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.