JPH06122517A - Denitration agent, production of denitration agent and denitration method - Google Patents

Abstract

PURPOSE:To form a denitration agent by immersing zeolite in an NaOH solution or an organic acid sodium salt solution and drying the zeolite to support the NaOH or the organic acid sodium salt on the zeolite. CONSTITUTION:A prescribed mount of an organic acid sodium salt of the formula RCOONa (R is H or alkyl), CH3COONa or NaOH is dissolved in water to prepare an aqueous solution having a concentration of 5wt.% to saturation. A dehydrated zeolite such as type A or type X zeolite is immersed in the aqueous solution for >=12hr to support RCOONa, CH3COONa or NaOH on the zeolite. The zeolite is taken out of the solution and dried by heating under reduced pressure to obtain a denitration agent. An NO-N2-O2 mixed gas is introduced into a denitration apparatus 1 through a gas introducing pipe 3, passed at a prescribed flow rate through a denitration agent 8 filled in a metal mesh 11 heated at >=300 deg.C with a heater 12 to remove NO in the mixed gas by the catalytic reaction, the NO concentration is determined by an NO concentration analyzer 6 and a mass spectrometer 7 and the gas is discharged through a treated gas discharging pipe 4.

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]

However, in this direct decomposition method, even if Cu-ZSM-5, which has the highest activity, is used as a catalyst, the catalyst performance deteriorates due to SO _x or H ₂ O in the exhaust gas, and the denitration rate is increased. 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 in view of the above background, and provides a denitration agent having a high denitration rate and capable of maintaining the high denitration rate for a long period of time, a method for producing the denitration agent, and a denitration method. With the goal.

[0010]

Means and Actions for Solving the Problems In order to solve the above problems, the present invention provides a denitration agent obtained by supporting Na on zeolite. Moreover, R ₁ -CO is added to zeolite.
A denitration agent obtained by supporting ONa (wherein R ₁ represents hydrogen or an alkyl group), and in this denitration agent, R
_A denitration agent in which ₁ is methyl and a denitration agent obtained by supporting zeolite on NaOH are also provided.

Further, the denitration is characterized in that after immersing the zeolite in a solution of R ₂ -COONa (wherein R ₂ represents hydrogen or an alkyl group), the zeolite is dried to support R ₂ -COONa. In the method for producing a denitrifying agent, and the method for producing a denitrifying agent, R ₂ is methyl, and a method for producing a denitrifying agent, and after immersing the zeolite in a NaOH solution, the zeolite is dried to obtain NaOH. There is also provided a method for producing a denitration agent, which comprises supporting

Furthermore, denitration method and performing denitration by circulating NO _x containing gas into the processing container that comprises a one of said denitration agent are also provided.

The above Na-supporting zeolite, R ₁ -COONa
In the supported zeolite, the CH ₃ COONa (sodium acetate) -supported zeolite, and the NaOH (sodium hydroxide) -supported zeolite, each of these denitration agents and NO _x react with each other, and NO _x is removed by the interaction.

The present invention will be described in more detail below. The denitration agent can be obtained by a conventional method, but is preferably obtained as follows. First, as the zeolite as the supporting base material, preferably, X-type, A-type, Y-type zeolite, mordenite and the like can be mentioned.

Further, A type, B type, D having an 8-membered oxygen ring
Type, G type, R type, W type, ZK-5, chabazite, deuteriofluoric acid, erionite, etc., ZSM-5 having a 10-membered oxygen ring, and X type, Y type having a 12-membered oxygen ring,
L-type, S-type, mordenite, Ω-type, gmelinite, offretite, cancrinite and the like are also included.

Next, Na or R- is added to this zeolite.
COONa (R is hydrogen or an alkyl group), or CH ₃ C
Support OONa or NaOH. Incidentally, R is preferably a lower alkyl group. Preferably, the zeolite is held in advance in a drying oven or vacuum to remove the water content in the zeolite.

In the present specification, the integration of substances (adsorption, layer formation, etc.) with each other, regardless of physical adsorption, chemical adsorption, etc., is collectively referred to as "supporting".

When supporting Na on the zeolite, Na may be directly supported by ion exchange or by a method such as precipitating a Na compound on the zeolite surface.
May be supported in the form of a compound. In the present specification, these are collectively referred to as K-supporting zeolite. Examples of the Na compound supported on this zeolite include CH ₃ COO
Na, NaOH, etc. are mentioned.

