JP2018103132A - Catalyst for exhaust gas purification - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wall flow type catalyst for exhaust gas purification having high exhaust gas purification performance.SOLUTION: A catalyst 100 for exhaust gas purification disclosed here is a wall flow type catalyst for exhaust gas purification which is arranged in an exhaust tube of an internal combustion engine and performs purification of exhaust gas discharged from the internal combustion engine. The catalyst 100 for exhaust gas purification has: an inside cell 20 in which an end part 14 in an exhaust gas outlet side is encapsulated by an outlet side encapsulation member 32; an outlet side cell 22 in which an end part 12 of an exhaust gas inlet side is encapsulated by an inlet side encapsulation member 34: a substrate 10 with a wall flow structure having a porous barrier 40; and an inside catalyst layer 60 formed on the barrier 40 in the substrate 10. The catalyst 100 for exhaust gas purification has an end part catalyst layer 70 formed at least on an end surface 34a in the exhaust gas inlet side of the inlet side encapsulation member 34.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an exhaust gas purifying catalyst provided in an exhaust pipe of an internal combustion engine. Specifically, the present invention relates to an exhaust gas purifying catalyst provided with a base material having a wall flow structure.

  Exhaust gas emitted from internal combustion engines such as automobile engines contains harmful substances such as particulate matter (particulate matter: PM), hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). In order to efficiently remove these harmful components, an exhaust gas purifying catalyst having a catalyst layer including a catalyst body in which a catalyst metal is supported on a carrier has been conventionally used. The catalyst layer of such an exhaust gas purifying catalyst is generally formed inside a honeycomb structure substrate having a plurality of flow paths (cells).

As an example of the base material of the exhaust gas purifying catalyst, a wall flow structure base material that has porous partition walls and allows exhaust gas to permeate the porous description is used (for example, Patent Documents 1 and 2). . As shown in FIG. 1, the base material 10 having such a wall flow structure includes an inlet cell 20 in which only an end portion 12 on the exhaust gas inflow side is open, and an outlet cell 22 in which only an end portion 14 on the exhaust gas outflow side is open The porous partition walls 40 partitioning the cells 20 and 22 are formed, and a catalyst layer (not shown) including the above-described catalyst body is formed on the partition walls 40 inside the substrate 10.
In the exhaust gas purifying catalyst (hereinafter also referred to as “wall flow type exhaust gas purifying catalyst”) provided with the base material 10 having such a wall flow structure, as shown by an arrow A in FIG. Flows in and the exhaust gas passes through the porous partition wall 40. At this time, the catalyst layer formed on the partition 40 inside the substrate 10 and the exhaust gas come into contact with each other, thereby removing harmful components in the exhaust gas.

JP 2009-82915 A JP 2007-185571 A

By the way, in recent years, exhaust gas regulations for vehicles and the like tend to be further strengthened, and in order to meet the exhaust gas regulations, the above-described wall flow type exhaust gas purification catalyst has an ability to remove harmful components in exhaust gas (exhaust gas It is required to improve the purification capacity.
The present invention has been made in view of such a demand, and an object of the present invention is to provide a wall flow type exhaust gas purifying catalyst having a higher exhaust gas purifying ability than conventional ones.

  In order to achieve the above object, the present invention provides an exhaust gas purifying catalyst having the following configuration.

The exhaust gas purifying catalyst disclosed here is a wall flow type exhaust gas purifying catalyst that is disposed in an exhaust pipe of an internal combustion engine and purifies exhaust gas discharged from the internal combustion engine.
Such a wall flow type exhaust gas purifying catalyst includes an inlet cell in which an end portion on the exhaust gas inflow side is open and an end portion on the exhaust gas outflow side is sealed with an outlet side sealing member, and the inlet cell An exit cell in which an end on the exhaust gas outflow side is adjacent and an end on the exhaust gas inflow side is sealed with an entrance sealing member, and a porous partition wall that partitions the entrance cell and the exit cell A wall flow structure base material, and an internal catalyst layer formed on a partition wall inside the base material, the internal catalyst layer including a catalyst body made of a substance that functions as an oxidation and / or reduction catalyst. .
The exhaust gas purifying catalyst disclosed herein is characterized in that an end catalyst layer including a catalyst body made of the above-described substance is formed at least on an end surface of the inlet side sealing member on the exhaust gas inflow side.

