JP2001159307A - Method of deteriorating exhaust emission control catalyst, and exhaust emission control catalyst obtained by the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and rapidly and besides advantageously in terms of a cost provide an exhaust emission control catalyst in a state equivalent to various deterioration states capable of occurring on a market. SOLUTION: In this method for forcibly deteriorating an exhaust emission control catalyst, containing a precious metal as an active material, being durable in high temperature atmosphere, the temperature of high temperature atmosphere is changed along with the lapse of time, and a time ratio to hold the temperature at 1000 deg.C or higher is in a range of 10-80% of a total high temperature durable time. Preferably, the high temperature atmosphere is achieved by feeding high temperature gas discharged when an air-fuel mixture of fuel and air is burnt in an internal combustion engine. A ratio of unreacted fuel in the high temperature atmosphere and air is changed along with the lapse of a time and a time ratio in which an air-fuel ratio is brought into a lean state is set to 30-80% of a total durable time. Further, the catalyst for purifying exhaust gas is coated with silica and further catalyst poison, such as catalyst poison, against a precious metal is adhered to deteriorate the exhaust emission control catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas purifying catalyst for purifying harmful substances contained in exhaust gas,
The present invention relates to a method for forcibly or simulated deterioration and a deteriorated exhaust gas purifying catalyst obtained by the method.

[0002]

2. Description of the Related Art Nitrogen oxides (NO _x ) and carbon monoxide (CO) contained in exhaust gas from internal combustion engines such as automobiles
Platinum (Pt), Palladium (Pd), Rhodium (Rh) are the most widely used catalysts for purifying harmful substances such as hydrocarbons and hydrocarbons (HC).
A so-called three-way catalyst using a noble metal such as a noble metal as an active substance is known. This three-way catalyst performs a reduction reaction from NO _x to N ₂ , or CO to CO ₂ and HC to CO ₂ ,
It is intended to act as a catalyst for the oxidation reaction to H ₂ O.
That is, the three-way catalyst acts as a catalyst for both oxidation and reduction reactions, and includes NO _x , CO,
Purifies harmful substances such as HC.

[0003] Such a three-way catalyst is usually held in a wash coat layer formed on the inner surface of each cell of the honeycomb carrier and constitutes an exhaust gas purifying catalyst. The exhaust gas purifying catalyst is directly supplied with exhaust gas from the internal combustion engine to purify harmful components. However, since this exhaust gas has a high temperature, when the exhaust gas purifying catalyst is used for a long time,
Its catalytic activity deteriorates. In particular, exhaust gas regulations for automobiles and the like are becoming increasingly strict, so that the temperature of the exhaust gas purifying catalyst can be raised at an early stage, and the exhaust gas can be purified at an early stage immediately after the start of the internal combustion engine. There is a tendency to place the catalyst for use in a location close to the internal combustion engine. In this case, the temperature of the exhaust gas purifying catalyst rises immediately after the start of the internal combustion engine, but on the other hand, the exhaust gas purifying catalyst is exposed to a more severe environment.
In addition, a system for detecting catalyst deterioration (OBD: On-Board D
iagnostics).
According to the regulations for mounting the OBD, it is required to guarantee a high catalyst activity even after traveling, for example, hundreds of thousands of km, and it is necessary to issue a warning when the catalyst activity falls below a predetermined value.

[0004]

However, in order to guarantee the catalyst performance after traveling hundreds of thousands of kilometers, an engine and a catalyst are mounted on an actual vehicle, and the catalyst is actually degraded after traveling hundreds of thousands of kilometers. It is necessary to determine whether the degree is within an allowable range. It is practically difficult to evaluate the catalyst performance of all the designed exhaust gas purifying catalysts by running the vehicle. For this reason, the exhaust gas purifying catalyst is forcibly deteriorated by passing the high temperature exhaust gas through the exhaust gas purifying catalyst, and a state corresponding to the deteriorated state after traveling a predetermined distance is realized. A durable method is adopted. And, in this way, the deterioration behavior of the exhaust gas purifying catalyst is accurately grasped, and the exhaust gas purifying catalyst is designed so that the expected performance can be maintained for a long time.
A method for evaluating the catalytic activity of an exhaust gas purifying catalyst for which a significant result has been obtained in actual vehicle running has been adopted. However, conventional high-temperature endurance methods still require hundreds of hours even in high-temperature endurance in order to realize a catalyst that will be exposed to severe environments in the future and a deterioration state equivalent to the deterioration level. It is disadvantageous not only in energy and time but also in cost.

[0005] Further, since the composition and temperature change of the exhaust gas vary depending on the displacement of the internal combustion engine, the operating condition, and the type of fuel used, various catalysts for purifying exhaust gas are available in the market. A degraded state can occur. For this reason, it is also necessary to construct a method for deteriorating an exhaust gas purifying catalyst that can easily achieve states corresponding to various degraded states that can occur in the market.

