Catalysis of nanocrystalline mesoporous TiO 2 on cyclohexene epoxidation with H 2O 2: Effects of mesoporosity and metal oxide additives

Abstract

Nanocrystalline mesoporous TiO 2-based catalysts prepared by a surfactant-assisted templating sol–gel process were tested on epoxidation of cyclohexene in tert-butanol–H 2O 2 system. The mesoporous TiO 2 showed exceptional potential for epoxidation of cyclohexene, exhibiting both higher cyclohexene conversion and higher cyclohexene oxide selectivity than non-mesoporous commercial TiO 2 powders, i.e. Ishihara ST-01 and Degussa P-25. The oxides of Fe, Co, Ni, and Ru were also loaded by incipient wetness impregnation method onto the synthesized mesoporous TiO 2, aiming to enhance the catalytic performance. Among metal oxide-loaded catalysts, RuO 2-loaded mesoporous TiO 2 was proved to possess noticeably high catalytic performance based on cyclohexene oxide selectivity. The 1 mol% RuO 2-loaded mesoporous TiO 2 was the best catalyst, showing the highest cyclohexene oxide selectivity and lowest cyclohex-2-en-1-ol (undesired product) selectivity. Plausible reaction pathways were also proposed.