US2573900A - Treatment of glyceride oils - Google Patents

Description

Nov. 6, 1951 Filed Nov. 26, 1948 5. E. FREEMAN TREATMENT OF GLYCERIDE OILS 2 SHEETSSHEET l Jnnentor STEP/105" T/TQEEMAA/ 5. E. FREEMAN TREATMENT OF GLYCERIDE} OILS Nev. 6, 1951 2 SHEETS-SHEET 2 Filed Nov. 26, 1948 Patented Nov. 6, 1951 TREATMENT OF GLYCERIDE OILS Stephen E. Freeman, Pittsburgh, Pa., assignor to Pittsburgh Plate Glass Company, Allegheny County, Pa., a corporation of Pennsylvania Application November 2c, 1948, Serial No. 62,089

or zoo-428.5)

19 Claims.

The present invention relate to an improved 4 process for treatment of fats and glyceride oils which contain glycerides of different degrees of unsaturation and which may contain various oth-' er components, including free fatty acids, tocopherols, sterols, antioxidants or inhibitols, vita mins, and break constituents such as phospholipids, lecithin, gums and the like, The invention is particularly concerned with the provision of methods which may be suitably used to fractionate such glyceride oils and thereby to obtain concentrates of certain of the components.

It will be understood that glyceride oils such as linseed oil, tung oil, soybean oil, cottonseed oil, etc., comprise. a mixture of glycerides of fatty acids such as stearic acid, palmitic acid, oleic acid, linoleic acid, clupanodonic acid, linolenic acid, licanic I acid, elaeostearic acid and numerous others.

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

and are mono -,.di-, or triglycerides, according 2 It will be apparent that natural glycerides may difler widely, in degree of unsaturation, due to the number of glycerol hydroxyls which are esterifled and due to the nature of the acid with which the glycerol is esterifled. For example, simple mono-, or dior triglycerides, in which all of the esterifled glycerol hydroxyls are esterlfied with the same acid such as glycerol tristearate, may be present in a glyceride 011, Moreover, mixed glycerides such as a stearic-oleic-linoleic glyceride may be present. Numerous other combinations also exist. Consequently, a natural glyceride oil is a mixture of many different type 01' glycerides of different degrees of unsaturation.

In performance of the. present invention, the glyceride oil of the type mentioned above, or other glyceride mixture, is subjected to a liquid extraction by means of a polar organic solvent which is not completely miscible with the glyceride oil at the temperature of extraction. It has been found that when a glyceride oil, containing glycerides of different degrees of unsaturation, is extracted with an amount of such polar solvent sufllcient to cause separation of a pair of liquid phases, the oil becomes distributed in thetwo phases, the more unsaturated glycerides generally concentrating in one phase, and

to the number of acyl groups in positions R1, R2

contains 16 carbon atoms while stearic acid contains 18 carbon atoms. The formula of stearic acid is' Y Both are free of double bonds and are non-drying. Oleic acid-of the probable formula CH3 (CH2) 7CH:CH(CH2) 1COOH has 18 carbon atoms and contains a single double bond, but its glyceride is non-drying. 'Linoleic acid which also contains 18 carbon atoms has two non-conjugate double bonds and these bonds, by

reason of their number, are of such activity that the less unsaturatedor completely saturated glycerides concentrating in the other phase. With a few oils, such as palm oil, cocoanut oil and similar non-drying oils, which contain large amounts (50 percent or more) of glycerides of fatty acids containing less than 16 carbon atoms, the glycerides which are glycerides of unsaturated fatty acids containing more than 16 carbon atoms, and which may be more unsaturated, tend to concentrate in one phase which will contain a minor'portion of the solvent. In such a case, the glycerides of the shorter chain-fatty acids tend to concentrate in the other phase'which contains most of the solvent and which generally forms the lower layer.

On the other hand, upon treatment of most oils which contain 50 percent or more of glycerides of fatty acids containing more than 16 carbon atoms, such as soya bean oil; linseed oil and other oils, including semi-drying and drying oils, the more unsaturated glycerides tend to concentrate in the phase (usually lower phase) containing the most of the polar solvent, leaving more saturated glycerides in a raflinate (usually upper) phase or layer. In any event, extraction of the glyceride oil with the partially miscible polar solvent affords a convenient means for obtaining the relatively more unsaturated glycerides and the relatively less unsaturated glycerides, in separate fractions. In addition, the other components of the oil tend to distribute themselves with these two fractions. Thus, the break components, including phosphatides, generally enter the liquid the glycerides thereof possess drying properties phase containing the lower amount. of solvent,

. 3 for example, the more saturated glyceridc oil fraction. On the other hand, fatty acids, vitamin A, vitamin E and other oil soluble vitamins (if present), and soluble unsaponifiable components of the glyceride oil tend to concentrate in the phase containing the larger amount of solvent, that-is, with the more unsaturated glyceride oil fraction.

In the performance of this fractionation process to iractionate drying oil glycerides using a polar solvent such as furfural, a heavy phase, which contains most of the furfural together with a concentrate or the relatively more unsaturated glycerides, separates from a lighter, upper phase which contains only a small portion of the furfural used and a fraction of the oil which is less saturated than is the original oil. The amount of oil in the upper-fraction or rafiinate will vary, dependent upon the nature of the oil treated and also upon the amount of furfural which is used, and the temperature of treatment.

After separation of the furfural extract from the rafl'inate or upper .phase, the glyceride oil concentratemay be recovered simply by evaporating off the furfural. However, for many purposes, additional processing is advantageous, in order to achieve -a more complete separation of the components of the extract or more unsaturated fraction.

According to the present invention, it has been found advantageous to extract the polar solvent (furfural) extract phase, either as such, or after removal of a portion of the furfural or other are usually polar and which may be selected from 4 the ramnates and extracts, obtained by extraction of certain furfural-oil solutions with varying quantities of hydrocarbon, and

Fig. 2 is a diagrammatic schematic flow diagram, illustrating suitable methods of extraction of glyceride oils, according to the present invention.

