US3065167A - Process for separating aromatic hydrocarbons - Google Patents

Process for separating aromatic hydrocarbons Download PDF

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Publication number
US3065167A
US3065167A US848418A US84841859A US3065167A US 3065167 A US3065167 A US 3065167A US 848418 A US848418 A US 848418A US 84841859 A US84841859 A US 84841859A US 3065167 A US3065167 A US 3065167A
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temperature
extraction system
zone
solvent
phase
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US848418A
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Frederick J Zuiderweg
Gerrit H Reman
Schaafsma Albert
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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

Definitions

  • the solvent employed is a high boiling aromatic selective material having an atmospheric (normal) boiling temperature within the range of 225 to 295 C., and should contain not more than 2% by weight of water.
  • Suitable solvents include diethylene glycol, dipropylene glycol, sulfolane, and mixtures thereof.
  • the temperature in the extraction zone should be between and 155 C.
  • the extract-phase from the extraction system should enter the stripping zone with a temperature between 140 and 155 C.
  • the pressure in the stripping zone should be lower than the pressure in the extraction system, but not so low as to cause appreciable flash vaporization (i.e. vaporization by pressure reduction without heating) and should be at least 1.5 atm. abs.
  • the top temperature in this stripping zone ⁇ should be between 140 and 155 C. and the bottom temperature should be at least 190 C.
  • the bottom product from the stripping zone should be cooled before expansion to distilling zone pressure by at least 15 C. to a temperature between 170 and 180 C.
  • the pressure in the distilling zone should be below 0.5 atm. abs.
  • the bottom temperature in the distilling zone should be at least C., but should be at least 30 C. below the bottom temperature in the stripping zone.
  • a process for the extraction and recovery of aromatic hydrocarbons from a liquid hydrocarbon mixture containing one or more aromatic hydrocarbons by introducing the mixture into a counterflow multistage extraction system, introducing, at one end of the system, a high boiling, aromatic selective solvent having an atmospheric boiling temperature within the range of 225 C. to 295 C.
  • the stripping zone is operated at a pressure of at least 1.5
  • the vapors from said stripping zone are condensed and recycled to the extraction system after removing substantially all water present as a second liquid phase.
  • the condensed vapors are introduced into the extraction system at the end at which the extract phase is withdrawn and/or at an intermediate point of the extraction zone the bottom product of the stripping zone is cooled before expansion to the distilling zone pressure, by at least C. to a temperature between 170 and 180 C.
  • the distilling zone is operated at a pressure of less than 0.5 atm. abs. and at a bottom temperature of at least 150 C., with the bottom temperature being at least 30 C. lower than the bottom temperaure in the stripping zone.
  • the present process can be applied to feedstocks having a wide or a narrow boiling range. It is especially suitable for separating aromatics from catalytically reformed gasolines, such as hydroformates and platformates, or from fractions thereof.
  • feedstock should have an ASTM nal boiling point of not higher than 220 C.
  • the upper cutting point should be not higher than 160 C.
  • the upper cutting point should advantageously be approximately the same as the upper cutting point of the feedstock for the reforming operation.
  • the volumetric ratio of solvent to hydrocarbon feed should be between 3:1 and 8:1, preferably between 4:1 and 6:1, whereas the ratio ⁇ of the amount of top product returned from the stripping zone to the extraction system to the amount of hydrocarbon feed should be between 0.2:1 and 0.7:1, preferably between 0.3:1 and 0.5:1.
  • Suitable solvents boil within the temperature range of 225 C. to 295 C.
  • the solvent used in the extraction systeml may contain a small amount, not exceeding 2% by Weight, of water.
