US2276517A - Treatment of tall oil - Google Patents

Description

- Patented Mar. 17, 1942 TREATMENT OF TALL OIL Ernst Segessemann, Newark, N. J., assignor to -National Oil Products Company, Harrison,

N. J a corporation of New Jersey No Drawing. Application December 16, 1939, Scrial'No. 309,704

(Cl. zoo-97.5)

8 Claims.

This invention relates to the production of valuable products from tall oil and more particularly to the separation of tall oil into its main constituents, rosin and fatty acids.

Tall oil" or talloel which literally means "pine oil is the resinous and fatty by-product obtained chiefly in the production of paper pulp from resin-bearing woods by the so-called sulphate process. In the sulphate process wood is digested with an alkaline liquor containing sodium sulphate during which process tall oil accumulates in the form of its sodium soap on the surface of the waste liquor. The main constituents of this oil after acidification comprise fatty acids and resinic acids each of which are valuable commodities in substantially pure form.

Various processes have been proposed in an attempt to effect separation of tall oil into its main constituents, i. e., fatty acids and resinic acids. One process comprises esterify'mg the fatty acids in tall oil with a low boiling alcohol and separating the resulting fatty ester from the free rosin acids by distillation or by alkali extraction. Another known process comprises esterifying the fatty acids with a polyhydric alcohol and distilling off the resinic acids. According to another process both the fatty acids and the resinic acids are esterified with a polyhydric alcohol and the resin esters are then catalytically split and the liberated resinic acids distilled off. While the foregoing and other known processes have been employed with varying degrees of success,'they all exhibit certain disadvantages, primarily in that only partial separation is efiected. Moreover, the

fatty acid fraction obtained by these processes,

consisting mainly of a mixture of oleic, linoleic and linoleic acids, is not particularly suitable for a wide variety of industrial uses. Usually having an iodine value of about 120 to 130, this fatty acid fraction (or its esters) shows some drying properties but these drying properties are not pronounced enough for a drying oil of good quality. On the other hand, this fatty acid fraction is too highly unsaturated to find extensive application in some of the largest fat-consuming industries, namely, the soap industry and in the manufacture of specialties for l the textile and tanning trades, the bulk of fats used in these industries being of the more highly saturated type.

The general object of this invention is to provide an improved process of recovering from tall oil the fatty acids in substantially pure and uncontaminated form.

A further object of the invention is to provide an improved and more eflicient process for separating the main constituents in tall oil, whereby the fatty acids recovered are in a substantially saturated form.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

These objects are accomplished according to the broader aspects of the invention whereby tall oil is hydrogenated and then saponified with an alkali metal hydroxide or with ammonia, and the resulting soap in the presence of a solvent therefor is chilled, whereupon the soap of the fatty acids crystallizes out and is separated from the rosin soap remaining in solution by filtration or centrifuging. The fatty acids may then be recovered from the soap, if desired, by splitting the latter with an acid. Upon distilling off the solvent from the filtrate the rosin soap may be recovered.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others thereof, which will be exemplified in the process hereinafter disclosed, and the scope of the invention will be indicated in the claims In carrying out the process of the invention the tall oil is first subjected to hydrogenation under the influence of heat and pressure by passing hydrogen gas therethrough. The tall oil may be in a crude or a partially or completely refined state. as such, or it may first be dissolved in a suitable solvent, preferably a soap solvent, and the solvent solution of the tall oil hydrogenated. Durins the step of hydrogenation, any suitable known catalyst may be used, such for example as nickel, which functions very well. It is obvious of course, that other catalysts may also be used alone or in combination with a nickel catalyst. The temperature during hydrogenation may range from 100 C. to 250 C. or more, the preferred range being about 145 C. to 185 C. The pressure during the hydrogenating step may vary from atmospheric to the highest pressure possible under practical commercial conditions.

