Showing papers by "Keigo Kamata published in 2019"
TL;DR: The successful synthesis of high-surface-area β-MnO2 significantly improves the catalytic activity for the aerobic oxidation of HMF to FDCA and is in good agreement with the DFT calculation results.
Abstract: Aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) as a bioplastics monomer is efficiently promoted by a simple system based on a nonprecious-metal catalyst of MnO2 and NaHCO3. Kinetic studies indicate that the oxidation of 5-formyl-2-furancarboxylic acid (FFCA) to FDCA is the slowest step for the aerobic oxidation of HMF to FDCA over activated MnO2. We demonstrate through combined computational and experimental studies that HMF oxidation to FDCA is largely dependent on the MnO2 crystal structure. Density functional theory (DFT) calculations reveal that vacancy formation energies at the planar oxygen sites in α- and γ-MnO2 are higher than those at the bent oxygen sites. β- and λ-MnO2 consist of only planar and bent oxygen sites, respectively, with lower vacancy formation energies. Consequently, β- and λ-MnO2 are likely to be good candidates as oxidation catalysts. On the other hand, experimental studies reveal that the reaction rates per surface area for the slowest step (FFCA oxidation to FDCA) decrease in the order of β-MnO2 > λ-MnO2 > γ-MnO2 ≈ α-MnO2 > δ-MnO2 > e-MnO2; the catalytic activity of β-MnO2 exceeds that of the previously reported activated MnO2 by three times. The order is in good agreement not only with the DFT calculation results, but also with the reduction rates per surface area determined by the H2-temperature-programmed reduction measurements for MnO2 catalysts. The successful synthesis of high-surface-area β-MnO2 significantly improves the catalytic activity for the aerobic oxidation of HMF to FDCA.
267 citations
TL;DR: The synthesis of amines from biomass-based feedstock is in high demand given the depletion of fossil fuels as discussed by the authors, which is one of the most straightforward synthetic methods to obtain a vari...
Abstract: The synthesis of amines from biomass-based feedstock is in high demand given the depletion of fossil fuels. Reductive amination is one of the most straightforward synthetic methods to obtain a vari...
44 citations
TL;DR: The catalytic function of perovskite oxides has received significant attention because of their structural flexibility and controllable physicochemical properties as mentioned in this paper, in contrast to their catalytic ap...
Abstract: The catalytic function of perovskite oxides has received significant attention because of their structural flexibility and controllable physicochemical properties. In contrast to their catalytic ap...
40 citations
01 Feb 2019
TL;DR: In this article, Ru-based compounds, which are electrochemical compounds, were shown to be suitable for hydrogen evolution reaction (HER) for water splitting. But they require highly active, easily prepared, and inexpensive electrocatalysts.
Abstract: Water splitting requires highly active, easily prepared, and inexpensive electrocatalysts for hydrogen evolution reaction (HER). Herein, we report that Ru-based compounds, which are electrochemical...
25 citations
TL;DR: CePO4 nanorods with uniform surface Ce sites could work as a durable catalyst and showed the highest C2 yield of 18% in an electric field without the need for external heating, which was comparable to that reported for high-performance catalysts at high temperature (>900 K).
21 citations
TL;DR: In this paper, several porous ionic crystals with a Keggin-type polyoxometalate [PW12O40]3− and a macrocation [Cr3O(OOCCH2CN)6(H2O)3]- as building blocks are synthesized, and the structures are solved by single crystal X-ray diffraction analysis.
Abstract: 5‐Hydroxymethylfurfural (HMF) is an important bio‐based chemical, which has been recognized as a key platform chemical for furan‐based polymers, biomass‐derived fuels, fine chemicals, and pharmaceuticals. Catalytic conversion of fructose into HMF is an important reaction, and the development of an efficient heterogeneous catalysts with high selectivity towards HMF is highly desired. In this study, several porous ionic crystals with a Keggin‐type polyoxometalate [PW12O40]3− and a macrocation [Cr3O(OOCCH2CN)6(H2O)3]+ as building blocks are synthesized, and the structures are solved by single crystal X‐ray diffraction analysis. The catalytic activities are basically dependent on the porosity, and the compound with a mesopore (aperture: 3 nm×2 nm) showed the highest HMF yield (30 % at 353 K in methanol/toluene solvent).
5 citations
TL;DR: In this paper, the authors reveal that silver particles supported on a metal oxide act as an efficient catalyst for the benzylic C H fluorination of 4-methylbiphenyl with 1-fluoro-4-methyl-1,3-diazoniabicyclo[2.2] octane bis(tetrafluoroborate) (Selectfluor II) as a fluorinating reagent to give 4-(fluoromethyl)-1,1′-biphensyl, whereas silver oxides resulted in aromatic fluorination
3 citations