JP3667365B2 - Exhaust purification device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an exhaust emission control device capable of efficiently adsorbing and desorbing hydrocarbons in engine exhaust gas.
[0002]
[Prior art]
As a method for purifying exhaust gas from an automobile engine, there is a method using a ternary catalyst device that supports a noble metal such as platinum or rhodium as a catalyst. In this case, the hydrocarbon (HC) in the exhaust gas generally requires a catalyst activation temperature of 350 ° C. However, when the engine is started, hydrocarbons are hardly purified because the catalyst device is at a low temperature and therefore does not reach the catalyst activation temperature.
[0003]
Therefore, in order to cope with this, an exhaust purification device has been proposed in which a catalyst device is disposed in the exhaust passage of the engine, and an adsorption device for adsorbing unburned hydrocarbons at the time of engine start is provided downstream of the catalyst device. (Japanese Patent Laid-Open No. 4-31618).
[0004]
An adsorbent is disposed in the adsorption device. When the engine is started, exhaust gas discharged from the catalyst device is introduced into the adsorption device to adsorb the hydrocarbons. On the other hand, when the exhaust gas temperature of the engine rises, the introduction of exhaust gas into the adsorption device is stopped. Then, the hydrocarbons adsorbed by the adsorption device are released and returned to the upstream side of the catalyst device for purification in the catalyst device.
As an adsorbent for adsorbing hydrocarbons in exhaust gas, a zeolite adsorbent has been proposed because of its excellent hydrocarbon adsorption performance.
[0005]
[Problems to be solved]
However, the conventional exhaust purification device has the following problems.
That is, hydrocarbons in the exhaust gas are distributed in a wide range from low molecular weights such as methane and ethylene to high molecular weights such as toluene.
Therefore, for example, in the case of a zeolitic adsorbent having a crystal structure with a large pore diameter such as 7 to 9 mm (angstrom), the hydrocarbon adsorption power is large for a hydrocarbon having a relatively large molecular weight such as toluene. However, it is small for relatively small molecular weight hydrocarbons such as methane.
[0006]
The reason for this is considered that the zeolite adsorbent having a large pore diameter mainly adsorbs hydrocarbons having a large molecular weight, and thus hardly adsorbs hydrocarbons having a small molecular weight.
On the other hand, in the case of a zeolitic adsorbent having a crystal structure with a small pore diameter of 4 to 6 mm, hydrocarbons having a relatively large molecular weight cannot be adsorbed because they cannot enter the pores. Adsorbed.
[0007]
In the above conventional example, the adsorption device is arranged in parallel with the exhaust passage. Therefore, when releasing the hydrocarbon adsorbed by the adsorption device, a means such as heating is required separately. In addition, a reflux pump is required to return the released hydrocarbons to the upstream side of the catalyst device. Therefore, the cost is high.
[0008]
In view of the conventional problems, the present invention is intended to provide a low-cost exhaust purification apparatus that can efficiently adsorb and desorb hydrocarbons in exhaust gas.
[0009]
[Means for solving problems]
The present invention includes a first flow path having a catalyst device for purifying engine exhaust gas,
A second flow path located downstream of the first flow path;
An adsorption device disposed in the second flow path for adsorbing unburned hydrocarbons;
A discharge path located downstream of the adsorption device and the second flow path;
A flow path switching valve for introducing exhaust gas into the adsorption device or the second flow path;
A return flow path having a one-way valve for returning hydrocarbons desorbed in the adsorption device to the upstream side of the catalyst device together with a part of exhaust gas;
And, the above adsorber possess relatively a large molecular adsorption layer for adsorbing hydrocarbons of a large molecular weight, for adsorbing hydrocarbons of a relatively small molecular weight small molecules adsorbing layer,
An exhaust gas purification apparatus characterized in that hydrocarbons of the large molecule adsorption layer are desorbed on the upstream side and then hydrocarbons of the small molecule adsorption layer are desorbed on the downstream side when desorbing the hydrocarbons. It is in.
[0010]
What should be noted most in the present invention is that the adsorbing device is disposed in the second flow path, the return flow path is provided with the one-way valve, and the adsorbing apparatus is the large molecule adsorbing layer. And a small molecule adsorbing layer.
In the present invention, the catalyst system is platinum - rhodium catalysts, for example, NO _X in the exhaust gas, HC, use those provided with the three-way catalyst capable of simultaneously purifying CO.
