Isobaric Vapor–Liquid–Liquid Equilibrium for the 1-Propanol–Propyl Propanoate–Water Ternary System at 80.00 and 101.32 kPa

This work focuses on studying the vapor–liquid–liquid equilibrium (VLLE) of the ternary system 1-propanol–propyl propanoate–water. Experiments were carried out under isobaric conditions at 80.00 and 101.32 kPa by using a Fischer Labodest VLLE 602 equilibrium cell with an ultrasonic probe in the boiling chamber. According to results, the data sets exhibit the presence of binary and ternary heterogeneous azeotropes. Besides, aiming to obtain a unique set of thermodynamic parameters to predict the behavior of the whole system involved in the propyl propanoate synthesis (propionic acid–1-propanol-propyl propanoate–water), the phase equilibria of the quaternary system were also studied. To correlate the set of binary parameters for NRTL-HOC and UNIQUAC-HOC thermodynamic models, literature data on binary and ternary vapor–liquid equilibrium (VLE), liquid–liquid equilibrium (LLE), and VLLE data from this work were used altogether. The obtained results from correlated models depict good agreement with experiments, with average deviations lower than 1.83 K and 3.57% in temperature and molar composition, respectively. The thermodynamic consistency of experimental data was validated by means of the McDermott–Ellis method, the Wisniak method, and topological analysis. The new set of thermodynamic parameters can be used to simultaneously represent the behavior of VLE, LLE, and VLLE in the propyl propanoate production process.