Selective Oxidation of Benzyl Alcohol by Heteropolytungstate as Reaction-Controlled Phase-Transfer Catalyst with Hydrogen Peroxide

Abstract The catalytic oxidation of benzyl alcohol to benzaldehyde was studied using heteropolytungstates as reaction-controlled phase-transfer catalysts with 35% aqueous H2O2 as oxidant. Under optimal conditions, 95.0% conversion of benzyl alcohol based on H2O2 and over 99% selectivity of benzaldehyde was obtained with [C7H7N(CH3)3]9PW9O34 as catalyst. In this system, once the H2O2 was consumed, the catalyst could be recovered from the system easily as a solid deposit. The catalysts were characterized by FT-IR, 31P NMR, XRD, and TGA, and the results indicated that the insoluble catalyst [C7H7N(CH3)3]9PW9O34 formed a soluble active species [C7H7N(CH3)3]3[(PO4){WO(O2)2}4] under the action of H2O2; the structure of the fresh catalyst was maintained well after the reaction. The results of catalyst recycling showed that this catalyst exhibits good stability. The effects of various reaction factors, such as solvent and the amount of H2O2 used, were studied.