US2062837A - Process of preparing color-stable fatty acids - Google Patents

Description

Patented Dec. 1, 1936 UNITED STATES 2,062,837 JROOESS OF PREPARING COLOR-STABLE FATTY ACIDS Madison L. Sheely, Des Plaines, Ill., assignor to Armour and Company, tion of Illinois Chicago, 111., a corpora- No Drawing. Application October 16, 1935, Serial No. 45,360

13 Claims.

This invention relates to processes of preparing color-stable fatty acids, and it comprises processes wherein crude fatty acid-containing materials, such as garbage grease, acidulated fatty acid foots,

crude fatty acids from the splitting of fats, and similar materials containing substantial amounts of free fatty acids, are treated, prior to distillation, to render color-forming bodies in such materials', less effective to discolor the distilled fatty acids, to improve the odor and to stabilize the acids against rancidity, and the thus treated crude niateriais then distilled.

Free fatty acids, such as oleic, palmitic, stearic, lauric, linoleic, linolenic, and others are substances produced in enormous quantities from fatty acid-containing materials. Hitherto the better grades of fatty acids, namely those having but little color, or substantially colorless, have been commercially produced only from rather high quality raw materials. The problem of color is a serious one in the industry.

Many crude products containing commercial quantitiesof free and combined fatty acids would be extremely valuable sources of high grade fatty acids were it not for the fact that such fatty acids, when distilled with steam under vacuum in the usual way, rapidly discolor.

Black cottonseed fatty acids, acidulated fatty acid foots, garbage grease, brown grease, and sim- 30 ilar crude materials, all contain commercially important quantities of free fatty acids, and these fatty acids can be distilled therefrom in the usual way. These sources of free, distillable fatty acids, however, contain color-forming bodies which ap- 35 pear to distil over with the fatty acids. Although a fatty acid distilled from such a crude, highly colored mixture, may initially be quite colorless,

or substantially so, in the course of aging in storage, or in transit, the fatty acid soon colors.

40 This phenomenon has greatly limited the uses to which distilled fatty acids from these crude sources can be put, and any process of preventing such coloration, in other words, of rendering the distilled fatty acids color-stable, would be of great economic significance in the art. Various attempts to bleach the distilled, colored fatty acids have been suggested. Decolorizing agents, bleaching solutions, etc., have been used with indifferent success, and the problem has hitherto been regarded as most difficult of solution. Although the art has continued to distil' free fatty acids from these very crude, in many instances, almost waste, sources, the fatty acids obtained have naturally been of low grade. 55 One source of distillable free fatty acids, yielding however, only low grade products, is that material collectively referred to as acidulated fatty acid foots. 'Most naturally occurring vegetable and animal oils are predominantly glycerides as sociated with some free fatty acid, color bodies,

albuminous material and other impurities. In the refining of such fats and oils to fit them for use in edible products for instance, they are customarily treated with alkaline solutions. The alkali reacts with the free fatty acids to form soap and dissolves coloring matter from the oil. The "foots thus formed settle to the bottomof the tank carrying with them some entrained neutral oil. There may also be some saponification of the fat, although this is ordinarily restricted. The alkali washings are removed from the treated fat or oil and neutralized with a mineral acid. The acidulated products, after washing with water and drying, are the acidulated foots. Cottonseed, corn oil, coconut oil, and many others are alkalirefined in this way and great quantities of acidulated foots accumulate. All of the foots are highly colored. Acidulated cottonseed foots may contain from 50 to 90 percent of free fatty acids calculated as oleic, and from 1 to 50 percent of neutral fat (glycerides) extracted along with the fattyv acids from the alkali-treated oil. An aver- -age analysis is about 70 percent free fatty acid, and about percent neutral fat, the rest being moisture (1 percent), coloring matter and other impurities.

Acidulated coconut foots will average about 50 percent free fatty acid, as lauric, about 47 percent neutral fat, and about 1 percent moisture, the rest being coloring matter and other impurities.

