GB785296A - A process for the production of fatty acids - Google Patents

Abstract

Branched chain fatty acids are obtained by subjecting an intermediate distillation fraction containing branched-chain primary alcohols and one or more saturated aliphatic hydrocarbons and obtained in the distillation of a mixture of alcohols produced by the catalytic addition of carbon monoxide and hydrogen to olefins, to treatment with a molten alkali metal hydroxide at superatmospheric pressure and at a temperature in the range 250-350 DEG C., the quantity of alkali metal hydroxide employed corresponding to or being slightly in excess of the amount required by the hydroxyl number of the intermediate fraction, separating the hydrocarbons from the oxygen-containing product by distillation, injecting water under superatmospheric pressure into the molten oxygencontaining product with agitation of the melt to yield an aqueous paste-like mass of soap, dissolving the paste-like mass in water and treating the solution with a mineral acid to release the fatty acids. The separation of the hydrocarbons by distillation and the injection of water to produce the aqueous paste-like mass of soap is preferably carried out in the same zone or vessel as that in which the intermediate fraction is treated with the alkali metal hydroxide, the aqueous paste-like mass being withdrawn from the zone or vessel at a temperature not exceeding 200 DEG C. prior to solution with water and decomposition of the soap with mineral acid. The reaction with the molten alkali metal hydroxide is preferably carried out at a pressure greater than 10 kg. per sq. cm. and preferably at a pressure of about 50 kg. per sq. cm. and it is preferred to use the alkali metal hydroxide in an amount not exceeding 110 per cent of the theoretical quantity. The quantity of water injected into the molten reaction product is preferably from 10 per cent to 50 per cent by weight of the molten mass and the aqueous paste-like mass of soap may be removed by means of a gas under pressure or by suction. The aqueous solution obtained on dissolving the paste-like soap mass in water may be extracted with a water-insoluble solvent, e.g. a hydrocarbon fraction, to remove unsaponifiable constituents before the treatment with mineral acid, e.g. sulphuric acid, and it is advantageous to add a water-soluble alcohol to the aqueous solution prior to the extraction step to reduce loss of soaps in the extraction step. The process is particularly advantageous for the processing of raw alcohols derived from olefines obtained by the Fischer-Tropsch synthesis but is also applicable to alcohols derived from olefins formed from paraffins by chlorination and subsequent dehydrochlorination, or to crude alcohol mixtures derived from polymerized olefins produced from liquid or gaseous unsaturated petroleum hydrocarbons. Examples are given for the production of C15 branched-chain fatty acids from (1) a saturated hydrocarbon-alcohol mixture obtained in the recovery by distillation of a C15 alcohol produced by the catalytic addition of water gas to a C14 olefin-containing hydrocarbon mixture (formed by the catalytic hydrogenation of carbon monoxide) and subsequent hydrogenation of the reaction product, and (2) a saturated hydrocarbon - alcohol mixture obtained in the distillation of a C15 alcohol produced by the catalytic addition of water gas to olefines and subsequent hydrogenation of the reaction product, the olefines used being obtained by the dehydrochlorination of chlorinated C14 hydrocarbons. Sodium hydroxide is used in each case in the alkali fusion step. It is stated that the fatty acid products generally may be converted into low pour point ester oils, textile auxiliary agents, cold resistant plasticizers, or mineral oil additives.