JP2007000697A - Exhaust gas purification catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas purification catalyst which prevents the agglomeration of nobel metal particles and suppresses the deterioration of activities of a catalyst. <P>SOLUTION: The exhaust gas purification catalyst is characterized by having a carrier 2 formed by a porous oxide, nobel metal particles 3 carried on the micro pore inner part of the carrier 2 and an agglomeration suppressing material (inclusion material 4) to control the agglomeration of the nobel metal particles 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification catalyst that purifies exhaust gas containing hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), and the like discharged from an internal combustion engine represented by an automobile.

The exhaust gas emitted from internal combustion engines such as automobiles contains harmful gases such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). A three-way catalyst is used for purification. A three-way catalyst is a catalyst in which noble metal particles (for example, Pt, Pd, Rh, etc.) are supported on the surface of a support (for example, alumina (γ-Al ₂ O ₃ )). The quantity is increasing rapidly.

  The exhaust gas purification catalyst is a catalytic reaction in which the reaction proceeds on the surface of the noble metal particles, and the activity of the catalyst is substantially proportional to the surface area of the noble metal particles. For this reason, a catalyst in which noble metal particles having a small particle size (for example, a particle size of 1 nm or less) are uniformly dispersed and supported on the support surface is used, and the surface area of the noble metal particles is increased to increase the activity of the catalyst. However, since noble metal particles having a small particle diameter have a large surface energy and are easily aggregated, it is important to suppress aggregation of the noble metal particles. There are two factors that cause the aggregation of the noble metal particles, that is, the noble metal particles themselves move and aggregate, and that the aggregation of the noble metal particles on the support occurs as the support contracts.

  For example, a catalyst is disclosed in which a second component such as an aggregation inhibitor is added in order to suppress aggregation due to movement of noble metal particles (see Patent Document 1). In this catalyst, noble metal particles are supported on the surface of the support, and further, aggregation agents such as Al, Mg, Ca, Ce, Sr, Zn, W, and Mo oxides are formed on the surface to aggregate the noble metal particles. This suppresses the decrease in the activity of the catalyst. However, the noble metal particles are only supported on the surface of the carrier, and it has been difficult to suppress aggregation of the noble metal particles.

Therefore, a catalyst prepared by using the reverse micelle method, in which noble metal particles are included by a carrier component and noble metal particles are supported inside the carrier is disclosed (see Patent Document 2).
Japanese Patent No. 34668856 Japanese Patent Laid-Open No. 2003-80077

  However, in the catalyst prepared using the reverse micelle method, the surface area of the initial support is high. However, when the catalyst is exposed to a high temperature environment, the surface area of the support decreases due to thermal deterioration, and noble metal particles supported on the support surface. Moved to cause agglomeration of noble metal particles, leading to a decrease in the activity of the catalyst.

  Moreover, in the catalyst prepared by the reverse micelle method, the contact rate between the exhaust gas and the noble metal particles is lowered, and the activity of the catalyst is likely to be lowered accordingly.

  The present invention has been made in order to solve the above-mentioned problems. By supporting noble metal particles inside the pores of the carrier and further forming an aggregation inhibitor, the activity of the catalyst can be reduced due to aggregation of the noble metal particles. Suppressed.

  That is, the exhaust gas purification catalyst of the present invention has a support formed from a porous oxide, noble metal particles supported inside the pores of the support, and an aggregation inhibitor that suppresses aggregation of the noble metal particles. The gist.

  According to the exhaust gas purification catalyst of the present invention, aggregation of noble metal particles can be suppressed, and a decrease in the activity of the catalyst can be prevented.

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

  FIG. 1 shows a partial cross-sectional view of an exhaust gas purification catalyst according to an embodiment of the present invention. The exhaust gas purification catalyst 1 includes a carrier 2 formed of a porous oxide, noble metal particles 3 supported inside the pores of the carrier 2, and an inclusion material 4 that encloses the surface of the noble metal particles 3. The enclosure material 4 functions as an aggregation suppressing material that suppresses aggregation of the noble metal particles 3. Although not shown in FIG. 1, at least one of transition metal particles or promoter particles may be supported inside the pores of the carrier 2, and in this case, the transition metal particles or promoter particles are It is preferable to place the metal particles in contact with the noble metal particles 3 and cover the transition metal particles or the promoter particles with the inclusion material 4.

