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

Abstract

The carbon dioxide reforming of methane over the reduced supported Rh (0.5 wt.%) catalysts was investigated. Two kinds of oxides, reducible (CeO 2, Nb 2O 5, Ta 2O 5, TiO 2, and ZrO 2) and irreducible (γ-Al 2O 3, La 2O 3, MgO, SiO 2, and Y 2O 3) were used as supports. Among the irreducible metal oxides, γ-Al 2O 3, La 2O 3 and MgO provided stable catalytic activities during the period of study, and the activity increased in the sequence: La 2O 3<MgO≈γ-Al 2O 3. Deactivation, however, occurred over the SiO 2 and Y 2O 3 supported catalysts. Possible explanations for stability, based on the strong interactions between Rh 2O 3 and support, were proposed on the basis of TPR and XRD studies. Among the reducible oxides, Nb 2O 5 provided a low activity, ZrO 2 and CeO 2 exhibited a very long activation period, and deactivation occurred over Ta 2O 5 and TiO 2. 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 CO 2 reforming of methane. In summary, MgO and γ-Al 2O 3 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 60 000 ml/h/g.