Preparation Of FeMnO_x/TiO₂and Its Performance Study Of NO_x Catalytic Oxidation

The NO emissions have presented a rising trend since the development ofscience and technology in China. It will bring terrible influence to our life if thecontrol measures do not take to reduce NOx. NOxcatalytic oxidation ismeaningful to SCR technique and wet denitration proeessing since NO2is moreeasier to be removed than NO. It is necessary to develop one catalyst which hashigh NOxoxidation efficiency and good resistance to SO2and H2O. Consideringthe current status of denitrification, FeMnOx/TiO2was prepared by impregnationmethod and applied for NO oxidation in this article.Firstly, the effects of MnOxand FeOxloading were studied andFe(0.15)-Mn(0.3)/TiO2exhibited the highest NOxoxidation rate. ThenFeMnOx/TiO2with different loading sequence were prepared throughisovolumetric impregnation and tested for catalytic oxidation of NO with O2. Itwas found that the sample obtained from one-step impregnation method had thebest catalytic activity. The results of XRD, BET, SEM, and XPS showed that theexcellent activity was attributed to higher surface area, lower crystalline ofmanganese oxides, abundant Mn3+, Fe3+and chemisorbed oxygen species on thesurface. Furthermore, the catalyst Fe(0.15)/Mn(0.3)/TiO2that made by loadingMnOxfirst showed much higher NO convertion than Mn(0.3)/Fe(0.15)/TiO2. Thestudy showed that loading FeOx before MnOx would increase the crystallinity ofMn oxides but promote the generation of Mn2O3. Besides that adding FeOxtoMn(0.3)/TiO2could increase the surface area of the catalyst.In addition, the influence of GHSV, concentration of O2and NO wereinvestigated. It was found that the conversion of NO would reduce when theconcentration of NO and GHSV were increased. The oxidation reaction of NOhardly happened when there was no O2and the increased concentration of O2would strongly promote NOxoxidation rate. When the concentration of O2increased to5%, the promotion deduced. The lifetime of Fe(0.15)-Mn(0.3)/TiO2was studied at320℃,GHSV=30000h-1with800ppmNO, the NO conversionstaied at43%during60h.The sulfur tolerance, and water resistance testing were also investigated.The results showed that the catalyst had a strong tolerance at320℃and inhibiting effect of H2O on catalytic activity was reversible. While the conversionof NO was strongly inhibited by SO2and it could only recovere to40%when SO2were cut off. XPS analysis between used and fresh catalyst revealed the electrontransfer between Fen+and Mnn+ions in FeMnOx/TiO2. Possible reactionmechanism was put forward by comprehensive analysis of XPS and FT-IRresults.