JP2002361047A - Method for cleaning exhaust and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cleaning exhaust by which NOx and PM can be continuously self-removed under ordinary burning conditions without requiring specified control and to provide an exhaust cleaning catalyst and an apparatus for cleaning exhaust. SOLUTION: In the method for cleaning exhaust, PM particles and NOx in exhaust are removed by converting the PM particles to HC by a reaction represented by the formula mC+nH2 O→H2n Cm +n/2.O2 . The apparatus for cleaning exhaust has a filter obtained by carrying a noble metal and fine oxide particles of <=1 μm average particle diameter on the inner walls of pores in a monolithic filer and disposed in an exhaust flue. In the method for cleaning exhaust, hydrogen generation reactions represented by the formulae C+H2 O→H2 +CO and C+2H2 O→2H2 +CO2 are carried out at <=500 deg.C exhaust temperature. The exhaust cleaning catalyst contains an H2 generation catalyst and an NOx removal catalyst, the H2 generation catalyst contains Rh-carrying porous particles and metals such as Fe, Co, Mn and Ni, and these metals are contained at a ratio of 0.1-10 when Rh is represented by 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification method, an exhaust gas purification catalyst, and an exhaust gas purification apparatus, and more particularly, to particulate (PM) particles and nitrogen oxide (PM) in exhaust gas generated from an internal combustion engine or the like. The present invention relates to an exhaust gas purification method, an exhaust gas purification catalyst, and an exhaust gas purification device capable of purifying NOx) with high efficiency.

[0002]

2. Description of the Related Art In recent years,
From the viewpoint of improving fuel efficiency and reducing carbon dioxide emission, lean burn engines that operate even at an air-fuel ratio higher than the stoichiometric air-fuel ratio have become widespread. In particular, diesel engines
Due to its low fuel consumption, it is attracting attention again.

[0003] However, since the exhaust gas contains PM as solid particles and the exhaust temperature is low, it is difficult to purify the exhaust gas with high efficiency using the conventional catalyst. In recent years, exhaust gas purification has become increasingly difficult due to the remarkable progress in engine fuel efficiency technology and the tendency for exhaust temperatures to further decrease, resulting in highly efficient removal of harmful components in diesel engine exhaust. An effective method that can purify is desired.
As a conventional catalyst for exhaust gas purification of diesel engines,
An oxidation catalyst in which platinum (Pt) is supported on a refractory high surface area inorganic carrier material such as alumina (Al ₂ O ₃ ) is used, but the main function is oxidation of CO and HC, and the SOF content is also to some extent. Although it can be oxidized, it has no effect on the purification of dry soot (C = carbon particles) which is a main component of PM.

In order to purify exhaust gas containing PM, such as exhaust gas from a diesel engine, a filter technology is indispensable. A number of porous sintered bodies made of cordierite and silicon carbide and fibrous filters have been proposed. ing. As the material of the fibrous filter, those made of various materials such as alumina and silica have been proposed. In addition, preprints of the Automotive Engineering Society Academic Lecture No. 103-98 (19
1998 Fall Meeting), a diesel particulate filter (DPF) using silicon carbide fiber has been proposed, but a heater for removing trapped PM and regenerating the filter is indispensable. It is difficult to apply it to passenger cars with a small mounting space because of the need for a simple system.

As a method of regenerating a filter without using a heater, a Pt-based catalyst is disposed in front of the filter to convert NO in exhaust gas into NO _{2 having} a strong oxidizing power.
And a method of burning the PM trapped in the filter using the oxidizing power of NO ₂ (JP-A-1-318715, JP Warren,
et. al. , "Effects on after-
treatmentton particulateic m
after when using the Conti
Nuusly Regenerating Tra
p ", ImechE 1998 S491 / 006,
B. Carvery, et. al. , "A focus
s on current and future p
article after-treatments
systems ", Imech 1998 S491 / 0
07). This method utilizes a reaction between components in exhaust gas, and is capable of continuously burning and purifying trapped PM components. Therefore, this method is called a continuous regeneration trap. However, since carbon (C) in PM is a solid particle,
The reaction speed with NO ₂ is relatively slow, and in order to burn C discharged from the engine at a sufficient speed, the condition of the exhaust requires relatively high temperature conditions of 400 ° C. or more. It is necessary to increase the amount of NO _{2 serving as an} oxidant in a suitable temperature range. That is, it is necessary to increase the NOx emission from the engine, and as a result, the increased NOx
In order to purify x, a high-performance NOx catalyst is required.

Various methods for simultaneously purifying PM and NOx have been proposed. For example, Japanese Patent Application Laid-Open No. Hei 7-11651
No. 9 proposes an exhaust gas purifying material in which a catalyst having a perovskite structure is supported on a porous filter, which makes fine particles and / or hydrocarbons contained in exhaust gas act as a reducing agent. A method of reducing nitrogen oxides in exhaust gas, using the catalyst, and represented by the following reaction formulas 5 and 6: C + 2NO → N ₂ + CO ₂ (5) 4HC + 10NO → 5N ₂ + 4CO ₂ + 2H ₂ O (6) It is said that NOx is reduced by such a reaction.
In the above reaction, the reaction formula 6 is a reaction between gas molecules, and therefore, a catalytic action is expected. On the other hand, the reaction formula 5 is a reaction between a solid and a gas, so it is difficult to expect a catalytic action. It is unknown whether the filter regeneration can be performed under the running mode conditions.

On the other hand, Japanese Patent Publication No. 2722987 proposes disposing a NOx absorbent and a filter at a position where heat can be transferred, and burning PM after reducing and releasing NOx from the NOx absorbent. Also, Japanese Patent Application Laid-Open No. 9-94434
Japanese Patent Laid-Open Publication No. HEI 9-214686 proposes a catalyst in which a NOx absorbent is supported inside the partition pores of a wall flow type filter, and the filter and the NOx absorbent are integrated.

[0008] These are techniques obtained by combining a catalyst for treating NOx and a filter.
Separate engine controls are required for M combustion. Control of changing the air-fuel ratio (A / F) of exhaust gas is required to absorb and reduce NOx by operating the NOx absorbent. Further, in order to burn the deposited PM for regenerating the filter and to remove the sulfur compounds trapped in the NOx absorbent, it is necessary to raise the temperature of the NOx absorbent and / or the filter to 600 ° C. or more. Further NO
While the removal of sulfur compounds from the x-absorbent is performed under a reducing atmosphere, the regeneration of the filter needs to be performed under oxidizing atmosphere conditions. Further, there is a problem that the catalyst is deteriorated by the high temperature and the cost is increased in terms of the system. Such control of the exhaust temperature and the atmosphere (A / F) is complicated, and involves sacrificing fuel efficiency and drivability.
There is a long-felt need for an exhaust gas purification method that can continuously perform self-purification without adding specific control under normal driving conditions. In addition, although a proposal has been made to carry a catalyst on a filter for the purpose of simultaneous removal of PM and NOx, no device has been devised from the viewpoint of contact probability or collision probability between a catalyst component and PM particles.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to produce NOx under ordinary combustion conditions without requiring specific control. An object of the present invention is to provide an exhaust gas purification method, an exhaust gas purification catalyst, and an exhaust gas purification device capable of continuously self-purifying PM.