[0011]
The adsorbing device is disposed in a second flow channel located downstream of the catalyst device. Therefore, the adsorption device is entirely or partially exposed to the exhaust gas flowing in the second flow path, and can receive the heat in the exhaust gas.
The return channel is provided between the adsorption device and the upstream side of the catalyst device. This return flow path is provided with a one-way valve that returns hydrocarbons desorbed by the adsorption device only to the upstream side of the catalyst device together with some exhaust gas, and does not cause a gas flow in the opposite direction.
[0012]
This one-way valve operates only when hydrocarbons adsorbed by the adsorption device are desorbed and opens. This operation is performed by, for example, an engine control ECU after the exhaust gas temperature, a predetermined time has elapsed after the engine is started, or the like.
When the one-way valve is opened, hydrocarbons and a part of the exhaust gas are introduced upstream of the catalytic device and do not flow backward to the opposite side.
[0013]
The flow path switching valve is an on-off valve for leading exhaust gas to the exhaust path through the adsorption device when the engine is started and exhausting the exhaust gas to the exhaust path through the second flow path when the adsorbed hydrocarbon is desorbed. . This flow path switching valve is arranged on the downstream side (FIG. 1) or upstream side (FIG. 4) of the adsorption device or in the middle part thereof.
[0014]
Next, the adsorption apparatus has a large molecule adsorption layer for adsorbing hydrocarbons having a relatively large molecular weight and a small molecule adsorption layer for adsorbing hydrocarbons having a relatively small molecular weight. Here, relatively large molecular weight hydrocarbons are hydrocarbons such as toluene and xylene, while relatively small molecular weight hydrocarbons are hydrocarbons such as methane, ethane, ethylene, and propylene.
[0015]
Of course, the large molecule adsorption layer and the small molecule adsorption layer do not adsorb only the large molecule and small molecule hydrocarbons. Adsorbed to either. If necessary, an intermediate molecular adsorption layer for adsorbing hydrocarbons having an intermediate molecular weight can be provided as described later.
[0016]
For example, a zeolitic adsorbent having a large pore diameter of 6 to 9 mm is disposed in the large molecule adsorption layer. On the other hand, a zeolitic adsorbent having a small pore diameter of, for example, 3 to 6 mm is disposed in the small molecule adsorption layer. For example, a zeolite-based adsorbent having an intermediate pore diameter of 5 to 7 mm is disposed in the intermediate molecule adsorption layer.
[0017]
The large molecule adsorption layer and the small molecule adsorption layer are preferably arranged along the flow direction of the exhaust gas (FIGS. 1 and 2). Thereby, large, small, and molecular weight hydrocarbons of exhaust gas can be adsorbed sequentially and efficiently.
Moreover, it is preferable to arrange the large molecule adsorbing layer so as to be positioned upstream of the small molecule adsorbing layer when desorbing the adsorbed hydrocarbons (FIGS. 1 and 3).
[0018]
In this case, hydrocarbons with large molecular weight are first desorbed on the upstream side, and then hydrocarbons with small molecular weight are desorbed on the downstream side, so that the hydrocarbons desorbed on the upstream side again become the adsorbent on the downstream side. It is not adsorbed. Therefore, hydrocarbons can be desorbed with certainty.
[0019]
Next, the large molecule adsorption layer and the small molecule adsorption layer are laminated in a direction perpendicular to the exhaust gas flow in the adsorption apparatus, and the large molecule adsorption layer is arranged on the side in direct contact with the exhaust gas. It can also be set as the structure which is. In this case, since the large molecule adsorption layer is arranged on the side directly connected to the exhaust gas, at the time of desorption, the large molecular weight hydrocarbon adsorbed on the large molecule adsorption layer is first desorbed, and then the small molecule adsorption is performed. Small molecular weight hydrocarbons adsorbed on the layer are desorbed. Therefore, hydrocarbon desorption is performed smoothly.
[0020]
Further, the adsorption device has one or a plurality of intermediate molecular adsorption layers for adsorbing hydrocarbons having a relatively intermediate molecular weight between the large molecule adsorption layer and the small molecule adsorption layer. Is preferred. In this case, hydrocarbons can be efficiently adsorbed and desorbed efficiently according to the molecular weight in each adsorbing layer.
