US2352546A - Solvent extraction of oils and acids - Google Patents

Description

June 27, 1 944.

J. D. JENKINS SOLVENTYEXTRACTION OF OILS AND ACIDS Filed May' 13, 1940 highly unsaturated or Patented June 27, 1944 I 2,352,546 SOLVENT EXTRACTION OILS AND ACIDS John D.

Jenkins, Forest mus, ra., assigner 'to Pittsburgh Plate Glass County. Pa., a. corporation Company, Allegheny of Pennsylvania Application May 1.3, 1940, Serial No. 335,006 11 Claims. (.Cl. 260-419) The present invention relates to rening ci glycerides of fatty acids andthe free acids derived therefrom, and it has particular relation to the refinement by liquid phase extraction with a polar solvent of such glycerides and acids consisting of components .which substantially differ urated or less actively unsaturate'i` material in which is dissolved a small amount of the solvent.

These two liquid phases may be separated by from each other by reason of a difference in degree of unsaturation or activity of unsaturation, or in chain length of the molecule.

One object of the invention is to provide a process of removing a component from glycerides and free fatty acids of glycerides by extraction with av selective solvent, which process does not produce objectionable reactions that impair the value of one or more of the components of the material treated.

This and other objects of the invention will be apparent from consideration of the following specication and the appended claims.

In copending applications Serial No.` 144,315, now issued'as Patent 2,200,390 led May 22, 1937 and 251,340, now issued as Patent 2,200,391 tiled January 17, 1939, to Stephen-E. Freeman are disfree acids of glycerides into components by liquid phase extraction with furfural, furfuryl alcohol and other active or polar solvents, which include various activating groups such as OH, COO, NO2, P04, and numerous other groups. These active solvents are found to have a substantially higher ailinity for unsaturated glycerides and acids derived from such glycerides than for the more saturated or otherwise less active glycerides or acids. Correspondingly the more actively unsaturated glycerides Iand free acids thereof exhibit a substantially greater solubility in the solvents than the more completely saturated glycerides and acids or the unsaturated glycerides which by reason of the arrangement of groups are less active.

Under the provisions of the foregoing applications, oils and acids Acorfsisting of mixtures of more completely saturated and less'completelysaturated or actively unsaturated components are treated with anactive or polar solvent to dissolve out a fraction enriched in the more un. saturated'or actively unsaturated componentsl and correspondingly to leave a rafnate of oil or acid which is enriched in the relatively highly saturated components, together with a certain `amount of the active solvent dissolved therein.

The mixture can then'be separated into liquid appropriate means, and by distillation or other suitable treatment, the solvent may be removed therefrom, leaving the desired fractions of oils or acids.

Although it was thus possible to separate glycerideoils or the acids derived therefrominto fract ns according to the degree orthemolecula arrangement of unsaturation 'the unsaturated fraction did not always exhibit the characteristics desired in it. to the degree that might have been expected. VFor example, where the fraction was to be employed as av paint or varnish vehicle, it was often found that the extracted fraction dried slowly even though its iodine value soV ` closed processes of separating glycerides and also phases,lone consisting of the solvent andthe fraction richin unsaturates or active unsaturates and the other consisting of the more Satwas relatively high. Food products might be discolored.

It has now been discovered that this peculiar behavior is apparently due to some obscure chemical reactions within the oil or solvent or possibly between the two. It has further been discovered, thatl if an unsaturated'glyceride or the free acids therefrom is extracted with a suitable selective-polar solvent such as furfural, while it is blanketed or covered with an inert gas, such as carbon dioxide, ilue gas, or nitrogen, the tendency is substantially eliminated. From this it may. perhaps, be deduced that the peculiar beto the action of atmospheric oxygen which is blanketed out or excluded by the inert medium covering the oil.

In the application of the principles of the invention various methods of extracting the oil with solvent may be employed. For example, extraction may be conductedas a simp batch operation by mixing the oil and solven under a blanket .of inert gas in a suitable container,

`havior of the extracted oil is in some way duey then allowing the resultant fractions-to separate into liquid layers anddrawing o .the layers into separate containers for removal of the solvent. However, the preferred method 'involves countercurrent extraction in columns in which all -free surfaces of the glycerides or acids ,are protected by a blanket of inert gas. The gas may be almost any inert gas, such, as carbon dioxide; however, nitrogen or nitrogen containing gases, Vsuch as ilue gas, are preferred.

f A suitable embodiment of apparatus for .countercurrent extraction is illustrated in the accom- Danying4 drawing in which the single sure is a diagrammatical or schematic view -oi' a suitable conduit 28 discharges solvent is the .heavier inlet foi the solventembodiment of apparatus for use in' practice of the invention.

