Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACS Catalysis  

Hydrogenation of toluene (TOL) to methylcyclohexane (MCH) is one of the hydrogen carrier systems desired for social integration. Supported Pt nanoparticle catalysts are effective for this application. However, Pt is rare, expensive, and in short supply, limiting its practical applications. Therefore, the key issue for TOL hydrogenation is how to substantially reduce the amount of Pt required for the catalyst. Because a specific ensemble of Pt atoms, that is dominantly formed on the surface of the Pt nanoparticle, is required for achieving higher catalytic performance, there is a limit to the number of precious Pt that can be conserved by simply reducing the particle size. The structure sensitivity established in the existing heterogeneous catalyst so far makes it difficult to design precious metal-conserving catalysts with both high activity and atomic efficiency. Here, a strategy for breaking the above limitations is reported. Our approach uses the heteroatom ensemble (HAE) on Pt single-atom alloyed 3d transition-metal nanoparticle catalysts (Pt1M SAAs, M = Co, Ni, Cu). The role of the TOL fixation/activation site is assigned to the atomic M sites on HAE, whereas the H2-activation site is to the Pt single-atom site on HAE. The atomic-scale division of roles within the HAE improves the efficiency of competitive adsorption of TOL/H2, which is important for boosting TOL hydrogenation. To maximize the synergistic effect at the adjacent sites, the atomic composition, geometric configuration, and electronic state of these active sites as well as the density of the HAE were tuned by the chemical composition and particle size of Pt1M SAAs. High activity was observed on the Pt1Co SAA with a particle size of 1.8 nm and Pt/Co molar ratio of 0.002. The Pt mass-specific activity reached 219 mol/gPt/h, which was 23 times higher than that in a conventional Pt nanoparticle-supported catalyst. Using a set of well-defined Pt1M SAAs, high-angle annular dark-field scanning transmission electron microscopy, Pt LIII-edge X-ray absorption fine structure spectroscopy, coupled with periodic density functional theory and ab initio molecular dynamics simulation, we proved the origin of the structure sensitivity at an atom-to-nanometer scale. The present work sheds light on the significance of regulations of the coordination environment of the Pt single-atom site, atomic composition, and particle size of Pt1M SAA for creating high activity, durability, and Pt-utilization efficiency for catalytic applications relevant to hydrogen carrier systems.

DOI： 10.1021/acscatal.3c02132

Scopus

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Catalysis Today  

Cobalt spinel oxides, containing octahedral (Oh) and tetrahedral (Td) sites, exhibit high activity for NO reduction by CO. The active sites of cobalt spinel oxides for NO–CO reaction was identified using various cobalt spinel oxides having different CoOh/CoTd ratio. Comparing the CoOh/CoTd ratio determined by EXAFS fitting analysis and the rate of NO reduction, it was clarified that octahedral site is responsible for NO reduction by CO. Furthermore, synchrotron-based in-situ XAFS measurements unveiled the contribution of CoOh sites: The cobalt spinel oxides with high CoOh fraction were more easily reduced by CO to form oxygen vacancies than those with low CoOh fraction, and resulted in the higher activity for NO reduction by CO.

DOI： 10.1016/j.cattod.2022.06.031

Scopus

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Catalysis Today  

Twinned structure of metal nanoparticles can strongly affect catalysis because of its unique atomic alignment and bond strain in metal nanoparticles. Here, the twin and single crystal structures of supported Ag nanoparticles are controlled reversibly by gas treatment. The single crystal Ag nanoparticles were formed in Ag/Al2O3 by H2 treatment, and subsequent CO gas treatment changed the Ag particle structure to twin. The change in the Ag particle structure from single to twin caused enhancement of CO oxidation activity. In addition, the catalytic activity was reversibly changed from low to high by applying H2 and CO gas treatment to Ag/Al2O3. The kinetic analysis for CO oxidation revealed that the twin Ag nanoparticles have stronger CO adsorption energy than the single crystal ones, which is responsible for the enhanced CO oxidation activity of twin Ag nanoparticles.

DOI： 10.1016/j.cattod.2022.06.029

Scopus

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Catalysis Surveys from Asia  

A combination of two base-metal oxides in tandem configuration can realize three-way reaction without platinum group metals. For this purpose, catalysts for hydrocarbon preferential oxidation (HC-PROX) and for NO reduction by CO are required. For the design of HC-PROX catalysts, competitive oxidation of propene and CO on spinel-type MFe2O4 (M = Co, Cu, Mg, Mn, Ni, Zn) was investigated. MnFe2O4 preferentially oxidized propene in the co-presence of CO showing the best propene oxidation activity. Among the series of MFe2O4, the activity controlling factor was correlated to the M-O bond energy of the second metal oxides, and the preference for HC oxidation was dependent on the electronegativity of the second ion. A tandem catalyst using MnFe2O4 for HC-PROX and CuCo2O4 for NO-CO reaction showed TWC activity comparable to a Rh/CeO2.

DOI： 10.1007/s10563-022-09373-9

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Applied Surface Science  

We theoretically investigated surface modification of MCr2O4 (M = Mg and Zn) by Cu-doping and doping effects on catalytic activity for CO oxidation. DFT + U calculations elucidated that Cu-dopants in MCr2O4(1 1 1) exist on the surface layer, CO oxidation by Cu-doped MCr2O4(1 1 1) occurs through Mars van Krevelen mechanism, rate-determining step (RDS) is the first CO2 desorption with oxygen vacancy (OV) formation, and the catalytic activity is enhanced very much by Cu-doping. Also, we experimentally observed that CO conversion was dramatically improved to 70% by the Cu-doped ZnCr2O4 from 5.2% by non-doped ZnCr2O4 at 300 °C. Bader charge analysis and difference density map show that M atom on the MCr2O4 surface receives electron density from the dissociating O atom in the OV formation step and the Cu-dopant can receive more electron density than Mg and Zn atoms to facilitate the OV formation and accelerate the first CO2 desorption(RDS). This larger capability of Cu-dopant for receiving electron density results from the facts that the Cu atom has large electronegativity and + I oxidation state besides + II in metal oxide but Mg and Zn have small electronegativity and only + II oxidation state.

DOI： 10.1016/j.apsusc.2022.154681

Scopus

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Catalysis Science and Technology  

Direct catalytic conversion of methane to value-added chemicals with a high reaction rate and selectivity under mild conditions remains a great challenge. Rh-supported zeolite is one of the promising heterogeneous catalysts capable of selectively oxidizing methane to acetic acid using carbon monoxide and oxygen at low temperatures. However, the difficulty in the preparation of the catalytically active species, i.e., zeolite-confined RhI single-atom sites, has limited the mass activity. Here, we successfully prepared a highly-active Rh-containing zeolite using RhCl3 molten salt. By high-temperature treatment of the physically-mixed H+-MFI zeolite and bulk RhCl3, the RhCl3 molten salt was formed under in situ conditions and then diffused into the zeolite pores, resulting in being trapped within the zeolite cavity via host-guest interaction and ion-exchange with H+. The encapsulated RhCl3 species are efficiently dispersed with the formation of RhI single-atom species as the active sites in the catalytic reaction, boosting the direct conversion of methane to acetic acid with a record turnover frequency (592 mol molRh−1 h−1) and yield (14.6 mmol gcat−1 h−1) with high selectivity (76.9%).

DOI： 10.1039/d2cy01471h

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of Physical Chemistry C  

Noble gas (Ng) elements are stable because of their octet electronic configuration, and thus Ng capture and purification are highly challenging. Here, we show a new concept for these applications: an orbital trap for Xe. This concept was found in Xe adsorption/separation processes at room temperature (RT) at the single Ag(I) site in MFI zeolite. Experiments and calculations showed the zeolite lattice-coordinated Ag(I) single ion has excellent electron-accepting nature and thereby induces the Xe 5p → Ag(I) 5s donation orbital interaction, forming a stable σ-bond with Xe even in the lower-pressure region and at RT. By contrast, the stable σ-bond for Kr adsorption is not established at RT because of the instability of the orbital interactions of the Kr 4p → Ag(I) 5s donation, as reflected from the relatively high energy of the Kr 4p orbital. Thus, the single Ag(I) site allows it to distinguish between Xe and Kr at RT; the Xe separation from the Xe/Kr gas mixture was achieved at RT using the Ag/MFI containing a high concentration of single Ag(I) sites. Our findings suggest that the orbital Xe trap using the local structure of porous materials shows promise as an efficient approach to selectively collect Xe (air concentration 0.087 ppm only). It will help to expand the range of applications of the costly Xe.

