JPH11319566A - Catalyst for removing nitrogen oxide and method for removing nitrogen oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst and a method for reducing and removing nitrogen oxide in exhaust gas which reduces and removes nitrogen oxide in exhaust gas in the presence of hydrocarbons which is added in a small amt. to the exhaust gas or exists in the exhaust gas under an atmosphere of oxidation condition where excess oxygen exists. SOLUTION: A catalyst wherein 0.1-50% by mass barium sulfate to the total mass of the catalyst are physically mixed to alumina is provided. The alumina may have 0.01-15 mass % at least one selected from transition elements and typical elements of the group IIIb, the group IVb and the group Vb in the periodic table, pref. at least one selected from Sn, Co, Ag, In, Ga and Sb. A method using the catalyst in an atmosphere where oxygen exists in the presence of hydrocarbons or a oxygen-contg. org. compd. is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for producing hydrocarbons and oxygen containing nitrogen oxides in an exhaust gas in a small amount in an atmosphere under an oxidizing condition in which excess oxygen is present. The present invention relates to a catalyst and a method for reducing and removing nitrogen oxides in an exhaust gas in the presence of an organic compound.

[0002]

2. Description of the Related Art Nitrogen oxides (hereinafter, referred to as "NOx") emitted from various internal combustion engines and combustors not only adversely affect the human body but also cause photochemical smog and acid rain. Therefore, there is an urgent need to reduce it in environmental measures.

Conventionally, as a method of removing this NOx,
Several methods for reducing NOx in exhaust gas using a catalyst have already been put to practical use. Examples of the method include (a) a three-way catalytic method for gasoline vehicles and (b) a selective catalytic reduction method using ammonia for exhaust gas from a large facility discharge source such as a boiler. In addition, (c) a method of reducing NOx using hydrocarbons as a reducing agent in an oxygen atmosphere has been proposed. In this method, zeolites supporting various metals are used as a catalyst (Japanese Patent Application Laid-Open No. Sho 63/1988). −
No. 283727).

In the above method (a), the hydrocarbon component and carbon monoxide contained in the exhaust gas from the automobile are converted into water and carbon dioxide by a catalyst containing a platinum group, and simultaneously N 2
Ox is reduced to nitrogen. in this way,
It is necessary to adjust the oxygen concentration so that the total amount of oxygen in the exhaust gas and oxygen contained in NOx and the amount of oxygen required to oxidize hydrocarbon components and carbon monoxide are stoichiometrically equal. However, in an atmosphere containing a large amount of oxygen in exhaust gas such as a diesel engine or a lean burn engine, there is a problem that it is not applicable in principle. Recently, a platinum group-containing three-way catalyst capable of purifying NOx even in an oxygen-excess atmosphere has been proposed (Japanese Patent Application No. 5-2 / 1993).
No. 44174), the purification rate is still low, and there are problems such as the generation of a large amount of nitrous oxide as a reduction by-product, and the problem has not been solved.

[0005] In the method of (2) using ammonia as a reducing agent, NOx can be reduced and purified even in an oxygen atmosphere. However, ammonia is toxic and is often used as a high-pressure gas. It is technically difficult to apply to a small exhaust gas generation source, particularly a mobile generation source, because it is not easy and the equipment becomes huge, and the economic efficiency is not good.

On the other hand, the above method (c) has attracted attention as a new method capable of reducing and removing NOx even in an oxygen atmosphere, but lacks the activity and durability in actual exhaust gas. As a catalyst used in this method, a zeolite catalyst supporting a metal such as copper has been proposed, and exhibits a relatively high activity in the initial use, but has a water content of several% to tens of% in actual exhaust gas. Under such conditions, metal aggregation and dealumination from the zeolite skeleton occur, causing catalyst deterioration.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the various problems existing in the above methods (a) to (c), and is intended to solve the above problems in an oxidizing atmosphere containing oxygen and under practical conditions. In addition to the above, a catalyst for efficiently reducing and removing NOx in exhaust gas generated from various facilities including an exhaust gas of a diesel engine as well as a gasoline engine, and a method of removing NOx in the exhaust gas using the catalyst are described. The purpose is to provide.