Ordinarily the free fatty acid in such materials is first distilled therefrom in ways well known, and then the still residue is hydrolyzed, or split to liberate further quantities of free acids from the neutral fat. But, as stated, fatty acids distilled from such sources, are of poor grade.

Anothercommercial source of fatty acids is waste grease-like materials such as garbage grease and brown grease. These products are of low grade, as would be expected, and their content of free fatty acid will average, in the case of brown grease, about 25 percent expressed as oleic, and in the case of garbage grease, about 37 percent, as oleic, the remainder being mostly neutral fat, about 1 percent of moisture, and a few percent of coloring matter and other impurities.

The problem of color stability in distilled fatty acids is not restricted tothe very low grade fatty acid-containing materials just described. Disadvantageous discoloration may occur in the distillation of fatty acids obtained from the hydrolysis or saponification of neutral fats, and may even occur in the distillation of oleic acid, or red oil, obtained from high grade fats such as tallow. It is also a problem of significance in connection with. the distillation of fatty acids made synthetically, as by treatment of petroleum products.

Just why fatty acids distilled from crude sources should develop color is not at all clear.

There have been theories advanced, and attempts have been made to determine the nature of the coloring matter. But what it actually is is still unsettled. The fact remains, however, that color does develop. The color bodies may be highly complex organic compounds distillable along with the fatty acids. Possibly they are latent color bodies. That is to say, they may initially be colorless, but exposure to air and light, or other atmospheric influences initiates molecular changes therein whereby colored compounds are formed. Or they may be both initially colored and latent color bodies, so that they initially color the distilled fatty acids, and the color is increased as the latent color bodies undergo change to the colored form. Conceivably they are highly reactive, unsaturated compounds.

To illustrate the peculiar behavior of distilled fatty acids, I distil the acids from an ordinary commercial sample of so-called autoclaved black cottonseed fatty acids. This is a material with which the art is familiar, and is a commercial product. The initially distilled acids show, in a Lovibond colorimeter, a red of 0.9 and a yellow of 8 when read through a 1%" column. (All color readings hereafter given are read through a 1% column). After this initially distilled acid is submitted to an accelerated aging test by heating for one hour at 120 C. the color of the distillate is red 11 and yellow 30. The accelerated aging test indicates quickly the expected color stability of the fatty acids. Similar rapid coloration on accelerated aging is characteristic of fatty acids distilled from other crude sources, such as acidulated foots and greases.

I have now set myself to the problem of increasing the color stability of fatty acids distilled from sources containing color-forming constituents, and I have discovered ways by which the normal discoloration can be markedly reduced, and in many cases wholly prevented. I have been able to obtain distilled fatty acids which have color characteristics comparing favorably with the color characteristics of the high grade fatty acids, and thus 1 have been able to obtain high quality fatty acids from sources hitherto regarded as commercially incapable of yielding fatty acids, except at great expense, which are suitable for uses where a white material is desired.

I have discovered ways of treating the fattyacid-containing materials prior to distillation so that the color-forming constituents therein are so modified, destroyed, or chemically converted that they either do not distil with the fatty acids, or, if they do distil in modified form, they are rendered incapable of markedly coloring the distilled fatty acids. In other'words, the processes of my invention are diametrically opposed to those hitherto suggested. Whereas prior workers in the art have sought to bleach or decolorize the distilled fatty acids, I go to the root of the problem and act upon the color-forming substances in the fatty acid source prior to such distillation. To put it another way, I pretreat the material prior to distillation.

As stated, the processes of the present invention are primarily directed to the treatment of the cruder materials containing free fatty acids in commercially distillable quantities. These materials include acidulated foots, low grade grease such as garbage grease and brown grease, and hydrolyzed fatty acid mixtures, such as autoclaved or twitchellized black cottonseed fatty acids. All of these products are well known in the art. In addition, the processes of the present invention are, of course, limited to those fatty acid sources which contain color-forming constituents tending to discolor the distilled fatty acids. Such color-forming constituents are present in all of the crude materials enumerated.

