JP2001038209A - Catalyst for removing organohologen compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new catalyst capable of efficiently and inexpensively oxidizing and decomposing dioxins contained in exhaust gas discharged from an incinerator or the like even in a low temp. region to remove them. SOLUTION: A catalyst for removing dioxins contains α-MnO2 and further pref. contains at least one kind of a salt and/or oxide of an element selected from the group consisting of group VA elements, group VIA elements, ferrous elements and group IB elements.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst capable of oxidatively decomposing dioxins in exhaust gas generated from an incinerator for incinerating municipal garbage, industrial waste, sewage sludge, etc., a metal melting furnace and the like. The dioxins in the present invention include PC
DDs (polychlorinated dibenzodioxins) and PCDF
dioxins represented by s (polychlorinated dibenzofurans); dioxins containing bromine instead of chlorine in the dioxins; coplanar PCB (coplanar polychlorinated biphenyls);

[0002]

2. Description of the Related Art In order to remove dioxins contained in exhaust gas, various catalysts and decomposition removal methods using the catalyst have been proposed.

JP-A-2-280816 discloses a method for decomposing and removing aromatic halogen compounds such as dioxins at 300 to 700 ° C. using an iron oxide catalyst or an iron oxide catalyst containing manganese oxide and / or chromium oxide. Have been. The catalyst includes V, Sn, Co, W, Ni, M
It is described that it is preferable to add an element such as o, a rare earth, or a compound thereof.

[0004] Japanese Patent No. 2609393 discloses Ti, S
containing an element selected from i, Zr, Al, V, and V
And Pt, Pd, Ru, Mn, C
a catalyst containing at least one metal selected from u, Cr, Fe or an oxide thereof; Mo, Sn, C
catalyst containing at least one metal selected from the group consisting of e, W and Rh or an oxide thereof (for example, TiO ₂ +
SiO ₂ + ZrO ₂ + Al ₂ O ₃ : 88%, V ₂ O ₅ : 5%,
Pt + Pd: 0.5%, MoO ₃ : 5%), and the use of such a catalyst simultaneously decomposes and removes organic halogen compounds such as dioxins contained in exhaust gas at 150 to 450 ° C. A method is described.

[0005]

However, each of the above removal catalysts and removal methods has the following problems.

First, a preferable temperature for using the catalyst is 300 to 700 ° C., whereas a gas discharged from a bag filter generally used for removing dust in exhaust gas generally has a temperature of about 150 to 180 ° C. It is a low-temperature gas, and the temperature is often as low as 300 ° C. or less even in an electric dust collector. Therefore, in order to treat such a low-temperature gas with a catalyst, it is necessary to newly reheat to around 300 ° C., which is uneconomical, and re-synthesis of dioxins occurs with the reheating. Removal efficiency is significantly reduced.

The catalyst (1) can remove dioxins at a relatively low temperature as compared with the catalyst (2), but the removal activity at 200 ° C. or lower is not sufficient, and is insufficient as a catalyst applied to the exhaust gas of a bag filter at 150 to 180 ° C. It is. Therefore, when using in this low temperature range,
The catalyst loading needs to be significantly increased, which is uneconomical.

[0008] The present invention has been made in view of the above problems, and an object of the present invention is to reduce the amount of gas discharged from an incinerator or the like even in a low temperature range (around 150 to 180 ° C) applied to bag filter exhaust gas. To provide a novel removal catalyst capable of efficiently oxidatively decomposing and removing dioxins contained in water, and a method capable of efficiently producing the removal catalyst.

[0009]

The dioxin removal catalyst of the present invention, which has achieved the above objects, comprises α-Mn.
It has a gist where O ₂ is contained.

In a preferred embodiment of the present invention, those containing at least one salt and / or oxide selected from the group consisting of group 5A, 6A, iron and 1B elements are preferred.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have proposed that any of the conventionally proposed dioxin removal catalysts has at least 20
It exhibits practical activity in a temperature range of 0 ° C. or higher, and has a low temperature range (150 to 1) discharged from a bag filter.
In order to treat exhaust gas (around 80 ° C.), it is necessary to reheat the exhaust gas, and in view of the problem that resynthesis of dioxins and the like is caused, a removal catalyst having excellent activity even in such a low temperature range is provided. To this end, research has been conducted based on oxides containing Mn.

