US2316512A - Liquid phase extraction of glyceride oils and acids - Google Patents

Description

Patented Apr. 13, 1943 UNITED STATES PATENT OFFICE a 2,310,512 mourn mass sx'rascnos or GLYCERIDE OILS AND ACIDS Stephen E. Freeman, Wauwatosa, Wia, assignmto Pittsburgh Plate Glass Company, Allegheny County, Pa... a corporation of Pennsylvania No Drawing. Orizinal application January 17,

1939, Serial No. 251,340. Divided plication May 13, 1940, Serial No. 334,997

Ind this lD 3 Claims. (01. 260-428) The present invention relates to the treatment of fat and'oils, oi the glyceride type, and it has particular relation to the treatment of glyceride oils such as linseed oil, oiticica oil, tung oil, soybean oil, cottonseed oil, hempseed oil, fish oil,

diflerent degree or types of unsaturation into fractions certain of which contain a higher ratio of the more unsaturated or more actively unsat urated components than the original mixture.

A second object oi the invention is to provide a method of extractin such glyceride oils as linseed, soy-bean. cottonseed, fish oil, train all and similar oils from pulps or meals containing them,

while leaving most oi the phosphatldes in a readily removable form in the meal.

. A third object of the invention involves the provision of a simple and convenient method of separating mixtures of saturated and unsaturated iree iatty acids into fractions, one of which is relatively more saturated than the other.

These and other objects will be apparent from consideration of the following specification and the appended claims.

Oils the glyceride type such as are employed in the preparation'oi foods, soaps, or as filmiorming ingredients in many paints, varnishes and enamels are found in certain plants or in the seeds thereof, andas fatty constituents in the bodies or animals and fish, and are essentially diiferent from petroleum or mineral oil, since they are composed mainly of mixtures of the glycerides of the fatty acids such stearic, palmitic,

oleic,- linoleic, clupanodonic, linolenic, licanic,

elaeostearic, and many others.

The number and type of glycerides present'will vary, depending uponthe specific oil. The general or type structure or these glycerides may be represented by the formula:

and are monodi or tri glycerides according to the number 0! acyl groups in positions R1, R2 and R: which have been introduced by esteriflcatlon of the glycerol with a i'atty acid. 1

The principal diii'erence between these glycerideaaside from variations inthe number of ester groups, consists in variation in the length oi.

' tains '18 carbon atoms.

groups or residues.

the carbon chains; and in the number and arrangement oi the double bonds in the alkyl For example, palmitic acid of theiormula cmwrmno on V 7 contains 16 carbon atoms while stearic acid con- The formula of stearic acid is cmwrmiec Both are free of double bonds and are non-dry ing. Oleic acid of the probable formula crmcm' 'zcn CH(CH2) 'zCOOH acid) is of the formula:

non-conjugate double bonds and these bonds by reason of their number are of such activity that the glycerides possess drying properties. I

The following constitutes the formula of this acid:

Linolenic acid (9,12,l5-octadecatrienoic acid) diifers only in having an additional double bond:

Elaeostearic acid and licanic acid, glycerides of which occur in tung oil and oiticica oil respectively contain double bonds in conjugate relationship in which they are extremely active, and

' their glycerides dry faster than any of the foregoing.

Elaeostearic acid (9,11,13 octode catrienoic' 'HHHHHHHHH These glyceride oils are customarily extracted from the seed meals or other material containing them by application of highpressure, or by extraction with a suitable organic solvent, such as v hexane; Both 01. these methods are objectionable Ior numerous reasons. For example, in case pressing is resorted to, the removal of oil is incomplete and in event the percentage of oil in the meal or. pulp is initially low, the unextracted oil may constitute a very large percentage of the jtotal. Extraction by means of organic solvents, such as hexane involves a very high explosion hazard ,"and violent explosions often resulting in loss or life are not uncommon in plants employing such process. Both processes are objectional because of non-selectivity. For example, in

- either the pressing operation or the solvent extraction with a hydrocarbon solvent 0.5- to 1% phosphatides, 1 or 2% free fatty acids are obtained in the extracted oils. Non-drying constituents such as relatively highly saturated glycerides are'also removed in the oil. At the same time certain materials which seem to exert an anti-oxidant effect upon the drying oils are obp tained in the mixture.

