The Group Contribution Concept:  A Useful Tool To Correlate Binary Systems and To Predict the Phase Behavior of Multicomponent Systems Involving Supercritical CO₂ and Fatty Acids

Abstract

In this paper, a purely predictive model for the phase equilibria computation of mixtures involving fatty acids (FA) and supercritical carbon dioxide (SC-CO2) is proposed. In a first step, the phase equilibria modeling of FA/CO2 binary systems were performed using the Peng−Robinson equation of state. To obtain a purely predictive model, the group contribution method developed by Abdoul et al. which allows the prediction of the binary interaction parameters (k ij ) was extended to FA compounds. In a second step, the proposed model was used to predict the phase equilibria data of ternary and quaternary systems found in the literature. In a last step, bubble-point and dew-point pressures of systems involving CO2 and multicomponent mixtures of FA were measured in our laboratory, and the previous model was used in order to check its capability in predicting these data.

Relationship between the binary interaction parameters (kij) of the Peng–Robinson and those of the Soave–Redlich–Kwong equations of state: Application to the definition of the PR2SRK model

“…As recently shown [11], such a model is perfectly able to predict the behavior of petroleum fluids. A GCM has been chosen to estimate the BIPs because we were aware that the group contribution concept could be useful to model complex processes like those involving supercritical fluids [25][26][27] and because the number of binary systems for which phase equilibrium data are available is at most several thousands while the number of the compounds used now by industry is estimated at around 100,000. …”

Predicting the phase equilibria of synthetic petroleum fluids with the PPR78 approach

“…A cubic EoS has been chosen because in process design, due to their low complexity and their high accuracy for nonpolar compounds, such EoS allow for fast screening of a large number of design alternatives and preselection of the most favorable candidate structures. A GCM has been chosen to estimate the binary interaction parameters because we were aware that the group contribution concept could be useful to model complex processes like those involving supercritical fluids [15][16][17] and because the number of binary systems for which phase equilibrium data are available is at most several thousands while the number of the compounds used now by industry is estimated at around 100,000. It is thus necessary to be able to predict the binary interactions from the mere knowledge of the molecular structure.…”

High-pressure phase behaviour of the binary system {CO2+cis-decalin} from (292.75 to 373.75)K

“…Moreover, reliable experimental data are needed for the development of predictive thermodynamic models [10][11][12][13], to compare equation of state (EOS) or to fit model parameters. For example, to build a group contribution method (GCM), many phase equilibrium data are needed for the adjustment of group interaction parameters.…”