(574f) A Wertheim Activity Coefficient Model for Associating Mixtures
Wertheimâs theory has been incorporated into a number of models as a means of calculating non-ideality due to association. Equations of state (EOS) have traditionally been the approach of choice and models such as SAFT, CPA and ESD have been used to represent a range of industrially important systems. However, the accuracy of an EOS hinges on its ability to simultaneously fit both vapor pressure and excess Gibbs energy data. In contrast, activity coefficient model parameters are fitted only to excess Gibbs and are therefore more favored by industry.
In the present work, an activity coefficient model combining NRTL and Wertheimâs theory is used to model two classes of systems. Class 1 systems, such as alcohols in alkanes, are those in which one component self-associates and the others are âinertâ or inactive in hydrogen bonding. In contrast, class 2 systems involve components that only cross-associate and do not have any hydrogen bonding in their pure states. The proposed model is used to fit binary and ternary liquid-liquid equilibria data and the parameters are evaluated using infrared spectroscopy data.
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