Cleaner one-pot transformation of glycerol to acrylic acid and 1,2-propanediol over bifunctional Cu2O/montmorillonite catalysts without external oxygen and hydrogen

Abstract

Efficient conversion of glycerol, an inevitable by-product in the transesterification process producing biodiesel, to acrylic acid (AA) and 1,2-propanediol (1,2-PDO) via a cleaner process is attractive and challenging. In this work, the simultaneous production of AA and 1,2-PDO from glycerol over Cu₂O/acid-activated montmorillonite (Cu₂O/MMT-H) catalysts without external oxygen and hydrogen was first reported. A 100% conversion of glycerol, 72% selectivity to AA, and 10% selectivity to 1,2-PDO were obtained under optimal conditions. The nanostructure and chemical state of Cu₂O and MMT-H played important roles in the conversion of glycerol. The corresponding mechanism for the oxydehydration and hydrogenolysis of glycerol to AA and 1,2-PDO over the Cu₂O/MMT-H catalysts was proposed. Dehydration of glycerol occurred at the primary carbon to form acetol which was subsequently hydrogenated to form 1,2-PDO. Acrolein was obtained by a dehydration reaction of glycerol at secondary carbon, followed by the oxidation of acrolein to AA. The Cu₂O/MMT-H-150 catalysts were reused three times without significant deactivation and structural changes. This work provides a new route for producing AA and 1,2-PDO simultaneously from glycerol in a one-pot way.