JPH10314588A - Active carbon catalyst and flue gas desulfurization process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active carbon catalyst of superior desulfurization efficiency for carrying out the flue gas desulfurization of superior economic efficiency by applying water-repellent treatment to active carbon composed of coal as a main raw material. SOLUTION: This active carbon catalyst is used for oxidizing sulfurous acid gas in flue gas by coexisting oxygen in flue gas and recovering and removing the gas as sulfuric acid, and the catalyst is prepared by applying water repellency treatment to active carbon composed of coal as a main material. In the case of water repellency treatment, it is preferable to select a water-repellent polymer substance not modifying micropores of active carbon for the purpose of developing high activities. As the repellent substance, polyethylene, polypropylene, polystyrene, fluororesin or the like can be used. As for the repellency treatment for the active carbon of coal family, a process of melting the repellent substance in an organic solvent and impregnating the active carbon of coal family with the solvent and deposit the solvent on the active carbon or a process of impregnating active carbon of coal family with a dispersion of repellent substance of average particle diameter of 15-100 nm and deposit the dispersion on the active carbon is utilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an activated carbon catalyst for recovering and removing sulfur oxides contained in exhaust gas as sulfuric acid by a catalytic sulfation reaction, and to a flue gas desulfurization method using the same.

[0002]

2. Description of the Related Art Heretofore, sulfur oxides such as sulfurous acid gas contained in exhaust gas have been oxidized by coexisting oxygen at a low temperature to finally produce sulfuric acid, which can be used as it is as sulfuric acid, or can be combined with calcium compounds. The process of recovering as gypsum by reacting is known.
Activated carbon is said to be the most preferable catalyst for oxidizing sulfurous acid gas and the like in exhaust gas. That is, when a ceramic-based carrier such as alumina, silica, titania, or zeolite is used as the above catalyst, the activity alone is insufficient, so it is necessary to add a metal or metal oxide as a catalyst species to this. is there. However, these catalyst species have a drawback that they cannot maintain stable activity for a long period of time because they are attacked by generated sulfuric acid and are dissolved or deteriorated. On the other hand, the activated carbon has a feature that the activity is exhibited without carrying any catalyst species and the activity is maintained without deterioration for a long time.

However, in the case of industrial use as a flue gas desulfurization apparatus, when commercially available activated carbon is used as it is, the catalytic activity in the catalytic sulfation reaction is low.
In order to obtain a desired desulfurization effect, the amount of catalyst charged becomes extremely large, and therefore, there is a problem that it cannot be economically competitive as compared with other desulfurization processes such as a wet flue gas desulfurization process. Therefore, there are roughly two approaches for increasing the catalytic activity of activated carbon used in such a flue gas desulfurization process. One is to increase the active sites of adsorption and oxidation reaction of sulfurous acid gas, and the other is to discharge the sulfuric acid generated in the pores of activated carbon out of the pores as soon as possible. is there.

In the former approach, it is necessary to determine what the active sites of adsorption and oxidation of activated carbon to sulfur dioxide gas are. In this regard,
For example, the Chemical Society of Japan (1975) No. 10, P1705-1712 suggests that it is a basic surface compound.
plied Catalysis B: Environmental 3 (1994) P229-23
In No. 8, it is suggested that the number of strong basic points on the activated carbon is proportional to the adsorption and oxidation activities of sulfurous acid gas, and that the basic points are oxygen-containing functional groups. And
In particular, the former document describes that the activation and activation of sulfur dioxide gas can be increased by activating activated carbon at 800 ° C. with ammonia gas.
However, neither document describes at all what activated carbon can be selected to achieve high activity, and thus the approach has not yet reached a practical application.

Regarding the other approach, the activity of sulfur dioxide adsorption and oxidation of activated carbon (hereinafter simply referred to as activity) is very large unless the exhaust gas contains moisture. However, the product sulfuric acid has a very high hygroscopicity, so in the presence of water vapor, it absorbs water on the activated carbon surface to generate dilute sulfuric acid, which fills the pores of the activated carbon to form sulfurous acid gas. As a result of impeding the diffusion and contact, the surface activity of the activated carbon is not sufficiently exerted. Therefore, various methods have been proposed for imparting water repellency to activated carbon and quickly discharging the generated sulfuric acid from the pores of the activated carbon to maintain the high activity of the activated carbon.

