Catalytic Oxidation of Methane to C 2 ‐C 4 Hydrocarbons over CeO 2 Promoted W‐Mn/SiO 2 Catalysts at Higher Pressure

CeO 2 ‐promoted Na‐Mn‐W/SiO 2 catalyst has been studied for catalytic oxidation of methane in a micro‐stainless‐steel reactor at elevated pressure. The effect of operating conditions, such as GHSV, pressure and CH 4 /O 2 ratio, has been investigated. 22.0% CH 4 conversion with 73.8% C 2 ‐C 4 selectivity (C 2 /C 3 /C 4 = 3.8/1.0/3.6) was obtained at 1003 K, 1.5 × 10 5 h −;1 GHSV and 1.0 MPa. The results show: Elevated pressure disadvantages the catalytic oxidation of methane to C 2 ‐C 4 hydrocarbons. Large amounts of C 3 and C 4 hydrocarbons are observed. The unfavorable effects of elevated pressure can be overcome by increasing GHSV; the reaction is strongly dependent on the operating conditions at elevated pressure, particularly dependent on GHSV and ratio of CH 4 /O 2 . Analyses by means of XRD, XPS and CO 2 ‐TPD show that CO 2 produced from the reaction makes a weakly poisoning capacity of the catalyst; information of changeful valence on Ce and Mn was detected over the near‐surface of the Ce‐Na‐W‐Mn/SiO 2 catalyst; the existence of Ce 3+ /Ce 4+ and Mn 2+ /Mn 3+ ion couple supported that the reaction over the catalyst followed the Redeal‐Redox mechanism. Oxidative re‐coupling of C 2 H 6 and CH 4 in gas phase or over surface of catalyst produces C 3 or C 4 hydrocarbons.