Catalytic synthesis of methyl caprylate using multi-SO3H functionalized Bronsted acidic ionic liquid as catalyst

Environmentally benign Bronsted acidic ionic liquids with multi-SO3H functionality were prepared using N-methyl imidazole and 1,3-propane sultone as the source chemicals. The prepared ionic liquid catalysts were characterized by infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and thermogravimetry (TG) and their catalytic activity in esterification of caprylic acid with methanol was investigated. The results showed that the novel catalyst was very efficient for the reaction, with excellent water and acid resistant ability. Under optimum conditions, the yield of methyl caprylate reached 94.8%. The ionic liquids could be reused six times without a noticeable drop in activity. The kinetic study for the esterification indicated that the reaction order was 1.54 and the activation energy E-alpha was 24.61 kJ/mol.