Insight into N2O Formation Over Different Crystal Phases of MnO2 During Low-Temperature NH3–SCR of NO

Yang, Jie; Ren, Shan; Su, Buxin; Zhou, Yuhan; Hu, Geng; Jiang, Lijun; Cao, Jun; Liu, Weizao; Lu, Yong; Kong, Ming; Yang, Jian; Liu, Qingcai

doi:10.1007/s10562-021-03541-8

Cited by 51 publications

(19 citation statements)

References 30 publications

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“…The H 2 -TPR results are shown in Figure e. The peak at 180 °C corresponds to the removal of surface-adsorbed oxygen from the surface of Ce-SMO; the peak at 395 °C originates from the reduction of Mn 4+ to Mn 3+ ; and the peak at 485 °C is attributed to the reduction of Mn 3+ to Mn 2+ in the mullite structure. , The reduction of CeO 2 generally occurs from ∼450 to >700 °C; , thus, it is difficult to identify the reduction of Ce 4+ to Ce 3+ because of the overlapping reduction process. The two Mn reduction peaks both shift to lower temperatures after acid etching, indicating that the binding energy of Mn–O in Ce-SMO–H is weakened, thereby activating the lattice oxygen and facilitating the transfer of oxygen species.…”

Section: Results and Discussionmentioning

confidence: 99%

Synergistic Effects of a CeO₂/SmMn₂O₅–H Diesel Oxidation Catalyst Induced by Acid-Selective Dissolution Drive the Catalytic Oxidation Reaction

Yang

Wang

et al. 2022

ACS Appl. Mater. Interfaces

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A diesel oxidation catalyst (DOC) is installed upstream of an exhaust after-treatment line to remove CO and hydrocarbons and generate NO2. The catalyst should possess both good oxidation ability and thermal stability because it sits after the engine. We present a novel high-performance DOC with high steam resistance and thermal stability. A selective dissolution method is adopted to modify the surface physicochemical environment of CeO2–SmMn2O5. The X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, Raman, electron paramagnetic resonance, hydrogen temperature-programmed reduction, and temperature-programmed desorption results reveal that surface Sm cations are partially removed with the exposure of more Mn4+ and Ce3+ cations and the presence of active surface oxygen species. This mechanism benefits the oxygen transformation from Ce to Mn and promotes the Ce3+ + Mn4+ ↔ Ce4+ + Mn3+ redox cycle according to the in situ near-ambient pressure X-ray photoelectron spectroscopy and in situ diffuse reflectance infrared Fourier transformation spectroscopy results. Under laboratory-simulated diesel combustion conditions, the catalyst demonstrates excellent low-temperature oxidation catalytic activity (CO and C3H6 conversion: T 100 = 250 °C) compared to a Pt-based catalyst (CO and C3H6 conversion: T 100 = 310 °C) with a WHSV of 120,000 mL g–1 h–1. Specifically, NO conversion reaches 68% when the temperature is approximately 300 °C.

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Section: Results and Discussionmentioning

confidence: 99%

Synergistic Effects of a CeO₂/SmMn₂O₅–H Diesel Oxidation Catalyst Induced by Acid-Selective Dissolution Drive the Catalytic Oxidation Reaction

Yang

Wang

et al. 2022

ACS Appl. Mater. Interfaces

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“…The disadvantage of CeO 2 is that its surface acidity is weak, and it cannot effectively adsorb NH 3 . Therefore, a common strategy is to modify CeO 2 by doping, such as with transition metal species (W, , Mo, Nb, Al, Ti, Cu) or with oxoacids (SO 4 , − PO 4 − …”

Section: Development Of Nh3-scr Catalystsmentioning

confidence: 99%

“…The performance of MnO x catalysts can be enhanced by tuning the crystal phase, morphology, and spatial structure. Yang et al38 studied the effect of the MnO 2 crystalline form on deNO x performance. Compared with β-MnO 2 \γ-MnO 2 \δ-MnO 2 , α-MnO 2 showed better catalytic activity.…”

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confidence: 99%

Toward an Atomic-Level Understanding of the Catalytic Mechanism of Selective Catalytic Reduction of NO_x with NH₃