A large number of polar organic solvents are contemplated within the scope of this invention. Such solvents contain activating groups, which a relatively large class, among which may be enumerated the following:

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

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

. variable. In general, there must be at least one polar solvent with a liquid aliphatic hydrocarbon,

such as hexane or other hydrocarbon hereinafter set forth. The hydrocarbon serves to pull out glycerides from the furfural or other polar solvent, usually the relatively more saturated glyca polar solvent extract and a rafiinate, and the polar solvent extract is extracted with hydrocarbon with the resulting hydrocarbon solution being returned to the first zone or at least brought into contact with rafilnate. This process is especially well conducted in a column by introducing glyceride oil into an intermediate point in the column while introducing polar solvent above the oil inlet and liquid hydrocarbon below the oil inlet. In such a case, the polar solvent and hydrocarbon flow in countercurrent direction, and the oil rises countercurrently to the downward flow of the polar solvent, with a polar solvent solution being withdrawn from the bottom and a hydrocarbon solution from the top of the column. Such process provides an especially valuable fractionation. The polar solvent fraction thus obtained from the bottom of the column may be extracted with further hydrocarbon to extract glyceride therefrom.

The invention will be more fully understood by reference to the ensuing specification, when taken in consideration with the accompanying drawings, in which Fig. 1 is a graph showing the iodine values of activating or polarizing group for every four carbon atoms and, in many cases, the ratio of the groups must be substantially increased.

The permissible number of carbon atoms in the molecule of the solvent for each activating group may be tabulated as follows:

TABLE A Permissible Activating Group mgllgegecargroup ent in the nucleus of the solvent molecule, the

latter can usually be employed selectively to dissolve unsaturated glycerides from more saturated glycerides. The operation of the rule is illustrated by furfural The latter contains two double bond (:0) groups, one oxy linkage group. The sum of permissible carbon atoms for these groups is 1+1+1+2 or 5, which exactly corresponds to the number of carbon atoms in the furfural nucleus.

In the cases of groups having but low activating power, e. g.

and an aldehyde -0-, 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.

Most of the solvents, if sufficiently heated, will become miscible with all components of the 011. Accordingly, the temperature must be sufiiciently low and ratio of the solvent must be maintained in a region where solution is incomplete. Usually, the lower the temperature of treatment (within reasonable limits) the more selective will be the solvent and the higher will be the proportion of the unsaturates in the fraction dissolved. However, the proportion of the glycerides recovered in the dissolved fraction is also decreased. Therefore, in commercial operations, it is preferred to compromise between extreme selectivity and high yields, 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 fraction. Temperatures in the range of minus 20 C. up to the miscibility temperature,'generally, are suitable.

In the practice of the invention, it is desired to treat the oils containing relatively more unsaturated and relatively less unsaturated glycerides at the temperature and in a ratio at which separation into fractions occurs. This treatment may be by batch, or multi-stage or continuous countercurrent or concurrent flow, or countercurrent batch, or by combinations of these methods.

The ratio of solvent must not be too low because an unduly small fraction of the oil will be extracted by the solvent. On the other hand, if too much solvent is employed, an excessive amount of the glycerides may be taken into solution with the polar solvent and/or solvent recovery may become unduly expensive. Probably, in most instances, the solvent should be within a range of 2 to 12 parts by volume of solvent to 1 part of oil, although as many as 30 volumes, or even more, of solvent per volume of oil has been used, in some instances. In batch or countercurrent extractions, a volume ratio of about 4 to 10 parts of solvent to 1 part of oil has been found to be a good average.

A series of batch tests was conducted upon soybeen all having an iodine number of 136, the solvents were employed in the volume ratio of 4 parts to 1 part of oil. In the event liquid separation did not occur at room temperature, the mixtures were chilled. The chilling was continued until separation of two liquid fractions occurred, or if no separation took place, to a temperature of minus 20 C. The solvents tested are listed in the following table. In the event that solidification of one or more components of the mixture occurred before liquid separation took place, the mixture was recorded as miscible. The third column in which the number of carbon atoms in the molecule is 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 included in the last column.

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

. TABLE B Carbon Atoms Miscibility Calculated Solvent at 20 C. as maxior above In the Molemum ercule missi is for immiscibility Hudroryl Methyl alcohol I 1 3 Ethyl alcohol-.- I 2 3 n-Propyl alcohol I 3 3 Iso-propyl alcoho I 3 3 n-Butyl alcohol- M 3 Iso-butyl alcohol M 4 3 Tertiary-butyl alcohol M 4 3 n-Amyl alcohol M 5 3 Iso-amyl alcohol M 5 3 Sec.-amyl alcoho M 5 3 Capryl a1cohol.... M 8 3 Cyclohexyl alcohol. M 6 3 Ethylene glycol.--. I 2 6 Propylene glycol-.- I l 6 Glycerinc I i 9 Hudroryl, ester I i 6 I 4 6 I 4 6 I 4 6 I 5 6 M 7 6 I 5 9 I 7 9 Hydrozul, carbonyl Methyl butanolone. I 5 6 Aoetyl methyl carbin I 4 6 Diacetone alcohol I 6 Hudrozul, ether Methyl cellosolve (h-methoxy ethanol) I 3 4 Cellosolve (b-ethoxy ethanol). I 4 4 Butyl cellosolve (B-butoxy ethanol) M 6 4 Diethylene glycol I i 7 Triethylene glycol. I 6 8 Mono-ethyl ether of diethylene glycol I 6 5 Mono-butyl ether of diethylene glycol M 8 5 2-hydroxy methyl 1,3-dioxolane I 4 5 Ethy chloroaeetate TABLE B-Contlnuod Mlsclbili at 20 Solvent or above Carbon atoms Calculated as maxi- In the Molercule Hydrant, double bonds Allyl alcohol Phenol. Cresylic 801d o-A my] phenol. 2,4-dlamyl phenol Benzyl alcohol Geranlol Hydrozyl, triple bond Dimethyl ethynyl earblnol.

Hydrozyl, halogen Ethylene chlorohydrin Propylene chlorohydrln Glycerol monochlorohydrin...

