JP4998350B2 - Exhaust gas purification catalyst - Google Patents

Description

  The present invention relates to an exhaust gas purifying catalyst suitable for applying to a process for purifying exhaust gas discharged from an internal combustion engine, and a method for manufacturing the same.

In recent years, in order to remove harmful substances such as hydrocarbon compounds (HC), carbon monoxide (CO), and nitrogen oxides (NO _x ) contained in exhaust gas discharged from an internal combustion engine, alumina (Al ₂ Exhaust gas purification catalysts in which noble metal particles such as platinum (Pt) are supported on a metal oxide carrier such as O ₃ ) are widely used. In conventional exhaust gas purification catalysts, a large amount of noble metal particles is used in order to improve the durability of the noble metal particles against ambient fluctuations. However, using a large amount of noble metal particles is not desirable from the viewpoint of protecting earth resources.

Against this background, recently, transition metals or transition metal compounds such as cerium (Ce) and manganese (Mn), which function as OSC (Oxygen Storage Component) materials, are disposed in the vicinity of noble metal particles by an impregnation method. Attempts have been made to improve the durability of noble metal particles by suppressing changes in the atmosphere around the noble metal particles with a transition metal or a transition metal compound (see Patent Documents 1 to 4). In addition, according to such a method, in addition to the improvement in durability of the noble metal particles, an improvement in the activity of the noble metal particles can be expected.
JP-A-8-131830 JP-A-2005-000829 Japanese Patent Laid-Open No. 2005-000830 JP 2003-117393 A

  In order to suppress the change in atmosphere around the noble metal particles with the transition metal compound, both the noble metal particles and the transition metal compound particles need to be fine particles and in contact with each other. However, when the impregnation method is used, even if the noble metal particles and the transition metal compound particles can be brought into contact with each other, both of them do not become fine particles, or even if both become fine particles, they cannot be brought into contact with each other or are in contact with each other. Since the amount that can be produced is small, it is difficult to arrange the transition metal compound particles in the vicinity of the noble metal particles as designed. Further, when improving the durability of the noble metal particles, the average particle diameter of the noble metal particles is 2 [nm] or more, and when improving the activity of the noble metal particles, the average particle diameter of the noble metal particles is 5 [nm] or less. It is desirable. However, when the impregnation method is used, the average particle diameter of the noble metal particles is 1.5 [nm] or less, and it is difficult to expect improvement in durability and activity of the noble metal particles.

  In addition, since transition metal compounds are easily dissolved in alumina, which is widely used as a metal oxide support, it is difficult to obtain an effect of improving the activity of noble metal particles simply by placing the transition metal compound in the vicinity of the noble metal particles. . In order to solve such a problem, a method of supporting a transition metal compound on a support that does not form a solid solution with the transition metal compound has been considered, but when this method is used, a high temperature atmosphere is considered. The transition metal compound moves below, and the transition metal compounds come into contact with each other, causing the transition metal compounds to aggregate. In order to prevent agglomeration of the transition metal compound, a method of producing transition metal compound particles having a large surface area by using the reverse micelle method may be considered. However, in this method, an organic solvent is used. And environmental load is large.

In order to solve the above problems, the exhaust gas purifying catalyst according to the present invention, the noble metal particles, in contact with the noble metal particles, a first compound comprising an oxide containing at least one of cerium and zirconium, the noble metal enclosing the particle first compound and a second compound that inhibits aggregation of the first compounds with the first compound contact between suppresses the movement of the noble metal particles, the first compound carrying the noble metal particles and elemental or aggregates of the first compounds carrying the noble metal particles, comprising the second compartment separated by compound, said second compound, said The first compound alone or aggregate is prevented from moving beyond the compartments and coming into contact with each other to agglomerate, and the amount of O ₂ released in the temperature programmed desorption test is 150 [° C.] to 500 [° C.] Precious metal used in range 1 [g] , And summarized in that a 400~1200 [mmol / g].

Further, the exhaust gas purifying catalyst according to the present invention, the noble metal particles, the contact between the noble metal particles, a first compound comprising an oxide containing at least one of cerium and zirconium, said first and said noble metal particles the compound was included, the first to the second compound inhibits the aggregation of compounds first compound caused by the contact between suppresses the movement of the noble metal particles, and a third compound having the capability of adsorbing and releasing oxygen, the wherein the first compound carrying the noble metal particles, and includes a simple substance or aggregates of the first compounds carrying the noble metal particles, the second compartment separated by compounds, wherein the The second compound suppresses that the simple substance or aggregate of the first compound moves beyond the compartment and agglomerates in contact with each other , and the third compound includes the first compound carrying noble metal particles. Compound inclusion That is disposed in the vicinity of the second compound, O ₂ emissions in the temperature-programmed desorption test 150 [℃] ~500 [℃] Use precious 1 [g] per in the range of, 400~1200 [mmol / g] It is a summary.

  According to the exhaust gas purifying catalyst according to the present invention, the durability and activity of the noble metal particles can be improved by the configuration in which the effect of containing the promoter component is further exhibited.

  Hereinafter, embodiments of an exhaust gas purification catalyst of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view of an embodiment of an exhaust gas purifying catalyst according to the present invention.

  The exhaust gas purifying catalyst 1 according to an embodiment of the present invention is a first catalyst that has at least one of a noble metal particle 2 and an ability to contact the noble metal particle 2 to suppress the movement of the noble metal particle 2 and to absorb and release oxygen. A second compound that contains the compound 3, the noble metal particle 2 and the first compound 3 and suppresses the movement of the noble metal particle 2 and suppresses the aggregation of the first compound 3 due to the contact between the first compounds 3; A compound 4 and a third compound 5 having oxygen absorbing / releasing ability are provided.

  The first compound 3 carries noble metal particles 2. The first compound 3 carrying the noble metal particles 2 is contained in a compartment separated by the second compound 4. The first compound 3 is shown as a simple substance in the illustrated example, but may be an aggregate in which a plurality of first compounds 3 are included in the compartments separated by the second compound 4. The third compound 5 is disposed in the vicinity of the second compound 4 enclosing the first compound 3 carrying the noble metal particles 2 outside the section separated by the second compound 4.

  The catalyst of this invention is not limited to embodiment which has the particle | grain unit structure which consists of each component shown in FIG. As another embodiment, the third compound 5 in the embodiment shown in FIG. 1 is not provided, and the first compound 3 has a particle unit structure in which the first compound 3 has an oxygen absorption / release capability. You can also

  The exhaust gas purifying catalyst 1 according to the embodiment of the present invention shown in FIG. 1 suppresses the movement of the noble metal particles 2 by covering the noble metal particles 2 and the first compound 3 with the second compound 4, Aggregation of the first compounds 3 is also suppressed. Therefore, according to the exhaust gas purifying catalyst 1 according to the embodiment of the present invention, the effect of improving the activity of the noble metal particles 2 by the first compound 3 can be maintained without increasing the manufacturing cost and the environmental load.

