Iron oxide-based catalysts for low-temperature selective catalytic reduction of NOx with NH3

Selective catalytic reduction (SCR) is now an established NOx removal technology for industrial flue gas as well as for diesel engine exhaust gas. However, it is still a big challenge to develop a novel low-temperature catalyst for NH3-SCR of NOx, especially at a temperature below 200 degrees C. In the past few years, many studies have demonstrated the potential of iron (Fe)-based catalysts as low-temperature catalysts for NH3-SCR of NOx. Herein, we summarize the recent progress and performance of Fe-based catalysts for low-temperature NH3-SCR of NOx. Catalysts are divided into three categories: single FexOy, Fe-based multimetal oxide, and Fe-based multimetal oxide with support catalysts. The catalytic activity and selectivity of Fe-based catalysts are systematically analyzed and summarized in light of some key factors such as activation energy, specific surface area, morphology, crystallinity, preparation method and precursor, acid sites, calcination temperature, other metal dopant/substitute, and redox property of catalysts. In addition, H2O/SO2 tolerance and the NH3-SCR reaction mechanism over Fe-based catalysts, including Eley-Rideal and Langmuir-Hinshelwood mechanism, are emphasized. Lastly, the perspectives and future research directions of low-temperature NH3-SCR of NOx are also proposed.