羰基合成与选择氧化国家重点实验室（OSSO）知识库

CeO₂-promoted Na-Mn-W/SiO₂ catalyst has been studied for catalytic oxidation of methane in a microstainless-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.