CN1665961A - Process for producing alkali metal chlorate - Google Patents

Abstract

The invention relates to a process for the production of alkali metal chlorate in an electrolytic cell which is divided by a cation selective separator into an anode compartment in which an anode is placed and a cathode compartment in which a gas diffusion electrode is placed. The process includes introducing an electrolyte solution containing an alkali metal chloride into the anode chamber and introducing an oxygen-containing gas into the cathode chamber. The invention also relates to an electrolytic cell for the production of alkali metal chlorate, which electrolytic cell is divided by a cation selective separator into an anode compartment in which an anode is placed and a cathode compartment in which a gas diffusion electrode is placed. An inlet for an electrolyte solution and an outlet for the electrolyte are provided in the anode chamber and an inlet for introducing an oxygen-containing gas is provided in the gas chamber. The invention also relates to a plant comprising such an electrolytic cell and to its use for the production of alkali metal chlorate and/or chlorine dioxide.

Description

Process for producing alkali metal chlorates

The present invention relates to a process for the production of alkali metal chlorates, as well as electrolytic cells and apparatus for carrying out the process. The invention furthermore relates to the use of the electrolytic cell and the device for the production of alkali metal chlorates and/or chlorine dioxide.

Background of the Invention

Alkali metal chlorates, especially sodium chlorate, are an important chemical in the cellulose industry, which uses it as a raw material in the production of chlorine dioxide, an important chemical for bleaching cellulose fibers reagent. Alkali metal chlorates are usually produced by electrolysis of alkali metal chlorides in open non-isolated electrolyzers equipped with hydrogen evolution cathodes. The overall chemical reactions that take place in this electrolyzer are , where Me is an alkali metal. The reaction had a cell voltage of 3V.

In the past, attempts have also been made to produce chlorate using electrolyzers equipped with oxygen-consuming gas diffusion electrodes. The English Chemical Abstracts of Chinese Patent Application No. 1076226 (AN 1994: 421025) discloses such an electrolytic cell for the production of sodium chlorate. The gas diffusion electrode can reduce oxygen provided to a gas chamber adjacent to the gas diffusion electrode. The reduction reaction occurring on the gas diffusion electrode (gas diffusion cathode) is . The oxidation reaction at the anode is . The cell voltage for the total chemical reaction in the gas diffusion electrode cell is about 2V, which means that considerable operating cost savings can be achieved by replacing the above-mentioned hydrogen evolution cathode with a gas diffusion electrode as the cathode.

However, the operation of the electrolyzer disclosed in the English abstract of Chinese Patent Application No. 1076226 would immediately lead to poisoning of the gas diffusion electrodes, since the reaction products HClO, ClO ⁻ , and ClO ₃ ⁻ formed on the anode would freely diffuse into the electrolyte and Undesirable side reactions according to the following formula will inevitably occur on the gas diffusion electrode:

(1)

(2)

(3)

In many alkali metal chlorate processes, alkali metal chromates are used to inhibit reactions 1-3. At the same time, however, alkali metal chromates negatively affect the gas diffusion electrode, which rapidly deactivates when it comes into contact with chromate ions.

The production of chlorates may require large quantities of hydrochloric acid and alkali metal hydroxides, which likewise imply considerable costs. In addition, the handling of these chemical agents is complicated due to the strict safety requirements involved in transportation, storage and use.

It is an object of the present invention to overcome the above mentioned problems while providing an energy efficient electrolytic process for the production of alkali metal chlorates. Another object of the present invention is to provide a process in which most of the external pH adjustment chemicals can be omitted.

this invention

The invention relates to a process for the production of alkali metal chlorates in an electrolytic cell which is divided by a cation-selective partition into an anode compartment in which the anode is placed and a cathode compartment in which a gas diffusion electrode is placed. The process includes introducing into the anode compartment an electrolyte solution containing an alkali metal chloride and introducing an oxygen-containing gas into the cathode compartment; electrolyzing the electrolyte solution to produce an electrolysed solution in the anode compartment, which is electrolyzed into the cathode compartment Oxygen in the chamber results in the formation of alkali metal hydroxide in the cathode chamber; the electrolyzed solution is transferred from the anode chamber to the chlorate reactor to react the electrolyzed solution to further form concentrated alkali metal chlorate salt electrolyte.

