JPH08229404A - Exhaust gas purifying catalyst and apparatus - Google Patents

Abstract

PURPOSE: To purify NOX in exhaust gas with high efficiency and to also purify soot and HC at the same time by using a first catalyst component consisting of a noble metal, a transition metal and an amorphous double chain structure type clay mineral and a second catalyst component consisting of multiple oxide having a perovskite structure represented by a specific formula in a mixed state. CONSTITUTION: A first catalyst component is formed from a noble metal, a transition metal and an amorphous double chain structure type clay mineral, for example, platinum, vanadium and zeolite. A second catalyst component is formed from multiple site oxide having a perovskite structure represented by chemical formula ABO3 (wherein A is lanthanum, strontium, cerium, barium or calcium, B is cobalt, iron, nickel, chromium, manganese or magnesium and 0 is oxygen) and mixed with the first catalyst component to obtain an exhaust gas purifying catalyst.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention, nitrogen oxides contained in exhaust gas discharged from an internal combustion engine such as diesel over an engine (hereinafter, also referred to as NO _X) an exhaust gas purifying catalyst and a catalyst capable of reducing removed The exhaust gas purifying apparatus used. More specifically, the present invention relates to an exhaust gas purification catalyst and an exhaust gas purification device that can reduce the generation of nitrous oxide (N ₂ 0) of nitrogen oxides in exhaust gas and reduce it to nitrogen (N ₂ ) at a high purification rate.

[0002]

2. Description of the Related Art In recent years, the protection of the atmosphere has been an important theme from the viewpoint of protecting the global environment, and research has been conducted on this problem in a wide range of technical fields. Especially, ozone in the atmosphere, NO _X, suspended particulate matter, in order to be harmful to human body and the natural environment, eradication of the sources has become an issue.

N discharged from a diesel engine or the like
O _X, hydrocarbons and particulate carbonaceous material (hereinafter, also referred to as soot) method of removing them from the viewpoint has been studied also. One of them is to collect the soot by filtering the exhaust gas using a heat resistant filter, and when the filter's ability to collect falls, heat the filter to burn the collected soot and regenerate the filter. There is a method (for example, JP-A-61-46413).

A method has also been proposed in which a reducing agent such as hydrogen, ammonia or low molecular weight hydrocarbon is added to the exhaust gas to positively reduce and purify NO _X (Japanese Patent Laid-Open No. 1-79).
30 publication). On the other hand, in JP-A-4-363119, an alkali metal element, copper, and
An exhaust gas purifying apparatus carrying one or more kinds of cobalt, manganese, and vanadium and a rare earth element, and using the exhaust gas purifying apparatus, soot and hydrocarbon in the exhaust gas mainly act as reducing agents to reduce NO _x . Techniques for reducing are disclosed. This method, hydrocarbons, soot acts as a reducing agent, is an excellent method of NO _X is simultaneously reduced and removed.

[0005]

In the method of combusting soot trapped by the filter [0006], soot in the exhaust gas is being removed NO _X is firstlings problems when would be discharged. Furthermore, when the filter is regenerated, the collected matter burns, and the temperature of the filter rises rapidly, which shortens the life of the filter.

Further, in the method of adding the reducing agent,
Loading of a reducing agent needs to be further examined from the viewpoint of safety for a vehicle such as an automobile that generates exhaust gas while moving, and there is a problem that soot is released. In was further disclosed in JP-A 4-363119 discloses a method, not sufficient activity is obtained for adsorption sites to absorb NO _X is not sufficient for the action of the catalytic metal element carried on the exhaust gas purifying device, more active to increase the, it is necessary to increase the adsorption sites that absorbs NO _X.

In addition, although NO _X is purified by the above-mentioned technique, as a result, harmful N ₂ O may be produced in addition to harmless nitrogen, so that generation of N ₂ O is suppressed and NO ₂ is suppressed. _A technique capable of reducing _X to nitrogen (N ₂ ) (improvement of nitrogen selectivity) is desired. The present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to purify at least NO _{x in} exhaust gas with higher efficiency and to purify soot and / or HC in exhaust gas at the same time. It is an object to provide a catalyst and a device. A further object of the present invention is to provide an exhaust gas purifying catalyst and an exhaust gas purifying apparatus with improved nitrogen selectivity.

