JP2003012316A - Activated carbon and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide activated carbon capable of adsorbing effectively a material whose molecular weight is small and its manufacturing method. SOLUTION: A pore diameter of the activated carbon is uniform, its specific surface area is 500-3,000 m<2> /g and adsorbing quantity is 10 ml/g or more. The activated carbon is manufactured by the activation of a carbonaceous material at 600-1,200 deg.C in an atmosphere of which the main component is carbon dioxide and which contains steam by 2 vol.% or less and carbon monoxide by 2 vol.% or more.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to activated carbon and a method for producing activated carbon. More specifically, the present invention relates to activated carbon having a large specific surface area and excellent adsorption of small molecule gas such as nitrogen, and a method for producing activated carbon by activating a carbonaceous material containing few alkali metals in a specific atmosphere. The activated carbon of the present invention has a uniform pore size and a large specific surface area, and hydrogen, nitrogen, oxygen, carbon dioxide, hydrogen chloride, hydrogen fluoride, methane, ethane, argon, krypton, xenon, methanol, ethanol, formic acid, chloride. It is suitable for adsorbing small molecule gases such as methylene and has excellent adsorption performance under normal pressure to under pressure, and thus can be suitably used for occlusion and adsorption separation of these gases. Further, since it is excellent in adsorbing small molecule substances such as trihalomethane in water, it can be used for water treatment.

[0002]

2. Description of the Related Art Conventionally, activated carbon has been used for adsorption and removal of harmful gases, purification and separation and recovery of gases, occlusion of gases, molecular sieves,
It is widely used in various fields such as decolorization purification, water treatment, electric double layer capacitors, etc. in the fields of food and chemical industry. Usually, activated carbon is a carbonaceous material that has been previously carbonized.
It is produced by activating with an oxidizing gas containing steam as a main component, but the activated carbon obtained is generally one having a large pore size and a relatively broad pore distribution. Such activated carbon can be widely applied to various purposes and is practical.

In recent years, the application of activated carbon has been greatly expanded. As one of the applications, activated carbon is used.
Attempts have been made to adsorb the aforementioned small molecule substances such as hydrogen and nitrogen. Small molecule substances have a relatively small molecular diameter,
Moreover, since many have a low boiling point and a low concentration, it is conceivable to use activated carbon having a small pore size to adsorb small molecule substances. However, conventional activated carbon having a high degree of activation has an excessively large pore size, which leads to a decrease in adsorption capacity and cannot sufficiently adsorb a small molecule substance. Therefore, it is the current situation that small molecule substances are adsorbed by using activated carbon whose activation rate is kept low and whose specific surface area is small.

On the other hand, activated carbon fiber is known as activated carbon having a fine pore size and a large specific surface area. However, activated carbon fibers have a large proportion of micropores but a low bulk density, so the amount adsorbed per volume is not so large and, in addition, it is very expensive compared to ordinary activated carbon, so it is practically used as an adsorbent for small molecule substances. It cannot be said that there is a nature.

Heretofore, as a method for producing activated carbon suitable for adsorbing small molecule substances, Japanese Patent Laid-Open Publication No. 51-28590 discloses that a plant-based carbide such as coconut shell contains carbon dioxide as a main component and water vapor. Activated by using an activating gas having a concentration of a contaminant gas such as oxygen of 2% or less, and when the activation loss reaches 5 to 20%, the soluble components including alkali components are removed by washing with acid and water. However, a method of activating again is known. Further, in Japanese Unexamined Patent Publication No. 7-155589, a carbonaceous material having pores or activated carbon is acidified, boiled or sonicated to reduce the ash content to less than 4 wt%, and then activated in an oxidizing gas atmosphere to obtain a uniform ash content. A method for producing activated carbon having fine pores and a high specific surface area is disclosed.