As a result, the intended purpose can be achieved by using α-MnO ₂ ; the above-mentioned oxide is further selected from the group consisting of a group 5A element, a group 6A element, an iron group element and a group 1B element. It has been found that when at least one kind of salt and / or oxide is contained, the ability to remove dioxins is further improved, and the present invention has been completed.

Incidentally, prior to the present invention, the present inventors have found that Mn
-Fe composite oxide and / or Mn-Cu composite oxide, β
It found that Mn-containing oxides -MnO ₂ is effective for the removal of dioxins, that I already filed (Japanese Patent Application No. 10-280254, and Japanese Patent Application No. 10-31111
6). However, when the present inventors further studied,
It was found that the use of α-MnO ₂ showed the same activity as the Mn-containing oxide.

It is already known that MnO ₂ including α-MnO ₂ itself has an activity of oxidatively decomposing organic substances. However, it has not been known until now that α-MnO ₂ has excellent removal activity for dioxins, and this is the first finding by the present inventors. In the present invention, it is important to use α-MnO ₂ , and MnO ₂ (γ-
Even if MnO ₂ or the like is used, the desired effect cannot be obtained (see Examples described later). Although the reason is not clear in detail, it is considered that the reason may be that the crystal structure of α-MnO ₂ has a structure suitable for the purpose of the present invention.

Α-MnO ₂ is the same as the above-mentioned Mn-containing oxide (β-MnO ₂ , Mn-Cu composite oxide,
-Fe composite oxide), which is useful in that it has excellent heat resistance, has little change in crystal form even when exposed to a heating atmosphere for a long time, and has excellent activity persistence.

The present inventors have proposed that α-MnO ₂ (further, a Mn-containing oxide containing β-MnO ₂ and a Mn—Cu / Mn—Fe composite oxide) be converted to a predetermined carrier component (Ti Oxide, Ce oxide, Zr oxide, and at least one compound selected from the group consisting of aluminum phosphate)
It has been found that the use of a catalyst supported on an organic solvent allows the halogenated organic compound to be continuously removed for a long period of time and that the SOx resistance can be improved. As described above, α-MnO ₂ is extremely useful because it has an excellent action of removing halogenated organic compounds by itself, and when combined with a predetermined carrier component, the durability can be significantly increased.

Here, in order to obtain more excellent dioxin removal activity, the specific surface area of α-MnO ₂ is 100 m ² /
g or more. More preferably 120m
² / g or more.

The catalysts of the present invention may further contain at least one salt and / or oxide selected from the group consisting of group 5A, group 6A, iron group and group 1B elements, as well as dioxins. It is extremely effective in increasing the removal ability.

The above elements include V, a 5A group element,
Nb, Ta (use of V is recommended in consideration of the economic efficiency and the effect of improving the removal performance); Cr and M as Group 6A elements
o, W (use of Mo, W is recommended in consideration of easiness of disposal, etc.); Fe, Co, Ni as an iron group element (use of Ni is recommended in consideration of sustainability of removal performance) );
Examples of group 1B elements include Cu, Ag, and Au (the use of Ag is recommended in consideration of the raw material cost and the effect of improving the removal ability).

It is recommended that the above metal elements be used in the form of a salt and / or an oxide. Salts and / or oxides of the metal elements is not observed desired dioxins removal effect be supported on an inert carrier such as aluminum oxide, silicon oxide, if supported on alpha-MnO _2, significantly It has been confirmed that it exhibits excellent removal activity. These metal element salts and / or oxides may be used alone or in combination of two or more.

The salt and / or oxide of the above metal element in the dioxin removal catalyst of the present invention is preferably 0.1 to 10% (mass%, hereinafter the same) in terms of metal. If it is less than 0.1%, the oxidation activity is poor. More preferably, it is 0.5% or more. On the other hand, even if it is added in excess of 10%, the removal performance is not improved. It is more preferably at most 5%.

