JPH09192455A - Decomposing method of chlorinated organic compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decompose a chlorinated organic compound with a low cost catalyst having durability against impurities by bringing a chlorinated organic compound-containing gas into contact with the catalyst containing vanadium oxide, tungsten oxide or the like in the presence of oxygen having a specific concentration at a specific temp.. SOLUTION: The gas containing the chlorinated organic compound such as 2,3,7,8-tetrachlorodibenzodioxin, which is an incineration waste gas of municipal refuse, is decomposed by bringing the gas into contact with the catalyst. In this case, the gas is brought into contact with the catalyst containing vanadium oxide, tungsten oxide and an oxide of an element selected from yttrium, boron or the like in the presence of oxygen of 0.5-25vol.% concentration at 100-350 deg.C. Thus, the harmful chlorinated organic compound such as the dioxin is removed by using the low cost catalyst having durability against the impurities.

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 catalytic cracking method proposed hitherto lacks durability against impurities such as nitrogen oxides, sulfur oxides, and heavy metal fumes contained in combustion exhaust gas. There is a problem to say. Further, conventional catalysts using platinum or palladium are expensive.

The present invention has been made in view of the above circumstances, and an object thereof is an economically advantageous chlorinated organic substance using a catalyst which is resistant to impurities and is relatively inexpensive. It is to provide a method for decomposing a compound.

[0005]

That is, the gist of the present invention is to provide a method of decomposing a gas containing a chlorinated organic compound by contacting it with a catalyst, wherein the gas is (1) 100 to 3
From (3) (A) vanadium oxide, (B) tungsten oxide, and (C) yttrium, boron, tin and lead in the presence of 0.5 to 25 vol% oxygen at a temperature of 50 ° C. A method for decomposing a chlorinated organic compound, which comprises contacting with a catalyst containing an oxide of at least one element selected from the group consisting of :, and the gist of the present invention is that the catalyst is supported on titania. (A) vanadium oxide for titania, (B) molybdenum oxide, and (C) yttrium, boron, at least one element oxide selected from the group consisting of tin and lead, the amount of each carried (A) 0.5-5
0 wt%, (B) 0.5 to 50 wt% and (C) 0.1 to 50
It also exists in the above decomposition method, which is wt%. .

Further, another subject matter of the present invention also resides in the above-mentioned 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. There is.

[0007]

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, as the decomposition catalyst of the chlorinated organic compound, at least one selected from the group consisting of (A) vanadium oxide, (B) tungsten oxide, and (C) yttrium, boron, tin and lead. A catalyst containing an oxide of one element 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.

The loading amounts of vanadium oxide and tungsten oxide are usually 0.5 to 50 w for each carrier.
t%, preferably 2 to 40 wt%. Further, the amount of the oxide of at least one element selected from the group consisting of yttrium, boron, tin and lead is usually 0.1 to 50 wt%, preferably 0.3 to 40 wt% with respect to the carrier.
It is.

Further, the content of the tungsten oxide relative 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 yttrium, boron, tin and lead with respect to the content of vanadium oxide is usually 0.01 to 3 times by weight, preferably 0.1 to 10. 1 times the 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 yttrium nitrate hexahydrate, boric acid, lead nitrate and tin chloride are dissolved in water or dilute hydrochloric acid. (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 having a desired shape such as a columnar shape, a spherical shape, a honeycomb shape or a plate shape is first coated with a carrier component, and then the above-mentioned (1), ( It is possible to use a method in which the catalyst component is impregnated with the aqueous solution prepared as in 2) and then calcined. 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 for the oxides of yttrium, boron, tin and lead are not particularly limited, but as a raw material for yttrium oxide, yttrium nitrate hexahydrate is used as a raw material for boron oxide (diboron trioxide). Is boric acid,
As a raw material of tin oxide, tin chloride is preferable, and as a raw material of lead oxide (lead monoxide), lead nitrate is preferable in terms of water solubility, etc., and they are dissolved in hot water or oxalic acid aqueous solution, etc. Use as liquid.

