Electrochemical synthesis of dimethyl carbonate from methanol, CO2 and propylene oxide in an ionic liquid

BACKGROUND: Dimethyl carbonate (DMC) can be used effectively as an environmentally benign substitute for highly toxic phosgene and dimethyl sulfate in carbonylation and methylation, as well as a promising octane booster owing to its high oxygen content. Two-step transesterification from epoxide, methanol, and CO2 is widely used in the bulk production of DMC. However, major disadvantages of this process are high energy consumption, and high investment and production costs. A one pot synthesis of DMC from carbon dioxide, methanol, and epoxide was, therefore, developed. But the yields of DMC are below 70% due to the thermodynamic limitation. RESULTS: Electrochemical synthesis of DMC was conducted with platinum electrodes from methanol, CO2 and propylene oxide in an ionic liquid was conducted. The bmimBr (1-butyl-3-methylimidazolium bromide)-methanol-propylene oxide system with CO2 bubbling allows DMC to be effectively synthesized and a high yield (75.5%) was achieved. CONCLUSION: In this electrolysis, redox reactions of substrates, CO2, methanol, and propylene oxide, on Pt electrodes were carried out, producing the activated particles, CH3O-, CH3OH+, CO2- and PO-, resulting in the effective synthesis of DMC with a 75.5% yield in an ionic liquid (bmimBr). Finally, a mechanism for this synthesis reaction was proposed, which is very different from those reported in the literature. (C) 2011 Society of Chemical Industry