JPH08332388A - Ammonia decomposing agent - Google Patents

Abstract

PURPOSE: To decompose and remove ammonia efficiently by causing a carrier to bear the active species of an oxide of a specific element and a group of nitrate as an ammonia decomposing agent. CONSTITUTION: A carrier of an oxide of titanium or aluminum and zeolite is caused to bear an active species selected from among oxides group Ib elements such as Cu and Ag of the periodic table, group IIb, elements such as Zn, group IIIa elements such as La, Ce, group IIIb elements such as Al, Ca, group IVa elements such as Ti, Zr group IVb elements such as Ge, Sn group Va elements such as V, Nb, group VIa elements such as Cn, Mo group VIIa elements such as Mn, or group VIII elements such as Fe, Co, Ni, and a nitrate group of manganese nitrate or iron nitrate. The catalyst thus obtained demonstrates a high activity in the decomposition of ammonia, because the selective reduction reaction of NOX is generated by ammonia by deposition of an NOX source on the catalyst.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ammonia decomposing agent which can efficiently remove ammonia contained in the atmosphere or exhaust gas from various factories.

[0002]

2. Description of the Related Art Ammonia, which is the eight major substances with a legal odor, is conventionally treated by a wet method of absorbing it in water or an acidic solution, an adsorption method using impregnated activated carbon, or a method of oxidative decomposition using a noble metal catalyst. It has been.
However, all of these methods have some problems. That is, the wet method is suitable for treating relatively high-concentration ammonia such as factory exhaust gas, but the equipment cost including wastewater treatment is high. Although the adsorption method does not have these problems, it does not have sufficient adsorption efficiency and has a risk that the adsorption heat accumulates in the adsorption layer to raise the temperature and cause ignition. Further, the oxidative decomposition method is not preferable because the product thereof becomes a nitrogen compound such as NO ₂ .

[0003]

The present invention has been made to solve the above problems, and an object thereof is to provide a decomposing agent for efficiently decomposing and removing ammonia.

[0004]

[Means for Solving the Problems] One or more types of carriers are provided with periodic tables Ib, IIb, IIIa, IIIb, IVa, and I.
At least one active species selected from oxides of Vb, Va, VIa, VIIa, or VIII group elements and nitrate radicals (NO ₃ ) are supported.

The carrier may be any known carrier and is not particularly limited, but oxides such as titanium, aluminum, zirconium and silicon and zeolite are preferable, and these are used alone or in combination of two or more. When an oxide composed of these active species is supported on the carrier as described above, the suitable supporting rate is usually in the range of 0.1 to 10% by weight.

The rate of nitrate radical loading may be adjusted in accordance with the amount of ammonia to be treated. If nitrate radicals disappear due to the reaction as will be described later, a new feed is provided to recycle them. It is also possible to do so.

Examples of these active elements include Cu, Ag, etc., as elements of Group Ib of the periodic table.
As the group IIb element, for example, Zn or the like is added to the group III
As the a-group element, for example, La, Ce or the like may be used
As the group element, for example, Al, Ga, etc., as the group IVa element, eg, Ti, Zr, etc., as the group VIb element, eg, Ge, Sn, etc., as the group Va element, eg, V, Nb And the like as a group VIa element, for example,
Cr, Mo, W, etc., as the Group VIIa element, for example, Mn, etc., and as the Group VIII element, for example,
Fe, Co, Ni, etc. can be mentioned respectively.

The nitrate radicals are supplied from HNO ₃ or the like, but may be supplied in the form of nitrates of various active elements described above. Examples of such compounds include manganese nitrate, iron nitrate, nickel nitrate, etc.
Illustrative examples include nitrates of Ib, VIb, VIIb, and VIII elements.

[0009] exhibit a high activity in the degradation of these catalysts is ammonia, by carrying the NO _X source in the catalyst is believed to be due to selective reduction of the NO _X is occurred with ammonia. This reaction
It is thought that, unlike NH ₃ SCR, which is usually performed, shows high activity because the NO _x source is pre-supplied to the reaction point to increase the efficiency of the reaction.

The preferred temperature range in which these reactions are effectively carried out is in the range of 100 to 350 ° C, more preferably 150 to 300 ° C. Reaction temperature is 100 ℃
When it is lower, the activity of this reaction is low, and when the reaction temperature exceeds 300 ° C., the carried HNO ₃ is scattered, which is not preferable. The heat may be supplied to these catalysts by, of course, a method of heating a gas which is usually performed, but the catalyst may be supported on a conductive structure and electrically heated.

