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

Abstract

In situ X-ray diffraction was used to study the reduction of unsupported CoO, and Co3O4 under different conditions of time and temperature, and the effect of lanthanum, ruthenium, or zinc doping of γ-alumina 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 °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 °C only when the reduction was performed stepwise. Metallic Co(fcc) was obtained after reduction at 350 °C of supported Co3O4 on doped alumina; however, the reduction of unsupported CoO under the same conditions produced Co(hcp). Doping alumina with ruthenium oxide favors the reduction of Co3O4 to CoO and then to metallic Co(fcc). The crystal size apparently affects the phase of metallic cobalt obtained.

Preparation and characterization of lanthanum-promoted cobalt–copper catalysts for the conversion of syngas to higher oxygenates: Formation of cobalt carbide

“…1 Table 3). The literature suggests that the cobalt on Co 1 La may be completely reduced to metallic form, which is active at the conditions tested here [40].…”

The Reduction Temperature Effect of Fe–Co/MgO Catalyst on Characteristics of Multi-Walled Carbon Nanotubes

“…This result can be explained by the fact that the agglomeration of metallic iron atoms in the catalyst is much activated when reduction temperature is higher. [26][27][28][29]. All the peaks become narrow and sharpen with increasing reduction temperature.…”

“…01-070-2855) and magnesium oxide (periclase, JCPDS card No. 01-071-1176) phases [26][27][28][29]. All the peaks become narrow and sharpen with increasing reduction temperature.…”

“…Especially, the peak intensity of iron which is observed at 2θ = 44 • , 65 • , and 82 • is much increased as reduction temperature increases. The XRD peaks of both the cobalt oxide and magnesium oxides appeared at almost the same positions, and it is difficult to distinguish each peak clearly [26,27]. However, the peak intensity of the cobalt oxide becomes high as reduction temperature increases.…”

Theoretical Study on Influence of Cobalt Oxides Valence State Change for C6H5COOH Pyrolysis

“…In the case, some unstable catalysts are possibly reduced. For example, it is found that the reduction process of Co 3 O 4 under reducing gases is in this order: Co 3 O 4 →CoO→Co [23,24]. What is the influence of the catalyst valence state change for coal catalytic pyrolysis?…”