JP2002136873A - Catalyst for decomposing coplanar pcbs and method for treating coplanar pcbs - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst for decomposing coplanar PCBs, by which the toxicity of coplanar PCBs can be lowered at the generation source or in the existence environment of the coplanar PCBs. SOLUTION: This catalyst for decomposing coplanar PCBs contains at least partially an active component containing vanadium oxide and/or tungsten oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a coplanar PCB.
More specifically, the present invention relates to a catalyst for decomposing coplanar PCBs used for reducing the toxicity of coplanar PCBs contained in exhaust gas from a waste incineration plant or a sludge incineration plant, for example.

[0002]

2. Description of the Related Art From January 15, 2000, polychlorodibenzoparadioxin (hereinafter referred to as dioxin) has been used as dioxins.
In addition to PCDDs and polychlorodibenzofurans (hereinafter referred to as "PCDFs"), laws and regulations that newly include coplanar PCBs (hereinafter referred to as "Co-PCBs") have been enforced in Japan. The ratio of Co-PCBs to the total toxic equivalents of dioxins in waste incineration exhaust gas is generally as low as 10% or less, but PCDDs / PCDF
As compared with s, a method for decomposing and removing Co-PCBs has not yet been fully established.

According to the study of the present inventors, Co-
It has been found that PCBs, unlike PCDDs / PCDFs, have a large difference between the degradation rate on an actual concentration basis and the degradation rate on a toxic equivalent equivalent (TEQ) basis. Therefore, in terms of environmental safety, it is more important to improve the decomposition rate on a TEQ basis and reduce toxicity than to increase the decomposition rate on an actual concentration basis.

[0004]

The object of the present invention is to provide a source of Co-PCBs represented by refuse incineration facilities and the like,
In an environment where Co-PCBs exist, Co-PCB
An object of the present invention is to provide a catalyst for decomposing Co-PCBs, which can reduce the toxicity of s.

[0005]

In order to solve the above-mentioned problems, the present invention according to claim 1 is characterized by containing at least partially a catalytically active component containing vanadium oxide and / or tungsten oxide. A co-planar PCB decomposition catalyst.

According to the present invention, a catalyst containing at least partially a catalytically active component containing vanadium oxide and / or tungsten oxide can reduce its toxicity by decomposing Co-PCBs. Therefore, it is suitable for actual use in a waste incineration facility or the like where safety to the environment is the highest priority.

[0007] The invention of a catalyst for decomposing coplanar PCBs according to a second aspect is characterized in that, in the first aspect, the catalyst comprises 3
It has a selective resolution for 3'44'5-P5CB. Here, "33'44'5-
“P5CB” is a substance that has the highest toxicity equivalent coefficient (TEF) and is considered to be the most toxic among many chemical species contained in Co-PCBs.

According to the present invention, 33'44'5-P5CB, which is a particularly toxic substance among Co-PCBs, can be decomposed selectively and at a high rate.
A high decomposition rate can be achieved on a TEQ basis, and the toxicity of Co-PCBs can be reduced. That is, as shown in Examples below, by specifically decomposing 33'44'5-P5CB, which accounts for most of the toxicity of Co-PCBs, the toxicity of Co-PCBs can be significantly reduced. Become.

[0009] The invention of a catalyst for decomposing Co-PCBs according to claim 3 is characterized in that, in claim 1 or 2, the catalyst is:
It is characterized by being used under the condition of a water concentration of 1 to 70% by volume.

According to the present invention, Co-PCBs can be decomposed at a high level on a TEQ basis by using the decomposition catalyst for Co-PCBs under the condition of a water concentration of 1 to 70% by volume. That is, the catalyst of the present invention exhibits excellent activity in the presence of 1 to 70% by volume of water to improve the decomposition rate of Co-PCBs on a TEQ basis, and usually contains the same amount of water. It is suitable for treating exhaust gas from refuse incinerators, etc.
High practicality.

According to a fourth aspect of the present invention, there is provided a catalyst for decomposing Co-PCBs according to any one of the first to third aspects, wherein vanadium oxide is contained in the catalyst in an amount of 0.01 to 30 wt.
% Of tungsten oxide and / or 0.01 to 30% by weight of the total weight of the catalyst. According to this feature, the performance of the cracking catalyst of the present invention is sufficiently exhibited.

According to a fifth aspect of the present invention, there is provided a catalyst for decomposing Co-PCBs according to any one of the first to fourth aspects, wherein the catalytically active component is supported on titanium oxide. I do.

According to this feature, the titanium oxide contributes to the maintenance of the structure such as securing the pores and the specific surface area of the catalyst and assists the dispersion of the catalytically active component on the catalyst surface. It is fully demonstrated.

