US2895976A - Process for fractionation of fatty acid mixtures - Google Patents

Description

July 21, 1959 PROCESS FOR FRACTIONATION 0F FATTY ACID MIXTURES Filed July 9. 1956 S. KAIRYS ET! AL 2 Sheets-Sheet 1 UNSATURATED FATTY ACiDS AQUEOUS SOAP A5 1 FREE CONC' 1 (FATTY ACIDS TEMPERATURE ABOVE G-ELLING- FREE FATTY CAUSTIC P NT AclDS SOLUTION IMOL. ZQMOL. ACIDIFYING AGENT CONTACTING C02,FLUEGAS, FATTY Acms, ZONE 0R MINERAL ACIDS 4-1070 SOLUTION l a SOLUTION CONTAINING NEUTRAL SOAP AND H L FREE FATTY ACIDS IN P APPROXIMATELY EQUIMOLAR PROPORTIONS COOL AND CRYSTALLIZE 3-6 HOURS ACID SOAPS 0F SEPARATION ACID SOAPS OF MORE SATURATED FATTY ACIDS LESS SATURATED FATTY AClDS INVENTORS Steins [Ca/613's Edi/i610 M Meade William 0. Manna Dilys A. Walder ATTORNEYS July 21, 1959 s. KAIRYS ETAL PROCESS FOR FRACTIONATION OF FATTY ACID MIXTURES 2 Sheets- Sheet 2 Filed July 9. 1956 wnjon QPEZQMES ww moxw INVENTORS Stqms Kaiz' s Edwm M. Me mam 0. Mums Days A. Wa/ldez' a: s HEI-LLOW NI fl f ATTORNEYS 2,895,976 Patented .July 21, 1959 PROCESS FOR FRACTIONATION OF FATTY ACID MIXTURES Stepas Kairys, Toronto, Ontario, Edwin M. Meade, Richmond Hill, Ontario, and William Oakley Munns, and Dilys A. Walder, Toronto, Ontario, Canada, assignors to Canada Packers Limited, Toronto, Ontario, Canada Application July 9, 1956, Serial No. 596,523

18 Claims. (Cl. 260419) This invention relates to a process for the fractionation of fatty acid mixtures and, more particularly, to the fractional separation of unsaturated fatty acids from mixed fatty acids containing acids of a greater degree of saturation. An important aspect of the invention is the separation of mixed fatty acids of generally similar chain length into fractions, one a solid fraction relatively rich in saturated acids, and the other a liquid fraction relatively rich in unsaturated acids. For example, one of the important uses of the invention is the fractionation of tallow acids into commercial stearic and oleic acids. Other mixed animal fatty acids, as well as mixed fatty acids from vegetable and marine sources may be similarly fractionated. The process is applicable to fatty acid mixtures or their soaps found in raw soapstock, acidulated soapstock, undistilled, and distilled fatty acids.

Two main separation processes have been practiced in the prior art, one involving fractional crystallization of the more saturated fatty acids from a melt followed by pressing through burlap bags to provide so-called red oil and stearic acid press cake, and the other involving solvent crystallization, usually wtih relatively expensive organic solvents. The first process involves a large expenditure of labor and is limited to a particular class of fatty acids. The second-process involves the use and recovery of the volatile solvents with inevitable solvent loss, and the solvents utilized are frequently inflammable, toxic, or both. The use of such solvents also involves the necessity of installing explosion-proof equipment; This adds considerably to the capital cost-an important point.

It has also been proposed to fractionate higher-molecular-weight saturated fatty acids from lower-molecularweight saturated fatty acids by acidification of the soaps of such fatty acids, and separation of the liberated weaker high-molecular-weight acids from an aqueous solution. For example, the saturated acids obtained by oxidation of petroleum fractions and the like have been separated in this manner.

