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Propane Dehydrogenation Catalyzed by ZSM-5 Zeolites. A Mechanistic Study Based on the Selective Energy Transfer (SET) Theory.

Larsson, Ragnar LU (2015) In Molecules 20(2). p.2529-2535
Abstract
Experimentally determined activation energies of propane dehydrogenation catalyzed by ZSM-5 zeolites have been used to test the SET theory. The basis of this theory is that the catalyst system transfers vibrational energy via a resonance process to a specific vibration mode of the reacting molecule. Being excited up to a certain number of vibrational quanta the molecule is brought to reaction. By analyzing the above-mentioned activation energies we found the wave number of this "specific mode" to be 1065 cm-1. This is very close to the rocking vibration of propane (1053 cm-1). We suggest that the propane molecule reacts when excited so that the CH3 group has been forced towards a flat structure with a carbon atom hybridization that is more... (More)
Experimentally determined activation energies of propane dehydrogenation catalyzed by ZSM-5 zeolites have been used to test the SET theory. The basis of this theory is that the catalyst system transfers vibrational energy via a resonance process to a specific vibration mode of the reacting molecule. Being excited up to a certain number of vibrational quanta the molecule is brought to reaction. By analyzing the above-mentioned activation energies we found the wave number of this "specific mode" to be 1065 cm-1. This is very close to the rocking vibration of propane (1053 cm-1). We suggest that the propane molecule reacts when excited so that the CH3 group has been forced towards a flat structure with a carbon atom hybridization that is more sp2 than sp3. Consequently there is no way for three H-atoms to bind to the carbon and one of them must leave. This is the starting point of the reaction. The isokinetic temperature of the system was found as Tiso = 727 ± 4 K. From the SET formula for Tiso when both energy-donating (ω) and energy-accepting (ν) vibrations have the same frequency, viz., Tiso = Nhcν/2R, we obtain ν = ω = 1011 ± 6 cm-1. This agrees rather well with the CH3 rocking mode (1053 cm-1) and also with asymmetric "TO4" stretching vibrations of the zeolite structure (ω). (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Molecules
volume
20
issue
2
pages
2529 - 2535
publisher
Molecular Diversity Preservation International
external identifiers
  • pmid:25648595
  • wos:000350748200040
  • scopus:84923304048
ISSN
1420-3049
DOI
10.3390/molecules20022529
language
English
LU publication?
yes
id
703011c7-2559-44bd-bdd9-eaa1bd4eb948 (old id 5145539)
date added to LUP
2015-03-09 17:07:40
date last changed
2017-01-01 05:36:27
@article{703011c7-2559-44bd-bdd9-eaa1bd4eb948,
  abstract     = {Experimentally determined activation energies of propane dehydrogenation catalyzed by ZSM-5 zeolites have been used to test the SET theory. The basis of this theory is that the catalyst system transfers vibrational energy via a resonance process to a specific vibration mode of the reacting molecule. Being excited up to a certain number of vibrational quanta the molecule is brought to reaction. By analyzing the above-mentioned activation energies we found the wave number of this "specific mode" to be 1065 cm-1. This is very close to the rocking vibration of propane (1053 cm-1). We suggest that the propane molecule reacts when excited so that the CH3 group has been forced towards a flat structure with a carbon atom hybridization that is more sp2 than sp3. Consequently there is no way for three H-atoms to bind to the carbon and one of them must leave. This is the starting point of the reaction. The isokinetic temperature of the system was found as Tiso = 727 ± 4 K. From the SET formula for Tiso when both energy-donating (ω) and energy-accepting (ν) vibrations have the same frequency, viz., Tiso = Nhcν/2R, we obtain ν = ω = 1011 ± 6 cm-1. This agrees rather well with the CH3 rocking mode (1053 cm-1) and also with asymmetric "TO4" stretching vibrations of the zeolite structure (ω).},
  author       = {Larsson, Ragnar},
  issn         = {1420-3049},
  language     = {eng},
  number       = {2},
  pages        = {2529--2535},
  publisher    = {Molecular Diversity Preservation International},
  series       = {Molecules},
  title        = {Propane Dehydrogenation Catalyzed by ZSM-5 Zeolites. A Mechanistic Study Based on the Selective Energy Transfer (SET) Theory.},
  url          = {http://dx.doi.org/10.3390/molecules20022529},
  volume       = {20},
  year         = {2015},
}