JP2019103967A - Catalyst for exhaust purification, and method for producing the same, and integrated-structure-type catalyst for exhaust purification - Google Patents

Abstract

To provide a catalyst for exhaust purification having excellent heat resistance as well as excellent catalyst performance after high temperature exposure, and a method for producing the same, and an integrated-structure-type catalyst for exhaust purification or the like.SOLUTION: A catalyst for exhaust purification 100 has a composite particle at least having a base particle 11 that contains a Y-dissolved zirconia oxide and has 1 μm or more and 30 μm or less of an average particle size D, and LaSrFeOδ supported on a surface 11a of the base particle 11 (where, x is the number satisfying 0.25≤x≤0.80, δ shows an oxygen deficiency amount and is the number satisfying 0≤δ≤1).SELECTED DRAWING: Figure 1

Description

The present invention, La on base particles _{(1-x) Sr x FeO} 3-δ catalyst for purifying exhaust gas carried, and a method of manufacturing the same, and a catalytic converter for exhaust gas purification.

  In the purification of hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx) emitted from internal combustion engines such as automobiles, platinum group elements such as platinum, palladium, rhodium, iridium, ruthenium, osmium A three-way catalyst (TWC: Three-Way Catalyst) using PGM: Platinum Group Metal) as a catalytic active component is widely used. However, PGM is relatively expensive, and there are concerns about securing a stable supply over the medium to long term. Therefore, development of a new catalyst material not requiring PGM is being considered.

  For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2005-125317) discloses a carrier containing a ceria-zirconia solid solution having a specific pore diameter and pore volume, and iron oxide as an active species mixed or supported on the carrier. And an oxygen storage and release material characterized by comprising

Patent Document 2 (Japanese Patent Application Laid-Open No. 10-216509) discloses a cerium-based composite oxide of Y solid solution ceria-zirconia Ce _0.6 Zr _0.30 Y _0.10 O _1.95 , and Fe supported on the cerium-based composite oxide. An oxygen storage cerium-based composite oxide is disclosed.

On the other hand, Patent Document 3 (Japanese Patent Application Laid-Open No. 2010-069451) is a spherical particle made of an oxide fired body having a perovskite structure, and the average particle diameter of the particle is in the range of 10 to 50 μm, and the specific surface area is perovskite oxide catalyst lies in the range of 10m ² / g~40m ² / g are disclosed.

Furthermore, exhaust gas purification catalysts in which an alkaline earth metal oxide or an alkali metal is used in combination with the perovskite type complex oxide are being studied. For example, Patent Document 4 (Japanese Unexamined Patent Publication No. 2010-194487) discloses a defective perovskite type complex oxide (BaY _2-x Sc _x O ₄ or BaY _2-x In _x O ₄ ) and an alkaline earth metal oxide ( A NOx purification catalyst is disclosed, which contains BaO) and in which powder diffraction analysis substantially only detects the diffraction pattern of the defective perovskite complex oxide.

On the other hand, Patent Document 5 (WO2014 / 038294) discloses a second catalyst including a first catalyst in which a LaSrFeO ₃ composite oxide having a predetermined particle diameter is supported on an oxide having a predetermined particle diameter capable of absorbing and releasing oxygen, and a noble metal. And an exhaust gas purification catalyst is disclosed.

JP 2005-125317 A Japanese Patent Application Laid-Open No. 10-216509 Unexamined-Japanese-Patent No. 2010-06591 JP, 2010-194487, A WO 2014/038294

  In recent years, in the exhaust gas purification of an internal combustion engine, further improvement of the purification performance of the catalyst is required as the global exhaust gas regulations are strengthened. In addition, to improve the purification performance at the time of so-called cold start immediately after engine start, or to improve the purification performance at the time of use in cold regions, a direct type in which a catalytic converter is disposed directly under an exhaust manifold with high exhaust gas temperature. Adoption of catalytic converters etc. is progressing. Along with this, the exhaust gas purification catalyst is also required to further improve the heat resistance.

Furthermore, the lean environment (oxidative atmosphere), the stoichiometric environment (theoretical air-fuel ratio), and the rich environment (reducing atmosphere) with the advancement of air-fuel ratio (A / F) control to cope with exhaust gas regulations and fuel efficiency improvement. The switching of the processing atmosphere is becoming precise. Here, in the catalyst system of Patent Document 1, iron (Fe) is reduced and generated from iron oxide (Fe ₂ O ₃ ) in a rich environment, and this functions as a highly active active species. However, in fact, in the catalyst system of Patent Document 1, when exposed to a high temperature environment, particles on the support are sintered to grow as particles on the support, and the number of catalytically active sites (particles of active species on the support) is significantly reduced. There is a problem that the catalyst performance is greatly deteriorated after high temperature exposure. That is, the oxygen storage and release material of Patent Document 1 has a large difference between the performance immediately after synthesis (initial performance) and the performance after high temperature exposure (running performance), and the number of catalytically active sites after high temperature exposure is small. Therefore, there is a large room for improvement, and the catalyst is not practical as an exhaust gas purification catalyst used under high temperature environments. These problems also apply to the catalyst system of Patent Document 2 as well.

On the other hand, there is a problem that the perovskite type oxidation catalyst has a small surface area and it is difficult to obtain a desired activity. In order to solve this, in the catalyst system of Patent Document 3, the oxidation catalyst performance of propylene is enhanced by granulating the CaMnO ₃ catalyst to several tens of μm order and securing a predetermined specific surface area. However, the catalyst system of Patent Document 3 still has insufficient catalytic activity sites, and when it is used as an exhaust gas purification catalyst exposed to a high temperature environment, its specific surface area can be maintained even after high temperature exposure. It was difficult and it was not practical as an exhaust gas purification catalyst used under high temperature environment. Furthermore, in the catalyst system of Patent Document 4, although the catalytic activity, particularly the low temperature activity is improved by using an alkaline earth metal oxide or an alkali metal in combination, these have insufficient heat resistance, and the high temperature environment It was not practical as an exhaust gas purification catalyst to be used below.

  Furthermore, the exhaust gas purification catalyst described in Patent Document 5 still has insufficient performance.

  The present invention has been made in view of the above problems. That is, an object of the present invention is to provide an exhaust gas purifying catalyst and a method for producing the same, an exhaust gas purifying catalyst, and the like having not only excellent heat resistance but also excellent catalytic performance even after high temperature exposure.

