JPH11276889A - Pitch type fibrous active carbon for adsorbing gas phase - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pitch type fibrous active carbon with a narrow pore distribution and a small mean pore radius and being suitable for adsorbing gas phase. SOLUTION: A fibrous active carbon prepd. by using pitch as a raw material and with a controlled pore distribution is provided. In this pore distribution, R (a mean pore radius) expressed by [total pore vol. (measured by means of a low temp. nitrogen adsorption method at a liq. nitrogen temp.)/specific surface area (measured by means of the BET method)]×2 is R=5-12 Å and the pore vol. (measured by means of the low temp. nitrogen adsorption method at a liq. nitrogen temp.) existing in radius of 10-20 Å is 2-8% of the total pore vol. and the pore vol. existing in radius of 20-30 Å is 0-5% of the total pore vol. and the radius where the accumulated pore vol (measured by means of the low temp. nitrogen adsorption method at a liq. nitrogen temp.) converges is at most 50 Å.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-performance pitch-based fibrous activated carbon characterized by having a pore distribution different from that of a conventional fibrous activated carbon.

[0002]

2. Description of the Related Art The technology for producing fibrous activated carbon (FAC) from pitch and liquefied coal is known. For example,
JP-A-56-140019, JP-B-51-332.
No. 23 is known. However, these known techniques only showed that FACs could be produced from pitch-like materials, and actively controlled the distribution of micropores and some transitional pores forming adsorption sites on the FAC surface. A pitch-based FAC has not yet been proposed.

[0003] On the other hand, in the case of FAC produced from precursor fibers such as rayon, polyacrylonitrile and special phenol resin which are currently produced industrially, the pore distribution is uniquely controlled by the type of precursor. Although it is difficult or possible to actively control the pore distribution, the range is considered to be extremely narrow (for example, Susumu Omori, Journal of the Textile Society of Japan, 1985, 41 (6), P1).
67-172, Minoru Hirai, 1983 Seminar on Carbon Materials, New Development of Carbon Fiber, pp. 27-36).

[0004]

When FAC is practically used for gas phase adsorption, it is necessary to improve the selective adsorption as a molecular sieve, so that the pore distribution is narrow and the average pore radius is small. A small FAC is desired. However, as described above, existing FACs do not sufficiently meet such needs. An object of the present invention is to provide a pitch-based FAC for gas phase adsorption with a controlled pore distribution, which meets such needs.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that an FAC having a controlled pore distribution can be obtained using pitch as a raw material. Reached. That is, according to the present invention, the pore distribution is a)
[Total pore volume (measured by low-temperature nitrogen adsorption method at liquid nitrogen temperature) / specific surface area (measured by BET method)] × 2 expressed by R
(Average pore radius) is R = 5 to 12 °, b) radius 1
The pore volume existing at 0 to 20 ° (measured by the low-temperature nitrogen adsorption method at liquid nitrogen temperature) is 2 to 8% of the total pore volume, and c) The pore volume existing at a radius of 20 to 30 ° is the total pore volume. D) a radius at which the cumulative pore volume (measured by the low-temperature nitrogen adsorption method at the temperature of liquid nitrogen) converges is 5%;
The gist of the present invention is a pitch-based fibrous activated carbon for gas phase adsorption characterized by being 0 ° or less.

Here, the total pore volume, pore volume, cumulative pore volume, and specific surface area are, for example, Quanta S
It can be measured using orb. That is, it can be obtained from 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 measured at a relative pressure set to 0.98 when measuring the cumulative pore volume by the low-temperature nitrogen adsorption method at liquid nitrogen temperature. Is the highest radius.

The FACs of the present invention are essentially amorphous materials whose X-ray diffractogram shows a broad halo corresponding to 002 diffraction. The counter curve of the 002 diffraction halo shows a broad diffraction distribution, and the 002 diffraction plane spacing calculated therefrom corresponds to 3.5 to 4.0 °.

The raw material spinning pitch for giving such amorphous carbon is an optically isotropic pitch having a softening point (SP) of 180 to 3 as measured by the Mettler method or the R & B method.
The quinoline-insoluble matter (QI) at 00 ° C. is 0 to 40%. Mesophase pitch, premesophase pitch, potentially anisotropic pitch, etc. are undesirable because they fall into the category of graphitizable carbon precursors. Isotropic pitch for spinning is a petroleum-based and coal-based heavy oil, such as crude oil distillation residue, naphtha cracking residue, ethylene bottom oil, coal liquefied oil, coal tar, etc. It can be prepared through steps such as hydrogenation treatment, heat treatment, heat treatment for adding an active or inert gas, and / or heat treatment under reduced pressure.

[0009] Melt spinning of pitch can be performed according to a known melt spinning method. The melting temperature and the spinning temperature are not lower than the softening point temperature of the pitch, preferably 30 to 1 from the softening point.
00 ° C high temperature. The melted pitch is sent to a nozzle of a spinning machine, and discharged from a nozzle having a large number of pores while forming fibers into an atmosphere controlled at a spinning temperature or lower. Examples of the method of thinning the discharged yarn include thinning by a take-off roller, air soccer, etc., thinning in a centrifugal force field, and thinning by hot air flow, but are not limited to these. Not something. Here, as a form of the fibrous pitch, a chop, a swoof, a filament, a tow, a spun-bonded nonwoven fabric and the like can be considered.

