Multiphase multicomponent equilibria for mixtures containing polymers by the perturbation theory

The correlating and predictive capabilities of a thermodynamic model based on the perturbation theory are investigated, with reference to mixtures con taining components of different size and molecular interactions. The simpli fied Perturbed-Hard-Sphere-Chain (PHSC) equation of state is applied to a s eries of pure polymers, a number of solvents and pure carbon dioxide, and b oth volumetric and equilibrium properties are considered. The ability: of t he proposed model to reproduce experimental phase equilibrium data is discu ssed and tested with reference to binary and multicomponent mixtures, in th e presence of vapor-liquid, liquid-liquid and vapor-liquid-liquid equilibri a. Attention is focused on the ternary system polystyrene-cyclohexane-carbo n dioxide, to test the proposed thermodynamic model in view of simulating s upercritical antisolvent-induced fractionation processes. It is shown that the PHSC equation of state can be reliably used for calculating the phase b ehavior of such a complex system in different conditions. (C) 2000 Elsevier Science Ltd. All rights reserved.