| Zusammenfassung: | Cr-Mn mixed-oxide based catalysts were prepared for the low-temperature selective catalytic reduction of NOx with ammonia in the presence of excess oxygen. It was found that the Cr(0.4)-MnOx showed the highest activity and yielded 98.5% NOx conversion at 120 °C. XRD, TPR and Raman data results suggested that a crystalline phase of CrMn 1.5O4 was present in the Cr-MnOx catalysts, which contained the active species. XPS results of fresh, used and regenerated Cr(0.4)-MnOx catalysts illustrated clearly the presence of Mn 2+, Mn3+, Mn4+ and Cr2+, Cr 3+, Cr5+ oxidation states. Efficient electron transfer between Cr and Mn in the crystal of CrMn1.5O4 was thought to be the reason for the high activity and long lifetime of the Cr(0.4)-MnO x catalyst. In addition, the SCR activity was gradually suppressed in the presence of SO2, while such an effect was shown to be reversible after switching off the SO2 injection. © 2010 Elsevier Inc. All rights reserved.
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