Kinetic features and mechanism of oxidation of cyclohexene in the presence of heterogenized Co(II) on the surface of polyethylene

Abstract

1. The catalyst prepared by attachment of Co(II) ions on granules of the graft copolymer of polyethylene with acrylic acid effectively catalyzes liquid-phase oxidation of cyclohexene, ensures chain propagation (in the initial stage of the reaction) due to activation of oxygen by Co(II) ions, and catalytic decomposition of hydroperoxide with emission of radicals into the volume. 2. Chain breaking takes place both in bimolecular recombination of alkenyl peroxide radicals in the bulk and with the participation of cobalt ions on the surface of the catalyst (linear breaking). 3. The reactions of complexing and decomposition of cyclohexenyl hydroperoxide with Co(II) and Co(III) acetylacetonates were studied. The corresponding complexing constants, initiation constants, and order of the reactions were estimated. 4. The structure of the heterogeneous catalyst was studied by IR spectroscopy. Free carboxyl groups are present on the surface near the catalytic sites, and chemisorption of hydroperoxide molecules on these groups results in a high local concentration of hydroperoxide in the region of the active sites regardless of its concentration in bulk. The constancy of the rate of initiation and the rate of oxidation of the olefin is a consequence of this.