Tasuku Komanoya

Synthesis of sugar alcohols by hydrolytic hydrogenation of cellulose over supported metal catalysts

Cellulose is converted into sorbitol and related sugar compounds over water-tolerant and durable carbon-supported Pt catalysts under aqueous hydrogenation conditions. Pre-treatment of cellulose with ball-milling effectively reduces the crystallinity and particle size of cellulose, which results in high conversion of cellulose to sorbitol and mannitol. The selectivity of sorbitol increases by using Cl-free metal precursors in the catalyst preparation as residual Cl on the catalysts promotes the side-reactions. The transformation of cellulose to sorbitol consists of the hydrolysis of cellulose to glucoseviawater-soluble oligosaccharides and the successive hydrogenation of glucose to sorbitol. The hydrolysis of cellulose is the rate-determining step, and the Pt catalysts promote both the hydrolysis and the hydrogenation steps.

Kinetic Study of Catalytic Conversion of Cellulose to Sugar Alcohols under Low‐Pressure Hydrogen

Efficient hydrolytic hydrogenation of cellulose to sugar alcohols under low H2 pressures has remained a challenge. This article deals with the conversion of cellulose by using a carbon‐supported Ru catalyst under H2 pressures as low as 0.7–0.9 MPa (absolute pressure at room temperature). Kinetic studies revealed that the Ru catalyst not only enhances the hydrolysis of cellulose to glucose and hydrogenation of glucose to sugar alcohols (sorbitol and mannitol), but also the degradation of sugar alcohols to C2–C6 polyols and gasses. The degradation path limits the total yield of sugar alcohols to less than 40 %. The yield of sugar alcohols is theoretically improved by increasing the ratio of the reaction rates of the cellulose hydrolysis, which is the rate‐determining step in the reaction, to the decomposition. Thus, a mix‐milling pretreatment of cellulose and the Ru catalyst together selectively accelerated the hydrolysis step and raised the yield up to 68 %, whereas the addition of acids in the cellulose conversion was less effective as a result of promotion of side‐reactions. These results demonstrate superior applicability of the mix‐milling treatment in the depolymerization of cellulose to its monomers.

Chemo-microbial conversion of cellulose into polyhydroxybutyrate through ruthenium-catalyzed hydrolysis of cellulose into glucose

Cellulose-derived glucose generated using the supported ruthenium catalyst was applied to poly(3-hydroxybutyrate) [P(3HB)] production in recombinant Escherichia coli. By the reaction with the catalyst at 220°C, 15-20 carbon mol% of cellulose was converted into glucose. The hydrolysate also contained byproducts such as fructose, mannose, levoglucosan, oligomeric cellulose, 5-hydroxymethylfurfural (5-HMF), and furfural together with unidentified compounds. Setting the reaction temperature lower (215°C) improved the ratio of glucose to 5-HMF, which was a main inhibiting factor for the cell growth. Indeed, the recombinant E. coli exhibited better performance on the hydrolysate generated at 215°C and accumulated P(3HB) up to 42 wt%, which was the same as the case of the same concentration of analytical grade glucose. The result indicated that the ruthenium-mediated cellulose hydrolysis has a potency as a useful biorefinery process for production of bio-based plastic from cellulosic biomass.

Electronic Effect of Ruthenium Nanoparticles on Efficient Reductive Amination of Carbonyl Compounds

Highly selective synthesis of primary amines over heterogeneous catalysts is still a challenge for the chemical industry. Ruthenium nanoparticles supported on Nb2O5 act as a highly selective and reusable heterogeneous catalyst for the low-temperature reductive amination of various carbonyl compounds that contain reduction-sensitive functional groups such as heterocycles and halogens with NH3 and H2 and prevent the formation of secondary amines and undesired hydrogenated byproducts. The selective catalysis of these materials is likely attributable to the weak electron-donating capability of Ru particles on the Nb2O5 surface. The combination of this catalyst and homogeneous Ru systems was used to synthesize 2,5-bis(aminomethyl)furan, a monomer for aramid production, from 5-(hydroxymethyl)furfural without a complex mixture of imine byproducts.

Heterogeneously-Catalyzed Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid with MnO2

A simple non-precious-metal catalyst system based on costeffective and ubiquitously available MnO2 , NaHCO3 , and molecular oxygen was used to convert 5-hydroxymethylfurfural (HMF) to 2,5-difurandicarboxylic acid (FDCA) as a bioplastics precursor in 91 % yield. The MnO2 catalyst could be recovered by simple filtration and reused several times. The present system was also applicable to the aerobic oxidation of other biomass-derived substrates and the gram-scale oxidation of HMF to FDCA, in which 2.36 g (86 % yield) of the analytically pure FDCA could be isolated.

A Combined Catalyst of Pt Nanoparticles and TiO2 with Water-Tolerant Lewis Acid Sites for One-Pot Conversion of Glycerol to Lactic Acid

Catalytic conversion of glycerol to valuable chemicals has been recognized as an attractive and challenging reaction in biorefinery. In this paper, we demonstrated that a combined catalyst of Pt nanoparticles and TiO2 worked as a highly active catalyst for the one‐pot conversion of glycerol to lactic acid in water. The yield of lactic acid reached 63 % under oxygen atmosphere without the use of any additives such as strong bases, and the catalyst could be reused without significant loss of the catalytic performance. The mechanistic studies revealed that Pt nanoparticles on TiO2 selectively oxidized glycerol to C3 aldehyde/ketone, and Lewis acid sites on TiO2 smoothly promoted the dehydration and rehydration/rearrangement reactions of the intermediates to produce lactic acid efficiently.

Simultaneous formation of sorbitol and gluconic acid from cellobiose using carbon-supported ruthenium catalysts

A carbon-supported Ru catalyst, Ru/BP2000, is able to simultaneously convert cellobiose into sorbitol and gluconic acid. This reaction occurs as the result of hydrolytic disproportionation in water at 393 K under an Ar atmosphere, without bases or sacrificial reagents. In-situ XANES measurements suggest that the active Ru species involved is composed of partially oxidized Ru metal.

Fabrication of nanocatalyst-enhanced enzyme electrode and application in glucose biofuel cells

Here we report a nano-size catalyst-enhanced enzymatic bioanode for glucose biofuel cells. The bioanode was constructed by coating a crosslinked mixture of glucose oxidase (GOx), 2,5-dihydroxybenzaldehyde (DHB), bovine serum albumin (BSA) and glutaraldehyde on a MWCNT-modified screen printed carbon electrode (SPCE). By presenting Ru-supported CMK-3 (Ru-CMK-3) in the bioanode, the biofuel cells power output was significantly enhanced and could reach 60 W·cm−2 at 25°C. And we found that the enhancement was attributed to CMK-3 or Ru-CMK-3-catalyzed oxidation of gluconic acid. Therefore, Ru-CMK-3 can work synergistically with GOx and achieve more complete oxidation of glucose in a biofuel cell.