US2576841A

US2576841A - Solvent fractionation

Info

Publication number: US2576841A
Application number: US641712A
Authority: US
Inventors: William M Leaders; Felix E Lacey
Original assignee: Swift and Co Inc
Current assignee: JBS USA LLC
Priority date: 1946-01-17
Filing date: 1946-01-17
Publication date: 1951-11-27
Anticipated expiration: 1968-11-27

Description

NOV- 27, 1951 w. M. LEADERS ETAL SOLVENT FRACTIONATION Filed Jan. 17, 1946 .Al jab NW. QW* F ...Y N IY mv 3 wv k |\|0h. m FZN JOW u ^w\\ M t v z mw ON a WM a u w LI k\ |.Y N 0 NM\ .N AI m..\. www v @N Q m a How NN N N d ...ru Al 9:5 dzb .AI 1 .5 Al um AI .5 QM! m @Y ww MN m\ e w s f M, \.Q\ WM.. {JNW IY l SW mm aw uw w) ww Patented Nov. 27, 1951 soLvENT 'FRAoTI'oNATI/ William M. Leaders-and Felix E. Lacey, Chicago, Ill., assignors to Swift & Company, Chicago, Ill.;- a `corporation of Illinois Application January 17, 1946, s'eriai No. 641312 This invention relates to the treatment of fatty materials and has to do particularly with the treatment of fatty materials with solvents to separate valuable constituents therefrom.

The invention is applicable to the treatment of 3 Claims. (Cl. 2611-419) fats and fatty oils, either animal and vegetable,

such as greases and tallows, soybean oil, cotton- Vseed oil, linseed oil, fish oils, peanut oil, and sunflower seed'oil. FattyV acids derived from the aforesaid oils may also be treated in accordance with the`invention.

Commercial fats and fatty acids vare generally composed of components of different degrees vof saturation. The proportion of the saturated and unsaturated constituents varies with the different products, depending on their origins. ample, fats and fatty/oils derived from animal sources contain from about'40% to 60% saturated compounds and the remainder of unsaturated compounds of varying degrees of unsaturation.

For ex- Fatty oils of vegetable and marine origin usually posed of compounds having substantially the same degree of saturation. This is particularly true in the manufacture `of paint oils and resins, in the compounding of edibleproducts, and in the manufacture lof chemical derivatives. For such specific purposes the fatty material becomes more valuable as the degree of purity of the desired components is improved in the product. As applied to commercial fats and fatty acids, the separation is usually on the basis of the number of unsaturated bonds. Accordingly, it is possible to separate a fat and fatty acid into components containing substantially saturated constituents, compounds having one double bond, compounds containing two double bonds and materials of even a higher degree of unsaturation.

An object of the present invention is to provide a more eiiicient process for the separation of fatty materials into components of different degrees of unsaturation.

Another object of the invention is to provide a process for the fractional separation of fatty materials to produce improved yields of desired products.

V.A further object of the invention is toprovide a process for the fractionation Vofv fatty-materials wherein a sharper separation between the materials of different degreesfof unsaturation is obtained. v' "W Also an object of the invention is to provide an improved process whereby fatty materials may be separated intoproducts of improved quality.

Heretofore attempts have been made to separate fatty materials into the various constituents by distillation, `and while some success lhas been obtained inthe separationA of fatty acids into components of varying degrees of unsaturation by distillation, this method has not beenv entirely satisfactory; The boiling points of certain saturated and unsaturatedrc'onstituents are so nearly alike, it is often difficult to obtain any substantial degree of separation by fractional distillation.

Attempts have also been made heretofore to separate the constituentsr of fatty materials by seeding and crystallization of aportion of the material, particularly the more saturated components, and then the separation ofthe crystals from the oily materials by pressing. Such a process is useful for the separation ofthe wholly saturated components,l butr the method has not proved satisfactory for the fractionation of the unsaturated constituents.

It has also been proposediheretofore 'to fractionate fatty materials `with the aid of solvents. For exampla'fa'irly good success has been obtained with the'separationof saturatedl compounds, such as stearine-from'animal :fats by the use of-a crystallization solvent. Some success has also been obtained in the fractionation of unsaturated compoundsvby Vtheu'se of solvents both by crystallization yand liquid-liquid phase'fractionation.' However. infthe fractionationr of fatty materials, on the basis of unsaturation with theuse of solvents, excessive amounts of solvents and `extreme temperatures are required, and even under 3 saturated components. We have found that liquid-liquid phase separation is more efficiently accomplished if the more saturated constituents are first removed, particularly such saturated constituents as can be eciently separated by solvent crystallization.

