JPH0671141A - Method for denitrification, denitrification agent and preparation of denitrification agent - Google Patents

Abstract

PURPOSE:To provide a method for denitrification and a denitrification agent with high degree of denitrification and keeping the high degree of denitrification for a long period. CONSTITUTION:Denitrification is performed by allowing a hydrocarbon to be present by means of spraying in a treating vessel wherein a denitrification agent obtd. by depositing iron on zeolite exists and passing an NOx-contg. gas through it. In addition, the denitrification agent can be also obtd. by depositing iron on zeolite by means of ion exchanging. Furthermore, the denitrification agent can be prepd. by depositing iron on zeolite by immersing zeolite into an iron salt soln, and then, drying it.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a relates to a method for removing the NO _x, particularly to a method for removing NO _x from the NO _x containing gas such as flue gas of the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, NO _x treatment technology has been put to practical use as, for example, flue gas denitration technology. This flue gas denitration method is roughly classified into a dry method and a wet method, and the most advanced of these is the selective catalytic reduction method, which is a type of dry method. This main reaction is shown below.

4NO + 4NH ₄ + O ₂ → 6H ₂ O + 4N ₂ This reaction uses ammonia as a reducing agent as a reducing agent, and even if oxygen coexists, it selectively reacts with NO _x , so exhaust gas of a diesel engine, etc. Used to process. In this case, as a catalyst, a precious metal such as Pt or Al ₂ O ₃ ,
Various metal oxides supported on TiO ₂ or the like are used.
Since the selective catalytic reduction method can treat NO _x with a simple system, a high denitration rate can be obtained. Moreover, NO _x
Since it can be decomposed into harmless N ₂ and H ₂ O, there is an advantage that waste liquid treatment becomes unnecessary.

However, in this method, since harmful and dangerous ammonia gas is used, it is necessary to handle it with caution, and the reduction catalyst is deteriorated by components other than NO _x in the exhaust gas, so catalyst replacement is required. Is required, which is economically disadvantageous especially when an expensive precious metal-based catalyst is used.

Further, at high temperatures, there arises inconveniences such as progress of sintering of the catalyst components, and at low temperatures ammonia reacts with water or SO _x , so that salts such as ammonium sulfate are formed on the catalyst surface and the denitration rate decreases. To do. Therefore, the operating temperature range is limited to 320 to 450 ° C.

As described above, since there are many problems in the method using ammonia, other denitration methods are currently being researched, and the direct decomposition method has been attracting attention.

This direct decomposition method is the most ideal method for removing NO _x , and in recent years, catalysts such as Cu-ZSM-5 zeolite and perovskite type complex compounds have been found.

[0008]

[0008] However, the denitration rate even the most highly active Cu-ZSM-5 as the catalyst, the catalyst performance is deteriorated by SO _x or of H ₂ O in the exhaust gas in the direct decomposition method Is decreased, and it is very difficult to obtain a high denitration rate over a long period of time.

The present invention has been made under the above background, and an object thereof is to provide a denitration method and a denitration agent which have a high denitration rate and can maintain the high denitration rate for a long period of time.

[0010]

Means and Actions for Solving the Problems In order to solve the above problems, the present invention provides an X-type zeolite containing Na, Na.
Iron is supported on one or two or more zeolites selected from the group consisting of Y-type zeolites containing Na, mordenite containing Na, and A-type zeolites containing at least one of (K, Na, Ca). It is characterized in that a NO _x -containing gas is circulated in the coexistence of a hydrocarbon in the processing container having the obtained denitration agent to perform denitration.

Further, a denitration agent obtained by supporting iron on zeolite is also provided.

Further, there is provided a method for producing a denitration agent, which comprises immersing zeolite in an iron salt solution and then drying the zeolite to support iron.

[0013] As described above, by flowing the NO _x iron as a catalyst active component in the presence of component and partially supported by ion exchange is allowed to denitrating agent obtained by hydrocarbons in the zeolite, the nitrogen oxides Can be decomposed.

The present invention will be described in more detail below. First, as the supporting base material zeolite, NaY type zeolite, Na type mordenite, A type zeolite, X
Type zeolite and the like, and any of these zeolites can provide good denitration action. In the present specification, the above various zeolites are collectively referred to as zeolite.

Further, since the denitration efficiency increases with the contact area between NO _x and the denitration agent, it is desirable that the denitration agent has a large surface area, preferably a honeycomb structure.

