Heavy Metal Challenge in NH₃-SCR DeNO_x Catalysts: Poisoning Deactivation Mechanisms and Enhanced Resistance Strategies

Ammonia selective catalytic reduction (NH₃-SCR) is the most widely used technology in the field of industrial flue gas denitrification. However, the presence of heavy metals in flue gas can seriously affect the performance of SCR catalysts, leading to their deactivation or even failure. Therefore, it is of great significance to deeply study the poisoning mechanism of SCR catalysts under the action of heavy metals and how to enhance their resistance to poisoning. This article reviews the reaction mechanism of NH₃-SCR technology, compares the impact of heavy metals on the activity of different SCR catalysts, and then discusses in detail the poisoning mechanism of SCR catalysts by heavy metals, including pore blockage, reduction of specific surface area, and destruction of active centers caused by heavy metal deposition, all of which jointly lead to the physical or chemical poisoning of the catalyst. Meanwhile, the mechanism of action when multiple toxicants coexist was analyzed. To effectively address these challenges, the article further summarizes various methods to improve the catalyst's resistance to heavy metal poisoning, such as element doping, structural optimization, and carrier addition, which significantly enhance the heavy metal resistance of the catalyst. Finally, the article provides a prospective analysis of the challenges faced by NH₃-SCR catalysts in anti-heavy metal poisoning technology, emphasizing the necessity of in-depth research on the poisoning mechanism, exploration of the mechanism of synergistic action of multiple pollutants, development of comprehensive anti-poisoning strategies, and research on catalyst regeneration technology, in order to promote the development of efficient anti-heavy metal poisoning NH₃-SCR catalysts.