Relay catalysis of copper-magnesium catalyst on efficient valorization of glycerol to glycolic acid

Abstract

The exploration of potential application of glycerol is of particular importance for solving the oversupply of glycerol as an unavoidable byproduct of biodiesel and affording profitable possibilities for sustainable biodiesel. Herein, we developed a simple, cheap but robust Cu1Mg4 catalyst, which exhibited outstanding catalytic activity for the selective conversion of glycerol towards valuable glycolic acid, eliminating the addition of extra inorganic base. As high as 71.8% yield of glycolic acid was achieved, the highest value to date as far as we know. In combination of experiment and DFT calculations, it was revealed that Cu, Mg species in catalyst enabled the relay catalysis for the cascade reactions in glycerol transformation. Cu species in catalyst dominated the first dehydrogenation reaction of glycerol to glyceraldehyde, which was promoted by Mg species. Mg species followed to catalyze the next cleavage of C2-C3 bond in glyceraldehyde to generate glycolaldehyde. The final oxidation of glycolaldehyde to glycolic acid was achieved by the catalysis of Cu species. This relay catalysis of Cu1Mg4 catalyst significantly inhibited the formation of glyceric acid and lactic acid by-products, thereby enabling the selective generation of glycolic acid.