The present invention was conceived under the circumstances described above, and is intended to provide an exhaust gas purifying catalyst in a state corresponding to various deterioration states that can occur in a market in a simple and short time. It is an object of the present invention to provide a cost-effective solution.

[0007]

DISCLOSURE OF THE INVENTION In order to solve the above-mentioned problems, the present invention takes the following technical means.

[0008] That is, the method for deteriorating an exhaust gas purifying catalyst provided by the first aspect of the present invention is such that an exhaust gas purifying catalyst containing a noble metal as an active substance is endured in a high-temperature atmosphere and forcibly degraded. A method wherein the temperature of the high temperature resistant atmosphere is changed over time and
It is characterized in that the time ratio of maintaining at 000 ° C. or higher is in the range of 10 to 80% of the total high temperature durability time.

One of the factors that deteriorate the exhaust gas purifying catalyst is heat (high-temperature atmosphere). That is, in a state where the exhaust gas purifying catalyst is actually used, high-temperature exhaust gas is supplied from the internal combustion engine, and heat energy is added from the internal combustion engine by being disposed near the internal combustion engine, The catalyst for purifying exhaust gas is deteriorated due to grain growth of the noble metal. Therefore, the first of the present invention
If the exhaust gas purifying catalyst is exposed to a high-temperature atmosphere as in the method of deteriorating the side surface described in the above, the exhaust gas purifying catalyst can be forcibly deteriorated. In particular, in the above-described deterioration method, the ratio of time during which the ambient temperature is maintained at 1000 ° C. or higher is set to be in the range of 10 to 80% of the total high-temperature durability time, and the environment is set to be extremely severe. Therefore, according to the present deterioration method, a thermally deteriorated state of the exhaust gas purifying catalyst can be achieved easily and in a short time.

Further, in the present deterioration method, the temperature of the high-temperature atmosphere is changed over time to deteriorate the exhaust gas purifying catalyst. Then, the exhaust gas purifying catalyst can be deteriorated in a manner closer to the form of deterioration in a state where the exhaust gas purifying catalyst is actually used. The change with time in the temperature of the high-temperature atmosphere may be a periodic change (cycle change) or a non-periodic change.

The high temperature atmosphere may be achieved by heating the exhaust gas purifying catalyst in an electric furnace.
This may be achieved by supplying a high-temperature gas discharged when a mixture of fuel and air is burned in the internal combustion engine to the exhaust gas purifying catalyst.

When the latter method is adopted, the ratio of unreacted combustion to air in a high-temperature atmosphere is changed with time, and the ratio of a certain period of time during high-temperature endurance is set so that the ratio of air exceeds the stoichiometric ratio. (Lean state), and the exhaust gas purifying catalyst may be easily oxidized. In this case, it is preferable to set the range of 30 to 80% of the total durability time to the lean state. When the temperature of the high-temperature atmosphere is 100
As long as the temperature is maintained at 0 ° C. or higher, it is preferable that the ratio of the unreacted fuel and air be in a lean state. In this case, deterioration due to heat and deterioration due to oxidation can be performed at the same time, and the exhaust gas purifying catalyst can be durable in a more severe environment. Here, as a method of making the ratio of unreacted fuel and air lean, other than a method of making the ratio of fuel and air in the air-fuel mixture lean, a method of separately mixing air with exhaust gas from the internal combustion engine is available. No.

The time ratio for maintaining the high-temperature atmosphere at 1000 ° C. or higher is, as described above, 10 to 10 in the total durability test.
The range is 80%, preferably 40-80%, and more preferably 40-60%.

According to a second aspect of the present invention, there is provided a method for forcibly deteriorating an exhaust gas purifying catalyst in which a coating layer containing a noble metal as an active substance is formed on a heat-resistant support carrier. A method for deteriorating an exhaust gas purifying catalyst, characterized by causing a catalyst poison component for a noble metal to adhere to the surface of the catalyst.

One of the causes of deterioration of the exhaust gas purifying catalyst is adhesion of a catalyst poison component to a noble metal. For example, fuels supplied to internal combustion engines and oils used as lubricating oils for internal combustion engines include phosphorus, sulfur,
Since elements such as lead, sodium, potassium, zinc, and iron are contained in a small amount in the form of a compound or the like, the exhaust gas from the internal combustion engine also contains a small amount of each of the exemplified elements. Each of the exemplified elements is a catalyst poison component that lowers the activity of the noble metal by, for example, adsorbing or coordinating to an active site of the noble metal, and an exhaust gas purifying catalyst (noble metal) is placed in an atmosphere containing the catalyst poison component. If exposed, the catalytic performance of the exhaust gas purifying catalyst decreases. Therefore, when the catalyst poison component is positively attached to the surface of the coating layer as in the present deterioration method, the exhaust gas purifying catalyst can be forcibly deteriorated.

