JPH024453A - Preparation of catalyst for nitrogen oxide contact reduction - Google Patents

Abstract

PURPOSE:To reduce preparation cost of a catalyst of superior resistance to poison by carrying gel solution of Al, Si, alkali metal or an alkali earth metal compound on the zeolite and carrying out water heat treatment. CONSTITUTION:Gel solution, having molar ratio of oxide composition as SiO2/ Al2O3=10-200, H2O/SiO2=20-120, transition metal salt to SiO2 as Si/M=5-50 (M is transition metal element) and 0.1-0.7 molar ratio/l of effective alkali concentration, is prepared. Said gel solution and zeolite and brought into contact, and water heat treatment is carried out to prepare a transition metal catalyst carrying on zeolite. As zeolite, moldenite, pentacyl type zeolite or the like is used. As the transition metal, hydrochloride and sulfate of a metal selected out of copper, iron, nickel, cobalt and vanadium can be used.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a catalyst for catalytic reduction of nitrogen oxides,
In particular, the present invention relates to a method for producing a catalyst for selectively catalytically reducing nitrogen oxides (hereinafter referred to as NOx) in flue gas with ammonia (NH3).

[Conventional technology]

NOx emitted from power plants, sintering furnaces, various chemical factories, automobiles, etc. is a photochemical memo. Since it is said to be the causative agent of 7-g, effective treatment means are desired. Among the flue gas denitrification methods that have been proposed in the past, the NOx catalytic reduction method uses NH3 as a reducing agent.
Even if the above amount is contained, NH3 selectively reacts with NOx, so it is considered to be an advantageous method in that it requires less reducing agent.

As catalysts used in this method, catalysts in which a transition metal compound is supported on a carrier such as activated alumina, silica gel, alumina, zeolite, or titanium oxide are known.

Among these, those currently in practical use are
The main component is titanium oxide disclosed in No. 0-51966 and JP-A-52-122293, to which transition metals such as vanadium (■), molybdenum (MO), and tungsten (W) are added. . These catalysts are excellent in that they are resistant to deterioration due to sulfur oxides (SOx) in exhaust gas. However, no consideration was given to deterioration caused by volatile gold-Bmide and oxides such as selenium, tellurium, thallium, arsenic, and antimony, which are mainly produced from minerals in the fuel. For this reason, when coal or Chinese crude oil containing a large amount of mineral substances is used as fuel and the concentration of the volatile substances in the flue gas increases, there is a problem in that the activity of the catalyst decreases significantly.

Such deterioration can be alleviated to some extent by using a zeolite-based catalyst that can introduce active ingredients into micropores where the volatile oxidizing substances are difficult to diffuse, and several patents have already been published. have been applied for (Japanese Patent Application Laid-open No. 51-11063, Japanese Patent Application Laid-open No. 59-23064)
No. 2, etc.). Furthermore, a zeolite-based denitrification catalyst that has extremely high durability against volatile oxidizing substances such as arsenic has been proposed, which was invented by the present inventors.

The silica-alumina ratio (hereinafter referred to as S
Those with a low i 02 /Aff203 ratio (denoted as i 02 /Aff203 ratio) of less than 10 had a problem in that the catalytic activity decreased due to acidic substances (particularly sulfur oxides, 5Ox) contained in the stone bed. This is thought to be because the acidic substance reacts with the aluminum compound in the zeolite and destroys its structure. On the other hand, 5t02/AI! Those with a high 203 ratio (10 or more) are less susceptible to deterioration due to acidic substances, so Si
O2/A! ! Zeolites with a 2o3 ratio of 10 or more, such as mordenite and ferrierite, which are relatively easily available as zeolites with a high 3i02/Aβ203 ratio, and the well-known ZSM-5 published by Mopil Oil Co., Ltd.
Catalysts using pentasil-type zeolite) have been investigated.

