US2273045A - Process for recovering sterols - Google Patents

Description

pressed out or extracted from such seeds.

Patented Feb. 17, 1942 PROCESS FOR RECOVERING STEROLS Percy L. Julian, Maywood, and John Wayne Cole,

Chicago, Ill., assignors to The Glidden Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Application July 8, 1940, Serial No. 344,384

Claims. (Cl. 260397.2)

The present invention relates to the recovery of sterols and particularly to the recovery of sterols which are found in oil-bearing seeds such as soybean, cotton seed, etc. It is also applicable with certain alterations to the extraction of sterols from Tall Oil and the juices and saps secured by pressing certain plants, among which may be mentioned sugar cane.

Inthe recovery of sterols it is conventional to seek to use as'raw material the oil pressed out of oil bearing seeds inasmuch as the most of the sterols dissolve in the oil when it is either The conventional-method of working up this oil has been to convert the oil into a soap, and to extract from said soap the unsaponifiables consisting of sterols along with waxes, etc. The amount of unsaponifiables present in the oils varies from oil to oil. In soybean oil the usual figure is given as 0.8%. been obtained ranging from 0.5 to 1.6% when the determinations are made by the official method of the Association of Official Agricultural Chemists. soap the conventional method has been to dissolve the soap in alcohol, or to form the soap with alcoholic alkali, and to shake out the resulting soap solution with water-immiscible solvents such as-ether, benzene, ethylene dichloride, petroleum ether, carbon tetrachloride, etc. These reagents extract as a general rule not only the sterols but also most of the other unsaponifiables which represent materials of a gummy or wax-like nature. For this reason such a method is commonly employed in a quantitative determination of the percentage of unsaponifiables in the oil. Naturally the extract contains some alcohol and therefore some dissolved soap and is washed frequently with water and alkali to remove alcohol and soap. Even after such washing, which constitutes a laborious procedure and is difiicult to carry out on a large scale, there remain in the washed extract the gummy and waxy material spoken of above and these interfere seriously with the crystallization of the sterols from said extract. For a clean crystallization of the sterols, these materials are best removed before crystallization. For example, when ether is used as the extract, the washed ether extract may be concentrated, and the addition of hot alcohol to the concentrate throws down a large amount of gummy material. If this is removed immediately by filtration (difiicult in this case) the sterols will usually crystallize, fromthe ether extract. Ethyl ether is,

. however, a difi'icult solvent to use in a commercial extraction of sterols, first because of the large volumes which are required and because of the hazard in employing a solvent like ethyl ether. Isopropyl ether has been recommended.

Figures, however, have,

In extracting the sterols from the.

It, however, forms explosive peroxides unless inhibitors are added and the maintenance of these inhibitors in the distilled solvent is diflicult and fraught with dangers.

According'to the present invention, a method is provided whereby the sterols may be recovered by a simplified procedure. It is the purpose of the present invention to employ a solvent which will extract substantially only the sterol portion of the unsaponifiables and leave behind certain objectionable gummy and wax-like materials which are usually extracted along with the sterols when extracted in accordance with every published method .for extracting the sterols. For this purpose we have found water-miscible volatile ketones such as acetone, methyl ethyl ketone especially suitable. Moreover these water-miscible volatile ketones are superior to the usual water immiscible solvents employed for the extraction of sterols, because--in addition to leaving behind much gummy and Wax-like material-they do not swell a solid lime soap such as described in application Serial No. 266,408, and which soap has been shown to be very superior to the usual alcoholic solutions of a soap as starting material for the extraction of sterols. Solvents like ether, benzene, and the chlorinated solvents swell these lime soaps decreasing somewhat the ease of filtering or percolation through these inherently easily extractable soaps. Water miscible ketones like acetone tend O H t (1) 2011300011 '--0 CH -CH2COCH3 Acetone Diacetone alcohol Diacetone alcohol in the absence of the basic substances in whose presence Equation 1 is reversible, loses a molecule of water to form mesityl oxide by a nonreversible reaction according to Equation 2 OH 2 ong--cnzoo OH; on,- O=CHC 0 CHa+H1O Diacetone alcohol Mesityl oxide Similar reactions occur in the case of methylethyl ketone and similar ketones (Organic Syntheses, vol. 1, p. 193, John Wiley Sons, New York, 1932) In extracting soap with acetone the conditions are present which result in the reaction of Equation 1 taking place. After the extract of the sterols is drained away from the soaps there is no base present to catalyze Reaction 1. acetone is more volatile than diacetone alcohol, evaporation of the acetone will result in an accumulation of diacetone alcohol and mesityl ox,- ide at the point of evaporation, and if continuous or successive concentrations are employed the condition is aggravated so that there is formed a syrupy mixture of diacetone alcohol, mesityl oxide and sterols.

