EP0219157B1 - Process for the electrolytic production of metals - Google Patents
Process for the electrolytic production of metals Download PDFInfo
- Publication number
- EP0219157B1 EP0219157B1 EP19860201679 EP86201679A EP0219157B1 EP 0219157 B1 EP0219157 B1 EP 0219157B1 EP 19860201679 EP19860201679 EP 19860201679 EP 86201679 A EP86201679 A EP 86201679A EP 0219157 B1 EP0219157 B1 EP 0219157B1
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- EP
- European Patent Office
- Prior art keywords
- metal
- cathode
- alloy
- titanium
- molten
- 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.)
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/26—Electrolytic production, recovery or refining of metals by electrolysis of melts of titanium, zirconium, hafnium, tantalum or vanadium
- C25C3/28—Electrolytic production, recovery or refining of metals by electrolysis of melts of titanium, zirconium, hafnium, tantalum or vanadium of titanium
Definitions
- the invention relates to a process for the electrolytic production of metals from metal halides in the presence of a salt melt of one or more alkali metal or alkaline earth metal halides, in particular chlorides, an example thereof being production of titanium from titanium tetrachloride.
- Winning metals by electrolysis in the presence of molten salts is an area in which increasing research is being carried out.
- An embodiment of this process is known from US-A 2 757 135.
- titanium tetrachloride is supplied to the electrolysis cell by introducing into the salt melt.
- that process has to be carried out with a diaphragm that prevents the flow of titanium in lower valencies to the anode. If this were not done, the titanium would be re-oxidized at the anode to tetravalent titanium and would thus give rise to a loss of current and raw material.
- the build-up of titanium in the diaphragm shortens its life, which is a significant disadvantage.
- the present invention proposes a process for the production of metals Me by electrolysis in the presence of a salt melt of one or more alkali metal or alkaline earth metal halides without using any bipolar electrode which comprises introducing a metal halide MeXn into a cathode consisting of a molten metal M or a molten alloy M.Me x , in which Me represents a metal selected from Ti, Hf, Ta, AI, Zr, W, Nb, V, Mo, In, and Ag, M represents a metal selected from Zn, Cd, Sn, Pb, In, Bi and Ga, X represents halogen, n represents the valency of the metal Me and X represents the atomic ratio of Me to M, thus producing an alloy M.Mey in which y represents the atomic ratio of Me to M, y:x being > 1, withdrawing alloy M.Mey from the cathode into which the metal halide was introduced and recovering metal Me from the alloy.
- Me represents a metal selected
- cell 1 is in a jacket of thermally insulating material 2, for example refractory brick.
- Cathode 3 consists of liquid zinc to which current is fed via insulating pipe 4 and feed rod 4a.
- Supply of titanium tetrachloride takes place via pipe 5 and distributor 6, for example a metal grid with outlets at intervals or a body of porous ceramic material.
- Anode 7 is positioned in electrolyte 8 near the interface between cathode and electrolyte.
- the horizontal surface area of the anode is chosen to be as large as possible.
- Electrolyte 8 for example a lithium chloride/potassium chloride melt, is heated to a high temperature, for example 350 to 900 ° C or higher if operations are carried out under pressure.
- Through lid 9 runs a supply pipe 10 for inert gas, for example argon, and a discharge pipe 11 for chlorine gas which is generated at the anode.
- the current and the supply of titanium tetrachloride are adjusted to match each other such that all or substantially all titanium is reduced in the cathode, thus forming a zinc/titanium alloy.
- Vaporization of titanium tetrachloride before its introduction into the cathode is not necessary, since its temperature rises in any case to above its boiling point (136 ° C) during its passage through the salt melt.
- the cell can also be provided with means for a correct temperature control of the process.
- the space above electrolyte 8 can also be cooled or any vaporized salt melt of zinc can be internally or externally condensed and fed back.
- Supply and discharge of cathode liquid takes place via lines 12 and 13, in particular in the continuous embodiment.
