JPS63134057A - Production of catalyst for denitrification of flue gas - Google Patents

Abstract

PURPOSE:To improve denitrification activity and to permit suppression of said reaction as well by depositing a vanadium compd. which is an active metal component into a catalyst carrier surface layer at a high concn. within 200mum of the surface layer. CONSTITUTION:V2O5 which is a main active component is thinly and uniformly deposited, within 200mum from the catalyst surface layer, on the V2O5/TiO2 denitrification catalyst which reduces the NOx in the exhaust gas contg. NOx by adding ammonia to acid exhaust gas so as to provide the pollution-free gas. High concn. V2O5 is eventually incorporated within 200mum of the catalyst surface and the content in the bulk is correspondingly decreased. The initial activity of the denitrification reaction is thereby improved and the activity against catalyst poisoning is maintained as well, by which the durability is improved and the side reaction is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a catalyst that is applied to remove nitrogen oxides from exhaust gas from combustion furnaces such as large power boilers.

[Conventional technology]

As an exhaust gas denitrification catalyst, vanadium, tungsten, iron,
Those supporting activated gold S such as copper are known. However, these catalysts have conventionally been produced by impregnating or kneading a solution of various active metal salts dissolved in an aqueous or organic solvent into a pellet-shaped or honeycomb-shaped carrier, or by impregnating or kneading a solution into a powdered carrier. It is manufactured by molding into a pellet shape or a honeycomb shape.

In particular, the 17205-No and -T102 denitrification catalysts have a denitration effect in exhaust gas (4NO+ 4Nl(3+02-+
4N2+6H20) It is used as a high-performance exhaust gas denitrification catalyst, promoting t- while suppressing side reactions such as SOx oxidation reaction and ammonia decomposition reaction. Usually, the v205'Ik supported on the carrier is 0. I wt%~5
．． Owt%wo, the amount is widely applied from 3 wt% to 20 wt%. However, although increasing the amount of v205 improves the denitrification activity, the oxidizing power of Sox also increases, so the amount of v205 is limited to the above supported range.

However, when trying to improve the denitrification activity, the oxidation ability of SOx becomes significant.Furthermore, depending on the type of boiler feedstock fuel, catalyst poisoning substances such as arsenic compounds may be present in the exhaust gas, which may cause damage to the catalyst. The deposition causes the clogging of pores and the disappearance of catalytic active sites, which has the drawback of rapidly reducing the catalytic activity.

[Problem that the invention seeks to solve]

The present invention eliminates the drawbacks of conventional exhaust gas denitrification catalysts, improves the initial activity of the denitrification reaction, has the durability to maintain catalytic activity even after poisonous substances are deposited on the catalyst, and prevents side reactions such as Sox oxidation. The present invention aims to provide a method for manufacturing a flue gas denitrification catalyst that suppresses exhaust gas denitrification.

[A precautionary measure to resolve the problem]

The present invention is a VO system that completely adds ammonia to exhaust gas containing nitrogen oxides to reduce and render harmless nitrogen compounds in the exhaust gas.
/TLO2-based denitrification catalyst manufacturing method, which is characterized in that a vanadium compound, which is an active metal compound, is supported on the catalyst carrier surface layer at a high concentration within 200 nm of the surface layer.

The present inventors compared the reaction rates of the denitrification reaction (4NO+ 4NH3 → 4N2 + 6H20) and the 802 oxidation reaction (2S02 + 02 → 2So5) using a v2o5-wo3-'r1o2 thread catalyst, and found that the denitrification reaction is significantly better. , I found that the reaction was fast. In addition, with a honeycomb-shaped catalyst, the denitrification reaction progresses sufficiently only in the catalyst surface layer.
On the other hand, it was found that the oxidation reaction of S02 involves the reaction even inside the bulk of the catalyst.

Therefore, we discovered that in order to improve the denitrification activity and prepare a catalyst that suppresses side reactions, it is sufficient to uniformly support v205, the main active ingredient, on the surface layer of the catalyst. .

In particular, it is preferable to support v2o5'2 at a high concentration within 200 μm of the surface layer. Also, the surface layer is uniformly thin <v
As a method for supporting 205t, a vapor phase evaporation method (CVO method) can be applied.