  Moreover, the partial cross section figure of the exhaust gas purification catalyst which concerns on other embodiment in this invention is shown in FIG. The exhaust gas purification catalyst 5 includes a carrier 2 formed of a porous oxide, noble metal particles 3 supported inside the pores of the carrier 2, and a coating material 6 that covers the pores on the surface of the carrier 2. The covering material 6 functions as an aggregation suppressing material that suppresses the movement of the noble metal particles 3 supported inside the pores and suppresses the aggregation of the noble metal particles 3.

  In the exhaust gas purification catalysts 1 and 5, the noble metal particles 3, the transition metal particles, and the promoter particles each have a depth X of 100 nm or more from the surface of the carrier 2 as shown in FIGS. 3 (a) and 3 (b). It is preferable to be carried as the position. When each particle such as the noble metal particle 3 is supported at a position where the depth (X) is less than 100 nm from the surface of the carrier 2, the noble metal particle 3 easily moves from the inside of the pore to the outside and is released to the outside of the pore. This is because the precious metal particles 3 aggregated and the activity of the catalyst may be reduced.

  The average particle diameter of the noble metal particles 3 is preferably 2 nm or more and 8 nm or less. This is because when the average particle diameter of the noble metal particles 3 is less than 2 nm, the surface energy increases and the particles easily aggregate. When the average particle diameter of the noble metal particles 3 exceeds 8 nm, the surface area of the noble metal particles 3 decreases. This is because the activity of the catalyst decreases. Here, the average particle diameter of the noble metal particles 3 means the diameter when the noble metal particles are spherical, and when the noble metal particles are not spherical, the maximum and minimum values of the diameters. Mean value.

  The average diameter of the pores on the surface of the carrier 2 in the exhaust gas purification catalysts 1 and 5 is preferably 30 nm or less. When the average diameter of the pores on the surface of the carrier 2 exceeds 30 nm, the noble metal particles 3 supported inside the pores escape from the pores and move to the surface of the carrier 2 to aggregate and coarsen the noble metal particles 3. This is because there is a possibility that the activity of selenium may decrease.

  The noble metal particles 3 are preferably exposed from the carrier 2 within a range of 50% to 90% of the surface area. Hereinafter, a method for measuring the exposure rate will be described.

  The exposure rate means the ratio of the precious metal particles exposed on the support surface to the precious metal particles present in the exhaust gas purification catalyst. Specifically, the precious metal outer surface area (PMSA) calculated by CO adsorption described later and TEM observation It is calculated from the ratio of the particle surface area (TSA) theoretically calculated from the average particle diameter of the noble metal particles obtained as a result. The noble metal particles observed by TEM can also observe noble metal particles that are not exposed on the surface of the carrier. For this reason, if all the precious metal particles are exposed on the support surface, a gas adsorption amount stoichiometrically adsorbed to TSA is obtained, and TSA and PMSA have the same value. However, when the noble metal particles are supported in a state of being coated on the support surface, a gas adsorption amount stoichiometrically adsorbed with respect to the surface area of the noble metal determined from the particle diameter of the noble metal particles cannot be obtained. Therefore, the ratio of the surface area of the noble metal exposed on the surface of the carrier is calculated from the average particle diameter of the noble metal particles observed by TEM and the amount of gas adsorbed on the sample.

PMSA is calculated by the following formula.

TSA is calculated by the following method. Let [D] be the average particle diameter of the noble metal particles by TEM observation. [D] When the number of atoms of the noble metal constituting one is [A], the number (n) of [D] contained in the catalyst can be calculated from the number of noble metal atoms [N] charged at the time of preparation.

  The exposure rate is calculated from the ratio of PMSA and TSA obtained.

Exposure rate (%) = (PMSA / TSA) x 100
If this is simplified, the following equation is obtained, and the exposure rate can be obtained from this equation. The values used in the formula are shown in Table 1.