In this process, the same cathode chamber space functions both as a gas chamber for oxygen-containing gas and as a chamber for alkali metal hydroxide production.

According to a preferred embodiment, the gas diffusion electrodes are placed on the cation selective separator in order to minimize the ohmic resistance.

According to another preferred embodiment, the process is carried out in an electrolytic cell, wherein the gas diffusion electrode divides the cathode chamber into a gas chamber on one side of the gas diffusion electrode and a gas chamber on the other side of the electrode delimited by the gas diffusion electrode and the cation selective compartment. Alkali metal hydroxide chamber between plates. The process comprises introducing into the anode compartment an electrolyte solution comprising an alkali metal chloride, introducing an alkali metal hydroxide solution into an alkali metal hydroxide compartment and introducing an oxygen-containing gas into the gas compartment; thereby electrolyzing the electrolyte solution In order to produce an electrolyzed solution in the anode compartment, the electrolysis of oxygen introduced into the gas compartment results in the formation of additional alkali metal hydroxide in the alkali metal hydroxide compartment; this electrolyzed solution is transferred from the anode compartment to the chlorate Reactor to react the electrolyzed solution to further form a concentrated alkali metal chlorate electrolyte.

Preferably, a pressure of up to about 10 bar, preferably up to about 5 bar, can be applied to the electrolytic cell. This can be achieved by applying an appropriate overpressure to the oxygen-containing gas in the gas chamber and the inert gas in the anode chamber.

The cation selective barrier is preferably substantially resistant to chlorine and alkali metal hydroxide, the barrier enables efficient production of the solution being electrolyzed and concentrated alkali metal hydroxide to occur, and in the alkali metal hydroxide chamber Has low levels of chlorate ions and chloride ions. The cation selective separator is preferably a cation selective membrane. The cation selective membrane may suitably be made of an organic material such as a fluoropolymer such as a perfluorinated polymer. Other suitable membranes may be made of polyethylene, polypropylene and sulfonated polyvinyl chloride, polystyrene or Teflon based polymers or ceramics. There are also commercially available membranes suitable for use such as Nafion ^™ 324, Nafion ^™ 550 and Nafion ^™ 961 produced by Du Pont, and Flemion ^™ produced by Asahi Glass.

Suitably, supports may be placed on the anode and/or cathode side to support the cation selective separator.

The anode can be made of any suitable material, such as titanium. The anode may be suitably coated with eg _RuO2 / _TiO2 or Pt/Ir. The anode is preferably a DSA (dimensionally stable anode) with an expanded mesh substrate.

The gas diffusion electrode may be a weeping gas diffusion electrode, a semi-hydrophobic gas diffusion electrode or any other gas diffusion electrode, such as European patent applications No. , 766,429 those gas diffusion electrodes described in. There is no particular limitation on the gas diffusion electrode. For example, a gas diffusion electrode comprising only a reaction layer and a gas diffusion layer may be used. The gas diffusion layer can be made of a mixture of carbon and PTFE resin. The reactive layer may suitably have a certain content of hydrophobic materials such as fluorocarbons in order to maintain suitable water repellency and hydrophilicity. In addition, a protective layer may be formed on the surface of the gas diffusion layer in order to more effectively prevent the gas diffusion layer from becoming hydrophilic.

