JP2007229654A - Catalyst for cleaning exhaust gas and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accomplish enhancement of an activity of a precious metal particle without increasing a manufacturing cost and an environment load. <P>SOLUTION: The catalyst for cleaning the exhaust gas has the precious metal particle 11, a compound particle 12 carrying this precious metal particle 11, a promotor layer 13 for covering at least a part of a surface of the precious metal particle 11 on the compound particle 12, and an oxide particle 14 formed on a periphery of the compound particle 12 and separating the compound particles 12 from each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

An exhaust gas purifying catalyst generally has noble metal particles supported on the surface of particles made of a metal oxide, and contains harmful components such as unburned hydrocarbon (HC) and carbon monoxide ( CO) is oxidized with the noble metal particles and converted into water and CO ₂ gas which are harmless components.

  In recent years, exhaust gas regulations for automobiles are becoming more and more strict, and the above-mentioned unburned hydrocarbons (HC) and carbon monoxide (CO) can be purified with higher efficiency for exhaust gas purification catalysts. Is required. In order to meet such demands, various improvements have been made. For example, by utilizing the fact that the purification performance of the catalyst generally increases as the surface area of the noble metal particles increases, the surface area of the noble metal particles is increased by reducing the particle size of the noble metal particles in the exhaust gas purification catalyst. Thus, the surface energy is increased to improve the performance of the exhaust gas purifying catalyst.

Here, the noble metal particles of the exhaust gas purifying catalyst are in an ultrafine particle state of several nm or less in the initial stage. However, while the exhaust gas purifying catalyst is actually used and exposed to a high-temperature oxidizing atmosphere, the surface of the noble metal particles is oxidized, and the adjacent noble metal particles aggregate and coalesce with each other, resulting in a coarseness of several tens of nm. There is a problem that the surface area of the noble metal particles is reduced and the purification rate of harmful substances is lowered with time. In addition, in a catalyst containing a co-catalyst such as ceria (CeO ₂ ), when the ceria itself aggregates, the interval between the noble metal particles is narrowed.

  The reverse micelle method has been developed as a production method capable of producing noble metal particles having a large surface area with the aim of preventing a decrease in surface area due to the coarsening of the noble metal particles and further increasing the activity. This reverse micelle method is a production method using an emulsion solution in which reverse micelles of an aqueous solution containing a noble metal particle raw material are formed in the course of the production process. In an example of the reverse micelle method, first, an aqueous solution containing a surfactant and a catalytically active component (for example, a noble metal element) is mixed in an organic solvent. Thereafter, an emulsion solution in which reverse micelles containing an aqueous solution containing a noble metal are formed in an organic solvent is prepared, and after precious metal is precipitated, it is reduced or insolubilized to precipitate the precious metal atomized in the reverse micelle. .

  With respect to this reverse micelle method, there is a method of producing a catalyst by incorporating an element having an oxygen storage effect into reverse micelles in the emulsion solution preparation step (Patent Document 1). In this reverse micelle method, after supporting the catalytically active component on the base material in the reverse micelle contained in the emulsion solution, the reverse micelle is disintegrated, and the resulting precipitate is filtered, dried, pulverized, and calcined. Each step is used as a catalyst. The catalyst produced using this production method not only supports an element having an oxygen storage effect on the base material, but also contains a catalytically active component on the outermost surface of the base material and the surface of the pores formed in the base material. Since it is supported, the activity of the catalyst can be increased.

JP 2000-42411 A

  However, the reverse micelle method described above has a problem in terms of mass productivity because the manufacturing process becomes complicated and the manufacturing cost increases. Therefore, there is a demand for an exhaust gas purifying catalyst that can suppress agglomeration of noble metals with a structure different from the structure manufactured by the reverse micelle method and that can be manufactured in a manufacturing process that does not become complicated.

  The exhaust gas purifying catalyst according to the present invention comprises noble metal particles, compound particles supporting the noble metal particles, a promoter layer covering at least a part of the surface of the noble metal particles on the compound particles, The gist is to have oxide particles formed around and separating the compound particles from each other.

  The method for producing an exhaust gas purifying catalyst according to the present invention includes a step of supporting noble metal particles on compound particles, and selective precipitation on at least a part of the surface of the noble metal particles of the compound particles supporting the noble metal particles. A step of depositing a base metal for the promoter layer by a method, a step of oxidizing the base metal by heat treatment in an oxidizing atmosphere to form a promoter layer made of a metal oxide, and the promoter layer being formed And a step of forming oxide particles around the compound particles on which the noble metal particles are supported.

  According to the exhaust gas purifying catalyst of the present invention, since the promoter layer is formed in contact with the noble metal particles, the promoter layer improves the catalytic activity and suppresses the movement and aggregation of the noble metal particles. The activity improving effect of the noble metal particles can be maintained without increasing the cost and environmental burden.

  According to the method for producing an exhaust gas purifying catalyst according to the present invention, the exhaust gas purifying catalyst according to the present invention can be easily produced without using the reverse micelle method.

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

  FIG. 1 is a schematic view of an example of an exhaust gas purifying catalyst according to the present invention. In the figure, an exhaust gas purifying catalyst is a noble metal particle 11 that is an active metal particle that contacts an exhaust gas to purify harmful components, a compound particle 12 that supports the noble metal particle 11, and the compound particle 12. Thus, the promoter layer 13 formed by covering at least a part of the noble metal particles 11, and the oxide formed around the compound particles 12 on which the promoter layer 13 is formed and on which the noble metal particles 11 are supported. Particles 14.

  In the exhaust gas purifying catalyst of the present embodiment shown in the figure, since the compound particles 12 carry the noble metal particles 11, the compound particles 12 act as an anchor material for chemical bonding. Suppress movement. In addition, by covering the periphery of the compound particles 12 carrying the noble metal particles 11 with oxide particles 14 such as alumina, the oxide particles 14 physically move the noble metal particles 11 away from the compound particles 12. Suppress it. Further, by separating the compound particles 12 from each other, the oxide particles 14 prevent the compound particles 12 from moving, contacting, and aggregating, and as a result, the noble metal particles supported on the compound particles. Suppresses aggregation.

  Further, the promoter layer 13 is formed so as to cover at least a part of the noble metal particles 11 supported on the compound particles 12, so that the promoter layer 13 improves the catalytic activity of the noble metal particles 11, or Since the cocatalyst layer 13 itself has a function as an exhaust gas purification catalyst, the exhaust gas purification performance can be further improved. In addition, since the promoter layer 13 covers at least a part of the noble metal particles 11 supported on the compound particles 12 on the compound particles 12, the movement of the noble metal particles 11 is physically suppressed. Therefore, the movement and aggregation of the noble metal particles 11 are further suppressed.

