Oxidação catalitica de cicloexano com peroxido de hidrogenio em condições ambientais

AUTOR(ES)
DATA DE PUBLICAÇÃO

1992

RESUMO

The oxidation of cyclohexane by the GoAgg system (FeCl3.6H2O, H2O2, pyridine, acetic acid) was studied at ambient conditions. The principal product obtained is cyclohexanone together with some cyclohexanol. The turnover number, the selectivity (ONE/OL) and the efficiency with respect to hydrogen peroxide were studied as a function of the temperature, the quantities of catalyst, hydrogen peroxide and cyclohexane, the concentration of hydrogen peroxide and the molar ratio pyridine:acetic acid. The best results were obtained between 20°C and 40°C with a molar ratio catalyst:H2O2:cyclohexane of 1:10:20, a solvent ratio pyridine:acetic acid of 4:1 and a 30% hydrogen peroxide solution. Large quantities of water inhibit the reaction. Using these conditions, a turnover number of 4.7, a selectivity of 15.8 and an efficiency with respect to H2O2 of 91% can be obtained after 10 h of reaction time. Cyclohexanol is only formed obtained in the beginning of the reaction, which turns selective for cyclohexanone formation after 30 min. The addition of picolinic acid (GoAgg system) in a molar ratio of 3:1 with iron(III) chloride strongly accelerates the oxidation reaction, which finishes in 15 min, but reduces the efficiency to 53%. The addition of new portions of iron(III) chloride and H2O2 allows accumulation of the oxidation products. We accumulated thirteen reactions, reaching oxidation a final concentration of cyclohexanone plus cyclohexanol of 0.4 M after 180 min of reaction time, which is the same concentration obtained in the industrial process after 40 min. We have not observed any coupling products with pyridine, but were able to identify over-oxidation products of cyclohexanone and cyclohexanol in very small amounts. The results obtained allow proposing a mechanism for the reaction.

ASSUNTO(S)

quimica inorganica catalise

ACESSO AO ARTIGO

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