JP2001205085A - Hydrogen supply/exhaust gas cleaning catalyst and exhaust gas cleaning system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen supply/exhaust gas cleaning catalyst which is capable of adjusting a hydrogen concentration on the downstream side of the catalyst and an exhaust gas cleaning system for upgrading the cleaning performance of an NOx cleaning catalyst to be installed on the downstream side of the hydrogen supply/exhaust gas cleaning catalyst. SOLUTION: This hydrogen supply/exhaust gas cleaning catalyst contains a hydrogen generating catalyst component and a hydrogen occluding material and performs the generation, occlusion retention and emission of hydrogen to adjust the hydrogen concentration of an exhaust gas on the downstream side. In addition, the catalyst contains a hydrogen occlusion alloy as a hydrogen occluding material and/or a carbon nanotube. Further, the exhaust gas cleaning system has the NOx cleaning catalyst arranged on the downstream side of the hydrogen supply/exhaust gas cleaning catalyst. In addition, the system restricts the oxidation/consumption of hydrogen by occluding and retaining the hydrogen in the hydrogen occluding material and thereby increases the supply of the hydrogen to the NOx cleaning catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying catalyst for purifying exhaust gas discharged from an internal combustion engine, a combustor or the like, and an exhaust gas purifying system using the same. The present invention relates to an exhaust gas purification system that purifies nitrogen oxides (NOx) in exhaust gas from a burn internal combustion engine with high efficiency.

[0002]

2. Description of the Related Art Heretofore, as a catalyst or a system for purifying carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx) and the like contained in exhaust gas discharged from an internal combustion engine of an automobile or the like. A three-way catalyst that operates at a stoichiometric air-fuel ratio and an exhaust gas purification system using the same are known. Further, as a method for purifying nitrogen oxides in a case where purification of nitrogen oxides is impossible with a three-way catalyst, such as when the exhaust gas of an internal combustion engine is excessive in oxygen, a method disclosed in Japanese Patent Publication No. 2640029 is disclosed. As described above, a purification system has been used in which NOx is absorbed when the exhaust gas is in excess of oxygen, and the absorbed NOx is released by reducing the concentration of oxygen in the exhaust gas flowing into the NOx absorbent, thereby purifying the NOx. I have.

However, in such an exhaust gas purifying system using a three-way catalyst or a purifying system as described in Japanese Patent Publication No. 2600429, when the absorbed NOx is desorbed and purified, HC or a reducing agent is used as a reducing agent. CO is used, and in these conventional techniques, it is necessary to supply HC or CO to the purification catalyst in order to purify NOx by reaction.
For this reason, a part of HC and CO may remain in the NOx purification catalyst, and it has been difficult to purify exhaust gas at a higher level.

On the other hand, JP-A-6-126174, JP-A-8-10574 and JP-A-9-195858.
Japanese Patent Application Publication No. JP-A-2005-115139 discloses an exhaust gas purification system using hydrogen as a reducing agent used for NOx purification. Specifically, JP-A-6-126174 discloses an alloy having a hydrogen storage activity composed of a rare earth metal, a noble metal and hydrogen (Mn-Pd-based, Ce-Ru-based, Ce-Pd-based, La-
Disclosed is an exhaust gas purifying catalyst that selectively reacts NOx with hydrogen discharged when the alloy is heated by the heat of the exhaust gas using an Ru-based or La-Pd-based alloy). .

In Japanese Patent Application Laid-Open No. Hei 8-10574,
Nitrogen oxide purification by reacting and removing NOx in exhaust gas containing excess oxygen and in which hydrogen coexists with a nitrogen oxide purification catalyst containing a porous carrier noble metal and molybdenum in the range of 90 ° C to 250 ° C. A method is disclosed.

Further, in Japanese Patent Application Laid-Open No. 9-195858, a tank containing a hydrogen storage alloy is connected to an intake passage connected to a combustion chamber as an exhaust gas purifying device for a diesel engine, and hydrogen is supplied from the tank at a high load. A method for reducing soot emissions during combustion is disclosed.

