JP2002349235A - Usage for molten salt catalyst and exhaust emission controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To regenerate a catalytic component and reuse it for combustion of PM. SOLUTION: The molten salt catalyst containing nitrate as the catalytic component is regenerated by feeding NOX to it. Nitrate is reproduced by reaction of rich NOX with nitrate oxide or the PM. By generating plasma in the exhaust gas or arranging an NOX occlusion/reduction catalyst in an upstream side, NO2 can be fed to the molten salt catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a particulate matter (hereinafter referred to as PM) contained in exhaust gas from a diesel engine or the like.
The present invention relates to a method for using a molten salt type catalyst capable of efficiently purifying the same in the exhaust gas temperature range, and an exhaust gas purification control device using the molten salt type catalyst.

[0002]

2. Description of the Related Art The exhaust gas of a diesel engine contains PM composed of carbon, SOF (Soluble Organic Fraction), high molecular weight organic compound, sulfuric acid mist, etc., and emits PM due to air pollution and adverse effects on human bodies. There is a growing movement to curb this. There are two methods for suppressing the emission of PM: a method of trapping PM by a filter and a method of burning and removing PM. Technology development combining each or both of them is being promoted.

In order to burn PM, it is conceivable to use an oxidation catalyst carrying a noble metal such as Pt.
However, in this case, since the solid phases come into contact with each other, the probability of contact between the PM and the catalyst component is low, and it has been difficult to efficiently burn and purify the PM. In particular, the effect of noble metals such as Pt on the carbon component in PM is hardly recognized.

It is recalled that the catalyst is brought into contact with PM as a liquid phase. For example, Appl. Cat. B21 (1999) 35-49 discloses Cs ₂ MoO ₄ -V ₂ O ₅ , CsVO ₃ -MoO ₃ , Cs have been reported for molten salt type catalyst such as ₂ SO ₄ -V ₂ O _5. In such a molten salt type catalyst, it is preferable conditions that the oxidizing power of carbon is strong, the evaporation of the catalyst is small, the combustion temperature is low, and the like.In this document, Cs ₂ MoO ₄ -V ₂ O ₅ and CsVO ₃ -MoO ₃ is 6
High activity above 20K (347 ° C), 1025K (7
Up to 52 ° C.) and is described as a preferred catalyst.

Japanese Patent Application Laid-Open No. Hei 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 and K ₂ O · V ₂ O ₅ having a catalytic activity in soot combustion of 00 to 500 ° C. is supported on a carrier such as a monolith body is used. It has been disclosed.

[0006] 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 the exhaust gas at about 185 to 270 ° C.

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

The molten salt must be in a liquid phase. However, since the molten salt is in a liquid phase, when it comes into contact with an exhaust gas flow, it may flow downstream and condense. For that purpose, International Publication WO00 / 431
The technique disclosed in No. 09 uses a primitive technique called a liquid reservoir. However, it is not practical to be mounted on an automobile because the exhaust pressure increases and the liquid level becomes unstable due to vibration during running.

Therefore, the present inventors have developed a catalyst for purifying particulate matter mainly composed of carbon contained in exhaust gas from an internal combustion engine, comprising a solid carrier, silver nitrate and alkali metal nitrate carried on the solid carrier. And a catalyst component containing at least one selected from the group consisting of nitrates of alkaline earth metals and nitrates of rare earth elements.

According to this molten salt type catalyst, P
A practical molten salt catalyst which can remove M by combustion and can be stably disposed in the exhaust system of an automobile can be obtained.

However, it has been clarified that a molten salt type catalyst using a nitrate may be decomposed or react with PM under high temperature conditions to deteriorate the nitrate. Therefore, it is necessary to replace the catalyst when the nitrate has deteriorated, but frequent replacement is not practical.

The present invention has been made in view of such circumstances, and has as its object to regenerate deteriorated nitrate so that it can be reused for PM combustion.

[0013]

The feature of the method for using the molten salt type catalyst of the present invention which solves the above-mentioned problems is that a solid carrier and silver nitrate, an alkali metal nitrate and an alkaline earth metal supported on the solid carrier are used. It consists of a catalyst component comprising at least one selected from the nitrates of nitrates and rare earth elements, and supplies the NO _x in the molten salt type catalyst for purifying particulate matter mainly containing carbon included in an exhaust gas from an internal combustion engine reproduction Is to do.

[0014] In the above method of use, it is desirable to provide a NO _x generating means disposed on an exhaust gas upstream side of the molten salt type catalyst, the NO _x generated in the NO _x generating means in a molten salt type catalyst.

The exhaust gas purification control device of the present invention includes a solid carrier and at least one selected from silver nitrate, alkali metal nitrate, alkaline earth metal nitrate and rare earth element nitrate supported on the solid carrier. consists of a catalyst component, a molten salt type catalyst for purifying particulate matter that mainly carbon contained in the exhaust gas from an internal combustion engine, the NO _x generating means disposed in the exhaust gas upstream side of the molten salt type catalyst, melting a deterioration detecting means for detecting a physical quantity related to the degree of deterioration of the catalyst component of the salt type catalyst, the degree of deterioration of the catalyst component control supplies to drive the NO _x generation unit NO _x in a molten salt type catalyst when a predetermined range Department and more to be.

