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WO1994013857A1 - Fluoration electrochimique - Google Patents

Fluoration electrochimique Download PDF

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Publication number
WO1994013857A1
WO1994013857A1 PCT/GB1993/002463 GB9302463W WO9413857A1 WO 1994013857 A1 WO1994013857 A1 WO 1994013857A1 GB 9302463 W GB9302463 W GB 9302463W WO 9413857 A1 WO9413857 A1 WO 9413857A1
Authority
WO
WIPO (PCT)
Prior art keywords
cell
hydrogen fluoride
hydrogen
compound
substrate
Prior art date
Application number
PCT/GB1993/002463
Other languages
English (en)
Inventor
Richard Llewellyn Powell
Stephen Robert Forsyth
Original Assignee
Imperial Chemical Industries Plc
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
Priority claimed from GB929225391A external-priority patent/GB9225391D0/en
Priority claimed from GB929225384A external-priority patent/GB9225384D0/en
Priority claimed from GB929225375A external-priority patent/GB9225375D0/en
Priority claimed from GB929225390A external-priority patent/GB9225390D0/en
Application filed by Imperial Chemical Industries Plc filed Critical Imperial Chemical Industries Plc
Priority to JP6513910A priority Critical patent/JPH08504001A/ja
Priority to EP94900947A priority patent/EP0672198A1/fr
Publication of WO1994013857A1 publication Critical patent/WO1994013857A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B3/00—Electrolytic production of organic compounds
    • C25B3/20—Processes
    • C25B3/27—Halogenation
    • C25B3/28—Fluorination

