In situ IR and pulse reaction studies on the active oxygen species over SrF2/Nd2O3 catalyst for oxidative coupling of methane

✍ Scribed by Li-Hua Wang; Xiao-Dong Yi; Wei-Zheng Weng; Hui-Lin Wan

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 490 KB
• Volume: 131
• Category: Article
• ISSN: 0920-5861
• DOI: 10.1016/j.cattod.2007.10.014

✦ Synopsis

Pulse reaction method and in situ IR spectroscopy were used to characterize the active oxygen species for oxidative coupling of methane (OCM) over SrF 2 /Nd 2 O 3 catalyst. It was found that OCM activity of the catalyst was very low in the absence of gas phase oxygen, which indicated that lattice oxygen species contributed little to the yield of C 2 hydrocarbons. IR band of superoxide species (O 2 À ) was detected on the O 2 -preadsorbed SrF 2 /Nd 2 O 3 . The substitution of 18 O 2 isotope for 16 O 2 caused the IR band of O 2 À at 1128 cm À1 to shift to lower wavenumbers (1094 and 1062 cm À1 ), consistent with the assignment of the spectra to the O 2 À species. A good correlation between the rate of disappearance of surface O 2 À and the rate of formation of gas phase C 2 H 4 was observed upon interaction of CH 4 with O 2 -preadsorbed catalyst at 700 8C. The O 2 À species was also observed on the catalyst under working condition. These results suggest that O 2 À species is the active oxygen species for OCM reaction on SrF 2 /Nd 2 O 3 catalyst.