US2416146A - Refining fats and oils - Google Patents

Description

' quantity of such material required.-

' duce a high quality loses.

7 operation.

Patented Feb. s. 1947 UNITED STATE s PATENT OFFICE au its DEFINING FATS AND OILS Howard 0. Black and Walter F. Bollens, Chicago,

alllgnon to Industrial Patents Corporation,

Chicago,- Il l., a corporation of Delaware No Application July 11, 1042, Sfllll N0. 451,310

This invention relates to the refining of fatty material and more particularly to the refining of crude glyceride oils to remove therefrom gums, free fatty acids and coloring matter.

The present invention is concerned with the removal or'free fatty acids and gum and coloring matter from jsuch'oil by a process involving a quality oil while minimizingrefininglosses. In the most widely employed process of refinin vegetable oils with strong caustic alkali solutions,

agreat deal of the valuable neutral oil is lost.

both as the result" of saponification of neutral oil by the caustic solution employed and by entrainment of the oil in the foots or soapstock separated from the oil after the caustic treatment. Prior attempts to'treat crude glyceride oils with a selective solvent for the fatty acids in an attempt to produce neutral or substantially neutral oils has resulted in oils having relatively high free fatty acids, poor color and also the removal of considerable amounts of the neutral oil with the fatty acidsso as to result in relatively high refining losses. Any attcmptto remove additional fattyacids and mprove the color of the oil by alkali treatment has resulted in additional refining losses, and furthermore attempts to reduce the colorof the oil by treatment with adsorbent material such as -adsorbent earths after solvent treatment has been largely ineffective and resulted in the loss of'considerable oil in the residuai' adsorbent material because of the large An object of the present invention is to provide an improved process involving'solvent treatment for'refining glyceride oils and fats so as topr'ooil with mini i d refining Another object of the invention is to provide an improved process of refiningglyceride oils and fats 'toremove impurities therefrom by a series of cooperating steps involving degumming and a cum. (Cl. zoo-42a) residual color and fatty acids without substantial refining losses.

In accordance with the present invention, it has been found that'removal of the gums from the crudeoil prior to solvent treatment results in much more eiiective extraction of the free fatty acids and produces an oil of relatively low color solvent extraction step so as to produce a high which can be easilyi'reduced in color and fatty acid content by a mild caustic wash. The degumming operation involves precipitation of the gums with an' aqueous medium which may be water or an aqueous solution of various. salts which may be neutral or slightly acidic or slight- 1y basic. Depending upon the amount of gums contained in the oil the amount of wateror aqueous medium employed may range from approximately 1% to 10% but will usually range between 2.% and 5%. Precipitated gums which include phosphatides, proteinaceous material,

carbohydrates, resins, etc., may be separated from the bodyof oil by decantation, filtration or centrifugal separation, continuous centrifugal separation at temperatures ranging from approximately 90 to 140 F. depending upon the nature of the oil being preferred. This 'degumming operation referred to, materially reduces the color of the oil and in most cases somewhat solvent treatment to produce a refined oil hav-Q ing-low color and fatty acid content with re-' duoed refining losses.

' A further object of the invention is to provide 'an improved process of refining glyceride oils in which gums and substantial amounts of .fatty acids are simultaneously removed from the oil by a combined degumming and solvent treatment a still" further provide the fatty material is soluble in the solvent. As

obiectof the invention is to I an' improved process orlrefining' oil in which a solvent treated oil treated to remove decreases the acidity of the oil as certain of the gummy materials are acidic. .If-properly carried on losses of neutral oil by entrainment of the oil in the separated gums can be made very small and the resulting oil is conditioned for solvent treatment.

