US2588506A - Extractive fractionation pbocess - Google Patents

Extractive fractionation pbocess Download PDF

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US2588506A
US2588506A US74167747A US2588506A US 2588506 A US2588506 A US 2588506A US 74167747 A US74167747 A US 74167747A US 2588506 A US2588506 A US 2588506A
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complexes
urea
mixture
thiourea
hydrocarbons
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Priority to FR964694D priority patent/FR964694A/fr
Priority to GB10496/48A priority patent/GB671459A/en
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G31/00—Refining of hydrocarbon oils, in the absence of hydrogen, by methods not otherwise provided for
    • C10G31/06—Refining of hydrocarbon oils, in the absence of hydrogen, by methods not otherwise provided for by heating, cooling, or pressure treatment

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  • 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 useof vsuch complex-forming agents as urea and thiourea.
  • the complexes. so formed are of indeterminate structure, but appear to be unstable molecular complexes rather than true chemicalv reaction products. This is indicated by their unstable character and the consequent ease of the regeneration of their components, namely urea and the unaltered organic compound.
  • agent employed lthe complexes formed thereby are usually of a substantially different character ⁇ in that thiourea forms complexes with organic compounds having either a branched configura tion or a cycloaliphatic structure.
  • thiourea forms only minor amounts of complexes with organic Vcompounds or normal 'structuragsuch as the normal paraiiins;
  • an improvement upon the known process would comprise a revision thereof whereby the final product substantially excluded naphthenes and largely comprised isoparaflins.
  • a mixture of organic compounds contains a relatively minor fraction of material which will form crystalline complexes with one of theV 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 clogr the lter cloth and thus to reduce the eiiciency of the filtration step.
  • the fractionation of mixtures of organic compounds by the subject extractive fractionation processes may be improved by recycling part of the raffinate separated from the complexes formed as described above. Still in accordance with this invention, it has been found that further improvements may be effected by subjecting the rafnate toj conversion processes and thereafter fractionating the product and returning a portion thereof to the original mixture of organic compounds.
  • raiiinate is meant that portion of the original mixture of organic compounds not forming complexes with the complex-forming agent.
  • conversion processes is meant a process wherein the raffinate is substantially changed by such means as alkylation, isomerization, hydrogenation, or by the formation of other complexes.
  • mixtures of organic compounds are contacted with a complex-forming agent (suitably either urea or thiourea) and passed to a separator wherein the complexes are separated from the raffinate. Following isolation of the rafnate,
  • a complex-forming agent suitable either urea or thiourea
  • the process according to the present invention comprises one of two alternative steps: either the fractionation of the raffinate or the conversion thereof.
  • the fractionation of the raflinate may take place by any of the well known means such as distillation, solvent extraction, or extractive fractionation with a complex-forming agent other than the one originally employed.
  • the raffinate is separated into portions having desired configurations or properties, at least one of said portions being so i.
  • the original desired fraction is concentrated and may be returned to the feed.
  • the efficiency of conversion operations such as isomerization is limited by similar equilibrium phenomena. For example, if the feed in an isomerizer contains isomerized material the degree of isomerization taking place is reduced to a corresponding extent. In order to improve the efficiency of such reactions it is highly desirable to remove from the feed any isomerized material prior to subjecting such feed to isomerization. Consequently, the process of the present invention comprises a means whereby the eciency of conversion operations may be improved according to the following scheme: the feed for an isomerizer is subjected to extractive fractionation with a complex-forming agent after which the complexes are removed vand the raffinate is subjected to an isomerization treatment.
  • the resulting product is fractionated as well as Dossible by distillation and then the fraction thereof containing minor amounts of the isomerized product and major amounts 0f a fraction undesirable in the isomerizer is returned to the original feed and subjected to the action of complexforming agents.
  • the raffinate resulting from such an operation consequently has a reduced amount of product undesirable in the isomerizer.
