JPH0764530B2 - Method for producing spherical fiber lump activated carbon - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention uses tar pitch as a raw material and is a highly functional fibrous activated carbon that is indispensable for advanced treatment technology used in pollution prevention and environmental purification, food industry, petroleum industry and the like. The present invention relates to a method of manufacturing.

(Prior Art) Activated carbon has innumerable fine pores, has a large outer surface area per unit weight, and is capable of adsorbing, retaining, and desorbing various molecules in the gas phase and liquid phase. have. Therefore, conventionally, activated carbon has taken advantage of its adsorptive and desorbing ability to separate, remove, adsorbent, decomposer,
It is used as a recovery agent, catalyst, catalyst carrier, etc.

(Problems to be Solved by the Invention) Activated carbon is roughly classified according to its form into powdered activated carbon having a particle size of 149 μm or less, granular activated carbon having a particle size of about 1 mm to 3 mm, and amorphous fibrous activated carbon. It Here, the powdered activated carbon has an advantage in that the outer surface area per unit weight is larger and the adsorption rate is faster than the granular activated carbon, but the particle size is 14
Since it is as small as 9 μm or less, it easily scatters, is generally difficult to handle, and has a risk of dust explosion. Further, since it has a large ventilation resistance when used in a fixed bed, it is difficult to use in a gas phase, and it is used in a catalytic batch method in which a treatment liquid and an appropriate amount of activated carbon are mixed and then filtered, and generally, a liquid is used. Separators, removers, adsorbents, decomposers, recovery agents of molecules in the phase,
It has the drawback that it can only be used as a catalyst carrier. If it is attempted to obtain the effect of adsorbing various molecules of a harmful substance in the gas phase, the amount of treatment, that is, the so-called adsorption efficiency is lowered, which is not preferable.

On the other hand, granular activated carbon is easier to handle than powdered activated carbon,
It does not easily scatter, there is no danger of dust explosion, and since it has a low airflow resistance when used in a fixed bed, it has the advantage that it can be used in the gas phase or liquid phase and can be reused, but it is crushed powder. It also has the drawbacks of being easy to be processed, having a small outer surface area per unit weight, and having a low adsorption rate and desorption rate. Therefore, if the gas or liquid to be purified is flowed through the granular activated carbon layer and various molecules of low-concentration harmful substances are sufficiently adsorbed and removed, a large-capacity granular activated carbon layer is required, and the amount of treatment is reduced. That is, the so-called adsorption efficiency is lowered. Also, if the gas or liquid to be purified is passed through a fluidized bed of granular activated carbon and various molecules of harmful substances are adsorbed and removed, the large particle size is about 1 to 3 mm and the large particle density. The above gas or liquid flow is required, which leads to a decrease in the adsorption removal rate, which causes wear of the granular activated carbon and crushing loss.

On the other hand, fibrous activated carbon is a fibrous activity that is generally produced by gas-activating or chemical-activating carbon fiber, has a large outer surface area per unit weight, and has the advantage of high adsorption / desorption rate. However, the strength and shape retention of the fiber assembly itself is poor, and the workability and handleability are poor because the fibers are easily scattered. It also has the drawbacks of high porosity and low packing density. Further, even when it is recycled and reused, it easily scatters and the shape retention is poor, so that there is a problem that the reproducibility of the porosity and the packing density is poor. Therefore, if the gas or liquid to be purified is
Pour fibrous activated carbon into a cotton-filled fibrous activated carbon layer,
In order to sufficiently remove various molecules of harmful substances, a large-capacity fibrous activated carbon layer is required, which is not economical and results in a reduction in throughput, so-called a decrease in adsorption efficiency.
In addition, when the gas or liquid to be purified is flowed through a fibrous activated carbon fluidized bed filled with fibrous activated carbon in a cotton-like state to adsorb and remove various molecules of harmful substances, the cotton-like fibrous body retains its shape. However, it causes scattering, scattering, wear, and crushing loss, and also causes a reduction in adsorption removal rate, a reduction in treatment amount, and so-called adsorption efficiency. Furthermore, for the purpose of improving this shape retention, woven fabric, non-woven fabric, felt,
In order to process and use it for mats, papers, etc., it is often necessary to use blended fibers for imparting strength, which is costly and uneconomical, and in the processed products, the content of activated carbon fibers becomes low. Therefore, there is a problem that the outer surface area per unit weight is reduced. In addition, there is a problem in that the heat regeneration method using an activated carbon regenerating furnace which is generally performed becomes difficult and the reusing cannot be performed.

On the other hand, in recent years, the functionality of activated carbon has been enhanced against the backdrop of social excitement such as creation of amenity space such as countermeasures for groundwater pollution problems due to trichlorethylene, trihalomethane countermeasures for tap water, CFC gas countermeasures, deodorization, deodorization, comfort, etc. And improvement of shape are required.

Therefore, the object of the present invention is to eliminate the drawbacks of the conventional activated carbons described above, that is, powdered activated carbons, granular activated carbons, and fibrous activated carbons, and have high adsorption power, high adsorption / desorption rate, and good handling property. It is an object of the present invention to provide a method for producing a highly functional spherical activated carbon fiber which has good shape retention and is easy to recycle.