[0008]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides
The Ox removal catalyst was added to alumina in an amount of 0.1 to the total mass of the catalyst.
The alumina is characterized by being physically mixed with 1 to 50% by mass of barium sulfate. This alumina contains 0.01 to 1 or more elements selected from transition elements described later and specific typical elements. Preferably, it contains 15% by mass. Further, the NOx removal method of the present invention is characterized in that the above catalyst is used in an atmosphere where oxygen is present, in the presence of hydrocarbons or an oxygen-containing organic compound.

Alumina includes types such as α, θ, and γ. In the catalyst of the present invention, any of these types of alumina can be used. Generally, γ-alumina having a high surface area and high catalytic activity is used. Is preferred. These aluminas may be commercially available products, or may be those obtained by an ordinary production method.

As barium sulfate, commercially available products and those obtained by a usual production method can be used, and there is no particular limitation. For example, a carrier such as silica, titania, or zirconia is impregnated and supported with a water-soluble barium compound such as barium chloride, barium nitrate, or barium oxide, and treated with sulfuric acid or sulfur oxide (SOx). A barium sulfate can be used instead of barium. At this time, if a water-soluble barium compound is present on the carrier, as will be described later, the barium compound is dissolved by water or the like generated during the NOx removal operation, causing an adverse effect. It is important to treat it unacceptably. The carrier at this time is used as it is as a component of the catalyst of the present invention.

[0011] Alumina itself has an activity of reducing and removing NOx itself, but when physically mixed with barium sulfate which does not exhibit an activity of reducing and removing itself,
The activity of reducing and removing alumina is dramatically improved.

Barium sulfate is hardly soluble in water and other solutions, but barium compounds other than barium sulfate,
For example, the above-mentioned barium chloride, barium nitrate, barium oxide and the like dissolve in water. Accordingly, a catalyst in which these water-soluble barium compounds are impregnated and supported on alumina is conceivable, but this catalyst does not improve the activity of alumina for reducing and removing NOx. Although the reason for this is not clear in detail, it is presumed that barium ions of the dissolved barium compound migrate to the alumina component and poison the active sites of alumina.

A catalyst in which a water-soluble barium compound is physically mixed with alumina is also conceivable. This catalyst is also used in the presence of steam present in the exhaust gas or hydrocarbons or oxygen-containing organic compounds. The dissolution of the barium compound proceeds by water and the like generated in the process of reducing and removing NOx, which is not preferable because the barium ion causes an adverse effect.

The method of physically mixing barium sulfate with alumina is not particularly limited, and physical mixing of ordinary powders, for example, mixing with a mortar, mixing with a ball mill, and adding barium sulfate to an alumina slurry A method of mixing can be adopted.

The mixing amount of barium sulfate is 0.1 to 50% by mass, preferably 0.5 to 40% by mass, more preferably 0.5 to 30% by mass based on the total mass of the catalyst. If the mixing amount of barium sulfate is less than 0.1% by mass, the above-mentioned dramatic improvement effect of the NOx reduction and removal activity cannot be obtained,
If it is more than 50% by mass, the amount of alumina becomes relatively too small, and the activity due to alumina is rather reduced.

In the catalyst of the present invention, the alumina is at least one element selected from the group consisting of transition elements and typical elements of Group IIIb, Group IVb and Group Vb of the Periodic Table.
More than one metal element, preferably Sn, Co, Ag, I
It may contain at least one selected from n, Ga, and Sb.

In the present invention, the transition element is an ordinary transition element.
An element whose d or f electron orbital is not filled with electrons, which is represented by Group IIIa, IVa, Va, V
In addition to the Ia group, the VIIa group, the VIII group, and the Ib group, Zn, Cd, and Hg of the IIb group can be included, and in addition to Co and Ag, V, Ni, Rh, Ir, and the like are also included. . In addition, general typical elements are elements that do not have d electron orbitals or are filled with potential,
Refers to elements other than transition elements, Group Ia and IIa
Group, group IIIb, group IVb, group Vb, group VIb
Group, group VIIb, and group 0;
Of these typical elements, groups IIIb and IV of the periodic table
Group b and Vb group metal elements are used.