In this exhaust gas purification control device, the deterioration detecting means may be a deterioration calculating means for calculating the degree of deterioration of the catalyst component from the operation history of the internal combustion engine. Also place the NO _x sensor, respectively upstream and downstream of the molten salt type catalyst, the deterioration detecting means has detected at each of the NO _x sensor
It may be the concentration of NO _x difference degradation calculating means for calculating a degree of deterioration of the catalyst component.

[0017] The NO _x generation means is a plasma generating apparatus, the control unit is that the degree of deterioration of the catalyst component is supplied in a molten salt type catalyst the NO in the exhaust gas to drive the plasma generator when the predetermined range as NO ₂ Preferably, the NO _x generating means is NO
an _x storage reduction catalyst, the control unit it is also preferable that the degree of deterioration of the catalyst component is supplied to and drained the NO ₂ from the NO _x storage-and-reduction type catalyst molten salt type catalyst at a predetermined range.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a molten salt catalyst used in the present invention, a catalyst component containing nitrate is supported on a solid support. Therefore, even when the nitrate is in the liquid phase, the state of attachment to the solid carrier is maintained by the interaction with the solid carrier,
There is no problem such as flowing downstream. Further, since the catalyst component is solid at room temperature, handling of the catalyst is easy, and mounting on the exhaust passage can be performed similarly to a conventional three-way catalyst.

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

[0020] Even further decomposition to nitrate in a high temperature region caused again nitrate is produced by reacting with NO _x contained in the exhaust gas. As a result, the catalyst is regenerated, and the durability is excellent.

As the solid carrier, alumina, zirconia, titania, silica, zeolite and the like used in conventional three-way catalysts and the like can be used. Magnesia spinel, zirconia, alkali metal oxides, magnesia and the like can be used. Particularly preferred are basic carriers such as oxides of alkaline earth metals and oxides of rare earth elements such as lanthana and neodia. By using such a basic carrier, the solid phase reaction between the nitrate and the carrier is suppressed, so that the durability is improved.

The catalyst component contains at least one selected from silver nitrate, alkali metal nitrate, alkaline earth metal nitrate and rare earth element nitrate. Examples of the alkali metal nitrate include KNO ₃ , CsNO ₃ , NaNO ₃ , and LiNO ₃ . As the alkaline earth metal nitrate, Ba
(NO ₃ ) ₂ , Sr (NO ₃ ) ₂ , Ca (NO ₃ ) ₂ , Mg (NO ₃ ) _{2 and the} like. As rare earth element nitrates, Y ₂ (NO ₃ ) ₃ , La ₂ (N
O ₃ ) ₃ , Nd ₂ (NO ₃ ) ₃ , Pr ₂ (NO ₃ ) _{3 and the} like. Of these, only one kind may be used, or a complex nitrate in which a plurality of kinds are complexed may be supported. The use of a composite nitrate often lowers the melting temperature.

The composite nitrate includes 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 composite nitrates are used, the melting temperature can be reduced to 200 ° C or lower.

As the nitrate contained in the catalyst component, those having a low melting temperature and a high decomposition temperature are desirable. Thereby, PM can be efficiently burned and removed in exhaust gas having a wide temperature range and a wide space velocity. For example, among the above nitrates, those containing alkali metal nitrates are preferable, and those containing LiNO ₃ are most preferable.

The loading amount of the nitrate is desirably 1% by weight or more based on the solid carrier. If the carrying amount is less than this, combustion of PM becomes difficult. Also, as the amount of nitrate carried increases, the PM combustion temperature tends to decrease.
If the carrier is carried in an amount of 20% by weight or more, the stability on the carrier becomes insufficient, and the carrier may flow downstream and agglomerate.

It is desirable that the catalyst component further contains an oxidation promoting component. The oxidation promotion component promotes the combustion of PM due to oxidation of SOF in PM and the like. Noble metals such as Pt, Pd and Rh, or CeO ₂ ,
ZrO ₂ , CeO ₂ -ZrO ₂ solid solution, BaO, CaO, V ₂ O ₅ , ZnO, W
O ₃ , MoO ₃ , NiO, FeO, Fe ₃ O ₄ , Fe ₂ O ₃ , MnO ₂ , Cr
Various oxides such as ₂ O ₃ , CuO, CoO, and Co ₃ O ₄ can be used. Among them, it is particularly desirable to contain Pt. Pt effect of reducing the NO _x in the exhaust gas with the oxidation of SOF is achieved by, also if supporting Pt in the vicinity of the nitrates, NO in the exhaust gas reacts with the nitrate decomposed becomes NO ₂ by Pt, nitrates The durability is improved because of the regeneration.

The amount of the oxidation promoting component to be carried is preferably in the range of 0.1 to 10% by weight for the noble metal and 1 to 50% by weight for the various oxides based on the solid carrier. If the amount is less than this range, the effect is not exhibited, and if the amount is more than that, the effect may be saturated and an adverse effect may appear.

