SYNTHESIS AND CHARACTERIZATION OF PLATINUM-RHODIUM SUPPORTED ON SIC AND SIC DOPED WITH CERIUM - CATALYTIC ACTIVITY FOR THE AUTOMOBILE EXHAUST REACTIONS

The synthesis, characterization and catalytic use of SiC and SiC doped with cerium as Pt-Rh support for the automobile exhaust reaction are described. Their resistance during two accelerated deactivation proces ses in the presence of water vapour at high temperature was also teste d. The supports and the catalysts were characterized by mercury porosi metry, single point B.E.T., X-ray fluorescence, X-ray diffraction (XRD ), transmission electronic microscopy (TEM) and X-ray energy dispersiv e spectroscopy (EDS) and their catalytic activities were measured in a synthetic exhaust containing carbon monoxide, nitric oxide, hydrocarb ons and nitrogen. From the results it can be concluded that SiC can re place the wash-coat of alumina on cordierite as support. The presence of cerium in the SiC support allows a good dispersion of the metal par ticles and confers high resistance towards sintering. In addition, the chemical inertness of the SiC support allows easy recovery of the act ive phase and the support by acid washing.