Quaternary Liquid–Liquid Equilibria Measurements and NRTL Modeling for the (Water + Cyclohexane + Ethanol + 1-Propanol) System at 298.2 K to 328.2 K

Quaternary liquid–liquid equilibrium (LLE) data of the {water + cyclohexane + ethanol + 1-propanol} system are presented for the temperature range of 298.2 to 328.2 K at 0.1 MPa. The data were measured at four ethanol:1-propanol ratios and approximately equal aqueous-to-organic phase volumes. The data illustrate the influence of temperature and the presence of a second alcohol on the phase behavior. An evolutionary behavior between the two respective {water + entrainer + alcohol} systems in terms of the size of the heterogeneous region and the total alcohol distribution between the aqueous and organic phases was observed. The less polar 1-propanol molecules increased the recovery of the more polar, smaller ethanol molecules into the organic phase. Conversely, ethanol increased the recovery of 1-propanol into the aqueous phase. Therefore, the interaction between the ethanol and 1-propanol molecules has a significant effect on the phase behavior of the alcohols in the quaternary system. The nonrandom two-liquid activity coefficient model parameters were fitted to the ternary LLE data and used to predict the measured quaternary system LLE phase behavior. The fitted model could accurately describe the ternary LLE phase behavior but struggled to quantitatively describe the LLE phase behavior of the quaternary system.