Naoki Mimura

金を主成分とする触媒を用い，酸素を酸化剤として用いるグリセロールの酸化反応の研究を行った。本研究において，グリセロールを原料にして得られる生成物はカルボン酸類であり，高付加価値 · 高機能な分子として期待される。反応は，バッチ式反応器とフロー式反応器の両者を用いて行った。特に，フロー式反応器に適した触媒の開発に重点を置き，高活性と長寿命を両立する触媒を見出した。反応機構については，Au/Al₂O₃触媒に着目し，添加アルカリの効果を明らかにするとともに，触媒上で酸素が活性化する機構を提案した。また，高分解能電子顕微鏡を用いることで，触媒の活性を担っているナノサイズの金，および金と複合化した他の貴金属の状態を明らかにし，反応に与える影響について考察した。

Charcoal-supported metal catalysts enhanced conversion of cellulose to aromatic compounds in high-temperature water even at 523 K.

Economizing low-temperature CO oxidation using Ag/TiO₂ catalyst to achieve complete conversion with and without water vapor through the activation of CO, initiated by the highly abundant reducible oxidic-Ag species at the metal–oxide interface.

Here, we report the development of catalysts comprising highly dispersed Au on an alumina (Al₂O₃) support for the oxidation of glycerol to high-value carboxylic acids in a liquid-phase flow reactor. The catalysts were prepared by means of a deposition–precipitation method. To ensure that the catalysts could be used for long-term catalytic conversions in a liquid-phase flow reactor, we chose an alumina support with high temperature stability and a particle size (50–200 μm) large enough to prevent leakage of the catalyst from the reactor. One of the five catalysts had a high catalytic activity for the conversion of glycerol to the high-value carboxylic acids, glyceric acid and tartronic acid (conversion of glycerol >70%), and the catalyst retained its catalytic activity over long-term use (up to 1770 min). Pretreatment of the catalyst with fructose, a mild reductant, increased the activity of the catalyst. Scanning transmission electron microscopy revealed three Au species highly dispersed on the surface of the alumina support—Au nanoparticles (mode = 7.5–10 nm), Au clusters (1–2 nm), and atomic Au.

Lactic acid has a wide range of applications in many industries, both as an ingredient and as an intermediate. Here, we investigated the catalytic conversion of cellulose to lactic acid by using heterogeneous mixed-oxide catalysts containing ZrO₂. Although pure ZrO₂ has catalytic activity for the conversion of cellulose to lactic acid, the yield of lactic acid obtained is not satisfactory. In contrast, a series of ZrO₂–Al₂O₃ catalysts containing various percentages of ZrO₂ provided higher yields of lactic acid. The ZrO₂–Al₂O₃ catalysts had more Lewis acid sites and far fewer base sites than ZrO₂. This suggests that the Lewis acid sites on ZrO₂–Al₂O₃ catalysts are more important than the base sites for the conversion of cellulose to lactic acid.