Synthesis of dimethyl carbonate from CO2 and ethylene oxide catalyzed by K2CO3-based binary salts in the presence of H2O

We systematically screened binary catalysts for synthesis of dimethyl carbonate (DMC) from CO2, CH3OH and ethylene oxide (EO) in the presence of H2O by two-step transesterification process, and found the commercial quaternary ammonium salts/K2CO3, pyridinium salts/K2CO3 and KI/K2CO3 were effective binary catalysts for two-step synthesis of DMC with no need for separation of ethylene carbonate (EC). Near 100% conversion of EO and 82% yield of DMC were obtained under mild reaction conditions. However, the imidazolium salts were not compatible with inorganic alkaline possibly because of the reactive C(2)-H in the imidazolium ring. Furthermore, the KI/K2CO3 could be easily recovered and reused 12 times without obvious loss of its catalytic activity. The process avoids EC separation, and represents a simple, ecologically safer, cost-effective and energy-saving route for synthesis of DMC with high product quality, as well as easy catalyst recycling.