JP2003214138A - Exhaust emission control device and exhaust emission control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further lower a temperature in which oxidation combustion of PM can be preformed and further increase an oxidation reaction speed of the PM. <P>SOLUTION: At least one of a catalyst for exhaust emission control and a hydrocarbon adsorbent, and an ultrasonic device 3 which applies ultrasonic wave to them are provided, and the ultrasonic wave is applied to a liquid catalyst component and a liquid hydrocarbon. By the application of the ultrasonic wave, a cavitation is generated in a liquid, and by an adiabatic compression occurring there, an energy is concentrated. When a cavity (bubble) is broken, high temperature and high pressure state locally occurs, whereby an oxidation (combustion) of the PM is accelerated. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to particulate matter (hereinafter referred to as PM), which is contained in exhaust gas from a diesel engine or the like, and which contains particulate matter mainly composed of carbon and liquid hydrocarbons (hereinafter referred to as SOF), in an exhaust gas temperature range. The present invention relates to an exhaust gas purifying apparatus and an exhaust gas purifying method that can efficiently purify the exhaust gas.

[0002]

2. Description of the Related Art The exhaust gas of a diesel engine contains PMs such as carbon, SOF (Soluble Organic Fraction), high molecular weight organic compounds, and sulfuric acid mist, which are emitted from the viewpoint of air pollution and adverse effects on the human body. There is a growing movement to curb this. There are two types of methods of suppressing PM emission, that is, a method of trapping PM by a filter and a method of burning PM to remove it, and technological development combining both or both is in progress.

In order to burn PM, it is considered to use an oxidation catalyst carrying a noble metal such as Pt. However, in this case, since the solid phases are in contact with each other,
The probability of contact between PM and catalyst components was low, and it was difficult to efficiently burn and purify PM. Especially for the carbon component in PM, the effect of noble metals such as Pt is hardly recognized.

It was then envisaged to contact the catalyst in the liquid phase with PM, for example Appl. Cat. B21 (1999) 35-49:
Molten salt catalysts such as Cs ₂ MoO ₄ -V ₂ O ₅ , CsVO ₃ -MoO ₃ and Cs ₂ SO ₄ -V ₂ O ₅ have been reported. In such a molten salt catalyst, strong oxidizing power of carbon, low evaporation of the catalyst, low combustion temperature and the like are preferable conditions, and in this document, Cs ₂ MoO ₄ -V ₂ O ₅ and CsVO ₃ -MoO ₃ is 620K
High activity above (347 ° C), 1025K (752
It is described that it is stable up to (.degree. C.) and is a preferred catalyst.

Further, JP-A-9-144528 discloses that the melting point is 3
A catalyst device in which a eutectic composition such as Cs ₂ O · V ₂ O ₅ , K ₂ O · V ₂ O ₅ having a catalytic activity in soot combustion at a temperature of 00 to 500 ° C. is carried on a carrier such as a monolith is provided. It is disclosed.

International publication WO00 / 43109 (PCT / JP00 / 0
[0194] describes that PM can be burned and removed by putting magnesium nitrate and magnesium carbonate in a liquid reservoir and contacting exhaust gas at about 185 to 270 ° C.

[0007]

The temperature of the exhaust gas from a diesel engine is usually below 300 ° C.
It is even lower at startup. Therefore, if the melting point of the molten salt catalyst is 300 ° C or higher, it is difficult to efficiently burn and remove PM because it does not become a liquid phase in the exhaust gas from the diesel engine.

Further, the molten salt needs to be in a liquid phase, but since it is in a liquid phase, if it comes into contact with the exhaust gas flow, it may flow to the downstream side and be condensed. For that purpose, international publication WO00 / 431
The technology disclosed in No. 09 uses a primitive technology called a liquid reservoir. However, when it is mounted on an automobile, it is not practical because the exhaust pressure rises and the liquid level becomes unstable due to vibration during traveling.

