Selective oxidation of liquid hydrocarbons over photoirradiated TiO2 pillared clays

Selective photo-oxidation of benzene and cyclohexane were investigated by using TiO2 pillared clays (mica, montmorillonite and saponite). The characterization results indicated that all the TiO2 pillared clays contain TiO2 with similar structure, anatase-like small particles, in the different silicate layers of clays. The solvent effect on the photo-oxidation of benzene on TiO2 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, TiO2 pillared clays showed higher selectivity to oxygenates than TiO2 (Degussa P25). The product distribution among oxygenates also depends on the type of the clay host, indicating that the photocatalytic properties of TiO2 depend strongly on the type of clay host. For the cyclohexane photo-oxidation, TiO2 pillared clay showed much higher selectivity than TiO2, possibly because of the hydrophobic nature of pillared clay, (C) 2002 Elsevier Science B.V. All rights reserved.