In the case of supporting CH ₃ COONa, this zeolite is preferably immersed in a CH ₃ COONa solution having a predetermined concentration, and after confirming that the CH ₃ COONa has sufficiently diffused into the pores of the zeolite, the solution is left as it is. Evaporate.

Further, the zeolite immersed in the above CH ₃ COONa is pulled up and taken out from the solution, and then the water contained in the zeolite is removed to remove CH ₃ COO.
It is also preferable to carry Na.

Similarly, in the above method, CH ₃ COONa
By using R-COONa or NaOH instead of R-COONa and NaOH, respectively.
A supported zeolite can be obtained.

It should be noted that the above-mentioned immersion time is R in the zeolite pores.
It is sufficient that —COONa, CH ₃ COONa or NaOH can sufficiently diffuse, and it is preferably about 12 hours.

At this time, R-COONa, CH ₃ COONa
Alternatively, if the diffusion of NaOH is sufficient, there is no problem even if the impregnation time is shortened. Further, even if the impregnation time is set to 12 hours or more, there is no deterioration of the zeolite, so the impregnation time is set to 12 hours.
May be longer than time.

The R-COONa, CH ₃ COONa or NaOH solution is not particularly limited as long as the above-mentioned loading is sufficiently carried out, and for example, an aqueous solution of these is used. When an aqueous solution is used, when CH ₃ COONa is supported, the concentration range is preferably 5 wt% to saturated concentration, more preferably 20 wt% to saturated concentration, whereby a particularly high denitration rate can be obtained.

In the case of supporting NaOH, the concentration range is preferably 5.0 wt% to saturation concentration,
A particularly high denitrification rate can be obtained by more preferably adjusting the concentration to 20 wt% to the saturated concentration.

Further, by arranging each of the above-mentioned denitration agents in a processing container through which NO _x gas flows, a denitration device can be constructed. At this time, each of the denitration agents is used alone, but a plurality of these denitration agents can be used in combination.

[0027]

EXAMPLE In this example, CH ₃ COONa and N
Each is supported on zeolite NaOH, to decompose the NO _x each of these zeolites as denitration agent. At this time, the NO _x concentration was measured using the denitration device shown in FIG.

In FIG. 1, 2a is a glass container having a standard gas introducing pipe 3 and 2b is a glass container having a processing gas discharging pipe 4. In this embodiment, the inner diameters of both 2a and 2b are 42 mm.

These glass tubes 2a, 2b are connected to the metal jig 9a,
9b, 42 mm inner diameter spacer 10, stainless wire mesh 1
A denitration device 1 is configured by being connected via a denitration agent holding unit 13 configured by 1. Also, the glass tubes 2a, 2
A heater 12 was provided in each of b to make it possible to adjust the temperature in the denitration device 1.

The glass tube 2a is attached to the metal jig 2a.
The glass tubes 2b are adhered to the metal jigs 2b, respectively. The metal jigs 9a and 9b are insertable with each other, and the denitration device 1 can be divided into two parts.

The stainless wire net 11 is provided perpendicularly to the joint of the glass tube 2a, and the denitration agent 8 is held on the stainless wire net 11.

.. In this embodiment, the denitration agent 8 has a height of 50.
It was supposed to fill up to mm.

The standard gas containing NO is introduced into the glass container 2 through the standard gas introducing pipe 3. At this time, in order to measure the NO (nitrogen monoxide) concentration in the standard gas before the denitration treatment, the standard gas introduction pipe 3 is provided with the NO gas sampling port 5.

Similarly, NO is provided at the latter stage of the treated gas discharge pipe 4.
A concentration analyzer 6 and a mass spectrometer 7 are provided to analyze the processing gas.

In the above device configuration, NO / N ₂ (NO: 1000 pp) is supplied to the denitration device 1 through the gas introduction pipe 3.
Mix the standard gas of m) and oxygen gas to adjust the oxygen gas concentration to 1
2 liters of N ₂ —NO—O ₂ mixed gas, which is kept constant at 0%, is fed in every minute.

In the denitration device 1, NO in the standard gas is removed by contact reaction with the denitration agent. The mixed gas that has been subjected to the denitration processing becomes a processing gas and is discharged through the processing gas discharge pipe 4. At this time, the NO concentration in the processing gas was measured by the NO concentration analyzer 6 and the mass spectrometer 7.

As the NO _x concentration analyzer, Shimadzu CLM100 was used, and as the mass spectrometer, Nichiden Anelva mass filter 400 was used. Denitration reaction is 200
° C. measured at to 500 ° C., decomposition rate of NO _x (denitration ratio) was calculated by the following equation.

