JPH07278865A - Carbonaceous electrode for generating carbon dioxide and its production - Google Patents

Abstract

PURPOSE:To provide a carbonaceous electrode for generating carbon dioxide and the producing method capable of stably and quantitatively generating carbon dioxide by water electrolysis. CONSTITUTION:This carbonaceous electrode for generating carbon dioxide is composed of a carbonaceous molding of a composition containing 35-70wt.% activated carbon component. It is produced by blending 35-70wt.% activated carbon powder, 15-50wt.% clayey material, 5-15wt.% lubricant powder of at least one kind selected from graphite, boron nitride and mica and 0.5-10wt.% binder component, kneading them with added water, molding the mixture into a prescribed shape and firing it in a non-oxidizing atmosphere at 900-1400 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbonaceous electrode for generating carbon dioxide which is used as an anode when electrolyzing water to dissolve carbon dioxide in water, and a method for producing the same.

[0002]

2. Description of the Related Art For example, carbon dioxide gas required for photosynthesis must be supplied to aquatic plants such as aquatic plants that grow for a long time in an aquarium for ornamental fish. Conventionally, a method of supplying carbon dioxide to a water tank has been adopted in which carbon dioxide is introduced into water from an external supply source and dissolved by gas-liquid contact. As a carbon dioxide supply source, a gas cylinder or a cylinder filled with carbon dioxide has been used, but this type of supply source is difficult to control the flow rate of carbon dioxide, and replacement or replenishment when carbon dioxide is consumed There was a drawback that it was troublesome.

One of the applicants of the present invention has developed a dissolved carbon dioxide gas supply device having a mechanism for electrolyzing water by using carbon as an anode in a liquid intended to supply dissolved carbon dioxide gas in order to solve such a drawback. Proposed (Japanese Patent Application No. 5-133797).

[0004]

[Problems to be Solved by the Invention] Japanese Patent Application No. 5-13379
In the dissolved carbon dioxide gas supply device by No. 7, a carbon anode is installed in water at a distance from a metal cathode, and oxygen generated by electrolysis of water and a carbon component of the anode come into contact when a constant current is passed between the electrodes. By utilizing a reaction mechanism for generating carbon dioxide gas, carbon dioxide gas can be stably generated and dissolved in water for a long period of time. However, in the subsequent research, it was found that the degree of reaction with oxygen varies depending on the type and composition of the carbon material forming the anode, and the use stability of the anode material varies depending on the manufacturing method.

The inventors of the present invention have focused their attention on the above-mentioned phenomenon, and have conducted extensive studies on the relationship between the component composition of the carbon material used for the anode and the improvement of the performance as the carbon dioxide gas generating electrode.
It was clarified that the composition containing the activated carbon in the specific range was the most effective, and at the same time, the suitable manufacturing technique for obtaining the electrode material having this composition was found.

The present invention was developed on the basis of the above findings, and provides a carbonaceous electrode for carbon dioxide gas generation, which is capable of continuously and quantitatively generating carbon dioxide gas with excellent usage performance, and a method for producing the same. It is an object.

[0007]

The carbonaceous electrode for carbon dioxide gas generation according to the present invention for achieving the above object comprises a carbonaceous compact having a composition containing an activated carbon component in the range of 35 to 70% by weight. This is a structural feature.

The carbonaceous electrode for generating carbon dioxide of the present invention is formed as a columnar, cylindrical, or plate-like carbonaceous compact, and the composition of the compact has an activated carbon component of 35 to 35.
It is an important requirement that the content is 70% by weight. When the ratio of the activated carbon component in the carbonaceous electrode is less than 35% by weight, the oxidation reaction with oxygen generated during electrolysis does not proceed smoothly, the amount of carbon dioxide gas generated is small, and the stability,
It also becomes inferior in quantification. On the other hand, if the ratio of activated carbon exceeds 70% by weight, molding during manufacturing becomes difficult, and the structure of the sintered body tends to collapse at the consumption stage. A more preferable activated carbon content ratio is in the range of 40 to 65% by weight.

