GB629429A - Decomposition of organic peroxides - Google Patents

Abstract

Alkyl benzene hydroperoxides wherein the peroxide group is linked to an aliphatic tertiary carbon atom attached to the benzene ring and the alkyl groups do not contain more than five carbon atoms on reaction at elevated temperatures, preferably between 40 and 80 DEG C., with aqueous sulphuric acid of a strength substantially more than 10 per cent, but not exceeding 70 per cent weight/volume yield phenols and ketones. The acid strength is preferably within 25 and 60 per cent. Peroxides instanced are those of isopropylbenzene, secondary butyl benzene and p-cymene. The rate of decomposition of the peroxides depends on their concentration and continuous rather than batch processes are preferred since the reaction is faster and less liable to side p reactions. Thus peroxides may be fed into the acid at the same rate as they are decomposed so that their concentration does not exceed a low, e.g. 2 per cent, figure. They are preferably added in an inert solvent, e.g. the corresponding alkyl hydrocarbon or the mixture obtained in their preparation from such a hydrocarbon by treatment with molecular oxygen, preferably containing 10 to 45 per cent of hydroperoxide. The reaction vessel is fitted with agitators and a decanter which enables the recovery of a light oily layer containing the phenol and ketone whilst the acid recovered may be recycled. The presence of ketone in the reaction mixture acts as a promotor and ketones obtained are recycled in part although a homogeous solution is avoided, ketones may be obtained from the oily layer by, e.g. distillation and phenols, recovered from the residue. Another method of effecting the decomposition consists in passing the acid and hydroperoxide, preferably dissolved in a solvent such as benzene, toluene, xylene and the corresponding alkylbenzene to the hydroperoxide, through a narrow tube at a velocity sufficient to produce turbulent flow. An inert mutual solvent such as a ketone, e.g. acetone or an alcohol, e.g. ethanol may be added although heterogeneous reactions are preferred. With a batch process the presence of a mutual solvent such as low molecular weight water soluble alcohols, ketones and ethers, e.g. methanol, propanol, isopropanol, tertiary butanol, acetone, methyl ethyl ketone, dioxane and ethers of ethylene and diethylene glycols, is an advantage. Since the decomposition rate increases with the volume ratio of the aqueous to the oil phase it is preferred to use an initial phase ratio of greater than one. In examples phenol and acetone are obtained by treating isopropyl benzene hydroperoxide dissolved in isopropyl benzene with (2) 55 per cent aqueous sulphuric acid at 60 DEG C. for 20 and 30 minutes and at reflux temperature for 15 minutes; (3) 55 per cent aqueous sulphuric acid at 60 DEG C. in a continuous process, and (5) 25 per cent aqueous sulphuric acid for 3 hours at 70 DEG C., in (1) the hydrated sodium salt of isopropyl benzene hydroperoxide is treated with 60 per cent aqueous sulphuric acid at 60 DEG C. for 20 minutes to give phenol and acetone, in (5) a homogeneous mixture of approximately 28 per cent aqueous sulphuric acid, ethanol and isopropyl benzene hydroperoxide is reacted at 70 DEG C. for 50 minutes to yield phenol and in (6) secondary butyl benzene hydroperoxide is treated with 25 per cent aqueous sulphuric for two hours at 65 DEG C. and phenol obtained on extraction of the product with ether.