Takuya Yoshikawa

A metal-free, high nitrogen-doped nanoporous graphitic carbon catalyst for an effective aerobic HMF-to-FDCA conversion

We report a metal-free catalysis of the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acids (FDCA), employing zeolitic-imidazole framework (ZIF-8) derived, nitrogen-doped nanoporous carbon (denoted as NNC) as an effective heterogeneous catalyst. The effect of high graphitic nitrogen loading in the NNC on the catalytic production of FDCA was demonstrated and discussed.

Fractionation of Degraded Lignin by Using a Water/1‐Butanol Mixture with a Solid‐Acid Catalyst: A Potential Source of Phenolic Compounds

Fractionation of a lignin‐derived liquid using a water/1‐butanol mixture was investigated with the aim of developing a source of phenols. The effect of various phases on lignin depolymerization by using a water/1‐butanol mixture with a solid acid catalyst was investigated. The water/1‐butanol solvent was confirmed to be heterogeneous under the reaction conditions, and the liquid phase was essential for effective depolymerization of lignin. To make optimum use of the depolymerized lignin and to understand its chemical structure, solvent fractionation was performed by using a water/tetrahydrofuran solution, ethyl acetate, and n‐hexane as solvents. Catalytic cracking of the n‐hexane soluble fraction was performed over an iron oxide catalyst by using a high‐pressure fixed‐bed flow reactor at 673 K. The production of phenol was confirmed, and the demethoxylation reaction was examined by using model compounds. In addition, as the heavy components were extracted during the solvent fractionation, as confirmed by analysis of the molecular structures of the fractionated components, the formation of solid products could be suppressed to a level below 2.5 molC % based on lignin.

Hydrogen Peroxide Assisted Selective Oxidation of 5‐Hydroxymethylfurfural in Water under Mild Conditions

An effective and selective method for the oxidation of 5‐hydroxymethylfurfural (HMF) by using hydrogen peroxide (H2O2) as the liquid oxygen source and activated‐carbon‐supported ruthenium (Ru/AC) as the catalyst was developed. This reaction system allowed HMF to be oxidized in water under mild reaction conditions efficiently, as it was shown to have lower mass‐transfer resistance than gaseous oxygen‐assisted oxidation systems. In addition, we could selectively control the components of the oxidation products by adjusting the reaction conditions. We optimized several reaction parameters such as the reaction temperature (75 °C), time (t=1 or 6 h), base additive (sodium carbonate), and the HMF/catalyst ratio (50 or 10) to attain the desired products in maximum yields. Thus, 5‐formyl‐2‐furoic acid was obtained in a high yield up to 92 % with a HMF/catalyst ratio of 50 and a reaction time of 1 h, whereas 2,5‐furandicarboxylic acid was obtained in a maximum yield of 91.3 % with a HMF/catalyst ratio of 10 and a reaction time of 6 h. A possible mechanism for the selective oxidation of HMF was also discussed. We envision that the H2O2‐mediated oxidation systems proposed in this study would be of great benefit to other organic oxidation systems.

Conversion of Inedible Biomass Wastes as Alternative Petroleum-Related Chemicals Using Iron Oxide Catalysts

We developed iron-oxide catalysts for producing petroleum-related chemicals from inedible biomass wastes containing water by oxidative cracking. These catalysts composed basically of iron-oxide and zirconia. The usefulness of the catalysts was examined by the reactions of several inedible biomass wastes, such as palm waste, livestock excreta, fermentation residue, raw glycerin, raw bioethanol and lignin. It was found that ketones, mainly acetone, were produced from palm waste, livestock excreta, fermentation residue and raw bioethanol at high yields. Phenol was obtained from palm waste. In the case of raw glycerin, even if high contents of alkali, allyl-alcohol, propene and acetone were successfully produced. Furthermore, phenols could be recovered from lignin.