JPH0832972B2 - Pitch-based fibrous activated carbon - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a high-performance pitch-based fibrous activated carbon having a pore distribution different from that of conventional fibrous activated carbon.

(B) Conventional technology Fibrous activated carbon (FA with pitch and liquefied coal as raw materials)
The production technique of C) is known. For example, JP-A-56-140019
Japanese Patent Publications, Japanese Patent Publication No. 51-33223, etc. are known. However, these known techniques only show that FACs can be formed from pitch-like materials, and pitch systems that actively control the distribution of micropores and partial transitional pores that form adsorption sites on the FAC surface. No FAC proposal has been made yet. On the other hand, with regard to FAC using precursor fibers such as rayon, polyacrylonitrile, and special phenol resin, which are currently industrially produced, as a raw material, the pore distribution is uniquely controlled by the type of raw material precursor, Even if it is difficult or even possible to positively control the pore distribution, its range is considered to be extremely narrow (for example, Susumu Omori, The Textile Society of Japan, 1985, 41 (6), P-167-172). , Hirai Minoru, 1983 Carbon Material Society Seminar, New Development of Carbon Fiber, pages 27-36).

(C) Problems to be solved by the invention When the FAC is practically used, vapor phase adsorption and liquid phase adsorption can be considered. In the case of gas-phase adsorption, it is necessary to improve the selective adsorption property as a molecular sieve, and thus FACs having a narrow pore distribution and a small average pore diameter are desired. In the case of liquid phase adsorption, FAC having a wide pore distribution and a large average pore radius is required in order to cope with adsorption of a substance having a large molecular size. However, as mentioned above, the existing FAC does not fully meet these needs.

An object of the present invention is to provide a pitch FAC having a controlled pore distribution, which meets these needs.

(D) Means for Solving the Problems As a result of earnest research to solve such problems, the inventors of the present invention have used FA as a raw material to control the pore distribution of FA.
It was found that C was obtained and the present invention was achieved.

That is, R (average pore radius) expressed by (1) pore distribution as a) [total pore volume (measured by low temperature nitrogen adsorption method at liquid nitrogen temperature) / specific surface area (measured by BET method)] x 2
Is R = 10 to 20Å, b) Pore volume existing in a radius of 10 to 20Å (measured by a low temperature nitrogen adsorption method at liquid nitrogen temperature)
Is 20 to 30% of the total pore volume, and c) the pore volume existing in a radius of 20 to 30Å is 2 to 10% of the total pore volume, and the pitch-based fibrous activated carbon, and ( 2) Pore distribution is R expressed by a) (total pore volume / specific surface area) × 2
(Average pore radius) is R = 5 to 12Å, b) radius is 10 to
The pore volume present at 20Å is 2-10% of the total pore volume, c) the pore volume present at a radius of 20-30Å is 0-5% of the total pore volume, and d) the cumulative pores. The radius where the volume converges
It is a pitch-based fibrous activated carbon characterized by being 50 Å or less.

Here, the total pore volume, the pore volume, the cumulative pore volume, and the specific surface area can be measured using, for example, Quanta Sorb manufactured by Quanta Chrome. That is, it can be determined by an isothermal adsorption curve and an isothermal desorption curve measured by a low temperature nitrogen adsorption method using a gas in which nitrogen and helium are mixed at various ratios at a liquid nitrogen temperature. The radius at which the cumulative pore volume converges is calculated from the cumulative pore volume when the cumulative pore volume is measured by the low temperature nitrogen adsorption method at liquid nitrogen temperature and the relative pressure is set to 0.98. Is the highest radius.

The FAC of the present invention is an essentially amorphous material whose X-ray diffractogram shows a broad halo corresponding to 002 diffraction. The counter curve of the 002 diffraction halo shows a wide diffraction distribution, and the calculated interplanar spacing of 002 diffraction corresponds to 3.5 to 4.0Å.

The pitch for spinning the raw material that gives such amorphous carbon is an optically isotropic pitch, and the pitch is determined by the Mettler method or the R & D method.
It has a softening point (SP) of 180 to 300 ° C. and a quinoline insoluble matter (QI) of 0 to 40% as measured by the B method. Mesophase pitch, premesophase pitch, latent anisotropic pitch, etc. are not desirable as they fall into the category of graphitizable carbon precursors. Isotropic pitch for spinning is a petroleum-based and coal-based heavy oil, for example, crude oil distillation residual oil, naphtha cracked residual oil, ethylene bottom oil, coal liquefied oil, coal tar, etc., purified,
It can be prepared through steps such as distillation, solvent extraction, hydrogenation treatment, heat treatment, heat treatment with active or inert gas addition, and / or heat treatment under reduced pressure.

