Investigation of the catalytic performances of supported noble metal based catalysts in the NO + H2 reaction under lean conditions

This paper compares the catalytic performances of various supported palladium and platinum catalysts on a conventional γ-Al2O3, and LaCoO3 perovskite that exhibits peculiar redox properties in the reduction of NO by hydrogen under lean conditions. A particular attention has been paid towards the catalytic behaviour of noble metals at low temperature, mainly below 120 °C. Clearly, their catalytic properties in the selective reduction of NO into N2 strongly depend on the feed gas composition, and on the nature of the support. In that temperature range, Pt/Al2O3 exhibits the better activity, unfortunately undesirable N2O is predominantly formed. The most prominent results have been obtained on Pd/LaCoO3 because H2O promotes the reduction of NO without affecting the selectivity behaviour, whereas a strong inhibiting effect on the rate of NO transformation into N2 is observed on Pd/Al2O3. Such differences in the catalytic behaviour of palladium could be related to different interactions between Pd and LaCoO3 generated during the activation thermal treatment under reductive atmosphere.