JPH04342408A - Active carbon and its production - Google Patents

Abstract

PURPOSE:To efficiently produce active carbon having characteristics of both excellent elasticity and electrical conductivity. CONSTITUTION:Active carbon having characteristics of both excellent elasticity of >=50% recovery ratio at 10-90% compression ratio even at >=1.0g/cm<3> packing density and an electrical conductivity, produced by chemically treating a carbonaceous substance having an atomic ratio (C/H) of carbon to hydrogen of 0.55-4.1 and the increase in oxygen content by elemental analysis value of >=20.0wt.% when a chemical treatment is carried out to the carbonaceous substance having >=40 deg.C softening point, then dissolving the chemicaly treated carbonaceous substance in an organic solvent containing a polar group or a basic aqueous solution to give a solution for activation, and bringing the solution for activation into contact with an elastic graphite material to activate the elastic graphite material.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to carbon materials, and particularly to activated carbon that has low packing density, compressive elasticity, and conductivity, and is suitably used as a constituent material of electric double layer capacitors, etc., and a method for producing the same. It is.

0002

[Prior Art] Capacitors, which are important components that perform a power storage function in the electronics industry, have become increasingly popular due to the miniaturization of electronic equipment in the home appliances and industrial fields and the demand for compact backup power supplies for microcontrollers due to the recent development of the electronics industry. There is a strong demand for miniaturization.

On the other hand, activated carbon, which is an important carbon material, has been widely used in fields that utilize adsorption activity, such as wastewater treatment and catalysts. The use of electric double layer capacitors has been expanding in recent years, and this also meets the above-mentioned demand for miniaturization of capacitors.

By the way, conventional activated carbon has a relatively poorly developed graphite crystal structure due to the characteristics of the starting materials and manufacturing process.
The conductivity required for capacitor parts is generally not very high. Therefore, when using this, it was necessary to separately mix other conductive materials with the carbon material.

The applicant first brought the carbonaceous material into contact with nitric acid or a mixed acid of nitric acid and sulfuric acid and rapidly heated it to expand and foam the material, and then graphitized it to increase the packing density. A method for manufacturing an elastic graphite body having low compressive elasticity and electrical conductivity is provided (Japanese Patent Application Laid-Open No. 63-139080 and JP-A No. 64-9808).
(see issue).

[0006] The present applicant has further proposed a method of imparting conductivity to electric double layer capacitors by blending this elastic graphite with activated carbon, sandwiching the mixture between current collector plates, and laminating the mixture under pressure. (Patent Application No. 2-337583).

[0007] In the electric double layer capacitor as described above, the elastic graphite material not only provides conductivity but also performs the following functions due to its properties. ■Since the packing density is low, in other words, the volume is large for a given weight, only a small amount is required to incorporate it into activated carbon. (2) Since the structure has pores with a diameter of 0.2 to 2 μm, the capacitor electrolyte is held within these pores. ■Since it has compressive elasticity, the laminate does not collapse even when laminated under pressure, and maintains good formability, and pressurization increases the contact between elastic graphite particles, contributing to improved conductivity. do.

However, the method for obtaining a mixed carbon material as described above requires a separate relatively complicated process of mixing activated carbon powder and elastic graphite powder, which is disadvantageous in terms of the manufacturing process and economically. Become. Moreover, since these powders have different specific gravity, it is not always easy to uniformly disperse and mix them, and depending on the process operation, the effect of addition may be impaired.

[0009]

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned points, and provides an activated carbon having both excellent elastic properties and electrical conductivity, and an efficient method for producing the same. The purpose is to

0010

[Means for Solving the Problems] The activated carbon according to the present invention is
Packing density 1.0g/cm3 or less and compression ratio 10~
It is characterized by having elastic properties with a recovery rate of 50% or more at 90% and also having electrical conductivity.

