Toward Evaluation of Diethylene Glycol-Based Deep Eutectic Solvents for the Separation of Benzene and n-Hexane Using Pseudoternary Liquid-Liquid Equilibrium Data

The pseudoternary systems of deep eutectic solvents (DESs) has attracted interest in separation technology due to its novel physicochemical properties. Two DESs of [ChCl][DEG] with molar ratios of 1:4 (DES1) and 1:8 (DES2) were prepared. The pseudoternary systems of n-hexane + benzene + DES1 and n-hexane + benzene + DES2 measured the tie lines of liquid–liquid equilibrium (LLE) data at T = 298.15–318.15 K and at atmospheric pressure. The assumption of DESs as the pseudopure component was performed to investigate pseudoternary LLE, which implies that the DESs remain unaltered in a single phase. DES2 was found to substantially increase the selectivity (S) values for the separation of benzene and n-hexane. The Othmer–Tobias and Bachman correlations were used to evaluate the reliability of the experimental tie-line data. The NRTL model shows a good agreement of the calculated and experimental values of n-hexane + benzene + DES1 with the root-mean-square deviation of 0.0076. The pseudoternary system of n-hexane + benzene + DES2 shows a good agreement with the UNIQUAC model with the RMSD of 0.0095. To verify the tie-line consistency, G^M/RT was used to topologically analyze the Gibbs mixing energy.