Selective catalytic reduction of NO with NH3 over Mo–Fe/beta catalysts: the effect of Mo loading amounts

Abstract

A series of Mo_x–Fe/beta catalysts with constant Fe and variable Mo content were synthesized and investigated for selective catalytic reduction (SCR) of NO_x with NH₃. It was found that the Mo_0.2–Fe/beta catalyst exhibited excellent activity, N₂ selectivity and preferable resistance to H₂O and SO₂. The Mo_x–Fe/beta catalysts were characterized by various analytical techniques. TEM and SEM images showed that the addition of Mo could enhance the dispersion of iron oxides. The results of NH₃-TPD and Py-IR indicated that the introduction of Mo resulted in a change of Brønsted acidity, which was associated with high-temperature SCR activity. XPS and XANES results showed that the introduction of Mo resulted in a change of Fe²⁺ content, which determined the low-temperature activity. DFT calculations showed the strong effects of Mo on the crystal structure, charge distribution and oxygen vacancy formation energy of iron oxides, which further explained the role of Mo in the catalyst behaviors during the SCR process.