Fluid Phase Equilibria, Vol.194, 579-586, 2002
Equation of state based on the thermodynamic perturbation theory of sequential polymerization for associating molecules and polymers
Recently, we developed new equations of state for the freely jointed hard sphere chain fluids, which are based on the thermodynamic perturbation theory (TPT) of sequential polymerization. The equations of state use the contact values of the radial distribution function (RDF) for monomer-dimer mixtures, which is derived from the multidensity Ornstein-Zernike (MOZ) theory. In this work, we extend one of these equations of state to real fluids such as hydrocarbons. alkanols and polymers. In order to calculate the phase equilibrium proper-ties of real fluids, a dispersion contribution is added to the repulsive hard chain reference term. We also use the dispersion term that is a power series initially fitted by Alder et al. for square-well fluid. The universal constants that are included in the dispersion term are revised to accurate PVT for ethane. The vapor pressures and the coexisting densities of several real fluids are calculated with the new equation. We find a good agreement between the predictions of the model and experimental data.
Keywords:perturbation theory;hard sphere chain fluid;SAFT;integral equation theory;equation of state