JPH1085559A - Decomposing method for chlorinated organic compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decompose a harmful chlorinated organic compound such as dioxin by bringing gas containing the chlorinated organic compound into contact with a catalyst containing specified three components at the specified temperature and under the presence of oxygen of specified vol.%. SOLUTION: Gas containing a chlorinated organic compound is brought into contact with a catalyst at the temperature of 100-350 deg.C and under the presence of oxygen of 0.5-25vol.%. The catalyst is composed of three components of an oxide of at least an element selected out of a vanadium oxide, a tungsten oxide, an erbium, a neodymium and the like. The shape of the oxide catalyst is the columnar shape, spherical shape, honeycomb shape or the like. The catalyst is particularly of superior resistance to toxicity against sulflur oxide. A chlorinated organic compound such as dioxin contained in exhaust combustion gas in municipal waste or the like, an aromatic chlorinated compound as a precursor of dioxin or the like is decomposed and removed by the catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for decomposing chlorinated organic compounds, and more particularly, to chlorinated organic compounds such as dioxins in exhaust gas generated by combustion of municipal waste and industrial waste. Is brought into contact with a catalyst to decompose it.

[0002]

2. Description of the Related Art Combustion exhaust gas such as municipal waste and industrial waste contains chlorinated organic compounds such as dioxins and aromatic chlorine compounds which are considered to be precursors thereof. In general, chlorinated organic compounds are more or less toxic, but dioxin is a very toxic substance that has a significant adverse effect on animals and plants, such as teratogenicity, and its content in flue gas should be reduced as much as possible. is required. Therefore, various methods for removing chlorinated organic compounds such as dioxin have been proposed, for example, an activated carbon adsorption method, a thermal decomposition method, or a catalytic decomposition method. Among them, the catalytic cracking method is 500
This is an excellent method that can perform the treatment under the condition of not more than ℃.

[0003]

However, the catalyst in the conventionally proposed catalytic cracking method has a durability against impurities such as nitrogen oxides, sulfur oxides and heavy metal fumes contained in flue gas. There is a problem of lacking. Further, conventional catalysts using platinum or palladium are expensive. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an economically advantageous method for decomposing chlorinated organic compounds using a relatively inexpensive catalyst that is resistant to impurities. To provide.

[0004]

That is, the gist of the present invention is to provide a method for decomposing a gas containing a chlorinated organic compound by bringing the gas into contact with a catalyst at a temperature of 100 to 350 ° C.
At a temperature of 0.5 to 25% by volume of oxygen,
A method for decomposing a chlorinated organic compound, comprising contacting with a catalyst containing the three components (A), (B) and (C).

(A) Vanadium oxide (B) Tungsten oxide (C) Oxide of at least one element selected from the group consisting of erbium, neodymium, ytterbium and holmium Supported on the titania (A) vanadium oxide, (B) tungsten oxide, and (C) erbium, neodymium, oxide of at least one element selected from the group consisting of ytterbium and holmium, the loading amount of Each (A) 0.5-5
0% by weight, (B) 0.5-50% by weight and (C) 0.1-50%
The above-mentioned decomposition method, which is weight%, also exists. Furthermore,
The gist of the present invention also resides in the above-described decomposition method in which the content of tungsten oxide is 0.1 to 30 times by weight the content of vanadium oxide in the catalyst.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail. Examples of the exhaust gas to be treated in the present invention include combustion exhaust gas such as municipal waste and industrial waste. Such flue gases usually include 2,
3,7,8-tetrachlorodibenzodioxin, 2,
Dioxins represented by 3,4,7,8-pentachlorodibenzofuran are contained in an amount of 10 to 40 ng / Nm ³ . Further, chlorinated organic compounds such as monochlorobenzene, dichlorobenzene, o-chlorophenol, and chlorobenzofuran, which are precursors of these dioxins, are also included.

