JPH0985049A - Apparatus for purifying exhaust gas of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively purify an HC component having a property especially easy to form ozone among HC components contained in exhaust gas. SOLUTION: A first HC adsorbent 5 consisting of Y-type zeolite of which the silica-alumina ratio is set to 80 or more having excellent adsorbability to an HC component high in ozone productivity, a second HC adsorbent 6 consisting of β-type zeolite high in the holding capacity of an HC component and converting the HC component high in the productivity of ozone to an HC component low in the productivity of ozone and an exhaust gas purifying catalyst 4 are arranged on the upstream side of an exhaust system composed of the exhaust pipe 2 of an engine 1 in this order.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying device for purifying HC components and the like contained in engine exhaust gas.

[0002]

2. Description of the Related Art Conventionally, as shown in, for example, Japanese Unexamined Patent Publication (Kokai) No. 5-59941, an HC composed of Y-type zeolite or the like in which a large number of pores having a large pore size are formed in an upstream portion of an exhaust system.
An exhaust gas purifying apparatus for an engine has been proposed in which an adsorbent is provided and an HC adsorbent made of ZSM-5 or the like in which a large number of small pores having small pore sizes are formed in a downstream portion of an exhaust system. ing.

In the above exhaust gas purifying apparatus, the HC component having a large molecular diameter is adsorbed by the HC adsorbent in the upstream portion,
By adsorbing the HC component having a small molecular size to the HC adsorbent on the downstream side, the pores of the HC adsorbent on the downstream side are converted into HC.
It is prevented from being blocked by the component to improve the HC adsorbing performance of the HC component, and further, the HC component in the exhaust gas is effectively purified by a three-way catalyst or the like arranged downstream of the HC adsorbent. Is configured.

[0004]

When the HC adsorbent having a small pore size and the HC adsorbent having a large pore size are arranged in the upstream and downstream portions of the exhaust system as described above, Is
Of the HC components, those that have the property of easily generating ozone,
For example, even if an olefin such as ethylene or an aroma such as xylene can be temporarily adsorbed to the HC adsorbent in the upstream portion, its holding power is weak, so that the three-way catalyst is not activated sufficiently before activation. At the stage, the HC component having a property of easily generating ozone is desorbed and released from the HC adsorbent in the upstream portion.

Since the HC adsorbent in the downstream portion composed of ZSM-5 or the like has a low adsorbability for the HC component having a property of easily generating ozone, the adsorbent passes directly through the HC adsorbent and is installed in the installation portion of the three-way catalyst. However, there is a problem that the three-way catalyst is not sufficiently purified and it is impossible to prevent the three-way catalyst from being discharged into the atmosphere.

The present invention has been made in view of the above points, and among the HC components contained in the exhaust gas, particularly the HC components having a property of easily generating ozone are effectively purified, and An exhaust gas purifying apparatus capable of reducing the amount of the above-mentioned HC components discharged into the exhaust gas purifying apparatus.

[0007]

The invention according to claim 1 is
An exhaust gas purification device installed in an exhaust system of an engine, wherein HC having a high ozone generation rate is arranged in order from the upstream side of the exhaust system.
A first HC adsorbent having excellent adsorptivity for components,
A second HC adsorbent, which has a high retention of HC components and a function of converting HC components having a high ozone production rate into HC components having a low production rate and releasing the ozone, and an exhaust gas purification catalyst are provided. It is a thing.

According to this structure, among the HC components in the exhaust gas discharged immediately after the engine is started, the HC component having a high ozone generation rate is effectively adsorbed by the first HC adsorbent in the upstream portion. Become. Then, the HC component having a high ozone generation rate desorbed from the first HC adsorbent at the desorption temperature of the HC component is adsorbed by the second HC adsorbent in the downstream portion, and then ozone is generated. It is converted into HC components having a low rate and discharged.

According to a second aspect of the present invention, in the exhaust gas purifying apparatus for an engine according to the first aspect, the first HC adsorbent is superior to C _{2 to} C ₄ olefins and C _{7 to} C ₉ aromas. It is made of a material having adsorptivity.

According to this structure, among the HC components in the exhaust gas discharged immediately after the engine is started, the above C _{2 to} C ₄ olefin and C having the property of easily generating ozone.
_After the HC component such as _7- C ₉ aroma is effectively adsorbed by the upstream first HC adsorbent, ozone is generated when the first HC adsorbent reaches the desorption temperature of the HC component. The above C _{2 to} C ₄ olefins and C having easy properties
HC components such as _{7 to} C ₉ aroma are desorbed from the first HC adsorbent and are led out to the downstream second HC adsorbent installation portion.

