US3445537A - Plurality of extractive-distillation zones and stripping zones - Google Patents

Plurality of extractive-distillation zones and stripping zones Download PDF

Info

Publication number
US3445537A
US3445537A US627788A US3445537DA US3445537A US 3445537 A US3445537 A US 3445537A US 627788 A US627788 A US 627788A US 3445537D A US3445537D A US 3445537DA US 3445537 A US3445537 A US 3445537A
Authority
US
United States
Prior art keywords
column
distillation
extractive
extraction
substances
Prior art date
Legal status (The legal status 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 status listed.)
Expired - Lifetime
Application number
US627788A
Other languages
English (en)
Inventor
Gunter Luther
Jurgen Ludwig
Martin Schulze
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Heinrich Koppers GmbH
Original Assignee
Heinrich Koppers GmbH
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 Heinrich Koppers GmbH filed Critical Heinrich Koppers GmbH
Application granted granted Critical
Publication of US3445537A publication Critical patent/US3445537A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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

  • This invention relates to an extractive-distillation method which can be used mainly for the simultaneous extraction of aromatic substances of different boiling points from feedstocks that contain non-aromatic substances in addition to such aromatic substances.
  • This method has many advantages over liquid-liquid extraction.
  • the following may be mentioned as examples: the omission of equipment for the recovery of the extrac- 3,445,537 Patented May 20, 1969 ice tion agent from the refined product, and the omission of large-scale mechanical equipment, such as a large number of circulating pumps and similar items.
  • the viscosity of the extraction agent is greatly reduced in the extractive-distillation as a result of the fairly high temperatures used, so that the exchange of material between the extraction agent and the feedstock is substantially improved.
  • the dimensions of the extractor can also usually be reduced. The latter two measures thus also reduce the cost of extractive-distillation in comparison with liquid-liquid extraction.
  • extractive-distillation has two disadvantages in comparison with liquid-liquid extraction. Firstly, the refined product of extractive-distillation installations sometimes contains very high proportions of extraction agent. Secondly, the extraction of extractionproduct cuts having fairly wide boiling ranges by extractive-distillation is expensive.
  • Extractive-distillation has therefore hitherto been used in practice only for feedstocks having a nonaromatic content of up to about 20% by weight, since the above-described disadvantages have no significance in these cases, or extractivedistillation has been carried out in combination with liquid-liquid extraction.
  • the object of the invention is to obviate the disadvantages described; it is intended that the method developed should be suitable in particular for the simultaneous extraction of aromatic substances of different boiling points.
  • the extraction agent contains aromatic substances that are not to be extracted from the feedstock
  • the feature (a) may be adopted by the expedient of not stripping from the extraction agent highboiling aromatic substances, derived from the feedstock, that are not required extracts.
  • Other aromatic substances, which are not derived from the feedstock in this way, may of course also be added to the extraction agent.
  • Toluene is a compound that is selected from the extraction agent.
  • Benzene and xylene may be added to the extraction agent in extractive-distillation in which benzene and xylene are to be extracted.
  • Xylene or C aromatic substances, which, for example, are not wanted extracts may be added to the extraction agent in an installation in which benzene is to be extracted from a feedstock.
  • the proportion of the aromatic substances added to the extraction agent may be up to by volume in relation to the extraction agent.
  • the proportion of the aromatic substances needed to be added to the extraction agent depends on the pressure at which extractive-distillation is carried out.
  • the rule is that this addition can be correspondingly reduced as the operating pressure is increased above atmospheric.
  • Such an addition may be made quite superfluous by an appropriately high operating pressure.
  • the extraction of the individual extract products takes place in columns allotted to each pure-extract product.
  • the nonaromatic substances that are difiicult to separate and may still be present in the extract are withdrawn, according to the invention, from the tray above the feeding tray. Any low-boiling aromatic substances that may be present in this product can be stripped in a stripper.
  • these products can be treated with distilled-off extraction agent, either together in a common small extraction-distillation column or in columns allocated to each product. If the various stripperbase products are treated in individual extractive-distillation processes, the losses of each of the aromatic substances treated may be kept as low as desired. If common extractive-distillation is used for all the stripper run-offs, only the losses of the highest-boiling aromatic substances can be kept as low as desired. The choice between these two possibilities should be made with a view to the economic and operational circumstances.
  • the stripper run-offs may, of course, also be worked up by means of normal distillation instead of extractive-distillation.
  • the solubility of extraction agents in the condensate of the nonaromatic fraction may sometimes be impaired by the addition of aromatic substances to the extraction agent. Some losses of extraction agent may then occur. But these can easily be avoided by not adding directly to the extraction agent a small part of the high-boiling aromatic additives to that agent, but by introducing these as a washing agent into the extractivedistillation column above the extraction-agent feeding point. These aromatic substances then cause the extraction agent to be washed out of the nonaromatic substances in the form of a vapour.
