Migration of zeolite-encapsulated Pt and Au under reducing environments

Hou, Dianwei; Heard, Christopher J.

doi:10.1039/d1cy02270a

Cited by 4 publications

(3 citation statements)

References 72 publications

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“…At temperatures between 100 and 200 °C, however, Pt 2+ was reduced and converted to clusters in the presence of H 2 . Reported DFT and kinetic Monte Carlo calculations indicate that PtH 2 units are highly mobile in zeolites and that adsorption of CO enhances platinum mobility, forming Pt(CO) species with weakened bonding to the zeolite framework and thus lowered barriers to diffusion. , The results showing that Pt δ+ (CO) species are stable in H 2 at 100 °C but reduced to form clusters when CO is present with H 2 (Figure f) demonstrate that Pt δ+ with multiple carbonyl ligands is more mobile in the zeolite than Pt δ+ (CO).…”

Section: Discussionmentioning

confidence: 68%

“…Understanding of the adsorptive properties of atomically dispersed noble metals and their mobility within zeolites is essential for understanding the synthesis or oxidative redispersion of the catalysts. ,, Infrared (IR) spectra have shown how the structures of rhodium and iridium in zeolites reversibly alternate between single-atom cationic complexes and few-atom clusters when the conditions are mild. − The essentially molecular-supported species in these catalysts have distinctive spectroscopic signatures, and when probed with CO, the atomically dispersed species form metal gem -dicarbonyls, which are essential for understanding of the chemistry. − The comparable chemistry of platinum in zeolites is less well understoodeven though platinum dominates as an industrial catalyst and has been the subject of extensive research to elucidate its intrazeolite chemistry. − Thus, surprisingly, characterization of well-defined structures of platinum in zeolites, such as platinum gem -dicarbonyls, is not well represented in the literature.…”

Section: Introductionmentioning

confidence: 99%

“…29,30 Understanding of the adsorptive properties of atomically dispersed noble metals and their mobility within zeolites is essential for understanding the synthesis or oxidative redispersion of the catalysts. 14,31,32 Infrared (IR) spectra have shown how the structures of rhodium and iridium in zeolites reversibly alternate between single-atom cationic complexes and few-atom clusters when the conditions are mild. 33−35 The essentially molecular-supported species in these catalysts have distinctive spectroscopic signatures, and when probed with CO, the atomically dispersed species form metal gemdicarbonyls, which are essential for understanding of the chemistry.…”

Section: ■ Introductionmentioning

confidence: 99%

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Interconversion of Atomically Dispersed Platinum Cations and Platinum Clusters in Zeolite ZSM-5 and Formation of Platinum gem-Dicarbonyls

et al. 2022

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Catalysts composed of platinum dispersed on zeolite supports are widely applied in industry, and coking and sintering of platinum during operation under reactive conditions require their oxidative regeneration, with the platinum cycling between clusters and cations. The intermediate platinum species have remained only incompletely understood. Here, we report an experimental and theoretical investigation of the structure, bonding, and local environment of cationic platinum species in zeolite ZSM-5, which are key intermediates in this cycling. Upon exposure of platinum clusters to O2 at 700 °C, oxidative fragmentation occurs, and Pt2+ ions are stabilized at six-membered rings in the zeolite that contain paired aluminum sites. When exposed to CO under mild conditions, these Pt2+ ions form highly uniform platinum gem-dicarbonyls, which can be converted in H2 to Ptδ+ monocarbonyls. This conversion, which weakens the platinum–zeolite bonding, is a first step toward platinum migration and aggregation into clusters. X-ray absorption and infrared spectra provide evidence of the reductive and oxidative transformations in various gas environments. The chemistry is general, as shown by the observation of platinum gem-dicarbonyls in several commercially used zeolites (ZSM-5, Beta, mordenite, and Y).

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Section: Discussionmentioning

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Interconversion of Atomically Dispersed Platinum Cations and Platinum Clusters in Zeolite ZSM-5 and Formation of Platinum gem-Dicarbonyls

et al. 2022

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Encapsulating Metal Nanoparticles into a Layered Zeolite Precursor with Surface Silanol Nests Enhances Sintering Resistance**

Zhang

Heard

et al. 2022

Angewandte Chemie

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Supported metal nanoparticles are used as heterogeneous catalysts but often deactivated due to sintering at high temperatures. Confining metal species into a porous matrix reduces sintering, yet supports rarely provide additional stabilization. Here, we used the silanol-rich layered zeolite IPC-1P to stabilize ultrasmall Rh nanoparticles. By adjusting the IPC-1P interlayer space through swelling, we prepared various architectures, including microporous and disordered mesoporous. In situ scanning transmission electron microscopy confirmed that Rh nanoparticles are resistant to sintering at high temperature (750 °C, 6 hrs). Rh clusters strongly bind to surface silanol quadruplets at IPC-1P layers by hydrogen transfer to clusters, while high silanol density hinders their migration based on density functional theory calculations. Ultimately, combining swelling with long-chain surfactant and utilizing metal-silanol interactions resulted in a novel, catalytically active material-Rh@IPC_C22.

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Encapsulating Metal Nanoparticles into a Layered Zeolite Precursor with Surface Silanol Nests Enhances Sintering Resistance**

Zhang

Heard

et al. 2022

Angew Chem Int Ed

Self Cite

View full text Add to dashboard Cite

Supported metal nanoparticles are used as heterogeneous catalysts but often deactivated due to sintering at high temperatures. Confining metal species into a porous matrix reduces sintering, yet supports rarely provide additional stabilization. Here, we used the silanol‐rich layered zeolite IPC‐1P to stabilize ultra‐small Rh nanoparticles. By adjusting the IPC‐1P interlayer space through swelling, we prepared various architectures, including microporous and disordered mesoporous. In situ scanning transmission electron microscopy confirmed that Rh nanoparticles are resistant to sintering at high temperature (750 °C, 6 hrs). Rh clusters strongly bind to surface silanol quadruplets at IPC‐1P layers by hydrogen transfer to clusters, while high silanol density hinders their migration based on density functional theory calculations. Ultimately, combining swelling with long‐chain surfactant and utilizing metal‐silanol interactions resulted in a novel, catalytically active material—Rh@IPC_C22.

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Migration of zeolite-encapsulated Pt and Au under reducing environments

Abstract: The encapsulation of noble metal atoms into zeolites is a promising route to generate controlled size distributions of stable metal catalysts. Pinning of single metal atoms to particular binding sites...

Cited by 4 publications

References 72 publications

Interconversion of Atomically Dispersed Platinum Cations and Platinum Clusters in Zeolite ZSM-5 and Formation of Platinum gem-Dicarbonyls

Interconversion of Atomically Dispersed Platinum Cations and Platinum Clusters in Zeolite ZSM-5 and Formation of Platinum gem-Dicarbonyls

Encapsulating Metal Nanoparticles into a Layered Zeolite Precursor with Surface Silanol Nests Enhances Sintering Resistance**

Encapsulating Metal Nanoparticles into a Layered Zeolite Precursor with Surface Silanol Nests Enhances Sintering Resistance**

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