GB693981A - A process for isomerising unsaturated fatty acids or esters thereof - Google Patents

Abstract

Unsaturated fatty acids or their esters are isomerized by heating them to a temperature not exceeding 140 DEG C. in presence of a catalyst prepared by reduction of a nickel or cobalt compound and comprising nickel or cobalt, nickel or cobalt silicate and a proportion of sulphur not exceeding 10 per cent based on the weight of the metal. Thus oleic acid, linseed oil fatty acids, linseed oil itself, other fatty oils of the drying, semi-drying and non-drying types, and alkyl esters of unsaturated fatty acids, particularly the ethyl esters, may be isomerized by this method. As a result of the isomerization, cis-stereoisomers become converted to the corresponding trans-stereoisomers, while double bonds become conjugated. In the examples, a catalyst is prepared by boiling together nickel sulphate, diatomaceous earth, sodium carbonate and water, boiling the precipitate obtained with further nickel sulphate solution and finally reducing the precipitate with hydrogen; this catalyst is used to isomerize linseed oil, soyabean oil, sunflower seed oil, cottonseed oil, sesame oil, whale oil, teaseed oil, ground nut oil, palm oil, linseed oil fatty acids, methyl esters of linseed oil fatty acids and methyl oleate. In the case of linseed oil, the oil may be neutralized and bleached before isomerization, while in the case of linseed oil fatty acids, the isomerization may be followed by sulphuric acid treatment. The isomerization is conducted under an atmosphere of carbon dioxide and at various temperatures. Specifications 645,872 and 646,919, [both in Group III], are referred to.ALSO:Unsaturated fatty acids or their esters are isomerized by heating them to a temperature not exceeding 140 DEG C in presence of a catalyst prepared by reduction of a nickel or cobalt compound and comprising nickel or cobalt, nickel or cobalt silicate and a proportion of sulphur not exceeding 10 per cent based on the weight of the metal. Thus oleic acid, linseed oil fatty acids, linseed oil itself, other fatty oils of the dry, semi-drying and non-drying types, and alkyl esters of unsaturated fatty acids, particularly the ethyl esters, may be isomerized by this method. As a result of the isomerization, cisstereoisomers become converted to the corresponding trans - stereoisomers, while double bonds become conjugated. In the examples, a catalyst is prepared by boiling together nickel sulphate, diatomaceous earth, sodium carbonate and water, boiling the precipitate obtained with further nickel sulphate solution and finally reducing the precipitate with hydrogen; this catalyst is used to isomerize linseed oil, soyabean oil, sunflower seed oil, cottonseed oil, sesame oil, whale oil, teaseed oil, groundnut oil, palm oil, linseed oil fatty acids, methyl esters of linseed oil fatty acids and methyl oleate In the case of linseed oil, the oil may be neutralized and bleached before isomerization, while in the case of linseed oil fatty acids, the isomerization may be followed by sulphuric acid treatment. The isomerization is conducted under an atmosphere of carbon dioxide and at various temperatures. Specifications 645,872 and 646,919 are referred to. Preparation of catalysts. Nickel or cobalt may be precipitated in the form of an insoluble compound from a solution of the metal salt, for example nickel or cobalt sulphate, in the presence of a material capable of forming a silicate with part of the p precipitate, for example diatomaceous earth or waterglass. Alternatively, the catalyst may be prepared by boiling a precipitate of a compound of the metal, for example nickel or cobalt hydroxide, with a material such as diatomaceous earth or water glass in an alkaline aqueous solution and separating the precipitate. The separated precipitate formed by either method is then reduced in a current of hydrogen at a temperature at which metallic nickel or cobalt is formed, for example 500 DEG C. The sulphur content can be imparted by treating the precipitate formed with alkali with a solution of a sulphur-containing nickel or cobalt compound, for example nickel sulphate, or by mixing the filtered and dried precipitate with sulphur or a sulphur compound before reduction takes place. Alternatively, the sulphur content can be imparted by treating the reduced catalyst with hydrogen sulphide or by using the reduced catalyst to hydrogenate a sulphur-containing oil. The catalysts may contain conventional ingredients such as carriers.ALSO:Unsaturated fatty acids or their esters are isomerized by heating them to a temperature not exceeding 140 DEG C in presence of a catalyst prepared by reduction of a nickel or cobalt compound and comprising nickel or cobalt, nickel or cobalt silicate and a proportion of sulphur not exceeding 10 per cent based on the weight of the metal. Thus oleic acid, linseed oil fatty acids, linseed oil itself, other fatty oils of the drying, semi-drying and non-drying types, and alkyl esters of unsaturated fatty acids, particularly the ethyl esters, may be isomerized by this method. When unsaturated fatty acids or their esters with a single double bond, for example oleic acid or its esters, are treated by this method, the conversion of the cis-stereoisomer to the trans-stereoisomer causes a rise in melting point which is useful in the manufacture of margarine and other edible fats.