Fluid phase behavior modeling of CO2 + molten polymer systems using cubic and theoretically based equations of state

Abstract

Phase equilibrium data of CO2 + molten polymer systems are of great relevance for chemical engineers because these are necessary for the optimal design of polymer final-treatment processes. This kind of processes needs information about gas solubilities in polymers at several temperatures and pressures. In this work, CO2 solubilities in molten polymers were modeled by the perturbed chain-statistical associating fluid theory (PC-SAFT) equation of state (EoS). For comparison, the solubilities were also calculated by the lattice gas theory (LGT) EoS, and by the well-known Peng-Robinson (PR) cubic EoS. To adjust the interactions between segments of mixtures, there were used classical mixing rules, with one adjustable temperature-dependent binary parameter for the PC-SAFT and PR EoS, and two adjustable binary parameters for the LGT EoS. The results were compared with experimental data obtained from literature. The results in terms of solubility pressure deviations indicate that the vapor–liquid behavior for CO2 + polymer systems is better predicted by the PC-SAFT model than by LGT and PR models.