n-hexane reactions on EUROPT-1 at different hydrogen pressures: The possibility of calculating kinetic parameters

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Abstract

Skeletal reactions of n-hexane on 6.3% Pt/SiO2 (EUROPT-1) have been studied as a function of hydrogen pressure between 483 and 633 K. Turnover frequencies were calculated for the overall reaction as well as for individual processes, i.e., hydrogenolysis, isomerization, C5-cyclization, and aromatization as well as dehydrogenation to hexenes. Curves with a maximum were observed for the conversion as a function of hydrogen pressure. Arrhenius plots could be calculated for constant hydrogen pressures as well as for maximum rates. The former lines "bend down" at higher temperatures. This may explain the different values determined in different experimental setups. Different straight Arrhenius lines were determined in the negative and in the positive hydrogen order range. We regard activation energies calculated at constant hydrogen pressures as "apparent" while those computed at the maximum rates may approximate "true" values. The apparent activation energies show compensation effect and give different compensation lines in the range of positive and negative hydrogen orders. In the case of bent Arrhenius plots, the computation resulted in virtual isokinetic parameters. Arrhenius parameters and compensation phenomena were determined for individual reactions, too. These results are in a good agreement with the mechanism suggested earlier for each reaction.

Original languageEnglish
Pages (from-to)192-198
Number of pages7
JournalJournal of Catalysis
Volume185
Issue number1
Publication statusPublished - 1999

Fingerprint

Hexane
Kinetic parameters
Hydrogen
kinetics
hydrogen
Arrhenius plots
Activation energy
plots
activation energy
Aromatization
hydrogenolysis
Hydrogenolysis
hexenes
Cyclization
Dehydrogenation
dehydrogenation
Isomerization
isomerization
n-hexane
curves

Keywords

  • Compensation effect
  • EUROPT-1
  • Hydrogen pressure effect
  • n-hexane transformation
  • Pt/SiO
  • Turnover frequency
  • Virtual isokinetic parameters

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

Cite this

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abstract = "Skeletal reactions of n-hexane on 6.3{\%} Pt/SiO2 (EUROPT-1) have been studied as a function of hydrogen pressure between 483 and 633 K. Turnover frequencies were calculated for the overall reaction as well as for individual processes, i.e., hydrogenolysis, isomerization, C5-cyclization, and aromatization as well as dehydrogenation to hexenes. Curves with a maximum were observed for the conversion as a function of hydrogen pressure. Arrhenius plots could be calculated for constant hydrogen pressures as well as for maximum rates. The former lines {"}bend down{"} at higher temperatures. This may explain the different values determined in different experimental setups. Different straight Arrhenius lines were determined in the negative and in the positive hydrogen order range. We regard activation energies calculated at constant hydrogen pressures as {"}apparent{"} while those computed at the maximum rates may approximate {"}true{"} values. The apparent activation energies show compensation effect and give different compensation lines in the range of positive and negative hydrogen orders. In the case of bent Arrhenius plots, the computation resulted in virtual isokinetic parameters. Arrhenius parameters and compensation phenomena were determined for individual reactions, too. These results are in a good agreement with the mechanism suggested earlier for each reaction.",
keywords = "Compensation effect, EUROPT-1, Hydrogen pressure effect, n-hexane transformation, Pt/SiO, Turnover frequency, Virtual isokinetic parameters",
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T1 - n-hexane reactions on EUROPT-1 at different hydrogen pressures

T2 - The possibility of calculating kinetic parameters

AU - Wootsch, A.

AU - Paál, Z.

PY - 1999

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AB - Skeletal reactions of n-hexane on 6.3% Pt/SiO2 (EUROPT-1) have been studied as a function of hydrogen pressure between 483 and 633 K. Turnover frequencies were calculated for the overall reaction as well as for individual processes, i.e., hydrogenolysis, isomerization, C5-cyclization, and aromatization as well as dehydrogenation to hexenes. Curves with a maximum were observed for the conversion as a function of hydrogen pressure. Arrhenius plots could be calculated for constant hydrogen pressures as well as for maximum rates. The former lines "bend down" at higher temperatures. This may explain the different values determined in different experimental setups. Different straight Arrhenius lines were determined in the negative and in the positive hydrogen order range. We regard activation energies calculated at constant hydrogen pressures as "apparent" while those computed at the maximum rates may approximate "true" values. The apparent activation energies show compensation effect and give different compensation lines in the range of positive and negative hydrogen orders. In the case of bent Arrhenius plots, the computation resulted in virtual isokinetic parameters. Arrhenius parameters and compensation phenomena were determined for individual reactions, too. These results are in a good agreement with the mechanism suggested earlier for each reaction.

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