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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

DOI： 10.1021/acscatal.1c02887

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

Strong basic oxidesupported Ru catalysts are easily prepared and handled, and they have been used as effective catalysts for ammonia synthesis under mild reaction conditions since the 1970s. Recent research has revealed that precise control of the boundary states between the basic oxide (i.e., rare-earth oxide, alkali earth oxide), oxygen defect sites, and Ru nanoparticles can be used to enhance ammonia synthesis under mild reaction conditions and inhibit hydrogen poisoning, which is a typical drawback of strong basic oxidesupported Ru catalysts.

DOI： 10.1246/cl.200855

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Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

© 2020 American Chemical Society. To mitigate global problems related to energy and global warming, it is helpful to develop an ammonia synthesis process using catalysts that are highly active under mild conditions. Here we show that the ammonia synthesis activity per weight of catalyst of Ru/Ba/LaCeOx, prereduced at 700 °C, is the highest among reported oxide-supported Ru catalysts, 52.3 mmol h-1 gcat-1 at 350 °C, 1.0 MPa. The turnover frequency of Ru/Ba/LaCeOx at 350 °C was more than 8 times that of Cs+/Ru/MgO, which is a well-known active catalyst used as a benchmark; furthermore, hydrogen poisoning, a typical drawback for oxide-supported Ru catalysts, was effectively suppressed. Scanning transmission electron microscopy observations with energy dispersive X-ray spectrometry and electron energy loss spectroscopy analysis revealed that a low-crystalline, oxygen-deficient nanofraction including Ba2+, Ce3+, and La3+ had accumulated on the Ru particles. This unique structure was obtained by exploiting the surface dynamics of alkaline earth compounds and thermostable rare earth oxides that contain redox-active atoms during the reduction at an unusually high temperature. The nanofraction showed strong electron-donating ability because of the strong basicity of the included cations, removal of carbonate, and formation of oxygen defect sites that eliminated electron-withdrawing O2- anions from the interface between the nanofraction and Ru atom. Electrons were therefore effectively donated to antibonding π -orbitals of the N2 molecules via Ru in contact with the nanofraction, and NN triple bond cleavage, which is the rate-determining step for ammonia synthesis, was promoted.

DOI： 10.1021/acssuschemeng.9b06299

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

Abstract

Conversion of CO2 with H2 to CH4 is a potential route for the utilization of CO2. Because CO2 methanation is an exothermic reaction, the equilibrium yield decreases with increasing temperature. A catalyst that exhibits high activity at low temperatures is thus highly desirable. We report here that a tetragonal-type ZrO2 supported Ru catalyst prepared by low-temperature calcination showed significant low-temperature activity for CO2 methanation. We surmise that an intermediate formate species formed over the tetragonal-type ZrO2 and enhanced the catalytic activity.

DOI： 10.1093/chemle/upae178

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.energyfuels.3c03034

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Supported Ru catalysts were prepared by using different Ru precursors and examined for the hydrogenation of benzaldehyde to CHM. The catalyst prepared from Ru-3(CO)(12) precursor and HT support exhibited high yield of CHM. Moderate acidic and basic nature of HT was favourable to control the selectivity for CHM. The physicochemical properties analysis revealed that highly dispersed Ru nanoparticles were effective for the hydrogenation of benzaldehyde. Ru-CO/HT catalyst was tolerant to different functional groups and was stable until 7(th) cycle of recycle study.

DOI： 10.1002/cctc.202200241

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.ijhydene.2021.12.191

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Colloidal metal nanoparticles were examined for reductive amination of phenol by ammonia under mild reaction conditions. The results showed that Rh-PVP was the most active catalyst for reductive amination reaction. Linear, cyclic, and amino alcohols were used as nucleophiles and converted to primary/secondary/tertiary amines. Using this strategy, the synthesis of an industrially important chemical, N-cyclohexyl- 2-pyrrolidone was explored.

DOI： 10.1246/cl.210574

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

Catalytic hydrogenation of nitriles is a cost-effective and green method for synthesizing amines and imines, which have many industrial applications. However, this reaction generally requires harsh reaction conditions and produces a mixture of amine and imine products due to its chemodiversity. Therefore, it is a challenge to selectively hydrogenate nitriles to a single product under ambient conditions (1 bar of H2 at 25 °C). Here, we report an effective method for selective hydrogenation of nitriles that does not require heat, pressurization, or long reaction times. We achieved this by means of bimetalization between palladium (Pd) and platinum (Pt) nanoparticles, which resulted in a catalyst that showed high yield of secondary amines. Although Pd and Pt are thermodynamically immiscible, we have successfully alloyed the two metals by means of rapid chemical reduction assisted by microwave heating. X-ray absorption spectroscopy suggested the formation of heteroatomic Pdδ+Ptδ− sites via charge transfer between neighboring Pd and Pt atoms in the alloy structure. Moreover, Fourier transform IR spectroscopy and scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy indicated that decreasing the size of the PdPt (50 : 50) nanoparticles improved the degree of alloying and facilitated the formation of electron-enriched Ptδ− species. On the basis of kinetics studies and density functional theory calculations, we concluded that cyano group activation, which was the rate-determining step over monometallic Pd and Pt catalysts, was accelerated over the heteroatomic Pdδ+Ptδ− sites because of strong back-donation from electron-enriched Ptδ− species to the carbon atom of the cyano groups. The PdPt random alloy nanoparticles catalyzed the reactions of various aromatic and heterocyclic nitriles, and the corresponding secondary amines were selectively obtained in just a few hours.

DOI： 10.1039/d1cy02302k

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

Ammonia synthesis catalysts with high activity under mild reaction conditions for use in synthetic chemical processes powered by renewable energy are needed. Here, we investigated the physicochemical properties and ammonia synthesis activity of lanthanoid oxide–supported Ru catalysts. The basicity of the Ru/lanthanoid oxide catalysts, as estimated by CO2 temperature-programmed desorption, was higher than that of Ru/MgO, a representative catalyst with high ammonia synthesis activity, and a positive relationship was observed between basicity and turnover frequency. The turnover frequency of Ru/Pr2O3 and Ru/La2O3 (both 0.24 s−1) was eight times that of Ru/MgO (0.03 s−1). A kinetic analysis revealed that hydrogen poisoning, which is a typical drawback of oxide-supported Ru catalysts, was markedly retarded in the Ru/lanthanoid oxide catalysts. As a result, the ammonia synthesis rate of the Ru/Pr2O3 catalyst increased with increasing reaction pressure, reaching 49 mmol g−1 h−1 at 400 °C and 1.0 MPa, which was 12 times that of Ru/MgO under the same conditions.

DOI： 10.1016/j.cattod.2020.08.031

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Since 1970, people have been making every endeavor to reduce toxic emissions from automobiles. After the development of a three-way catalyst (TWC) that concurrently converts three harmful gases, carbon monoxide (CO), hydrocarbons (HCs), and nitrogen oxides (NOx), Rh became an essential element in automobile technology because only Rh works efficiently for catalytic NOx reduction. However, due to the sharp price spike in 2007, numerous efforts have been made to replace Rh in TWCs. Nevertheless, Rh remains irreplaceable, and now, the price of Rh is increasing significantly again. Here, it is demonstrated that PdRuM ternary solid-solution alloy nanoparticles (NPs) exhibit highly durable and active TWC performance, which will result in a significant reduction in catalyst cost compared to Rh. This work provides insights into the design of highly durable and efficient functional alloy NPs, guiding how to best take advantage of the configurational entropy in addition to the mixing enthalpy.

DOI： 10.1002/adma.202005206

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

Solid-solution alloy nanoparticles (NPs), where the constituents mix at the atomic level, show a variety of attractive properties due to their tunable electronic structures. However, it is still difficult to stably synthesize them, particularly nonequilibrium alloys that consist of combinations immiscible in the bulk. Here, we first report the successful syntheses of solid-solution alloy NPs including PdRu and PdRuIr, which are immiscible in the bulk, and of IrPdPtRhRu high-entropy alloy NPs through a continuous-flow reactor providing a high productivity with high reproducibility. The designed solvothermal flow reactor enabled us to use a lower alcohol as a reductant that cannot be applied in a batch synthesis for these NPs.

DOI： 10.1021/acs.jpcc.0c08871

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry ({RSC})  

<p>The direct synthesis of cyclohexylamine <italic>via</italic> hydrogenation of nitrobenzene over monometallic (Pd, Ru or Rh) and bimetallic (Pd_xRu_1−x) catalysts was studied.</p>

DOI： 10.1039/d1nj00922b

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

Ammonia has received attention as a hydrogen carrier for energy use, and although ammonia decomposition can produce hydrogen at a high rate, there is currently no simple process for decomposing ammonia that is easily and rapidly initiated at any time without an input of external energy. Here, we report the discovery of a process for initiating and sustaining the production of hydrogen from ammonia without heating the catalyst externally. The oxidative decomposition of ammonia to produce hydrogen at a high rate was repeatedly triggered at ambient temperature (∼25 °C) immediately after NH3 and O2 were supplied to a Ru/Ce0.5Zr0.5O2 catalyst that had been previously reduced at ambient temperature. For this catalyst, active hydrogen atoms formed on Ru0 nanoparticles reduced Ce0.5Zr0.5O2 even at ambient temperature, and the very exothermic oxidation of Ce0.5Zr0.5O2-x as well as Ru0 heated the catalyst bed to the catalytic auto-ignition temperature for ammonia combustion, which was lowered by the contribution of mobile (active) oxygen over the Ce0.5Zr0.5O2. Oxidative ammonia decomposition was thereby triggered.

