EP1059366B1 - Electrolytic cell for producing an alkali metal - Google Patents
Electrolytic cell for producing an alkali metal Download PDFInfo
- Publication number
- EP1059366B1 EP1059366B1 EP00111875A EP00111875A EP1059366B1 EP 1059366 B1 EP1059366 B1 EP 1059366B1 EP 00111875 A EP00111875 A EP 00111875A EP 00111875 A EP00111875 A EP 00111875A EP 1059366 B1 EP1059366 B1 EP 1059366B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- alkali metal
- solid electrolyte
- sodium
- electrolytic cell
- amalgam
- 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.)
- Expired - Lifetime
Links
- 229910052783 alkali metal Inorganic materials 0.000 title claims abstract description 53
- 150000001340 alkali metals Chemical class 0.000 title claims abstract description 53
- 229910000497 Amalgam Inorganic materials 0.000 claims abstract description 52
- 239000007784 solid electrolyte Substances 0.000 claims abstract description 40
- 238000005868 electrolysis reaction Methods 0.000 claims abstract description 26
- 239000011244 liquid electrolyte Substances 0.000 claims abstract description 14
- 238000000034 method Methods 0.000 claims description 56
- 239000011734 sodium Substances 0.000 claims description 49
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 47
- 229910052708 sodium Inorganic materials 0.000 claims description 47
- 230000008569 process Effects 0.000 claims description 37
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 32
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 26
- 239000000203 mixture Substances 0.000 claims description 25
- 229910052700 potassium Inorganic materials 0.000 claims description 25
- 239000011591 potassium Substances 0.000 claims description 25
- 239000007788 liquid Substances 0.000 claims description 20
- 229910000831 Steel Inorganic materials 0.000 claims description 14
- 239000010959 steel Substances 0.000 claims description 14
- 239000003513 alkali Substances 0.000 claims description 11
- 239000003792 electrolyte Substances 0.000 claims description 10
- 239000000155 melt Substances 0.000 claims description 10
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 6
- 239000000243 solution Substances 0.000 claims description 6
- 239000000460 chlorine Substances 0.000 claims description 5
- 229910052801 chlorine Inorganic materials 0.000 claims description 5
- 230000001143 conditioned effect Effects 0.000 claims description 5
- ODZPKZBBUMBTMG-UHFFFAOYSA-N sodium amide Chemical compound [NH2-].[Na+] ODZPKZBBUMBTMG-UHFFFAOYSA-N 0.000 claims description 4
- 230000001476 alcoholic effect Effects 0.000 claims description 3
- 239000007864 aqueous solution Substances 0.000 claims description 3
- 125000004432 carbon atom Chemical group C* 0.000 claims description 3
- 229910001514 alkali metal chloride Inorganic materials 0.000 claims description 2
- 238000003756 stirring Methods 0.000 claims description 2
- 229910021055 KNH2 Inorganic materials 0.000 claims 3
- 229910018954 NaNH2 Inorganic materials 0.000 claims 3
- 229910000851 Alloy steel Inorganic materials 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 description 18
- 229910052753 mercury Inorganic materials 0.000 description 13
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 13
- 239000000919 ceramic Substances 0.000 description 12
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 11
- 239000000463 material Substances 0.000 description 9
- 239000010935 stainless steel Substances 0.000 description 9
- 229910001220 stainless steel Inorganic materials 0.000 description 9
- 229910001023 sodium amalgam Inorganic materials 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 6
- MJGFBOZCAJSGQW-UHFFFAOYSA-N mercury sodium Chemical compound [Na].[Hg] MJGFBOZCAJSGQW-UHFFFAOYSA-N 0.000 description 6
- 239000007787 solid Substances 0.000 description 6
- 229910001413 alkali metal ion Inorganic materials 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 150000001875 compounds Chemical class 0.000 description 5
- 230000003750 conditioning effect Effects 0.000 description 5
- 229910000567 Amalgam (chemistry) Inorganic materials 0.000 description 4
- KEAYESYHFKHZAL-UHFFFAOYSA-N Sodium Chemical compound [Na] KEAYESYHFKHZAL-UHFFFAOYSA-N 0.000 description 4
- 239000000654 additive Substances 0.000 description 4
- 238000007789 sealing Methods 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 239000010439 graphite Substances 0.000 description 3
- 229910002804 graphite Inorganic materials 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000010416 ion conductor Substances 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 235000002639 sodium chloride Nutrition 0.000 description 3
- 229910001415 sodium ion Inorganic materials 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 239000005662 Paraffin oil Substances 0.000 description 2
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 238000011109 contamination Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910001950 potassium oxide Inorganic materials 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- JHJLBTNAGRQEKS-UHFFFAOYSA-M sodium bromide Chemical compound [Na+].[Br-] JHJLBTNAGRQEKS-UHFFFAOYSA-M 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 229910000679 solder Inorganic materials 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910000873 Beta-alumina solid electrolyte Inorganic materials 0.000 description 1
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 1
- 229910000799 K alloy Inorganic materials 0.000 description 1
- 239000002228 NASICON Substances 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000012080 ambient air Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000005587 bubbling Effects 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 238000005341 cation exchange Methods 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000009795 derivation Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000003292 diminished effect Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
- 239000010433 feldspar Substances 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000000543 intermediate Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- -1 mercury ions Chemical class 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- FEMRXDWBWXQOGV-UHFFFAOYSA-N potassium amide Chemical class [NH2-].[K+] FEMRXDWBWXQOGV-UHFFFAOYSA-N 0.000 description 1
- 239000001103 potassium chloride Substances 0.000 description 1
- 235000011164 potassium chloride Nutrition 0.000 description 1
- 159000000001 potassium salts Chemical class 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 229910000033 sodium borohydride Inorganic materials 0.000 description 1
- 239000012279 sodium borohydride Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 125000003107 substituted aryl group Chemical group 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 239000010457 zeolite Substances 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
Images
Classifications
-
- 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
- C25C3/02—Electrolytic production, recovery or refining of metals by electrolysis of melts of alkali or alkaline earth metals
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D1/00—Electroforming
- C25D1/12—Electroforming by electrophoresis
- C25D1/14—Electroforming by electrophoresis of inorganic material
Definitions
- the present invention relates to an electrolytic cell used for electrochemical Production of alkali metal from alkali metal amalgam can be used.
- alkali metal denotes sodium and potassium.
- the invention further relates to a method for electrochemical production of alkali metal from alkali metal amalgam using this electrolytic cell.
- Sodium is an important inorganic basic product that is used, for example, for Production of sodium amide, sodium alcoholates and sodium borohydride used becomes. It is technically after the Downs process by electrolysis of melted table salt. This process has a high energy consumption of ⁇ 10 kWh / kg sodium (Büchner et al., Industrial inorganic Chemistry, 2nd edition, Verlag Chemie, p. 228 f). Furthermore, the process the serious disadvantage that the electrolysis cells when turned off by the Solidification of the molten salt can be destroyed. It also has the Downs process sodium metal gained the disadvantage that it is process-related with calcium is contaminated, its residual content only by subsequent cleaning steps diminished, but can never be completely excluded.
- Potassium is also an important basic inorganic product, for example for the production of potassium alcoholates, potassium amides and potassium alloys is used.
- a good yield is achieved in that Potassium vapor is continuously withdrawn from the reaction zone, whereby the Balance is shifted to the potassium side (Ullmann's Encyclopedia of Industrial Chemistry, 6th edition 1998, Electronic Release).
- the disadvantage is that Process at high temperatures (870 ° C) works. It also contains the resulting Potassium approx. 1% sodium as an impurity and must therefore still pass through another rectification can be cleaned up.
- the main disadvantage is that sodium used is expensive. This is also due to the fact that sodium is technically after the Downs process obtained by electrolysis of molten table salt with an energy expenditure of at least 10 kWh / kg sodium. This corresponds to about 5.3 kWh / kg of potassium (with 100% yield).
- Sodium amalgam and potassium amalgam are intermediates used in chlor-alkali electrolysis accrued in large quantities after the amalgam process and usually immediately after preparation with water to alkali metal lye be implemented.
- the low alkali metal or alkali metal free alkali metal amalgam is usually immediately returned to chlor-alkali electrolysis.
- the sodium concentration of this solution to values of less than 1% by weight, preferably Values in the range of 0.2 to 0.5 wt .-% are kept.
- Potassium amalgam Keeping it in liquid form is the potassium concentration of the solution less than 1.5% by weight, preferably in the range of 0.3 to 0.6% by weight.
- the amalgams obtained on an industrial scale essentially contain metallic impurities such as copper, iron, potassium (in sodium amalgam), Sodium (in potassium amalgam), lead and zinc in the concentration range from 1 to 30 ppm.
- GB 1,155,927 describes a process by which sodium metal can be obtained from sodium amalgam electrochemically using a solid sodium ion conductor, such as, for example, ⁇ -Al 2 O 3 , with amalgam as the anode and sodium as the cathode.
- a solid sodium ion conductor such as, for example, ⁇ -Al 2 O 3
- amalgam as the anode
- sodium as the cathode.
- the execution of the method described in GB 1,155,927 does not lead to the results described there with regard to sodium conversion, product purity and current density.
- the system described there behaves unstably over the course of a few days if the claimed temperature range is maintained.
- Electrolysis cells used in an electrochemical process for the production of Alkali metal from alkali metal amalgam are used and a solid ion conductor are often not suitable for long periods in permanent operation to be held.
- One reason for this is the mechanical instability of the solid ion conductor that occurs after a certain period of operation.
- the alkali metal conversion on the anode side must meet the balance sheet requirements of the product group with chlor-alkali electrolysis are sufficient. That is, the drain concentration of alkali metal in the amalgam corresponds to chlor-alkali electrolysis the feed concentration in the alkali metal electrolysis according to the invention. Further must between the chlor-alkali electrolysis and alkali metal electrolysis according to the invention circulated quantities of amalgam in a technical and economically justifiable size. Usually this is achieved if the alkali metal content of the incoming amalgams is implemented to 50%.
- the sodium metal must be primary occur in such a purity that further process steps for mercury separation can be omitted and the disadvantage of the Downs process Calcium contamination is avoided.
- the potassium metal must primarily in one such purity arise that further process steps for mercury separation can be omitted and the sodium content is lower than in the reduction with Sodium, where the primary potassium produced contains 1% sodium.
- the procedure is supposed to be feasible on an industrial scale and must therefore be sufficiently high Enable current densities and space-time yields. Due to the statics of the Production building, security, environmental protection and capital lockup an apparatus concept is required, which has a relatively small mercury content gets along.
- the process should be stable in continuous operation and the usual metallic ones occurring in technical alkali metal amalgam Tolerate contamination undamaged.
- alkali metal amalgam refers to a solution of an alkali metal in mercury at the reaction temperature is liquid.
- the present invention relates to an electrolytic cell comprising a moving Liquid containing alkali metal amalgam Anode, the liquid anode being stirred in and / or using a pump one under atmospheric pressure or slightly overpressure Circulation is moved an alkali metal ion conductive Solid electrolyte and a cathode, which is characterized in that the solid electrolyte and the cathode is separated from one another by a liquid electrolyte are.
- the present invention also relates to a method for producing an alkali metal using this electrolytic cell.
- the liquid electrolyte is expediently chosen so that it is compared to alkali metal is stable.
- a liquid electrolyte is preferably used, which is in the Electrolysis reaction not used up.
- an electrolyte melt is used as the liquid electrolyte.
- the present invention therefore relates to a Electrolysis cell as described above, which is characterized in that the Liquid electrolyte is a molten electrolyte.
- electrolyte melts are expediently used as the liquid electrolyte.
- NaOH melts, NaNH 2 melts or mixtures thereof are preferably used in the production of sodium, KOH melts, KNH 2 melts or mixtures thereof in the production of potassium.
- the present invention relates to an electrolysis cell as described above, which is characterized in that the electrolyte melt is a NaOH melt, a NaNH 2 melt or a mixture thereof or a KOH melt, a KNH 2 melt or a mixture thereof ,
- melts or Mixtures of these are used in anhydrous form.
- suitable additives include additives that lower the melting point.
- additives that lower the melting point In principle, all additives which lower the melting point and which do not interfere with the use of the electrolytic cell and the method according to the invention are suitable.
- melting point-lowering additives which are selected in the production of sodium from the group consisting of NaI, NaBr, Na 2 CO 3 and a mixture of two or more thereof, and are selected in the production of potassium from the group consisting of KI, KBr , K 2 CO 3 and a mixture thereof.
- the anode and cathode compartments of the electrolytic cell according to the invention are separated from one another by a solid electrolyte which conducts helium-tight alkali metal ions.
- Ceramic materials such as NASICON®, the composition of which is specified in EP-A 0 553 400, are suitable for this purpose in the production of sodium. Glasses that conduct sodium ions as well as zeolites and feldspar are also suitable.
