, 5, 7, -tetrametyltetracyclosiloxane (H-4), followed by catalytic hydrosilylation with vinylacetic acid. The CVD of H-4 was performed for making the surface of glass beads hydrophobic and the successive hydrosilylation allowed us to prepare particles with moderate hydrophilic surfaces. The CVD conditions to adjust hydrophobicity of glass beads were explored. The surface properties of these particles and their distribution were evaluated by means of a film flotation technique. The bubble-particle attachment probability was preliminary studied using these model particles.

A coal-water slurry was prepared by mixing 250ml of distilled water and a given amount of Datong Coal. The concentrations of slurry prepared was 0.596, 5.66 and 23.1wt%. The slurry was stirred for 3h. One ml of the slurry was taken by a syringe every 20min to investigate the elution rate of inorganic ions. Water-soluble inorganic matters in coal was attempted to quantitatively analyzed using ion chromatography. In comparison with ICP-AES, ion chromatography could be a method much easier to operate and cost effective. Three types of columns, YK-421 (HITACHI) for cations analysis, #2740 for anions analysis, and #2617 (HITACHI) for trace elements analysis, were used. It was found that cations were mostly eluted within 20min, while the elution of SO_4^<2-> continued up to 80min, leading to a decrease of pH from 5.3 to 2.6.

Mordenite membranes prepared on alpha-alumina tubular supports by in situ hydrothermal synthesis using organic template-free media showed high water permselectivity for pervaporation of water-isopropyl alcohol mixtures.

Mordenite membranes prepared on alpha-alumina tubular supports by in situ hydrothermal synthesis using organic template-free media showed high water permselectivity for pervaporation of water-isopropyl alcohol mixtures.

The active site in ZSM-5 zeolite-supported palladium, which shows the catalytic activity for NO reduction with methane as a reducing agent, has been investigated qualitatively and quantitatively by means of NO chemisorption and NaCl titration, comparing with PdO supported on silica. Palladium species in 0.4 wt.% Pd loaded H-ZSM-5 can adsorb NO equimolarly after calcination at 773 K, and almost all the NO was desorbed at around 673 K; while the palladium species on PdO/SiO2 hardly adsorbed NO. The palladium species in Pd(0.4)/H-ZSM-5 are ion-exchangeable with Na+ in NaCl solution, indicating that they exist in a cationic state of an isolated Pd2+. This method for quantitative analysis of the isolated Pd2+ cations is named as 'NaCl titration'. The amount of the isolated Pd2+ cationic species increased with increasing palladium content on Pd/H-ZSM-5, and PdO co-existed above 1 wt.%. The amount of the isolated Pd2+ cation was unchanged after the reaction of NO2-CH4, NO2-CH4-O-2, or CH4-O-2 at 673 K, while the adsorbed amount of NO per the Pd2+ as determined by NO-TPD decreased after the NO2-CH4-O-2 reaction. It was found by NaCl titration that the catalytic activity of Pd/H-ZSM-5 for NO2-CH4-O-2 reaction increased with increasing amount of the isolated Pd2+ cationic species up to 0.7 wt.%, while the increase in the amount of PdO led to decrease in selectivity towards NO2 reduction. The palladium species that are active and selective for NO reduction with CH4 will be proposed. (C) 1999 Elsevier Science B.V. All rights reserved.

The active site in ZSM-5 zeolite-supported palladium, which shows the catalytic activity for NO reduction with methane as a reducing agent, has been investigated qualitatively and quantitatively by means of NO chemisorption and NaCl titration, comparing with PdO supported on silica. Palladium species in 0.4 wt.% Pd loaded H-ZSM-5 can adsorb NO equimolarly after calcination at 773 K, and almost all the NO was desorbed at around 673 K; while the palladium species on PdO/SiO2 hardly adsorbed NO. The palladium species in Pd(0.4)/H-ZSM-5 are ion-exchangeable with Na+ in NaCl solution, indicating that they exist in a cationic state of an isolated Pd2+. This method for quantitative analysis of the isolated Pd2+ cations is named as 'NaCl titration'. The amount of the isolated Pd2+ cationic species increased with increasing palladium content on Pd/H-ZSM-5, and PdO co-existed above 1 wt.%. The amount of the isolated Pd2+ cation was unchanged after the reaction of NO2-CH4, NO2-CH4-O-2, or CH4-O-2 at 673 K, while the adsorbed amount of NO per the Pd2+ as determined by NO-TPD decreased after the NO2-CH4-O-2 reaction. It was found by NaCl titration that the catalytic activity of Pd/H-ZSM-5 for NO2-CH4-O-2 reaction increased with increasing amount of the isolated Pd2+ cationic species up to 0.7 wt.%, while the increase in the amount of PdO led to decrease in selectivity towards NO2 reduction. The palladium species that are active and selective for NO reduction with CH4 will be proposed. (C) 1999 Elsevier Science B.V. All rights reserved.

The formation of a ferrierite (FER) membrane by a vapor-phase transport method is discussed. The formation process was studied using X-ray diffraction, scanning electron microscopy (SEM), field emission-SEM and energy dispersive X-ray analysis. The same location on the top surface was repeatedly observed at different crystallization times using SEM. It was found that an aluminosilicate species formed from a dry gel layer was mobile over the surface of support during crystallization. This intermediate aluminosilicate species penetrated into the pores of the alumina support to fill them, generating a compact FER-alumina composite layer. (C) 1999 Elsevier Science B.V. All rights reserved.

The formation of a ferrierite (FER) membrane by a vapor-phase transport method is discussed. The formation process was studied using X-ray diffraction, scanning electron microscopy (SEM), field emission-SEM and energy dispersive X-ray analysis. The same location on the top surface was repeatedly observed at different crystallization times using SEM. It was found that an aluminosilicate species formed from a dry gel layer was mobile over the surface of support during crystallization. This intermediate aluminosilicate species penetrated into the pores of the alumina support to fill them, generating a compact FER-alumina composite layer. (C) 1999 Elsevier Science B.V. All rights reserved.

We propose a new technique, "position-controlled CVD using catalytic reaction," to modify pore structure. By loading the catalyst for the reverse water gas shift reaction on a support that is to be modified, He can confine the hydrolysis reaction zone to a narrow region surrounding the catalyst where H2O is generated, An anodic alumina membrane with pore size of 26 nm was used as the support. Reactant gases, H-2, CO2 and TiCl4, were led into the same side of the membrane. The effects of reaction conditions on pore modification are investigated on the basis of FE-SEM observations and permeation tests, The pore size and permeance through the membrane gradually decrease with reaction time. Deposition morphology changes with reaction conditions, such as temperature, and H-2, CO2 and TiCl4 feed rates. In some cases, particles with 0.1-1 mu m diameter are formed on the outer surface of membrane.

A new method was proposed to assess the surface properties of coal hy adsorption of metanil yellow using a continuous feed sg stem. The area fraction of the hydrophobic site on the exterior surface, alpha(m), was measured for Datong, Tyanfu, Shanxi No. 1, Illinois No. 6 and Blair Athol. Except for Tyanfu coal, the order of the values of alpha(m) is consistent with that of carbonaceous materials recovery. The,metanil yellow adsorption experiment requires no specific preparation, and can be applied to powder samples.

The behavior of Datong coal particles in a flotation column was investigated in a batchwise operation using a gas distributor evolving uniform bubbles by varying the superficial gas velocity and column height. The value of superficial gas velocity was controlled at 0.66 or 1.99 cm s(-1)
The time course of ash content in floats was measured when column height was 1.85 In, The ash content in clean coal was larger for higher superficial gas velocity. The hydrophobicity of coal particles recovered from the top of the column was evaluated by means of a film flotation method. Hydrophilic particles having the critical wetting surface tension of particles, gamma(c), greater than 60 mN m(-1) floated well for higher superficial gas velocity, The weight percent of fractions having gamma(c) above 60 mN m(-1) was 29.5, 31.9 and 40.5% for 0.25, 2.00 and 4.25 min. respectively. These values increased with sampling time, and were much greater than those for the lower superficial gas velocity. At lower superficial gas velocity, the hydrophobic coal particles seem to be selectively floated by colliding and attaching to the bubble surfaces. On the other hand, at higher superficial gas velocity, hydrophilic particles that are difficult to attach to bubbles seem to be entrained in the turbulent wake of bubble swamis and float.
The grade of clean coal was better for the lower superficial gas velocity, however, carbonaceous materials recovery was lower than that for higher superficial gas velocity. Carbonaceous materials recovery was improved by increasing the recovery zone height.

