Competitive Pathways of Methane Activation on Zn2+-Modified ZSM-5 Zeolite: H/D Hydrogen Exchange with Brønsted Acid Sites: Versus Dissociative Adsorption to Form Zn-Methyl Species Full article
| Journal |
Catalysis Science and Technology
ISSN: 2044-4753 , E-ISSN: 2044-4761 |
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| Output data | Year: 2016, Volume: 6, Number: 16, Pages: 6381-6388 Pages count : 8 DOI: 10.1039/c6cy00878j | ||||||
| Tags | Activation analysis; Chemical activation; Dissociation; Hydrogen; Methane; Nuclear magnetic resonance spectroscopy; Paraffins; Positive ions; Reaction intermediates; Zeolites | ||||||
| Authors |
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| Affiliations |
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Funding (3)
| 1 | Federal Agency for Scientific Organizations | V.44.2.11. |
| 2 | Russian Foundation for Basic Research | 14-03-00040 |
| 3 | German Research Foundation | HA 1893/16 |
Abstract:
To clarify the pathways of methane activation on Zn-modified high-silica zeolites, the kinetics of both dissociative adsorption of the alkane C-H bond to form Zn-methyl species and H/D hydrogen exchange between the alkane and Brønsted acid sites (BAS) have been analyzed for Zn2+/H-ZSM-5 containing exclusively Zn2+ cations (no ZnO species in the zeolite) and BAS. Analysis of the kinetics was performed by 1H MAS NMR spectroscopy in situ at 410-540 K. In spite of the activation barrier for H/D hydrogen exchange (68 kJ mol-1) being larger than that for Zn-methyl formation (46 kJ mol-1), the rate of H/D hydrogen exchange has been found to be one order of magnitude higher than the rate of the formation of Zn-methyl species within the studied temperature range. This implies that Zn-methyl species cannot be involved in the reaction of H/D hydrogen exchange as the intermediate responsible for facilitation of this reaction due to the presence of Zn2+ cations in the zeolite (J. Catal., 2008, 253, 11). A new mechanism has been suggested for C-H bond activation in methane on the zeolite modified with Zn2+ cations. It includes first the formation of a transient molecular complex of methane with Zn2+ cations. The complex either is further involved in the reaction of H/D hydrogen exchange or evolves toward the formation of Zn-methyl species and BAS.
Cite:
Arzumanov S.S.
, Gabrienko A.A.
, Freude D.
, Stepanov A.G.
Competitive Pathways of Methane Activation on Zn2+-Modified ZSM-5 Zeolite: H/D Hydrogen Exchange with Brønsted Acid Sites: Versus Dissociative Adsorption to Form Zn-Methyl Species
Catalysis Science and Technology. 2016. V.6. N16. P.6381-6388. DOI: 10.1039/c6cy00878j WOS Scopus РИНЦ ANCAN OpenAlex
Competitive Pathways of Methane Activation on Zn2+-Modified ZSM-5 Zeolite: H/D Hydrogen Exchange with Brønsted Acid Sites: Versus Dissociative Adsorption to Form Zn-Methyl Species
Catalysis Science and Technology. 2016. V.6. N16. P.6381-6388. DOI: 10.1039/c6cy00878j WOS Scopus РИНЦ ANCAN OpenAlex
Dates:
| Submitted: | Apr 21, 2016 |
| Accepted: | May 31, 2016 |
| Published online: | May 31, 2016 |
Identifiers:
| Web of science: | WOS:000381439400023 |
| Scopus: | 2-s2.0-84981313520 |
| Elibrary: | 27135173 |
| Chemical Abstracts: | 2016:882866 |
| Chemical Abstracts (print): | 165:214159 |
| OpenAlex: | W2414826031 |