微波促进酸性离子液体催化水杨酸酯化

Esterification of Salicylic Acid Using Acidic Ionic Liquid as Catalyst under Microwave Irradiation

用自制的硫酸氢1-甲基-3-(3-磺酸基丙基)咪唑([MIMPS]HSO4)酸性离子液体作为水杨酸与醇的酯化反应催化剂,考察了温度、时间、物料配比和离子液体用量等因素对酯化反应的影响,优化的最佳反应条件为:微波辐射时间20 min,反应温度95℃,醇与酸摩尔比3∶1(水杨酸的量为0.02 mol),[MIMPS]HSO4用量10 mmol,水杨酸甲酯的产率和选择性分别为91.9%和99.0%。离子液体回收循环使用4次,催化效率不变。与热催化酯化反应相比,微波辐射可缩短反应时间;水杨酸与不同碳链醇的酯化产率随着碳链的增加而降低,同碳链的伯醇酯化率比仲醇高。

A acidic ionic liquid [MIMPS]HSO4 was synthesized and used for the esterification of salicylic acid.Factors including reaction temperature,reaction time,ratio of reactant and amount of ionic liquid were investigated.It was found that the optimized conditions were at 95 ℃,microwave irradiation for 20 min,molar ratio of methanol to salicylic acid with 3∶1,amount of [MIMPS]HSO4 10 mmol.The yield and selectivity of methyl salicylate were 91.9% and 99.0%,respectively.[MIMPS][HSO4]as a catalyst can be recycled for 4-times without obvious decrease in activity.Microwave irradiation could reduce reaction time under the same conditions.The yield of esterification decreased as the carbon chain increases,and also when the secondary alcohols were used instead of the primary alcohols.