[0006]

However, since most of the ash content is often taken deep inside the closed pores and the tissue, it is difficult to use acid or water as disclosed in JP-A-7-155589. Cleaning is very inefficient and difficult to remove sufficiently. In addition, JP-A-51-
The pore size distribution of the activated carbon disclosed in Japanese Patent No. 28590 is 9-
It has a sharp peak near 10Å and can adsorb small molecule substances to some extent, but it is hard to say that it is an activated carbon with good adsorption efficiency, and there is room for improvement. Therefore, it is an object of the present invention to provide activated carbon capable of efficiently adsorbing small molecule substances and a method for producing the same.

[0007]

[Means for Solving the Problems] The present inventors have conducted diligent studies, focusing on the importance of making the pore diameters uniform and increasing the specific surface area in order to effectively adsorb small molecule substances. As a result of stacking, by activating the carbonaceous material in a specific atmosphere, it is possible to obtain activated carbon having a uniform pore size and a large specific surface area. According to the activated carbon, small molecule substances can be efficiently adsorbed. The inventors have found that the above can be achieved and have reached the present invention. That is, the present invention has a uniform pore size and a specific surface area of 5
The activated carbon is characterized in that it has an adsorption amount of nitrogen of from 0 to 3000 m ² / g and at 25 ° C. under 1 atmospheric pressure of 10 ml / g or more.

Another aspect of the present invention is that the carbonaceous material contains carbon dioxide gas as a main component, an amount of water vapor of not more than 2% by volume and an amount of carbon monoxide gas of not less than 2% by volume.
This is a method for producing activated carbon which is activated at a temperature of 1200 ° C.

Another aspect of the present invention is that, when carbonized by heating at 600 ° C. in an inert gas, a carbonaceous material in which the content of alkali metals contained in the carbide is 0.5 wt% or more is used. In an atmosphere containing water vapor of 2% by volume or less and carbon monoxide gas of 2% by volume or more as a main component,
Activated at a temperature of 600 to 1200 ° C., washed with acid and water when the weight loss of the carbonaceous material reaches 5 to 50%, the content of alkali metals is adjusted to 0.5 wt% or less, and then carbonic acid is added again. In an atmosphere containing gas as a main component, water vapor of 2% by volume or less, and carbon monoxide gas of 2% by volume or more, 600
It is a method for producing activated carbon which is activated at a temperature of up to 1200 ° C.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The carbonaceous material used in the present invention includes coconut shells, palm palms, fruit seeds, sawdust, eucalyptus, pine, and other plant-based, coal-based, petroleum-based cokes and raw materials thereof. Examples thereof include carbide of pitch, phenol resin, vinyl chloride resin, vinylidene chloride resin and the like. The shape and size of the carbonaceous material are not particularly limited, but a crushed, granular, or columnar material having a size of about 1 mm to 10 mm is generally used. Further, as the shape of the carbonaceous material, it is also possible to use it by carbonizing it after it is molded by adding a binder such as granular, powdery or tar, pitch or phenol resin. The shape of these molded bodies can be any shape such as granular, powdery, honeycomb or fibrous.

These carbonaceous materials are used in 60% in an inert gas.
It is preferable to use the one in which the content of alkali metals such as sodium, potassium and calcium contained in the carbide when heated and carbonized at 0 ° C. is 0.5 wt% or less. The inert gas referred to here is a gas such as nitrogen, argon, or helium. The content of alkali metals in the carbonaceous material can be determined by a fluorescent X-ray method after heating and carbonizing the carbonaceous material heated and carbonized at 600 ° C. in the above-mentioned inert gas in a muffle furnace at 850 ° C.

In the present invention, the above-mentioned carbonaceous material is preferably used to activate the activated carbon. However, in order to change the activated carbon from the carbonaceous material, it is preferable that the above-mentioned carbonaceous material containing less alkali metals. Is activated at a temperature of 600 to 1200 ° C. in an atmosphere containing carbon dioxide as a main component, water vapor of 2% by volume or less and carbon monoxide gas of 2% by volume or more. The activation time is not particularly limited, but when a carbonaceous material having a particle size of 3 mm or more is used, if it is performed for too short time, the uniformity of pores will be impaired, so activation is performed for at least 1 hour or more. Is preferred. Usually, it is carried out in about 50 hours.

