卤化烷基咪唑催化碳酸二甲酯与乙醇酯交换反应性能研究

Catalytic performance of alkyl-imidazole-halides on transesterification of dimethyl carbonate with ethanol

研究了烷基咪唑卤化物{[Rmim]X}对碳酸二甲酯(DMC)与乙醇酯交换反应的催化作用,考察了烷基取代基、卤素和温度对[Rmim]X催化性能的影响。当温度在78℃或以上时,[Rmim]X对DMC与乙醇的酯交换反应有明显的催化活性。当反应温度和烷基取代基相同时,催化活性为烷基咪唑碘化物≥烷基咪唑溴化物>烷基咪唑氯化物;当反应温度和卤素相同时,催化活性为甲基咪唑卤化物>乙基咪唑卤化物>丁基咪唑卤化物。若以碘化-1,3-二甲基咪唑为催化剂,当DMC与乙醇的摩尔比为1.0,催化剂对反应混合物的质量比为3.0%时,在130℃反应1 h,乙醇和DMC的摩尔转化率分别约为60%和55%,EMC的选择性在82%左右。催化剂在同样条件下重复使用25次不失活。

The catalysis of alkyl-imidazole halides{[Rmim]X}to transesterification of dimethyl carbonate(DMC)with ethanol was studied.The effects of alkyl,halogen,and temperature on the catalytic performance of[Rmim]X were investigated.[Rmim]X showed catalytic activity at temperatures of 78 ℃ or higher.When the reaction temperatures and the alkyl groups were the same,the catalytic activity was ranked as alkyl-imidazole iodide ≥ alkyl-imidazole bromide>alkyl-imidazole chloride;when the reaction temperatures and the halogens were the same,the catalytic activity was ranked as methyl-imidazole halides>ethyl-imidazole halides>butyl-imidazole halides.When 1,3-dimethyl-imidazole iodide was used as catalyst,the molar ratio of DMC versus ethanol was 1.0,and the dosage of catalyst was 3.0 wt%based on the reaction mixture,the molar conversion of ethanol and DMC,after reaction for 1 h at 130 ℃,were about 60%and 55%,respectively;the selectivity of ethyl methyl carbonate(EMC)was about 82%.The catalytic activity of 1,3-dimethyl-imidazole iodide was maintained after 25 times of reuse at the same reaction condition.