Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C7/00—Purification; Separation; Use of additives
  • C07C7/148—Purification; Separation; Use of additives by treatment giving rise to a chemical modification of at least one compound
  • C07C7/152—Purification; Separation; Use of additives by treatment giving rise to a chemical modification of at least one compound by forming adducts or complexes
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C7/00—Purification; Separation; Use of additives
  • C07C7/04—Purification; Separation; Use of additives by distillation
  • C07C7/05—Purification; Separation; Use of additives by distillation with the aid of auxiliary compounds
  • C07C7/08—Purification; Separation; Use of additives by distillation with the aid of auxiliary compounds by extractive distillation

Definitions

• This invention relates to a process for the extractive fractionation of organic compounds. More particularly, it relates to improvements in the process of fractionally extracting organic compounds from mixtures thereof by the use of such complex-forming agents as urea and thiourea.
• thiourea is the complex-forming agent employed the complexes formed thereby are usually. of a substantially different character in that thiourea forms complexes with organic compounds having either a branched configuration zoo-s74) from mixtures containing other types of compounds usually in excess. This latter process is usually employed for the purification of aromatics such as benzene, toluene, etc.
• a mixture of organic compounds contains a relatively minor fraction of material which will form crystalline complexes with one of the above agents. It has been noted that if only a minor amount of complexes are formed and thereafter separated from the mixture by filtration the thin layer of crystals tends to clog the filter cloth and thus to reduce the efiior a cycloaliphatic structure. Under normal operating conditions. thiourea forms only minor amounts of complexes with organic compounds normal parafpounds.
• mixtures 01 organic compounds containing aromatic and non-aromatic fractions may be contacted with a complex-forming agent in the presence of a selective solvent for the aromatic fraction.
• the mixture may then be passed to a settling tank wherein phase separation occurs, the mixture settling into three or more phases, one of which is a solution of the aromatics.
• Two other phases which will be present are the crystalline complexes formed between the agent employed and at least a part of the non-aromatic constituents of the mixture of organic compounds as well as a raflinate phase immiscible with the solution of the aromatics, said raflinate being substantially free of any aromatic constituents.
• the three phases may be individually recovered such as by filtration of the crystalline complexes and decanting of the solution of aromatics from the immiscible rafilnate phase.
• the selective solvent for aromatic constituents should be substantially a non-solvent for the other components of the reaction mixture and especially for the non-aromatic constituents which may be present as well as for any com- .plexes which may be formed.
• Such selective solvents include especially alcohols, modified by the addition thereto of substances such as acetamide, phenols, nitrobenzenes, aniline or ethanolamines.
• Other suitable selective solvents include dimethyl sulfolane, furfural, ,e',p'-dichloroethyl ether, and liquid sulfur dioxide.
• the alcoholic solutions containing modifying agents such as the ethanolamines should contain from about to about 50% of such modifiers.
• the selective solvent described above may be added to the mixture of organic compounds prior to contacting with either urea or thiourea.
• the phase separation may be effected prior to complex formation, the aromatics then never passing through the zone wherein complexes are formed.
• the phase containing the aromatic constituents may pass through the latter zone and may be separated from the reaction mixture in a subsequent operation.
• the selective solvent may be added to the mixture of organic compounds during or after complex formation. It has been found that the presence of substantially inert selective solvents do not appreciably affect the complex formation.
• the mixtures of organic compounds which may be treated with urea by the process of the present invention comprise compounds having substantially normal structure and/or compounds having a predominating substituent of substantially normal structure. Conditions may be employed whereby certain normal organic compounds are separated from other normal organic compounds, or from other organic compounds such as isoparafiins, aromatics, naphthenes, etc.
