Cobalt supported on ZrO2: catalysts characterization and their activity for the reduction of NO with C3H6 in the presence of excess O-2

CoOx/ZrO2 samples, prepared by adsorption from cobalt solutions or by impre gnation, were characterised by means of DRS, XPS, FTIR and volumetric CO ad sorption. In samples prepared by adsorption the maximum Co-uptake was 2.2 a toms nm(-2). XPS evidenced cobalt dispersion up to about 2 atoms nm(-2). DR S evidenced Co3O4 above 2 atoms nm(-2). Volumetric CO adsorption, combined with FTIR, showed that cobalt was highly dispersed on the ZrO2 surface in s amples containing 0.4 and 0.9 atoms nm(-2). The selective catalytic reducti on (SCR) of NO with C3H6 in the presence of excess O-2 was studies on sampl es containing up to 4.8 Co atoms nm(-2) with a reactant mixture containing NO=4000 ppm, C3H6=2000 ppm, O-2=2%. Isolated cobalt in CoOx/ZrO2 containing up to about 2 atoms nm(-2) is active and selective for NO reduction in the presence of excess O-2. Aggregated cobalt present as Co3O4 in more concent rated samples is active for C3H6 combustion, thus rendering the relevant Co Ox/ZrO2 samples non-selective. (C) 2000 Elsevier Science B.V. All rights re served.