JPH09248456A - Molecular sieve activated carbon fiber having selective adsorbing capacity and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adsorbent excellent in selective adsorbing activity and having molecular sieve capacity by thermally polymerizing a compd. having a specific molecular size and thermal polymerization reactivity within pores of activated carbon fibers. SOLUTION: Activated carbon fibers wherein the greater part of pores are micropores of 2mm or less are used and an aromatic compd. containing atoms selected from carbon, hydrogen, nitrogen, sulfur and oxygen such as benzene or toluene is thermally polymerized within the pores of activated carbon fibers. For example since, a carbocylic compd. has a planar molecular structure, it is laminated and adsorbed on the wall surfaces of pores of activated carbon fibers in a planar state. Subsequently, when these activated carbon fibers are heated, the adsorbed aromatic compd. such as benzene is thermally polymerized and carbonized to be deposited. By this method, an adsorbent narrowed and controlled in its pore size and showing excellent selectivity even to a mixture approximate in molecular size such as oxygen/nitrogen and having the selectivity of properties caused by atoms deposited to pores is obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an activated carbon fiber which selectively adsorbs only specific molecules from a mixture.

More specifically, the activated carbon fiber according to the present invention is useful in the production of high-purity oxygen, nitrogen, argon, etc. by air separation; various gas separation purification / production by selective adsorption separation of carbon dioxide and methane, etc. Is. Further, the activated carbon fiber according to the present invention is used for gas treatment such as selective adsorption / separation and removal of acid gases such as nitrogen dioxide, sulfur dioxide and hydrogen chloride in exhaust gas of exhaust gas from chemical plants, selective adsorption / separation of metal ions, etc. It is also useful in technology. further,
Activated carbon fiber according to the present invention, halogen in tap water, adsorption removal of halogenated hydrocarbons, acidic ions in wastewater,
It is also useful in water purification such as adsorption removal of metal ions. Furthermore, the activated carbon fibers according to the present invention also exert a catalytic function based on basicity.

[0003]

2. Description of the Related Art Conventionally, zeolite-based substances (MSZ-5A) have been used as substances having a molecular sieve action.
Etc.) and molecular sieve carbon (molecular sieving carbon, MSC-5A, etc.) are known. Of these, for molecular sieving carbon (MSC), 1948
In the year PHEmmet, Chem. Rev., 43, 69 (194
Since 8) reported the molecular sieving ability of Saran coal, there are many reports. After that, products that were commercialized were Takeda Pharmaceutical Co., Ltd.'s products (see Japanese Patent Publication No. 49-37036), West Germany.
There is a product of Bergbau Forshung (see Japanese Patent Publication No. 52-18675).

These production methods are classified into the following five types: (1) a thermal decomposition method of a resin or the like, (2) an activation method using a carbide as a raw material, and (3) an organic substance using a carbide or an activated carbon as a raw material. After impregnating with, heat treatment, (4) CVD method using carbide or activated carbon as a raw material, and (5) heat shrinking method using carbide or activated carbon as a raw material.

However, in the conventional MSC production, a technique for precisely controlling the pore diameter to a certain value has not been established. The reason for this is that in the thermal decomposition method of resins, plastics (saran, polyvinylidene chloride, phenol resin, urea resin, etc.) are only carbonized at 600 to 900 ° C, which is a method far from pore control. The activation method is also a method of mildly activating the carbide with steam or carbon dioxide at 700 to 800 ° C., and it is difficult to precisely control it.

In the method of impregnating a raw material such as carbide or activated carbon with an organic substance or by CVD, the pore controllability is improved to some extent, but the distribution of the pore diameter of the raw material itself is 0.5 to 500 nm.
As described above, it is almost impossible to obtain uniform and wide pores.

Further, in the conventional impregnation method, coal tar pitch, resins and the like are used as the impregnating agent.
In the CVD method, benzene, toluene, styrene, etc. are vapor-deposited, but none of them was a technology for imparting the characteristics of their chemical functional groups to molecular sieve coal.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has used activated carbon fiber as a base material and activated a compound having a specific molecular size and thermal polymerization reactivity. We succeeded in producing an adsorbent having excellent selective adsorption ability and molecular sieve performance by thermally polymerizing and depositing in the pores of carbon fiber.

That is, the present invention provides a molecular sieve activated carbon fiber having the following selective adsorption ability and a method for producing the same: An aromatic compound containing carbon atoms and at least one atom selected from the group consisting of hydrogen, nitrogen, sulfur and oxygen is thermally polymerized in pores of 2 nm or less of the activated carbon fiber,
A molecular sieve activated carbon fiber with selective adsorption ability deposited.

[0010] 2. Item 2. The activated carbon fiber according to Item 1, wherein the pore size is arbitrarily controlled by the molecular thickness of the aromatic compound.

3. Item 3. The activated carbon fiber according to Item 1 or 2, which has selective performance due to a nitrogen atom and / or a sulfur atom and / or an oxygen atom in the carbon compound deposited in the pores.

4. Within the pores of 2 nm or less of activated carbon fiber,
Molecular sieve activated carbon fiber having selective adsorption ability, characterized by thermally polymerizing and depositing an aromatic compound containing carbon atoms and at least one atom selected from the group consisting of hydrogen, nitrogen, sulfur and oxygen. Manufacturing method.

5. Item 5. The method for producing activated carbon fiber according to Item 4, wherein the pore size is arbitrarily controlled by the molecular thickness of the aromatic compound.

6. Item 6. The method for producing activated carbon fiber according to Item 4 or 5, wherein the aromatic compound is monocyclic or bicyclic.

[0015] 7. 7. The method for producing activated carbon fiber according to any one of items 4 to 6, wherein the aromatic compound is pyridine.

8. Item 8. The method for producing an activated carbon fiber according to any one of Items 4 to 7, wherein the thermal polymerization is performed at a temperature of 600 to 800 ° C.

9. Item 9. The method for producing an activated carbon fiber according to Item 8, wherein the thermal polymerization is performed at a temperature of 650 to 750 ° C.

10. 10. The method for producing an activated carbon fiber according to any one of items 4 to 9, wherein the thermal polymerization and the deposition are stopped at the time when the invasion of the aromatic compound into the activated carbon fiber pores is stopped due to the molecular size.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, since activated carbon fiber having a structure different from that of conventional activated carbon is used as a base material, the pores of the base material itself are extremely uniform. FIG. 1 shows a comparison between activated carbon fibers used in the present invention and conventional granular activated carbon.

The conventional granular activated carbon has a wide pore size distribution ranging from micropores of about 0.5 nm to macropores of 500 nm or more. On the other hand, the activated carbon fiber used in the present invention has most of the pores composed of micropores of 2 nm or less and has a uniform pore distribution, so that the compound is heated in the pores. By polymerizing and depositing, a molecular sieve activated carbon fiber having a very uniform pore distribution can be obtained.

Further, by using an aromatic compound as the compound to be deposited, the pore size can be precisely controlled by the mechanism shown in FIG. As the aromatic compound, a monocyclic or bicyclic compound is suitable in terms of its molecular size and thermal polymerization reactivity, and more specifically, benzene, toluene, xylene, ethylbenzene, styrene, naphthalene, pyridine, Methylpyridine, quinoline and the like are particularly useful. In Fig. 2, benzene is illustrated as an example of the compound to be deposited, but such a carbocyclic compound has a planar molecular structure and a molecular diameter of 0.
The thickness is 7 nm and the molecular thickness is 0.37 nm. When this is adsorbed in the pores of the activated carbon fiber having a diameter of 2 nm or less, it is planarly adsorbed on the inner wall surface of the pore (first step).

Therefore, the pore diameter can be arbitrarily controlled by the molecular thickness of the compound to be deposited. Further, after the pore diameter is narrowed to the molecular thickness or less, the deposition compound cannot enter and the reaction is stopped.

Next, 600 to 800 activated carbon fibers having the molecules of the aromatic compound such as benzene deposited as described above are prepared.
By heating at a temperature of ° C, the adsorbed molecules of the aromatic compound such as benzene are thermally polymerized, carbonized, and deposited. This is non-graphitizable carbon (second stage).

When the heating temperature is lower than 600 ° C., the reaction rate becomes very slow even if the aromatic compound does not heat-polymerize or heat-polymerizes. On the other hand, when the heating temperature exceeds 800 ° C, thermal polymerization occurs in the vapor phase before the aromatic compound reaches the inside of the activated carbon fiber pores, which covers the outer surface of the activated carbon fiber. Since the pores are blocked, the molecular sieving ability is not expressed at all.

The molecular sieve-activated carbon fiber obtained as described above has a narrow pore size and is controlled, so that gases having similar molecular sizes such as oxygen / nitrogen, carbon dioxide / methane, etc. It also exhibits excellent selective adsorptive separation performance even for a mixture containing.

Furthermore, by using an aromatic compound containing at least one atom of hydrogen, nitrogen, sulfur and oxygen as the compound to be deposited, the nitrogen atom and / or the sulfur atom of the carbon compound deposited in the pores and It is possible to produce a molecular sieve activated carbon fiber having selective properties such as basicity, metal coordination ability, and catalytic function due to oxygen atoms.

For example, an aromatic compound containing a nitrogen atom is suitable for producing a basic molecular sieve activated carbon fiber, and more specific examples thereof include pyridine, methylpyridine and quinoline. Among these, pyridine is particularly effective. That is, due to the effect of the nitrogen functional group derived from pyridine, basicity can be imparted to the activated carbon fiber, the adsorption performance of acidic gas such as sulfur dioxide is dramatically improved, and the catalytic function is remarkably exhibited.

[0028]

EXAMPLES Examples are shown below to further clarify the features of the present invention.

Example 1 A Cahn balance device 7 shown in FIG. 3 was used to deposit an aromatic compound on an activated carbon fiber (hereinafter referred to as ACF) to have a selective adsorption ability. A molecular sieve activated carbon fiber was prepared.

That is, a pitch type ACF (trade name "OG-20A" manufactured by Osaka Gas Co., Ltd.) is used as the ACF, and its 0.2 to 0.3
The quartz basket 10 was filled with g, and 150 ml / mim of helium was passed from the carrier gas cylinder 1 through the pipe 2 into the system. Next, a tubular furnace 9 was attached so as to surround the quartz basket 10, the temperature was raised from room temperature to a predetermined temperature at 10 ° C./min, and the temperature was maintained at the predetermined temperature for 1 hour. Then, pyridine was introduced from the microsyringe 5. The amount of pyridine deposited with respect to ACF was confirmed by a balance. After the pyridine was precipitated to a predetermined amount, its introduction was stopped, and then it was cooled to room temperature by air.

In the entire apparatus shown in FIG. 3, 3 is a three-way cock, 4 is a stop valve, 6 is a heater, and 8 is a frame.

FIG. 4 shows the change with time in the precipitation of pyridine. Almost no pyridine was precipitated at a temperature of 400 ° C and 500
Even at ℃, 600 ℃ and 650 ℃, the weight increase due to precipitation is very slow. However, if you raise the temperature to 700 ° C, after 180 minutes
There was precipitation of 30% (= 300 mg / g · AFC). In addition, 725
When it was precipitated at ℃, it reached saturation in about 120 minutes, 45% precipitation occurred, and thereafter the amount of precipitation does not increase.

The deposition location of ACF in which pyridine was deposited at 725 ° C. was divided into four stages of Points 1 to 4, and a sample was taken out and analyzed. The results are shown in Table 1.

[0034]

[Table 1]

In Table 1, Points 1, 2, 3 and 4
Is the amount of precipitated carbon derived from pyridine, 8, 16, 25 and 4 respectively.
This corresponds to the sample at 5%. Specific surface area (m ² /
The data of g), pore volume (ml / g) and average pore diameter (nm) were measured by the nitrogen adsorption BET method using an “ASAP2400” measuring device manufactured by Shimadzu Corporation.

From the results shown in Table 1, the specific surface area, the pore volume and the average pore diameter decreased as the amount of pyridine deposited increased, and the deposition and precipitation of pyridine occurred in the ACF pores. Was confirmed. In particular, Point
When carbon was deposited to 45% saturation of No. 4, the pore size was narrowed to 0.47 nm, and further deposition of carbon did not occur.

Example 2 With respect to ACF (“OG-20A” manufactured by Osaka Gas Co., Ltd.) in which 11% of carbon derived from pyridine was deposited at 725 ° C., an adsorption isotherm of carbon dioxide and methane at 760 Torr and room temperature was plotted. 5 shows.

Carbon dioxide is rapidly adsorbed in about 3 minutes, and 35 ml of carbon dioxide is adsorbed on 1 g of ACF. On the other hand, since methane is hardly adsorbed, it is clear that only carbon dioxide can be selectively adsorbed and separated from the carbon dioxide / methane coexisting gas.

Example 3 For ACF (“OG-20A” manufactured by Osaka Gas Co., Ltd.) in which 11% of carbon derived from pyridine was deposited at 700 ° C., adsorption isotherms of oxygen and nitrogen at 760 Torr and room temperature are shown in FIG. Shown in. Oxygen is rapidly adsorbed in about 3 minutes, and 4.5 ml of oxygen is adsorbed on 1 g of ACF. On the other hand, since the adsorption of nitrogen is slow, it is clear that only oxygen can be selectively adsorbed and separated from the air.

Example 4 and Comparative Example 1 Table 2 shows ACF in which 20% of pyridine-derived carbon was deposited at 725 ° C.
About "OG-20A" manufactured by Osaka Gas Co., Ltd., 760Torr, 3
Table 2 shows the saturated adsorption amount of sulfur dioxide at 0 ° C.
Table 2 shows the same amount of adsorption to untreated ACF as Comparative Example 1.

[0041]

[Table 2]

The total adsorption amount of the molecular sieve activated carbon fiber according to the present invention is more than doubled as compared with the untreated ACF.

In Table 2, the physical adsorption amount is the number of the total adsorption amount, and is the amount of sulfur dioxide desorbed when the ACF is heated to 150 ° C. after saturated adsorption. This value is. The precipitation of carbon increased about 1.6 times.

The chemical adsorption amount is the amount of sulfur dioxide adsorbed more strongly than physical adsorption. It is the number of total adsorption amount and is the amount of sulfur dioxide desorbed when ACF is heated to 400 ° C. after saturated adsorption. Is the amount. This value increased 13 times or more when carbon was deposited. That is, AC in which carbon derived from pyridine is deposited
In F, the nitrogen atom of pyridine remains as a nitrogen functional group and exhibits basicity, and thus strongly adsorbs acidic sulfur dioxide.

Example 5 and Comparative Examples 2 to 3 FIG. 7 shows the change over time in the precipitation of benzene when the activated carbon fiber was treated in the same manner as in Example 1. Almost no precipitation of benzene occurs at a temperature of 400 ° C, and the weight increase due to precipitation is very slow even at 500 ° C and 600 ° C. However, the temperature
When the temperature is raised to 700 ° C, 10% (= 100mg / g ・ AC) after 120 minutes
There was precipitation of F).

Furthermore, when precipitation was carried out at 725 ° C. and 800 ° C. respectively, saturation was reached in 45 minutes and 30 minutes, respectively, and
% Precipitation occurs and thereafter does not increase.

However, if the temperature is raised to 900 ° C.,
The amount of precipitation exceeds 10%, increases with time and does not converge. This is because the carbon derived from benzene that was thermally polymerized in the gas phase
This is because it will be deposited on the surface of the ACF.

In FIG. 7, an ACF in which 10% of benzene-derived carbon was deposited at 725 ° C. for 60 minutes was designated as Example 5, and the same 10% of ACF deposited at 900 ° C. for 40 minutes was compared. Example 2 and untreated ACF as Comparative Example 3
FIG. 8 shows adsorption isotherms of carbon dioxide and methane at 60 Torr and room temperature.