The unit CO adsorption amount is measured in order to obtain the above exposure rate. The unit CO adsorption amount is measured using a metal dispersion measuring device (BEL-METAL-3 manufactured by Nippon Bell Co., Ltd.) as follows. Measured according to the procedure. The sample was heated to 400 ° C. at 10 ° C./min in a He 100% gas stream, and then oxidized at 400 ° C. for 15 minutes in an O ₂ 100% gas stream. Thereafter, purging was performed with He100% gas for 5 minutes, and reduction treatment was performed at 400 ° C. for 15 minutes in a H ₂ 40% / He balance gas stream. Next, after the temperature was lowered to 50 ° C. in a He100% gas stream, CO10% / He balance gas was introduced in a pulsed manner to determine the unit CO adsorption amount.

  The exhaust gas purification catalysts 1 and 5 are preferably made of the following materials.

  As the support, it is preferable to use a metal oxide, for example, as a metal oxide, a kind of simple substance selected from oxides of elements selected from Al, Zr, Ti, Ce and Si and derivatives thereof Or two or more solid solutions. Note that the notation as a metal oxide is MxOy as in MxOy, and x and y can be variously changed. Moreover, it is preferable to use the same metal oxide as that of the carrier as the clathrating material or the covering material as the aggregation suppressing material. Further, the noble metal particles are at least one selected from Pt, Pd and Rh, the transition metal particles are at least one selected from Fe, Co, Ni and Mn, and the promoter particles are La , Ce and Zr are preferably included.

  Further, the exhaust gas purification catalyst according to the embodiment of the present invention is actually used as an exhaust gas purification catalyst having a catalyst layer by coating the catalyst slurry on a refractory inorganic base material, for example, as a catalyst slurry containing the catalyst described above. It is preferable to be used for.

  A method for producing the exhaust gas purification catalyst will be described.

  Initially, the manufacturing method of the exhaust gas purification catalyst shown in FIG. 1 is demonstrated.

  First, a solution containing a noble metal salt of at least one element selected from Pt, Pd and Rh in an organic solvent and a carrier material are mixed, and ions of the clathrate are mixed in the resulting mixture. A solution containing the catalyst and a wettable powder of the inclusion material are added to obtain a catalyst precursor. Thereafter, the obtained catalyst precursor is filtered, washed, dried, and calcined to obtain a catalyst.

  The obtained catalyst was obtained by calcining a catalyst precursor in which noble metal particles were incorporated by the precursor of the carrier, so that a large number of pores were formed in the carrier, and the inside of the pores of the carrier incorporated in the hydroxide. The catalyst has noble metal particles supported on the surface. In this way, the noble metal particles are uniformly dispersed and fixed firmly on the surface inside the pores of the carrier, and the noble metal particles are coated with the inclusion material to suppress the movement of the noble metal particles, so that the noble metal particles are aggregated. This can prevent the decrease in the activity of the catalyst.

  As the noble metal salt used here, either an organic salt or an inorganic salt can be used. Examples of the organic salt include acetylacetonato salt, amine compound (for example, dinitrodiamine salt, triammine salt, tetraammine salt, hexaammine). Salt) and the like, and carbonyl compounds can be used. As inorganic salts, nitrates, acetates, chlorides, sulfates and the like can be used.

  As the organic solvent, cyclohexane, cycloheptane, octanol, isooctane, n-hexane, n-decane, benzene, toluene, xylene and the like can be used, and a mixed solution of these two or more kinds may be used.

As the support, at least one or two or more metal oxides selected from alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), titania (TiO ₂ ), ceria (CeO ₂ ), and silica (SiO ₂ ) are used. Things can be used.

The solution containing ions of the clathrate contains at least one precursor of alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), titania (TiO ₂ ), ceria (CeO ₂ ), and silica (SiO ₂ ). It is preferable to use an organic salt. For example, by using an organic salt such as an aluminum isopropoxide salt, the heat resistance of the inclusion material can be increased.

As the wettable powder of the inclusion material, an aqueous solution containing a reducing substance can be used,
Examples of reducing substances include ammonia, tetramethylammonium, alkali metal hydrate, hydrazine, sodium borohydride, and the like. By adding the wettable powder of the clathrate and adjusting the pH of the solution, the rate at which the noble metal particles are clathrated by the clathrate can be controlled.

  In the above method for producing an exhaust gas purifying catalyst, noble metal ions may be deposited in advance using a reducing agent before adding the solution containing the ions of the inclusion material. By precipitating the noble metal ions with the reducing agent in this way, it becomes possible to selectively carry the noble metal particles inside the pores of the carrier.