It hasbeen proposed heretofore to separate a fatty material into saturated/and unsaturated fractions and then fractionally distill the two fractions separately. Thus, the saturated constituents of a fatty acid mixture are separated from the unsaturated constituents by solvent crystallization. The two fractions are then subjectedl separately to fractional distillation. The process, however, is applicable only to fatty acids since glyceride oils cannot be separated by fractional distillation. Furthermore, high losses occur in the process on account of the high temperatures required; for example, polymerization losses as high. as 15% are not uncommon.

The present invention contemplates a two-stage processjwherein the fatty material is rst subjected to solvent crystallization to separate the more saturated portion, .and then the lesser saturated portion is subjected to solvent fractionation yin a liquid-liquid phase `operation to separate the material into fractions of diiferent degrees of unsaturation. The amount and type of materials separated in the rst step of our process will depend on the nature of the materials treated. If the material to be treated contains a substantial amount of saturated constitutents,

, the fraction separated in the first step will consist mainly of saturated materials. The latter .will usually be the case in treating fatty acids derivedfrom tallow, greases, or mixtures of tallow and grease of animal origin.

When treating glycerideoils, the fatty acids are often combined in a glyceride moleculeY in combination withV the.unsaturated fatty acid radicals present to give mixed triglycerides. Usually the material separated in the crystallization stage will be substantially di-saturated mono-unsaturated triglycerides, and will contain all of the tri-saturated fat present and a minor portion of di-unsaturated .mono-saturated material. In thisv way, substantially all the saturated: fattyacid groups present in the original -fatty material will be separated as one or more of these triglycerides. Thek distribution of the Ifatty'acids in natural occurring fats is such as to practically `eliminate the presence of simple triglycerides. containing .three radicals of the same fatty acids.. For. this reason, the degree of separation that is possible, even from a theoretical consideration, is less than when treating .fatty acids or mono-hydric esters of the fatty acids.

When treating materials containing very little or substantially nov saturated constituents in the first step of vour process, the fraction separated in the first stage may not be a highly saturated Vmaterial but contain substantial amounts of the less saturated materials. For example, in treating oils such as soybean oil, cottonseed oil, etc., the fraction initiallyseparated Will contain substantially all of the saturated fatty acid groups present along with a considerable amount of the unsaturatedgroups of the lowest degree of unsaturation. With the oils just mentioned, the glycerides separated would be composed substantially of estersl of the fatty acids such as palmitic, oleic, andrlinoleic, with only minor amounts f .the estrsofmorehighly, unsaturated fatty acids..

In the second step of our process, We intend to fractionate materials from the first stage of our process into two or more fractions of varying degrees of unsaturation. If the fatty materials treated are fatty acids, 'the fatty materials will be separated into fractions containing substantially one type of fatty acids. For example, one fraction will contain substantiallyvall of the oleic acid and the allied fatty acids of one double bond. The next fraction will contain substantially all of the linoleic acid and isomers containing two double bonds. And the third fraction will contain linolenic acid and some less highly unsaturated fatty acids.

In treating fats and oils, a fractionation similar to that described in connection with the fatty acids is desirable; However, the mixed composition of the triglycerides makes it impossible to obtain as high a degree of resolution when the individual fatty acids are combined as glycerides. The rst fraction will contain a substantial amount of esters of oleic acid with a minor portion of esters of linoleic acids and linolenic acids combined as glycerides. The second fraction will contain glycerides with substantial quantities of linolenic acids with minor quantities of oleic and linoleic. The third fractionY will contain substantial quantities of linolenic acid and more highly unsaturated fatty acids, with only minor quantities of oleic and linoleic acids.

The rst step of our process is essentially a crystallizing operation wherein the fatty material is mixed with the required amount of solvent and the mixture chilled to cause crystallization of the more saturated constituents. The amount and type of material crystallized will depend upon the type and amount of solvent, the temperature and the nature of the fatty material treated. In carrying out this initial. step of the operation one maybe lguided by the principles set forth above as .to the type of materials to be crystallized, and this material may be predetermined by iodine number, titer, melting point, thiocyanogen value, and, in the case of fatty acids, lead salt precipitation.

