EP0241633B1 - Process for the electrolysis of alkali chloride solutions - Google Patents
Process for the electrolysis of alkali chloride solutions Download PDFInfo
- Publication number
- EP0241633B1 EP0241633B1 EP87100085A EP87100085A EP0241633B1 EP 0241633 B1 EP0241633 B1 EP 0241633B1 EP 87100085 A EP87100085 A EP 87100085A EP 87100085 A EP87100085 A EP 87100085A EP 0241633 B1 EP0241633 B1 EP 0241633B1
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- cathode
- anode
- chamber
- gas space
- membrane
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- 238000000034 method Methods 0.000 title claims abstract description 23
- 238000005868 electrolysis reaction Methods 0.000 title claims description 22
- 239000003513 alkali Substances 0.000 title description 9
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 title description 8
- 239000007789 gas Substances 0.000 claims abstract description 49
- 239000012528 membrane Substances 0.000 claims abstract description 33
- 210000004027 cell Anatomy 0.000 claims abstract description 32
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 16
- 239000001257 hydrogen Substances 0.000 claims abstract description 16
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 16
- 229910001514 alkali metal chloride Inorganic materials 0.000 claims abstract description 10
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims abstract description 8
- 239000000460 chlorine Substances 0.000 claims abstract description 8
- 229910052801 chlorine Inorganic materials 0.000 claims abstract description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 7
- 150000001768 cations Chemical class 0.000 claims abstract description 6
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 5
- 210000002421 cell wall Anatomy 0.000 claims abstract description 4
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims abstract description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 23
- 239000007868 Raney catalyst Substances 0.000 claims description 15
- 229910000564 Raney nickel Inorganic materials 0.000 claims description 15
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 8
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 8
- -1 polytetrafluoroethylene Polymers 0.000 claims description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 4
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 239000001301 oxygen Substances 0.000 claims description 4
- 229910052760 oxygen Inorganic materials 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 2
- 239000011888 foil Substances 0.000 claims 1
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 28
- 239000000243 solution Substances 0.000 description 13
- 238000005341 cation exchange Methods 0.000 description 10
- 230000015572 biosynthetic process Effects 0.000 description 3
- 239000012267 brine Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 3
- 229920000557 Nafion® Polymers 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 150000003608 titanium Chemical class 0.000 description 2
- 229910000497 Amalgam Inorganic materials 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical class [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 229910001854 alkali hydroxide Inorganic materials 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
- C25B1/46—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in diaphragm cells
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
- C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
- C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
- C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
- C25B11/095—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds at least one of the compounds being organic
Definitions
- the invention relates to a method for the electrolysis of aqueous alkali metal chloride solutions by the membrane method in an electrolysis cell which is equipped with a porous cathode and in which the cell wall together with that side of the cathode which faces away from the cathode space form a closed space ("gas space ”) forms.
- the membrane cell for the alkali chloride electrolysis usually consists of two electrolysis chambers, each with a gas-generating electrode, which are separated from one another by a cation exchange membrane.
- perforated materials such as perforated sheets, expanded metal, nets etc. are used as the electrode substrates.
- the perforated electrode structure is necessary so that the resulting gas can be discharged to the back of the electrode as quickly as possible and thus the electrolyte resistance is not unnecessarily increased by the formation of a gas cushion between the anode and the cathode.
- the object was therefore to develop a process for the electrolysis of alkali chloride solutions in which the formation of the gas cushion between the cathode and membrane is eliminated as far as possible.
- this method should be suitable when using porous, foil-like Raney nickel cathodes.
- the method is characterized in that a higher pressure is set
- the gas space has a device (in practice mostly a pipe connection) for removing hydrogen and possibly condensed water.
- Current densities of at least 500 Alm 2 are preferred, in particular at least 1000 A / m 2 .
- a sensible upper limit for the current density used is a maximum of 8000 Alm 2 , better a maximum of 6000 Alm 2, in particular a maximum of 4000 A / M 2 no oxygen or oxygen-containing gas are introduced into the process according to the invention.
- Raney nickel electrodes behave particularly favorably, in particular those which consist of a nickel mesh which is covered on at least one side by a compressed mixture of Raney nickel and polytetrafluoroethylene. Gas side may be coated this Raney-nickel electrode even with a film of polytetrafluoroethylene L.
- Such electrodes are described in DE-OS-3 42 969, to which reference is expressly made here.
- the figure shows schematically a cross section through an electrochemical cell for the electrolysis of aqueous alkali chloride solutions, which is equipped with a porous, film-like cathode.
- the cell is divided into an anode compartment (1), a cathode compartment (2) and a gas compartment (3).
- saturated sodium chloride brine is pumped into the anode compartment (1) via a feed line (4).
- Chloride ions are discharged to elemental chlorine at the anode (5).