According to a third aspect of the present invention, in the engine exhaust gas purifying apparatus according to the first aspect, the first HC adsorbent is made of Y-type zeolite having a Cavan ratio of 80 or more.

According to this structure, the above-mentioned Cavern ratio is 80.
Since the Y-type zeolite set above has excellent adsorbability for the HC component having a high ozone generation rate,
Of the HC components in the exhaust gas discharged immediately after the engine is started, the HC components having a high ozone generation rate are effectively adsorbed by the first HC adsorbent made of the Y-type zeolite.

[0014] The invention according to claim 4 is the above-mentioned claims 1-3.
In the exhaust gas purifying apparatus for an engine according to any one of items 1 to 5, the second HC adsorbent is composed of β-type zeolite.

According to this constitution, the β-type zeolite is
The C component has a high holding power, and also has a function of converting ozone having a high production rate of ozone into HC component having a low production rate and releasing the same. Therefore, the desorption from the first HC adsorbent is performed. After the HC component having a high ozone generation rate is adsorbed and held by the second HC adsorbent made of β zeolite, it is converted into the HC component having a low ozone generation rate and discharged.

According to a fifth aspect of the present invention, there is provided an exhaust gas purifying device installed in an exhaust system of an engine, wherein the exhaust system has an HC adsorbent having excellent adsorbability for HC components having a high ozone production rate. And an electrically heated catalyst disposed downstream thereof, and the electrically heated catalyst is heated when it is confirmed that the HC adsorbent has reached the desorption temperature of the HC component having a low ozone generation rate. The control means for setting the state is provided.

According to this structure, among the HC components in the exhaust gas discharged immediately after the engine is started, the HC components having a high ozone generation rate are effectively adsorbed by the HC adsorbent. Then, the HC adsorbent reaches the desorption temperature of the HC component having a low ozone generation rate, and the HC component desorbed from the HC adsorbent is discharged after being purified by the electric heating catalyst.

According to a sixth aspect of the present invention, in the engine exhaust gas purifying apparatus according to the fifth aspect, the HC adsorbent is made of Y-type zeolite having a Cavan ratio of 80 or more.

According to this structure, the above-mentioned Caban ratio is 80.
In the exhaust gas discharged immediately after the engine is started, the Y-type zeolite set above has pores of various pore sizes and has excellent adsorbability for HC components with a high ozone generation rate. HC with high ozone generation rate
The components are effectively adsorbed and retained by the HC adsorbent composed of the Y-type zeolite. Then, among the HC components adsorbed on the HC adsorbent, the HC components having a low ozone generation rate are desorbed from the HC adsorbent at an early stage and purified by the electric heating catalyst.

According to a seventh aspect of the present invention, in the exhaust gas purifying apparatus for an engine according to the fifth or sixth aspect, an exhaust gas purifying catalyst is arranged downstream of the electrically heated catalyst.

According to the above construction, the exhaust gas purifying catalyst is heated and activated early by the heat generated when the HC component having a low ozone generation rate is purified by the electrically heated catalyst.

[0021]

1 shows an embodiment of an exhaust gas purifying apparatus for an engine according to the present invention. This exhaust gas purifying apparatus includes an exhaust pipe 2 connected to an engine 1, an adsorbent case 3 installed at an upstream portion of an exhaust system including the exhaust pipe 2, and an exhaust gas purifying device disposed downstream of the adsorbent case 3. In the adsorbent case 3, a first HC adsorbent 5 is disposed upstream of the adsorbent case 3, and a second HC adsorbent 6 is disposed downstream of the adsorbent case 3.

The first HC adsorbent 5 has a Cavan ratio of 8
It is composed of Y-type zeolite (USY) set to 0 or more. In the Y-zeolite having the Cayvan ratio set to 80 or more, fine pores having various pore sizes are formed, and among the HC components in the exhaust gas, H having a high ozone generation rate as described below.
It has excellent adsorbability for the C component and low adsorbability for the HC component having a low ozone generation rate.