The structure of the zeolite is not particularly limited, but it is preferable that the zeolite has a large contact area with the NO _x containing gas, and the honeycomb structure as described above forms the NO _x containing gas and the zeolite. The area of contact with the can be widened, and the denitration rate can be increased.

Further, when the denitration agent is formed into a honeycomb shape, mechanical strength becomes a problem, and it is preferable to add 20 to 50% by weight of a structural reinforcing material to zeolite.

This is because if the compounding amount of the structural reinforcing material is 20 wt% or less, the mechanical strength of the honeycomb body may be deteriorated to make it unusable for practical use, and if the structural reinforcing material is 50 wt% or more, zeolite may be used. This is because the active points that perform the denitration action inevitably decrease, and the denitration rate required for practical use may not be obtained.

The zeolite thus formed into a honeycomb body and fired is preferably held in a drying oven or vacuum in advance to remove the water content in the zeolite.

Next, iron is supported on this zeolite.
There are various methods for supporting iron, but preferably the zeolite is immersed in an iron salt solution having a predetermined concentration, and after confirming that the iron salt is sufficiently diffused in the pores of the zeolite, it is as it is. Evaporate the iron salt solution or pull up the immersed zeolite from the aqueous solution,
Next, iron is supported by removing water contained in the zeolite.

Iron is considered to be carried by entering into the zeolite pores by diffusion and being partially ion-exchanged. Therefore, when immersing the zeolite in the iron salt solution, the immersing time is determined by the zeolite fineness. It is sufficient that the iron salt can sufficiently diffuse in the pores, and it is preferably about 12 hours.

At this time, if the diffusion of the iron salt is sufficient, it is possible to shorten the impregnation time. Further, even if the impregnation time is 12 hours or longer, there is no deterioration of the zeolite, so the impregnation time should be 12 hours or longer. But there is no problem.

The iron salt solution is not particularly limited as long as the above ion exchange is sufficiently carried out, but iron nitrate, iron sulfate and iron chloride solutions are preferable, and other iron salt solutions are preferable. May be used.

[0024] Next, the denitration by circulating NO _x containing gas in the presence of hydrocarbons in the iron-loaded zeolite. At this time, as the hydrocarbon, for example, fuel oil such as heavy oil, light oil, kerosene can be used.

As a method of providing the hydrocarbon, for example, a method of spraying the hydrocarbon when the NO _x containing gas is passed through the iron-supported zeolite can be mentioned.

The coexistence of hydrocarbon as described above can remarkably enhance the denitration effect.

For example, the partially ion-exchanged iron-supported zeolite honeycomb obtained by the above method is used as a denitration agent to pass a sample gas of NO (1000 PPM) + N ₂ and an SV value (space velocity) of 2000 / h. When the denitration rate was measured under the conditions, a denitration rate of 30% was obtained.

However, when the NOx removal rate was similarly measured using the exhaust gas of an actual engine using a diesel engine, almost no NOx was removed. This is SOx in the actual exhaust gas,
This is because soot, H ₂ O, etc. are catalyst poisons. Therefore, when a small amount of hydrocarbons (fuel oil, kerosene, fuel oil such as A heavy oil) was added to the exhaust gas and an experiment was conducted again, a denitration rate of 90% or more was obtained. Even after conducting a field test for 1000 hours, no decrease in the denitration rate was observed, and it was found that the denitration agent was stable. This is considered to be due to the following reasons.

SO _x gas (sulfur oxide) which is a catalyst poison coats the surface of zeolite or reacts with iron which is a catalytically active metal to reduce the activity of the catalyst. However, if hydrocarbons (light oil, kerosene, heavy oil A, etc.) are added to the exhaust gas, S
_Ox gas reacts preferentially with hydrocarbons, so naturally S
_Ox gas does not cover the surface of zeolite and does not react with the active metal iron. Therefore, deterioration of the catalytic action can be suppressed.

Further, hydrocarbons have an exhaust gas temperature (400 ° C.).
Since the soot contained in the exhaust gas is also burned at a temperature of up to 450 ° C., catalyst poisoning due to soot is avoided and the catalyst life is greatly extended. Therefore, as a hydrocarbon,
It is preferable that the ignition point be equal to or lower than the temperature at the time of denitration.

In general, when zeolite is used as a denitration carrier, the SO _x resistance of zeolite becomes a problem,
High SO _x resistance is required.

