Influence of MgO-modified SBA-15 on the structure and catalytic activity of supported vanadium oxide catalysts

• Highly dispersed V oxide tetrahedra formed on alkaline, high-surface area support.
• Polymerization degree of V oxide units increased with increasing surface coverage.
• Investigation of structure–activity correlations by DR-UV–Vis, XAS, and GC analysis.
• Acrolein formation rate exhibited a “vulcano curve” as a function of surface coverage.
• Maximum in catalytic performance at an average of one to two VOV bonds.

Vanadium oxides on an alkaline, high-surface-area MgO/SBA-15 support are introduced as a model system for investigating structure–activity correlations in selective oxidation reactions. The supported vanadium oxide catalysts were investigated by X-ray diffraction, N2 physisorption, X-ray absorption spectroscopy, and diffuse reflectance UV–vis spectroscopy. The vanadium oxide species consisted of tetrahedral units, while the oligomerization degree depended on catalyst loading and vanadium oxide dispersion. Low-oligomeric [VO4] tetrahedra could be stabilized at comparably high coverage due to the alkaline surface of the oxide support. The structure was compared to higher-oligomeric vanadium oxide species present on acidic supports such as SBA-15. Catalytic performance of the oxide catalysts in selective propene oxidation was investigated by gas chromatography. Acrolein turnover frequency as a function of surface coverage exhibited volcano-type behavior. At optimal surface coverage, the catalyst structure consisted mainly of dimeric [V2O7] units.

Figure optionsDownload high-quality image (67 K)Download as PowerPoint slide