- a variety of materials can also be used in the production of potassium. Both the use of ceramics and the use of glasses are possible. For example, the following materials can be considered: KBiO 3 (TN Nguyen et al., Chem. Mater.
- Sodium ⁇ "aluminum oxide, sodium ⁇ aluminum oxide and sodium ⁇ / ⁇ " aluminum oxide are preferred or potassium- ⁇ "aluminum oxide, potassium- ⁇ -aluminum oxide and potassium ⁇ / ⁇ "alumina.
- the present invention therefore also relates to an electrolysis cell, as described above, which is characterized in that the solid electrolyte is selected from the group consisting of sodium ⁇ -aluminum oxide, sodium ⁇ "aluminum oxide and sodium ⁇ / ⁇ "alumina or selected from the group from potassium-beta-alumina, potassium-beta "-alumina and potassium-beta / beta" -alumina.
- Potassium ⁇ "aluminum oxide, potassium ⁇ aluminum oxide or potassium ⁇ / ⁇ " aluminum oxide can start from sodium beta “alumina, sodium beta” alumina or sodium ⁇ / ⁇ "aluminum oxide by cation exchange getting produced.
- the solid electrolyte expediently has the shape of a thin-walled and nevertheless pressure-resistant, one-sided closed pipe (EP-B 0 424 673), on the open end an electrically insulating ring using a helium-tight, likewise electrically insulating glass solder connection is applied (GB 2 207 545, EP-B 0 482 785).
- the wall thickness of the electrolyte conducting alkali metal ions lies generally in the range from 0.3 to 5 mm, preferably in the range from 1 to 3 mm, particularly preferably in the range from 1 to 2 mm.
- cross-sectional shape of the tube closed on one side is the preferred one Circular embodiment.
- cross-sectional shapes are also conceivable enlarged surface, for example from a composite of several circular Areas can be derived.
- the design of the alkali metal ion-conducting solid electrolyte with regard to its Leak tightness has decisive factors in the method according to the invention Influence, because mercury can only over leaks in the solid electrolyte or Sealing system in the liquid electrolytes and thus also in the alkali metal produced arrive because in the method according to the invention the anode potentials be adjusted so that the formation of mercury ions is excluded becomes.
- solid electrolytes are used that have leak rates of less than 10 -9 (mbar • l) / s in a helium leak test, i.e. are helium-tight within the detection limit.
- the releasable sealing connections are preferably carried out so that the Liquid electrolyte and amalgam are each sealed off from the ambient atmosphere become. Detachable seals between liquid electrolyte and amalgam avoided if possible, since the removable seals are usually liquid-tight, but are not gas-tight.
- the Seals with an inert gas such as Flushed with argon or nitrogen to a To prevent oxygen from diffusing through.
- inert gas such as Flushed with argon or nitrogen to a To prevent oxygen from diffusing through.
- helium-tight electrolytes and the listed sealing arrangement are alkali metals with a Mercury residual content in the range of 0.05 to 0.3 ppm obtained.
- the geometry of the solid electrolyte is essentially arbitrary and can be special Process conditions are adjusted.
- the solid electrolyte as already mentioned above, has the shape of a closed on one side Pipe on.
- this is Tube in contact with the anode on its outside.
- This anode compartment is more preferably, delimited on its outside by an outer tube that consists of is made of a material that is very dense and resistant to hot Is amalgam.
- Stainless steel and graphite are particularly suitable as materials.
- stainless steel is selected as the material.
- the outer tube can essentially have any cross section.
- An outer tube is preferably used which is concentric with the solid electrolyte tube is.
- annular gap between the outer tube and the ceramic tube is within the scope of the invention Flow in the longitudinal direction of the liquid anode.
- the annular gap has a preferred gap width of 1 up to 10 mm. More preferably, the annular gap has a width in the range of 2 to 5 mm, particularly preferably a width in the range from 2.5 to 3 mm.
- the present invention relates to an electrolytic cell as described above, which is characterized in that the solid electrolyte is closed on one side Tube is formed, which is installed in a concentric stainless steel tube is that there is an annular gap with a gap width in the range of 1 to 10 mm.
- the process according to the invention is carried out in an electrolysis cell with a moving liquid alkali metal amalgam anode operated.
- This is a moving liquid anode, during operation with regard to its alkali metal content is depleted, so that it is enriched with alkali metal-rich amalgam, that in a normal amalgam cell of a chlor-alkali production or by electrolysis of sodium or potassium salts with a mercury or Amalgam cathode, e.g. NaOH or KOH, can be replaced can be.
- the concentrated amalgam flow a normal amalgam cell in a heat exchanger the operating temperature of the method according to the invention is heated and the hot fed moving liquid anode. This is best done in one Counterflow heat exchanger so that the hot drained depleted Amalgam heated the inlet.
- depleted amalgam can be both discontinuous as well done continuously.
- the continuous procedure is operational easier to do.
- the disadvantage that usually the incoming concentrate diluted with circulated, already depleted alkali metal amalgam can be compensated for by the fact that the process has several stages is performed.
- the liquid anode is expediently stirred and / or with a Pump in an atmospheric pressure or slightly overpressure Circulation moves.
- the caused by the sales-related exchange of amalgam Movement and / or thermal convection are compared to that in the required movement negligible and sufficient not reaching the preferred current densities.
- the present invention also relates to a method as described above, which is characterized in that it is carried out at a current density of more than 250 A / m 2 .
- the anode is moved, for example, by stirring. for example Bubbling gas or using a mechanical stirrer or with a pump.
- a movement in the form of a forced flow is preferred, such as with an amalgam circuit driven by a pump can be achieved.
- the flow rate is generally in the range of 0.03 to 1.0 m / s, preferably in the range from 0.05 to 0.6 m / s and particularly preferably in the range from 0.1 to 0.3 m / s.
- a higher flow rate allows in the Usually higher current densities.
- Another design advantage of the anode in The shape of an annular gap lies in the relatively small area of the anode Anode volume. This makes it possible to meet the demand for moderate apparatus weight and acceptable mercury circulating capacity.
- cathode material in the cell according to the invention suitable materials.
- suitable materials include steel, Pure nickel with, for example, the DIN material number 2.4066 or electrode graphite.
- the cathode is made of steel.
- the present invention also relates to an electrolytic cell as above described, which is characterized in that the cathode is a steel cathode.
- Suitable steels include stainless steel, austenitic steel or carbon steel.
- the preferred austenitic steels include Steels with the DIN material numbers 1.4541 or 1.4571 to name as preferred unalloyed steels the steels with the DIN material numbers 1.0305 or 1.0346.
- Unalloyed steels are used in electrolysis cells.
- the cathode is designed as a rod, which is built into the solid electrolyte designed as a tube.
- the rod is installed in such a way that between the solid electrolyte and the Rod creates a gap with a gap width in the range of 1 to 6 mm.
- the present invention also relates to a cell as described above which is characterized in that the steel cathode is designed as a rod, which is installed in the solid electrolyte in the form of a tube such that between a gap with a gap width in the inner wall of the solid electrolyte and the rod Range from 1 to 6 mm arises.
- the cathode can of course also all in the cell according to the invention have other suitable geometries.
- a tube as Wire mesh or be designed as expanded metal.
- the alkali metal is formed on the solid cathode. This increases on the rod which is designed according to the preferred embodiment Cathode in the liquid electrolyte and can be used as a pure metallic Phase are deducted.
- the present invention also relates to a method as described above, which is characterized in that it is at a temperature in the range of 260 to 400 ° C is carried out.
- the current density is generally 0.5 to 10 kA / m 2 , preferably 1.0 to 3 kA / m 2 (sodium) or 0.3 to 3 kA / m 2 , preferably 0.5 to 1, 5 kA / m 2 (potassium).
- the current density is specifically set at the external power source, usually a line rectifier.
- the electrolysis cell according to the invention integrated into the power supply of an amalgam-supplying chlorine cell, so that a additional line rectifier can be omitted.
- the alkali metal ions conducting solid electrolytes are used for the first time, a too high a ceramic resistance is observed, which in the course of further operation remains high.
- the resistance of the solid electrolyte can be compared be too high by a factor of 30. This is believed to be due to the lack of reactivity of the surface.
- the cause is in the action of water in the form of the water content of the ambient air to search. This damage can occur particularly when the ceramics or done during assembly. Therefore, the ceramic tubes are convenient after sintering under vacuum in diffusion-proof aluminum / plastic Packed composite films.
- the original packaging is used for storage '' Ceramic tubes in tightly closing, argon-filled metal containers locked in.
- the solid electrolyte is conditioned in order to lower its resistance to reach.
- the present invention also relates to a method as described above, which is characterized in that the solid electrolyte before the implementation the process is conditioned.
- R denotes a straight-chain or branched-chain alkyl radical having 1 to 5 carbon atoms.
- R can likewise denote a suitable, optionally suitably substituted aryl or aralkyl radical.
- the present invention also relates to a method as described above, which is characterized in that the solid electrolyte with NaOH, NaNH 2 , NaOR or a mixture of two or more thereof or with KOH, KNH 2 , KOR or a mixture of two or more of which is conditioned, where R denotes a straight-chain or branched-chain alkyl radical having 1 to 5 carbon atoms.
- the present invention also relates to a process as described above, which is characterized in that NaOH, NaNH 2 , NaOR or the mixture of two or more thereof or KOH, KNH 2 , KOR or the mixture of two or more thereof as a melt or / and as an aqueous solution or / and as an alcoholic solution.
- the solid electrolyte is designed as a tube in a preferred embodiment, it is possible to treat one side or both sides of the tube by treating them to condition chemical compounds. Of course it is too possible to condition the solid electrolyte several times in two or more steps, wherein the chemical compound or the mixture of two or more of which may be the same or different in the individual conditioning steps can.
- Another possibility of conditioning the solid electrolyte and lowering the ceramic resistance is to first operate the cell with reversed polarity, ie to operate the anode first as the cathode and the cathode as the anode.
- the cathode like the anode, can consist of sodium amalgam and mercury.
- the current density in the reversed state is linear over a period of 1 to 44 h, preferably 2 to 6 h, from 50 A / m 2 to 3000 A / m 2 (sodium) or from 30 A / m 2 to 1000 A / m 2 (potassium) increased.
- the lowest ceramic resistances are obtained when starting for 1 to 24 Hours at an operating temperature of 300 to 350 ° C (sodium) or 250 to 350 ° C (potassium) first liquid alkali metal is used as anode, which then replaced by amalgam. This embodiment of conditioning is particularly preferred.
- the current direction is in time intervals from 1 to 24 hours for 1 to 10 minutes reversed by Anode and cathode are short-circuited via an external resistor.
- the Resistance is dimensioned so that the current strength during polarity reversal is about 1.5 times corresponds to the current in operation.
- the yield of alkali metal recovered is complete in the process according to the invention, based on the alkali metal converted on the anode side.
- the current yield of the alkali metal obtained is in normal polarity mode of operation within the measurement accuracy 100%.
- the averaged current yield is reduced due to the intermittent polarity reversal to values in the range of 95 to 98%.
- the amalgam supplied to the anode is in a preferred embodiment depleted from 0.4% by weight to 0.1% by weight of alkali metal.
- the not implemented Alkali metal is not lost when coupled with chlor-alkali electrolysis, because it is returned to the chlor-alkali cell and via the amalgam cycle comes back from there.
- the core of the cell according to FIG. 1 consisted of a cell closed on one side Tube (1) made of ⁇ "aluminum oxide (32 mm outer diameter, 210 mm length, Wall thickness 1.7 mm). At the open end was a ring made of ⁇ -aluminum oxide (2) attached helium-tight using a glass solder connection. By means of this ring (2) was the tube which was conductive with respect to sodium ions and was made of ⁇ "aluminum oxide with the opening into a concentric stainless steel tube (3) (with an inner diameter of 37 mm and a length of approx. 215 mm). The inside diameter of the steel tube was matched to the outside diameter of the ceramic tube, so that an annular gap with a gap width of 2.5 mm was created.
- the ring cross-section allowed one in terms of the current density very effective flow through the anode space in the axial Direction.
- the ring was made of ⁇ -aluminum oxide (2) with one each Flat gasket below (4) and above (5) over the housing (6) and the cover flange (7) with four clamping screws (8).
- An anode power supply (9) was attached to the stainless steel container.
- For the Amalgam was supplied at the bottom with a pipe socket (10) for the drain at the side a pipe socket (11) welded on top. Protruded from the cover flange Rod made of stainless steel (18) as a cathode in the opening of the tube made of ⁇ "aluminum oxide.
- a tube (13) was passed through the cover flange and was used for free removal of liquid sodium.
- the cell could be wrapped with electrical heating tapes (14) and be isolated or together with several cells in a heated Chamber to be installed.