[0010]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, once converted C solid particles (particulate particles) in PM into hydrocarbons and hydrogen; The inventors have found that the above problem can be solved by increasing the contact (collision) rate between the catalyst component and PM particles to promote the conversion reaction, and have completed the present invention.

That is, the exhaust gas purification method of the present invention is a method for purifying particulate particles and nitrogen oxides in exhaust gas. The following reaction formula 1 mC + nH ₂ O → H _2n C _m + n / 2 · O ₂ (1) is characterized by including a process of converting particulate particles into hydrocarbons by the reaction represented by the following formula (1).

[0012] Preferred embodiments of the exhaust gas purifying method of the present invention, the hydrocarbon is reacted with the nitrogen oxides, in the following reaction scheme _{2 H 2n C m + 4NO →} 2N 2 + mCO 2 + nH 2 O ... (2) It is characterized by including a process of converting into nitrogen, carbon dioxide, and water by the represented reaction.

Further, an exhaust gas purifying apparatus according to the present invention is an apparatus for purifying particulate particles and nitrogen oxides in exhaust gas by using the above-mentioned exhaust gas purifying method. Carrying at least one noble metal component selected from the group consisting of rhodium and at least one oxide fine particle selected from the group consisting of alumina, titania, zirconia and silica having an average particle size of 1 μm or less; The filter having a catalytic function is disposed in an exhaust flue of an internal combustion engine.

Further, in a preferred embodiment of the exhaust gas purifying apparatus according to the present invention, the monolithic filter has a porosity of 30 to 80%.
And an average pore diameter of 5 to 40 μm.

Another preferred embodiment of the exhaust gas purifying apparatus according to the present invention is characterized in that the filter with a catalytic function is divided into two or more stages and arranged in series.

Further, still another preferred embodiment of the exhaust gas purifying apparatus of the present invention is arranged on the exhaust gas upstream side of the filter having a catalytic function.
H having a function of removing hydrocarbons and soluble organic components
It is characterized by comprising a C / SOF removal material.

Further, the method of manufacturing an exhaust gas purifying apparatus according to the present invention is a method of manufacturing the above exhaust gas purifying apparatus, wherein the noble metal is dispersed and supported on the inner wall of the pores of the monolithic filter. The components are supported by an impregnation method and / or a plating method.

Another method of purifying exhaust gas according to the present invention is a method of purifying particulate particles and nitrogen oxides in exhaust gas, wherein the temperature of exhaust gas discharged from an internal combustion engine is 5%.
When the temperature is not higher than 00 ° C., a process of performing a hydrogen generation reaction represented by the following reaction formula 3 and / or 4 C + H ₂ O → H ₂ + CO (3) C + 2H ₂ O → 2H ₂ + CO ₂ (4) It is characterized by including.

Further, the exhaust gas purifying catalyst of the present invention is an exhaust gas purifying catalyst including a hydrogen generating catalyst and a nitrogen oxide purifying catalyst used in the above exhaust gas purifying method, wherein the hydrogen generating catalyst is a porous material carrying at least rhodium. Powder, and at least one metal selected from the group consisting of iron, cobalt, manganese and nickel, wherein these metals are contained in a ratio of 0.1 to 10 when rhodium is defined as 1. It is characterized by.

Further, another exhaust gas purifying apparatus of the present invention comprises:
An apparatus for purifying particulate particles and nitrogen oxides in exhaust gas using the exhaust gas purification catalyst, wherein the hydrogen generation catalyst is disposed upstream of an exhaust flue of an internal combustion engine, and the nitrogen An oxide purification catalyst is provided.

Further, still another exhaust gas purifying apparatus of the present invention comprises:
An apparatus for purifying particulate particles and nitrogen oxides in exhaust gas using the exhaust gas purification catalyst, wherein a stack of the nitrogen oxide purification catalyst is disposed on an exhaust flue of an internal combustion engine, and the It is characterized by being coated with a hydrogen generation catalyst.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The exhaust gas purifying method of the present invention will be described below in detail. In this specification, “%” indicates a percentage by mass unless otherwise specified.

The exhaust gas purifying method of the present invention is a method of purifying particulate (PM) particles and nitrogen oxides (NOx) in exhaust gas, and usually converts PM particles into hydrocarbons (HC) by converting them into hydrocarbons (HC). The present invention is characterized in that PM particles in exhaust gas, which are difficult to combust under the traveling conditions, are highly efficiently purified.
Further, by reacting the generated HC with NOx in the exhaust gas, NOx is converted into harmless nitrogen (N ₂ ), CO ₂ and H ₂ O. The generated HC may be immediately oxidized and converted into carbon dioxide (CO ₂ ) or water (H ₂ O).

That is, in the exhaust gas purification method of the present invention, the following reaction formulas 1 and 2 mC + nH ₂ O → H _2n C _m + n / 2 · O ₂ (1) H _2n C _m + 4NO → 2N ₂ + mCO ₂ + nH ₂ O 2 (2) NOx and PM
Are almost simultaneously removed. Here, H by C and H ₂ O
The details of the mechanism by which C in PM is converted to HC in the C generation reaction (Equation 1) are not known at this time, but the present inventors, for example, use Pt / alumina-based catalyst to convert C (graphite) / An evaluation was performed by reacting with an O ₂ / H ₂ O / N ₂ system model gas, and as shown in the graph of FIG.
Was detected. In addition, evaluation was performed by additionally introducing NO into the model gas, and it was confirmed that the NO concentration decreased as shown in FIG. Therefore, the HC generation reaction (Equation 1)
It can be inferred that the -NO reaction (Equation 2) is occurring.

Further, the above HC generation reaction (Equation 1) and HC
To make the -NO reaction (Equation 2) proceed, an example is shown in FIG.
As can be seen from the graph of FIG.
The temperature is preferably set to 0 ° C or lower, more preferably 280 ° C or lower. The lower limit temperature varies depending on the performance of the catalyst and the like, but a remarkable reaction rate can be obtained at a temperature of approximately 200 ° C. or higher. Here, under a temperature condition higher than 350 ° C., H generated by the above-described HC generation reaction (Equation 1) is used.
It is considered that the oxidation reaction of C becomes dominant and the HC-NO reaction (Equation 2) also becomes inferior. On the other hand, the HC-NOx reaction (Equation 2) on a Pt-based catalyst under exhaust conditions with a large amount of oxygen (e.g., a lean-burn engine)
It is known that the temperature significantly progresses in a temperature range of 00 ° C.
As described above, by using the exhaust gas purification method of the present invention, the above H
Since the C generation reaction (Equation 1) and the HC-NO reaction (Equation 2) can proceed under relatively low temperature conditions, the exhaust from the diesel engine where PM is a serious problem can be removed without performing specific engine control. Can be purified with high efficiency.

Next, the exhaust gas purifying apparatus of the present invention will be described in detail. The above-mentioned HC generation reaction (Equation 1) and the above-mentioned HC-
In order for the NO reaction (Equation 2) to proceed, it is essential to use a catalyst. However, the present inventors have found that direct contact between the catalyst and PM particles is very effective in such a reaction. I learned. For example, the above HC generation reaction (Equation 1)
Progresses only when the Pt / alumina-based catalyst powder and the carbon (C) powder are sufficiently mixed well, and does not progress when the mixing is insufficient. From such a viewpoint, the exhaust gas purification apparatus of the present invention positively utilizes the filtration function as means for increasing the contact (collision) probability between the catalyst component and the PM particles. That is, an exhaust purification device having a filtering function and a catalytic function,
By dispersing and supporting the catalyst component on the inner wall surface of the pores of the filter, the probability of contact (collision) between the PM particles flowing into the narrow pores and the catalyst component is increased. As a method for supporting the above-mentioned catalyst component, a supporting method in which the entire inner wall is covered by plating or the like is effective, as described later.

