Hydroxyl-functionalized ionic liquid for activation and conversion of CO2 and methanol into dimethyl carbonate

•Xyl-functionalized ionic liquid as an effective catalyst.•Activation of CO2 and methanol by anion OH−.•Formation of hydrogen bonding acidity.•The acidic species activating CH3OH to CH3+.•Promoting rate-determined step for DMC.

A series of hydroxyl-functionalized ionic liquids such as dialkyl (or alkyl) di-(tri-) hydroxyethyl ammonium hydroxide, tetrahydroxyethyl ammonium hydroxide and alkylhydroxyethyl or dihydroxyethyl immidazolium hydroxide were synthesized and characterized by FT-IR and 1H NMR. These ionic liquids containing hydroxyls were used as catalysts for direct synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide. The results showed that benzylmethyldihydroxyethyl ammonium hydroxide (BzMDH) is an effect catalyst with raised catalytic activity and high selectivity to DMC. The effect of hydroxyl groups on the activation of methanol and CO2 were explored. Furthermore, the reaction mechanism of this synthetic reaction was discussed.

Graphical abstractHydroxyl-functionalized ionic liquid is found to be an effective catalyst for direct synthesis of dimethyl carbonate from methanol and carbon dioxide, which is likely ascribed to the synergism effect of basic species and hydrogen bonding acidity of the catalyst.Figure optionsDownload full-size imageDownload as PowerPoint slide