The process of the present invention can be described as cyclic because in a first step an electrolyte solution comprising an alkali metal chloride solution is passed into an electrolytic cell in which at least a portion of the chloride is electrolyzed to form inter alia hypochlorite and chlorate. The electrolyzed solution is suitably discharged to a conventional chlorate reactor such as that described in US 5,419,818 for further reaction to produce chlorate. The chlorate reactor may contain several chlorate vessels. The chlorate electrolyte can then be transferred to a crystallizer where solid alkali metal chlorate is separated by crystallization and the mother liquor containing, inter alia, unreacted chloride ions, hypochlorite, chlorate Return to the electrolyzer for further electrolysis. It is also possible to use an alkali metal hydroxide scrubber as a chlorate reactor in which chlorate is formed by reacting an alkali metal hydroxide supplied, for example, from an alkali metal hydroxide chamber with chlorine gas discharged from an anode chamber. According to a preferred embodiment, an alkali metal hydroxide scrubber to which chlorine gas is supplied and a chlorate reactor to which the solution to be electrolyzed are supplied are used simultaneously in the process.

The concentrated chlorate electrolyte may contain from about 200 to about 1200 g/l, and preferably from about 650 to about 1200 g/l.

The electrolyte solution introduced into the anode compartment may suitably contain at least some chlorate, suitably in the range of about 1 to about 1000 g/l, preferably about 300 to about 650 g/l, and most preferably about 500 to about 650g/l. Suitably, the electrolyte solution may comprise chloride ions in a concentration range of about 30 to about 300 g/l, preferably about 50 to about 250 g/l, and most preferably about 80 to about 200 g/l, expressed as sodium chloride.

According to another preferred embodiment, the concentration of chlorate in the electrolyte solution introduced into the anode compartment is from about 1 to about 50 g/l, preferably from about 1 to about 30 g/l.

Suitably, most of the chlorine gas produced in the anode compartment dissolves into the solution being electrolyzed. Partial hydrolysis of dissolved chlorine to form hypochlorous acid occurs automatically according to the following formula:

In the presence of buffer or hydroxide ions (B ^- ), hypochlorous acid dissociates into hypochlorite according to the following formula:

The pH of the electrolyzed solution in the anode compartment is preferably 4 or higher in order to promote the dissolution of chlorine. The electrolyzed solution containing chlorine and/or hypochlorous acid may be transferred to a chlorate reactor. A suitable range for the pH of the electrolyzed solution provided to the anode chamber is from about 2 to about 10, preferably from about 5.5 to about 8. A suitable range for the concentration of alkali metal hydroxide in the alkali metal hydroxide compartment is about 10 to about 500 g/l, preferably about 10 to about 400 g/l, more preferably about 20 to about 400 g/l, and most preferably about 40 to about 160 g/l as sodium hydroxide. The produced alkali metal hydroxide can be directly discharged or recycled to the alkali metal hydroxide chamber for further electrolysis until the desired concentration is reached. The resulting alkali metal hydroxide can be used in the chlorate reactor to alkalinize the chlorate electrolyte prior to crystallization of the chlorate. The alkali metal hydroxides can also be used to precipitate alkaline earth metal, iron and aluminum hydroxides for purification of new alkali metal chlorides used in the electrolyte solution. Alkali metal hydroxides can also be used to absorb chlorine gas from the process outlet of the chlorate reactor and, as mentioned earlier, to absorb chlorine gas vented from the anode chamber for direct production of alkali metal in the alkali metal hydroxide scrubber Chlorate.

According to a preferred embodiment, an alkali metal chromate is added to the electrolyte solution as a pH buffer and to suppress unwanted reactions. Chromate is added in an amount of about 0.01 to about 10 g/l, preferably up to about 6 g/l. According to another preferred embodiment, no chromate is added to the electrolytic unwanted liquid.

A suitable range for the temperature in the electrolytic cell is about 20 to about 105°C, preferably about 40 to about 100°C.

Chlorate is preferably produced by a continuous process, but discontinuous processes may also be used. Preferably, the process according to the invention can be combined with the production of chlorine dioxide, using chlorate electrolytes or alkali metal chlorates as feedstock.