The amount of material crystallized in the rst step may vary from 10% to 60%. For example, in the case of cottonseed oil, the amount will be approximately 10% andin the case of tallow and fatty acids, as much as 60%. Other materials may vary withinv the above range. The solution containing vthe crystallized compounds is subjected to appropriate separation operations, preferably filtration in. a continuous filter, wherein the crystallized portion is, `filtered from the solution. -A .e

We may use a number of solvents in the crystallization step including both polar and non-polar solvents, such as propane, butane, pentane, hexane and members of the alkane series up to decane; methyl and ethyl alcohol; ethyl ether; carbon disulfide; B-Bl-dichlor ethyl ether; nitro propane; ,ethylene dichloride; acetone; methyl ethyl ketone; isopropyl acetate; amylacetate; monomethyl ether of ethylene glycol; and monoethyl ether of ethylene glycol.

When using volatile solvents, for example, a normal gaseous solvent, such as propane or butane, we may obtain chilling of the solution by vaporization of a portion of the solvent. When using less volatile solvents, chilling with an extraneous refrigerant is desirable.

In the second step of the process we prefer to further separate thefatty materials treated in the first step into two or more fractions of gli?? @84.1.

'varying degreeslof; unsaturation.; as. indicated by iodine value. The product .,from., he .first stage may be chargedto. the second,` stage with or without the addition of more of the same solvent or a different solvent. When using certain solvents, such as the ,normal gaseous hydro? carbons, for example, propaneor b utane, the solution from the rst stage Aafter the separation ofthe crystallized fraction may bev charged directly to the second stage. In case it is desired to use a dilerent solventy in the second `stage than was used in the rst stage, then the solvent employed in the initial stage maybe removed, all or in part, from the fatty material.

.In the case where two'solvents are to beused in the second stage, the solvent used in the first stage may be retained ywith the fatty. material and charged directly to the sec-ond stagewherein asecond solvent charge is introduced.'y For example, in the separation of `fatty acids using normally liquid hydrocarbonsr as a, crystallizing solvent, a combination of hydrocarbon-and furfural may be employed to accomplish the separation in the second stage. l Y Suitable solvents that may be used alone in the second stage include furfural, sulfur dioxide, furfuryl alcohol, phenol, and nitro benzene.

When using such solvents, the solvent used in the first stage is usually partially or completely removed. Suitable 4solvents which may be used in both stages of our process are butane, propane, acetone, hexane, beta-beta-dichlorethyl. ether, methyl Cellosolvefand ethyl Cellosolve.' When using the latter solvents all or a portion of. the solvent used in the first stage may be used in the last stage.

' The operating conditions in the second step will vary depending on the type and amounts of solvent and the nature of the oil treated. The operation is usually carried out .at above vroom temperatures and may vary from slightly above room temperature, for example, 100 F. to 110 F. in the case of furfural, up to aroundv 200 F. in the case of propane.

When using a volatile solvent, such aspropane, sufcient pressure is maintained to keep the solvent in the liquid phase. Such pressures may be up to 650 pounds to '100l pounds per square inch. The s-olvent treatment may be conducted in' a batch, semi-batch, or continuous system. We prefer to use a continuous countercurrent tower wherein one Ifraction is drawn from the top of the tower and the :other fraction .from the bottom of the tower. In most cases the less unsaturated fraction will be withdrawn from the top of the tower and the more unsaturated fraction from the'bottom of the tower, but the relative positions for drawing olf fractions of different degrees of unsaturation will depend on the density of the solvent. For example, with a high density solvent the more Vsaturated fraction may be withdrawn from'the bottomof the tower and the more unsaturated fraction from the top of the tower.

The invention willV be more fully understood from the following description read in connection with the accompanying drawing.y

Referring to the drawing, thev fatty material to be treated is introduced through' the line i and forced by the pump 2 through theV mixer 3, wherein the oil is thoroughly mixed with the solvent which may be introduced through the line 5 or the line 6. The mixerl may be any 'suitable mechanism for vthoroughly mixing the solventl and oil,. such asafspaddle typeA mixer,

