Methane-induced Activation Mechanism of Fused Ferric Oxide-Alumina Catalysts during Methane Decomposition.

Activation of Fe₂O₃-Al₂O₃ with CH₄ (instead of H₂) is a meaningful method to achieve catalytic methane decomposition (CMD). This reaction of CMD is more economic and simple against commercial methane steam reforming (MSR) as it produces CO _x-free H₂. In this study, for the first time, structure changes of the catalyst were screened during CH₄ reduction with time on stream. The aim was to optimize the pretreatment conditions through understanding the activation mechanism. Based on results from various characterization techniques, reduction of Fe₂O₃ by CH₄ proceeds in three steps: Fe₂O₃→Fe₃O₄→FeO→Fe0. Once Fe0 is formed, it decomposes CH₄ with formation of Fe₃C, which is the crucial initiation step in the CMD process to initiate formation of multiwall carbon nanotubes. [ABSTRACT FROM AUTHOR]