Characterization study on the promoting effect of F-doping V2O5/TiO2 SCR catalysts

V2O5/TiO2 catalysts were prepared in the presence of (NH4)(2)TiF6 with controlled fluorine to titanium molar ratios (RF/Ti x 100) (0, 0.5, 1, 1.35 and 2) for selective catalytic reduction of nitrogen oxides (NOx) by NH3 (SCR process). It was found that the NOx conversion over F-doping V2O5/TiO2 was greatly improved compared with pure V2O5/TiO2. The effects of F-doping on the structure of the catalysts were systematically examined using XRD, Raman spectrum, BET, TEM, H-2-TPR, NO-TPD, XPS and EPR. The XPS results showed that F ions were incorporated into the TiO2 lattice. The high catalytic activity was ascribed to several beneficial effects produced by F-doping - preventing of grain growth, inhibiting of phase transformation from anatase to rutile, higher reducibility of good dispersion of vanadia species, creation of oxygen vacancies, and increasing active sites. It was interesting to point out that the better catalytic activity of F-doped V2O5/TiO2 was achieved by the creation of surface oxygen vacancies.