  Specifically, as a result of intensive research, the inventors have been able to chemically inhibit the movement of the noble metal particles by chemically bonding the noble metal particles to the oxide, It was found that the movement of the noble metal particles can be physically suppressed by covering with another oxide. Furthermore, it has been found that by covering both the noble metal particles and the oxide with another oxide, not only the movement of the noble metal particles but also the aggregation of the oxide can be suppressed.

  The exhaust gas purifying catalyst 1 shown in FIG. 1 constructed based on this knowledge is supported by the first compound 3 in contact with the noble metal particles 2 so that the first compound 3 is an anchor material having a chemical bond. Acts to suppress the movement of the noble metal particles 2. Further, the movement of the noble metal particles 2 is physically suppressed by covering and enclosing the noble metal particles 2 and the first compound 3 with the second compound 4. Further, the catalyst 1 having a particle unit structure includes a noble metal particle 2 and a first compound 3 in a compartment separated by the second compound 4, thereby separating the compartment separated by the second compound 4. The first compound 3 moves beyond the range and is prevented from aggregating in contact with each other. From these facts, the exhaust gas purification catalyst having the structure of the catalyst 1 shown in FIG. 1 can prevent a decrease in catalytic activity due to aggregation of the noble metal particles 2 without increasing the manufacturing cost and the environmental load. The activity improving effect of the noble metal particles 2 by the first compound 3 can be maintained. Therefore, an exhaust gas purification catalyst having high heat resistance and excellent durability over a long period of time can be obtained.

  By providing the exhaust gas purifying catalyst of the present invention with the above-described structure, the aggregation of the noble metal particles 2 is suppressed even after high temperature-long time exhaust gas treatment, so that the performance of the catalyst is improved. This is because by adopting this structure, the noble metal particles can be maintained in a finely divided state, and the surface area of the noble metal that is the active point is maintained.

  However, under an actual exhaust gas atmosphere, the atmosphere of the exhaust gas that contacts the exhaust gas purification catalyst fluctuates, resulting in an oxygen-excess (lean) atmosphere or an oxygen-deficient (rich) atmosphere. Therefore, depending on the atmosphere, there is a possibility that the reaction on the noble metal particles 2 does not proceed. In order to avoid this, the exhaust gas purifying catalyst of the present invention includes a compound having an oxygen absorption / release capability, that is, an OSC material (a material having an oxygen storage capability) in the catalyst. In the example shown in FIG. 1, at least one of the first compound 3 and the third compound 5 is a compound having an oxygen storage / release capability. By arranging this OSC material in the catalyst, even if the exhaust gas atmosphere fluctuates, the OSC material absorbs oxygen in the atmosphere when the atmosphere is excessive in oxygen, and the OSC material is the atmosphere when the atmosphere is insufficient in oxygen. Release oxygen into it. Therefore, the catalyst performance can be maintained even if the exhaust gas atmosphere fluctuates.

The amount of the OSC material has an appropriate range, and the catalyst performance can be further improved by optimizing the amount of the OSC material. In the catalyst having the particle unit structure of the present invention, the OSC material amount is 400 to 1200 with respect to 1 [g] of the noble metal in the temperature range of O ₂ release amount in the temperature programmed desorption test of 150 to 500 [° C.]. It is effective to arrange the OSC material so that it is [mmol / g]. In the region where the amount of OSC is less than the above range, the active site becomes oxygen deficient and the oxidation reaction does not proceed, resulting in poor performance. Further, in a large region, oxygen is excessive, and the active point is deteriorated in performance because oxygen poisoning occurs.

  The amount of oxygen released per unit weight of the noble metal is larger than that of conventionally known catalysts. Since the oxygen release amount is proportional to the amount of the OSC material, the amount (weight) of the OSC material per noble metal of the present invention is larger than that of the conventional catalyst. This is because the catalyst of the present invention maintains the fine particle state as a result of suppressing the aggregation of the noble metal particles, and the surface area per unit weight of the noble metal particles is much larger than that of the conventional catalyst. Since the amount of the OSC material added to the catalyst has an appropriate range according to the surface area of the noble metal particles, the amount of the OSC material per unit weight of the noble metal particles of the catalyst of the present invention is higher than that of the conventional catalyst. Become more.

  Since the exhaust gas purifying catalyst of the present invention has a remarkably larger surface area per unit weight of the noble metal particles than the conventional catalyst as described above, the active points for purifying the exhaust gas increase. For this reason, the amount (weight) of noble metal particles necessary for obtaining a predetermined exhaust gas purification performance is smaller than that of a conventional catalyst. Therefore, the amount of expensive noble metal used is likely to be depleted of resources and can be reduced as compared with conventional catalysts.

400 to 1200 [mmol / g per 1 [g] of the precious metal used in the range of 150 to 500 [° C.] O ₂ release amount in the temperature programmed desorption test, which is a characteristic of the exhaust gas purifying catalyst in the present invention. The temperature of the catalyst is raised from room temperature to 600 [° C.] under atmospheric flow, held at 600 [° C.] for 30 minutes, then lowered to 100 [° C., and under H ₂ flow. By increasing the temperature from 100 [° C] to 500 [° C] at a rate of 10 [° C / min], reducing the oxygen released from the catalyst with hydrogen, and quantifying the generated water with a mass spectrometer It can be measured by a temperature programmed desorption test that quantifies the amount of oxygen in the catalyst. In order to measure the amount of O ₂ released from the OSC material in the exhaust gas purification catalyst, a temperature-programmed desorption test has been conventionally performed. According to the temperature-programmed desorption test defined in the present invention, it is possible to accurately measure the O ₂ emission amount of the exhaust gas purifying catalyst of the present invention.

  FIG. 2 shows a graph of a time-dependent temperature change pattern of the temperature programmed desorption test defined in the present invention, with the horizontal axis representing time and the vertical axis representing temperature. In the example of the preferred temperature-programmed desorption test of the present invention shown in the figure, first, about 0.1 [g] of the catalyst is weighed, and 20 [ The temperature is raised at [° C / min], held at 600 [° C] for 30 minutes, and then lowered to 100 [° C]. This is a pretreatment, in which impurities such as oil that may adhere to the catalyst are oxidized and removed, and the OSC material in the catalyst absorbs oxygen.

Next, hold for 15 minutes under He (100 [%]) gas flow, then switch the flow gas to H ₂ gas and hold for another 15 minutes. This is because the oxygen component physically adsorbed on the surface of the catalyst is removed so that oxygen is released only from the OSC material during the subsequent heating.

Next, the temperature is raised from 100 [° C.] to 500 [° C.] at a rate of 10 [° C./min] under the flow of H ₂ (100 [%]). The oxygen released from the catalyst during the temperature rise is quantified with a mass spectrometer, for example, a quadrupole mass spectrometer. Oxygen released from the catalyst during the temperature increase becomes H ₂ O instantaneously by H _2. Therefore, oxygen that has actually come out of the catalyst is confirmed as H ₂ O.

  After that, the temperature is lowered to 100 ° C (10 [° C / min]).

  The oxygen release amount per gram of noble metal of the catalyst is calculated by using 0.1 [g] of CuO as a reference sample and comparing it with the OSC amount obtained from this peak area. The reaction formula when oxygen is released from CuO is as follows.