We propose a new technique, "position-controlled CVD using catalytic reaction," to modify pore structure. By loading the catalyst for the reverse water gas shift reaction on a support that is to be modified, He can confine the hydrolysis reaction zone to a narrow region surrounding the catalyst where H2O is generated, An anodic alumina membrane with pore size of 26 nm was used as the support. Reactant gases, H-2, CO2 and TiCl4, were led into the same side of the membrane. The effects of reaction conditions on pore modification are investigated on the basis of FE-SEM observations and permeation tests, The pore size and permeance through the membrane gradually decrease with reaction time. Deposition morphology changes with reaction conditions, such as temperature, and H-2, CO2 and TiCl4 feed rates. In some cases, particles with 0.1-1 mu m diameter are formed on the outer surface of membrane.

A new method was proposed to assess the surface properties of coal hy adsorption of metanil yellow using a continuous feed sg stem. The area fraction of the hydrophobic site on the exterior surface, alpha(m), was measured for Datong, Tyanfu, Shanxi No. 1, Illinois No. 6 and Blair Athol. Except for Tyanfu coal, the order of the values of alpha(m) is consistent with that of carbonaceous materials recovery. The,metanil yellow adsorption experiment requires no specific preparation, and can be applied to powder samples.

The behavior of Datong coal particles in a flotation column was investigated in a batchwise operation using a gas distributor evolving uniform bubbles by varying the superficial gas velocity and column height. The value of superficial gas velocity was controlled at 0.66 or 1.99 cm s(-1)
The time course of ash content in floats was measured when column height was 1.85 In, The ash content in clean coal was larger for higher superficial gas velocity. The hydrophobicity of coal particles recovered from the top of the column was evaluated by means of a film flotation method. Hydrophilic particles having the critical wetting surface tension of particles, gamma(c), greater than 60 mN m(-1) floated well for higher superficial gas velocity, The weight percent of fractions having gamma(c) above 60 mN m(-1) was 29.5, 31.9 and 40.5% for 0.25, 2.00 and 4.25 min. respectively. These values increased with sampling time, and were much greater than those for the lower superficial gas velocity. At lower superficial gas velocity, the hydrophobic coal particles seem to be selectively floated by colliding and attaching to the bubble surfaces. On the other hand, at higher superficial gas velocity, hydrophilic particles that are difficult to attach to bubbles seem to be entrained in the turbulent wake of bubble swamis and float.
The grade of clean coal was better for the lower superficial gas velocity, however, carbonaceous materials recovery was lower than that for higher superficial gas velocity. Carbonaceous materials recovery was improved by increasing the recovery zone height.

Coal particles contain oxygen functional groups such as hydroxyl, carbonyl, and carboxyl, and mineral matters that contribute surface hydrophilicity, The occurrence of them varies considerably from coal to coal, hence the characteristics of column flotation changes from coal to coal. We expected that the characteristics of column flotation could be simply evaluated by using the area fraction of oxygen functional group sites on the exterior surface of the coal particles.
In this work, we conducted column flotation for Shanxi (anthracite), Tyanfu (bituminous), Blair Athol (bituminous), Datong (bituminous), and Illinois (brown coal). The order of carbonaceous materials recovery was found to be Tyanfu &gt; Shanxi &gt; Blair Athol &gt; Datong &gt; Illinois, We also evaluated the area fraction of hydroxyl group on the exterior surface of the coal particles, alpha(ex-OH), and that in the coal particles, alpha i(n-OH). For Datong coal, the value of alpha(ex-OH) was larger than that of alpha(in-OH). It means that Datong coal was slightly oxidized. The order of carbonaceous materials recovery was inconsistent with that of alpha(ex-OH) for the three kinds of bituminous coal. For Shanxi anthracite coal, the flotability is evaluated by considering the wettability of the hydrophobic sites as well as the hydrophilic sites.

Coal particles contain oxygen functional groups such as hydroxyl, carbonyl, and carboxyl, and mineral matters that contribute surface hydrophilicity, The occurrence of them varies considerably from coal to coal, hence the characteristics of column flotation changes from coal to coal. We expected that the characteristics of column flotation could be simply evaluated by using the area fraction of oxygen functional group sites on the exterior surface of the coal particles.
In this work, we conducted column flotation for Shanxi (anthracite), Tyanfu (bituminous), Blair Athol (bituminous), Datong (bituminous), and Illinois (brown coal). The order of carbonaceous materials recovery was found to be Tyanfu &gt; Shanxi &gt; Blair Athol &gt; Datong &gt; Illinois, We also evaluated the area fraction of hydroxyl group on the exterior surface of the coal particles, alpha(ex-OH), and that in the coal particles, alpha i(n-OH). For Datong coal, the value of alpha(ex-OH) was larger than that of alpha(in-OH). It means that Datong coal was slightly oxidized. The order of carbonaceous materials recovery was inconsistent with that of alpha(ex-OH) for the three kinds of bituminous coal. For Shanxi anthracite coal, the flotability is evaluated by considering the wettability of the hydrophobic sites as well as the hydrophilic sites.

Crystallization of zeolite using an organic compound as a structure-directing agent (SDA) and phase transformation of zeolite into another phase were investigated by means of a new crystallization method of dry gel conversion (DGC). Different types of zeolite were crystallized by DGC with SDAs having different sizes in alkyl chains of organics. Not the size of SDAs but the type of them determines the phase crystallized. Phase transformation of zeolite beta occurred into a new phase of zeolite OU-1, which has the same topology as zeolites SSZ-31 and NCL-1. From XRD and SEM observations, it can be concluded that the phase transformation occurs via surface-mediated nucleation and growth without significant dissolution nor destruction of zeolite structure.

Recently the dry gel conversion (DGC) technique, where a hydrogel is dried and the resultant dry gel is converted into microporous crystals in steam or in a mixed vapor of steam and organic structure-directing agents (SDAs), has been developed. It has been shown that a wide variety of microporous crystals, pure silica microporous crystals, aluminosilicates, metallosilicates, and aluminophosphates, can be synthesized using the DGC method. Remarkable results have been reported in the synthesis of BEA types zeolites, namely aluminosilicate, titaniumsilicate, zincosilicate, and borosilicate with BEA topology, using tetraethylammonium hydroxide, a commercially available SDA. It has also been found that zeolite OU-1, probably analogous to SSZ-31 and NCL-1, is formed via phase transformation from BEA. Dense zeolite coatings like membranes are possible using this method. Characteristics of the DGC method are discussed in detail.

Crystallization of zeolite using an organic compound as a structure-directing agent (SDA) and phase transformation of zeolite into another phase were investigated by means of a new crystallization method of dry gel conversion (DGC). Different types of zeolite were crystallized by DGC with SDAs having different sizes in alkyl chains of organics. Not the size of SDAs but the type of them determines the phase crystallized. Phase transformation of zeolite beta occurred into a new phase of zeolite OU-1, which has the same topology as zeolites SSZ-31 and NCL-1. From XRD and SEM observations, it can be concluded that the phase transformation occurs via surface-mediated nucleation and growth without significant dissolution nor destruction of zeolite structure.

Recently the dry gel conversion (DGC) technique, where a hydrogel is dried and the resultant dry gel is converted into microporous crystals in steam or in a mixed vapor of steam and organic structure-directing agents (SDAs), has been developed. It has been shown that a wide variety of microporous crystals, pure silica microporous crystals, aluminosilicates, metallosilicates, and aluminophosphates, can be synthesized using the DGC method. Remarkable results have been reported in the synthesis of BEA types zeolites, namely aluminosilicate, titaniumsilicate, zincosilicate, and borosilicate with BEA topology, using tetraethylammonium hydroxide, a commercially available SDA. It has also been found that zeolite OU-1, probably analogous to SSZ-31 and NCL-1, is formed via phase transformation from BEA. Dense zeolite coatings like membranes are possible using this method. Characteristics of the DGC method are discussed in detail.

State-of-the art of hydrocarbon separation technology by inorganic membranes is reviewed. Targets for hydrocarbon separation are classified into five groups : H₂/Lower hydrocarbons, alkane/alkene, straight chain hydrocarbons/branched hydrocarbons, aliphatic hydrocarbons/aromatic hydrocarbons, and aromatic hydrocarbon mixtures. Various types of microporous inorganic membranes, amorphous silica, zeolites and carbon membranes, have been under development. Some of them show very high permselectivities, indicating the promising prospects of inorganic membrane technology. While molecular sieving property has long been anticipated to appear on the basis of size recognition by micropores smaller than 1 nm, there have been a few reports with conclusive evidence on the separation by molecular sieving. On the other hand, the difference in adsorption properties into a membrane can lead to the appearance of permselectivity particularly at lower temperatures.

Synthesis of borosilicate zeolites, namely [B]-BEA, [B]-MFI and [B]-MTW by dry gel conversion (DGC) method was described for the first time. Phase selection and thereby the outcome of the product was dependent upon the gel composition, mainly on the SiO2/B2O3 ratio and the TEAOH content.

