β-Scission of Olefins on Acidic Zeolites: A Periodic PBE-D Study in H-ZSM-5
| Autor: | Mark N. Mazar, Matteo Cococcioni, Aditya Bhan, Saleh Al-Hashimi |
|---|---|
| Rok vydání: | 2013 |
| Předmět: |
chemistry.chemical_classification
biology Chemistry Active site Activation energy Potential energy Transition state Surfaces Coatings and Films Electronic Optical and Magnetic Materials Crystallography General Energy Hydrocarbon Computational chemistry Atom biology.protein Density functional theory Physical and Theoretical Chemistry ZSM-5 |
| Zdroj: | The Journal of Physical Chemistry C. 117:23609-23620 |
| ISSN: | 1932-7455 1932-7447 |
| Popis: | Eight β-scission modes involving C6 and C8 olefin isomers are investigated using dispersion-corrected density functional theory (i.e., PBE-D) calculations. Potential energy surfaces are evaluated within an acidic H-ZSM-5 supercell containing a single, isolated active site. Minimum energy pathways are localized using the nudged elastic band method. The relative enthalpic barriers of β-scission steps can be described by the substitution order of the carbocationic carbon atom present in the reactant and transition states. Specifically, the total charge on the hydrocarbon fragment containing the β C atom increases going from the physi- or chemisorbed reactant state to the β-scission transition state; the magnitude of this change (+0.37e–0.97e) is found to correlate nearly monotonically with the activation energy (89–233 kJ mol–1). A comparison of 1° to 3° (E1) and 3° to 1° (E2) β-scission modes as well as 2° to 3° (B1) and 3° to 2° (B2) β-scission modes reveals that the barrier heights depend on the substitut... |
| Databáze: | OpenAIRE |
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