Hydroryl, other Beta-hydroxy gropionitrile. B'eta-ethoxy et yl lactateu." Beta-ethoxy ethyl glycolate--. Furfuryl alcohol Eugenol Acetoehlorohydrin Dichloro trlethylene glycol 2,4-diehloropheno1 2-bromo 4-tertlary-butyl phenol Diethy] amino ethanol Salicyleldehyde Carbozyl Formlc acid- Acetlc acid Propionlc eel ZEEEEE- HHH gar-1H Isobutyrlc acid- Acid anhydride Eater Methyl formate Ethyl formats Glycol diiormate Methyl acetate yl yl glyoolate- Ethylidine diacetate Methyl melonate Ethyl oxalate Eater, carbonyl Methyl levulinate Ethyl levulinate Methyl aoetoaeetate. Ethyl aoetoacetate Ester, ether Methyl cellosolve acetate Cellosolve aoetate.-

Dimethyl ethynyl earblnol acetate HHHH as I Exter, halogen Meth 1 chloroaoet'ate Chloro eth l acetate- Ethyl at are acetate KHZ D ca sqor vaw wcnaaaaawour NNNN 'ootao aacnaeeaqqa IUG GOO

Methyl eymo mm....-.-..

ll Thlopheue Octallydehyde TLBLI B-Coatlnued Solvent Mlmlbillg at -20 or above Carbon Mom;

In the Molecule Calculated maximum rmiaal le tor-lmmlsclblllty Eater, cyanide Aldahl Aeetaldehyde Proplonaldeh do- Butyraldehy Aldehyde, other Methoxy aeetaldehyde Furtural Carbonyl, ether, double bond:

Furlural acetone I Carbonyl, double bonds Benz acetone Carbonyl, amtdo Formamlde Acetamide.

Methoxy methylal Dlmethoxy tetraglyool Ether, double bond:

Tetromethyl dlhydrotumne... Dlmethyl Iurane Anisole Ether, triple bond:

Ethyl ether of dlmethyl ethynyl eerbinol a Ether, chloro Beta, beta'dlchloro dlethyl ether Dichloro diisoprop le Monochloro dlethy ether 2 chloro dloxane-- dhloroacetal o-Nln'o anlsole o-Nltro phenotole Ether, carbonate Beta-methoxy ethyl carbonate Sulfide, double bond:

3 SSZZS KKS ZZK was szzzazaazzgg HHW ma cara- 0: -z-zw-ouw mower CNS - 4 anal-m spw-taclaw-awoecnu been.

aawwweao: Qmwmuu NNNN acme awaooo 10 TABLE a-continued a, quantity (four volume, more or less) or active solvents such as:

mm n-Propyl alcohol Ethylidene diacetate Isopropyl alcohol Methyl levulinate 801m. $95 2 3 ggg gjg Methyl lactate Methylacetoacetate or above IntheMolemum Ethyl lactate Ethyl acetoacetate flfif f Dlacetone alcohol Acetaldehyde billty Methyl Cellosolve Furfural Mono-ethyl of diethyl- Diacetyl I Nitro ene glycol Acetonyl acetone Allyl alcohol Formamide 315331 11133. 1 i 3 Ethylene chlorohydrin Nitromethane ts, g g g Furfuryl alcohol Nitroethane Acetic acid Triethylene tetramine Acetic acid anhydride Aniline 1 g 5 Methyl formate Propionitrile M 16 1 Glycol diformate Trimethyl phosphate g :3 t Glycol diacetate Triethyl phosphate M 5 1 Ethyl acetyl glycolate and many others, to obtain immiscible systems M 4 5 that separate into two phases which can be sepa- M 5 rated by decantation or other methods. g g Most of these solvents will also behave simi- M 7 5 larly with fish oil, linseed oil, tung oil, olive oil M 8 5 and animal fats, such as tallow.

Chlormdoublc bonds In a series of quantitative tests to determine the selectivity of certain liquids for unsaturated #33323355521333133: 2 1 components of a glyceride oil, a soybean oil, hav- MM ing an iodine number of 136. was treated with liquids in the volume ratio of 1 part of oil to 4 mpimflh'fle I 3 3 parts of extracting liquid. Extraction was ef- Carbonate fected by agitating together the oil andthe extracting agent at the tempertaures indicated in e tfi y fia ar l i t fi:z::: 2 g the following table. They were subsequently al- Phmmm lowed to separate into two layers. One layer consisted of an oil fraction, relatively poor in w ggq g gggig ggf 6 6 unsaturates, in which was dissolved some of the Tflbutyl phosphate M 12 a solvent. The other layer comprised the solvent, in which was dissolved oil rich in unsaturates.

s z t The layers were then separated and the solvent methyl I 2 mama was eliminated by vacuum distillation. Iodine numbers were determined by the Wijs method. Similarly, cottonseed oil may be extracted with The results are tabulated below:

TABLE 0 Per Cent Iodine Number Temp. of 1 Dmep Solvent Separa- 7 mm tion O Extract Raflinate Extract Rafiinate Nitroethane 0 28. 3 71. 7 148. 2 130.3 17. 9 Methyl formats 0 13. 8 86. 2 149. 6 133. 8 15. 8 12 28. 5 71. 7 144. 2 132. 9 11. 3 Methyl cellosolve 28 9.0 91 147.0 132. 2 14. 8 43.0 57 138. 0 131. 5 6. 5 Math 1 levulinate 27 15 85 147.0 132. 5 14. 5 Prnn rmifrfln O 33. 2 66. 8 145. 5 131. 2 14. 3 mutual 27 28 72 146. 0 132. o 14. 0 40 38 62 144. 5 131. 0 13. 5 Trimethyl phosphate 70 2 90 147. 0 134. 0 .13. 0 128 11 89 144. 0 132. 8 11. 2 Aoetaldehyde 0 27. 9 72. 1 144. 3 181. 9 12. 4 Tflethyl phosphate. 0 41 59 142. l 130. 0 l2. 1 Acetonyl acetone 27 20 146. 0 134. 0 l2. 0 i 50 47 53 141. 0 131. 0 10. 0 Acetone (3% water) 27 41 59 139. 6 132. 8 6. 8 Diaeetyl 0 18 82 145. 0 133. 2 11. 8 Nitrom 27 6 94 145. 0 133. 5 11. 5 95 14. 3 143. 0 134. 5 8. 5 Glycol dlaeetate 65 38 62 141.0 129. 7 11. 3 5O 23 77 141. 0 132. 0 9. 0 Eth 1 ohm 0 55. 8 44. 2 140. 3 129. 2 11. 1 Met y oellosolve acetate 0 41 59 140. 2 130. 2 10. 0 Meth 70 23. 3 76. 7 139. 5 131. 7 9. 7 Ethy 27 56 44 138. 5 130. 2 8. 3 Cellosolve 0 56. 5 43. 5 138. 8 130. 7 8. 1 Ethyl I 0 26 74 140. 1 132. 0 8. 1 Acetic anhydride 51 49 138. 2 131.0 7. 2 01 125 22. 5 77. 5 139. 0 2. 8 6. 2 27 5 139. 0 135. 0 4. 0 50 62 38 137. 8 133. 8 4. 0 Methyl bfltflmflmm 0 49 51 137. 0 132. 2 3. 8 N-Buty 30 70 136. 2 132. 5 3. 7 Isnnmpannl E 9 91 138. 0 135. 0 3. 0 Etfi l glyco1ate 17 21 71 13s 0 135. o s. o