[0008]

The exhaust gas purifying catalyst of the present invention is a catalyst for purifying nitrogen oxides contained in the exhaust gas by contacting with the exhaust gas containing at least a particulate carbon material and / or hydrocarbon, and a noble metal And a first catalyst component composed of a transition metal and an amorphous double-chain structure type clay mineral, and a mixture of the first catalyst component and ABO ₃ (A is lanthanum La, strontium Sr, cerium Ce) , Barium Ba, or calcium Ca, B is cobalt Co, iron Fe,
(At least one selected from nickel Ni, chromium Cr, manganese Mn, or magnesium Mg, O is oxygen)
And a second catalyst component composed of a complex oxide having a perovskite structure represented by:

In addition, the exhaust gas purifying apparatus of the present invention comprises a precious metal and a transition metal which are brought into contact with a carrier and an exhaust gas containing at least a particulate carbon material and / or a hydrocarbon to purify nitrogen oxides contained in the exhaust gas. And a first catalyst component composed of an amorphous double-chain structure type clay mineral and a chemical formula of ABO, which is used by mixing with the first catalyst component.
₃ (A is at least one selected from lanthanum La, strontium Sr, cerium Ce, barium Ba, or calcium Ca, B is at least selected from cobalt Co, iron Fe, nickel Ni, chromium Cr, manganese Mn, or magnesium Mg) And a second catalyst component composed of a complex oxide having a perovskite type structure represented by O (oxygen), and a catalyst supported on the carrier,
It is characterized by having.

The catalyst of the present invention comprises a first catalyst component composed of a noble metal and a transition metal, and an amorphous double-chain structure type clay mineral, and a second catalyst component composed of a complex oxide having a perovskite structure. As the noble metal constituting the first catalyst component, platinum Pt, palladium Pd, iridium Ir
And rhodium Rh. Of these, platinum is superior. That is, platinum exhibits a high NO _x purification rate and a high nitrogen selectivity in an oxygen excess atmosphere,
In addition, it is possible to promote lowering of the reaction temperature. The supported amount of the noble metal is preferably in the range of 0.1 to 10% by weight. When the amount of the noble metal supported is less than 0.1% by weight, the catalytic action is almost lost.
On the other hand, if it exceeds 10% by weight, the supported noble metal becomes coarse and becomes coarse, and the catalytic activity decreases. In addition, the amount of the noble metal supported increases and the cost increases, which is not preferable.

As the transition metal constituting the first catalyst component, vanadium V, manganese Mn, iron Fe, cobalt C
o, nickel Ni, copper Cu and zinc Zn can be used. Of these, iron is the best. Iron is
Most excellent in sulfur poisoning resistance and suppression of sulfate formation. These transition metals can be supported by, for example, ion exchange. The amount of ion exchange is preferably 5 to 10% by weight with respect to magnesium and / or aluminum in the clay mineral. The amount of transition metal supported is 5
If it is less than 10% by weight, the amount of competitive reaction between the transition metal and the noble metal decreases, and the catalytic activity decreases. On the other hand, if it exceeds 10% by weight, the activity of the catalyst is lowered because the fiber spaces, diffusion paths such as channels and adsorption sites existing in the double-chain structure type clay mineral are crushed.

As the amorphous double-chain structure type clay mineral constituting the first catalyst component, sepiolite (Si ₁₂ Mg ₈ O) is used.
_{30 (OH) 4 · 8H 2} O), attapulgite and palygorskite _{((MgAl) 5 (SiAl)} 8 O
It is an amorphized clay mineral such as ₂₀ (OH) ₂ .8H ₂ O). These clay minerals are mainly composed of hydrous magnesium silicate, and have reactive hydroxyl groups on their surfaces. These clay minerals have a diameter of 0.05
.About.0.6 .mu.m of fibers and about 1 in parallel with the fibers.
There is a so-called channel with a rectangular cross section of about 0.6 nm. Further, it has a large BET specific surface area of 350 to 400 m ² / g.

The first catalyst component is a multi-chain structure type clay mineral 4
A heat treatment step of changing the structure of the clay mineral by heat treatment at a temperature of 00 to 800 ° C. to make it amorphous, and a substitution step of ion-exchanging magnesium and / or aluminum ions in the clay mineral with transition metal ions. A supporting step of supporting a noble metal by causing a noble metal ion to act on the ion-exchanged double-chain structure type clay mineral.