It has now been discovered that the fractionation of the more saturated fatty acids from the less saturated fatty acids of mixed fatty acids from animal, vegetable, or marine sources may be accomplished by formation of acid soaps and crystallization of such acid soaps from an aqueous solution under special process conditions, without the use of extraneous solvents or extraction agents. Soaps may exist as the normal salts or soaps having the general formula RCO M, or as the acid salts or soaps having the general formula RCO M.RCO H. These two series of soaps possess markedly different solubilities in water and organic solvents. The acid soaps of the saturated and unsaturated fatty acids apparently possess different solubility characteristics in aqueous solution even when such acids are of generally similar chain length, and of almost the sameacid strength.

Accordingly, an object of the present invention is to provide an improved process for the fractionation of unsaturated fatty acids from the more saturated fatty acids of a fatty acid mixture containing such constituents.

Another object of the invention is to provide an improved method for the crystallization and separation of fatty acid soaps of relatively saturated fatty acids from an aqueous solution containing soaps of both saturated aud unsaturated fatty acids.

A further object of the invention is to provide a process for fractionation of unsaturated fatty acids from the more saturated fatty acids of a fatty acid mixture containing such constituents while avoiding the use of non-aqueous solvents.

The invention will be further illustrated by reference to the accompanying drawing, wherein:

Fig. l is a flow sheet diagrammatically illustrating the steps and conditions of the process;

Fig. 2 is a graph showing the effect of the crystallization period on the iodine value of the unsaturated fatty acid fraction in the mother liquor obtained by carbonating mixed *tallow fatty acids (I.V. 40-45) in 2% aqueous solution to a pH of about 7.3; and

Fig. 3 is a diagrammatic illustration of the process wherein continuous carbonation of an aqueous soap solution is employed for formation of the acid soaps of fatty acids.

The process of the invention as may be observed from the flow sheet of Fig. 1, briefly, comprises the formation of an aqueous solution containing the acid soaps of at least a portion of the mixed fatty acids, said aqueous solution having a pH between about 6.5 and 8.5, a concentration below about 10% and preferably in the range of about 2.5 to 7%, and a temperature above about 25 C. to 30 C.; aging the resultant partially acidified soap solution for at least about three hours at a temperature not above about 25 C. to 30 C. and preferably while cooling to an optimum temperature of about 10 C. to crystallize the acid soaps of the more highly saturated acids; and separating the crystallized fraction from the liquid phase containing the less saturated fatty acids, their soaps or acid soaps.

The soap solution used may be derived from any animal, vegetable, or fish oil source which contains at least 5% of crystallizable fatty acids, but if it is made by dilute refinery soap-stock it is best first to complete the saponification of any neutral oil present by addition of alkali. About 5% of crystallizable acids in the total fatty acid seems to be a minimum figure for economical operation of the process. Fatty acid mixtures derived from tallows and greases, from palm, coconut, rapeseed, cottonseed, linseed, peanut, and soybean oils, or fish oils, are particularly suitable.

By the present process, tallow acids of an iodine value (I.V.) of about 40-45 yield about 45% of red oil of I.V. to and 55% of crude stearic acid of I.V. 10 to 20. Tallow acids of I.V. 60 give approximately equal weight yields of oleic acid of I.V. and stearic acid of I.V. 25. Cottonseed acids give liquid fractions of I.V. up to soya acids, I.V.s up to and fish acids, I.V.s up to 240. The yields vary with the quality of the starting material, but are generally similar to those obtainable by crystallization from organic solvents.

Any suitable alkali, for example sodium, potassium, or ammonium hydroxides, carbonates, or other alkaline salts, may be used'for formation of the fatty acid soaps. It has been found that the iodine values of the fractionated products are not affected by the type of cation used in formation of the soap.

Suitable sources of acidity for formation of the acid soaps from the completely saponified fatty acids are carbon dioxide, mineral acids such as HCl or H 80 and free fatty acids. The soap solution is acidified to the point where the fatty acids are approximately one-half free acid and one-half soap. This point is obtained by the addition of one-half an equivalent proportion of strong mineral acid or by the addition of a full molar proportion of fatty acid, or, in the case of carbon dioxide, by carbonation until the pH is in the range of 7 to 8. As an alternative procedure, two mols of the mixed fatty acids can be dissolved directly in one mol of caustic. A pH in the range of 7.1 to 7.6 is optimal for the carbon dioxide process and constitutes a convenient control factor. The pH control factor is less useful when using fatty or mineral acids as it varies with the electrolyte content, even within the small limit tolerated, by onehalf unit. Nevertheless the pH of the solution obtained by acidification with these acids falls within the range of about 7.0 to 8.0.

