US2351249A - Treating fatty acids - Google Patents

Description

June 13, 1944. A' ,.A. H. zExGLER ET A1. 2,351,249

TREATING FATTY ACIDS lFiled sept. 28, .1940

orzdcinser rWier l Patented June 13,v 1944l` FFICE TREATIN G FATTY ACIDS Albert H. Zeigler, Evanston, Dale V.

Downers Grove, and James M. Kiefer, Ill., assignors to Armour and Company, Chicago, Ill.. a corporation of Illinois l Stingley. Chicago,

ApplicationV September 28, 1940, Serial No. 358,792

7 Claims. (Cl- 2oz-62) In the practice heretofore employed for fractionally distilling fatty acids to effect a separa- Vtion thereof substantially according to boiling point, the saturated and unsaturated fractions have been treated snnultaneously.Y lwhiley'a" vacuum of mm. can be maintained at the top of the fractionating tower, the pressure at the aA-bottomofg the tower, due to the large number of bubble trays by meansof which the upwardly rising fatty acid vapors contact the downwardly owing reflux liquid fatty acids, is ofthe order of 35 to 40 mm. mercury absolute. Because of the higher pressure in the lower portion of the tower, relatively high temperatures have to be tion and then subsequently fractionally distilling the two products separately to separate the L acids substantially according to chain length.

employed such as, for example, temperatures of the order of 240C. Furthermore, since fractional distillation involves the returning of substantial amounts of fatty-acid as reux, the heat input at the base of the tower must be from two to iive times as much asthat necessary for straight distillation. With such higher temperatures and with the increased required amount ofheat input, unsaturated fatty acids are subject to considerable thermo-alteration. Since unsaturated fractions of fatty acids are extremely desirable for use in paints, varnlshes, lacquers, baking and air drying enamels, etc., a considerable loss is encountered through the reduction in the iodine value of the unsaturated fractions recovered in the na1 product.

Efciency ofseparation is often sacrificed by reducing the temperatures employed in the lower portion of the tower and in order to prevent an excessive thermo-alteration of the unsaturated acids. y 1

An object, of the present invention is toxprovide a method for separating to a substantial degree the saturated from the unsaturated` acids without-thermo-alterattion of the unsaturated fraction separately AO'ther specinc objects and advantages will appear as the specification proceeds.

The invention` is illustrated, in a preferred embodiment, by the accompanying drawing, in which the single figure represents, diagramvmatically, the method and certain of the apparatus employed in carrying out the process.

'Ihe new method comprises the broad steps of first separating the saturated fraction from the unsaturated fraction to a fair or substantial degree by means which do not subject the unsaturated fraction to high temperatures likely tov produce thermo-alteration, and then subse- 'quently fractionally distilling the saturated from the unsaturated fraction. Y

Any suitable means for separating the'saturatedsfrom the unsaturateds without the employment of such injurious high temperatures may be employed. The fatty acids ay be crystallized with or without solvents or diluents and the solid fraction. consisting predominantly of saturateds thus separated from the soluble 'or liquid fractionv consisting predominantly of 'unsaturateds Another method for separating the saturateds from the unsaturateds without the employment of high temperature isl by selective adsorption. The-mixtures of fatty acids are treated with large quantities of a surfacev active material which tends to adsorb the saturateds but not the unsaturateds.V Other vmethods for producing a separation of the saturated acids from the unsaturated acids .to a substantial deacids and 'then subsequently fractionauy disto-10 ling thesaturated fractions and the unsaturated fractinns separately. A -further object is to `provide a method and means for separately fractionally distilling saturated acids with an accompanying high yield. A further object is to provide a method and means for separately fractionally distilling unsaturated acids under conditions which obviate thermo-alteration while producing a greater yield of the high iodine fraction. Still another object is to provide a method and means for effecting a substantial separation between saturated and unsaturated fatty acids without the employment of high temperatures and thus preserving unaltered the .iodine value of the `unsaturated fracsree will occur to those skilled in the art and vmay be employed so long as high temperatures deleterious to the iodine value of unsaturated fractions are avoided.

AsV illustrative of the process, we will describe herein specifically the method of separation v ...wherein crystallization is'the means employed. Fractional crystallization of saturated fatty acids from unsaturated fatty -acids may be accomplished by simply cooling a fatty acid mixture containing preferably a relatively low amount of saturated acids, such as, for example, 10% or less, to a temperature at vwhich partialcrystallization occurs. The crystallized fracte tion may be separated then by filtering or other' means.

