US1965961A - Production of unsaturated fatty acids - Google Patents

Description

Patented July 10. 1934 PRODUCTION OF UNSATURATED FATTY ACID Martin Luther and Hans Klein, Mannheim, Germany.

assignors to I. G.

Farbenindustrie Aktiengesellschaft, Frankfort on the Main, Germany, a corporation of Germany No Drawing. Application May 29, 1929, Serial No. 367,116. In Germany June 4, 1928 Claims. (Cl. 260-119) The present invention relates to the production of unsaturated fatty acids.

The oxidation of paraflin hydrocarbons, waxes and the like by means of gases containing oxy- 5 gen, at an elevated temperature furnishes products which contain, inter alia, large amounts of dark colored acid compounds and conversion products thereof, both of which are insoluble in petroleum ether. For many purposes, such for example as soapmaking, it is essential that these admixtures should be eliminated from the oxidation products.

We have now found that valuable mixtures of unsaturated and saturated carboxylic acids can be, obtained from the oxidation products by subjecting the crude oxidation product to distillation. For example, the crude oxidation product may be distilled, preferably under reduced pressure, the operation proceeding smoothly and the unsaturated and saturated acids and the like dis tilling over and leaving only a comparatively small residue. The heat of distillation effects an extensive conversion of the hydroxy carboxylic acids into unsaturated fatty acids, so that the 5 distillate no longer contains any hydroxy carboxylic acids and is suitable for direct use for many purposes. If esters of the hydroxy carboxylic acids and of saturated fatty acids be present in the crude oxidation products a considerable portion of the esters of the latter and those of the unsaturated acids corresponding to the aforesaid esters of hydroxy carboxylic acids is found in the distillate. If desirable the distillation may be repeated one or more times. The losses of material during the distillation are very slight, and above all, there is no appreciable splitting ofi of carbon dioxide from the acids, in

contrast to the results obtained in a distillationof pure hydroxy carboxylic acids after isolating 0 these acids from a crude oxidation product of the aforesaid nature. This is evident from the saponiflcation values of the products before and after distillation. Particularly in this respect good results are obtained by applyin a current of carbon dioxide during the distillation wherefore or after removing unsaponifiable materials, if such be present, the unsaturated acids being thereby converted into the saturated state.

The operation may also be carried out with an acid product which has been freed from unoxidized initial materials, for example by subjecting the crude oxidation product to mechanical pressure or to sweating below the melting point of the acids present, or with the entire acid portion of the oxidation product, both 5 which materials will be referred to, for the sake ofbrevity, in the following as a pretreated oxidation product. Particularly good yields of unsaturated acids are obtained when the oxidation of the parafiin hydrocarbons, waxesandthe like 7 has been performed rather strongly, for example with the aid of catalysts, since also such pretreated product is not liable-to give the bad results obtainable" with pure hydroxy carboxylic acids stated above.

As a rule the distillation is preferably carried out in the presence of a current of an inert gaseous agent, such as carbon dioxide or water vapor and the like.

The distillation is advantageously carried out rather quickly and with an addition of. steam. After the second distillation the distillates are practically free from hydroxy carboxylic acids, and consist almost exclusively of valuable unsaturated fatty acids. For some purposes, such as the preparation of solid edible fats, they may be subsequently hydrogenated. If desired, a catalyst may be employed in the distillation, for example red phosphorus, sulphuric acid or metal oxides, but usually the employment thereof may be dispensed with, very good results being obtainable without the use of a catalyst.

The following examples will further illustrate the nature of the invention, but the invention is not restricted to these examples. The parts are. by weight.

Example 1 500 parts of an oxidation product obtained from hard paraffin wax, with the acid value of 108, a saponification value of 205, and containing 2'7 per cent of acids insoluble in petroleum ether, are distilled in a vacuum of 8 millimeters (mercury gauge) at 110 to 280 C. 432 partsof distillate are obtained which has an acid value of 153, a saponification value of 200, and a content of only 5 per cent of acids insoluble in petroleum ether.

400 parts of the distillate are re-distilled, under 3 millimeters pressure and in an atmosphere of 110 CO2, whereupon 384 parts pass over at from 140 to 290 C. The distillate has an unaltered acid value of 153 and a saponification value of 200, and contains only 2 per cent of acids insoluble in petroleum ether. The same procedure for the production of unsaturated acids may be followed in the treatment of the oxidation products from Montan wax, beeswax, ozokerite and the like.

Example 2 100 parts of a crude oxidation product obtained from an oxidation of soft parafiin wax of brown coal tar and possessing an acid value of 108 and a saponification value of 205 are distilled at 15 millimeters mercury gaugewhile passing through a current of steam and raising the temperature up to about 260 C. 90 parts of a practically anhydrous mixture of an acid product are obtained after fractional condensation, the product showing an acid value of 146 and a saponification value of 200. When carbon dioxide is employed in the place of steam about the same yield with the same acid value is obtained and the saponificatior. value is that of the initial material. The process is similar when an oxidation product of liquid paraflln hydrocarbons or of Montan wax be employed.

What we claim is:

1. The process for the production of unsaturated fatty acids, which comprises subjecting to distillation, at a temperature between about 110 and about 290 C. and at a pressure up to atmospheric pressure a crude product containing a substantial proportion of long chain hydroxy carboxylic acids from the super-oxidation of difilcultly volatile parafiin hydrocarbons and waxes, thereby converting said long chain hydroxy-carboxylic acids into long chain unsaturated fatty acids.

2. The process for the production of unsatu-' rated fatty acids, which comprises subjecting to distillation, at a. temperature between about 110 and about 290 C. and at a pressure up to atmospheric pressure a crude product containing a substantial proportion of long chain hydroxy carboxylic acids from the'super-oxidation of difficultly volatile parafiin hydrocarbons and waxes, while passing an inert gaseous agent through the reaction vessel, thereby converting said long chain hydroxy-carboxylic acids into long chain unsaturated fatty acids.

3. The process for the production of unsaturated fatty acids, whichcomprises subjecting to distillation, at a temperature between about 110 and about 290 C. and at a pressure below atmospheric pressure, a crude product containing a substantial proportion of long chain hydroxy carboxylic acids from the super-oxidation of dimcultly volatile paraffin hydrocarbons and waxes, which crude product has been freed from unoxidized initial materials thereby converting the said long chain hydroxy carboxylic acids into long chain unsaturated fatty acids.

4. The process for the production of unsaturated fatty acids, which comprises subjecting to distillation, at a temperature between about 110 and about 280 C. and at a pressure of about 8 100 millimeters of mercury, a crude super-oxidation product of hard paraffin wax, thereby converting the long chain hydroxy carboxylic acids contained in said super-oxidation product into long chain unsaturated fatty acids.

5. The process for the production of unsaturated fatty acids which comprises subjecting to distillation, at a temperature between about 110 and about 260 C. and atv a pressure of about 15 millimeters of mercury, a crude oxidation prod- 110 uct from soft paraffin wax, while passing a current of steam through the distilling batch, thereby converting the long chain hydroxy carboxylic acids contained in said oxidation'product into long chain unsaturated fatty acids.

' MARTIN LUTHER.

HANS KLEIN.