- the liquid sodium formed was over with pressure generated by reaction the heated drain pipe (13) in an inert, partially filled with paraffin oil
- the vessel was discharged and solidified in paraffin oil in the form of small balls.
- the commercial pipe made of sodium ⁇ "aluminum oxide was installed promptly within an hour in the laboratory atmosphere after using a vacuum package was removed. After that, both chambers of the cell flooded with argon and the cell closed. The installation in the apparatus took place 2 to 5 days later.
- the apparatus was heated to 330 ° C. with a temperature increase from 20 ° C./h.
- the cathode space inside the ceramic tube which was closed on one side, was then filled via a feed line with an externally melted melt of 60% by weight NaNH 2 and 40% by weight NaOH.
- the anode space outside the ceramic tube was filled with liquid sodium. Over a period of 35 minutes, the current was increased once from 5 A to 40 A in increments of 5 A and then held at 40 A for 4 hours.
- This first filling was discarded and the circuit was filled with fresh amalgam heated to 330 ° C. and containing 0.4% by weight of sodium.
- An average flow rate of 0.3 m / s was set, which corresponded to a circulation volume flow of 0.29 m 3 / h.
- a cell voltage of 0.82 V was set in the de-energized state.
- the output voltage a DC power supply was limited to 2 volts and the Circuit closed with the cell. It was done in a time frame of 3 hours the current increased linearly from 0 A to 40 A. After that were in the time interval of 30 min each drained 7.8 kg of amalgam from the circulatory contents and replaced by fresh amalgam. It was observed that the cell voltage fluctuated between values in the range of 1.5 to 1.7 volts.
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Abstract
Description
Die vorliegende Erfindung betrifft eine Elektrolysezelle, die zur elektrochemischen Herstellung von Alkalimetall aus Alkalimetallamalgam eingesetzt werden kann. Dabei bezeichnet erfindungsgemäß der Begriff "Alkalimetall" Natrium und Kalium.The present invention relates to an electrolytic cell used for electrochemical Production of alkali metal from alkali metal amalgam can be used. According to the invention, the term “alkali metal” denotes sodium and potassium.
Weiterhin betrifft die Erfindung ein Verfahren zur elektrochemischen Herstellung von Alkalimetall aus Alkalimetallamalgam unter Verwendung dieser Elektrolysezelle.The invention further relates to a method for electrochemical production of alkali metal from alkali metal amalgam using this electrolytic cell.
Natrium ist ein wichtiges anorganisches Grundprodukt, das beispielsweise für die Herstellung von Natriumamid, Natriumalkoholaten und Natriumborhydrid verwendet wird. Es wird technisch nach dem Downs-Prozeß durch Elektrolyse von geschmolzenem Kochsalz gewonnen. Dieser Prozeß weist einen hohen Energieverbrauch von ≥ 10 kWh/kg Natrium auf (Büchner et al., Industrielle Anorganische Chemie, 2. Auflage, Verlag Chemie, S. 228 f). Weiterhin hat das Verfahren den gravierenden Nachteil, daß die Elektrolysezellen beim Abstellen durch das Erstarren der Salzschmelze zerstört werden. Ferner hat das nach dem Downs-Prozeß gewonnene Natriummetall den Nachteil, daß es prozeßbedingt mit Calcium verunreinigt ist, dessen Restgehalt durch nachträgliche Reinigungsschritte nur vermindert, aber niemals völlig ausgeschlossen werden kann. Sodium is an important inorganic basic product that is used, for example, for Production of sodium amide, sodium alcoholates and sodium borohydride used becomes. It is technically after the Downs process by electrolysis of melted table salt. This process has a high energy consumption of ≥ 10 kWh / kg sodium (Büchner et al., Industrial inorganic Chemistry, 2nd edition, Verlag Chemie, p. 228 f). Furthermore, the process the serious disadvantage that the electrolysis cells when turned off by the Solidification of the molten salt can be destroyed. It also has the Downs process sodium metal gained the disadvantage that it is process-related with calcium is contaminated, its residual content only by subsequent cleaning steps diminished, but can never be completely excluded.
Kalium ist ebenfalls ein wichtiges anorganisches Grundprodukt, das beispielsweise für die Herstellung von Kaliumalkoholaten, Kaliumamiden und von Kaliumlegierungen verwendet wird. Heute wird es technisch vor allem durch Reduktion von Kaliumchlorid mit Natrium gewonnen. Dabei entsteht zunächst NaK, das dann fraktioniert destilliert wird. Eine gute Ausbeute wird dadurch erreicht, daß ständig Kaliumdampf aus der Reaktionszone abgezogen wird, wodurch das Gleichgewicht auf die Kaliumseite verschoben wird (Ullmann's Encyclopedia of Industrial Chemistry, 6. Auflage 1998, Electronic Release). Nachteilig ist, daß das Verfahren bei hohen Temperaturen (870 °C) arbeitet. Außerdem enthält das entstehende Kalium ca. 1 % Natrium als Verunreinigung und muß daher noch durch eine weitere Rektifikation aufgereinigt werden. Der größte Nachteil ist, daß das eingesetzte Natrium teuer ist. Dies liegt auch daran, daß Natrium technisch nach dem Downs-Prozeß durch Elektrolyse von geschmolzenem Kochsalz gewonnen wird, wobei ein Energieaufwand von mindestens 10 kWh/kg Natrium nötig ist. Dies entspricht etwa 5,3 kWh/kg Kalium (bei 100 % Ausbeute).Potassium is also an important basic inorganic product, for example for the production of potassium alcoholates, potassium amides and potassium alloys is used. Today it is technically mainly through reduction obtained from potassium chloride with sodium. This creates NaK, the then fractionally distilled. A good yield is achieved in that Potassium vapor is continuously withdrawn from the reaction zone, whereby the Balance is shifted to the potassium side (Ullmann's Encyclopedia of Industrial Chemistry, 6th edition 1998, Electronic Release). The disadvantage is that Process at high temperatures (870 ° C) works. It also contains the resulting Potassium approx. 1% sodium as an impurity and must therefore still pass through another rectification can be cleaned up. The main disadvantage is that sodium used is expensive. This is also due to the fact that sodium is technically after the Downs process obtained by electrolysis of molten table salt with an energy expenditure of at least 10 kWh / kg sodium. This corresponds to about 5.3 kWh / kg of potassium (with 100% yield).
Natriumamalgam und Kaliumamalgam sind Zwischenprodukte, die bei der Chlor-Alkali-Elektrolyse nach dem Amalgamverfahren in großen Mengen anfallen und in der Regel unmittelbar nach der Herstellung mit Wasser zu Alkalimetall-Lauge umgesetzt werden. Das alkalimetall-arme oder alkalimetall-freie Alkalimetallamalgam wird normalerweise umgehend in die Chlor-Alkali-Elektrolyse zurückgeführt. Um das Natriumamalgam in flüssiger Form zu halten, muß die Natriumkonzentration dieser Lösung auf Werten von weniger als 1 Gew.-%, bevorzugt auf Werten im Bereich von 0,2 bis 0,5 Gew.-% gehalten werden. Um ein Kaliumamalgam in flüssiger Form zu halten, liegt die Kaliumkonzentration der Lösung bei weniger als 1,5 Gew.-%, vorzugsweise im Bereich von 0,3 bis 0,6 Gew.-%. Die im technischen Maßstab gewonnenen Amalgame enthalten im wesentlichen metallische Verunreinigungen wie zum Beispiel Kupfer, Eisen, Kalium (im Natriumamalgam), Natrium (im Kaliumamalgam), Blei und Zink im Konzentrationsbereich von 1 bis 30 ppm. Sodium amalgam and potassium amalgam are intermediates used in chlor-alkali electrolysis accrued in large quantities after the amalgam process and usually immediately after preparation with water to alkali metal lye be implemented. The low alkali metal or alkali metal free alkali metal amalgam is usually immediately returned to chlor-alkali electrolysis. To keep the sodium amalgam in liquid form, the sodium concentration of this solution to values of less than 1% by weight, preferably Values in the range of 0.2 to 0.5 wt .-% are kept. Potassium amalgam Keeping it in liquid form is the potassium concentration of the solution less than 1.5% by weight, preferably in the range of 0.3 to 0.6% by weight. The amalgams obtained on an industrial scale essentially contain metallic impurities such as copper, iron, potassium (in sodium amalgam), Sodium (in potassium amalgam), lead and zinc in the concentration range from 1 to 30 ppm.
Die GB 1,155,927 beschreibt ein Verfahren, nach dem unter Einsatz eines festen Natriumionenleiters, wie z.B. β-Al2O3, mit Amalgam als Anode und Natrium als Kathode auf elektrochemischem Wege Natriummetall aus Natriumamalgam gewonnen werden kann. Die Ausführung des in GB 1,155,927 beschriebenen Verfahrens führt aber nicht zu den dort beschriebenen Ergebnissen hinsichtlich Natriumumsatz, Produktreinheit und Stromdichte. Ferner verhält sich das dort beschriebene System im Verlauf weniger Tage instabil, wenn der beanspruchte Temperaturbereich eingehalten wird.GB 1,155,927 describes a process by which sodium metal can be obtained from sodium amalgam electrochemically using a solid sodium ion conductor, such as, for example, β-Al 2 O 3 , with amalgam as the anode and sodium as the cathode. The execution of the method described in GB 1,155,927 does not lead to the results described there with regard to sodium conversion, product purity and current density. Furthermore, the system described there behaves unstably over the course of a few days if the claimed temperature range is maintained.
Elektrolysezellen, die in einem elektrochemischen Verfahren zur Herstellung von Alkalimetall aus Alkalirnetallamalgam verwendet werden und einen festen Ionenleiter aufweisen, sind häufig nicht geeignet, über lange Zeit hinweg im Permanentbetrieb gehalten zu werden. Ein Grund hierfür ist die mechanische Instabilität des festen Ionenleiters, die nach einer gewissen Betriebsdauer eintritt.Electrolysis cells used in an electrochemical process for the production of Alkali metal from alkali metal amalgam are used and a solid ion conductor are often not suitable for long periods in permanent operation to be held. One reason for this is the mechanical instability of the solid ion conductor that occurs after a certain period of operation.
Eine Aufgabe der vorliegenden Erfindung war es daher, eine Elektrolysezelle bereitzustellen, die diese Nachteile nicht aufweist.It was therefore an object of the present invention to provide an electrolysis cell which does not have these disadvantages.
Eine weitere Aufgabe bestand darin, ein Verfahren zur elektrochemischen Herstellung von Alkalimetall aus einem Alkalimetallamalgam unter Verwendung dieser Elektrolysezelle bereitzustellen, das eine energetisch günstigere Herstellung von Natrium als das Downs-Verfahren bzw. eine energetisch günstigere Herstellung von Kalium als das eingangs diskutierte technische Verfahren erlaubt. Weiter soll das Verfahren in den bestehenden Verbund einer Chlor-Alkali-Elektrolyse nach dem Amalgamverfahren integrierbar sein, wobei diejenigen Nachteile vermieden werden sollen, die bei der Ausführung des Verfahrens gemäß der GB 1,155,927 auftreten. Dazu müssen folgende wesentliche Forderungen erfüllt werden:Another task was to create a process for electrochemical manufacture of alkali metal from an alkali metal amalgam using this To provide electrolytic cell, which is a more energy-efficient production of Sodium as the Downs process or an energy-efficient production of potassium as the technical process discussed at the beginning. Should continue the process in the existing combination of a chlor-alkali electrolysis after the amalgam process can be integrated, avoiding those disadvantages should be used in the execution of the method according to GB 1,155,927 occur. The following essential requirements must be met:
Der Alkalimetallumsatz auf der Anodenseite muß den Bilanzforderungen des Produktverbundes mit der Chloralkali-Elektrolyse genügen. Das heißt, die Ablaufkonzentration an Alkalimetall im Amalgam der Chloralkali-Elektrolyse entspricht der Zulaufkonzentration in der erfindungsgemäßen Alkalimetallelektrolyse. Ferner müssen die zwischen Chloralkali-Elektrolyse und erfindungsgemäßer Alkalimetallelektrolyse im Kreis geführten Umlaufmengen an Amalgam in einer technisch und wirtschaftlich vertretbaren Größenordnung gehalten werden. In der Regel wird dies erreicht, wenn in der Alkalimetallelektrolyse der Alkalimetallgehalt des zulaufenden Amalgams zu 50 % umgesetzt wird. Das Natriummetall muß primär in einer solchen Reinheit anfallen, daß weitere Prozeßschritte zur Quecksilberabtrennung entfallen können und der beim Downs-Prozeß gegebene Nachteil einer Calciumkontamination vermieden wird. Das Kaliummetall muß primär in einer solchen Reinheit anfallen, daß weitere Prozeßschritte zur Quecksilberabtrennung entfallen können und der Natriumgehalt geringer ist als bei der Reduktion mit Natrium, wo das primär erzeugte Kalium 1 % Natrium enthält. Das Verfahren soll im industriellen Maßstab realisierbar sein und muß deshalb ausreichend hohe Stromdichten und Raum-Zeitausbeuten ermöglichen. Aus Gründen der Statik des Produktionsgebäudes, der Sicherheit, des Umweltschutzes und der Kapitalbindung ist ein apparatives Konzept gefordert, welches mit einem relativ kleinen Quecksilberinhalt auskommt. Das Verfahren soll im Dauerbetrieb stabil zu betreiben sein und die üblichen im technischen Alkalimetallamalgam auftretenden metallischen Verunreinigungen unbeschadet tolerieren. Der Begriff "Alkalimetallamalgam" bezeichnet eine Lösung von einem Alkalimetall in Quecksilber, die bei der Reaktionstemperatur flüssig ist.The alkali metal conversion on the anode side must meet the balance sheet requirements of the product group with chlor-alkali electrolysis are sufficient. That is, the drain concentration of alkali metal in the amalgam corresponds to chlor-alkali electrolysis the feed concentration in the alkali metal electrolysis according to the invention. Further must between the chlor-alkali electrolysis and alkali metal electrolysis according to the invention circulated quantities of amalgam in a technical and economically justifiable size. Usually this is achieved if the alkali metal content of the incoming amalgams is implemented to 50%. The sodium metal must be primary occur in such a purity that further process steps for mercury separation can be omitted and the disadvantage of the Downs process Calcium contamination is avoided. The potassium metal must primarily in one such purity arise that further process steps for mercury separation can be omitted and the sodium content is lower than in the reduction with Sodium, where the primary potassium produced contains 1% sodium. The procedure is supposed to be feasible on an industrial scale and must therefore be sufficiently high Enable current densities and space-time yields. Due to the statics of the Production building, security, environmental protection and capital lockup an apparatus concept is required, which has a relatively small mercury content gets along. The process should be stable in continuous operation and the usual metallic ones occurring in technical alkali metal amalgam Tolerate contamination undamaged. The term "alkali metal amalgam" refers to a solution of an alkali metal in mercury at the reaction temperature is liquid.
