JP3973831B2 - Exhaust purification catalyst device and exhaust purification method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust purification technology using a catalyst, and more particularly to a technology that enables purification of PM (particulate matter).
[0002]
[Prior art]
Conventionally, various exhaust purification catalyst devices have been devised for purifying exhaust gas from an internal combustion engine. As one of the exhaust gas purification catalyst devices, for example, as disclosed in JP-A-10-202107, an active component made of a noble metal is formed on a porous material having pores having a diameter of 0.7 to 20.0 nm. A material in which an additive component made of a Group IIA metal is dispersed and supported is known. In such an exhaust purification catalyst device, HC (hydrocarbon) trapping by the pores of the porous material, low temperature activity by the noble metal, and synergistic effect of promoting the purification of CO (carbon monoxide) by the group IIA metal, HC having a large number of carbon atoms. (C6-C20) and CO are purified from a relatively low temperature.
[0003]
[Problems to be solved by the invention]
However, in such an exhaust purification catalyst device, since the pore diameter of the porous material is set to 0.7 to 20.0 nm, for example, PM of about 100 nm that is often contained in the exhaust of a diesel engine is not trapped, Most of them passed by.
[0004]
Therefore, in view of the conventional problems as described above, the present invention provides an exhaust purification catalyst device and an exhaust purification method that can not only purify HC and CO but also purify PM by reexamining the structure of the catalyst carrier. The purpose is to provide.
[0005]
[Means for Solving the Problems]
For this reason, the invention relating to the exhaust purification catalyst device according to claim 1 is a porous material having pores having a diameter of 0.7 to 300 nm on the surface of the base of the catalyst carrier interposed in the exhaust passage of the internal combustion engine. And coating a porous material formed by substantially uniformly mixing β-type zeolite, mesopore silicate, and alumina having a pore diameter of 20 to 300 nm , and an active ingredient comprising a noble metal on the porous material And an additive component made of a rare earth metal are dispersedly supported.
[0006]
According to such a configuration, when the exhaust discharged from the internal combustion engine is introduced into the catalyst carrier through the exhaust passage, HC, CO, and PM contained in the exhaust are trapped in the pores of the porous material. For this reason, even if the oxidation reaction below the activation temperature is not sufficiently performed, HC, CO, and PM are trapped, so that they are suppressed from being discharged without being purified. On the other hand, after reaching the activation temperature, in addition to trapping HC, CO, and PM, oxidation of HC, CO, and PM is performed by an active component composed of noble metal dispersed and supported on the porous material and an additive component composed of rare earth metal. Is done. At this time, the oxidation of the PM trapped in the porous material is promoted by an additive component made of a rare earth metal.
[0007]
Further, β-type zeolite having pores having a major diameter of 0.7 nm and a minor diameter of 0.5 to 0.6 nm, mesopore silicate having a pore having a diameter of 2.0 nm, and a pore having a diameter of 20 to 300 nm. A porous material having pores having a diameter of 0.7 to 300 nm can be easily formed by mixing the alumina having a substantially uniform density.
[0008]
In the invention of claim 2 , the noble metal is platinum Pt, and the rare earth metal is at least one metal selected from cerium Ce, lanthanum La, neodymium Nd, yttrium Y, praseodymium Pr, and samarium Sm. It is characterized by.
According to such a configuration, oxidation of HC, CO, and PM is efficiently performed by using platinum Pt as the noble metal as the active component. Moreover, oxidation of PM trapped in the porous material can be achieved by using at least one metal selected from cerium Ce, lanthanum La, neodymium Nd, yttrium Y, praseodymium Pr, and samarium Sm as the additive component. Promoted efficiently.
[0009]
In the invention relating to the exhaust gas purification method according to the third aspect, the porous material having pores having a diameter of 0.7 to 300 nm in the exhaust passage of the internal combustion engine , the β-type zeolite, the mesopore silicate, and the diameter of 20 to 300. A catalyst carrier in which an active component made of a noble metal and an additive component made of a rare earth metal are dispersed and supported on a porous material formed by mixing alumina having pores of nm in a substantially uniform manner. The exhaust gas of the internal combustion engine is brought into contact with the exhaust gas to purify the exhaust gas.
According to such a configuration, when the exhaust discharged from the internal combustion engine is introduced into the catalyst carrier through the exhaust passage, HC, CO, and PM contained in the exhaust are trapped in the pores of the porous material. For this reason, even in a state where the oxidation reaction below the activation temperature is not sufficiently performed, HC, CO, and PM are trapped, so that they are suppressed from being discharged unpurified. After reaching the temperature, in addition to trapping HC, CO, and PM, oxidation of HC, CO, and PM is performed by an active component made of noble metal dispersed and supported on the porous material and an additive component made of rare earth metal. . At this time, the oxidation of the PM trapped in the porous material is promoted by an additive component made of a rare earth metal. Further, β-type zeolite having pores having a major diameter of 0.7 nm and a minor diameter of 0.5 to 0.6 nm , mesopore silicate having a pore having a diameter of 2.0 nm , and a diameter of 20 to 300 nm. The porous material having pores having a diameter of 0.7 to 300 nm can be easily formed by mixing the alumina having the pores of approximately uniformly .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a monolith type exhaust purification catalytic apparatus to which the present invention is applied.