The invention also relates to an electrolytic cell for the production of alkali metal chlorates comprising a cation selective partition separating the electrolytic cell into an anode compartment in which the anode is placed and a cathode compartment in which the gas diffusion electrode is placed. An inlet for the electrolytic solution and an outlet for the solution to be electrolyzed are provided in the anode chamber, and an inlet for introducing an oxygen-containing gas is provided in the cathode chamber.

According to a preferred embodiment, the gas diffusion electrodes are arranged on the separator in order to minimize the ohmic resistance.

According to another preferred embodiment, the gas diffusion electrode divides the cathode compartment into a gas compartment on one side of the gas diffusion electrode and an alkali metal hydroxide compartment defined between the gas diffusion electrode and the cation selective separator on the other side of the electrode. Inlets and outlets for the alkali metal hydroxide solution are provided in the alkali metal hydroxide chamber.

Preferably, the cation selective separator may be any of the cation selective membranes described above. Furthermore, an outlet for oxygen-containing gas is preferably provided in the gas chamber. A separate outlet for chlorine gas is preferably provided in the anode compartment and/or in the chlorate reactor. Chlorine gas can also leave the anode chamber through the outlet of the solution being electrolyzed. According to one embodiment of the invention, the anode chamber is not provided with a separate outlet for chlorine gas.

The construction of the above-described embodiment of the electrolytic cell is so robust that the electrolytic cell can withstand the flow of electrolyte and other physical conditions conventional in the field of chlorate production. Preferably, the electrolytic cell is constructed to withstand a flow rate in the anode and/or cathode compartment of preferably at least about 0.5 m ³ h ⁻¹ m ⁻² , more preferably at least about 1 m ³ h ⁻¹ m ⁻² , still more preferably at least about 3 m ³ h ⁻¹ m ⁻² , and most preferably at least about 5 m ³ h ⁻¹ m ⁻² . Preferably, the inlet and outlet are also designed to satisfy these conditions.

The invention furthermore relates to a device comprising an electrolysis cell as described above, wherein the outlet of the anode chamber is suitably connected to the chlorate reactor via the outlet of the solution to be electrolyzed. The chlorate reactor can correspondingly be connected to a crystallizer for transferring chlorate electrolyte, in which the chlorate electrolyte can be precipitated and separated from the mother liquor. A chlorate reactor can be suitably connected to the anode compartment so that part of the alkali metal chlorate electrolyte can be recycled to the anode compartment.

The apparatus may suitably contain a storage vessel for an alkali metal chloride and/or electrolyte treating agent, such as an alkali metal chromate.

The reactor may also be an alkali metal hydroxide scrubber into which chlorine gas withdrawn from the anode compartment may be fed and reacted with the alkali metal hydroxide to produce alkali metal chlorate. Suitably, an alkali metal hydroxide container may be connected to the alkali metal hydroxide chamber for supplying and recycling alkali metal hydroxide. The vessel may be a suitable sump into which water and recycled alkali metal hydroxide may be continuously supplied in order to regulate the concentration of alkali metal hydroxide supplied to the alkali metal hydroxide chamber. The outlet of the alkali metal hydroxide chamber can be connected to several units for alkalization in the chlorate plant, for example to the inlet of an alkali metal hydroxide scrubber or other chlorate reactor, or to Crystallizers for the transfer of alkali metal hydroxides. Preferably, not only an alkali metal hydroxide scrubber but also a conventional chlorate reactor receiving the solution being electrolyzed is placed in the plant.

The invention also relates to the use of the electrolytic cell and the device, including for the production of alkali metal chlorates, preferably sodium chlorate, furthermore eg potassium chlorate. Sodium chlorate can be produced as a solid sodium chlorate salt or as a sodium chlorate electrolyte, which can be used for chlorine dioxide production, preferably by an on-site chlorine dioxide generator.