Ein weiteres Verfahren zur Altrennung von Alkalimetall vom entsprechenden Amalgam wird in der FR-A-15 55 128 beschrieben.Another method for the old separation of alkali metal from the corresponding Amalgam is described in FR-A-15 55 128.
Die vorliegende Erfindung betrifft eine Elektrolysezelle, umfassend eine bewegte, Alkalimetallamalgam enthaltende flüssige Anode, wobei die flüssige Anode durch Rühren und/oder mit einer Pumpe in einem unter Atmosphärendruck oder leichtem Überdruck stehenden Kreislauf bewegt wird einen Alkalimetallionen leitenden Festelektrolyten und eine Kathode, die dadurch gekennzeichnet ist, daß der Festelektrolyt und die Kathode durch einen Flüssigelektrolyten voneinander separiert sind.The present invention relates to an electrolytic cell comprising a moving Liquid containing alkali metal amalgam Anode, the liquid anode being stirred in and / or using a pump one under atmospheric pressure or slightly overpressure Circulation is moved an alkali metal ion conductive Solid electrolyte and a cathode, which is characterized in that the solid electrolyte and the cathode is separated from one another by a liquid electrolyte are.
Ebenso betrifft die vorliegende Erfindung ein Verfahren zur Herstellung eines Alkalimetalls unter Verwendung dieser Elektrolysezelle. The present invention also relates to a method for producing an alkali metal using this electrolytic cell.
Der Flüssigelektrolyt wird zweckmäßigerweise so gewählt, daß er gegenüber Alkalimetall stabil ist. Bevorzugt wird ein Flüssigelektrolyt eingesetzt, der sich bei der Elektrolysereaktion nicht verbraucht. In einer besonders bevorzugten Ausführungsform wird als Flüssigelektrolyt eine Elektrolytschmelze eingesetzt.The liquid electrolyte is expediently chosen so that it is compared to alkali metal is stable. A liquid electrolyte is preferably used, which is in the Electrolysis reaction not used up. In a particularly preferred embodiment an electrolyte melt is used as the liquid electrolyte.
In einer bevorzugten Ausführungsform betrifft die vorliegende Erfindung daher eine Elektrolysezelle, wie oben beschrieben, die dadurch gekennzeichnet ist, daß der Flüssigelektrolyt eine Elektrolytschmelze ist.In a preferred embodiment, the present invention therefore relates to a Electrolysis cell as described above, which is characterized in that the Liquid electrolyte is a molten electrolyte.
Je nachdem, welches Alkalimetall unter Verwendung der erfindungsgemäßen Elektrolysezelle hergestellt wird, werden zweckmäßigerweise unterschiedliche Elektrolytschmelzen als Flüssigelektrolyt eingesetzt. Bevorzugt werden in den erfindungsgemäßen Elektrolysezellen bei der Herstellung von Natrium NaOH-Schmelzen, NaNH2-Schmelzen oder Gemische davon, bei der Herstellung von Kalium KOH-Schmelzen, KNH2-Schmelzen oder Gemische davon eingesetzt.Depending on which alkali metal is produced using the electrolytic cell according to the invention, different electrolyte melts are expediently used as the liquid electrolyte. In the electrolytic cells according to the invention, NaOH melts, NaNH 2 melts or mixtures thereof are preferably used in the production of sodium, KOH melts, KNH 2 melts or mixtures thereof in the production of potassium.
Demgemäß betrifft die vorliegende Erfindung eine Eletrolysezelle, wie oben beschrieben, die dadurch gekennzeichnet ist, daß die Elektrolytschmelze eine NaOH-Schmelze, eine NaNH2-Schmelze oder ein Gemisch davon oder eine KOH-Schmelze, eine KNH2-Schmelze oder ein Gemisch davon ist.Accordingly, the present invention relates to an electrolysis cell as described above, which is characterized in that the electrolyte melt is a NaOH melt, a NaNH 2 melt or a mixture thereof or a KOH melt, a KNH 2 melt or a mixture thereof ,
In einer besonders bevorzugten Ausführungsform werden diese Schmelzen oder Gemische davon in wasserfreier Form eingesetzt. In einer weiter besonders bevorzugten Ausführungsform werden als Eletrolytschmelzen Gemische und wiederum besonders bevorzugt wasserfreie Gemische eingesetzt. Darunter sind wiederum eutektische Gemische bevorzugt.In a particularly preferred embodiment, these melts or Mixtures of these are used in anhydrous form. In another particularly preferred Embodiment are mixtures and again as electrolyte melts particularly preferably anhydrous mixtures used. Among them are eutectic ones Mixtures preferred.
Selbstverständlich ist es denkbar, den Flüssigelektrolyten mit einem oder mehreren geeigneten Zusätzen zu versetzen. Beispielsweise seien hierbei unter anderem schmelzpunkterniedrigende Zusätze zu nennen. Prinzipiell sind sämtliche schmelzpunktemiedrigenden Zusätze geeignet, die den erfindungsgemäßen Einsatz der Elektrolysezelle und das erfindungsgemäße Verfahren nicht stören. Bevorzugt werden schmelzpunkterniedrigende Zusätze, die bei der Herstellung von Natrium ausgewählt werden aus der Gruppe bestehend aus NaI, NaBr, Na2CO3 und einem Gemisch aus zwei oder mehr davon, bei der Herstellung von Kalium ausgewählt werden aus der Gruppe bestehend aus KI, KBr, K2CO3 und einem Gemisch davon.It is of course conceivable to add one or more suitable additives to the liquid electrolyte. Examples include additives that lower the melting point. In principle, all additives which lower the melting point and which do not interfere with the use of the electrolytic cell and the method according to the invention are suitable. Preferred are melting point-lowering additives which are selected in the production of sodium from the group consisting of NaI, NaBr, Na 2 CO 3 and a mixture of two or more thereof, and are selected in the production of potassium from the group consisting of KI, KBr , K 2 CO 3 and a mixture thereof.
Der Anoden- und der Kathodenraum der erfindungsgemäßen Elektrolysezelle sind durch einen heliumdichten Alkalimetallionen leitenden Festelektrolyten voneinander getrennt. Für diesen Zweck kommen bei der Natriumherstellung keramische Materialien wie NASICON® in Betracht, deren Zusammensetzung in der EP-A 0 553 400 angegeben ist. Auch Natriumionen leitende Gläser sowie Zeolithe und Feldspate sind geeignet. Bei der Herstellung von Kalium kommen ebenfalls eine Vielzahl von Materialien in Frage. Sowohl die Verwendung von Keramiken als auch die Verwendung von Gläsern sind möglich. Beispielsweise kommen folgende Materialien in Betracht: KBiO3 (T. N. Nguyen et al., Chem. Mater. 1993, 5, 1273-1276), Galliumoxid-Titandioxid-Kaliumoxid-Systeme (S. Yoshikado et al., Solid State Ionics 1992, 53-56, 754-762), Aluminiumoxid-Titandioxid-Kaliumoxid-Systeme und KASICON®-Gläser (M. Lejeune et al., J. Non-Cryst. Solids 1982, 51, 273-276).The anode and cathode compartments of the electrolytic cell according to the invention are separated from one another by a solid electrolyte which conducts helium-tight alkali metal ions. Ceramic materials such as NASICON®, the composition of which is specified in EP-A 0 553 400, are suitable for this purpose in the production of sodium. Glasses that conduct sodium ions as well as zeolites and feldspar are also suitable. A variety of materials can also be used in the production of potassium. Both the use of ceramics and the use of glasses are possible. For example, the following materials can be considered: KBiO 3 (TN Nguyen et al., Chem. Mater. 1993, 5 , 1273-1276), gallium oxide-titanium dioxide-potassium oxide systems (S. Yoshikado et al., Solid State Ionics 1992, 53 -56 , 754-762), alumina-titanium dioxide-potassium oxide systems and KASICON® glasses (M. Lejeune et al., J. Non-Cryst. Solids 1982, 51 , 273-276).
Bevorzugt sind Natrium-β"-Aluminiumoxid, Natrium-β-Aluminiumoxid und Natrium-β/β"-Aluminiumoxid bzw. Kalium-β"-Aluminiumoxid, Kalium-β-Aluminiumoxid und Kalium-β/β"-Aluminiumoxid.Sodium β "aluminum oxide, sodium β aluminum oxide and sodium β / β" aluminum oxide are preferred or potassium-β "aluminum oxide, potassium-β-aluminum oxide and potassium β / β "alumina.
Daher betrifft die vorliegende Erfindung auch eine Elektrolysezelle, wie oben beschrieben, die dadurch gekennzeichnet ist, daß der Festelektrolyt ausgewählt wird aus der Gruppe bestehend aus Natrium-β-Aluminiumoxid, Natrium-β"-Aluminiumoxid und Natrium-β/β"-Aluminiumoxid oder aus der Gruppe bestehend aus Kalium-β-Aluminiumoxid, Kalium-β"-Aluminiumoxid und Kalium-β/β"-Aluminiumoxid. The present invention therefore also relates to an electrolysis cell, as described above, which is characterized in that the solid electrolyte is selected from the group consisting of sodium β-aluminum oxide, sodium β "aluminum oxide and sodium β / β "alumina or selected from the group from potassium-beta-alumina, potassium-beta "-alumina and potassium-beta / beta" -alumina.
Kalium-β"-Aluminiumoxid, Kalium-β-Aluminiumoxid bzw. Kalium-β/β"-Aluminiumoxid können ausgehend von Natrium-β"-Aluminiumoxid, Natrium-β-Aluminiumoxid bzw. Natrium-β/β"-Aluminiumoxid durch Kationenaustausch hergestellt werden.Potassium β "aluminum oxide, potassium β aluminum oxide or potassium β / β" aluminum oxide can start from sodium beta "alumina, sodium beta" alumina or sodium β / β "aluminum oxide by cation exchange getting produced.
Zweckmäßigerweise hat der Festelektrolyt die Form eines dünnwandigen und dennoch druckfesten, einseitig geschlossenen Rohres (EP-B 0 424 673), an dessen offenem Ende ein elektrisch isolierender Ring mittels einer heliumdichten, ebenfalls elektrisch isolierenden Glaslotverbindung aufgebracht ist (GB 2 207 545, EP-B 0 482 785). Die Wandstärke des Alkalimetallionen leitenden Elektrolyten liegt im allgemeinen im Bereich von 0,3 bis 5 mm, bevorzugt im Bereich von 1 bis 3 mm, besonders bevorzugt im Bereich von 1 bis 2 mm.The solid electrolyte expediently has the shape of a thin-walled and nevertheless pressure-resistant, one-sided closed pipe (EP-B 0 424 673), on the open end an electrically insulating ring using a helium-tight, likewise electrically insulating glass solder connection is applied (GB 2 207 545, EP-B 0 482 785). The wall thickness of the electrolyte conducting alkali metal ions lies generally in the range from 0.3 to 5 mm, preferably in the range from 1 to 3 mm, particularly preferably in the range from 1 to 2 mm.