[Problem to be solved by the invention]

When supporting transition metals on zeolite, first synthesize the zeolite by hydrothermal synthesis, and then repeatedly ion-exchange the resulting zeolite with an acid or ammonium salt aqueous solution to remove alkali metal ions such as sodium ions in the synthesis raw materials. After that, a method is used in which the transition metal ions, which are catalytically active components, are ion-exchanged. The reason for this is (1) Zeolite immediately after hydrothermal synthesis contains a large amount of alkali metal ions, so if it is simply mixed with an aqueous solution of transition metal salts, the pH of the aqueous solution will become too high and the active metal components will not be hydrolyzed. This occurs, and metal ions that have been hydrolyzed to a certain degree are less likely to be supported on zeolite. (2) Since ion exchange is interfered with by alkali metal ions, transition metal ions cannot be carried by ion exchange as it is.

In the synthesis of metallosilicates having a pentasil-type zeolite structure, it is possible to perform hydrothermal synthesis in a state where metal ions, silicon components, and alkali metal ions are mixed, and incorporate atoms other than aluminum into the crystal skeleton. It is essential to (1) not add aluminum ions, and (2) use a template agent (an organic substance such as a quaternary ammonium salt or amine is used). It is known that in the absence of a template agent, it is difficult to produce zeolite having a pentasil type crystal structure or metallosilicate. In addition, since the hydrothermal synthesis conditions for zeolite are an alkaline solution with a pH of 10 or more, when aluminum coexists, aluminum is preferentially taken in, and other metal ions are hydrolyzed to form hydroxide precipitates. It was thought that it was not incorporated into the zeolite crystal as an exchangeable ion.

For this reason, in the hydrothermal synthesis of zeolite, there has been no attempt to synthesize active metal components by directly adding them to the raw materials for zeolite synthesis, other than research on the synthesis of metallosilicates, which incorporates metal components other than aluminum into a zeolite-like crystal structure. .

An object of the present invention is to synthesize a transition metal-supported zeolite denitrification catalyst having excellent toxicity resistance using a simpler operation than conventional methods.

[Means to solve the problem]

The above object is achieved by preparing synthetic raw materials in which the reaction composition consists of aluminum, silicon, an alkali metal or alkaline earth metal compound, and a transition metal salt as follows, and performing hydrothermal synthesis.

The present invention relates to a method for producing a denitrification catalyst for catalytically reducing nitrogen oxides in flue gas in the presence of ammonia using zeolite supporting a transition metal. The raw material is a transition metal salt, and the molar ratio of its oxide composition is 5iOz
/Aβ203=10-200, H20/S i 02
= 20 to 120, and the transition metal salt is Si
7M-5 to 50 (M is a transition metal element) and the effective alkali concentration is 0.1 to Q, by hydrothermally treating a gel solution adjusted to have a transition metal element. It is characterized by producing a supported zeolite catalyst.

When synthesizing transition metal-supported mordenite, the molar ratio of the oxide composition is S i02 /Al2O3 = 10 to 100.
, H20/SiO2 = 20-120, the effective alkali concentration was adjusted to be 0.3-0.7 m of f2/l, and the transition metal salt was adjusted so that Si/M = 5-50 (M is a metal element). Hydrothermally synthesize an aqueous gel solution. When synthesizing transition metal-supported ZSM-5, the molar ratio of the oxide composition is Si02/Al2O3=30-100, H2
0/Si02 = 20-120, the effective alkali concentration was adjusted to 0.1-Q, 3 mol/l, and the transition metal salt was adjusted to Si/M = 5-50 (M is a metal element). Hydrothermally synthesize an aqueous gel solution. The effective alkali concentration in this case is expressed by the following formula.

Ceff = Σ(rn x CBmya) - Σ(n
CAz-)m and n are each 1 or 2.

Note that the symbols in the formula are the same as those described in the claims.

According to the present invention, excellent toxicity resistance can be achieved using only hydrothermal synthesis without the need for complicated methods including zeolite hydrothermal synthesis, salt-alkali treatment, and transition metal ion exchange processes that have been used up to now. A transition metal-supported zeolite denitrification catalyst can be obtained.

