Preparation of amorphous MnOx/TiO2 catalyst and its performance in low temperature NH3-SCR
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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。Abstract: 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 SO2 poisoning.
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图 2 MnOx/TiO2(s)催化剂的HRTEM(a)、STEM(b)和TEM-EDS mapping(c)照片
Figure 2 HRTEM image (a), STEM (b) and TEM-EDS mapping (c) results of MnOx/TiO2(s)
图 3 催化剂的N2吸附-脱附等温线和孔径分布
Figure 3 N2 sorption isotherms and pore size distribution of the catalysts
图 4 催化剂的Mn 2p (a)和O 1s (b) XPS谱图
Figure 4 Mn 2p (a) and O 1s (b) XPS spectra of the catalysts
图 9 催化剂的SO2和H2O的阶跃应答实验
Figure 9 Step transient response of SO2 and H2O over the catalysts
表 1 催化剂的物理化学性质
Table 1 Physical chemical properties of the catalysts
表 2 催化剂的表面原子浓度
Table 2 Surface atomic concentration of the catalysts
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