Epoxidation of olefins on photoirradiated TiO2-pillared clays

The epoxidation of cyclohexene by molecular oxygen was investigated by photoirradiated TiO2-pillared 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 TiO2 (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 TiO2 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.