WO2009074562A1 - Process for the purification of elemental fluorine - Google Patents

Process for the purification of elemental fluorine Download PDF

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Publication number
WO2009074562A1
WO2009074562A1 PCT/EP2008/067088 EP2008067088W WO2009074562A1 WO 2009074562 A1 WO2009074562 A1 WO 2009074562A1 EP 2008067088 W EP2008067088 W EP 2008067088W WO 2009074562 A1 WO2009074562 A1 WO 2009074562A1
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WO
WIPO (PCT)
Prior art keywords
fluorine
manganese
fluoride
process according
equal
Prior art date
Application number
PCT/EP2008/067088
Other languages
French (fr)
Inventor
Ulrich Seseke-Koyro
Placido Garcia-Juan
Stefan Palsherm
Alf Schulz
Original Assignee
Solvay Fluor 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 Solvay Fluor Gmbh filed Critical Solvay Fluor Gmbh
Publication of WO2009074562A1 publication Critical patent/WO2009074562A1/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B7/00—Halogens; Halogen acids
    • C01B7/19—Fluorine; Hydrogen fluoride
    • C01B7/20—Fluorine

Definitions

  • the invention concerns a process for the purification of elemental fluorine.
  • Elemental fluorine can be applied to introduce one or more fluorine atoms into chemical compounds, e.g. by substituting fluorine atoms for hydrogen atoms or by the addition to carbon-carbon double bonds. Further, it is applicable as etching agent in the production of semiconductors, e.g. those based on silicon. It also can be used as purifying gas for reactor chambers used in the production of semiconductors. It is well known that in reactor chambers, residues may form, for example, after application of NF3 or hydrofluorocarbons as etching gas. Such residues can be removed with elemental fluorine. Especially when applied in the semiconductor industry, fluorine has to be of a high purity.
  • a method for the purification of fluorine is described in US patent 3,989,808.
  • a mixture of KF and NiF 2 in a molar ratio of 3:1 is prepared, and then, in a reactor, the mixture is contacted in a batch process with impure fluorine at a pressure of about 10 atm.
  • the temperature is slowly brought to 500 0 C and then lowered to 25O 0 C.
  • K 2 NiF 6 is formed in this process.
  • the temperature is brought to 225 0 C, and the reactor is evacuated. Gaseous impurities are removed during evacuation.
  • the content of the reactor when heated to 500 0 C, liberates purified fluorine.
  • the remaining nickel salt can again be contacted with impure fluorine, and the purification process can be started again.
  • EP patent application 1580163 discloses a process for production of fluorine in which binary metal fluorides or complex metal fluorides with a high degree of oxidation are heated to a temperature between 15O 0 C and 400 0 C.
  • the metal compound is applied in the form of granules or pellets of a size between 1.0 to 3.0 mm.
  • the process according to the present invention for the preparation of purified elemental fluorine comprising a step wherein fluorine which includes impurities is contacted with solid manganese fluoride passing the fluorine over and/or through solid manganese fluoride. Fluorine with a reduced content in impurities is obtained and leaves the reactor ; usually, the amount of fluorine fed into the reactor in a period of time corresponds approximately to the amount of fluorine leaving the reactor in the same period of time.
  • the fluorine leaving the reactor can be compressed and stored. Passing the fluorine over and/or through solid manganese fluoride and withdrawing purified fluorine from the reactor thus is a continuous process, not a process performed batch wise.
  • the continuous passing of fluorine can, of course, be interrupted, if desired, and continued after any interruption. For example, passing fluorine through the reactor can be interrupted if manganese fluoride must be regenerated.
  • the process of the present invention is suitable to purify fluorine which comprises water, hydrogen fluoride, oxygen and/or heavy metals, especially, oxygen and heavy metals, especially tungsten and arsenic.
  • the source for impurities in fluorine e.g. those mentioned above, can be impurities already contained in the raw material used for fluorine preparation, e.g. in hydrogen fluoride (which may comprise small amounts of arsenic compounds) as a fluorine source, handling, or impurities as a result of the specific use of the fluorine (for example, as mentioned above, as etching gas or chamber cleaning gas.
  • heavy metal impurities may be introduced from the metal of the walls of the reactor chamber, e.g. nickel or iron, or from reactants used in the chamber, e.g. tungsten).
  • gallium compounds can be removed (gallium arsenide is for example used in semiconductor manufacture).
  • impure fluorine is passed over and/or through solid manganese fluoride.
