Studies Of The Catalysis Of Biopolymer-Metalloporphyrins For Aerobic Oxidation Of Cyclohexane

Modeling cytochrome P-450 monooxygenase with supported metalloporphyrins is very useful in research and application of them. In the work we studied the aerobic oxidation of cyclohexane catalyzed by biopolymer (chitosan, chitin and cellulose) supported tetraphenylporphyrins, and explored the mechanism of the aerobic oxidation of cyclohexane catalyzed by chitosan-ironporphyrin. Five chapters in this thesis are presented as follows:1. In the introduction we summarized the effect of immobilization of metalloporphyrins to supports on their catalysis for the hydrocarbon oxidation. The present of the studies about employing nitrogenous ligand such as imidazole and pyridine et al. as axial ligation of metalloporphyrin was emphasized. At one time, the significance of using the metalloporphyrin supported on nitrogenous biopolymer as catalyst for the cyclohexane oxidation with air was further explained.2. In the second chapter we presented that the chitosan-ironporphyrin (or -menganeseporphyrin and -cobaltporphyrin),chitin-ironporphyrin (or -menganeseporphyrin and -cobaltporphyrin), cellulose- ironporphyrin (or -menganeseporphyrin and -cobaltporphyrin) were synthesized by the coordinating or adsorbing metalloporphyrin method and characterized by UV-Vis, IR and ESR techniques et al. and then their coordinate (or inclusion) constants were measured in Langmuir method combined with UV-Vis technique . The catalysis of the 9 supported metalloporphyrins on biopolymer and the reuse of chitosan-ironporphyrin for the aerobic oxidation of cyclohexane was investigated under the optimum reaction conditions. The experiments of exploring the catalytic mechanism of the cyclohexane oxidation by chitosan-ironporphyrin with air were carried out.3. In the third chapter the methods of immobilizing tetraphenylporphinato-iron (-manganese and -cobalt) on biopolymer, determining their structure and measuring .the coordinate (or inclusion) constants of metalloporphyrin on the supports were discussed. The structure of chitosan (or chitin )-metalloporphyrin were confirmed as bi-ligated (amino or amido and chlorine) supported metalloporphyrin and the cellulose-supported metalloporphyrins are the physical-adsorbed ones. The capacity of coordinating or adsorbing metalloporphyrin to the biopolymer, i.e. the coordinate (or inclusion)constants of them estimated in Langmuir isotherm equation, were 9.69-1.90 X 104 Lmol-1.4.In the fourth chapter the catalysis of chitosan-ironporphyrin, as well as its reuse as catalyst and the other 8 catalysts for the aerobic oxidation of cyclohexane were discussed respectively. Compared with the metalloporphyrin immobilized on supports with pyridine or imidazole, the marked enhancement of products selectivity (with over 80%) were obtained when the chitosan-, chitin- or cellulose-supported metalloporphyrin was respectively employed to catalyze cyclohexane oxidation with air. The best one among the 9 catalysts was the chitosan-ironporphyrin with 97% selectivity (ketone and alcohol) and 8.8% cyclohexane conversion, in addition, with 92% selectivity and 1-2% cyclohexane conversion in its reuse. The catalysis of the 9 catalysts was better than the corresponding metalloporphyrin as well.5. In the fifth chapter the influence of immobilizing metalloporphyrin to supports on the corresponding catalysis for aerobic oxidation of cyclohexane were discussed. The products selectivity was affected by the cyclohexane oxidation rate controlled by the capacity of coordinating chitosan or chitin to metalloporphyrin. The stronger the coordination was, the higher the selectivity, the cyclohexane conversion and the catalyst turnover were obtained. As far as cellulose was concerned, the adsorption for manganeseporphyrin than iron (or cobalt ) porphyrin produced a better products selectivity.The hypothetic mechanism of the cyclohexane oxidation catalyzed by chitosan-ironporphyrin was a radical reaction.