In Situ Elucidation of the Active State of Co–CeOx Catalysts in the Dry Reforming of Methane: The Important Role of the Reducible Oxide Support and Interactions with Cobalt

The activation of methane and its dry reforming with CO2 was systematically studied over a series (2–30 wt %) of Co (∼5 nm in size) loaded CeO2 catalysts, with an effort to elucidate the interplay between Co and CeO2 during the catalytic process using in situ methods. The results of in situ time-resolved X-ray diffraction (TR-XRD) show a strong interaction of methane with the CoOx–CeO2 systems at temperatures between 200 and 350 °C. The hydrogen produced by the dissociation of C–H bonds in methane leads to a full reduction of Co oxide, Co3O4 → CoO → Co, and a partial reduction of ceria with the formation of some Ce3+. Upon the addition of CO2, a catalytic cycle for dry reforming of methane (DRM) was achieved on the CoOx–CeO2 powder catalysts at temperatures below 500 °C. A 10 wt % Co–CeO2 catalyst was found to possess the best catalytic activity among various cobalt loading catalysts, and it exhibits a desirable stability for the DRM with a minimal effect of carbon accumulation. The phase transitions and ...