Ammonia, which can be decomposed on-site to produce CO2-free H2, is regarded as a promising hydrogen carrier because of its high hydrogen density, wide availability, and ease of transport. Unfortunately, ammonia decomposition requires high temperatures (>773 K) to achieve complete conversion, thereby hindering its practical applicability. Here, we demonstrate that high conversion can be achieved at markedly lower temperatures using an applied electric field along with a highly active and readily producible Ru/CeO2 catalyst. Applying an electric field lowers the apparent activation energies, promotes low-temperature conversion, and even surpasses equilibrium conversion at 398 K, thereby providing a feasible route to economically attractive hydrogen production. Experimentally obtained results and neural network potential studies revealed that this reaction proceeds via HN-NH intermediate formation by virtue of surface protonics.

The elimination of unburned methane produced by internal combustion engines is extremely important because of the strong greenhouse effect of methane. Difficulties in controlling unburned methane arise from its characteristics, such as its difficulty of adsorption, low exhaust gas temperatures in an efficient engine, low concentrations of unburned emitted methane, and the coexistence of steam and residual oxygen as coexisting substances in the exit gas. Results of the present study demonstrate that the removal activity of methane by complete combustion was improved dramatically at low temperatures by the application of a DC electric field to the Pd/CexZr1−xO2 catalyst system, even under a humid atmosphere. Specifically, 1 wt% Pd/Ce0.25Zr0.75O2 showed very higher methane conversion under humid conditions than under dry conditions at 473 K in the presence of an electric field. To elucidate the reaction mechanisms involved in this process of steam adsorption, we conducted partial pressure dependence tests and activity tests with steam under an electric field.

Nitrous oxide (N2O) exerts strong effects on global warming and environmental destruction. Various catalytic technologies have been investigated for N2O abatement. We investigated a catalytic system in an electric field, revealing that N2O can be decomposed efficiently, even at low temperatures and in the presence of excess oxygen and water vapour. Reaction mechanisms with and without an electric field have been investigated using kinetics and various operando analyses, which revealed that surface-lattice oxygen on catalyst supports plays a crucially important role in N2O decomposition in an electric field at low temperatures.

DFT calculation of Keggin-type polyoxometalates provided the first protonation sites and HOMO-LUMO gaps related to their total charge and bond valence.

To prevent global warming, improvements in the efficiency of internal combustion engines and the introduction of hybrid electric vehicles are gaining popularity as ways of controlling carbon dioxide emissions. Because of the lower average temperature of the exhaust gases from these systems, catalytic reactions mediated by an electric field have attracted attention because catalysts can have higher catalytic activity at lower temperatures than conventional catalysts. In addition, they consume less power than electrically heated catalysts. In this study, we determined the catalytic activity of a palladium/ceria-zirconia catalyst in an electric field with exhaust gas temperatures lower than conventional gas temperatures. Further evaluation using catalytic materials with modified ceria-zirconia ratios revealed the importance of the electrical resistance of the materials during electric field–mediated catalytic reactions. Upon modulating the applied current, the current strength was found to be related to a change in the electrical resistance of the catalyst during the reaction. Furthermore, we observed that the activity and electrical resistance of the catalysts were intrinsically linked. These results suggest that electron-promoted surface proton transport and intra-lattice oxygen defects in metal oxide catalysts, as well as their structural changes, significantly contribute to their catalytic activity in an electric field. These electric field–mediated catalytic reactions using modified catalysts can adapt to the growing shift in engine operating conditions by ensuring that the benefits associated with the use of hybrid vehicles and high-efficiency combustion engines are not offset by an increase in the production of carbon monoxide, nitrogen oxide, and unburned hydrocarbons.

In the advent of an energy shift towards renewable energy sources, ammonia is considered a promising energy carrier for convenient hydrogen storage and transport. However, ammonia decomposition requires temperatures higher than 500 °C to achieve 100% conversion. Here, we present the facile synthesis and use of nanocluster RuCeO2 catalysts for the low-temperature electric field-assisted ammonia decomposition reaction. The catalysts obtained desirable properties and achieved high conversions for ammonia decomposition under conventional conditions. Interestingly, catalyst activities significantly increased upon exposure to an electric field, achieving 100% conversion at 450 °C and obtaining exceptional conversions of up to 34% at a low temperature of 200 °C and a high GHSV of 30,000 mLNH3/gcath. Optimization of reaction parameters effectively increased NH3 conversions, allowed highly stable long-term activities, and enabled the catalyst to achieve equilibrium conversions at remarkably lower temperatures. Further studies reveal that the electric field essentially reduces apparent activation energies and boosts the ammonia decomposition reaction by promoting the recombinative desorption of N2 and H2, thereby alleviating the rate-determining step and preventing deactivation due to H2 poisoning. The occurrence of surface protonics as a result of N-H bond scission and transport of H+ species to the support, along with increased NH3 activation and oxygen vacancy migration improves charge transfer between the support and the Ru active sites, thereby resulting in increased desorption of N2 and H2 products. Thus, an energy-efficient route toward economical hydrogen production is achieved by combining electric field effects with a highly active RuCeO2 catalyst.

Reverse water gas shift (RWGS) can convert CO2 into CO by using renewable hydrogen. However, this important reaction is endothermic and equilibrium constrained, and thus traditionally performed at 900 K or higher temperatures using solid catalysts. In this work, we found that RWGS can be carried out at low temperatures without equilibrium constraints using a redox method called chemical looping (CL), which uses the reduction and oxidation of solid oxide surfaces. When using our developed MGa2Ox (M = Ni, Cu, Co) materials, the reaction can proceed with almost 100% CO2 conversion even at temperatures as low as 673 K. This allows RWGS to proceed without equilibrium constraints at low temperatures and greatly decreases the cost for the separation of unreacted CO2 and produced CO. Our novel gallium-based material is the first material that can achieve high conversion rates at low temperatures in reverse water gas shift using chemical looping (RWGS-CL). Ni outperformed Cu and Co as a dopant, and the redox mechanism of NiGa2Ox is a phase change due to the redox of Ga during the RWGS-CL process. This major finding is a big step forward for the effective utilization of CO2 in the future.

Methane dry reforming at 373 K in a DC electric field was carried out using Ni/CeO2 and Ni0.8Fe0.2/CeO2 alloy catalysts, and their alloying effects were investigated in detail using XAFS and in-situ surface spectroscopy. For the Ni catalyst, there was a decrease in the adsorption of carbonate species, an increase in the proportion of bidentate carbonate species, and an observed degradation in activity caused by carbon deposition over time. Conversely, the alteration of electronic state occurring as a result of the ligand effect (electronic interaction among atoms by alloying) on the Ni-Fe catalyst contributed to the stabilization of intermediates involved in rate-determining steps specific to electric-field catalysis. Carbon deposition was less likely to occur, resulting in significantly higher activity when compared to the Ni catalyst.

Quantum annealing has been used to predict molecular adsorption on solid surfaces. Evaluation of adsorption, which takes place in all solid surface reactions, is a crucially important subject for study in various fields. However, predicting the most stable coordination by theoretical calculations is challenging for multimolecular adsorption because there are numerous candidates. This report presents a novel method for quick adsorption coordination searches using the quantum annealing principle without combinatorial explosion. This method exhibited much faster search and more stable molecular arrangement findings than conventional methods did, particularly in a high coverage region. We were able to complete a configurational prediction of the adsorption of 16 molecules in 2286 s (including 2154 s for preparation, only required once), whereas previously it has taken 38 601 s. This approach accelerates the tuning of adsorption behavior, especially in composite materials and large-scale modeling, which possess more combinations of molecular configurations.

Selective CO₂ hydrogenation to CO at low temperature (473 K or lower).

Low-temperature ammonia synthesis by applying an electric field to a solid heterogeneous catalyst was investigated to realize an on-demand, on-site catalytic process for converting distributed renewable energy into ammonia. By applying an electric field to the catalyst, even at low temperatures, the reaction proceeds efficiently by an “associative mechanism” in which proton-conducting species on the support surface promote the formation of N2Had intermediates through surface protonics. Kinetics, isotope exchange, infrared spectroscopy, X-ray spectroscopy, and AC impedance analysis were performed to clarify the effect of metal and catalyst support structure on the reaction, and an evaluation method for the surface protonics of the support was established to analyze the reaction mechanism, and further analysis using computational chemistry was also conducted. The elementary step determining catalytic activity changed from N2 dissociation to N2H formation, and this difference resulted in high activity for ammonia synthesis at low temperatures even when using base metal catalysts such as Fe and Ni.

Low-cost carbon dioxide (CO2) capture technologies have been studied widely. Among such technologies, the control of CO2 adsorption by the application of an electric field to solid materials has been shown to be a promising technology that can combine high CO2 adsorption with low energy consumption. Suitable materials must be found for electric field-assisted CO2 adsorption. For this study, the CO2 adsorption energies of CeO2 partially substituted with hetero-cations were investigated using theoretical calculations. The differences in adsorption performance attributable to the application of an electric field were clarified for different doped cations. The results show that the amount of change in the CO2 adsorption energy by the application of an electric field depended on the different doped cations. Furthermore, it is found that this difference in cations is related to the electronegativity of the doped cations. These results suggest a tuning strategy for the material properties necessary for CO2 capture and separation using an electric field.

Dry reforming of methane (DRM) is a promising reaction able to convert greenhouse gases (CO2 and CH4) into syngas: an important chemical feedstock. Several difficulties limit the applicability of DRM in conventional thermal catalytic reactions; it is an endothermic reaction that requires high temperatures, resulting in high carbon deposition and a low H2/CO ratio. Catalysis with the application of an electric field (EF) at low temperatures can resolve these difficulties. Synergistic effects with alloys have also been reported for reactions promoted by the application of EF. Therefore, the synergistic effects of low-temperature DRM and Ni-Fe bimetallic catalysts were investigated using various methods and several characterisations (XRD, XPS, FE-STEM, etc.), which revealed that Ni-Fe binary catalysts show high performance in low-temperature DRM. In particular, the Ni0.8Fe0.2 catalyst supported on CeO2 was found to carry out DRM in EF effectively and selectively by virtue of its bimetallic characteristics.

The effect of OH-groups on the surface of a Ni catalyst for low-temperature (473 K) steam reforming of methane in an electric field (EF) was investigated. Ni-doped YSZ (Zr0.65Y0.05Ni0.3O2) was chosen as a highly active catalyst for this purpose. The effects on catalyst activity of adding hydrogen and steam in the pre-treatment were assessed with and without EF. When an EF was applied, activity increased irrespective of the electronic state of Ni, whereas the metallic Ni state was necessary for activity without EF. Furthermore, the highest activity with EF was observed for the pre-treatment with a mixture of H2 and H2O. Investigation of the superiority using XPS measurements showed an increase in the amount of Ni(OH)2, OH groups and H2O near the surface after the activity test, which are regarded as the reaction sites with EF. This finding suggests that a pre-treatment with steam increases the surface OH groups and Ni(OH)2 on the Ni catalyst, and enhances surface proton conduction, thereby improving the activity.

This report is the first describing a study quantitatively analysing aspects of oxide surface protonics in a dry H2 atmosphere. Elucidating surface protonics is important for electrochemical and catalytic applications. In this study, AC impedance spectroscopy was used to investigate surface conduction properties of porous CeO2 at low temperatures (423-573 K) and in a dry H2 atmosphere. Results demonstrated that the conductivity increased by several orders of magnitude when H2 was supplied. Dissociative adsorption of H2 contributes to conduction by forming proton-electron pairs. Also, H/D isotope exchange studies confirmed protons as the dominant conduction carriers. Furthermore, H2 adsorption equilibrium modelling based on the Langmuir mechanism was applied to explain the H2 partial pressure dependence of conductivity. For the first time, the obtained model explains the experimentally obtained results both qualitatively and quantitatively. These findings represent new insights into surface protonics in H2 atmosphere.

Catalytic ethane dehydrogenation (EDH) was investigated to improve the efficient production of ethylene, an extremely important chemical feedstock. The perovskite oxide YCrO3 was found to be more suitable than earlier reported catalysts because it exhibits greater activity and C2H4 selectivity (94.3%) in the presence of steam at 973 K. This catalyst shows the highest activity than ever under kinetic conditions, and shows very high ethane conversion under integral reaction conditions. Comparison with EDH performance under conditions without steam revealed that steam plays an important role in stabilizing the high activity. Raman spectra of spent catalysts indicated that steam prevents coke formation, which is responsible for deactivating YCrO3. Transmission IR and XPS measurements also revealed a mechanism by which H2O forms surface oxygen species on YCrO3, consequently removing C2H6-derived coke precursors rapidly and inhibiting coke accumulation.

With increasing expectations for carbon neutrality, dry reforming is anticipated for direct conversion of methane and carbon dioxide: the main components of biogas. We have found that dry reforming of methane in an electric field using a Pt/CeO2 catalyst proceeds with sufficient rapidity even at a low temperature of about 473 K. The effect of the electric field (EF) on dry reforming was investigated using kinetic analysis, in situ DRIFTs, XPS, and DFT calculation. In situ DRIFTs and XPS measurements indicated that the amount of carbonate, which is an adsorbed species of CO2, increased with the application of EF. XPS measurements also confirmed the reduction of CeO2 by the reaction of surface oxygen and CH4. The reaction between CH4 molecules and surface oxygen was promoted at the interface between Pt and CeO2

CO2 conversion to CO by reverse water-gas shift using chemical looping (RWGS-CL) can be conducted at lower temperatures (ca. 723-823 K) than the conventional catalytic RWGS (>973 K), and has been attracting attention as an efficient process for CO production from CO2. In this study, Co-In2O3 was developed as an oxygen storage material (OSM) that can realize an efficient RWGS-CL process. Co-In2O3 showed a high CO2 splitting rate in the mid-temperature range (723-823 K) compared with previously reported materials and had high durability through redox cycles. Importantly, the maximum CO2 conversion in the CO2 splitting step (ca. 80%) was much higher than the equilibrium conversion of catalytic RWGS in the mid-temperature range, indicating that Co-In2O3 is a suitable OSM for the RWGS-CL process.

Methane is an important chemical resource, not only in natural gas but also in biogas, which can be regarded as a renewable energy resource. Reforming of methane with steam or carbon dioxide, which is important for producing hydrogen and syngas, is conducted at high temperatures using heterogeneous catalysts. To achieve high activity, stability, and low carbon deposition, many studies have been conducted in recent years on the use of alloys as active sites in these catalysts. This review presents a summary of recent studies of alloy catalysts, for which various secondary metals have been added to active metals, such as Ni. Then we summarize the current status of these alloys in terms of their structure, electronic state, and adsorption. The reported effects of alloying include improvement of dispersion and reducibility of the supported metal, change in catalytic performance such as activity and selectivity, and improvement of durability against carbon deposition, sulphur poisoning, and sintering. The directions of future research and development are summarized in terms of sulphur resistance, sintering inhibition, and high activity at low temperatures.

As automobiles increasingly become electrically driven and as more engines and motors are used together, the exhaust temperatures of internal combustion engines are decreasing. Further improvement of exhaust gas purification catalyst performance is necessary. To purify nitrogen oxides, unburned hydrocarbons, and carbon monoxide simultaneously at low temperatures, electrothermal heating and plasma catalysis have been proposed, but these methods require high power consumption. Results of this study indicate that a direct current electric field applied to a Pd-supported catalyst shows high purification rates even at temperatures lower than 473 K under TWC conditions (NO-CO-C3H6-O2-H2O). For clarifying the reaction mechanism in this process, the adsorption of reactants was evaluated using in situ DRIFTS measurements in an electric field. Factors that improve the activity at low temperatures in the electric field were clarified.

Considering the expansion of the use of renewable energy in the future, the technology to store and transport hydrogen will be important. Hydrogen is gaseous at an ambient condition, diffuses easily, and its energy density is low. So liquid organic hydrogen carriers (LOHCs) have been proposed as a way to store hydrogen in high density. LOHC can store, transport, and use hydrogen at high density by hydrogenation and dehydrogenation cycles. In this review, we will focus on typical LOHCs, methylcyclohexane (MCH), 18H-dibenzyltoluene (DBT), and 12H-N-ethylcarbazole (NECZ), and summarize recent developments in dehydrogenation catalytic processes, which are key in this cycle.

A Pd catalyst (Pd/Ce0.7Zr0.3O2) in an electric field exhibits extremely high three-way catalytic activity (TWC: NO-C3H6-CO-O2-H2O). By applying an electric field to the semiconductor catalyst, low-temperature operation of TWC can be achieved even at 473 K by virtue of the activated surface-lattice oxygen.

<p>Schematic reaction mechanisms; (A) without an applied electric field, (B) with an applied electric field.</p>

Introducing a catalyst for dehydrogenation of ethane (EDH) for steam cracking represents a promising solution with high feasibility to realize efficient ethylene production. We investigated EDH over transition-metal-doped CeO2 catalysts at 873 K in the presence of steam. Ce0.8Co0.2O2 exhibited high EDH activity and selectivity to ethylene (ca. 95%). In the absence of H2O, the catalytic activity dropped rapidly, indicating the promotive effect of H2O on ethylene formation. Catalytic experiments with water isotopes (D2O and H218O) demonstrated that EDH over Ce0.8Co0.2O2 proceeds through the Mars-van Krevelen (MvK) mechanism in which the reactive lattice oxygen in Ce0.8Co0.2O2 contributes to EDH. The consumed lattice oxygen was subsequently regenerated with H2O. X-ray diffraction and in situ X-ray absorption fine structure spectroscopy revealed that cobalt species were mainly present as CoO under EDH conditions and that redox between Co2+ and Co0 proceeded concomitantly with EDH. In contrast with Ce0.8Co0.2O2, no contribution of the lattice oxygen of CoO to EDH was verified in the case of CoO supported on α-Al2O3, which exhibited lower activity than Ce0.8Co0.2O2. Therefore, Co-CeO2 interactions are expected to play a crucially important role in controlling the characteristics of the reactive lattice oxygen suitable for EDH via the MvK mechanism.

Aromatization of light hydrocarbons can contribute to a secure supply of aromatics for the chemical industry. In this work, we investigate the influence of modification of zeolite ZSM-5 with Ga and Mo on the reaction mechanism underlying the activation and aromatization of ethane. Well-defined Mo/ZSM-5 and Ga/ZSM-5 zeolites efficiently promote ethane aromatization to benzene-toluene-xylene mixtures. Both catalysts suffer from coke formation, which leads to rapid deactivation. From catalytic tests, temperature-programmed surface reaction and pulsed reaction experiments, we infer that ethane conversion on Ga/ZSM-5 follows a conventional sequential dehydrogenation-oligomerization-aromatization mechanism, while the reaction over Mo/ZSM-5 involves reactive surface carbon (hydrocarbon pool) species.

The performance of metal atoms chemically bonded to oxide supports cannot be explained solely by the intrinsic properties of the metals such as the d-band center. Herein, we present an in-depth study of the correlation between metal-oxide interactions and the properties of the supported metal using CO adsorption on Me1 (Fe1, Co1, and Ni1) loaded over CeO2 (111) doped with divalent (Ca, Sr, and Ba), trivalent (Al, Ga, Sc, Y, and La), and quadrivalent (Hf and Zr) heterocations. CO adsorption over Me1 is strongly dependent on the binding energies of Me1. Two factors led to this trend. First, the extent of the Me1-surface oxygen (Me1-O) bond relaxation during CO adsorption played a key role. Second, the d-band center shifted drastically because of charge transfer to the oxides. The shift is related to the oxophilicity of metals. Adsorption energies of Me1 over oxides include the contributions of the factors described above. Therefore, we can predict the activities of Me1 using the strength of anchoring by oxide supports. Results show that smaller ionic radii of the doped heterocations were associated with more tightly bound Me1. This finding sheds light on the possibility of heterocation-doping manipulating the reactivity of the Me1 catalyst based on theoretical predictions.