  As shown in FIG. 1, the promoter layer 13 can be coated on the compound particles 12 so as to cover all of the individual noble metal particles 11, or to cover a part of the individual noble metal particles 11. It can also be coated. If the promoter layer 13 in the exhaust gas purifying catalyst according to the present invention is laminated on the compound particle 12 so as to be in contact with one noble metal particle 11, the function of the promoter layer of the present invention can be exhibited.

  As the material of the promoter layer 13, the noble metal particles 11 can be activated by contacting the noble metal particles 11, or a metal oxide having the same catalytic activity as that of the noble metal particles 11 can be used. The amount of the metal oxide is preferably in the range of 0.1 to 50 in terms of the molar ratio of the metal oxide metal to the metal of the noble metal particles. If the amount of the metal oxide is less than 0.1 in terms of the molar ratio of the metal oxide to the metal of the noble metal particles 11, the effect of the promoter is poor. On the other hand, when the molar ratio exceeds 50, the amount of the metal oxide in contact with the noble metal particles 11 is relatively reduced, and the effect as a promoter is saturated. Therefore, the molar ratio is preferably in the range of 0.1-50.

  A more preferable range of the molar ratio is 10-30. When the amount of the metal oxide is 10 to 30 in terms of the molar ratio of the metal in the metal oxide to the metal of the noble metal particles 11, the effect as a promoter can be obtained reliably and sufficiently, and the low temperature activity Thus, a catalyst having an improved exhaust gas purification performance can be obtained.

  The noble metal particles 11 are preferably at least one metal selected from platinum, palladium and rhodium. Platinum, palladium and rhodium are all metals having catalytic activity for exhaust gas. For the noble metal particles 11, platinum, palladium, or rhodium can be used alone, or two or more of these metals can be used in combination.

  The promoter layer 13 is preferably made of an oxide of at least one metal selected from Co, Ni, Fe, Cu, Sn, Mn, Ce, and Zr. All metal oxides such as Co, Ni, Fe, Cu, Sn, Mn, Ce, and Zr exhibit a function as a promoter when in contact with the noble metal particles 11. Further, any of these metals listed above is a metal that can be selectively deposited around the noble metal particles 11, and this works advantageously in the production of the exhaust gas purifying catalyst according to the present invention. In the process of producing the exhaust gas purifying catalyst, one or more of these metals are selectively deposited around the noble metal particles 11 supported on the compound particles 12, and then the deposited metal is deposited. By oxidization, the promoter layer 13 made of the above-mentioned metal oxide can be formed on the noble metal particles 11 by coating. Since such a production method can be applied, the promoter component is preferably an oxide of the metal described above.

  The compound particles 12 supporting the noble metal particles 11 are preferably oxide particles containing cerium, composite oxide particles of cerium and zirconium, oxide particles containing zirconium, or oxide particles containing aluminum. The kind of the compound particle 12 can be appropriately selected according to the kind of the noble metal particle to be supported. For example, when the noble metal particle 11 is platinum, it is advantageous to select a cerium oxide or a composite oxide of ceria and zirconia for the compound particle 12. This is because these oxides have an anchor effect on platinum. When the noble metal particle 11 is palladium, it is advantageous to select an oxide containing aluminum for the compound particle 12. This is because these oxides have an anchoring effect on palladium. Further, when the noble metal particle 11 is rhodium, it is advantageous to select an oxide containing zirconium for the compound particle 12. This is because zirconium has no solid solution with rhodium and can stably support rhodium.

  The oxide particles 14 formed around the compound particles 12 are preferably alumina or zirconia because they have the heat resistance required when used as an exhaust gas purifying catalyst. These oxide particles are preferably primary particles having a size of several tens of nanometers to several hundreds of nanometers. A more preferable size is 10 nm to 200 nm in length and 5 nm to 20 nm in width. The oxide particles 14 are not limited to those having a fibrous or needle shape as shown in FIG. For example, a spherical shape may be sufficient and a flaky shape may be sufficient.

  Next, the manufacturing method of the exhaust gas purifying catalyst of the present invention will be described.

  First, the noble metal particles 11 are supported on the compound particles 12. A method of supporting the noble metal particles 11 on the compound particles 12 can be a conventionally known method, and is not particularly limited. However, the particle size of the noble metal particles 11 is adjusted to a particle size suitable for the noble metal particles for the catalyst. In order to control, it is preferable to carry the noble metal particles 11 on the compound particles 12 by a reduction precipitation method.

  Next, base metal for the promoter layer 13 is deposited on at least a part of the surface of the noble metal particle 11 of the compound particle 12 carrying the noble metal particle 11 by a selective deposition method. In order to form the promoter layer 13 in contact with the noble metal particles 11 on the compound particles 12, the base metal may be selectively deposited using the noble metal particles 11 as nuclei. At this time, the molar ratio of the base metal and the metal of the noble metal particles can be controlled within a suitable range by controlling the amount of the base metal deposited.

  Thereafter, the base metal formed around the noble metal particles 11 is oxidized by a heat treatment in an oxidizing atmosphere such as firing to form the promoter layer 13 made of a metal oxide. As an example of the heating conditions, heating can be performed in the atmosphere at about 400 ° C. for about 1 hour.

  Thereafter, the periphery of the compound particle 12 on which the promoter layer 13 is formed and the noble metal particles 11 are supported is coated with the oxide particles 14 to obtain catalyst powder. The exhaust gas purifying catalyst according to the present invention can be manufactured by slurrying using this powder, applying it to a honeycomb carrier, and drying and firing.

[Example 1]
Example 1 is an example in which the noble metal particles are Pt, the compound particles are ceria (particle size 10 nm), and the promoter layer is an oxide of Co (the molar ratio of Co in the promoter layer to Pt is 0.1).

  Add 99.126g of ceria particles (particle size 10nm) to 200g of dinitrodiamine Pt solution dissolved so that Pt is 0.842g, add sodium borohydride 3 times mole of Pt with stirring, reduce, filter Then, ceria particles with Pt were prepared by washing. The fine particles were added to a cobalt nitrate solution (dissolved as 0.025 g as cobalt), sodium borohydride was added in 3 times mole of cobalt while stirring, and the mixture was reduced to selectively precipitate cobalt on Pt. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Co (0.025%)-carrying ceria particles with 0.82% Pt (fine particles a).

  Next, acicular boehmite alumina was used as alumina and 100 g equivalent was dispersed in water, and the pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles a were added to this, sufficiently stirred, dried, and then fired at 400 ° C. to prepare fine particles A in which the fine particles a were coated with alumina.

