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

To realize a carbon-neutral society, developing highly active and inexpensive catalysts for ammonia (NH₃) production working at moderate conditions (<400 °C, <10 MPa) using hydrogen fabricated from the electrolysis of...

DOI： 10.1039/d4se00411f

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DOI： doi.org/10.1021/acs.energyfuels.3c03034

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

Abstract

An important part of realizing a carbon‐neutral society using ammonia will be the development of an inexpensive yet efficient catalyst for ammonia synthesis under mild reaction conditions (<400 °C, <10 MPa). Here, we report Fe/K(3)/MgO, fabricated via an impregnation method, as a highly active catalyst for ammonia synthesis under mild reaction conditions (350 °C, 1.0 MPa). At the mentioned conditions, the activity of Fe/K(3)/MgO (17.5 mmol h⁻¹ g_cat⁻¹) was greater than that of a commercial fused iron catalyst (8.6 mmol h⁻¹ g_cat⁻¹) currently used in the Haber‐Bosch process. K doping was found to increase the ratio of Fe⁰ on the surface and turnover frequency of Fe in our Fe/K(3)/MgO catalyst. In addition, increasing the pressure to 3.0 MPa at the same temperature led to a significant improvement of the ammonia synthesis rate to 29.6 mmol h⁻¹ g_cat⁻¹, which was higher than that of two more expensive, benchmark Ru‐based catalysts, which are also potential alternative catalysts. A kinetics analysis revealed that the addition of K enhanced the ammonia synthesis activity at ≥300 °C by changing the main adsorbed species from NH to N which can accelerate dissociative adsorption of nitrogen as the rate limiting step in ammonia synthesis.

DOI： 10.1002/cssc.202300942

DOI： 10.1002/cssc.202300942

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

DOI： 10.1021/acsomega.2c01973

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DOI： 10.1021/jacsau.2c00195

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The hydrogen production capabilities of the membrane reactor combining V-10 mol%Fe hydrogen permeable alloy membrane with Ru/Cs2O/Pr6O11 ammonia decomposition catalyst are studied. The ammonia conversion is improved by 1.7 times compared to the Ru/Cs2O/Pr6O11 catalyst alone by removing the produced hydrogen through the V-10mol%Fe alloy membrane during the ammonia decomposition. 79% of the hydrogen atoms contained in the ammonia gas are extracted directly as high-purity hydrogen gas. Both the Ru/Cs2O/Pr6O11 catalyst and the V-10 mol% Fe alloy membrane are highly durable, and the initial performance of the hydrogen separation rate lasts for more than 3000 h. The produced hydrogen gas conforms to ISO 14687–2:2019 Grade D for fuel cell vehicles because the ammonia and nitrogen concentrations are less than 0.1 ppm and 100 ppm, respectively.

DOI： 10.1016/j.ijhydene.2021.12.191

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

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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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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DOI： 10.26434/chemrxiv-2021-1qb7z

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

To realize a carbon-free society, catalysts are needed for the synthesis of ammonia under mild reaction conditions (<400 °C, <10 MPa) that use hydrogen produced from renewable energy. Ru-based catalysts are currently the most promising candidates; however, Ru is expensive and of low abundance. Here, we discovered that the encapsulation of Co nanoparticles with BaO enhanced the ammonia synthesis activity of Co and that a simple Ba-doped Co/MgO catalyst prereduced at an unusually high temperature of 700 °C (Co@BaO/MgO-700red) showed outstanding ammonia synthesis activity. The ammonia synthesis rate (24.6 mmol gcat−1 h−1) and turnover frequency (0.246 s−1) of the catalyst at 350 °C and 1.0 MPa were about 80 and 250 times higher, respectively, than those of the nondoped parent catalyst. At the same temperature but higher pressure (3.0 MPa), the ammonia synthesis rate was increased to 48.4 mmol gcat−1 h−1, which is higher than that of active Ru-based catalysts. In addition, at 1.0 MPa, our catalyst produced ammonia even at temperatures as low as 150 °C. Scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy investigations revealed that after reduction at 700 °C, the Co nanoparticles had become encapsulated by a nanofraction of BaO. The mechanism underlying the formation of this unique structure was considered to comprise reduction of oxidic Co to metallic Co, decomposition of BaCO3 to BaO, and migration of BaO and Co nanoparticles. Spectroscopic and density functional theory investigations revealed that adsorption of N2 on the Co atoms at the catalyst surface weakened the N2 triple bond to the strength of a double bond due to electron donation from Ba2+ of BaO via adjacent Co atoms; this weakening accelerated the cleavage of the triple bond, which is the rate-determining step for ammonia synthesis.

DOI： 10.1021/acscatal.1c02887

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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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The direct synthesis of cyclohexylamine via the hydrogenation of nitrobenzene over monometallic (Pd, Ru or Rh) and bimetallic (PdxRu1-x) catalysts was studied. The Pd0.5Ru0.5-PVP catalyst was the most effective catalyst for this reaction. The catalyst can be reused and applied for the synthesis of N-aryl pyrroles and quinoxalines from nitrobenzenes.

DOI： 10.1039/d1nj00922b

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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：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

DOI： 10.1246/cl.200855

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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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Monometallic (Pd, Ru or Rh) and bimetallic (Pd0.5-Ru0.5) alloy NPs catalysts were examined for the hydrogenation of quinoline. Pd-Ru alloy catalyst showed superior catalytic activity to the traditional Rh catalyst. The characterization of Pd0.5-Ru0.5 catalysts, HAADF-EDX mapping and XPS analysis suggested that the alloy state of PdRu catalysts remained unchanged in the recovered catalyst. Furthermore, the catalyst was highly selective for the hydrogenation of different arenes. This journal is

DOI： 10.1039/d0ra09981c

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The synthesis of pyrrolidones via reductive amination of levulinic acid with aniline was examined over polypyrrolidone-stabilized metal nanoparticle catalysts. Among them, Ir metal was the most effective and applicable for the reductive amination of levulinic acid with nitroarenes/nitriles. Importantly, this catalyst was used for the one-pot synthesis of the anti-inflammatory drug indoprofen from 2-formylbenzoic acid and 2-(4-nitrophenyl)propanoic acid.