Here, the exhaust gas purifying apparatus of the present invention specifically includes platinum (Pt), palladium (Pd) or (R) as the catalyst component on the pore inner wall of the monolithic filter.
h) and a noble metal component comprising any combination thereof. At this time, the precious metal component does not need to be used alone, and when two or more components are used in combination, the above-described HC generation reaction (Equation 1) and the HC-NO reaction (Equation 2) should proceed more smoothly. Can be. For example, P
In the combination of t and Rh, Pt can promote the HC generation reaction (Equation 1), and Rh can promote the HC-NO reaction (Equation 2).

On the inner wall of the pores of the monolithic filter, fine oxide particles having an average particle diameter of 1 μm or less, specifically, alumina (Al ₂ O ₃ ) conventionally used as a carrier for a noble metal component are used. ), Titania (TiO ₂ ), zirconia (ZrO ₂ ) or silica (SiO ₂ ), and oxide fine particles of any combination thereof.
As a result, the pores are not closed, and the catalyst component is favorably dispersed on the surface of the pore inner wall. Further, the average particle size is 0.6 μm
It is more preferred that: Furthermore, the above oxide fine particles can be used alone, but when two or more kinds of catalyst components are supported, it may be more effective to use two or more kinds of oxide fine particles in combination. If the average particle diameter exceeds 1 μm, the pores of the monolithic filter may be closed. Further, the oxide fine particles can be dispersed and carried by allowing an aqueous solution of a hydroxide or a nitrate capable of producing the oxide fine particles to penetrate into the pore inner wall of the filter.

Further, as a method for supporting the noble metal component and the oxide fine particles, there is a method in which the powder of the oxide fine particles is permeated and supported on the inner wall of the pores of the filter, and then the noble metal component is supported. Then, the oxide fine particles are immersed and supported on the inner wall of the pores of the filter. In particular, the former is more effective for exposing the noble metal component to the particle surface as much as possible.

Further, a monolithic filter having a filtering function is used as a carrier for the above-mentioned noble metal component and oxide fine particles. At this time, the monolithic filter desirably has excellent basic characteristics as a filter, that is, a high collection rate, a high collection amount, and a low pressure loss. Also,
It is preferable that the catalyst component (noble metal component) can be supported on the inner surface of the pores, and that this catalyst component can be brought into contact with the PM particles in the exhaust gas at a high probability.

In the above monolithic filter,
The porosity is preferably 30 to 80%. When the porosity is less than 30%, the filter size for satisfying the predetermined performance must be increased, and the mountability may be deteriorated. On the other hand, if it exceeds 80%, the strength may be reduced and the mountability may be deteriorated. Further, the average pore diameter is preferably 5 to 40 μm. In this case, the size of the pores is appropriate for the particle size of the catalyst component to be supported, and it is effective because PM particles can easily enter and the probability of contact with the pore walls can be increased. If it is smaller than 5 μm, it becomes difficult for the PM particles to enter, and even if it enters, it may be difficult to move through the pores. On the other hand, if it is larger than 40 μm, the probability of contact between the PM particles and the pore walls decreases, and the PM particles pass through the pores without reacting.

Further, as the above-mentioned monolith type filter, a ceramic sintered body such as cordierite, mullite and SiC, a woven cloth of ceramic fiber (fiber) and / or
Alternatively, a nonwoven fabric or the like can be used. The filter shape may be, for example, the above-mentioned ceramic sintered body, a honeycomb alternating plugging type, or the above-mentioned ceramic fiber woven or non-woven fabric, which may be wound on any substrate or formed into a desired shape. it can. The monolithic filter is not particularly limited, but it is important to properly use the monolithic filter according to each characteristic. For example, a filter made of a fiber is disadvantageous for enhancing the collection efficiency, but can relatively widen the pore size distribution, and is easily applicable to exhaust with a wide range of PM particle diameters. In particular, since the fiber is relatively flexible, the probability of contact with the PM particles is high, which is effective for treating large PM particles that are more difficult to react. When the filter is divided into two or more stages,
A filter using a woven and / or non-woven fabric of ceramic fibers is preferably provided on the exhaust upstream side, and a honeycomb filter using a ceramic sintered body is preferably provided on the exhaust downstream side. The honeycomb filter is a typical filter having a low pressure loss, a high trapping amount, and a high trapping rate because a large contact area can be obtained even with a relatively small size.

It is preferable that the filter having a catalytic function in which a catalyst component is carried on the monolithic filter be divided into two or more stages. In this case, a filter with a catalytic function having different characteristics between the upstream side and the downstream side of the exhaust gas can be disposed, which is effective. For example, as shown in FIG. 4, the filter with a catalytic function can be divided into two stages and arranged in series. As a result, the passage distance of the PM particles through the pores can be increased, and the number of collisions of the PM particles with the inner wall of the filter pore carrying the catalyst component increases, so that the HC generation reaction (Equation 1) and the HC-NO reaction The efficiency of (Equation 2) can be greatly improved.

Further, in the catalyst-equipped filter having the divided arrangement, it is preferable that the pressure loss of the filter on the upstream side of the exhaust gas is larger than the pressure loss of the filter on the downstream side of the exhaust gas. Usually, the divided arrangement increases the pressure loss, but in this case, the influence can be suppressed. This is also important in increasing the probability of contact between the PM particles and the catalyst component,
When most of the PM particles are captured by the filter on the upstream side, the deposition rate becomes dominant over the reaction rate, and the filter is likely to be clogged. The pressure loss of the filter can be controlled by changing the porosity and the average pore diameter of the filter. As a result, P
The M collection rate can also be changed.

Further, from the viewpoint of the PM trapping rate, it is preferable to arrange a filter having a relatively low trapping rate upstream of the exhaust gas and a filter having a high trapping rate downstream of the exhaust gas. In other words, it is preferable that the average pore diameter and the porosity of the filter on the exhaust upstream side be larger than the average pore diameter and the porosity of the filter on the exhaust downstream side. In this case, the effective utilization rate of C particles for HC generation can be increased, and the NOx purification rate can be improved.

At this time, the PM particles having a relatively large particle diameter are captured by the filter on the exhaust upstream side, but each time the PM particles come into contact with the catalyst component in the filter, the particle surface is converted into HC,
Move in pores while reducing particle size. However, if there is a portion in the filter where no catalyst component is present, the PM particles may be fixed there and become a nucleus of blockage. For this reason, the filter installed on the upstream side of the exhaust gas has a rather low PM trapping rate, and a type that does not easily cause blockage is effective.
It is preferable that the filter has a so-called collision filtration type structure. For example, a foam type or a fiber type having a three-dimensional network random structure may be used. In particular, in the above-mentioned fiber type filter, since the portion coated with the catalyst component can flexibly expand and contract, the PM particles captured between the fibers can move while pushing the fiber particles by the exhaust pressure, so that the filter pores are closed. In addition, the reaction is easily promoted because the contact probability between the catalyst component and the PM particles can be increased. On the other hand, it is preferable to arrange a filter having a high collection rate, a high collection amount, and a low pressure loss on the downstream side of the exhaust gas. This is because PM particles on the downstream side of the exhaust react to some extent on the upstream side and are reduced in size, so that it is necessary to have a characteristic of reliably capturing and completely reacting. For example, a filter having a surface filtration function can be used.