In the present invention, the following three components (A), (B) and (C) are used as catalysts for decomposing chlorinated organic compounds:
(A) vanadium oxide, (B) tungsten oxide, and
(C) A catalyst containing an oxide of at least one element selected from the group consisting of erbium, neodymium, ytterbium and holmium is used. Such an oxide catalyst is particularly excellent in poisoning resistance to sulfur oxides. The oxide catalyst is usually used by being supported on a carrier. As the carrier, silica, alumina, diatomaceous earth and the like can be used, but titania (TiO ₂ ) is preferably used. In particular, when sulfur oxides are contained in the combustion exhaust gas, it is preferable to use titania.

[0008] The loading amount of vanadium oxide and tungsten oxide is usually 0.5 to 50% by weight, preferably 2 to 40% by weight, based on the carrier. The amount of the oxide of the oxide of at least one element selected from the group consisting of erbium, neodymium, ytterbium and holmium is usually 0.1 to 50% by weight, preferably 0.3 to 40% by weight based on the carrier. is there.

Further, the content of the tungsten oxide to the content of the vanadium oxide is usually 0.1 to 30 times by weight, preferably 1 to 10 times by weight. The content of the oxide of at least one element selected from the group consisting of erbium, neodymium, ytterbium and holmium with respect to the content of the vanadium oxide is usually 0.01 to
It is 3 times by weight, preferably 0.1 to 1 time by weight.

The size and shape of the catalyst are generally determined by the properties of the raw material, the presence or absence of dust, the amount of gas, the size of the reactor, and the like. Examples of the shape of the catalyst include a columnar shape, a spherical shape, a honeycomb shape, and a plate shape. When manufacturing a catalyst having a shape such as a honeycomb catalyst, the support component and the catalyst component or the raw material thereof are kneaded together with a forming aid, and then formed into a desired shape such as a honeycomb shape by a forming method such as an extrusion forming method. And a method in which a carrier component such as titania and a catalyst component are impregnated and supported on a substrate constituting a honeycomb.

Specifically, the following method is exemplified. (1) Dissolve ammonium metavanadate and ammonium paratungstate in a 10% aqueous monoethanolamine solution. (2) One or more of erbium nitrate hexahydrate, neodymium nitrate hexahydrate, ytterbium nitrate tetrahydrate, and holmium nitrate tetrahydrate are dissolved in water. (3) Kneading the powdery titania and the aqueous solution prepared in (1) and (2) with a kneader. (4) The kneaded material is (a) extruded and formed at 50 to 150 ° C.
After drying for ~ 50 hours, the space velocity (hereinafter referred to as "S
V "), 100-2000 (h ^-1 ), temperature 45
Baking under the condition of 0 to 650 ° C, or (b) 50 to
After drying at 150 ° C. for 3 to 50 hours, 450 under an air atmosphere.
After firing under the condition of 条件 下 650 ° C., it is molded.

When the catalyst is prepared by the impregnation method, a carrier component is first coated on a substrate having a desired shape such as a columnar shape, a spherical shape, a honeycomb shape, and a plate shape, and then the above-mentioned (1), ( A method in which the catalyst component is impregnated with the aqueous solution prepared as in 2) and then calcined can be used. The raw material of the vanadium oxide is not particularly limited, but it is preferable to use vanadium pentoxide (V ₂ O ₅ ) or ammonium metavanadate. These are dissolved in an aqueous oxalic acid solution or an aqueous monoethanolamine solution to prepare a vanadium raw material liquid. Although there is no particular limitation on the raw material of the tungsten oxide, ammonium paratungstate or ammonium metatungstate is preferable, and this is dissolved in hot water or the like to form a tungsten raw material liquid.

The raw materials of the oxides of erbium, neodymium, ytterbium and holmium are not particularly limited, but erbium oxide raw material is erbium nitrate hexahydrate, and neodymium oxide raw material is neodymium nitrate hexahydrate. As a raw material of ytterbium oxide, ytterbium nitrate tetrahydrate is preferable, and as a raw material of holmium oxide, holmium nitrate tetrahydrate is preferable in terms of water solubility and availability. Etc. to make each raw material liquid.

