GB532866A - Treatment of black liquor soap - Google Patents

Abstract

532,866. Acids from black liquor soap. AMERICAN CYANAMID CO. May 30, 1939, No. 15856. Convention date, June 8, 1938. [Class 2 (iii)] [Also in Group III] Mixture of fatty acids and rosin acids from black liquor soap are separated by forming a hot substantially dehydrated solution of the rosin acids and of the salts of the fatty acids in a solvent particularly amyl alcohol in which the fatty acid salts are soluble hot but not cold and in which the rosin acids are soluble both hot and cold and then cooling the solution to precipitate the salts of the fatty acids. The mixture of fatty acid salts and rosin acids may be prepared from mixture of the two acids either by treating black liquor soap with an acid such as sulphuric acid in an amount sufficient only to liberate the rosin acids, or by treating the soap with an amount of acids sufficient to liberate both fatty acid and rosin acids and then adding sufficient alkali to neutralize only the fatty acids. The black liquor soap is preferably purified to remove lignens and sulphur compounds prior to the process of the present invention by first dissolving in water and reprecipitating one or more times by adding caustic soda and sodium sulphate. In the preferred form of the invention the purified black liquor soap is converted to talloel by treatment with sulphuric acid and this partially neutralized to form fatty acid salts which are then separated from the free rosin acids and the unsaponifiable fat by precipitation from amyl alcohol under substantially anhydrous conditions. The filter cake of fatty acid salts which results after the separation of the rosin acids is washed with a further amount of solvent, and then if desired converted to the free fatty acids by treatment with sulphuric acids. The free fatty acids so obtained are preferably then purified by vacuum distillation. The main acids and neutral fat are recovered from the amyl alcohol filtrate from the fatty acid soap filter cake, by adding an amount of sulphuric acid slightly in excess of that necessary for neutralization, removing the amyl alcohol by direct distillation and the excess of sulphuric acid by washing with water, and finally separating the rosin acids from the neutral fat by dissolving in naphtha and extracting with 4 per cent. aqueous caustic soda. The neutral fat which remains in the naptha solution contains a high percentage of phytosteols together with some hydrocarbons. The aqueous alkali solution of rosin acids (principally abietic acid) is diluted with naphtha, acidified with sulphuric acid and the naphtha solution of free rosin acids separated and then purified by agitation with kieselguhr to remove a sludge of water and sapinic acids. These sapinic acids are dark oxidized and polymerized rosin acids. The rosin acids so obtained may be further purified by treatment with extractants such as furfural or resorcinol or with absorbants such as charcoal or clays.