In order to support the nitrate on the solid carrier, the solid carrier may be impregnated with an aqueous solution of nitrate and dried. In addition, in order to carry the oxidation promoting component, the oxidation promoting component may be carried out using an aqueous solution of the metal compound, and may be fired.

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

Further, for example, a cylindrical body having a fluid passage therein, a lump having a maximum diameter smaller than the inner diameter of the cylindrical body,
A vertical plate having a plate-like shape and a large vertical surface having a maximum area being substantially parallel to the central axis direction of the cylindrical body and being arranged between the massive body and the inner surface of the cylindrical body in contact with the massive body and the inner surface of the cylindrical body. A unit consisting of a horizontal plate having a plate-like shape and a large horizontal surface having a maximum area, which is substantially perpendicular to the center axis direction of the cylindrical body, abuts on the vertical plate, and comes into contact with the block and the inner surface of the cylindrical body; A catalyst comprising a packing structure in which one or more units are packed in series in the direction of the center axis of the cylindrical body, and each of which supports a catalyst component using a lump, a vertical plate and a horizontal plate as carriers. It is also preferable to do so. By doing so, the exhaust gas flowing through the cylinder becomes turbulent and the contact area between the exhaust gas and the carrier becomes extremely large, so that PM in the exhaust gas can be efficiently burned and removed.

In the above-mentioned catalyst component, not only the nitrate is decomposed by high-temperature heat to form an oxide, but also a catalyst component composed of a nitrate or an oxidation-promoting component reacts with PM to form a complex compound. This makes it difficult to melt the nitrate, making it difficult to burn off PM. Therefore, in the use of molten salt type catalyst of the present invention, when the catalyst component is degraded in this manner, it is positively supplied to the NO _x in the molten salt type catalyst. Thereby rich NO _x again nitrate is produced by reacting with the oxide or a compound of the PM nitrate, it reproduces the molten salt type catalyst.

[0032] NO _x, it is NO and NO _2, NO ₂
Is particularly preferred.

In order to supply NO _x to the molten salt type catalyst, NO ₂
Although gas or the like can be directly added to the exhaust gas and supplied, it is preferable to use NO abundantly present in the exhaust gas. Thus to, it is desirable to use a NO _x generation means as referred to in the exhaust gas purification controller of the present invention.

As the NO _x generating means, for example, a plasma generator, an oxidation catalyst or a NO _x storage reduction type catalyst is typically exemplified.

The exhaust gas contains NO.
It is difficult to directly react with oxides of metals that constitute the acid salt.
No, because it ’s difficult_Two It is preferred that Also in the exhaust gas
When plasma is generated in the exhaust gas, NO in the exhaust gas becomes NO_Two Becomes
I know that. Therefore, the exhaust gas on the upstream side of the molten salt catalyst is
When plasma is generated in gas, NO in exhaust gas becomes NO. _Two 
And flows into the molten salt catalyst,
Can play minutes.

The conditions for generating plasma are not particularly limited. However, since the reaction rate for generating NO ₂ from NO differs depending on the exhaust gas temperature, the relationship between the temperature and the NO ₂ generation rate and the relationship between the plasma irradiation time and the NO ₂ generation rate Preferably, a map is created by measuring the relationship in advance, and the plasma irradiation time is determined by referring to the map.

As the plasma generator, a device in which a pair of electrodes are arranged in an exhaust gas flow path and discharge is performed between the pair of electrodes can be used. The pair of electrodes may be arranged at intervals in the flow direction of the exhaust gas, or may be arranged at intervals in the direction perpendicular to the flow direction of the exhaust gas.

An oxidation catalyst or NO_x Storage reduction catalyst
Is located upstream of the molten salt catalyst, diesel exhaust gas
Exhaust gas in lean atmosphere comes in contact with precious metals such as Pt
NO by doing_Two As a molten salt catalyst
Thus, the molten salt catalyst can be regenerated. in this case
NO_x It is desirable to use a storage reduction catalyst. NO _x 
If an occlusion reduction catalyst is used, NO generated by precious metals
_x Not only NO_x NO stored in the storage material_x Also molten salt type
Can be supplied to the catalyst, so supply to the molten salt type catalyst
NO in exhaust gas_x The concentration can be even higher
And the regeneration efficiency is improved. For example, at low temperatures,
NO rich pulse with less agent_x Given to occlusion reduction type catalyst
In case NO_x NO from storage reduction catalyst_Two Raw spitting
It is known that this NO_Two The catalyst component
It is desirable to use it for life.

The exhaust gas purification control device of the present invention includes a deterioration detecting means for detecting the degree of deterioration of the catalyst component in the molten salt type catalyst. Supplying a NO _x in the catalyst component is not deteriorated, NO _x because the result is directly discharged, when the catalyst component is supplied only NO _x at the time when a predetermined deterioration state, waste of the NO _x It is possible to prevent the emission of NO _x due to a sufficient supply.

