CA2115135A1 - Process for purifying hydrogen fluoride - Google Patents
Process for purifying hydrogen fluorideInfo
- Publication number
- CA2115135A1 CA2115135A1 CA002115135A CA2115135A CA2115135A1 CA 2115135 A1 CA2115135 A1 CA 2115135A1 CA 002115135 A CA002115135 A CA 002115135A CA 2115135 A CA2115135 A CA 2115135A CA 2115135 A1 CA2115135 A1 CA 2115135A1
- Authority
- CA
- Canada
- Prior art keywords
- hydrogen fluoride
- water
- electrolysis
- electrolyte
- process according
- 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.)
- Abandoned
Links
Classifications
-
- 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
- C01B7/191—Hydrogen fluoride
- C01B7/195—Separation; Purification
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
- Water Treatment By Electricity Or Magnetism (AREA)
Abstract
Process for purifying hydrogen fluoride A b s t r a c t The invention relates to a process for purifying anhydrous industrial hydrogen fluoride by means of electrolysis with a water concentration of at least 200 ppm being maintained in the electrolyte.
Description
2 ~ 3 ~ ~
Process for purifying hydrogen fluoride The invention relates to a process for purifying anhydrous industrial hydrogen fluoride by means of electrolysis. -`
Industrially manufactured hydrogen fluoride (CaF2 ~ H2S0 2 HF ~ CaS04) generally occurs as anhydrous hydrogen fluoride, which contains some ~mpurities and small amounts of water, depending on the starting material (normally fluorspar).
The term "anhydrous hydrogen fluoride9' is understood to 15 mean a hydrogen fluoride as obtained by a conventional ~ ~
industrial process and having a water content of less than ~-5,000 mg of water/kg of hydrogen fluoride.
. , ~ , The impurities are substantially compounds of the elements arsenic, phosphorus, boron, silicon and sulphur.
. :
These compounds cause problems in many applications, and are therefore undesirable.
When aqueous hydrogen fluoride solutions are utilisPd in ;~ the manufacture of electronic components, the compounds of ; the elements arsenic, phosphorus, silicon and boron, particularly, cause problems. -In applications in which hydrogen fluoride and a catalyst :-are utilised, for example in the manufacture of fluorocarbons - substances which replace chlorofluoro- -carbons - it is the sulphur compounds which particularly ~ ~
give rise to problems. ;
---Le A 29 56~ - FC 1 .. ,. :, : ~ ~."`"' 2~513~
DE-A 4 031 967 and wo 91/13024 describe purification of anhydrous industrial hydrogen fluoride by means of electrolysis. In both processes the impurities are removed from the hydrogen fluoride by electrolysis using nickel or carbon electrodes.
When nickel electrodes are utilised a high level of electrode corrosion is observed during electrolysis. The resulting corrosion products lead to blockages of the 10 electrode gaps and of pipework and valves, giving rise to - ~
problems in terms of carrying out the process industrially. ~-'': .~.. ::
Carbon electrodes have proved to be not particularly suitable because of their short service life in anhydrous industrial hydrogen fluoride electrolysis.
. ,~
The object of the invention was therefore to provide a process for purifying industrial anhydrous hydrogen fluoride which does not have the disadvantages mentioned ~ -and which does not simultaneously complicate purification.
~; The process according to the invention was able to achieve ~ -this object.
~.
The present invention provides for a process for purifying industrial anhydrous hydrogen fluoride by means of electrolysis, characterised in that a water concentration in the electrolyte of at least 200 mg water/kg hydrogen ~
fluoride is maintained during electrolysis.
, The process according to the invention is carried out such $hat water or an aqueous hydrogen fluoride solution is ~dded to the electrolyte before or during electrolysis in order thus to maintain the required water content in case the hydrogen fluoride utilised contains insufficient water or water consumption during electrolysis is excessive.
Le A 29 568 2 - 2 ~
, ~ .. .. ~
Particularly preferably, the amount of water added is equal to that consumed by electrolysis, as long as the concentration in the electrolyte is at least 200 mg HzO/kg HF.
The water present in the hydrogen fluoride and that which is added is converted to oxygen, oxygen difluoride and hydrogen during electrolysis, based on the following reaction equations:
Equation I:
107.2 Ah -2 HzO > 2 H2 + 2 Equation II:
107.2 Ah H2O + 2 HF - ~ OF2 + 2 H2 .: ., .
; If more water is added than is consumed, electrolysis in `~
accordance with equations I and II must be prolonged in order to obtain a desired low water concentration.