  • the method of the invention is not bound to be a certain extraction agent, provided that the agent has a suflicient degree of selectivity for the separation of the aromatic substances.
  • the method of the invention can also be used for the separation of any classes of substance with any desired extraction agents, if the attainable purity of the top product of the extractive-distillation is restricted by a miscibility gap.
  • the equipment illustrated is that appropriate to refining of a feedstock comprising a hydrocarbon mixture of the following composition by weight.
  • Nonaromatic substances 500 Benzene 290 Toluene Xylene 70
  • 1000 kg. of such feedstock is to be refined in unit time (e.g., per hour) and the amounts of materials quoted are those used or obtained in the same time unit.
  • the extraction agent used is 3150 kg. of propylene carbonate with which 3150 kg. of C aromatic substances have been admixed, so that the total quantity of the circulating extraction agent is 3500 kg.
  • the feedstock is introduced on to a middle tray of a first extractive-distillation column 2, which is operating at a pressure of about 3.5 atmospheres, through pipe 1.
  • 2000 kg. of the extraction-agent mixture is fed through a pipe 3 to one of the upper trays of the column 2.
  • 450 kg. of nonaromatic substances escape from the top of the column through a pipe 4 in the form of vapour, and are fed into a collecting pipe 5.
  • the base product of the column 2 which contains the aromatic substances and the extraction-agent mixture in addition to a small residue of nonaromatic substances, is pumped through a pipe 6 into a second extractive-distillation column 7, which is operating at normal atmospheric pressure.
  • the base product is introduced on to one of the middle trays of the column 7. 1000 kg. of the extraction-agent mixture are fed through a pipe 8 on to one of the upper trays of the column 7 and 30 kg. of nonaromatic substances escape from the top of the column through a pipe 9 in the form of vapour and are also fed into the collecting pipe 5 after condensation.
  • the base product of the column 7 is conveyed into a first stripping column 11 through a pipe 10, being introduced on to one of the middle trays of the column 11.
  • the column 11 is used for the refinement of the benzene, which is drawn 01f from the top through a pipe 12.
  • a product containing nonaromatic substances is drawn off from the tray above the feeding tray through a pipe 13, and freed from benzene residues in a stripper 14.
  • the base product of the column 14 is fed into a collecting pipe 16 through a pipe 15, while the base product of the column 11 is conveyed into a second stripping column 18, which is used for refining the toluene, through a pipe 17.
  • the base product is introduced at one of the middle trays of the column 18 in this case as well, a side product containing nonaromatic substances also being drawn off through a pipe 20 from the tray above the feeding tray.
  • the toluene escapes from the top of column 18 through a pipe 19.
  • a stripper 21 is used to strip aromatic residues from the side product.
  • the base product of the column 21 is also conveyed through a pipe 22 into the collecting pipe 16, while the base product of the column 18 passes through a pipe 23 into a third stripping column 24, in which the xylene is stripped.
  • the xylene escapes from the top of column 24 through a pipe 25, while a side product containing nonaromatic substances is drawn off through a pipe 26 from the tray above the feeding tray in the middle of the column.
  • a stripper 27 is used to strip aromatic residues from the side product, the base product of the column 27 being conveyed into the collected pipe 16 through a pipe 28.
  • the product flows combined in the collecting pipe 16 and containing nonaromatic substances are conveyed into an extractive-distillation column 29 for after-refining. These flows are introduced on to one of the middle trays of the column 29. 500 kg. of extraction-agent mixture are introduced through a pipe 30 onto one of the upper trays of the column 29.
  • the base product of this column is drawn off through a pipe 32, whence it passes into the pipe and is thereby returned into the downstream stripping columns, while 20 kg. of nonaromatic substances escape from the top of the column through a pipe 31; these nonaromatic substances are fed to the collecting pipe 5.
  • the extraction-agent mixture freed from the aromatic substances, is drawn off from the base of the last stripping column 24 through the pipe 32 and returned to the extractive-distillation columns through the branch pipes 3, 8 and 30.
  • the extraction-agent mixture is introduced into the process through the pipe 33 when the installation is started up.
  • the pipe sections 34, 35 and 36 are inlets to the extractive-distillation columns, which are situated above the inlet trays for the extraction agent and through which part of the aromatic substances to be added to the extraction agent can be introduced into the process.
  • the nonaromatic substances could also be drawn off practically entirely through the collecting pipe 5.
  • the method of the invention is therefore characterised by extraordinarily good separating efliciency and high yields for all the fractions to be extracted. All the aromatic substances extracted have a good degree of purity.
  • the mixture of aromatic substances often contains still higher-boiling substances, e.g., C aromatic substances, in addition to benzene, toluene and xylene. If these aromatic substances are also to be extracted, the mixture drawn off from the base of the column 24 can be worked up appropriately as in the case of the preceding columns. If quantitative separation of the C aromatic substances is not planned, the base product of the column 24 can be worked up in a simple stripping column.
  • C aromatic substances e.g., C aromatic substances
  • Extractive-distillation process for simultaneously obtaining different aromatics with diiferent boiling point ranges from a feed stock containing varied amounts of nonaromatics along with the desired aromatic compounds comprising, in combination,