- Dimensionally stable anodes made of expanded titanium mesh or perforated sheets are preferably used, which are equipped with an activation in order to keep the chlorine overvoltage low.
- the chlorine formed and the depleted brine leave the anode compartment (1) via line (6).
- the cation exchange membrane (7) Between the anode compartment (1) and the cathode compartment (2) is the cation exchange membrane (7) through which sodium ions migrate into the cathode compartment (2).
- Water is fed to the cell in the form of deionized water or dilute sodium hydroxide solution via the feed line (9).
- Alkaline lye is formed in the cathode compartment (2) and leaves the cell via the opening (10).
- Cathode compartment (2) and gas compartment (3) are separated from each other by the porous, foil-like Raney nickel cathode (8).
- the gas compartment (3) is provided with an opening (11) through which the hydrogen generated is removed.
- the porous, film-like cathode (8) consists of a carrier mesh (13) which e.g. is made of nickel and at the same time serves for power supply and current distribution in the catalyst made of Raney nickel (14).
- the cathode can be provided with a thin, porous polytetrafluoroethylene layer (15) on the side facing the gas space.
- This PTFE film is gas-permeable, but liquid-impermeable and is therefore used for gas-liquid separation in the cell. It is not mandatory. If the electrolysis is operated without said film, however, an increased amount of condensate in the gas space (3) is to be expected.
- the pressure is set in a simple manner by providing the line (10) with a throttle valve (12) or extending the line (10) upwards to an overflow in such a way that a defined lye column is formed.
- the gas space is usually at atmospheric pressure, i.e. operated without pressure.
- a 40 cm 2 membrane electrolysis cell equipped with an activated titanium anode and a cation exchange membrane from the company DU PONT of the type Nafion ( R ) NX 90209, was equipped with a Raney nickel electrode without a PTFE film on the gas space side in accordance with DE-OS-3 342 969 (area 40 cm 2 ) operated so that the cathode separated a 3 mm deep cathode space from a 10 mm deep gas space.
- the operating conditions for the electrolysis were 80 ° C., 3 kA / m 2 , input molecule concentration of 300 g / I, anolyte concentration of 200 g / I and lye concentration of 33% by weight.
- the cell voltage was 3.12 V under the specified conditions.
- the electrolysis was carried out under the same conditions, with the same electrodes and the same cation exchange membrane as in Example 1, but the gas space was flooded with sodium hydroxide solution. Only the pressure difference between the cathode compartment and the gas compartment was left at 25-30 cm WS (overpressure in the cathode compartment). 98% of the gas came from the gas space and 2% from the cathode space. At a current density of 3 kAlm 2 , the cell voltage was 3.15 V.
- a 450 cm 2 membrane electrolysis cell with an activated titanium anode and a cation exchange membrane of the type Nafion ( 1 ) NX 90209 was equipped with a Raney nickel cathode with PTFE film on the gas space side in accordance with DE-OS-3 342 696.
- the cathode was 9 cm wide and 50 cm long.
- the electrolysis cell was operated horizontally, so that the anode came to lie above and the cathode below the cation exchange membrane.
- the distance between the cathode and the membrane was about 4 mm.
- a coarse mesh polypropylene mesh was used as a spacer in the cathode compartment.
- the sodium hydroxide solution flowed longitudinally through the cathode compartment.
- the brine in the cell was depleted from 300 g / I to about 220 g / I and 33% by weight sodium hydroxide solution was produced.
- the cathode compartment of 150 cm WS 92% of the hydrogen formed left the cell via the gas compartment; an attack of sodium hydroxide solution in the gas space was not observed.
- the cell voltage was 3.20 V.
- the electrolysis was carried out in a 40 cm 2 cell under the same conditions as in Example 1, but there was pressure equalization between the cathode compartment and the gas compartment. More than 90% of the hydrogen was generated in the cathode compartment, and the cell voltage rose rapidly to values above 3; 40 V.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
Description
Gegenstand der Erfindung ist ein Verfahren zur Elektrolyse von wäßrigen Alkalichlorid-Lösungen nach dem Membran-Verfahren in einer Elektrolysezelle, die mit einer porösen Kathode ausgerüstet ist und in der die Zellwand zusammen mit dem der dem Kathodenraum abgewandten Seite der Kathode einen abgeschlossenen Raum ("Gasraum") bildet.The invention relates to a method for the electrolysis of aqueous alkali metal chloride solutions by the membrane method in an electrolysis cell which is equipped with a porous cathode and in which the cell wall together with that side of the cathode which faces away from the cathode space form a closed space ("gas space ") forms.