CuO + H ₂ → Cu + H ₂ O
Since H ₂ O equivalent to the number of moles of CuO is released, 1.3 × 10 ⁻³ moles of O ₂ are released from 0.1 gram (1.3 × 10 ⁻³ moles) of Cu. Therefore, the oxygen release amount per gram of noble metal of each catalyst can be calculated by the following equation.

Oxygen release amount of each catalyst (mol / noble metal 1g) = (1.3 × 10 ⁻³ mol × catalyst peak area) ÷ (CuO peak area × noble metal amount in sample)
The amount of oxygen released per gram of noble metal calculated in this way is in the range of 400 to 1200 [mmol / g] for the catalyst of the present invention.

  The OSC material contained in the exhaust gas purifying catalyst of the present invention may be contained in the exhaust gas purifying catalyst 1 as the third compound 5 as shown in FIG. Or may be contained in the exhaust gas-purifying catalyst as both the first compound 3 and the third compound 5. Further, regarding the exhaust gas purification catalyst having a particle unit structure that does not include the third compound 5 in the exhaust gas purification catalyst 1 shown in FIG. 1, an OSC material is included in the exhaust gas purification catalyst as the first compound. Also good.

The compound having oxygen releasing ability contained in at least one of the first compound 3 and the third compound is preferably an oxide containing ceria (CeO ₂ ). As a characteristic of Ce, there is a characteristic that the valence is changed with respect to atmospheric fluctuation. Therefore, the oxide containing Ce has an ability to absorb or release oxygen with an atmosphere. Therefore, in order to utilize this characteristic for the exhaust gas purifying catalyst, it is important that at least one of the first compound 3 and the third compound 5 contains ceria. Ceria is a particularly excellent material as an OSC material for exhaust gas purification catalysts.

  This ceria may be included in the first compound 3 or the third compound 5 in the form of a single oxide, or may be included in the form of a complex oxide. An example of the complex oxide is a complex oxide of ceria and zirconia.

  The compound having an oxygen releasing ability contained in at least one of the first compound 3 and the third compound is an oxide, and the oxide having the oxygen absorbing / releasing ability further includes Y, Nd, Pr It is more preferable that at least one element selected from Al, Ga and In is included.

  The element added to the compound having oxygen releasing ability is preferably at least one element selected from Y, Nd, Pr, Al, Ga and In. By adding at least one of these additive elements, the oxygen adsorption rate of the exhaust gas purifying catalyst is improved. This means that oxygen is efficiently absorbed even when the atmosphere in which the catalyst is placed is lean. That is, the exhaust gas purifying catalyst of the present invention containing at least one element selected from Y, Nd, Pr, Al, Ga and In in the OSC material is considered to have a high ability to alleviate atmospheric fluctuations in the lean region. It is done. In addition, since the OSC material containing at least one element selected from Y, Nd, Pr, Al, Ga and In absorbs or releases oxygen in response to changes in the atmosphere, it releases oxygen even in a rich atmosphere. The rate is thought to be improving. The reason why the oxygen adsorption rate of the OSC material is improved by containing at least one element selected from Y, Nd, Pr, Al, Ga, and In is unknown, but Y, Nd, Pr, Al, Ga And In are both trivalent elements, and these trivalent additive elements are dissolved in Ce to form oxygen vacancies. This is probably because the speed is improved. Moreover, it is thought that an effect becomes large, so that an oxygen absorption rate becomes quick. Among elements selected from Y, Nd, Pr, Al, Ga and In, Y is a particularly preferable element.

  In FIG. 3, in the two types of exhaust gas purification catalysts, when Y is added to the OSC material, oxygen is further introduced from a state in which a predetermined amount of oxygen is adsorbed in advance on the OSC material in the catalyst. The result of examining the adsorption rate of oxygen in this case is shown in a graph. In FIG. 3, 0 [mol] on the horizontal axis indicates a state in which no oxygen preliminarily adsorbed in the OSC material exists, and 0.007 [mol] indicates a state in which the oxygen preliminarily adsorbed in the OSC material is saturated. . Within these ranges, various amounts of oxygen were previously adsorbed on the OSC material. The vertical axis represents the ratio of oxygen adsorbed when a certain amount of oxygen is further introduced under these circumstances. From FIG. 3, the example in which Y was added to the OSC material showed a higher oxygen absorption rate, regardless of the amount of oxygen in the catalyst, compared to the example in which Y was not added to the OSC material. This indicates that the oxygen can be efficiently absorbed even when the catalyst is placed in various atmospheres. That is, it can be said that the exhaust gas purifying catalyst of the present invention in which Y is added to the OSC material has a high ability to alleviate atmospheric fluctuations.

The exhaust gas purifying catalyst of the present invention is applied and formed on the inner wall surface of a honeycomb structure made of a refractory inorganic material, and is actually used in the form of a catalyst coat layer. In the form of the catalyst coat layer, the exhaust gas purifying catalyst of the present invention preferably contains 10 to 40 wt% of the compound having the ability to absorb and release oxygen as CeO _{2 in} the catalyst coat layer. By containing 10 to 40 wt% of CeO ₂ in the catalyst coat layer, 400 to 1200 mmol / g of O ₂ can be released per 1 g of the precious metal used in the temperature programmed desorption test described above, thereby improving the catalyst performance. For example, the conversion rate is improved. As described above, the exhaust gas purifying catalyst of the present invention has a larger amount of OSC material per noble metal than the conventional catalyst, and the amount of CeO ₂ contained in the catalyst coat layer is also relative to that of the conventional catalyst. It becomes a lot of things.

  In the exhaust gas purifying catalyst of the present invention, the noble metal particles preferably contain at least one of Pt, Pd and Rh. Pt, Pd and Rh are all noble metals suitable as exhaust gas purification catalysts, and are suitable for use in exhaust gas purification catalysts having the particle unit structure according to the present invention.

  The exhaust gas purifying catalyst according to the present invention may be coated with a single layer, but more preferably has at least two catalyst coating layers. This is because by forming a plurality of layers having different types of catalytic noble metals, it is possible to take advantage of the characteristics of each catalytic noble metal and improve the catalyst performance.

  When at least two catalyst coat layers are provided, the inner layer of the catalyst coat layer is preferably a layer containing Pt or Rd as a noble metal, and the surface layer side of the catalyst coat layer is preferably a layer containing Rh as a noble metal. This is because, when considering gas diffusivity, it is more effective to improve the catalytic activity when the catalyst containing Rh is arranged on the surface layer side having high contact with the gas.

  Further, when having at least two catalyst coat layers, the OSC material may be contained in at least one of the coat layers. For example, when the inner layer of the catalyst coat layer is a layer containing Pt in the noble metal and the surface layer side of the catalyst coat layer is a layer containing Rh in the noble metal, it is sufficient that the OSC material is contained in the inner layer containing Pt.

  Hereinafter, the present invention will be specifically described based on examples.

