Role of the cation on the liquid extraction of levulinic acid from water using NTf2-based ionic liquids: Experimental data and computational analysis

Levulinic acid is usually obtained from a complex aqueous mixture from which it has to be separated and purified. In this work, the liquid extraction of this acid from water using ionic liquids (Its) is studied, and the effect of the cationic structure of the Its is analyzed and discussed from experimental and computational data. For that, liquidliquid equilibrium data were experimentally determined for {water + levulinic acid + ionic liquid} ternary mixtures. Specifically, the studied extraction agents were NTf2-based ILs with imidazolium, pyridinium, and sulfonium cations. This work is based on the tie-lines determination through the concentration of the equilibrium phases, which were obtained by density measurements. From these data, the ability of the Its as solvents was evaluated in terms of selectivity and solute distribution ratio. The obtained results show that high values of S and moderated values of beta are achieved, which indicates that these ionic solvents could be considered as a potential alternative to extract this acid from aqueous mixtures. Aiming to gain an improved understanding of the effect of the cation on the phase behavior of these systems, a theoretical study was also carried out with the quantum chemical COSMO-RS. This tool has quite satisfactorily applied to find an explanation of the phase equilibria in terms of molecular interactions between the involved compounds. (C) 2020 Elsevier B.V. All rights reserved.