A modified SAFT equation of state is developed by applying the perturbation theory of Barker and Henderson to a hard-chain reference fluid. With conventional one-fluid mixing rules, the equation of state is applicable to mixtures of small spherical molecules such as gases, nonspherical solvents, and chainlike polymers. The three pure-component parameters required for nonassociating molecules were identified for 78 substances by correlating vapor pressures and liquid volumes. The equation of state gives good fits to these properties and agrees well with caloric properties. When applied to vapor-liquid equilibria of mixtures, the equation of state shows substantial predictive capabilities and good precision for correlating mixtures. Comparisons to the SAFT version of Huang and Radosz reveal a clear improvement of the proposed model. A brief comparison with the Peng-Robinson model is also given for vapor-liquid equilibria of binary systems, confirming the good performance of the suggested equation of state. The applicability of the proposed model to polymer systems was demonstrated for high-pressure liquid-liquid equilibria of a polyethylene mixture. The pure-component parameters of polyethylene were obtained by extrapolating pure-component parameters of the n-alkane series to high molecular weights.
The perturbed-chain SAFT (PC-SAFT) equation of state is applied to pure associating components as well as to vapor-liquid and liquid-liquid equilibria of binary mixtures of associating substances. For these substances, the PC-SAFT equation of state requires five purecomponent parameters, two of which characterize the association. The pure-component parameters were identified for 18 associating substances by correlating vapor pressure and liquid density data. A comparison to an earlier version of SAFT confirms the good results for pure substances. When only one associating compound is present in a mixture, the PC-SAFT equation of state does not require mixing rules for the association term. Using one binary interaction parameter k ij for the dispersion term only, the model was applied to azeotropic and nonazeotropic vapor-liquid equilibria at low and at high pressures, as well as to liquid-liquid equilibria. Simple mixing and combining rules were adopted for mixtures with more than one associating compound, introducing no additional binary interaction parameter. The simultaneous description of liquidliquid and vapor-liquid equilibrium was also possible with a single k ij parameter.
The perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state is applied to binary and ternary mixtures of polymers, solvents, and gases. The three pure-component parameters required for nonassociating molecules were identified for six polymer compounds. The phase equilibrium of polymer systems, which often involves high-pressure liquid-liquid mixtures as well as vapor-liquid mixtures at lower pressures, was investigated. Using a constant binary interaction parameter (k ij ), the PC-SAFT equation of state gives good correlations of the appropriate phase behavior over wide ranges of conditions. Comparisons to an earlier version of SAFT reveal an improvement of the proposed model.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.