Hydrogen (H) atom adsorption and migration over the CeO2-based materials surface are of great importance because of its wide applications to catalytic reactions and electrochemical devices. Therefore, comprehensive knowledge for controlling the H atom adsorption and migration over CeO2-based materials is crucially important. For controlling H atom adsorption and migration, we investigated irreducible divalent, trivalent, and quadrivalent heterocation-doping effects on H atom adsorption and migration over the CeO2(111) surface using density functional theory (DFT) calculations. Results revealed that the electron-deficient lattice oxygen (Olat) and the flexible CeO2matrix played key roles in strong adsorption of H atoms. Heterocations with smaller valence and smaller ionic radius induced the electron-deficient Olat. In addition, smaller cation doping enhanced the CeO2matrix flexibility. Moreover, we confirmed the influence of H atom adsorption controlled by doping on surface proton migration (i.e.surface protonics) and catalytic reaction involving surface protonics (NH3synthesis in an electric field). Results confirmed clear correlation between H atom adsorption energy and surface protonics.

Hydrogen (H) atomic migration over a metal oxide is an important surface process in various catalytic reactions. Control of the interaction between H atoms and the oxide surfaces is therefore important for better catalytic performance. For this investigation, we evaluated the adsorption energies of the H atoms over perovskite-type oxides (Sr1−xBaxZrO3; 0.00 ≤x≤ 0.50) using DFT (Density Functional Theory) calculations, then clarified the effects of cation-substitution in the A-site of perovskite oxides on H atom adsorption, migration, and reaction. Results indicated local distortion at the oxide surface as a key factor governing H atom adsorption. Subtle Ba2+substitution for Sr2+sites provoked local distortion at the Sr1−xBaxZrO3oxide surface, which led to a decrement in the H atom adsorption energy. Furthermore, the effect of Sr2+/Ba2+ratio on the H atoms' reactivities was examined experimentally using a catalytic reaction, which was promoted by activated surface H atoms. Results show that the surface H atoms activated by the substitution of Sr2+sites with a small amount of Ba2+(x= 0.125) contributed to enhancement of ammonia synthesis rate in an electric field, which showed good agreement with predictions made using DFT calculations.

Efficient activation of CO2at low temperature was achieved by reverse water-gas shiftviachemical looping (RWGS-CL) by virtue of fast oxygen ion migration in a Cu-In structured oxide, even at lower temperatures. Results show that a novel Cu-In2O3structured oxide can show a remarkably higher CO2splitting rate than ever reported. Various analyses revealed that RWGS-CL on Cu-In2O3is derived from redox between Cu-In2O3and Cu-In alloy. Key factors for high CO2splitting rate were fast migration of oxide ions in the alloy and the preferential oxidation of the interface of alloy-In2O3in the bulk of the particles. The findings reported herein can open up new avenues to achieve effective CO2conversion at lower temperatures.

The process of combining heterogeneous catalysts and direct current (DC) electric fields can achieve high catalytic activities, even under mild conditions (<500 K) with relatively low electrical energy consumption. Hydrogen production by steam reforming of methane, aromatics and alcohol, dehydrogenation of methylcyclohexane, dry reforming of methane, and ammonia synthesis are known to proceed at low temperatures in an electric field. In situ/operando analyses are conducted using IR, Raman, X-ray absorption fine structure, electrochemical impedance spectroscopy, and isotopic kinetic analyses to elucidate the reaction mechanism for these reactions at low temperatures. The results show that surface proton hopping by a DC electric field, called surface protonics, is important for these reactions at low temperatures because of the higher surface adsorbate concentrations at lower temperatures. This journal is

更なる排ガス低減が可能、かつ、低コスト/コンパクトにより様々な電動車両に普及可能な電場触媒のフィジビリティスタディを実施した．Pd/CZ触媒への電場印加により、従来の触媒反応では非活性の低温域において活性の発現を確認できた．また，触媒諸元と電場強度により活性を最適化できることが見いだされた．

To prevent global warming, further reductions in carbon dioxide are required. It is therefore important to promote the spread of electric vehicles powered by internal combustion engines and electric vehicles without internal combustion engines. As a result, emissions from hybrid electric vehicles equipped with internal combustion engines should be further reduced. Interest in catalytic reactions in an electric field with a higher catalytic activity compared to conventional catalysts has increased because this technology consumes less energy than other electrical heating devices. This study was therefore undertaken to apply a catalytic reaction in an electric field to an exhaust emission control. First, the original experimental equipment was built with a high voltage system used to conduct catalytic activity tests. Second, experiments with palladium cerium-zirconium oxide support catalysts showed that a three-way catalytic activity in an electric field could be found. at lower exhaust temperatures than conventional catalysts. Then it became clear that catalytic compositions that include semiconductor properties are a key for researching and developing this technology. In addition, applied electrical current control has been shown to be another focus of research and development. Finally, experimental results with several reducing species demonstrate that the electron-promoted surface proton and lattice oxygen greatly contributed to catalytic activity in an electric field.

© 2020 the Owner Societies. Hydrogen migration over a metal oxide surface is an extremely important factor governing the activity and selectivity of various heterogeneous catalytic reactions. Passive migration of hydrogen governed by a concentration gradient is called hydrogen spillover, which has been investigated broadly for a long time. Recently, well-fabricated samples and state-of-the-art measurement techniques such as operando spectroscopy and electrochemical analysis have been developed, yielding findings that have elucidated the migration mechanism and novel utilisation of hydrogen spillover. Furthermore, great attention has been devoted to surface protonics, which is hydrogen migration activated by an electric field, as applicable for novel low-temperature catalysis. This article presents an overview of catalysis related to hydrogen hopping, sophisticated analysis techniques for hydrogen migration, and low-temperature catalysis using surface protonics.

© 2020 The Royal Society of Chemistry. Low temperature (<500 K) methane steam reforming in an electric field was investigated over various catalysts. To elucidate the factors governing catalytic activity, activity tests and various characterization methods were conducted over various oxides including CeO2, Nb2O5, and Ta2O5 as supports. Activities of Pd catalysts loaded on these oxides showed the order of CeO2 > Nb2O5 > Ta2O5. Surface proton conductivity has a key role for the activation of methane in an electric field. Proton hopping ability on the oxide surface was estimated using electrochemical impedance measurements. Proton transport ability on the oxide surface at 473 K was in the order of CeO2 > Nb2O5 > Ta2O5. The OH group amounts on the oxide surface were evaluated by measuring pyridine adsorption with and without H2O pretreatment. Results indicate that the surface OH group concentrations on the oxide surface were in the order of CeO2 > Nb2O5 > Ta2O5. These results demonstrate that the surface concentrations of OH groups are related to the proton hopping ability on the oxide surface. The concentrations reflect the catalytic activity of low-temperature methane steam reforming in the electric field.

© 2018 Elsevier B.V. Development of a highly efficient ammonia synthesis process is desirable for achieving a sustainable society. Regarding conventional heterogeneous catalysts, Ru-supported catalyst exhibits higher turn-over frequency (TOF) than Fe-supported or Ni-supported catalysts. However, we found that Fe-supported and Ni-supported catalysts show higher TOF than Ru-supported catalyst in an electric field at the low temperature of 373 K. Density functional theory (DFT) calculations revealed that N2 dissociation through the “associative mechanism” plays a key role in the electric field. The ammonia synthesis activity in the electric field is determined by the N2H formation energy at the metal-support interface.

© The Royal Society of Chemistry 2020. Chemical utilization of ethane to produce valuable chemicals has become especially attractive since the expanded utilization of shale gas in the United States and associated petroleum gas in the Middle East. Catalytic conversion to ethylene and aromatic hydrocarbons through non-oxidative dehydrogenation and dehydroaromatization of ethane (EDH and EDA) are potentially beneficial technologies because of their high selectivity to products. The former represents an attractive alternative to conventional thermal cracking of ethane. The latter can produce valuable aromatic hydrocarbons from a cheap feedstock. Nevertheless, further progress in catalytic science and technology is indispensable to implement these processes beneficially. This review summarizes progress that has been achieved with non-oxidative EDH and EDA in terms of the nature of active sites and reaction mechanisms. Briefly, platinum-, chromium- and gallium-based catalysts have been introduced mainly for EDH, including effects of carbon dioxide co-feeding. Efforts to use EDA have emphasized zinc-modified MFI zeolite catalysts. Finally, some avenues for development of catalytic science and technology for ethane conversion are summarized.

Copyright © 2020 American Chemical Society. For effective utilization of ethane in natural gas, catalytic dehydrogenation of ethane is a promising option that offers better efficiency than ethane cracking to produce ethylene, the most important fundamental chemical. Recently, it was reported that catalytic dehydrogenation of ethane proceeds effectively on doped perovskite oxide via the Mars-van Krevelen (MvK) mechanism. For this work, the reaction mechanism was investigated using density functional theory calculations. Results demonstrated that ethane activation over perovskite (La1-xBaxMnO3-δ) proceeds at the surface lattice oxygen coordinated with Ba, resulting in a low energy barrier of the C-H bond activation. Based on Bader charge analysis, the electron-deficient surface lattice oxygen, which is favorable for hydrogen abstraction from light alkanes, forms around Ba. In addition, the electronic charges of the surface lattice oxygen are important for H2 desorption. The electronic charge depends on hydrogen coverage: electron-rich surface lattice oxygen, which is favorable for H2 desorption, forms at high hydrogen coverage. Therefore, a part of the surface lattice oxygens of perovskite would be covered with hydrogen atoms under the reaction atmosphere, leading to effective H2 desorption and the proceeding catalytic cycle via the MvK mechanism.

This journal is © The Royal Society of Chemistry. Light aromatic compounds (BTX: benzene, toluene and xylenes) represent an important class of building blocks in the chemical industry. Currently, light aromatics are obtained exclusively from fossil feedstock, whose utilization is associated with serious environmental concerns. Developing new routes for a more sustainable BTX production is, therefore, of high importance. In this work, aromatization of ethylene over well-defined metal-modified HZSM-5 zeolite catalysts is examined. The results show that modification of zeolite with gallium, zinc and silver leads to a significant increase in aromatics production. Metal species are responsible for catalysing dehydrogenation pathways with Ga being the most efficient for BTX production. Increasing temperature and ethylene partial pressure facilitate ethylene aromatization. Employing a combination of isotope labelling with a thorough characterization of zeolite-entrapped species by means of IR and MAS NMR spectroscopy provides evidence for the involvement of intra-zeolite aromatic hydrocarbon species in the catalytic cycle.

This journal is © 2020 The Royal Society of Chemistry. Catalytic methane steam reforming was conducted at low temperature using a Pd catalyst supported on Ce1-xMxO2 (x = 0 or 0.1, M = Ca, Ba, La, Y or Al) oxides with or without an electric field (EF). The effects of the catalyst support on catalytic activity and surface proton hopping were investigated. Results show that Pd/Al-CeO2 (Pd/Ce0.9Al0.1O2) showed higher activity than Pd/CeO2 with EF, although their activity was identical without EF. Thermogravimetry revealed a larger amount of H2O adsorbed onto Pd/Al-CeO2 than onto Pd/CeO2, so Al doping to CeO2 contributes to greater H2O adsorption. Furthermore, electrochemical conduction measurements of Pd/Al-CeO2 revealed a larger contribution of surface proton hopping than that for Pd/CeO2. This promotes the surface proton conductivity and catalytic activity during EF application.

© 2020 American Chemical Society. Fe-supported heterogeneous catalysts are used for various reactions, including ammonia synthesis, Fischer-Tropsch synthesis, and exhaust gas cleaning. For the practical use of Fe-supported catalysts, suppression of Fe particle agglomeration is the most important issue to be resolved. As described herein, we found that Al doping in an oxide support suppresses agglomeration of the supported Fe particle. Experimental and computational studies revealed two tradeoff Al doping effects: the Fe particle size decreased and remained without agglomeration by virtue of the anchoring effect of doped Al. Also, some Fe atoms anchored by Al cannot function as an active site because of bonding with oxygen atoms. Using an appropriate amount of Al doping is effective for increasing the number of active Fe sites and catalytic activity. This optimized catalyst showed high practical activity and stability for low-temperature ammonia synthesis in an electric field. The optimized catalyst of 12.5 wt % Fe/Ce0.4Al0.1Zr0.5O2-δ showed the highest ammonia synthesis rate (2.3 mmol g-1 h-1) achieved to date under mild conditions (464 K, 0.9 MPa) in an electric field among the Fe catalysts reported.

© 2020 The Royal Society of Chemistry. Low-temperature heterogeneous catalytic reaction in an electric field is anticipated as a novel approach for on-demand and small-scale catalytic processes. This report quantitatively reveals the important role of proton coverage on the catalyst support for catalytic ammonia synthesis in an electric field, which shows an anti-Arrhenius behaviour.

This journal is © The Royal Society of Chemistry. This is the first direct observation that surface proton hopping occurs on SrZrO3 perovskite even under a H2 (i.e. dry) atmosphere. Understanding proton conduction mechanisms on ceramic surfaces under a H2 atmosphere is necessary to investigate the role of proton hopping on the surface of heterogeneous catalysts in an electric field. In this work, surface protonics was investigated using electrochemical impedance spectroscopy (EIS). To extract the surface proton conduction, two pellets of different relative densities were prepared: a porous sample (R.D. = 60%) and a dense sample (R.D. = 90%). Comparison of conductivities with and without H2 revealed that only the porous sample showed a decrease in the apparent activation energy of conductivity by supplying H2. H/D isotope exchange tests revealed that the surface proton is the dominant conductive species over the porous sample with H2 supply. Such identification of a dominant conductive carrier facilitates consideration of the role of surface protonics in chemical reactions.

© 2019 Elsevier B.V. Ethanol steam reforming (ESR) is a promising reaction as a sustainable, carbon-neutral hydrogen production process. Because of their high activity and low cost, Co-based and Ni-based catalysts are suitable for industrial ESR processes. Nevertheless, these catalysts present several issues, such as deactivation by coke formation and methane formation as a by-product. This review summarizes the most recent three years works related to ESR for hydrogen production over non-noble transition metal catalysts, exploring their catalytic performance, coke formation, and reaction mechanisms, to provide direction for the development of high-performance catalysts. Findings suggest the particle size and oxidation state of the active metal, acid–base and redox properties of the support, and appropriate promoter selection as important factors to minimize coke and by-product formation.

Copyright © 2019 American Chemical Society. Eutectic mixture (EM)-promoted MgO sorbents exhibit high CO2 sorption capacities but experience a significant decrease in uptake after multiple sorption-regeneration cycles due to EM movement and redistribution at high temperatures. Encapsulation of a pseudoliquid, phase-changing EM promoter with MgO may thus prevent the loss of active interface by confining the EM within a fixed area inside a MgO shell. In this work, we successfully embedded an EM composed of KNO3 and LiNO3 in a MgO fiber matrix via core-shell electrospinning. The synthesized sorbent achieved relatively high and steady sorption capacities, maintaining a stable uptake of ∼20 wt % after 25 sorption-regeneration cycles. The sorbent was also characterized using various techniques including in situ transmission electron microscopy (TEM) to describe its morphology, from which it was confirmed that the eutectic salt existed in distributed hollow pockets within the MgO fiber matrix and stayed confined within these fixed areas, favorably limiting its movement and redistribution when exposed to high temperatures where it exists in the liquid form. The EM may also be described as a glue that holds the fiber together, while MgO acts as a protective shell that prevents structural changes and rearrangement caused by EM movement, allowing the sorbent to retain its cyclic stability after multiple cycles and demonstrating its potential for industrial use after further improvement. Thus, the microencapsulation of a phase-changing EM material with pure MgO metal oxide was successfully achieved and might be explored for various material applications.

© 2020 Author(s). Understanding heteroatom doping effects on the interaction between H2O and cerium oxide (ceria, CeO2) surfaces is crucially important for elucidating heterogeneous catalytic reactions of CeO2-based oxides. Surfaces of CeO2 (111) doped with quadrivalent (Ti, Zr), trivalent (Al, Ga, Sc, Y, La), or divalent (Ca, Sr, Ba) cations are investigated using density functional theory (DFT) calculations modified for onsite Coulomb interactions (DFT + U). Trivalent (except for Al) and divalent cation doping induces the formation of intrinsic oxygen vacancy (Ovac), which is backfilled easily by H2O. Partially OH-terminated surfaces are formed. Furthermore, dissociative adsorption of H2O is simulated on the OH terminated surfaces (for trivalent or divalent cation doped models) and pure surfaces (for Al and quadrivalent cation doped surfaces). The ionic radius is crucially important. In fact, H2O dissociates spontaneously on the small cations. Although a slight change is induced by doping as for the H2O adsorption energy at Ce sites, the H2O dissociative adsorption at Ce sites is well-assisted by dopants with a smaller ionic radius. In terms of the amount of promoted Ce sites, the arrangement of dopant sites is also fundamentally important.

© 2020 The Chemical Society of Japan CO2 methanation was conducted at low temperatures with an electric field. Results show that 5 wt %Ru/CeO2 catalyst exhibited high and stable catalytic activity for CO2 methanation with the electric field. The kinetic investigations and in-situ DRIFTS measurements revealed that Ru/CeO2 catalyst promoted CO2 methanation and Ru at the RuCeO2 interface (low-coordinated Ru sites) contributes to the reverse water gas shift reaction at low temperatures in the electric field.

© 2019 Hydrogen Energy Publications LLC For a liquid organic hydride system used for a hydrogen carrier, methylcyclohexane (MCH)–toluene cycle is promising. In this cycle, dehydrogenation of MCH is an endothermic reaction and a key step. We have conducted dehydrogenation of MCH over Pt/anatase-TiO2 catalyst in an electric field to promote MCH dehydrogenation at a temperature as low as 448 K. The electric field application brought high activity of 37% conversion even at 448 K, exceeding the thermodynamic equilibrium of 12%. This Pt/anatase-TiO2 catalyst showed only a small amount of methane and carbon by-production and showed high activity for 360 min because of surface protonics.

© 2019 Author(s). Efficient ammonia synthesis at low temperatures is anticipated for establishing a hydrogen carrier system. We reported earlier that application of an electric field on the Cs/Ru/SrZrO3 catalyst enhanced catalytic ammonia synthesis activity. It is now clear that N2 dissociation is activated by hopping protons in the electric field. Efficient ammonia synthesis proceeds by an "associative mechanism" in which N2 dissociates via an N2H intermediate, even at low temperatures. The governing factor of ammonia synthesis activity in an electric field for active metals differed from that in the conventional mechanism. Also, N2H formation energy played an important role. The effects of dopants (Al, Y, Ba, and Ca) on this mechanism were investigated using activity tests and density functional theory calculations to gain insights into the support role in the electric field. Ba and Ca addition showed positive effects on N2H formation energy, leading to high ammonia synthesis activity. The coexistence of proton-donating and electron-donating abilities is necessary for efficient N2H formation at the Ru-support interface.

