An Efficient and Super Stable Immobilized Ionic Liquid Catalyst Application in the Catalytic Synthesis of Carbonates

Homogeneous catalysts suffer from difficulty in product separation and recycling. To solve these problems, a strong basicity immobilized ionic liquid catalyst (PS-IMC4IM) was constructed. Various characterizations were applied to identify the differences in the structure and active components of the catalyst during the preparation process and with the spent catalyst. The results indicated that a bis-imidazole ionic liquid (IMC4IM) was successfully immobilized on the polystyrene resin (PS) by covalent bonding. The basic amount of PS-IMC4IM was 0.84 mmol/g, and its basic strength was 9.8 < H_ < 12.8. Its structure and the number of active components remained unchanged after 2000 h of reaction. PS-IMC4IM displayed an admirable catalytic performance in the transesterification of ethylene carbonate (EC) and methanol (MeOH) to synthesize dimethyl carbonate (DMC) at a mild reaction condition. The EC conversion was 76.9%, and the turnover frequency (TOF) was 12.5 h-1 in a fixed-bed reactor. What is more, the TOF value was raised to 76.7 h-1 in the slurry phase reactor. Compared with other reported catalysts, PS-IMC4IM exhibited excellent catalytic ability and stability. Besides, PSIMC4IM has the capability to synthesize a series of carbonates via transesterification, including diethyl carbonate (DEC), methyl ethyl carbonate (EMC), and glycerol carbonate (GLC). PS-IMC4IM provides a new method to develop highly efficient and stable heterogeneous catalysts for transesterification reactions.