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The Development And Properties Study Of Mn/TiO2Catalyst For NO Oxidation

Posted on:2014-11-09Degree:MasterType:Thesis
Country:ChinaCandidate:Z Y AnFull Text:PDF
GTID:2181330452453658Subject:Power Engineering and Engineering Thermophysics
Abstract/Summary:PDF Full Text Request
Mn/TiO2catalysts have shown good performance in NO oxidation and havepotential advantages when compared with other catalysts. In this paper, a fixed-bedreactor was used as the platform to study the influences of different factors on thecatalytic activity of Mn/TiO2, including the crystalline phases of TiO2, and thepreparation and reaction conditions. The catalysts were characterized by X-raydiffraction, field emission scanning electron microscope, X-ray photoelectronspectroscopy, H2temperature programmed reduction, and O2temperature programmeddesorption to study the role of different factors in affecting catalytic activity ofMn/TiO2.Mn-based catalysts impregnated on TiO2with different crystalline phases(Rutile(R), Anatase(A) and P25(P)) were used to study the influence of TiO2crystallinephases. It was shown that P25TiO2was more beneficial to the catalytic activity ofMn/TiO2catalyst. The catalysts activity was in the order of Mn/TiO2(P)> Mn/TiO2(A)>Mn/TiO2(R). Analysis showed that, compared to anatase and rutile TiO2, P25TiO2gavebetter dispersion of MnOxon the support surface, suppressed the agglomeration ofcatalyst particles, and produced more Mn2O3, which was more active for the oxidationof NO. In addition, P25enhanced the reduction of MnOx, especially for Mn2O3, andmore easily desorbed O2–could be generated from the Mn3+–O bond.The influence of preparation and reaction conditions on the catalytic activity ofMn-based catalysts impregnated on P25TiO2was studied. The results showed that,compared with manganese nitrate, manganese acetate as a precursor could giveMn/TiO2(P) better catalyst activity, because it could produce a higher proportion ofMn2O3. In addition, manganese nitrate might cause agglomeration of catalyst particles,surface deterioration, and the undecomposed Mn-nitrate residues, and thus lowering thecatalytic activity.Relatively low calcination temperature was beneficial to promote thecatalytic activity of Mn/TiO2catalysts since it could enhance the percentage of Mn2O3in MnOx, promote the dispersion of MnOxon TiO2, as well as increase the reductioncapability of Mn/TiO2catalysts and the desorption of chemisorbed O2-on catalystssurface, thus raising the catalytic activity of Mn/TiO2. Reaction conditions could also greatly influence the catalytic activity ofMn/TiO2(P). When GHSV was less than20000h-1, NO conversion decreased with theincrease of GHSV, but the catalytic ability per unit volume of catalyst was increased,however, when GHSV was higher than20000h-1, the catalytic ability did not increasewith GHSV any more, and NO conversion decreased linearly with the increase ofGHSV. Within a certain range, theincreasedO2concentration could help to increase theNO conversion, but when O2concentration exceeded6%, NO conversion was no longeraffected. There existed an optimal value for NO concentration in NO oxidation tests.When NO concentration was around500ppm, NO had the highest conversion, whichsuggested that if NO concentration differed from this value, NO conversion rate wouldbe decreased.
Keywords/Search Tags:Nitricoxide, Manganeseoxides, Titaniumdioxide, Catalyticoxidation
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