JPH06254397A - Catalyst for denitration - Google Patents

Abstract

PURPOSE:To provide a denitration catalyst capable of satisfactorily maintaining its denitration effect even if the amt. of expensive TiO2 is reduced. CONSTITUTION:This denitration catalyst is a compacted catalyst consisting of 0.5-3wt.% V2O5, 0.5-5wt.% WO3 and 10-30wt.% TiO3 as catalytically active components and the balance compacting agent contg. at least 5wt.% montmorillonite with Na or Ca ions substd. for contained exchangeable ions by exchange as a smectite group mineral. The porosity of the compacted catalyst is 40-60% and the average pore diameter is 300-2,000Angstrom .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst for a denitration device, and more particularly to a denitration catalyst which can be advantageously applied to denitration of engine exhaust gas.

[0002]

2. Description of the Related Art At present, the mainstream of catalysts for denitration equipment is TiO ₂ as a main component, to which V ₂ O ₅ and WO ₃ are mixed. It is desirable that the catalyst for the denitration device has a large contact area with the gas and does not hinder the gas flow, and is used after being molded and fired into a normal honeycomb. The general composition of the conventional catalyst is TiO ₂ : about 90 wt%, V ₂ O ₅ :
About 0.5 wt% and WO ₃ : about 8 wt%.

[0003]

The conventional catalyst has a very high cost ratio of about 25% in the denitration equipment plant. Although the denitration equipment is indispensable for the preservation of the global environment, this high cost is a major obstacle to the introduction. In particular, demand for small equipment such as cogeneration plants is expected to increase significantly due to the high efficiency of energy use, but this high cost is likely to have a significant impact on that growth. . The high cost of conventional catalysts is due to the high material cost of using TiO ₂ as the main raw material and the difficulty of formability. Since TiO ₂ is produced by refining Ti, which is a finite resource of the global environment, it is very expensive due to complicated steps.

In view of the above-mentioned state of the art, the present invention is to provide an inexpensive denitration catalyst having excellent denitration performance.

[0005]

Means for Solving the Problems The present invention includes (1) by weight, V ₂ O ₅ : 0.5 to 3%, WO ₃ :
0.5~5%, TiO _2: 10~30% becomes catalytically active component and the remainder of the exchangeable ions of at least 5% are included N
a forming agent which is a smectite group montmorillonite mineral exchanged with a ions, and the porosity of the forming catalyst is 40
-60% and the average pore size is 300-2000
A denitration catalyst characterized by being Å. (2) In weight%, V ₂ O ₅ : 0.5 to 3%, WO ₃ :
0.5~5%, TiO _2: 10% to 30% consisting catalytically active component and balance the exchangeable ions of at least 5% are included C
a forming agent which is a smectite group montmorillonite mineral exchanged with a ions, and the porosity of the forming catalyst is 40
-60% and the average pore size is 300-2000
A denitration catalyst characterized by being Å. Is.

[0006]

The present invention is based on V ₂ O ₅ , which is the active component of conventional catalysts,
It started by suppressing the amounts of WO ₃ and TiO ₂ used. When suppressing, what should be selected for other alternative components, and in this case, the porosity and pore size of the product also change from the conventional catalyst, so how much to set this value is a big point. there were. The present invention has been completed by solving these points.

The role of the catalyst is the oxidation of nitrogen generated in the combustion reaction.
Things NOx (NO is the main, NO₂Is slightly) NH₃Etc. reduction
N in the presence of the agent₂It is to make it harmless. To this reaction
Is V ₂O_Five, Fe₂O₃, WO₃Etc. are active,
V in terms of sex selectivity and durability₂O_Five, WO₃Is advantageous
is there. Also, TiO₂He directly contributes to this denitration reaction
No, but V₂O_Five, WO₃Has an advantageous effect on fixing
It

In the present invention, in consideration of the above points, V in% by weight is obtained.
₂ O ₅ 0.5 to 3%, WO ₃ 0.5 to 5%, TiO
The ratio of ₂ is 10 to 30%.
No activity is exhibited when V ₂ O ₅ is 0.5% or less and WO _{3 is} 0.5% or less. Further, when V ₂ O _{5 is} 3% or more and WO _{3 is} 5% or more, good activity is exhibited, but the cost becomes high and the moldability becomes poor. TiO ₂ is V ₂ O ₅ , WO as described above.
Used to fix ₃ .