Zeolite BEA with SiO2/Al2O3 ratios ranging from 30 to 740 were crystallized at 413 and 453 K by the dry gel conversion technique. The particle size of the products increased with increasing SiO2/Al2O3 ratio as well as with increasing crystallization temperature. In as-synthesized BEA, the TEA+ ions interacting with Si-O- decomposed between 473 and 673 K and those interacting with Al-O- were cleaved between 673 and 798 K. During their elimination, the TEA+ ions interacting with Al-O- underwent higher degradation than those interacting with Si-O-. Chemical compositions showed the least influence on the fractions of decomposition product during the elimination between 473 and 673 K. The framework of H-BEA and NH4-BEA zeolites with SiO2/Al2O3 ratios ranging from 400 to 740 were stable even at 1373 K, whereas H-BEA with SiO2/Al2O3 = 30 was stable only up to 1173 K and became amorphous when calcined at 1373 K. After calcination at 1373 K, Na-BEA with SiO2/Al2O3 = 400 and 730 were transformed to tridymite (dense phase) whereas that with SiO2/Al2O3 = 30 became amorphous. The elimination of Na+ ions is necessary to have a BEA remain stable above 1173 K. © 1998 Elsevier Science B.V. All rights reserved.

Zeolite with BEA structure was prepared using a new crystallization method called 'Dry Gel Conversion Technique'. This dry gel conversion technique is a convenient method to prepare zeolites and enables one to synthesize zeolite BEA with SiO2/Al2O3 ratios from 30 to infinity using tetraethylammonium hydroxide (TEAOH) as a structure directing agent. Zeolite BEA with SiO2/Al2O3 ratios from 30 to 730 were rapidly crystallized in 3 and 12 h, respectively. The Al-27 NMR spectrum for BEA with SiO2/Al2O3 ratio of 30 confirmed the absence of octahedrally coordinated aluminum. The crystallization rates were higher for BEA with low SiO2/Al2O3 ratios than for those with high SiO2/Al2O3 ratios. BEA crystallized by this method had uniform particles of about 60 nm. Higher Na+ ion concentrations in the gel promoted the formation of high silica BEA. Elimination of occluded TEA cations took place at lower temperatures (around 623 K) in high silica BEA than that in BEA with low SiO2/Al2O3 ratios (around 900 K). This method also allowed to synthesize BEA in the form of self-bonded pellets. (C) 1998 Elsevier Science B.V.

Synthesis of borosilicate zeolites, namely [B]-BEA, [B]-MFI and [B]-MTW by dry gel conversion (DGC) method was described for the first time. Phase selection and thereby the outcome of the product was dependent upon the gel composition, mainly on the SiO2/B2O3 ratio and the TEAOH content.

Zeolite BEA with SiO2/Al2O3 ratios ranging from 30 to 740 were crystallized at 413 and 453 K by the dry gel conversion technique. The particle size of the products increased with increasing SiO2/Al2O3 ratio as well as with increasing crystallization temperature. In as-synthesized BEA, the TEA+ ions interacting with Si-O- decomposed between 473 and 673 K and those interacting with Al-O- were cleaved between 673 and 798 K. During their elimination, the TEA+ ions interacting with Al-O- underwent higher degradation than those interacting with Si-O-. Chemical compositions showed the least influence on the fractions of decomposition product during the elimination between 473 and 673 K. The framework of H-BEA and NH4-BEA zeolites with SiO2/Al2O3 ratios ranging from 400 to 740 were stable even at 1373 K, whereas H-BEA with SiO2/Al2O3 = 30 was stable only up to 1173 K and became amorphous when calcined at 1373 K. After calcination at 1373 K, Na-BEA with SiO2/Al2O3 = 400 and 730 were transformed to tridymite (dense phase) whereas that with SiO2/Al2O3 = 30 became amorphous. The elimination of Na+ ions is necessary to have a BEA remain stable above 1173 K. © 1998 Elsevier Science B.V. All rights reserved.

Zeolite with BEA structure was prepared using a new crystallization method called 'Dry Gel Conversion Technique'. This dry gel conversion technique is a convenient method to prepare zeolites and enables one to synthesize zeolite BEA with SiO2/Al2O3 ratios from 30 to infinity using tetraethylammonium hydroxide (TEAOH) as a structure directing agent. Zeolite BEA with SiO2/Al2O3 ratios from 30 to 730 were rapidly crystallized in 3 and 12 h, respectively. The Al-27 NMR spectrum for BEA with SiO2/Al2O3 ratio of 30 confirmed the absence of octahedrally coordinated aluminum. The crystallization rates were higher for BEA with low SiO2/Al2O3 ratios than for those with high SiO2/Al2O3 ratios. BEA crystallized by this method had uniform particles of about 60 nm. Higher Na+ ion concentrations in the gel promoted the formation of high silica BEA. Elimination of occluded TEA cations took place at lower temperatures (around 623 K) in high silica BEA than that in BEA with low SiO2/Al2O3 ratios (around 900 K). This method also allowed to synthesize BEA in the form of self-bonded pellets. (C) 1998 Elsevier Science B.V.

The mechanism of formation of ferrierite (FER) membrane on an alumina support by a vapor-phase transport (VPT) method was studied using XRD, SEM, FE-SEM and EDX. The XRD measurement for a FER membrane after the removal of FER particles formed on the support showed that FER was formed in the pores of the alumina support, namely, a FER-alumina composite layer was formed. The FE-SEM image for the cross-sectional view of the FER-alumina composite layer showed that FER nanocrystals of about 50 nm diameter grew in the pores of the alumina support. Pervaporation tests for benzene/p-xylene mixtures were performed at 303 K. Even when the concentration of benzene in the feed solution was extremely small (0.5 mol%), the flux of benzene through the FER membrane was still greater than that of p-xylene. Therefore, a separation factor as high as 600 was obtained in the low feed concentration of benzene. Such a high selectivity for the benzene/p-xylene mixture suggested that the selectivity for the benzene/p-xylene mixture appears at the pore mouths of FER on the feed side of the FER-alumina composite layer. (C) 1997 Elsevier Science B.V.

This article is intended to describe recent progress in the synthesis of zeolitic membranes and their permeation properties. While hydrothermal synthesis has been widely employed for zeolitic-membrane synthesis, the development of a new technique for zeolite synthesis, vapor-phase transport (VPT), has enabled us to prepare pinhole-free, zeolite-porous support composite membranes. This article consists of three sections that describe: a survey of the hydrothermal synthesis of zeolitic membranes, our synthesis results and the formation mechanism of zeolitic membranes by the VPT method as well as some permeation results to show the prospects of zeolitic membranes.

This article is intended to describe recent progress in the synthesis of zeolitic membranes and their permeation properties. While hydrothermal synthesis has been widely employed for zeolitic-membrane synthesis, the development of a new technique for zeolite synthesis, vapor-phase transport (VPT), has enabled us to prepare pinhole-free, zeolite-porous support composite membranes. This article consists of three sections that describe: a survey of the hydrothermal synthesis of zeolitic membranes, our synthesis results and the formation mechanism of zeolitic membranes by the VPT method as well as some permeation results to show the prospects of zeolitic membranes.

Zeolitic membranes were synthesized on a porous alumina support by the vapor-phase transport method using one of two alumina sources: aluminum sulfate and sodium aluminate. By choosing the appropriate period and temperature for drying the aluminosilicate gel on the alumina support, MOR, FER and MFI could be synthesized. MOR was formed when the water content in the dry gel was high. As the water content decreased, FER and MFI were formed sequentially. Preferential formation of MFI was achieved by treating the dry gel at 373 K. The temperature at which the support was dipped in the parent gel also influenced the type of zeolite formed, although the effect of drying conditions was more pronounced. A similar trend was found for both aluminum sulfate and sodium aluminate. When the alumina source was sodium aluminate and the aluminosilicate gel was treated at 373 K, a preferentially oriented MFI membrane could be synthesized, as the (a00) and (0b0) crystal faces were oriented in parallel to the surface of porous alumina support. The uniform and dense morphology of the dry gel seems to account for the appearance of the orientation. © 1997 Elsevier Science B.V.

Mordenite (MOR) and ferrierite (FER) membranes without any pinhole and crack were synthesized by a vapor-phase transport method. The permeance of H-2, He, CH4, N-2, O-2 and CO2 was determined at 290-400 K; which showed minimum with increasing temperatures for most cases. In the parallel diffusion model was proposed, molecules adsorbed in a micropore are assumed to diffuse in parallel through the central region of the pore and along the wall region of the pore. This parallel diffusion model accounts for the effect of pore Size of MOR and FER on the permeation and expresses the experimental data well. The interaction between gas molecules and pore walls are evaluated for each gas.

