JP2012172522A - Exhaust emission control device for hybrid vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device for a hybrid vehicle capable of efficiently and sufficiently purifying HC in an exhaust gas discharged immediately after start of drive of an internal combustion engine.SOLUTION: The exhaust emission control device 1 used in the hybrid vehicle comprising an engine (internal combustion engine) 10 and a motor as driving sources has an electrothermal type catalyst carrier 3 disposed in an exhaust passage 12 of the engine 10 for carrying a catalyst for purifying exhaust gas, and capable of heating by energization for heating the catalyst carrier 3 preliminary before start of drive of the engine 10 to a predetermined temperature or higher. An HC adsorber 2 comprising an HC adsorbent for adsorbing HC in the exhaust gas is disposed on the upstream side of the catalyst carrier 3 in the exhaust passage 12. The HC adsorbent includes zeolite as the main component, and has an HC desorption peak temperature of 180°C or higher.

Description

  The present invention relates to an exhaust gas purifying apparatus for a hybrid vehicle for purifying exhaust gas discharged from an internal combustion engine.

2. Description of the Related Art Conventionally, there is known an exhaust gas purifying apparatus for a hybrid vehicle in which an electrically heated catalyst carrier that carries an exhaust gas purifying catalyst is disposed in an exhaust passage of an internal combustion engine.
For example, in Patent Document 1, when switching from driving by a motor to driving by an internal combustion engine, the catalyst carrier is preheated before starting the internal combustion engine to activate the catalyst, and the exhaust gas purification efficiency immediately after the internal combustion engine is started. An exhaust gas purification device for a hybrid vehicle that enhances the power consumption is disclosed.

  However, the exhaust gas immediately after starting the internal combustion engine contains a large amount of HC (hydrocarbon) which is a harmful component. Therefore, when exhaust gas containing such high-concentration HC flows into the catalyst carrier, the HC in the exhaust gas is sufficiently purified even if the catalyst carrier is preheated and the catalyst is activated. Without passing through the catalyst carrier. That is, HC in the exhaust gas discharged immediately after the internal combustion engine is started cannot be sufficiently purified.

  Thus, Patent Documents 2 to 5 disclose exhaust gas purification apparatuses in which an HC adsorbent such as zeolite is disposed on the upstream side of an electrically heated catalyst carrier. According to these, immediately after starting the internal combustion engine, the HC in the exhaust gas is once adsorbed on the upstream HC adsorbent, and then the HC desorbed from the HC adsorbent due to the temperature rise of the exhaust gas is supported on the downstream catalyst. It can be purified in the body. These exhaust gas purification devices are not applied to hybrid vehicles, but are considered to be applicable to hybrid vehicles as well.

JP-A-8-338235 JP-A-5-31359 JP-A-9-94433 Japanese Patent Laid-Open No. 11-81997 Japanese Patent Laid-Open No. 11-81999

However, even if the techniques disclosed in Patent Documents 2 to 5 are applied to the exhaust gas purification apparatus for a hybrid vehicle disclosed in Patent Document 1, the above-described problems cannot be solved.
That is, the techniques disclosed in the above Patent Documents 2 to 5 are such that HC in the exhaust gas is once adsorbed to the upstream HC adsorbent immediately after the start of the internal combustion engine. The material has a very low temperature (HC desorption peak temperature) at which the desorption amount of adsorbed HC is the largest at around 100 ° C.

  Therefore, when the HC adsorbent becomes around 100 ° C. as the temperature of the exhaust gas rises, the adsorbed HC is quickly desorbed and liquefied at a low temperature, that is, the catalyst has a low reactivity and is difficult to purify. It will flow into the carrier. Then, even if the catalyst carrier is preheated to bring the catalyst into an active state, HC in the exhaust gas passes through the catalyst carrier without being sufficiently purified. That is, the above-described problem cannot be solved.

  The present invention has been made in view of such problems, and intends to provide an exhaust gas purifying apparatus for a hybrid vehicle that can efficiently and sufficiently purify HC in exhaust gas discharged immediately after starting an internal combustion engine. Is.