  • a specific case in point is that of the preparation of high anti-knock gasoline by a combined process of fractional extraction and isomerization.
  • a gasoline having relatively low anti-knock value is subjected to the action of thiourea whereby the branched hydrocarbons having high anti-knock values are removed from the original mixture leaving a feed substantially comprising hydrocarbons of straight-chain configuration as a raffinate.
  • This raiiinate is then subjected to an isomerization reaction whereby a portion thereof is converted to branched hydrocarbons having improved anti-knock values.
  • the resultingmixture is fractionated by distillation into the portions having high anti-knock value and another portion having unconverted normal hydrocarbons in admixture with a minor amount of branched hydrocarbons.
  • the raffinate passes from the separator directly to the fractionator 5 through by-pass line 6 or alternatively to the convertor 4.
  • the conversion step has been described above as comprising isomerization, alkylation, etc. If such conversion is employed the product thereof is conducted to the fractionator 5 wherein the product is separatedinto one portion with which it is desired to enrich the original feed. This portion is returned to the mixer I.
  • mixtures of organic compounds whichmay be treated with urea by the process of the pres:- ent invention comprise compounds having substantially normal structure and/or compounds having a predominating substituent of substantialy 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 isoparaiiins, aromatics, naphthenes, etc.
  • the organic compounds of normal structure which may be formed into complexes by theproc-y ess of the present inventioninclude bothsaturated and unsaturated compounds, especially the parailins, varrdl olens;
  • the normall compounds' maybeof a number of types, sucha's hydrocarbons, alcohols, kei-onesI aldehydes, kesters;amines, amides, suldes, disuldes, mercaptans,. acids; halogenated compounds, others, nitro-compounds, silicones, carbohydrates, etc.
  • the hydrocarbons respond especially well to the ⁇ 'processi of the presentinvention.
  • Suitable hydrocarbons which form crystalline complexes with urea include the paraflinic hydrocarbons such as butane, pentane, hexane,V heptane, octane, nonane, decane, undecane, dodec'ane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, eicosane, etc.
  • paraflinic hydrocarbons such as butane, pentane, hexane,V heptane, octane, nonane, decane, undecane, dodec'ane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, eicosane, etc.
  • Olefin .hydrocarbons which may be. treated by the process of the present invention-include' l-butene, 2-butene', l-penten'e, 2-pentene, l-hexene, 2-hexene, 3-hexene, l-heptene, 2-heptene, 3-heptene', 1octene, 2octene, 3-octene, 4-octene', 2nonene, 3-nonene, 4-nonene, l-decene', 2-decene, 3-decene, 5decene, l-undecene, 2unde cene, 5-undecene, l-dodecene', 6dodecene, l-tridecene, ⁇ G-tridecene, l-pentadecene, S-heptadecene, 13-heptacosene
  • Another class of hydrocarbons which may be formed into complexes with urea, according to the process of the present invention are the normal diolens 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-hexadene, 2,3-hexadiene, 2,4-hexadiene, 1,3-heptadiene, 1,6-heptadiene, 2,4-heptadiene, 1,4-octadiene, 1,5-octadiene, 1,7-octadiene, f
  • nonadiene 2,6-nonadiene, 1,3-decadiene, lai-decadiene, 1,9-decadiene, 2,8-decadiene, 3,7-decadiene, 2,6-dodecadiene, 1,17-octadecadiene, etc.
  • Normal hydrocarbons of a greater degreev of unsaturation which form crystalline' complexes with urea by the process of the" present invention include the triolenes, acetylenes, diacetylenes, olen-acetylenes and the diolen-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, l-hepten-S-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 struc-- ture also respond to the process of this invention, including butyraldehyde, valeraldehyde, c aproaldehyde, palmitic aldehyde, citral adipaldehyde. etc.
  • Ketones which form urea complexes are exemplified by S-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 lmore carbon atoms, such as butyric, valerio, caproic, enanthy1ic,'caprylic, pelargonic, capric, undecylic, lauric, tridecoic, myristic, pentadecanoic, palmitic, margaric, stearic, etc., acid.
  • Acrylic acids also respond, such as methylacrylic acid, tiglic acid,v oleic acid, ⁇ etc.
  • the acetylene acids form 'urea complexes.y Thes'e include :sorbic4 and;
  • types of normal-structured compounds which may be treated accordingto the processiof the presentv inventionV include esters; l such as amyl acetate, ethyl stearate, etc.; amines such as'n.- de'cyl 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, nitroparains, etc.
