Soot oxidation performance with a HZSM-5 supported Ag nanoparticles catalyst and the characterization of Ag species

Ruan, Hongcheng; Nishibori, Maiko; Uchiyama, Tomoki; Ninomiya, Kakeru; Kamitani, Kazutaka; Kato, Kazúo; Konishi, Yuko; Haensch, Alexander; Bârsan, Nicolae; Shimanoe, Kengo

doi:10.1039/c7ra06712g

Cited by 14 publications

(17 citation statements)

References 56 publications

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“…Ag in both materials, EXAFS χ( k ) (Figure S50) and |χ( R )| (Figure S63), suggests a distribution of supported species formed that could lead to destructive interference in the EXAFS. Similar low-amplitude EXAFS oscillations have been reported by Ruan et al for Ag species supported on H-ZSM5, in which case the authors concluded a combination of Ag + ions in the zeolite framework and Ag nanoparticles . The EXAFS fit for Ag/LMO indicates a mixture of oxidized and metallic Ag (Table S10), although uncertainties preclude direct structure assignment due to low fitting range ( k : 3–8 Å –1 ).…”

Section: Resultssupporting

confidence: 81%

“…Ag/MnO 2 could be fit with oxygen in the first shell, but with manganese in the second shell (Table S10), suggesting that species on the support may be more isolated than on LMO. Despite fit uncertainties, Ag–O bond lengths in Ag/MnO 2 and Ag/LMO (Table S10) are on average longer than estimated lengths for Ag + –O bonds in Ag 2 O (approximately 2.1 Å); however, coordination numbers fit for both materials support a low coordinate structure, more akin to linear Ag + .…”

Section: Resultsmentioning

confidence: 88%

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Oxidative Grafting for Catalyst Synthesis in Surface Organometallic Chemistry

Hall,

Chapovetsky,

Kanbur

et al. 2023

ACS Appl. Mater. Interfaces

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The development of new methods of catalyst synthesis with the potential to generate active site structures orthogonal to those accessible by traditional protocols is of great importance for discovering new materials for addressing challenges in the evolving energy and chemical economy. In this work, the generality of oxidative grafting of organometallic and well-defined molecular metal precursors onto redox-active surfaces such as manganese dioxide (MnO2) and lithium manganese oxide (LiMn2O4) is investigated. Nine molecular metal precursors are explored, spanning groups 4–11 and each of the three periods of the transition metal series. The byproducts of the oxidative grafting reaction, a mixture of protodemetalation and ligand homocoupling for several organometallic precursors, was found to provide insights into the mechanism of the grafting reaction, suggesting oxidation of both the metal d-orbitals, as well as the metal–carbon σ-bonds, resulting in ejection of the ligand radical fragment. Analysis of the supported structures and oxidation state by X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) suggests that several of the chemisorbed metal ions are intercalated into interstitial vacancies of the surface structure while other complexes form intact molecular fragments on the surface. Proof of concept for the use of this metalation protocol to generate diverse, metal-dependent catalytic performance is demonstrated by the application of these materials in the conversion of cyclohexane to K/A oil (cyclohexanol and cyclohexanone) with tert-butyl hydroperoxide, as well as in the low-temperature (T ≤ 50 °C) oxidation of carbon monoxide to carbon dioxide.

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Section: Resultssupporting

confidence: 81%

Section: Resultsmentioning

confidence: 88%

Oxidative Grafting for Catalyst Synthesis in Surface Organometallic Chemistry

Hall,

Chapovetsky,

Kanbur

et al. 2023

ACS Appl. Mater. Interfaces

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“…The lack of features in the Ag K-edge XANES for AgNO 3 and Ag-MOR beyond the absorption edge has previously been attributed to the significant positional disorder of Ag, which suppresses spectral features . Similar to Ag-MOR, Ag-exchanged levyne and HZSM-5 zeolites show only broad spectral features in Ag K-edge XANES. , …”

Section: Resultsmentioning

confidence: 92%

“…60 Similar to Ag-MOR, Ag-exchanged levyne and HZSM-5 zeolites show only broad spectral features in Ag Kedge XANES. 61,62 The data in Table 2 and Figure 6 show that the sorbents prior to iodine loading contained mostly Ag + with some reduced Ag 0 being present, even though no steps were implemented in the procedure to actively reduce the Ag + to Ag 0 . This has been seen in some of our previous studies using a similar AgNO 3 exchange process to incorporate Ag into porous aluminosilicate scaffolds.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Role of Zeolite Structural Properties toward Iodine Capture: A Head-to-head Evaluation of Framework Type and Chemical Composition