The higher the SiO ₂ / Al ₂ O ₃ ratio is, the more excellent the SO _x resistance is. The above ZSM-5 and mordenide type zeolites have the following ZSM-5.
Has the highest SO _x resistance.

ZSM-5> mordenide type> Y type> A type> X type Therefore, ZSM-5 is usually used as a zeolite for a denitration carrier.
It is preferable to use -5.

However, as described above, in the present invention, denitration is performed in the presence of hydrocarbons to prevent poisoning of the catalyst by SO _x . Therefore, the zeolite to be used is not particularly limited, and for example, the above-mentioned mordenide type, Y type, A type,
Various natural or synthetic zeolites such as X-type or the like can be used.

[0035]

Example In this example, iron nitrate, iron sulfate, and iron chloride were used to carry out ion exchange of iron with a part of the components of the zeolite to support it on the zeolite, and the iron-supported zeolite was used as a denitration agent for carbonization. NO _x was decomposed in the presence of hydrogen.
At this time, the NO _x concentration was measured using the denitration device shown in FIG.

In FIG. 4, 1 is a diesel generator, 2
Is a denitration catalyst tank, and the exhaust gas discharged from the diesel generator 1 flows into the lower portion of the denitration catalyst tank 2 through the ventilation pipe 7. This exhaust gas flows through the denitration catalyst tank 2 in which the iron-supported zeolite 12 is stored and is treated with NO _x to become a treated gas. This processing gas is configured to flow out through a ventilation pipe 9 provided above the ventilation pipe 7 of the denitration catalyst tank 2.

Further, a hydrocarbon spray pipe 8 having a hydrocarbon spray port 5 is provided at the exhaust gas inflow portion of the denitration catalyst tank 2, and hydrocarbons are introduced into the denitration catalyst tank 2 through the hydrocarbon spray pipe 8. It is configured to be ejected.

[0038] Further, in the vent pipe 7 is provided with a concentration of NO _x measurement port 3, a part of the exhaust gas through the exhaust gas sampling pipe 10 provided in the concentration of NO _x measurement port 3 NO
_{The x} concentration analyzer 6 is configured to measure the NO _x concentration.

[0039] Similarly, in the above vent pipe 9 is provided with a concentration of NO _x measurement port 4, a portion of the process gas through the process gas extraction tube 11 provided in the concentration of NO _x measurement port 4 N
In O _x concentration analyzer 6 has a configuration for measuring the concentration of NO _x. Using this device, denitration of exhaust gas from a diesel generator was performed under various conditions. The results are shown below.

In each of the examples, the exhaust gas temperature was in the range of 400 to 450 ° C., the average NO _x concentration was about 900 ppm, the average SO _x concentration was about 150 ppm, the average oxygen concentration was 13%, and the average oxygen concentration was 13%. H ₂ O volume is about 7 vol%, average SV
The value (space velocity) was 2000 / h.

As the NO _x concentration analyzer, CLM100 manufactured by Shimadzu Corporation was used, and the NO _x decomposition rate (denitration rate)
Was calculated by the following equation, where α is the NO _x concentration of the exhaust gas and β is the NO _x concentration of the processing gas.

Denitration rate = (α-β) / α Further, the shape of the structure-reinforcing material-containing zeolite used as the denitration agent is not particularly limited, but a shape having a large contact area with the NO _x -containing gas is preferable, and the present Example The honeycomb body was used.

Example 1 (Denitration method using a denitration agent having iron nitrate as a supported catalyst) 1-1: First, NaY type zeolite (320 NAA manufactured by Tosoh Corporation) was used as a carrier zeolite, and 30 wt% of a structural reinforcing material was used. %, The honeycomb formed body having a hole number of 16 × 16/65 mm square was fired.

In order to support iron on this honeycomb body, an aqueous solution of 0.1 mol / l was prepared using iron nitrate, and each honeycomb formed body was dipped in this aqueous solution and left as it was for 12 hours to prepare the zeolite. Was impregnated with iron.

Then, each zeolite was taken out from the aqueous solution and dried at 150 ° C. for 5 hours to obtain a denitration agent.
A plurality of this denitration agent was installed in the denitration catalyst tank of FIG. 4 to measure the denitration rate. At this time, light oil was used as the hydrocarbon sprayed at the time of denitration. The amount of light oil sprayed was adjusted so that the average molecular weight of light oil was about 200 and the light oil concentration was the same as 900 ppm, which is the average NO _x concentration in the exhaust gas.

