Carbon dioxide reforming of methane to synthesis gas over supported rhodium catalysts: the effect of support

The carbon dioxide reforming of methane over the reduced supported Rh (0.5 wt.%) catalysts was investigated. Two kinds of oxides, reducible (CeO2, Nb2O5. Ta2O5, TiO2. and ZrO2) and irreducible (gamma -Al2O3, La2O3, MgO, SiO2, and Y2O3) were used as supports. Among the irreducible metal oxides, gamma -Al2O3, La2O3 and MgO provided stable catalytic activities during the period of study, and the activity increased in the sequence: La2O3 < MgOgamma -Al2O3. Deactivation, however, occurred over the SiO2 and Y2O3 supported catalysts. Possible explanations for stability, based on the strong interactions between Rh2O3 and support, were proposed on the basis of TPR and XRD studies. Among the reducible oxides, Nb2O5 provided a low activity, ZrO2 and CeO2 exhibited a very long activation period, and deactivation occurred over Ta2O5 and TiO2. Most of the reducible oxides provided much lower yields to CO and H-2 than the irreducible ones, and they are not suitable supports for Rh in the CO2 reforming of methane. In summary, MgO and gamma -Al2O3 are the most promising supports: they provided a stable high activity with a CO yield of 83-85% and a H-2 yield of 76-79% at the high space velocity of 60000ml/h/g. (C) 2000 Elsevier Science B.V. All rights reserved.