  • the extraction system should be a countercurrent multistage extraction system, e.g. a column containing packing material, or sieve plates, a rotating disc contactor, a multiplicity of mixer-settler combinations, and the like.
  • the number of theoretical stages should preferably be at least 5.
  • the feed to the extraction system may be introduced as an intermediate point, but it is generally preferred to introduce it at or at least near that end of the extraction system at which the aromatic rich extract phase is withdrawn, because in that case the best compromise between product purity and recovery (yield) is usually realized.
  • Suitable inlet points are at said end of the extraction system (viz. at the first theoretical stage) or at the second theoretical stage, the latter embodiment being preferred because in that case the purity is distinctly higher whereas the recovery is ⁇ only slightly decreased. Feed introduction at a plurality of points between the middle and the extract phase end of the system may be useful under specific circumstances.
  • the stream of hydrocarbons and solvent that is obtained as top product from the stripping zone and (after condensation and after removing substantially all water separating as a second liquid phase in the condensing operation) is returned to the extraction system should also be introduced at one or more points at or near the end of the extraction system at which the aromatic rich extract phase is withdrawn. It is preferred to introduce this stream at ⁇ or near the end of the system (i.e. at the rst or second theoretical stage of the system) because in these cases the best compromise between product purity and recovery is realized.
  • the recycle material may 4 in some instances be advantageously returned to the ex.- traction system in a plurality of streams between the middle and the extract phase end of the system. If necessary, the recycle stream may be vheated before entering the extraction system.
  • the temperature in the extraction system should be between and 155 C. There may be a certain temperature gradient over the system, provided that the above limits are adhered to.
  • the extract phase leaving the extraction system ⁇ is introduced in the stripping zone, at or near its top, with a temperature between 140 and 155 C., which implies that there will be no or substantially no intentional cooling of this stream between extraction system and stripping zone.
  • the stripping zone is operated at a pressure that is lower than that prevailing in the extraction system but that is at least 1.5 atm. abs.
  • the diierence in pressure in the extraction system and in the stripping zone should be not so large as to cause appreciable flash vaporization.
  • the gravimetric ratio of this vaporous material to the fresh feed to the extraction system should not exceed 1:10.
  • this ratio should be below 5:100, and in the most preferred embodiment no vaporous material will be present at all.
  • the top temperature should be between 140 and 155 C., and the bottom temperature should be at least 190, the difference between top andV bottom temperature being at least 40 C.
  • the top product contains substantially all water and non-aromatic hydrocarbons present in the extract phase, and, in addition, some solvent and aromatic hydrocarbons.
  • the solvent should contain a minor proportion, e.g. between 0.05 and 1% by weight of phenothiazine or of a substituted phenothiazine.
  • a minor proportion e.g. between 0.05 and 1% by weight of phenothiazine or of a substituted phenothiazine.
  • the bottom product leaving the stripping zone is cooled by at least 15 C. to a temperature between 170 and 180 C., and then passed to the distilling zone operating at a pressure below 0.5 atm. abs., preferably 0.2 atm. abs. and at a bottom temperature of at least C., which temperature should always be at least 30 C. and preferably at least 40 C. lower than the bottom temperature in the stripping zone.
  • direct steam should be introduced into the distilling zone because otherwise the temperatures required to obtain a substantially hydrocarbon-free solvent as the bottom product would be so high as to cause decomposition of the solvent.
  • the present process has the advantage that a greater proportion of the non-aromatics still present in the extract phase is removed in the overhead of the stripping zone, which results in a higher purity of the final extract as compared with the previous process.
