Patent GB-681246-A (GB)
Title: Extractive crystallisation process
IPC: C10G31/06
Filed: 1948-10-22
Abstract: Crystalline complexes of organic compounds and urea or thiourea are formed by contacting the compounds with an aqueous solution of urea or thiourea in the presence of a ketone soluble both in the feed mixture and in the aqueous solution.  Complexes are formed between urea and straight-chain compounds, these being saturated and unsaturated hydrocarbons, mono- and polyhydric alcohols containing 6 or more carbon atoms, esters, amines, amides, sulphides, disulphides, mercaptans, saturated and unsaturated carboxylic acids, ethers, halogenated compounds, including halogenated products of many of the preceding compounds, and nitro-compounds; and between thiourea and branched chain or naphthenic compounds, these being aliphatic or cycloaliphatic hydrocarbons, or hydrocarbons containing a cycloaliphatic or branched-chain aliphatic radical with at least 5 carbon atoms and specifically alkaryl hydrocarbons having at least one isoparaffin radical of about 6 or more carbon atoms and the naphthenes.  Many examples of these types of compounds are given. Ketones specified are aliphatic ketones such as acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, diisopropyl ketone and methyl tertiary butyl ketone.  The aqueous solution of urea or thiourea is preferably saturated.  The complexes may be decomposed to obtain the straight or branched-chain or naphthenic compounds by heating with water at 100-175 DEG  F.  Specifications 650,571 and 671,456 are referred to.  The Specification as open to inspection under Sect. 91 refers also to the formation of complexes with selenourea and to the formation of urea complexes with various aldehydes, thioaldehydes, ketones, silicones, carbohydrates and alkyl hydrazines; and also with methacrylic and tiglic acids, acetal, paraldehyde, 1,3-dimethyl-butylamine, iodobenzene, dioxane, and some other heterocyclic compounds.  Additional examples of compounds of the classes described in the preceding paragraph are also furnished. Cyclohexanol, cyclohexanone, p-methylcyclohexanol, dimethallyl ether, 2,4,6-trimethylpyridine, chlorobenzene, chlorocyclohexane and cyclohexylamine are also referred to as compounds forming complexes with thiourea.  It is also stated that sulpholane, acetonyl acetone or various alcohols, esters, and ethers may be used as solvents in place of the ketones referred to above.  This subject-matter does not appear in the Specification as accepted.ALSO:Oils are fractioned to separate straightchain and branched-chain or naphthenic components, by contacting with an aqueous solution of urea or thiourea in the presence of a ketone soluble both in the feed mixture and in the aqueous solution. Crystalline complexes are formed between urea and the straight chain compounds or between thiourea and the branched-chain or naphthenic compounds.  Many examples of these types of compounds are given.  Ketones specified are aliphatic ketones such as acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, diisopropyl ketone and methyl tertiary butyl ketone. The aqueous solution of urea or thiourea is preferably saturated. The complexes may be decomposed to obtain the straight- or branched-chain or naphthenic compounds by heating with water at 100-175 DEG F.  In an example, urea is dissolved in a mixture of water and methanol having a volumetric ratio of 6:1 and this solution then reacted at 85 DEG F with a mineral lubricating oil fraction diluted wih methyl isobutyl ketone.  The slurry of crystalline complexes is passed to a rotary filter and the filter cake washed with methylisobutyl ketone.  The complexes are mixed with the aqueous urea solution separated from the raffinate oil and heated to 140 DEG F for 5 minutes.  The oil phase formed is separated from the aqueous urea and the ketone flashed off.  The crystallization process may also be conducted continuously. Specifications 650,571 and 671,456 are referred to.  The Specification as open to inspection under Sect. 91, refers also to the formation of complexes with selenourea and to the use as solvents of sulpholane, acetonyl acetone and various alcohols, esters and ethers in place of the ketones referred to above.  This subject-matter does not appear in the Specification as accepted.