Influence of reduction temperature on the catalytic behavior of Co/TiO2 catalysts for CH4/CO2 reforming and its relation with titania bulk crystal structure

The influence of reduction temperature on the catalytic behavior of 10 wt% Co/TiO2 catalysts, for CO2 reforming of methane to synthesis gas under atmospheric pressure, was investigated. Co/TiO2-anatase catalysts reduced at lower temperatures (⩽1073 K) showed stable activities. On the other hand, the catalyst reduced at higher temperatures (⩾1123 K), where the crystal phase of TiO2 is transformed from anatase to rutile during the reduction, provided almost no activity. In addition, Co/TiO2-rutile also showed very low activity, regardless of the reduction temperature. No carbon deposition (<0.01 wt%) was observed for any of the Co/TiO2 catalysts. XPS and XRD analysis revealed that the main cause of low activity and deactivation of the catalyst was the oxidation of metallic cobalt. Experimental observations suggest that the large difference in initial activity corresponds to the different crystal structure of TiO2 after reduction.