The raw materials used in the present invention include conventional zeolite manufacturing raw materials, such as silicic acid, sodium silicate, aqueous silica sol, amorphous solid silica, etc. as silicon raw materials, sodium aluminate, aluminum hydroxide, aluminum sulfate, aluminum chloride, etc. as aluminum raw materials, Aluminum nitrate, etc. These raw materials need to be subjected to appropriate pretreatment as necessary and used as alkali-soluble.

Of course, when using soluble raw materials from the beginning, such pretreatment is not necessary. It is also possible to use natural raw materials (1), but if used as is, contamination with impurities such as quartz or coloring of the product due to iron contained in the raw materials cannot be avoided. , washing with mineral acids followed by sufficient alkaline treatment for solubilization is required.

The active metal components of the catalyst in the present invention include copper, iron,
Nitric acid, acetic acid, hydrochloric acid, or sulfate of a metal selected from nickel, cobalt, and vanadium is used.

In the present invention, the order in which the raw materials are added to the reaction system is not particularly limited, but usually a silica source such as a mixed aqueous solution of aluminum sulfate and sulfuric acid, an aqueous sodium aluminate solution and an aqueous water glass solution, or silica sol is stirred into water. However, it is preferable to add the transition metal salt at the same time, and then add the transition metal salt.

When the reaction composition is expressed as a composition ratio of oxides, it is 510
The concentration of 2 is preferably H20/S 1o2 = 20 to 120, particularly preferably H20/S t02 = 30 to 70. The transition metal salt has a Si/M=5 to SiO2 concentration.
50, but even if the Si/M ratio is set to 10 or less and the amount of transition metal salt is increased, the dispersion of the transition metal salt will be poor (and the denitrification rate will not increase), so it is difficult to use the raw material effectively. In order to use the zeolite, it is desirable that Si/M is in the range of 10 to 30.The effective alkali concentration is 0.3 to 0.7 m o when the zeolite produced is mordenite!
! /β, and 0.1 to 0.3 m in the case of ZSM-5
.

It is desirable to adjust it to R//l.

Here, the effective alkali concentration is defined as in the above-mentioned equation (1). That is, when silicon and aluminum components are excluded from the reaction components, the alkali metal or alkaline earth metal and the mineral acid added to adjust the pH remain. The concentration of hydroxide ions generated from the alkali metal or alkaline earth metal hydroxide remaining after neutralization with mineral acid is defined as the effective alkali concentration.

S i 02 /Aj! of the reaction composition. 203 ratio is the transition metal-supported mordenite or transition metal-supported ZS produced.
M-5's S i 02 /AA! Since it has almost no effect on the 203 ratio, mordenite's 5iOz/AI! 2 o
3 ratio ranges from 10 to 100, preferably from 20 to 60, and 5t02/AI in ZSM-5! 203 ratio is 30~
200, preferably from the range of 40 to 150.

However, in order to utilize raw materials effectively, it is necessary to have a raw material composition close to that of the transition metal-supported zeolite that will be produced.
Therefore, it is desirable to understand in advance the relationship between the effective alkali concentration and the SiO2/A#203 ratio of the zeolite produced.

After that, hydrothermal treatment is performed as in the synthesis of zeolite.
Hydrothermal treatment is from 100℃ to 200℃, preferably 150℃
to 180℃ for 5 hours to 400 hours under autogenous pressure,
It is preferably carried out for 20 to 200 hours. If the hydrothermal treatment temperature is less than 100°C, crystallization will be difficult to proceed, whereas if it exceeds 200°C, by-products such as quartz will easily occur, which is not preferable. Further, if the hydrothermal treatment time is less than 5 hours, crystallization will be insufficient, and if it exceeds 400 hours, quartz etc. will be likely to be produced as by-products, which is not preferable.

The product is filtered and thoroughly washed with water. It is preferable to wash with water until the pH of the distilled water after washing becomes 7.5 or less.

After washing with water, it is filtered and dried at a drying temperature of 80 to 200℃.
, preferably from 110 to 150°C.

By using the above method, a zeolite catalyst supporting a transition metal can be easily synthesized without using the complicated methods used so far.