[0007]

However, when the hydrogen storage alloy is arranged to further reduce the residual ratio of the entire exhaust gas component, the influence of the HC and CO components causes N
Since the reaction between Ox and H ₂ is inhibited, not NOx only, there is a problem that the resulting longer sufficient purification performance of HC and CO. Further, in the method disclosed in Japanese Patent Application Laid-Open No. H8-10574, in order to make hydrogen act as a reducing agent, nitrogen oxides cannot be effectively reduced unless the exhaust gas temperature is set to 250 ° C. or less. In the gas purification, there is a problem that the exhaust gas temperature becomes 300 ° C. or more in most cases after warming, and it is insufficient to effectively reduce NOx.

Further, in the method disclosed in Japanese Patent Application Laid-Open No. 9-195858 and the like, it is necessary to install an H ₂ supply device, and there is a problem that the exhaust system becomes complicated and large in size. .

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 provide a hydrogen supply exhaust gas purifying catalyst capable of adjusting the hydrogen concentration downstream of the catalyst. It is an object of the present invention to provide an exhaust gas purification system capable of improving the purification performance of a NOx purification catalyst installed downstream of the hydrogen supply exhaust gas purification catalyst.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has found that the hydrogen storage catalyst is used together with the hydrogen storage material, and the hydrogen stored and held in the hydrogen storage material is It has been found that the above-mentioned problems can be solved by discharging at an appropriate timing, and the present invention has been completed.

That is, the hydrogen supply exhaust gas purifying catalyst of the present invention is installed in an exhaust gas passage of an internal combustion engine or a combustion device,
A hydrogen generation catalyst component that purifies at least hydrocarbons and carbon monoxide to generate hydrogen, and contains a hydrogen storage material, and generates, stores, releases, and releases hydrogen from the installation position of the exhaust gas passage. Is characterized in that the concentration of hydrogen in the exhaust gas on the downstream side can be adjusted.

In a preferred embodiment of the hydrogen supply exhaust gas purifying catalyst of the present invention, the hydrogen generating catalyst component comprises a hydrocarbon,
At least one selected from the group consisting of platinum, rhodium and palladium for purifying carbon monoxide and nitrogen oxides;
It is characterized by containing a kind of noble metal element.

Further, in another preferred embodiment of the hydrogen supply exhaust gas purifying catalyst according to the present invention, the hydrogen generating catalyst component forms a hydrogen generating catalyst portion, and the hydrogen storage material forms a hydrogen storage material portion. The hydrogen generation catalyst section is arranged on the upstream side of the exhaust gas passage from the hydrogen storage section.

Still further, in still another preferred embodiment of the hydrogen supply exhaust gas purifying catalyst of the present invention, the hydrogen generation catalyst component forms a hydrogen generation catalyst portion, and the hydrogen storage material forms a hydrogen storage material portion. And the hydrogen generating catalyst portion is covered with the hydrogen storage material portion.

Further, in another preferred embodiment of the hydrogen supply exhaust gas purifying catalyst of the present invention, the nitrogen oxide purifying catalyst section containing the nitrogen oxide purifying catalyst component is provided more than the hydrogen generation catalyst section and the hydrogen storage catalyst section. It is characterized by being arranged downstream of the exhaust gas passage.

Still another preferred embodiment of the hydrogen supply exhaust gas purifying catalyst of the present invention is characterized in that the hydrogen storage material contains a hydrogen storage alloy and / or a carbon nanotube.

Still further, the exhaust gas purifying system of the present invention further comprises:
The hydrogen supply exhaust gas purifying catalyst is disposed, and a NOx purifying catalyst that purifies nitrogen oxides using at least hydrogen as a reducing agent is disposed downstream of the catalyst. The hydrogen is stored in the hydrogen storage material of the hydrogen supply purifying catalyst. By keeping the hydrogen, the hydrogen is suppressed from being oxidized and consumed, and the amount of hydrogen supplied to the NOx purification catalyst can be increased.

