Metal Sites in Zeolites: Synthesis, Characterization, and Catalysis

Chemical Reviews, Journal Year: 2022, Volume and Issue: 123(9), P. 6039 - 6106

Published: Sept. 1, 2022

Zeolites with ordered microporous systems, distinct framework topologies, good spatial nanoconfinement effects, and superior (hydro)thermal stability are an ideal scaffold for planting diverse active metal species, including single sites, clusters, nanoparticles in the framework-associated sites extra-framework positions, thus affording metal-in-zeolite catalysts outstanding activity, unique shape selectivity, enhanced recyclability processes of Brønsted acid-, Lewis metal-catalyzed reactions. Especially, thanks to advances zeolite synthesis characterization techniques recent years, zeolite-confined (denoted as metal@zeolite composites) have experienced rapid development heterogeneous catalysis, owing combination merits both intrinsic properties. In this review, we will present developments strategies incorporating tailoring zeolites advanced identification location, distribution, coordination environment species zeolites. Furthermore, catalytic applications demonstrated, emphasis on composites hydrogenation, dehydrogenation, oxidation Finally, point out current challenges future perspectives precise synthesis, atomic level identification, practical application catalyst system.

Language: Английский

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Influence of framework Al density in chabazite zeolites on copper ion mobility and reactivity during NOx selective catalytic reduction with NH3

Nature Catalysis, Journal Year: 2023, Volume and Issue: 6(3), P. 276 - 285

Published: March 20, 2023

Language: Английский

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Competition between Mononuclear and Binuclear Copper Sites across Different Zeolite Topologies

JACS Au, Journal Year: 2024, Volume and Issue: 4(1), P. 197 - 215

Published: Jan. 4, 2024

A key challenge for metal-exchanged zeolites is the determination of metal cation speciation and nuclearity under synthesis reaction conditions. Copper-exchanged zeolites, which are widely used in automotive emissions control potential catalysts partial methane oxidation, have particular evidenced a wide variety Cu structures that observed to change with exposure conditions, zeolite composition, topology. Here, we develop predictive models CHA, MOR, BEA, AFX, FER topologies using interatomic potentials, quantum chemical calculations, Monte Carlo simulations interrogate this vast configurational compositional space. Model predictions rationalize experimentally differences between Cu-zeolites wide-body literature, including populations, structural variations, methanol per yields. Our results show both topological features commonly Al-siting biases MOR increase population binuclear sites, explaining small mononuclear sites these materials relative other such as CHA BEA. Finally, machine learning classification model determine preference form or at different Al configurations 200 international database. reveal several extreme ends vs spectrum, highlighting synthetic options realization strong preferences.

Language: Английский

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Coal bottom ash derived zeolite (SSZ-13) for the sorption of synthetic anion Alizarin Red S (ARS) dye

Journal of Hazardous Materials, Journal Year: 2021, Volume and Issue: 416, P. 125925 - 125925

Published: April 21, 2021

Language: Английский

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Onset of High Methane Combustion Rates over Supported Palladium Catalysts: From Isolated Pd Cations to PdO Nanoparticles

JACS Au, Journal Year: 2021, Volume and Issue: 1(4), P. 396 - 408

Published: March 25, 2021

Industrial low-temperature methane combustion catalyst Pd/Al2O3 suffers from H2O-induced deactivation. It is imperative to design Pd catalysts free this deactivation and with high atomic efficiency. Using a small-pore zeolite SSZ-13 as support, herein we report well-defined dominant active species finely dispersed cations, uniform PdO particles embedded inside the framework, or decorating external surface. Through detailed reaction kinetics spectroscopic microscopic studies, show that sites are much less than nanoparticles. We further demonstrate can be readily circumvented by using supports Si/Al ratios. Finally, provide few rational suggestions for oxidation based on new knowledge learned in study.

Language: Английский

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Cold-Start NO_x Mitigation by Passive Adsorption Using Pd-Exchanged Zeolites: From Material Design to Mechanism Understanding and System Integration

Environmental Science & Technology, Journal Year: 2023, Volume and Issue: 57(9), P. 3467 - 3485

Published: Feb. 21, 2023

It remains a major challenge to abate efficiently the harmful nitrogen oxides (NOx) in low-temperature diesel exhausts emitted during cold-start period of engine operation. Passive NOx adsorbers (PNA), which could temporarily capture at low temperatures (below 200 °C) and release stored higher (normally 250–450 downstream selective catalytic reduction unit for complete abatement, hold promise mitigate emissions. In this review, recent advances material design, mechanism understanding, system integration are summarized PNA based on palladium-exchanged zeolites. First, we discuss choices parent zeolite, Pd precursor, synthetic method synthesis Pd-zeolites with atomic dispersions, review effect hydrothermal aging properties performance Pd-zeolites. Then, show how different experimental theoretical methodologies can be integrated gain mechanistic insights into nature active sites, storage/release chemistry, as well interactions between typical components/poisons exhausts. This also gathers several novel designs modern exhaust after-treatment systems practical application. At end, challenges, important implications, further development real application Pd-zeolite-based mitigation.

Language: Английский

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Facile synthesis of Pt/polyoxometalate/hollow carbon sphere tri-component nanoparticles via a “double gain strategy” for high-performance electrochemical sensing of adrenaline

Talanta, Journal Year: 2023, Volume and Issue: 258, P. 124450 - 124450

Published: March 11, 2023

Language: Английский

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Structural Interconversion between Agglomerated Palladium Domains and Mononuclear Pd(II) Cations in Chabazite Zeolites

Chemistry of Materials, Journal Year: 2021, Volume and Issue: 33(5), P. 1698 - 1713

Published: Feb. 15, 2021

Palladium-exchanged zeolites are candidate materials for passive NOx adsorption in automotive exhaust aftertreatment, where mononuclear Pd cations behave as precursors to the purported sites. Yet, structures of zeolite lattice binding sites capable stabilizing Pd2+ ions, and mechanisms that interconvert agglomerated PdO domains into ions during redispersion treatments, remain incompletely understood. Here, we use a suite spectroscopic methods quantitative site titration techniques characterize species on with varying material properties treatment history. Aqueous-phase introduce onto NH4-form initially form [Pd(NH3)4]2+ complexes, but subsequent thermal treatments (573–723 K; air) lead situ formation H2 first reduces metallic domains, which then oxidized by air domains. Progressive Pd-zeolites higher temperatures (723–1023 K) converts larger fractions Pd2+, quantified temperature programmed reduction, because facilitate toward deeper locations within chabazite (CHA) crystallites, is corroborated complementary titrimetric data. Pd-CHA synthesized similar bulk framework Al content, arrangement, provide evidence six-membered rings (6-MR) hosting paired (Al–O–(Si–O)x–Al, x = 1, 2) stabilize otherwise isolated can [PdOH]+ species, identifiable an IR OH stretch at 3660 cm–1. These findings clarify underlying chemical processes gas environments cause agglomeration their prefer 6-MR CHA, indicate more uniform spatial distributions throughout crystallites.

Language: Английский

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Progress and future challenges in passive NO adsorption over Pd/zeolite catalysts

Catalysis Science & Technology, Journal Year: 2021, Volume and Issue: 11(18), P. 5986 - 6000

Published: Jan. 1, 2021

Proposed NO adsorption cycles over Pd/zeolite materials.

Language: Английский

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Investigation of crystal size effect on the NOx storage performance of Pd/SSZ-13 passive NOx adsorbers

Applied Catalysis B Environment and Energy, Journal Year: 2021, Volume and Issue: 291, P. 120026 - 120026

Published: Feb. 26, 2021

Language: Английский

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