Thermodynamics of mixtures with strongly negative deviations from Raoult'slaw. Part 3. Application of the DISQUAC model to mixtures of triethylaminewith alkanols. Comparison with Dortmund UNIFAC and ERAS results

Binary mixtures of triethylamine (TEA) and alkanols have been investigated in the framework of DISQUAC. The systems are built by three contacts: aliph atic-hydroxyl, aliphatic-nitrogen, and hydroxyl-nitrogen. The corresponding interaction parameters are reported and discussed. The former are avalilab le in the literature but were modified (particularly the third dispersive ( DIS) and quasichemical (QUAC) interchange coefficients) for sec- and tert-a lkanols + n-alkanes using recent data on excess heat capacities at constant pressure (C-P(E)) for systems of these alkanols with n-heptane. The intera ction parameters for aliphatic-nitrogen contacts are purely dispersive. The structure dependence of the DIS and QUAC interchange coefficients of the h ydroxyl-nitrogen contacts in 1-alkanols + TEA systems is similar to that fo und in other solutions previously investigated. The QUAC interchange coeffi cients remain constant from ethanol and are also valid for 2-alkanols and t ert-butanol. Methanol behaves differently. A short discussion in terms of e ffective dipole moments is also included. DISQUAC represents well the therm odynamic properties examined: vapor-liquid equilibria (VLE), molar excess G ibbs energies (G(E)) and molar excess enthalpies (H-E). DISQUAC provides be tter results than the Dortmund version of UNIFAC using the published geomet rical and interaction parameters. ERAS parameters for 1-alkanols + TEA syst ems are also reported. Interactions between unlike molecules are stronger f or solutions with methanol or ethanol. DISQUAC improves ERAS results on H-E , while both models give similar results for G(E). However, ERAS needs an s pecific parameter, with unknown temperature-dependence, to describe properl y G(E). The main advantage of ERAS is its ability to provide information on V-E. Its main limitation is that can be only applied to those systems wher e association is expected. DISQUAC, a purely physical model, can be applied to any type of binary mixture, as it is followed from this and previous st udies.