JPH09103678A - Exhaust gas-purifying catalyst and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce NOx in exhaust gas without being deteriorated under a high temperature condition containing water vapor or the like by a method wherein at least one kind of a catalytic compound selected from a group composed of a compound having a platinum group element and a compound having silver is supported by a support containing perovskite and is burned. SOLUTION: Perovskite power, a catalytic compound, and a binder are kneaded. After molding by extruding in a pellet shape, it is dried, and burned at for example 600-900 deg.C. Thereby, a pellet wherein a catalytic compound (platinum group element, and silver element) is supported with a perovskite support, is formed. By occlusion of NOx by provskite itself and rise of temperature, NOx is dissociated on a surface of a supported catalyst constituent to release N2 , and O2 remains. The O2 is consumed by HC and CO in exhaust gas, and removed. By the repetitive reaction, an excellent effect on a reduction percentage of NOx can be obtained over a wide range of catalyst inlet temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an exhaust gas purifying catalyst for reducing nitrogen oxides (NOx) in exhaust gas of a diesel engine.

[0002]

BACKGROUND OF THE INVENTION Nitrogen oxides (NO) contained in exhaust gas of diesel engines
x) as a catalyst for reducing copper-zeolite (Cu-ZS
Although catalysts such as M5) are known, the usual conditions of use are high temperature conditions containing water vapor, and therefore, the above catalysts are prone to deterioration and have not yet been put to practical use.

Therefore, an object of the present invention is to effectively reduce nitrogen oxides (NOx) contained in exhaust gas of a diesel engine without deterioration even under high temperature conditions containing water vapor and the like. It is to provide an exhaust gas purifying catalyst.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a catalyst in which a compound having a platinum group or silver is supported on a specific carrier can achieve the above object. The present invention has been completed and the present invention has been completed.

That is, according to the present invention, one or more catalyst compounds selected from the group consisting of compounds containing elements of the platinum group and compounds containing silver are supported on a carrier containing perovskites and then calcined. An exhaust gas purifying catalyst is provided.

Further, the present invention provides the above exhaust gas purifying catalyst, which is characterized in that it is in the form of pellets, and the perovskite powder, the above catalyst compound and the binder are kneaded and molded into pellets. , Further dried,
Then, the exhaust gas purifying catalyst obtained by firing at 600 to 900 ° C. is provided.

The present invention also provides the above exhaust gas purifying catalyst, which is characterized in that it has a honeycomb shape, and a binder is mixed with perovskite powder to obtain a mixture, and the obtained mixture is formed into a honeycomb shape. After being extruded and dried, it is dried and further baked at 600 to 900 ° C. to obtain a honeycomb-shaped carrier, and the obtained carrier is immersed in an aqueous solution of the catalyst compound to impregnate the carrier with the catalyst compound. An exhaust gas purifying catalyst obtained by supporting, drying, and calcining at 500 to 800 ° C., and a powder of perovskite are immersed in an aqueous solution of the above catalyst compound, dried, and further dried at 500 to 800.
After calcination at ℃, pulverized into powder form, then kneaded with a binder, extruded into a honeycomb shape, dried, and further calcined at 600 to 900 ℃, and a cordierite ceramics Honeycomb
After immersing in a slurry formed by mixing perovskite powder, a binder and water, it is dried and then 600-90.
A honeycomb-shaped carrier is obtained by baking at 0 ° C., the obtained carrier is immersed in an aqueous solution of the above-mentioned catalyst compound to support the catalyst compound on the carrier, dried, and further baked at 600 to 900 ° C. And an exhaust gas purifying catalyst.

Further, according to the present invention, the catalyst compound is one or more kinds selected from the group consisting of chloroplatinic acid, dinitrodiammineplatinum, rhodium nitrate, iridic acid chloride, palladium nitrate, silver nitrate and ruthenium chloride. It provides a catalyst.

Further, in the present invention, the mixing ratio of the catalyst compound is 0.1 with respect to 100 parts by weight of the perovskite.
The present invention provides the above exhaust gas purifying catalyst, which is up to 5 parts by weight.

The present invention also provides the above exhaust gas purifying catalyst, wherein the binder is silica sol, alumina sol, aluminum nitrate or talc.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The exhaust gas purifying catalyst of the present invention will be described in detail below.

The carrier used in the present invention contains perovskite (LaCoO ₃ , LaNiO ₃ , LaFeO _3, etc.). The carrier may be formed of only the perovskite, but strontium (S
It may contain other components such as r). The carrier can also be applied on the surface of a molded body of ceramics such as cordierite ceramics.