We have found that a mnupmmqre effective 'separation of the saturateds from the unsaturateds can be produced through .the use of solcontact with liquid butane which the solvent before vents in coniunction mitlLthe crystallizing Step anu further, that solvents which differ substantially in density from the density of fatty acids increase the formation of crystals free from occluded. normally-llquidfatty acids with the result that a sharper separation of saturateds. from unsaturatetis is brought about.' For example, low density solvents having a density not above 0.63, anchas butane, propane or pentane; such density beingL well below that of fatty acids, are extremely effective in promoting a satisfactory crystal growth. Such crystals'l may be allowed to separate xt by their own weight or, when placed in a centrifugal machine or in a filter, permit the liquid phase to be readily and sharply separated therefrom. t

In crystallizing fatty acids, it is found that the solid phase is composed of mixed crystals' of fatty acids in which the saturated fatty acids o are to be found "lh higher iconcentration than in the original mixture of fatty acids. In the absence of solvents, the normally liquid unsat urated fatty acids tend to become occluded with covered, the liquid phase consisting 4almost en-4 tirely of the unsatia'ted fatty acids passed from the separator through a heater, -preferably of the tubular type. to the fractionating column A. The solid phase consisting almost entirely of the saturated acids ispassedthrough a similar heater into asimilar frctlonating column B. It

' will be understoodwthaa'if desired, a single fracthe normally crystallinesaturated fatty acids.

When low areemployed, we nnd that there is asubstandensity solvents of the type described tially complete elimination of occludedY unset.T

urated fatty acids from the crystalline phaser We dnd-that the higher the'ratioof solvent tofatty acid, the freer is the crystalline phase of occluded unsaturated fatty acids.

'In a specific description of the-method, `butane, which has a density of approximately 0.58, will be referred to as the solvent or' diluent.

The mixture of fatty acids or fatty acid stock is introduced into a mixer and there brought into der pressure into the mixer from a compressor or pressure reservoir. It is important that the fatty acid mixture be completely dissolved in allowing crystallization to proceed. The butane may be mixed with the fatty acids in theproportion of five volumes of butane to one volume of fatty acidmixture, or in any ther suitable proportion. From the mixer, the 'terial goes tn the crystallizer where the temperature is reduced to-a point at which crystallization occurs. The crystallization may be produced by any suitable cooling method. In the illustration given, .crystallization is induced by allowing a portion of thetbutane to evaporate, the evaporated butanegbeing recovered and returned to the compressoror-p s'sure reservoir. It will be that the butane may also be recovered from portions of matemeans not shown.` Riecovery stills, compressors and pressure reservoirs arewell-knowntothoseskllledintheartfor lammala-.hrecover! purposes and need not be shown mcthemmisfarmeditna fattyacidsthusrecovered frolnthe is forced untionating column may be employed and the liq'- uid phase passed through the column at one time and subsequently the solid phase treated in the fractionating tower. If two towers are employed, as illustrated, it will be found that a lesser number of bubble trays are required in tower A.

In the case of either fractionating tower A or fractionating tower B, the introduced charging stock of unsaturated fatty acids or saturated fatty acids is first passedthrough the tube heater, as in the usual practice, and thence'into the fractionating tower. The fractionating operation is carried on by passing' the vapors upwardly through the bubble trays as reflux liquid flows downwardly over the trays. A vacuum of approximately 5 mm. is preferably maintained at the top of the tower, while the pressure in the lower portion of the tower may be from 35 to 40 mercury absolute but it is preferably appreclably lessthan 3 5 mm. Heat is introduced through the coils"by the circulation of Dowtherm" fluid or other suitable heating means-tn produce the desired vaporization. Steamdsintroduced preferably in the lower portion'of the tower. A portion of the bottoms from the tower 'in the present instance consist, in the case of tower A, almost entirely `of unsaturated acids Separated alfCOldng 00 their Chain length and,

V in the case of tower B, of saturated fatty acids separated according to chain length. v

