WO2000044692A1 - Separation of aromatic hydrocarbons and naphtenes from mixtures thereof by extractive distillation - Google Patents

Separation of aromatic hydrocarbons and naphtenes from mixtures thereof by extractive distillation Download PDF

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Publication number
WO2000044692A1
WO2000044692A1 PCT/IB2000/000075 IB0000075W WO0044692A1 WO 2000044692 A1 WO2000044692 A1 WO 2000044692A1 IB 0000075 W IB0000075 W IB 0000075W WO 0044692 A1 WO0044692 A1 WO 0044692A1
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Prior art keywords
extractive distillation
naphtenes
aromatic hydrocarbons
mixture
separation
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PCT/IB2000/000075
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French (fr)
Inventor
Izak Nieuwoudt
Braam Van Dyk
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Izak Nieuwoudt
Braam Van Dyk
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Izak Nieuwoudt, Braam Van Dyk filed Critical Izak Nieuwoudt
Priority to AU30698/00A priority Critical patent/AU3069800A/en
Publication of WO2000044692A1 publication Critical patent/WO2000044692A1/en
Priority to US09/671,333 priority patent/US6395141B1/en

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    • 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

  • the present invention relates to the separation of aromatic hydrocarbons and naphtenes from mixtures thereof by extractive distillation.
  • Extractive distillation is a process to separate close-boiling compounds from each other by introducing a selectively-acting third component, the extractive distillation solvent, with the result that the relative volatility of the mixture to be separated is increased and azeotropes, if present, are overcome.
  • the extractive distillation solvent is to be selected such that it does not form an undesired azeotrope with any of the compounds in the mixture.
  • extractive distillation is the method of separating close boiling compounds from each other by carrying out the distillation in a multiplate rectification column in the presence of an added liquid or liquid mixture, said liquid(s) having a boiling point higher than the compounds being separated.
  • the extractive distillation solvent is introduced near the top of the column and flows downward until it reaches the stillpot or reboiler. Its presence on each plate of the rectification column alters the relative volatility of the close boiling compounds in a direction to make the separation on each plate greater and thus require either fewer plates to effect the same separation or make possible a greater degree of separation with the same number of plates.
  • the extractive distillation solvent should boil higher than any of the close boiling liquids being separated and not form minimum azeotropes with them. Usually the extractive distillation solvent is introduced a few plates from the top of the column to ensure that none of the extractive distillation solvent is carried over with the lowest boiling component.
  • a method of separation of aromatic hydrocarbons and naphtenes includes the step of distilling a mixture of aromatic hydrocarbons / naphtenes containing at least aromatic hydrocarbons and naphtenes by way of an extractive distillation process in the presence of an extractive distillation solvent selected from the group consisting of a dione, an ester of a dibasic acid, N-methyl-2- pyrrolidone and a morpholine.
  • the aromatic hydrocarbons / naphtenes mixture may contain only aromatic hydrocarbons and naphtenes.
  • the aromatic hydrocarbons may be benzene.
  • the naphtenes may be cyclohexane.
  • the dione may be acetonyl acetone.
  • the ester of a dibasic acid may be dimethylmaleate.
  • the ester of a dibasic acid may be dimethylphtalate.
  • vapour-liquid equilibrium still 10 including a bulb flask 12 having a tube 14 leading to a condenser 16 and terminating in an outlet 18.
  • the outlet 18 has an electromagnetic closure mechanism 20.
  • a liquid phase sample conduit 22 leads into the flask 12.
  • a further liquid phase sample conduit 24 leads into the tube 14.
  • a first thermometer 26 is adapted to read the temperature of the liquid contained in the flask 12, and a second thermometer 28 is adapted to read the temperature of the vapour in the tube 14.
  • the flask 12 can be heated by a heating mantle 30.
  • the extractive distillation procedure is as follows:
  • a liquid mixture is prepared consisting of cyclohexane (naphtenes), benzene (aromatic hydrocarbons) and an extractive distillation solvent.
  • the liquid is introduced into the bulb flask 12 via conduit 22.
  • the mixture in the bulb flask 12 is then heated by the heating mantle 30 and kept at boiling point.
  • the mixture separates into a liquid phase remaining in the bulb flask 12 and a vapour phase in the tube 14.
  • the vapour phase is cooled by the condenser 16, whereafter it condenses and returns as liquid to the bulb flask 12.
  • the mixture is boiled and condensed for several hours, normally 5 to 6 hours. The process of evaporation and condensation is repeated until equilibrium is reached between the vapour and liquid phases. Thereafter, a liquid sample of the liquid phase in the bulb flask 12 is extracted through conduit 22 and a liquid sample of the condensed vapour phase in the tube 14 is extracted through conduit 24.
  • thermometer 26 The temperature of the liquid phase in the bulb flask 12 is continuously monitored by the thermometer 26, and the temperature of the vapour phase in the tube 14 is continuously monitored by the thermometer 28.
  • a cyclohexane/benzene liquid mixture with a molar ratio of 1 :1 has a relative volatility of 0.97.
  • the separation was effected by using a suitable dione as an extractive distillation solvent.
  • a benzene/cyclohexane mixture with a molar ratio of 1 :1 has a relative volatility of 0.97.
  • the separation was effected by using a suitable ester of a dibasic acid as an extractive distillation solvent.
  • a cyclohexane/benzene mixture with a molar ratio of 1.1 :1 has a relative volatility of 0.95.
  • the separation was effected by using N-Methyl-2-Pyrolidone(NMP) as an extractive distillation solvent.
  • NMP N-Methyl-2-Pyrolidone
  • a mixture of cyclohexane (34.7g), benzene (28.5g) and NMP (283.3g) was charged into the flask 12 of the vapour-liquid equilibrium 10 and the above procedure was applied.
  • the liquid and vapour phases were analysed.
  • the liquid and vapour molar fractions were determined to be as follows:
  • a cyclohexane/benzene mixture with a molar ratio of 0.63:1 has a relative volatility of 1.05.
  • the separation was effected by using morpholine as an extractive distillation solvent.
  • a benzene/cyclohexane mixture with a molar ratio of 1 :1.37 has a relative volatility of 0.92.
  • the separation was effected by using a suitable ester of a dibasic acid as an extractive distillation solvent.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

