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

In the two phase system of water and supercritical carbon dioxide, the part itioning behavior of two single solutes, aniline and benzaldehyde, was meas ured 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 a nd analyzed either by UV-spectroscopy or gas chromatography. The partition coefficient in this case is defined as the ratio of molar fractions of a su bstance in the carbon dioxide-rich phase and the aqueous phase in equilibri um. 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 measurem ents, the distribution behavior of an aqueous solution of phenol, benzyl al cohol, cyclohexanol and 2-hexanone was examined at 323 K, While the alcohol s were entrained in the fluid phase, the other compounds were retained in t he aqueous phase. Analogous to high pressure binary solid fluid phase equil ibria, an enhancement factor is introduced to describe partitioning equilib ria. Differences in the distribution behavior of single solutes are discuss ed in terms of the enthalpy of hydration. (C) 1999 Elsevier Science B.V. Al l rights reserved.