Further, in a preferred embodiment of the exhaust gas purifying system of the present invention, the inlet gas of the NOx purifying catalyst is expressed by the following formula (A) H ₂ / TR amount ≧ 0.3 (A) (TR in the formula) The amount indicates the amount of all reducing components in the exhaust gas.)
Satisfies the gas composition represented by

Further, in another preferred embodiment of the exhaust gas purifying system of the present invention, the air-fuel ratio A / F of the exhaust gas of the internal combustion engine or the combustion device is varied from lean to stoichiometric to rich. The hydrogen stored in the hydrogen storage material of the purification catalyst is released.

In still another preferred embodiment of the exhaust gas purifying system of the present invention, the NOx purifying catalyst stores nitrogen oxides when the air-fuel ratio A / F of the exhaust gas is lean, and the NOx purifying catalyst is stoichiometric. It is a NOx storage purification catalyst that releases nitrogen oxides stored when it is rich.

[0021]

In the hydrogen supply exhaust gas purifying catalyst of the present invention, a hydrogen generating catalyst component and a hydrogen storage material are contained.
Therefore, these generate, store, and release hydrogen, thereby adjusting the hydrogen concentration in the exhaust gas downstream of the catalyst installation position in the exhaust gas passage. Further, in the exhaust gas purifying system of the present invention, a NOx purifying catalyst for purifying nitrogen oxides using at least hydrogen as a reducing agent is disposed downstream of the hydrogen supply exhaust gas purifying catalyst. Therefore, if hydrogen stored and held in the hydrogen storage material of the hydrogen supply purification catalyst is released at an appropriate timing, N
Ox can be efficiently purified.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a hydrogen supply exhaust gas purifying catalyst of the present invention will be described in detail. As described above, the hydrogen supply exhaust gas purifying catalyst of the present invention is provided in the exhaust gas passage of an internal combustion engine or a combustion device, and includes a hydrogen generating catalyst component and a hydrogen storage material.

Here, it is sufficient for the hydrogen generation catalyst component to purify at least hydrocarbons (HC) and carbon monoxide (CO) to generate hydrogen (H ₂ ). Component, or a plurality of types of purification catalyst components corresponding to each exhaust gas component such as HC and CO. Particularly, the component purifies HC, CO, and NOx, and contains platinum (Pt). , Rhodium (R
h) or palladium (Pd) and a precious metal element according to any combination thereof. Typically, a three-way catalyst component can be exemplified. With such a hydrogen generating catalyst components, HC, and more efficiently purify CO and NOx, since H ₂ is likely to be effectively generated.

Further, it is preferable that the hydrogen-producing catalyst component is contained at a ratio of 1 to 40 g in 1 L of the hydrogen-supplying exhaust gas purifying catalyst. If the amount is less than 1 g, the low-temperature activity and purification performance cannot be sufficiently exhibited, and if it exceeds 40 g, the catalytic activity tends to be saturated, and it is difficult to obtain a performance improvement commensurate with the added amount. In addition, the economy tends to be poor.

On the other hand, as the hydrogen absorbing material, and H ₂ occludes held, it can be used as long as it has a function of releasing, in particular, is preferably used comprising a hydrogen storage alloy and / or carbon nanotubes. For example, as a hydrogen storage alloy, La—Ni, Mg—Ni, Ti—Fe
And Pd-Ce-based alloys. Examples of carbon nanotubes include an outer diameter of 10 to 100 nm and a length of 1 to 100 nm.
One having a thickness of about 0 to 100 μm can be exemplified. When such a hydrogen storage material is used, the hydrogen supply / exhaust gas purification catalyst 1 L
It is preferable that the content is contained at a ratio of about 10 to 100 g in the capacity.

The hydrogen supply exhaust gas purifying catalyst of the present invention generates, stores, retains and releases hydrogen from the exhaust gas of an internal combustion engine or a combustion device by using the above-described hydrogen generating catalyst component and the hydrogen storage material. The concentration of hydrogen in the exhaust gas downstream of the installation position can be adjusted.

