Patent GB-641220-A (GB)
Title: Improvements in or relating to the separation of fatty oil substances
IPC: C11C1/00
Filed: 1946-07-11
Abstract: Mixtures of esters, amides or nitriles derived from mixtures of higher fatty acids and containing saturated and unsaturated constituents (the unsaturated constituents differing in their degree of unsaturation) are separated into saturated, moderately unsaturated and highly unsaturated fractions by treating the mixture to be separated with a substantial amount of an organic solvent, chilling the mixture to a temperature at which the saturated constituents are substantially completely insoluble in the solvent and the unsaturated constituents completely soluble, and filtering the chilled mixture. The filtrate is then extracted with an additional quantity of the same or a different solvent under such conditions that a liquid extract phase is formed comprising relatively highly unsaturated constituents dissolved in the solvent(s) and a liquid raffinate phase comprising moderately unsaturated constituents, and the respective phases are separately discharged from the system.  The solvent extraction of the filtrate may be of the continuous counter-current type and may be carried out at atmospheric temperature or above while the precipitation of the saturated constituents may be carried out at about 0 DEG  F.  The discharged liquid raffinate phase either with or without additional solvent may be chilled to a temperature substantially below the temperature at which the moderately unsaturated constituents are completely soluble in the solvent and the constituents which are thus caused to come out of solution may be removed from the chilled liquid.  The solvent may be acetone, methylethyl ketone or other low-boiling ketone, alcohols or acetonitrile, or nitrobenzene, furfural, aniline or phenol may be used as the extraction solvent (see Group III).  The Specification as open to inspection under Sect. 91 comprises also the fractionation by the above method of fatty amine salts, and refers to the use of liquid sulphur dioxide as an extraction solvent.  This subject-matter does not appear in the Specification as accepted.ALSO:Mixtures of soap-forming fatty acids containing saturated fatty acids and unsaturated fatty acids of varying degrees of unsaturation, (or similar mixtures of glycerides) are separated into fractions by treating the mixture with an organic solvent, chilling the acids-solvent mixture to a temperature at which the saturated fatty constituents are substantially insoluble and the unsaturated fatty constituents substantially completely soluble (e.g. about 0 DEG  F.), filtering off the saturated constituents and subjecting the filtrate to liquid-liquid extraction with an additional quantity of the same or a different solvent under such conditions (e.g. at or above room temperature) that a liquid extract phase is formed comprising relatively highly unsaturated fatty constituents and a liquid raffinate phase comprising relatively moderately unsaturated constituents, and separately discharging the phases.  The solvent-extraction of the filtrate may be effected continuously and in counter-current.  The discharged liquid raffinate phase, either with or without additional solvent, may be chilled to a temperature substantially below the temperature at which the moderately unsaturated constituents are completely soluble in the solvent and the constituents which are thus caused to come out of solution may be removed from the chilled liquid.  The latter may be recycled through the extraction zone.  The process may be used for the fractional separation of fatty acid mixtures comprising saturated fatty acids (such as palmitic and stearic acids) and oleic and linoleic acids, such as may be derived from soya bean oil or cottonseed oil.  It may also be applied in the fractionation of fatty acid derivatives other than glycerides (see Group IV (b)). In the example, a mixture of the above fatty acids is mixed with acetone or other low-boiling ketone, cooled to about - 5 DEG  F. and filtered at - 5 DEG  F.  The filter cake is washed with chilled solvent and subsequently freed from solvent by distillation.  The filtrate, from which all or part of the solvent may be removed by distillation is heated and extracted in counter-current with an additional quantity of acetone in a tower at 70-150 DEG  F., the filtrate travelling downwards by gravity in the extractor.  The extract phase accumulating in the top of the tower and consisting of a solution of linoleic acid in acetone is drawn off continuously and stripped of acetone.  A portion of the acid may be recycled to the top of the extraction tower.  The raffinate phase collecting in the bottom of the tower and consisting of an acetone solution of oleic and linoleic acid is drawn off and may either be discharged from the system or mixed with a further quantity of acetone or of wash liquor from the previous filtration, cooled to about - 60 DEG  F. and filtered.  The filter cake consisting of substantially pure oleic acid is freed from solvent and the filtrate may be recycled to the top of the extraction tower.  Instead of acetone other solvents such as methylethyl ketone, acetonitrile, or alcohols or mixed solvents, may be used.  When the extraction solvent is of higher specific gravity than the fatty acid mixture to be extracted, e.g. nitrobenzene, furfural, aniline or phenol, the solvent is introduced into the upper part of the extraction tower and the filtrate from the saturated fatty acid removal stage (optionally completely or partly stripped of the first stage solvent) introduced into the lower portion of the extractor.  The Specification as open to inspection under Sect. 91 refers to the use of liquid sulphur dioxide as a solvent in the liquid-liquid extraction stage.  This subject-matter does not appear in the Specification as accepted.