Die Querschnittsform des einseitig geschlossenen Rohres ist in der bevorzugten Ausführungsform kreisrund. Denkbar sind jedoch auch Querschnittsformen mit vergrößerter Oberfläche, die beispielsweise aus einem Verbund mehrerer kreisrunder Flächen abgeleitet werden können.The cross-sectional shape of the tube closed on one side is the preferred one Circular embodiment. However, cross-sectional shapes are also conceivable enlarged surface, for example from a composite of several circular Areas can be derived.
Die Ausführung des Alkalimetallionen leitenden Festelektrolyten hinsichtlich seiner Leckagedichtheit hat auf das erfindungsgemäße Verfahren entscheidenden Einfluß, denn Quecksilber kann nur über Leckstellen im Festelektrolyten oder Dichtungssystem in den Flüssigelektrolyten und somit auch in das erzeugte Alkalimetall gelangen, da bei dem erfindungsgemäßen Verfahren die Anodenpotentiale so eingestellt werden, daß eine Bildung von Quecksilberionen ausgeschlossen wird.The design of the alkali metal ion-conducting solid electrolyte with regard to its Leak tightness has decisive factors in the method according to the invention Influence, because mercury can only over leaks in the solid electrolyte or Sealing system in the liquid electrolytes and thus also in the alkali metal produced arrive because in the method according to the invention the anode potentials be adjusted so that the formation of mercury ions is excluded becomes.
In der Regel kommen Festelektrolyte zum Einsatz, die bei einem Helium-Lecktest Leckraten von weniger als 10-9 (mbar • l)/s aufweisen, also im Rahmen der Nachweisgrenze heliumdicht sind. As a rule, solid electrolytes are used that have leak rates of less than 10 -9 (mbar • l) / s in a helium leak test, i.e. are helium-tight within the detection limit.
Ferner werden die lösbaren Dichtverbindungen bevorzugt so ausgeführt, daß der Flüssigelektrolyt und Amalgam jeweils zur Umgebungsatmosphäre hin abgedichtet werden. Lösbare Dichtungen zwischen Flüssigelektrolyt und Amalgam werden nach Möglichkeit vermieden, da die lösbaren Dichtungen in der Regel zwar flüssigkeitsdicht, nicht jedoch gasdicht sind.Furthermore, the releasable sealing connections are preferably carried out so that the Liquid electrolyte and amalgam are each sealed off from the ambient atmosphere become. Detachable seals between liquid electrolyte and amalgam avoided if possible, since the removable seals are usually liquid-tight, but are not gas-tight.
In einer bevorzugten Ausführungsform kommen als lösbare Dichtverbindungen Flachdichtungen zum Einsatz, vorzugsweise aus Graphit, zum Beispiel aus unverstärktem GRAPHIFLEX®. In einer bevorzugten Ausführungsform werden die Dichtungen mit einem Inertgas wie z.B. Argon oder Stickstoff umspült, um ein Durchdiffundieren von Sauerstoff zu verhindern. Mit heliumdichten Elektrolyten und der aufgeführten Dichtungsanordnung werden Alkalimetalle mit einem Quecksilberrestgehalt im Bereich von 0,05 bis 0,3 ppm erhalten.In a preferred embodiment come as releasable sealing connections Flat seals for use, preferably made of graphite, for example made of unreinforced GRAPHIFLEX®. In a preferred embodiment, the Seals with an inert gas such as Flushed with argon or nitrogen to a To prevent oxygen from diffusing through. With helium-tight electrolytes and the listed sealing arrangement are alkali metals with a Mercury residual content in the range of 0.05 to 0.3 ppm obtained.
Die Geometrie des Festelektrolyten ist im wesentlichen beliebig und kann speziellen Verfahrensbedingungen angepaßt werden. In einer bevorzugten Ausführungsform weist der Festelektrolyt, wie bereits oben erwähnt, die Form eines einseitig geschlossenen Rohres auf. In einer weiter bevorzugten Ausführungsform steht dieses Rohr an seiner Außenseite mit der Anode in Kontakt. Dieser Anodenraum ist, weiter bevorzugt, an seiner Außenseite durch ein Außenrohr begrenzt, das aus einem Material gefertigt ist, das sehr dicht und beständig gegenüber heißem Amalgam ist. Insbesondere kommen als Materialien Edelstahl und Graphit in Frage. In einer weiter bevorzugten Ausführungsform wird als Material Edelstahl gewählt.The geometry of the solid electrolyte is essentially arbitrary and can be special Process conditions are adjusted. In a preferred embodiment the solid electrolyte, as already mentioned above, has the shape of a closed on one side Pipe on. In a further preferred embodiment, this is Tube in contact with the anode on its outside. This anode compartment is more preferably, delimited on its outside by an outer tube that consists of is made of a material that is very dense and resistant to hot Is amalgam. Stainless steel and graphite are particularly suitable as materials. In a further preferred embodiment, stainless steel is selected as the material.
Das Außenrohr kann im wesentlichen einen beliebigen Querschnitt aufweisen. Bevorzugt wird ein Außenrohr verwendet, das konzentrisch mit dem Festelektrolyten-Rohr ist.The outer tube can essentially have any cross section. An outer tube is preferably used which is concentric with the solid electrolyte tube is.
Der Ringspalt zwischen Außenrohr und Keramikrohr wird im Rahmen des erfindungsgemäßen Verfahrens in Längsrichtung von der flüssigen Anode durchströmt. The annular gap between the outer tube and the ceramic tube is within the scope of the invention Flow in the longitudinal direction of the liquid anode.
Dabei weist der Ringspalt, wie bereits erwähnt, eine bevorzugte Spaltweite von 1 bis 10 mm auf. Weiter bevorzugt hat der Ringspalt eine Weite im Bereich von 2 bis 5 mm, besonders bevorzugt eine Weite im Bereich von 2,5 bis 3 mm.As already mentioned, the annular gap has a preferred gap width of 1 up to 10 mm. More preferably, the annular gap has a width in the range of 2 to 5 mm, particularly preferably a width in the range from 2.5 to 3 mm.
Demgemäß betrifft die vorliegende Erfindung eine Elektrolysezelle, wie oben beschrieben, die dadurch gekennzeichnet ist, daß der Festelektrolyt als einseitig geschlossenes Rohr ausgebildet ist, das in ein konzentrisches Edelstahlrohr derart eingebaut ist, daß ein Ringspalt mit einer Spaltweite im Bereich von 1 bis 10 mm entsteht.Accordingly, the present invention relates to an electrolytic cell as described above, which is characterized in that the solid electrolyte is closed on one side Tube is formed, which is installed in a concentric stainless steel tube is that there is an annular gap with a gap width in the range of 1 to 10 mm.
Das erfindungsgemäße Verfahren wird in einer Elektrolysezelle mit einer bewegten flüssigen Alkalimetallamalgamanode betrieben. Hierbei handelt es sich um eine bewegte flüssige Anode, die während des Betriebes hinsichtlich ihres Alkalimetallgehaltes abgereichert wird, so daß sie durch alkalimetallreicheres Amalgam, das in einer betriebsüblichen Amalgamzelle einer Chlor-Alkaliproduktion oder durch Elektrolyse von Natrium- oder Kaliumsalzen mit einer Hg- oder Amalgamkathode, wie z.B. NaOH oder KOH, gewonnen werden kann, ersetzt werden kann.The process according to the invention is carried out in an electrolysis cell with a moving liquid alkali metal amalgam anode operated. This is a moving liquid anode, during operation with regard to its alkali metal content is depleted, so that it is enriched with alkali metal-rich amalgam, that in a normal amalgam cell of a chlor-alkali production or by electrolysis of sodium or potassium salts with a mercury or Amalgam cathode, e.g. NaOH or KOH, can be replaced can be.
Dies kann in technisch einfacher Weise geschehen, da das flüssige Alkalimetallamalgam problemlos zu fördern ist. In der Regel wird der konzentrierte Amalgamablauf einer betriebsüblichen Amalgamzelle in einem Wärmeaustauscher auf die Betriebstemperatur des erfindungsgemäßen Verfahrens erhitzt und der heißen, bewegten flüssigen Anode zugeführt. Zweckmäßigerweise führt man dies in einem Gegenstrom-Wärmeaustauscher so aus, daß das heiß ablaufende abgereicherte Amalgam den Zulauf beheizt.This can be done in a technically simple manner, since the liquid alkali metal amalgam is easy to promote. As a rule, the concentrated amalgam flow a normal amalgam cell in a heat exchanger the operating temperature of the method according to the invention is heated and the hot fed moving liquid anode. This is best done in one Counterflow heat exchanger so that the hot drained depleted Amalgam heated the inlet.
Der Ersatz von abgereichertem Amalgam kann sowohl diskontinuierlich als auch kontinuierlich erfolgen. Die kontinuierliche Verfahrensweise ist dabei betrieblich einfacher durchzuführen. Der Nachteil, daß in der Regel das zulaufende Konzentrat mit im Kreis geführtem, bereits abgereichertem Alkalimetallamalgam verdünnt wird, kann dadurch ausgeglichen werden, daß das Verfahren mehrstufig ausgeführt wird.The replacement of depleted amalgam can be both discontinuous as well done continuously. The continuous procedure is operational easier to do. The disadvantage that usually the incoming concentrate diluted with circulated, already depleted alkali metal amalgam can be compensated for by the fact that the process has several stages is performed.
Die flüssige Anode wird zweckmäßigerweise durch Rühren und/oder mit einer Pumpe in einem unter Atmosphärendruck oder leichtem Überdruck stehenden Kreislauf bewegt. Die durch den umsatzbedingten Austausch von Amalgam verursachte Bewegung und/oder die Thermokonvektion sind im Vergleich zu der im erfindungsgemäßen Verfahren geforderten Bewegung vemachlässigbar und reichen nicht aus, die bevorzugten Stromdichten zu erreichen.The liquid anode is expediently stirred and / or with a Pump in an atmospheric pressure or slightly overpressure Circulation moves. The caused by the sales-related exchange of amalgam Movement and / or thermal convection are compared to that in the required movement negligible and sufficient not reaching the preferred current densities.
Wenn die flüssige Anode, wie in GB 1,155,927 beschrieben, unbewegt betrieben wird, sind nur Stromdichten von 40 bis 70 A/m2 zu erreichen. Mit einer Erhöhung der Zellspannung kann die Stromdichte nur unwesentlich gesteigert werden, weil der Widerstand der Zelle mit zunehmender Stromdichte zunimmt. Überraschenderweise werden bei moderaten Zellspannungen, d.h. Zellspannungen im Bereich von 0,9 bis 1,6 Volt für Natriumamalgam und von 0,95 bis 2,1 Volt für Kaliumamalgam, Stromdichten von 250 bis 3000 A/m2 erreicht, wenn die Anode bewegt wird.If the liquid anode is operated without moving, as described in GB 1,155,927, only current densities of 40 to 70 A / m 2 can be achieved. With an increase in the cell voltage, the current density can only be increased insignificantly because the resistance of the cell increases with increasing current density. Surprisingly, at moderate cell voltages, ie cell voltages in the range from 0.9 to 1.6 volts for sodium amalgam and from 0.95 to 2.1 volts for potassium amalgam, current densities of 250 to 3000 A / m 2 are achieved when the anode is moved ,
Demgemäß betrifft die vorliegende Erfindung auch ein Verfahren, wie oben beschrieben, das dadurch gekennzeichnet ist, daß es bei einer Stromdichte von mehr als 250 A/m2 durchgeführt wird.Accordingly, the present invention also relates to a method as described above, which is characterized in that it is carried out at a current density of more than 250 A / m 2 .
Die Bewegung der Anode erfolgt beispielsweise über eine Rührung durch. beispielsweise Einperlen von Gas oder über einen mechanischen Rührer oder mit einer Pumpe. Bevorzugt ist eine Bewegung in Form einer erzwungenen Strömung, wie sie zum Beispiel mit einem von einer Pumpe getriebenen Amalgamkreislauf erreicht werden kann.The anode is moved, for example, by stirring. for example Bubbling gas or using a mechanical stirrer or with a pump. A movement in the form of a forced flow is preferred, such as with an amalgam circuit driven by a pump can be achieved.
