Effect of SO2 on the Selective Catalytic Reduction of NOx over V2O5-CeO2/TiO2-ZrO2 Catalysts

摘要

The effect of SO2 on the selective catalytic reduction of NOx by NH3 over V2O5-0.2CeO2/TiO2-ZrO2 catalysts was studied through catalytic activity tests and various characterization methods, like Brunner−Emmet−Teller (BET) surface measurement, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray fluorescence (XRF), hydrogen temperature-programmed desorption (H2-TPR), X-ray photoelectron spectroscopy (XPS) and in situ diffused reflectance infrared Fourier transform spectroscopy (DRIFTS). The results showed that the catalyst exhibited superior SO2 resistance when the volume fraction of SO2 was below 0.02%. As the SO2 concentration further increased, the NOx conversion exhibited some degree of decline but could restore to the original level when stopping feeding SO2. The deactivation of the catalyst caused by water in the flue gas was reversible. However, when 10% H2O was introduced together with 0.06% SO2, the NO_x conversion was rapidly reduced and became unrecoverable. Characterizations indicated that the specific surface area of the deactivated catalyst was significantly reduced and the redox ability was weakened, which was highly responsible for the decrease of the catalytic activity. XPS results showed that more Ce³⁺ was generated in the case of reacting with SO₂. In situ DRIFTS results confirmed that the adsorption capacity of SO₂ was enhanced obviously in the presence of O₂, while the SO₂ considerably refrained the adsorption of NH₃. The adsorption of NO_x was strengthened by SO₂ to some extent. In addition, NH₃ adsorption was improved after pre-adsorbed by SO₂ + O₂, indicating that the Ce³⁺ and more oxygen vacancy were produced.