The above transition elements and Periodic Table IIIb
A catalyst obtained using alumina containing at least one or more metal elements (hereinafter, referred to as a third component) selected from group IV, IVb and Vb typical elements includes:
As will be shown in the examples below, the NOx reduction and removal activity at low temperature is improved as compared with a catalyst obtained using alumina containing no third component. The reason for this is not clear in detail, but when the third component is contained, the oxidation of hydrocarbons or oxygen-containing organic compounds as a reducing agent proceeds at a lower temperature than when the third component is not contained. Therefore, it is considered that the activity of reducing and removing NOx at low temperatures is improved. At this time, the content of the third component is 0.01 to 15% by mass, preferably 0.05% by mass, based on the total mass of the third component and alumina.
10 to 10% by mass, more preferably 0.1 to 7% by mass. When the content of the third component is less than 0.01% by mass, the effect of containing the third component cannot be obtained. When the content exceeds 15% by mass, the aggregation of the third component is promoted or the catalyst surface area decreases. There is a possibility that the effect of containing the third component may not be exhibited.

As a method for incorporating the third component into alumina, conventionally known impregnation methods, coprecipitation methods, kneading methods, ion exchange methods, and other various methods can be employed, and there is no particular limitation. The impregnation method is preferred because it can be easily obtained.

In the impregnation method, alumina may be impregnated with a solution of the compound of the third component, dried, and fired in the air. Examples of the compound of the third component include inorganic salts such as nitrates, chlorides and sulfates, and organic salts such as oxalates and acetates. The firing temperature of the alumina containing the third component in the air stream is about 400 to 700 ° C, preferably about 45 ° C.
0 to 600 ° C., and the firing time is about 1 to 10 hours. When the firing temperature is too low or the firing time is too short, the decomposition of the compound of the third component does not sufficiently proceed, and activation cannot be achieved. Conversely, if the firing is carried out at a high temperature for a long time, aggregation and sintering of the compound of the third component on alumina occur,
The activity of the catalyst is reduced.

The above-mentioned catalyst of the present invention may be in the form of powder, granules, pellets, honeycomb, etc., regardless of its shape and structure. It may be one coated on a metal honeycomb.

In the method of the present invention using the catalyst of the present invention, the NOx-containing gas to be treated includes a diesel exhaust gas from a diesel automobile or a stationary diesel engine, a gasoline exhaust gas from a gasoline automobile, and a nitric acid gas. Exhaust gas from production facilities, various combustion facilities, and the like can be mentioned.

The process of the present invention is carried out by bringing the above-mentioned exhaust gas into contact with the above-mentioned catalyst of the present invention in an atmosphere containing oxygen in the presence of hydrocarbons or oxygen-containing organic compounds. The oxygen-containing atmosphere refers to a state in which a large amount of oxygen is contained in the exhaust gas, and is based on a theoretical amount of oxygen necessary for burning unburned components such as carbon monoxide, hydrogen, and hydrocarbons contained in the exhaust gas. Also refers to a state of high oxygen.
For example, in the case of an internal combustion engine such as an automobile, in a state where the air-fuel ratio is larger than the stoichiometric air-fuel ratio (lean region), compared with exhaust gas discharged in the state of the stoichiometric air-fuel ratio in which the conventional three-way catalyst works effectively. This is the atmosphere of the exhaust gas that is discharged. In the case of a diesel vehicle or a lean burn gasoline vehicle, the oxygen concentration in the exhaust gas is several vol% to several tens vol%. The oxygen concentration in the exhaust gas in the method of the present invention is not particularly limited.
ol% to more than ten vol%. The upper limit is not particularly limited, and may be the oxygen concentration in the atmosphere (about 20%).

The reducing agent for reducing and removing hydrocarbons and oxygen-containing organic compounds to be present, that is, NOx, is incomplete combustion products such as hydrocarbons, oxygen-containing organic compounds and fuel remaining in the exhaust gas. It may be a particulate or the like, or may be a hydrocarbon, an oxygen-containing organic compound, or a fuel added from the outside. As specific examples, hydrocarbons, in the gaseous state, include methane, ethane, propane, propylene, butane, butylene, and the like,
Examples of the liquid form include pentane, hexane, heptane, octane, octene, benzene, toluene, xylene, and mineral oils such as gasoline, kerosene, light oil, and heavy oil. The oxygen-containing organic compounds include alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, and octyl alcohol; ethers such as dimethyl ether, ethyl ether, and propyl ether; esters such as methyl acetate, ethyl acetate, and fats and oils; and acetone. And ketones such as methyl ethyl ketone. These hydrocarbons and oxygen-containing organic compounds can be used alone or in combination of two or more.