Die Strömungsgeschwindigkeit liegt im allgemeinen im Bereich von 0,03 bis 1,0 m/s, bevorzugt im Bereich von 0,05 bis 0,6 m/s und besonders bevorzugt im Bereich von 0,1 bis 0,3 m/s. Eine höhere Strömungsgeschwindigkeit gestattet in der Regel höhere Stromdichten. Ein weiterer bauartbedingter Vorteil der Anode in Form eines Ringspaltes liegt in dem relativ kleinen, auf die Anodenfläche bezogenen Anodenvolumen. Damit wird es möglich, die Forderung nach moderatem Apparategewicht und akzeptablem Quecksilberumlaufvermögen zu erfüllen.The flow rate is generally in the range of 0.03 to 1.0 m / s, preferably in the range from 0.05 to 0.6 m / s and particularly preferably in the range from 0.1 to 0.3 m / s. A higher flow rate allows in the Usually higher current densities. Another design advantage of the anode in The shape of an annular gap lies in the relatively small area of the anode Anode volume. This makes it possible to meet the demand for moderate apparatus weight and acceptable mercury circulating capacity.
Als Kathodenmaterial können in der erfindungsgemäßen Zelle im wesentlichen alle geeigneten Materialien dienen. Beispiele hierfür sind unter anderem etwa Stahl, Reinnickel mit beispielsweise der DIN-Werkstoffnummer 2.4066 oder Elektrodengraphit. In einer bevorzugten Ausgestaltungsform der erfindungsgemäßen Zelle ist die Kathode aus Stahl gefertigt.Essentially all of them can be used as cathode material in the cell according to the invention suitable materials. Examples include steel, Pure nickel with, for example, the DIN material number 2.4066 or electrode graphite. In a preferred embodiment of the cell according to the invention the cathode is made of steel.
Demgemäß betrifft die vorliegende Erfindung auch eine Elektrolysezelle, wie oben beschrieben, die dadurch gekennzeichnet ist, daß die Kathode eine Stahlkathode ist.Accordingly, the present invention also relates to an electrolytic cell as above described, which is characterized in that the cathode is a steel cathode.
Geeignete Stähle sind unter anderem etwa Edelstahl, austenitischer Stahl oder unlegierter Stahl. Als bevorzugte austenitische Stähle sind unter anderem die Stähle mit den DIN-Werkstoffnummern 1.4541 oder 1.4571 zu nennen, als bevorzugte unlegierte Stähle die Stähle mit den DIN-Werkstoffnummern 1.0305 oder 1.0346. In einer ganz besonders bevorzugten Ausführungsform der erfindungsgemäßen Elektrolysezelle werden unlegierte Stähle eingesetzt.Suitable steels include stainless steel, austenitic steel or carbon steel. The preferred austenitic steels include Steels with the DIN material numbers 1.4541 or 1.4571 to name as preferred unalloyed steels the steels with the DIN material numbers 1.0305 or 1.0346. In a very particularly preferred embodiment of the invention Unalloyed steels are used in electrolysis cells.
In einer weiter bevorzugten Ausführungsform ist die Kathode als Stab ausgebildet, der in den als Rohr ausgebildeten Festelektrolyten eingebaut ist. Vorzugsweise wird der Stab dergestalt eingebaut, daß zwischen dem Festelektrolyten und dem Stab ein Spalt mit einer Spaltweite im Bereich von 1 bis 6 mm entsteht.In a further preferred embodiment, the cathode is designed as a rod, which is built into the solid electrolyte designed as a tube. Preferably the rod is installed in such a way that between the solid electrolyte and the Rod creates a gap with a gap width in the range of 1 to 6 mm.
Demgemäß betrifft die vorliegende Erfindung auch eine Zelle, wie oben beschrieben, die dadurch gekennzeichnet ist, daß die Stahlkathode als Stab ausgebildet ist, der in den als Rohr ausgebildeten Festelektrolyten derart eingebaut ist, daß zwischen der Innenwand des Festelektrolyten und dem Stab ein Spalt mit einer Spaltweite im Bereich von 1 bis 6 mm entsteht.Accordingly, the present invention also relates to a cell as described above which is characterized in that the steel cathode is designed as a rod, which is installed in the solid electrolyte in the form of a tube such that between a gap with a gap width in the inner wall of the solid electrolyte and the rod Range from 1 to 6 mm arises.
Die Kathode kann in der erfindungsgemäßen Zelle selbstverständlich auch alle anderen geeigneten Geometrien aufweisen. Beispielsweise kann sie als Rohr, als Drahtnetz oder als Streckmetall ausgebildet sein.The cathode can of course also all in the cell according to the invention have other suitable geometries. For example, as a tube, as Wire mesh or be designed as expanded metal.
An der festen Kathode entsteht im erfindungsgemäßen Verfahren das Alkalimetall. Dieses steigt an der gemäß der bevorzugten Ausführungsform als Stab ausgebildeten Kathode in dem Flüssigelektrolyten auf und kann als reine metallische Phase abgezogen werden.In the process according to the invention, the alkali metal is formed on the solid cathode. This increases on the rod which is designed according to the preferred embodiment Cathode in the liquid electrolyte and can be used as a pure metallic Phase are deducted.
Beim Betreiben des erfmdungsgemäßen Verfahrens muß die Einwirkung von Wasserdampf auf die Alkalimetallionen leitenden Keramiken ebenfalls unbedingt ausgeschlossen werden. In der Regel wird dazu das Wasserspuren führende Amalgam erhitzt, der Wasserdampf abgeführt und erst dann das wasserfreie Amalgam-Quecksilbergemisch der flüssigen Anode zugeführt. Die Abfuhr des Wasserdampfes wird zweckmäßigerweise durch Strippen mit Inertgas oder dem Anlegen von Unterdruck unterstützt.When operating the method according to the invention, the action of Water vapor on the ceramics that conduct alkali metal ions is also essential be excluded. As a rule, this leads to the amalgam that traces water heated, the water vapor removed and only then the water-free amalgam-mercury mixture fed to the liquid anode. Removal of water vapor is conveniently by stripping with inert gas or by applying Negative pressure supported.
Weiter betrifft die vorliegende Erfindung auch ein Verfahren, wie oben beschrieben, das dadurch gekennzeichnet ist, daß es bei einer Temperatur im Bereich von 260 bis 400 °C durchgeführt wird.The present invention also relates to a method as described above, which is characterized in that it is at a temperature in the range of 260 to 400 ° C is carried out.
Die Stromdichte liegt im allgemeinen bei 0,5 bis 10 kA/m2, bevorzugt bei 1,0 bis 3 kA/m2 (Natrium) bzw. 0,3 bis 3 kA/m2, bevorzugt bei 0,5 bis 1,5 kA/m2 (Kalium). Die Stromdichte wird an der äußeren Stromquelle, in der Regel einem Netzgleichrichter, gezielt eingestellt. The current density is generally 0.5 to 10 kA / m 2 , preferably 1.0 to 3 kA / m 2 (sodium) or 0.3 to 3 kA / m 2 , preferably 0.5 to 1, 5 kA / m 2 (potassium). The current density is specifically set at the external power source, usually a line rectifier.
In einer besonderen Ausführungsform wird die erfindungsgemäße Elektrolysezelle in die Stromversorgung einer amalgamliefernden Chlorzelle integriert, so daß ein zusätzlicher Netzgleichrichter entfallen kann.In a special embodiment, the electrolysis cell according to the invention integrated into the power supply of an amalgam-supplying chlorine cell, so that a additional line rectifier can be omitted.
Beim Ersteinsatz der Alkalimetallionen leitenden Festelektrolyten wird häufig ein zu hoher Keramikwiderstand beobachtet, der im Laufe des weiteren Betriebes unverändert hoch bleibt. Der Widerstand des Festelektrolyten kann im Vergleich zu den erreichbaren Werten bis um den Faktor 30 überhöht sein. Dies ist vermutlich auf die mangelnde Reaktivität der Oberfläche zurückzuführen. Die Ursache ist in der Einwirkung von Wasser in Form des Wassergehaltes der Umgebungsluft zu suchen. Diese Schädigung kann insbesondere bei Lagerung der Keramiken oder während der Montage erfolgen. Deshalb werden die Keramikrohre zweckmäßigerweise nach dem Sintern unter Vakuum in diffussionsdichte Aluminium/Kunststoff Verbundfolien verpackt. Zur Lagerung werden die originalverpackten 'Keramikrohre in dicht schließende, mit Argon gefüllte Metallbehälter eingeschlossen.When the alkali metal ions conducting solid electrolytes are used for the first time, a too high a ceramic resistance is observed, which in the course of further operation remains high. The resistance of the solid electrolyte can be compared be too high by a factor of 30. This is believed to be due to the lack of reactivity of the surface. The cause is in the action of water in the form of the water content of the ambient air to search. This damage can occur particularly when the ceramics or done during assembly. Therefore, the ceramic tubes are convenient after sintering under vacuum in diffusion-proof aluminum / plastic Packed composite films. The original packaging is used for storage '' Ceramic tubes in tightly closing, argon-filled metal containers locked in.
In einer weiter bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens wird der Festelektrolyt konditioniert, um so eine Absenkung seines Widerstandes zu erreichen.In a further preferred embodiment of the method according to the invention the solid electrolyte is conditioned in order to lower its resistance to reach.
Demgemäß betrifft die vorliegende Erfindung auch ein Verfahren, wie oben beschrieben, das dadurch gekennzeichnet ist, daß der Festelektrolyt vor der Durchführung des Verfahrens konditioniert wird.Accordingly, the present invention also relates to a method as described above, which is characterized in that the solid electrolyte before the implementation the process is conditioned.
Hierbei ist es unter anderem denkbar, zur Konditionierung den Festelektrolyten vor und/oder nach dem Einbau in die Elektrolysezelle mit einer oder mehreren chemischen Verbindungen zu behandeln, um so beispielsweise eine oder mehrere ionenleitende Schichten aufzubringen. Hierfür sind prinzipiell alle geeigneten chemischen Verbindungen denkbar. Here it is conceivable, among other things, for conditioning the solid electrolyte before and / or after installation in the electrolytic cell with one or more to treat chemical compounds, for example one or more to apply ion-conducting layers. In principle, all are suitable for this chemical compounds conceivable.
Wird im erfindungsgemäßen Verfahren Natrium hergestellt, ist es beispielsweise möglich, den Festelektrolyten mit NaOH, NaNH2, NaOR oder einem Gemisch aus zwei oder mehr davon zu behandeln. Wird im erfindungsgemäßen Verfahren Kalium hergestellt, ist es beispielsweise möglich, den Festelektrolyten mit KOH, KNH2, KOR oder einem Gemisch aus zwei oder mehr davon zu behandeln. Hierbei bezeichnet R einen geradkettigen oder verzweigtkettigen Alkylrest mit 1 bis 5 Kohlenstoffatomen. Ebenso kann R einen geeigneten, gegebenenfalls geeignet substituierten Aryl- oder Aralkylrest bezeichnen.If sodium is produced in the process according to the invention, it is possible, for example, to treat the solid electrolyte with NaOH, NaNH 2 , NaOR or a mixture of two or more thereof. If potassium is produced in the process according to the invention, it is possible, for example, to treat the solid electrolyte with KOH, KNH 2 , KOR or a mixture of two or more thereof. Here, R denotes a straight-chain or branched-chain alkyl radical having 1 to 5 carbon atoms. R can likewise denote a suitable, optionally suitably substituted aryl or aralkyl radical.
Demgemäß betrifft die vorliegende Erfindung auch ein Verfahren, wie oben beschrieben, das dadurch gekennzeichnet ist, daß der Festelektrolyt mit NaOH, NaNH2, NaOR oder einem Gemisch aus zwei oder mehr davon oder mit KOH, KNH2, KOR oder einem Gemisch aus zwei oder mehr davon konditioniert wird, wobei R einen geradkettigen oder verzweigtkettigen Alkylrest mit 1 bis 5 Kohlenstoffatomen bezeichnet.Accordingly, the present invention also relates to a method as described above, which is characterized in that the solid electrolyte with NaOH, NaNH 2 , NaOR or a mixture of two or more thereof or with KOH, KNH 2 , KOR or a mixture of two or more of which is conditioned, where R denotes a straight-chain or branched-chain alkyl radical having 1 to 5 carbon atoms.
Denkbar ist hierbei unter anderem, den Festelektrolyten mit einer Schmelze, mit alkoholischer Lösung und/oder mit wäßriger Lösung der oben genannten Verbindungen zu behandeln.It is conceivable, among other things, to use the solid electrolyte with a melt alcoholic solution and / or with aqueous solution of the above compounds to treat.
Demgemäß betrifft die vorliegende Erfindung auch ein Verfahren, wie oben beschrieben, das dadurch gekennzeichnet ist, daß NaOH, NaNH2, NaOR oder das Gemisch aus zwei oder mehr davon oder KOH, KNH2, KOR oder das Gemisch aus zwei oder mehr davon als Schmelze oder/und als wäßrige Lösung oder/und als alkoholische Lösung eingesetzt werden.Accordingly, the present invention also relates to a process as described above, which is characterized in that NaOH, NaNH 2 , NaOR or the mixture of two or more thereof or KOH, KNH 2 , KOR or the mixture of two or more thereof as a melt or / and as an aqueous solution or / and as an alcoholic solution.
