Study On Properties Of Ce,Co,Ni/V-W/TiO₂ Modified By Composite Sol For Selective Catalytic Reduction

The pollution of nitrogen oxides is a global environmental problem. NO accounts for about 90 percent of the nitrogen oxide from fuel combustion, which reaches more than 5×10't every year. The atmosphere features of our county will be changed fundamentally with the increase of NOx emission, which results to a series of environmental program, and threat to human health. It is of great practical significance to develop denitration technology.In this thesis, the cordierite honeycomb ceramics were modified by TiO2-SiO2 composite sol. The main factors of the specific surface area were optimized by orthogonal designed method:mass ratio of TiO2 sol and SiO? sol is 1:1; CMC was 8 percent of TiO2-SiO2 composite sol; dipping for six times; calcination temperature at 300℃. Under the optimized process of TS washcoating by orthogonal designed methods, the surface area of TS modified cordierite reached up to 59.29 m2/g, which is about 200 times larger than that of the blank cordierite. The results of NH3-TPD test suggested that the catalyst with the TS mass ratio of 1:1 showed the maxium acidity. Compared with catalyst activity and the acidity of catalyst surface, the moderate acidity was in favor of catalytic activity, and the catalyst shows the optimal activity at the mass ration of TS was 4:1.The TS carrier supported V2O5 with different metal oxides was prepared by impregnation. The catalytic activity was investigated by using the method of temperature progressing and urea was used as reductant. The results of activity active test, it showed that NO conversion on Ni-V-W/TS4 was 88% at 400℃, which performes much better than that on Ni-V-W/TS4 and Co-V-W/TS4. And the complex catalyst Ce-Ni-V-W/TS4 had the highest activity. on which NO conversion was nearly 100% at 400℃.The catalytic samples were characterized by BET, XRD, TPD and XPS techniques. The research results showed that the larger BET surface area of the catalysts may contribute to improve catalyst activity; there was not a linear relationship between peak temperature or peak area and activity; in the oxidation-reduction process, Ni and Co could make the reduction peak of the catalysts move to lower temperature, and they make the catalysts more reducing; the ration of Vx+/V5+ increased could enhance activity of Ce-Ni-V-W/TS4, because Ce varied from Ce3+ to Ce4, which made surface oxygen of Ce-Ni-V-W/TS4 faster.