  The present invention is not limited to the purpose mentioned here, and is an operation and effect derived from each configuration shown in the embodiments for carrying out the invention described later, and it is also possible to exhibit the operation and effect that can not be obtained by the prior art. It can be positioned for other purposes.

  The present inventors diligently studied to solve the above problems. As a result, it has been found that an exhaust gas purification catalyst in which a predetermined composite metal oxide is supported on a predetermined matrix particle has not only excellent heat resistance but also excellent catalytic performance even after high temperature exposure. We came to complete the invention.

That is, the present invention provides various specific embodiments shown below.
<1> Base material particles containing Y solid solution zirconia-based oxide and having an average particle diameter D ₅₀ of 1 μm to 30 μm, and La _(1-x) Sr _x FeO supported on the surface of the base material particles _3-δ (however, x is a number satisfying 0.25 ≦ x ≦ 0.80, δ represents an oxygen deficiency amount, and is a number satisfying 0 ≦ δ ≦ 1.) An exhaust gas purification catalyst characterized by containing composite particles.
<2> The exhaust gas purifying catalyst according to <1>, wherein the composite particles do not substantially contain a noble metal element and a platinum group element.

A <3> catalyst carrier and a catalyst layer provided on at least one surface of the catalyst carrier at least, wherein the catalyst layer at least contains the exhaust gas purifying catalyst according to <1> or <2>. An integrated structure exhaust gas purification catalyst characterized by

A step of applying an aqueous solution containing at least a lanthanum ion, a strontium ion and an iron ion to the surface of a matrix particle containing a <6> Y solid solution zirconia-based oxide and having an average particle diameter D ₅₀ of 1 to 30 μm And the treated base material particles are heat-treated at 500 ° C. or more and 1490 ° C. or less to obtain base material particles containing Y solid solution zirconia-based oxide and La _(1-x supported on the surface of the base material particles ₎ Sr _x FeO _3-δ (where, x is a number satisfying 0.25 ≦ x ≦ 0.80, δ indicates an oxygen deficiency, and is a number satisfying 0 ≦ δ ≦ 1) Obtaining a composite particle having at least the following steps:
The manufacturing method of the catalyst for exhaust gas purification as described in <4> whose content ratio (Fe / La) of Fe with respect to La in <5> said aqueous solution is 1.2 or more and 2.5 or less by molar ratio.
The exhaust gas purification as described in <4> or <5> whose content ratio (Fe / (La + Sr)) of Fe with respect to La and Sr is 0.8-1.5 in molar ratio in <6> said aqueous solution. For producing a catalyst
The manufacturing method of the catalyst for exhaust gas purification as described in any one of <4>-<6> in which the <7> above-mentioned composite particles do not contain a precious metal element and a platinum group element substantially.

  According to the present invention, it is possible to realize an exhaust gas purifying catalyst and a method for producing the same, an exhaust gas purifying catalyst, and the like having excellent heat resistance and excellent catalytic performance even after high temperature exposure. The catalyst for purification of exhaust gas of the present invention is a catalyst particle of a composite structure in which minute catalyst active points are supported on a matrix particle, and based on the composition and structure thereof, NOx, CO, HC, etc. in exhaust gas are reduced. It can be particularly preferably used as a three-way catalyst (TWC: Three-Way Catalyst). In addition, since the catalyst for purifying exhaust gas of the present invention does not need to use a noble metal element (PM) or a platinum group element (PGM) as an essential component, it is also excellent in economy. Moreover, unlike the conventional catalyst using zeolite or the like which is inferior in heat resistance, the exhaust gas purifying catalyst of the present invention can be mounted on an engine-direct catalytic converter, a direct-type catalytic converter in a tandem arrangement, etc. And can reduce the cost of canning.

It is a schematic diagram which shows schematic structure of the exhaust gas purification catalyst 100 of one Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The positional relationship such as upper, lower, left, and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratio in the drawings is not limited to the illustrated ratio. However, the following embodiments are examples for explaining the present invention, and the present invention is not limited to these. That is, the present invention can be implemented with arbitrary modifications without departing from the scope of the invention. In the present specification, for example, the notation of the numerical range “1 to 100” includes both of the upper limit “1” and the lower limit “100”. In addition, the notation of other numerical ranges is the same.

FIG. 1 is a schematic view showing a schematic configuration of an exhaust gas purification catalyst 100 according to an embodiment of the present invention. The exhaust gas purification catalyst 100 contains yttrium solid solution zirconia-based oxide (hereinafter sometimes referred to as "Y solid solution zirconia-based oxide") and has an average particle diameter D ₅₀ of 1 μm to 30 μm. a base material particles 11, the base particles 11 surface 11a supported on the La of _{(1-x) Sr x FeO} 3-δ 21 ( here, x is a number satisfying 0.25 ≦ x ≦ 0.80 Is an oxygen deficiency amount and is a number satisfying 0 ≦ δ ≦ 1. Hereinafter, it may be simply referred to as “LaSrFeO ₃ 21”, which contains composite particles at least It features. The exhaust gas purification catalyst 100 is formed by reducing 31 such as LaFeO ₃ , SrFeO ₃ , iron oxide (FeO or Fe ₂ O ₃ ), iron simple substance (Fe), etc. generated from LaSrFeO ₃ according to the external environment etc. Objects may be included. Each component will be described in detail below.

The Y solid solution zirconia oxide used as the base material particle 11 is excellent in heat resistance, and thus is suitable as a base material of an exhaust gas purification catalyst used in a high temperature environment. In addition, the Y solid solution zirconia-based oxide has a high oxygen exchange rate at a high temperature of 600 ° C. or higher, and is excellent in the response of switching the processing atmosphere of the exhaust gas. Therefore, by using the Y solid solution zirconia-based oxide as the matrix particle 11, oxygen on the surface of the matrix particle is easily activated, and as a result, the catalytic reaction is promoted, and high NOx purification performance can be obtained. Furthermore, in the present catalyst system, there is also a merit that the solid solution of La, Sr or Fe is suppressed as compared to alumina, for example, by using the Y solid solution zirconia-based oxide. In this specification, the zirconia-based oxide, the total amount is one which contains an oxide (ZrO ₂₎ of zirconium in terms of more than 50 wt%. Here, the Y solid solution zirconia-based oxide may contain hafnium (Hf), which is usually contained in an ore of about 1 to 2% by mass, as an unavoidable impurity. The total amount of unavoidable impurities excluding hafnium is preferably 0.3% by mass or less. For example, a part of cerium or zirconium may be substituted by an alkali metal element, an alkaline earth metal element or the like. Further, transition metal elements such as iron (Fe), cobalt (Co), nickel (Ni), titanium (Ti) and copper (Cu) may be contained.

