Synthesis of highly effective [Emim]IM applied in one-step CO2 conversion to dimethyl carbonate

Ionic liquid 1-ethyl-3-methylimidazolium ([Emim]IM) with high thermal stability and strong basicity was successfully synthesized. Using [Emim]IM as catalyst, dimethyl carbonate (DMC) was directly synthesized from epoxy propane (PO), CO 2 , and methanol under mild reaction conditions. A continuous two-stage DMC synthesis process was developed. The cycloaddition of CO 2 and PO was first conducted to produce propylene carbonate (PC), and then methanol was introduced into the system to synthesize DMC. During the cycloaddition process, 97.40% PO conversion and 97.40% PC yield were achieved with TON of 99.49. In the subsequent transesterification stage, DMC yield attained 83.63% with selectivity higher than 99% and TON of 70.15. [Emim]IM was reused for seven times without obvious deactivation, exhibiting good stability. The effects of reaction temperature, reaction time, the initial pressure of CO 2 , and catalyst weight on cycloaddition and transesterification reactions were systematically investigated. The kinetic study showed that the activation energies (E a ) of cycloaddition and transesterification reactions were 28.02 and 38.53 KJ·mol −1 , respectively, much lower than those of catalysts reported in the literatures. In addition, [Emim]IM displayed superior catalytic activity for the cycloaddition of CO 2 with various epoxy compounds. • 1-ethyl-3-methylimidazolium ([Emim]IM) ionic liquid was successfully synthesized. • Two-stage DMC synthesis process was developed, achieving 83.63% DMC yield. • [Emim]IM was reused for seven times without deactivation, showing good stability. • The reaction mechanisms of cycloaddition and transesterification were proposed. • Kinetic studies of cycloaddition and transesterification reactions were conducted.