Phase equilibria calculation of binary and ternary mixtures of associating fluids applying PC-SAFT equation of state

Abstract

Using the PC-SAFT equation of state to the correlation and prediction of the phase equilibria of associating systems, the vapor–liquid, the liquid–liquid and the vapor–liquid–liquid equilibria of binary and ternary mixtures were investigated. In this equation of state five pure-component parameters are required for each associating substance, two of which characterize the association interactions. Pure-component parameters for 23 self-associating and 6 non-associating substances are identified by correlating vapor pressure and liquid density data. A comparison of calculated values to literature data shows a good agreement for pure fluids. Binary systems with two self-associating compounds and others with one self-associating component and another non-self associating but can have cross-associating interactions with the first component are investigated. Binary parameters correcting the cross-dispersive interactions, kij, and the cross-associating interactions, υij and λij, are fitted to the phase equilibrium data. In addition, when a simple non-self associating pure fluid is a part of a binary system and can have cross-associating interactions with the other component, its association fictive volume and energy are regressed simultaneously with the binary interaction parameters to the phase equilibrium data. The found results have shown that the PC-SAFT equation of state demonstrates high potential of correlation and prediction of vapor–liquid, liquid–liquid and vapor–liquid–liquid phase equilibria of 38 binary systems of associating fluids. The same observations are made for the phase behavior prediction of 22 ternary mixtures of associating fluids. The PC-SAFT equation of state with its theoretical base represents a great tool for modeling and prediction of phase equilibria and thermodynamic properties of mixtures of associating fluids.