Superior activity of iron-manganese supported on kaolin for NO abatement at low temperature

A series of Fe-Mn catalysts was prepared using different supports (kaolin, diatomite, and alumina) and used for NO abatement via low-temperature NH₃-selective catalytic reduction (SCR). The results showed that 12Fe-10Mn/Kaolin (with the concentration of Fe and Mn 12 and 10wt.%, respectively) exhibited the highest activity, and more than 95.8% NO conversion could be obtained within the wide temperature range of 120-300°C. The properties of the catalysts were characterized by inductively coupled plasma-atomic emission spectrometry (ICP-AES), thermogravimetry (TG), Brunner-Emmet-Teller (BET) measurements, X-ray diffraction (XRD), H₂-temperature programmed reduction (H₂-TPR), NH₃-temperature programmed desorption (NH₃-TPD), X-ray photoelectron spectroscopy (XPS), scanning electron microprobe (SEM) and energy dispersive spectroscopy (EDS) techniques. The support effects resulted in significant differences in the components and structures of catalysts. The 12Fe-10Mn/Kaolin catalyst exhibited better dispersion of active species, optimum low-temperature reduction behavior, the largest amount of normalized Brønsted acid sites, and the highest Mn⁴⁺/Mn and Fe³⁺/(Fe³⁺+Fe²⁺), all of which may be major reasons for its superior catalytic activity.