Here, the term “hydrogen” includes not only H ₂ generated by the hydrogen generation catalyst component but also H ₂ contained in exhaust gas. Further, the “downstream side” means downstream of the hydrogen supply exhaust gas purifying catalyst with respect to the flow of exhaust gas, and not only a position immediately after the catalyst but also a position at a certain distance from the catalyst. Is also included. Furthermore, the adjustment of the hydrogen concentration, not only the increase or decrease of the hydrogen concentration, H ₂ amount supplied to the downstream side is also included if it is zero, specifically the supply of H ₂ in storage of H ₂ is the downstream The amount will be almost zero.

The hydrogen concentration (the amount of H ₂ supplied downstream) in the exhaust gas on the downstream side of the hydrogen supply exhaust gas purifying catalyst is determined by the fact that the hydrogen occluding material is H ₂ generated by the hydrogen generation catalyst component. And / or by storing and releasing H ₂ in the exhaust gas without being oxidized and consumed by O ₂ or the like, and releasing it. If this hydrogen is released at an appropriate timing, for example, in an atmosphere with little oxidizing component,
The hydrogen concentration on the downstream side increases. The release of H ₂ can be controlled by decompressing the hydrogen storage material or heating the hydrogen storage material.

[0029] From the function of the hydrogen storage material as described above, when the storage retention by the hydrogen storage material is directed of H ₂ produced is the hydrogen generating catalyst component, hydrogen storage material, after the hydrogen generating catalyst component It can be said that it is desirable that the catalyst be activated after being in contact with the exhaust gas or almost simultaneously or earlier than the hydrogen generation catalyst component. On the other hand, such storage retention when the target of H ₂ in the exhaust gas, so occludes held without passing through the hydrogen generating catalyst component, hydrogen storage material can be said to be desirable to have activated prematurely.

From such a viewpoint, in the hydrogen supply exhaust gas purifying catalyst of the present invention, it is possible to arrange the hydrogen storage material separately from the hydrogen generation catalyst component.

As shown in FIG. 4, the hydrogen generation catalyst component formed by the hydrogen generation catalyst component (three-way catalyst component) is:
The hydrogen storage material may be disposed on the upstream side of the exhaust gas passage with respect to the hydrogen storage material portion formed by the hydrogen storage material. In this case, the hydrogen storage material section suppresses consumption (oxidation) of H _{2 in the} hydrogen generation catalyst section, and H ₂ generated in the hydrogen generation catalyst section.
₂ can be more efficiently stored and released, which is preferable. Specifically, such a catalyst arrangement is such that the hydrogen generation catalyst section and the hydrogen storage material section are separately arranged on a single carrier, or the hydrogen generation catalyst section and the hydrogen storage material section are made independent on separate carriers. It can be realized by tandem arrangement.

Further, as shown in FIGS. 2 and 5, the hydrogen storage material portion, typically, the hydrogen storage material layer is replaced with the hydrogen generation catalyst portion (three-way catalyst portion), typically, the hydrogen generation catalyst layer. It can also be coated on. This is effective because H ₂ in the exhaust gas can be more easily stored and held in addition to H ₂ generated in the hydrogen generation catalyst section. When the hydrogen generation catalyst layer is coated with the hydrogen storage material layer and integrated as described above,
It is more preferable that the hydrogen storage material part is coated at a rate of 10 to 50 g per 1 L of the catalyst to efficiently exhibit the activity of the hydrogen generation catalyst part.

Further, in the hydrogen supply exhaust gas purifying catalyst according to the present invention, the nitrogen oxide containing a nitrogen oxide purifying catalyst component is located downstream of the hydrogen generation catalyst section and the hydrogen storage material section in the exhaust gas passage. A purification catalyst section can be arranged. In this case, H released from the hydrogen storage material portion
_This is effective because the nitrogen oxide purifying catalyst section can efficiently purify NOx by utilizing NO.2 and the NOx purifying catalyst in the exhaust gas purifying system of the present invention described later can reduce NOx to be purified. Examples of the nitrogen oxide purification catalyst component include, for example, Pt, Pd, and Rh. Note that HC and CO are located upstream of the nitrogen oxide purifying catalyst section.
Since most of the nitrogen oxides can be purified, the nitrogen oxide purification catalyst section does not necessarily need to have HC and CO purification performance.

