Mobility of Stable pi-Complexes of Ethylene with Ag+ Cations in Ag/H-ZSM-5 Zeolite: A H-2 Solid-State NMR Study Full article
| Journal |
The Journal of Physical Chemistry C
ISSN: 1932-7447 , E-ISSN: 1932-7455 |
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| Output data | Year: 2016, Volume: 120, Number: 9, Pages: 4993-5000 Pages count : 8 DOI: 10.1021/acs.jpcc.5b12687 | ||||||
| Tags | Light polarization; Methane; Molecules; Nuclear magnetic resonance spectroscopy; Positive ions; Rotation; Silver; 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 | 14-03-91333 |
| 3 | German Research Foundation | HA 1893/16 |
Abstract:
Ethylene has-been established to form stable pi-complexes with Ag+ cations in Ag-modified zeolite H-ZSM-5 (Ag/H-ZSM-5), which strongly affect the reactivity of ethylene on this catalyst. With the aim Of revealing the catalytic and adsorptive properties of Ag+ cations in Ag/H-ZSM-5, a characterization of the mobility of ethylene pi-complex, located in the zeolite pores, has been performed with H-2 solid-state NMR spectroscopy. Ethylene molecules were established to remain bound to the Ag+ cations at temperatures up to 556 K. In the bound state, ethylene exhibits a H-2 NMR line shape typical for anisotropic motions. It is inferred that being adsorbed on Ag+ cation, ethylene molecule is involved in two internal rotations about its symmetry axes: along the C-2 axis aligned with the C=C bond and about the second C-2' axis orthogonal to the molecule plane. The first rotation occurs with the rate, k(1), of 10-40 kHz and activation barrier E-1 = 2.3 kJ mol(-1), while the second motion occurs with the rate k(2) of 10-400 kHz and E-2 = 4.7 kJ mol(-1). The latter motion is faster than the former One. Both motions occur by four-site jump exchange mechanism. When methane is coadsorbed on the zeolite, the dynamical picture becomes different within two different temperature regions, with T <= 392 K and T > 392 K. Below 392 K, the rotation mechanism is similar to that without methane coadsortion. However, the barrier for the rotation about the C-2' axis increases (E-2(II) = 7.4 kJ mol(-1)), which is evidence for the methane interaction with the ethylene pi-complex. At temperatures as high as 392 K, the 2H NMR line shape of adsorbed ethylene becomes typical for isotropic-like motion. The barrier of the motion, E = 25 kJ mol(-1), is accounted for by involvement of ethylene in the presence of methane in some isotropic or translational motions. At T >= 491 K, the line shape analysis reveals an H/D exchange between C2D4 and CH4.
Cite:
Kolokolov D.I.
, Arzumanov S.S.
, Freude D.
, Haase J.
, Stepanov A.G.
Mobility of Stable pi-Complexes of Ethylene with Ag+ Cations in Ag/H-ZSM-5 Zeolite: A H-2 Solid-State NMR Study
The Journal of Physical Chemistry C. 2016. V.120. N9. P.4993-5000. DOI: 10.1021/acs.jpcc.5b12687 WOS Scopus РИНЦ ANCAN OpenAlex
Mobility of Stable pi-Complexes of Ethylene with Ag+ Cations in Ag/H-ZSM-5 Zeolite: A H-2 Solid-State NMR Study
The Journal of Physical Chemistry C. 2016. V.120. N9. P.4993-5000. DOI: 10.1021/acs.jpcc.5b12687 WOS Scopus РИНЦ ANCAN OpenAlex
Dates:
| Submitted: | Dec 29, 2015 |
| Accepted: | Feb 16, 2016 |
| Published online: | Feb 26, 2016 |
| Published print: | Mar 10, 2016 |
Identifiers:
| Web of science: | WOS:000372042600030 |
| Scopus: | 2-s2.0-84961118098 |
| Elibrary: | 27098799 |
| Chemical Abstracts: | 2016:283645 |
| Chemical Abstracts (print): | 164:338419 |
| OpenAlex: | W2280978860 |