The cationic cobalt(H) porphyrin complex: 5,10,15,20-tetrakis[4-(diethylmethylammonio)phenyl]porphyrinatocobalt(II ) tetraiodide has been found to be an efficient catalyst for the oxidation of 2,6-di-tert-butylphenol by dioxygen in aqueous medium. The oxidation reaction afforded mainly the corresponding diphenoquinone and some of the 2,6-di-tert-butyl-1,4-benzoquinone. The initial rate constant of autoxidation reaction was found to increase with increasing pH from 7.0 to 10.0. The rate of autoxidation reaction showed linear dependence on catalyst concentration and dioxygen pressure. The rate of autoxidation reaction was found to fit a Michealis-Menten kinetic model for saturation of catalyst sites with increasing 2,6-di-tert-butylphenol concentration. The catalyst showed reduced activity in repeat oxidation reactions. (c) 2006 Elsevier B.V All rights reserved.