Liquid−Liquid Equilibria for the Quaternary System Water + Methyl tert-Butyl Ether + Benzene + Cyclohexane and Its Constituent Partially Miscible Ternary Systems at 303.15 K

Tie-line data for the water, methyl tert-butyl ether, and cyclohexane [w 1H2O + w 2C5H12O + (1 − w 1 − w2)C6H12] and water, methyl tert-butyl ether, and benzene [w 1H2O + w 2C5H12O + (1 − w 1 − w 2)C6H6] ternary systems (where w is the mass fraction) were investigated at a temperature of T = 303.15 K. A quaternary system containing these four compounds [w 1H2O + w 2C5H12O + w 3C6H6 + (1 − w 1 − w 2 − w 3)C6H12] was also studied at the same temperature. Data for the other partially miscible ternary system [w 1H2O + w 3C6H6 + (1 − w 1 − w 3)C6H12] were taken from the literature, whereas the fourth ternary system [w 2C5H12O + w 3C6H6 + (1 − w 2 − w 3)C6H12] was completely miscible. The mutual hydrocarbon−water solubility with the addition of methyl tert-butyl ether was investigated. The equilibrium data of the three ternary systems (including that taken from the literature) were used to determine interaction parameters for the UNIQUAC and NRTL equations. The UNIQUAC parameters were then averaged to predict equilibrium data for the quaternary system using this model. The liquid−liquid equilibrium (LLE) were also predicted with the UNIFAC group contribution method. The UNIQUAC equation seems to be more accurate than the other methods both for the ternary systems and the quaternary system, as can be observed from the values of both residuals. However, its predicted distribution coefficients have high deviation percentages. On the other hand, the solubility curves are well-correlated by the UNIQUAC and NRTL equations for these ternary systems.