The role of monolayer dispersed copper oxide for benzene catalytic combustion over Cu/Al2O3 catalyst

The surface dispersion behavior of a series of Cu/γ-A12O3 catalysts calcined at 300, 450 and 600？ were investigated. The dispersion status of copper species obtained from surface and bulk characterization, studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR), has been correlated with benzene oxidation activity of the catalysts. The results indicated that copper oxide present in a monolayer dispersed state below the dispersion loading threshold, which could be reduced at lower temperature. The remarkable increase of activity was observed over Cu/γ-A12O3 catalyst when higher copper loading was imputed even total copper amount was less than threshold. Further increase of copper loading (higher than threshold) resulted in comparatively lower activity. The monolayer dispersed phase was thermodynamically unstable. Dispersion threshold increased with increasing calcination temperature because copper ions diffused into the support, which led to lower catalytic activity for benzene oxidation.