The present invention is used in a hybrid vehicle equipped with an internal combustion engine and a motor as a drive source, and an exhaust gas of the internal combustion engine is provided with an electrically heated catalyst carrier that carries an exhaust gas purifying catalyst and can be heated by energization. An exhaust gas purifying device arranged in a passage and configured to preheat the catalyst carrier to a predetermined temperature or higher before starting the internal combustion engine;
An HC adsorbent comprising an HC adsorbent that adsorbs HC in the exhaust gas is disposed upstream of the catalyst carrier in the exhaust passage,
The HC adsorbent is in an exhaust gas purifying apparatus for a hybrid vehicle, characterized by having zeolite as a main component and an HC desorption peak temperature of 180 ° C. or higher (Claim 1).

  The exhaust gas purification device is used in a hybrid vehicle, and is configured to heat the catalyst carrier in advance to a predetermined temperature or higher before starting the internal combustion engine. The HC adsorbent is disposed upstream of the catalyst carrier, and the HC adsorbent in the HC adsorbent is mainly composed of zeolite and has an HC desorption peak temperature of 180 ° C. or higher. It is. As a result, it is possible to efficiently and sufficiently purify HC in the exhaust gas discharged immediately after starting the internal combustion engine.

  Specifically, a large amount of HC contained in the exhaust gas discharged immediately after starting the internal combustion engine is once adsorbed by the HC adsorbent of the HC adsorbent disposed upstream of the catalyst carrier. Here, the HC adsorbent mainly composed of zeolite has an HC desorption peak temperature of 180 ° C. or higher. That is, the temperature at which the desorption amount of HC adsorbed on the HC adsorbent is the largest is 180 ° C. or higher, which is very high compared to the conventional HC adsorbent.

  Therefore, HC in the exhaust gas discharged immediately after the start of the internal combustion engine can be adsorbed to the HC adsorbent for a longer time than before and to a higher temperature. As a result, HC in a liquefied state at a low temperature, that is, in a state of low reactivity and difficult to be purified, quickly desorbs from the HC adsorbent and flows into the catalyst carrier, and passes through the catalyst carrier without being sufficiently purified. Can be suppressed.

  When the temperature of the HC adsorbent becomes around the HC desorption peak temperature (temperature of 180 ° C. or higher) as the exhaust gas temperature rises, the HC adsorbed on the HC adsorbent is vaporized, that is, the reactivity is high. Detach with. Here, the catalyst carrier on the downstream side of the HC adsorbent (HC adsorbent) is heated before the internal combustion engine is started, and is in a state where the activity of the supported catalyst is enhanced. Therefore, HC desorbed from the HC adsorbent can be sufficiently purified in the downstream catalyst carrier. As a result, it is possible to efficiently and sufficiently purify HC in the exhaust gas discharged immediately after starting the internal combustion engine.

  Thus, according to the present invention, it is possible to provide an exhaust gas purification apparatus for a hybrid vehicle that can efficiently and sufficiently purify HC in exhaust gas discharged immediately after the start of the internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the structure of the exhaust gas purification apparatus in Example 1. FIG. In Example 1, (a) Explanatory drawing which shows HC adsorbent, (b) Explanatory drawing which shows the radial direction cross section of HC adsorbent. In Example 1, (a) Explanatory drawing which shows an electrically heated catalyst carrier, (b) Explanatory drawing which shows the radial direction cross section of an electrically heated catalyst carrier. The graph which shows the result of a temperature-programmed desorption test in Example 2. 10 is a graph showing the HC purification rate of each sample in Example 3. Explanatory drawing which shows the structure of the exhaust gas purification apparatus in Example 4. FIG. In Example 4, (a) Explanatory drawing which shows an additional catalyst carrier, (b) Explanatory drawing which shows the radial direction cross section of an additional catalyst carrier. In Example 5, (a) Explanatory drawing which shows HC adsorption body, (b) Explanatory drawing which shows the radial direction cross section of HC adsorption body.

