JP2012180787A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device that is capable of preventing discharge of an evaporation component containing a non-noble metal transition element into an atmosphere, while using the non-noble metal transition element as the component of an exhaust gas purifying catalyst.SOLUTION: The exhaust emission control device 1 is disposed in an exhaust pipe 61 for forming an exhaust gas flow path 62 where an exhaust gas G exhausted from an internal combustion engine 6 passes. The device includes: catalyst supports 2, 3 comprising catalyst components containing the non-noble metal transition element on a honeycomb structure; and porous materials 4 for adsorbing the evaporation component containing the non-noble metal transition element evaporated from the catalyst components. In the exhaust pipe 61, the porous materials 4 are disposed at the downstream side of the exhaust gas flow path 62 rather than the catalyst supports 2, 3.

Description

  The present invention relates to an exhaust gas purifying apparatus including a catalyst carrier formed by supporting a catalyst component containing a non-noble metal transition element on a honeycomb structure.

  The exhaust gas discharged from an internal combustion engine such as an automobile contains harmful components such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). In order to purify these harmful components, an exhaust gas purifying catalyst carried on a honeycomb structure is used. As exhaust gas purification catalysts, for example, three-way catalysts such as platinum (Pt), palladium (Pd), rhodium (Rh), which are noble metals, are widely known.

An example of the exhaust gas purification apparatus using the exhaust gas purification catalyst is shown in FIG.
As shown in the figure, the exhaust gas purification device 7 is a catalyst carrier in which an exhaust gas purification catalyst is supported on a honeycomb structure in an exhaust pipe 71 that forms an exhaust gas passage 72 through which exhaust gas G discharged from an internal combustion engine 70 passes. It is constructed by arranging 81 and 82. In the exhaust gas purification device 7, the exhaust gas G discharged from the internal combustion engine 70 is discharged into the atmosphere from the tail pipe 79 through the catalyst carrier 81, 82 in the exhaust pipe 71 via the muffler 78. At this time, HC, CO, NOx, etc. in the exhaust gas are purified by the exhaust gas purification catalyst such as a noble metal supported on the catalyst carriers 81, 82, so that clean exhaust gas is released into the atmosphere.

  By the way, the noble metal used as an exhaust gas purification catalyst is expensive, and there is a concern about stable supply from the viewpoint of resource depletion. Therefore, in recent years, exhaust gas purification catalysts using non-noble metal transition elements such as Cu have been developed.

Moreover, although harmful components, such as a hardly decomposable halogen compound (PCB), are contained in exhaust gas, the method of decomposing | disassembling PCB etc. is also developed (refer patent document 1).
As described above, in the automobile industry, harmful components contained in exhaust gas are required to be purified into harmless components by decomposition or the like before being released into the atmosphere.

JP 2003-305335 A

  However, when an exhaust gas purifying catalyst supported on the catalyst carriers 81 and 82, for example, containing a non-noble metal transition element such as Cu, transition metals such as Cu and CuO and oxides thereof from the catalyst carriers 81 and 82 are used. May evaporate into the exhaust gas G (see FIG. 4). Then, the exhaust gas G containing the transpiration component may be directly released from the tail pipe 79 into the atmosphere via the muffler 78.

  Since transition metals and their oxides are harmful, it is necessary to prevent the release of transpiration components containing them. In order to put the exhaust gas purification catalyst containing a non-noble metal transition element into practical use, measures to prevent the release of transpiration components are required.

  The present invention has been made in view of such problems, and while using a non-noble metal transition element as a component of an exhaust gas purification catalyst, it is possible to prevent emission of a transpiration component containing the non-noble metal transition element into the atmosphere. It is intended to provide a purification device.

The present invention is an exhaust gas purification apparatus disposed in an exhaust pipe that forms an exhaust gas passage through which exhaust gas discharged from an internal combustion engine passes,
A catalyst carrier comprising a catalyst structure containing a non-noble metal transition element supported on a honeycomb structure, and a porous body that adsorbs the transpiration component containing the non-metal transition element evaporated from the catalyst component of the catalyst carrier. Have
In the exhaust pipe, the porous body is disposed on the downstream side of the exhaust gas flow path with respect to the catalyst carrier (claim 1).

The exhaust gas purifying apparatus of the present invention includes a catalyst support formed by supporting a catalyst component containing a non-noble metal transition element on a honeycomb structure.
Therefore, in the catalyst carrier, HC, CO, NOx and the like contained in the exhaust gas can be purified by the catalyst component.