DOI： 10.1039/d0gc01725f

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This study provides a coreduction methodology for solid solution formation in immiscible systems, with an example of a whole-region immiscible Cu-Ru system. Although the binary Cu-Ru alloy system is very unstable in the bulk state, the atomic-level well-mixed CuRu solid solution nanoparticles were found to have high thermal stability up to at least 773 K in a vacuum. The exhaust purification activity of the CuRu solid solution was comparable to that of face-centred cubic Ru nanoparticles. According to in situ infrared measurements, stronger NO adsorption and higher intrinsic reactivity of the Ru site on the CuRu surface than that of a pure Ru surface were found, affected by atomic-level Cu substitution. Furthermore, CuRu solid solution was a versatile catalyst for purification of all exhaust gases at a stoichiometric oxygen concentration. This journal is

DOI： 10.1039/d0sc03373a

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

© 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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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：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-V C H VERLAG GMBH  

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

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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DOI： 10.26434/chemrxiv.7763657.v1

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

<p>Herein, we report a protocol for rapid preparation of uniformly sized Ru, Rh, Pd, Ir, and Pt nanoparticles stabilized by poly(<i>N</i>-vinyl-2-pyrrolidone) via microwave-assisted chemical reduction with ethanol. Although the boiling point of ethanol, which has high reduction ability, is much lower than the temperature required for metal cation reduction, this solvent could be used as a reductant because the preparation was carried out in a sealed vessel. All metal nanoparticles showed similar sizes and amounts of poly(<i>N</i>-vinyl-2-pyrrolidone). The crystallite size of the Pd and Pt nanoparticles could be controlled by changing the ethanol concentration. The catalytic performance of the prepared metal nanoparticles was evaluated for the hydrogenation of benzonitrile under ambient conditions (25 °C, 1 bar H₂). Rh nanoparticles showed the highest benzonitrile conversion and highest selectivity for secondary imine product. Interestingly, the particle-size dependence of the catalytic activity of the Rh nanoparticles showed volcano-type behavior; that is, the second smallest Rh nanoparticles (3.3 nm) showed the highest activity, which was attributed to high metal surface area and high turnover frequency. Notably, this is the first report of nitrile hydrogenation to afford a secondary imine under ambient conditions.</p>

DOI： 10.1627/jpi.62.220

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Electromagnetic Wave Energy Applications  

Rh nanoparticle catalysts were prepared via liquid phase reduction assisted by microwave-heating. Different kinds of alcohols as reductant including Rh precursor and stabilizer (Polyvinylpyrrolidone) were equally and quickly heated by microwave-heating. Conventional liquid phase reduction using electric heater requires long-heating time (2-3 h) . However,microwave-heating leads to formation of uniform Rh nanoparticles within 15 min. In EXAFS analyses, local structure of prepared Rh nanoparticles was identical to that of pure Rh powder, indicating that Rh atoms were reduced to metallic state.Coordination number (Rh-Rh) decreased from 12.5±1.1 to 9.4±0.7 when Rh particle size determined by TEM decreased from 6.7 nm to 3.3 nm. It was revealed that smaller Rh nanoparticles which have low coordination number (i.e., many dangling bond)show higher catalytic activity in CO oxidation reaction

DOI： 10.32304/jemeajournal.3.0_1

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

© 2018 The Chemical Society of Japan. Various metal nanoparticle catalysts (Ru, Rh, Pd, Ir, and Pt) were prepared via liquid-phase reduction and their activity was studied for selective hydrogenation of benzonitrile to corresponding secondary imine under mild conditions (3bar H2and 30°C). The Rh catalyst with particle size of 2.7 nm exhibited excellent activity for the hydrogenation of benzonitrile to secondary imine. The catalyst was reused and applied to transform various nitriles to corresponding secondary imines.

DOI： 10.1246/cl.180349

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DOI： 10.1002/chem.201800938

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Language：Japanese   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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Language：Japanese   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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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：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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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：Japanese   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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Language：Japanese   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：Google Patents  

US Patent 9,452,417

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

The catalytic activity of monoatomically dispersed Pd supported on TiO2 toward propylene epoxidation in the presence of H-2 and O-2 was studied at ambient temperature, and both propylene oxide (PO) and propane were obtained. Short-chain alkanes also reacted but epoxide formation was not observed in those reactions except in the case of isobutane, which formed isobutylene oxide at a low rate. The optimum surface concentration of Pd on TiO2 was 0.005-0.01 atom/nm(2); because the supported amount of Pd is extremely small relative to the surface area of the support, the supported Pd is thought to be monoatomically dispersed. Pd/TiO2 catalysts prepared from a tetraphenylporphyrin-Pd chloride complex showed almost the same product distribution for propylene epoxidation as did catalysts prepared from Pd(NO3)(2). Isotope exchange between H-2 and D-2 proceeded over Pd/TiO2 with a low surface concentration (0.0001 atom-Pd/nm(2)), and chemical potential calculations suggested that H-2 molecules could dissociatively adsorb onto the monoatomically dispersed Pd/TiO2. A PO formation mechanism over the catalyst is proposed on the basis of these results. The results presented here may provide the first clear evidence of catalysis by monoatomically dispersed noble metals. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molcata.2012.03.001

