Influence of preparation methods on the physicochemical properties and catalytic performance of MnO -CeO2 catalysts for NH3-SCR at low temperature

Yao, Xin‐Kan; Ma, Kaili; Zou, Weixin; He, Sheng‐Gui; An, Jibin; Yang, Fumo; Dong, Lin

doi:10.1016/s1872-2067(16)62572-x

Cited by 136 publications

(43 citation statements)

References 65 publications

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“…Furthermore, it is proposed that the redox couples of Fe 3+ /Fe 2+ and Ce 4+ /Ce 3+ contained in Mn−Fe−Ce−O x /γ-Al 2 O 3 nanocatalysts strengthened the redox cycle of Mn 4+ /Mn 2+ and improve the amount of active oxygen, which would further promote the catalytic reactions [9,35]. The percentage of Fe 2+ /Fe n+ and Ce 3+ /Ce n+ improved with the Mn/Fe molar ratio of 1.0, probably attributed to the strong electron transfer between Fe 2+ ↔ Mn 4+ [50], Ce 3+ ↔ Mn 3+ [35] and Ce 3+ ↔ Mn 4+ [37]. Hence, it is proposed that the appropriate Mn/Fe molar ratio could develop the intimate electronic interaction among manganese, iron and cerium.…”

Section: Reaction Mechanism Analysismentioning

confidence: 97%

“…Thus, it was proposed that the quantity improvement of oxygen vacancies on the catalyst was conducive to facilitating the intermediate formation and enhancing catalytic performance in the fast SCR reaction. In the crystal lattice of Mn15Fe15−Ce/Al sample, the negative charge transferred from manganese to cerium intensifying the interaction between Mn and Ce: Mn 2+ + Ce 4+ ↔ Mn 3+ + Ce 3+ [16,35], Mn 3+ + Ce 4+ ↔ Mn 4+ + Ce 3+ [36,37]. The course of oxygen storage and release on the Ce 3+ /Ce 4+ redox couple was brought forward: Ce 2 O 3 + 1/2O 2 → 2CeO 2 and 2CeO 2 → Ce 2 O 3 + O* (adsorbed) [36].…”

Section: X-ray Photoelectron Spectroscopy (Xps) Analysismentioning

confidence: 99%

“…Among these catalytic reactions, the NO transformation to NO 2 was considered as the crucial step in the reaction mechanism of fast SCR through the nitrate process. It had been revealed that MnO 2 was abundant in active oxygen and conducive to NO oxidation to NO 2 [37]. Mn 4+ had the highest catalytic activity for NO elimination in consideration of the promotion effect on the reaction of NO oxidation to NO 2 , which accelerated the fast SCR reaction remarkably [30].…”

Section: Reaction Mechanism Analysismentioning

confidence: 99%

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Structure–Activity Relationship Study of Mn/Fe Ratio Effects on Mn−Fe−Ce−Ox/γ-Al2O3 Nanocatalyst for NO Oxidation and Fast SCR Reaction

et al. 2018

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A series of Mn−Fe−Ce−Ox/γ-Al2O3 nanocatalysts were synthesized with different Mn/Fe ratios for the catalytic oxidation of NO into NO2 and the catalytic elimination of NOx via fast selective catalytic reduction (SCR) reaction. The effects of Mn/Fe ratio on the physicochemical properties of the samples were analyzed by means of various techniques including N2 adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H2-temperature-programmed reduction (TPR), NH3-temperature-programmed desorption (TPD) and NO-TPD, meanwhile, their catalytic performance was also evaluated and compared. Multiple characterizations revealed that the catalytic performance was highly dependent on the phase composition. The Mn15Fe15−Ce/Al sample with the Mn/Fe molar ratio of 1.0 presented the optimal structure characteristic among all tested samples, with the largest surface area, increased active components distributions, the reduced crystallinity and diminished particle sizes. In the meantime, the ratios of Mn4+/Mnn+, Fe2+/Fen+ and Ce3+/Cen+ in Mn15Fe15−Ce/Al samples were improved, which could enhance the redox capacity and increase the quantity of chemisorbed oxygen and oxygen vacancy, thus facilitating NO oxidation into NO2 and eventually promoting the fast SCR reaction. In accord with the structure results, the Mn15Fe15−Ce/Al sample exhibited the highest NO oxidation rate of 64.2% at 350 °C and the broadest temperature window of 75–350 °C with the NOx conversion >90%. Based on the structure–activity relationship discussion, the catalytic mechanism over the Mn−Fe−Ce ternary components supported by γ-Al2O3 were proposed. Overall, it was believed that the optimization of Mn/Fe ratio in Mn−Fe−Ce/Al nanocatalyst was an extremely effective method to improve the structure–activity relationships for NO pre-oxidation and the fast SCR reaction.

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Section: Reaction Mechanism Analysismentioning

confidence: 97%

Section: X-ray Photoelectron Spectroscopy (Xps) Analysismentioning

confidence: 99%

Section: Reaction Mechanism Analysismentioning

confidence: 99%

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Structure–Activity Relationship Study of Mn/Fe Ratio Effects on Mn−Fe−Ce−Ox/γ-Al2O3 Nanocatalyst for NO Oxidation and Fast SCR Reaction

et al. 2018

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“…It was demonstrated that the hydrolysis process method suggested higher SCR activity in the temperature range of 80-260 • C; meanwhile, this catalyst showed higher Mn 4+ /Mn 3+ , Ce 4+ /Ce 3+ ratio, higher specific area and higher O a /O p ratio. Apart from some mature preparation methods, many researchers have made innovative works about preparation methods; Yao et al [57] reported that the MnO x -CeO 2 catalyst prepared by the hydrothermal treatment method revealed the best NH 3 -SCR performance and good resistance to SO 2 and H 2 O (Figure 7a,b). The XRD patterns and Raman spectra characterization were shown in Figure 7c,d, where it was demonstrated that CeO 2 and MnO x had a strong interaction under the conditions of high temperature and high pressure.…”