In the present invention, the catalyst compound supported on the perovskite is one or more selected from the group consisting of a compound containing an element of the platinum group and a compound containing silver.

Examples of the compound having the platinum group element include the following compounds.

[H ₂ PtCl ₆ .6H ₂ O] Platinum chloroplatinate [Pt (NH ₃ ) ₂ (NO ₂ ) ₂ ] Dinitrodiammine platinum [Rh (NO ₃ ) ₃ ] Rhodium nitrate [H ₂ IrCl ₆・ 6H ₂ O] iridium chloride [Pd (NO ₃ ) ₂ ] palladium nitrate [RuCl ₃ .3H ₂ O] ruthenium chloride Also, as a compound having the above silver, [AgNO ₃ ]
Examples thereof include silver nitrate.

In the exhaust gas purifying catalyst of the present invention, the mixing ratio of the catalyst compound is preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the carrier.
It is particularly preferable that the amount is 0 to 2.0 parts by weight. This is because if the mixing ratio is less than 0.1 parts by weight, the reaction cannot proceed because the amount of active metal is small, and if it exceeds 5 parts by weight, the amount of metal is agglomerated in large amounts.

In the exhaust gas purifying catalyst of the present invention, if the catalyst compound is supported on the carrier,
The shape and the like are not particularly limited, but a pellet shape or a honeycomb shape is preferable.

As the above-mentioned pellet-shaped exhaust gas purifying catalyst, perovskite powder, the above-mentioned catalyst compound and a binder are kneaded, extruded into pellets, further dried, and then calcined at 600 to 900 ° C. Preferred are pellets and the like. In the pellet,
By the above-mentioned calcination, the catalyst compound (or platinum-based element or silver element) in the carrier composed of the perovskite [hereinafter, when referred to as a catalyst, the catalyst compound itself or the platinum-based element such as platinum, ruthenium, rhodium, iridium, palladium, etc. Or pointing to silver].

At this time, the particle size of the pellets is 1.0 to
It is preferably 5.0 mm.

When an organic binder is used as the binder, it disappears by firing, but an inorganic binder is preferably used. The inorganic binder has a great effect as a binder. Preferred inorganic binders are silica sols, alumina sols, aluminum nitrate or talc. Further, a plasticizer such as methyl melulose may be added.

The kneading can be carried out at a speed of 50 to 100 revolutions per minute by using a device such as a rocking mixer. Further, it can be formed into pellets by extrusion molding using a device such as an extruder. In this case, the mixing ratio of each component is preferably perovskite powder: catalyst compound: binder = 70 to 90: 0.5 to 4: 29.5 to 6. In addition, the drying is performed at 80 to 150 ° C. for 5
It can be performed under drying conditions for 10 hours.

The above firing can be carried out in an air atmosphere at 600 to 900 ° C. for 3 to 5 hours.

Examples of the above-mentioned honeycomb-shaped exhaust gas purifying catalyst include the following honeycomb bodies.

The perovskite powder is kneaded with a binder to obtain a mixture. The obtained mixture is extruded into a honeycomb shape, dried, and then fired at 600 to 900 ° C. (fired before loading) to obtain a honeycomb shape. A carrier is obtained, and the obtained carrier is immersed in an aqueous solution of the above-mentioned catalyst compound to impregnate the carrier with the catalyst compound to carry the carrier, and then dried.
A honeycomb body that is fired (fired after being carried) at 00 to 800 ° C.

The perovskite powder is dipped in an aqueous solution of the above-mentioned catalyst compound, dried, calcined at 500 to 800 ° C. (first calcining after supporting it), pulverized into a powder, and then the above-mentioned binder. After kneading and extruding into a honeycomb shape, it is dried and then 600-900 ℃
A honeycomb body obtained by firing (second firing after supporting).

The cordierite ceramic honeycomb body was dipped in a slurry obtained by mixing the perovskite powder, the above binder and water, and then dried, and further 6
A honeycomb-shaped carrier is obtained by baking at 00 to 900 ° C. (baking before supporting), the obtained carrier is immersed in an aqueous solution of the catalyst compound to support the catalyst compound on the carrier, and then dried. Furthermore, a honeycomb body obtained by firing (baking after supporting) at 500 to 800 ° C.

That is, the above-mentioned honeycomb body is a honeycomb body in which a catalyst is carried on the surface of a honeycomb body made of a carrier, and the honeycomb body is a honeycomb body in which a carrier and a catalyst are kneaded. The above-mentioned honeycomb body is a honeycomb body in which the above-mentioned carrier is fixed to the surface of a honeycomb made of cordierite ceramics, and a catalyst is supported on the surface.