In previous methods, it was thought that transition metal ions would precipitate in the zeolite gel solution because metal ions would be hydrolyzed in the presence of alkali, making it impossible to support transition metal ions on heptaolide. However, the catalyst produced by this method is considered to be a zeolite supporting transition metal ions for the following reasons.

(1) The results of fluorescence X-ray measurements indicate that transition metal atoms are present in the product.

(2) The obtained product was calcined at 500°C for 2 hours,
Transition metal oxides do not precipitate. The transition metal ions supported on the zeolite also do not become oxides under these firing conditions.

(3) All the peaks appearing in the X-ray diffraction diagram of the product before calcination are based on zeolite (peaks), and no peaks based on transition metal compounds appear.

(4) Systematizing the possibility of crystalline metallosilicates produced from silicon and transition metal ions, the present inventors discovered that a conventional method (method similar to ZSM-5, Jun Yoshimura, Seitabe Namba, Takeaki Hejima: The results of tests on crystalline metallosilicates synthesized by Catalyst, Volume 1, 232 (1981) showed that most of the transition metals were eliminated in about one day when treated with 1M hydrochloric acid or an equivalent acid. However, with the catalyst according to the present invention, it takes about one week for the same degree of desorption to occur. This has acid resistance equivalent to that of zeolite that supports transition metals through ion exchange. From this result, the catalyst according to the present invention
It was found that this is not a metallosilicate formed by incorporating a transition metal into the skeleton.

(5) Furthermore, when we investigated the possibility of using amorphous silica-alumina catalysts supporting transition metals, we found that the denitrification rate of silica-alumina catalysts supporting copper was only about 45%, according to our test results. I found out something.

(6) The denitrification rate of this catalyst has reached 90% or more, which is equivalent to that of zeolite supporting transition metals by ion exchange.

From the above experimental facts and raw material composition, it became clear that the product was nothing other than zeolite supporting metal ions.

Under the synthesis conditions of the present invention, the raw materials before hydrothermal synthesis are gel-like hydrated compounds of silicon, aluminum, and transition metals, and are dispersed almost uniformly. When a zeolite skeleton is formed by hydrothermal synthesis, negatively charged sites on the zeolite lattice strongly adsorb transition metal hydrates in their vicinity.

Furthermore, the concentration of alkali metal ions under the production conditions of the present invention is relatively low, and therefore transition metal ions adsorbed on the negatively charged sites of the zeolite are difficult to be replaced with alkali metal ions. This is thought to be the reason why zeolite supporting transition metal ions is produced only by hydrothermal synthesis.

〔Example〕

Examples of the present invention will be described below, and various properties in the examples were measured as follows.

(a) BET specific surface area measurement The specific surface area of dry transition metal-supported zeolite is approximately 0.1
Take 5 g and use Quantachrome\Auto
It was measured using a SORB-1 type gas adsorption test device. The specific surface area has a relative pressure (P/Po) of 0.025 to 0.
B, E, and T in 3 were calculated by the multi-point method.

(b) Powder X-ray diffraction (X RD) measurement An apparatus manufactured by Rigaku Denki Co., Ltd. (RAD-C system, 12 kW) was used.

(c) Measurement of S i02 /Af203 ratio and Si/M ratio A fluorescent X-ray apparatus manufactured by Rigaku Denki Co., Ltd. was used.

(d) Activity measurement In the catalyst activity test in Examples and Comparative Examples, 2 ml of the catalyst was molded, calcined, and sieved into 10 to 20 meshes.
Oxygen 3% by volume, carbon dioxide gas 12% by volume, 7 to 12% by volume,
The test was carried out by a method in which a mixed gas of 200 ppm of NOx, 240 ppm of ammonia, and the remainder nitrogen was passed through at a space velocity of 200.0 OOh-1 to decompose NOx.

The NOx content was measured using a chemiluminescent NOx meter, and the NOx decomposition rate (NOx removal rate) was calculated by measuring the NOx concentration before and after adding ammonia, and using the following formula.