- the titanium content in the Zn/Ti alloy will be allowed to increase to a predetermined value, preferably between 6 and 20 %wt. Recovery of titanium metal from the alloy may be carried out by conventional methods, e.g. by distilling off cathode metal.
- FIG. 2 shows a cell with a vertically positioned anode.
- the same reference numerals have been retained for the same elements of the construction.
- a tray 14 is placed in which liquid zinc is present. Titanium tetrachloride vapour now enters via perforations in the lower part of supply pipe 5.
- Anode 7 is constructed as a closed cylinder which completely surrounds the cathode.
- metal Me proceeds via the direct electrolytic conversion of for example Ti4+ ⁇ + 4e -7 Ti.
- Introduction of TiC1 4 into a liquid zinc cathode at elevated temperature may result in a chemical reduction of metal Me to lower valencies, for example 2TiCI 4 + Zn - 7 2TiCl ⁇ + ZnCi 2 , this may then be followed by electrolytic reduction of trivalent titanium to metallic (zerovalent) titanium, coupled with electrolytic regeneration of cathode material by reducing divalent zinc to metallic (zerovalent) zinc.
- Such combined chemical and electrolytic reductions of metal Me in a higher valency to zerovalent metal are included expressis verbis in the scope of this invention, so is the production of zerovalent tantalum from TaCls in a liquid zinc cathode which probably proceeds entirely via chemical reduction by metallic zinc and electrolytic regeneration (reduction) of cathode material.
- What is essential to this invention is the application of an electrolytic cell with a liquid metal or alloy cathode, an introduction of metal halide MeXn directly into the liquid cathode and production of (zerovalent) metal Me within the cathode material, the latter as distinguished from production of metal Me somewhere else, i.e. in the molten salt electrolyte or by deposition on a second or auxiliary cathode. Absence of a diaphragm is also important.
- the salt melts may be free from impurities but this is not strictly necessary, while in addition it may be advantageous to work under an inert atmosphere of, for example, argon or nitrogen.
- suitable salt melts are LiCI/NaCl, NaCI/KCI, LiCI/KCI, LiCl/CaCl 2 , NaCl/BaCl 2 and KCI/CaCI 2 , but, as has already been pointed out, the invention is not limited to the above-mentioned melts.
- suitable processing temperatures are above the melting point of the cathode material and below the temperature at which that material has such a vapour pressure that undesirably large losses occur.
- Preferred temperatures are between 400 and 900 °C, for zinc 425 to 890 ° C, for cadmium 400 to 700 °C.
- the processing temperature should not be so high that loss of molten salt electrolyte by evaporation or decomposition becomes substantial.
- the current and the supply of metal halide feedstock are so adjusted that complete reduction of metal Me in the cathode can take place.
- at least n F.mol- I metal halide MeX n is supplied, n being the valency of the metal.
- the current is, however, restricted to a certain maximum, since deposition of salt-melt metal in the cathode should preferably be prevented as far as possible.
- the feedstock should preferably be introduced under homogeneous distribution into the cathode. The easiest way for achieving this is by using feedstocks that are in gaseous form on the moment of their introduction into the cathode material. However, introduction into the cathode of compounds in finely dispersed, solid form is also included within the scope of this invention.
- M.Mey that is withdrawn from the electrolysis cell y represents the atomic ratio of Me to M. This ratio will usually be kept below 0.5, preferably below 0.3. For easier ways of recovering metal Me from the alloy it is preferred to process alloys in which the content of metal Me is of from 6 to 20 %wt, based on the weight of the alloy.
- the invention is elucidated below by a number of experiments.
- Residual oxygen compounds and metallic impurities are then removed by electrolysis under vacuum at a cell voltage of 2.7 V.
- An electrolytic cell of externally heated stainless steel was employed with a molten zinc cathode (90 g) which was placed in a holder of A1 2 0 3 on the bottom of the cell.
- a graphite rod served as anode, no diaphragm was used and 250 g salt melt was used as electrolyte.
- the cell voltage was 5.0 V
- the cathode potential was -2.0 V (relative to an Ag/AgCI reference electrode) and the other conditions are given in Table I.
