Influence of thiourea modification on the NH3-SCR activity of CeO2: Simultaneous tuning morphology and surface acidity

Wang, Wei; Xiong, Zhibo; Wang, He; Lu, Wei; Shi, Huancong

doi:10.1016/j.joei.2021.07.009

Cited by 29 publications

(19 citation statements)

References 83 publications

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“…At present, rare earth metals, especially CeO 2 , have been extensively used as active components or structure promoters of heterogeneous catalysts due to their providential LAS catalytic centers and favorable reducibility. − The introduction of CeO 2 into HUSY and HY zeolites could enhance the stability of the structure and acidity by interacting with BAS, as reported by Zhang et al and Borges et al The interaction between Ce and BAS can endow the catalytic reaction with precise control for attaining the desired goals. Zhang et al realized control of the BAS/LAS ratio through the regulation of the Ce loadings in the HY zeolite.…”

Section: Introductionmentioning

confidence: 98%

Catalytic Upgrading of Cellulose Pyrolysis Volatiles over Ce Modified Hierarchical ZSM-5 Zeolite: Insight into the Effect of Acid Properties on Light Aromatics and Catalyst Stability

Zhang

Cao

Ren

et al. 2022

Ind. Eng. Chem. Res.

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CeO2 receives extensive researches as an active component due to its providential catalytic center and favorable reducibility. Herein, a series of Ce-modified hierarchical ZSM-5 zeolites (FZ5) were prepared by HF (0.5 mol/L) etching followed by impregnation with different Ce loadings. The role of incorporating extra-framework Ce elements was assessed by catalytic upgrading of the cellulose pyrolysis volatiles to produce light aromatics (LAs). Introducing CeO2 could effectively regulate the acid properties of catalysts with an increase in Lewis acid sites and a decrease in Brönsted acid sites, which could significantly improve the catalytic performance. As a result, the selectivity toward LAs were significantly enhanced and the coke content dramatically decreased. The highest selectivity to LAs and the lowest coke content obtained over 1.0Ce-FZ5 zeolite (loading 1.0 wt % Ce) were 84.0% and 2.42 wt %, respectively. Additionally, the 1.0Ce-FZ5 catalyst exhibited excellent stability, maintaining nearly 90% carbon yield of LAs after the seventh regeneration test. CeO2 modification opened a simple and feasible way for promoting the LAs selectivity and catalyst stability during the reforming of biomass volatiles.

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Section: Introductionmentioning

confidence: 98%

Catalytic Upgrading of Cellulose Pyrolysis Volatiles over Ce Modified Hierarchical ZSM-5 Zeolite: Insight into the Effect of Acid Properties on Light Aromatics and Catalyst Stability

Zhang

Cao

Ren

et al. 2022

Ind. Eng. Chem. Res.

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“…[25] In our previous research, a novel sulfate modification with thiourea as the structuredirecting agent had been proposed to improve the NH 3 -SCR activity of CeO 2 catalyst synthesized by a one-pot hydrothermal method, and the results demonstrated that the introduction of thiourea not only regulated the morphology of CeO 2 catalyst, but also enhanced its acidity and surface oxygen vacancies, thus significantly improved the NH 3 -SCR activity of catalyst. [26] In brief, the catalytic performance of NO x reduction over cerium oxide could be remarkably improved by the doping of Zr or sulfate modification through optimizing the surface acidity and redox properties of single CeO 2 . However, the influence of Zr doping on the structure and de-nitrogen performance of the thiourea modified CeO 2 catalyst had been scarcely studied.…”

Section: Introductionmentioning

confidence: 99%

Promotional Effect of Zirconium Doping on the NH₃‐SCR Activity of CeO₂ and CeO₂‐TA Modified by Thiourea: A Comparative Study

Zhou

Xiong

et al. 2023

ChemCatChem

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Zirconium (Zr) was doped to optimize the NH3‐SCR activity of both CeO2 and thiourea modified CeO2‐TA catalysts for comparison. Different from the promotional influence of thiourea modification on the agglomeration of CeO2, the transformation from nanoparticles to nanocubes and the formation of highly crystallized CeOSO4, Zr doping lowers the agglomeration of nanoparticles, loosens the surface morphology of catalyst and promotes the formation of Ce‐Zr solid solution. Furthermore, Zr doping exhibits a synergistic promotional effect of thiourea modification on the dispersion of Ce3+ and S6+ species on the surface of CeO2, and increases the concentrations of the surface total oxygen and chemisorbed oxygen of CeO2‐TA. Interestingly, Zr doping instead decreases the promotional effect of thiourea modification on the high‐temperature or medium/low‐temperature reducibility of catalyst, but increases both Brønsted and Lewis acid sites of CeO2‐TA by inducing the highly dispersive sulfate species rather than the CeOSO4 crystal, which might be crucial to the NH3‐SCR activity of Ce‐based catalyst.