In order to provide an exhaust gas purifying catalyst having a high exhaust gas purifying ability, the present inventor considered developing a structure capable of efficiently contacting the exhaust gas and the catalyst layer.
In developing an exhaust gas purifying catalyst having such a structure, first, the flow path through which the exhaust gas is in contact with the catalyst layer in the wall flow base material was examined. As a result of such examination, in the case of the base material 10 having the wall flow structure as shown in FIG. 1, not only the exhaust gas directly flowing into the entry side cell 20 (see arrow A in FIG. 1) but also as indicated by arrow B It was found that there was exhaust gas flowing into the inlet side cell 20 after colliding with the inlet side sealing member 34.
Based on this knowledge, the present inventor forms a catalyst layer (end catalyst layer) on the end surface 34a of the inlet side sealing member 34 of the base material 10 on the exhaust gas inflow side, whereby the inlet side sealing member 34 is formed. It was thought that the exhaust gas colliding with the end face 34a of the catalyst could be purified by contacting the end catalyst layer. As a result of various experiments, it was confirmed that the exhaust gas purifying catalyst in which the end catalyst layer was formed had higher exhaust gas purifying ability than the conventional one, and the present invention was completed. .

  That is, the exhaust gas purifying catalyst disclosed herein has an end catalyst layer formed at least on the end surface of the inlet side sealing member on the exhaust gas inflow side, and a part of the exhaust gas supplied to the exhaust gas purifying catalyst is input. Since it can purify | clean before flowing into a side cell, the exhaust gas purification capability higher than before can be exhibited.

In a preferred aspect of the exhaust gas purifying catalyst disclosed herein, the exhaust gas inflow side end surface of the partition wall is formed on the exhaust gas inflow side end surface of the inlet side sealing member.
In order to further improve the exhaust gas purification ability of the exhaust gas purification catalyst in which the above-described end catalyst layer is formed, the present inventor examined again the flow path of the exhaust gas supplied to the catalyst.
As a result of such examination, the wall flow type exhaust gas purifying catalyst enters the inside of the partition wall 40 from the end portion 12 on the exhaust gas inflow side and then flows out to the exit side cell 22 as indicated by an arrow C in FIG. It was found that there was a lot of exhaust gas. Since the exhaust gas that has passed through the flow path indicated by the arrow C does not flow into the inlet cell 20 and is discharged to the outside of the exhaust gas purification catalyst, there is a possibility that harmful components may not be appropriately removed.
The present inventor has made various studies in order to appropriately purify the exhaust gas entering the partition wall 40 from the end portion 12 on the exhaust gas inflow side, and the end catalyst layer described above is used as the entrance-side sealing member 34. The exhaust gas purification catalyst of this embodiment has been conceived in consideration of the formation on the end portion 12 of the partition wall 40 on the exhaust gas flow side as well as the end surface 34a of the partition wall 40a.

In a preferred aspect of the exhaust gas purifying catalyst disclosed herein, the catalyst body contains at least one metal element selected from Pd, Pt, and Rh.
In the exhaust gas purifying catalyst disclosed herein, the type of the catalyst body can be appropriately changed according to the type of harmful component to be purified. For example, as described above, by using a catalyst body including at least one kind of palladium (Pd), platinum (Pt), and rhodium (Rh), among harmful components (PM, HC, CO, NOx) in exhaust gas A three-way catalyst that purifies HC, CO, and NOx can be constructed.

In a preferred aspect of the exhaust gas purifying catalyst disclosed herein, the catalyst body is a transition metal ion exchange zeolite in which at least one metal element selected from Cu and Fe is supported on the zeolite. .
As described above, the catalyst body of the exhaust gas purification catalyst disclosed herein can appropriately change the type of the catalyst body according to the type of harmful component to be purified, and a catalyst body other than the three-way catalyst Can also be used. Another example of such a catalyst body is an SCR catalyst. This SCR catalyst has a transition metal ion exchange zeolite in which a transition metal is supported on zeolite, and reacts the NOx in the exhaust gas by reacting the reducing agent (urea, etc.) supplied to the exhaust gas with NOx in the exhaust gas. It can be purified selectively.

