Differential scanning calorimetry determination of Solid−Liquid equilibria phase diagrams for binary monocarboxylic acids solutions

Abstract

In this work, solid−liquid equilibria of the binary monocarboxylic acid mixtures: formic acid + acetic acid, formic acid + propionic acid, formic acid + butyric acid, formic acid + pentanoic acid, acetic acid + propionic acid, acetic acid + butyric acid, acetic acid + pentanoic acid, propionic acid + butyric acid, propionic acid + pentanoic acid and butyric acid + pentanoic acid have been measured by the differential scanning calorimetry (DSC) method at atmospheric pressure. The experimental results indicated that all the binary systems present a eutectic point in their respective phase diagrams, which were obtained experimentally. Solvent activities have also been determined from the freezing point depression of the monocarboxylic acids. Furthermore, the activity coefficients of two components in the liquid phase have been satisfactorily correlated by the Wilson and nonrandom two-liquid (NRTL) models. The results show that for all ten binary mixtures, the best correlations of the solid–liquid equilibrium data were obtained when employing the NRTL model. Finally, the results obtained have been discussed based on the interactions that exist in these solutions.