RESUMO
Five metal oxides (ZnO, SnO2 , Fe2 O3 , CeO2 , La2 O3 ) were produced by the sol-gel method and tested in the direct carbonation of glycerol with CO2 . Initial tests with Fe2 O3 showed that the best reaction condition was 180 °C, 150â bar, and 12â 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 °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.