Temperature independent mixing rules to correlate the solubility of solids in supercritical carbon dioxide

Temperature independent mixing rules in cubic equations of state (EoS) have been used to correlate the solubility of solids in supercritical carbon dioxide. The mixing rules of [Chem. Eng. Sci. 41 (5) (1986) 1303] who proposed a transformation of standard cubic equations of state so that the equations of state constants are really constants, have been evaluated and modified. The modification consists of introducing a volume interaction parameter that affects the solute contribution only as proposed by one of the authors [Ing. Quim. Spain 34 (394) (2002) 380], into the Peng–Robinson equation of state. Literature data for eight binary mixtures containing supercritical carbon dioxide and a solid solute were used for testing the proposed models. The systems studied were binary mixtures containing supercritical carbon dioxide with 2,3-dimethylnaphthalene, 2,6-dimethylnaphthalene, naphthalene, phenanthrene, anthracene, pyrene, benzoic acid and caffeine. The proposed model, in which the equation of state constants and the mixing rules are all temperature independent, correlates the solute concentration in the gas phase similar and better than models that use temperature dependent constants and temperature dependent mixing rules.