Thermodynamics of mixtures with strongly negative deviations from Raoult's Law: Part 4. Application of the DISQUAC model to mixtures of 1-alkanols with primary or secondary linear amines. Comparison with Dortmund UNIFAC and ERAS results

Abstract

Binary mixtures of 1-alkanols with primary or secondary linear amines have been characterized in the framework of DISQUAC. The interaction parameters for the corresponding OH/NH 2 and OH/NH contacts are reported. DISQUAC represents fairly well the thermodynamic properties examined, which are critically evaluated: vapor–liquid equilibria (VLE), molar excess Gibbs energies ( G E) and molar excess enthalpies ( H E). For example, polyazeotropy of the methanol+diethylamine mixture is well reproduced. The methanol+ammonia system can be treated similarly to other 1-alkanols+primary amine systems (i.e., ammonia is assumed, as in a previous work, to be a primary amine without C atoms). The results are discussed in terms of effective dipole moments. The information derived from the concentration–concentration structure factors is briefly analyzed. DISQUAC provides better results than the Dortmund version of UNIFAC using the published geometrical and interaction parameters. Particularly, DISQUAC improves results on G E and for systems containing methanol. DISQUAC results on H E are also compared to those obtained from the ERAS model. For systems containing primary amines, parameters available in literature were used along calculations. In the case of methanol+diethylamine and 1-alkanols+dibutylamine mixtures, new ERAS parameters are reported in this work. The mean standard deviations for H E obtained using DISQUAC and ERAS, are 151 and 216 J mol -1, respectively. DISQUAC also improves results on G E, while ERAS describes properly the available excess volume ( V E) data.