  • the mixtures containing the organicv compounds of" normal structure may be composed solely lof mixed normal compounds', or vthey may. contain materials substantially inert toward urea, such as branched para'ns, isoolens, aromatics,v cycloparains, etc, Usually, especially when treating natural products such as lpetroleum, the inert ingredients are present as isomers of the normal structure compounds, and may occur therewith naturally or by reason ofv some; treatment to which ⁇ the organic material has been subjected, such as alkylation, cyclization, isomer.- ization, etc. However, 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 here-- inafter.
  • Hydrocarbons which form complexes with thiourea are those having a predominating member which is a substantially branched radical or anaphthene radical, such as alkaryl hydrocar-fbons wherein at least one alkyl group is. an isoparailin radical of abouty six or more: carbon. atoms.
  • 2,2,S-trimethylbutane Z-methylheptane, S-methylheptane, 4-methylheptane, 3- ethylhexane, 2,2-dimethylhexane, 2,3-dimethylhexane, 2.4-dimethylhexane, 2.5-di1nethylhexane, 3,3-dimethylhexane, 3,4-dimethylhexane; 2,2,3-trimethylpentane', 2,2,4-trimethylpentane,
  • diisoamyldecane 4,8,13,17 tetramethylicosane, 2,11dimethyl5,-diisoamyldodecane, l-nonylnonadecane, 2,6,10,14,18,22 hexamethyltetracosane, 2,6,12,16tetramethyl9(2,6-dimethyloctyl) heptadecane, etc.
  • Typical species of this group include cyclopropane, methylcyclopropane, 1,1 dimethylcyclopropane, 1,2-dimethylpropane, ethylcyclopropane, 1,1,2- trimethylcyclopropane, 1,2,3 trimethylcyclopropane, 1-methyl-2-ethylcyclopropane, propylcyclopropane, 1-methyl-2-propylcyclopropane, cyclobutane, methylcyclobutane, ethylcyclobutane, 1,2- dimethylcyclobutane, propylcyclobutane, isopropylcyclobutane, 1,2diisopropy1cyclobutane.
  • 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 processv 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.
  • Avfurther 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'l separate from the solution of the complex-'forming agent and subsequently may .be fractionated by normal purification or fractionation procedures.
  • a more preferred type ofregeneration 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 byv 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-formingagent for further use.
  • the process of the present invention is useful for the Apreparation of high octane gasoline or high diesel index fuel as well as for the preparation of internal combustion vengine fuels having a narrow boiling range.
  • The. extractive fractionation process which comprises treating mixtures of petroleum hydrocarbons with a -complex-forming agent selected from the group consisting of urea andthiourea, separating the complexes thus formed, between said agent with a fraction of the hydrocarbon mixture, from the rai'linate comprising the remaining fraction of the mixture, subjecting the raffinate to fractionation and returning'a fraction thereofrich in compounds. capable ofform'- ing complexes with said agent to enrich further portions of the original mixture.
  • a -complex-forming agent selected from the group consisting of urea andthiourea
  • the extractive fractionation process which comprises treating mixtures of petroleum hydrocarbons containing substantially straight chain hydrocarbons with va, complex-forming agent select'ed from the' group consisting of urea vand thiourea, vseparating the complexes thus form-ed, between ⁇ said-agent with a fraction of the hydrocarbon mixture, from the rafnate comprising the remaining fraction of the mixture, subjecting the raiinate to fractionation and returning a fraction ⁇ thereof rich in compounds capable of forming complexes with *said agent to enrich further portions of theoriginal mixture.
  • the extractive yfractionation process which comprises treating mixtures of petroleum hydro; carbons containing substantially straight chain hydrocarbons with urea, separating the complexes thus formed between urea and said -s-ubstantially straight chain hydrocarbons from the ranate comprising the remaining fraction of the petroleum hydrocarbons, subjectingthe ramnate to Yfractionation returning a Yfraction thereof rich in Ycompos-.nails capableV of forming complexes with said agent to enrich further portions of the original petroleum mixture;
  • the extractive fractionation process which comprises treating mixtures of a petroleum prod'- uct containing branched' chain hydrocarbonsv withv a complex-forming agent selected from the group consisting of urea and thiourea, separating the complexes thus formed, between said agent with a fraction ofthe hydrocarbon mixture, from the raffinate comprising the remaining fraction of the mixturegsubjecting the rafl-Vv nate to fractionation and returning' a 'fraction thereof' rich inl compoundsl capable of' forming complexes'with said 'agent' to enrich further por'- formed between thiourea and said branched chain' hydrocarbons from the railnate comprising the remaining portion of the petroleum iprodu'ct, subjecting the raffinate to fractionation and' returning a fraction thereof rich in compounds capable of forming complexes with s'aijd agent to enrich furtherportions of the original petroleum product;