  Next, a method for manufacturing the exhaust gas purification catalyst 5 shown in FIG. 2 will be described.

  First, a solution containing a noble metal salt of at least one element selected from Pt, Pd, and Rh and a support material are mixed and stirred, and then a noble metal ion is reduced by adding a reducing agent to reduce noble metal particles. Precipitate. Thereafter, it is filtered and dried, and ammonia water corresponding to the pore volume of the carrier is added. Further, a solution containing ions of the coating material is added to obtain a catalyst precursor in which the coating material is formed on the pore surface of the support. The obtained catalyst precursor is filtered, washed, dried, and calcined to obtain a catalyst. Note that the materials used here are the same as those described above.

  The resulting catalyst is a catalyst precursor in which noble metal particles are supported inside the pores of the carrier and a coating material is formed on the surface of the pores of the carrier, so that the state where the noble metal particles are supported inside the pores is maintained. And agglomeration associated with the movement of the noble metal particles can be suppressed to prevent a decrease in the activity of the catalyst.

  In addition, in the method for producing a catalyst according to the present embodiment, the activity of the catalyst varies depending on the type and use conditions of the element. Therefore, depending on the target catalyst, the type of element used, the reducing agent and the wettable powder The conditions such as reaction temperature and reaction time may be appropriately changed.

  Hereinafter, more specific description will be given using examples.

Example 1
First, cyclohexane and alumina (specific surface area (about 200 m ² / g)) were mixed in an acetylacetonato Pt solution and stirred to obtain a solution. After aluminum isopropoxide was added to the obtained solution, an aqueous ammonia solution was further added to obtain an aluminum hydroxide to obtain a catalyst precursor.

  Thereafter, the obtained catalyst precursor was dried and calcined at 400 ° C. in an air atmosphere to obtain catalyst powder supporting 0.3 wt% Pt.

  50 g of catalyst powder, 10 g of boehmite, and 157 g of a 10% nitric acid-containing aqueous solution obtained by repeating the above operation were placed in an alumina magnetic pot, and shaken and ground with alumina balls to obtain a catalyst slurry. This catalyst slurry is put into a cordierite honeycomb carrier (900 cells / 2.5 mil, capacity 0.06L), excess slurry is removed with an air stream, dried at 120 ° C, and then 400 ° C in an air stream. The catalyst was calcined with

Example 2
First, alumina was mixed in an aqueous solution of dinitrodiammine Pt and stirred to obtain a solution. Sodium borohydride was added to the resulting solution to reduce and precipitate Pt ions. Then, after filtering and drying and impregnating with aluminum nitrate, an aqueous ammonia solution was further added to obtain a catalyst precursor as an aluminum hydroxide.

  Thereafter, the obtained catalyst precursor was filtered, dried, and calcined at 400 ° C. in an air atmosphere to obtain a catalyst powder carrying 0.3 wt% Pt.

  Using 50 g of the catalyst powder obtained by repeating the above operation, a catalyst was prepared in the same manner as in Example 1.

Example 3
First, alumina was mixed in an aqueous solution of dinitrodiammine Pt and stirred to obtain a solution. Sodium borohydride was added to the resulting solution to reduce and precipitate Pt ions. Thereafter, the mixture was filtered and dried, and ammonia water corresponding to the pore volume was added. Thereafter, aluminum isopropoxide was further added to obtain an aluminum hydroxide to obtain a catalyst precursor.

  Thereafter, the obtained catalyst precursor was filtered, dried, and calcined at 400 ° C. in an air atmosphere to obtain a catalyst powder carrying 0.3 wt% Pt.

  Using 50 g of the catalyst powder obtained by repeating the above operation, a catalyst was prepared in the same manner as in Example 1.

Example 4
In Example 4, cyclohexane and alumina (specific surface area (about 200 m ² / g)) were mixed in an acetylacetonato Pt solution, and then sodium borohydride was added without stirring to reduce and precipitate Pt ions. It was. The subsequent procedure was the same as in Example 1 to prepare a catalyst.

Example 5
In Example 5, a catalyst was prepared using the same procedure as in Example 2, except that ZrO ₂ was used as the carrier and the inclusion material.

