Characterization and Reactivity of Niobia Supported Copper Oxide Catalysts

Abstract

A series of niobia supported copper catalysts with varying copper loadings (1−15 wt %) were prepared by incipient wet impregnation method. The catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), UV−vis diffused reflectance spectra (UV-DRS), electron spin resonance (ESR), and X-ray photoelectron spectroscopy. Copper dispersion and metal area were determined by N2O decomposition by passivation method. X-ray diffraction patterns indicate the presence of crystalline CuO phase above 2.5 wt % Cu on niobia. XPS peaks intensity ratio of Cu 2p3/2 to Nb 3d5/2 were compared with the Cu dispersion calculated from N2O decomposition. ESR results suggest the presence of two types of copper species on niobia. TPR patterns 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 copper dispersion.