Etwa 50% der Weltkapazität zur Erzeugung von elementarem Chlor werden in Elektrolysezellen produziert, die nach dem Amalgamverfahren arbeiten. Die theoretische Zersetzungsspannung von Alkalichlorid in der Quecksilberzelle beträgt etwa 3,15 bis 3,20 Volt. Demgegenüber ergibt sich eine theoretische Zersetzungsspannung von etwa 2,20 Volt, wenn man die Alkalichloridelektrolyse in einer Membranzelle mit wasserstofferzeugender Kathode durchführt. Durch die Einführung des Membranverfahrens läßt sich folglich theoretisch die Zellspannung um etwa 1 Volt senken, was in Zeiten steigender Energiekosten von erheblicher wirtschaftlicher Bedeutung ist.Around 50% of the world's capacity for the production of elemental chlorine is produced in electrolysis cells that use the amalgam process. The theoretical decomposition voltage of alkali chloride in the mercury cell is approximately 3.15 to 3.20 volts. In contrast, there is a theoretical decomposition voltage of about 2.20 volts if the alkali metal chloride electrolysis is carried out in a membrane cell with a hydrogen-generating cathode. By introducing the membrane process, the cell voltage can theoretically be reduced by about 1 volt, which is of considerable economic importance in times of increasing energy costs.
Die Membranzelle für die Alkalichlorid-Elektrolyse besteht üblicherweise aus zwei Elektrolysekammern mit jeweils einer gasentwickelnden Elektrode, die durch eine Kationenaustauscher- membran voneinander getrennt sind. Als Elektrodensubstrate werden in der Praxis durchbrochene Materialien wie Lochbleche, Streckgitter, Netze etc. verwendet. Die durchbrochene Elektrodenstruktur ist erforderlich, damit entstehendes Gas möglichst rasch zur Elektrodenrückseite abgeführt werden kann, und somit der Elektrolytwiderstand durch Bildung eines Gaspolsters zwischen Anode und Kathode nicht unnötig erhöht wird.The membrane cell for the alkali chloride electrolysis usually consists of two electrolysis chambers, each with a gas-generating electrode, which are separated from one another by a cation exchange membrane. In practice, perforated materials such as perforated sheets, expanded metal, nets etc. are used as the electrode substrates. The perforated electrode structure is necessary so that the resulting gas can be discharged to the back of the electrode as quickly as possible and thus the electrolyte resistance is not unnecessarily increased by the formation of a gas cushion between the anode and the cathode.
Wegen der Überspannungen für die Chlor- und Wasserstoffentwicklung verwendet man katalysierte Elektroden. Anodenseitig hat sich Titan als Elektrodensubstrat, welches mit Edelmetalloxiden aktiviert ist, bewährt. Für die kathodische Wasserstoffentwicklung setzt man Normalstahl-, Edelstahl- oder Nickelelektroden ein, die mit Edelmetallen oder Raney-Nickel aktiviert sein können. Insbesondere Raney-Nickel ist, nicht zuletzt aufgrund seiner extrem großen inneren Oberfläche, besonders geeignet, die Wasserstoffabscheidung zu katalysieren. Andererseits ist es jedoch schwierig, Raney-Nickel auf durchbrochene Elektrodenstrukturen wie Lochbleche oder Streckgitter aufzubringen. Raney-Nickelektroden stehen deshalb bisher nur in Form von beschichteten Platten oder beschichteten Blechen zur Verfügung. Beim Einbau solcher flächigen Elektroden in eine Elektrolysezelle besteht dann aber die Gefahr des "Gasblaseneffektes", d.h. es bildet sich ein Gaspolster zwischen Kathode und Kationenaustauscher- membran aus, da der Wasserstoff bevorzugt auf der Elektrodenvorderseite abgeschieden wird. Der Elektrolytwiderstand steigt an, und Zellspannung und Energieaufwand werden unwirtschaftlich hoch.Because of the surge voltages for the chlorine and hydrogen evolution, catalyzed electrodes are used. On the anode side, titanium has proven itself as an electrode substrate which is activated with noble metal oxides. Normal steel, stainless steel or nickel electrodes, which can be activated with precious metals or Raney nickel, are used for the cathodic hydrogen evolution. Raney nickel in particular, not least because of its extremely large inner surface, is particularly suitable for catalyzing hydrogen deposition. On the other hand, however, it is difficult to apply Raney nickel to perforated electrode structures such as perforated sheets or expanded metal. So far, Raney pitch electrodes have only been available in the form of coated plates or coated sheets. When installing such flat electrodes in an electrolytic cell, however, there is then the risk of the "gas bubble effect", i.e. a gas cushion forms between the cathode and the cation exchange membrane, since the hydrogen is preferably deposited on the front of the electrode. The electrolyte resistance increases, and cell voltage and energy consumption become uneconomically high.
