Immobilization of metalloporphyrins on P(4VP-co-St)/SiO2 by the quaternarization reaction

Poly(4vinylpyridine-co-styrene) (P(4VP-co-St)) was grafted on silica gel particles in the manner of “grafting from”, and the grafting particle P(4VP-co-St)/SiO2 was gained. The chloromethylation reaction for the tetraphenylporphyrin (TPP) was performed using a chloromethylation reagent, 1,4-bis(chloromethyoxy)butane which was uncarcinogenic, and the tetra-chloromethylphenyl-porphyrin (TMCPP) was prepared. Then, the quaternization reaction between the benzyl chloride groups on TMCPP and pyridine groups of the grafted P(4VP-co-St) macromolecules occurred and the bonding of TMCPP on the particles P(4VP-co-St)/SiO2 was realized, resulting in the functional composite-type particles TMCPP-P(4VP-co-St)/SiO2. Subsequently, the metallation of the bonded particles TMCPP-P(4VP-co-St)/SiO2 was carried out via the coordination reaction between TMCPP-P(4VP-co-St)/SiO2 and metal salt, resulting in the supported metalloporphyrin (MP) catalysts MP-P(4VP-co-St)/SiO2. The supported catalysts were characterized by UV–Vis spectra. The effects of various factors on the bonding process of TMCPP on P(4VP-co-St)/SiO2 were studied in detail. In addition, the catalytic activity of the supported catalysts MP-P(4VP-co-St)/SiO2 have been studied in oxidation process of ethyl benzene with molecular oxygen to acetophenone without the use of sacrificial co-reductant. The experimental results showed that the tetra-chloromethylphenyl-porphyrin (TMCPP) could be successfully bonded onto the P(4VP-co-St)/SiO2 surfaces by means of the quaternization reaction between TMCPP and the pyridine groups on grafted P(4VP-co-St) macromolecules. The supported catalysts MP-P(4VP-co-St)/SiO2 exhibited the fine catalytic activity. Moreover, the supported cobalt porphyrin was more active than the supported iron and manganese porphyrins.