Therefore, the present inventors have proposed a catalyst for purifying carbon-based particulate matter contained in exhaust gas from an internal combustion engine, which comprises a solid support, and silver nitrate or a nitrate of an alkali metal supported on the solid support. , A catalyst component containing at least one selected from nitrates of alkaline earth metals and nitrates of rare earth elements.

According to this molten salt type catalyst, PM is generated even in a low temperature range.
It is possible to obtain a practical molten salt catalyst that can be oxidized and removed by combustion and can be stably arranged in the exhaust system of an automobile. However, the temperature at which the catalyst components of the molten salt catalyst melt,
There is a gap between the minimum temperature at which PM is oxidized by the catalyst component, and generally the minimum temperature at which PM is oxidized by the catalyst component is higher than the melting temperature of the catalyst component. In other words, the oxidation of PM does not occur from the melting temperature of the catalyst component.

Further, since SOF is liquid at exhaust gas temperature, it can be purified with a normal oxidation catalyst without using a molten salt type catalyst. However, when starting the engine when the temperature of the oxidation catalyst is lower than the activation temperature, S
Purifying OF is difficult. Therefore, one reliable means is to heat the oxidation catalyst with a heater or the like, but it requires a large amount of energy to heat the catalyst having a large heat capacity to a required temperature, which is not practical.

[0012] Further, S is used as a hydrocarbon adsorbent such as zeolite.
Although OF can be adsorbed and removed, it becomes difficult to remove it after the adsorption amount is saturated. Therefore, it is also used in combination with an oxidation catalyst, but the problem remains that purification is difficult at the time of starting.

The present invention has been made in view of the above circumstances, and an object thereof is to further lower the temperature at which PM can be oxidatively burned and to further improve the oxidation reaction rate of PM.

[0014]

The features of the exhaust gas purifying apparatus of the present invention for solving the above problems are to purify at least one of liquid hydrocarbons and carbon-based particulate matter contained in exhaust gas from an internal combustion engine. An exhaust gas purifying apparatus, wherein at least one of an exhaust gas purifying catalyst and a hydrocarbon adsorbent disposed in an exhaust gas passage, and an ultrasonic device that irradiates ultrasonic waves to at least one of the exhaust gas purifying catalyst and the hydrocarbon adsorbent Is equipped with.

In this exhaust gas purifying apparatus, the exhaust gas purifying catalyst comprises a solid carrier, silver nitrate supported on the solid carrier,
A molten salt type catalyst comprising a catalyst component containing at least one selected from alkali metal nitrates, alkaline earth metal nitrates and rare earth element nitrates, and melted from an ultrasonic device when the catalyst components are in a molten state. It is desirable to irradiate the salt-type catalyst with ultrasonic waves to purify particulate matter mainly containing carbon.

In the exhaust gas purifying apparatus of the present invention, at least one of the exhaust gas purifying catalyst and the hydrocarbon adsorbent is SOF.
It is intended for purification, and it is desirable to purify SOF by applying ultrasonic waves from an ultrasonic device.

The exhaust gas purifying apparatus of the present invention preferably further comprises a temperature detecting means for detecting the temperature of at least one of the exhaust gas purifying catalyst and the hydrocarbon adsorbent.

The feature of the exhaust gas purifying method of the present invention which solves the above-mentioned problems is at least selected from a solid carrier, silver nitrate, a nitrate of an alkali metal, a nitrate of an alkaline earth metal and a nitrate of a rare earth element carried on the solid carrier. Irradiating ultrasonic waves to a molten salt type catalyst while circulating an exhaust gas containing particulate matter mainly containing carbon when the molten salt type catalyst consisting of one type of catalytic component and the catalytic component of the molten salt type catalyst is in a molten state. It is in.