(Means for Solving the Problem) As a result of intensive studies to solve the above problems, the present inventors have found that after pitching tar pitch as a raw material, the pitch fiber is subjected to a spheroidizing treatment to obtain a spherical pitch fiber. Get a lump,
The inventors have found that a highly functional spherical activated carbon fiber can be obtained by infusibilizing and further activating this under appropriate conditions, and completed the present invention.

That is, the present invention prepares a pitch for spinning using tar pitch as a raw material, prevents melting of this pitch, and then performs spheroidizing treatment, and then infuses while partially fusing in an oxygen atmosphere, and more preferably Relates to a method for producing spherical fibrous lump activated carbon, which comprises heating in an inert atmosphere, infusibilizing it in an oxidizing atmosphere, and further performing activation treatment.

(Operation) Hereinafter, the method for producing the spherical fiber lump activated carbon of the present invention will be described in detail.

The raw material used in the present invention is tar pitch. This is because the raw material is cheaper and the activation yield is higher when tar pitch is used as a raw material, as compared with conventionally produced polyacrylonitrile-based, phenolic resin-based, cellulose-based and the like. Further, the tar pitch used here is suitably one having a high softening point that is appropriately heavy so as to be suitable for spinning in the subsequent step, infusibilization, and carbonization, and has a softening point of 200 ° C. or higher. Those are preferable. As a method for producing such a pitch, a method prepared by subjecting to purification, solvent extraction, distillation, heat treatment and the like, as proposed in Japanese Patent Publication No. 61-2712, is suitable.

Spinning of the pitch can be performed by a known method, and for example, methods such as melt extrusion spinning and centrifugal spinning can be adopted.

Next, the pitch fibers are made spherical, and as this method,
For example, a method has been proposed in which a short fiber aggregate of carbon fibers is mixed in a cylindrical container in which a swirling airflow is generated and swirled together with the airflow (JP-A-62-114636), and this method is also used in the present invention. Can be used.

Then, in the infusibilizing step, in order to maintain the spherical fiber shape when activating the obtained spherical pitch fiber at high temperature, an oxidation treatment is performed, for example, 150 to 350 ° C. under an oxidizing atmosphere. Perform at moderate temperature. Here, as a result of diligent studies, the inventors of the present invention selected an appropriate infusibilizing condition to cause fusion and adhesion in a portion in which the fibers are in contact with each other among the spherically entangled fibers to form a shape-maintaining property. Is significantly improved, and as a result of this, fibers fall off during handling,
It was found that scattering and the like can be extremely reduced. The preferable infusibilizing condition at this time varies depending on the raw material pitch to be used, but for example, at the time of infusibilization, the temperature is raised at a relatively fast temperature rising rate in an inert atmosphere up to near the softening point temperature of the pitch to cause fusion and then oxidation. It is possible to adopt a method of performing a normal infusibilizing treatment by changing to a neutral atmosphere and setting a relatively slow temperature rising rate. Here, the infusibilizer can be infusibilized by using a batch infusibilizing furnace, but in the present invention, since the fiber is processed into a spherical shape, the handling property is good, so that the continuous infusibilizer is used. Infusibilization can be efficiently performed using a melting furnace. Furthermore, an advantage of the present invention is that even in the case of batchwise treatment as described above, the infusibilized spherical fibers are continuously switched to a gas for activation in the atmosphere in the furnace to further raise the temperature. Since the inactivation treatment can be performed at a predetermined temperature, there is little heat loss. That is, in the conventional method, in order to form the final product in the form of a non-woven fabric, felt, mat, paper or the like, infusibilization treatment, and in some cases, after the carbonization treatment at high temperature, it was once cooled to room temperature. After that, it was necessary to raise the temperature again for activation again.

As the activation treatment method, a usual gas activation method using water vapor, carbon dioxide gas, oxygen, air or the like can be adopted.
Alternatively, chemical activation can also be applied. Normally, in the gas activation method, the characteristics of the activated carbon fiber are controlled by the temperature, the time of the activation treatment, the type and concentration of the gas, etc., but also in the present invention, the pore size of the fibrous activated carbon to be the final product in the same manner. The pore size distribution and specific surface area can be controlled. When activating the gas, preferable activation conditions include an activation temperature of 700 to 1000 ° C. and an activation time of 0.
~ 240 minutes. However, it is necessary to select the conditions according to the required characteristics. That is, in order to obtain a fibrous activated carbon having a wide pore size distribution and a large average pore radius, it is preferable to treat at a high temperature for a short time, while having a narrow pore size distribution and a small average pore radius. In order to obtain the fibrous activated carbon, it is preferable to perform the treatment at a low temperature for a long time. Further, as the activation device, a batch type, or in the present invention, since the fibers are spheroidized, it is possible to employ a continuous type activation furnace because it has good handleability, but as described above, an infusible furnace It is preferable to appropriately select and use a known device that can be used in common.

