| Abstract: | CeO2‐promoted Na‐Mn‐W/SiO2 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 CH4/O2 ratio, has been investigated. 22.0% CH4 conversion with 73.8% C2‐C4 selectivity (C2/C3/C4 = 3.8/1.0/3.6) was obtained at 1003 K, 1.5 × 105 h?;1 GHSV and 1.0 MPa. The results show: Elevated pressure disadvantages the catalytic oxidation of methane to C2‐C4 hydrocarbons. Large amounts of C3 and C4 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 CH4/O2. Analyses by means of XRD, XPS and CO2‐TPD show that CO2 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/SiO2 catalyst; the existence of Ce3+/Ce4+ and Mn2+/Mn3+ ion couple supported that the reaction over the catalyst followed the Redeal‐Redox mechanism. Oxidative re‐coupling of C2H6 and CH4 in gas phase or over surface of catalyst produces C3 or C4 hydrocarbons. |