The solvent treatment of the'present invention involves treating the oil with' a solvent'or solvent mixture which selectively dissolves fatty acids in preference to glycerides and thesolvent employed may be any one of a large number of solvents. The solvent selected'shouldnot react with the fatty material, and examples of such solvents which can be used in the present'invention are furiural and isopropyl alcohol. The solvent power of .the selective solvents, including those spe-"" cifically mentioned, increase with temperature and at higher temperatures substantially all of the'temperature is decreased'the various glycerides become progressively insoluble inthe solvent depending upon the number of carbons-toms in the fatty acid radicalsand the "degree of unsaturation of the fatty acid radicals; The free fatty acids are more soluble than glycerides and' oils and selective solvent a.

for any' given oil or I v I temperature is found at which the glycerides are tially all insoiublein the' solvent while the f fatty acid 's are substantially all soluble therein.

At such temperature two phases will be formed, one a solvent phase containing the free fatty acids and the other an oil phase. These phases.

can be separated by decantation or centrifugal 6 separation. In most cases the separation can be carried on at temperatures at which both phases are liquid, but in some instances at least certain of the glycerides may be nuin solid 'forrn The amount of,.solvent' employed will likewise hepend upon the nature of the oil being treated and the,

solvent selected, but will. usually range between one volume to one volume of oil being treated and ten volumes of solvent to one volume of oil.

The greater the amount. of solvent the more selective the separation between the fatty acids and glycerides, but in most cases eifective separation can be effected with an amount of solvent ranging between two volumes of solvent to one of oil** up to live volumes of solvent per volume of oil, 80"

the least amount of solvent which will produce effective separation being preferred.

The solvent extraction step may be carried on in batch by mixing solvent and degummed oil and allowing the resulting mixture to'stand, al-

though a preferred operation is a continuous countercurrent extraction of the-oi1 in an extraction tower. The resulting -oil after separation of the solvent phase containing the free fatty acids is much reduced in color and acidity. 80

lute alkali solution eflectively neutralizes remaining free fatty acids to reduce the oil to a neutral oil commercially acceptable for edible purposes, oils containing between approximately 02% to .05% free fatty acids being easily obtained. After mixing the alkali'solution with the oil, the 40 oil; and aqueous solution will separate into two phases upon standing, one an upper oil phase and the second a lower aqueous phase containing soap,'coloring material and small amounts of-residual gums which may be left in the oil after 8 the degumming operation and solvent treatment. These phases may be separated by decantation or alternatively the mixture may be subjected to continuous centrifugal separation to cause the phases to separate in the centrifuge and be dis charged in separate efliuents. i The amount and concentration ofaikali solution will vary with the nature of the oil but will usually range in concentration between that approximately equal to 1% to 5% caustic soda and be employed in amountsbetween approximately 1% and 20% of the oil. In most cases 10%of a I 2% caustic soda solution will produce a substantially neutral oil having colors at least as low as those obtained by conventional causticalkali reso fining employing large excesses of strong caustic 1 solutions followed by a treatment with adsorbent earth. The temperatureof separation between the oil phase and aqueous phase of the caustic I 2 Wash will also depend upon the nature of the oil cipitated gums separate with the solvent phase being refined and the'amount of concentration. of the caustic solution. In general these :temperatures will rangev between and 200 F., the usual temperature being in-the neighborhood of to 180 F. It has beenfound that very 70 little if any neutral oil is saponified in the alkali washing operation even when caustic soda is employed and that very little ifany neutral oil is entrained in the aqueous phase during separation ii the oil to be washed contains no more. 7

than about 0.2 of free fatty acids. 'The solvent treatment is effective to reduce'the free fatty acid content of the oil to at least 0.2% and the refining losses for the entire process are therefore extremely low. While caustic soda is preferred because of its cheapness, availability and excellent color reducing properties, other caustic alkalies such as caustic potash or even non-caustic. alkalies such as carbonates, etc., may be employed in the alkali washing step although they are not; in general, as eifective for color reduction as caustic alkalies.

The gums removed in the degumming operationare notsubjected to partial or complete destruction by strong caustic solutions as in conventional refining processes and constitute a val-' uable'byeproduct as they may be employed in their crude form as emulsifying agents in certain instances, and valuable materials such as phosphatides, useful for many purposes, can be relatively easily recovered therefrom. Also, the fatty acids from the solvent treatment step are of relatively high quality as they are substantially free. of sums and much of the coloring matter is removed in the degumming step.

