GB626095A - Manufacture of phenols - Google Patents

Abstract

Phenols are obtained by acid treatment at elevated temperatures of percompounds formed by the liquid phase oxidation with molecular oxygen of alkyl benzenes containing at least one tertiary carbon atom in the alpha position to the nucleus, the oxidation being effected to such an extent that a substantial amount, e.g. 50-90 per cent of unchanged alkyl benzene remains. Oxygen may be passed through either the heated alkyl benzene optionally dissolved in enert solvents such as toluene or ixylene or a heated oil-in-water dispersion of the alkyl benzene advantageously in the presence of emulsifying agents such as sodium stearate or ricinoleate. A two-phase decomposition results from the use of such acids as sulphuric, phosphoric and hydrochloric and a vinyl phase decomposition by the use of organic acids such as glacial acetic or p-toluene-sulphonic. The decomposition is preferably carried out at the boiling point of the mixture and 1-10 per cent by weight aqueous sulphuric acid is preferred. Instead of acids hydrogen-ion exchange material such as sulphonated phenol-formaldehyde resins or coals may be used. Styrenes, e.g. methyl styrene, acetophenone and acetone are obtained as bye-products. Phenols may be isolated from the two phase decomposition by decantation of the aqueous acid, which is returned to the decomposing vessel, followed by distillation of the alkyl benzene, preferably under reduced pressure, the phenols being recovered from the still together with acetophenone from which they are separated by fractionation. The alkyl benzene may be returned to the oxidation stage after removal of phenols by e.g. adsorption or treatment with aqueous alkali metal hydroxide solution and styrenes by e.g. hydrogenation or treatment with sulphuric acid and/or alkali permanganate solution. Alternatively the products of decomposition may be steam distilled and the phenols recovered from the aqueous residue by fractionation or preferably extraction. In examples: (1) isopropyl benzene maintained in a dilute aqueous alkaline emulsion is treated at 85 DEG C. with molecular oxygen, allowed to separate and part of the oil layer decomposed by refluxing with dilute sulphuric acid and part by treatment with concentrated aqueous caustic soda, the aqueous layer formed being acidified and refluxed with dilute sulphuric acid to give phenol which is distilled off, the above reaction mixture is also decomposed by heating with (2) glacial acetic acid; (3) 1 per cent sulphuric acid acetone, methyl styrene, acetophenone and phenol being obtained; (5) p-toluene sulphonic acid to give phenol and acetone, and (6) sulphonated coal and phenol-formaldehyde resins, and in (7) p-cymene is treated at 90 DEG C. with molecular oxygen and the peroxide obtained decomposed with hot 10 per cent sulphuric acid to give p-cresol.