NOx (inlet) - NOx (outlet) Denitrification rate (%) = . 8 Yes. ,×100 Example 1 Distilled water 33mA! (a) Water glass No. 1 (Na20:1
8%, containing 36.5% SiO2), 45g of distilled water
solution and (b) aluminum sulfate (
A solution prepared by dissolving 5.0 g of 13,5 hydrate and 3.56 g of 98% sulfuric acid in 69 mff of distilled water is mixed dropwise with stirring. After sufficient stirring, 4.51 g of copper sulfate pentahydrate is added to the mixed solution. Distilled water was added to the slurry after mixing, and the total amount was 250m/300m after binding! ! Transfer to a stainless steel container and hydrothermally treat at 170°C for 20 hours. The oxide composition of this reaction solution is H20/S i02
=51, S i02 /A1203 =31, S i
/M = 15.1, effective NaOH concentration = 0.55
m o I! / 1.

Stirring is continued at about 30 rpm during the hydrothermal treatment.

After the hydrothermal treatment, it is filtered and washed with about 50 ml of distilled water while being filtered under suction. It is then dried at 120°C for 5 hours. A portion of this was taken and the XRD pattern was examined. The results are shown in FIG. 1, and it was confirmed that the product was mordenite. Furthermore, no peaks due to total bending compounds were observed. BET
The specific surface area was 375 rrr/g. In addition, using a fluorescent X-ray device, the SiO2/Aβ203 ratio and 347M
Table 1 shows the results of examining the ratio and the results of a NOx decomposition test after firing this catalyst at 500° C. for 2 hours.

Example 2.3 Synthesis was performed in the same manner as in Example 1 except that aluminum sulfate was changed to 15 g, 2.6 g/1 sulfuric acid was changed to 0.72 g, and 4.8 g. The oxide composition of the reaction solution is ■]20/
5io2=5LSio2/Aβ203 ratio is each 10.3
．． 60, Si/M=15.1. Effective NaOH 1 degree = 0
．． 55mof/1"??A6° All of the products were mordenite, but in the case of SiO2 /A1203 = 60, a trace amount of ZSM-5 was produced as a by-product. In addition, peaks based on metal compounds were confirmed in both cases. Not done.BE
The T specific surface areas were 345 m/g and 37 Or&/g, respectively.

In addition, the results of examining the SiO2/AA203 ratio and 347M ratio using a fluorescent X-ray device and the results of testing this catalyst at 500℃
Table 1 shows the results of a NOx decomposition test conducted after firing for 2 hours.

Example 4.5 In Example 1, aluminum sulfate was added to Log, 2.5 g, 1
90g and 22.5g of No. 1 water glass, 1 each of sulfuric acid
Synthesis was carried out in the same manner except that the amounts were changed to 2.3 g and 1.09 g.

The oxide composition of this reaction solution is as follows: H20/SiO2 ratio is 25.100, S i 02 /A j < 03=3
1, Si/M=15.1, effective NaOH concentration is 0 respectively
．． 69 mo Il/7! , 0.33 m o 1
/ l.

The product was mordenite, and no peaks based on metal compounds were observed. The BET specific surface areas were 336rrr/g and 354i/g, respectively. Also,
The results of examining the SiO2/Aj22 o3 ratio and 347M ratio using a fluorescent X-ray device, and the
Table 1 shows the results of a NOx decomposition test conducted after firing at C for 2 hours.

Example 6.7 Synthesis was carried out in the same manner as in Example 1 except that sulfuric acid was changed to 6.31 g and 1.81 g.

The oxide composition of this reaction solution is H20/5iO2=51
, S to2/Ajiz 03 =31, Si/M=1
5. L effective NaOH 1/1 degree is each 0.33 mo
1/l, 0.69 m on/ET:
be.

The products were mordenite, and both were based on metal compounds (no peaks were observed. The BET specific surface areas were 378rd/g and 365rrf/g, respectively. //1203 ratio and 3
Table 1 shows the results of examining the 47M ratio and the results of a NOx decomposition test after firing this catalyst at 500° C. for 2 hours.