The mechanism of formation of ferrierite (FER) membrane on an alumina support by a vapor-phase transport (VPT) method was studied using XRD, SEM, FE-SEM and EDX. The XRD measurement for a FER membrane after the removal of FER particles formed on the support showed that FER was formed in the pores of the alumina support, namely, a FER-alumina composite layer was formed. The FE-SEM image for the cross-sectional view of the FER-alumina composite layer showed that FER nanocrystals of about 50 nm diameter grew in the pores of the alumina support. Pervaporation tests for benzene/p-xylene mixtures were performed at 303 K. Even when the concentration of benzene in the feed solution was extremely small (0.5 mol%), the flux of benzene through the FER membrane was still greater than that of p-xylene. Therefore, a separation factor as high as 600 was obtained in the low feed concentration of benzene. Such a high selectivity for the benzene/p-xylene mixture suggested that the selectivity for the benzene/p-xylene mixture appears at the pore mouths of FER on the feed side of the FER-alumina composite layer. © 1997 Elsevier Science B.V.

Zeolitic membranes were synthesized on a porous alumina support by the vapor-phase transport method using one of two alumina sources: aluminum sulfate and sodium aluminate. By choosing the appropriate period and temperature for drying the aluminosilicate gel on the alumina support, MOR, FER and MFI could be synthesized. MOR was formed when the water content in the dry gel was high. As the water content decreased, FER and MFI were formed sequentially. Preferential formation of MFI was achieved by treating the dry gel at 373 K. The temperature at which the support was dipped in the parent gel also influenced the type of zeolite formed, although the effect of drying conditions was more pronounced. A similar trend was found for both aluminum sulfate and sodium aluminate. When the alumina source was sodium aluminate and the aluminosilicate gel was treated at 373 K, a preferentially oriented MFI membrane could be synthesized, as the (a00) and (0b0) crystal faces were oriented in parallel to the surface of porous alumina support. The uniform and dense morphology of the dry gel seems to account for the appearance of the orientation. © 1997 Elsevier Science B.V.

Mordenite (MOR) and ferrierite (FER) membranes without any pinhole and crack were synthesized by a vapor-phase transport method. The permeance of H-2, He, CH4, N-2, O-2 and CO2 was determined at 290-400 K; which showed minimum with increasing temperatures for most cases. In the parallel diffusion model was proposed, molecules adsorbed in a micropore are assumed to diffuse in parallel through the central region of the pore and along the wall region of the pore. This parallel diffusion model accounts for the effect of pore Size of MOR and FER on the permeation and expresses the experimental data well. The interaction between gas molecules and pore walls are evaluated for each gas.

The mechanism of formation of ferrierite (FER) membrane on an alumina support by a vapor-phase transport (VPT) method was studied using XRD, SEM, FE-SEM and EDX. The XRD measurement for a FER membrane after the removal of FER particles formed on the support showed that FER was formed in the pores of the alumina support, namely, a FER-alumina composite layer was formed. The FE-SEM image for the cross-sectional view of the FER-alumina composite layer showed that FER nanocrystals of about 50 nm diameter grew in the pores of the alumina support. Pervaporation tests for benzene/p-xylene mixtures were performed at 303 K. Even when the concentration of benzene in the feed solution was extremely small (0.5 mol%), the flux of benzene through the FER membrane was still greater than that of p-xylene. Therefore, a separation factor as high as 600 was obtained in the low feed concentration of benzene. Such a high selectivity for the benzene/p-xylene mixture suggested that the selectivity for the benzene/p-xylene mixture appears at the pore mouths of FER on the feed side of the FER-alumina composite layer. © 1997 Elsevier Science B.V.

The value of pH for gel preparation has a significant influence on the compactness of a dry gel. A compact gel was prepared at high pH of ca. 12. An amorphous dry gel on a porous alumina support was crystallized by a vapor-phase transport (VPT) method. Membranes of low silica zeolites, analcime (ANA) and mordenite (MOR), were formed because alumina was partly dissolved and incorporated into the framework of zeolite. Coating of the alumina support with colloidal silica depressed the dissolution of alumina. On the alumina support coated with colloidal silica, ferrierite (FER) and ZSM-5 (MFI) membranes were obtained. Compactness of the MOR membrane was examined by a permeation test of 1,3,5-triisopropylbenzene (TIPB) at room temperature. Since no permeation of TIPB was detected, it was concluded that there existed no pinholes and cracks in the MOR membrane. The pervaporation test of a benzene/p-xylene mixture of which the molar ratio was 0.860, was carried out. The separation factor ((benzene/p-xylene)permeate/(benzene/p-xylene)feed) exceeded 160. Thus some shape selectivity appeared at the pore mouths of MOR. The formation process of the MOR membrane was studied by using SEM and XRD. The gel which penetrated in the alumina pores crystallized to MOR and formed a defect-free MOR-alumina composite layer.

The value of pH for gel preparation has a significant influence on the compactness of a dry gel. A compact gel was prepared at high pH of ca. 12. An amorphous dry gel on a porous alumina support was crystallized by a vapor-phase transport (VPT) method. Membranes of low silica zeolites, analcime (ANA) and mordenite (MOR), were formed because alumina was partly dissolved and incorporated into the framework of zeolite. Coating of the alumina support with colloidal silica depressed the dissolution of alumina. On the alumina support coated with colloidal silica, ferrierite (FER) and ZSM-5 (MFI) membranes were obtained. Compactness of the MOR membrane was examined by a permeation test of 1,3,5-triisopropylbenzene (TIPB) at room temperature. Since no permeation of TIPB was detected, it was concluded that there existed no pinholes and cracks in the MOR membrane. The pervaporation test of a benzene/p-xylene mixture of which the molar ratio was 0.860, was carried out. The separation factor ((benzene/p-xylene)permeate/(benzene/p-xylene)feed) exceeded 160. Thus some shape selectivity appeared at the pore mouths of MOR. The formation process of the MOR membrane was studied by using SEM and XRD. The gel which penetrated in the alumina pores crystallized to MOR and formed a defect-free MOR-alumina composite layer.

The value of pH for gel preparation has a significant influence on the compactness of a dry gel. A compact gel was prepared at high pH of ca. 12. An amorphous dry gel on a porous alumina support was crystallized by a vapor-phase transport (VPT) method. Membranes of low silica zeolites, analcime (ANA) and mordenite (MOR), were formed because alumina was partly dissolved and incorporated into the framework of zeolite. Coating of the alumina support with colloidal silica depressed the dissolution of alumina. On the alumina support coated with colloidal silica, ferrierite (FER) and ZSM-5 (MFI) membranes were obtained. Compactness of the MOR membrane was examined by a permeation test of 1,3,5-triisopropylbenzene (TIPB) at room temperature. Since no permeation of TIPB was detected, it was concluded that there existed no pinholes and cracks in the MOR membrane. The pervaporation test of a benzene/p-xylene mixture of which the molar ratio was 0.860, was carried out. The separation factor ((benzene/p-xylene)permeate/(benzene/p-xylene)feed) exceeded 160. Thus some shape selectivity appeared at the pore mouths of MOR. The formation process of the MOR membrane was studied by using SEM and XRD. The gel which penetrated in the alumina pores crystallized to MOR and formed a defect-free MOR-alumina composite layer.

Dry aluminosilicate gels were crystallized to MFI and FER by a vapor-phase transport (VPT) method using ethylenediamine (EDA), triethylamine (Et(3)N) and water as vapor sources. The roles of water and amines in this crystallization were investigated. While Et(3)N and water encouraged crystallization, EDA acted as a structure-directing agent. A dry gel was crystallized to FER when no water was added. The Al-27- and the Si-29-NMR spectra indicated that all Al atoms were incorporated into the zeolitic framework in the early stage of crystallization and that the rest of the Si-rich phase gradually crystallized. Full crystallization of Si and Al atoms in dry gel was possible by selecting optimum synthetic conditions. FER was transformed to MFI with prolonged crystallization. The structure and crystallinity of zeolite significantly depended on the sort of support on which the dry gel was placed.

Dry aluminosilicate gels were crystallized to MFI and FER by a vapor-phase transport (VPT) method using ethylenediamine (EDA), triethylamine (Et(3)N) and water as vapor sources. The roles of water and amines in this crystallization were investigated. While Et(3)N and water encouraged crystallization, EDA acted as a structure-directing agent. A dry gel was crystallized to FER when no water was added. The Al-27- and the Si-29-NMR spectra indicated that all Al atoms were incorporated into the zeolitic framework in the early stage of crystallization and that the rest of the Si-rich phase gradually crystallized. Full crystallization of Si and Al atoms in dry gel was possible by selecting optimum synthetic conditions. FER was transformed to MFI with prolonged crystallization. The structure and crystallinity of zeolite significantly depended on the sort of support on which the dry gel was placed.