By conducting the evaporation under the conditions of Equation 1 (i. e. in the presence of basicsubstances to catalyze the reversible reaction) the removal of the acetone causes Beaction 1 to go to the left and a minimum formation of mesityl oxide results, substantially no diacetone alcohol remaining in the evaporated extract. Any basic substances such as alkalies and organic bases may be used. It is good practice to use a basic substance which is subsequently easily removed, as for example barium No. 266,408, filed April 6, 1939-and which soaps Since O au have been made by treating a wet aqueous concentrated soap with sufficient quick lime to cause the drying and pufiing of the soap due to the formation of steam by the heat of reaction between water and quick lime-are the preferred soaps for such an extraction with water miscible ketones. The procedure, however, can be applied to any dry soap such as a vacuum dried soap, or a soap dried on drums. Such dry soaps may be made from ordinary soybean oil, ordinary cottonseed oil or from other vegetable and animal sources and is advantageously treated in accordance with the present invention to recover thesterols therefrom.

readily in these alcohols in the presence of small quantities of oil. Thus when the oil is scrubbed with the alcohols the latter become quickly sa'turated with oil and the most of the unsaponiflables leave the oil and go into the alcohol phase which forms a separate layer and can be drawn off from the oil layer. 'Thus, on evaporation of the alcohol, an oil more concentrated in sterols than the original oil is obtained. This is the "concentrate referred to in this paragraph. This procedure is described in Circular No. 212, from the United States Department of Agriculture, Bureau of Animal Industry, and is employed as a tentative method for formation of oil concentrates containing Cholesterol and Phytosterol as described in .Ofiicial and Tentative Methods of Analyses of the Association of the Oflicial Agricultural Chemists in the 1930 edition of this book, page 327. Dry lime soaps made from such concentrates of vegetable and animal oils are easily extracted by the method employed in the present invention and indeed this method constitutes what is considered a novel and greatly improved method of securing sterols from' such concentrates.

In addition to ordinary oils and the concentrates of such oils, it has been found that the method of the present invention works well with the "sludge secured on the alkali refining of vegetable and animal oils. In this alkali refining aqueous alkali is added to the oil under agitation and a sludge containing phosphatides l0- and unsaponifiables is thrown down. This sludge usually contains from 40 to 50% water. Such a sludge as is drawn off of the alkali refining tanks can be treated with a small quantity of flake caustic to complete saponification and then with a quantity of quick lime (depending upon the amount of water present) to form a dry crumbly and porous soap. This soap is very conveniently extracted with water miscible ketones according to the method of the present invention and the use of such material permits a cheap recovery of the sterols therein.

High acid oil or other sterol containing residues resulting from the purification of phosphatides such as soybean phosphatides, cottonseed phosphatides, etc. may also be used as raw material.

In addition to all of the above raw materials sterol containing distillation residues secured on rectifying the fatty acids may be converted into dry lime soaps and extracted according to the method of the present invention.

. Particularly useful is the method of the present invention in working up a residue such as secured by Kraybill and others in U. S. Patent No. 2,174,177. This method adsorbs the sterols and phosphatides onto an adsorbent consisting of sodium and aluminum silicate. When this adsorbent is washed with acetone there is secured an acetone solution substantially free of phosphatides, which are insoluble therein, consisting of a. goodly portion of oil containing sterols. This is another method of securing a concentrate. Such a concentrate is most conveniently worked up for recovery of sterols by converting it into the dry lime soap discussed above and extracting according to the method of the present invention.

