Insight into the temperature-dependent SO2 resistance over Mn-based de-NOx catalyst

Herein, two simple model catalysts (Mn3O4 and MnFeOx) were fabricated and operated under different temperatures (100, 150, 200, 250 degrees C) in SCR atmosphere with the presence of SO2, followed by thermal regeneration and characterizations to reveal the deactivation mechanism and the role of FeOx. The results indicated both catalysts exhibited temperature-dependent deactivation behavior, where the total activity loss displayed volcano-type SO2 resistance tendency within 100-250 degrees C and the most severe activity loss (98 % for Mn3O4 and 81 % for MnFeOx) was found at 150 degrees C. Meanwhile, the higher relative proportion of irreversible activity loss was found at lower temperatures, which is associated with the more easily saturated chemical adsorption of SO2 as evidenced by SO2+O2 breakthrough test. At higher temperatures, the SO2 oxidation and its further transformation into NH4HSO4 could be favored, thus resulting in increased reversible activity loss. The FeOx modification can protect MnOx species from sulfation to a certain degree and lower the irreversible deactivation, which is evidenced by the binding energy upshift and downshift of Fen+ species after being poisoned and regenerated, as well as the slightly changed binding energy of Mnn+ species from the XPS analysis.