[0010] The fibrous pitch thus obtained is heat-treated in an oxidizing atmosphere to make it infusible. As the infusibilization treatment, for example, a wet method in which an oxidizing agent solution is applied and then a heat treatment is performed, a dry method in which an oxidizing gas is introduced into a heat treatment atmosphere, or the like can be used. The treatment temperature is 400 ° C. or lower, and the temperature is raised from the temperature below the softening point to 400 ° C.
It is preferable to carry out the method in which the temperature is maintained at a temperature of not more than ° C for a required time. The treatment time varies depending on the oxidizing agent used, but is generally within 90 minutes for the heat treatment under atmospheric pressure. As the processing apparatus, for example, a batch type heat treatment furnace, a continuous type heat treatment furnace, or the like can be used. As the oxidizing agent, for example, nitric acid, sulfuric acid,
Air, ozone, oxygen, NOx, SOx, chlorine and the like can be used, but are not limited thereto.

Next, the infusible fibrous pitch is activated. In order to obtain a gas phase FAC having a narrow pore distribution and a small average pore radius, as an example, a method of directly activating without passing through a separate pre-activation step can be considered. As an activation method, the infusibilized fibrous pitch is activated with steam, carbon dioxide, oxygen (air), or a mixed gas thereof. Preferred activation temperatures and times are 70
0 to 1000 ° C. for 5 to 120 minutes. As the activation device, a known device such as a batch type or continuous activation furnace can be used as appropriate.

[0012]

The present invention will be described below in more detail with reference to examples. Example 1 Coal tar was filtered at 150 ° C. under pressure 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 upper space was 1 hour.
The mixture was heat-treated at 350 ° C. for 2 hours with stirring while blowing air at a constant flow rate so as to give 00 minutes to obtain an isotropic pitch for spinning. The obtained pitch has a softening point of 287 ° C. (Mettler method), QI = 38%, benzene-insoluble matter (BI) = 80%.
Met. As a result of observation with a polarizing microscope, this pitch was optically isotropic. The powder X-ray diffraction pattern is
It only showed a wide range of amorphous / halo corresponding to 002 reflection.

The thus obtained isotropic pitch for spinning was crushed at room temperature and supplied to a melting section of a melt spinning machine. The melting temperature and the spinning temperature were set to 340 ° C., and the melt pitch was fed to a spinning nozzle, discharged from a nozzle die having a nozzle diameter of 0.3 mm and 24 holes, and spun. The discharged yarn was thinned in a controlled atmosphere to obtain a fibrous pitch having a single yarn diameter of 20 μm. The fibrous pitch obtained as described above was heated from room temperature to 250 ° C. for 15 minutes, and further heated from 250 ° C. to 400 ° C. for 75 minutes to obtain an infusible fibrous pitch. . The fibers exhibited a red-white color without melting even when placed in a flame of a Bunsen burner, and were completely infusible. The oxygen content obtained by elemental analysis is 1
0.1 wt%, and the ESCA spectrum (E Shimadzu E
The surface oxygen content determined from the integrated intensity of the O1s and C1s bands (measured by SCA750) was 12.4 mol%.

Next, the infusibilized fiber is directly
Activated with steam containing 5% air at 0 ° C for 25 minutes, yield 4
5% (gravimetric analysis), specific surface area 1300 m ² / g (Quanta
Using Quanta Sorb manufactured by Chrome Co., measured by the BET one-point method), single yarn diameter 17 μm, fiber strength 13 kg / mm ² (JIS
-Measured at R7601). Various parameters representing the pore distribution of the FAC for gas phase adsorption, ie, a)
The average pore radius is 9.6 °, b) the ratio of the pore volume existing at a radius of 10 to 20 ° to the total pore volume is 5%, and c) the pore volume existing at a radius of 20 to 30 ° is the total pore volume. The ratio is 0%, and d) the radius at which the cumulative pore volume converges is 17
Was Å. Here, the total pore volume, the pore volume, the cumulative pore volume, and the specific surface area were 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 obtained by mixing nitrogen and helium at various ratios at a liquid nitrogen temperature. Example 2 Using the same method as in Example 1, activated at 850 ° C. for 35 minutes, with a yield of 20%, a specific surface area of 1800 m ² / g and a single yarn diameter.
An FAC for gas phase adsorption having a particle size of 16.5 μm and a fiber strength of 14 kg / mm ² was obtained. Table 1 shows parameters indicating the pore distribution of the FAC. Table 1 shows the results of various parameters representing the pore distribution of the FACs obtained in Examples 1 and 2.

[0015]

[Table 1] The FACs obtained in Examples 1 and 2 had a narrow pore radius distribution and a small average pore radius, and were suitable for use in the gas phase.

[0016]

According to the present invention, using pitch as a raw material,
It is possible to provide a gas phase adsorption FAC having a narrow pore radius distribution and a small average pore radius.
It is possible to extend the use of FAC to high-performance molecular sieves.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuaki Otsuki 5-1-1, Hirano-cho, Higashi-ku, Osaka-shi, Osaka Prefecture Inside the Osaka Gas Co., Ltd. (72) Keiji Sakai 5-1-1, Hirano-cho, Higashi-ku, Osaka, Osaka Inside Osaka Gas Co., Ltd. (72) Inventor Kazuo Tai 23 Uji Kozakura 23 Uji-city, Kyoto Pref.

Claims (1)

[Claims] 1. The pore distribution is a) [total pore volume (measured by a low-temperature nitrogen adsorption method at liquid nitrogen temperature) / specific surface area (B
R (mean pore radius) represented by × 2 is R
B) the pore volume present at a radius of 10-20 ° (measured by the low temperature nitrogen adsorption method at the temperature of liquid nitrogen) is 2-8% of the total pore volume, and c) the radius of 20-3
The pore volume existing at 0 ° is 0 to 5% of the total pore volume, and d) the radius at which the cumulative pore volume (measured by the low-temperature nitrogen adsorption method at liquid nitrogen temperature) converges is 50 ° or less. Pitch-based fibrous activated carbon for gas phase adsorption.