An analytical pressure–temperature–composition correlation for the VLE of CO2 binary mixtures

An analytical expression relating the vapour–liquid equilibrium pressure, temperature and composition of binary mixtures formed by CO2 and a non-polar fluid is proposed. The model is based on a simple analytical expression for the vapour pressure of pure non-polar fluids which, for a given temperature, only requires as input the Lennard-Jones molecular parameters and the acentric factor values. A properly modified Lorentz–Berthelot mixing rule is used, the interaction parameters being given as simple functions of temperature and composition with eight constants for each binary mixture. The model is shown to reproduce accurately and in a simple way the pressure (for a given liquid mole fraction) or the liquid composition (for a given pressure) of nine CO2+hydrocarbon systems at different temperatures.