A series of manganese-based catalysts supported on foamed metal nickel (FMN) with various Mn/Ni ratios was prepared for low-temperature selective catalytic reduction (SCR) of NO with NH3 (NH3-SCR). The effects of calcination temperature, amount of added Mn, optimal operating conditions, and H2O on the elimination of nitrogen oxides (de-NOx) performance of catalysts were studied. The catalysts were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and temperature-programmed desorption experiments of NH3 analyses. The experimental results revealed that the Mn7.5/FMN catalyst calcined at 350 ºC exhibited the best NO conversion that was ca. 100% at 120-200 ºC. Moreover, it had excellent H2O tolerance. The superior activity of the Mn7.5/FMN catalyst, which was calcined at 350 ºC, was attributed to the presence of amorphous manganese oxide, more unsaturated Ni atoms and structural defects, an increase in NH3 adsorbance, and the number of surface acid sites. Based on these studies, we established that the reaction of the NH3-SCR with Mn7.5/FMN catalyst mainly exhibits an Eley-Rideal mechanism.

A series of iron-based catalysts supported on activated carbon (AC) and manganese-modified Fe2O3/AC catalysts with various Fe:Mn ratios were prepared for selective catalytic reduction (SCR) of NO by ammonia at low temperature. It was found that the addition of a small amount of MnOx into the Fe2O3/AC catalyst contributed to an improvement of the NO conversion. NO conversions of approximately 100% were obtained for the 10FexMn/AC (x = 1, 3, 5) catalysts at 180-240 ºC. The characterization results indicate that the addition of a certain amount of MnOx into the 10Fe/AC catalyst increased the dispersion of the amorphous state, increased the ratios of Fe3+/(Fe3+ + Fe2+) and Mn4+/Mn3+, and improved the surface area and pore volume.