Heat-treatment of isomorphously substituted ZSM-5 zeolites and its structural consequences. An X-ray diffraction, 29Si MAS-NMR, XPS and FT-IR spectroscopy study

P. Fejes, János B. Nagy, J. Halász, A. Oszkó

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67 Citations (Scopus)

Abstract

The structural consequences of template removal by calcination, and (under non-caring conditions) those caused by overheating have been studied by X-ray diffraction, 29Si MAS-NMR, FT-IR and XPS spectroscopies using Fe-ZSM-5 (Si/ Fe=15.0) and Ti-ZSM-5 (Si/Ti=29.8) samples. The heat-treatments bring about in either case dislodgement of Fe and Ti framework species, respectively; causing thereby a linear/quasi-linear decrease of isomorphously substituted framework Fe3+ and Ti4+ sites as the temperature of treatments increases. The ejected materials seem to have extremely high dispersity. The heat-treatments increase the Si/T ratio and concomitantly lattice shrinkage and a slight (≤9 cm-1) blue-shift of the respective IR spectra takes place. The framework contraction occurs almost exclusively along the sinusoidal channels (i.e. vertical to the [1 0 0] crystallographic plane). Though the differences in the binding energies are slight (≥1.9 eV) it seems to be possible to estimate the framework/extra-framework T ratio by deconvolution of the respective XPS spectra. The catalytic consequences caused by non-caring calcination in the quality and quantity of potential active sites are briefly discussed.

Original languageEnglish
Pages (from-to)89-104
Number of pages16
JournalApplied Catalysis A: General
Volume175
Issue number1-2
Publication statusPublished - Dec 14 1998

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Zeolites
Calcination
Infrared spectroscopy
X ray photoelectron spectroscopy
Heat treatment
Nuclear magnetic resonance
X ray diffraction
Deconvolution
Binding energy
Spectroscopy
Temperature

Keywords

  • Catalysis
  • Fe- and Ti-ZSM-5 zeolites
  • Heat-treatment
  • Structural changes

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

Cite this

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abstract = "The structural consequences of template removal by calcination, and (under non-caring conditions) those caused by overheating have been studied by X-ray diffraction, 29Si MAS-NMR, FT-IR and XPS spectroscopies using Fe-ZSM-5 (Si/ Fe=15.0) and Ti-ZSM-5 (Si/Ti=29.8) samples. The heat-treatments bring about in either case dislodgement of Fe and Ti framework species, respectively; causing thereby a linear/quasi-linear decrease of isomorphously substituted framework Fe3+ and Ti4+ sites as the temperature of treatments increases. The ejected materials seem to have extremely high dispersity. The heat-treatments increase the Si/T ratio and concomitantly lattice shrinkage and a slight (≤9 cm-1) blue-shift of the respective IR spectra takes place. The framework contraction occurs almost exclusively along the sinusoidal channels (i.e. vertical to the [1 0 0] crystallographic plane). Though the differences in the binding energies are slight (≥1.9 eV) it seems to be possible to estimate the framework/extra-framework T ratio by deconvolution of the respective XPS spectra. The catalytic consequences caused by non-caring calcination in the quality and quantity of potential active sites are briefly discussed.",
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AU - Fejes, P.

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AU - Halász, J.

AU - Oszkó, A.

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N2 - The structural consequences of template removal by calcination, and (under non-caring conditions) those caused by overheating have been studied by X-ray diffraction, 29Si MAS-NMR, FT-IR and XPS spectroscopies using Fe-ZSM-5 (Si/ Fe=15.0) and Ti-ZSM-5 (Si/Ti=29.8) samples. The heat-treatments bring about in either case dislodgement of Fe and Ti framework species, respectively; causing thereby a linear/quasi-linear decrease of isomorphously substituted framework Fe3+ and Ti4+ sites as the temperature of treatments increases. The ejected materials seem to have extremely high dispersity. The heat-treatments increase the Si/T ratio and concomitantly lattice shrinkage and a slight (≤9 cm-1) blue-shift of the respective IR spectra takes place. The framework contraction occurs almost exclusively along the sinusoidal channels (i.e. vertical to the [1 0 0] crystallographic plane). Though the differences in the binding energies are slight (≥1.9 eV) it seems to be possible to estimate the framework/extra-framework T ratio by deconvolution of the respective XPS spectra. The catalytic consequences caused by non-caring calcination in the quality and quantity of potential active sites are briefly discussed.

AB - The structural consequences of template removal by calcination, and (under non-caring conditions) those caused by overheating have been studied by X-ray diffraction, 29Si MAS-NMR, FT-IR and XPS spectroscopies using Fe-ZSM-5 (Si/ Fe=15.0) and Ti-ZSM-5 (Si/Ti=29.8) samples. The heat-treatments bring about in either case dislodgement of Fe and Ti framework species, respectively; causing thereby a linear/quasi-linear decrease of isomorphously substituted framework Fe3+ and Ti4+ sites as the temperature of treatments increases. The ejected materials seem to have extremely high dispersity. The heat-treatments increase the Si/T ratio and concomitantly lattice shrinkage and a slight (≤9 cm-1) blue-shift of the respective IR spectra takes place. The framework contraction occurs almost exclusively along the sinusoidal channels (i.e. vertical to the [1 0 0] crystallographic plane). Though the differences in the binding energies are slight (≥1.9 eV) it seems to be possible to estimate the framework/extra-framework T ratio by deconvolution of the respective XPS spectra. The catalytic consequences caused by non-caring calcination in the quality and quantity of potential active sites are briefly discussed.

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