Comparison of two association models (Elliott-Suresh-Donohue and simplified PC-SAFT) for complex phase equilibria of hydrocarbon-water and amine-containing mixtures

Two Wertheim-based association models, the simplified PC-SAFT and the Elliott-Suresh-Donohue (ESD) equation of state, are compared in this work for the description of vapor-liquid equilibria (VLE) and liquid-liquid equilibria (LLE) in binary systems of aniline, cyclohexylamine (CHA), hydrocarbons, and water. Furthermore, the predictive capabilities of the models are investigated for four ternary systems composed of these components, which exhibit complex liquid-liquid(-liquid) equilibria (LLLE). Various aspects of association models which have an influence in the results are studied for the PC-SAFT equation of state, e.g., the choice of various association schemes for the amines and parametrization of water as well as different approaches for describing solvation. It is shown that simplified PC-SAFT using water parameters estimated in this work can describe successfully water-alkane LLE. In general, both models perform overall similarly for the binary systems, although ESD shows a remarkably good behavior despite its simplicity and the use of only the two-site scheme for all associating compounds. The prediction of the LLE in the ternary systems water + octane + aniline and water + CHA + aniline is satisfactory whereas larger deviations were obtained for the systems water + octane + CHA and octane + CHA + aniline.