Catalysts prepared from solid wastes for efficient removal of NOx in NH3-SCR process: A review

Abstract

The increase of solid wastes exerted great pressure on the environment and even damaged human health. Given this, the resource utilization of solid wastes became an inevitable trend of the industrial development. However, many researchers recognized that solid wastes with the component of Fe2O3, SiO2, Al2O3, TiO2, etc., could be utilized as the low-cost materials for preparing NH3-SCR catalysts, which could solve both the accumulation of solid wastes and the emission of NOx in industrial processes. Herein, some typical solid wastes, such as blast furnace slag (BFS), red mud (RM), coal fly ash (CFA), Fenton sludge (FS), etc., were extensively studied for their potential in NH3-SCR catalysts. Although the presence of some harmful components in solid wastes led to catalysts deactivation, they could still be excellent supports applied on NH3-SCR catalysts after proper pretreatment. In fact, these catalyst supports derived from solid wastes provided larger specific surface areas, thereby enhancing the NH3 adsorption and redox capacity and facilitating the active ingredients loaded uniformly. Meanwhile, some useful impurities in solid wastes might also facilitate the NH3-SCR performance, achieving denitrification efficiency comparable to other catalysts made from costly materials. Moreover, most of these NH3-SCR catalysts performed significant SO2 and/or H2O tolerance via metal oxides-doping, which would expand their potential for practical application in industry. Finally, the prospects for the application of solid wastes in NH3-SCR catalysts were also proposed.