JPH044244B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing porous activated carbon. More specifically, the present invention relates to a method for producing porous activated carbon having extremely fine communicating pores and having an extremely large specific surface area of at least 600 m ² /g.

[Conventional technology]

Grassy carbon, which is obtained by firing a phenolic resin in a non-oxidizing atmosphere, is a carbon material with excellent mechanical strength and chemical resistance, as is well known. Therefore, attempts to obtain porous bodies of glassy carbon are being actively made in various countries around the world. In other words, it is certain that by taking advantage of the excellent chemical resistance and corrosion resistance of Grassy Carbon, the porous body of Grassy Carbon can be suitably used in various industrial fields as various separation materials, especially as materials. It is.

Conventionally, the method for manufacturing such a glassy carbon porous body includes impregnating a synthetic resin porous body with a resin that can be converted into glassy carbon when fired, such as a phenolic resin, and then curing the impregnated resin. Next, a method is known in which the impregnated resin is converted into glassy carbon by firing in a non-oxidizing atmosphere, and at the same time, the synthetic resin of the porous body is decomposed to produce a glassy carbon porous body (especially (Refer to Publication No. 70207 of 1983).

In order to obtain a glassy carbon porous body with excellent performance by such an impregnation method, it is necessary that the impregnated resin penetrates into the internal pores of the synthetic resin porous body uniformly and well, and that the impregnated resin itself It is necessary to form a resin matrix with This is because, as mentioned above, the synthetic resin porous body disappears upon firing, and only the impregnated resin is converted into glassy carbon.

However, depending on the impregnation method, there are limits to the surface properties such as wetting of the synthetic resin porous material that can be used, or the pore size that allows uniform impregnation of the impregnating resin, such as phenolic resin, so for example, the average diameter is less than 10 μm. Grassy carbon porous bodies having fine continuous pores have not been obtained.

On the other hand, activated carbon, which has a large non-surface area and has an active function, is used in various fields because it has the ability to adsorb and separate various molecules in various gases or liquids. In particular, activated carbon obtained from phenolic resin has a large non-surface area and high activity, so it is an activated carbon with excellent physical properties.

Therefore, activated carbon, which has excellent mechanical strength and chemical resistance, has fine communicating pores that allow fluid to flow in and out smoothly, and has a large specific surface area, is suitable for use in various applications, especially as a separation and adsorbent. Therefore, there is a strong desire to develop such activated carbon, but no such activated carbon has been developed yet.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a method for producing porous activated carbon having fine continuous pores and exhibiting a large specific surface area.

Another object of the present invention is to provide a method for producing porous activated carbon that has fine continuous pores and exhibits a large specific surface area and has excellent mechanical strength and corrosion resistance.

Still another object of the present invention is to produce porous activated carbon that allows gas or liquid to pass through or come in and out smoothly, and has a large specific surface area, so it exhibits excellent activity and is susceptible to various chemical reactions and physical adsorption. It is about providing law.

Further objects and advantages of the present invention will become apparent from the description below.

[Means and actions for solving problems]

According to the present invention, the above objects and advantages of the present invention are as follows. (2) Prepare an aqueous solution containing this initial condensate and an inorganic salt, (3) Pour this aqueous solution into a suitable mold, ( 4) Curing the aqueous solution in a mold by heating it while suppressing water evaporation, (5) firing the resulting cured product in a non-oxidizing atmosphere, and then (6) washing the resulting fired product. A method for producing porous activated carbon having continuous pores with an average pore diameter of 0.03 to 10 μm and having a specific surface area value of at least 600 m ² /g by the BET method, the method comprising: removing inorganic salts in the fired body by achieved by.

In the present invention, the phenolic resin is a condensate of an aromatic hydrocarbon compound having a phenolic hydroxyl group and an aldehyde. Suitable examples of such aromatic hydrocarbon compounds include so-called phenols such as phenol, cresol, and xylenol, but they are not limited thereto. For example, the following formula Here, x and y are each independently 0, 1
or 2, or hydroxy-biphenyls or hydroxynaphthalenes. Among these, phenols, particularly phenol, are preferred from a practical standpoint.