Another feature of the exhaust gas purifying method of the present invention that solves the above problems is that at least one of the exhaust gas purifying catalyst and the hydrocarbon adsorbent adsorbed by SOF is irradiated with ultrasonic waves to purify SOF. is there.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION In the exhaust gas purifying apparatus of the present invention, at least one of the exhaust gas purifying catalyst and the hydrocarbon adsorbent disposed in the exhaust gas passage and at least one of the exhaust gas purifying catalyst and the hydrocarbon adsorbent are superposed. And an ultrasonic device that emits sound waves. And in one exhaust gas purification method of the present invention, when the catalyst component of the molten salt type catalyst is in a molten state, ultrasonic waves are radiated to the molten salt type catalyst while circulating the exhaust gas containing particulate matter mainly containing carbon. is doing. In another exhaust gas purification method, ultrasonic waves are applied to at least one of the exhaust gas purification catalyst and the hydrocarbon adsorbent that have adsorbed SOF.

In the molten salt type catalyst used in the present invention, the nitrate-based molten salt melts into a liquid phase at the exhaust gas temperature of an automobile diesel engine, so that the probability of contact with PM increases,
Combustion reaction occurs. Further, since it is in the liquid phase, PM is easily collected, which also increases the contact probability. Therefore, PM can be efficiently burned and removed. If a nitrate-based molten salt that melts at a low temperature, such as lithium nitrate, is used, the contact between PM and the catalyst is improved even in a low temperature range, so it is possible to burn and remove PM in a wide temperature range from a low temperature range to a high temperature range. it can.

In the exhaust gas purifying apparatus and the exhaust gas purifying method of the present invention, ultrasonic waves are applied when the catalyst component of the molten salt type catalyst is in a molten state. As a result, the oxidation reaction of PM is promoted, and PM can be burned and removed from the low temperature range. SOF adsorbed on at least one of the exhaust gas purifying catalyst and the hydrocarbon adsorbent is also liquid, and by irradiating it with ultrasonic waves, SOF can be burned and removed in a wide temperature range from a low temperature range to a high temperature range.

The reason for this is not clear, but it is considered as follows. It is known that when a liquid is irradiated with ultrasonic waves, a cavitation phenomenon (cavitation) occurs due to the interaction. Then, this cavitation is considered to occur. It is considered that such cavitation occurs even when ultrasonic waves are applied to the molten liquid catalyst component. Energy is concentrated by adiabatic compression there, and when the cavity (foam) collapses, the temperature and pressure rise locally, so that only the liquid SOF has a high temperature even if the heat capacity of the catalyst or hydrocarbon adsorbent is large. Further, the temperature of the molten liquid catalyst component becomes high. It is thought that this promotes the oxidation (combustion) of PM even if the exhaust gas temperature is in the low temperature range.

As the solid carrier of the molten salt type catalyst, alumina, zirconia, which has been used for conventional three-way catalysts,
Although titania, silica, zeolite, etc. can be used, basic carriers such as magnesia spinel, zirconia, oxides of alkali metals, oxides of alkaline earth metals such as magnesia, oxides of rare earth elements such as lantana, neodia, etc. Is particularly preferable. By using such a basic carrier, the solid phase reaction between the nitrate-based molten salt and the carrier is suppressed, so that the durability is improved.

The catalyst component of the molten salt type catalyst contains at least one molten nitrate salt selected from silver nitrate, alkali metal nitrates, alkaline earth metal nitrates and rare earth element nitrates. Examples of alkali metal nitrates include KNO ₃ ,
CsNO _3, NaNO _3, etc. LiNO ₃ are exemplified. Also, as nitrates of alkaline earth metals, Ba (NO ₃ ) ₂ , Sr (NO ₃ ) ₂ , Ca
_{(NO 3) 2, Mg (} NO 3) such as _2. Examples of the nitrates of the rare earth _{element, Y 2 (NO 3) 3} , La 2 (NO 3) 3, Nd 2 (NO 3) 3, Pr 2 (NO
₃ ) _{3 and the} like are exemplified. Of these, only one kind may be used, or a composite nitrate in which plural kinds are combined may be supported. By using a complex nitrate, the melting temperature is often lowered.

