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The Study of NO Low-temperature Catalytic Oxidation Over MnFeO_x Catalyst

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Tutor: TangXiaoLong
School: Kunming University of Science and Technology
Course: Environmental Science
Keywords: NO,NO2,low-temperature catalytic oxidation,MnFeO_x
CLC: X701
Type: Master's thesis
Year:  2011
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Nitrogen oxides damage to the environment with the atmosphere of photochemical smog, acid rain. Not only endanger human health, but also a serious damage to the ecological environment. Therefore, it is necessary to study the NOx pollution control technology to protect air environment. Much more research work had been done for the De-NOx technology in worldwide.In this work, the NO catalytic oxidation process had been discussed on the MnFeOx catalysts, which was prepared by organic solvent method. The preparation conditions had been given more attention for its significant effect to the catalyst activity. And the NO catalytic oxidation process characters were also investigated. The effects of catalyst composition, main active component ratio, preparation conditions were all discussed in this work. Then the water resistance capacity of the optimized catalyst modified by rare earth had been investegeated. The conversion efficiency of NO oxidation was evaluated by simulated flue gas. In this thesis, the main results are as follows:1. The transition metal Mn was the main active component. The effects of different precursors on the NO catalytic oxidation were studied. The not calcinations catalysts Mn-Fe, Mn-Cu and Mn-Co were used to study oxidation efficiency. As shown in results, both in low and high temperature addition ferric can effectively promote the NO oxidation. The ferric compounds and cobalt compounds were in favor to low-temperature oxidation, but the copper compounds were in favor to high-temperature oxidation. The calcinations is not obvious improve oxidation efficiency. Then, the influence of different precursors of manganese and ferric catalyst was prepared. The catalysts prepared from a variety of precursors are amorphous catalyst. The results show that the catalyst composition was prepared by manganese acetate, ferric nitrate benefit to NO oxidation.2. The effect of polyethylene glycol and ferric on catalysts on the NO catalytic oxidation efficiency was investigated. The better oxidation efficiency was gained when the catalyst was washed by distilled water. The NO conversion decreases with decreasing of pH value after wash filtrate. The effect of order of feeding the reactants (Normal, Reverse, Parallel-flow) and the methods of combining the reactants on NO conversion efficiency. It can be observed that the combination method¢ñhad similar conversion efficiency. The reagents-feeding orders in combination method¢òhave a little impact on the conversion. It is obvious that the reagents feeding orders affect the combination method¢ó. The combination method II with prepared by normal was the optimum catalyst, which would be used in the later studies. The catalysts were prepared in simultaneously of physical function and chemical reaction was benefit to NO catalytic oxidation. The study shows that coexist of PEG 1000 and ferric were in favor to low temperature NO catalytic oxidation.3. The effect of preparation conditions and catalyst formulations prepared by orthogonal experiment. Orthogonal experimental results show that the calcination temperature the greatest impact on conversion efficiency. When the experimental temperature at 125¡æ, the preparation effect on conversion efficiency decreased as follow:calcinations temperature>PEG1000/(Mn7++Mn2++Fe3+)>Mn7+:Mn2+> (Mn7++Mn2+):Fe3+> water bath temperature.4. The manganese and ferric oxides (MnFeOx) catalysts were prepared by organic solvent method, and the catalytic oxidation process characters of NO were investigated. The effects of main preparation conditions on NO conversion, calcination temperature, mole percentage of polyethylene glycol 1000 (PEG1000) /(Mn7++Mn2++Fe3+), proportion of Mn7+:Mn2+, proportion of (Mn7++Mn2+):Fe3+ and temperature of water bath, were all discussed in this work. The optimal preparation is manganese and ferric oxides (MnFeOx) catalysts prepared by 400¡æ,1%,4:1,1:1 and 70¡æ, respectively. Appropriate number of holes and the crystallinity is conducive to NO oxidation. Add too much polyethylene glycol led to catalyst bond, reduce the number of holes, pore width decreases. Change Mn7+:Mn2+ and (Mn7++Mn2+):Fe3+ ratio have a certain influence on the crystallinity and oxide structure of the catalyst. The results show that the MnFeOx catalyst with amorphous or nano-crystallite structure shows the notable activity for NO oxidation. More than 90% NO could be converted to NO2 over the MnFeOx catalyst at 100¡æ.
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