In the heat treatment step, the double-chain structure type clay mineral is heated to amorphize its structure. The heat treatment temperature is
The range of 400 to 800 ° C is preferable. Heat treatment temperature is 400 ℃
If the amount is less than the above, the structure of the double-chain structure type clay mineral cannot be sufficiently amorphized. Further, when the temperature exceeds 800 ° C., the double-chain structure type clay mineral changes to an enstatite type crystal, which makes it difficult to carry the metal element and the pores disappear, which is not preferable. When the pores disappear, it becomes impossible to secure a gas adsorption site and a passage effective for gas diffusion. More preferably, the heat treatment is performed in the range of 600 to 700 ° C. Amorphization of the double-chain structure type clay mineral most often occurs in the above temperature range.

The substitution step is a step of substituting magnesium and / or aluminum in the amorphized double-chain structure type clay mineral with at least one selected from transition metal elements. In this step, first, an amorphous double chain structure type clay mineral is dispersed in water to form a suspension. At this time, the amount of water is preferably 10 parts by weight or more of the amorphous double-chain structure type clay mineral. 1
If the amount is less than 0 parts by weight, the suspension state of the amorphous double-chain structure type clay mineral is poor and it is difficult to uniformly replace the transition metal with magnesium and / or aluminum. The substituting transition metal is preferably introduced in the form of a salt.

When a transition metal ion is allowed to act on an amorphous double-chain structure type clay mineral in water, magnesium and / or aluminum having a lower binding force among the elements constituting the amorphous double-chain structure type clay mineral. Are ionized and replaced with ions of the transition metal. As a result, the transition metal is introduced into the structure of the amorphous double-chain structure type clay mineral, and the transition metal is strongly and highly dispersed.

In addition, the multi-chain structure type clay mineral is added in an amount of 400-80.
Amorphous double chain structure type clay mineral heat-treated at 0 ° C.
Although it has a BET specific surface area of m ² / g or more, the specific surface area does not decrease due to ion substitution. Rather, the structure is strong and stable, and the specific surface area is also increased. In the noble metal supporting step, the noble metal compound solution is added to the suspension of the amorphous double-chain structure type clay mineral obtained by substituting the transition metal produced in the above step, and the noble metal is supported on the amorphous double-chain structure type clay mineral. Let
Thereby, the first catalyst component can be obtained.

The second catalyst component has a chemical formula of ABO ₃ (A is at least one selected from lanthanum La, strontium Sr, cerium Ce, barium Ba, and calcium Ca, B is cobalt Co, iron Fe, nickel Ni,
At least one selected from chromium Cr, manganese Mn, or magnesium Mg, and O is oxygen), which is a complex oxide having a perovskite structure.

The second catalyst component is mixed with the first catalyst component and supported on the porous filter or the porous honeycomb carrier. In the second catalyst component, platinum as a catalyst metal and / or
Alternatively, it is preferable to include palladium in the perovskite crystal lattice. In this case, platinum and / or palladium are incorporated into the B-site position of the perovskite structure represented by the chemical formula ABO ₃ , that is, they are solid-solved, and the chemical formula A
A structure represented by B _1-X C _X O ₃ (0.05 ≦ X ≦ 0.2) is preferable.

By dissolving platinum and / or palladium in the catalyst as a solid solution, the platinum and / or palladium is incorporated into the catalyst in a highly dispersed state without agglomeration.
Therefore, in particular, activation of hydrogen and an increase in the amount of NOx absorbed can be caused. When the value of X is larger than 0.2, the cost becomes higher than the effect, which is not preferable. If it is less than 0.05, the effect of platinum and / or palladium is small. Therefore, the range of X is 0.05 ≦ X ≦
0.2 is preferable.

The mixing ratio of the first catalyst component to the second catalyst component is preferably in the range of 0.1-20 by weight.
If the weight ratio is less than 0.1, the NOx purification reaction in the oxygen excess atmosphere does not proceed sufficiently, which is not preferable. If it is larger than 20, NO from the low temperature range
Oxidation of soot and combustion reaction of soot do not proceed sufficiently, and NOx
Is not preferable because the simultaneous purification ability in a low temperature range is reduced due to a decrease in the absorption amount of

Next, a method for producing a second catalyst component composed of a complex oxide having a perovskite structure will be described. This production method comprises a first step of preparing an aqueous solution in which salts of metal elements A and B constituting a complex oxide having a perovskite structure (ABO ₃ ) and citric acid are dissolved, and drying the aqueous solution to obtain the above metal. A second step of forming a citric acid complex of the element, a third step of heating / pre-baking the citric acid complex at 350 ° C. or higher in a vacuum or an inert gas, and then baking in an oxidizing atmosphere It can be done in four steps.

