Abstract
A new correlation and prediction model for the solubility of metal complexes in supercritical carbon dioxide (scCO2) based on the regular solution theory was developed in this study and the solubilities were calculated for metal(III) acetylacetonates: chromium(III) acetylacetonate (Cr(acac)3), cobalt(III) acetylacetonate (Co(acac)3), iron(III) acetylacetonate (Fe(acac)3), and rhodium(III) acetylacetonate. The physical properties, enthalpies of vaporization, and molar volumes of the metal acetylacetonates that are required to obtain the solubility parameters were estimated using the COSMOtherm program based on the conductor-like screening model for real solvents (COSMO-RS) method. The predicted molar volumes of Co(acac)3 and Fe(acac)3 and the solubility parameter of Cr(acac)3 were in good agreement with the data from the material safety data sheets and the group contribution method, respectively. The binary interaction parameter was introduced into the cross-term of the solubility parameters to calculate solubility. Although some deviations were found in the low-pressure region where the solubility dramatically increased with increasing pressure, the correlated results reproduced the experimental data for all metal acetylacetonates investigated using the physical properties estimated from the COSMOtherm program.
The relationship was nearly linear between the values of the interaction parameters optimized by correlation and the pseudo residual chemical potentials of the metal acetylacetonates obtained using the COSMO-RS method. Therefore, the prediction was carried out using the interaction parameters determined from the pseudo residual chemical potentials of the metal acetylacetonates. The predicted results deviated somewhat from the experimental data in the low-pressure region; however, the predicted results reproduced the experimental data in the high-pressure region.