Further, the Y solid solution zirconia-based oxide may be a solid solution of a rare earth element other than Y (hereinafter sometimes referred to as "other rare earth element"). Adjustment of lattice oxygen deficiency (δ) is easy, and Y solid solution zirconia-based oxide further solid-solved with other rare earth elements is used, for example, to improve exhaust gas purification performance and heat resistance, or to support is the La _(1-x) or can improve the dispersibility of the Sr _x FeO 3-δ _21. Here, as the other rare earth elements, cerium, scandium, lanthanum, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium can be mentioned. Among these, cerium (Ce), lanthanum (La), and praseodymium (Pr) are preferable from the viewpoint of stability of the crystal structure, heat resistance, and the like. These other rare earth metals can be used singly or in appropriate combination of two or more. Moreover, when other rare earth elements are contained, the content ratio is not particularly limited, but the total amount in terms of oxides of the rare earth elements listed above with respect to the total amount of Y solid solution zirconia-based oxides (for example, La ₂ O ₃ and the sum of CeO _2, etc.), preferably 40 wt% or more 0.01 wt% or less, more preferably 20 wt% or less than 0.1 wt%.

  Preferred examples of the Y solid solution zirconia-based oxide include Y-Zr-Ox, Y-Nd-Zr-Ox, Y-La-Zr-Ox, Y-Pr-Zr-Ox, and Y-Nd-La-Zr. -Ox, Y-Nd-Pr-Zr-Ox, Y-La-Pr-Zr-Ox, Y-Zr-Ce-Ox, Y-Nd-Zr-Ce-Ox, Y-La-Zr-Ce-Ox Y solid such as Y-Pr-Zr-Ce-Ox, Y-Nd-La-Zr-Ce-Ox, Y-Nd-Pr-Zr-Ce-Ox, Y-La-Pr-Zr-Ce-Ox, etc. Although a solution zirconia is mentioned, it is not limited to these in particular. The Y solid solution zirconia-based oxide can be used singly or in appropriate combination of two or more. Note that these examples are displayed focusing on the combination of the constituent elements contained in the respective oxides, and do not indicate the stoichiometric ratio of each constituent element. That is, the stoichiometry ratio of each constituent element can be arbitrarily adjusted.

Here, the base material particle 11 is 1 μm to 30 μm from the viewpoint of maintaining a large specific surface area to increase the loading amount of LaSrFeO ₃ 21 and increasing the heat resistance to increase the number of catalytic activity sites of its own. preferably it has an average particle diameter D ₅₀ of less, more preferably 1μm or more 15μm or less, more preferably 1μm or more 10μm or less. In the present specification, the average particle diameter D ₅₀ means a median diameter measured by a laser diffraction particle size distribution measuring device (for example, a laser diffraction particle size distribution measuring device SALD-7100 manufactured by Shimadzu Corporation). Do

  As the matrix particles 11, commercially available products of various grades can be used. Moreover, the base material particle 11 which consists of Y solid solution zirconia-type oxide of the various composition mentioned above can also be manufactured by a well-known method in this industry. Although the manufacturing method of Y solid solution zirconia system oxide is not specifically limited, The coprecipitation method and the alkoxide method are preferable.

  As the coprecipitation method, for example, an alkaline substance is added to an aqueous solution in which a zirconium salt, an yttrium salt, and an optional rare earth metal element are mixed at a predetermined stoichiometric ratio to be hydrolyzed or a precursor It is preferable to co-precipitate and calcine the hydrolysis product or co-precipitate. The type of various salts used here is not particularly limited. In general, hydrochloride, oxyhydrochloride, nitrate, oxynitrate, carbonate, phosphate, acetate, oxalate, citrate and the like are preferable. Moreover, the kind of alkaline substance is also not particularly limited. In general, an aqueous ammonia solution is preferred. As the alkoxide method, for example, a method of hydrolyzing a mixture in which zirconium alkoxide, yttrium, and an optional rare earth metal element are mixed at a predetermined stoichiometric ratio, and thereafter firing is preferable. The type of alkoxide used here is not particularly limited. In general, methoxide, ethoxide, propoxide, isopropoxide, butoxide, ethylene oxide adducts thereof and the like are preferable. The rare earth metal element may be blended as a metal alkoxide or may be blended as the various salts described above.

  The firing conditions are not particularly limited according to a conventional method. The firing atmosphere may be any of an oxidizing atmosphere, a reducing atmosphere, and an air atmosphere. The firing temperature and the treatment time vary depending on the desired composition of the Y solid solution zirconia-based oxide and the stoichiometric ratio thereof, but from the viewpoint of productivity etc., generally, it is 1 at 150 ° C. or more and 1300 ° C. or less 12 hours are preferable, More preferably, it is 2 to 4 hours by 350 degreeC or more and 800 degrees C or less. In addition, it is preferable to perform reduced-pressure drying using a vacuum dryer etc. prior to high-temperature baking, and to perform a drying process at about 50 to 200 ° C. for about 1 to 48 hours.

The exhaust gas purification catalyst 100 of the present embodiment has one feature in that it has a structure of composite particles in which LaSrFeO ₃ 21 is supported on the surface 11 a of the base material particle 11 described above. Typically, the exhaust gas purifying catalyst 100, the microparticles of LaSrFeO ₃ 21 is, fine particles of derivative 31, further described above by the external environment (e.g., LaFeO ₃ or SrFeO _3, reduction products, such as iron oxide or iron alone) Have a composite structure attached to the surface 11 a of the matrix particle 11 in a highly dispersed manner. By employing such a composite particle structure, in the exhaust gas purification catalyst 100, the deterioration of the catalyst performance after exposure to high temperature is largely suppressed. The reason is not clear, but LaSrFeO ₃ 21 has fine particles of derivatives (eg, LaFeO ₃ , SrFeO ₃ , iron oxide, iron (Fe simple substance), etc.) on the surface 11 a of the matrix particle 11 according to the external environment. These fine particles are dispersed among the fine particles of LaSrFeO ₃ 21. Therefore, it is presumed that the presence of these fine particles reduces the chance of contact between LaSrFeO ₃ 21, thereby inhibiting the sintering and grain growth of LaSrFeO ₃ 21 due to high temperature exposure.