Example 8.9.10.11 In Example 1, 2.26 g of copper sulfate pentahydrate, 9.09
Synthesis was carried out in the same manner except that the amounts were changed to 1.51 g, 1.51 g, and 12.4 g.

The oxide composition of this reaction solution is H20/5iO2=51
, S i02 /A1203 =31. Si/M ratio is 30.2.7.5.45.5.5 respectively, effective NaOH
Concentration - 0,55 mol/l.

The product was mordenite, and no peaks based on metal compounds were observed. BET specific surface area is 36
6m/g, 325rrr/g, 369rrr/g, 33
It was 1rrr/g. Table 1 also shows the results of examining the SiO2/A#203 ratio and 347M ratio using a fluorescent X-ray device, and the results of a NOx decomposition test after firing this catalyst at 500°C for 2 hours. show.

Example 12 Synthesis was performed in the same manner as in Example 1 except that 7.81 g of sulfuric acid was used.

The oxide composition of this reaction solution is H20/5iO2=51
, S i02 /A1203 =31. Si/M=1
5.1, effective Na0Hi, 55 degrees = 0.21 moI!
/1.

The results of examining the XRD pattern of this product are shown in FIG. 2, and it was confirmed that the product was ZSM-5. Furthermore, no peaks due to metal compounds were observed. B
The ET specific surface area was 356 rrr/g. In addition, the SiO2/Af203 ratio and 3
Table 1 shows the results of examining the 47M ratio and the results of a NOx decomposition test after firing this catalyst at 500° C. for 2 hours.

Example 13.14.15 In Example 1, 2.5 g and 1.25 g of aluminum sulfate
, 0.772g, sulfuric acid 9.13g and 9.80g respectively,
Synthesis was carried out in the same manner except that the amount was changed to 10.05 g.

The oxide composition of this reaction solution is H20/5iO2=51
, S i 02 /Al2O3 ratio is 62.124.20
0.3 i/M = 15.1, effective NaOH
Concentration = 0.21 moff/#.

The product was ZSM-5, and no peaks based on metal compounds were observed. BET specific surface area is 3 each
They were 81 i/g, 370 m/g, and 359 n(/g).

In addition, the results of examining the SiO2/Aβ203 ratio and Si/M ratio using a fluorescent X-ray device and the results of testing this catalyst at 500℃
Table 1 shows the results of a NOx decomposition test conducted after firing for 2 hours.

Example 16 Synthesis was performed in the same manner as in Example 13 except that 10.26 g of sulfuric acid was used.

The oxide composition of this reaction solution is H20/5iO2=51
, S ioz /A42203 =62, Si/M=1
5. L effective NaOH concentration - 0,12m o R/β.

The product was ZSM-5, and no peaks due to metal compounds were observed. The BET specific surface area was 390 m/g. In addition, using a fluorescent X-ray device, S io2/A
Table 1 shows the results of examining the 1203 ratio and Si/M ratio, and the results of a NOx decomposition test after firing this catalyst at 500° C. for 2 hours.

Example 17 Synthesis was performed in the same manner as in Example 13 except that 8.38 g of sulfuric acid was used.

The oxide composition of this reaction solution is H20/5iO2-51
, S io2/Aj! 203 =62, Si/M=15
．． 1. Effective NaOH21m degree = 0.27 m o
It is E/1.

The products were ZSM-5 and a trace amount of mordenite, and no peaks due to metal compounds were observed. The BET specific surface area was 381 m/g. In addition, SiO2/Aj! using a fluorescent X-ray device! Table 1 shows the results of examining the 203 ratio and Si/M ratio, and the results of a NOx decomposition test after firing this catalyst at 500°C for 2 hours.

Example 18.19 In Example 13, 2.26 g of copper sulfate pentahydrate, 9°09
It was synthesized in the same manner except for changing to g.

The oxide composition of this reaction solution is H20/SiO2=51
．． S ioz /Al2O3=62, Si/M ratio is 30.2.7.5 respectively, effective NaOH1 degree=0, 21 m
o 1/1.