- 7 Most of the components or the natural oils and the substances '(meals or the like) containing the oils are, of themselves of substantial value for various purposes.

For example, the pulps are valuable as cattle foods, the more highly unsatu rated glycerides or the glycerides containing conjugate double bonds, which are more highly active than the more saturated glycerides, are useful as film-forming constituents in paints. varnishes.

, involves the application either of strong sulphuric space for storage purposes.

acid which chars and coagulates the by-product portions, or treatment with sodium hydroxide. Both of these methods are drastic intheir action upon the oil destroying some portions entirely, thus producing a by-product which has little or no value. In addition to causing destruction or degradation of the by-products, such treatment also tends to decompose a part of the drying, or film-forming glycerides. The methods are tedious and require considerable equipment and much Furthermore, the reagents employed in the process are not recoverable and along with the by-products which are obtained in a degraded form constitute a considerable source or loss.

The present inventioninvolves as one Ieature the discovery thatcertain types of non-reactive organic polar solvents notably those which, at low temperatures, are not completely miscible with V glyceride oils, may by proper control of temperature be employed preferentially to dissolve unsaturated or more actively unsaturated components ofglyceride oils either from simple or crude mixtures of the glycerides, or from materials'such as seed meals or pulps containing the glycerides. Accordingly, by treating the oils, or materials, such as seed meals or 'pulps containing the oils, with one ormore of the selective solvents at a temperature sufliciently low to obviate complete solution of the oil and at a temperature high enough Ior the solvent to be liquid, it becomes possible to separate the mixture into two liquid components, one comprising the solvent saturated with a fraction rich in unsaturates, the second consisting of glycerldes which are relatively poor in unsaturates.

These liquids contain activating groups, which usually are polar and which may be selected from a relatively large class among which may be enumerated the following: 1

- Secondary or tertiary carbon atoms in a hydrocarbon nucleus and the positions of the various groups inthe molecule exert a substantial influence upon the characteristics of treating liquid.

The capacity of these groups to activate the molecules of which they are constituents is variable.

In most cases the applicability of a particular solvent for the fractionation of giyceride oils can be determined from the above table in which .the permissible carbon atoms for each of the more common of the polar or activating groups are listed. In order to determine if a particular solvent is applicable, the number of permissible solution is incomplete. Usually, the lower the I temperature or treatment (within reasonable limits) the more selective will be the solvent and the higher will be the proportion of the unsaturates in the traction dissolved. However, the proportion of the-glycerides recovered in the dissolved fraction is also decreased. Therefore, in

- commercial operation it is preferred to compromise between extreme selectivity and high yields,

carbon atoms for all of the activatinggroupsare added together. If the sum is equal to or greater than the number of carbon atoms actually pre-. sent in the nucleus of. the solvent molecule, the

latter can usually be employed selectively to dis- I solve unsaturated glycerides from more saturated glycerides; The operation of the rule 'is'illustrated by iuriural n-( :-n 11- 6 ri-cno The latter contains two double bond (c=c) groups, one oxy linkage O and an aldehyde v group. The sum of permissible carbon atoms for these groups is l+l+l+2 or 5, which exactly corresponds to the number of carbon atoms in the Iuriural nucleus.

In the cases of groups having but low activating power, e. g.'C=C, -O-, etc., it is usually necessary that an additional and more active group be included in the molecule. However, the groups of low activating power then increase the selective action of the molecule for unsaturates. This is also true with the halogens, such as chlorine and bromine.

It will be apparent that most oithe solvents,

and to employ the solvent at such temperature and in such proportion that two fractions separate but'that a reasonable yield is obtained in the dissolved traction.

In the practice 01' the invention, it" is preferred to treat the 0115 containing saturated and unsaturated glycerides at the temperatureand in a ratio at which separation into fractions occurs.

' The treatment of oil or meal maybe by batch,

or multi-stage, or counter-current or concurrent flow, or bycombination of these methods.