In addition, the presence of LaSrFeO ₃ 21 on the base material particle 11 is observed by a scanning transmission electron microscope (STEM), powder X-ray diffraction (XRD: X-ray Diffraction, for example, 2θ = 32.2 °) (110) peak of LaSrFeO _{3 in} the vicinity, (110) peak of LaSrFeO ₃ near 2θ = 32.1 °, etc., electron probe micro analyzer (EPMA: Electron Probe Micro Analyzer), X-ray photoelectric spectroscopy (XPS: X) It can be grasped by various measurement methods such as -ray Photoelectron Spectroscopy or ESCA (Electron Spectroscopy for Chemical Analysis).

Further, LaSrFeO ₃ (and LaFeO ₃ and SrFeO ₃ ) is an oxide capable of having a perovskite crystal structure. The catalytic action of the exhaust gas purification by this LaSrFeO ₃ 21 exhibits catalytic activity over the whole range of lean environment to stoichiometric environment to rich environment. Although the reason is not clear, LaSrFeO ₃ 21 itself not only functions as a catalytically active component, but also the above-mentioned various derivatives generated according to the external environment also function as a catalytically active component, and reduction In the state, Fe (a single substance) which is a highly active species is present, and it is therefore presumed to be due to exhibiting particularly strong catalytic activity in a stoichiometric environment to a rich environment. As a result of combining these, the catalyst 100 for exhaust gas purification of the present embodiment reinforces the catalytic action of exhaust gas purification over the whole range of lean environment to stoichiometric environment to rich environment, and as a result, noble metal elements (PM) and platinum group elements ( Excellent exhaust gas purification performance is exhibited even though PGM) is not used as an essential component.

Here, LaSrFeO ₃ 21 preferably has an average crystallite diameter of 1 nm or more and 80 nm or less, more preferably 10 nm or more and 70 nm or less, from the viewpoints of enhancing the catalytic activity and inhibiting sintering and grain growth. Is 20 nm or more and 65 nm or less. The average crystallite of LaSrFeO ₃ 21 can be calculated, for example, from the XRD diffraction pattern of the exhaust gas purifying catalyst 100 after the durability treatment. By causing LaSrFeO ₃ 21 having such a fine particle size to be present on the surface 11 a of the matrix particle 11, the surface area tends to be maintained at a higher level, and a large number of catalytically active sites tend to be maintained.

The term "crystallite" generally refers to the largest group that can be regarded as a single crystal, and the size of the crystallite is called the crystallite diameter. Moreover, in the present specification, the average crystallite size is a value obtained by measuring a diffraction pattern using an X-ray diffractometer, and based on the measurement result, the value calculated by the Scherrer formula represented by the following formula (2). Do.
Crystallite diameter D (Å) = K · λ / (β · cos θ) (2)
In Formula (2), K is a Scherrer constant, and it is referred to as K = 0.9 here. Further, λ is the wavelength of the X-ray tube used, β is the half width, and θ is the diffraction angle (rad).

Here, in the exhaust gas purifying catalyst 100 of the present embodiments, x represented the La in _{(1-x) Sr x FeO} 3 illustrates the relative proportion of the Sr and Ln. Although x is not particularly limited, it is preferably 0.25 or more and 0.80 or less, more preferably 0.30 or more and 0.75 or less from the viewpoint of obtaining a high-performance catalyst excellent in heat resistance and catalyst performance after high temperature exposure. Or less, more preferably 0.35 or more and 0.70 or less.

Further, the content of LaSrFeO ₃ 21 in the exhaust gas purification catalyst 100 is not particularly limited, but from the viewpoint of improving the catalyst performance over the whole range of lean environment to stoichiometric environment to rich environment, the total amount of exhaust gas purification catalyst 100 The amount is preferably 1% by mass to 30% by mass, more preferably 3% by mass to 25% by mass, and still more preferably 5% by mass to 20% by mass.

Incidentally, in the exhaust gas purifying catalyst 100 of the present embodiment, LaSrFeO ₃ 21 described above, further LaFeO ₃ or SrFeO ₃ a derivative thereof, iron oxide _{(Fe 2 O 3, Fe 3} O 4, FeO) , iron ( In addition to Fe alone, oxides of rare earth elements or transition metal elements other than La, Sr and Fe described above (hereinafter sometimes referred to as “other rare earth elements” or “other transition metal elements”) Etc. may be present on the matrix particles 11. Other rare earth elements include, but are not particularly limited to, cerium, scandium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium and the like. Moreover, although other transition metal elements include chromium, cobalt, nickel, titanium, manganese, tungsten, copper and the like, they are not particularly limited thereto.

On the other hand, when the exhaust gas purification catalyst 100 of the present embodiment contains iron oxide, the content of iron oxide is not particularly limited, but the total amount of the exhaust gas purification catalyst 100 from the viewpoint of improving catalyst performance and low temperature activity. On the other hand, 0.05 mass% or more and 10 mass% or less is preferable, more preferably 0.1 mass% or more, in terms of Fe ₂ O _{3 in} total of three kinds of Fe ₂ O ₃ , Fe ₃ O ₄ and FeO. It is 8% by mass or less, more preferably 1.0% by mass or more and 6% by mass or less.

  The exhaust gas purification catalyst 100 according to the present embodiment includes gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), and osmium (Os). And the like, they have excellent heat resistance without using noble metal elements (PM) and platinum group elements (PGM) as essential components, and have excellent catalytic performance even after high temperature exposure. Therefore, from the viewpoint of economy and stable supply, etc., an exhaust gas purification catalyst 100 substantially containing no precious metal element (PM) and platinum group element (PGM) can be mentioned as one preferred embodiment. Here, the term "does not substantially contain" means that the total amount of the noble metal element (PM) and the platinum group element (PGM) is in the range of 0 mass% or more and less than 1.0 mass% with respect to the total mass of the exhaust gas purifying catalyst 100. More preferably, it is 0% by mass or more and less than 0.5% by mass, and more preferably 0% by mass or more and less than 0.3% by mass.

