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Comparison of catalytic activity and selectivity of Pd/(OSC + Al2O3) and (Pd + OSC)/Al2O3 catalysts |
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| Authors: | Tanja Kolli Katariina Rahkamaa-Tolonen Ulla Lassi Auli Savim ki and Riitta L Keiski |
| Affiliation: | aDepartment of Process and Environmental Engineering, University of Oulu, P.O. Box 4300, FIN-90014 Oulu, Finland bECOCAT Oy, Catalyst Research, Typpitie 1, FIN-90650 Oulu, Finland cCentral Ostrobothnia Polytechnic, Department of Technology, FIN-67100 Kokkola, Finland |
| Abstract: | The effect of the Pd addition method into the fresh Pd/(OSC + Al2O3) and (Pd + OSC)/Al2O3 catalysts (OSC material = CexZr1?xO2 mixed oxides) was investigated in this study. The CO + NO and CO + NO + O2 model reactions were studied over fresh and aged catalysts. The differences in the fresh catalysts were insignificant compared to the aged catalysts. During the CO + NO reaction, only small differences were observed in the behaviour of the fresh catalysts. The light-off temperature of CO was about 20 °C lower for the fresh Pd/(OSC + Al2O3) catalyst than for the fresh (Pd + OSC)/Al2O3 catalyst during the CO + NO + O2 reaction. For the aged catalysts lower NO reduction and CO oxidation activities were observed, as expected. Pd on OSC-containing alumina was more active than Pd on OSC material after the agings. The activity decline is due to a decrease in the number of active sites on the surface, which was observed as a larger Pd particle size for aged catalysts than for fresh catalysts. In addition, the oxygen storage capacity of the aged Pd/(OSC + Al2O3) catalyst was higher than that of the (Pd + OSC)/Al2O3 catalyst. |
| Keywords: | Al2O3 Ceria–zirconia mixed oxides DeNOx Nitrogen oxides Palladium Three-way catalysts |
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