Further, HC and SOF contained in exhaust gas
Can enhance the purification efficiency by using a catalyst to enhance the adsorption function and oxidation function, but when it reaches the filter, it reacts with NOx on the catalyst component on the inner wall of the pores, It may have adverse effects such as covering up and hindering the catalytic action. Therefore,
It is effective to trap HC and SOF in advance upstream of the filter and to promote a selective reaction between HC and NOx generated from C in the filter in order to exert an exhaust gas purifying action. Specifically, on the exhaust upstream side of the filter,
H having a function of removing hydrocarbons and soluble organic components
It is preferable to provide a C / SOF removing material. Thus, even under relatively low exhaust temperature conditions of 350 ° C. or less, PM and NOx
High-efficiency purification. HC / SOF removal material
For example, they can be arranged as shown in FIG. 3 or FIG. Also,
Mordenite, MF
I, β-type zeolites, silica or layered clay minerals having an average pore diameter of 1 to 5 nm, and zeolites and / or silica-containing inorganic substances according to any combination thereof can be suitably used. In addition, as said silica, the porous body of the oxide called what is called a so-called mesoporous silica is mentioned, For example, it can obtain using a surfactant as a template. If the average pore diameter is less than 1 nm, the pore diameter is too small and H
If C and SOF are not sufficiently adsorbed and trapped, if it exceeds 5 nm, the pore size is too large and the adsorption efficiency of HC and SOF may decrease. Further, as the layered clay mineral,
Hectorite, montmorillonite and the like can be mentioned. These porous materials adsorb and capture HC and SOF with high efficiency on the upstream side of the filter, and by adding a catalyst component such as Pt or Pd, can be oxidized and removed using gas phase oxygen. HC generated on the inner wall of filter pore
The effective utilization rate of is increased. The porous material can be used by coating a so-called flow-through type cordierite honeycomb carrier having about 400 holes per square inch, for example. In order to coat the porous body powder on the honeycomb body and adhere and fix it on the honeycomb surface, a sintering agent (binder) such as alumina sol or silica sol is generally used. Further, by adding a catalyst component such as Pt or Pd, the oxidative removal of HC and SOF adsorbed on the porous material can be promoted. In this case, the catalyst component may be directly supported on the porous material, or a powder in which the catalyst component is previously supported on a carrier such as alumina or titania may be mixed with the porous material powder and used.

The above-mentioned exhaust gas purifying device is obtained by dispersing and supporting the above-mentioned oxide fine particles on the inner wall of the pores of the above-mentioned monolithic filter, and then supporting the above-mentioned noble metal component by an impregnation method and / or a plating method. Although the impregnation method commonly used in ordinary catalyst preparation methods is also effective, it is more effective to use a plating method capable of covering the inner wall of the pores of the filter, and it is also effective to use a combination of the plating method and the impregnation method. It is. Various methods are effective as a plating method, and typically, an electrolytic method, an electroless method, or the like can be appropriately applied.

As described above, the exhaust gas purifying apparatus of the present invention
Various exhaust gas temperature raising controls for burning PM deposited on the filter, exhaust A / F fluctuation control for removing NOx,
Further, since the NOx adsorption function is not used, specific control such as S desorption control from the NOx adsorption catalyst is not required, and deterioration of fuel efficiency can be suppressed. Also, since C can be purified at low temperatures,
There is no risk of damage due to heat of the filter, and it can be used for a long time. For example, in a diesel engine, a clean exhaust gas can be realized, and an automobile excellent in economic efficiency (fuel efficiency) with little environmental pollution including the problem of global warming can be provided.

Next, another exhaust gas purifying method, exhaust gas purifying catalyst and exhaust gas purifying apparatus of the present invention will be described in detail. In this exhaust gas purification method, hydrogen is generated from soot (PM particles) attached to the catalyst, and NOx is purified using the hydrogen. That is, when the temperature of the exhaust gas discharged from the internal combustion engine is 500 ° C. or lower, the following reaction formulas 3 and / or 4 C + H ₂ O → H ₂ + CO (3) C + 2H ₂ O → 2H ₂ + CO ₂ (4) The hydrogen generation reaction represented by) is performed. As a result, hydrogen is generated from the PM particles even at a temperature of 500 ° C. or less, and NOx can be purified using the hydrogen.

[0041] Here, normally, HC and CO in the exhaust as NOx reducing agent, further when using the _{H 2,} due to the presence of oxygen are many in a lean atmosphere, these reducing agents are _H 2 O
Or CO ₂ . Therefore, when the lean atmosphere purifies the exhaust gas under most operating conditions (such as lean burn engine), the hydrogen generation reaction (Equations 3 and 4) cannot be used effectively. In a lean atmosphere with excess oxygen, PM adhering to the catalyst
Hardly reacts with water vapor to produce hydrogen (Equations 3 and 4).

The exhaust gas purifying catalyst of the present invention causes the PM present in the exhaust gas to adhere to the catalyst surface regardless of the rich or lean atmosphere. This PM is used in the hydrogen generation reaction (Equations 3 and 4) mainly by the action of Rh to generate hydrogen in not only the rich atmosphere but also the lean atmosphere. Therefore, NOx can be reduced by the generated hydrogen even in a lean atmosphere, and the NOx purification performance can be improved. Further, SOx at the sulfur-poisoned NOx adsorption site can also be reduced by hydrogen, so that the NOx adsorption ability can be restored and new sulfur poisoning can be prevented. This also improves the NOx purification performance.

Specifically, as the H ₂ generation catalyst,
Powder of porous particles supporting at least rhodium (Rh), iron (Fe), cobalt (Co), manganese (M
n) or nickel (Ni), and a metal containing any combination thereof are used. At this time, F
Metals such as e, Co, Mn and Ni are preferably supported on the porous particles. By using such an H ₂ generation catalyst, high NOx purification performance can be exhibited by H ₂ generated from PM and H ₂ O at a temperature of 500 ° C. or lower. As will be described later, further use of the NOx adsorbent, for adsorbing NOx in the lean, the reactivity of _{H 2} and NOx generated from the PM and _{H 2} O is increased, NO
x can promote the purification reaction. Further, the SOx in the exhaust gas becomes N
Reacts with the Ox adsorption site and causes SOx adsorbed species and S
It may NOx adsorption capability is lost (so-called sulfur poisoning) which by forming a Ox salts, but can prevent sulfur poisoning because SOx is reduced with H ₂ obtained by the generated. Furthermore, NOx adsorption sites that received sulfur poisoning is reduced by H _2, easily revived NOx adsorbing capability.