Furthermore, the method for producing activated carbon of the present invention is a method for producing activated carbon having both elasticity and conductivity, and is a method for producing activated carbon having an atomic ratio of carbon to hydrogen (C/H) of 0.55 to 4.1. By chemically treating a carbonaceous material with a softening point of 40° C. or higher, the carbonaceous material is prepared so that the increase in oxygen content in the elemental analysis value of the carbonaceous material is 20.0% by weight or more. Then, this chemically treated carbonaceous material is dissolved in an organic solvent having a polar group or a basic aqueous solution to obtain a recycle solution, and the recycle solution thus obtained is brought into contact with the elastic graphite body. The method is characterized in that the elastic graphite body is subjected to an activation treatment.

The activated carbon according to the present invention obtained as described above has a structure in which an activated carbon substance is retained on at least a portion of the surface of the base material made of elastic graphite or the inner wall of micropores. are doing.

The present invention will be described in detail below.

The activated carbon of the present invention has the following characteristics and can be produced by the method described below. (1) Carbonaceous material The carbonaceous material that is the raw material for the elastic graphite body according to the present invention is coal, petroleum-based heavy bituminous materials, and/or coal-based pitch and/or heavy oils, or Carbonaceous mesophase and/or raw coke produced by heat treatment of these pitches and/or heavy oils may be used.

Coal used as a raw material for these carbonaceous materials includes coals such as lignite, black coal, and anthracite; pitch and/or heavy oil include coal tar pitch,
Coal-based pitch from coal liquefaction, petroleum distillation residue oil, naphtha tar pitch produced as a by-product during the thermal decomposition of naphtha, petroleum-based pitch such as FCC decant oil produced as a by-product in the fluid catalytic cracking method (FCC method) of naphtha, etc. (or) heavy oil, PV
Examples include pitch obtained by thermal decomposition of synthetic polymers such as C, but any type may be used as long as it can provide easily graphitized carbon through carbonization treatment. However, the carbonaceous material in the present invention has an atomic ratio of carbon to hydrogen (C/H) in the range of 0.55 to 4.1, and a softening point of 40
Use a temperature higher than ℃. If the atomic ratio is less than 0.55 or more than 4.1, it is not preferable because it becomes difficult to obtain the desired activated carbon. Moreover, it is important that the softening point be 40° C. or higher. In the method of the present invention, the method of chemically treating carbonaceous materials is carried out by a heterogeneous reaction, and by converting this heterogeneous reaction into a liquid-solid system or a gas-solid system reaction, the chemical treatment operation can be carried out. This is preferable because it can be carried out efficiently. Therefore, if the softening point of the carbonaceous material is less than 40° C., it is not preferable because it becomes difficult to carry out efficient chemical treatment operations.

[0016] When using pitch having a softening point of less than 40°C, it is preferable to adjust the softening point to 40°C or higher by performing air blowing treatment in advance. Of course, air blowing treatment has a softening point of 4.
It may also be carried out in advance for pitches having a temperature of 0°C or higher,
Such embodiments are also included within the scope of the present invention.

Furthermore, in the present invention, carbonaceous mesophase and raw coke obtained by heat treating pitches can also be used as raw materials as long as the above conditions are met. (2) Chemical treatment Chemical treatment is performed on the carbonaceous material.

[0018] This chemical treatment involves introducing functional groups such as nitro groups, carboxyl groups, hydroxyl groups, sulfonic acid groups, etc. into the carbonaceous material through an aromatic nucleus substitution reaction in order to cause solubilization in the next step. However, it is important to control the increase in oxygen content in the elemental analysis value of the chemically treated carbonaceous material to 20.0% by weight or more. The rate of increase in oxygen content is particularly important in achieving excellent solubilization and activation of the resulting chemically treated product. That is, when the amount of increase in oxygen content is less than 20.0% by weight, it is not preferable because a good solubility state is not caused and it becomes difficult to obtain activated carbon having sufficient pores.

[0019] As a method for carrying out the above-mentioned chemical treatment,
This can be removed by bringing carbonaceous materials into contact with nitric acid, sulfuric acid, a mixed acid of sulfuric acid and nitric acid, or oxidizing agents such as hydrogen peroxide, dichromate, permanganate, nitrogen oxide gas, etc. It can be carried out.