In the application or the process to-meal's or pulp in order to remove the oil therefrom, thematerial to be treated containing an oil, e. g. soy-bean oil, or linseed oil, or marine oil, or the like may be treated at a temperature sufllcient to dissolve all or a substantial proportion'oi' the oil therein. The liquids are separated from the solids and the temperature is adjusted to obtain separation into two liquid phases, one of which is rich in relatively saturated glycerides,

and contains a small amount 01 solvent and the second consists of solvent in which is dissolved a fraction rich in unsaturates. The ratio or solvent to 011 must not be too low because an undue proportion of it will be dissolved in themore saturated iraction and there will not then be sum- 1 cient amount satisfactorily to dissolve and separate the more unsaturated fraction. Conversely,

if too much solvent is employed an excessive amount of saturates will be taken into solution and-fractionation cannot be accomplished. Probably .in most instances the solvent should be within-a range of two to twelve parts by volume of solvent to one part or oil- In batch extractions, a ratio of about four parts of solvent to one part of oil has been found to be a good aver- .age. Mechanical separation 01' the two fractions by settling and decantation, or,by centrii'ugation may be easily eflected. The solvent canbe re-f covered by steam distillation or by'crystallization or by the addition of a 'non-solventior' ;the oil.

such as water, in order to cause an'alteration' oi the characteristics of the-solvent; etc.

A series of tests was conducted upon soy-bean, oil having arr-iodine number of 136, the solvents were employed in the ratio of tour parts'to one recorded as miscible. The third column in which a the number of carbon atoms in the molecule is ii suillciently heated, will become miscible with I all components of the oil. Accordingly, the temperature must be suillcie'ntly low and ratio of the solvent must be maintained in a region where listed in the column and the maximum number of carbon atoms theoretically permissible as calculated by assignment of numbers from table A to the activating groups are includedin the'last column. a

Those solvents capable of separating the oil into two fractions are designated as I. Those which do not so separate are designated asfM.

' Tsar: B-Continued Carbon atoms- Mlscibilig Solvent at 20 o1- sbove I t e molecule Nitro:

Nltromethane.-- Nltroethane..--- l-nitro propane- Nitro benmne iocty amine Tetraoctyl ethylene diam amm l'fi'fikmlm Pl dlneiu fn l Amino (or imino), double bonds:

Allyl or! Triahloro ethylene Nin- Proplonitrils Garbo a Dimethyl sulfate cure as a: mmesa-cum F N new: are: W M @QOQOIL More thanil H was as sz sss as: ssa Similarly cottonseed oil may beextracted with 35 a quantity (iour volume, .more or less) or active solvents such as:

and many others to obtain immiscible systems that separate into two phases which can be separated by decantation or other methods.

Most of these solvents will also behave similarly with fish oil, linseed oil, tung oil, olive oil and animal fats such as tallow.

In a series of quantitative tests to determine -the selectivity oi certain liquids for unsaturated Tans: C

Iod Temp. 0! Pet num gr Dm Solvent "0Q? fer- 0. Ex- Ram- Ex- Ramtract nate tract nate Nitroethane 0 2.8 71.7 148.2 130.3 17.9 l\dethy1l0rml1to.- 0 13.8 86.2 149.6 133.8 16.8 12 28.6 71.7 144.2 1320 11.3 Methyl cellosolve 28 9.0 91 147.0 132.2 14.8 70 43.0 67 138.0 131.6 6.6 Methy11evullnate.. 27 85 147.0 132.5 14.5 Propion1trflc.-.- 0 33.2 66.8 146.5 131.2 14.3 FurluraL. 1 27 28 72 146.0 132.0 14.0 40 88 62 144.5 131.0 13.5 'lrlmsthyl phosphate... 70 2 90 147.0 134.0 13.0 128 11 89 144.0 132.8 11.2 Aoetlldeh do 0 27.9 72.1 144.813L9 12.4 Triethylp osphatc 0 41 '59 142.1'130.0 -12.1 Acetonylaoetonc 27 80 146.0 134.0 12.0 50 .47 53 141.0 131.0 10.0 Acetone (3% water)-..- 27 41 69 139.6 132.8 6.8 tyl 0 1s a: 145013211 11.11 Nltromethane 1 1 13 3:7 132.5 11.6 3 .5 8.5 Glyooldlacetatc 66 88 02 141.0 129.7 11.3 1 :15 1 .11... 8 as 4 1.2 120% 1 13" 1 0 6-. 1 .2 1 M oyl cellooolvc ace- 0 59 no 1 L .2 30.2 10. Methlyllactateu 70 23.3 76.7 139.5 131.7 0. Ethy lactate. 27 .50. 44 138.5 130.2 8. el10|0lve-..-. 0 50.5 40.5 138.8 130.7 s s. thyl maleate... 0 26 74 140.1 132.0 8. Anetldmhydrldg m 51 49 138.2 131.0 -1. Carbltol 125 22.5 77.5 139.0 182.8 6. Propylene glycol 27 5 95 139.0 135.0 -4. ti0Ic1d...- 60 62 38. 137.8 133.8 '4. Methyl butanolone. 0 49 51 137.0 132.2 8. n-Butyramide 120 so 10 1as;2 132.5 a. lsotgropanol 28 9' 91 138.0 135.0 8. E yl glycolate 7'1 21. 77 138.0 135.0 8.