That is, as shown in Table 1 below, among various HC components, methane (CH ₄ ) and ethane (CH ₃ )
C _{1 to} C ₂ paraffins (saturated chain hydrocarbons having the general formula of C _n H _{2n + 2} ) consisting of CH ₃ ) have a low ozone production coefficient (g ozone / g NMOG) and a low ozone production rate. And ethylene (CH ₂ = CH ₂ ), propylene (C
H ₃ CH = CH ₂₎ and 1-butene clogging ethyl ethylene _{(CH 3 CH 2 CH = CH} 2) of the C ₂ -C ₄ consisting of olefins (C _n H having a double bond represented by _2n unsaturated hydrocarbons It is known that hydrogen, that is, an alkene, has a small ozone generation coefficient and a high ozone generation rate.

Among various HC components, pentane [CH ₃ (CH ₂ ) ₃ CH═CH ₂ ], hexane [CH
₃ (CH ₂ ) ₄ CH = CH ₂ ], heptane [CH ₃ (CH ₂ )]
₅ CH = CH ₂ ] and octane [CH ₃ (CH ₂ ) ₆ CH
= And paraffins C ₅ -C ₈ consisting of CH _2], benzene C ₆ consisting of (C ₆ H ₆₎ Aroma (aromatic hydrocarbon having a benzene ring, i.e. arene) and has a low ozone generation rate , And toluene or methylbenzene (C ₆ H ₅
CH ₃ ) and ethylbenzene (C ₆ H ₅ C ₂ H ₃ ) aroma of C _{6 to} C ₈ and xylene [C ₆ H ₄ (C
H _{3) 2],} ethyl methyl benzene clogging ethyl toluene (C ₉ C _12), the aroma consisting trimethylbenzene (C ₉ C _12), it is known that high ozone generation rate.

[0025]

[Table 1]

The Y-type zeolite having a Cavan ratio of 80 or more is a C ₂ -C ₄ olefin composed of propylene or the like among the HC components and a C ₇ -C ₉ composed of toluene, xylene and trimethylbenzene. It has been confirmed by experiments that the adsorption rate for the HC component having a high ozone production rate, which is composed of the aroma of, is high. That is, H consisting of Y-type zeolite with a Cavern ratio set to 80
The data shown in FIG. 2 was obtained by an experiment for measuring the amount of the HC component adsorbed on the C adsorbent, and the C _{2 to} C ₄ olefin and the C _{7 to} C ₉ aroma were the above HC adsorption. It has been confirmed that the agent is efficiently adsorbed.

The second HC adsorbent 6 is composed of β-type zeolite (PQB) in which a large number of substantially oval pores having different vertical and horizontal caliber are formed. This β-type zeolite is
As shown in FIG. 3, it has been confirmed by experiments that the adsorption rate for HC components such as propylene and toluene having a high ozone production rate is high.

Further, the β-type zeolite converts the HC component having a high ozone production rate, which is made of triethylbenzene, into the HC component having a low production rate, which is made of methylbenzene. It has also been confirmed by experiments that it has a function of converting the component into an HC component composed of ethylbenzene having a relatively low ozone production rate and releasing the HC component.

The exhaust gas purifying catalyst 4 has excellent purifying performance for HC components and has an activation temperature of 2
A catalyst component composed mainly of palladium (Pd) set at a low temperature of about 50 ° C., to which a noble metal such as platinum (Pt) or rhodium (Rh) is added, is used as a catalyst component. It is formed by being supported on a honeycomb carrier made of a duerite ceramic material or the like. The honeycomb carrier may have a structure in which a platinum-rhodium-based three-way catalyst is mainly supported.

In the above structure, a large amount of the HC component discharged immediately after the start of the engine 1 is first adsorbed by the first HC adsorbent 5 arranged upstream of the HC adsorbent case 2. The first HC adsorbent 5 has excellent adsorbability for HC components having a high ozone production rate among the HC components and low adsorbability for HC components having a low ozone production rate. Therefore, as shown in FIG. 4, the HC component having a low ozone generation rate is desorbed and begins to be released at an early stage after the engine is started, and at the time t1 when a predetermined time has elapsed, the HC component having a high ozone generation rate is released. Will be desorbed and be released.

HC desorbed from the first HC adsorbent 5
The component is a second component arranged downstream of the HC adsorbent case 2.
It is adsorbed by the HC adsorbent 6. Since the second HC adsorbent 6 has a high HC component holding force, as shown in FIG. 5, the HC component begins to desorb at a time point t2 when a considerable time has elapsed after the engine 1 was started. In addition, the second HC
The HC components having a high ozone production rate, such as triethylbenzene and methylethylbenzene, which are adsorbed by the adsorbent 6, are converted into HC components having a low production rate, and the ozone components, such as benzene and ethylbenzene, are released.

