One-step Synthesis of Dimethyl Carbonate by Reaction of Ethylene Oxide, Carbon Dioxide and Methanol Catalyzed by Inorganic Salts

In this study, various inorganic salts were investigated for the one-step synthesis of dimethyl carbonate (DMC) by reaction of ethylene oxide (EO), carbon dioxide (CO₂), and methanol (MeOH). The bi-component catalytic system of KI/NaCl achieved high activities and selectivity with a DMC yield of 83% and a by-product, 2-methoxyethanol (2-MET), yield of 2%. The reaction involved two tandem reactions of the cycloaddition of EO and CO₂ and the transesterification of EC and MeOH. Kinetic studies were conducted to investigate the reaction mechanism and found that the strongly nucleophilic KI was the active species of cycloaddition and weak Lewis basic NaCl was the active species of transesterification, respectively. In addition, transesterification was the rate-determining step in the synthesis of DMC. CO₂/KI was capable of synergistically suppressing the by-product 2-MET. This catalytic system exhibited a substrate generality for different epoxides. (Figure presented.)