  Next, 173.4 g of fine particles A and 1.6 g of boehmite alumina were added to a ball mill, and then 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to disperse the fine particles A and pulverize the substrate. To obtain a slurry having an average particle size of 3 μm (slurry a).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. did. (Slurry R).

  A honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 cells and 6 mils is coated with 141g / L of slurry a and dried, and then coated with 59g / L of slurry R, dried and fired at 400 ° C. The sample of Example 1 was obtained. The obtained catalyst of Example 1 was a catalyst carrying Pt at 0.588 g / L and Rh at 0.236 g / L.

[Example 2]
Example 2 is an example in which the noble metal particles are Pt, the compound particles are ceria (particle size: 10 nm), the promoter layer is an oxide of Co, and the molar ratio of Co in the promoter layer to Pt is 1.

  Add 200.835 g of ceria particles (10 nm) to 200 g of a solution of dinitrodiamine Pt solution so that Pt is 0.842 g, add sodium borohydride 3 times mol of Pt while stirring, reduce, filter and wash. Ct particles with Pt were prepared. The fine particles were added to a cobalt nitrate solution (dissolved as 0.254 g as cobalt), sodium borohydride was added in 3 times mole of cobalt while stirring, and the mixture was reduced to selectively precipitate cobalt on Pt. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Pt0.842% supported ceria particles with Co (0.254%) (fine particles b).

  Next, acicular boehmite alumina was used as alumina and 100 g equivalent was dispersed in water, and the pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles b were added thereto and stirred sufficiently, dried, and then fired at 400 ° C. to prepare fine particles B in which the fine particles b were coated with alumina.

  Next, after adding 173.4 g of fine particles B and 1.6 g of boehmite alumina to a ball mill, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution are further added to disperse the fine particles B and pulverize the substrate. And a slurry having an average particle diameter of 3 μm was obtained (slurry b).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. (Slurry R).

  A honeycomb carrier with a diameter of 36φ, 400 cells and 6 mil (capacity 0.04L) was coated with 141g / L of slurry b and dried, then 59g / L of slurry R was coated, dried and fired at 400 ° C. The sample of Example 2 was obtained. The obtained catalyst of Example 2 was a catalyst carrying Pt at 0.588 g / L and Rh at 0.236 g / L, respectively.

[Example 3]
Example 3 is an example in which the noble metal particles are Pt, the compound particles are ceria (particle size: 10 nm), the promoter layer is an oxide of Co, and the molar ratio of Co in the promoter layer to Pt is 5. .

  To 200 g of a solution obtained by dissolving a dinitrodiamine Pt solution so that Pt is 0.863 g, add 97.541 g of ceria particles (10 nm), add sodium borohydride 3 times mol of Pt while stirring, reduce, filter and wash Ct particles with Pt were prepared. The fine particles were added to a cobalt nitrate solution (dissolved as 1.272 g of cobalt), sodium borohydride was added in 3 times mole of cobalt while stirring, and the mixture was reduced to selectively precipitate cobalt on Pt. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Pt 0.842% supported ceria particles with Co (1.272%). (Fine particles c).

  Next, acicular boehmite alumina was used as alumina and 100 g equivalent was dispersed in water, and the pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles c were added to this, sufficiently stirred, dried, and then fired at 400 ° C. to prepare fine particles C in which the fine particles c were coated with alumina.

  Next, 173.4 g of fine particles C and 1.6 g of boehmite alumina were added to a ball mill, and then 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to disperse the fine particles C and pulverize the substrate. And a slurry having an average particle diameter of 3 μm was obtained (slurry c).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. (Slurry R).

  A honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 cells and 6 mils was coated with 141g / L of slurry c, dried, then coated with 59g / L of slurry R, dried and fired at 400 ° C. The sample of Example 3 was obtained. The obtained catalyst of Example 3 was a catalyst carrying Pt at 0.588 g / L and Rh at 0.236 g / L.

[Example 4]
Example 4 is an example in which the noble metal particles are Pt, the compound particles are ceria (particle size: 10 nm), the promoter layer is a Co oxide, and the molar ratio of Co to Pt in this promoter layer is 10. is there.

  Add 95.924g of ceria particles (10nm) to 200g of dinitrodiamine Pt solution so that Pt is 0.842g, add sodium borohydride 3 times mole of Pt while stirring, reduce, filter and wash. Ct particles with Pt were prepared. The fine particles were added to a cobalt nitrate solution (dissolved as 2.543 g as cobalt), and sodium borohydride was added in 3 times mole of cobalt while stirring to reduce the cobalt, and cobalt was selectively deposited on Pt. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Pt 0.842% supported ceria particles with Co (2.543%). (Fine particles d).

  Next, acicular boehmite alumina was used as alumina, 100 g equivalent was dispersed in water, and pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles d were added to this, sufficiently stirred, dried, and then fired at 400 ° C. to prepare fine particles D in which the fine particles d were coated with alumina.

  Next, after adding 173.4 g of fine particles D and 1.6 g of boehmite alumina to a ball mill, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution are further added to disperse the fine particles D and pulverize the substrate. And a slurry having an average particle diameter of 3 μm was obtained (slurry d).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. did. (Slurry R).

  A honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 cells and 6 mils was coated with 141g / L of slurry d, dried, and then coated with 59g / L of slurry R, dried and fired at 400 ° C. The sample of Example 4 was obtained. The obtained catalyst of Example 4 was a catalyst carrying Pt at 0.588 g / L and Rh at 0.236 g / L.

[Example 5]
Example 5 is an example in which the noble metal particles are Pt, the compound particles are ceria (particle size 10 nm), the promoter layer is an oxide of Co, and the molar ratio of Co in the promoter layer to Pt is 30.

  Add 200.458g of ceria particles (10nm) to 200g of a solution of dinitrodiamine Pt solution so that Pt is 0.842g, add sodium borohydride 3 times mole of Pt while stirring, reduce, filter, wash Ct particles with Pt were prepared. The fine particles were added to a cobalt nitrate solution (dissolved as 7.63 g as cobalt), sodium borohydride was added in 3 times mole of cobalt while stirring, and the mixture was reduced to selectively precipitate cobalt on Pt. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Pt0.842% supported ceria particles with Co (7.63%) (fine particles e).

  Next, acicular boehmite alumina was used as alumina, 100 g equivalent was dispersed in water, and pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles e were added thereto, sufficiently stirred, dried, and then fired at 400 ° C. to prepare fine particles E in which the fine particles e were coated with alumina.