DOI： 10.1021/acs.jpcc.2c01515

Scopus

Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Catalysis Science and Technology  

A Pt-based CO oxidation catalyst that works even at low temperatures is desirable for industrial applications; however, its development is highly challenging because of Pt's high affinity toward CO. Here, we develop a PtIV single-atom/β-MnO2 composite metal-oxide surface (PtIV1/β-MnO2). Single PtIV sites were stably formed on the high surface β-MnO2 by strong interaction with MnIV defect sites. The resulting PtIV-O-MnIV local structures served the lattice oxygens as an oxidant to catalyze low-temperature oxidation of CO. PtIV1/β-MnO2 was highly resistant to CO poisoning because of the high-valence state of the PtIV single-atom sites. Aided by these geometric and electronic features, the CO oxidation was catalyzed with reaction rates of 0.676 and 0.206 molCO h−1 gPt−1 at 25 °C and 0 °C, respectively, under the O2-rich conditions (O2 : CO ratio of 66.7). These are record rates in the literature for Pt-based catalyst application for low-temperature CO oxidation under near atmospheric conditions.

DOI： 10.1039/d2cy00677d

Scopus

Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Journal of Catalysis  

For the design of a high-performance platinum group metal-free three-way catalyst, we propose a new C3H6-preferential oxidation (C3H6-PROX) catalyst under stoichiometric automobile exhaust gas (NO–CO–C3H6–O2) using supported vanadia catalysts. Among various V2O5 supported catalysts, V2O5/TiO2 (anatase, coverage of around one monolayer) showed the best activity for C3H6-PROX with preferable formation of CO. The tandem catalyst combination using V2O5/TiO2 as the upstream C3H6-PROX catalyst and Cu/CeO2 as the downstream NO–CO reaction catalyst showed comparable activity for NO reduction as a Rh/ZrO2 catalyst. The reaction mechanism of C3H6 oxidation was analyzed using in situ Infrared spectroscopy. The C3H6 oxidation progressed with the formation of surface acetate as an intermediate, and acetate consumption was the key step of C3H6 oxidation. It is suggested that the Brønsted acid promoted the cleavage of the C–C bond of acetate, therefore, the number of Brønsted acid sites is one of the critical factors for the higher performance of C3H6-PROX catalysts.

DOI： 10.1016/j.jcat.2022.03.012

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acsomega.1c06208

Scopus

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.apcata.2021.118425

Scopus

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

Iron-containing zeolites possess active sites capable of catalyzing the low-temperature partial oxidation of methane using hydrogen peroxide as an environmentally benign oxidant. However, only a trace number of active sites have been found in zeolites so far. The high turnover frequency was limited to low loading samples, resulting in an upper limit of similar to 50 mmol g(cat)(-1) h(-1) yield of C1 oxygenates. In this study, we synthesized a ZSM-5 catalyst containing a high concentration of single Fe sites with a high turnover frequency, and achieved a conversion of methane to C1 oxygenates of similar to 200 mmol g(cat)(-1) h(-1) yield. It was important to use ZSM-5 as a carrier, which can be synthesized by hydrothermal treatment of aluminosilicate gel containing only tetra-propyl ammonium cations as the structure-directing agent (SDA). This ZSM-5 carrier has a large fraction of local environments possessing the nearest framework AlO4 tetrahedra required for the fixation of Fe cations in the mononuclear state while suppressing the co-generation of oligomeric Fe sites, making it possible to design a reaction field for the highly efficient partial oxidation of methane. The findings in the present study clearly showed that the fraction of single Fe cations and the Al distribution in the zeolite matrix are powerful activity descriptors for this class of materials. Furthermore, Al-distribution modification based on previously-established protocols, i.e., rational choice of an SDA used in the zeolite synthesis, is a meaningful way to tune not only the fabrication efficiency of single Fe cations but also the catalytic performance of Fe/ZSM-5 catalysts.

DOI： 10.1039/d1cy01987b

Web of Science

Scopus

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

DOI： 10.1021/acs.jpcc.1c06760

Scopus

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

The structure-catalytic property relationships of Al2O3-supported Pt-Sn nanoparticles (Pt-Sn/Al2O3) in the dehydrogenation of methylcyclohexane (MCH) were investigated by varying the Sn/Pt ratios of the catalysts. The initial activity and the deactivation rate of the Pt-Sn/Al2O3 catalysts in the MCH dehydrogenation decreased in line with an increase in the Sn/Pt ratio from 0 to 3. The Pt-Sn/Al2O3 catalyst with a Sn/Pt ratio of 2 showed good activity, durability, and toluene selectivity in the MCH dehydrogenation among the series of catalysts. The dispersion of Pt in the Pt-Sn/Al2O3 catalysts was observed to decrease with an increase in the Sn/Pt ratio. Structural changes in the catalysts from Pt-Sn clusters to intermetallic Pt3Sn and PtSn nanoparticles were also observed using scanning transmission electron microscopy and X-ray diffraction. According to structural analysis using X-ray absorption fine-structure spectroscopy and infrared spectroscopy using carbon monoxide as a probe, the electron density of Pt increased, and the fraction of Pt-Pt adjacent sites decreased with an increase in the Sn/Pt ratio. Comparing the catalytic properties and the structures of the Pt-Sn/Al2O3 catalysts, their initial activities were correlated with the dispersion of Pt. In addition, the durability and selectivity of the catalysts were enhanced due to an increase in the electron density of Pt and a decrease in the number of Pt-Pt adjacent sites. Overall, the properties of the catalysts in the MCH dehydrogenation are determined by the local structure of Pt atoms rather than the crystal structure of the Pt-Sn alloy nanoparticles on Al2O3.

DOI： 10.1021/acsanm.1c00128

Scopus

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Pd/Al2O3 catalysts were prepared using various Al2O3 supports with different structural features such as crystalline phase and crystallinity related to Al3+ coordination, revealing a significant insight into the methane (CH4) combustion activity of Pd nanoparticles with the fraction of penta-coordinated Al3+ sites in the Al2O3 supports.

DOI： 10.1039/d1cy00098e

Web of Science

Scopus

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

DOI： 10.1021/acs.jpcc.1c01042

Scopus

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

In the present study, the redispersion behavior of Ag particles on ZSM-5 in the presence of coke was observed usingin situX-ray absorption fine structure (XAFS) spectroscopy. The dynamics of Ag particle redispersion into the ZSM-5 pores were evaluated by linear combination fitting (LCF) of the X-ray absorption near edge structure (XANES) spectra. In addition, the behavior of coke combustion in Ag-ZSM-5 was observed by thermogravimetric analysis (TGA). The rate constant of Ag particle redispersion was smaller than that of coke combustion at ≥500 °C, but it was three times larger than that of coke combustion at &lt
500 °C. According to27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR), the Ag+ions in the ZSM-5 pores improved the hydrothermal stability of Ag-ZSM-5. Therefore, a two-step regeneration process, in which the Ag particle redispersion proceeded first at low temperature (&lt
500 °C) followed by a complete combustion of the coke at high temperature (≥500 °C) to prolong the catalyst lifetime, was used.

DOI： 10.1039/d0cy01989e

Web of Science

Scopus

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

Catalysts to improve the hydrogen oxidation reaction (HOR) were developed via control of Ru nanoparticle size, alloying Ru with Ir, and surface modification of metal nanoparticles. The performance of these developed anode catalysts for anion exchange membrane fuel cells had improved, which is dependent on the hydrogen binding energy and the bifunctional mechanism. Surface modification of metal nanoparticles further enhanced the HOR activity based on the bifunctional mechanism. Such surface medication could form reactive OH species and remove surface poisoning of the hydrogen adsorption sites.

DOI： 10.1627/jpi.64.166

Scopus

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

We found a positive correlation between C=C selective hydrogenation activity of cinnamaldehyde (CAL) and the fraction of the Pd step site on Pd nanoparticles. Owing to a high fraction of step sites, Pd/θ-Al2O3 catalysts with Pd particle size of 510 nm were highly active for the C=C selective hydrogenation of CAL.

DOI： 10.1246/CL.200856

Scopus

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

DOI： 10.1016/j.jcat.2020.11.006

Scopus

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

To develop highly active soot combustion catalysts for gasoline direct injection exhausts under low oxygen concentration conditions, CeO2 supported-metal catalysts (M/CeO2, M = Mn, Fe, Co, Ni, Cu, Rh, Pd, and Ag) were examined. Among the catalysts tested, Cu/CeO2 and Rh/CeO2 displayed the highest soot combustion activity. By comparing the activities of Cu-based catalysts with and without a Cu-CeO2 interface, the importance of such an interface for soot combustion was inferred. The oxygen release rate of CeO2-based catalysts, enhanced by metal-CeO2 interactions, was indicated as the controlling factor of catalytic activity. The soot oxidation activity and oxygen release rate were also demonstrated to correlate with metal-oxygen bond energy. Based on the redox properties and structural characteristics of CeO2-based catalysts, loading CeO2 with Cu or Rh, which have moderate M-O bond energy, was concluded to be optimal both in terms of the dispersion of supported-metal species and reducibility of the CeO2-based catalyst.