ACF (Comparative Example 2) carbon-deposited at 900 ° C. had low adsorption amounts of carbon dioxide and methane,
It is lower than the value of untreated ACF of Comparative Example 3, and the gas species selectivity is low.

The untreated ACF of Comparative Example 3 has a large carbon dioxide adsorption amount of 37.3 ml / g, but also has a methane adsorption amount of 1%.
As large as 5.8 ml / g, selectivity (carbon dioxide / methane)
However, it is as low as 2.36, and the molecular sieve performance is not expressed.

On the other hand, the ACF precipitated in Example 5 at 725 ° C.
Has a carbon dioxide adsorption capacity of 32 ml / g, but has a methane adsorption capacity of only 1 ml / g, which is selective (carbon dioxide / methane).
However, it is extremely high at 32 and exhibits excellent molecular sieve performance.

[Brief description of drawings]

FIG. 1 is a diagram showing characteristics of activated carbon fibers and granular activated carbon in comparison.

FIG. 2 is a schematic diagram showing a process in which benzene is deposited on activated carbon fibers, thermally polymerized, and deposited.

FIG. 3 is a schematic cross-sectional view showing an apparatus for depositing and depositing an aromatic compound on activated carbon fibers used in Examples.

FIG. 4 is a graph showing changes in the precipitation of pyridine in Example 1.

FIG. 5 is a graph showing adsorption isotherms of CO ₂ and CH ₄ of the molecular sieve activated carbon fiber of the present invention in Example 2.

FIG. 6 is a graph showing adsorption isotherms of O ₂ and N ₂ of the molecular sieve activated carbon fiber of the present invention in Example 3.

FIG. 7 is a graph showing changes over time in benzene precipitation in Example 5 and Comparative Example 2.

FIG. 8 is a graph showing adsorption isotherms of CO ₂ and CH ₄ of activated carbon fibers in Example 5 and Comparative Examples 2 and 3.

[Explanation of symbols]

 1 ... Carrier gas cylinder 2 ... Piping 3 ... Three-way cock 4 ... Stop valve 5 ... Micro syringe 6 ... Heater 7 ... Cahn balance 8 ... Frame 9 ... Tubular furnace 10 ... Quartz basket

Claims (10)

[Claims] 1. An aromatic compound containing carbon atoms and at least one atom selected from the group consisting of hydrogen, nitrogen, sulfur and oxygen is thermally polymerized in pores of 2 nm or less of activated carbon fiber, A molecular sieve activated carbon fiber with selective adsorption ability deposited. 2. The activated carbon fiber according to claim 1, wherein the pore size is arbitrarily controlled by the molecular thickness of the aromatic compound. 3. The activated carbon fiber according to claim 1, which has selective performance due to nitrogen atoms and / or sulfur atoms and / or oxygen atoms in the carbon compound deposited in the pores. 4. An aromatic compound containing carbon atoms and at least one atom selected from the group consisting of hydrogen, nitrogen, sulfur and oxygen is thermally polymerized in pores of 2 nm or less of activated carbon fiber, A method for producing a molecular sieve activated carbon fiber having selective adsorption ability, which comprises depositing. 5. The method for producing activated carbon fiber according to claim 4, wherein the pore size is arbitrarily controlled by the molecular thickness of the aromatic compound. 6. The method for producing activated carbon fiber according to claim 4, wherein the aromatic compound is monocyclic or bicyclic. 7. The method for producing activated carbon fiber according to claim 4, wherein the aromatic compound is pyridine. 8. The method for producing an activated carbon fiber according to claim 4, wherein the thermal polymerization is carried out at a temperature of 600 to 800 ° C. 9. The method for producing activated carbon fiber according to claim 8, wherein the thermal polymerization is carried out at a temperature of 650 to 750 ° C. 10. The activated carbon fiber according to claim 4, wherein the thermal polymerization and the deposition are stopped at the time when the invasion of the aromatic compound into the activated carbon fiber pores is stopped by its molecular size. Production method.