In this paper we compare the properties and catalytic activities of immobilised forms of in situ formed cobalt complexes of pyridin-4-ylmethylpropyl-amine (PYPA), immobilised via grafting of pyridin-4-ylmethyl-(3-triethoxysilanyl-propyl)-amine on pre-formed HMS, and various cobalt salts, formed in aqueous solution. To investigate the role of peroxo species on the catalytic activity, materials with cobalt-alkyl- or hydroperoxo groups were also prepared by addition of TBHP or H2O2 in the loading step of the preparation. The support material and the catalysts were characterised by STA, DRUV, and N-2 adsorption. All catalysts are active in the aerial oxidation of styrene and, with few exceptions, 1-decene, and exhibit different reactivities and selectivities towards epoxidation. (C) 2003 Elsevier B.V. All rights reserved.