- the TiC1 4 was injected as a liquid in an argon stream and fed into the cathode. An argon atmosphere was maintained above the salt melt.
- a current of 6 F.mol- 1 TiCI 4 was employed. The following results were determined by microprobe and chemical analysis of the cooled solids.
- TiCl 4 was electrolysed in the manner described in example la, under the same conditions except those indicated in Table II.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electrolytic Production Of Metals (AREA)
Description
- The invention relates to a process for the electrolytic production of metals from metal halides in the presence of a salt melt of one or more alkali metal or alkaline earth metal halides, in particular chlorides, an example thereof being production of titanium from titanium tetrachloride.
- Winning metals by electrolysis in the presence of molten salts is an area in which increasing research is being carried out. An embodiment of this process is known from US-A 2 757 135. In this event titanium tetrachloride is supplied to the electrolysis cell by introducing into the salt melt. In practice, that process has to be carried out with a diaphragm that prevents the flow of titanium in lower valencies to the anode. If this were not done, the titanium would be re-oxidized at the anode to tetravalent titanium and would thus give rise to a loss of current and raw material. Furthermore, the build-up of titanium in the diaphragm shortens its life, which is a significant disadvantage.
- The present invention proposes a process for the production of metals Me by electrolysis in the presence of a salt melt of one or more alkali metal or alkaline earth metal halides without using any bipolar electrode which comprises introducing a metal halide MeXn into a cathode consisting of a molten metal M or a molten alloy M.Mex, in which Me represents a metal selected from Ti, Hf, Ta, AI, Zr, W, Nb, V, Mo, In, and Ag, M represents a metal selected from Zn, Cd, Sn, Pb, In, Bi and Ga, X represents halogen, n represents the valency of the metal Me and X represents the atomic ratio of Me to M, thus producing an alloy M.Mey in which y represents the atomic ratio of Me to M, y:x being > 1, withdrawing alloy M.Mey from the cathode into which the metal halide was introduced and recovering metal Me from the alloy.
- The invention will be discussed in more detail with reference to figures 1 and 2, which illustrate possible electrolytic cells, taking the electrolysis of titanium tetrachloride to produce metallic titanium in a liquid zinc cathode as example.
- In Fig. 1 cell 1 is in a jacket of thermally insulating material 2, for example refractory brick.
Cathode 3 consists of liquid zinc to which current is fed via insulating pipe 4 andfeed rod 4a. Supply of titanium tetrachloride takes place via pipe 5 and distributor 6, for example a metal grid with outlets at intervals or a body of porous ceramic material. Anode 7 is positioned in electrolyte 8 near the interface between cathode and electrolyte. The horizontal surface area of the anode is chosen to be as large as possible. Electrolyte 8, for example a lithium chloride/potassium chloride melt, is heated to a high temperature, for example 350 to 900 °C or higher if operations are carried out under pressure. Throughlid 9 runs asupply pipe 10 for inert gas, for example argon, and a discharge pipe 11 for chlorine gas which is generated at the anode. The current and the supply of titanium tetrachloride are adjusted to match each other such that all or substantially all titanium is reduced in the cathode, thus forming a zinc/titanium alloy. This means that the anode does not need to be shielded by a diaphragm. This can be achieved with, for example a current of at least 4 Faraday per mol titanium tetrachloride. Vaporization of titanium tetrachloride before its introduction into the cathode is not necessary, since its temperature rises in any case to above its boiling point (136 °C) during its passage through the salt melt. If desired, the cell can also be provided with means for a correct temperature control of the process. The space above electrolyte 8 can also be cooled or any vaporized salt melt of zinc can be internally or externally condensed and fed back. Supply and discharge of cathode liquid takes place vialines 12 and 13, in particular in the continuous embodiment. The titanium content in the Zn/Ti alloy will be allowed to increase to a predetermined value, preferably between 6 and 20 %wt. Recovery of titanium metal from the alloy may be carried out by conventional methods, e.g. by distilling off cathode metal. - Figure 2 shows a cell with a vertically positioned anode. The same reference numerals have been retained for the same elements of the construction. In the salt melt a
tray 14 is placed in which liquid zinc is present. Titanium tetrachloride vapour now enters via perforations in the lower part of supply pipe 5. Anode 7 is constructed as a closed cylinder which completely surrounds the cathode. - Although in the preceding section the process of this invention has been described by reference to the most preferred embodiment, i.e. production of titanium from titanium tetrachloride employing a liquid zinc cathode, the invention is not limited thereto. Analogous processing can be carried out with different cathode materials, i.e. cadmium, tin, lead, bismuth, indium and gallium, from which tin and lead are preferred. Likewise other feedstocks may be processed, i.e. halides of hafnium, tantalum, aluminium, zirconium, tungsten, niobium, vanadium, molybdenum, indium, and silver. Preferred metal halides to be processed are those of tantalum, tungsten, vanadium and niobium. The preferred halogen atom is chlorine, as it is for the molten salt compositions.
