| The nature of active oxygen species participated in the oxidative coupling of methane was still controversial. The purpose of this thesis was that the active oxygen species for the oxidative coupling of methane over 20%SrF2/La2O3 and 50% SrF2/Nd2O3 catalysts were studied, using by O2-TPD, pulse reaction, in situ Raman, in situ IR and EPR. And the 18O2 isotopic exchange experiment was also performed, such that the active oxygen species for the OCM reaction was ascertained.The pulse reaction results on 20%SrF2/La2O3 catalyst indicated that lattice oxygen species did not participate directly in the OCM reaction, and that the presence of gas-phase oxygen was necessary to achieved high C2 hydrocarbon yield The result was also supported by the pulse reaction of the interval of time between O2 and CH4.In situ IR spectroscopy has been used to show that superoxide species (O2-) was present on 20%SrF2/La2O3 catalyst at temperatures up to 700°C. After being treated with 16O2, the peak at 1120 cm?1, which was ascribed to (16O-16O)?, was detected at 700°C. And then the temperature of the cell was decreased to 50°C in the presence of 16O2, the position of the major peak shifted to 1130 cm?1. The introduction of 18O2 isotope caused the peak at 1130 cm?1 to shift to lower wavenumbers (1095 cm?1 and 1064 cm?1), consistent with the assignment of the spectra to superoxide species. At 700°C, superoxide species could react with CH4 accompanied by the formation of gas phase C2H4. A good correlation between the rate of consumption of O2- species and that of the formation of C2H4 was observed, so the superoxide species was believed to be responsible for the activation of CH4. The IR spectra recorded under a stream of CH4/O2 on the O2-preadsorbed SrF2/La2O3 catalyst showed that the IR band of gas phase C2H4 was much stronger than that of under the CH4 stream, and the intensity of O2- band at 1127 cm?1 was increased simultaneously, showing that the O2- species was maintainable under the OCM condition. These results indicated that the superoxide species not only remained stable but also could activate CH4 on SrF2/La2O3 catalyst at 700°C. The EPR results (gxx=2.0001, gyy=2.0045, gzz=2.0685) also showed that there was superoxide species on the O2-preadsorbed SrF2/La2O3 catalyst. Therefore the superoxide species was the active oxygen species for the oxidative coupling of methane on 20%SrF2/La2O3 catalyst.The results also indicated that the superoxide species was the active oxygen species for the oxidative coupling of methane on 50%SrF2/Nd2O3 catalyst. Keywords: superoxide species (O2-); 18O2 isotopic exchange experiment; the oxidative coupling of methane...
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