Vapor-liquid equilibria in the propyl acetate + ethanoic acid binary system from (323.15 to 353.15) K: Measurement with a static method and modeling with the NRTL, Wilson, UNIQUAC, and COSMO-SAC approaches

A static total pressure method was employed to determine the vapor pressures of pure propyl ethanoate (propyl acetate), pure ethanoic acid, and the corresponding propyl acetate + ethanoic acid binary system at different feeding compositions over the temperature range (323.15 to 353.15) K. The isothermal vapor-liquid equilibrium (VLE) data of the binary mixture at various temperatures were obtained from classical thermodynamic relations and mass-balance equations. The nonrandom two-liquid (NRTL), Wilson, and universal quasi-chemical (UNIQUAC) models were used to represent the nonideality of the liquid phase, and a modified Peng-Robinson equation of state was used to compute the properties of the vapor phase. The overall average relative deviations between the experimental equilibrium pressures and the NRTL, Wilson, and UNIQUAC models were (0.95, 0.96, and 0.94) %, respectively. The three models gave about the same equilibrium pressures and vapor compositions. A new version of the conductor-like screening model-segment activity coefficient (COSMO-SAC) model was applied to predict the VLE of propyl acetate + ethanoic acid mixtures, and good agreement with the experimental data was obtained.