Phase-equilibria calculation by group-contribution perturbed-hard-sphere-chain equation of state

A group-contribution (GC) method was coupled with the perturbed-hard-sphere-chain (PHSC) equation of state (EOS) to predict its characteristic parameters. This model can describe both equilibrium and volumetric properties of regular fluids and chain-like molecules. The estimation of group contributions for the characteristic volume, surface area, and interaction energy was based only, on vapor-pressure and saturated liquid-density values of low-molecular-weight compounds. It was successful in estimating the EOS parameters of high-molecular-weight compounds and chain-like molecules. Some application results show its reliability but the method was not applied to all classes of compounds. Good estimation of polymer density was obtained by GC PHSC with only the knowledge of their molecular structure. For mixtures, the original model was retained; binary interaction parameters were regressed from vapor-liquid equilibria of binary systems. In most cases, only one binary interaction parameter is enough to describe binary systems in a wide range of temperatures. The same model is extended to the calculation of liquid-liquid equilibria of a system exhibiting both upper critical solution temperature (UCST) and lower critical solution temperature (LCST). In summary, the data required for calculating multicomponent phase equilibria are the molecular structure in term of functional groups and binary interaction parameter values.