Wertheim's Association Theory for Phase Equilibrium Modeling in Chemical Engineering Practice

Association and complex formation are the most important contributors to nonidealities in modeling phase equilibria. Models based on Wertheim's association theory are reviewed in the context of current industrial practice, showing great promise in resolving many of the shortcomings of the currently available models. Several pitfalls of common models are highlighted, showing the advantages of association theory. Infinite dilution activity coefficients can provide valuable insights into the liquid phase nonidealities. Trends for various mixture classifications are tabulated and explained simply in terms of "differences in molecular association". The need for a systematic procedure to characterize association parameters is cited as the most important barrier to broader implementation of these models. Improper characterizations can undermine the advantages of association theory, possibly confusing whether it offers any advantage. Resolving these issues will improve traditional small molecule phase equilibrium modeling and many other applications as well.