The product was ZSM-5, and no peaks based on metal compounds were observed. BET specific surface area is 3 each
30n? /g, 350rd/g. Also, fluorescent X
3i02/Az2 o3 ratio and S
The results of examining the i/M ratio and the results of this catalyst at 500℃
The results of a NOx decomposition test after being fired for an hour are shown in the first
Shown in the table.

Example 20.21.22.23 In Example 1, copper sulfate pentahydrate was replaced with cobalt nitrate hexahydrate 5
．． 26 g, vanadium trichloride 2.84 g, nickel acetate tetrahydrate 4.5 g, and iron sulfate heptahydrate 5.03 g.

The oxide composition of this reaction solution is H20/5iO2=51
,S ioz /Aj? 203 =31, Si/M=1
5.1, effective NaOH concentration -0.55 moff/1.

The products were each mordenite, and no peaks based on metal compounds were observed in any of them. BET specific surface area is 371r+(/g, 355n?/g, 360rrf
/g, 332n (/g. Also, using a fluorescent X-ray device, the S i 02 /A1203 ratio and Si/M
Table 2 shows the results of examining the ratio and the results of a NOx decomposition test after firing this catalyst at 500° C. for 2 hours.

Examples 24, 25, 26 Synthesis was carried out in the same manner as in Example 1 except that the hydrothermal treatment temperature was changed to 90.140.200°C.

The oxide composition of this reaction solution is H20/5iO2=51
, S ioz /Al2O3=31, Si/M=15.
1.Effective NaOH concentration is 0.55 mol/each
j! It is.

The product was mordenite, but the degree of crystallization was low when hydrothermally treated at 90°C. In addition, no peaks based on metal compounds were observed in any of the samples. The BET specific surface area is 331n (/g).

They were 393 m/g and 411 m/g. In addition, the SiO+/Af203 ratio and Si/M
Table 2 shows the results of examining the ratio and the results of a NOx decomposition test after firing this catalyst at 500° C. for 2 hours.

Examples 27, 28, 29 Examples 27, 28, 29 Synthesis was carried out in the same manner as in Example 3 except that the hydrothermal treatment time was changed to 48,100,200 hours.

The oxide composition of this reaction solution is H20/5iO2-51
, S i 02 /A 1203 zero 31, Si/M=1
5. L effective NaoHfi degree is 0.55 moz/l. The product is mordenite, but a slight quartz peak was observed in the product subjected to hydrothermal treatment for 200 hours. In addition, no peaks based on metal compounds were observed in any of the samples. BET specific surface area is 425rrf/g and 39, respectively.
It was 0rrf/g and 311d/g. Also, using a fluorescent X-ray device, S i02 /A/! 203 ratio and S
The results of examining the i/M ratio and the results of a 1iNOx decomposition test performed by firing this catalyst at 500"C for 2 hours are summarized in the second section.
Shown in the table.

Example 30 In Example 1, water glass was mixed with Nissan Chemical's silica sol (0) (
S i02: 20.5%) Synthesis was performed in the same manner except that the amount was changed to 80 g.

The oxide composition of this reaction solution is H20/5iO2-51
, S i 02 /Alz 03=31, Si/M=1
5.1, effective NaOH concentration = 0.55 mol/l.

The product was mordenite, and no peaks based on metal compounds were observed. BET specific surface area is 392m/g
Met. In addition, using a fluorescent X-ray device, S io2/
The results of examining the AA203 ratio and S i / M ratio,
This catalyst was calcined at 500° C. for 2 hours and then subjected to a NOx decomposition test. The results are shown in Table 2.

Comparative Example 1 In Example 1, 90 g of water glass 1 1 aluminum sulfate
Synthesis was carried out in the same manner except that the amount of sulfuric acid was changed to 3.38 g.

The oxide composition of this reaction solution is H20/5iO2=25
, S i 02 /Aj2z03 =31 S i/M
=15.1. Effective NaOH 1 degree = 1.4 moff/l
It is.