In a preferred embodiment of the exhaust gas purifying catalyst disclosed herein, the weight ratio of the catalyst bodies contained in the end catalyst layer when the total amount of the catalyst bodies contained in the inner catalyst layer and the end catalyst layer is 100 wt%. Is 0.06 wt% to 3 wt%.
The weight of the catalyst body contained in the end catalyst layer is preferably adjusted as appropriate in consideration of the weight of the catalyst in the internal catalyst layer, the concentration of harmful components to be purified, the flow rate of exhaust gas, and the like. For example, when the total amount of the catalyst bodies included in the internal catalyst layer and the end catalyst layer is 100 wt% as in the above-described aspect, the weight of the catalyst bodies in the end catalyst layer is 0.06 wt% to 3 wt%. % Is preferable. As a result, the exhaust gas in contact with the end catalyst layer can be appropriately purified to exhibit a sufficiently high exhaust gas purification capability.

In a preferred aspect of the exhaust gas-purifying catalyst disclosed herein, the total amount of catalyst bodies contained in the inner catalyst layer and the end catalyst layer per liter of the base material is 10 g or more and 150 g or less. .
The exhaust gas purifying catalyst disclosed herein is a catalyst body in the whole catalyst in consideration of the concentration of harmful components in exhaust gas, the volume of the base material (total volume of the inlet side cell and the outlet side cell), the manufacturing cost, etc. It is preferable to adjust the total amount. For example, the total amount of catalyst bodies contained in the internal catalyst layer and the end catalyst layer per liter of the base material is preferably 10 g or more and 150 g or less.

It is a figure which shows typically the cross-sectional structure of the base material of a wall flow structure. 1 is a perspective view schematically showing an exhaust gas purifying catalyst according to an embodiment of the present invention. 1 is a cross-sectional view schematically showing an exhaust gas purifying catalyst according to an embodiment of the present invention. It is sectional drawing which shows typically the exhaust gas purification catalyst which concerns on other embodiment of this invention. It is sectional drawing which shows typically the exhaust gas purification catalyst which concerns on other embodiment of this invention. It is sectional drawing which shows typically the exhaust gas purification catalyst which concerns on other embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following drawings, members / parts having the same action are denoted by the same reference numerals, and redundant description may be omitted or simplified. In addition, the dimensional relationship (length, width, thickness, etc.) in each drawing does not necessarily reflect the actual dimensional relationship. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be implemented based on the contents disclosed in the present specification and technical knowledge in the field.

1. Hereinafter, the exhaust gas purifying catalyst according to the present embodiment will be described in detail. FIG. 2 is a perspective view schematically showing the exhaust gas purifying catalyst according to the present embodiment. As shown in FIG. 2, the exhaust gas purifying catalyst 100 according to the present embodiment includes a base material 10 that is a honeycomb structure having a cylindrical outer shape, and a catalyst layer (not shown) formed on the base material 10. I have. Note that the outer shape of the base material 10 is not limited to the cylindrical shape as shown in FIG. 2, and may be an elliptical cylindrical shape, a polygonal cylindrical shape, or the like.

(1) Substrate For the exhaust gas purifying catalyst 100 according to the present embodiment, a base material 10 having a wall flow structure as shown in FIG. 1 is used as in the case of a conventional exhaust gas purifying catalyst.
As described above, the base material 10 having such a wall flow structure includes the entry side cell 20, the exit side cell 22, and the partition 40.
The inlet cell 20 is a gas flow path into which the exhaust gas supplied to the exhaust gas purification catalyst 100 flows, and the end 12 on the exhaust gas inflow side is open and the end 14 on the exhaust gas outflow side is the outlet sealing member. 32 is sealed. The outlet cell 22 is a gas flow path for discharging the exhaust gas to the outside of the exhaust gas purification catalyst 100. The exhaust gas outflow side end 14 is open and the exhaust gas inflow end 12 is the input side. Sealed by a sealing member 34.
And in the base material 10 of a wall flow structure, the above-mentioned entrance side cell 20 and the exit side cell 22 are formed adjacently, and this adjacent entrance side cell 20 and exit side cell 22 are porous partition walls. It is partitioned by 40.

  As the material of the base material 10, various materials that can be used for a base material of a general exhaust gas purifying catalyst can be used. Preferable examples of the material of the base material 10 include cordierite, silicon carbide (SiC), ceramics such as aluminum titanate, and alloys such as stainless steel. Since these materials have high heat resistance, even when the internal combustion engine is operated under a high load condition and the exhaust gas purification catalyst is exposed to a high temperature environment (for example, 400 ° C. or higher), the temperature rise causes the base material. 10 can be prevented from being damaged.