As the complex nitrate, AgNO ₃ -CsNO ₃ ,
CsNO ₃ -KNO ₃ , CsNO ₃ -NaNO ₃ , CsNO ₃ -LiNO ₃ , KNO ₃ -Mg (N
O ₃ ) ₂ , LiNO ₃ -NaNO ₃ , NaNO ₃ -Ca (NO ₃ ) ₂ , NaNO ₃ -Mg (N
O ₃ ) ₂ , AgNO ₃ -KNO ₃ -NaNO ₃ , AgNO ₃ -NaNO ₃ -Ba (NO ₃ ) ₂ , KNO _{3
-LiNO 3 -NaNO 3, KNO 3 -NaNO} 3 -Mg (NO 3) 2, KNO 3 -Ba (NO 3) 2 -
_{Ca (NO 3) 2, KNO} 3 -Ba (NO 3) 2 -Sr (NO 3) 2, KNO 3 -Ca (NO 3) 2 -Sr
(NO ₃ ) ₂ , LiNO ₃ -NaNO ₃ -Ca (NO ₃ ) ₂ , NaNO ₃ -Ca (NO ₃ ) ₂ -Mg (N
_{O 3) 2, NaNO 3 -Ca} (NO 3) 2 -Sr (NO 3) 2, KNO 3 -NaNO 3 -Ca (NO 3)
_2- Mg (NO ₃ ) _{2 and the} like are preferable. If these complex nitrates are used, the melting temperature can be set to 200 ° C. or lower, for example.

The nitrate-based molten salt contained in the catalyst component preferably has a low melting temperature and a high decomposition temperature.
As a result, in exhaust gas with a wide temperature range and wide space velocity
PM can be captured efficiently and removed by combustion. For example, among the above-mentioned nitrate-based molten salts, those containing a nitrate of alkali metal are preferable, and those containing LiNO ₃ are most preferable.

The amount of the nitrate-based molten salt supported is preferably 1% by weight or more based on the solid carrier. If the supported amount is less than this, it becomes difficult to burn PM. Also, the burning temperature of PM tends to decrease as the amount of nitrate molten salt supported increases, but if 120 wt% or more is loaded, the stability on the carrier becomes insufficient and it may flow to the downstream and agglomerate.
It is preferably less than 120% by weight.

It is desirable that the catalyst component further contains an oxidation promoting component. This oxidation-promoting component promotes the combustion of PM due to the oxidation of SOF in PM. As oxidation-promoting components, precious metals such as Pt, Rh, and Pd, CeO ₂ , ZrO ₂ , CeO ₂ −
ZrO ₂ solid solution, BaO, CaO, V ₂ O ₅ , ZnO, WO ₃ , MoO ₃ , N
iO, FeO, Fe ₃ O ₄ , Fe ₂ O ₃ , MnO ₂ , Cr ₂ O ₃ , CuO, Co
Various oxides such as O and Co ₃ O ₄ can be used.

The supported amount of the oxidation promoting component is preferably 0.1 to 10% by weight in the case of a noble metal and 1 to 50% by weight in the case of various oxides with respect to the solid support. If the amount is less than this range, the effect is not exhibited, and even if the amount is further supported, the effect may be saturated and adverse effects may appear.

In order to support the molten nitrate salt on the solid carrier, an aqueous solution of nitrate may be impregnated into the solid carrier and dried. Further, in order to support the oxidation promoting component, it may be supported by using an aqueous solution of the metal compound and then baked.