DOI： 10.1039/d0cy01294g

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Journal of Physical Chemistry Letters  

Isolation of the atomic O radical anion bound to a metal ion (metal-oxyl) on solid surfaces is highly desirable for an understanding of how we should design the surface structure for using oxyl as the reactive site. Owing to the analytical difficulty of oxyl, however, even identification of oxyl remains scarce. Herein, we report isovalent ZnII-oxyl and GaIII-oxyl bonds isolated in the zeolite matrix. Close similarities in reactivity, spectroscopic property, and bonding nature were observed between them, but their site requirements were entirely different; the former is generated at the monovalent ion-exchangeable site, whereas the latter at the divalent ion-exchangeable site. This study strongly suggests that tuning the polarization of the metal-oxygen bond using the charge-controlled lattice oxygens is a useful way to constrain surface metal-oxyl bonds.

DOI： 10.1021/acs.jpclett.0c02980

Web of Science

Scopus

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acscatal.0c03425

Web of Science

Scopus

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

The effects of the Pd particle size and the Al2O3 crystalline phase of Pd/Al2O3 catalysts on the CH4 combustion in the presence of H2O were investigated. According to X-ray absorption fine structure (XAFS) measurements, it was revealed that, during the CH4 combustion, the Pd nanoparticles existed on the Al2O3 support as a PdO phase, while the crystallinity of PdO depended on the Pd particle size. On the basis of X-ray diffraction (XRD), amorphous PdO particles with a size of &lt
7 nm exhibited low activity for CH4 combustion. In contrast, as the Pd particle size increased, larger crystalline PdO particles (&gt
7 nm) were formed, which were highly active for CH4 combustion. Comparing the effects of the different Al2O3 crystalline phases, Pd/α-Al2O3 was proved to be more resistant to deactivation by H2O than Pd/γ-Al2O3 and Pd/θ-Al2O3. Moreover, according to H2O temperature-programmed desorption (TPD) and infrared (IR) measurements, since α-Al2O3 was relatively hydrophobic compared to γ-Al2O3 and θ-Al2O3, a faster and reversible adsorption/desorption of OH/H2O species was achieved, while the H2O poisoning on PdO species in the vicinity was limited.

DOI： 10.1021/acscatal.0c02050

Web of Science

Scopus

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

DOI： 10.1016/j.cattod.2019.12.002

Web of Science

Scopus

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

One of the problems in a diesel oxidation catalyst is its insufficient activity for injected diesel fuel at low temperatures caused by strong adsorption of hydrocarbons. This study systematically clarified the poisoning effect of various hydrocarbons having carbon numbers from 3 to 16. As the carbon number in alkanes increased, the light-off temperature over a Pt-Pd/Al2O3 catalyst gradually shifted to a lower temperature. While alkenes and aromatics showed an opposite trend, the light-off shifted to a higher temperature as the carbon number increased. In situ FTIR spectra indicated that the amount of adsorbed hydrocarbons on the metal surface increased with the increase in the carbon number of alkanes and alkenes. Kinetic analysis showed that the reaction orders with respect to O2 were below zero in light alkane combustion, while those with respect to hydrocarbons were zero or lower in alkene and aromatic combustion. The shift of the light-off temperatures was rationalized by competitive adsorption of hydrocarbons and oxygen. This journal is

DOI： 10.1039/d0cy00017e

Web of Science

Scopus

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

Carbon monoxide (CO) molecules are attracting attention as capping agents that control the structure of metal nanoparticles. In this study, we aimed to control the shape and surface structure of Pd particles by reducing the supported Pd precursor with CO. The reduction of Pd nanoparticles with CO promoted the exposure of step sites and generated spherical and concave-tetrahedral Pd particles on carbon and SiO2 supports. On the other hand, conventional H2-reduced Pd particles show a flattened shape. The preferential exposure of the step sites by the adsorbed CO molecules was supported by the density functional theory-calculated surface energy and the Wulff construction. Morphology- and surface-controlled Pd nanoparticles were used to study the surface structure and morphology effects of Pd nanoparticles on cinnamaldehyde (CAL) hydrogenation. With an increase in the fraction of step sites on Pd nanoparticles, the hydrogenation activity and selectivity of hydrocinnamaldehyde (HCAL) increased. On step sites, the adsorption of the C-C bond of CAL proceeded preferentially, and HCAL was efficiently and selectively generated.

DOI： 10.1021/acsami.0c05938

Web of Science

Scopus

PubMed

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

The selective catalytic reduction of NO with ammonia (NH3-SCR) catalyzed by Cu-CHA zeolites is thoroughly investigated using in situ spectroscopic experiments combined with on-line mass spectroscopy (MS) under steady-state NH3-SCR conditions and transient conditions for Cu(II)/Cu(I) redox cycles. Quantitative analysis of the in situ XANES spectra of Cu-CHA under steady-state conditions of NH3-SCR show that NH3-coordinated Cu(II) species is the dominant Cu species at low temperatures (100-150 degrees C). At higher temperatures, Cu(II) species and [Cu(NH3)(2)](+) complex coexist, possibly because the rate of the Cu(II) -> Cu(I) reduction step is comparable to that of the Cu(I)-> Cu(II) oxidation step. In situ XANES, IR/MS, and UV-vis/MS experiments on the reduction half cycle demonstrate that the reduction of Cu(II) species occurs via the reaction of NH3-liganded Cu(II) with NO to yield N-2 and H2O. For the oxidation half cycle, in situ XANES experiments of Cu(I) oxidation in 10 % O-2 at 200 degrees C indicate that an increased density in CHA zeolite exhibits a higher oxidation rate. In situ UV-vis experiments of Cu(I) reoxidation using different mixtures of oxidant feed gas demonstrate the key role of O-2 in the oxidation cycle. It is suggested that the reoxidation of Cu(I) to Cu(II) species occurs with only O-2 as the oxidant, and a high Cu density in CHA zeolite promotes SCR activity by enhancing the oxidative activation of Cu(I) to Cu(II) during the catalytic cycle.

DOI： 10.1002/cctc.202000024

Web of Science

Scopus

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

DOI： 10.1021/acsami.0c00506

Web of Science

Scopus

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

Anion exchange membrane fuel cells (AEMFCs) have been developed to the extent that the cell performance is nearing that of conventional proton exchange membrane fuel cells. For further improvement of AEMFC cell performance, it is necessary to develop the catalysis of hydrogen oxidation reactions (HORs) under basic conditions at the anode. Here, significant poisoning of Pt/C under basic conditions is demonstrated by electrochemical active surface area (ECSA) analysis using not only electrochemical measurement but also in situ Pt L-3-edge X-ray adsorption spectroscopy (XAS). Furthermore, the in situ XAS analysis reveals that the surface modification of Pt/C with another metal species improves the ECSA of the Pt nanoparticles by removal of the surface poisoning, which contributes to the enhanced HOR performance of the modified Pt/C catalysts. Therefore, the removal of poisoning is proposed as a mechanism for improving the HOR on Pt-based catalysts.

DOI： 10.1021/acsaem.9b02274

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

The modification of Cu-exchanged zeolites with phosphorus represents a promising method to enhance their hydrothermal stability, which is of pivotal importance for catalysts that promote the selective catalytic reduction of NO with ammonia (NH –SCR). In this study, we investigated the reaction mechanism of NH –SCR catalyzed by a phosphorus-modified CHA zeolite that contains active Cu species (Cu-P-CHA), and assessed the effect of the phosphorus modification on the hydrothermal stability of the catalyst by employing in situ/operando spectroscopic methods. In their entirety, the combined results from in situ/operando IR, UV–vis, and XANES experiments revealed that the NH –SCR process over Cu-P-CHA proceeds via the reduction of Cu(II) to Cu(I) followed by a reoxidation of Cu(I) to Cu(II). In addition, we found that the phosphorus modification improved the hydrothermal durability of the catalyst by retaining a higher amount of the redox-active Cu species and the zeolite framework. 3 3 3

DOI： 10.1016/j.cattod.2020.07.084

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/ACSCATAL.9B04524

Web of Science

Scopus

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

DOI： 10.1039/c9cy00158a

Web of Science

Scopus

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

DOI： 10.1021/acscatal.9b00526

Web of Science

Scopus

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

DOI： 10.1039/c9cc00582j

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ECS Transactions  

The cell performance of anion exchange membrane fuel cells (AEMFCs) has been getting closer to that of proton exchange membrane fuel cells (PEMFCs) by improvement of hydrogen oxidation reaction (HOR) catalysts on anodes with the help of the state-of-the-art AEMs having high ion conductivity. However, development of the alkaline HOR catalysts is still demanded to reduce the usage of precious metals on AEMFC anode. Here, Pt/C catalyst is modified to improve the HOR activity using fifteen metals on the group 4-11 of the 4th and 5th period in the periodic table except for Tc, i.e., Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Ag. In addition, the hydrogen binding energy of modified Pt/C and the oxophilicity of modifying metals are evaluated to reveal the mechanism of improved/lowered HOR activity.

