Active-oxygen species on non-reducible rare-earth-oxide-based catalysts in oxidative coupling of methane

Abstract

From supplementary in situ Raman spectroscopic studies of active-oxygen species on non-reducible rare-earth-oxide-based catalysts in the oxidative coupling of methane (OCM) and structural adaptability considerations, further support has been obtained for our proposal that there may be an active and elusive precursor (of O 2− and O 22− adspecies), most probably O 32− formed from reversible redox coupling of an O2 adspecies at an anionic vacancy with a neighboring O2− in the surface lattice. This active precursor may initiate H abstraction from CH4 and be itself converted to OH−+O 2−, or it may abstract an electron from the oxide lattice and be converted to O 22−+O−. The prospect of developing this type of OCM catalysts is discussed.