Although the optimum temperature in the method of the present invention is slightly different depending on the type of the catalyst and the hydrocarbons or oxygen-containing organic compounds used, the temperature close to the exhaust gas temperature does not require exhaust gas heating equipment and the like. Preferably, it is generally suitable to be in the range of about 100-800C, especially about 200-600C. The pressure at this time is
Although the reaction proceeds under pressure or under reduced pressure, it is convenient to introduce the exhaust gas into the catalyst layer at a normal exhaust pressure to allow the reaction to proceed. Further, the space velocity is determined by the type of catalyst, other reaction conditions, a desired NOx removal rate, and the like, and is not particularly limited.

In the method of the present invention, there is a concern that unburned hydrocarbons, oxygen-containing organic compounds, or incomplete combustion products such as carbon monoxide may be discharged into the processing gas depending on the processing conditions. May be done. This concern can be solved by contacting the gas treated by the method of the present invention with an oxidation catalyst in an oxidizing atmosphere.

As the oxidation catalyst, one that completely burns the above-mentioned incomplete combustion products can be used.
Silica, zirconia, titania and other porous carriers, platinum, palladium, precious metals such as ruthenium, lanthanum,
Catalyst components such as cerium, copper, iron, base metal oxides such as molybdenum, and perovskite-type crystal structures such as cobalt lanthanum trioxide, iron lanthanum trioxide, and cobalt strontium trioxide, supported alone or in combination of two or more. Is mentioned. Of course, in particular, base metal oxides and the like can be used without being supported on a carrier. The amount of the catalyst component to be supported on the carrier can be appropriately selected according to the required performance. In general, the amount of the noble metal is about 0.01 to 5% by mass relative to the total mass of the catalyst.
For a base metal oxide or the like, the content is about 5 to 70% by mass. This oxidation catalyst may be in the form of powder, granules, pellets, honeycomb, or the like, regardless of its shape or structure.The oxidation catalyst is coated on a cordierite or metal honeycomb. There may be.

The use ratio of the catalyst of the present invention (reduction catalyst) and the above-mentioned oxidation catalyst can be appropriately selected according to the required performance, but generally, the total of the reduction catalyst (A) and the oxidation catalyst (B) is used. Is 10 and (A): (B), about 0.
It is used in the range of 5: 9.5 to 9.5: 0.5.

The mode of use of the reduction catalyst and the oxidation catalyst is as follows.
Generally, a reduction catalyst is arranged on the exhaust gas upstream side, and an oxidation catalyst is arranged on the exhaust gas downstream side. Specifically, a reactor in which a reduction catalyst is disposed is used in an exhaust gas introduction section (previous stage), and a reactor in which an oxidation catalyst is disposed is used in an exhaust gas discharge section (rear stage). The respective catalysts may be used at a ratio corresponding to the required performance, with the reduction catalyst being arranged in the first stage and the oxidation catalyst being arranged in the second stage.

The temperature at which the oxidation catalyst is used may not be the same as the temperature at which the reduction catalyst is used. However, in general, a heating / cooling equipment that can be used within the above-mentioned range of the temperature at which the reduction catalyst is used is selected. Is not particularly necessary and is preferable.

[0031]

Example 1 (Preparation of catalyst) 4.5 g of γ-alumina (manufactured by Mizusawa Chemical Co., Ltd.) having a particle size of 2-3 mm and 0.5 g of barium sulfate (Ba (SO ₄ ) ₂ , manufactured by Kanto Chemical Co., special grade) Was thoroughly pulverized using a mortar and physically mixed to obtain a catalyst A in which alumina was mixed with 10% by mass of barium sulfate based on the total mass of the catalyst.

