Solubility of solid carnosic acid in supercritical CO2 with ethanol as a co-solvent

The present study is devoted to the experimental measurement and thermodynamic modeling of solid carnosic acid solubility in supercritical CO2 + ethanol as a co-solvent. Measurements were carried out at temperatures in the range of 313.15 and 333.15 K, pressures ranging from 280 to 400 bar, and at different content of the modifier ethanol (from 0.7 to 10%). The Group Contribution Associating Equation of State (GCA-EoS) [H.P. Gros, S.B. Bottim, E.A. Brignole, High pressure phase equilibrium modeling of mixtures containing associating compounds and gases, Fluid Phase Equilibria 139 (1997) 75-87] was applied in this work to represent the experimental solubility data obtained. Due to the lack of information in the literature about pure carnosic acid parameters, its solid volume, critical properties, and sublimation pressures were estimated in this work. The key step in the thermodynamic modeling proved to be the introduction of a solute hard-sphere parameter in the Carnahan-Starling repulsive term of the model, which depends on both temperature and pressure. (c) 2004 Published by Elsevier B.V.