(262al) SAFT-Q: A Transferable Parameter Quartic Equation of State Version of the Statistical Associating Fluid Theory for Pure Fluids and Mixtures

Compressibility factor contributions for segment repulsion, covalent bonding, dispersion and association from the early Huang-Radosz (HR) version of the statistical associating fluid theory (SAFT) equation of state [1] are recast in a series of simple terms in packing fraction that results in an overall â??quarticâ? in molar volume equation of state. The pure fluid version of this new model contains two universal parameters in the athermal-plus-covalent bonding EOS backbone [2], three dispersion parameters that are directly predictable (transferable) from the SAFT-HR segment number and segment energy and three pseudo-association strengths that are also directly predictable (transferable) from the SAFT-HR segment number and energy and the association energy and volume. Theoretically-based mixing rules for the dispersion and association parameters are derived. Results are given for representative substances including single-segment, long-chain non-associating and associating pure fluids. Liquid density, vapor pressure and coexistence curve predictions using the new SAFT-Q EOS with parameters transferred from SAFT-HR are compared with predictions from the conventional SAFT-HR model on which it is based. Vapor-liquid equilibria are predicted for binary systems containing self-associating with non-associating components and with cross-associating components. Extension of the model/approach to other SAFT versions (e.g., soft-SAFT, PC-SAFT and SAFT-VR) is briefly discussed.

REFERENCES

[1] Huang, S. H. and M. Radosz, Equation of State for Small, Large, Polydisperse, and Associating Molecules, Ind. Eng. Chem. Res. 29, 2284-2294 (1990).

[2] Gow, A. S., S. Alkhaldi and S. Demir, Cubic and Quartic Hard-Sphere and Lennard-Jones Chain Equations of State as Foundations for Complex Fluid Modeling, Fluid Phase Equilibria 399, 1-15 (2015).