  Next, after adding 173.4 g of fine particles E and 1.6 g of boehmite alumina to a ball mill, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution are further added to disperse the fine particles E and grind the substrate. And a slurry having an average particle diameter of 3 μm was obtained (slurry e).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. (Slurry R).

  A honeycomb carrier with a diameter of 36φ, 400 cells and 6 mil (capacity 0.04L) was coated with 141g / L of slurry e, then dried, and then coated with 59g / L of slurry R, dried and fired at 400 ° C. The sample of Example 5 was obtained. The obtained catalyst of Example 5 was a catalyst carrying Pt at 0.588 g / L and Rh at 0.236 g / L, respectively.

[Example 6]
Example 6 is an example in which the noble metal particles are Pt, the compound particles are ceria (particle size 10 nm), the promoter layer is an oxide of Co, and the molar ratio of Co in the promoter layer to Pt is 50.

  Add 200 g of ceria particles (10 nm) 82.988 g to a solution of dinitrodiamine Pt solution so that Pt is 0.842 g, add sodium borohydride 3 times mol of Pt with stirring, reduce, filter and wash Ct particles with Pt were prepared. The fine particles were added to a cobalt nitrate solution (dissolved as 12.72 g as cobalt), and sodium borohydride was added in 3 times mole of cobalt while stirring to reduce the cobalt, and cobalt was selectively deposited on Pt. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Pt 0.842% supported ceria particles with Co (12.72%) (fine particles f).

  Next, acicular boehmite alumina was used as alumina and 100 g equivalent was dispersed in water, and the pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles f were added to this, sufficiently stirred, dried, and then fired at 400 ° C. to prepare fine particles F in which the fine particles f were coated with alumina.

  Next, after adding 173.4 g of fine particles F and 1.6 g of boehmite alumina to a ball mill, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution are further added to disperse the fine particles F and grind the substrate. A slurry having an average particle diameter of 3 μm was obtained (slurry f).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. (Slurry R).

  A honeycomb carrier with a diameter of 36φ, 400 cells and 6 mil (capacity 0.04L) was coated with 141g / L of slurry f, dried, and then coated with 59g / L of slurry R, dried and fired at 400 ° C. The sample of Example 6 was obtained. The obtained catalyst of Example 6 was a catalyst carrying Pt at 0.588 g / L and Rh at 0.236 g / L.

[Example 7]
Example 7 is an example in which the noble metal particles are Pt, the compound particles are cerium zirconate (particle size 30 nm), the promoter layer is an oxide of Co, and the molar ratio of Co to Pt in this promoter layer is 0.1. It is.

  99.126 g of cerium zirconate particles (particle size 30 nm) are added to 200 g of a solution obtained by dissolving a dinitrodiamine Pt solution so that Pt is 0.842 g, and sodium borohydride is added 3 times as much as Pt while stirring. Filtered and washed to prepare cerium zirconate particles with Pt. The fine particles were added to a cobalt nitrate solution (dissolved as 0.025 g as cobalt), sodium borohydride was added in 3 times mole of cobalt while stirring, and the mixture was reduced to selectively precipitate cobalt on Pt. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Pt 0.842% -supported cerium zirconate particles with Co (0.025%) (fine particles g).

  Next, acicular boehmite alumina was used as alumina and 100 g equivalent was dispersed in water, and the pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles g were added to this, sufficiently stirred, dried, and then fired at 400 ° C. to prepare fine particles G in which the fine particles g were coated with alumina.

  Next, 173.4 g of fine particles G and 1.6 g of boehmite alumina are added to a ball mill, and then 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution are added to disperse the fine particles G and grind the substrate. And a slurry having an average particle diameter of 3 μm was prepared (slurry g).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. (Slurry R).

  A honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 cells and 6 mils is coated with 141g / L of slurry g and dried, and then coated with 59g / L of slurry R, dried and fired at 400 ° C. The sample of Example 7 was obtained. The obtained catalyst of Example 7 was a catalyst carrying Pt at 0.588 g / L and Rh at 0.236 g / L, respectively.

[Example 8]
Example 8 is an example in which the noble metal particles are Pt, the compound particles are cerium zirconate (particle size 30 nm), the promoter layer is an oxide of Co, and the molar ratio of Co in the promoter layer to Pt is 1. is there.

  Add 200.835 g of cerium zirconate particles (30 nm) to 200 g of a solution of dinitrodiamine Pt solution so that Pt is 0.842 g, add sodium borohydride 3 times mol of Pt while stirring, reduce, and filter And washed to prepare cerium zirconate particles with Pt. The fine particles were added to a cobalt nitrate solution (dissolved as 0.254 g as cobalt), sodium borohydride was added in 3 times mole of cobalt while stirring, and the mixture was reduced to selectively precipitate cobalt on Pt. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Pt0.842% -supported cerium zirconate particles with Co (0.254%) (fine particles h).

  Next, acicular boehmite alumina was used as alumina and 100 g equivalent was dispersed in water, and the pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles h were added to this, sufficiently stirred, dried, and then fired at 400 ° C. to prepare fine particles H in which the fine particles h were coated with alumina.

  Next, 173.4 g of fine particles H and 1.6 g of boehmite alumina were added to a ball mill, and then 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to disperse the fine particles H and pulverize the substrate. A slurry having an average particle diameter of 3 μm was prepared (slurry h).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. (Slurry R).

  A honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 cells and 6 mils was coated with 141g / L of slurry h, dried, and then coated with 59g / L of slurry R, dried and fired at 400 ° C. The sample of Example 8 was obtained. The obtained catalyst of Example 8 was a catalyst carrying Pt at 0.588 g / L and Rh at 0.236 g / L.

[Example 9]
Example 9 is an example in which the noble metal particles are Pt, the compound particles are cerium zirconate (particle size 30 nm), the promoter layer is a Co oxide, and the molar ratio of Co to Pt in this promoter layer is 5 It is.

  97.541 g of cerium zirconate particles (particle size 30 nm) are added to 200 g of a solution obtained by dissolving dinitrodiamine Pt solution so that Pt is 0.842 g, and sodium borohydride is added 3 times as much as Pt while stirring to reduce. Filtered and washed to prepare cerium zirconate particles with Pt. The fine particles were added to a cobalt nitrate solution (dissolved as 1.272 g of cobalt), sodium borohydride was added in 3 times mole of cobalt while stirring, and the mixture was reduced to selectively precipitate cobalt on Pt. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Pt0.842% -supported cerium zirconate particles with Co (1.272%) (fine particles i).

  Next, acicular boehmite alumina was used as alumina, 100 g equivalent was dispersed in water, and pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles i were added to this, sufficiently stirred, dried, and then fired at 400 ° C. to prepare fine particles I in which the fine particles i were coated with alumina.

