Patent GB-815568-A (GB)
Title: Method of producing photostable phenols
IPC: C07C37/86
Filed: 1957-12-20
Abstract: Pure phenols are obtained from crude phenols or phenol containing oils by extracting the same with alkali metal phenolate lye, containing no free alkali and extracting the phenolate lye which is supersaturated with phenols, with paraffinic benzine and/or a benzine containing aromatic substances and then steaming clear by means of water vapour.  The phenols are then extracted by means of oxygen containing solvents, and obtained by distilling off the solvent, preferably after treating with acids.  The extracted phenolate lye which has been steamed clear may also be subjected to an oxidation treatment at normal or elevated temperature before the final extraction of the refined phenols. The process may be applied to phenol-containing oil fractions, and crude phenols produced by extraction from low-temperature carbonization liquors, or mixtures thereof.  When mixtures are used, the crude phenols are added to the loaded, weakly supersaturated alkali phenolate lye from a foregoing oil dephenolation.  The extraction may be carried out by means of a multi-stage countercurrent extractor, in which case the alkali phenolate lye is added on one side, the benzine on the other, the oil fraction to be dephenolized is added in one of the middle stages and crude phenol in one of the stages between the admission of the oil and that of the benzine.  The extraction is preferably carried out at elevated temperature, under pressure, if desired.  The aqueous phenolate usually has a concentration of 10 to 50 per cent.  After extraction of the lye with benzine, the benzine-oil mixture is distilled and the benzine recycled, the neutral oil being collected as a bottom product.  If light-ends or low temperature carbonization benzine is used, however, the benzine-oil mixture may be returned to the existing benzine or washing oil distillation process.  The distillate from the steam treatment which follows the benzine extraction, is preferably returned to the waste liquor which is to be worked up by extraction, and the non-aqueous distillate added to the oil fraction to be dephenolized, if desired after acid washing.  The benzine used may be a low-boiling fraction, e.g. 40-70 DEG  C., obtained, for example, from low temperature carbonization or gasefication benzine.  It may also contain up to 50 per cent of aromatic substances, e.g. that obtained from coal distillation (B.P. 60-150 DEG  C.).  During the extraction the phenolate lye is preferably supersaturated to the extent of not more than 0.6 mol. of phenols per mol. of alkali phenolate.  The oxidation step may be carried out with e.g. air (which may be freed from carbondioxide) at about 80 DEG  C., potassium permanganate, or hydrogen peroxide.  The oxidizing agents are preferably added in the phenol distillation column.  The phenols may be extracted from the final product with e.g. hexanol, isopropyl ether, methyl isobutyl ether, methyl isobutyl ketone or cyclohexanol, and obtained by distillation and subsequent fractionation.  The phenol charged solvent or the phenol mixture free from solvent may alternatively be washed with e.g. sulphuric acid, first.  Examples are given of the process of the invention carried out in 6-11 state extractors and in an extraction tower.