These raw material liquids may be prepared by mixing the raw materials, or may be used by mixing the prepared solutions, as long as there is no inconvenience such as precipitation or reaction. In the catalyst using the base material, as a carrier component, for example, silica (SiO ₂ ) or alumina (Al ₂ O ₃ ) may be used in addition to titania. Is preferably 30% by weight or more based on the weight of the catalyst. The total amount of the carrier component and the catalyst component is 5 to 70% by weight, preferably 10 to 50% by weight based on the weight of the catalyst after production.

[0015] When it can be considered that all the raw materials added as in the kneading and molding method can be considered as the catalyst components, the raw material components such as salts of each metal and the like are converted to the corresponding oxides of the metal and the like. As a change, it can be estimated from the added amount. In the case where the catalyst is manufactured by the impregnation method or the manufacturing method is unknown, the catalyst can be measured by a method of treating the catalyst with hydrofluoric acid, melting it with ammonium sulfate, and then performing a plasma emission analysis (ICP-AES analysis).

In the present invention, the catalyst prepared as described above is used at 100 to 350 ° C. and 0.5 to 2 ° C.
In the presence of 5% by volume, preferably 1 to 15% by volume of oxygen,
Decomposes chlorinated organic compounds. When the temperature is lower than 100 ° C., the decomposition reaction hardly occurs. When the temperature is higher than 350 ° C., the decomposition proceeds, but the heat consumption is large, the durability of the catalyst is easily affected, and dioxin is regenerated from the decomposition products. The likelihood is high.

A more preferred decomposition temperature is 150 to 350.
° C, and particularly preferably 200 to 300 ° C. The pressure at the time of decomposition is usually 0 to 9 kg / cm ² , preferably 0.01 to 5 kg / cm ² as a gauge pressure. Also, SV
Is usually 100 to 50,000 h ^-1 , preferably 1000
２０20,000 h ⁻¹ .

The method of the present invention comprises the steps of:
It is suitable for treating a gas containing a chlorinated organic compound at a concentration of about 0.05 to 500 ng / Nm ^{3 in} terms of (7,8-tetrachlorodibenzodioxin), and burns the aforementioned municipal solid waste and industrial waste. The effect is great when applied to the treatment of exhaust gas. In addition, when ammonia gas is introduced into the gas before the above-mentioned catalytic decomposition, it is possible to simultaneously decompose nitrogen compounds and remove chlorinated substances. Furthermore, even if a small amount of water is contained in the gas to be treated, it does not affect the decomposition of the chlorinated product. Therefore, from such a point, the catalyst of the present invention is practically preferable.

The above-mentioned treatment of the chlorinated organic compound comprises
Usually, it is performed after the combustion exhaust gas is passed through a bag filter to remove dust and the like, and the exhaust gas after the decomposition treatment is released to the atmosphere after removing the acidic gas by an alkali washing tower or the like. However, in the case of a combustion exhaust gas containing little dust and heavy metals, the pretreatment by the bag filter can be omitted.

[0020]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. [Example 1] <Preparation of catalyst> 19.3 g of ammonium metavanadate
And 54.6 g of ammonium paratungstate in 80
10% by weight aqueous monoethanolamine solution heated to 3 ° C
The solution was dissolved in 00 g to obtain a raw material liquid (1). Next, in another container, 7.2 g of erbium nitrate hexahydrate was dissolved in 60 g of water to obtain a raw material liquid (2). The raw material liquid (1) and the raw material liquid (2) and 435 g of titania powder were kneaded for 2 hours using a double-arm kneader, and the obtained kneaded product was formed into a cylindrical shape having a diameter of 3 mm by an extruder. The molded product was dried at 130 ° C. overnight and calcined at 600 ° C. for 3 hours to obtain a catalyst.
The composition of the catalyst is as shown in the table.