-As a specific example, sardine fatty acids were separated by the process described. being first mixed with five volumes of butane topne volume of fatty acid and then refrigerated by permitting the butane to evaporate. The liquid phase was removed by withdrawing it from the settled saturated Vacid crystals and after the removal of all solvent remaining therein, is passed through the tube heater and thence into tower A. The

distillate fraction obtained from tower A constituted 50% of the original sardine fatty acid mixture and had same sardine fatty acid mixture" when not subjected to the crystallizing andiseparation operation andwhen fractionally distilled together gave only a 20% yield at an iodinevalue of 254. Since the high iodine fraction is by far the'most important product recovered from 'the processing of the oil. the value of the preliminary stepof separating the Aunsaturateds from the sahirateds without heat treatmentxthus becomes apparent.

with respect to the saturateds and senttotowerB or'passedthmugliY towerainaseparaterlmhlsresultedina much increased yield since temperatures mid be raisedfr beyond those formerly employedin viewofthefactthatthere werepresmtsubstantially-no unsaturateds to undergo. thermal changeduetothehighheat.`

In the` distillation separately.- of the unsaturateds,itwasfound thata-twerequippedemy with three trays might ntisfatorlly be ern-,

ployedsthus enabling a much-higher vacuumlf and lower distillation temperahires to be used.

solidphaseeonsistingdf an iodine value of 254. The

In connection with the foregoing fractional distillation process, it lwill be notedv that the low density solvents already describedare useful/not only for separating saturateds from unsaturateds but also unsaturated fatty acids of comparatively low degree from unsaturated fatty acids possessing a high degree'of unsaturation. For example, the process will result in some separation of linolic acid from oleic acida commercially desirable separation.

While in )the foregoing description, we have referred to crystallization as an example of a method whereby separation of the saturated fatty acids from the unsaturated may be accomplished without the useV of destructively high temperatures, itv will be understood that other methods may be utilized for producing the same i results. As already mentioned. selective adsorption may be used. Itxis found that certain sur-- face active 'materials may be used which will select ,or adsorb the saturateds while not aifecting substantially the unsaturateds.. As a specific example, if fatty acids, preferably v admixeci with a solvent, are passed through va long layer ofv anhydrous aluminum oxide, the saturated fraction will be retained in the layer while the unsaturateds pass through the filter. Any suitable adsorbents such as alumina, charcoal,

bleaching earth, gypsum, calcium carbonate,

magnesium nude, finely divided clay and other inorganic or organic materials may be used.

The portion passing tln'ough the lter may be sent to tower A after the removal of the solvent while the adsorbed fraction may be recovered in the usual manner and sent to tower B.

We claim: Y 1

1. In a method for treating a mixture of saturated and unsaturated fatty acidsincluding relatively low boiling saturated fatty acids and relatively high boiling highly unsaturated fatty acids, to obtain a. high yield of highly unsaturated fatty acids, the steps'of subjecting the mixture to low temperatures to bring' about crystallization of a saturated acid portion, sepa- `rating the crystallized saturated portion from the uncrystallized unsaturated portion, and sep-'i arately fractionally distilling said unsaturated fatty acid portion, without imparting sufiicient heat to the same to produce substantial thermoalteration of the unsaturated fatty acids, to obtain a plurality of fractions of said portion of different boiling points, including a relatively large' high boiling fraction consisting predominantly of highly unsaturated fatty acids.

2. Inl a process for treating a mixture of .saturated and unsaturated fatty acids including relatively low boiling saturated fatty acids and relatively high boiling unsaturated fatty acids,

withdrawing from 'said pools a fraction consisting predominantly of unsaturated fatty acids of iiigher boiling point than said low boiling frac- 3. In a method for treating a mixture of saturated and unsaturated fatty acids 'including relatively low boiling lsaturated fatty acids and relatively high boiling unsaturated fatty acids, to obtain a high yield of highly unsaturated fatty acids, the steps of mixing said fatty acids with a solvent, reducing the temperature of the mixture to crystallize a saturatedl acid portion, separating the crystallized saturated portion from the uncrystallized unsaturated portion, .and treating separately the unsaturated fatty acid portion by vaporizing portions thereof and subjecting such vapors under reduced pressure to contact with a series of heat exchanging pools of condensed fatty acid mixtures having succes'- sively lower boiling points, the pressure to which said vapors are subjected being so low that the boiling point of the fatty acids in the portion being treated at such pressures is below the temperature at which substantial thermo-alteration of the unsaturated fatty acids in such portion occurs, condensing the low boiling vapors ,passing through the last of said pools, returning a portion of said condensed low boiling vapors to said pools as reflux liquid, and withdrawing from said pools a fraction of fatty acid of higher boiling point than said low boiling fraction.

