Preparation, characterization and catalytic testing of cobalt oxide and manganese oxide catalysts supported on zirconia

Zirconia-supported dehydrogenation catalysts based on manganese oxide and cobalt oxide were investigated. Preparation of zirconia-supported Mn(-K) and Co(-K) catalysts was carried out by (co-) impregnation of zirconia pellets to incipient wetness. Characterization of the fresh catalysts was performed using nitrogen adsorption, electron microscopy (TEM), X-ray diffraction (XRD), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). The dehydrogenation of I-butene was used as a catalytic test reaction. It was shown that catalysts containing finely divided cobalt oxide or manganese oxide homogeneously distributed over zirconia supports can be prepared using a pre-shaped zirconia support. From the results obtained with various characterization techniques it was concluded that preparation using complex organic precursors results in the best dispersion of the active phase. The metal-EDTA complex seems the most suitable for producing the desired catalyst systems. Catalysts without potassium carbonate deactivate due to carbon deposition. The deactivation behaviour of supported cobalt oxide is similar to that of supported iron oxide, while supported manganese oxide shows a more gradual deactivation. The Mn- or Co-based catalysts containing potassium carbonate did not show deactivation up to at least 10 h on stream. The activity and selectivity are different, however. The activity ranking was found to be Fe,K > Mn,K > Co,K. The selectivity of the manganese oxide-based system was found to be higher than in the iron oxide-based catalyst.