A new iron-based catalyst for carbon monoxide oxidation, as a potential substitute for precious-metal systems, has been prepared by using a facile impregnation method with iron tris-acetylacetonate as a precursor on γ-Al2 O3 . Light-off and full conversion temperatures as low as 235 and 278 °C can be reached. However, the catalytic activity strongly depends on the loading; lower loadings perform better than higher ones. The different activities can be explained by variations of the structures formed. The structures are thoroughly characterized by a multimethodic approach by using X-ray diffraction, Brunauer-Emmett-Teller surface areas, and Mössbauer spectroscopy combined with diffuse reflectance UV/Vis and X-ray absorption spectroscopy. Consequently, isolated tetrahedrally coordinated Fe(3+) centers and phases of AlFeO3 are identified as structural requirements for high activity in the oxidation of carbon monoxide.
Keywords: Moessbauer spectroscopy; coordination modes; iron; oxidation; structure-activity relationships.
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