[0014] The invention of the catalyst for decomposing Co-PCBs according to claim 6 provides the invention according to any one of claims 1 to 5, wherein
0 m ² / g or more specific surface area and / or 0.2 cm ³
/ G or more of pore volume.

According to this feature, by setting the specific surface area and the pore volume within the above ranges, it is possible to secure a sufficient contact opportunity between the object to be treated containing Co-PCBs and the catalytically active component. Processing efficiency can be obtained.

According to a seventh aspect of the present invention, there is provided a method for decomposing Co-PCBs, comprising using the Co-PCBs decomposing catalyst according to any one of the first to sixth aspects.

According to the present invention, for example, Co-PCB
In aspects such as the actual treatment of exhaust gas containing s, it is possible to obtain the same effects as in claims 1 to 6.

[0018]

DETAILED DESCRIPTION OF THE INVENTION The decomposition catalyst for Co-PCBs of the present invention (hereinafter simply referred to as "decomposition catalyst") contains at least partially a catalytically active component containing vanadium oxide and / or tungsten oxide. Is what you do. When this decomposition catalyst is used, Co-PCBs can be sufficiently oxidatively decomposed to a harmless level on a TEQ basis. That is, T
Efficiently degrading Co-PCBs on an EQ basis means, in other words, reducing the toxicity of Co-PCBs. Here, examples of the vanadium oxide include divanadium pentoxide, vanadium dioxide, and divanadium trioxide, and examples of the tungsten oxide include tungsten trioxide.

More specifically, vanadium oxide is contained in the catalyst in an amount of 0.01 to 30% by weight, preferably 1 to 30% by weight of the total weight of the catalyst.
And / or 0.01 to 30% by weight, preferably 1 to 30% by weight of the total weight of the catalyst.
Those containing 0 to 20% by weight are desirable. In this range, the catalyst performance is sufficiently exhibited.

The decomposition catalyst is preferably one in which the above-mentioned catalytically active component is supported on titanium oxide. Here, in order to “support” the catalytically active component on the titanium oxide, for example, by mixing the catalytically active component and the titanium oxide, by various methods described later or a similar method thereto,
All means for obtaining a supported catalytic effect are included.

Examples of the titanium oxide include titanium dioxide of anatase type and rutile type.
This titanium oxide mainly plays a role as a catalyst carrier in maintaining the structure such as securing pores and specific surface area of the catalyst and assisting dispersion of the catalytically active component on the catalyst surface.

The specific surface area of the cracking catalyst of the present invention is 30 m ²
/ G or more, preferably 45 m ² / g or more, more preferably 80 m ² / g or more. In general, it is preferable that the specific surface area is large. However, if the specific surface area is too large, the pore size becomes small, so that it may be difficult for Co-PCBs to enter the inside. Further, the pore volume of the decomposition catalyst can be at least 0.2 cm ³ / g or more, and preferably 0.3 cm ³ / g or more. The pore volume is preferably as large as possible from the viewpoint of improving the catalyst activity, but if it is too large, the strength of the catalyst may decrease.
Therefore, the upper limit of the specific surface area and the pore volume can be set in a range that can be manufactured, but as the upper limit of the specific surface area,
The upper limit of the pore volume is about 1000 m ² / g,
It is preferable to be about 6 cm ³ / g. By setting the specific surface area and the pore volume within the above ranges, it is possible to increase the chance of contact between the treatment target containing Co-PCBs and the catalytically active component, and it is possible to obtain good treatment efficiency.

The outer shape of the catalyst is not particularly limited.
For example, a packed layer of catalyst particles such as granules, columns, and cylinders, and a honeycomb-shaped column / square column molded product are used.

The decomposition catalyst of the present invention can be prepared by, for example, a kneading method, an impregnation method, a coprecipitation method, a sol-gel method or the like, and a catalyst component and a carrier component, and a supporting method.

In the case of the kneading method, raw material particles having an average particle diameter of 1 μm or less, preferably 0.1 μm or less, more preferably 0.01 μm or less are used, and a catalyst component and preferably a carrier are used as a molding aid. , Kneaded with various additives such as a binder, and molded and calcined to prepare a catalyst. The catalyst component is a raw material that changes to an oxide when calcined,
For example, hydroxides, halides, ammonium salts, sulfates, carbonates, acetates of vanadium oxide and / or tungsten oxide (or metal oxoate ions),
Complex compounds such as alkoxides and acetylacetonates may be used. For example, as the vanadium oxide, vanadyl sulfate, ammonium metavanadate, or the like is used, and in the latter case, a material obtained by adding an appropriate amount of oxalic acid or the like can be used as a raw material. In the case of tungsten oxide, for example,
A starting material can be used by using ammonium paratungstate or the like together with an appropriate amount of oxalic acid.

