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WO1998015511A1 - Procede de separation de pentafluoroethane et de chloropentafluoroethane - Google Patents

Procede de separation de pentafluoroethane et de chloropentafluoroethane Download PDF

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Publication number
WO1998015511A1
WO1998015511A1 PCT/US1997/018279 US9718279W WO9815511A1 WO 1998015511 A1 WO1998015511 A1 WO 1998015511A1 US 9718279 W US9718279 W US 9718279W WO 9815511 A1 WO9815511 A1 WO 9815511A1
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WO
WIPO (PCT)
Prior art keywords
hfc
cfc
pentafluoroethane
chloropentafluoroethane
entraining agent
Prior art date
Application number
PCT/US1997/018279
Other languages
English (en)
Inventor
Paul Gene Clemmer
Peter Brian Logsdon
Hang Thanh Pham
Original Assignee
Alliedsignal Inc.
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 Alliedsignal Inc. filed Critical Alliedsignal Inc.
Priority to AU47520/97A priority Critical patent/AU4752097A/en
Publication of WO1998015511A1 publication Critical patent/WO1998015511A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C17/00—Preparation of halogenated hydrocarbons
    • C07C17/38—Separation; Purification; Stabilisation; Use of additives
    • C07C17/383—Separation; Purification; Stabilisation; Use of additives by distillation
    • C07C17/386—Separation; Purification; Stabilisation; Use of additives by distillation with auxiliary compounds