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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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Palladium supported at extremely low loading on TiO2 catalyzed epoxidation of light olefins (except ethylene) in the presence of O-2 and H-2 at ambient temperature. Propylene oxide (PO) was obtained from propylene (1-2% yield; 30-60% selectivity) together with propane. Simple oxidation of H-2 to water was slow, and the ratio of H-2 used for PO formation in the reacted H-2 was 10-25%. A Pd concentration of 0.005-0.01 atom-Pd/nm(2)-TiO2 was optimum for epoxidation, and the major product at 0.02 atom-Pd/nm(2) was acetone. That the distributions for a Pd/TiO2 catalysts prepared from Pd nitrate and from a Pd-tetraphenylporphyrin complex at the same Pd loading were similar suggests that Pd was supported mono-atomically on TiO2. We propose that PO formed via reaction between propylene adsorbed on Pd and an active species derived from reaction of H-2 and O-2 on TiO2 (perhaps center dot OOH). (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.catcom.2011.05.020

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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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NF3 was decomposed over various ortho, pyrophosphates and some fluorides at 450-600 K. Mn2P2O7 and CePO4 were the most active. The catalytic activity of Co2P2O7, Co-3(PO4)(2), CrPO4, Cu2P2O7, and Cr-4(P2O7)(3) followed in this order. Zn-3(PO4)(2) and AlPO4 were less active. Activity of pyrophosphate was comparable to that of ortho-phosphate. Products were NO2 and a very small amount of N2O except for HE An essential reaction was 2NF(3) + 3H(2)O -&gt; 6HF + NO + NO2. Catalytic activity of phosphates was proportional to not the amount but the concentration of surface hydroxyls, suggesting that the reaction proceeds via a bidentate surface intermediate. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.catcom.2009.09.005

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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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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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SF6 was selectively hydrolyzed to SO3 over rare earth (RE) phosphates above 800 K. CePO4 was the most active catalyst, followed by GdPO4, YbPO4, DyPO4, ErPO4, SmPO4, PrPO4, TbPO4, NdPO4, and LaPO4. The middle RE phosphates were found to be more active than the light RE phosphates, but the reason for the high activity of CePO4, which belongs to the light RE group, is not clear. The catalytic activity was independent of the specific surface area (SSA), acid amount, and acid concentration of the catalysts. RE phosphates were single-phase, and a broad inversely proportional relation was observed between the crystallite size and SSA, except in the case of CePO4. The combination of highly active AlPO4 and CePO4 creates synergetic effects in the catalytic activity and SO3 selectivity over all ranges of composition. Binary catalysts were a mixture of small crystalline AlPO4 and CePO4. The addition of Ce promoted the crystallization of AlPO4, which was controlled to about 10 nm at 10-50% Ce content. The turnover frequency for SF6 decomposition was proportional to the surface concentration of hydroxyls of binary catalysts. Therefore, synergy effects may come from the number of hydroxyl (OH) pair sites on which a bidentate intermediate of hydrolysis of SF6 may be formed by the moderate crystallization of AlPO4. The addition of Ce, Pr, or Y to AlPO4 brings about a small promotion effect for SF6 decomposition, but the addition of La, Nd &gt; Gd &gt; Yb diminishes the activity. The addition of Gd, Pr, or Nd greatly improved the SO3 selectivity. A linear relationship between catalytic activity and the concentration of surface hydroxyls of the catalysts supports a reaction mechanism in which two F atoms of an SF6 molecule interact with two surface hydroxyls to form a bidentate intermediate. (c) 2008 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcis.2008.12.003

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Nanotube-shaped precursor which is composed of layered structured sodium dodecylsulfate (SDS) calcium carbonate were obtained by titration of an aqueous solution of Na(2)CO(3) into an aqueous solution containing CaCl(2) and SDS at 333-335 K. A unit of the repetition of the precursor was about 4 nm. Nanotube-shaped composite which is composed of CaCO(3) and CaSO(4) of 100-200 nm in diameter and 0.5-2 mu m in length was obtained from nanotube-shaped precursor composed of layers of CaCO(3) and SDS by calcinations at 673 K in air. The precursor sheet composed of CaCO(3) layers on which SDS molecules attached to both side seemed to curl up and form a pipe. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matlet.2008.10.025

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SF6 decomposed stably over AlPO4, CePO4, YPO4, and Zr-3(PO4)(4) at 800-1000 K, but Ca2P2O7, Mg2P2O7, and Sr2P2O7 were less active. Active catalysts crystallized during the reaction. SO3, SO2F2, and HF were obtained as major products. SO3 was selectively formed over YPO4 and Zr-3(PO4)(4), but SO2F2 formed over AlPO4 and CePO4 in a significant selectivity at lower temperatures. Decomposition activity was independent of the concentration of oxygen, but it was dependent on the concentration of water vapor, suggesting that hydrolysis is the essential reaction. Catalytic activity was independent of the acidity of the catalysts. Catalytic activity was independent of the amount of surface hydroxyls, but it was correlated with the concentration of surface hydroxyls. From an analogy of hydrolysis Of CCl2F2 on AlPO4, degradation may proceed via a similar bidentate surface intermediate, OsurfaceH center dot center dot center dot F(SF4)F center dot center dot center dot HOsurface, in which two fluorine atoms of SF6 interacted with two surface hydroxyls. AlPO4 showed a steady activity and high selectivity at 843 K for 25 h, suggesting a long catalyst life. AlF3 was significantly less active than metal phosphates. This suggests that development of the catalysts which are not transformed into metal fluorides is important.