  Next, 173.4 g of fine particles I and 1.6 g of boehmite alumina were added to a ball mill, and then 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were further added to disperse the fine particles I and pulverize the substrate. And a slurry having an average particle diameter of 3 μm was obtained (slurry i).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. (Slurry R).

  A honeycomb carrier with a diameter of 36φ, 400 cells and 6 mil (capacity 0.04L) was coated with 141g / L of slurry i and then dried, and then coated with 59g / L of slurry R, dried and fired at 400 ° C. The sample of Example 9 was obtained. The obtained catalyst of Example 9 was a catalyst carrying Pt at 0.588 g / L and Rh at 0.236 g / L.

[Example 10]
Example 10 is an example in which the noble metal particles are Pt, the compound particles are cerium zirconate (particle size 30 nm), the promoter layer is an oxide of Co, and the molar ratio of Co to Pt in this promoter layer is 10. It is.

  Add 95.924 g of cerium zirconate particles (particle size 30 nm) to 200 g of a solution of dinitrodiamine Pt solution so that Pt is 0.842 g, and add sodium borohydride 3 times mol of Pt while stirring. Filtered and washed to prepare cerium zirconate particles with Pt. The fine particles were added to a cobalt nitrate solution (dissolved as 2.54 g as cobalt), and sodium borohydride was added in 3 times mole of cobalt while stirring to reduce the cobalt, so that cobalt was selectively deposited on Pt. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Pt0.842% cerium zirconate particles with Co (2.54%) (fine particles j).

  Next, acicular boehmite alumina was used as alumina, 100 g equivalent was dispersed in water, and pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles j were added thereto and stirred sufficiently, dried, and then fired at 400 ° C. to prepare fine particles J in which the fine particles j were coated with alumina.

  Next, 173.4 g of fine particles J and 1.6 g of boehmite alumina were added to a ball mill, and then 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to disperse the fine particles J and pulverize the substrate. And a slurry having an average particle diameter of 3 μm was obtained (slurry j).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. (Slurry R).

  A honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 cells and 6 mils was coated with 141g / L of slurry j and dried, and then coated with 59g / L of slurry R, dried and fired at 400 ° C. The sample of Example 10 was obtained. The obtained catalyst of Example 10 was a catalyst carrying Pt at 0.588 g / L and Rh at 0.236 g / L.

[Example 11]
Example 11 is an example in which the noble metal particles are Pt, the compound particles are cerium zirconate (particle size 30 nm), the promoter layer is an oxide of Co, and the molar ratio of Co to Pt in this promoter layer is 30. It is.

  To 200 g of a solution obtained by dissolving dinitrodiamine Pt solution so that Pt is 0.842 g, add 89.458 g of cerium zirconate particles (particle size 30 nm), and add sodium borohydride 3 times mol of Pt while stirring to reduce. Filtered and washed to prepare cerium zirconate particles with Pt. The fine particles were added to a cobalt nitrate solution (dissolved as 7.63 g as cobalt), sodium borohydride was added in 3 times mole of cobalt while stirring, and the mixture was reduced to selectively precipitate cobalt on Pt. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Pt0.842% -supported cerium zirconate particles with Co (7.63%) (fine particles k).

  Next, acicular boehmite alumina was used as alumina and 100 g equivalent was dispersed in water, and the pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles k were added thereto, and the mixture was sufficiently stirred, dried, and then fired at 400 ° C. to prepare fine particles K in which the fine particles k were coated with alumina.

  Next, after adding 173.4 g of fine particles K, 1.6 g of boehmite alumina, and a ball mill, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to disperse the fine particles K, and the substrate was pulverized. A slurry having an average particle diameter of 3 μm was prepared (slurry k).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. (Slurry R).

  A honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 cells and 6 mils was coated with 141g / L of slurry k, then dried, and then coated with 59g / L of slurry R, dried and fired at 400 ° C. The sample of Example 11 was obtained. The obtained catalyst of Example 11 was a catalyst carrying Pt at 0.588 g / L and Rh at 0.236 g / L.

[Example 12]
Example 12 is an example in which the noble metal particles are Pt, the compound particles are cerium zirconate (particle size 30 nm), the promoter layer is an oxide of Co, and the molar ratio of Co to Pt in this promoter layer is 50. It is.

  Add 82.988 g of cerium zirconate particles (particle size 30 nm) to 200 g of a solution of dinitrodiamine Pt solution so that Pt is 0.842 g, and add sodium borohydride 3 times mol of Pt while stirring. Filtered and washed to prepare cerium zirconate particles with Pt. The fine particles were added to a cobalt nitrate solution (dissolved as 12.72 g as cobalt), and sodium borohydride was added in 3 times mole of cobalt while stirring to reduce the cobalt, and cobalt was selectively deposited on Pt. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Pt 0.842% -supported cerium zirconate particles with Co (12.72%) (fine particles 1).

  Next, acicular boehmite alumina was used as alumina and 100 g equivalent was dispersed in water, and the pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles 1 were added thereto, and the mixture was sufficiently stirred, dried, and then fired at 400 ° C. to prepare fine particles L in which the fine particles 1 were coated with alumina.

  After adding 173.4 g of fine particles L and 1.6 g of boehmite alumina to a ball mill, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to disperse the fine particles L, and the base material was pulverized. A slurry having a particle diameter of 3 μm was prepared (slurry 1).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. (Slurry R).

  A honeycomb carrier with a diameter of 36φ, 400 cells and 6 mil (capacity 0.04L) was coated with 141g / L of slurry l and then dried, then 59g / L of slurry R was coated, dried and fired at 400 ° C. The sample of Example 12 was obtained. The obtained catalyst of Example 12 was a catalyst carrying Pt at 0.588 g / L and Rh at 0.236 g / L.

[Example 13]
Example 13 is an example in which the noble metal particles are Pt, the compound particles are ceria (particle size: 10 nm), the promoter layer is an oxide of Co, and the molar ratio of Co in the promoter layer to Pt is 0.01.

  To 200 g of a solution obtained by dissolving a dinitrodiamine Pt solution so that Pt is 0.842 g, add 99.155 g of ceria particles (10 nm), add sodium borohydride 3 times mole of Pt while stirring, reduce, filter, and wash Ct particles with Pt were prepared. The fine particles were added to a cobalt nitrate solution (dissolved as 0.0025 g of cobalt), sodium borohydride was added in 3 times mole of cobalt while stirring, and the mixture was reduced to selectively precipitate cobalt on Pt. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Pt0.842% supported ceria particles with Co (0.0025%) (fine particles m).