Further, the above-mentioned H ₂ generation catalyst includes the above-mentioned Fe,
Metals such as Co, Mn and Ni are contained in a ratio of 0.1 to 10 when Rh is 1. In particular, it is more preferably 1 to 5. If it is smaller than 0.1, the effect of these metals does not appear, and it is not different from the case of only Rh. on the other hand,
If it exceeds 10, the activity of Rh decreases and the reactivity between PM and Rh deteriorates. Further, the above Rh is the value of the porous particles 1
It is desirable that the amount is carried in the range of 0.05 to 20 g per 20 g. If the supported amount of Rh is less than 0.05 g / 120 g, the durability tends to decrease, and if it is more than 20 g / 120 g, the above effects are saturated and the cost tends to increase. Furthermore, platinum (Pt), palladium (P
d) and iridium (Ir) can also be supported, and the amount of support at this time may be the total of Rh and these metals within the above range. The Pt supported on the porous particles is 0.1 to 10 g per 120 g of the porous particles.
Is desirably within the range. 0.1 g of Pt carried
If it is less than / 120 g, the purification rate of HC, CO and NOx tends to decrease, and if it is more than 10 g / 120 g, the effect is saturated and the cost tends to increase.

The porous particles include, for example,
Alumina, silica, titania, zirconia, silica-a
Lumina, zeolite, etc. can be appropriately selected, and one type may be used alone.
Used alone or by mixing or compounding multiple types
it can. However, heat resistance is poor, Zr is compatible with Rh
For this reason, alumina, zirconium
It is desirable to use zirconia-alumina.
Further, the particle diameter of the porous particles is in the range of 0.1 to 20 μm.
It is preferred that it is an enclosure. Particle size smaller than 0.1 μm
And Rh dispersibility decreases, PM and H₂H from O₂Generate
It is difficult to obtain sufficient effect, and if it is larger than 20 μm, Rh
The probability that the powders are close to each other increases, and as a result, the Rh
Dispersion decreases, PM and H₂H by O ₂Generating effect is sufficient
May not be available in minutes.

It should be noted that a NOx adsorbent can be further supported on the porous particles, and in this case, the NOx adsorbing ability can be further improved. As the NOx adsorbent, an alkali metal, an alkaline earth metal or a rare earth metal, and a metal according to any combination thereof can be used. Specifically, examples of the alkali metal include lithium (Li), sodium (Na), potassium (K), and cesium (Cs). As alkaline earth metals, Periodic Table 2
Group A element magnesium (Mg), calcium (C
a), strontium (Sr), barium (Ba) and the like. As rare earth metals, lanthanum (L
a), cerium (Ce) and praseodymium (Pr). It is desirable that the NOx adsorbent is supported in a range of 0.05 to 3.0 mol per 120 g of the porous particles. If the supported amount is less than 0.05 mol / 120 g, the NOx purification rate is liable to decrease, and it is 3.0 mol / l.
Even if more than 20 g is supported, the effect is likely to be saturated. Further, when Rh and Pt are supported on the porous particles, Rh
And Rh-supporting porous particles (first powder) and P in order to fully extract the action of metals such as Ni, Fe, Co, and Mn.
It is preferable to separately produce the t-supported porous particles (second powder) and then mix them. In this case, the mixing ratio of the first powder and the second powder is desirably in the range of 0.05: 1 to 1: 1 of the first powder: the second powder in terms of the weight ratio of Rh and Pt. When alumina is used as the porous particles for both the first powder and the second powder, it is desirable that the first powder: second powder = 0.1: 1 to 2: 1 in terms of the weight ratio of alumina. Outside these ranges, Rh and P
In some cases, the same problem as in the case where t is excessive or insufficient may occur. When a transition metal is supported on the porous particles, it is desirable to further support Mg. Use of this cocatalyst is effective because the hydrogen generation reaction is easily promoted.

According to the present invention, there can be provided an exhaust gas purifying apparatus for purifying particulate particles and nitrogen oxides in exhaust gas using the above-mentioned exhaust gas purifying catalyst. That is, the exhaust gas purifying apparatus of the present invention includes the above-mentioned hydrogen generation catalyst disposed upstream of an exhaust flue of an internal combustion engine, and the above-mentioned nitrogen oxide purification catalyst disposed downstream thereof. With such a configuration, an exhaust gas purification device that promotes the hydrogen generation reaction (Equations 3 and 4) is provided. Further, another exhaust gas purifying apparatus of the present invention includes:
A stack of the nitrogen oxide purification catalyst is disposed on an exhaust flue of an internal combustion engine, and the stack is coated with the hydrogen generation catalyst. For example, the NOx catalyst is multi-layered, and F
Rh powder can be coated comprising a metal consisting of e, Co, Mn or Ni, and any combination thereof.

[0048]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

In the following Examples 1 to 3 and Comparative Examples 1 to 3, performance evaluation tests were performed on the exhaust gas purifying apparatus of the present invention, that is, an exhaust gas purifying apparatus using a hydrocarbon (HC) generating catalyst.

Example 1 An aqueous nitric acid solution obtained by dispersing ultrafine alumina having an average particle size of 0.5 μm in an aqueous solution of aluminum nitrate was mixed with a porosity of 60% and an average pore diameter of 18 μm.
After immersing 2.5 L of cordierite honeycomb type alternating clogging filter having vent holes of about 200 cells per square inch, the hot air drying-firing step is repeated three times to disperse alumina on the inner wall of the pores of the filter. Supported.
The amount of alumina carried at this time was about 85 g per liter of filter volume. Further, this filter is immersed in an aqueous solution of dinitrodiammine Pt having a Pt concentration of about 2.5%,
The hot-air drying-firing step was repeated twice, and Pt was carried on alumina dispersedly carried on the pore inner wall of the filter. Further, this filter was subjected to electroless plating to obtain a filter catalyst 1A. The plating method was obtained by immersing the honeycomb filter in an aqueous plating bath solution containing Pt and a reducing agent to precipitate Pt. At this time, the supported amount of Pt is 1 L of filter volume.
The weight was about 10 g.

H arranged before the filter catalyst 1A
Honeycomb-type module having a function of adsorbing and removing C and SOF
A Norris material (honeycomb catalyst 1B) was obtained as follows.
Approximately 220m specific surface area by impregnation method²/ G of gamma alumina
2.5% Pt supported on activated alumina mainly composed of
Of the obtained Pt / γ alumina powder is about 830 m ²
/ G, porous silica having an average pore diameter of about 3.2 nm, and a ratio of
Surface area 450m²/ G zeo with a silica-alumina ratio of about 90
Light β, 350m specific surface area²/ G in silica aluminum
MFI zeolite having a weight ratio of about 70 was mixed at a weight ratio of 1: 4: 1.
And mixed with boehmite powder in a weight ratio of 5: 6: 1.
Add 1% nitric acid acidic alumina sol and mix with water
Thus, a slurry liquid was obtained. The slurry was applied per square inch.
Cordierite honeycomb having 400 cell vents
1.5L coated, dried and fired,
Honeycomb touch with a function to adsorb and decompose HC and SOF
Medium 1B was obtained. The above-mentioned honeycomb catalyst 1B and filter catalyst
1A and the first and second stages, respectively,
By incorporating it into an inverter, the exhaust gas purification device 1 is obtained.
Was.

(Example 2) An exhaust gas purifying apparatus 2 was obtained by repeating the same operation as in Example 1 except that no honeycomb catalyst was provided in the previous stage and only the filter catalyst 2A was used.

