Vapour–liquid equilibrium of propanoic acid+water at 423.2, 453.2 and 483.2K from 1.87 to 19.38bar. Experimental and modelling with PR, CPA, PC-SAFT and PCP-SAFT

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Colleges, School and Institutes


Vapour–liquid equilibrium data were measured for the propanoic acid + water system at 423.2, 453.2 and 483.2 K from 1.87 to 19.38 bar over the entire range of concentrations. An experimental apparatus based on the static–analytical method with sampling of both phases was used with quantitative analysis by GC. The system is highly non-ideal showing azeotropic behaviour. The Peng–Robinson (PR), the cubic plus association (CPA), the perturbed chain statistical associating fluid theory (PC-SAFT) and the PC-polar-SAFT (PCP-SAFT) equations of state modelled the data. Two association sites were assumed for both compounds. A single–binary interaction parameter (kij ) was used in all models, and predictive (kij=0) and correlative (View the MathML source) capabilities were assessed. Available data at 313.1, 343.2 and 373.1 K from the open literature were included in the analysis. PCP-SAFT presented higher predictive and correlative capabilities over the entire temperature range. PC-SAFT in predictive mode was not able to represent the azeotropic behaviour but resulted in the second best correlations. CPA presented a satisfactory balance between the two modes. PR predictions were rather poor but correlations were better than those of CPA, at the expense of a larger kij.


Original languageEnglish
Pages (from-to)151-159
Number of pages9
JournalFluid Phase Equilibria
Early online date7 Jan 2015
Publication statusPublished - 27 Feb 2015


  • Propanoic acid, Water, Vapour liquid equilibrium, PC-SAFT, CPA, PR