JPH0485394A - Production of precursor pitch for active carbon fiber - Google Patents

Abstract

PURPOSE:To improve the efficiently of activation in the production of precursor pitch for active carbon fiber by compounding an arom. nitro compd. with a pitch contg. no quinoline-insol. fraction and heat-treating the compounded mixture at a specified temp. CONSTITUTION:100 pts.wt. coal tar pitch or petroleum tar pitch substantially free from the quinoline-insol. fraction (e.g. a coal tar pitch contg. no coat tar- insol. fraction) is compounded with 1-20 pts.wt. arom. nitro compd. (e.g. dinitronaphthalene). Then, the compounded mixture is heat-treated at 150-350 deg.C prepare a precursor pitch having a softening temp. of 200-250 deg.C, a toluene-insol. fraction content of 45-60wt.% and a quinoline-insol. fraction content of 0.5wt.%, having a nitrogen-contg. functional group such as nitro, nitroso, amino or the like, and having an optically isotropic texture.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing precursor pitch for activated carbon fibers having micropores.

<Prior Art> Activated carbon is a carbon material with a developed porous structure, and is widely used industrially as an adsorbent or catalyst carrier. As activated carbon, granular carbon and powdered carbon made from coconut shells, coal, etc. have traditionally been widely used, but in recent years fibrous activated carbon has been attracting attention. Its characteristics include that compared to granular activated carbon, it has a larger outer surface area, narrower pore distribution, and higher adsorption and desorption rates. It can be processed into shapes.

Raw materials for this activated carbon fiber include regenerated cellulose, polyacrylonitrile, phenolic resin, and pitch.

The activated carbon fiber obtained from these raw materials has a pore size of 30
Although their structural feature is that they have pores of Å or smaller (hereinafter referred to as micropores), the yield of activated carbon fibers obtained from these raw materials is extremely low at 5 to 15%.

However, among them, pitch has the highest carbon content and is most expected to improve yield.

The method for manufacturing activated carbon fiber using pinch as a raw material involves adjusting coal-based tar pitch and petroleum-based cool pitch through operations such as heat treatment and solvent extraction so that they have a softening point and molecular weight distribution suitable for melt spinning. This is used as a precursor pitch for carbon fibers, which is made into fibers by centrifugal spinning or extrusion spinning, and then subjected to infusibility treatment and further activation treatment using gases such as water, carbon dioxide, and oxygen. ing.

Activation refers to further developing the micropore structure on the surface of the carbon fiber by eroding the surface of the carbon fiber through the oxidation reaction of carbon by these gases. In other words, the carbon in the fiber reacts with the activation gas through the activation treatment, resulting in C011]2,
It becomes CO□ and HzO and is gasified and released, leaving behind as micropores. For example, in the case of steam activation, the yield in this activation treatment is very small at 5 to 15 wt% when trying to obtain a product with a specific surface area of 2000 rrf/g or more, and even more when trying to obtain a product with a higher specific surface area. The decline in the rate was inevitable.

<Problems to be Solved by the Invention> An object of the present invention is to propose a method for producing precursor pinches for activated carbon fibers with high activation yields using coal-based and petroleum-based tar pitches as raw materials.

<Means for Solving the Problems> The present invention provides pitch 1 containing substantially no quinoline insoluble matter.
1 to 20 MW parts of an aromatic nitro compound to 0.00 parts by weight and heat-treated at 150 to 350'C.

Effect> As a result of extensive research into the manufacturing method of activated carbon fibers having micropores, the present inventors have found that by incorporating appropriate amounts of nitrogen and oxygen into the precursor pinch for carbon fibers, extremely It has been found that activation can be performed under mild activation conditions and activated carbon fibers having micropores with a pore diameter of 30 Å or less can be produced.

That is, the nitrogen-containing functional groups (nitro groups) in the carbon fiber precursor pitch heat-treated with the aromatic nitro compound of the present invention
N02, nitroso group -NO, amino group Nl+□) are eliminated during activation, and this elimination forms micropores on the carbon fiber surface. Furthermore, gas is released by the reaction between these functional groups and the activating gas, and micropores are formed on the remaining fiber surface, but this reaction proceeds under mild conditions. Therefore, it is believed that an improvement in yield is achieved.

