Enhanced use of renewable resources: Transesterification of glycerol catalyzed by hydrotalcite-like compounds

The increase in bio-diesel production is generating high quantities of glycerol as by-product. Glycerol carbonate and its esters are key multifunctional compounds employed as chemical intermediates, monomers, solvents, additives and fuel contents. In this study, glycerol carbonate and glycerol dicarbonate were synthesized as glycerol value-added products via a transesterification reaction using diethyl carbonate as co-substrate. This green, efficient and selective process involved catalysis with different hydrotalcite-like compounds containing a Mg/Al molar ratio of 4 that were activated by calcination and by calcination followed by rehydratation under ultrasound. The correlation between the basic properties of the solid catalysts and the activity in the glycolysis reaction was investigated. The catalytic activity shown by the different activated Mg/Al solids was not proportional to the number of basic sites present in the catalyst. The highest activity was found for the rehydrated hydrotalcite catalyst, which showed basic Brønsted sites and which can be reused several times without significant loss of activity.