Direct Carbonation of Glycerol with CO2 Catalyzed by Metal Oxides

Five metal oxides (ZnO, SnO2, Fe2O3, CeO2, La-2 O-3) were produced by the sol-gel method and tested in the direct carbonation of glycerol with CO2. Initial tests with Fe2O3 showed that the best reaction condition was 180 degrees C, 150 bar, and 12 h. The other oxides were evaluated at these conditions and were all active to the formation of glycerol carbonate. Zinc oxide was the most active catalyst, with a yield of 8.1% in the organic carbonate. The catalytic activity decreased upon washing and drying the ZnO catalyst between the runs. Nevertheless, the activity is maintained if the ZnO is washed and calcined at 450 degrees C between the runs. FTIR and TGA results indicated the formation of ZnCO3 as the main cause of catalyst deactivation, which may be decomposed upon calcination of the material. No appreciable leaching of Zn was observed, indicating a truly heterogeneous catalysis.