Structural Evolution of Highly Active Ir-Based Catalysts for the Selective Reduction of NO with Reductants in Oxidizing Conditions |
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Authors: | Nakatsuji Tadao Komppa Veikko |
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Affiliation: | (1) VTT Chemical Technology, Espoo, FIN-02044, Finland |
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Abstract: | NO
x
reduction over Ir-based catalysts in the presence of excess oxygen with hydrocarbon as a reductant was investigated in the focus on observing microstructure of Ir particle supported on various carriers and structural evolution of highly active Ir-based catalysts in the NO
x
reduction. Characterization of Ir-based catalysts using SEM, TEM, XRD, CO chemisorption and XPS, and reaction studies on various Ir-based catalysts have proved that the formation of relatively large Ir metal particle with 40–60 nm of nanocrystal size carried on inert supports has been a prerequisite for the evolution of high activities in the NO
x
reduction rather than the formation of Ir metal state on the catalyst. Furthermore, in inert gas conditions in a high temperature range of 850–950°C, Ir metal was easily formed by using the support such as TiO2 and ZrO2 that drastically decreased its specific surface area in the temperature range. |
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Keywords: | lean NO
x
catalyst Ir TiO2 ZrO2 microstructure XRD TEM SEM |
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