Mechanistic insight into low temperature SCR by ceria–manganese mixed oxides incorporated into zeolites

Nelson, Nicholas C.; Andana, Tahrizi; Rappé, Kenneth G.; Wang, Yong

doi:10.1039/d2cy01921c

Cited by 10 publications

(2 citation statements)

References 33 publications

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“…Figure 14b presents the XPS spectra of O 1s for the composite material before and after the reaction. When fitted according to the O 1s peaks, the spectra can be divided into three regions between 528 eV and 534 eV: lattice oxygen (Olatt) at 529 eV, oxygen vacancies (Ovs) at 531-532 eV, and adsorbed oxygen (Oads) predominantly in the form of -OH above 533 eV [46]. After the reaction, most of the lattice oxygen and all of the adsorbed oxygen were converted into oxygen vacancies.…”

Section: Reaction Mechanismmentioning

confidence: 99%

Synthesis of Ce-La-Pr/Mn-O Ternary Oxide Composites via Co-Precipitation and Synergistic Photocatalytic Degradation of Cr(VI)

Feng,

2024

Water

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This study utilized a straightforward co-precipitation method to successfully synthesize Ce-La-X(Mn/Pr)-O composite materials for treating simulated hexavalent chromium (Cr(VI)) wastewater with distinctively porous and fluffy textures, along with tubular morphologies. Notably, Ce-La-Mn-O demonstrated a remarkable specific surface area of 96.2698 m2/g, mesoporous architecture with a pore diameter of 6.9511 nm, and an impressive adsorption capacity of 88.79 mg/g. Under optimized conditions, specifically an initial Cr(VI) concentration of 20 mg/L, a Ce-La-Mn-O dosage of 0.8 g/L, a reaction temperature of 40 °C, an initial pH of 6, and with the application of simulated daylight, the removal rate of Cr(VI) exceeded 98% within 15 min. Even after three cycles, the removal rate was maintained at above 80%. Based on a comprehensive suite of morphological, structural, and performance characterizations, the introduction of Mn/Pr was found to modify the structure of Ce-La-O and enhance the synergistic interactions among the metals within the Ce-La-O framework. In addition, Ce-La-Mn-O exhibited superior visible light absorption properties and dual functionality for catalytic reduction and adsorption. All three materials were found to form -OH polar bond functional groups, converting it to Cr(III) and subsequently forming Cr(OH)3. The Ce-La-X(Mn/Pr)-O composite materials provide a robust theoretical foundation for exploring the dual functional synergistic effects in the efficient removal of Cr(VI) from aqueous systems, indicating their vast potential for practical applications.

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Section: Reaction Mechanismmentioning

confidence: 99%

Synthesis of Ce-La-Pr/Mn-O Ternary Oxide Composites via Co-Precipitation and Synergistic Photocatalytic Degradation of Cr(VI)

Feng,

2024

Water

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“…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%

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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Basic understanding of Cu‐SSZ‐13 in catalyzing low‐temperature selective catalytic reduction of NO_x by ammonia

Wang,

Zhu,

Zhao

et al. 2024

J Chinese Chemical Soc

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The development of Cu‐SSZ‐13 represents a significant breakthrough in the field of NOx removal from mobile exhaust, demonstrating excellent selective catalytic reduction (SCR) activity across a broad temperature range (200–500°C). However, the limited reactivity of Cu‐SSZ‐13 at temperatures below 200°C poses a challenge for the removal of NOx emitted during vehicle cold starts. To stimulate new efforts to enhance low‐temperature SCR performance, this review provides a fundamental understanding of the nature of Cu‐SSZ‐13 in catalyzing the SCR reaction. The structures, coordination environments, and oxidation states of Cu2+ during the SCR reaction, as well as the redox cycle pathway of Cu2+ ions and the characteristics of the rate‐determining step, were discussed. Based on these insights, several strategies for improving the low‐temperature activity of Cu‐SSZ‐13 are proposed. Finally, the review offers a perspective on the future of low‐temperature SCR of NOx over Cu‐SSZ‐13.

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Mechanistic insight into low temperature SCR by ceria–manganese mixed oxides incorporated into zeolites

Abstract: Recent efforts to increase the low-temperature activity of zeolite-based selective catalytic reduction (SCR) catalysts has led to the exploration of hybrid materials comprised of a metal oxide and zeolite phase....

Cited by 10 publications

References 33 publications

Synthesis of Ce-La-Pr/Mn-O Ternary Oxide Composites via Co-Precipitation and Synergistic Photocatalytic Degradation of Cr(VI)

Synthesis of Ce-La-Pr/Mn-O Ternary Oxide Composites via Co-Precipitation and Synergistic Photocatalytic Degradation of Cr(VI)

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

Basic understanding of Cu‐SSZ‐13 in catalyzing low‐temperature selective catalytic reduction of NO_x by ammonia

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Mechanistic insight into low temperature SCR by ceria–manganese mixed oxides incorporated into zeolites

Abstract: Recent efforts to increase the low-temperature activity of zeolite-based selective catalytic reduction (SCR) catalysts has led to the exploration of hybrid materials comprised of a metal oxide and zeolite phase....

Cited by 10 publications

References 33 publications

Synthesis of Ce-La-Pr/Mn-O Ternary Oxide Composites via Co-Precipitation and Synergistic Photocatalytic Degradation of Cr(VI)

Synthesis of Ce-La-Pr/Mn-O Ternary Oxide Composites via Co-Precipitation and Synergistic Photocatalytic Degradation of Cr(VI)

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

Basic understanding of Cu‐SSZ‐13 in catalyzing low‐temperature selective catalytic reduction of NOx by ammonia

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Basic understanding of Cu‐SSZ‐13 in catalyzing low‐temperature selective catalytic reduction of NO_x by ammonia