The phenolic resin in the present invention further includes a modified aromatic polymer in which a part of the aromatic hydrocarbon compound having a phenolic hydroxyl group is substituted with an aromatic hydrocarbon compound not having a phenolic hydroxyl group, such as xylene, toluene, etc., such as phenol. A modified aromatic polymer which is a condensation product of xylene and formaldehyde can also be used. As the aldehyde, not only formaldehyde but also other aldehydes such as acetaldehyde and furfural can be used, but formaldehyde is preferred. The phenol-formaldehyde condensate may be a novolac type, a resol type, or a composite thereof.

The above-mentioned inorganic salt used together with the initial condensate is a pore-forming agent that is removed in a later step and used to provide communicating pores to the activated carbon, such as zinc chloride, tin chloride, sodium chloride, sodium phosphate, potassium hydroxide, or Hardened potassium, etc. Among these, zinc chloride is particularly preferably used. The inorganic salt can be used in an amount of, for example, 2.5 to 10 times the weight of the initial condensate. If the amount is less than the lower limit, it is difficult to obtain porous activated carbon having communicating pores, and if the amount is more than the upper limit, the mechanical strength of the porous activated carbon tends to decrease undesirably. The aqueous solution of the initial condensate and the inorganic salt can be prepared using, for example, water in an amount of 0.1 to 1 times the weight of the inorganic salt, although it varies depending on the type of inorganic salt used.

An aqueous solution of an initial condensate of a phenolic resin and an inorganic salt can be prepared as a homogeneous solution by, for example, adding an aqueous zinc chloride solution to a water-soluble resol and then stirring, or a methanol solution of a resol and a zinc chloride solution can be prepared. A highly viscous slurry can also be prepared by mixing an aqueous solution. At this time, other additives, such as hardened phenolic resin powder or fibers, or cellulose fine particles, may be mixed into the aqueous solution. Further, as mentioned above, an organic solvent such as methanol, ethanol, or acetone may be added for uniform mixing. Thus, an aqueous solution having a viscosity of e.g.
Heated to a temperature of 50-200°C. During this heating,
It is important to suppress evaporation of water in the aqueous solution. That is, it is thought that the initial condensate is heated in an aqueous solution and gradually hardens, growing into a three-dimensional network structure while separating from an inorganic salt such as zinc chloride and water.

By firing the obtained cured body in a non-oxidizing atmosphere, the cured body can be converted into carbon. Firing is usually carried out until a temperature of 800°C or higher is reached. The preferred rate of temperature increase during firing varies somewhat depending on the phenolic resin used or its shape, but generally it is possible to achieve a relatively high rate of temperature increase from room temperature to a temperature of about 300°C. For example, a rate of 100°C/hour is also possible. When the temperature exceeds 300℃, the resin starts to thermally decompose and gases such as water vapor (H ₂ O), hydrogen, methane, and carbon monoxide begin to be generated.
After reaching 300°C, it is advantageous to raise the temperature at a sufficiently slow rate. Examples of the non-oxidizing atmosphere include nitrogen, argon, helium, neon, carbon dioxide, etc., and nitrogen is preferably used. Such a non-oxidizing atmosphere may be stationary or flowing.

Inorganic salts contained in the fired body can be removed by thoroughly washing the fired body with water, dilute hydrochloric acid, or the like. After removing the inorganic salt, if necessary, drying is performed to obtain porous activated carbon with developed communicating pores.

The porous activated carbon of the present invention thus obtained has excellent mechanical strength and chemical resistance, and can be formed into any shape such as a film, plate, or cylinder, making it a highly practical industrial material. be.

The porous activated carbon of the present invention has a three-dimensional network structure of carbon parts or communicating pores, so that it has communicating pores that allow fluid to freely enter and exit fine details. The average pore size is as fine as 0.03 to 10 μm, and the pore size is uniform, that is, the pore size distribution is sharp. For example, in the above production method, the average pore size can be adjusted by selecting the composition or heat curing conditions of the uncured phenolic resin aqueous solution containing an inorganic salt.
Porous bodies with extremely fine pores of 0.03 to 0.1 μm to porous bodies with an average pore diameter of about 10 μm can be obtained, so they can be used depending on the purpose.
For example, it can be applied to materials for separating extremely minute substances such as colloidal substances or bacteria.