The salt of the metal elements A and B in the first step is preferably nitrate or acetate. This is because residual substances other than metal elements can be decomposed by the calcination in the third step. For example, when the metal element is a chloride, chlorine remains even after the calcination and affects characteristics such as catalytic activity and adsorption activity, which is not preferable. The salts of these metal elements are mixed in proportions such that the composition of the chemical formula ABO ₃ is obtained.

The content of citric acid is 2 to 1 mol of the complex oxide having a perovskite structure to be formed.
It is preferable that the range is 2.4 mol. If the content is less than 2 mol, complex formation may be difficult, and if it exceeds 2.4 mol, it may be sufficient for complex formation, but uniform mixing of metal elements may be difficult, which is not preferable. As a method of preparing an aqueous solution in which a salt of a metal element and citric acid are dissolved, for example, a salt of a metal element is dissolved in ion-exchanged water,
Further, there is a method in which citric acid is dissolved in another ion-exchanged water and the both are mixed.

As the drying conditions in the second step, water is rapidly removed within a temperature range where the citric acid complex is not decomposed (for example, room temperature to 150 ° C., 2 to 12 hours).
Is appropriate. In the third step, the citric acid complex of the above metal element is heated at 350 ° C. or higher in a vacuum or an inert gas to be calcined. The calcination atmosphere is in vacuum or in an inert gas. It should be noted that a vacuum is more preferable than an inert gas because the decomposition is promoted.

If the heating temperature is lower than 350 ° C., the residues (organic substances, nitrates) from the citric acid and the salt of the metal element as the starting material cannot be thermally decomposed and remain. Also,
The heating temperature may exceed 500 ° C., but this is not preferable because energy is wasted and the calcining device is damaged. In the fourth step, the above calcined body is calcined. Although the firing method is not limited, since an oxide is formed,
It is preferable to use an oxidizing atmosphere in which oxygen exists such as in the atmosphere.

The firing temperature is 700 to 950.
The range of ° C is preferred. At a temperature lower than 700 ° C., crystals having a perovskite structure are difficult to grow. Also, 950 ℃
If the temperature exceeds, the crystal growth will proceed too much, so the precious metal existing in the lattice with a suitable lattice defect may go out of the crystal lattice, or the specific surface area may decrease and the activity may decrease. is there.

The firing time is about 1 hour, but a fired product can be obtained. However, a longer time is preferable because a composite oxide having a high crystallization rate can be obtained. Chemical formula AB _1-X C
_A catalyst composed of a complex oxide having a perovskite structure represented by _X O ₃ disperses most of the C element as crystal constituent atoms in a highly dispersed state, thereby oxidizing NO to NO ₂ and adsorbing NO _X. The decomposition action and the oxidation action of fine particles and / or hydrocarbons are enhanced. Therefore,
It is preferable that 90% or more of the C element (Pt or Pd), which is a catalytically active species, is incorporated and present in the crystal lattice in terms of the effect of incorporating the element and the significance in terms of cost.

Next, the first catalyst component and the second catalyst component are mixed. This mixing method is not particularly limited. Conventionally used physical mixing methods can be used. For example, either a wet or dry mixing method using an automatic mortar, a ball mill or the like may be used. In the case of wet mixing, it is preferable to mix using ion-exchanged water or to use ion-exchanged water to which a binder such as zirconia sol has been added in advance.

Next, when supporting the mixed first catalyst component and second catalyst component on the carrier, polyvinyl alcohol (PVA) or the like is used as a dispersion medium in order to support the mixed catalyst in high dispersion. Is good. Further, the amount of the dispersant and the binder is preferably 3 to 15% by weight in terms of solid content ratio, and it is preferable to use the necessary minimum amount that does not reduce the catalytic activity.

As the carrier, it is preferable to employ a filter or a honeycomb carrier for filtering the particulate carbon material in the exhaust gas of the diesel engine. As a filter, a bubble-shaped filter that forms a communication hole, has a large number of honeycomb-shaped parallel through holes that open at one end side and close at the other end side and adjoin open and closed through holes alternately opposite to each other. It is possible to use a honeycomb filter in which partition walls separating the through holes function as a filter. The filter has a high thermal shock resistance, and its pores may be those having sufficient pores to collect a particulate carbon material having an average particle size of 0.1 to 1 μm. What is used can be adopted.