A reformer using a circulating fluidized bed has been proposed for the production of hydrogen and syngas. A catalyst is circulated between two reactors for the catalytic decomposition of methane to hydrogen and carbon, and for the gasification of carbon deposited on the catalyst. Catalytic activities of Ni/SiO2 for both CH4 decomposition and CO2 gasification of deposited carbon were investigated at 873-1023 K in a periodically-operated fixed bed reactor. Carbon which had a moss-like morphology was hardly gasified and caused deactivation of the catalyst. Such a type of carbon became dominant with raising reaction temperature and with increasing amount of Ni loaded on SiO2. In contrast, filamentous carbon which had a graphitic structure could be gasified with CO2 and became dominant with decreasing amount of Ni loaded and with lowering reaction temperature. It was found that Ni(5 wt%)/SiO2 had a stable activity against the cycles of decomposition/gasification because Ni on Ni(5)/SiO2 was difficult to sinter at 873 K and as a result, the filamentous carbon was exclusively formed.

In under-developing countries as China, coal is mainly used as an energy source, considerable amount of which is for daily living use. However it is very difficult to equip a desulphurizer to each personal furnace. The air pollution problem there is now serious and is becoming an environmental problem on earth. If clean coal can be obtained at a coal field, the air pollution problem can be cleared. Recently, column floatation has been paid much attention as a prospective technique to remove minerals including inorganic sulphur from coal at a coal field. In this article, the prospective aspects of the column floatation as a coal cleaning process at a coal field is described putting special emphasis on the possible application in under developing countries. The floatation mechanisms are also illustrated on the basis of recent data of column floatation. It was shown that the coal recovery and ash rejection strongly depend on hydrophobicity of coal particles and that a surrounding flow of each bubble plays a roll in catching particles regardless of its hydrophobicity for the case of high gas feed.

In order to analyze HCl and SO2 retention in fluidized bed combustors of coal and wastes, chlorination and sulphation of calcined limestone were investigated at 1023 K and atmospheric pressure using thermogravimetry. The rate of chlorination of calcined limestone slightly depended on its particle size and was kept almost constant against the progress of chlorination. In contrast, the rate of sulphation increased with decreasing particle size and steeply decreased with the progress of sulphation as commonly reported. It was found that the sulphation was markedly accelerated in the presence of HCl. Such acceleration of sulphation was remarkable for larger limestone. The level of conversion of CaO to (CaSO4 + CaCl2) always approached 100% in the simultaneous absorption of HCl and SO2. It was observed by SEM that in the chlorination a number of spherical aggregates and large voids were formed on the surface of limestone and that large aggregates with very flat surface and large voids have been formed in the course of the simultaneous chlorination and sulphation. These chlorination behavior and the acceleration of SO2 absorption in the presence of HCl can be due both to the formation of a mobile Cl- ion-containing phase and to the formation of voids playing a role of the diffusion paths for HCl and SO2 toward the interior of a limestone particle. Melting of a eutectic mixture of CaCl2 and CaSO4 might largely contribute to the promotion of SO2 absorption in the case of simultaneous absorption of HCl and SO2.

A reformer using a circulating fluidized bed has been proposed for the production of hydrogen and syngas. A catalyst is circulated between two reactors for the catalytic decomposition of methane to hydrogen and carbon, and for the gasification of carbon deposited on the catalyst. Catalytic activities of Ni/SiO2 for both CH4 decomposition and CO2 gasification of deposited carbon were investigated at 873-1023 K in a periodically-operated fixed bed reactor. Carbon which had a moss-like morphology was hardly gasified and caused deactivation of the catalyst. Such a type of carbon became dominant with raising reaction temperature and with increasing amount of Ni loaded on SiO2. In contrast, filamentous carbon which had a graphitic structure could be gasified with CO2 and became dominant with decreasing amount of Ni loaded and with lowering reaction temperature. It was found that Ni(5 wt%)/SiO2 had a stable activity against the cycles of decomposition/gasification because Ni on Ni(5)/SiO2 was difficult to sinter at 873 K and as a result, the filamentous carbon was exclusively formed.

Attempting to utilize natural zeolites as catalysts, characterization and modification of two kinds of those produced in Indonesia (Z1 and Z2) were carried out and their properties for hydrocracking of paraffins were evaluated using n-hexadecane as a petroleum model compound. The Z1 and Z2 samples were first treated with 6 N HCl at 90°C for 0.5 h or 20 h. X-Ray diffraction analysis of the HCl-treated samples (Z1-0.5 h, Z2-0.5 h, Z1-20 h, and Z2-20 h), as well as Z1 and Z2, indicated that both original samples mainly consist of mordenite type crystalline matter and the acid treatment removes some of crystalline impurities X-Ray fluorescence data revealed that Z1 and Z2 have Si/Al ratios of 4.3 and 3.1, respectively, and the treatment increases the ratio by dealumination as expected. The examination of hydrocracking properties showed that Z1 and Z2 have similar catalytic properties and the acid treatment considerably improves their activities. On the other hand, Z1- and Z2-20 h were less active than were Z1- and Z2-0.5 h, respectively. NH3-TPD and 29Si MAS NMR suggested that this may be due to the significant decrease of active acid sites by the prolonged treatment. It was also found that the loading of a small amount of nickel (0.8 wt%) onto Z1-0.5 h by ion exchange, significantly improves the catalytic property
the conversion of the paraffin was comparable with that using a synthetic H-mordenite.

In order to analyze HCl and SO2 retention in fluidized bed combustors of coal and wastes, chlorination and sulphation of calcined limestone were investigated at 1023 K and atmospheric pressure using thermogravimetry. The rate of chlorination of calcined limestone slightly depended on its particle size and was kept almost constant against the progress of chlorination. In contrast, the rate of sulphation increased with decreasing particle size and steeply decreased with the progress of sulphation as commonly reported. It was found that the sulphation was markedly accelerated in the presence of HCl. Such acceleration of sulphation was remarkable for larger limestone. The level of conversion of CaO to (CaSO4 + CaCl2) always approached 100% in the simultaneous absorption of HCl and SO2. It was observed by SEM that in the chlorination a number of spherical aggregates and large voids were formed on the surface of limestone and that large aggregates with very flat surface and large voids have been formed in the course of the simultaneous chlorination and sulphation. These chlorination behavior and the acceleration of SO2 absorption in the presence of HCl can be due both to the formation of a mobile Cl- ion-containing phase and to the formation of voids playing a role of the diffusion paths for HCl and SO2 toward the interior of a limestone particle. Melting of a eutectic mixture of CaCl2 and CaSO4 might largely contribute to the promotion of SO2 absorption in the case of simultaneous absorption of HCl and SO2.

A reformer using a circulating fluidized bed has been proposed for the production of hydrogen and syngas. A catalyst is circulated between two reactors for the catalytic decomposition of methane to hydrogen and carbon, and for the gasification of carbon deposited on the catalyst. Catalytic activities of Ni/SiO2 for both CH4 decomposition and CO2 gasification of deposited carbon were investigated at 873-1023 K in a periodically-operated fixed bed reactor. Carbon which had a moss-like morphology was hardly gasified and caused deactivation of the catalyst. Such a type of carbon became dominant with raising reaction temperature and with increasing amount of Ni loaded on SiO2. In contrast, filamentous carbon which had a graphitic structure could be gasified with CO2 and became dominant with decreasing amount of Ni loaded and with lowering reaction temperature. It was found that Ni(5 wt%)/SiO2 had a stable activity against the cycles of decomposition/gasification because Ni on Ni(5)/SiO2 was difficult to sinter at 873 K and as a result, the filamentous carbon was exclusively formed.

Attempting to utilize natural zeolites as catalysts, characterization and modification of two kinds of those produced in Indonesia (Z1 and Z2) were carried out and their properties for hydrocracking of paraffins were evaluated using n-hexadecane as a petroleum model compound. The Z1 and Z2 samples were first treated with 6 N HCl at 90°C for 0.5 h or 20 h. X-Ray diffraction analysis of the HCl-treated samples (Z1-0.5 h, Z2-0.5 h, Z1-20 h, and Z2-20 h), as well as Z1 and Z2, indicated that both original samples mainly consist of mordenite type crystalline matter and the acid treatment removes some of crystalline impurities X-Ray fluorescence data revealed that Z1 and Z2 have Si/Al ratios of 4.3 and 3.1, respectively, and the treatment increases the ratio by dealumination as expected. The examination of hydrocracking properties showed that Z1 and Z2 have similar catalytic properties and the acid treatment considerably improves their activities. On the other hand, Z1- and Z2-20 h were less active than were Z1- and Z2-0.5 h, respectively. NH3-TPD and 29Si MAS NMR suggested that this may be due to the significant decrease of active acid sites by the prolonged treatment. It was also found that the loading of a small amount of nickel (0.8 wt%) onto Z1-0.5 h by ion exchange, significantly improves the catalytic property
the conversion of the paraffin was comparable with that using a synthetic H-mordenite.

