The studies of the process in esterification of succinate with butanediol over sulfonic functionalized imidazolium ionic liquids catalysts

Using imidazole, 1, 3-propane sultone, 1, 2-ethyl bromide, 1, 4-butane bromide and PEG-200 as raw materials, a series of sulfonic acid functional imidazole ionic liquids were synthesized, and the catalytic performances of the synthesized ionic liquids were investigated respectively by the esterification of butylene glycol with succinic acid over these ionic liquid catalysts. The effects of the reaction conditions, such as the amount of catalyst used, reaction time and molar ratio of alcohol to acid, on the esterification were investigated, and the catalytic esterification effects of the ionic liquids were compared with those of the catalysts tetrabutyl titanate and titanium isopropoxide. It was found that the optimal esterification conditions are as follows: use bis-(3-propane-1-butylene imidazole) sulfonic acid functional ionic liquid as catalyst and its used amount is about 0.40% molar weight of the succinate acid, the molar ratio of alcohol to acid is 1.3:1, reaction temperature is 160°C and the reaction time is 2 h. Under above conditions, the esterification ratio can reach 94.2%.