Hydroxylation of cyclohexane with molecular oxygen catalyzed by highly efficient heterogeneous Mn(III) porphyrin catalysts prepared by special synthesis and immobilization method

Abstract

A novel method to synthesize and immobilize porphyrins as well as manganese porphyrins on crosslinked polystyrene (CPS) microspheres was designed. The chloromethyl groups of chloromethylated CPS microspheres (CMCPS microspheres) were first oxidized to aldehyde groups via Kornblum oxidation reaction, obtaining aldehyde group-functionalized microspheres, and then, the synchronous synthesis and immobilization of porphyrins on CPS microspheres were carried out via the Adler reaction between solid–liquid phases, obtaining three kinds of functional microspheres, on which phenyl porphyrin (PP), p-chlorophenyl porphyrin (CPP) and p-nitrophenyl porphyrin (NPP) were immobilized. Finally, three manganese porphyrin-immobilized microspheres, MnPP–CPS, MnCPP–CPS and MnNPP–CPS, were prepared, these solid catalysts were used in the catalytic hydroxylation reaction of cyclohexane with molecular oxygen as oxidant, and their catalytic performances were mainly investigated in this work. Some surprising experimental results were obtained. The prepared immobilized manganese porphyrin catalysts display amazing catalytic activity and selectivity, and cyclohexane conversion can get up to 45 % and cyclohexanol selectivity in the reaction product can be up to 90–100 %.