The exhaust gas purifying catalysts of Examples 1 to 7 and Comparative Example 1 shown in Table 1 were coated on the inner wall surface of the honeycomb carrier.

  A three-layer coat was used, with the layer closest to the honeycomb carrier being one layer and the farthest layer being three layers. Although the precious metal loading concentration is not specified, it was supported appropriately so that each coating amount was the specified amount. The numbers in parentheses in the table indicate the mol ratio.

  Each Example and Comparative Example was produced as follows.

Example 1
1. Powder preparation (step 1): A solution in which dinitrodiamine platinum nitrate aqueous solution (Pt: 8.83 wt%) was dispersed in ion-exchanged water was added to a solution in which CeO ₂ was dispersed in ion-exchanged water, followed by stirring for 1 hour. This was evaporated to dryness, pulverized and sized, and calcined at 400 ° C. for 1 h to obtain Pt- supported CeO ₂ . 40 g of the powder and 50 g of PVP (polyvinylpyrrolidone) were dispersed in 150 ml of ion-exchanged water and stirred for 1 hour.

(Step 2): Next, a solution in which a rhodium nitrate solution (Rh: 13.81 wt%) was dispersed in ion-exchanged water was added to a solution in which Zr-La was dispersed in ion-exchanged water, followed by stirring for 1 hour. This was evaporated to dryness, pulverized and sized, and fired at 400 ° C. for 1 h to obtain Rh- supported Zr-La.

(Step 3): Next, 43.5 g of boehmite was added to 300 ml of ion-exchanged water, followed by stirring for 1 hour. A solution prepared by dissolving 10 g of cerium nitrate in ion-exchanged water was added thereto and stirred for 30 minutes. The solution obtained in step 1 was added to this and stirred for 1 hour. After heating and drying this solution, the powder was taken out, dried at 150 ° C. for 1 h, pulverized to 500 μm or less, and calcined at 550 ° C. for 3 h.

(Step 4): 75 g of the powder obtained in Step 2 and 305 g of ion-exchanged water were put into a magnetic pot, shaken and pulverized with alumina balls, and 43.6 g of PVP was added to 257.3 g of the taken slurry, followed by stirring for 1 hour. To this was added a solution in which 60.4 g of boehmite was dispersed in 700 g of ion-exchanged water, and the mixture was stirred for 1 hour. This solution was heated and dried, then the powder was taken out, dried at 150 ° C. for 1 h, pulverized to 500 μm or less, and calcined at 550 ° C. for 3 h.

2. Coating (Step 5): 118.7 g of alumina, 14 g of 10% nitric acid, and 360.3 ml of ion-exchanged water were put in a magnetic pot, and shaken and pulverized with alumina balls to obtain a first layer slurry.

(Step 6): 58.8 g of the powder obtained in Step 3, 12.4 g of Zr-La-Ce, 7.5 g of 10% nitric acid, and 216.2 g of ion-exchanged water are put into a magnetic pot, shaken and ground with alumina balls, and two layers An eye slurry was obtained.

(Step 7): 45.3 g of the powder obtained in Step 4, 45.3 g of Zr-La, 37.6 g of alumina, 13.5 g of 10% nitric acid, and 349.1 g of ion-exchanged water are put into a magnetic pot and shaken and ground together with alumina balls. A third layer slurry was obtained.

(Step 8): The catalyst slurry of Step 5 is put into a cordierite-made honeycomb carrier (600 cells / 4 mil), excess slurry is removed by air flow, dried at 120 ° C., 400 ° C., air flow Medium fired. The coat amount was 50 g / L.

  Similarly, the catalyst slurry was applied in the order of the slurry obtained in step 6 and the slurry obtained in step 7. The coating amounts were 100 g / L and 70 g / L, respectively.

(Example 2)
1. Powder preparation Powder was prepared in the same procedure as in Example 1 (steps 1 to 4).

2. Coating (Step 5): 118.7 g of alumina, 14 g of 10% nitric acid, and 360.3 ml of ion-exchanged water were put in a magnetic pot, and shaken and pulverized with alumina balls to obtain a first layer slurry.

(Step 6): 58.8 g of the powder obtained in Step 3, Ce-Zr 12.4 g, 7.5% of 10% nitric acid, and 216.2 g of ion-exchanged water are put into a magnetic pot, shaken and ground with alumina balls, and the second layer A slurry was obtained.

(Step 7): 45.3 g of the powder obtained in Step 4, 45.3 g of Zr-La, 37.6 g of alumina, 13.5 g of 10% nitric acid, and 349.1 g of ion-exchanged water are put into a magnetic pot and shaken and ground together with alumina balls. A third layer slurry was obtained.

(Step 8): The catalyst slurry of Step 5 is put into a cordierite-made honeycomb carrier (600 cells / 4 mil), excess slurry is removed by air flow, dried at 120 ° C., 400 ° C., air flow Medium fired. The coat amount was 50 g / L.

  Similarly, the catalyst slurry was applied in the order of the slurry obtained in step 6 and the slurry obtained in step 7. The coating amounts were 100 g / L and 70 g / L, respectively.

(Example 3)
1. Powder preparation Powder was prepared in the same procedure as in Example 1 (steps 1 to 4).

2. Coating <Step 5>: 54.4 g of the powder obtained in Step 3, Ce-Zr 24.7 g, 14 g of alumina, 10.4 g of 10% nitric acid, and 281.9 g of ion-exchanged water are put in a magnetic pot and shaken and ground with alumina balls. A second layer slurry was obtained.

(Step 6): 50.4 g of the powder obtained in Step 4, 50.4 g of Zr-La, 34.3 g of alumina, 15 g of 10% nitric acid, and 329.7 g of ion-exchanged water are put into a magnetic pot and shaken and ground together with alumina balls. A layer of slurry was obtained.

(Step 7): The catalyst slurry of Step 5 is put into a cordierite-made honeycomb carrier (600 cells / 4 mil), excess slurry is removed by air flow, drying at 120 ° C., 400 ° C., air flow Medium fired. The coating amount was 150 g / L.

  Similarly, the catalyst slurry obtained in Step 6 was applied. The coat amount was 70 g / L.

Example 4
1. Powder preparation Powder was prepared in the same procedure as in Example 1 (steps 1 to 4).

2. Coating (Step 5): 58.8g of the powder obtained in Step 3, Ce-Zr 39.2g, 10.4g of 10% nitric acid, and 281.9g of ion-exchanged water are put into a magnetic pot, shaken and ground with alumina balls, and the second layer A slurry of was obtained.

(Step 6): 50.4 g of the powder obtained in Step 4, 50.4 g of Zr-La, 34.6 g of alumina, 15 g of 10% nitric acid, and 329.7 g of ion-exchanged water are put into a magnetic pot and shaken and ground together with alumina balls. A layer of slurry was obtained.

(Step 7): The catalyst slurry of Step 5 is put into a cordierite-made honeycomb carrier (600 cells / 4 mil), excess slurry is removed by air flow, drying at 120 ° C., 400 ° C., air flow Medium fired. The coating amount was 150 g / L.

  Similarly, the catalyst slurry obtained in Step 6 was applied. The coat amount was 70 g / L.

