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US3868310A - Selective solvent extraction process - Google Patents

Selective solvent extraction process Download PDF

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Publication number
US3868310A
US3868310A US070192A US7019270A US3868310A US 3868310 A US3868310 A US 3868310A US 070192 A US070192 A US 070192A US 7019270 A US7019270 A US 7019270A US 3868310 A US3868310 A US 3868310A
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United States
Prior art keywords
mixture
aromatic
aromatic hydrocarbons
distillation
hydrocarbon
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Expired - Lifetime
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US070192A
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English (en)
Inventor
Kleef Alfred L Van
Derk Roffel
Vollenhoven Frits W Van
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Shell USA Inc
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Shell Oil Co
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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
    • C10G21/00—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents
    • C10G21/28—Recovery of used solvent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D11/00—Solvent extraction
    • B01D11/04—Solvent extraction of solutions which are liquid
    • B01D11/0488—Flow sheets

Definitions

  • the low boiling hydrocarbon fraction may 2,434,322 H1948 Latchum 203/43 be obtained from the feed mixture to the process.
  • This invention relates to an improved process for separating mixtures of hydrocarbons. More particularly, it relates to a liquid-liquid extraction process wherein aromatic hydrocarbons are separated from non-aromatic hydrocarbons by means of a selective solvent which boils at a higher temperature than feed mixture to be separated.
  • a hydrocarbon feed mixture containing aromatic and non-aromatic hydrocarbons is subjected to a liquid-liquid extraction with a solvent which boils higher than the starting mixture and is selective for aromatic hydrocarbons, thereby obtaining an extract phase enriched in the aromatic components and a raffinate phase enriched in non-aromatic components.
  • the dissolved aromatic components are recovered from the extract phase by using one or more distillation steps from which at least one stream containing non-aromatics is obtained.
  • the boiling ranges of lower boiling fraction and starting feed mixture may overlap. That is, the lower boiling mixture may comprise components having a higher boiling point than certain components of the starting mixture.
  • the highest boiling, non-aromatic hydrocarbon of the lower boiling mixture boil not more than 100C higher than the lowest boiling aromatic hydrocarbon in the starting mixture.
  • aromatic hydrocarbon components to be recovered are understood to mean those components which it is desired to recover in the purest possible state.
  • Other aromatic or non-aromatic hydrocarbon components, the recovery of which in a highly pure state is not particularly valued, can, of course, be present in the starting mixture.
  • the purity of recovered components is also favorably influenced if the lower boiling hydrocarbon mixture is introduced into the distillation step at least in part below the level at which extract phase (or a material recovered therefrom in one or more previous steps) is supplied to this step.
  • introduction of the lower boiling hydrocarbon at the same or at a higher level is also possible.
  • this introduction may also be effected at more than one point of the distillation step, it being possible to use either the same lower boiling mixture at each point, or two or more different mixtures of this type.
  • lf lower boiling mixture is introduced into more than one distillation step, the same lower boiling mixture, or two or more different mixtures of this type, may be used.
  • the stream of streams recovered from one or more of such distillation steps may contain the non-aromatic hydrocarbon components either substantially free from selective solvent and/or from more readily soluble components, or in admixture with one of these two substances.
  • the optimum composition of these stream or streams in any particular case will depend on the means selected for the processing of the extract phase (type of distillation steps used. the way they are arranged in respect to each other, etc.).
  • the additional solvent be introduced into the distillation steps at a higher level than that of the lower boiling mixture.
  • the non-aromatics containing stream from the distillation step or steps as mentioned above, is preferably recycled, at least in part, to the liquid-liquid extraction as backwash".
  • the recycling of this stream has been found to favorably promote the separation of the starting mixture by extraction, just as lower boiling mixture itself promotes the recovery in a pure state of the dissolved aromatics from the extract phase.
  • the extraction and distillation steps can be carried out using any suitable equipment known in the art.
  • extraction can be very desirably effected with the aid of a rotating disc contactor such as described, for example, in UK. Pat. specification No. 659,241, while distillation is conveniently carried out with the aid of a column provided with valve trays or trays with preferential discharge (such as described in U.K. Pat. specification Nos. 591,929 and 764,640, respectively). Distillation may be effected in one or more of the steps present, by expansion, if desired.
