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Title
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Structural investigation of vanadyl-acetonate-containing precursors of mixed oxides on SBA-15
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Author
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Abstract
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| TiO(x)-VO(x) mixed-oxide supported SBA-15 catalysts were prepared by the molecular designed dispersion method (MDD) using acetylacetonate complexes. Two different synthesis route depositions are presented to prepare these mixed-oxide catalysts in a very controlled way. Continuous wave and pulse EPR spectroscopy is employed to determine the location of the VO(acac)(2) complexes in the mixed-oxide precursors (before calcination) in comparison to other supports. It is shown that the different synthesis pathways lead to differences in the local structure of the VO(2+) complexes and to a distinctive degree of spreading of the metals on the support surface. This is confirmed by additional characterizations of the final catalyst in terms of chemical composition and porosity. Depending on the way of preparation of the mixed oxides, the final catalysts present significant differences in pore structure, showing partially blocked or open mesopores. In the case of the mixed-oxide samples a higher dispersion of the metals is observed compared to the disposition of VO(acac)2 on the pure SBA-15 support. Both hyperfine sublevel correlation (HYSCORE) and IR spectroscopy show that the VO(acac)(2) complex, in contrast to the TiO(acac)(2) complex, has a great tendency to increase its coordination sphere by coordinating water molecules, but that this tendency is highly reduced when VO(acac)(2) is present in a Ti environment. |
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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 : condensed matter, materials, surfaces, interfaces and biophysical. - Washington, D.C.
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Publication
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Washington, D.C.
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2004
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ISSN
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1520-6106
1520-5207
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DOI
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10.1021/JP046611L
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Volume/pages
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108
:50
(2004)
, p. 19404-19412
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ISI
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000225695100053
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Full text (Publisher's DOI)
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