JPH01312092A - Production of ozone by electrolysis - Google Patents

Abstract

PURPOSE:To stably produce high purity ozone without deteriorating the function of the anode owing to the suspension of supply of electric current by using an electrode obtd. by adhering a Pt layer to one side of a porous electrode and press bonding a cation exchange membrane to the surface of the Pt layer as the anode in an apparatus for producing ozone by electrolysis of water. CONSTITUTION:An electrode obtd. by adhering a Pt layer of 5-100mum thickness to one side of a porous electrode such as a sintered body of fibrous Ti or Ti powder and press bonding a perfluorosulfonic acid type cation exchange membrane to the surface of the Pt layer is used as the anode in an apparatus for generating ozone by electrolysis of water. A sintered body of fibrous carbon or powdery carbon, carbon felt, paper or cloth is used as the cathode. Water at 5-20 deg.C is electrolyzed at about 200A/dm<2> current density and high purity ozone having about 0.05-0.5% concn. is stably produced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for the electrolytic production of ozone. More specifically, sterilization,
This invention relates to an electrolytic production method for ozone that can continuously supply ozone or pure ozone water useful for storage, etc.

Conventional technology and its problems It is known that ozone can be produced by water electrolysis.

According to the conventional water electrolysis method, platinum electrode/cation exchange membrane/
By using a cell combined with a lead dioxide electrode (anode) and electrolyzing while sending pure water to the anode side, ozone with a high concentration of 14% by weight or more can be obtained. In order to generate high concentration ozone, a lead dioxide electrode is an indispensable catalytic electrode.

However, the above water electrolysis method has the following problems.

In other words, if electrolysis is stopped due to a power outage while electrolysis is being performed using the above method, a reverse current flows through the cell or self-discharge occurs, and the lead contained in the lead dioxide electrode becomes PB''. -pb"+ reaction occurs and diffuses onto the ion exchange membrane as Pb2+.

As a result, the lead dioxide electrode loses active sites that contribute to the movement of protons necessary for the water electrolysis reaction, and its function as a solid electrolyte deteriorates. Therefore, in the conventional method, the current cannot be turned on and off arbitrarily.

Furthermore, since the ozonated water produced is contaminated by lead dissolved from the lead dioxide electrode, in order to use the obtained ozonated water in the above-mentioned consumer fields, it is necessary to perform treatments such as removing lead.

For this reason, in conventional cells, in order to protect the lead dioxide electrode, a backup power supply must be activated to supply a protective current during a power outage. That is, an electrolytic device using a lead dioxide electrode always requires an electrode protection circuit, and the subsystem required for this makes it difficult to make the device compact and reduce costs. Moreover,
The manufacturing cost of the lead dioxide electrode itself is also very high.

On the other hand, water electrolysis can be performed using an electrode-membrane assembly in which catalyst electrodes are bonded to both sides of a cation membrane such as platinum/cation exchange membrane/platinum, platinum/cation exchange membrane/iridium or its oxide, etc. It is known that oxygen and oxygen can be obtained.

However, since the ozone production reaction and the catalytic decomposition reaction occur concurrently on the platinum electrode, even when water electrolysis is performed using such a platinum-membrane assembly, the amount of ozone produced is extremely small.

Means for Solving the Problems In view of the problems of the prior art described above, the inventor of the present invention conducted a detailed study on the ozone generation mechanism in water electrolysis using an ion exchange membrane, and as a result, developed a method using a platinum layer on one side as an anode. When water electrolysis is performed using a porous power feeder having a specific ion exchange membrane pressed against the platinum surface of the power feeder, (1) almost no ozone catalytic decomposition reaction occurs; ~0. 5% by weight
(2) Even if the current is stopped, the anode does not melt, and the backup power supply required for conventional ozone production equipment equipped with lead dioxide electrodes can be omitted. (3) Since the anode does not collapse, the obtained ozonated water is not contaminated and can be used as it is in the consumer field; (4) A backup power supply is required. The present invention was completed based on the discovery that the on-site production apparatus for high-purity ozone or ozonated water can be made more compact, cost-effective, and labor-saving because the process can be omitted.