In the catalyst carrier on which the catalyst component containing the non-noble metal transition element is supported, the transpiration component containing the non-noble metal transition element is easily evaporated from the catalyst component. Therefore, the exhaust gas that has passed through the catalyst carrier includes a transpiration component containing a non-transition metal element.
In the exhaust gas purifying apparatus of the present invention, the porous body that adsorbs the transpiration component is disposed on the downstream side of the exhaust gas flow channel with respect to the catalyst carrier. The transpiration component can be adsorbed by the material. Therefore, in the exhaust gas purification apparatus, it is possible to prevent the transpiration component including the non-noble metal transition element from being released into the atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the structure of the exhaust gas purification apparatus concerning Example 1. FIG. Explanatory drawing (a) which shows the whole catalyst carrier concerning Example 1, (b) which shows a mode that the cross section of the radial direction of the catalyst carrier was expanded partially. Explanatory drawing (a) which shows the whole porous body concerning Example 1, and explanatory drawing (b) which shows a mode that the cross section of the radial direction of the porous body was expanded partially. Explanatory drawing which shows the structure of the conventional exhaust gas purification apparatus.

Next, a preferred embodiment of the present invention will be described.
The exhaust gas purification apparatus contains the catalyst carrier and the porous body.
The catalyst support is formed by supporting a catalyst component containing a non-noble metal transition element on a honeycomb structure.
The catalyst component is a catalyst for purifying exhaust gas containing a non-noble metal transition element, and may be a transition metal, a transition metal alloy, or an oxide containing a transition metal element. As the catalyst component, an oxidation catalyst capable of oxidizing and purifying HC, CO, NO _{x and the} like contained in the exhaust gas can be used.

  Examples of the non-noble metal transition element include one or more selected from Cu, Co, Fe, W, Nb, Mo, Ni, Mn, Cr, and the like.

Preferably, the catalyst component contains at least one selected from Cu, Co, Ni, and Mn (Claim 4).
In this case, the catalyst carrier can exhibit excellent exhaust gas purification performance, and a transpiration component containing Cu, Co, Ni, or Mn can be adsorbed by the porous body. Further, transpiration of Cu and / or CuO is particularly likely to occur from a catalyst component containing Cu having a low melting point. Therefore, when a catalyst component containing Cu is used, the above-described significance of disposing the porous body on the downstream side of the exhaust gas passage becomes even more remarkable.
Examples of the catalyst component containing the transition metal element include transition metals, transition metal alloys, transition metal oxides, transition metal oxide solid solutions, and composite oxides of transition metals and other metals.

  The honeycomb structure may be made of, for example, cordierite ceramics and the like, and may have porous cell walls arranged in a polygonal lattice shape and a large number of polygonal cells surrounded by the cell walls. .

  The porous body adsorbs the transpiration component containing the transition metal element transpiration from the catalyst component of the catalyst carrier. As the porous body, a porous body that adsorbs transpiration components can be used.

The porous body is preferably formed by supporting at least one adsorbent selected from zeolite, mesoporous silica, and silica gel on a honeycomb structure.
In this case, the adsorptivity of the transpiration component in the porous body can be improved. Moreover, an increase in pressure loss can be prevented.
The honeycomb structure is made of, for example, cordierite ceramics, as in the above-described catalyst carrier, and has a porous cell wall arranged in a polygonal lattice, and a number of polygonal shapes surrounded by the cell wall. A cell having a cell can be used.

As the zeolite, for example, one having a pore diameter of 2 to 15 mm can be employed. Further, as mesoporous silica, for example, those having a pore diameter of 10 to 150 mm can be employed.
When these pore diameters are below the lower limit, the pore volume becomes too small and the amount of adsorption may be reduced. Moreover, when exceeding the above-mentioned upper limit, there exists a possibility that it may become difficult to fully improve the adsorption | suction performance with respect to the said transpiration component.

The adsorbent is preferably at least one selected from A-type zeolite, L-type zeolite, β-type zeolite, Y-type zeolite, MFI, mordenite, ferrierite, and sodalite.
In this case, the adsorptivity of the transpiration component in the porous body can be further improved.

