酸性咪唑类离子液体催化合成2-氯丙酸乙酯

The synthesis of ethyl 2-chloropropinate catalyzed by acidic imidazolium ionic liquids

研究了酸性咪唑类离子液体中2-氯丙酸乙酯的合成。制备了4种咪唑类离子液体作为催化剂用于酯化反应,通过Hammett方法测定其酸度,讨论了酸度-催化活性之间的关系。实验发现[Hmim]HSO4拥有比其它几种离子液体更好的催化效果。考察了离子液体用量、反应物配比、反应时间和反应温度对反应结果的影响。得到较佳的反应条件:n(离子液体)∶n(2-氯丙酸)∶n(乙醇)=1∶1∶2,反应时间2 h,反应温度90℃。产品收率85.5%,GC纯度99%。该离子液体具有良好的重复使用性能,重复使用5次催化活性基本保持不变。

The synthesis of ethyl 2-chloropropanoate in acidic imidazolium ionic liquids was studied.Four imidazolium ionic liquids were prepared and employed as catalysts in the esterification.Their acidities were measured by Hammett method and the acidity-catalytic activity relationship was investigated.HSO4 was found to be the most efficient catalyst.The effects of reaction time,reaction temperature,the molar ratio of alcohol to acid,the amount of ILs on the yield of n-butyl benzoate were investigated.The optimum esterification conditions were obtained：reaction time was 2h,n（2-chloropropanoic acid）∶n（IL）∶n（ethanol）=1∶1∶2 and reaction temperature was 90℃,The yield of ethyl 2-chloropropanoate was 85.5%and the purity of product detected by GC was 99%under the optimum conditions.Even if the catalyst was repeatedly used for 5 times,the catalytic activity maintains stable.The reusability of the IL was excellent and it could be reuse 5 times without obviously catalytic activity decrease.