Synchronistic Synthesis And Immobilization Of Cobalt Porphyrins On Microspheres GMA/MMA And Researching On Catalytic Property Of Supported Cobaltporphyrins

As models of cytochrome P-450, metalloporphyrins have been used to oxidate hydrocarbons with molecular oxygen under mild conditions. Especially, the catalytic oxidation of polymer immobilized metalloporphyrins has been paid more attention to. A new preparation method of metalloporphyrins catalyst has been designed in this paper, succeeding in realizing synchronistic synthesis and immobilization of porphyrins on crosslinked microspheres GMA/MMA via the Adler reaction. Then reacted with cobalt, producing cobalt porphyrins. The polymer-supported catalyst was used in the catalytic oxidation of ethyl benzene andβ-Naphthol with molecular oxygen as oxidant, and some valuable research results for the field of heterogeneous biomimetic catalyst were found.Firstly, the crosslinked copolymer microspheres GMA/MMA were prepared in a suspension polymerization system. The microspheres were chemically modified using p-hydroxyl benzaldehyde (HBA) as reagent via the ring-opening reaction of the epoxy groups on the surface of microspheres, resulting in the modified microspheres HBA-GMA/MMA on which HBA was chemically bound. The effects of main factors such as reaction temperature, solvent variety and the feed ratio on the modification reaction were investigated emphatically. The experimental results show that p-hydroxyl benzaldehyde is a Br?nsted acid itself, and it can effectively be bound onto the surface of microspheres without the addition of catalyst via SN2 nucleophilic substitution reaction. It is advantageous to the modification reaction to use the solvent with stronger polarity and enhance temperature. In the modification reaction, a maximum bonding capacity of 0.21g/g of the modified microspheres can be achieved with DMF as the solvent, the feed ratio of epoxy group to HBA as 1:1.8 at 110℃under 12 hours.Subsequently, Adler reaction was performed at the interface of solid/solution by using microspheres HBA-GMA/MMA, derivant of benzaldehade and pyrrole in solution as co-reactants, so that the synchronistic synthesis and immobilization of porphyrins on the microspheres GMA/MMA were realized successfully, resulting in porphyrin- supported microspheres PP-GMA/MMA, CPP-GMA/MMA and NPP-GMA/MMA. In this investigation, the effects of the main factors on the process of synchronistic synthesis and immobilization of porphyrins were studied. The experimental results show that the acidity of the catalysts, the polarity of the solvents and substituent on phenyl porphyrins affect the reaction greatly. As the temperature is 130℃, the stronger polarity solvent DMSO and catalyst with a pKa value in the region of 3.0-3.9 is used, the porphyrin microspheres with a higher immobilization amount of 7.86g/100g will be obtained. In comparison, the synthesis of CPP-GMA/MMA using chlorobenzaldehyde is carried out most easily, while the synthetic NPP-GMA/MMA using nitrobenzaldehyde most difficult.Via the coordination reaction between the functional microspheres and cobalt salt, polymer-supported cobaltporphyrins CoPP-GMA/MMA,CoCPP-GMA/MMA and CoNPP-GMA/MMA were prepared. The cobalt content of solid catalyst was determined by the atomic absorption spectrometry. The catalytic activities of the solid catalysts were tested in the catalytic oxidation reaction of ethyl benzene by dioxygen, and the main factors on the catalytic activity were studied. The experimental results show that the cobaltporphyrin catalyst can effectively activate dioxygen, has excellent catalytic activity and fine selectivity. The yield of acetophenone at ordinary pressure of oxygen and 120℃in 12h can get up to 21.5%. As the biomimetic catalyst, excess addition will inhibit the catalyst activity; the smaller the immobilization density on the surface of microspheres, the higher the catalyst activity is; and the catalyst has a good reuse performance. In comparison, the catalytic activity of CoNPP-GMA/MMA is the highest. Using the solid catalysts on which cobaltporphyrins (CoP) were loaded as catalyst, the catalytic oxidation ofβ-Naphthol to 2-hydroxy-1,4-naphthoquinone was performed in methanol solution of NaOH, and with molecular oxygen as oxidant. The experimental results show that as the amount of NaOH is 5.0g and the used amount of cobaltporphyrin is 0.231g, the product nearly is 2-hydroxy-1,4-naphthoquinone, and the yield can get up to 30%. It is found that sodium hydroxide plays an important role, though not as a catalyst itself, but it can accelerate the reaction rate; In the catalytic oxidation system, the substituent types on phenyl porphyrin affect the reaction greatly, the catalytic activity of metalloporphyrin can be significantly improved with the exclusion of the electron substituents and thus a higher yield.