Here, in the above-mentioned honeycomb body, the mixing is carried out by using a device such as a rocking mixer.
It can be stirred at a rotation speed of -100 rpm. Further, a honeycomb can be formed by extrusion molding using a device such as an extruder.

In the case of an organic binder, the mixing ratio of each component at this time is preferably perovskite powder: binder = 80-98: 20-2. In the case of an inorganic binder, the mixing ratio of each component at this time is perovskite powder: binder = 70 to 95:30 to 5
It is preferred that

In the case of an organic binder, the drying after the above-mentioned molding can be carried out at 80 to 150 ° C. for 5 to 10 hours. 80 to 1 for inorganic binders
The drying can be performed at 50 ° C. for 5 to 10 hours.

The above-mentioned baking before loading can be carried out in an air atmosphere at 500 to 900 ° C. for 3 to 5 hours.

The concentration of the aqueous solution is preferably adjusted so that the catalyst compound is 1 to 5% by weight.
Further, the immersion time is preferably 1 to 20 hours.

The drying is carried out at 80 to 150 ° C. for 5 to 5.
It can be performed under drying conditions for 10 hours.

The above-mentioned firing after supporting may be carried out in an air atmosphere at 500 to 800 ° C. for 3 to 5 hours.

In the above honeycomb body, the concentration of the aqueous solution is preferably adjusted so that the catalyst compound is 1 to 5% by weight. The mixing ratio of the perovskite powder and the aqueous solution is preferably perovskite powder: aqueous solution = 60-80: 40-20.

The above-mentioned first firing can be carried out in an air atmosphere under the firing conditions of 500 to 800 ° C. and 3 to 5 hours.

The powder of the mixture and the binder can be mixed with a device such as a rocking mixer at a rotation speed of 50 to 100 rpm. In addition, a honeycomb can be formed by extrusion molding using a device such as an extruder. In this case, the mixing ratio of the respective components is preferably a powder of the above mixture: binder = 70 to 95:30 to 5.

The drying is performed at 80 to 150 ° C. for 5 to 5 hours.
It can be performed under drying conditions for 10 hours.

The second firing described above can be carried out in an air atmosphere under the firing conditions of 600 to 900 ° C. and 3 to 5 hours.

Further, in the above honeycomb body, the mixing ratio of the perovskite powder, the binder and water in the slurry is, in the case of an organic binder, the perovskite powder: binder: water = 50 to 70:20.
It is preferably 25:10 to 5. In the case of an inorganic binder, perovskite powder: binder: water = 40
It is preferable to be set to -60: 20-30: 20-10.

The above immersion is preferably carried out for an immersion time of 10 seconds to 10 minutes.

The above drying is carried out at 80 to 150 ° C. for 5
It can be performed under drying conditions for 10 hours.

The above-mentioned firing before loading can be carried out in an air atmosphere under firing conditions of 3 to 5 hours.

The concentration of the above-mentioned catalyst compound is 1
It is preferable to adjust the content to be about 5% by weight. Also,
The immersion in the aqueous solution is preferably carried out for an immersion time of 1 to 20.

Further, the above-mentioned drying after supporting is 8 to 1
The drying can be performed at 50 ° C. for 5 to 10 hours.

The above-mentioned firing after carrying can be carried out in an air atmosphere at 500 to 800 ° C. for 3 to 5 hours.

The exhaust gas purifying catalyst of the present invention is obtained as described above, and more specifically, it is used in the form shown in Examples described later.

In the exhaust gas purifying catalyst of the present invention, the perovskite itself used as a carrier is NOx.
When the temperature further rises, NOx spills over the catalyst component such as a platinum-based element supported on the perovskite to dissociate on the surface of the catalyst component, and N ₂ is released to release O _2. It remains on the surface of the catalyst component.
Further, the remaining O ₂ is hydrocarbons, HC,
It is consumed and removed by CO. The exhaust gas purifying catalyst of the present invention can effectively reduce NOx contained in the exhaust gas to N ₂ by repeating this reaction.

[0049]

The present invention will be described in more detail with reference to the following examples with reference to the drawings, but the present invention is not limited thereto.