A monolith type catalyst carrier 14 having a honeycomb-shaped cross section is interposed in the exhaust passage 10 of the internal combustion engine via a holding member 12. As shown in FIG. 2, the catalyst carrier 14 has β-type zeolite A, mesopore silicate B, and large pore diameter alumina C on the surface of a base 14a made of ceramic cordierite or Fe—Cr—Al heat-resistant steel. It is formed by thinly coating a substantially uniform mixture. The coat layer 14b is usually called a “wash coat layer”, and an active component made of a noble metal and an additive component made of a rare earth metal are dispersedly supported thereon.
[0011]
As shown in FIG. 2, the washcoat layer 14b is composed of β-type zeolite A having pores having a major diameter of 0.7 nm and a minor diameter of 0.5 to 0.6 nm, and mesopores having a pore of 2.0 nm. It is composed of silicate B and large pore diameter alumina C having pores with a diameter of 20 to 300 nm. For this reason, the entire washcoat layer 14b has pores having a diameter of 0.7 to 300 nm. The large pore diameter alumina C is desirably manufactured by, for example, a PHS (pH swing) method in order to suppress variation in pore diameter.
[0012]
For example, platinum Pt is used as the noble metal as the active component, and the rare earth metal as the additive component is at least one selected from, for example, cerium Ce, lanthanum La, neodymium Nd, yttrium Y, praseodymium Pr, and samarium Sm. It is desirable to use two metals.
Next, the operation of the exhaust purification catalyst apparatus having such a configuration will be described.
[0013]
When exhaust gas discharged from the internal combustion engine is introduced into the catalyst carrier 14 through the exhaust passage 10, the exhaust gas contacts the washcoat layer 14 b of the catalyst carrier 14. At this time, HC (6 to 20 carbon atoms) and CO having a large number of carbon atoms contained in the exhaust gas are trapped by the pores of β-type zeolite A and mesopore silicate B. For this reason, even in a state where the oxidation reaction below the activation temperature is not sufficiently performed, HC and CO having a large number of carbon atoms are suppressed from being discharged without being purified, and the exhaust properties can be improved. After reaching the activation temperature, the oxidation reaction of HC and CO is carried out by the noble metal and rare earth metal supported on the β-type zeolite A and the mesopore silicate B in addition to the trap of HC and CO. The properties can be further improved.
[0014]
Further, PM (particle size around 100 nm) contained in the exhaust is trapped by the pores of the large pore diameter alumina C. For this reason, even if it is below activation temperature, it is suppressed that PM is discharged without being purified, and the exhaust property can be improved. After reaching the activation temperature, PM is oxidized and purified by the noble metal and rare earth metal supported on the large pore diameter alumina C. Thereafter, PM trapping and oxidation are repeated, whereby PM purification is continuously performed. At this time, the oxidation of the PM trapped in the large pore diameter alumina C is promoted by the rare earth metal.
[0015]
Thus, according to the exhaust purification catalyst device of the present invention, not only HC and CO purification but also PM can be purified, so that a so-called “Soot oxidation catalyst” can be realized. Therefore, even if it is a diesel engine containing a large amount of PM in the exhaust, if the exhaust purification catalyst device according to the present invention is mounted, not only the purification of HC and CO in the exhaust but also the purification of PM can be performed simultaneously.
[0016]
In the embodiment described above, the monolith type exhaust purification catalyst device is assumed. However, it goes without saying that the same operation and effect can be obtained even with a pellet type exhaust purification catalyst device.
[0017]
【The invention's effect】
As described above, according to the invention described in claim 1 or claim 3 , not only HC and CO but also PM can be simultaneously purified. In addition, a porous material having pores with a diameter of 0.7 to 300 nm can be easily formed.
[0018]
According to the second aspect of the present invention, oxidation of HC, CO and PM can be efficiently performed by using platinum Pt as the noble metal as the active component. Further, the rare earth metal as the active component is at least one metal selected from cerium Ce, lanthanum La, neodymium Nd, yttrium Y, praseodymium Pr, and samarium Sm, thereby oxidizing the PM trapped in the porous material. Can be promoted efficiently.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a monolith type exhaust purification catalytic apparatus to which the present invention is applied. FIG. 2 is a detailed view of a porous material coated on a base of a catalyst carrier.
10 Exhaust passage 14 Catalyst support 14a Base 14b Wash coat layer

Claims (3)

A porous material having pores with a diameter of 0.7 to 300 nm on the surface of a base of a catalyst carrier interposed in an exhaust passage of an internal combustion engine, having a β-type zeolite, mesopore silicate, and a fine particle with a diameter of 20 to 300 nm . A porous material formed by substantially uniformly mixing alumina having pores is coated, and an active component made of a noble metal and an additive component made of a rare earth metal are dispersedly supported on the porous material. Exhaust purification catalyst device. 2. The noble metal is platinum Pt, and the rare earth metal is at least one metal selected from cerium Ce, lanthanum La, neodymium Nd, yttrium Y, praseodymium Pr, and samarium Sm. Exhaust gas purification catalyst device. In the exhaust passage of the internal combustion engine, the diameter is 0.7 to 300 nm A porous material having β-type zeolite, mesopore silicate, and a diameter of 20 to 300 nm A catalyst carrier in which an active component made of a noble metal and an additive component made of a rare earth metal are dispersed and supported on a porous material formed by mixing alumina having a plurality of pores substantially uniformly, and an internal combustion engine is mounted on the catalyst carrier. An exhaust gas purification method comprising purifying exhaust gas by contacting exhaust gas of an engine.

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