The manufacturing method according to the present invention for obtaining a carbonaceous electrode for carbon dioxide gas generation having the above composition comprises 35 to 70% by weight of activated carbon powder, 15 to 50% by weight of clay substance, graphite,
5 to 10 wt% of at least one lubricant powder selected from boron nitride and mica, and a binder component of 0.5 to 1
It is characterized in that 0% by weight is blended, water is added and kneaded, and the mixture is molded into a predetermined shape, and then the mixture is baked in a temperature range of 900 to 1400 ° C. in a non-oxidizing atmosphere.

Activated carbon powder is a main raw material component constituting a carbonaceous electrode, and should be used regardless of the type, such as plant-based materials such as palm shell and wood powder, mineral-based material such as coal. You can However, the powder property has a particle size of 500.
Those having a specific surface area of 800 μm ² / g or more and an iron content of 0.1% by weight or less and having purity characteristics are preferably applied. When the particle size exceeds 500 μm and the specific surface area falls below 800 m ² / g, the reaction rate with generated oxygen decreases, and when the iron content exceeds 0.1% by weight, it is dissolved in the electrolysis. It is not preferable because it contaminates water and causes coloring.

Clay material is a component that functions as a binder,
For example, various clays such as kaolin type, halosite type, pyroferrite type and montmorillonite type can be used. However, kaolin clay is preferably used for the purpose of the present invention. The compounding amount of these clay substances is 1
Set in the range of 5 to 50% by weight. With this composition, the contained ceramic components such as SiO ₂ and Al ₂ O ₃ serve as a skeleton during firing to strongly sinter while supporting the activated carbon component, which is effective in removing the activated carbon component and collapsing the structure during the consumption process. To prevent it. If the blending amount is less than 15% by weight, the above function is not effectively exhibited, and if the blending amount exceeds 50% by weight, the amount of the activated carbon component is relatively insufficient and the carbon dioxide gas generating function is deteriorated.

The graphite powder, boron nitride powder and mica powder are components added as a lubricant for smoothing the molding and improving the shape retention in the molding step, and at least one selected from these is 5 to 10 Blend in the range of wt%. If the blending amount is less than 5% by weight, the molding will not be smoothly carried out, and if the blending amount exceeds 10% by weight, it will cause water to be contaminated during electrolysis.

Examples of the binder component include carboxymethyl cellulose (CMC), methyl cellulose, starch,
Modified starch, dextrin, polyvinyl alcohol and the like can be mentioned, but carboxymethyl cellulose (CMC) is most preferably used. The binder component is 0.5 to 1
The content is 0% by weight, preferably 3 to 5% by weight. If the content is less than 0.5% by weight, the molded body becomes brittle, and if it exceeds 10% by weight, cracks or fractures will occur in the structure during the firing stage, which is not preferable.

The above raw material components are blended in a predetermined weight ratio, an appropriate amount of water is added thereto, and the resulting mixture is sufficiently kneaded, followed by extrusion molding.
A cylindrical, cylindrical, or plate-like shape is formed by using an appropriate forming means such as molding. Next, the molded body is dried, and then placed in a heating furnace kept in a non-oxidizing atmosphere such as nitrogen or argon, and fired in a temperature range of 900 to 1400 ° C.

By the firing treatment, the organic component such as the binder component is carbonized, and at the same time, the ceramic component in the clay substance is strongly sintered. By attaching an energizing terminal member to the sintered body thus obtained, the activated carbon component
A carbonaceous electrode for carbon dioxide gas generation having a composition mainly composed of a carbonaceous structure contained in an amount of 70 wt% is formed.

