Multiphase Equilibria Modeling with GCA-EoS. Part II: Carbon Dioxide with the Homologous Series of Alcohols

Abstract

Modeling multiphase equilibria of mixtures comprising carbon dioxide (CO2) and organic compounds is a challenge for any equation of state. CO2 shows a highly nonideal phase behavior with most organic compounds, which is even more pronounced with hydrogen-bonding compounds. In this work, we have extended the Group-Contribution with Association equation of state (GCA−EOS) to represent vapor−liquid, liquid−liquid, and vapor−liquid−liquid equilibria of CO2 mixtures with primary alcohols. The final set of parameters has been challenged against an experimental database covering C1−C16 primary alcohols, temperatures from 230 to 573 K, and pressures up to 400 bar. Particular attention has been given to describe the critical curves for each binary system correctly, which means attaining the phase equilibria transformation of the CO2 + 1-alcohol homologous series as the alcohol alkyl chain length increases. This parametrization strategy allows reducing the risk of incorrect liquid−liquid split predictions. In addition, using a single set of parameters, fitted to binary data of CO2 with normal alcohols, the model is able to predict the phase behavior of binary mixtures not included in the parametrization procedure, comprising normal and branched alcohols. The GCA-EOS predicts properly the overall phase behavior, that is, the binary critical curves, without losing accuracy in the prediction of saturation points.