DOI： 10.1021/acssuschemeng.0c04126

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© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Ammonia is a potential carrier of hydrogen as a zero-emission fuel. Herein, the effects of calcination and reduction temperatures on the ammonia-synthesis activity of Ru/La0.5Ce0.5O1.75 are investigated under mild synthesis conditions (≤400 °C, ≤3 MPa), which are the preferred conditions for the storage of hydrogen as an energy source. The highest catalytic activity is obtained after calcination of the support at 700 °C and reduction of the catalyst at 650 °C. Calcination using a higher temperature than that used for reduction results in the induction of a strong metal–support interaction (SMSI) effect. This high-temperature calcination also provides heat resistance to the support, which prevents sintering of the primary support particles during reduction. Thus, calcination and reduction at temperatures higher than those normally used for the preparation of Ru catalysts provide a novel approach for obtaining supported highly dispersed Ru catalysts exhibiting the SMSI effect and high catalytic activities.

DOI： 10.1002/ente.202000264

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Pr2O3 supported Ru nanolayers and Ru nanoparticles catalysts were examined for the synthesis of quinolines. The Ru nanolayer was most active catalyst and showed a broad substrate scope. Structure-activity relationship demonstrated that the metallic state and morphology of Ru as well as the basic site of Pr2O3 were indispensable factors of this catalytic system.

DOI： 10.1002/cctc.201902311

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>Recyclable Pd_0.5Ru_0.5–PVP catalyst showed higher activity than monometallic Pd or Ru catalyst for the hydrogenation of quinoline. Furthermore, Pd_0.5Ru_0.5–PVP was able to hydrogenate different arenes.</p>

DOI： 10.1039/D0RA09981C

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry ({RSC})  

<p>Recyclable Ir-PVP catalyzed one-pot syntheses of pyrrolidones were achieved under mild reaction conditions.</p>

DOI： 10.1039/D0GC01725F

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry ({RSC})  

<p>This study provides a coreduction methodology for solid solution formation in immiscible systems, with an example of a whole-region immiscible Cu–Ru system.</p>

DOI： 10.1039/D0SC03373A

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

We investigated the kinetics of NH3 synthesis over a catalyst consisting of low-crystalline Ru nano-layers supported on Pr2O3. We determined the reaction orders with respect to N2, H2, and NH3 at various temperatures and pressures over Ru/Pr2O3, as well as Ru/CeO2 and Ru/MgO. The reaction orders with respect to N2 were always almost unity for all the catalysts under all the reaction conditions, indicating that the rate-determining step was NN bond cleavage. In contrast, the reaction orders with respect to H2 differed among the catalysts and decreased with increasing pressure and increased with increasing temperature. Under all conditions, the reaction order with respect to H2 was largest over Ru/Pr2O3 and smallest over Ru/MgO, indicating that hydrogen poisoning of the Ru surface was retarded to a greater extent over Ru/Pr2O3 than over Ru/MgO. In agreement with the trends of the H2 reaction orders, the NH3 synthesis rates over Ru/Pr2O3 at 400 °C rose drastically (64 mmol h−1 g−1) as the pressure was increased from 0.1 to 3.0 MPa. Furthermore, decreasing the feed gas H2/N2 ratio at 3.0 MPa effectively increased the NH3 synthesis rate over Ru/Pr2O3, which reached 45 mmol h−1 g−1 at 350 °C at a H2/N2 ratio of 1/0.5.<br />

DOI： 10.1016/j.jtice.2019.10.006

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Petroleum Institute  

DOI： 10.1627/jpi.62.220

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

Various transition metal nanoparticles, prepared by microwave-assisted alcohol reduction method were examined for hydrogenation of benzoic acid to cyclohexanecarboxylic acid under solvent-free conditions. Rh metal was the most effective catalyst over other metal catalyst. The catalyst showed moderate to high yield for the hydrogenation of substituted benzoic acid and substituted quinolines. Rh-PVP was recycled four times with a minor loss in catalytic activity.

DOI： 10.1016/j.catcom.2019.02.019

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Solid oxide fuel cells (SOFCs) show high energy-conversion efficiency and thus emit less CO2 than conventional combustion engines. Although SOFCs can directly convert hydrocarbons such as liquefied petroleum gas, these fuels readily induce coking on the electrodes of fuel cell stacks. To avoid coking, hydrocarbons can be subjected to a preliminary endothermic steam-reforming step at a relatively low temperature using waste heat from the stack. Herein, we report that a Rh/Ce0.25Zr0.75O2 catalyst exhibited higher propane-steam-reforming activity than other Rh/Ce1-xZrxO2 catalysts and Rh/gamma-Al2O3. Catalyst characterization revealed that Rh/Ce0.25Zr0.75O2 had excellent redox property and high H2O-adsorption activity, which contributed to the activation of steam and thus enhanced the propane-steam-reforming activity of this catalyst.

DOI： 10.1002/cctc.201801824

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Ru is an important catalyst in many types of reactions. Specifically, Ru is well known as the best monometallic catalyst for oxidation of carbon monoxide (CO) and has been practically used in residential fuel cell systems. However, Ru is a minor metal, and the supply risk often causes violent fluctuations in the price of Ru. Performance-improved and cost-reduced solid-solution alloy nanoparticles of the Cu-Ru system for CO oxidation are now presented. Over the whole composition range, all of the Cux Ru1-x nanoparticles exhibit significantly enhanced CO oxidation activities, even at 70 at % of inexpensive Cu, compared to Ru nanoparticles. Only 5 at % replacement of Ru with Cu provided much better CO oxidation activity, and the maximum activity was achieved by 20 at % replacement of Ru by Cu. The origin of the high catalytic performance was found as CO site change by Cu substitution, which was investigated using in situ Fourier transform infrared spectra and theoretical calculations.

DOI： 10.1002/anie.201812325

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© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim There is interest in minimizing or eliminating the use of Pt in catalysts by replacing it with more widely abundant and cost-effective elements. The alloying of Pt with non-noble metals is a potential strategy for reducing Pt use because interactions between Pt and non-noble metals can modify the catalyst structure and electronic properties. Here, a γ-Al2O3-supported bimetallic catalyst [Pt(0.1)Co(1)/Al2O3] was prepared which contained 0.1 wt % Pt and 1 wt % Co and thus featured an extremely low Pt : Co ratio (<1 : 30 mol/mol). The Pt and Co in this catalyst formed alloy nanoparticles in which isolated electron-rich Pt atoms were present on the nanoparticle surface. The activity of this Pt(0.1)Co(1)/Al2O3 catalyst for the purification of automotive exhaust was comparable to the activities of 0.3 and 0.5 wt % Pt/γ-Al2O3 catalysts. Electron-rich Pt and metallic Co promoted activation of NOx and oxidization of CO and hydrocarbons, respectively. This strategy of tuning the surrounding structure and electronic state of a noble metal by alloying it with an excess of a non-noble metal will enable reduced noble metal use in catalysts for exhaust purification and other environmentally important reactions.

DOI： 10.1002/cplu.201800542

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

© 2018 American Chemical Society. To exploit the use of hydrogen as a source of sustainable energy, development of an efficient process for synthesizing an energy carrier such as ammonia under mild conditions will be necessary. Here, we show that Ru/La0.5Pr0.5O1.75 prereduced at an extraordinary high temperature of 650 °C catalyzes high NH3-synthesis rates under mild conditions. At 400 °C under 1.0 MPa, the synthesis rate was comparable with that of most active oxide-supported Ru catalysts. Kinetic analysis revealed that hydrogen poisoning, which is a typical drawback for oxide-supported Ru catalysts such as Cs+/Ru/MgO, was effectively suppressed over Ru/La0.5Pr0.5O1.75. The high activity induced by high-temperature reduction was attributable to the good thermal stability of the support and a phase change of the La0.5Pr0.5O1.75 support during prereduction. Fourier transform-infrared spectroscopy measurements after N2 adsorption on the catalyst revealed that electrons were efficiently donated from trigonal La0.5Pr0.5O1.5 to the antibonding π orbital of the N≡N bond of N2 via Ru atoms. Cleavage of the N≡N bond, the rate-determining step for ammonia synthesis, was thus accelerated. Our results expand the range of possibilities for developing more effective ammonia synthesis catalysts under mild conditions. Such catalysts will be needed to enable development of hydrogen-based sustainable energy resources.

DOI： 10.1021/acssuschemeng.8b04683

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The oxidation of carbon monoxide (CO) over PdRu solid solution nanoparticles was studied by the combined theoretical and experimental approaches. In this work, CO and O adsorptions on PdRu alloy surface models were theoretically investigated to understand the kinetics of CO oxidation reaction. It was found that CO adsorption on Pd atom in the PdRu alloy surfaces is weaker than on monometallic surfaces. From the experiment, reaction order of CO on the PdRu surface was observed to be smaller than that on Pd surface. While, the positive first order with respect to O-2 obtained for both Pd and PdRu alloy surfaces. Catalytic reaction mechanism is discussed on the basis of both theoretical and experimental observations.

DOI： 10.1016/j.apcata.2018.10.002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

In the presence of a palladium-loaded TiO2 photocatalyst, the cleavage of benzyl phenyl ether in low-molecular-weight alcohol solvents under de-aerated conditions afforded toluene and phenol simultaneously in a 1:1 molar ratio.

DOI： 10.1039/c8cc03362e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley-VCH Verlag  

Solid oxide fuel cells (SOFCs) with liquefied petroleum gas (LPG) reduce CO2 emissions due to their high-energy-conversion efficiency. Although SOFCs can convert LPG directly, coking occurs easily by decomposition of hydrocarbons, including C−C bonds on the electrode of fuel cell stacks. It is therefore necessary to develop an active steam pre-reforming catalyst that eliminates the hydrocarbons at low temperature, in which waste heat of SOFCs is used. Herein, we show that the crystal structure of the TiO2 that anchors Rh particles is crucial for catalytic activity of Rh/TiO2 catalysts for propane pre-reforming. Our experimental results revealed that strong metal support interaction (SMSI) induced during H2 pre-reduction were optimized over Rh/TiO2 with a rutile structure
this catalyst catalyzed the reaction much more effectively than conventional Rh/γ-Al2O3. In contrast, the SMSI was too strong for Rh/TiO2 with an anatase structure, and the surface of the Rh particles was therefore covered mostly with partially reduced TiO2. The result was very low activity.

