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Issue 7, 2011
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Nature of dispersed vanadium oxide: influence of the silica support structure and synthesis methods

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Abstract

Dispersed vanadium oxide samples were prepared on the basis of two differently structured high surface area silica materials (Aerosil 300, SBA-15). For each support material incipient wetness impregnation and a grafting/ion exchange procedure were applied to prepare catalyst samples with comparable vanadium density. The influence of the silica support material and preparation method on the vanadium oxide structure and dispersion has been studied using diffuse reflectance UV-Vis spectroscopy, visible Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). By independent spectroscopic characterization a fully consistent picture regarding the relation of the structure (UV-Vis, Raman) and dispersion (XPS) is developed. Based on the present structural data and recent findings the dispersed vanadium oxide is proposed to consist of monomers and oligomers with a distorted tetrahedral (VO4) structure containing one short V[double bond, length as m-dash]O bond. A different degree of hydroxylation of vanadium gives rise to two V[double bond, length as m-dash]O stretching bands at 1027 and 1040 cm−1. The structure and dispersion of vanadium oxide are more strongly influenced by the support material than by the synthesis method. In this regard the Aerosil 300 samples show a higher degree of oligomerization, i.e. less dispersion of the surface vanadium oxide species, than the SBA-15 samples. Likewise incipient wetness impregnation leads to more oligomerized species than grafting/ion-exchange.

Graphical abstract: Nature of dispersed vanadium oxide: influence of the silica support structure and synthesis methods

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Publication details

The article was received on 23 Feb 2011, accepted on 30 May 2011 and first published on 30 Jun 2011


Article type: Paper
DOI: 10.1039/C1CY00062D
Catal. Sci. Technol., 2011,1, 1175-1181

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    Nature of dispersed vanadium oxide: influence of the silica support structure and synthesis methods

    R. Chlosta , G. Tzolova-Müller, R. Schlögl and C. Hess, Catal. Sci. Technol., 2011, 1, 1175
    DOI: 10.1039/C1CY00062D

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