Selective cyclohexane oxidation over vanadium incorporated silica pillared clay catalysts: The effect of VOx content and dispersion

4 years ago

Selective cyclohexane oxidation over vanadium incorporated silica pillared clay catalysts: The effect of VOx content and dispersion

The design of efficient and stable clay based materials for catalytic technologies is a great challenge. We demonstrated a new approach of fabricating vanadium incorporated silica-pillared clay by interlayered self-assembly synthetic route. And such synthetic route utilized tartaric acid as the complexing reagent, both dodecyl dimethyl benzyl ammonium bromide and octadecylamine as the mixed structure-directing agent. The obtained vanadium-containned silica-pillared clay samples were characterized by X-ray fluorescence, X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption isotherms, Fourier-transform infrared spectroscopy, diffuse reflectance ultraviolet–visible spectroscopy and X-ray photoelectron spectroscopy techniques. Characterization results indicate that there is an important correlation between the concentration of octadecylamine and uniform structure of the obtained vanadium-containned sample. The octadecylamine is not only used as swelling agency but also decreases the polarity to confirm the uniform mesoporous structure form in the interlayered regions. It was generally considered that hydrothermal synthesis bears the advantage of incorporating active metal ions into the framework in the tetrahedral coordination with V⁴⁺ state under the combined action of complexing reagent and mixed structure-directing agent. And the V2O5 phase was gradually formed via aggregation and agglomeration of increasing highly dispersed vanadium species. The catalytic behaviour and performance was examined using the selective oxidation of cyclohexane. The obtained catalyst possesses larger surface area and mesoporous volume and uniform slit-shaped mesopores, which are beneficial to the diffusion of the vanadium atom and responsible for higher yield of the KA oil. And the mechanism associated with the porous structure change has also been discussed.

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DOI: S1387181117304171