US3284528A - Process for the extraction of aromatic hydrocarbons in admixture with paraffinic and naphthenic hydrocarbons by means of a selective solvent - Google Patents

Process for the extraction of aromatic hydrocarbons in admixture with paraffinic and naphthenic hydrocarbons by means of a selective solvent Download PDF

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Publication number
US3284528A
US3284528A US227875A US22787562A US3284528A US 3284528 A US3284528 A US 3284528A US 227875 A US227875 A US 227875A US 22787562 A US22787562 A US 22787562A US 3284528 A US3284528 A US 3284528A
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solvent
water
extraction
aromatic hydrocarbon
aromatic
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US227875A
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English (en)
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Cousserans Gilbert
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Office National Industriel de lAzote
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Office National Industriel de lAzote
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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
    • C10G21/06—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents characterised by the solvent used
    • C10G21/12—Organic compounds only
    • C10G21/22—Compounds containing sulfur, selenium, or tellurium
    • 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
    • C10G21/06—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents characterised by the solvent used
    • C10G21/12—Organic compounds only

Definitions

  • This invention relates to the separation of aromatic hydrocarbon components from their mixtures with aliphatic and occasionally naphthenic hydrocarbons by solvent extraction methods. More particularly, the invention concerns a solvent extraction process utilizing, as a solvent medium, water mixtures of the esters of carbamic and/ or thiocarbamic acids.
  • 3,014,807 proposes the use of mixtures of alkyl carbamates, such as ethyl and methyl carbamates, in a eutectic composition as solvents for aromatics.
  • Beinfest contemplates binary, ternary and quaternary mixtures as well as other multicornponent mixtures,
  • the ideal solvent for an extraction process of the invention should conform to many requirements. It should be stable and chemically inert at normal conditions of use,
  • the primary object of this invention is to provide an improved solvent extraction process, utilizing highly effective solvents.
  • Another object of this invention is to provide a process for extracting aromatic hydrocarbons from hydrocarbon mixtures, utilizing particular carbamate solvents.
  • Still another object of this invention is to provide particular carbamic ester solvents which are both chemically inert and stable at the temperatures employed for solvent extraction.
  • Another object of this invention is to provide particular carbamate solvents which have low solubility in aliphatic hydrocarbons and yet are highly miscible with aromatic hydrocarbons.
  • Yet a further object of this invention is to provide particular carbamate solvents which have widely diiferent boiling points and specific gravities from aromatic hydrocarbons miscible therewith.
  • FIGURES 1 to 4 are conventional miscibility diagrams, illustrating the phase relationship between the components of the inventive process.
  • FIGS. 3 and 4 are flow diagrams illustrating examples of the inventive extraction system.
  • the miscibility diagrams ABS should be of either the type shown in FIG. 1 or FIG. 2.
  • the non-miscibility areas are shaded.
  • Solvents which conform to the diagram of FIG. 2, while meeting in all other respects the requirements set out above, are a mixture of Water and one or more of the components chosen from among esters of carbamic acid and thiocarbamic acid.
  • the general formulae of such compounds are ROCONH (carbamic ester), e.g. CH (CH OCONH and ROCSNH (thiocarbamic ester), e.g. CH OCSNH wherein R represents an alkyl radical of between 1 and 6 carbon atoms.
  • methylcarbamate ethyl carbarnate and methylthiocarbamate.
  • Such solvents may be used singly or in mixtures with one another.
  • the following table sets forth average partition co-efiicients and the average selectivity measured at 50 C. of two solvents constituted respectively by mixtures of 10% of water and of methyl carbamate.
  • the partition -co-eiiicient D Ca/ Cb where Ca and Cb respective- -ly represent the concentration of solute in the solvent phase and in the hydrocarbon phase.
  • the operation of the process of the invention can be carried out in apparatus of reduced size.
  • the process according to the invention is effected by a succession of simple operations in an apparatus of smaller size than that required in carrying out the known processes.
  • the losses of solvent by decomposition or entrainment, burdening the economy of the extraction processes using prior art solvents are negligible due to the high stability of the inventive carbamic solvents and their very low solubility in the aliphatic and naphthenic hydrocarbons.
  • the solvents according to the invention also present the advantage of making possible very high speeds of exchange between the existing liquid phases, due to their low viscosity, and of not raising corrosion problems or regeneration problems.
  • the aromatic components of a light fraction of petroleum catalytic reforming can be ex tracted by means of a :carbamic or thiocarbamic solvent.
  • a :carbamic or thiocarbamic solvent consists of carbamic esters with water, thiocarbamic esters with water or admixtures of carbamic and thiocarbamic ester with water.
  • the starting petroleum fraction boiling in a temperature range between 65 and 175 C. and containing about 50% of C6 to C11 aromatic components and 50% of C to C12 non-aromatic components, is passed, through inlet 1, into an extraction column 2 fed with solvent at its upper end 3.
  • the extraction column 2 is internally provided with any conventional means to effect good contact between the liquids present.
  • the aromatic components are extracted from the starting petroleum fraction and as their solution in the solvent is denser than the aliphatic and naphethenic fractions, they flow down to the lower end of the column.
  • the :raffinate leaving the upper end of the extraction column 2 is taken by piping 4 and fed into the lower part 5 of a washing column 6 in which the aliphatic and. naphthenic components are separated from the entrained carbamate-water solvent by water washing.