In the drawing like numerals refer to like parts throughout.

The apparatus as disclosed includes an extraction tower o'r column` III which may be packed with Raschig rings or Berl saddles, etc.. and may be of substantially any diameter dependent upon the quantity of glycerides or acids to be passed f therethrough. The height of the column preferably is approximately within the range of 30 to 50 feet. However, these limits may be sul) stantially exceeded, if so desired. It also is provided with a. cover or jacket II,'which, as shown, may be formed in separate sections, such as I2, I3 and I4, which may be of substantially any number dependent upon the gradation of temperature within the lcolumn which it may be desired to maintain. The sections may -be supplied through eaclr section of the jacket individually or to cause the iluidto flow from the outlet of one section to the inlet of the adjacent section as miLv be desired.

Glyceride oil or free acids of glyceride oils may be stored Vin a clod container 2I, which, may be provided with a jacket 22 by means of which it may be maintained at any desired temperature.

' Oil from the container nows through conduit 22 and is forced by suitable pump 24 into an intermediate portion of the column III, preferably at a distance of about 12 feet from the bottom of the column.

solvent gradually extracts a fraction which is rich in the more soluble component, such as the more unsaturated or actively unsaturated glycerides and acids, or the glycerides or acids which are more solublev by reason of differences in chain length in the molecule. The less soluble components of the oil do not dissolvein the solvent, at least not completely but do tend to take up a certain amount of the solvent. In a zone near or slightly above the inlet for the conduit 28 the less soluble component or raffinate will collect as a body 36 of insoluble glyceride oil, or' oil acid, which is free of the extract phase and which is saturated or substantiallysaturated with solvent and may be drawn oil througha conduit 31, that leads to suitable apparatus (to be later described) for the separation of the solvent dissolved therein. Inert gas is admitted through conduit 31a to blanket the railinate.

The undissolved solvent with the vextract phase therein ultimately separates out inthe bottom of the column as a distinct layer or fraction 39', which may bedrawnoi through a conduit 4I, that extends upwardly a sufficient height to admit of hydrostatically balancing of the liquid therein against the liquid contained in the extraction column I0.

Since the solvent and the oils are of different specific gravity, and since Eunder varyirm conditions there will be a tendency for the relative amounts thereof in the column III to vary somewhat, it isrdesirable to provide at the upper exl tremity of the conduit 4I a section 42 which can be elevated or lowered to accommodate for the variations, thus making it possible to assure that the various strata in the column I0 are approximately at the desired levels. 'I'he upper exf tremity of the adjustable section 42 is provided with a head 43', in which the pressure may be atmospheric. This head is filled with inert gas through conduit 42a.

Solvent for the extraction may' be stored in ,a container 2l and is fed through conduit 2l to a pump 21, connected to conduit 28 in a heater jacket 2l, having atjone extremity an inlet II for heated fluid such as water and at the opposite extremity an outlet 22 for the waste fluid. In some instances it may be desirable to add water or other fluid at least partially miscible with the solvent, but immiscible with the material to be refined, in order to reduce miscibility thereof in the solvent. Such addition may be made through conduit 32a. The upper extremity of ofthe column Il at a short distance' froml the top thereof. Inert gas may, also. be supplied to container through conduit #2b. v A

It will be apparent that by reason of thedifference inspeciiic gravity of the solvent and the glyceride oil or the acids derived therefrom the' will tend to ilow counter-currently to each other. Assuming that the component it will descend while the undissolved oil will rise. Y Therefore, in a zone 33 extending approximately from the down some distance below the 'inlet for the glyceride oil orthe acids, there will be a-mixture of countercurrently flowing components. Also, the oil will be carried by the solvent a certain distance below .the oil inlet. In the sone of countercurrent flow of selective solvent and oil or acid it will be apparentthat there is very intimate contact, and the selective two liquids with respect into the-upper extremity 'I'he solvent charged with extract discharges through this head to a conduit 44 leading to the upper extremity of a flash vaporizing column 40, provided with a jacket 41 to which steam at a pressure of 20 or 30 pounds per square inch ory other heat exchange mediu'm may be admitted through conduit 48 and from which spent medlum is discharged through conduit 49.. The oil is delivered into column 4l as a shower or spray that falls into a spray trap 5I in which the droplets of separated oil, largely freed of the solvent, are collected. The column 46 preferably 'is maintained under partial vacuum, e. g. under a pressure of 100 or 300 m. m. Vaporization of solvent in the column is valmost instantaneous. The solvent vapors pass oil! from the trap through conduit 52 to `a condenser 53, which in turn discharges through conduit 5,4 and pump 58 back to the solvent container 2l.