The product was mordenite, and no peaks based on metal compounds were observed. BET specific surface area is 3'lOm/
It was g. Also, using a fluorescent X-ray device, S i 0
2 The results of examining the /A12o3 ratio and Si/M ratio,
This catalyst was calcined at 500° C. for 2 hours and then subjected to a NOx decomposition test. The results are shown in Table 2.

Comparative Example 2 Synthesis was performed in the same manner as in Example 1, except that the amount of water glass was changed to 135 g, the amount of aluminum sulfate was changed to 15 g, and the amount of sulfuric acid was changed to 22.6 g.

The oxide composition of this reaction solution is H20/5iO2-15
, S i02 /AI! 203 =31, Si/M=1
5.1, effective NaOH concentration = 0.7 m o It
/l. The product was mostly amorphous material.

Comparative Example 3 In Example 1, 15 g of water glass and 1 g of aluminum sulfate were added.
．． Synthesis was carried out in the same manner except that the amount of sulfuric acid was changed to 0.33 g.

The oxide composition of this reaction solution is H20/5iO2=15
3, S i 02 /AA'203 = 31, Si/M
= 15.1, effective NaOH concentration = 0.25m.

It is 1/12. The products were mostly quartz and ZSM-5.

Comparative Example 4.5 3.6% by weight of copper sulfate pentahydrate was added to commercially available silica/alumina catalyst powder (Si20: 87% by weight, Al2O2: 13% by weight), and water was added to form a slurry. The resulting product was left to stand for one day and then dried at 110°C. The oxide composition of this catalyst is SiO2/Al-203=11.4.
The 347M ratios are 30 and 9.15.5, respectively. This catalyst was calcined at 500° C. for 2 hours and then subjected to a NOx decomposition test. The results are shown in Table 2.

〔Effect of the invention〕

According to the present invention, a zeolite a-nitrate catalyst supporting a transition metal can be obtained only by a synthetic operation using hydrothermal treatment.

Therefore, it is possible to produce a transition metal-supported zeolite denitrification catalyst with excellent toxicity resistance without requiring complicated operations using conventional methods, and it is possible to simplify the catalyst production process and reduce production costs.

[Brief explanation of the drawing]

FIG. 1 shows the XRD pattern of transition fully supported mordenite synthesized by the method of Example 1, and FIG. 2 shows the XRD pattern of transition fully supported mordenite synthesized by the method of Example 13.
It is a figure showing an RD pattern. Agent Patent Attorney Takeshi Kawakita

Claims (4)

[Claims] (1) A method for producing a denitrification catalyst in which nitrogen oxides in flue gas are catalytically reduced in the presence of ammonia using zeolite supporting a transition metal. A metal salt is used as a raw material, and the molar ratio of its oxide composition is SiO_2/
Al_2O_3=10~200, H_2O/SiO_2
= 20 to 120, and the transition metal salt is S with respect to SiO_2
i/M = 5 to 50 (M is a transition metal element), and the transition metal is supported by hydrothermally treating a gel solution adjusted so that the effective alkali concentration is 0.1 to 0.7 mol/l. A method for producing a catalyst for catalytic reduction of nitrogen oxides, the method comprising producing a zeolite catalyst. (2) The method for producing a catalyst for catalytic reduction of nitrogen oxides according to claim (1), wherein the zeolite is one or more of mordenite and pentasil type zeolite. (3) The transition metal is one or more elements selected from copper, iron, nickel, cobalt, and vanadium, and these are salts of nitric acid, acetic acid, hydrochloric acid, and sulfuric acid. Claim (1) characterized in that
The method for producing the catalyst for catalytic reduction of nitrogen oxides described above. (4) The method for producing a catalyst for catalytic reduction of nitrogen oxides according to claim (1), wherein the effective alkali concentration (Ceff) is expressed by the following formula. Ceff=Σ(m×C_B_m_+)−Σ(n×C_A
_n_-) where C_B_m_+ is the concentration of alkali ions, C_A_n_- is the concentration of acid ions, m and n are each 1 or 2, B^m^+ is one or more of alkali metal ions and alkaline earth metal ions, A^n^- is one of sulfate ion, chloride ion, bromide ion, and nitrate ion
Represents more than one species.