Non-stationary catalytic cracking of methane over ceria-based catalysts: Mechanistic approach and catalyst optimization

The non-stationary cracking of methane over various noble metal/CeO2-doped catalysts at 400 and 600 °C was followed by DRIFT spectroscopy and on the basis of the identified elementary steps a simplified kinetic modeling is proposed. The production of H2 by direct decomposition of CH4 on the noble metal is improved by the capacity of ceria to store carbonaceous surface species thanks to: (i) the spillover of carbonyls from noble metal particles towards basic hydroxyls formed on partially reduced Ce sites and (ii) the reverse spillover of ceria oxygen towards metal to oxidize the carbon issued from methane cracking. The resulting formate adspecies are in turn oxidized into carbon dioxide during the regeneration step. Doping the ceria with basic lanthanide oxides and replacing Pt by more efficient and eventually better dispersed metals for methane decomposition like Rh and Ir lead to significant improvements in the hydrogen productivity.