Multiphase equilibria modeling with GCA-EOS. Part III: CO2 with the homologous series of carboxylic acids

Abstract

Knowledge of phase equilibria and critical properties of CO2 + carboxylic acid systems is essential for supercritical fluid extraction (SCFE) processes, such as oil deacidification. However, modeling these systems is challenging due to their highly asymmetrical behavior. In this study, we apply the Group Contribution with Association Equation of State (GCA-EOS) to model vapor−liquid and liquid−liquid equilibria of the homologous series of CO2 + carboxylic acids. The GCA-EOS, previously validated for alkanes and alcohols, is extended to cover short and long-chain carboxylic acids. Using a single set of parameters, we validate the model against experimental data for C2−C20 acids, temperatures from 293 K to 473 K, and pressures up to 400 bar. The model successfully predicts phase equilibria across the entire homologous series, making it a reliable tool for assessing the multiphase behavior of these systems in SCFE applications.