When acidifying with carbon dioxide, various methods of carbonation can be used. Thus, carbon dioxide can be passed concurrent or countercurrent to the soap solution in a reaction tower, or the gas may be passed into a batch of the soapstock, or, alternatively, a solution of carbon dioxide in water may be added to the soapstock. Pure carbon dioxide may be used or a crude form, such as stack gases may be employed as such, or else compressed and contacted with Water to give a crude carbon dioxide solution. When using stack gases from ordinary combustion processes, the sulfur dioxide content does not interfere, owing to the strong bufier action of the soapcarbon dioxide system.

Regardless of the acid used, it is important that the final concentration of inorganic salts in the solution from which the fatty acids are crystallized does not exceed 1% of the total bulk of solution. Excess electrolyte interferes with the smooth operation of the crystallization process, and in the case of carbonate refining soapstock, for example, it is necessary to lower the electrolyte content by acidulating part of the stock fully, separating the free fatty acids obtained and adding them back to another part of the soap stock so as to obtain an acid soap liquor of lower electrolytic concentration.

In order to facilitate the formation of a separable crystalline fraction the concentration of the initial soap solution should not be above about 10%, the optimum concentration varying slightly according to the gelling characteristics of the particular soaps. Thus, for the more saturated soapstock-s, such as those of tallow fatty acids a 2 to 5% solution appears to be optimal, and for the more highly unsaturated soapstocks such as cottonseed and soybean a concentration of 5 to 7% is best. The concentrations are independent of the mode of acidification. The following table illustrates the effect of concentration of a tallow (I.V. 40-45) soap solution on the separation of the acid soaps, after crystallizing overnight at 25 C.:

1 Too thick to separate.

2 Most readily separable.

On partial acidification, the gelling tendency of the soaps decreases and the partially acidified solutions can be rapidly cooled down to about 25 to 30 C. during the final stages of partial acidification. The initial temperature of the soap solution is not critical, provided it is above the gelling temperature, but the temperature after partial acidification and before crystallization should be above about 20 C. and the solution must be iodine value of the crystallized fraction.

aged at a temperature not above about 30 C. preferably while cooling in order to produce satisfactory crystallization of the saturated fraction. The solution preferably is aged over a period of 3 to 6 hours in order to complete crystallization. The rate of cooling controls the crystal growth and subsequent physical separation, and accordingly is an important factor. Cooling during the crystallization period to a temperature of about 10 C. provides generally satisfactory results. Lower temperatures down toward 0 C. are also useful when a maximum iodine value of the soluble fraction is desired, though this may be achieved at the expense of a higher The threehour cooling period appears to be the minimum, and longer periods of around five or six hours give more consistent results.

While separation can be accomplished by centrifugation, settling, or flotation, filtration with a precoat filter has been found to be most effective. Flotation of the solids fraction is facilitated by the addition of water saturated with carbon dioxide to the acidulated solution.

It may be observed from Fig. 2 that very little enrichment of the mother liquor in unsaturated fatty acid content, as indicated by the iodine value, occurred during the first two hours of the crystallization period, but that during the next hour rapid increase in unsaturated acids took place. At the end of a four-hour period, crystallization was substantially complete and very little further enrichment of the mother liquor occurred. During the four-hour crystallization period the solution was gradually cooled from a final carbonation temperature of 30 C. to a temperature of about 10 C.