DOI： 10.1149/09208.0733ecst

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Catalysis  

In situ and operando analyses are the methods to observe the real features of catalysts under the reaction conditions. These methods can clarify the dynamics of active species of catalysts and reaction scheme on catalyst surface through transient response method, kinetic study, temperature dependence of catalysts and products, and so on. In this review, progress in in situ and operando analyses is summarized with emphasis on environmental catalysts, i.e., catalysts for combustion, selective reduction of NO, automotive three-way catalysis, and related materials.

DOI： 10.1039/9781788016971-00242

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/CHEM.201902994

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1246/CL.190462

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/ACS.JPCC.9B03687

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C9CP03943K

Web of Science

Scopus

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

DOI： 10.1093/jmicro/dfy036

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Chemical Record  

Supported bimetallic catalysts have been studied because of their enhanced catalytic properties due to metal-metal interactions compared with monometallic catalysts. We focused on galvanic deposition (GD) as a bimetallization method, which achieves well-defined metal-metal interfaces by exchanging heterogeneous metals with different ionisation tendencies. We have developed Ni@Ag/SiO2 catalysts for CO oxidation, Co@Ru/Al2O3 catalysts for automotive three-way reactions and Pd−Co/Al2O3 catalysts for methane combustion by using the GD method. In all cases, the catalysts prepared by the GD method showed higher catalytic activity than the corresponding monometallic and bimetallic catalysts prepared by the conventional co-impregnation method. The GD method provides contact between noble and base metals to improve the electronic state, surface structure and reducibility of noble metals.

DOI： 10.1002/tcr.201700084

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ChemCatChem  

The highly active species of Pd/Al2O3 catalysts for methane combustion was revealed by in situ time-resolved dispersive X-ray absorption fine structure (DXAFS) spectroscopy. By using CH4 as a reduction agent, PdO in Pd/Al2O3 is reduced in a 2-step model involving Pd0 nucleation and growth of Pd0 domain in a PdO particle. Kinetic analysis of the 2-step model reduction of PdO nanoparticles leads to a suggestion that partial formation of Pd0 in a PdO particle accelerates methane combustion.

DOI： 10.1002/cctc.201800573

Scopus

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

A series of ceria-supported Rh nanoparticles (NPs) that have various particle sizes of 2–7 nm was prepared to investigate the size effect of Rh NPs on NO reduction in NO–CO–C3H6–O2 under stoichiometric conditions. The turnover frequency (TOF) for NO reduction on Rh NPs increased drastically according to their particle size. The strong size dependence of the TOF was attributed to the oxidation states of Rh NPs but not to particle geometries, which include fractions of surface local sites (e.g., corner, edge, plane) and the surface crystal structures (e.g., Rh(1 1 1), (1 0 0)). The variation of the TOF with the Rh metal fraction suggested that Rh metal ensembles are highly active species for NO reduction.

DOI： 10.1002/cctc.201701842

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier B.V.  

The NOx reduction activity of NiFe2O4 in automotive three-way catalysis was enhanced by physical mixing with CeO2, MgO, ZrO2, and Al2O3, while the mixing with TiO2 and Nb2O5 did not promoted the catalytic activity. On both pure NiFe2O4 and the physically mixed catalysts, NO was mainly reduced by C3H6 under the NO-C3H6-CO-O2 reaction conditions, because the temperature dependence of NO conversion in NO-C3H6-CO-O2 reaction was the same as that in NO-C3H6-O2 reaction. The in-situ FT/IR measurement revealed that the NO reduction proceeded with (1) partial oxidation of C3H6 to surface carboxylates, i.e., acetate and formate as good reductants for NO, and (2) reduction of NO by surface carboxylates. The metal oxide additives did not have catalytic activity for partial oxidation of C3H6 nor for NO oxidation to NO2, except CeO2. The main promotion effect was attributed to storage and release of surface carboxylates by metal oxide additives.

DOI： 10.1016/j.cattod.2017.07.026

Scopus

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

We report herein the first general catalytic system for the direct synthesis of N-substituted γ- and δ-lactams by reductive amination/cyclization of keto acids (including levulinic acid) with nitriles and H2 under mild conditions (7 bar H2, 110 °C, solvent free). The most effective catalyst, Pt and MoOx co-loaded TiO2 (Pt-MoOx/TiO2), shows a wide substrate scope, high turnover number (TON), and good reusability.

DOI： 10.1002/cctc.201701355

Scopus

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

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

DOI： 10.1021/jacs.7b07114

Scopus

PubMed

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

DOI： 10.1007/978-981-10-5137-1_5

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

The particle size effect of Pd nanoparticles supported on alumina with various crystalline phases on methane combustion was investigated. Pd/, -Al2O3 with weak metal-support interaction showed a volcano-shaped dependence of the catalytic activity on the size of Pd particles, and the catalytic activity of the strongly interacted Pd/-Al2O3 increased with the particle size. Based on a structural analysis of Pd nanoparticles using CO adsorption IR spectroscopy and spherical aberration-corrected scanning/transmission electron microscopy, the dependence of catalytic activity on Pd particle size and the alumina crystalline phase was due to the fraction of step sites on Pd particle surface. The difference in fraction of the step site is derived from the particle shape, which varies not only with Pd particle size but also with the strength of metal-support interaction. Therefore, this interaction perturbs the particle size effect of Pd/Al2O3 for methane combustion.

DOI： 10.1002/anie.201709124

Web of Science

Scopus

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

We studied the dynamic redox behavior of Cu species in zeolite matrix under NH3-SCR using in situ XAFS. Cu2+ species were slowly reduced to Cu+ in flowing NH3, and subsequent addition of NO promoted the reduction to Cu+. In the oxidation step, oxygen alone did not fully oxidize Cu+ to Cu2+, but the Cu+ species were completely oxidized to Cu2+ by NO-O-2. The oxidation step was slower than the reduction step, which suggested that the oxidation step (Cu+ -> Cu2+) is the slow step of the NH3-SCR reaction.

DOI： 10.1246/cl.170451

Web of Science

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

To elucidate the reaction mechanism of NO-C3H6-CO-O2 over NiFe2O4, we investigated the dynamics of the adsorbed and gaseous species during the reaction using operando Fourier transform infrared (FTIR). The NO reduction activity dependent on the C3H6 and CO concentrations suggested that NO is reduced by C3H6 under three-way catalytic conditions. From FTIR measurements and kinetic analysis, it was clarified that the acetate species reacted with NO-O2 to form N2 via NCO, and that the rate-limiting step of NO reduction was the reaction between CH3COO- and NO-O2. The NO reduction mechanism of the three-way catalyst on NiFe2O4 is different to that on platinum-group metal catalysts, on which NO reduction proceeds through N-O cleavage.

DOI： 10.1021/acsomega.7b00165

Web of Science

Scopus

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

Glucose isomerization was performed using various titanate catalysts, which include SrTiO3, BaTiO3, CaTiO3, Na2Ti6O13, K2Ti6O13, and Sr3Ti2O7, prepared using a conventional solid-phase method. Among the titanates, SrTiO3, CaTiO3, and Na2Ti6O13 offered a relatively high fructose yield (32%) with a high selectivity (68-78%). The yields are comparable to yields reported previously using a Sn-modified BEA zeolite, which shows a high efficiency for glucose isomerization as a Lewis acid catalyst. A study of the mechanism of glucose isomerization on a SrTiO3 catalyst surface by using H-1 NMR spectroscopy suggested that the titanates catalyze the isomerization as base catalysts. Thus, the effect of the basicity of the titanates on glucose isomerization was investigated in terms of the base quantity and strength. The analysis was performed by using an acid-base titration method and FTIR spectroscopy with CHCl3 as a probe molecule. It is proposed that glucose isomerization on the titanates depends not only on the base amount but also on the base strength.

