Preparation, Characteration And Catalytic Performance Of Metalloporphyrin-bound Magnetic Nanocomposites

The method of the preparation of metalloporphyrins immobilized by silica-coated magnetic Fe₃O₄ nanoparticles was studied in this paper. A novel strategy of solid silanation was applied to prepare metalloporphyrin bonded magnetic nanocomposites. The structure and magnetism of the metalloporphyrin bonded magnetic nanocomposites were characterized by various instrument. The effects of the loading of metalloporphyrins, central metal ions, substituents and saturated magnetizations on the catalysis of the metalloporphyrin bonded magnetic nanocomposites are investigated and a primary mechanism about the ethylbenzene oxidation catalyzed by the metalloporphyrin bonded magnetic nanocomposites is proposed. A new possibility will be offered for the applications of metalloporphyrins and the studies in the effects of the magnetic field on the chemical reaction.Firstly, the studies in the hydrocarbon oxidation catalyzed by the metalloporphyrins and supported metalloporphyrins were summarized. The achievements and the problems in this subject were pointed out. Also the brief introduction of the magnetic nanoparticle supported catalysts was presented.Secondly, a series silica-coated magnetic Fe₃O₄ nanoparticles with different amount of Fe₃O₄ were prepared by the water-in-oil microemulsion approach. Their structure and magnetism were characterized by atomic absorption spectrophotometer (AAS), scanning electron microscopy (SEM), X-ray diffraction (XRD), low-temperature N2 adsorption (BET method), vibration sample magnetometer (VSM). All silica-coated magnetic Fe₃O₄ nanoparticles had uniform nanometer scale, spherical morphology and different saturated magnetizations. The silica-coated magnetic Fe₃O₄ nanoparticles S(4) with 38.3% Fe₃O₄ content was more suitable as the supporter of metalloporphyrins.Thirdly, A novel strategy of solid silanation was applied to prepare metalloporphyrin bonded magnetic nanocomposites with different loading of metalloporphyrins or different saturated magnetizations. This strategy could maximize the surface concentration of APTES derivatized metalloporphyrins and minimize the bulk of their self-condensation. When the input ratio of metalloporphyrins vs silica-coated magnetic Fe₃O₄ nanoparticles is smaller than 0.147:1(mmol/g), the metalloporphyrin bonded magnetic nanocomposites could be quantitative synthesized by this solid silanation method. Their structure and magnetism were characterized by SEM, TEM, XRD, UV-vis spectroscopy, infrared spectroscopy, and VSM.Fourthly, the cyclohexane oxidation with iodosylbenzene catalyzed by the metalloporphyrin bonded magnetic nanocomposites with different loading of metalloporphyrins was studied. The yield of cyclohexanol and cyclohexanone increased with the increase of the loading of metalloporphyrin. When the input ratio of metalloporphyrins vs silica-coated magnetic Fe₃O₄ nanoparticles is equal 0.147:1(mmol/g), the obtained metalloporphyrin bonded magnetic nanocomposites was more suitable catalysts.Fifthly, the cyclohexane oxidation with iodosylbenzene catalyzed by the metalloporphyrin bonded magnetic nanocomposites with different saturated magnetizations was studied under the geomagnetic field (5×10^-5 T). The yield of cyclohexanol increased with the increase of the saturated magnetizations. The effect of the saturated magnetizations on the catalytic abilities of metalloporphyrins follows the order of ironporphyrin > manganeseporphyrin > cobaltporphyrin. The silica-coated magnetic Fe₃O₄ nanoparticles S(4) supported metalloporphyrins was more suitable catalysts.Sixthly, the ethylbenzene oxidation with air catalyzed by the metalloporphyrin bonded magnetic nanocomposites with different substituents was studied. Under the same conditions, the effect of the substituents on the conversion of ethylbenzene in the ethylbenzene oxidation followed the order of -Cl > -H > -OCH₃.Seventhly, the ethylbenzene oxidation and the cyclohexane oxidation catalyzed by the metalloporphyrin bonded magnetic nanocomposites with different central metal ions were studied. Under the same conditions, the effect of the central metal ions on the yields of products in the oxidation reactions followed the order of manganeseporphyrin > cobaltporphyrin > ironporphyrin.Eighthly, The recovery and recyclability of the metalloporphyrin bonded magnetic nanocomposites were measured in the cyclohexane oxidation and the ethylbenzene oxidation, respectively. Due to their superparamagnetic performance and excellent stability, all metalloporphyrin bonded magnetic nanocomposites could be recovered and reused for 5 times, only showing minor loss of activity during the last runs. At the same time, the recovery ratio of all metalloporphyrin bonded magnetic nanocomposites was more than 97%.Ninthly, a primary mechanism about the ethylbenzene oxidation catalyzed by the metalloporphyrin bonded magnetic nanocomposites is proposed. The selectivity of hypnone in the products of the ethylbenzene oxidation catalyzed by the metalloporphyrin bonded magnetic nanocomposites is more than that catalyzed by the metalloporphyrins. A possible reason is that more 1-phenylethanol could be adsorbed at the polar surface of the metalloporphyrin bonded magnetic nanocomposites, the produce of the hypnone will benefit from these 1-phenylethanol.In a summary, the preparation and characterization of the metalloporphyrin bonded magnetic nanocomposites were studied, and the effects of the loading of metalloporphyrins, central metal ions, substituents and saturated magnetizations on the catalysis of the metalloporphyrin bonded magnetic nanocomposites are investigated in this dissertation. A possible reaction mechanism about the ethylbenzene oxidation catalyzed by the metalloporphyrin bonded magnetic nanocomposites is also proposed. This dissertation provides a new way of thinking for the expansion of metalloporphyrins as a biomimetic catalyst in the basic research and other hydrocarbons and new materials in the field of the other application aspects of metalloporphyrins.