Recent advances in low-temperature NH3-SCR of NOx over Ce-based catalysts: Performance optimizations, reaction mechanisms and anti-poisoning countermeasures

Selective catalytic reduction of nitrogen oxide (NOx) by ammonia (NH3-SCR) is an effective method to remove NOx from major atmospheric pollutants such as coal-burning industry and diesel engines. Among the many low-temperature (<250 °C) NH3-SCR catalysts, Ce-based catalysts have attracted much attention due to their wide operating temperature window, high low-temperature catalytic activity and environmental friendliness. In this review, the research progress of different kinds of Ce-based catalysts (such as pure CeO2, mixed CeO2 oxides depending on the role of Ce species) based on composition, structure and morphology for NH3-SCR in recent six years was reviewed, and the relationship between their structure and performance was analyzed. In addition, this review summarizes the poisoning mechanism for SO2, H2O vapor, alkali/heavy metals and reviews the important published work of Ce-based catalysts. It highlights the reaction mechanism and anti-poisoning strategies of Ce-based catalysts at different levels: including structural design, metal modification, carrier introduction, and acid treatment. Finally, the challenges and prospects of Ce-based NH3-SCR catalysts are presented. And the catalyst design strategies to achieve wide operating temperature window and high stability (high toxicity resistance) of NH3-SCR reaction are proposed.