Modifying the acidic properties of PtZSM-5 and PtY zeolites by appropriately varying reduction methods

A. Tamási, K. Niesz, I. Pálinkó, L. Guczi, I. Kiricsi

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6 Citations (Scopus)

Abstract

PtZSM-5 and PtY catalysts were prepared by the wet ion-exchange method from their Naforms. The modified zeolites were reduced by either NaBH4 or gaseous H2. Reduction with NaBH4 did not alter the original Lewis acidity of the samples (Lewis acidity due to the sodium ions), while reduction with H2 generated new Brønsted and Lewis acid sites. Reduction with NaBH4 did not modify the ZSM-5 crystal lattice, however, treatment with H2 led to some structural decomposition. Thus, Lewis sites due to extraframework alumina and Brønsted sites due to hydroxyl groups of the heeled defect sites were formed. For the Y zeolite, after reduction the platinum atoms moved out from the ion-exchange positions and started to migrate toward the supercage. On their way they aggregated and the large crystallites pushed apart portions of the zeolite crystal. The detrimental effect was of a higher extent when reduction occurred with gaseous H2. The resulting SiO2-Al2O3 supported catalyst contained many "true" Lewis sites due to extraframework alumina species as well as acidic OH groups connected to defect sites, however, it has lost shape-selective properties connected to the zeolitic structure.

Original languageEnglish
Pages (from-to)1801-1808
Number of pages8
JournalStudies in Surface Science and Catalysis
Volume142 B
Publication statusPublished - 2002

Fingerprint

Zeolites
zeolites
Aluminum Oxide
Acidity
acidity
Ion exchange
Alumina
aluminum oxides
catalysts
Lewis Acids
Defects
ions
defects
Platinum
Crystallites
Catalyst supports
crystal lattices
Crystal lattices
Hydroxyl Radical
crystallites

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Catalysis

Cite this

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abstract = "PtZSM-5 and PtY catalysts were prepared by the wet ion-exchange method from their Naforms. The modified zeolites were reduced by either NaBH4 or gaseous H2. Reduction with NaBH4 did not alter the original Lewis acidity of the samples (Lewis acidity due to the sodium ions), while reduction with H2 generated new Br{\o}nsted and Lewis acid sites. Reduction with NaBH4 did not modify the ZSM-5 crystal lattice, however, treatment with H2 led to some structural decomposition. Thus, Lewis sites due to extraframework alumina and Br{\o}nsted sites due to hydroxyl groups of the heeled defect sites were formed. For the Y zeolite, after reduction the platinum atoms moved out from the ion-exchange positions and started to migrate toward the supercage. On their way they aggregated and the large crystallites pushed apart portions of the zeolite crystal. The detrimental effect was of a higher extent when reduction occurred with gaseous H2. The resulting SiO2-Al2O3 supported catalyst contained many {"}true{"} Lewis sites due to extraframework alumina species as well as acidic OH groups connected to defect sites, however, it has lost shape-selective properties connected to the zeolitic structure.",
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T1 - Modifying the acidic properties of PtZSM-5 and PtY zeolites by appropriately varying reduction methods

AU - Tamási, A.

AU - Niesz, K.

AU - Pálinkó, I.

AU - Guczi, L.

AU - Kiricsi, I.

PY - 2002

Y1 - 2002

N2 - PtZSM-5 and PtY catalysts were prepared by the wet ion-exchange method from their Naforms. The modified zeolites were reduced by either NaBH4 or gaseous H2. Reduction with NaBH4 did not alter the original Lewis acidity of the samples (Lewis acidity due to the sodium ions), while reduction with H2 generated new Brønsted and Lewis acid sites. Reduction with NaBH4 did not modify the ZSM-5 crystal lattice, however, treatment with H2 led to some structural decomposition. Thus, Lewis sites due to extraframework alumina and Brønsted sites due to hydroxyl groups of the heeled defect sites were formed. For the Y zeolite, after reduction the platinum atoms moved out from the ion-exchange positions and started to migrate toward the supercage. On their way they aggregated and the large crystallites pushed apart portions of the zeolite crystal. The detrimental effect was of a higher extent when reduction occurred with gaseous H2. The resulting SiO2-Al2O3 supported catalyst contained many "true" Lewis sites due to extraframework alumina species as well as acidic OH groups connected to defect sites, however, it has lost shape-selective properties connected to the zeolitic structure.

AB - PtZSM-5 and PtY catalysts were prepared by the wet ion-exchange method from their Naforms. The modified zeolites were reduced by either NaBH4 or gaseous H2. Reduction with NaBH4 did not alter the original Lewis acidity of the samples (Lewis acidity due to the sodium ions), while reduction with H2 generated new Brønsted and Lewis acid sites. Reduction with NaBH4 did not modify the ZSM-5 crystal lattice, however, treatment with H2 led to some structural decomposition. Thus, Lewis sites due to extraframework alumina and Brønsted sites due to hydroxyl groups of the heeled defect sites were formed. For the Y zeolite, after reduction the platinum atoms moved out from the ion-exchange positions and started to migrate toward the supercage. On their way they aggregated and the large crystallites pushed apart portions of the zeolite crystal. The detrimental effect was of a higher extent when reduction occurred with gaseous H2. The resulting SiO2-Al2O3 supported catalyst contained many "true" Lewis sites due to extraframework alumina species as well as acidic OH groups connected to defect sites, however, it has lost shape-selective properties connected to the zeolitic structure.

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