Although not particularly limited in the present invention, T
iO₂V to powder₂O_Five, WO₃Hugged in the raw material stage
It is desirable to let it. Specifically, T with a particle size of about 1000Å
iO ₂Powder, V₂O_FiveAmmonium metavanadate as a source
Umm (NH_FourVO₃), WO ₃Paratangu as a source
Ammonium acid salt ((NH_Four)_Ten・ W₁₂O₄₁・ 5H
₂O) was added as a methylamine solution and water was added to it.
After making it into a slurry, dry it with a spray dryer etc.
After firing, it is used as the pre-supported powder (active catalyst component powder) that is baked
Is the law. In this method, V₂O_Five, WO₃The activity of
There is an advantage that can be effectively used. Including use in this way
TiO₂Needs 10% or more, and below 10%
The activity of the catalyst is not fully exerted. Also, at 30% or more
Results in poor moldability and reduced product yield. Above, catalyst
After identifying the active ingredient formulation, the remaining ingredients are seeded.
I examined each.

As a result, at least 5% or more of the remaining components were smectite group montmorillonite minerals, and it was necessary for the smectite group montmorillonite minerals to have exchangeable ions contained therein exchanged for Na ions or Ca ions. In the present invention, it is necessary to make the average pore diameter larger than that of the conventional catalyst as described later, but if the amount of the above ion-exchanged smectite group montmorillonite mineral is 5% or less, the strength of the product is low and it cannot be put to practical use. The addition amount of the smectite group montmorillonite mineral exchanged with Na ions or Ca ions used in the present invention is 40 wt%.
When it exceeds the above range, the relative amount of the catalyst component decreases, and the catalyst performance decreases. Therefore, the added amount is preferably 40 wt% or less. In the present invention, the smectite group montmorillonite mineral used is one in which exchangeable ions contained therein are exchanged with Na ions or Ca ions. Further, it is desirable that the remaining component of the forming agent other than the smectite group montmorillonite mineral is a material mainly composed of SiO ₂ such as silica stone, porcelain stone, and wax.
The remaining components of the molding agent other than the smectite group montmorillonite mineral are intended to increase the porosity and average pore diameter of the product, and do not limit the present invention. Therefore,
Gypsum other than SiO ₂ or alumina may be used.

[0011]

【Example】

(Example 1) The catalytically active components of V ₂ O ₅ , WO ₃ and TiO ₂ were used as the preceding supported powder. Specifically ammonium metavanadate (NH ₄ VO _3), ammonium paratungstate and _{{(NH 4) 10 · W} 12 O 41 · 5H 2 O} was dissolved in methylamine 10 wt% solution, and this solution TiO _2:
V ₂ O ₅ : WO ₃ = 87.5: 5.0: 7.5 was added to the TiO ₂ powder, and then mixed in a ball mill for about 2 hours. The slurry concentration at this time was about 60% TiO ₂ . After this slurry was spray-dried with a spray dryer, this powder was calcined at 500 ° C. for 3 hours to obtain a preceding supported powder.

The remaining smectite group montmorillonite mineral as a forming agent component contains exchangeable ions,
A dry powder of a smectite group montmorillonite mineral in which all the Na ions were exchanged was prepared. As other molding agent components, silica stone powder (average particle size 2 μm), type II anhydrous gypsum (average particle size 2 μm), glass fiber, and chopped stride (length 5 mm) were prepared. These are the constituents of the product after firing.

In addition to the above, although not limited to the present invention, materials and procedures for preparing a honeycomb-shaped product are shown below. 7 parts by weight of methyl cellulose was added as a binder for imparting plasticity to the product of the present invention and having a factor of honeycomb formation (hereinafter, the addition amount is based on 100 parts by weight of the components). value.). In addition to this, 3 parts by weight of glycerin was added. The two components were fixed, and in addition to this, cellulose (trade name: Avicel), pulp fiber, and the like were added as a porosity-imparting material as needed, and water was added to these ingredients to mix. The amount of water added is about 4
The amount was increased or decreased while observing the kneading state based on 0 part by weight.

