Sn-doped rutile TiO2 for vanadyl catalysts: Improvements on activity and stability in SCR reaction

Sn-doped rutile TiO2 supports (SnxTi1−xO2, X = 0.1, 0.2, 0.5) were designed and V2O5/SnxTi1−xO2 catalysts were synthesized by incipient wetness impregnation. The V2O5/Sn0.2Ti0.8O2 exhibited higher low-temperature SCR activity and better H2O and SO2 resistance than the traditional V2O5/TiO2 (anatase) catalyst. In situ DRIFTs, XPS, H2-TPR and NH3/NO+O2-TPD results showed that Sn doping improved the redox property, NH3/NO adsorption and the amount of surface chemisorbed oxygen. The kinetic study indicated that Sn doping had little effect on SCR reaction pathways, but promoted SCR reaction, mainly through Eley-Rideal mechanism. More importantly, the V2O5/Sn0.2Ti0.8O2 showed better thermal stability than V2O5/TiO2. For V2O5/TiO2, the aggregation and sintering of the catalyst occurred, and the surface area decreased significantly after thermal aging. The monomeric vanadyl species partially transferred to crystalline V2O5. But for V2O5/Sn0.2Ti0.8O2, the surface area did not decrease as much as that for V2O5/TiO2, and the monomeric vanadyl species partially transferred to the polymeric vanadyl species.