Here, FIG. 1 is a radial cross-sectional view showing a cylindrical exhaust gas purifying device filled with the pellet-shaped exhaust gas purifying catalyst of the present invention, and FIG. 2 is a honeycomb-shaped present invention. FIG. 3 is a perspective view showing a cylindrical exhaust gas purifying device filled with the exhaust gas purifying catalyst of FIG. 3, and FIG. 3 is an enlarged view of a III portion of FIG. 2. FIG. 4 is an enlarged plan view (corresponding to FIG. 3) showing another example of the exhaust gas purifying catalyst of the present invention.

Example 1 An exhaust gas purifying apparatus shown in FIG. 1 was manufactured using the pellet-shaped exhaust gas purifying catalyst manufactured as follows.

The exhaust gas purifying apparatus 1 shown in FIG. 1 has a cylindrical main body 2, a cylindrical exhaust gas inlet 3 provided in front of the main body 2 and having a diameter smaller than that of the main body 2, and the main body. 2, a cylindrical exhaust gas discharge port 4 having a diameter smaller than that of the main body 2, a pellet-shaped exhaust gas purifying catalyst 5 filled in the main body 2, and front and rear sides of the main body 2. In, a net-shaped catalyst holding portion 6 that holds the exhaust gas purification catalyst 5 is provided.

In the exhaust gas purifying catalyst 5, the perovskite powder (particle size: 10 to 100 μm) is mixed with dinitrodiammine platinum so that the amount of platinum is 2 parts by weight with respect to 100 parts by weight of the perovskite. This was extruded into pellets, dried at 100 ° C. for 10 hours, and then heated and baked at 600 ° C. for 3 hours.

Example 2 An exhaust gas purifying apparatus was manufactured in the same manner as in Example 1 except that the exhaust gas purifying catalyst 5 manufactured as described below was used.

A perovskite powder having a particle diameter of 10 to 100 μm was extruded into pellets, dried at 100 ° C. for 10 hours, and then calcined at 600 ° C. for 3 hours to produce pelletized carriers, which were then obtained. The pellet-shaped carrier was immersed in a 1% by weight aqueous solution of dinitrodiammineplatinum for 3 hours, then withdrawn, dried at 100 ° C. for 10 hours, and
Obtained by heating and baking at 00 ° C. for 3 hours.

Example 3 An exhaust gas purifying apparatus shown in FIGS. 2 and 3 was manufactured using the honeycomb-shaped exhaust gas purifying catalyst manufactured as described below.

The exhaust gas purifying apparatus 1'shown in FIG. 2 comprises a cylindrical main body 2'and a honeycomb-shaped exhaust gas purifying catalyst 5'shown in FIG. 3 filled in the main body. The purification catalyst 5 ′ is composed of a honeycomb-shaped carrier 5a and a catalyst 5b attached to the surface of the carrier 5a.

Here, in the exhaust gas purifying catalyst 5 ', the perovskite is made into a powder having a particle size of 10 to 100 µm, and 100 parts by weight of the powder is mixed with 25 parts by weight of talc as a binder to form the honeycomb 1. Extruded into
It was dried at 100 ° C. for 10 hours and then heated and calcined at 700 ° C. for 3 hours to obtain a honeycomb-shaped carrier. The resulting honeycomb-shaped carrier is immersed in a 1% by weight dinitrodiaminoplatinum aqueous solution for 3 hours to impregnate and support dinitrodiaminoplatinum,
It was dried at 100 ° C. for 10 hours and further heated and baked at 600 ° C. for 3 hours.

(Embodiment 4) FIG. 4 shows an exhaust gas purifying catalyst.
An exhaust gas purifying apparatus was manufactured in the same manner as in Example 3 except that the honeycomb catalyst shown in 1 was used.

The exhaust gas purifying catalyst 5 "shown in FIG. 4 has a honeycomb-shaped cordierite ceramic 5c with a particle size of 10
100 parts by weight of powdered perovskite and 20 parts by weight of alumina sol as a binder are mixed, and 40 parts by weight of water is further added to form a slurry, and 60 parts of the cordierite ceramics 5c is added to the obtained slurry.
Immerse for 2 seconds, pull up and dry at 100 ° C. for 10 hours, and then heat and bake at 600 ° C. for 3 hours to form carrier portion 5d, and then obtain the honeycomb body on which carrier portion 5d is formed by using dinitrodiammine. The catalyst portion 5e is formed by immersing in a 1 wt% platinum aqueous solution for 3 hours, further drying at 100 ° C. for 10 hours, and then heating and baking at 600 ° C. for 3 hours.

(Test Example) Conventional copper-zeolite (Cu-
An exhaust gas purification test was conducted under the following conditions (same conditions) for ZSM-5) and the exhaust gas purification catalyst of the present invention of Example 4, and the results shown in FIG. 5 were obtained.