2115x211u for. Creatiggftllrblilegtw 91 a passager provided Awith. orifices on b aiilesorl both', The pfoportionsof -theAsol'ynrent and thfoilwill usually bearoundfour to five parts of'solvent to one part of oilby volume. Ihe solutionY of ouiland fatty'material is conducted through the line 8` to a chiller Y9. In the chiller the solution cooled toal temperature sufficiently low to crystallize out the desired amount of more sat--V urated compounds.y The temperature in the chiller vmayrange from` about +30 F. Vto as low as Yabout 70 F., depending on the solvent and fatused. The chiller maybe a double pipe scraped wall type for the use of extraneous refrigerant or a simple enclosed tank fitted with a vapor escape lock for use with normally gaseous hydrocarbon or other low boiling, self-refrigerating solvent. If a self-refrigerating solventA used, the portion of the solvent vaporized will be removed through the pipe I0 and condensed and recycled to the ysystem through the iine`6. The mixture of liquid and crystals from lthe chiller 9 is conducted through line I2 to the filter I4. The lter is preferably a rotary drum type filter and may be 'vapor tight for use with volatile solvent and should be equipped t0r oper; ate ,under both positive pressure` and reduced pressures as low as 10mm. of mercury absolute. The crystallized portion of the fatty material along with some solvent is discharged from the lter through the line I5 into`the stripper I6, wherein the solvent is stripped from the more saturated fraction. The stripper may be operated under reduced pressure and with injected steam, if necessary. The solvent is. removed from the upper portion of the stripper through the :line l1 and may be discharged from the system through the line I8 or recycled to the system through the line 20.v The more saturated fatty constituents are withdrawn from the lower portion of the stripper through the line 2|.

'Y VThe solution of fatty material and solvent separated as a filtrate in the lter I4 is discharged through the line 23 and may be further treated in either of two ways. If it is desired to remove the solvent from the fatty material at this stage, as may be the case when it is preferred to use a different solvent in the second stage, the solution is conducted through the line `24 to a still 25. In the still the solvent may i;yejremoved all or in part as vapors. v'Ihe distilled solvent may be removed from the system through the line 21 or recycled through the line 28. 'Y The bottoms vin the still containing the fatty material may be drawn off of the lower portion thereof through the line 29 and conducted through the communicating line 30 to fractiona# tion column 32. In some cases, as for instance When it is desired to use the same solvent in the secondstage as was used in the first stage, the still 25 may be by-passed and the solution in line 23 conducted through the line 3| and line 30 to the fractionation column 32.

While we have shown the charge line 30 as entering lthe fractionation tower in the upper section, the position for introduction of the fatty material into the fractionation tower will vary, vdepending on the type of solvent used. In case v.the solvent density is greater than the density Vof the fatty material, as in the case of furfural, thefatty material will be introduced into the llower section of the tower and rise through the `falling tower of solvent. When the density of the solvent is less than the fatty material, as

awash bons, such as propaneor buta-ne, the fattymaterial will `be introduced into the upper portion of the tower and descend through a rising column of solvent.- As an illustration, if the fatty material charged to the fractionation tower is the ltrate directly from the filter l4--say, a solution of Vfatty material and propanethe solution would be chargedV into the upper portion of the tower. Additional solvent, which might be propane or butane, would be charged into the lower portion of the tower. the rst stage is removed in the still 'and the straight fatty material is charged to the fractionation column, such charge may be introduced into the lower portion of the tower when it is intended to use a high-density solvent such as fu-rfural Vor beta-beta-dichlorethylether, which solvent would be introduced into the upper portion of the tower. In the drawing we have shown the solvent introduced into the lower portion of the tower through the line 35. Such position of introducing the solvent is suitable when using a low-density solvent such as propane. When using a solvent which has a higher density than the fatty material, then the relative positions of introducing the solvent and fatty material should be the reverse of those shown in the drawing.

f The fractionation tower is operated under temperature and pressure conditions to maintain the solvent in the liquid phase and to cause a separation of phases. The interface is ordinarily between the points of introduction of the solvent and of the fatty material. The materials are drawn off from each phase from the top and bottom of the tower. Again, as shown in the drawing wherein a low density solvent is used, the upper layer or phase containing the major portion of the solvent and relatively rich in fatty material of lower degree of unsaturaton is drawn oi from the top of the tower through the line 36 and discharged into the still 38. In the still the solvent is vaporized and removed through the line 39 or recycled to the system through the line 40. Line 40 communicates with branch line 4|, whereby the solvent may be returned to the first stage, and with the branch line 42, whereby the solvent may be returned to the fractionation tower 32. The fatty material may be withdrawn from the bottom of the still 38 through the line 45. The layer collected in the lower portion of fractionation tower 32 containing a minor proportion of the solvent and fatty `material relatively rich inv materials of a higher degree of unsaturation is drawn from thebottom of the tower through the line 45 and discharged into the still 48. Solvent removed in still 48 may be returned through the line 49 and branch line 50 to the fractionation tower 32 or through the line 49 and branch line 5l to the first stage of -the system. Fatty material removed in the still 48 may be withdrawn through the line 52.

