O2 Isotopic Exchange in the Presence of O- Anion Rradicals on the FeZSM-5 Surface Full article
| Journal |
Journal of Catalysis
ISSN: 0021-9517 , E-ISSN: 1090-2694 |
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| Output data | Year: 2009, Volume: 263, Number: 1, Pages: 173-180 Pages count : 8 DOI: 10.1016/j.jcat.2009.02.009 | ||
| Tags | α-Oxygen, α-Sites, FeZSM-5, O2 activation, O2 isotopic exchange, Oxygen anion radicals | ||
| Authors |
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| Affiliations |
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Funding (2)
| 1 | Russian Foundation for Basic Research | 06-03-72551 |
| 2 | Russian Foundation for Basic Research | 06-03-33087 |
Abstract:
Oxygen anion radicals O− play an important role in various physico-chemical processes, including those taking place on solid surfaces, where their behavior is especially difficult to follow. This work presents a detailed study on the behavior of O− radicals adsorbed on FeZSM-5 surface in the reaction of O2 isotopic exchange carried out over a wide range of temperatures (198–513 K). High concentration of O− in this unique system (called alpha-oxygen) made it possible to identify two exchange mechanisms, R0 and R1, operating in the presence of Oα. The R1 mechanism (E=15 kJ/mol) dominates in the high-temperature region and can be represented by the following equation:
18O2 + 16O−α ⇄ [O−3]α ⇄ 16O18O + 18O−α.
This mechanism is convincingly supported by several arguments: the first order reaction with respect to O2; the linear dependence of reaction rate on Oα concentration; the ESR observation of O−3 species (in other systems); and, according to isotopic exchange theory, by a twofold excess of the rate of homoexchange over the rate of heteroexchange.
The R0 exchange (E=0.8 kJ/mol) is a new reaction pathway that appears at cryogenic temperatures and leads to isotope redistribution only between O2 molecules, not affecting the isotopic composition of Oα. This exchange mechanism is not quite clear. The necessity of the presence of Oα without its direct involvement in the exchange process seems to be quite surprising. The reaction may proceed via a hypothetical complex [O−5]α, which allows cleavage and redistribution of chemical bonds between two O2 molecules adsorbed on the α-oxygen. The cleavage and redistribution of such strong bonds at cryogenic temperatures with nearly zero activation energy are an intriguing phenomenon worthy of further study.
Cite:
Parfenov M.V.
, Starokon E.V.
, Semikolenov S.V.
, Panov G.I.
O2 Isotopic Exchange in the Presence of O- Anion Rradicals on the FeZSM-5 Surface
Journal of Catalysis. 2009. V.263. N1. P.173-180. DOI: 10.1016/j.jcat.2009.02.009 WOS Scopus РИНЦ ANCAN OpenAlex
O2 Isotopic Exchange in the Presence of O- Anion Rradicals on the FeZSM-5 Surface
Journal of Catalysis. 2009. V.263. N1. P.173-180. DOI: 10.1016/j.jcat.2009.02.009 WOS Scopus РИНЦ ANCAN OpenAlex
Dates:
| Submitted: | Nov 6, 2008 |
| Accepted: | Feb 10, 2009 |
| Published online: | Feb 27, 2009 |
| Published print: | Apr 1, 2009 |
Identifiers:
| Web of science: | WOS:000265000800019 |
| Scopus: | 2-s2.0-61849160399 |
| Elibrary: | 13612919 |
| Chemical Abstracts: | 2009:326208 |
| Chemical Abstracts (print): | 150:407459 |
| OpenAlex: | W2165129668 |