Patent GB-762124-A (GB)
Title: A process for the separation of unsaturated fatty acids having two or more double bonds from unsaturated fatty acids having a single double bond
IPC: C11C1/00
Filed: 1954-02-19
Abstract: Unsaturated fatty acids having two or more double bonds are separated from unsaturated fatty acids having one double bond or the esters thereof, by heating the mixture of fatty acids or esters in the presence of iodine, or a compound capable of generating iodine, with maleic acid anhydride, maleic acid or methacrylic acid in a proportion of about 100-200 mol. per cent, calculated on the unsaturated fatty acids having two or more double bonds, the reaction being interrupted when the fatty acids having two or more double bonds have been transformed substantially completely into mono-adducts, whereupon the unchanged fatty acids or esters are separated from said condensation products by distillation and/or by treatment with solvents.  The process may be used to prepare substantially pure oleic acid by removing the more unsaturated fatty acids therefrom, or to obtain linoleic acid monoadducts from cotton seed oil, sunflower oil and soya bean oil.  Catalysts used instead of iodine are hydriodic acid, iodine trichloride, iodine monochloride, bromide or fluoride, iodoform, hydriodic acid salts of, e.g. hexadecylamine or pyridine, and inorganic iodides, e.g. zinc iodide. The proportion of catalyst varies from 0.1-2 per cent calculated on the fatty acids and the reaction temperature ranges from 120-300 DEG C., preferably 175-250 DEG  C.  It is advantageous to add the catalyst to the mixture of fatty acids and maleic anhydride after the mixture has become homogeneous, generally above 100 DEG  C., and preferably after the mixture has reached reaction temperature.  The condensation may be effected in the presence of a high boiling non-oxidizing solvent such as hydrocarbons, ketones, " Tetralin " or " Decalin " (Registered Trade Marks).  After the condensation, iodine may be removed by means of activated zinc and water and the maleic anhydride may be washed out with hot water.  Suitable solvents for the separation of the unconverted fatty acids are petrol ether, gasoline, cyclohexane or decalin.  Non-volatile esters, such as triglycerides, may, after the condensation, be saponified or converted by re-esterification into volatile esters and the mixture thus obtained may be separated by distillation.  In examples: (1) commercial oleic acid is condensed with maleic anhydride in the presence of iodine and separated from the condensation products by distillation; (2) sunflower oil fatty acids are heated with maleic anhydride and iodine and the product distilled to obtain oleic acid; (3) sunflower oil fatty acids are condensed with methacrylic acid in the presence of iodine and the reaction mixture distilled in vacuo to separate unchanged fatty acids leaving the mono-adduct of linoleic acid.  Specifications 500,348, [Group IV], 762,122 and U.S.A. Specifications 2,306,281, 2,444,328, 2,459,054 and 2,482,760 are referred to.ALSO:Unsaturated fatty acids (or esters thereof) having two or more double bonds are separated from unsaturated fatty acids (or esters thereof) having one double bond by heating the mixture of fatty acids or esters in the presence of iodine, or a compound capable of generating iodine, with maleic anhydride, maleic acid or or methacrylic acid in a proportion of about 100-200 mole per cent, calculated on the unsaturated fatty acids having two or more double bonds, the reaction being interrupted when the fatty acids or esters having two or more double bonds have been transformed substantially completely into mono-adducts, whereupon the unchanged fatty acids or esters are separated from the condensation products by distillation and/or by treatment with solvents.  The process may be used to prepare substantially pure oleic acid by removing the more unsaturated fatty acids therefrom, or to obtain linoleic acid mono-adducts from cotton seed oil, sun-flower oil and soya bean oil. Catalysts used instead of iodine are hydriodic acid, iodine trichloride, iodine monochloride, bromide or fluoride, iodoform, hydriodic acid salts of, e.g., hexadecylamine or pyridine, and inorganic iodides, e.g. zinx iodide.  The proportion of catalyst varies from 0.1-2 per cent, calculated on the fatty acids, and the reaction temperature ranges from 120-300 DEG C., preferably 175-250 DEG C.  It is advantageous to add the catalyst to the reaction mixture after the latter has become homogenous, generally above 100 DEG C., and preferably after the mixture has reached reaction temperature.  The condensation may be effected in the presence of a high boiling non-oxidizing solvent such as "Tetralin" or "Decalin" (Registered Trade Marks).  After the condensation, iodine may be removed by means of activated zinc and water and the maleic anhydride or like reagent may be washed out with hot water.  Suitable solvents for the separation of the unconverted fatty acids or esters are petrol ether, gasoline, cyclohexane or "Decalin."  Nonvolatile esters, such as triglycerides, may, after the condensation, be saponified or converted by re-esterification into volatile esters and the mixture thus obtained may be separated by distillation. In examples (1) commercial oleic acid is condensed with maleic anhydride in the presence of iodine and purified oleic acid is separated from the condensation products by distillation; (2) sun-flower oil fatty acids are heated with maleic anhydride and iodine and the product is distilled to obtain oleic acid; (3) sun-flower oil fatty acids are condensed with methacrylic acid in the presence of iodine and the reaction mixture is distilled in vacuo to separate unchanged fatty acids, leaving the mono-adduct of linoleic acid.  Specifications 500,348, 762,122, and U.S.A. Specifications 2,306,281, 2,444,328, 2,459,054 and 2,482,760 are referred to.