With certain'selective solvents. namely those which are substantially immiscible with water or have limited solubility in water, the solvent treatment step may be carried on simultaneously with the degumming step. In such a process the crude oil is simultaneously admixed with both the solvent and water or other aqueous medium.

In general the solvent is saturated with water and employed in substantially the proportions discussed above for solvent treatment of the degummed oil and is admixed with additional water so as to provide substantially the amount of additional water discussed above relative to the degumming step. .The presence of water ad- I mixed with the solvent in most cases renders the solvent even more selective in its action. The free fatty acids are selectively dissolved by the solvent and at the same time the gums are precipitated by the aqueous medium. Uponallowing the mixture to stand, in general three phases are formed, one an aqueous phase containing the gums, another a solvent phase containingthe free fatty acids, and the third an oil phase. A small amount of solvent may be present in the aqueous phase and the oil phase. Thes phases can ordinarily be separated by decantation. The precipitated gums may also be removed from the mixture prior to separation of the oil and solvent phases by filtering the gums from the mixture in which case it is desirable to employ substantially only that amount of water or aqueous medium which will be absorbed by the gums in the precipitation thereof, thus avoiding excess water forming a substantial aqueous phase in subsequent separation of the oil and solvent phase.

As a. preferred operation, the mixture containing oil solvent and precipitated gums is subjected to continuous centrifugal separation to separate the oil andsolvent phases. If the solvent phase is of greater specific gravity than the oil the pre decantation or in some cases by a. subsequent centrifugal separation operation.

By employing a selective'solvent which is sub- 5 stantially immiscible with water or has slight I low.

tinuous centrifugal separation at 135 1"., the re- .sulting oil having a free fatty acid content of .44.

eolubilityonlyinwaterJheso' 'tandaqueom medium Operate substantially independently and an'oil of relatively low color and low acidity is produced. The aqueous medium renders the gums insoluble in the oil, fatty acids and solvents so as to eifectively remove the gums from the oil and amas a v simultaneous degummingand solvent extraction, the same crude cottonseed oil having a free fatty acid content of .45% was treated with two volfatty acids even prior to physical separation so that the solvent doesnot act on. the oil and'fatty acidsin the presence of the gums. 'Ifdesired,thisoil can be subjected to a caustic washing operation as above described to further reduce the color acidity. As in "the modification of the present process involving separate degumming and solvent steps, the refining losses are extremely In operations involving simultaneous degumming and solvent extraction, the temperature of separation of the oil phase andsolvent phase will be determined by the temperature at which free fatty acids are still soluble in the solvent phase whilethe glycerides remain insoluble. 1

As a specific example of the modification of the v present process involving separate degumming and solvent treatment steps, a crude cottonseed oil having a free fatty acid content of .45% and a color of 85 yellow-2 1.8 red, andcontaining subumes of saturated furfural to whichwater in an amount equal to 2% ofthe oil had been added and the resulting mixture was continuously centrifugally separated intoan oil phase-and a solvent phase containing the precipitated gums, the

latterphase being the heavy eiiiuent from the centrifugal. The precipitated gums were then removed from the solvent phase. by filtration. The resulting oil contained .15 free fatty acids.

.This oil was then washed with10% of 2% caus tic'soda solution at 180' I". and-the resulting mixture continuously centrifugally separated. The refining loss was substantiallythe same as the example previously given in which the crude cottonseed oil was first degmnmed, then extracted with wet furfural, and washed with a dilute caus tic soda solution and the color was only slightly higher.'. It is thus apparent that low refining 'losses and high quality oil can also be obtained by employing a simultaneousdegumming and stantial amounts of'gum, was degummed with 2% water. the water being intimately mixedwith the oil. The resulting mixture was subiected to con- This oil was then extracted with two volumes of furfural saturated with water at 110 F. by continuous countercurrent. operation. The resulting oil had a freefatty acid content of .11. This resulting oil was then washed with 10% of a 2% caustic soda solution, separation being accomplishedby continuous centrifugal separation at 180 F. The resulting oil had a free fatty'acid content of .04 and 'a color of '35 yellow-4.5 red,

the refining losses in the entire process being 2.4%. I

To illustrate the improved results obtained over attempting to apply solvent extractionto the crude-oil without desumming, th same crude oil was directly extracted with two volumes of wet furfural at 110 1". by the said countercurrent oil is as good orbetter in quality.

