Comparative analysis of the dual origins of the N2O byproduct on MnOx, FeOx, and MnFeOx sphere catalysts for a low-temperature SCR of NO with NH3. Issue 40 (26th September 2022)

• Record Type: Journal Article
• Authors: Chen, Zhichao; Guo, Rui-tang; Ren, Shan; Chen, Lin; Li, Xiaodi; Wang, Mingming
• Is Part Of: Journal of materials chemistry. Volume 10:Issue 40(2022)
• Page Start: 21474
• Page End: 21491
• Publication Date: 2022-09-26
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d2ta06199f
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : The formation mechanism of N2 O byproduct from NSCR and NH3 over-oxidation dual pathways on MnO x, FeO x, and MnFeO x sphere catalysts were revealed during the low-temperature SCR process. Abstract : Herein, the origin and evolution mechanism of N2 O formation over the MnFeO x spherical catalyst were investigated in detail, accompanied by a comparison analysis of pristine MnO x and FeO x catalysts. The results showed that the MnFeO x catalyst possessed higher catalytic activity but poorer N2 selectivity than the sole oxide catalysts, and the N2 O concentration could even reach 300 ppm over 175 °C. Further activation tests under separate NH3 /NO oxidation conditions revealed the N2 O accumulation of the MnFeO x catalyst that was primarily derived from the NSCR pathway below 150 °C and then gradually turned to NH3 over-oxidation with temperature. The coupling of Mn and Fe cations induced electron migration and released more Mn 4+ and Os, contributing to the upgraded redox capacity, which served as the inherent motivation of high activity but poor N2 selectivity over the MnFeO x catalyst. For the NH3 over-oxidation pathway, both gaseous O and catalyst oxygen acted as the oxidizers, and the double –NH2 /NH species with the assistance of O was deemed as the restricted step for N2 O generation. For the NSCR pathway, the byproduct N2 O was generated through both E–R and L–H mechanisms, and the former contributed to more N2 O. In addition, the kinetic analysis further verified the obtained conclusions. Finally, a possible mechanism model of N2 O origins over the MnFeO x catalyst was proposed.