Unraveling the synergy between MnOx and CeO2 in MnOx-CeO2 SCR catalysts based on experimental and DFT studies

Wang, Fei; Li, Songda; You, Ruiyang; Han, Zhongkang; Yuan, Wentao; Zhu, Beien; Gao, Yi; Yang, Hangsheng; Wang, Yong

doi:10.1016/j.apsusc.2023.158124

Cited by 12 publications

(5 citation statements)

References 31 publications

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“…NO x conversion and N 2 selectivity as a function of reaction temperature between 150 and 600 • C in the Cu-SSZ-39, CeO 2 /Cu-SSZ-39, CeMnO x /Cu-SSZ-39, and MnO x /Cu-SSZ-39 catalysts are shown in Figure 3a and Figure S3a. Cu-SSZ-39 showed a so-called "seagull shape" curve resulting from its low Cu loading [18], while MnO x /Cu-SSZ-39 presented an evident decline in NO x conversion over 400 • C. The presence of CeO 2 and CeMnO x significantly benefitted the low-temperature NO x reduction performance of the catalysts, particularly for CeMnO x /Cu-SSZ-39, whose active temperature window is from 180 to 600 • C. The higher catalytic performance of CeMnO x /Cu-SSZ-39 in comparison with those of CeO 2 /Cu-SSZ-39 and MnO x /Cu-SSZ-39 indicated the existence of synergetic effects between Ce and Mn in CeMnO x in improving the low-temperature activity of Cu-SSZ-39 [18,41], which is consolidated by varying Mn/(Ce + Mn) ratios (Figure S4). After hydrothermal aging at 800 • C, NO x conversions of the Cu-SSZ-39-A, CeO 2 /Cu-SSZ-39-A, and MnO x /Cu-SSZ-39-A catalysts declined, and their active temperature window became narrow (Figure 3b).…”

Section: Scr Performancementioning

confidence: 99%

“…Catalysts 2024, 14, x FOR PEER REVIEW 5 of 18 [18,41], which is consolidated by varying Mn/(Ce + Mn) ratios (Figure S4). After hydrothermal aging at 800 °C, NOx conversions of the Cu-SSZ-39-A, CeO2/Cu-SSZ-39-A, and MnOx/Cu-SSZ-39-A catalysts declined, and their active temperature window became narrow (Figure 3b).…”

Section: Scr Performancementioning

confidence: 99%

“…Inspired by previous studies on optimizing the SCR performance of small-pore zeolite catalysts and developing highly effective oxide catalysts [33][34][35][36][37][38][39][40], we selected Ce-Mn oxide to modify the Cu-SSZ-39 catalyst, not only because it possesses excellent low-temperature SCR activity [41], but also because it provides access to the fast SCR reaction pathway via NO 2 generation [42]. Herein, Ce-Mn oxide-modified Cu-SSZ-39 catalysts (CeMnO x /Cu-SSZ-39) as well as references (CeO 2 /Cu-SSZ-39 and MnO x /Cu-SSZ-39) are prepared, and the activity and hydrothermal aging performance of pure and oxide-modified Cu-SSZ-39 catalysts are evaluated for SCR reactions.…”

Section: Introductionmentioning

confidence: 99%

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Enhanced Low-Temperature Activity and Hydrothermal Stability of Ce-Mn Oxide-Modified Cu-SSZ-39 Catalysts for NH3-SCR of NOx

Tang,

Yang,

Xin

et al. 2023

Catalysts

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Cu-SSZ-39 zeolite with an AEI structure exhibits excellent hydrothermal stability and can be a potential alternative to Cu-SSZ-13 zeolite SCR catalysts for NOx removal in diesel vehicles. However, the inferior low-temperature performance of Cu-SSZ-39 leads to substantial NOx emissions during the cold-start period, impeding its practical application. In this study, Ce-Mn oxide-modified Cu-SSZ-39 catalysts (CeMnOx/Cu-SSZ-39) and references (CeO2/Cu-SSZ-39 and MnOx/Cu-SSZ-39) were prepared by the ion-exchange of Cu ions followed by impregnation of the oxide precursors, with the aim of enhancing the NH3-SCR performance at low temperatures. The modified catalysts exhibited improved low-temperature activity and hydrothermal stability compared to the unmodified counterpart. In particular, CeMnOx/Cu-SSZ-39 showed the highest activity among the three catalysts and achieved NOx conversions above 90% within the temperature range of 180 °C to 600 °C, even after undergoing hydrothermal aging at 800 °C. Experimental results indicated that the synergistic effect between Ce and Mn in CeMnOx improves the redox properties and acidity of the catalyst due to the presence of Ce3+, Mn4+, and abundant adsorbed oxygen species, which facilitate low-temperature SCR reactions. Furthermore, the interaction of CeMnOx with Cu-SSZ-39 stabilizes the zeolite framework and hinders the agglomeration of Cu species during the hydrothermal aging process, contributing to its exceptional hydrothermal stability. The kinetics and NO oxidation experiments demonstrated that CeMnOx provides access to fast SCR reaction pathways by oxidizing NO to NO2, resulting in a significant increase in low-temperature activity. This study provides novel guidelines for the design and preparation of Cu-SSZ-39 zeolite with outstanding SCR performance over a wide temperature range.