For example, Chem. Eng. Comm. Vol. 60 (1987),
P253 is sprayed with a dispersion of polytetrafluoroethylene (hereinafter abbreviated as PTFE) on activated carbon having an average diameter of 0.78 mm, thereby adsorbing and oxidizing sulfurous acid gas in a region where the amount of PTFE added is 8 to 20%. An example is disclosed in which the rate constant of the reaction has increased three-fold. Japanese Unexamined Patent Publication (Kokai) No. 59-36531 discloses that a water-repellent treatment is applied to activated carbon to increase the activity of adsorbing and oxidizing sulfurous acid gas. Specifically, a PTFE dispersion liquid is applied to granular activated carbon of 5 to 10 mm. It is disclosed that by impregnating and heat-treating at 200 ° C. for 2 hours, the catalyst exhibits a much higher activity than activated carbon alone.

[0007]

The present inventors conducted the following confirmation experiments in order to verify such a two-way approach for increasing the activity of activated carbon as a conventional catalyst. First, one approach is to adsorb sulfur dioxide on activated carbon and try to increase the oxidation point, without being bound by the limited idea of adding a basic point. I tried surface treatment. Here, when an acid or an alkali was used as the surface treatment agent, it and the activated carbon were boiled. Further, gas treatment with high-temperature HBr, HCl, ammonia or the like was also attempted. Further, a method was studied in which a small amount of a reducing gas (hydrogen) or an oxidizing gas (fluorine, chlorine, oxygen) was mixed into a gas such as steam or CO ₂ to perform a high-temperature treatment at 800 ° C. As a result, the high temperature treatment with ammonia gas exhibited the highest activity, but after several hundred hours of operation, the activity was reduced to a level equivalent to that of untreated activated carbon. In contrast, steam, CO ₂
In the method in which a small amount of oxygen is mixed in an activation gas such as that described above and the high-temperature treatment is carried out, the activity improving effect is maintained for a long time, but the activity improving width is small and the initial target could not be attained.

Next, the present inventors conducted verification on the other approach, that is, water repellency of activated carbon. First,
Based on the above-mentioned conventional water-repellent technology, it is considered that the water-repellent treatment of activated carbon having many active sites for adsorption and oxidation is most effective for improving the activity of the catalytic sulfation reaction. .
PTFE was supported on various types of commercially available activated carbon having a particle size range of 0 mmφ by the spray method or the impregnation method, and the activity was measured. Persistence was observed.
However, considering large-scale industrial practice, this level of activity as a catalyst is still not sufficient to surpass other competing flue gas desulfurization processes, and further improvement in catalytic activity Recognized that it is necessary.

As the activated carbon used as this type of catalyst, wood, lignite, etc. are treated with a chemical as an activator, or charcoal is activated with steam, or coal is used as a raw material. Various types of activated carbon, such as those using coconut shells and those using peat or petroleum pitch as a raw material, are known. Therefore, the present inventors,
By changing the viewpoint from the above approach, the activated carbon itself was used as a prerequisite for confirming whether or not the activation effect would be different when the water-repellent treatment was performed due to the difference in the raw materials. The change in activity before and after the chemical treatment was compared. As a result, by the water repellent treatment, the activated carbon catalyst using coal as a main raw material, in particular, exhibited high activity, while activated carbon using other coconut shells, peat, petroleum pitch, etc. as the raw material. It has been found that the catalyst has a much lower activity. As described above, it is not clear why activated carbon using coal as a raw material shows superiority when subjected to a water-repellent treatment, but it can be estimated as follows at this stage.

That is, it is considered that activated carbon of coal system has a larger number of active sites for adsorption and oxidation of sulfurous acid gas than activated carbon originally made of other raw materials. However, coal-based activated carbon is inferior in hydrophobicity to activated carbon made of other raw materials, so that the generated sulfuric acid is discharged slowly, and as a result, the overall activity is not considered to be so high. Therefore, when water-repellent treatment is applied to this, the superiority of activated carbon is determined only by the number of active points, and it is considered that the excellent activity in the original coal-based activated carbon was remarkably exhibited. . From the above, it can be said that a flue gas desulfurization process excellent in the performance of oxidizing and removing sulfur oxides in exhaust gas can be developed by using an activated carbon catalyst obtained by performing water repellent treatment on activated carbon made of coal as a main raw material. The present invention has been completed.