n-Propyl alcohol Ethylidene dlacetate Isopropyl alcohol Methyl levulinate Methyl lactate Methyl acetoacetate Ethyl lactate Ethyl acetoacetate Diacetone alcohol Acetaldehyde Methyl cellosolve Furlural Mono-ethyl ether of di- Diacetyl ethylene glycol Acetonyl acetone Allyl alcohol Formamide Ethylene chlorhydrin Nitromethane Furturyl alcohol Nitroethane Acetic acid Triethylene tetramine 6o Acetic acid anhydride Amlline Methyl tormate Propionitrile Glycol ditormate Trimethyl phosphate Glycol diacetate Triethyl phosphate Ethyl acetyl glycolate v I Iodine number Solvent H 011 11111 3 g; 111.01. 1.11

Methyl cellosolvc 187. 5 208 182 186 201 161 dissolved oil rich inunsaturates. The layers acid with the following results:

were'then separated and the extracting agent was eliminated by vacuum distillation. Iodine numbers were determined by the Wljs method. The results are tabulated below:

- Linseed oil w... 8111111111111 extracted with scene Iodine number origimloil 5211f; 111101111111 Marine oil (me'nhaden) was extracted with a series of solvents as follows: I 1

In the example in which ethyl acetoacetate and phenol were employed in admixture, the ratio of the two was ethylacetoacetate parts, phenol 20 parts.

Where phenol and petroleum ether were employed the ratios of the two ingredients were of insoluble oil having a lower index of refrac- 5 tion than the original material andthe other having a substantially higher index than the I original oil. The results are as follows:

Indices of refraction Iodine value of acid in hydrocarbon Extracting agent g Soluble Insoluble Ethylene cblorohydrin 1, 4820 1, 4869 1.4809 Pyridine 1.4820 1. 4x50 1. 4810 These solvents indicated by the letter M in Table B could not be used by themselves to effect fractionation of highly unsaturated glycerides from less highly unsaturated ones, because of undue miscibility with both types. However, in many cases it is possible to mix the active solvent with an aliphatic hydrocarbon such as hexane, butane, propane, dodecane, or the like, which is relatively immiscible with the selectiv solvent. The hydrocarbons tend to pull the saturated glycerides away from the active solvent and permits separation of the oil into two fractions.

The ratio of hydrocarbon to active solvent may broad range, e. g. 1 to parts of hythe active solvent. Howvary over a drocarbon per 1 part of ever, good results have been obtained by employment of a ratio of 4 to 1. In general the greater the proportion of hydrocarbon employed, the stronger willbe the tendency to pull away the saturated glycerides from the polar solvent.

Similar methods may fractionation. of mixtures saturated fatty acids. in polar or active solvents such as are, listed above. However, by suflicient admixing oi the solvent with a hydrocarbon it is possibleto effect, separation offree acids into two phases, one consisting essentially of active solvent which is rich in unsaturated acids and the other consisting essentially of hydrocarbon which is rich in saturated acids. This process is illustrated by acids from linseed oil:

' Parts by volume Linseed oil acids 200 Petroleum ether (B. P. -60 C.) 200 Anhydrous furfural 400 These were agitated together at room temperature and allowed to separate into layers. The solvents were then distilled off from the two fraccomponents pass into solution. The dissolved material may then b suitably fractionated by manipulation of temperatures or by modification of the solubility characteristics by addition of hexane or the like. Subsequently the dissolved unsaturates may be separated from the selective solvent.