DOI： 10.1002/chem.201800936

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Publisher：Google Patents  

US Patent 9,962,683

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© 2017 American Chemical Society. The dynamic behavior of Rh species in 1 wt% Rh/Al2O3 catalyst during the three-way catalytic reaction was examined using a micro gas chromatograph, a NOx meter, a quadrupole mass spectrometer, and time-resolved quick X-ray absorption spectroscopy (XAS) measurements at a public beamline for XAS, BL01B1 at SPring-8, operando. The combined data suggest different surface rearrangement behavior, random reduction processes, and autocatalytic oxidation processes of Rh species when the gas is switched from a reductive to an oxidative atmosphere and vice versa. This study demonstrates an implementation of a powerful operando XAS system for heterogeneous catalytic reactions and its importance for understanding the dynamic behavior of active metal species of catalysts.

DOI： 10.1021/jacs.7b07114

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

Ammonia is an important feedstock for producing fertiliser and is also a potential energy carrier. However, the process currently used for ammonia synthesis, the Haber-Bosch process, consumes a huge amount of energy
therefore the development of new catalysts for synthesising ammonia at a high rate under mild conditions (low temperature and low pressure) is necessary. Here, we show that Ru/La0.5Ce0.5O1.75 pre-reduced at an unusually high temperature (650 °C) catalysed ammonia synthesis at extremely high rates under mild conditions
specifically, at a reaction temperature of 350 °C, the rates were 13.4, 31.3, and 44.4 mmol g-1 h-1 at 0.1, 1.0, and 3.0 MPa, respectively. Kinetic analysis revealed that this catalyst is free of hydrogen poisoning under the conditions tested. Electron energy loss spectroscopy combined with O2 absorption capacity measurements revealed that the reduced catalyst consisted of fine Ru particles (mean diameter &lt
2.0 nm) that were partially covered with partially reduced La0.5Ce0.5O1.75 and were dispersed on a thermostable support. Furthermore, Fourier transform infrared spectra measured after N2 addition to the catalyst revealed that N2 adsorption on Ru atoms that interacted directly with the reduced La0.5Ce0.5O1.75 weakened the NN bond and thus promoted its cleavage, which is the rate-determining step for ammonia synthesis. Our results indicate that high-temperature pre-reduction of this catalyst, which consists of Ru supported on a thermostable composite oxide with a cubic fluorite structure and containing reducible cerium, resulted in the formation of many sites that were highly active for N2 reduction by hydrogen.

DOI： 10.1039/c7sc05343f

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Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

DOI： 10.1246/cl.180349

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Size-controlled Rh nanoparticles stabilized by poly(vinylpyrrolidone) were quickly synthesized via alcohol reduction. Microwave-assisted synthesis in closed vessels allowed alcohols with low-to-high boiling points to be used as reductants under the same preparation conditions. Pure ethanol has not been used previously because its boiling point is lower than the temperature required for Rh3+ reduction. Alcohols with relatively strong reduction ability were found to lead to smaller Rh nanoparticles. The ability to oxidize CO was enhanced as the Rh particle size decreased.

DOI： 10.1246/cl.170440

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER ASSOC ADVANCEMENT SCIENCE  

Ammonia has been suggested as a carbon-free hydrogen source, but a convenient method for producing hydrogen from ammonia with rapid initiation has not been developed. Ideally, this method would require no external energy input. We demonstrate hydrogen production by exposing ammonia and O-2 at room temperature to an acidic RuO2/gamma-Al2O3 catalyst. Because adsorption of ammonia onto the catalyst is exothermic, the catalyst bed is rapidly heated to the catalytic ammonia autoignition temperature, and subsequent oxidative decomposition of ammonia produces hydrogen. A differential calorimeter combined with a volumetric gas adsorption analyzer revealed a large quantity of heat evolved both with chemisorption of ammonia onto RuO2 and acidic sites on the gamma-Al2O3 and with physisorption of multiple ammonia molecules.

DOI： 10.1126/sciadv.1602747

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We report on novel solid-solution alloy nanoparticles (NPs) of Ru and Cu that are completely immiscible even above melting point in bulk phase. Powder X-ray diffraction, scanning transmission electron microscopy, and energy-dispersive X-ray measurements demonstrated that Ru and Cu atoms were homogeneously distributed in the alloy NPs. Ru0.5Cu0.5 NPs demonstrated higher CO oxidation activity than fcc-Ru NPs, which are known as one of the best monometallic CO oxidation catalysts.

DOI： 10.1021/jacs.7b01186

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Ni catalysts with high surface areas were prepared from Mg-Al hydrotalcite-like compounds containing Ni with different Mg-to-Al ratios for the production of hydrogen via ammonia decomposition. At atomic ratios of Mg-to-Al from 3:1 to 6:1, Ni reduction was greater than 90%, and the amounts of Ni-0 exposed were kept at more than 200 mu mol g(-1). With the increase in Mg-to-Al ratio, turnover frequency was increased due to an increase in the basicity of the support. Of the catalysts examined, Ni_MgAl(6:1) exhibited the highest NH3 conversion, which was attributed to its relatively high basicity and large amount of Ni exposed. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijhydene.2016.11.150

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Ammonia is a crucial chemical feedstock for fertilizer production and is a potential energy carrier. However, the current method of synthesizing ammonia, the Haber-Bosch process, consumes a great deal of energy. To reduce energy consumption, a process and a substance that can catalyze ammonia synthesis under mild conditions (low temperature and low pressure) are strongly needed. Here we show that Ru/Pr2O3 without any dopant catalyzes ammonia synthesis under mild conditions at 1.8 times the rates reported with other highly active catalysts. Scanning transmission electron micrograph observations and energy dispersive X-ray analyses revealed the formation of low-crystalline nano-layers of ruthenium on the surface of Pr2O3. Furthermore, CO2 temperature-programmed desorption revealed that the catalyst was strongly basic. These unique structural and electronic characteristics are considered to synergistically accelerate the rate-determining step of NH3 synthesis, cleavage of the N N bond. We expect that the use of this catalyst will be a starting point for achieving efficient ammonia synthesis.

DOI： 10.1039/c6sc02382g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The first synthesis of pure Rh1-xCux solid-solution nanoparticles is reported. In contrast to the bulk state, the solid-solution phase was stable up to 750 degrees C. Based on facile density-functional calculations, we made a prediction that the catalytic activity of Rh1-xCux can be maintained even with 50 at% replacement of Rh with Cu. The prediction was confirmed for the catalytic activities on CO and NOx conversions.

DOI： 10.1002/chem.201604286

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

The change in electronic structure of extremely small RhxCuy alloy nanoparticles (NPs) with composition variation was investigated by core-level (CL) and valence-band (VB) hard X-ray photoelectron spectroscopy. A combination of CL and VB spectra analyses confirmed that intermetallic charge transfer occurs between Rh and Cu. This is an important compensation mechanism that helps to explain the relationship between the catalytic activity and composition of RhxCuy alloy NPs. For monometallic Rh and Rh-rich alloy (Rh0.77Cu0.23) NPs, the formation of Rh surface oxide with a non-integer oxidation state (Rh(3-delta)+) resulted in high catalytic activity. Conversely, for alloy NPs with comparable Rh: Cu ratio (Rh0.53Cu0.47 and Rh0.50Cu0.50), the decreased fraction of catalytically active Rh(3-delta)+ oxide is compensated by charge transfer from Cu to Rh. As a result, ensuring negligible change in the catalytic activities of the NPs with comparable Rh: Cu ratio to those of Rh-rich and monometallic Rh NPs.

DOI： 10.1038/srep41264

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US Patent 9,452,417

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Rh is one of the most important noble metals for industrial applications. A major fraction of Rh is used as a catalyst for emission control in automotive catalytic converters because of its unparalleled activity toward NOx reduction. However, Rh is a rare and extremely expensive element; thus, the development of Rh alternative composed of abundant elements is desirable. Pd and Ru are located at the right and left of Rh in the periodic table, respectively, nevertheless this combination of elements is immiscible in the bulk state. Here, we report a Pd-Ru solid-solution-alloy nanoparticle (PdxRu1-x NP) catalyst exhibiting better NOx reduction activity than Rh. Theoretical calculations show that the electronic structure of Pd0.5Ru0.5 is similar to that of Rh, indicating that Pd0.5Ru0.5 can be regarded as a pseudo-Rh. Pd0.5Ru0.5 exhibits better activity than natural Rh, which implies promising applications not only for exhaust-gas cleaning but also for various chemical reactions.

DOI： 10.1038/srep28265

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

This article anticipates the development of dual Lewis acidic/basic alloyed nanoparticle (NP) of poly(N-vinyl-2-pyrrolidone)stabilized Pd0.5Ru0.5 solid solution, revealing equivalent Pd delta+ and Ru-delta on the NP surface. This unsupported NP disclosed excellent catalytic efficiency with high turnover frequency, 15000 h(-1) in Suzuki-Miyaura cross-coupling under notable drop of both Pd loading (0.08 mol%) and time (5 min) in air, attributed for its bifunctional acidic/basic modes. The bifunctional modes exposed the most interesting new reaction mechanism ascribed by the inductive effects of p-substituents in arylboronic acid, accelerated reactivity by electron-withdrawing group, revealing an opposite reactivity trend relative to other Pd-based catalysts. Besides, the significant drops of Pd loading and reaction time impeded the metal leaching associated with no changes in NP surface composition/structure after the 3rd cycle (>99% efficiency), revealing a line-up for this NP in the environmental sustainability.