(Reduction and removal reaction of NOx)
0.2 g of the catalyst A obtained by the above process was supplied to a normal pressure flow reactor.
And the apparatus is charged with about 1000 ppm of nitric oxide.
(Hereinafter referred to as "NO"), about 9 vol% oxygen, about 8
vol% steam and about 1000 ppm propyle
Helium-balanced gas containing 240 ml / min
Flow rate (SV = 40000h ^-1In Table 1)
The reaction was performed at the indicated temperature. Analysis of reaction gas by gas chromatography
Using a graph, N₂, N₂Quantify O etc.
The Ox removal rate (%) was calculated. The results are shown in Table 1.
You.

Comparative Example 1 Only barium sulfate used in Example 1 was ground in a mortar in the same manner as in Example 1 to obtain a catalyst B. Using this catalyst B,
The reduction removal reaction of NOx was performed in the same manner as in Example 1,
The Ox removal rate (%) was calculated. The results are shown in Table 1.

Comparative Example 2 Only the alumina used in Example 1 was ground in a mortar in the same manner as in Example 1 to obtain a catalyst C. Using this catalyst C, a reduction and removal reaction of NOx was performed in the same manner as in Example 1, and NOx was removed.
The removal rate (%) was calculated. The results are shown in Table 1.

Example 2 1.18 g of tin chloride (SnCl _4.5 H ₂ O, manufactured by Kanto Chemical Co., Ltd., special grade) was dissolved in 6.72 g of distilled water, and 9.6 g of alumina used in Example 1 was added to this aqueous solution. After being immersed and allowed to stand for 5 hours, dried by an evaporator (70 ° C.), calcined in air at 550 ° C. for 3 hours to obtain 4% by mass of Sn-supported alumina (catalyst D) based on the total amount of alumina and tin. Obtained. 4.85 g of this and 0.15 g of barium sulfate used in Example 1 were mixed well in a mortar in the same manner as in Example 1 to obtain Catalyst E in which 3% by mass of barium sulfate was mixed with respect to the total mass of the catalyst. Was. Using this catalyst E, a NOx reduction reaction was performed in the same manner as in Example 1 except that the temperature was changed as shown in Table 2, and the NOx removal rate (%) was calculated. The results are shown in Table 2.

Example 3 4.0 g of the catalyst D prepared in Example 2 and 1.0 g of barium sulfate used in Example 1 were mixed well in a mortar in the same manner as in Example 1, and 20% by mass relative to the total mass of the catalyst. Catalyst F mixed with barium sulfate was obtained. Using this catalyst F, a reduction removal reaction of NOx was performed in the same manner as in Example 1, and the NOx removal rate (%) was calculated. The results are shown in Table 2.

Example 4 2.80 g of barium nitrate (Ba (NO ₃ ) ₂ , manufactured by Kanto Chemical Co., Ltd., special grade) was dissolved in 1.75 g of distilled water, and commercially available silica (SiO ₂ , Fuji Silysia Chemical Ltd.) was added to the aqueous solution. Made)
2.5 g was immersed, left for 5 hours, dried with an evaporator, and calcined in air at 550 ° C. for 3 hours to obtain 50% by mass of Ba-supported silica with respect to the total amount of barium and silica. One liter of 0.1N sulfuric acid was applied thereto in several portions, dried, and calcined at 600 ° C. for 3 hours to obtain barium sulfate-supported silica (referred to as catalyst G). 1.0 g of this
And 4.0 g of the catalyst D prepared in Example 2 were mixed well in a mortar in the same manner as in Example 1 to obtain Catalyst H in which 20% by mass of Catalyst G was mixed with respect to the total mass of the catalyst. Using this catalyst H, a reduction removal reaction of NOx was performed in the same manner as in Example 1, and NO
x removal rate (%) was calculated. The results are shown in Table 2.

Comparative Example 3 Catalyst D prepared in Example 2 was replaced with N in the same manner as in Example 1.
A reduction removal reaction of Ox was performed, and a NOx removal rate (%) was calculated. The results are shown in Table 2.

Comparative Example 4 0.29 g of barium nitrate used in Example 4 was added to distilled water 3.
Dissolved in 40 g, 4.85 g of the catalyst D prepared in Example 2 was immersed in this aqueous solution, allowed to stand for 5 hours, dried with an evaporator, calcined at 550 ° C. for 3 hours in air, and 3 masses with respect to the total mass of the catalyst. % Of the supported catalyst I on Ba was obtained. This catalyst I
, A reduction removal reaction of NOx was performed in the same manner as in Example 1, and the NOx removal rate (%) was calculated. The results are shown in Table 2.

