US3591490A - Process of separating pure aromatic hydrocarbons from hydrocarbon mixtures - Google Patents

Process of separating pure aromatic hydrocarbons from hydrocarbon mixtures Download PDF

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Publication number
US3591490A
US3591490A US876885A US3591490DA US3591490A US 3591490 A US3591490 A US 3591490A US 876885 A US876885 A US 876885A US 3591490D A US3591490D A US 3591490DA US 3591490 A US3591490 A US 3591490A
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solvent
column
fed
aromatic
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Eckart Muller
Bergen Enkheim
Kamar Percy John
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GEA Group AG
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Metallgesellschaft AG
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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
    • C10G7/00—Distillation of hydrocarbon oils
    • C10G7/08—Azeotropic or extractive distillation
    • 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

  • Aromatic hydrocarbons such as benzene and its lower alkyl substituted derivatives having up to ten carbon atoms in the molecule, have been employed as pure materials in numerous chemical processes. These aromatic compounds are found together with non-aromatic compounds in various hydrocarbon mixtures such as cracked naphtha, hydrofining products, or the like, and in this state form azeotropic mixtures therewith from which the aromatic hydrocarbons cannot be distilled off as pure prod ucts.
  • Extractive distillation It is known to recover pure aromatic hydrocarbons from such mixtures by extraction, such as extractive distillation. Extractive distillation has been employed generally when it is desired to recover only a single aromatic compound or aromatic components having the same number of carbon atoms in the molecule. In carrying out such an extractive distillation, a selective solvent is used which has a boiling point that is preferably 50100 C. above the boiling point of the aromatic compound or fraction to be recovered.
  • Such hydrocarbon mixtures from which the pure aromatic hydrocarbons can be recovere'd by extractive distillation often contain, in addition to the main component, small proportions of undesirable higher boiling aromatic materials which have a boiling point within or above the boiling range of the solvent used.
  • aromatic admixtures could not be removed from the system and gradually build up and enrich the solvent, and after a period of time will reduce the selective activity thereof.
  • the presence of these higher boiling aromatic materials in the mixture may be due to various reasons.
  • the gasoline is initially treated with hydrogen at a relatively low temperature to hydrogenate a major portion of the dioleice fins'present therein to monoolefins while preserving the monoolefins as such.
  • the benzene cut is thereafter distilled from that product and is treated once more with hydrogen at a higher temperature to remove substantially all the sulfur compounds present therein.
  • the olefins will at the same time be hydrogenated to form saturated compounds.
  • This hydrogenation involves a secondary reaction in which the benzene will be alkylated by the olefins.
  • the resulting reaction product will be found to contain alkylbenzenes boiling in the range of -250 C. in relatively minor amounts and, in most cases, below 1%
  • the platformate is subjected to a first distillation step to remove an over head product containing all components having a lower boiling point than xylene.
  • This product is subjected to a second distillation step and a xylene fraction is recovered as a top product.
  • both steps may be combined in a single distillation operation carried out in a main column and an auxiliary column which will result in a reduction of the prime and operating costs.
  • the distillative separation is not highly efficient in that the xylene cut will be found to contain small amounts of C and C aromatic compounds. This material will remain in the solvent phase when the extract produced by the extractive distillation is processed in the usual manner.
  • the raffinate dissolves the high boiling aromatic compound out of the solvent, and the added water insures that the raffinate flowing out of the extractor is free of solvent. In this way, even solvent vapors which have left the extractive distillation column at the top and have entered the raifinate in uncondensed form are recovered from the latter. From that end stage where the raflinate enters, a mixture of solvent and water is withdrawn and may be separated into its two components either in a separate column or in the solvent stripping column of the extractive distillation column. In the event the latter procedure is followed, the separation will be combined with the processing of the feedstock.
  • the present invention accordingly provides a process of separating pure aromatic hydrocarbons from mixtures containing such aromatic compounds together with nonaromatic hydrocarbons by an extractive distillation procedure utilizing a selective solvent.
