Radical-driven selective oxidation of benzyl alcohol on MnCoOx catalysts with no oxidant other than air in reactor

Abstract

Mn reinforced Co3O4 catalysts (MnCoOx) were prepared by a facile solid phase mixed foaming method with an in-situ heating enhancement for the formation of spinel phase mixed oxide species, and studied in the selective oxidation of benzyl alcohol just the air in reactor as oxygen donor. It was found that the MnCoOx catalysts are composed of relatively minimal spinel MnCo2O4 mixed oxide and massive Co3O4 to form MnCo2O4-Co3O4 oxide pair. The micro-domains of MnCo2O4-Co3O4 oxide pair present two redox couples of Mn3+/Mn2+ and Co3+/Co2+ instead of the single one of Co3+/Co2+ in Co3O4, and then dramatically enhance the formation of superoxide radicals (•O2–) species from the O2 in air, which can efficiently initiate the conversion of benzyl alcohol to benzaldehyde in a Fenton-like processes. With no oxidant other than air in reactor, the interaction between MnCo2O4 and Co3O4 in MnCoOx catalysts leads to a benzyl alcohol conversion up to 98 % with a 100 % benzaldehyde selectivity at atmospheric pressure while single component Co3O4 can only present a benzyl alcohol conversion at 37 %. This embodiment of highly efficient heterogeneous selective oxidation just with air as oxidant provides a probability for developing a low-cost and super-facile radical-induced selective oxidation process for alcohols.