The decomposing agent according to the present invention can be molded into a seed shape such as a honeycomb shape or a spherical shape by a conventionally known molding method. At the time of this molding, a molding aid, a molding reinforcement, an inorganic fiber, an organic binder and the like may be appropriately mixed. It is also possible to carry the coating on a preformed base material by a wash coating method or the like. Furthermore, it is possible to use other conventionally known methods for adjusting the adsorbent.

[0012]

[Examples] Specific examples will be described below. (1) Preparation of catalyst Example 1 100 g of activated titanium dioxide having a specific surface area of 115 m ² / g
Then, 33.3 cc of an oxalic acid solution of ammonium metavanadate of 150 g / l as V ₂ O ₅ was added thereto, an appropriate amount of water was further added, and the mixture was thoroughly mixed with a milk bee and then dried up. After this was baked at 350 ° C. for 4 hours, it was crushed with a sample mill and V ₂ O ₅ —TiO ₂ (weight ratio 5 /
100) powder was obtained. This powder, using SiO ₂ sol as a binder, has a pitch of about 1.8 mm and a wall thickness of 0.
A 4 mm cordierite honeycomb was wash-coated. Next, after drying these, it is immersed in HNO ₃ Soln and further dried to obtain V ₂ O ₅ —TiO ₂ (weight ratio 5 /
100) 0.19 g / cc, HNO ₃ 25 mg / c
A honeycomb molded body carrying c was obtained.

Example 2 Fe ₂ O ₃ —TiO ₂ (weight ratio: 5/10) was used in the same manner as in Example 1 except that an iron nitrate solution was used instead of the oxalic acid solution of ammonium metavanadate.
0) and 0.18 g / cc of HNO ₃ and 23 mg / cc of HNO ₃ were carried to obtain a honeycomb formed body.

Example 3 In the same manner as in Example 1 except that the manganese nitrate solution was used instead of the oxalic acid solution of ammonium metavanadate, MuO ₂ —TiO ₂ (weight ratio 5/1) was used.
00) 0.20 g / cc, HNO ₃ 26 mg / cc
A supported honeycomb molded body was obtained.

Example 4 CrO ₂ —TiO ₂ (weight ratio 5/10) was used in the same manner as in Example 1 except that the solution of ammonium metavanadate was replaced with the solution of chromium nitrate instead of the solution of chromium nitrate.
0) and 0.18 g / cc of HNO ₃ and 25 mg / cc of HNO ₃ were carried to obtain a honeycomb formed body.

Example 5 CoO—TiO ₂ (weight ratio 5/10) was used in the same manner as in Example 1 except that ammonium oxalate solution of ammonium metavanadate was replaced with cobalt nitrate solution.
A honeycomb molded body carrying 0. 9) of 0.19 g / cc and HNO ₃ of 23 mg / cc was obtained.

Example 6 In the same manner as in Example 1 except that the ammonium oxalic acid solution of ammonium metavanadate was replaced by a copper nitrate solution, CuO—TiO ₂ (weight ratio 5/100) was adjusted to 0. A honeycomb molded body carrying 0.18 g / cc and HNO ₃ of 25 mg / cc was obtained.

Example 7 Example 1 was repeated except that a zinc nitrate solution was used instead of the oxalic acid solution of ammonium metavanadate.
Similarly to, ZnO-TiO ₂ (weight ratio 5/100)
Of 0.20 g / cc and HNO ₃ of 23 mg / cc were carried to obtain a honeycomb formed body.

Example 8 NiO—TiO ₂ (weight ratio: 5/10) was used in the same manner as in Example 1 except that ammonium oxalate solution of ammonium metavanadate was replaced with nickel nitrate solution.
A honeycomb molded body carrying 0. 9) of 0.19 g / cc and HNO ₃ of 23 mg / cc was obtained.

Example 9 WO _3- TiO 2 was prepared in the same manner as in Example 1 except that ammonium metatungstate solution was used instead of the oxalic acid solution of ammonium metavanadate.
₂ (weight ratio 5/100) is 0.19 g / cc, HNO ₃
A honeycomb molded body carrying 24 mg / cc of was obtained.

Example 10 Example 1 was repeated except that a tin chloride solution was used instead of the oxalic acid solution of ammonium metavanadate.
Similarly to, SnO ₂ —TiO ₂ (weight ratio 5/10
0) was loaded with 0.20 g / cc and HNO ₃ was loaded with 25 mg / cc to obtain a honeycomb molded body.

Example 11 MoO—TiO ₂ (weight ratio 5/100) was used in the same manner as in Example 1 except that ammonium oxalate solution of ammonium metavanadate was replaced with ammonium molybdate solution. 0.18 g / cc, HNO ₃ 22
A honeycomb molded body carrying mg / cc was obtained.