  • any mixture of lower boiling hydrocarbons having the boiling point relationship of the starting mixture he'reinbefore outlined is suitable for use in accordance with the invention. It is especially preferred to use at least one lower boiling mixture which has been obtained at least in part from an original material from which the feed mixture has also been obtained.
  • the original starting mixture e.g., a C to C mixture of. aromatic and non-aromatic hydrocarbons
  • the original starting mixture e.g., a C to C mixture of. aromatic and non-aromatic hydrocarbons
  • the higher boiling of which e.g., C to C is used as feed to the extraction step
  • one or more of the lower boiling fractions e.g., the lower boiling fractions
  • C to C is employed, either separately or in admixture with another low boiling hydrocarbon fraction, in one or more of the distillation steps as previously discussed.
  • the separation of the starting mixture may be conveniently accomplished by distillation or other suitable fractionation means, e.g., extractive distillation.
  • Suitable starting mixtures and/or lower boiling mixtures include straight-run hydrocarbon fractions, or hydrocarbon fractions'obtained from a conversion process such as thermal cracking, catalytic cracking and- [or hydrocracking, including gasolines, kerosenes or gas oils.
  • Particularly suitable starting mixtures and/or lower boiling mixtures include normally liquid, catalytically reformed hydrocarbon fractions, such as gaso lines, and/or such fractions obtained from a pyrolysis process.
  • the latter type of fraction is preferably first refined, for example, by using a catalytic treatment with hydrogen or a hydrogen-containing mixture.
  • a variety of selective solvents may be used, for example, furfural, phenol, acetonitrile, sulphoxide (such as dimethyl sulphoxide), fattyacid alkyl amides (such as dimethyl formamide).
  • sulphoxide such as dimethyl sulphoxide
  • fattyacid alkyl amides such as dimethyl formamide.
  • Especially preferred solvents are those of the sulfolane, glycol, and/or the pyrrolidone/piperidone type; i.e., respectively: sulfolane (cyclic tetramethylene sulphone), the unsaturated analogues thereof and the derivatives of both, as described, for example in U.K. Pat. specification No.
  • the selective solvent may contain a quantity of a substance, such as water, which has a favorable effect on the selectivity and/or the solvent power thereof.
  • a substance such as water, which has a favorable effect on the selectivity and/or the solvent power thereof.
  • sulfolane has been found to be particularly advantageous.
  • a feed mixture is supplied through line 1 to extractor 2, in this case at one point and in the lower part of the column. If desired, the feed may be supplied at more than one point and at higher levels.
  • the starting mixture is subjected to ex traction at a suitable temperature and pressure, if desired with the use ofa temperature gradient.
  • Fresh and- /or recycled solvent is supplied through line 3, in this case separately and at one point, but possibly also together with the starting mixture and/or through more than one inlet (not shown).
  • non-aromatic components possibly admixed with aromatic components, originating from the process itself or not, may be introduced as backwash into the lower part of extractor 2 (not shown).
  • Raffinate is withdrawn from column 2 through line 4. If desired, this raffinate may be subjected to a further treatment, for example, a washing treatment with a suitable washing agent (such as water) to remove any solvent present (not shown).
  • An extract phase containing both aromatic and non-aromatic components and solvent is passed through line 5 to distillation column 6 (if desired, operated under reflux not shown and/or with reboiling). From column 6, a stream containing primarily nonaromatics with lesser amounts, if any, of solvent, water or aromatics is withdrawn through line 7. In this case, column 6 is the only distillation step from which such a stream is withdrawn. However, it is understood that there can be more of such distillation steps and/or streams, possibly differing in composition from the stream mentioned.
  • a mixture containing aromatic and non-aromatic hydrocarbons boiling lower than the starting mixture and either of the same type, at least in part, or not of the same type as those of the starting mixture, is introduced into column 6 through line 8. in this case only one such mixture is supplied and the supply is'effected together with that of the extract phase.
  • the non-aromatic hydrocarbons originating from the lower boiling mixture together with the non-aromatics originating from the starting mixture are withdrawn in vapor phase from column 6, through line 7.
  • column 6 is operated in such a manner that the material withdrawn from the bottom part contains selective solvent and dissolved aromatic hydrocarbons, with little or no non-aromatic hydrocarbons.
  • the material from the bottom of column 6 is passed through line 9 to distillation column 10 wherein it is separated into solvent and aromatic hydrocarbons, the latter being discharged through line 11 as a single stream containing aromatic components originating both from the starting mixture and from the lower boiling mixture.
  • the stream containing the aromatic components can, if desired, be subjected to further separation, for example, by distillation into one or more fractions, by treatment with a washing agent or solvent to obtain the individual components, or groups of components which differ slightly from each other in nature. Further distillation may also be employed to remove the very last traces of solvent and/or non-aromatic hydrocarbons (not shown).
  • the selective solvent is withdrawn from column l0 and in this case recycled wholly or partly to column 2, for use in extraction. Alternatively, this solvent may be recycled, at least in part, to column 6 and- /or withdrawn, for example, to a purifying plant (not shown).