Brief description of attached drawings

Figure 1 schematically illustrates an electrolytic cell according to one embodiment of the present invention. Figure 2 schematically illustrates a plant for the production of sodium chlorate according to the invention.

Description of implementation plan

Figure 1 shows an electrolytic cell 1 for sodium chlorate production. The electrolytic cell comprises an anode compartment 2 in which an anode 2a is placed, a cation selective membrane 3, a cathode compartment 5 divided into an alkali metal hydroxide compartment 4 and a gas compartment 6 by a gas diffusion electrode. Inlets and outlets for sodium chloride and electrolyte in the anode chamber 2 are indicated by arrows 7 . A separate outlet for chlorine gas (not shown) may be provided in the anode compartment. The inlet and outlet for sodium hydroxide in the alkali metal hydroxide chamber are indicated by arrows 8 . The inlet and outlet for oxygen in the gas chamber 6 are indicated by arrows 9 . Other configurations of electrolyzers (not shown) include two divided cells, ie without separate gas chambers, where the gas diffusion electrodes are placed directly on the cation selective separator.

Figure 2 schematically illustrates the plant for producing sodium chlorate. Into the anode compartment 2 of the electrolytic cell 1 are introduced an electrolyte solution 7 containing sodium chloride and a chlorate electrolyte obtained from a chlorate reactor 10 . The electrolyte solution is electrolyzed to form an electrolyzed solution which is pumped through the anode compartment 2 to the chlorate reactor 10 where chlorate formation continues. The chlorate electrolyte in the chlorate reactor 10 is alkalized with the alkali metal hydroxide produced in the cathode chamber 4 before discharge to the crystallizer 12 for sodium chlorate crystallization. The chlorate electrolyte may also be discharged into a reaction vessel (not shown) for chlorine dioxide production. In the anode chamber 2, a certain amount of chlorine gas is generated during the electrolysis. The chlorine gas produced can be transferred to a sodium hydroxide scrubber 11 where it is absorbed in sodium hydroxide, which can lead to the formation of sodium chlorate. The sodium hydroxide scrubber can therefore also be used as a sodium chlorate reactor. Sodium chloride can be continuously added to the electrolyte solution 7 before being introduced into the anode compartment. Water can be continuously added to the sodium hydroxide tank 4a in order to maintain an appropriate concentration of sodium hydroxide passing through the sodium hydroxide chamber. Sodium hydroxide can also be used in the crystallizer 12 for alkalization.

Example 1

The test was carried out in a batch process with an initial volume of the reactor vessel of 2 liters. The starting concentrations of the electrolyte in the anode compartment were 110 g of NaCl per liter, 550 g of NaClO ₃ and 3 g of Na ₂ Cr ₂ O ₇ per liter. The solution was pumped through the anode compartment of the electrolysis cell at a rate of 25 l/h, which corresponds to a linear velocity across the anode of approximately 2 cm/s. A sodium hydroxide solution having a concentration of 50 g/l was pumped through the cathode chamber at a linear velocity across the cathode of 2 cm/s. Feed excess oxygen into the gas chamber. The cell was a pilot cell comprising an anodic compartment with a dimensionally stable (DSA) chlorine anode and a cathodic compartment with a silver-coated nickel wire loaded with uncatalyzed carbon (5-6 mg/ ^cm2 ) Gas Diffusion Electrodes. The area of each electrode is 21.2 cm ² . The anode and cathode compartments were separated by a cation selective membrane, Nafion 450, and the distance between each electrode and the membrane was 8mm.

Solid sodium chloride was added to the reactor vessel and fed into the anode compartment at a rate of 0.71 g·amp ^-1 h ^-1 to maintain a constant concentration of sodium chloride in the reactor vessel. Water was added to the cathode compartment at a rate of 0.5ml·amp ^-1 min ^-1 to maintain a constant concentration of sodium hydroxide. Electrolysis was carried out in this cell at a temperature of 70°C, a current density of 0.2-3 kA/m ² and a pH of 6.2. This current varies between 0.5-6.3A. This electrolysis was carried out for 30 h.