  Next, acicular boehmite alumina was used as alumina and 100 g equivalent was dispersed in water, and the pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles m were added thereto and stirred sufficiently, dried, and then fired at 400 ° C. to prepare fine particles M in which the fine particles m were coated with alumina.

  After adding 173.4 g of fine particles M and 1.6 g of boehmite alumina to a ball mill, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution are added to disperse the fine particles M, and the base material is pulverized. A slurry having a particle diameter of 3 μm was prepared (slurry m).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. (Slurry R).

  A honeycomb carrier with a diameter of 36φ, 400 cells and 6 mil (capacity 0.04L) was coated with 141g / L of slurry m, dried, and then coated with 59g / L of slurry R, dried, and fired at 400 ° C. The sample of Example 13 was obtained. The obtained catalyst of Example 13 was a catalyst carrying Pt at 0.588 g / L and Rh at 0.236 g / L.

[Example 14]
Example 14 is an example in which the noble metal particles are Pd, the compound particles are cerium zirconate (particle size 30 nm), the promoter layer is an oxide of Co, and the molar ratio of Co in the promoter layer to Pd is 0.1. is there.

  Add 99.098 g of cerium zirconate particles (particle size 30 nm) to 200 g of a solution of dinitrodiamine Pd solution so that Pd is 0.842 g, and add sodium borohydride 3 times mol of Pd while stirring. Filtered and washed to prepare cerium zirconate particles with Pd. The fine particles were added to a cobalt nitrate solution (dissolved as 0.047 g as cobalt), and sodium borohydride was added in 3 times mole of cobalt while stirring to reduce the cobalt, and cobalt was selectively deposited on Pd. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Pd0.842% -supported cerium zirconate particles with Co (0.047%) (fine particles n).

  Next, acicular boehmite alumina was used as alumina and 100 g equivalent was dispersed in water, and the pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles n were added thereto and stirred sufficiently, dried, and then fired at 400 ° C. to prepare fine particles N in which the fine particles n were coated with alumina.

  Next, after adding 173.4 g of fine particles N and 1.6 g of boehmite alumina to a ball mill, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution are further added to disperse the fine particles N and grind the substrate. A slurry having an average particle diameter of 3 μm was obtained (slurry n).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. (Slurry R).

  A honeycomb carrier (capacity 0.04L) with a diameter of 36φ and 400 cells is coated with 141g / L of slurry n and dried, and then coated with 59g / L of slurry R, dried and fired at 400 ° C. The sample of Example 14 was obtained. The obtained catalyst of Example 14 was a catalyst in which Pd was supported at 0.588 g / L and Rh was supported at 0.236 g / L.

[Example 15]
Example 15 is an example in which the noble metal particles are Pd, the compound particles are cerium zirconate (particle size 30 nm), the promoter layer is an oxide of Co, and the molar ratio of Co in the promoter layer to Pd is 10. is there.

  To 200 g of a solution obtained by dissolving a dinitrodiamine Pd solution so that Pd is 0.842 g, 93.18 g of cerium zirconate particles (particle size 30 nm) is added, and sodium borohydride is added 3 times as much as Pd while stirring to reduce. Filtered and washed to prepare cerium zirconate particles with Pd. The fine particles were added to a cobalt nitrate solution (dissolved as 4.70 g as cobalt), and sodium borohydride was added in 3 times mole of cobalt while stirring to reduce the cobalt, and cobalt was selectively deposited on Pd. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Pd0.842% -supported cerium zirconate particles with Co (4.70%) (fine particles o).

  Next, acicular boehmite alumina was used as alumina and 100 g equivalent was dispersed in water, and the pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles o were added to this, sufficiently stirred, dried, and then fired at 400 ° C. to prepare fine particles O in which the fine particles o were coated with alumina.

  After adding 173.4 g of fine particles O and 1.6 g of boehmite alumina to a ball mill, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to disperse the fine particles O, and the substrate was pulverized. A slurry having a particle size of 3 μm was prepared (slurry o).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. (Slurry R).

  A honeycomb carrier with a diameter of 36φ, 400 cells and 6 mil (capacity 0.04L) was coated with 141g / L of slurry o and dried, and then coated with 59g / L of slurry R, dried and fired at 400 ° C. The sample of Example 15 was obtained. The obtained catalyst of Example 15 was a catalyst in which Pd was supported at 0.588 g / L and Rh was supported at 0.236 g / L.

[Example 16]
Example 16 is an example in which the noble metal particles are Pd, the compound particles are cerium zirconate (particle size: 30 nm), the promoter layer is an oxide of Co, and the molar ratio of Co in the promoter layer to Pd is 30. is there.

  To 200 g of a solution obtained by dissolving a dinitrodiamine Pd solution so that Pd is 0.842 g, add 81.37 g of cerium zirconate particles (30 nm), add sodium borohydride 3 times mol of Pd while stirring, reduce, and filter Then, cerium zirconate particles with Pd were prepared by washing. The fine particles were added to a cobalt nitrate solution (dissolved as 13.99 g as cobalt), sodium borohydride was added in 3 times mole of cobalt while stirring, and the mixture was reduced to selectively precipitate cobalt on Pd. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Pd0.842% -supported cerium zirconate particles with Co (13.99%) (fine particles p).

  Next, acicular boehmite alumina was used as alumina, 100 g equivalent was dispersed in water, and pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles p were added to this, sufficiently stirred, dried, and then fired at 400 ° C. to prepare fine particles P in which the fine particles p were coated with alumina.

  After adding 173.4 g of fine particles P and 1.6 g of boehmite alumina to a ball mill, 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added to disperse the fine particles P, and the substrate was pulverized. A slurry having a particle diameter of 3 μm was prepared (slurry p).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. (Slurry R).

  A honeycomb carrier with a diameter of 36φ, 400 cells and 6 mil (capacity 0.04L) was coated with 141g / L of slurry p, dried, then coated with 59g / L of slurry R, dried and fired at 400 ° C. The sample of Example 16 was obtained. The obtained catalyst of Example 16 was a catalyst in which Pd was supported at 0.588 g / L and Rh was supported at 0.236 g / L.

[Example 17]
Example 17 is an example in which the noble metal particles are Pd, the compound particles are cerium zirconate (particle size 30 nm), the promoter layer is an oxide of Co, and the molar ratio of Co in the promoter layer to Pd is 50. is there.

  69.51 g of cerium zirconate particles (particle size 30 nm) are added to 200 g of a solution obtained by dissolving a dinitrodiamine Pd solution so that Pd is 0.842 g, and sodium borohydride is added 3 times as much as Pd while stirring. Filtered and washed to prepare cerium zirconate particles with Pd. The fine particles were added to a cobalt nitrate solution (dissolved as 23.317 g as cobalt), and sodium borohydride was added in 3 times mole of cobalt while stirring to reduce the cobalt, and cobalt was selectively deposited on Pd. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Pd0.842% -supported cerium zirconate particles with Co (23.317%) (fine particles q).

