Glycerol Carbonate Synthesis by Hierarchically Structured Catalysts: Catalytic Activity and Characterization

Abstract

The surge in biodiesel production in recent years has resulted in enhanced research interest in the conversion of glycerol to other valuable chemicals such as glycerol carbonate (GLC). In the present study, the catalytic transesterification of glycerol with dimethyl carbonate (DMC) for the production of GLC was studied with calcium–lanthanum mixed-oxide catalysts at different Ca/La molar ratios. These catalysts were synthesized using an exo- and endotemplating method. The physicochemical characteristics of the catalysts were determined using powder X-ray diffraction (XRD), N 2 sorption, scanning electron microscopy (SEM), and temperature-programmed desorption (TPD) of CO 2 and NH 3 . The transesterification of glycerol was found to be highly dependent on the basicity of the catalysts. The catalyst with a Ca/La molar ratio of 3 (3CaLa) showed the highest glycerol conversion and GLC yield. Optimization of the reaction parameters and reusability of the catalyst were studied with the 3CaLa catalyst in terms of glycerol conversion, GLC yield, and turnover frequency (TOF). At the optimum operating conditions, namely, a reaction time of 90 min, a DMC/glycerol molar ratio of 5, a catalyst mass of 0.217 g, and a temperature of 90 °C, the glycerol conversion and GLC yield were found to be 94% and 74%, respectively, with a reaction rate of ∼0.14 mol L –1 h –1 (with respect to glycerol).