solvent extraction step and such operation has the advantageoi' being a less complicated process requiring less apparatus and less laborand time. In any of the modifications and processes above described, the refining losses are markedly lower than with the conventionally employed refining operations employing strong caustic solutions and bleaching with adsorbent earth and the resulting above, a large number of solvents can be employed for fatty acidextraction' when the extraction is carriedon separately from degumming. In general, these solvents are non-reactive polar solvents, preferably organic. These solvents usually contain one orxmore' of the following groups; alcohol, phenol, carboxylic acid,

extraction operation. The oil resulting from this operation had a fatty acid content of .15, a color of 85 yellow-20 red. This oil was then washed with 10% of 2% causticsoda solution at 180. F.

in the same manner as above. described to produce anoil containing .04 free fattv acids and a color of 35 yellow-16.6 red, the refining losses for the process being 3.5%. Thus the total refining loss in the example involving degumming. solvent extraction and caustic washing was 2.4% as against 3.5% when the degumming step was omitted. Also the color of the oil resultingfrom the example involving prior degumming was- 35yellow- 4.5 red in contrastto a color of 35 yellow-16.6 red when prior degumming was omitted." As another specific example of a processinacid nitrile, acid anhydride, acid amide, carboxylic-ester, aldehyde, ketone, mercaptan, primary amineLor primary amine bases, nitro, sulphate, carbonate, and phosphate groups, and also ties of these materials and the temperatures em-' ployed should be such that two phases are formed and that the solvents are not reactive under the w 1 treatment conditions.

Miscible polar solvents, which; do not meet the, above requirements and also miscible non-polar solvents may. be used in conjunction with the selective polar solvents employed in the present process in order to alter the solubility of certain of the constituents under treatment.

volving degummlng, solvent extraction and caustic washing, the same crude abovediscussed was degummed with 2% water at 135 F. and extracted withtwo volumes of 90% isopropyl alcohol at 90 F. in a continuous countercurrent operation. The resulting oil had a free fatty acid content of .15. This oil was then washed with 10% of a 2% caustic soda solution at 180 F. and produced an oil having .0396 free fatty acids and a" color of 30 yellow-4.0 red, the total refining loss being 1.4%. a

As a specific example of a process involving" Likewise it is possible to increase the .selectivity of the proc'essby employing nonmiscible non-polar solvents which tend to hold the glycerideswhile the polar solvent extracts the fatty acids.

The polar solvents the present purposes include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, allyl alcohol, methylallyl alcohol, phenoLresorcinol, ethylene glycol, ethylene chlorhydrim'diethylene glyco, diethylene thioglycol, ethylene glycol monomethyl ether. ethylene glycol monowhichrnay be employed for aciensa a 1 3 1 ethyl ether, ethylene glycolmonoacetate, ethylene glycol diacetate, ethylene glycold-iformate, eth- 1 ylene'glycol monolactate, ethylene glycol mono-' iglycolataftriethyleneglycol, propylene glycol, 1 butyle'ne' glycol, 1,4, pentandiol, pentantrlol 1,2,5, propylene'glycol-chlorhydrin, glycerol, glycerol r monoacetate, glycerol 'diacetate, glycerol triacejtate, glycerol monobutyrate, glycerol dibutyrate,

, glycerol'monocaproate, glycerol monoproprionate, 1methyl glycolate, etlwl glycolate, ethyl acetoglycolate,methy'l lactate, ethyl lactate, methyl malonate,' ethyl oxylate, lactonitrile, propioniethyl formate, methyl levulina'te, ethyl N.-methyl v trlle, methyl allylnitrlle, formic acid, acetic acid, acetic anhydride, lactic acid, methyl formats, 1