The exhaust gas purification device is used in a hybrid vehicle, and when switching from driving by a motor to driving by an internal combustion engine, the catalyst carrier is preheated to a predetermined temperature or higher before starting the internal combustion engine. belongs to.
In order to keep the catalyst supported on the catalyst carrier in an active state before starting the internal combustion engine, it is preferable to heat the catalyst carrier to, for example, 300 ° C. or higher at which the activity of the catalyst is obtained. It is preferable to heat to 500 ° C. or higher.

Further, the HC adsorbent disposed on the upstream side of the catalyst carrier has an HC desorption peak temperature of 180 ° C. or higher.
When the HC desorption peak temperature of the HC adsorbent is less than 180 ° C., HC in a liquefied state at a low temperature, that is, low in reactivity and difficult to be purified, desorbs from the HC adsorbent and flows into the catalyst carrier. In addition, the catalyst carrier may pass through without being sufficiently purified.

The HC desorption peak temperature of the HC adsorbent is a temperature at which the amount of HC desorbed on the HC adsorbent is maximized.
Further, the HC desorption peak temperature of the HC adsorbent can be obtained, for example, by performing a temperature-programmed desorption test using a temperature-programmed desorption gas analyzer. Specifically, HC is adsorbed on the target HC adsorbent, and the behavior of HC desorption when the HC adsorbent is heated is analyzed by a gas chromatograph mass spectrometer (GC-MS) or the like. Can be obtained.

The HC adsorbent is preferably composed mainly of Cs-modified zeolite (claim 2).
In this case, the HC desorption peak temperature of the HC adsorbent can be reliably set to 180 ° C. or higher. Therefore, it is possible to efficiently and sufficiently purify HC in the exhaust gas discharged immediately after starting the internal combustion engine. Further, since the Cs-modified zeolite containing an alkali metal has excellent water absorption, it is possible to prevent the catalyst carrier disposed on the downstream side from being wetted.
The Cs-modified zeolite is a zeolite obtained by substituting and modifying Al, which is a constituent element of zeolite, with Cs, which is an alkali metal.

In addition, the zeolite as the main component of the HC adsorbent generally has a crystal structure formed with a three-dimensional tetrahedral structure composed of Si (silicon), Al (aluminum) and O (oxygen) as a basic unit. Have.
As the zeolite, for example, one having a structure such as medium pore (10-membered ring) MFI, FER, large pore (12-membered ring) BEA, FAU, MOR or the like can be used. Here, the number of member rings is the number of oxygen atoms contained in the ring structure.

  In addition, in the above zeolite, among the medium pore (10-membered ring) structures, the FER structure has a feature that the pores are smaller than the MFI structure and the adsorption performance of C2 class to C3 class lower HC is high. On the other hand, the MFI structure is characterized in that HC can be adsorbed in a wide range from the C3 class to the aromatic component (C7 class with a benzene ring). In addition, the MFI structure is characterized by high heat resistance because the Si / Al ratio can be kept high.

  In the above zeolite, among the structures of large pores (12-membered rings), the BEA structure has a space at the intersection in the skeletal pores, and the actual structure in the exhaust gas compared to the FAU structure and the MOR structure. It is characterized by high HC component adsorption performance. The BEA structure is characterized by high heat resistance because the Si / Al ratio can be kept high.

  Moreover, as said zeolite, what has structures, such as said medium pore (10-membered ring) and large pore (12-membered ring), can be used individually or in combination. In particular, in order to adsorb HC in a wide range, it is preferable to use a combination of a medium pore (10-membered ring) structure and a large pore (12-membered ring) structure. In particular, a combination of an MFI structure with high heat resistance and a BEA structure is preferable.

The weight of the HC adsorbent is preferably not more than the weight of the catalyst support. The weight of the HC adsorbent is more preferably ¼ or less of the weight of the catalyst support.
In this case, it is possible to prevent the heat of the exhaust gas after starting the internal combustion engine from being deprived by the heat capacity of the HC adsorbent, and the temperature of the catalyst carrier that has been heated in advance is reduced.