  • the solid manganese fluoride can, for example, be arranged as fixed bed or as fluidized bed in the form of particulate material, e.g. as a powder. While in the state of the art, the contact between impure fluorine and manganese fluoride was performed batch wise in a manner that fluorine was adsorbed and later released, in the process of the present invention, the contact is performed continuously. After contact with the manganese fluoride, purified fluorine leaves the reactor in which it was contacted with manganese fluoride. A part of fluorine reacts with the manganese fluoride to form higher fluorinated manganese fluoride. It can be released by thermal treatment.
  • the contact between manganese fluoride and fluorine to be purified is performed at a temperature above room temperature.
  • the temperature is equal to or greater than 100 0 C. More preferably, the temperature is equal to or greater than 15O 0 C. Generally, the temperature is equal to or lower than 55O 0 C.
  • the temperature is equal to or lower than 500 0 C. More preferably, the temperature is equal to or lower than 45O 0 C.
  • a highly preferred range is between 25O 0 C and 400 0 C.
  • the pressure during contact between fluorine and the manganese fluoride is variable. Preferably, it is equal to or greater than 1 bar (abs). More preferably, it is equal to or greater than 2 bars( abs). Preferably, it is equal to or lower than 10 bars (abs).
  • manganese fluoride in a preferred embodiment, denotes manganese difluoride, manganese trifluoride and manganese tetrafluoride and any mixtures of two or all compounds. It is possible to apply manganese difluoride, manganese trifluoride or manganese tetrafluoride as single compounds. In a preferred embodiment, manganese difluoride or manganese trifluoride is applied. During contact with the elemental fluorine, it is oxidized, and manganese trifluoride and/or manganese tetrafluoride is formed. Often, during contact of the manganese fluoride with elemental fluorine, mixtures comprising essentially manganese trifluoride and manganese tetrafluoride are formed.
  • the particle size of the manganese fluoride is likewise variable. Particles with a size of equal to or greater than 0.1 ⁇ m up to some millimeters, e.g. up to 5 mm, are suitable. Preferably, the particle size is equal to or greater than l ⁇ m. Preferably, the particle size is equal to or smaller than 0.5 mm, especially preferably, equal to or smaller than 200 ⁇ m. It is understood that some amount of undersized or oversized particles may be present. Preferably, equal to or less than 5 % of the number of particles are smaller than the lower size limits mentioned above, and equal to or less than 5 % of the number of particles are greater than the upper size limits mentioned above.
  • At least two reactors are applied alternating.
  • the process according to the present invention can be performed permanently in a continuous manner ; if only one reactor is used, the continuous process must be stopped from time to time when manganese fluoride must be regenerated. If two or more reactors are used, then one or more reactors are used for purification, the other one or other ones are treated to regenerate manganese fluoride. Regeneration can be effected by heating it up to 55O 0 C, for example in a flow of inert gas, e.g. nitrogen. Manganese trifluoride forms hereby. - A -
  • spent manganese fluoride can be substituted by fresh material (manganese difluoride or manganese trifluoride or their mixtures).
  • the content of water, hydrogen fluoride, oxygen or heavy metals and other impurities in elemental fluorine can be reduced ; especially the oxygen content and the content in heavy metals.
  • manganese fluoride forms manganese oxyfluorides, hydroxyfluorides or manganese metallates with the impurities.
  • the purification treatment can be repeated until the desired degree of purity is achieved.
  • impure fluorine to be treated must not contain all of said impurities. Impure fluorine comprising only one or two of said impurities can likewise be treated.
  • the purified fluorine passing through the manganese fluoride can then be used for those purposes for which purified fluorine is needed.
  • the fluorine which reacts with the manganese fluoride to form manganese tetrafluoride can be released by heating the manganese tetrafluoride to about 400 0 C and then is ready for use in reactions where purified fluorine is needed.
  • the process is very advantageous because it allows a continuous purification treatment of elemental fluorine.
  • Manganese difluoride is filled in two reactors made from nickel, Monel or other fluorine-resistant metal. Then, the temperature is raised to 35O 0 C, and elemental fluorine comprising an arsenic compound is passed through the manganese difluoride. Simultaneously to the adsorption of the arsenic compound, manganese trifluoride and later manganese tetrafluoride is formed. Pruified fluoride leaves the reactor, can be compressed and stored for later use. To regenerate the first reactor, the flow of fluorine through the first of the reactors is stopped, the second reactor is heated and the impure elemental fluorine is passed through that reactor. The content of the first reactor can be dumped, or it can be regenerated by heating it up to 500 0 C, optionally passing nitrogen through it. Here, fluorine is split off.