The catalyst poison components used in the present invention include the catalyst poison components exemplified above, ie, phosphorus (P),
Sulfur (S), lead (Pb), sodium (Na), calcium (Ca), zinc (Zn), and iron (Fe). These elements may be used alone or in combination of two or more, and may be attached to the exhaust gas purifying catalyst in the form of a compound.

Here, as a method of adhering the catalyst poison component to the coating layer, a method of bringing a gas containing the catalyst poison component into contact with the exhaust gas purifying catalyst (coating layer) can be mentioned. Then, if a gas containing a high concentration of a catalyst poison component is brought into contact with the coating layer, the intended deterioration state can be achieved in a short time. In addition, as a method of bringing the catalyst poison component into contact with the coating layer, for example, a gas containing a catalyst poison component at a high concentration is prepared and brought into direct contact with the coating layer, or supplied to the internal combustion engine. A high concentration of catalyst poison is contained in fuel or oil used as a lubricating oil of an internal combustion engine, and the exhaust gas containing a high concentration of catalyst poison is discharged from the internal combustion engine and brought into contact with a coating layer. Method. Examples of the method of adding a catalyst poison component to a fuel in a high concentration include a method of adding engine oil to a fuel, a method of dissolving a catalyst poison component in a solvent such as light oil, and adding this to the fuel, or a method such as ZnDTP. And adding the compound as a compound soluble in the fuel to the fuel.

According to a third aspect of the present invention, there is provided a method for deteriorating an exhaust gas purifying catalyst as described in the first aspect of the present invention, and an exhaust gas purifying method as described in the second aspect of the present invention. And a method for deteriorating the exhaust gas purifying catalyst, wherein the method is performed in combination with the method for deteriorating the exhaust gas purifying catalyst.

The degradation method according to the first aspect of the present invention is a degradation method using heat alone or in combination with oxidation, and the second aspect of the present invention is a degradation method for attaching a catalyst poison component.
For this reason, if the deterioration method according to the first aspect of the present invention and the deterioration method according to the second aspect of the present invention are performed in combination, the deterioration states corresponding to various deterioration states that may occur in the market can be easily and quickly reduced. Can be achieved in time.

Note that the deterioration method according to the first aspect of the present invention includes:
When the deterioration method according to the second aspect of the present invention is performed in combination, these deterioration methods may be performed simultaneously, or one deterioration method may be performed, and then the other deterioration method may be performed.

According to a fourth aspect of the present invention, there is provided a method for artificially deteriorating an exhaust gas purifying catalyst in which a coating layer containing a noble metal as an active substance is formed on a heat-resistant support carrier. A method for deteriorating an exhaust gas purifying catalyst, characterized in that a surface of the catalyst is coated with a pseudo-deterioration substance.

If at least a part of the coating layer is coated with the pseudo-deteriorating substance, the active site of the noble metal is directly or indirectly covered with the pseudo-deteriorating substance, and the component to be treated (NO _x , CO, and H
The adsorption or coordination of C) is hindered, and the catalytic performance of the exhaust gas purifying catalyst is impaired. That is, by coating with the pseudo-deteriorating substance, a state in which the noble metal or the exhaust gas purifying catalyst is deteriorated is pseudo-achieved. Also,
By adjusting the amount of coating of the pseudo-deterioration substance, the intended deterioration state can be achieved. As described above, in the present deterioration method, a desired deterioration state can be achieved in a very short time by a very simple operation such as coating the surface of the coating layer.

Here, the pseudo-deterioration substance used in the present invention does not volatilize in a high-temperature atmosphere (at least about 1000 ° C.) and does not permeate (internally diffuse) components to be treated in exhaust gas at all. Or a component that is hardly permeated, such as a vitreous component, a resin, a fat, and a metal. These pseudo-deterioration substances may be used alone or in combination of two or more, and a vitreous component is particularly preferably used.

The vitreous component includes all that is generally thought of as glass. Naturally, in addition to one made of silica (quartz glass), one made of silica and other components (soda lime glass or borosilicate glass) Etc.) are included. Further, in the network structure of silica to be a network former, an alkali metal element (Li, Na,
K) ions and alkaline earth metal elements (Mg, Ca, B
The ion of a) may be partially contained. Then, a part of Si of silica as a network former, B,
Substituted by P, Ge, As, V or the like is also included in the vitreous component in the present invention. Further, ions such as Al, Ti, or Zr, which plays both roles of network formation and network modification, may be included.

Here, as a method of coating the pseudo-deterioration substance on the coating layer, for example, when the pseudo-deterioration substance is solid at room temperature, it is dissolved in a solvent to form a viscous liquid, and if necessary, Is diluted with a solvent such as water to obtain a liquid state, and then the pseudo-deterioration substance is applied or adsorbed on the surface of the coating layer and then heat-treated. The heat treatment in this case is, for example, 600 to
It is performed by heating at 800 ° C. for 2 to 5 hours. If the pseudo-deteriorated substance is solid at room temperature, a slurry is formed using the fine powder, and the slurry is impregnated or adhered to the surface of the coating layer, and then heat-treated to form a pseudo-degraded substance on the coating layer. Deterioration substances may be coated,
After applying the pseudo-deterioration substance in a molten state to the surface of the coating layer, the pseudo-deterioration substance may be cooled and solidified to coat the coating layer. Further, when the pseudo-deteriorating substance is a liquid at room temperature, it is only necessary to apply or adsorb the pseudo-deteriorating substance on the surface of the coating layer.

The coating amount of the vitreous component is as follows:
It varies depending on the composition of the coating layer (including the type and amount of the noble metal), the type of the internal combustion engine, the degree of intended deterioration, and the like, and cannot be unconditionally determined, but is usually in the range of 10 to 1000 g per 1 dm ^{3 of the} exhaust gas purifying catalyst. , Preferably 10 to 500 g
Range.

According to a fifth aspect of the present invention, there is provided any one of the above-described degradation methods according to the first to third aspects of the present invention, the degradation method described in the fourth aspect of the present invention,
And a method of deteriorating the exhaust gas purifying catalyst, characterized in that the method is performed in combination.

The deterioration method according to the fifth aspect of the present invention includes a deterioration method of coating a pseudo-deterioration substance in addition to a deterioration method of single or combination of deterioration due to high temperature, deterioration due to oxidation, and deterioration due to catalyst poison components. Combine. Therefore, the degree of freedom of combination is higher than that of the deterioration method described in the third aspect of the present invention described above, and it is possible to more reliably and easily achieve a deterioration state corresponding to various deterioration states in the market. it can.

When the exhaust gas purifying catalyst is deteriorated by combining the deterioration method of coating the pseudo-deterioration substance with another deterioration method, the surface of the coating layer is coated with the pseudo-deterioration substance and then the other method is applied. It is preferable to coat the surface of the coating layer with the pseudo-deterioration material after performing another deterioration method, rather than performing the deterioration method.

According to a sixth aspect of the present invention, there is provided a catalyst for purifying a deteriorated exhaust gas, which is obtained by the deterioration method described in the first to fifth aspects of the present invention.

[0031]

Next, the present invention will be described with reference to examples, but the technical scope of the present invention is not limited to the examples described below.

[0032] EXAMPLE 1 In this example, first, the exhaust gas purifying catalyst was subjected to durability test in the actual vehicle in operation pattern that assumes domestic market, a travel distance, CO, HC, and the _the NO _x purification rate The relationship was discussed. The result is shown in FIG.
(B) and (c) indicate-■-. In addition, FIG.
(B) and (c) correspond to the results for CO, HC, and NO _x purification rates, respectively.

Next, CO, HC, and NO _x were obtained for each of the exhaust gas purifying catalyst deteriorated by the 1050 ° C. durability test and the exhaust gas purifying catalyst deteriorated by the combined use of the 1100 ° C. durability test and phosphorus poisoning. The purification rate was evaluated. The result is shown in FIG.
(B) and (c).

(Design of Exhaust Gas Purifying Catalyst) As the exhaust gas purifying catalyst of this embodiment, a catalyst having a wash coat layer formed on the inner surface of each cell of the monolithic carrier was used. As a monolith carrier, the diameter is 80 mm and the length is 9
5 mm, 0.477 dm ³ capacity column, wall thickness 0.1
A cordierite product having cells formed at a density of 400 cells / inch ² mm (62 cells / cm ² ) was used. The composition of the wash coat layer is Ce _0.60 Zr _0.32 Y _0.08
90 g of cerium-based composite oxide of O _1.96 , alumina 110
g, platinum 1.0 g, and rhodium 0.3 g. Note that platinum and rhodium were supported on a cerium-based composite oxide.

(Durability test of actual vehicle) In this durability test, an exhaust gas purification catalyst was mounted on a 0.66 liter displacement, three-cylinder engine, and 100,000 driving on an urban area and a highway with a real vehicle.
It was done by running km.

(Endurance test at 1050 ° C.)
This corresponds to a conventional deterioration method.
That is, in a state where the exhaust gas purifying catalyst is mounted in one bank (for four cylinders) of a V-type 8-cylinder engine having a displacement of 4.0 liters, the high temperature atmosphere of the cycle shown in FIG.
This cycle was repeated (60 seconds), and this cycle was repeated 3000 times, for a total of 50 hours. In the above cycle, 0-4
During 0 seconds, the air-fuel mixture maintained at the stoichiometric air-fuel ratio (stoichiometric state) by feedback control is supplied to the engine, and the internal temperature of the exhaust gas purifying catalyst (catalyst bed) is set to be around 850 ° C. . During 40 to 44 seconds, the feedback was opened and the fuel was excessively injected to supply a fuel-rich mixture to the engine. During 44 to 56 seconds, while the feedback is open and the fuel is excessively supplied, secondary air is blown from the outside of the engine through the introduction pipe from the upstream side of the exhaust gas purifying catalyst, and the catalyst is The temperature was increased by reacting the excess fuel with the secondary air inside the bed. At this time, the maximum temperature of the catalyst bed is 1050 ° C., and the air-fuel ratio in the catalyst bed is in a lean state in which air is more than the stoichiometric ratio. During the last 56 to 60 seconds, only the air is supplied to keep the air condition in the lean state. In this endurance test, the time ratio when the catalyst bed temperature was maintained at 1000 ° C. or higher was 8%, the air-fuel ratio of the gas inside the catalyst bed was in a lean state, and the time ratio was 31%.
%. The temperature of the catalyst bed was measured by a thermocouple inserted at the center of the catalyst bed.

(1100 ° C. Endurance Test)
This was carried out by mounting an exhaust gas purifying catalyst in one bank (for four cylinders) of a 4.0-liter V-type eight-cylinder engine. Specifically, the cycle shown in FIG. 2 was defined as one cycle (60 seconds), and this cycle was repeated 3000 times, for a total of 50 hours. As shown in FIG. 2, during 0 to 40 seconds, the air-fuel mixture maintained at the stoichiometric air-fuel ratio (stoichiometric state) by feedback control is supplied to the engine, and the internal temperature of the exhaust gas purifying catalyst (catalyst bed) is reduced. 85
It was set to be around 0 ° C. During 40 to 44 seconds, the feedback was opened and the fuel was excessively injected to supply a fuel-rich mixture to the engine. During a period of 44 to 56 seconds, while the feedback is kept open and the fuel is excessively supplied, secondary air is blown from the outside of the engine through the introduction pipe from the upstream side of the exhaust gas purifying catalyst, and the catalyst bed is discharged. Inside, the excess fuel was reacted with the secondary air to raise the temperature. At this time, the maximum temperature inside the catalyst bed is 1100 ° C., and the air-fuel ratio of gas in the catalyst bed is in a lean state in which air is more than the stoichiometric ratio. During the last 56 to 60 seconds, air is supplied to keep the air condition in a lean state. In this durability test, the time ratio of keeping the catalyst bed at 1000 ° C. or higher was 13%, and the time ratio of keeping the air-fuel ratio of the gas inside the catalyst bed lean was 31%.
%. The internal temperature of the catalyst bed was measured by a thermocouple inserted at the center of the catalyst bed.

(Phosphorus Poisoning) In the 1100 ° C. endurance test, phosphorus poisoning was carried out by adding engine oil containing a high concentration of a phosphorus compound to gasoline. This engine oil contains 1 wt% of phosphorus in elemental conversion,
The supply amount was 17 cc (0.017 dm ³ ) per hour.

[0039] As shown in (a result of the study) 5, the conventional degradation methods at a 1050 ° C. in 50 hour endurance treated exhaust gas purifying catalyst, the 60000km running about the deterioration of the real vehicle, phosphorus poisoning The catalyst subjected to the durability treatment at 1100 ° C. for 50 hours corresponds to the deterioration of about 100,000 km running in the actual vehicle. That is, the 1100 ° C. endurance test (1000% or more, 13% lean state 31%) + the degradation method using phosphorus poisoning has the same durability as the conventional degradation method (1000 ° C. or more 8%, lean state 31%). The degradation state of about 1.7 times in time is realized. In addition, the endurance by the actual vehicle is usually carried out by running at 20,000 km per month. Therefore, in the degradation method of 1100 ° C. endurance test + phosphorus poisoning, the actual vehicle is 5 months (100,000 km).
m) A deterioration state corresponding to a test performed over a very short time such as 50 hours can be realized.

[0040] Example 2 In this example, the exhaust gas purifying catalyst was subjected to the durability test in an actual vehicle in first European market assumed driving patterns, a travel distance, CO, HC, and the _the NO _x purification rate The relationship was discussed. The results are shown in FIG.
(B) and (c) indicate-■-. In addition, FIG.
(B) and (c) correspond to the results for CO, HC, and NO _x purification rates, respectively.

Next, the exhaust gas purifying catalyst deteriorated by using both the 1100 ° C. endurance test and the phosphorus poisoning described in Example 1 and the 1150 ° C. endurance test (A type) described below and the phosphorus poisoning were used. It was evaluated CO, HC, and _the NO _x purification rate for each combination with the degrade exhaust gas purifying catalyst. The results are shown in FIGS. 5 (a), 5 (b) and 5 (c) simultaneously with the results of the actual vehicle.

(Catalyst Design) Exhaust gas purifying catalyst of this embodiment
As a medium, wash the inner surface of each cell of the monolithic carrier.
One having a coat layer formed thereon was used. Monolith carrier and
The diameter is 105.7 mm, the length is 137 mm,
1.2 dm^ThreeCylindrical, wall thickness 0.1mm, 600ce
ll / inch^Two(93cell / cm^TwoA cell with a cell density of
-Dulite. Wash coat layer
The composition is Ce_0.55Zr_0.38Y _0.07O_1.96Seriu
System composite oxide 80g, composition Zr_0.80Ce_0.16La
_0.04O _1.98Zirconium-based composite oxide 50 g, aluminum
105 g, platinum 1.5 g, rhodium 1.0 g,
Radium was 1.0 g. In addition, platinum and rhodium
The cerium-based composite oxide carries 0.75 g each
And 0.5 g each was supported on a zirconium-based composite oxide.
Was.

(Durability test of actual vehicle) In this durability test, an exhaust gas purifying catalyst was mounted on a 1.5-liter displacement four-cylinder engine, and 100,000 was used in an urban area and on a highway by a real vehicle.
It was done by running km.

(1150 ° C. Endurance Test (Type A)) In this endurance test, a catalyst (catalyst bed) for purifying exhaust gas was installed in one bank (for four cylinders) of a V-type eight-cylinder engine with a displacement of 4.0 liters. It was done by doing. Specifically, the cycle shown in FIG. 3 was defined as one cycle (60 seconds), and this cycle was repeated 3000 times, for a total of 50 hours. As shown in FIG. 3, during 0 to 20 seconds, the air-fuel mixture maintained at the stoichiometric air-fuel ratio (stoichiometric state) by feedback control is supplied to the engine, and the internal temperature of the catalyst bed becomes 850.
It was set to be around ℃. During the period of 20 to 24 seconds, the feedback was opened and the fuel was excessively injected to supply the fuel-rich mixture to the engine. During 24 to 56 seconds, while the feedback is open and the fuel is excessively supplied, secondary air is blown from the outside of the engine through the inlet pipe from the upstream side of the catalyst bed, and the excess The temperature was raised by reacting the fuel with the secondary air. At this time, the maximum temperature of the catalyst bed was 1150 ° C., and the air-fuel ratio of gas in the catalyst bed was in a lean state in which air was more than the stoichiometric ratio. Last 56-6
During 0 seconds, air is supplied and the air conditioner is in a lean state. At this time, the catalyst is discharged for 10 cycles in one cycle (60 seconds).
The percentage of time kept at 00 ° C. or higher was 50%, and the percentage of time kept in the lean state was 60%. The internal temperature of the catalyst bed was measured by a thermocouple inserted at the center of the catalyst bed.

(Phosphorus poisoning) 1100 ° C durability test and 1
The phosphorus poisoning in the 150 ° C durability test (A type) was performed in the same manner as the phosphorus poisoning in the 1100 ° C durability test described in Example 1.

(Examination of Results) Endurance treatment at 1100 ° C. for 50 hours under phosphorus poisoning (1000% or more, 13% lean state: 31%) + The exhaust gas purifying catalyst deteriorated by phosphorus poisoning is used in actual vehicle running. Is equivalent to the degradation of about 60000 km traveling, and endured under phosphorus poisoning at 1150 ° C. for 50 hours (A type) (1000 ° C. or more, 50%, lean state 60%) + The exhaust gas purifying catalyst deteriorated by phosphorus poisoning is , Which corresponds to deterioration of the actual vehicle over 100,000 km. In other words, a deterioration state equivalent to actual vehicle running, which usually takes about three months (60000 km), can be achieved in 50 hours by performing a durability test at 1100 ° C. + a phosphorus poisoning deterioration method, and a 50-hour durability at 1150 ° C. Test (A type) + phosphorus poisoning deterioration method, 5 months (100,000k
m) Deterioration state requiring about 50 hours can be realized.

The 1150 ° C. 50-hour endurance test (type A) + phosphorus poisoning deterioration method is a 50-hour endurance treatment at 1100 ° C. + phosphorus treatment which can obtain about 1.7 times the effect of the conventional deterioration method. The exhaust gas purifying catalyst can be deteriorated in a shorter time than poisoning.

EXAMPLE 3 In this example, an exhaust gas purifying catalyst was prepared in the same manner as in Example 2, and the exhaust gas purifying catalyst was subjected to pseudo-degradation with a silica coat to remove HC. Performance and the HC purification performance after the 1150 ° C. endurance test (B type) were evaluated. FIG. 7 shows the result.

(Silica Coat) The silica coat of the exhaust gas purifying catalyst is prepared by immersing the exhaust gas purifying catalyst in an aqueous solution obtained by diluting a silica adhesive (trade name: Corefix, manufactured by FOSECO) three times with water. After the silica is sufficiently adsorbed on the surface of the wash coat layer, about 60
The heat treatment was performed at 0 ° C. for about 2 hours. The coating amount of silica was 160 per 1 dm ³ of the monolith carrier.
g, 220 g, 310 g, and 420 g.

(1150 ° C. Endurance Test (Type B)) In this endurance test, a catalyst (catalyst bed) for purifying exhaust gas was installed in one bank (for four cylinders) of a V-type eight-cylinder engine with a displacement of 4.0 liters. It was done by doing. Specifically, the cycle (30 seconds) shown in FIG. 4 is defined as one cycle, and this cycle is performed a predetermined number of times (3000 times, 6000 times, 9000 times,
12,000 times). As shown in FIG. 4, in the above cycle, during the first 0 to 5 seconds, the air-fuel mixture maintained at the stoichiometric air-fuel ratio (stoichiometric state) by the feedback control was supplied to the engine. During 5 to 7 seconds, the feedback was opened and the fuel was injected excessively to supply a fuel-rich mixture to the engine. During the period of 7 to 28 seconds, while the feedback is open and the fuel is excessively supplied, secondary air is blown from the outside of the engine through the introduction pipe from the upstream side of the catalyst bed, and the inside of the catalyst bed is blown. The temperature was increased by reacting the excess fuel with the secondary air. At this time, the maximum temperature of the catalyst bed is 1150 ° C., and the air-fuel ratio of gas in the catalyst bed is in a lean state in which air is more than the stoichiometric ratio. During the last 28 to 30 seconds, air is supplied to keep the air condition in a lean state. In this endurance test, the proportion of time during which the catalyst bed was maintained at 1000 ° C. or higher was 50%, and the proportion of time during which the gas in the catalyst bed was in a lean state was 70%. The temperature inside the catalyst bed was measured by a thermocouple inserted at the center of the catalyst bed.

(Examination of Results) As is apparent from FIG.
Only by coating 160 g of silica per 1 dm ^{3 of the} monolith carrier, it is possible to realize a deteriorated state corresponding to a durability of 200 hours or more (about 300 hours) in a 1150 ° C. durability test (B type). In this 1150 ° C. endurance test (B type), the proportion of time during which the catalyst bed was maintained at 1000 ° C. or higher was 50%, the proportion of time during which the gas in the catalyst bed was in a lean state was 70%, Is 50% and the ratio of the lean state is 6%
This is a severe endurance test even when compared to the 0% endurance test at 1150 ° C (A type). That is, in the method of pseudo-deteriorating the exhaust gas purifying catalyst by the silica coating, a deteriorated state that cannot be easily achieved in a high-temperature oxidizing atmosphere can be simply and reliably realized. Of course, if the silica coating amount is larger than 160 g, a further deteriorated state can be realized. For example, if the silica coating amount is about 400 g, the exhaust gas purification catalyst has deteriorated to the OBD required level. A state corresponding to the state can be realized.

[0052]

As described above, according to the present invention, an exhaust gas purifying catalyst in a state corresponding to various deterioration states that can occur in the market can be provided simply, in a short time, and advantageously at a low cost. .

[Brief description of the drawings]

FIG. 1 is a cycle diagram for explaining a high-temperature durability test at 1050 ° C. (conventional deterioration method).

FIG. 2 is a cycle diagram for explaining a high-temperature durability test at 1100 ° C.

FIG. 3 is a cycle diagram for explaining a durability test (A type) at 1150 ° C.

FIG. 4 is a cycle diagram for explaining a durability test (B type) at 1150 ° C. ]

FIG. 5 shows the catalytic performance of an exhaust gas purifying catalyst that has been durable in an actual vehicle;
High temperature endurance test under phosphorus poisoning (1050 ° C endurance, 1100
4 is a graph showing the catalytic performance of an exhaust gas purifying catalyst that has been subjected to (C endurance).

FIG. 6 shows the catalytic performance of an exhaust gas purifying catalyst that is durable in an actual vehicle;
High temperature endurance test under phosphorus poisoning (1100 ° C endurance, 1150
4 is a graph showing the catalytic ability of an exhaust gas purifying catalyst that has been subjected to a (C endurance A type).

FIG. 7 is a graph showing the change in the HC purification ability of the exhaust gas purification catalyst with time at 1150 ° C. endurance test (B type) and the HC purification ability of the exhaust gas purification catalyst after silica coating. is there.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) F02D 29/02 F02D 45/00 314Z 4G069 41/14 310 B01D 53/36 103B 45/00 314 B01J 23/56 301A (72) Inventor Mari Uenishi 2-1-1 Taoyuan, Ikeda-shi, Osaka F-term in Daihatsu Industries Co., Ltd. (reference) 3G084 BA09 DA27 EA07 EB16 EC01 EC03 3G091 AA02 AA12 AA17 AA28 AA29 AB03 BA14 BA15 BA19 BA33 CA15 CA22 CB02 DA01 DA02 DA03 DB10 DC01 EA18 EA30 EA38 FA14 FB03 FB10 FB11 FB12 FC02 FC08 GA06 GA16 GB01W GB01X GB04W GB05W GB06W GB07W GB10X GB17X 3G093 BA04 DB23 EA04 FA06 3G301 HA08 JB09 A01 NE13 A01 NE13 A01 NE13 A03 NE01 A18 NE13 A03 NE13 A01 NEA BA19X BA42X BB02 BC05 4G069 AA03 AA08 AA09 AA14 AA15 BA13B BC02A BC03A BC21A BC35A BC66A BC69A BC75B BD07A BD07B BD08A CA03 CA09 DA06 ED07 ED10 FB01 FC04

Claims (13)

[Claims] 1. A method for forcibly deteriorating an exhaust gas purifying catalyst containing a noble metal as an active substance by durable in a high-temperature atmosphere, wherein the temperature of the high-temperature atmosphere is changed with time and the temperature is changed. The method for deteriorating an exhaust gas purifying catalyst, characterized in that the ratio of time during which the temperature is maintained at 1000 ° C. or higher is in the range of 10 to 80% of the total high-temperature durability time. 2. The exhaust gas purifying catalyst according to claim 1, wherein the high-temperature atmosphere is achieved by supplying a high-temperature gas discharged when a mixture of fuel and air is burned in an internal combustion engine. Degradation method. 3. The ratio of the unreacted fuel and air in the high-temperature atmosphere is changed with time, and the time ratio of the lean state where the air is excessive than the stoichiometric ratio is set to 30 to 80% of the total durability time. 3. The method for deteriorating an exhaust gas purifying catalyst according to claim 2, wherein the temperature falls within the range. 4. The exhaust gas purifying catalyst according to claim 3, wherein the ratio of unreacted fuel and air in the high-temperature atmosphere is kept in a lean state while the temperature of the high-temperature atmosphere is maintained at 1000 ° C. or higher. Degradation method. 5. A method for forcibly deteriorating an exhaust gas purifying catalyst in which a coating layer containing a noble metal as an active substance is formed on a heat-resistant support carrier, wherein a catalyst poison for the noble metal is formed on the surface of the coating layer. A method for deteriorating an exhaust gas purifying catalyst, which comprises adhering components. 6. The deterioration of the exhaust gas purifying catalyst according to claim 5, wherein the catalyst poison component is at least one selected from the group consisting of phosphorus, sulfur, lead, sodium, potassium, zinc, and iron. Method. 7. The exhaust gas purification according to claim 5, wherein the exhaust gas purification catalyst is durable in a high-temperature atmosphere, and the catalyst poison component adheres to the surface of the coating layer during the high-temperature durability. How to degrade the catalyst. 8. The high-temperature atmosphere is achieved by supplying a high-temperature gas discharged when a mixture of fuel and air is burned in an internal combustion engine, and the high-temperature gas contains the catalyst poison component. The method for deteriorating an exhaust gas purifying catalyst according to claim 7, which is performed. 9. Any one of claims 1 to 4
A method for deteriorating an exhaust gas purifying catalyst, wherein the method for deteriorating one exhaust gas purifying catalyst and the method for deteriorating one exhaust gas purifying catalyst according to any one of claims 5 to 8 are performed in combination. Method. 10. A method for simulating deterioration of an exhaust gas purifying catalyst in which a coating layer containing a noble metal as an active substance is formed on a heat-resistant support carrier, wherein a pseudo-deteriorating substance is formed on the surface of the coating layer. A method for deteriorating an exhaust gas purifying catalyst, which comprises coating. 11. The pseudo-deteriorating substance is a vitreous component,
The method for deteriorating an exhaust gas purifying catalyst according to claim 10, wherein the catalyst is at least one selected from a resin, a fat, and a metal. 12. A method for deteriorating an exhaust gas purifying catalyst according to any one of claims 1 to 9 and a method for deteriorating one exhaust gas purifying catalyst according to claim 10 or 11. Characterized by performing in combination,
How to degrade an exhaust gas purification catalyst. 13. An exhaust gas purifying catalyst obtained by the deterioration method according to claim 1. Description: