Liquid–Liquid Equilibria of Toluene–Alkanol Azeotrope Mixtures Using a Deep Eutectic Solvent: Measurement and Thermodynamic Modeling

Ternary liquid–liquid equilibrium (LLE) data were experimentally determined and systematically compared for the systems containing binary azeotrope mixtures {toluene + alkanols (from C1 to C5)} and a deep eutectic solvent (DES) at 298.2 K and 101 kPa. The prepared DES was a binary mixture of choline chloride and ethylene glycol (DES; 1:4 mol ratio). The DES was stable during the LLE experiments and was used to remove a series of short chain n-alcohols (from C1 to C5) from an aromatic hydrocarbon (toluene) through LLE experiments. The equilibrium data of the studied systems and extraction capacity of the DES for each system was compared and interpreted. The local composition model of the NRTL was correlated with the measured equilibrium data, and the model parameters were regressed. The reliability of the obtained model parameters was confirmed by topological analysis associated with the Gibbs tangent law and stability test. Evaluation of the extraction capacity of the studied systems was carried out through the solute distribution coefficient and selectivity data. The prepared DES lead to different selectivity values for the studied systems. The solute distribution coefficient values were found to be different for the ternary systems containing methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol.