Co3O4, and a CPA-impregnated physical mixture of Co3O4 and silica are shown in
Figure 13.15a. The results show that the reduction of silica-supported CPA begins
at 50°C and is complete by 200°C. Reduction of pure Co3O4 begins at 200°C and
ends at 360°C; the reduction profile is consistent with stepwise reduction of Co+3
to Co+2, followed by Co+2 to metal. The reduction of the CPA-impregnated Co3O4
occurs at almost 100° lower than the Pt-free cobalt oxide. Finally, the TPR pattern
of the CPA-impregnated physical mixture of silica and cobalt oxide is very similar
to that of the CPA-impregnated Co3O4 pattern; this provides indirect evidence that
the CPA adsorbed selectively onto the Co3O4.