COMPARATIVE EXAMPLE 5 2.0 g of the catalyst D prepared in Example 2 and 3.0 g of barium sulfate used in Example 1 were mixed well using a mortar, and mixed with the total amount of Catalyst D and barium sulfate by 60 mass. % Of barium sulfate was obtained. Using this catalyst J, a NOx reduction and removal reaction was performed in the same manner as in Example 1, and NO
x removal rate (%) was calculated. The results are shown in Table 2.

Comparative Example 6 4.0 g of the catalyst D prepared in Example 2 and barium chloride (B
1.0 g of aCl ₂ (manufactured by Kanto Chemical Co., Ltd., special grade) was mixed well using a mortar to obtain a catalyst K in which 20 mass% of barium chloride was mixed with respect to the total amount of catalyst D and barium chloride. Using this catalyst K, a NOx reduction removal reaction was performed in the same manner as in Example 1, and the NOx removal rate (%) was calculated. The results are shown in Table 2.

Comparative Example 7 4.0 g of the catalyst D prepared in Example 2 and barium oxide (B
aO, manufactured by Kanto Chemical Co., Ltd.) 1.0 g was mixed well using a mortar, and 20% by mass relative to the total amount of Catalyst D and barium oxide.
The catalyst L obtained by mixing the barium oxide was obtained. Using this catalyst L, a reduction removal reaction of NOx was performed in the same manner as in Example 1, and the NOx removal rate (%) was calculated. The results are shown in Table 2.

Example 5 0.85 g of cobalt acetate (Co (CH ₃ CO ₂ ) ₂ .4H ₂ O, manufactured by Kanto Chemical Co., Ltd., special grade) was dissolved in 6.86 g of distilled water. 9.8g of alumina
Immersed and allowed to stand for 5 hours, dried with an evaporator (7
0 ° C.), calcined in air at 550 ° C. for 3 hours, 2 mass% C
o-supported alumina (referred to as catalyst M) was obtained. 4.5 g of this and 0.5 g of barium sulfate used in Example 1 were mixed well in a mortar in the same manner as in Example 1 to obtain a catalyst N in which 10% by mass of barium sulfate was mixed with respect to the total mass of the catalyst. Was. Using this catalyst N, a NOx reduction removal reaction was performed in the same manner as in Example 1, and the NOx removal rate (%) was calculated. The results are shown in Table 3.

[0044] Example 6 of indium nitrate _{(In (NO 3) 3 ·} 3H 2 O, manufactured by Kanto Chemical Co., Inc., special grade) 0.62 g were dissolved in distilled water 6.86 g, alumina used in Example 1 to the aqueous solution 9.8 g was immersed and left for 5 hours, and dried with an evaporator (70 g).
℃), calcined in air at 550 ℃ for 3 hours, 2 mass% In
A supported alumina (referred to as catalyst O) was obtained. 4. of these
0 g and 1.0 g of barium sulfate used in Example 1 were mixed well in a mortar in the same manner as in Example 1, and 20 g with respect to the total mass of the catalyst.
Catalyst P was obtained by mixing barium sulfate in a mass%. Using this catalyst P, a reduction removal reaction of NOx was performed in the same manner as in Example 1, and the NOx removal rate (%) was calculated. Table 3 shows the results
Shown along with.

Example 7 0.16 g of silver nitrate (AgNO ₃ , manufactured by Kanto Chemical Co., Ltd., special grade)
Was dissolved in 6.93 g of distilled water, 9.9 g of the alumina used in Example 1 was immersed in this aqueous solution, allowed to stand for 5 hours, dried by an evaporator (70 ° C.), and dried at 550 ° C. in air at 550 ° C.
Calcination was performed for 1 hour to obtain 1% by mass of Ag-supported alumina (referred to as catalyst Q). 4.75 g of this and 0.25 g of barium sulfate used in Example 1 were mixed well in a mortar in the same manner as in Example 1 to obtain Catalyst R in which 5% by mass of barium sulfate was mixed with respect to the total mass of the catalyst. Was. Using this catalyst R, a NOx reduction and removal reaction was performed in the same manner as in Example 1, and the NOx removal rate (%) was calculated. The results are shown in Table 3.