  Next, acicular boehmite alumina was used as alumina and 100 g equivalent was dispersed in water, and the pH was adjusted to 3 with nitric acid. 100 g of the above-mentioned fine particles q were added to this, sufficiently stirred, dried, and then fired at 400 ° C. to prepare fine particles Q in which the fine particles q were coated with alumina.

  Next, 173.4 g of fine particles Q and 1.6 g of boehmite alumina were added to a ball mill, and then 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were further added to disperse the fine particles Q and pulverize the substrate. And a slurry having an average particle diameter of 3 μm was obtained (slurry q).

  Next, rhodium nitrate was impregnated into a composite compound of γ-alumina and zirconium oxide containing 3% as zirconium to prepare rhodium 0.6% supported powder. Further, zirconia base material was prepared by compounding 24% of cerium oxide with zirconium oxide. Add 116.55 g of rhodium 0.6% powder, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina to a ball mill, add 307.5 g of water and 17.5 g of 10% nitric acid aqueous solution, and pulverize it. (Slurry R).

  A honeycomb carrier with a diameter of 36φ, 400 cells and 6 mil (capacity 0.04L) was coated with 141g / L of slurry q and dried, then 59g / L of slurry R was coated, dried and fired at 400 ° C. The sample of Example 17 was obtained. The obtained catalyst of Example 17 was a catalyst in which Pd was supported at 0.588 g / L and Rh was supported at 0.236 g / L.

[Example 18]
Example 18 is an example in which the noble metal particles are Rh, the compound particles are zirconia (particle size: 10 nm), the promoter layer is an oxide of Co, and the molar ratio of Co in the promoter layer to Rh is 10.

  An alumina substrate (composite of γ-alumina with 9% cerium oxide, 6% zirconium oxide and 6% lanthanum oxide) is impregnated with an aqueous solution of dinitrodiamine platinum, dried and calcined at 400 ° C. to give a Pt of 0.44. % Supported alumina substrate was prepared. Further, a ceria base material (compound containing 25% zirconium oxide in ceria) was impregnated with a dinitrodiamine platinum aqueous solution, dried and fired at 400 ° C. to prepare a ceria base material supporting 0.375% Pt. .

  124.8 g of an alumina base material carrying 0.44% Pt, 48.6 g of a ceria base material carrying 0.375% Pt and 1.6 g of boehmite alumina were added to a ball mill, and 307.5 g of water, 10% 17.5 g of an aqueous nitric acid solution was added and the powder was pulverized to obtain a slurry having an average particle diameter of 3 μm. This slurry is designated as Slurry X.

  Next, 90.06 g of zirconia particles (particle size: 10 nm) is added to 200 g of a solution obtained by dissolving a rhodium nitrate solution so that Rh becomes 1.2 g, and sodium borohydride is added 3 times mol of Rh while stirring to reduce. Filtered and washed to prepare Rh-attached zirconia particles. The fine particles were added to a cobalt nitrate solution (dissolved as 6.87 g as cobalt), sodium borohydride was added in 3 times mole of cobalt while stirring, and reduced to selectively precipitate cobalt on Rh. This was filtered, washed, dried, and fired at 400 ° C. for 1 hour to prepare Rh1.2% -supported zirconia particles with Co (6.87%) (fine particles s).

  Next, acicular boehmite alumina was used as alumina and 100 g equivalent was dispersed in water and adjusted to pH 3 with nitric acid. 100 g of the above-mentioned fine particles s were added thereto and stirred sufficiently, dried, and then fired at 400 ° C. to prepare fine particles S in which the fine particles s were coated with alumina.

  Add 116.55g of fine particles S, 44.45g of zirconia base material, 11g of alumina base material, 3g of boehmite alumina to a ball mill, add 307.5g of water and 17.5g of 10% nitric acid aqueous solution, and grind them to obtain an average particle size. A slurry having a diameter of 3 μm was prepared (slurry S).

  The slurry carrier was coated with 141g / L of slurry X on a honeycomb carrier (capacity 0.04L) with a diameter of 36φ, 400 cells and 6 mil, dried, then coated with 59g / L of slurry S, dried and fired at 400 ° C. The sample of Example 18 was obtained. The obtained catalyst of Example 18 was a catalyst carrying Pt at 0.588 g / L and Rh at 0.236 g / L.

[Example 19]
Example 19 is an example in which the noble metal particles are Rh, the compound particles are zirconia (particle size 10 nm), the promoter layer is an oxide of Co, and the molar ratio of Co in the promoter layer to Rh is 30.

  An alumina substrate (composite of γ-alumina with 9% cerium oxide, 6% zirconium oxide and 6% lanthanum oxide) is impregnated with an aqueous solution of dinitrodiamine platinum, dried and calcined at 400 ° C. to give a Pt of 0.44. % Supported alumina substrate was prepared. Further, a ceria base material (compound containing 25% zirconium oxide in ceria) was impregnated with a dinitrodiamine platinum aqueous solution, dried and fired at 400 ° C. to prepare a ceria base material supporting 0.375% Pt. .

  124.8 g of an alumina substrate carrying 0.44% Pt, 48.6 g of a ceria substrate carrying 0.375% Pt, and 1.6 g of boehmite alumina were added to a ball mill, and 307.5 g of water was added. The powder was pulverized by adding 17.5 g of a 10% nitric acid aqueous solution to obtain a slurry having an average particle diameter of 3 μm. This slurry is designated as Slurry X.

  Next, 72.59 g of zirconia particles (particle size: 10 nm) are added to 200 g of a solution obtained by dissolving a rhodium nitrate solution so that Rh is 1.2 g, and sodium borohydride is added 3 times as much as Rh while stirring to reduce the amount. Filtered and washed to prepare Rh-attached zirconia particles. The fine particles were added to a cobalt nitrate solution (dissolved in 20.62 g as cobalt), sodium borohydride was added in 3 times mole of cobalt while stirring, and the mixture was reduced to selectively precipitate cobalt on Rh. This was filtered, washed, dried, and calcined at 400 ° C. for 1 hour to prepare Rh1.2% supported zirconia particles with Co (20.62%) (fine particles t).

  Next, acicular boehmite alumina was used as alumina and 100 g equivalent was dispersed in water and adjusted to pH 3 with nitric acid. 100 g of the above-mentioned fine particles t were added to this, sufficiently stirred, dried, and then fired at 400 ° C. to prepare fine particles T in which the fine particles t were coated with alumina.