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

In the obtained catalyst composition, when it can be considered that all the added raw materials become catalyst components as in the kneading / molding method, the raw material components such as salts of respective metals are converted into corresponding oxides of metals or the like. It can be estimated from the added amount as a change. 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 and the temperature is 100 to 350 ° C. and 0.5 to 2
Chlorinated organic compounds are decomposed in the presence of 5 vol%, preferably 1-15 vol% oxygen. 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 preferable decomposition temperature is 150 to 350.
The temperature is 200 ° C., and when it contains yttrim or boron as a catalyst component and does not contain lead, 200 to 300 ° C. is particularly preferable. The pressure during decomposition is usually 0 to 9 kg / gauge pressure.
cm ² , preferably 0.01 to 5 kg / cm ² . Moreover, SV is normally 100～50000H ^-1, preferably 1000~20000h ^-1.

The method of the present invention comprises the steps of dioxins (2, 3,
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 treatment of the above chlorinated organic compound is
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.

[0021]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Example 1 <Preparation of catalyst> Ammonium metavanadate 19.3 g
And 54.6 g of ammonium paratungstate in 80
10 wt% monoethanolamine aqueous solution heated to ℃ 3
The solution was dissolved in 00 g to obtain a raw material liquid (1). Then, 5.1 g of yttrium nitrate hexahydrate was dissolved in 30 g of water in another container to prepare 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 (hereinafter, referred to as “catalyst A”). The composition of the catalyst is as shown in Table 1.

<Activity test> A glass reactor having an inner diameter of 43 mm was filled with 30 cc of the catalyst described above, and an activity test was carried out in an atmospheric fixed bed flow reactor. The source gas composition is monochlorobenzene (MCB) 100 ppm, nitric oxide (NO)
100pp, ammonia 100ppm, oxygen 10vol
%, 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 Table 1.

Example 2 In Example 1, 5.1 g of yttrium nitrate hexahydrate
Example 1 except that 5.3 g of boric acid was used in place of
A catalyst was prepared in the same manner as in (Catalyst B). Using this catalyst, a catalyst activity test was conducted in the same manner as in Example 1. Table 1 shows the composition of the catalyst and the evaluation results.

Example 3 In Example 1, 5.1 g of yttrium nitrate hexahydrate
Example 1 except that 4.5 g of lead nitrate was used in place of
A catalyst was prepared in the same manner as in (Catalyst C). Using this catalyst, a catalyst activity test was conducted in the same manner as in Example 1. Table 1 shows the composition of the catalyst and the evaluation results.

Example 4 In Example 1, 5.1 g of yttrium nitrate hexahydrate
Was replaced with the raw material solution (2) dissolved in 30 g of water, and a raw material solution prepared by dissolving 4.5 g of tin (II) chloride dihydrate in 30 g of 1 wt% hydrochloric acid was used in the same manner as in Example 1. To prepare a catalyst (referred to as "catalyst D"). Using this catalyst, a catalyst activity test was conducted in the same manner as in Example 1. Table 1 shows the composition of the catalyst and the evaluation results.

Comparative Example 1 In Example 1, raw material liquid (1) was prepared without adding ammonium paratungstate, and 4 parts of titania powder was added.
A catalyst (Catalyst E) was prepared in the same manner as in Example 1 except that 85 g was used. This catalyst was tested for activity in the same manner as in Example 1. Table 1 shows the composition of the catalyst and the evaluation results.

Comparative Example 2 In Example 2, the raw material liquid (1) was prepared without adding ammonium paratungstate, and 4 parts of titania powder was added.
A catalyst (catalyst F) was prepared in the same manner as in Example 2 except that 84 g was used. Using this catalyst, a catalyst activity test was conducted in the same manner as in Example 1. Table 1 shows the composition of the catalyst and the evaluation results.

Comparative Example 3 In Example 3, the raw material liquid (1) was prepared without adding ammonium paratungstate, and 4 parts of titania powder was added.
A catalyst (catalyst G) was prepared in the same manner as in Example 3 except that 84 g was used. Using this catalyst, a catalyst activity test was conducted in the same manner as in Example 1. Table 1 shows the composition of the catalyst and the evaluation results.

Comparative Example 4 In Example 4, raw material liquid (1) was prepared without adding ammonium paratungstate, and 4 parts of titania powder was added.
A catalyst (catalyst H) was prepared in the same manner as in Example 4 except that 84 g was used. Using this catalyst, a catalyst activity test was conducted in the same manner as in Example 1. Table 1 shows the composition of the catalyst and the evaluation results.