Example 8 Antimony chloride (SbCl ₃ , Kanto Chemical Co., special grade)
0.94 g was dissolved in 6.65 g of distilled water, 9.5 g of the alumina used in Example 1 was immersed in this aqueous solution, allowed to stand for 5 hours, dried by an evaporator (70 ° C.), and dried in air.
The mixture was calcined at 50 ° C. for 3 hours to obtain 5 mass% Sb-supported alumina (referred to as catalyst S). 4.5 g of this and 0.5 g of barium sulfate used in Example 1 were mixed well in a mortar in the same manner as in Example 1 to obtain a catalyst T in which 10% by mass of barium sulfate was mixed with respect to the total mass of the catalyst. Was. Using this catalyst T, a reduction removal reaction of NOx was performed in the same manner as in Example 1, and NOx was removed.
The removal rate (%) was calculated. The results are shown in Table 3.

Comparative Examples 8 to 11 Catalyst M prepared in Example 5 (Comparative Example 8), Catalyst O prepared in Example 6 (Comparative Example 9), Catalyst Q prepared in Example 7
(Comparative Example 10), Catalyst S prepared in Example 8 (Comparative Example 1)
Using each of 1), a NOx reduction removal reaction was performed in the same manner as in Example 1, and the NOx removal rate (%) was calculated. The results are shown in Table 3.

[0048] Tin 0.59g nitrate gallium chloride used in Example 9 Example _{2 (Ga (NO 3) 3} · 8H 2 O, manufactured by Kanto Chemical Co., Inc., special grade)
1.15 g was dissolved in 6.72 g of distilled water, 9.6 g of the alumina used in Example 1 was immersed in this aqueous solution, allowed to stand for 5 hours, dried with an evaporator (70 ° C.), and dried in air.
It was calcined at 50 ° C. for 3 hours to obtain 2 mass% Sn-2 mass% Ga-supported alumina (referred to as catalyst U). 4.5 of these
g and 0.5 g of barium sulfate used in Example 1.
In the same manner as in the above, the mixture was mixed well in a mortar to obtain a catalyst V in which 10% by mass of barium sulfate was mixed with the total mass of the catalyst. Using this catalyst V, a NOx reduction removal reaction was performed in the same manner as in Example 1, and the NOx removal rate (%) was calculated. The results are shown in Table 4.

Comparative Example 12 Using the catalyst U prepared in Example 9, a reduction removal reaction of NOx was carried out in the same manner as in Example 1, and the NOx removal rate (%) was calculated. The results are shown in Table 4.

Comparative Example 13 20 prepared in the same manner as in the method for preparing catalyst O of Example 6.
The mass% In-supported alumina and the barium sulfate used in Example 1 were mixed well using a mortar to obtain a catalyst W in which 20 mass% of barium sulfate was mixed with respect to the total amount of the In-supported alumina and barium sulfate. . Using this catalyst W, a NOx reduction removal reaction was performed in the same manner as in Example 1, and the NOx removal rate (%) was calculated. The results are shown in Table 4.

COMPARATIVE EXAMPLE 14 0.79 g of silver nitrate used in Example 7 was replaced with 4.56 g of distilled water.
9.5 g of barium sulfate used in Example 1 was immersed in this aqueous solution, allowed to stand for 5 hours, dried by an evaporator (70 ° C.), and calcined at 550 ° C. for 3 hours in air.
Barium sulfate (mass% Ag) (catalyst X) was obtained.
1.0 g of this and the alumina 4.0 used in Example 1 were used.
g was mixed well in a mortar in the same manner as in Example 1 to obtain a catalyst Y in which 20% by mass of the above-mentioned barium sulfate carrying Ag was mixed with respect to the total mass of the catalyst. Using this catalyst Y, a NOx reduction removal reaction was performed in the same manner as in Example 1, and the NOx removal rate (%)
Was calculated. The results are shown in Table 4.

Comparative Example 15 A catalyst Z in which 1% by weight of Ag was supported on the catalyst A prepared in Example 1 in the same manner as in the preparation method of the catalyst Q in Example 7 was obtained. Using this catalyst Z, NOx was obtained in the same manner as in Example 1.
, And a NOx removal rate (%) was calculated. The results are shown in Table 4.