Definitions

  • the present invention pertains to a process for separating pentafluoroethane ("HFC- 125”) from chloropentafluoroethane ("CFC- 115"). More particularly, the invention relates to a process for separating pentafluoroethane from chloropentafluoroethane by distillation.
  • HFC- 125 is a non-chlorine containing fluorocarbon that is especially useful as a refrigerant, blowing agent, propellant, fire extinguishing agent and sterilant carrier gas.
  • HFC-125 may be prepared by hydrofluorinating tetrachloroethylene by various known processes which result in a mixture containing HFC- 125, CFC-115 and other fluorinated compounds.
  • the mixture of HFC-125 and CFC-115 forms an azeotrope at atmospheric pressure and a near-azeotrope at elevated pressures.
  • the boiling points of these halogenated hydrocarbons are close, -48.5° C for HFC-125 and -38.7° C for CFC-115, and their relative volatility is below 1.1 at concentrations of HFC- 125 greater than 87.5 mole percent, and below 1.01 at concentrations above 95 mole percent.
  • a key problem when considering an azeotropic distillation process is discovering an entraining agent, which agent undergoes a non-ideal interaction with a component, that will sufficiently aid the desired separation process.
  • the present invention employs an entraining agent that forms an azeotrope with CFC-115, which azeotrope boils at a temperature lower than HFC- 125. It has been found that CFC-115 can efficiently and effectively be removed from HFC- 125 by azeotropic distillation with such an entraining agent.
  • the invention provides a process for separating HFC- 125 from a mixture of HFC-125 and CFC-115 which comprises contacting a mixture comprising HFC-125 and CFC-115 with an effective amount of an entraining agent to form an azeotrope of CFC-115 and the entraining agent which azeotrope has a boiling point of about -48.5° C or less at atmospheric pressure.
  • the invention also provides a process for separating HFC- 125 from an azeotropic mixture of HFC-125 and CFC-115 which comprises contacting a mixture comprising HFC-125 and CFC-115 with an effective amount ofHFC-32 to form an azeotropic mixture of CFC-115 and HFC-32.
  • the invention further provides a process for the purification of HFC-125 by removing CFC-115 therefrom which comprises adding to the impure HFC- 125 a component which undergoes a non-ideal interaction with CFC-115 and/or with the azeotrope of CFC-115 and HFC- 125 such that the volatility of CFC-115 and/or the azeotrope of CFC-115 and HFC-125 relative to bulk HFC-125 is increased and distilling the mixture.
  • HFC- 125 may be efficiently purified, or separated, from a mixture of HFC- 125 and CFC-115 by the use of an entraining agent that forms an azeotrope with CFC-115.
  • an entraining agent that forms an azeotrope with CFC-115 is added to a mixture of HFC-125 and CFC-115.
  • the mixture of HFC- 125 and CFC-115 will be the result of the hydrofluorination of tetrachloroethylene.
  • the process of the invention is useful for any mixture of HFC-125 and CFC-115, especially azeotropic mixtures of HFC-125 and CFC-115. The process is most effectively used for HFC-125/CFC-115 mixtures in which the weight of HFC- 125 is about 90 weight percent or more.
  • Entraining agents useful in the invention are any agents that form azeotropes, preferably minimum boiling azeotropes so that the entraining agent/CFC-115 azeotrope can be separated from HFC-125.
  • minimum boiling is meant an azeotrope that boils at a temperature less than the boiling point of its individual components.
  • Useful entraining agents for this invention non-exclusively include difluoromethane (“HFC-32”), 1,1,1-trifluoroethane (“HFC- 143 a”) and mixtures thereof.
  • the azeotropes HFC-32/CFC-115 and HFC-143a/CFC-l 15 are known azeotropes with boiling points less than the boiling point of HFC-125/CFC-115, which is approximately -48.7° C at 1 atm. pressure, and HFC- 125.
  • a mixture of entraining agents may also be used, as long as the entraining agent mixture with CFC-115 has a boiling point below that of HFC-125.
  • Illustrative mixtures suitable for use as entraining agents include, without limitation, HFC-125 HFC-32 and HFC-125/HFC-143a.
  • An effective amount of entraining agent is used which amount is an amount effective to form a minimum boiling azeotrope with CFC-115.
  • the precise amount of agent used will depend on the entraining agent used.
  • the weight ratio of the entraining agent to the amount of CFC-115 to be removed is typically in the range of from about 2: 1 to about 500: 1. Higher ratios may be used to minimize the amount of CFC- 115 left in HFC- 125, especially when the resulting entraining agent/HFC- 125 mixture is a desired product, as is the case for HFC-32 HFC-125 and HFC-143a/HFC-125, which are commercial refrigerant azeotropic blends.
  • the preferred weight ratio is at least about 0.5:1.
  • the preferred ratio is at least about 1.3:1.
  • the methods of this invention can treat any mixture of HFC-125 and CFC-115, provided the above weight ratios of entraining agent to CFC-115 are used.
  • the entraining agent is added so that the separation of HFC- 125 from CFC-115 is optimized. Optimization occurs when the maximum efficiency in separation, or the minimum amount of CFC-115 in the bottoms, is achieved while energy and capital costs along with entraining agent loss are minimized.
