Structure and activity relationships of AMn2O4 (A = Mg and Zn) spinels in selective catalytic reduction of NOx with NH3

Abstract

Mn-based spinel as a catalyst for low-temperature selective catalytic reduction with ammonia (NH3-SCR) has been widely studied. However, most researchers have focused on double transition metal Mn-based spinel and the reports about doping with non-transition metal are not common. Herein, Mg2+ and Zn2+ with similar ionic radii were used to prepare high purity MgMn2O4 and ZnMn2O4 (named MMO and ZMO) to study their structure and activity relationships in NH3-SCR. It was found that the denitration performance of the two showed significant differences at low temperature despite have a very similar crystal structure. A series of characterization methods and first-principles calculations demonstrates that the relatively weak bonding strength and basic adsorption sites of MMO catalyst are the key factors contributing to its superior reactivity at low temperatures. This work provides novel insights and ideas in comprehending the catalytic function of non-transition metal-doped Mn-based spinels in NH3-SCR reactions.