A STUDY OF SURFACE OXYGEN SPECIES FROM LA -ME-O (ME=MG, CA, SR, BA) CATALYSTS FOR METHANE OXIDATIVE COUPLING

CO2-TPD was used to study the surface basicity of La-Me-O mixed oxides and O-2-TPD, CH4-TPD were employed to study the surface active oxygen species. Comparing the CO2-TPD with O-2-TPD, we can see that the basi city of catalyst is in parallel with the catalystic activity. The stro nger basicity is more profitable for the catalyst to adsorb oxygen to form active oxygen species and to activate CH4 by breaking a C-H bond, By comparing the catalytic activity, the results showed that La-Ba-O( La/Ba=7/3) catalyst had the strongest basicity, and it gave the highes t CH4 conversion and C-2 selectivity, The results from the pulse react ion showed that the lattice oxygen participated in the OCM reaction wi thout gas oxygen, and it was the selective oxygen species.