(1) Department of Chemistry and Institute of Physical Chemistry, Xiamen University, and State Key Laboratory for Physical Chemistry of the Solid Surface, Xiamen, 361005 Fujian, PR China
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 O2– and O22– adspecies), most probably O32– 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–+O2–, or it may abstract an electron from the oxide lattice and be converted to O22–+O–. The prospect of developing this type of OCM catalysts is discussed.