[0016]

The carbonaceous electrode for generating carbon dioxide according to the present invention is used as an anode when a small constant current is electrolyzed between the carbonaceous electrode and a metal cathode. During electrolysis, oxygen generated by the decomposition of water comes into contact with the carbon component of the anode, and is dissolved in water as carbon dioxide while oxidatively consuming carbon.However, the carbonaceous electrode of the present invention is mainly composed of oxygen. The reaction proceeds extremely stably and quantitatively because it is composed of activated carbon having excellent reactivity. Further, the generation degree of carbon dioxide can be controlled within a desired range by adjusting the current density to be applied. Therefore, carbon dioxide gas can be smoothly supplied to water for a long period of time, which is extremely effective for the purpose of growing an aqueous plant by photosynthesis.

Further, according to the production method of the present invention, activated carbon powder is the main component, and a clay substance which serves as a binder during sintering, a lubricant powder such as graphite, boron nitride and mica which serves as a molding aid, Since a raw material system is prepared by blending a binder component as an excipient at the time of molding in a predetermined weight ratio, the molding process proceeds smoothly and, at the time of firing, SiO ₂ or Al ₂ O ₃ which constitutes a clay substance is formed. The ceramic component functions to give a strong sintered structure. In particular, when kaolin-based clay is used as the binder, the active carbon has a large specific surface area, and the active pore characteristic inherent to the activated carbon is maintained as it is, so that a suitable microstructure is obtained. Therefore, it can be stably used in a state where the powder does not fall off or the tissue collapses during electrolysis.

[0018]

EXAMPLES Examples of the present invention will be described in detail below in comparison with comparative examples. However, the present invention is not limited to these examples.

Examples 1 to 11 and Comparative Examples 1 to 6 Coconut shell activated carbon powder having an iron content of 0.1% by weight or less [“DIASORB F” manufactured by Mitsubishi Kasei Co., Ltd.], kaolin clay [Kyoritsu Ceramic Raw Material ( Ltd.], graphite powder, boron nitride powder or mica powder, and carboxymethyl cellulose (CM
C) was blended in the ratio shown in Table 1, and 75 to 80 parts by weight of water was added to 100 parts by weight of the blended mixture and kneaded sufficiently. The kneaded material is a plunger type extrusion molding device with a diameter of 15 mm,
It was molded into a cylindrical shape having a length of 150 mm and dried at a temperature of 50 ° C. to cure the binder component. Then, the cured molded body was transferred to a heating furnace maintained in an argon atmosphere, and 100 ° C / hr.
At a heating rate of 1000 ° C.
A time calcination process was performed.

[0020]

[Table 1]

A current-carrying terminal was attached to the upper part of each of the obtained carbonaceous electrode sintered bodies for carbon dioxide gas generation having a diameter of 15 mm and a length of 100 mm to serve as an anode, which was 18 mm in inner diameter, 0.5 mm in wall thickness and 110 mm in length. It has a cylindrical shape with 29 mm diameter hole
A stainless steel cathode, which was drilled at equal intervals, was placed and fixed in the center of the cathode so that there were evenly spaced gaps around the periphery, and a water tank containing 6 liters of water containing ornamental fish (water pH 7.2).
Was set in a dipped state. The lead wire was connected to a constant current generator, and electrolysis was performed for 30 days under the conditions of a current of 120 mA and an anode current density of 2.8 mA / cm ² .

After the start of electrolysis, a commercially available dissolved carbon dioxide reagent for fresh water (manufactured by Tetra) was measured, and it was confirmed that carbon dioxide gas was stably generated. No abnormalities were observed in ornamental fish and aquatic plants through electrolysis. The state of carbon dioxide gas generation during electrolysis, the change in pH, the texture state of the anode after electrolysis, the coloring state of water after electrolysis, etc. were evaluated, and the results are shown in Table 2.

