Metal-Catalyzed Decomposition of Methane

NASA conducted studies on the development of the catalysts for methane decomposition process for space life-support systems [94], A special catalytic reactor with a rotating magnetic field to support Co catalyst at 850°C was designed. In the 1970s, a U.S. Army researcher M. Callahan [95] developed a fuel processor to catalytically convert different hydrocarbon fuels to hydrogen, which was used to feed a 1.5 kW FC. He screened a number of metals for the catalytic activity in the methane decomposition reaction including Ni, Co, Fe, Pt, and Cr. Alumina-supported Ni catalyst was selected as the most suitable for the process. The following rate equation for methane decomposition was reported  

The authors showed that the Grabke-type kinetic model can explain the results at a low carbon activity for Ni-Cu catalysts, but that at higher carbon activities, the rates for the Ni0 9Cu0 j catalysts are higher than the model-predicted rates. Low-temperature decomposition of methane over the silica-supported Ni catalyst has been reported by Kuijpers et al. [101]. It was demonstrated that at temperatures as low as 175°C, methane adsorbed on the Ni catalysts dissociates completely into adsorbed carbon atoms and hydrogen. 

Decomposition of methane to H2 and carbon over Ni/Si02 was carried out in a membrane reactor (membrane 90Pd-10Ag) [106]. The use of the membrane reactor allowed increasing the H2 yield by shifting the reaction equilibrium toward the products. An excellent review of the literature data on nonoxidative methane activation over the surface of transition metals was recently published by Choudhary et al. [107]. 

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Schematic representation of carbon filaments of different structure produced by metal-catalyzed decomposition of methane, (a) Platelet structure, (b) "herringbone" structure, and (c) ribbon structure. MP denotes a nanosized metal particle.

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