Epoxidation of olefins on photoirradiated TiO_2-pillared clays

摘要

The epoxidation of cyclohexene by molecular oxygen was investigated by photoirradiated TiO_2-pilIared montmorillonite (Ti-montmorillonite). This reaction selectively produced cyclohexene epoxide as major product. The effects of reaction parameters such as reaction time, pillaring process of the clay mineral, Ti-montmorillonite concentration and solvent nature in the epoxidation of cyclohexene are discussed. Ti-montmorillonite showed higher selectivity for cyclohexene epoxide than TiO_2 (Degussa P25), due to the different specific surface area and hydrophobic nature of the pillared montmorillonite. The maximum yields of cyclohexene epoxide using Ti-montmorillonite and TiO_2 P25 were 45 and 30%, and the maximum selectivities were 45 and 30%, after 8 h reaction time at optimal experimental conditions. Other olefins were also tested, and the activity decreased in the order cyclooctene> cyclohexene >1-hexene>1-octene.