US3271410A - Rehydrogenation of hydrogenated fatty acids - Google Patents

Description

United States Patent 3,271,410 REHYDROGENATIQN 0F HYDROGENATED FATTY ACHDS Lucien J. Cagneron, Pekin, IlL, and Eugene A. Skaradzinski, Minneapolis, Minn, assignors to Archer-Daniels- Midland Company, Minneapolis, Minn., a corporation of Delaware No Drawing. Filed July 19, 1965, Ser. No. 473,204 11 Claims. (Cl. 260-400) This application is a continuation-in-part of Serial No. 218,125, filed August 20, 1962, now abandoned.

The present invention relates to the preparation of fatty acids having improved quality characteristics. In one aspect, this invention concerns the rehydrogenation of hydrogenated tallow fatty acids using a palladium catalyst during the rehydrogenation step.

In the ordinary preparation of fatty acids for commercial consumption, hydrogenation of the fatty aicds is frequently employed. Typically, this hydrogenation is carried out until the iodine value of the fatty acid is reduced below 10. Frequently, the iodine value is reduced below 5, e.g., below 2. However, the non-fat constituents commonly present in fatty acids (generally known as unsaponifiable matter) are not completely reduced by hydrogenation. These non-fat portions are primarily responsible for poor color stability, objectionable odor, and poor stability towards concentrated sulfuric acid, ammonia, and amines frequently encountered with fatty acids. Consequently, fatty acids of high quality have heretofore been produced by either treating the fatty acids prior to hydrogenation (or subsequent to hydrogenation) by such techniques as solvent crystallization, solvent leaching, acid treatment, alkali refining, and the like. Such processes can produce fatty acids having improved qualities, but such processes are sometimes wasteful of materials, and may consume a great deal of time and labor. Further, merely continuing the original hydrogenation process, as such, is generally believed to produce no significant improvement.

We have now discovered, and this discovery forms one basis for the present invention, that fatty acids having improved quality characteristics can be conveniently produced by rehydrogenating conventionally hydrogenated fatty acids. These results are particularly surprising since little hydrogenation (as evidenced by the reduction in iodine value) appears to take place during rehydrogenation. In any event, the net result of rehydrogenation is the production of fatty acids having improved color stability, improved odor, and improved stability towards concentrated sulfuric acid, ammonia, and amines.

The process of the present invention, in the broad sense, involves the rehydrogenation of a catalytically hydrogenated fatty acid of conventional character at temperatures of from 200 to 500 F. under pressure of from 10 p.s.i.g. to 5,000 p.s.i.g. for from five minutes to about hours in the presence of a catalytic amount of hydrogenation catalyst. Preferably, the hydrogenated fatty acid to be rehydrogenated is freed of its initial hydrogenation catalyst. For maximum improvement and for extending the catalyst life, the initial hydrogenated fatty acid is preferably distilled before rehydrogenation.

It should be noted that the present invention is directed to the rehydrogenation of a substantially completely hydrogenated fatty acid. Thus, the process of the present invention can be readily distinguished from prior art processes which, for example, have involved the hydrogenation of a triglyceride in a two-step fashion. In such prior art processes, the effect of the multiple hydrogenat-ion was merely to approach that degree of hydrogenation which now can be commercially obtained, in most instances, in a single hydrogenation step. For

3,271,410 Patented Sept. 6, 1966 such a non-analogous prior art process, see US. 2,307,065.

The fatty acids which can be used in the process of the present invent-ion include the C to C fatty acids, individually or as mixture-s. Typically, C to C fatty acids will be processed according to the present invention. Such fatty acids include the fish oi'l fatty acids, tallow fatty acids, tall oil acids, oleic acid, and the like. The manner of hydrogenating the fatty acids, in the first instance, is not critical, and we have successfully employed our process using hydrogenated fatty acids which are commercially available. However, we have obtained improved results by hydrogenating fatty acids, in the first instance, using our process conditions. This seems particularly true where palladium (in one form or another) is used as the hydrogenation catalyst.

The temperatures used for the rehydrogenation step will typically range from 225 to 450 F. We generally prefer to use a temperature within the range of 350 to 450 F., e.g., 375 F. As regards pressure, the rehydrogenation can be effected at pressures within the range of 10 p.s.i.g. to 5,000 p.s.i.g.

We generally prefer to employ a pressure within the range of 50 p.s.i.g. to 2,500 p.s.i.g. Our rehydrogenation process can be conducted on a batch or continuous basis and, if desired, can be integrated with the original bydrogenation process. When operating a batch process, we have found pressures of from 300 to 500 p.s.i.g., e.g., about 400 p.s.i.g., to be satisfactory. In a continuous system, we prefer to employ pressures of from 750 p.s.i.g. to 2,000 p.s.i.g., e.g., about 1,500 p.s.i.g.