The honeycomb carrier means a honeycomb-shaped exhaust gas which has no plugs at both ends of a large number of parallel through holes and which flows from one end opening into the other end opening. Examples of the material constituting the carrier include alumina, silica,
Zirconia, titania, silica-alumina, alumina-
Zirconia, silica-zirconia, silica-titania,
Alumina-titania, mullite, cordierite and the like can be used.

As the honeycomb carrier, in addition to the ceramic honeycomb, a metal honeycomb made of stainless steel, iron-chromium-aluminum alloy, or the like can be used. These carriers have high thermal shock resistance.

[0034]

According to the exhaust gas purifying catalyst of the present invention, the combustion reaction of the particulate carbon material and / or the hydrocarbon and the excessive oxidation due to the synergistic effect of mixing the first catalyst component and the second catalyst component. N under the atmosphere
A NOx purification reaction by a reaction between Ox and a reducing agent can be realized with high efficiency from a low temperature range.

That is, the particulate catalyst and / or hydrocarbons start to burn from the low temperature region by the second catalyst,
Further, NO is promoted to be oxidized to NO ₂ and is temporarily absorbed by the catalyst as NOx. The absorbed NOx reacts with the reducing species on the first catalyst, and is harmless N even in an oxygen excess atmosphere.
Can be reduced and purified to ₂ . Further, in the exhaust gas purifying apparatus using the filter as the carrier, in addition to the effect of the exhaust gas purifying catalyst, it is possible to collect the particulate carbon material discharged from the diesel engine and effectively remove the particulate carbon material from the exhaust gas.

In the exhaust gas purifying apparatus using the honeycomb as the carrier, in addition to the effect of the exhaust gas purifying catalyst, the particulate carbon material is not excessively accumulated inside the honeycomb, so that the pressure loss can be reduced. When Pt and / or Pd is contained in the second catalyst component, since Pt and / or Pd are uniformly dispersed on the support surface without being aggregated, the activity for the particulate carbon material and / or hydrocarbon is increased. Also, the NOx purification rate is improved as the NOx absorption amount is increased. Moreover, since the oxidation temperature of the particulate carbon material and / or hydrocarbon is lowered, the filter or the honeycomb carrier can be regenerated at a low temperature. Since the regeneration temperature is lowered, the filter or the honeycomb carrier is less likely to be damaged, and thus the life of the filter or the honeycomb carrier is extended. Further, since the temperature of the filter or the honeycomb carrier can be kept lower than before, the oxidation of the sulfur dioxide gas existing in the exhaust gas is suppressed, so that the generation of sulfuric acid (sulfate) can also be suppressed.

[0037]

EXAMPLES The present invention will be specifically described below with reference to examples. (Adjustment of First Catalyst Component) As the double-chain structure type clay mineral, Turkish sepiolite powder was used. This sepiolite powder was put into an alumina crucible and heated at a temperature of 65 in a nichrome furnace.
It was kept at 0 ° C. for 4.5 hours and heat-treated to be amorphized.
30 g of this heat-treated sepiolite and 90 of deionized water
0 ml was placed in a domestic mixer and stirred for 10 minutes, and sepiolite was dispersed in ion-exchanged water. After the dispersion, iron chloride as a transition metal compound was added in an amount of 3 mol as a metal atom to 1 mol of sepiolite, and the mixture was dissolved using a mixer to prepare a sepiolite dispersion solution. Next, this dispersion solvent was stirred for 30 minutes in a dispa to ion-exchange magnesium and iron in sepiolite. After ion exchange,
Suction and filtration were repeated several times to sufficiently remove chlorine ions and the like by washing. After washing and removing, ion-exchanged water was added again for redispersion, and then a dinitrodiamine platinum nitric acid solution containing 0.4 to 5% by weight of Pt as a noble metal was added to the dispersion. After the addition, the mixture was stirred on a heating stirrer and heated with a heater at a temperature of 110 to 120 ° C. under uniform stirring to evaporate water. After evaporating the water content, the first catalyst component (No. 1a (Pt / Fe-ASP; (ASP: Am:
orphous Sepiolite))) was obtained.