DOI： 10.1002/cctc.201500758

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

This article anticipates the development of dual Lewis acidic/basic alloyed nanoparticle (NP) of poly(N-vinyl-2-pyrrolidone)stabilized Pd0.5Ru0.5 solid solution, revealing equivalent Pd delta+ and Ru-delta on the NP surface. This unsupported NP disclosed excellent catalytic efficiency with high turnover frequency, 15000 h(-1) in Suzuki-Miyaura cross-coupling under notable drop of both Pd loading (0.08 mol%) and time (5 min) in air, attributed for its bifunctional acidic/basic modes. The bifunctional modes exposed the most interesting new reaction mechanism ascribed by the inductive effects of p-substituents in arylboronic acid, accelerated reactivity by electron-withdrawing group, revealing an opposite reactivity trend relative to other Pd-based catalysts. Besides, the significant drops of Pd loading and reaction time impeded the metal leaching associated with no changes in NP surface composition/structure after the 3rd cycle (>99% efficiency), revealing a line-up for this NP in the environmental sustainability.

DOI： 10.1002/cctc.201500758

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Language：English   Publisher：JAPAN PETROLEUM INST  

Efficient cold-start process of hydrogen production by oxidative reforming (OR) of hydrocarbon was developed using Rh catalyst supported on carriers with redox properties. In this process, the heat generated by re-oxidation of reduced catalyst rapidly heats the catalyst from ambient temperature to the catalytic auto-ignition temperature of the OR. OR was triggered at ambient temperature over Rh/CeO2 after reduction at 873 K, but not over Rh catalysts supported on Pr6O11 and Tb4O7, oxides of rare earth elements with redox characters like cerium. Over the latter catalysts, reduction of the carrier occurred at lower temperatures than over CeO2, but the reduced oxides were not re-oxidized at ambient temperature. Our results emphasized that re-oxidation as well as reduction of the catalyst are the key characteristics of the carrier for triggering OR at ambient temperature. With the use of Rh/Ce0.5Zr0.5O2 with excellent redox properties at low temperature, triggering OR of hydrocarbons at ambient temperature was achieved even under non-adiabatic conditions, where heat losses occur, over the catalyst after reduction at 373 K and after in-situ reduction by hydrogen formed during the OR. This new catalytic process is expected to be useful for the development of self-sufficient reforming processes for a new generation of fuel cells.

DOI： 10.1627/jpi.58.274

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8440

DOI： 10.1149/06801.0651ecst

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Petroleum Institute  

Efficient cold-start process of hydrogen production by oxidative reforming (OR) of hydrocarbon was developed using Rh catalyst supported on carriers with redox properties. In this process, the heat generated by re-oxidation of reduced catalyst rapidly heats the catalyst from ambient temperature to the catalytic auto-ignition temperature of the OR. OR was triggered at ambient temperature over Rh/CeO2after reduction at 873 K, but not over Rh catalysts supported on Pr6O11and Tb4O7, oxides of rare earth elements with redox characters like cerium. Over the latter catalysts, reduction of the carrier occurred at lower temperatures than over CeO2, but the reduced oxides were not re-oxidized at ambient temperature. Our results emphasized that re-oxidation as well as reduction of the catalyst are the key characteristics of the carrier for triggering OR at ambient temperature. With the use of Rh/Ce0.5Zr0.5O2 with excellent redox properties at low temperature, triggering OR of hydrocarbons at ambient temperature was achieved even under non-adiabatic conditions, where heat losses occur, over the catalyst after reduction at 373 K and after in-situ reduction by hydrogen formed during the OR. This new catalytic process is expected to be useful for the development of self-sufficient reforming processes for a new generation of fuel cells.

DOI： 10.1627/jpi.58.274

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Basic oxides such as alkali metal oxides, alkaline earth metal oxides, and rare earth oxides were added to Ru/Pr6O11, and the activity of the catalysts with respect to hydrogen production by ammonia decomposition was investigated. Ru/Pr6O11 doped with alkali metal oxides, except for Li2O, achieved higher NH3 conversions than bare Ru/Pr6O11 center dot Cs2O, the most basic of the alkali metal oxides, was the most effective dopant. In contrast, other dopants with lower basicity than the alkali metal oxides achieved lower NH3 conversions than bare Ru/Pr6O11. Changing the Cs/Ru molar ratio revealed that the best Cs/Ru ratio was 0.5-2; the reaction was effectively promoted without negative effects from coverage of the Ru surface by the Cs2O. Varying the order of loading the Ru and Cs2O onto Pr6O11 revealed that loading Ru onto Cs2O/Pr6O11 was an effective way to enhance NH3 conversion, and coverage of the Ru surface was reduced. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijhydene.2014.07.142

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

In polymer electrolyte fuel cell (PEFC) systems, small amounts of ammonia (NH3) present in the reformate gas deactivate the supported ruthenium catalysts used for preferential oxidation (PROX) of carbon monoxide (CO). In this study, we investigated how the addition of a small amount of platinum to a Ru/alpha-Al2O3 catalyst (Pt/Ru=1:9 w/w) affected the catalyst's PROX activity in both the absence and the presence of NH3 (130 ppm) under conditions mimicking the reformate conditions during steam reforming of natural gas. The activity of undoped Ru/alpha-Al2O3 decreased sharply upon addition of NH3, whereas Pt/Ru/alpha-Al2O3 exhibited excellent PROX activity even in the presence of NH3. Ruthenium K-edge X-ray absorption near-edge structure (XANES) spectra indicated that in the presence of NH3, some of the ruthenium in the undoped catalyst was oxidized in the presence of NH3, whereas ruthenium oxidation was not observed with Pt/Ru/alpha-Al2O3. These results suggest that ruthenium oxidation is retarded by the platinum, so that the catalyst shows high activity even in the presence of NH3.

DOI： 10.1002/cssc.201402583

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A hybrid catalyst consisting of polymer-coated Ru nanoparticles (Ru-PVP, PVP: poly(N-vinyl-2-pyrrolidone)) embedded in a porous metal-organic framework of ZIF-8 (Ru-PVP@ZIF-8) was synthesized by the crystallization of ZIF-8 in a methanol solution of Ru-PVP. The structural properties of Ru-PVP@ZIF-8 were examined by N-2 gas adsorption, infrared spectra, and X-ray powder diffraction measurements. We successfully identified the most appropriate pretreatment conditions for surface activation of the Ru nanoparticles in the catalyst. The pretreated Ru-PVP@ZIF-8 was applied for a CO oxidation reaction with H-2 gas feeds. Ru-PVP@ZIF-8 was found to exhibit higher catalytic activities and higher CO2 selectivity than those observed on a carbon-supported Ru-PVP (Ru-PVP/C), implying that the pores of the ZIF-8 provide a more suitable environment for the reaction with O-2 and CO gases.

DOI： 10.1039/c4dt00996g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Three Rh catalysts supported on CeO2 with different specific surface areas and redox properties were prepared and evaluated for their ability to trigger the oxidative reforming of n-butane from ambient temperature (approximate to 300K). The reference CeO2 catalysts supplied by the Catalyst Society of Japan (JRC-CEO-1, -3, and -4) were used as supports. Temperature-programmed reduction and O-2 titration measurements over the reduced catalysts indicated that a high number of surface CeO2 sites that were reducible below 573K were present on the Rh/CEO-3 catalyst; this catalyst had the largest specific surface area, and it generated sufficient heat by oxidizing CeO2-x [H(298K)=-368kJ; x=0.5] after H-2 reduction at 773K. Furthermore, the temperature-programmed reactions revealed that forming fine Rh particles on the high surface area of CEO-3 lowers the autoignition temperature (498K) of the oxidative reforming of n-butane because the number of exposed Rh sites initiating reactions between n-butane and O-2 is large. Thus, the Rh/CEO-3 catalyst could trigger the oxidative reforming of n-butane at ambient temperature after H-2 reduction at 773K owing to the heat generated by the spontaneous oxidation of CeO2-x. In contrast, other catalysts could not trigger the reaction after reduction at the same temperature.

DOI： 10.1002/cctc.201300826

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Three Rh catalysts supported on CeO2 with different specific surface areas and redox properties were prepared and evaluated for their ability to trigger the oxidative reforming of n-butane from ambient temperature (approximate to 300K). The reference CeO2 catalysts supplied by the Catalyst Society of Japan (JRC-CEO-1, -3, and -4) were used as supports. Temperature-programmed reduction and O-2 titration measurements over the reduced catalysts indicated that a high number of surface CeO2 sites that were reducible below 573K were present on the Rh/CEO-3 catalyst; this catalyst had the largest specific surface area, and it generated sufficient heat by oxidizing CeO2-x [H(298K)=-368kJ; x=0.5] after H-2 reduction at 773K. Furthermore, the temperature-programmed reactions revealed that forming fine Rh particles on the high surface area of CEO-3 lowers the autoignition temperature (498K) of the oxidative reforming of n-butane because the number of exposed Rh sites initiating reactions between n-butane and O-2 is large. Thus, the Rh/CEO-3 catalyst could trigger the oxidative reforming of n-butane at ambient temperature after H-2 reduction at 773K owing to the heat generated by the spontaneous oxidation of CeO2-x. In contrast, other catalysts could not trigger the reaction after reduction at the same temperature.