(Example 5)
1. Powder preparation (step 1): A solution in which dinitrodiamine platinum nitrate aqueous solution (Pt: 8.83 wt%) was dispersed in ion-exchanged water was added to a solution in which Ce-Zr was dispersed in ion-exchanged water, followed by stirring for 1 hour. . This was evaporated to dryness, pulverized and sized, and calcined at 400 ° C. for 1 h to obtain Pt-supported Ce-Zr. Ion-exchanged water (2400 g) was added to 600 g of the powder obtained by repeating the above operation, put into a magnetic pot, and shaken and ground with alumina balls.

(Step 2): A solution in which a rhodium nitrate solution (Rh: 13.81 wt%) was dispersed in ion-exchanged water was added to a solution in which Zr-La was dispersed in ion-exchanged water, and the mixture was stirred for 1 hour. This was evaporated to dryness, pulverized and sized, and fired at 400 ° C. for 1 h to obtain Rh- supported Zr-La. Ion-exchanged water (2400 g) was added to 600 g of the powder obtained by repeating the above operation, put into a magnetic pot, and shaken and ground with alumina balls.

(Step 3): 51.4 g of boehmite was added to 262.2 g of ion-exchanged water and stirred for 1 hour. A solution in which 12.6 g of cerium nitrate was dissolved in 100 ml of ion-exchanged water and a solution in which 5.3 g of zirconium nitrate was dissolved in 100 ml of ion-exchanged water were sequentially added to this and stirred for 30 minutes. After adding 500 g of the slurry obtained in step 1 and stirring for 1 h, heating and drying were performed, the powder was taken out, dried at 150 ° C. for 1 h, pulverized to 500 μm or less, and then fired at 550 ° C. for 3 h did.

(Step 4): 60.9 g of boehmite was added to 547.7 g of ion-exchanged water, 9.8% nitric acid was added to adjust the pH to 4.5, and the mixture was stirred for 1 hour. After adding 271.6 g of the slurry obtained in step 2 and stirring for 1 h, the mixture was transferred to an evaporator, heated and dried, then the powder was taken out, dried at 150 ° C. for 1 h, and pulverized to 500 μm or less. Baked at 550 ° C. for 3 h.

2. Coating (Step 5): 118.7 g of alumina, 14 g of 10% nitric acid, and 360.3 ml of ion-exchanged water were put in a magnetic pot, and shaken and pulverized with alumina balls to obtain a first layer slurry.

(Step 6): 107.1 g of the powder obtained in Step 3, Zr-Ce 29.1 g, 20 g of 10% nitric acid, and 273.5 g of ion-exchanged water are put into a magnetic pot, shaken and pulverized with alumina balls, and a second layer slurry Got.

(Step 7): 73.5 g of the powder obtained in Step 4, Zr-La19 g, 31.5 g of 10% nitric acid, and 694.2 g of ion-exchanged water are put into a magnetic pot, shaken and pulverized with alumina balls, and the third layer slurry is formed. Obtained.

(Step 8): The catalyst slurry of Step 5 is put into a cordierite-made honeycomb carrier (600 cells / 4 mil), excess slurry is removed by air flow, dried at 120 ° C., 400 ° C., air flow Medium fired. The coat amount was 50 g / L.

  Similarly, the catalyst slurry was applied in the order of the slurry obtained in step 6 and the slurry obtained in step 7. The coating amounts were 110 g / L and 60 g / L, respectively.

(Example 6)
1. Powder preparation (step 1): A solution in which dinitrodiamine platinum nitrate aqueous solution (Pt: 8.83 wt%) was dispersed in ion-exchanged water was added to a solution in which Ce-Zr was dispersed in ion-exchanged water, followed by stirring for 1 hour. . This was evaporated to dryness, pulverized and sized, and calcined at 400 ° C. for 1 h to obtain Pt-supported Ce-Zr. Ion-exchanged water (2400 g) was added to 600 g of the powder obtained by repeating the above operation, put into a magnetic pot, and shaken and ground with alumina balls.

(Step 2): A solution in which a rhodium nitrate solution (Rh: 13.81 wt%) was dispersed in ion-exchanged water was added to a solution in which Zr-La was dispersed in ion-exchanged water, and the mixture was stirred for 1 hour. This was evaporated to dryness, pulverized and sized, and fired at 400 ° C. for 1 h to obtain Rh- supported Zr-La. Ion-exchanged water (2400 g) was added to 600 g of the powder obtained by repeating the above operation, put into a magnetic pot, and shaken and ground with alumina balls.

(Step 3): 77 g of boehmite was added to 493.3 g of ion-exchanged water and stirred for 1 h. A solution in which 18.9 g of cerium nitrate was dissolved in 100 ml of ion-exchanged water and a solution in which 7.9 g of zirconium nitrate was dissolved in 100 ml of ion-exchanged water were sequentially added to this and stirred for 30 minutes. After adding 500 g of the slurry obtained in step 1 and stirring for 1 h, heating and drying were performed, the powder was taken out, dried at 150 ° C. for 1 h, pulverized to 500 μm or less, and then fired at 550 ° C. for 3 h did.

(Step 4): 304.3 g of boehmite was added to 2738.6 g of ion-exchanged water, pH was adjusted to 4.5 by adding 9.8% nitric acid, and the mixture was stirred for 1 hour. 1358 g of the slurry obtained in step 2 was added to this, stirred for 1 h, heated and dried, then the powder was taken out, dried at 150 ° C. for 1 h, ground to 500 μm or less, and calcined at 550 ° C. for 3 h did.

2. Coating (Step 5): 118.7 g of alumina, 14 g of 10% nitric acid, and 360.3 ml of ion-exchanged water were put in a magnetic pot, and shaken and pulverized with alumina balls to obtain a first layer slurry.

(Step 6): 107.1 g of the powder obtained in Step 3, Zr-Ce 29.1 g, 20 g of 10% nitric acid, and 273.5 g of ion-exchanged water are put into a magnetic pot, shaken and pulverized with alumina balls, and a second layer slurry Got.

(Step 7): 73.5 g of the powder obtained in Step 4, Zr-La 19 g, 31.5 g of 10% nitric acid and 694.2 g of ion-exchanged water are put into a magnetic pot, shaken and pulverized with alumina balls, and the third layer slurry is obtained. Obtained.

(Step 8): The catalyst slurry of Step 5 is put into a cordierite-made honeycomb carrier (600 cells / 4 mil), excess slurry is removed by air flow, dried at 120 ° C., 400 ° C., air flow Medium fired. The coat amount was 50 g / L.

  Similarly, the catalyst slurry was applied in the order of the slurry obtained in step 6 and the slurry obtained in step 7. The coating amounts were 110 g / L and 60 g / L, respectively.