According to the present invention, by activating a carbonaceous material in such a special atmosphere, activated carbon having uniform pore size, large specific surface area and excellent adsorption of small molecule substances such as nitrogen is produced. can do. 6 in inert gas
When using a carbonaceous material in which the content of alkali metals contained in the carbide when heated and carbonized at 00 ° C. is 0.5 wt% or more, carbon dioxide is the main component, and water vapor is 2 vol% or less. And activated at a temperature of 600 to 1200 ° C. in an atmosphere containing carbon monoxide gas of 2% by volume or more, and the weight loss due to activation of the carbonaceous material reached 5 to 50%, preferably 10 to 30%. At this point, the content of the alkali metals is reduced to 0.5 wt% or less by washing with acid and water, and after being dried or put in an activation furnace while containing water, after that,
It is activated again at a temperature of 600 to 1200 ° C. in an atmosphere containing carbon dioxide gas as a main component, water vapor of 2% by volume or less and carbon monoxide gas of 2% by volume or more.

As the acid, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid,
Inorganic acids such as hydrofluoric acid and carbonic acid, or organic acids such as formic acid and acetic acid are preferable. Generally, it is used as an aqueous solution, and its concentration is usually 1 to 30 wt%. Further, by washing with water or washing with warm water after acid washing, it is possible to further enhance the washing effect by removing salts and acids remaining in the carbonaceous material, and at the same time, when moving to a subsequent activation step, corrosion of the device or It is also suitable in terms of waste gas treatment. The amount of water in that case is not particularly limited, but it is practical to carry out 10 to 50 times by weight of the carbonaceous material.

The carbonaceous material after the washing is preferably activated after being dried, but it is also possible to omit the drying and immediately put it in an activation furnace to activate it. In the activation step of the present invention, it is important to use carbon dioxide gas as an oxidizing gas, to contain carbon monoxide gas in an amount of 2% by volume or more, and to set water vapor in an amount of 2% by volume or less. There is no problem in diluting carbon dioxide with the above inert gas.

The activation temperature is 600 to 1200 ° C, preferably 800 to 1100 ° C. Further, if the activation time is too short, activation spots are generated inside and outside the particles, and the uniformity of the pores is impaired. Therefore, when the particle diameter of the carbonaceous material as the raw material is less than 1 mm, 30 minutes after reaching the predetermined temperature As described above, when it is 3 mm or more, it is preferable to activate it for 1 hour or more, and it is preferable to activate it for 3 to 30 hours regardless of the particle size. The maximum activation time is not particularly limited from the viewpoint of the performance of activated carbon, but it is preferably within 30 hours from the industrial viewpoint. The activation furnace may be of any type as long as it can uniformly react, and various types can be used. Generally, a fluidized furnace, a multi-stage furnace, a rotary furnace and the like are suitable. The activation method may be either a batch method or a continuous method.

The activated carbon of the present invention has a uniform pore size,
The specific surface area is 500 to 3000 m ² / g, and the adsorption amount of nitrogen at 25 ° C. and 1 atmosphere is 10 ml / g or more.
The specific surface area can be measured by a nitrogen gas adsorption BET method, and the nitrogen adsorption amount can be measured by a constant pressure capacity method (Nikka 47,716 (Sho 1)). FIG. 1 shows a pore radius frequency distribution diagram of the activated carbon of the present invention measured by a water vapor adsorption method, and FIG. 2 shows a cumulative pore volume curve.

As is clear from FIG. 1 and Examples described later, the activated carbon of the present invention has uniform pore diameters, the specific surface area (m ² / g) is X, and the pore radius frequency distribution value ΔV / Δ. lo
When gr (cc / Å · g) (r is pore radius (Å), ΔV is pore volume change amount (cc)) is Y, Y> 2.1
{1-exp [-0.0032 (X-1000)]} +
It is preferably 1. More specifically, when the specific surface area is 1100 m ² / g or less, ΔV / Δlogr is 1.4 or more, and the specific surface area is 1101 to 1300 m ²
In the case of / g, ΔV / Δlogr is 2.2 or more, and when the specific surface area is 1301 to 1500 m ² / g, ΔV / Δ
logr is 2.8 or more, and the specific surface area is 1501 m ^2.
In the case of / g or more, ΔV / Δlogr is preferably 3.2 or more.

