Catalytic combustion of benzene over γ-alumina supported chromium oxide catalysts

• Chromia could be well dispersed on γ-Al2O3 with a monolayer dispersion capacity of 7.5 wt.%.
• For catalytic combustion of benzene the catalyst with a Cr loading near the monolayer dispersion capacity showed the best activity.
• Surface Cr6+ played an important role for the benzene oxidation.

The γ-alumina supported chromium oxide catalysts with Cr loadings varying from 1.7 to 13.6 wt.% were prepared by the impregnation method and characterized using N2 adsorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy and Raman spectroscopy. Benzene combustion catalyzed by the catalysts was investigated. The results showed that chromia was well dispersed on the surface of γ-Al2O3 with a monolayer dispersion capacity of 7.5 wt.%. For the supported chromia catalyst with a Cr loading of 1.7 wt.%, only Cr6+ species were observed. Increasing Cr loading to 5.1 wt.% led to the presence of both Cr3+ and Cr6+ species. Catalytic benzene combustion over the catalysts was found to be strongly dependent on Cr loading amount. For supported chromia catalyst with a Cr loading of 8.5 wt.%, complete benzene combustion was achieved at 350 °C which was substantially lower than the temperature for other catalysts, indicating that supported chromia catalyst at a near monolayer dispersion capacity exhibited the optimum catalytic behavior for benzene combustion.

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