Influence of different supports on the physicochemical properties and denitration performance of the supported Mn-based catalysts for NH3-SCR at low temperature

The commonly used supports of SiO2, gamma-Al2O3, TiO2, and CeO2 were synthesized, and used for preparing MnOx/SiO2, MnOx/gamma-Al2O3, MnOx/TiO2, and MnOx/CeO2 catalysts with the purpose of investigating the influence of crystal structure and coordination status on the physicochemical properties and denitration performance of these supported Mn-based catalysts for low-temperature NH3-SCR. The obtained samples were characterized by XRD, Raman, BET, H-2-TPR, NH3-TPD, in situ DRIFTS, NO + O-2-TPD, XPS, and NH3-SCR model reaction. XRD results indicate that MnOx species can be highly dispersed on the surface of),gamma-Al2O3, TiO2, and CeO2, which is because that there are some octahedral and tetrahedral vacancy sites, octahedral vacancy site, and cubic vacancy site exist on the surface of defective spinel structure gamma-Al2O3, anatase TiO2, and cubic fluorite-type structure CeO2, respectively. However, there is no any vacancy site on the surface of SiO2 due to its unique SiO4 tetrahedral structure, which results in the appearance of crystalline beta-MnO2 on the surface of MnOx/SiO2 catalyst. Furthermore, H-2-TPR results exhibit obvious different reduction behavior among these supported Mn-based catalysts, which is explained by the coordination status of Mn species. Finally, NH3-SCR model reaction results show that MnOx/gamma-Al2O3 catalyst presents the best catalytic performance among these supported Mn-based catalysts due to its high dispersion, suitable reduction behavior, largest amount of acid sites, optimal NOx adsorption capacity, and abundant Mn4+ content.(C) 2017 Elsevier B.V. All rights reserved.