JPS6367566B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for producing activated carbon fibers. Activated carbon has been industrialized for a long time and has been widely used as an adsorbent for removing impurities from liquids and gases, for recovering useful substances, and as a carrier for catalysts. Activated carbon that has long been used in these applications has been in the form of powder or granules, but in recent years fibrous activated carbon has been discovered, and its morphology and unique properties have further expanded the applications of activated carbon. However, the pores of conventionally obtained activated carbon fibers are mainly 30 Å or less in diameter;
Since the pore volume in the 30 to 300 Å region is less than 0.1 cc/g, it cannot be said to be a suitable material depending on the field of use. Of course, by appropriately selecting the starting carbonaceous fibers and the activation conditions, it is possible to increase the pore volume to 30 Å or more, but only brittle fibers with extremely low yields can be obtained. In view of these circumstances, the present inventors have arrived at the present invention as a result of intensive research. That is, the present invention provides carbon fibers with a surface area of 30 to 1200 m ² /g, a pore diameter of 30 to 300 Å, and a pore volume of 0.1 g/cc or less, which is made of magnesium, calcium, barium, iron, cobalt, nickel, or manganese. After supporting at least one type of compound,
Activation treatment is performed by heating at 650 to 1050℃ in oxidizing gas or combustion waste gas, and the pore diameter is 30 to 30.
The present invention relates to a method for producing activated carbon fibers having a 300 Å pore volume of 0.27 g/cc or more. The starting carbonaceous fiber used in the present invention is BET
Specific surface area is 30~1200m ² /g, and pore diameter is 30~
It is necessary that the carbon fiber has a 300 Å pore volume of 0.1 cc/g or less. Even if an activation aid described below is attached to a carbonaceous fiber having a BET surface area of 30 m ² /g or less, the effect of adding the activation aid of the present invention cannot be obtained. Meanwhile bet surface area 1200
If activated carbon fibers having a carbon fiber density of m ² /g or more are used as starting fibers, the yield of activated carbon fibers obtained by reactivation will be extremely low and only brittle ones will be obtained. The use of an activation aid is essential to the practice of the present invention. If no activation aid is used, even if reactivation is performed, only the pore volume of 30 Å or less will increase, and the pores of 30 to 300 Å will hardly increase. As the activation aid, periodic table group A elements such as magnesium, calcium, and barium, or
Compounds of transition metal elements such as iron, cobalt, nickel, and manganese are used. magnesium chloride,
Magnesium acetate, calcium chloride, chloride chloride
Water-soluble salts such as iron, cobalt chloride, nickel acetate, and manganese chloride are the easiest to use. The method for supporting the activation aid includes, but is not limited to, a method in which the starting carbon fiber is immersed in the aqueous solution of the compound, followed by dehydration, and then dried, or a method in which the aqueous solution of the compound is sprayed and then dried. The amount of the activation aid impregnated onto the carbonaceous fibers is preferably in the range of 0.01 to 40% by weight in terms of metal elements. If it is less than 0.01% by weight, it is difficult to obtain the effect of the activation aid, while if it is more than 40% by weight, the activation aid will block the existing pores and the effect of adding the activation aid will not be recognized, which is not preferable. The reactivation treatment in the present invention is performed by a method commonly used in the production of activated carbon, that is, in an oxidizing gas containing steam, carbon dioxide, etc., or in combustion waste gas.
