Classic deep oxidation CuMnOx catalysts catalyzed selective oxidation of benzyl alcohol

Abstract

This work presents an extension of classic deep oxidation CuMnOx catalysts to a selective oxidation of alcohol with high efficiency and in an environmental-friendly reaction system. A series of CuMnOx catalysts characterized by CuO-Cu1.4Mn1.6O4 and Mn2O3-Cu1.4Mn1.6O4 oxide pairs were prepared via a novel half carbonized citrus grandis peel assisted hard template method. A shift of the oxide pairs from CuO-Cu1.4Mn1.6O4 to Mn2O3-Cu1.4Mn1.6O4 has been achieved by tuning Cu/Mn molar ratio, and then leads to a one-pass benzaldehyde yield more than 50% with 100% benzaldehyde selectivity in the selective oxidation of benzyl alcohol using H2O2 as oxidant. Higher relative amount of Cu1.4Mn1.6O4 in either Mn2O3-Cu1.4Mn1.6O4 or CuO-Cu1.4Mn1.6O4 oxide pair is found to be essential for achieving high catalytic activity. The interaction between the Cu1.4Mn1.6O4 constituent and Mn2O3 constituent of Mn2O3-Cu1.4Mn1.6O4 oxide pair is found to able to enhance the formation of Cu+ species, which can reacts with H2O2 to produce •OH and then touch off a Fenton-like catalytic oxidation process of benzyl alcohol, in the current CuMnOx-H2O2 system, to produce benzaldehyde with high selectivity. This work presents a new perspective in the development of highly effective and low cost CuMnOx catalysts for heterogeneous catalytic oxidation reactions.