Example 6
In Example 6, ZrO ₂ as a carrier, except for using CeO ₂ as inclusion material to produce a catalyst with the same procedure as in Example 2.

Example 7
In Example 7, a catalyst was prepared using the same procedure as in Example 1 except that the acetylacetonato Pt solution was changed to an acetylacetonato Pd solution.

Example 8
In Example 8, a catalyst was prepared using the same procedure as in Example 3 except that the acetylacetonato Pt solution was changed to an acetylacetonato Pd solution.

Example 9
In Example 9, a catalyst was prepared using the same procedure as in Example 1 except that the acetylacetonato Pt solution was changed to an acetylacetonato Rh solution.

Example 10
In Example 10, a catalyst was prepared using the same procedure as in Example 2 except that the acetylacetonato Pt solution was changed to an acetylacetonato Rh solution.

Example 11
In Example 11, a catalyst was prepared using the same procedure as in Example 1 except that an aqueous Mn acetate solution was further added to the acetylacetonato Pt solution.

Example 12
In Example 12, a catalyst was prepared using the same procedure as in Example 1 except that an aqueous Co nitrate solution was further added to the acetylacetonato Pt solution.

Example 13
In Example 13, a catalyst was prepared using the same procedure as in Example 1 except that an aqueous Mn acetate solution and Ce nitrate were further added to an acetylacetonato Pt solution.

Example 14
In Example 14, a catalyst was prepared using the same procedure as in Example 1 except that an aqueous Mn acetate solution, Ce nitrate and Zr nitrate were further added to an acetylacetonato Pt solution.

Comparative Example 1
Al ₂ O ₃ as a support was impregnated with dinitrodiamine Pt and supported on the support (Al ₂ O ₃ ) so that the supported concentration of Pt was 0.3 wt%. Then, after drying all day and night at 120 ° C., the catalyst powder was obtained by calcining at 400 ° C. for 1 hour.

  Using 50 g of the catalyst powder obtained by repeating the above operation, a catalyst was prepared in the same manner as in Example 1.

Comparative Example 2
In Comparative Example 2, a catalyst was prepared using the same method as in Comparative Example 1 except that dinitrodiamine Pt was changed to dinitrodiamine Pd.

Comparative Example 3
In Comparative Example 3, a catalyst was prepared using the same method as Comparative Example 1 except that dinitrodiamine Pt was changed to dinitrodiamine Rh.

  For each of the catalysts obtained from Examples 1 to 14 and Comparative Examples 1 to 3, the depth X from the surface of the carrier on which the noble metal particles are supported and the average pore diameter of the carrier were examined.

The average pore diameter of the support was determined by the N ₂ gas adsorption method.

  The depth X from the surface of the carrier on which the noble metal particles are supported was determined by performing the TEM measurement described below and measuring the distance between the surface of the carrier and the noble metal particles.

  Thereafter, each catalyst was baked in a muffle furnace under an air stream at 700 ° C. for 30 hours to be durable. After the durability test of the catalyst, the exposure rate and the average particle diameter of the noble metal particles were examined. In addition, about the exposure rate, the above-mentioned measuring method was used.

  The average particle diameter of the noble metal particles is first measured by TEM (transmission electron microscope) using a catalyst. HF-2000 (manufactured by Hitachi, Ltd.) was used as a TEM (transmission electron microscope), the acceleration voltage was 200 kV, and the cutting conditions were room temperature. Specifically, the catalyst powder was embedded with an epoxy resin, and after the epoxy resin was cured, an ultrathin section was prepared with an ultramicrotome. Using the prepared slices, the dispersion state of various crystal grains was examined by TEM observation. In the obtained image, focus on the contrast (shadow) part, limit the metal type, measure the particle size of the metal, calculate the average value of the measured value, and calculate the average particle size of the noble metal particles It was.

  Furthermore, T50 (NOx) temperature was calculated | required about each catalyst obtained from the said Example 1- Example 14 and Comparative Example 1- Comparative Example 3.

