The Effect of Temperature and Support on the Reduction of Cobalt Oxide: An in Situ X-ray Diffraction Study

In situ X-ray diffraction was used to study the reduction of unsupported CoO, arid Co3O4 under different conditions of tirne and temperature; and the effect of lanthanum, ruthenium, Or zinc doping of gamma-alurnina on the reduction of supported cobalt oxide The reduction of unsupported cobalt oxide (Co3O4) produced CoO, then hexagOnal close-packed Co (Co(hcp)) and at temperatures above 400 degrees C, only face-centered cubic Co (Co(fcc)) was obtained However, it was possible to obtain a Mixture of Co(hcp) and Co(fcc) at 450 degrees C Only when the reduction was,perforined stepwiSe. Metallic Co(fcc) was obtained after reduction at 350 degrees C of.siippotted Co3O4 on doped alumina; however, the reduction of unsupported CoO under the same conditions produced Co(hcp). Doping alumina with ruthenium oiciflO favors the reduction of Co3O4 to CoO an then to metallic Co(fcc). The Crystal size apparently affects the phase of Metallic cobalt obtained.