(560g) Direct Carbonylation of Glycerol with CO2 to Organic Carbonates Catalyzed By Cerium Oxide/Zinc Oxide

Direct carbonylation of glycerol with CO₂ with cerium oxide/zinc oxide catalysts and 2-cyanopyridine (2-CP) as a dehydrating agent was studied under a CO₂ pressure (P_CO2) from 30 bar to 50 bar and a reaction temperature from 120°C to 200 °C in a Parr 4563 reactor. The incipient wetness impregnation was employed to load cerium oxide, using Ce(NO₃)₃·6H₂O as precursor, onto the surface of zinc oxide, forming cerium oxide/zinc oxide catalysts. The properties of the catalysts were identified using equipment and methods such as XRD, SEM, EDS, ICP-OES, XPS, BET porosimetry and CO₂-TPD. The experimental results showed that cerium oxide/zinc oxide synthesized at a weight ratio of 30:70 could achieve generally the highest yield of glycerol carbonate. Notably, increasing the reaction pressure demonstrated a dual benefit in enhancing both yield and selectivity of glycerol carbonate. For example, a yield of glycerol carbonate from glycerol exceeding 40% could be attained from a reaction at 180 °C. In general, an insufficient amount of catalyst present in the reaction system could result in a lower yield of glycerol carbonate, probably owing to fewer active sites available, while catalyst present in excess led to a slightly inferior catalysis and a lower yield of glycerol carbonate as well. Thus, a catalyst dosage comprising 3 wt% of glycerol would be the optimal, based on empirical results available.