Reference is made to Fig. 3 for a typical example of operation of the process by carbonation with CO A 2.5 to 5% solution of the sodium soaps of tallow fatty acids of an I.V. of 40 to 45 and at a temperature above about 35 C. may be passed from a feed tank 10 through a steam-jacketed line 12 to a heat exchanger 14, where temperature adjustment to constant carbonation temperature is accomplished by means of water circulated through heat exchanger coil 16 from a constant-temperature circulating bath. From the heat exchanger 14, the soap solution at, for example, 50 C. is passed into the bottom of reaction tower 18 into which carbon dioxide from a suitable source 20 is introduced near the bottom by means of fritted gas diifusors 22. Following the initial acidification by C0 in the bottom of the tower, the partially acidified solution is passed upwardly in contact with heat exchanger 24 whereby the temperature may be reduced to for example about 35 C., after which further CO is introduced from the source 20 through additional fritted gas diffusers 26. The CO and partially acidified soap solution rise concurrently through the tower in contact with a further heat exchanger 28 whereby the temperature may be further reduced to about 25 C. Excess CO is separated from the acidified solution by means of separator 29, and is passed overhead by means of line 30 to exhaust or recovery. Suitable flow meters 32 and 34 on the inlet lines and exhaust lines, respectively, determine the amount of CO used up in tower 18. The rate of flow of the soapstock through the tower and the quantity of the CO are correlated by means of valves 34 and 36, respectively, to provide a pH of about 7.2 as the solution leaves the carbonation tower. This pH is determined by pH meter 38. The acidified solution of 25 C. is then passed into crystallization vat 40, wherein it may be held under relatively quiescent conditions for a crystallization period of about three to six hours at room temperature or below. The vat may be located in a refrigerated room so that the solution during the crystallization period may be cooled to a temperature below 10 C., or may be provided with a jacket 42 to permit circulation of cooling fluid. The crystallized mass is then passed to a continuthis precoat filter 44 for separation of the solid. components containing the acid soaps of the more highly saturated fatty acids from the liquid fraction containing the soaps of the less saturated fatty acids. Recovery of the free fatty acids from the separated fractions may be accomplished by further acidification with strong mineral acids in a manner-known to the art.

The invention will be further illustrated by the following examples of practice:

Example 1 Commercial anhydrous sodium soap of tallow fatty acids was dissolved in water to give 6% solution, and this solution was passed concurrently with a stream. of carbon dioxide gas up a vertically disposed heat exchanger. The effluent, at 20 C. and of pH about 8, was a milky liquid which thickened on standing at room temperature, giving a small amount of clear supernatant liquid. The mixture was passed through a Sharples super centrifuge, giving a heavily opalescent liquor and a residue in the centrifuge bowl of some 30% solids content. On acidification, the solids gave a solid fatty acid of I.V. 20, and the liquid a semi-solid acid of I.V. 62.

Example 2 A 2.5% solution of the above mentioned tallow soap was carbonated as in Example 1, and cooled simultaneously to give a liquid of pH 7.5 at 40 C. On cooling slowly over night to 20 C., a precipitate settled out, leaving some two thirds of a total volume as clear opalescent supernatant liquor. The white sludge was centrifuged as in Example 1, to give a residue of 35% solid content and a cloudy mother liquor. On acidification, the solid gave a white solid acid of I.V. 9.0 and the supernatant liquor and centrifuge mother liquors gave semi-solid acids of I.V. 73.1 and 70.5 respectively.

Example 3 A 5% solution of the above tallow soaps was carbonated and cooled to give a milky liquid of pH 7.4 at 20 C., which was allowed to cool to C. in a refrigerated container over night. by weight of diatomaceous earth was then added, and the whole filtered through a pre-coat of diatomaceous earth. The filtrate, on acidification, gave a liquid acid of I.V. 79.8.

Example 4 A 5% solution of lard sodium soaps was carbonated and cooled to give a pH of 7.4 at 20 C. as in Example 1, stood for three hours at room temperature, and was added to four volumes of water saturated with carbon dioxide. On standing over night, relatively saturated solid fatty acids floated and were concentrated in a cream separator type centrifuge.