Example 3 Porosity 60%, Average Porosity 1
1.25 L of cordierite honeycomb type alternating plugging filter having a pore size of 8 μm and having about 200 cells per square inch, a porosity of 65%, and an average pore diameter of 32 μm.
1.25 L of a cordierite honeycomb type alternately plugged filter having a vent of about 200 cells per square inch was prepared, and the same operation as in Example 1 was repeated to obtain two filter catalysts 3A _1. and it was obtained 3A _2. These filter catalyst 3A ₁ and 3A ₂ and honeycomb catalyst 3B arranged in series to obtain an exhaust gas purifying device 3. That is, these catalysts are supplied from the upstream side of the exhaust gas to the honeycomb catalyst 3B.
- were placed in the order of the filter catalyst 3A ₁ - filter catalyst 3A _2.

Comparative Example 1 A specific surface area of about 2 was obtained by the impregnation method.
Pt / γ alumina powder obtained by supporting 2.5% of Pt on activated alumina containing 20 m ² / g of γ alumina as a main component was mixed with boehmite powder at a weight ratio of 10: 2, and further nitric acid acidic alumina sol was mixed. Was added and mixed with water to obtain a slurry liquid. The slurry was coated at a rate of 100 g / L on 1.5 L of cordierite honeycomb having vent holes of 400 cells per square inch, dried, and fired to obtain a honeycomb-shaped oxidation catalyst R1B. This honeycomb-shaped oxidation catalyst R1B, a porosity of 60%, and an average pore diameter of 18 μm
And a cordierite honeycomb type alternating plugging filter 2.5 having a vent of about 200 cells per square inch.
By arranging L in series and incorporating it into one converter, an exhaust gas purification apparatus R1 of Comparative Example 1 was obtained. The device R1 has a configuration similar to that of a conventional continuous regeneration trap.

(Comparative Example 2) The same Pt / γ alumina catalyst slurry as in Comparative Example 1 was coated on the same cordierite honeycomb type alternating plugging filter (2.5 L) as in Example 1, and the hot air drying-firing step was carried out in 4 hours. By repeating the process twice, the Pt / alumina catalyst was supported on one side of the filter to obtain a filter catalyst R2A. At this time, the carried amount of the Pt / alumina catalyst was about 100 g per liter of the filter volume. The exhaust gas purifying device R2 is formed only by the filter catalyst R2A.
I got The exhaust gas purification device R2 is different from the exhaust gas purification device 2 of the second embodiment in that the manufacturing method of the filter catalyst is changed, that is, the Pt / alumina catalyst is not supported on the inner wall surface of the filter, and A catalyst layer was formed.

COMPARATIVE EXAMPLE 3 The same honeycomb catalyst 1B as in Example 1 was arranged in front of the same filter catalyst R2A as in Comparative Example 2, and was incorporated into one converter to obtain an exhaust gas purification device R3.

<Evaluation Test Example> A performance evaluation test was performed on the exhaust gas purifying apparatus of the example and the comparative example using an engine dynamo device equipped with a 2.5-liter 4-cylinder direct-injection diesel engine equipped with a common rail system. . The evaluation apparatus used was one capable of controlling the exhaust gas temperature at the catalyst system inlet by engine load, intake throttle, and post injection by a common rail system. The performance evaluation method of the exhaust gas purification apparatus is a transient performance evaluation method in which the inlet temperature of the apparatus is maintained at 250 ° C. for 2 minutes, then maintained at 300 ° C. for 3 minutes, and further maintained at 350 ° C. for 1 minute for 5 hours. Was used. In this evaluation test, Swedish class 1
Light oil was used.

In the above evaluation test, the exhaust gas purification device 1
When the average reduction rates of PM and NOx were calculated for (Example 1), the PM removal rate was 93% and the NOx removal rate was 46%. The increase in pressure loss after 5 hours of operation from the initial stage was 25 mmHg. Similarly, for the exhaust gas purification device 2 (Example 2), the reduction rate in the two hours of operation is 90% for the PM removal rate and 55% for the NOx removal rate.
Met. Further, the pressure loss rise after 4 hours of operation from the initial stage was 32 mmHg, and it is considered that the catalyst component was covered with SOF in PM and the oxidation performance decreased with time. From this, it can be seen that, as in the exhaust gas purification apparatus 1, removing the SOF on the upstream side prevents coating of the catalyst and increases the durability. Further, with respect to the exhaust gas purification device 3 (Example 3), the PM removal rate was 95% and NO
The x removal rate was 57%. The increase in pressure loss after 5 hours of operation from the initial stage was 18 mmHg. From this, it can be seen that the effect of dividing the filter is exhibited.

On the other hand, with respect to the exhaust gas purification apparatus R1 (Comparative Example 1), the PM removal rate is 95%, the NOx removal rate is 2%, the NOx reduction rate is lower than that of the embodiment, and the operation 3
The operation was stopped at that point because the pressure loss rise after time exceeded 40 mmHg and the engine load increased. Further, with respect to the exhaust gas purification apparatus R2 (Comparative Example 2), the PM removal rate was 92% and the NOx removal rate was 8%, and the rise in pressure loss after 3 hours of operation from the initial stage exceeded 40 mmHg, and the engine load At that point, I stopped driving because of the increase in size. Further, for the exhaust gas purification device R3 (Comparative Example 3), the PM removal rate was 92%.
%, The NOx removal rate was 11%, and the increase in pressure loss after 4 hours of operation over the initial period exceeded 40 mmHg, resulting in an increase in engine load. Therefore, the operation was stopped at that point.

When the performance evaluation condition of the exhaust gas purification apparatus is changed to a pattern in which the inlet temperature is maintained at 300 ° C. for 5 minutes and further maintained at 400 ° C. for 2 minutes, the PM by the exhaust gas purification apparatus 1 after the operation for 5 hours is changed. The average reduction rates of NOx and NOx are 91% for the PM removal rate and 16% for the NOx removal rate, which indicates that the NOx reduction rate particularly deteriorates under high-temperature exhaust conditions. The exhaust gas purification apparatus of the present invention has an exhaust gas temperature of 35.
It is clear that it is suitable for exhaust gas purification of a high-efficiency internal combustion engine with a low exhaust gas temperature because it is highly effective when used at 0 ° C. or lower.
This can be achieved by adjusting the temperature condition by appropriately selecting the arrangement position.

As described above, since the exhaust gas purifying apparatus of the present invention can purify exhaust gas under relatively low exhaust temperature conditions of about 200 to 350 ° C. with high efficiency, it is possible to use a special engine control method. Clean exhaust can be easily realized.

Next, the following Examples 4 to 9 and Comparative Examples 4 to
In No. 7, a performance evaluation test was performed on the exhaust purification catalyst of the present invention, that is, an exhaust purification catalyst including a hydrogen (H ₂ ) generation catalyst and a nitrogen oxide (NOx) purification catalyst.

Example 4 An aqueous solution of Fe nitrate was impregnated into activated alumina powder (average particle size: 1 μm), dried and dried in air.
The mixture was calcined at 00 ° C. for 1 hour to obtain Fe-supported alumina powder (powder 1). The Fe concentration of this powder was 2%. It was impregnated with Rh nitrate aqueous solution powder 1, dried in _{N 2} 400 ° C.
For 1 hour to obtain Rh and Fe-supported alumina powder (powder 2). The Rh concentration of this powder was 2% (F
e / Rh is a molar ratio of 0.54). Diatrodiamine Pt
The aqueous solution is impregnated with activated alumina powder, dried and then dried in air.
It was calcined at 0 ° C. for 1 hour to obtain Pt-supported alumina powder (powder 3). The Pt concentration of this powder was 2%.