Ein einfaches Verfahren zur Herstellung einer porösen folienartigen Gaselektrode auf Basis von Raney-Nickel wird in der DE-OS-3 342 969 beschrieben. Jedoch tritt auch mit einer solchen Elektrode bei der Alkalichlorid-Elektrolyse der "Gasblaseneffekt", d.h. die Ausbildung eines Gaspolsters zwischen Elektrode und Membran auf.A simple method for producing a porous, foil-like gas electrode based on Raney nickel is described in DE-OS-3 342 969. However, even with such an electrode, in the alkali chloride electrolysis, the "gas bubble effect", i.e. the formation of a gas cushion between the electrode and membrane.
Es bestand daher die Aufgabe, ein Verfahren zur Elektrolyse von Alkalichloridlösungen zu entwicklen, bei dem die Ausbildung des Gaspolsters zwischen Kathode und Membran möglichst ausgeschaltet wird. Insbesondere sollte dieses Verfahren geeignet sein bei Einsatz von porösen folienartigen Raney-Nickel-Kathoden.The object was therefore to develop a process for the electrolysis of alkali chloride solutions in which the formation of the gas cushion between the cathode and membrane is eliminated as far as possible. In particular, this method should be suitable when using porous, foil-like Raney nickel cathodes.
Es wurde nun ein Verfahren zum Elektrolysieren von wäßrigen Alkalichlorid-Lösungen in einer Membranzelle gefunden, die einen Anodenraum mit Anode und eine Kathodenraum mit Kathode enthält, beide Räume durch eine Kationenaustauscher-Membran voneinander getrennt sind, wobei die Kathode eine poröse Folie ist, Kathode und Kationenaustauscher-Membran den eigentlichen mit Katholyt gefüllten Kathodenraum bilden, die der Membran abgewandte Seite der Kathode und Zellenwand einen Gasraum bilden, man in den Kathodenraum Wasser einspeist und aus ihm Alkalihydroxyd-Lösung abzieht, aus Kathodenraum und Gasraum Wasserstoff abzieht, in den Anodenraum wäßrige Alkalichlorid-Lösung einspeist und aus ihm gasförmiges Chlor zusammen mit verarmter Alkalichlorid-Lösung abzieht und man an Kathode und Anode eine Gleichspannung anlegt, die mindestens gleich der Zersetzungspannung ist. Das Verfahren ist dadurch gekennzeichnet, daß im Kathodenraum ein höherer Druck eingestellt wird, als im Gasraum.A method has now been found for the electrolysis of aqueous alkali metal chloride solutions in a membrane cell which contains an anode space with an anode and a cathode space with a cathode, both spaces being separated from one another by a cation exchange membrane, the cathode being a porous film, cathode and Cation exchanger membrane form the actual cathode space filled with catholyte, the side of the cathode and cell wall facing away from the membrane form a gas space, water is fed into the cathode space and alkali hydroxide solution is drawn off from it, hydrogen is drawn off from the cathode space and gas space, and aqueous alkali metal chloride into the anode space - Feeds solution and withdraws gaseous chlorine from it together with depleted alkali chloride solution and a DC voltage is applied to the cathode and anode which is at least equal to the decomposition voltage. The method is characterized in that a higher pressure is set in the cathode compartment than in the gas compartment.
Aus der DE-OS-3 332 566 ist bereits ein elektrolytisches Verfahren zur Herstellung von Natronlauge unter Verwendung einer Kationenaustauscher-Membran und einer folienförmigen Kathode bekannt. Dabei wird jedoch die Kathode als Sauerstoffdiffusionskathode betrieben, so daß kein Wasserstoff gewonnen wird.From DE-OS-3 332 566 an electrolytic process for the production of sodium hydroxide solution using a cation exchange membrane and a film-shaped cathode is already known. However, the cathode is operated as an oxygen diffusion cathode so that no hydrogen is obtained.
Es ist ein Vorteil des erfindungsgemäßen Verfahrens, daß der überwiegende Teil des bei der Elektrolyse erzeugten Wasserstoffs durch die Kathode zu deren Rückseite transportiert wird, und dort in einfacher Weise entsorgt werden kann. Daher erfolgt die Trennung des Wasserstoffs von der produzierten Lauge bereits in der Elektrolysezelle.It is an advantage of the method according to the invention that the major part of the hydrogen generated in the electrolysis is transported through the cathode to the rear and can be disposed of there in a simple manner. For this reason, the hydrogen is separated from the lye produced in the electrolysis cell.
Auf diese Weise wird der "Gasblaseneffekt" erheblich reduziert und die Elektrolyse kann mit niedriger Zellspannung durchgeführt werden. Der Gasraum weist eine Einrichtung (in der Praxis meist ein Rohranschluß) zum Abführen von Wasserstoff und eventuell kondensiertem Wasser auf.In this way the "gas bubble effect" is considerably reduced and the electrolysis can be carried out with a low cell voltage. The gas space has a device (in practice mostly a pipe connection) for removing hydrogen and possibly condensed water.
Je höher die Stromdichte des erfindunggemä- ßen Verfahrens an der Kathode ist, umso höher ist die Tendenz zur Entwicklung eines Gaspolsters. Bevorzugt sind Stromdichten von mindestens 500 Alm2 insbesondere mindestens 1000 A/ m2. Eine sinnvolle Obergrenze für die verwendete Stromdichte liegt bei maximal 8000 Alm2, besser maximal 6000 Alm2 insbesondere maximal 4000 A/M 2. In den Gasraum der Zelle soll nach dem erfindungsgemäßen Verfahren kein Sauerstoff oder Sauerstoff enthaltendes Gas eingeführt werden.The higher the current density of the method according to the invention at the cathode, the higher the tendency to develop a gas cushion. Current densities of at least 500 Alm 2 are preferred, in particular at least 1000 A / m 2 . A sensible upper limit for the current density used is a maximum of 8000 Alm 2 , better a maximum of 6000 Alm 2, in particular a maximum of 4000 A / M 2 no oxygen or oxygen-containing gas are introduced into the process according to the invention.
Besonders günstig verhalten sich beim erfindungsgemäßen Verfahren als Kathode Raney-Nickel-Elektroden, insbesondere solche die aus einem Nickelnetz bestehen, das mindestens auf einer Seite von einem komprimierten Gemisch aus Raney-Nickel und Polytetrafluoräthylen bedeckt ist. Gasseitig kannLdiese Raney-Nickel-Elektrode noch mit einer Folie aus Polytetrafluoräthylen überzogen sein. Solche Elektroden sind beschrieben in der DE-OS-3 42 969 auf die hier ausdrücklich Bezug genommen wird.In the process according to the invention, Raney nickel electrodes behave particularly favorably, in particular those which consist of a nickel mesh which is covered on at least one side by a compressed mixture of Raney nickel and polytetrafluoroethylene. Gas side may be coated this Raney-nickel electrode even with a film of polytetrafluoroethylene L. Such electrodes are described in DE-OS-3 42 969, to which reference is expressly made here.
Der Druckunterschied zwischen Katholytraum und Gasraum beträgt ca. 10 mbar bis 0,5 bar, insbesondere 20 mbar bis 0,2 bar (1 mbar=1 hPa).The pressure difference between the catholyte space and the gas space is approximately 10 mbar to 0.5 bar, in particular 20 mbar to 0.2 bar (1 mbar = 1 hPa).
Da sich in einer vertikalen Zelle ein Laugedruckgradient aufbaut, ist es günstig das Verfahren in einer Zelle zu betreiben, bei der Kathode, Anode und Membran horizontal angeordnet sind, so daß die vom Anolyt bedeckte Anode oberhalb der Membran und die vom Katholyt bedeckte Kathode unterhalb der Kationenaustauscher- membran zu liegen kommt und der Gasraum unterhalb der porösen folienartigen Kathode angeordnet ist. Bei dieser Ausgestaltung herrscht an jeder Stelle der Kathode der gleiche Druck. Damit wird verhindert, daß an Stellen mit höheren Laugedrücken Lauge durch die Kathode in den "Gasraum" übertritt.Since a lye pressure gradient builds up in a vertical cell, it is advantageous to operate the method in a cell in which the cathode, anode and membrane are arranged horizontally, so that the anode covered by the anolyte above the membrane and the cathode covered by the cathode below Cation exchange membrane comes to rest and the gas space is arranged below the porous film-like cathode. With this configuration, the same pressure prevails at every point on the cathode. This prevents alkali from passing through the cathode into the "gas space" at locations with higher alkali pressures.
Die Figur zeigt schematisch einen Querschnitt durch eine elektrochemische Zelle zur Elektrolyse wäßriger Alkalichloridlösungen, die mit einer porösen, folienartigen Kathode ausgerüstet ist. Die Zelle ist in einen Anodenraum (1), einen Kathodenraum (2) und einen Gasraum (3) unterteilt. Über eine Zuleitung (4) wird beispielsweise gesättigte Natriumchlorid-Sole in den Anodenraum (1) gepumpt. An der Anode (5) werden Chloridionen zu elementarem Chlor entladen. Vorzugsweise werden dimensionsstabile Anoden aus Titan-Streckgittern oder -Lochblechen eingesetzt, die mit einer Aktivierung ausgestattet sind, um die Chlorüberspannung gering zu halten. Über Leitung (6) verlassen das gebildete Chlor und die verarmte Sole den Anodenraum (1). Zwischen Anodenraum (1) und dem Kathodenraum (2) befindet sich die Kationenaustauscher- Membran (7) durch die Natriumionen in den Kathodenraum (2) wandern.The figure shows schematically a cross section through an electrochemical cell for the electrolysis of aqueous alkali chloride solutions, which is equipped with a porous, film-like cathode. The cell is divided into an anode compartment (1), a cathode compartment (2) and a gas compartment (3). For example, saturated sodium chloride brine is pumped into the anode compartment (1) via a feed line (4). Chloride ions are discharged to elemental chlorine at the anode (5). Dimensionally stable anodes made of expanded titanium mesh or perforated sheets are preferably used, which are equipped with an activation in order to keep the chlorine overvoltage low. The chlorine formed and the depleted brine leave the anode compartment (1) via line (6). Between the anode compartment (1) and the cathode compartment (2) is the cation exchange membrane (7) through which sodium ions migrate into the cathode compartment (2).