Example 10 The same procedure as in Example 1 was carried out except that the catalyst A prepared in Example 1 was used, a gas containing about 3000 ppm of methanol was used instead of propylene, and the reaction temperature was as shown in Table 3. NOx reduction reaction is performed and NOx removal rate (%)
Was calculated. The results are shown in Table 5.

Example 11 The procedure of Example 1 was repeated, except that the catalyst F prepared in Example 3 was used, a gas containing about 1000 ppm of propane was used instead of propylene, and the reaction temperature was as shown in Table 4. The NOx reduction reaction was performed, and the NOx removal rate (%) was calculated. The results are shown in Table 4.

Comparative Example 16 Example 10 was repeated except that the catalyst C prepared in Comparative Example 2 was used.
NOx reduction reaction was performed in the same manner as described above, and the NOx removal rate (%) was calculated. The results are shown in Table 3.

Comparative Example 17 Example 11 was repeated except that the catalyst D prepared in Example 2 was used.
NOx reduction reaction was performed in the same manner as described above, and the NOx removal rate (%) was calculated. The results are shown in Table 4.

Comparative Example 18 Using the catalyst F prepared in Example 3, the oxygen concentration was 0 vol.
%, A reduction and removal reaction of NOx was performed in the same manner as in Example 1. The NOx removal rate (%) was calculated. Table 5 shows the results.

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

[Table 3]

[0061]

[Table 4]

As is clear from Tables 1 to 4, it is found that the catalyst obtained by physically mixing barium sulfate with alumina or alumina carrying the third component has an improved activity of reducing NO to N ₂ . Further, the catalyst obtained by physically mixing barium sulfate with the third component-supported alumina can obtain a higher NO reduction rate at a lower temperature than the catalyst obtained by physically mixing barium sulfate with alumina not supporting the third component, It can be seen that the adaptability to the actual exhaust gas temperature is high. Furthermore, it can be seen that the catalyst obtained by physically mixing barium sulfate impregnated and supported on silica with alumina or alumina containing the third component has a much higher low-temperature activity and a better effect than the above can be obtained. On the other hand, it can be seen that the catalyst in which barium is supported on the third component-supported alumina and the catalyst in which barium chloride or barium oxide is physically mixed have low NO reduction activity.

[0063]

[Table 5]

[0064]

[Table 6]

As is clear from Table 5, the catalyst of the present invention works effectively even when methanol or propane is used as the reducing agent. Further, as is apparent from Table 6, it is understood that the catalyst of the present invention does not work effectively in an atmosphere in which oxygen does not exist.

[0066]

As described in detail above, according to the present invention,
Under practical conditions in an oxidizing atmosphere in which oxygen is present, NOx in exhaust gas generated from gasoline engines, diesel engines, and various other facilities can be efficiently removed.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tomohiro Yoshinari 1134-2 Gongendo, Satte City, Saitama Prefecture, Cosmo Research Institute R & D Center

Claims (4)

[Claims] 1. A catalyst for reducing and removing nitrogen oxides, wherein the catalyst is added to alumina in an amount of 0.1% based on the total mass of the catalyst.
What is claimed is: 1. A catalyst for removing nitrogen oxides, which is obtained by physically mixing barium sulfate in an amount of up to 50% by mass. 2. The method according to claim 1, wherein the alumina is selected from the group consisting of transition elements and Periodic Table I.
At least one metal element selected from the group consisting of typical elements of the IIb group, the IVb group and the Vb group;
The nitrogen oxide removing catalyst according to claim 1, wherein the catalyst is contained in an amount of 15% by mass. 3. The transition element and at least one metal element selected from the group IIIb, group IVb and group Vb of the periodic table selected from Sn, Co, Ag, In, Ga and Sb. The nitrogen oxide removal catalyst according to claim 2, wherein the catalyst is one or more types. 4. The method according to claim 1, wherein in an atmosphere in which oxygen is present, in the presence of a hydrocarbon or an oxygen-containing organic compound.
3. A method for removing nitrogen oxides, comprising using the catalyst according to any one of 3.