Characterization and reactivity of pure TiO2-SO42- SCR catalyst:: influence of SO42- content

The modifications of textural and surface properties of sulfated TiO2 have been investigated by means of XRD, surface area, XPS, Raman, FT-IR, NH3-TPD, and catalytic tests in the reduction of NO by NH3. According to sulfate content, the isolated sulfate transforms to a polynuclear sulfate type. Between SO42- = 3.0 and 6.6 wt.%, the amount of S=O species per unit area is almost constant and equal. Total number of acid sites increases with the SO42- content, while the strongest sites are maximum at 1.5 Wt.% loading. The areal TOF (turnover frequency, mole NO converted/s m(2)) is also higher at SO42- = 1.5 Wt.% and is directly related to the number of strong Lewis acid sites. Accordingly, it is suggested that the strong Lewis site generated by doping TiO2 with SO42- is responsible for the higher reactivity of TiO2-SO42- at high temperature. (C) 2000 Elsevier Science All rights reserved.