  It should be noted that the specific dimensions and the like of the substrate 10 are preferably adjusted as appropriate in consideration of the dimensions of the exhaust pipe of the internal combustion engine, the concentration of harmful components in the exhaust gas, and the like. For example, the volume of the base material 10 (the total volume of the entry side cell 20 and the exit side cell 22) is preferably set to 0.1 L to 5 L (preferably 0.5 L to 3 L, for example, 1 L). The total length of the substrate 10 in the direction X is preferably set within a range of 10 mm to 500 mm (for example, 50 mm to 300 mm). Moreover, it is preferable that the thickness of each partition 40 is set in the range of 0.05 mm or more and 2 mm or less from a viewpoint of durability of the base material 10 and air permeability.

(2) Catalyst Layer FIG. 3 is a sectional view schematically showing the exhaust gas purifying catalyst according to this embodiment. As shown in FIG. 3, the exhaust gas purifying catalyst 100 according to this embodiment includes two types of catalyst layers, an internal catalyst layer 60 and an end catalyst layer 70.

Each of the internal catalyst layer 60 and the end catalyst layer 70 includes a catalyst body made of a substance that functions as an oxidation catalyst (and / or a reduction catalyst) against harmful components in the exhaust gas. Such a catalyst body is composed of a catalyst metal that is the main component of the catalytic action and a carrier that supports the catalyst metal.
In the exhaust gas purifying catalyst 100 according to the present embodiment, the type of the catalyst body is not particularly limited, and can be appropriately changed according to the type of harmful component to be purified.
For example, when the exhaust gas purifying catalyst 100 according to the present embodiment is used as a three-way catalyst that performs oxidation of CO, HC and reduction of NOx, palladium (Pd), platinum (Pt), and rhodium (Rh) are used. It is preferable to use a catalyst body containing at least one selected element as a catalyst metal. Further, when using a catalyst metal containing these platinum group elements (PGM), as a carrier for supporting the PGM, for example, alumina-added ceria-zirconia composite oxide (Al ₂ O ₃ / ZrO ₂ —CeO ₂ composite) Body).
Further, when the exhaust gas purifying catalyst 100 according to the present embodiment is used as an SCR catalyst that selectively purifies NOx in exhaust gas, as a catalyst body included in the internal catalyst layer 60 and the end catalyst layer 70, It is preferable to use a transition metal ion exchange zeolite in which a transition metal such as copper (Cu) or iron (Fe) is supported on the zeolite.

  The inner catalyst layer 60 and the end catalyst layer 70 may contain the same type of catalyst body or different types of catalyst bodies. Further, as will be described in detail later, the internal catalyst layer 60 of the exhaust gas purifying catalyst 100 according to the present embodiment is composed of two types of catalyst layers, an inlet side catalyst layer 62 and an outlet side catalyst layer 64. Similarly, when the internal catalyst layer 60 is composed of a plurality of catalyst layers, the catalyst bodies included in each catalyst layer may be the same type of catalyst body or different types of catalyst bodies. Also good.

  The total amount of the catalyst bodies contained in the internal catalyst layer 60 and the end catalyst layer 70 is preferably adjusted as appropriate in consideration of the concentration of harmful components in the exhaust gas, the volume of the base material, the manufacturing cost, and the like. For example, the total amount of the catalyst bodies contained in the internal catalyst layer 60 and the end catalyst layer 70 per 1 L of the volume of the substrate 10 is preferably 10 g or more and 150 g or less (more preferably 50 g or more and 150 g or less, for example, 100 g). .

  Next, the structure of each of the internal catalyst layer 60 and the end catalyst layer 70 will be specifically described.