The above materials were sufficiently kneaded to give plasticity, and then formed into a honeycomb shape with a die having a cross-sectional dimension of 150 mm square in external dimension, 1 mm in wall thickness, and 6 mm in pitch. This was molded based on a length of 500 mm and then dried. The dried honeycomb was fired at 500 ° C. for 4 hours to obtain a catalyst test body.

The physical properties of a catalyst test piece are evaluated by dividing the weight of a small test piece cut out from the test piece by the volume obtained by dimensional measurement, and by inserting mercury into a similar small test piece under pressure and volume. The average pore diameter was measured using a mercury porosimetry porosimeter, which measures the pore diameter from the change. For the strength evaluation of the catalyst test piece, the test piece was cut into a cube of 150 mm, and the compressive strength at which the test piece was compressed and broken from both side walls in equilibrium in the extrusion direction was obtained. In addition, the denitration performance of the catalyst test body was evaluated at a temperature of 38.
A NOx-containing gas of about 500 ppm was flown at a flow rate of 2.3 m / sec into the test body set at 0 ° C., and NOx at the inlet and the outlet was discharged.
The denitration rate was calculated from the difference between

The characteristics of the catalyst of the present invention produced and evaluated by the above method are shown in Table 1. In addition to the materials shown in the table, the glass fiber is uniformly added in a weight ratio of 2.6 for both the catalyst of the present invention and the catalyst of the present invention.

The conventional catalysts (TiO ₂ : 91% by weight, V ₂ O ₅ : 0.5% by weight, WO ₃ : 8% by weight), which are comparative agents, show high denitration performance even with an average pore diameter of 250 Å. In the case of No. 2, the porosity is small. With 7 (outside the catalyst of the present invention), the target value of denitration performance of 70% or more cannot be achieved. What can be achieved is No. 2 in which both the porosity and the average pore diameter are large. 1 to 5. Further, No. shown as outside the scope of the present invention. In No. 6, the amount of precedingly supported powder is outside the scope of the present invention, and the denitration performance is low. In addition, No. Since No. 8 has a small content of smectite group montmorillonite mineral, it has a low compressive strength and is insufficient as a product. No. No. 9 had a sufficient denitration performance, but the strength decreased because the pore size was too large.

[0018]

[Table 1]

(Example 2) A pre-supported powder was produced in the same manner as in Example 1, and the balance of the forming agent component was all Na.
Instead of the dry powder of the ion-exchanged smectite group montmorillonite mineral, a dry powder of the Ca ion-exchanged smectite group montmorillonite mineral was prepared, and otherwise the same operation as in Example 1 was carried out to obtain a catalyst test body. The physical properties were evaluated and the results shown in Table 2 below were obtained. From the results in Table 2, the same conclusions as in Table 1 shown in Example 1 were obtained.

[0020]

[Table 2]

[0021]

According to the present invention, Na ions or Ca
By using an ion-exchanged smectite group montmorillonite mineral as a molding agent, expensive TiO ₂
It is possible to provide a denitration catalyst which has excellent denitration performance and satisfactory strength by reducing the amount used.

Claims (2)

[Claims] 1. V ₂ O ₅ by weight%: 0.5 to 3%, W
O ₃ : 0.5 to 5%, TiO ₂ : 10 to 30%, and a forming agent which is a smectite group montmorillonite mineral in which exchangeable ions containing Na at least 5% of the rest are contained. The molded catalyst has a porosity of 40 to 60% and an average pore diameter of 300 to 2
A denitration catalyst characterized by being 000Å. 2. V ₂ O ₅ by weight%: 0.5 to 3%, W
O ₃ : 0.5 to 5%, TiO ₂ : 10 to 30%, and a forming agent which is a smectite group montmorillonite mineral in which exchangeable ions containing Ca 5 at least 5% of the rest are contained. The molded catalyst has a porosity of 40 to 60% and an average pore diameter of 300 to 2
A denitration catalyst characterized by being 000Å.