Extractive distillation is a process to separate close-boiling compounds from each other by introducing a selectively-acting third component, the extractive distillation solvent, with the result that the relative volatility of the mixture to be separated is increased and azeotropes, if present, are overcome. The extractive distillation solvent is to be selected such that it does not form an undesired azeotrope with any of the compounds in the mixture. The invention suggests a method of separation of aromatic hydrocarbons and naphtenes by distilling a mixture of aromatic hydrocarbons / naphtenes by way of an extractive distillation process in the presence of an extractive distillation solvent selected from the group consisting of a dione, ester of dibasic acid, N-methyl-2-pyrrolidone and a morpholine.

Description

Separation of aromatic hydrocarbons and naphtenes from mixtures thereof by extractive distillation.
FIELD OF INVENTION
The present invention relates to the separation of aromatic hydrocarbons and naphtenes from mixtures thereof by extractive distillation.
BACKGROUND TO INVENTION
Extractive distillation is a process to separate close-boiling compounds from each other by introducing a selectively-acting third component, the extractive distillation solvent, with the result that the relative volatility of the mixture to be separated is increased and azeotropes, if present, are overcome. The extractive distillation solvent is to be selected such that it does not form an undesired azeotrope with any of the compounds in the mixture.
As an example, the separation of benzene (aromatic hydrocarbons) and cyclohexane (naphtenes) is complicated due to the existence of an azeotrope. Aniline has been proposed in the literature as extractive distillation solvents to produce cyclohexane as distillate.
As has been stated in US Patent 5,800,681 (Berg) extractive distillation is the method of separating close boiling compounds from each other by carrying out the distillation in a multiplate rectification column in the presence of an added liquid or liquid mixture, said liquid(s) having a boiling point higher than the compounds being separated. The extractive distillation solvent is introduced near the top of the column and flows downward until it reaches the stillpot or reboiler. Its presence on each plate of the rectification column alters the relative volatility of the close boiling compounds in a direction to make the separation on each plate greater and thus require either fewer plates to effect the same separation or make possible a greater degree of separation with the same number of plates. The extractive distillation solvent should boil higher than any of the close boiling liquids being separated and not form minimum azeotropes with them. Usually the extractive distillation solvent is introduced a few plates from the top of the column to ensure that none of the extractive distillation solvent is carried over with the lowest boiling component.
It is an object of this invention to suggest at least one further extractive distillation solvent for the separation of aromatic hydrocarbons and naphtenes from mixtures thereof.
SUMMARY OF INVENTION
According to the invention, a method of separation of aromatic hydrocarbons and naphtenes includes the step of distilling a mixture of aromatic hydrocarbons / naphtenes containing at least aromatic hydrocarbons and naphtenes by way of an extractive distillation process in the presence of an extractive distillation solvent selected from the group consisting of a dione, an ester of a dibasic acid, N-methyl-2- pyrrolidone and a morpholine.
The aromatic hydrocarbons / naphtenes mixture may contain only aromatic hydrocarbons and naphtenes.
The aromatic hydrocarbons may be benzene.
The naphtenes may be cyclohexane.
The dione may be acetonyl acetone.
The ester of a dibasic acid may be dimethylmaleate.
The ester of a dibasic acid may be dimethylphtalate. BRIEF DESCRIPTION OF DRAWING
The invention will now be described by way of example with reference to the accompanying schematic drawing.
In the drawing there is shown a schematic view of an experimental apparatus for testing an extractive distillation solvent for separating aromatic hydrocarbons and naphtenes from mixtures thereof in accordance with the invention.
DETAILED DESCRIPTION OF DRAWING AND EXPERIMENTS
In the drawing there is shown a vapour-liquid equilibrium still 10 including a bulb flask 12 having a tube 14 leading to a condenser 16 and terminating in an outlet 18. The outlet 18 has an electromagnetic closure mechanism 20.
A liquid phase sample conduit 22 leads into the flask 12.
A further liquid phase sample conduit 24 leads into the tube 14.
A first thermometer 26 is adapted to read the temperature of the liquid contained in the flask 12, and a second thermometer 28 is adapted to read the temperature of the vapour in the tube 14.
