Nature of the Metal–Support Interaction in Supported Pt Catalysts: Shift in Pt Valence Orbital Energy and Charge Rearrangement

Ramaker, David E.; Graaf, Joost de; Veen, J.A.R. van; Koningsberger, D.C.

doi:10.1006/jcat.2001.3299

Cited by 101 publications

(146 citation statements)

References 40 publications

(65 reference statements)

Supporting

Mentioning

132

Contrasting

Unclassified

Order By: Relevance

“…Therefore, the changes in the TOF cannot be ascribed to a bifunctional mechanism. The results presented here and those shown previously by our group [16][17][18][19] show that the TOF of neopentane hydrogenolysis over supported Pt catalysts strongly depends on the acid/base properties and composition of the support. Detailed studies ( [48]; de Graaf, van Bokhoven, and Koningsberger, in preparation) also show that the increase in TOF of both reactions cannot be related to a change in absorption directly onto the support or to diffusion limitations in the support.…”

Section: Neopentane Conversionsupporting

confidence: 83%

“…Recent work by our group ( [19,20] and submitted articles) has also revealed that the nature of the metal-support interaction involves a change in the electronic properties of the metal cluster, induced by and correlated to the electron richness of the support oxygen atoms as summarized on the right side of Fig. 1.…”

Section: Introductionmentioning

confidence: 92%

“…The TOF also increases for zeolite supports with (i) increasing number of protons (Pt/LTL and Pt/Y) [17,18], (ii) increasing charge compensating cations (Na + /K + in Pt/LTL [17]; La 3+ in Pt/Y [18]), and (iii) increasing number of extra-framework Al in Pt/H-USY [18]. The activity of Pt/NaY, Pt/NaLaY, Pt/NaH-USY, and Pt/H-USY for the hydrogenation of tetralin at 350 • C, in 60-bar hydrogen with 165 parts per million weight (ppmw) dibenzothiofene added to the feed, also depends on the composition of the zeolite support [19]. These process conditions (Center) Possible changes in adsorbate structure and/or change in intrinsic or apparent kinetics, which might mediate the relationship between changes in the electronic structure of the metal particle and catalytic reactivity.…”

Section: Introductionmentioning

confidence: 99%

“…(i) The complete Pt density of states (DOS) shifts to higher energy (lower binding energy) on basic supports and to lower energy on acidic supports, an effect directly reflected by the intensity of the experimental atomic XAFS (AXAFS) [19,20] and by shifts in the XPS binding energies [20]. (ii) The Madelung potential of a basic support draws some 6s and 6p valence states below the Fermi level, where they consequently become filled at the expense of 5d states.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

In situ X-ray absorption spectroscopy as a unique tool for obtaining information on hydrogen binding sites and electronic structure of supported Pt catalysts: towards an understanding of the compensation relation in alkane hydrogenolysis

Koningsberger

Oudenhuijzen

Graaf

et al. 2003

Journal of Catalysis

Self Cite

View full text Add to dashboard Cite

L 2 and L 3 X-ray absorption near edge spectra (XANES) on supported Pt particles, with and without chemisorbed hydrogen, are shown to reflect the type of hydrogen-binding site on the Pt surface. FEFF8 ab initio multiple scattering calculations are used to determine XANES spectral fingerprints for the atop vs threefold H binding sites on Pt. Comparison of the experimental XANES data with the theoretical fingerprints, and further theoretical results, show that the acid/base properties of the support have a profound influence on the hydrogen coverage, and therefore on the mode of hydrogen adsorption on the Pt surface. As the electron richness of the support oxygen atoms increases (i.e., with increasing alkalinity of the support), the H coverage increases and the hydrogen-binding site of the strongly adsorbed hydrogen changes from atop to threefold. This site change is primarily responsible for the observed changes in previously reported kinetic data, which show an increase in negative order (roughly from −1.5 to −2.5) in hydrogen partial pressure for neopentane hydrogenolysis with increasing support alkalinity. This change in negative order directly reflects the greater number of vacant Pt sites that must be available to allow adsorption of the neopentane. A compensation relation is found in the kinetic data of Pt on different supports resulting directly from this change in hydrogen coverage. This implies that the experimentally determined kinetic parameters are apparent values. These apparent values are correlated to the intrinsic kinetic parameters via the thermodynamic properties of the sorption of the reactants, described by the Temkin equation. The TOF of neopentane hydrogenolysis over several catalysts, measured in previous work, decreases with the increasing alkalinity of the support. This can now be directly explained as the result of the change in hydrogen coverage using a Frumkin isotherm, implying that the neopentane adsorption becomes weaker with increased hydrogen coverage. These conclusions, that hydrogen drives the catalysis, are further supported by density functional calculations on small Pt 4 clusters, which show that the acid/base properties of the support have a much larger direct influence on Pt-H bonding than on Pt-CH n bonding.

show abstract

Section: Neopentane Conversionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

In situ X-ray absorption spectroscopy as a unique tool for obtaining information on hydrogen binding sites and electronic structure of supported Pt catalysts: towards an understanding of the compensation relation in alkane hydrogenolysis

Koningsberger

Oudenhuijzen

Graaf

et al. 2003

Journal of Catalysis

Self Cite

View full text Add to dashboard Cite

show abstract

“…[8][9][10][11][12][13][14][15] In particular, the application of AXAFS has, in our opinion, led to a better understanding of metal-support interaction effects. [8,[15][16][17] AXAFS is sensitive to changes in the potential around the X-ray absorbing atom. The potential field around an atom is mainly determined by the first and second coordination spheres.…”

