Patent GB-665248-A (GB)
Title: Improvements in or relating to the fractionation of mixtures of organic compounds of differing degrees of unsaturation
IPC: C11C1/00
Filed: 1949-08-11
Abstract: A mixture of straight-chain polar organic compounds containing components of different degrees of unsaturation is contacted with urea to form crystalline compounds with the more saturated components, which compounds are separated from the unreacted components.  Temperature is preferably 0-75 DEG  C. and a solvent or diluent may be present, e.g. a ketone or an alcohol of 4-5 carbon atoms or mixtures thereof.  Mixtures of fatty acids or their esters or fatty alcohols may be separated.  Drying characteristics of vegetable and animal oil acids may be improved by removal of acids of a low degree of unsaturation.  Natural fats and oils may be hydrolysed to give the acids or esters with monohydric straight-chain alcohols which are then separated.  Saturated fatty acids of 4-50 carbon atoms, and mono-olefinic acids such as oleic, readily form the compounds.  Unsaturated acids reacting with some reluctance include linolenic and elaeostearic.  Fish oils, tall oil, isomerized oils, and dehydrated castor oil as well as mixtures of amines, amides, nitriles, esters, alcohols, aldehydes or ketone are also referred to. Fractionation of mixtures according to molecular weight as well as unsaturation is possible by variation of temperature, since at temperatures of about 35-75 DEG  C. the shorter chain components do not react.  By using a temperature gradient a number of desired fractions may be separated.  Urea may be used as crystals or in a solvent, for example as a saturated aqueous solution.  The concentration of the solution may be adjusted to give a selective effect as may the ratio of urea to the mixture treated, a large excess giving maximum removal.  After reaction the mixture is separated.  If a settling tank is used, a mixture of the crystalline compounds and dilute urea solution separates from raffinate and is heated to 80-125 DEG  C. to decompose said compounds, giving, for example, fatty acids and urea which latter may redissolve to give a solution for recycle.  When employing centrifuging or filtration, the crystals are separated and regenerated by heat, steam distillation or treatment with hot solvents.  Corrosion of apparatus may be prevented by blanketing with inert gas, by coating or adding inhibitors.  In examples, mixtures of linseed, soybean, or dehydrated castor oil fatty acids or their methyl esters are treated with saturated aqueous urea at 22-25 DEG  C., methyl isobutyl ketone being used as diluent; alcohols obtained by reduction of linseed oil acids, tall oil, a mixture of stearic and oleic acids, a raffinate from the urea extraction of methyl linseedate, ethyl esters of soybean fatty acids, and methyl esters of tung oil fatty acids are similarly treated. Methyl esters of soybean acids are also treated with solid urea, the product being centrifuged or treated with methyl isobutyl ketone and filtered.ALSO:A mixture of straight-chain polar organic compounds containing components of different degrees of unsaturation is contacted with urea to form crystalline compounds with the more saturated components, which compounds are separated from the unreacted components.  Temperature is preferably 0 to 75 DEG C. and a solvent or diluent may be present, e.g. a ketone or an alcohol of 4 to 5 carbon atoms or mixtures thereof.  Mixtures of fatty acids or their esters or fatty alcohols may be separated.  Drying characteristics of vegetable and animal oil acids may be improved by removal of acids of a low degree of unsaturation.  Natural fats and oils may be hydrolyzed to give the acids or esters with monohydric straight chain alcohols which are then separated. Saturated fatty acids of 4 to 50 carbon atoms and mono-olefinic acids such as oleic readily form the compounds.  Unsaturated acids reacting with some reluctance include linolenic and elaeostearic. Fish oils, tall oil, isomerized oils and dehydrated castor oil are also referred to. Fractionation of mixtures according to molecular weight as well as unsaturation is possible by variation of temperature since at temperatures of about 35 to 75 DEG C. the shorter chain components do not react.  By using a temperature gradient a number of desired fractions may be separated.  Urea may be used as crystals or in a solvent, for example as a saturated aqueous solution.  The concentration of the solution may be adjusted to give a selective effect as may the ratio of urea to the mixture treated, a large excess giving maximum removal. After reaction the mixture is separated.  If a settling tank is used, a mixture of the crystalline compounds and dilute urea solution separates from raffinate and is heated to 80 to 125 DEG C. to decompose said compounds, giving, for example, fatty acids and urea which latter may redissolve to give a solution for recycle. When employing centrifuging or filtration, the crystals are separated and regenerated by heat, steam distillation or treatment with hot solvents.  Corrosion of apparatus may be prevented by blanketing with inert gas, by coating or adding inhibitors.  In examples, mixtures of linseed, soybean or dehydrated castor oil fatty acids or their methyl esters are treated with saturated aqueous urea at 22 to 25 DEG C., methyl isobutyl ketone being used as diluent; alcohols obtained by reduction of linseed oil acids, tall oil, a mixture of stearic and oleic acids, a raffinate from the urea extraction of methyl linseedate, ethyl esters of soybean fatty acids, and methyl esters of tung oil fatty acids are similarly treated. Methyl esters of soybean acids are also treated with solid urea, the product being centrifuged or treated with methyl isobutyl ketone and filtered.