The catalysts useful in practicing the present invention are the hydrogenation catalysts. Suitable hydrogenation catalysts include the noble metals, the noble metal oxides, nickel, activated or promoted nickel, copper, cobalt, copper chromite, and the like. These catalysts can be used alone or in combination. They can be used in such diverse forms as powders, pellets, rods, and the like. They can be used free or supported on alumina, refractory oxides, silica, carbon, kieselguhr, and the like. Palladium, in any one of its ordinary catalytic forms, is the preferred catalyst. Particularly preferred as a catalyst is palladium supported on carbon.

The amount of catalyst used will be a catalytic amount, usually within the range of from 0.001 to 1.0 percent by weight (neglecting the Weight of the support) based on the amount of fatty acid to be treated. Commonly, the amount of catalyst will be within the range of from 0.001 to 0.15 weight percent, on the same basis. When using the preferred catalyst (i.e., palladium), we prefer to use, sufiicient commercial catalyst (e.g., palladium on carbon) to provide about 0.01 weight percent palladium, per se.

As previously indicated, any conventional hydrogenation catalyst can be used in a conventional manner in the first or original hydrogenation. This original hydrogenation is ordinarily carried out to the lowest economically feasible iodine value. Typically, this would be an iodine value of 10 or below. For optimum results, the catalyst used in the first hydrogenation should be removed (e.g., as by filtration), although this is not absolutely necessary. However, it is desirable. This is particularly true where a palladium catalyst has not been used in the first hydrogenation step (but is used in the second step) since removal facilitates the reuse and recovery of the palladium catalyst. Distillation of the fatty acids after rehydrogenation is especially desirable since it allows maximum benefits to be derived from the rehydrogenation.

The present invention will be further understood by reference to the following specific examples, which include a preferred embodiment. Unless otherwise indicated, all parts and percentages are by weight.

Example I.A split, bleachable, fancy tallow acid 3 was hydrogenated at 375 F. and 400 p.s.i.g. for a period of 5 hours using 0.2% of a commercial catalyst (5% palladium lOIl carbon), thereby providing 0.01% palladium, per se. After hydrogenation, the catalyst was removed by filtration and the hydrogenated tallow acid was rehydrogenated at 375 F. and 400 p.s.i.g. for 2 hours. Again, 0.2% of a 5% palladium on carbon catalyst was used to thereby provide 0.01% palladium. After rehydrogenation, the catalyst was removed by filtration and the acids were distilled. Rehydro genation appreciably improved the odor of the tallow acids. Color improvement is shown in Table I which follows:

TABLE I Lovibond Color Before Rcliy- After Robydrogenation drogcuation Original color 5% 4Y0.7 R 2Y-0.0R. Color after 2 hrs. at 205 C Y2.1R 7Y0.1R.

Example lI.-Hydrogenated menhaden acids were rehydrogenated at 380 p.s.i.g. and 375 F. for 3 hours, using 0.2% of a 5% palladium on carbon catalyst (thereby providing 0.01% palladium). After rehydrogenation had been completed, the catalyst was removed by filtration and the acids were distilled.

Rehydrogenation caused a noticeable improvement in the odor of the acids. Other improvements in the quality of the acids are shown in Table II, which follows:

Example IlI.Menhaden fatty acids were hydrogenated at 400 F. and 200 p.s.i.g. for 5 hours using 0.1% of a reduced nickel catalyst. The acids were substantially completely hydrogenated (i.e., an iodine value below 10). The hydrogenated menhaden acids were then rehydrogenated without filtration at 375 F. and 1500 p.s.i.g. for 5 hours using 0.15 of a nickel catalyst. After rehydrogenation, the acids were distilled.

The odor of the fish acids, after rehydrogenation, was appreciably improved. The additional processing had provided a fresh, clean odor as compared to the smell of the raw and initially hydrogenated product. Improvement in other qualities are shown in Table III, which follows:

Example lV.Fish oil fatty acids (the same as used in Example III) were hydrogenated as described in Example III. The hydrogenated fatty acids were then fil- TABLE IV Before Rehy- After Rehydrogenation drogenatiou Original color (Lovibond) 5YO.GR 0.5Y0.1R. Colorgfter 2 hrs. at 205 C. (Lovi- 30Y-3R 2.5Y0.5R.

on Stability to cone. sulfuric acid 11 3.

(Barrett color).

