Environmentally-benign catalysts for the selective catalytic reduction of NOx from diesel engines: structure–activity relationship and reaction mechanism aspects

Abstract

Selective catalytic reduction of NO_x using NH₃ or hydrocarbons (NH₃-SCR or HC-SCR) in oxygen-rich exhaust from diesel engines remains a major challenge in environmental catalysis. The development of highly efficient, stable and environmentally-benign catalysts for SCR processes is very important for practical use. In this feature article, the structure–activity relationship of vanadium-free catalysts in the NH₃-SCR reaction is discussed in detail, including Fe-, Ce-based oxide catalysts and Fe-, Cu-based zeolite catalysts, which is beneficial for catalyst redesign and activity improvement. Based on our research, a comprehensive mechanism contributing to the performance of Ag/Al₂O₃ in HC-SCR is provided, giving a clue to the design of a catalytic system with high efficiency.