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

From supplementary in situ Raman spectroscopic studies of active-oxygen spe cies on non-reducible rare-earth-oxide-based catalysts in the oxidative cou pling 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) under bar (-)(2) and (O) under bar (2-)(2) adspec ies), most probably (O) under bar (2-)(3) formed from reversible redox coup ling of an (O) under bar (2) adspecies at an anionic vacancy with a neighbo ring O2- in the surface lattice. This active precursor may initiate H abstr action from CH4 and be itself converted to (O) under barH(-) + (O) under ba r (-)(2), or it may abstract an electron from the oxide lattice and be conv erted to (O) under bar (2-)(2) + (O) under bar (-). The prospect of develop ing this type of OCM catalysts is discussed.