An improved method for predicting the vapor—liquid equilibria of subcritical mixtures

Abstract

A simple modification of a previous method for calculating the vapor—liquid equilibria of mixtures of subcritical compounds is proposed. The improvement mainly consists of the use of an ad hoc value of the constant m in the Vetere equation of state (EOS) for each family of mixtures considered instead of a fixed value of equal to 2.4. Better results with respect to the previous work are obtained for the following classes of mixtures: aqueous soluble mixtures, aqueous mixtures with a miscibility gap, polar—polar mixtures, polar—non-polar mixtures, mixtures which exhibit a negative deviation from Raoult's law, and nearly ideal mixtures. For the remaining case, i.e. non-aqueous mixtures with a miscibility gap, the improvement is negligible. The possibility of introducing a binary interaction value for the entropy part of the Vetere EOS, instead of assuming a nil value for this quantity, is also considered.