The catalyst for purifying hydrogen-supplied exhaust gas of the present invention can be used in the form of granules or pellets. However, in order to improve the reaction efficiency, the above-mentioned hydrogen-producing catalyst component, hydrogen-absorbing material component and nitrogen oxide-purifying catalyst are used. It is preferred that the components are coated on a monolithic carrier for use. Examples of the monolithic carrier include a monolith carrier and a metal carrier made of a heat-resistant material. In particular, when used for purification of exhaust gas from automobiles, a honeycomb carrier is coated to form a contact area (reaction surface area) between catalyst and the like and exhaust gas.
And the pressure loss can be reduced, which is more effective. Note that, as such a honeycomb-shaped carrier, cordierite-based materials such as ceramics are generally used in many cases, but it is also possible to use a honeycomb material made of a metal material such as a ferritic stainless steel. It may be formed into a honeycomb shape.

When the present hydrogen-supplying exhaust gas purifying catalyst is coated on the honeycomb-shaped carrier, the amount of the catalyst component is 50 g to 4 g per liter of the total of the above-mentioned catalyst components.
It is preferably set to 00 g. This is because the catalyst component-supporting layer is thick in terms of catalyst activity and catalyst life (the amount of support is large).
However, if the coat layer is too thick, the diffusion of the reaction gas becomes insufficient and the catalyst inside the coat layer cannot be sufficiently contacted.In other words, the effect of increasing the amount of the active substance is saturated, and the gas passage resistance increases. It is.

Next, an exhaust gas purification system according to the present invention will be described.
And will be described in detail. Such an exhaust gas purification system is:
On the upstream side of the exhaust gas passage of the internal combustion engine or the combustion device,
The hydrogen supply exhaust gas purification catalyst of
At least H ₂To purify nitrogen oxides using nitrogen as a reducing agent
An Ox purification catalyst is provided. For example, as shown in FIG.
Exhaust gas purification system with a catalyst
You.

In the exhaust gas purifying system, the hydrogen supply exhaust gas purifying catalyst installed on the upstream side generates, stores, holds and releases H ₂ from the exhaust gas component as described above. adjust the H _2, on the downstream side the N
The inlet gas of the Ox purification catalyst is expressed by the following equation (A) H ₂ / TR amount ≧ 0.3 (A) (The TR amount in the equation indicates the total amount of reducing components in the exhaust gas.)
It is desirable to control so as to satisfy the gas composition represented by If this relationship is satisfied, a reducing agent suitable for NOx purification can be reliably supplied to the NOx purification catalyst.

Further, in the exhaust gas purifying system, the H ₂ stored and held in the hydrogen storage material of the hydrogen supply purifying catalyst may be used.
Is released to the downstream side at a desired timing, the amount of hydrogen supply is increased, and the NOx purification catalyst can perform an efficient NOx purification process. Release timing of H _2, for example, may be a time when the air-fuel ratio A / F of the exhaust gas was varied from lean to stoichiometric-rich of the internal combustion engine or a combustion device.

The NOx purification catalyst is a catalyst that stores nitrogen oxides when the air-fuel ratio A / F of the exhaust gas is lean, and releases the stored nitrogen oxides when the air-fuel ratio A / F of the exhaust gas is stoichiometric to rich. In this case, in accordance with the release timing of H ₂ , which is the main component of the reducing agent,
Since Ox is also released, the purification process of NOx can be performed more efficiently.

As described above, in the exhaust gas purifying system of the present invention, when the amount of reducing agent required for purifying NOx fluctuates due to changes in the air-fuel ratio A / F, the temperature of exhaust gas, etc., the NOx purifying catalyst is typically used. If you need more reducing agent,
Of H ₂ and moderate amount supplied, NOx can be efficiently reduced and purified.

[0041]

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.

