Influence of support ionicity on the hydrogen chemisorption of Pt particles dispersed in Y zeolite: consequences for Pt particle size determination using the H/M method

Ji, Yaying; Eerden, Ad M. J. van der; Koot, Vincent; Kooyman, Patricia J.; Meeldijk, Johannes D.; Weckhuysen, Bert M.; Koningsberger, D.C.

doi:10.1016/j.jcat.2005.06.030

Cited by 56 publications

(76 citation statements)

References 35 publications

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“…The increase of hydrogen coverage may reach a H/Pt atomic ratio greater than 1.4, which induces a cluster reconstruction from the BP to a cuboctahedral (CUB) morphology. The H/Pt ratio exceeding 1 -often observed in experimental analysis conditions 130,159 -is rationalized by this reconstruction process. Charge analysis reveals that a hydride phase is obtained for the Pt 13 CUB structure, with the partial loss of the metallic nature.…”

Section: Size and Morphology Effects In Ultra-dispersed Platinum Catamentioning

confidence: 71%

“…The reaction network in which they are involved is also very complex, due to the bifunctional nature of the system (metallic and acidic phase) and the various desired (isomerization, dehydrogenation, dehydrocyclization) and undesired (coking, hydrogenolysis, cracking) reactions. HRTEM [129][130][131][132][133] …”

Section: Acidity Of Oh Groups On Asa: On the Dominant Role Of The Stamentioning

confidence: 99%

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Density functional theory simulations of complex catalytic materials in reactive environments: beyond the ideal surface at low coverage

Chizallet

Raybaud

2014

Catal. Sci. Technol.

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Most efficient heterogeneous catalysts used industrially are generally very complex systems. Far away from perfect crystallinity and well-defined oriented surfaces at low coverage, they involve structural disorder, heterogeneous site distribution with variable coordination and structural dependence upon the chemical environment. Unravelling their atomic-scale structures and understanding their roles in the catalytic reaction are not easy tasks, as the respective contributions of each type of site to the spectroscopic or catalytic responses are generally convoluted. Computational chemistry is of great help to address these issues. In the present perspective review, we highlight two relevant systems involved in numerous industrial applications: the amorphous silica alumina support; and subnanometric platinum clusters, possibly doped with tin and/or indium, supported on γ-Al 2 O 3 . The structural complexity is inherent to the amorphous nature of an oxide support on the one hand, and to the ultra-dispersed form of a mono-and multi-metallic catalyst on the other hand. In each case, Density Functional Theory (DFT) calculation was used to provide an original structure for active sites and to reveal how the corresponding multi-step reactions are influenced. Moreover, we highlight how theoretical studies including coverage effects on complex systems, induced by (T, P) reaction conditions, offer enriched perspectives with respect to studies on ideal surfaces at low coverage.

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Section: Size and Morphology Effects In Ultra-dispersed Platinum Catamentioning

confidence: 71%

Section: Acidity Of Oh Groups On Asa: On the Dominant Role Of The Stamentioning

confidence: 99%

Density functional theory simulations of complex catalytic materials in reactive environments: beyond the ideal surface at low coverage

Chizallet

Raybaud

2014

Catal. Sci. Technol.

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“…Direct experimental proof for the influence of the support ionicity on the H coverage has been obtained from hydrogen chemisorption experiments on Pt particles dispersed in zeolite NaY, where the ionicity of the support oxygen is tuned by exchange of Na with different types of cations (H + , Mg 2+ , La 3+ ) [9]. DFT calculations [4,10] show that the Pt sp orbitals are important for H bonding, and that the rearrangement of the Pt 6s and 6p interstitial bond orbitals (IBO) with change of the support ionicity can explain these different Pt-H bonding properties.…”

Section: Introductionmentioning

confidence: 99%

A three-site Langmuir adsorption model to elucidate the temperature, pressure, and support dependence of the hydrogen coverage on supported Pt particles