The flask 12 can be heated by a heating mantle 30.
The extractive distillation procedure is as follows:
A liquid mixture is prepared consisting of cyclohexane (naphtenes), benzene (aromatic hydrocarbons) and an extractive distillation solvent. The liquid is introduced into the bulb flask 12 via conduit 22.
The mixture in the bulb flask 12 is then heated by the heating mantle 30 and kept at boiling point.
During boiling the mixture separates into a liquid phase remaining in the bulb flask 12 and a vapour phase in the tube 14. In the tube 14 the vapour phase is cooled by the condenser 16, whereafter it condenses and returns as liquid to the bulb flask 12.
The mixture is boiled and condensed for several hours, normally 5 to 6 hours. The process of evaporation and condensation is repeated until equilibrium is reached between the vapour and liquid phases. Thereafter, a liquid sample of the liquid phase in the bulb flask 12 is extracted through conduit 22 and a liquid sample of the condensed vapour phase in the tube 14 is extracted through conduit 24.
The temperature of the liquid phase in the bulb flask 12 is continuously monitored by the thermometer 26, and the temperature of the vapour phase in the tube 14 is continuously monitored by the thermometer 28.
Experiment 1
A cyclohexane/benzene liquid mixture with a molar ratio of 1 :1 has a relative volatility of 0.97.
The separation was effected by using a suitable dione as an extractive distillation solvent.
A mixture of cyclohexane (34.8g), benzene (33.2g) and acetonylacetone (181 Jg) was charged into the flask 12 of the vapour-liquid equilibrium still 10 and the above procedure was applied. The liquid and vapour phases were analysed. The liquid and vapour molar fractions were determined to be as follows:
Table 1 :
Figure imgf000006_0001
This translates to a relative volatility of 4.87 for the system cyclohexane/benzene in the ternary system shown above, the cyclohexane being the distillate.
Experiment 2
A benzene/cyclohexane mixture with a molar ratio of 1 :1 has a relative volatility of 0.97.
The separation was effected by using a suitable ester of a dibasic acid as an extractive distillation solvent.
A mixture of cyclohexane (24.9g), benzene (24.6g) and dimethylmaleate (339.0g) was charged into the flask 12 of the vapour-liquid equilibrium still 10 and the above procedure was applied. The liquid and vapour phases were analysed. The liquid and vapour molar fractions were determined to be as follows:
Table 2:
Figure imgf000007_0001
This translates to a relative volatility of 2.06 for the system benzene/cyclohexane in the ternary system shown above, the cyclohexane being the distillate.
Experiment 3
A cyclohexane/benzene mixture with a molar ratio of 1.1 :1 has a relative volatility of 0.95.
The separation was effected by using N-Methyl-2-Pyrolidone(NMP) as an extractive distillation solvent. A mixture of cyclohexane (34.7g), benzene (28.5g) and NMP (283.3g) was charged into the flask 12 of the vapour-liquid equilibrium 10 and the above procedure was applied. The liquid and vapour phases were analysed. The liquid and vapour molar fractions were determined to be as follows:
Table 3:
Figure imgf000008_0001
This translates to a relative volatility of 6.0 for the system cyclohexane/benzene in the ternary system shown above, the cyclohexane being the distillate.
Experiment 4
A cyclohexane/benzene mixture with a molar ratio of 0.63:1 has a relative volatility of 1.05.
The separation was effected by using morpholine as an extractive distillation solvent.
A mixture of cyclohexane (22.5g), benzene (22.0g) and morpholine (175.5g) was charged into the flask 12 of the vapour-liquid equilibrium still 10 and the above procedure was applied. The liquid and vapour phases were analysed. The liquid and vapour molar fractions were determined to be as follows: Table 4:
Figure imgf000009_0001
This translates to a relative volatility of 2.21 for the system cyclohexane/benzene in the ternary system shown above, the cyclohexane being the distillate.
Experiment 5
A benzene/cyclohexane mixture with a molar ratio of 1 :1.37 has a relative volatility of 0.92.
The separation was effected by using a suitable ester of a dibasic acid as an extractive distillation solvent.
A mixture of benzene (13.5g), cyclohexane (20.0g) and dimethylphthalate (258.4g) was charged into the flask 12 of the vapour- liquid equilibrium still 10 and the above procedure was applied. The liquid and vapour phases were analysed. The liquid and vapour molar fractions were determined to be as follows:
Table 5:
Figure imgf000010_0001
This translates to a relative volatility of 1.50 for the system cyclohexane/benzene in the ternary system shown above, the cyclohexane being the distillate.

