Search results for "chromium supported oxide"
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Chromia on silica and zirconia oxides as recyclable oxidizing system: structural and surface characterization of the active chromium species for oxid…
2004
Chromium oxide samples supported over silica and zirconia were prepared by wet impregnation of the supports with aqueous solution of CrO3. In order to investigate the influence of the preparation method on the chromium dispersion and oxidation state, one sample was prepared by sol-gel technique. The materials were structurally characterized by XRD analysis. The oxidation states of chromium species were investigated by XPS, DRS and TPR/TPO techniques. EPR analyses were also carried out for the sample Cr/SiO2, that due to the low crystalline state exhibits broad XPS signals. In this case, particular attention was paid to the presence of Cr(V) and Cr (III) species and their concentration. The …