Although it is not always possible to clearly explain the reason why activated carbon suitable for adsorbing small molecule substances having uniform pore diameters and large specific surface areas can be produced by the present invention, steam is used as an oxidizing gas. The reaction rate was reduced by using carbon dioxide gas containing almost no carbon dioxide and coexisting with carbon monoxide gas in an amount of 2% by volume or more, and a slow activation condition was achieved in which the activation gas could sufficiently reach the deep pores. It is speculated that In addition, rapid activation is suppressed by reducing the amount of alkali metals such as sodium, potassium, and calcium in the carbonaceous material used for the production of activated carbon, and a uniform activation reaction has been performed to deep pores. It is speculated that this also contributes to the manifestation of the effect. Hereinafter, the present invention will be specifically described with reference to examples.

[0020]

Examples Examples 1 to 7 and Comparative Examples 1 to 7 Carbides obtained by carbonizing a phenol resin having an alkali metal content of 0.5 wt% or less at 600 ° C. and crushing it to a particle size of 1 to 3 mm. Is a carbonaceous material with an inner diameter of 50 mm
Was activated at 900 ° C. in an atmosphere containing carbon dioxide as a main component, water vapor of 2% by volume or less, and carbon monoxide gas of 2% by volume or more (Examples 1 to 7). ). Further, activated carbon (Comparative Examples 1 to 5) activated at 900 ° C. in an atmosphere containing only carbon dioxide and containing no carbon monoxide, and activated at 900 ° C. in an atmosphere containing 2% by volume or more of water vapor are obtained. Table 1 also shows the physical properties of the activated carbons (Comparative Examples 6 to 7).

[0021]

[Table 1]

Examples 8 to 14 and Comparative Examples 8 to 14 Palm shells and palm charcoal were activated in the same manner as in Example 1 (Examples 8 to 14). For palm shell coal with an alkali metal content of about 0.8 wt%, the activation loss is 20%.
When it reaches the wt%, it is taken out of the furnace, cooled, and washed with hydrochloric acid and water to add 0.5 wt% of alkali metals.
It was reduced to the following, and activation was performed again under the same conditions (Example 15). Table 2 shows the physical properties of the obtained activated carbon. In addition,
Comparative Example 12 is an activated carbon produced according to the method disclosed in JP-A-51-28590.

[0023]

[Table 2]

Examples 15 to 18 and Comparative Examples 15 to 18 The same as in Example 1, except that coconut shell charcoal and a charcoal raw material made from Australia's Yarun coal and Chinese Daido coal at 600 ° C. were used as the carbonaceous material. Activated carbon was obtained under the conditions of. Table 3 shows the physical properties of the obtained activated carbon and the measurement results of the n-butane working capacity. Note that n
-Butane Working Capacity is ASTM-D
5228-92, which is simply the effective adsorption amount obtained by subtracting the weight after desorption from the weight after adsorption per 100 ml of activated carbon.

[0025]

[Table 3]

The krypton and xenon adsorption performances of the activated carbons obtained in Example 8, Comparative Example 8 and Comparative Example 12 were measured. The results are shown in Fig. 3. Further, the adsorption performance of chloroform, which is a representative of trihalomethane, was measured and shown in FIG. The amount of chloroform adsorbed was determined by the following measuring method.

The activated carbon sample was finely pulverized with a sample mill until the amount passed through 45 microns became 90% or more, and then 11
Dry for 3 hours at 5 ° C and let cool in a desiccator. Chloroform aqueous solution 100 ml adjusted to a concentration of 100 ppb beforehand
Separately prepare a vial bottle to which is added, finely sample the fine powder, and weigh it into the vial bottle. The vial is sealed with a Teflon (registered trademark) sheet, a butyl rubber cup, and an aluminum seal, and shaken at 25 ° C. for 2 hours with a shaker. In addition, the same operation is performed in parallel for a vial bottle to which no sample is added as a blank.