In order to keep the description of my invention within reasonable bounds, I shall describe it with more specific reference to the treatment of autoclaved black cottonseed fatty acids, it being understood, however, that the processes to be described are equally effective inthe treatment of acidulated foots, greases and any other crude, commercial source of free fatty acids containing color-forming substances tending to impart color to fatty acids distilled from such sources.

In its broadest aspects my invention comprises the heat treatment of crude or waste materials containing substantial quantities of free fatty acids, and containing color-forming bodies normally tending to discolor fatty acid distillates obtained from such crude materials. I have dis covered that when such crude products are heated for varying periods of time at a temperature of about 175 C. to 225 C. they will thereafter give fatty acid distillates having markedly improved color stability in comparison with fatty acid distillates distilled directly from the crude materials.

For example, I beat at atmospheric pressure a batch of black autoclaved cottonseed fatty acids for three hours at a temperature of about 190 C. After this heat treatment I then distil the free fatty acids from the heated black acids with steam under vacuum. The steam distillation which I employ is that customarily used in the distillation of fatty acids, and distillation practice in this step is so well known that I shall not describe it in detail.

I compare the advantages of my heat treatment prior to distillation with distillation without such heat treatment by determining the color of the fatty acids both before and after accelerated aging. In this example, fatty acids distilled directly from the black acids (without pretreatment) showed a distillate color of red 0.9 and yellow 8. After accelerated aging at 120 C. for one hour the distillate was red 11 and yellow 30. When I pretreat the black fatty acids by heating, as described above, prior to distillation, and then distil, the distillate is red 1.7 and yellow 8. After accelerated agingfor one hour at 120 C. the distillate is red 3.6 and yellow 20. This shows a marked improvement in the color stability of the fatty acids.

This broadest aspect of my invention is, of course, subject to modifications. The length of time the fatty acid-containing materials should be heated will naturally vary with the material treated. If the color constituents appear to be present in large quantities, a somewhat longer heating period will be necessary, up to five or six hours, for example. at temperatures much in excess of 250 C., since this may result in decomposition of the fatty material. It is to be expected that those practising my invention will make brief tests on batches of fatty acid containing materials in order to determine the best time and temperature in accordance with the principles which I have laid down.

At this point I wish to distinguish from methods hitherto proposed for the heat treatment of fats and fatty oils. It is not new to heat treat fats for the precipitation of albuminous mate- Ordinarily I do not heat rials therein, and in such heat treatment there may be some incidental distillation of free fatty acids. But the quantity of fatty acids present is minute. Although I am utilizing a heat treat- .ment, I am heating a class of substances not hitherto treated in this way. No one has hitherto heat-treated commercial sources of free fatty acids prior to distillation for the express purpose of so changing or modifying volatile color constituents therein that they no longer color the distilled fatty acids.

This phase of my invention is also not to be confused with the ordinary distillation of free fatty acids since in that case insufiicient time is given for the conversion of the color constituents to harmless substances. In the distillation they tend to distill out directly along with the fatty acids and thus contaminate the distillates.

The heat treatment described above, while beneficial, is greatly improved when catalysts are present in the mixture. I have discovered that better results are obtained when the fatty acid-containing material is heated at the temperatures specified above in the presence of about 0.5 percent of nickel-containing catalysts. These catalysts can be nickel catalysts ordinarily used in the hydrogenation of oils or they can be, and advantageously are, spent nickel catalysts which are no longer efiective for the hydrogenation of oils. Thus, for example, autoclaved black cottonseed fatty acids when heated for three hours at 180 C. in the presence of 0.5 percent of a hydrogenation catalyst of the nickel type, will give, on distillation, fatty acids which, after accelerated aging, show a red of 2.8 and a yellow of 10. It is apparent that the color of these fatty acids, after accelerated aging, is somewhat better than that when no catalyst is present.

