BrФnsted-Lewis双酸性离子液体催化合成二苯甲烷二氨基甲酸甲酯

合成了具有不同ZnCl2摩尔分数的BrФnsted-Lewis双酸性离子液体HO3S-(CH2)4-mim]Cl-xZnCl2,采用Hammett指示剂与紫外联用法测定了其酸强度,考察了其在苯氨基甲酸甲酯(MPC)与甲醛(HCHO)缩合制备二苯甲烷二氨基甲酸甲酯(MDC)反应中的催化性能,并考察了反应条件对MDC收率和MPC转化率的影响。结果表明,当x=0.7时该离子液体的催化活性最高。以HO3S-(CH2)4-mim]Cl-0.7ZnCl2为催化剂兼溶剂,在反应温度70℃、反应时间60min、MPC与HCHO的摩尔比为10、离子液体与MPC的质量比为2的条件下,MDC收率最高可达99.1%。用水处理反应液并通过减压蒸馏回收的离子液体可以循环使用5次,其催化活性基本不变。

Synthesis of Methylene Diphenyl Dimethylcarbamate Catalyzed by BrØnsted-Lewis Acidic Ionic Liquid

BrØnsted-Lewis acidic ionic liquids HO₃S-(CH₂)4-mim]Cl-xZnCl₂ with different molar fractions of zinc chloride were prepared and their acid strength was determined by the Hammett method combined with UV-visible spectroscopy. The catalytic performance of ［HO₃S-(CH₂)₄ mim]Cl-xZnCl₂ for the synthesis of methylene diphenyl dimethylcarbamate(MDC) from methyl N-phenyl carbamate(MPC) and formaldehyde(HCHO) was evaluated. The effects of reaction conditions on MDC yield and MPC conversion of the reaction were investigated. The results showed that ［HO₃S-(CH₂)₄-mim]Cl-0.7ZnCl₂ had the highest catalytic activity. With HO₃S-(CH₂)₄mim]Cl-0.7ZnCl₂ as catalyst and solvent under the reaction conditions of temperature 70℃, time 60 min, n(MPC)/n(HCHO)=10 and m(ILs)/m(MPC)=2, the yield of MDC was 99.1%. ［HO₃S(CH₂)₄-mim]Cl-xZnCl₂ could be reused more than five times without significant loss in its catalytic performance after the removal of water by vacuum distillation.