Dynamic Behavior in Methanation Activity During the Reaction on Supported Nickel-based Catalysts

Abstract

Increase in the methanation activity of supported Ni-based composite catalysts during the H₂-CO₂ reaction was studied. A gradual increase in the activity with repeated use was observed in the Ni-La₂O₃ catalysts supported on alumina, whereas the Ni-La₂O₃ catalysts supported on silica gave an almost constant activity through repeated use. This difference was attributed to the reducibility of the catalysts. The nickel oxide part in the composite catalyst supported on silica was reduced sufficiently to nickel metal by hydrogen reduction at 400°C. On the other hand, some portion of the nickel oxide in the composite catalyst supported on alumina was considered to have formed some NiAl₂O₄ spinel which was difficult to be reduced with hydrogen at 400°C. However, this NiAl₂O₄ spinel was reduced gradually during the methanation reaction even at a much lower temperature, 300°C, with the aid of coexisting water vapor formed by the reaction, resulting in the increase in activity.