Powder 3 70 g, alumina 70 g, water 1
40 g was charged into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry solution was attached to a cordierite-based monolithic carrier (1.3 L, 400 cells), and excess slurry in the cells was removed by an air stream and dried at 130 ° C.
It was baked at 400 ° C. for 1 hour to obtain a catalyst support (A) having a coat layer weight of 140 g / L. 70 g of powder 2 and 70 of powder 3
g and 140 g of water were charged into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry liquid is attached to the catalyst carrier (A), and the excess slurry in the cell is removed by an air stream to remove the slurry.
After drying at 30 ° C., it was baked at 400 ° C. for 1 hour to obtain a catalyst carrier (B) having a total coat layer weight of 280 g / L. The catalyst carrier (B) was impregnated with an aqueous solution of Ba acetate in an amount of 15 g per liter of catalyst in terms of oxide to obtain an exhaust purification catalyst (C).

(Example 5) Instead of Fe nitrate, Co nitrate was used.
The same operation as in Example 1 was repeated, except that
An exhaust purification catalyst was obtained (CO / Rh was 0.5
7).

(Example 6) Nitrate N instead of Fe nitrate
Except for using i, the same operation as in Example 1 was repeated to obtain an exhaust purification catalyst (Ni / Rh was 0.5
7).

Example 7 Instead of Fe nitrate, Mn nitrate was used.
The same operation as in Example 1 was repeated, except that
An exhaust purification catalyst was obtained (Mn / Rh was 0.5 in molar ratio).
3).

(Embodiment 8) The operation is substantially the same as that of Embodiment 1,
That is, 70 g of powder 2, 140 g of powder 3, 70 g of alumina, and 280 g of water were charged into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry solution was attached to a cordierite monolithic carrier (1.3 L, 400 cells),
Excess slurry in the cell was removed by an air stream, dried at 130 ° C., and baked at 400 ° C. for 1 hour to obtain a coat layer weight of 2
80 g / L catalyst carrier (B) was obtained. On the catalyst carrier (B),
An aqueous Ba acetate solution was impregnated and supported in an amount of 15 g per 1 L of the catalyst in terms of oxide to obtain an exhaust purification catalyst (C).

Example 9 The same operation as in Example 1 was repeated, except that zirconium oxide was used instead of activated alumina, to obtain an exhaust purification catalyst.

Comparative Example 4 A Rh aqueous nitrate solution was impregnated with activated alumina powder (average particle diameter: 1 μm), dried, and calcined at 400 ° C. for 1 hour in N ₂ to obtain Rh-supported alumina powder (powder 4). Was. The Rh concentration of this powder was 2%. An activated alumina powder was impregnated with an aqueous solution of ditrodiamine Pt, dried and calcined at 400 ° C. for 1 hour in the air to obtain a Pt-supported alumina powder (powder 3). The Pt concentration of this powder was 2%. 70 g of powder 3, 70 g of alumina, and 140 g of water were charged into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry solution was attached to a cordierite type monolith carrier (1.3 L, 400 cells), excess slurry in the cells was removed by air flow, dried at 130 ° C., baked at 400 ° C. for 1 hour, and coated. Layer weight 140g /
An L catalyst carrier (A) was obtained. 70 g of powder 2 and 7 of powder 3
0 g and 140 g of water were put into a magnetic ball mill and mixed and pulverized to obtain a slurry liquid. This slurry solution is attached to the catalyst carrier (A), excess slurry in the cell is removed by an air stream, dried at 130 ° C., and then calcined at 400 ° C. for 1 hour to obtain a total coat layer weight of 280 g / L catalyst carrier. (B) was obtained. The catalyst carrier (B) was impregnated with an aqueous solution of Ba acetate in an amount of 15 g per liter of catalyst in terms of oxide to obtain an exhaust purification catalyst (C).

Comparative Example 5 The same operation as in Example 1 was repeated except that the concentration of Fe nitrate in Powder 1 was changed to 0.2%, to obtain an exhaust gas purifying catalyst.

(Comparative Example 6) The same operation as in Example 1 was repeated except that the concentration of Fe nitrate in Powder 1 was changed to 40%, to obtain an exhaust gas purifying catalyst.

Comparative Example 7 The same operation as in Example 1 was repeated, except that the average particle size of the activated alumina powder in Powder 1 was changed to 50 μm, to obtain an exhaust purification catalyst.

<Evaluation Test Example> Endurance Method An exhaust purification catalyst was installed in the exhaust system of an engine with a displacement of 4400 cc, and the catalyst inlet temperature at the preceding stage was set to 700 ° C., and the system was operated for 30 hours. Evaluation method An exhaust purification catalyst was attached to the exhaust system of a diesel engine, the catalyst inlet temperature was set to 300 ° C, and the system was operated for 15 minutes. An exhaust gas purifying catalyst was attached to the exhaust system of the gasoline engine, and the operation was performed for 10 minutes at an A / F of 50 and an inlet temperature of 300 ° C. The NOx conversion rate is given by the following equation: NOx conversion rate = (1−NOx amount at catalyst outlet / NO at catalyst inlet)
x amount) × 100%.

[0075]

[Table 1]

[0076]

[Table 2]

As shown in Tables 1 and 2, as a result of the above evaluation tests, it can be seen that in Examples 4 to 9, the NOx conversion rate is good even with relatively low-temperature exhaust gas. On the other hand, in Comparative Examples 4 to 7, it is found that the NOx conversion rate is poor.

Although the present invention has been described in detail with reference to preferred embodiments and comparative examples, the present invention is not limited to these embodiments, and various modifications can be made within the scope of the present invention. . For example, the catalyst of the present invention is desirably used by being supported on a monolithic carrier. As the monolithic carrier, a monolith carrier made of a heat-resistant material is desirable. For example, a ceramic carrier such as cordierite or a metal carrier such as ferrite stainless steel can be used.
Also, NOx and PM can be separated by coating the catalyst on the carrier separately.
Exhaust purification rate can be increased.

[0079]

As described above, according to the present invention, the C solid particles (particulate particles) in PM are temporarily converted into hydrocarbons and hydrogen, and the contact between the catalyst component and the PM particles (collision). A) an exhaust purification method capable of continuously purifying NOx and PM under normal combustion conditions without the need for specific control because the conversion reaction is promoted by increasing the rate. A purification catalyst and an exhaust purification device can be provided.

[Brief description of the drawings]

FIG. 1 is a graph showing the behavior of generating HC from C in a model gas evaluation test.

FIG. 2 is a graph showing NOx reduction purification characteristics by a model gas evaluation test.

FIG. 3 is a schematic diagram illustrating a configuration example of an exhaust gas purification device.