DOI： 10.1021/ie8001099

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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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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

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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The anaerobic oxidation of isobutane over complex oxide catalysts of the type CunV2Ox (n = 0, 1, 2,3, and 5) was studied. V2O5, CuV2O6, and Cu2V2O7 showed high oxidizing activity, and Cu3V2O8 and Cu5V2O10 were less active. Over the active catalysts, CO2 was selectively formed only at the beginning of the reaction, and the rate Of CO2 formation decreased with reaction time. Isobutene formation became dominant 15-30 min after the start of the reaction. The rates of CO2 and isobutene formation were lower over the less active catalysts, Cu3V2O8 and Cu5V2O10. The catalytic activity at 623 K decreased in the order V2O5 &gt; CuV2O6, Cu2V2O7 &gt;&gt; Cu3V2O8, Cu5V2O10. Because CO2 formed at the beginning of the reaction, this system should be applicable for the selective formation of isobutene at appropriate reduction degrees. We concluded that CuV2O6 and Cu2V2O7 should be applicable in a thin-layer reactor, in which isobutane and oxygen are separately supplied to opposite sides of the layer; in such a reactor, the catalyst surface on the isobutane side could be kept at a certain degree of reduction. Using the rate constants for isobutane consumption over Cu2V2O7, we calculated the apparent activation energy for anaerobic oxidation of isobutane to be 87.6 kJ/mol, which agrees well with the reported value for a metal oxide catalyst. XPS analysis indicated that not V5+ but Cu2+ was reduced during the reduction of Cu2V2O7 by H-2 at 473 K. Our results indicate that selective oxidation should be achievable over complex oxides that contain highly redox-active metal ions such as Cu2+ if the reaction is carried out in a thin-layer reactor. (C) 2008 Published by Elsevier B.V.

DOI： 10.1016/j.apcata.2008.04.022

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DOI： 10.1021/cm800651m

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

The catalytic activity of MV2O6 and M2V2O7 type oxides prepared by the molten method (MM) for anaerobic oxidation of isobutane was studied in order to construct a system for the selective oxidation of isobutene using a thin layer reactor. Isobutene, CO and CO2 were formed by every catalyst tested. The activities for isobutene formation were CuV2O6 &gt; ZnV2O6, NiV2O6, CoV2O6 &gt; MgV2O6 &gt; MnV2O6 &gt;&gt; CaV2O6. Isobutene was a major product over M2V2O7 (MM). Co2V2O7 showed the highest activity and high isobutene selectivity exceeded 90%, demonstrating that CO2V2O7 is a suitable oxide for a thin layer reactor for anaerobic oxidation of isobutane. Partial substitution of Mg by Cu in Mg2V2O7 (MM) improved the activity. It is shown by the oxidation at low O-2 concentration as 2-3% that two types of oxidations occurred simultaneously: isobutene formation by the lattice oxygen ions diffused from the bulk, and CO and CO2 formation by the oxygen species derived from molecular oxygen in the gas phase. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molcata.2007.09.028

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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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The oxygen storage capacity including OSC, OSCC and dynamic OSC was measured for Ce-Pr oxides using a temporal analysis of products (TAP) reactor system. The exact features of reduction and re-oxidation were obtained by accurately measuring the uptake of CO and O, and the production of CO2. It was found that the reduction temperature of Ce-Pr oxides was lowered 50-100 degrees C in comparison to that of CeO2. The substitution of cerium by praseodymium in the Ce1-xPrxO2-delta oxides enhanced both OSC and OSCC. However, OSCC was much influenced by the increase of praseodymium content more than OSC. It was interpreted that the addition of Pr significantly increased the amount of oxygen migrating from bulk to surface while the migration rate of bulk oxygen was slightly accelerated. On the basis of analyses of the Cc 3d, Pr 3d and O 1s X-ray photoelectron spectra, the promotion effect of Pr on oxygen storage capacity could be attributed to the CC4+/Ce3+, Pr4+/Pr3+ redox behaviour and the enrichment of oxygen vacancies in Ce1-xPrxO2-delta. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apcata.2007.06.023

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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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When NaCl is added in the formation of CaCO3 from CaCl2 and Na2CO3 solutions, large CaCO3 structures with complex, overlapping plates-like shapes of high calcite composition were obtained. The addition of NaCl increased the solubility of CaCO3, which promotes the transformation of vaterite to calcite and the resulting high concentration of CaCO3 promotes crystal growth rather than nucleation. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matlet.2006.11.005

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Ni particles and Ni3C whiskers with a novel morphology, grew on the Ni-carbon composite by heat treatment at 1073 K in Ar. Ni-carbon composites were prepared by spray pyrolysis of a solution of sucrose and NiSO4 in Ar at 1073 K.

DOI： 10.1246/cl.2007.512

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Calcination parameters, such as atmosphere, duration and catalyst bed depth have a marked influence on the catalytic and spectroscopic properties of sulfated zirconia. Sulfated zirconia calcined in nitrogen or synthetic airflow, in deep bed, exhibited comparable activity in n-butane isomerization at 373 K, which suggests that oxygen is not necessary for formation of active sites. Catalysts calcined in shallow bed are catalytically inactive. Thus, the bed depth is concluded to be crucial for the formation of active sites. The samples calcined in shallow bed possessed lower sulfate content and the S=O stretching vibration was located at lower frequency. Calcination in the presence of water vapor also led to lower catalytic activity, sulfate content, and BET area. Extended calcination reduced gradually the activity and the sulfate content, which underlines the labile property of the active sites. A new interpretation of the function of the calcination step is proposed and compared with models described in the literature.

DOI： 10.1007/s10562-006-9005-5

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Redox properties of CeO2 and Pt-Rh/CeO2 were studied by temporal analysis of products (TAP) method using alternative pulses of CO and O-2. A portion of pulsed CO was oxidized to CO2 and a portion of CO was adsorbed on the surface. Pulsing O-18(2) onto the catalyst which has surface species derived from CO, evolved CO2 contained no O-18 suggesting that the surface species will be carbonate ions.

