Efficient and selective alcoholysis of furfuryl alcohol to alkyl levulinates catalyzed by double SO3H-functionalized ionic liquids

The production of alkyl levulinates from furfuryl alcohol (FAL) in alcohol media was investigated at moderate temperature in the presence of Brønsted acidic ionic liquids. The reaction was examined and optimized under batch conditions, where it was found that furfuryl alcohol was rapidly and almost quantitatively converted into intermediate products including 2-alkoxymethylfuran and 4,5,5-trialkoxypentan-2-one, and high alkyl levulinates yield of 95% can be achieved after reaching a steady state in 2 h. An advantage of this catalyst system is that undesired dialkyl ether (DEE) formed by a side reaction of the dehydration of alcohol is negligible. The Hammett method was used to determine the acidities of these ionic liquids, which indicated that the acidity and the molecular structure have strong effects on the catalytic activity of ionic liquids. Based on the experimental results, a possible mechanism for the alcoholysis of FAL is proposed.