At the time t2 when the HC component is released from the second HC adsorbent 6, the exhaust gas purifying catalyst 4 is sufficiently activated, so that the HC component desorbed from the second HC adsorbent 6 is After being reliably purified by the exhaust gas purifying catalyst 4, it is discharged into the atmosphere.

As described above, from the upstream side of the exhaust passage 2, the first HC adsorbent 5 made of Y-type zeolite and the second HC adsorbent 6 made of β-type zeolite whose Cavan ratio is set to 80 or more are arranged in order from the upstream side. Since a gas purifying catalyst 4 is provided, a large amount of HC is discharged immediately after the engine 1 is started.
The component can be adsorbed to and retained by the first HC adsorbent 5, and the HC component desorbed from the first HC adsorbent 5 can be adsorbed and retained by the second HC adsorbent 6.

Therefore, before the exhaust gas purifying catalyst 4 is activated, both the first HC adsorbent 5 and the second HC adsorbent 6 are saturated, so that the HC component in the exhaust gas is Until the exhaust gas purifying catalyst 4 is activated, the HC component is prevented from passing through the installation portion of the exhaust gas purifying catalyst 4, and the first HC adsorbent 5 or the second H adsorbs the HC component.
By making the C adsorbent 6 hold the C adsorbent 6, it is possible to effectively prevent the HC component from being discharged into the atmosphere.

A conventional apparatus in which the first and second HC adsorbents 5 and 6 are not provided, and a first HC adsorbent 5 and β consisting of the above Y-type zeolite having a Cavern ratio set to 80
An experiment for measuring the amount of HC component discharged into the atmosphere was conducted in the apparatus according to the embodiment of the present invention in which the second HC adsorbent 6 made of type zeolite is provided, and the following data are obtained. It was

That is, in the above-mentioned conventional apparatus, it is inevitable that a large amount of exhaust gas is released into the atmosphere immediately after the engine 1 is started, as shown by the broken line in FIG. In the apparatus according to the embodiment, since the HC component starts to be desorbed from the second HC adsorbent 6 after the exhaust gas purification catalyst 4 is activated, the HC component is surely purified, and as shown by the solid line in FIG. It was confirmed that the emission amount of the HC component released from the gas purification catalyst 4 into the atmosphere can be significantly reduced.

And, the Y-type zeolite constituting the first HC adsorbent 5 and having the Cavern ratio set to 80 or more is:
Since pores having various diameters are formed, it has excellent adsorbability for C _{2 to} C ₄ olefins and C _{7 to} C ₉ aromas having a high ozone production rate. Therefore, it is possible to effectively adsorb a large amount of the HC component having a high ozone generation rate immediately after the engine 1 is started and effectively prevent the HC component from being discharged into the atmosphere. .

As shown in FIG. 7, the adsorption amount of propylene (C ₃ olefin) adsorbed on the first HC adsorbent 5 made of the Y-type zeolite increases as the Caban ratio of the Y-type zeolite increases. Therefore, by setting the above-mentioned Cayvan ratio to 80 or more, C _{2 to} C ₄ made of propylene or the like having a high ozone generation rate.
Can effectively adsorb the olefins. In addition,
As shown in FIG. 8 and FIG. 9, the adsorption amount of toluene and xylene (aroma of C _{7 to} C ₈ ) adsorbed on the first HC adsorbent 5 made of Y-type zeolite does not change so much depending on the size of the Cayvan ratio. There is a relationship.

Further, β constituting the second HC adsorbent 6
The type zeolite has a large number of substantially elliptical pores with different vertical and horizontal diameters, so it can effectively adsorb various HC components and has a high holding power for the HC components once adsorbed. It has a function of adsorbing the HC component desorbed from the first HC adsorbent 5 to the first HC adsorbent 6 and holding it for a long period of time. Therefore, before the exhaust gas purification catalyst 4 is activated, the second HC adsorbent 6
It is possible to reliably prevent the occurrence of a situation in which the HC component is desorbed from the exhaust gas and passes through the installation portion of the exhaust gas purification catalyst 4 as it is.