© 2019 Elsevier B.V. Modified Ga-α-Al2O3 catalyst with Ba showed high catalytic activity, selectivity and low carbon formation on catalytic ethane dehydrogenation to ethylene even in the presence of steam. The resultant Ba-Ga-α-Al2O3 (Ba/Ga molar ratio = 0.10) catalyst showed high ethylene selectivity (98%), high activity, and stability. Temperature-programmed oxidation measurements revealed that Ba addition suppressed coke formation at Ga sites. XRD, XAFS and TEM results showed the existence of highly dispersed β-Ga2O3 on the α-Al2O3 support, irrespective of Ba addition. Observation of hydrogen adsorption using FT-IR spectroscopy revealed a decrease in the surface tetrahedrally coordinated Ga (designated as Ga(T)) sites by Ba modification, indicating that the surface Ga(T) sites are covered with Ba. Density functional theory calculation revealed that coke formation through ethylene decomposition is likely to occur at surface Ga(T) sites, and revealed that the addition of an optimal amount of Ba to Ga-α-Al2O3 inhibits coke formation at the surface Ga(T) sites, leading to high ethylene selectivity.

© Copyright 2019 American Chemical Society. Oxidative coupling of methane (OCM) over La1-xMxAlO3-δ (M = Ca, Sr, Ba; x = 0, 0.1, 0.2, 0.3) in an electric field at low temperature (423 K) was investigated. Among the tested catalysts, the La0.7Ca0.3AlO3-δ catalyst showed the highest performance in terms of C2H6 + C2H4 yield (11.1%). Surface mobile oxygen species (O22- or O-), which were considered as active oxygen species for the OCM reaction, increased with increasing Ca doping amount, and thereby the La0.7Ca0.3AlO3-δ catalyst showed the best catalytic activity.

Copyright © 2019 American Chemical Society. The role of the electric field and surface protonics on low temperature catalytic dry reforming of methane was investigated over 1 wt %Ni/10 mol %La-ZrO2 catalyst, which shows very high catalytic activity even at temperatures as low as 473 K. We investigated kinetic analyses using isotope and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and kinetic analyses revealed synergetic effects between the catalytic reaction and the electric field with less than one-fifth the apparent activation energy at low reaction temperatures. Results of kinetic investigations using isotopes such as CD4 and 18O2, in situ DRIFTS in the electric field, and density functional theory calculation indicate that methane dry reforming proceeds well by virtue of surface protonics. CH4 and CO2 were activated by proton collision at the Ni-La-ZrO2 interface based on the "inverse" kinetic isotope effect.

© 2019 Elsevier B.V. Toluene steam reforming was conducted over Ni-supported La0.7Sr0.3AlO3-δ (LSAO) perovskite oxide at 473 K in an electric field, and high toluene conversion was achieved even at such low temperature. Steam reforming is generally done at higher temperatures because of the endothermic nature of this reaction and coke prevention, which requires the contribution of heat energy in great amounts. Reportedly, water activation is particularly difficult to achieve at lower temperatures. Results of kinetic analyses such as Arrhenius plots and partial pressure dependence have revealed that imposing an electric field promotes water activation over Ni/LSAO catalyst. According to steady state isotopic kinetic analysis (SSITKA) and temperature programmed desorption infrared (TPD-IR) measurements, such water activation was accelerated via a redox mechanism using surface lattice oxygen of LSAO. The stimulated mobile lattice oxygen oxidized the adsorbed toluene and formed coke precursor in the electric field. The electric field achieved a lowered reaction temperature for efficient hydrogen production and coke suppression with redox property of LSAO support during toluene steam reforming.

自動車の排ガスの低温化に伴い、排ガス浄化触媒の低温域での活性向上が求められている。また、実際の排ガスには水蒸気が必ず含まれていることから、本研究ではPdを担持したペロブスカイト型酸化物を用いて、水蒸気の共存下におけるCOを還元剤としたNOx還元反応に着目した。その結果、Pd/La_0.9Ba_0.1AlO_3-δがCarbonateの脱離によってNOの吸着点を再生することで、水蒸気存在下において低温(150℃)で高活性を示すことを明らかにした。

© 2019 The Royal Society of Chemistry. Liquid organic hydrides are regarded as promising for use as hydrogen carriers via the methylcyclohexane (MCH)-toluene-hydrogen cycle. Because of the endothermic nature of MCH dehydrogenation, the reaction is usually conducted at temperatures higher than 623 K. In this work, low-temperature catalytic MCH dehydrogenation was demonstrated over 3 wt% Pt/CeO 2 catalyst by application of electric field across a fixed-bed flow reactor. Results show that a high conversion of MCH beyond thermodynamic equilibrium was achieved even at 423 K. Kinetic analyses exhibited a positive correlation of hydrogen to the reaction rates and an "inverse" kinetic isotope effect (KIE), suggesting that accelerated proton hopping with the H atoms of MCH promotes the reaction. Operando analyses and DFT calculation proved that the reverse reaction (i.e. toluene hydrogenation) was suppressed by the facilitation of toluene desorption in the electric field. The electric field promoted MCH dehydrogenation by surface proton hopping, even at low temperatures with an irreversible pathway.

© 2019 The Royal Society of Chemistry. CePO4 nanorods with uniform surface Ce sites could work as a durable catalyst and showed the highest C2 yield of 18% in an electric field without the need for external heating, which was comparable to that reported for high-performance catalysts at high temperature (>900 K).

© 2019 ISIJ Hypercoal (HPC) is examined as a caking additive to the mixture of strongly coking coal and non-slightly coking coal. Samples were coked, then their strength and crystallinity of the carbon structure by Raman spectra were measured. Hypercoal addition increased strength of coke, and a good correlation was observed between the mechanical strength of coke and the Raman parameter defined by the ratio of D3-band to G-band. Results suggest that mutual melting between blended coal and HPC brought strong carbonaceous structure with highly crystallized. The Raman parameter can predict the coke strength to some extent.

© 2019 The Royal Society of Chemistry. A Pd catalyst supported on Ba-substituted LaAlO3 perovskite (Pd/La0.9Ba0.1AlO3-δ) was investigated for NO reduction at low temperature by propylene, which revealed that Pd/La0.9Ba0.1AlO3-δ has remarkably higher activity than other Pd catalysts at low temperatures (≤573 K) for NO reduction by propylene. To elucidate the surface reaction pathway, transient response tests were conducted using 18O2. Also, X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements were conducted. Comparison with a Ba-impregnated catalyst (Pd/Ba/LaAlO3) demonstrated that Pd/La0.9Ba0.1AlO3-δ shows higher activity for the formation of oxygenated species (CxHyOz) as an intermediate for NO reduction because the surface lattice oxygen has improved mobility via Ba2+ substitution in LaAlO3. Therefore, Pd/La0.9Ba0.1AlO3-δ have high activity for NO reduction, even at low temperatures in a humid condition.

© 2019 The Chemical Society of Japan Heterogeneous catalytic reaction at low temperatures (<500 K) has been proposed and investigated by our group. As described in this report, recent trends of low-temperature catalytic reaction for hydrogen production by reforming and ammonia synthesis are summarized. Furthermore, our findings obtained using surface protonics for these two reactions are introduced. Surface protonics occurs by application of an electric field to a heterogeneous catalyst. It makes low-temperature catalytic reactions possible for hydrogen production and ammonia synthesis.

<p>Electric field facilitated MCH dehydrogenation at 423 K without methane and coke by-production over Pt/TiO₂ catalyst by surface protonics.</p>

A novel electrocatalytic reaction system that involves catalytic reaction in an electric field, for low-temperature catalytic ethanol steam reforming using low-grade waste heat for H2 production, was developed. The application of an electric field to Pt/CeO2 catalyst enabled the reaction to proceed even at 423 K, at which a conventional catalytic reaction only slightly proceeded. Results of activity tests conducted using isotopes revealed that the electric field contributed to activation of the adsorbed OHx species. In-situ DRIFTS measurements revealed that an electric field promoted the formation of reactive adsorbed intermediate acetate species and showed that the steam reforming reaction of the formed acetate species proceeded even at low temperatures. Results showed that ethanol steam reforming proceeded efficiently in the electric field at low temperatures. In this electrocatalytic reaction system, H2 was produced efficiently from ethanol using less electricity, even at low temperature. Applying the electric field lowered the apparent activation energy of three elementary reactions, namely ethanol dehydrogenation, acetaldehyde decomposition, and acetaldehyde steam reforming. In particular, the electric field preferentially promoted acetaldehyde steam reforming. Energy demand for H2 production in this electrocatalytic process was sufficiently low, at 79 MJ/kg H2, which was about half of the combustion enthalpy of hydrogen.

© 2018 American Chemical Society. 10wt%Ni-10wt%Mg-La0.1Zr0.9O2-x (LZO) catalyst shows high reforming activity of methane while suppressing methane combustion on tri-reforming of methane at low temperatures of 473 K in an electric field. On the basis of results of light-on and light-off tests for methane oxidation and temperature dependencies for catalytic methane steam reforming activity with or without the electric field, we found that Mg addition to 10wt%Ni-LZO catalyst suppresses methane combustion, while the methane steam reforming proceeds well by virtue of surface protonics in the electric field. Ni2+ on 10wt%Ni-10wt%Mg-LZO catalyst was more cationic than that on 10wt%Ni-LZO catalyst, and NiO-MgO solid solution formed on LZO support played an important role in combustion suppression.

© 2018 Elsevier B.V. Recent trends on the direct conversion of methane, employing carbon dioxide as an oxidizing agent are reviewed. While oxidation using molecular oxygen involves the sequential oxidation of various intermediates to generate carbon dioxide and exhibits low selectivity for the desired products, methane activation using carbon dioxide as an oxidant eliminates this sequential oxidation and has considerable promise. In this context, supported metal catalysts can promote the dry reforming of methane, and structured oxide catalysts have been found to enable methane coupling to C2 products, using carbon dioxide as the oxidizing agent. This review also summarizes recent research regarding the use of nonconventional processes for methane activation in conjunction with carbon dioxide.

© 2018 Elsevier B.V. The structure of Pt-Mn/Al2O3 catalyst which shows high performance for dehydrogenation of methylcyclohexane, a prospective hydrogen carrier, was investigated by XAFS and DFT calculations. Mn addition on Pt/Al2O3 brings higher activity, selectivity, and stability for dehydrogenation of MCH than with Pt/Al2O3 alone. Results of XAFS and DFT calculations revealed that MnOx selectively covered the unsaturated coordination of Pt. On the unsaturated step facets such as Pt (1 1 0) and Pt (3 1 1), demethylation proceeds easily. Addition of Mn on Pt/Al2O3 catalyst brought selective dehydrogenation of MCH by coverage of such step sites with MnOx.

© 2018 Hydrogen Energy Publications LLC The catalytic steam reforming of dimethyl ether (DME) in an electric field was carried out and the effects of proton hopping induced by the electric field on a Pd-supported CeO2 catalyst surface were investigated. The hydrolysis of DME was promoted even on Pd/CeO2 catalyst by the application of the electric field at low temperatures (in the range of 423–623 K), while the direct decomposition of DME was suppressed. The apparent activation energy in this temperature range was much lower with (17.2 kJ mol−1) than without (79.0 kJ mol−1) the electric field. Kinetic analyses demonstrated that the effect of the reactant partial pressures was also markedly different with and without the electric field. The effect of the partial pressure of water and electrochemical impedance spectra strongly suggest that surface proton hopping promotes the steam reforming of DME in an electric field at low temperatures.

© 2018, Springer Science+Business Media, LLC, part of Springer Nature. Abstract: Ammonia is an important chemical feedstock and is produced by Ru or Fe catalyst so far. We investigated Co catalyst for low temperature ammonia synthesis in an electric field. Well-reduced Co/Ce0.5Zr0.5O2 catalyst showed high activity for ammonia synthesis even at 473 K in the electric field. Various characterizations including kinetic tests, operando DRIFTS measurements, TEM observations, and XAFS measurements, revealed that the active site is the interface between supported Co and Ce0.5Zr0.5O2 oxide support, thanks to the surface protonics derived from an electric field. Graphical Abstract: [Figure not available: see fulltext.].

© 2017 Elsevier B.V. To elucidate the reaction mechanism of catalytic steam reforming of methane in an electric field, operando–diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) has been used to investigate methane dissociative adsorption at low temperatures using CH4, H2O, and their isotopes. Operando-analyses demonstrated that methane was adsorbed and converted into CO and CO2 more when CD4 and/or D2O was used instead of CH4 and/or H2O. This observed “inverse” kinetic isotope effect is based on the difference of C–H–H vibrational energy level at the transition state. Furthermore, CO2-methanation, which is the reverse reaction of steam reforming of methane, was irreversible with H2O in an electric field. These results demonstrate that the proton collision promoted methane activation irreversibly, even at low temperatures in an electric field.

© 2017 Elsevier B.V. We have found that an electric field brings high yield on low temperature catalytic ammonia synthesis over Cs/Ru/SrZrO3 catalyst. The role of the electric field is investigated based on kinetics and isotope effects.Results show that the electric field promotes proton hopping on the catalyst surface, and it brings a change in the reaction mechanism from the conventional one to the N2H+ intermediate mechanism. In the electric field, N2H+ intermediate plays an important role, enabling low-temperature ammonia synthesis.

© 2017 Elsevier Ltd Surface protonic transport on cerium oxide (CeO2) was investigated using electrochemical impedance spectroscopy (EIS). CeO2 pellets showing low relative density: approximately 60%, was prepared for the purpose. The structure and morphology of the prepared CeO2 pellets were confirmed from XRD and SEM measurements. Results show that the pellets had a pure cubic phase, with open pores on which water can be adsorbed. Electrochemical impedance spectroscopy measurements were taken to evaluate the surface protonic transport on CeO2 as a function of temperature and as a function of partial pressure of water (PH2O) at 400 °C. Investigations of the temperature dependence of the conductivity revealed that only the conductivities of surface grain bulk (σintra) and surface grain boundary (σinter) increased with decreasing temperatures under wet conditions (PH2O = 0.026 atm). The PH2O dependence of surface conductivities (σintra and σinter) revealed that σintra increases strongly with PH2O at 400 °C. These findings provide evidence that water adsorbates play an important role in surface protonic transport on CeO2 at low temperatures. Surface protonic transport at low temperatures can contribute to the expansion of applications for electrical and catalytic processes.

© 2018 American Chemical Society. Detailed reaction mechanisms for the oxidative coupling of methane (OCM) over Ce2(WO4)3 catalysts at low temperatures in an electric field were investigated. The influence of Ce cations in the Ce2(WO4)3 catalyst was evaluated by comparing the OCM activity over various Ln2(WO4)3 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy) catalysts in an electric field. The electronic states of Ln and W cations and the relationship between the distorted Ce2(WO4)3 structure and methane activation were examined using X-ray absorption fine structure (XAFS) measurements and first-principles calculations. The results reveal that the Ln2(WO4)3 catalysts with redox-active Ln cations (Ce, Pr, Sm, Eu, and Tb) show OCM activity. First-principles calculations indicate that Ce3+ species in the Ce2(WO4)3 structure are oxidized to Ce4+ species in an electric field by extracting electrons from the Ce 4f orbitals near the Fermi level; as a result, its structure is distorted. The results indicate that the redox reaction of Ln cations in Ln2(WO4)3 induced by an electric field brings lattice strain and a high OCM activity in an electric field.

© 2017 Elsevier B.V. We examined oxidative coupling of methane (OCM) and oxidative dehydrogenation of ethane (ODE) over various polyoxometalate supported CeO2 catalysts at 423 K in an electric field. Tetrabutylammonium (TBA) salt of Keggin-type phosphotungstate (PW12O40) supported CeO2 catalysts ((TBA)3PW12O40/CeO2) showed high activities for OCM and ODE in the electric field (3 mA) at 423 K, although the catalyst without the electric field showed extremely low activities at such low temperature. FT-IR spectra and XRD patterns confirmed that the structure of (TBA)3PW12O40/CeO2 was changed to Ce2(WO4)3/CeO2 after reactions with the electric field, and it acted as an active site structure for OCM and ODE with the electric field. Results of activity tests revealed that the C2H6 production was a main reaction in OCM with the electric field, and C2H4 was formed through a successive oxidative dehydrogenation of the formed C2H6. Periodic operation tests demonstrated that reactive oxygen species suitable for ODE were formed on the catalyst surface of Ce2(WO4)3 in the electric field.

© 2017 Elsevier B.V. The effect of steam treatment on Zn/H-ZSM-5 catalysts prepared by an ion-exchange method for non-oxidative ethane dehydroaromatization was investigated. Steam treatment of Zn/H-ZSM-5 after Zn loading improved its catalytic stability on aromatic hydrocarbon formation including benzene, toluene and xylene. Temperature programmed oxidation measurements demonstrated that the steam treatment brought suppression of coke formation and it contributed to the improvement in the catalytic stability. Characterization of the local structure of the zeolites by 27Al and 29Si magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy revealed that dealumination of the framework Al in the MFI structure proceeded by steam treatment. Results of temperature programmed desorption of ammonia indicate the decrease in the amount of acid sites by the steam treatment. The slight changes in Zn content and its electronic state indicated that bared Al related with H+, not with Zn2+, in the MFI structure was preferentially dealuminated by steam treatment. The preferential dealumination led to suppression of coke formation by the selective removal of undesirable Brønsted acid sites.

Organic chemical hydrides are one of the most potential methods for hydrogen storage, however, aromatic compound remains unreacted after the hydrogenation process due to equilibrium limitations. To address this, a solid-state adsorbent which could selectively adsorb toluene from methylcyclohexane - toluene mixture was developed. Several La-based oxides were tested and La0.8Ba0.2CoO3-d (LBCO) exhibited high adsorption and selectivity for toluene. Analyses of the electronic state and adsorption state of toluene found part of the Co ions in the LBCO lattice were Co4+. The high oxidation state of Co4+ in the LBCO lattice and surface lattice oxygen mediates the selective adsorption of toluene.

© 2018 The Chemical Society of Japan. We investigated a highly active hydrogen production system by decomposition of water through the redox reaction of metal oxide at 623 K in an electric field (EF). Although Ce0.67Cr0.33O2 oxide showed high activity in the EF for oxygen release with the formation of lattice oxygen defects, it showed no hydrogen production activity by the regeneration of lattice oxygen defects with water. However, addition of Pd into the Ce0.67Cr0.33O2 structure promoted the hydrogen formation rate while maintaining its oxygen release activity. Results of optimization of the doping Pd amount demonstrated that 5 mol% Pd-doped oxide (Ce0.62Cr0.33Pd0.05O2) had the highest oxygen release rate and hydrogen formation rate. Doped Pd contributes to lattice strain induction and thereby increases the reaction rates.

© 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Direct conversion of methane, other hydrocarbons, and alcohol at lower temperatures can be achieved using plasma or an electric field and catalysts. Non-equilibrium plasma enables activation of stable molecules including methane, carbon dioxide, and water, even at low temperatures, by virtue of high electron energy. Use of a hybrid system of plasma and catalyst provided high conversion and selectivity to products by virtue of adsorption on the catalyst. Imposing a DC electric field to the catalyst bed also promotes catalytic reactions, even at low temperatures. Two mechanisms for electro-catalytic reactions are proposed for the DC electric field imposition: reactant activation by surface protonics and production of active surface oxygen species on the catalyst. This review presents summaries of these novel processes.

