Influence of reduction temperature on the catalytic behavior of Co/TiO ₂ 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/TiO ₂-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.