On-line synthesis of highly stable product-derived catalysts applied in DEC/EMC synthesis without azeotrope generation

Abstract

One-step transesterification between ethylene carbonate (EC) and ethanol (EtOH) can effectively prevent the formation of azeotropes in the synthesis of diethyl carbonate (DEC) / ethyl methyl carbonate (EMC). However, owing to the influence of volume and electronic effects of EtOH molecules, the catalytic activity is insufficient. In this study, we propose an on-line synthesis technique for catalysts and prepare a unique heterogeneous alkali catalyst, PS-(NR₃OH)EG. This technique simplifies the catalyst preparation process and protects it from exposure to water and carbon dioxide in the air. The active sites of PS-(NR₃OH)EG are derived from the product ethylene glycol (EG). PS-(NR₃OH)EG exhibits excellent catalytic performance in promoting EC and EtOH transesterification. The physicochemical properties of PS-(NR₃OH)EG are analysed, and the reaction conditions are optimized. The results indicate that PS-(NR₃OH)EG has superior catalytic activity and stability compared to the similar previously reported catalysts. Notably, after continuous reaction in a fixed-bed reactor for 500 h, PS-(NR₃OH)EG maintain its initial catalytic activity. This study provides theoretical and experimental guidance for catalyst preparation and transesterification reaction process design.