[0020] Both sulfuric acid and nitric acid in this case have high concentrations, that is, sulfuric acid has a concentration of 95% or more, and nitric acid has a concentration of 60%.
Those with a higher concentration are preferably used. Further, mixed acids of sulfuric acid and nitric acid are used in various mixing ratios. (3) Elastic graphite body The elastic graphite body as a base material to be activated has a packing density of 1.0 g/cm3 or less, a recovery rate of 50% or more at a compression ratio of 10 to 90%, and has a sponge structure. things are used. Regarding the manufacturing method of such elastic graphite body, please refer to JP-A-63-139080 and JP-A-64.
-9808, and these methods can be adopted in the present invention. (4) Mixing The chemically treated product prepared in (2) above is a carbonaceous material that is dissolved in a basic aqueous solution or a polar It is known to be soluble in organic solvents (Japanese Patent Application Laid-Open No. 64-9288). Therefore, in this soluble state, the elastic graphite body is added and thoroughly stirred and mixed.

Examples of dissolving agents for chemically treated substances include methanol, ethanol, ethylene glycol, glycerin, acetone, methyl ethyl ketone, ethyl acetate, tetrahydrofuran, dioxane, diethylene glycol dimethyl ether, dimethyl sulfoxide, formic acid, phenol, cresol, ethylene diamine, aniline, When using a polar organic solvent such as pyridine, dimethylformamide, or nitromethane, or a basic aqueous solution such as aqueous ammonia, adjust the pH by evaporating the solvent or water, or adding an acid aqueous solution, and then filter and dry the precipitate. A precipitate can be obtained by doing this.

[0022] The soluble components of the chemically treated product have binder properties and are firmly adhered and held to the partition walls of the elastic graphite added during precipitation. Moreover, since it is in a dissolved state, it is included in the partition walls inside the sponge structure of the elastic graphite body when it is precipitated, and the compressive elasticity and conductivity, which are characteristics of the elastic graphite body, are not impaired. Further, since the adhesive property is strong, the solubilization rate at this time does not necessarily have to be 100%, and the insoluble matter is also adhered and activated. The blending ratio at this time is preferably in the range of 0.1 to 0.4 parts by weight of the elastic graphite material per 1 part by weight of the chemically treated material.

When an alkali metal hydroxide aqueous solution is used as the basic aqueous solution, it is preferable that the alkali metal be mixed with the carbonaceous material in a solution state and uniformly dispersed. Therefore, in this case, the precipitate obtained by evaporating and drying the solution is a carbonaceous material in which the alkali metal is uniformly dispersed. On the other hand, alkali metals are known as activation aids in the production of activated carbon (e.g., "Activated Carbon" edited by the Carbon Materials Society), and metal carbonates are produced by reaction with carbon during firing, which is then removed by washing with water. to form micropores. Therefore, the precipitate obtained by this method already contains an alkali metal as an activation aid, and after firing the precipitate, an activated carbon material can be obtained by washing with water. Moreover, in this case, since the activation aid is uniformly dispersed in the carbonaceous material,
The activation effect is improved and activated carbon with uniform pores can be obtained. The compounding ratio at this time is preferably 0.1 to 0.4 parts by weight of the elastic graphite and 0.2 to 5 parts by weight of the alkali metal hydroxide to 1 part by weight of the chemically treated product. In this case, it should be noted that if there is too much elastic graphite compared to the chemically treated material, the compressive elasticity will increase, but the specific surface area will tend to decrease. On the other hand, if there is too little elastic graphite, the compressive elasticity will decrease. If there is too much alkali metal hydroxide compared to the chemically treated product, the activation effect will be excessive,
This is not preferable since it will instead increase the size of the pores that are formed, resulting in a decrease in the specific surface area, and will also lead to a decrease in yield due to excessive reaction with carbon. On the other hand, if it is too small, the activation effect will be insufficient and formation of fine pores will be small, resulting in a decrease in specific surface area. (5) Activate precipitate at 500-1000°C, preferably 600-80°C
Activation with water vapor, carbon dioxide gas, etc. while firing at 0℃,
Or NaOH, KOH, CSOH, ZnCl2, H
Activation is promoted using an activation aid such as 3PO4, K2SO4, K2S, etc., and fine pores are formed.

