Comparative Study on the Formation and Reduction of Bulk and Al2O3-Supported Cobalt Oxides by H2-TPR Technique

Abstract

A systematic and comparative study of the decomposition procedures of unsupported and Al2O3-supported Co(NO3)2·6H2O, as well as the reduction procedures of bulk Co3O4 and Al2O3-supported Co3O4 was carried out. A series of decomposition products of bulk and Al2O3-supported Co(NO3)2·6H2O, and bulk cobalt oxides (Co3O4 and CoOOH) and Al2O3-supported Co3O4 (Co/Al2O3 catalysts) were prepared by the methods of calcination, deposition-precipitation, and incipient-wetness impregnation. The bulk and supported samples were characterized by different techniques, including XRD, UV−vis−NIR, TG-DTA, gas analyzer, and H2-TPR. The results show that the CoO species first appears in the calcination process of bulk Co(NO3)2·6H2O decomposition, and then CoO is oxidized to form Co3O4. CoO-Al2O3 composite oxide first appears in the calcination process of Al2O3-supported Co(NO3)2·6H2O decomposition. CoO disperses on the surface of Al2O3 support at first and then forms a multilayer with the decomposition of Co(NO3)2. Finally, Co...