Example V.Fish oil fatty acids were hydrogenated with a nickel catalyst in the manner described in Example III. After hydrogenation (which was substantially complete), the fatty acids were filtered to remove the catalyst. Then, the hydrogenated fish oil fatty acids were rehydrogenated at 376 F. and 1500 p.s.i.g. for 5 hours using 0.15% copper chromite catalyst. After rehydrogenation, the acids were distilled. Improvements in the quality characteristics of the fatty acids are set forth in Table V, which follows:

TAB LE V Before Rehy- After Rehydrogenation drogeuation Original color (Lovibond) 5Y0.6R 1Y0.1R. 0%101 after 2 hrs. at 205 C. (Lovi- 30Y-3R 0Y-1.3R.

cnc Stability to cone. sulfuric acid 7.

(Barrett color).

Example VI.A bleachable fancy tallow was batch split with water and then hydrogenated with a nickel catalyst in a conventional manner to thereby produce hydrogenated tallow fatty acids having an iodine value of 1.2. After filtering the hydrogenated tallow fatty acids to remove the nickel catalyst, the fatty acids were rehydrogenated in a batch autoclave (using different catalysts in different runs) at 375 F. and 1500 p.s.i.g. of hydrogen for 2 hours. After rehydrogenation, the fatty acids were filtered to remove the catalyst and then distilled. The effectiveness of the rehydrogenation and a comparison of various hydrogenation catalysts is set forth in Table VI which follows:

From the foregoing examples and description, it is clear that the rehydrogenation of a normally or conventionally hydrogenated fatty acid, especially with the use of a palladium catalyst, can significantly improve odor,

stability to heat, and stability to concentrated sulfuric acid, ammonia, and amines.

Having described the present invention with a certain degree of particularity, it will be realized that numerous minor changes and variations, falling within the spirit and scope of this invention, will become obvious to those skilled in the art. It is not intended that this invention be limited to any of the materials which have been mentioned as specific examples nor by any of the specific proportions which have been given for the sake of illustration, but it is intended to claim all novelty inherent in the invention, as well as all obvious modifications and variations thereof.

What is claimed is:

1. The process of improving the quality of a catalytically-hydrogenated fatty acid which comprises catalytically rehydrogenating said hydrogenated fatty acid at a temperature of from 200 to 500 F. and at a pressure of from p.s.i.g. to 5000 p.s.i.g.

2. The process of claim 1 wherein said hydrogenated fatty acid has an iodine value below 10, wherein said pressure is from 50 to 2500 p.s.i.g., and wherein said temperature is from 225 to 450 F.

3. The process of claim 2 wherein said rehydrogenation is conducted as a batch process and wherein said pressure is from 300 to 500 p.s.i.g.

4. The process of claim 2 wherein said rehydrogenation is conducted on a continuous basis and wherein said pressure is from 750 to 2000 p.s.i.g.

5. The process of claim 2 wherein rehydrogenated fatty acids are subsequently distilled.

6. The process of rehydrogenating a catalyticallyhydrogenated long chain fatty acid which comprises the steps of adding to said hydrogenated fatty acid a catalytic amount of from 0.001% to 1% of palladium by weight based on the weight of said fatty acid, and further hydrogenating said hydrogenated fatty acid at a temperature of from 200 to 500 F. for a period of from 5 minutes to 5 hours under a pressure of from about 380 to about 400 p.s.i.g.

7. The process of rehydrogenating a tallow fatty acid which has hen catalytically hydrogenated with palladium which comprises the steps of adding to said hydrogenated tallow fatty acid a catalytic amount of from 0.001% to 1% of fresh palladium based on the weight of said fatty acid, and further hydrogenating said hydrogenated tallow fatty acid at a temperature of about 375 F. at a pressure of about 400 p.s.i.g. for a period of from 5 minutes to '5 hours.

8. The integrated process of rehydrogenating a catalytically hydrogenated C to C fatty acid having an iodine value below 5 which comprises the steps of removing hydrogenation catalyst from said hydrogenated fatty acid, adding to said hydrogenated fatty acid a catalytic amount of a palladium catalyst and further hydrogenating said hydrogenated fatty acid at a temperature of from 350 to 400 F. for a period of from 5 minutes to 5 hours under a pressure of from to 2500 p.s.i.g.

9. The process of claim 8 wherein the hydrogenation catalyst used to initially hydrogenate said fatty acid is also a palladium catalyst.

10. The process of claim 8 wherein said palladium catalyst is palladium on carbon.

11. The process of claim 8 wherein the rehydrogenated fatty acids are subsequently distilled.

CHARLES B. PARKER, Primary Examiner. ANTON H. SUTTO, Assistant Examiner.

Claims (1)

1. THE PROCESS OF IMPROVING THE QUALITY OF A CATALYSTICALLY-HYDROGENATED FATTY ACID WHICH COMPRISES CATALYTICALLY REHYDROGENATING SAID HYDROGENATED FATTY ACID AT A TEMPERATURE OF FROM 200* TO 500*F. AND AT A PRESSURE OF FROM 10 P.S.I.G. TO 5000 P.S.I.G.