© 2017 Elsevier Ltd. Methane conversion was conducted over various perovskite oxide catalysts at 423 K using carbon dioxide as an oxidant in an electric field. La0.7Ca0.3AlO3-δ catalyst showed high CO2-OCM activity. The highest CO2-OCM activity, C2 yield of 7.4%, was obtained even at 348 K, that value was higher than those of other earlier reports. Dry reforming of methane to produce syngas (H2 + CO) proceeded simultaneously, and no other byproduct was observed. Results of in-situ IR, XRD and TG measurements demonstrated that CO2 adsorption on the catalyst surface and formation of La2O2CO3 intermediate are important for progress of the CO2-OCM reaction, even at low temperature in an electric field. Ca atom incorporated in LaAlO3 perovskite played an important role in C2 hydrocarbon formation.

© 2016 Elsevier B.V. Ba addition to supported Ni catalysts was investigated on steam reforming of toluene, as a model compound of biomass tar. Ba addition showed drastic promotive effects on catalytic activity and tolerance against oxidation. Various catalytic tests and characterization were conducted, including pressure dependence, Arrhenius plots, STEM and XAFS observations, dispersion of supported Ni, and temperature programmed reduction. Results revealed that the electron donation from Ba to Ni enabled high catalytic performance of Ba/Ni/LaAlO3 perovskite catalyst.

<p>Catalytic reaction of biomass cellulose into C₃ and C₄ light hydrocarbons over Pt supported catalyst was investigated. Pt supported on NH₄⁺-form ultra-stable Y type (NH₄-USY) zeolite catalyst (Pt/NH₄-USY) enabled direct conversion of cellulose into C₃ and C₄ hydrocarbons without hydrogen and other expensive reagents. Results revealed that 1wt%Pt/NH₄-USY(14) catalyst showed higher C₃+C₄ hydrocarbon yield than 1wt%Pt/H-USY(14). The yield reached 14.5C-% during reaction over the 1wt%Pt/NH₄-USY(14) at 443 K for 72 h reaction. Furthermore, because of their structural sensitivity, Pt/zeolite catalysts with Pt particle larger than 5 nm showed higher TOF values than catalysts with Pt particle smaller than 5 nm. The high index {311} facet was observed on Pt particles only when the Pt particle size was 5 nm or larger, suggesting that hydrocarbon formation mainly proceed over the facet.</p>

Dehydrogenation catalysts were analyzed to improve the performance of the ethane cracking tube. Ga, Ge, In, and Sn were studied as dehydrogenation catalysts. Catalytic activity tests showed that the Ga catalyst has the best performance among them. Because the γ-Al2O3 supported Ga catalyst calcined at 1323 K showed high catalytic activity and stability, the structure and the role of Ga using BET, XRD, TEM-EDX, and XAFS measurements were studied. Screening results revealed that the Ga catalyst exhibited a high ethylene formation rate and better ethylene selectivity.

Tri-reforming of CH4 for syngas production was studied over Ni supported catalysts in an electric field at low temperature of 473 K. The main objective is to gain enthalpy from exhaust gases of automobiles using an exhaust gas recirculation system, so high CH4 conversion and low combustion were anticipated. Results showed that La0.1Zr0.9O2 catalyst was the most appropriate support in the electric field. Also, Results showed that the addition of Mg to Ni-supported catalyst suppressed CH4 combustion.

© 2017 The Chemical Society of Japan. Pyrolysis of propylene in a DC electric field was investigated. The resulting nanostructure of carbon particles differs drastically depending on the electrode potential. It indicates that regulating ion species in hydrocarbon pyrolysis presents a means to control the nanoform of carbon particles.

© 2016 Elsevier B.V. Dry reforming of methane (DRM) was conducted over various transition metal supported ZrO2catalysts in an electric field. Catalyst of 1wt%Ni/10 mol%La-ZrO2showed high DRM activity even at 423 K of external temperature, at which no DRM proceeds in the conventional catalytic systems. By virtue of the low reaction temperature, low amounts of carbon deposition were confirmed even in conditions of high CH4conversion in the electric field. The imposed electric power was correlated to with the catalytic activities in the electric field. Syngas is producible at low temperature with high energy efficiency.

© 2017 The Chemical Society of Japan. Co/Sr-hydroxyapatite catalyst (Co/Sr10(PO4)6(OH)2: Co/ Sr-P) shows high activity and low carbon formation on ethanol steam reforming. H2-TPR measurements revealed that the Co species supported on Co/Sr-P was reduced only slightly more than that on typical Co/α-Al2O3. XAFS measurements revealed that Co2+ species was observed mainly on the Co/Sr-P catalyst after H2-reduction at reaction temperature of 823 K. Co2+, i.e. CoO particle, on Co/Sr-P catalyst plays an important role as an active site for ethanol steam reforming with high coke resistance.

© 2017 Elsevier B.V. To elucidate specific functions of supports, we investigated steam reforming of toluene as a model compound of biomass tar over Co catalyst supported on perovskite-type oxide. Co-supported La0.7Sr0.3AlO3-δ catalyst showed the highest activity among various Co-supported catalysts. STEM measurements and XPS measurements revealed the coexistence of La cation and lattice oxygen defect produces an anchoring effect to Co particles. The lattice oxygen release rate on each catalyst was measured with H218O steady-state isotopic transient kinetic analysis (SSITKA). The anchoring effect, higher dispersion of Co and redox property, are important for the high catalytic performance of Co/La0.7Sr0.3AlO3-δ catalyst on toluene steam reforming.

<p>We accomplished efficient electrocatalytic low-temperature ammonia synthesis with the highest yield reported to date.</p>

© 2017 Elsevier B.V. Methylcyclohexane (MCH) is a prospective hydrogen carrier candidate. Although Pt/Al2O3 catalyst shows high conversion for dehydrogenation of MCH at 623 K, methane formation and deactivation caused by coke deposition are issues over the catalyst. Results of this study demonstrate that Mn addition to Pt/Al2O3 brought higher selectivity and stability for dehydrogenation of MCH than with Pt/Al2O3 alone. Although Pt and Mn do not form an alloy structure, Pt and Mn form an adjacent structure, and the unsaturated coordination of Pt which promotes methane formation and deactivation decreased. Pt-Mn/Al2O3 shows high catalytic performance by virtue of the coverage of such sites by MnOx.

© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Direct catalytic hydrothermal conversion of cellulose to C3+C4 hydrocarbons at a low temperature (443 K) over a Pt/zeolite catalyst without hydrogen or other expensive reagents was investigated. Pt supported on NH4+-form ultra-stable Y-type (NH4-USY) zeolite catalyst, which showed the highest activity among the tested Pt/zeolite catalysts, has appropriate acidity and a suitable active Pt site. The C3+C4 hydrocarbon yield reached 14.5 C-% during the reaction over the Pt/NH4-USY catalyst at 443 K after 72 h of the reaction. Results showed that the acid strength of the zeolite support was an important factor affecting the cellulose decomposition activity. Because of their structural sensitivity, Pt/zeolite catalysts with Pt particles larger than 5 nm, including Pt/NH4-USY catalyst, showed higher TOF values than catalysts with Pt particles smaller than 5 nm.

© 2017 The Chemical Society of Japan. Non-oxidative ethane dehydroaromatization to form aromatic hydrocarbons was investigated over various metal supported on H-ZSM-5 catalysts. Co/H-ZSM-5 prepared using an ion-exchange (IE) method exhibited high catalytic performance with a small amount of carbon deposition. Results obtained from temperature-programmed reduction and X-ray absorption fine structure spectroscopy indicate that stable Co2+ cations exist on Co/H-ZSM-5 IE during the reaction. Co2+ cations efficiently activate ethane without coke formation.

© The Author(s) 2016. Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando-IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd-CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics.

© 2016 Elsevier B.V. All rights reserved. Water gas shift (WGS) reaction over a noble metal free Co-system catalyst was investigated. Although K/Co3O4 showed no WGS activity with no pre-treatment, it showed high and stable activity after reduction by CO + H2 (syngas). Moreover, the high activity was retained even after post-treatment in water vapor. Characterization of the catalyst was conducted using XRD, XPS, and XAFS, which revealed that conducting pre-reduction, especially using CO + H2 caused the formation of Co2C, which is a potential candidate as an active site, and that K donated electrons during reduction to form stable Co2C, suppressing the formation of metallic Co. The catalyst has high competence in activity with noble metal WGS catalysts and conventional LTS catalyst, which can be a promising candidate for a WGS reaction catalyst.

© 2016, Springer Science+Business Media New York. Abstract: Catalytic water gas shift for hydrogen production in the temperature range of 423–873 K, was examined imposing an electric field to the catalyst bed. Reaction trends were investigated based on thermodynamic equilibrium and chemical kinetic law. Pt/La–ZrO2 was chosen as an active catalyst through our screening tests, and the effect of the electric field on the catalytic activity was investigated by changing reaction temperatures and applied electric currents. Although the reaction was ruled by thermodynamic equilibrium at high temperatures, drastic promotion of the reaction by applying the electric field was observed at low temperatures in a kinetic region. Drastic decrease of apparent activation energy for WGS was observed by imposing the electric field to the catalyst bed. Various isotopic transient tests revealed that the reaction mechanism changed by the application of electric field, and redox mechanism using surface lattice oxygen played an important role in case of the catalytic WGS in the electric field. Graphical Abstract: [Figure not available: see fulltext.]

© 2015 Elsevier B.V. All rights reserved. We investigated steam reforming of toluene as a model compound of aromatic hydrocarbons included in biomass tar over Co supported La0.7Sr0.3AlO3-δ (LSAO), perovskite oxide. Ni-supported LSAO catalyst has shown high activity and coke resistance from the redox property of lattice oxygen in/on the LSAO support. Co is known as an active metal for this reaction, so Co/LSAO catalyst was investigated in this work. Co/LSAO catalyst, which showed high steady-state activity and stability, was characterized using H218O isotopic transient response tests, STEM, FT-IR, Arrhenius plot and partial pressure dependence to elucidate high and stable catalytic activity. In situ FT-IR measurements revealed that reaction intermediates on Co/LSAO desorbed at 873 K or lower temperatures. Although redox property of lattice oxygen did not change at around 848 K based on isotopic transient tests, the Arrhenius plots indicate that the rate-determining step changed at around 848 K because of reaction intermediate decomposition desorption. Fast reaction and desorption of absorbed intermediates on Co/LSAO enable catalytic stability during toluene steam reforming.

We examined oxidative coupling of methane (OCM) over various Ce-W-O catalysts at 423 K in an electric field. Ce2 (WO4)3/CeO2 catalyst showed high OCM activity. In a periodic operation test over Ce2 (WO4)3/CeO2 catalyst, C 2 selectivity exceeded 60% during three redox cycles. However, Ce2 (WO4)3/CeO2 catalyst without the electric field showed low activity, even at 1073 K: CH 4 Conv., 6.0%; C 2 Sel., 2.1%. A synergetic effect between the Ce2 (WO4)3 structure and electric field created the reactive oxygen species for selective oxidation of methane. Results of XAFS, in-situ Raman and periodic operation tests demonstrated that OCM occurred as the lattice oxygen in Ce2 (WO4)3 (short W-O bonds in distorted WO 4 unit) was consumed. The consumed oxygen was reproduced by a redox mechanism in the electric field.

第117回触媒討論会B講演予稿

電場印加したエタノール水蒸気改質による水素製造において、触媒の物性や反応条件が反応の活性および選択性に及ぼす影響について検討した。これまでに当研究室では、電場を印加することにより423Kでのエタノール水蒸気改質の反応進行を実現している。本報告では、低温でのさらなる活性向上を目的として、担体の比表面積やPt担持量といった触媒の物性、外熱供給温度や印加電流値といった反応条件が反応の活性および選択性に及ぼす影響を検討したので報告する。

水素の貯蔵・運搬法として知られる有機ハイドライド法には、芳香族炭化水素の水素化反応において平衡制約により未反応の芳香族化合物が残存してしまうという問題がある。本研究では、トルエン-メチルシクロヘキサン系をモデルとして、水素化過程での未反応のトルエンを選択的に吸着する材料の開発を目的としている。種々の材料のトルエン選択吸着性について検討を行ったところ、La0.8Ba0.2CoOが高い選択吸着性を示したため、これについて報告する。

Niをペロブスカイト型酸化物担体に担持した触媒を用いて、トルエン・メチルシクロヘキサン・ヘプタンなどの水蒸気改質による水素製造を比較した。また、それらの吸着挙動についても詳細に検討した。その結果、格子内に異価カチオンを導入した場合は、比較的低温で格子酸素が酸化還元でき、トルエンの水蒸気改質が酸化還元を介して選択的に進行した。一方で、異価カチオンを導入していない場合は酸化還元が起こりにくく、炭素析出が起こりやすいことがわかった。その際の吸着のしやすさの点では、環化できる化合物は容易に環化して吸着したが、C5以下あるいは2,2−DMBのような環化できない化合物の場合は吸着・反応が起こりにくいことがわかった。

水素の貯蔵・運搬方法として有機ハイドライド法に着目し、中でもメチルシクロヘキサン（以下MCH）の脱水素反応に対して有効な触媒の開発を行った。MCH脱水素においてPt/Al2O3触媒が高活性であることが知られているが、副反応であるメタン生成によって反応選択性が低下してしまうことが問題である。本研究室では、Pt/Al2O3に対するMnの微量添加によって脱水素活性及び反応選択性が向上することを見出した。今回はMn添加効果による触媒性能の向上の要因を詳細に検討した。

K/Co3O4触媒に対して、CO/H2混合ガスを用いた前還元処理を行うことにより、高価な貴金属を用いなくても水性ガスシフト反応に対する高い活性を定常的に得られることが分った。XRD測定からは、還元処理によって担体表面がCo2Cへと変化していることが分かり、XPS測定やXAFS測定からはCo3O4に対して適切な量のKを担持することで、活性を示さないCo metalの生成を抑止し、2価のCoが効率的に形成されるということがわかった。

本研究では、エタンクラッカーの反応器表面における触媒作用を検討し、新たな触媒作用を発現させることを目的とした。反応器表面に異なる金属酸化物を析出させたクラッキングチューブのエタン転化率・エチレン選択率を測定し、同体積・表面積の石英と比較することによってその触媒特性を検討した。また、チューブ内面を修飾するための脱水素触媒について、種々の金属を担持させたα－アルミナを触媒として、脱水素活性を比較した。今回は以上の二点について報告する。

自動車の燃費向上のために、排気ガスを用いた燃料の改質を行う。排気ガス温度域が低いため電場を用いて反応場の低温化を行った。エンタルピー回収のためには燃料モデルであるメタンの燃焼を抑制し、改質を選択的に進行させる必要がある。スクリーニング結果からNi担持触媒へのMg添加により燃焼を抑制することがわかった。その燃焼抑制機構の検討のために、Ni-Mg担持方法や担持量の検討およびキャラクタリゼーションを用いた。

種々のCo/酸化物触媒上でトルエン改質活性試験及び各種キャラクタリゼーションを実施した。FE-TEM測定やXPS測定より、担体格子にLaと格子欠陥が共存する場合にCo粒子と担体間でアンカリング効果が確認され、Coが高い分散性を持つことがわかった。また、同位体交換試験やXPS測定から原料の活性化には担体の酸素レドックス能が重要であることがわかった。アンカリング効果とレドックス能の両立により、10wt% Co/La_0.7Sr_0.3AlO_2.85が最も高い活性を示した。<br><br>

従来のエタンクラッカーは高温、無触媒でエタンの脱水素反応を起こしており、如何に副反応を抑えるかに焦点を当てている。その点において、クボタ社のAFTALLOYは最高レベルの性能を示すということを前回報告した。本研究では、AFTALLOY以上の性能を持ったクラッキングコイルを開発するため、触媒の導入を試みている。今回、Gaを用いて高い活性安定性を示すことに成功したので報告する。

C₃H₆を還元剤に用いたNO還元においてPdを活性金属として種々の担体を用いた触媒について検討を行った。Pdと担体との相互作用による活性の向上効果を狙い、担体にペロブスカイト型酸化物などを用いて検討を行った。その結果、LaAlO₃などの担体を用いた場合にPd/Al₂O₃と比較し低温で高いNO転化率を示した。またLaAlO₃のLaサイトにBaを一部置換した際にBaを担持した際よりも高い活性を示した。そこで、Ba置換による触媒構造の変化がPdへ与える影響の検討を行った。また。FT-IR測定によって反応中間体の検討を行ったので報告する。

これまで電場中においてOCM活性を示す活性点構造はCe₂(WO₄)₃であると報告した。電場中でCe₂(WO₄)₃が高OCM選択性を示す理由を検討するためエタンを出発物質とした電場触媒反応を実施した。その結果C₂H₄の選択率が50%を超えることが分かった。OCMにより得られたC₂H₆の脱水素反応は優先的に進行するが，メタンへの分解やC₃₊の生成が殆ど起こらないため，高いC₂選択性を示すと考えられる。

エタンの芳香族化反応ではZn、Ga、PtなどをH-ZSM-5に担持した触媒が高活性であることが報告 されているが、その他の金属においては報告がほとんどされていない。そのため、遷移金属を中心に担持金属のスクリーニングを行った結果、Co、Zn、Ga が比較的高い芳香族収率を示した。しかし、経時的には芳香族選択率が低下し、エチレン選択率が増加したことから、析出した炭素による細孔閉塞あるいは活性 点被覆が起こっていると考えられる。

これまで当研究室で報告してきた電場触媒反応では、触媒担体に半導体性が必要であった。従来は電場印加が不可能で放電を起こす絶縁体材料や、通電し特異な触媒活性を示さない導体材料をコアとして用い、その表面に電場印加が可能な半導体性酸化物を担持し、電場を印加するためのシェルを形成した。コアの電気伝導性が異なる種々のコアシェル触媒に電場を印加してメタン転換反応を試み、消費電力や反応活性等について検討した。

現在、水素は様々な用途に使用され、さらなる需要の増大が予想される。水素製造法には水蒸気改質や電気分解等があげられるが、化石資源を使用する点や効率性の点で問題があり、高効率で持続的な水素製造法が必要である。当研究室では触媒層に微弱な電流を流し反応を高効率に進行させる電場触媒反応を用いて水素製造を行った。複合酸化物を用いた触媒のRedoxを利用し、高効率な水素製造に成功した。また水素生成機構の分析を行った。<br>

水素の貯蔵・運搬法として知られる有機ハイドライド法には、芳香族化合物の水素化過程で平衡制約により残存する未反応物への対策が課題として残されている。そこで本研究では特にメチルシクロヘキサン・トルエン系に着目し、トルエンを選択的に吸着分離するための吸着材の開発を目的としている。<br>今回は既にトルエン選択吸着性を持つことを確認したLa_0.8Ba_0.2CoO₃について、吸着したトルエンの脱離挙動について検討を行ったためこれについて報告する。

セルロースからC₃、C₄炭化水素への1段転換反応について検討した。今回の報告では、Pt担持ゼオライト触媒を用いた様々な触媒調整法による活性の違いを調べた。担体や前駆体の違いから触媒の物性が大きく変化したことで活性に違いが見られた。それに対し、触媒のキャラクタリゼーションから触媒物性とC₃、C₄軽質炭化水素選択性など各種パラメーターとの相関を検討した。併せて液体成分の分析結果も報告する。

© 2015 Elsevier B.V. All rights reserved. One-pot direct catalytic conversion of cellulose to light hydrocarbon at low temperature (443 K) in the presence of Pt-zeolite catalysts and water was investigated. Results revealed that Pt supported on H+-form ultra stable Y-type (H-USY) zeolite catalyst (Pt/H-USY) enabled direct conversion of cellulose into C3 and C4 hydrocarbons without hydrogen and other expensive reagents. This production trend is attributable to the bifunctional catalysis of supported Pt and acid site in H-USY zeolite, which has a large pore system and effective acidity. Results revealed that the pre-treatment of catalyst was important for selective olefin production. Air-oxidized Pt/H-USY catalyst showed higher olefin selectivity than the catalyst reduced with hydrogen. The Pt/H-USY catalysts showed high stability under the reaction condition. Results suggest that C5 sugars were the reaction intermediate for the C3 hydrocarbons, and C6 sugars were the intermediate for C4 hydrocarbon formation from cellulose over Pt/H-USY catalysts.

