Alkoxyl side‐chain effects of acidic ionic liquids catalysts for the esterification of n‐butyl butyrate

Three kinds of alkoxy group‐functionalized acidic ionic liquids (ILs) are reported in this work, namely, 1‐(methoxyethyl)‐3‐methylimidazolium hydrogen sulphate [MOE‐MIM]HSO4, 1‐(ethyoxyethyl)‐3‐methylimidazolium hydrogen sulphate [EOE‐MIM]HSO4, and 1‐(propyoxyethyl)‐3‐methylimidazolium hydrogen sulphate [POE‐MIM]HSO4. The short side chain on the cation of [MOE‐MIM]HSO4 decreases the solubility of the IL in butanol and butyric acid and facilitates the separation of the IL from a reaction medium. The yield of butyl butyrate is up to 99.5%. After 10 rounds of recycling, the catalytic performance of [MOE‐MIM]HSO4 shows no significant changes. Three kinds of Alkoxyl side‐chain containing acidic ionic liquids are used to catalyze the esterification of butyl butyrate. The shorter side chain on the cation of [MOE‐MIM]HSO4 makes it less soluble in butanol and butyric acid, and easier separation from the reaction medium. The yield of the butyl butyrate is up to 99.5%. After reuse for 10 times, the catalytic activity of [MOE‐MIM]HSO4 shows no significant changes.