Definitions

  • This invention relates to an electrolytic process for the replacement of hydrogen by fluorine in partially fluorinated organic compounds, in particular compounds containing the group -CH2 .
  • Electrochemical fluorination using a liquid hydrogen fluoride electrolyte which involves the replacement of hydrogen atoms in the starting material by fluorine is known and has been described for example in US 2,519,983.
  • known electrochemical fluorinations of the type using a liquid hydrogen fluoride electrolyte have hitherto suffered from the disadvantage that the process is highly unselective.
  • the products resulting from known electrochemical fluorination processes for example the electrochemical fluorination of ethane, ethylene and 1 , 1-dichloroethane comprise a complex mixture of all the possible higher fluorinated products.
  • the compound of formula R-0 n - (R 1 ) m -CH2F ma-y comprise halogen atoms other than fluorine, for example chlorine, which may be unaffected by the electrolytic process but the compound usually comprises a fluorine containing compound having no other halogen atoms.
  • the compounds are usually therefore hydrofluoroalkanes and fluorinated dialkyl ethers, which are characterised by containing the group -CH2 .
  • R-0 n - (R 1 ) m _CH 2 F (hereafter referred to as "the substrate") to be fluorinated comprises a compound of formula R-CH2 wherein R is hydrogen or a fluorine containing C ⁇ _ alkyl group. Preferably it is a group comprising hydrogen, or a fluorine-containing alkyl group having 1 or 2 carbon atoms.
  • the substrate preferably comprises a hydrofluoro-methane , -ethane or -propane. Particularly preferred substrates include CH3F and CF3CH2F.
  • the substrate comprises a partially fluorinated dialkyl ether of formula R-0-R-*-CH2F where R is a fluorine-containing C ⁇ _ alkyl group.
  • the group R 1 may comprise a fluorinated methylene group, that is -CH 2 -1-CHF-, and -CF2- and the substrate may be a partially fluorinated ethyl ether.
  • m 0 and the substrate comprises a monofluoromethyl ether.
  • the group R preferably also comprises a partially fluorinated methyl group, and preferred dialkyl ether substrates comprise partially fluorinated dimethyl ethers.
  • Especially preferred substrates include CH2F-O-CH2F and CH3-O-CH 2 F.
  • hydrogen atoms in the group R of the substrate may be replaced by fluorine such that in the product of the process, the group R will usually comprise a perfluorinated group, although where the group R in the substrate comprises a -CH2F group, the group R of the product of the process may comprise a -CF2H group.
  • -1134 comprising an electrode stack of alternating anodes and cathodes, separated by an insulating material .
  • the anode material may be for example iron or carbon but is preferably nickel.
  • a particularly preferred anode material due to its particularly high surface area per unit volume ratio is a nickel foam, commercially available under the trade name "Retimet” from Dunlop Ltd.
  • the cathode material may be for example iron or steel, but preferably the cathode is also constructed from nickel .
  • the cell may also comprise a reference electrode which may also comprise nickel, for example a nickel wire.
  • the nickel wire may be sheathed in an insulating material, for example polytetrafluoroethylene .
  • the process may be carried out at temperatures in the range from about -80°C to about 30°C, preferably at temperatures in the range from about -10°C to about 10°C and at atmospheric pressure although superatmospheric or subatmospheric pressures m y be employed if desired.
  • the operating temperature and pressure are chosen such that the products of the reaction distill from the cell.
  • the substrates of the invention may be in the liquid or vapour phase depending upon the particular substrate and the operating conditions.
  • the substrate may be fed to the cell as a vapour, for example bubbled into the cell through an inlet in the bottom of the cell.
  • the substrate vapour feed may be diluted with an inert gas, for example nitrogen, if desired.
  • the feed flow rate may vary within a wide range depending inter alia upon the capacity of the cell but will usually be in the range from about 10 ml/minute to about lOOml/minute for an electrochemical cell having a capacity of 1.5 litres.
  • the liquid may be charged to the cell and the cell may be provided with means for example a pump, for circulating the hydrogen fluoride and liquid substrate within or to and from the cell.
  • the proportion of substrate to liquid hydrogen fluoride may vary within a wide range but we have found that the higher partially fluorinated products are formed with high selectivity where substantially more substrate is employed relative to hydrogen fluoride than would be employed following conventional practice.
  • the substrate and hydrogen fluoride in a molar ratio from about 1:2 to about 1:10, preferably from about 1:3 to about 1:5.
  • liquid hydrogen fluoride is charged to the cell.
  • the hydrogen fluoride is preferably anhydrous and if desired a potential may be applied across the electrodes of the cell in order to dry the hydrogen fluoride before the substrate is added.
  • the anode surface is preferably conditioned following the removal of water from the hydrogen fluoride. Conditioning of the anode surface may be carried out by applying an anode potential prior to feeding the substrate to the cell.
  • the conditioning potential may be in the range from about 3V to about 8V , and preferably from about 4V to about 6V.
  • the substrate may be fed to the cell whilst an electrode potential is applied across the cell.
  • the gaseous products of fluorination may be recovered through vents in the top of the cell and may be passed through various, conventional scrubbers in order to remove any hydrogen fluoride and OF2 which may have become entrained in the product stream. Liquid products of fluorination may be drained from the bottom of the cell.
  • the substrate is a liquid
  • a portion of the dried hydrogen fluoride may be carefully withdrawn from the cell (so as to avoid contamination with water), the liquid substrate may be mixed with the hydrogen fluoride and the mixture may be returned to the cell.
  • the process may be operated with a direct current anode potential in the range from about 3V to about 7V, preferably from about 4V to about 6V.
  • a direct current anode potential in the range from about 3V to about 7V, preferably from about 4V to about 6V.
  • the selectivity with which the group -CH2F is fluorinated to the group -CHF2 is substantially increased by pulsing the anode potential, known also as applying a periodic potential.
  • This may be achieved, for example, by superimposing on a fixed direct current potential a periodic, fluctuating potential in a pulsating ,- and preferably alternating waveform, that is a pulsating waveform in which the maximum and minimum potentials of the pulse are of opposite polarity.
  • We particularly prefer to apply an alternating waveform which may have a square or rectangular waveform.
  • the increase in selectivity achieved by pulsing the anode potential is dependent, inter alia, upon the difference between the maximum and minimum potentials of the pulsed potential. It is preferred that the difference in potential between the maximum and minimum potentials of the pulse is at least 3V, preferably at least 4V and more preferably at least 5V.
  • Figure 1 is a vertical cross section through an electrochemical cell in which the process of the invention may be effected.
  • a 1.5 litre capacity electrochemical cell 1 comprises a Monel cell body 2 having channels 3 for circulation of a coolant fluid.
  • a Monel cell head 4 is provided having a series of ports 5 for a nickel reference electrode (not shown), thermocouple (not shown), hydrogen fluoride and nitrogen feeds (not shown) , a nickel anode connection 6 and a nickel cathode connection 7 and product vent port 8.
  • a Monel cell base 9 is provided having a substrate feed port 10 and drain ports 11.
  • an electrode stack 12 comprising alternating nickel mesh cathodes 13 and nickel foam anodes 14 separated by polytetrafluoroethylene spacer rings 15.
  • a nickel anode annulus 16 and nickel cathode annulus 17 are provided and the stack is supported on a polytetrafluoroethylene support ring 18. Electrical contact is made between the electrodes and the electrode connections with nickel tape 19 partially insulated with polytetrafluoroethylene sleeving.
  • the electrode stack is held together by nickel tie rods 20 and nickel end plates 21.
  • the cell In operation of the cell, the cell is charged with hydrogen fluoride and a potential is applied across the cell to first dry the hydrogen fluoride and to condition the anode surfaces.
  • the substrate is then fed to the cell through inlet 10 in the base of the cell and product and unreacted gas is collected through product vent port 8 in the head of the cell.
  • the invention is further illustrated by the following examples.
  • Example 1 Using the cell shown in Figure 1, 1.5 litres of hydrogen fluoride were charged to the cell and the hydrogen fluoride was dried electrochemically by applying an anode potential of 6V (with respect to the Nickel reference electrode). The anode potential was then reduced to 3.8V and the anode surface was conditioned for 48 hours.
  • a 10ml laboratory cell comprising a polytetrafluoroethylene ring sandwiched between two nickel sheet end plates to form a cylindrical cell body sealed with "0" rings constructed from hexafluoropropylene /vinylidene fluoride copolymer. Electrical contact was made from a source of electrical power to each of the nickel end plates, one of which acted as a cathode.
  • the anode consisted of a nickel foam cylinder (30mm diameter and 7mm thickness having a surface area of 5600cm 2 /cm 3 ) in ' electrical contact with the other nickel end plate through a nickel washer which served to form a small cavity behind the anode.
  • the substrate was fed into this cavity via a transfer pot connected by a vacuum line and fitted with a nitrogen purge.
  • the transfer pot was filled with hydrogen fluoride which acted as a pre-saturator and so as to minimise electrolyte loss from the cell.
  • the cell was charged with hydrogen fluoride, the hydrogen fluoride was dried and the anode surface conditioned by applying an anode potential of between 4V and 5V for 3-4 hours without a 1 , 1 , 1 , 2-tetrafluoroethane feed.
  • Undiluted 1 ,1 , 1 , 2-tetrafluoroethane was then fed to the cell with a flow rate of about 2.5ml/minute at an anode potential of 4.5V for a period of 8 hours.
  • the off gases from the cell were scrubbed with (i) potassium carbonate solution and (ii) water, to remove hydrogen fluoride and scrubbed with rubber chippings to remove OF2.
  • the gaseous products were collected in a liquid nitrogen cold trap and analysed by gas chromatography .
  • the average yield of pentafluoroethane over the 8 hour period was 402.
  • Example 4 The procedure of example 2 was repeated except that the anode potential was 6V and it was maintained for 3 hours. The yield of pentafluoroethane (excluding start-up time of 1 hours operation) was 602. Example 4.
  • Each pulsed anode potential was applied for about 2 hours .