The reaction between the T-02 carrier and Woo/, proceeds as follows. Note that oxygen on the surface of the carrier is bonded to hydrogen,
Acts as an acidic point.

HC1-V-C1 Since C/ etc. in this reaction product may become catalyst poisoning substances, they should be removed by calcination or o
o o
.

+l It
II. Remove by hydrolysis.

II 1
CI! -1/-0/H
O-V-OH Thus, v205 supported on the surface layer
All have functions as activators, and as a result, sufficient denitrification activity can be ensured by simply supporting a small amount of v2o5'2 in a thin layer on the surface layer, and side reactions can also be suppressed.

[Effect]

By the gas phase loading method (CVO method) of the present invention, vanadium is applied to the surface layer of a honeycomb-shaped or pellet-shaped carrier with a thickness of 200 μm.
Compared to a catalyst supported in the bulk of the carrier by the conventional impregnation method, a catalyst supported at a high concentration within 1% has almost no change in SOx oxidation ability and remains low, but the denitrification effect is significantly improved.

In the catalyst preparation method of the present invention, tungsten is supported by a conventional impregnation method, in which an aqueous solution of paratungsten amsonium or the like is adjusted to a predetermined concentration, and the carrier is immersed in the solution, then dried and calcined. On the other hand, the vanadium compounds supported in the gas phase are VOOI, , VCl2., which are liquid substances at room temperature.
VOBr3 Also solid state VO/,,VC! ,,V
OOJP2. Examples include VBr3, and all of them are brought into contact with a carrier in a gas phase to support V on the surface layer.

It is preferable that the carrier is reacted with a vapor phase vanadium compound at a temperature in the range of 100C to 800C, preferably 150C to 700C, so that vanadium is supported on the surface layer.

The present invention will be explained in detail below using examples.

[Example 1] Tz0804 aqueous solution with T10 equivalent concentration of 15% 1500
．． Cool to below 9t-20C and neutralize by gradually adding 15X ammonia water to a concentration of 8. The water-dispersed titanium precipitate to be used for insect removal is filtered and washed with water until no 802- ions are detected in the solution. After drying, it was calcined in air at 500C for 3 hours to obtain about 200g of titanium oxide powder.

To 80 parts by weight of this titanium oxide, 15 parts by weight of dispersible clay and 5 parts by weight of Glass 7 IPA were added, and water was added and mixed thoroughly using a mixer to obtain an appropriate moisture content, and then using a honeycomb forming machine. The holes were square in shape and formed into a honeycomb shape with an opening of 60 m and a wall thickness of 1.35 fl. 500 after drying
Bake at C for 3 hours.9. This honeycomb carrier will be referred to as carrier 1.

After measuring the saturated water content of this honeycomb carrier 1, WO5
The carrier 1 was immersed in an aqueous paratungsten ammonium solution so that 10 wt % of the paratungsten ammonium was supported on the carrier 1, and after drying, it was fired at 500 C for 3 hours. Next, this W
O3-T10□ The sample was placed in a reactor at a constant temperature of 400C, and N2 carrier gas was blown into the liquid vanadium compound voat3 at room temperature at a rate of t-40i1j/min. did. Furthermore, the catalyst was taken out from the reactor and 50 (Ic
The amount of T205 supported within 200 μm of the surface layer of the obtained catalyst^ was 0.95 wtX, and the amount of V2O5 supported inside the bulk was 0.32 wtX.

[Example 2] A catalyst was prepared in the same manner as in Example 1 except that VOBr3i was used as the V raw material to obtain a catalyst Bt-. The amount of V2O5 supported within 200 μm of the surface layer of catalyst B was 1.01 wtX, and the amount of T205 supported inside the dibulk was 0.38 wtX.

[Example 3] Using the VAT2 raw material as the V raw material, a catalyst was prepared in the same manner as in Example 1, and catalyst a was prepared. Surface layer 2 of catalyst C
The amount of V2O5 supported within 00 μm is 0.89 wtX, and the amount of T205 supported inside the bulk is 0.56 wtX.
Met.

[Example 4] "100/" was used as the V raw material, and 9 voc as shown in Example 1
t, steam treatment for 10 minutes, and catalyst o for 30 minutes, respectively.
, mt-obtained. The amount of V2O5 supported within 200 μn of the surface layer of catalysts o and g is 0.55 wtX.