Iodine number Soluble Orl incl 61! Fraction Insoluble Marine oil (menhaden) was extracted with a series of solvents as follows Iodine number Solvent Original 1235 Insoluble Methyl cellosolve 187. 6 208 182 Ethyl acetoacetate and phenol 186 201 161 Ethyl acetoacetate 186 281 161 Phenol and petroleum ether- 184 189 181 Furiual 184 206 157 In the example in which ethyl acetoacetate and phenol were employed in admixture, the ratio of the two was, ethyl acetoacetate 80 parts, phenol 20 parts.

Where phenol and petroleum ether were employed, the ratios of the two ingredients were, phenol 1 part, petroleum ether 10 parts, or 1:1 ratio using phenol plus 10% water.

Index of refraction also constitutes a measure for the drying powers of an oil. Samples of a marine oil having an index of refraction of 1.4820 were treated with ethylene chlorohydrin and pyridine to obtain two layers, one consisting of insoluble oil having a lower index of refraction than the original material and the other having a, substantially higher index than the original oil. The results are as follows:

, Indices of refraction Those solvents indicated by the letter M" in Table B could not be used by themselves to efiect 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 selective solvent. The hydrocarbons tend to pull the saturated glycerides away from the active solvent and permit separation of the oil into two fractions. The ratio of hydrocarbon to active solvent may vary over a broad range, e. g. 1 or less than 1 to 10 parts of hydrocarbon per 1 part of the active solvent. However, 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 will be the tendency to pull away the saturated glycerides from the polar solvent.

In countercurrent treatment of oil with the. polar solvent in a. column, it has been found to be advantageous to introduce hydrocarbon, such as listed below, into the oil or at least into the column, in order to improve phase separation 12 such a, process, the furfural or similar polar solvent is introduced into an upper portion of the column, hydrocarbon into a lower portion of the column, and the glyceride to be fractionated into an intermediate portion of the column. In such a case, oil and hydrocarbon flow upward and are countercurrently contacted with furfural or the like. The resulting more saturated oil fraction is removed from the top of the column. The furfural and the more unsaturated oil fraction pass downwardly and, below the point of entry of the oil, are scrubbed or washed with the upwardly flowing hydrocarbon, thus losing some more saturated components. The furfural solution then is removed at the bottom of the column.

Following extraction of glyceride oil with a polar solvent by batch, countercurrent batch, continuous countercurrent extraction, etc., and separation of the resulting liquid phases, the more unsaturated polar solvent phase is extracted with a parafii'n or like hydrocarbon, in liquid state, in order to further fractionate the oil in the polar solvent. The hydrocarbon serves to remove glycerides, usually the more saturated glycerides, from the polar solvent and to leave the major portion of the unsaponifiable components (antioxidants, inhibitols, sterols, etc.), together with a. quantity of the relatively more unsaturated components, including highly unsaturated glycerides and free fatty acids.

Typical hydrocarbons which are suitable for use, according to this invention, include liquid aliphatic hydrocarbon, including paraflinic and cycloaliphatic hydrocarbons, such as propane, butane, pentane, dodecane, hexane, heptane, octane, nonanes, propylene, liquid hydrocarbon mixtures such as naphtha and other analogous hydrocarbons, such as cyclohexane, methyl cyclohexance, cyclopentane and similar cycloaliphatics, in liquid state. Certain of such hydrocarbons are normally gases, but may be used when liquefied.

The amount of hydrocarbon which may be used may vary over a wide range and may be in the range of 1 to 10 parts by volume of hydrocarbon per part by volume of furfural or like polar solvent in the solution undergoing extraction. However, lower amounts of hydrocarbon may be used. As previously stated, the hydrocarbon removes more saturated glycerides and tends to leave more unsaturated glycerides, antioxidants, sterols, color components and other unsaponifiables in the polar solvent. For a given furfural or similar glyceride solution, the more hydrocarbon used, the more glyceride is removed. Consequently, the effect is to increase the degree of unsaturation (iodine value) of the unsaturated glycerides in the furfural.

So long as the concentration of unsaturated glycerides in the fraction remaining in the furfural or like solvent, remains large, with respect to the unsaponifiable and other components of low iodine value therein, the hydrocarbon extraction serves to increase the iodine value of the entire fraction remaining in the furfural. As the amount of hydrocarbon per unit of furfural is increased, the iodine value of the fraction remaining in the furfural increases to a maximum and then begins to decrease slowly. This is due to the increasing effect of components other than glycerides which do not exhibit, upon analysis, a higher iodine value. For example, a fraction which may exhibit an iodine value of 145 may comprise glycerides-having an iodine and to avoid emulsion formation. Generally, in value substantially above 145, and sterols and furfural solution, prior to treatment with hydrocarbon.

The degree of unsaturation (iodine value) of the glyceride fraction, which is extracted by thehydrocarbon, generally is between that of the feedvoil which is extracted with furfural or like solvent, and that of the oil fraction in the polar solvent. In certain unusual circumstances, the iodine value of this fraction may be lower than that of the feed oil. However, this is the case only when low amounts of hydrocarbon are used, and use of such small amounts, in many cases, is difficult from a practical point of view because separation of the phases becomes diflicult. Use of as little as to 8 percent by volume of hydrocarbon per volume of furfural, produces a naphtha phase having an iodine value greater than the feed oil, in many cases.