Further, in the same manner as described above, various kinds of first catalyst components (No. 1b (Pd / Fe-
ASP), No. 1c (Pd / Mn-ASP), No.
1d (Pt / Fe-ASP), No. 1e (Pt / Co
-ASP) was adjusted. (Adjustment of second catalyst component) Lanthanum nitrate 21.67 g
(0.05 mol) was dissolved in 50 ml of deionized water.
Further, 11.56 g (0.045 mol) of cobalt acetate was dissolved in 50 ml of ion-exchanged water. Also, citric acid 2
5.22 g (0.12 mol) of ion-exchanged water 120 ml
Dissolved in. Mix these three types of aqueous solutions to about 25
A 0 ml mixed solution was prepared.

The mixed solution was evaporated to dryness in a hot water bath at 80 ° C. for about 4 hours under reduced pressure by an evaporator to prepare a citric acid complex. While the pressure of this citric acid complex was reduced by a vacuum pump (10 ^-2 torr or less), the temperature was slowly raised by a mantle heater from 80 ° C to 400 ° C so that the temperature did not rise sharply. Note that acetic acid and citric acid began to decompose at around 130 ° C. 250 ° C-400
Since nitrate radicals decomposed and yellow gas was generated at ° C, the heat treatment was completed after confirming that the generated gas was gone (processing time about 3 hours). As a result, a pre-sintered body from which organic substances and nitrates were removed was produced.

After powdering this temporary sintered body, put it in a crucible.
LaCoO was calcined in air at a temperature of 750 ° C. for 3 hours.
₃Is it a perovskite structure composite oxide with the composition
The second catalyst component (No. 2a) was prepared. Also,
Change A site element and B site element in the same manner as above.
Then, various second catalyst components ((No. 2b (LaMnO
₃), No. 2c (LaFeO₃), No. 2d (La
Co_0.9Pt_0.1O₃), No. 2e (LaCo_0.9P
d_0.1O ₃)) Was adjusted.

(Preparation of Pelletized Catalyst Mixing First Catalyst Component and Second Catalyst Component) No. 1a with 0.79 g of the first catalyst component. An average diameter of 1 to 2 mm was obtained by mixing 0.41 g of the second catalyst component of 2a and 0.5 g of powdery carbon as a fine particulate carbon material in a mortar, crushing and crushing.
Pellet catalyst (No. A) was produced.

By the same operation as in the preparation of the above pellet catalyst (No. A), pellet catalysts (No. B to N) composed of a mixed catalyst of the first catalyst component and the second catalyst component shown in Table 1 were prepared.
o. H) was prepared. In addition, the above pellet catalyst (N
o. Pelletized catalysts (No. I to No. K) consisting of only the first catalyst component or the second catalyst component shown in Table 1 were produced by the same operation as the production of A).

The composition of the produced pellet-shaped catalyst is summarized in Table 1.

[0044]

[Table 1]

(Performance Evaluation Test of Pelletized Catalyst) Before manufacturing the exhaust gas purifying apparatus of the present invention, a performance evaluation test of each of the pelletized catalysts prepared above was conducted. In the test, each of the above pelletized catalysts was packed in a fixed bed reactor. And the composition is NO; 250 ppm, O ₂ ; 10%, He
A model gas composed of a balance gas (excess oxygen atmosphere) is circulated (space velocity; SV = 80000h ^-1 ), and the temperature is raised step by step, and the resulting gas is gas chromograph and NO _x.
The conversion was measured in the conversion to nitrogen of NO _X (NO) and N ₂ to O by analyzer. The results are shown in FIGS. In the figure, the solid line shows the conversion rate to nitrogen, and the dotted line shows the conversion rate to nitrogen + N ₂ O.

From the results shown in FIGS. 1 to 4, pellet catalysts A to H prepared by mixing the first catalyst component and the second catalyst component.
In comparison with the pellet-shaped catalysts I to K consisting of the first catalyst component or the second catalyst component alone, it is understood that NO _x can be purified from the low temperature region at a high purification rate even in an oxygen excess atmosphere.
From the results shown in FIG. 1, it is understood that when the mixing amount of the first catalyst component is small (in the case of C), the NO _x purification rate in the oxygen excess atmosphere decreases. Further, if the mixing amount of the first catalyst component is too large (in the case of B), the NO _x purification rate also tends to decrease.

From the results shown in FIG. 2, it can be seen that Pt is superior to Pd as the supported noble metal of the first catalyst component and that the purification rate is excellent even when the supported catalytic metal is Mn. From the results shown in FIG. 3, it can be seen that the purification rate is excellent even when the catalyst metal to be carried is Co, and that the purification rate is further improved when the second catalyst component contains a noble metal.