• the organic compounds of normal structure which may be formed into complexes by the process of the present invention include both saturated and unsaturated compounds, especially the paraffins, and olefins.
• the normal compounds may be of a number of types, such as hydrocarbons, alcohols, ketones, aldehydes,
• esters amines, amides, sulfides, disulfides, mercaptans, acids, halogenated compounds, ethers, nitro-compounds, silicones, carbohydrates, etc.
• the hydrocarbons respond especially well to the process of the present invention.
• Suitable hydrocarbons which form crystalline complexes with urea include the parafiinic hydrocarbons such as butane, pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, eicosane, etc.
• parafiinic hydrocarbons such as butane, pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, eicosane, etc.
• Olefin hydrocarbons which may be treated by the process of the present invention include 1- butene, 2-butene, l-pentene, 2-pentene, l-hexene, 2-hexene, 3-hexene, l-heptene, Z-heptene, B-heptene, l-octene, 2-octene, 3-octene, 4-octene, 2-nonene, 3-nonene, 4-nonene, l-decene, 2-decene, 3decene, 5-decene, l-undecene, 2-undecene, 5-undecene, l-dodecene, G-dodecene, l-tridecene, 6-tridecene, l-pentadecene, 8-heptadecene, 13-heptacosene, etc.
• Another class of hydrocarbons which may be formed into complexes with urea, according to the process of the present invention are the normal diolefins such as 1,2-butadiene, 1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, 1,4- pentadiene, 1,2-hexadiene, 1,3-hexadiene, 1,4- hexadiene, 1,5-hexadiene, 2,3-hexadiene, 2,4- hexadiene, 1,3-heptadiene, 1,6-heptadiene, 2,4- heptadiene, 1,4-octadiene, 1,5-octadiene, 1,7- octadiene, 2,6-octadiene, 3,5-octadiene, 1,5-nonadiene, 1,8-nonadiene, 2,6-nonadiene, 1,3-decadiene, 1,4-decadiene, 1,9
• Normal hydrocarbons of a greater degree of unsaturation which form crystalline complexes with urea'by the process of the present invention include the triolefines, acetylenes, diacetylenes, olefin-acetylenes and the diolefln-acetylenes, including 1,3,5-hexatriene, 1,3,5-heptatriene, 2,3,6- octatriene, ethylacetylene, propylacetylene, butylacetylene, amylacetylene, caprylidene, 4- octyne, diacetylene, propyl-diacetylene, 1,8-nonadiyne, 1-hepten-3-yne, 1,5-hexadien-3-yne, etc.
• Normal alcohols especially those having six or more 'carbon atoms, may be treated by the present process to form complexes with urea.
• These include the aliphatic monohydric alcohols such as hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, dodecyl alcohol, cetyl alcohol, carnaubyl alcohol, and the polyhydric alcohols, such as ethylene glycol, diethylene glycol, propylene glycol and hexitol.
• Ethers of normal structure forming complexes with urea include acetal, dioxane, paraldehyde, crotonyl ether, etc.
• Aldehydes of normal structure also respond to the process of this invention, including butyraldehyde, valeraldehyde, caproaldehdye, palmitic aldehyde, citral adipaldehyde, etc.
• Ketones which form urea complexes are exemplified by 3-hexanone, palmitone, 2,3-pentanedione, etc. Acids also may be treated according to the subject process.
• Typical normal acids forming urea complexes are the normal fatty acids, especially those having four or more carbon atoms, such as butyric, valeric, caproic, enanthylic, caprylic, pelargonic, capric, undecylic, lauric, tridecoic, myristic, pentadecanoic, palmitic, margaric, stearic, etc., acid.
• Acrylic acids also respond, such as methacrylic acid, tiglic acid, oleic acid, etc.
• the acetylene acids form urea complexes. These include sorbic and linoleic acids.
• esters such as amyl acetate, ethyl stearate, etc.
• amines such as n-decyl amine, dibutyl amine and triethyl amine
• amides such as stearamide
• mercaptans such as heptyl mercaptan: and other organic compounds of normal structure, including halogenated derivatives of the above compounds, thioalcohols, alkyl hydrazines, thioaldehydes, amino acids, nitroparaffins, etc.
• Themixturescontainingtheorganiccompounds of normal structure may be composed solely of mixed normal compounds, or they may contain materials substantially inert toward urea, such as branched parafiins, isoolefins, aromatics, cycloparaffins, etc.
• the inert ingredients are present as isomers of the normal structure compounds, and may occur therewith naturally or by reason of some treatment to which the organic material has been subjected, such as alkylation, cyclization, lsomerization, etc.
• active or inert diluents or solvents may be added to normal organic compounds in order to modify the type and degree of crystallization of the latter with urea. The reason for and use of diluents is discussed hereinafter.
• Hydrocarbons which form complexes with thiourea are those having a predominating member which is a substantially branched radical or a naphthene radical, such as alkaryl hydrocarbons wherein at least one alkyl group, is an isoparaifin radical of about six or more carbon atoms.