Example 12 In Example 1, the specific surface area was changed to 1 instead of activated titanium oxide.
Example 1 except 30 m ² / g zirconium oxide
In the same manner as in V ₂ O ₅ —ZrO ₂ (weight ratio 5/10
0) was loaded with 0.21 g / cc and HNO ₃ was loaded with 25 mg / cc to obtain a honeycomb molded body.

Example 13 In Example 1, the specific surface area was changed to 2 instead of activated titanium oxide.
Except that the r- alumina 20 m ² / g in the same manner as in Example _{1, V 2 O 5 -Al 2} O 3 ( weight ratio 5/100)
Of 0.19 g / cc and HNO ₃ of 23 mg / cc were obtained.

Example 14 In Example 1, the specific surface area was changed to 3 instead of activated titanium oxide.
50 m ² / g of acid type mordenite (SiO ₂ / Al ₂
O ₃ ratio of 16, Nippon Chemical Industrial Co., except that the HM-23) in the same manner as in Example _1, V 2 _{O 5} - acid mordenite (weight ratio 5/100) 0.18 g / cc, HNO
A honeycomb molded body carrying 22 mg / cc of ₃ was obtained.

Example 15 In Example 1, the specific surface area was changed to 3 instead of activated titanium oxide.
In the same manner as in Example 1 except that 20 m ² / g of silicon oxide (manufactured by Fuji Devison Chemical Co., Ltd., Syloid 978) was used.
V ₂ O ₅ -SiO ₂ (weight ratio 5/100) 0.15 g
A honeycomb molded body carrying 22 mg / cc of / cc and HNO ₃ was obtained.

Comparative Example 1 In Example 1, V ₂ O ₅ —TiO ₂ (weight ratio 5/100) was added to 0.2 without immersion in HNO ₃ Soln.
A honeycomb molded body carrying 0 g / cc was obtained.

[0028] In Comparative Example 2 Example _2, and without immersion in _{HNO 3 Soln, Fe 2 O 3} -TiO 2 (weight ratio 5/100) 0.
A honeycomb molded body supporting 18 g / cc was obtained.

Comparative Example 3 Pitch of about 1.8 using activated titanium dioxide powder having a specific surface area of 115 m ² / g and SiO ₂ sol as a binder.
mm, wall thickness 0.4 mm, cordierite honeycomb was wash-coated, and TiO ₂
Of 0.20 g / cc and HNO ₃ of 26 mg / cc were obtained.

Comparative Example 4 Commercially available impregnated activated carbon having an acidic surface (crushed charcoal Shirasagi G manufactured by Takeda Yakuhin Kogyo Co., Ltd.) was crushed, and SiO ₂ sol was used as a binder to give a pitch of about 1.8 mm and a wall thickness of 0.4 mm.
The cordierite honeycomb of Example 1 was wash-coated to obtain a honeycomb formed body carrying activated carbon at 0.15 g / cc.

Comparative Example 5 100 g of activated titanium dioxide having a specific surface area of 115 m ² / g was repaved (200 g / l), and H ₂ PtCl ₆ solution was added to Pt.
And 1.0 g was added. After stirring the slurry for 1 hour, the pH was adjusted to 9 with NH ₄ OH solution,
While stirring, 100 cc of a 10 wt% hydrazine solution was added for reduction. This slurry is filtered, washed with water, dried,
The cake is baked at 400 ° C. for 4 hours and then crushed to obtain Pt-Ti.
O ₂ (weight ratio 1/100) powder was obtained. Using this powder with SiO ₂ sol as a binder, a pitch of about 1.
A cordierite honeycomb having a wall thickness of 8 mm and a wall thickness of 0.4 mm was wash-coated with Pt-TiO ₂ (weight ratio: 1/10).
A honeycomb molded body carrying 0.15 g / cc of 0) was obtained.

(2) Evaluation test The honeycomb molded bodies obtained in Examples 1 to 15 and Comparative Examples 1 to 5 were subjected to catalytic oxidation of ammonia under the following test conditions, and the removal rate was calculated by the following formula. It was still,
The ammonia concentration was measured using a detector tube. (Test conditions) NH ₃ 25 ppm Air balance Space velocity 15,000 Hr ⁻¹ Reaction temperature 150 ° C., 200 ° C., 250 ° C., 300 ° C.

The results are shown in Table 1.

[0034]

[Table 1]

[0035]

As shown in Table 1, the present invention can efficiently remove ammonia.

Claims (1)

[Claims] 1. Periodic Table Nos. Ib and II on one or more carriers.
b, IIIa, IIIb, IVa, IVb, Va, VI
An ammonia decomposing agent, comprising at least one active species selected from oxides of a, VIIa or VIII elements and nitrate radicals (NO ₃ ).