  • any convenient means for separating the HFC- 125 from the CFC-115/entraining agent azeotrope may be used.
  • the HFC- 125 is then separated from the azeotrope of CFC-115 and entraining agent by distillation.
  • the separating may be conducted in a standard distillation column in which the azeotrope of CFC-115 and entraining agent is removed as an overhead distillation fraction and the HFC- 125 is removed as a bottoms distillation fraction. Because not all of the HFC -125 may be separated from the CFC-115 by addition of the entraining agent, some HFC- 125 may exit the column with the CFC-115/entraining agent azeotrope.
  • the entraining agent/CFC-115 azeotrope can be optionally treated to recover and reuse the entraining agent. Also, if the entraining agent/CFC-115 stream contains HFC-125, the entraining agent/CFC-115 overhead stream may be treated by any convenient method to recover the HFC- 125. Additionally, the entraining agent may form a mixture with the HFC- 125 and exit with the HFC-125. For example, if HFC-32 or HFC-143a are used as the entraining agents, the HFC- 125 distillation fraction may be a mixture of HFC-32/HFC-125 or HFC-32/HFC-143a.
  • the distillation is conducted at a temperature below the boiling point of HFC- 125 at the distillation pressure.
  • the distillation is conducted at a temperature that is about 0.2 to about 50° Below the boiling point of HFC-125 at the distillation pressure, which may be subatmospheric to 500 psia.
  • the HFC-125/CFC-115 mixture may be treated to concentrate the CFC-115 content, for example, by pressure swing distillation as described in U.S. Patent 5,346,595, which is incorporated in its entirety herein by reference.
  • the entraining agent can also be used on a HFC-125/CFC-115 mixture following a separate treatment which reduces the CFC-115 content before treatment with the entraining agent.
  • the resulting entraining agent/CFC-115 mixture can be treated by physical or chemical means to recover the entraining agent and/or convert the CFC-115 to a useful product such as conversion to a hydrofluorocarbon by hydrogenation or reaction with a reducing agent.
  • a batch still equipped with a packed column of approximately 40 stages was charged with a mixture of 98.2 wt.% HFC-125, 0.7 wt.% CFC-115, 1 wt.% HFC-32 and approximately 0.1 wt.% of higher-boiling halogenated hydrocarbon impurities.
  • the still was operated at total reflux for a time sufficient to obtain stable conditions with reboiler temperature of 2°C.
  • Still pressure was 89 psig.
  • Samples of the column top vapor and reboiler liquid were removed and analyzed by gas chromatography and found to have the following compositions:
  • Reboiler liquid 98.7 wt. % HFC-125; 0.5 wt. % CFC-115; 0.5 wt. % HFC-32.
  • Reboiler liquid 98.4 wt.% HFC-125; 0.6 wt. % CFC-115; 0.6 wt.% HFC-32
  • a mixture containing 64 wt % HFC-32, 26 wt. % CFC-115, and 10 wt. % HFC- 125 was loaded into a still equipped with a packed column of approximately 140 stages. The still was run at atmospheric pressure and at total reflux for the first 1.5 hours and at about 20: 1 reflux ratio later while withdrawing vapor from the condenser. A first sample of the overhead vapor was withdrawn and collected, with a weight equal to 0.35 wt. % of the initial charge. A second sample of the overhead vapor was withdrawn and collected, with a weight equal to 0.53 wt. % of the initial charge. A third sample of the overhead vapor was then withdrawn and collected. Analyses of the three samples by gas chromatography gave the following results: First sample: 41.1 wt. % HFC-32; 0.7 wt. % HFC-125; 58.2 wt. % CFC-115
  • the second and third sample analyses demonstrate that there is no ternary azeo- trope between 32/115/125.
  • the mixture fractionates and the lower boiling 32/115 distills out at the top of the column.
  • Second sample 42 wt.% HFC-125; 57 wt. % HFC-143a; 1 wt. % CFC-115.
  • Residual liquid 54 wt. % HFC-125; 46 wt. % HFC-143a.
  • a mixture containing 0.7 wt. % CFC-115 and 99.3 wt. % HFC- 125 was fed to a first continuous distillation column with about 50 stages operating at about 25 psia.
  • An overhead stream containing 5 wt. % CFC-115 and 95 wt. % HFC- 125 was removed and fed continuously to a second continuous distillation column with 50 stages operating at about 160 psia.
  • the overhead stream from the second distillation column was recycled to the first Column.
  • a sample of the bottoms stream of this second distillation column containing 9 wt. % CFC-115 and 91 wt. % HFC- 125 was obtained and fed to a third continuous distillation column along with a stream of HFC-32.
  • the weight ratio of HFC-32 to the 125/115 stream was 1:5 and the weight ratio of HFC-32: HFC-115 was 2.2: 1.
  • Analysis by GC of the overhead and bottoms streams of the third distillation column
  • a mixture containing 8 wt. % CFC-115 and 92 wt. % HFC- 125 was fed to the same third distillation column described in Example 5 along with a stream of HFC- 143 a.
  • the weight ratio of HFC-143a to the 125/115 stream was 1.3:1 and the weight ratio of HFC-143A:HFC-115 was 16: 1.
  • Analysis by GC of the overhead and bottoms streams of the third distillation column gave the following analyses:
  • HFC- 143a can be used as an entraining agent to remove CFC-115 from a CFC-115/HFC-125 mixture in a continuous distillation column.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