This deterioration detecting means may be a deterioration calculating means for calculating the degree of deterioration of the catalyst component from the operation history of the internal combustion engine, for example. For example by detecting the temperature of the exhaust gas flowing into the molten salt type catalyst to estimate the amount of degradation of the nitrate, can the integrated value control unit After exceeds a predetermined value is configured to drive the NO _x generator.

The upstream and downstream sides of the molten salt catalyst are
NO each_x It is also preferable to arrange a sensor. Catalyst component
Deteriorates, the upstream and downstream NO_x The density difference is small
Therefore, the deterioration calculation means_x Detected by sensor
NO_x Calculate density difference, NO _x If the density difference is less than
Control means is NO_x Configured to drive the generating means
Can be

In the exhaust gas purification control device of the present invention,
It is desirable to determine whether or not the catalyst component has been regenerated, and if it has not been sufficiently regenerated, it is desirable to perform feedback control so as to further drive the NO _x generation means. For example the information such as operating conditions and exhaust gas temperature of the internal combustion engine, NO _x generating means recovery rate of the catalyst component is calculated from the generated amount of NO _x information by further NO _x when the recovery rate is less than a predetermined value Preferably, the generating means is driven.

[0043] In addition to calculating the amount of NO _x absorbed in the molten salt type catalyst by the detection value of each of the NO _x sensor disposed upstream and downstream of the molten salt type catalyst, if the value is less than a predetermined value May further drive the NO _x generation means.

As this NO _x sensor, NO _x in exhaust gas
As long as it can detect a physical quantity relating to the quantity, or the like can be used NO _x sensor, for example a semiconductor type.

When a NO _x storage-reduction catalyst is used as the NO _x generation means, it is desirable to provide exhaust gas control means for adjusting the atmosphere of the exhaust gas flowing into the NO _x storage-reduction catalyst. When it is determined by the deterioration detecting means that regeneration of the catalyst component is necessary, a small amount of a reducing agent is added to the exhaust gas to make the exhaust gas atmosphere a lower rich atmosphere. Thus the NO _x storage-and-reduction type catalyst, since the NO _x which had stored in the NO _x storage material is released as NO _2, it is possible to regenerate the catalyst component of the molten salt type catalyst efficiently.

In this case, the addition amount of the reducing agent is determined according to the exhaust gas temperature. A map for obtaining the NO ₂ emission amount from the exhaust gas temperature and the amount of the reducing agent is formed in advance, and the control means refers to the map. It may be configured as follows.

It should be noted as a NO _x storage-and-reduction type catalyst can be used NO _x storage-and-reduction type catalyst which is used in gasoline engine systems, be easy to release NO ₂ is desirable. Further, as the reducing agent, light oil which is a fuel of a diesel engine, or a hydrocarbon such as propane can be used.

[0048]

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

First, a foam-shaped substrate (13 cells / inch) was prepared, and a magnesia spinel powder was wet-coated to form a coat layer. The coating amount was 100 g per liter of the base material. Next, a predetermined amount of an aqueous solution of LiNO _{3 having a} predetermined concentration was impregnated into the coat layer, and dried to prepare a molten salt catalyst. The supported amount of LiNO ₃ is 20 g per liter of the base material.

<Test Example 1> The above molten salt catalyst was heat-treated at 700 ° C. for 1 hour in the atmosphere to deteriorate it, and then the model gas shown in Table 1 was subjected to a heating at a temperature and a space velocity of 30,000 / hr at each temperature.
After flowing for a time, the amount of NO ₂ absorbed by the catalyst was measured. Figure 1 shows the percentage of the absorbed NO ₂ to total NO ₂ content as a recovery rate.

FIG. 1 shows that the higher the temperature, the lower the recovery rate of the catalyst, and that the regeneration of the catalyst with NO ₂ is preferably performed at a low temperature. Also recovery rate
It can be seen that if the target is 45%, the regeneration temperature should be set to 150 ° C or less.

<Test Example 2> This molten salt catalyst was heat-treated at 700 ° C. for 1 hour in the air to deteriorate it, and then the model gas shown in Table 1 was passed at 150 ° C. and a space velocity of 30,000 / hr. Then, the amount of NO ₂ absorbed by the catalyst was measured every hour.
FIG. 2 shows the ratio of the absorbed NO _{2 to} the total NO ₂ amount as the recovery rate.

FIG. 2 also shows that the longer the reproduction processing time is, the more preferable the reproduction processing time is and the recovery rate is in direct proportion within a range where the recovery rate does not exceed 100%. In addition, if the recovery rate is set to 45%, it is understood that the reproduction processing time is desirably 2 hours or more.

<Test Example 3> Further, this molten salt type catalyst was heat-treated at 700 ° C. for 1 hour in the atmosphere to be deteriorated.
Model gas that differs only in the NO ₂ concentration of the model gas shown in
The mixture was passed for 2 hours at 150 ° C. and a space velocity of 30,000 / hr, and the amount of NO ₂ absorbed by the catalyst was measured. FIG. 3 shows the ratio of the absorbed NO _{2 to} the total NO ₂ amount as the recovery rate.

