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Bucko T, Benco L, Dubay O, et al. Mechanism of alkane dehydrogenation catalyzed by acidic zeolites: Ab initio transition path sampling. J Chem Phys. 2009;131(21):214508doi: 10.1063/1.3265715.
Bucko, T., Benco, L., Dubay, O., Dellago, C., & Hafner, J. (2009). Mechanism of alkane dehydrogenation catalyzed by acidic zeolites: Ab initio transition path sampling. The Journal of chemical physics, 131(21), 214508. https://doi.org/10.1063/1.3265715
Bucko, Tomás, et al. "Mechanism of alkane dehydrogenation catalyzed by acidic zeolites: Ab initio transition path sampling." The Journal of chemical physics vol. 131,21 (2009): 214508. doi: https://doi.org/10.1063/1.3265715
Bucko T, Benco L, Dubay O, Dellago C, Hafner J. Mechanism of alkane dehydrogenation catalyzed by acidic zeolites: Ab initio transition path sampling. J Chem Phys. 2009 Dec 07;131(21):214508. doi: 10.1063/1.3265715. PMID: 19968352.
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J Chem Phys. 2009 Dec 07;131(21):214508. doi: 10.1063/1.3265715.

Mechanism of alkane dehydrogenation catalyzed by acidic zeolites: Ab initio transition path sampling.

The Journal of chemical physics

Tomás Bucko, Lubomir Benco, Orest Dubay, Christoph Dellago, Jürgen Hafner

Affiliations

  1. Fakultät für Physik and Center for Computational Materials Science, Universität Wien, Sensengasse 8, Wien 1090, Austria. [email protected]

PMID: 19968352 DOI: 10.1063/1.3265715

Abstract

The dehydrogenation of propane over acidic chabazite has been studied using ab initio density-functional simulations in combination with static transition-state searches and dynamic transition path sampling (TPS) methods at elevated temperatures. The acidic zeolite has been modeled both using a small cluster and a large periodic model consisting of two unit cells, the TPS simulations allow to account for the effect of temperature and entropy. In agreement with experimental observations we find propene as the dominant reaction product and that the barrier for the dehydrogenation of a methyl group is higher than that for a methylene group. However, whereas all studies based on small cluster models (including the present one) conclude that the reaction proceeds via the formation of an alkoxy intermediate, our TPS studies based on a large periodic model lead to the conclusion that propene formation occurs via the formation of various forms of propyl cations stabilized by entropy, while the formation of an alkoxy species is a relatively rare event. It was observed only in 15% of the reactive trajectories for methyl dehydrogenation and even in only 8% of the methylene dehydrogenation reactions. Our studies demonstrate the importance of entropic effects and the need to account for the structure and flexibility of the zeolitic framework by using large periodic models.

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