Melt spinning of the pitch can be performed by a known melt spinning method. The melting temperature and the spinning temperature are not lower than the softening point temperature of the pitch, and preferably 30 to 100 ° C. higher than the softening point.
The melted pitch is fed to the nozzle portion of the spinning machine, and discharged from a nozzle having a large number of fine holes while forming fibers into an atmosphere controlled at a spinning temperature or lower. Possible methods for thinning the discharged yarns include, but are not limited to, pulling rollers, pulling with an air sucker, thinning in a centrifugal force field, and blowing with a hot air stream. Not something. Here, as the form of the fibrous pitch, a chop, a staple, a filament, a tow, a spunbonded non-woven fabric and the like can be considered.

The fibrous pitch thus obtained is heat-treated in an oxidizing atmosphere to make it infusible. As the infusibilizing treatment, for example, a wet method of applying an oxidant solution and then performing heat treatment, a dry method of introducing an oxidant gas into a heat treatment atmosphere, or the like can be adopted. The treatment temperature is preferably 400 ° C. or lower, the temperature is raised from the softening point or lower, and the temperature is kept at the softening point or higher and 400 ° C. or lower for a required time. The treatment time varies depending on the oxidizing agent used, but it is generally 90 for heat treatment under atmospheric pressure.
Within minutes. As the processing device, for example, a batch heat treatment furnace, a continuous heat treatment furnace, or the like can be used. Examples of the oxidizer include nitric acid, sulfuric acid, air, ozone, oxygen, NOx, S
Ox, chlorine, etc. can be used, but are not limited thereto.

Then, the infusibilized fibrous pitch is activated. When obtaining FAC with a wide pore distribution and a large average pore radius,
As an example, a method is conceivable in which fibrous precursor activated carbon is once subjected to the previously-specified activation step and then activated to be converted into FAC. As a first-stage activation process, in a weakly oxidizing atmosphere
It is desirable that the temperature is 1200 ° C or less and the treatment time is 5 to 30 minutes. Here, as the weakly oxidizing atmosphere, 0.01 to 20% of oxygen, an oxidizing gas such as NO ₂ or SO ₂ is preferably added to a non-oxidizing gas such as nitrogen or a rare gas.
It is possible that the content is 0.05 to 5%, but the content is not limited thereto. As the activation method, an ordinary gas activation method using water vapor, carbon dioxide gas, or oxygen (air) can be applied. The preferred activation temperature and time are 70
It is 0 to 1000 ° C. and 5 to 120 minutes. As an example of obtaining FAC having a narrow pore distribution and a small average pore radius, a method of directly activating without going through a distinctive pre-activation step can be considered. That is, as an activation method, the infusible fibrous pitch is activated by steam, carbon dioxide gas, oxygen (air), or a mixed gas thereof. The preferred activation temperature and time are 700 to 1000 ° C. and 5 to 120 minutes, respectively. As the activation device, a known device such as a batch type or continuous type activation furnace can be appropriately used.

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

Example 1 Coal tar was filtered under pressure at 150 ° C. to remove the primary quinoline-insoluble matter (QI), and the tar was distilled under reduced pressure to remove low-boiling components. Next, the distillation residue was transferred to an autoclave, and the residence time of air in the autoclave head space was 10
While blowing air at a constant flow rate for 0 minutes, heat treatment was performed at 350 ° C. for 2 hours with stirring to obtain an isotropic pitch for spinning. The softening point of the obtained pitch was 287 ° C (Mettler method), QI = 38%, and benzene insoluble content (BI) = 80%. As a result of observation with a polarization microscope, this pitch was optically isotropic. The powder X-ray diffraction pattern is 002
It only showed wide amorphous halo corresponding to reflection. The isotropic pitch for spinning thus obtained was crushed at room temperature and supplied to the melting section of the melt spinning machine. The melting temperature and the spinning temperature were set to 340 ° C., the molten pitch was fed to the spinning nozzle portion, and discharged from a nozzle spinneret having a nozzle diameter of 0.3 mm and 24 holes for spinning. The discharged yarn was thinned in a controlled atmosphere to obtain a fibrous pitch with a single yarn diameter of 20 μm.

The fibrous pitch obtained as described above is heated from room temperature to 250 ° C.
The temperature was raised for 15 minutes, and then from 250 ° C. to 400 ° C. for 75 minutes to obtain an infusible fibrous pitch. The fiber did not melt when placed in the flame of a Bunsen burner, exhibited a reddish white color, and was completely infusible. Oxygen content obtained by elemental analysis is 10.1 wt%, 01s and C1s of ESCA spectrum (measured with ESCA750 manufactured by Shimadzu Corporation)
The surface oxygen content calculated from the integrated intensity of the band is 12.4 mol.
%Met.