In the present invention, an oxide of a Group 4A element may be contained for the purpose of improving durability. Thereby, the halogenated organic compound can be continuously removed for a long time, and the SOx resistance can be improved. Examples of the above elements include Ti and Zr (the use of Ti is recommended in consideration of raw material costs and the like), and these elements may be used in the form of an oxide. Here, it is preferable that the oxide of the above-mentioned element in the dioxin removal catalyst of the present invention is 10 to 50% as a metal oxide. If it is less than 10%, the effect of improving durability is insufficient. However, even if it is added in excess of 50%, the durability performance is not improved.

The salt and / or oxide of the above metal is α-Mn
For supporting on O ₂ , a method of immersing α-MnO ₂ in an aqueous solution of the above-mentioned metal nitrate, sulfate, chloride or the like, followed by drying and supporting can be adopted. For example, when Ni chloride is used, α-MnO ₂
Immersed in an aqueous nickel chloride solution, followed by filtration and drying.

Hereinafter, the present invention will be described in detail with reference to examples.
However, the following examples do not limit the present invention,
All modifications and alterations without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention.

[0025]

Example 1 In this example, the removal rate of O-dichlorobenzene (one type of halogenated organic compound, hereinafter abbreviated as DCB) by various MnO ₂ species was examined.

Incidentally, DCB is a typical dioxin simulating substance which is known to exhibit similar decomposition characteristics to dioxins, and is a substance which is more difficult to decompose than dioxin (for example, 79th Annual Meeting of the Catalysis Society of Japan, p200).

In the following method, No. After preparing the catalyst of No. 1, this catalyst was sequentially charged into a stainless steel reaction tube having an inner diameter of 3.0 cm, and the DCB removal ability was measured under the following conditions. Catalyst filling height: 6.0 cm SV: 5000 h ^-1 DCB concentration: 10 ppm Reaction temperature: 170 ° C. Reaction time: 6 h The average DCB removal rate of each catalyst for 6 hours was calculated by the following formula. DCB removal rate (%) = ｛1- (outlet DCB concentration / inlet D
CB concentration) x 100

[No. 1] Cryptomelane ore Mn oxide was pulverized, and alumina sol and water were added to powder of 100 mesh or less. The resulting slurry was extruded into cylindrical pellets having a diameter of 1/8 "and dried to obtain an α-MnO ₂ catalyst. No. 1 had a specific surface area of 128 m ² / g.

[No. 2] MnSO ₄ , K ₂ SO ₄ , KMn
The hot aqueous solution containing O ₄ was electrolyzed using carbon as an anode to obtain fine particles of γ-MnO ₂ as an anode deposit.
This γ-MnO ₂ was designated as No. Molded in the same manner as 1
o. 2 were obtained (specific surface area: 120 m ² / g).

[No. 3] An anatase type titanium oxide powder was obtained by calcining the hydrated titanium oxide obtained by hydrolyzing titanyl sulfate. Vanadium oxide and colloidal titania were added to this titanium oxide, and the diameter was 1 /
Extruded into 8 ″ cylindrical pellets, dried and dried.
Was obtained.

The results are shown in Table 1.

[0032]

[Table 1]

From the results shown in Table 1, the catalyst containing α-MnO ₂ (No. 1) was different from that of MnO ₂ catalyst (No. 1) having different crystal forms.
2), and a titanium oxide catalyst supported on vanadium oxide (No.
It can be seen that a significantly higher DCB removal rate can be obtained than in 3).

Example 2 In this example, the DCB removal performance when a specific metal salt or metal oxide was carried on α-MnO ₂ was examined.

[No. 4] No. No. 1 was sprayed with an aqueous solution of oxalic acid of ammonium metavanadate (NH ₄ VO ₃ ) on the catalyst containing α-MnO ₂ , dried and calcined. 4 were obtained.

[No. 5-No. 9] No. 5: No. 5 except that an aqueous solution of CrCl ₃ was used instead of the NH ₄ VO ₃ solution. No. 4 is processed in the same manner. 5
Was obtained.