The shape of the exhaust gas purification catalyst 100 is not particularly limited. The catalyst powder which is an aggregate of catalyst particles in which LaSrFeO ₃ 21 is supported on the matrix particles 11 can be used as it is. Also, for example, this catalyst powder can be formed into an arbitrary shape to make a granular or pellet-like formed catalyst. Furthermore, the exhaust gas purification catalyst 100 can be held (carried) on a catalyst carrier and used as a monolithically structured exhaust gas purification catalyst. As a catalyst carrier used here, those known in the art can be appropriately selected. Typical examples include ceramic monolith carriers such as cordierite, silicon carbide and silicon nitride, metal honeycomb carriers such as stainless steel, wire mesh carriers such as stainless steel, and knitted conductors such as steel wool. It is not particularly limited. In addition, the shape is also not particularly limited, and, for example, one having an arbitrary shape such as a prismatic shape, a cylindrical shape, a spherical shape, a honeycomb shape, or a sheet shape can be selected. These can be used singly or in appropriate combination of two or more.

  The exhaust gas purifying catalyst 100 described above can be used as a catalyst for purifying exhaust gases such as diesel engines, gasoline engines, jet engines, boilers, gas turbines, etc. For example, exhaust gas purifying catalysts for internal combustion engines, especially automotive exhaust gases It is useful as a purification catalyst.

The method for producing the exhaust gas purifying catalyst 100 of the present embodiment is not particularly limited as long as the configuration in which LaSrFeO ₃ 21 is supported on the base material particles 11 is obtained as described above. From the viewpoint of producing the exhaust gas purifying catalyst 100 having the above-described structure with high reproducibility and at low cost, evaporation to dryness (impregnation method) or the like is preferable.

  As the evaporation to dryness method, a production method is preferable in which the above-described base material particles 11 are impregnated with an aqueous solution containing at least lanthanum ions, strontium ions and iron ions, and then firing is carried out. By this impregnation treatment, lanthanum ions, strontium ions and iron ions are adsorbed (adhered) to the surface 11 a of the matrix particle 11 in a highly dispersed state. Here, the lanthanum ion, the strontium ion and the iron ion can be blended into the aqueous solution as various salts. The type of various salts used here is not particularly limited. Generally, sulfates, hydrochlorides, oxyhydrochlorides, nitrates, oxynitrates, carbonates, phosphates, chlorides, oxides, complex oxides, complexes, acetates, oxalates, citrates, etc. Is preferred.

  After the impregnation treatment, solid-liquid separation treatment, water washing treatment, for example, drying treatment for removing water at a temperature of about 50 ° C. or more and 200 ° C. or less in the atmosphere can be performed according to a conventional method as needed. The drying process may be natural drying, or a dryer such as a drum dryer, a vacuum dryer, or a spray dryer may be used. Further, the atmosphere for the drying treatment may be in the air, in vacuum, or in an inert gas atmosphere such as nitrogen gas. In addition, before and / or after drying, pulverization treatment, classification treatment and the like may be performed as necessary.

The firing conditions are not particularly limited according to a conventional method. A heating means is not specifically limited, For example, well-known apparatuses, such as an electric furnace and a gas furnace, can be used. The firing atmosphere is preferably an oxidizing atmosphere or an air atmosphere. The firing temperature and the treatment time vary depending on the desired composition and the stoichiometry ratio, but from the viewpoints of formation of LaSrFeO ₃ 21 and productivity etc., it is generally 0.1 at a temperature of 500 ° C. to 1490 ° C. 12 hours are preferable, More preferably, it is 0.5 to 6 hours at 550 degreeC or more and 800 degrees C or less. Prior to high-temperature firing, drying under reduced pressure may be performed using a vacuum dryer or the like, and drying may be performed at 50 ° C. to 200 ° C. for about 1 to 48 hours. As a result of this baking process, LaSrFeO ₃ 21 highly dispersed in nano-order size and, depending on the processing conditions, further, LaFeO ₃ and various kinds of iron oxide and fine particles of iron single substance etc. are formed on the surface 11 a of the matrix particle 11 (synthesis ).

  The content ratio (Fe / La) of La and Fe in the aqueous solution can be appropriately adjusted, and is not particularly limited. However, the catalytic activity of the obtained exhaust gas purifying catalyst 100 is further enhanced, and sintering and particle growth are inhibited to high temperature From the viewpoint of suppressing deterioration of the catalyst performance after exposure, the content ratio of Fe to La in the aqueous solution (Fe / La) is preferably 1.2 or more, more preferably 1 in terms of molar ratio of La and Fe. .3 or more, more preferably 1.4 or more. The upper limit of Fe / La is not particularly limited, but is preferably 2.5 or less, more preferably 2.3 or less, and still more preferably 2.1 or less.

  Similarly, the content ratio of Fe to La and Sr (Fe / (La + Sr)) in the aqueous solution can be appropriately adjusted, and is not particularly limited. However, while the catalyst activity of the resulting exhaust gas purifying catalyst 100 is further enhanced, sintering and From the viewpoint of inhibiting grain growth and suppressing deterioration of the catalyst performance after high temperature exposure, 0.8 or more and 1.5 or less are preferable in molar ratio conversion of La, Sr and Fe, and more preferably 0.9 or more. It is 4 or less, more preferably 0.95 or more and 1.3 or less.

  The aqueous solution may contain, if necessary, rare earth elements such as cerium, scandium, lanthanum, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. It may contain an alkali metal element such as sodium and potassium, an alkali earth metal element such as beryllium, magnesium, calcium, strontium and barium, and a transition metal element such as cobalt, nickel, titanium and copper. In addition, these can be used individually by 1 type or in combination of 2 or more types suitably. These rare earth elements, alkali metal elements, alkaline earth metal elements and transition metal elements are supplied to the aqueous solution as inorganic acid salts such as sulfates, nitrates, acetates, chlorides, oxides, complex oxides, and complex salts etc. can do.

