Characterization of Immobilized Composite Catalysts of Cationic Metalloporphyrin and Heteropoly Anion in Oxidation of Ethyl Benzene by Molecular Oxygen

Abstract

An immobilized cationic phenyl porphyrin was prepared with crosslinked polystyrene (CPS) microspheres as carriers via synthesis and immobilization.A kind of immobilized cationic cobalt porphyrin was obtained through a coordination reaction between the immobilized cationic phenyl porphyrin and the cobalt salt.In the composite reactions,phosphotungstic acid (HPW) and phosphomolybdic acid (HPMo) with Keggin structures were used as reagents,respectively,and the combination of the cationic cobalt porphyrin (CoP) with the heteropoly anions by electrostatic interaction led to the formation of the immobilized composite catalysts of CoPPW-CPS and CoPPMo-CPS.We then characterized these immobilized composite catalysts.The immobilized composite catalysts were used in the oxidation of ethylbenzene by molecular oxygen,and their catalytic characters were investigated.The results show that the immobilized composite catalysts possess high catalyst activity.They can transform ethyl benzene into acetophenone with high selectivity,and the yield of acetophenone after 12 h reaches 30.1%.The catalytic activity of the immobilized composite catalysts is 75% higher than that of the immobilized cobalt porphyrin.The catalytic activity of CoPPW-CPS is higher than that of CoPPMo-CPS.The cobalt porphyrin in the composite is the catalyst component as the heteropoly has no catalytic activity.However,the heteropoly anion has a protective effect on the metalloporphyrin against its deactivation during the catalytic reaction.In the oxidation reaction,there is an optimum addition for catalyst,and adding excessive catalyst inhibits its activity.The composite catalysts show good recycle properties.