The present invention will be described in detail below using a coal tar pinch as an example.

In the present invention, 1 to 100 parts by weight of an aromatic nitro compound is added to 100 parts by weight of coal tar pitch that does not substantially contain quinoline-insoluble matter.
A precursor pitch for activated carbon fibers is produced by adding 20 parts by weight and heat-treating at 150 to 350'C.

It is desirable that the coal tar pitch does not contain quinoline-insoluble substances such as free carbon and ash.These quinoline-insoluble substances may clog the nozzle during melt spinning.
Furthermore, since it significantly reduces the strength of the fibers, it should be removed in advance. The quinoline insoluble content is desirably 0.01 wt% or less.

Aromatic nitro compounds are aromatic compounds containing a nitro group such as nitroaniline, nitrotoluene, nitrophenol, nitrohenzene, nitronaphthalene, dinitroanthracene, dinitrobenzene, dinitrophenol, dinitrobenzoic acid, dinitronaphthalene. The amount of this aromatic nitro compound added to the coal tar pinch is 1 to 20 parts by weight per 100 parts by weight of the coal tar pinch.
Limited to parts by weight. By mixing coal cool pitch and an aromatic nitro compound and heat-treating the mixture at 150 to 350°C, a polycondensation reaction occurs, and the softening point of the polymerized pitch increases. While the nitro group of the aromatic nitro compound functions as a polymerization accelerator, the unreacted nitro group remains in the polymerized pitch as a functional group. If the amount of the aromatic nitro compound added is less than 1 part by weight, it will not function as a polymerization accelerator. If it exceeds 20 parts by weight, polymerization will proceed too much and mesophase will be produced, making it unsuitable as a precursor pitch for carbon fibers.

If the heat treatment temperature is less than 150°C, the polymerization reaction will not proceed.
If it exceeds 350°C, the polymerization reaction will proceed too much and mesophase will be likely to be generated.

The precursor pitch for activated carbon fiber thus obtained has a softening point of 200 to 250"C, a toluene insoluble content (hereinafter referred to as TI) of 45 to 60%, and a quinoline insoluble content (Q
0.5% by weight or less, nitrogen-containing functional groups such as nitro group N02, nitroso group -NO, amino group -Nllz are present, and furthermore, when observed under a polarizing microscope, it is completely optically isotropic. Has sexual tissue.

After melt spinning this precursor pitch for carbon fiber,
By performing infusibility treatment and activating at a low temperature of 500 to 700° C. using an activating gas such as water vapor or carbon dioxide, activated carbon fibers can be obtained with good yield.

Normally, the activation is an oxidation reaction of carbon with an activation gas, and the carbon fiber surface is eroded to develop a microporous structure on the surface of the carbon fiber. Reactions utilizing existing nitrogen-containing functional groups (formation of micropores due to elimination of these functional groups,
(Formation of micropores due to the gas generated by the reaction between these functional groups and the activation gas), the activation temperature can be lower than the normal processing temperature (800-1000℃), resulting in a higher activation yield. It's also big.

Although the above description relates to coal tar pitch, the present invention is also applicable to petroleum-based pinches.

<Examples> Example 1 Coal tar pitch containing no quinoline insoluble matter (softening point -86.5°C, T I =15.6 wt%, Q1≦0.
01wt%, these pinch characteristic values are measured according to JIS
According to K2425. 1 part of dinitronaphthalene was added to 100 parts by weight and heat treated at 250°C for 15 minutes to obtain a precursor pitch for activated carbon fibers. When this precursor pitch is analyzed by infrared spectroscopy, it becomes 1525.
cm-' and 1358 cm-' absorption lines of the nitro group were observed, confirming the presence of the nitro group.