(Example 7)
1. Powder preparation (step 1): A solution in which dinitrodiamine platinum nitrate aqueous solution (Pt: 8.83 wt%) was dispersed in ion-exchanged water was added to a solution in which Ce-Zr was dispersed in ion-exchanged water, followed by stirring for 1 hour. . This was evaporated to dryness, pulverized and sized, and calcined at 400 ° C. for 1 h to obtain Pt-supported Ce-Zr. Ion-exchanged water (2400 g) was added to 600 g of the powder obtained by repeating the above operation, put into a magnetic pot, and shaken and ground with alumina balls.

(Step 2) A solution in which a rhodium nitrate solution (Rh: 13.81 wt%) was dispersed in ion-exchanged water was added to a solution in which Zr-La-Ce was dispersed in ion-exchanged water, and the mixture was stirred for 1 hour. This was evaporated to dryness, pulverized and sized, and fired at 400 ° C. for 1 h to obtain Rh- supported Zr—La—Ce. Ion-exchanged water (2400 g) was added to 600 g of the powder obtained by repeating the above operation, put into a magnetic pot, and shaken and ground with alumina balls.

(Step 3): 77 g of boehmite is added to 493.3 g of ion-exchanged water and stirred for 1 hour. A solution in which 18.9 g of cerium nitrate was dissolved in 100 ml of ion-exchanged water and a solution in which 7.9 g of zirconium nitrate was dissolved in 100 ml of ion-exchanged water were sequentially added to this and stirred for 30 minutes. After adding 500 g of the slurry obtained in step 1 and stirring for 1 h, heating and drying were performed, the powder was taken out, dried at 150 ° C. for 1 h, pulverized to 500 μm or less, and then fired at 550 ° C. for 3 h did.

(Step 4): 304.3 g of boehmite is added to 2738.6 g of ion-exchanged water, pH is adjusted to 4.5 by adding 9.8% nitric acid, and the mixture is stirred for 1 hour. 1358 g of the slurry obtained in step 2 was added to this, stirred for 1 h, heated and dried, then the powder was taken out, dried at 150 ° C. for 1 h, ground to 500 μm or less, and calcined at 550 ° C. for 3 h did.

2. Coating (Step 5): 118.7 g of alumina, 14 g of 10% nitric acid, and 360.3 ml of ion-exchanged water were put in a magnetic pot, and shaken and pulverized with alumina balls to obtain a first layer slurry.

(Step 6): 107.1 g of the powder obtained in Step 3, Zr-Ce 29.1 g, 20 g of 10% nitric acid, and 273.5 g of ion-exchanged water are put into a magnetic pot, shaken and pulverized with alumina balls, and a second layer slurry Got.

(Step 7): 73.5 g of the powder obtained in Step 4, Zr-La19 g, 31.5 g of 10% nitric acid, and 694.2 g of ion-exchanged water are put into a magnetic pot, shaken and pulverized with alumina balls, and the third layer slurry is formed. Obtained.

(Step 8): The catalyst slurry of Step 5 is put into a cordierite-made honeycomb carrier (600 cells / 4 mil), excess slurry is removed by air flow, dried at 120 ° C., 400 ° C., air flow Medium fired. The coat amount was 50 g / L.

  Similarly, the catalyst slurry was applied in the order of the slurry obtained in step 6 and the slurry obtained in step 7. The coating amounts were 110 g / L and 60 g / L, respectively.

(Comparative Example 1)
1. Powder preparation (Step 1) A solution in which dinitrodiamine platinum nitrate aqueous solution (Pt: 8.83 wt%) is dispersed in ion-exchanged water is added to a solution in which Ce-Zr-La-Al is dispersed in ion-exchanged water. Stir for hours. This was evaporated to dryness, pulverized and sized, and fired at 400 ° C. for 1 h to obtain Pt-supported Ce—Zr—La—Al.

(Step 2): A solution in which an aqueous rhodium nitrate solution (Pt: 13.81 wt%) was dispersed in ion-exchanged water was added to a solution in which Zr-Al was dispersed in ion-exchanged water, and the mixture was stirred for 1 hour. This was evaporated to dryness, pulverized and sized, and fired at 400 ° C. for 1 h to obtain Rh-supported Zr—Al.

2. Coating (Step 3): Pt-supported Ce-Zr-La-Al powder obtained in Step 1 67.5 g, Ce-Zr-La-Al powder 77.9 g, Ce-Zr powder 23.2 g, 10% nitric acid 40 g, ion-exchanged water 258.7 g was put into a magnetic pot and shaken and ground together with alumina balls to obtain a second layer slurry.

(Step 4): 14.6 g of Rh-supported Zr-Al powder obtained in Step 2, 43.9 g of Zr-Al powder, 74.4 g of Ce-Zr powder, 30 g of 10% nitric acid, and 319.1 g of ion-exchanged water were put into a magnetic pot. The mixture was pulverized with alumina balls to obtain a third layer slurry.

(Step 5): The catalyst slurry of Step 3 is put into a cordierite-made honeycomb carrier (600 cells / 4 mil), excess slurry is removed by air flow, dried at 120 ° C., 400 ° C., air flow Medium fired. The coat amount was 84.5 g / L.

  Similarly, the catalyst slurry obtained in Step 4 was applied. The coat amount was 60.5 g / L.

[Evaluation]
The honeycomb carrier on which the exhaust gas purifying catalysts of Examples 1 to 7 and Comparative Example 1 described above are formed is mounted on the exhaust system of a gasoline engine having a displacement of 3500 cm ³ , the catalyst inlet temperature is 900 ° C., and the operation is performed for 30 hours. A durability test was conducted. After this endurance test, these honeycomb carriers were installed in the exhaust system of a gasoline engine with a displacement of 2400 cm ³ and operated at an exhaust gas temperature of 400 ° C under the conditions of air-fuel ratio A / F = 14.6 and amplitude 1. Confirmed.

This purification rate is obtained by examining the conversion rate. Further, after about 0.1 g of the catalyst was scraped off from the honeycomb carrier, 0.1 g of the catalyst was weighed out and the amount of released O ₂ was measured by an automatic temperature programmed desorption spectrometer. The results are shown in Table 2, and are shown graphically in FIG.

In Table 2, the conversion rate was determined by the average value of HC, CO, and N O x. The oxygen release amount was calculated as the amount of oxygen required per 1 g of noble metal. Furthermore, the amount of CeO ₂ was calculated as CeO ₂ (% by weight) of Ce present in the coat layer.

  From Table 2 and FIG. 4, Examples 1-7 according to the present invention had an oxygen release amount in the range of 400-1200 mmol / g, and showed a conversion rate superior to that of Comparative Example 1. Therefore, it can be seen that the exhaust gas purifying catalyst of the present invention has excellent exhaust gas purifying performance.

  Next, exhaust gas purifying catalysts of Examples 8 to 10 containing various elements in the OSC material and Example 11 not containing these elements in the OSC material were prepared for comparison. These catalysts had a two-layer structure applied to a honeycomb ceramic substrate. Of the two layers, the layer close to the honeycomb substrate was the inner layer, and the layer close to the surface was the surface layer.