Example 1
Next, an embodiment of the exhaust gas purifying apparatus of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the exhaust gas purification apparatus 1 of this example is disposed in an exhaust pipe 61 that forms an exhaust gas passage 62 through which the exhaust gas G discharged from the internal combustion engine 6 passes.
The exhaust gas purification apparatus 1 includes a catalyst carrier 2 and 3 formed by supporting a catalyst component containing a non-noble metal transition element on a honeycomb structure, and a non-noble metal transition element evaporated from the catalyst component of the catalyst carrier 2 and 3. And a porous body 4 that adsorbs the transpiration component. In the exhaust pipe 61, the porous body 4 is arranged on the downstream side of the exhaust gas passage 62 with respect to the catalyst carriers 2 and 3.

Hereinafter, the exhaust gas purification apparatus 1 of this example will be described in detail.
As shown in FIG. 1, the exhaust gas purification apparatus 1 of this example includes two catalyst carriers 2 and 3 in an exhaust pipe 61. When these two catalyst carriers are respectively referred to as a first catalyst carrier 2 and a second catalyst carrier 3, the first catalyst carrier 2 is upstream of the second catalyst carrier 3 in the exhaust pipe, that is, an internal combustion engine. It is arranged on the side close to 6.

  As shown in FIGS. 1, 2A and 2B, each of the first catalyst support 2 and the second catalyst support 3 is a cylindrical honeycomb (diameter φ103 mm × length L105 mm) made of cordierite ceramics. The structures 20 and 30 carry copper oxide as the catalyst components 25 and 35. In this example, the catalyst components 25 and 35 are supported on the honeycomb structures 20 and 30 together with a binder made of alumina.

  The honeycomb structures 20 and 30 have porous cell walls 21 and 31 arranged in a hexagonal lattice shape, and a large number of hexagonal cells 22 and 32 surrounded by the cell walls 21 and 31. The honeycomb structures 20 and 30 each have 600 cells 22 and 32 per square inch, and the thickness of the cell walls 21 and 31 is 3.5 mil (mil is 1/1000 inch). In the first catalyst carrier 2 and the second catalyst carrier 3, the catalyst components 25 and 35 are supported on at least the cell walls 21 and 31 of the honeycomb structures 20 and 30.

  Further, as shown in FIG. 3, the porous body 4 carries zeolite (β-type zeolite) as the adsorbent 45 on a honeycomb structure 40 having a cylindrical shape (diameter φ103 mm × length L105 mm) made of cordierite ceramics. It becomes. In this example, the adsorbent 45 is supported on the honeycomb structure 40 together with a binder made of silica.

  The honeycomb structure 40 has the same shape as the honeycomb structures 20 and 30 of the catalyst supports 2 and 3, and is surrounded by porous cell walls 41 arranged in a hexagonal lattice, and the cell walls 41. A large number of hexagonal cells 42 are provided. The honeycomb structure 40 has 400 cells 42 per square inch, and the thickness of the cell wall 41 is 4 mil (mil is 1/1000 inch). In the porous body 4, the adsorbent 45 is supported on at least the cell walls 41 of the honeycomb structure 40.

  Further, as shown in FIG. 1, in the exhaust gas purification apparatus 1 of this example, in order to evaluate the adsorption performance of the transpiration component containing the non-noble metal transition element (Cu) by the porous body 4, the porous material in the exhaust gas flow channel 62 is used. A non-noble metal transition element trap 5 for detecting breakthrough is further provided on the downstream side of the body 4.

  As shown in FIG. 3, the non-noble metal transition element trap 5 has the same configuration as the porous body 4 except for the dimensions. In other words, the non-noble metal transition element trap 5 is formed by supporting the same adsorbent 55 as the porous body 4 on a cylindrical honeycomb structure 50 (diameter φ103 mm × length L50 mm) made of cordierite ceramics. The honeycomb structure 50 in the non-noble metal transition element trap 5 is surrounded by the porous cell walls 51 arranged in a hexagonal lattice shape and the cell walls 51 in the same manner as the honeycomb structure 40 of the porous body 4 described above. A large number of hexagonal shaped cells 52 are provided. The honeycomb structure 50 has 400 cells 52 per square inch, and the thickness of the cell wall 51 is 4 mil (mil is 1/1000 inch). In the non-noble metal transition element trap 5, the adsorbent 55 is supported on at least the cell wall 51 of the honeycomb structure 50.

  As shown in FIG. 1, in the exhaust gas purification apparatus 1, the first catalyst carrier 2, the second catalyst carrier 3, the porous body 4, and the non-noble metal transition element trap 5 for breakthrough detection are respectively in this order. The exhaust gas channel 62 is disposed from the upstream side to the downstream side. Therefore, the exhaust gas G discharged from the internal combustion engine 6 includes the first catalyst carrier 2, the second catalyst carrier 3, the porous body 4, and the non-noble metal transition element trap 5 for breakthrough detection in this order. Passes through the muffler 68 and is discharged from the tail pipe 69.