The .extract separated from the vaporlzed sol-l vent in the trap is discharged through conduit 51 to a surge tank it, having inlet Bl for inert gas. From the latter, it, or any suitable portionthereof, is dischargedthrough conduit llrto stripping apparatus (to be described later) for removal of the last traces of the solvent contained therein. A portion of the extract with the small amount of solvent therein is discharged through conduit 42 to pump which forces it'through conduits 4 back'into the column Il at a point preferably below the feed oil inlet, but slightly above the upper limit ofthe separated solvent phasein the lower portion of theicontainer. The concentra,-

:conduit 8l. y Column 1B preferably is packed with an inert ,material such as Raschig rings, Berl saddles or other packing material designed to check the 'discharged into he une 12. The remate cu tion'of the more soluble component is thus increased in a zone adjacent to solvent-extract layer and this results in the separation of more of theless soluble component from the oil so that ultimately an extract is obtained, which isricher in the more soluble component and poorerin the less soluble component, than would otherwise be obtained. Substantially any ratio of the extract, for example 10 to 90% of the extract may be recycled.

As previously stated the inlet for the recycled oil is slightly above the level of the separatedl solvent and preferably it is at such distance below the level of the inlet for theA oil that the recycled oil, as it passes upwardly through the solvent, will reach approximately the same composition as the feed oil from the container 22. Assuming that furfural is employed as the selective solvent the distance between the inlets of the feed oil and the recycled oil'may be approximately l2 feet. The distance between the inlets for the feed oil and the solvent may vary over a substantial range, but preferably is about l to 35 feet.

1f preferred, separation of the extract from the A solvent may be eected by addition of water, e. g. 3 to 15% of water or other non-solvent. The vaporizer 46 may then be eliminated or may be bypassed by conduit 65 interconnecting conduit 44 and conduit 5l. Separation of the extract may be eiected in the surge tank 58 by addition of .water through conduit 65a.

The apparatus for removing the dissolved solvent from the rainate includesla vaporizer column 66 into the upper extremity of lwhich the conduit 3l discharges the railinate as av spray. 'Ihe column is provided with a heating packet 61, which is supplied with steam or. other heated iiuid by means of conduit 88 and the spent iluid is discharged from the jacket through y'conduit 69. The pressure within the column 66 like that in column 46 is subatmospheric-e. g., about 100 to 300 m. m. of mercury and Aevaporation of the most of the solvent is almost instantaneous. -At

now freed of solvent is discharged through conyduit 84 at the bottom of the column and is passed to storage or is passed on for further treatment,

for example, for an additional extraction in further stages of apparatus. Such stages obviously may assume substantially th form of the apparatus herein disclosed and by such treatment it is possible to remove an additional fraction or fractions of more soluble component from the rainate. y

The conduit 6l carrying the more soluble or extract components of the glyceride oil or the its lower extremity the column discharges into a conventional Spray trap lli, in which the droplets of railinate from which much of the dissolved solventhas been evaporated are collected.

The solvent freed of raiiinate and in vapor acids thereof, namely the more unsaturated components, is disharged into a second stripping v column 86 substantially'corresponding in construction tothe column 'i6 and having a jacket 81 for steam or other iluid as previously vdescribed in connection with the column 16.' The column is also packed as indicated at `88 and is supplied with steam or inert gas through conduit 09. The steam or gas charged with solvent discharges fromthe upper extremityoifV the column through conduit 9i, which also dischargesinto the vapor line 13 and passes on to suitable apparatus for separation' of the solvent from the water vapors or gas. 'Ihe component of the oil which initially is dissolved in the solvent and which is liberated in the column 88 is discharged from the bottom of the latter through a conduit S2, is either passed to storage or is subjected to further treatment, for exaniple, to further fractionation in additional stages of apparatus in order more completely to separate out any saturated or less soluble 4components which may be carried therein. In this way a fraction which is very rich in unsaturates. or other component, which is selectively soluble in the solvent employed, may be obtained.

