JP2004300543A - Electrode for electrolysis and ion-exchange membrane electrolytic cell using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode which can be deformed freely, further has adequate conductivity, and can be surely electrically connected with an electrode current collector, instead of a conventional electrode of a rigid body for electrolysis, and to provide an electrolytic cell. <P>SOLUTION: This electrode for electrolysis used as an anode or a cathode comprises a metallic coil body 5 carrying an electrode catalyst thereon, or an elastic cushioning material 4 carrying the electrode catalyst composed of a corrosion resistant frame 3 having the metallic coil body wound around it. The metallic coil body can be freely deformed and further has adequate conductivity, so that the electrode can be surely electrically connected with the electrode current collector. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrode for electrolysis that can be used for electrolysis of an aqueous alkali metal chloride solution and an ion exchange membrane electrolytic cell using the same.
[0002]
[Prior art]
The electrolysis industry represented by chloralkali electrolysis plays an important role as a material industry. Although having such an important role, the energy consumption required for chloralkali electrolysis is large, and in countries with high energy costs such as Japan, there is a strong demand for achieving energy savings.
For example, chloroalkali electrolysis has been converted from a mercury method to an ion exchange membrane method via a diaphragm method in order to solve environmental problems and achieve energy saving, and has achieved about 40% energy saving in about 25 years. . However, even this energy saving is not enough, and the power cost, which is energy, accounts for about half of the total manufacturing cost. However, no further power saving is possible as long as the current method is used.
[0003]
In the electrolytic cell equipped with a hydrogen generating cathode used for salt electrolysis, the anode, ion exchange membrane and hydrogen generating cathode are arranged in close contact with each other to reduce the electrolytic voltage, but the electrolytic area reaches several square meters. In a large-sized electrolytic cell, when the anode and the cathode are made of an electrode chamber with rigid members, it is difficult to keep both electrodes in close contact with the ion exchange membrane to maintain a predetermined distance between the electrodes.
As a means for reducing the distance between the electrodes or the distance between the electrodes and the electrode current collector, or for maintaining the distance between the electrodes at a substantially constant value, an electrolytic cell using an elastic material is known.
As the elastic material, a non-rigid material such as a woven fabric, a nonwoven fabric, and a net of a thin metal wire, and a rigid material such as a leaf spring are known.
[0004]
The non-rigid material is disadvantageous in that when it is excessively pressed from the counter electrode after being attached to the electrolytic cell, it is partially deformed and the distance between the electrodes becomes non-uniform, and a thin line of the non-rigid material pierces the ion exchange membrane. There is. In addition, rigid materials such as leaf springs have the drawback that the ion exchange membrane is damaged or plastic deformation occurs, making reuse impossible.
In addition, in an ion exchange membrane electrolytic cell such as a salt electrolytic cell, it is desirable that the anode and the cathode can be brought into close contact with the ion exchange membrane so that the operation can be continued at a low voltage, and various methods for pressing the electrode toward the ion exchange membrane are available. Proposed.
[0005]
[Patent Document 1]
JP-B-63-53272 (FIGS. 1 to 8)
[0006]
[Problems to be solved by the invention]
As described above, the structural characteristics of the electrolytic cell in which the ion-exchange membrane is sandwiched between the positive and negative electrodes are that the electrode is uniformly adhered to the ion-exchange membrane to prevent damage to the ion-exchange membrane, and that the positive and negative electrodes are both used. In order to keep the distance between the electrodes at a minimum, at least one of the electrodes has a structure that can freely move in the direction of the distance between the poles, and the electrode can be pushed by an elastic member to adjust the holding pressure.
Examples of the elastic member include a knitted or woven fabric made of a metal wire or a laminate thereof, or a three-dimensionally knitted shape, a three-dimensionally knitted shape, and a swelled shape, and a metal fiber. , A coil spring (spring), a leaf spring, etc., each of which has some spring elasticity.
[0007]
On the other hand, in an industrial electrolytic cell such as a salt electrolytic cell, a leaf spring, a metal mesh, or the like may be used in order to smoothly supply power from the electrode current collector to the electrode.
However, as described above, since the leaf spring and the metal mesh are rigid, the ion exchange membrane may be damaged, the deformation rate may be small, and sufficient electrical connection may not be obtained.
In order to solve such a drawback, an electrolytic cell in which a metal coil body is mounted between the cathode and the cathode end plate instead of the metal mesh to uniformly press the cathode in the direction of the diaphragm to bring the respective members into close contact with each other. It is disclosed (Patent Document 1).
[0008]
This metal coil body has a very small coil wire diameter and a high deformation rate, so that the members can be brought into close contact with each other and stable operation of the electrolytic cell can be performed.
