Deactivation Mechanism of an Ionic Liquid Catalyst in Transesterification to Dimethyl Carbonate

The catalytic activity of an ionic liquid catalyst decreased during the transesterification of propylene carbonate (PC) with methanol to dimethyl carbonate (DMC). The interaction between the strong basic sites of ionic liquid catalyst and carbonyl compounds of PC and/or DMC was considered to attribute to this deactivation. The presence of H2O accelerated this process by the formation of OH–. The strong basic ionic liquid reacted with the trace amount of H2O in the reaction system to generate OH–, which then reacted with the carbonyl structure in PC and/or DMC to form the inactive compound HCO3–, resulting in the deactivation of the ionic liquid catalyst. A plausible mechanism was proposed for the deactivation of the ionic liquid catalyst in this reaction. During transesterification of propylene carbonate (PC) with methanol to dimethyl carbonate, the ionic liquid catalyst will be deactivated. The strongly basic imidazole anion in the ionic liquid catalyst reacted with the trace amount of H2O to generate OH–, which attacks the carbonyl group of reactant PC to form the inactive compound HCO3–, resulting in deactivation of the ionic liquid catalyst.