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“…A similar phenomenon of the high elemental affinity between REE(III) and sulfate is also observed in the selective catalytic reduction (SCR) of the NO x system. For example, CeO 2 -based catalysts were widely employed in SCR systems since the preferential sulfation of CeO 2 over transition metal oxides (such as Fe 2 O 3 ) could alleviate the deactivation of the catalysts. − Besides, owing to the unique Ce(III)/Ce(IV) redox cycle, an oxygen vacancy can be generated on the surface of CeO 2 , resulting in the generation of new Lewis acidic sites by the adjacent Ce(III), which may play the key roles on CeO 2 transformation, but few studies are carried out to reveal these changes on its sulfation process.…”

Section: Introductionmentioning

confidence: 99%

Insights into the Selective Transformation of Ceria Sulfation and Iron/Manganese Mineralization for Enhancing the Selective Recovery of Rare Earth Elements

Zhou

Xiao

Guo

et al. 2023

Environ. Sci. Technol.

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To cope with the urgent and unprecedented demands for rare earth elements (REEs) in sophisticated industries, increased attention has been paid to REE recovery from recycled streams. However, the similar geochemical behaviors of REEs and transition metals often result in poor separation performance due to nonselectivity. Here, a unique approach based on the selective transformation between ceria sulfation and iron/ manganese mineralization was proposed, leading to the enhancement of the selective separation of REEs. The mechanism of the selective transformation of minerals could be ascribed to the distinct geochemical and metallurgical properties of ions, resulting in different combinations of cations and anions. According to hardsoft acid-base (HSAB) theory, the strong Lewis acid of Ce(III) was inclined to combine with the hard base of sulfates (SO 4 2− ), while the borderline acid of Fe(II)/Mn(II) prefers to interact with oxygen ions (O 2-). Both in situ characterization and density functional theory (DFT) calculation further revealed that such selective transformation might trigger by the generation of an oxygen vacancy on the surface of CeO 2 , leading to the formation of Ce 2 (SO 4 ) 3 and Fe/Mn spinel. Although the electron density difference of the configurations (CeO 2−x -SO 4 , Fe 2 O 3−x -SO 4 , and MnO 2−x -SO 4 ) shared a similar direction of the electron transfer from the metals to the sulfate-based oxygen, the higher electron depletion of Ce (Q Ce = −1.91 e) than Fe (Q Fe = −1.66 e) and Mn (Q Mn = −1.64 e) indicated the higher stability in the Ce−O−S complex, resulting in the larger adsorption energy of CeO 2−x -SO 4 (−6.88 eV) compared with Fe 2 O 3−x -SO 4 (−3.10 eV) and MnO 2−x -SO 4 (−2.49 eV). This research provided new insights into the selective transformation of REEs and transition metals in pyrometallurgy and thus offered a new approach for the selective recovery of REEs from secondary resources.

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Influence of thiourea modification on the NH3-SCR activity of CeO2: Simultaneous tuning morphology and surface acidity

Cited by 29 publications

References 83 publications

Catalytic Upgrading of Cellulose Pyrolysis Volatiles over Ce Modified Hierarchical ZSM-5 Zeolite: Insight into the Effect of Acid Properties on Light Aromatics and Catalyst Stability

Catalytic Upgrading of Cellulose Pyrolysis Volatiles over Ce Modified Hierarchical ZSM-5 Zeolite: Insight into the Effect of Acid Properties on Light Aromatics and Catalyst Stability

Promotional Effect of Zirconium Doping on the NH₃‐SCR Activity of CeO₂ and CeO₂‐TA Modified by Thiourea: A Comparative Study

Insights into the Selective Transformation of Ceria Sulfation and Iron/Manganese Mineralization for Enhancing the Selective Recovery of Rare Earth Elements

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Influence of thiourea modification on the NH3-SCR activity of CeO2: Simultaneous tuning morphology and surface acidity

Cited by 29 publications

References 83 publications

Catalytic Upgrading of Cellulose Pyrolysis Volatiles over Ce Modified Hierarchical ZSM-5 Zeolite: Insight into the Effect of Acid Properties on Light Aromatics and Catalyst Stability

Catalytic Upgrading of Cellulose Pyrolysis Volatiles over Ce Modified Hierarchical ZSM-5 Zeolite: Insight into the Effect of Acid Properties on Light Aromatics and Catalyst Stability

Promotional Effect of Zirconium Doping on the NH3‐SCR Activity of CeO2 and CeO2‐TA Modified by Thiourea: A Comparative Study

Insights into the Selective Transformation of Ceria Sulfation and Iron/Manganese Mineralization for Enhancing the Selective Recovery of Rare Earth Elements

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Promotional Effect of Zirconium Doping on the NH₃‐SCR Activity of CeO₂ and CeO₂‐TA Modified by Thiourea: A Comparative Study