功能特异性杂多酸离子液体催化丁二酸水溶液直接酯化

Functional Specific Heteropoly Acid Ionic Liquid Catalyzed Direct Esterification of Aqueous Succinate Solution

将以磺化六亚甲基四胺([HMT-4PS])制备的阳离子与以杂多酸([HPA])制备的阴离子结合,制备了一系列功能特异性离子液体催化剂([HMT-4PS][HPA]);将其用于催化甲醇(MeOH)与丁二酸(SA)水溶液的直接酯化反应.结果表明,该系列离子液体在反应过程中以"乳状液"的形式均匀分散在体系中.反应结束后,通过降低体系极性即可实现催化剂的快速分离.在合成的系列催化剂中,[HMT-4PS]3[PW]4表现出最佳的催化活性.分别探讨了反应温度、催化剂用量、酸醇摩尔比和反应时间等因素对反应的影响,确定了最优反应条件:温度80℃,催化剂用量5%(质量分数,按丁二酸水溶液计),n(SA)∶n(MeOH)=1∶30,反应时间8 h.最优条件下丁二酸的转化率达到79. 3%,二酯选择性达到92. 9%;该催化剂重复使用5次后,丁二酸转化率及二酯选择性仍分别保持在77%及90%以上.

A series of functionally specific acid ionic liquid catalysts([HMT-4 PS][HPA]) was synthesized by combining sulfonated hexamethylenetetramine[HMT-4 PS] with heteropoly acid anions,and then used for catalyzing the direct esterification of methanol with aqueous succinic acid(SA) solution. The results indicated that the series of ionic liquids were uniformly dispersed in the system as "emulsion"during the reaction. After the reaction was completed,the rapid separation of the catalyst could be accomplished by reducing the polarity of the system.[HMT-4 PS]3[PW]4 exhibited the best catalytic activity during the series of synthesized catalysts. The effects of temperature,amount of catalyst,molar ratio of acid to alcohol and reaction time were fully investigated. The optimal reaction conditions were determined: reaction temperature 80 ℃,catalyst mass fraction of 5%(based on SA aqueous solution),n(SA)∶ n(MeOH)= 1 ∶ 30,reaction time 8 h. The conversion of succinic acid could reach 79. 3%,the diester selectivity could reach 92. 9%. After 5 times reused,the conversion of succinic acid and the selectivity of the diester still reached above 77% and 90%.