(53b) Thermodynamic Modeling of Hydrogen-Bonded Mixtures
Several thermodynamic models have been developed that incorporate association either through chemical theory or Wertheimâ??s perturbation theory. While the two approaches differ in the underlying assumptions, the apparent fugacities modeled by both approaches depend on the fraction of molecules that remain nonbonded â?? the â??monomersâ??. The majority of modern association models are equations of state using the Wertheim method, such as SAFT, CPA and ESD. Equations of state association parameters are fitted to macroscopic pure component properties and subsequently used to predict mixture behavior. The model parameters depend on the quality/quantity of pure component data available. An equation of state requires accurate vapor pressure and excess Gibbs energy from the same model. A gamma model requires only the excess Gibbs energy from the mixture model. Activity coefficient (gamma) models have been the favored by industry for many applications (typically low or moderate pressures) because the pure-component vapor pressures are usually known to good accuracy and attention can be focused on the mixture nonideality. However, to date, the Wertheim method has not been widely applied in activity coefficient models.
This project is a collaboration between academic and industrial partners to merge the Wertheim association approach with an activity coefficient model. Microscopic tools including spectroscopy and quantum simulations are used to gain insight into association at the molecular level. The fundamental physical measurements and simulations provide additional insights into the hydrogen bonding.
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