Liquid–Liquid Equilibrium Determination and Correlation for Ethylbenzene and <i>n</i> -Butanol with Deep Eutectic Solvents

Separation of the azeotropic mixture of ethylbenzene (EB) and n-butanol (n-BuOH) is of critical importance, since EB can be catalytically converted from renewable n-BuOH, yet it remains challenging by conventional distillation. Three deep eutectic solvents (DESs) were formulated wherein 1,4-butanediol served as the hydrogen bond donor, paired with choline chloride (ChCl), l-lactic acid, and dl-menthol acting as hydrogen bond acceptors (HBAs). The liquid–liquid equilibrium (LLE) data were acquired for the pseudoternary mixtures (EB + n-BuOH + DESs) at 298.15 K and 101.3 kPa. The extraction performance was quantified based on the distribution coefficient and selectivity. The results showed that DES (ChCl: 1,4-butanediol, 1:2, molar ratio) indicated its strong potential as an efficient and eco-friendly extractant. The NRTL thermodynamic model was employed for the purpose of correlating the collected LLE data, resulting in lower values of root-mean-square deviation (RMSD), confirming its reliability for modeling the pseudoternary mixtures.