FIG. 4 is a schematic diagram showing another configuration example of the exhaust gas purification device.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01J 23/89 B01J 35/06 A 4G069 29/74 F01N 3/02 301E 35/06 3/08 A F01N 3 / 02 301 3/10 3/08 3/24 C 3/10 E 3/24 3/28 301C B01D 46/00 302 3/28 301 46/42 B // B01D 46/00 302 53/36 104A 46 / 42 ZAB 104B (72) Inventor Motohisa Kamijo 2 Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture F-term (reference) 3G090 AA02 AA04 3G091 AA02 AA18 AB05 AB13 BA11 BA13 BA14 CA19 GA17 GA19 GA20 GB02Y GB03Y GB04Y GB05W GB06W07 GB09Y GB17X GB17Y HA08 HA18 4D019 AA01 BA05 BB03 BB06 BC07 BD01 CA01 CB04 4D048 AA06 AA14 AA17 AA18 BA03X BA06Y BA07Y BA08X BA11X BA12X BA28X BA30X BA31Y BA33X BA36X BA37X BA38 X BA41X BB02 BB08 CC32 CC36 CC41 CC46 DA03 DA06 EA04 4D058 JA32 JB06 JB22 JB25 MA44 QA01 QA07 SA08 TA06 4G069 AA02 AA06 BA01A BA01B BA02A BA04A BA06A BA06B BA07A BA10A BC13B BCBC BCA BCBC BCA BC66A BC66B BC CC21 DA06 EA09 EA19 EB18X EB18Y EC13X EC22Y EE06 FA01 FA02 FA03 FB13 FB21 FB23 FB30 FC08 ZA06A ZA10A ZA10B ZA19A

Claims (25)

[Claims] 1. A method for purifying particulate particles and nitrogen oxides in exhaust gas, which is represented by the following reaction formula: 1 mC + nH ₂ O → H _2n C _m + n / 2 · O ₂ (1) An exhaust gas purification method comprising a step of converting particulate particles into a hydrocarbon by a reaction. 2. Reacting the hydrocarbon with nitrogen oxides;
2. The process according to claim 1, further comprising a step of converting into nitrogen, carbon dioxide, and water by a reaction represented by the following reaction formula: 2 H _2n C _m + 4NO → 2N ₂ + mCO ₂ + nH ₂ O (2) Exhaust purification method. 3. The reaction represented by the above reaction formula 1 is carried out at 350
The exhaust gas purification method according to claim 1 or 2, wherein the method is performed at a temperature of not more than ℃. 4. The reaction represented by the above reaction formula 1 is performed at 280
The exhaust gas purification method according to claim 3, wherein the method is performed at a temperature of not more than ° C. 5. 5. The reaction represented by the above reaction formula 2 is carried out at 350
The exhaust gas purification method according to any one of claims 1 to 4, wherein the method is performed at a temperature of not more than ° C. 6. The reaction represented by the above reaction formula 2 is performed at 280
The exhaust gas purification method according to claim 5, wherein the method is performed at a temperature of not more than 属 C. 7. An apparatus for purifying particulate particles and nitrogen oxides in exhaust gas by using the exhaust gas purification method according to claim 1, wherein the monolithic filter has a pore inner wall. , At least one noble metal component selected from the group consisting of platinum, palladium and rhodium, and at least one oxide fine particle selected from the group consisting of alumina, titania, zirconia and silica having an average particle size of 1 μm or less And a filter having a catalytic function carrying the filter is disposed in an exhaust flue of an internal combustion engine. 8. An oxide fine particle having an average particle diameter of 0.6 μm.
The exhaust gas purification apparatus according to claim 7, wherein m is equal to or less than m. 9. The porosity of the monolithic filter is 30.
The exhaust gas purification apparatus according to claim 7, wherein the exhaust gas purification apparatus has an average pore diameter of 5 to 40 μm. 10. The exhaust gas purifying apparatus according to claim 7, wherein the filter having a catalytic function is divided into two or more stages and arranged in series. 11. The exhaust gas purifying apparatus according to claim 10, wherein a pressure loss of the filter with a catalytic function on the exhaust upstream side is larger than a pressure loss of the filter with a catalytic function on the exhaust downstream side. 12. The filter according to claim 10, wherein the average pore diameter of the filter with a catalytic function on the exhaust upstream side is larger than the average pore diameter of the filter with a catalytic function on the exhaust downstream side.
2. The exhaust gas purification device according to 1. 13. The filter according to claim 10, wherein the porosity of the filter with a catalytic function on the exhaust upstream side is larger than the porosity of the filter with a catalytic function on the exhaust downstream side. Exhaust gas purification device. 14. The exhaust gas-equipped filter with a catalytic function has a collision filtration function.
An exhaust gas purification apparatus according to any one of items 0 to 13. 15. The filter with a catalytic function downstream of the exhaust gas has a surface filtering function.
An exhaust gas purification apparatus according to any one of items 0 to 14. 16. The exhaust gas purifying apparatus according to claim 10, wherein the filter having a catalytic function on the upstream side of the exhaust gas is made of a woven and / or non-woven fabric of ceramic fibers. apparatus. 17. The exhaust gas purifying apparatus according to claim 10, wherein the filter having a catalytic function on the exhaust downstream side is formed using a ceramic sintered body. 18. An HC / SOF removing material having a function of removing hydrocarbons and soluble organic components is disposed on the exhaust gas upstream side of the filter with a catalytic function. An exhaust purification device according to any one of the preceding items. 19. The HC / SOF-removing material is mordenite, MFI, β-zeolite, and has an average pore diameter of 1 to 5
19. The exhaust gas purifying apparatus according to claim 18, wherein the exhaust gas purifying apparatus is at least one zeolite and / or a silica-containing inorganic substance selected from the group consisting of silica having a thickness of nm and a layered clay mineral. 20. The method for manufacturing an exhaust gas purifying apparatus according to claim 7, wherein the oxide fine particles are dispersed and supported on the pore inner wall of the monolithic filter. Noble metal component impregnation method and / or
Alternatively, a method for manufacturing an exhaust gas purification apparatus, wherein the method is carried by plating. 21. A method for purifying particulate particles and nitrogen oxides in exhaust gas, wherein when the temperature of exhaust gas discharged from the internal combustion engine is 500 ° C. or less, the following reaction formula 3 and / or 4 C + H _{2 O → H 2 + CO ...} (3) C + 2H 2 O → 2H 2 + CO 2 ... exhaust purification method characterized by comprising the step of performing the hydrogen generation reaction represented by (4). 22. An exhaust gas purifying catalyst comprising a hydrogen generating catalyst and a nitrogen oxide purifying catalyst used in the exhaust gas purifying method according to claim 21, wherein the hydrogen generating catalyst is a porous particle carrying at least rhodium. Powder, and at least one metal selected from the group consisting of iron, cobalt, manganese, and nickel, wherein the metal is 0.1 to 1 when rhodium is defined as 1.
An exhaust gas purifying catalyst characterized by being contained at a ratio of 0. 23. The porous particles having an average particle size of 0.1.
The exhaust purification catalyst according to claim 22, wherein the thickness is 1 to 20 m. 24. An apparatus for purifying particulate particles and nitrogen oxides in exhaust gas using the exhaust gas purification catalyst according to claim 22 or 23, wherein the hydrogen generation is provided upstream of an exhaust flue of an internal combustion engine. An exhaust gas purification apparatus comprising a catalyst and a nitrogen oxide purification catalyst disposed downstream of the catalyst. 25. An apparatus for purifying particulate particles and nitrogen oxides in exhaust gas using the exhaust gas purification catalyst according to claim 22 or 23, wherein the nitrogen oxide purification catalyst is provided on an exhaust flue of an internal combustion engine. An exhaust gas purification apparatus comprising: a stacked body of the above (1), and the above-mentioned hydrogen generation catalyst coated thereon.