<Activity Test> A glass reactor having an inner diameter of 43 mm was charged with 30 cc of the above-mentioned catalyst, and an activity test was carried out in a fixed-bed flow reactor under normal pressure. The source gas composition is monochlorobenzene (MCB) 100 ppm, nitric oxide (NO)
100 ppm, ammonia 100 ppm, oxygen 10% by volume, and the balance was nitrogen. This source gas is SV5000
At h- ¹ , the temperature was raised while passing through the reactor, and the temperature was maintained at 200 ° C. for 1 hour. Then, the gas passing through the reactor was sampled with a microsyringe and analyzed by gas chromatography. The analysis was performed by the absolute calibration method. The results are shown in the table.

Example 2 A catalyst was prepared in the same manner as in Example 1 except that 7.8 g of neodymium nitrate hexahydrate was used instead of 7.2 g of erbium nitrate hexahydrate. Prepared. Using this catalyst, a catalyst activity test was conducted in the same manner as in Example 1. The composition of the catalyst and the evaluation results are shown in the table.

Example 3 A catalyst was prepared in the same manner as in Example 1 except that 10.9 g of ytterbium nitrate tetrahydrate was used instead of 7.2 g of erbium nitrate hexahydrate. Prepared. Using this catalyst, a catalyst activity test was conducted in the same manner as in Example 1. The composition of the catalyst and the evaluation results are shown in the table.

Example 4 A catalyst was prepared in the same manner as in Example 1 except that 6.7 g of holmium nitrate tetrahydrate was used instead of 7.2 g of erbium nitrate hexahydrate. Prepared. Using this catalyst, a catalyst activity test was conducted in the same manner as in Example 1. The composition of the catalyst and the evaluation results are shown in the table.

Comparative Example 1 A catalyst was prepared in the same manner as in Example 1 except that erbium nitrate hexahydrate was not added (that is, raw material liquid (2) was not added). Was prepared. This catalyst was tested for activity in the same manner as in Example 1. The composition of the catalyst and the evaluation results are shown in the table.

[0026]

[Table 1] * 1 Ratio: Comparative example * 2 MCB: Monochlorobenzene NO: Nitric oxide

Comparing the data of each of the above examples with the data of the comparative example, it is clear that (A) vanadium oxide, (B) tungsten oxide, and (C) erbium, neodymium, ytterbium and holmium. It can be seen that the decomposition reaction of monochlorobenzene is efficiently performed by the method of the present invention in which the gas containing the chlorinated organic compound is treated with the catalyst containing the three components of the oxide of at least one selected element. . Therefore, it is considered that chlorinated organic compounds such as dioxin can be decomposed by the mixed oxide catalyst. When ammonia is introduced, nitrogen oxides can be removed at the same time.

[0028]

As described above, according to the method of the present invention, (A) vanadium oxide, (B) tungsten oxide, and (C) erbium, neodymium, which are inexpensive and resistant to impurities. By using a mixed oxide catalyst containing three components of oxides of at least one element selected from the group consisting of ytterbium and holmium, municipal solid waste and industrial waste, which are socially problematic An effective method for removing harmful chlorinated organic compounds such as dioxin in combustion exhaust gas is provided.

Claims (3)

[Claims] 1. A method for decomposing a gas containing a chlorinated organic compound by contacting the gas with a catalyst,
A chlorinated organic compound, which is brought into contact with a catalyst containing the following three components (A), (B) and (C) at a temperature of ~ 350 ° C and in the presence of 0.5 to 25% by volume of oxygen: How to decompose the compound. (A) Vanadium oxide (B) Tungsten oxide (C) Oxide of at least one element selected from the group consisting of erbium, neodymium, ytterbium and holmium 2. The catalyst is supported on titania, and (A) vanadium oxide, (B) tungsten oxide for titania,
And (C) an oxide of at least one element selected from the group consisting of erbium, neodymium, ytterbium and holmium, in which (A) 0.5 to 50% by weight and (B) 0.5 to 50% by weight, respectively. % By weight and (C) 0.1 to 50% by weight
The decomposition method according to claim 1, wherein 3. The decomposition method according to claim 1, wherein the content of the tungsten oxide is 0.1 to 30 times by weight the content of the vanadium oxide in the catalyst.