The graphs in Fig. 1 illustrate the change in the iodine value of the fractions obtained, using different quantities of hexane to extract, at 27 C., the fractions which are obtained by extracting, at 27 C., soybean oil having an iodine value of 130.7, with 2, 4 and 12 parts by volume of furfural, respectively.

In this instance, the soybean oil was fractionated batchwise 'by shaking one volume of the oil with 2, 4 and 12 volumes of furfural at 27 C. and permitting the phases to separate, after equilibrium had been attained. Following separation of the phases, the layers were separately drained ofi and fractions of each furfural layer were batch extracted with quantities of hexane. The circled points denote results obtained, using 0.015, 0.05, 0.10 and 1 volume, respectively, of hexane per volume of furfural in the extract.

Thus, when two volumes of furfural was used to extract one volume of soybean oil, the iodine value of the oil in the railinate or lighter phase was found to be 128.8, where as the iodine value of the oil in the furfural was found to be 141.6. This furfural phase contained 5.59 percent by weight of glyceride oil, 12.8 percent of the initial oil being in the furfural phase. When this furfural phase was extracted with 0.015 volume of naphtha per volume of furfural (approximately the smallest amount of naphtha which would give a separation of phases) the iodine value of the oil remaining in the furfural was 142.8 (an increase of only 1.2).-whereas the iodine value of the oil in the hexane was 130.6, which is substantially that of the feed oil. Extraction of further portions of the furfural phase with 0.05, 0.10 and 1 volume of hexane per volume of furfural, gave iodine values of the fraction in the furfural of 144.1, 145.6 and 140.5, respectively, and iodine values of the fraction in the hexane of 132.5, 135.3 and 142.2, respectively.

When soybean oil of 130.7 iodine value was extracted with 4 volumes of furfural, the oil in the raflinate (73.7 percent of the treated oil) had an iodine value of 127.0, whereas the oil inthe furfural extract had an iodine value of 140.6. The oil content of the furfural solution was 5.28 percent by weight. When this furfural extract solution was extracted with 0.015, 0.05, 0.10 and 1 volume, respectively, of hexane per volume of furfural, the iodine. value of the oil in the furfural phase was 140.7, 142.5, 143.8 and 143.1, respectively, and the iodine value of the oil in 14 the hexane phase was 128.2. 131.4. 133.6 and 139.2, respectively.

When soybean oil of iodine value 130.7 was extracted with 12 volumes of furfural per volume of oil, the solution contained 4.6 percent by weight of oil, 73.1 percent-of the total glyceride oil being in the furfural solution, and oil in-this furfural solution had an iodine value of 134.5, whereas the oil in the raffinate had an iodine value of 119,5. When the furfural solution, so obtained, was extracted with 0.015, 0.05, 0.10, 0.5 and 1 volume of hexane, respectively, per volume of furfural, the iodine value of the oil in the furfural was 134.6, 138.1, 140.1, 141.9 and 142.7, respectively, and the oil in the hexane was 121.3, 124.1, 127.6, 133.2 and 133.8, respectively.

It will be observed that when 1 volume of hexane was used per volume of furfural in the extract, obtained using 2 and 4 volumes of furfural per volume of soybean oil, the iodine value of the furfural'fraction was lower than that ohtained using less hexane. This is due to the fact that the non-glyceride components of the fraction are high and of relatively low iodine value, thus reducing the iodine value of the fraction even though this fraction is a concentrate of a glyceride having a high iodine number.

The results obtained using hexane, as set forth in the curve, are typical of the results which may be obtained from liquid hydrocarbons, generally.

Similar results accrue when linseed oil is treated. For example, linseed oil, having an iodine value of 179.9, was extracted at 27 C. with furfural in the proportion of 4 volumes of furfural to one of oil. The heavy furfural phase contained 10.52 percent by weight of oil, 55.4 percent by weight of the oil being in this phase. This extract oil had an iodine value of 188.

When this linseed oil-furfural phase was extracted at 27 C. with 0.015, 0.05, 0.10, 0.20 and 0.40 volume of hexane per volume of furfural,

the results were as follows:

figfig of Iodine Value Iodine Value Hexane to of Oil in of Oil in Furfural Hexane Furiural The flow diagram of Fig.2 diagrammatically illustrates the manner in which the process may be performed. The apparatus therein diagrammatically illustrated, includes columns I, II and III, the first of which is operated with a selective polar solvent, in order to fractionate the oil upon the basis of the degree of unsaturation. Oil, such as soybean oil, linseed oil, fish liver oil, cottonseed oil or the like, is stored in a container l0 and may be diluted with liquid hydrocarbon such as naphtha, hexane, etc., in an amount usually at least 5 to 20 percent by volume (based upon the oil) fed into the oil from container II by means of a feed line l2. The oil or the oil-hydrocarbon mixture is fed into the middle portion of column I by means of a feed line 13, at such rate as can conveniently pass through the column with phase separation. If desired, hydrocarbon may be introduced into a lower point ofthe column, several feet below the oil inlet, by means of feed line H from container II, This hydrocarbon may be in addition to, or in lieu of, the hydrocarbon added directly to the oil. The flow of liquids through the various teed lines l2, l3 and I4 is regulated by means of suitable valves I6 and I! of conventional design.

Selective polar solvent, such as furfural, which is relatively immiscible with the naphtha and is but partially miscible with the oil at the temperature of operation, is supplied at or near the top of column I by means or a feed line ",connected to a suitable source (not shown) of supply. The raflinate phase, comprising the more highly saturated glycerides together with the major portion of the break constituents of the oil (if they are present), passes out at or near the top of the column and is passed through line I9 to a still 2| for vacuum distillation of the solvents dissolved therein. The solvent free raffinate ofl passes out through line to storage or for further treatment. If desired, the raifinate may be sent to a fourth column (not shown) and refractionated in a manner similar to that described above. The solvent is drawn off through line 23.

The percent of the feed oil in the rafllnate may vary, but usually will be within a range of 10 to 80 percent, dependent upon the character of the oil treated and the product desired. If it drops too low, some portion of the break" may tend to remain in the extract. The percent of ratflnate can be controlled by varying the solvent ratio, the temperature, the amount of naphtha in the feed oil or the amount of naphtha or oil reflux feed.

