功能特异性杂多酸离子液体催化丁二酸水溶液直接酯化

A series of functionally specific acid ionic liquid catalysts([HMT-4PS][HPA]) was synthesized by combining sulfonated hexamethylenetetramine[HMT-4PS] 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-4PS]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%.