Industrial & Engineering Chemistry Research, Vol.37, No.4, 1567-1573, 1998
Polymer-solvent vapor-liquid equilibrium : Equations of state versus activity coefficient models
A Soave-Redlich-Kwong (SRK) cubic equation of state (EOS) combined with the Flory-Huggins activity coefficient (G(ex)) model in a Huron-Vidal type (EOS + G(ex)) mixing rule was used to correlate binary vapor-liquid equilibrium (VLE) of polymer-solvent mixtures. To extend the SRK EOS to pure polymers, suitable critical constants were selected based on available information for long-chain hydrocarbons. In mixture applications, the only binary interaction parameter, chi of the Flory-Huggins model, was obtained from the infinite-dilution activity coefficient data of solvent in polymer, without using any experimental VLE information. The results show that this EOS + G(ex) approach can represent polymer-solvent VLE accurately. It was also observed that chi is much less temperature-and composition-dependent when the Flory-Huggins model is coupled with the SRK EOS than it is when used directly as an activity coefficient model.