Section: Ceo 2 -Mno 2 Catalystmentioning

confidence: 99%

Preparation and Performance of Cerium-Based Catalysts for Selective Catalytic Reduction of Nitrogen Oxides: A Critical Review

et al. 2021

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Selective catalytic reduction of nitrogen oxides with NH3 (NH3-SCR) is still the most commonly used control technology for nitrogen oxides emission. Specifically, the application of rare earth materials has become more and more extensive. CeO2 was widely developed in NH3-SCR reaction due to its good redox performance, proper surface acidity and abundant resource reserves. Therefore, a large number of papers in the literature have described the research of cerium-based catalysts. This review critically summarized the development of the different components of cerium-based catalysts, and characterized the preparation methods, the catalytic performance and reaction mechanisms of the cerium-based catalysts for NH3-SCR. The purpose of this review is to highlight: (1) the modification effect of the various metal elements for cerium-based catalysts; (2) various synthesis methods of the cerium-based catalysts; and (3) the physicochemical properties of the various catalysts and clarify their relations to catalytic performances, particularly in the presence of SO2 and H2O. Finally, we hope that this work can give timely technical guidance and valuable insights for the applications of NH3-SCR in the field of NOx control.

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“…Cerium oxide (CeO 2 ) has been confirmed to have enhanced oxygen storage capacity and redox property through storing and releasing oxygen via the redox shift between Ce 4+ and Ce 3+ under oxidizing and reducing conditions, and the addition of CeO 2 might lead to smaller grain size and increases the surface area of some transition metal oxides by inducing the creation of structure defect in the host oxides, thereby improves their catalytic activity . Niu et al used the sol–gel (SG) method to prepare MnO x /Ti based catalysts, adding Ce and V to synergistically remove NO and inhibit nitrous oxide (N 2 O) formation, and studied the mechanism.…”

Section: Introductionmentioning

confidence: 99%

Selective catalytic reduction of NO_x with NH₃ over iron‐cerium mixed oxide catalyst prepared by different methods

Tang

Gao

et al. 2019

J of Chemical Tech & Biotech

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BACKGROUND: Nitrogen oxide (NO x ) is one of the important atmospheric pollutants, causing damage to the environment and the human body. Currently, selective catalytic reduction (SCR) technology is the main denitration method, and SCR catalyst is the key to this technology. Iron (Fe)-based catalysts have recently been widely studied because of their low cost and good catalytic effect on medium and low temperature effects. In this article, iron-cerium mixed oxide (FeO x -CeO 2 ) catalysts were prepared by five common preparation methods, and their physicochemical properties and low temperature NH 3 -SCR catalytic activity were studied. RESULTS: The results show that the preparation method has a certain influence on the catalytic performance [activity and nitrogen (N 2 ) selectivity] of the catalyst. The order of activity is microemulsion method (MM) ≈ sol-gel (SG) method > coprecipitation method > hydrothermal synthesis method > solid-phase mixing (SPM) method.CONCLUSION: This result is related to the specific surface area of the catalyst, the microstructure, the valence distribution of the elements, the redox ability and the surface acidic sites. It is worth noting that the activity of the catalyst prepared by the SG method is good, but the selectivity of N 2 is poor, which is related to the oxidizing ability of the catalyst. The catalyst prepared by the MM has moderate oxidizing ability and large specific surface area, provides abundant acidic sites and has excellent catalytic performance.[J Chem Technol Biotechnol 2020; 95: 232-245

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Influence of preparation methods on the physicochemical properties and catalytic performance of MnO -CeO2 catalysts for NH3-SCR at low temperature

Cited by 136 publications

References 65 publications

Structure–Activity Relationship Study of Mn/Fe Ratio Effects on Mn−Fe−Ce−Ox/γ-Al2O3 Nanocatalyst for NO Oxidation and Fast SCR Reaction

Structure–Activity Relationship Study of Mn/Fe Ratio Effects on Mn−Fe−Ce−Ox/γ-Al2O3 Nanocatalyst for NO Oxidation and Fast SCR Reaction

Preparation and Performance of Cerium-Based Catalysts for Selective Catalytic Reduction of Nitrogen Oxides: A Critical Review

Selective catalytic reduction of NO_x with NH₃ over iron‐cerium mixed oxide catalyst prepared by different methods

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Influence of preparation methods on the physicochemical properties and catalytic performance of MnO -CeO2 catalysts for NH3-SCR at low temperature

Cited by 136 publications

References 65 publications

Structure–Activity Relationship Study of Mn/Fe Ratio Effects on Mn−Fe−Ce−Ox/γ-Al2O3 Nanocatalyst for NO Oxidation and Fast SCR Reaction

Structure–Activity Relationship Study of Mn/Fe Ratio Effects on Mn−Fe−Ce−Ox/γ-Al2O3 Nanocatalyst for NO Oxidation and Fast SCR Reaction

Preparation and Performance of Cerium-Based Catalysts for Selective Catalytic Reduction of Nitrogen Oxides: A Critical Review

Selective catalytic reduction of NOx with NH3 over iron‐cerium mixed oxide catalyst prepared by different methods

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Selective catalytic reduction of NO_x with NH₃ over iron‐cerium mixed oxide catalyst prepared by different methods