Measurement and modeling of osmotic coefficients of binary mixtures (alcohol + 1,3-dimethylpyridinium methylsulfate) at T = 323.15 K

Measurement of osmotic coefficients of binary mixtures containing several primary and secondary alcohols (1-propanol, 2-propanol, 1-butanol, 2-butanol, and 1-pentanol) and the pyridinium-based ionic liquid 1,3-dimethylpyridinium methylsulfate were performed at T = 323.15 K using the vapor pressure osmometry technique, and from experimental data, vapor pressure, and activity coefficients were determined. The extended Pitzer model modified by Archer, and the NRTL model modified by Jaretun and Aly (MNRTL) were used to correlate the experimental osmotic coefficients, obtaining standard deviations lower than 0.017 and 0.054, respectively. From the parameters obtained with the extended Pitzer model modified by Archer, the mean molal activity coefficients and the excess Gibbs free energy for the studied binary mixtures were calculated. The effect of the cation is studied comparing the experimental results with those obtained for the ionic liquid 1,3-dimethylimidazolium methylsulfate.

Research highlights
► The osmotic coefficients of binary mixtures (alcohol + ionic liquid) were determined.
► The measurements were carried out with a vapor pressure osmometer at 323.15 K.
► The Pitzer–Archer, and the MNRTL models were used to correlate the experimental data.
► Mean molal activity coefficients and excess Gibbs free energies were calculated.