The Study of SCR Mechanism on LaMn_1−<i>x</i>Fe<i>_x</i>O₃ Catalyst Surface Based DFT

Abstract

Perovskite SCR catalysts have become a hot research topic in the field of de-NOx catalyst development. This article selects LaMnO3 with high performance as the research object, modifies the catalyst by doping some iron elements instead of manganese elements, and applies density functional theory to study its reaction mechanism, providing theoretical reference for further research on perovskite. Research has found that several main reactants such as NH3, NO, and O2 can form stable adsorption at the active site, with NO more inclined to adsorb at the nitrogen atom end at the active site. The oxidation of O2 molecules after adsorption is greater than that of the active site. The adsorption capacity of the Mn active site of the catalyst before modification on the above molecules is weaker than that of the Fe active site introduced after modification. Under both anaerobic and aerobic conditions in the SCR reaction process, NH3 molecules are first adsorbed at the active site, and then influenced by lattice oxygen under anaerobic conditions. Under aerobic conditions, they are gradually dehydrogenated and produce NH2 and NH radicals. These two radicals react with NO molecules to form intermediate products in the form of NH2NO and NHNO molecules. Due to the instability of the intermediate products, they ultimately decompose into N2 and H2O molecules. The introduction of Fe active sites can increase the generation of NH2 and NH radicals during the reaction process and simplify the reaction process between NH2 radicals and NO molecules, which will be conducive to the completion of the reaction.

Keywords

• perovskite
• NH₃-SCR
• first principle
• mechanism