The T50 (NOx) temperature is set at the catalyst position so that each catalyst is installed in the exhaust system of a V-type 6-cylinder engine (manufactured by Nissan Motor Co., Ltd.) with a displacement of 3500cc and the inlet temperature of the catalyst is 700 ° C. And adjusted for 30 hours. At this time, unleaded gasoline was used as fuel. Thereafter, a part of each catalyst was cut out, and each catalyst having a catalyst capacity of 40 cc was incorporated into a simulated exhaust gas distribution device. After that, the model gas having the composition shown in Table 2 was circulated through the simulated exhaust gas distribution device at a gas flow rate of 40 L / min, and the catalyst temperature was increased from room temperature to 400 ° C at a rate of 30 ° C / min. The temperature T at which is 50% was examined.

Table 3 shows the measurement results.

  As shown in Table 3, the performance of the catalyst varies depending on the type of the noble metal, but in each of the examples of the examples using the aggregation inhibitor, compared to the comparative example not using the aggregation inhibitor, It was found that the particle size was small and the T50 temperature was lowered. In particular, in Examples 9 and 10 using Rh as the noble metal, the particle diameter of the noble metal particles after the durability test could be maintained at a small value, and the T50 temperature could be lowered. In addition, catalysts containing transition metal elements such as Mn and Co and elements such as Ce and Zr can maintain the particle size of noble metal particles after endurance testing at a small value and a low T50 temperature. There was found.

  Further, comparing Example 1 to Example 4 in which the same kind of noble metal is used, when the distance X from the support surface, which is the position where the noble metal particles are supported, exceeds 100 nm, the T50 temperature decreases, and the noble metal particles It was found that the aggregation of the particles can be suppressed and the decrease in the activity of the catalyst can be prevented.

1 is a partial cross-sectional view of an exhaust gas purification catalyst according to an embodiment of the present invention. It is a partial cross section figure of the exhaust gas purification catalyst which concerns on other embodiment in this invention. (a) And (b) is a figure explaining the depth X from the support | carrier surface of each exhaust gas purification catalyst shown in FIG.1 and FIG.2.

Explanation of symbols

1 ... Exhaust gas purification catalyst,
2 ... carrier
3 ... Precious metal particles,
4 ... Inclusion material (aggregation suppression material),

Claims (14)

An exhaust gas purification catalyst comprising: a support formed of a porous oxide; a noble metal particle supported inside the pores of the support; and an aggregation inhibitor that suppresses aggregation of the noble metal particle. 2. The exhaust gas purifying catalyst according to claim 1, further comprising at least one of transition metal particles or promoter particles supported inside the pores of the carrier. The exhaust gas purifying catalyst according to claim 1 or 2, wherein the agglomeration suppressing material is an inclusion material that encloses the surfaces of the noble metal particles, transition metal particles, and promoter particles. The exhaust gas purification catalyst according to claim 1 or 2, wherein the aggregation suppressing material is a coating material that covers the pore surface of the carrier. The exhaust gas purification catalyst according to any one of claims 1 to 4, wherein the noble metal particles, transition metal particles, and promoter particles are supported at a depth of 100 nm or more from the support surface. . The exhaust gas purification catalyst according to any one of claims 1 to 5, wherein an average particle diameter of the noble metal particles is 2 nm to 8 nm. The said support | carrier is formed from the metal oxide containing the at least 1 sort (s) of element selected from Al, Zr, Ti, Ce, and Si, The any one of Claim 1 thru | or 6 characterized by the above-mentioned. Exhaust gas purification catalyst. The said aggregation suppression material is formed from the metal oxide containing at least 1 type of element selected from Al, Zr, Ti, Ce, and Si, In any one of Claim 1 thru | or 7 characterized by the above-mentioned. The exhaust gas purification catalyst as described. The exhaust gas purification catalyst according to any one of claims 1 to 8, wherein the noble metal particles include at least one selected from Pt, Pd, and Rh. The exhaust gas purification catalyst according to any one of claims 1 to 9, wherein the transition metal particles include at least one selected from Fe, Co, Ni, and Mn. The exhaust gas purification catalyst according to any one of claims 1 to 10, wherein the promoter particles include at least one selected from La, Ce, and Zr. The exhaust gas purification catalyst according to any one of claims 1 to 11, wherein an average diameter of pores on the surface of the carrier is 30 nm or less. The exhaust gas purification catalyst according to any one of claims 1 to 12, wherein an exposure rate of the noble metal particles is 50% to 90%. An exhaust gas purification catalyst comprising a catalyst layer containing the catalyst according to any one of claims 1 to 13.

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