DOI： 10.1007/s10562-006-0142-7

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A series of lanthanide (LA) phosphate were prepared by using N-(2-hydroxyethyl) ethylenediane-N,N',Ntriacetic acid (H(3)hedtra) as a chelating agent. The obtained samples were characterized by using X-ray diffraction (XRD), nitrogen adsorption-desorption isotherm, thermal analysis (TG-DTA), transmission electron microscope (TEM) and TPD-ammonia desorption. The results showed that samples prepared through chelating agent route possessed smaller particle size which led to higher specific surface area with increased acidic sites compared with the reference samples prepared free of H(3)hedtra. It was also found that the acidic strength increased gradually from the light lanthanide phosphate to heavy lanthanide phosphate. Besides, pore size of the samples could be controlled by altering the mole ratio of the lanthanide(LA): H(3)hedtra. Pore size distribution of the samples became narrower through synthesis in the presence of H3hedtra. The precursor sol complex was investigated by FTIR and XRD and mesopore formation mechanism had been discussed.

DOI： 10.1007/s10934-006-8010-9

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A synthesis of molybdenum incorporated mesoporous aluminophosphate with long-chain n-alkylarnine as template material had been prepared under non-aqueous condition. These materials were extensively characterized by using X-ray diffraction (XRD), nitrogen sorption isotherms, nuclear magnetic resonance of Al-27 and P-31 (NMR), inductive coupled plasma (ICP), electron spin resonance (ESR), Fourier transform infrared (FTIR) and thermogravitnetric-differential thermal analysis (TG-DTA). Morphology of the materials had been observed by using transmission electron microscope (TEM) that revealed the mesoporous materials possessed wormhole-like structures. Alkaline solvent extraction using n-butylamine/ethanol had been efficiently removed the n-alkylamine from the mesoporous samples which yielded BET surface areas around 550-730 m(2)/g. BJH analysis showed a narrow pore size distribution which increased with increasing of the carbon chain length of alkylamine (template). Valence state and coordination of the molybdenum in the obtained samples were investigated by using ESR and FTIR where it was found that Mo4+ and Mo6+ molybdenum species existed in the molybdenum incorporated mesoporous aluminophosphate in tetrahedral coordination. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apsusc.2005.08.064

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The stability of metal phosphate during H-2 reduction is one of the critical factors that determine the catalytic behavior of Ni/(metal phosphate) in CH4 autothermal reforming. Ni/(rare earth phosphate), particularly Ni/(Gd, Cc, or ErPO4), has been found to be a new family of effective catalysts.

DOI： 10.1246/cl.2006.580

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Anaerobic oxidation of isobutane was studied using MgV2O6, Mg2V2O7 and Mg3V2O8. Isobutene, a small amount of COx, and trace amount of oxygen containing compounds were formed. CO2 Was formed mainly at the beginning of the reaction and decreased with reaction time. Catalytic activity of Mg2V2O7 was slightly higher than that of MgV2O6 but the CO., formation over MgV2O6 was more than over Mg2V2O7. Mg3V2O8 was the least active. Therefore, Mg2V2O7 is the most suitable for oxidative hydrogenation of isobutane under the anaerobic reaction conditions. The equilibration between O-16(2) and O-18(2) over MgV2O6 was faster than over Mg2V2O7 or Mg3V2O8 at 673 K. The rate of equilibration between O-18(2) and lattice oxygen over MgV2O6 was similar to that over Mg2V2O7, which was faster than over Mg3V2O8. Highest yield of isobutene formation over Mg2V2O7 would come from the character of Mg2V2O7, in which mobility of the lattice oxygen is great but surface reaction of isobutane was not so fast. Higher activity for isobutene formation may come from the nature Of Mg2V2O7, of which mobility of the lattice oxygen is great but surface reaction of isobutane was not so much fast. Mn, Cr, Fe, Ni and Co can be introduced into Mg2V2O7 to give a single phase. Substitution of Co, Cu and Cr for Mg increased the activity Of Mg2V2O7 for isobutane oxidation and substitution of Ni and Mn scarcely affected the activity but substitution of Fe and Zn decreased the activity. Substitution of all the metal ions slightly increased the isobutene selectivity. MgO, MgV2O4 and Mg3V2O8 were observed in the sample after the anaerobic oxidation of isobutane. Cu containing catalyst was reduced to give Cu metal. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molcata.2005.12.012

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

Highly active sulfated zirconia (SZ) materials were prepared by sulfation of crystalline zirconia with gaseous SO3. This direct method circumvents the use of liquid sulfation agents, as well as a final calcination step. The amount of sulfur species retained by SO3-SZ samples was directly proportional to the fraction of monoclinic phase and the concentration of Bronsted acid sites. However, the catalytic activity in n-butane isomerization at 373 K was proportional to the concentration of labile chemisorbed SO3, most likely in the form of pyrosulfate species showing a characteristic IR band at 1404 cm(-1). Tetragonal zirconia favors the formation of these labile sulfur species, playing a key role in light alkane activation. (c) 2005 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcat.2005.11.039

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The catalytic conversion of chlorobenzene (CB) over some metal phosphates and sulfate was studied in the presence of water vapor and oxygen. The conversion of CB proceeded in the order of AlPO4, Zr-3(PO4)(4), CePO4-AlPO4, and La-2(SO3)(3) above 673 K. The major products were CO, CO2, and HCl. The reaction proceeded in the absence of water vapor; however, the activity was greatly reduced in the absence of oxygen. Even in the presence of oxygen, 30 mol % of water vapor inhibited the reaction. No intermediate hydration products were observed. There was no correlation between each of the catalytic activity, the acidity, and the concentration of the surface hydroxys of the catalysts. These results suggest that the essential reaction for CB conversion is oxidation. The specific surface area (SSA) of the catalysts was not changed during the CB conversion.