This precursor pitch is melt-spun, and further
After infusibility treatment at 80°C for 12 hours, the water vapor concentration was 15vo.
Activation treatment was performed at 700° C. for 11 hours in an atmosphere of 1% (residual N2). The activation yield (yield from infusible fibers to activated carbon fibers) was 55 wt%. The obtained activated carbon fiber was analyzed using the BET method using the N2 adsorption method (-195°C), and as a result, it had a specific surface area of 208 On (7 g). Furthermore, the pore distribution peaked at a pore diameter of 9.6. All pore diameters were 30 Å or less.

Example 2 Coal cool pitch containing no quinoline insoluble matter (softening point = 96.5°C, T l-18, 2wt%, Q+≦0.0
18 parts by weight of dinitrophenol was added to 100 parts by weight (1-t%) and heat treated at 330°C for 10 minutes to obtain a precursor pitch for activated carbon fibers.

This precursor pitch was melt-spun, and then spun in air for 3
After 11 hours of infusibility treatment at 00°C, the water vapor concentration was 10vo.
Activation treatment was performed at 700° C. for 130 minutes in an atmosphere of 1% (remaining NZ). The activation yield was 61 wt%.

The obtained activated carbon fiber had a specific surface area of 1580 rrf/g, and the pore distribution had a peak at a pore diameter of 8.2 mm, and all pore diameters were 30 Å or less.

Example 3 Coal tar pitch containing no quinoline insoluble matter (softening point = 60.5°C, T I = 9.6 wt%, Ql≦0.
15 parts by weight of nitrotoluene was added to 100 parts by weight (01-t%), and heat treated at 320°C for 30 minutes to prepare a precursor pinch for activated carbon fiber.

This precursor pitch is melt-spun, and further
After infusibility treatment at 90°C for 12 hours, the water vapor concentration was 10vo.
Activation treatment was performed at 600° C. for 12 hours in an atmosphere of 1% (remaining NZ). The activation yield was 65 wt%.

The obtained activated carbon fiber had a specific surface area of 1400r+ (7 g), and the pore distribution had a peak at a pore diameter of 8.9, and all pore diameters were 30 Å or less.

Comparative Example 1 The coal tar pitch used in Example 1, which does not contain any quinoline insoluble matter, was heat-treated at 380"C for 110 minutes to obtain precursor pitch for carbon fiber. This precursor pitch was melt-spun and further heated at 310°C in air. After infusibility treatment for 12 hours, activation treatment was performed at 900° C. for 11 hours in an atmosphere with a water vapor concentration of 33vo 1% (residual N2).

The activation yield was extremely low at 20 wt%, and the specific surface area of the obtained activated carbon fiber was 1800 po/g.

Comparative Example 2 0.5 parts by weight of dinitronafucrin was added to 100 parts by weight of the coal tar pitch containing no quinoline insolubles used in Example 1, and the mixture was heat-treated at 380°C for 110 minutes to obtain a precursor pitch for carbon fibers.

Although the carbon fibers were melt-spun, infusible and activated in the same manner as in Example 1, the specific surface area of the obtained carbon fibers was extremely low at 70 ho/g.

Comparative Example 3 1 part of dinitronaphthalene was added to 100 parts by weight of the coal cool pitch containing no quinoline insolubles used in Example 1, and heat treated at 250°C for 10 minutes.

When the obtained heat-treated pitch was observed under a polarizing microscope, many mesophase spherules were observed. This pinch could not be melt-spun and could not be made into fibers.

<Effects of the Invention> As described above, by adding an aromatic nitro compound to a coal tar pinch that does not substantially contain quinoline insoluble matter,
Precursor pitch for activated carbon fibers with a high activation yield can be produced by heat treatment at ~350''C.

Patent applicant: Kawasaki Steel Corporation

Claims (1)

[Claims] Adding 1 to 20 parts by weight of an aromatic nitro compound to 100 parts by weight of pitch that does not substantially contain quinoline-insoluble matter,
A method for producing precursor pitch for activated carbon fibers, the method comprising heat-treating at ~350°C.