The denitrification rate = - concentration of NO _x / exhaust gas (the concentration of NO _x exhaust gas concentration of NO _x process gas) or less, the measurement of the NOx removal efficiency using CH ₃ COONa supported zeolite, the NaOH loaded zeolite respectively as denitrating agent I went.

Example 1 (Measurement of denitration rate in CH ₃ COONa-supported zeolite) 1-1: 41 g of CH ₃ COONa was dissolved in 300 cc of water, and 12.0 wt% of CH ₃ C was added.
An OONa aqueous solution was prepared.

X-type zeolite as the zeolite of the carrier
(Zeorum F-9; manufactured by Tosoh Corporation, pore size 10Å)
The spherical products of 4 to 8 mesh were subjected to vacuum treatment at 160 ° C. for 5 hours in advance and then stored in vacuum.

200 g of this zeolite was added to the above 12.0 wt.
% CH ₃ COONa aqueous solution and allowed to stand for 12 hours to support CH ₃ COONa in the zeolite.

Thereafter, the zeolite was taken out of the aqueous solution, dried at 110 ° C. for 5 hours, and further vacuum-treated at 160 ° C. for 5 hours to completely remove the water content in the zeolite to obtain a denitration agent sample 1.

1-2: CH ₃ COONa 41 g in water 300
It was dissolved in cc to prepare a 12.0 wt% CH ₃ COONa aqueous solution.

As the zeolite of the carrier, spherical type 4 to 8 mesh of X-type zeolite (Zeorum F-9; manufactured by Tosoh Corporation, pore size 10 Å) was used in the same manner as in 1-1, and 1
It was dried at 60 ° C. for 5 hours and stored in a desiccator.

200 g of this zeolite was added to the above 12.0 wt.
% CH ₃ COONa aqueous solution, stirred for several minutes, and then left to stand for 12 hours to form CH _{3 in the} zeolite.
COONa was supported.

After that, the zeolite was taken out of the aqueous solution and placed in a drying furnace at 160 ° C. for 5 hours to remove the water content in the zeolite to obtain a denitration agent sample 2.

In 1-3: 1-1, CH ₃ COONa
The denitration agent sample 3 was obtained in the same manner as in 1-1, except that the concentration was 1.0 wt%. Similarly, in 1-1, CH ₃ COO
Denitration agent samples 4, 5 and 6 were prepared with Na concentrations of 5.0, 8.0 and 20.0 wt%, respectively.

In 1-1, an aqueous solution (saturated aqueous solution) having a solid solubility limit or more obtained by adding 160 g of CH ₃ COONa to 300 cc of water was used. Got 7.

A denitration agent was obtained by using A-type zeolite, Y-type zeolite, and mordenite in place of the X-type zeolite (F-9) used in 1-4: 1-1.

These zeolite species are shown below.

[0051]

[Chemical Formula 1] A-type zeolite: A-3 (manufactured by Tosoh Corporation,
Pore diameter 3Å) A-4 (Tosoh Corporation, pore diameter 4Å) A-4 (Tosoh Corporation, pore diameter 5Å) Y-type zeolite: NaY (Toyo CCI, Z6-)
01-01) HY (Toyo CCI, Z6-03-02) USY (Toyo CCI, Z6-05-01) Mordenite: H Mordenite (Tosoh Corporation, HS
Z-620HOD): Na mordenite (Tosoh Corporation, HSZ-640NA)
D) The Y-type zeolite and the mordenite were both pellets.

First, the zeolite F used in 1-1
A denitration agent sample 8 was obtained by using A-3 instead of -9.

Similarly, instead of F-9, A-4, A-5,
Denitrifying agent samples 9, 10, 11, 12 using NaY, HY, USY, H mordenite, and Na mordenite, respectively.
13, 14, and 15 were obtained.

1-5: CH ₃ COONa was not carried on F-9, and used as it was as a denitration agent. Comparative Example 1
And

Similarly, zeolites which do not carry CH ₃ COONa are A-3, A-4, A-5, NaY and H.
Comparative Examples 2, 3, 4, 5, 6, 7, 8, and 9 were Y, USY, H mordenite, and Na mordenite, respectively.

1-6: The denitration rate of the denitration agent sample 1 was measured using the above denitration device. At this time, the denitration temperature is 200 ° C,
The denitration rate at each temperature was measured at 300 ° C and 400 ° C.

Further, denitration agent samples 2 to 15 and Comparative Example 1
The denitration rate was similarly measured for Nos. 9 to 9. The results are shown in Table 1.

