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Free keywords:
VOx; V2O5; Al2O3; Preparation method; Ball-milling; Propane; Oxidative dehydrogenation (ODH); Edge energy
V-oxides: clusters and catalysts; preparation & internal structure
Abstract:
Two preparation methods (wet saturation impregnation with vanadyl acetylacetonate and ball-milling of γ-Al2O3 with crystalline V2O5) were applied to produce two sets of VOx/γ-Al2O3 catalysts with increasing vanadium loadings. Materials from both sets were characterized by XRD, SEM, Raman, TPR and UV/vis-DRS (UV/vis diffuse reflectance spectroscopy) to elucidate the influence of the preparation method on the morphology of VOx species and on their behavior in the oxidative dehydrogenation of propane (ODP). Edge energies from UV/vis-DRS experiments were correlated with activity and selectivity data; the lower the edge energy, the lower catalytic activity and the higher propene selectivity. Both preparation methods result in materials with comparable physico-chemical and catalytic properties although very different precursors were used. Especially the calcination step during catalyst preparation seems to transform the different precursor molecules to dispersed VOx species by an equilibration process on the support material surface.