Alternatively, excess water may be separated by distillation. ~ ;
The water or the aqueous hydrogen fluoride solution may be 30 added continuously or intermittently during electrolysis. ;
If the electrolysis to purify industrial hydrogen fluoride- ~`
; is carried out in accordance with the prior art, that is to -say not maintaining a certain water concentration in the electrolyte, the water concentration in the industrial ~' ' Le A 29 568 3 -;
2~13~
.-hydrogen fluoride to be purified will fall to zero, and severe electrode corrosion sets in. ~ .
It is particularly advantageous to carry out the electrolysis such that between 5 and 36 g of water areadded to the electrolyte for a charge of 107.2 Ah.
A markedly lower level of electrode corrosion is achieved when carrying out the process according to the invention ;~.
for purifying anhydrous industrial hydrogen fluoride than is the case with processes according to the prior art The process according to the invention is explained in greater detail with the aid of the Examples which follow.
~ ~ ' ~ ~ .
.
2~5~L3~
Example 1 (prior art according to DE 4 031 967~
An anhydrous industrial hydrogen fluoride containing 300 mg of water per kg of hydrogen fluoride was utilised to carry out the process according to DE 4 031 967. An electrolytic cell having a volume of 650 ml and an electrode pack comprising 4 nickel plate anodes (70 x 50 x 2 mm) and 5 nickel plate cathodes (70 x 50 x 2 mm~, with the electrodes disposed alternately, was filled with the hydrogen fluoride to be purified. The hydrogen fluoride -~
contained as an impurity, for example, 27 mg of arsenic per kg of hydrogen fluoride. ~ ~
15 A 1 Amp current was adjusted at the rectifier at 4.8 V. --This was equivalent to a current density of 3.69 mA~cm2. It was possible to keep the current density constant by constantly increasing the electrolytic voltage. The electrolytic voltage increased from an initial value of ~;
4.8 V to 6.7 ~ at the end of the experiment. The experiment was terminated after 4 hh charge had flowed. ;
-. :- ' ' i The content of the cell was analysed. The hydrogen fluoride present in the cell contained less than O.OZ mg arsenic per kg of hydrogen fluoride. More than 99.9% of the arsenic was removed.
Electrode corrosion was around 225 mg nickel loss per Ampere-hour. ~-Le A 29 568 5 . ~ . ' ;:
Process for purifying hydrogen fluoride The invention relates to a process for purifying anhydrous industrial hydrogen fluoride by means of electrolysis. -`
Industrially manufactured hydrogen fluoride (CaF2 ~ H2S0 2 HF ~ CaS04) generally occurs as anhydrous hydrogen fluoride, which contains some ~mpurities and small amounts of water, depending on the starting material (normally fluorspar).
The term "anhydrous hydrogen fluoride9' is understood to 15 mean a hydrogen fluoride as obtained by a conventional ~ ~
industrial process and having a water content of less than ~-5,000 mg of water/kg of hydrogen fluoride.
. , ~ , The impurities are substantially compounds of the elements arsenic, phosphorus, boron, silicon and sulphur.
. :
These compounds cause problems in many applications, and are therefore undesirable.
When aqueous hydrogen fluoride solutions are utilisPd in ;~ the manufacture of electronic components, the compounds of ; the elements arsenic, phosphorus, silicon and boron, particularly, cause problems. -In applications in which hydrogen fluoride and a catalyst :-are utilised, for example in the manufacture of fluorocarbons - substances which replace chlorofluoro- -carbons - it is the sulphur compounds which particularly ~ ~
give rise to problems. ;
---Le A 29 56~ - FC 1 .. ,. :, : ~ ~."`"' 2~513~
DE-A 4 031 967 and wo 91/13024 describe purification of anhydrous industrial hydrogen fluoride by means of electrolysis. In both processes the impurities are removed from the hydrogen fluoride by electrolysis using nickel or carbon electrodes.
When nickel electrodes are utilised a high level of electrode corrosion is observed during electrolysis. The resulting corrosion products lead to blockages of the 10 electrode gaps and of pipework and valves, giving rise to - ~
problems in terms of carrying out the process industrially. ~-'': .~.. ::
Carbon electrodes have proved to be not particularly suitable because of their short service life in anhydrous industrial hydrogen fluoride electrolysis.
. ,~
The object of the invention was therefore to provide a process for purifying industrial anhydrous hydrogen fluoride which does not have the disadvantages mentioned ~ -and which does not simultaneously complicate purification.
~; The process according to the invention was able to achieve ~ -this object.
~.
The present invention provides for a process for purifying industrial anhydrous hydrogen fluoride by means of electrolysis, characterised in that a water concentration in the electrolyte of at least 200 mg water/kg hydrogen ~
fluoride is maintained during electrolysis.
