JPH07171394A - Catalyst for reduction and removal of nitrogen oxide and usage method of catalyst thereof - Google Patents

Abstract

PURPOSE:To provide a catalyst which is highly active to remove nitrogen oxides from an exhaust gas and has excellent activity even at a high temperature. CONSTITUTION:A catalyst for nitrogen oxide removal is a catalyst composed of either alumina or silica-alumina in which at least one element selected from among Cu, Co, Fe, Cr, Zn, Ni, and V is contained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst for treating exhaust gas containing nitrogen oxides discharged from a boiler, an automobile engine or the like, and a method of using the same, and more particularly, to a catalyst having a very high activity. The present invention relates to an excellent catalyst for removing nitrogen oxides and a method of using the same.

[0002]

2. Description of the Related Art As a method for removing nitrogen oxides in exhaust gas discharged from a boiler, an automobile engine, etc., a selective catalytic reduction method in which ammonia is treated in the presence of a catalyst, and an exhaust gas is passed through a catalyst A non-selective catalytic reduction method of reducing carbon monoxide and hydrocarbons by combustion has been put into practical use. Furthermore, for example, JP-A-60-125, 250
In the publication, there is proposed a method of using a copper ion-exchanged zeolite as a catalyst capable of directly catalytically decomposing nitrogen oxides in the absence of a reducing agent.

Further, as a catalyst capable of selectively reducing nitrogen oxides by reducing components such as unburned carbon monoxide and hydrocarbons even in the presence of excess oxygen, a catalyst containing a base metal such as Cu in zeolite is proposed. (Japanese Patent Laid-Open No. 63-10
0,919, etc.). However, even with these proposed catalysts, the activity cannot be said to be sufficient, and the activity at high temperatures required for high-speed operation of automobiles is insufficient, so that they are not yet put into practical use. Has not reached the end.

[0004]

An object of the present invention is to efficiently purify exhaust gas emitted from internal combustion engines such as boilers, automobile engines, etc., especially diesel engines, etc. without adding a reducing agent such as ammonia. In particular, the present invention provides a catalyst for removing nitrogen oxides, which is highly active even at high temperatures.

[0005]

The inventor of the present invention has completed the present invention as a result of extensive studies on the above problems.
That is, the present invention is a catalyst for removing nitrogen oxides from a combustion exhaust gas containing nitrogen oxides, hydrocarbons, and oxygen, wherein Cu, Co, F is added to alumina or silica alumina.
The present invention provides a catalyst for removing nitrogen oxides, characterized by containing at least one selected from e, Cr, Zn, Ni and V, and a method for using the same.

The present invention will be described in more detail below. Although many types of alumina and silica alumina are known, the types of alumina and silica alumina used in the present invention may be any types. The surface area is not limited, but alumina or silica alumina having a large surface area is preferable. Preferably, the surface area is 100 m ² / g or more. If the surface area is less than 100 m ² / g, Cu, C
O, Fe, Cr, Zn, Ni or V may not be supported easily and may be non-uniformly supported, which may result in insufficient catalyst performance.

The catalyst for reducing nitrogen oxides according to the present invention is C
It is essential to contain at least one selected from u, Co, Fe, Cr, Zn, Ni and V. Cu,
The content of Co, Fe, Cr, Zn, Ni or V is not particularly limited, but it is preferably 0.1 to 4% by weight. If Cu, Co, Fe, Cr, Zn, Ni or V is less than 0.1% by weight, sufficient activity may not be obtained, and if it exceeds 4% by weight, Cu, Co, F
e, Cr, Zn, Ni or V may not be carried in a uniform state, resulting in poor performance.

The catalyst for removing nitrogen oxides of the present invention comprises alumina, silica, alumina, Cu, Co, Fe, Cr,
It is manufactured by containing at least one selected from Zn, Ni and V. Cu, Co, Fe, Cr, Zn, N
The method of introducing i or V is not particularly limited,
It is contained by a method such as impregnating and supporting, evaporation to dryness, etc., but a method of impregnating and supporting is particularly preferable.

[0009] Cu, Co, Fe, Cr, Zn, Ni or V may be impregnated and supported by an ordinary method. For example, Cu, Co, Fe, C may be added to raw material alumina or silica alumina.
A method of impregnating with an aqueous solution containing at least one kind of raw material compound selected from r, Zn, Ni and V and drying it is adopted. The raw material compound of Cu, Co, Fe, Cr, Zn, Ni or V is not particularly limited, but Cu, C
Neutral salts such as o, Fe, Cr, Zn, Ni or V chlorides, nitrates, sulfates and acetates are preferably used.
Two or more kinds of these compounds may be used.

The catalyst for reducing nitrogen oxides of the present invention can be used by molding it into a columnar shape, a spherical shape, a honeycomb shape or the like. Also, alumina or silica alumina is molded in advance, and the molded body is made of Cu, Co, Fe, Cr, Zn, N.
It is also possible to contain i or V. In the method for reducing and removing nitrogen oxides of the present invention, the combustion exhaust gas containing nitrogen oxides, hydrocarbons and oxygen is converted into Cu, Co, Fe,
It is essential to contact with alumina or silica alumina containing Cr, Zn, Ni or V. The nitrogen oxides are NO, NO ₂ , N ₂ O, N ₂ O _{2 and the} like. Further, the kind of hydrocarbon is not particularly limited, but the effect of the method of the present invention is remarkable in the combustion exhaust gas containing a large amount of hydrocarbons having 6 or less carbon atoms.