(1) H at the outlet of the hydrogen supply exhaust gas purification catalyst
_{In the} following Examples and Comparative Examples, a hydrogen supply exhaust gas purifying catalyst and another catalyst (comparative example) installed in an exhaust gas passage were manufactured, and the exhaust gas was passed through the catalyst and the exhaust gas was discharged from the catalyst outlet. of _{H 2} amount was measured.

Example 1 Activated alumina powder was impregnated with an aqueous solution of palladium nitrate, dried at 150 ° C. for 12 hours, and calcined at 400 ° C. for 1 hour to obtain Pd-supported activated alumina powder (powder A). The Pd concentration of this powder A was 6.0.
% By weight. 150 g of the powder A, 50 g of the activated ceria powder B, and 200 g of an aqueous nitric acid solution were charged into a magnetic ball mill, mixed and pulverized to obtain a slurry. This slurry liquid is adhered to 50% of the entire length of the cordierite monolithic carrier (0.1 L, 400 cells / square inch) from the exhaust inlet end to the outlet side of the carrier, and the excess slurry in the cells is air-flowed. It was removed, dried and calcined at 500 ° C. for 1 hour. A catalyst A having a coat weight of 100 g / L-carrier was obtained.
The supported amount of Pd was 4.5 g / L-carrier.

A La-Fe-based hydrogen storage alloy (100 g), activated alumina (100 g), and pure water (200 g) were charged into a magnetic ball mill, mixed and pulverized to obtain a slurry. This slurry liquid is adhered to 50% of the entire length of the carrier from the exhaust outlet end to the inlet side of the catalyst A, and the excess slurry in the cell is removed and dried by an air flow, and calcined at 500 ° C. for 1 hour to obtain hydrogen. A supply exhaust gas purification catalyst was obtained. The coat weight of the hydrogen storage material coat layer was 100 g / L-carrier.

Example 2 A Pd-containing layer was coated on a monolithic carrier (0.1 L, 400 cells / square inch) as a first coat layer, and then a hydrogen storage material layer was coated on the Pd-containing layer. The same operation as in Example 1 was repeated to obtain a hydrogen supply exhaust gas purifying catalyst.

(Comparative Example 1) Hydrogen storage alloy layer (La-Fe
The same operation as in Example 2 was repeated except that the catalyst layer configuration was made only of the Pd-containing layer without coating with the Pt-based hydrogen storage alloy) to obtain an exhaust gas purification catalyst.

(Comparative Example 2) A hydrogen storage material layer (a hydrogen storage material instead of Pd) was disposed on the exhaust inlet side of the monolithic carrier.
A Pd-containing layer is formed on the exhaust outlet side (Pd instead of hydrogen storage material).
)), But the same operation as in Example 1 was repeated to obtain an exhaust gas purifying catalyst.

Comparative Example 3 A hydrogen storage material layer was coated as a first coat layer on a monolithic carrier (0.1 L, 400 cells / square inch), and then a Pd-containing layer was coated on the hydrogen storage material layer ( Except that the positions of the first coat layer and the second coat layer in Example 2 were reversed, the same operation as in Example 2 was repeated to obtain an exhaust gas purification catalyst.

The amount of the noble metal carried (the content of Pt and Pd in 1 L of the catalyst), the amount of the hydrogen storage material carried, and the structure of the catalyst in the exhaust gas purifying catalysts obtained in the above Examples 1-2 and Comparative Examples 1-3 The arrangement is shown in Table 1.

[0050]

[Table 1]

[Evaluation of Performance] Examples 1 and 2 and Comparative Examples 1 and 2
About the exhaust gas purification catalyst obtained in 3,₃H ₆, H
₂, O₂And N₂Rich Lee with model gas containing
In switching mode (10 sec each)₂Consumption evaluation
Was done. Evaluation temperature is 400 ° C, gas flow rate is 20L / m
in (SV = 12,000h^-1Equivalent). model
Table 2 shows the gas composition when the gas is lean and when the gas is rich.
In addition, H at the catalyst outlet₂Quantity (H₂Consumption)) and compare
The comparison was made in the form of a relative ratio based on Example 1. This evaluation result
Is shown in the graph of FIG.