Section: Introductionmentioning

confidence: 99%

Application of AXAFS Spectroscopy to Transition‐Metal Oxides: Influence of the Nearest and Next Nearest Neighbour Shells in Vanadium Oxides

Keller

Weckhuysen

Koningsberger

2007

Chemistry A European J

View full text Add to dashboard Cite

IntroductionMany parameters affect the catalytic properties of transition-metal oxide catalysts, for example, metal oxide loading, pre-treatment conditions, molecular structure, electronic structure, and the nature of the supporting oxide. [1][2][3][4][5][6][7] Various researchers have investigated the activities and selectivities of metal oxide catalysts. However, little is known about the parameters that are truly responsible for the catalytic action of transition-metal oxides.To study the effect of the support on the catalytic performance, one has to find a tool that is capable of probing the influence of the local environment (e.g., the support or promoters) on the properties of the catalytically active species, that is, a metal particle or metal oxide cluster. Metal-A C H T U N G T R E N N U N G (oxide)-support interactions can be ascribed to a structural (particle/cluster size and shape) effect, but can also have an electronic origin. For supported metal particles, the effect of the support on the catalytic properties has been determined by several techniques, for example, XPS, FT-IR analysis of adsorbed CO, and newly developed delta XANES and atomic XAFS (AXAFS) techniques. [8][9][10][11][12][13][14][15] In particular, the application of AXAFS has, in our opinion, led to a better understanding of metal-support interaction effects. [8,[15][16][17] AXAFS is sensitive to changes in the potential around the X-ray absorbing atom. The potential field around an atom is mainly determined by the first and second coordination spheres. O Grady et al. have shown for Pt/Ru alloys that the AXAFS intensity changes systematically with the composition of the alloy. [18] Thus, when the number of Ru atoms around a Pt atom increases, the intensity of the FT AXAFS peak increases and the peak centroid shifts to lower values of R. Comparison of these effects with the effects observed for a Pt electrode as a function of the applied voltage suggests that the first coordination shell of the Pt in the Pt/Ru alloy influences the electronic properties (inter-A C H T U N G T R E N N U N G atomic potential) of the Pt atom. [18,19] The effect of changes in the coordination around the absorber atom has been further illustrated for Pt by van Dorssen et al., who compared the AXAFS of a Pt foil with that of bulk Na 2 Pt(OH) 6 . The AXAFS intensity was found to be significantly higher in the Abstract: The influence of changes in coordination number, interatomic distances, and oxidation state on the intensity and centroid position of the Fourier transform (FT) of the atomic X-ray absorption fine structure (AXAFS) peak of vanadium oxide bulk model compounds and aluminasupported vanadium oxide clusters has been investigated. Using Na 3 VO 4 and V 2 O 5 as model compounds, it has been shown that the nearest neighbour shells have a pronounced influence on the AXAFS intensity; specifically, a 40 % decrease in intensity was observed between these two compounds. Secondly, the influence of partial reduction of the vanadium oxide species has been dete...

show abstract

Dehydrocyclization—Heterogeneous

Paál¹

2010

Encyclopedia of Catalysis

View full text Add to dashboard Cite

The formation of aromatic rings from alkanes such as hexane, heptane, octane, and so on (aromatization or dehydrocyclization) on oxide catalysts: chromia, lanthana, metals, such as platinum, palladium, and so on, and nonacidic (Na‐ or Ba‐L zeolite) supports is a “monofunctional” route, catalyzed by the active ingredient itself. A bifunctional route prevails in naphtha reforming (platforming) over Pt on acidic supports (eg, alumina). Interactions of Pt with acidic or alkaline support can be important for aromatization. The metallic function can also catalyze the formation of five‐membered ring(s): C5‐cyclization. The effect of added metallic components resulting in bimetallic catalysts (such as PtRe, PtSn, and so on) as well as the effect of nonmetallic components (Cl, S, C, H) is discussed. Aromatization requiring skeletal rearrangement (eg, of alkylpentane feeds) can also take place. Cyclic hydrocarbons may undergo ring enlargement and ring contraction. The same catalyst may promote the formation of a second ring in alkylcyclopentanes. The buildup of aromatic rings is also possible from smaller molecules (ethane, propane, butane) by dehydrocyclodimerization over bifunctional catalysts, such as ZSM 5 zeolites containing Pt, Zn, but first of all Ga (eg, in the CYCLAR process). Aromatics can be produced even from methane (Mo carbide‐ZSM‐5 or Pd‐Co catalysts).

show abstract

Nature of the Metal–Support Interaction in Supported Pt Catalysts: Shift in Pt Valence Orbital Energy and Charge Rearrangement

Cited by 101 publications

References 40 publications

In situ X-ray absorption spectroscopy as a unique tool for obtaining information on hydrogen binding sites and electronic structure of supported Pt catalysts: towards an understanding of the compensation relation in alkane hydrogenolysis

In situ X-ray absorption spectroscopy as a unique tool for obtaining information on hydrogen binding sites and electronic structure of supported Pt catalysts: towards an understanding of the compensation relation in alkane hydrogenolysis

Application of AXAFS Spectroscopy to Transition‐Metal Oxides: Influence of the Nearest and Next Nearest Neighbour Shells in Vanadium Oxides

Dehydrocyclization—Heterogeneous

Contact Info

Product

Resources

About