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

Abstract

Phase equilibrium data of CO 2 1 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, CO 2 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 vaporliquid behavior for CO 2 1 polymer systems is better predicted by the PC-SAFT model than by LGT and PR models.

Predicting the Phase Behavior of Polymer Systems with the GC-SAFT-VR Approach

“…Several versions of the SAFT equation of state (EOS) have been applied to describe the phase behavior of polymer − and copolymer systems. − In particular, Huang and Radosz proposed an engineering version of the original SAFT EOS (HR-SAFT) , that has been applied to a wide range of polymers and, in particular, polyolefin systems. − , More recently, Sadowski et al , developed the perturbed-chain SAFT (PC-SAFT) equation which has been shown to provide excellent results in the description of VLE and LLE for a wide range of polymer systems. − ,,− ,, At a similar level of theory, the SAFT-VR approach proposed by Gil-Villegas et al , has been successfully applied to study the phase behavior of a wide range of systems, − …”

“…[11][12][13]45 More recently, Sadowski et al 46,47 developed the perturbed-chain SAFT (PC-SAFT) equation which has been shown to provide excellent results in the description of VLE and LLE for a wide range of polymer systems. [16][17][18][19][20][21]26,[28][29][30][31]42,48 At a similar level of theory, the SAFT-VR approach proposed by Gil-Villegas et al 49,50 has been successfully applied to study the phase behavior of a wide range of systems, including the absorption of light hydrocarbons in polyethylene 22,24,83 and the cloud-point curves of polyethylene solutions. 23 One of the issues when modeling polymer systems is characterizing branching (i.e., side chains on the backbone) and heterogeneity (e.g., functional groups of different molecular composition) in the polymer structure.…”

A Novel Theory for Predicting Critical Constants and the α Function for Pure Polymers

“…Ji estimated the parameters from the experimental PVT data of polymer melts. Arce et al and Arce and Aznar obtained the pure polymer parameters a and b for the CEoS by fitting available pure liquid PVT data and assuming that parameters a /MW and b /MW are independent of MW. Arce’s methodology is the same as that of Louli and Tassios .…”