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Processes occurring in the preparation of the Co/ZrO2 + 6% Y2O3 catalyst are studied by temperature-programmed reduction (TPR). The effects of the concentration of Co, the porosity of the support, and the calcination temperature on catalyst reduction were studied. As was shown by continuous magnetization measurements in the course of TPR, metallic cobalt appeared on the microporous support in two temperature ranges irrespective of the precalcination temperature and the concentration of supported cobalt. These factors affect the reduction rate but do not change the maximum temperatures of the corresponding peaks. It is suggested that the first maximum of the Co formation rate is due to the reduction of CoO particles on the surface of the support and within macropores, whereas the second maximum is due to the reduction of CoO particles located within support micropores. Only one temperature range of CoO reduction was found in the macroporous ZrO2 + 6% Y2O3. This effect is likely due to mass transfer in support micropores.