(A) Internal Catalyst Layer As described above, the internal catalyst layer 60 is formed on the partition wall 40 inside the base material 10. The internal catalyst layer 60 in the present embodiment is composed of an entry side catalyst layer 62 and an exit side catalyst layer 64.
The inlet side catalyst layer 62 of the inner catalyst layer 60 is formed with a predetermined thickness from the surface 40a of the partition wall 40 in contact with the inlet side cell 20 to the inside of the partition wall 40, and from the end 12 on the exhaust gas inflow side in the cylinder axial direction. A predetermined length is formed along X. On the other hand, the outlet catalyst layer 64 is formed with a predetermined thickness from the surface 40b of the partition wall 40 in contact with the outlet cell 22 to the inside of the partition wall 40, and extends along the cylinder axis direction X from the end portion 14 on the exhaust gas outlet side. And a predetermined length.
When the internal catalyst layer 60 having a two-layer structure including the inlet catalyst layer 62 and the outlet catalyst layer 64 is formed as in the present embodiment, each catalyst layer is considered in consideration of the flow rate of the exhaust gas supplied. The dimensions (length and thickness) of 62, 64 can be adjusted. As a result, the exhaust gas can be efficiently brought into contact with the internal catalyst layer 60, so that the exhaust gas purification ability can be improved.

(B) End Catalyst Layer In the exhaust gas purifying catalyst 100 according to this embodiment, the end catalyst layer 70 is formed at the end 12 on the exhaust gas inflow side of the base material 10. Specifically, the end catalyst layer 70 in the present embodiment is formed so as to cover the end surface 34 a on the exhaust gas inflow side of the inlet side sealing member 34 in the end portion 12 on the exhaust gas inflow side of the base material 10. Yes. As a result, the exhaust gas flowing as shown by the arrow B in the figure can be purified before flowing into the inlet side cell 20, so that the exhaust gas purification capability of the exhaust gas purification catalyst 100 as a whole can be improved.

Specifically, as described above, in the exhaust gas purifying catalyst 100 having the wall flow structure, not only the exhaust gas directly flowing into the inlet cell 20 (see arrow A) but also the inlet side sealing member as shown by the arrow B Exhaust gas that flows into the entry-side cell 20 after colliding with the battery 34 may also occur.
In the exhaust gas purifying catalyst 100 according to the present embodiment, the end catalyst layer 70 is formed so as to cover the end surface 34a on the exhaust gas inflow side of the inlet side sealing member 34 on which the exhaust gas indicated by the arrow B collides. The exhaust gas indicated by the arrow B can be purified before flowing into the inlet cell 20. Thus, according to the exhaust gas purifying catalyst 100 according to the present embodiment, the exhaust gas and the catalyst layer can be brought into contact with each other more efficiently than before, and a high exhaust gas purifying ability can be exhibited.

  The weight of the catalyst body included in the end catalyst layer 70 is appropriately determined in consideration of the weight of the catalyst body of the internal catalyst layer 60, the type of harmful component to be purified, the concentration of the harmful component, the exhaust gas flow rate, and the like. It is preferable to adjust. For example, when the total amount of the catalyst bodies included in the internal catalyst layer 60 and the end catalyst layer 70 is 100 wt%, the weight of the catalyst bodies included in the end catalyst layer 70 is about 0.06 wt% to 3 wt%. It is preferable that the content be 0.1 wt% to 3 wt%. Thereby, a sufficiently high exhaust gas purification ability can be exhibited.

2. Exhaust gas purification catalyst according to another embodiment The exhaust gas purification catalyst according to an embodiment of the present invention has been described above, but the exhaust gas purification catalyst disclosed herein is not limited to the above-described embodiment, and various The structure of can be changed. Hereinafter, an exhaust gas purifying catalyst according to another embodiment of the present invention will be described.

(1) Region for Forming End Catalyst Layer In the exhaust gas purifying catalyst 100 according to the above-described embodiment, the end catalyst layer 70 is formed only on the end surface 34a of the inlet side sealing member 34 on the exhaust gas inflow side. However, the end catalyst layer 70 only needs to be formed at least on the end surface 34a on the exhaust gas inflow side of the inlet side sealing member 34, and may be formed in a region other than the end surface 34a of the inlet side sealing member 34. Good.