DOI： 10.1002/cctc.201300826

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

PdxRu1-x solid solution alloy nanoparticles were successfully synthesized over the whole composition range through a chemical reduction method, although Ru and Pd are immiscible at the atomic level in the bulk state. From the XRD measurement, it was found that the dominant structure of PdxRu1-x changes from fcc to hcp with increasing Ru content. The structures of PdxRu1-x nanoparticles in the Pd composition range of 30-70% consisted of both solid solution fcc and hcp structures, and both phases coexist in a single particle. In addition, the reaction of hydrogen with the PdxRu1-x nanoparticles changed from exothermic to endothermic as the Ru content increased. Furthermore, the prepared PdxRu1-x nanoparticles demonstrated enhanced CO-oxidizing catalytic activity; Pd0.5Ru0.5 nanoparticles exhibit the highest catalytic activity. This activity is much higher than that of the practically used CO-oxidizing catalyst Ru and that of the neighboring Rh, between Ru and Pd.

DOI： 10.1021/ja409464g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Adding Cr to heat-tolerant Co0.054Ni0.018Mg0.93O solid-solution catalysts for CH4/CO2/H2O reforming at 2.1 M.Pa allowed us to control the key properties determining the behavior of the supported catalysts, such as the reduction degree of the metal, metal particle size, and amount of exposed zerovalent metals. A small load of Cr [Cr/(Co + Ni) = 0.11 mol %] efficiently catalyzed Co2+ and Ni2+ reduction. This catalyst, which had abundant small alloy particles on the support material, resisted coking and oxidative deactivation, even under accelerated deterioration conditions: X-ray photoelectron spectroscopy, X-ray absorption near-edge structure, extended X-ray absorption fine structure, and scanning transmission electron microscopy energy-dispersive X-ray measurements indicated that Cr existed as a trivalent cation in a CrxCo0.054Ni0.018Mg0.93O1+1.5x solid solution, leading to the formation of a divalent cation vacancy and that Cr3+ was abundant on the surface of the catalyst particles after calcination at 1373 K. The Cr3+ destabilized Co2+ and Ni2+ in the solid solution, especially on the surface of the catalyst particles and, thus, promoted Co2+ and Ni2+ reduction. However, excess Cr3+ induced sintering of the catalyst particles, resulting in aggregation of alloy particles and, thus, in an increased risk of coking.

DOI： 10.1021/cs400199b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We report the first discovery of pure face-centered-cubic (fcc) Ru nanoparticles. Although the fcc structure does not exist in the bulk Ru phase diagram, fcc Ru was obtained at room temperature because of the nanosize effect. We succeeded in separately synthesizing uniformly sized nanoparticles of both fcc and hcp Ru having diameters of 2-5.5 nm by simple chemical reduction methods with different metal precursors. The prepared fcc and hcp nanoparticles were both supported on gamma-Al2O3, and their catalytic activities in CO oxidation were investigated and found to depend on their structure and size.

DOI： 10.1021/ja311261s

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J-GLOBAL

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOC INC  

Evaluation of the SOFC performance was carried out by supplying simulated reformate gases of dimethyl ether (DME) and propane to an anode-supported small tubular cell, in order to clarify the potential of DME as a fuel for solid oxide fuel cell (SOFC) systems designed for liquefied petroleum gas (LPG). The SOFC obtained similar performance when either DME (S/C 2.0) or propane reformate gas (S/C 3.5) was supplied to the cell. In addition, about the same level of DC electrical efficiency was realized when either DME (S/C 1.5) or propane reformate gas (S/C 3.5) was used. The results show that DME can be used as a fuel for an SOFC system designed for LPG without drastic alterations to the system.

DOI： 10.1149/05101.0137ecst

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOC INC  

A method to evaluate current efficiency was developed for high temperature electrolysis using solid oxide cells (SOECs). For a fuel electrode, depending on range, our gas analysis system achieved +/- 0.4-0.6% uncertainty for 10-90% mole fraction analysis of H-2 and H2O. For an air electrode, O-2 and N-2 was measured with +/- 0.2% and +/- 0.4% uncertainty, respectively. Case studies for both electrodes clarified that current efficiency can be evaluated with +/- 1.1-2.8% uncertainty at practical 90-50% steam utilizations in the case of +/- 1.0% uncertainty in gas-flow-rate measurement.

DOI： 10.1149/05049.0081ecst

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Prototype of efficient anode-off gas recycle blowers was developed with a 3D turbo impeller and a DC brush-less built-in motor for high efficiency SOFCs. Performance test of the blowers clarified 26% and 52% total blower efficiency for the type SSR-70 for 10 kW-class SOFC and SSR-140 for 250 kW, respectively. System performance simulation of an SOFC system with the SSR-70 blower elucidated that 59% net AC electrical efficiency can be expected. When the blower efficiency is improved to 50% as of SSR-140, electrical efficiency will become 60%. We will continue developing more efficient recycle blowers.

DOI： 10.1149/05701.0443ecst

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

To clarify the potential of dimethyl ether (DME) as a fuel for solid oxide fuel cell (SOFC) systems designed for liquefied petroleum gas (LPG), steam reforming and evaluation of an SOFC fueled by DME and propane, a main component of LPG, were carried out.
Steam reforming of DME was tested over a commercial reforming catalyst, which easily converted DME to reformate gas with equilibrium gas composition. No carbon deposition over the catalyst's surface was observed at steam-carbon (S/C) ratio of 1.5. In addition, propane was easily reformed under steam reforming conditions at S/C 3.5. These results indicate that both DME and LPG are reformed well over the same catalyst and reformer. Evaluation of the SOFC performance was carried out by supplying reformate gases with equilibrium composition to an anode-supported small tubular cell. The SOFC obtained similar performance when either DME (S/C 2.0) or propane reformate gas (S/C 3.5) was supplied to the cell. In addition, when evaluation of cell performance was carried out under steady power, about the same level of DC electrical efficiency was realized when either DME (S/C 1.5) or propane reformate gas (S/C 3.5) was used.
The results show that DME can be used as a fuel for an SOFC system designed for LPG without drastic alterations to the system. In addition, DME and propane realize the same levels of power and power generating efficiency when the fuels are reformed at adequate S/C values. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2012.06.001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

Three rhodium catalysts supported on rare earth oxides with redox properties, Rh/CeO2, Rh/Pr6O11, and Rh/Tb4O7, were tested for their ability to trigger oxidative reforming of n-butane at room temperature. Only Rh/CeO2 triggered the oxidative reforming, owing to the heat generated by the spontaneous oxidation of the CeO2-x species produced by prior reduction of the supported catalyst with H-2. Although the three rare earth oxides were reduced to CeO1.91. Pr2O3, and Tb2O3, respectively, by H-2 at &gt;= 873 K. CeO1.91 was the only reduced oxide that was oxidized upon exposure to O-2 at room temperature. These results indicate that the ability of the reduced oxide support to undergo oxidation at room temperature was crucial for triggering oxidative reforming of n-butane at room temperature. (C) 2011 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcat.2011.12.007

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To carry out performance test of solid oxide fuel cells (SOFCs) simply and safely without dealing with toxic carbon monoxide, validity of substituting H-2-H2O gas mixtures for reformate gases was investigated with practical-sized single cells. H-2-H2O gas mixtures were prepared by replacing CO with H-2 and CO2 with H2O in equilibrium reformate compositions at high temperatures (&gt;= 750 degrees C) where CH4 concentration is negligible. It was clarified that cell voltages for the H-2-H2O substitutes agreed to ones for reformate gas of kerosene or methane by 0.6-0.2% at 0-90% fuel utilization and 650-750 degrees C. It was concluded that the way of H-2-H2O substitution will be valid as long as for SOFCs show good internal reforming performance.

DOI： 10.1149/1.4705505

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASME-AMER SOC MECHANICAL ENG  

Background: In general, solid oxide fuel cell (SOFC) systems are said to be flexible to various kind of fuels such as natural gas and petroleum gas. The fuels are reformed at a reformer and supplied to anode. Cell testing for 10 to 100 W-class SOFCs needs steady supply of a real reformate gas or a simulated reformate gas. However, it is difficult to reform heavier hydrocarbons without know-how and to evaporate small flow-rate of water. In addition, cell performance comparison with reformate gases of various fuels has been scarcely reported. Method of approach: A new testing system, what we call "simulated-reformate-gas generator" was developed to simulate reformate gases from H(2), O(2), and CO(2) stably and safely without dealing with toxic CO. An anode-supported planar Ni-YSZ/YSZ/LSCF cell (100 cm(2)) was subjected to voltage-current density (V-J) characteristic to discuss validity of the generator and to evaluate fuel flexibility with practical size of the cell. Results: It was clarified that equilibrium compositions at steam reforming of hydrocarbons and oxygen-containing biodiesel (C(17)H(33)COOCH(3)) can be simulated with +/- 1.0 mol.% precision by the generator. It was found that anode gas conditions can change quickly to shorten voltage stabilizing time at testing. Furthermore, it was elucidated that V-J characteristics hardly changed for simulated reformate of CH(4), C(3)H(8), kerosene (C(12)H(24)), and biodiesel at S/C = 3.0. DC electrical efficiency was estimated for the fuels as 54.2, 52.9, 52.5, 52.3% (LHV), respectively. Conclusions: The developed simulated-reformate-gas generator is so precise and useful for cell testing, making it easy to change anode gas conditions. As long as fuels for SOFC systems are reformed to thermodynamic equilibrium, cell performance and electrical efficiency will be comparable. [DOI: 10.1115/1.4004466]

DOI： 10.1115/1.4004466

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN PETROLEUM INST  

Triggering oxidative steam reforming of ethanol was examined at low temperature over different supported Ni catalysts. Ni/Ce0.5Zr0.5O2, Ni/CeO2, and Ni/MgAl2O4 reduced at 800 degrees C enabled triggering the reaction at 100 degrees C without external energy input. This behavior was rationalized by internal heat supply by heat evolution from oxidation of Ce3+ and metallic Ni-0. The generated heat increased catalyst bed temperature up to autoignition temperature and thus the reaction was initiated. Especially, Ni/Ce0.5Zr0.5O2 triggered the reaction repeatedly without H-2 treatment from the second cycle. This is related to superior redox property and low autoignition temperature of ethanol oxidative steam reforming over Ni/Ce0.5Zr0.5O2 comparing with other supported Ni catalysts.