FIG. 3 shows that the higher the NO ₂ concentration, the more preferable.
It can also be seen that the NO ₂ concentration and the recovery rate are in direct proportion within the range where the recovery rate does not exceed 100%. 45% recovery rate
It can be seen that it is desirable to set the NO ₂ concentration at 650 ppm or more.

In each of the test examples described above, it is possible to recover the molten salt catalyst by 100%. However, if the recovery rate is 15% or more, the effect of regeneration is exhibited, so that the recovery is always 100%. No need.

[0057]

[Table 1]

<Test Example 4> In addition, a new catalyst of the above-mentioned molten salt type catalyst, a catalyst which had been deteriorated by heat treatment at 700 ° C. for 1 hour in the air, and a catalyst which had deteriorated were tested under the same conditions as in Test Example 1. ° C
Each of the regenerated products was mounted on the exhaust system of a diesel engine, and 0.2 g of each PM was collected.

Under the flow of helium gas containing 10% of O ₂ through these catalysts, the temperature was increased to 700 ° C. at a rate of 20 ° C./min.
The combustion characteristics of PM were investigated by measuring the amount of CO ₂ emitted. CO emitted per unit time at each temperature
₂ amount, and normalizes the amount of CO ₂ in the most amount of CO ₂ is large temperature 1, shown in FIG. A catalyst not supporting LiNO ₃ as a blank was measured in the same manner, and the results are shown in FIG.

It is apparent from FIG. 4 that the catalyst regenerated by flowing NO ₂ can burn and remove PM in a low temperature range as in the case of a new catalyst.

(Embodiment 1) FIG. 5 shows a block diagram of an exhaust gas purification control apparatus according to an embodiment of the present invention. This exhaust gas purification control device includes a diesel engine 1 having an engine control system 10, a molten salt catalyst 2 provided in an exhaust system thereof, a plasma generator 3 provided upstream of the molten salt catalyst 2, A temperature sensor 4 for detecting the temperature of exhaust gas flowing into the molten salt catalyst 2, and an engine control system
The control unit 5 includes a computer that controls the driving of the plasma generator 3 based on information from the apparatus 10 and a signal from the temperature sensor 4.

The molten salt type catalyst 2 is the same as that used in the above test example.

The plasma generator 3 is composed of a pair of electrodes provided in the exhaust passage of the diesel engine 1 at intervals in the exhaust gas flow direction, and is configured to generate a corona discharge in the exhaust gas by applying a voltage. I have.

Hereinafter, the control contents of the exhaust gas purification control device of this embodiment will be described with reference to the flowchart of FIG.

Step of mounting a new molten salt type catalyst 2
When the engine 1 is driven at 100, the exhaust gas in an oxygen-rich lean atmosphere passes through the molten salt catalyst 2. Then, LiNO ₃ of the molten salt type catalyst 2 is melted, and comes into contact with PM, so that P
M is oxidized and burned for purification. In this state, the plasma generator 3 is not driven.

On the other hand, the control unit 5 includes an engine control system.
The operation information from 10 and the signal from the temperature sensor 4 are input, and the control unit 5 calculates the decomposition state of LiNO ₃ from the torque and rotation speed of the engine 1 and the exhaust gas temperature, and constantly monitors the integrated value thereof. I have. No operation is performed until the integral value reaches the predetermined value in step 101, and when the integral value exceeds the predetermined value, the control unit 5 drives the plasma generator 3 in step 102.

[0067] Note that the "predetermined value" is the type of engine, operating conditions, is different depending on the amount of NO _x in the exhaust gas, is determined by trial and error.

The plasma generator 3 generates corona discharge in the exhaust gas. Then, the control unit 5 calculates the target time (T) of corona discharge in step 104 with reference to the data 103 measured in advance. The data 103 is created based on a graph (FIG. 7) in which the rate of change of NO to NO ₂ is measured at each temperature during corona discharge in a model gas (space velocity 60,000 / hr) shown in Table 2, for example. be able to. That is, by referring to the data 103, the exhaust gas temperature detected by the temperature sensor 4 and the NO
Since the amount of NO ₂ to be generated can be calculated from the amount, the target time (T) of corona discharge can be calculated from the amount of NO ₂ necessary for the regeneration of LiNO ₃ .

[0069]

[Table 2]

Then, in step 105, the corona discharge is continued until the duration (t) of the corona discharge reaches the target time (T).
Then, the driving of the plasma generator 3 is stopped, the integrated value is initialized to zero, and the process returns to step 101.

(Embodiment 2) In the exhaust gas purification control apparatus of Embodiment 1, the control of the control unit 5 can be performed as follows. That is, as shown in FIG. 8, when the integral value becomes equal to or more than the predetermined value in step 201, the control unit 5
Drives the plasma generator 3. Next, in step 204, the control unit 5 detects the detected temperature from the temperature sensor 4 and
The recovery rate of the molten salt catalyst 2 is calculated with reference to
If the recovery rate is less than the predetermined value in 205, the driving of the plasma generator 3 is continued. When the recovery rate reaches a predetermined value, the driving of the plasma generator 3 is stopped in step 206, the integrated value is initialized to zero, and the process returns to step 201.

