Choline chloride-based deep eutectic solvents as green extractant for the efficient extraction of 1-butanol or 2-butanol from azeotropic n-heptane + butanol mixtures

Abstract

In this study, choline chloride-based deep eutectic solvents are used as green extractant for the efficient extraction of 1-butanol or 2-butanol from azeotropic n-heptane + butanol mixtures at 298.15 K and atmospheric pressure. Choline chloride as hydrogen bond acceptor (HBA) is mixed with urea, ethylene glycol, glycerol, and 1,2-propanediol (propylene glycol) as hydrogen bond donors (HBDs) to study the effect of different choline chloride-based deep eutectic solvents on the extraction efficiency. The obtained results show that, although all the DESs provide solute distribution ratios smaller than unity (β < 1), the measured experimental selectivity values are much higher than unity (S> > 1), which is of interest for the economic feasibility of industrial extraction operations. The extraction capacity of the studied deep eutectic solvents for the separation of n-heptane +1-butanol mixture is compared with seven commonly used imidazolium-based ionic liquids. The experimental results are compared to UNIQUAC Functional-group Activity Coefficients (UNIFAC) model. It is visually observed that UNIFAC model predicts satisfactorily the equilibrium tie-lines, where the root-mean-square deviation (RMSD) for extraction of 1-butanol by ChCl-urea, ChCl-ethylene glycol, ChCl-glycerol and ChCl-1,2-propanediol are 2.99, 4.38, 1.12, and 1.56, respectively. In the case of 2-butanol extraction using the mentioned DESs, the RMSD is 0.69, 3.13, 1.47, and 1.11, respectively.