  • FIG. 2 Another embodiment of the process according to the invention is shown in FIG. 2.
  • the lower boiling mixture supplied through line 28, as well as the feed mixture supplied through line 16 originate (in this case entirely but possibly also in part) from one and the same original material supplied through line 14.
  • the lower boiling mixture and feed mixture have been prepared from the original material, as top product and bottom product, respectively, by simple distillation in fractionating column 15. It is also possible, however, to prepare these mixtures from the original material (if desired, in
  • extractive distillation it is alsopossible to carry out distillation in more than one column and/or with obtainment of more than one fraction, all of which, or only part of which, may be used as the feed mixture or the lower boiling mixture, respectively.
  • the high boiling hydrocarbon fraction is withdrawn from column 15 and is introduced as feed to extractor 17 wherein it is subjected to extraction as hereinbefore discussed.
  • Raffinate containing a larger proportion of nonaromatics than the feed mixture, is withdrawn from the extraction column through line 26, while the extract phase containing a greater proportion of aromatics than the feed mixture is withdrawn through line 18 and is passed to distillation column 19 together with additional solvent via line 25.
  • the lower boiling hydrocarbon material withdrawn from column 15 is introduced into column 19 via line 28 at a point lower than the level of the extract phase and additional solvent, which are supplied through line 18, in accordance with the preferred embodiment of the invention. While the additional solvent in this instance is introduced into column 19 together with the extract phase, it is also possible to effect the introduction of the solvent with the lower boiling mixture instead, or alternatively partly with the extract phase and partly with the lower boiling hydrocarbon fraction.
  • the overhead stream (line 20) from column 19 is partly recycled as backwash to a lower part of column 17.
  • the overhead stream may be condensed prior to recycle and/or subjected to phase separation to separate the phase containing solvent and/or, for example, water (not shown). While the recycling in this case is effected at one point in column 17, it is understood that recycling may be effected at several points, or may be omitted entirely, or effected employing a non-aromatic stream originating from elsewhere than column 17.
  • the stream withdrawn from the bottom of column 19 (line 21) containing primarily solvent and aromatic hydrocarbons, with lesser amounts of water and/or nonaromatics, is passed to distillation column 22 wherein it the aromatic hydrocarbons are separated and recovered as the overhead stream via line 23. Stripping stream as required is introduced into column 22 via line 24.
  • the stripping medium might also originate from the reboiler of column 19 which for simplicitys sake is not shown.
  • the additional solvent is not substantially pure but instead contains a minor quantity of dissolved aromatic components. While the additional solvent added to column 19 may be substantially pure, it is preferred that a solvent stream contain a small concentration of aromatics be employed as described in copending U.S. Pat. application Ser. No. 31,981 filed Apr. 27, 1970, now abandoned.
  • the material in question consisted partly of catalytically reformed gasoline, and partly of gasoline from a pyrolysis process which had subsequently been hydrorefined.
  • C01- umn 19 was operated at a pressure at 1.2 atm. abs., with a top temperature of 1 13C and a bottom temperature of 145C.
  • the extract was subsequently separated by distillation to give a benzene, a toluene and a xylene fraction;
  • the process described was modified to the extent that no lowerboiling mixture was employed in column 19.'The same original material was directly introduced into extraction column 17 and subjected to extraction (with the same quantity of sulfolane), the same quantity of sulfolane-rich fraction again being supplied to column 19.
  • the benzene, toluene and xylene fractions obtained from the extract contained 340, 1,360 and 2,770 parts by weight per million of non-aromatics, respectively, indicating that, by application of the process according to the invention, the purity ofbenzene, toluene and xylene is increased by a factor of approximately 3%, 7-% and 21, respectively;
  • a process for separating aromatic hydrocarbons from a mixture of aromatic and non-aromatic hydrocarbons boiling in the C to C range which comprises (1) splitting said mixture by distillation into a higher boiling, C to C hydrocarbon fraction and a lower boiling C to C hydrocarbon fraction, (2) subjecting said higher boiling fraction to a liquid-liquid extraction with a solvent selective for aromatics to obtain an extract phase enriched in aromatic hydrocarbons and an raffinate phase enriched in non-aromatic hydrocarbons.
  • hydrocarbon mixture to be separated comprises a catalytically reformed, normally liquid hydrocarbon fraction, or a refined, normally liquid fraction obtained from a pyrolysis process.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Engineering & Computer Science (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
US070192A 1969-09-26 1970-09-08 Selective solvent extraction process Expired - Lifetime US3868310A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL6914611.A NL163966C (nl) 1969-09-26 1969-09-26 Werkwijze voor het scheiden van een uitgangsmengsel met behulp van vloeistof-vloeistofextractie.