- 4. In a method for treating a mixture of saturated and unsaturated fatty acids, including relatively low boiling saturated fatty acids and relatively high boiling highly unsaturated fatty acids, to obtain a high yield of highly unsaturated fatty acids, the steps of mixing said fatty acids with a solvent, separating the mixture into two portions, one of the portions containing a predominant proportion of saturatedfatty acids and the other portion containing a predominant proportion of unsaturated fatty acids, the separation being carried out at temperatures substantially below those at which thermo-altera-A tion of vthe fatty acids occurs, and fractionally distil'ling said unsaturated fatty acid portion,` without imparting sufficient heat to the same to produce substantial thermo-alteration of the unsaturated fatty acids, to obtain a plurality of fractions of said p0rtion of different boiling points, including a relatively large high boiling fraction consisting predominantly of highly unsaturated fatty acids.

5. Ina method for treating a mixture of saturated and unsaturated fatty acids including relatively low boiling saturated fatty acids and relatively high boiling unsaturated fatty acids,

the steps ofmixing the fatty acid mixture with y j contact with a 'series ofheat exchanging pools of condensed fatty acid mixtures having successively lower boiling points, the heat imparted to said vapors being insufficient to produce substantial thermo-alteration ofl the unsaturated fatty acids. condensing the low boiling vapors passing through the last ofsaid pools, returning a portion of said condensed low boilto obtain a high yield of unsaturated fatty acids,

the steps of mixing said fatty acids with a solvent, separating the mixture into two portions, one of the portions containing a predominant proportion of saturated fatty acids and the other portion containing a predominant proportion of unsaturated fatty acids, the separation being 'carried out at temperatures substantially below those at which thermo-'alteration of the fatty acids occurs, and treating separately the unsat-v urated fatty acid portion by vaporizing, portions thereof and subjecting such vapors under reduced pressure to contact with a series of heat exchanging pools of condensed fatty acid mixtures ing vapors to said `pools as 'reflux liquid, and 75 havingsuccessively lower boiling points, the heat imparted to saidfvapors being insuillcient to produce substantial thermo-alteration of the unsaturated fatty acids, condensing the low boil.

i A "ing vapors passing through the last of said iheaiito umtedlnd relatively high boiling highly unsaturated fatty acids, to obtain a high vyield of highly -unsat- I -urated fatty. acids, the steps of first separating the mixture into two portions, one of the portions containing a predominant proportion of saturated fatty acids and the other portion containing a predominant proportion of unsaturated fatty acids, the separation being carried out Vat temperatures substantially below those at which thermo-alteration of the fatty acids occurs, and fractionally the unsaturated fatta acid portion, without imparting sumcient i the same to produce substantial thermoalteration of the unsaturated fatty acids, to ob- Y tain a plurality, of fractions of said portion of .different boiling Points, includingI a relatively large high boiling fraction, consisting predominantly-of highly unsaturated fatty acids.

'1. Ina method for treating a mixture of vsath unsaturatedfatty acids'including relatively low boiling saturated fatty acids'and relatively nigh mmm aman-.tea mty acids. to obtain a high yield of unsaturated fatty acids,

the steps of first separating the mixture into two portions. one of the' portions containing a pre-v dominant proportion of saturated fatty acids and the other poridon containing a predominant proportion of unsaturated fatty acids. the separation being carried out at temperatures substantially below those at-'whichthermo-alteration of the fatty acids occurs, snd'treating sepa. rately theunsaturated fatty acid -portion by vaporising. portions thereof and subjecting such vapors under reduced pressure to contact with a series of heat exchanging P0018 of. condensed fatty acid having successively lower boiling points, the pressures t'o-which said vapors are subjected being so low-that the boiling point of the fatty acids -in perature at which substantial thermo-alteration of the .unsaturated fatty acids occurs, condens- .last of said pools, returning a portion of said' ing-the low boiling vapors passing through the condensed lo'rwboiling vapors t0 said pools as reilux liquid, and withdrawing frein said pools L a relatively large fraction consisting pxedomi-v,

nantly of fatty acids of higher boiling point than 'said lowboiling fraction.

ALBER Y fr H. mama. peut vs'rmom. Jaime is.V man.

the unsaturated heing treated at is below the tem

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