Optimization of the transesterification process of glycerol and diethyl carbonate to synthesize glycerol carbonate using a response surface methodology (RSM) approach

Abstract

Glycerol carbonate (GC) is a value-added chemical widely produced through the transesterification of glycerol with dialkyl carbonates. In the present study, the optimization of glycerol transesterification with diethyl carbonate using 1-ethyl-3-methylimidazolium acetate ([Emim][Ac]) as a catalyst was investigated using response surface methodology (RSM). The experiments were carried out using a central composite design (CCD) to evaluate the effects of important parameters including reaction temperature (110.0 °C to 130.0 °C), reaction time (1.5 hours to 2.5 hours), substrate ratio (1.5 to 2.5 equivalent ratio) and catalyst loading (0.30 mol% to 0.70 mol%) on two responses, glycerol conversion and GC yield. The developed quadratic models showed good agreement between predicted and experimental values, with coefficients of determination (R²) of 0.93 and 0.96 for glycerol conversion and GC yield, respectively. The optimum conditions were found to be 118.0 °C at 1.8 hours with a 2.2 diethyl carbonate/glycerol ratio and 0.42 mol% [Emim][Ac] to obtain 92.40% glycerol conversion and a GC yield of 91.80%. Reaction temperature was identified as the most influential parameter affecting both responses. The results demonstrate that [Emim][Ac] is an efficient ionic liquid catalyst for glycerol valorization via transesterification. The integration of catalytic evaluation with statistically guided optimization provides a systematic approach for improving GC synthesis under relatively mild reaction conditions.