The extract solution comprising as its main constituents most of the solvent saturated with the more highly unsaturated glycerides, passes out through line 24 or near the bottom of the column and, optionally, may pass in its entirety through line 25 directly to the top of column II, or a portion may pass to a still 26 where some or all of the solvent is stripped off and returned through a line 21. for re-use in the system. The partially or completely stripped oil is drawn off through line 28 and may all pass (along with some oil and solvent by-passed through line 25) through line 29 to the top of column 11. However, usually it is preferable to return a portion,- e. g. 10-90 percent of the extract oil as a reflux through line 3| to the lower portion of the column I. Line 25, between line 24 and line 29, provides a by-pass for the still 26. Conventional valves 33 in the lines 24, 25, 29 and 3| permit the control of the flow of the extract phase in such manner as to bypass any desired portion of the oil about still 26, or to enable the stripping and refluxing of any desired portion. A convenient mode of operation is to evaporate the extract solution to such a degree that approximately to A, of the furfural is removed before the solution is fed to column II.

Liquid hydrocarbon, generally within a range of 1 to 10 parts by volume per part of original oil, is fed from container 34 to the lower portion of the column II by means of a feed line 26, in order countercurrently to wash the extract oil from column I. In this column the hydrocarbon, containing most 'of the extract oil from column I, passes out through line 31 at the top,

16 the oil, containing hydrocarbon, may be returned as a reflux through an optional line 39 to the lower portion of column I. If desired, the ratio of hydrocarbon to oil in such reflux may be reduced by passing the reflux through a suitable still 4|, connected in the line. Glyceride ex tracted by the hydrocarbonis obtained through line 42 from the still 38.

The extract from column 11, comprising the polarsolvent having dissolved therein most of the free fatty acids, highly unsaturated glycerides, coloring matter, unsaponifiables, vitamin A or E and the like, passes out through line 43 to a suitable stripping device such as a still 44 where the solvent may be removed. The extract from the still passes oil? at 48 to storage or for further treatment in order to fractionate out the various components. The solvent from the distillation may be returned from the still through line 41 for re-use or for storage, as may be desired.

In some instances, it may be desirable to wash the hydrocarbon solution of oil passing out through line 31 from column II with additional polar solvent, such as furfural. This wash may be of low volume, e. g. 1 to 1 on the basis of the oil fraction and is designed to reduce the free fatty acid content. This may be accomplished in column III into the bottom portion of which it is discharged by feed line 48, branching from line 31. Valves 49 control the flow of naphtha and oil to column III and still 38. Furfural, or other polar solvent immiscible with the hydrocarbon, is fed into the top of the column by line 5|, and the extract of solvent and acids or other furfural soluble impurities from the hydrocarbon-glyceride solution passes off through the line 52. The naphtha and the glycerides, together with vitamin A or other oil soluble vitamins (if present) pass oil? through line 53. Of course, the solutions from column 111 can be vacuum distilled to eliminate the solvents, thus providing a refined oil fraction, free of or low in break, color, odor, inhibitols, free fatty acids and the like. The polar solvent extract from column 111 is a concentrate of all the latter constituents remaining in the polar solvent.

The following tables contain the operating conditions and product data for extracting and refining cottonseed oil, soybean oil, and linseed oil in a system such as that above described. In these runs, column I was operated with naphtha saturated furfural, column II was operated with naphtha to extract the glycerides from the furfural extract of column 11, and column III was operated with naphtha saturated furfural as an extra wash for the naphtha solution from column II.

RUN NO. 1COTTONSEED OIL Oransrmc Connrrrons Column temperatures I 118 FL II 82 F. III

Column feedsasraooo possible to so operate asto obtain a refined extract of substantially increased iodine value dissolved in naphtha from column II. In either Column feeds Oil feed to column I, 12% by weight naphtha Furfural feed to column I, 8 to 1 by volume based on oil feed rate Oil reflux to column I. 1.1 to 1 by volume based on oil feed rate- Naphtha reflux to column I, non I Naphtha feed to column II, 5 to 1 by volume based on oil feed rate Product data Furiurel Furfural o 1 N hth Product "53 gg Eggs? Taken from line 37 19 43 Yield a2. 2 4o. 6 1. z 150.3 111.1 139.2 Acid Value 0. as .18 .12 32. 0

RUN NO. 3--LINSEED OIL Orsnermc CONDITIONS Column temperatures I 95 F. II 66-71 F.

- Column feeds Oil feed to column I, 12% by weight naphtha Furfural feed to column I, 6 to 1 by volume based on oil feed rate Oil reflux to column I, .67 to l by volume based on oil feed rate event, a solution of fatty acids, inhibitols, tocopherols, and sterols together with a little glycerlde oil is obtained in the by-product from column 11. l

The following tabulates dimensional and operating data employed in certain large scale runs, using naphtha which is a liquid petroleum 'hydrocarbon mixture of heptanes, octanes, nonanes and decanes:

A. Primary column I 1. Total height, 84 ft., 8 in. 2. Packed height, 66, ft., 3 in. 3. Clearing sections.

a. Top, 3 ft., 6 in. 1). Bottom, 8 ft., 3 in. j 4. Diameter of column, 22 in.

5. Feed positions (height from bottom of column) a. Furfural, 80 ft., 10 in. b. 011, 32 ft., 8 in. c. Naphtha, 7 ft., 10 in. 6. Phase interface position-from 23 ft., 5 in. to

30 ft., 5 in. from bottom of column. 7. Condition of operation column I a. Rates Feed Gala/hr. g zg fi Furluml 250-350 5-1 Oil -70 Naphtha reflux 15-21 0. 3-1

b. Temperatures (1) Top of column, 107 to 115 F.

(2) Bottom of column, 103 to 108 F. (3) Furfural feed, 108 to 115 F. (4) Oil feed, 105 to 110 F. (5) Naphtha reflux feed, 104 to 107 F.

