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Title
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Creation of VOx surface species on pure silica MCM-48 using gas-phase modification with VO(acac)(2)
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Author
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Abstract
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| Pure silica MCM-48 is prepared by a novel synthesis method, using the [C18H37N+(CH3)(2)-(CH2)(12)-N+(CH3)(2)C18H37].2Br(-) surfactant, abbreviated as GEMINI 18-12-18. The MCM-48, obtained after careful calcination, is a highly crystalline, mesoporous material with the characteristics of the Ia3d cubic phase, a surface area exceeding 1000 m(2)/g, and a narrow mesoporous pore size distribution (r = 1.4 nm; fwhh < 0.2 nm). This MCM support is grafted with VOx species using a designed dispersion of VO(acac)(2) in a gas-deposition reactor. In the first step, the complex is anchored to the support. In a subsequent step the adsorbed complex is thermolyzed to yield chemically bonded VOx surface species, The final material contains 1.7 mmol V/g (8.7 wt % V) and still has a narrow pore-size distribution and a surface area of 800 m(2)/g. It is observed that all silanols are consumed during the adsorption of the VO(acac)(2) complex to the MCM support. Therefore, the maximum achievable number of surface V species is limited by the silanol number and not by the geometrical surface, which has a higher capacity, After calcination of the adsorbed complex, the supported VOx species are present in a strictly tetrahedral configuration, mainly as chains of linked tetrahedra and not as isolated species. |
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Language
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English
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Source (journal)
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The journal of physical chemistry : B : materials, surfaces, interfaces and biophysical. - Washington, D.C., 1997, currens
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The journal of physical chemistry: B
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Publication
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Washington, D.C.
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1998
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ISSN
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1089-5647
[print]
1520-5207
[online]
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DOI
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10.1021/JP9727761
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Volume/pages
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102
:3
(1998)
, p. 585-590
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ISI
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000071802700015
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Full text (Publisher's DOI)
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