A method of heating to ~1050°C can be applied. In order to effectively carry out the present invention, it is preferable to introduce water vapor at a temperature lower than the temperature at which the activation aid begins to decompose and sublimate. The reason why pores with a pore diameter of 30 to 300 Å are particularly enlarged when the activation aid of the present invention is used is that the reaction rate between the carbon and the activation gas around the activation aid attached to the walls of the micropores is greatly increased. This is thought to be due to the progress of expansion and coalescence of micropores. As the starting carbonaceous fiber used in the present invention, any form such as filament tow, nonwoven fabric, or woven fabric can be suitably used. The surface area of the carbonaceous fiber is calculated using the so-called BET method (Kei Tominaga "Adsorption" Kyoritsu Shuppan) from the adsorption isotherm of nitrogen gas at liquid nitrogen temperature. And the pore diameter and pore volume of fibrous activated carbon are
It was determined by the Cranston-Inkley calculation method (Keii Tominaga "Adsorption" Kyoritsu Shuppan) using the nitrogen gas adsorption isotherm on the adsorption side at the boiling point of liquid nitrogen (-195.8℃) under normal pressure. . However, the total pore volume is considered to be the value obtained by multiplying the amount of nitrogen gas adsorbed at a relative pressure corresponding to a pore diameter of 300 Å by the ratio of the density of gaseous nitrogen to the density of liquid nitrogen in standard conditions (1.584 × 10 ^-3 ). Also, the value obtained by subtracting the cumulative pore volume from the pore diameter of 300 Å to the pore diameter of 30 Å from the total pore volume was defined as the pore volume with a pore diameter of 30 Å or less. The relationship between the multimolecular adsorption layer and the relative pressure is Frenkel-Halsey, where t (Å) = 4.3 [5/ln (Ps/P)] ^1/3 .
Calculated from the formula (Kei Tominaga "Adsorption" Kyoritsu Shuppan). The fibrous activated carbon of the present invention has a pore diameter of 30 to 300 Å,
Since the volume of so-called transitional pores is larger than in conventional fibrous activated carbon, which is mainly composed of micropores with a diameter of 30 Å or less, gas molecules reach the inner surface of the activated carbon at a high speed. For this reason, harmful gas removal materials such as acetone, benzene, carbon tetrachloride, aldehyde, ozone, hydrogen sulfide, and sulfur dioxide,
It is effective for application in liquid phase systems such as methylene blue and phenol. It can also be used as a carrier for catalysts such as palladium, platinum, and silver, and is also effective in removing ozone and carbon oxides. The present invention will be explained in more detail below with reference to Examples, but the scope of the present invention is not limited to these Examples. Example 1 A 1.5-d cellulose fiber was impregnated with 10% by weight of ammonium phosphate, dried, and then heat-treated in an inert gas from room temperature to 300°C at a temperature increase rate of 60°C/h to produce a flame-resistant fiber. Obtained. This flame-resistant fiber was then heated to 900°C at a heating rate of 400°C/h in an inert gas.
The carbonaceous fibers (B) were taken out after cooling and holding for 30 minutes. Carbon fiber (B) is treated in an inert gas containing water vapor at 800℃ for 30 minutes to form activated carbon fiber (C).
I got it. Furthermore, the carbonaceous fiber (B) was treated in an inert gas containing water vapor at 900°C for 60 minutes to obtain an activated carbon fiber (D).
Further, the carbonaceous fiber (B) was treated in a nitrogen stream at 1200° C. for 3 hours to obtain a carbonaceous fiber (A). Table 1 shows the BET surface area and pore volume of these four types of carbon fibers.

[Table] Comparison of fibers (C) and (D) shows that when no activation aid is used, the pore volume of 30 to 300 Å hardly increases even if activation is advanced. Adding ferric chloride to carbonaceous fibers (A), (B), (C), and (D)
After adhering and drying as shown in the table, the temperature was raised to 850-900°C at a rate of 600°C/h, and reactivation treatment with water vapor was performed. The obtained activated carbon fiber M,
Table 2 shows the pore volumes of the four types, N, P, and Q. It can be seen that the volume of 30 to 300 Å pores of activated carbon fibers N, P, and Q has increased dramatically. However, compared to activated carbon fiber P, activated carbon fiber Q was brittle despite having a smaller pore volume. Also activated carbon fiber M
Further activation did not increase the pore volume between 30 and 300 Å.

[Table] Example 2 The activated carbon fiber (C) obtained in Example 1 was impregnated with 4.4% by weight of nickel chloride, and after drying, water vapor was added to the activated carbon fiber (C) from 200°C at a heating rate of 600°C/h from room temperature in a nitrogen stream. The fibers were introduced and brought to 850°C, and reactivated for 60 minutes at this temperature. After cooling, the fibers were taken out, washed with IN hydrochloric acid, washed with water, and dried to obtain activated carbon fibers. The 30-300 Å pore volume of this material was 0.35 cc/g. Example 3 The activated carbon fiber (C) obtained in Example 1 was impregnated with 4.2% by weight of cobalt chloride and reactivated in the same manner as in Example 2, resulting in an active carbon fiber with a pore volume of 30 to 300 Å of 0.38 cc/g. Carbon fiber was obtained. Example 4 The activated carbon fiber (C) obtained in Example 1 was impregnated with 7.0% by weight of manganese sulfate and reactivated in the same manner as in Example 2 to form pores with a pore diameter of 30 to 300 Å with an activation yield of 49%. Activated carbon fibers with a volume of 0.41 cc/g were obtained. Example 5 The activated carbon fiber (C) obtained in Example 1 was impregnated with 6.2% by weight of magnesium acetate, and reactivated in the same manner as in Example 2, resulting in a pore volume of 0.40 with a pore diameter of 30 to 300 Å.
cc/g of activated carbon fiber was obtained. Example 6 Oxine iron was added to the activated carbon fiber (C) obtained in Example 1.
9.1% by weight was impregnated and reactivated in the same manner as in Example 2 to obtain activated carbon fibers with a pore diameter of 30 to 300 Å and a pore volume of 0.33 cc/g. Example 7 A 1.5 denier acrylic fiber obtained by wet spinning a copolymer of 95 mol% acrylonitrile and 5 mol% methyl acrylate was heated from 150°C to 300°C at a heating rate of 1°C/min in an air atmosphere. The fibers were heat-treated to create flame-resistant fibers. Next, this flame-resistant fiber was heated from room temperature to 850°C at a rate of 400°C/h in a nitrogen stream, and then water vapor was introduced for 30 minutes to obtain activated carbon fiber. The 30-300 Å pore volume of this material was 0.07 cc/g. After impregnating 5.1% by weight of ferric chloride on this activated carbon fiber and drying it,
While increasing the temperature at a rate of 600°C/h, water vapor was introduced from 200°C to 850°C, maintained for 30 minutes, and then cooled in a nitrogen stream to obtain activated carbon fibers. The pore volume of this material from 30 to 120 Å is 0.33 cc/
It was hot at g. Example 8 Four types of activated carbon fibers C, D, obtained in Example 1,
70 parts by weight of N and P with 5% Pd catalyst supported on them, 30 parts by weight of wood pulp, and 5 parts of polyvinyl alcohol fiber are made into paper using a normal wet paper making method, and activated carbon supporting Pd catalyst is made. Four types of paper containing fiber were made. All of these papers have a basis weight of 50g/
m ² and thickness was 0.25 mm. Air containing 1.0 ppm of ozone at a temperature of 20°C and relative humidity of 50% was passed through the thickness of the mixed paper produced in this way at a superficial flow rate of 0.45 m/sec, and the initial ozone removal rate was measured. The results shown in 3 tables were obtained. The activated carbon fibers (N) and (P) according to the present invention are conventional activated carbon fibers.
Compared to (C) and (D), the ozone removal rate was extremely high.

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Claims (1)

[Claims] 1 Surface area is 30~1200m ² /g and pore diameter is 30~
Carbon fibers with a 300 Å pore volume of 0.1 cc/g or less are loaded with at least one compound selected from magnesium, calcium, barium, iron, cobalt, nickel, and manganese, and then subjected to oxidizing gas or combustion. A method for producing activated carbon fiber, which comprises performing an activation treatment by heating at 650 to 1050°C in waste gas.