[0011] Then, the present inventors, in addition to the activated carbon using coal as a main raw material, in general various activated carbon,
In order to further enhance the activity of the activated carbon by making it water-repellent, it was examined which part of the activated carbon was effective to make it water-repellent. First, the distribution of fluorine in the activated carbon catalyst prepared by the conventional method of spray-supporting or impregnating the PTFE dispersion on activated carbon was analyzed by EPMA. As a result, it was found that the PTFE particles did not penetrate into the activated carbon particles at all, and were all attached to the outer surfaces of the particles. This is because commercially available activated carbon hardly has pores of 1 μm or more, and thus has a diameter of 0.2 to 0.4.
It is considered that the resistance is too large for the PTFE particles in the range of μm to enter the pores. By the way,
Similar experimental results were obtained when a dispersion of polystyrene particles having an average particle size of 0.3 μm was used instead of the PTFE dispersion. Then, when an activity test was performed on the activated carbon catalyst supporting these two types of water-repellent particles, it was found that the activated carbon catalyst supporting PTFE had slightly higher activity than the activated carbon catalyst supporting polystyrene particles. However, none of them exhibited the expected high activity.

The inventors of the present invention hope that uniform discharge of the entire surface of the activated carbon including the vicinity of the active point will greatly promote the discharge of the produced sulfuric acid. The entire surface including the pores having a pore diameter of (hereinafter abbreviated as micropores) is subjected to a water-repellent treatment. As a first method, 100 to 4
Various activated carbon catalysts having different surface fluorination degrees were prepared by flowing an appropriate amount of fluorine gas at 00 ° C. As a second method, stearic acid, a styrene oligomer (average molecular weight of about 320), a fluorine-containing oil (average molecular weight of about 500) and the like, which are small water-repellent substances, are dissolved in a suitable low-boiling solvent, Activated carbon was immersed under reduced pressure, the solution was sufficiently penetrated into the pores, and then dried under reduced pressure to evaporate the solvent, thereby coating the inside of the activated carbon pores with a water-repellent substance. The specific surface area of the activated carbon catalyst prepared in this manner is within an apparent decrease range due to an increase in weight due to the support of the water-repellent substance, and these supports may block or destroy the pores. Not confirmed.

[0013] Next, 1 to 3 obtained by the first method
Using various activated carbon catalysts having a fluorination rate of 20%,
As a result of the sulfur dioxide gas reaction activity test, it was found that the water repelling property gradually increased as the fluorination rate increased. It floats gently and takes the average value of the sedimentation start time and sedimentation end time, which is a simple method for relative comparison of water repellency.)
It was found that the sulfuric acid gas adsorption and oxidation activities decreased rather in inverse proportion to the increase in the fluorination rate. Also, the second
In the activated carbon catalyst supporting stearic acid, styrene oligomer, fluorinated oil, and the like obtained by the method described above, the water repellency was similarly increased by the water surface floating time test as the supported amount increased. Although observed, the sulfur dioxide adsorption and oxidation activity only slightly exceeded the catalytic activity of activated carbon alone in the addition region of 0.5 to 2%, and the activity rapidly decreased as the amount of addition increased. It turns out.

From the above, it is presumed that the full water repellency of activated carbon, including the micropores, would not be able to obtain a sufficient activity improving effect because it would cover or destroy active sites for adsorption and oxidation of activated carbon. did. Therefore, the present inventors have proposed that the activated carbon micropores are not made water-repellent, but are macropores (5 nm).
(Pores having a pore diameter exceeding) was attempted to be water-repellent. First, a polyethylene or polystyrene powder having a molecular weight of 100,000 or more is dissolved in toluene heated to 60 to 70 ° C. by several percent, and activated carbon particles are immersed under reduced pressure. Scattered. The activated carbon catalyst thus obtained showed a considerable improvement in activity when the water-repellent substance was loaded in the range of 0.3 to 1.5% by weight based on the raw material activated carbon. This is because if polyethylene or polystyrene having a molecular weight of 100,000 or more is spherical and dispersed in a toluene solvent, its diameter becomes 7 nm or more even if it does not swell in the solvent. Not the size you can do. Therefore, it should be considered that the activated carbon catalyst makes the macropores and the outer surface of the activated carbon particles water-repellent. And, as described above, in this reaction system, the water repellency of the outer surface of the activated carbon does not significantly contribute to the improvement of the reaction activity. It is inferred that it contributes to

