JP3909957B2 - Electrolyzer for hydrogen peroxide production - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an electrolytic cell for producing salt water or seawater containing hydrogen peroxide using a gas diffusion electrode. More specifically, oxygen gas and hydrogen gas are produced by water electrolysis, and both gases are used as raw materials. The present invention relates to an electrolytic cell for hydrogen peroxide production that can eliminate the need for flow rate adjustment when producing hydrogen oxide production.
[0002]
[Prior art and its problems]
Hydrogen peroxide is a useful basic chemical indispensable in the food, pharmaceutical, pulp, fiber and semiconductor industries. Conventionally, hydrogen peroxide is industrially obtained by auto-oxidizing 2-alkylanthraquinol, and at the same time, the anthraquinone obtained at the same time is hydrogen-reduced to return to the original anthraquinone, and mass synthesis is continuously performed. . The purification requires complicated operations such as repeated rectification, and hydrogen peroxide is unstable and cannot be stored for a long period of time. Therefore, demand for on-site hydrogen peroxide production equipment is increasing.
In power plants and factories that use seawater as cooling water, it has traditionally been used to generate hypochlorous acid by directly electrolyzing seawater to prevent the attachment of organisms inside the condenser. However, the use of hypochlorous acid is being regulated from the viewpoint of environmental conservation. In other words, this is to prevent organochlorine compounds from being formed due to the reaction of hypochlorous acid with the organisms and organic substances in the sea water, which causes secondary pollution. On the other hand, it has also been reported that when a small amount of hydrogen peroxide is added to the cooling water, there is a good biofouling prevention effect. There are also reports that the addition of hydrogen peroxide is effective in maintaining the quality of fish farm water. However, as described above, there are still problems of safety and pollution control associated with the transport of hydrogen peroxide.
[0003]
The production of hydrogen peroxide using a reduction reaction of oxygen gas has been proposed. US Pat. No. 3,693,749 has several types of hydrogen peroxide electrolytic production equipment, and US Pat. A method for producing a hydrogen peroxide solution is disclosed. US Pat. No. 3,969,201 proposes an apparatus for producing hydrogen peroxide comprising a three-dimensional carbon cathode and an ion exchange membrane. However, in these methods, the amount of alkali essential for the production of hydrogen peroxide increases almost in proportion to the produced hydrogen peroxide, so the alkali concentration becomes too high with respect to the concentration of hydrogen peroxide obtained, and the application is limited. End up.
US Pat. No. 4,406,758, US Pat. No. 4,891,107 and US Pat. No. 4,457,953 disclose a method for producing hydrogen peroxide using a porous membrane and a hydrophobic carbon cathode, and a weight ratio (sodium hydroxide / hydrogen peroxide). ) Is obtained. However, these methods have the disadvantages that it is difficult to control the amount and rate of transfer of the electrolyte solution from the anode chamber to the cathode chamber, the management of operating conditions is complicated, and the proportion of hydrogen peroxide produced is not particularly constant.
[0004]
Furthermore, Journal of Electrochemical Society, vol.130, 1117- (1983) proposed a method for stably obtaining an acidic hydrogen peroxide solution by using a cation / anion exchange membrane and supplying sulfuric acid to an intermediate chamber. Yes. Furthermore, Electrochemical 57, p1073 (1989) reports a method for improving performance by using a membrane electrode assembly as an anode. Further, Journal of Applied Electrochem. 25 (1995) 613 to 627 describes a hydrogen peroxide electrolytic synthesis process known at that time. However, these methods have a problem in terms of power consumption and economical efficiency, and further have the disadvantage that the use and mixing of sulfuric acid is unavoidable, and until now there have been no satisfactory methods for producing hydrogen peroxide. Absent.
The aqueous hydrogen peroxide solution having a high alkali concentration described above is at a satisfactory level of the hydrogen peroxide concentration itself, but since hydrogen peroxide can be obtained efficiently only in an alkaline aqueous solution atmosphere, the supply of alkali components is inevitable. There are transportation and safety issues.
[0005]
On the other hand, as described above, various problems have been studied as the environmental problem and the economically desirable direction to use hydrogen peroxide for seawater treatment because of problems in direct electrolysis of seawater. In addition to the above-mentioned problems, the use of commercially available hydrogen peroxide in these studies has the environmental problem of adding new chemicals synthesized in seawater to contaminate the seawater itself. May occur. When hydrogen peroxide is produced by alkaline electrolysis, the same problem occurs when alkali is added from the outside.