That is, the present invention provides an ozone electrolysis method characterized in that water electrolysis is carried out by using a porous electrode having a platinum layer on one side as an anode and pressing a perfluorosulfonic acid type cation exchange membrane onto the platinum surface of the electrode. It concerns the manufacturing method.

The electrode used in the present invention is not particularly limited as long as it is a porous electrode having a platinum layer on one side.

The smaller the degree of roughness of the platinum layer, the more preferable it is. An electrode having such a structure can quickly (desorb) ozone generated in the platinum layer behind the electrode through the platinum layer and the pores of the porous electrode.

As the porous electrode material, known materials can be used, such as porous titanium material. Any commonly used porous titanium material can be used, such as sintered titanium in the form of fibers or spherical powder, expanded plates, and sintered layers of mesh.

A platinum layer is bonded to one side of the porous electrode material. Any known method can be used for joining, but a sintering method is preferred. Although the thickness of the platinum layer is not particularly limited, it may normally be about 5 to 100 μm. If a laminated product is used without bonding, the contact surface between platinum and titanium will be easily oxidized and the resistance of the cell will increase.

Specific examples of porous electrodes bonded with platinum include platinum mesh, platinum expanded plate, platinum photoetched plate, perforated plates processed from clad plates made of platinum and titanium, tantalum, niobium, etc., made of porous titanium material. Examples include those bonded by sintering.

Alternatively, one side of an expanded plate made of titanium, tantalum, etc., plated with platinum with a low degree of roughness may be bonded to the porous titanium material. May be plated on one side.

As the cathode material, those employed in conventional methods can be used. Specific examples include sintered bodies of fibrous carbon, powdery carbon, etc., carbon felt, carbon paper, carbon cloth, etc., and carbon powder made of PT.
Examples include those molded with FE resin and those made by sintering expanded graphite. Platinum may be bonded to these carbon materials for use. Further, it is also possible to use a carbon molded plate plated with platinum on one side, or a molded carbon plate in which platinum is dispersed and molded with a fluororesin or the like.

The perfluorosulfonic acid type cation exchange membrane used in the present invention operates as a solid electrolyte in a water electrolysis reaction and is resistant to ozone generated at the anode. A specific example thereof is, for example, DuPont's Nafion membrane.

Electrolytic production of ozone involves assembling a cell by arranging the above-mentioned electrode on the cathode side and arranging the platinum electrode according to the present invention on the anode side across the perfluorosulfonic acid type cation exchange membrane. Platinum electrodes are pressed together and electrolysis is carried out while sending pure water to the anode side.

Electrolytic conditions are not particularly limited and may be selected as appropriate.

Electrolysis is usually carried out at a temperature of about 0 to 50°C, preferably 5 to 20°C.
The process is carried out at a temperature of about C.

Further, the current density is not particularly limited and can be selected as appropriate, but in consideration of the concentration of ozone obtained, damage to the cation exchange membrane, etc., it is usually about 50 to 20 OA/drrr. In this range, 0.05 to 0. 5% by weight
A certain amount of ozone can be obtained.

The concentration of ozone obtained can be adjusted by changing the current density.

Effects of the Invention According to the present invention, the following excellent effects can be achieved. ' (1) Almost no ozone catalytic decomposition reaction occurs, and 0.05
It is possible to produce high purity ozone with a concentration of ~0.5% by weight.

(2) Dissolution of the anode does not occur when the current is stopped. For this reason,
The backup power supply required in conventional ozone production equipment using lead dioxide electrodes can be omitted, and the current can be turned on and off at will.

(3) Since there is no contamination of the anolyte due to the collapse of the anode, etc., the purity of the ozonated water obtained on the anode side is high.

Moreover, the obtained ozonated water can be used as it is in the consumer field.

(4) It becomes possible to make the on-site production equipment for high-purity ozone or ozone water more compact, reduce costs, and save labor.

