Investigation On The Preparation And Properties Of F And N-F Doped V₂O₅/TiO₂ Catalyst For Low Temperature SCR

The effective and widely used technique to remove the nitrogen oxide is Selective Catalytic Reduction (SCR) in home and abroad. The catalysts of traditional SCR will be affected by corrosion and abrasion from the high concentration of ash and SO2, so its lifespan be shortened. More and more researchers have paid attention to the low temperature SCR which can solve these problems. The aim of this study was to approach the problem from a different angle, by targeting the non-metal part of the catalyst.Firstly, SCR activity measurements were carried out in a fixed-bed. Investigate the effect of catalyst support preparation methods, such as the way of F-doping, the amounts of F-doping and the calcination temperature. When the reacting gas contained 0.05% NO+5 vol% O2+0.06% NH3 balanced with N2 at a gas hour space velocity (GHSV) of 15000 h-1 The results showed the optimum preparation conditions, the TiO2 support was prepared by a sol-gel method, the amount of F-doping was [F]/[Ti]=1.35%, the calcination temperature of support was 500℃and the calcination temperature of catalyst was 350℃. The activity of this catalyst reached 90% at 200℃-240℃, which was increased by two times to non F-doped sample.The chemical and physical properties were measured by the analysis of XRD, Raman, XPS, NH3-TPD and H2-TPR. This high catalytic activity was ascribed to several beneficial effects produced by F-doping:inhibition of rutile phase, enhancement of surface acidity, creation of oxygen vacancies and superoxide radical anions O2-. Moreover, the generation and evolution of O2- was measured by EPR. The data showed O2- was generated at the calcination stage, the higher the calcination temperature was, the more O2-; generated, the longer the calcination time was, the more O2- generated.Secondly, keeping the optimum amount 1.35% of F-doping, introducing another non-metal nitrogen doped to the catalyst. The paper studied the effect of nitrogen amounts. The catalyst with the amount of 1% N-doping showed the highest NO removal. The activity of N-F co-doping catalyst was higher by 3% than F-doped sample. N-F co-doping increased the capable of restoring deeply.Finally, the operating condition such as O2 concentration, gas hour space velocity (GHSV), H2O and SO2 concentration was investigated. The results showed the optimum operating conditions, the O2 concentration was 5%, the GHSV was 9000 h-1. The resistance to SO2 of F-doped and N-F doped catalysts was well, but the resistance to H2Owas not well. When H2O and SO2 existed together, the catalytic activity of F-doped and N-F doped catalysts were inhibited. Their activity would be recovered after cutting off H2O and SO2.