Thermodynamic study on binary mixtures of propyl ethanoate and an alkan-1-ol (C2–C4). Isobaric vapor–liquid equilibria and excess properties

This paper presents an analysis on binary mixtures of propyl ethanoate and an alkan-1-ol (ethanol to butanol) using the results obtained for different thermodynamic quantities such as the isobaric vapor–liquid equilibrium (VLE) data at pressures of 101.3 kPa and 160.0 kPa, excess enthalpies and excess volumes. Vapor pressures for the same normal alkanols used, determined using the same equilibrium still, are also presented. The three mixtures present expansive and endothermic effects during the mixing process. All investigated mixtures show positive deviations from ideality. For two mixtures, azeotropes are found: for propyl ethanoate+ethanol, xaz=0.078, Taz=351.02 K at p=101.3 kPa, while xaz=0.041, Taz=363.14 K at p=160.0 kPa; for propyl ethanoate+propan-1-ol, xaz=0.387, Taz=367.63 K at p=101.3 kPa, while xaz=0.313, Taz=381.02 K at p=160.0 kPa. Correlations of the activity coefficients, reduced excess Gibbs energy, and mixing enthalpy using a new equation containing temperature-dependent coefficients were good for all three binary mixtures. The ASOG and Nitta et al. models yielded the best prediction of equilibrium properties for the mixtures containing ethanol while one of the modified versions of UNIFAC model gave the best predictions of equilibrium properties for the remaining binary systems. Using the same set of parameters the UNIFAC and Nitta et al. models also yielded acceptable estimates of the excess enthalpies for the same mixtures.