From the results shown in FIG. 4, the pellet catalyst A prepared by mixing the first catalyst component and the second catalyst component was found to be the pellet catalyst I to the first catalyst component or the second catalyst component alone.
Compared to K, even in an oxygen-excess atmosphere, NO _x can be generated in the low temperature range.
It can be seen that can be purified at a high purification rate. In addition, a rapid temperature change of the catalyst was observed from a certain temperature accompanying the combustion of the particulate carbonaceous material as the step temperature was raised. The temperature at this change is the combustion temperature of the particulate carbon material (carbon combustion temperature)
And the nitrogen production amount at the carbon burning temperature was measured. The results are summarized in Table 1.

From the results shown in Table 1, pelletized catalysts A to
It can be seen that H has a lower carbon combustion start temperature than I to K, and further has a large amount of nitrogen generation at the carbon combustion start temperature. This indicates that the NO _x absorbed in the oxygen excess atmosphere can be efficiently purified to nitrogen during carbon combustion. (Preparation of Exhaust Gas Purification Device) 100% by weight of a first catalyst component composed of Pt / Fe-ASP, 20% by weight of zirconia sol, and 75% by weight of water were mixed to prepare a first suspension.
Next, 100% by weight of the second catalyst component consisting of LaCoO ₃ ,
A second suspension was prepared by mixing 20% by weight of zirconia sol and 75% by weight of water. Next, the first suspension and the second suspension were mixed in predetermined amounts to prepare a third suspension.

Next, after impregnating the above-mentioned third suspension into a monolithic carrier composed of a honeycomb-shaped porous body composed of a large number of cells containing cordierite as a main component, which was molded by an extrusion molding method, the temperature was 700 ° C. It was calcined for 3 hours to support the catalyst. At this time, the amount of the first catalyst component supported on the second catalyst component was about 2 in weight ratio. Then, 50 parts by weight of alumina powder, 15 parts by weight of zirconia sol, 2 parts by weight of polyvinyl alcohol, and 50 parts by weight of water were mixed and stirred to prepare a cell injection material for both end surfaces of the monolithic carrier made of a honeycomb porous body.

Next, by alternately injecting the same amount of the cell injection material into both ends of the honeycomb-shaped porous body carrying the catalyst, the exhaust gas flowing into one cell passes through the cell wall and the other cells are injected. The exhaust gas inlet side and outlet side closed portions were formed so that the exhaust gas was discharged after the transition. 700 in the air
Firing at 3 ° C. for 3 hours, an exhaust gas purifying apparatus of Example 1 was prepared in which the carrier was a porous filter.

Next, Example No. 1 was operated in the same manner as in Example 1 except that the compositions of the first catalyst component and the second catalyst component were changed to those shown in Table 2. 2 and No. An exhaust gas purifying device was produced in No. 3.

[0053]

[Table 2]

Further, the exhaust gas purifying apparatus N of the comparative example in which the supported catalyst comprises only the first catalyst component or the second catalyst component
o. 4 to No. 6 was produced. Example No. In Example No. 1, except that the cell injection material was not injected into both ends of the honeycomb-shaped porous body. Table 3 by the same operation as 1
Example No. 1 in which the carrier having the composition shown in FIG. 7-No. 9, and Comparative Example No. 10-N
o. Twelve exhaust gas purification devices were produced.

(Performance Evaluation Test of Exhaust Gas Purification Device) An evaluation test of the produced exhaust gas purification device was conducted. The test was conducted by disposing an exhaust gas purifying device in the exhaust gas pipe of a swirl type diesel engine having a displacement of 2.45 liters and introducing the exhaust gas into the exhaust gas purifying device. In addition, an electric heater was provided in the exhaust gas purifying device and the exhaust gas pipe upstream of the exhaust gas purifying device so that heating was possible.

A gas introducing pipe for exhaust gas analysis is connected to the exhaust gas pipe on the downstream side of the exhaust gas purifying apparatus, and this gas introducing pipe is connected to an automobile exhaust gas analyzer to guide the exhaust gas, thereby NO _x (NO) in the exhaust gas. The concentration and the HC concentration were measured. The measured value is NO when measured without installing an exhaust gas purification device.
_The NO _x purification rate and the HC purification rate were calculated based on the _X concentration and the HC concentration.

The particulates were measured by alternately collecting the particulates on the upstream side and the downstream side of the exhaust gas purifying apparatus for a certain period of time with a filter and measuring the weight. In addition,
Particulates include hydrocarbons and sulphates in addition to particulate carbon material (soot). Also,
The temperature at which the particulates collected in the exhaust gas purifying apparatus start to ignite and burn was determined by the pressure measurement sensor and used as the regeneration starting temperature.