Ist der Festelektrolyt in einer bevorzugten Ausführungsform als Rohr ausgebildet, ist es möglich, eine Seite oder beide Seiten des Rohres durch Behandlung mit diesen chemischen Verbindungen zu konditionieren. Selbstverständlich ist es auch möglich, den Festelektrolyten in zwei oder mehr Schritten mehrfach zu konditionieren, wobei die chemische Verbindung oder das Gemisch aus zwei oder mehr davon in den einzelnen Konditionierungsschritten gleich oder unterschiedlich sein kann.If the solid electrolyte is designed as a tube in a preferred embodiment, it is possible to treat one side or both sides of the tube by treating them to condition chemical compounds. Of course it is too possible to condition the solid electrolyte several times in two or more steps, wherein the chemical compound or the mixture of two or more of which may be the same or different in the individual conditioning steps can.
Eine weitere Möglichkeit, den Festelektrolyten zu konditionieren und den Kermaikwiderstand abzusenken, besteht darin, die Zelle zunächst umgepolt zu betreiben, d.h. die Anode zuerst als Kathode und die Kathode zunächst als Anode zu betrieben. Die Kathode kann in diesem Fall wie sonst die Anode aus Natriumamalgam und Quecksilber bestehen. Die Stromdichte wird im umgepolten Zustand über eine Zeit von 1 bis 44 h, bevorzugt 2 bis 6 h, linear von 50 A/m2 auf 3000 A/m2 (Natrium) bzw. von 30 A/m2 auf 1000 A/m2 (Kalium) gesteigert.Another possibility of conditioning the solid electrolyte and lowering the ceramic resistance is to first operate the cell with reversed polarity, ie to operate the anode first as the cathode and the cathode as the anode. In this case, the cathode, like the anode, can consist of sodium amalgam and mercury. The current density in the reversed state is linear over a period of 1 to 44 h, preferably 2 to 6 h, from 50 A / m 2 to 3000 A / m 2 (sodium) or from 30 A / m 2 to 1000 A / m 2 (potassium) increased.
Die geringsten Keramikwiderstände erhält man, wenn beim Anfahren für 1 bis 24 Stunden bei einer Betriebstemperatur von 300 bis 350 °C (Natrium) bzw. 250 bis 350 °C (Kalium) zunächst flüssiges Alkalimetall als Anode eingesetzt wird, welches danach durch Amalgam ersetzt wird. Diese Ausführungsform der Konditionierung ist besonders bevorzugt.The lowest ceramic resistances are obtained when starting for 1 to 24 Hours at an operating temperature of 300 to 350 ° C (sodium) or 250 to 350 ° C (potassium) first liquid alkali metal is used as anode, which then replaced by amalgam. This embodiment of conditioning is particularly preferred.
Selbstverständlich ist es auch möglich, die oben genannten Arten der Konditionierung in Kombination miteinander durchzuführen, wobei sämtliche Kombinationen denkbar sind.Of course, it is also possible to use the above types of conditioning perform in combination with each other, all combinations are conceivable.
In einer bevorzugten Verfahrensweise wird die Stromrichtung in Zeitintervallen von 1 bis 24 Stunden für jeweils 1 bis 10 Minuten umgepolt betrieben, indem Anode und Kathode über einen äußeren Widerstand kurzgeschlossen werden. Der Widerstand ist so bemessen, daß die Stromstärke beim Umpolen etwa dem 1,5-fachen der Stromstärke im Betrieb entspricht. Die Ausbeute an gewonnenem Alkalimetall ist bei dem erfindungsgemäßen Verfahren vollständig, bezogen auf das anodenseitig umgesetzte Alkalimetall. Die Stromausbeute an gewonnenem Alkalimetall ist bei normal gepolter Betriebsweise im Rahmen der Meßgenauigkeit 100%ig. Durch das intervallweise Umpolen vermindert sich die gemittelte Stromausbeute auf Werte im Bereich von 95 bis 98 %. In a preferred procedure, the current direction is in time intervals from 1 to 24 hours for 1 to 10 minutes reversed by Anode and cathode are short-circuited via an external resistor. The Resistance is dimensioned so that the current strength during polarity reversal is about 1.5 times corresponds to the current in operation. The yield of alkali metal recovered is complete in the process according to the invention, based on the alkali metal converted on the anode side. The current yield of the alkali metal obtained is in normal polarity mode of operation within the measurement accuracy 100%. The averaged current yield is reduced due to the intermittent polarity reversal to values in the range of 95 to 98%.
Das der Anode zugeführte Amalgam wird in einer bevorzugten Ausführungsform von 0,4 Gew.-% auf 0,1 Gew.-% Alkalimetall abgereichert. Das nicht umgesetzte Alkalimetall geht bei Kopplung mit einer Chloralkalielektrolyse nicht verloren, weil es in die Chloralkalizelle zurückgeführt wird und über den Amalgamkreislauf von dort zurückkommt.The amalgam supplied to the anode is in a preferred embodiment depleted from 0.4% by weight to 0.1% by weight of alkali metal. The not implemented Alkali metal is not lost when coupled with chlor-alkali electrolysis, because it is returned to the chlor-alkali cell and via the amalgam cycle comes back from there.
Somit betrifft die vorliegende Erfindung auch ein integriertes Verfahren zur Herstellung
von Chlor und Alkalimetall ausgehend von Alkalimetallchlorid, das die
folgenden Stufen (i) und (ii) umfaßt:
Die vorliegende Erfindung wird im folgenden Beispiel näher erläutert. In diesem Beispiel wird Bezug genommen auf die beiden dieser Anmeldung beiliegenden Figuren 1 und 2. Hierbei zeigt
- Fig.1:
- Schematische Darstellung einer erfindungsgemäßen Eletrolysezelle, umfassend einen einseitig geschlossenen rohrförmigen Festelektrolyten, der in ein konzentrisches Edelstahlrohr eingebaut ist, wobei in den rohrförmigen Festelektrolyten selbst wiederum eine stabförmige Edelstahlelektrode eingebaut ist.
- Fig.2:
- Schematische Darstellung einer für den Dauerbetrieb konzipierten Apparatur, in der die erfindungsgemäße Elektrolysezelle eingebaut ist.
- Fig.1:
- Schematic representation of an electrolysis cell according to the invention, comprising a tubular solid electrolyte which is closed on one side and which is installed in a concentric stainless steel tube, a rod-shaped stainless steel electrode itself being installed in the tubular solid electrolyte itself.
- Figure 2:
- Schematic representation of an apparatus designed for continuous operation, in which the electrolytic cell according to the invention is installed.
Die Zelle nach Figur 1 bestand in ihrem Kern aus einem einseitig geschlossenen Rohr (1) aus β"-Aluminiumoxid (32 mm Außendurchmesser, 210 mm Länge, Wandstärke 1,7 mm). Am offenen Ende war ein Ring aus α-Aluminiumoxid (2) mittels einer Glaslotverbindung heliumdicht angebracht. Mittels dieses Ringes (2) war das bzgl. Natriumionen leitfähige Rohr aus β"-Aluminiumoxid mit der Öffnung nach oben in ein konzentrisches Edelstahlrohr (3) (mit einem Innendurchmesser von 37 mm und einer Länge von ca. 215 mm) eingebaut. Der Innendurchmesser des Stahlrohres war auf den Außendurchmesser des Keramikrohres abgestimmt, so daß ein Ringspalt mit einer Spaltweite von 2,5 mm entstand. Der über den Ringspalt und die Rohrlänge definierte Anodenraum erfüllte zum einen die Forderung nach einem apparativen Konzept, welches mit relativ kleinem Queck- , silberinhalt auskam. Zum anderen gestattete der Ringquerschnitt eine hinsichtlich der Stromdichte sehr effektive Durchströmung des Anodenraumes in axialer Richtung. Zur Abdichtung wurde der Ring aus α-Aluminiumoxid (2) mit je einer Flachdichtung unten (4) und oben (5) über den Gehäuse- (6) und den Deckelflansch (7) mit vier Spannschrauben (8) verpreßt.The core of the cell according to FIG. 1 consisted of a cell closed on one side Tube (1) made of β "aluminum oxide (32 mm outer diameter, 210 mm length, Wall thickness 1.7 mm). At the open end was a ring made of α-aluminum oxide (2) attached helium-tight using a glass solder connection. By means of this ring (2) was the tube which was conductive with respect to sodium ions and was made of β "aluminum oxide with the opening into a concentric stainless steel tube (3) (with an inner diameter of 37 mm and a length of approx. 215 mm). The inside diameter of the steel tube was matched to the outside diameter of the ceramic tube, so that an annular gap with a gap width of 2.5 mm was created. The over the anode space defined by the annular gap and the tube length fulfilled on the one hand the Demand for an apparatus concept that uses a relatively small mercury, silver content came out. Secondly, the ring cross-section allowed one in terms of the current density very effective flow through the anode space in the axial Direction. The ring was made of α-aluminum oxide (2) with one each Flat gasket below (4) and above (5) over the housing (6) and the cover flange (7) with four clamping screws (8).
An den Edelstahlbehälter war eine Anodenstromzuführung (9) angebracht. Für die Zufuhr von Amalgam war seitlich unten ein Rohrstutzen (10), für den Ablauf seitlich oben ein Rohrstutzen (11) angeschweißt. Vom Deckelflansch aus ragte ein Stab aus Edelstahl (18) als Kathode in die Öffnung des Rohres aus β"-Aluminiumoxid.An anode power supply (9) was attached to the stainless steel container. For the Amalgam was supplied at the bottom with a pipe socket (10) for the drain at the side a pipe socket (11) welded on top. Protruded from the cover flange Rod made of stainless steel (18) as a cathode in the opening of the tube made of β "aluminum oxide.
In den Deckelflansch war ein Abscheideraum eingelassen, in den sich unter Einfluß der Schwerkraft das schmelzflüssige Natrium von der schwereren Elektrolytschmelze trennte. A separating space was let into the cover flange, which could be influenced gravity the molten sodium from the heavier electrolyte melt separated.
Ein Rohr (13) war durch den Deckelflansch geführt und diente zur freien Abfuhr von flüssigem Natrium. Die Zelle konnte mit elektrischen Heizbändern (14) umwickelt und isoliert werden oder zusammen mit mehreren Zellen in eine beheizte Kammer eingebaut werden.A tube (13) was passed through the cover flange and was used for free removal of liquid sodium. The cell could be wrapped with electrical heating tapes (14) and be isolated or together with several cells in a heated Chamber to be installed.
Das gebildete flüssige Natrium wurde mit reaktionsbedingt erzeugtem Druck über das beheizte Ablaufrohr (13) in ein inertisiertes, teilweise mit Paraffinöl gefülltes Gefäß ausgetragen und erstarrte im Paraffinöl in Form kleiner Kugeln.The liquid sodium formed was over with pressure generated by reaction the heated drain pipe (13) in an inert, partially filled with paraffin oil The vessel was discharged and solidified in paraffin oil in the form of small balls.
Die Elektrolysezelle wurde in eine für den Dauerbetrieb konzipierte Apparatur mit folgenden Funktionen integriert (Figur 2).
- Dauerversorgung (19) mit trockenem vorgeheiztem Na-reichem Amalgam.
- Beheizung (20), ausgestaltet für Beheizung im Bereich von 310 °C bis 360 °C.
- Gleichstromversorgung (21).
- Definierte Strömungsgeschwindigkeit in der Anode durch einen internen, mit einer Pumpe (23) getriebenen Amalgamkreislauf (22), stufenlos einstellbar im Bereich von 0,02 bis 0,8 m/s.
- Ableitung von flüssigem Natrium (24).
- Dauerentsorgung von Na-armem Amalgam (25).
- Abgasbehandlung (26).
- Sicherheitsüberwachung besonders hinsichtlich Hg-Emission (27).
- Permanent supply (19) with dry preheated Na-rich amalgam.
- Heating (20), designed for heating in the range from 310 ° C to 360 ° C.
- DC power supply (21).
- Defined flow rate in the anode through an internal amalgam circuit (22) driven by a pump (23), continuously adjustable in the range from 0.02 to 0.8 m / s.
- Derivation of liquid sodium (24).
- Permanent disposal of low-sodium amalgam (25).
- Exhaust treatment (26).
- Security monitoring especially with regard to mercury emissions (27).
Der Einbau des handelsüblichen Rohres aus Natrium-β"-Aluminiumoxid erfolgte umgehend im Laufe einer Stunde in der Laboratmosphäre, nachdem es einer Vakuumverpackung entnommen wurde. Danach wurden beide Kammern der Zelle mit Argon geflutet und die Zelle verschlossen. Der Einbau in die Apparatur erfolgte 2 bis 5 Tage später. The commercial pipe made of sodium β "aluminum oxide was installed promptly within an hour in the laboratory atmosphere after using a vacuum package was removed. After that, both chambers of the cell flooded with argon and the cell closed. The installation in the apparatus took place 2 to 5 days later.
