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Statistical associating fluid theory

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Statistical associating fluid theory (SAFT) is a chemical theory, based on perturbation theory, that uses statistical thermodynamics to explain how complex fluids and fluid mixtures form associations through hydrogen bonds.[1] Widely used in industry and academia, it has become a standard approach for describing complex mixtures.[2][3] Since it was first proposed in 1990, it has evolved a number of variations, including PC-SAFT (perturbed chain-SAFT) for polymer solutions.[2]

Overview

SAFT is essentially an equation of state that describes the thermodynamic and phase equilibrium properties of pure fluids and fluid mixtures using statistical mechanics. It assumes that the Helmholtz free energy includes not just dispersion and repulsion but must also take account of association.[4] SAFT models molecules as chains of hard spheres and works for a wide range of fluids, including supercritical fluids, polymers, liquid crystals, electrolytes, surfactant solutions, and refrigerants.[2]

Development

SAFT evolved from thermodynamic theories, including perturbation theories developed in the 1960s, 1970s, and 1980s by John Barker and Douglas Henderson, Keith Gubbins, and Chris Gray, and, in particular, Michael Wertheim's first-order, thermodynamic perturbation theory outlined in a series of papers in the 1980s.[5]

SAFT was originally proposed in a 1990 paper titled "New reference equation of state for associating liquids" by Walter Chapman, Keith Gubbins, George Jackson, and Maciej Radosz,[6] which, in 2007, was recognized by Industrial and Engineering Chemistry Research as one of the most highly cited papers of the previous three decades.[7] SAFT improved on earlier, over-simplified theories, which were based on hard spherical molecules that don't associate, by focusing on molecular chain length and association.[3]

Variations

Many variations of SAFT have been developed since the 1990s, including PC-SAFT (perturbed chain SAFT),[8] Soft-SAFT (for certain alkenes, alkanes, and alcohols), polar soft-SAFT,[9] SAFT-VR (SAFT variable range, for taking account of molecular polarity),[10] and numerous others.[2]

Alternative models

Alternative equation of state models include the Cubic-Plus-Association (CPA) model, developed in the 1990s by Shell,[11] and non-random-lattice (NLF) models based on lattice field theory.[1]

References

  1. ^ a b Kontogeorgis, Georgios M.; Folas, Georgios K. "The Statistical Associating Fluid Theory (SAFT)". Thermodynamic Models for Industrial Applications. John Wiley & Sons, Ltd. pp. 221–259. doi:10.1002/9780470747537.ch8.
  2. ^ a b c d Economou, Ioannis G. (4 October 2001). "Statistical Associating Fluid Theory:  A Successful Model for the Calculation of Thermodynamic and Phase Equilibrium Properties of Complex Fluid Mixtures". Industrial & Engineering Chemistry Research. 41 (5): 953–962. doi:10.1021/ie0102201. eISSN 1520-5045. ISSN 0888-5885.
  3. ^ a b Huang, Stanley H.; Radosz, Maciej (November 1990). "Equation of state for small, large, polydisperse, and associating molecules". Industrial & Engineering Chemistry Research. 29 (11): 2284–2294. doi:10.1021/ie00107a014. eISSN 1520-5045. ISSN 0888-5885.
  4. ^ Dufal, Simon; Lafitte, Thomas; Haslam, Andrew J.; Galindo, Amparo; Clark, Gary N.I.; Vega, Carlos; Jackson, George (19 May 2015). "The A in SAFT: developing the contribution of association to the Helmholtz free energy within a Wertheim TPT1 treatment of generic Mie fluids". Molecular Physics. 113 (9–10): 948–984. doi:10.1080/00268976.2015.1029027. eISSN 1362-3028. ISSN 0026-8976.
  5. ^ Jiang, Shaoyi; Hall, Carol (24 October 2017). "Preface to the Tribute to Keith E. Gubbins, Pioneer in the Theory of Liquids Special Issue". Langmuir. 33 (42): 11095–11101. doi:10.1021/acs.langmuir.7b03390. eISSN 1520-5827. ISSN 0743-7463. PMID 29061054.
  6. ^ Chapman, Walter G.; Gubbins, Keith E.; Jackson, George; Radosz, Maciej (August 1990). "New reference equation of state for associating liquids". Industrial & Engineering Chemistry Research. 29 (8): 1709–1721. doi:10.1021/IE00104A021. eISSN 1520-5045. ISSN 0888-5885.
  7. ^ "One of the most cited pieces of research gets its due". Imperial College, London. 12 October 2007. Retrieved 3 October 2022.
  8. ^ Gross, J.; Sadowski, G. (2004). "Perturbed-Chain-SAFT". Supercritical Fluids as Solvents and Reaction Media. Elsevier. pp. 295–322. doi:10.1016/B978-044451574-2/50012-2.
  9. ^ Alkhatib, Ismail I. I.; Pereira, Luís M. C.; Torne, Jordi; Vega, Lourdes F. (2020). "Polar soft-SAFT: theory and comparison with molecular simulations and experimental data of pure polar fluids". Physical Chemistry Chemical Physics. 22 (23): 13171–13191. doi:10.1039/d0cp00846j. eISSN 1463-9084. ISSN 1463-9076. PMID 32497165.
  10. ^ McCabe, Clare; Jackson, George (1999). "SAFT-VR modelling of the phase equilibrium of long-chain n-alkanes". Physical Chemistry Chemical Physics. 1 (9): 2057–2064. doi:10.1039/A808085B. eISSN 1463-9084. ISSN 1463-9076.
  11. ^ Kontogeorgis, Georgios M.; Michelsen, Michael L.; Folas, Georgios K.; Derawi, Samer; von Solms, Nicolas; et al. (1 June 2006). "Ten Years with the CPA (Cubic-Plus-Association) Equation of State. Part 1. Pure Compounds and Self-Associating Systems". Industrial & Engineering Chemistry Research. 45 (14): 4855–4868. doi:10.1021/ie051305v. eISSN 1520-5045. ISSN 0888-5885.
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