I do not, however, regard the heat treatment in the absence of a catalyst equivalent to the heat. treatment in the presence of a catalyst. In the first place it is obvious from calorimeter analysis of the distilled fatty acids that marked improvement is obtained by the use of a catalyst. In the second place I believe that the catalyst exerts a definite catalytic effect on the color bodies in the initial material so that polymerization, or conversion to substances no longer distilling with the fatty acids, is greatly facilitated.

Garbage grease and acidulated foots can, of course, be similarly heat treated either with or without a catalyst and the fatty acids then distilled therefrom. Neutral glycerides are constituents of such greases and foots and I can split these glycerides to liberate further quantities of free fatty acids after'the distillation of the original fatty acids in the material. Or I can subject the original material, prior to heat treatment, to a splitting, hydrolysis, or saponification, in the usual way, recover crude fatty acids therefrom, and then subject the crude fatty acids to the heat treatment prior to distillatlon.

It is sometimes advantageous to introduce an inert gas such as nitrogen or carbon dioxide into the fatty acid-containing material during the heat treatment described. Steam, and even air, is also beneficial in aiding in the conversion of color-forming bodies to harmless substances and, in the appended claims, heat treating, of course, is intended to broadly include heat treating in the presence of these added gases.

' I shall now describe still further modifications of my invention which are superior to those just described. I have discovered that the best results are obtained when the fatty acid-containing material is subjected to the action of hydrogen gas in the presence of a catalyst at elevated temperatures and pressures.

For example, I treat autoclaved black cottonseed fatty acids with hydrogen for two hours at a temperature of about 200 C. and under a pressure of 75 pounds per square inch inthe presence of 0.5 percent of a hydrogenation catalyst such as the nickel-bearing type. Free fatty acids distilled from such a pre-treate'd source of fatty acids show, on accelerated aging at C. for one hour, a red of 1 and a yellow 01' 5. This, it may be noted, is very much better than that obtained by the simple heat operation previously described.

This hydrogen treatment is susceptible to a number of modifications. I need not operate at pressures above atmospheric. I can, for instance, work at ordinary pressure, and I can vary the pressure from atmospheric to 75 pounds per square inch or higher. Similarly, I can vary the temperature from about C. to 200 C. or 225 C. and obtain good results. The length of time is also not particularly critical although it will be governed, of course, by the nature of the materi al undergoing treatment. Ordinarily, about 2 to 3 hours is sufficient at elevated pressures of the order of 50 to '75pounds. At atmospheric pressure I find that the time is somewhat extended and about six hours is best. Likewise,

at a temperature of C. a somewhat longer time is desirable. Thus, for example, black fatty acids can be heated at 150 C. at atmospheric pressure for six hours in the presence 'of 0.1 percent of a nickel-chromium catalyst and will give a fatty acid distillate which, after accelerated aging, shows a red of 3.9 and a yellow of 9.

The catalysts which I use are advantageously those useful in hydrogenating fats and fatty modification of my invention resides in the fact that spent catalysts from a hydrogenation operation can be used most effectively. That is to say, I can use catalysts which are no longer. efiective in the hydrogenation of fats and fatty oils.

This modification of my invention should be clearly distinguished from the ordinary hydrogenation of Vegetable and animal oils. It is very unusual .to hydrogenate materials containing large quantities of free fatty acids. Most' of the catalysts, such as those mentioned above, are poisoned by the presence of free fatty acids and other impurities in the mixture undergoing hydrogenation. In this modification of my invention I am not hydrogenating any fat, fatty oil, or free fatty acid to any substantial extent. The iodine number of the materials which I treat with hydrogen does not drop, or will not drop more than a few points, usually notmore than 1 or 2, and at the most 15 or 20. This means that the hydrogen treatment which I use is not hydrogenation at all in the ordinary sense. Were there hydrogenation, the iodine number of the oleic acid present, for instance, would decrease greatly. The drop in iodine number may possibly be due to hydrogen absorption by the color bodies if they be highly unsaturated, and have iodine values of the order of three hundred. There maybe, of course, some slight incidental absorption of hydrogen by the fatty material itself but I endeavor to keep this as low as possible. When treating cottonseed fatty acids, the final products contain large amounts of oleic and linoleic acid, thus indicating that the stabilization treatment by the present invention is not comparable with the more or less complete satu ration of these components in ordinary hydrogenation processes.