  • the process according to the invention is characterized in that a partial stream of the solvent is fed directly into the middle stage of an extraction unit while water is fed to one end stage, and the non-aromatic compounds which have been separated from the aromatic compounds and are present in the overhead product or raifinate of the extractive distillation column of the system are fed to the opposite end stage of said extraction unit, whereby aromatic admixtures are separated which have a higher boiling point than the aromatic compound to be recovered and which remain in the solvent when the aromatic compound to be recovered is separated, and/or residual solvent is removed from the overhead product of the extractive distillation.
  • the selective solvents employed are preferably N- methyl-pyrrolidone or dimethylformamide.
  • the plant basically consists essentially of the extractive distillation column 2, a stripping column 15 for processing the product mixture, the countercurrent extractor 10 and the phase separator 18.
  • the hydrocarbon mixture to be separated is heated by an indirect heat exchange in the heat exchanger 22 with hot solvent which has been obtained from the processing of the product mixture.
  • the hydrocarbon mixture is then fed through line 1 to the extractive distillation column 2 on a medium level while the hot solvent is fed through line 3 at the top of the column 2.
  • the overhead product from the extractive distillation column is the raflinate and consists predominantly of non-aromatic compounds and is withdrawn from the column 2 through line 5 and condensed. Part of the condensate is fed through line 6 into an end stage of the countercurrent extractor while the remainder is returned as a reflux through line 7 to the top of the column 2.
  • An extract or product mixture consisting of a mixture of solvent and aromatic hydrocarbons is withdrawn from the sump of the extractive distillation column 2 and is passed through lines 8 and 14 into the stripping column at a medium level.
  • the distillation residue from the stripping column 15 consists of the recovered solvent, which is recycled for re-use in the distillation column through conduits 21 and 3 and the heat exchanger 22.
  • a partial stream of the hot recycled solvent is withdrawn from line 21 and is passed through line 9 and fed directly into an intermediate stage of a multiple stage countercurrent extractor unit 10. While the raflinate from column 2 is fed to one end stage of the extractor 10 through line 6, water is supplied to the opposite end stage of the extractor through line 11. A mixture of water and solvent is recovered from the ratfinate phase and removed through line 13 from the countercurrent extractor 10 and is fed through line 14 to the stripping column 15 and processed therein.
  • a mixture of the hydrocarbons recovered from the product mixture or extract and of water is withdrawn from the top of the stripping column through line 17 and is fed to the phase separator 18, in which water settles as a heavy phase.
  • Water is returned to the countercurrent extractor through line 11 and thereafter may be circulated from the extractor 10 through the stripping column 15, the phase separator 18, and then back to the countercurrent extractor 10.
  • the pure aromatic compounds are recovered from the stripping column 15 and are separated in the phase separator 18 as a light phase. Part of that light phase is returned as a reflux through conduit 20 to the top of the stripping column 15. The balance of the pure aromatic compounds is recovered from the phase separator 18 through conduit 19.
  • the xylene cut was fed through line 1 to the thirtieth plate of an extractive distillation column 2 having sixty actual plates at a rate of 500 kilograms per hour and at a temperature of C.
  • a selective solvent stream consisting of a mixture of 96% N-methylpyrrolidone, hereinafter referred to as NMP, and 4% C aromatic compounds was fed to the extractive distillation column 2 through line 3 at a temperature of 100 C. and at a rate of 1230 kilograms per hour.
  • a portion of the solvent stream is taken off before the stream passes through line 3 and used at a later point in the system, as described more fully hereinafter.
  • Heat was supplied at a rate of 130,000 kilocalories per hour in the evaporator 4 of the extractive distillation column 2.
  • a mixture of the solvent and aromatic hydrocarbons forming the extract or product mixture was withdrawn from the sump of the extractive distillation column 2 through line 8 and passed to the stripping column 15 at a rate of 1696 kilograms per hour.
  • the resulting vapors formed as the overhead product were withdrawn from the top of the extractive distillation column 2 through line 5 and condensed.
  • the resulting condensate constitutes the raflinate and was found to have the following composition:
  • the solvent-water mixture consisting of 48% NMP (solvent) 52% water was withdrawn from the bottom end stage of the extractor through line 13 at a rate of 28.6 kilograms per hour and was combined with the product mixture or extract collected from the sump of the distillation column 2 through line 8.
  • the combined mixture was fed through line 14 to the fifteenth plate of the stripping column 15 having 40 actual plates and operating under a pressure of 0.2 kilogram per square centimeter, absolute pressure, and heat at a rate of 100,000 kilocalories per hour supplied to the evaporator 16 of column 15.