[0021]
[Action and effect]
In the exhaust emission control device of the present invention, the exhaust gas discharged from the engine first enters the catalyst device provided in the first flow path, and then enters the second flow path. When starting the engine, the flow path switching valve is operated to introduce the entire amount of exhaust gas into the adsorption device.
[0022]
As a result, hydrocarbons in the exhaust gas are adsorbed in the adsorption device such that relatively large molecular weight hydrocarbons are adsorbed on the large molecule adsorption layer and relatively small molecular weight hydrocarbons are adsorbed on the small molecule adsorption layer. Exhaust gas with adsorbed hydrocarbons is discharged from the adsorber to the discharge path.
[0023]
On the other hand, when the exhaust gas flowing out from the catalyst device rises to a temperature higher than the catalyst activation temperature for hydrocarbon purification in the catalyst device, for example, 350 ° C. or higher, the above-mentioned flow path switching valve is operated to exhaust gas to the adsorption device. The introduction is stopped and the exhaust gas is discharged from the second flow path to the discharge path.
[0024]
Next, the one-way valve is opened, and the return flow path between the adsorption device and the upstream side of the catalyst device is communicated. Thereby, a part of the exhaust gas flows from the adsorption device to the upstream side of the catalyst device via the one-way valve. Since this exhaust gas has already reached a high temperature, the hydrocarbon adsorbed by the adsorption device is desorbed and transferred to the upstream side of the catalyst device. The hydrocarbons transferred to the upstream side of the catalyst device enter the catalyst device together with the exhaust gas from the engine, and are decomposed and purified into carbon dioxide gas and water in the catalyst device that has already reached a high temperature, via the second flow path. It is discharged to the discharge path.
[0025]
As described above, in the present invention, hydrocarbons having a relatively large molecular weight and hydrocarbons having a relatively small molecular weight are adsorbed on the large molecule adsorption layer or the small molecule adsorption layer, respectively, and desorbed as described above. Therefore, all hydrocarbons can be efficiently adsorbed and desorbed regardless of the molecular weight.
[0026]
Further, since the adsorption device is disposed in the second flow path, it is possible to always receive the heat of the exhaust gas from the second flow path even when the exhaust gas temperature rises after the engine is started. .
Therefore, the temperature of the adsorption device rises rapidly compared to the case where the adsorption device is arranged outside the second flow path.
[0027]
Therefore, at the time of desorption of hydrocarbons, hydrocarbons can be efficiently desorbed within a short time from the adsorption device.
Further, the desorbed hydrocarbon and a part of the exhaust gas are automatically returned to the upstream side of the catalyst device by the one-way valve, so that a recirculation pump and its power are not required. Therefore, the cost of the exhaust purification device is also low.
[0028]
As described above, according to the present invention, hydrocarbons in exhaust gas can be efficiently adsorbed and desorbed, and a low-cost exhaust purification device can be provided.
[0029]
【Example】
Example 1
An exhaust emission control device according to an embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the exhaust purification apparatus of the present example includes a first flow path 21 that includes a catalyst device 15 that purifies exhaust gas from the engine 12, and a second flow path that is located downstream of the first flow path 21. It has a flow path 22 and an adsorption device 3 that is disposed inside the second flow path 22 and adsorbs unburned hydrocarbons in the engine.
[0030]
Further, the adsorption device 3, a discharge passage 24 located downstream of the second flow path 22, a flow path switching valve 26 for introducing exhaust gas into the adsorption apparatus 3 or the second flow path 22, and the adsorption A return flow path 25 having a one-way valve 42 is provided for returning hydrocarbons desorbed in the apparatus 3 to the upstream side of the catalyst apparatus 15 together with some exhaust gas.
Further, as shown in FIGS. 1 to 3, the adsorption device 3 includes a large molecule adsorption layer 31 for adsorbing hydrocarbons having a relatively large molecular weight and a small molecule for adsorbing hydrocarbons having a relatively small molecular weight. And an adsorbing layer 32.
[0031]
These will be described in detail below.
The flow path switching valve 26 is disposed in the second flow path 22 so as to be openable and closable at the rear end of the adsorption device 3. The flow path switching valve 26 is connected to an actuator 41 operated by the engine control unit ECU. The actuator 41 is connected to a surge tank 711 via a negative pressure pipe 45 and an electromagnetic valve 451.
[0032]
The ECU is electrically connected to a water temperature sensor for detecting the temperature of engine cooling water, an exhaust temperature sensor for detecting the exhaust gas temperature in the second flow path, and the like.