Catalytic ethanol steam reforming over Pt/CeO2 catalyst in an electric field at low temperature and the effect of the electric field and controlling factors for the activity and selectivity were investigated. With the electric field ethanol steam reforming proceeded at temperatures as low as 423 K at which the conventional catalytic reaction hardly proceeded. Conversion of ethanol and H2 yield significantly increased with the electric field and apparent activation energies for ethanol dehydrogenation acetaldehyde decomposition and acetaldehyde steam reforming were lowered by the electric field. In-situ DRIFTS measurements revealed that the adsorbed ethanol formed reactive acetate species with the electric field even at low temperature which improved H2 selectivity.

© 2016 The Chemical Society of Japan. We synthesized a characteristic graphene-layered carbon particle composite using pyrolysis of hydrocarbon in an electric field and consecutive activation treatment under CO2 atmosphere. TEM, N2 adsorption isotherm, Raman spectroscopy, and XPS revealed structural features of this unique composite. Graphenes and carbon particles in the resultant composite are combined homogeneously in nanoscale with a mesoscale structure and with high carbon purity. When Pt nanoparticles are loaded on the composite, they show high performance as an electrocatalyst because of their higher electrochemical active surface area and higher durability against the sintering of Pt nanoparticles. Resulting material is a multifunctional composite by virtue of its nanostructural features.

© 2015 Springer Science+Business Media New York. Methylcyclohexane (MCH) is expected as a hydrogen carrier. Dehydrogenation of MCH was conducted over supported Pt catalysts at 623 K. Pt/TiO2 showed high stability for dehydrogenation and good resistance for coke formation. The partial pressure dependence of MCH, toluene, and H2 was investigated for Pt/TiO2 and Pt/Al2O3 catalysts, which showed different tendencies for toluene partial pressure. The reaction order of toluene partial pressure for Pt/TiO2 was almost zero, but that for Pt/Al2O3 was a negative value. Toluene inhibited the Pt/Al2O3 catalytic activity, but that of Pt/TiO2 was unaffected. The SMSI effect was confirmed on Pt/TiO2 by CO chemisorption measurement. Pt on TiO2 became an electron-rich state compared to Pt0 because of the electron donation from TiOx, and the toluene adsorption to Pt on TiO2 was weakened.

© 2015 American Chemical Society. 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. (Figure Presented).

© 2015 Elsevier Ltd. All rights reserved. Abstract For this study, pyrolytic carbon particles were synthesized in a pyrolytic reactor in which a moderate electric field by DC power was generated between two electrodes at the center of the pyrolysis zone at 1573 K. The resulting carbon particles, which were collected on the top of the electrode, were analyzed to assess their microstructure and nanostructure using TEM observation, Raman spectroscopy, X-ray diffraction measurement, and light scattering size distribution measurements. Results showed that the resulting carbon particles formed a characteristic structure; the anisotropic chain-like configuration (fractal dimension, Df = 1.65 ± 0.02), with graphitic thin nanolayers having high crystallinity covering the surface of these aggregates. Morphological analysis with the concept of the fractal dimension of the aggregate indicates that the electric field regulates the aggregate morphology. The other experiment which the carbon source was fed onto prefabricated pyrolysis carbon particles under 1537 K showed that surface graphitic layers on the aggregate was derived from gas phase carbon sources, not from graphitizing of the surface structure of carbon particles. The ultrasonication of carbon particles with/without surface graphitic layers in the ethanol solution also confirmed that the specific role of the layers that supports stabilization of the aggregate configuration.

© 2015 Elsevier B.V. All rights reserved. We investigated the catalytic activity of Co/K/α-Al<inf>2</inf>O<inf>3</inf> with various potassium (K) loadings for ethanol steam reforming. The promotion effect of K loading and the role of K in Co/K/α-Al<inf>2</inf>O<inf>3</inf> were investigated using TEM-EDX, H<inf>2</inf>-TPR, XAFS, XPS, and IR measurements. Results show that loading of 1-2 wt% K on Co/α-Al<inf>2</inf>O<inf>3</inf> was effective for improving catalytic activity, selectivity to hydrogen and suppressing by-product (CH<inf>4</inf>, C<inf>2</inf>H<inf>4</inf>, and coke) formations. Measurements by H<inf>2</inf>-TPR and XAFS showed that the reducibility of the supported Co species decreased by K loading. TEM measurements revealed that the Co⁰-CoO core-shell structure was formed over Co/K/α-Al<inf>2</inf>O<inf>3</inf> during ethanol steam reforming at 823 K, suggesting that the oxidized Co species (CoO) is a highly active species in ethanol steam reforming. In situ IR measurements revealed that the adsorbed ethanol forms stable acetate species by K loading, which improves hydrogen selectivity.

One-pot direct catalytic conversion of cellulose to light hydrocarbon at low temperature (443 K) in the presence of Pt-supported catalysts and water was investigated. Pt supported on H^+-form ultra-stable Y-type (H-USY) zeolite catalyst (Pt/H-USY) enabled direct conversion of cellulose into C_3 and C_4 hydrocarbons without hydrogen and other expensive reagents. Results revealed that the pre-treatment of catalyst was important for selective olefin production. Air-oxidized Pt/H-USY catalyst showed higher olefin selectivity than the catalyst reduced with hydrogen. The Pt/H-USY catalysts showed high stability under the reaction condition.

エタノール水蒸気改質による水素製造を低温で駆動させることを目的として、電場触媒反応の検討を行った。これまでにPt担持触媒を用い、電場を印加することで、423Kでもエタノール水蒸気改質が進行することを報告している。今回、Pt担持触媒を用いた低温でのエタノール水蒸気改質の活性・選択性・エネルギー効率に及ぼす電場の効果を検討するため、投入電流や反応温度、Pt担持量を変えて活性試験を行ったので報告する。

天然ガスの主成分であるメタンを用いた水蒸気改質に対し、当研究室が提案してきた電場触媒反応を適応した。その結果、メタンの水蒸気改質において本来熱では反応が進行しない低温域で活性がある事を見いだした。また、分圧変化試験の結果から電場印加中において反応速度が水分圧に大きく依存することが判明した。そのため、in-situ IRにより触媒表面上の測定を試み電場印加効果と、それに伴う反応機構の解析を行った。

エタノールの水蒸気改質反応を低温で進行させる高活性な触媒の開発を目的とした。今回、300℃程度の低温下でもエタノール脱水素能やアセテート種吸着能を持つアパタイトを担体として、担持する金属を数種類検討した。これらについて活性試験や各種キャラクタリゼーションを行い、低温下でのエタノールの水蒸気改質反応におけるアパタイトの担体効果や金属に及ぼす影響を検討したので報告する。

トルエンの水蒸気改質をCo/La0.7Sr0.3AlO3-&delta; (LSAO)触媒上で実施した。 LSAO担体はRedox特性によりトルエンの活性化および析出炭素を酸化除去すると考えられる。 Co/LSAO触媒が反応初期から安定した活性を示したため、各種キャラクタリゼーションを行った。その結果、CoはNiに比べ特異的な挙動を示した。

従来の触媒反応に電場という特殊な反応場を用いることで、メタンの水蒸気改質をはじめとした様々な反応の低温化を実現している。しかし、電場の印加効果については、未知の部分が多く、検討の余地を残している。そこで、水性ガスシフト反応をモデル反応として、電場の印加効果を速度論の観点から考察する。

セルロースからC₃、C₄炭化水素への転換について、セルロースの経時変化試験における液体成分の解析よりグルコースとキシロースが主な反応中間体であることがわかった。そこで今回、グルコース、キシロースを出発物として経時変化試験を中心に種々の反応試験を行い、想定する中間体からC₃、C₄炭化水素生成における反応機構を検討した。また、オレフィン収率向上を目的として担体や担持金属についても検討を行ったので合わせて報告する。

当研究室は、セルロースとPt/-USY触媒を443K、水熱条件下で反応させるとC3、C4炭化水素へ転換できることを見出している。その際にPt/H-USY触媒をH2流通下で還元前処理をするとパラフィンの選択性が大きくなるのに対し、Air流通下で酸化前処理するとオレフィン選択性が大きくなる事がわかった。この選択性の違いを明らかにするために触媒構造を詳細に分析するとともに、オレフィン生成の反応機構を検討したので報告する。

K/Co₃O₄に対してCOによる前還元処理を施した結果、300 ℃でも初期から90 %以上のWGS活性が維持された。前還元後の重量をTGで測定したところ、担体がCo metalまで還元された場合よりも大きな値を示し、後からH₂Oを導入した際の出口ガスをQ-Massで分析したところ、H₂、CO₂の生成が確認されたことから、KによりCOの吸着が促進されることがわかった。

これまでヘテロポリ酸担持触媒40wt%TBA-PW₁₂O₄₀/CeO₂が電場印加反応場において高いメタン酸化カップリング活性を示すことを報告してきた。その際, 反応中に構造が変化することで新たに形成されたWO₃, Ce₂(WO₄)₃がメタンを活性化する活性点として考えられた。そこで今回CeO₂上にWO₃, Ce₂(WO₄)₃をそれぞれ担持した触媒を調製し, 電場印加反応場においてメタンと酸素を供給したところ, それぞれC₂収率9.1 %を達成した。反応後の触媒の構造を比較したところ, 両者共にCe₂(WO₄)₃が形成していることを確認した。CH₄活性化の活性点はCe₂(WO₄)₃ではないかと考えられる。

二酸化炭素を用いたメタン酸化カップリングに着目し、低温で選択的にC₂炭化水素を得ることを目的とした。高密度な外部エネルギーを触媒層に供給できる電場印加触媒反応を用いることにより、反応性の低い二酸化炭素においても反応が可能となった。高いC₂炭化水素収率を示すペロブスカイト酸化物であるLa_0.7Ca_0.3AlO_3-&delta;を触媒として用い、電場印加効果や種々の電気的物性を変化させた時の生成物選択率に及ぼす影響、反応機構について詳細な検討を行った。<br>

排熱回収手段としての低温水蒸気改質について、電場中での n -ブタンの改質を行った。吸熱反応である水蒸気改質によって、水素・合成ガスが生成し、低温作動故に低位熱を取り込んでの反応が可能となった。その際の消費電力は十分に小さく、小型民生分野における燃料改質と熱回収の同時成立についての基礎的検討が出来た。触媒種の効果、反応操作因子の影響、反応メカニズムなどを検討したので報告する。

グルコースからC₃、C₄オレフィンへの転換を目的として、我々が独自に合成したグラフェンナノ構造体(GLP)を担体としたPt担持触媒を用いて、水熱条件下でグルコースのガス化実験を行った。結果として、Pt/GLP触媒は高いオレフィン収率・選択率を示した。このPt/GLP触媒が高活性を示す原因を調べるため、TEM、XPSなどのキャラクタリゼーションを行った。

水素の貯蔵・運搬方法として有機ハイドライド法に着目し、中でもメチルシクロヘキサンの脱水素反応に対して有効な触媒の開発を行った。Pt触媒の担体スクリーニングを行ったところ、Pt/TiO₂が他のPt触媒に比べて優れた劣化耐性を有していることを見出した。今回はPt/TiO₂の優れた劣化耐性の要因を詳細に検討した。

テトラブチルアンモニウム塩として単離したKeggin型ポリオキソタングステートである(Bu₄N)_2+xHPW_12-xV_xO₄₀(x =0～2)を合成した。合成したポリオキソタングステートを含浸法によりCeO₂上に40 wt%担持した。 担持した触媒にメタンと酸素を電場印加下において供給したところ、(Bu₄N)₂HPW₁₂O₄₀でC2収率13.0 %を達成した。電場印加による活性向上因子について、反応後触媒のキャラクタリゼーションを含め報告する。

エタノール水蒸気改質による水素製造を低温で駆動させることを目的として、電場触媒反応の検討を行った。これまでにPt担持触媒を用い、電場を印加することで、423Kでもエタノール水蒸気改質が進行することを報告している。今回、種々のPt担持触媒を用いた活性試験を行い、触媒担体が活性・選択性に及ぼす影響について検討を行った。また、エネルギー効率も算出し、エネルギー効率を向上させる因子についても検討した。

芳香族モデル化合物であるトルエンの水蒸気改質による水素製造において、ペロブスカイト酸化物であるLaAlO₃にNiを担持しBaを添加したNi/Ba/LaAlO₃触媒は、無還元でも高い活性を安定に示すことを見出した。Ni/Ba/LAOはNi/LAOよりも活性、炭素析出の面で優位性がある。金属分散度測定からCOが吸着しないことがわかったため、FE-TEMによる構造分析、IRによるCO吸着の雰囲気、温度の影響の検討を行う。

© 2014 Elsevier B.V. All rights reserved. Various Co3 O4 catalysts were investigated for the water gas shift (WGS) reaction for hydrogen production. Although the catalyst supporting only palladium (Pd/Co3 O4) showed low catalytic activity and higher selectivity to methanation, Pd/K/Co3 O4catalyst, with loading of potassium exceeding 0.78 wt%, showed high catalytic activity for the WGS reaction. Catalysts on which Pd and K exist closely showed high activity, as confirmed using various preparation methods. Results of XPS measurements for Pd/K/Co3 O4 revealed that supported potassium donated electrons to Pd and Co. The state of CO adsorption species was affected by the potassium loading, resulting in high catalytic activity for the Pd/K/Co3 O4 catalyst. These effects gave the Pd/K/Co3 O4 catalyst high catalytic activity for the WGS reaction. That reaction over Pd/K/Co3 O4 proceeds via surface cobalt carbonyl and then formate intermediates, as revealed by the TG and isotope exchange measurements using H218O and DRIFT.

© 2015, Japan Petroleum Institute. All rights reserved. Ni/perovskite-type oxide catalyst (Ni/La<inf>0.7</inf>Sr<inf>0.3</inf>AlO<inf>2.85</inf>: LSAO) shows high catalytic activity and low carbon formation during the steam reforming of aromatic hydrocarbons because of the high mobility of lattice oxygen in the support. The reaction mechanisms of the catalyst were investigated by characterizations and catalytic activity tests for steam reforming of various hydrocarbons including toluene, methylcyclohexane, and n-heptane. The catalytic performance was affected by the reactant structure, as revealed by Arrhenius plots and FT-IR analyses. Adsorption state and stability of reaction intermediates were very important factors in the catalytic activity for steam reforming.

© 2014 Elsevier B.V. All rights reserved. We investigated steam reforming of toluene as a biomass tar model on Ni/La0.7Sr0.3AlO3-δ, which has high activity and low carbon deposition for hydrogen production. Carbon deposition was suppressed by the oxidation of surface carbon species with lattice oxygen on support. The effects of Ni particle size and support surface area on catalytic features were evaluated by varying the calcination temperature of supported Ni and perovskite support independently. Activity tests, isotopic transient response tests, and characterization were performed to ascertain how interaction between Ni and support contributes to this reaction. Additionally, we evaluated the catalytic activity and carbon deposition per unit of Ni surface and perimeter. The lattice oxygen release rate depends on the specific surface area of the support, Ni-support interface, and catalyst structure. High surface area of the support accelerates the exchange of lattice oxygen through the redox cycle during steam reforming. Furthermore, the larger interface between Ni and support enables rapid lattice oxygen release. When the lattice oxygen release rate was higher, the catalytic activity was higher and carbon deposition was lower for each catalyst. These results confirm that lattice oxygen plays an important role in the activation of toluene and removal of carbon deposition on supported Ni.

© 2014 Springer Science+Business Media New York. Although diesel vehicles have high energy efficiency, the removal of emitted NOxat low temperature persists as an important issue. This report presents an examination of low-temperature NOxremoval using ozone injection and a plasma-lean NOxtrap (LNT) catalyst system. Ozone is readily producible by a dielectric barrier discharge reactor using oxygen in air, and its injection to emitted NO enables oxidation to NO2even at low temperatures. Results show that synergetic effects of ozone injection and plasma-LNT catalyst system enable low-temperature NOxremoval.

Catalytic reverse water gas shift reaction was conducted in an electric field (denoted as E-RWGS) over various catalysts at low temperature as 423 K. A platinum catalyst supported on lanthanum doped zirconia (Pt/La-ZrO2) showed the highest yield (ca. 40%) for the E-RWGS reaction even at such low temperature condition. In contrast to a bare oxide catalyst, metal loading catalysts showed higher activities and efficiencies for the reaction. Roles of the impregnated platinum and doped lanthanum on the catalytic activity were investigated, and we found that loaded platinum worked as an active site for the E-RWGS reaction, and La doping stabilized the structure of ZrO2. The effect of the electric field was discussed based on thermodynamic evaluation and experimental results. © 2013 Elsevier B.V. All rights reserved.

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 Pt0. 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 CrO 42- electrostatically stabilizes Pt2+ and inhibits migration and aggregation of platinum. © 2014 American Chemical Society.

We examined the promotion effect of Fe addition and the role of Fe on Co/α-Al2O3 catalyst for ethanol steam reforming using XAFS and IR. Activity tests of Fe/Co/α-Al2O3 with various Fe loadings show the addition of 0.22 wt% iron as an appropriate amount for the promotion of ethanol steam reforming. The investigation of apparent activation energies revealed that both ethanol steam reforming and acetaldehyde steam reforming were promoted by 0.22 wt%Fe addition. XAFS analyses revealed that Co and Fe on 0.22 wt%Fe/Co/α-Al2O3 produced Co-Fe alloy with an fcc-structure. Results of in situ IR measurements showed that acetate species were stabilized on the catalyst by loading 0.22 wt%Fe, and that the catalytic activity and selectivity to hydrogen were improved by Fe addition. © 2013 Elsevier B.V. All rights reserved.

Pt/Ni/La0.7Sr0.3AlO3-δ (Pt/Ni/LSAO) catalyst showed high catalytic activity and low coke formation for hydrogen production by steam reforming of toluene, even without pre-reduction. STEM-EDX and XAFS analyses revealed that Pt and Ni formed adjacent or alloy structure. Electron donation from supported Pt to Ni was observed by XPS observation, and the improvement of reducibility of Ni by Pt addition was observed by H 2-TPR. Catalytic activity of the reduced Ni was brought by the PtNi interaction. The impregnation order of Pt and Ni affected the catalytic activity and the amount of coke formation due to the difference of the structure of supported metals. Dilution effects of Pt on Ni metal and the contact between Ni and LSAO support apparently affect the suppression of coke formation. © 2013 Elsevier B.V.