Then, this infusible fibrous pitch was pre-activated for 5 minutes at 1000 ° C. in a nitrogen atmosphere containing 0.2% oxygen using a batch type carbonization furnace. This fibrous precursor activated carbon was activated by steam. That is, a batch activation furnace was used to flow a mixed gas of nitrogen and water vapor (volume ratio 10: 7), and the residence time in the furnace was set to 9
The flow rate of the mixed gas was controlled so as to be equal to the amount. Activation temperature 850
Yield 32% (gravimetric analysis), specific surface area 15 at 30 ° C for 30 minutes
00m ² / g (using Quanta Sorb manufactured by Quanta Chrome, BE
(Measured by T1 point method), single yarn diameter 17 μm, fiber strength 12 kg / mm
FAC of ² (measured by JIS-R7601) was obtained. Various parameters representing the pore distribution of the FAC, that is, a) the average pore radius is
10.4Å, b) The ratio of the volume of pores present in the radius 10 to 20Å to the total pore volume is 25%, and the ratio of the volume of pores present in the radius 20 to 30Å to the total pore volume is 3%. there were. Here, the total pore volume, the pore volume, the cumulative pore volume, and the specific surface area are
It was measured using Quanta Sorb manufactured by Quanta Chrome. That is, it was determined by an isothermal adsorption curve and an isothermal desorption curve measured by a low temperature nitrogen adsorption method using a gas in which nitrogen and helium were mixed at various ratios at a liquid nitrogen temperature.

Example 2 The infusible fiber obtained under the same conditions as in Example 1 was directly activated for 25 minutes at 850 ° C. with steam containing 5% of air without going through an independent previous activation step, and the yield was 45% (weight analysis ), Specific surface area 1300m ²
/ g (using Quanta Chrome, Quanta Sorb, BET 1-point method), single yarn diameter 17 μm, fiber strength 13 kg / mm ² (JIS
-Measured with R7601) was obtained. Parameters representing the pore distribution of the FAC, that is, a) the average pore radius is 9.6
Å, b) The ratio of the pore volume existing in the radius 10 to 20 Å to the total pore volume is 5%, c) The ratio of the pore volume existing in the radius 20 to 30 Å to the total pore volume is 0%, d) The radius of convergence of the cumulative pore volume was 17Å.

Example 3 Using the same method as in Example 2, activation was carried out at 850 ° C. for 35 minutes, yield 20%, specific surface area 1800 m ² / g, single yarn diameter 16.5 μm, fiber strength 1
An FAC of 4 kg / mm ² was obtained. The parameters showing the pore distribution of the FAC are shown in Table 1.

(F) Effect of the invention Table 1 summarizes various parameters expressing the pore distribution of FACs in Examples 1 and 2. From the table, it can be seen that in Example 1, the distribution of the pore radius is wide and the average pore radius is large.
It can be seen that in Example 2, an FAC having a small pore radius distribution and a small average pore radius was obtained.

INDUSTRIAL APPLICABILITY According to the present invention, (1) a FAC having a wide pore radius distribution and a large average pore radius and (2) a FAC having a narrow pore radius distribution and a small average pore radius can be provided. As a result, it has become possible to extend the application of FAC to liquid-phase adsorption and high-performance molecular sieves.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Keiji Sakai 5-1, Hirano-cho, Higashi-ku, Osaka City, Osaka Prefecture Osaka Osaka Gas Co., Ltd. Rika Fuchino, Examiner, Central Research Institute (56) References JP-A-60-167929 (JP, A)

Claims (2)

[Claims] 1. R (average pore radius) expressed as a) [total pore volume (measured by low temperature nitrogen adsorption method at liquid nitrogen temperature) / specific surface area (measured by BET method)] × 2 ) Is R = 10
~ 20Å, b) Pore volume present in radius 10-20Å (measured by low temperature nitrogen adsorption method at liquid nitrogen temperature) is 20-30% of total pore volume, and c) Existence in radius 20-30Å The pitch-based fibrous activated carbon characterized in that the pore volume of the activated carbon is 2 to 10% of the total pore volume. 2. The pore distribution is a) (total pore volume / specific surface area)
R (average pore radius) represented by × 2 is R = 5 to 12Å, b) Pore volume existing in radius 10 to 20Å is 2 to 10% of the total pore volume, and c) Radius 20 The pore volume existing at ~ 30Å is 0-5% of the total pore volume, and d) the cumulative pore volume (measured by the low temperature nitrogen adsorption method at liquid nitrogen temperature) has a radius of convergence of 50Å or less. Characteristic pitch-based fibrous activated carbon.