Further, the return flow path 25 opens to the downstream side of the adsorption device 3. The one-way valve 42 is interposed in the middle of the return flow path 25 and is electrically connected to the ECU. In FIG. 1, reference numeral 11 is a surge tank, and 13 is an exhaust manifold.
[0033]
Next, as shown in FIG. 2, the adsorption device 3 includes an unsupported layer having no adsorbent on the upstream side of the exhaust gas, the large molecule adsorption layer 31 in the central portion, and the downstream side of the exhaust gas. Has a small molecule adsorption layer 32. That is, the adsorption device 3 is a ceramic honeycomb structure, and includes a large number of lattice portions 35 and a large number of square pore passages 36 formed therebetween. As shown in FIG. 3, the large-molecule adsorbing layer 31 and the small-molecule adsorbing layer 32 are sequentially provided along the exhaust gas flow on the inner wall of the pore passage 36 as described above.
[0034]
Next, the function and effect will be described.
In the exhaust purification apparatus of this example, as shown in FIG. 1, the exhaust gas discharged from the engine 12 first enters the catalyst device 15 provided in the first flow path 21 and then enters the second flow path 22. When the engine is started, the flow path switching valve 26 is operated, the downstream side of the second flow path 22 is closed, and the entire amount of exhaust gas is introduced into the adsorption device 3.
[0035]
As a result, the hydrocarbons in the exhaust gas are adsorbed by the adsorption device 3 such that a relatively large molecular weight hydrocarbon is adsorbed on the large molecule adsorption layer 31 and a relatively small molecular weight hydrocarbon is adsorbed on the small molecule adsorption layer 32. Exhaust gas having adsorbed hydrocarbons is discharged from the adsorber 3 to the discharge path 24.
[0036]
On the other hand, when the temperature of the exhaust gas flowing out from the catalyst device rises and the exhaust gas temperature in the second flow path 22 rises to, for example, around 350 ° C., this is detected by the exhaust temperature sensor, and the actuator 41 is operated by the ECU. . Thus, the flow path switching valve 26 is operated to close the downstream side of the adsorption device 3 (solid line in FIG. 1), and exhaust gas is discharged from the second flow path 22 to the discharge path 24.
[0037]
In parallel with the operation of the flow path switching valve 26, the one-way valve 42 is opened by the ECU so that the return flow path 25 between the adsorption device 3 and the upstream side of the catalyst device 15 is communicated. As a result, a part of the exhaust gas flows from the adsorption device 3 to the upstream side of the catalyst device 15 via the one-way valve 42, and the reverse flow on the opposite side does not occur. Since the exhaust gas has already reached a high temperature, the hydrocarbon adsorbed by the adsorption device 3 is desorbed and transferred to the upstream side of the catalyst device 15.
[0038]
The hydrocarbons transferred to the upstream side of the catalyst device 15 enter the catalyst device 15 together with the exhaust gas from the engine 12, and are decomposed and purified into carbon dioxide gas and water in the catalyst device 15 that has already reached a high temperature. Further, in the catalyst device 13, NO _x , CO, and HC in the exhaust gas from the engine 15 are also purified. The purified exhaust gas is discharged to the discharge path 24 through the second flow path 22.
[0039]
As described above, in the present invention, hydrocarbons having a relatively large molecular weight and hydrocarbons having a relatively small molecular weight are adsorbed to the large molecule adsorption layer 31 or the small molecule adsorption layer 32, respectively. Therefore, all hydrocarbons can be adsorbed efficiently and desorbed efficiently regardless of the molecular weight.
[0040]
Further, since the adsorption device 3 is disposed in the second flow path 22, the heat of the exhaust gas can always be received from the second flow path 22 even in the process of increasing the exhaust gas temperature.
Therefore, the temperature of the adsorption device 3 rises more rapidly than when the adsorption device 3 is arranged outside the second flow path 22.
[0041]
Therefore, at the time of desorption of hydrocarbons, the hydrocarbons can be efficiently desorbed from the adsorption device 3 within a short time.
The desorbed hydrocarbons and some exhaust gases are automatically returned to the upstream side of the catalyst device 15 by the one-way valve 42, and no flow in the opposite direction occurs. Therefore, a reflux pump and its power are not required. Therefore, the cost of the exhaust purification device is also low.