No. 6: Instead of NH ₄ VO ₃ solution (N
No. 4 except that an aqueous solution of H ₄ ) ₁₀ W ₁₂ O ₄₁ was used. No. 4 is processed in the same manner. 6 were obtained.

No. 7: Co instead of NH ₄ VO ₃ solution
No. ₂ except that an aqueous solution of Cl ₂ was used. No. 4 is processed in the same manner. 7 were obtained.

No. 8: NiC instead of NH ₄ VO ₃ solution
The same treatment as in No. 4 except that an aqueous solution of l ₂ was used,
No. 8 catalyst was obtained.

No. 9: Ag instead of NH ₄ VO ₃ solution
No. 2 except that an aqueous solution of NO ₃ was used. No. 4 is processed in the same manner. 9 catalysts were obtained.

[No. 10] No. Α-Mn during fabrication of 1
No. 2 except that Nb ₂ O ₅ powder was added to O ₂ powder and mixed with a ball mill. No. 1 is processed. 10 catalysts were obtained.

[No. 11] Mo instead of Nb ₂ O ₅ powder
No. ₃ except that O ₃ powder was used. No. 10 was processed in the same manner. 11 catalysts were obtained.

Table 2 shows the results.

[0044]

[Table 2]

From the results shown in Table 2, the catalysts (No. 4 to No. 11) in which a salt and / or an oxide of a predetermined metal element is supported on a catalyst containing α-MnO ₂ , And / or a catalyst containing α-MnO ₂ not supporting an oxide (N
o. An excellent DCB removal rate was obtained as compared with 1).

Example 3 In this example, the performance of removing dioxins contained in exhaust gas was examined. In the experiment, the following three types of catalysts were used. No. 1: α-MnO ₂ catalyst No. 1: 4: α-MnO ₂ catalyst supporting V compound No. 4: 3: TiO ₂ catalyst supporting V compound

After the above catalyst was filled in a reaction tube having an inner diameter of 39 mm, the catalyst was contacted under the following conditions, and the concentration of dioxins (sum of PCDDs and PCDFs) at the outlet of the reaction tube was examined. The reaction conditions are as follows. Catalyst filling height: 18cm SV: 5000h- ¹ Reaction temperature: 170 ° C

The concentration of dioxins in the exhaust gas used in the experiment was 0.72 ng-TEQ / Nm ³ .

Table 3 shows the results.

[0050]

[Table 3]

As shown in Table 3, One α-MnO ₂ catalyst is
No. As compared with the TiO ₂ catalyst supporting the V compound of No. 3, higher dioxin removal performance was obtained. From this, α-M
It was found that by supporting the V compound on the nO ₂ catalyst, the dioxin removal activity was further improved.

[0052]

As described above, the catalyst for removing dioxins of the present invention is constituted as described above, so that dioxins contained in exhaust gas can be efficiently oxidatively decomposed and removed in a low temperature range. The removal catalyst of the present invention is excellent not only in dioxin removal ability but also in the production method, so that it is excellent in production efficiency and economically very excellent.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Katsuyuki Iijima 1-5-5 Takatsukadai, Nishi-ku, Kobe, Japan Inside Kobe Steel Research Institute Kobe Research Institute (72) Inventor Takefumi Yamashita 1-chome, Takatsukadai, Nishi-ku, Kobe-shi No.5 No.5 F-term in Kobe Research Institute, Kobe Steel, Ltd. (Reference) 4D048 AA11 AB03 BA07X BA07Y BA28X BA28Y 4G069 BA01B BA04B BB04A BB05B BC13B BC30A BC50B BC53A BC57A BC62A BC62B BC65A CA01 CA19 EC03Y

Claims (2)

[Claims] 1. A halogenated organic compound removing catalyst comprising α-MnO ₂ . 2. The method according to claim 1, further comprising at least one salt and / or oxide selected from the group consisting of a group 5A element, a group 6A element, an iron group element and a group 1B element. Catalyst for removing halogenated organic compounds.