摘要：

Three different Ir catalysts supported on H_ZSM-5 were prepared and tested for the selective reduction of NO under net oxidizing conditions using propene as reducing agent. The preparation of highly active Ir catalysts and the elaboration of a procedure for enhancing activity by on stream conditioning was targeted. Structural changes of the catalyst during conditioning were investigated by means of XRD, TEM and activity measurements. Under reaction conditions Ir was present at Ir~0 and IrO_2. The presence of Ir~0 was essential for high DeNOx activity. The ratio of Ir~0/Ir~(4+) was found to depend on the size of Ir-containing crystallites. Larger crystallites contained predominantly Ir~0. Crystallite size and oxidation state of Ir have been identified to be crucial for the NO reduction behaviour of Ir/N-ZSM-5.

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