2022

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As primary air pollutants, nitrogen oxides (NO x ) result in a series of environmental issues, such as photochemical smog, acid rain, ozone depletion, and fine particle pollution, which threaten the health of all human beings. Selective catalytic reduction with NH 3 (NH 3 -SCR) is the most powerful technique for the abatement of NO x . The development of NH 3 -SCR catalysts is the key to the normal operation of NO x removal systems. The currently used V 2 O 5 -WO 3 (MoO 3 )/TiO 2 catalysts are widely applicable for medium-/high-temperature conditions but are not suitable for NH 3 -SCR operated at low temperatures. The development of high-efficiency low-temperature SCR catalysts is the central issue at present. The rational design of efficient NH 3 -SCR catalysts requires an atomic-level understanding of their mode of operation, including the identification and characterization of the active sites, reaction paths, and rate-determining steps of NH 3 -SCR. Herein, we summarize the recent advances in catalysts for low-temperature NH 3 -SCR. The active sites, intermediates, and reaction pathways of oxide catalysts and molecular sieve catalysts mainly studied by researchers will be reviewed, with a particular focus on an atomic-level understanding of the mechanism. We provide an atomic-level understanding of the current general NH 3 -SCR catalytic mechanism and further combine the atomic-level understanding of the mechanism to provide design guidelines for low-temperature SCR catalysts. We hope that our account will trigger research activities and discussions in NH 3 -SCR catalysis and bridge the material gap between idealized and real catalytic systems.

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“…23 Among various catalysts, manganese-based catalysts have been widely studied and applied due to their low cost and outstanding low-temperature denitrication performance, whereby their abundant Lewis acid sites, variable valence states of Mn, and strong redox ability contribute to their excellent catalytic activity at low temperature, especially under 200 °C. 10,[24][25][26][27] For instance, Yang et al 28 found that a-MnO 2 exhibited the most superior SCR performance for NO x conversion compared with other crystal phases of b, g, and d-MnO 2 at a lower temperature of 50-120 °C. However, the low N 2 selectivity currently extremely restricts the application of Mn-based catalysts because the strong oxidation ability of tetravalent Mn leads to more N 2 O formation.…”

Section: Introductionmentioning

confidence: 99%

Revealing the crystal facet effect on N₂O formation during the NH₃-SCR over α-MnO₂ catalysts

et al. 2023

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Insight into N2O Formation Over Different Crystal Phases of MnO2 During Low-Temperature NH3–SCR of NO

Cited by 51 publications

References 30 publications

Synergistic Effects of a CeO₂/SmMn₂O₅–H Diesel Oxidation Catalyst Induced by Acid-Selective Dissolution Drive the Catalytic Oxidation Reaction

Synergistic Effects of a CeO₂/SmMn₂O₅–H Diesel Oxidation Catalyst Induced by Acid-Selective Dissolution Drive the Catalytic Oxidation Reaction

Toward an Atomic-Level Understanding of the Catalytic Mechanism of Selective Catalytic Reduction of NO_x with NH₃

Revealing the crystal facet effect on N₂O formation during the NH₃-SCR over α-MnO₂ catalysts

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Insight into N2O Formation Over Different Crystal Phases of MnO2 During Low-Temperature NH3–SCR of NO

Cited by 51 publications

References 30 publications

Synergistic Effects of a CeO2/SmMn2O5–H Diesel Oxidation Catalyst Induced by Acid-Selective Dissolution Drive the Catalytic Oxidation Reaction

Synergistic Effects of a CeO2/SmMn2O5–H Diesel Oxidation Catalyst Induced by Acid-Selective Dissolution Drive the Catalytic Oxidation Reaction

Toward an Atomic-Level Understanding of the Catalytic Mechanism of Selective Catalytic Reduction of NOx with NH3

Revealing the crystal facet effect on N2O formation during the NH3-SCR over α-MnO2 catalysts

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Synergistic Effects of a CeO₂/SmMn₂O₅–H Diesel Oxidation Catalyst Induced by Acid-Selective Dissolution Drive the Catalytic Oxidation Reaction

Synergistic Effects of a CeO₂/SmMn₂O₅–H Diesel Oxidation Catalyst Induced by Acid-Selective Dissolution Drive the Catalytic Oxidation Reaction

Toward an Atomic-Level Understanding of the Catalytic Mechanism of Selective Catalytic Reduction of NO_x with NH₃

Revealing the crystal facet effect on N₂O formation during the NH₃-SCR over α-MnO₂ catalysts