A methane reformer using a circulating fluidized bed is proposed for the production of hydrogen and synthesis gas (syngas). A catalyst is circulated between two reactors for the catalytic decomposition of methane to hydrogen and carbon and for the gasification of the carbon deposited on the catalyst. Of the metals Cu, Fe, Ni, and W, only Ni showed catalytic activity for the decomposition of methane at 873-1023 K. While studying the structure of the catalyst, it was found that the form of nickel was circulated between oxide and metal through reduction with methane and oxidation with carbon dioxide. X-ray diffraction (XRD) and scanning electron microscopy (SEM) suggested that filamentous carbon having a graphitic structure was gasified with carbon dioxide and that carbon having a mosslike morphology was hardly gasified and caused deactivation of the catalyst. The reactivity of the carbon which was able to be gasified was not altered with cycles of methane decomposition and carbon dioxide gasification.

A methane reformer using a circulating fluidized bed is proposed for the production of hydrogen and synthesis gas (syngas). A catalyst is circulated between two reactors for the catalytic decomposition of methane to hydrogen and carbon and for the gasification of the carbon deposited on the catalyst. Of the metals Cu, Fe, Ni, and W, only Ni showed catalytic activity for the decomposition of methane at 873-1023 K. While studying the structure of the catalyst, it was found that the form of nickel was circulated between oxide and metal through reduction with methane and oxidation with carbon dioxide. X-ray diffraction (XRD) and scanning electron microscopy (SEM) suggested that filamentous carbon having a graphitic structure was gasified with carbon dioxide and that carbon having a mosslike morphology was hardly gasified and caused deactivation of the catalyst. The reactivity of the carbon which was able to be gasified was not altered with cycles of methane decomposition and carbon dioxide gasification.

Effluent from the FCC process contains considerable concentrations of phenol, sulfide and ammonium ions. The pH of the effluent is around 9. In the present study, the possibility of the application of anion exchange membranes for its removal and recovery, was investigated. The equilibrium constant between phenol and hydroxide ions and the ion exchange capacity of a commercial anion exchange membrane were determined. The membrane was sandwiched between two glass cells filled with a phenol solution at pH 9, fed and withdrawn continuously to keep the phenol concentration constant, and a sodium hydroxide solution at various pH, respectively. The permeation rate increased with pH and reached a plateau at above pH 13. The permeation rate was measured for various concentrations of phenol in the feed side, keeping the pH of the strip side at 13. The rate linearly increased with the phenol concentration and reached a plateau at concentration greater than 1 mol/m3. The apparent diffusion coefficient of phenol in the membrane was determined from the plateau value. At a concentration of less than 1 mol/m3, the rate was found to be controlled by boundary film resistance. It was also found that the permeation rate of phenol was suppressed by the sulfide ion at a concentration comparable to or larger than that of phenol. © 1995.

Effluent from the FCC process contains considerable concentrations of phenol, sulfide and ammonium ions. The pH of the effluent is around 9. In the present study, the possibility of the application of anion exchange membranes for its removal and recovery, was investigated. The equilibrium constant between phenol and hydroxide ions and the ion exchange capacity of a commercial anion exchange membrane were determined. The membrane was sandwiched between two glass cells filled with a phenol solution at pH 9, fed and withdrawn continuously to keep the phenol concentration constant, and a sodium hydroxide solution at various pH, respectively. The permeation rate increased with pH and reached a plateau at above pH 13. The permeation rate was measured for various concentrations of phenol in the feed side, keeping the pH of the strip side at 13. The rate linearly increased with the phenol concentration and reached a plateau at concentration greater than 1 mol/m3. The apparent diffusion coefficient of phenol in the membrane was determined from the plateau value. At a concentration of less than 1 mol/m3, the rate was found to be controlled by boundary film resistance. It was also found that the permeation rate of phenol was suppressed by the sulfide ion at a concentration comparable to or larger than that of phenol. © 1995.

The effects of gasification conditions, namely bed temperature, static bed height, and nozzle diameter, on the concentrations of H-2, CO, and CO2 were investigated using a batchwise fluidized bed gasifier of coal char. Gas concentration profiles in the bed could be explained by the production of gases chiefly via combustion, steam gasification, CO2 gasification, and the diffusion of produced gases. The temperature dependence of gas concentrations indicates that steam gasification occurred in the lower part of the grid zone at a higher bed temperature and the selectivity of CO production via combustion in the boundary region of the jet and annulus also increased. The results of the effect of static bed height suggest that CO2 gasification mainly proceeded in the bubbling zone and the local reactions in the grid zone were hardly influenced by gas and solid behavior or reactions in the upper part of the bed. Though the diameter and height of the jet would be dependent on nozzle diameter, the effect of nozzle diameter on the local progress of gasification in the grid zone was hardly observed. It can be concluded that gasification proceeded in both the bubbling zone and annulus region, especially near the distributor, while combustion mainly occurred in the jet and boundary of the jet and annulus.

The effects of gasification conditions, namely bed temperature, static bed height, and nozzle diameter, on the concentrations of H-2, CO, and CO2 were investigated using a batchwise fluidized bed gasifier of coal char. Gas concentration profiles in the bed could be explained by the production of gases chiefly via combustion, steam gasification, CO2 gasification, and the diffusion of produced gases. The temperature dependence of gas concentrations indicates that steam gasification occurred in the lower part of the grid zone at a higher bed temperature and the selectivity of CO production via combustion in the boundary region of the jet and annulus also increased. The results of the effect of static bed height suggest that CO2 gasification mainly proceeded in the bubbling zone and the local reactions in the grid zone were hardly influenced by gas and solid behavior or reactions in the upper part of the bed. Though the diameter and height of the jet would be dependent on nozzle diameter, the effect of nozzle diameter on the local progress of gasification in the grid zone was hardly observed. It can be concluded that gasification proceeded in both the bubbling zone and annulus region, especially near the distributor, while combustion mainly occurred in the jet and boundary of the jet and annulus.

The local behavior of gas and solids in a grid zone was investigated using a jetting fluidized bed cold model. Spherical alumina particles (440 μm, 1500 kg/m3) were used as bed material. A pair of optical fiber sensors, an A D converter and a personal computer were used to measure particle velocity in the jet, jet diameter and jet height. Tracer gas introduced from a center nozzle was sampled from various points in the grid zone and its concentration was measured by gas chromatography to investigate gas interchange between the jet and the annulus, and the gas dispersion in the annulus region. The effects of operational conditions, i.e., the shape of the gas distributor, nozzle diameter and gas flow rates, on the gas and particle behavior are discussed. It was considered that many more particles entered into the jet when a cone-shaped distributor rather than a flat distributor was employed. Employment of a narrower nozzle caused an increase in particle velocity at the bottom of the bed. © 1995.

A defect-free MOR membrane is synthesized on a porous alumina plate by a vapour phase transport method: shape selectivity is apparent in the pervaporation of a benzene-p-xylene mixture (the separation factor exceeded 160).

Selective permeation of vanadium(V) and chromium(VI) using three types of membrane systems was studied. The first was an anion exchange membrane, the second and third were supported liquid membranes containing either a tertiary amine or a quaternary ammonium salt. The membrane was sandwiched between two glass cells. One cell was filled with a solution of identical concentrations of vanadium(V) and chromium(VI), and the other cell contained sodium hydroxide solution. The permeation rates of vanadium(V) and chromium(VI) were measured from the concentration change in the solution on the recovery side of the membrane. The selectivity of vanadium(V) over chromium(VI) was defined as the ratio of their rates. The selectivity of vanadium(V) over chromium(VI) was as high as 10 for pH of feed phase between 8 and 10 when using the quaternary ammonium salt and much better than these for the other membranes with an alkaline feed phase, which was used to simulate of the effluent from leaching of the heavy oil combustion ash and other wastes containing vanadium. Copyright © 1995 Publisher John Wiley &amp
Sons, Ltd.

