Mn负载量对nMnO_x/TiO₂催化剂NH₃-SCR催化性能的影响

A series of nMnO_x/TiO₂(n=2.5%, 5%, 10% and 15%)(Mass percentage) catalysts with different Mn loadings were prepared through impregnation method to investigate the effect of manganese loading on the selective catalytic reduction (SCR) of NO with NH₃. The physicochemical properties of nMnO_x/TiO₂ catalysts were characterized by N₂ physisorption/desorption, X-ray Diffraction (XRD), Scanning Electron Microscope(SEM), Temperature Programmed Reduction with H₂ (H₂-TPR), Temperature Programmed Desorption with NH₃ (NH₃-TPD) and X-ray Photoelectron Spectroscopy (XPS). The catalytic activities for the SCR reaction on nMnO_x/TiO₂ catalysts first increased and then decreased with increasing the manganese loading, showing "volcano" type, maximum at the manganese loading of 10%(Mass percentage). N₂ physisorption/desorption and XRD results indicated that all the catalysts showed similar texture properties. H₂-TPR results indicated that the amount and property of surface oxygen were highly dependent on the manganese loading. Moreover, the molar ratio of surface oxygen was linear relationship with the catalytic activity (T₅₀), suggesting that the surface oxygen played a crucial role on the SCR activity. XPS results showed the variation in surface oxygen was attributed to the surface Mn⁴⁺ molar ratio. Meanwhile, NH₃-TPD results indicated that the amount of weak acidity could also affect SCR activity. All these results provided a guideline for the development of superior SCR catalysts.