Therefore, even in the case where the activated carbon catalyst obtained by subjecting the above-described activated carbon made of coal as a main raw material to a water-repellent treatment is used, the macropores other than the micropores in the activated carbon raw material are further treated as the water-repellent treatment. This led to the finding that it is possible to develop a flue gas desulfurization process that is more excellent in the performance of removing sulfur oxides by oxidation. The present invention has been made on the basis of such knowledge, and the activated carbon catalyst which enables flue gas desulfurization which is comparable in desulfurization efficiency as compared with other flue gas desulfurization processes and is therefore more economical, and a flue gas using the same. It is an object of the present invention to provide a smoke desulfurization method.

[0016]

According to the first aspect of the present invention, an activated carbon catalyst according to the present invention is brought into contact with an exhaust gas containing a sulfur oxide to adsorb and oxidize the sulfur oxide to recover and remove the sulfur oxide as sulfuric acid. Activated carbon using coal as a main raw material is subjected to a water-repellent treatment. Here, the invention according to claim 2 is characterized in that the activated carbon has been subjected to a water-repellent treatment except for its micropores.

Further, the inventions according to claims 3 to 5 are embodiments of the water repellent treatment in the invention described in claim 2, respectively. 5. A method according to claim 4, wherein a high molecular weight water repellent substance having a molecular weight of 10,000 or more is dissolved in an organic solvent and impregnated and supported on the activated carbon. In the activating treatment, the activated carbon is impregnated and supported with a dispersion of a water-repellent substance having an average particle size of 15 to 100 nm. Further, the invention according to claim 5 is characterized in that the activated carbon powder is kneaded and formed with fluororesin particles having an average particle diameter of 0.1 to 1.0 μm or a dispersion thereof. And the flue gas desulfurization method according to the present invention according to claim 6 is characterized in that the activated carbon catalyst according to any one of claims 1 to 5 is brought into contact with an exhaust gas containing a sulfur oxide, whereby The method is characterized in that the sulfur oxide is adsorbed and oxidized on the activated carbon catalyst, and is recovered and removed as sulfuric acid.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of an activated carbon catalyst according to the present invention will be specifically described. The activated carbon catalyst according to the present invention is used for recovering and removing sulfuric acid as sulfuric acid by oxidizing sulfurous acid gas in exhaust gas by coexisting oxygen, and is obtained by subjecting activated carbon mainly made of coal to a water-repellent treatment. It is. Here, when performing the above-mentioned water-repellent treatment, it is preferable to select a high-molecular-weight water-repellent substance that does not modify the micropores of the activated carbon as described above in order to exhibit high activity. Examples of such a water-repellent substance include polyethylene, polypropylene, polystyrene, and fluorine resin. Further, as the water-repellent treatment for the coal-based activated carbon, a method of dissolving the water-repellent substance in an organic solvent and impregnating and supporting the coal-based activated carbon while utilizing the shape of the raw activated carbon as it is, 15 to 100 nm of the dispersion of the water-repellent substance,
There is a method of impregnating and supporting the above-mentioned coal-based activated carbon. In the case of performing the water-repellent treatment by utilizing the shape of the raw material activated carbon as it is, the latter method can obtain the highest activity, and the preferable addition amount of the water-repellent substance at that time is based on the raw material activated carbon. , 0.2 to 3% by weight.

