Benzene methylation by acetic acid with platinum-loaded titanium oxide photocatalyst

Abstract

Photocatalytic functionalization of aromatic rings with simple small molecules has been intensively studied by using metal-loaded titanium oxide photocatalyst. In the present study, the photocatalytic direct methylation of benzene was examined by using acetic acid as a promising methylation reagent. Over 15% yield of toluene was achieved with a platinum-loaded TiO2 photocatalyst (Pt/TiO2) under light irradiation without any extra solvent. The kinetic investigations with isotopic compounds and temperature-controlled experiments elucidated that Pt nanoparticles on the TiO2 surface have a dual role, i.e., working as an electron receiver to improve the charge separation and catalyzing a radical addition-elimination process to form toluene molecule. Two competitive reaction mechanisms were proposed in this reaction system.