For example, like the exhaust gas purification catalyst 100 shown in FIG. 4, the end catalyst layer 70 is also provided at the end 12 of the partition wall 40 on the exhaust gas inflow side, following the end surface 34 a on the exhaust gas inflow side. Preferably it is formed. Thereby, the exhaust gas purification capability of the exhaust gas purification catalyst 100 can be further improved.
Specifically, when the base material 10 having the wall flow structure as shown in FIG. 1 is used, as shown by an arrow C, the exhaust gas flowing into the porous partition wall 40 from the end portion 12 on the exhaust gas inflow side is discharged. May occur. Since the exhaust gas that has flowed into the partition wall 40 from the end portion may not come into contact with the catalyst layer (internal catalyst layer), the exhaust gas purification ability may be reduced.
On the other hand, in the exhaust gas purifying catalyst 100 shown in FIG. 4, the end catalyst layer 70 is also formed at the end 12 on the exhaust gas inflow side of the partition wall 40, so that the partition wall 40 starts from the end as shown by the arrow C. It is possible to purify the exhaust gas flowing into the interior. For this reason, according to the exhaust gas purifying catalyst 100 shown in FIG. 4, it is possible to prevent the generation of exhaust gas discharged outside the exhaust gas purifying catalyst without contacting the catalyst layer, and to exhibit higher exhaust gas purifying ability. Can do.
The end catalyst layer 70 formed at the end portion 12 of the partition wall 40 on the exhaust gas inflow side may be formed not only in the end face of the partition wall 40 but also in the partition wall 40 as shown in FIG. .

(2) Other Forms of Internal Catalyst Layer Further, the exhaust gas purifying catalyst 100 according to the embodiment shown in FIG. 3 includes an internal catalyst layer 60 composed of an entry side catalyst layer 62 and an exit side catalyst layer 64. However, the structure of the internal catalyst layer 60 is not particularly limited. For example, as shown in FIG. 5, the inner catalyst layer 60 may be formed uniformly in the entire interior of the partition wall 40, or as shown in FIG. 6 so as to cover the surface 40 a of the partition wall 40 in contact with the entry side cell 20. An internal catalyst layer 60 may be formed.
In the case of the exhaust gas purification catalyst 100 in which the inner catalyst layer 60 is formed on the surface 40a of the partition wall 40 as shown in FIG. 6, the exhaust gas flowing into the partition wall 40 from the end 12 on the exhaust gas inflow side (arrow) There is a possibility that the possibility that the gas is discharged to the outside of the exhaust gas purifying catalyst 100 without contacting the internal catalyst layer 60 may increase. For this reason, when the internal catalyst layer 60 is formed on the surface 40a of the partition wall 40, as shown in FIG. 6, the end catalyst layer 70 is connected to the end surface 34a on the exhaust gas inflow side of the inlet side sealing member 34 and the partition wall 40. It is preferable to form both of the end portions 12 on the exhaust gas inflow side.

3. Manufacturing Method Next, an example of a method for manufacturing the exhaust gas-purifying catalyst 100 shown in FIG. 3 will be described. Note that the following description is not intended to limit the exhaust gas-purifying catalyst disclosed herein.

  Here, first, a raw material slurry that is a precursor of each catalyst layer is prepared. Specifically, a raw material slurry is prepared by dispersing a catalyst body (catalyst metal and carrier), which are essential components, and other optional components (for example, a promoter and a thickener) in an aqueous solvent (for example, ion-exchanged water). To prepare.

Next, a base material 10 having a wall flow structure as shown in FIGS. 1 and 3 is prepared, and an internal catalyst layer 60 is formed on a partition wall 40 inside the base material 10.
Specifically, the raw material slurry described above is introduced into the inlet cell 20 from the end portion 12 on the exhaust gas inflow side of the base material 10 and permeated into the porous partition wall 40. Then, the entrance catalyst layer 62 is formed inside the partition wall 40 by heating and drying and baking the base material 10 at a predetermined temperature. In addition, as a method of introduce | transducing raw material slurry into the entrance side cell 20 of the base material 10, an air blow etc. can be used, for example.
Then, the outlet catalyst layer 64 is formed by the same procedure as that for the inlet catalyst layer 62 described above. That is, after the prepared raw material slurry is introduced into the outlet cell 22 from the end portion 14 on the exhaust gas outlet side, the substrate 10 is dried and fired to form the outlet catalyst layer 64 inside the partition wall 40.
Through the above steps, the internal catalyst layer 60 composed of the entrance catalyst layer 62 and the exit catalyst layer 64 is formed on the partition wall 40 inside the base material 10.

