Deactivation Influence of HF on the V₂O₅-WO₃-TiO₂SCR Catalyst

The electrolytic aluminum waste contains harmful components, such as fluorides. Sending it to coal-fired boilers seems to be a prospective scheme to achieve the harmless treatment of waste. However, the negative influence of F on the SCR catalyst should be examined. In this study, a fixed-bed reactor system is built up to study the deactivation of the V2O5-WO3-TiO2 SCR catalyst by HF when the electrolytic aluminum waste is co-fired with coal in boilers. The activity of the catalyst is evaluated by the NH3-SCR reaction. The deactivation mechanism is investigated through tests of NH3 temperature-programmed desorption, H2 temperature-programmed reduction, X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller (BET), in situ diffuse reflectance infrared Fourier transform spectroscopy, and Raman spectroscopy. The results show that for deactivated catalyst samples, the SCR catalytic activity drops obviously, especially when they work at lower temperatures. Although HF could enhance Brønsted acid sites, increase the Oα (adsorbed oxygen) concentration, and facilitate the Lewis acid site formation, it would not compensate for decreases of V5+ on the catalyst surface and BET surface area, which results in an activity reduction of the catalyst sample.