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

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....

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Autor principal: Larsson, Ragnar
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6272274/
https://www.ncbi.nlm.nih.gov/pubmed/25648595
http://dx.doi.org/10.3390/molecules20022529
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author Larsson, Ragnar
author_facet Larsson, Ragnar
author_sort Larsson, Ragnar
collection PubMed
description 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 CH(3) group has been forced towards a flat structure with a carbon atom hybridization that is more sp(2) than sp(3). 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 T(iso) = 727 ± 4 K. From the SET formula for T(iso) when both energy-donating (ω) and energy-accepting (ν) vibrations have the same frequency, viz., T(iso) = Nhcν/2R, we obtain ν = ω = 1011 ± 6 cm(−1). This agrees rather well with the CH(3) rocking mode (1053 cm(−1)) and also with asymmetric “TO(4)” stretching vibrations of the zeolite structure (ω).
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spelling pubmed-62722742018-12-13 Propane Dehydrogenation Catalyzed by ZSM-5 Zeolites. A Mechanistic Study Based on the Selective Energy Transfer (SET) Theory Larsson, Ragnar Molecules Article 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 CH(3) group has been forced towards a flat structure with a carbon atom hybridization that is more sp(2) than sp(3). 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 T(iso) = 727 ± 4 K. From the SET formula for T(iso) when both energy-donating (ω) and energy-accepting (ν) vibrations have the same frequency, viz., T(iso) = Nhcν/2R, we obtain ν = ω = 1011 ± 6 cm(−1). This agrees rather well with the CH(3) rocking mode (1053 cm(−1)) and also with asymmetric “TO(4)” stretching vibrations of the zeolite structure (ω). MDPI 2015-02-02 /pmc/articles/PMC6272274/ /pubmed/25648595 http://dx.doi.org/10.3390/molecules20022529 Text en © 2015 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Larsson, Ragnar
Propane Dehydrogenation Catalyzed by ZSM-5 Zeolites. A Mechanistic Study Based on the Selective Energy Transfer (SET) Theory
title Propane Dehydrogenation Catalyzed by ZSM-5 Zeolites. A Mechanistic Study Based on the Selective Energy Transfer (SET) Theory
title_full Propane Dehydrogenation Catalyzed by ZSM-5 Zeolites. A Mechanistic Study Based on the Selective Energy Transfer (SET) Theory
title_fullStr Propane Dehydrogenation Catalyzed by ZSM-5 Zeolites. A Mechanistic Study Based on the Selective Energy Transfer (SET) Theory
title_full_unstemmed Propane Dehydrogenation Catalyzed by ZSM-5 Zeolites. A Mechanistic Study Based on the Selective Energy Transfer (SET) Theory
title_short Propane Dehydrogenation Catalyzed by ZSM-5 Zeolites. A Mechanistic Study Based on the Selective Energy Transfer (SET) Theory
title_sort propane dehydrogenation catalyzed by zsm-5 zeolites. a mechanistic study based on the selective energy transfer (set) theory
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6272274/
https://www.ncbi.nlm.nih.gov/pubmed/25648595
http://dx.doi.org/10.3390/molecules20022529
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