The correlation between the elapsed time and the denitration rate in the above measuring method is shown in FIG. As shown in this figure, in the above measurement, almost no change in the denitration rate with time was observed.
Even after the lapse of time, the denitration rate is maintained at 90% or more.

Next, the denitration rate was measured for each of the cases where kerosene and heavy fuel oil A were sprayed during denitration in the above measuring method.

Further, in each of the denitration methods using the above light oil, kerosene, and A heavy oil as a comparative example, N which does not carry iron is used.
Denitration was performed using aY type zeolite as a denitration agent as it was, and the denitration rate was measured. Furthermore, in each of the above denitration methods, denitration was performed without spraying hydrocarbons, and the denitration rate was measured.

Table 1 shows the denitration rate after 1000 hours in each of the above denitration methods.

[0050]

[Table 1]

As is clear from this table, when hydrocarbons were sprayed using a denitrification agent supporting iron, denitrification rate of 90% or more was maintained even after 1000 hours for any hydrocarbon species. And a very good denitration rate was obtained.

When the hydrocarbons are not sprayed, the denitrification rate is 0% regardless of the type of denitrification agent. Even when the hydrocarbons are sprayed, the denitrification agent that does not support iron is Was about 5 to 10%, which was a very low denitration rate as compared with the denitration agent supporting iron.

Accordingly, excellent denitration performance can be obtained by injecting hydrocarbons such as light oil, kerosene, heavy oil A, etc. at the time of denitration and using a zeolite supporting iron using iron nitrate as a supported catalyst as a denitration agent. I understand.

1-2: Instead of the NaY type zeolite used in the above 1-1, Na type mordenite (manufactured by Tosoh Corp., 6
10NAA) was used, and the denitration rate was measured in the same manner as in 1-1. The results are shown in Table 2.

[0055]

[Table 2]

From this table, it can be seen that even when a denitration agent in which iron is supported on Na-type mordenite is used, a high denitration rate can be obtained by spraying hydrocarbons during denitration as in 1-1. X-type zeolite (F-9 manufactured by Tosoh Corporation) was used instead of the NaY-type zeolite used in 1-3: 1-1.
The denitration rate was measured in the same manner as in -1. The results are shown in Table 3.

[0057]

[Table 3]

From this table, it can be seen that even when a denitration agent in which iron is supported on X-type zeolite is used, a high denitration rate can be obtained by spraying hydrocarbons at the time of denitration as in 1-1.

The denitration rate was measured in the same manner as in 1-1 except that the AY type zeolite (A-5, manufactured by Tosoh Corporation) was used in place of the NaY type zeolite used in 1-4: 1-1. The results are shown in Table 4.

[0060]

[Table 4]

From this table, it can be seen that even when a denitration agent in which iron is supported on A-type zeolite is used, a high denitration rate can be obtained by spraying hydrocarbons during denitration as in 1-1. Example 2 (Denitration method using a denitration agent having ferrous chloride and ferric chloride as a supported catalyst) 2-1: First, a NaY type zeolite (320 NAA manufactured by Tosoh Corporation) was used as a zeolite for a carrier, A honeycomb molded body containing 30 wt% of a reinforcing material and having a shape of 16 × 16/65 mm square holes was fired.

In order to support iron on this honeycomb body, 0.1 mol / l aqueous solutions of ferrous chloride and ferric chloride were prepared, respectively, and the honeycomb formed body was immersed in this aqueous solution for 12 hours, respectively. Was impregnated with iron.

Then, each zeolite was taken out of the aqueous solution and dried at 150 ° C. for 5 hours to obtain a denitration agent.
A plurality of this denitration agent is installed in the denitration catalyst tank of FIG.
The denitration rate was measured under the condition of a value of 2000 / h. At this time, light oil was used as the hydrocarbon sprayed at the time of denitration. FIG. 2 shows the correlation between the elapsed time and the denitration rate when ferrous chloride was used as the supported catalyst in the above measuring method. As shown in this figure, there was almost no change in the denitration rate with time in the above measurement, and the denitration rate was 90% even after 1000 hours.
% Or more is maintained.

Next, the denitration rate was measured for each of the cases where kerosene and heavy fuel oil A were sprayed during denitration in the above measuring method.

As a comparative example, the above diesel oil, kerosene, A
N that does not support iron in each denitration method using heavy oil
Denitration was performed using aY type zeolite as a denitration agent as it was, and the denitration rate was measured. Furthermore, in each of the above denitration methods, denitration was performed without spraying hydrocarbons, and the denitration rate was measured.