However, in the electrolytic cell described in Patent Document 1, since a metal coil body is installed in the electrolytic cell in addition to the anode or the cathode, the number of parts is increased, and sufficient adhesion is obtained when the cathode is a rigid body. There is a disadvantage that it may not be possible.
An object of the present invention is to provide an electrode for electrolysis used as an electrode itself and an electrolytic cell using the electrode, instead of using a conventional metal coil body in a mode in which the electrode is pressed in the direction of the ion exchange membrane. .
[0009]
[Means for Solving the Problems]
The electrolysis electrode according to the present invention is characterized in that the electrolysis electrode comprises a metal coil body carrying an electrode catalyst or an elastic cushion material carrying an electrode catalyst formed by winding a metal coil body around a corrosion-resistant frame. Electrode. The metal coil and the elastic cushioning material may be replaced with a metal floc. Further, the ion exchange membrane electrolytic cell of the present invention is an ion exchange membrane electrolytic cell partitioned into an anode chamber containing an anode and a cathode chamber containing a cathode by an ion exchange membrane, wherein at least one of the anode and the cathode serves as an electrode catalyst. An ion exchange membrane electrolytic cell comprising a supported elastic electrode.
[0010]
Hereinafter, the present invention will be described in detail.
In the ion exchange membrane electrolytic cell to which the present invention is applied, an elastic electrode such as a metal coil, an elastic cushion material, or a metal floc is used as at least one of the anode and the cathode.
As a result, the electrode itself has elasticity, so that it is not necessary to install a member having elasticity in addition to the electrode in the electrolytic cell as in the related art. Pressure, thereby producing an effect that, for example, the electrode and the ion exchange membrane are uniformly adhered. For example, a metal coil body, an elastic cushion material, or a metal cotton body is dented when locally pressed with a finger, and is restored when the finger is released, and has extremely high adhesion to unevenness of other members.
The electrolytic reaction in the ion exchange membrane electrolytic cell of the present invention is desirably a reaction for producing alkali hydroxide (caustic soda) by chloralkali (salt) electrolysis, but any reaction in which the above-mentioned elastic electrode can be used as an electrode. There is no particular limitation.
[0011]
The elastic electrode that can be used as the anode or the cathode of the ion exchange membrane electrolytic cell of the present invention is selected from a metal coil, an elastic cushion material, a metal floc, and the like.
The metal coil body is made by rolling a wire made by coating a metal with small specific resistance such as nickel, nickel alloy, stainless steel, or copper with good corrosion resistance by plating etc. with nickel etc. showing good corrosion resistance. It is obtained by processing into a spiral coil. The cross-sectional shape of the wire is preferably a circle, an ellipse, a rectangle with rounded corners, or the like. Cross-sectional shapes with sharp corners, such as triangles or rectangles, are undesirable in order to prevent damage to the ion exchange membrane. For example, when a nickel wire (NW2201) having a diameter of 0.17 mm is roll-processed, a coil wire having a cross-sectional shape of about 0.05 mm × 0.5 mm having a rounded corner and a winding diameter of about 6 mm was obtained. A coil wire can be preferably used.
The metal coil body may be used as it is as an anode or a cathode in the electrolytic cell. However, in the present invention, it is desirable to use the metal coil body as an elastic cushion material formed by winding a metal coil body around a corrosion-resistant frame.
[0012]
That is, since the metal coil body has a high deformation rate, it is difficult to handle it and it is often difficult to install the metal coil body at a predetermined location in the electrolytic cell as intended by the operator. In addition, because it is easily deformed (insufficient strength), even if it is once installed at a predetermined location in the electrolytic cell, the position is biased due to the electrolytic solution or generated gas in the electrolytic cell, making it difficult to uniformly adhere each member. There is.
For example, one or a plurality of metal coil bodies are wound around the elastic cushion material so as to have a substantially uniform density between two opposing rods of four rectangular corrosion-resistant frames. Is obtained by In this elastic cushioning material, usually two layers of metal coil bodies are laminated on the left and right sides of the corrosion-resistant frame. However, since the metal coil bodies themselves are easily deformed, the adjacent coils are meshed with each other in a comb-tooth shape, so that the apparent appearance is obtained. Above, it is one layer. The elastic cushion material thus obtained has an appearance like a metal scourer for washing dishes.
[0013]
Since the assembly of the elastic cushion material using the metal coil body is an operation outside the electrolytic cell, it can be easily performed, and the obtained elastic cushion material can be used as a target electrode in the electrolytic cell at the time of assembling the electrolytic cell. At this time, the elastic cushioning material itself does not deform so much as to hinder assembly due to the strength of the corrosion-resistant frame, so that it can be easily installed at a predetermined location.
