| Nitride oxide (NOx) is one of the important pollutants in the atmosphere. Selective Catalytic Reduction (SCR) has been generally recognized as the best removal technology of NOX emitted from the stationary sources. Research and development of the catalysts with highly activity for low-temperature SCR of NOx become a research hotspot. In this paper, nanosized ZrO2particles with different crystal structures as the vector, the Mn-Ce/ZrO2catalyst was prepared by impregnation method and the low-temperature SCR reaction was systematically investigated.First of all, the room-temperature stable nanosized ZrO2particles with different crystal structures was prepared by coprecipitation, as the catalyst vector. The microstructure parameters of the resulting products such as crystal structures, grain size and specific surface area were characterized by powder X-ray diffraction (XRD), Laser Raman Spectroscopy and transmission electron microscopy (TEM), respectively to study the effect of temperature and modifier doping on crystal structures and it was got stabilized preparation of different polymorphs nano ZrO2powders.Secondly, the Mn-Ce/ZrO2catalyst was prepared by impregnation method with three different nanosized ZrO2particles with different crystal structures as the vector, catalyst denitration performancestudy was studied by influence of composition ratio, adding additives category, carriers and other conditions. It was found that Mn-Ce/ZrO2catalyst showed the denitration efficiency with temperature rising characteristics, and with the increase of the active component (Mn-Ce oxide) loadings, SCR activity strengthen. Where in the temperature ranges60-120℃, three catalysts10m,10t, and10c exhibited good low temperature SCR activity. With three metallic elements (Fe, Ag, and Cu) oxide as an additive, the secondary load doping reduce the low temperature SCR catalyst activity of Mn-Ce/ZrO2.Furthermore, the influence on denitration catalyst performance of crystal structure on the nanosized ZrO2were investigated. It was found that in the same amount of Mn-Ce load conditions, different polymorphs of ZrO2as the catalyst vector Mn-Ce/ZrO2catalyst will exhibit different low temperature SCR activity, the overall embodied [Conv.]c.>[Conv.]t>[Conv.]m.Properties of the catalysts were characterized by XRD, Scanning Electron Microscopy (SEM), Brunauer Emmett Teller (BET) and other methods and it found that surface hole structure of catalysts favor Mn-Ce/ZrO2catalytic denitrification reaction proceeds; the XPS analysis of5%Mn-Ce/c-ZrO2catalyst showed5c with the most abundant surface lattice oxygen,5m contains the most surface hydroxyl oxygen; and reduction capability of5%Mn-Ce/c-ZrO2catalyst is in the order of a (5c)> A (5t)> A (5m); NH3is adsorbed mainly on Lewis acid sites of the catalyst5c and5t, and part of NH3is adsorbed on Bronsted acid sites of the catalyst5m, Mn-Ce/t-ZrO2and Mn-Ce/c-ZrO2has moer Lewis acid sites then Mn-Ce/c-ZrO2, as Mn-Ce/m-ZrO2has more Bronsted acid sites, and NH3in the form of NH4+and-NO2generates intermediate product NH4NO2.The influence of these properties such as phase structure, specific surface area, pore volume and so on, on the catalysts activity were studied.Finally, The sulfur dioxide poisoning of the catalyst was investigated. The characters of the catalyst before and after the reaction were detected by SEM, FT-IR and BET analysis. And research the effects of density of sulfur dioxide on the catalyst. The major factors include:active component is sulfide, Lewis acid site disappear. Also it found that5c can still maintain good denitrification performance influenced by SO2in the anti-curing reaction, followed5t,5m for the worst, which is described as a vector zirconia crystal structure of the Mn-Ce/ZrO2sulfidation resistance catalysts have a significant effect. |
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