Moreover, a conventionally well-known structure can be employ | adopted as said catalyst carrier of an electric heating type. For example, it is possible to catalyze an energizable substrate made of a ceramic resistor such as C, SiC, Si—SiC, or MoSi ₂ , a metal foil such as a heat resistant stainless steel foil, a porous metal formed by forming a heat resistant metal by powder metallurgy, Can be used. Further, it is also possible to use a material in which a catalyst is supported on a base material made of a ceramic insulator and a resistance heating element such as a ceramic resistor or a high resistance metal wire is incorporated in the base material. Further, a honeycomb structure or the like can be used as the base material for supporting the catalyst.
Moreover, a conventionally well-known catalyst can be used as said catalyst. For example, a three-way catalyst composed of Pt, Pd, Rh, or the like can be used.

As the HC adsorbent, a substrate made of ceramic, metal, etc. having a thermal shock resistance and coated with an HC adsorbent can be used. Moreover, a honeycomb structure etc. can be used as a base material which coat | covers HC adsorption material.
In addition, as the HC adsorbent, for example, an HC adsorbent itself made of an HC adsorbent can be used. That is, the HC adsorbent itself may be an HC adsorbent.

Example 1
An exhaust gas purification apparatus for a hybrid vehicle according to an embodiment of the present invention will be described.
As shown in FIGS. 1 to 3, the exhaust gas purification apparatus 1 of this example is used in a hybrid vehicle including an engine (internal combustion engine) 10 and a motor (not shown) as drive sources, and carries a catalyst 32 for exhaust gas purification. An electrically heated catalyst carrier 3 that can be heated by energization is disposed in the exhaust passage 12 of the engine 10 so that the catalyst carrier 3 is heated to a predetermined temperature or higher in advance before the engine 10 is started. Has been.

An HC adsorbing body 2 including an HC adsorbing material 22 that adsorbs HC in the exhaust gas is disposed upstream of the catalyst carrier 3 in the exhaust passage 12.
The HC adsorbent 22 is mainly composed of zeolite and has an HC desorption peak temperature of 180 ° C. or higher.
This will be described in detail below.

As shown in FIG. 1, the exhaust gas purification apparatus 1 is used for a hybrid vehicle including an engine 10 and a motor as drive sources.
The exhaust gas purification apparatus 1 includes an electrically heated catalyst carrier 3 disposed in an exhaust passage 12 in an exhaust pipe 11 of an engine 10, and an HC adsorber 2 disposed upstream of the catalyst carrier 3. Have

As shown in FIGS. 3A and 3B, the electrically heated catalyst carrier 3 is configured by carrying a catalyst 32 for exhaust gas purification on a catalyst base 31.
As shown in FIG. 3A, the catalyst base 31 includes a partition wall 311 provided in a quadrangular lattice shape, a large number of quadrangular cells 312 surrounded by the partition walls 311, and a cylindrical outer peripheral wall covering the outer peripheral side surface. 313. The catalyst base 31 is made of a porous ceramic resistor whose main component is SiC.

As shown in FIG. 3A, a pair of electrodes 39 are provided on the outer peripheral wall 313 of the catalyst base 31. The catalyst carrier 3 is configured to heat the catalyst base 31 by energizing between the pair of electrodes 39 via the catalyst base 31.
As shown in FIG. 3B, the catalyst 32 is coated on the surface of the partition wall 311 of the catalyst base 31. The catalyst 32 is a three-way catalyst made of Pt, Rh or the like.

As shown in FIGS. 2A and 2B, the HC adsorbent 2 is configured by supporting an HC adsorbent 22 that adsorbs HC in exhaust gas on an HC adsorbing base material 21.
As shown in FIG. 2 (a), the HC adsorbing substrate 21 includes a partition wall 211 provided in a square lattice shape, a large number of square cells 212 surrounded by the partition wall 211, and a cylindrical outer periphery covering the outer peripheral side surface. A honeycomb structure having a wall 213. The HC adsorption base material 21 is made of porous ceramics mainly composed of cordierite.