The local behavior of gas and solids in a grid zone was investigated using a jetting fluidized bed cold model. Spherical alumina particles (440 μm, 1500 kg/m3) were used as bed material. A pair of optical fiber sensors, an A D converter and a personal computer were used to measure particle velocity in the jet, jet diameter and jet height. Tracer gas introduced from a center nozzle was sampled from various points in the grid zone and its concentration was measured by gas chromatography to investigate gas interchange between the jet and the annulus, and the gas dispersion in the annulus region. The effects of operational conditions, i.e., the shape of the gas distributor, nozzle diameter and gas flow rates, on the gas and particle behavior are discussed. It was considered that many more particles entered into the jet when a cone-shaped distributor rather than a flat distributor was employed. Employment of a narrower nozzle caused an increase in particle velocity at the bottom of the bed. © 1995.

A defect-free MOR membrane is synthesized on a porous alumina plate by a vapour phase transport method: shape selectivity is apparent in the pervaporation of a benzene-p-xylene mixture (the separation factor exceeded 160).

Selective permeation of vanadium(V) and chromium(VI) using three types of membrane systems was studied. The first was an anion exchange membrane, the second and third were supported liquid membranes containing either a tertiary amine or a quaternary ammonium salt. The membrane was sandwiched between two glass cells. One cell was filled with a solution of identical concentrations of vanadium(V) and chromium(VI), and the other cell contained sodium hydroxide solution. The permeation rates of vanadium(V) and chromium(VI) were measured from the concentration change in the solution on the recovery side of the membrane. The selectivity of vanadium(V) over chromium(VI) was defined as the ratio of their rates. The selectivity of vanadium(V) over chromium(VI) was as high as 10 for pH of feed phase between 8 and 10 when using the quaternary ammonium salt and much better than these for the other membranes with an alkaline feed phase, which was used to simulate of the effluent from leaching of the heavy oil combustion ash and other wastes containing vanadium. Copyright © 1995 Publisher John Wiley &amp
Sons, Ltd.

Environmental issues in deleloping countires is significantly linked to energy issues. Partiuculraly, energy supply in Pacific Rim including Asian countries will become a main issue in the 21st century. Coal will still be one of main enegy source in the mid-21st century. What we must do is to develop technologies to supply and utilize coal at higher efficiency. For this porpose, strategy to utilize coal incuding all process from coal mining to enery production process is required.

A thin zeolitic membrane on porous alumina support has been synthesized
the permeability of the film to N2 and O2 indicated that the membrane was formed in a compact form.

Vapor-phase oxidative acetoxylation of toluene on Pd-based bimetallic catalysts was investigated. The main products were benzylacetate, produced via side-chain acetoxylation, and CO and CO2 resulted from combustion. Nuclear acetoxylation hardly occurred. A K-doped Pd-Au/SiO2 gave the highest activity and selectivity for synthesis of benzylacetate among the catalysts tested
the yield of benzylacetate on the K-doped Pd-Au/SiO2 was about 150 times greater than that on a Pd/SiO2. It was found that the addition of an adequate amount of Au to Pd/SiO2 inhibited the formation of CO2, and that potassium species worked as sites for adsorption and activation of acetic acid. © 1994, The Japan Petroleum Institute. All rights reserved.

The synthesis method to obtain a tight and thin zeolitic membrane was investigated. It was found that the most important factor to prepare a zeolitic membrane in a compact form was the pH to prepare the parent aluminosilicate gel. The aluminosilicate gel was supported on a porous alumina plate and treated in the vapor of templating reagents. It was found that a thin layer of ferrierite was formed on the surface of the plate. The rates of permeation of H-2, He, CH4, O-2, N-2 and CO2 through the ferrierite membrane were measured. Permeation results indicated that the ferrierite membrane is formed in a compact form.

We developed a fluidized bed-chemical vapor deposition (CVD) reactor for a novel method of particle processing, such as particle coating and surface treatment. Microwave plasma was applied as an excitation source of reactive gases, and alumina and silicon were used as bed materials. The hydrodynamic behavior of the plasma-bubbling fluidized bed was studied and the field of plasma generation was investigated optically. Only minor plasma generation was noted in the dense phase. Plasma emission was observed in most of the bubbles in the alumina-fluidized bed, while plasma generated at the surface of the silicon-fluidized bed where bubbles splashed. Methane conversion was carried out in the alumina-fluidized bed as a model reaction. Although excitation of methane occurred in bubbles, excited species entered into the dense phase from bubbles and were effectively converted to carbon on the surface of the particles. Thus, heterogenous CVD on the surface of particles may occur in this reactor. © 1994.

A thin zeolitic membrane on porous alumina support has been synthesized
the permeability of the film to N2 and O2 indicated that the membrane was formed in a compact form.

Vapor-phase oxidative acetoxylation of toluene on Pd-based bimetallic catalysts was investigated. The main products were benzylacetate, produced via side-chain acetoxylation, and CO and CO2 resulted from combustion. Nuclear acetoxylation hardly occurred. A K-doped Pd-Au/SiO2 gave the highest activity and selectivity for synthesis of benzylacetate among the catalysts tested
the yield of benzylacetate on the K-doped Pd-Au/SiO2 was about 150 times greater than that on a Pd/SiO2. It was found that the addition of an adequate amount of Au to Pd/SiO2 inhibited the formation of CO2, and that potassium species worked as sites for adsorption and activation of acetic acid. © 1994, The Japan Petroleum Institute. All rights reserved.

The synthesis method to obtain a tight and thin zeolitic membrane was investigated. It was found that the most important factor to prepare a zeolitic membrane in a compact form was the pH to prepare the parent aluminosilicate gel. The aluminosilicate gel was supported on a porous alumina plate and treated in the vapor of templating reagents. It was found that a thin layer of ferrierite was formed on the surface of the plate. The rates of permeation of H-2, He, CH4, O-2, N-2 and CO2 through the ferrierite membrane were measured. Permeation results indicated that the ferrierite membrane is formed in a compact form.

We developed a fluidized bed-chemical vapor deposition (CVD) reactor for a novel method of particle processing, such as particle coating and surface treatment. Microwave plasma was applied as an excitation source of reactive gases, and alumina and silicon were used as bed materials. The hydrodynamic behavior of the plasma-bubbling fluidized bed was studied and the field of plasma generation was investigated optically. Only minor plasma generation was noted in the dense phase. Plasma emission was observed in most of the bubbles in the alumina-fluidized bed, while plasma generated at the surface of the silicon-fluidized bed where bubbles splashed. Methane conversion was carried out in the alumina-fluidized bed as a model reaction. Although excitation of methane occurred in bubbles, excited species entered into the dense phase from bubbles and were effectively converted to carbon on the surface of the particles. Thus, heterogenous CVD on the surface of particles may occur in this reactor. © 1994.

A new system to measure very short bubble coalescence time was developed using a laser. The system's reliability was confirmed by comparing the system output with photographic observation by high-speed video camera. The result for aqueous solutions of n-alcohol was in good agreement with the previous data. The system was applied to various kinds of aqueous solutions more dilute than those in previous work where the value of bubble coalescence time was expected to be less than 2 ms. It was revealed that the bubble coalescence time reported in previous work was composed of two parts. The first part was the time length of the contacting period of two bubbles and the second was the time length of the initial stage of a film rupture between the bubbles. The former decreased considerably, even to an undetectably small value, with decrease in concentration, but the latter was constantly at about 0.3 ms regardless of concentration. Effects of bubble age and bubble approach velocity were examined. It was also found that the bubble coalescence time in surfactant solution was significantly influenced in a narrow concentration region as low as ppb order and that the bubbles did not coalesce in solution of higher concentration.

A new system to measure very short bubble coalescence time was developed using a laser. The system's reliability was confirmed by comparing the system output with photographic observation by high-speed video camera. The result for aqueous solutions of n-alcohol was in good agreement with the previous data. The system was applied to various kinds of aqueous solutions more dilute than those in previous work where the value of bubble coalescence time was expected to be less than 2 ms. It was revealed that the bubble coalescence time reported in previous work was composed of two parts. The first part was the time length of the contacting period of two bubbles and the second was the time length of the initial stage of a film rupture between the bubbles. The former decreased considerably, even to an undetectably small value, with decrease in concentration, but the latter was constantly at about 0.3 ms regardless of concentration. Effects of bubble age and bubble approach velocity were examined. It was also found that the bubble coalescence time in surfactant solution was significantly influenced in a narrow concentration region as low as ppb order and that the bubbles did not coalesce in solution of higher concentration.

The present study found that aluminosilicate gels were crystallized to ZSM-5, ferrierite, KZ-2 or analcime under a vapor atmosphere. The structure and crystallinity of the resultant zeolite significantly depended on the composition of the organic vapor as well as that of the parent gel. © 1993.