Further, the β-zeolite has a function of converting HC components such as triethylbenzene and methylethylbenzene having a high ozone production rate into ozone components having a low production rate, respectively, and releasing ozone composed of benzene and ethylbenzene and the like. have. Therefore, by configuring the second HC adsorbent 6 with the β-type zeolite, it is possible to effectively reduce the amount of the HC component having a high ozone generation rate into the atmosphere.

FIG. 10 shows another embodiment of the exhaust gas purifying apparatus for the engine 1 according to the present invention. This exhaust gas purifying apparatus comprises an HC adsorbent 7 made of Y-type zeolite (USY) having a Cavan ratio set to 80 or more, an electric heating catalyst (EHC) 8 installed on the downstream side, and an electric heating catalyst (EHC) 8 on the downstream side. An exhaust gas purifying catalyst 4 provided, a control means 9 for controlling the electrically heated catalyst 8 and a first O ₂ sensor 1 for detecting the oxygen concentration of the exhaust gas discharged from the engine 1.
0 and a second O ₂ sensor 11 for detecting the oxygen concentration of the exhaust gas derived from the HC adsorbent 7 are provided.

The electric heating catalyst 8 is brought into a heating state by electric power supplied from a power source (not shown).
And a catalyst component 13 mainly composed of palladium or the like which is activated at a low temperature, and the catalyst component 13 is heated by the electric heater 12 to be activated.

The control means 9 controls the oxygen concentration of the upstream side of the HC adsorbent 7 detected by the first O ₂ sensor 10 and the downstream side of the HC adsorbent 7 detected by the _second O ₂ sensor 11. When it is confirmed that the oxygen concentration in the downstream side of the HC adsorbent 7 is lower than that in the upstream side, the HC adsorbent 7 removes HC components having a low ozone generation rate. It is configured to output a control signal for determining that the temperature has become the separated temperature and bringing the electrically heated catalyst 8 into a heating state.

In the above structure, a large amount of the HC component discharged immediately after the engine 1 is started is first adsorbed by the HC adsorbent 7 arranged in the upstream portion of the exhaust system. This HC adsorbent 7 is composed of a Y-type zeolite having excellent adsorbability for HC components having a high ozone production rate among the HC components and low adsorbability for HC components having a low ozone production rate. As shown in FIG. 11, since the HC component having a low ozone generation rate starts to be desorbed at an early stage t0 after the engine is started, the ozone generation rate is High H
The C component will start to desorb.

The control means 9 indicates that the HC component having a low ozone production rate has started to desorb from the HC adsorbent 7.
At the time point t0 confirmed in step 1, a control signal for heating the electric heater 12 of the electric heating catalyst 8 is output,
As shown in FIG. 12, the temperature of the electrically heated catalyst 8 (EHC) rises and the catalyst component 13 is activated.

When the catalyst component 13 of the electrically heated catalyst 8 is activated, the HC desorbed from the HC adsorbent 7 is discharged.
The components are purified by the catalyst component 13, and
The heat generated during the purification of the HC component is transferred to the exhaust gas purification catalyst 4 to activate the exhaust gas purification catalyst 4, and as shown in FIG. 13, the purification rate of the HC component by the exhaust gas purification catalyst 4 is increased. Will rise.

As described above, the exhaust system has a Caban ratio of 80.
H consisting of Y-type zeolite (USY) set above
Since the C adsorbent 7 is disposed and the electric heating catalyst 8 is disposed downstream of the C adsorbent 7, the HC component having a high ozone generation rate out of the HC components in the exhaust gas discharged immediately after the engine 1 is started. By adsorbing to the adsorbent 7, it is possible to effectively prevent the HC component having a high ozone generation rate from being discharged into the atmosphere.

Then, the first and second O ₂ sensors 10,
At the time t0 when it is confirmed by the control means 9 that the HC adsorbent 7 has reached the desorption temperature of the HC component having a low ozone generation rate according to the detection signal of 11, the electrically heated catalyst 9 is discharged.
Since it is configured to be in a heating state, the HC component having a low ozone production rate desorbed from the HC adsorbent 7 can be effectively purified by the electric heating catalyst 9, and the ozone production rate discharged thereafter is It is possible to purify high-HC components and prevent these HC components from being discharged into the atmosphere.

