Process for separating 3-hydroxy steroids or sterols from mixtures such as lipids

A process for separating 3-hydroxy steroids from sterol concentrate mixtures by combining a solution of the sterol-containing mixture in a cosolvent of a dialkyl ketone and a low molecular weight alcohol with a slurry or solution of calcium bromide. The complexed sterols are isolated by filtration and the sterols can be subsequently liberated from the complex by treatment with an aqueous/alcohol and isolated by filtration and drying. The complexed sterols are of large particle size which allows rapid filtration.

DESCRIPTION 
The present invention relates to a process for separating sterols from 
sterol concentrate mixtures. 
Various processes are known in the art for separating sterols such as 
3-hydroxy steroids from mixtures of such sterols and other components such 
as lipids. One such mixture is phytosterols in soybean oil deodorizer 
distillate. The separation of the 3-hydroxy steroids from such mixtures is 
important because these 3-hydroxy steroids are useful as raw materials for 
production of steroid drugs such as hydrocortisone. One such known process 
is described in German Pat. No. 827,199 wherein the mixture is dissolved, 
preferably in a hydrocarbon solvent, and is heated with a four- to 
sixteen-fold excess of anhydrous zinc chloride. After cooling of the 
solution, the precipitated ZnCl-sterol adduct can be separated out and the 
complex separated into the individual components. Another such known 
process as set forth in British Pat. No. 1,164,769 describes a method for 
the isolation of sterols from mixtures wherein the mixture is dissolved, 
preferably in a hydrocarbon solvent, the solution is mixed with an aqueous 
solution of a metal salt which is suitable for complex formation, the 
water is progressively removed by azeotropic distillation, and the 
precipitated adduct is isolated and the sterol recovered in a conventional 
manner after cooling of the mixture. 
Such known methods have the disadvantage that they are technically very 
costly on account of the high reaction temperature (customarily over 
100.degree. C.) and that in the isolation of many 3-hydroxy steroids and 
3-oxo steroids considerable loss of product is experienced, since these 
steroids can be destroyed under these conditions. In addition, these known 
methods often have the disadvantage that the recovery of the metal salt 
used for formation of the adduct, which is necessary in a method carried 
out on large scale simply with regard to environmental considerations, is 
often very costly. 
Another prior art process for separating 3-hydroxysteroids from mixtures of 
such steroids and lipids as disclosed in U.S. Pat. No. 4,057,541 is 
carried out by forming a solution of a mixture of one or more 3-hydroxy 
steroids and lipids in methyl isobutyl ketone or methyl n-amyl ketone, or 
mixtures thereof, which is mixed with calcium bromide or a solution of 
calcium bromide in methyl isobutyl ketone or methyl n-amyl ketone, or 
mixtures thereof, and the precipitated sterol complex separated and 
recovered in a known manner. However, in this process the sterol bromide 
complex which forms precipates out in very small particles which requires 
long filtration times. It would therefore be a significant advance in the 
state of the art to provide a relatively simple process useful 
commercially which provides excellent separation and requires short 
filtration times to separate 3-hyroxy steroids from mixtures of sterols 
concentrate. 
In accordance with the present invention, a process is provided for 
isolating 3-hydroxy steroids from sterols concentrates by merely combining 
a solution of the sterol-containing mixture in a cosolvent of a dialkyl 
ketone and a low molecular weight alcohol with a slurry or solution of 
calcium dibromide. The resulting mixture can then be stirred or agitated 
at ambient temperature for a suitable period to form the sterol-CaBr.sub.2 
complex. The sterol-CaBr.sub.2 complex precipitates out in large particles 
which can be easily and quickly isolated by filtration. The sterols are 
then liberated from the sterol-CaBr.sub.2 complex by treatment with an 
aqueous alcoholic wash and isolated by filtration. 