  • the extractive fractionation process which comprises treating mixtures of organic com-V pounds with a complex-forming agent selected from the group consisting of rurea and thiourea, separating the complexes thus formed, between said agentv with a fraction of'said. mixture, from theralinate comprising the remaining fraction 0f themixture, subjecting. therainnate to an a1-.
  • a complex-forming agent selected from the grou-p consisting of urea and: thiourea
  • AThe extractive'fractionation process'w-hicn comprises treating mixtures of organic compounds with thiourea separating the complexes thus formed between thiourea and a fraction of said mixture from the raflnate comprising the remaining fraction of the mixture, subjecting the 1l raffinate to the action of urea whereby complexes are formed between a portion of the rainate and urea, removing said complexes and returning the remaining portion of the rainate to the original mixture of organic compounds.
  • the extractive fractionation process which comprises treating mixtures of organic compounds with a complex-forming agent selected from the group consisting of urea and thiourea, separating the complexes thus formed between said agent with a fraction of said mixture, from the rafnate comprising the remaining fraction mixture, subjecting the raffinate to a conversion operation, fractionating the conversion product thus formed'and returning a fraction thereof to the original mixture of organic compounds.
  • a complex-forming agent selected from the group consisting of urea and thiourea
  • the extractive fractionation process which comprises treating mixtures of organic compounds with a complex-forming agent selected from the group consisting of urea and thiourea; separating the complexes thus formed, between said agent with a fraction of said mixture, from the raffinate comprising the remaining fraction of the mixture; subjecting the raffinate to fractionation and returning a fraction thereof rich in compounds capable of forming complexes with said agent to enrich further portions of the original mixture.
  • a complex-forming agent selected from the group consisting of urea and thiourea
  • the process which comprises treating a feed comprising mixtures of petroleum distillates containing straight-chain hydrocarbons and branched-chain hydrocarbons with urea, separating crystalline complexes thus formed between urea and a portion of the straightchain hydrocarbons from a raflinate comprising branched-chain and unreacted hydrocarbons, contacting said ramnate with thiourea, separating crystalline complexes thus formed between thiourea and a, portion of the branched-chain hydrocarbons from a second raffinate comprising predominantly straight-chain and minor amounts of unreacted branched-chain hydrocarbons, and returning said second raffinate to further portionsof the original feed to enrich said feed, and subjecting the enriched feed to the first described urea fractionating operation.
  • the extractive fractionation process which comprises treating a mixture of organic compounds, some of which form solid complexes with urea and some of which form complexes with thiourea, with a, first complex-forming agent selected from the group consisting of urea and thiourea, under conditions to form solid complexes between said first agent and only a portion of the organic compounds present which are capable of forming solid complexes therewith, separating the solid complexes thus formed between said rst agent with a fraction of said mixture from a first raiiinate comprising the remaining fraction of the mixture, contacting said first raiiinate with a second complex-forming agent selected from the group consisting of urea and thiourea, which second agent is different from said first agent, separating the complexes thus formed between said second agent with a fraction of the first raffinate from a second raffinate comprising the remaining fraction of said first raiiinate, and returning said second raffinate to a further portion of the original mixture to enrich said mixture and subject
  • the process which comprises treating a feed comprising a petroleum distillate mixture containing straight-chain hydrocarbons and branched-chain hydrocarbons with thiourea under conditions to form solid complexes between said thiourea and only a portion of the branchedchain hydrocarbons, separating crystalline complexes thus formed between thiourea and a portion of the branched-chain hydrocarbons from a raiiinate comprising straight-chain hydrocarbons and uncomplexed branched-chain hydrocarbons, contacting said raiiinate with urea, separating crystalline complexes thus formed between urea and a portion of the straight-chain hydrocarbons from a second ralinate comprising predominantly branched-chain hydrocarbons and minor amounts of straight-chain hydrocarbons, and returning said second raffinate to a further portion of the original feed to enrich said feed, and subjecting the enriched feed to the first described thiourea fractionating operation.