[0042]
At the time of the adsorption, as shown in FIG. 3B, the adsorption amount of relatively high molecular weight hydrocarbons sequentially increases in the large molecule adsorption layer with time (curve 314), and the small molecule adsorption layer. , The amount of adsorption of relatively low molecular weight hydrocarbons gradually increases (curve 324).
[0043]
Example 2
This example shows a specific example in which adsorption and desorption of hydrocarbons are performed using the exhaust purification apparatus shown in the first embodiment.
In this example, the adsorber used was a cordierite honeycomb structure. The large molecule adsorption layer 31 and the small molecule adsorption layer 32 were separately formed on the honeycomb structure. The honeycomb structures provided with the unsupported layer 30, the large molecule adsorbing layer 31, and the small molecule adsorbing layer 32 were connected in series as shown in FIGS.
[0044]
The large molecule adsorption layer 31 and the small molecule adsorption layer 32 were formed by immersing each honeycomb structure in a slurry composed of zeolite powder, silica sol, and water and drying.
The zeolite powder used was MHSZ-765 with a pore diameter of 8 mm for the large molecule adsorption layer and MHSZ-420 (manufactured by UPO) with a pore diameter of 6 mm for the small molecule adsorption layer.
[0045]
Next, as shown in Example 1, the adsorption apparatus was assembled in an exhaust purification apparatus, and exhaust gas purification, hydrocarbon adsorption and desorption were measured.
The adsorption rate of hydrocarbons in the adsorber was measured by comparing the hydrocarbon concentration in the exhaust gas discharged for 40 seconds immediately after the engine was started before and after the adsorber 3.
[0046]
As a result, when the large molecule adsorption layer 31 and the small molecule adsorption layer 32 were provided as in this example, the hydrocarbon adsorption rate for the 40 seconds was 73%.
On the other hand, as a comparative example, when the small molecule adsorption layer 32 is continuously provided in the small molecule adsorption layer 32 and the small molecule adsorption layer 32 is not provided, the adsorption rate of 64% is reduced. When only two molecular adsorption layers 32 were provided in succession, the adsorption rate was 65%.
[0047]
As described above, according to this example, a wide range of molecular weight hydrocarbons can be adsorbed with high efficiency.
Further, since the adsorption device 3 is provided in the second flow path 22 when desorbing hydrocarbons, desorption can be performed with high efficiency and in a short time.
[0048]
Example 3
In this example, as shown in FIG. 4, the order of the large molecule adsorption layer 31 and the small molecule adsorption layer 32 in the adsorption device 3 is changed, and a flow path switching valve 26 is provided on the upstream side of the adsorption device 3.
What is important in this example is that the large molecule adsorbing layer 31 is arranged so as to be positioned upstream of the small molecule adsorbing layer 32 when the adsorbed hydrocarbon is desorbed.
That is, in this example, the small molecule adsorption layer 32 is provided upstream of the exhaust gas of the adsorption device 3, and the large molecule adsorption layer 31 is provided downstream. A flow path switching valve 26 is provided to open and close the upstream side of the adsorption device 3.
[0049]
The flow path switching valve 26 is connected to the actuator 44. The actuator 44 has a negative pressure pipe 45 connected to the surge tank 11 on the intake side of the engine 12. The negative pressure pipe 45 has an electromagnetic valve 451 operated by the ECU.
[0050]
The return channel 25 is provided with a one-way valve 46 similar to that of the first embodiment. The one-way valve 46 has an opening / closing valve 461 that opens and closes the return passage. The on-off valve 461 is connected to the negative pressure pipe 45 through an electromagnetic valve 47 for controlling communication of negative pressure to the on-off valve 461.
Others are the same as in the first embodiment.
[0051]
In this example, when adsorbing hydrocarbons, the flow path switching valve 26 is operated, the upstream side of the second flow path 22 is closed, and the entire amount of exhaust gas is introduced into the adsorption device 3. As a result, the exhaust gas hydrocarbons are adsorbed to the small molecule adsorption layer 32 and the large molecule adsorption layer 31, respectively, as in the first embodiment.
[0052]
Next, when desorbing hydrocarbons, the solenoid valve 451 of the negative pressure pipe 45 is opened according to a command from the ECU, and the actuator 44 and the flow path switching valve 26 are operated using the load of the surge tank 11. Then, the upstream side of the adsorption device 3 is closed. Then, the exhaust gas is discharged from the second flow path 22 to the discharge path 24.
