Thermodynamic consistency test for high pressure gas–solid solubility data of binary mixtures using genetic algorithms

A new computer method to test the thermodynamic consistency of incomplete phase equilibrium data in binary mixtures containing a solid solute and a supercritical fluid, is presented. The method is specially designed for treating solubility data that do not cover the whole range of concentration of the components in the mixture. The method is based on the Gibbs–Duhem equation and on the appropriate combination between equations of state, mixing rules and combining rules. The Peng–Robinson equation of state with the Wong–Sandler mixing rules including the van Laar model for the excess Gibbs free energy required in the mixing rules, are used. The model parameters are calculated using genetic algorithms and six gas–solid systems, including 19 isotherms and a total of 362 P–T–y data points were used for the study. The systems studied were binary mixtures containing supercritical carbon dioxide with naphthalene, biphenyl, 2,6-dimethylnaphthalene, phenanthrene, anthracene, and pyrene. The proposed consistency test method can be used with confidence to determine consistency or inconsistency of a set of experimental solubility data of solids in high pressure gases.