In CH3CN:H2O = 1:1 (v/v) medium, the oxidation of styrene by water-soluble oxidants (KHSO5, NaClO, NaIO4 or H2O2) catalyzed by metalloporphyrins (MPs) with various structures and central ions was investigated. The effect of imidazole and pyridine was also studied. The results indicated that the oxidation of styrene catalyzed by MPs is related to the pH of reaction medium, structure and central ions of MPs, oxidants and axial ligands. In neutral medium, MPs showed higher activity and yield of epoxide compared with that in acidic medium. For different MPs, phenyl-substituted manganese porphyrins can effectively catalyze KHSO5 and NaClO to oxidize styrene and pyridine-substituted manganese porphyrin can effectively catalyze KHSO5 and NaIO4 to oxidize styrene. But all MPs studied cannot effectively catalyze H2O2 to oxidize styrene. For different central metal ions, KHSO5 is effective for manganese and cobalt porphyrins, NaClO is effective for manganese porphyrins and NaIO4 is effective for iron porphyrins. Imidazole can markedly enhance the activity of MPs when KHSO5, NaIO4 and H2O2 were used as oxidants and inhibit the activity of MPs when NaCIO was used as oxidant. Pyridine can markedly enhance the activity of MPs when KHSO5 and NaCIO were used as oxidants, but no effect was found when NaIO4 and H2O2 were used as oxidants. (C) 2002 Elsevier Science B.V. All rights reserved.