In order to avoid this problem, the present inventors obtained a method in which seawater is salt-separated to obtain an alkali, hydrogen peroxide is obtained from this alkali, and the alkali is finally neutralized with the separated acid. Proposed. This method does not require any chemical addition from the outside, so the occurrence of environmental problems can be minimized, and the required power is very small and close to the ideal. A simpler and easier device would be a more ideal hydrogen peroxide production method.
[0006]
OBJECT OF THE INVENTION
An object of the present invention is to provide an apparatus for producing hydrogen peroxide suitable for various hydrogen peroxide utilization processes, in particular, sterilization treatment of seawater or the like, with a simpler mechanism than before.
[0007]
[Means for solving problems]
The present invention relates to a hydrogen peroxide production unit comprising a hydrogen gas diffusion anode and an oxygen gas diffusion cathode, and an electrolysis comprising a basic unit of three pure water electrolysis units for one hydrogen peroxide production unit. The two units supply oxygen generated on the anode side of the pure water electrolysis unit to the oxygen gas diffusion cathode and hydrogen generated on the cathode side of the pure water electrolysis unit to the hydrogen gas diffusion anode, respectively. And producing salt water or seawater containing hydrogen peroxide by flowing salt water or seawater through the gas diffusion electrodes of the hydrogen peroxide production unit and electrolyzing them. An electrolyzer, wherein both units include oxygen generated on the anode side of the pure water electrolysis unit on the oxygen gas diffusion cathode, and hydrogen generated on the cathode side of the pure water electrolysis unit on the hydrogen gas diffusion anode. A peroxidation characterized in that it is disposed so as to be supplied and salt water or seawater is electrolyzed by flowing salt water or seawater to both gas diffusion electrodes of the hydrogen peroxide production unit to produce hydrogen peroxide-containing salt water or seawater. It is an electrolytic cell for hydrogen production.
[0008]
The present invention will be described in detail below.
The present invention uses a hydrogen gas diffusion anode as an anode of an electrolytic cell in the production of hydrogen peroxide by salt water electrolysis of seawater or the like. As a result, the oxidizability of the anode is usually suppressed, and oxidation of chloride ions, bromide ions, etc. contained in seawater does not theoretically occur, so that generation of carcinogenic substances such as trihalomethane and trihaloethane can be suppressed. In the conventional oxygen generating anode, the production of the substance cannot be ignored, whereas the present invention has fundamentally environmental compatibility.
Furthermore, in the present invention, an alkali can be used, but hydrogen peroxide can be produced without using an alkali, which is optimal for applications that do not like the use of an alkali.
[0009]
In the present invention, oxygen gas (or oxygen-containing gas) is required at the cathode of the unit for producing hydrogen peroxide, and hydrogen gas is required at the anode. The gas can also be supplied from the outside such as a cylinder. However, in the present invention, both gases are basically produced by water electrolysis, which makes it possible to produce salt water containing hydrogen peroxide with a high concentration of several tens to 1,000 ppm, and further contributes to downsizing of the apparatus. Can do.
Each electrode reaction in electrolytic production of hydrogen peroxide is as follows.
Cathodic reaction: O ₂ + H ₂ O + 2e ⁻ → OH ⁻ + HO ₂ ⁻
Anodic reaction: H ₂ → 2H ⁺ + 2e ⁻
On the other hand, the electrode reaction of normal water electrolysis is as follows.
Cathodic reaction: 2H ₂ O + 2e ⁻ → H ₂ + 2OH ⁻
Anodic reaction: 2H ₂ O → O ₂ + 4H ⁺ + 4e ⁻
From these reaction equations, it can be seen that the amount of oxygen required for the hydrogen peroxide production reaction is twice the amount of oxygen generated by the water electrolysis reaction with the same amount of electricity.
