Preparation of amorphous MnO_x/TiO₂ catalyst and its performance in low temperature NH₃-SCR

MnO_x/TiO₂ catalysts were prepared by spontaneous deposition, co-precipitation and impregnation methods, respectively. The structure and properties of the MnO_x/TiO₂ catalysts were studied by means of XRD, TEM, N₂ adsorption-desorption, XPS, H₂-TPR and NH₃-TPD. The activity of the catalysts in the selective catalytic reduction of NO was investigated. The results showed that the MnO_x/TiO₂(s) catalyst prepared by the spontaneous deposition method had a completely amorphous structure and a strong interaction between Mn and Ti, showed stronger redox ability than other two catalysts. In addition, the MnO_x/TiO₂(s) catalyst exhibited larger surface area, more surface acid sites, which were beneficial to NH₃ adsorption and activation, as well as the high Mn⁴⁺ and adsorbed oxygen content of catalyst surface, which could greatly enhance the activity for NO oxidation to NO₂, as a result, facilitating the "fast-SCR" reaction. Thus, a superior denitrification activity was exhibited over MnO_x/TiO₂(s) catalyst. For MnO_x/TiO₂(s) catalyst, the conversion of NO reached 92.8% at 150 ℃ and retained over 90% in the range of 150-350 ℃. Moreover, the MnO_x/TiO₂(s) catalyst also showed strong resistance to H₂O and SO₂ poisoning.