The cosolvent used in the present invention is a mixture of a dialkyl 
ketone and a low molecular weight alcohol. The dialkyl ketone preferably 
has about 5 to 6 carbon atoms. Such dialkyl ketones are preferably 
methylisobutyl ketone and methylisoamyl ketone. The low molecular weight 
alcohols are preferably methyl alcohol, ethyl alcohol and isopropyl 
alcohol. The cosolvent contains about 1 to 5 parts alcohol per 100 parts 
ketone, preferably 2 to 4 parts alcohol per 100 parts ketone. If the 
cosolvent contains less than one part alcohol the particle size of the 
complex precipitate is decreased so that the filtration time is not 
considerably decreased. Amounts greater than 5 parts do not appreciably 
increase the particle size and decrease the yield of complex. 
The process of this invention is carried out by dissolving the sterol 
containing concentrate in the cosolvent. About 100 parts of sterol 
concentrate can be dissolved in about 30 to 150 parts of dialkyl ketone 
having about 5 to 6 carbon atoms and about 0.8 to 6 parts of a low 
molecular weight alcohol. About 15 parts calcium bromide can be dissolved 
in about 30 to 150 parts of the ketone used in preparing the cosolvent. 
The two solutions are mixed, preferably at ambient temperature for a 
period of 1 to 60 minutes, preferably 5 to 15 minutes. The sterol complex 
precipitates out in large particles and the slurry is filtered and washed. 
The sterol can be recovered from the complex by processes well known in 
the art such as for example by slurrying in methanol or water followed by 
filtration and drying. 
The amount of cosolvent used depends on the solubility of the sterol-lipid 
concentrate. The amount of calcium dibromide used depends on the 
concentration of the sterols in the sterol concentrate. The greater the 
amount of sterol present, the greater the amount calcium dibromide 
necessary to provide sufficient CaBr.sub.2 to form complexes with the 
sterols. 
The solvent used to wash the filtered sterol-complex obtained after removal 
of the solvent or diluents can be any suitable solvent which does not 
dissolve the complex. Such solvents include heptane, hexane, toluene, 
cyclohexane, methyl ethyl ketone, methyl isobutyl ketone and the like. 
It should be noted that heat may be used to dissolve the sterol concentrate 
in the cosolvent and during complex formation, but is not necessary. 
This invention can be further illustrated by the following examples, 
although it will be understood that these examples are included merely for 
purposes of illustration and are not intended to limit the scope of the 
invention unless otherwise specifically indicated.

EXAMPLE 1 
About 200 grams of sterol concentrate containing 22% sterols is dissolved 
in 150 ml of methyl isobutyl ketone. About 30 grams of calcium bromide 
dihydrate is dissolved in 250 ml methyl isobutyl ketone. The two solutions 
are mixed and intimately mixed at ambient temperature, about 25.degree. 
C., for a period of one hour. The slurry was filtered which required nine 
minutes. 
Repeating this procedure using 200 grams of sterol concentrate containing 
16% sterols required a filtration time of 15 minutes. 
EXAMPLE 2 
About 200 grams of sterol concentrate containing 22% sterols is dissolved 
in a mixture of 200 ml methyl isobutyl ketone and 6.3 ml methanol. About 
30 grams of calcium bromide dihydrate is dissolved in 200 ml of methyl 
isobutyl ketone. The solutions were mixed and reacted at ambient 
temperature for one hour. The slurry was filtered which required 3.7 
minutes. 
Repeating this procedure using 200 grams of sterol concentrate containing 
16% sterols required a filtration time of only 4.5 minutes and 29.8 grams 
sterol complex was recovered. 
EXAMPLE 3 
About 200 grams of sterol concentrate containing 16% sterols is dissolved 
in 200 ml methyl isobutyl ketone. About 30 grams of calcium bromide 
dihydrate is dissolved in 200 ml of methyl isobutyl ketone and 6.3 ml 
methanol. The two solutions are mixed and reacted according to the 
procedure of Example 2. After reaction the slurry was filtered which 
required 17 minutes. This example shows that the solvent used to dissolve 
the sterol concentrate must contain the low molecular weight alcohol. 