  • the vapors formed at the top of the stripping column 15 were withdrawn through line 17, condensed and fed into the phase separator 18 wherein an aqueous phase was separated and fed into the extractor 10 through line 11.
  • the upper phase formed in the phase separator consists of a hydrocarbon mixture having the following composition:
  • Part of the upper phase mixture is withdrawn as pure aromatic compounds from the unit at a rate of 408 kilograms per hour through line 19 and collected.
  • the balance of the separated hydrocarbon mixture was fed through line 20 as a reflux to the stripping column 15.
  • a solvent mixture of 96% NMP (solvent) and 4% C aromatic compounds was removed from the sump of the stripping column 15 through line 21 at a rate of 1250 kilograms per hour.
  • the main part of the solvent mixture was fed back to the extractive distillation column 2 while the remaining portion of the stream amounting to about 1% was fed directly into the extractor 10.
  • EXAMPLE 2 A cracked gasoline produced by thermal cracking in the production of ethylene was initially subjected to a hydrogenation whereby substantially only the diolefins were hydrogenated. The resulting hydrogenated product was distilled to recover a benzene out having 'a boiling range of 70-82 C. and containing about 80% benzene. This benzene cut was subjected to a second hydrogenation to effect a removal of the sulfur compounds therefrom and to transform all olefins into saturated compounds. Higher alkyl aromatic compounds and partly hydrogenated, condensed ring materials having boiling points between 150 and 250 C. were also formed during this hydrogenation and were present in an amount of 0.2% of the benzene cut. These compounds will be referred to hereinafter as alkylaromatic compounds.
  • the hydrogenated benzene cut was found to have the following composition:
  • the formed benzene cut was fed through line 1 to the thirtieth plate of the extractive distillation column 2 having sixty actual plates at a rate of 1,000 kilograms per hour and at a temperature of 80 C.
  • a selective solvent consisting of 92.6% dimethylformamide, hereinafter referred to as DMF, and 7.4% alkylaro-matic compounds was fed through line 3 to that extractive distillation column 2 at a temperature of 90 C. and at a rate of 2672 kilograms per hour.
  • Heat at a rate of 300,000 kilocalories per hour was supplied in the evaporator 4 of the extractive distillation column 2.
  • the raffinate was drawn off from the column 2 through line 6 at a rate of 238 kilograms per hour while the balance of the condensed vapor was fed through line 7 as a reflux to the extractive distillation column 2.
  • the resulting extract or mixture of solvent and aromatic hydrocarbons was drawn off the sump of the distillation column 2 at a rate of 3432 kilograms per hour through line 8 and fed to the stripping column 15.
  • a part of the selective solvent stream was divided from line 3, and was fed through line 9 at a rate of 27 kilograms per hour, directly to one of the medium stages of the extractor unit 10 of the same construction as the one used in Example 1.
  • the overhead product withdrawn through line 6 from the distillation column 2 was fed to the bottom end stage of the extractor unit 10.
  • Water at a rate of 35 kilograms per hour was fed to the top end stage of the extractor 10 through line 11.
  • the alkylaromatic compounds present in an amount of 7.4% in the divided solvent stream supplied through line 9 to the column 2 were dissolved out of the solvent stream in extractor 10 and withdrawn from the top stage of the extractor.
  • a hydrocarbon mixture having the following composition Percent Benzene 16.7 Alkylaromatic compounds 0.8
  • a solvent/ water mixture consisting of 42% DMF (solvent) 58% water was withdrawn from the bottom stage of the countercurrent extractor through line 13 at a rate of 60 kilograms per hour and combined with the product mixture or extract drawn from the sump of the extractive distillation column 2 through line 8.
  • the combined mixture was carried through line 14 into the stripping column 15 at the fifteenth plate thereof.
  • the stripping column 15 being of the same design as that used in Example 1 was operated under a pressure of 0.4 kilogram per square centimeter, absolute pressure, with heat being supplied in the evaporator 16 of column 15 at a rate of 200,000 kilocalories per hour.
  • the vapors present at the top of the stripping column 15 were withdrawn through line 17, condensed and then fed into the phase separator 18 wherein an aqueous phase was separated which was fed back into the extractor 10 through line 11.
  • a portion of the top phase product consisting of pure benzene was withdrawn from the plant through line 19 at a rate of 760 kilograms per. hour and collected.
  • the balance of the pure benzene product was fed as a reflux back to the stripping column 15 through line 20.
  • a process according to claim 2 characterized in that dimethylformamide is used as a selective solvent.
  • hydrocarbon mixtnre is a Xylene cut having a boiling range of 135-160" C.
  • one product material from the extraction zone is a water-solvent mate- References Cited UNITED STATES PATENTS 3,146,190 8/1964 Papadopoulos et al. 208313 3,338,824 8/1967 Oliver 208-313 3,476,681 11/1969 Davies et al. 208-326 HERBERT LEVINE, Primary Examiner US. Cl. X.R. 208321

