Study on Core-shell Structured CoZr/AC@ZSM-5Catalyst for Fischer-Tropsch Synthesis

Fischer-Tropsch (F-T) synthesis is an important way of transferring syngas into pure liquid fuel via a catalytical reaction. This process could be of great significance both practically and economically, especially when it comes to the maintenance of energy security and alleviate of environmental pollution. The research over the development of a high-performance catalyst for F-T synthesis has attracted much attention. Recently, the core-shell structured composite catalyst, which is produced by coating a zeolite layer over the surface of the catalyst particles, attracts wide attention of the researchers for its excellent performance. This thesis studied mainly on the F-T reaction properties of core-shell structured CoZr/AC@ZSM-5catalyst in a fixed-bed reactor, and the reaction mechanism was also explored. The main contents of this thesis as follows:In this project, the core-shell structured CoZr/AC@ZSM-5catalyst have been prepared, whose performance was investigated by Fischer-Tropsch synthesis in a fixed-bed reactor. In comparison with. CoZr/AC catalyst without ZSM-5shell membrane, an improvement over the selectivity of light hydrocarbons on CoZr/AC@ZSM-5and suppression over the production of heavy hydrocarbons and alcohols compressed has been seen clearly.No significant difference can be found between active species of CoZr/AC@ZSM-5and CoZr/AC via catalyst characterization. However, in consideration of specific surface area, pore diameter, the CoZr/AC catalyst has a relatively higher value, while the core-shell structured catalyst exhibits certain acidity.As the analytical results of the research indicated, in this system, the mechanism of hydrocarbons generation in F-T synthesis matches the Carbide mechanism, while the mechanism of alcohols generation matches the CO insertion mechanism. Combining with the reaction mechanism, it is concluded that the micropore structure of ZSM-5membrane can promote the hydrogenation reaction, meanwhile weaken the carbon chain growth and CO insertion reaction, and in addition, ZSM-5membrane has certain effect in catalytical hydrocracking.