Prediction of vapor-liquid equilibria and thermodynamic properties for a quinary hydrocarbon system from optimized binary data using the kohler method

Abstract

For organic systems, the models usually used to predict thermodynamic properties of multicomponent liquid solutions from data for binary sub-systems (Wilson, NRTL, UNIQUAC) suffer from the drawback that the binary data must be fitted to a specific Gibbs energy equation of fixed functional form with a limited number of adjustable parameters. Furthermore, these models do not permit all binary data to be optimized simultaneously. The “CALPHAD approach” of simultaneous optimization of binary data to general polynomial expansions followed by the prediction of multicomponent properties with the Kohler (or Muggianu) equation, yields superior results. An example of an optimization of a binary system is presented for the hexane + benzene system. The Kohler equation is then used to calculate phase equilibria in the quinary hexane + benzene + toluene + methylcyclopentane + cyclohexane system and the results are compared with published experimental data.