One-pot direct catalytic conversion of cellulose biomass into valuable chemicals, such as C_3 and C_4 hydrocarbons, at low temperature (443 K) in the presence of Pt/H-USY zeolite catalysts and water were investigated. Acidic properties of Pt/H-USY zeolite catalysts were characterized by NH_3-TPD, which played important roles for the Pt-supported state and the formation of C_3 and C_4 hydrocarbons. To clarify the reaction intermediate for the C_3 and C_4 hydrocarbons, catalytic conversions of various substrates were conducted. Results suggested that C_5 compounds (xylose and furfural) might be imermediates of C_3 hydrocarbon formation, while C_6 mono- and di-saccharides (cellobiose, glucose, and fructose) might be intermediates of C_4 hydrocarbon formation from cellucose over Pt/H-USY zeolite catalyst.

© 2014 ISIJ. Oil sand bitumen and hypercoal are examined as a caking additives to the mixture of strongly coking coal and non-slightly coking coal. Samples were coked, then their strength, crystallinity of the carbon structure, and an anisotropic microstructure were measured. Oil sand bitumen addition enhanced strength, but 15% addition caused a strength decline because of the formation of large pores and cracks. Hypercoal addition increased strength with increased its content. Correlation was observed between increased strength and the crystallinity of a carbon structure or the anisotropic microstructure. Results suggest that mutual melting occurred between a coal blend and a caking additive. Then the caking additive took a carbon structure with high crystallinity by coking, achieved a function as a binder material that connects coal-particle interfaces, and ultimately enhanced strength.

This study demonstrated that a plasma-catalyst system using Pt catalyst provides high performance for NO decomposition under a humidified condition. In this work, we optimized the catalyst using various supported metals, oxides, and investigated the effects of the loading amount of metal and imposed voltage of plasma for highly efficient NO conversion. Results show that Pt is the most active metal and that it promotes formation of N2 and N2O from NO, and that N2O was an intermediate of N2 formation from NO over Pt. Regarding the effect of support, Pt catalysts supported on SiO2 and Al2O3, showed higher activity. We investigated the effects of metallic surface area of Pt and imposed voltage. Results show that both the energy input and metallic surface area of Pt plays important roles for NO decomposition to N2 in the plasma-catalyst system. The maximum peak current in plasma is extremely important. © 2013 Elsevier B.V. All rights reserved.

Oxidative resistance of Ni catalysts supported on various oxides La 0.7Sr0.3AlO3-δ, LaAlO3, and α-Al2O3 were investigated for hydrogen production by steam reforming of model aromatic hydrocarbons. Ni/α-Al2O 3 lost its steam reforming activity by oxidation treatment. In contrast, Ni/La0.7Sr0.3AlO3-δ and Ni/LaAlO3 catalysts showed steam reforming activity even after the oxidation treatment. The XANES (X-ray absorption near-edge structure) spectra at Ni K-edge for Ni/La0.7Sr0.3AlO3-δ and Ni/α-Al2O3 after oxidation treatment revealed that the supported Ni on La0.7Sr0.3AlO3-δ and α-Al2O3 were oxidized completely. Although the mean particle size of Ni on Ni/α-Al2O3 increased by oxidation treatment or reduction treatment, Ni particles on Ni/La 0.7Sr0.3AlO3-δ retained the fine structure after oxidation treatment or reduction treatment. Moreover, TPR (temperature programmed reduction) and XPS (X-ray photoelectron spectroscopy) measurements for elucidating the reducibility of Ni/La0.7Sr 0.3AlO3-δ showed that the supported Ni on La 0.7Sr0.3AlO3-δ was easily reduced even after the oxidation treatment. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.

Catalytic activity for oxidative methane conversion (partial oxidation of methane) over Pt catalyst supported on La1-xSrxAlO 3-0.5x was investigated. Pt/La0.7Sr0.3AlO 2.85 showed higher and more stable hydrogen yield than Pt/α-Al2O3 did. Pt/La0.7Sr 0.3AlO2.85 showed higher catalytic activity for steam reform of methane even in an oxidative atmosphere, which was attributable to high Pt dispersion in the oxidative reaction atmosphere. Pt dispersion over La0.8Sr0.2AlO2.9 or La0.7Sr 0.3AlO2.85 increased concomitantly with increasing calcination temperature in air. This phenomenon was not observed by aging in He flow. From structural analyses using XRD, XPS, EXAFS, and XANES, the interaction or coordination between Pt and surface oxygen (Os) was observed. This coordination was weakened in a reductive atmosphere and regenerated in an oxidative atmosphere. This interaction or coordination between the Pt and La1-xSrxAlO3-0.5x contributed to high Pt dispersion in an oxidative atmosphere and to high catalytic activity for the partial oxidation of methane. © 2013 Elsevier B.V. All rights reserved.

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 ~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. Graphical Abstract: [Figure not available: see fulltext.] © 2013 Springer Science+Business Media New York.

We investigated one pot direct catalytic conversion of cellulose to light hydrocarbon selectively at low temperature in the presence of Pt and solid-acid zeolite catalysts. Results revealed that Pt/H-beta zeolite catalyst prepared by ion exchange enabled selective production of C3 and C4 hydrocarbons. © 2013 Springer Science+Business Media New York.

Pd/K/Fe2O3 catalyst shows high activity for water gas shift (WGS) reaction. The K/Pd molar ratio on the catalyst has a remarkable effect on WGS activity. The optimum K/Pd molar ratio is about 2. In this study, to clarify the role of alkali metal (potassium), WGS activities of Pd/alkali/Fe2O3 (alkali: Li, Na, K or Cs) catalysts were investigated and the reaction mechanism over the Pd/K/Fe2O 3 catalyst was examined with transient response analyses using a concentration jump method with a quadrupole mass spectrometer (Q-Mass). Results showed that the addition of alkali metals such as Na, K and Cs drastically enhanced WGS activity, except for Li-loaded catalyst. WGS reaction over the highly active Pd/K/Fe2O3 catalyst was found to proceed via reduction-oxidation (redox) using lattice oxygen. Thereby, CO was oxidized by lattice oxygen in Fe2O3. The consumed lattice oxygen was regenerated by H2O. The results of CO-TPR revealed that oxidation of CO by lattice oxygen were enhanced by K, Cs or Na addition. H2-TPR results showed that reduction of Fe2O3 was suppressed by an increment of loading amount of potassium, which brought a high stability for the WGS reaction. The result of CO/H2O-TPR showed that steam can promote the regeneration of consumed lattice oxygen. The synergistic effect brought a high release ability of lattice oxygen for CO oxidation and also high regenerating ability of consumed lattice oxygen by H2O to produce hydrogen, to the Pd/K/Fe2O3 catalyst. It enabled high catalytic performance of the Pd/K/Fe2O3 catalyst with K/Pd molar ratio of 2. © 2013 Elsevier B.V.

La0.8Ba0.2Fe0.4Mn0.6O 3-δ (LBFMO) perovskite oxide has been found to be an active catalyst for oxidative dehydrogenation of ethylbenzene working with a characteristic Mars-van Krevelen redox mechanism in which steam functions as an oxidant. Results of this study showed that LBFMO oxide exhibited higher activity in the presence of both steam and gaseous oxygen compared with that of steam redox system. The reaction rate of oxidative dehydrogenation of ethylbenzene was zero-th order in oxygen partial pressure and 1.3 order in the amount of the surface lattice oxygen, which demonstrates that the reaction proceeded with redox system and the activity was determined mainly by the available amount of surface lattice oxygen. Kinetics of regeneration of the lattice oxygen from both steam and gaseous oxygen were also investigated, which confirmed that steam and gaseous oxygen mutually function as the oxidant for lattice vacancy on LBFMO. Results of thermogravimetric analysis showed that the available amount of the lattice oxygen in the presence of both steam and gaseous oxygen was 115 mmol mol-cat-1, almost twice as high as that in steam alone (63 mmol mol-cat-1). High activity in the presence of both steam and oxygen is attributable to the fact that these can simultaneously perform as the oxidant leading to a rich amount of the surface lattice oxygen of LBFMO oxide during the reaction. © 2013 Elsevier B.V. All rights reserved.

Effects of K and Pd loading on Co3O4 catalyst for the water gas shift (WGS) reaction were investigated. Pd/K/Co3O 4 catalyst showed high and stable activity and high selectivity to WGS. Regarding loading amounts of Pd and K, the latter is important for WGS activity and selectivity. XRD, XAFS, and TPR measurements confirmed potassium loading benefits. Supported Pd promoted oxidation of CO with lattice oxygen. The synergetic effect of these functions of K and Pd protected high catalyst activity and stability. © 2013 Springer Science+Business Media New York.

Catalytic steam reforming of methane in an electric field (electroreforming) at low temperatures such as 423 K was investigated. Pt catalysts supported on CeO2, CexZr1-xO 2 solid solution and a physical mixture of CeO2 and other insulators (ZrO2, Al2O3 or SiO2) were used for electroreforming. Among these catalysts, Pt catalyst supported on CexZr1-xO2 solid solution showed the highest activity for electroreforming (CH4 conv. = 40.6% at 535.1 K). Results show that the interaction among the electrons, metal loading, and catalyst support was important for high catalytic activity on the electroreforming. Catalytic activity of the electroreforming increased in direct relation to the input current. Characterizations using X-ray diffraction (XRD), temperature programmed reduction with H2 (H2-TPR), and alternate current (AC) impedance measurement show that the catalyst structure is an important factor for activity of electroreforming.

Catalytic steam reforming of aromatic hydrocarbon using toluene as a model compound for hydrogen production over Ni catalyst supported on perovskite oxide was investigated. Ni/La0.7Sr0.3AlO3-δ catalyst showed higher activity and lower coke formation than other Ni-supported catalysts on hydrogen production by toluene steam reforming. Transient response using H218O revealed that the surface lattice oxygen of La0.7Sr0.3AlO3-δ worked as active oxygen by redox mechanism at 873 K. Coke deposited on the catalyst surface after the reaction was removed oxidatively by lattice oxygen in/on the perovskite support. The working temperature of the lattice oxygen depended on the catalyst support characteristics. Analyses of the support structure by XRD and XPS revealed that the lattice distortion and the increasing of oxygen vacancies by partial Sr substitution enhanced the redox ability of lattice oxygen. Arrhenius plots showed that the rate-determining step of the reaction changed at a certain temperature at which the lattice oxygen was able to contribute to reaction over Ni/La0.7Sr0.3AlO3-δ and Ni/LaAlO 3. The dependence of the reaction rate on the partial pressure of H2O and toluene revealed that the rate-determining step might be the formation of hydroxyl group on the support surface in a lower temperature region and the adsorption of toluene on the Ni surface in a higher temperature region. © 2012 Elsevier B.V.

Hydrogen production by steam reforming of toluene as a model aromatic hydrocarbon has been investigated with various Ni/perovskite catalysts. Among them, Ni/LaAlO3 catalyst showed high catalytic activity. Partial substitution of the La site of LaAlO3 support with other elements (Sr, Ba or Ca) was conducted for the Ni/LaAlO3 catalyst, and substitution with 30% Sr promoted catalytic activity and selectivity to hydrogen. Optimization for the Ni loading amount over Ni/La0.7Sr 0.3AlO3-δ catalyst revealed that 5 wt% Ni/La 0.7Sr0.3AlO3-δ had the highest toluene conversion and the smallest amount of carbon deposition. To elucidate the role of doped Sr, the catalytic natures of Sr-substituted catalyst Ni/La 0.7Sr0.3AlO3-δ and Sr-supported catalyst Ni/Sr/LaAlO3 were compared. Results show that Sr-ions should be incorporated in the LaAlO3 perovskite structure to show high catalytic performance. Based on results of transient response test with H 218O on Ni/La0.7Sr0.3AlO 3-δ, Ni/Sr/LaAlO3, and Ni/LaAlO3 at reaction temperature of 873 K, the formation of 18O-products was observed only on Ni/La0.7Sr0.3AlO3-δ catalyst derived from redox between the lattice oxygen in the perovskite and water. Lattice oxygen in the La0.7Sr0.3AlO 3-δ support worked as active oxygen species to enhance its catalytic nature. © 2012 Elsevier B.V.

将来の水素エネルギー社会に向けた取り組みの一つとして、水素の高効率な運搬方法の確立が必要である。有機ハイドライドを利用した水素輸送は高圧、液体水素に比べ危険性が小さいだけでなく、既存のインフラを利用できる利点がある。この方法は有機物に水素を水素化物として貯蔵し、利用する際に脱水素反応させる事で取り出す事が出来る。これらを高収率かつ低温度で反応させるための触媒開発を行っており、担体にペロブスカイト型酸化物を用いることで炭素析出量の低減を図った。

ペロブスカイト型酸化物であるLBFMOは酸素、水蒸気共存下で、優れたEB脱水素活性を示す。本研究では反応速度論的検討により、格子酸素を介したEBの酸化的脱水素が進行し、水蒸気と酸素が同時に格子酸素を再生させていることがわかった。さらにin-situ TG測定により、表面格子酸素量と活性に相関がみられ、酸素、水蒸気共存による格子酸素再生速度の促進が活性向上の原因であることを明らかにした。

水素を製造する水蒸気改質は、工業的に973 K以上で稼働しており、高温プロセスに起因する問題が生じる。抜本的な解決のためには、低温領域での反応の進行が要求される。そのため、通常の触媒反応に電気的な要素として「電場」を印加した「電場触媒反応」を提案している。メタンを原料にした電場触媒反応において、担体基材や担持金属に工夫をして、触媒構造の最適化を図った。そして、塩基点担持触媒を考案し、活性を向上させることに成功した。

二酸化炭素を用いたメタン酸化カップリングに注目し、高密度な外部エネルギーを触媒層に供給することができる電場を印加させることで、低温で選択的にエチレンを得ることを目的とした。様々な酸化物のスクリーニングを行った結果、La0.7Ca0.3AlO3が高い収率を示したので、本触媒反応の詳細な検討を行った。

バイオガスの有効利用および二酸化炭素の再資源化を背景として、近年メタン炭酸ガス改質が注目されている。本反応により得られる合成ガス(水素+一酸化炭素)はC1化学の原料であり、種々の炭化水素として有効利用できる。しかし本反応は高温によるエネルギー効率の低下、および炭素析出による触媒活性の経時劣化が問題となる。そこで我々は電場という外力を触媒反応と併用することにより、反応の低温化、およびそれに伴う析出炭素の低減を狙った。

本研究室では芳香族炭化水素のモデル物質として芳香環を持ち、かつ簡単な構造であるトルエンを用いた水蒸気改質の研究を行ってきた。この反応では活性金属を安価で高活性なNi、担体をLa0.7Sr0.3AlO3-δとした場合最も高い活性を示し析出炭素量が少ないという結果が得られた。このことからLa0.7Sr0.3AlO3-δがいかに活性の向上、析出炭素量の減少に寄与するか活性化エネルギーの比較、同位体を用いた濃度ジャンプ過渡応答実験により検討を行う。

水素は炭化水素の水蒸気改質によって製造されるが、炭化水素源に灯油などの液体燃料を適用できることは利便性、燃料コストの点で望ましい。本研究室では石油系液体燃料のモデル化合物としてトルエンを用いた水蒸気改質において5 wt%Ni/La0.7Sr0.3AlO3-xが高活性、耐炭素析出性、耐酸化性を持つことを見出した。そこで、この触媒におけるトルエンの水蒸気改質の反応機構を解明し、他の触媒と比較することによって高活性、耐炭素析出性、耐酸化性の原因を探った。

水素は現在主に炭化水素の水蒸気改質によって製造されている。この反応は大きな吸熱反応であり、工業的に973 K以上の高温が要求される。こうした高温下では触媒の耐熱安定性や多段の熱交換過程が必要になる事などが問題となる。我々はこれらを解決するため、在来型触媒反応に対して電場を印加し、低温で水蒸気改質を進行させる新規触媒反応形態(Electreforming)を提案してきた。今回は酸化・還元前処理が活性に及ぼす影響を検討する。

Hydrogen production from methane, including shale gas, or biomass has been investigated using nonconventional catalytic systems. Conventional catalytic steam reforming requires high temperature, and includes several issues. Non-conventional catalytic reactions enable highly active catalytic system by electreforming or utilization of perovskite which has redox ability. We summarize these our recent researches in this paper.

We investigated catalytic steam reforming of aromatic hydrocarbon using toluene as a model compound. Ni/La0.7Sr0.3AlO 3-δ catalyst showed high catalytic activity and low coke formation. Although the lattice oxygen in a perovskite-type support plays an important role for oxidizing CHx and coke precursor, the role of interaction between Ni and the support has not been clarified. In this study, Ni/La0.7Sr0.3AlO3-δ catalyst calcined at various temperatures (1073, 1173, 1273 and 1373 K) was prepared and used to elucidate the effect of Ni particle size on the lattice oxygen mobility. The Ni particle size increased concomitantly with increased calcination temperature, and the C1 yield decreased from 72.9 to 15.5%. Enhancement of lattice oxygen mobility by the decrease of Ni particle size was observed by transient response tests using H218O over Ni/La0.7Sr 0.3AlO3-δ calcined at various temperatures. The interface between Ni and perovskite support played an important role for oxidizing coke precursor by lattice oxygen. © 2013 Elsevier B.V. All rights reserved.

Dehydrogenation of propane with steam was investigated using novel LaCoxMn1-xO3 (0≤x≤1) perovskite-type oxide (ABO3) catalysts. Optimization of the Co substitution ratio (x = 0.2) enabled high propylene yield and selectivity. The perovskite structure of LaCO0.2Mn0.8O3 remained stable during dehydrogenation, as confirmed by XRD measurements. Dehydrogenation of propane over LaCo0.2Mn0.8O3 perovskite catalyst proceeded via reduction-oxidation (redox) of the perovskite oxide; oxidative dehydrogenation of propane consumed lattice oxygen in the perovskite and the consumed lattice oxygen was regenerated by H2O. Surface analyses conducted using XPS and XANES showed that a part of Mn4+ and Co 3+ in LaCo0.2Mn0.8O3 was reduced to Mn3+ and Co2+ during the reaction. The LaCo 0.2Mn0.8O3 catalyst showed higher selectivity at the same propane conversion compared with the selectivity to propylene over an industrial CrOx/γ-Al2O3 catalyst. © 2013 Elsevier B.V. All rights reserved.

Oxidative coupling of methane using carbon dioxide (CO2-OCM) as an oxidant was conducted over several La- and Zr-based catalysts in an electric field at low external temperature of 423 K. Higher catalytic activity was obtained than in a conventional catalytic reaction over 10 mol% lanthanum-doped zirconia (La-ZrO2) in the electric field. Although the catalytic activity for the CO2-OCM was low over the La-ZrO2 at 1173 K without the application of the electric field, the electric field promoted catalytic activity even at 423 K external temperature. We optimized the amount of doping-La in the La-ZrO2 system, and characterized the effect of doping-La with XRD measurement. From these examinations, 5 mol% La-ZrO 2 catalyst showed the highest activity. High catalytic activity was provided by the synergistic effect of the La-cation, tetragonal-ZrO2, and the electric field. © 2013 Elsevier Ltd. All rights reserved.