DOI： 10.1002/cctc.201700068

Web of Science

Scopus

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

Combination catalyst systems composed of Pt/SiO2 and lanthanoid oxides (Pt/SiO2 + LOx) efficiently catalyze the hydrogenative ring-rearrangement of 5-(hydroxymethyl) furfural (HMF) in water to produce 3-(hydroxymethyl) cyclopentanol (HCPO), which can be a unique building block for new materials derived from biomass. We investigated the reason for the efficient hydrogenative ring-rearrangement on Pt/SiO2 + LOx in terms of the acid-base properties of reaction systems, since H+ and Lewis acids can affect the rearrangement of the furan ring. It is indicated that the ring-rearrangement efficiently proceeds under slightly acidic conditions (pH = 5-7) with moderate or a little weak Lewis acidity of lanthanoid oxides.

DOI： 10.1039/c7cy00712d

Web of Science

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

Recently, it has been reported that the morphology of Au nanoparticles (NPs) affects the catalytic activity of CO oxidation; twin crystal NPs show higher activity for CO oxidation than single-crystal NPs. In this study, density functional calculations have been carried out to investigate the morphology effect of Au NPs using CO as a probe molecule. In the case of Au NPs with a size of more than 2 nm, CO adsorption energy on the Au NPs is mainly determined by a coordination number (CN) of adsorption sites. CO binding to a multiple twin NP with a size of about 1 nm is stronger than that on a single-crystal NP with the same size. A simple CN explanation cannot be applied to the enhancement of CO binding to the small multiple twin NP. This enhancement is related to a deformation of the NP structure before and after CO adsorption. It is suggested that the multiple twin NP with a size of less than 1 nm, which shows the deformation upon CO adsorption, contributes to the higher activity for CO oxidation.

DOI： 10.3390/catal7060191

Web of Science

Scopus

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

Pd/CoAl2O4/Al2O3 methane combustion catalysts were synthesized using a galvanic deposition (GD) method (PdCoAl-GD). This PdCoAl-GD catalyst showed higher activities and turnover frequencies (TOFs) than conventional Pd/Al2O3. According to X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) and scanning transmission electron microscopy (STEM) measurements, PdCoAl-GD was composed of a CoAl2O4 phase supported on gamma-Al2O3 and dispersed Pd nanoparticles of 2-7 nm in size on CoAl2O4. Operando Pd K-edge XAFS measurements indicated that the Pd in PdCoAl-GD was oxidized to highly active methane combustion PdO species at low temperatures. PdCoAl-GD also showed high activity (light-off tests) when PdO was initially present on the catalysts. Methane temperature-programmed reaction (CH4-TPR) measurements on PdCoAl-GD revealed that PdO was reduced by CH4 at low temperatures. The GD method used herein achieved PdO species that were effective for C-H activation.

DOI： 10.1039/c7ra06150a

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Chemistry Letters  

We studied the dynamic redox behavior of Cu species in zeolite matrix under NH3-SCR using in situ XAFS. Cu2+ species were slowly reduced to Cu+ in flowing NH3, and subsequent addition of NO promoted the reduction to Cu+. In the oxidation step, oxygen alone did not fully oxidize Cu+ to Cu2+, but the Cu+ species were completely oxidized to Cu2+ by NOO2. The oxidation step was slower than the reduction step, which suggested that the oxidation step (Cu+ ¼ Cu2+) is the slow step of the NH3-SCR reaction.

DOI： 10.1246/cl.170451

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Catalysis Science and Technology  

Combination catalyst systems composed of Pt/SiO2 and lanthanoid oxides (Pt/SiO2 + LOx) efficiently catalyze the hydrogenative ring-rearrangement of 5-(hydroxymethyl)furfural (HMF) in water to produce 3-(hydroxymethyl)cyclopentanol (HCPO), which can be a unique building block for new materials derived from biomass. We investigated the reason for the efficient hydrogenative ring-rearrangement on Pt/SiO2 + LOx in terms of the acid-base properties of reaction systems, since H+ and Lewis acids can affect the rearrangement of the furan ring. It is indicated that the ring-rearrangement efficiently proceeds under slightly acidic conditions (pH = 5-7) with moderate or a little weak Lewis acidity of lanthanoid oxides.

DOI： 10.1039/c7cy00712d

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Japan Society of Mechanical Engineers  

DPF (Diesel Particulate Filter) is effective for trapping diesel soot from diesel engines. The trapped diesel soot is removed by combustion above 600°C using excess fuels, which results in reduction of fuel economy. An effective design of DPF is strongly required to improve DPF regeneration efficiency and fuel economy
however, the internal phenomenon of diesel soot combustion on DPF is still not clarified. For an effective design of DPF, in this study, we investigated the effect of diesel soot structure on combustion temperature using real diesel soot. Soot samples were characterized by means of various physicochemical techniques: XPS (X-ray photoelectron spectroscopy), EELS (Electron Energy Loss Spectroscopy), Raman spectroscopy, TEM (transmission electron microscopy), and elemental analysis. TEM images and Raman spectra of real diesel soot showed that the difference in the crystallinity of soot was small. XPS, EELS, and elemental analysis revealed that oxygen content, which is derived from surface functional groups of - COOH, -OH, and - C=O at defect sites, was strongly affected by the engine operating conditions. The ignition temperature of diesel soot was dependent on O/C ratio measured by elemental analysis. With the increase in oxygen content of diesel soot, combustion temperatures of soot became lower. It was concluded that the concentration of oxygen containing functional groups is an essential factor for the control of the ignition temperature of diesel soot.

Scopus

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

DOI： DOI: 10.1039/C6TA05517F

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

DOI： DOI: 10.1039/c6cy00795c

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

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

DOI： doi.org/10.1246/bcsj.20160102

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

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

DOI： DOI: 10.1016/j.cattod.2015.11.043

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

DOI： DOI: 10.1016/j.jcat.2015.11.021

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

DOI： doi:10.1007/s10562-015-1658-5

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

DOI： 10.1016/j.cattod.2015.03.047

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

DOI： 10.1039/c5cc05484b

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

DOI： 10.1039/C5GC01723H

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

DOI： 10.1246/cl.150123

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C4RA10167G

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.cattod.2014.05.046

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

DOI： 10.1246/cl.140165

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

DOI： 10.1039/C3CC49591D

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

DOI： 10.1007/s11244-014-0274-8

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

DOI： 10.1093/jmicro/dfu001

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

DOI： 10.1016/j.jpowsour

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

DOI： DOI: 10.1021/ja4021638

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

DOI： dx.doi.org/10.1021/cs4001267

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

DOI： DOI: 10.1039/c3cy00033h

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI: 10.1016/j.apcatb.2012.12.025

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.cattod.2012.03.048

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

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

DOI： DOI: 10.1039/C2RA22190J

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

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

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

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

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

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

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

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

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

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

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

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

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

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

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

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

DOI： 10.1016/j.apcatb.2011.11.002

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

DOI： 10.1627/jpi.54.347

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

DOI： 10.1002/cctc.201100171

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

DOI： 10.1039/C1GC15835J

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

DOI： 10.1039/C1RA00560J

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

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

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

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

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

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

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C0CY00077A

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

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

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

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

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

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

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

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

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

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

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

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

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

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

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

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

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

The mechanistic cause of the dramatic activity improvement of alumina-supported silver (Ag/Al2O3)byH2 addition for the selective catalytic reduction of NO with propane (C3H8-SCR) was investigated by catalytic and spectroscopic studies. In situ UV-vis, in situ EXAFS, IR, and microcalorimetric experiments show that
H2 reduction of Ag+ ions on Ag/Al2O3 at 573 K yields protons on alumina and partially reduced Agn clusters, which are subsequently aggregated to larger Ag clusters. During H2 + O2 and H2-assisted C3H8-SCR reactions, Ag+ ions and Agn .+ coexist. Reoxidation with O2 results in the redispersion of the cluster to Ag+ ion, accompanying a reaction of protons. The relationship between cluster size, redox properties, and catalytic activity is examined using Ag/Al2O3 of different Ag loadings. The steady-state NO reduction rate correlates fairly well with the amount of Agn .+ during the H2-assisted C3H8-SCR reaction. It is shown that Agn .+ is the active species, whereas monomeric Ag+ ion and metallic Ag particles are inactive. With Ag loading, the Ag+ reduction rate increases and the rate of cluster reoxidation decreases. A balance between the rate of reduction and reoxidation of Ag species is an important factor that controls the size and oxidation state of the Ag species and consequently the catalytic activity of Ag/Al2O3. ESR has provided evidence, for the first time, for the in situ generation of superoxide ions in H2 + O2 and H2-assisted C3H8-SCR reactions. The comprehensive reason for the hydrogen effect in HC-SCR is discussed, focusing on the role of the cluster and protons on the reductive O2 activation to superoxide ion.