(Preparation of catalyst powder for surface layer)
Regarding the preparation of the catalyst powder for the surface layer of Example 8, after a predetermined amount of Rh was supported on a commercially available zirconium oxide-lanthanum oxide-cerium oxide composite compound and calcined at 400 [° C.] for 1 [h] in an air stream, The obtained powder was pulverized to obtain a composite compound carrying Rh. On the other hand, a slurry in which boehmite, nitric acid and pure water were mixed was prepared, and mixed and stirred with the slurry containing the composite compound supporting Rh. Thereafter, the mixed slurry was dried and then fired at 550 [° C.] for 3 hours in an air stream. As a result, composite particles of zirconium oxide, lanthanum oxide and cerium oxide existed around the Rh particles, and a catalyst covered with alumina was obtained.

  For the preparation of the catalyst powder for the surface layer of Examples 9 and 10, composite particles of zirconium oxide, lanthanum oxide, and cerium oxide were present around the Rh particles in the same procedure as in Example 8, and were further covered with alumina. A catalyst was obtained.

  For the preparation of the catalyst powder for the surface layer of Example 11, a composite particle of zirconium oxide, lanthanum oxide and cerium oxide is present around the Rh particles in the same procedure as in Example 8, and a catalyst covered with alumina is further added. Obtained.

(Preparation of catalyst powder for inner layer)
The catalyst powder for the inner layer of Example 8 is obtained after Pd is supported on a commercially available zirconium oxide-lanthanum oxide-cerium oxide composite compound and calcined at 400 [° C.] for 1 [h] in air stream. The obtained powder was pulverized to obtain a compound carrying Pd. On the other hand, this slurry in which boehmite, cerium nitrate, zirconium nitrate, nitric acid, and pure water were mixed with the slurry containing the compound supporting Pd was mixed and stirred. Thereafter, the mixed slurry was dried and then fired at 550 [° C.] for 3 hours in an air stream. As a result, composite particles of zirconium oxide, lanthanum oxide, and cerium oxide were present around the Pd particles, and a catalyst covered with alumina, cerium oxide, and zirconium oxide was obtained.

  For the preparation of the inner layer catalyst powders of Examples 9 and 10, composite particles of zirconium oxide, lanthanum oxide, and cerium oxide exist around the Pd particles in the same procedure as in Example 8, and alumina, cerium oxide, A catalyst covered with zirconium oxide was obtained.

  For the preparation of the inner layer catalyst powder of Example 11, composite particles of zirconium oxide, lanthanum oxide, and cerium oxide exist around the Pd particles in the same procedure as in Example 1, and further, alumina, cerium oxide, zirconium oxide The catalyst covered with was obtained.

(Preparation of washcoat layer)
For Example 8, 363.6 [g] of the inner layer catalyst powder of Example 8 obtained by the above-described operation for preparing the inner layer catalyst powder, 50.9 [g] of boehmite, 42.0 [g] of 10% nitric acid, ion-exchanged water Each of 575.3 [g] was put in a magnetic pot and shaken and ground with alumina balls to obtain an inner layer catalyst slurry. Also, 363.6 [g] of the surface layer catalyst powder of Example 8 obtained by the above-described operation of preparing the surface layer catalyst powder, 276 [g] of ceria-zirconia composite oxide which solidly dissolves Y as the third compound, boehmite 86.5 [g], 10% nitric acid 71.4 [g], and ion-exchanged water 978 [g] were charged in a magnetic pot, and shaken and ground with alumina balls to obtain a catalyst slurry for the surface layer. Next, the above catalyst slurry for the inner layer is put into a ceramic honeycomb support (900 cells / 2.5 mil, 0.92 [L]), excess slurry is removed by air flow, and drying is performed at 120 [° C.]. Firing was performed in an air stream at 400 [° C.]. The coating amount was 149 [g / L]. Next, the catalyst slurry for the surface layer was applied in the same manner. The coating amount was 76 [g / L]. As a result, the catalyst of Example 8 containing Pd of 5.2 [g / L] in the inner layer and Rh of 0.4 [g / L] in the surface layer was obtained.

  About Example 9, Pd was 5.2 [in the inner layer in the same procedure as in Example 8 except that ceria-zirconia composite oxide that solidly dissolves Nd was used as the third compound in the slurry for the surface layer. g / L], and the catalyst of Example 9 containing Rh of 0.4 [g / L] on the surface layer was obtained.

  For Example 10, the same procedure as in Example 8 was used except that a ceria-zirconia composite oxide capable of dissolving Pr as a third compound was used as the third compound in the surface layer slurry. g / L], and the catalyst of Example 10 containing Rh of 0.4 [g / L] in the surface layer was obtained.

  For Example 11, 363.6 [g] of the inner layer catalyst powder of Example 11 obtained by the above-described operation for preparing the inner layer catalyst powder, 50.9 [g] of boehmite, 42.0 [g] of 10% nitric acid, and ion exchange Each of 575.3 [g] of water was put into a pot and shaken and ground with alumina balls to obtain an inner layer catalyst slurry. Further, the surface layer catalyst powder of Example 11 obtained by the above-described operation for preparing the surface layer catalyst powder was 363.6 [g], the third compound was ceria-zirconia composite oxide 162 [g], and boehmite 69.2 [g]. Then, 57.1 [g] of 10% nitric acid and 782 [g] of ion-exchanged water were put in a magnetic pot, and shaken and pulverized with alumina balls to obtain a catalyst slurry for the surface layer. Next, the above catalyst slurry for the inner layer is put into a ceramic honeycomb support (900 cells / 2.5 mil, 0.92 [L]), excess slurry is removed by air flow, and drying is performed at 120 [° C.]. Firing was performed in an air stream at 400 [° C.]. The coating amount was 170 [g / L]. Next, the surface layer catalyst slurry was applied in the same manner. The coating amount was 66 [g / L]. As a result, the catalyst of Example 11 containing Pd of 5.2 [g / L] in the inner layer and Rh0.4 [g / L] in the surface layer was obtained.

About these Examples 8-11 and the above-mentioned Example 4 and Example 7 shown for reference, they were measured by the O ₂ pulse method for evaluating the amount of OSC and the oxygen adsorption rate measured by the temperature programmed desorption test. Table 3 shows the OSC amount, CeO ₂ amount and HC emission amount.

  In Examples 8 to 11, the coating amount is the coating amount per unit volume of the honeycomb base material of each layer, and is the dry coating amount at 150 [° C.] after the final firing. In each example, the amount of noble metal supported in each powder is not described, but the amount supported was appropriately adjusted so that the amount of noble metal shown in Table 3 was obtained in each layer coating amount.

The amount of OSC 1 in Table 3 shows the result of measurement by a measurement method based on the temperature programmed desorption test (temperature programmed desorption method). The OSC amount 2 indicates a result measured by the O ₂ pulse method. This O ₂ pulse method is measured through the following processes (1) to (7). (1) The catalyst (with honeycomb) is pulverized and powdered, and 0.2 [g] is weighed. (2) Set this in a flow reactor, raise the temperature to 600 [° C.] in a He stream, and hold for 1 h. (3) Lower the catalyst temperature to 500 ° C. (4) A certain amount of oxygen is introduced into the catalyst. (5) Check the amount of unadsorbed oxygen with TCD. (6) The introduction of a certain amount of oxygen into the catalyst in (4) and the confirmation of the amount of unadsorbed oxygen in (5) are repeated until the amount of introduced oxygen is equal to the amount of unadsorbed oxygen. (7) The amount of adsorbed oxygen (OSC amount) is calculated by calculation (the amount of adsorbed oxygen is determined by subtracting the amount of unadsorbed oxygen from the amount of oxygen introduced in advance).