Abstract

Elemental fluorine can be purified by contact with manganese fluoride. Especially heavy metals can be remove d from the elemental fluorine which is passed over and/or through the manganese fluoride. Purified fluorine leaves the reactor. A part of the fluorine may react with manganese fluoride to form manganese tetrafluoride. Manganese tetrafluoride can be heated so that fluorine splits off which also is ready for use.

Description

Process for the purification of elemental fluorine
The invention concerns a process for the purification of elemental fluorine. Elemental fluorine can be applied to introduce one or more fluorine atoms into chemical compounds, e.g. by substituting fluorine atoms for hydrogen atoms or by the addition to carbon-carbon double bonds. Further, it is applicable as etching agent in the production of semiconductors, e.g. those based on silicon. It also can be used as purifying gas for reactor chambers used in the production of semiconductors. It is well known that in reactor chambers, residues may form, for example, after application of NF3 or hydrofluorocarbons as etching gas. Such residues can be removed with elemental fluorine. Especially when applied in the semiconductor industry, fluorine has to be of a high purity. A method for the purification of fluorine is described in US patent 3,989,808. A mixture of KF and NiF2 in a molar ratio of 3:1 is prepared, and then, in a reactor, the mixture is contacted in a batch process with impure fluorine at a pressure of about 10 atm. The temperature is slowly brought to 5000C and then lowered to 25O0C. K2NiF6 is formed in this process. After several cycles of heating up and cooling down, the temperature is brought to 2250C, and the reactor is evacuated. Gaseous impurities are removed during evacuation. The content of the reactor, when heated to 5000C, liberates purified fluorine. After termination of fluorine liberation, the remaining nickel salt can again be contacted with impure fluorine, and the purification process can be started again.
EP patent application 1580163 discloses a process for production of fluorine in which binary metal fluorides or complex metal fluorides with a high degree of oxidation are heated to a temperature between 15O0C and 4000C. The metal compound is applied in the form of granules or pellets of a size between 1.0 to 3.0 mm.
It is an object of the present invention to provide a process for the purification of fluorine which allows the purification of elemental fluorine in a quick and simple manner. This object and other objects are achieved by the process of the present invention.
The process according to the present invention for the preparation of purified elemental fluorine comprising a step wherein fluorine which includes impurities is contacted with solid manganese fluoride passing the fluorine over and/or through solid manganese fluoride. Fluorine with a reduced content in impurities is obtained and leaves the reactor ; usually, the amount of fluorine fed into the reactor in a period of time corresponds approximately to the amount of fluorine leaving the reactor in the same period of time. The fluorine leaving the reactor can be compressed and stored. Passing the fluorine over and/or through solid manganese fluoride and withdrawing purified fluorine from the reactor thus is a continuous process, not a process performed batch wise. The continuous passing of fluorine can, of course, be interrupted, if desired, and continued after any interruption. For example, passing fluorine through the reactor can be interrupted if manganese fluoride must be regenerated.
The process of the present invention is suitable to purify fluorine which comprises water, hydrogen fluoride, oxygen and/or heavy metals, especially, oxygen and heavy metals, especially tungsten and arsenic. The source for impurities in fluorine, e.g. those mentioned above, can be impurities already contained in the raw material used for fluorine preparation, e.g. in hydrogen fluoride (which may comprise small amounts of arsenic compounds) as a fluorine source, handling, or impurities as a result of the specific use of the fluorine (for example, as mentioned above, as etching gas or chamber cleaning gas. Here, heavy metal impurities may be introduced from the metal of the walls of the reactor chamber, e.g. nickel or iron, or from reactants used in the chamber, e.g. tungsten). Further, gallium compounds can be removed (gallium arsenide is for example used in semiconductor manufacture).
In the purification step, impure fluorine is passed over and/or through solid manganese fluoride. The solid manganese fluoride can, for example, be arranged as fixed bed or as fluidized bed in the form of particulate material, e.g. as a powder. While in the state of the art, the contact between impure fluorine and manganese fluoride was performed batch wise in a manner that fluorine was adsorbed and later released, in the process of the present invention, the contact is performed continuously. After contact with the manganese fluoride, purified fluorine leaves the reactor in which it was contacted with manganese fluoride. A part of fluorine reacts with the manganese fluoride to form higher fluorinated manganese fluoride. It can be released by thermal treatment.