In the practice of the present invention 'substantially any of the lselective solvents disclosed glycol diacetate, ethyl oxylate, methyl cellosolve state is discharged through'a conduit 12, to a line 73 leading to a condenser and source of vacuum (not shown). The ramnate, separated from the vapors in the trap 1| and still containing -some solvent, isdischarged through conduit i4 into the upper extremity of a strippingv column 16, which column is provided with a -jacket Il supplied with steam or other heated nuid through conduits 18, having a connection to a supply line 19. Where steam is employed the pressure is .preferably about lbs. per square inch corresponding to about 280 F'. The spent iluid is discharged from the bottom of the jacket through descent of the oil and to cause it to be spread out into thin' lms presenting large surfaces.

Steam or other distilling medium is introduced charged with solvent through conduit 83 and is 76g acetate and others. 'Ihe ratio of solvent to oil may vary over a broad range extending for example of 1 to 1 all the way to 10 to 1.

i The solvent system may include a solvent iml miscible therewith, such as a paraillnic".hydro carbon having la boiling point above thatI of operation of the extraction system. Isooctane is va good example of such solvent. It may lbe-used in a range of from about 1/2 to 5 parts for each part of polar solvent. It often asists in separating the less active componentsv oi' the oil or acids by dissolving them out of the'polar solvent.

Among'the glyceride oils that may be fractionl ated are included bodied or unbodied linseed oil.

marineoilasuch as -menhademsardine and whale oils, soya bean oil, perilla oil, Vcottonseed oil, com oil, sunflower oil, peanut oil, olive oil, lard, tallow and the like. These oils comprise mixtures oi' glycerides of varying degrees of satu-`l ration andfractionation thereof is eifected-by the selective solvent by reason of the'higher de.

gree of solubility of 'the more unsaturated components'in the selective solvent.l The oils and free fatty acids may be deaerated prior to-extraction, by heating them to C. or thereabout and simultaneouslyqsubjecting them-to vacuuml -ortoblowingwithnitrogenorotherinertgasyThe'oilsmay-be raw oilsormaybealkallrelined, or may be reilned by other methods. 'I'hey mmalso, be bodied or unbodied.

. It'has also been found that certain of the oils. suchas ,palm oil and coconut oil, which include intheirqcompositions glycerides of fatty acids of varying chain length can similarly be separated into fractions,l because of the greater solubility ofv the short chain acid glyeerides in the selective solvent. For example, coconut oil which comprises essentially mixtures o fglycerides of straight chain aliphaticacids of a chain lensth from 6 or 8 up to 1 8 or more may beseparaied into fractions which are greatly enriched in speciilc glycerides.

`*It is of course obvious that the apparatus and process as herein disclosed is-also applicable to the fractionation .of mixtures of relatively saturated and relatively unsaturated fatty acids derived from the oils herein disclosed.`

Almost any inert gas, such as carbon dioxide, carbon monoxide, nitrogen, or a nitrogen containing sas such as flue gas may be employed as The gases may be preliminarily dried in order toprevent hydrolysis of the solvent in the system.' If the solvent does nottendto hydrolyze, suchsdrying is'- not usually necessax'yf, The inert gases not; only prevent objiectionable chemical reactions;4 but they also reduce nre hazards in the system, especially where immiscible hydrocarbons-are present. They also help to reduce objectionable discoloration of the fractions ob- `Under,some conditions it may be possible to get' substantially the same effects-as obtained by blanketing the liquids in-the apparatusby-so constructing ,it as to exclude all contact of the .iiuidswith air.

The extracted oils as obtained from linseed, soya bean. marine oils, perilla oil and others containing substantial amounts of slycelldes su s ceptible of air drying are excellently adapted for use-as drying oils in the fabrication of paints and tively more soluble in a furane compound.- which process comprises providing a mixture of a furane compound and the material under a blanket oi inert gas and thenseparating the mixture, into liquid phases, one comprising the furane'compound saturated with the more soluble component and the other comprising the less soluble component saturated with the furane-compound.