The use of phenol a d petroleum ether, as shown in the above tabl constitutes an example in which a relatively miscible but polar solvent is employed in combination with a nonpolar hydrocarbon to obtain fractionation of the oil into less saturated and more saturated cuts.

An extension of the ioregoing method would involve treatment of mixed fatty glycerides, e. g.

I linseed oil or soybean oil with a selective polar solvent such as furfural or ethyl acetoacetate or the like, to obtain two liquid phases. The phase comprising the solvent and the more unsaturated glycerides could then be treated by batch or by counter-current or concurrent extraction with hexane or other hydrocarbon to pull out. additional saturated glycerides, thus leaving a higher concentration of unsaturates in the fraction obtained from the solvent.

The immiscible fraction of oil containing a p more fully saturated glyceride after separation 30 be employed to effect of saturated and un--' 1 l hese are usually soluble solve acetate which from remove therefrom additional unsaturated inaterial.

" An example of such p'rocedure would involve initialextraction of soy-bean or similar oil with furfural followed by treatment of the immiscible are miscible at all practicable temperatures with glycerides such as occur in tions-separately under vacuum. v Iodine value of original acid 173 Iodine value of acid in hydrocarbon; 166 Iodine value of acid in furiural 193 A 30 per cent mixture of linseed oil fatty acids in the same hydrocarbon was agitated with 1 volume of furfuryl alcohol and separated into fractions at room temperature.

Iodine value of original acid 1'7 3 162 Iodine value of acid in solvent 203 Iodine value or original acids Iodine value of acids in hydrocarbon 168 Iodine value oi acids in solvent 1'75 Where the herein-described selective polar solvents are employed to extract glycerid oils and free fatty acids from seed meals, extraction preferably is effected under conditions such that all tung oil and oiticica oil may be employed in combination with hexane or other open chain hydrocarbons to obtainseparation into a hydrocarbon soluble fraction and a fraction soluble in the polar or active solvent. In this process the proportion of hydrocarbon to the polar solvent may vary over a broad range. However, the higher the ratio of hydrocarbon the more selective will be the system.

J In some cases where extreme selectivity of the system is not required, a readily miscible solvent such as phenol may be incorporated with a more selective solventto increase yield of extract. Such system is illustrated by ethyl acetoacetate-phenol above described. These ingredients may be employed in a ratio of 1 part of phenol to 4 parts of ethyl acetoacetate.

Separation of the glyceride or acid fractions and the solvents may be effected, as previously stated, by crystallization, vacuum distillation,

steam distillation or other methods. A convenient method involves addition of water, which tends to reduce the solubility of th glycerides in the solvent. The water may be employed in an amount sufiicient to saturate the solvent or if the solubility of water in the solvent is high it may be added until the glycerides or the free fattyacids separate. a

Appropriate variations in the mode of manipulating the fractions obtained by solvent ex- "traction of a glyceride oil would involve further fractionating or splitting one of the fractions, e. g. the solution of highly unsaturated glycerides, to obtain a portion which is richer in unsaturates than the initial fraction and a fraction which is poorer in unsaturates. The latter fraction can the solvent may be treated in an additional stage with v a more. sharply selective solvent to then be recycled by admixing it with fresh glycerides at an appropriate stage of extraction. For example, a fraction comprising furfural saturated with glycerides of high drying power may be steam distilled to drive ofi some 01' the solvent, or may be chilled, thus causing some of the less soluble (more saturated) glycerides to be separated. This latter fraction can then be recycled. I

Mamiestly, the highly miscible'solvents which can not be conveniently employed by themselves in the fractionation oi. mixed glycerides can still be employed to extract the glycerides from seed meals and pulp. Afterwards the more selective solvents can be applied to the whole oil after or before elimination oi. the initial solvent to separate a highly unsaturated traction. Ethyl acetoaceducted upon the 1 not shown any break even tate is of particular value in the extraction 01' fish oils.

