离子液体催化氨基甲酸甲酯和甲醇合成碳酸二甲酯

在温和的条件下,制备了一系列以溴代1-丁基-3-甲基咪唑(Bmim]Br)为阳离子、不同金属氯化物为阴离子的离子液体,并考察了它们催化氨基甲酸甲酯和甲醇合成碳酸二甲酯(DMC)的性能;同时考察了反应时间、反应温度和催化剂用量对催化效果的影响,并探讨了可能的反应机理。实验结果表明,以Bmim]Br-ZnCl2为催化剂,在反应温度170℃、反应时间8h、氨基甲酸甲酯7.5g、甲醇64g、催化剂用量2.0g的条件下,DMC的选择性和收率分别达到89.4%和24.4%。由于离子液体中阴阳离子间的极性和电子作用力比单纯的ZnCl2中阴阳离子的极性和电子作用力大很多,在催化过程中形成的中间体更稳定,所以与ZnCl2催化剂相比,Bmim]Br-ZnCl2催化剂对于该反应具有更高的选择性。

Synthesis of Dimethyl Carbonate from Methyl Carbamate and Methanol Catalyzed by Ionic Liquids

A series of 1-butyl-3-methylimidazolium bromide(Bmim]Br)ionic liquids with different metal chlorides as anions were prepared under mild condition.Then they were used as catalysts in synthesis of dimethyl carbonate(DMC)from methyl catbamate and methanol.Under the condition of reaction temperature 170 ℃,reaction time 8 h,methyl carbamate 7.5 g,methanol 64 g and Bmim]Br-ZnCl2 catalyst dosage 2.0 g,selectivity and yield of DMC could be 89.4% and 24.4%,respectively.Furthermore,because the ionic liquid possessed higher polarity and stronger electrostatic interaction between anions and cations than that of simple zinc chloride,high selectivity of the catalyst were maintained according to the possible reaction mechanism.