Riley

Chong

Schmid

et al. 2022

ACS Appl. Mater. Interfaces

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This study evaluated zeolite-based sorbents for iodine gas [I2(g)] capture. Based on the framework structures and porosities, five zeolites, including two faujasite (FAU), one ZSM-5 (MFI), one mesoMFI, one ZSM-22 (TON), as well as two mesoporous materials, were evaluated for I2(g) capture at room temperature and 150 °C in an iodine-saturated environment. From these preliminary studies, the three best-performing zeolites were ion-exchanged with Ag+ and evaluated for I2(g) capture under similar conditions. Energy-dispersive X-ray spectroscopy data suggest that Ag-FAU frameworks were the materials with the highest capacity for I2(g) in this study, showing ∼3× higher adsorption compared to Ag-mordenite (Ag-MOR) at room temperature, but X-ray diffraction measurements show that the faujasite structure collapsed during the adsorption studies because of dealumination. The Ag-MFI zeolites are decent sorbents in real-life applications, showing both good sorption capacities and higher stability. In-depth analyses and characterizations, including synchrotron X-ray absorption spectroscopy, revealed the influence of structural and chemical properties of zeolites on the performance for iodine adsorption from the gas phase.

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“…Obviously, the Ag K-edge RSF profiles of the Ag-supported catalysts are similar to that of Ag foil with the Ag−Ag coordination peak at 0.270 nm, suggesting the metallic state of the Ag species in Ag/Co-LDO-H and Ag/Co-LDO-C. Moreover, the Ag−Ag coordination peak in Ag/Co-LDO-H is broader and weaker than that in Ag/ Co-LDO-C, indicating that the smaller-sized Ag NPs are highly dispersed on Ag/Co-LDO-H. 38 It is in agreement with the XRD results in Figure 1b. Table 1 provides the EXAFS parameters of the first Ag−Ag coordination shell for the Agsupported catalysts.…”

Section: Kinetic Measurementsmentioning

confidence: 97%

Identifying Oxygen Activation/Oxidation Sites for Efficient Soot Combustion over Silver Catalysts Interacted with Nanoflower-Like Hydrotalcite-Derived CoAlO Metal Oxides

et al. 2019

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Catalytic oxidation is an effective way to eliminate soot pollution emitted from diesel engines. However, the origination and specific location of active oxygen species are still unclear over noble metal catalysts because of the complex gas (oxygen)–solid (catalyst)–solid (reactant) reaction systems. Herein, we report the high catalytic performance of the nanoflower-like hydrotalcite-derived CoAlO-supported Ag catalyst synthesized by a facile hydrothermal method for soot combustion. Our characterization results demonstrate that metallic Ag nanoparticles (NPs) are highly dispersed on the CoAlO support because of their interactions through electron donation from Co to Ag species. The isotopic 18O2 adsorption/desorption results reveal that gaseous oxygen is readily adsorbed and dissociated on these electron-enriched Ag NPs rather than oxygen vacancies of the CoAlO support. From the 18O2 isothermal soot oxidation results, we newly discover that surface oxygen species adsorbed on Ag sites directly participate in soot oxidation, while those on the CoAlO support only play a negligible role. The kinetic results show that the strengthened Ag–CoAlO interactions can promote not only the quantity but also the intrinsic activity of oxygen species on Ag sites for soot combustion. In addition, the nanoflower-like morphology of the catalyst can greatly improve the soot–catalyst contact efficiency to further enhance the catalytic performance. Our work brings an insight into the identification of oxygen activation/oxidation sites involved in soot oxidation over Ag catalysts supported on hydrotalcite-derived CoAlO metal oxides by systematic isotopic and kinetic investigations, which is beneficial to the rational design of other related catalytic systems.

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Soot oxidation performance with a HZSM-5 supported Ag nanoparticles catalyst and the characterization of Ag species

Abstract: A HZSM-5 supported Ag nanoparticles catalyst, which has a Si/Al ratio of 1500, is synthesized by a simple impregnation method for soot oxidation.

Cited by 14 publications

References 56 publications

Oxidative Grafting for Catalyst Synthesis in Surface Organometallic Chemistry

Oxidative Grafting for Catalyst Synthesis in Surface Organometallic Chemistry

Role of Zeolite Structural Properties toward Iodine Capture: A Head-to-head Evaluation of Framework Type and Chemical Composition

Identifying Oxygen Activation/Oxidation Sites for Efficient Soot Combustion over Silver Catalysts Interacted with Nanoflower-Like Hydrotalcite-Derived CoAlO Metal Oxides

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