Direct conversion of methane to other valuable products such as ethylene, methanol, benzene, carbon, hydrogen, and syngas has been widely investigated. Such conversion requires high temperatures because of the strong C-H bond in CH4, and such high-temperature reactions present various problems: sequential reaction to decrease the selectivity to target products, need for multiple heat exchangers to use or recover high-temperature waste heat, materials that are stable at high temperatures, etc. To solve these problems, several trials have been undertaken to lower reaction temperatures using plasma, Non-Faradaic Electrochemical Modification of Catalytic Activity (NEMCA), and electric fields. This review describes recent trends in methane conversion, and describes our methods to lower the reaction temperature.

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. © 2012 Elsevier Ltd. All rights reserved.

Low temperature partial oxidation of methane to produce syngas was investigated over Ni catalysts supported on various perovskite oxides. Pre-reduced Ni catalyst supported on LaAlO3 perovskite showed high catalytic activity at 673 K, the lowest temperature reported to date. Ni particles on LaAlO3 perovskite showed weaker interaction between metal and support, and were reduced at lower temperature than on other Ni catalysts. Partial oxidation proceeded via methane combustion and steam reforming, and the reduced Ni particles were active sites for both of these reactions. Additional impregnation of Pd enabled catalysis of the reaction without pre-reduction. The functions of Ni particles, LaAlO3 perovskite, and supported Pd were investigated by various methods, and found that Pd promoted the oxidation of methane, and catalytic partial oxidation proceeded over reduced Ni.

Steam reforming of toluene as a model compound of biomass tar was conducted on supported Ni catalysts. The Ni catalyst supported on perovskite oxide (La0.7Sr0.3AlO3-δ: LSAO) showed the highest toluene conversion (58%) and lowest coke formation (57 mg g-cat -1) at 873 K thanks to the smaller Ni particle size and larger perimeter between Ni and perovskite support, confirmed by XRD, BET, STEM and XAFS. In this paper, adsorption of toluene on Ni/LSAO catalyst was investigated using FT-IR method to estimate the reaction mechanism. IR spectra during temperature programmed desorption revealed that strong adsorption of toluene was observed only on LSAO and Ni/LSAO. The decomposition of adsorbate to CO or CO2 was promoted by supported Ni metal. Lattice oxygen of perovskite support contributed to the oxidation of the intermediate at the interface of Ni and perovskite. In addition, the oxidation of intermediate was promoted by introducing steam. Investigating adsorptions of various probe molecules (benzene, n-heptane, ethylene and benzaldeyde) revealed that decomposition of aromatic ring proceeded on Ni/LSAO. © 2013 Elsevier B.V. All rights reserved.

Details of the reaction mechanism of ethylbenzene (EBDH) dehydrogenation were investigated using kinetic analyses of highly active and stable La 0.8Ba0.2Fe0.4Mn0.6O 3-δ (LBFMO) perovskite oxide catalyst with a quadrupole mass spectrometer by measuring the instantaneous behavior. Under EBDH with a steam condition, the stoichiometric factor of oxygen in LBFMO catalyst in the steady-state reaction was found to be 2.927, which is lower than 3. The catalyst worked in the reduced state in which a few layers of lattice oxygen were consumed, supported by X-ray photoelectron spectroscopic analyses. Additionally, the reactive lattice oxygen and vacancy were involved with the reduction-oxidation (redox) mechanism of EBDH with steam. The respective amounts were 17.0 mmol mol-cat-1 for available lattice oxygen and 68.5 mmol mol-cat-1 for vacancy over LBFMO under the steady state condition. LBFMO catalyst showed high and stable EBDH activity by virtue of the redox mechanism using this lattice oxygen and vacancy. © 2013 Elsevier B.V. All rights reserved.

H-beta (*BEA) zeolite catalyst has high activity/stability for the alkylation of isobutane with 1-butene in a CSTR, based on the catalytic nature of H-*BEA. Various preparation methods for H- *BEA were investigated to optimize the catalytic activity for alkylation, including Si/Al ratio, H+/Na+ ion exchange rate, and grain size of zeolite. The relationship between Brønsted acid amount and butene consumption over the catalyst lifetime showed a positive correlation. H-*BEA zeolite with larger grain size and prepared with longer crystallization time achieved higher alkylate yield based on the higher hydride transfer activity.

芳香族炭化水素からの水素製造を狙い、トルエンの水蒸気改質を行った。我々は同反応に対して高活性かつ高安定性を示す触媒開発を目的として研究を行ってきた。Ni/ペロブスカイト触媒を中心に触媒探索を行ったところ、Ni/La0.7Sr0.3AlO3が高い活性を示し、なおかつ析出炭素量も小さいことがわかった。本発表ではトルエンの水蒸気改質におけるペロブスカイト担体の役割および反応機構の解明を目的とした。

地球温暖化や化石資源問題を抑止するため、再生可能資源であるバイオマスが注目されている。<br>この有効利用法の一つとして、燃料への転換が挙げられる。近年、バイオマスは酵素や液体酸、<br>超臨界水により分解されているが、これらのプロセスには安全性、運転条件の制御などに難点がある。<br>また、バイオマス関連のプロセスには多段系のものが多く、目的生成物への直接転換が望まれている。<br>そこで、本研究では、固体酸触媒を用いた一段のプロセスによるセルロースから軽質炭化水素への転換を目的とした。

水性ガスシフト反応は主にCOの除去および合成ガスのH2/CO比の調整に用いられており、高純度水素製造、燃料電池などに利用されている。本研究室では、安価で高活性な触媒の開発を目的とし、Fe2O3を担体とした触媒の探索を行った結果、Fe2O3にPdとKを担持した触媒が高活性を示し、またK/Pdのmol比=2において最も高い活性を示すことを報告した。今回は、Pd/K/Fe2O3の高活性の原因の解明のためTGによるTPR測定により、Pd/K/Fe2O3でのPd、K担持による還元性への効果を検討した。

二酸化炭素を用いたメタンの酸化カップリングは、高い選択率でエチレン生成を望むことが可能である。一方で反応性の乏しさから、高い転化率の達成が難しい。そこで我々は高密度なエネルギーを選択的に触媒に投入できる電場に注目し、電場中で本反応を行った。種々の触媒を用いて電場中での試験を行った結果、従来の触媒反応を上回る高い活性を得ることができた。またその際の反応メカニズムについても検討した。

石油の代替燃料として水素が期待されている。そこで当研究室では重質炭化水素（トルエン）を用いた水蒸気改質の研究を行い、これまでにNi/La1-xSrxAlO3-&delta;が高活性を示した例を報告している。これはSrの部分置換により触媒内の格子酸素の易動性が向上し、L-H機構だけでなくRedox機構でも反応が進行していることを示唆している。そこで、ディスク型反応器を用いて、トルエンと水蒸気を別々に供給し反応を行うことで、Redox機構の反応への影響を検討した。

当研究室ではこれまでにLa0.8Ba0.2Fe0.4Mn0.6O3の組成を有するペロブスカイト型酸化物が優れたエチルベンゼンの脱水素活性と安定性を有することを見出した。本発表ではこのペロブスカイト型酸化物に原料のエチルベンゼンと等モルの酸素を供給することによりスチレン収率が大きく向上し、さらに従来に比べ30 K低い反応温度においても優れたスチレン収率が得られることを報告する。

メタンの反応（水蒸気改質、酸化的改質、部分酸化）について、Pt/LaSrAlOxペロブスカイト型酸化物を用いて検討を行った。Pt/LaSrAlOxペロブスカイト型酸化物触媒は、他の担体に担持した触媒と異なり、酸素共存雰囲気では高温ほど高い分散度を取ることがわかった。構造についてはSPring-8でのEXAFS/XANESスペクトル解析や、XPSスペクトルおよびSTEM/EDXなどから詳細な解析を行った。この触媒は、酸素が存在する酸化的改質及び部分酸化において、高い活性を安定に発現した。

再生可能エネルギーの1つとしてバイオマスが注目されており、発酵によって得られる低濃度のバイオエタノールを水蒸気改質によって水素に変換する方法はエネルギープロセスとして期待されている。本研究室では、エタノールの水蒸気改質に対して高活性なCo触媒を中心に研究を行っており、Co/a-Al2O3への微量なFe添加が活性を向上させることを見出した。またSTEM-EDX測定の結果から、CoとFeが共存することで活性が向上すると考えられた。これらの結果を踏まえ、活性試験、XAFS測定、IR測定を行い、Co/a-Al2O3へのFe添加効果について検討した。

メタンの部分酸化反応を行い、水素製造を行った。私達は同反応に対して低温域にて高活性を示す触媒開発を目的として研究を行ってきた。Ni/a-Al2O3触媒を中心に触媒探索を行ったところ、Coを第二金属として担持したNi/Co/a-Al2O3が低温域において高い活性を示し、加えて炭素析出量も少なく安定性が高いことが分かった。本発表ではNi/Co/a-Al2O3におけるCoの最適担持量を検討し、その役割の解明を目的とした。

Pt触媒は高活性なため様々な反応に用いられているが、高温酸化雰囲気における分散度の低下が大きな問題である。担体としてペロブスカイト酸化物であるLaSrAlOxを用いたところ、高温酸化雰囲気においてもPtの高分散が維持されることを確かめた。また、高温域でメタンの部分酸化反応に対して高活性を有することがわかった。本研究では触媒構造を詳細に解析することで、これらの要因を明らかにすることを目的とした。

We found that LaInO 3 perovskite catalyst showed high activity for oxidative coupling of methane (OCM). Partial substitution of La 3+ site in the LaInO 3 catalyst with Ba 2+ increased its catalytic activity and selectivity to C2 hydrocarbons drastically. The partial substitution of La 3+ site in LaInO 3 with Ba 2+ 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.

Oxidative coupling of methane (OCM) assisted by a dark current in an electric field was investigated at low external temperature (423 K). The Sr-La2O3 catalyst showed higher yield of C2 (C2H4, C2H6) in the electric field than in the conventional catalytic reaction. Catalytic properties in the electric field and electrical properties of the catalyst were investigated. Results show that the electrical conductivity of dark current of the catalyst is an important factor for applying the electric field. A higher CH4/O2 ratio enabled high selectivity to C2 hydrocarbons. The maximum selectivity to C2 hydrocarbons was 59%.

Oxidative coupling of methane (OCM) on La 2O 3 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 C 2H 6 and C 2H 4 over Sr-La 2O 3 (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). © 2012 The Chemical Society of Japan.

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 NH 3-TPD and pyridine-sorption monitored by FT-IR showed that high acid density and high Brønsted acid ratio promoted alkylation of isobutane with 1-butene over H-*BEA zeolite.

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 Ce xZr1-xO2 as a catalyst support promoted electreforming, the lattice oxygen of CexZr1-xO 2 playing an important role. Energy efficiency of electreforming, reaction mechanism, and the role of lattice oxygen were investigated and are discussed in this paper. © 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 C2 hydrocarbon without coke formation at a ratio of CO 2/Cfuel = 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. © 2011 IOP Publishing Ltd.

Previously we reported that La0.8Ba0.2Fe 0.4Mn0.6O3-δ (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 H2O/H2 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 2O. 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. © 2011 Elsevier B.V.

硫黄を含まない軽質なガスからオクタン価の高いガソリンを作ることができるアルキレーションプロセスは重要なガソリン製造プロセスの一つである。工業化されているプロセスは、HFとH2SO4が触媒として用いられているが、いずれも毒性、腐食性が強く、多くの問題点を抱えているため、ゼオライトを触媒として用いたプロセスの開発が望まれている。ゼオライトを用いたプロセスは腐食性、毒性がなく比較的安価であるが、急速な活性劣化が原因で工業化には至っていない。そこで、本研究では、重合を抑え、選択的にC8を生成する反応条件および触媒の探索を目的とした。

低温での触媒反応を実現するために、電場及び放電の応用について検討を重ねてきた。これまでに、高温を要する吸熱反応、選択性維持が難しい酸化反応、速やかな起動停止が要求される反応に対して、放電・電場の併用による低温での触媒反応をおこなった。排気ガス浄化や、触媒表面の固相酸素による酸化還元型メタン転換、バイオメタン転換と脱硫の同時実現、酸化還元型触媒による固体炭素の酸化除去など数多くのプロセスを総括する。

合成ガスの製造法としてメタンの部分酸化があげられる。この反応は発熱反応であるため、低温域で高活性を示す触媒の開発が望まれる。我々は高価な貴金属を用いないNi/La0.8Sr0.2Al0.8Co0.2O3-触媒が前還元処理を行うことで623 Kという低温域で活性を示すことを明らかにした。本研究では活性試験や様々なキャラクタリゼーションを通して、同触媒の低温域での活性発現理由を解明することを目的とした。

本研究室では、コバルトを担持した触媒に微量の鉄を添加することにより、エタノールの水蒸気改質に対する転化率、水素収率が大きく向上することを見出してきた。そして、担体の違いによるコバルト系触媒への微量の鉄添加効果の違いを検討した結果、コバルトをアルミナに担持した場合の鉄の効果が最大であった。そこで、鉄添加効果について、XANES/EXAFSやIRによりキャラクタリゼーションを行い、プロモーションの効果について検討したので報告する。

芳香族炭化水素から水素を製造することは重質油やバイオマスタールの有効利用につながると考えられる。芳香族炭化水素のモデル物質としてトルエンを用いた水蒸気改質においてNi/La0.7Sr0.3AlO3-dを用いることで高活性、耐炭素析出性を実現し、また酸化に対する耐性を持つことを見出した。この触媒に第二金属としてPtを担持したところ、更なる析出炭素量の減少、前処理還元なしでの活性発現を実現した。これらの効果について、キャラクタリゼーションを用いて検討した。

天然ガスの有効利用として、メタンの酸化カップリングによるエチレン（C2化合物）の直接合成があるが、工業的に満足する収率が得られる触媒は見つかっていない。そこで、メタンの酸化カップリングにおいて高いC2選択率・収率が得られる触媒の探索を行った。その結果、ペロブスカイト型酸化物であるLaInO3が比較的高いC2選択率を示した。また、LaInO3をベースとして触媒設計を行い、Laの一部をBaで置換したLaBaInO3-dがより高いC2選択率を示した。

選択性の高いプロピレン製造技術としてプロパン脱水素がある。この反応に活性を示すCr系触媒は析出炭素による活性劣化が問題となっている。また、Cr系触媒は水蒸気存在下では活性が著しく低下するため、析出炭素の抑制を目的とした水蒸気の同伴が出来ない。そこで我々は、水蒸気存在下のプロパン脱水素において活性・選択性・安定性に優れた触媒の探索を行った。その結果、ペロブスカイト型酸化物触媒が安定な活性を示すことを見出した。

石油化学工業における主要なモノマーであるスチレンはエチルベンゼン脱水素を用いて製造されている。工業的には安価な元素からなり、かつ高活性・高安定性を有する触媒が望まれる。そこで高価な希土類元素を含まないペロブスカイト型酸化物を触媒として用いて検討したところ、Ba0.4Sr0.6Fe0.6Mn0.4O3-δが高い活性と比較的高い安定性を示した。

メタン酸化カップリングは、メタンが構造的に安定であるため、反応には900 K以上の高温を必要とする。そこで我々は反応の低温化を目的として電場中でメタン酸化カップリングを試みた。その結果、外熱供給423 Kという低温で反応が進行した。その際の生成物組成や経時変化から安定な反応場であることが示された。本発表では電場印加による活性向上のメカニズムの解明を目的とし、電場中での活性の挙動について詳細に検討する。

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.

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 Fe2O3 to Fe3O4. However, impregnation of potassium on iron oxide makes the catalyst structure robust. The promotion effect of Pd and potassium was not observed on SiO2 support. We therefore concluded that the synergetic effect among Pd, K, and iron oxide, was important for the WGS reaction. © 2010 Springer Science+Business Media, LLC.

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 α-Al2O3 showed remarkable effects of iron loading onto cobalt catalyst. The Fe-loaded Co/α-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. © 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. © 2010 Springer Science+Business Media, LLC.

We investigated four catalytic reactions assisted with an 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, and apparent activation energies for these four reactions were lowered by the application of the electric field. This process can produce hydrogen and syngas by using a considerably small energy demand and has quick response. © 2010 American Chemical Society.

トルエンの水蒸気改質反応に対して、高い活性、水素選択性、耐炭素析出性を有するNi触媒の担体について検討を行った。中でもNi/La0.7Sr0.3AlOxが高活性であり、参照用Rh触媒を上回る水素収率が得られた。高い水素収率は副生成物であるベンゼンとメタンの生成が少ないことに起因し、Ni触媒はRh触媒で顕著な脱アルキル反応が起こりにくい水素製造に適した触媒であることがわかった。

これまでの当研究室の研究より、ペロブスカイト型酸化物であるLaCoO3に、Pt、Pdを担持した触媒が、水性ガスシフト反応において高い活性を示すことがわかっている。ただ、その挙動は異なっており、Pt/LaCoO3については、初期活性は高いが経時的に活性劣化を起こし、Pd/LaCoO3については、Ptを担持した触媒に比べて初期活性は劣るものの、活性は安定していた。この違いは何に起因するものであるのか、また、Pt、Pdの役割を解明するため、反応メカニズムの検討を行っている。

メタンの水蒸気改質を低温にて電場アシスト存在の環境で行った。電場の存在によって、わずか150度という低温でもメタンの水蒸気改質が進行し、その際の生成物選択率は触媒による水性ガスシフト平衡組成に近い値をとった。このことから、メタンの活性化に対して電場がポジティブに活性化をアシストし、その後の逐次的な反応に対しては触媒上での反応制御が支配していると考えられることがわかった。また、ディスク状の触媒を用いた反応の結果から、電子リッチな担持金属が活性点を構成しており、電子プアな担持金属はその活性を失っていることがわかった。

石油精製やアンモニア合成に利用される水素は、主に炭化水素の水蒸気改質から製造されている。触媒の活性金属として安価なNiが用いられるが、炭素析出による触媒の劣化が問題である。また芳香族炭化水素は水蒸気改質において炭素析出が起きやすい反応である。以上のことから、我々は芳香族炭化水素の水蒸気改質において、炭素析出を抑制し、水素製造に適したNi触媒の開発を目的として研究を行った。

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 H2S 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 H2S into solid sulfur, but methane and CO2 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. © 2009 Elsevier Ltd. All rights reserved.

Steam reforming of ethanol was examined over Co/SrTiO3 with addition of another metal-Pt, Pd, Rh, Cr, Cu, or Fe-for promotion of the catalytic activity. Ethanol conversion and H2 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/SiO2 catalyst. High activity of Fe/Co/SrTiO3 catalyst came from interaction among Fe, Co, and SrTiO3. © 2009 Springer Science+Business Media, LLC.

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 CeO2 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/CeO2 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. © 2009 Elsevier B.V. All rights reserved.

We investigated novel LaMnOx perovskiteoxide (ABO3) catalysts for effective catalytic dehydrogenation of ethylbenzene to produce styrene monomer. Comparison with industrial Fe-K catalyst, our La0.8Ba 0.2 Mn0.6Fe0.4O3-δ 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. © Springer Science+Business Media, LLC 2009.

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. ©2009 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.

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 O2 conversion). Our investigation revealed that the Fe-doped La2O 3 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 O2-based C2 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 C2 selectivity (83%). Moreover, modification with Bi compounds also enhanced C2 selectivity of the Fe-doped La2O3 catalyst. This catalyst showed higher C2 yield than the Fe-doped La2O3 catalyst. © 2009 American Chemical Society.