Next, the manufacturing method of the exhaust gas purification apparatus 1 of this example is demonstrated.
First, the first catalyst carrier 2 and the second catalyst carrier 3 are prepared as follows (see FIG. 2).
In producing the first catalyst carrier 2, copper oxide as the catalyst component 21 is dispersed in water, and alumina sol as a binder is further added and dispersed. Thereby, a catalyst slurry is obtained. Next, a honeycomb structure (diameter φ103 mm × length L105 mm, cell wall thickness: 3.5 mil, number of cells: 600 / square inch) 20 is immersed in the catalyst slurry and pulled up. Then, the catalyst slurry applied to the honeycomb structure 20 is dried and heated. Thereby, the first catalyst carrier 2 is obtained. In this example, copper oxide was used as a catalyst component. However, any catalyst containing non-noble metal transition elements whose exhaust gas purifying ability, that is, purifying ability for HC, CO, and NOx has been confirmed can be applied. It is.
Further, in the production of the second catalyst carrier 3 of this example, the second catalyst carrier 3 can be constructed by performing the same operation as that of the first catalyst carrier 2 described above.

Next, the porous body 4 and the non-noble metal transition element trap 5 are respectively produced as follows (see FIG. 3).
In producing the porous body 4, first, 200 g of zeolite (Beta type zeolite HSZ-980HOA manufactured by Tosoh Corporation, pore diameter of about 9 mm) as the adsorbent 45 is weighed and added to 1000 ml of pure water for 30 minutes. Stir. Next, milling is performed for 3 hours using a zirconia ball having a diameter of 20 mm and a pot mill made of zirconia to obtain a zeolite slurry. To this zeolite slurry, 100 g of binder (Snowtex O, manufactured by Nissan Chemical Industries, Ltd., particle size 10 to 20 nm, solid ratio 20%) is added and stirred for 1 hour. Next, a honeycomb structure (diameter φ103 mm × length L105 mm, cell wall thickness: 4 mil, number of cells: 400 / square inch) 40 is immersed in the slurry and pulled up. Thereby, 110 g of the adsorbent and the binder are supported on the honeycomb structure 40 (of which 10 g of the binder). Then, the slurry applied to the honeycomb structure 40 is dried and fired at a temperature of 600 ° C. for 2 hours in an air atmosphere. Thereby, the porous body 4 is obtained.

  Further, in producing the non-noble metal transition element trap 5 of this example, the same operation as that of the porous body 4 described above was performed except that a honeycomb structure having a diameter of 103 mm and a length of L50 mm was used. A non-noble metal transition element trap 5 can be constructed.

  Next, as shown in FIG. 1, the first catalyst carrier 2, the second catalyst carrier 3, the porous body 4, and the breakage are formed in the exhaust pipe 61 of the internal combustion engine 6 in order from the upstream side of the exhaust gas passage 62. A non-noble metal transition element trap 5 for overdetection is arranged. Thereby, the exhaust gas purification apparatus 1 of this example can be constructed.

Next, the effect of the exhaust gas purifying apparatus of this example will be described.
As shown in FIGS. 1 and 2, the exhaust gas purification apparatus 1 of the present example includes catalyst carriers 2 and 3 in which catalyst components 25 and 35 containing non-noble metal transition elements are supported on honeycomb structures 20 and 30. . Therefore, in the catalyst carriers 2 and 3, HC, CO, NOx and the like contained in the exhaust gas G can be purified by the catalyst components 25 and 35.

  In the catalyst carriers 2 and 3 on which the catalyst components 25 and 35 containing the non-noble metal transition element are supported, the transpiration component containing the non-noble metal transition element easily evaporates from the catalyst components 25 and 35. Therefore, the exhaust gas G that has passed through the catalyst carriers 2 and 3 contains a transpiration component containing a non-transition metal element.

  In the exhaust gas purifying apparatus 1 of this example, the porous body 4 that adsorbs the transpiration component is disposed on the downstream side of the exhaust gas passage 62 with respect to the catalyst carriers 2 and 3. Therefore, even if a transpiration component evaporates in the exhaust gas G, the transpiration component can be adsorbed by the porous body 4. Therefore, in the exhaust gas purification apparatus 1 of this example, it is possible to prevent the transpiration component containing the non-noble metal transition element from being released into the atmosphere.