Koot

Eerden

et al. 2007

Journal of Catalysis

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The three-site adsorption model, previously developed to describe H adsorption on small Pt particles, was used to gain insight into dependence of hydrogen coverage on temperature, pressure, and support ionicity. The three sites, in order of decreasing Pt-H bond strength, involve H in an atop, a threefold, and an ontop Pt site. The ontop site designates H bonded in an atop site surrounded by occupied threefold sites (hence referred to as ontop site). The model includes an emptying of the H atop sites into H threefold sites with increasing H pressure to reduce lateral interactions. Hydrogen chemisorption on an acidic Pt/H-USY and a basic Pt/NaY and TPD results on a acidic Pt/H-LTL and basic Pt/K-LTL are modeled using a Langmuir isotherm for each H site. The H/M data can be directly compared with Pt L 2,3 XANES results on the same samples. A new analysis method (Delta XANES technique) using the difference in the absorption coefficient, μ = μ(H/Pt) − μ(Pt), allows an in situ spectroscopic determination of the type of H adsorption site and H coverage. The adsorption enthalpies ( H 's) for the atop, threefold, and ontop sites are found to be highly dependent on the support ionicity, increasing for ionic (basic) supports consistent with previous results. The calculations using the three-site model confirm that the support-induced changes in the Pt-H bond strength produce dramatically different H coverages and dominant adsorption sites at catalytic reaction temperatures and pressures. Depending on uptake versus desorption of H, a hysteresis is found in the atop to threefold site rearrangement, believed to result from a requirement for collective rearrangement involving an entire domain or island of H on the surface.

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“…22b, right) as shown by molecular dynamics. The H/Pt ratio exceeding 1 -often observed in experimental analysis conditions [34,35] -is rationalized by this reconstruction process. The electrostatic charge analysis reveals that a hydride phase is obtained for the CUB structure, with the partial loss of the metallic nature of DFT results of the simulation of model reforming catalysts: a) calculated binding energy (including Pt-Pt cohesion and metal-support interaction) of Pt n clusters, isolated or supported on c-Al 2 O 3 [25]; the most stable Pt 3 cluster supported on chlorinated c-Al 2 O 3 is shown in inset; b) effect of hydrogen pressure on the morphology change of supported Pt 13 [33]; c) relative stabilities of adsorbed ethylene (H 2 CCH 2 ) and ethylidyne (CCH 3 ) on Pt 13 supported cluster at various J = P(H 2 )/P(C 2 H 6 ) values; insets: illustrations of adsorbed ethylene and ethylidyne at J = 1 [42]; d) models of supported PtSn catalysts, without (top) or with (bottom) indium incorporated in the support [23].…”

Section: Dft Calculations: Models Of Reforming Catalystsmentioning

confidence: 65%

Catalytic Reforming: Methodology and Process Development for a Constant Optimisation and Performance Enhancement

Avenier

Bazer-Bachi

et al. 2016

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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-Catalytic reforming process has been used to produce high octane gasoline since the 1940s. It would appear to be an old process that is well established and for which nothing new could be done. It is however not the case and constant improvements are proposed at IFP Energies nouvelles. With a global R&D approach using new concepts and forefront methodology, IFPEN is able to: -propose a patented new reactor concept, increasing capacity; -ensure efficiency and safety of mechanical design for reactor using modelization of the structure; -develop new catalysts to increase process performance due to a high comprehension of catalytic mechanism by using, an experimental and innovative analytical approach ( 119 Sn Mössbauer and X-ray absorption spectroscopies) and also a Density Functional Theory (DFT) calculations; -have efficient, reliable and adapted pilots to validate catalyst performance.Résumé -Le reformage catalytique : méthodologie et développement procédé pour une optimisation et une amélioration constante des performances -Le reformage catalytique est utilisé pour produire des essences à haut indice d'octane depuis les années 40. Il pourrait apparaître comme un « vieux » procédé mature et pour lequel aucune innovation n'est possible. Ce n'est pourtant pas le cas, et des améliorations permanentes y sont apportées par IFP Energies nouvelles. À l'aide d'une stratégie de recherche globale, IFPEN est en mesure de : -proposer un nouveau concept de réacteur breveté augmentant la capacité ; -assurer l'efficacité et la fiabilité des designs mécaniques des réacteurs via la modélisation fine des structures ; -développer des nouveaux catalyseurs augmentant les performances du procédé grâce à une compréhension poussée des mécanismes, ceci par le couplage d'expérimentation et de techniques analytiques innovantes ( 119 Sn Mössbauer et X-ray absorption spectroscopies) et aussi par modélisa-tion moléculaire quantique ; -proposer des évaluations fiables, précises et optimisées des catalyseurs sur une gamme d'unité pilote adaptée.

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Influence of support ionicity on the hydrogen chemisorption of Pt particles dispersed in Y zeolite: consequences for Pt particle size determination using the H/M method

Cited by 56 publications

References 35 publications

Density functional theory simulations of complex catalytic materials in reactive environments: beyond the ideal surface at low coverage

Density functional theory simulations of complex catalytic materials in reactive environments: beyond the ideal surface at low coverage

A three-site Langmuir adsorption model to elucidate the temperature, pressure, and support dependence of the hydrogen coverage on supported Pt particles

Catalytic Reforming: Methodology and Process Development for a Constant Optimisation and Performance Enhancement

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