[0010]
Therefore, the oxygen gas is insufficient by simply making a one-to-one correspondence between the unit for producing hydrogen peroxide and the pure water electrolysis unit. In order to solve this problem, the energization amount of the pure water electrolysis unit is doubled to match the oxygen generation amount with the oxygen consumption amount in the hydrogen peroxide production reaction, or oxygen gas from an oxygen source such as an oxygen cylinder is excessively passed. Although it is possible to supply the unit for hydrogen oxide production together with the electrolytic oxygen-containing gas, in the present invention, only the electrolytic production gas is used as hydrogen gas and oxygen gas for hydrogen peroxide production. In this case, theoretically, if two pure water electrolysis units are used for one hydrogen peroxide production unit, hydrogen peroxide is produced without excess or deficiency, but oxygen gas is not produced unless the flow rate is adjusted in actual operation. The stoichiometric amount of hydrogen gas may not be supplied twice, and efficient hydrogen peroxide production may not be performed. Therefore, in the present invention, a basic unit is constituted by using three pure water electrolysis units for a single hydrogen peroxide production unit. As a result, 1.5 times the theoretical amount of oxygen gas is supplied, and the required amount of oxygen gas is reliably supplied without adjusting the flow rate, so that hydrogen peroxide can be produced with maximum efficiency. The electrolytic cell of the present invention is composed of one hydrogen peroxide production unit and three pure water electrolysis units, as well as two hydrogen peroxide production units and six pure water electrolysis units, An arbitrary number of hydrogen peroxide production units and pure water electrolysis units in which the ratio of the number of hydrogen peroxide production units to pure water electrolysis units is 1: 3 can be used.
[0011]
As described above, in the present invention, an electrolytic cell for producing hydrogen peroxide is constituted by the basic unit of the pure water production unit 3 with respect to the unit 1 for producing hydrogen peroxide, and oxygen gas and hydrogen gas generated by electrolysis are contained in the same electrolytic cell. This makes it possible to reduce the size of the apparatus.
The pure water production unit installed in the same electrolytic cell as the unit for producing hydrogen peroxide is a unit capable of producing oxygen gas at the anode and hydrogen gas at the cathode by ordinary water electrolysis, and is not particularly limited. It is a structure that supplies gas to adjacent units for hydrogen peroxide production, and in order to supply gas uniformly, it is desirable that there is sufficient space between both units, and in order to prevent liquid mixture It is also preferable to install a buffer such as a sheet that allows only gas to pass between both units. In order to further simplify the structure, for example, a thick ion exchange membrane is used as the ion exchange membrane of the water production unit, both electrodes are brought into close contact with the ion exchange membrane, and water is dropped on the peripheral portion of the ion exchange membrane. If water is supplied and spread over the entire surface of the ion exchange membrane, it is not necessary to provide a separate water supply means. In this case, it is more effective to make the other surface of the electrode water-repellent because water is retained in the electrode. In addition, there is a method of using a porous membrane impregnated with alkali, moisture is supplied to the alkaline porous membrane, and excess moisture is recovered from below.
[0012]
The electrolytic cell comprising the hydrogen peroxide production unit and the pure water production unit may be a bipolar electrolytic cell in which each unit is partitioned by a partition and electrodes between adjacent units are connected. Salt water such as seawater or saline is passed between the two electrodes of this hydrogen peroxide production unit, and electrolysis is performed while supplying hydrogen produced by the pure water electrolysis unit to the anode of the hydrogen peroxide production unit and oxygen to the cathode. To produce hydrogen peroxide according to the above formula. The anode of the unit for producing hydrogen peroxide is a gas diffusion anode as described above. This gas diffusion anode can be a normal gas electrode, and any hydrogen gas diffusion anode can be used, but in order to minimize the effects of impurities in the seawater used frequently, its gas and liquid permeability are considered as liquid and gas permeable. It is preferable that an ion exchange membrane is in close contact with the seawater side of the surface. With this configuration, the influence of impurity ions and salt in seawater on the gas diffusion electrode is minimized, and long-term stability is maintained.
[0013]
The gas diffusion cathode is preferably a so-called semi-hydrophobic cathode so that the oxygen gas supplied from the back side can be used effectively. This makes it unnecessary to supply an excessive amount of oxygen and to smooth the electrode surface. Thus, precipitation as calcium hydroxide or magnesium hydroxide, which is a seawater component accompanying pH change due to a hydroxyl group generated by the cathode reaction, can be easily removed from the electrode surface. Even if it is a semi-hydrophobic gas diffusion electrode, if the porosity of the hydrophobic part is improved and nitrogen is contained in the air supply gas, the nitrogen can be extracted to the hydrogen peroxide production unit side. The generated precipitate can be blown away.
The catalyst material for this gas diffusion cathode requires that a two-electron reaction should occur selectively, and is not particularly limited as long as it can be achieved. Usually, carbon (graphite, carbon black), or gold powder is supported on carbon. Or a gold catalyst coated with a solution in which a gold salt is dissolved and calcined in air or in a reducing atmosphere is used.
