Characterization and reductive amination of cyclohexanol and cyclohexanone over Cu/ZrO2 catalysts

Reductive amination of cyclohexanol/cyclohexanone was studied over copper catalysts supported on zirconia. The effect of copper loading and dispersion was studied on the activity and selectivity of the reaction. A series of zirconia 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) and temperature-programmed reduction (TPR). Copper dispersion and metal area were determined by N2O decomposition by passivation method. X-ray diffraction patterns indicate the presence of crystalline CuO phase from 4.0 wt% Cu on zirconia. TPR patterns reveal the presence of highly dispersed copper oxide at lower temperatures and bulk CuO at higher temperatures. The acid–base properties of catalysts were investigated by means of a model reaction cyclohexanol dehydrogenation to cyclohexanone and compare with the results of TPD of ammonia, which allows to measure the acid–base properties of the support and to investigate the changes in surface acidity or basicity, resulting from the metal impregnation.