Reactive extraction for synthesizing long chain ester butyl hexanoate intensified by deep eutectic solvent

Butyl hexanoate (BuHE) is an important long-chain ester that is widely used in the food, beverage and cosmetic industries. In this work, reactive extraction concept was proposed to intensify the BuHE formation in a biphasic system, in which deep eutectic solvent (DES) comprising 2-methylimidazole (2-MIm) and p -toluenesulfonic acid (PTSA) was used as dual solvent-catalyst. First, the effect of 2-MIm to PTSA molar ratio on esterification was investigated to determine the optimum DES of [2-MIm:2PTSA], which was characterized by FT-IR and TGA. Then, the liquid–liquid equilibrium (LLE) and esterification experiments were carried out to confirm the extraction and catalytic effect of [2-MIm:2PTSA], respectively. Afterwards, the pseudo-homogeneous kinetic model was employed to describe the esterification kinetics. Finally, the intensification mechanism of reactive extraction for BuHE formation was proposed according to the experiments and interaction effect analysis.