EXAMPLES Below, Examples and Comparative Examples will be given to further clarify the present invention.

Example 1 Platinum expanded band plate [thickness 0.1 mm, wire diameter 0].

1mm, Product name: MloF, Carrada grating ■
] was pressed and processed into a disc with a diameter of 85 mm.

The porous titanium plate is a circular plate (manufactured by Tokyo Seimi ■) with a porosity of 70% and a thickness of 3III111 and a diameter of 85 mm, which is made by vacuum sintering fibrous titanium (60 μm in diameter and approximately 3 mm in length) by cracking and cutting. did.

Place a platinum perforated plate on a porous titanium plate, 100g/cd
The electrodes were processed and bonded in a vacuum sintering furnace at 1170° C. under a load of 1,170° C. to produce an electrode with a diameter of 85 mm.

Example 2 Titanium expanded plate [thickness 0. 1 mrn, wire diameter 0
．． 1 mm, trade name: MloF, manufactured by Carrada Grating ■] was pressed and processed into a disc with a diameter of 85+nn+. This was degreased, washed with water, and etched for 2 minutes with a 10% oxalic acid aqueous solution, and then electrolyzed at 5A for 30 minutes using a platinum plating solution [Platanex 11 solution, manufactured by Kuninaka Kikinzoku ■] to a thickness of approximately 5 μm. Platinum plating was applied.

Next, a titanium extract band plate, TiO, 1-MloF, 0
．． 2-M20F and 0.3-M20F were stacked in order of hole diameter, and a platinum-plated titanium plate was placed on the expanded plate with the smallest hole diameter and sintered in a vacuum furnace to produce a disk electrode with a diameter of 85 mm.

Example 3 A platinum-tantalum clad plate [thickness 0.25 mm, platinum layer 7 μm 1 manufactured by Ishifuku Kinzoku Co., Ltd.] was subjected to expansion band processing and M3
A disc with 0F and a diameter of 85 mm was produced. Next, Example 1
Vacuum sintered with a porous titanium plate similar to
An electrode of mm was fabricated.

Example 4 Ozone was produced by water electrolysis using the electrolysis apparatus shown in FIG. The conditions are as follows.

Anode: Example 1. 2. 3 each electrode, effective area 50c
Cathode: Porous carbon plate manufactured by sintering expanded graphite [thickness 0. 5mm, effective area 50c♂, made in Kobe w4■
Ion exchange membrane: Nafion 117 (manufactured by DuPont) Anode plate: Titanium Cathode plate: SUS 304 Temperature: 12 to 32°C Electrolyte: Water current : 5OA and 75A Current density = 100-150A/di Voltage = 6.1-6.6v The ozone concentration and amount generated from the electrodes of each example are shown in Table 1 below.

Comparative Example 1 Adsorption,
An electrode-membrane assembly in which platinum was bonded to a Nafion membrane was fabricated using a reduction and growth method. Use this as an anode,
Water electrolysis was carried out in the same manner as in Example 4, except that a laminate of titanium expanded plates was used as the anode power supply material. The results are shown in Table 1 below.

Comparative Example 2 Water electrolysis was carried out in the same manner as in Example 4, except that a porous plate made of fibrous titanium (manufactured by Tokyo Rope Corporation) with platinum plating on one side was used as an anode. The results are shown in Table 1 below.

Table 1

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a cell for water electrolysis according to the method of the present invention. (1) Ion exchange membrane (2)... Anode (3)... Cathode (4)... Anode side end plate (5)... Cathode side end plate (6)... Gas separator ( 7)...Anode generated gas (8)...Cathode generated gas (and more) Figure 1

Claims (1)

[Claims] (1) When producing ozone by water electrolysis, a porous electrode having a platinum layer on one side is used as an anode, and a perfluorosulfonic acid type cation exchange membrane is pressure-bonded to the platinum surface of the porous electrode to perform water electrolysis. An electrolytic ozone production method characterized by: