Abstract: 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 O2, the IR peak at 1108-1118 cm-1appeared, which was assigned toO-Obond stretching vibration in O-2 species. After the introduction of18O2isotope, the IR peak at 1108-1118 cm-1was weakened, and the absorption peaks appeared at1086and1051cm-1, which was consistent with the assignment of theO-18Obond and18O-18Obond stretching vibrations in the superoxide species, respectively. At 700 ℃, 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.

Key words: isotopic exchange, superoxide species, infrared spectroscopy, oxidative coupling, methane, barium fluoride, lanthanum oxide