JP2001259421A - Catalyst and method for treating stack gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst for treating stack gas capable of completely decomposing harmful substances such as halogenated organic compounds contained in the stack gas discharged from a refuse incinerator, etc., at low temperatures and to provide a method for treating the stack gas using the catalyst. SOLUTION: The catalyst for treating the stack gas is obtained by depositing platinum particles in platinum colloid on a carrier, and in the method for treating the stack gas, the harmful substances in the stack gas are decomposed by allowing the stack gas to contact with the catalyst for treating the stack gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flue gas treatment catalyst and a flue gas treatment method, and an object of the invention is to remove harmful substances such as halogenated organic compounds contained in flue gas discharged from a refuse incinerator or the like. It is an object of the present invention to provide a flue gas treatment catalyst capable of almost completely decomposing a substance at a low temperature and a flue gas treatment method using the catalyst.

[0002]

2. Description of the Related Art Conventionally, flammable general household waste and flammable industrial waste have been incinerated at garbage incineration plants. However, during the flue gas generated by incineration,
It contains various harmful substances such as nitrogen oxides that cause acid rain or halogenated organic compounds such as dioxins and PCBs.

[0003] In particular, halogenated organic compounds such as dioxins and PCBs are known to have carcinogenic and teratogenic properties, and thus, when taken into a living body, have a serious effect on health. I have. Furthermore, it is feared that the thyroid gland and the reproductive organs may be adversely affected as a kind of environmental hormone. In recent years, environmental pollution due to halogenated organic compounds such as dioxins and PCBs contained in flue gas generated by incineration of waste has been increasing. It has become a serious social problem.

As a method for preventing generation of harmful substances such as dioxins from an incinerator, there is a method of incinerating waste at an extremely high temperature when incinerating waste. Although this method can suppress the generation of harmful substances, it has to be heated to extremely high temperatures, which increases costs and cannot be easily applied to existing incineration facilities. did.

[0005] Therefore, as a method applicable to existing facilities, there is a method that removes harmful substances from flue gas generated from an incinerator to suppress discharge of harmful substances into the environment. As such a method, for example, there is a method of adsorbing and removing harmful substances such as dioxins in flue gas using a filter material such as a filter. However, this method has a problem in that a large amount of harmful substances are adsorbed to a filter material such as a filter, and thus a used filter must be separately treated.

[0006]

Therefore, in recent years, treatment of harmful substances which does not require extra labor such as post-processing of used filters and which can be easily applied to existing incinerators. Methods have been studied, and as such a method, for example, a method of decomposing and removing harmful substances in flue gas using a specific catalyst has been proposed. As a specific catalyst used in such a decomposition treatment method, for example, a catalyst in which a metal oxide such as vanadium pentoxide, tungsten trioxide, or a noble metal oxide is supported on a carrier such as titanium oxide, zeolite, or activated carbon is known. Have been.

However, the conventional catalyst as described above can decompose harmful substances in a high temperature range of 200 to 450 ° C., but cannot decompose harmful substances in a low temperature range of 200 ° C. or lower. There was a point. Furthermore, harmful substances such as dioxins and PCBs may not be completely decomposed even if such a conventional catalyst is used, and the decomposition reaction may stop at an intermediate thereof. There is also a problem that harmful substances such as PCBs and the like are synthesized.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems.
The present invention relates to a catalyst for flue gas treatment, wherein a platinum particle in platinum colloid is supported on a carrier.
The invention according to claim 2 relates to the catalyst for exhaust gas treatment according to claim 1, wherein the carrier is made of activated carbon fiber. The invention according to claim 3 relates to a method for treating flue gas, which comprises contacting flue gas with the catalyst for flue gas treatment according to claim 1 or 2 to decompose harmful substances in the flue gas.
The invention according to claim 4 is the smoke exhaust treatment method according to claim 3, wherein the contact temperature between the exhaust gas and the exhaust gas treatment catalyst is 100.
To 200 ° C., which relates to a smoke exhaust treatment method.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A flue gas treatment catalyst according to the present invention comprises:
Platinum particles in a platinum colloid are supported on a carrier. This is because the platinum particles in the platinum colloid have a negative charge, and are physically confined in the carrier, thereby being confined in the pores of the carrier and increasing the contact area. For this reason, the exhaust gas treatment catalyst according to the present invention can exhibit an extremely high catalytic ability for a decomposition reaction of harmful substances in exhaust gas.