The current efficiency of this electrolysis is 92% calculated on the hydroxide ions generated in the cathode chamber. The current efficiency was calculated as the quotient of the actual and theoretical maximum production of sodium hydroxide. The production of hydroxide ions is determined by analyzing the amount of hydroxide ions in the catholyte and multiplying this by the collected flux. The production of _NaClO3 was calculated according to the total amount of _NaClO3 formed in the anode chamber throughout the electrolysis process. The current efficiency for chlorine formation is estimated to be close to 100%. Calculated as the quotient of actual recovered and theoretical maximum sodium chlorate production, the current efficiency for chlorate production is 95%.

Example 2

The test was carried out in a batch process with an initial volume of the reactor vessel of 2 liters. The starting concentrations of the electrolyte in the anode compartment were 110 g of NaCl per liter, 550 g of NaClO ₃ and 3 g of Na ₂ Cr ₂ O ₇ per liter. The solution was pumped through the anode compartment of the electrolysis cell at a rate of 25 l/h, which corresponds to a linear velocity across the cathode of approximately 2 cm/s. Pass excess oxygen into the gas chamber. The cell is a pilot cell comprising an anode compartment with a dimensionally stable (DSA) chlorine anode and a cathode compartment with a gas diffuser made of silver, PTFE and carbon on silver screen. electrode. The area of each electrode is 21.2 cm ² . The anode compartment was separated from the gas diffusion electrode by a cation selective membrane (Nafion 450). The distance between the anode and the membrane was 8mm. There is no distance between the membrane and the gas diffusion electrodes. Solid sodium chloride was fed into the reactor vessel and fed into the anode compartment at a rate of 0.71 g*A ⁻¹ h ⁻¹ to maintain a constant concentration of sodium chloride in the reactor vessel. Electrolysis was carried out in this cell at a temperature of 70°C, a current density of 0.2-3 kA/m ² and a pH of 6.2. The current varies between 0.5-6.3A. This electrolysis was carried out for 30 h. The _NaClO3 production was calculated based on the total amount of _NaClO3 formed in the anode chamber throughout the electrolysis process. The current efficiency for chlorine formation is estimated to be close to 100%. Calculated as the quotient of the actual recovered and theoretical maximum sodium chlorate production, the current efficiency for chlorate production is 97%.

Claims (23)

