Toward Understanding the Unusual Reactivity of Nb-Containing Catalysts in Epoxidation of C=C Bonds with Hydrogen Peroxide Научная публикация
| Журнал |
Journal of Catalysis
ISSN: 0021-9517 , E-ISSN: 1090-2694 |
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| Вых. Данные | Год: 2017, Том: 356, Страницы: 85-99 Страниц : 15 DOI: 10.1016/j.jcat.2017.09.011 | ||||
| Ключевые слова | Epoxidation, Heterogeneous catalysis, Hydrogen peroxide, Kinetics, Mechanism, Mesoporous niobium silicate | ||||
| Авторы |
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| Организации |
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Информация о финансировании (2)
| 1 | Федеральное агентство научных организаций России | 0303-2016-0005 |
| 2 | Российский фонд фундаментальных исследований | 16-03-00827 |
Реферат:
Nb-containing mesoporous silicates reveal superior activity and selectivity in epoxidation of alkenes using hydrogen peroxide as green oxidant and, in contrast to mesoporous titanium-silicates, catalyze epoxidation of both electron-rich and electron-deficient C=C bonds. This report describes a kinetic and mechanistic investigation of epoxidation of two representative substrates, cyclooctene (CyO) and 2-methyl-1,4-naphthoquinone (MNQ), over two mesoporous niobium-silicates with predominantly di(oligo)meric or isolated Nb(V) sites. The observed kinetic regularities did not depend on the state of Nb but were strictly determined by the nature of the organic substrate. The rate law established for CyO is consistent with a mechanism that involves interaction of Н2О2 with Nb(V) sites to give a hydroperoxo species ‘NbOOH’ and water, followed by oxygen transfer to nucleophilic С=С bond, producing epoxide and regenerating the initial state of the catalyst. This mechanism is strongly supported by stereospecificity in epoxidation of cis-alkenes and high heterolytic pathway selectivity in the oxidation of cyclohexene. The ‘NbOOH’ species is manifested by an absorption feature at 307 nm in diffuse reflectance UV-vis spectra. The addition of base (NaOAc) causes shift of the absorption band to 293 nm and produces a rate-retarding effect on the epoxidation reaction. Several lines of evidence, including zero reaction order in MNQ, rate-accelerating effect of base, detection of acetamide in the reaction mixture, negligible reaction rate in ethylacetate, and recognition of weak basic sites in the niobium-silicates using infrared spectroscopy of adsorbed CDCl3, all indicate the MNQ epoxidation proceeds by another mechanism that involves rate-limiting oxidation of the solvent molecule (MeCN) to generate peroxycarboximidic acid, which reacts with electron-deficient C=C bond, producing epoxy derivative and acetamide.
Библиографическая ссылка:
Ivanchikova I.D.
, Skobelev I.Y.
, Maksimchuk N.V.
, Paukshtis E.A.
, Shashkov M.V.
, Kholdeeva O.A.
Toward Understanding the Unusual Reactivity of Nb-Containing Catalysts in Epoxidation of C=C Bonds with Hydrogen Peroxide
Journal of Catalysis. 2017. V.356. P.85-99. DOI: 10.1016/j.jcat.2017.09.011 WOS Scopus РИНЦ CAPlusCA OpenAlex
Toward Understanding the Unusual Reactivity of Nb-Containing Catalysts in Epoxidation of C=C Bonds with Hydrogen Peroxide
Journal of Catalysis. 2017. V.356. P.85-99. DOI: 10.1016/j.jcat.2017.09.011 WOS Scopus РИНЦ CAPlusCA OpenAlex
Даты:
| Поступила в редакцию: | 29 июн. 2017 г. |
| Принята к публикации: | 15 сент. 2017 г. |
| Опубликована online: | 6 нояб. 2017 г. |
| Опубликована в печати: | 1 дек. 2017 г. |
Идентификаторы БД:
| Web of science: | WOS:000418223300009 |
| Scopus: | 2-s2.0-85032336253 |
| РИНЦ: | 31082218 |
| Chemical Abstracts: | 2017:1696699 |
| Chemical Abstracts (print): | 168:285389 |
| OpenAlex: | W2768008091 |