[0014]
The diameter of the metal coil body (apparent diameter of the coil) is usually reduced to 10 to 70% by being mounted in the electrolytic cell, and elasticity is generated. It becomes possible to hold between the bodies, and the power supply from the current collector to the electrodes becomes easy. If a metal coil having a small wire diameter is used, the number of contact points between the electrode and the current collector and the elastic cushioning material inevitably increases, and uniform contact can be achieved. Since the elastic cushion material after being mounted on the electrolytic cell is maintained in shape by the corrosion-resistant frame, it is hardly subjected to plastic deformation, and can be reused in most cases even when disassembling and reassembling the electrolytic cell.
[0015]
When assembling an ion exchange membrane electrolytic cell using the elastic cushion material (or metal coil body) of the present invention as an electrode, the elastic cushion material or the like is positioned between the ion exchange membrane and the electrode current collector, and thereafter, as usual. When assembled, an electrolytic cell in which an elastic cushion material or the like is held at the position of the electrode is obtained.
[0016]
In order to perform salt electrolysis using the ion exchange membrane electrolysis cell having the above-described configuration, an electric current such as a salt solution is supplied to the anode chamber, and a diluted caustic soda solution is supplied to the cathode chamber, and electricity is supplied between both electrodes. . In an electrolytic cell in which an elastic cushioning material or the like functions as an electrode, this state is maintained for a long time due to the high strength and toughness of the elastic cushioning material or the like, so that the ion exchange membrane and the like are not mechanically damaged, and Caustic soda and the like can be manufactured with high efficiency without excessive deformation and insufficient power supply.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
An example of an elastic cushion material usable in the electrolytic cell according to the present invention will be described with reference to FIGS. 1 is a perspective view of a corrosion-resistant frame, FIG. 2 is a perspective view illustrating an example of an elastic cushion material, FIG. 3 is a vertical sectional view taken along line AA of FIG. 2, and FIG. 4 is a vertical sectional view taken along line BB of FIG. .
[0018]
As shown in FIG. 1, the corrosion-resistant frame 3 includes a rectangular frame 1 made of a metal round bar such as nickel and a reinforcing bar 2 laid between a pair of round bars in the longitudinal direction.
The metal coil body 4 shown in FIGS. 3 and 4 is obtained by rolling a small-diameter metal wire into a coil shape, and is made of a material having no rigidity and being freely deformable, such as a metal scrubber for cleaning. I have. As shown in FIG. 2, the metal coil body 4 is wound over substantially the entire length between a pair of round bars in the longitudinal direction of a nickel corrosion-resistant frame 3 having a diameter of, for example, about 2 mm to produce an elastic cushion material 5. Is done.
Since the metal coil body 4 is wound around the corrosion-resistant frame 3, the elastic cushion material 5 manufactured in this manner is maintained in the shape of the corrosion-resistant frame 3, and the metal coil body 4 is separated from the corrosion-resistant frame 3. There is almost no detachment, and the metal coil body 4 can be handled as being integrated with the corrosion-resistant frame 3.
[0019]
FIG. 5 is a schematic plan view showing an example in which an elastic cushion material is used as a cathode of a monopolar salt electrolytic cell.
In the figure, a pair of conductive rods 41 extending in the vertical direction are erected in an electrolytic cell 40, and a catholyte circulation current-carrying member 42 is installed around the conductive rod 41, and along the surface of the current-carrying member 42. The cathode current collector 43 is electrically connected.
Next, an elastic cushion material 5 functioning as a cathode is electrically connected to the cathode current collector 43.
[0020]
FIG. 6 is a schematic plan view showing an example in which an elastic cushion material is used as a cathode of a bipolar salt electrolytic cell.
In the figure, in the electrolytic cell 50, four integrated anode holding members 53, which face in the vertical direction on the anode side of the joined anode partition wall 51 and cathode partition wall 52, connect the strip-shaped joint portion 54 to the anode partition wall 51. The anolyte circulation passage 55 is secured in each anode holding member 53 by being joined.
[0021]
A cathode holding member 56 corresponding to the anode holding member 53 is fixed to the cathode side of the joining partition by joining a strip-shaped joining portion 57 to the cathode partition 52. Catholyte circulation is performed in each cathode holding member 56. A passage 58 is provided.
A convex portion 59 is formed outside the center of the anode holding member 53, and power is supplied to the expanded metal anode 60 through the convex portion 59.
The elastic cushion member 5 (or the metal coil body 4) functioning as a cathode is in electrical contact with the flat surfaces of the four cathode holding members 56, and power is supplied from the cathode holding member 56 to the elastic cushion member 5. Done.