Titanium dioxide used as a carrier is generally prepared by subjecting ilmenite ore to sulfuric acid and extracting it.
i (SO ₄ ) ₂ , TiO ₄ , TiCl _4, etc. are alkali-hydrolyzed to form a titanate gel having an average particle size of 1 μm or less, preferably 0.1 μm or less, more preferably 0.01 μm or less. It is obtained by firing into granules.

In the case of the impregnation method, for example, the carrier has an average particle size of 1 μm or less, preferably 0.1 μm or less,
More preferably, the catalyst component is impregnated using titanium dioxide particles of 0.01 μm or less or a molded product thereof. The impregnation may be carried out using raw materials that change to oxides during firing, for example, hydroxides, halides, ammonium salts, sulfates, carbonates of vanadium oxides and / or tungsten oxides (or metal oxoate ions), The reaction can be performed using a solution of an acetate, an alkoxide, or a complex compound such as acetylacetonate.

In the case of the coprecipitation method, an aqueous solution of a carrier component [eg
For example, Ti (SO₄)₂And TiO ₄Or TiC
l₄] And an aqueous solution of a catalyst component [eg, sulfuric acid
Nasil or ammonium metavanadate (oxalic acid
May be mixed in an appropriate amount), and / or paratan
Do not contain ammonium gustinate and an appropriate amount of oxalic acid.
And co-precipitate by adding a precipitant,
Thereafter, it is washed, dried, molded, and fired.

Furthermore, the catalyst component and / or the carrier component can be prepared alone or simultaneously using a sol-gel method. In the sol-gel method, a metal alkoxide of each component (vanadium oxide and / or tungsten oxide, and furthermore, titanium oxide) or a complex such as acetylacetonate is dissolved in a predetermined organic solvent in a predetermined amount in a sol state. A predetermined amount of acid or alkali and water are added to the solution to form a gel polymer, which is molded and fired to prepare a target oxide. In preparing the present catalyst, the catalyst components (vanadium oxide and / or
Or a tungsten oxide) and / or a carrier component (titanium oxide) are preliminarily mixed at a predetermined ratio in a sol-like solution stage, and the mixture is gel-formed and fired,
The former is a method of impregnating the carrier component with the sol-like mixed solution and then gelling and firing, and the other is a method of individually preparing each oxide fine particle by the sol-gel method, and kneading, molding and firing them. It is.

In addition to the above, the catalyst component (vanadium oxide and / or tungsten oxide) and the carrier component (titanium oxide) are mixed in a fine state by a means such as pulverization and dispersed to each other. A similar supported catalyst effect is obtained.

The cracking catalyst of the present invention is packed in a tubular or box-shaped catalytic cracking reactor or a catalyst tower in the case of catalyst particles, and in such a manner that the honeycomb cross section becomes perpendicular to the exhaust gas channel in the case of a honeycomb-shaped molded article. Array. At this time, the required SV
It can be suitably used by determining the filling amount or the number of serial / parallel arrangements so as to satisfy the (space velocity) value and the exhaust gas throughput. Also, it can be used in combination with a denitration catalyst or a dioxin decomposition catalyst.

FIG. 3 schematically shows a refuse incineration plant as an example to which the decomposition catalyst of the present invention can be applied.

Co-PCB using the cracking catalyst of the present invention
The conditions for the decomposition process of s are as follows.

The decomposition catalyst of the present invention can be expected to have high decomposability under the condition that 1 to 70% by volume, more preferably 5 to 50% by volume of water is present. The reasons are as follows.
In addition, Co-P, which has the same polarity as the polar water molecule
CBs is easily adsorbed on the surface of the decomposition catalyst to which water molecules are attached. Second, some water contributes to hydrolysis on the decomposition catalyst. Third, some water is used for decomposition catalyst. The active oxidizing species (hydrogen radicals, OH radicals) are formed on the catalyst to accelerate the catalytic decomposition reaction. Fourth, the decomposition catalyst is deprived of oxygen in the active form of the solid oxide by the decomposition reaction.
It contributes to the decomposition reaction in the cycle of being re-oxidized by the oxygen gas in the atmosphere and returning to the active form again, but in this process water acts as a catalyst and promotes the re-oxidation of the decomposition catalyst,
Alternatively, it is considered that a part of water becomes an oxygen supply source of solid oxide of the decomposition catalyst, and fifthly, that a part of oxygen of water becomes an oxygen supply source of oxidative decomposition of hydrocarbon. Can be For example, since the actual exhaust gas discharged from a refuse incinerator or the like usually contains about 5 to 50% by volume of water, the amount of Co is reduced in the presence of the same amount of water as the actual exhaust gas.
-The ability to decompose PCBs efficiently is a great advantage of decomposition catalysts.

