CHARACTERIZATION AND CATALYTIC ACTIVITY OF SILICON-CARBIDE POWDER AS CATALYST SUPPORT IN EXHAUST CATALYSTS

Silicon carbide (alpha-SiC) powder was used as a washcoat in exhaust catalysts. The platinum and rhodium metal particles were obtained either by reduction of metal salts dissolved in microemulsions or by an impregnation technique. The influence of the degree of oxidation of the SiC powder on the properties of the SiC-based catalyst was studied. The catalysts were characterized by X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM) and Fourier transform-IR (FTIR), and their catalytic activities were tested in a synthetic exhaust. From XPS and STEM results it can be concluded that the best dispersion of the metal particles on the support is obtained when SiC powder is superficially highly oxidized and the metal particles are prepared from microemulsion. The activity of these catalysts was compared to a commercial catalyst based on an alumina washcoat. It was shown that a catalyst containing calcined SiC and metal particles prepared in microemulsion has a catalytic activity in the exhaust cleaning reaction similar to the commercial one. It should be noted that the industrial catalyst contains certain additives that are not present in the SiC based one.