Über die Zuleitung (9) wird Wasser der Zelle in Form von entionisiertem Wasser oder verdünnter Natronlauge zugeführt. Im Kathodenraum (2) wird Alkalilauge gebildet, die die Zelle über die Öffnung (10) verläßt. Kathodenraum (2) und Gasraum (3) werden durch die poröse, folienartige Raney-Nickel-Kathode (8) voneinander getrennt, Der Gasraum (3) ist mit einer Öffnung (11) versehen, über die der erzeugte Wasserstoff entfernt wird.Water is fed to the cell in the form of deionized water or dilute sodium hydroxide solution via the feed line (9). Alkaline lye is formed in the cathode compartment (2) and leaves the cell via the opening (10). Cathode compartment (2) and gas compartment (3) are separated from each other by the porous, foil-like Raney nickel cathode (8). The gas compartment (3) is provided with an opening (11) through which the hydrogen generated is removed.
Wie in der Figur zu erkennen ist, besteht die poröse, folienartige Kathode (8) aus einem Trägernetz (13), das z.B. aus Nickel gefertigt ist und gleichzeitig für Stromversorgung und Stromverteilung im Katalysator aus Raney-Nickel (14) dient. Auf der dem Gasraum zugewandten Seite kann die Kathode mit einer dünnen, porösen Polytetrafluorethylenschicht (15) versehen sein. Diese PTFE-Folie ist gasdurchlässig, jedoch flüssigkeitsundurchlässig und dient somit zur Gas-Flüssigkeitstrennung in der Zelle. Sie ist nicht zwingend erforderlich. Falls die Elektrolyse ohne besagte Folie betrieben wird, ist jedoch mit einem erhöhten Kondensatanfall im Gasraum (3) zu rechnen.As can be seen in the figure, the porous, film-like cathode (8) consists of a carrier mesh (13) which e.g. is made of nickel and at the same time serves for power supply and current distribution in the catalyst made of Raney nickel (14). The cathode can be provided with a thin, porous polytetrafluoroethylene layer (15) on the side facing the gas space. This PTFE film is gas-permeable, but liquid-impermeable and is therefore used for gas-liquid separation in the cell. It is not mandatory. If the electrolysis is operated without said film, however, an increased amount of condensate in the gas space (3) is to be expected.
Die Druckdifferenz zwischen Kathodenraum (2) und Gasraum beträgt 10-5000 cm Wassersäule (cm WS) insbesondere 20-200 cm WS (1 cm WS=0,98 hPa). In der Praxis erfolgt die Druckeinstellung in einfacher Weise dadurch, daß man die Leitung (10) mit einem Drosselventil (12) versieht oder die Leitung (10) nach oben zu einem Überlauf hin verlängert, daß sich eine definierte Laugesäule ausbildet. Der Gasraum wird üblicherweise mit Atmosphärendruck, d.h. überdrucklos betrieben.The pressure difference between the cathode compartment (2) and the gas compartment is 10-5000 cm water column (cm WS), in particular 20-200 cm WS (1 cm WS = 0.98 hPa). In practice, the pressure is set in a simple manner by providing the line (10) with a throttle valve (12) or extending the line (10) upwards to an overflow in such a way that a defined lye column is formed. The gas space is usually at atmospheric pressure, i.e. operated without pressure.
Unter den beschriebenen Bedingungen entweichen mehr als 90% des entstehenden Wasserstoffs über den Gasraum.Under the conditions described, more than 90% of the hydrogen produced escapes through the gas space.
Die Erfindung wird im folgenden anhand der Figur und der Beispiele näher erläutert.The invention is explained in more detail below with reference to the figure and the examples.