[0052]

[Table 2]

(2) Construction of exhaust gas purification system and N
Ox Purification Amount Measurement The NOx purification catalyst was arranged downstream of the hydrogen supply exhaust gas purification catalyst used in (1) above to construct an exhaust gas purification system of each example, and the NOx purification amount at the NOx purification catalyst outlet was measured. .

(Embodiments 3 and 4) Embodiment 1 or 2
By combining the hydrogen supply exhaust gas purification catalyst obtained in the above with a NOx purification catalyst (Pd, Rh + Ba / activated alumina), an exhaust gas purification system of each example was obtained.

(Comparative Examples 4 to 6) Except for using the hydrogen supply exhaust gas purifying catalysts obtained in Comparative Examples 1 to 3, the same configuration as in Example 3 was adopted, and the exhaust gas purifying system of each example was used. Obtained.

[Evaluation of Performance] Regarding the obtained exhaust gas purification system, C ₃ H ₆ , H ₂ , O ₂ , NO, H ₂ O, C
The NOx purification performance was evaluated in a rich / lean switching mode (10 sec each) using a model gas containing O ₂ and N ₂ . Evaluation temperature is 400 ° C, gas flow rate is 20L / m
in. Table 3 shows the gas composition at the time of lean and rich model gas. In addition, the average NOx purification amount was compared with Comparative Example 1.
The comparison was made in the form of a relative ratio based on. The evaluation results are shown in the graph of FIG.

[0057]

[Table 3]

As shown in FIG. 3, Embodiment 1 and Embodiment 2
Is a hydrogen supply exhaust gas purification catalyst that is within the preferred range of the present invention.
The exhaust gas discharged from the catalyst outlet
H ₂It turns out that it has a presence rate. Example
1 and Example 2, two layers more than the tandem arrangement (FIG. 4)
The exit H is more in the court arrangement (Fig. 5).₂Large amount
Understand. In contrast, Comparative Examples 1 to 3 use a hydrogen storage material.
No configuration (Comparative Example 1) or each catalyst
Exhaust gas having a configuration (Comparative Examples 2 and 3) arranged at a position
Purification catalysts, which deviate from the preferred form of the present invention.
Exit H₂That the amount is smaller than in the example.
I understand.

Also, in an exhaust gas purifying system in which the exhaust gas purifying catalysts obtained in Examples and Comparative Examples are combined with a NOx purifying catalyst, an exhaust gas using a hydrogen supply exhaust gas purifying catalyst falling within a preferable range of the present invention is also used. In the purification system (Examples 3 and 4), since the amount of released H ₂ is large,
It can be seen that the NOx purification amount is better than the exhaust gas purification systems of Comparative Examples 4 to 6 (FIG. 6).

[0060]

As described above, according to the present invention, the hydrogen storage catalyst component and the hydrogen storage material are used in combination, and the hydrogen stored and held in the hydrogen storage material is released at an appropriate timing. A hydrogen supply exhaust gas purification catalyst capable of adjusting the hydrogen concentration downstream of the catalyst, and an exhaust gas purification system capable of improving the purification performance of a NOx purification catalyst installed downstream of the hydrogen supply exhaust gas purification catalyst. be able to. Further, by using the hydrogen supply exhaust gas purifying catalyst and the exhaust gas purifying system of the present invention, HC and CO contained in the exhaust gas can be purified at a high conversion rate, and NOx in the lean region can be reduced by controlling the reducing agent concentration. It can be purified at a high conversion rate.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of an exhaust gas purification system of the present invention.

FIG. 2 is a partial sectional view showing an example of a coat layer of a hydrogen supply exhaust gas purifying catalyst of the present invention and an enlarged view thereof.

FIG. 3 is a graph comparing H ₂ consumption characteristics of a hydrogen supply exhaust gas purifying catalyst.