In the case of a precipitate of an aqueous alkali metal hydroxide solution, fine pores can be formed by firing alone. (6) Washing with water If it is necessary to remove used auxiliary agents and reaction products after activation, wash with water. The voids caused by removal become micropores.

Further, the washing in this case may be carried out with either hot water or cold water, and the removal of unnecessary used auxiliary agents and reaction products can also be confirmed by measuring the pH of the washing water.

[0026]

[Examples] The present invention will be explained in more detail with reference to Examples below. However, the following Examples are for illustrating the present invention and are not intended to limit the scope of the present invention.

Activated carbon was prepared in the following order. (1) Preparation of acid-treated product 3. Petroleum coke produced by delayed coker method
5g of the powder crushed to 30 mesh or less was mixed with a mixed acid of 70% concentrated nitric acid and 90% concentrated sulfuric acid in a ratio of 50/50 (volume ratio).
ml slowly with stirring, and kept in an oil bath heated to 80°C for 4 hours.

After the reaction, cool to room temperature and pass through a glass filter (
No. The mixed acid was filtered off in step 4), and the filtrate was washed with water until the pH reached 4 or more, and then dried to obtain an acid-treated product.

The yield of the acid-treated product was 140% by weight. (2) As a mixed dissolving agent, 1N aqueous solutions of alkali metal hydroxides of NaOH, KOH, and CSOH were used, and as an elastic graphite body, the packing density was 0.20 g/cm3, the compressibility was 92%,
Using a product with a recovery rate of 95% (measured at a load of 275 kg/cm2), which was pulverized to 330 mesh or less, 0.35% of the alkali metal hydroxide was added to 1 part by weight of the acid-treated product.
, 0.7, 1.4, and 2.8 parts by weight, further 0.14 parts by weight of elastic graphite, and further 20 parts by weight of water were added, and the mixture was stirred at room temperature for 24 hours. (3) Dryness and then drying in a dryer at 90 to 110°C for 24 hours to evaporate water. (4) The calcined and dried product was heated at a heating rate of 30°C/Hr under N2 gas flow.
The temperature was raised to 00°C, maintained at the same temperature for 1 and 5 hours, and then allowed to cool. This firing was similarly performed at 700°C and 800°C. (5) Washing with water The baked product was washed 6 to 8 times with 10 ml of hot water per gram of the baked product. (6) Drying Drying was performed in a dryer at 90 to 110°C for 5 hours. (7) Measurement of physical properties Regarding the obtained activated carbon, yield, specific surface area, pore radius, pore volume, packing density, compressive elasticity (275Kg/cm2
The compressibility (compressibility, recovery rate) and electrical resistance (under a load of 100 kg) were measured under pressure. (2) The specific surface area, pore radius, and pore volume were determined from the nitrogen adsorption isotherm curve and BET plot at liquid nitrogen temperature. ■Filling density and compressive elasticity were determined by the following methods.

That is, the sample was made to be 0.30 mm or less, and 0.5 g of the sample was placed in a cylindrical container with an inner diameter of 10 mm, and a load of 1 kg/cm 2 was applied from the top. The sample volume at this time was taken as a reference (h0). And 275Kg/c
A load of m2 was applied and the volume was measured. This volume was defined as h1. Next, the load was removed, and the compressibility and recovery rate were determined from these values using the following equations, with the volume at that time being h2.

Compression rate (%) = [(h0-h1)/h0] x 100 Recovery rate (%) = [(h2-h1)/(h0-h1)] x 10
0 Also, the packing density was determined from h0.