Example 5 Menhaden soap stock was heated with extra caustic soda to complete the saponification and to digest impurities and was then acidulated. 60 g. of the resultant fatty acids were dissolved in each of l-liter quantities of 0.20 N sodium, ammonium and potassium hydroxides, and the 6% soap solutions obtained were shaken with carbon dioxide gas until a sudden diminution in foam was noticed, this being behavior characteristic of the formation of acid soaps. The three solutions were left to crystallize at 10 C. over night and Were filtered on precoat filters, the solids and filtrate being acidulated separately with results as follows:

Na soap-Solids I.V. 77.9, filtrate I.V. 223 NH, soapSolids I.V. 99.2, filtrate I.V. 222 K soapSolids I.V. 92.5, filtrate I.V. 224

Example 6 Distilled soybean oil fatty acids of low iodine value (120.0) were dissolved in caustic soda to give a soap solution containing 8.25% of fatty acids. This solution at 50 C. was passed up a vertically disposed series of heat exchangers concurrently with carbon dioxide gas, emerging from the system at 20 C. and pH 7.6, and then being cooled to 12 C. over six hours. The prodnot was filtered on a precoat filter to give a solid containing acids of I.V. 57.0, and a filtrate containing acids of I.V. 140.5.

Example 7 Crude soapstock from the refining of cottonseed oil was fully saponified by heating with alkali, and the resultant black liquor diluted to 6.0% total solids. This solution was then carbonated and cooled simultaneously as in Example 6, giving an efliuent of pH 7.2 at 33 C., which was divided into two parts, one being allowed to stand over night at 25 C., and the other at 15 C. The products were then filtered and the solids and filtrates acidulated and the fatty acids vacuum-distilled. The saponified and acidulated soapstock gave a distillate of I.V. 103, the 25 C. experiment gave distilled fractions fractions of I.V. 129 and 43.

Example 8 Acidulated foots from the refining of coconut oil were dissolved in the calculated amount of caustic soda soluation and diluted to give a fully saponified and neutralized soap solution of 8.1% fat concentration. This was carbonated and cooled as in Example 7 to give an efiluent at pH 7.6 and 20 C., which was cooled to 4 C. over four hours and then filtered, the solid and the filtrate being acidulated and vacuum fractionated. The filtrate contained some 20% of the original fat, including almost all the caprylic acid, two-thirds of the capric acid, and one-half of the unsaturation, and the solid contained the bulk of the lauric acid and higher saturated acids. When the solid fraction was distilled from a pot still without a fractionating column, a considerable fraction averaging 70% lauric acid was obtained.

Example 9 A 2.8% solution of tallow (I.V. 63) sodium soaps was passed up a vertically disposed heat exchanger and a further pipe 5 feet in height concurrently with a combustion gas containing 15% of carbon dioxide. Considerable foaming occurred, and an efiiuent of pH 7.4 and at 30 C. was obtained. After cooling to 8 C. over night, the product was filtered, and the filtrate acidulated, whereupon a red oil of I.V. 92 was obtained.

The following examples show the separations of fatty acid mixtures obtained when mineral or fatty acids were used as the source of acidity for the formation of acid soaps.

When acidulating with mineral acid, the acid is best added to the well agitated soap solution; it is probable that local excesses of acidity cause free fatty acids to separate, and that these then redissolve in the less fully acidulated portions, and the temperature at which the acid addition is made should be such as to facilitate this redissolution, and temperatures of around 50 C. for the more saturated stocks. such as beef tallow and of around 35 C. for the more unsaturated stocks such as soybean stock are suitable.

Example 10 Tallow fatty acids of I.V. 63.0 were made into a fully neutralized 2.5% soap solution at 45 C., and aqueous hydrochloric acid of 2% concentration wasadded with good agitation until the pH fell to 7.3. The product was allowed to stand in a room at 8 C. over night, when crystallization proceeded and the pH rose to 7.8, and on filtration a precipitate containing acids of I.V. 30.6 and a filtrate containing acids of I.V. 98.8 were obtained in approximately equal proportions. 7

Example 11 Cottonseed oil soapstock of fat concentration was agitated at 40 C., and dilute sulfuric acid added until the pH fell to 8.0. After standing over night in a room at 8 C. the pH rose to 8.35, and on filtration a solid containing acids of I.V. 17 and a filtrate containing acids of I.V. 128 were obtained.