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

Authorship：Lead author   Language：English  

Language：English  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Selective catalytic reduction of NO by hydrocarbons (HC-SCR) is one of the promising technologies for removal of NO in exhausts containing excess oxygen, such as diesel and lean burn gasoline engines. Supported Ag catalysts, especially Ag/Al2O3, are thought to be the promising candidates for use in diesel exhausts, as con.rmed by several reports on engine bench tests. The HC-SCR performance of supported Ag catalysts is very sensitive to the reaction conditions, especially the type of hydrocarbons and the addition of H2. The control of reaction conditions would be key for practical use. The current research of supported Ag catalysts is reviewed from the viewpoints of practical use and the reaction mechanism, i.e., the reaction scheme, the role of surface adsorbed species, and the structure of active Ag species.

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

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

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Involvement of active sites in the selective oxidation of propane was investigated using (VO)2P2O7 catalysts promoted by Sb, Ti, Zr, Hf, Cu, and Ce. Based on X-ray diffraction patterns, infrared spectra, and Raman spectra, the formation of a (VO)2P2O7 phase was con.rmed for all of the promoted catalysts; no other phases were detected. After the addition of Sb, Ti, and Zr, the selectivity to acrylic acid increased, whereas Cu-, Ce-, and Hf-promoted catalysts showed lower selectivity than pure (VO)2P2O7. The effect of promoters on the activity and selectivity for the propane oxidation was investigated on the basis of the nature of surface active sites. The surface V=O species, evaluated by the nitric oxide.ammonia rectangular pulse technique, decreased with the addition of the promoters. A proportional correlation between the number of surface V=O species and reaction rate of propane clari.ed that the surface V=O species is the controlling factor for the catalytic activity of propane oxidation. In the case of Sb-, Ti-, and Zr-promoted catalysts, the selectivity to acrylic acid increased signi.cantly. The selectivity was compared with the number and strength of Bronsted and Lewis acid sites estimated from dimethylpyridine temperature-programmed desorption. A good correlation was observed between the selectivity to acrylic acid and the surface concentration of Lewis acid sites. It was experimentally demonstrated that Lewis acid sites represent the key factor in selective oxidation.

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

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

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

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

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

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

Language：English  

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

Language：Japanese  

Authorship：Lead author   Language：Japanese  

Authorship：Lead author   Language：English  

Authorship：Lead author   Language：English  

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

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

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

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

Authorship：Lead author   Language：English  

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

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

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

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

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

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

Authorship：Lead author   Language：English  

Language：English  

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

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

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

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

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

Language：English  

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

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

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

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

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

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

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

Silver-alumina catalysts prepared by sol.gel method (Ag-Al2O3) and impregnation method (Ag/Al2O3) were studied for the selective catalytic reduction (SCR) of NO by higher alkanes (n-hexane and n-octane). UV.VIS and Ag K-edge XAFS results established the structure of the catalysts; below 2 wt.%, highly dispersed Ag+ ions are predominant Ag species, while at higher Ag loading, Agn clusters are predominant. A relationship between the structure of Ag species and their catalytic function for SCR by n-octane was clari.ed. Ag+ ions are responsible for the selective reduction of NO to N2, while the Agn clusters are responsible for the hydrocarbon combustion and N2O formation. The mechanism of SCR by n-hexane on Ag-Al2O3, which mainly consists of Ag+ ions, were investigated by in situ FTIR spectroscopy. During NO + n-hexane + O2 reaction, the acetate produced via the partial oxidation of n-hexane and the nitrates produced via the oxidation of NO were main adspecies in the steady-state condition at 473.623 K. The acetate, which was stable in O2 or NO, was reactive in NO+O2. Nitrates, which were relatively stable in n-hexane, were quite reactive toward n-hexane+O2. The rate of nitrates reaction in n-hexane+O2 was close to the steady-state rate of NO reduction over wide range of temperature, indicating that the nitrate is a possible intermediate in the SCR. A proposed mechanism, suggesting the reaction of nitrates with partially oxidized hydrocarbon species as a crucial step, explains the steady-state kinetic results. At relatively high NO concentration or at low temperature, nitrates should inhibit the reaction by strongly adsorbing on the catalyst surface.

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

Language：English  

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English  

Language：English  

Authorship：Lead author   Language：English  

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

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

Language：English  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

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

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English  

Language：English  

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

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

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Total pages：12   Responsible for pages：75-86   Language：Japanese Book type：Scholarly book

一昨年に報道された排気ガス規制偽装の報道は記憶に新しいかと思われますが、ディーゼルエンジンの需要は新興国市場で伸び、また日本でも従来のイメージから脱却し、燃料代が安く、熱の効率が良いディーゼルエンジンがあらためて注目されています。欧米では日本と事情は異なりますがそれぞれ独自の需要と市場を形成しています。しかしながら各市場・規制が要求するレベルで排出ガスをクリーンにすることが最大の課題となっております。そこで弊社では排出ガス浄化技術においてキーマテリアルである触媒およびそのシステムの開発、要素技術に焦点をあてた書籍を発刊します。

Language：Japanese

Language：Japanese

Language：Japanese

Language：Japanese

Language：Japanese

Language：Japanese

Responsible for pages：5-10   Language：Japanese

Language：English

Responsible for pages：98-103  

Responsible for pages：98-103  

Responsible for pages：57-62  

Language：Japanese

Language：Japanese

Responsible for pages：60-66  

DOI： doi:10.20731/zeoraito.24.2.60

Responsible for pages： 544-548  

Language：Japanese

Responsible for pages：64-65  

Language：Japanese

Language：Japanese

Responsible for pages：696-699  

Responsible for pages：35-37  

Language：Japanese

DOI： doi:10.20731/zeoraito.18.2.58

Responsible for pages：57-58  

Language：Japanese

Language：Japanese

Language：Japanese

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：Wiley Blackwell  

We report herein the first general catalytic system for the direct synthesis of N-substituted γ- and δ-lactams by reductive amination/cyclization of keto acids (including levulinic acid) with nitriles and H2 under mild conditions (7 bar H2, 110 °C, solvent free). The most effective catalyst, Pt and MoOx co-loaded TiO2 (Pt-MoOx/TiO2), shows a wide substrate scope, high turnover number (TON), and good reusability.

DOI： 10.1002/cctc.201701355

Scopus

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)  

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

DOI： 10.1021/jacs.7b07114

Scopus

PubMed

J-GLOBAL

J-GLOBAL

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)  

DOI： 10.1007/978-981-10-5137-1_5

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The particle size effect of Pd nanoparticles supported on alumina with various crystalline phases on methane combustion was investigated. Pd/, -Al2O3 with weak metal-support interaction showed a volcano-shaped dependence of the catalytic activity on the size of Pd particles, and the catalytic activity of the strongly interacted Pd/-Al2O3 increased with the particle size. Based on a structural analysis of Pd nanoparticles using CO adsorption IR spectroscopy and spherical aberration-corrected scanning/transmission electron microscopy, the dependence of catalytic activity on Pd particle size and the alumina crystalline phase was due to the fraction of step sites on Pd particle surface. The difference in fraction of the step site is derived from the particle shape, which varies not only with Pd particle size but also with the strength of metal-support interaction. Therefore, this interaction perturbs the particle size effect of Pd/Al2O3 for methane combustion.

DOI： 10.1002/anie.201709124

Web of Science

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The particle size effect of Pd nanoparticles supported on alumina with various crystalline phases on methane combustion was investigated. Pd/, -Al2O3 with weak metal-support interaction showed a volcano-shaped dependence of the catalytic activity on the size of Pd particles, and the catalytic activity of the strongly interacted Pd/-Al2O3 increased with the particle size. Based on a structural analysis of Pd nanoparticles using CO adsorption IR spectroscopy and spherical aberration-corrected scanning/transmission electron microscopy, the dependence of catalytic activity on Pd particle size and the alumina crystalline phase was due to the fraction of step sites on Pd particle surface. The difference in fraction of the step site is derived from the particle shape, which varies not only with Pd particle size but also with the strength of metal-support interaction. Therefore, this interaction perturbs the particle size effect of Pd/Al2O3 for methane combustion.

DOI： 10.1002/anie.201709124

Web of Science

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The particle size effect of Pd nanoparticles supported on alumina with various crystalline phases on methane combustion was investigated. Pd/, -Al2O3 with weak metal-support interaction showed a volcano-shaped dependence of the catalytic activity on the size of Pd particles, and the catalytic activity of the strongly interacted Pd/-Al2O3 increased with the particle size. Based on a structural analysis of Pd nanoparticles using CO adsorption IR spectroscopy and spherical aberration-corrected scanning/transmission electron microscopy, the dependence of catalytic activity on Pd particle size and the alumina crystalline phase was due to the fraction of step sites on Pd particle surface. The difference in fraction of the step site is derived from the particle shape, which varies not only with Pd particle size but also with the strength of metal-support interaction. Therefore, this interaction perturbs the particle size effect of Pd/Al2O3 for methane combustion.