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

Méthode de production d'un composé de formule: R-On-(R1)m-CHF2, dans laquelle R représente hydrogène ou un groupe alkyle C1-4 contenant du fluor, R1 représente un groupe méthylène éventuellement fluoré, m et n valent indépendamment 0 ou 1 à condition que lorsque n = 0, m = 0 et que lorsque n = 1, R ne représente pas hydrogène. La méthode consiste à soumettre un composé de formule: R-On-(R1)m-CH2F, dans laquelle R, R1, m et n sont comme définis ci-dessus, à une fluoration électrochimique dans un électrolyte constitué de fluorure d'hydrogène liquide.
PCT/GB1993/002463 1992-12-04 1993-11-30 Fluoration electrochimique WO1994013857A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP6513910A JPH08504001A (ja) 1992-12-04 1993-11-30 電気化学的弗素化方法
EP94900947A EP0672198A1 (fr) 1992-12-04 1993-11-30 Fluoration electrochimique

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
GB9225390.5 1992-12-04
GB9225375.6 1992-12-04
GB929225391A GB9225391D0 (en) 1992-12-04 1992-12-04 Electrochemical fluorination
GB929225384A GB9225384D0 (en) 1992-12-04 1992-12-04 Electrochemical fluorination
GB9225384.8 1992-12-04
GB929225375A GB9225375D0 (en) 1992-12-04 1992-12-04 Production of partially fluorinated ethers
GB9225391.3 1992-12-04
GB929225390A GB9225390D0 (en) 1992-12-04 1992-12-04 Production of pentafluorethane