Next, the end catalyst layer 70 is formed so as to cover at least the end surface 34 a on the exhaust gas inflow side of the inlet side sealing member 34 in the end portion 12 on the exhaust gas inflow side of the base material 10.
Specifically, first, the raw material slurry prepared in the same procedure as the above-described internal catalyst layer 60 is applied so as to cover at least the end surface 34 a on the exhaust gas inflow side of the inlet side sealing member 34. The exhaust gas purifying catalyst in which the end catalyst layer 70 is formed on the end surface 34a on the exhaust gas inflow side of the inlet side sealing member 34 by drying and firing the base material coated with the raw material slurry at a predetermined temperature. 100 can be obtained.

[Test example]
Next, test examples relating to the present invention will be described. However, the following description is not intended to limit the present invention.

  In this test example, an exhaust gas purification catalyst in which an internal catalyst layer and an end catalyst layer were formed was produced, and the exhaust gas purification ability of the exhaust gas purification catalyst was examined. Hereinafter, specific test conditions will be described.

1. Production of each test example (1) Test example 1
In Test Example 1, as an object to be compared, an exhaust gas purification catalyst in which an end catalyst layer was not formed and only an internal catalyst layer was formed was produced.
Specifically, first, palladium nitrate (Pd (NO ₃ )), aluminum oxide (Al ₂ O ₃ ) powder, and ceria-zirconia complex (ZrO ₂ —CeO ₂ complex) powder are used as ion-exchanged water. A raw material slurry was prepared by dispersing. At this time, each addition amount was adjusted so that the weight ratio of Pd, Al ₂ O ₃ and ZrO ₂ —CeO ₂ composite in the raw slurry was 2:60:38. And after adjusting a particle size with respect to the raw material slurry after preparation, the thickener was added and the viscosity was adjusted, and also ion-exchange water was added, and solid content concentration was adjusted.

  Next, after introducing 100 g of the prepared raw material slurry into the wall flow structure base (capacity: 1 L), the base is dried at 200 ° C. for 60 minutes, and then fired at 500 ° C. for 10 minutes. Thus, an exhaust gas purifying catalyst having an internal catalyst layer formed on the partition walls inside the substrate was produced.

(2) Test Example 2 to Test Example 7
In Test Example 2 to Test Example 7, an exhaust gas purification catalyst in which two types of catalyst layers, an internal catalyst layer and an end catalyst layer, were formed.
Specifically, in Test Example 2 to Test Example 7, first, 100 g of raw material slurry was prepared in the same procedure as in Test Example 1 described above, and a part of the 100 g of raw material slurry was introduced into the base material. The internal catalyst layer was formed by performing drying and baking later. And after applying the remaining raw material slurry which was not used for formation of an internal catalyst layer to the edge part by the side of the exhaust gas inflow of a base material, the edge part catalyst layer was formed by performing drying and baking again. In Test Examples 2 to 7, the amount of the raw slurry used for forming the internal catalyst layer and the amount of the raw slurry used for forming the end catalyst layer were different.

  And about the exhaust gas purification catalyst of each test example after preparation, it exists in the whole exhaust gas purification catalyst based on the Pd concentration in the used raw material slurry and the raw material slurry amount used for forming the catalyst layer. The weight ratio (%) of Pd present in each of the internal catalyst layer and the end catalyst layer when the weight of Pd was 100% was calculated as “Pd abundance ratio”. The calculation results are shown in Table 1.

2. Evaluation Test In this test example, the warm-up performance of CO purification was measured as an index for evaluating the exhaust gas purification ability of the exhaust gas purification catalysts of Test Examples 1 to 7.
Specifically, first, the exhaust gas purifying catalyst of each test example is arranged in the exhaust path of the internal combustion engine, the internal combustion engine is rotated at 2500 ± 10 rpm, the intake air amount is 25.0 ± 0.5 g / s, and the stoichiometric air-fuel ratio. It was operated under the conditions of (Stoichi). The exhaust gas was continuously discharged to the outside of the exhaust path until the temperature of the exhaust gas discharged from the internal combustion engine reached the measurement start temperature (50 ± 1 ° C.), and supplied to the exhaust gas purification catalyst when the measurement start temperature was reached. .
Then, the carbon monoxide (CO) concentration in the exhaust gas is measured on both the upstream side and the downstream side of the exhaust gas purification catalyst, and the CO concentration on the downstream side of the exhaust gas purification catalyst becomes 50% of the CO concentration on the upstream side. The internal combustion engine continued to operate until the CO emission rate of the exhaust gas purification catalyst reached 50%. Then, the time (sec) required for the CO purification rate to reach 50% was evaluated as the warm-up performance of CO purification. The results are shown in Table 1.