[0010] The carrier used in the exhaust gas treatment catalyst according to the present invention is not particularly limited, and examples thereof include activated carbon fibers, titanium oxide, zeolite, and activated carbon. In the present invention, as the carrier, only one of the above carriers may be used, or a mixture of two or more carriers may be used.

As will be described later, the exhaust gas treating catalyst according to the present invention needs to be treated in a certain temperature zone when treating exhaust gas. For this reason, as the carrier, activated carbon fibers that can be easily temperature-controlled by energization are preferably used. As activated carbon fibers, organic fibers such as rayon or polyacrylonitrile, or fibers obtained by spinning coal tar pitch or refined petroleum pitch can be obtained by heat treatment in an inert gas and carbonized. it can. In the flue gas treatment catalyst according to the present invention, any activated carbon fiber can be suitably used,
For example, polyacrylonitrile-based activated carbon fibers, pitch-based activated carbon fibers, rayon-based activated carbon fibers, phenol resin-based activated carbon fibers, lignin-poval-based activated carbon fibers, and the like can be exemplified.

Usually, such activated carbon fibers are
It has a specific surface area of not less than 500 m2 / g. In the present invention, at least 500 m 2 / g, more preferably 1000 m 2 / g
It is preferable to use activated carbon fibers having a specific surface area of 2 / g or more. Since activated carbon fibers have an extremely large specific surface area as described above, they can be suitably used as a carrier of a flue gas treatment catalyst containing a hardly decomposable compound such as a halogenated organic compound.

In the exhaust gas treatment catalyst according to the present invention, platinum particles in platinum colloid are supported on a carrier. This is because the platinum particles in the platinum colloid have a negative charge and are physically carried in the carrier, thereby being confined in the pores of the carrier and increasing the contact area. Also, since the platinum colloidal platinum particles have a large specific surface area,
Extremely high catalytic ability can be exhibited.

The method for obtaining the platinum colloid used for supporting the platinum particles on the carrier is not particularly limited.
For example, a bladed method of flying an arc between two platinum electrodes immersed in pure water, adding chloroplatinic acid to boiling distilled water, further adding an aqueous solution of sodium citrate and boiling the solution until it turns black, , Cooling, microemulsion, etc. Further, a platinum colloid can be prepared using a protective colloid.

By supporting the platinum particles in the platinum colloid thus obtained on the above-mentioned carrier, the catalyst for exhaust gas treatment according to the present invention can be obtained.
The method of supporting the platinum particles in the platinum colloid on the carrier is not particularly limited, and examples thereof include an impregnation method, a precipitation-precipitation / supporting method, a coprecipitation method, a vapor deposition method, and a method of supporting the carrier while energizing the carrier.

The amount of the platinum particles to be supported on the carrier is not particularly limited, but is preferably 0.005 to 0.1 in the flue gas treatment catalyst.
%, More preferably 0.01 to 0.02% by weight. When the content is less than 0.005% by weight, the catalytic effect due to the loading of the platinum particles cannot be exhibited, and when the content is more than 0.1% by weight, the active sites decrease with a decrease in the specific surface area. Therefore, in any case, it is not preferable.

The flue gas treatment catalyst according to the present invention, which is obtained by the above-described method, almost completely decomposes harmful substances contained in flue gas into harmless substances such as carbon dioxide and water in a low temperature range. Can be processed. To this end, no harmful substances are synthesized again.

The catalyst for flue gas treatment according to the present invention can be used for various purposes such as flue gas from various incineration facilities such as general refuse incinerators, industrial waste incinerators and sludge incinerators, smoke from a melting furnace or various plants. It can be applied to the decomposition treatment of harmful substances contained in flue gas. Such flue gas contains harmful substances such as halogenated organic compounds and nitrogen oxides, and the flue gas treatment catalyst according to the present invention can decompose such harmful substances. It is. Specifically, as the halogenated organic compound, polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (P
Dioxins such as CDFs) and P such as 2,6-dichlorobiphenyl and 2,3,5-trichlorobiphenyl
Examples include CBs, chlorobenzenes, chlorophenols, chlorotoluenes, chlorinated alkyl compounds, benzene, phenol, and the like.

