Using supercritical CO2 for preparation of Pd supported on SiO2: Phase equilibria data and supercritical fluid deposition technique

The aim of this study was to prepare palladium supported on silica (SiO2) using supercritical carbon dioxide (CO2). The first stage involved measuring the equilibrium solubility data of palladium hexafluoroacetylacetonate (Pd(hfac)2) in CO2, and the second stage focused on the deposition of the precursor on SiO2 using CO2. Experimental data on the solutiliby of Pd(hfac)2 with CO2 were obtained at temperatures ranging from 35 to 60 degrees C and pressures up to 115 bar, along with the deposition of Pd(hfac)2 on SiO2 in CO2 using supercritical fluid deposition technique in a batch reactor. The results showed that the addition of Pd(hfac)2 to the system leads to changes in transition pressure. The experimental data on the precursor deposition on silica using CO2 were well correlated (R2 values from 93.08 % to 97.40 %) with adsorption models for two isotherms (60 and 80 degrees C). The use of the supercritical fluid deposition method, such as CO2, in the synthesis of palladium on silica, represents a significant advance towards green chemistry. This method offers a sustainable approach as it uses supercritical CO2, a green and abundantly available solvent, as a dispersion medium for metallic precursors. This eliminates the need for highly toxic and flammable organic solvents, thus reducing risks to human health and the environment.