Making Equation of State Models Predictive−Part 3: Improved Treatment of Multipolar Interactions in a PC-SAFT Based Equation of State

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Recent investigations have demonstrated the merit of quantum mechanically determined molecular parameters and new combination rules in equation of state (EOS) models. In this paper we study several perturbation theory models for application in a predictive EOS. Two models have been compared, namely, the perturbation theory with a spherical reference and an approach where the free energy has been fitted directly to molecular simulation results of certain polar fluids. We apply both methods without adjustable binary parameters. A comparison with experimental phase equilibirum data reveals that both models have strengths and weaknesses. This insight leads to an improved perturbation theory based EOS model that performes better than the two preceding ones and is likely to lend itself to further improvements in the future.