DOI： 10.1246/bcsj.79.145

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Among rare earth phosphates, only CePO4 and LaPO4 exhibit very high activity for oxidative dehydrogenation (ODH) of isobutane. This phenomenon was studied in comparison with the corresponding oxides. Isobutene was formed over NdPO4, which was used as a representative of inactive phosphate catalysts, by simple dehydrogenation with 30-32% selectivity, C3H6 and CO2 were formed with a selectivity of 25-33% and 20-30%, respectively. Isobutene was obtained at a higher selectivity of 79-86% over CePO4 and LaPO4. No H, formation Suggests that the essential reaction wits the ODH of isobutane. In the oxidation over metal oxides, isobutene selectivity was relatively high: 60-70% over CeO2; however, the essential reaction was considered to be a simple dehydrogenation. Isobutene was formed at 40-47% selectivity, but simple dehydrogenation of isobutane would proceed over Nd2O3 and La2O3. La2O3, Nd2O3, and NdPO4 have only weak acidic sites. CeO2 has weak acidic sites and those with intermediate strength; LaPO4 and CePO4 have relatively strong acidic sites in addition to the weak acidic sites and those of intermediate strength. Oxidative dehydrogenation activity was correlated with strong acidic sites. ODH of isobutane occurred in the reaction between lattice oxygen of CePO4 and isobutane. Introduction of NH3 into the reaction system reduced both ODH of isobutane and CO2 formation; and stopping the NH3 supply led to a resumption of the activity, which suggests the participation of acidic sites. CePO4 catalyst contained 2% excess Ce to P; in the prepared CePO4 sample, Ce4+ was detected by XPS. We conclude that acidic sites and redox between Ce4+ and Ce3+ play important roles in the ODH of isobutane. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apcata.2005.07.049

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Catalytic activation and conversion of light alkanes by sulfated zirconia is unequivocally shown to be initiated by producing small concentrations of olefins. This occurs via stoichiometric oxidative dehydrogenation of butane by SO3 or pyrosulfate groups to butene (present mostly as alkoxy groups), water, and SO2. Thermal desorption and in situ IR spectroscopy have been used to determine all three reaction products. The concentration of butene formed determines both the catalytic activity of sulfated zirconia as well as the deactivation via formation of oligomers. The thermodynamics of the oxidative dehydrogenation of n-butane by different SZ surface structures has been examined by density functional (DFT) calculations. The calculations show that pyrosulfate or re-adsorbed SO3 species have the highest oxidizing ability.

DOI： 10.1021/ja054126d

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Sodium aluminate has been used as the aluminium precursor in the synthesis of mesoporous aluminophosphate where cetylpyridinium chloride (CTPC) was used as structure directing agent. Synthesis of the materials was performed in a broad range of pH from 3 to 10. The obtained materials were characterized by using XRD, TEM, ICP, nitrogen sorption isotherms, solid state NMR, TG-DTA and FTIR. The samples prepared at pH 5-8 were thermally stable up to 450 degrees C and presented specific surface areas in the range of 420-640 m(2) g(-1) after calcination for removal of the surfactant material. TEM image revealed the obtained mesoporous aluminophosphate possessed disordered porous structures. DH analysis derived from the adsorption branch showed that the average pore size of the sample was 2.6 nm in the 5-8 pH range. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.colsurfa.2005.05.015

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The catalytic behavior of bi-metallic Co-Ni/TiO2 catalysts for CO2 reforming of CH4 to synthesis gas was investigated under atmospheric pressure with a particular attention to carbon deposition. The catalysts with optimized Co/Ni ratios showed high catalytic stability towards the reaction with very little amount of deposited carbon at a wide range of reaction temperature (773-1123 K). The results suggest that adjusting of composition of the active metals (Co and Ni) can kinetically control the elementary steps (formation of carbon species and its removal by oxygen species) of CH4/CO2 reaction.

DOI： 10.1007/s10562-005-5848-4

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A kinetic model of the skeletal isomerization of n-butane and isobutane on sulfated zirconia in the absence of Pt is presented. The skeletal isomerization of butane on sulfated zirconia has been shown to be initiated by oxidative dehydrogenation of the alkane. This is followed by the formation of alkoxy groups/carbenium ions at the surface, induced by strong Bronsted acid sites. The isomerization of the sec-butyl carbenium ion occurs mono-molecularly, as suggested by the 100% selectivity for isomerization extrapolated to zero conversion. With increasing conversion, the selectivity decreased linearly, leading to propane and pentanes up to 40% of conversion. The lower selectivity for isomerization is qualitatively explained by reactions of isobutene present in small concentrations in the reactor at higher conversions. Transient experiments show conclusively that the isomerization of the carbenium ion and not the hydride transfer from the alkane to the carbenium ion is the rate-determining step. (c) 2005 Published by Elsevier Inc.

DOI： 10.1016/j.jcat.2005.03.025

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Titania-supported cobalt and nickel bimetallic catalysts were investigated for CO2 reforming of methane to synthesis gas at 1023 K under ambient pressure. Bimetallic Co-Ni/TiO2 catalysts with an appropriate Co/Ni ratio showed highly stable activities without carbon deposition. Whereas the monometallic Co/TiO2 catalyst deactivated rapidly because of the oxidation of metal, 10 mol% substitution of nickel for cobalt suppressed the oxidation of metal, providing a high catalytic stability. However, the catalysts with excess nickel content (&gt; 80 mol%) underwent carbon formation. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses revealed that a homogeneous alloy of cobalt and nickel was formed from bulk to the surface by the H-2 reduction. and the alloy was stabte during reforming The advantages of the bimetallic catalysts are high resistance to undesirable metal oxidation and coking, through the control of reactions between CH4 and CO2. (c) 2005 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcat.2005.03.011

