Preparation And Catalytic Performance Of Monolithic Catalysts For Oxidative Coupling Of Methane

Oxidative coupling of methane to C₂ hydrocarbon is an important part in the research of natural gas utilization. It can provide important chemical materials as ethylene when the world is short of petroleum resource in future. Metal based monolithic catalyst is a new developed catalyst, it attracted huge attention in scientific field. Comparing with particle catalysts, monolithic catalyst has lower pressure lost, smaller temperature grads in radial and axial of reactor. Therefor, it has remarkable referenced value for future industrial scale-up when monolithic catalyst is used for oxidative coupling of methane.In this paper, a series of Ce-W-Mn/SBA-15 catalysts with different Na₂WO₄,Mn and Ce contents were prepared by the incipient wetness impregnation method. Then Ce-Na₂WO₄-Mn/S-A/H monolithic catalysts were prepared using FeCrAl alloy foils as support, Al₂O₃ as washcoat layer and Ce-Na₂WO₄-Mn/SBA-15 as active component. The catalytic activity of the catalysts for oxidative coupling of methane was evaluated in a conventional quartz flow reactor. The preparation technic of metal based monolithic catalyst and the effects of reactive condition over activity were investigated. The structure of the catalysts was characterized using XRD,TPR techniques.The results of the catalytic activity indicated that multicomponent Ce-W-Mn/SBA-15 catalysts had better catalytic performance than W/SBA-15 or Mn/SBA-15 catalysts. Catalyst of 2%Ce-5%Na₂WO₄-2%Mn/SBA-15 had the highest methane conversion and C₂ selectivity. The partial oxidation of methane may occur together with oxidative coupling of methane during the process over metal based monolithic catalysts. Multicomponent Ce-W-Mn/S-A/H catalysts had the better activity than other series of metal based monolithic catalysts, 3%Ce-5%Na₂WO₄-2%Mn/S-A/H catalyst showed the best activity, it achieved the methane conversion of 28.9% and C₂ selectivity of 22.0%, while the selectivity of CO and H₂ were 60.3% and 21.6% respectively.The results of the structural characterization of both particle catalysts and metal based monolithtic catalysts indicated that the surface phase of Si in SBA-15 transformed intoα-cristobalite phase. Other surface phase structure of Na₂WO₄,Mn₂O₃ and CeO₂ were existed in catalysts. The redox of metal based monolithtic catalysts showed there may existed strong interaction between Ce,W and Mn, the lattice oxygen in CeO₂ component improved the oxidation performance of catalysts.