High-Pressure Phase Behavior of CO₂ + (C₁₂/C₁₄ n-Alkane and/or C₈/C₁₀ Carboxylic Acid and/or C₁₂/C₁₄ Methyl Ester) Systems

Abstract

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 (CO 2 ) are presented in this study. For these mixtures, (C 8 and C 10 ) ncarboxylic acids, (C 12 and C 14 ) methyl esters, and (C 12 and C 14 ) nalkanes 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 CO 2 + n-tetradecane binary which exhibits type III phase behavior. Additionally, both the n-alkane + (ncarboxylic acid or methyl ester) groups showed indications of enhanced mixture solubility in comparison to the comprising binaries, with the ntetradecane + 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 ncarboxylic 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.