DESCRIPTION Technical field

The present invention relates to qualitative control of the isolation of sterols.

Background

Sterols are valuable intermediates for the manufacture of a se¬ ries of important pharmaceutical. Different derivatives of cor- tisone and contraceptive agents relate to this area. Sterols have a biological activity of its own, as well. They are pre¬ sent in most organisms. Physio-chemically the sterols function as barrier compounds as they are readily piled onto each other. Compounds, which in this way provide mono or oligomeric sur- faces are called spreading.

It is known that sterols can be isolated from several natural sources. Soya desodorisates , bile, and tall oil are the most common. As the sterols are most often present in esterified form these are released suitably by hydrolysis. The sterols can then be extracted using any suitable solvent, and are then pre¬ cipitated.

As an alternative method distillation has been described. In order to bring over the sterols into the distillate in a quan¬ titative maximum amount as possible it is an advantage to co- distil them using a so called dragging liquid, e.g. as de¬ scribed in USP 4,374,776. Then a methyl ester of mainly fatty acids is used as a dragging liquid. The methyl esters are form- ed by re-esterification using methanol when the sterols are set free from their fatty acid esters. This process has, however, a great process technical disadvantage as one can not control the ratio of sterol to dragging liquid. Stoichiometricly it will become what it will depending on how large part of the sterols which are esterified. At a subsequent purification step it will be a considerable disadvantage that the concentration of the sterols of the ingoing product stream is too low and/or that it

contains side products which are difficult to separate.

The present invention discloses a solution to this problem, whereby not only a constant ratio can be obtained, but moreover a ratio which is optimal with regard to the subsequent isola¬ tion of sterols.

The process is aimed at transforming a determined part of the acids and/or esters to derivatives which do not distil with the mixture of sterols. One way is hereby to add a limited amount of sodium or potassium hydroxide, whereby one obtains salts of mainly fatty acids. These salts will not distil but one adds then a complementing amount of an amine or ammonia, which gives amides which can constitute a dragging liquid. Another way is to add a determined amount of two or more polyalcohols at the re-esterification. This results in esters having a higher boil¬ ing point which do not distil under prevailing conditions. The¬ reby a complementing amount of an amine or ammonia is added, as well, for the formation of amides being a dragging liquid. A third way is to add a determined amount of di or polyvalent amines or high boiling amines or amino alkanols. These form different amides which do not distil under prevailing condi¬ tions. Like in the previous cases one may then add a certain amount of a lower amine for the formation of an amide having a lower boiling point to obtain a dragging liquid.

In all these cases the distillation will nevertheless function without any addition of any amine or ammonia as the higher al¬ cohols and other organic compounds present having a lower boil- ing point will distil over together with the sterols. In such a case the distillation will not be optimally efficient, which leads to a lower yield of sterols. This is due in accordance with SE-C-461,793 wherein a process is disclosed using an amine or ammonia only, which results in that one can not control the amount of dragging liquid which then becomes unnecessary large. The distillate thereby contains large amounts of impurities which give raise to problems in subsequent steps.

The result of the above described process step is that one can determine exactly the amount of dragging liquid to the con¬ centration of sterols in the distillate. One is then able to increase the concentration of sterol in the distillate which facilitates and makes the subsequent isolation step more effi¬ cient.

The invention will now be described more in detail in the fol¬ lowing with reference to some non-limiting examples.

Example 1

40 g of NH_ and 240 g of 1, 6-diaminohexane were added to 4.2 kg of tall oil pitch having an acid value of 40 and a total con¬ centration of sterols of 12%. The mixture was heated to 195°C in an autoclave while stirred for 80 min. After the end of the reaction time the pressure was released and easily volatile components were evaporated in vacuo (2-3 mbar). The mixture was fed continuously to a thin layer evaporator. At 230°C on the heating surface and about 80 C on the cooling surface and a pressure of 0.05 mbar 38% of the added material distilled over. The concentration of sterols was 30% of the distillate.

Example 2

40 g of NH-. and 240 g of 1, 6-diaminohexane were added to 4.2 kg of tall oil pitch having an acid value of 40 and a total con¬ centration of sterols of 12% in accordance with the process of Example 1. At the distillation in the thin layer evaporator 24% distilled over. The concentration of sterols was 45% of the distillate .

Example 3

4.2 kg of tall oil pitch, 40 g of NH ₃ , 300 g of glycerol and 20 g of NaOH were treated in accordance with the process of Examp¬ le 1. 35% distilled over, whereby the concentration of sterols was 29% of the distillate.

Example 4

4.2 kg of tall oil pitch, 300 g of glycerol and 120 g of NaOH were treated in accordance with the process of Example 1. 21% distilled over in the thin layer evaporator, whereby the con- centration of sterols was 52% of the distillate.

Example 5

4.2 kg of tall oil pitch, 105 g of NaOH, and 50 g of NH_ were treated in accordance with the process of Example 1. 45% dis- tilled over in the thin layer evaporator, whereby the concent¬ ration of sterols was 25% of the distillate.