The Preparation And Performance Of Fe-doping V₂O₅/TiO₂ Catalysts For Diesel Vehicle

With the development of automobile industry around the world, the amount of vehicles raises year by year. The vehicle emission issues, especially the NO_X from diesel engine becomes more serious. In order to control the severe environment problems effectively, China has established strict regulations to control diesel engine emissions. In consideration of the domestic circumstances, the Selective catalytic reduction（SCR） has been proved to be the most promising aftertreatment technology for diesel NO_X emission. Basing on the present situation of SCR catalysts, This thesis investigated the novel Fe-doping V₂O₅/TiO₂ catalyst,With the purpose for achieving the higher performance SCR catalysts.The modified Fe-doping V₂O₅/TiO₂ catalysts were prepared by sol-gel method and impregnation method. Aiming to acquire the optimum condition of preparation and reaction,the influence of Fe doping amout and the calcination temperature were explored by a catalyst activity test device. The test results showed that catalysts could exhibit the best catalytic activity when the Fe mass ratio was 0.05% and the calcination temperature reached 500℃. The NO_X conversion efficiency could exceed90% when the reaction temperature was 240℃ and achieved the best 99.5% on 330℃ under the test condition of 500 ppm NO, 500 ppm NH3, 5% O2, N2（balance gas）,500 ppm and the GHSV 23885h-1.The influence of reaction conditions on NO_X conversion were inspected, such as the GHSV, the O2 concentration, the NO inlet concentration, the ratio of NH3/NO and so on. In addition, the effects of SO2 and H2 O on SCR activities were investigated.Test results showed that the NO_X conversion on VTiFe（0.05%） catalyst reduced to33.2%、 12.8% and 51.2% separately under 500 ppm SO2, 10% H2 O and common action. The descent ranges of three condition were all less than VTiFe（0） catalyst.To obtain a detailed understanding of Fe additives on SCR performance, The optimum VTiFe（0.05%） catalyst and VTiFe（0） catalyst were conducted a variety of characterization techniques such as XRD, BET, TEM, XPS, H2-TPR, NH3-TPD 、NO-TPD、O2-TPD. The results showed that the Fe existed in form of Fe3+and Fe2+.What’s more, Fe-doping not only could inhibit the rutile TiO2 formation, but also increased the surface area and acid of catalyst. Those all were beneficial to SCR catalytic activity.The monolith Fe-doping V₂O₅/TiO₂ catalysts were prepared by slurry coating process. The coated weight could ascend to 15.19% by adding adhesives. By comparison, the max NO_X conversion of Fe-doping monolith catalyst could attain97.5%, which was better than some SCR commercial catalysts.