Tunable Oxygen Vacancies in CeO2-Dolomite Catalysts for Gas-Phase Conversion of Glycerol to 1,2-Propanediol without External Hydrogen

Selective conversion of glycerol to 1,2-propanediol (1,2-PDO) provides a sustainable approach to the valorization of an unavoidable by-product in biodiesel industry. However, achieving selective cleavage of the primary hydroxyl group (C1–OH) to form 1,2-PDO under hydrogen-free conditions remains a challenge. Herein, we report a CeO2–dolomite-based catalyst prepared by mechanochemical ball milling and the catalyst can catalyze the conversion of gas-phase glycerol to 1,2-PDO under 0.4 MPa N2 without external H2. This preparation method introduced a high density of oxygen vacancies (OV) into CeO2 and dispersed CeO2 onto the surface of calcined dolomite (CaO–MgO), creating a synergistic acid, base, and defect sites for interface. Under optimized conditions (20 wt % CeO2, 320 °C, 0.4 MPa N2), the catalyst achieved 94.08% glycerol conversion with 47.59% selectivity to 1,2-PDO, comparable to or higher than many reported non-noble catalysts and hydrogen-free systems. The results show that medium-strong basic sites on the calcined dolomite promoted dehydration of glycerol to acetol and Ce3+–OV defect pairs facilitated water-assisted hydrogen transfer, which was likely involved in the hydrogenation of acetol to 1,2-PDO under hydrogen-free conditions. This work demonstrates an alternative efficient hydrogen-free catalytic system and provides a defect-engineering methodolgy for making catalysts for the selective cleavage of C–O bonds in glycerol.