- It is not known to what extent the production of metal Me proceeds via the direct electrolytic conversion of for example Ti4+ →+ 4e -7 Ti. Introduction of TiC14 into a liquid zinc cathode at elevated temperature may result in a chemical reduction of metal Me to lower valencies, for example 2TiCI4 + Zn -7 2TiClε + ZnCi2, this may then be followed by electrolytic reduction of trivalent titanium to metallic (zerovalent) titanium, coupled with electrolytic regeneration of cathode material by reducing divalent zinc to metallic (zerovalent) zinc. Such combined chemical and electrolytic reductions of metal Me in a higher valency to zerovalent metal are included expressis verbis in the scope of this invention, so is the production of zerovalent tantalum from TaCls in a liquid zinc cathode which probably proceeds entirely via chemical reduction by metallic zinc and electrolytic regeneration (reduction) of cathode material. What is essential to this invention is the application of an electrolytic cell with a liquid metal or alloy cathode, an introduction of metal halide MeXn directly into the liquid cathode and production of (zerovalent) metal Me within the cathode material, the latter as distinguished from production of metal Me somewhere else, i.e. in the molten salt electrolyte or by deposition on a second or auxiliary cathode. Absence of a diaphragm is also important.
- The salt melts may be free from impurities but this is not strictly necessary, while in addition it may be advantageous to work under an inert atmosphere of, for example, argon or nitrogen. Examples of suitable salt melts are LiCI/NaCl, NaCI/KCI, LiCI/KCI, LiCl/CaCl2, NaCl/BaCl2 and KCI/CaCI2, but, as has already been pointed out, the invention is not limited to the above-mentioned melts.
- In principle, suitable processing temperatures are above the melting point of the cathode material and below the temperature at which that material has such a vapour pressure that undesirably large losses occur. Preferred temperatures are between 400 and 900 °C, for zinc 425 to 890 °C, for cadmium 400 to 700 °C. Similarly, the processing temperature should not be so high that loss of molten salt electrolyte by evaporation or decomposition becomes substantial.
- The current and the supply of metal halide feedstock are so adjusted that complete reduction of metal Me in the cathode can take place. Preferably, at least n F.mol-I metal halide MeXn is supplied, n being the valency of the metal. The current is, however, restricted to a certain maximum, since deposition of salt-melt metal in the cathode should preferably be prevented as far as possible. The feedstock should preferably be introduced under homogeneous distribution into the cathode. The easiest way for achieving this is by using feedstocks that are in gaseous form on the moment of their introduction into the cathode material. However, introduction into the cathode of compounds in finely dispersed, solid form is also included within the scope of this invention. This all results in no metal Me, or practically none, in any valency ending up in the salt melt. It is then not necessary to employ a diaphragm to shield the anode, so that no undesired current and voltage losses occur, resulting in great technical and economical benefits. Cells having no diaphragm are preferred.
- In the alloy M.Mey that is withdrawn from the electrolysis cell y represents the atomic ratio of Me to M. This ratio will usually be kept below 0.5, preferably below 0.3. For easier ways of recovering metal Me from the alloy it is preferred to process alloys in which the content of metal Me is of from 6 to 20 %wt, based on the weight of the alloy.
