聚离子液体催化碳酸乙烯酯与甲醇的酯交换反应

A series of poly(ionic liquid)s containing carboxylate anions was synthesized by free radical copolymerization of N-vinylimidazolium ionic liquids, sodium acrylate and crosslinker divinylbenzene(DVB) or 1, 8-triethylene glycoldiyl-3, 3'-divinylimidazolium bromide｛[(EG)₃-DVIm]Br₂｝. These poly(ionic liquid)s were characterized by nuclear magnetic resonance(NMR) spectroscopy, Fourier transform infrared spectro⁃scopy(FTIR) and thermogravimetric analysis(TGA). The swelling properties of poly(ionic liquid)s in methanol-EC mixed solvents could be regulated by cross-linking agents and 3-alkyl-substituents on imidazolium. These poly(ionic liquid)s were used to catalyze the transesterification of methanol and ethylene carbonate(EC) to synthesize dimethyl carbonate(DMC). The catalytic activity of poly(ionic liquid)s increased with the increase of swelling ratio. And poly[VOIm-AA-DVIm], which had the highest swelling ability(Q=25.9) in the mixed solvent of methanol and EC, had the highest catalytic activity. The effects of temperature, reaction time, amount of catalyst and molar ratio of methanol to EC on the transesterification process over the poly[VOIm-AA-DVIm] were investigated and discussed, respectively. Under the optimized reaction conditions[120 ℃, 6 h, 1.0% catalyst(molar fraction, based on carboxylate), n(methanol)n(/EC)=10:1], the yield of DMC was 76.6% and the selectivity was 90.1%. The catalytic activity was comparable to that of the homogeneous catalyst 1-butyl-3-methylimidazole acetate([BMIm]OAc).