Optimization of a cubic equation of state and van der Waals mixing rules for modeling the phase behavior of complex mixtures

A thermodynamic modeling for the vapor–liquid equilibrium of binary systems of supercritical fluids and ionic liquids is presented. The van der Waals mixing rules and a cubic equation of state are used to evaluate the fugacity coefficient on the systems. Then, a particle swarm algorithm was used to minimize the difference between calculated and experimental bubble pressure, and calculate the interaction parameters for all systems used. The results show that the bubble pressures were correlated with low deviations between experimental and calculated values. These deviations show that the proposed model is a good technique to optimize the interaction parameters of the phase equilibrium of binary systems containing supercritical fluids and ionic liquids.