[0058]

[Table 1]

As shown in this table, by supporting CH ₃ COONa on any of the zeolite species, the denitration effect is greatly improved.
It can be seen that the denitration rate is greatly improved by the above.

Further, in the comparative example which does not support zeolite, the denitrification rate becomes lower as the temperature rises, whereas in each denitration agent sample supporting zeolite, the denitrification rate becomes higher as the temperature rises. Therefore, it can be said that the effect of supporting the zeolite is remarkable.

Although the denitration agent sample 2 was obtained in the same process as the denitration agent sample 1 except that the vacuum treatment was omitted in the manufacturing process of the denitration agent sample 1, it was almost the same as the denitration agent sample 1 (denitration agent sample 1). The denitration rate of the agent sample 1 is about 86 to 100%). Therefore, it is expected that other denitration agent samples will have almost the same denitration efficiency even if the vacuum treatment step is omitted.

Comparing the denitration rates of the denitration agent samples 1 and 3-7, the denitration agent sample 4 having a CH ₃ COONa concentration of 5 wt% has about twice the denitration agent sample 3 having a CH ₃ COONa concentration of 1 wt%. denitration rate has been obtained, also CH ₃ C
It can be seen that a high denitration rate of 80% or more can be obtained when the OONa concentration is 20 wt% to the saturated concentration.

Therefore, it is understood that the concentration range of CH ₃ COONa is preferably 5 wt% to saturated concentration, more preferably 20 wt% to saturated concentration. From the results of Example 1 above, it is expected that other salts of sodium and carboxylic acid will have the same denitration effect as CH ₃ COONa.

Example 2 (Measurement of denitration rate in zeolite loaded with NaOH) 2-1: 40 g of NaOH was dissolved in 300 cc of water, and 11.
An 8 wt% NaOH aqueous solution was prepared.

X-type zeolite as the zeolite of the carrier
(Zeorum F-9; manufactured by Tosoh Corporation, pore size 10Å)
The spherical products of 4 to 8 mesh were subjected to vacuum treatment at 160 ° C. for 5 hours in advance and then stored in vacuum.

200 g of this zeolite was added to the above 11.8 wt.
% NaOH aqueous solution and allowed to stand for 12 hours to support NaOH in the zeolite.

Thereafter, the zeolite was taken out of the aqueous solution, dried at 110 ° C. for 5 hours, and further vacuum-treated at 160 ° C. for 5 hours to completely remove the water content in the zeolite to obtain a denitration agent sample 21.

2-2: 40 g of NaOH was dissolved in 300 cc of water to prepare a 11.8 wt% NaOH aqueous solution.

As the carrier zeolite, an X-type zeolite (Zeoramu F-9; manufactured by Tosoh Corporation, similar to 2-1)
Use a spherical product with a pore size of 10Å)
It was dried at 5 ° C for 5 hours and stored in a desiccator.

200 g of this zeolite was added to the above 11.8 wt.
% NaOH aqueous solution and stirred for several minutes, then 1
The zeolite was allowed to support NaOH by leaving it to stand for 2 hours.

Thereafter, the zeolite was taken out of the aqueous solution and placed in a drying furnace at 160 ° C. for 5 hours to remove the water content in the zeolite to obtain a denitration agent sample 22.

In 2-3: 2-1, the denitration agent sample 23 was obtained in the same manner as in 2-1 except that the concentration of NaOH was 1.0 wt%. Similarly, in 2-1 the concentration of NaOH was set to 3.0, 5.0, and 20 wt%, and the denitration agent sample 2 was prepared.
It was set to 4, 25, and 26.

Further, in 2-1, a denitration agent sample 27 was prepared in the same manner as in 2-1 except that an aqueous solution (saturated aqueous solution) having a solid solubility limit or more obtained by adding 200 g of NaOH to 300 cc of water was used. Obtained.

2-4: A denitration agent was obtained by using A-type zeolite, Y-type zeolite, and mordenite in place of the X-type zeolite (F-9) used in 2-1. The same zeolite species as in Example 1 were used.

First, the zeolite F used in 2-1
A denitration agent sample 28 was obtained by using A-3 instead of -9.

Similarly, instead of F-9, A-4, A-5,
DeNOx agent samples 29, 30, 31, 3 using NaY, HY, USY, H mordenite, and Na mordenite, respectively.
2,33,34,35 were obtained.

2-5: F-9 was not loaded with NaOH and used as it was as a denitration agent. This is Comparative Example 21.