  The exhaust gas purification catalyst 100 thus obtained can be used as a powder which is an aggregate of catalyst particles, and can be mixed with a catalyst, a cocatalyst, a catalyst carrier known in the art, and additives known in the art. Can be used. Furthermore, the exhaust gas purifying catalyst 100 can be used as a particulate or pellet-like formed body (formed catalyst) by previously preparing a composition containing the same, forming the composition into an arbitrary predetermined shape. In addition, at the time of preparation of a molded object, various known dispersing devices, kneading devices, and molding devices can be used. Here, when used as a molded body, the content of the exhaust gas purifying catalyst 100 in the molded body is not particularly limited, but 10% by mass to 99% by mass is preferable, and 20% by mass to 99% by mass is preferable. % Or less, more preferably 30% by mass or more and 99% by mass or less.

  Examples of known catalysts, co-catalysts and catalyst carriers that can be used in combination include, for example, metal oxides such as silica, alumina, ceria, zirconia, ceria-zirconia, lanthanum oxide, neodymium oxide, praseodymium oxide and the like, metal complex oxides; Composite oxides such as zirconia or ceria-zirconia doped with an element and / or transition element; perovskite oxides; composite oxides including alumina such as silica-alumina, silica-alumina-zirconia, silica-alumina-boria; Although a barium compound, a zeolite, etc. are mentioned, it is not specifically limited to these. The use ratio of the catalyst, co-catalyst and catalyst support to be used in combination can be appropriately set according to the required performance and the like, and is not particularly limited, but preferably 0.01 to 20 mass% in total with respect to the total amount A total of 0.05% to 10% by mass is more preferable, and a total of 0.1% to 8% by mass is more preferable.

  In addition, examples of additives that can be used in combination include various binders, dispersion stabilizers such as nonionic surfactants and anionic surfactants, pH adjusters, viscosity adjusters, etc., but are not particularly limited thereto. . The binder includes, but is not particularly limited to, various sols such as alumina sol, titania sol, silica sol, and zirconia sol. In addition, soluble salts such as aluminum nitrate, aluminum acetate, titanium nitrate, titanium acetate, zirconium nitrate and zirconium acetate can also be used as the binder. In addition, acids such as acetic acid, nitric acid, hydrochloric acid and sulfuric acid can also be used as the binder. In addition, the usage-amount of a binder is not specifically limited, What is necessary is just the quantity of the extent required for maintenance of a molded object. In addition, the use ratio of the additive mentioned above can be set suitably according to required performance etc., Although it is not limited in particular, 0.01-20 mass% is preferable in total with respect to the total amount, 0.05-10 mass in total % Is more preferable, and in total, 0.1 to 8% by mass is more preferable.

  The exhaust gas purification catalyst 100 obtained as described above may further support a noble metal element or a platinum group element as necessary. A known method can be applied to the method of supporting the noble metal element and the platinum group element, and is not particularly limited. For example, a solution of a salt containing a noble metal element or a platinum group element is prepared, the catalyst for exhaust gas purification 100 is impregnated with the salted solution, and then the noble metal element or the platinum group element is supported by firing. it can. The salt-containing solution is not particularly limited, but is preferably a nitrate aqueous solution, a dinitrodiammine nitrate solution, a chloride aqueous solution and the like. Also, the baking treatment is not particularly limited, but is preferably at about 350 ° C. to 1000 ° C. for about 1 to 12 hours. In addition, it is preferable to perform reduced-pressure drying using a vacuum dryer etc. prior to high-temperature baking, and to perform a drying process at about 50 to 200 ° C. for about 1 to 48 hours.

  The integrated structural catalyst described above is a catalyst member (laminated catalyst member) of a laminated structure provided with at least a catalyst carrier and a catalyst layer provided on at least one surface of the catalyst carrier. Adoption of such a configuration increases the applicability to various applications, such as facilitating incorporation into a device. For example, in exhaust gas purification applications, a honeycomb structure carrier or the like is used as a catalyst carrier, and this integral structure type catalyst is installed in a flow path through which the gas flow passes, and the gas flow is allowed to pass through the cells of the honeycomb structure carrier. The exhaust gas purification can be performed with high efficiency.

  Here, in the present specification, “provided on at least one side of the catalyst support” means any other layer (eg, primer layer, adhesive layer) between one side of the catalyst support and the catalyst layer. Etc. is meant to encompass the embodiment in which the That is, in the present specification, “provided on one side” means an embodiment in which the catalyst support and the catalyst layer are directly mounted, and the catalyst support and the catalyst layer are separated via any other layer. It is used in the meaning including both of the aspect arrange | positioned. In addition, the catalyst layer may be provided only on one surface of the catalyst carrier, or may be provided on a plurality of surfaces (for example, one main surface, the other main surface, etc.).

  The monolithic structural catalyst having the above-described layer configuration can be produced according to a conventional method. For example, it can be obtained by coating (supporting) the catalyst for exhaust gas purification described above on the surface of a catalyst carrier. Specifically, the above-mentioned catalyst for purification of exhaust gas, aqueous medium, and, if necessary, a binder, another catalyst, cocatalyst, OSC material, base material particles, additives and the like known in the art are contained in desired proportions. It is preferable to use a method of mixing to prepare a slurry-like mixture, applying the obtained slurry-like mixture to the surface of a catalyst carrier such as a honeycomb structure carrier, drying, and calcining. At this time, it is preferable to use the above-described binder or the like in order to firmly attach or bond the above-mentioned catalyst for exhaust gas purification to a support.

  The aqueous medium used when preparing the slurry-like mixture may be used in such an amount that the exhaust gas purification catalyst can be uniformly dispersed in the slurry. At this time, it is possible to blend an acid or a base for pH adjustment as needed, or to blend a surfactant, a dispersing resin or the like for viscosity adjustment or slurry dispersibility improvement. As a method of mixing the slurry, known grinding methods or mixing methods such as grinding and mixing with a ball mill etc. can be applied. In applying the slurry-like mixture onto the catalyst carrier, various known coating methods, wash coat methods and zone coat methods can be applied according to a conventional method.

  After the slurry-like mixture is applied onto the catalyst carrier, drying and calcination are performed according to a conventional method, whereby the monolithic structural catalyst of the present embodiment can be obtained. In addition, although a drying temperature is not specifically limited, For example, 70-200 degreeC is preferable, and 80-150 degreeC is more preferable. Moreover, although a calcination temperature is not specifically limited, For example, 300-650 degreeC is preferable, and 400-600 degreeC is more preferable. About the heating means used at this time, it can carry out by well-known heating means, such as an electric furnace and a gas furnace, for example.