La présente invention concerne un procédé de séparation de pentafluoroéthane d'un mélange avec du chloropentafluoroéthane. Un mélange de pentafluoroéthane et de chloropentafluoroéthane est mis en contact avec un agent d'entraînement pour constituer un azéotrope formé de l'agent d'entraînement et de chloropentafluoroéthane. Par la suite, le pentafluoroéthane est séparé par distillation de l'azéotrope binaire formé de chloropentafluoroéthane et d'un agent d'entraînement. La distillation est effectuée de telle sorte que l'azéotrope formé de chloropentafluoroéthane et d'un agent d'entraînement est retiré sous la forme d'un distillat de tête et le pentafuoroéthane est retiré sous la forme d'un résidu de distillation.
PCT/US1997/018279 1996-10-10 1997-10-10 Procede de separation de pentafluoroethane et de chloropentafluoroethane WO1998015511A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU47520/97A AU4752097A (en) 1996-10-10 1997-10-10 Process for separating pentafluoroethane and chloropentafluoroethane

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US72926496A 1996-10-10 1996-10-10
US08/729,264 1996-10-10

Publications (1)

Publication Number Publication Date
WO1998015511A1 true WO1998015511A1 (fr) 1998-04-16

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AU (1) AU4752097A (fr)
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7060165B2 (en) 2002-02-14 2006-06-13 Pcbu Services, Inc. Processes for purification and production of fluorocarbons
JP2017222689A (ja) * 2010-03-29 2017-12-21 ハネウェル・インターナショナル・インコーポレーテッドＨｏｎｅｙｗｅｌｌ Ｉｎｔｅｒｎａｔｉｏｎａｌ Ｉｎｃ． 第３の化合物を加えることによる沸点の近い化合物の分離

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5087329A (en) * 1991-05-16 1992-02-11 E. I. Du Pont De Nemours And Company Process for separating pentafluoroethane from a mixture of halogenated hydrocarbons containing chloropentafluoroethane
WO1995027689A1 (fr) * 1994-04-08 1995-10-19 Imperial Chemical Industries Plc Procede de purification du pentafluoroethane
WO1996006063A1 (fr) * 1994-08-24 1996-02-29 Imperial Chemical Industries Plc Purification du pentafluoroethane
WO1997003936A1 (fr) * 1995-07-14 1997-02-06 E.I. Du Pont De Nemours And Company Procedes de distillation pour l'elimination du hcf-125 le cfc-115 et l'acide fluorhydrique

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5087329A (en) * 1991-05-16 1992-02-11 E. I. Du Pont De Nemours And Company Process for separating pentafluoroethane from a mixture of halogenated hydrocarbons containing chloropentafluoroethane
WO1995027689A1 (fr) * 1994-04-08 1995-10-19 Imperial Chemical Industries Plc Procede de purification du pentafluoroethane
WO1996006063A1 (fr) * 1994-08-24 1996-02-29 Imperial Chemical Industries Plc Purification du pentafluoroethane
WO1997003936A1 (fr) * 1995-07-14 1997-02-06 E.I. Du Pont De Nemours And Company Procedes de distillation pour l'elimination du hcf-125 le cfc-115 et l'acide fluorhydrique

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7060165B2 (en) 2002-02-14 2006-06-13 Pcbu Services, Inc. Processes for purification and production of fluorocarbons
JP2017222689A (ja) * 2010-03-29 2017-12-21 ハネウェル・インターナショナル・インコーポレーテッドＨｏｎｅｙｗｅｌｌ Ｉｎｔｅｒｎａｔｉｏｎａｌ Ｉｎｃ． 第３の化合物を加えることによる沸点の近い化合物の分離

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Publication number Publication date
AU4752097A (en) 1998-05-05

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