After the tall oil has been hydrogenated to the desired extent, it is dissolved in a soap solvent (if it was not hydrogenated in such a solvent solution). Any suitable soap solvent may be used, it being preferred to employ the lower aliphatic alcohols, such as, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, etc., alcohols. The quantity of solvent used may be varied ,within wide limits depending upon the type of solvent used and the degree to which the tall oil has been hy- Moreover, the tall oil mav be hydrogenated drogenated. Ordinarily the amount of solvent used should vary between 5 to parts per each part of soap by weight. The resulting hydrogenated tall oil solution is then subjected to saponification by treatment with a uitable alkaline saponifying agent, such as sodium hydroxide, sodium carbonate, potassium hydroxide, ammonia, etc. In view of the fact that potassium and ammonium hydroxides yield soaps which are more readily filtered after they are precipitated out, their use is preferred. The alkaline saponifying agent should be added in at least the stoichiometrical quantity and preferably in excess thereof to insure complete saponification of both the fatty and rosin acids in the tall oil.

Upon completion of the saponification step, the resulting soap-solvent mass is chilled or cooled to low temperatures whereby the: fatty acid soaps, which are not as soluble as the rosin acid soaps, precipitate out. Preferably the soap solution is cooled down to and maintained at a temperature ranging'from 10 C. to -25 C. for a period of time sufilcient to permit precipitation of all the fatty acid soaps or at least the major portion thereof. The precipitated soaps may then be removed from the resinate solution by filtration, centrifuging or by any other suitable method. In order to free the fatty acid soaps from resinates, the former may be washed with a chilled solvent of substantially the same temperature as the precipitated soap cake. The resulting fatty acid soaps, particularly the stearates, are pure white solids containing no or only a minute quantity of resin or rosin soap. If the fatty acids are desired, the soaps may, of course, be acidified in the usual manner. It is obvious that the steps of hydrogenation and saponification may be reversed in order, 1. e., the tall oil may first be subjected to saponification with subsequent hydrogenation before the chilling step.

For a fuller understanding of the nature and objects of the invention, reference should be had iodine value of 24.5) were dissolved in 800 ml. of methanol and sufiicient ammonia of 28% strength was added to neutralize all the fatty and resinic acids and leaving an excess of 10% of free ammonia in solution. The soap solution was then allowed to stand at C. for 6 hours, which treatment caused the ammonia soap of the fatty acids to crystallize out of solution in a fine granular form. The precipitate was filtered off and washed with 400 ml. of methanol containing 3% of ammonia. The fatty acids, after splitting of the ammonia soap, consist of a pure white solid having a rosin content of 1.2%.

The ammonium resinate was then recovered from the filtrate by distilling off the methanol.

Example III 100 gms. of distilled tall oil (having a rosin content of 35%) was dissolved in 1200 ml. of ethyl alcohol. 18 gms. of dry potassium hydroxide were added and the mixture was refluxed until the potassium hydroxide had completely dissolved. The soap solution was then hydrogenated with 3 gms. of nickel catalyst at a pressure of 100 atmospheres and at a temperature of 150 C. until no further hydrogen was absorbed. After removal of the catalyst by filtration, the soap solution was allowed to stand at 0 C. overnight. .The potassium soap of the fatty acids which had crystallized out in a fine granular form was then filtered off and washed with 400 ml. of fresh ethyl alcohol which had previously been cooled to 0' C. The soap of the fatty acids was then dissolved in hot water and split with sulphuric acid to recover the fatty acids in their free state. The fatty acids thus obtained are practically free from rosin consisting for the largest part of stearic acid.

to the following examples which are given merely to illustrate the invention and are not to be construed in a limiting sense.

