Oxidative, photo-activated TiO2nanoparticles in the catalytic acetylation of primary alcohols

Abstract

A series of TiO₂ particles of varying particle sizes from nano to micro scales was treated with three different oxidants (O₂, TBHP, and aqueous H₂O₂) under irradiation conditions to form activated TiO₂ particles bearing surface peroxo Ti(O₂) species. The resultant, heterogeneous catalysts were tested for photo-catalytic acetylation of 2-phenylethanol by acetic anhydride in 8 different solvents. The best scenario involves the use of 32 nm grade of TiO₂ nanoparticles and aqueous H₂O₂ for pre-activation and the use of CH₂Cl₂ as the reaction solvent. The 2-phenethyl acetate product can be completely formed in 10 h and isolated in essential quantitative yield. It was also found that catalysts derived from TiO₂ nanoparticles are superior to those from ZrO₂, Y₂O₃ and WO₃ nanoparticles by using the oxidative, photo-activation protocol. The newly developed heterogeneous catalytic system can be smoothly applied to photocatalytic acetylation of several representative primary aliphatic and aromatic alcohols. The intermediacy of Ti–OH or TiO surface groups was proposed in the photo-catalytic acetylation conditions.