Similarly, zeolites A-3, A-4, A-5, NaY, HY, USY, which do not carry NaOH,
Comparative Example 2 using H mordenite and Na mordenite, respectively
2, 23, 24, 25, 26, 27, 28, 29.

2-6: The denitration rate of the denitration agent sample 21 was measured using the above denitration device. At this time, the denitration temperature is set to 200.
The denitration rate was measured at each temperature of ℃, 300 ℃ and 400 ℃.

Further, the denitration rates of the denitration agent samples 22 to 35 and the comparative examples 21 to 29 were measured in the same manner. The results are shown in Table 2.

[0081]

[Table 2]

As shown in this table, the denitration effect is greatly improved by supporting NaOH in any zeolite species.

Further, in the comparative example not supporting zeolite, the denitrification rate becomes lower as the temperature rises, whereas in each denitration agent sample supporting zeolite, the denitrification rate becomes higher as the temperature rises. Therefore, it can be said that the effect of supporting the zeolite is remarkable.

Although the denitration agent sample 22 was obtained in the same process as the denitration agent sample 21 except that the vacuum treatment was omitted in the manufacturing process of the denitration agent sample 21, it was almost the same as the denitration agent sample 21 ( A denitration rate of 97 to 105% of that of the denitration agent 21 is obtained. Therefore, even in other denitration agent samples,
It is expected that almost the same denitration efficiency can be obtained even if the vacuum treatment step is omitted.

Denitrifying agent sample 21, and denitrifying agent samples 23 to 2
Comparing the denitrification rates of No. 7, the denitrification rate of the denitration agent sample 25 having a NaOH concentration of 5.0 wt% was 1.5 times or more that of the denitration agent sample 24 having a NaOH concentration of 3.0 wt%.
It can be seen that when the OH concentration is 20 wt% to the saturated concentration, a very high denitration rate of about 89 to 94% can be obtained.

Therefore, it is understood that the concentration range of NaOH is preferably 5.0 wt% to saturated concentration, more preferably 20 wt% to saturated concentration.

[0087]

As described above, since CH ₃ COONa or NaOH is supported on zeolite in the present invention, a high denitrification rate can be realized by the synergistic effect of CH ₃ COONa, NaOH and zeolite.

Since a solid denitration catalyst is used, processing and handling are easy.

Further, since CH ₃ COONa and NaOH are both inexpensive, they are economically advantageous.

[Brief description of drawings]

FIG. 1 is an explanatory view of a denitration device according to an embodiment of the present invention.

[Explanation of symbols]

 1 ... Denitration device 2a, 2b ... Glass container 3 ... Standard gas introduction pipe 4 ... Process gas discharge pipe 5 ... NO gas sampling port 6 ... NO concentration analyzer 7 ... Mass spectrometer 8 ... Denitration agent 9a, 9b ... Metal jig 10 ... Spacer 11 ... Stainless Wire Mesh 12 ... Heater 13 ... Denitration Agent Holding Unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Hashimoto 2-11-17 Osaki, Shinagawa-ku, Tokyo Stock Company Inside the company Meidensha (72) Toshiya Ishikawa 2-1-117 Osaki, Shinagawa-ku, Tokyo Stockholder Inside the Shaimeiden (72) Inventor Tatsutoshi Tamura 2-17 Osaki Osaki, Shinagawa-ku, Tokyo Stock Association Inside Saimeidou (72) Inventor Yoshiaki Arai 2-17-17 Osaki Shinagawa-ku Stock Tokyo

Claims (8)

[Claims] 1. A denitration agent obtained by supporting Na on zeolite. 2. R ₁ --COONa (however, R
₁ represents hydrogen or an alkyl group), and is a denitration agent obtained by supporting the same. 3. The denitration agent according to claim 2, wherein R
A denitration agent characterized in that ₁ is methyl. 4. A denitration agent obtained by supporting NaOH on zeolite. 5. Denitration, characterized in that after immersing the zeolite in a solution of R ₂ —COONa (where R ₂ represents hydrogen or an alkyl group), the zeolite is dried to support R ₂ —COONa. Method of manufacturing agent. 6. The method for producing a denitration agent according to claim 5, wherein R ₂ is methyl. 7. A method for producing a denitration agent, which comprises immersing zeolite in a NaOH solution and then drying the zeolite to support NaOH. 8. A denitration method which comprises carrying out the denitration by circulating NO _x containing gas into the processing container having a denitrating agent according to any one of claims 1 to 4.