As the exhaust gas purifying catalyst used for purifying SOF, conventionally used oxidation catalysts, three-way catalysts or NO _x storage reduction type catalysts can be used, such as alumina, zirconia, titania and ceria. It is desirable to use a catalyst in which a noble metal having high oxidation activity such as Pt is supported on the carrier. As the hydrocarbon adsorbent, zeolite such as ferrierite, ZSM-5, mordenite and Y-type zeolite is preferable, but any one having an ability to adsorb SOF can be used. It is also preferable to use a zeolite on which a noble metal such as Pd or Ag is supported as a hydrocarbon adsorbent. By supporting the noble metal in this manner, the adsorptivity of low molecular weight hydrocarbons is further improved. Alternatively, it is also preferable to use an exhaust gas purifying catalyst obtained by mixing a hydrocarbon adsorbent powder with a catalyst powder such as an oxidation catalyst. With such a configuration, the purification rate is often further improved.

The shape of the molten salt type catalyst, the exhaust gas purifying catalyst or the hydrocarbon adsorbent used in the present invention is not particularly limited, and may be pellet shape, filter shape, foam shape, flow through type honeycomb shape and the like. it can.
For example, in the case of a filter shape, a honeycomb shape, or a foam shape, it can be manufactured by coating the surface of a base material with a carrier and supporting a molten nitrate salt or a noble metal thereon. In addition, it is desirable that the exhaust gas has a turbulent flow shape, and it is particularly desirable that the exhaust gas has a turbulent shape in the gas flow rather than a honeycomb shape, for example, a foam shape. As the material of the base material, heat-resistant ceramics, metal or the like can be used as in the conventional three-way catalyst.

In consideration of mounting on an automobile, it is desirable that the ultrasonic device be small in size and have an ultrasonic wave generator installed in a converter equipped with an exhaust gas purifying catalyst or a hydrocarbon adsorbent. The type and shape are not particularly limited. The frequency of the ultrasonic waves emitted is 20
A frequency of ~ 5000kHz is preferable. The optimum frequency depends on the type of molten salt or SOF. The output of ultrasonic waves is not particularly limited, but is preferably about 5 to 1000 W.

However, when ultrasonic waves are applied when the catalyst component of the molten salt type catalyst is not melted or when the amount of SOF adsorbed is small, not only the effect is not exhibited but also energy loss occurs. Therefore, it is desirable that the exhaust gas purifying apparatus of the present invention further includes temperature detecting means for detecting the temperature of at least one of the exhaust gas purifying catalyst and the hydrocarbon adsorbent. Then, for example, when the temperature of the molten salt type catalyst is equal to or higher than the melting temperature of the catalyst component, ultrasonic waves are applied. Alternatively, ultrasonic waves are emitted when the exhaust gas temperature is lower than a predetermined value. With this structure, PM combustion efficiency can be improved and energy can be saved. In order to detect the temperature of at least one of the exhaust gas purifying catalyst and the hydrocarbon adsorbent, the temperature of at least one of the exhaust gas purifying catalyst and the hydrocarbon adsorbent may be directly detected, or the exhaust gas temperature and the like may be detected. Therefore, the temperature of at least one of the exhaust gas-purifying catalyst and the hydrocarbon adsorbent can be indirectly detected.

As the temperature detecting means, a general temperature sensor or the like can be used. Further, it is desirable that the temperature detecting means is arranged so as to detect the temperature of a portion of the molten salt type catalyst where the temperature rises most, for example. This makes it possible to irradiate ultrasonic waves even when a part of the catalyst component is in a molten state, and the PM combustion efficiency is improved. When it cannot be arranged in such a position, it is desirable to set in advance so that ultrasonic waves can be emitted even when the detected temperature is lower than the melting temperature of the catalyst component.

Further, together with the temperature detecting means or instead of the temperature detecting means, means for detecting the hydrocarbon concentration in the exhaust gas, means for detecting the weight change of the hydrocarbon adsorbent, and change in the electric conductivity of the molten salt catalyst are used. Means for detecting may be provided.

