Abstract
The nature and oxidation state of iron species in Fe-exchanged BEA zeolites treated in synthetic air or nitrogen were determined by a combination of Mössbauer and X-ray absorption spectroscopy. The linear correlation between the edge energy of the X-ray absorption near edge structure (XANES) and the oxidation state determined by Mössbauer spectroscopy allowed determining the fraction of Fe2+ in situ. The distribution of Fe2+ and Fe3+ in the catalysts depends on the Fe concentration and the conditions of the thermal treatment. It is possible to stabilize isolated Fe2+ cations under ambient atmosphere in the zeolite pores, while FeBEA catalysts show a temperature-dependent oxidation and reduction of the active Fe species during the selective catalytic reduction of nitrogen oxides by NH3 (NH3-SCR), reflecting the equilibrium for NO oxidation.
Original language | English |
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Pages (from-to) | 950-955 |
Number of pages | 6 |
Journal | Journal of Physical Chemistry Letters |
Volume | 2 |
Issue number | 9 |
DOIs | |
State | Published - 5 May 2011 |