[0053]
Further, the one-way valve 46 is opened via the electromagnetic valve 47 and the on-off valve 461 using the negative pressure of the surge tank 11 in the same manner as described above. As a result, a part of the exhaust gas is introduced into the adsorption device 3 from the downstream side of the adsorption device 3, and the exhaust gas is returned to the upstream side of the catalyst device 15 through the return channel 25.
[0054]
At this time, the exhaust gas enters the large molecule adsorption layer 31 from the exhaust passage 24, desorbs the large molecular weight hydrocarbons therein, and then desorbs the small molecular weight hydrocarbons from the small molecule adsorption layer 32. , And transferred to the upstream side of the catalyst device 15.
Others are the same as in the first embodiment.
Also in this example, the same effect as that of the first embodiment can be obtained.
[0055]
Example 4
In this example, as shown in FIGS. 5 and 6, the arrangement of the large molecule adsorption layer and the small molecule adsorption layer in the adsorption apparatus will be described.
That is, in the adsorption apparatus of this example, the large molecule adsorption layer 310 and the small molecule adsorption layer 320 are stacked in a direction orthogonal to the flow of the exhaust gas. Further, the large molecule adsorption layer 310 is arranged so as to be in direct contact with the exhaust gas. That is, in the honeycomb structure of the adsorption device, the small molecule adsorption layer 320 is further supported on the surface of the lattice portion 35 and the large molecule adsorption layer 310 is supported thereon.
[0056]
In this example, as shown in FIG. 6B, with a lapse of time, relatively high molecular weight hydrocarbons are sequentially adsorbed to the large molecule adsorption layer 310 (curve 315), and the small molecule adsorption layer 320 has a relatively high molecular weight. The hydrocarbons are sequentially adsorbed (curve 316). On the other hand, at the time of desorption, first the large molecular weight hydrocarbons adsorbed on the large molecule adsorption layer 310 are desorbed, and then the small molecular weight hydrocarbons adsorbed on the small molecule adsorption layer 320 are desorbed.
Others are the same as in the first embodiment, and the same effects as in the first embodiment can be obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an exhaust emission control device according to a first embodiment.
2 is a partially cutaway perspective view of the suction device according to Embodiment 1. FIG.
3 is an explanatory diagram of a large molecule adsorption layer, a small molecule adsorption layer, and a hydrocarbon adsorption state in Example 1. FIG.
FIG. 4 is an explanatory diagram of an exhaust purification device according to a third embodiment.
FIG. 5 is a cross-sectional view of a main part of an adsorption device according to a fourth embodiment.
6 is an explanatory diagram of a large molecule adsorption layer, a small molecule adsorption layer, and a hydrocarbon adsorption state in Example 4. FIG.
[Explanation of symbols]
11. . . engine,
15. . . Catalytic equipment,
21. . . First flow path,
22. . . Second flow path,
24. . . Discharge path,
25. . . Return flow path,
26. . . Flow path switching valve,
3. . . Adsorption device,
31, 310. . . Large molecule adsorption layer,
32, 320. . . Small molecule adsorption layer,
42. . . One-way valve,

Claims (2)

A first flow path having a catalyst device for purifying engine exhaust gas;
A second flow path located downstream of the first flow path;
An adsorption device disposed in the second flow path for adsorbing unburned hydrocarbons;
A discharge path located downstream of the adsorption device and the second flow path;
A flow path switching valve for introducing exhaust gas into the adsorption device or the second flow path;
A return flow path having a one-way valve for returning hydrocarbons desorbed in the adsorption device to the upstream side of the catalyst device together with a part of exhaust gas;
And, the above adsorber possess relatively a large molecular adsorption layer for adsorbing hydrocarbons of a large molecular weight, for adsorbing hydrocarbons of a relatively small molecular weight small molecules adsorbing layer,
An exhaust gas purification apparatus characterized in that hydrocarbons of the large molecule adsorption layer are desorbed on the upstream side and then hydrocarbons of the small molecule adsorption layer are desorbed on the downstream side when desorbing the hydrocarbons. .   2. The large molecule adsorbing layer and the small molecule adsorbing layer according to claim 1, wherein the large molecule adsorbing layer and the small molecule adsorbing layer are laminated in a direction orthogonal to the exhaust gas flow in the adsorption device, and the large molecule adsorbing layer is arranged on the side in direct contact with the exhaust gas. An exhaust emission control device characterized by that.

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