Prediction of Vapor-Liquid Equilibria in Binary System

Abstract

Previously the authors derived the theoretical equations (1) and (2) for the vapor-liquid equilibria in a binary system by introducing the factor a into the equations proposed by Guggenheim and McGlashan. It was also shown that the calculated activities (P/P0) and the experimental values are in good agreement if suitable values are given to the two parameters α and η in those equations.A method of predicting the vapor-liquid equilibria in a binary system, which does not require the knowledge of binary systems, is developed here by employing Equations (1) and (2). Many parameters are determined from the experimental values obtained from various binary systems at constant temperature, and the values of wAAB/zkT and wABB/zkT (generally by expressed as wXXY/zkT) are evaluated from the parameters by employing Equations (6) and (7). The values of wXXY/zkT are classified according to the type of the component X in the triplet XXY, and plotted against component Y as shown in Fig.1. Fig.2 is formed by collecting the straight lines of Fig.1. The parameters α and η can be predicted from Fig.2 by means of the method illustrated in Fig.3 and Equation (11).As the parameters α and η have been predicted, activities (P/P0) can be obtained from Equations (1) and (2), and the vapor-liquid equilibria at constant temperature can be predicted. If the parameters α and η are assumed to be independent of temperature, the vapor-liquid equilibria at constant pressure can also be predicted by the trial and error method. The predicted results are compared with experimental values in Fig.5-8. Both are in fairly good agreement and it is seen that the vapor-liquid equilibria in a binary system can be predicted by the method given in this paper without recourse to experimental data.