The morphology and properties of the carbon deposition of the nickel-based catalysts for carbon dioxide reforming of methane are investigated. Silica supported nickel catalysts were more facile to carbon deposition than alumina supported catalysts. The decomposition of methane resulted in the formation of at least three kinds of surface carbon species on supported nickel catalysts. Carbidic C_α, carbonaceous C_β and carbidic clusters C_γ surface carbon species formed by decomposition of methane showed different thermal stability and reactivity. The carbidic carbon was a very active and important intermediate in the carbon dioxide reforming of methane and the carbidic clusters C_γ species might be the precursor of the surface carbon deposition. The partially dehydrogenated C_β species can react with H_2 or CO_2 to form CH_4 or CO.
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