Liquid-Liquid Equilibria of the (Hexane + Alcohol + Deep Eutectic Solvents) Systems: Measurement and Correlation

A study on the type 1 liquid–liquid equilibrium (LLE) behavior of the {n-hexane +1-butanol or 3-methyl-1-butanol (isopentanol) + deep eutectic solvents (DESs)} systems was performed at 298.2 K and 101 kPa. This investigation evaluates the efficiency of DESs as extractants in the green separation of hexane-alcohol azeotropic/nonazeotropic mixtures via liquid–liquid extraction. Three choline-chloride-based DESs were prepared: choline chloride +1,2-propanediol (DES1; 1:3 mol ratio), choline chloride +1,2-ethanediol (DES2; 1:2 mol ratio), and choline chloride + glycerol (DES3; 1:2 mol ratio). These DESs were used to remove 1-butanol and isopentanol from n-hexane in LLE experiments. The equilibrium phase diagram and extraction capacity were compared with those of the (n-heptane + isopentanol + DES1 or DES2) system. The NRTL model successfully correlated the measured tie-lines, and the calculated binary interaction parameters were validated through topological analysis. The extraction capacity of the DESs was evaluated through distribution coefficients and selectivities, confirming their potential as effective and environmentally friendly extractants for separating hexane-alcohol mixtures.