Eine 40 cm2-Membranelektrolysezelle, ausgerüstet mit einer aktivierten Titananode und einer Kationenaustauschermembran der Firma DU PONT vom Typ Nafion (R)NX 90209, wurde mit einer Raney-Nickel-Elektrode ohne PTFE-Folie auf der Gasraumseite gemäß DE-OS-3 342 969 (Fläche 40 cm2) so betrieben, daß die Kathode einen 3 mm tiefen Kathodenraum von einem 10 mm tiefen Gasraum trennte. Die Betriebsbedingungen der Elektrolyse waren 80°C, 3 kA/m2, Eingangssolekonzentration von 300 g/I, Anolytkonzentration von 200 g/I und Laugekonzentration von 33 Gew.-%. Der Überdruck des Katholyts betrug 25-30 mbar (=25-30 hPa), der des Gasraumes 0 mbar, bezogen auf Atmosphäre. Unter diesen Bedingungen kamen 99% des produzierten Wasserstoffs aus dem Gasraum und lediglich 1% aus dem Kathodenraum. Die Zellspannung betrug bei den angegebenen Bedingungen 3,12 V.A 40 cm 2 membrane electrolysis cell, equipped with an activated titanium anode and a cation exchange membrane from the company DU PONT of the type Nafion ( R ) NX 90209, was equipped with a Raney nickel electrode without a PTFE film on the gas space side in accordance with DE-OS-3 342 969 (area 40 cm 2 ) operated so that the cathode separated a 3 mm deep cathode space from a 10 mm deep gas space. The operating conditions for the electrolysis were 80 ° C., 3 kA / m 2 , input molecule concentration of 300 g / I, anolyte concentration of 200 g / I and lye concentration of 33% by weight. The overpressure of the catholyte was 25-30 mbar (= 25-30 hPa), that of the gas space 0 mbar, based on the atmosphere. Under these conditions, 99% of the hydrogen produced came from the gas space and only 1% from the cathode space. The cell voltage was 3.12 V under the specified conditions.
Die Elektrolyse wurde unter den gleichen Bedingungen, mit den gleichen Elektroden und der gleichen Kationenaustauschermembran wie in Beispiel 1 durchgeführt, jedoch wurde der Gasraum mit Natronlauge geflutet. Lediglich die Druckdifferenz zwischen Kathodenraum und Gasraum wurde bei 25-30 cm WS (Überdruck im Kathodenraum) belassen. 98% des Gases kamen aus dem Gasraum und 2% aus dem Kathodenraum. Bei einer Stromdichte von 3 kAlm2 betrug die Zellspannung 3,15 V.The electrolysis was carried out under the same conditions, with the same electrodes and the same cation exchange membrane as in Example 1, but the gas space was flooded with sodium hydroxide solution. Only the pressure difference between the cathode compartment and the gas compartment was left at 25-30 cm WS (overpressure in the cathode compartment). 98% of the gas came from the gas space and 2% from the cathode space. At a current density of 3 kAlm 2 , the cell voltage was 3.15 V.
Eine 450 cm2-Membranelektrolysezelle mit einer aktivierten Titananode und einer Kationenaustauschermembran vom Typ Nafion (1)NX 90209 wurde mit einer Raney-Nickel-Kathode mit PTFE-Folie auf der Gasraumseite gemäß DE-OS-3 342 696 ausgerüstet. Die Kathode hatte eine Breite von 9 cm und eine Länge von 50 cm. Die Elektrolysezelle wurde horizontal betrieben, so daß die Anode oberhalb und die Kathode unterhalb der Kationenaustauschermembran zu liegen kam. Der Abstand der Kathode von der Membran betrug dabei etwa 4 mm. Im Kathodenraum befand sich als Abstandshalter ein grobmaschiges Polypropylennetz. Der Kathodenraum wurde in Längsrichtung von der Natronlauge durchströmt. Bei einer Betriebstemperatur von 80°C und einer Stromdichte von 3 kA/m2 wurde die Sole in der Zelle von 300 g/I auf etwa 220 g/I abgereichert und 33 Gew.-%ige Natronlauge produziert. Bei einem Überdruck im Kathodenraum von 150 cm WS verließen 92% des gebildeten Wasserstoffs über den Gasraum die Zelle; ein Anfall von Natronlauge im Gasraum wurde nicht beobachtet. Unter den angegebenen Bedingungen betrug die Zellspannung 3,20 V.A 450 cm 2 membrane electrolysis cell with an activated titanium anode and a cation exchange membrane of the type Nafion ( 1 ) NX 90209 was equipped with a Raney nickel cathode with PTFE film on the gas space side in accordance with DE-OS-3 342 696. The cathode was 9 cm wide and 50 cm long. The electrolysis cell was operated horizontally, so that the anode came to lie above and the cathode below the cation exchange membrane. The distance between the cathode and the membrane was about 4 mm. A coarse mesh polypropylene mesh was used as a spacer in the cathode compartment. The sodium hydroxide solution flowed longitudinally through the cathode compartment. At an operating temperature of 80 ° C and a current density of 3 kA / m 2 , the brine in the cell was depleted from 300 g / I to about 220 g / I and 33% by weight sodium hydroxide solution was produced. At an overpressure in the cathode compartment of 150 cm WS, 92% of the hydrogen formed left the cell via the gas compartment; an attack of sodium hydroxide solution in the gas space was not observed. Under the specified conditions, the cell voltage was 3.20 V.
