AN IMPROVED METHOD TO PREDICT VLE EQUILIBRIA OF SUBCRITICAL MIXTURES

Previous methods proposed by the author to predict VLE of subcritical aqueous and non-aqueous mixtures are revised. The improvement is linke d to a more accurate evaluation of the polar character of compounds an d to a more articulated subdivision of binary mixtures in various clas ses. For each of them, ''ad hoc'' rules are proposed to calculate the binary parameters of the NRTL equation. The improved accuracy of the m ethod is particularly relevant for the following classes: amines in wa ter, polar/non-polar mixtures, and mixtures with negative deviation fr om Raoult's law. Furthermore, the field of applicability of the method is enlarged to the prediction of liquid/liquid equilibria of hydrocar bon/water systems. For these latter, the relevance of the liquid molar volume ratio of components as a correlating parameter is stressed in the light of the coordination number concept. Rules of assignement to classify binary mixtures are also given. The proposed method is applie d to nearly 200 binary systems which are representative of nearly all the corpus of literature data on subcritical non-reactive mixtures. A comparison with the accuracy of previous methods is also reported.