The contact between manganese fluoride and fluorine to be purified is performed at a temperature above room temperature. Preferably, the temperature is equal to or greater than 1000C. More preferably, the temperature is equal to or greater than 15O0C. Generally, the temperature is equal to or lower than 55O0C. Preferably, the temperature is equal to or lower than 5000C. More preferably, the temperature is equal to or lower than 45O0C. A highly preferred range is between 25O0C and 4000C. The pressure during contact between fluorine and the manganese fluoride is variable. Preferably, it is equal to or greater than 1 bar (abs). More preferably, it is equal to or greater than 2 bars( abs). Preferably, it is equal to or lower than 10 bars (abs).
The term "manganese fluoride" in a preferred embodiment, denotes manganese difluoride, manganese trifluoride and manganese tetrafluoride and any mixtures of two or all compounds. It is possible to apply manganese difluoride, manganese trifluoride or manganese tetrafluoride as single compounds. In a preferred embodiment, manganese difluoride or manganese trifluoride is applied. During contact with the elemental fluorine, it is oxidized, and manganese trifluoride and/or manganese tetrafluoride is formed. Often, during contact of the manganese fluoride with elemental fluorine, mixtures comprising essentially manganese trifluoride and manganese tetrafluoride are formed.
The particle size of the manganese fluoride is likewise variable. Particles with a size of equal to or greater than 0.1 μm up to some millimeters, e.g. up to 5 mm, are suitable. Preferably, the particle size is equal to or greater than lμm. Preferably, the particle size is equal to or smaller than 0.5 mm, especially preferably, equal to or smaller than 200 μm. It is understood that some amount of undersized or oversized particles may be present. Preferably, equal to or less than 5 % of the number of particles are smaller than the lower size limits mentioned above, and equal to or less than 5 % of the number of particles are greater than the upper size limits mentioned above.
In a preferred embodiment, at least two reactors are applied alternating. In this manner, the process according to the present invention can be performed permanently in a continuous manner ; if only one reactor is used, the continuous process must be stopped from time to time when manganese fluoride must be regenerated. If two or more reactors are used, then one or more reactors are used for purification, the other one or other ones are treated to regenerate manganese fluoride. Regeneration can be effected by heating it up to 55O0C, for example in a flow of inert gas, e.g. nitrogen. Manganese trifluoride forms hereby. - A -
Alternatively, spent manganese fluoride can be substituted by fresh material (manganese difluoride or manganese trifluoride or their mixtures).
With the purification process according to the present invention, the content of water, hydrogen fluoride, oxygen or heavy metals and other impurities in elemental fluorine can be reduced ; especially the oxygen content and the content in heavy metals. It is assumed that manganese fluoride forms manganese oxyfluorides, hydroxyfluorides or manganese metallates with the impurities. If desired, the purification treatment can be repeated until the desired degree of purity is achieved. Of course, impure fluorine to be treated must not contain all of said impurities. Impure fluorine comprising only one or two of said impurities can likewise be treated. The purified fluorine passing through the manganese fluoride can then be used for those purposes for which purified fluorine is needed. The fluorine which reacts with the manganese fluoride to form manganese tetrafluoride can be released by heating the manganese tetrafluoride to about 4000C and then is ready for use in reactions where purified fluorine is needed.
The process is very advantageous because it allows a continuous purification treatment of elemental fluorine.
The following example is intended to explain the invention further without limiting it. Example
Manganese difluoride is filled in two reactors made from nickel, Monel or other fluorine-resistant metal. Then, the temperature is raised to 35O0C, and elemental fluorine comprising an arsenic compound is passed through the manganese difluoride. Simultaneously to the adsorption of the arsenic compound, manganese trifluoride and later manganese tetrafluoride is formed. Pruified fluoride leaves the reactor, can be compressed and stored for later use. To regenerate the first reactor, the flow of fluorine through the first of the reactors is stopped, the second reactor is heated and the impure elemental fluorine is passed through that reactor. The content of the first reactor can be dumped, or it can be regenerated by heating it up to 5000C, optionally passing nitrogen through it. Here, fluorine is split off.

