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Activity Self-Optimization Steered by Dynamically Evolved Fe³⁺@Fe²⁺ Double-Center on Fe₂O₃ Catalyst for NH₃-SCR.

ABSTRACT: Identification of the active centers dynamically stable under the reaction condition is of paramount importance but challenging because of the limited knowledge of steady-state chemistry on catalysts at the atomic level. Herein, focusing on the Fe₂O₃ catalyst for the selective catalytic reduction of NO with NH₃ (NH₃-SCR) as a model system, we reveal quantitatively the self-evolving Fe³⁺@Fe²⁺ (∼1:1) double-centers under the in-situ condition by the first-principles microkinetic simulations, which enables the accurate prediction of the optimal industry operating temperature (590 K). The cooperation of this double-center achieves the self-optimization of catalytic activity and rationalizes the intrinsic origin of Fe₂O₃ catalyzing NH₃-SCR at middle-high temperatures instead of high temperatures. Our findings demonstrate the atomic-level self-evolution of active sites and the dynamically adjusted activity variation of the catalyst under the in-situ condition during the reaction process and provide insights into the reaction mechanism and catalyst optimization.

SUBMITTER: Yuan HY

PROVIDER: S-EPMC9597592 | biostudies-literature | 2022 Oct

REPOSITORIES: biostudies-literature

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Activity Self-Optimization Steered by Dynamically Evolved Fe3+@Fe2+ Double-Center on Fe2O3 Catalyst for NH3-SCR.

Yuan Hai Yang HY Sun Ningning N Chen Jianfu J Yang Hua Gui HG Hu P P Wang Haifeng H

JACS Au 20220921 10

Identification of the active centers dynamically stable under the reaction condition is of paramount importance but challenging because of the limited knowledge of steady-state chemistry on catalysts at the atomic level. Herein, focusing on the Fe2O3 catalyst for the selective catalytic reduction of NO with NH3 (NH3-SCR) as a model system, we reveal quantitatively the self-evolving Fe3+@Fe2+ (∼1:1) double-centers under the in-situ ...[more]

PMID: 36311837

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Project description:The group has shown that Baiyun Ebo rare earth concentrate has excellent performance in NH3-SCR denitrification when used as a carrier, where rare earth elements are mainly present in cerium fluorocarbon ore (CeCO3F) and monazite (CePO4) mineral phases. In this paper, a new low-temperature NH3-SCR catalyst of Mn-Fe/CeCO3F-monazite was prepared by an impregnation method, using synthetic CeCO3F and purified monazite as carriers. By exploring its denitrification performance and mechanistic analysis, it provides theoretical guidance for the use of rare earth concentrates as low-temperature NH3-SCR catalysts. Our previous studies have determined the optimum loading of Fe, so this paper needs to be investigated for the optimum doping ratio of the active substance Mn. The results of the activity tests, XRD and BET have determined that the best denitrification rate and catalytic performance was achieved at a ratio of Mn : Ce of 1 : 5. The denitrification activity of the different catalysts was investigated by loading Fe, Mn and Fe and Mn together. The results obtained by means of experimental analyses such as XRD, SEM, BET and activity tests showed that the composite catalyst loaded with Fe and Mn at the same time, had the highest activity and its denitrification rate could reach 94.8% at 250 °C. This is mainly attributed to the fact that the interaction of Fe, Mn can promote the dispersion of each other on the carrier surface, which greatly improves the specific surface area of the catalyst. The introduction of Fe and Mn increases the acidic sites and the amount of acid on the catalyst surface, which results in the formation of a large number of oxygen vacancies and the presence of more oxygen species on the catalyst surface, which facilitate the migration of oxygen. The new catalyst was investigated by Fourier transform infrared (FTIR) spectroscopy to characterise the adsorption and transformation behaviour of the reactive species on the surface of the catalyst, and to investigate the reaction mechanism. The results showed that the entire reaction process followed the L-H mechanism, with the gaseous NO adsorption and activation on the catalyst surface generating bidentate nitrate, bridging nitrate species and NH3/NH4 + species as the main intermediate species involved in the reaction, both of which underwent redox reactions on the catalyst surface to produce N2 and H2O. The above results indicated that the CeCO3F-monazite carrier has excellent performance, and provided a theoretical basis for the high-value utilization of rare earth concentrates.

Dataset Information

Activity Self-Optimization Steered by Dynamically Evolved Fe³⁺@Fe²⁺ Double-Center on Fe₂O₃ Catalyst for NH₃-SCR.

Publications

Activity Self-Optimization Steered by Dynamically Evolved Fe<sup>3+</sup>@Fe<sup>2+</sup> Double-Center on Fe<sub>2</sub>O<sub>3</sub> Catalyst for NH<sub>3</sub>-SCR.

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