In particular, as shown in the embodiment, when the exhaust gas purifying catalyst 4 is disposed downstream of the electrically heated catalyst 9, this occurs when the electrically heated catalyst 9 purifies the HC component. The heat can heat the exhaust gas purifying catalyst 4 to activate it early. Therefore, at the time point t1 when the HC adsorbent 7 reaches the desorption temperature of the HC component having a high ozone generation rate, the exhaust gas purification catalyst 4 can be sufficiently activated, whereby the ozone generation rate is high. It is possible to surely purify the HC component and effectively prevent the HC component from being released into the atmosphere.

That is, in the conventional apparatus in which the HC adsorbent 7 and the electrically heated catalyst 8 are not provided, a large amount of exhaust gas is released into the atmosphere immediately after the engine 1 is started, as shown by the broken line in FIG. However, in the embodiment of the present invention in which the HC adsorbent 7 and the electric heating catalyst 8 are provided, the exhaust gas purifying catalyst is formed before the HC component having a high ozone generation rate is desorbed. Since 4 can be activated, as shown by the solid line in FIG.
The exhaust gas purifying catalyst 4 can surely purify the HC component to effectively prevent the HC component having a high ozone generation rate from being discharged into the atmosphere.

Further, in the above-described embodiment, since the pores having various diameters are formed, C having a high ozone generation rate is formed.
_{Since the} HC adsorbent 7 is composed of a Y-type zeolite having excellent adsorptivity for _{2 to} C ₄ olefins and C _{7 to} C ₉ aromas, that is, a Y type zeolite having a Cavan ratio of 80 or more, The HC adsorbent 7 effectively adsorbs a large amount of the above-mentioned HC component having a high ozone generation rate immediately after the start-up of the engine and can effectively prevent the HC component from being discharged into the atmosphere. is there.

The HC adsorbent 7 and the electric heating catalyst 8 are used.
A secondary air supply means such as an air pump for supplying secondary air is provided in the exhaust passage between and, and when the HC adsorbent 7 reaches the desorption temperature of the HC component having a low ozone generation rate,
At the same time that the electrically heated catalyst 8 is brought into a heated state, the secondary air supply means is driven to supply the secondary air between the HC adsorbent 7 and the electrically heated catalyst 8 to generate the ozone. It may be configured to promote the purification of the HC component having a low rate.

Further, in the above embodiment, the first and second
Although it is configured to determine whether or not the HC adsorbent 7 has reached the desorption temperature of the HC component having a low ozone generation rate according to the detection signals of the O ₂ sensors 10 and 11, instead of this configuration, According to the detection signal of the temperature sensor that detects the temperature of the HC adsorbent 7, the HC adsorbent 7 has a low ozone generation rate.
It may be configured to determine whether or not the component desorption temperature has been reached.

Further, as shown in FIG. 1, the adsorbent case 3
The electrically heated catalyst 8 is provided between the installation portion of the first HC adsorbent 5 and the second HC adsorbent 6 which is disposed therein, and the installation portion of the exhaust gas purification catalyst 4 which is disposed downstream thereof. The structure may be arranged.

[0055]

As described above, according to the present invention, in order from the upstream side of the exhaust system, the first HC adsorbent having excellent adsorbability for HC components having a high ozone generation rate and the holding power for the HC components are provided. Immediately after the engine is started because the second HC adsorbent having the function of converting the HC component having a high ozone generation rate to the HC component having a low ozone generation rate and releasing the HC component having a high ozone generation rate and the exhaust gas purifying catalyst are disposed. C discharged in large quantities
_A HC component having a high ozone generation rate, which is composed of an olefin of _{2 to} C ₄ and an aroma of C _{7 to} C ₉ , etc., is adsorbed and held by the first and second HC adsorbents, whereby the HC component is released into the atmosphere. There is an advantage that it can be effectively prevented from being discharged.

Of the above HC components adsorbed by the second HC adsorbent, HC composed of triethylbenzene, methylethylbenzene or the like and having a high ozone generation rate.
As for the components, ozone composed of benzene and ethylbenzene, for example, is converted into HC components having a low production rate and released, so that the emission of the HC components having a high ozone production rate to the atmosphere is effectively reduced. can do.

