Partition coefficients of aromatic organic substances in two-phase mixtures of water and carbon dioxide at pressures from 8 to 30 MPa and at temperatures of 313 to 333 K. Part II

Abstract In the two phase system of water and supercritical carbon dioxide, the partitioning behavior of two single solutes, aniline and benzaldehyde, was measured at temperatures of 313, 323 and 333 K and pressures up to 30 MPa using a recirculation view cell apparatus. Samples were taken from both phases and analyzed either by UV-spectroscopy or gas chromatography. The partition coefficient in this case is defined as the ratio of molar fractions of a substance in the carbon dioxide-rich phase and the aqueous phase in equilibrium. Partition coefficients between 0.21 and 3.03 were found for aniline and 2.5 up to 62.9 for benzaldehyde. In addition to the single solute measurements, the distribution behavior of an aqueous solution of phenol, benzyl alcohol, cyclohexanol and 2-hexanone was examined at 323 K. While the alcohols were entrained in the fluid phase, the other compounds were retained in the aqueous phase. Analogous to high pressure binary solid fluid phase equilibria, an enhancement factor is introduced to describe partitioning equilibria. Differences in the distribution behavior of single solutes are discussed in terms of the enthalpy of hydration.