The oxygen concentration is preferably about 1 to 50% by volume, more preferably about 5 to 15% by volume.
The reason is that the supply of oxygen is necessary for catalytic oxidative decomposition, and the oxygen concentration in the actual exhaust gas generally generated from the refuse incinerator is about 5 to 10% by volume,
The decomposition catalyst of the present invention can be used in an oxygen atmosphere similar to actual exhaust gas.
This is because the toxicity of o-PCBs can be reduced.

The temperature is about 100 to 410 ° C., preferably about 140 to 260 ° C. Within this range, dew condensation of moisture in the exhaust gas can be prevented, and sufficient decomposition performance can be exhibited while keeping the amount of supplied heat as low as possible.

The space velocity (SV) is 400 to 100,0
About 00 / hr, preferably 800 to 5,000 / hr
It is about. Within this range, Co-PCBs can be decomposed with a margin while using as little catalyst as possible.

[0038]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. Example 1 (1) Catalyst used: Cracking catalyst of the present invention (V-W /
The actual exhaust gas was subjected to PCB treatment using Ti). This catalyst was produced by the above-mentioned kneading method. <VW / Ti-based catalyst> Active ingredient composition: Vanadium pentoxide 4%, tungsten trioxide 14% Carrier: titanium oxide Specific surface area: 45 m ² / g Pore volume: 0.30 cm ³ / g Shape: square lattice Honeycomb type Outside dimensions: 150 mm ^□ × 520 mm (2) Test method: A part of the actual exhaust gas from the refuse incineration facility is branched at the outlet of the dust collection facility, guided to the test catalyst reactor, and the gas at each inlet / outlet position. Was collected. In the experiment, the processing gas volume was 74
0m ³ N / h, temperature about 200 ° C, SV3200h
r ⁻¹ , NH ₃ / NO molar ratio of about 0.7
H ₃ was injected. Other compositions of real gas are:
O ₂ : 6% by volume, CO ₂ : 6% by volume: N ₂ : 57% by volume, and water: 30% by volume.

For reference, PCDDs and PCDFs
A similar test was also conducted for. Co-PCBs, P
The collection and quantification of CDDs and PCDFs is based on JIS K0311.
Was analyzed by (2) Results Table 1 shows that PCDDs, PCDFs, and C in exhaust gas at the inlet and outlet of the reactor at 200 ° C. using a VW / Ti-based catalyst.
The composition ratio of the toxic equivalent of o-PCBs is shown. Here, the toxic equivalent of Co-PCBs in the exhaust gas at the inlet was about 5% of the total toxic equivalent.

[0040]

[Table 1] The concentration of dioxins is 0.060 ng at the reactor inlet.
-TEQ / m ³ N was changed to the reactor outlet (SV3
0.00020 ng-TEQ / m at 200 hr ^-1 )
It was removed to ³ N, and the decomposition rate at a toxic equivalent was 99.7%.

FIG. 1 shows the PCDDs and PCDs shown in Table 1.
The decomposition rate of each of Fs and Co-PCBs was determined by the toxic equivalent (TE
Q) The results are summarized on a base and actual density basis.
SV3 200 hr ^-1 , under a temperature condition of about 200 ° C.
Comparing the decomposition rates based on actual concentration, PCDDs, P
CDFs show high values of 93.7% and 98.9%, respectively, while Co-PCBs show 60.9%
Was low. On the other hand, the decomposition rates of PCDDs and PCDFs on a TEQ basis are 98.5% and 100% (PC
The total decomposition rate of DDs and PCDFs was 99.7%), and that of Co-PCBs was 99.5%. From this, the cracking catalyst of the present invention is PCD based on TEQ base.
Similar to Ds / PCDFs, it was shown that Co-PCBs can be decomposed at a high rate and almost detoxified.

