Synthesis of benzaldehyde from toluene by a photocatalytic oxidation using TiO2-pillared clays

Photo-oxidation of toluene was investigated by using TiO2-pillared montmorillonite (Ti-montmorillonite). The main intermediates of toluene oxidation were benzaldehyde and p-cresol while traces of benzyl alcohol, benzoic acid, pyrogallol and hydroquinone were also found. The solvent effect on the photo-oxidation of toluene on Ti-montmorillonite was significant; the activity was increased by an addition of 10% water in acetonitrile solvent and it was further increased when the reaction was performed in an aqueous environment. In the latter condition, Ti-montmorillonite showed higher activity to benzaldehyde (the desired product) than TiO2 (Degussa P25), possibly because of the difference value of its surface area and the hydrophobic nature of pillared clay. The maximum yields in benzaldehyde using Ti-montmorillonite and TiO2 P25 as photocatalysts were 48 and 27%, respectively, after 1 h reaction time in the best experimental conditions.