  In the integrated structural catalyst described above, the layer configuration of the catalyst layer may be either a single layer or a multiple layer, but in the case of automotive exhaust gas applications, catalyst performance is considered taking into consideration trends in exhaust gas regulation, etc. From the viewpoint of increasing the thickness, a laminated structure of two or more layers is preferable. At this time, the total coating amount of the exhaust gas purifying catalyst described above is not particularly limited, but is preferably 20 to 350 g / L, and more preferably 50 to 300 g / L from the viewpoint of balance of catalyst performance and pressure loss.

  In automotive exhaust gas applications, the exhaust gas purifying catalyst and the integrated structural catalyst described above can be disposed in the exhaust system of various engines. The installation number and installation location can be suitably designed according to exhaust gas regulation. For example, in the case where exhaust gas regulations are strict, the installation location may be two or more, and the installation location may be located at a position under the floor just behind the catalyst just below the exhaust system.

  EXAMPLES The features of the present invention will be more specifically described below with reference to test examples, examples and comparative examples, but the present invention is not limited thereto. That is, the materials, amounts used, proportions, treatment contents, treatment procedures and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. The values of various manufacturing conditions and evaluation results in the following examples have meanings as preferable upper limit values or preferable lower limit values in the embodiment of the present invention, and the preferable range is the value of the upper limit or the lower limit described above. And a range defined by a combination of the values of the following examples or the values of the examples.

Example 1
As matrix particles, Y solid solution zirconia-based oxide (described as Y-ZrO ₂ , Y ₂ O ₃ : 35 mass%, ZrO ₂ : 65 mass%, D ₅₀ = 6.4 μm, BET specific surface area: 72 m ² / g) was used. In the present specification, the BET specific surface area refers to a specific surface area / pore distribution measuring device (trade name: BELSORP-mini II, manufactured by Microtrac Bell Co., Ltd.) and analysis software (trade name: BEL_Master, Microtrac, It means a value obtained by BET single point method using Bell Co., Ltd.).
Next, lanthanum nitrate hexahydrate, strontium nitrate, and iron nitrate nonahydrate are dissolved in water, and the molar ratio of each oxide (La ₂ O ₃ , SrO, Fe ₂ O ₃ ) is converted to 0. An aqueous solution 1 was prepared containing .031 mol La, 0.031 mol Sr, and 0.047 mol Fe.
Impregnated with the aqueous solution 1 to the base particles by 30min calcined at 600 ℃, La _(1-x powder catalyst (x = 0.33 in Example 1) Sr _x FeO _3-δ is 14.07 Mass% supported Y-ZrO ₂ powder catalyst, La content in La ₂ O ₃ conversion: 6.80 mass%, Sr content in SrO conversion: 2.13 mass%, Fe content in Fe ₂ O ₃ conversion : 5.00 mass%) was obtained.
The obtained powder catalyst of Example 1 was dispersed in water, milled with a pot mill, and ground until D ₅₀ = 4.1 μm, to obtain a catalyst slurry. This catalyst slurry is coated on a cordierite honeycomb carrier of 600 cpsi and 3.5 mil by the wash coat method and then dried to provide a catalyst layer, whereby 150 g of catalyst is supported per liter of honeycomb carrier volume. A honeycomb catalyst (exhaust gas purification catalyst, integral structural catalyst) of 1 was obtained.
Thereafter, the obtained honeycomb catalyst was subjected to high temperature exposure treatment (durability treatment) in an endurance furnace. In addition, as high temperature exposure processing, heat processing for 6 hours was performed at 980 ° C. while repeatedly switching the external atmosphere to A / F = 12.8 and the oxygen atmosphere sequentially.

(Example 2)
Dissolve lanthanum nitrate hexahydrate, strontium nitrate, and iron nitrate nonahydrate in water, and convert 0.024 mol of each oxide (La ₂ O ₃ , SrO, Fe ₂ O ₃ ) in terms of molar ratio. An aqueous solution 2 was prepared containing La, 0.046 mol Sr, and 0.047 mol Fe.
A powder catalyst and a catalyst for purifying an exhaust gas of Example 2 (La _(1-x) Sr _x FeO _{3 with} x = 0.49 _{) in the same} manner as in Example 1 except that the aqueous solution 2 is used instead of the aqueous solution 1 Y-ZrO ₂ powder catalyst supported at 13.56% by mass, _δ content of La ₂ O ₃ equivalent: 5.13% by mass, Sr content equivalent to SrO: 3.20% by mass, Fe ₂ O Fe content in ₃ conversions: 5.00% by mass) was obtained.

(Reference Example 1)
Lanthanum nitrate hexahydrate and ferric nitrate nonahydrate are dissolved in water, and 0.033 mol of La in terms of molar ratio of respective oxides (La ₂ O ₃ , Fe ₂ O ₃ ), and 0. An aqueous solution 3 containing 047 mol of Fe was prepared.
A powder catalyst and a catalyst for purification of exhaust gas of Reference Example 1 (La _(1-x) Sr _x FeO _{3 with} x = 0.00 _{) of} the reference example 1 are used except that the aqueous solution 3 is used instead of the aqueous solution 1. Y-ZrO ₂ powder catalyst supported by 10.63% by mass of _-δ , La content in La ₂ O ₃ conversion: 7.13% by mass, Fe content in Fe ₂ O ₃ conversion: 5.00% by mass) I got

(Comparative example 1)
Lanthanum nitrate hexahydrate, strontium nitrate, iron nitrate nonahydrate are dissolved in water, and the molar ratio of the respective oxides (La ₂ O ₃ , SrO, Fe ₂ O ₃ ) is converted to 0.039 mol An aqueous solution 4 was prepared containing La, 0.016 mol Sr, and 0.047 mol Fe.
A powder catalyst of Comparative Example 1 and a catalyst for exhaust gas purification (La _(1-x) Sr _x FeO _{3 of} x = 0.17, except that this aqueous solution 4 is used instead of the aqueous solution 1 ₎ Y-ZrO ₂ powder catalyst supported at 14.71% by mass, _δ content of La ₂ O ₃ equivalent: 8.53% by mass, Sr content equivalent to SrO: 1.08% by mass, Fe ₂ O Fe content in ₃ conversions: 5.00% by mass) was obtained.

