Synthesis of long-chain aliphatic acid methyl esters catalyzed by Brφnsted-acidic ionic liquids

The Brφnsted-acidic ionic liquids based on 1-n-butyl-3-methylimidazolium cation with anions HSO4-、H2PO4-and BF4-,were synthesized.The catalytic activities of the acidic ionic liquids for the esterification of long-chain aliphatic acids with methanol were investigated.The effects of the reaction time,amount of catalyst and mole ratio of reactants on the esterification reaction were studied to optimize the reaction conditions.The experimental results showed that the esterification could be promoted by the ionic liquid (1-n-butyl-3-methylimidozalium sulfonated salt).The reactions were carried out smoothly under the mild reaction conditions with excellent catalytic activity(more than 93.4% conversion of aliphatic acid) having 100% selectivity towards aliphatic acid methyl esters without removal of water during the esterification.Moreover,the products could be facilely separated by simple decantation,and the ionic liquids can be reused more than five times without a significant decrease in the activity.