Methane as alternative in the selective reduction of NO over supported palladium catalysts in lean conditions: role of redox properties of support materials

The reduction of CH4 by NO has been investigated in the presence of oxygen on palladium supported on alumina, ceria–zirconia mixed oxides and perovskite materials, mainly LaCoO3. The activation procedure, under oxygen or hydrogen, drastically influences the catalytic performances of both catalysts. The stabilisation of a metallic or oxidic Pd phase leads to poor activity in the conversion of NO in the absence of oxygen. On the other hand, oxygen enhances the activity, particularly on the reduced Pd/LaCoO3, in the CH4 + NO reaction. Such results have been explained by different interactions between palladium and the support.