In order to decompose the above-mentioned harmful substances in flue gas using the flue gas treatment catalyst according to the present invention described above, the flue gas treatment catalyst and the flue gas may be brought into contact. The temperature when contacting the flue gas treatment catalyst with the flue gas is 100 to
The temperature is set to 200 ° C, more preferably 120 to 150 ° C.
This is because if the temperature is lower than 100 ° C., the harmful substance cannot be completely decomposed in a short time, and even if heated to a temperature higher than 200 ° C., no further effect can be expected. is there. If the temperature is within the above-mentioned temperature range, the high-temperature flue gas may be cooled so as to come into contact with the catalyst in this temperature range. By heating the catalyst, it may come into contact with the flue gas within this temperature range.

In the flue gas treatment method according to the present invention, since a flue gas treatment catalyst in which platinum particles in platinum colloid are supported on a carrier, the halogenated organic compound contained in the flue gas at a low temperature region. Can be almost completely decomposed into harmless substances such as water and carbon dioxide. Therefore, the harmful substances are not synthesized again.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. However, the present invention is not limited at all by the following examples. (Preparation of Sample) Preparation of Platinum Colloid A round bottom three-necked flask having an inner volume of 1 liter was prepared, a condenser was attached to the center of the flask, and the other flasks were sealed with a ground glass stopper. 480 ml of purified water (purified by Milli-QII manufactured by Millipore) was added into the flask, and the mixture was boiled for 1 hour using a mantle heater. Next, a chloroplatinic acid aqueous solution (0.38 g-Pt / L) 80 m separately prepared using hexachloroplatinic acid (IV) hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd., special grade)
1 was added and boiled again for 30 minutes. 60 ml of an aqueous sodium citrate solution (1% by weight) separately prepared using trisodium citrate dihydrate (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) was added thereto, and the mixture was refluxed for 4 hours. A platinum colloid was prepared by reducing the acid. In addition, all equipment used should be aqua regia (hydrochloric acid:
Washing was performed using nitric acid = 3: 1). For the preparation of the sample, purified water (purified by Milli-QII manufactured by Millipore)
Was used. Preparation of Example To 30 ml of the prepared platinum colloid, activated carbon fiber FE-100 (0.5 g, 50 ×) manufactured by Toho Veslon Co., Ltd. was added.
(50 × 30 mm, felt shape) and left in a cool and dark place at 4 ° C. for 12 hours. Next, take out the activated carbon fiber,
After leaving it at a constant temperature of 100 ° C. for 3 hours, it was allowed to cool in a desiccator at room temperature for 12 hours or more, whereby the platinum particles in the platinum colloid were supported on the activated carbon fibers, and the sample of the example was obtained.

(Test example: Decomposition of chlorobenzene using platinum-supported activated carbon fiber) Preparation of reaction vessel Motor (2) and fan (3) as shown in FIG.
And a cover for a three-neck separable flask provided with a support rod (4) and a thermometer (5) for fixing the
A container (with an internal volume of 800 ml) in which a 0 ml separable flask was fixed using a separa clamp (6) was used as a reaction container (1). Grease for high vacuum was applied to the contact portion between the separable flask and the three-neck separable flask cover. In addition, the flask port provided with the support rod (4) and the thermometer (5) (the center and right flask ports in the figure) is provided with a rubber stopper (7), and the flask port provided with nothing is provided. Then, the left flask opening was sealed with a rubber double cap (8). The sampling and addition of the sample were performed from the flask port where nothing was provided (left flask port in the figure). In FIG. 1, the illustration of the motor (2) and the power supply cords provided on the copper plate electrode (10) described later is omitted.

Preparation of Calibration Curve for Chlorobenzene Concentration Measurement The above-prepared reaction vessel (1) was allowed to stand in a 55 ° C. water bath for 30 minutes to equilibrate the water bath water temperature and the temperature inside the reaction vessel (50 ° C.). Next, 10 μL (3250 ppm) of chlorobenzene (manufactured by Wako Pure Chemical Industries, Ltd., special grade) was added to the weighing bottle (9) installed in the reaction vessel (1), and sealed with a double cap (8). The mixture was stirred for 10 seconds by a fan (3) provided for 1 minute and left for 1 minute. Finally, 10 μL of the gas phase gas was sampled using a gas tight syringe, and the obtained sample was subjected to gas chromatography (FID) analysis under the conditions shown in Table 1. Chlorobenzene 5 μL (1625 ppm), 2.5 μL (813
ppm). Based on the relationship between the peak area of the elution position of chlorobenzene in the obtained chromatograph and the chlorobenzene concentration, a calibration curve for chlorobenzene determination shown in FIG. 2 was prepared. The chlorobenzene concentration was measured using a gas chromatograph G-8000 manufactured by Hitachi, Ltd. with an FID detector. A chromatographic integrator G-2500 manufactured by Hitachi, Ltd. was used for chromatographic analysis.