-2. A process as defined in claim l in which the furane compound and mixture to be separated into components are tlowed countercurrently in a tower and the Iliquid phases are collected respectively at the top and bottom of the column, separated by the vintervening mixture of countercurrently flowing materials.

3. A process as'deilned in claim 1 in which the furane compound isfurfural and the inert gas consists mainly of nitrosen.

4. A process of separating into components a mixture selected from a class consisting of a mixture of a plurality oi' glycerides and a. mixture of a, plurality of fatty acids derived from said glycerides, said mixtures each including component which is relatively diilicultly soluble and a component which is relatively more soluble in a furane compound. which process comprises countercurrently i'lowing a furane compound and theL material to be separated into components in a tower, collecting as separate liquid phases a soluti t n of the furane compound in the less soluble com s 2- t and a solution of the more soluble component the furane compound drawing off the |latter phase through 'a stand-pipe balancing the liquids in the columns, the material in the column and the stand-pipe under a blanket of inert gas.

5. A process of separating into fractions a material selected from a class consisting of Glycerlde oils and free acids of said oils, one fraction being of a relatively high degree of saturation and a second fraction being of a relatively high degree of unsaturation, which process comprises contacting the mixture with a furane compound solvent for the unsatmated component which has relawhich comprises the first component saturated By application of the extraction process extracted oil having good drying properties and smiiietly free of obieconble mme* auch as free acids, anti-oxidants break producing constituegtsand the like canA be obtained without ecting' the oil to severe treatment with acid f In the fabrication of paints and varnishe'sthe Vconventional pigments, colors, thinners 'and the like are added as with conventional drying oils. For example, titanium oxide, lithopone` and other pigments may be added in amounts of 5 to 90%. Turpentine or any other volatile thinner may be also added in an amount of 5 to 90%. more or less. based upon weight.

The forms of the inv tionherein disclosed constitute only a part o the possible applications ofthe invention. It will be apparent that numerous modifications can be made therein without departure from the spirit of the invention or the scope of the claims.

i. A process of separating into components aj mixture selected from a class consisting of a* of a plurality of glycerldes and a mixture consisting of, `a plurality of 'fatty acids" derived from said glycerides, said mixture including a component which -is relatively diiiicultly soluble and a component which isl relawith the furane compound and the second of which isv the furane compound saturated with the second component, said extraction being effected in the absence of oxygen.

6. A process oi'. separating into fractions a material selected from a'class consisting of glyceride oils and free4 acids of said oils, one fraction being of a relatively high degree of saturation and a second fraction :being off-a relatively high'degree removing the furfural therefrom and recycling the furfural for extraction of additional mixture, the furfural and the mixture being at all times excluded from contact with oxygen.

7. A process of separating into fractions a ma-V terial selected from a class consisting of glyeride oils and freeacid'sofsaid oils, one fraction being' of a relatively highrliegree of saturation and a second fractionbeing of a relatively high degree o funsaturatign. which. process comprises contactingthe. mixture with f urfural to form two liquid, phases, one comprising the relatively saturated fraction having some tui-tural dissolved 2,852,546 therein, the other comprising furfural in which is dissolved a relatively large amount of the unsaturated i'raction, separating the two phases. removing the furfural therefrom and recycling the furfural for extraction of additional mixture, the iurfural and the mixture being at all times excluded from contact with oxygen, by blanketing them with an inert gas.

8. A process of separating into fractions a matei-iai selected from a class consisting of glyceride oils and free acids of said oils, one fraction being of a relatively high degree of saturation and a second traction being of a relatively high degree of unsaturatlon, which process comprises contacting the mixture with iurfural 'to form two liquid phases, one comprising the relatively satuis dissolved e relatively :me amount of the un.

saturated fraction, separating the two phases, removingthe mrtural therefrom' and recycling the furi'ural for .extraction oi additional mixture, the furiural and the mixture being at all times excluded from contact with oxygen. by blanketing them with a gas consisting mainly of tree nitrogen.

9. A process as deiined in claim 5 in which the solvent is iuriural and the material treated is rated fraction having some furfural dissolved therein, the other comprising furfural in which from a class consisting oi' soya bean oil, cottonseed oil, coconut oil, and linseed oil. 10. A process as defined in claim 1 in which th solvent is further admixed with a hydrocarbon immiscible therewith.

11. A process as dened in claim l in which the material treated is preliminarily deaerated.

JoHN D. JENKINS.

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