Shape-selective catalysts: Quasi-two-dimensional Pd-particles encapsulated in graphite

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Abstract

Pd-graphites were prepared by reduction of PdCl2-graphite intercalation compounds (PdCl2-GICs). Transmission electron microscope (TEM) measurements on the samples indicated that Pd nanoparticles with a wide size distribution were formed, mostly encapsulated inside the graphite host. The quasi-two-dimensional character of the Pd nanoparticles was confirmed by H2 sorption studies, which revealed the absence of Β-hydride formation over a broad range of pressure. Although the structures of the three Pd-graphites studied were very similar, differences were found between them in terms of their catalytic performance in the gas-phase reactions of 1-butene, cis-2-pentene and cyclohexene. It was established that the transformations of both 1-butene and cis-2-pentene took place in the interlamellar space of the graphite, whereas, in consequence of the the non-planar character of the substrate, the diffusion of cyclohexene between the graphite layers was sterically hindered. This molecular sieving effect implies that the Pd-graphites may be regarded as shape-selective catalysts. Pretreatment at 473 K was found to lower the catalytic activities considerably. The experimental evidence indicated that restructuring of the Pd crystallites resulted in a moderate aggregation of the active Pd-particles available for the reactant molecules.

Original languageEnglish
Pages (from-to)205-213
Number of pages9
JournalJournal of Molecular Catalysis A: Chemical
Volume175
Issue number1-2
DOIs
Publication statusPublished - Oct 23 2001

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Graphite
graphite
Alkenes
Butenes
catalysts
Catalysts
butenes
Nanoparticles
Intercalation compounds
Crystallites
Hydrides
nanoparticles
Sorption
Catalyst activity
Electron microscopes
Agglomeration
Gases
intercalation
pretreatment
sorption

Keywords

  • 1-Butene
  • Cis-2-pentene
  • Deactivation
  • Encapsulation
  • Graphite
  • H sorption
  • Palladium
  • Rearrangement
  • Shape-selectivity
  • TEM

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

Cite this

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title = "Shape-selective catalysts: Quasi-two-dimensional Pd-particles encapsulated in graphite",
abstract = "Pd-graphites were prepared by reduction of PdCl2-graphite intercalation compounds (PdCl2-GICs). Transmission electron microscope (TEM) measurements on the samples indicated that Pd nanoparticles with a wide size distribution were formed, mostly encapsulated inside the graphite host. The quasi-two-dimensional character of the Pd nanoparticles was confirmed by H2 sorption studies, which revealed the absence of Β-hydride formation over a broad range of pressure. Although the structures of the three Pd-graphites studied were very similar, differences were found between them in terms of their catalytic performance in the gas-phase reactions of 1-butene, cis-2-pentene and cyclohexene. It was established that the transformations of both 1-butene and cis-2-pentene took place in the interlamellar space of the graphite, whereas, in consequence of the the non-planar character of the substrate, the diffusion of cyclohexene between the graphite layers was sterically hindered. This molecular sieving effect implies that the Pd-graphites may be regarded as shape-selective catalysts. Pretreatment at 473 K was found to lower the catalytic activities considerably. The experimental evidence indicated that restructuring of the Pd crystallites resulted in a moderate aggregation of the active Pd-particles available for the reactant molecules.",
keywords = "1-Butene, Cis-2-pentene, Deactivation, Encapsulation, Graphite, H sorption, Palladium, Rearrangement, Shape-selectivity, TEM",
author = "A. Mastalir and Z. Kir{\'a}ly and J{\"u}rgen Walter and F. Notheisz and M. Bart{\'o}k",
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T1 - Shape-selective catalysts

T2 - Quasi-two-dimensional Pd-particles encapsulated in graphite

AU - Mastalir, A.

AU - Király, Z.

AU - Walter, Jürgen

AU - Notheisz, F.

AU - Bartók, M.

PY - 2001/10/23

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N2 - Pd-graphites were prepared by reduction of PdCl2-graphite intercalation compounds (PdCl2-GICs). Transmission electron microscope (TEM) measurements on the samples indicated that Pd nanoparticles with a wide size distribution were formed, mostly encapsulated inside the graphite host. The quasi-two-dimensional character of the Pd nanoparticles was confirmed by H2 sorption studies, which revealed the absence of Β-hydride formation over a broad range of pressure. Although the structures of the three Pd-graphites studied were very similar, differences were found between them in terms of their catalytic performance in the gas-phase reactions of 1-butene, cis-2-pentene and cyclohexene. It was established that the transformations of both 1-butene and cis-2-pentene took place in the interlamellar space of the graphite, whereas, in consequence of the the non-planar character of the substrate, the diffusion of cyclohexene between the graphite layers was sterically hindered. This molecular sieving effect implies that the Pd-graphites may be regarded as shape-selective catalysts. Pretreatment at 473 K was found to lower the catalytic activities considerably. The experimental evidence indicated that restructuring of the Pd crystallites resulted in a moderate aggregation of the active Pd-particles available for the reactant molecules.

AB - Pd-graphites were prepared by reduction of PdCl2-graphite intercalation compounds (PdCl2-GICs). Transmission electron microscope (TEM) measurements on the samples indicated that Pd nanoparticles with a wide size distribution were formed, mostly encapsulated inside the graphite host. The quasi-two-dimensional character of the Pd nanoparticles was confirmed by H2 sorption studies, which revealed the absence of Β-hydride formation over a broad range of pressure. Although the structures of the three Pd-graphites studied were very similar, differences were found between them in terms of their catalytic performance in the gas-phase reactions of 1-butene, cis-2-pentene and cyclohexene. It was established that the transformations of both 1-butene and cis-2-pentene took place in the interlamellar space of the graphite, whereas, in consequence of the the non-planar character of the substrate, the diffusion of cyclohexene between the graphite layers was sterically hindered. This molecular sieving effect implies that the Pd-graphites may be regarded as shape-selective catalysts. Pretreatment at 473 K was found to lower the catalytic activities considerably. The experimental evidence indicated that restructuring of the Pd crystallites resulted in a moderate aggregation of the active Pd-particles available for the reactant molecules.

KW - 1-Butene

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KW - Encapsulation

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KW - H sorption

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KW - Rearrangement

KW - Shape-selectivity

KW - TEM

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