DOI： 10.1002/anie.201709124

Web of Science

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

We studied the dynamic redox behavior of Cu species in zeolite matrix under NH3-SCR using in situ XAFS. Cu2+ species were slowly reduced to Cu+ in flowing NH3, and subsequent addition of NO promoted the reduction to Cu+. In the oxidation step, oxygen alone did not fully oxidize Cu+ to Cu2+, but the Cu+ species were completely oxidized to Cu2+ by NO-O-2. The oxidation step was slower than the reduction step, which suggested that the oxidation step (Cu+ -> Cu2+) is the slow step of the NH3-SCR reaction.

DOI： 10.1246/cl.170451

Web of Science

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

We studied the dynamic redox behavior of Cu species in zeolite matrix under NH3-SCR using in situ XAFS. Cu2+ species were slowly reduced to Cu+ in flowing NH3, and subsequent addition of NO promoted the reduction to Cu+. In the oxidation step, oxygen alone did not fully oxidize Cu+ to Cu2+, but the Cu+ species were completely oxidized to Cu2+ by NO-O-2. The oxidation step was slower than the reduction step, which suggested that the oxidation step (Cu+ -> Cu2+) is the slow step of the NH3-SCR reaction.

DOI： 10.1246/cl.170451

Web of Science

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：American Chemical Society  

To elucidate the reaction mechanism of NO-C3H6-CO-O2 over NiFe2O4, we investigated the dynamics of the adsorbed and gaseous species during the reaction using operando Fourier transform infrared (FTIR). The NO reduction activity dependent on the C3H6 and CO concentrations suggested that NO is reduced by C3H6 under three-way catalytic conditions. From FTIR measurements and kinetic analysis, it was clarified that the acetate species reacted with NO-O2 to form N2 via NCO, and that the rate-limiting step of NO reduction was the reaction between CH3COO- and NO-O2. The NO reduction mechanism of the three-way catalyst on NiFe2O4 is different to that on platinum-group metal catalysts, on which NO reduction proceeds through N-O cleavage.

DOI： 10.1021/acsomega.7b00165

Scopus

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：American Chemical Society  

To elucidate the reaction mechanism of NO-C3H6-CO-O2 over NiFe2O4, we investigated the dynamics of the adsorbed and gaseous species during the reaction using operando Fourier transform infrared (FTIR). The NO reduction activity dependent on the C3H6 and CO concentrations suggested that NO is reduced by C3H6 under three-way catalytic conditions. From FTIR measurements and kinetic analysis, it was clarified that the acetate species reacted with NO-O2 to form N2 via NCO, and that the rate-limiting step of NO reduction was the reaction between CH3COO- and NO-O2. The NO reduction mechanism of the three-way catalyst on NiFe2O4 is different to that on platinum-group metal catalysts, on which NO reduction proceeds through N-O cleavage.

DOI： 10.1021/acsomega.7b00165

Scopus

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：American Chemical Society  

To elucidate the reaction mechanism of NO-C3H6-CO-O2 over NiFe2O4, we investigated the dynamics of the adsorbed and gaseous species during the reaction using operando Fourier transform infrared (FTIR). The NO reduction activity dependent on the C3H6 and CO concentrations suggested that NO is reduced by C3H6 under three-way catalytic conditions. From FTIR measurements and kinetic analysis, it was clarified that the acetate species reacted with NO-O2 to form N2 via NCO, and that the rate-limiting step of NO reduction was the reaction between CH3COO- and NO-O2. The NO reduction mechanism of the three-way catalyst on NiFe2O4 is different to that on platinum-group metal catalysts, on which NO reduction proceeds through N-O cleavage.

DOI： 10.1021/acsomega.7b00165

Scopus

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Glucose isomerization was performed using various titanate catalysts, which include SrTiO3, BaTiO3, CaTiO3, Na2Ti6O13, K2Ti6O13, and Sr3Ti2O7, prepared using a conventional solid-phase method. Among the titanates, SrTiO3, CaTiO3, and Na2Ti6O13 offered a relatively high fructose yield (32%) with a high selectivity (68-78%). The yields are comparable to yields reported previously using a Sn-modified BEA zeolite, which shows a high efficiency for glucose isomerization as a Lewis acid catalyst. A study of the mechanism of glucose isomerization on a SrTiO3 catalyst surface by using H-1 NMR spectroscopy suggested that the titanates catalyze the isomerization as base catalysts. Thus, the effect of the basicity of the titanates on glucose isomerization was investigated in terms of the base quantity and strength. The analysis was performed by using an acid-base titration method and FTIR spectroscopy with CHCl3 as a probe molecule. It is proposed that glucose isomerization on the titanates depends not only on the base amount but also on the base strength.

DOI： 10.1002/cctc.201700068

Web of Science

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Combination catalyst systems composed of Pt/SiO2 and lanthanoid oxides (Pt/SiO2 + LOx) efficiently catalyze the hydrogenative ring-rearrangement of 5-(hydroxymethyl) furfural (HMF) in water to produce 3-(hydroxymethyl) cyclopentanol (HCPO), which can be a unique building block for new materials derived from biomass. We investigated the reason for the efficient hydrogenative ring-rearrangement on Pt/SiO2 + LOx in terms of the acid-base properties of reaction systems, since H+ and Lewis acids can affect the rearrangement of the furan ring. It is indicated that the ring-rearrangement efficiently proceeds under slightly acidic conditions (pH = 5-7) with moderate or a little weak Lewis acidity of lanthanoid oxides.

DOI： 10.1039/c7cy00712d

Web of Science

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Glucose isomerization was performed using various titanate catalysts, which include SrTiO3, BaTiO3, CaTiO3, Na2Ti6O13, K2Ti6O13, and Sr3Ti2O7, prepared using a conventional solid-phase method. Among the titanates, SrTiO3, CaTiO3, and Na2Ti6O13 offered a relatively high fructose yield (32%) with a high selectivity (68-78%). The yields are comparable to yields reported previously using a Sn-modified BEA zeolite, which shows a high efficiency for glucose isomerization as a Lewis acid catalyst. A study of the mechanism of glucose isomerization on a SrTiO3 catalyst surface by using H-1 NMR spectroscopy suggested that the titanates catalyze the isomerization as base catalysts. Thus, the effect of the basicity of the titanates on glucose isomerization was investigated in terms of the base quantity and strength. The analysis was performed by using an acid-base titration method and FTIR spectroscopy with CHCl3 as a probe molecule. It is proposed that glucose isomerization on the titanates depends not only on the base amount but also on the base strength.

DOI： 10.1002/cctc.201700068

Web of Science

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Glucose isomerization was performed using various titanate catalysts, which include SrTiO3, BaTiO3, CaTiO3, Na2Ti6O13, K2Ti6O13, and Sr3Ti2O7, prepared using a conventional solid-phase method. Among the titanates, SrTiO3, CaTiO3, and Na2Ti6O13 offered a relatively high fructose yield (32%) with a high selectivity (68-78%). The yields are comparable to yields reported previously using a Sn-modified BEA zeolite, which shows a high efficiency for glucose isomerization as a Lewis acid catalyst. A study of the mechanism of glucose isomerization on a SrTiO3 catalyst surface by using H-1 NMR spectroscopy suggested that the titanates catalyze the isomerization as base catalysts. Thus, the effect of the basicity of the titanates on glucose isomerization was investigated in terms of the base quantity and strength. The analysis was performed by using an acid-base titration method and FTIR spectroscopy with CHCl3 as a probe molecule. It is proposed that glucose isomerization on the titanates depends not only on the base amount but also on the base strength.

DOI： 10.1002/cctc.201700068

Web of Science

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：MDPI AG  

Recently, it has been reported that the morphology of Au nanoparticles (NPs) affects the catalytic activity of CO oxidation; twin crystal NPs show higher activity for CO oxidation than single-crystal NPs. In this study, density functional calculations have been carried out to investigate the morphology effect of Au NPs using CO as a probe molecule. In the case of Au NPs with a size of more than 2 nm, CO adsorption energy on the Au NPs is mainly determined by a coordination number (CN) of adsorption sites. CO binding to a multiple twin NP with a size of about 1 nm is stronger than that on a single-crystal NP with the same size. A simple CN explanation cannot be applied to the enhancement of CO binding to the small multiple twin NP. This enhancement is related to a deformation of the NP structure before and after CO adsorption. It is suggested that the multiple twin NP with a size of less than 1 nm, which shows the deformation upon CO adsorption, contributes to the higher activity for CO oxidation.