Landscapes

  • 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)
US627788A 1966-04-01 1967-04-03 Plurality of extractive-distillation zones and stripping zones Expired - Lifetime US3445537A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DEK0058899 1966-04-01

Publications (1)

Publication Number Publication Date
US3445537A true US3445537A (en) 1969-05-20

Family

ID=7228888

Family Applications (1)

Application Number Title Priority Date Filing Date
US627788A Expired - Lifetime US3445537A (en) 1966-04-01 1967-04-03 Plurality of extractive-distillation zones and stripping zones

Country Status (6)

Country Link
US (1) US3445537A (xx)
BE (1) BE695567A (xx)
DE (1) DE1545318B1 (xx)
FR (1) FR1514023A (xx)
GB (1) GB1138004A (xx)
NL (1) NL6704639A (xx)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4617038A (en) * 1985-07-26 1986-10-14 El Paso Hydrocarbons Company Process for using preferential physical solvents for selective processing of hydrocarbon gas streams
US4692179A (en) * 1982-05-03 1987-09-08 Advanced Extraction Technologies, Inc. Process for using alkyl substituted C8-C10 aromatic hydrocarbons as preferential physical solvents for selective processing of hydrocarbon gas streams
US5009772A (en) * 1989-02-27 1991-04-23 Kerr-Mcgee Corporation Solvent extraction process
US5573645A (en) * 1995-06-29 1996-11-12 Mobil Oil Corporation Process and apparatus for the separation of aromatic hydrocarbons

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2215915A (en) * 1937-08-17 1940-09-24 Standard Oil Co California Selective solvent extraction of petroleum
US2434424A (en) * 1942-03-10 1948-01-13 Shell Dev Plural stage extractive distillation with inverse solvents
US2455803A (en) * 1944-02-11 1948-12-07 Shell Dev Extractive distillation process
US2834822A (en) * 1958-05-13 Toluene
US2981663A (en) * 1958-05-05 1961-04-25 Shell Oil Co Extractive distillation of aromatic compounds
US2981662A (en) * 1958-05-05 1961-04-25 Shell Oil Co Extractive distillation of aromatic compounds
US3227632A (en) * 1962-10-22 1966-01-04 Koppers Co Inc Recovery of aromatic hydrocarbon by extractive distillation with anhydrous liquid propylene carbonate

