Methane oxidation on the surface of mixed-conducting La0.3Sr0.7Co0.8Ga0.2O3-δ

Mixed-conducting La0.3Sr0.7Co0.8Ga0.2O3-delta (LSCG) possesses substantial oxygen permeability, but exhibits a high activity to complete CH4 oxidation, thus making it necessary to incorporate reforming catalysts in the membrane reactors for methane conversion. Dominant CO, formation is observed for the steady-state conversion of CH4 by atmospheric oxygen (methane/air ratio of 30:70) in a fixed bed reactor with LSCG as catalyst, and for the oxidation of CH4 pulses supplied in helium flow over LSCG powder. The conversion of dry CH4 by oxygen permeating through dense LSCG ceramics, stable operation of which under the air/CH4 gradient is possible due to the surface-limited oxygen transport, yields CO2 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. (C) 2004 Elsevier B.V. All rights reserved.