The cyclohexanol dehydrogenation on Rh-Cu/Al2O3 catalysts .1. Characterization of the catalyst

In this first part, we examined the structure and morphology of Rh-Cu/Al2O3 catalysts with low metal contents, which have been used in cyclohexanol dehydrogenation. The catalysts were prepared by successive wet impregnation after intermediate calcination. They were characterized by TPR, DRS, XPS, XRD and CO FT-IR in the oxide form. The results indicate a high degree of reduction and the presence of copper ions located in octahedral sites. The Rh/Al2O3 and Rh-Cu/Al2O3 catalysts display an enrichment of rhodium at the surface, and the presence of copper allows the restructuring of the surface complexes, as shown by DRS and XPS measurements. The cluster formation during reduction is attributed to the promoting effect of copper. Infrared results show that the interaction of copper with the support prevents the redispersion or oxidation of rhodium crystallites acting as a ''sacrificed anode.''