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2837585A (en) * 1954-02-23 1958-06-03 Union Carbide Corp Separation of aromatics and aliphatics using alkylene carbonate

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2834822A (en) * 1958-05-13 Toluene
US2215915A (en) * 1937-08-17 1940-09-24 Standard Oil Co California Selective solvent extraction of petroleum
US2434424A (en) * 1942-03-10 1948-01-13 Shell Dev Plural stage extractive distillation with inverse solvents
US2455803A (en) * 1944-02-11 1948-12-07 Shell Dev Extractive distillation process
US2981663A (en) * 1958-05-05 1961-04-25 Shell Oil Co Extractive distillation of aromatic compounds
US2981662A (en) * 1958-05-05 1961-04-25 Shell Oil Co Extractive distillation of aromatic compounds
US3227632A (en) * 1962-10-22 1966-01-04 Koppers Co Inc Recovery of aromatic hydrocarbon by extractive distillation with anhydrous liquid propylene carbonate

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4692179A (en) * 1982-05-03 1987-09-08 Advanced Extraction Technologies, Inc. Process for using alkyl substituted C8-C10 aromatic hydrocarbons as preferential physical solvents for selective processing of hydrocarbon gas streams
US4617038A (en) * 1985-07-26 1986-10-14 El Paso Hydrocarbons Company Process for using preferential physical solvents for selective processing of hydrocarbon gas streams
US5009772A (en) * 1989-02-27 1991-04-23 Kerr-Mcgee Corporation Solvent extraction process
US5573645A (en) * 1995-06-29 1996-11-12 Mobil Oil Corporation Process and apparatus for the separation of aromatic hydrocarbons

Also Published As

Publication number Publication date
BE695567A (xx) 1967-09-01
NL6704639A (xx) 1967-10-02
DE1545318B1 (de) 1970-05-14
GB1138004A (en) 1968-12-27
FR1514023A (fr) 1968-02-16

Similar Documents

Publication Publication Date Title
US4081355A (en) Process for recovering highly pure aromatics from a mixture of aromatics and non-aromatics
US3591490A (en) Process of separating pure aromatic hydrocarbons from hydrocarbon mixtures
US3361664A (en) Flashing and extractively distilling an extract
US3207692A (en) Process for separation of a solvent by distillation
US3590092A (en) Method for aromatic hydrocarbon recovery
US3306849A (en) Hydrocarbon solvent refining process
US2711433A (en) Process for extraction and recovery of aromatic hydrocarbons from hydrocarbon mixtures
US3445537A (en) Plurality of extractive-distillation zones and stripping zones
US2786085A (en) Solvent extraction process applied to feed stocks of high boiling points
US3679579A (en) Process for recovering highly pure aromatic substances from hydrocarbon mixtures containing both aromatic and non-aromatic substances
US3725257A (en) Process of separating aromatic hydrocarbons from hydrocarbon mixtures
US2921015A (en) Preparation of aromatics from a naphtha feed
US3725255A (en) Process for separating aromatic hydrocarbons from mixtures containingthem by liquid-liquid extraction and azeotropic distillation
US3721620A (en) Process for the extraction of aromatic hydrocarbons
US3431199A (en) Method of separating aromatic hydrocarbons from mixtures containing them
US3210269A (en) Dry solvent extraction of hydrocarbons
US3492365A (en) Separation of aromatic hydrocarbons from nonaromatic hydrocarbons
US2848387A (en) Separation of aromatic and nonaromatic hydrocarbons
US3059037A (en) Extractive distillation process
US3065169A (en) Process for separating aromatic hydrocarbons
US2905637A (en) Combined liquid-vapor phase separation process
US3558480A (en) Light and heavy reflux streams in solvent extraction of aromatics
US3725256A (en) Process for separating aromatic hydrocarbons from mixtures thereof with paraffins and naphthene hydrocarbons
US3470088A (en) Method for aromatic hydrocarbon recovery
US3065167A (en) Process for separating aromatic hydrocarbons