Comments on the correlation of vapor-liquid equilibrium (VLE) data in azeotropic ternary systems

The analysis has been carried out of the possible theoretical types of ternary systems regarding the distillation boundaries, for systems involving up to three binary azeotropes and one ternary azeotrope. The study reveals that there are some of these theoretical behaviors that classical activity coefficient models such as NRTL cannot predict. The objective of the present work is to show these limitations, analyze their causes and suggest possible solutions. The addition of one ternary interaction term to the Gibbs energy of excess function removes many of the limitations of classical models expanding the number and type of systems that could be correlated with the models and, what is more important, markedly improving the correlation capability of the model.