山田 泰弘

Abstract The hydrogenation of citronellal to citronellol proceeded over SiO2-supported copper (Cu/SiO2) catalysts prepared by organic additive-assisted impregnation protocol. Introducing Cu species on SiO2 support reduced the rate of the cyclization of citronellal to isopulegol and promoted the formation of citronellol. The utilization of organic additives, especially glucose, highly dispersed Cu nanoparticles, i.e., increased Cu surface area, which promoted catalytic hydrogenation activity. The proportional correlation between Cu surface area and the formation rate of citronellol substantiated this behavior.

Vapor-phase intramolecular aldol condensation of 2,5-hexanedione (2,5-HD) to 3-methyl-2-cyclopentenone (MCP) was performed over several rare-earth zirconate catalysts, with yttrium zirconate (YZrO) emerged as the most efficient catalyst. Several parameters, such as Y content, calcination temperature, reaction temperature, and contact time, highly influenced the catalytic performance of the YZrO catalyst: YZrO calcined at 700 °C exhibited the highest catalytic activity but still suffered from catalyst deactivation due to coke formation. Modifying the YZrO with Ag and employing the modified catalyst in an H2 flow effectively reduced the coke accumulation, thus improving the catalytic stability during the aldol condensation of 2,5-HD at 350 °C. The poisoning experiment with the co-fed of acidic CO2 gas and basic molecules of 2,6-, and 3,5-dimethylpyridine suggested that the aldol condensation proceeded via an acid-base concerted mechanism.