Oxidação Baeyer-Villiger de cicloexanona com peroxido de hidrogenio catalisada por alumina / Alumina-catalyzed-Villiger oxidation of cyclohexanone with hydrogen peroxide

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Two aluminas, one comercial (Fluka) and the other obtained by sol-gel methods, were used as catalysts for the Baeyer-Villiger oxidation using cyclohexanone as substrate and hydrogen peroxide as oxidant. The catalysts were characterized by X-ray diffraction and thermogravimetric analysis and the oxidation products were analysed by gas chromatography and H and C nuclear magnetic resonance. Both aluminas showed to be high efficient catalysts for Baeyer- Villiger oxidation with aqueous hydrogen peroxide 70 % (w/w), reaching yields as high as 75 % for the e-caprolactona with selectivity of 98 %. The optimized conditions was found to be 20 h of reaction at 90 ± 2 ºC, with peroxide:cyclohexanone molar ratio of 8:1, 300 mg of catalyst, ethyl acetate as solvent and a Dean-Stark system coupled for water removal. The catalysts showed lower selectivity in the presence of water, losing the activity at the first recycling test. However, when the water was removed, the catalysts presented the same activity in 5 consecutive cycles. Tests comparing the alumina as epoxidation and Baeyer-Villiger oxidation catalyst showed that there is a competition between the catalytic sites for these reactions. Based on the results obtained we were able to propose a mechanism, admitting that the reaction could occur by two different pathways

ASSUNTO(S)

agua oxigenada alumina oxidação baeyer-villiger oxidation alumina hydrogen peroxide cyclohexanone

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