Here, the data 203 can be created, for example, based on the graphs shown in FIGS. That is, the detected temperature from the temperature sensor 4 and the data 203
, The recovery rate of the molten salt catalyst 2 can be calculated.

(Embodiment 3) FIG. 9 shows a block diagram of an exhaust gas purification control apparatus according to a third embodiment of the present invention.
This exhaust gas purification control device includes a diesel engine 1 having an engine control system 10, a molten salt catalyst 2 provided in an exhaust system thereof, a plasma generator 3 provided upstream of the molten salt catalyst 2, a temperature sensor 4 for detecting the temperature of exhaust gas flowing into the molten salt type catalyst 2, NO _x sensor 60 for detecting the concentration of NO _x in the exhaust gas flowing into the molten salt type catalyst 2
If a NO _x sensor 61 for detecting the concentration of NO _x in the exhaust gas flowing out of the molten salt type catalyst 2, and a control unit 5 which consists computer for controlling the driving of the plasma generator 3.

[0074] The exhaust gas purification control unit, NO _x sensor 6
The configuration is the same as that of the exhaust gas purification control device of the first embodiment except that the exhaust gas purification control device of the first embodiment is provided. Note that semiconductor sensors are used as the NO _x sensors 60 and 61.

Hereinafter, the control contents of the exhaust gas purification control device of this embodiment will be described with reference to the flowchart of FIG.

Step of installing new molten salt type catalyst 2
When the engine 1 is driven at 300, the exhaust gas in an oxygen-excess lean atmosphere passes through the molten salt catalyst 2. Then, LiNO ₃ of the molten salt type catalyst 2 is melted, and comes into contact with PM, so that P
M is oxidized and burned for purification. In this state, the plasma generator 3 is not driven.

On the other hand, the control unit 5 includes an engine control system.
The operation information from 10 and the signal from the temperature sensor 4 are input, and the control unit 5 calculates the decomposition state of LiNO ₃ from the torque and rotation speed of the engine 1 and the exhaust gas temperature, and constantly monitors the integrated value thereof. I have. No operation is performed until the integral value reaches the predetermined value in step 301, and when the integral value exceeds the predetermined value, the control unit 5 drives the plasma generator 3 in step 302.

The plasma generator 3 generates corona discharge in the exhaust gas, and NO in the exhaust gas becomes NO ₂ . The control unit 5 calculates the concentration of NO _x difference [Delta] NO _x before and after the detection value of the NO _x sensor 60 and 61 of the molten salt type catalyst 2 in step 303.

Since the molten salt type catalyst is recovered (regenerated) by absorbing NO ₂ into the deteriorated molten salt type catalyst, ΔNO _x is large while the recovery rate is low, and if recovery is completed, it is theoretically possible. The upper ΔNO _x becomes zero. Therefore, the degree of recovery of the molten salt catalyst can be determined by calculating ΔNO _x .

In step 304, if ΔNO _x is equal to or more than the predetermined value, the corona discharge is continued. If ΔNO _x becomes less than the predetermined value, the driving of the plasma generator 3 is stopped in step 305, and the integrated value is set to zero. And the process proceeds to step 3.
Return to 01.

(Embodiment 4) FIG. 11 is a block diagram of an exhaust gas purification control apparatus according to a fourth embodiment of the present invention.
The exhaust gas purification controller includes a diesel engine 1 with an engine control system 10, a molten salt type catalyst 2 provided in the exhaust system, NO _x storage reduction catalyst provided in an upstream side of the molten salt type catalyst 2 7, a temperature sensor 4 for detecting the temperature of exhaust gas flowing into the molten salt catalyst 2, and a molten salt catalyst 2
NO _x sensor 60 for detecting the concentration of NO _x in the exhaust gas flowing into the
If a NO _x sensor 61 for detecting the concentration of NO _x in the exhaust gas flowing out of the molten salt type catalyst 2, a control unit 5 comprising a computer, a fuel injection device provided on the upstream side of the NO _x storage reduction catalyst 7 8 is comprised.

[0082] The exhaust gas purification control unit, except that with a NO _x storage-and-reduction type catalyst 7 and that the fuel injection device 8 using in place of the plasma generator 3 have the same structure as in Example 3. Note that the control unit 5 also controls the fuel injection device 8.

The NO _x storage-reduction type catalyst comprises a monolith substrate having a honeycomb shape and a coat layer made of a solid solution of Al ₂ O ₃ , TiO ₂ and CeO ₂ —ZrO ₂ formed thereon. 1 g of Pt, 0.5 mol of Ba, 0.1 mol of K, Li
Is supported by 0.1 mol.

The fuel injection device 8 is a device for injecting light oil, which is a fuel, into the exhaust gas, and whether or not the ejection is possible, the ejection amount and the ejection time are controlled by the control unit 5.

Hereinafter, control contents of the exhaust gas purification control device of this embodiment will be described with reference to the flowchart of FIG.