1. Process for the production of alkali metal chlorates in an electrolytic cell (1) which is divided by a cation-selective partition (3) into an anode chamber (2) in which the anode (2a) is placed and a gas diffusion chamber (2) in which is placed A cathode chamber (5) of an electrode (5a), the process comprising introducing an electrolyte solution containing an alkali metal chloride into the anode chamber (2) and introducing an oxygen-containing gas into the cathode chamber (5); electrolyzing the electrolyte solution so that An electrolyzed solution is produced in the anode compartment (2), the electrolysis of oxygen introduced into the cathode compartment (5) leads to the formation of alkali metal hydroxides in the cathode compartment (5); the electrolyzed solution is transferred from the anode compartment (2 ) is transferred to the chlorate reactor (10, 11) so that the electrolyzed solution reacts to further produce a concentrated alkali metal chlorate electrolyte. 2. Process according to claim 1, wherein said gas diffusion electrode (5a) divides the cathode chamber (5) into a gas chamber (6) on one side of the gas diffusion electrode (5a) and the other side of the electrode is limited to gas diffusion Alkali metal hydroxide chamber (4) between the electrode (5a) and the cation selective separator (3), introducing the alkali metal hydroxide solution into the alkali metal hydroxide chamber (4) and feeding the gas chamber (6) Introduce oxygen-containing gas. 3. A process according to claim 1 or any one, wherein the cation selective separator (3) is a cation selective membrane. 4. A process as claimed in any one of the preceding claims, wherein the electrolyte solution has a pH of from about 5.5 to about 8. 5. A process as claimed in any one of the preceding claims, wherein the electrolyte solution has an alkali metal chloride concentration of from about 50 to about 250 g/l. 6. A process as claimed in any one of the preceding claims, wherein the electrolyte solution introduced into the anode compartment (2) has an alkali metal chlorate concentration of about 300 to about 650 g/l. 7. A process as claimed in any one of the preceding claims, wherein the electrolyte solution has an alkali metal chlorate concentration of from about 1 to about 50 g/l. 8. A process as claimed in any one of the preceding claims, wherein the electrolyte solution has an alkali metal chromate concentration of from about 0.01 to about 10 g/l. 9. A process as claimed in any one of the preceding claims, wherein the electrolyte solution does not contain alkali metal chromates. 10. A process as claimed in any one of claims 1-9, wherein the cathode compartment has an alkali metal hydroxide concentration of from about 10 to about 400 g/l. 11. The process as claimed in any one of the preceding claims, wherein the electrolytic cell (1) has a temperature of about 40 to about 100°C. 12. A process as claimed in any one of the preceding claims, wherein the alkali metal hydroxide is transferred from the alkali metal hydroxide chamber (4) to the chlorate reactor (10, 11). 13. An electrolytic cell (1) for the production of alkali metal chlorates comprising a cation selective partition (3) which divides the electrolytic cell (1) into an anode compartment (2) in which the anode (2a) is placed ) and the cathode chamber (5) where the gas diffusion electrode (5a) is placed, the inlet of the electrolyte solution and the outlet of the electrolyzed solution are provided in the anode chamber (2), and the introduction of oxygen-containing gas is provided in the cathode chamber (5) wherein the electrolytic cell can withstand a flow of at least about 0.5 m ³ h ⁻¹ m ⁻² through the anode compartment. 14. The electrolytic cell (1) according to claim 13, wherein said gas diffusion electrode (5a) divides the cathode chamber (5) into a gas chamber (6) on one side of the gas diffusion electrode (5a) and the other side of the electrode. an alkali metal hydroxide chamber (4) between the gas diffusion electrode (5a) and the cation selective separator (3), providing an inlet and an outlet for the alkali metal hydroxide in the alkali metal hydroxide chamber (4), And an inlet for introducing oxygen-containing gas is provided in the gas chamber (6). 15. The electrolytic cell (1) according to any one of claims 13 or 14, wherein the cation selective separator (3) is a cation selective membrane. 16. The electrolytic cell (1) according to any one of claims 13-15, wherein a separate outlet for chlorine gas is provided in the anode compartment (2). 17. The electrolytic cell (1) according to any one of claims 13-16, wherein no outlet for chlorine gas is provided in the anode compartment (2). 18. The electrolytic cell (1) according to any one of claims 13-17, wherein an outlet for oxygen-containing gas is provided in the cathode chamber (5). 19. A device comprising an electrolyzer (1) according to any one of claims 13-18, wherein the electrolyzer (1) is connected to the chlorate reactor (10, 11) through the outlet of the anode compartment (2) 20. The plant according to claim 19, wherein the reactor (10, 11) has an outlet connected to the alkali metal chlorate electrolyte of the crystallizer (12). 21. The device according to claims 19-20, wherein an alkali metal chlorate reactor (10, 11) is connected to the anode chamber (2) so that part of the alkali metal chlorate solution can be circulated to the anode reaction chamber (2 ). 22. Apparatus according to any one of claims 19-21 comprising storage vessels for alkali metal chlorides and/or electrolyte treatment reagents. 23. Use of an electrolytic cell (1 ) according to any one of claims 13-18, or a device according to any one of claims 19-22, for the production of alkali metal chlorates and/or chlorine dioxide.

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