HC emissions were evaluated as follows. First, for the endurance treatment, one catalyst converter is used for each exhaust system of both banks of the V-type 6-cylinder 3.5 [L] engine V-type engine made by Nissan Motor, which uses unleaded gasoline as the catalyst of the example and the comparative example. And the position of the converter was adjusted so that the catalyst BED temperature was 920 [° C]. Under such an exhaust gas atmosphere, a catalyst BED temperature 920 [° C.] × 200 [Hr] durability treatment was performed. After performing the above-mentioned endurance treatment, a catalyst is placed on the engine out of a vehicle manufactured by Nissan (U31, 2.5 [L]), running in vehicle evaluation mode (LA4 mode, A, B, C-Bag) and running The outlet gas composition was measured with a continuous analyzer, and the amount of accumulated exhaust gas in the mode was calculated from the obtained outlet gas concentration.

From Table 3, Y, Examples 8-10 containing Nd or Pr in the third compound, as compared with Example 11 that does not contain these elements, has been OSC of 2 number measured by O ₂ pulse method, It can be seen that the oxygen adsorption rate is improved as compared with Example 11. And as for HC discharge | emission amount, Example 8-10 was less than Example 11, and it had the outstanding exhaust gas purification performance. Among Examples 8 to 10, Example 8 containing Y has a large amount of OSC 2, a small amount of HC emissions, an excellent oxygen adsorption rate, and an excellent exhaust gas purification performance. In Examples 8-11, the amount of CeO ₂ as OSC material, a CeO ₂ amount in Example 4 As shown in Table 3 and 37 [wt%], is the amount of CeO ₂ Example 7 The value is within the range of 14 [wt%]. Therefore, the OSC amount (OSC amount 1) measured by the temperature programmed desorption test in Examples 8 to 11 is not shown in the table, but this It is confirmed that the value is between the OSC amount of 1053 [mmol / g] of Example 4 and the OSC amount of Example 7 of 472 [mmol / g]. That is, it conforms to the OSC amount specified in the present invention.

  As mentioned above, although the embodiment to which the invention made by the present inventors was applied has been described, the present invention is not limited by the description and the drawings that form part of the disclosure of the present invention according to this embodiment. That is, it should be added that other embodiments, examples, operation techniques, and the like made by those skilled in the art based on the above embodiments are all included in the scope of the present invention.

1 is a schematic diagram of an exhaust gas purifying catalyst according to an embodiment of the present invention. It is a graph which shows the relationship between time and temperature for demonstrating a thermal desorption test. It is a graph which shows the relationship between the amount of oxygen in a catalyst, and an adsorption rate. It is a graph which shows the relationship between the oxygen release amount and the conversion rate in an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification catalyst 2 Noble metal particle 3 1st oxide 4 2nd oxide 5 3rd compound

Claims (8)

Precious metal particles,
A first compound comprising an oxide in contact with the noble metal particles and containing at least one of cerium and zirconium ;
A second compound that encapsulates the noble metal particles and the first compound, suppresses movement of the noble metal particles, and suppresses aggregation of the first compound due to contact between the first compounds;
With
The first compound carrying the noble metal particles and the elemental or aggregates of the first compounds supporting the noble metal particles, comprising the second compartment separated by compounds, the second The compound suppresses that the simple substance or aggregate of the first compound moves beyond the compartment, agglomerates in contact with each other,
An exhaust gas purifying catalyst characterized in that the amount of O ₂ released in a temperature programmed desorption test is 400 to 1200 mmol / g per gram of precious metal used in the range of 150 to 500 ° C. Precious metal particles,
A first compound comprising an oxide in contact with the noble metal particles and containing at least one of cerium and zirconium ;
A second compound that encapsulates the noble metal particles and the first compound, suppresses movement of the noble metal particles, and suppresses aggregation of the first compound due to contact between the first compounds;
A third compound having an oxygen storage / release capability;
With
The first compound carrying the noble metal particles and the elemental or aggregates of the first compounds supporting the noble metal particles, comprising the second compartment separated by compounds, the second The compound suppresses that the simple substance or aggregate of the first compound moves beyond the compartment, agglomerates in contact with each other ,
The third compound is disposed in the vicinity of the second compound containing the first compound carrying the noble metal particles,
An exhaust gas purifying catalyst characterized in that the amount of O ₂ released in a temperature programmed desorption test is 400 to 1200 mmol / g per gram of precious metal used in the range of 150 to 500 ° C. In the temperature-programmed desorption test, the catalyst was heated from room temperature to 600 ° C. under atmospheric flow, held at 600 ° C. for 30 minutes, then cooled to 100 ° C., and 100 ° C. to 500 ° C. under H ₂ flow. The amount of oxygen in the catalyst is determined by reducing the oxygen released from the catalyst with hydrogen and quantifying the generated water with a mass spectrometer. The exhaust gas purifying catalyst according to claim 1 or 2.   At least one of the first compound and the third compound is an oxide having oxygen absorbing / releasing ability, and the oxide having oxygen absorbing / releasing ability is an oxide containing ceria. The exhaust gas-purifying catalyst according to any one of claims 1 to 3.   At least one of the first compound and the third compound is an oxide having oxygen absorbing / releasing ability, and the oxide having oxygen absorbing / releasing ability further includes Y, Nd, Pr, Al, Ga and The exhaust gas-purifying catalyst according to any one of claims 1 to 4, comprising at least one element selected from In. The catalyst coating layer formed on the inner wall surface of the refractory inorganic substrate comprises an exhaust gas purifying catalyst according to any one of claims 1 to 5, in the catalyst coating layer, the oxygen release capacity A catalyst for exhaust gas purification, characterized in that the compound having 10 to 40 wt% of CeO ₂ is contained.   The exhaust gas purifying catalyst according to any one of claims 1 to 6, wherein the noble metal particles include at least one of Pt, Pd, and Rh. Precious metal particles,
A first compound comprising an oxide in contact with the noble metal particles and containing at least one of cerium and zirconium ;
A second compound that encapsulates the noble metal particles and the first compound, suppresses movement of the noble metal particles, and suppresses aggregation of the first compound due to contact between the first compounds;
A particle unit structure comprising a third compound having an oxygen storage / release capacity; and
The first compound carrying the noble metal particles and the elemental or aggregates of the first compounds supporting the noble metal particles, comprising the second compartment separated by compounds, the second The compound suppresses that the simple substance or aggregate of the first compound moves beyond the compartment, agglomerates in contact with each other ,
The exhaust gas purifying catalyst, wherein the third compound is disposed in the vicinity of the second compound containing the first compound carrying the noble metal particles.

Images