GB491320A - Improvements in the recovery of phenols from oils - Google Patents

Abstract

Phenols are recovered from oils which have been subjected to hydrogenation or prepared under hydrogenating conditions by extracting with salt solutions having an alkaline reaction, treating the salt solution with weak gaseous acid, separating the phenols from the solutions and heating the latter to free them for further use from the gaseous acid. Suitable salts are the alkaline or alkaline earth metal salts of weak inorganic acids such as boric, vanadic, silicic, or phosphoric acid, or of hydrogen sulphide, or of weak organic acids such as alanine, glycocoll or their alkyl derivatives such as methylalanine, dimethylalanine, hydroxyethylalanine, ethylenediaminoacetic acid, or triethylenetetramino acetic acid. Suitable weak gaseous acids are carbon dioxide, or hydrogen sulphide. The extraction and acidification steps may be carried out at raised temperature, e.g. 50-60 DEG C. and heating of the solution may be at 120-150 DEG C. under pressure. Phenols remaining in the salt solution after acidification may be extracted with liquid hydrocarbons, or with ether. A preliminary treatment with ammonia, milk of lime, soda or potash may be employed to remove aromatic hydroxy acids which may be present in the oil. Suitable oils are obtained by hydrogenating the products of high or low temperature coking or extraction of coal or peat; or during the preparation of oils by methods involving hydrogenation. In examples: (1) phenol is extracted from a mineral oil obtained by destructive hydrogenation with an aqueous solution of the sodium salt of glycocoll. Carbon dioxide frees the phenol from the aqueous solution which after separation and heating to expel the carbon dioxide is ready for re-use; (2) sodium sulphide is used as extracting agent for a hydrogenated brown coal low temperature carbonization tar. Hydrogen sulphide is used as the gaseous acid; (3) an extract from mineral coals, treated with hydrogen at 450 DEG C. under pressure is extracted with calcium sulphide liquor which is then treated with hydrogen sulphide to release the phenols. The separated liquor is heated to remove hydrogen sulphide and the extracted oil which still contains some phenol is again treated with the revived liquor. Specification 338,638, [Class 2 (iii)], is referred to.