, The process according to the invention is carried out such $hat water or an aqueous hydrogen fluoride solution is ~dded to the electrolyte before or during electrolysis in order thus to maintain the required water content in case the hydrogen fluoride utilised contains insufficient water or water consumption during electrolysis is excessive.
Le A 29 568 2 - 2 ~
, ~ .. .. ~
Particularly preferably, the amount of water added is equal to that consumed by electrolysis, as long as the concentration in the electrolyte is at least 200 mg HzO/kg HF.
The water present in the hydrogen fluoride and that which is added is converted to oxygen, oxygen difluoride and hydrogen during electrolysis, based on the following reaction equations:
Equation I:
107.2 Ah -2 HzO > 2 H2 + 2 Equation II:
107.2 Ah H2O + 2 HF - ~ OF2 + 2 H2 .: ., .
; If more water is added than is consumed, electrolysis in `~
accordance with equations I and II must be prolonged in order to obtain a desired low water concentration.
Alternatively, excess water may be separated by distillation. ~ ;
The water or the aqueous hydrogen fluoride solution may be 30 added continuously or intermittently during electrolysis. ;
If the electrolysis to purify industrial hydrogen fluoride- ~`
; is carried out in accordance with the prior art, that is to -say not maintaining a certain water concentration in the electrolyte, the water concentration in the industrial ~' ' Le A 29 568 3 -;
2~13~
.-hydrogen fluoride to be purified will fall to zero, and severe electrode corrosion sets in. ~ .
It is particularly advantageous to carry out the electrolysis such that between 5 and 36 g of water areadded to the electrolyte for a charge of 107.2 Ah.
A markedly lower level of electrode corrosion is achieved when carrying out the process according to the invention ;~.
for purifying anhydrous industrial hydrogen fluoride than is the case with processes according to the prior art The process according to the invention is explained in greater detail with the aid of the Examples which follow.
~ ~ ' ~ ~ .
.
2~5~L3~
Example 1 (prior art according to DE 4 031 967~
An anhydrous industrial hydrogen fluoride containing 300 mg of water per kg of hydrogen fluoride was utilised to carry out the process according to DE 4 031 967. An electrolytic cell having a volume of 650 ml and an electrode pack comprising 4 nickel plate anodes (70 x 50 x 2 mm) and 5 nickel plate cathodes (70 x 50 x 2 mm~, with the electrodes disposed alternately, was filled with the hydrogen fluoride to be purified. The hydrogen fluoride -~
contained as an impurity, for example, 27 mg of arsenic per kg of hydrogen fluoride. ~ ~
15 A 1 Amp current was adjusted at the rectifier at 4.8 V. --This was equivalent to a current density of 3.69 mA~cm2. It was possible to keep the current density constant by constantly increasing the electrolytic voltage. The electrolytic voltage increased from an initial value of ~;
4.8 V to 6.7 ~ at the end of the experiment. The experiment was terminated after 4 hh charge had flowed. ;
-. :- ' ' i The content of the cell was analysed. The hydrogen fluoride present in the cell contained less than O.OZ mg arsenic per kg of hydrogen fluoride. More than 99.9% of the arsenic was removed.
Electrode corrosion was around 225 mg nickel loss per Ampere-hour. ~-Le A 29 568 5 . ~ . ' ;:
3 ~
Example 2 (process according to the invention) A hydrogen fluoride containing 300 mg of water per kg of hydrogen fluoride was utilised to carry out the process according to the invention. An electrolytic cell having a volume of 650 ml and an electrode pack comprising 4 nickel plate anodes (70 x 50 x 2 mm) ancl 5 nickel plate cathodes ~70 x 50 x 2 mm), with the electrodes disposed alternately, lo was filled with the hydrogen fluoride to be puri~ied. The hydrogen fluoride contained as an impurity, ~or example, 25 mg of arsenic per kg of hydrogen fluoride.
A 1 Amp current was adjusted at the rectifier at 4.65 V.
This was equivalent to a current density of 3.69 mA/cm2. A
total of 800 mg of water was added continuously during electrolysis, so that the water concentration in the electrolyte was 300 mg HzO~ The experiment was terminated after a charge of 4 Ah had flowed through.
The content of the cell was analysed. The hydrogen fluoride present in the cell contained less than 0.02 mg of arsenic per kg of hydrogen fluoride. More than 99.9% of the arsenic was removed.
No corrosion of the electrodes was observed.
.
~ , .