When the exhaust gas purifying apparatus was not installed, the NO _x concentration in the exhaust gas at an engine speed of 1600 rpm was 300 ppm. Also, the concentration of HC is 90p
It was pmC. Also, the particulate is 4.0 g /
It was h. Table 2 shows the NO _x purification rate and the regeneration start temperature of the filter when the exhaust gas purifying apparatus whose carrier is a porous filter is used.

[0059] In addition, shows the gas temperature entering when the carrier using the exhaust gas purifying apparatus comprising a porous honeycomb carrier, the purification rate of NO _X, HC and particulates at this temperature in Table 3.

[0060]

[Table 3]

From the results of Tables 2 and 3, the exhaust gas purifying apparatus of this embodiment has a higher NO than the exhaust gas purifying apparatus of the comparative example.
_It has a purification rate of _X , HC, and particulates, and is also shown to have a high purification rate of NOx to nitrogen N ₂ . That is, it can be seen that the exhaust gas purifying apparatus of the present example performed excellent purification of exhaust gas.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a conversion rate of nitrogen into a model gas by a catalyst of Examples A, B, and C and an inlet gas temperature.

FIG. 2 is a graph showing a relationship between a conversion rate of nitrogen into a model gas by a catalyst of Examples A, D, E, and F and an inlet gas temperature.

FIG. 3 is a graph showing a relationship between a conversion rate of nitrogen into a model gas by a catalyst of Examples A, G and H and an inlet gas temperature.

FIG. 4 is a graph showing the relationship between the conversion rate of nitrogen into model nitrogen by the catalysts of Example A and Comparative Examples I, J, and K and the inlet gas temperature.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B01D 53/36 102H 104A 104B (72) Inventor Haruo Doi 41, Nagakute, Nagakute, Aichi-gun, Aichi Address 1 Inside Toyota Central Research Institute Co., Ltd. (72) Inventor Masahiro Sugiura 41 Nagahote, Nagakute-cho, Aichi-gun, Aichi Prefecture

Claims (8)

[Claims] 1. A noble metal, a transition metal, and an amorphous double-chain structure type clay mineral which are brought into contact with an exhaust gas containing at least a particulate carbon material and / or a hydrocarbon to purify nitrogen oxides contained in the exhaust gas. Which is used as a mixture with the first catalyst component
O ₃ (A is at least one selected from lanthanum La, strontium Sr, cerium Ce, barium Ba, or calcium Ca, and B is selected from cobalt Co, iron Fe, nickel Ni, chromium Cr, manganese Mn, or magnesium Mg. An exhaust gas purifying catalyst comprising: a second catalyst component composed of a complex oxide having a perovskite structure represented by at least one kind, and O is oxygen. 2. The exhaust gas purifying catalyst according to claim 1, wherein the second catalyst component contains a noble metal supported and / or solid-dissolved in the complex oxide having the perovskite structure. 3. The exhaust gas purifying catalyst according to claim 1, wherein the exhaust gas is exhaust gas emitted from a diesel engine. 4. A noble metal and a transition metal, and an amorphous double-chain structure type, in which a carrier is contacted with an exhaust gas containing at least a particulate carbon material and / or a hydrocarbon to purify nitrogen oxides contained in the exhaust gas. A chemical formula of ABO ₃ (A is lanthanum La, strontium Sr, cerium Ce, barium Ba, or calcium Ca, which is used by mixing with the first catalyst component composed of a clay mineral and the first catalyst component is used. Type 1, B is cobalt Co, iron Fe, nickel Ni,
At least one selected from chromium Cr, manganese Mn, or magnesium Mg, and O is oxygen), and a second catalyst component having a complex oxide having a perovskite structure, which is supported on the carrier. An exhaust gas purification device comprising: a catalyst. 5. The exhaust gas purifying apparatus according to claim 4, wherein the second catalyst component contains a noble metal supported and / or solid-dissolved in the complex oxide having the perovskite structure. 6. The exhaust gas purifying apparatus according to claim 4, wherein the carrier is a porous filter. 7. The exhaust gas purifying apparatus according to claim 4, wherein the carrier is a porous honeycomb carrier. 8. The exhaust gas purifying apparatus according to claim 4, wherein the exhaust gas is exhaust gas emitted from a diesel engine.