Oxidação de cicloexano por terc-butil hidroperoxido catalisada por complexos de ferro (III) e cobre (II) soluveis em cicloexano

AUTOR(ES)
DATA DE PUBLICAÇÃO

1997

RESUMO

Cyclohexane oxidation by tert-butyI hydroperoxide in the presence of Fe(tma)3, Fe(fod)3, Cu(tma)2 and [Cu(en)2](NO3)2 was studied under reflux and under an oxygen pressure of 25 bar at 70°C. The iron catalysts produced cyclohexanone and cyclohexanol as main products, while the copper catalysts form cyclohexene as well. Over-oxidation produts were formed in minor amounts. Under reflux, the seIectivity for one, ol and ene was higher than 90%, with conversions of 4% and 5% for iron and copper catalysts, respectively. Under an oxygen pressure, the selectivity was around 80% and the conversions between 9 and 11 %. The best results under reflux and under oxygen pressure were found for the copper catalysts, with 97 and 91 % selectivities and 5 and 10,9% conversions, respectively. With the iron catalysts, cyclohexanone and cyclohexanol were detected from the beginning of the reaction, while the copper catalysts initially produced only cyclohexene. After 24 h, the reaction stopped due the decomposition of hydroperoxide. The reactivation of the process required addition of fresh portions of oxidant. The catalysts deactivated by complexation with the polar over-oxidation products. Mechanistic studies indicated that the tert-butoxy radicaIs, formed by metal catalytic decomposition of the hydroperoxide, abstracts a hydrogen of the cycIohexane, producing alkyl radicaIs which react with moIecular oxygen forming an cyclohexylperoxy radical. The final products were formed by disproportionation and hydrogen abstraction of the cyclohexyIperoxy radical.

ASSUNTO(S)

cicloexano

ACESSO AO ARTIGO

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