In situ IR spectroscopy was used to study the superoxide species (O-2(-)) for oxidative coupling of methane (OCM) over the BaF2,/La2O3 catalyst. After the pretreatment of the catalyst with O-2, the IR peak at 1108-1118 cm(-1) appeared, which was assigned to O-O bond stretching vibration in O-2(-) species. After the introduction Of 1802 isotope, the IR peak at 1.108-1118 cm-1 was weakened, and the absorption peaks appeared at 1086 and 1051 cm(-1), which was consistent with the assignment of the O-18O bond and O-18 O-18 bond stretching vibrations in the superoxide species, respectively. At 700 degrees C, the superoxide species could react with CH4, accompanied by the formation of gas phase C2H4. A good correlation between the rate of O-2 consumption and the rate of C2H4 formation was observed, so the superoxide species was believed to be responsible for the OCM reaction over the BaF2/La2O3 catalyst