The amount of T205 supported inside the bulk was 0.22 wtX and 0.45 wtX. In addition, the voat and steam treatment shown in Example 1, wo, -
Catalyst F was obtained by placing and feeding the 'rio2 sample into a reactor at a constant temperature of 500C. The amount of V2O5 supported within 200 μm of the surface layer of this catalyst 2 was 1.21 wtX, and the amount of V2O5 supported inside the bulk was 0.29 wtX.

[Comparative Example 1] A sample of No. 3-Tie 2 prepared in the same manner as in Example 1 was impregnated with an aqueous ammonium solution of metavanazine and dried for 50 minutes.
By firing at 0C for 3 hours, V2O inside the bulk is removed.
5 The supported amount is 0.4 wtX, 0.8 wtX, 2. O
wtXll 0 wtX catalysts a, b, o.

I got d. These catalysts a% b, c, (1 is 200μ
The amount of V2O5 supported on the surface layer within 1 was the same as that inside the bulk.

[Comparative Example 2] A No3-TIO2 sample prepared in the same manner as in Example 1 was placed in a reactor at room temperature, and VOC/, 'e N2
The carrier gas was blown for 5 minutes at 2 to 7 minutes. After that, the catalyst was taken out from the reactor and heated at 500C, 3
Baked for an hour. The bulk interior of the obtained psychocatalyst e and 200
The amount of V2O5 supported on the surface layer within μm is both 0.95 w.
It was tX.

B, O, O, K to the catalysts obtained in Examples 1 to 4.

F and the catalyst aSbSc, a obtained in Comparative Example 1.2.

A denitrification performance test was conducted under the conditions shown in Table 1, and the initial activity and test results after 5000 hours of use are shown in Table 2.

Catalytic activity test Furthermore, each prepared catalyst ^, B, O, Dl ESFa, bS
C, el, and a were treated with a gas containing arsenic oxide vapor, which is a catalyst poisoning substance, for 5000 hours under the conditions shown in Table 3, and the catalytic activity after the treatment was measured. The catalyst activity test was conducted under the conditions shown in Table 1, and the test results are shown in Table 4.

In order to obtain the line profile of the amount of v205 supported on the carrier, the distribution state of 5v was analyzed using an X-ray microanalyzer for the catalyst O and the honeycomb with a wall thickness of 1.35 m. The distribution curve is shown in FIG. The horizontal axis indicates the thickness direction of the honeycomb, and the vertical axis indicates the V content.

(!L) shows the distribution state of V for catalyst C,
It can be seen that a large amount of v205 is bound to the surface layer within 200 μm. On the other hand, (b) is for the catalyst, and it can be seen that there is no change in the content of v205 between the surface layer and the inside of the bulk.

As is clear from the results in Tables 1 and 3, the gas phase loading method (cv
A thin catalyst (catalysts A and B) was uniformly and thinly supported on the surface layer of the v205t-catalyst carrier using the method.

0, D, ElF) are conventional catalysts (catalyst a1
Compared to b, c% d, e), the initial activity is clearly improved, the denitrification activity can be maintained even after the deposition of poisonous substances such as A'a 20 s, and the durability can be improved. It has become clear that the denitrification reaction can be carried out while suppressing side reactions such as oxidation of Sox.

〔Effect of the invention〕

By adopting the above configuration, the present invention provides p1 catalyst surface 20
By containing a high concentration of V205 within 0 μm and completely reducing the Jl content inside the bulk, it improves the initial activity of the denitrification reaction, maintains activity against catalyst poisoning, and improves durability. This made it possible to suppress side reactions.

[Brief explanation of the drawing]

Figure 1 (al) is a diagram showing the distribution of v205 content in the cross-sectional direction of the honeycomb catalyst; (a)
is for catalyst C +1)) is for catalyst S. Table 1 Table 2

Claims (1)

[Claims] By adding ammonia to exhaust gas containing nitrogen oxides,
V_2O_5/ which reduces nitrogen oxides in exhaust gas and makes them harmless
A method for producing a TiO_2-based denitrification catalyst, characterized in that a vanadium compound, which is an active metal compound, is supported on the catalyst carrier surface layer at a high concentration within 200 μm of the surface layer.