Imidazolium ionic liquid-supported sulfonic acids: Efficient and recyclable catalysts for esterification of benzoic acid

Several imidazolium ionic liquid (IL)-supported sulfonic acids with different anions, [C3SO3Hmim]HSO4, [C3SO3Hmim]BF4, [C3SO3Hmim]PF6, and [C3SO3Hmim]CF3SO3, were synthesized and applied as catalysts for esterification reaction of benzoic acid. The experimental results indicate that imidazolium IL-supported sulfonic acid containing anion of HSO4− shows the best catalytic activity. Only when less [C3SO3Hmim]HSO4 (0.3 equiv.) applied, was the product obtained with high yield of 97%. Furthermore, the produced esters could be separated by decantation, and the catalyst could be reused after the removal of water.