Review on the latest developments in modified vanadium-titanium-based SCR catalysts

Vanadium-titanium-based catalysts are the most widely used industrial materials for NOx removal from coal-fired power plants. Owing to their relatively poor low-temperature deNOx activity, low thermal stability, insufficient Hg0 oxidation activity, SO2 oxidation, ammonia slip, and other disadvantages, modifications to traditional vanadium-titanium-based selective catalytic reduction (SCR) catalysts have been attempted by many researchers to promote their relevant performance. This article reviewed the research progress of modified vanadium-titanium-based SCR catalysts from seven aspects, namely, (1) improving low-temperature deNOx efficiency, (2) enhancing thermal stability, (3) improving Hg0 oxidation efficiency, (4) oxidizing slip ammonia, (5) reducing SO2 oxidation, (6) increasing alkali resistance, and (7) others. Their catalytic performance and the influence mechanisms have been discussed in detail. These catalysts were also divided into different categories according to their modified components such as noble metals (e.g., silver, ruthenium), transition metals (e.g., manganese, iron, copper, zirconium, etc.), rare earth metals (e.g., cerium, praseodymium), and other metal chlorides (e.g., calcium chloride, copper chloride) and non-metals (fluorine, sulfur, silicon, nitrogen, etc.). The advantages and disadvantages of these catalysts were summarized. Based on previous studies and the author's point of view, doping the appropriate modified components is beneficial to further improve the overall performance of vanadium-titanium-based SCR catalysts. This has enormous development potential and is a promising way to realize the control of multiple pollutants on the basis of the existing flue gas treatment system.