• Isoparafllns which form complexes with thiourea include isobutane, isopentane, 2,2-dimethylpropane, isohexane, 2,3-dimethylbutane, 2- methylpentane, 3-methylpentane, 2-ethylbutane, 2 ethylpropane, 1,1 dimethylpentane, 1,2 dimethylpentane, 1,3 dimethylpentane, 1,4 dimethylpentane, 2-ethylpentane, 3-ethylpentane, 2-n-propylbutane, 2-isopropylbutane, 2-methylhexane, 3-methylhexane, 2,2-dimethylpentane, 2,3-dimethylpentane, 2,4-dimethylpentane, 3,3- dimethylpentane, 2,2,3-trimethylbutane, 2-methylheptane, 3-methylheptane, 4-methylheptan
• 2-cyclopentylpentane 1-methyl-3-butylcyclopentane, 1-methyl-2,5-diethylcyclopentane, 1,2,3- trimethyl-4-isopropylcyclopentane, heptylcyclopentane, cyclohexane, methylcyclohexane, ethyl-- cyclohexane, 1,1-dimethylcyclohexane, 1,2-dimethylcyclohexane, 1,3 dimethylcyclohexane, 1,2,3-trimethylcyclohexane, 1,3,5-trimethylcyclohexane, butylcyclohexane, l-methyli-ethylcyclohexane, 1-methyl-3-propylcyclohexane, l-methyl-3-isopropyl-cyclohexane, 1,3-dimethyl-5-ethylcyclohexane, 1,3-diethylcyclohexan
• the ratio of the complex-forming agent to active organic compounds will vary with the type of mixture to be treated and with the conditions of complex formation.
• the extractive fractionation may be carried out with the intention of removing from the mixture the maximum amount possible of the compounds of normal structures present.
• Complexes may be formed having varying amounts of the complex-forming agent combined with the active organic compound.
• the temperature or other conditions during complex formation are such that about 3 mols of the agent combined with about every 4 carbon atoms of the active organic compound-it is preferred practice to contact the active organic compound with an amount of the agent somewhat in excess of this ratio.
• the complexes are relatively unstable formations which appear to be loose combinations involving hydrogen bonding or some form of molecular attraction, the exact nature of which has not been deduced. It has been found that due to their unstable character, splitting into the component parts of the complex may be readily accomplished, the complex-forming agent and the organic compounds in complex combination therewith separately recovered in their original state.
• Steam distillation is a refinement of the above process and the principle of regeneration and fractionation applies here as well. Steam distillation is preferable where the organic compounds to be regenerated are of such high boiling point that their distillation would be accomplished by substantial decomposition.
• a further type of regeneration comprises addition of a solvent for the complex-forming agent such as water or alcohol to the complex and the application of heat to facilitate the regeneration.
• a solvent for the complex-forming agent such as water or alcohol
• the regenerated organic compounds separate from the solution of the complex-forming agent and subsequently may be fractionated by normal purification or fractionation procedures.
• a more preferred type of regeneration comprises the addition of a solvent for one or more fractions of the organic compounds to be regenerated from the complexes.
• a solvent for one or more fractions of the organic compounds to be regenerated from the complexes.
• Fractionation by simple heating is satisfactory for some purposes. Following the regeneration by such means it is usually necessary to purify or fractionate the regenerated compounds and the regenerated complex-forming agent for further use.
• the process of the present invention is useful for the preparation of high octane gasoline for minutes the reaction mixture was allowedto settle into three phases.
• the crystalline complexes so formed were removed by filtration and the two liquid phases were separated by decantation.
• One of the liquid phases comprised the alcoholic solution of acetamide containing dissolved therein substantially all of the alkylated benzenes in the original gasoline.
• the other liquid'phase comprised the raifinate and contained substantially no aromatics but the entire quantity of iso-octane present in the original gasoline.
• the crystalline complexes were heated in the presence of water to about 75 C., at which temperature the complexes decomposed to yield the normal octane originally present in the gasoline and an aqueous solution of urea and two phases were separately recovered by decantation.

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Cited By (42)

Citations (4)

• 1947
  • 1947-03-29 US US73821347 patent/US2520715A/en not_active Expired - Lifetime
• 1948
  • 1948-03-30 FR FR963979D patent/FR963979A/fr not_active Expired

Patent Citations (4)

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