DOI： 10.1627/jpi.54.331

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Slurry coating method for fabricating tubular solid oxide electrolysis stacks operated at 700 similar to 800 degrees C is developed. To improve cell performance at low temperatures, the thickness of the electrolyte layer is attempted to be controlled to about 10 mu m. By using this process, the SOEC stack whose input power is about 100 W is fabricated and its performance is measured. From the measurement, it is clarified that the hydrogen production rate at 750 degrees C goes up to 678 sccm (3.08 sccm/cm(2)) at the thermoneutral voltage and steam utilization of 75%. Furthermore, impedance of the stack is analysed by AC impedance method.

DOI： 10.1149/1.3570298

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOCIETY INC  

In this study, we investigated the possibility of constructing a portable SOFC system using DME as fuel. It was clarified that DME have some suitable properties as a fuel for the portable device. Tubular SOFC was fabricated and measurements of cell performance with different conditions were carried out. The fabricated cell successfully obtained 0.122 Wcm(-2) as the maximum power density at 750 degrees C. The impedance spectra showed that the resistances for electrochemical reactions were dominant factors for voltage drops. Thus it was clarified that decreasing these activation overvoltages is the most promising approach to improve power generation property of our fabricated cell.

DOI： 10.1149/1.3570050

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Numerical simulations were implemented to predict a disc-type single cell performance with gas seal at anode off-gas recycle from the previous experimental results without gas seal. It was clarified that 70% DC electrical efficiency with seal could be expected at 700 degrees C, 387 mA cm(-2) (90% fuel and 45% air utilizations) and recycle ratio r = 0.67 by 17 mV enhancement in the cell voltage with gas sealing. The efficiency would be increased by 1 percentage point compared to one without seal. Distribution of current density, anode gas composition, and electromotive force in the cell with seal was also elucidated. Furthermore, it was revealed that change in current density, H-2 concentration, and electromotive force between the cell inlet and outlet could become smaller as the recycle ratio increases. It was also found that differences in recycle ratio (r = 0.56, 0.67, 0.74) could influence cell voltage only by +/- 1%.

DOI： 10.1149/1.3570053

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOC INC  

Anode gas recycle (AGR) is one of the methods to enhance fuel utilization. In this paper, electrochemical performance of a single planar solid oxide fuel cell (SOFC) was investigated with/without AGR. Cell performance at AGR was successfully evaluated by our simulated-reformate generator without carrying out AGR actually. It was clarified that cell voltage more than 0.8 V could be obtained with AGR at utilization of 90% methane fuel and 45% air, 700 degrees C and 400 mA cm(-2). The cell voltage was by 20 mV higher than one without AGR at the same utilizations. DC electrical efficiency more than 69%-LHV can be expected at AGR-SOFC which is by 2 percent points higher than one without AGR. Furthermore, it was found that deviation of cell voltage against change in current at a constant flow-rate and time constant for gas conversion in anode would be twice smaller with AGR than without AGR.

DOI： 10.1149/1.3562470

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Tubular solid oxide electrolysis cells (SOECs) whose operating temperature is reduced to 700 similar to 800 degrees C are developed. To improve cell performance at the low temperature, Sc2O3 stabilized ZrO2 is chosen as electrolyte material and the thickness of the electrolyte layer is tried controlling about 10 mu m by slurry coating method. As a result of performance test, it is clarified that current density at thermoneutral point goes up to 0.46 Acm(-2) at 750 degrees C. Furthermore, degradation phenomena in long term operation more than 1200 h are observed.

DOI： 10.1149/1.3562487

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The use of a new catalyst, namely, Cs2O/5 wt % Ru/Pr6O11 (mole ratio of Cs to Ru: 1), in which Ru is supported on strong basic Pr6O11 and the strong basic promoter Cs2O is added, resulted in almost complete NH3 consumption at 673 K and an NH3 conversion of 14% even at temperatures as low as 523 K.

DOI： 10.1246/cl.2010.918

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Oxidative steam reforming of n-C(4)H(10) over MgO-supported Ni catalysts is described. The Ni/MgO catalysts were prepared by the impregnation method from aqueous Ni(NO(3))(2) precursor solutions at two pH values. Ni/MgO prepared at pH 7 exhibited considerably higher activity than Ni/MgO prepared from a conventional acidic aqueous precursor solution (pH 3.5). The H(2) formation rate for the modified Ni/MgO was up to 2.3 times that for conventional Ni/MgO under a high space velocity of 1660 L(h g)(-1). Furthermore, after reduction at high temperature (1273 K), the modified Ni/MgO showed a higher H(2) formation rate than did Rh/MgO. The superior performance of the modified Ni/MgO was ascribed to stronger resistance to oxidation of Ni(o) due to the formation of relatively large Ni(o) particles. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijhydene.2010.03.028

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DOI： 10.1002/cssc.201000221

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Catalytic behaviors of TiO2-, Zr0.5Ti0.5O2-, and ZrO2-supported Ni catalysts were investigated for oxidative steam reforming of n-C4H10 at 723 K. The composite oxide support, Zr0.5Ti0.5O2, shows high specific surface area (136 m(2)/g), leading to fine Ni particles. Thus, the Ni/Zr0.5Ti0.5O2 catalyst exhibits higher and more stable activity than that exhibited by other catalysts. However, relatively large amounts of coke are deposited on the catalyst during reaction. Thus, to retard carbon deposition, the influence of SiO2 additive was studied. Large amounts of SiO2 additive (5 or 10 mol%) decrease initial activity; at 10 mol%, degradation is also induced by oxidation of Ni-o. However, small amounts of SiO2 additive (1.5 mol%) effectively retard coking without lowering initial activity. The resultant Ni/Zr0.5Ti0.5O2-SiO2 (1.5 mol%) catalyst exhibits high and stable activity without coking. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijhydene.2009.08.005

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The catalytic characteristics of various rare-earth oxide supports for Ni catalysts were investigated for the initiation of the oxidative reforming (OR) of C4H10 at ambient temperature. Ni/PrO1.83, reduced at 873 K, successfully initiated the OR of C4H10 as previously reported for Ni/CeO2. PrO1.83 undergoes reduction by H-2 at 873 K and subsequent oxidation at ambient temperature, so the catalyst is heated to initiate the auto-ignition temperature (633 K) of C4H10 OR over the catalyst.

DOI： 10.1627/jpi.52.295

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We investigated the oxidative reforming (OR) of n-C4H10 over Ni/CeO2 catalysts with different amounts of Ni loading at ambient temperature by feeding a reaction mixture. The OR of n-C4H10 was triggered rapidly over all the Ni/CeO2 catalysts reduced at 1073 K. O-2 absorption at 323 K revealed that the support was composed of CeO1.76 regardless of Ni loading after reduction. We concluded that the heat produced by spontaneous oxidation of CeO1.76 to CeO2 heated the catalysts to catalytic autoignition temperature. Among the catalysts, 1 wt% Ni/CeO2 exhibited durability against carbon deposition as well as excellent catalytic activity for OR in a cyclic activity test. (C) 2009 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.catcom.2009.03.028

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We report n-C4H10 autothermal reforming over MgO-supported base metal catalysts at 723 K. Catalytic performance was investigated not only after H-2 treatment at 1073 K (reductive treatment) but also after subsequent O-2/Ar treatment at the reaction temperature (oxidative treatment) to mimic the shutdown and startup of a domestic fuel cell system. After reductive treatment, both Ni/MgO and Co/MgO exhibited high n-C4H10 conversion and hydrogen formation activity; the stability of Ni/MgO was better than that of Co/MgO. The reaction route was investigated by measuring activity at various contact times. The results revealed that n-C4H10 autothermal reforming over Ni/MgO is a multi-step reaction composed of combustion, steam reforming, water gas shift reaction, and methanation. In contrast, Cu/MgO and Fe/Mgo did not show reforming activity but cracking and combustion of n-C4H10. Ni/MgO and Co/MgO catalyzed H-2 formation even after the oxidative treatment. However, the initial activity of Co/MgO after the oxidative treatment was lower than that after the reductive treatment and a decrease in H-2 formation rate was again observed after 6 h in Co/MgO, similar to the measurements after the reductive treatment. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijhydene.2008.10.014

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DOI： 10.1002/cssc.200900194

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Addition of Al2O3 or Cr2O3 promotes metal reduction in a CoO-NiO-MgO solid Solution catalyst and provides great resistance to oxidative deactivation in steam reforming of methane.