  As shown in FIG. 2 (b), the HC adsorbent 22 is coated on the surface of the partition wall 211 of the HC adsorbing substrate 21. The HC adsorbent 22 is mainly composed of Cs-modified zeolite having an MFI structure. Further, the HC adsorbent 22 has an HC desorption peak temperature of 180 ° C. or higher. The Cs-modified zeolite used as the HC adsorbent 22 in this example has an HC desorption peak temperature of 205 ° C.

  As shown in FIG. 1, the exhaust gas purification apparatus 1 is configured to heat the catalyst carrier 3 in advance to a predetermined temperature or higher (300 ° C. or higher) before starting the engine 10 when switching from driving by the motor to driving by the engine 10. Has been. In this example, the catalyst carrier 3 is heated to 500 ° C. by energization before starting the engine 10 so that the catalyst 32 carried on the catalyst carrier 3 is activated when the engine 10 is started. Has been.

Next, the manufacturing method of the exhaust gas purification apparatus 1 of this example is demonstrated.
In constructing the exhaust gas purification device 1, first, the catalyst carrier 3 (FIG. 3) and the HC adsorbent 2 (FIG. 2) are produced. Next, the HC adsorbent 2 is disposed on the upstream side of the exhaust passage 12, and the electrically heated catalyst carrier 3 is disposed on the downstream side.
Thereby, the exhaust gas purification apparatus 1 (FIG. 1) of this example is constructed.

  In preparing the catalyst carrier 3, the catalyst 32 is composed of γ-alumina, ceria-zirconia composite oxide, dinitrodiammine nitrate Pt solution, rhodium chloride, and alumina sol as a binder, which are components of the catalyst 32. To prepare a catalyst slurry. Next, the catalyst base material 31 that is a honeycomb structure is immersed in the catalyst slurry, pulled up, and air blown. And the catalyst slurry apply | coated to the catalyst base material 31 is dried at 150 degreeC, and it heats at 550 degreeC. As a result, a catalyst carrier 3 in which the catalyst 32 is carried on the catalyst base 31 is obtained.

  In preparing the HC adsorbent 2, Cs-modified zeolite as a component of the HC adsorbent 22 and silica sol as a binder are dispersed in a solvent to prepare an HC adsorbent slurry. Next, the HC adsorbing substrate 21 that is a honeycomb structure is immersed in the HC adsorbent slurry, pulled up, and air blown. Then, the HC adsorbent slurry applied to the HC adsorbing substrate 21 is dried at 150 ° C. and heated at 550 ° C. Thereby, the HC adsorbent 2 formed by supporting the HC adsorbent 22 on the HC adsorbing base material 21 is produced.

Next, the effect of the exhaust gas purification apparatus 1 of this example is demonstrated.
The exhaust gas purification device 1 is used in a hybrid vehicle, and is configured to heat the catalyst carrier 3 in advance to a predetermined temperature or higher (300 ° C. or higher, 500 ° C. in this example) before the engine 10 is started. An HC adsorbent 2 is disposed on the upstream side of the catalyst carrier 3, and the HC adsorbent 22 in the HC adsorbent 2 is mainly composed of zeolite and has an HC desorption peak temperature of 180 ° C. That's it. Thereby, HC in the exhaust gas discharged immediately after the engine 10 is started can be efficiently and sufficiently purified.

Specifically, the hybrid vehicle first starts traveling by a motor. In the exhaust gas purification device 1, the electrically heated catalyst carrier 3 is heated by energization to prepare for the start of the engine 10.
Next, after raising the temperature of the catalyst carrier 3 to 500 ° C., the engine 10 is started, and running by the engine 10 and charging of the battery are started.

