非晶态MnO_x/TiO_2催化剂的制备及其低温NH_3-SCR性能

采用自发沉积法、共沉淀法及浸渍法制备MnO_x/TiO_2催化剂,通过XRD、TEM、N2吸附-脱附、XPS、H_2-TPR、NH_3-TPD等一系列表征手段研究MnO_x/TiO_2催化剂的结构与性质,并考察MnO_x/TiO_2催化剂低温NH_3-SCR性能。结果表明,自发沉积法制备的MnO_x/Ti O2(s)催化剂具有完全非晶态结构,Mn和Ti之间存在强相互作用,较共沉淀法制备的MnO_x/TiO_2(c)及浸渍法制备的MnO_x/Ti O2(i)表现出更强的氧化还原能力。MnO_x/TiO_2(s)具有较高的比表面积、较多的表面酸量,有利于NH_3的吸附与活化。且表面高浓度的Mn4+离子及吸附氧,有利于将NO氧化为NO2,促进发生"fast-SCR"反应,进而使其表现出优异的低温脱硝性能。MnO_x/TiO_2(s)催化剂在150℃时NO的转化率高达92.8%,在150-350℃NO的转化率保持在90%以上,此外其还具备较强的抗H_2O和SO_2毒化能力。

Preparation of amorphous MnOx/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.