Effect of Cosolvents on Solute Solubility in and Separability Between Liquid Phases in Liquid-liquid vapor Equilibrium Systems

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ABSTRACT CTS-9730853 K. Luks/U. of Tulsa Support is sought for the experimental study of liquid-liquid-vapor (llg) equilibria of selected ternary mixtures of common gas solvents + solutes + cosolvents. This research will contribute to the understanding of how cosolvents may enhance the capacity of the gas-solvent-rich liquid phase (l2) for extracting solutes from a solute-rich liquid phase (11) in an llg subcritical system. Detailed studies of the llg regions of several ternary mixtures will be carried out to evaluate the roles that cosolvent polarity and phase concentration may have in enhancing the molar concentration of a variety of relatively non-volatile liquid solutes in the gas-solvents-rich liquid l2. It is proposed that the llg phase equilibria be studies for nine ternary mixtures composed of gas solvent + solute + cosolvent, six containing the gas solvent carbon dioxide and three containing the gas solvent ethane. The solute will be selected from species of distinctly different molecular structure (n-tetradecane, l-methylbenzene, l- decanol), species that have heretofore exhibited llg partial miscibility with these gas solvents. The cosolvent will be selected according to it polarity (methanol or acetone, species that has attracted previous interest with respect to enhancing gas-phase solubility in prototype supercritical extraction systems). The studies will be performed in the temperature range of 250 to 325 K at pressure to 90 bars (9 Mpa) in existing visual cell apparatuses especially designed for and dedicated to the study of multiphase equilibria phenomena. Subcritical llg extraction systems offer a dense (i.e., liquid) gas-solvent phase at modest temperatures and pressures. The data resulting from this study will be of value for suggesting possible new ways to separate at benign conditions certain molecular types of species from complex mixtures that occur in environmental, manufacturing, and refining applications. Additionally, these studies will further expand our understanding of multiphase equilibrium phenomena in general by adding to the limited existing experimental database of llg systems.