The method of the present invention is also particularly applicable the concentrated oil solution of unsaponifiables secured on the molecular distillation of vegetable and animal oils such as described by H. W. Rawlings in Oil and Soap, December 1939,' volume 16, number 12, page 231. This concentrate is readily convertible into adry lime soap for extraction according to the method of the present invention. This results in saving of time and in much more quantitative recovery of sterols than any other known commercial method.

Example I 400# of a concentrated soybean oil wasconverted to 600# of dried soap according to the aforementioned application Serial No. 266,408. This soap was then extracted six times in an extractor of the percolator type with 500600 gallons of acetone, and the acetone drained off to a still which had been charged with 1# of barium hydroxide. This amount of barium hydroxide is sufficient for 10-20 extractions or. more, if none is drawn off, since it acts as a catalyst and is not used up in the concentration. The extract was distilled down to an oily mass which contained the sterols, a small amount of mesityl oxide, a small quantity of soap carried over as fines or in the form of water soluble soap, a small quantity of unsaponified oil, and pigment impurities.

The extract thus obtained was concentrated to about 1 gallons and taken up in about A; its volume of hot glacial acetic acid. This solution was slowly cooled, the sterols crystallizing out in large crystals which were easily filtered or centrifuged. The crystalline sterols may then be washed with methyl alcohol and recovered as practically colorless crystals consisting of about 3 to 5# of substantially pure soybean sterols having a melting point of 131 C.-133 C.

Example II Example III 670%; of sludge from the alkali refining .of soybean oil wer treated with 30 pounds of caustic flakes using good mechanical agitation. This action insured complete saponification of all free oil present. 280# of quick lime were mixed into the soft plastic mass with mechanical agitation to insure a homogeneous mixture. Within a few minutes, pufiing and swelling occurred and the soap dried to a granular porous mass. This mass was placed in an extractor and extracted with acetone. The acetone extract was concentrated under vacuo yielding 6 gallons of extract. The concentrated extract wasworked up for the recovery of the sterols therefrom. A yield of 3.81 pounds of sterols was obtained, representing a yield of 0.57% based upon the weight of sludge.

Example IV 670# of sludge from the alkali refining of cottonseed oil were treated with 20.7# caustic flakes in the same manner as described above. The mass was treated with 241 pounds of quick lime as described above. The soap was extracted in the usual manner, yielding 6 gallons of extract. Upon working up the extract for the recovery of the sterols 3.69 pounds of sterols were isolated. Based upon the weight of foots processed, this represented a yield of 0.55%. I

A previously pointed out other volatile ketones than acetone and methyl-ethyl ketone may be used. However, they should be sufiiciently volatile to permit ready concentration of the extract by evaporation or distillation. The basic substances are preferably alkalies but organic bases may be used.

While the use of dry porous soaps such as the dry lime soaps referred to are preferable, in general any substantially dry and substantially oilfree material containing sterols and basic substances may be treated in accordance with the present invention for the recovery of sterols.

When using dry lime soaps it is preferable to dry the soap down to a moisture content of about 2% by the Dean-Starkmethod. This method will not remove water from calcium hydroxide or hydrated calcium chloride and will only show up excess water not combined with calcium oxide.

preciable quantities of soap may be dissolved in the acetone or other water miscible ketone. Thus it is preferable to keep the moisture content of the soap in the neighborhood of 2 to 3%, as this renders subsequent purification easier. The invention, however, is not limited to these percentages as extracts free from other unsaponifiables, etc. may be obtained when extracting materials containing other percentages of water. 4/

We claim:

- 1. The process of recovering sterols which comprises extracting substantially dry, substantially oil-free soybean material containing sterols and a basic substance with awater miscible volatile ketone, separating the extract from the insoluble residue and concentrating the extract by evaporating the ketone in the presence of a basic substance.

2. The process of recovering sterols which comprises extracting substantially dry soybean soap containing sterols with a water miscible volatile ketone, separating the extract from the insoluble residue, and concentrating the extract by evaporating the ketone in the presence of a basic substance.