As shown in Table 1, when each of Test Example 1 to Test Example 7 was compared, in Test Example 2 to Test Example 5, the warm-up performance of CO purification was improved as compared with Test Example 1. From this, it was confirmed that by forming the two catalyst layers of the internal catalyst layer and the end catalyst layer as in the exhaust gas purification catalysts of Test Example 2 to Test Example 5, high exhaust gas purification ability can be exhibited. .
Further, in Test Example 3 to Test Example 5 in which the Pd abundance ratio was in the range of 0.10 wt% to 3.00 Wt%, it was confirmed that the CO purification warm-up performance could exhibit particularly preferable exhaust gas purification performance of 16 sec or less. did it.

In Test Example 6 and Test Example 7, although the external catalyst layer was formed, the exhaust gas purification capacity was about the same as Test Example 1 (or lower than Test Example 1). This is because, as a result of fixing the total amount of the catalyst body (Pd) of the internal catalyst layer and the end catalyst layer to 100 g under the test conditions of this test example, the presence of Pd in the end catalyst layer as in Test Examples 6 and 7 It is understood that when the ratio is increased, the Pd existence ratio of the internal catalyst layer, which is a main catalytic reaction field, decreases.
However, this result is limited to the case where the total amount of the catalyst bodies of the internal catalyst layer and the end catalyst layer is fixed to 100 g as in this test example, and the catalyst body amount of the internal catalyst layer is fixed to 100 g. In this case, even if the Pd existence ratio of the end catalyst layer is 5.00 wt% or more, the CO purification warm-up performance does not deteriorate, and a high exhaust gas purification ability can be exhibited.

  As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

DESCRIPTION OF SYMBOLS 10 Base material 12 End part 14 in exhaust gas inflow side End part 20 in exhaust gas outflow side Inlet cell 22 Outlet cell 32 Outlet sealing member 34 Inlet side sealing member 34a End surface 40 of the inlet side sealing member on the exhaust gas inflow side Partition wall 40a Partition wall surface 40b in contact with the inlet side cell Partition wall surface 60 in contact with the outlet side cell Internal catalyst layer 62 Inlet catalyst layer 64 Outlet catalyst layer 70 End catalyst layer 100 Exhaust gas purification catalyst X

Claims (6)

A wall flow type exhaust gas purification catalyst that is disposed in an exhaust pipe of an internal combustion engine and purifies exhaust gas discharged from the internal combustion engine,
An end of the exhaust gas inflow side is opened and an end of the exhaust gas outflow side is sealed with an exit side sealing member, and an end of the exhaust gas outflow side is opened adjacent to the entrance side cell. And an outlet side cell whose end on the exhaust gas inflow side is sealed with an inlet side sealing member, and a base material of a wall flow structure having a porous partition wall that partitions the inlet side cell and the outlet side cell; ,
An internal catalyst layer formed on the partition inside the base material, the internal catalyst layer including a catalyst body made of a substance that functions as an oxidation and / or reduction catalyst; and
With
Here, the exhaust gas purifying catalyst is characterized in that an end catalyst layer including the catalyst body made of the substance is formed on at least an end surface of the inlet side sealing member on the exhaust gas inflow side.   The end catalyst layer is also formed on an end of the partition wall on the exhaust gas inflow side following an end surface of the inlet side sealing member on the exhaust gas inflow side. Exhaust gas purification catalyst.   The exhaust gas purifying catalyst according to claim 1 or 2, wherein the catalyst body contains at least one metal element selected from Pd, Pt, and Rh.   The exhaust gas purifying catalyst according to claim 1 or 2, wherein the catalyst body is a transition metal ion-exchanged zeolite in which at least one metal element selected from Cu and Fe is supported on zeolite. .   When the total amount of the catalyst bodies contained in the internal catalyst layer and the end catalyst layer is 100 wt%, the weight ratio of the catalyst bodies contained in the end catalyst layer is 0.06 wt% to 3 wt%. The exhaust gas-purifying catalyst according to any one of claims 1 to 4, wherein the exhaust gas-purifying catalyst is provided. 6. The total amount of the catalyst bodies contained in the inner catalyst layer and the end catalyst layer per 1 L of the base material is 10 g or more and 150 g or less, 6. The exhaust gas-purifying catalyst according to Item.

Images