Chemicals from biomass: Synthesis of glycerol carbonate by transesterification and carbonylation with urea with hydrotalcite catalysts. The role of acid-base pairs

摘要

Synthesis of glycerol carbonate has been performed by transesterification of ethylene carbonate with glycerol catalyzed by basic oxides (MgO, and CaO), and mixed oxides (Al/Mg, Al/Li) derived from hydrotalcites. The results showed that the optimum catalyst in terms of activity and selectivity is a strong basic Al/Ca-mixed oxide (AlCaMO) which is able to catalyze the reaction at low temperature (35 °C), and low catalyst loading (0.5 wt%) giving high glycerol conversions with 98% selectivity to glycerol carbonate. When the synthesis of glycerol carbonate was carried out by carbonylation of glycerol with urea, the results showed that balanced bifunctional acid-base catalysts where the Lewis acid activates the carbonyl of the urea and the conjugated basic site activates the hydroxyl group of the glycerol were the most active and selective catalysts.