Engine used: 4 L NA engine Gas oil used: JIS fuel (sulfur content: 0.05% by weight) Exhaust gas inflow: 2000 liters / minute Catalyst usage: 5 liter As is clear from the results shown in FIG. It is understood that the exhaust gas purifying catalyst of the present invention has an excellent effect of reducing the rate of nitrogen oxides (NOx) over a wide range of catalyst inlet temperatures.

[0063]

EFFECT OF THE INVENTION The exhaust gas purifying catalyst of the present invention does not deteriorate even under high temperature conditions containing water vapor and the like, and is a nitrogen oxide (NO) contained in the exhaust gas of a diesel engine.
x) can be effectively reduced.

[Brief description of the drawings]

FIG. 1 is a radial cross-sectional view showing a cylindrical exhaust gas purifying apparatus which is filled with a pellet-shaped exhaust gas purifying catalyst of the present invention.

FIG. 2 is a perspective view showing a cylindrical exhaust gas purifying apparatus which is filled with a honeycomb-shaped exhaust gas purifying catalyst of the present invention.

FIG. 3 is an enlarged view of a part III in FIG.

FIG. 4 is an enlarged plan view (corresponding to FIG. 3) showing another example of the exhaust gas purifying catalyst of the present invention.

FIG. 5 is a chart showing test results in a test example.

[Explanation of symbols]

l: Exhaust gas purification device, 2: Main body, 3: Exhaust gas inlet, 4: Exhaust gas outlet, 5: Exhaust gas purification catalyst, 6:
Catalyst holding part 1 ': Exhaust gas purifying device, 2': Cylindrical main body, 5 ':
Exhaust gas purification catalyst, 5a: carrier, 5b: catalyst 5 ": exhaust gas purification catalyst, 5c: honeycomb-shaped cordierite ceramics 5d: carrier portion, 5e: catalyst portion

Claims (10)

[Claims] 1. A carrier comprising perovskite,
An exhaust gas purifying catalyst obtained by carrying at least one catalyst compound selected from the group consisting of compounds containing platinum group elements and compounds containing silver and then firing. 2. The exhaust gas purifying catalyst according to claim 1, wherein the exhaust gas purifying catalyst has a pellet shape. 3. The exhaust gas purifying catalyst according to claim 1, wherein the exhaust gas purifying catalyst has a honeycomb shape. 4. The catalyst compound is chloroplatinic acid, dinitrodiammineplatinum, rhodium nitrate, iridic acid chloride,
The exhaust gas purifying catalyst according to any one of claims 1 to 3, which is one or more selected from the group consisting of palladium nitrate, silver nitrate, and ruthenium chloride. 5. The exhaust gas according to claim 1, wherein the mixing ratio of the catalyst compound is 0.1 to 5 parts by weight with respect to 100 parts by weight of the perovskite. Purification catalyst. 6. The exhaust gas purifying catalyst according to claim 1, wherein the binder is silica sol, alumina sol, aluminum nitrate or talc. 7. The exhaust gas according to claim 2, wherein the perovskite powder, the catalyst compound and the binder are kneaded, molded into pellets, dried, and then calcined at 600 to 900 ° C. Method for producing purification catalyst. 8. A perovskite powder and a binder are kneaded to obtain a mixture, and the obtained mixture is extruded into a honeycomb shape, dried, and then fired at 600 to 900 ° C. to obtain a honeycomb carrier. The obtained carrier is dipped in an aqueous solution of the above-mentioned catalyst compound to impregnate the carrier with the catalyst compound, and the carrier is dried and then calcined at 500 to 800 ° C. Item 4. A method for producing an exhaust gas purification catalyst according to Item 3. 9. A perovskite powder is dipped in an aqueous solution of the above catalyst compound, dried, further fired at 500 to 800 ° C., pulverized into a powder form, and then kneaded with a binder and extruded into a honeycomb form. The method for producing an exhaust gas purifying catalyst according to claim 3, wherein the method is followed by drying and further firing at 600 to 900 ° C. 10. A cordierite ceramic honeycomb body is dipped in a slurry obtained by mixing perovskite powder, a binder and water, and then dried, and further 60
A honeycomb-shaped carrier is obtained by firing at 0 to 900 ° C., the obtained carrier is immersed in an aqueous solution of the above-mentioned catalyst compound to support the catalyst compound on the carrier, then dried, and further 500 to 80.
The method for producing an exhaust gas purifying catalyst according to claim 3, characterized in that the method is performed by firing at 0 ° C.