EXAMPLE 4 
About 200 grams of sterol concentrate containing 16% sterols is dissolved 
in 200 ml methyl isobutyl ketone and 3.15 ml. methanol. About 30 grams of 
calcium bromide dihydrate is dissolved in 200 ml of methyl isobutyl 
ketone. The two solutions are mixed and reacted according to the procedure 
of Example 2. After reaction the slurry was filtered which required only 
5.8 minutes and 29.2 grams sterol complex recovered. 
EXAMPLE 5 
About 200 grams of sterol concentrate containing 16% sterols is dissolved 
in 200 ml methyl isobutyl ketone and 12.6 ml. methanol. About 30 grams of 
calcium bromide dihydrate is dissolved in 200 ml of methyl isobutyl 
ketone. The two solutions are mixed and reacted according to the procedure 
of Example 2. After reaction the slurry was filtered which required only 
3.3 minutes and only 21.2 grams sterol complex recovered. 
EXAMPLE 6 
About 200 grams of sterol concentrate containing 22% sterols is dissolved 
in 150 ml of methyl isoamyl ketone. About 30 grams of calcium bromide 
dihydrate is dissolved in 250 ml methyl isoamyl ketone. The two solutions 
are mixed and intimately mixed at ambient temperature, about 25.degree. 
C., for a period of one hour. The slurry was filtered which required 18.5 
minutes. 
EXAMPLE 7 
The procedure of Example 6 was repeated except that 6.3 ml of methanol as 
cosolvent was added to the methyl isoamyl ketone used to dissolve the 
sterol concentrate. Filtration time was only 3.5 minutes. 
EXAMPLE 8 
About 200 grams of sterol concentrate containing 20% sterols is dissolved 
in 200 ml of methyl isobutyl ketone. About 30 grams of calcium bromide 
dihydrate is dissolved in 200 ml methyl isobutyl ketone. The two solutions 
are mixed and intimately mixed at ambient temperature, about 25.degree. 
C., for a period of one hour. The slurry was filtered which required 10.8 
minutes. 
EXAMPLE 9 
The procedure of Example 8 is repeated except that 6.3 ml methanol as 
cosolvent was added to the methyl isobutyl ketone used to dissolve the 
sterol concentrate. Filtration required only 4.5 minutes. 
EXAMPLE 10 
The procedure of Example 9 is repeated except that 6.3 ml of ethanol 
replaces the 6.3 ml of methanol in the cosolvent. Filtration time was only 
3 minutes. 
EXAMPLE 11 
The procedure of Example 10 is repeated except that 6.3 ml of isopropanol 
replaces the 6.4 ml of ethanol in the cosolvent. Filtration time was only 
3 minutes. 
EXAMPLE 12 
About 200 grams of sterol concentrate containing 20% sterols is dissolved 
in 200 ml methyl isobutyl ketone and 6.3 ml methanol. About 30 grams of 
calcium bromide dihydrate is dissolved in 200 ml of methyl isobutyl 
ketone. The two solutions are mixed and reacted at ambient temperature for 
15 minutes and filtered which required only 1 minute and gave a yield of 
37.9 grams sterol complex. 
EXAMPLE 13 
The procedure of Example 12 was repeated except that the two solutions were 
mixed and stirred and filtered after only 1 minute reaction time. The 
filtration required only 30 seconds and 37.8 grams sterol complex 
recovered. 
The process of the present invention provides an improved process for 
separating 3-hydroxy steroids from sterol concentrates. Further, the 
3-hydroxy steroids can be used to provide starting materials for 
preparation of valuable steroids. 
The invention has been described in detail with particular reference to 
preferred embodiments thereof, but it will be understood that variations 
and modifications can be effected within the spirit and scope of the 
invention.