A correlation method for isobaric vapor–liquid and vapor–liquid–liquid equilibria data of binary systems

A correlation method for isobaric vapor–liquid equilibria (VLE) and vapor–liquid–liquid equilibria (VLLE) of binary systems was proposed. Taking the coordination number in UNIQUAC model as a fitting parameter (three-parameter UNIQUAC model) and employing an objective function of relative difference between the experimental and the predicted temperatures of VLE data, the experimental VLLE data were fairly reproduced both for water + 1-butanol and 2-butanol + water systems. Especially for 2-butanol + water system, the calculated homogeneous azeotropic point was also in good agreement, which could not be obtained by the conventional procedure. The proposed method was also validated by several examples.