Example 12 Soybean brown grease was dissolved in an equivalent of aqueous caustic soda to give a 5% fully neturalized soapstock, and to this with agitation was added exactly half an equivalent of dilute sulfuric acid: after treatment as in Example 11, solid acids of I.V. 32.5 and liquid acids of I.V. 136 were obtained.

Example 13 Fish oil fatty acids (50 g.) of I.V. 196 were stirred with water (1 liter) containing caustic soda (3.5 g. of 100%) at 40 C., giving an opalescent solution which was then cooled in a room at 8 C. over night. On filtration a filtrate was obtained which contained fatty acids of I.V. 236.

Example 14 Soapstock from the re-refining of soybean oil, containing 20% fatty matter and 2.7% free caustic soda was heated to 100 C. for two hours to complete the saponification of the small amount of neutral oil, and three-quarters of the product was split with mineral acid, and the free fatty acids obtained were added back to the one-quarter which had not been split, thereby giving a dark rather turbid liquid which was cooled to 8 C. over night and then filtered. The filtrate contained fatty acids of I.V. 139, whereas the original unseparated stock contained acids of I.V. 118.

Example 15 560 g. distilled soybean oil fatty acids of I.V. 122 were stirred with liters of water at 40 C., and 10 N caustic soda added. When 100 ml. had been added, oil no longer separated on standing, but the solution Wm heavily opalescent. A further 20 ml. was added, which gave an almost clear solution, and 20 ml. of 10 N sulfuric acid were added to bring the neutralization of the fatty acids back to 50%. After cooling to 8 C. over night and filtering, a filtrate containing fatty acids of I.V. 145 was obtained.

Example 16 An aqueous solution of peanut soapstock of 5% concentration was carbonated and cooled to give a pH of about 7.2 at 30 C. The resulting solution was allowed to stand over night and to cool to a temperature of C. The solids were then separated by filtration on an Oliver precoat filter to provide a solid fraction containing about 17.2% of the original fatty acid content having an I.V. of 30.3, and a liquid fraction containing about 82.8% of the original fatty acid content having an I.V. of about 103. The original, unseparated soapstock contained fatty acids of I.V. 90.5.

We claim:

1. A process for the separation of a mixture of saturated and unsaturated fatty acids into relatively saturated and relatively unsaturated fractions, comprising: forming from said mixture an aqueous solution containing acid soaps of said saturatedand unsaturated fatty acids, said solution having a concentration of less than about 10%; aging said solution at a temperature below about 30 C. to crystallize the acid soaps of the more saturated fatty acids and separating the solid fraction containing the acid soaps of the more saturated fatty acids from the liquid fraction containing the acid soaps of the less saturated fatty acids.

2. A process for the separation of mixed saturated and unsaturated fatty acid compounds into relatively saturated and relatively unsaturated fractions, comprising: converting said fatty acid compounds to their acid soaps and unsaturated fatty acid compounds into relatively ing a concentration of less than about 10%, a pH between about 7 and 8, a low electrolyte content, and a temperature above the gelling point of said soaps; aging said solution at a temperature below about 30 C. for a period of at least three hours to crystallize the acid soaps of the more saturated fatty acids; and separating the solid fraction containing the acid soaps of the more saturated fatty acids from the liquid fraction containing the acid soaps of the less saturated fatty acids.

3. The process of claim 2, wherein said fatty acid compounds are converted to acid soaps and said aqueous solution of acid soaps is formed by acidifying a solution of substantially neutral soap.

4. The process of claim 3, wherein said solution of substantially neutral soap is acidified with carbon dioxide to a pH in the range of about 7.1 to 7.6.

5. The process of claim 3, wherein said solution of substantially neutral soap is acidified by addition of approximately one-half equivalent of a mineral acid per mol of neutral soap.

6. The process of claim 2, wherein the solution from which said acid soaps of the more saturated fatty acids are crystallized contains less than about one percent of dissolved electrolyte.

7. The process of claim 2, wherein the solution containing the acid soaps is cooled to a temperature below about 10 C. during the aging and crystallization period.

8. The process of claim 2, wherein the solution of acid soaps prior to crystallization of the more saturated fraction is formed by reacting a fatty acid mixture with an alkali solution in proportions of approximately two mols of fatty acids to one mol of alkali.