Table 5 shows the denitration rate after 1000 hours in each of the above denitration methods.

[0067]

[Table 5]

As is clear from this table, when hydrocarbons were sprayed using a denitrification agent supporting iron, denitrification rate of 90% or more was maintained even after 1000 hours for any hydrocarbon species. And a very good denitration rate was obtained.

When the hydrocarbons are not sprayed, the denitrification rate is 0% regardless of the type of denitrification agent, and even when the hydrocarbons are sprayed, the denitrification agent that does not carry iron is Was about 5 to 10%, which was a very low denitration rate as compared with the denitration agent supporting iron.

Therefore, at the time of denitration, hydrocarbons such as light oil, kerosene, and heavy oil A are injected, and at the same time, the first chloride is used as a supported catalyst.
It can be seen that excellent denitration performance can be obtained by using, as a denitration agent, a zeolite in which iron or ferric chloride is used to support iron.

2-2: Na-type mordenite (manufactured by Tosoh Corp., 6
10NAA) was used and the denitration rate was measured in the same manner as in 2-1. The results are shown in Table 6.

[0072]

[Table 6]

From this table, it can be seen that even when a denitration agent in which iron is supported on Na-type mordenite is used, a high denitration rate can be obtained by spraying hydrocarbons at the time of denitration as in 2-1. 2-3: Use X-type zeolite (F-9 manufactured by Tosoh Corporation) instead of the NaY-type zeolite used in 2-1 and 2
The denitration rate was measured in the same manner as in -1. The results are shown in Table 7.

[0074]

[Table 7]

From this table, it can be seen that even if a denitration agent in which iron is supported on X-type zeolite is used, a high denitration rate can be obtained by spraying hydrocarbons at the time of denitration as in 2-1.

2-5: The type A zeolite (A-5, manufactured by Tosoh Corporation) was used in place of the NaY type zeolite used in 2-1, and the denitration rate was measured in the same manner as in 2-1. The results are shown in Table 8.

[0077]

[Table 8]

From this table, it can be seen that even when a denitration agent in which iron is supported on A-type zeolite is used, a high denitration rate can be obtained by spraying hydrocarbons during denitration as in 2-1. Example 3 (Denitration method using a denitration agent using ferrous sulfate and ferric sulfate as supported catalysts) 3-1: First, a NaY-type zeolite (manufactured by Tosoh Corporation, 320NAA) was used as the zeolite for the structure. A honeycomb molded body containing 30 wt% of a reinforcing material and having a shape of 16 × 16/65 mm square holes was fired.

In order to support iron on this honeycomb body, 0.1 mol / l aqueous solutions of ferrous sulfate and ferric sulfate were prepared respectively, and the honeycomb formed body was immersed in this aqueous solution for 12 hours, respectively, so that Was impregnated with iron.

Then, each zeolite was taken out from the aqueous solution and dried at 150 ° C. for 5 hours to obtain a denitration agent.
A plurality of this denitration agent is installed in the denitration catalyst tank of FIG.
The denitration rate was measured under the condition of a value of 2000. At this time, light oil was used as the hydrocarbon sprayed at the time of denitration. FIG. 3 shows the correlation between the denitration rate and the elapsed time when ferrous sulfate was used as the supported catalyst in the above measuring method. As shown in this figure, in the above measurement, the denitration rate hardly changed with time, and the denitration rate remained at 90% or more even after 1000 hours.

Next, the denitration rate was measured for each of the cases where kerosene and heavy fuel oil A were sprayed during denitration in the above measuring method.

As a comparative example, the above diesel oil, kerosene, A
N that does not support iron in each denitration method using heavy oil
Denitration was performed using aY type zeolite as a denitration agent as it was, and the denitration rate was measured. Furthermore, in each of the above denitration methods, denitration was performed without spraying hydrocarbons, and the denitration rate was measured.

Table 9 shows the denitration rate after 1000 hours in each of the above denitration methods.

[0084]

[Table 9]

As is clear from this table, when hydrocarbons were sprayed using a denitrification agent supporting iron, denitrification rate of 90% or more was maintained after 1000 hours for any hydrocarbon species. And a very good denitration rate was obtained.

When the hydrocarbons are not sprayed, the denitrification rate is 0% regardless of the type of denitrification agent. Even when the hydrocarbons are sprayed, the denitrification agent that does not support iron is Was about 5 to 10%, which was a very low denitration rate as compared with the denitration agent supporting iron.