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Metal fluorides are more stable than metals and metal oxides; therefore, no oxides can be applied as catalyst supports for the reactions in which hydrogen fluoride is involved. The authors observed that metal phosphates are not reactive to HF at higher reaction temperatures such as 973 K. Hence, the decomposition of CCIF2CCIF2 was studied over Pt-supported SiO2, Al2O3, and AlPO4-based catalysts. Hydrodehalogenation proceeded and CHF2CCIF2 and C2H6 were formed as major products, small amounts of CHF2CHF2, CH2FCCIF2, CH2FCF3. and CH4 were also formed. Pt/SiO2 was the most active; however, SiO2 reacted with HF and the SiF4 formed sublimated. Following these, Al2O3 was the most active; however, it reacted with HF to form AlF3 and was deactivated. Similar hydrodehalogenation proceeded over Pt/AlPO4 and Pt/ (CePO4-AIPO(4)). The crystal structure of these catalysts did not change during the catalytic reaction, although the reduction of specific surface areas (SSA) was observed. Therefore, AlPO4 and Ce containing AlPO4 are suitable as catalyst supports in reactions in which HF is involved. XPS showed that the electronic effects of AlPO4 lie between that of SiO2 and Al2O3. A good linear relationship is found to exist between the initial reaction rates per unit Surface area of Pt metal supported on the supports and the binding energy of supported Pt. This suggests that the more cationic the Pt. the more easily it could abstract Cl- from CCIF2CCIF2. (c) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apcata.2004.12.033

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Isobutane oxidation over sin-le metal oxides of V, Nb, Ta, and Mo and over their complex oxides was studied. The most active was V2O5, while medium activity was shown by LaVO4, BiVO4, CaV2O6, Ta2O5, TaV2O6, ZnNb2O6, Nb2PO5, MgV2O6, YVO4, Cu2V2O7, MoO3 and MnNb2O5. The less active oxides were Na2MoO4 and Ag2MoO4. lsobutane was oxidized mainly to isobutene and COx. but isobutene selectivity was generally lower than 50% below 673 K. Relatively high isobutene selectivity was shown by MgTa2O6, TaV2O6, and ZnNb2O6. Methacroleine was only obtained over MoO3 and methanol was formed only over V2O5 and Cu2V2O7. Acetic acid was formed over certain V-containing oxides. No oxygen-containing products were formed over Nb- and Ta-containing oxides. On a unit surface area basis, Nb2O5 and Ta2O5 have higher oxidizing activity than V2O5 and MoO3.
Isobutane oxidation was studied in the absence of gaseous O-2 over MV2-type complex oxides. Catalytic activity was determined as follows: CuV2O6 &gt;&gt; CoV2O6 &gt; MgV2O6 &gt; ZnV2O6 &gt;&gt; ZrV2O7 &gt; CaV(2)O(6)center dot MgV2O6 is the most selective for isobutene formation. Combination to easily redoxable metal ions tends to accelerate the deep oxidation process. There may be a threshold for the initial reaction rate of lattice oxygen per unit surface area for selective isobutene formation. Selective isobutene formation continued until a reduction of MgV2O6 by least 4.5%, had finished and the reduced catalyst was recovered by the calcination at 773 K. Selective formation of isobutene made it possible to combine oxidations of isobutane with MgV2O6 and with the oxidations of reduced catalysts. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apcata.2005.01.008

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Autothermal reforming of methane (in the presence or absence of ethane) over Ni and/or Rh catalysts prepared from hydrotalcites is reported. Surface and bulk structures of the reduced supported metal catalysts were characterized by various physicochemical techniques. XANES and EXAFS at the Ni and Rh K-edges indicate that the reduction of Ni2+ and Rh3+ in the support matrix with H-2 was incomplete for all catalysts. NiRh alloy particles are formed in NiRh/MgAl. IR spectra of adsorbed CO indicate that the surface of the NiRh alloy particles is enriched in Ni. All catalysts hardly catalyzed coke formation during CH4 autothermal reforming. The surface concentration of reduced Ni was critical for the catalytic activity, i.e., the catalytic activity decreased in the order NiRh/MgAl &gt; Ni/MgAl-2 &gt; Rh/MgAl-1. However, Ni/MgAl-2 lost its activity, when cycling between 1073 and 773 K at very high space velocities (1.2 x 10(4) l/(h g)) through oxidation of metallic Ni. In contrast, NiRh/MgAl was relatively stable, while Rh/MgAl-1 did not deactivate. The enhanced stability of NiRh/MgAl by Rh against oxidation is attributed to H-2 spillover from Rh in the NiRh alloy as well as to its high activity (larger fraction with reducing atmosphere). The activity of all catalysts in converting hydrocarbons increased in the presence of ethane, with ethane showing a high tendency to react preferentially. Ethane could be converted completely in the presence of partly converted methane. NiRh/MgAl and Rh/MgAl-1 showed stable activity at 1073 and 773 K, while Ni/MgAl-2 gradually deactivated at 773 K. The deactivation attributed to Ni oxidation was reduced by addition of C2H6. (C) 2004 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcat.2004.10.006

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A wide variety of sulfate species exists on sulfated zirconia and many of these species have been connected to the catalytic performance. Some of these groups show strong interactions with polar molecules, indicating that they may play a role for the catalytic properties. In order to differentiate between these groups and to explore the role of labile soluble sulfate for n-butane skeletal isomerization, active sulfated zirconia was washed with water. Water washing removed around 40% of the sulfate species and led to a catalyst inactive for the alkane isomerization. This indicates that the labile sulfate plays a key role for the catalysis. The water-soluble fraction of the sulfate exists as highly covalent sulfate species characterized by an S=O vibration between 1390 and 1410 cm(-1) on the activated sulfated zirconia. Bronsted acid sites related to the sulfate groups are shown to be indispensable for activating n-butane, while Lewis acid sites do not directly participate in the alkane conversion catalysis. (C) 2004 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcat.2004.07.003

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Influences of an addition of trace amounts of Pt (Pt/Co = 0.005-0.05 in atomic ratio) or Ru (Ru/Co = 0.01-0.05) and of replacement of Co by Ni (Ni:Co = 1:99-100:0) to 0.5 wt.% Co/TiO2 have been investigated for the dry reforming of methane at 2MPa. Co/TiO2 reduced at 1123 K showed slow deactivation due to oxidation of Co. The addition of noble metals improved the catalytic stability of Co/TiO, drastically. The strong resistant nature of Co/TiO, to coke deposition was also retained by the catalysts. TPR revealed that noble metals improved the reducibility of cobalt oxide. The replacement of Co by a small amount of Ni also enhanced the catalytic stability of Co/TiO2, but replacement by an excess of Ni resulted in the decrease of catalytic stability because of coking. CoNi/TiO2 with an optimum Co:Ni ratio of 90:10 presented high stability with only an insignificant amount of coke deposition under 2 MPa, where coke deposition is highly favorable. (C) 2004 Published by Elsevier B.V.

