Zinc/Lanthanum Mixed-Oxide Catalyst for the Synthesis of Glycerol Carbonate by Transesterification of Glycerol

ZnO/La2O3 mixed oxides are prepared by a coprecipitation method at different molar ratios and used as catalysts for the synthesis of glycerol carbonate by transesterification of glycerol with dimethyl carbonate (DMC). X-ray diffraction, N2 adsorption, transmission electron microscopy, scanning electron microscopy, and thermal-programmed desorption methods were used for characterization of the catalysts. The surface area and porosity of the catalysts prepared by the precipitation method proved to be better than those prepared by combustion and modified-citrate methods. Zn4La1 and Zn2La1 (mole ratio Zn:La of 4:1 and 2:1, respectively) were found to be the best proportions in view of both higher activity and higher selectivity. The rates offered by these catalysts were substantially high compared to reported Mg/La and other catalysts. The effects of parameters such as the temperature, catalyst loading, and mole ratio of DMC to glycerol were examined, and a suitable kinetic model was proposed for the Zn4La1 catalyst.