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 LaCoO3 support showed high catalytic activity. Interaction between Pt or Pd and the support is considered to promote the WGS reaction: Pt/LaCoO3 had high initial activity but deactivated immediately; Pd/LaCoO3 was less active than Pt/LaCoO3, but had superior stability. Catalysts were characterized using XRD, STEM, XPS, and H2-temperature programmed reduction (TPR). Results of this study showed that reduction of the support decreased the CO conversion on Pt/LaCoO3. On the other hand, Pd/LaCoO3 showed stable activity for the WGS reaction. Therefore, Pd was added to Pt/LaCoO3 for stabilizing the catalyst activity, and 0.5 wt.% Pd/1 wt.% Pt/LaCoO3 catalyst showed higher activity and stability. © 2008 Elsevier B.V. All rights reserved.

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.

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.

我々は、メタンの水蒸気改質において、電場中の触媒反応によって著しい低温でも触媒活性を発現することを見いだした。電場の存在によって、反応温度は423Kまで低温化することが可能であった。このような温度では、触媒反応のみでは平衡の制約からメタンの水蒸気改質はほとんど起こりえない。電場の存在で大幅な転化率の向上が達成できた。また、このプロセスは水素あるいは合成ガスを非常に低いエネルギー投入で合成可能であり、素早い応答性も有していた。メタン以外に、エタノール、DMEの水蒸気改質なども検討し、電場の影響が大きいことがわかった。

水性ガスシフト反応は水素製造ならびに合成ガス製造プロセスにおいて重要な反応である。工業的には、高温シフト反応(HTS)は593-723 Kで行われ、Fe-Cr系触媒が用いられる。また、低温シフト反応(LTS)は573 K以下で行われ、Cu-Zn系触媒や貴金属触媒が用いられる。Fe-Cr系触媒は低温域では活性が低く、Cu-Zn系触媒は熱や酸化による活性劣化が問題となっている。これまで本研究室はCu-Zn系触媒を超える活性を示す触媒としてPd/Pt/LaCoO3を報告してきた。貴金属触媒は比較的安定ではあるが、Fe-Cr系触媒やCu-Zn系触媒と比べてコストがかかってしまうことから、貴金属量を削減することは重要である。本研究は、反応温度の低温化を目的とした水性ガスシフト反応における新規触媒の開発を行い、酸化還元特性を活かした活性及び熱に対する耐性の向上を期待して、酸化鉄やペロブスカイト型酸化物(LaCoO3)を用いた触媒の検討を行った。

We investigated the synthetic parameters of MCM-41, prepared through the evaporation-to-dryness treatment of alkali-free surfactant-silicate mixture, and their thermal stability and water resistance. The product obtained by this method gave a well-ordered 2D-hexagonal structure after the removal of surfactant molecules by either solvent-extraction or calcination. It is noteworthy that the d 100 value of MCM-41 remained almost the same after calcination, indicating that the pore wallsof the as-made product were dense and rigid. This MCM-41 shows a high degree of thermal stability and water resistance due to the highly dense silicate framework in the mesopore walls. © 2009 The Chemical Society of Japan.

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 Süd-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 O2- anions. This study demonstrated that steam works not only as a diluent but also as a reactant to form hydrogen and lattice oxygen. © 2008 Springer Science+Business Media, LLC.

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 α-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 α-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. © 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 on 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. © 2007 Elsevier B.V. All rights reserved.

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 × 10-7 mol m-2 s-1 Pa-1 at 503 K and reached to 1.4 × 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. © 2007 Elsevier B.V. All rights reserved.

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 Hg, 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 Hg, Se, Sb, and Zn release from coal. © 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.

A mordenite membrane was prepared on the outer surface of a porous α-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. Copyright © 2008 The Society of Chemical Engineers, Japan.

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. Co/LaAlO3 showed higher catalytic activity and stability than Co catalysts supported on LaCrO3, LaFeO3 and LaMnO3. The molar La/Al ratio significantly influenced the stability of Co/LaAlO3 catalyst and a molar La/Al ratio of 1:1 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 La3+ in LaAlO3 led to further remarkable improvement of catalytic activity and hydrogen yield. Enhanced mobility of lattice oxygen in La1-xSrxAlO3-δ allows more frequent participation in the oxidation of intermediates over metallic cobalt, leading to both high catalytic activity and stability of Co/La1-xSrxAlO3-δ in comparison with Co/LaAlO3.

It is possible to directly convert biomethane into syngas at ambient temperatures and atmospheric pressure without gas cleaning, as showed by a recent experiment. The experiment made use of a flow-type reaction apparatus equipped with two oppositely charged electrodes and a high-voltage electric discharge within the electrode gas. Composed of a mixture of 59.7% methane and 40.2% carbon dioxide, the reaction gas has a flow rate of 20 cc/min. It was showed that the method is highly effective since total energy was very high and the H2S was converted straight to solid sulfur.

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 °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 °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. © 2006 Elsevier Inc. All rights reserved.

電場中での触媒反応を、エタノールの分解などをモデル反応として検討した。触媒には白金など活性金属を担持した触媒を用い、電場を印加して反応を行った。白金を担持したセリア触媒などがとりわけ高い活性を示し、300度以下の低温で高い転化率を示した。従来の触媒反応に比べ、低温で高い活性を発現することができ、また投入する電力も小さいことから、小型装置においてはとりわけ、飛躍的に効率の高いプロセスとすることが可能である。

水素製造法である水蒸気改質反応では触媒上に析出する炭素による活性劣化が問題となっており、炭素析出を抑制することで小型燃料電池へ早期導入が期待されている。これまでに本研究室では、易動性の酸素を有するペロブスカイト型酸化物を担体に適用し、担体の格子酸素を反応に利用するサイクルを提案している。そこでこれらNi/perovskite触媒について、担体が触媒性能に与える影響について検討を行った。

近年、環境問題の関心が高まる中、硫黄、芳香族を含まないガソリン基材を製造することのできるアルキレーションプロセスが注目されている。現行のプロセスでは触媒として液体酸が用いられているが、様々な問題点があるため固体酸触媒によるプロセスの開発が望まれている。本研究において、固体酸であるゼオライトを触媒とし、連続式完全混合層型反応器を用いることで良い反応成績が得られたので、これを報告する。

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. © 2005 Elsevier Ltd. All rights reserved.

Continuous column flotation is one of an economical coal cleaning processes. In this study, we examined the effect of hydrophilicity and hydrophobicitiy of coal surface on the continuous column flotation processes. We found that Wallarah coal was most suitable coal for the coal cleaning by the column flotation. From a static separation of film flotation, we found that the floatability of coal particle strongly depended on the hydrophilicity and hydrophobicity of coal surface. On the other hand, the trend of demineralization and the ratio of carbonaceous recovery could be predicted by the observation of methylene-blue adsorption test.

A disk-type Sm0.4Ba0.6Co0.2Fe 0.8O3 - δ perovskite-type mixed-conducting membrane was applied to a membrane reactor for the partial oxidation of methane to syngas (CO + H2). 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 CH 4 was fed to the permeation side, whereas the oxygen flux was enhanced when CO or H2 was fed. It is implied that the oxidation of CO and H2 with the surface oxygen on the permeation side improves the oxygen flux through the membrane, and that CO2 and H 2O react with CH4 by reforming reactions to form syngas. © 2005 Elsevier B.V. All rights reserved.

We investigated hydrogen production by the steam-iron reaction using iron oxide modified with very small amounts of palladium and/or zirconia at a temperature of 723 K and under atmospheric pressure. Reduction of iron oxide with hydrogen and oxidation of partially reduced iron oxide with steam (Fe 3O4 + 4H2 ↔ 3Fe + 4H2O) were repeated in the range of reduction degree of 30-50 mol%. Changes in the weight of the samples were monitored using a tapered element oscillating microbalance (TEOM) to control the degree of reduction. Unmodified iron oxide caused significant deactivation due to sintering with increasing number of redox cycles. The addition of a very small amount (0.23 mol%) of palladium or zirconia onto the surface of the iron oxide enhanced the reduction and/or oxidation of the partially reduced iron oxide, which suppressed sintering. Palladium accelerated both the reduction and oxidation rates of partially reduced iron oxide, while zirconia increased only the oxidation rate. Addition of both palladium and zirconia together to the iron oxide resulted in marked enhancement of both reduction and oxidation. © 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, BaTiO 3, La0.4Ba0.6Co0.2Fe 0.8O3-8, to compare the catalytic activity and resistance to coking of these catalysts to those of the conventional Ni/α-Al 2O3 catalyst. Ni/LaAlO3 and Ni/SrTiO 3 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/α-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. © 2005 Published by Elsevier B.V.

We used a novel liquid-fuel-reforming system, with a diaphragm and discharge hybrid apparatus that can be operated under ambient temperature and atmospheric pressure, to obtain 50% hydrogen by steam reforming of ethanol with high energy efficiency of up to 95%. 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 SrFeCo0.5Ox 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 SrFeCo0.5Ox 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. © 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. Copyright © 2005 The Chemical Society of Japan.

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.

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.

Rapid synthesis of Si-MCM-41 was accomplished in successive two steps; (1) aging of a mixture of silica, hexadecylammonium bromide and water with an aqueous ammonia solution for a short period of 30 min, and (2) successive evaporation-to-dryness of the resultant mixture at 80°C in about 2 h. The yield of Si-MCM-41 reached 99% after calcination at 550°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. © 2005 Elsevier B.V. All rights reserved.

SrFeCo0.5Ox 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 SrFeCo0.5Ox powder was placed in a die, and then a mixture of SrFeCo0.5Ox powder and ethyl cellulose powder was added on top of the SrFeCo0.5Ox 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. Copyright © 2005 The Society of Chemical Engineers, Japan.

The influence of carbonaceous structural change and ash behavior affecting reactivity was clarified using an analysis method that employs microscopy. Detailed analysis with this method was possible. Furthermore, the effect that ash had on the change of carbonaceous structure was clarified.

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.

Direct dehydrogenation of methane to produce more useful chemicals was examined using low temperature plasmas such as DBD, corona and spark discharge under the conditions of room temperature and atmospheric pressure. In spark discharge, acetylene was produced with the selectivity higher than 85% and small amount of deposited carbon. The energy efficiency in spark discharge was much higher than that in DBD and corona discharge. By the emission spectroscopy, it was found that methane was highly dissociated to atomic carbon and hydrogen in spark discharge. The gas temperature in spark discharge channel remained as low as 420-460K determined by Boltzmann plot method of CH rotational band (431 nm). The specific energy requirement for acetylene was improved by the optimization of reactor size and residence time and reached 12.1 kWh/kg-C 2H2, which was as same as Huels process with DC arc plasma. © 2003 Elsevier B.V. All rights reserved.

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.

Non-catalytic methane activation with spark discharge showed high energy efficiency and high selectivity to acetylene by the collision of electrons possessing high energy enough to dissociate methane into atomic carbon. The application of spark discharge to steam reforming of methane was effective for hydrogen production at low temperature. The selectivity to desired product was improved by the combination with catalyst.

The reaction mechanism of methane activation using non-equilibrium pulsed discharge was largely clarified from the emission spectroscopic study and experiments with higher hydrocarbons and some kinds of isotopes. The strong emission of atomic carbon and C2 swan band system was observed as well as H Balmer series emission. This indicates that methane was highly dissociated into C and H by electron impact, which is consistent with the result of high C2D2 composition in produced acetylene when the mixture of CH4 and D2 was fed into discharge region. High electron energy contributed to produce atomic carbon directly from methane, and high electron density promoted the dehydrogenation from CH 3, CH2 and CH to produce atomic carbon consecutively. The reason for the high selectivity to C2H2 was the high concentration of CH or C2 formed from atomic carbon, and the repetition mechanism of decomposition and recombination among C, CH, C 2 and C2H2. © 2003 Elsevier Ltd. All rights reserved.

Non-catalytic direct conversion of methane to valuable products was studied using non-equilibrium pulsed discharge under the conditions of ambient temperature and atmospheric pressure. Acetylene was produced with 95% selectivity and 52% methane conversion. An addition of oxygen, carbon dioxide and steam contributed significantly to suppress the carbon deposition and produced carbon monoxide as well as acetylene. Methane conversion increased with an increase in the pulse frequency while the product selectivity remained almost constant. The selectivity depended on the composition of the feed gas. The effect of the partial pressure of oxygen was examined, and it was found that the pulsed discharge would be able to produce synthesis gas by partial oxidation of methane. Carbon monoxide selectivity of 79% with methane conversion of 76% was obtained under the conditions of CH4/O2 = 25/25cm3min-1, gap distance of 10mm and the frequency of 45Hz. © 2003 Elsevier Science Ltd. All rights reserved.

The comparison between DC corona and pulsed discharge was made for the formation of C2 hydrocarbons. Using the corona discharge, the consecutive dehydrogenation from ethane was observed. On the other hand, in the pulsed discharge reaction, acetylene was produced with 95% selectivity independent of methane conversion. In addition, the combination of catalyst and pulsed discharge had a great effect on the selectivity. The use of Ni-catalyst with the pulsed discharge promoted carbon dioxide reforming selectively at room temperature. And the yield of ethane reached 49% by using 1 wt% Pt/SiO2.

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.

Selective formation of C2H2 and/or CO was achieved using a periodic pulsed spark discharge, with and without catalysts, at room temperature. The selective formation of C2H2 with high conversion was achieved. A 49% yield of C2H6 was obtained in Pt/SiO2 and discharge combined system. With the increased of CO2 content, C2 selectivity decreased sharply, while CO selectivity increased drastically. Under the condition of high CH4 concentration, the formation of C2H2 was predominant whereas under the condition of high CO2 concentration, CO became the main product. The use of pretreated NiMgO solid solution catalyst increased CO selectivity to 85% at CH4/CO2 = 1:1, while no remarkable effect was observed without pretreated catalysts. The pulsed spark discharge reaction of CH4 in the presence of O2 produced CO and C2H2 at room temperature while suppressing carbon deposition and CO2 formation.

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.

Effect of the reactor in methane reforming with carbon dioxide and oxygen over NiO-MgO catalysts under atmospheric and pressurized conditions was investigated. Under atmospheric pressure, the stable activity was observed using the fluidized bed reactor. However, in the fixed bed reactor, the activity decreased gradually with time on stream. On the other hand, at low temperature and high space velocity, methane conversion decreased rapidly to the level of methane combustion using fluidized bed reactor. Under pressurized condition, the stable production of syngas was possible even at high space velocity since the catalyst is in more reducing atmosphere at higher pressure. The fluidized bed reactor enhanced more effective conversion of methane to syngas than the fixed bed reactor.

The effect of catalyst fluidization on the conversion of methane to syngas in methane reforming with CO2 and H2O in the presence of O2 under pressurized conditions was investigated over Ni and Pt catalysts. Methane and CO2 conversion in the fluidized bed reactor was higher than those in the fixed bed reactor over Ni0.15Mg0.85O catalyst under 1.0 MPa. This reactor effect was dependent on the catalyst properties. Conversion levels in the fluidized and fixed bed reactor were almost the same over MgO-supported Ni and Pt catalysts. It is suggested that this phenomenon is related to the catalyst reducibility. On a catalyst with suitable reducibility, the oxidized catalyst can be reduced with the produced syngas and the reforming activity regenerates in the fluidized bed reactor. Although serious carbon deposition was observed on Ni0.15Mg0.85O in the fixed bed reactor, it was inhibited in the fluidized bed reactor. © 2002 Elsevier Science B.V. All rights reserved.

Synthesis gas was produced by pulsed irradiation of electrons on a mixture of CH4 and CO2 (or H2O) at low temperature and atmospheric pressure without catalysts; especially in the CO2 reforming reaction, the H2 : CO ratio could be controlled and depended on the concentration of CO2 in the feed gas.

For the purpose of chemical recycling of plastic wastes, catalytic degradation and liquefaction of Polypropylene (PP). subjected to high pressure H2 was examined with a batch reactor. Iron supported active carbon (Fe/A.C.) acted to decrease solids and also increase liquid yield in condition of 673-693 K at H2 pressure of 4.0 MPa (NTP) for 1 h. Compared with thermal degradation, liquid products became lighter because residue produced was degradated by the catalyst. Compared H2 with Ar as reaction gas at 683 K, degradation of PP was promoted by H2 in 0.5-1.0 h. In the results of the effect of H2 pressure, degradation of PP was proceeded as the increase of H2 under 3.0 MPa but was suppressed over 4.0 MPa. These results show that H2 plays an important role in catalytic degradation of PP over Fe/A.C. catalyst.

Methane was oxidized by oxygen in the absence of a catalyst with the microwire initiation (MWI) method, which was composed of an electrically heated small wire and a low-temperature reaction zone. With the existence of initiation reaction, methanol and carbon monoxide were formed at 393 K gas phase temperature. The main products of the reaction were methanol, hydrogen, carbon monoxide, carbon dioxide, and water. With the batch-wise MWI system, methanol selectivity was higher than 80% at the initial stage of the reaction. In the absence of MWI, no products were formed under 653 K of gas phase temperature in the chain reaction zone. We proposed a new model for the oxidation of methane with microwire initiation.

The method of micro wire initiation(MWI) was applied to partial oxidation of methane under normal pressures. Consequently, the formation of acetone was identified besides CO, CO2, C2, hydrogen and methanol. Under the condition that the temperature of filament surface was low and gas phase was high, the selectivity of acetone was 67 %. It was proved that the selective conversion of methane to oxygen-containing compounds can proceed directly with the MWI method.

Methane is oxidized by oxygen in the absence of catalyst with micro wire initiation (MWI; the concept is shown in Fig. 1) method, which is composed of electrically heated small wire and low temperature reaction zone. With the existence of initiation reaction, methanol and CO was formed even under 400 K gas phase temperature. Main products of the reaction were methanol, hydrogen, CO, CO2 and water. We claimed a new model for the oxidation of methane with MWI. © 1998 Elsevier Science B.V. All rights reserved.

Although the chemical utilization of methane has been considered promising highly, the majority of uses are via the reforming of methane to synthesis gas, which is attributed to the high stability of methane. In this study, the authors tried to keep separate the location of the initial activation of methane at high temperature and that of the consecutive chain reaction at low temperature. A method of MWI (abbreviation of Micro Wire Initiation) activates the methane molecule and the activated species are smoothly introduced into the tandem chain reaction zone, which is connected downstream of the initiation zone. In the MWI system, methanol was formed at 393 K and its selectivity increased as increasing in total pressure. No reaction proceeded without MWI below 683 K, and there are no obvious differences in either methane conversion or product distribution for different reaction temperatures. Over 683 K, the conversion of methane and the selectivity to methanol increased with reaction temperatures. The selectivity to methanol depends on the reaction pressure. Low total pressure favors the formation of CO. It is important to note that if methyl radical is produced by MWI activation, successive chain reaction could proceed at temperature as low as 393 K.

Methane was oxidized by oxygen at temperatures as low as 473K or lower under pressurized conditions. The reaction was initialed by heated wire, which was set in the center of a pressurized reaction chamber. At the initial stage of the reaction, the methanol selectivity was as high as 90%, but its level decreased quickly with proceeding of the reaction time. When the reaction pressure was raised from 5 to 40atm, the methanol selectivity (at high O2 conversion level) was increased from 2% to 30% whereas selectivities of C2 hydrocarbons of CO2 decreased 30% to 10% or less. A new reaction model was claimed for the present reaction system. © 1997 Elsevier Science B.V. All rights reserved.