Preparation And Properties Of Metalloporphyrin Composited Mesoporous SiO₂ Nanoparticles As Catalyst

Up to date, most of the well-known catalysts with high activity for the epoxidation of alkene and oxidation of alkane are composed of precious metal, such as V(V), Mo(VI) , W(VI) and Ti(IV), etc., with high oxidation station in complexes and usually the reaction conditions employed are very harsh during the catalytic oxidation process. Metalloporphyrin derivatives have been widely used as the model compounds of cytochrome P-450 monooxygenase in the study of various catalytic oxidation reactions, usually used as biomimic catalysts in homogeneous solutions, which possess the merits of moderate reaction conditions, high activity, selectivity and so on. The main shortcoming is the difficulty for the recovery of the catalysts from the reaction system for recycle use. Therefore, loading of metalloporphyrin catalyst onto insoluble solid such as mesoporous materials as heterogeneous catalysts attracts great attention in this research field.This dissertation mainly focuses on the preparation of metalloporphyrins and their loading on mesoporous SiO₂ nanopartcles by chemical covalent linkage. Their catalytic ability for the epoxidation of cyclohexene and oxidation of cyclohexane were examined. The main research is presented as the following:1. The preparation and applications of the metalloporphyrins were reviewed. The preparation of mesoporous materials and their application as the loading base of metalloporphyrin catalysts were introduced.2. Tetraphenylporphyrin (TPP) was synthesized by the method of using pyrrole as raw material, organic acid as catalyzer, reacting with benzaldehyde. The reaction conditions were varied and detailly investigated, including the influence of catalyzer, oxidizer and solvent on the yield of tetraphenylporphyrin. Based on the Alder method, nitrobenzene is used as the oxidant and the yield of the title compound can be reached higher than 40%, and meanwhile, the problem of the synthetic scale enlargement resulting low yields by other methods is overcome.3. Based on the modification of Alder synthesis of TPP, 5-(p-hydroxy)phenyl -10,15,20-triphenylporphyrin (HTPP) and its metal complexes (Mn,Fe and Co) were synthesized. Mesoporous silica MCM-41 was synthesized and modified with 3-amino propyl-three methoxy silane. Then HTPP metal complexes were linked to the modified MCM-41 through the succinic ester and amido linkage. The mesoporous materials-supported metalloporphyrins have been characterized by XRD, Solid UV-vis diffuse reflectance spectra, thermogravimetric analysis, and the results shows that metalloporphyrin have been successfully loaded on mesoporous nanopartciles and the loading is estimated as 8% on weight.4. Mesoporous SiO₂ nanoparticles modified with different metalloporphyrins were applied to catalyze the epoxidation of cyclohexene and the oxidation of cyclohexane with molecular oxygen. Factors affecting catalytic activities were invesstigated. The order of the catalytic activities in different metal ions coordinated porphyrin is Mn³⁺>Fe³⁺>Co²⁺. Among the three mesoporous nanopartcile catalysts, the catalytic activities of MCM41-HTPP-Mn is the most efficiency. In catalyzing the epoxidation of cyclohexene, the cyclohexene conversion reached to 98%, and the catalyst turnover was 45857; In catalyzing the oxidation of cyclohexane with molecular oxygen, the cyclohexane conversion reached to 45% and the catalyst turnover was 95658.