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

Abstract

Deposition and reduction of an organometallic platinum complex from a supercritical Pt(COD)Me 2 /CO 2 solution was carried out to produce Pt/ SnO 2 catalysts supported on Al 2 O 3 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)Me 2 /CO 2 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)Me 2 in CO 2 increases from 5.9 Â 10 À4 mol/mol at 11.2 MPa and 313 K to 3.4 Â 10 À3 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. #

Preferential oxidation of CO over Pt–Sn/AC catalyst: Adsorption, performance and DRIFTS studies

“…This increase was ∼2 folds (190%) for Pt/AC-N and 113% for Pt-Sn/AC-N catalyst which is in agreement with the evolution of PROX; reaction intermediate hydroxyl species diminish to a lower value due to production of water for Pt-Sn/AC-N catalyst having greater activity. The band at ∼2875 cm −1 appearing in all spectra can be attributed to formate species present on the catalysts which are unaffected from the reaction at any temperature [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”

“…120 • C), where neither platinum nor tin dioxide alone has stable activity. The high activity of Pt-SnO x system has been ascribed to a synergistic bifunctional mechanism in which Pt provides the adsorption sites for CO, while oxygen adsorbs dissociatively on SnO x [4]. On the other hand, the reactive sites situated at the border between SnO x and Pt particles could not be distinguished; thus the possibility of oxygen spillover from tin dioxide onto Pt has been considered for Pt-SnO x /Al 2 O 3 catalysts [5].…”

“…The following preferential CO oxidation step is necessary since platinum based cathode catalysts of PEM fuel cells require carbon monoxide levels as low as 1-100 ppm for stable operation [2,3]. Therefore, an efficient PROX unit must reduce carbon monoxide level from 1 to 2% down to below 100 ppm while suppressing possible hydrogen oxidation under the presence of CO 2 , water vapor and CH 4 .…”

Impregnation of Crushed Stone with Bitumenous Compounds Using Propane/Butane Impregnation Process Carried out in Supercritical Fluid Conditions

“…The presence of kinematic viscosity in denominators of the Grasgof and Reinolds numbers indicates the considerable intensity of the free and forced forms of movement in the super-critical fluid mediums. The diffusion (binary diffusion and self-diffusion) of the super-critical fluid mediums exceeds by 1 -2 levels the similar index for the same liquid organic solvents [10]. In the case of super-critical fluid mediums, there is no phase interface, the surface tension and, accordingly, the capillary effect.…”

Estimation of the Properties Porous Structures by Experiment and Modeling

“…Al., 2006), (Garrido et al, 2008). The interest in porous ceramic materials is connected above all with their unique properties, such as low relative weight, large specific surface area and high thermal insulation properties.…”