  At this time, a large amount of HC contained in the exhaust gas discharged immediately after the start of the engine 10 is once adsorbed by the HC adsorbent 22 of the HC adsorbent 2 disposed on the upstream side of the catalyst carrier 3. Here, the HC adsorbent 22 mainly composed of zeolite has a temperature (HC desorption peak temperature) at which the amount of HC adsorbed on the HC adsorbent 22 is maximized (HC desorption peak temperature) of 180 ° C. or higher (205 ° C. in this example) ) And very high compared to conventional HC adsorbents.

  Therefore, it is possible to adsorb HC in the exhaust gas discharged immediately after the start of the engine 10 to the HC adsorbent 22 for a longer time than before and to a higher temperature. As a result, the HC in a liquefied state at a low temperature, that is, in a state of low reactivity and difficult to be purified, quickly desorbs from the HC adsorbent 22 and flows into the catalyst carrier 3, and the catalyst carrier is not purified sufficiently. 3 can be suppressed.

  When the temperature of the HC adsorbent 22 becomes around the HC desorption peak temperature (205 ° C. in this example) as the exhaust gas temperature rises, the HC adsorbed on the HC adsorbent 22 is vaporized, that is, the reactivity is increased. Desorbs in high state Here, the catalyst carrier 3 disposed on the downstream side of the HC adsorbent 2 (HC adsorbent 22) is heated before the engine 10 is started, and is in a state in which the activity of the supported catalyst is enhanced. . Therefore, HC desorbed from the HC adsorbent 22 can be sufficiently purified in the catalyst carrier 3 on the downstream side. Thereby, HC in the exhaust gas discharged immediately after the engine 10 is started can be efficiently and sufficiently purified.

  In this example, the HC adsorbent 22 is mainly composed of Cs-modified zeolite. Therefore, the HC desorption peak temperature of the HC adsorbent 22 can be reliably set to 180 ° C. or higher. Therefore, HC in the exhaust gas discharged immediately after the engine 10 is started can be efficiently and sufficiently purified. Further, since the Cs-modified zeolite containing an alkali metal has excellent water absorption, it is possible to prevent the catalyst carrier 3 disposed on the downstream side from being wetted.

  Thus, according to this example, it is possible to provide the exhaust gas purification device 1 for a hybrid vehicle that can efficiently and sufficiently purify HC in the exhaust gas discharged immediately after the engine 10 is started.

(Example 2)
In this example, as shown in FIG. 4, the HC desorption peak temperature of the HC adsorbent used in the exhaust gas purification apparatus of the present invention was evaluated.

In this example, the zeolite (sample Z1) used as the HC adsorbent in Example 1 was prepared, and the HC desorption peak temperature was determined. The zeolite of sample Z1 is a Cs-modified zeolite having an MFI structure.
Further, in this example, zeolite (sample Z2) that has been conventionally used as an HC adsorbent was prepared for comparison, and the HC desorption peak temperature was similarly determined. The zeolite of sample Z2 is H-ZSM5 type high silica zeolite (Si / Al ₂ = 1880) having an MFI structure.

The HC desorption peak temperature of each sample (Z1, Z2) was determined by conducting a temperature-programmed desorption test using a temperature-programmed desorption gas analyzer (TPD-R: manufactured by Rigaku Corporation).
Specifically, first, a sample is set in the temperature-programmed desorption gas analyzer. Next, the sample is pretreated with air at 500 ° C. for 1 hour, and then cooled to 25 ° C. Next, a mixed gas of 1000 ppm of toluene, H ₂ O 3%, and N ₂ is adsorbed on the sample. Next, purging with air at 25 ° C. (removing adsorbed moisture) and confirming that HC desorption has ceased, the temperature is raised to 600 ° C. at a temperature increase rate of 10 ° C./min. Then, the behavior of the HC desorption amount with respect to the temperature was analyzed by a gas chromatograph mass spectrometer (GC-MS), and the temperature at which the HC desorption amount was the largest was obtained as the HC desorption peak temperature.

Next, the results of the temperature programmed desorption test are shown in FIG. In the figure, the horizontal axis represents temperature (° C.) and the vertical axis represents the desorption index (au).
As can be seen from the figure, the sample Z2, which is a conventional zeolite, had an HC desorption peak temperature of 92 ° C. On the other hand, sample Z1, which is the zeolite (Cs-modified zeolite) used in Example 1, had a higher HC desorption peak temperature than that of sample Z2, which was 205 ° C.

