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Twelve new ternary high-pressure bubble- and dew-point data sets for (n-carboxylic acid + n-alkane), (methyl ester + n-alkane), and (methyl ester + n-carboxylic acid) mixtures in carbon dioxide (CO2) are presented in this study. For these mixtures, (C8 and C10) n-carboxylic acids, (C12 and C14) methyl esters, and (C12 and C14) n-alkanes are considered. A liquid–liquid or liquid–liquid–vapor phase equilibria region was observed in the low solute fraction region for the 50 wt % n-tetradecane +50 wt % methyl myristate system, similar to the phase behavior observed for the CO2 + n-tetradecane binary which exhibits type III phase behavior. Additionally, both the n-alkane + (n-carboxylic acid or methyl ester) groups showed indications of enhanced mixture solubility in comparison to the comprising binaries, with the n-tetradecane + n-octanoic acid and n-tetradecane + methyl myristate mixtures presenting cosolvency at the experimental conditions considered. This is indicative of significant solute + solute interactions within these systems. In contrast the phase behavior of the n-carboxylic acid + methyl ester systems were essentially the average of the two comprising binaries, indicating that the phase behavior in these systems is not significantly affected by solute + solute interactions. Finally, the thermodynamic modeling of the data with the RK-ASPEN property method was considered, taking only solvent + solute binary interaction parameters (BIPs) into account. The solvent + solute BIPs were found to be sufficient to provide an adequate description of the experimental data, with the dew-point region generally being the best described region.
Plessis et al. (Wed,) studied this question.