Step of installing new molten salt type catalyst 2
When the engine 1 is driven at 400, the exhaust gas in an oxygen-excess lean atmosphere passes through the molten salt catalyst 2. Then, LiNO ₃ of the molten salt type catalyst 2 is melted, and comes into contact with PM, so that P
M is oxidized and burned for purification.

In the NO _x storage-reduction catalyst 7, NO in the exhaust gas is oxidized to NO _x and is composed of Ba, K and Li.
It is stored in the NO _x storage material. When the NO _x storage amount is saturated, the NO _x flows into the molten salt catalyst 2 to regenerate the deteriorated LiNO ₃ .

The control unit 5 receives an instruction from the engine control system 10.
Operation information and the signal from the temperature sensor 4 are input and controlled.
The part 5 includes the torque and rotation speed of the engine 1 and the exhaust gas temperature.
From LiNO_ThreeCalculates the state of deterioration and constantly monitors the integrated value
are doing. Then, at step 401, the integral value becomes a predetermined value.
No operation is performed until the integral value exceeds a predetermined value.
5 drives the fuel injection device 8 in step 402 to generate
Inject light oil. As a result, the reducing atmosphere in the exhaust gas atmosphere
A slightly rich atmosphere exceeding the oxidized component is created,
Gas is NO_x It is occluded by flowing into the occlusion reduction type catalyst 7.
NO_x Is NO _Two And released to the molten salt catalyst 2
Enter. This is rich NO_x Flows into the molten salt catalyst 2
Degraded LiNO_ThreeIs played.

[0089] Then, the control unit 5, before and after the detection value of the NO _x sensor 60 and 61 of the molten salt type catalyst 2 in Step 403
Computing the concentration of NO _x difference [Delta] NO _x. At step 404, ΔNO _x
There continues to fuel injection in the case of more than the predetermined value, the driving of the fuel injection device 8 is stopped at step 405 When the [Delta] NO _x becomes less than a predetermined value, and initializes the integrated value to zero, the process in step 401 Return.

(Embodiment 5) FIG. 13 is a block diagram of an exhaust gas purification control apparatus according to a fifth embodiment of the present invention.
The exhaust gas purification controller includes a diesel engine 1 with an engine control system 10, a molten salt type catalyst 2 provided in the exhaust system, NO _x storage reduction catalyst provided in an upstream side of the molten salt type catalyst 2 7, a temperature sensor 4 for detecting the temperature of exhaust gas flowing into the molten salt catalyst 2, a control unit 5 composed of a computer, and a fuel injection device 8 provided on the upstream side of the NO _x storage reduction catalyst 7. It is configured.

[0091] The exhaust gas purification control unit, NO _x sensor 6
The configuration is the same as that of the fourth embodiment except that it does not have 0 and 61.

Hereinafter, the control contents of the exhaust gas purification control device of this embodiment will be described with reference to the flowchart of FIG.

Step of installing new molten salt type catalyst 2
When the engine 1 is driven at 500, exhaust gas in an oxygen-rich lean atmosphere passes through the molten salt catalyst 2. Then, LiNO ₃ of the molten salt type catalyst 2 is melted, and comes into contact with PM, so that P
M is oxidized and burned for purification.

In the NO _x storage-reduction catalyst 7, NO in the exhaust gas is oxidized to NO _x and is composed of Ba, K and Li.
It is stored in the NO _x storage material. When the NO _x storage amount is saturated, the NO _x flows into the molten salt catalyst 2 to regenerate the deteriorated LiNO ₃ .

The control unit 5 receives an instruction from the engine control system 10.
Operation information and the signal from the temperature sensor 4 are input and controlled.
The part 5 includes the torque and rotation speed of the engine 1 and the exhaust gas temperature.
From LiNO_ThreeCalculates the state of deterioration and constantly monitors the integrated value
are doing. Then, at step 501, the integral value reaches a predetermined value.
No operation is performed until the integral value exceeds a predetermined value.
5 drives the fuel injection device 8 in step 502 to generate
Inject light oil. As a result, the reducing atmosphere in the exhaust gas atmosphere
A slightly rich atmosphere exceeding the oxidized component is created,
Gas is NO_x It is occluded by flowing into the occlusion reduction type catalyst 7.
NO_xIs NO _Two And released to the molten salt catalyst 2
Enter. This is rich NO_x Flows into the molten salt catalyst 2
Degraded LiNO_ThreeIs played.

Then, the control unit 5 determines in step 504 that the map
Referring to 503, the NO ₂ generation amount is calculated. On map 503,
Data is accumulated from which the NO ₂ generation amount can be estimated from the exhaust gas temperature and the amount of injected fuel. NO generated
₂ is supplied to the molten salt type catalyst 2 and used for regeneration. Therefore, if the NO ₂ generation amount is less than the predetermined value in step 505, the fuel injection is continued, and if the NO ₂ generation amount is Then, in step 506, the driving of the fuel injection device 8 is stopped, the integrated value is initialized to zero, and the process returns to step 501.