  From these results, it was found that zeolite (Cs-modified zeolite), which is an HC adsorbent used in the exhaust gas purification apparatus of the present invention, has a very high HC desorption peak temperature compared to conventional zeolite.

(Example 3)
In this example, as shown in FIG. 5, the exhaust gas purification performance of the exhaust gas purification apparatus of the present invention was evaluated.

In this example, an exhaust gas purification apparatus (Example E1) having the same configuration as that of Example 1 was prepared, and the exhaust gas purification performance was evaluated.
The exhaust gas purifying apparatus of Example E1 has an HC adsorber disposed on the upstream side and an electrically heated catalyst carrier disposed on the downstream side (see FIG. 1), and the HC adsorbent is a Cs-modified zeolite (Example). 2 and sample Z1). The amount of HC adsorbent supported on the upstream HC adsorbent is 110 g / L, and the amount of catalyst supported on the downstream catalyst support is Pt: 1.5 g / L and Rh: 0.3 g / L.

Moreover, in this example, the exhaust gas purification apparatus (comparative example C1, C2) as a comparison was prepared and exhaust gas purification performance was evaluated similarly.
The exhaust gas purification apparatus of Comparative Example C1 is provided with only an electrically heated catalyst carrier. The catalyst loading on the catalyst carrier is Pt: 1.5 g / L, Rh: 0.3 g / L.
The exhaust gas purifying apparatus of Comparative Example C2 is provided with an HC adsorber on the upstream side and an electrically heated catalyst carrier on the downstream side, and the HC adsorbent is a conventional zeolite (similar to the sample Z2 of Example 2). ). The amount of HC adsorbent supported on the upstream HC adsorbent is 110 g / L, and the amount of catalyst supported on the downstream catalyst support is Pt: 1.5 g / L and Rh: 0.3 g / L.

The exhaust gas purification performance of each exhaust gas purification device (Example E1, Comparative Examples C1, C2) was evaluated by the purification rate of HC in the exhaust gas.
Specifically, first, an exhaust gas purification device is set in a gasoline engine (in-line 4 cylinders, displacement of 2.4 L). Next, the engine is started after motoring under the condition of an engine speed of 1200 rpm. Next, the HC concentration until 60 seconds after the engine is started is measured with an automobile exhaust gas analyzer (MEXA-9100D: manufactured by Horiba). And the HC purification rate was calculated | required by dividing the density | concentration difference of the measured HC density | concentration of the inlet_port | entrance of an exhaust gas purification apparatus and outlet HC density | concentration by the HC density | concentration of an inlet_port | entrance.

Next, the results of the exhaust gas purification performance (HC purification rate) are shown in FIG. In the figure, the vertical axis represents the HC purification rate (%).
As can be seen from the figure, the HC purification rates of the exhaust gas purification apparatuses of Comparative Examples C1 and C2 were 45% and 68%, respectively. On the other hand, the exhaust gas purification device of Example E1 had a higher HC purification rate than the exhaust gas purification devices of Comparative Examples C1 and C2, and was 82%.

  From this result, it was found that the exhaust gas purifying apparatus of the present invention can efficiently and sufficiently purify HC in the exhaust gas discharged immediately after starting the internal combustion engine.

Example 4
In this example, as shown in FIGS. 6 and 7, the configuration of the exhaust gas purification device 1 is changed.
As shown in FIG. 6, the exhaust gas purification apparatus 1 of this example further includes an additional catalyst carrier 4 on the downstream side of the electrically heated catalyst carrier 3. In other words, the HC adsorber 2, the electrically heated catalyst carrier 3, and the additional catalyst carrier 4 are disposed in the exhaust passage 12 in order from the upstream side.