DOI： 10.1016/j.apcata.2004.03.029

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Catalytic behaviour of 0.5wt%Co/TiO2, prepared from TiO2containing only anatase phase, in CH4/CO2reforming at 2 MPa was strongly affected by reduction temperature. Co/TiO2reduced at relatively lower temperatures (<1123 K) lost all of its activity at the beginning of the reaction, whereas the catalyst reduced at higher temperatures (1123 K) showed relatively stable activity with only a slight amount of deposited coke. However, the latter catalyst lost all of activities at a higher space velocity after the reaction for 20 h, mainly due to oxidation of metallic Co. The addition of trace amounts of noble metals (Pt or Ru) improved the catalytic stability drastically by retarding the oxidation. It was confirmed that the strong resistant nature of Co/TiO2to coke deposition was retained after the addition of the noble metals.

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0.5 wt.% Co/TiO2 was prepared by incipient wetness impregnation with Co(NO3)(2)(.)6H(2)O and TiO2, which contains only anatase as crystal structure. The influence of reduction temperature (973-1223 K) on the catalytic activity of the 0.5 wt.% Co/TiO2 was investigated for the CH4/CO2 reaction under 2.0 MPa mainly at a space velocity (SV) of 6000 ml g(-1) h(-1). Co/TiO2 reduced below 1123 K lost its activity completely at the beginning of the reaction. The results of TPO revealed that large amounts of coke (greater than or equal to2.9 wt.% carbon for 24 h) were deposited on the catalysts during the CH4/CO2 reaction. On the other hand, Co/TiO2 reduced at and above 1123 K kept relatively stable activity for 24 h and did not show significant amounts of deposited coke (less than or equal to0.25 wt.% carbon). The natures causing different catalytic behavior among the catalysts were discussed with the results of TEM, XRD, and TPR. In addition, slow deactivation of the Co/TiO2 reduced at 1123 K, probably due to the oxidation of the metallic cobalt, was inhibited by the addition of small amount of ruthenium (Ru/Co = 0.05) and it was found that the strong resistance to the coking of the Co/TiO2 reduced at 1123 K was retained after the addition of ruthenium. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/S0926-860X(03)00631-8

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The phase transfer of TiO2 from anatase to rutile for a 10wt% Co/TiO2 catalyst during the reduction causes serious disappearance of activity at 0.1 MPa during CH4/CO2 reforming, whereas the transfer for 0.5wt% Co/TiO2 brings about relatively stable activity at 2 MPa.

DOI： 10.1039/b201717m

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Support (SiO2, Al2O3, MgO, and TiO2) effects on catalytic behavior of Ru catalysts for the CH4/CO2 reforming were investigated under 2 (industrial condition) and 0.1 MPa at 1023 K. The order of the catalytic activity of the four catalysts investigated was dependent on the reaction pressure. High coking rate was observed at high pressure. 2 wt% Ru/TiO2, showing a low coking extent, is a promising candidate for industrial use. © 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S1566-7367(01)00043-7

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DOI： 10.1006/jcat.1998.2281

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DOI： 10.1002/ente.202000264

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DOI： 10.1002/cctc.201902311

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DOI： 10.1021/acssuschemeng.9b06299

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DOI： 10.1016/j.catcom.2019.02.019

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DOI： 10.1627/jpi.62.220

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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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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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&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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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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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.

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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;

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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.

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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/CeO&lt;sub&gt;2&lt;/sub&gt; after reduction at 873 K, but not over Rh catalysts supported on Pr&lt;sub&gt;6&lt;/sub&gt;O&lt;sub&gt;11&lt;/sub&gt; and Tb&lt;sub&gt;4&lt;/sub&gt;O&lt;sub&gt;7&lt;/sub&gt;, oxides of rare earth elements with redox characters like cerium. Over the latter catalysts, reduction of the carrier occurred at lower temperatures than over CeO&lt;sub&gt;2&lt;/sub&gt;, 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/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; 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 &lt;i&gt;in-situ&lt;/i&gt; 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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We have constructed cold-start process for oxidative reforming of hydrocarbons or oxidative decomposition of ammonia without external energy input. For example, n-butane and O2 are just supplied to reduced Rh/CeO&lt;sub&gt;2&lt;/sub&gt; in the reactor at room temperature, and immediately after that, catalyst bed temperature rises to 850&amp;nbsp; &amp;deg;C and H&lt;sub&gt;2&lt;/sub&gt; and CO are produced. In this process, the heat produced by oxidation of CeO&lt;sub&gt;2-x&lt;/sub&gt; to CeO&lt;sub&gt;2&lt;/sub&gt; increases catalyst bed temperature from room temperature to the catalytic auto-ignition temperature of the n-butane oxidative reforming. I will report cold-start mechanism, performance of developed catalysts, and strategy for designing effective catalysts.

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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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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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Language：Japanese   Publisher：The Japan Petroleum Institute  

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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Language：Japanese   Publisher：The Japan Petroleum Institute  

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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Language：Japanese   Publisher：The Japan Petroleum Institute  

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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