[0022]
When the elastic cushioning material 5 is used as the cathode, the metal coil body 4 is wound around the corrosion-resistant frame 3, so that it is easy to handle and the shape is hardly deformed.
In this state, when a salt solution is supplied to the anode chamber and a diluted caustic soda aqueous solution is supplied to the cathode chamber, and a current is applied between both electrodes, a concentrated aqueous caustic soda solution is obtained in the cathode chamber.
[0023]
Next, Examples and Comparative Examples relating to the ion exchange membrane electrolytic cell using the hydrogen generating cathode according to the present invention will be described, but these do not limit the present invention.
[0024]
[Example 1]
The unit ion exchange membrane electrolytic cell was assembled as follows.
The anode uses a dimensionally stable electrode with an effective area of 1540 cm ² (width 11 cm × height 140 cm), formed by forming an electrode catalyst coating having a platinum group metal oxide on titanium expanded metal manufactured by Permelec Electrode Co., Ltd. did. This anode was attached to the partition wall of the anode chamber of the electrolytic cell using an anode rib.
A nickel expanded metal cathode current collector was attached to the cathode chamber partition wall using a cathode rib made of flat nickel.
[0025]
The metal coil body has a wire diameter of 0.17 mm, and a nickel wire (NW2201) having a tensile strength of 620 to 680 N / m ² is formed into a coil wire having a width of about 0.5 mm by rolling, and the winding diameter of the coil is reduced to about 6 mm. What was used was used.
This metal coil body was wound around a nickel round bar frame (corrosion-resistant frame) having a diameter of 2 mm to be shaped into a rectangular parallelepiped, thereby obtaining an elastic cushion material having a general size of 10 mm thick × 110 mm wide × 350 mm long. The coil linear density of this elastic cushion material was about 7 g / dm ² .
[0026]
Next, platinum plating was performed on the elastic cushion material as follows to obtain an elastic cathode.
In other words, brush plating using the elastic cushion material as a cathode and a plastic brush containing a titanium rod impregnated with an aqueous solution of hexachloroplatinic acid (20 g / liter) as an anode (current 0.5 A, plating time 5 minutes per dm ² ) Then, platinum plating was performed on the surface of each metal coil constituting the elastic cushion material on the side of the ion exchange membrane.
Four such platinum-carrying elastic cushion members were arranged on the cathode current collector.
A cation exchange membrane (Flemion-F8934 manufactured by Asahi Glass Co., Ltd.) was arranged between the anode and the cathode to assemble an ion exchange membrane electrolytic cell.
Electrolysis was performed under the conditions of a current density of 40 A / dm ² and a temperature of 85 ° C. while supplying a saline solution having a concentration of 310 g / liter to the anode chamber and an aqueous solution of caustic soda to a concentration of 32 wt% in the cathode chamber. went. The electrolytic cell voltage was 2.89V.
[0027]
[Example 2]
The ion exchange membrane electrolytic cell was assembled as follows.
The anode is a dimensionally stable electrode having an effective area of 1540 cm ² (width 11 cm × height 140 cm) in which an electrode catalyst coating having a platinum group metal oxide is formed on a titanium expanded metal manufactured by Permelec Electrode Co., Ltd. used. This anode was attached to the partition wall of the anode chamber of the electrolytic cell using an anode rib.
A nickel expanded metal cathode current collector was attached to the cathode chamber partition wall using a cathode rib made of flat nickel.
[0028]
A 5 mm thick × 11 cm wide × 20 cm long nickel fiber is woven into a uniform flocculent fiber by opening with a fiber opening machine, and mixed with a mixed solution of an aqueous solution of hexachloroplatinic acid (20 g / l) and hydrochloric acid (10 g / l) at room temperature for 1 hour. It was immersed to deposit platinum to form a cathode.
Seven cathodes (platinum-supported fabric) were arranged on a cathode current collector, and a cation exchange membrane (Flemion F8934 manufactured by Asahi Glass Co., Ltd.) was arranged between the anode and the cathode to assemble an ion exchange membrane electrolytic cell.
Electrolysis was performed under the conditions of a current density of 40 A / dm ² and a temperature of 85 ° C. while supplying a saline solution having a concentration of 310 g / liter to the anode chamber and an aqueous solution of caustic soda to a concentration of 32 wt% in the cathode chamber. went. The electrolytic cell voltage was 2.87V.
[0029]
[Comparative Example 1]
The anode was produced in the same manner as in Example 2, and the cathode current collector was attached in the same manner as in Example 2.
