Process optimization and kinetics of microwave assisted transesterification of crude glycerol for the production of glycerol carbonate

Abstract

The production of glycerol carbonate (GC) from industrial grade crude glycerol was catalyzed by calcium oxide (CaO) via microwave assisted transesterification (MAT). Influencing process parameters including reaction temperature, time and molar ratio of dimethyl carbonate/glycerol (DMC/Gly) were examined and optimized by applying Box Behnken Design (BBD). The reaction was modelled into a reduced cubic model with good predictive accuracy. A high GC yield of 99.5% was achieved with 1 wt% CaO at optimized conditions such as reaction temperature of 65 °C, reaction time of 3 min and DMC/Gly molar ratio of 2.5. The study performed on the reaction kinetics suggests that the reaction follows an irreversible second order rate equation. A relatively low activation energy of 4.53 kJ mol⁻¹ was determined for the microwave assisted transesterification of crude glycerol for the production of GC. The values of rate constants between 45 °C to 65 °C were in the range of 0.023–0.026 L mol⁻¹ min⁻¹, which are of one magnitude order higher than that of the conventional heating.