[0014]
The anode and the cathode used in the pure water production unit are not particularly limited. For example, the anode is a titanium mesh or an insoluble metal electrode called DSE having a perforated plate coated with an electrode material, and the cathode is also a mesh or a hole. When a nickel material such as a bright plate is used and the electrolyte is alkaline, the anode may be the same nickel as the cathode instead of the DSE. Furthermore, the same gas diffusion anode and gas diffusion cathode as in the case of the hydrogen peroxide production unit can be used.
The surface opposite to the electrolytic surface of these electrodes may be subjected to a water repellent treatment with a fluororesin or the like. Any water repellent method can be used. For example, in the case of nickel, nickel plating in which PTFE resin is dispersed may be performed on the surface to be water repellent. In the case of titanium, graphite fluoride is used as the electrode material. Water repellency can be achieved by applying a mixture mixed with the chemical at the time of baking, or mixed with a tantalum chloride or titanium chloride solution and baking at 350 to 500 ° C.
[0015]
Next, an electrolytic cell for producing hydrogen peroxide according to the present invention will be illustrated based on the accompanying drawings, but the present invention is not limited to these.
FIG. 1 is a schematic longitudinal sectional view showing an example of an electrolytic cell for producing hydrogen peroxide according to the present invention.
The electrolytic cell main body 1 includes a pure water electrolysis unit, a hydrogen peroxide production unit, a pure water electrolysis unit, and a pure water electrolysis unit in order from the left by three pure water electrolysis units 2 and one hydrogen peroxide production unit 3. The units 2 and 3 are partitioned by a partition wall 4. Each pure water electrolysis unit 2 is configured such that a pure water electrolysis anode 6 is located on the left side of the cation exchange membrane 5 and a pure water electrolysis cathode 7 is located on the right side.
[0016]
The hydrogen peroxide production unit 3 is made of carbon and connected to the partition wall 4 via the anode current collector 8 on the left side, and the gas diffusion anode 9 is located on the right partition wall 4 via the cathode current collector 10. A gas diffusion cathode 11 for producing hydrogen peroxide carrying an electrode material capable of selectively electrolytically producing hydrogen peroxide is located at a distance and partitioned into an anode chamber and a cathode chamber by a cation exchange membrane 12. ing. The anodes 6 and 9 and the cathodes 7 and 11 of the hydrogen peroxide production unit 3 and the pure water electrolysis unit 2 are connected in a bipolar manner, and the electrodes of the units 2 and 3 are energized by energizing the anode 6 and the cathode 7 at both ends. Is supplied with power.
A salt water inlet 13 is installed on the bottom plate of the hydrogen peroxide production unit 3, and a hydrogen inlet 14, a hydrogen peroxide outlet 15 and an oxygen inlet 16 are installed in order from the left on the top plate. A pure water inlet 17 is provided at the anode chamber side and the cathode chamber side of the bottom plate, an oxygen gas outlet 18 is provided at the top plate of each anode chamber, and a hydrogen gas outlet 19 is provided at the top plate of each cathode chamber. is set up.
[0017]
When seawater is supplied from the salt water inlet 13 of the electrolytic cell main body 1 having such a structure, and each unit 2 and 3 is energized while supplying pure water from the pure water inlet 17 to each pure water electrolysis unit 2. Oxygen is generated at the anode of each pure water electrolysis unit 2 and is taken out from the oxygen gas outlet 18 and supplied to the gas diffusion cathode 11 of the hydrogen peroxide production unit 3, and at the cathode of each pure water electrolysis unit 2. Hydrogen is generated and taken out from the hydrogen gas outlet 19 and supplied to the gas diffusion anode 9 for hydrogen peroxide production in the hydrogen peroxide production unit 3. At this time, the oxygen supplied to the hydrogen peroxide production unit 2 is 3 moles per 2 moles of stoichiometry, and hydrogen peroxide is produced at the maximum level of the hydrogen peroxide production capacity in the hydrogen peroxide production unit 2. The hydrogen peroxide is taken out from the hydrogen peroxide outlet 15 in a form dissolved in salt water.
[0018]
【Example】
Next, although the Example which electrolyzes the salt water by this invention and manufactures the salt water containing hydrogen peroxide is described, this Example does not limit this invention.
[0019]
[Example 1]
A gas-liquid permeable carbon porous anode carrying a platinum catalyst and a carbon cathode carrying a gold catalyst, each having an electrode area of 1.4 dm ² , were prepared, and the anode was a Nafion 117 cation made by DuPont. The cathode was placed in close contact with the exchange membrane, and the distance from the anode was 5 mm on the opposite side of the cation exchange membrane, to obtain a hydrogen peroxide production unit.