Further, the raw activated carbon is not directly subjected to the water-repellent treatment, but the activated carbon powder is used, and the activated carbon powder is mixed with fluororesin particles having an average particle size of 0.1 to 1.0 μm or a dispersion thereof. Can be kneaded and molded to obtain a water-repellent activated carbon catalyst. In this case, as the fluororesin used, in addition to the above-mentioned PTFE, a perfluoroalkoxy resin (PFA), a tetrafluoroethylene hexafluoropropylene copolymer (FEP), and a trifluorinated ethylene chloride resin (PCTE)
F) and the like are preferred. These fluororesins have higher water repellency than polystyrene, polyethylene and the like, and the average particle size of these fluororesins in the dispersion is from 0.2 to
Since it is relatively large at 0.4 μm, it does not enter the micropores of the activated carbon powder, and therefore, by kneading and molding these, it is possible to obtain a desired activated carbon catalyst in which even macropores are made water-repellent. According to the method,
Activated carbon powder can be used as a raw material to make an arbitrary shape, which is suitable from the viewpoint of production cost in addition to the above-mentioned improvement in activity. Examples of the shape of the catalyst include a honeycomb shape, a plate shape, a spherical shape, a columnar shape, a saddle shape, and the like. A catalyst shape having a high blocking resistance and a small pressure loss of the catalyst layer is preferable.

[0020]

Next, the present invention will be described more specifically with reference to examples. (Example 1) First, 18 kinds of activated carbons having different raw materials such as commercially available coal, coconut shell, peat, wood, and petroleum pitch were pulverized in a coarse crusher, and 2.8 to 4.0 with a stainless steel sieve.
50 g of each of the granular catalysts of mmφ were obtained. However, the activated carbon using petroleum pitch as a raw material had a particle diameter of 0.71 to 1 m, because only one type of activated carbon was available as a commercial product.
A mφ granular catalyst was used. Next, each of the 18 types of activated carbon was fired at 800 ° C. for 1 hour in a nitrogen stream.
Hereinafter, this is referred to as an untreated catalyst. Next, an aqueous dispersion of a commercially available spherical polystyrene (average particle diameter 28 nm) (10 wt.
%) With deionized water to dilute it 50-fold, immerse 20 g of each unsupported polystyrene catalyst in 100 cc of each of the obtained spherical polystyrene dispersions, and dry under reduced pressure with a rotary evaporator. For 12 hours. The amount of spherical polystyrene carried was determined from the difference in dry weight of activated carbon before and after carrying polystyrene. The values were all about 1 wt%.

Next, the untreated activated carbon and the activated carbon carrying spherical polystyrene were subjected to a catalytic sulfation reaction test apparatus to conduct an activity test. Each catalyst was filled in a jacketed glass reactor having an inner diameter of 16 mmφ with a capacity of 40 ml, and SO ₂ ;
00 vol ppm, O ₂ ; 4 vol%, CO ₂ ; 10 vol%,
A gas having a composition of N ₂ : balance and relative humidity of 100% was passed through this reactor at 50 ° C. and 165 dm ³ / hr, and the outlet SO ₂ concentration was measured by a SO ₂ meter (ultraviolet / infrared) to determine the catalytic activity. evaluated. FIG. 2 shows the desulfurization performance of each catalyst 100 hours after the start of the test (sample names: A1 to G1).
From this figure, it has been found that activated carbon made from water-repellent coal has a relatively high desulfurization performance and is suitable for a catalytic sulfation reaction.

(Example 2) Six types of commercially available activated carbon (coal: A1, F2 / coconut shell: A2 / peat: C2 /
Wood-based: A4 / petroleum pitch-based: G1) was fired at 800 ° C. for 1 hour in a nitrogen stream. Next, the activated carbon was pulverized by a commercially available pulverizer, and then activated carbon (about 100 g / time) was passed through a stainless steel sieve (106 μm).
(212 μm or less), a classification operation was performed for 2 hours with a sieve shaker. The activated carbon obtained by repeating such an operation is hereinafter referred to as fine activated carbon, and the representative diameter of the obtained fine activated carbon particles (hereinafter referred to as a crushed particle diameter) is an average value of the mesh of each combined sieve. That is, in the case of the above operation, the pulverized particle size of the obtained pulverized activated carbon was 159 μm.
m. Next, water was added to a commercially available PTFE dispersion (60 wt%) to dilute it 6-fold, and the fine powdered activated carbon was kneaded with each of the PTFE dispersions, followed by molding with a compression molding machine (forming pressure 500 kgf / cm). ² ) A catalyst containing 10% by weight of PTFE was obtained. Next, the mixed molded catalyst was used for 45 to 50 times.
After drying at 12 ° C for 12 hours, it was crushed and classified,
A 4.0 mmφ granular catalyst was obtained.

