Greener separation of n-butanol/isobutanol from azeotropic methyl isobutyl ketone (MIBK) mixtures using deep eutectic solvents

Separation with deep eutectic solvent (DES) is a sustainable method to extract valuable compounds from various matrices. DES, formed from hydrogen bond donors and acceptors, are eco-friendly solvent alternatives. They show high selectivity and solubility for target compounds, enabling phytochemical, pharmaceutical, and metal extraction. This research deals with experimentally and computationally studying the capability of DESs to obtain an efficient liquid – liquid extraction at atmospheric pressure and 298.15 K. The utilized DESs are ChCl – urea, ChCl – ethylene glycol, ChCl – glucose, ChCl – glycerol, and ChCl – 1,2-propanediol. In this direction, the extraction efficiency of DESs to separate n-butanol/isobutanol from azeotropic systems, Methyl isobutyl ketone (MIBK) + n-butanol/isobutanol, is studied. The obtained results showed that all the investigated DESs exhibit a distribution coefficient, β, exceeding unity (β>1). Furthermore, the determined selectivity values for the utilized extractants significantly surpass unity (S>>1) that is beneficial from industrial applications point of view. The highest β and S values are respectively observed with ChCl-Urea and ChCl-EG for n-butanol and isobutanol separation. Furthermore, the Othmer–Tobias approach was utilized to examine the consistency of the tie-line compositions. The findings from the group contribution UNIFAC model align well with the experimental data. For the MIBK–n-butanol–DES mixtures, the smallest RMSD occurs with ChCl– ethylene glycol at 1.07, while the largest is observed for ChCl–1,2-propanediol at 2.06. In contrast, among systems with isobutanol, the minimum RMSD is found for ChCl– ethylene glycol and the maximum for ChCl–glucose, with values of 0.55 and 2.47, respectively.