Characterization and Reactivity of Copper Oxide Catalysts Supported on TiO2−ZrO2

Abstract

A series of copper catalysts supported on TiO₂−ZrO₂ with copper loading varying from 1.0 to 21.6 wt % were prepared by a wet impregnation method. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV−vis diffuse reflectance spectroscopy, electron spin resonance (ESR), temperature programmed reduction (TPR), and Brunauer−Emmett−Teller specific surface area measurements. Copper dispersion and metal area were determined by N₂O decomposition by the passivation method. XRD results suggest that the copper oxide is present in a highly dispersed amorphous state at copper loadings 3/2/Ti 2p_3/2 and Cu 2p_3/2/Zr 3d_5/2 were compared with the copper dispersion calculated from N₂O decomposition. ESR results suggest the presence of two types of copper species on the TiO₂−ZrO₂ support. TPR profiles reveal the presence of highly dispersed copper oxide at lower temperatures and bulk CuO at higher temperatures. The catalytic properties were evaluated for the vapor-phase dehydrogenation of cyclohexanol to cyclohexanone and related to the dispersion of Cu on TiO₂−ZrO₂.