As shown in FIGS. 7A and 7B, the additional catalyst carrier 4 is configured by carrying a catalyst 42 for exhaust gas purification on a catalyst base 41.
As shown in FIG. 7A, the catalyst base 41 is a honeycomb structure having partition walls 411 provided in a quadrangular lattice, a large number of quadrangular cells 412, and a cylindrical outer peripheral wall 413. The catalyst base 41 is made of porous ceramics mainly composed of cordierite.
As shown in FIG. 7B, the catalyst 42 is coated on the surface of the partition wall 411 of the catalyst base 41. The catalyst 42 is a three-way catalyst made of Pt, Rh or the like.
Other configurations are the same as those in the first embodiment.

Next, the function and effect of this example will be described.
The exhaust gas purifying apparatus 1 of this example further includes an additional catalyst carrier 4 on the downstream side of the electrically heated catalyst carrier 3. Therefore, for example, even when the exhaust amount of the engine 10 is large and the exhaust gas treatment amount is increased, the HC in the exhaust gas can be efficiently and sufficiently purified.

In addition, the exhaust gas that has passed through the catalyst carrier 3 flows into the additional catalyst carrier 4 due to its arrangement. Here, the catalyst carrier 3 is preheated before the engine 10 is started. Therefore, the exhaust gas heated through the catalyst carrier 3 flows into the additional catalyst carrier 4 immediately after the engine 10 is started. Thus, the activity of the catalyst 42 supported on the additional catalyst support 4 can be increased immediately after the engine 10 is started.
In addition, the same effects as those of the first embodiment are obtained.

(Example 5)
In this example, as shown in FIG. 8, the configuration of the HC adsorbent 2 is changed.
As shown in FIGS. 8A and 8B, the HC adsorbent 2 of the present example further includes an additional HC adsorbent 23 on the HC adsorbent 22 coated on the surface of the partition wall 211 of the HC adsorbent base 21. Is formed. That is, the HC adsorbent 22 and the additional HC adsorbent 23 are sequentially laminated on the surface of the partition wall 211 of the HC adsorbent base 21.

The additional HC adsorbent 23 is mainly composed of beta zeolite (H-BEA) having a BEA structure. Beta zeolite (H-BEA) has a lower HC desorption peak temperature than that of Cs-modified zeolite, which is the HC adsorbent 22, and is 95 ° C. Further, beta zeolite (H-BEA) has an HC adsorption amount of 5 times or more as compared with Cs-modified zeolite which is the HC adsorbent 22.
Other configurations are the same as those in the first embodiment.

Next, the function and effect of this example will be described.
In the case of this example, the HC adsorbent 22 having a high HC desorption peak temperature can adsorb HC in the exhaust gas discharged immediately after the start of the internal combustion engine for a longer time until it reaches a higher temperature. it can. Then, more HC can be adsorbed by the additional HC adsorbent 23 having a large amount of HC adsorption. This makes it possible to achieve both high temperature retention of HC in the HC adsorbent 2 and securing of the adsorption amount.
In addition, the same effects as those of the first embodiment are obtained.

1 Exhaust gas purification device 10 Engine (internal combustion engine)
12 Exhaust passage 2 HC adsorbent 22 HC adsorbent 3 Catalyst carrier 32 Catalyst

Claims (2)

An electric heating type catalyst carrier which is used in a hybrid vehicle having an internal combustion engine and a motor as a drive source and carries an exhaust gas purification catalyst and which can be heated by energization is disposed in the exhaust passage of the internal combustion engine. An exhaust gas purification apparatus configured to heat the catalyst carrier to a predetermined temperature or higher in advance before starting the internal combustion engine,
An HC adsorbent comprising an HC adsorbent that adsorbs HC in the exhaust gas is disposed upstream of the catalyst carrier in the exhaust passage,
An exhaust gas purifying apparatus for a hybrid vehicle, wherein the HC adsorbent contains zeolite as a main component and has an HC desorption peak temperature of 180 ° C or higher.   2. The exhaust gas purification apparatus according to claim 1, wherein the HC adsorbent contains Cs-modified zeolite as a main component.

Images