Modeling of the separation of polydisperse polymer systems by compressed gases

Phase equilibria in systems with monodisperse and polydisperse polystyrene, cyclohexane and carbon dioxide have been investigated. Calculations of clo ud-point curves as well as molecular weight distributions of the polymer in the coexisting phases have been carried out for CO2 concentrations of up t o 22.4 wt.%, temperatures up to 250 degrees C and pressures up to 150 bar. The SAFT equation of state was used within a multicomponent flash algorithm which incorporates the concept of pseudocomponents. A direct comparison of experiment and calculation shows the performance of SAFT for calculations of molecular-weight fractionation in complex systems. (C) 1999 Elsevier Sci ence B.V. All rights reserved.