It possesses low solvent powers for the break and color constituents of various oils and accordingly by application of it, it is possible directly to dissolve out most of the constituents of the product which is low in break and color and warm, it may also be used directly to extract materially improved. The

material are tabulated as follows:

on Acid value Raw marine 15. 3 80% extract 5. 6 Furiuml-diO extracted oil 0. 9

Marine oils, which normally produce tacky films when treated with solvents, in accordance with the provisions oi the present invention, do when heated to up ward of 600 F. They dry faster than linseed oil. The films produced by them are non-tacky, tree of fishy odor and are highly resistant to blistering.

Upon extracting linseed oil with 2 by weight 01' ethyl acetoacetate, 80% of the oil oil, useful in paints and varnishes, to obtain a,

vegetable oils such as linseed oil, or soy-bean oil from the meal or pulp. The following constitutes a specific example of its application to the treatment of raw fish oil, such as sardine or menhaden oils.

011 in the ratio of one part was contacted in three steps with three parts of ethyl acetoacetate at room temperature to obtain a fraction in solution constituting 60 per cent 01 the total volume of oil. This fraction upon separation from the solvent by evaporation oi the solvent, or by adding water was found to be oi a pale green color and to dry practically free of tack. The fish-like odor was substantially less pronounced than in ordinary oil. The residue was of a deep reddish 'brown color of substantially lower index of refraction and iodine number than the original oil. It dried very slowly and remained permanentily tacky. The yield oi oil can be increased though with slight impairment oi' quality by the addition oi phenol in considerable portions (15 to percent more or less). The use of methyl alcohol or ethyl alcohol in 2:1 ratio on the ethyl acetoacetate extract of the raw fish oil produced a rafilnate whose acid number was 0.0 and whose iodine number had increased to the remarkable value oiv 212.5. This oil was pale green; it had a very bright appearance. The drying test showed the film to be slightly better than raw linseed oil in regard to tack. The test values are as follows:

' Iodine Oil value (was) va ue Raw oil 186 15.3 1st extract l 201 7. 7 Alcohol treated 212. 5 0. 0

was dissolved and upon recovery from the solvent it was found to be tree from break and oi a pale yellow color which changed to green the oil was heated to 800' 1''.

Other drying oils such as hempseed oil, soybean oil, perilla oil, etc. may be treated with iuriural, ethyl acetoacetate, or the like, in order to obtain refined iractio if so desired.

Detailed discussion of the treatment of glyceride oils with furi'ural are contained in copending application Serial No. 144,315, to Stephen E. Freeman, filed May 22, 1937, of which the present case is a continuation in part.

The foregoing examples are to be considered merely as illustrative" and numerous modifications may be made therein without departure i'rom the spirit of the invention or the scope of extraction was only 2 or 3% and the color was the following claims.

The present application is a division of my copending application Serial No. 251,340, filed January 1'7, 1939. y

What I claim is:

1'. A process 01' selectively separating a frac-v tion which is rich in unsaturated glycerides from a material containing said glyceride's in admixture with more completely saturated glycerides, which process comprises contacting the material with an organic polar solvent in which the polar group is 9. nitro group, which solvent at a low temperature is relatively immiscible with the saturated glycerides, but being completely miscible at elevated temperatures, the temperatune of treatment being above about minus 20 C., the ratio 01' solvent and the temperature being below that of complete miscibility with the glycerides, separating the two resultant phases while they are both in liquid state, one containing primarily undissolved glycerides relatively poor in unsaturated glycerides and containing some solvent and the, other consisting of solvent in which is dissolved glycerides relatively rich in unsaturates.

2. A process oi selectively separating a iraction which is rich in unsaturated glycerides from a material containing said glycerides in admixturewith a more completely saturated glyceride, which process comprises contacting the material with an organic polar solvent, the solvent being selected from a class consisting of nitro methane, nitro ethane, n-nitrobenzaldehyde, orthonitroanisole, said solvent at a low temperature being relatively immiscible with the saturated glycerides, the temperature oi treatment being above about minus 20' 0., the ratio of solvent and the temperature being below that of complete misresults of tests conto 3 partsm when 1n sired traction.

in; the oil with anorganic polar solvent conpolarizing group, which solvent at low temperatures is relatively chain zlycerides, the conditions or contacting the glyceride and solvent being such that the system remains liquid and the zlycerides are separating the two resultant liquid phases and removing the solvent phase. to obtain said des'rnrrmn E. FREEMAN.

incompletely dissolved, v