\ carbamate, ethylidine diacetate, ethyl acetoacel tate', methyl acetoacetate, methyl maleate, methj,

yl furoate', methyl chloracetate; metlrvlbyanoace tate, acetaldehyde, methoxyacetaldehyde, fur- 3 fural, furfuryl alcohol, nitrobenzaldehyde, uitro-' ;methane, nitroethane, 2-nitroethyl propionate acetone, diacetyl, diacetone alcohol, acetonyl acetone, fo'rmamide, acetamide, propionamide, bu-' tyramidc, N-ethanolacetamide, aniline, ethyl diamine, diethyl triamine, triethylene tetramine, ethanolamine, diethanolamine, triethanolaminc,

j mono-gly'cerolamine, diglycerolamine, triglycerolamine, tris-hydroxymethyl aminoethane, hy-

1 droxyethyl ethylene diamine, trimethylphosphate,

itriethylph'osphate, diethylsulphate, acetylmethylcarbinol,

;glycol, 2-.hydroxymethyl, 1,3 dioxolone, methyl acetochlorhydrin, dichlorotriethylene 1 butanolone, acetone plus'sulphur, dioxide, liquid 1 sulphur dioxide, liquid carbon dioxide, carbon bijsulphide," and the like.

For simultaneous degumming and solvent exa s trifugally separating by cooling to the temperature at which separate phases can be separated either by-centrifugal separation or by settling and decanting. Since degumming can be eflected over a considerable I range'of temperatures, it is usually possible to carry on such degumming simultaneously with solvent extraction with solvents which are substantially immiscible with water at the temperature of separation between the solvent phase and the 011 Phase. v s

While we have disclosed the preferred embodiments of our invention, it is understood that the within the scope details thereof may be varied of the following claims:

We claim:

'1. The process of refining glyceride oils'con taining gums, free fatty acids and coloring matter, which comprises, degumming said'oilswith; van aqueous mediumv to effectively remove gums from said 011 and treating said 011 with a selective solvent for fatty acids, said process including the stepsof separating from the oil a solventphase containing free fatty acids and an aqueous phase traction of fatty acids," in addition to being non- 1 reactive, the selective solvents employed must be 7 substantially immiscible with water or have limiited solubility therein. Thus, such solvents as Phenol, glycerol triacetate, ethyl oxylate, methyl formate,,ethyl formate, ethyl acetoacetate, methi yl acetoacetate, methyl furoate, furfural, nitrcinconjunction with the polar solvent or solvents 1 in order to set up opposed solubilizing action on 1 the oil and fatty acids, particularly when using a polar solvents possessing very high solvent action. It is also possible to employ miscibl non-polar solvent or miscibleanti-solvents along with the I polar solvents in order to improve or produce or otherwise control solvent properties on the matcrials which are not desired to be extracted.

Various types of solvent extractiontreatment may be employed. For example, continuous coun- 1 tercurrent extraction in an extraction towerat constant temperature as employed intthe specific examples above given are particularly effective, a Such countercurrent operations may also be car- 1 ried on in a series of chambers through which the 1 oil phase progresses in onedirection and the sol- I vent fatty phase in the other direction.- Also, the j extraction steps may be carried out in batch either by mixing the solvent with the oil at the 1 temperature desired forsebaration and then'cencontaining gums to produce a resulting oil sub-\ stantially free from gums and having reduced color and fatty acid content, and the step of further treating the resulting oil with a dilute alkali solution to further reduce the color and fatty acid content of the oil.

2. The process of refining glyceride oils containing gums, free fatty acids and coloring matter, which comprises, mixing said oil with an aqueous medium in an amount betweenabcut 1% and 10% of the oil to precipitate gums there in, separating the recipitated gums from said oil, and thereafter treating said oil with a selective solvent for fatty acids in an amount between approximately one and ten volumes of solvent per volume of oil to remove a substantial amount of fatty acids from said oil and produce a resulting oil substantially free from gums and having a. reduced color and fatty acid content and thereafter treating the resulting oil with a dilute alkali solution having a concentration equivalent to approximately 1% to 5% caustic soda and in an amount of between approximately 5% and 20% of the oil to further reduce the color and fatty acid content of said oil.