Therefore, at the time of denitration, hydrocarbons such as light oil, kerosene, and heavy oil A are injected, and the first catalyst of sulfuric acid is used as the supported catalyst.
It can be seen that excellent denitration performance can be obtained by using, as a denitration agent, a zeolite in which iron or ferric sulfate is used to support iron.

3-2: Na-type mordenite (manufactured by Tosoh Corp., 6
10NAA) was used, and the denitration rate was measured in the same manner as in 3-1. The results are shown in Table 10.

[0089]

[Table 10]

From this table, it can be seen that even when a denitration agent in which iron is supported on Na-type mordenite is used, a high denitration rate can be obtained by spraying hydrocarbons during denitration as in 3-1.

3-3: Instead of the NaY type zeolite used in 3-1, an X type zeolite (F-9, manufactured by Tosoh Corporation) was used, and the denitration rate was measured in the same manner as in 3-1. The results are shown in Table 11.

[0092]

[Table 11]

From this table, it can be seen that even when a denitration agent in which iron is supported on X-type zeolite is used, a high denitration rate can be obtained by spraying hydrocarbons at the time of denitration as in 3-1.

3-4: In place of the NaY-type zeolite used in 3-1, A-type zeolite (A-5, manufactured by Tosoh Corporation) was used, and the denitration rate was measured in the same manner as in 3-1. The results are shown in Table 12.

[0095]

[Table 12]

From this table, it can be seen that even if a denitration agent in which iron is supported on A-type zeolite is used, a high denitration rate can be obtained by spraying hydrocarbons at the time of denitration as in 3-1. As explained above, when carrying out denitration by carrying iron on zeolite, it is necessary to spray hydrocarbons at the time of denitration in order to obtain a high denitration rate. Further, it is shown that the zeolite species used at this time, the iron salt species used to support iron, and the hydrocarbon species used during denitration have almost no effect on the denitration rate.

[0097]

INDUSTRIAL APPLICABILITY In the present invention, denitration is carried out in the presence of hydrocarbons by passing a NO _x -containing gas through zeolite carrying iron.

Therefore, by supporting iron, the denitration capacity of the zeolite is enhanced, and the coexistence of hydrocarbons suppresses the catalyst deterioration due to SO _x in the exhaust gas, so that the catalyst life is greatly improved. In addition, it is also possible to use A-type, X-type, etc. zeolite, which has a large catalyst deterioration due to SO _x .

Further, since the soot in the exhaust gas is burned by the hydrocarbons, the clogging of the zeolite due to the soot is suppressed and a very high denitration rate can be obtained.

Particularly, when denitration of the exhaust gas of a diesel engine is performed, light oil as fuel is used as the hydrocarbon, and the denitration can be performed by spraying this, so that a special hydrocarbon storage tank or cylinder is required. Therefore, denitration can be performed compactly and economically.

[Brief description of drawings]

FIG. 1 is a graph showing a denitration rate in a denitration device using a denitration agent according to an example of the present invention.

FIG. 2 is a graph showing a denitration rate in a denitration device using a denitration agent according to an example of the present invention.

FIG. 3 is a graph showing a denitration rate in a denitration device using a denitration agent according to an example of the present invention.

FIG. 4 is an explanatory diagram of a denitration device according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Diesel generator 2 ... Denitration catalyst tank 3 ... NO _x concentration measurement port 4 ... NO _x concentration measurement port 5 ... Hydrocarbon spray port 6 ... NO _x concentration analyzer 7 ... Vent pipe 8 ... Hydrocarbon spray pipe 9 ... Communication Trachea 10 ... Exhaust gas sampling tube 11 ... Process gas sampling tube 12 ... Iron-supporting zeolite

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Miki Haba 2-1-117 Osaki, Shinagawa-ku, Tokyo Inside the Meidensha Co., Ltd.

Claims (3)

[Claims] 1. An X-type zeolite containing Na, a Y-type zeolite containing Na, a mordenite containing Na,
And (K, Na, Ca), a hydrocarbon contained in a treatment vessel having a denitration agent obtained by supporting iron on one or more zeolites selected from the group consisting of A-type zeolites containing at least one of denitration method characterized in that by circulating the NO _x containing gas in the presence of performing denitration. 2. A denitration agent obtained by supporting iron on zeolite. 3. A method for producing a denitration agent, which comprises immersing zeolite in an iron salt solution and then drying the zeolite to support iron.