The criteria for each evaluation judgment are as follows. (1) State of carbon dioxide gas generation ○: Uniform and stable large amount generation Δ: Large amount generation but slight unstable generation ×: Small amount generation, non-uniform and unstable (2) Change in pH ○; No change Δ ； Slightly fluctuated × ； Vastly fluctuated (3) Anode microstructure ○: Uniform wear, no tissue collapse △: Uniform wear, slightly tissue collapse ×: Tissue disintegration was large (4) Water coloring ○: No coloration △; Some Coloring x: Many colors

Comparative Example 7 A carbonaceous electrode for generating carbon dioxide gas was used under the same conditions as in Example 4, except that carbon black [“SEAST 6” manufactured by Tokai Carbon Co., Ltd.] was used instead of the activated carbon powder of Example 4. Manufactured. Using this electrode as an anode, an electrolytic test was conducted in the same manner as in Example 4, and the obtained evaluation results are also shown in Table 2.

Comparative Example 8 A carbonaceous electrode for generating carbon dioxide gas was produced under the same conditions as in Example 4 except that coke powder was used instead of the activated carbon powder of Example 4. Using this electrode as an anode, an electrolytic test was performed in the same manner as in the example, and the obtained evaluation results are also shown in Table 2.

Comparative Example 9 A carbonaceous gas generating carbonaceous electrode was produced under the same conditions as in Example 4 except that charcoal powder was used instead of the activated carbon powder of Example 4. Using this electrode as an anode, an electrolytic test was performed in the same manner as in the example, and the obtained evaluation results are also shown in Table 2.

Comparative Example 10 Commercially available porous carbon material [Tai Carbon Co., Ltd., "T"
-50 ″] was processed to produce a carbonaceous electrode for generating carbon dioxide gas. Using this electrode as an anode, an electrolytic test was conducted in the same manner as in the example, and the obtained evaluation results are also shown in Table 2.

Comparative Example 11 Commercially available glassy carbon material [manufactured by Tokai Carbon Co., Ltd.,
"PC-3564"] was processed to produce a carbonaceous electrode for generating carbon dioxide gas. Using this electrode as an anode, an electrolytic test was performed in the same manner as in the example, and the obtained evaluation results are also shown in Table 2.

[0029]

[Table 2]

From the results shown in Table 2, when the carbonaceous electrode for generating carbon dioxide having a composition containing the activated carbon component obtained by the production method of the present invention in the range of 35 to 70% by weight was used,
It is possible to develop an excellent carbon dioxide gas generation state for a long period of time without changing the water quality or contaminating it, and without accompanying the collapse of the material structure. On the other hand, in the comparative examples that deviate from the requirements of the present invention, one of the evaluation items was inferior and normal performance was not obtained.

[0031]

As described above, according to the present invention, a carbonaceous gas generating carbonaceous electrode capable of continuously and quantitatively continuously generating carbon dioxide gas by water electrolysis and a method for producing the same are provided. In addition, since it can be manufactured at a low cost, a great effect is brought about for supplying carbon dioxide gas when aquatic plants such as ornamental fish tanks are bred through photosynthesis.

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Yoichi Ishikawa 4-15 Higashigokencho, Shinjuku-ku, Tokyo Able Co., Ltd.

Claims (3)

[Claims] 1. A carbonaceous electrode for generating carbon dioxide, comprising a carbonaceous compact having a composition containing an activated carbon component in a range of 35 to 70% by weight. 2. Activated carbon powder 35-70% by weight, clay substance 15-50% by weight, at least one lubricant powder 5-10% by weight selected from graphite, boron nitride and mica, and binder component 0.5-. A carbonaceous electrode for carbon dioxide gas generation, characterized in that 10% by weight is blended, water is added and kneaded to form a predetermined shape, and then the mixture is fired in a temperature range of 900 to 1400 ° C. in a non-oxidizing atmosphere. Manufacturing method. 3. The carbon dioxide for carbon dioxide generation according to claim 2, wherein the powder property is an activated carbon powder having a particle size of 500 μm or less, a specific surface area of 800 m ² / g or more, and an iron content of 0.1% by weight or less. Of manufacturing a high quality electrode.