B. Secondary column II Total height, 46 ft., 0 in. Packed height, 39 ft., 0 in. Clearing sections a. Top, 3 ft., 0 in. b. Bottom, 3 ft.', 0 in. Diameter of column, 15 in. Feed positions (height from bottom of column) a. Extract solution, 43 ft. b. Naphtha, 3 ft. 6. Packing used, 1 in. Raschig rings 01th carol-1 7. Interface positionfrom 38 ft. to 43 ft. from Naphtha reflux to column 1. none 50 Naphtha feed to column II, 4 to 1 by volume based on oil feed rate Product data Furiural Furfural Product 1 Extract g f Extract No. 1 a N o. 2

Taken from line"-.. 37 19 43 Yield "per cent-. 59 38.4 2.6 60 Iodine Value 172 196. 6 146. 5 172. 8 Acid Value 2. 33 l. 3 l. 2 30. 0

In these three runs the extract solution from column I was pumped directly to the top of column II with no intermediate distillation.

The process described may be operated primarily for refining crude or raw oil by taking out break constituentssuch as phosphatides and lecithin in a glyceride railinate from column I and refined extract oil in a naphtha wash from column II. In such process it. is desirable to make the raiiinate of column I as small as'possible consistent with adequate separation ofthe break from the furiural extract. It 15 also bottom of the column 8.,Conditions of operation column II a. Rates Ratio to Feed 011 Feed Extract solutionm. Naphtha all from primary column I b. Temperatures (1). Top of column, 64 to 78 F. (2) Bottom of column, 58 to 65 (3) Extract solution, 65 to 80 (4) Naphtha, 58 to 65 F.

C. Quality of feed oils used The oils used in these runs were degumrned soya 011 whose constants fell within the following ranges:

Iodine value, 129.8 to 137.3 Percent free fatty acid, 0.28-0.99 Color (Gardner), 9% to 10% Percent chlorophyll, .00014-30034 Percent carotene, .0041-.0068

D. Quality of products produced Finiural Furiural Extract No. 1 m

Per Cent Yield 26. 2-37. 8 01. 3-72. 6 0. 7-1.3 Iodine Value 151. 4-163. 123. 6426.3 137. 9 Per oenti'reefatty acid 0.20.8 Ali-.075 16.2 Per cent tocophernl 2. 6 Per cent unsaponiiiable matter 7. 89

It should be understood that the above examples are purely illustrative and are capable of many variations. For example, less unsatu rates may be extracted from the furfural by hydrocarbon, thus leaving 1 to 25 percent of the oil in the furfural. Moreover, more or less oil may be extracted into the furfural in the first extraction according to the results desired.

Other solvents, such as ethyl acetoacetate or others listed above may be used in lieu of furfural. The invention is applicable to glyceride oils generally and is particularly applicable to those lard, etc.

Moreover, the process may be applied to treatment of seed meals or other compositions containing these oils. In such a case, the polar solvent may be used to extract the seed meals, etc., and thus to produce the furfural or like solution to be extracted with hydrocarbon as herein contemplated.

The various products obtained are capable of numerous uses. The more saturated fraction from the first extraction may be used to produce foods and soaps.

The fraction obtained from the hydrocarbon may be used as a drying oil or as a raw material for production of foods. The fraction obtained from the furfural second extract may be further extracted with hydrocarbon to separate unsaturated glycerides and fatty acids from the sterols etc. and then used for drying purposes. Valuable sterols, such as stigmasterol, vitamin E, etc., may be recovered from this product by convenient methods.

This application is a continuation-in-part of my applications, SerialNo. 251,340, filed January 17, 1939, now Patent No. 2,200,391, and Serial No. 608,119, filed August 1,1945.

Although the present invention has been described with particular reference :to the specific.

details of certain embodiments, it is not intended that such details shall be regarded as limitations upon the scope of the invention, except insofar as included in the accompanying claims.

I claim:

1. In a method of recovering a glyceride from a furfural solution obtained by extraction 0i unsaturated glycerideoil which contains glyceridea of difierent degrees of unsaturation with.

furfural to separate a relatively more unsaturated fraction in furfural from a relatively less unsaturated fraction, the improvement which comprises extracting the furfural solution with a liquid aliphatic hydrocarbon to pull out relatively more saturated glycerides therefrom and to leave in the furfural an oil fraction including relatively more unsaturated glycerides.

2. The process of claim 1 wherein the oil is soybean oil. I

3. The process of claim 1 wherein the oil is linseed oil.

4. In a method of treating an oil comprising a mixture of glycerides of different degrees of unsaturation, the steps which comprise extracting the oil with suflicient furfural to provide a liquid furfural solution which contains relatively more unsaturated glycerides and a second'liquid phase which contains relatively more saturated glycerides, separating the furfural phase, removing a substantial portion of the furfural therefrom and extracting the resulting liquid residue with a liquid aliphatic hydrocarbon.

5. In the process of selectively fractionating glyceride oil comprising a mixture of diiferent degrees of unsaturation, by contacting the oil with an organic solvent which contains at least one of the activating groups listed in Table A, the total number of carbon atoms in the molecule of solvent not exceeding the sum permissiblefor the activating groups as determined by the table, which solvent at a low temperature is immiscible with the more saturated components of the oil, the temperature of treatment being above about minus 20 0., the ratio of solvent and the temperature being below that of complete miscibility with the glycerides and separating the two phases thus formed while both are in liquid state, one being relatively poor in unsaturated glycerides and containing some of said solvent, the second comprising said solvent and being relatively rich in unsaturates, the improvement which comprises extracting the second solution with a liquid aliphatichydrocarbon to pull out relatively more saturated glycerides therefrom and to leave in the organic solvent an oil fraction including relatively more unsaturated glycerides.

6. In a method of recovering a glyceride from a polar solvent solution obtained by extraction of an unsaturated glyceride oil which contains glycerides of different degrees of unsaturation with a polar solvent which is a selective solvent for the more unsaturated glycerides of the oil to separate a solution of a relatively more unsaturated oil fraction in the solvent from a relatively less unsaturated fraction, the improvement which comprises extracting the polar solvent solution with a liquid aliphatic hydrocarbon to pull out relatively more saturated glycerides therefrom and to leave in the polar solvent an oil fraction including relatively more unsaturated glycerides.

7. A process of treating natural glyceride oils comprising mixtures of glycerides of fatty acids of different degrees of unsaturation, free fatty acids, break constituents and unsaponifiables in order to separate them into fractions, which process comprises extracting the oil in a column with furfural to obtain two liquid phases, one comprising a rafdnate enriched in highly satu-' rated glycerides and "break and containing dissolved furfural and an extract phase comprising oil enriched in more highly untsaturated glycer- 21 solved in furfural, then in a second stage extracting the latter phase with naphtha to remove the glycerides and to leave in the furfural a concentrate of fatty acids and unsaponifiables unsaturated glycerides and a second liquid phase which contains relatively more saturated glycerides, separating the furfural phase, removing a substantial portion of furfural therefrom and extracting the resulting liquid residue with a paramn liquid hydrocarbon.

9. A method of treating an unsaturated glyceride oil which contains glycerides of different degrees of unsaturation which comprises extracting the oil with organic polar solvent incompletely miscible therewith which solvent is a selective solvent for the more unsaturated glycerides of the oil, to provide a liquid extract containing unsaturated glycerides dissolved in said organic solvent, separating said extract, removing a portion of the solvent from the extract and extracting the liquid residue with a parafiin liquid hydrocarbon.

10. A method of treating an oil which comprises a mixture of glycerides of different degrees of unsaturation which comprises extracting the oil with furfural to provide a liquid furfural extract which contains unsaturated glycerides and oils which contain fractions of different degrees of unsaturation, which comprises counter-currently contacting flowing streams of a selective polar solvent and glyceride oil in an extraction zone, withdrawing polar solvent extract thus produced, contacting the extract with liquid aliphatic hydrocarbon whereby to produce a liquid aliphatic hydrocarbon fraction and a second liquid polar solvent fraction, and introducing the liquid hydrocarbon fraction into thefirst extraction zone.

15. A method of treating soybean oil, which comprises counter-currently contacting flowing streams of iurfural and soybean oil in an extraction zone, withdrawing furfural extract thus produced, contacting the extract with liquid aii phatic hydrocarbon whereby to produce a liquid aliphatic hydrocarbon fraction and a second fura second liquid phase which contains relativelymore saturated glycerides, separating the iurfural solution from the second liquid phase removing one-half to three-fourths of the furfural from hydrocarbon immiscible with said solvent whereby to produce a liquid hydrocarbon fraction and a second polar solvent fraction and passing oil 01' the hydrocarbon traction into the first extraction zone. 5 I

' 12. The process of claim 11 wherein at least a portion of the hydrocarbon is vaporized from the hydrocarbon traction, prior to passing to the first extraction zone.

13. A process or preparing a concentrate comprising unsaponifiable matter comprising sterols and tocopherols, from glyceride oils including them in low concentration, which process comprises flowing the oil into an intermediate portion of an elongated extraction zone, introducing turi'ural above the point of introduction of oil, introducing a reflux of naphtha below the point of introducing the oil, withdrawing raffinate solution near the top 01' said extraction zone and extract oil in furiural below the point. 01' introduction of the naphtha, then backwashing the extract solution with naphtha to extract out most of the glycerides and to leave in solution in the Mural fural extract, and introducing the liquid hydrocarbon fraction into the first extraction zone.

16. A method of treating unsaturated glyceride oil, which comprises counter-currently contacting an upwardly flowing stream of glyceride oil with a downwardly flowing stream of furfural in an extraction zone, withdrawing furfural extract thus produced from a lower portion of said zone.

ing the liquid hydrocarbon fraction into said extraction zone.

' solvent extract, contacting the extract with liquid 18. A method of treating unsaturated glyceride oils which contain fractions of diflerent degrees of unsaturation, which comprises introducing glyceride oil into an intermediate point in an extraction column, introducing selective polar solvent intothe column at a point above the oil inletand liquid aliphatic hydrocarbon into the column at a point below the oil inlet whereby oil and hydrocarbon flow countercurrently to the polar solvent, and withdrawing an oil rafilnate tromthe upper portion.and a polar solvent solution of the more unsaturated glycerides of the oil from the lower portion of the column from which polar solvent solution the liquid aliphatic hydrocarbon has pulled out relatively more saturated glycerides.

19. The processor claim 18 wherein thepolar solvent is tux-rural.

STEPHEN E. manna.

REFERENCES crrEn The following references are of record in the die of this patent:

rmrran sums PATENTS Number Name Date OTHER REFERENCES Ruthrufi et al., Transactions oi American Institute of Chemical Engineers, August 25, 1941. Page: 649-867.

Ruthrufi et al. Aug. 15. 194

Claims (2)

1. 4. IN A METHOD OF TREATING AN OIL COMPRISING A MIXTURE OF GLYCERIDES OF DIFFERENT DEGREES OF UN SATURATION, THE STEPS WHICH COMPRISE EXTRACTING THE OIL WITH SUFFICIENT FURFURAL TO PROVIDE A LIQUID FURFURAL SOLUTION WHICH CONTAINS RELATIVELY MORE UNSATURATED GLYCERIDES AND A SECOND LIQUID PHASE WHICH CONTAINS RELATIVELY MORE UNSATURATED GLYCERIDES, SEPARATING THE FURFURAL PHASE, REMOVING A SUBSTANTIAL PORTION OF THE FURFURAL THEREFROM AND EXTRACTING THE RESULTING LIQUID RESIDUE WITH A LIQUID ALIPHATIC HYDROCARBON.
2. 18. A METHOD OF TREATING UNSATURATED GLYCERIDE OILS WHICH CONTAIN FRACTIONS OF DIFFERENT DEGREES OF UNSATURATION, WHICH COMPRISES INTRODUCING GLYCERIDE OIL INTO AN INTERMEDIATE POINT IN AN EXTRACTION COLUMN, INTRODUCING SELECTIVE POLAR SOLVENT INTO THE COLUMN AT A POINT ABOVE THE OIL INLET AND LIQUID ALIPHATIC HYDROCARBON INTO THE COLUMN AT A POINT BELOW THE OIL INLET WHEREBY OIL AN HYDROCARBON FLOW COUNTERCURRENTLY TO THE POLAR SOLVENT, AND WITHDRAWING AN OIL RAFFINATE FROM THE UPPER PORTION AND A POLAR SOLVENT SOLUTION OF THE MORE UNSATURATED GLYCERIDES OF THE OIL FROM THE LOWER PORTION OF THE COLUMN FROM WHICH POLAR SOLVENT SOLUTION AND LIQUID ALIPHATIC HYDROCARBON HAS PULLED OUT RELATIVELY MORE SATURATED GLYCERIDES.

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