Intensification of Ethylene Carbonate Synthesis via Microwave-Induced Phase-Change Cycles

This study reports for the first time on the application of microwave (MW) heating under ambient pressure reflux conditions to intensify the transesterification reaction of ethylene glycol with dimethyl carbonate (DMC) for the synthesis of ethylene carbonate (EC), a relevant industrial compound for polycarbonate products, lubricants and li-ion batteries. Conventional heating (CH) methods often require high-temperature autoclave systems to achieve elevated temperatures and suppress vaporization of the reactant DMC (bp ≈ 90 °C). However, these systems usually entail extended reaction times and significant process cost. It is demonstrated that application of the MW-assisted reflux technique to the aforementioned transesterification reaction intensifies the energy transfer rate to the reactor by leveraging on the polarity of the reactive mixture and enhances phase transition of the lowest boiling point by-product (MeOH), thereby achieving 81% EC yield in half the time required under CH reflux conditions to reach only 52% EC yield. Further, compared to CH, MW heating enables 20-fold lower catalyst loading for comparable EC yields, 9-fold decrease in energy consumption per mole EC, and 92% reduction in energy consumption during the mixture preheating stage.