  116.55 g of fine particles T, 44.45 g of zirconia base material, 11 g of alumina base material, and 3 g of boehmite alumina were added to a ball mill, and 307.5 g of water and 17.5 g of a 10% nitric acid aqueous solution were added and pulverized. The slurry was 3 μm (slurry T).

  A honeycomb carrier with a diameter of 36φ, 400 cells and 6 mil (capacity 0.04L) was coated with 141g / L of slurry X and then dried, then 59g / L of slurry T was coated, dried and fired at 400 ° C. The sample of Example 19 was obtained. The obtained catalyst of Example 19 was a catalyst carrying Pt at 0.588 g / L and Rh at 0.236 g / L.

[Comparative Example 1]
Comparative Example 1 is a catalyst impregnated with a so-called ordinary noble metal.

  An alumina substrate (composite of γ-alumina with 9% cerium oxide, 6% zirconium oxide and 6% lanthanum oxide) is impregnated with an aqueous solution of dinitrodiamine platinum, dried and calcined at 400 ° C. to give a Pt of 0.44. % Supported alumina substrate was prepared. Further, a ceria base material (compound containing 25% zirconium oxide in ceria) was impregnated with a dinitrodiamine platinum aqueous solution, dried and fired at 400 ° C. to prepare a ceria base material supporting 0.375% Pt. .

  124.8 g of an alumina substrate carrying 0.44% of Pt, 48.6 g of a ceria substrate carrying 0.375% of Pt, and 1.6 g of boehmite alumina were added to a ball mill, and 307.5 g of water, 10% 17.5 g of an aqueous nitric acid solution was added and the powder was pulverized to obtain a slurry having an average particle diameter of 3 μm. This slurry is designated as Slurry X.

  A honeycomb carrier (capacity 0.04 L) having a diameter of 36φ and 400 cells of 6 mil was coated with 141 g / L of slurry X, dried, and further coated with 59 g / L of slurry R prepared in Example 1, and dried at 400 ° C. The sample of Comparative Example 1 was fired. The obtained catalyst of Comparative Example 1 was a catalyst carrying Pt at 0.588 g / L and Rh at 0.236 g / L.

  The samples of Examples 1 to 19 and Comparative Example 1 described above were subjected to a durability test, and the catalyst performance after the durability test was examined. In this endurance test, the exhaust system of a 3500cc V-type engine is equipped with five exhaust gas purification catalysts obtained in the above examples per bank, domestic regular gasoline is used, and the catalyst inlet temperature is set. The temperature was set to 650 ° C. and the system was operated for 30 hours.

  After the endurance test, the sample catalyst of each example was incorporated into the simulated exhaust gas circulation device, and the simulated exhaust gas having the composition shown in Table 1 was circulated (the space velocity was SV = 60000 / h), and the catalyst temperature was 30 ° C / The temperature at which the NOx, CO, and HC purification rates were 50% was examined while raising the temperature at a rate of minutes. The component composition of each sample is summarized in Table 2, and the evaluation results are summarized in Table 3.

Of the results shown in Table 3, the results of T50 of HC are shown in FIG.

  The sample of Comparative Example 1 is a conventional catalyst prepared by impregnating an alumina base material or a ceria base material with a Pt solution according to a commonly used production method. After carrying Pt, Pd, Rh, etc. on the particles, Co is further coated. For Co coating, for example, a Pt-supported fine particle was added to a Co-dissolved solution and stirred, and then a sample supporting Co by adding sodium borohydride and reducing and precipitating Co was examined by TEM. It was confirmed that Co was present where Pt was present.

  The reason why Co exists in the presence of Pt in this way is that when Co is reduced, Pt attached to the compound particles is the nucleus, and Co is selectively deposited around Pt. Conceivable. Since it is fired after depositing Co, it is considered that Co exists as an oxide on the compound particles.

  The samples of Examples and Comparative Examples were evaluated after receiving a heat history due to durability. From the results of Table 3 showing this evaluation, the samples of Examples 1 to 19 have better T50 performance than the catalyst of Comparative Example 1. This is because the Co oxide is formed in contact with Pt, Pd, Rh on the compound particles carrying the noble metal particles such as Pt, Pd, or Rh used in the examples, and the cocatalyst effect is obtained. Suppression of Pt sintering by suppressing the movement of Pt particles by Co oxide and ensuring that the distance between the compound particles carrying Pt is separated by alumina. This is probably due to the fact that

  These effects are not limited to Co, but Fe, Ni, Cu, Mn, Sn, Ce, Zr, etc. can also be used.

It is a schematic diagram of an example of the exhaust gas purification catalyst according to the present invention. It is a graph which shows the result of T50 of HC about the sample in an Example.

Explanation of symbols

11 noble metal particles 12 compound particles 13 promoter layer)
14 Oxide particles

Claims (7)

Precious metal particles,
Compound particles carrying the noble metal particles,
A co-catalyst layer covering at least a part of the surface of the noble metal particles on the compound particles;
An exhaust gas purification catalyst comprising oxide particles that are formed around the compound particles and separate the compound particles.   The promoter layer is made of a metal oxide, and the amount of the metal oxide is in the range of 0.1 to 50 in terms of the molar ratio of the metal in the metal oxide to the metal of the noble metal particles. The exhaust gas purifying catalyst according to claim 1.   The promoter layer is made of a metal oxide, and the amount of the metal oxide is within a range of 10 to 30 in terms of a molar ratio of the noble metal particles to the metal with respect to the amount of metal in the metal oxide. The exhaust gas purifying catalyst according to claim 1.   The exhaust gas purification catalyst according to claim 1, wherein the noble metal is at least one kind of noble metal selected from platinum, palladium and rhodium.   2. The exhaust gas purifying apparatus according to claim 1, wherein the promoter layer is made of an oxide of at least one metal selected from Co, Ni, Fe, Cu, Sn, Mn, Ce, and Zr. catalyst.   2. The compound particles according to claim 1, wherein the compound particles are oxide particles containing cerium, composite oxide particles of cerium and zirconium, oxide particles containing zirconium, or oxide particles containing aluminum. Exhaust gas purification catalyst. A step of supporting noble metal particles on compound particles;
Depositing a base metal for the promoter layer by a selective deposition method on at least a part of the surface of the noble metal particles of the compound particles carrying the noble metal particles;
A step of oxidizing the base metal to form a promoter layer made of a metal oxide by heat treatment in an oxidizing atmosphere;
And a step of forming oxide particles around the compound particles on which the promoter layer is formed and the noble metal particles are supported.

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