DOI： 10.3390/catal7060191

Web of Science

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：MDPI AG  

Recently, it has been reported that the morphology of Au nanoparticles (NPs) affects the catalytic activity of CO oxidation; twin crystal NPs show higher activity for CO oxidation than single-crystal NPs. In this study, density functional calculations have been carried out to investigate the morphology effect of Au NPs using CO as a probe molecule. In the case of Au NPs with a size of more than 2 nm, CO adsorption energy on the Au NPs is mainly determined by a coordination number (CN) of adsorption sites. CO binding to a multiple twin NP with a size of about 1 nm is stronger than that on a single-crystal NP with the same size. A simple CN explanation cannot be applied to the enhancement of CO binding to the small multiple twin NP. This enhancement is related to a deformation of the NP structure before and after CO adsorption. It is suggested that the multiple twin NP with a size of less than 1 nm, which shows the deformation upon CO adsorption, contributes to the higher activity for CO oxidation.

DOI： 10.3390/catal7060191

Web of Science

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：MDPI AG  

Recently, it has been reported that the morphology of Au nanoparticles (NPs) affects the catalytic activity of CO oxidation; twin crystal NPs show higher activity for CO oxidation than single-crystal NPs. In this study, density functional calculations have been carried out to investigate the morphology effect of Au NPs using CO as a probe molecule. In the case of Au NPs with a size of more than 2 nm, CO adsorption energy on the Au NPs is mainly determined by a coordination number (CN) of adsorption sites. CO binding to a multiple twin NP with a size of about 1 nm is stronger than that on a single-crystal NP with the same size. A simple CN explanation cannot be applied to the enhancement of CO binding to the small multiple twin NP. This enhancement is related to a deformation of the NP structure before and after CO adsorption. It is suggested that the multiple twin NP with a size of less than 1 nm, which shows the deformation upon CO adsorption, contributes to the higher activity for CO oxidation.

DOI： 10.3390/catal7060191

Web of Science

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Pd/CoAl2O4/Al2O3 methane combustion catalysts were synthesized using a galvanic deposition (GD) method (PdCoAl-GD). This PdCoAl-GD catalyst showed higher activities and turnover frequencies (TOFs) than conventional Pd/Al2O3. According to X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) and scanning transmission electron microscopy (STEM) measurements, PdCoAl-GD was composed of a CoAl2O4 phase supported on gamma-Al2O3 and dispersed Pd nanoparticles of 2-7 nm in size on CoAl2O4. Operando Pd K-edge XAFS measurements indicated that the Pd in PdCoAl-GD was oxidized to highly active methane combustion PdO species at low temperatures. PdCoAl-GD also showed high activity (light-off tests) when PdO was initially present on the catalysts. Methane temperature-programmed reaction (CH4-TPR) measurements on PdCoAl-GD revealed that PdO was reduced by CH4 at low temperatures. The GD method used herein achieved PdO species that were effective for C-H activation.

DOI： 10.1039/c7ra06150a

Web of Science

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Pd/CoAl2O4/Al2O3 methane combustion catalysts were synthesized using a galvanic deposition (GD) method (PdCoAl-GD). This PdCoAl-GD catalyst showed higher activities and turnover frequencies (TOFs) than conventional Pd/Al2O3. According to X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) and scanning transmission electron microscopy (STEM) measurements, PdCoAl-GD was composed of a CoAl2O4 phase supported on gamma-Al2O3 and dispersed Pd nanoparticles of 2-7 nm in size on CoAl2O4. Operando Pd K-edge XAFS measurements indicated that the Pd in PdCoAl-GD was oxidized to highly active methane combustion PdO species at low temperatures. PdCoAl-GD also showed high activity (light-off tests) when PdO was initially present on the catalysts. Methane temperature-programmed reaction (CH4-TPR) measurements on PdCoAl-GD revealed that PdO was reduced by CH4 at low temperatures. The GD method used herein achieved PdO species that were effective for C-H activation.

DOI： 10.1039/c7ra06150a

Web of Science

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Pd/CoAl2O4/Al2O3 methane combustion catalysts were synthesized using a galvanic deposition (GD) method (PdCoAl-GD). This PdCoAl-GD catalyst showed higher activities and turnover frequencies (TOFs) than conventional Pd/Al2O3. According to X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) and scanning transmission electron microscopy (STEM) measurements, PdCoAl-GD was composed of a CoAl2O4 phase supported on gamma-Al2O3 and dispersed Pd nanoparticles of 2-7 nm in size on CoAl2O4. Operando Pd K-edge XAFS measurements indicated that the Pd in PdCoAl-GD was oxidized to highly active methane combustion PdO species at low temperatures. PdCoAl-GD also showed high activity (light-off tests) when PdO was initially present on the catalysts. Methane temperature-programmed reaction (CH4-TPR) measurements on PdCoAl-GD revealed that PdO was reduced by CH4 at low temperatures. The GD method used herein achieved PdO species that were effective for C-H activation.

DOI： 10.1039/c7ra06150a

Web of Science

Event date： 2021.3

Language：Japanese   Presentation type：Poster presentation  

Venue：オンライン  

Event date： 2021.3

Language：Japanese   Presentation type：Poster presentation  

Venue：オンライン  

Event date： 2020.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン  

Event date： 2020.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン  

Event date： 2020.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本城ホール  

Event date： 2020.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本城ホール  

Event date： 2020.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン  

Event date： 2020.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Poster presentation  

Venue：オンライン   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2019.11

Language：English   Presentation type：Oral presentation (keynote)  

Venue：Yancheng, China   Country：Japan  

Event date： 2019.8

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Lotte Hotel, Jeju, South Korea   Country：Korea, Republic of  

Event date： 2019.5

Language：English   Presentation type：Oral presentation (general)  

Country：Korea, Republic of  

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京大学   Country：Japan  

Event date： 2018.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ホテルウェルシーズン浜名湖   Country：Japan  

Event date： 2018.9

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Tianjin, China   Country：China  

Event date： 2018.8

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2018.1

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：京都ガーデンパレスホテル(京都市上京区）   Country：Japan  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：古屋大学東山キャンパス   Country：Japan  

Event date： 2016.11

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：タワーホール船堀（東京都江戸川区船堀4-1-1）   Country：Japan  

Event date： 2016.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Newcastle City Hall, New South Wales, Australia   Country：Australia  

Event date： 2016.3

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：分子科学研究所   Country：Japan  

Event date： 2015.10

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：慶應義塾大学 矢上キャンパス 創想館   Country：Japan  

自動車の燃費向上に伴って、排気ガスの平均温度が低下し、触媒の低温領域での活性向上が求められている。本講演では、Galvanic Deposition法による卑金属とのバイメタル化と担体の修飾により低温領域での触媒燃焼活性を向上させた例を紹介する。

Event date： 2015.6

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：日本大学生産工学部スプリングホール   Country：Japan  

Event date： 2015.6

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：愛媛大学南加記念ホール   Country：Japan  

Event date： 2015.5

Language：English   Presentation type：Oral presentation (keynote)  

Country：Korea, Republic of  

Event date： 2015.1

Language：English   Presentation type：Oral presentation (invited, special)  

Country：India  

Event date： 2014.12

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：名古屋大学ベンチャー・ビジネス・ラボラトリー   Country：Japan  

Event date： 2014.12

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：富山大学水素同位体科研究センター会議室   Country：Japan  

Event date： 2014.10

Language：English   Presentation type：Oral presentation (invited, special)  

Country：Japan  

Event date： 2013.11 - 2013.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Dhahran, Saudi Arabia   Country：Japan  

Event date： 2013.11

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：ホテル ルブラ王山(名古屋市)   Country：Japan  

Event date： 2013.11

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：静岡大学浜松キャンパス   Country：Japan  

Event date： 2013.1

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：名古屋大学   Country：Japan  

Event date： 2012.11

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：あいち産業科学技術総合センター 愛知県刈谷市   Country：Japan  

Event date： 2012.11

Language：English   Presentation type：Oral presentation (invited, special)  

Country：Japan  

Event date： 2012.10

Language：English   Presentation type：Oral presentation (invited, special)  

Country：Australia  

Event date： 2012.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学   Country：Japan  

Event date： 2012.9

Language：English   Presentation type：Poster presentation  

Country：France  

Event date： 2012.9

Language：English   Presentation type：Poster presentation  

Country：France  

Event date： 2012.7

Language：English   Presentation type：Poster presentation  

Country：Japan  

Event date： 2012.7

Language：English   Presentation type：Poster presentation  

Country：Japan  

Event date： 2012.5

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：名古屋大学   Country：Japan  

Event date： 2011.11

Language：English   Presentation type：Oral presentation (general)  

Country：China  

Event date： 2011.11

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：広島大学   Country：Japan  

Event date： 2011.10

Language：English   Presentation type：Oral presentation (invited, special)