  • the hydrocarbons leave the washing column 6 at its upper end 7 and the aqueous wash solution, containing carbamatewater solvent washed from the hydrocarbons, is injected through piping 8 into the lower part 9 of column 2 in which it acts as an anti-solvent.
  • the extraction column 2 may be provided m'th any conventional means to effect liquid-liquid contact.
  • the extract containing the carbamate-water solvent and the aromatic components leaves the lower part of the extraction column 10 and is fed through inlet 11 into the distillation column 13 through piping 12.
  • the top fraction containing the aromatic components and water, is condensed in cooler 15 and passed into a settling tank 16 in which it separates into two layers.
  • the upper layer which is essentially a mixture Olf extracted hydrocarbons, is sent to storage tank 17 through piping 18, and from there to the final separations of henzene, toluenes and xylenes from each other.
  • the lower layer in settling tank 16 which is essentially water, is recycled to both columns 13 and 6 at inlets 14 and 19, respectively.
  • the carbamate material, taken from the distillation column 13 through outlet 20, is forwarded into tank 21 from which it is pumped through pump 22 into the extraction column 2 at inlet 3.
  • the diagram according to FIG. 3 can be modified according to FIG. 4 in order to make possible the production of the very pure aromatic hydrocarbons.
  • the extract traction containing the solvent, water and aromatic constituents leaves the bottom of the extraction column 2 at 10 and is introduced at 11 into one of the upper plates of the distillation column 13.
  • the fraction at the head of the distillation which contains water, aromatic hydrocarbons and aliphatic and naphthenic hydrocarbons having escaped separation, is condensed in the cooler condenser 15 and is sent to the decantation tank 16 where it separates into two layers.
  • the upper layer containing the hydrocarbons is used to assure reflux in column 13 into which a part is injected at 14, and also to assure reflux in the extraction column 2 into the bottom of which another part of the said hydrocarbons is introduced at 9.
  • the intermediate distillation fraction withdrawn at 23 contains aromatic hydrocarbons of a degree of purity greater than 99.8% and water.
  • the aromatic hydrocarbons are sent to storage 17.
  • the water coming from tank 25 is combined with that from decantation tank 16 and serves, on the one hand, for washing the aliphatic and naphthenic fraction by recycling at 19 in the washing column 6 and, on the other hand, makes possible entrainment of the hydrocarbons by recycling at 26 into the boiler of the distillation column.
  • the water no longer .plays the role of anti-solvent in extraction column 2, but entrains recovered solvent to the distillation, and facilitates distillation of aliphatic and naphthenic hydrocarbons which have escaped by separation.
  • Example 1 Into an apparatus of the type shown diagrammatically in FIG. 4, there is fed, at the top of the third stage of the extraction column comprising 10 theoretical stages, 10 tons per hour of a petroleum fraction containing by weight 51.5% of aromatics and 48.5% of aliphatics and naphthenics.
  • the solvent employed is methyl carbamate containing 15% of water and the extraction operation is carried out under 4 atmospheres pressure and at a temperature of C.
  • the rafiinate sent to washing then contains 0.41 t./h. of aromatics, 4.85 t./h. of aliphatics and 0.10 t./h. of solvent. Washed in countercurrent with 1.05 t./h. of water, 5.26 t./h. of raffinate are separated from 0.10 t./h. of solvent.
  • the extract which contains 8.9 t./h. of aromatics and 144.9 t./h. of solvent is sent to distillation at 120 C.
  • the head fraction yields after condensation and decantation 9.05 t./h. of hydrocarbons (66.63 t./h. of aromatics and 2.42 t./h. of aliphatics and naphthenics) of which 5.61 t./h. serve for reflux in the distillation column and 3.44 t./h. for reflux in the extraction column.
  • Intermediate withdrawal from the distillation column yields, after condensation and decantation, 4.74 t./h. of aromatics of 99.9% purity and 0.92 t./h. of water. This water is combined with 1.22 t./h.
  • Example 2 In an apparatus of the type shown diagrammatically in FIG. 3 and comprising an extraction column with 8 theoretical plates, there are introduced into the latter at the level of the 2.5 t./h. stage a feed of 10 cubic meter/ hour of the same petroleum fraction as that used in Example 1.
  • the solvent constituted by a mixture of 95% of methyl thiocarbamate and 5% of water, is introduced into the head of the column at the rate of 95 cubic meters/ hour.
  • the non-aromatic fraction leaving the extraction column at the top part thereof is introduced into a washing column comprising two theoretical plates and in which it is brought into contact, in countercurrent, with cubic meters/hour of Water.
  • the solvent entrained by the water is recycled into the extraction column where the Water acts as antisolvent.
  • the extraction yield is about 99% relative to the benzene and 97% relative to the toluene, the 4.8 cubic meters/hour of extract containing only traces of nonaromatic hydrocarbons.
  • the extract fraction is subjected to water reflux distillation in a distillation column maintained at about C. at the head and at C. at the boiler.
  • the tail fraction is integrally recycled to the extraction column, loss of solvent by thermal decomposition does not exceed grams/ton of pure aromatics obtained after decantation of th head fraction.
  • Process for the extraction and purification of aro- -matic hydrocarbon from a mixture of aromatic hydrocarbon and a member selected from the group consisting of aliphatic and naphthenic hydrocarbons comprising the steps of (a) contacting the hydrocarbon mixture with a liquid solvent consisting essentially of water and a compound of the formula ROCSNH wherein R is alkyl of 1 to 6 carbons,
  • said extract phase comprising the solvent and aromatic hydrocarbon
  • liquid solvent consists essentially of water and methyl thiocarbamate.
  • Process for the extraction and purification of ammatic hydrocarbon from a mixture of aromatic hydrocarbon and a member selected from the group consisting of aliphatic and naphthenic hydrocarbons comprising the steps of (a) contacting the hydrocarbon mixture With a liquid solvent consisting essentially of water, methyl carbamate and compound of the formula ROCSNH wherein R is alkyl of l to 6 carbons,
  • said extract phase comprising the solvent and aromatic hydrocarbon
  • said extract phase comprising the solvent and aromatic hydrocarbon