Local concentrations of gases in the jetting fluidized bed coal gasifier, particularly in the grid zone of the bed were measured to discuss gas exchange between the jet and annulus and local progress of chemical reactions. Air was introduced from the gas injection nozzle and steam was introduced from the coneshaped distributor plate. Gas exchange between the annulus and the jet rapidly occurred. Compared with the case that only steam was introduced, it was found that air introduced from the nozzle produced carbon oxides at around the boundary of the jet and as a result decreased the rate of steam gasification in the annulus. Both for physical and chemical phenomena the grid zone cannot be regarded as uniform. The grid structure strongly influenced the performance of the gasifier. © 1993.

Oxidative acetoxylation of toluene and benzene using molecular oxygen was carried out over supported palladium catalysts in the temperature range of 453-493 K at atmospheric pressure. It was found that the addition of gold on silica-supported palladium promoted acetoxylation of toluene and benzene. © 1993, The Japan Petroleum Institute. All rights reserved.

Dynamic light scattering (DLS) based on a monodisperse model was applied to ultrafine particle formation in a flame where particles grow and deform within several ms, with occasional high number density and broad size distribution. DLS was experimentally evaluated as an in-situ technique of measuring mean particle size by comparing with TEM (transmission electron microscope) photographs. The following results were obtained. 1. For particles formed in a flame, a mean particle size of several tens of nanometers by DLS with monodisperse assumption was in good agreement with the volume mean diameter obtained from TEM photographs, except for particles strongly deviated to small size. 2. For particles with a size distribution strongly deviated to the fine side, DLS with monodisperse assumption gives a considerably large value, around twice the volume mean diameter. This value still reflects a plausible mean size of large particles contained in the measuring volume. © 1993, The Society of Chemical Engineers, Japan. All rights reserved.

The present study found that aluminosilicate gels were crystallized to ZSM-5, ferrierite, KZ-2 or analcime under a vapor atmosphere. The structure and crystallinity of the resultant zeolite significantly depended on the composition of the organic vapor as well as that of the parent gel. © 1993.

Local concentrations of gases in the jetting fluidized bed coal gasifier, particularly in the grid zone of the bed were measured to discuss gas exchange between the jet and annulus and local progress of chemical reactions. Air was introduced from the gas injection nozzle and steam was introduced from the coneshaped distributor plate. Gas exchange between the annulus and the jet rapidly occurred. Compared with the case that only steam was introduced, it was found that air introduced from the nozzle produced carbon oxides at around the boundary of the jet and as a result decreased the rate of steam gasification in the annulus. Both for physical and chemical phenomena the grid zone cannot be regarded as uniform. The grid structure strongly influenced the performance of the gasifier. © 1993.

Oxidative acetoxylation of toluene and benzene using molecular oxygen was carried out over supported palladium catalysts in the temperature range of 453-493 K at atmospheric pressure. It was found that the addition of gold on silica-supported palladium promoted acetoxylation of toluene and benzene. © 1993, The Japan Petroleum Institute. All rights reserved.

Dynamic light scattering (DLS) based on a monodisperse model was applied to ultrafine particle formation in a flame where particles grow and deform within several ms, with occasional high number density and broad size distribution. DLS was experimentally evaluated as an in-situ technique of measuring mean particle size by comparing with TEM (transmission electron microscope) photographs. The following results were obtained. 1. For particles formed in a flame, a mean particle size of several tens of nanometers by DLS with monodisperse assumption was in good agreement with the volume mean diameter obtained from TEM photographs, except for particles strongly deviated to small size. 2. For particles with a size distribution strongly deviated to the fine side, DLS with monodisperse assumption gives a considerably large value, around twice the volume mean diameter. This value still reflects a plausible mean size of large particles contained in the measuring volume. © 1993, The Society of Chemical Engineers, Japan. All rights reserved.

The variations in the amounts of alkali and alkaline earth species actually existing on the surface of carbon black in the courses of heat treatment up to 1123 K and steam gasification at 1073 K were investigated, in order to understand the actual amount of catalyst existing on the surface of carbon in the working state. These gasification catalysts were classified into three groups based on the fact that some of them sunk into the bulk of carbon in the course of heat treatment and some of them vaporized from the surface of carbon. It was found that the migration of species into the bulk of carbon was profoundly associated with the reducibility of their oxide state.

The variations in the amounts of alkali and alkaline earth species actually existing on the surface of carbon black in the courses of heat treatment up to 1123 K and steam gasification at 1073 K were investigated, in order to understand the actual amount of catalyst existing on the surface of carbon in the working state. These gasification catalysts were classified into three groups based on the fact that some of them sunk into the bulk of carbon in the course of heat treatment and some of them vaporized from the surface of carbon. It was found that the migration of species into the bulk of carbon was profoundly associated with the reducibility of their oxide state.

The mobility of alkali and alkaline earth elements loaded on carbon black during heat treatment up to 1123 K in an inert atmosphere was investigated by different spectroscopic methods. The objective was to improve our understanding of gasification by catalysts containing these elements. It was found that Na, Rb, Cs, Sr and Li species migrated into the bulk of carbon on heating up to 1123 K in a flowing inert atmosphere.

The mobility of alkali and alkaline earth elements loaded on carbon black during heat treatment up to 1123 K in an inert atmosphere was investigated by different spectroscopic methods. The objective was to improve our understanding of gasification by catalysts containing these elements. It was found that Na, Rb, Cs, Sr and Li species migrated into the bulk of carbon on heating up to 1123 K in a flowing inert atmosphere.

It has been pointed out that polycrystalline silicon particles produced from monosilane by the fluidized-bed CVD method contain residual hydrogen that causes disturbance of flow in a crucible in the CZ process. In the present work, the residual hydrogen was desorbed from produced Si particles by heat treatment. The activation energy for the hydrogen desorption was determined by the temperature-programmed desorption (TPD) technique. By FTIR, various types of Si-H bonds were found in the Si particles produced. The adsorbance area was decreased with increase in the desorbed hydrogen by TPD. From this relationship, the total amount of residual hydrogen was determined to be around 0.05% of the hydrogen contained in the reacted monosilane. The particle density of Si particles increased linearly almost up to the true density, with a decrease in the absorbance area of FTIR by the heat treatment.

A plasma jetting fluidized bed reactor was developed for coating particles via PCVD. Conversion of methane was carried out to investigate characteristics of this type of reactor. It was found that introduction of reactive gases from the side of a d.c. plasma jet resulted in no deterioration of the stability of plasma and that the reactive gases were effectively activated even in the presence of particles. Particles packed in the reactor promoted reactions to give carbon in the presence of hydrogen in a large excess, strongly suggesting that PCVD on fluidized particles can be realized.

Characterization of polycrystalline silicon particles produced in a fluidized bed reactor via CVD from monosilane was carried out. It was observed that part of the hydrogen from monosilane remained in the particles. Most of hydrogen was bonded to silicon and temperatures as high as 1300 K were required to dehydrogenate the silicon particles. Particles were contaminated with metal elements which were diffused from the reactor wall, suggesting that the material used in constructing the fluidized bed reactor wall also needed to be controlled to improve the purity of product.

A plasma jetting fluidized bed reactor was developed for coating particles via PCVD. Conversion of methane was carried out to investigate characteristics of this type of reactor. It was found that introduction of reactive gases from the side of a d.c. plasma jet resulted in no deterioration of the stability of plasma and that the reactive gases were effectively activated even in the presence of particles. Particles packed in the reactor promoted reactions to give carbon in the presence of hydrogen in a large excess, strongly suggesting that PCVD on fluidized particles can be realized.

Characterization of polycrystalline silicon particles produced in a fluidized bed reactor via CVD from monosilane was carried out. It was observed that part of the hydrogen from monosilane remained in the particles. Most of hydrogen was bonded to silicon and temperatures as high as 1300 K were required to dehydrogenate the silicon particles. Particles were contaminated with metal elements which were diffused from the reactor wall, suggesting that the material used in constructing the fluidized bed reactor wall also needed to be controlled to improve the purity of product.

The benzene-steam reaction on MgO doped with Ca, Sr, Ba, and K was investigated at 1,173K and at atmospheric pressure to understand the action of steam as gasifying reagent in hydrocarbon gasification. The results were discussed by comparing with those of the benzene-CO2reaction. The benzene-steam reaction was proposed to proceed via the decomposition of benzene to give an intermediate carbon and subsequent gasification of the carbon. The steam adsorbed on the catalyst was found to hinder the decomposition of benzene to give the intermediate. Catalytic activity for the benzene-steam reaction could be interpreted mainly by a combination of catalytic activity for gasification of deposited carbon and the degree of hindrance to the decomposition of benzene by adsorbed steam. The mobility of catalytic species in the layers of the deposited carbon was found to be an important factor governing the rate of gasification of the deposited carbon. © 1991, The Japanese Association of Educational Psychology. All rights reserved.