Although the ultrasonic device can be manually driven by receiving a detection signal from the temperature detecting means or the like, a control unit for automatically controlling the driving of the ultrasonic device upon receiving a detection signal from the temperature detecting means is provided. It is desirable to prepare. This controller is C
It can be configured by a digital circuit including PU, and by comparing the preset value with the above detection value, the ultrasonic device
It is desirable to perform ON / OFF control or output control.

[0039]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples.

(Embodiment 1) FIG. 1 shows an exhaust gas purifying apparatus of this embodiment. This exhaust gas purifying apparatus includes a catalytic converter 1
The cylindrical molten salt catalyst 2 arranged in the position, the ultrasonic generator 3 arranged along the cylindrical surface of the molten salt catalyst 2, and the temperature of the central portion of the molten salt catalyst 2 are detected. It is composed of a temperature sensor 4 and a control device 5 which receives a signal from the temperature sensor 4 and drives the ultrasonic wave generation oscillator 3.

Molten salt type catalyst 2 is a ceramic foam substrate (20 cells / in ² ) made of foamed cordierite.
This is a foam catalyst in which a carrier layer made of MgAl ₂ O ₄ is coated to form a coat layer, and the coat layer is impregnated with a LiNO ₃ aqueous solution, dried and calcined to carry LiNO ₃ , and MgAl per 1 L of catalyst volume. _It contains 100g of ₂ O _{4 and} 20g of LiNO ₃ .

The ultrasonic wave generating oscillator 3 is made of lead zirconate titanate porcelain and generates ultrasonic waves of 25 kHz and 30 W by applying an AC voltage of 100V, respectively. The ultrasonic wave generating oscillator 3 is arranged along the inner peripheral surface of the catalytic converter 1. Thus, the LiNO ₃ carried on the molten salt catalyst 2 can be irradiated with ultrasonic waves as directly as possible. However, the arrangement shape of the ultrasonic wave generation oscillator 3 is not limited to this, and various arrangement shapes can be considered according to the shape of the molten salt catalyst 2 or the shape of the catalytic converter 1.

(Comparative Example 1) An exhaust gas purifying apparatus similar to that of Example 1 except that the ultrasonic wave generating oscillator 3, the temperature sensor 4 and the controller 5 are not provided was used as a comparative example.

<Test / Evaluation> Each of the above exhaust gas purifying devices was mounted on the exhaust system of a 2400cc diesel engine, and after steady operation for 30 minutes under the conditions of an engine speed of 2500 rpm, a torque of 5.0 kgm, and an exhaust gas temperature of 350 ° C. The PM purification rate of each was measured. In the exhaust gas purifying apparatus according to the first embodiment, when the temperature detected by the temperature sensor 4 reaches 250 ° C. or higher, the ultrasonic wave generating oscillator 3 is driven to 25 kHz.
, 100 W of ultrasonic waves were emitted from the ultrasonic wave generator 3. The ultrasonic irradiation was continued while the temperature detected by the temperature sensor 4 was 250 ° C or higher.

The PM purification rate was calculated by measuring the PM emission amount using a full dilution tunnel and calculating the ratio with the PM emission amount in the case of a blank without the exhaust gas purification device. The results are shown in Table 1.

[0046]

[Table 1]

It can be seen from Table 1 that the exhaust gas purifying apparatus of Example 1 has a PM purification rate improved by about 30% as compared with Comparative Example 1, and it is clear that this is the effect of ultrasonic irradiation. is there.

That is, in the exhaust gas purifying apparatus of Example 1,
Ultrasonic waves are emitted when the catalyst components of the molten salt catalyst 2 are in a molten state. Then, a cavitation phenomenon (cavitation) occurs in the liquid catalyst component due to ultrasonic waves, energy is concentrated by adiabatic compression there, and when the cavity (bubble) collapses, the temperature and pressure become locally high. As a result, even if the heat capacity of the molten salt catalyst 2 is large, the temperature of the liquid catalyst component becomes high, and even if the exhaust gas temperature is in the low temperature range, the particulate matter mainly containing carbon captured by the molten salt catalyst 2 Oxidation (combustion) is promoted. When the molten salt catalyst 2 is not in a molten state, ultrasonic waves are not applied. Therefore, the power consumption can be suppressed.