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  • Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
US74167747 1947-04-15 1947-04-15 Extractive fractionation pbocess Expired - Lifetime US2588506A (en)

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US74167647 US2549372A (en) 1947-04-15 1947-04-15 Extractive fractionation process
US74167747 US2588506A (en) 1947-04-15 1947-04-15 Extractive fractionation pbocess
NL139931A NL72935C (xx) 1947-04-15 1948-04-14
FR964694D FR964694A (xx) 1947-04-15 1948-04-15
GB10496/48A GB671459A (en) 1947-04-15 1948-04-15 Extractive fractionation process

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US2849511A (en) * 1953-05-25 1958-08-26 Union Oil Co Separation of organic compounds
US3164579A (en) * 1965-01-05 Tffiourea abducts of dimethyl-

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US2681333A (en) * 1954-06-15 Gorin
US2681303A (en) * 1954-06-15 separation of hydrocarbons and hydrocarbon
US2681335A (en) * 1954-06-15 Gorin
US2666048A (en) * 1954-01-12 Separation of low molecular weight
US2890161A (en) * 1959-06-09 Production of low cold-test oils using urea
US2681904A (en) * 1954-06-22 Separation process
US2739144A (en) * 1956-03-20 Iio hsvm
US2691009A (en) * 1954-10-05 Atent office
US2666020A (en) * 1949-06-07 1954-01-12 Sepaeation of wax-like constituents
US2773858A (en) * 1950-03-27 1956-12-11 Manuel H Gorin Method of preparing expanded urea
US2700664A (en) * 1950-11-17 1955-01-25 Phillips Petroleum Co Separation of organic compounds by adduct formation
US2812373A (en) * 1951-08-02 1957-11-05 Monsanto Chemicals Vulcanization of rubber with crystalline adducts of urea
US2756222A (en) * 1952-06-17 1956-07-24 Swern Daniel Purification of long-chain vinyl esters and ethers
US2801993A (en) * 1953-08-11 1957-08-06 Rosenstein Ludwig Expanded thiourea
DE1040730B (de) * 1955-12-21 1958-10-09 Chem Fab Dueren G M B H Verfahren zur Herstellung von Waschmitteln
US2926206A (en) * 1958-02-24 1960-02-23 Union Oil Co Separation of c-8 aromatic hydrocarbon isomers utilizing werner complexes
US3082228A (en) * 1959-12-18 1963-03-19 Escambia Chem Corp Method for producing monoesters of polyunsaturated fatty acids
US3158541A (en) * 1959-12-18 1964-11-24 Escambia Chem Corp Product for reduction of blood cholesterol concentration
US4044052A (en) * 1972-11-03 1977-08-23 Sumitomo Chemical Company, Limited Process for recovery of urea from its phenolic solution
JPS5343736B2 (xx) * 1974-01-08 1978-11-22
CN101157871B (zh) * 2007-11-20 2013-02-13 济南钢铁股份有限公司 煤气精脱萘废柴油再生工艺方法

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US2386335A (en) * 1942-04-06 1945-10-09 Phillips Petroleum Co Process for the separation of hydrocarbons
US2376008A (en) * 1942-08-15 1945-05-15 Pittsburgh Coke & Iron Company Production of lutidine-urea compounds
US2423414A (en) * 1943-04-07 1947-07-01 United Gas Improvement Co Process for recovering diolefins from hydrocarbon mixtures

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3164579A (en) * 1965-01-05 Tffiourea abducts of dimethyl-
US2849511A (en) * 1953-05-25 1958-08-26 Union Oil Co Separation of organic compounds
US2813851A (en) * 1953-06-22 1957-11-19 Phillips Petroleum Co Organic separation with urea and thiourea

Also Published As

Publication number Publication date
NL72935C (xx) 1953-08-15
FR964694A (xx) 1950-08-22
GB671459A (en) 1952-05-07
US2549372A (en) 1951-04-17

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