3. The process of recovering sterols which comprises extracting a porous, dry, lime soap contain- When the amount of free water exceeds 3%, ap-

4. The process of recovering sterols which comprises extracting substantially dry, substantially oil free material containing sterols and a basic substance witha ketone selected from the class consisting of acetone and methyl ethyl ketone, separating the extract from the insoluble residue and concentrating the extract by evaporating the ketone in the presence of a basic substance.

5. The process of recovering sterols which comprises extracting substantially dry soap containing sterols with a ketone selected from the class consisting of acetone and methyl ethyl ketone, separating the extract from the insoluble residue and concentrating the extract by evaporating the ketone in the presence of a basic substance.

6. The process of recovering sterols which comprises extracting a porous, dry soap obtained from the sludge resulting from the alkali refining of oils containing sterols with a water miscible volatile ketone, separating the extract from the insoluble residue and concentrating the extract by evaporating the ketone in the presence of a basic substance.

'7. The process of recovering sterols which comprises extracting substantially Jdry, substantially oil free material containing sterols and an alkaline substance with a water miscible volatile ketone, separating the extract from the insoluble residue and concentrating the extract by evaporating the ketone in the presence of an alkaline substance.

8. The process of recovering sterols which comprises extracting substantially dry soap containing sterols with a water miscible volatile ketone, separating the extract from the insoluble residue and concentrating the extract by evaporating the ketone in the presence of an alkaline substance.

9. The process of recovering sterols which comprises extracting a porous, dry, lime soap containing sterols with a water miscible volatile ketone, separating the extract from the insoluble residue and concentrating the extract by evaporating the ketone in the presence of an alkaline substance.

10. The process of recovering sterols which comprises extracting sterol containing substantially dry soaps made from the tarry residue remaining upon the distillation of fatty acids with a water miscible volatile ketone, separating the extract from the insoluble residue and concentrating the extract by evaporating the ketone in the presence of a basic substance.

11. The process of recovering sterols which comprises extracting sterol containing substantially dry soaps made from-the tarry residue remaining upon the distillation of fatty acids with a ketone selected from the class consisting of acetone and methyl ethyl ketone, separating the extract from the insoluble residue and concentrating the extract by evaporating the ketone in the presence of a basic substance.

12. The process of recovering sterols which comprises extracting soaps made from the tarry residue remaining upon the distillation of soya oil fatty acids with a water miscible volatile ketone, separating the extract from the insoluble residue, and concentrating the extract by evaporating the ketone in the presence of an alkaline substance.

13. The process of recovering sterols which comprises extracting a porous, dry, lime soap of soybean oil containing sterols with acetone, separating the extract from the insoluble residue, and concentrating the extract by evaporating the acetone in the presence of barium hydroxide.

14. The process of recovering sterols which comprises extracting a porous, dry, lime soap of soybean oil containing sterolswith methyl ethyl ketone, separating the extract from the insoluble residue and concentrating the extract by evaporating the methyl ethyl ketone in the presence of barium hydroxide.

15. The process of recovering sterols which comprises extracting substantially dry, substantially oil free soybean material containing sterols and a basic substance with a water miscible volatile ketone, separating the extract from the insoluble .residue, concentrating the extract by evaporating the ketone in the presence of a basic substance and recovering the sterols from the thus concentrated extract.

16. The process of recovering sterols comprising concentrating a volatile water miscible ketone extract of sterols by evaporating said extract in the presence of a basic substance.

17. The process of recovering sterols which comprises extracting a substantially dry,'substantially oil free material containing sterols and a basic substance with a water miscible volatile ketone, separating the extract from the insoluble residue, and concentrating the extract by evaporation in the presence of a basic substance. s

18. The process of claim 17 in which the material extracted is substantially dry soap.

19. The process of recovering sterols which comprises forming a substantially dry soap from a glyceride oil concentrate containing sterols, extracting said soap with a water miscible volatile ketone, separating the extract from the insoluble residue and concentrating said extract by evaporation in the presence of a basic substance.

20. The process of recovering sterols from the sludge resulting from the alkali refining of cottonsee'd oil which comprises converting said sludge into a substantially dry soap, extracting said soap with a water miscible volatile ketone, separating the extract from the insoluble resition in the presence of a basic substance.

PERCY L. JULIAN. JOHN WAYNE COLE.