Moreover the amount of hydrogen which I use is very low. For example, for a charge of 35,000 pounds of autoclaved cotton seed fatty acids only 2,800 cubic feet of hydrogen is necessary.

In one commercial adaptation of my process I charge an autoclave with 25,000 pounds of twitchellized black cottonseed fatty acids containing about 1 percent of a spent nickel catalyst from an ordinary hydrogenation-of-oils process. This catalyst is no longer effective to hydrogenate unsaturated fats or fatty acids. I then heat the charge to about 130 C.-l50 C. and pass in hydrogen gas so that the pressure in the autoclave is maintained at '75 pounds per square inch. The hydrogen is kept in contact with the charge for two hours and thirty minutes at 75 pounds pressure, and at the temperature stated. Then the temperature is allowed to fall and the'batch kept in the atmosphere of hydrogen for another hour and thirty minutes. Thereupon the catalyst is, if desired, filtered out of-the treated charge for reuse and the fatty acids distilled. The total amount of hydrogen used is 1,760 cubic feet.

The original iodine number of the charge is 105.6. The final iodine number, after the hydrogen treatment is 102.8, a decrease of but 2.8, which indicates practically no hydrogenation of any unsaturated fats or fatty acids. Fatty acids distilled from the original material without the hydrogen treatment show a red of 2.7 and a yellow of 9 after accelerated aging. Fatty acids distilled from the hydrogen-treated material show a red of 0.9 and a yellow of 4 after accelerated aging.

Just what happens in this hydrogen treatment is not clear but I believe that, as stated above, the color bodies present in the crude fatty acid material are possibly highly unsaturated and hydrogen may unite with them to form compounds less highly saturated and which no longer ,have the property of distilling over with the fatty acids and developing color. These color forming bodies may possible be latent color bodies. That is to say, they may be initially colorless, but on contact with air, they may go over to colored compounds. The saturated latent color bodies may possibly distil with the free fatty acids but, because they are now saturated, they no longer develop color on aging.

The hydrogen treatment in the presence of a catalyst is to be regarded as a distinct specie of my invention and is not equivalent to the simple heat treatment described above. In the simple heat treatment I am inclined to believe that the color bodies or latent color bodies are either chemically decomposed, oxidized, or polymerized to form substances which quite possibly no longer vaporize with the free fatty acids. In the case of the hydrogen treatment it is more likely that the color bodies are saturated with hydrogen to give substances which do not develop color in the presence of air or light and hence it does not matter whether they distil with the free fatty acids or remain in the residue. What actually happens is, of course, not definitely known, and I do not intend to be bound by any theories presented.

Although the above hydrogen treatment in the presence of a catalyst gives me the best results, I need not always have a catalyst present. For example, when autoclaved black cottonseed fatty acids are heated with hydrogen at 50 pounds pressure at 180 C. for three hours in the absence of any catalyst, the color of the fatty acid distillate after accelerated aging is red 4.3 and yellow 10. This is in contrast to autoclaved black cottonseed fatty acids directly distilled without any preliminary treatment, and which show on accelerated aging under identical conditions a red of 11 and a yellow of 30, and is further evidence that the action, whatever it may be, is not a hydrogenation in the ordinary sense of the word.

When using catalysts, the catalyst can be recovered for reuse by filtering it from the distillation residue, or it can be recovered from the treated material prior to distillation, and I am able to use the catalyst over and over again as many as ten times without noticing any particular lessening in efiiciency. I can also use hydrogen-containing gases such as water gas.