Example I Distilled tall oil (having a rosin content of 32%) was hydrogenated at a pressure of 15 atmospheres and a temperature of 160 C., using 2% of nickel powder as catalyst. After 2 hours the iodine value had decreased to 24.5. Analysis of the product showed that the fatty acids had been completely saturated and that one of the double bonds of the rosin had been saturated. 100 gms. of the hydrogenated product was dissolved in 1000 ml. of methanol and potassium hydroxide of strength was added in an amount sufficient to completely neutralize the fatty and resinic acids. The soap solution was then allowed to stand at 5 C. for 6 hours to effect precipitation of the potassium soap of the fatty acids. The precipitated soap was then filtered off and washed with 500 ml. of a 4% solution of potassium hydroxide in methanol to free it from residual rosin soap. The filter cake was then dissolved in water and split with dilute sulphuric acid to recover the fatty acids in their free state. The fatty acids consist of a pure white solid having a residual rosin content of .85%.

The rosin soap in the filtrate was then recovered by distilling off the methanol.

The potassium resinate (partially hydrogenated) was then recovered from the filtrate by distilling off the alcohol.

While the present invention is particularly adapted for the treatment of tall oil, it is within the purview of the invention to employ the process for separating resinic acids from fatty acids present in any mixture. While the process as hereinbefore described is highly preferred, 1. e., using tall oil as the starting material, it is within the purview of the invention to use as the starting material the crude tall oil soap as recovered in the aforementioned sulfate-cellulose process which may or may not be refined before hydrogenation. By such a process the soap is hydrogenated and a solvent solution thereof chilled to precipitate out the fatty acid soaps. Such a process eliminates the saponiflcation step, but due to the impurities in the crude soap which act as a poison for the hydrogenation catalyst, it is preferred, as above stated, to use as a starting material partially or completely refined tall oil.

Since certain changes may be made in carrying out the above process without departing from the scope of the invention, it is intended that all matter contained in the above description shallv as new and desire to secure by Letters Patent is:

1. A process of treating tall oil to separate the fatty and. resinous constituents thereof which comprises hydrogenating tall oil to convert the unsaturated fatty acids therein to saturated fatty acids, saponifying the hydrogenated tall oil, decreasing the temperature of an organic solvent solution of the resulting mass to effect precipitation of fatty acid soaps and removing the precipitated soaps from the remaining resinate solution. 7

2. A process of treating tall oil to separate the fatty and resinous constituents thereof which comprises saponifying the fatty and rosin acids of tall oil, hydrogenating the resulting soap mass to convert the unsaturated fatty acid soaps therein to saturated fatty acid soaps, decreasing the temperature of the soaps in the presence of an organic solventtherefor to effect precipitation of the fatty acid soaps and removing the precipitated fatty acid soaps from the remaining resinate solution.

3. A process of treating tall oil to separate the fatty and resinous constituents thereof which comprises hydrogenating tall oil under the infiuence of heat and pressure to convert substantially all of the unsaturated fatty acids into their saturated form, saponifying the acids in the resulting mixture in the presence of an allphatic alcoholic soap solvent with an alkaline agent, decreasing the temperature of the soap solution to effect precipitation of the fatty acid soaps and removing the precipitated fatty acid soaps from the remaining resinate solution.

4. The process of claim 3 wherein the alkaline agent used is potassium hydroxide.

mass in methanol, saponifylng the fatty and rosin acids with potassium hydroxide, decreasing the temperature of the resultant methanol soap solution to effect precipitation of the fatty acid soaps and removing the precipitated fatty acid soaps from the remaining methanol-resinate solutions.

7. A process of treating tall oil to separate the fatty and resinous constituents thereof which comprises dissolving distilled tall oil 'in ethanol, saponifying the fatty and rosin acids with potassium hydroxide, hydrogenating the soap-ethanol solution to convert the unsaturated fatty acid soaps therein to saturated fatty acid soaps, decreasing the temperature of the solution to effect precipitation of the fatty acid soaps and removing the precipitated fatty acid soaps from the remaining resinate-ethanol solution.

8. In a process of treating saponified tall oil of the type in which the unsaturated fatty portion has been saturated by hydrogenation, the step which comprises chilling a solution of such saponifled hydrogenated tall oil in an organic solvent therefor to effect; precipitation of fatty acid soaps.

ERNEST SEGESSEMANN.