  • a liquid hydrocarbon mixture containing both aromatic and non-aromatic hydrocarbons is extracted in a multi-stage countercurrent extractor 1, which operates under pressure and at a temperature between 140 and 155 C.
  • the feed is introduced into the extractor through one or more of the feed inlet lines 2 to 5, whereas the selective solvent, containing dissolved water, is introduced into the extractor 1 at or near its top through line 6.
  • the rainate phase which contains only relatively small amounts of water, solvent and aromatic hydrocarbons, is withdrawn from the top of the extractor 1 through line 7 and further processed to remove substantially all solvent present therein.
  • the aromatic-rich extract phase is withdrawn from the bottom of the extractor through line 8 and passes through a reducing valve (not shown) to the stripper column 10, the cooled extract phase being introduced at or near the top of the stripper.
  • the pressure in column 10 is at least 1.5 atm. abs., but lower than the pressure in extractor 1.
  • the stripper 10 is provided with a reboiler 11 .and is operated with a fairly high temperature drop over the column. ln the stripper, separation is eliected into a top product containing some solvent, part of the aromatic hydrocarbons and most of the Water and non-aromatic hydrocarbons present in the extract phase leaving the extractor 1, and a bottom product that contains only a small amount of water and contains solvent and aromatic hydrocarbons and at most a minor amount of nonaromatic hydrocarbons.
  • the top vapors are passed through line 12 to the condenser 13 and the resulting liquid passed to the settler 14, wherein separation in two layers, viz. a water-rich layer and a layer consisting mainly of solvent and hydrocarbons, takes place.
  • the water layer is removed via line 15, whereas the solventhydrocarbon layer is passed through line 16 and heater 17, to one or more of the lines 18 to 20, through which it enters the extractor in its lower part.
  • the bottoms product from the stripper is passed through line 21, provided with a cooler 33 and with a subsequent reducing valve (not shown) to distilling column 22.
  • column 22 which operates at subatmospheric pressure, separation is effected into a top product containing aromatic hydrocarbons and substantially free 6 from solvent, .and into a bottom product, that is substantially free from aromatic hydrocarbons.
  • the top vapors are withdrawn through line 23, provided with condenser 24 and the condensate is partly Withdrawn via line 25, as the aromatic-rich product, and partly passed through line 26 equipped with the settler 26A, wherein separation in two layers, viz. a lower watererich layer and an upper layer consisting mainly of hydrocarbons, takes place.
  • the upper layer is recycled as reliux to column 22.
  • the bottom product from this column is withdrawn through line 27 and returned to the extractor through line 6, if necessary after cooling in cooler 28. If desired, part of the bottom product may be withdrawn through line 29 for purification or rejection, and fresh orpuried solvent may be introduced through line 30.
  • Distilling column 22 is operated without a reboiler, hot steam being introduced into the bottom of this column via line 31 and heater 32 to strip dissolved hydrocarbons from the descending liquid.
  • a process for the extraction and recovery of aromatic hydrocarbons from a liquid hydrocarbon mixture containing aromatic and non-aromatic hydrocarbons cornprising (l) introducing the mixture into a counterflow multi-stage extraction system wherein the temperature is maintained between and 155 C.; (2) introducing, at one end of the extraction system, a high boiling, aromatic selective solvent having a normal boiling temperature within the range of 225 C. to 295 C. and which solvent contains dissolved water in the proportion of not more than 2% by weight; (3) passing the solvent in countercurrent flow to the hydrocarbon mixture to obtain a solvent extract phase enriched in aromatics; (4) removing the extract phase from the extraction system and introducing said extract phase at a temperature between 140 and 155 C.
  • aromatic selective solvent is selected from the group consisting of diethylene glycol, dipropylene glycol, sulfolane, and mixtures thereof.