DOI： 10.1246/cl.2008.982

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DOI： 10.1021/cm800651m

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Oxidative steam reforming of n-butane over supported Ni catalysts at relatively low temperature, 723 K, is reported. Among all the supported 20 wt% Ni catalysts studied, only Ni/MgO was able to convert n-butane directly after 02 oxidation. Additionally, when the Ni/MgO was prepared from an aqueous Ni(NO3)(2) Solution with pH 7, H-2 formation rate of Ni/MgO (pH 7) at a high SV (1660 l(h center dot g)(-1)) was 2.3 times as high as that of conventional Ni/MgO. The higher activity of Ni/MgO (pH 7) was ascribed to stronger resistance against oxidation of Ni-0 due to the formation of relatively large Ni-0 particles. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.catcom.2007.02.013

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Oxidative steam reforming of n-butane over supported Ni catalysts at relatively low temperature, 723 K, is reported. Catalytic performance was investigated not only after H, treatment at 1073 K "reductive treatment" but also after subsequent O-2/Ar treatment at the reaction temperature "oxidative treatment" to mimic the shutdown and startup of the domestic fuel cell system. After the reductive treatment, n-butane conversion attained 100%, for all the catalyst at a lower space velocity (SV) of 67 L(h g)(-1). Differences in catalytic activity were emphasized at a higher SV of 667 L(h a)(-1), and were attributed to corresponding differences in metal surface area. Since a fraction of Ni in some catalysts was oxidized during the reaction at the higher SV, the reaction at the higher SV was indicated to be kinetically more oxidative condition. Although Ni/Al2O3 was inactive at the lower SV after the oxidative treatment, n-butane conversion of the other catalysts attained 100%. In contrast, only Ni/MgO was able to convert n-butane at the higher SV after the oxidative treatment. Therefore it was revealed that nickel oxide species on the catalyst were reduced by n-butane in the reactant even under severe oxidative conditions. C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apcata.2007.05.004

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DOI： 10.1002/ente.202000264

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当研究グループでは、アンモニアの触媒への吸着熱を利用することで、アンモニアの酸化的分解を室温から急速に起動させることに成功している。これまでに、反応のトリガとなる吸着熱の発生には担体の酸性質が大きく影響することを見出した。そこで本研究では、アンモニアに対してすぐれた吸着特性を示すゼオライトなどの多孔性酸化物担体を用いて、酸化的分解の常温駆動に与える影響について検討した。

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排ガス浄化触媒には多くの貴金属が含まれており、これを削減する技術の開発が求められている。我々は合金化などの手段を経ることで、微量貴金属と非貴金属の複合化効果を発現させて触媒活性を向上させ、貴金属の使用量を減らすことを目的に、種々の貴金属－非貴金属の組み合わせについて検討した。その結果、Pd-Niなどの組み合わせにおいて、一定の複合化効果が発現することを見出したので報告する。

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近年、NH&lt;sub&gt;3&lt;/sub&gt;を水素キャリアとした高度エネルギー変換・利用プロセスが提唱されている。一般に、NH&lt;sub&gt;3&lt;/sub&gt;分解には高価なRu触媒が用いられているが、我々は粘土状化合物であるハイドロタルサイトを前駆体とし、非貴金属を活性成分として用いた安価で高活性なMg-Al oxide担持触媒を報告している。今回は、Co/Mg-Al oxideに対して、希土類元素などの少量の添加物を加えるとNH&lt;sub&gt;3&lt;/sub&gt;分解活性が向上することを見出したので、その結果を報告する。&lt;br&gt;

DOI： 10.11523/sekiyu.2016f.0_25

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In the SOFC system for next generation, operation temperature of the system will be decreased.&amp;nbsp; Hence pre-reforming catalyst which converts propane, a major component of LPG, into C&lt;sub&gt;1&lt;/sub&gt; products even at low temperature (&amp;le; 400&amp;ordm;C) is highly demanded. In this study, we prepared different kinds of oxide supported Rh catalysts and carried out catalytic activity tests of propane steam reforming. We have found that Ce&lt;sub&gt;0.25&lt;/sub&gt;Zr&lt;sub&gt;0.75&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; supported Rh catalysts exhibit high activity at low temperature compared with conventional Rh/&amp;gamma;-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;. Furthermore we carried out several kinds of characterizations to reveal the role of the supports and concluded that redox ability of Ce&lt;sub&gt;0.25&lt;/sub&gt;Zr&lt;sub&gt;0.75&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; contributes to activation of steam and thus enhances catalytic activity.

DOI： 10.11523/sekiyu.2016f.0_51

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近年、NH&lt;sub&gt;3&lt;/sub&gt;は水素キャリアとして注目されているが、NH&lt;sub&gt;3&lt;/sub&gt;から水素を取り出すNH&lt;sub&gt;3&lt;/sub&gt;分解反応は吸熱反応であるため、外部加熱が必要であり装置の起動に時間を要する。一方、当研究室では触媒上への酸点へのNH&lt;sub&gt;3&lt;/sub&gt;の吸着熱を利用し、NH&lt;sub&gt;3&lt;/sub&gt;と酸素を室温で流通させるだけで瞬時にNH&lt;sub&gt;3&lt;/sub&gt;の酸化分解による水素製造反応を駆動可能であることを見出した。今回は、担持Ru触媒での担体効果について検討を行った。&lt;br&gt;

DOI： 10.11523/sekiyu.2016f.0_118

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DOI： 10.20550/jietaikaiyoushi.25.0_248

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&lt;p&gt;We demonstrated the cold-start process for oxidative reforming (OR) of &lt;i&gt;n&lt;/i&gt;-butane. In this process, without heating the catalyst by external energy OR is triggered rapidly and repeatedly over reduced CeO&lt;sub&gt;2&lt;/sub&gt; supported Rh catalysts from ambient temperature. Redox property of oxide support, i.e. spontaneous oxidation of the reduced catalyst support, CeO&lt;sub&gt;2-x&lt;/sub&gt; to CeO&lt;sub&gt;2&lt;/sub&gt;, and in-situ reduction of the catalyst support during OR, CeO&lt;sub&gt;2&lt;/sub&gt; to CeO&lt;sub&gt;2-x&lt;/sub&gt;, are found to be key factors for construction of this process.&lt;/p&gt;

DOI： 10.20550/jietaikaiyoushi.25.0_248

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In recent years, with the innovation of shale gas excavation technology, dry reforming of methane has been attracting attentions. Co-Mg-O solid solution catalyst are known to resist coking. However, most of Co in this&lt;br&gt;catalyst remained unreduced even by H&lt;sub&gt;2&lt;/sub&gt; treatment at high temperature and number of active site is very small. Resultantly, this catalyst is easily deactivated due to oxidation of Co. In contrast, we revealed that Al doping on Co-Mg-O solid solution catalyst significantly improves reduction degree of Co and enhances durability of the catalyst. In this work, we investigated state of Al by using &lt;sup&gt;27&lt;/sup&gt;Al NMR and influence of Al loads on catalytic property.

DOI： 10.11523/sekiyu.2015f.0_72

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SOFCは理論上H&lt;sub&gt;2&lt;/sub&gt;だけでなくCOや炭化水素をも直接燃料として利用できるが、C&lt;sub&gt;2&lt;/sub&gt;以上の炭化水素は炭素析出の原因となるため燃料ガス中に含まれることは好ましくない。本研究ではLPGを用いるSOFCシステムを想定し、そのプレリフォーマーとして利用可能な、300～400℃という低温でもプロパンをC&lt;sub&gt;1&lt;/sub&gt;まで改質することのできる高性能な担持Rh触媒の開発を行った。

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自動車排ガス中のハイドロカーボンやCOの除去には主に担持Pd触媒が用いられているが、従来型の触媒はPdの分散度が低く、活性が十分でないという問題がある。本研究では錯体重合法や保護剤の導入による調製法の改良によって担体上のPdの分散度を向上させ、担持Pd触媒の活性を向上させることを目的とした。

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Si&lt;sup&gt;4+&lt;/sup&gt; doped Ce&lt;sub&gt;0.5&lt;/sub&gt;Zr&lt;sub&gt;0.5&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; composites oxide were prepared and influence of Si&lt;sup&gt;4+&lt;/sup&gt; on the physicochemical properties and catalytic activity of Ni/Si&lt;sup&gt;4+&lt;/sup&gt;- Ce&lt;sub&gt;0.5&lt;/sub&gt;Zr&lt;sub&gt;0.5&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; catalysts were investigated. Doping of Si&lt;sup&gt;4+&lt;/sup&gt; decreased crystallite size of Ce&lt;sub&gt;0.5&lt;/sub&gt;Zr&lt;sub&gt;0.5&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; and increased specific surface area. Furthermore, doping amount of Si&lt;sup&gt;4+&lt;/sup&gt; have an impact on O&lt;sub&gt;2&lt;/sub&gt; absorption capacity of the catalyst and this property is associated with catalytic behavior of Ni/Si&lt;sup&gt;4+&lt;/sup&gt;- Ce&lt;sub&gt;0.5&lt;/sub&gt;Zr&lt;sub&gt;0.5&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; for cold start process of n-butane oxidative reforming.

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アンモニアは次世代のエネルギーキャリアとして期待されている。担持Ni触媒は優れたアンモニア分解活性を示すが、熱力学的平衡上100%アンモニア分解が可能な400℃付近での性能にはまだ改善の余地がある。本研究では、陽イオンサイトをNiで置換したハイドロタルサイトを調製して担持Ni触媒の前駆体として用いたほか、塩基性酸化物の添加効果についても検討を行い、担持Ni触媒の高活性化に取り組んだ。

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当研究室では還元処理したRh/Ce&lt;sub&gt;0.5&lt;/sub&gt;Zr&lt;sub&gt;0.5&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;の自発的な酸化により触媒層が内部加熱されることを利用し、&lt;i&gt;n-&lt;/i&gt;ブタンの酸化的改質を常温から瞬時に駆動可能であることを報告した。しかし、Rhは高価な貴金属であるため、担持量を削減することが望ましい。今回は、安価なCoと少量のRhを担持量を変えてCe&lt;sub&gt;0.5&lt;/sub&gt;Zr&lt;sub&gt;0.5&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;に担持することで省貴金属化を志向した触媒の開発を行った。その結果、 0.0001 wt%のRhを加えた1 wt%Co/Ce&lt;sub&gt;0.5&lt;/sub&gt;Zr&lt;sub&gt;0.5&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;が非常に有望な触媒であることを見出した。

