Equilibria in the Copper Hexafluoroacetylacetonate–CO2–Al2O3 System1

The solubility of copper(II) hexafluoroacetylacetonate monohydrate Cu(hfa)2⋅H2O in carbon dioxide was studied. The solubility increases with increasing temperature in the range of 303–353 K and was observed to increase nonlinearly with increasing CO2 density in the supercritical (SC) region. The dependence of the solubility on the parameters of state (temperature, CO2 density) was described by the Chrastil equation. The adsorption of Cu(hfa)2⋅H2O from a solution in SC-CO2 on three γ-Al2O3 samples differing in the presence of acidic and basic additives was investigated. The adsorption isotherms have a shape with a sharp increase in the adsorption value in the initial part, which indicates a high affinity of the complex for the surface of the substrate and/or its heterogeneity, as well as the presence of sites with high adsorption energy. An increase in the CO2 density from 355 to 780 kg/m3 at a constant temperature (313 K) leads to a decrease in the adsorption of Cu(hfa)2⋅H2O on all three Al2O3 samples. At a constant medium density of 355 kg/m3 and an increase in temperature from 313 to 343 K, a more complex behavior of the adsorption isotherms is observed depending on the characteristics of the support and the concentration range of the adsorbed substance.