Example 3 The six types of activated carbons taken in Example 2 were fired at 800 ° C. for 1 hour in a nitrogen stream. Next, 0.5 g of commercially available polyethylene was dissolved in about 100 cc of toluene each heated to 60 to 70 ° C., and 50 g of the activated carbon was immersed in the polyethylene solution.
Vacuum impregnation and drying were performed with a rotary evaporator. Thereafter, drying was performed under reduced pressure in a dryer at 100 to 110 ° C. for 12 hours to prepare a catalyst having a polyethylene loading of about 1 wt%.

The catalysts prepared in Examples 2 and 3 were subjected to an activity test using the reaction test apparatus described in Example 1 under the same conditions to evaluate the respective catalyst activities. FIG. 1 shows the desulfurization performance of each catalyst obtained in this manner for 100 hours after the start of the test.
It is shown including the result of the above. From FIG. 1, it is clear that among the activated carbon raw materials, coal-based activated carbon in particular exhibits a much higher desulfurization performance than coconut shell-based activated carbon and pitch-based activated carbon, and furthermore, commercially available coal types (coal, coconut shell, It can be seen that the water-repellent methods except for micropores in Examples 1 to 3 above, which were performed on activated carbons having different peats, woods, and oil pitches, were all very effective.

[0025]

As described above, in the activated carbon catalyst according to any one of the first to fifth aspects, activated carbon using coal as a main raw material is used as a raw activated carbon, and the activated carbon is subjected to a water-repellent treatment. Therefore, taking advantage of the properties of coal-based activated carbon that it has a large number of adsorption and oxidation active sites, and by improving the emission performance of generated sulfuric acid, it is more excellent than activated carbon catalysts made from other raw materials. Activity against sulfur oxides. Particularly, as in the invention according to claim 2, by excluding the micropores that contribute most to the catalytic sulfation reaction, the macropores serving as the flow path for the generated sulfuric acid are subjected to the water-repellent treatment, whereby the activity is more significantly improved. Can be obtained. Therefore, according to the flue gas desulfurization method according to claim 6 using the activated carbon catalyst according to any one of claims 1 to 5, there is no inferiority in desulfurization efficiency as compared with other flue gas desulfurization processes, and therefore economical Exhaust gas desulfurization with excellent performance is enabled.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of an activity test in Examples of the present invention.

FIG. 2 is a table showing the results of an activity test of Example 1.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Naka Wakabayashi 2-1-1, Tsurumi Chuo, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Inside Chiyoda Kako Construction Co., Ltd. (72) Inventor Osamu Togawa Tsurumi-ku, Tsurumi-ku, Yokohama, Kanagawa Prefecture Chuo 2-chome No. 1 Chiyoda Kako Construction Co., Ltd. (72) Inventor Takashi Kimura 2-1-1 Tsurumi Chuo Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Chiyoda Kako Construction Co., Ltd.

Claims (6)

[Claims] An activated carbon catalyst for adsorbing and oxidizing the sulfur oxide to recover and remove it as sulfuric acid by contacting with an exhaust gas containing a sulfur oxide. Activated carbon catalyst characterized by being subjected to hydration treatment. 2. The activated carbon catalyst according to claim 1, wherein the activated carbon has been subjected to a water-repellent treatment except for pores having a pore diameter of 5 nm or less. 3. The method according to claim 2, wherein the water-repellent treatment is performed by dissolving a polymer water-repellent substance having a molecular weight of 10,000 or more in an organic solvent and impregnating and supporting the activated carbon. Activated carbon catalyst. 4. The water repellent treatment according to claim 1, wherein the average particle diameter is 15 to 10.
The activated carbon catalyst according to claim 2, wherein a dispersion of a water-repellent substance having a thickness of 0 nm is impregnated and supported on the activated carbon. 5. An activated carbon powder having an average particle size of 0.1 to 1.0.
3. The activated carbon catalyst according to claim 2, wherein the activated carbon catalyst is formed by kneading and molding a particle of a fluororesin having a particle diameter of μm or a dispersion thereof. 6. An activated carbon catalyst according to claim 1, which is contacted with an exhaust gas containing a sulfur oxide to adsorb and oxidize the sulfur oxide in the exhaust gas on the activated carbon catalyst. A flue gas desulfurization method comprising collecting and removing sulfuric acid.