Die Apparatur wurde mit einer Temperatursteigerung von 20 °C/h auf 330 °C aufgeheizt. Danach wurde der Kathodenraum innerhalb des einseitig geschlossenen Keramikrohres über eine Zufuhrleitung mit einer extern aufgeschmolzenen Schmelze aus 60 Gew.-% NaNH2 und 40 Gew.-% NaOH gefüllt. Der Anodenraum außerhalb des Keramikrohres wurde mit flüssigem Natrium gefüllt. Über eine Zeit von 35 Minuten wurde einmalig die Stromstärke von 5 A auf 40 A in Schrittstufen von jeweils 5 A gesteigert und dann über 4 Stunden bei 40 A gehalten.The apparatus was heated to 330 ° C. with a temperature increase from 20 ° C./h. The cathode space inside the ceramic tube, which was closed on one side, was then filled via a feed line with an externally melted melt of 60% by weight NaNH 2 and 40% by weight NaOH. The anode space outside the ceramic tube was filled with liquid sodium. Over a period of 35 minutes, the current was increased once from 5 A to 40 A in increments of 5 A and then held at 40 A for 4 hours.
Nach 4 Stunden war das Spannungs- / Stromverhältnis auf 0,18 V / 40 A eingelaufen. Danach wurden der Anodenraum entleert und der Amalgamkreislauf mit 39 kg Amalgam gefüllt. Der Inhalt des Amalgamkreislaufes wurde bei ausgeschalteter Pumpe auf 330 °C erwärmt. Anschließend wurde der Kreislauf in Betrieb gesetzt. Dabei wurde das noch im Anodenraum befindliche Natrium ausgespült und im Amalgam selbst verteilt.After 4 hours the voltage / current ratio had dropped to 0.18 V / 40 A. The anode compartment was then emptied and the amalgam circuit at 39 kg of amalgam filled. The content of the amalgam cycle was switched off Pump warmed to 330 ° C. The circuit was then started up. The sodium still in the anode compartment was rinsed out and distributed in the amalgam itself.
Diese erste Füllung wurde verworfen und der Kreislauf mit frischem, auf 330 °C erwärmtem Amalgam mit 0,4 Gew.-% Natriumanteil aufgefüllt. Es wurde eine mittlere Strömungsgeschwindigkeit von 0,3 m/s eingestellt, was einem Umlaufvolumenstrom von 0,29 m3/h entsprach.This first filling was discarded and the circuit was filled with fresh amalgam heated to 330 ° C. and containing 0.4% by weight of sodium. An average flow rate of 0.3 m / s was set, which corresponded to a circulation volume flow of 0.29 m 3 / h.
Im stromlosen Zustand stellte sich eine Zellspannung von 0,82 V ein. Die Ausgangsspannung eines Gleichstromnetzgerätes wurde auf 2 Volt begrenzt und der Stromkreis mit der Zelle geschlossen. Dabei wurde im Zeitrahmen von 3 Stunden der Strom von 0 A auf 40 A linear gesteigert. Danach wurden im Zeitintvervall von 30 min jeweils 7,8 kg Amalgam aus dem Kreislaufinhalt abgelassen und durch frisches Amalgam ersetzt. Dabei wurde beobachtet, daß die Zellspannung zwischen Werten im Bereich von 1,5 bis 1,7 Volt pendelte. A cell voltage of 0.82 V was set in the de-energized state. The output voltage a DC power supply was limited to 2 volts and the Circuit closed with the cell. It was done in a time frame of 3 hours the current increased linearly from 0 A to 40 A. After that were in the time interval of 30 min each drained 7.8 kg of amalgam from the circulatory contents and replaced by fresh amalgam. It was observed that the cell voltage fluctuated between values in the range of 1.5 to 1.7 volts.
Aus einem Strom von 40 A bei einer Anodenfläche von 200 cm2 errechnete sich eine Stromdichte von 2000 A/m2. Diese war doppelt so hoch im Vergleich zu derjenigen, die für eine industrielle Nutzung des Verfahrens erforderlich ist.From a current of 40 A at an anode area of 200 cm 2, a current density calculated from 2000 A / m 2. This was twice as high as that required for industrial use of the process.
Es kam zum stetigen Austrag von Natrium. Der Natriumaustrag und die Abreicherung des Amalgams entsprachen dem Faradayschen Gesetz. Der Versuch blieb über mindestens 4000 Betriebsstunden hinweg stabil.There was a constant discharge of sodium. Sodium discharge and depletion of the amalgam corresponded to Faraday's law. The attempt stayed stable for at least 4000 operating hours.
Claims (14)
- An electrolytic cell comprising an agitated, liquid anode containing an alkali metal amalgam, the liquid anode being agitated by stirring and/or by means of a pump in a circuit under atmospheric pressure or slight positive pressure, an alkali metal ion-conducting solid electrolyte and a cathode, wherein the solid electrolyte and the cathode are separated from one another by a liquid electrolyte.
- The electrolytic cell as claimed in claim 1, wherein the liquid electrolyte is an electrolyte melt.
- The electrolytic cell as claimed in claim 2, wherein the electrolyte melt is an NaOH melt, an NaNH2 melt or a mixture of these, or is a KOH melt, a KNH2 melt or a mixture of these.
- The electrolytic cell as claimed in any one of claims 1 to 3, wherein the solid electrolyte is selected from the group consisting of sodium β-aluminum oxide, sodium β"-aluminum oxide and sodium β/β"-aluminum oxide or from the group consisting of potassium β-aluminum oxide, potassium β"-aluminum oxide and potassium β/β"-aluminum oxide.
- The electrolytic cell as claimed in any one of claims 1 to 4, wherein the solid electrolyte is fashioned as a unilaterally closed tube which is mounted inside a concentric alloy steel tube in such a way as to produce an annular gap having a gap width in the range of from 1 to 10 mm.
- The electrolytic cell as claimed in any one of claims 1 to 5, wherein the cathode is a steel cathode.
- The electrolytic cell as claimed in claim 6, wherein the steel cathode is fashioned as a rod which is mounted in the solid electrolyte as claimed in claim 4 in such a way as to produce, between the inner wall of the solid electrolyte and the rod, a gap having a gap width in the range of from 1 to 6 mm.
- A process for producing an alkali metal using an electrolytic cell as claimed in any one of claims 1 to 7.
- The process as claimed in claim 8, which is carried out at a current density greater than 250 A/m2.
- The process as claimed in claim 8 or 9, which is carried out at a temperature in the range from 260 to 400°C.
- The process as claimed in any one of claims 8 to 10, wherein the solid electrolyte is conditioned.
- The process as claimed in claim 11, wherein the solid electrolyte is conditioned with NaOH, NaNH2, NaOR or a mixture of two or more of these, or with KOH, KNH2, KOR or a mixture of two or more of these, where R denotes a straight-chain or branched-chain alkyl radical having from 1 to 5 carbon atoms.
- The process as claimed in claim 12, wherein NaOH, NaNH2, NaOR or the mixture of two or more of these, or KOH, KNH2, KOR or the mixture of two or more of these are employed as a melt or/and as an aqueous solution or/and as an alcoholic solution.
- An integrated process for producing chlorine and alkali metal, starting from alkali metal chloride, which comprises the following steps (i) and (ii):(i) performing a chlor-alkali electrolysis to obtain elemental chlorine and alkali metal amalgam;(ii) performing a process as claimed in any one of claims 8 to 13 to obtain alkali metal.
Applications Claiming Priority (2)
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DE19926724 | 1999-06-11 | ||
DE19926724A DE19926724A1 (en) | 1999-06-11 | 1999-06-11 | Electrolytic cell for the production of an alkali metal |
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EP1059366A2 EP1059366A2 (en) | 2000-12-13 |
EP1059366A3 EP1059366A3 (en) | 2000-12-20 |
EP1059366B1 true EP1059366B1 (en) | 2004-04-07 |
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EP00111875A Expired - Lifetime EP1059366B1 (en) | 1999-06-11 | 2000-06-09 | Electrolytic cell for producing an alkali metal |
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US (1) | US6368487B1 (en) |
EP (1) | EP1059366B1 (en) |
JP (1) | JP4838410B2 (en) |
KR (1) | KR100672866B1 (en) |
CN (1) | CN1170960C (en) |
AT (1) | ATE263855T1 (en) |
DE (2) | DE19926724A1 (en) |
ES (1) | ES2218029T3 (en) |
RU (1) | RU2252981C2 (en) |
TW (1) | TWI232245B (en) |
Cited By (1)
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DE10360758A1 (en) * | 2003-12-23 | 2005-07-28 | Degussa Ag | Electrochemical production of alkali alcoholate, used as intermediate, reactant or catalyst in organic synthesis, uses sodium- or potassium-ion-conducting ceramic membrane separating anolyte containing salt and alcoholic catholyte |
Families Citing this family (8)
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US7108777B2 (en) * | 2002-03-15 | 2006-09-19 | Millennium Cell, Inc. | Hydrogen-assisted electrolysis processes |
DE102004044404A1 (en) * | 2004-09-14 | 2006-03-30 | Basf Ag | Electrolysis apparatus for the production of alkali metal |
DE102004044405A1 (en) * | 2004-09-14 | 2006-03-30 | Basf Ag | Electrolysis cell for the production of alkali metal |
KR101284571B1 (en) * | 2012-12-14 | 2013-07-11 | 한국지질자원연구원 | Method of manufacturing anode cell for electrolysis with enhanced current density, and furnace containing thereof |
CN103918854A (en) * | 2013-01-11 | 2014-07-16 | 杨福顺 | Fruit particle sugar adopting fruit particles as base material, fruit particle sugar powder, production method of fruit particle sugar and fruit particle sugar powder, and uses of fruit particle sugar and fruit particle sugar powder |
CN104805469B (en) * | 2015-05-11 | 2017-04-05 | 中国东方电气集团有限公司 | A kind of cathode electrolytic cell of electrolytic preparation metallic sodium device |
CH716315A1 (en) * | 2019-06-14 | 2020-12-15 | Ulrich Bech | Separating element for separating a cathode compartment from an anode compartment. |
CA3145506A1 (en) * | 2019-07-25 | 2021-01-28 | Maciej Urban JASTRZEBSKI | Molten salt membrane electrolyzer |
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GB1155927A (en) | 1967-02-20 | 1969-06-25 | Ici Ltd | Electrolytic manufacture of alkali metals. |
US4156635A (en) * | 1978-03-29 | 1979-05-29 | The United States Of America As Represented By The United States Department Of Energy | Electrolytic method for the production of lithium using a lithium-amalgam electrode |
JPH0665071B2 (en) * | 1988-03-14 | 1994-08-22 | 株式会社日立製作所 | Fluid sodium-sulfur battery |
JP2513953B2 (en) * | 1991-11-25 | 1996-07-10 | 日本碍子株式会社 | Sodium-sulfur battery |
EP0835951B1 (en) * | 1996-09-26 | 2002-05-08 | Ngk Spark Plug Co., Ltd. | Method and apparatus for extracting lithium by applying voltage across lithium-ion conducting solid electrolyte |
-
1999
- 1999-06-11 DE DE19926724A patent/DE19926724A1/en not_active Withdrawn
-
2000
- 2000-06-07 TW TW089111060A patent/TWI232245B/en not_active IP Right Cessation
- 2000-06-08 US US09/589,163 patent/US6368487B1/en not_active Expired - Lifetime
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- 2000-06-09 DE DE50005958T patent/DE50005958D1/en not_active Expired - Lifetime
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- 2000-06-09 EP EP00111875A patent/EP1059366B1/en not_active Expired - Lifetime
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DE10360758A1 (en) * | 2003-12-23 | 2005-07-28 | Degussa Ag | Electrochemical production of alkali alcoholate, used as intermediate, reactant or catalyst in organic synthesis, uses sodium- or potassium-ion-conducting ceramic membrane separating anolyte containing salt and alcoholic catholyte |
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DE19926724A1 (en) | 2000-12-14 |
TWI232245B (en) | 2005-05-11 |
KR20010007335A (en) | 2001-01-26 |
EP1059366A2 (en) | 2000-12-13 |
CN1279304A (en) | 2001-01-10 |
CN1170960C (en) | 2004-10-13 |
RU2252981C2 (en) | 2005-05-27 |
KR100672866B1 (en) | 2007-01-23 |
DE50005958D1 (en) | 2004-05-13 |
US6368487B1 (en) | 2002-04-09 |
JP4838410B2 (en) | 2011-12-14 |
EP1059366A3 (en) | 2000-12-20 |
JP2001059196A (en) | 2001-03-06 |
ES2218029T3 (en) | 2004-11-16 |
ATE263855T1 (en) | 2004-04-15 |
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