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Section: Scr Performancementioning

confidence: 99%

Section: Scr Performancementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Enhanced Low-Temperature Activity and Hydrothermal Stability of Ce-Mn Oxide-Modified Cu-SSZ-39 Catalysts for NH3-SCR of NOx

Tang,

Yang,

Xin

et al. 2023

Catalysts

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“…Ce-based SCR catalysts have attracted the interest of many researchers due to their satisfactory oxygen storage ability and redox performance . However, pristine CeO 2 exhibits fairly low catalytic activity and poor thermal stability at high temperature . A feasible approach is to add Zr in CeO 2 , which is conducive to combining the high refractory property of ZrO 2 and the superior oxygen storage capacity of CeO 2 , thus improving the thermostability and NH 3 -SCR efficiency at medium temperature. − However, low-temperature catalytic performance and SO 2 resistance of Ce–Zr mixed oxides are still lacking, which hinders their application in industry.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Promotional Effect of W Modification on Selective Catalytic Reduction Performance of Ce_0.4ZrO_x Catalysts

Feng,

Han,

et al. 2024

Energy Fuels

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Various amounts of W were modified on Ce 0.4 ZrO x catalysts via a wet impregnation method. Among them, the W 0.1 / Ce 0.4 ZrO x catalyst with W/Zr molar ratio of 0.1 exhibited a much better catalytic activity and a good SO 2 resistance. Its active temperature window corresponding to 80% NO x conversion was as wide as 210−450 °C. It could maintain a high NO x conversion efficiency (>96%) after treatment in 100 ppm SO 2 atmosphere for 18 h. Characterization results indicated that the W element successfully entered the lattice of the Ce−Zr solid solution via partially replacing Zr atoms. This led to an electron redistribution on the surface of the W 0.1 /Ce 0.4 ZrO x catalyst, which was beneficial to form Ce 3+ and oxygen vacancies, thus significantly improving the redox performance. In addition, WO x also significantly enhanced the surface acidity of the Ce 0.4 ZrO x catalyst, which was conducive to the adsorption of NH 3 . In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results confirmed that nitrate species adsorbed on the surface of the W 0.1 /Ce 0.4 ZrO x catalyst could be activated by W, thus reacting with NH 3 species efficiently. The reaction pathway over the W 0.1 /Ce 0.4 ZrO x catalyst followed both Eley−Rideal and Langmuir−Hinshelwood mechanisms at 300 °C. The enhancement effect of W modification on SO 2 resistance of W 0.1 /Ce 0.4 ZrO x catalyst was mainly ascribed to the balance between the redox and acidic properties.

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“…In recent decades, there has been an exponential increase in exhaust pollution, posing significant dangers to human health and natural systems. − Because nitrogen oxides (NO x ) will cause acid rain, photochemical smog, and damage to the ozone layer, removing NO x from the exhaust gas of various combustion sources (e.g., industrial pollution and vehicle exhaust) is one of the key steps toward pollution control. − Ammonia-selective catalytic reduction (NH 3 -SCR) is currently the most effective technology for NO x reduction. − However, commercialized SCR catalysts (V 2 O 5 /WO 3 /TiO 2 ) typically require an additional heat source to reach the working temperature of around 350–400 °C, which significantly increases the cost and thus is not suitable for most nonelectric factories as indicated in the previous references. − Thus, the scientific research area is focusing on low-temperature (LT) SCR (<300 °C) reactions, − which have become a current hot spot and a future trend of SCR catalyst studies.…”

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confidence: 99%

Probing the Atomistic Reaction Pathways in CuO/C Catalysts

Hu,

Zheng,

et al. 2023

Nano Lett.

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CuO x /C catalysts have been used in the selective catalytic reduction of NO x because of the exceptional low-temperature denitration (de-NO x ) activity. A fundamental understanding of the reaction between CuO and C is critical for controlling the component of CuO x /C and thus optimizing the catalytic performance. In this study, a transmission electron microscope equipped with an in situ heating device was utilized to investigate the atomic-scale reaction between CuO and C. We report two reaction mechanisms relying on the volume ratio between C and CuO: (1) The reduction from CuO to Cu2O (when the ratio is < ∼31%); (2) the reduction of CuO into polycrystalline Cu (when the ratio is > ∼34%). The atomistic reduction pathway can be well interpreted by considering the diffusion of O vacancy through the first-principle calculations. The atomic-scale exploration of CuO/C offers ample prospects for the design of industrial de-NO x catalysts in the future.

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Unraveling the synergy between MnOx and CeO2 in MnOx-CeO2 SCR catalysts based on experimental and DFT studies

Cited by 12 publications

References 31 publications

Enhanced Low-Temperature Activity and Hydrothermal Stability of Ce-Mn Oxide-Modified Cu-SSZ-39 Catalysts for NH3-SCR of NOx

Enhanced Low-Temperature Activity and Hydrothermal Stability of Ce-Mn Oxide-Modified Cu-SSZ-39 Catalysts for NH3-SCR of NOx

Investigation of the Promotional Effect of W Modification on Selective Catalytic Reduction Performance of Ce_0.4ZrO_x Catalysts

Probing the Atomistic Reaction Pathways in CuO/C Catalysts

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Unraveling the synergy between MnOx and CeO2 in MnOx-CeO2 SCR catalysts based on experimental and DFT studies

Cited by 12 publications

References 31 publications

Enhanced Low-Temperature Activity and Hydrothermal Stability of Ce-Mn Oxide-Modified Cu-SSZ-39 Catalysts for NH3-SCR of NOx

Enhanced Low-Temperature Activity and Hydrothermal Stability of Ce-Mn Oxide-Modified Cu-SSZ-39 Catalysts for NH3-SCR of NOx

Investigation of the Promotional Effect of W Modification on Selective Catalytic Reduction Performance of Ce0.4ZrOx Catalysts

Probing the Atomistic Reaction Pathways in CuO/C Catalysts

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Investigation of the Promotional Effect of W Modification on Selective Catalytic Reduction Performance of Ce_0.4ZrO_x Catalysts