Catalytic oxidative conversion of methane and ethane over polyoxometalate-derived catalysts in electric field at low temperature

We examined oxidative coupling of methane (OCM) and oxidative dehydrogenation of ethane (ODE) over various polyoxometalate supported CeO₂ catalysts at 423 K in an electric field. Tetrabutylammonium (TBA) salt of Keggin-type phosphotungstate (PW₁₂O₄₀) supported CeO₂ catalysts ((TBA)₃PW₁₂O₄₀/CeO₂) showed high activities for OCM and ODE in the electric field (3 mA) at 423 K, although the catalyst without the electric field showed extremely low activities at such low temperature. FT-IR spectra and XRD patterns confirmed that the structure of (TBA)₃PW₁₂O₄₀/CeO₂ was changed to Ce₂(WO₄)₃/CeO₂ after reactions with the electric field, and it acted as an active site structure for OCM and ODE with the electric field. Results of activity tests revealed that the C₂H₆ production was a main reaction in OCM with the electric field, and C₂H₄ was formed through a successive oxidative dehydrogenation of the formed C₂H₆. Periodic operation tests demonstrated that reactive oxygen species suitable for ODE were formed on the catalyst surface of Ce₂(WO₄)₃ in the electric field.