(591f) Predicting the Phase Behavior of Fluids with Multiple Polar Groups Using the GC-SAFT-VR Equation of State

Gaurav Das,¹ Jessica D. Haley¹, and Clare McCabe^1,2

¹Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN

²Department of Chemistry, Vanderbilt University, Nashville, TN

The statistical associating fluid theory¹ is a popular molecular-based equation of state (EOS) that has been successfully applied to predict the thermodynamics and phase behavior of a wide range of fluid systems. In recent developments, group contribution approaches have been combined with the SAFT equation in order to develop more predictive models.  The GC-SAFT-VR^2,3 equation is one such approach, based on the SAFT-VR equation in which attractive interactions are described through a potential of variable range (VR).  The GC-SAFT-VR EOS models chains composed of segments of different size and/or energy of interaction at both the monomer and chain levels of theory, thus molecules are described by heterosegmented chains in which each type of segment represents a functional group present in the molecule. Parameters for key functional groups (such as CH₃, CH₂, CH, CH₂=CH, C=O, C₆H₅, ether and ester, OH, NH₂, CH=O, COOH) have been obtained by fitting to experimental vapor pressure and saturated liquid density data and their transferability tested by comparing the theoretical predictions with experimental data for pure fluids and binary mixtures not included in the fitting process, as well as by studying the VLE and LLE of small molecules in polymer systems.^4,5-7 In general the GC-SAFT-VR approach is found to predict the phase behavior of the systems studied in excellent agreement with experimental data without adjusting the group parameters to binary mixture data; however deviations were seen for some of the polymer systems studied which contained multiple polar groups. Here we incorporate an explicit dipolar term into the GC-SAFT-VR EOS following the work of Zhao and McCabe.  The new equation is tested through the study of fluorinated ether (HFE’s) molecules and their mixtures with alcohols, ethers, and ketones.

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