Abstract
By using the in situ IR spectroscopy, the superoxide species (O −2 ), characterized by the O–O stretching peak at 1130 cm−1, was detected on the SrF2/La2O3 catalyst at temperatures up to 973 K. The introduction of 18O2 isotope caused the 1130 cm−1 peak to shift to lower wavenumbers (1095 and 1064 cm−1), consistent with the assignment of the spectra to the superoxide species. A good correlation between the rate of the disappearance of the O −2 species and that of the formation of C2H4 was observed, suggesting that O −2 was the active oxygen species responsible for the oxidative coupling of methane (OCM) on the SrF2/La2O3 catalyst. This conclusion was reinforced by the EPR experiments (gxx = 2.0001, gyy = 2.0045, gzz = 2.0685), showing that O −2 was the only paramagnetic oxygen species detectable on the O2-preadsorbed SrF2/La2O3 catalyst. These results suggest that superoxide O −2 can be a stable active oxygen species, whose role in the OCM reaction cannot be overlooked.
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This work was supported by the Ministry of Science and Technology of China (Grant No. 2005CB221408, 2004CB719902) and NSFC (20433030, 20525311, 20533030, 20423002).
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Wang, L., Yi, X., Weng, W. et al. Isotopic Oxygen Exchange and EPR Studies of Superoxide Species on the SrF2/La2O3 Catalyst. Catal Lett 118, 238–243 (2007). https://doi.org/10.1007/s10562-007-9176-8
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DOI: https://doi.org/10.1007/s10562-007-9176-8