The porous activated carbon of the present invention has a specific surface area value of at least 600 m ² /g by the BET method. If it is less than 600 m ² /g, the activity ability will decrease, which is not preferable. Various types of physical adsorption can occur smoothly, uniformly, and in large quantities by utilizing the fine interconnected pores and high specific surface area of the porous activated carbon of the present invention.
Suitable as an adsorbent or a separation material.

Apparent density (bulk density) of the porous activated carbon of the present invention
is usually 0.2 to 0.6 g/cm ³ . In other words, the porous activated carbon of the present invention includes porous bodies having a relatively high porosity to porous bodies having a relatively low porosity.
Although the mechanical strength of a porous body varies depending on its apparent density, for example, even the porous body of the present invention of 0.2 g/cm ³ has the strength required for practical use.

As described above, the porous activated carbon of the present invention has fine continuous pores, so it is a porous body through which fluid can smoothly flow in and out, and has a large specific surface area, so it has excellent activity. In addition, it is an industrially useful material that can be applied in many fields because it can take any shape such as a film, plate, or cylinder with excellent mechanical strength.

The present invention will be explained in more detail with reference to Examples below.

In addition, in this specification, the average pore diameter of the communicating pores is measured and defined as follows.

An electron micrograph is taken of the sample at a magnification of, for example, 1000 to 10000 times. If an arbitrary straight line is drawn on this photograph and the number of holes that intersect with the straight line is n, then the average pore diameter () is calculated by the following formula.

Here, li is the length cut by the hole where the straight line intersects, _o 〓 ⁱ⁼¹ li is the sum of the cut length for n holes, and n is the length cut by the hole where the straight line intersects. It is the number of holes. However, n shall take a value of 10 or more.

Example 1 An aqueous solution containing water-soluble resol (approximately 60% concentration)/zinc chloride/water mixed in a weight ratio of 10/25/4 was formed into a film on a glass plate using a film applicator. Next, a glass plate was placed over the formed aqueous solution to prevent moisture from evaporating, and then heated at a temperature of about 100° C. for 1 hour to cure it.

The phenolic resin composite was placed in a siliconite electric furnace and heated to 900°C in a nitrogen stream at a rate of 40°C/hour. Next, the heat-treated film was washed with dilute hydrochloric acid, water, and dried.

The film thus obtained has a thickness of approximately
200 μm, and the apparent density was about 0.3 g/cm ³ . It also had excellent mechanical strength, which was hard to believe for activated carbon, and even had some flexibility. next
Specific surface area value measured by BET method
The value was extremely high at 1800m ² /g.

Next, in order to observe the state of the pores in the film-like glassy carbon, an electron micrograph of a cross section of the film was taken. Shown in Figure 1. As is clear from the figure, it had a three-dimensional network structure with fine interconnected pores of 10 μm or less.

[Brief explanation of drawings]

FIG. 1 is an electron micrograph of the cross-sectional particle structure (porous structure) of the porous activated carbon film of the present invention. The length of the bar shown at the bottom right of the photo is 5 μm.

Claims (1)

[Scope of Claims] 1 (1) An initial condensate of an aromatic hydrocarbon compound having a phenolic hydroxyl group and an aldehyde, or an aromatic hydrocarbon compound having a phenolic hydroxyl group and an aromatic hydrocarbon not having a phenolic hydroxyl group Prepare an initial condensate of a compound and an aldehyde, (2) Prepare an aqueous solution containing this initial condensate and an inorganic salt, (3) Pour this aqueous solution into a suitable mold, (4) Prevent water evaporation. (5) The resulting cured product is fired in a non-oxidizing atmosphere, and (6) the resulting fired product is washed to remove inorganic matter in the fired product. A method for producing porous activated carbon having continuous pores with an average pore diameter of 0.03 to 10 μm and exhibiting a specific surface area value by BET method of at least 600 m ² /g, the method comprising: removing salt.