9. The process of claim 3, wherein said solution of substantially neutral soaps is acidified by addition of an approximately equal molar portion of free fatty acids.

10. The process as defined in claim 2, wherein the fatty matter present is derived from an animal source.

11. The process as defined in claim 2, wherein the fatty matter present is derived from a vegetable oil.

12. The process as defined in claim 2, wherein the fatty matter present is derived from the refining of cottonseed oil.

13. The process as defined in claim 2, wherein the fatty matter present is derived from the refining of soy bean oil.

14. The process as defined in claim 2, wherein the fatty matter present is derived from a highly unsaturated fish oil.

15. The process as defined in claim 2, wherein the fatty matter present is derived from coconut oil.

16. A process for the separation of a mixture of saturated and unsaturated fatty acids into relatively saturated and relatively unsaturated fractions, comprising: forming an aqueous solution of the neutral soaps of said acids of a concentration of about 2 to 7%, said solution having a temperature above the gelling point of said neutral soaps; carbonating said neutral soap solution to a pH in the range of about 7.1 to 7.6; cooling the solution during the carbonation to a temperature above about 20 C.; aging the resulting carbonated solution for a period of from about three to six hours while cooling to a temperature below about 10 C. to crystallize the acid soaps of the more highly saturated acids; and separating the crystallized fraction from the liquid phase containing the less saturated fatty acid material.

17. A process for the separation of a soapstock containing neutral salts of saturated and unsaturated fatty acids and free alkali into fractions containing relatively saturated fatty acid matter and relatively unsaturated fatty acid matter respectively, comprising: splitting a portion of the soapstock with a mineral acid; adding the free fatty acids obtained by splitting said soapstock to a portion of the soapstock which has not been split so that the content of free fatty acids and neutral soap in the resulting mixture is in approximately equal molar proportions and acid soaps of said fatty acids are formed, forming an aqueous solution from said mixture having a concentration of less than about 10 percent with respect to fatty acid matter; cooling said solution to a temperature of below about 10 C. for a period of at least three hours to crystallize the acid soaps of the more saturated fatty acids; and separating the solid fraction containing the acid soaps of the-more saturated fatty acids from the mother liquor containing the acid soaps of the less saturated fatty acids.

18. A process for the separation of mixed higher fatty acids containing saturated and unsaturated fatty acids of generally similar chain length into relatively saturated and relatively unsaturated fractions, comprising: forming an aqueous solution of the neutral soaps of said acids having a concentration below about 10 percent, acidifying said solution to a pH in the range of from about 7 to 8 References Cited in the file of this patent UNITED STATES PATENTS 2,232,331 Leithe et al Feb. 18, 1941 2,361,547 Jenkins et al Oct. 21, 1944 FOREIGN PATENTS 533 Great Britain Feb. 23, 1857 OTHER REFERENCES Fatty Acids and Their Derivatives, Ralston, published 20 by John Wiley & Sons, Inc., N.Y., 1948, pp. 888-890.

Claims (1)

1. A PROCESS FOR THE SEPARATION OF A MIXTURE OF SATURATED AND UNSATURATED FATTY ACIDS INTO RELATIVELY SATURATED AND RELATIVELY UNSATURATED FRACTIONS, COMPRISING: FORMING FROM SAID MIXTURE AN AQUEOUS SOLUTION CONTAINING ACID SOAPS OF SAID SATURATED AND UNSATURATED FATTY ACIDS, SAID SOLUTION HAVING A CONCENTRATION OF LESS THAN ABOUT 10%; AGING SAID SOLUTION AT A TEMPERATURE BELOW ABOUT 30* C. TO CRYSTALLIZE THE ACID SOAPS OF THE MORE SATURATED FATTY ACIDS AND SEPARATING THE SOLID FRACTION CONTAINING THE ACID SOAPS OF THE MORE SATURATED FATTY ACIDS FROM THE LIQUID FRACTION CONTAINING THE ACID SOAPS OF THE LESS SATURATED FATTY ACIDS.

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