Thermodynamic modeling of complex systems using PC-SAFT

Abstract

This contribution demonstrates the applications of the Perturbed-Chain SAFT (PC-SAFT) equation of state to a number of different systems containing non-polar as well as associating and polar substances including gases, solvents, homopolymers as well as copolymers. It demonstrates the strength and capability of PC-SAFT to model the phase behavior in such complex systems. In contrast to most other SAFT versions, where the hard-sphere fluid is assumed as a reference system for the attractive (dispersive) interactions, PC-SAFT considers the hard-chain fluid as reference for the perturbation theory. The molecular model can be refined by individually accounting for association (hydrogen bonding) and polar interactions (dipolar and quadrupolar). Three pure-component parameters are required for non-polar and non-associating compounds, two further parameters characterize the association contribution and one additional parameter is needed to account for polar interactions as well as the dipole or quadrupole moment of the molecule, respectively. Copolymers or polymers with short-chain branching can be described by allowing the chain segments to differ in size and in attractive forces. The modeling of copolymers can conveniently be performed using only the pure-component parameters of the appropriate homopolymers and one additional interaction parameter correcting the dispersive interactions between the unlike copolymer segments. Using a temperature-independent interaction parameter kij for each binary system only, PC-SAFT gives convincing modeling results of the phase behavior over wide ranges of conditions which confirms the strong predictive capabilities of the model and allows for save correlations as well as extrapolations.