Patent GB-650571-A (GB)
Title: Hydrocarbon complexes
IPC: C07C13/10
Filed: 1948-02-18
Abstract: Thiourea or a solution thereof is contacted with an aliphatic branched chain hydrocarbon, a cyclo-aliphatic hydrocarbon or a hydrocarbon containing a cyclo-aliphatic or branched chain aliphatic radical with at least 5 carbon atoms to form crystalline complexes. Isoparaffins, naphthenes, iso-olefins, cyclo-olefins or alkaryl hydrocarbons having at least one isoparaffin radical of 5 or more carbon atoms form complexes when used alone or in admixture with other materials.  Separation, concentration, and purification of hydrocarbons may be effected.  Complexes formed at about room temperature contain about 3-4 parts by weight of thiourea for each part of hydrocarbon.  If heated above 50 DEG  C. before crystallizing, the ratio is usually about 1 : 1.  When a solvent such as water or alcohol is present, solvent of crystallization may be present in the complex.  Non-crystalline complexes are formed at elevated temperatures or with larger amounts of solvents.  Numerous isoparaffins, naphthenes, including polycyclic naphthenes, iso-olefins, including di-iso-olefins, and cyclo-olefins, including terpenes, which form complexes, are specified.  They may be mixed with thiourea in the presence of solvents or diluents for the hydrocarbons, especially other hydrocarbons such as normal paraffins and aromatics, which may be present as an impurity, as in cracked gasoline.  Thiourea solvents may also be present and by choice of these, selected fractions or groups of hydrocarbons only permitted to form complexes.  Such solvents are water, lower alcohols and glycols, and expecially water-methanol mixtures.  Complex formation may be effected in stages, if desired with varying thiourea solution concentrations to yield different complexes.  By varying the temperature, desirable fractions only can be permitted to crystallize as complexes, other complexes remaining in solution.  Fractional crystallization of complexes is therefore used to separate hydrocarbon fractions.  Contact of reactants may be by concurrent or counter-current fluid processes, moving or fixed bed, slurry, emulsion or solvent extraction processes.  Separation of complex is effected by decantation, settling, filtration or centrifuging. It may then be washed prior to decomposition by heating or solvent extraction.  By heating to about 150 DEG  F., stratification into a hydrocarbon and a thiourea layer occurs.  By distillation, if desired with inert gas or steam, separation of the liberated hydrocarbons into fractions is possible.  Solvents for thiourea, such as water, alcohols or glycols, or for hydrocarbons, such as ether, may be added with mild heating when stratification occurs. By treating a hydrocarbon mixture with, for example, alcoholic ethanolamine or acetamide at the same time, prior to or after the thiourea treatment aromatics and normal paraffins may also be separated.  Similar separations may be made by combining with a urea treatment which gives complexes of normal hydrocarbons. Where large amounts of a complex are to be formed, a temperature above 75 DEG  C. may be used in treating with aqueous thiourea, when a hydrocarbon layer containing most of the complex is formed, said complex having a minimum thiourea: hydrocarbon ratio.  Similar complexes of low ratio are formed at about 50-75 DEG  C. using a minor proportion of water or alcohol.  Crystallization in stages may be effected by step-wise addition of thiourea, if desired using solutions of different concentrations, or by control or temperature.  The process is applicable to treatment of the feed or recycled feed of an isomerization process to remove iso hydrocarbons of an alkylate product to remove alkylate with or without isoparaffin, to the production of fuels by removal of isoparaffins or naphthenes from gasolines for blending purposes or for hydroforming, and to the separation of specific naphthenes or triptane.  The complexes may be modified as by treatment with hydrochloric acid or acetic anhydride to give the hydrochloride or acetate salts.  The complexes are useful for insecticides and fumigants, and for storage of volatile hydrocarbons.  Examples are given of the treatment with saturated methanol solution of thiourea at 22 DEG  C., and with a 50 per cent solution of thiourea in methyl or ethyl alcohol at 10-17 DEG  C. of various hydrocarbons and hydrocarbon mixtures including a straight run petroleum fraction, with complex formation and, in some cases, recovery of hydrocarbons.ALSO:Thiourea or a solution thereof is contacted with an hydrocarbon oil containing aliphatic branched chain hydrocarbons, cyclo-aliphatic hydrocarbons or hydrocarbons containing a cyclo-aliphatic or branched chain aliphatic radical with at least 5 carbon atoms to form crystalline complexes.  Isoparaffins, naphthenes, iso-olefins, cyclo-olefins or alkaryl hydrocarbons having at least one isoparaffin radical of 5 or more carbon atoms, form complexes whereby separation, concentration, and purification of hydrocarbons may be effected.  Complexes formed at about room temperature contain about 3-4 parts by weight of thiourea for each part of hydrocarbon.  If heated above 50 DEG  C. before crystallizing, the ratio is usually about 1 : 1.  When a solvent such as water or alcohol is present, solvent of crystallization may be present in the complex.  Non-crystalline complexes are formed at elevated temperatures or with larger amounts of solvents.  Mixing with thiourea may be effected in the presence of solvents or diluents for the hydrocarbons, especially other hydrocarbons such as normal paraffins and aromatics, which may be present as an impurity, as in cracked gasoline.  Thiourea solvents may also be present and by choice of these, selected fractions or groups of hydrocarbons only permitted to form complexes.  Such solvents are water, lower alcohols and glycols, and especially water-methanol mixtures.  Complex formation may be effected in stages, if desired with varying thiourea solution concentrations to yield different complexes.  By varying the temperature, desirable fractions only can be permitted to crystallize as complexes, other complexes remaining in solution. Fractional crystallization of complexes is, therefore, used to separate hydrocarbon fractions.  Contact of reactants may be by concurrent or countercurrent fluid processes, moving or fixed bed, slurry, emulsion or solvent extraction processes.  Separation of complex is effected by decantation, settling, filtration or centrifuging.  It may then be washed prior to decomposition by heating or solvent extraction.  By heating to about 150 DEG  F., stratification into a hydrocarbon and a thiourea layer occurs. By distillation, if desired with inert gas or steam, separation of the liberated hydrocarbons into fractions is possible. Solvents for thiourea, such as water, alcohols or glycols, or for hydrocarbons, such as ether, may be added with mild heating when stratification occurs.  By treating a hydrocarbon mixture with, for example, alcoholic ethanolamine or acetamide at the same time, prior to or after the thiourea treatment, aromatics and normal paraffins may also be separated.  Similar separations may be made by combining with a urea treatment which gives complexes of normal hydrocarbons.  Where large amounts of a complex are to be formed, a temperature above 75 DEG  C. may be used in treating with aqueous thiourea, when a hydrocarbon layer containing most of the complex is formed, said complex having a minimum thiourea: hydrocarbon ratio. Similar complexes of low ratio are formed at about 50-75 DEG  C. using a minor proportion of water or alcohol. Crystallization in stages may be effected by step-wise addition of thiourea, if desired using solutions of different concentrations, or by control of temperature.  The process is applicable to the production of fuels by removal of isoparaffins or naphthenes from gasolines for blending purposes or for hydroforming, and to the separation of specific naphthenes or triptane.  The complexes may be modified as by treatment with hydrochloric acid or acetic anhydride to give the hydrochloride or acetate salts.  Examples are given of the treatment with a saturated methanol solution of thiourea at 22 DEG  C. and with a 50 per cent solution of thiourea in methyl or ethyl alcohol at 10-17 DEG  C. of various hydrocarbons and hydrocarbon mixtures including a straight-run petroleum fraction.