Claims

PATENT CLAIMS
1. A method of separation of aromatic hydrocarbons and naphtenes, which includes the step of distilling a mixture of aromatic hydrocarbons / naphtenes containing at least aromatic hydrocarbons and naphtenes by way of an extractive distillation process in the presence of an extractive distillation solvent selected from the group consisting of a dione, an ester of a dibasic acid, N-methyl-2-pyrrolidone and a morpholine.
2. A method as claimed in claim 1 , in which the aromatic hydrocarbons / naphtenes mixture contains only aromatic hydrocarbons and naphtenes.
3. A method as claimed in claim 1 or claim 2, in which the aromatic hydrocarbons are benzene.
4. A method as claimed in claim 1 or claim 2, in which the naphtenes are cyclohexane.
5. A method as claimed in any one of the preceding claims, in which the dione is acetonyl acetone.
6. A method as claimed in any one of claims 1 to 4, in which the ester of a dibasic acid is dimethylmaleate.
7. A method as claimed in any one of claims 1 to 4, in which the ester of a dibasic acid is dimethylphtalate.
PCT/IB2000/000075 1999-01-28 2000-01-26 Separation of aromatic hydrocarbons and naphtenes from mixtures thereof by extractive distillation WO2000044692A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU30698/00A AU3069800A (en) 1999-01-28 2000-01-26 Separation of aromatic hydrocarbons and naphtenes from mixtures thereof by extractive distillation
US09/671,333 US6395141B1 (en) 1999-01-28 2000-09-28 Separation of components from aromatic hydrocarbon mixtures thereof by extractive distillation

Applications Claiming Priority (8)

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ZA99/0658 1999-01-28
ZA99657 1999-01-28
ZA99/0657 1999-01-28
ZA99659 1999-01-28
ZA99/0656 1999-01-28
ZA99/0659 1999-01-28
ZA99656 1999-01-28
ZA99658 1999-01-28

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102850158A (en) * 2011-06-29 2013-01-02 中国石油化工股份有限公司 Mixed solvent for C 5 separation
CN105606423A (en) * 2016-02-26 2016-05-25 河南中烟工业有限责任公司 Extracting device and extracting method for volatile and semivolatile components in sample

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4514262A (en) * 1982-08-02 1985-04-30 Lloyd Berg Separation of benzene from non-aromatic hydrocarbons by extractive distillation
EP0496060A2 (en) * 1991-01-23 1992-07-29 Krupp Koppers GmbH Process for separating aromatics from hydrocarbon mixtures of any given aromatic content
US5145562A (en) * 1991-07-01 1992-09-08 Phillips Petroleum Company Extractive distillation of mixtures containing aromatic and olefinic hydrocarbons

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4514262A (en) * 1982-08-02 1985-04-30 Lloyd Berg Separation of benzene from non-aromatic hydrocarbons by extractive distillation
EP0496060A2 (en) * 1991-01-23 1992-07-29 Krupp Koppers GmbH Process for separating aromatics from hydrocarbon mixtures of any given aromatic content
US5145562A (en) * 1991-07-01 1992-09-08 Phillips Petroleum Company Extractive distillation of mixtures containing aromatic and olefinic hydrocarbons

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102850158A (en) * 2011-06-29 2013-01-02 中国石油化工股份有限公司 Mixed solvent for C 5 separation
CN105606423A (en) * 2016-02-26 2016-05-25 河南中烟工业有限责任公司 Extracting device and extracting method for volatile and semivolatile components in sample

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