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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)
US227875A 1961-10-05 1962-10-02 Process for the extraction of aromatic hydrocarbons in admixture with paraffinic and naphthenic hydrocarbons by means of a selective solvent Expired - Lifetime US3284528A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR4740A FR1315754A (fr) 1961-10-05 1961-10-05 Procédé d'extraction, par solvant sélectif, d'hydrocarbures aromatiques en mélange avec des hydrocarbures paraffiniques et naphténiques

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US (1) US3284528A (xx)
BE (1) BE623242A (xx)
CH (1) CH401939A (xx)
DE (1) DE1289838B (xx)
FR (1) FR1315754A (xx)
GB (1) GB969994A (xx)
NL (1) NL283997A (xx)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2978520A (en) * 1958-06-16 1961-04-04 Pure Oil Co Process for recovery of aromatic hydrocarbons
US3003005A (en) * 1957-12-27 1961-10-03 Pure Oil Co Extraction process

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2770664A (en) * 1951-11-09 1956-11-13 Dow Chemical Co Aromatic hydrocarbons by solvent extraction with a solvent of diethylene glycol and water
US2770663A (en) * 1952-07-30 1956-11-13 Universal Oil Prod Co Solvent extraction of hydrocarbons
DE1102954B (de) * 1957-01-04 1961-03-23 Universal Oil Prod Co Loesungsmittel-Extraktionsverfahren
US2915569A (en) * 1957-12-23 1959-12-01 Pure Oil Co Extraction process for recovery of aromatics utilizing carbamate solvents

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3003005A (en) * 1957-12-27 1961-10-03 Pure Oil Co Extraction process
US2978520A (en) * 1958-06-16 1961-04-04 Pure Oil Co Process for recovery of aromatic hydrocarbons

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BE623242A (xx) 1963-02-01
DE1289838B (de) 1969-02-27
FR1315754A (fr) 1963-01-25
GB969994A (en) 1964-09-16
CH401939A (fr) 1965-11-15
NL283997A (xx) 1965-01-11

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