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US3868310A true US3868310A (en) 1975-02-25

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US (1) US3868310A (es)
JP (1) JPS5028916B1 (es)
BE (1) BE756198A (es)
CA (1) CA943490A (es)
DE (1) DE2047162C2 (es)
ES (1) ES383944A1 (es)
FR (1) FR2062598A5 (es)
GB (1) GB1321465A (es)
NL (1) NL163966C (es)
ZA (1) ZA706518B (es)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4419226A (en) * 1980-06-26 1983-12-06 Uop Inc. Recovery of aromatic hydrocarbons and a non-aromatic raffinate stream from a hydrocarbon charge stock
US5180474A (en) * 1991-03-23 1993-01-19 Krupp Koppers Gmbh Method of separation of aromates by extractive distillation
US5399244A (en) * 1993-12-06 1995-03-21 Glitsch, Inc. Process to recover benzene from mixed hydrocarbons by extractive distillation
US6483003B1 (en) * 1998-05-08 2002-11-19 Sasol Technology (Proprietary) Limited Removal of impurities from a hydrocarbon component or fraction

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2434322A (en) * 1943-11-23 1948-01-13 Phillips Petroleum Co Azeotropic distillation of toluene with propionic acid
US2461346A (en) * 1944-12-28 1949-02-08 Standard Oil Dev Co Separation of hydrocarbons
US2809925A (en) * 1954-12-20 1957-10-15 Phillips Petroleum Co Azeotropic distillation
US3294679A (en) * 1965-11-29 1966-12-27 Sun Oil Co Process of recovering aromatic hydrocarbons by solvent extraction
US3385783A (en) * 1966-10-10 1968-05-28 Universal Oil Prod Co Aromatic hydrocarbon solvent regenerated by filtration
US3396101A (en) * 1966-08-31 1968-08-06 Universal Oil Prod Co Solvent extraction of highly aromatic charge stocks
US3433849A (en) * 1966-08-02 1969-03-18 Metallgesellschaft Ag Process for recovering pure aromatics
US3468792A (en) * 1967-08-17 1969-09-23 Universal Oil Prod Co Simultaneous solvent extraction of a light and heavy fraction
US3590092A (en) * 1968-09-11 1971-06-29 Universal Oil Prod Co Method for aromatic hydrocarbon recovery

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL128650C (es) * 1961-03-23

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2434322A (en) * 1943-11-23 1948-01-13 Phillips Petroleum Co Azeotropic distillation of toluene with propionic acid
US2461346A (en) * 1944-12-28 1949-02-08 Standard Oil Dev Co Separation of hydrocarbons
US2809925A (en) * 1954-12-20 1957-10-15 Phillips Petroleum Co Azeotropic distillation
US3294679A (en) * 1965-11-29 1966-12-27 Sun Oil Co Process of recovering aromatic hydrocarbons by solvent extraction
US3433849A (en) * 1966-08-02 1969-03-18 Metallgesellschaft Ag Process for recovering pure aromatics
US3396101A (en) * 1966-08-31 1968-08-06 Universal Oil Prod Co Solvent extraction of highly aromatic charge stocks
US3385783A (en) * 1966-10-10 1968-05-28 Universal Oil Prod Co Aromatic hydrocarbon solvent regenerated by filtration
US3468792A (en) * 1967-08-17 1969-09-23 Universal Oil Prod Co Simultaneous solvent extraction of a light and heavy fraction
US3590092A (en) * 1968-09-11 1971-06-29 Universal Oil Prod Co Method for aromatic hydrocarbon recovery

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4419226A (en) * 1980-06-26 1983-12-06 Uop Inc. Recovery of aromatic hydrocarbons and a non-aromatic raffinate stream from a hydrocarbon charge stock
US5180474A (en) * 1991-03-23 1993-01-19 Krupp Koppers Gmbh Method of separation of aromates by extractive distillation
US5399244A (en) * 1993-12-06 1995-03-21 Glitsch, Inc. Process to recover benzene from mixed hydrocarbons by extractive distillation
US6483003B1 (en) * 1998-05-08 2002-11-19 Sasol Technology (Proprietary) Limited Removal of impurities from a hydrocarbon component or fraction

Also Published As

Publication number Publication date
NL163966C (nl) 1980-11-17
NL6914611A (es) 1971-03-30
DE2047162C2 (de) 1982-12-09
CA943490A (en) 1974-03-12
BE756198A (nl) 1971-03-16
JPS5028916B1 (es) 1975-09-19
GB1321465A (en) 1973-06-27
ES383944A1 (es) 1973-10-01
ZA706518B (en) 1971-05-27
DE2047162A1 (de) 1971-04-01
FR2062598A5 (es) 1971-06-25
NL163966B (nl) 1980-06-16

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