Supercritical deposition of Pt on SnO2-coated Al2O3 foams: Phase behaviour and catalytic performance

Deposition and reduction of an organometallic platinum complex from a supercritical Pt(COD)Me2/CO2 solution was carried out to produce Pt/SnO2 catalysts supported on Al2O3 foams for CO oxidation at moderate temperatures. The phase behaviour of the complex in supercritical carbon dioxide was investigated to find the optimum pressure and temperature conditions for the deposition. For the Pt(COD)Me2/CO2 mixture, the melting point decreased with increasing pressure from 378 K at 0.1 MPa to 360 K at 25.6 MPa. Additional investigations showed that the solubility of Pt(COD)Me2 in CO2 increases from 5.9 × 10−4 mol/mol at 11.2 MPa and 313 K to 3.4 × 10−3 mol/mol at 29.6 MPa and 353 K. The supercritical deposition yielded catalysts with highly dispersed platinum nanoparticles of approx. 3 nm having a narrow size distribution and thus, a superior activity towards oxidation of carbon monoxide in comparison to a catalyst prepared by the conventional aqueous impregnation of Pt.

The deposition of platinum from an organometallic platinum complex dissolved in supercritical CO2 solution produced Pt/SnO2 catalysts having a narrow particle size distribution around 3 nm. These catalysts had a much higher activity in the low-temperature oxidation of carbon monoxide than a Pt/SnO2 catalyst prepared by conventional wet deposition. The thermodynamics of the system Pt(COD)Me2/scCO2 were studied to determine the conditions for an optimal Pt deposition.Figure optionsDownload as PowerPoint slide