Packing density (g/cm3)=sample weight+h
0■Also, the electrical resistance is 100kg/100kg when compressive elasticity is applied.
cm2, measure the resistance value (Ω) by applying a voltage between the top and bottom ends of the sample, and calculate the volume resistivity (Ωcm) by multiplying this by (sample cross-sectional area ÷ sample height). It was determined by (8) Result CASE. No. 1 2 3
4 5 6 7 8 9
10 Solubilizer NaO
H KOH
CsOH chemical acid treatment amount
1 1 1
1 1 1 Amount of solubilizer 1.4 0.3
5 0.7 1.4 2.8
1.4 Amount of elastic graphite
0.14 0.14 0.14
0.14 0.14 0.14
Firing temperature (℃) 700 80
0 700 700 600 700 70
0 600 700 800 Heating rate (
°C/Hr) 30 30 30 30
30 30 30 30 30
30 Retention time (Hr)
1 1 1 1 5
1 1 1 1 1
Activated carbon yield 0.34 0.25
0.44 0.41 0.33 0.37 0.36
0.35 0.33 0.26 (from acid treated product)
0.20 0.11 0.30 0.27 0
．． 19 0.23 0.22 0.21 0.19 0
．． 12 (from elastic graphite body) 0.14 0.1
4 0.14 0.14 0.14 0.14 0.1
4 0.14 0.14 0.14 Specific surface area m2
/g 530 400 890 920
680 1100 860 610 160
0 1300 Pore radius A
15 15 8 8 9
9 23 10 10 11
Pore volume cc/g 0.5 0.6
0.2 0.4 0.6 1.0 1.3
0.3 0.9 1.0 Focused density g/cm
3 0.18 0.33
0.20 0.25
Compression rate %
91 85
70 88
Recovery rate % 84
65 81
78 Electrical resistance Ωc
m 0.12 0.18
0.14 0
．． 12 All of the activated carbons had fine pores, had low packing densities, had high compressive elasticity, and had electrical conductivity. Comparative Examples CASE. No. Regarding No. 6, the blending amount of the elastic graphite body was changed to 0.7 and 0.05. The results are as follows.

According to the above results, it can be seen that when the amount of elastic graphite is too large, the elastic properties are good but the specific surface area is reduced. On the other hand, if the amount of elastic graphite is too large, the specific surface area will be high, but the elastic properties will be lowered, and both cases fall outside the scope of the present invention.

Claims (9)

[Claims] 1. Activated carbon having a packing density of 1.0 g/cm 3 or less, having elastic properties with a recovery rate of 50% or more at a compressibility of 10 to 90%, and also having electrical conductivity. 2. The activated carbon according to claim 1, wherein an activated carbon substance is retained on at least a portion of the inner walls of the micropores. 3. The activated carbon according to claim 2, wherein the base material of the activated carbon is made of elastic graphite. Claim 4: The atomic ratio of carbon to hydrogen (C/H) is 0.5
By chemically treating a carbonaceous material that is in the range of 5 to 4.1 and has a softening point of 40°C or higher, the increase in oxygen content in the elemental analysis value of the carbonaceous material is 20.0% by weight. The above chemically treated carbonaceous material is then dissolved in an organic solvent having a polar group or a basic aqueous solution to obtain a mobilization solution, and the mobilization solution obtained in this way and 1. A method for producing activated carbon having both elasticity and conductivity, the method comprising performing an activation treatment on the elastic graphite body by bringing it into contact with the elastic graphite body, removing an organic solvent or moisture, and drying the body. 5. The method according to claim 4, wherein the utilization solution and the elastic graphite body are brought into contact by mixing the two. 6. A method using an alkali metal hydroxide aqueous solution as the basic aqueous solution according to claim 4, wherein the chemically treated carbonaceous material is dissolved in the alkali metal hydroxide aqueous solution and elastic graphite is added to the alkali metal hydroxide aqueous solution. 5. The method according to claim 4, wherein the activation treatment is performed by adding a substance, evaporating water, and drying the product, further baking the product, and then washing with water. 7. The method according to claim 4, wherein the carbonaceous material consists of carbonaceous mesophase, coal, coke, petroleum-based and/or coal-based pitch and/or heavy oil. 8. The method according to claim 4, comprising the step of adjusting the softening point of the carbonaceous material to 40° C. or higher by air blowing treatment. 9. Chemical treatment is carried out on carbonaceous materials using nitric acid, sulfuric acid, or a mixed acid of nitric acid and sulfuric acid, and/or an oxidizing agent such as hydrogen peroxide, dichromate, or permanganate. 5. The method according to claim 4, comprising processing.