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
  • Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
US876885A 1968-11-14 1969-11-14 Process of separating pure aromatic hydrocarbons from hydrocarbon mixtures Expired - Lifetime US3591490A (en)

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Application Number Priority Date Filing Date Title
DE1808758A DE1808758C3 (de) 1968-11-14 1968-11-14 Verfahren zur Abtrennung reiner aromatischer Kohlenwasserstoffe aus Kohlenwasserstoffgemische!!

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US (1) US3591490A (ar)
JP (1) JPS4835060B1 (ar)
AT (1) AT302268B (ar)
BE (1) BE741018A (ar)
BR (1) BR6913615D0 (ar)
CS (1) CS172318B2 (ar)
DE (1) DE1808758C3 (ar)
DK (1) DK130541B (ar)
FR (1) FR2023237A1 (ar)
GB (1) GB1227510A (ar)
IL (1) IL33255A (ar)
PL (1) PL80280B1 (ar)
SE (1) SE344322B (ar)
SU (1) SU361559A3 (ar)

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4982638A (ar) * 1972-11-29 1974-08-08
US3844902A (en) * 1973-04-02 1974-10-29 A Vickers Combination of extractive distillation and liquid extraction process for separation of a hydrocarbon feed mixture
US4948472A (en) * 1989-07-12 1990-08-14 Phillips Petroleum Company Extractive distillation of hydrocarbon mixtures employing mixed solvent
US4954224A (en) * 1989-09-08 1990-09-04 Brown Ronald E Extractive distillation of hydrocarbon feeds employing mixed solvent
US4955468A (en) * 1989-09-08 1990-09-11 Phillips Petroleum Company Separation of hydrocarbon mixtures
US5069757A (en) * 1990-07-02 1991-12-03 Phillips Petroleum Company Separation of aromatics from alkanes
US5135617A (en) * 1991-07-01 1992-08-04 Phillips Petroleum Company Separation of aromatic from olefinic hydrocarbons by extractive distillation
US5145562A (en) * 1991-07-01 1992-09-08 Phillips Petroleum Company Extractive distillation of mixtures containing aromatic and olefinic hydrocarbons
US5252200A (en) * 1990-12-15 1993-10-12 Krupp Koppers Gmbh Method of separating an aromatic from a hydrocarbon mixture
US6007707A (en) * 1996-07-31 1999-12-28 Krupp Uhde Gmbh Process for the recovery of pure hydrocarbons from a hydrocarbon mixture
US20030042125A1 (en) * 2000-04-28 2003-03-06 Fu-Ming Lee Aromatics purification from petroleum streams
US6616831B1 (en) * 1997-09-03 2003-09-09 Gtc Technology Inc. Aromatics separation process and method of retrofitting existing equipment for same
US20100300939A1 (en) * 2009-06-02 2010-12-02 Uop Llc Process for Removing a Contaminant from an Aromatic Selective Solvent
CN102126914A (zh) * 2011-01-13 2011-07-20 中冶焦耐(大连)工程技术有限公司 一种粗苯加氢精制过程中的萃取蒸馏工艺
WO2013087831A1 (en) 2011-12-15 2013-06-20 Sime S.R.L. Separation of hydrocarbon families or of individual components by consecutive extractive distillations performed in a single column
WO2014024206A1 (en) 2012-08-09 2014-02-13 Council Of Scientific & Industrial Research A process for production of benzene lean gasoline by recovery of high purity benzene from unprocessed cracked gasoline fraction containing organic peroxides
US20170240490A1 (en) * 2014-09-05 2017-08-24 Scg Chemicals Company Limited Process for the separation of ethylbenzene
US10427994B2 (en) * 2014-09-05 2019-10-01 Scg Chemicals Co., Ltd. Separation process for C8 aromatics mixture

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8460517B2 (en) * 2009-09-02 2013-06-11 Gtc Technology Us Llc Methods and apparatuses for steam addition to a reboiler coupled to an extractive distillation column for improved extractive distillation
DE102010051396A1 (de) * 2010-11-16 2012-05-16 Thyssenkrupp Uhde Gmbh Verfahren zur Entfernung schwersiedender Kohlenwasserstoffe aus Lösungsmittelströmen

Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4982638A (ar) * 1972-11-29 1974-08-08
JPS546537B2 (ar) * 1972-11-29 1979-03-29
US3844902A (en) * 1973-04-02 1974-10-29 A Vickers Combination of extractive distillation and liquid extraction process for separation of a hydrocarbon feed mixture
US4948472A (en) * 1989-07-12 1990-08-14 Phillips Petroleum Company Extractive distillation of hydrocarbon mixtures employing mixed solvent
US4954224A (en) * 1989-09-08 1990-09-04 Brown Ronald E Extractive distillation of hydrocarbon feeds employing mixed solvent
US4955468A (en) * 1989-09-08 1990-09-11 Phillips Petroleum Company Separation of hydrocarbon mixtures
US5069757A (en) * 1990-07-02 1991-12-03 Phillips Petroleum Company Separation of aromatics from alkanes
US5252200A (en) * 1990-12-15 1993-10-12 Krupp Koppers Gmbh Method of separating an aromatic from a hydrocarbon mixture
US5135617A (en) * 1991-07-01 1992-08-04 Phillips Petroleum Company Separation of aromatic from olefinic hydrocarbons by extractive distillation
US5145562A (en) * 1991-07-01 1992-09-08 Phillips Petroleum Company Extractive distillation of mixtures containing aromatic and olefinic hydrocarbons
US6007707A (en) * 1996-07-31 1999-12-28 Krupp Uhde Gmbh Process for the recovery of pure hydrocarbons from a hydrocarbon mixture
US6616831B1 (en) * 1997-09-03 2003-09-09 Gtc Technology Inc. Aromatics separation process and method of retrofitting existing equipment for same
US20030042125A1 (en) * 2000-04-28 2003-03-06 Fu-Ming Lee Aromatics purification from petroleum streams
US6781026B2 (en) 2000-04-28 2004-08-24 Gtc Technology Inc. Aromatics purification from petroleum streams
US20100300939A1 (en) * 2009-06-02 2010-12-02 Uop Llc Process for Removing a Contaminant from an Aromatic Selective Solvent
CN102126914A (zh) * 2011-01-13 2011-07-20 中冶焦耐(大连)工程技术有限公司 一种粗苯加氢精制过程中的萃取蒸馏工艺
CN102126914B (zh) * 2011-01-13 2013-03-13 中冶焦耐(大连)工程技术有限公司 一种粗苯加氢精制过程中的萃取蒸馏工艺
WO2013087831A1 (en) 2011-12-15 2013-06-20 Sime S.R.L. Separation of hydrocarbon families or of individual components by consecutive extractive distillations performed in a single column
US9556386B2 (en) 2011-12-15 2017-01-31 Sime S.R.L. Separation of hydrocarbon families or of individual components by consecutive extractive distillations performed in a single column
WO2014024206A1 (en) 2012-08-09 2014-02-13 Council Of Scientific & Industrial Research A process for production of benzene lean gasoline by recovery of high purity benzene from unprocessed cracked gasoline fraction containing organic peroxides
US8722952B2 (en) 2012-08-09 2014-05-13 Council Of Scientific & Industrial Research Process for production of benzene lean gasoline by recovery of high purity benzene from unprocessed cracked gasoline fraction containing organic peroxides
US20170240490A1 (en) * 2014-09-05 2017-08-24 Scg Chemicals Company Limited Process for the separation of ethylbenzene
US10427994B2 (en) * 2014-09-05 2019-10-01 Scg Chemicals Co., Ltd. Separation process for C8 aromatics mixture
US10479743B2 (en) * 2014-09-05 2019-11-19 Scg Chemicals Company Limited Process for the separation of ethylbenzene

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Publication number Publication date
JPS4835060B1 (ar) 1973-10-25
AT302268B (de) 1972-10-10
DK130541C (ar) 1975-07-28
DE1808758A1 (de) 1970-06-25
SE344322B (ar) 1972-04-10
BE741018A (ar) 1970-04-01
PL80280B1 (ar) 1975-08-30
IL33255A (en) 1972-11-28
DK130541B (da) 1975-03-03
CS172318B2 (ar) 1976-12-29
FR2023237A1 (ar) 1970-08-07
SU361559A3 (ar) 1972-12-07
GB1227510A (ar) 1971-04-07
DE1808758B2 (de) 1974-03-14
IL33255A0 (en) 1969-12-31
BR6913615D0 (pt) 1973-01-16
DE1808758C3 (de) 1974-10-17

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