SAFT Associating Fluids and Fluid Mixtures

While we could argue that the goals of modelling fluid phase equilibria have not changed greatly since the time of van der Waals, there is little doubt that the systems of interest have gradually increased in complexity; surfactants, polymers, hydrogen-bonding molecules such as water, and polyfunctional molecules such as amino acids and peptides are now routinely considered. The demand for effective, accurate theoretical tools grows constantly as more complex systems are considered and modelling is expected to play a more prominent role in the design of new products and processes. Thus, the need to develop a thermodynamic modelling framework that considers anisotropic association interactions (such as occur in hydrogen bonding fluids), molecular shape, and electrostatic interactions (Coulombic, dipolar, quadrupolar etc.) becomes increasingly acute. Wertheim’s work in the 1980’s on associating and polymeric fluids and its implementation as an equation of state in the statistical associating fluid theory (SAFT) have constituted a major advancement towards a theoretical framework for modelling these complex fluids.