Comparative Study of Liquid–Liquid Phase Equilibria of the Type II Systems Water + Carboxylic Acids (C5 and C6) + Acetate Esters: Measurement and Correlation

A study on the type 2 liquid–liquid equilibrium (LLE) behavior of the water + valeric or caproic acids + acetate esters (n-propyl, isopropyl, n-amyl, and n-hexyl acetates) ternary systems was performed at T = 298.2 K and p = 101.3 kPa. Solubility and tie-line data were experimentally determined using cloud point and HPLC methods, respectively. The results were validated through acid–base and Karl Fischer titration methods. For these systems, the thermodynamic models of NRTL and UNIQUAC were successfully applied to fit the experimental tie-lines and the values of the binary interaction parameters were obtained. Evaluation of the capacity of each solvent was performed using the calculation of distribution coefficients and separation factors. The influence of extraction temperature and the type of the esteric solvent on the immiscibility region was found to be minor. As a result, all the chosen acetate esters have relatively high separation factors and are suitable separating agents for aqueous valeric or caproic acid mixtures.