<Powder X-ray diffraction measurement>
Using the X-ray diffractometer (trade name: X'Pert PRO MPD, manufactured by Yamato Scientific Co., Ltd.), the catalyst layer of the honeycomb catalyst after the durability treatment of Example 1, Reference Example 1, and Comparative Example 1 was about 0. A 1 mg sample was collected, and powder X-ray diffraction measurement was performed under the following conditions. In Example 1, an intrinsic peak (131) of the LaSrFeO ₃ crystal was confirmed around 2θ = 32.0 °. On the other hand, in Reference Example 1 and Comparative Example 1, specific peak of LaSrFeO ₃ crystal in the vicinity of 2θ = 32.0 ° (131) not observed, intrinsic peak of LaFeO ₃ crystal in the vicinity of 2θ = 32.3 ° (002) Was confirmed.
Target: Cu
K-Alpha 1 [A]: 1.5406
X-ray output setting: 40 mA, 45 kV

<Measurement of average crystallite diameter>
Further the calculated average crystallite diameter of the above formula (2) based on _{La (1-x) Sr x} FeO 3-δ particles, La _(1-x) of the exhaust gas purifying catalyst of Example 1 Sr _x FeO The average crystallite diameter of the _three particles was 29.1 nm. On the other hand, the average crystallite diameter of the LaFeO ₃ particles of the catalyst for exhaust gas purification of Reference Example 1 was 63.1 nm. In addition, calculation by the Scheller method is based on the strong peak (131) in the vicinity of 2θ = 32.0 ° and the strong peak (002) in the vicinity of 2θ = 32.3 ° as described above. It carried out using X'Pert High Score Plus 3.0).

<Measurement of exhaust gas purification rate (HC, CO, NOx)>
The powder catalysts of Examples 1 to 2 and Reference Example 1 and Comparative Example 1 thus obtained are each coated on a honeycomb carrier by a wash coat method and dried to form a catalyst layer, and then subjected to high temperature exposure treatment in a durability furnace ( Durability treatment was carried out, and catalyst samples for exhaust gas purification (integral structure type catalyst) were produced respectively. In addition, as high temperature exposure processing, heat processing for 6 hours was performed at 980 ° C. while repeatedly switching the external atmosphere to A / F = 12.8 and the oxygen atmosphere sequentially.
[Preparation conditions]
Honeycomb carrier: Corning International, φ 1 inch x 50 mm L (25 cc), 600 cpsi / 3.5 mil
Catalyst loading amount: 150 g / L

Thereafter, the core sample taken out of the electric furnace was set in a model gas reactor. The exhaust gas purification rate analyzes the gas on the catalyst outlet side using a model gas of the following composition, and the formula of “purification rate (%) = 100 * (INLET gas concentration−catalyst OUT gas concentration) ÷ INLET gas concentration” Calculated based on
[Model gas evaluation conditions]
Model gas unit: SIGU 4012 HORIBA Analyzer: MEXA-7100 HORIBA Catalyst Inlet temperature: 600 ° C
Gas composition: CO ₂ = 14.00%, O ₂ = 0.49%, NO = 0.05%, CO = 0.50%,
H ₂ = 0.17%, iso-C ₅ H ₁₂ = 0.01%, C ₃ H ₆ = 0.02%,
H ₂ O = 10.00%, N ₂ balance
A / F perturbation = ± 14.7 ± 0.6, 1 Hz (adjusted with Rich = CO, Lean = O ₂ )

  Table 1 shows the measurement results of the exhaust gas purification rate. The integrated structural catalysts of Examples 1 and 2 corresponding to the present invention were compared to the integrated structural catalysts of Reference Example 1 and Comparative Example 1 in any of the CO purification rate, HC purification rate, and NOx purification rate. It was confirmed that the performance was significantly improved.

  INDUSTRIAL APPLICABILITY The present invention can be widely and effectively used as a catalyst for reducing NOx, CO, HC, etc. in exhaust gas, and in particular, an engine direct type catalytic converter requiring heat resistance and a direct type catalytic converter etc. in tandem arrangement. It can be used particularly effectively as a three-way catalyst (TWC: Three-Way Catalyst).

11 · · · Base material particle 11a · · · surface 21 · · · LaSrFeO ₃
31 ··· Derivative 100 ··· Catalyst for exhaust gas purification

Claims (7)

Matrix particles containing Y solid solution zirconia-based oxide and having an average particle diameter D ₅₀ of 1 μm to 30 μm,
Carried on the surface of the base _{particles, La (1-x) Sr} x FeO 3- δ (However, x is a number satisfying 0.25 ≦ x ≦ 0.80, δ indicates an oxygen deficiency, and is a number satisfying 0 ≦ δ ≦ 1.)
An exhaust gas purification catalyst comprising composite particles having at least The exhaust gas purification catalyst according to claim 1, wherein the composite particles do not substantially contain a noble metal element and a platinum group element. A catalyst carrier,
At least a catalyst layer provided on at least one surface side of the catalyst support,
The catalyst layer at least contains the exhaust gas purification catalyst according to claim 1 or 2,
Monolithic exhaust gas purification catalyst. Applying an aqueous solution containing at least a lanthanum ion, a strontium ion and an iron ion to the surface of a matrix particle containing Y solid solution zirconia-based oxide and having an average particle diameter D ₅₀ of 1 μm to 30 μm; The subsequent base material particles are heat-treated at 500 ° C. or more and 1490 ° C. or less, and base material particles containing Y solid solution zirconia-based oxide and La _(1-x) Sr _x supported on the surface of the base material particles FeO _3- δ (Where x is a number satisfying 0.25 ≦ x ≦ 0.80, δ is an oxygen deficiency, and is a number satisfying 0 ≦ δ ≦ 1). When,
At least comprising
Method for producing a catalyst for exhaust gas purification. The method for producing an exhaust gas purification catalyst according to claim 4, wherein a content ratio (Fe / La) of Fe to La in the aqueous solution is 1.2 or more and 2.5 or less in molar ratio. The method for producing an exhaust gas purification catalyst according to claim 4 or 5, wherein the content ratio (Fe / (La + Sr)) of Fe to La and Sr in the aqueous solution is 0.8 or more and 1.5 or less in molar ratio. . The method for producing an exhaust gas purification catalyst according to any one of claims 4 to 6, wherein the composite particles contain substantially no noble metal element and no platinum group element.