Further, an HC adsorbent having excellent adsorbability for HC components having a high ozone generation rate is arranged on the upstream side of the exhaust system, and an electric heating catalyst is arranged on the downstream side thereof, When it is confirmed that the HC adsorbent has reached the desorption temperature of the HC component with a low ozone generation rate, if the electrically heated catalyst is configured to be in a heating state, it is discharged immediately after the engine is started. By effectively adsorbing the HC component having a high ozone generation rate among the HC components in the exhaust gas to the HC adsorbent, it is possible to effectively prevent the HC component having a high ozone generation rate from being discharged into the atmosphere. You can

When it is confirmed that the HC adsorbent has reached the desorption temperature of the HC component having a low ozone production rate, the electrically heated catalyst is brought into a heated state, and thus the H
The HC component having a low ozone generation rate desorbed from the C adsorbent can be effectively purified by the electric heating catalyst, and the catalyst can be activated early and then the HC
There is an advantage that the HC component having a high ozone generation rate desorbed from the adsorbent can be effectively purified.

[Brief description of drawings]

FIG. 1 is an overall explanatory view showing an embodiment of an exhaust gas purification device according to the present invention.

FIG. 2 is a graph showing the adsorption amount of each HC component adsorbed by the first HC adsorbent.

FIG. 3 is a graph showing an adsorption amount of each HC component adsorbed by a second HC adsorbent.

FIG. 4 is a time chart showing a change state of the discharge amount of the HC component desorbed from the first HC adsorbent.

FIG. 5 is a time chart showing changes in the amount of HC component released from the second HC adsorbent.

FIG. 6 is a time chart showing changes in the amount of HC components discharged from the exhaust gas purifying catalyst.

FIG. 7 is a graph showing the relationship between the Cayban ratio of Y-type zeolite and the amount of propylene adsorbed.

FIG. 8 is a graph showing the relationship between the Cayban ratio of Y-type zeolite and the adsorption amount of toluene.

FIG. 9 is a graph showing the relationship between the Cayvan ratio of Y-type zeolite and the amount of xylene adsorbed.

FIG. 10 is an overall explanatory view showing another embodiment of the exhaust gas purification device according to the present invention.

FIG. 11 is a time chart showing a change state of the discharge amount of the HC component desorbed from the HC adsorbent.

FIG. 12 is a time chart showing how the temperature of the electrically heated catalyst changes.

FIG. 13 is a time chart showing changes in the purification rate of the exhaust gas purification catalyst.

FIG. 14 is a time chart showing changes in the amount of HC components discharged from the exhaust gas purifying catalyst.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 engine 2 exhaust pipe (exhaust system) 4 exhaust gas purification catalyst 5 first HC adsorbent 6 second HC adsorbent 7 HC adsorbent 8 electric heating catalyst 9 control means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location F01N 3/24 ZAB B01D 53/36 102H (72) Inventor Yuki Kokuda Shinchu, Fuchu-cho, Aki-gun, Hiroshima Prefecture No. 3 in Mazda Co., Ltd. (72) Inventor Satoshi Ichikawa No. 3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd.

Claims (7)

[Claims] 1. An exhaust gas purifying apparatus installed in an exhaust system of an engine, which has excellent adsorbability for HC components having a high ozone generation rate in order from the upstream side of the exhaust system.
An HC adsorbent, and a second HC adsorbent having a high retention of HC components and a function of converting HC components having a high ozone production rate into HC components having a low production rate and releasing the same.
An exhaust gas purifying apparatus for an engine, comprising an exhaust gas purifying catalyst. 2. The engine according to claim 1, wherein the first HC adsorbent is made of a material having excellent adsorbability for C _{2 to} C ₄ olefins and C _{7 to} C ₉ aromas. Exhaust gas purification device. 3. The exhaust gas purifying apparatus for an engine according to claim 1, wherein the first HC adsorbent is made of Y-type zeolite having a Cavan ratio set to 80 or more. 4. The engine exhaust gas purifying apparatus according to claim 1, wherein the second HC adsorbent is composed of β-type zeolite. 5. An exhaust gas purifying apparatus installed in an exhaust system of an engine, wherein the exhaust system comprises HC having a high ozone generation rate.
An HC adsorbent having excellent adsorptivity for the components is arranged, and an electric heating catalyst is arranged downstream thereof, and the HC adsorbent has a desorption temperature of the HC component having a low ozone generation rate. An exhaust gas purifying apparatus for an engine, comprising control means for bringing the electrically heated catalyst into a heated state when it is confirmed. 6. The exhaust gas purifying apparatus for an engine according to claim 5, wherein the HC adsorbent is composed of Y-type zeolite having a Cavan ratio set to 80 or more. 7. The exhaust gas purifying apparatus for an engine according to claim 5, wherein an exhaust gas purifying catalyst is arranged downstream of the electrically heated catalyst.