Publications (1)

Publication Number Publication Date
WO1994013857A1 true WO1994013857A1 (fr) 1994-06-23

Family

ID=27450966

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1993/002463 WO1994013857A1 (fr) 1992-12-04 1993-11-30 Fluoration electrochimique

Country Status (3)

Country Link
EP (1) EP0672198A1 (fr)
JP (1) JPH08504001A (fr)
WO (1) WO1994013857A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998050603A1 (fr) * 1997-05-02 1998-11-12 Minnesota Mining And Manufacturing Company Fluoration electrochimique au moyen de courant de rupture
WO1999058745A1 (fr) * 1998-05-08 1999-11-18 Minnesota Mining And Manufacturing Company Fluoration electrochimique d'un substrat alcane
US6267865B1 (en) 1997-05-02 2001-07-31 3M Innovative Properties Company Electrochemical fluorination using interrupted current
WO2007040415A1 (fr) 2005-10-05 2007-04-12 Instytut Wysokich Cisnien Polskiej Akademii Nauk Procede permettant de mener des reactions chimiques et reacteur chimique
CN115572210A (zh) * 2022-12-08 2023-01-06 暨南大学 一种(1,2,2,2-四氟乙基)芳烃衍生物及其制备方法和应用

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US392228A (en) * 1888-11-06 Half to john i
DE1803893A1 (de) * 1967-11-02 1969-07-31 Phillips Petroleum Co Elektrochemische Fluorierung
US3511761A (en) * 1967-11-02 1970-05-12 Phillips Petroleum Co Electrochemical fluorination of organic compounds
US3617453A (en) * 1969-09-17 1971-11-02 Phillips Petroleum Co Temperature control in electrochemical conversion process
GB1257184A (fr) * 1968-10-22 1971-12-15
US3728233A (en) * 1968-06-24 1973-04-17 Phillips Petroleum Co Porous electrode having open feed cavity
EP0127365A2 (fr) * 1983-05-20 1984-12-05 Imperial Chemical Industries Plc Pompes à chaleur
EP0385737A1 (fr) * 1989-02-28 1990-09-05 Hampshire Chemical Corporation Réfrigérant à base de bis(difluorométhyl)éther

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US392228A (en) * 1888-11-06 Half to john i
DE1803893A1 (de) * 1967-11-02 1969-07-31 Phillips Petroleum Co Elektrochemische Fluorierung
US3511761A (en) * 1967-11-02 1970-05-12 Phillips Petroleum Co Electrochemical fluorination of organic compounds
US3728233A (en) * 1968-06-24 1973-04-17 Phillips Petroleum Co Porous electrode having open feed cavity
GB1257184A (fr) * 1968-10-22 1971-12-15
US3617453A (en) * 1969-09-17 1971-11-02 Phillips Petroleum Co Temperature control in electrochemical conversion process
EP0127365A2 (fr) * 1983-05-20 1984-12-05 Imperial Chemical Industries Plc Pompes à chaleur
EP0385737A1 (fr) * 1989-02-28 1990-09-05 Hampshire Chemical Corporation Réfrigérant à base de bis(difluorométhyl)éther

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998050603A1 (fr) * 1997-05-02 1998-11-12 Minnesota Mining And Manufacturing Company Fluoration electrochimique au moyen de courant de rupture
US6267865B1 (en) 1997-05-02 2001-07-31 3M Innovative Properties Company Electrochemical fluorination using interrupted current
US6391182B2 (en) 1997-05-02 2002-05-21 3M Innovative Properties Company Electrochemical fluorination using interrupted current
WO1999058745A1 (fr) * 1998-05-08 1999-11-18 Minnesota Mining And Manufacturing Company Fluoration electrochimique d'un substrat alcane
WO2007040415A1 (fr) 2005-10-05 2007-04-12 Instytut Wysokich Cisnien Polskiej Akademii Nauk Procede permettant de mener des reactions chimiques et reacteur chimique
CN115572210A (zh) * 2022-12-08 2023-01-06 暨南大学 一种(1,2,2,2-四氟乙基)芳烃衍生物及其制备方法和应用

Also Published As

Publication number Publication date
JPH08504001A (ja) 1996-04-30
EP0672198A1 (fr) 1995-09-20

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