Kaolinite Exfoliation Mechanism Research And Catalytic Performance Of Modified Kaolinite Supported Cobalt Catalysts In Fischer-tropsch Synthesis

Clay minerals are indispensable resources in natural minerals.Due to the unique structure of kaolinite,kaolinite has good development prospects in the fields of ceramics manufacturing,environmental pollution and catalysis.In this thesis,different methods were used to modify kaolinite,and the reaction mechanism of kaolinite exfoliation was studied.The different forms of kaolinites were used as supports of the catalysts for Fischer-Tropsch synthesis reaction?FTS?,and the catalytic performance of the synthesis catalysts was explored.The main research contents and results are summarized as follows:?1?The exfoliation was performed through a reaction of pre-intercalated composite DMSO-Kaol with H₂O₂ aqueous solution.The reaction mechanism of the exfoliation was further explored.The results showed that H₂O₂ and Fe²⁺in the original kaolinite could form a Fenton reagent system,which oxidized the intercalated DMSO into CH₄ gas and methane sulfinic acid in a short time.The released gas broke the hydrogen bonds between the kaolinite layers and the exfoliation were achieved.It provides a new idea for kaolinite exfoliation.?2?The catalysts 15%-Co-Kaol and 15%-Co-H₂O₂-DK were prepared by using the kaolinite and two-dimensional kaolinite as the supports,and their effects on the activity of Fischer-Tropsch reaction were investigated.The 15%-Co-Kaol showed good stability during the reaction time while the 15%-Co-H₂O₂-DK behaved no activity due to the poison effect of the residual S species formed in the exfoliated process.?3?The kaolinite and NMF-Kaol were treated with HNO₃ to obtain porous nano-kaolinites,and two kinds of cobalt catalysts were prepared by these kaolinites.Due to their large increase in specific surface area,porosity,and the confinement of Co particles,the CO conversion and C₅₊selectivity of 15%-Co-KH and 15%-Co-NHK are greatly improved.?4?A large number of kaolinite nanoscrolls were prepared by a series of steps such as preintercalation,substitution intercalation and liquid phase exfoliation.The15%-Co-Nano-H and 15%-Co-Nano-M catalysts were prepared by water impregnation method and vacuum method respectively,where the Co particles were successfully loaded on the outer and inner surfaces of the nanoscrolls respectively by using different hydrophilicities of the outer and inner surfaces.The activity of the FTS reaction was studied.It was found that the vacuum method can effectively limit the size of the Co particles and significantly increase the activity of the catalyst.