Selective oxidation of liquid hydrocarbons over photoirradiated TiO 2 pillared clays

Abstract

Selective photo-oxidation of benzene and cyclohexane were investigated by using TiO 2 pillared clays (mica, montmorillonite and saponite). The characterization results indicated that all the TiO 2 pillared clays contain TiO 2 with similar structure, anatase-like small particles, in the different silicate layers of clays. The solvent effect on the photo-oxidation of benzene on TiO 2 pillared clay was significant; both the activity and selectivity were increased by an addition of 10% water in acetonitrile solvent and they were further increased when the reaction was performed in an aqueous environment. In the latter condition, TiO 2 pillared clays showed higher selectivity to oxygenates than TiO 2 (Degussa P25). The product distribution among oxygenates also depends on the type of the clay host, indicating that the photocatalytic properties of TiO 2 depend strongly on the type of clay host. For the cyclohexane photo-oxidation, TiO 2 pillared clay showed much higher selectivity than TiO 2, possibly because of the hydrophobic nature of pillared clay.