The spherical fiber lump activated carbon obtained as described above has a large outer surface area per unit weight, a high adsorption / desorption rate, and is spherical, so that it is excellent in workability and handleability and can be filled in any shape. Possible and precise packing can be performed. Further, since the shaped fiber characteristics are good, there is little regeneration loss, and recycling is easy. Furthermore, by utilizing its high functionality, it can be used for pollution prevention and environmental purification in both liquid and gas phases.

(Examples) Next, the present invention will be specifically described with reference to Examples.

Example 1 Coal tar pitch was purified by filtration and then heat-treated to obtain pitches having a benzene insoluble content (BI) of 57% and a quinoline insoluble content (QI). The viscosity of this pitch is 100 poise at 298 ° C.
And the softening point was 240 ° C. Also, under the polarizing microscope 4
When observed at 00 times, the entire surface had a uniform pitch showing optical isotropy.

Next, melt extrusion is performed at this pitch, and the fiber diameter is 20
Pitch fiber of μm was obtained, and then this fiber was cut into a length of 6 mm to form a chop, which was then inserted into a cylindrical container and swirled while generating a swirling airflow, whereby spherical pitch fiber could be obtained. .

Next, this spherical pitch fiber was heated to 240 ° C. in nitrogen gas at 5 ° C./min to be fused by using a batch type furnace, and then heated to 310 ° C. in air at 0.5 ° C./min to be infusibilized. The treatment was carried out to obtain spherical fused and infusible fibers. Subsequently, activation was carried out by raising the temperature while circulating nitrogen gas containing 33% steam in the furnace and holding it at 850 ° C. for 2 hours in this state.

The obtained spherical activated fibers consist of a three-dimensional fiber network in which the contact points of the fibers are bonded to each other, and the yield is 28%,
It was an activated carbon fiber having a specific surface area (measured by Asap 2000 manufactured by Micromeritics Co., Ltd. and analyzed by Langmuir method) 2020 m ² / g, fiber diameter 14 μm, and fiber strength 20 kg / mm ² . Further, the average pore diameter was 17Å, and the volume ratio of the pore diameter of 10Å or less by the t-plot method was 60%.

Example 2 The spherical fusible and infusible fiber obtained in Example 1 was heated in a batch type carbonization furnace by circulating nitrogen gas containing 33% steam in the atmosphere and raising the temperature to 800 ° C. The activation treatment was performed by holding for 2 hours.

The morphology of the obtained spherical activated fibers was a three-dimensional fiber network in which the contact points of the fibers were bonded to each other, as in Example 1.
Its yield is 53%, specific surface area 1250m ² / g, fiber diameter 17μ
m was an activated carbon fiber having a fiber strength of 32 kg / mm ² . Also,
The average pore size was 17Å, and the volume ratio of pores with a size of 10Å or less was 85%.

Example 3 The spherical fusible and infusible fiber obtained in Example 1 was heated in a batch type furnace by circulating nitrogen gas containing 33% steam in the atmosphere and raising the temperature at 800 ° C. The activation treatment was performed by holding for 4 hours.

The morphology of the obtained spherical activated fibers was a three-dimensional fiber network in which the contact points of the fibers were bonded to each other, as in Example 1.
Its yield is 42%, specific surface area 1480m ² / g, fiber diameter 16μ
m and a fiber strength of 28 kg / mm ² . Also,
The average pore size was 14Å, and the volume ratio with a pore size of 10Å or less was 75%.

(Effects of the Invention) As described above, the method of the present invention can be used to efficiently produce spherical fiber-shaped activated carbon having a three-dimensional fiber network in which the contact points of fibers are bonded to each other using coal tar pitch as a raw material. did it. Moreover, this spherical fibrous lump activated carbon has a higher adsorption capacity than conventional activated carbon, that is, granular activated carbon, powdered activated carbon, and fibrous activated carbon, has a high adsorption / desorption rate, and has good handleability and shape retention characteristics,
It is easy to recycle and has improved functionality.

Therefore, such spherical fiber lump activated carbon has extremely excellent characteristics as activated carbon used in a wide range of industrial fields by taking advantage of a high adsorption / desorption capacity and a large surface area, and in addition to pollution prevention and environmental purification, the food industry, It can be used in a wide range of fields such as the petroleum industry and is extremely useful industrially as an essential component of advanced processing technology.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Susumu Nakai 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Division (72) Seiji Hanaya 1 Kawasaki-cho, Chiba-shi Kawasaki Steel Co., Ltd. Research headquarters

Claims (2)

[Claims] 1. A pitch for spinning is prepared from tar pitch as a raw material, the pitch is melt-spun, spheroidized, and then infusible while partially fused in an oxidizing atmosphere, and further activated. A method for producing a spherical fiber lump activated carbon, which is characterized in that the activated carbon is treated. 2. A pitch for spinning is prepared from tar pitch as a raw material, the pitch is melt-spun, spheroidized, then heated in an inert atmosphere and then made infusible in an oxidizing atmosphere. A method for producing a spherical fiber lump activated carbon, which comprises performing an activation treatment.