Deactivation Influence of HF on the V₂O₅–WO₃–TiO₂ SCR Catalyst

Abstract

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.

Leaching Vanadium from the Spent Denitration Catalyst in the Sulfuric Acid/Oxalic Acid Combined Solvent

“…5 This has caused not only the waste of national strategic reserve metals, such as vanadium (V), tungsten (W), and titanium (Ti), but also a severe environmental risk. 6 Therefore, it is of great importance to realize the extraction of these valuable metals from spent denitration catalysts. 7,8 Numerous studies on the extraction and purification of V from spent denitration catalysts have been carried out.…”

“…About 60% of the catalyst have no regeneration value due to their damaged physical structure or decreased mechanical properties, which typically will be landfilled . This has caused not only the waste of national strategic reserve metals, such as vanadium (V), tungsten (W), and titanium (Ti), but also a severe environmental risk . Therefore, it is of great importance to realize the extraction of these valuable metals from spent denitration catalysts. , …”

Integrated Gas and Solid Model to Determine the Flow Performance in the SCR Reactor

“…6 Controlling the deactivation rate of the catalyst is of great significance for the long period stable operation of the SCR denitration system. 7 Among all the factors leading to SCR catalyst deactivation, fly ash is the most important one. 8,9 By analyzing the SCR denitration system operating conditions, 10,11 fly ash in the flue gas seriously influences the catalyst performance, including catalyst poisoning due to alkali metal elements and abrasion of the catalyst.…”

“…Coal combustion will produce a large number of pollutants, such as gaseous NO x and fly ash. − Selective catalytic reduction (SCR) denitration systems are widely used in power plants to treat NO x . , Catalysts are the key to SCR denitration technology . Controlling the deactivation rate of the catalyst is of great significance for the long period stable operation of the SCR denitration system . Among all the factors leading to SCR catalyst deactivation, fly ash is the most important one. , By analyzing the SCR denitration system operating conditions, , fly ash in the flue gas seriously influences the catalyst performance, including catalyst poisoning due to alkali metal elements and abrasion of the catalyst. , This has become a serious problem for the safe and stable operation.…”