Le A 29 568 6 ~~
Example 2 (process according to the invention) A hydrogen fluoride containing 300 mg of water per kg of hydrogen fluoride was utilised to carry out the process according to the invention. An electrolytic cell having a volume of 650 ml and an electrode pack comprising 4 nickel plate anodes (70 x 50 x 2 mm) ancl 5 nickel plate cathodes ~70 x 50 x 2 mm), with the electrodes disposed alternately, lo was filled with the hydrogen fluoride to be puri~ied. The hydrogen fluoride contained as an impurity, ~or example, 25 mg of arsenic per kg of hydrogen fluoride.
A 1 Amp current was adjusted at the rectifier at 4.65 V.
This was equivalent to a current density of 3.69 mA/cm2. A
total of 800 mg of water was added continuously during electrolysis, so that the water concentration in the electrolyte was 300 mg HzO~ The experiment was terminated after a charge of 4 Ah had flowed through.
The content of the cell was analysed. The hydrogen fluoride present in the cell contained less than 0.02 mg of arsenic per kg of hydrogen fluoride. More than 99.9% of the arsenic was removed.
No corrosion of the electrodes was observed.
.
~ , .
Le A 29 568 6 ~~
Claims (7)
1. Process for purifying anhydrous industrial hydrogen fluoride by means of electrolysis of an electrolyte comprising hydrogen fluoride, wherein a water concentration in the electrolyte of at least 200 mg of water/kg of hydrogen fluoride is maintained during the electrolysis.
2. Process according to claim 1, wherein the concentration of the water in the electrolyte is maintained by addition of water or of an aqueous hydrogen fluoride solution to the electrolyte before or during electrolysis.
3. Process according to claim 2, wherein between 5 and 36 g of water are added to the electrolyte for a charge of 107.2 Ampere-hours.
4. Process according to claim 2, wherein the water is added continuously during the electrolysis.
5. Process according to claim 2, wherein the water is added intermittently during electrolysis.
6. Process according to claim 2, wherein all of the water added to the electrolyte is consumed during the electrolysis.
7. Process according to claim 2, wherein a portion of the water added to the electrolyte is not consumed during the electrolysis and said portion is removed by distillation after said electrolysis.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4303836A DE4303836C1 (en) | 1993-02-10 | 1993-02-10 | Anhydrous technical hydrofluoric acid purificn. by electrolysis - in presence of small amt. of water to minimise electrode corrosion |
| DEP4303836.0 | 1993-02-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2115135A1 true CA2115135A1 (en) | 1994-08-11 |
Family
ID=6480049
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002115135A Abandoned CA2115135A1 (en) | 1993-02-10 | 1994-02-07 | Process for purifying hydrogen fluoride |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0610749A1 (en) |
| JP (1) | JPH06263406A (en) |
| KR (1) | KR940019885A (en) |
| CN (1) | CN1100152A (en) |
| CA (1) | CA2115135A1 (en) |
| CZ (1) | CZ26694A3 (en) |
| DE (1) | DE4303836C1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9260306B2 (en) | 2008-11-28 | 2016-02-16 | Kyoto University | Hydrogen fluoride purification method |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110656344A (en) * | 2019-11-05 | 2020-01-07 | 贵州理工学院 | Device and method for removing water by using anhydrous hydrogen fluoride |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ES2077842T3 (en) * | 1990-03-02 | 1995-12-01 | Du Pont | PROCEDURE TO PURIFY HYDROGEN FLUORIDE. |
| DE4031967C1 (en) * | 1990-10-09 | 1992-05-27 | Bayer Ag, 5090 Leverkusen, De |
-
1993
- 1993-02-10 DE DE4303836A patent/DE4303836C1/en not_active Expired - Fee Related
-
1994
- 1994-01-28 EP EP94101270A patent/EP0610749A1/en not_active Withdrawn
- 1994-02-04 JP JP6032074A patent/JPH06263406A/en active Pending
- 1994-02-07 CA CA002115135A patent/CA2115135A1/en not_active Abandoned
- 1994-02-08 CZ CZ94266A patent/CZ26694A3/en unknown
- 1994-02-08 KR KR1019940002424A patent/KR940019885A/en not_active Application Discontinuation
- 1994-02-09 CN CN94101809A patent/CN1100152A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9260306B2 (en) | 2008-11-28 | 2016-02-16 | Kyoto University | Hydrogen fluoride purification method |
Also Published As
| Publication number | Publication date |
|---|---|
| DE4303836C1 (en) | 1994-03-17 |
| CZ26694A3 (en) | 1994-08-17 |
| EP0610749A1 (en) | 1994-08-17 |
| CN1100152A (en) | 1995-03-15 |
| KR940019885A (en) | 1994-09-15 |
| JPH06263406A (en) | 1994-09-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |