JPH11190210A - Exhaust gas purification control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove a positioning substance of a catalyst accumulated in the lapse of time from the catalyst by making exhaust gas exhausted from an internal combus tion engine in a logical air-fuel ratio or rich fuel state and holding exhaust gas tempera ture at higher than specified for longer than a specified period of time. SOLUTION: An ECU 25 decides an operating air fuel ratio by evaluating an operating state and a state of a NOx adsorptive catalyst 18 and sets fuel concentration at a specified value by controlling injection time of an injector 5, etc. Air-fuel mixture is ignited and burnt by an ignition plug 6, and combustion exhaust gas is led to an exhaust gas purifying system provided with the NOx adsorptive catalyst 18. At the time of stoichiometrical driving, NOx, NH, CO in exhaust gas is purified by its catalytic converter rhodium function, and at the time of lean driving, NOx is purified by a NOx adsorptive function and HC, CO is purified by a combustion function. Additionally, NOx purifying capacity of the NOx adsorptive catalyst 18 is constantly judged at the time of lean driving by judgement and a control signal of the ECU 25, and the NOx adsorptive capacity is recovered by shifting an air-fuel ratio of combustion, etc., to the rich side and holding exhaust gas temperature higher than specified and for longer than specified time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for purifying exhaust gas emitted from an internal combustion engine of an automobile or the like, and more particularly to an internal combustion engine operable at a lean air-fuel ratio (lean burn) and an automobile equipped with the internal combustion engine. The present invention relates to a device for purifying exhaust gas discharged from a plant.

[0002]

2. Description of the Related Art Carbon monoxide (CO) and hydrocarbons (HC: H) contained in exhaust gas discharged from an internal combustion engine of an automobile or the like are used.
Hydrocarbons, nitrogen oxides (NOx), and the like adversely affect the human body as air pollutants and cause problems such as hindering plant growth. So far, great efforts have been made to reduce these emissions, and in addition to reducing the amount generated by improving the combustion method of the internal combustion engine, a method of purifying the exhaust gas using a catalyst or the like has been developed. Has been promoted and has achieved steady results. For gasoline engine vehicles, Pt and Rh, which are three-way catalysts, are the main components of activity, and HC and CO
The mainstream is a method using a catalyst that renders harmless by simultaneously oxidizing NO and reducing NOx.

[0003] By the way, due to its characteristics, the three-way catalyst effectively acts only on exhaust gas generated by burning near the theoretical air-fuel ratio called a window. So conventionally,
Although the air-fuel ratio fluctuates according to the driving conditions of the vehicle, the fluctuation range is in principle the stoichiometric air-fuel ratio (A (weight of air) / F (weight of fuel) for gasoline) = about 14.7; The air / twist ratio is represented by A / F = 14.7, but this value varies depending on the fuel type.)
However, if the engine can be operated at an air-fuel ratio leaner than the stoichiometric air-fuel ratio, the fuel efficiency can be improved. Therefore, the development of lean burn combustion technology has been promoted. It is not unusual for cars to burn gas. However, as described above, when purifying lean burn exhaust gas with the current three-way catalyst, HC and CO can be oxidized and purified, but NOx cannot be effectively reduced and purified. Therefore, in order to apply the lean burn method to a large-sized vehicle and to extend the burn time of the lean burn method (expansion of the operating range to which the lean burn method is applied), lean burn compatible exhaust gas purification technology is required. Therefore, development of lean burn compatible exhaust gas purification technology, that is, technology for purifying HC, NO, and NOx in exhaust gas containing a large amount of oxygen (O ₂ ), particularly technology for purifying NOx, has been vigorously pursued. .

Japanese Patent Application Laid-Open No. 63-61708 proposes a method in which HC is supplied to the upstream of lean burn exhaust gas to lower the O ₂ concentration in the exhaust gas to a concentration range in which the catalyst can function effectively, thereby extracting the ability of the catalyst. I have.

JP-A-62-97630, 62-106826, 62-11
No. 7620 NOx in exhaust gas by (NO in to after converting absorbed to easily NO ₂ oxidation) removing absorbed by contact with a catalyst having a NOx trapping ability, stop the passage of the exhaust gas at the time the absorption efficiency is lowered A method of reducing and removing accumulated NOx using a reducing agent such as H ₂ , HC such as methane and gasoline, and regenerating the NOx absorption capacity of the catalyst is disclosed.

In PCT / JP92 / 01279 and PCT / JP92 / 01330, a NOx absorbent that absorbs NOx when the exhaust gas is lean and releases the absorbed NOx when the oxygen concentration in the exhaust gas is reduced is provided in the exhaust passage. NOx is absorbed when the exhaust gas is lean, and the absorbed NOx is absorbed by the exhaust gas flowing into the NOx absorbent.
_2. Exhaust gas purifying devices have been proposed in which the concentration is reduced and released.

However, in JP-A-63-61708, an exhaust gas composition (O ₂ concentration of about 0.5%) corresponding to an air-fuel ratio (A / F) of about 14.7 at which the catalyst functions is achieved. Requires a large amount of HC. Although the use of the blow-by gas of the present invention is effective, it is not sufficient to treat the exhaust gas during operation of the internal combustion engine. Injecting fuel is not technically impossible, but will result in a reduction in fuel economy, which has been saved by the lean burn method.

Further, Japanese Patent Application Laid-Open No. 62-97630, 62-106826,
In JP 62-117620, for Upon regeneration of the NOx absorbent by stopping the flow of the exhaust gas a reducing agent such as HC is brought into contact with the NOx absorbent, the fuel consumption due to O ₂ in the exhaust gas of the reducing agent is significantly suppressed The amount of reducing agent used is drastically reduced. But,
An exhaust switching mechanism for providing two NOx absorbents and alternately flowing exhaust gas through them is necessary, and it cannot be denied that the structure of the exhaust treatment device becomes complicated.

Further, in PCT / JP92 / 01279 and PCT / JP92 / 01330, the exhaust gas is always N
Circulated through the Ox absorbent, and when the exhaust gas is lean,
To absorb ox, for regeneration of the absorbent by releasing the NOx absorbed by lowering the O ₂ concentration in the exhaust gas, the switching of the exhaust gas flow is not required, the problems of the method will be eliminated.
However, when the exhaust gas contains sulfur (SOx), the NOx absorbent combines with SOx to form sulfide,
There is a problem that the absorption capacity is rapidly deteriorated.

[0010]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention has a simple structure of an exhaust treatment device,
Further, it is an object of the present invention to provide an exhaust gas purification control device which is capable of effectively removing and detoxifying harmful components such as NOx from lean burn exhaust gas of an internal combustion engine, which consumes less reducing agent and has excellent durability.

[0011]

SUMMARY OF THE INVENTION The object of the present invention is to provide an exhaust gas discharged from an internal combustion engine at a stoichiometric air-fuel ratio or an excess of fuel (rich), and by maintaining the exhaust gas temperature at a predetermined value or more for a predetermined time or longer, By removing poisonous substances (SOx) of the catalyst accumulated in the catalyst from the catalyst, the deteriorated NOx adsorption ability can be recovered and solved. Below N
A method of adsorbing and reducing NOx on the Ox adsorption catalyst will be described. However, the NOx adsorbing ability becomes inferior as the amount of sulfur (SOx) contained in exhaust gas accumulates on the catalyst.

In the NOx adsorption catalyst used in the present invention,
In the oxidation-reduction stoichiometry relationship between the components in the exhaust gas, NOx is chemisorbed in a state where the oxidizing agent is large relative to the reducing agent,
NOx adsorbed with oxidizing agent in the same amount or more of reducing agent
A NOx adsorption catalyst for catalytic reduction of
In the oxidation-reduction stoichiometry relationship between each component in the exhaust gas, a state in which the oxidizing agent is large relative to the reducing agent is created, and NOx is chemisorbed on the adsorption catalyst. A state is created, and NOx adsorbed on the adsorption catalyst is brought into contact with a reducing agent to be reduced to N ₂ and rendered harmless.

Here, the adsorption catalyst refers to a material that has the ability to adsorb substances such as NOx and also has a catalytic function. In the present invention, it refers to a material having an ability to adsorb and capture NOx, an ability to catalytically reduce NOx, and an ability to catalytically oxidize HC, CO, and the like.

The oxidizing agent is O ₂ , NO, NO ₂ or the like, and is mainly oxygen. The reducing agent was H supplied to the internal combustion engine.
C is a reducing substance such as HC (including oxygen-containing hydrocarbon), CO, H ₂ or the like as a derivative thereof generated on the assumption of combustion, and HC added to exhaust gas as a reducing component described later.

As described above, HC, CO, H as reducing agents for reducing lean exhaust gas and NOx to nitrogen
_When they come into contact with ₂ etc., they cause a combustion reaction with O ₂ as an oxidizing agent in the exhaust gas. NOx (NO and NO ₂ )
Also reacts with these to be reduced to nitrogen. Usually, the utilization of the reducing agent is low in the presence of oxygen because both reactions proceed in parallel. Especially when the reaction temperature is 500 (depending on the catalyst material)
At a high temperature of ℃ or more, the ratio of the latter becomes considerably large. Therefore, NOx is separated from the exhaust gas in the adsorber (separated from O ₂ at least in the exhaust gas) it is possible to perform reduction to N ₂ in the NOx effectively by catalytic reaction with a reducing agent thereafter. In the present invention, NOx in lean exhaust gas is adsorbed and removed by the NOx adsorption catalyst to separate NOx in exhaust gas from O ₂ .

Next, in the NOx adsorption catalyst of the present invention, the oxidizing agent (O ₂ , NOx, etc.) and the reducing agent (H
C, CO, H ₂ etc.) in the oxidation-reduction system composed of the same amount or a predominant amount of the reducing agent, and the NOx adsorbed on the adsorption catalyst is contacted with the reducing agent such as HC to react with N ₂ to form N ₂ . To reduce.

By the way, NOx in exhaust gas is almost NO and N
Consists of O ₂ . NO ₂ is more reactive than NO. Therefore, adsorption removal and reduction of NO ₂ are easier than NO. Therefore, if NO is oxidized to NO ₂ , N
Adsorption removal and reduction of Ox are facilitated. The present invention is a method of removing oxidized to NO ₂ by O ₂ coexist NOx in lean exhaust gas, NO oxidation means such as adsorption catalyst therefor
It also includes providing an oxidation function or providing an oxidation catalyst before the adsorption catalyst.

The reduction reaction of chemically adsorbed NOx in the NOx adsorbing catalyst of the present invention can be approximately described by the following reaction formula.

M-NO ₃ + HC → MO + N ₂ + CO ₂ + H ₂
O → MCO ₃ + N ₂ + H ₂ O Here, M is a metal element (the reason why MCO ₃ is used as a reduction product will be described later). The above reaction is an exothermic reaction. Alkali metals and alkaline earth metals are taken as metals M, Na and B respectively.
When the reaction heat is evaluated as a representative, the standard state (1 atm,
(25 ° C.) is as follows.

2NaNO ₃ (s) + 5 / 9C ₃ H ₆ → Na ₂ C
O ₃ (s) + N ₂ + 2 / 3CO ₂ + 5 / 3H ₂ O [−ΔH = 8
73 kjule / mole] Ba (NO ₃ ) ₂ + 5 / 9C ₃ H ₆ → BaCO ₃ (s) + N ₂ +2
/ 3CO ₂ + 5 / 3H ₂ O [−ΔH = 751 kjule / mol
e] Here, s: solid g: gas The thermodynamic quantity of the adsorbed species used was the value of the corresponding solid.

Incidentally, the combustion heat of C ₃ H ₆ 5/9 mole is 1
070 kjule, and each of the above reactions has a calorific value comparable to the heat of combustion of HC. Naturally, this heat generation is transmitted to the contacting exhaust gas, and a local temperature rise on the surface of the adsorption catalyst is suppressed.

When the NOx trapping agent is a NOx absorbent, the NOx trapped in the bulk of the absorbing agent is also reduced, so that the calorific value increases. Bring. This exotherm shifts the equilibrium of the absorption reaction shown below to the emission side.

[0023] In order to reduce the NOx concentration in the exhaust gas discharged to rapidly reduced to the outside of the apparatus to release the NOx even enhance the concentration of reducing agent does not proceed much reaction of NO ₂ and HC in the gas phase. Therefore, the amount of NOx emission cannot be sufficiently reduced by increasing the amount of the reducing agent. It is also conceivable to perform an operation by a reduction reaction at a stage where the NOx absorption amount is small,
The frequency of regeneration of the NOx absorbent increases, which is not practical.

The adsorption catalyst of the present invention traps NOx only in the vicinity of its surface, so that the absolute amount of heat generation is small, and it is quickly transmitted to exhaust gas, so that the temperature rise of the adsorption catalyst is small. Therefore, release of the trapped NOx can be prevented.

The NOx adsorption catalyst of the present invention is characterized as a material that captures NOx on its surface by chemisorption and does not generate NOx by an exothermic reaction upon reduction of NOx. Further, the NOx adsorption catalyst of the present invention captures NOx by chemical adsorption on its surface or by chemical bonding near the surface, and generates NOx by an exothermic reaction upon reduction of NOx.
Is characterized as a material that does not cause the release of

The present inventors have proposed that at least potassium (K), sodium (Na), magnesium (Mg),
It has been found that the above characteristics can be realized by a NOx adsorption catalyst containing at least one element selected from strontium (Sr) and calcium (Ca) as a part of components.

The exhaust gas purifying apparatus for an internal combustion engine of the present invention comprises at least one element selected from the group consisting of potassium (K), sodium (Na), magnesium (Mg), strontium (Sr) and calcium (Ca). The NOx adsorption catalyst, which is included as a part, is disposed in the exhaust gas flow path, and in the oxidation-reduction stoichiometric relationship between the components in the exhaust gas, a state in which the amount of the oxidizing agent is large relative to the reducing agent is formed, and the NOx adsorption catalyst is formed on the adsorption catalyst.
Was chemically adsorbed, then the reducing agent to the oxidizing agent is made the same amount or more states, and characterized in that the detoxification is reduced to N ₂ by catalytic reaction with a reducing agent adsorbed NOx on adsorption catalyst I do.

The exhaust gas purifying apparatus for an internal combustion engine according to the present invention further comprises at least potassium (K), sodium (Na),
A NOx adsorption catalyst containing at least one element selected from magnesium (Mg), strontium (Sr) and calcium (Ca) as a part of components is disposed in the exhaust gas flow path;
In the oxidation-reduction stoichiometry, a state in which the oxidizing agent such as O ₂ is larger than the reducing agent such as HC is used to trap NOx by chemical bonding on the surface of the adsorption catalyst and in the vicinity of the surface. Make the same amount or more, and make NOx trapped by the adsorption catalyst react with the reducing agent to form N ₂
To make it harmless.

Particularly, the following can be suitably applied as the NOx adsorption catalyst in the present invention.

At least one selected from potassium (K), sodium (Na), magnesium (Mg), strontium (Sr) and calcium (Ca), and at least one selected from rare earths such as cerium and the like, platinum, rhodium, A composition comprising a metal and a metal oxide (or composite oxide) containing at least one element selected from precious metals such as palladium, and a composition comprising the composition supported on a porous heat-resistant metal oxide. The composition has excellent SOx resistance in addition to excellent NOx adsorption ability.

In the method of the present invention, the condition where the amount of the reducing agent is equal to or larger than the amount of the oxidizing agent can be prepared by the following method.

The combustion conditions in the internal combustion engine are set to the stoichiometric air-fuel ratio or excess fuel (rich). Further, a reducing agent is added to the lean burn exhaust gas.

The former can be achieved by the following method.

A method of controlling the fuel injection amount according to the output of an oxygen concentration sensor and the output of an intake flow sensor provided in an exhaust duct. In this method, a part of the plurality of cylinders is made excessive and the remaining fuel is made insufficient, and the components in the mixed exhaust gas from all the cylinders have the same amount or larger amount of the reducing agent than the oxidizing agent in the oxidation-reduction stoichiometry relationship. Includes methods for creating states.

The latter can be achieved by the following methods.

A method of introducing a reducing agent upstream of the adsorption catalyst in the exhaust gas stream. Gasoline as fuel for internal combustion engine
Light oil, kerosene, natural gas, their reformed products, hydrogen, alcohols, ammonia and the like can be applied.

It is also effective to introduce the blow-by gas and the canister purge gas upstream of the adsorption catalyst and to introduce a reducing agent such as a hydrocarbon contained therein. In a fuel direct injection type internal combustion engine, it is effective to inject fuel during an exhaust stroke and to input fuel as a reducing agent.

In the present invention, the adsorption catalyst can be applied in various shapes. Starting with the honeycomb shape obtained by coating the adsorption catalyst component on a honeycomb-like structure made of metal materials such as cordierite and stainless steel,
It can be applied as pellets, plates, granules, and powders.

In the present invention, the timing for forming a state in which the amount of the reducing agent is equal to or larger than that of the oxidizing agent can be determined by the following methods.

NOx emission during lean operation is determined from an air-fuel ratio setting signal determined by an ECU (Engine Control Unit), an engine speed signal, an intake air amount signal, an intake pipe pressure signal, a speed signal, a throttle opening, an exhaust gas temperature, and the like. When the amount is estimated and the integrated value exceeds a predetermined set value.

When an accumulated oxygen amount is detected by a signal from an oxygen sensor (or A / F sensor) placed upstream or downstream of the adsorption catalyst in the exhaust passage, and the accumulated oxygen amount exceeds a predetermined amount. As a variation thereof, when the accumulated oxygen amount during the lean operation exceeds a predetermined amount.

NOx placed upstream of the adsorption catalyst in the exhaust passage
When the accumulated NOx amount is calculated based on the sensor signal, and the accumulated NOx amount during the lean operation exceeds a predetermined amount.

NOx placed downstream of the adsorption catalyst in the exhaust passage
When the NOx concentration during the lean operation is detected based on a signal from the sensor, and the NOx concentration exceeds a predetermined concentration.

In the present invention, as described above, the time for maintaining the state in which the amount of the reducing agent is equal to or larger than the amount of the oxidizing agent or the amount of the reducing agent to be charged is, as described above, the characteristics of the adsorption catalyst and the specifications of the internal combustion engine. Although it can be determined in consideration of the characteristics and the like, these can be realized by adjusting the stroke of the fuel injection valve, the injection time and the injection interval.

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to specific embodiments of the present invention. The present invention is not limited to the following embodiments and examples, and it goes without saying that there are various embodiments within the scope of the idea.

[Adsorption Catalyst] The characteristics of the adsorption catalyst according to the method of the present invention will be described. The characteristics of N-N9 containing Na as an alkali metal and NK9 containing K are as follows << Adsorption catalyst preparation method >> Adsorption catalyst N-N9 was obtained by the following method.

Alumina sol as a binder obtained by mixing alumina powder and boehmite with nitric acid was mixed to obtain a nitric acid acidic alumina slurry. After the honeycomb was immersed in the coating liquid, it was quickly pulled up, and the liquid clogged in the cell was removed by air blowing, dried, and subsequently fired at 450 ° C. This operation was repeated to coat 150 g of alumina per 1 L of apparent volume of the honeycomb. A catalytically active component was carried on the alumina-coated honeycomb to obtain a honeycomb-shaped adsorption catalyst. For example, it was impregnated with a cerium nitrate (Ce nitrate) solution, dried, and fired at 600 ° C. for 1 hour. Subsequently, a mixed solution of a sodium nitrate (Na nitrate) solution, a titania sol solution and a magnesium nitrate (Mg nitrate) solution was impregnated, and dried and fired similarly. Further, the mixture was impregnated with a mixed solution of a dinitodiamine Pt nitric acid solution and a rhodium nitrate (Rh nitrate) solution, dried, and baked at 450 ° C. for 1 hour. Finally, it was impregnated with a Mg nitrate solution and fired at 450 ° C. for 1 hour. Alumina
(Al ₂ O ₃ ) Ce, Mg, Na, Ti, Rh, Pt supported honeycomb-shaped adsorption catalyst, 2Mg- (0.2Rh, 2.
7Pt)-(18Na, 4Ti, 2Mg) -27Ce / A
I ₂ O ₃ was obtained. Here, / Al ₂ O ₃ indicates that the active ingredient is Al ₂
The value before the element symbol indicates that it was supported on O ₃ , and the numerical value before the symbol of the element is the weight (g) of the indicated metal component supported per 1 L of the honeycomb apparent volume. The notation order indicates the loading order, and A
The components were carried in the order of components away from the components described close to l ₂ O ₃ , and the components enclosed in parentheses were carried simultaneously. Incidentally, the loading amount of each active ingredient can be changed by changing the active ingredient concentration in the impregnating solution.

The adsorption catalyst NK9 was prepared by the following method.

A potassium nitrate (K nitrate) solution was used in place of the Na nitrate solution in the preparation of the adsorption catalyst N-N9, and the other method was the same as that of the adsorption catalyst N-N9.
Rh, 2.7Pt)-(18K, 4Ti, 2Mg) -27C
e / Al ₂ O ₃ was obtained. In the same manner, the comparative catalyst NR
22Mg- (0.2Rh, 2.7Pt) -27Ce / Al
₂ O ₃ was obtained.

<< Performance Evaluation Method >> The adsorption catalyst obtained by the above method was heat-treated at 700 ° C. for 5 hours in an oxidizing atmosphere, and then its characteristics were evaluated by the following methods.

A 1.7-liter honeycomb-shaped adsorption catalyst prepared by the method of the present invention was mounted on a passenger car equipped with a lean-burn gasoline engine having a displacement of 1.8 L, and NOx
The purification properties were evaluated.

<< Characteristics of Adsorption Catalyst >> The adsorbent catalyst N-N9 is mounted, the A / F = 13.3 rich operation for 30 seconds and the A / F
= 22 was alternately repeated for about 20 minutes to obtain the NOx purification rate aging characteristics of FIG. From the figure, it can be seen that the present adsorption catalyst purifies NOx during the lean operation period. During lean operation, the NOx purification rate gradually decreased to 1
The purification rate of 00% becomes about 40% after 20 minutes. However, this reduced purification rate is 10 times in the rich operation for 30 seconds.
Recovers to 0%. When the lean operation is performed again, the NOx purification ability is restored and the above-described temporal change is repeated. NOx during lean operation even when lean operation and rich operation are repeated multiple times
The rate of reduction of the purification rate over time was unchanged, indicating that the NOx adsorption performance was sufficiently regenerated by the rich operation.

The vehicle speed is constant at about 40 km / h (the exhaust gas space velocity (SV) is constant at about 20,000 / h), and the ignition timing is changed to change the NOx concentration in the exhaust gas, thereby purifying the NOx concentration and the NOx purification in the lean exhaust gas. Figure 3 was obtained by determining the relationship between the rates. The NOx purification rate decreases with time, but the lower the NOx concentration, the lower the rate of decrease. NOx purification rate 50% and 30
% Is obtained from FIG.

The amount of trapped NOx is substantially constant regardless of the NOx concentration. The fact that the amount of adsorption does not depend on the concentration (pressure) of the adsorbate is a characteristic of chemisorption.

The first conceivable NOx adsorbent in the sample adsorption catalyst is Pt particles. Evaluation of the amount of CO adsorbed, which is frequently used as a means for evaluating the amount of exposed Pt, showed
The O adsorption amount (at 100 ° C.) was 4.5 × 10 ⁻⁴ mol. This value is about 1/100 of the NOx adsorption amount and P
Obviously, t is not the main player of the NOx adsorbent.

On the other hand, the BET specific surface area (measured by nitrogen adsorption) of the present adsorption catalyst measured for each cordierite is about 25 m ²
/ G was 28,050 m ² per 1.7 L of honeycomb. Further, when the chemical structure of Na of the adsorption catalyst of the present invention was examined, it was mainly determined from the fact that CO ₂ gas was generated and dissolved in the mineral acid and the value of the inflection point in the neutralization titration curve with the mineral acid was used. It was determined that it was present as Na ₂ CO ₃ . Assuming that the entire surface is occupied by Na ₂ CO ₃ , 0.275 mol of Na ₂ CO ₃ is exposed on the surface (the specific gravity of Na ₂ CO ₃ is 2.533 g / ml). the volume of Na ₂ CO ₃ 1 molecule is obtained since (Na ₂ CO ₃
Is assumed to be a cube, the area of one surface is obtained and this is calculated as the surface N
a ₂ CO ₃ occupied area). According to the above reaction formula, 0.275 mol of Na ₂ CO ₃ is capable of adsorbing 0.55 mol of NO ₂ . However, the amount of NOx actually removed by the adsorption catalyst of the present invention is on the order of 0.04 mol, which is 1/10 or less. This difference is due to the fact that the BET method evaluates the physical surface area and also evaluates the surface area other than Na ₂ CO ₃ such as Al ₂ O ₃ . The above evaluation indicates that the amount of adsorbed NOx is Na ₂ C
O ₃ is much less than the NOx trapping ability of the bulk, indicate that at least NOx is trapped in a region with limited or near the surface Na ₂ CO ₃ surface.

In FIG. 3, the NOx adsorbing ability decreases as the traveling distance of the vehicle increases, and the rate of decrease of the NOx purification rate after switching from the stoichiometric operation to the lean operation increases. This is a poisonous substance (SOx etc.) contained in exhaust gas.
Is to react with the NOx adsorbing substance to lower the adsorbing ability. This deterioration is caused by causing the exhaust gas discharged from the internal combustion engine to be in a stoichiometric air-fuel ratio or an excess fuel (rich) state and maintaining the exhaust gas temperature at a predetermined temperature or higher for a predetermined period of time, thereby removing catalyst poisoning accumulated over time. Can be recovered by exclusion.

FIG. 4 shows the NOx purification rate immediately after switching from the lean operation to the stoichiometric operation. It can be seen that with the present adsorption catalyst, a NOx purification rate of 90% or more can be obtained immediately after switching to the stoichiometric operation.

FIGS. 5 and 6 show NOx purification characteristics before and after switching from lean to stoichiometric or rich. FIG. 5 shows the NOx concentration at the inlet and outlet of the adsorption catalyst N-N9, and FIG.
This is the case where the air-fuel ratio is switched to rich /F=14.2. At the start of playback immediately after rich switching, A /
Since the exhaust gas NOx concentration at F = 14.2 is high, the inlet NOx concentration in the rich operation greatly increases, and the outlet NOx concentration transiently increases with this. However, the outlet NOx concentration is always significantly lower than the inlet NOx concentration. The regeneration proceeds promptly, and the outlet NOx concentration reaches near zero in a short time. Figure (b) shows A /
This is a case where the air-fuel ratio is switched from lean at F = 22 to rich at A / F = 14.2, but the outlet NOx concentration is always much lower than the inlet NOx concentration, as in FIG.
The outlet NOx concentration reaches near zero in a shorter time.

As is clear from the above, the A / F value as a reproduction condition affects the time required for reproduction. The A / F value, time, and amount of reducing agent suitable for regeneration are affected by the composition, shape, temperature, SV value, type of reducing agent, and shape and length of the exhaust passage of the adsorption catalyst. Therefore, reproduction conditions are comprehensively determined in consideration of these.

FIG. 6 shows N and N at the inlet and outlet of the adsorption catalyst NK9.
FIG. 4A shows the Ox concentration. FIG. 4A shows the case where the air-fuel ratio is switched from A / F = 22 lean to A / F = 14.2 rich, and FIG. 4B shows A / F = 22 lean. A / F = 1
In the case where the air-fuel ratio is switched to 4.2 rich, the NOx concentration at the outlet is always much lower than the NOx concentration at the inlet and the regeneration of the adsorbent catalyst is performed in a short time as in the case of the adsorption catalyst N-N9. I'm advancing.

[Exhaust Gas Purification Control Device] FIG. 1 shows the overall configuration of an exhaust gas purification control device according to an embodiment of the present invention.

The apparatus according to the present invention comprises an intake system having an engine 99 capable of lean burn, an air flow sensor 2, an electronically controlled throttle valve 3, etc., an oxygen concentration sensor (or
A / F sensor) 19, exhaust temperature sensor 17, NOx
Exhaust system and control unit (EC
U) and the like. The ECU includes an I / O LSI as an input / output interface, an arithmetic processing unit MPU, a storage device RAM storing a large number of control programs, and an R / O interface.
OM, timer counter, etc. The above exhaust gas purification control device functions as follows. The intake air to the engine is filtered by an air cleaner 1 and then measured by an air flow sensor 2, passes through an electronic control throttle valve 3, receives a fuel injection from an injector 5, and is supplied to the engine 99 as an air-fuel mixture. The airflow sensor signal and other sensor signals are sent to the ECU (En
gine Control Unit).

The ECU evaluates the operating state of the internal combustion engine and the state of the NOx adsorption catalyst by a method described later to determine the operating air-fuel ratio, and controls the injection time of the injector 5 and the like to adjust the fuel concentration of the air-fuel mixture to a predetermined value. Set. Further, the fuel concentration of the air-fuel mixture may be set to a predetermined value by adjusting the opening of the electronic control throttle valve 3. The air-fuel mixture sucked into the cylinder is ignited by the spark plug 10 controlled by a signal from the ECU 25 and burns. The combustion exhaust gas is led to an exhaust purification system. The exhaust gas purification system is provided with a NOx adsorption catalyst. During the stoichiometric operation, the NOx in the exhaust gas is controlled by the three-way catalyst function.
x, HC, CO, and NO during lean operation
HC and CO are purified by the combustion function which simultaneously purifies NOx with the x adsorption capability. Further, the NOx purifying ability of the NOx adsorbing catalyst is constantly determined at the time of lean operation based on the judgment and control signal of the ECU. Restores ability. With the above operation, the present device can perform the lean operation and the stoichiometric (including rich) operation.
Effectively purifies exhaust gas under all engine combustion conditions of operation.

The fuel concentration (hereinafter referred to as air-fuel ratio) of the air-fuel mixture supplied to the engine is controlled as follows. FIG. 7 is a block diagram showing the air-fuel ratio control method.

The output of the load sensor for outputting a signal corresponding to the depression of the accelerator pedal, the output signal of the intake air amount measured by the air flow sensor, the engine speed signal detected by the crank angle sensor, the exhaust gas temperature signal, and the throttle opening are obtained. ECU detects information from detected throttle sensor signal, engine coolant temperature signal, starter signal, etc.
25 determines the air-fuel ratio (A / F), and this signal is corrected based on the signal fed back from the oxygen sensor to determine the fuel injection amount. At low temperatures, at idle, at high load, etc., the feedback control is stopped by the signals of the sensors and switches. In addition, the air-fuel ratio correction learning function is used to accurately respond to subtle or sudden changes in the air-fuel ratio by the air-fuel ratio correction learning function.

When the determined air-fuel ratio is stoichiometric (A / F = 1)
In the case of 4.7) and rich (A / F <14.7), the injection condition of the injector is determined by the instruction of the ECU, and the stoichiometric and rich operation is performed. Electronically controlled throttle valve 3
The stoichiometric and rich operation may be performed by adjusting the opening degree. On the other hand, when the lean (A / F> 14.7) operation is determined, it is determined whether or not the NOx adsorbing catalyst has the NOx adsorbing ability, and when it is determined that the NOx adsorbing catalyst has the adsorbing ability, the lean operation as instructed is performed. When the fuel injection amount is determined and it is determined that there is no adsorption capacity, the air-fuel ratio is richly shifted for a predetermined period to regenerate the NOx adsorption catalyst. The lean operation may be performed by opening the electronic control throttle valve 3 and increasing the intake air amount.

In addition to the regeneration processing of the NOx adsorption catalyst, the engine is operated under operating conditions such that the exhaust gas temperature becomes equal to or higher than a predetermined value at every predetermined traveling distance or every time the integrated value of the intake air amount exceeds a predetermined value. By adding this process, it is possible to recover the NOx adsorption ability that has deteriorated due to the accumulation of the poisoning substance. Means for raising the exhaust gas temperature include delaying the ignition timing, opening the electronically controlled throttle valve 3 to increase the amount of intake air, introducing secondary air into the exhaust pipe, returning from lean to stoichiometric, misfiring and catalyzing. There is a method of raising the internal temperature of the device.

FIG. 8 (a) shows a flowchart of the above-described recovery process at the time of poisoning.

FIG. 8B shows a flowchart of the air-fuel ratio control. In step 1002, signals for instructing various operating conditions or detecting operating conditions are read. At step 1003, the air-fuel ratio is determined based on these signals, and at step 1004, the determined air-fuel ratio is detected. A comparison is made between the air-fuel ratio determined in step 1005 and the stoichiometric air-fuel ratio. The stoichiometric air-fuel ratio to be compared here is exactly the air-fuel ratio at which the speed of the catalytic reduction reaction of NOx exceeds the trapping speed by adsorption in the adsorption catalyst, and is determined in advance by evaluating the characteristics of the adsorption catalyst. , An air-fuel ratio near the stoichiometric air-fuel ratio is selected. If the set air-fuel ratio is smaller than or equal to the stoichiometric air-fuel ratio, the process proceeds to step 1006 to perform the air-fuel ratio operation as instructed without performing the regeneration operation of the adsorption catalyst. Set air-fuel ratio>
In the case of the stoichiometric air-fuel ratio, the process proceeds to step 1007. Step 1
In 007, an estimation calculation of the NOx adsorption amount is performed. The estimation calculation method will be described later. Subsequently, at step 1008, it is determined whether or not the estimated NOx adsorption amount is equal to or less than a predetermined limit amount. The limit adsorption amount is set to a value at which NOx in the exhaust gas can be sufficiently purified in consideration of the NOx trapping characteristics of the adsorption catalyst in advance by experiments and the like, and in consideration of the exhaust gas temperature and the temperature of the adsorption catalyst. If NOx adsorption capacity is present, step 100
Proceeding to 6, the air-fuel ratio operation is performed as instructed without performing the regeneration operation of the adsorption catalyst. If there is no NOx adsorption ability, the process proceeds to step 1009, and the air-fuel ratio is shifted to the rich side.
In step 1010, the rich shift time is counted,
If the elapsed time Tr exceeds a predetermined time (Tr) c, the rich shift ends.

The determination of the NOx adsorption ability can be performed as follows.

FIG. 9 shows N from various operating conditions during lean operation.
This is a method of integrating and determining the amount of Ox emission.

[0073] estimate the NOx amount E _N adsorbed on the signal and the signal and loading unit time for various engine operating conditions affecting the NOx concentration in the exhaust gas about the operating conditions of the NOx adsorbing catalyst of the exhaust gas temperature such as at step 1007-E01 I do. In step 1007-E02, E _N is integrated, and in step 1008-E01, the integrated value ΔE _N and the upper limit value (E
_N ) Compare magnitude with c. If ΣE _N ≤ (E _N ) c, the integration is continued. If ΣE _N > (E _N ) c, step 1008 is executed.
The integration is canceled at -E02, and the process proceeds to step 1009.

FIG. 10 shows a method of making a determination based on the integrated time of the lean operation.

In step 1007-H01, the lean operation time _HL is integrated, and in step 1008-H01, the integrated value ΣH
The magnitude of _L and the upper limit value (H _L ) c of the integration time are compared. Σ
If H _L ≦ (H _L ) c, the integration is continued. If ΣH _L > (H _L ) c, the integration is canceled in step 1008 -H 02 and step 1 is performed.
Proceed to 009.

FIG. 11 shows a method of making a determination based on the oxygen sensor signal during the lean operation.

At step 1007-O01, the oxygen amount Q _O in the lean operation is integrated, and at step 1008-01.
Then, the magnitude of the integrated value OQ _O and the upper limit value (Q _O ) c of the integrated oxygen amount are compared. When ΣQ _O ≤ (Q _O ) c, integration is continued and ΣQ
_{If O} > (Q _O ) c, the integration is canceled in step 1008 -O 02, and the flow advances to step 1009.

FIG. 12 shows a method of making a determination based on the NOx concentration sensor signal detected at the inlet of the NOx adsorption catalyst during the lean operation.

In step 1007-N01, the NOx at the inlet of the NOx adsorption catalyst is determined based on the NOx concentration sensor signal.
Integrating the amount Q _N. Integrated value [sum] Q _N and the accumulated NOx amount upper limit value at step 1008-N01 compares the magnitude of the (Q _N) c. When ΣQ _N ≤ (Q _N ) c, integration is continued and ΣQ _N >
(Q _N) to release the case accumulated at step 1008-N 02 of c proceeds to step 1009.

FIG. 13 shows a method of making a determination based on the NOx concentration sensor signal detected at the outlet of the NOx adsorption catalyst during the lean operation.

At step 1007-C01, the NOx at the inlet of the NOx adsorption catalyst is determined based on the NOx concentration sensor signal.
The concentration C _N is detected. Step 1008-C _{N in} C01
And comparing the magnitude of C upper limit of _N (C _N) c. C _N ≦
If (C _N ) c, the detection is continued, and if C _N > (C _N ) c, the process proceeds to step 1009.

FIG. 14 shows another embodiment of the exhaust gas purifying apparatus of the present invention. 1 in that a manifold catalyst 17 is provided in an exhaust duct near the engine.
The tightening of emission control of automobile exhaust gas requires purification of harmful substances such as HC discharged immediately after the engine is started. That is, in the past, the catalyst was discharged untreated until it reached the operating temperature, but this amount needs to be greatly reduced. For this purpose, a method of rapidly raising the temperature of the catalyst to the operating temperature is effective. FIG. 14 shows an apparatus configuration capable of coping with the reduction of HC and CO emissions at the time of engine startup and the purification of exhaust gas in lean and stoichiometric (including rich) operation. In the configuration of FIG. 14, Pt, Rh, CeO
So-called three-way catalysts containing ₂ as a main component and Pd
Or a combustion catalyst containing a combustion active component such as Pd as a central component. In this configuration, at the time of startup, the temperature of the manifold catalyst 17 rises in a short time to purify HC and CO immediately after the startup, and at the time of the stoichiometric operation, both the manifold catalyst and the adsorption catalyst 18 function so that HC, CO,
NOx is purified, and during lean operation, the adsorption catalyst
To adsorb and purify. When the air-fuel ratio is richly shifted during regeneration of the adsorption catalyst, HC and CO as reducing agents reach the adsorption catalyst without undergoing a large chemical change in the manifold catalyst, and are regenerated. A major feature of the adsorption catalyst is that it enables such a configuration.

FIG. 15 shows still another embodiment of the exhaust gas purifying apparatus of the present invention. The difference from the embodiment of FIG. 1 is that the engine 99 is a direct injection type. The device of the present invention can be suitably applied to a direct injection type engine.

FIG. 16 shows still another embodiment of the exhaust gas purifying apparatus of the present invention. 1 and 15 is that a rear catalyst 24 is provided downstream of the adsorption catalyst.
For example, a device in which the HC purification ability is improved by placing a combustion catalyst in the post-catalyst, and a device in which the three-way function at the time of stoichiometry is strengthened by placing a three-way catalyst, are realized.

FIG. 17 shows still another embodiment of the exhaust gas purifying apparatus of the present invention. The difference from FIG. 1 and FIGS. 14 to 16 is that fuel is added to the upstream of the adsorption catalyst through the reducing agent injector 23 in response to the instruction of the rich shift. This method has a great advantage that the operating state of the engine can be set independently of the state of the adsorption catalyst.

FIG. 18 shows the adsorption catalyst N according to the method of the present invention.
The last 10 modes of the 10 modes repeated three times and the subsequent 1 mode when -N9 is mounted, when the adsorption catalyst NK9 is mounted, and when the comparative catalyst NR2 is mounted.
The NOx concentrations before and after the adsorption catalyst in the five modes are shown.
The comparative catalyst had the composition shown in Table 2 below.

In FIG. 18, when the adsorption catalysts N-N9 and NK9 are mounted, the outlet NOx concentration is lower than the inlet NOx concentration in the entire operation range, and the lean operation and the stoichiometric operation are repeated so that the adsorption catalyst can be effectively used. It can be seen that it is regenerated and keeps the NOx purification function. On the other hand, in the comparative catalyst NR2, there is a portion where the outlet NOx concentration exceeds the inlet NOx concentration.

CVS obtained with various adsorption catalysts and comparative catalysts
The values are shown in Tables 2 and 3 together with the composition of the adsorption catalyst. Preparation of the adsorption catalyst and the comparative catalyst was carried out according to the above-mentioned method, but as the preparation raw materials, Ba nitrate Ba was used for barium (Ba) and silica sol was used for silicon (Si). It is presumed that Si exists as silica (SiO ₂ ) or its composite oxide.

As is evident from the above, according to the apparatus of the present invention, the NOx adsorbing catalyst is provided in the exhaust gas channel, NOx is adsorbed and captured in the oxidizing atmosphere of the lean exhaust gas, and the reducing catalyst is created to regenerate the adsorbing catalyst. As a result, NOx and the like in the lean burn exhaust gas can be purified with high efficiency without significantly affecting fuel efficiency.

[0090]

[Table 1]

[0091]

[Table 2]

[0092]

[Table 3]

[0093]

According to the present invention, even if the NOx adsorbing catalyst is poisoned by sulfur contained in the fuel and the adsorbing performance is degraded, the NOx adsorbing catalyst is decremented by a predetermined traveling distance or an integrated value of the intake air amount. Since the exhaust temperature is operated under the operating condition of the predetermined value every time the value exceeds the value, the accumulation of the poisoning substance is eliminated and the deteriorated NOx adsorption ability can be recovered. As a result, the poisoning resistance is improved, and NOx can be purified with high efficiency for a long time.

[Brief description of the drawings]

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

FIG. 2 is a time characteristic of the NOx purification rate when a rich operation and a lean operation are alternately repeated by the method of the present invention.

FIG. 3 shows a relationship between a traveling distance and a NOx purification rate.

FIG. 4 is a NOx purification rate in stoichiometric exhaust gas.

FIG. 5 shows the relationship between the NOx concentration at the inlet of the adsorption catalyst and the NOx concentration at the outlet when switching from rich (stoichiometric) operation to lean operation.

FIG. 6 shows the relationship between the NOx concentration at the inlet of the adsorption catalyst and the NOx concentration at the outlet when switching from rich (stoichiometric) operation to lean operation.

FIG. 7 is a block diagram showing a method for controlling an air-fuel ratio.

FIG. 8A is a flowchart illustrating a method of controlling an air-fuel ratio. (B) is a flowchart showing a method for controlling the air-fuel ratio.

FIG. 9 is a flowchart showing a method for determining the integrated NOx emission during lean operation.

FIG. 10 is a NOx amount estimation part in the flowchart of FIG. 8;

FIG. 11 is a NOx amount estimation part in the flowchart of FIG. 8;

FIG. 12 is a NOx amount estimation part in the flowchart of FIG. 8;

FIG. 13 is a NOx amount estimation part in the flowchart of FIG. 8;

FIG. 14 is a configuration diagram of an apparatus showing an embodiment provided with a manifold catalyst.

FIG. 15 is a configuration diagram of an apparatus showing an embodiment in a direct injection engine.

FIG. 16 is a configuration diagram of an apparatus showing an embodiment provided with a rear catalyst.

FIG. 17 is an apparatus configuration diagram showing an embodiment in which a reducing agent is added upstream of an adsorption catalyst.

FIG. 18 is a NOx purification characteristic diagram when a mode operation is performed.

[Description of Signs] 1 ... Air cleaner, 2 ... Air flow sensor, 3 ... Throttle valve, 5 ... Injector, 6 ... Spark plug, 7
... Accelerator pedal, 8 ... Load sensor, 9 ... Intake air temperature sensor, 12 ... Fuel pump, 13 ... Fuel tank, 17 ...
Manifold catalyst, 18: Adsorption catalyst, 19: Oxygen sensor, 20: Adsorption catalyst temperature sensor, 21: Exhaust gas temperature sensor, 22: NOx concentration sensor, 23: Reducing agent injector, 24: Rear catalyst, 25: ECU, 26: Knock Sensor, 28: water temperature sensor, 29: crank angle sensor, 99: engine.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI B01J 38/10 ZAB F01N 3/24 ZABE F01N 3/08 3/28 ZAB ZAB 301C 3/24 F02D 41/04 305A ZAB 45/00 ZAB 3/28 ZAB B01D 53/34 129A 301 53/36 ZAB F02D 41/04 305 101Z 45/00 ZAB (72) Inventor Masahiro Ichimaru 2477 Takaba, Hitachinaka City, Ibaraki Pref. Hitachi Car Engineering Co., Ltd. (72) Inventor Yuichi Kitahara 2520 Takahiro, Hitachinaka City, Ibaraki Pref.Hitachi, Ltd.Automotive Equipment Division (72) Inventor Toshifumi Hiratsuka 2520 Ojitakaba, Hitachinaka, Ibaraki Pref.Hitachi Ltd.Automotive Equipment Division (72) Inventor Osamu Kuroda 1-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture No. 7 Hitachi, Ltd. Hitachi Research Laboratories (72) Inventor Toshio Yamashita 7-1-1, Omikamachi, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratories Hitachi Research Laboratory (72) Inventor Kazuhiro Iizuka Omikamachi, Hitachi City, Ibaraki Prefecture No. 1-1, Hitachi Research Laboratory, Hitachi Ltd.

Claims (12)

[Claims] 1. In the oxidation-reduction stoichiometry relationship between components in exhaust gas, NOx is chemisorbed in a state where the oxidant is large relative to the reducing agent, and is adsorbed in a state where the amount of the reducing agent is equal to or more than the oxidizing agent. A NOx adsorption catalyst for catalytically reducing NOx is placed in the exhaust gas flow path, and in a redox stoichiometric relationship between the components in the exhaust gas, a state in which the amount of the oxidant is large relative to the reducing agent is formed, and NOx is reduced on the adsorption catalyst. is chemically adsorbed, then the reducing agent to the oxidizing agent is made the same amount or more states, harmless by reduction by catalytic reaction with a reducing agent to N ₂ adsorbed NOx on adsorption catalyst, the internal combustion engine exhaust gas In the purifier, the exhaust gas discharged from the internal combustion engine is set to a stoichiometric air-fuel ratio or an excess fuel (rich) state, and the exhaust gas temperature is maintained at a predetermined level or higher for a predetermined period or more, so that catalyst poisoning substances accumulated over time are removed. Exclude from catalyst Exhaust gas purification controller, characterized in that. 2. At least potassium (K), sodium (Na), magnesium (Mg), strontium (S)
r) and a NOx adsorption catalyst containing at least one element selected from the group consisting of calcium (Ca) as a part of the components is disposed in the exhaust gas flow path. To create a state with a large amount of oxidant to chemically adsorb NOx on the adsorption catalyst, and then create a state in which the amount of the reducing agent is equal to or more than that of the oxidizing agent, and contact the NOx adsorbed on the adsorption catalyst with the reducing agent to react. An exhaust gas purifying apparatus for an internal combustion engine that reduces the temperature of the exhaust gas to N ₂ to make the exhaust gas harmless by setting the exhaust gas discharged from the internal combustion engine to a stoichiometric air-fuel ratio or an excess fuel (rich) state, and keeping the exhaust temperature at a predetermined level or higher for a predetermined period or longer. An exhaust gas purification control apparatus characterized in that the catalyst poisoning substance accumulated with time is removed from the catalyst. 3. At least potassium (K), sodium (Na), magnesium (Mg), strontium (S
The NOx adsorbing catalyst disposed in the exhaust gas line comprising one or more elements selected from r) and calcium (Ca) as part of component, O ₂ or the like to a reducing agent such as HC in a redox stoichiometry NOx is trapped on the surface of the adsorption catalyst and near the surface by chemical bonding,
Then create a state reducing agent is the same amount whether or greater to oxidation agent, detoxifying and reduced to N ₂ by catalytic reaction with a reducing agent of NOx trapped in the adsorption catalyst, the exhaust gas purifying apparatus of an internal combustion engine The exhaust gas discharged from the internal combustion engine is set to a stoichiometric air-fuel ratio or a fuel excess (rich) state, and the exhaust gas temperature is maintained at a predetermined temperature or higher for a predetermined period of time, thereby eliminating catalyst poisoning accumulated over time from the catalyst. An exhaust gas purification control device comprising: 4. The method according to claim 1, wherein potassium (K), sodium (Na), magnesium (Mg),
Metals and metal oxides containing at least one selected from strontium (Sr) and calcium (Ca), at least one selected from rare earths such as cerium and the like, and at least one element selected from precious metals such as platinum, rhodium and palladium. Object (or composite oxide)
An exhaust gas purifying apparatus for an internal combustion engine using, as an adsorption catalyst, a composition comprising: or a composition comprising the composition supported on a porous heat-resistant metal oxide, wherein exhaust gas discharged from the internal combustion engine has a stoichiometric air-fuel ratio or fuel. An exhaust gas purification control device characterized in that an excess (rich) state is maintained, and an exhaust gas temperature is maintained at a predetermined level or higher for a predetermined period or more, thereby removing catalyst poisons accumulated over time from the catalyst. 5. The method according to claim 1, wherein potassium (K), sodium (Na), magnesium (Mg),
At least one selected from strontium (Sr) and calcium (Ca), at least one selected from rare earths such as cerium and the like, and at least one selected from precious metals such as platinum, rhodium and palladium;
Metals and metal oxides (or composite oxides) containing at least one element selected from titanium and silicon
An exhaust gas purifying apparatus for an internal combustion engine using a composition comprising the composition supported on a porous heat-resistant metal oxide as an adsorption catalyst, wherein exhaust gas discharged from the internal combustion engine is stoichiometric air-fuel ratio or fuel An exhaust gas purification control device characterized in that an excess (rich) state is maintained, and an exhaust gas temperature is maintained at a predetermined level or higher for a predetermined period or more, thereby removing catalyst poisons accumulated over time from the catalyst. 6. An air amount, a fuel amount, an ignition timing, a fuel injection timing, a shift speed, a fuel amount, an intake air amount, a fuel intake amount, and an intake time, which are taken into the internal combustion engine so that the drive shaft torque of the automobile or the output torque of the internal combustion engine does not change. An exhaust purification control device, wherein the control is performed by a control amount of any combination of a speed ratio of an engine and an engine speed. 7. A method according to claim 1, wherein the processing for removing the poisonous substance of the catalyst from the catalyst is performed at every predetermined period, at every predetermined traveling distance of the vehicle, any one of the intake air amount, the fuel supply amount, and the exhaust amount. An exhaust gas purifying apparatus characterized in that the exhaust gas purifying apparatus is performed every time the value reaches a predetermined value. 8. An exhaust gas purification apparatus according to claim 1, wherein a process of removing poisonous substances from the catalyst from the catalyst is performed when the degree of deterioration of the NOx adsorption capacity exceeds a predetermined value or more. 9. The method according to claim 1, wherein the amount of fuel supplied to the internal combustion engine is increased, and air is introduced into an exhaust pipe to bring the exhaust to a stoichiometric air-fuel ratio or an excess fuel (rich) state, and the exhaust temperature is set to a predetermined value. An exhaust gas purification control device characterized in that the catalyst poisoning substance accumulated over time is removed from the catalyst by holding the catalyst for a predetermined period or more. 10. The method according to claim 9, wherein the exhaust gas temperature is maintained at a predetermined value or more for a predetermined period or more by combining ignition timing retard control to eliminate catalyst poisons accumulated with time from the catalyst. Exhaust gas purification control device. 11. A method according to claim 9, wherein the processing for removing the poisonous substance of the catalyst from the catalyst is performed at every predetermined period, at every predetermined traveling distance of the automobile, and at least one of an intake air amount, a fuel supply amount, and an exhaust amount. An exhaust gas purifying apparatus characterized in that the exhaust gas purifying apparatus is performed every time the value reaches a predetermined value. 12. The exhaust gas purifying apparatus according to claim 9, wherein a process for removing poisonous substances from the catalyst from the catalyst is performed when the degree of deterioration of the NOx adsorption capacity exceeds a predetermined value or more.