Preparation And Characterization Of New Cobalt Based Catalyst For F-T Synthesis

Cobalt based catalysts have become one of the most promising catalysts for its high activity for CO hydrogenation and low activity for water-gas shift reaction. In this dissertation, the activated alumina and activated alumina modified by ZrO₂ as the support, the Cobalt based catalysts as the object, the properties of the supports and the preparation methods were investigated. At the same time, the catalytic performance for F-T synthesis was proved on the slurry phase reactor.The catalysts were prepared by wetness impregnation. The properties of the catalysts were characterized by BET, XRD, SEM, TEM, TPR, and so on.The content and corresponding conclusions obtained in this dissertation are summarized as follows:(1) Different kinds of CO/Al₂O₃ catalysts which include different Co contents were prepared via impregnation and the slow or rapid drying method. The results indicated the catalysts prepared by different drying methods have different charecteristice. The cobalt species on catalyst prepared from cobalt nitrate was mainly Co₃O₄. Catalysts prepared by slow drying method resulted the cobalt cluster bigger and the average aperture smaller which was disadvantageous to the catalytic reaction. Catalysts prepared by these two methods all formed species Co₂AlO₄ and AlO(OH) which were difficult to reduce in drying and calcining process and the utilizing rate of metal cobalt was influenced. We recovered that Catalysts prepared by slow drying method have more of the Co₂AlO₄ and AlO(OH).by the TPR and XRD results.(2) A kind of alumina carrier modified by ZrO₂ was prepared, and the structure, the performance and the cobalt based catalyst system supported on which was studied. The result indicated the alumina carrier modified by ZrO₂ was a little different comparing to the raw alumina in the texture. The catalysts supported by he alumina support modified by ZrO₂ impregnated by nitrate cobalt were prepared. The cobalt species on catalyst prepared from cobalt nitrate was also mainly Co₃O₄. Species Co₂AlO₄ and AlO(OH) were obviously reduced by the participated of ZrO₂.(3) The Catalytic performance for F-T synthesis was tested in a cetane slurry phase reactor built by ourselves. The influence to the percent conversion of reaction temperature, pressure, space velocity were studied to fix the best technological conditions such as 2.0MPa, 500h^-1, and 500K with a H₂ to CO ratio of 2, on which the performance of catalyst with or without accessory ingredient was examined.