The catalytic cracking of methane over nickel gauze is proposed as an attractive alternative for the production of CO-free hydrogen. The catalyst deactivates due to intensive coke deposition. Therefore, the reactor was operated periodically with the reaction followed by the catalyst regeneration by burning of coke in oxidative atmosphere. The optimal reaction performance was found to consist of reaction periods of 4 min followed by 4 min regeneration periods.

The oxidation of nickel gauze catalysts by O2 was investigated by transient response methods. Qualitative description of the experimental transient responses have shown that the oxidation of metallic nickel proceeds in two stages. The ÿrst step is a fast dissociation of gaseous oxygen on the catalytic surface, followed by oxygen di usion from the surface into the bulk. This slow second step explains the long tailing observed from the experimental transient responses. Furthermore, a rise of temperature was observed during the nickel oxidation. A kinetic model has been developed on the basis of the experimental results in order to provide quantitative information about this reaction. For nickel gauze oxidation, a non-isothermal model combining the subsurface oxygen di usion with an exponential distribution for the activity of surface sites gave a good agreement with experimental transient data. As a result, the activation energies and the pre-exponential factors of the rate constants as well as the characteristic oxygen di usion times were determined. ?

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