Actually, in the exhaust gas purification apparatus 1 of this example, the transpiration component was detected by ICP analysis for the porous body 4 and the non-noble metal transition element trap 5 arranged further downstream thereof.
Specifically, first, an endurance test equivalent to 150,000 miles of an actual vehicle was performed on the exhaust gas purification apparatus 1 of this example shown in FIG. Next, the porous body 4 and the non-noble metal transition element trap 5 were taken out and pulverized. Each pulverized product was put in an alumina pot mill having a capacity of 5 L, sealed, and stirred at 60 rpm for 1 hour. Next, each pulverized product was taken out from the pot mill and weighed 0.05 g. The weighed portion was dissolved in acid and diluted with 50 ml of pure water. Thereafter, ICP analysis was performed using an ICP analyzer (ICPS-7510) manufactured by Shimadzu Corporation.
As a result, Cu was detected from the pulverized product of the porous body 4, and about 3 g of Cu was adsorbed on the porous body 4. On the other hand, Cu was not detected from the ground product of the non-noble metal transition element trap 5.

  Therefore, in the exhaust gas purification apparatus 1 of this example, it can be understood that the release of the transpiration component containing the non-noble metal transition element into the atmosphere can be prevented while using the non-noble metal transition element (Cu) as the catalyst component. In this example, as the non-noble metal transition element, a catalyst component containing Cu that has a particularly low melting point and is likely to evaporate is used. In this case as well, the porous component 4 can sufficiently adsorb the transpiration component containing Cu. I understand.

(Example 2)
Next, in this example, instead of the copper oxide of Example 1 as the catalyst component to be supported on the first catalyst support and the second catalyst support, cobalt oxide, nickel oxide, and manganese oxide, respectively, A first catalyst carrier and a second catalyst carrier were constructed, and exhaust gas purification apparatuses were constructed using these catalyst carriers. These exhaust gas purification devices can be produced in the same manner as the exhaust gas purification device of Example 1 except that the catalyst component is changed.

In the exhaust gas purifying apparatus of this example, as in Example 1, the transpiration component adsorbed on the porous body and the non-noble metal transition element trap was detected by ICP analysis.
As a result, in the catalyst purification apparatus using the catalyst carrier carrying cobalt oxide, about 0.3 g of Co was detected from the porous body, but Co was not detected from the non-noble metal transition element trap.
Further, in the catalyst purification apparatus using the catalyst carrier carrying nickel oxide, about 0.2 g of Ni was detected from the porous body, but Ni was not detected from the non-noble metal transition element trap.
Further, in the catalyst purification apparatus using the catalyst carrier carrying manganese oxide, about 0.9 g of Mn was detected from the porous body, but Mn was not detected from the non-noble metal transition element trap.

  Thus, even if various non-noble metal transition elements that may evaporate in the exhaust gas are used as catalyst components, the transpiration containing the non-noble metal transition elements can be achieved by disposing the porous body downstream as in this example. It can be seen that the components can be adsorbed and the release of transpiration components into the atmosphere can be prevented.

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification apparatus 2 Catalyst support body (1st catalyst support body)
3 Catalyst carrier (second catalyst carrier)
4 Porous body 5 Non-noble metal transition element trap 6 Internal combustion engine 61 Exhaust pipe 62 Exhaust gas flow path

Claims (4)

An exhaust gas purification apparatus disposed in an exhaust pipe that forms an exhaust gas passage through which exhaust gas discharged from an internal combustion engine passes,
A catalyst support formed by supporting a catalyst component containing a non-noble metal transition element on a honeycomb structure, and a porous body that adsorbs the transpiration component containing the non-noble metal transition element evaporated from the catalyst component of the catalyst support; Have
In the exhaust pipe, the exhaust gas purifying apparatus is characterized in that the porous body is disposed on the downstream side of the exhaust gas flow path with respect to the catalyst carrier.   2. The exhaust gas purification apparatus according to claim 1, wherein the porous body has at least one adsorbent selected from zeolite, mesoporous silica, and silica gel supported on a honeycomb structure. .   The exhaust gas purifying apparatus according to claim 2, wherein the adsorbent is at least one selected from A-type zeolite, L-type zeolite, β-type zeolite, Y-type zeolite, MFI, mordenite, ferrierite, and sodalite. An exhaust gas purification apparatus characterized by that.   The exhaust gas purification apparatus according to any one of claims 1 to 3, wherein the catalyst component contains at least one selected from Cu, Co, Ni, and Mn.

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