Catalytic activity of LiSbTe2 for oxidative coupling of methane

Zintl phase LiSbTe2 was examined as a catalyst for the oxidative coupling of methane to ethane and ethylene in a single-pass flow reactor system using on-line gas chromatography which operated at atmospheric pressure. Catalytic reactions were performed by feeding the reaction mixture containing CH4/O-2/He or CH4/O-2/H2O/He in the temperature range from 873 to 1023 K. LiSbTe2 catalyst was found to be active and selective for the oxidative coupling of methane only when it was treated under oxygen flow prior to reaction. When the reaction mixture containing CH4/O-2/He was fed over the oxygen-pretreated LiSbTe2 catalyst, C-2 selectivities were in the range of 40-82%. The best C-2 yield was 12% with a selectivity of 69% at 973 K. When the reaction mixture containing CH4/O-2/H2O/He was fed over the oxygen-pretreated LiSbTe2 catalyst, C-2 selectivities were in the range of 88-91%, in which the best C-2 yield was 13% with a selectivity of 88% at 1023 K. It was found from the effect of contact time on the product distribution that ethane was an initial product and ethylene was a secondary product in the reaction. To characterize the catalyst, X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and thermogravimetry analyses were performed for the LiSbTe2 catalyst. The results suggest that oxygen ions chemisorbed on the surface are responsible for the selective activation of methane. (C) 2000 Elsevier Science B.V. All rights reserved.