非晶态MnOx/TiO2催化剂的制备及其低温NH3-SCR性能

摘要

采用自发沉积法、共沉淀法及浸渍法制备MnOx/TiO2催化剂,通过XRD、TEM、N2吸附-脱附、XPS、H2-TPR、NH3-TPD等一系列表征手段研究MnOx/TiO2催化剂的结构与性质,并考察MnOx/TiO2催化剂低温NH3-SCR性能.结果表明,自发沉积法制备的MnOx/TiO2 (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MnOx/TiO2(c)及浸渍法制备的MnOx/TiO2(i)表现出更强的氧化还原能力.MnOx/TiO2(s)具有较高的比表面积、较多的表面酸量,有利于NH3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.MnOx/TiO2(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H2O和SO2毒化能力.%MnOx/TiO2 catalysts were prepared by spontaneous deposition,co-precipitation and impregnation methods,respectively.The structure and properties of the MnOx/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 MnOx/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 MnOx/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 MnOx/TiO2(s) catalyst.For MnOx/TiO2(s) catalyst,the conversion of NO reached 92.8％ at 150 ℃ and retained over 90％ in the range of 150-350 ℃.Moreover,the MnOx/TiO2(s) catalyst also showed strong resistance to H2O and SO2poisoning.