After 2 hours, the vial was taken out, 10 μl of methanol was added with a microsyringe, the mixture was shaken, and then left still in a constant temperature water bath at 25 ° C. for 1 hour. 1 hour later 0.1 ml of head gas in the vial with a micro syringe
Collect and measure the chloroform concentration using an ECD gas chromatograph. The blank is measured similarly. From the chloroform concentration and residual concentration of the stock solution and the amount of activated carbon sample, calculate the amount of chloroform adsorbed from the following formula. Adsorption amount (mg / g activated carbon) = (A−B) / (C × 10000)
In addition, A is a stock solution chloroform concentration (ppb), B is a residual chloroform concentration (ppb), and C is a sample amount (g). Tables 1 and 2 also show the results of measuring the adsorption performance of methanol for Example 3, Example 4, Comparative Example 3, Comparative Example 4, Example 10, and Comparative Example 10. The effects of the present invention are clear from Tables 1 and 2.

[0029]

The activated carbon obtained by the present invention has a uniform pore size and a large specific surface area. Such activated carbon is
It excels in the adsorption of small molecule substances, and adsorption and separation of nitrogen, hydrogen, carbon monoxide, carbon dioxide, hydrogen chloride, hydrogen fluoride, etc.
Used for radioactive krypton generated from boiling water reactors, adsorption of rare gases such as xenon, storage of natural gas such as methane, gasoline adsorption canister, methanol and ethanol adsorption refrigerator, electric double layer capacitor, water purifier, etc. be able to.

[Brief description of drawings]

FIG. 1 is a pore radius frequency distribution chart of the activated carbons obtained in Examples 8 and 9 and Comparative Examples 8 and 10.

FIG. 2 is a cumulative pore volume curve of the activated carbons obtained in Examples 8 and 9 and Comparative Examples 8 and 10.

3 is a graph showing the krypton and xenon adsorption performance of the activated carbons obtained in Examples 8 and 12 and Comparative Example 8. FIG.

FIG. 4 is a graph showing the chloroform adsorption performance of the activated carbons obtained in Examples 8 and 12 and Comparative Example 8.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4G046 HA01 HA03 HA05 HB05 HC08                       HC09 HC10                 4G066 AA04A AA05B AC02A AC08A                       AC25A BA20 BA23 BA26                       BA36 CA21 CA27 CA32 CA33                       CA35 CA37 CA38 CA39 CA51                       CA56 DA01 DA08 FA18 FA22                       FA34 FA37 FA38

Claims (4)

[Claims] 1. The pore size is uniform, and the specific surface area is 500 to 30.
Activated carbon characterized in that the adsorption amount of nitrogen at 00 m ² / g and 25 ° C. under 1 atmospheric pressure is 10 ml / g or more. 2. A carbonaceous material containing carbon dioxide as a main component,
Water vapor is less than 2% by volume and carbon monoxide gas is 2% by volume
A method for producing activated carbon which is activated at a temperature of 600 to 1200 ° C. in the above atmosphere. 3. The carbonaceous material is 600 ° C. in an inert gas.
The method for producing activated carbon according to claim 2, wherein the content rate of the alkali metal contained in the carbide is 0.5 wt% or less when carbonized by heating. 4. When carbonized by heating at 600 ° C. in an inert gas, the content of alkali metals contained in the carbide is 0.
5 wt% or more of carbonaceous material, carbon dioxide as the main component,
Water vapor is less than 2% by volume and carbon monoxide gas is 2% by volume
In the above atmosphere, activation at a temperature of 600 to 1200 ° C., washing with an acid and water when the weight loss of the carbonaceous material reaches 5 to 50%, and an alkali metal content of 0.5 w
After t% or less, a method for producing activated carbon which is activated again at a temperature of 600 to 1200 ° C. in an atmosphere containing carbon dioxide gas as a main component, water vapor of 2% by volume or less, and carbon monoxide gas of 2% by volume or more. .