CATALYTIC PURIFICATION OF CAR EXHAUST OVER COBALT-BASED AND COPPER-BASED METAL-OXIDES PROMOTED WITH PLATINUM AND RHODIUM

25 Alumina-and silica-supported oxide-based catalysts were prepared, w ith the overall metal composition La(0.45)Sr(0.15)Ce(0.35)Zr(0.05)M(1. 0) (M=Co or Cu) and promoted with 0-0.5 mg Pt-Rh per gram catalyst. Th e catalysts were evaluated with respect to light-off temperatures and redox characteristics, using NO/CO/C3H6/O-2/N-2 gas mixtures to simula te car exhaust. The activities for complete oxidation of propene and c arbon monoxide increased with increasing content of metal oxides and n oble metals. The catalysts were characterized by X-ray powder diffract ion (XRD), scanning electron microscopy (SEM), transmission electron m icroscopy (TEM) combined with energy-dispersive spectroscopy (EDS) ana lysis, temperature-programmed reduction (TPR), and specific surface ar ea measurements (BET). SEM/TEM/XRD revealed that the alumina-supported catalysts contained well dispersed oxides of the added elements, wher eas the silica-supported catalysts contained significantly larger part icles of the copper or cobalt oxides, The TPR peak for reduction of co balt oxide shifted toward lower temperatures with increasing content o f Pt-Rh, indicating hydrogen spill-over from the noble metals to the c obalt oxide. The catalytic activity of the Co-based oxides supported o n alumina and promoted with 0.49 mg Pt-Rh per gram catalysts was compa rable to the activity of a commercial three-way catalyst (TWC), contai ning more than 4 times as much Pt-Rh.