Proton exchange of small hydrocarbons over acidic chabazite: Ab initio study of entropic effects

The proton-exchange reaction of a series of short hydrocarbons over an acidic zeolite (chabazite) was studied using periodic density functional theory (DFT) calculations. It was found that the chain length of hydrocarbons does not have a significant effect on the height of the potential-energy barri...

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Bibliographic Details
Published in:Journal of catalysis 2007-08, Vol.250 (1), p.171-183
Main Authors: Bučko, Tomáš, Benco, Lubomir, Hafner, Jürgen, Ángyán, János G.
Format: Article
Language:English
Subjects:
Ab initio
Catalysis
Chemical reactions
Chemistry
Entropy
Exact sciences and technology
Free-energy
General and physical chemistry
Hydrocarbons
Ion-exchange
Materials science
Molecular dynamics
Proton exchange
Surface physical chemistry
Theory
Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
Zeolites
Zeolites: preparations and properties
Citations: Items that cite this one
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Summary:The proton-exchange reaction of a series of short hydrocarbons over an acidic zeolite (chabazite) was studied using periodic density functional theory (DFT) calculations. It was found that the chain length of hydrocarbons does not have a significant effect on the height of the potential-energy barrier. The experimentally observed regioselectivity between methyl and methylene groups in propane and between methyl and methine groups in isobutane was shown to be an entropic effect. In addition to the direct H-exchange, a mechanism mediated by a methylpropene molecule recently suggested by experimentalists was explored. It was found that entropy plays a very important role in driving the reaction.
ISSN:0021-9517
1090-2694
DOI:10.1016/j.jcat.2007.05.025