Highly Selective Oxidation of Alkylphenols to Benzoquinones with Hydrogen Peroxide over Silica-Supported Titanium Catalysts: Titanium Cluster Site versus Titanium Single Site Научная публикация
| Журнал |
Advanced Synthesis and Catalysis
ISSN: 1615-4150 , E-ISSN: 1615-4169 |
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| Вых. Данные | Год: 2009, Том: 351, Номер: 11-12, Страницы: 1877-1889 Страниц : 12 DOI: 10.1002/adsc.200900109 | ||||||
| Ключевые слова | Alkylphenols, Heterogeneous catalysis, Hydrogen peroxide, Quiñ ones, Selective oxidation, Titanium-silica catalysts | ||||||
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Информация о финансировании (2)
| 1 | National Research Council | 30212 |
| 2 | National Research Council | 50558 |
Реферат:
Titanium-silica catalysts have been prepared by supporting titanium(IV) precursors with different nuclearity {mononuclear titanocene dichloride Ti(Cp)2Cl2, dinuclear titanium diethyl tartrate and the tetranuclear titanium peroxo complex (NH4)8[Ti4(C6H4O7)4(O2)4]⋅8 H2O} onto the surface of silica materials with different textural characteristics. The supported catalysts have been explored as highly active and reusable catalysts for the oxidation of 2,3,6-trimethylphenol (TMP) and 2,6-dimethylphenol (DMP) to 2,3,5-trimethyl-1,4-benzoquinone (TMBQ, vitamin E key intermediate) and 2,6-dimethyl-1,4-benzoquinone (DMBQ), respectively, using aqueous hydrogen peroxide as green oxidant. Catalysts prepared by grafting mononuclear Ti(Cp)2Cl2 revealed a strong dependence of the product selectivity on the surface concentration of titanium active centers. Mesoporous materials with titanium surface concentration in the range of 0.6–1.0 Ti/nm2 were identified as optimal catalysts for the transformation of alkylphenols to benzoquinones. Catalysts having <0.6 Ti/nm2 produced a mixture of benzoquinones and dimeric by-products. Conversely, when di-/tetranuclear titanium precursors were employed for the catalyst preparation, a diminution of the titanium surface concentration had no impact on the benzoquinone selectivity, which was typically as high as 96–99%. DR-UV spectroscopic studies revealed that the catalysts capable of producing alkylbenzoquinones with nearly quantitative yields possess titanium dimers and/or subnanometer-size clusters homogeneously distributed on a silica surface. On the contrary, catalysts with isolated titanium sites give a considerable amount of dimeric by-products. This is the first example which clearly demonstrates the advantages of titanium cluster-site catalysts over titanium single-site catalysts in hydrogen peroxide-based selective oxidation reaction.
Библиографическая ссылка:
Kholdeeva O.A.
, Ivanchikova I.D.
, Guidotti M.
, Pirovano C.
, Ravasio N.
, Barmatova M.V.
, Chesalov Y.A.
Highly Selective Oxidation of Alkylphenols to Benzoquinones with Hydrogen Peroxide over Silica-Supported Titanium Catalysts: Titanium Cluster Site versus Titanium Single Site
Advanced Synthesis and Catalysis. 2009. V.351. N11-12. P.1877-1889. DOI: 10.1002/adsc.200900109 WOS Scopus РИНЦ CAPlusCA OpenAlex
Highly Selective Oxidation of Alkylphenols to Benzoquinones with Hydrogen Peroxide over Silica-Supported Titanium Catalysts: Titanium Cluster Site versus Titanium Single Site
Advanced Synthesis and Catalysis. 2009. V.351. N11-12. P.1877-1889. DOI: 10.1002/adsc.200900109 WOS Scopus РИНЦ CAPlusCA OpenAlex
Даты:
| Поступила в редакцию: | 17 февр. 2009 г. |
| Опубликована online: | 27 июл. 2009 г. |
| Опубликована в печати: | 1 авг. 2009 г. |
Идентификаторы БД:
| Web of science: | WOS:000269583900027 |
| Scopus: | 2-s2.0-68949164927 |
| РИНЦ: | 15309726 |
| Chemical Abstracts: | 2009:1012108 |
| Chemical Abstracts (print): | 152:238436 |
| OpenAlex: | W2149426835 |