A mat-like body (nickel-made elastic current-carrying body) in which eight nickel-made wires each having a wire diameter of 0.08 mm were knitted together and knitted together and knitted together was placed on the cathode current collector.
[0030]
Next, a nickel wire net having a wire diameter of 0.15 mm, a porosity of 68% and an area of each hole of 0.49 mm ² was coated with the active substance by performing the following operation. That is, the nickel wire gauze was steam degreased and then etched in 15% nitric acid for 1 minute, and then hexachloroplatinic acid hexahydrate aqueous solution (20 g / liter), cesium nitrate hexahydrate aqueous solution (30 g / liter) and nitric acid (50 g / liter). Liter) of the composition was applied, dried at 50 ° C. for 5 minutes after application, then heated in a heater at 500 ° C. for 10 minutes and cooled to room temperature. This cycle (paint coating - drying - decomposition) platinum concentration was repeated until 5 g / m ^2.
A nickel wire mesh was arranged as a cathode in contact with the nickel mat thus obtained, and a cation exchange membrane (Flemion F8934 manufactured by Asahi Glass Co., Ltd.) was arranged between the anode and the cathode to form an ion exchange membrane electrolytic cell. Assembled.
[0031]
Electrolysis was performed under the conditions of a current density of 40 A / dm ² and a temperature of 85 ° C. while supplying a saline solution having a concentration of 310 g / liter to the anode chamber and an aqueous solution of caustic soda to a concentration of 32 wt% in the cathode chamber. went. The electrolytic cell voltage was 2.90V.
[0032]
When Examples 1 and 2 are compared with Comparative Example 1, the electrolytic cell voltage is higher in Examples 1 and 2 using a nickel elastic cushioning material as a cathode than in Comparative Example 1 using a nickel mat and a nickel wire mesh as a cathode. , And it was found that effective electrolysis can be performed.
[0033]
【The invention's effect】
The present invention is an electrode for electrolysis characterized by comprising an elastic cushion material carrying an electrode catalyst constituted by winding a metal coil around a metal coil body or a corrosion-resistant frame carrying an electrode catalyst. Alternatively, a metal floc may be used instead of the metal coil or the elastic cushion material.
Since the shape of the electrode for electrolysis is maintained for a long period of time due to its high strength and toughness, the ion exchange membrane and the like are not mechanically damaged, and are excessively deformed and the power supply becomes insufficient. And caustic soda can be produced with high efficiency.
Furthermore, in the electrolytic cell containing the elastic electrode, the elastic electrode can be freely deformed and has sufficient conductivity, so that the electrode and the electrode current collector can be reliably electrically connected, and reliable power supply is possible. .
[Brief description of the drawings]
FIG. 1 is a perspective view of a corrosion-resistant frame in an elastic cushion material usable in the present invention.
FIG. 2 is a perspective view illustrating an elastic cushion material usable in the present invention.
FIG. 3 is a vertical sectional view taken along line AA of FIG. 2;
FIG. 4 is a vertical sectional view taken along line BB of FIG. 2;
FIG. 5 is a schematic plan view showing an example of a monopolar salt electrolytic cell using an elastic cushion material as a cathode.
FIG. 6 is a schematic plan view showing an example of a bipolar salt electrolytic cell using an elastic cushion material as a cathode.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rectangular frame 2 Reinforcement rod 3 Corrosion-resistant frame 4 Metal coil body 5 Elastic cushion material 40 Monopolar electrolytic tank 41 Conductive rod 42 Catholyte circulation energizing member 43 Cathode current collector 50 Bipolar electrolytic tank 51 Anode partition 52 Cathode partition 53 Anode holding member 54 Band-shaped joint 55 Anolyte circulation path 56 Cathode holding member 57 Band-shaped joint 58 Catholyte circulation path 59 Convex part 60 Anode

Claims (5)

An electrode for electrolysis, comprising: a metal coil body carrying an electrode catalyst or an elastic cushion material carrying an electrode catalyst formed by winding a metal coil body around a corrosion-resistant frame. An electrode for electrolysis comprising a metal floc carrying an electrode catalyst. In an ion exchange membrane electrolytic cell partitioned into an anode chamber accommodating an anode by an ion exchange membrane and a cathode chamber accommodating a cathode, at least one of the anode and the cathode is an elastic electrode carrying an electrode catalyst. Ion exchange membrane electrolyzer. The ion exchange membrane electrolytic cell according to claim 3, wherein the elastic electrode is a metal coil, an elastic cushion material, and / or a metal floc. The ion exchange membrane electrolytic cell according to claim 3, wherein the elastic electrode is in contact with the electrode current collector, and power is supplied from the electrode current collector.

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