On the other hand, an insoluble metal electrode coated with iridium oxide as an electrode material on a titanium mesh is closely attached to a Nafion 117 cation exchange membrane manufactured by DuPont, and a titanium mesh is installed on the opposite side of the cation exchange membrane to provide a pure water electrolysis unit. It was.
One hydrogen peroxide production unit and three pure water electrolysis units were connected in a bipolar manner as shown in the accompanying drawings to form an electrolytic cell for producing hydrogen peroxide.
The hydrogen peroxide production unit was fed with 200 ml of neutral 3% saline solution per minute, the inlet temperature was set to 20 ° C, and the hydrogen gas generated by the pure water electrolysis unit was fed to the anode side of the hydrogen peroxide production unit. Moreover, when electrolysis was performed by supplying a current of 7 A (current density 5 A / dm ² ) to each unit while supplying oxygen gas to the cathode side, the cell voltage of the electrolytic cell was 2.0 V, producing hydrogen peroxide. A saline solution containing 350 ppm hydrogen peroxide was obtained from the unit with a current efficiency of 90%.
[0020]
【The invention's effect】
The present invention relates to a single hydrogen peroxide production unit comprising a hydrogen gas diffusion anode and an oxygen gas diffusion cathode spaced from the anode, and a basis for three pure water electrolysis units for the hydrogen peroxide production unit. An electrolytic cell constituted by a unit, wherein both the units are configured such that oxygen generated on the anode side of a pure water electrolysis unit is supplied to the oxygen gas diffusion cathode and hydrogen generated on the cathode side of the pure water electrolysis unit is supplied to the hydrogen gas It arranges so that it may supply to a diffusion anode, respectively, and salt water or seawater is made to flow through both gas diffusion electrodes of the hydrogen peroxide manufacture unit, and electrolysis is carried out, and salt water or seawater containing hydrogen peroxide is manufactured. This is an electrolytic cell for producing hydrogen peroxide.
The first feature of the present invention is that a hydrogen gas diffusion anode is used as an anode in hydrogen peroxide production by salt water electrolysis. When the gas diffusion anode is used, the oxidizability of a normal anode such as DSE can be suppressed, and therefore the generation of carcinogenic substances such as trihalomethane can be suppressed, and it has environmental conservation compatibility. Further, hydrogen peroxide can be produced with substantially the same efficiency without using alkali.
[0021]
The second feature of the present invention is that, in addition to the first feature, the gas supplied to both gas diffusion electrodes is produced by electrolysis. In the case of electrolysis, a hydrogen peroxide production unit and a pure water electrolysis unit are installed at a ratio of 3: 1, and the gas generated by the pure water electrolysis unit is used as it is for hydrogen peroxide production in the hydrogen peroxide production unit. The ratio of the supplied oxygen gas to the oxygen gas required for the hydrogen peroxide is 3: 2, and hydrogen peroxide can be produced with the maximum hydrogen peroxide production capacity of the hydrogen peroxide production unit.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view showing an example of an electrolytic cell for producing hydrogen peroxide according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electrolyzer main body 2 ... Pure water electrolysis unit 3 ... Unit for hydrogen peroxide production 4 ... Partition 5 ... Cation exchange membrane 6 ... Anode for pure water electrolysis 7 ...・ Cathode for pure water electrolysis 8 ... Anode current collector 9 ... Gas diffusion anode 10 ... Cathode current collector 11 ... Gas diffusion cathode 12 ... Cation exchange membrane 13 ... Salt water introduction Port 14 ... Hydrogen inlet 14 15 ... Hydrogen peroxide outlet 16 ... Oxygen inlet 17 ... Pure water inlet 18 ... Oxygen gas outlet 19 ... Hydrogen gas outlet

Claims (1)

A hydrogen peroxide production unit comprising a hydrogen gas diffusion anode and an oxygen gas diffusion cathode, and an electrolytic cell comprising basic units of three pure water electrolysis units for one hydrogen peroxide production unit; Both units are arranged so that oxygen generated on the anode side of the pure water electrolysis unit is supplied to the oxygen gas diffusion cathode and hydrogen generated on the cathode side of the pure water electrolysis unit is supplied to the hydrogen gas diffusion anode. An electrolytic cell for producing hydrogen peroxide, wherein salt water or sea water containing hydrogen peroxide is produced by flowing salt water or sea water through the two gas diffusion electrodes of the hydrogen peroxide production unit for electrolysis.

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