Die Elektrolyse wurde in einer40 cm2-Zelle unter den gleichen Bedingungen wieim Beispiel 1 durchgeführt, jedoch herrschte Druckausgleich zwischen Kathodenraum und Gasraum. Mehr als 90% des Wasserstoffs entstanden im Kathodenraum, und die Zellspannung stieg rasch auf Werte über 3;40 V an.The electrolysis was carried out in a 40 cm 2 cell under the same conditions as in Example 1, but there was pressure equalization between the cathode compartment and the gas compartment. More than 90% of the hydrogen was generated in the cathode compartment, and the cell voltage rose rapidly to values above 3; 40 V.
Claims (7)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT87100085T ATE54343T1 (en) | 1986-01-14 | 1987-01-07 | PROCESS FOR THE ELECTROLYSIS OF ALKALINE ICHORIDE SOLUTIONS. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3600759 | 1986-01-14 | ||
| DE19863600759 DE3600759A1 (en) | 1986-01-14 | 1986-01-14 | METHOD FOR THE ELECTROLYSIS OF ALKALICHLORIDE SOLUTIONS |
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| Publication Number | Publication Date |
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| EP0241633A1 EP0241633A1 (en) | 1987-10-21 |
| EP0241633B1 true EP0241633B1 (en) | 1990-07-04 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP87100085A Expired - Lifetime EP0241633B1 (en) | 1986-01-14 | 1987-01-07 | Process for the electrolysis of alkali chloride solutions |
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| Country | Link |
|---|---|
| US (1) | US4790915A (en) |
| EP (1) | EP0241633B1 (en) |
| AT (1) | ATE54343T1 (en) |
| CA (1) | CA1314836C (en) |
| DE (2) | DE3600759A1 (en) |
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| GB2316091B (en) * | 1996-10-23 | 1999-06-16 | Julian Bryson | Electrolytic treatment of aqueous salt solutions |
| BR112014031220A2 (en) | 2012-06-12 | 2017-06-27 | Univ Monash | breathable electrode structure and method and system for use in water separation |
| US9871424B2 (en) | 2013-02-06 | 2018-01-16 | Hitachi Koki Co., Ltd. | Electric tool |
| RU2016106905A (en) | 2013-07-31 | 2017-09-01 | Аквахайдрекс Пти Лтд | MODULAR ELECTROCHEMICAL CELLS |
| DE102016204718A1 (en) | 2016-03-22 | 2017-09-28 | Siemens Aktiengesellschaft | reactor |
| DE102016204717A1 (en) * | 2016-03-22 | 2017-09-28 | Siemens Aktiengesellschaft | Reactor for carrying out equilibrium-limited reactions |
| US20220145479A1 (en) | 2019-02-01 | 2022-05-12 | Aquahydrex, Inc. | Electrochemical system with confined electrolyte |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPS5376997A (en) * | 1976-12-20 | 1978-07-07 | Kanegafuchi Chem Ind Co Ltd | Sodium chlorde electrolyzing method using three chamber type ion exhange membrane cell |
| JPS6059304B2 (en) * | 1977-08-05 | 1985-12-24 | 旭硝子株式会社 | Horizontal alkaline chloride diaphragm electrolyzer |
| US4488947A (en) * | 1983-06-08 | 1984-12-18 | Olin Corporation | Process of operation of catholyteless membrane electrolytic cell |
| DE3332566A1 (en) * | 1983-09-09 | 1985-03-28 | Hoechst Ag, 6230 Frankfurt | GAS DIFFUSION ELECTRODE WITH HYDROPHILIC TOP LAYER AND METHOD FOR THEIR PRODUCTION |
| DE3342969A1 (en) * | 1983-11-28 | 1985-06-05 | Varta Batterie Ag, 3000 Hannover | POROESE GAS ELECTRODE |
-
1986
- 1986-01-14 DE DE19863600759 patent/DE3600759A1/en not_active Withdrawn
-
1987
- 1987-01-07 AT AT87100085T patent/ATE54343T1/en not_active IP Right Cessation
- 1987-01-07 DE DE8787100085T patent/DE3763506D1/en not_active Expired - Fee Related
- 1987-01-07 EP EP87100085A patent/EP0241633B1/en not_active Expired - Lifetime
- 1987-01-12 US US07/002,142 patent/US4790915A/en not_active Expired - Fee Related
- 1987-01-13 CA CA000527176A patent/CA1314836C/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| US4790915A (en) | 1988-12-13 |
| ATE54343T1 (en) | 1990-07-15 |
| DE3763506D1 (en) | 1990-08-09 |
| CA1314836C (en) | 1993-03-23 |
| EP0241633A1 (en) | 1987-10-21 |
| DE3600759A1 (en) | 1987-07-16 |
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