Role of CO in the Water-Induced Formation of Cobalt Oxide in a High Conversion Fischer-Tropsch Environment

A Co/C model catalyst was exposed to increasing partial pressures of water simulating high Fischer-Tropsch conversions at varying concentrations of synthesis gas. The stability of the metallic cobalt phase against oxidation and sintering under such conditions was monitored in an in situ magnetometer. Direct oxidation of cobalt to cobalt oxide with water-derived oxygen through a water splitting mechanism was shown to be kinetically hindered, even at high partial pressures of water. Combined threshold partial pressures of carbon monoxide and water were identified for rapid oxidation of cobalt, above which the removal of adsorbed oxygen species, originating from the dissociation of carbon monoxide on the metallic cobalt surface, by surface produced water was hindered resulting in water-induced oxidation.