FIG. 4 is a diagram showing a mechanism of H ₂ occlusion retention / release when a catalyst component is arranged in tandem.

FIG. 5 shows H ₂ in the hydrogen supply exhaust gas purifying catalyst of FIG. 2;
It is a figure showing the mechanism of occlusion retention and release.

FIG. 6 is a graph comparing the average NOx purification amount of the exhaust gas purification system.

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Claims (10)

[Claims] 1. A hydrogen generation catalyst component, which is provided in an exhaust gas passage of an internal combustion engine or a combustion device and purifies at least hydrocarbons and carbon monoxide to generate hydrogen, and a hydrogen storage material, and generates hydrogen. A hydrogen supply / exhaust gas purifying catalyst, wherein the hydrogen supply / exhaust gas purifying catalyst is capable of adjusting the concentration of hydrogen in the exhaust gas downstream of the installation position of the exhaust gas passage. 2. The method according to claim 1, wherein the hydrogen generating catalyst component is a hydrocarbon,
At least one selected from the group consisting of platinum, rhodium and palladium for purifying carbon monoxide and nitrogen oxides;
The catalyst for purifying hydrogen-supplied exhaust gas according to claim 1, wherein the catalyst contains at least one noble metal element. 3. The hydrogen generation catalyst component forms a hydrogen generation catalyst portion, the hydrogen storage material forms a hydrogen storage material portion, and the hydrogen generation catalyst portion is disposed in the exhaust gas passage more than the hydrogen storage material portion. The hydrogen supply exhaust gas purifying catalyst according to claim 1 or 2, wherein the catalyst is disposed upstream of the hydrogen supply exhaust gas. 4. The hydrogen generation catalyst component forms a hydrogen generation catalyst portion, the hydrogen storage material forms a hydrogen storage material portion, and the hydrogen generation catalyst portion covers the hydrogen storage material portion. The hydrogen supply exhaust gas purifying catalyst according to claim 1, wherein the catalyst is formed. 5. A nitrogen oxide purifying catalyst section containing a nitrogen oxide purifying catalyst component is disposed downstream of the exhaust gas passage with respect to the hydrogen generation catalyst section and the hydrogen storage catalyst section. The hydrogen supply exhaust gas purifying catalyst according to claim 3 or 4, wherein: 6. The method according to claim 1, wherein the hydrogen storage material is a hydrogen storage alloy and / or a hydrogen storage alloy.
The catalyst for purifying hydrogen-supplied exhaust gas according to any one of claims 1 to 5, further comprising a carbon nanotube. 7. A hydrogen supply exhaust gas purifying catalyst according to claim 1, which is disposed upstream of an exhaust gas passage of an internal combustion engine or a combustion device, and at least hydrogen is disposed downstream of the catalyst. NOx Purifies Nitrogen Oxide Using Oxygen as Reducing Agent
By arranging a purifying catalyst, and storing and holding hydrogen in the hydrogen storage material of the hydrogen supply purifying catalyst, the hydrogen can be suppressed from being oxidized and consumed, and the hydrogen supply amount of the NOx purifying catalyst can be increased. An exhaust gas purification system characterized in that: 8. The gas at the inlet of the NOx purification catalyst is expressed by the following equation (A) H ₂ / TR amount ≧ 0.3 (A) (wherein the TR amount represents the total reducing component amount in the exhaust gas. Show)
The exhaust gas purification system according to claim 7, wherein a gas composition represented by the following formula is satisfied. 9. The air-fuel ratio A / F of the exhaust gas of the internal combustion engine or the combustion device is varied from lean to stoichiometric to rich, and at this time, the hydrogen stored and held in the hydrogen storage material of the hydrogen supply purification catalyst is released. 8. The method according to claim 7, wherein
Or the exhaust gas purification system according to 8. 10. The NOx purifying catalyst stores nitrogen oxides when the air-fuel ratio A / F of the exhaust gas is lean,
8. A NOx storage / purification catalyst that releases stored nitrogen oxides during a stoichiometric to rich operation.
10. The exhaust gas purification system according to any one of items 9 to 9.