(Embodiment 2) FIG. 2 is a conceptual diagram of the exhaust gas purifying apparatus of this embodiment, and FIG. 3 is an enlarged view of the catalytic converter portion thereof. This exhaust gas purifying apparatus includes a columnar exhaust gas purifying catalyst 6 arranged in the catalytic converter 1, an ultrasonic wave generating oscillator 3 arranged along the columnar surface of the exhaust gas purifying catalyst 6, and the inside of the catalytic converter 1. The temperature sensor 4 detects the temperature of the exhaust gas, and the control device 5 that receives the signal from the temperature sensor 4 and drives the ultrasonic wave generation oscillator 3.

The ultrasonic wave generator 3 is the same as that in the first embodiment. The ultrasonic wave generating oscillator 3 is arranged along the inner peripheral surface of the catalytic converter 1. Thereby, the exhaust gas purifying catalyst 6 can be irradiated with ultrasonic waves as directly as possible. However, the arrangement shape of the ultrasonic wave generation oscillator 3 is not limited to this, and various arrangement shapes can be considered depending on the shape of the exhaust gas purifying catalyst 6 or the shape of the catalytic converter 1.

The exhaust gas-purifying catalyst 6 comprises a cordierite honeycomb substrate and a coat layer coated on the cell walls of the cell passages. The coat layer is a catalyst powder in which Pt is supported on alumina powder in advance. And mordenite powder are mixed at a weight ratio of 3: 4. The coat layer is formed in 240 g per 1 L of the honeycomb substrate, and Pt is supported in 1.5 g per 1 L of the honeycomb substrate.

The control device 5 is composed of a microcomputer, compares the signal from the temperature sensor 3 with a value stored in the ROM 50 in advance, and when the exhaust gas temperature is lower than the activation temperature of Pt, ultrasonic vibration is generated. The child 3 is driven, and when the exhaust gas temperature is equal to or higher than the activation temperature of Pt, the driving of the ultrasonic wave generation oscillator 3 is stopped.

Therefore, according to the exhaust gas purifying apparatus of this embodiment, ultrasonic waves are applied to the exhaust gas purifying catalyst 6 when the exhaust gas temperature is lower than the activation temperature of Pt. Then, a cavitation phenomenon (cavitation) occurs in the liquid SOF adsorbed on the coating layer of the exhaust gas purifying catalyst 6 due to ultrasonic waves, and energy is concentrated by adiabatic compression there, and when the cavity (bubble) collapses. High temperature and high pressure locally.
As a result, only the liquid SOF has a high temperature even if the heat capacity of the exhaust gas purifying catalyst 6 is large, and the oxidation (combustion) of SOF is promoted even if the exhaust gas temperature is in the low temperature range. If the exhaust gas temperature is equal to or higher than the activation temperature of Pt, SOF is efficiently oxidized and removed by the catalytic action of Pt, so that ultrasonic waves are not irradiated. Therefore, the power consumption can be suppressed.

[0054]

According to the exhaust gas purifying apparatus and the exhaust gas purifying method of the present invention, the PM purification rate in the low temperature range is further improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of an exhaust gas purifying apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic configuration of an exhaust gas purifying apparatus according to a second embodiment of the present invention.