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通常のアンモニア分解は吸熱反応でるため、外部加熱によるエネルギー供給が必要であり、装置の起動に時間を要するという欠点がある。一方、当研究室では触媒の自己発熱を利用し、アンモニアと酸素を室温で流通させるだけで瞬時にアンモニアの酸化分解による水素製造反応を駆動可能であることを報告した。今回は、担持Ru触媒の担体効果について検討を行い、Ce&lt;sub&gt;0.5&lt;/sub&gt;Zr&lt;sub&gt;0.5&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;が有効であることを見出した。

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当研究室ではMgOにCoNiを固溶化し、これを高温で還元し調製したCoNi/MgO触媒を用い、GTL(Gas to liquid)プロセスへの応用を目的とした高圧条件におけるメタンCO&lt;SUB&gt;2&lt;/SUB&gt;-H&lt;SUB&gt;2&lt;/SUB&gt;O改質反応について研究している。これまで、CoNi/MgOに微量のCrを添加すると、CoNiの還元度が8%からほぼ100%に増加し、高く安定した活性を示すことを見出した。今回はXAFS分析によりCrの存在状態について詳細に検討した結果を報告する。

DOI： 10.11523/sekiyu.2011f.0.138.0

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Language：Japanese   Publisher：The Japan Petroleum Institute  

アンモニアには原料にCが含まれず、400 ℃という低温で100%分解可能である。さらに圧縮、運搬が容易なため次世代の水素キャリアーとして注目されている。当研究室では、これまでにRu/希土類酸化物触媒に助触媒として強塩基性のCs&lt;sub&gt;2&lt;/sub&gt;Oを添加した触媒が高活性であることを見出した。そこで、今回はRu以外の金属を希土類酸化物に担持した触媒のアンモニア分解活性を評価した結果について報告する。

DOI： 10.11523/sekiyu.2011f.0.68.0

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アンモニアには原料にC原子が含まれず、400℃という低温で水素と窒素に100%分解可能である。さらに圧縮、運搬が容易なため、固体高分子型燃料電池へ供給する水素のキャリアーとして注目されている。本研究では、これまでに担持Ru触媒について触媒の塩基性が強いほど高活性を示し、さらに助触媒として強塩基性のCs&lt;SUB&gt;2&lt;/SUB&gt;Oを添加することでさらに活性が向上することを見出している。今回は種々の担体におけるCs&lt;SUB&gt;2&lt;/SUB&gt;Oの添加効果について検討を行ったので報告する。

DOI： 10.11523/sekiyu.2010f.0.157.0

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Language：Japanese   Publisher：The Japan Petroleum Institute  

当研究室ではナフサの模擬ガスとしてn-ヘキサンを用い，低温で水蒸気と反応させC1化合物に分解するというプレ改質用の触媒開発を行っている．これまでに，Ni/MgAl&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;4&lt;/SUB&gt;が高圧下(0.8MPa)での反応に&gt;おいて高い活性を示すことを見出しているが，炭素が析出するという問題があった。今回はこの触媒に強塩基性のLa&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt;を添加することで，炭素析出を劇的に抑制することに成功したので報告する

DOI： 10.11523/sekiyu.2010f.0.143.0

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アンモニアを改質し水素を取り出すと、炭化水素の改質と異なり燃料電池の電極を被毒するCOが生成しない。そのため、固体高分子型燃料電池に供給する水素の製造法としてアンモニア改質が注目されている。そこで、本研究ではアンモニアを改質し、水素を得るための触媒開発を目的している。今回、逆反応であるアンモニア合成に高活性を示す担持Ru触媒に注目し、その担体効果や促進剤の検討を行ったので報告する。

DOI： 10.11523/sekiyu.2009f.0.57.0

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Language：Japanese   Publisher：The Japan Petroleum Institute  

プロパンの水蒸気改質反応用Ni/γ-Al&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt;での活性に対する空間速度の影響を検討した。その結果、低空間速度では転化率が100%と安定していたが、高空間速度では転化率の低下と反応管内の圧力上昇が見られ、炭素析出により反応管が閉塞した。一方、La&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt;添加触媒では高空間速度で反応を行っても反応管の閉塞は見られなかった。現在、La&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt;の添加量が活性と炭素析出に及ぼす影響について検討しており、合わせて報告する。

DOI： 10.11523/sekiyu.2009f.0.47.0

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Rh/CeO&lt;SUB&gt;2&lt;/SUB&gt;は、873 K以上で還元処理することで、反応ガス中のO&lt;SUB&gt;2&lt;/SUB&gt;によって酸化される際の発熱を利用することにより、&lt;I&gt;n&lt;/I&gt;-ブタンの酸化的改質反応を常温かつ無加熱で駆動出来るようになる。また、CeO&lt;SUB&gt;2&lt;/SUB&gt;に25 mol%のZrO&lt;SUB&gt;2&lt;/SUB&gt;を複合化させることで、この還元温度は473 Kまで劇的に低下する。今回はCe/Zrの比が触媒の特性に与える影響について検討した。Ce/Zr比が低下するにつれ、触媒の還元性及び還元後のO&lt;SUB&gt;2&lt;/SUB&gt;吸収量が向上することが明らかとなった。

DOI： 10.11523/sekiyu.2009f.0.49.0

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Other Link： http://orcid.org/0000-0002-3998-7012

Language：Japanese   Publisher：公益社団法人 化学工学会  

DOI： 10.11491/scej.2008.0.547.0

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当研究室ではこれまでに、還元処理した希土類酸化物担持金属触媒上でn-ブタンの酸化的改質反応を常温かつ無加熱で駆動できることを報告している。しかし、CeO&lt;SUB&gt;2&lt;/SUB&gt;担持触媒の場合、反応を駆動させるためには873K以上での還元が必要であった。そこで、今回は反応の駆動に必要な還元処理の低温化を目的とし、希土類酸化物担体へのZrの複合化効果について検討した。その結果、Ce-Zr系複合酸化物を担体として用いると、473Kでの還元後に反応を駆動可能であることが明らかとなった。

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当研究室ではMgOにNiとCoを固溶化し、これを高温で還元し調製したMgO担持CoNi触媒が、高圧条件でのメタンの改質反応において高く安定した活性を示すことを報告した。しかし、低温で反応を行うと活性金属の酸化により触媒活性は徐々に低下した。そこで、この触媒に種々の元素をドープし酸化耐性の向上を試みたところ、活性金属の酸化が抑制され、安定した活性を示す数種の元素を見出した。

DOI： 10.11523/sekiyu.2007f.0.5.0

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炭化水素の改質反応における起動時の最大の問題点は、触媒を加熱するのに時間を要し、水素を迅速に生成できないことである。そこで、加熱を必要としない&lt;I&gt;n&lt;/I&gt;-C&lt;SUB&gt;4&lt;/SUB&gt;H&lt;SUB&gt;10&lt;/SUB&gt;の酸化的改質反応の常温駆動について検討を行った。その結果、還元処理後のCeO&lt;SUB&gt;2&lt;/SUB&gt;を担体とした担持金属触媒を用いることで、担体の自己発熱により触媒層が加熱され、反応の常温駆動が可能となる事を見出した。また、従来のAl&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt;、MgO等の金属酸化物担体を用いて検討したが、この様な機能を示す担体はCeO&lt;SUB&gt;2&lt;/SUB&gt;のみであった。

DOI： 10.11523/sekiyu.2007f.0.12.0

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Language：Japanese   Publisher：The Japan Petroleum Institute  

CeO&lt;SUB&gt;2&lt;/SUB&gt;担持触媒の活性金属をRhに比べて安価な卑金属に変えて実験を行った。その結果、Ni及びCoを活性金属としても、&lt;I&gt;n&lt;/I&gt;-C&lt;SUB&gt;4&lt;/SUB&gt;H&lt;SUB&gt;10&lt;/SUB&gt;の酸化的改質反応を常温で駆動させることが可能であった。更に、CeO&lt;SUB&gt;2&lt;/SUB&gt;以外で、酸化的改質反応の常温駆動が可能な触媒担体を探索するため、種々の希土類酸化物にNiを担持した触媒を調製して、実験を行った。その結果、CeO&lt;SUB&gt;2&lt;/SUB&gt;と同じ蛍石型構造を持つPrOx及びTbOxを担体にした触媒が、反応を常温、無加熱で開始可能であることを見出した。

DOI： 10.11523/sekiyu.2007f.0.13.0

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本研究室では燃料電池システム用改質器への応用を目的とし、低温での水素生成に優れた&lt;I&gt;n&lt;/I&gt;-ブタンオートサーマル改質反応について、担持卑金属触媒の開発を行っている。これまでに、調製法を改良したNi/MgOが優れた活性を示すことを報告した。今回はMgO以外の金属酸化物担体を用いた触媒を調製し、活性挙動とキャラクタリゼーションについて検討したので報告する。特に、改質器の起動停止を想定した活性測定実験においてNi/MgOやNi/CeO&lt;sub&gt;2&lt;/sub&gt;が特異的に高い耐久性を示す事を見出した。

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当研究室ではMgOに卑金属を固溶化し，これを高温で還元し調製したMgO担持卑金属触媒を用い，GTLプロセスへの応用を目的とした高圧条件におけるメタンの改質反応について研究している．今回はNi と Coの一方，又は両方を活性金属とし，H&lt;sub&gt;2&lt;/sub&gt;O改質，CO&lt;sub&gt;2&lt;/sub&gt;改質，さらにGTLに最適なH&lt;sub&gt;2&lt;/sub&gt;/COが2の合成ガスを得ることができるH&lt;sub&gt;2&lt;/sub&gt;O/CO&lt;sub&gt;2&lt;/sub&gt;=2の条件で混合改質を行い，金属組成の最適化を行った．なお，この反応では触媒の失活抑制が最大の課題であるため，金属の酸化および炭素析出が起こりやすい850℃，および650℃で触媒反応について検討した．

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