Effect of CO2 on the oxidation of cyclohexene by H2O2 using Co1.5PW12O40 catalyst

Resumo

Oxidation of cyclohexene by cheap and environmentally friendly oxidants, namely H₂O₂ and CO₂ has been catalyzed by Co_1.5PW₁₂O₄₀. It has been found that the main products of the oxidation are 2-cyclohexen-l-one (enone), 2-cyclohexen-l-ol (enol) and 1, 2-cyclohexanediol (diol) with the enone as the major product. Oxidation by CO₂ along with H₂O₂ remarkably increased the conversion compared to that by CO₂ and H₂O₂ separately. This might be due to the fact that CO₂ increases the percarbonate species (HCO₄⁻) responsible of the oxidation by oxygen transfer, which indicated that the CO₂/H₂O₂ mixture is a useful reagent system. The decrease of both the selectivity of the enone and epoxide in favor of that of diol at higher conversions indicated that the diol was formed from the epoxide by consecutive reaction and/or directly from cyclohexene.