Catalysis Today, Vol.127, No.1-4, 230-237, 2007
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 degrees C was followed by DRIFT spectroscopy and on the basis of the identified elementary steps a simplified kinetic modeling is proposed. The production of H-2 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. (C) 2007 Elsevier B.V. All rights reserved.
Keywords:methane cracking to hydrogen;noble metals supported on ceria;Pt;Ir;Rh;ceria doping;transient kinetic modeling;in situ DRIFT;non stationary processes