Immobilization Of Metalloporphyrins On Nanocomposite Microspheres And The Catalytic Properties For Ethylbenzene Oxidation

Metalloporphyrins play an important role in the catalytic oxidation of alkanes andalkenes because of their high catalytic activity and selectivity. Herein, the metalloporphyrinsas biomimetic catalyst have received increasing attention. However, metalloporphyrins havenot employed in industrial field because of the lack of the hydrophobic environment ascytochrome P450. It has been found that immobilization of metalloporphyrins on solidsupports benefits not only the improvement of the stability and selectivity but also thereusing. In order to further improve the stability and catalytic properties of immobilizedmetalloporphyrins, we have prepared CeO₂@SiO₂core-shell nanoparticles by microemulsionmethod, and metalloporphyrins were immobilized on the CeO₂@SiO₂core-shell nanoparticlessurface through amide bond; Then, we prepared silica coated magnetic Fe₃O₄nanoparticlesthrough Fe₃O₄as a hard template. Finally the catalysts were prepared by removing themagnetic Fe₃O₄nanoparticles.The catalytic performances of these two supportedmetalloporphyrin catalysts for the oxidation of ethylbenzene were investigated, and the mainwork is described as following:Firstly,5-（4-carboxyphenyl）-10,15,20,-triphenyl porphyrine and three kinds ofmatalloporphyrins（MnPs,CoPs,FePs） were synthesized by optimized method and a variety ofcharacterization including Mass, UV-Vis, FT-IR were employed. We also established adetection method to measure the concentration of metalloporphyrin.Secondly, the catalytic performance of the matalloporphyrin for oxidation ofethylbenzene in the absence of any solvent were investigated. A GC analysis method wasestablished for the simplicity and rapidly quantitatively analysis of ethylbenzene,benzaldehyde,1-phenylethanol and hypnone. The influence of reaction conditions, such asdifferent matalloporphyrins, amount of catalyst, temperature and flow of oxygen werestudied.Thirdly, we prepared CeO₂@SiO₂core-shell nanoparticles by microemulsion method,and metalloporphyrins were immobilized on the CeO₂@SiO₂core-shell nanoparticles surfacethrough amide bond. The supported metalloporphyrin catalysts were prepared andcharacterized by BET, SEM, TEM, XRD, UV-Vis and FT-TR. The results show that themorphology of CeO₂@SiO₂nanoparticles were microspheres with ca.30nm diameter, and themetalloporphyrins content was76mg/g-cat. CeO₂@SiO₂nanoparticles have no significantlycatalytic effect on the catalytic oxidation of ethylbenzene.But when matalloporphyrin was immobilied, the catalyst has been enhaced and possessed comparably high catalytic activityand stability,the catalytic activity showed little signifacant reduction after6times reuse.Forthly, we prepared silica coated magnetic Fe₃O₄nanoparticles by using the Fe₃O₄asa hard template. Finally the silica and metalloporphyrin nanocomposite microspheres catalystwas prepared by removing the magnetic Fe₃O₄nanoparticles and characterized by BET,SEM, TEM, XRD, UV-Vis and FT-TR. The results show that the nanocompositemicrospheres catalyst have hollow microspheres structures with ca.600nm diameter, and thematalloporphyrin was not damaged after removing magnetic Fe₃O₄. The nanocompositemicrospheres of silica and matalloporphyrin were used as catalysts for oxidation ofethylbenzene, and compared to the effects of Fe₃O₄core before and after removing. It wasfound that the Fe₃O₄before removing had little catalytic activity, but the catalytic activitysignificantly increased after removing magnetic Fe₃O₄. This may be the metalloporphyrin wascompletely coated and no space can contact with the substrate before the magnetic Fe₃O₄removed. The effect of amount of catalyst was investigated. When the amount of catalyst was0.2g, the conversion of ethylbenzene was up to22.94%. The silica and metalloporphyrinnanocomposite microspheres catalyst has high stability, and the catalytic activity was notsignifacantly reduced after6times reuse.