For purposes of illustration, examples will now be given of the operation of the invention. It is to' be understood, however, that the invention is not limited to the specific examples.

'the solution of fatty acids, and this solution was ycharged to a solventl removal tower where apart If the solvent in- Cal f the solvent was removed from-the filtrate to give a Asolvent to fatty acid ratio of approximately ve to three by volume. This solution was charged directly into the lower section of a packed tower at two-thirds the rate of charge of furf-ural which was-utilized as a fractionating selective solvent and introduced into the upper portion of the tower. The temperature of the tower was about 89 F. in the upper portion and about 88 F. in the lower portion. The interface was maintained approximately one-fourth the distance up from the foot of the column. A rainate fraction was withdrawn from the top of the tower and an extract was withdrawn from the bottom of the column. The rafnate fraction contained 50% petroleum ether, 13% furfural, and 37% fatty acids. The extract contained 13% petroleum ether, 73% furfural, and 14% fatty acids. The ratio of rafiinate to extract was approximately one to three. This ratiol of raffinate to extract, as well as the amount of solvents used, was determined experimentally so as to give approximately a 50-50 distribution of the fatty acids in the raiiinate and extract. The iodine number of the fatty acids obtained in the raffinate was 82.5. The iodine number of the fatty acids in the extract layer had an iodine number of 142.1. The crystallized fatty acids removed in the filtration step amountedrto approximately 15% Vof the original charge and had an iodine number of 23.2 and a saponication number of 208.0. lThis fraction consists mainly of palmitic acid in mixture with a small amount of stearic acidand oleic acid.

Example 2 Soybean oil, having an iodine number of l37.6,

was dissolved in four volumes of propane at a temperature of approximately F. and 270 pounds pressure. The pressure was slowly reduced to allow a small portion of the solvent to vaporize, thereby cooling the solution. The rate of temperature drop was controlled at approximately 1 F. per minute. The solution was cooled to 0 F. and filtered. The solid fraction obtained in the lter amounted to approximately 10% of the initial oil charged and had an iodine number of 63.0. This fraction contained substantially all the combined saturatedV fatty acids present in the original soybean oil along with some oleic and a small amount of linoleic acids. The solution from the` ltration operation was passed throughv a heating zone and the temperature raised ,to about 168 F. This warm solur tionwas introduced, under pressure, into a packed tower ooded with propane. The solution was introduced approximately two-thirds of the way up from the bottom of the tower. Additional solvent,'amounting to fifteen volumes on the basis of the oil charged, was introduced into the lower portion of the tower. The fractionating tower was maintained at a temperavture of 178"v F. at ,the top of the tower, dropping oif gradually to '170 l. at the lower portion or' the tower. The interface was maintained in K Suiiicient pressure was maintained in the tower to prevent vaporization of the solvent propane. The raffinate fraction, containing substantially all of the propane and the more saturated oil, was removed from the upper portion of the tower. The extract fraction containing approximately 'one volume of solvent on the basis of the oil, was

removed fromvthe bottom of the tower. These solutions of rainateand extract werev subjected -to a primary stripping operation to remove most `of the solvent and to a final step of steam stripping to remove the last traces of the solvent. The rafnate fraction had an iodine number of 91.5. The extract fraction had an iodine number of 165. Approximately 64% of the higher iodine fraction kand about 36% ofthe lower iodine fraction calculated on the basis of the oil charged to the fractionating column were obtained.

