Uncatalysed oxidation of cyclohexene

Abstract

The oxidation products of cyclohexene find several applications as intermediates for the manufacture of useful chemicals like cyclohexanol, cyclohexenol/cyclohexenone, cyclohexadiene, etc. The uncatalysed oxidation of cyclohexene with molecular oxygen was studied in a batch reactor. The products, cyclohexene hydroperoxide, cyclohexenol, cyclohexenone and cyclohexene oxide were realised in the temperature range of 343-393 K. The effect of various kinetic parameters such as temperature, speed of agitation and wall material was studied. The kinetic data were generated at different temperatures and fitted successfully with a rate equation based on autocatalysis by total products. The values of rate constants and activation energy were determined. Recognising the fact that the industrial route to cyclohexene from benzene hydrogenation yields a mixture of cyclohexene and cyclohexane which are difficult to separate, some experiments on oxidation of the mixture of cyclohexene and cyclohexane were also conducted. The values of rate constants remain unchanged in the presence of cyclohexane. The reaction was also studied in an aluminium lined reactor to examine the wall catalytic effect, if any, of the stainless steel wall. The reaction was found to be significantly slower in the aluminium reactor while the selectivity towards the hydroperoxide remained unchanged. The oxidation of cyclohexene represents a unique example of an uncatalysed liquid-phase organic oxidation which can be conducted up to relatively high conversions.