- The invention is elucidated below by a number of experiments.
- a. 1.5 kg of eutectic LiCI/KCI mixture (59:41 mol) was purified by passing HCI gas through it at above its melting point for 8 hours. The HCI forces the equilibria a) and b) shown below to the left, so that an anhydrous, almost oxygen-free melt is obtained.
-
- Residual oxygen compounds and metallic impurities are then removed by electrolysis under vacuum at a cell voltage of 2.7 V.
- An electrolytic cell of externally heated stainless steel was employed with a molten zinc cathode (90 g) which was placed in a holder of A1203 on the bottom of the cell. A graphite rod served as anode, no diaphragm was used and 250 g salt melt was used as electrolyte. The cell voltage was 5.0 V, the cathode potential was -2.0 V (relative to an Ag/AgCI reference electrode) and the other conditions are given in Table I. The TiC14 was injected as a liquid in an argon stream and fed into the cathode. An argon atmosphere was maintained above the salt melt. In all experiments a current of 6 F.mol-1 TiCI4 was employed. The following results were determined by microprobe and chemical analysis of the cooled solids.
- b. Alloy produced in the first experiment of Table I was subjected to distillation in order to remove all zinc. Upon analysis the remaining residue appeared to consist of very pure titanium.
-
-
Claims (11)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NL8502687A NL8502687A (en) | 1985-10-02 | 1985-10-02 | METHOD FOR PREPARING TITAN. |
NL8502687 | 1985-10-02 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0219157A1 EP0219157A1 (en) | 1987-04-22 |
EP0219157B1 true EP0219157B1 (en) | 1990-01-31 |
Family
ID=19846656
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19860201679 Expired EP0219157B1 (en) | 1985-10-02 | 1986-09-29 | Process for the electrolytic production of metals |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0219157B1 (en) |
JP (1) | JPS6286188A (en) |
AU (1) | AU585648B2 (en) |
DE (1) | DE3668646D1 (en) |
NL (1) | NL8502687A (en) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB8707781D0 (en) * | 1987-04-01 | 1987-05-07 | Shell Int Research | Electrolytic production of metals |
IL129239A0 (en) * | 1996-09-30 | 2000-02-17 | Claude Fortin | Process for obtaining titanium or other metals using shuttle alloys |
US6618104B1 (en) | 1998-07-28 | 2003-09-09 | Nippon Telegraph And Telephone Corporation | Optical device having reverse mode holographic PDLC and front light guide |
KR102004920B1 (en) * | 2019-01-28 | 2019-07-29 | 한국지질자원연구원 | Metal refining method by using liquid metal cathode |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB660908A (en) * | 1948-03-19 | 1951-11-14 | Johnson & Co A | Improvments in the production of alloys of high zirconium content |
DE1139985B (en) * | 1956-05-18 | 1962-11-22 | Timax Associates | Process for the continuous production of pure, ductile titanium by fused-salt electrolysis |
DK156731C (en) * | 1980-05-07 | 1990-01-29 | Metals Tech & Instr | METHOD OR MANUFACTURING METHOD OR METALOID |
-
1985
- 1985-10-02 NL NL8502687A patent/NL8502687A/en not_active Application Discontinuation
-
1986
- 1986-09-25 AU AU63143/86A patent/AU585648B2/en not_active Ceased
- 1986-09-29 DE DE8686201679T patent/DE3668646D1/en not_active Expired - Fee Related
- 1986-09-29 EP EP19860201679 patent/EP0219157B1/en not_active Expired
- 1986-10-01 JP JP23424586A patent/JPS6286188A/en active Pending
Also Published As
Publication number | Publication date |
---|---|
NL8502687A (en) | 1987-05-04 |
EP0219157A1 (en) | 1987-04-22 |
DE3668646D1 (en) | 1990-03-08 |
AU6314386A (en) | 1987-04-09 |
JPS6286188A (en) | 1987-04-20 |
AU585648B2 (en) | 1989-06-22 |
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