Example "3 Cottonseed oil fatty acids,v having an iodine number of 114.2 and a saponication value of 190.8, were` dissolved in four volumes of propane at 120 F. and 270 pounds pressure. The pressure was slowly reduced and the solution chilled by the evaporation of a portion of this solvent at arate of .1 F. per minute to a temperature vofl1" F.` The solution was filtered and the solid material washed with one-half a volume of cold solvent. The ltrate and the wash solution were .combined and passed through a heating zone, where-.the temperature was raised to 195 F.- This heated solution` was introduced into the middle section of a packed fractionating tower into the lower portion of which was charged an additional quantity of liquid propane, .amounting to forty-fivev volumes on the basis of the fatty acidcharged'. Thek upper portion of the tower ywas maintained at 204- F. and the .lowerportion ofthe column at 197 F. Necessary heat to maintain this temperature and the temperature gradient was supplied by a series of electrical heating coils spaced throughout the length of the tower. The overhead fraction, containing substantially all 'of the propane and the more saturated fatty acids, gave a fatty acid with an iodine number of 87.5 and a saponification value of 188.0. The bottom fraction, containing approximately one volume of solvent to fatty acids, had an iodine number of 134.2 and a saponii'lcation value of 196.5. The iodine number of the solid fraction separated in the filter vwas 11.0. ,A

Example! j Cottonseed oil`Y was -degummed-by treating the oil with 2% lwater at 160 F. and settling the gums.' volumes of acetone at a temperature of about 1'l0 F. to insure complete solution. The Y result ingsolution was slowly agitated and passed through a chiller wherein the temperature was gradually decreased by the use of cold brine solution circulating in a coil. The temperature of the solution was lowered at the rate of approximately 1 F. per minute to a temperature of about 30 F. A precipitate began to appear as the temperature reached 40 F. and a slurry developed slowly as the temperature ,was further reduced. The chilled slurry was passed through a filter operating under reduced pressure to remove the solid portion from the filtrate. The filter cake was washed with one-half volume of cold acetone and the wash solution combined with the filtrate. The filter cake, which amounted to about of the original oil charged, was melted and the solvent removed. The solid product had a free fatty acid content of 1.8% and an iodine number of 63. The combined filtrate and wash was introduced into a still wherein the solvent was removed under vacuum. The last traces of solvent were removed Thedegummed oil was mixed with four y Lil) by a five-minute steam stripping operation at a temperature of about F. under reduced pressure. The oil fromzthesolventV removal process was introduced into the upperfportion ofr a continuous countercurrent fractionating tower. Into the lower portionof the tower forty volumes of liquid propane'were introduced for every volume of the oil. The tower temperature was maintained at around F. A 5 .temperature gradient was maintained throughout the length of the fractionating tower, the higher temperature being maintained at the top of the tower. Two fractions were'continuously removed from the tower; one from the top and one from the bottom. The bottom fraction, consisting'of approximately50% vofthe oil charge and containing a small percentage ofY solvent,`was passed directly to a solvent Arecovery unit wherein the propane Wasremoved under atmospheric pressure.A Finalremovaln of= Vpropane was' accomplished by steam stripping 'at approximately 225 F. and atmospheric. pressure. -The bottom fraction vhad an' iodine lnumber of 131.0. The fraction removed from: the top of the tower contained a large proportion of the "solvent and the other 50% of the'oil.' The product was preheated to 200 F. and introduced into a solvent recovery tower, wherein the propane was removed under atmospheric pressure.' A steam stripping operation at'atmospheric pressureA of 225 F. was used as the nal step in the solvent removal. '.The top -fraction had an iodine number of 86.5 and a free fatty` acid content of approximately 1%.

y Example 5 Afsample ofncottonseed' oil' was subjected to a crystallization operation similarfto' that described in Example 4,"aboveif The filtrate from the filter was denuded of solvent'iir astill. The oil vwas then introduced into the lower section of. ay countercurrent fractionatingA tower. Into the upper portion `of the tower two volumes of furfural .to one of oil were introduced. The interface between the two liquid phases was maintained at approximately one-third" of the Ldistance up from the bottom-of the tower. An average temperaturev of about 100 F. was kmaintained in 'the tower;I the'temperature gradient from the" bottom to the'- top of the' tower Abeing about 3 F.V An extract fraction containing'the majority of the solvent and approximately 50% of the oil was removedy from lthe bottom of the tower. A raffinate,` containing approximately 20% solvent and the other..50% of the charged oil was drawn fromthe top of thetower. These solutions were-introduced into separate lsolvent recovery'units after pre-heating to a temperature of 250 C. The solvent recovery units were two-stage processes operated under high vacuum, the first stage being a simple fractional distillation, and the second a steam stripping operation at about 200 C. and around ten millimeters absolute pressure. The solvent furfural remaining in the oil was reduced to less than one part in ten million and showed only a faint test by the analine-acetic acid testing procedure, which is the common method of detecting traces of furfural. The overhead raffinate fraction had an iodine number of 91.5 and the extract fraction had an iodine number of 130.2. The extract had a free fatty acid content of approximately 1.3%. It will be noted that in this example the fatty acids are selectively withdrawn with the higher iodine fraction, whereas by the use of propane, as in Example 4, the fatty acids were selectively withdrawn with the lower iodine fraction.

