Deactivation mechanism of de-NOx catalyst (V2O5-WO3/TiO2) used in coal fired power plant

The fresh and deactivated Selective Catalytic Reduction (SCR) catalysts used in a coal fired power plant were studied in a fixed bed reactor. The physical-chemical properties of the catalysts were characterized by means of SEM-EDX, XRF, XPS, N2 adsorption/desorption, FT-IR, XRD and TG. The results showed that the used catalyst was seriously deactivated. The NOx removal efficiency and the specific surface area of the used catalyst (35.0%, 1.05 m2/g) were obviously less than those of the fresh catalyst (88.2%, 72.50 m2/g). The V5+ content in the deactivated catalyst was increased from 17.4% to 32.2% compared with the fresh one, and large quantities of Al2(SO4)3 can be found over the surface of the deactivated catalyst. The results of SEM and XRD showed that the thermal sintering occurred in the deactivated catalyst. Generally, the V2O5-WO3/TiO2 catalyst deactivation can be interpreted by the valence change of V atoms, thermal sintering and aluminum sulfate formation over catalyst surface.