The concentrations of these component gases in the flue gas to be treated are not particularly limited, but usually nitrogen oxides are 10 to 10000 ppm and hydrocarbons are 10 to 1000.
0 ppm, and oxygen is 0.1 to 15%. In particular,
Nitrogen oxides can be efficiently removed even when oxygen is contained in excess of the amount required to completely oxidize reducing components such as hydrocarbons contained in the exhaust gas. Further, nitrogen oxide can be reduced and removed by further adding hydrocarbon to the exhaust gas. The space velocity and temperature of the exhaust gas at the time of reducing and removing are not particularly limited, but the space velocity (volume basis) 1000 to 500,000 hr-1, the temperature 100 ° C.
-700 degreeC is preferable.

[0012]

The catalyst for nitrogen oxide reduction removal of the present invention is
It is possible to efficiently remove nitrogen oxides from combustion exhaust gas.

[0013]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Example 1 A catalyst 1 was prepared by impregnating 10 g of alumina (surface area: 174 m ² / g) with a copper nitrate aqueous solution so that the amount of supported copper would be 0.2% by weight and then drying at 110 ° C. Example 2 10 g of the alumina used in Example 1 was impregnated with an aqueous cobalt nitrate solution so that the supported amount of cobalt was 0.2% by weight, and then dried at 110 ° C. to prepare a catalyst 2. Example 3 10 g of the alumina used in Example 1 had an iron loading of 0.
After impregnating the iron nitrate aqueous solution to 2% by weight, 11
Catalyst 3 was prepared by drying at 0 ° C.

Example 4 10 g of the alumina used in Example 1 was impregnated with an aqueous solution of chromium nitrate so that the amount of chromium supported was 0.2% by weight, and then dried at 110 ° C. to prepare a catalyst 4. Example 5 10 g of the alumina used in Example 1 was impregnated with an aqueous zinc nitrate solution so that the amount of zinc supported was 0.2% by weight, and then dried at 110 ° C. to prepare a catalyst 5. Example 6 A catalyst 6 was prepared by impregnating 10 g of the alumina used in Example 1 with an aqueous solution of nickel nitrate so that the amount of nickel supported was 0.2% by weight and then drying at 110 ° C.

Example 7 10 g of the alumina used in Example 1 was impregnated with an aqueous solution of vanadium nitrate so that the supported amount of vanadium was 0.2% by weight, and then dried at 110 ° C. to prepare a catalyst 7. Example 8 10 g of the alumina used in Example 1 was impregnated with an aqueous solution of copper nitrate so that the amount of supported copper was 5% by weight, and then 110 ° C.
And dried to prepare catalyst 8. Example 9 A catalyst 9 was prepared by impregnating 10 g of alumina (surface area: 30 m ² / g) with a copper nitrate aqueous solution so that the amount of supported copper would be 0.2% by weight and then drying at 110 ° C.

Example 10 Catalyst 10 was prepared by impregnating 10 g of silica-alumina (surface area 410 m ² / g) with a copper nitrate aqueous solution so that the amount of supported copper would be 3.3% by weight and then drying at 110 ° C. did. Example 11 An activity test was conducted using the catalysts 1-10 obtained in Examples 1-10. Each catalyst is press molded and then crushed to 12 ~
The particles were sized to 20 mesh, and 0.5 g of the sized particles was attached to a flow reactor. After gradually raising the temperature under the flow of He gas, 50
Pretreatment was carried out at 0 ° C. for 5 hours. After cooling, NO: 1000
ppm, C ₂ H ₄ : 250 ppm, O ₂ : H containing 2%
The e gas was flowed at a rate of 150 cc / min, and the steady-state purification activity at each temperature was measured. The steady-state purification activity was evaluated as the conversion rate of NO into nitrogen after holding at each temperature for 2 hours. The conversion rate to nitrogen is the conversion rate to N ₂ = 2 × (N ₂ ) out / (NO) in (N ₂ ) out: N ₂ concentration at the catalyst layer outlet (NO) in: NO concentration at the catalyst layer inlet Shown. The results obtained are shown in Table 1.

[0017]

[Table 1] Comparative Example 1 In the same manner as in Example 11, the activity test was performed on the alumina used in Example 1. The obtained results are shown in Table 2.

[0018]

[Table 2] As is clear from the examples and comparative examples, according to the nitrogen oxide reduction / removal catalyst of the present invention and the method of the present invention, nitrogen oxides can be efficiently reduced and removed from combustion exhaust gas.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01J 23/06 ZAB A 23/22 ZAB A 23/26 ZAB A (72) Inventor Shinya Sato Sapporo City Kita-ku Shinkawa 2-5-6-8 (72) Inventor Yasunobu Hosose Sapporo Kita-ku Kita-ku 32 3-chome 2-18 (72) Inventor Yoshihiro Yuu Kita-ku Kita-ku Kita-ku Nishi 5chome 20

Claims (4)

[Claims] 1. A catalyst for removing nitrogen oxides from combustion exhaust gas containing nitrogen oxides, hydrocarbons and oxygen, wherein Cu, Co, F is added to alumina or silica alumina.
A catalyst for reducing and removing nitrogen oxides, which comprises at least one selected from e, Cr, Zn, Ni and V. 2. 0.1 to 4% by weight of at least one selected from Cu, Co, Fe, Cr, Zn, Ni and V.
The catalyst for reducing and removing nitrogen oxides according to claim 1, wherein the catalyst is contained. 3. A flue gas containing nitrogen oxides, hydrocarbons and oxygen, Cu, Co, Fe, Cr, Zn, N
A method for reducing and removing nitrogen oxides, which comprises contacting with alumina or silica alumina containing at least one selected from i and V. 4. Alumina or silica alumina is C
4. The method for reducing and removing nitrogen oxides according to claim 3, wherein 0.1 to 4% by weight of at least one selected from u, Co, Fe, Cr, Zn, Ni and V is contained.