When I employ gas treatment, such as hydrogen, nitrogen, air, or steam I use apparatus by means of which the batch of material under treatment can be agitated or stirred. This method of achieving better liquid-gas contact is, of

course, conventional and I do not describe it in detail. During the heat treatment, whether it be in the presence or absence of a catalyst, or added gas, there is practically no distillation. I deliberately avoid the distillation of any considerable quantity of fatty acids during the preliminary heat treatment since otherwise the benefit of my invention would be naturally lessened. In other words, I- do not wish to distil the free fatty acids until the color constituents in the mixture have been so modified that they will not cause coloration in the fatty acids after distillation thereof. In the appended table I summarize results obtained with the various methods described herein, and also give additional examples.

Treatment of autoclaved black cottonseed fatty aczd Color of distillate gggg a g after aging one Treatment prior to dis M 110111 at 120 C.

tillation Red Yellow Red Yellow Control-no treatment. 0, 9 3 11, 30

l. Heated 3 hours at 190 C.

o c alyst or s 1. 7 s 3. c 20 2. Same as l but 0.5 percent Ni catalyst 1. 2 8 2. 4 l0 3. Heated at 180 0. Steam at atmos. pressure. 0.5 percent Ni catalyst- 1. 9 12 5. 2 l7 4. Heated 3 hours at 180 0.

Hydrogen 50 pounds pressure. No catalyst. 1. 5 l0 4. 3 l0 5. Heated with nitrogen [or 6 hours at 150 C.atmos. pressure. 1 percent Ni catalyst 0. 9 9 4. 6 15 6. Stirred with hydrogen for fihours at 150 C. atmos. pressure. 1 percent Ni catalyst 0. 7 4. 4 l3 7. Stirred with water gas for Bhours at 150 C. etmos. pressure. 1 percent Ni catalyst 0. 8 9 3. 8 10 8. Heat 2 hours at 200 C. in hydrogen at 50 pounds pressure with 0.5 per cent Ni catalyst 0. 7 4 l. 4 6 9. Same as 8 but 75 pounds pressure 0.7 3 1.0 5 10. Heat 3 hours at 180 C. in

hydrogen at 50 pounds pressure with 0.1 percent Ni catalyst l. 0 5 1. 9 S 11. Same as 10 but 0.05 percent catalyst 1. 0 7 2. 5 10 In the above table it is to be noted that the color of the distillate both before and after accelerated aging is given. This will show the marked improvement obtained by the process of the present invention.

In the above table data for black cottonseed fatty acids is given in detail. Fatty acids of improved color-stability can be obtained in like manner from the many other sources of fatty acids described above. When dealing with mixtures containing substantial amounts of neutral fats, I can hydrogen-treat the original material, steam distil the fatty acids, and then split the still residue (neutral fat) or I can split the original material, recover crude black fatty acids therefrom and then hydrogen-treat the fatty acids as I have described. In other words, when my origi nal starting material contains considerable fat, I can first hydrolyze the fat and recover all available fatty acid (both free and combined as glycerides) from the starting material, and then heat-treat the recovered fatty acids.

I wish to point out that my invention is not concerned with the bleaching of ordinary fats or fatty oils which contain relatively small quantitles of free fatty acids. Such oils are substantially composed of neutral fats and the free fatty acid therein is to be regarded as an impurity. In the refining of such fats it is customary to remove free fatty acid prior to any bleaching or decolorizing of the neutral glycerides. And the decolorized or bleached product is not distilled. There have been proposals in the pastto heat treat the neutral glycerides for. the purpose of bleaching them. In this process some free fatty acid may be formed as a by-product during the heating action and distil out of the mixture. However, the quantity of free fatty acids formed in this way is insignificant and is not to be regarded as a commercial source of free fatty acid. As stated, all of the materials which I utilize in the present invention can be regarded as commercial sources of free fatty acids. They will all contain substantial quantities offree acid, generally at least 10 percent, this being about the minimum free fatty acid, as oleic, in brown grease. 'The direct distil- .lation of crude fatty acid containing materials in which the amount of fatty acid less than 10 percent is not commercially practical. Hence the processes of the present invention are to be distinguished from the. bleaching or decolorizing of the substantially neutral fats or fatty oils in which the amount of free fatty acid is most always less than 10 percent.

