Transient Isotopic Studies of the Role of Lattice Oxygen during Oxidative Coupling of Methane on Sr Promoted Lanthanum Oxide

Studies of the oxidative coupling of methane were performed by applying transient isotopic techniques on Sr promoted La2O3 catalysts. Pulses of methane with different oxygen concentrations and 13CH4/12CH4 isotopic switches show that the catalyst does not activate methane unless gas phase oxygen is present in the system. The above measurements also indicate that no long lived methane species can be detected on the surface of the catalyst under reaction conditions. Results of the steady state 18O/16O exchange experiments combined with temperature programmed isotopic exchange (TPIE) data suggest that Sr promotion increases the mobility of lattice oxygen by creating oxygen vacancies in the structure of La2O3.