Comparative Example 5 In Example 1, 5.1 g of yttrium nitrate hexahydrate
A catalyst (catalyst I) was prepared in the same manner as in Example 1 except that the above was not added (that is, the raw material liquid (2) was not added). Using this catalyst, a catalyst activity test was conducted in the same manner as in Example 1. Table 1 shows the composition of the catalyst and the evaluation results.

[0031]

[Table 1]

Example 5 A catalyst was prepared in the same manner as in Example 1 except that it was extruded into a honeycomb shape instead of a cylindrical shape having a diameter of 3 mm. Using this catalyst, a model exhaust gas treatment test for an urban refuse incinerator was conducted. As the test apparatus, the same activity test apparatus as in Example 1 was used, and dioxins (2,3,7,8-
Tetrachlorodibenzodioxin (TEQ) conversion 4
8.5 ng-TEQ / Nm ³ and nitrogen oxides (so-called NO
X) A gas containing 75 ppm is added to ammonia 75 pp
While adding m, the catalyst packed bed was SV30 at a temperature of 200 ° C.
The chlorinated organic compounds and NOX in the gas were continuously decomposed by passing them at 00 h ^-1 . The exhaust gas after the treatment was analyzed in the same manner as in Example 1. Table 2 shows the content and decomposition rate of dioxins and NOX in the exhaust gas before and after the treatment.

[0033]

[Table 2]

As is clear from each of the above-described examples, the catalyst containing a vanadium oxide, a tungsten oxide, and an oxide of at least one element selected from the group consisting of yttrium, boron, tin, and lead can be used It can be seen that the decomposition reaction (dechlorination reaction) of benzene occurs efficiently. Further, it can be seen from Example 5 that decomposition of chlorinated organic compounds such as dioxins, which is a particular problem in combustion exhaust gas, is efficiently performed. When ammonia is introduced, nitrogen oxides can be removed at the same time.

[0035]

As described above, according to the method of the present invention, it is selected from the group consisting of vanadium oxide, tungsten oxide and yttrium, boron, tin and lead, which are low in cost and resistant to impurities. By using a mixed oxide catalyst containing oxides of at least one element, harmful chlorinated organic compounds such as dioxins in combustion exhaust gas such as municipal waste and industrial waste, which are socially problematic, An effective method for removal is provided.

[Procedure amendment]

[Submission date] May 10, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 2

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005]

That is, the gist of the present invention is to provide a method of decomposing a gas containing a chlorinated organic compound by contacting it with a catalyst, wherein the gas is (1) 100 to 3
From (3) (A) vanadium oxide, (B) tungsten oxide, and (C) yttrium, boron, tin and lead in the presence of 0.5 to 25 vol% oxygen at a temperature of 50 ° C. A method for decomposing a chlorinated organic compound, which comprises contacting with a catalyst containing an oxide of at least one element selected from the group consisting of :, and the gist of the present invention is that the catalyst is supported on titania. (A) vanadium oxide for titania, (B) tungsten oxide, and (C) yttrium,
The amount of each of the oxides of at least one element selected from the group consisting of boron, tin and lead (A) is 0.5 to
50 wt%, (B) 0.5 to 50 wt% and (C) 0.1 to 5
It also exists in the above decomposition method, which is 0 wt%.

Claims (3)

[Claims] 1. A method of decomposing a gas containing a chlorinated organic compound by contacting it with a catalyst, wherein the gas is (1)
At a temperature of 100 to 350 ° C., (2) 0.5 to 25 vol
% Oxygen, in the presence of (3) vanadium oxide (A), tungsten oxide (B), and oxide of at least one element selected from the group consisting of (C) yttrium, boron, tin and lead. A method for decomposing a chlorinated organic compound, which comprises contacting with a catalyst containing the same. 2. The catalyst is supported on titania, and at least one element selected from the group consisting of (A) vanadium oxide, (B) molybdenum oxide, and (C) yttrium, boron, tin and lead for titania. The amount of oxides of (A) 0.5 to 50 wt%, (B) 0.5 to 50 wt%
% And (C) 0.1 to 50 wt%. 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.