Carbon dioxide reforming of methane to synthesis gas over supported cobalt catalysts

The CO2 reforming of CH4 over Co supported on an alkaline earth metal oxide (MgO, CaO, SrO, or BaO) as well as on gamma -Al2O3 and on SiO2 was investigated. Among these supports, only MgO exhibited a high and stable activity. It provided a CO yield of 93% and a H-2 yield of 90% at the high space velocity of 60 000 ml g(-1) h(-1), which remained unchanged during the period of study of 50 h, gamma -Al2O3 provided initially a high CO yield, which, however, rapidly decayed. All the other supports exhibited low CO yields and CaO and SiO2 also low stabilities. A solid solution of CoO and MgO was identified by XRD in the calcined MgO supported catalyst, but not in the other supports. Because the oxygens in the solid solution are shared by both Mg and Co and their interactions with Mg are strong, the solid solution is less reducible than the pure CoO and small clusters of metallic Co are generated. Being at least partially embedded in the substrate, these clusters are more stable to sintering than the usual ones; being small they do not favor coke formation. For these reasons, this catalyst exhibits high stability. (C) 2000 Elsevier Science B.V. All rights reserved.