Development of a reactive extraction process for isobutyl isobutyrate formation intensified by bifunctional ionic liquid

Abstract

Isobutyl isobutyrate (IBIBE) is a typical long-chain ester widely used as a solvent, additive, or raw material. To address problems such as acidic waste emission and tedious downstream separation in traditional synthesis routes, a reactive extraction process concept employing the ionic liquid (IL) 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIm][HSO4]) as a dual catalyst and solvent is proposed. To develop such an intensified process, thermodynamic analysis of the reaction system is firstly performed. Liquid-liquid equilibria indicate that [BMIm][HSO4] is a proper extractant that can not only remove the formed IBIBE from the esterification system via phase splitting but also keep the reactants in the IL phase, both facilitating the forward reaction and thus improving the conversion of the reactant and the purity of IBIBE. The kinetics of the esterification is then experimentally determined and fitted using the activity-based kinetic model, which suggests the good catalytic performance of [BMIm][HSO4]. Combining the NRTL model and activity-based kinetic model, a reactive extraction process for IBIBE formation is developed and simulated. High purity of IBIBE (0.9799) and high conversion (0.9931) are obtained.