[0097]

According to the method of using the molten salt type catalyst and the exhaust gas purification control device of the present invention, the deteriorated molten salt type catalyst can be continuously regenerated. Therefore PM
Can be stably burned and removed for a long period of time.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a temperature and a recovery rate when flowing a gas containing 650 ppm of NO ₂ through a deteriorated molten salt catalyst for 2 hours.

FIG. 2 is a graph showing the relationship between the recovery time and the time when a gas containing 650 ppm of NO ₂ is passed at 150 ° C. through a deteriorated molten salt catalyst.

FIG. 3 is a graph showing the relationship between the NO ₂ concentration and the recovery rate when a gas containing NO ₂ at various concentrations is passed at 150 ° C. for 2 hours through a deteriorated molten salt catalyst.

FIG. 4 is a graph showing PM combustion characteristics of a new catalyst, a deteriorated catalyst, a recovered catalyst, and a blank catalyst.

FIG. 5 is a block diagram illustrating a configuration of an exhaust gas purification control device according to the first embodiment.

FIG. 6 is a flowchart showing control contents of a control unit of the exhaust gas purification control device of the first embodiment.

FIG. 7 shows the relationship between the temperature by the plasma generator used in the embodiment and
4 is a graph showing a relationship with a NO ₂ generation rate.

FIG. 8 is a flowchart illustrating control contents of a control unit of the exhaust gas purification control device of the second embodiment.

FIG. 9 is a block diagram illustrating a configuration of an exhaust gas purification control device according to a third embodiment.

FIG. 10 is a flowchart illustrating control contents of a control unit of the exhaust gas purification control device of the second embodiment.

FIG. 11 is a block diagram illustrating a configuration of an exhaust gas purification control device according to a fourth embodiment.

FIG. 12 is a flowchart illustrating control contents of a control unit of the exhaust gas purification control device of the fourth embodiment.

FIG. 13 is a block diagram illustrating a configuration of an exhaust gas purification control device according to a fifth embodiment.

FIG. 14 is a flowchart illustrating control contents of a control unit of the exhaust gas purification control device of the fifth embodiment.

[Explanation of symbols]

1: Diesel engine 2: Molten salt catalyst 3: Plasma generator (NO _x generation means) 4: Temperature sensor 5: Control unit 7: NO _x storage reduction catalyst (NO _x generation means) 8: Fuel injection device (NO _x generation means)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01N 3/10 F01N 3/20 E 3/20 B01D 53/36 K (72) Inventor Yuji Sakakibara Aichi, Aichi 1F, 41, Toyoda Central R & D Laboratories, Inc. DA02 DA20 EA03

Claims (7)

[Claims] An internal combustion engine comprising: a solid support; and a catalyst component containing at least one selected from silver nitrate, alkali metal nitrate, alkaline earth metal nitrate and rare earth element nitrate supported on the solid support. using molten salt type catalyst particulate matter to carbon contained in the exhaust gas mainly in the molten salt type catalyst for purifying by supplying NO _x, characterized in that play. 2. An exhaust gas upstream side of said molten salt type catalyst having NO _x
The generating means is disposed, the use of molten salt type catalyst according to claim 1, the NO _x generated in the NO _x generating means and supplying to said molten salt type catalyst. 3. A solid carrier and a catalyst component containing at least one selected from silver nitrate, alkali metal nitrate, alkaline earth metal nitrate and rare earth element nitrate supported on the solid carrier. of a molten salt type catalyst for purifying particulate matter that mainly carbon contained in the exhaust gas, the NO _x generating means disposed in the exhaust gas upstream side of the molten salt type catalyst, of the catalyst component of the molten salt type catalyst a deterioration detecting means for detecting a physical quantity related to the degree of deterioration, and a control section for supplying to the molten salt type catalyst the NO _x by driving the NO _x generating means when the degree of deterioration of the catalyst component is a predetermined range,
An exhaust gas purification control device comprising: 4. The exhaust gas purification control device according to claim 3, wherein the deterioration detecting means is a deterioration calculating means for calculating a degree of deterioration of the catalyst component from an operation history of the internal combustion engine. 5. Place the NO _x sensor, respectively upstream and downstream of the molten salt type catalyst, said deterioration detecting means deterioration of the catalyst component from the NO _x concentration difference detected by each of the NO _x sensor 4. The exhaust gas purification control device according to claim 3, wherein the exhaust gas purification control device is a deterioration calculation unit that calculates a degree. Wherein said NO _x generating means is a plasma generating apparatus, wherein the control unit is NO in the exhaust gas about the deterioration of the catalyst component is driving the plasma generating device when a predetermined range NO ₂
The exhaust gas purification control apparatus according to claim 3, wherein the apparatus is supplied to the molten salt catalyst. Wherein said NO _x generating means is a NO _x storage-and-reduction type catalyst, the control unit the degree of deterioration of the catalyst component was drained NO ₂ from the NO _x storage-and-reduction type catalyst when a predetermined range 4. The method according to claim 3, wherein the catalyst is supplied to a molten salt catalyst.
An exhaust gas purification control device according to item 1.