FIG. 3 is an enlarged explanatory view of a main part of an exhaust gas purifying apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

1: Catalytic converter 2: Molten salt type catalyst 3: Ultrasonic wave generation oscillator 4: Temperature sensor 5: Control device 6: Exhaust gas purification catalyst

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B01D 53/94 F01N 3/18 B B01J 27/25 3/24 E F01N 3/08 B01D 53/36 104B 3 / 18 53/34 120D 3/24 ZAB (72) Inventor Hirofumi Shinjo 1 Nagatote, Nagakute-cho, Aichi-gun, Aichi Prefecture 1 41 Yokochi, Yokosuka Central Research Institute (72) Inventor Yuji Sakakibara Nagakute, Aichi-gun, Aichi Municipal Citizen's Choji-koji 41 Yokomichi 1 Toyota Central Research Laboratory Co., Ltd. (72) Inventor Takaaki Kanazawa 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor Kazunobu Ishibashi Toyota City, Toyota City, Aichi Prefecture No. 1 F-term in Toyota Motor Corporation (reference) 3G090 AA03 AA06 BA01 DA11 EA02 3G091 AA18 AA28 AB00 AB03 AB06 AB10 BA00 BA03 BA15 CA26 DB10 EA18 EA 19 FA02 FA04 FA12 FA13 FB02 FC07 GA01 GA06 GB01W GB01X GB02W GB02X GB03X GB04W GB04X GB05W GB06W GB07W GB09X GB09Y GB10W GB10X GB15W GB16X GB17X HA39 4D002 AA40 AC10 BA04BAX BAX14A10BA10X14 BA39Y BA41Y BA42X BA46X BB02 CD01 DA02 DA13 EA03 4G069 AA03 BA01A BA01B BA02A BA04A BA05A BA06A BA07A BA07B BA13A BA13B BA17 BB02A BB02B BB06A BB06B BB12A BB12B BC01A BC02A BC03A BC04A BC04B BC08A BC09A BC10A BC10B BC12A BC13A BC16A BC16B BC32A BC38A BC40A BC42A BC44A BC69A BC75A CA02 CA03 CA07 CA15 CA18 DA05 EA18 ZA06A ZA06B

Claims (6)

[Claims] 1. An exhaust gas purifying apparatus for purifying at least one of liquid hydrocarbons and particulate matter mainly containing carbon contained in exhaust gas from an internal combustion engine, the exhaust gas purifying catalyst being disposed in an exhaust gas passage, An exhaust gas purifying apparatus comprising: at least one of a hydrocarbon adsorbent; and an ultrasonic device that irradiates at least one of the exhaust gas purifying catalyst and the hydrocarbon adsorbent with ultrasonic waves. 2. The exhaust gas-purifying catalyst comprises a solid carrier, silver nitrate and alkali metal nitrate supported on the solid carrier,
A molten salt type catalyst comprising a catalyst component containing at least one selected from a nitrate of an alkaline earth metal and a nitrate of a rare earth element, and the molten salt type catalyst from the ultrasonic device when the catalyst component is in a molten state. The catalyst is irradiated with ultrasonic waves to purify the particulate matter mainly containing carbon.
The exhaust gas purifying apparatus according to. 3. The exhaust gas purifying apparatus according to claim 1, further comprising temperature detecting means for detecting the temperature of at least one of the exhaust gas purifying catalyst and the hydrocarbon adsorbent. 4. At least one of the exhaust gas-purifying catalyst and the hydrocarbon adsorbent is for the liquid hydrocarbon, and the liquid hydrocarbon is purified by irradiating ultrasonic waves from the ultrasonic device. The exhaust gas purifying apparatus according to 1. 5. A molten salt type comprising a solid support and a catalyst component containing at least one selected from silver nitrate, alkali metal nitrates, alkaline earth metal nitrates and rare earth element nitrates supported on the solid support. An exhaust gas purification method comprising irradiating an ultrasonic wave to the molten salt type catalyst while circulating an exhaust gas containing particulate matter mainly composed of carbon when the catalyst component of the catalyst is in a molten state. 6. An exhaust gas purification method comprising irradiating ultrasonic waves to at least one of an exhaust gas purification catalyst and a hydrocarbon adsorbent on which liquid hydrocarbons are adsorbed to purify the liquid hydrocarbons.