Claims

C L A I M S
1. Process for the preparation of fluorine with reduced content of impurities wherein fluorine containing impurities is contacted with solid manganese fluoride passing the fluorine over and/or through solid manganese fluoride.
2. Process according to claim 1 wherein fluorine is treated which contains water, HF, oxygen and/or heavy metals as impurities.
3. Process according to claim 1 wherein fluorine and manganese fluoride are contacted at a temperature equal to or greater than 1000C.
4. Process according to claim 1 wherein fluorine and manganese fluoride are contacted at a temperature of equal to or less than 5000C.
5. Process according to claim 1 wherein manganese difluoride, manganese trifluoride or manganese tetrafluoride, or mixtures of two or all three compounds are applied.
6. Process according to claim 5 wherein manganese difluoride or manganese trifluoride or their mixtures is applied.
7. Process according to claim 5 wherein regenerated manganese trifluoride is applied.
8. Process according to claim 1 wherein the particles of the manganese fluoride are equal to or greater than 0.5 μm.
9. Process according to claim 1 wherein the particles of manganese fluoride are equal to or smaller than 0.5 mm.
10. Process according to claim 1 wherein an apparatus comprising at least two reactors is applied which are used for fluorine treatment in alternating mode for purification and regeneration.
PCT/EP2008/067088 2007-12-11 2008-12-09 Process for the purification of elemental fluorine WO2009074562A1 (en)

Applications Claiming Priority (2)

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EP07122860.5 2007-12-11
EP07122860 2007-12-11

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3989808A (en) * 1975-07-28 1976-11-02 The United States Of America As Represented By The United States Energy Research And Development Administration Method of preparing pure fluorine gas
EP1580163A1 (en) * 2002-12-20 2005-09-28 Zakrytoye Aktsionernoye Obschestvo "Astor Electronics" Fluorine production method
WO2006033480A1 (en) * 2004-09-23 2006-03-30 Astor Electronics Jsc Method of manufacturing manganese tetrafluoride
JP2007176768A (en) * 2005-12-28 2007-07-12 Showa Denko Kk Method for producing fluorine gas
JP2007176770A (en) * 2005-12-28 2007-07-12 Showa Denko Kk Method of producing high purity fluorine gas and apparatus for producing high purity fluorine gas

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3989808A (en) * 1975-07-28 1976-11-02 The United States Of America As Represented By The United States Energy Research And Development Administration Method of preparing pure fluorine gas
EP1580163A1 (en) * 2002-12-20 2005-09-28 Zakrytoye Aktsionernoye Obschestvo "Astor Electronics" Fluorine production method
WO2006033480A1 (en) * 2004-09-23 2006-03-30 Astor Electronics Jsc Method of manufacturing manganese tetrafluoride
JP2007176768A (en) * 2005-12-28 2007-07-12 Showa Denko Kk Method for producing fluorine gas
JP2007176770A (en) * 2005-12-28 2007-07-12 Showa Denko Kk Method of producing high purity fluorine gas and apparatus for producing high purity fluorine gas

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
RAKOV E G ET AL: "MANUFACTURE OF PURE GASEOUS FLUORINE", CHEMICAL ABSTRACTS + INDEXES, AMERICAN CHEMICAL SOCIETY. COLUMBUS, US, vol. 110, no. 14, 3 April 1989 (1989-04-03), pages 169, XP000056099, ISSN: 0009-2258 *

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