3. The process of refining glyceride oils and fats containing gums, free fattyacids and 00101! ing matter, which comprises, simultaneously treating said oil -with an aqueous medium for precipitating'gums and a selective solvent for fatty acids for dissolving free fatty acids in preference to said oil and separating from said oil an aqueous phase containing said gums and a solvent phase containing a substantial amount of free fatty acids, to produce a resulting oilsub stantially free from gums and having a reduced I color and fatty acid content, and thereafter treating the resulting oil with a dilute alkali solution to further reduce the color and free fatty acid content of the oil. 7 v

4. The process of refining glyceride oils and fats containing gums, free fatty acids and coloring matter, which comprises, simultaneously. treating said oil with an aqueous medium for I precipitating gums and a selective solvent j-for.

fatty acids for dissolving free fatty acids in preference to said oil, said solvent being sufficiently the mixture or allowing 7 separate strata toform followed by decantation.- Also the temperature during the mixing maybe increased to an; extent which causes substantially all of'the fatty materialto be dissolved followed H said "aqueous medium, 16: 9- ara'ting from u st ti am un "duc'e aresulting oil substantially free from gums 'a reduced color and iatty acidcon 1 a d "h n -ten't,' and' -,tl'uereafter --treating the resulting oil thadilute alkali solution to further reduce the Ireefatty acid content of the oil.

The-process of] refining fj'glycerideoils and Y ats taming gums, free Iatty'acids andcobtreating saidyoil with aqueous medium for recipi' tating gums and 4 a selective solventv for tt fi l o "-er'e'nce to said. oil. saidsoiventbeing 'substan ----tiall'y. immiscible with 1 solvent ph a Y amountoffree I oil substantially iree fromv gums v saidilcfl' n adueousphasecontain gum'sand a soiventphase: containing a I water, andjsega'rating from said, oil an aqueous phase containing sald'gur'ns' containing 'a' substantial fatty acids-to produce a resulting a d ha n a.

includin 7 10- 4 fatty acidsin preference to said oil, said process the vsteps oi separating from the oil a substantial amount of free fatty acids to produce a resulting oil substantially free from gums tent, thereafter admixing with said oil a dilute solution o! caustic soda in suflici'ent amount to 'fneutralize the remaining free fatty acids and v v soapfand coloring matter. oring; matter,- which comprises," simultaneo mlyv v V v. ,,1s dissolving Ireeiatty acids in prerreduced color and fatty acid content and'thereafter mixing a dilute solution 01. caustic soda with said resulting oil and an aqueous phase -acid content of said oil.

" The process or ,reflnlnggiyceride-oil con said oils with I and coloring mat- .separating fromfsald 0111.5 .2 3 7 v 7 containing soap and coloring; matter to further'reduce the colorand tree 'fattyfrom-said oil 'and' treatfflie of this. patent:

' "further reduce the color of said oil and separatphase containing ing from said 011 an aqueous HOWARD 0. BLACK. WAL ER F. BOILERS. v unanimous crran The following'references are of record in the STATES PATENTS Number Name Date [2,254,101 Clayton Aug. 26, 1941 ;"1,194,'014 Handy et a1. Aug. 8, 1916 1,371,342 Bollmann Mar. 15, 1921 Tischer Aug. 24,193! I 2,190,588 Clayton Feb. 13, 1940 Thurman Oct. 29, 1940 stnanrem, Chemie andTechnologie der Fette und Fetterokukte," vol. 2, pgs.w 19, 20, and 21, 1937. (COD? in Div. 63.)

. 'Dean, Utilizati6n of Fats," pr). 162, 1'13 and 165. Pub. by A. Harvey, London 1938. 1 (Copy 1 acids in 'suflicient amounttose'lectively dissolve, a in m 53.)

said precipitated gums and solvent containing