Fatty acids obtained by the processes of the present invention, in addition to having color stability, are also improved with respect to odorand the development of rancidity.

Having thus described my invention, what I claim is:

1. In the process of distilling fatty acids from crude mixtures containing substantial amounts mally discoloring the distilled fatty acids, the

' steps which include subjecting the crude mixture, prior to distillation, to a heat treatment at a temperature ranging from about 150 C. upward but below the decomposition temperature of the fatty acids in the presence of hydrogen gas to render said color-forming bodies substantially less effective to discolor the distilled fatty acids, but without. any substantial hydrogenation of the fatty acids in said mixture, and then distilling fatty acids of improved color stability from said heat-treated mixture.

2. The process as in claim 1 wherein the temperature during the heat treatment is of the order of 150 C. to 225 C.

3. In the process of distilling fatty acids from crude mixtures containing substantial amounts thereof together with color-forming bodies normally discoloring the distilled fatty acids, the steps which include subjecting the crude mixture, prior to distillation, to a heat treatment at a temperature ranging from about 150 C. upward but below the decomposition temperature of the fatty acids in the presence of hydrogen gas and a nickelbearing catalyst to render said color-forming bodies substantially less effective to discolor the distilled fatty acids, but without any substantial hydrogenation of the fatty acids in said mixture, and then distilling fatty acids of improved color stability from said heat-treated mixture.

4. In the process of distilling fatty acids from crude mixtures containing substantial amounts thereof, together with color-forming bodies normally discoloring the distilled fatty acids, the steps which include subjecting the crude mix ture-prior to distillation, to a heat treatment at a temperature ranging from about 150 C. upward but below the decomposition temperature of the fatty acids in the presence of hydrogen gas and a catalyst of the hydrogenation type to render said color-forming bodies substantially less effective to discolor the distilled fatty acids, but without any substantial hydrogenation of the fatty acids in said mixture, and then distilling fatty acids of improved color stability from said heat-treated mixture.

5. In the process of distilling fatty acids from crude mixtures containing substantial amounts thereof, together with color-forming bodies normally discoloring the distilled fatty acids, the steps which include subjecting the crude mixture, prior to distillation, to a heat treatment at a temperature ranging from about 150 C. upward but below the decomposition temperature of the fatty acids in the presence'of hydrogen gas and a spent hydrogenation catalyst to render said color-forming bodies substantially less effective to discolor the distilled fatty acids, but without any substantial hydrogenation of the fatty acids in said mixture, and then distilling fatty acids of improved color stability from said Heat-treated mixture.

6. The process as in claim 3 wherein the temperature during the heat treatment is of the order of 150 C. to 225 C.

'7. The process as in claim 4 wherein the temperature during the heat treatment is of the order of 150 C. to 225 C.

8. The process as in claim 5 wherein the temperature during the heat treatment is of the order of 150 C. to 225 C.

9. In the process of distilling fatty acids from crude mixtures containing substantial amounts thereof together with color-forming bodies normally discoloring the distilled fatty acids, the steps which include subjecting the crude mixture, prior to distillation, to a heat treatment at a temperature ranging from about 150 C. upward but below the decomposition temperature of the fatty a temperature ranging from about 150 C. up-

ward but below the decomposition temperature of the fatty acids in the presence of hydrogen and a spent catalyst of the hydrogenation type to render color-forming bodies in said mixture substantially less eflective to discolor the distilled fatty acids, but without any substantial hydrogenation of the fatty acids in said mixture, and then distilling fatty acids of improved color stability from said heat-treated crude mixture.

12. The process as in claim 11 wherein the temperature of the heat treatment is about 150 C. to 225 C.

13.. The process as in claim 11 wherein the temperature is about 150 C. to 225 C. and the pressure is of the order of 50 to 75 pounds per square inch.

MADISON L. SHEELY.