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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)
US848418A 1959-03-24 1959-10-23 Process for separating aromatic hydrocarbons Expired - Lifetime US3065167A (en)

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GB10154/59A GB899281A (en) 1959-03-24 1959-03-24 Process for the extraction and recovery of aromatic hydrocarbons from a liquid hydrocarbon mixture

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DE (1) DE1165187B (en)van)
GB (1) GB899281A (en)van)
NL (1) NL249677A (en)van)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3207692A (en) * 1961-03-23 1965-09-21 Shell Oil Co Process for separation of a solvent by distillation
US3210269A (en) * 1961-04-21 1965-10-05 Shell Oil Co Dry solvent extraction of hydrocarbons
US4364821A (en) * 1980-07-30 1982-12-21 Uop Inc. Fluid contacting process
EP0202371A1 (en) * 1981-12-18 1986-11-26 Exxon Research And Engineering Company Method of extractive separation, particularly of aromatic and non-aromatic components
US20130026065A1 (en) * 2011-07-29 2013-01-31 Omer Refa Koseoglu Integrated Selective Hydrocracking and Fluid Catalytic Cracking Process

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2305038A (en) * 1939-09-16 1942-12-15 Standard Oil Dev Co Solvent treating process
US2407820A (en) * 1943-03-23 1946-09-17 Shell Dev Process for separating aromatic hydrocarbons
GB739200A (en) * 1952-06-02 1955-10-26 Dow Chemical Co Process for the extraction and recovery of aromatic hydro-carbons from hydrocarbon mixtures
US2766300A (en) * 1953-08-17 1956-10-09 Phillips Petroleum Co Solvent extraction process
US2803685A (en) * 1952-06-02 1957-08-20 Dow Chemical Co Process for the extraction and recovery of aromatic hydrocarbons from hydrocarbon mixtures
US2806071A (en) * 1953-01-21 1957-09-10 Phillips Petroleum Co Solvent extraction of aromatics from hydrocarbons
US2809222A (en) * 1953-11-27 1957-10-08 Phillips Petroleum Co Solvent extraction process
US2878261A (en) * 1956-11-15 1959-03-17 Universal Oil Prod Co Recovery and separation of naphthalenes by solvent extraction
US2905637A (en) * 1955-06-13 1959-09-22 Phillips Petroleum Co Combined liquid-vapor phase separation process

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2305038A (en) * 1939-09-16 1942-12-15 Standard Oil Dev Co Solvent treating process
US2407820A (en) * 1943-03-23 1946-09-17 Shell Dev Process for separating aromatic hydrocarbons
GB739200A (en) * 1952-06-02 1955-10-26 Dow Chemical Co Process for the extraction and recovery of aromatic hydro-carbons from hydrocarbon mixtures
US2803685A (en) * 1952-06-02 1957-08-20 Dow Chemical Co Process for the extraction and recovery of aromatic hydrocarbons from hydrocarbon mixtures
US2806071A (en) * 1953-01-21 1957-09-10 Phillips Petroleum Co Solvent extraction of aromatics from hydrocarbons
US2766300A (en) * 1953-08-17 1956-10-09 Phillips Petroleum Co Solvent extraction process
US2809222A (en) * 1953-11-27 1957-10-08 Phillips Petroleum Co Solvent extraction process
US2905637A (en) * 1955-06-13 1959-09-22 Phillips Petroleum Co Combined liquid-vapor phase separation process
US2878261A (en) * 1956-11-15 1959-03-17 Universal Oil Prod Co Recovery and separation of naphthalenes by solvent extraction

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3207692A (en) * 1961-03-23 1965-09-21 Shell Oil Co Process for separation of a solvent by distillation
US3210269A (en) * 1961-04-21 1965-10-05 Shell Oil Co Dry solvent extraction of hydrocarbons
US4364821A (en) * 1980-07-30 1982-12-21 Uop Inc. Fluid contacting process
EP0202371A1 (en) * 1981-12-18 1986-11-26 Exxon Research And Engineering Company Method of extractive separation, particularly of aromatic and non-aromatic components
US20130026065A1 (en) * 2011-07-29 2013-01-31 Omer Refa Koseoglu Integrated Selective Hydrocracking and Fluid Catalytic Cracking Process
US20190040328A1 (en) * 2011-07-29 2019-02-07 Saudi Arabian Oil Company Integrated selective hydrocracking and fluid catalytic cracking process
US11028332B2 (en) * 2011-07-29 2021-06-08 Saudi Arabian Oil Company Integrated selective hydrocracking and fluid catalytic cracking process

Also Published As

Publication number Publication date
NL249677A (en)van)
DE1165187B (de) 1964-03-12
GB899281A (en) 1962-06-20
BE588894A (nl) 1960-09-22

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