[Table 1]

Oxidative decomposition of chlorobenzene Wound asbestos around a wire (φ1.5 mm)
The sample (11) of the above-prepared example was fixed between the copper plate electrodes (9) attached to the framework, and placed in the reaction vessel (1) as shown in FIG. Next, the reaction vessel (1) was allowed to stand still in a 55 ° C. water bath to equilibrate the water bath water temperature with the reaction vessel (50 ° C.). The surface temperature of the sample of the example was set to 135 ° C. by voltage adjustment (not shown). 10 μL of chlorobenzene was added to a weighing bottle (9) placed in the reaction vessel (1), and the gas phase in the reaction vessel (1) was removed over time using a gas-tight syringe.
0 μL was sampled at a time, and the chlorobenzene concentration in the reaction vessel (1) was measured by performing gas chromatography (FID) analysis in the same manner as described above. Further, the surface temperature of the sample (11) of the example was set to 100 ° C., 120 ° C.,
The measurement was performed in the same manner when the temperature was 145 ° C. As a control, the change with time of the chlorobenzene concentration was measured in the same manner without placing the sample (11) of the example in the reaction vessel (1). The same measurement was performed when the surface temperature of activated carbon fibers not carrying platinum was 135 ° C.

The results are shown in Table 2.

[Table 2]

As shown in Table 2, since the catalyst is a flue gas treatment catalyst supporting platinum particles in platinum colloid, chlorobenzene can be oxidized and decomposed at low temperature and quickly. In addition, it can be seen that the oxidative decomposition rate of chlorobenzene can be increased by increasing the surface temperature of the activated carbon fiber supporting platinum in the platinum colloid. Furthermore, when the flue gas treatment catalyst according to the present invention is used for oxidative decomposition of chlorobenzene, no intermediate product (for example, allyl chloride, 3-chloro-1-butene, benzene) in the decomposition process is measured at all, and The increase in carbon dioxide concentration was measured. That is, the exhaust gas treatment catalyst according to the present invention completely decomposes chlorobenzene into harmless substances such as carbon dioxide, and chlorobenzene is not synthesized again. From this, it can be inferred that the exhaust gas treatment catalyst according to the present invention can decompose substances having a chlorobenzene skeleton such as dioxins and PCBs.

[0027]

As described above in detail, the exhaust gas treatment catalyst according to the present invention is useful in a low-temperature region in the presence of halogens such as dioxins and PCBs contained in exhaust gas discharged from a garbage incinerator or the like. A harmful substance such as a fluorinated organic compound can be almost completely decomposed into a harmless substance such as water or carbon dioxide. Furthermore, since the smoke exhaust treatment method according to the present invention is a smoke exhaust treatment method using the above-described smoke exhaust treatment catalyst, harmful substances in the smoke exhaust gas can be almost completely decomposed at low temperatures, and It can be easily applied to existing incinerators.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a reaction vessel.

FIG. 2 is a calibration curve for measuring chlorobenzene concentration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction container 2 Motor 3 Fan 4 Support rod 5 Thermometer 6 Separa clamp 7 Rubber stopper 8 Double cap 9 Weighing bottle 10 Copper plate electrode 11 Sample

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masayoshi Yoshikawa 4-8-23 Komaba, Toride-shi, Ibaraki Prefecture (72) Inventor Koyasu Tamagawa 1553 Shimobuchi, Oji, Oyodo-cho, Yoshino-gun, Nara F-term (reference) 4D048 AA17 AB03 BA30X BA45X BB08 BB17 CC38 DA03 DA13 4G069 AA03 AA08 AA09 BA08A BA08B BA37 BB02A BB02B BC75A BC75B BC75C CA04 CA10 CA11 CA19 EA03X EA03Y EA09 FA01 FB06 FB14 FB16 FC02

Claims (4)

[Claims] 1. A flue gas treatment catalyst comprising a carrier and platinum particles in platinum colloid supported thereon. 2. The exhaust gas treatment catalyst according to claim 1, wherein the carrier is made of activated carbon fibers. 3. A method for treating flue gas, comprising contacting flue gas with the catalyst for treating flue gas according to claim 1 to decompose harmful substances in the flue gas. 4. The flue gas treatment method according to claim 3, wherein the contact temperature between the flue gas and the flue gas treatment catalyst is 100 to 20.
A flue gas treatment method characterized by being at 0 ° C.