The presentinventionhas the 'advantage of Vproviding a process wherein a single solvent may 'be used forrseparating a saturated portion of a fatty material and' then the same'solvent used for fractionating -the remainder of the fatty Vmaterial into fractions of different degrees of Vespecially in the more unsaturated fractions where excessive temperatures cause polymerization and heat bodying.

A further advantage of the invention is that the saturated material present in the charged stock is removed by a simple method which eliminates one of the interfering elements normally encountered in a liquid-liquid phase extraction. By separating the saturated material first we are not troubled by the common phenomenon of the saturation of our selective solvent with this-saturated phase and we are able to obtain in a single countercurrent operation a much greater degree of resolution between the various unsaturated constituents present.

Obviously, manyV modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore. only such limitations should be imposed as are indicated in the appended claims.

We claim:

1; A process for the treatment of fatty materials containing relatively saturated and unsaturated constituents to obtain an improved separation of the highly unsaturated constituents, which comprises: rst cooling a solution of the fatty material in a liquefied normally gaseous hydrocarbon as a solvent to a temperature of between +30 and .-.70' F. by evaporation of a portion of the solventV to crystallize between and 60 percent ofthe more saturated constituents from the solution, and filtering the crys- -tals from the solution; then warming the solution free of the more saturated constituents in the presence of additional normally gaseous hydrocarbon as solvent to an elevated temperature and pressure to form two liquid phases. separatring thev phases andl recovering from the separated phases constituents of the fattymaterlal having a higher andlower iodine value respectively. Y

2.*A process for the treatment of fatty materials containingv relatively saturated and unsaturated constituents to obtain an improved separation of theV highly unsaturated constituents, which comprises: first cooling a solution of the fatty material in a liquefied normally gaseous hydrocarbon acting as a solvent to a temperature between ,-i-SO" and F. whereby between l0 and 60 percent of the more saturated constituents crystallize from the solution, and separating the crystals by filtration;V then subjecting the resulting solution containing the more unsaturated constituents free of the more saturatedV constituents to countercurrent extraction in the presence of additional normally gaseous hydrocarbon as solvent at an elevated temperature and pressure whereby the solution separates into two liquid'p'hases, one of said phases comprised substantially of constituents having an iodine value of at least 40 points higher than that of the other phase, and separating said phases.

3. A process substantially as described in claim 2 wherein the step of crystallization is carried out in propane as the solvent and the countercurrent extraction step is carried out at a temperature between about and 200 F. and at an elevated pressure between about 650 and 700 p. s, i.

WILLIAM M. LEADERS.

FELIX E. ,LACEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Great Britain Dec. 7, 1933

Claims

1. A PROCESS FOR THE TREATMENT OF FATTY MATERIALS CONTAINING RELATIVELY SATURATED AND UNSATURATED CONSTITUENTS TO OBTAIN AN IMPROVED SEPARATION OF THE HIGHLY UNSATURATED CONSTITUENTS,, WHICH COMPRISES: FIRST COOLING A SOLUTION OF THE FATTY MATERIAL IN A LIQUEFIED NORMALLY GASEOUS HYDROCARBON AS A SOLVENT TO A TEMPERATURE OF BETWEEN +30* AND -70* F. BY EVAPORATION OF A PORTION OF THE SOLVENT TO CRYSTALLIZE BETWEEN 10 AND 60 PERCENT OF THE MORE SATURATED CONSTITUENTS FROM THE SOLUTION; THEN FILTERING THE CRYSTALS FROM THE SOLUTION; THEN WARMING THE SOLUTION FREE OF THE MORE SATURATED CONSTITUENTS IN THE PRESENCE OF ADDITIONAL NORMALLY GASEOUS HYDROCARBON AS SOLVENT TO AN ELEVATED TEMPERATURE AND PRESSURE TO FORM TWO LIQUID PHASES, SEPARATING THE PHASES AND RECOVERING FROM THE SEPARATED PHASES CONSTITUENTS OF THE FATTY MATERIAL HAVING A HIGHER AND LOWER IODINE VALUE RESPECTIVELY.