FIG. 2 shows Co-PCBs obtained by an actual gas test.
Decomposition rate (based on actual concentration) for each chlorine valence. Here, Co-PCBs with 7 valences are the highest (decomposition rate about 100%).
%), The lowest degradation rate of the pentavalent Co-PCBs (about 39%).
%), And there was a gap of about 60% between the two. The figure also shows that the most toxic is 33'44'5-P5CB.
Decomposition rate based on actual concentration and TEQ of all Co-PCBs
The decomposition rate at the base is also shown. 33'44'5-P5C
Although B is a pentavalent Co-PCB, it can be seen that B is decomposed at a significantly high rate by the catalyst of the present invention.
In the case of PCDDs / PCDFs, it is known that the larger the chlorine valence, the more likely it is to be decomposed.
-The above results for PCBs did not show any particular tendency according to the magnitude of chlorine valence. FIG. 2 shows a pentavalent C
The decomposition rate of o-PCBs as a whole and the decomposition rate of 33'44'5-P5CB are shown, but it can be seen that the decomposition rate differs greatly for each isomer within the same valence.

FIG. 1 shows the actual concentration base of Co-PCBs.
Despite the low decomposition rate of 60.9%, TEQ
The reason why the decomposition rate on the base is as high as 99.5% is that, as shown in FIG. 2, the toxic equivalent coefficient (TEF) is particularly high as compared with each of the other species of Co-PCBs, and therefore the TEQ base is high. It shows that the selective decomposition rate by the catalyst of the present invention with respect to 33'44'5-P5CB which controls the decomposition rate of copper is remarkably high (for reference, TEF of Co-PCBs is shown in Table 2).

[0044]

[Table 2] Summarizing the above results, the decomposition catalyst for Co-PCBs of the present invention, when evaluated on a TEQ basis, shows that Co-PCBs
, And showed a markedly decomposing property, and specifically act on 33'44'5-P5CB among Co-PCBs to decompose this substance. This shows that Co-PCBs can be almost detoxified by using the decomposition catalyst of the present invention, and has important significance from the viewpoint of practicality in exhaust gas treatment where environmental safety is the highest priority. is there.

[0045]

Industrial Applicability The decomposition catalyst of the present invention can significantly reduce the toxicity of Co-PCBs, and is suitable for actual use in refuse incineration facilities where safety to the environment is the highest priority. is there.

[Brief description of the drawings]

FIG. 1 is a graph showing the degradability of Co-PCBs.

FIG. 2 is a graph showing the degradability of each chemical species of Co-PCBs.

FIG. 3 is a schematic diagram showing an example of a refuse incineration facility.

[Explanation of symbols]

 Reference Signs List 1 Waste incineration facility 2 Waste heat boiler 3 Water cooling / cooling tower 4 Dust collection equipment 5 Catalytic reaction tower 6 Blower 7 Exhaust tower A Gas sampling position at catalyst tower inlet B Gas sampling position at catalyst tower outlet

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideyuki Tsuboi 1-Yawata Kaigan-dori, Ichihara-shi, Chiba Mitsui Engineering & Shipbuilding Co., Ltd. (72) Inventor Nobuyasu Kanda 1-Yawata-Kaigan-dori Ichihara-shi, Chiba Mitsui Engineering & Shipbuilding Co., Ltd. Inside Chiba Works (72) Inventor Makoto Yamamoto 1 Yawata Kaigandori, Ichihara City, Chiba Prefecture Mitsui Engineering & Shipbuilding Co., Ltd.F-term (reference) BB06B BC54A BC54B BC60A BC60B CA04 CA10 CA19 EA19 EB14Y EC02X EC02Y EC06X EC06Y FC08 4H006 AA02 AC13 AC26 BA12 BA14 4H039 CA99 CL00

Claims (7)

[Claims] A catalyst for decomposing coplanar PCBs, comprising at least partially a catalytically active component containing vanadium oxide and / or tungsten oxide. 2. The method according to claim 1, wherein the catalyst is 33 ′.
A catalyst for decomposing coplanar PCBs, which has a selective resolution for 44'5-P5CB. 3. The decomposition catalyst for coplanar PCBs according to claim 1, wherein the catalyst is used under the condition of a water concentration of 1 to 70% by volume. 4. The method according to claim 1, wherein
In the catalyst, vanadium oxide was added in an amount of 0.01 wt.
A catalyst for decomposing coplanar PCBs, wherein the catalyst contains 0.01 to 30% by weight of tungsten oxide and / or 0.01 to 30% by weight of the total weight of the catalyst. 5. The method according to claim 1, wherein:
A catalyst for decomposing coplanar PCBs, wherein the catalyst is obtained by supporting the catalytically active component on titanium oxide. 6. The method according to claim 1, wherein:
The catalyst is 30m ²/ G or more specific surface area and / or
Is 0.2cm³/ G or more pore volume
A catalyst for decomposing coplanar PCBs. 7. A method for decomposing coplanar PCBs, comprising using the catalyst for decomposing coplanar PCBs according to any one of claims 1 to 6.