Methane oxidation on the surface of mixed-conducting La_(0.3)Sr_(0.7)Co_(0.8)Ga_(0.2)O_(3-delta)

摘要

Mixed-conducting La)(0.3)Sr_(0.7)Co_(0.8)Ga_(0.2)O_(3-delta)(LSCG)possesses substantial oxygen permeability,but exhibits a high activity to complete CH_4 oxidation,thus making it necessary to incorporate reforming catalysts in the membrane reactors for methane conversion.Dominant CO_2 formation is observed for the steady-state conversion of CH_4 by atmospheric oxygen(methane/air ratio of 30:70)in a fixed bed reactor with LSCG as catalyst,and for the oxidation of CH_4 pulses supplied in helium flow over LSCG powder.The conversion of dry CH_4 by oxygen permeating through dense LSCG ceramics,stable operation of which under the air/ CH_4 gradient is possible due to the surface-limited oxygen transport,yields CO_2 concentrations higher than 90%.The prevailing mechanism of total methane combustion is probably associated with weak Co-O bonding in the perovskite-related LSCG lattice,in correlation with data on oxygen desorption,phase stability and ionic transport.