JP2019166450A - Exhaust gas purification catalyst, method for manufacturing the same and integral structure type exhaust gas purification catalyst - Google Patents

Abstract

To provide an exhaust gas purification catalyst not only excellent in heat resistance, but also excellent in catalyst performance even after high temperature exposure; a method for manufacturing the same; and an integral structure type exhaust gas purification catalyst.SOLUTION: An exhaust gas purification catalyst 100 comprises composite particles including at least: base material particles 11 including a rare earth solid solution zirconia based oxide and having an average particle size Dof 1 μm or more and 30 μm or less; and SrFeO(where, δ shows the amount of oxygen deficiency and satisfies 0≤δ≤0.5.) carried on the surface 11a of the base material particle 11 and used as perovskite type catalytic activity particles 21. The exhaust gas purification catalyst 100 may further include FeO(where, δ shows the amount of oxygen deficiency and satisfies 0≤δ≤1) carried on the surface 11a of the base material particle 11.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust gas purification catalyst in which perovskite-type catalytically active particles are supported on base material particles, a manufacturing method thereof, and an exhaust gas purification catalyst converter.

  Platinum group elements such as platinum, palladium, rhodium, iridium, ruthenium, and osmium in the purification of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) emitted from internal combustion engines such as automobiles A three-way catalyst (TWC) using PGM (Platinum Group Metal) as a catalytically 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 that does not require PGM is being studied.

  For example, Patent Document 1 (Japanese Patent 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 / release material characterized by comprising:

Patent Document 2 (Japanese Patent 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) discloses spherical particles made of an oxide fired body having a perovskite structure, the average particle diameter of which is in the range of 10 to 50 μm, and the specific surface area. perovskite oxide catalyst lies in the range of 10m ² / g~40m ² / g are disclosed.

Furthermore, exhaust gas purification catalysts in which alkaline earth metal oxides or alkali metals are used in combination with perovskite complex oxides have been studied. For example, Patent Document 4 (JP 2010-194487), a defect perovskite-type composite oxide _{(BaY 2-x Sc x O} 4 or _{BaY 2-x In x O 4} ) and alkaline earth metal oxides ( NOO purification catalyst is disclosed in which, in powder X-ray diffraction, substantially only the diffraction pattern of the defect perovskite complex oxide is detected in powder X-ray diffraction.

On the other hand, Patent Document 5 (WO2014 / 038294) discloses a second catalyst comprising 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 having oxygen absorption / release capacity and a noble metal. And an exhaust gas purifying catalyst is disclosed.

JP 2005-125317 A Japanese Patent Laid-Open No. 10-216509 JP 2010-069451 A JP 2010-194487 A WO2014 / 038294

  In recent years, in exhaust gas purification of internal combustion engines, further improvement in catalyst purification performance has been demanded as global exhaust gas regulations are strengthened. In order to improve the purification performance at the time of so-called cold start immediately after the engine is started or to improve the purification performance at the time of use in a cold region, a catalytic converter is disposed directly under the exhaust manifold where the exhaust gas temperature is high. Adoption of catalytic converters is progressing. Along with this, further improvement in heat resistance has been required for exhaust gas purification catalysts.

Furthermore, with the advancement of air-fuel ratio (A / F) control to meet exhaust gas regulations and fuel efficiency improvements, the lean environment (oxidizing atmosphere), stoichiometric environment (theoretical air-fuel ratio), and rich environment (reducing atmosphere) The switching of the processing atmosphere has become more precise. Here, in the catalyst system of Patent Document 1, iron (Fe) is reduced and produced from iron oxide (Fe ₂ O ₃ ) in a rich environment, and this functions as a highly active active species. However, in actuality, when the catalyst system of Patent Document 1 is exposed to a high temperature environment, the particles on the support grow to a large particle size of 300 nm or more by sintering, and the catalyst active site (active species particles on the support). ) Was significantly reduced, and the catalyst performance was greatly deteriorated after high temperature exposure. That is, the oxygen storage / 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 lot of room for improvement, and it was poor in practicality as an exhaust gas purification catalyst used in a high temperature environment. These problems also apply to the catalyst system of Patent Document 2.

On the other hand, the perovskite type oxidation catalyst has a problem that it 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 CaMnO ₃ catalyst is granulated to the order of several tens of μm, and a predetermined specific surface area is ensured to improve the oxidation catalyst performance of propylene. However, since the catalyst system of Patent Document 3 is composed of spherical particles of the order of several tens of μm, the catalytically active site is still insufficient, the gas contact efficiency is inferior, and this is used as an exhaust gas purification catalyst that is exposed to a high temperature environment. When used, it was difficult to maintain its specific surface area even after high temperature exposure, and it was poor in practicality as an exhaust gas purification catalyst used in a 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 are in a high temperature environment. As an exhaust gas purification catalyst used below, it was not practical.

  Furthermore, the exhaust gas purifying catalyst described in Patent Document 5 still has insufficient performance, and is relatively expensive because it requires noble metal as a catalytically active species.

  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, a manufacturing method thereof, an exhaust gas purifying catalyst, and the like that have not only excellent heat resistance but also excellent catalytic performance even after high temperature exposure.

  Note that the present invention is not limited to the purpose described here, and is an operational effect derived from each configuration shown in the embodiment for carrying out the invention described later, and can also exhibit an operational effect that cannot be obtained by the conventional technology. It can be positioned as another purpose.

  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 predetermined perovskite-type catalytically active particles are supported on predetermined base material particles has not only excellent heat resistance but also excellent catalytic performance even after high temperature exposure, The present invention has been completed.

That is, the present invention provides various specific modes shown below.
<1> Base material particles containing a rare earth solid solution zirconia-based oxide and having an average particle diameter D ₅₀ of 1 μm or more and 30 μm or less, and SrFeO ₃ which is perovskite type catalytically active particles supported on the surface of the base material particles _-δ (wherein δ represents the amount of oxygen deficiency and is a number satisfying 0 ≦ δ ≦ 0.5).
<2> The exhaust gas purification catalyst according to <1>, wherein a diffraction peak of SrFeO ₃ is expressed at 2θ = 32.6 ± 0.5 ° in powder X-ray diffraction measurement.
<3> The exhaust gas-purifying catalyst according to <1> or <2>, wherein the average particle diameter of SrFeO _3-δ is 1 to 90 nm.
<4> SrFeO _3−δ (where δ represents an oxygen deficiency and is a number satisfying 0 ≦ δ ≦ 0.5) is 1 to The exhaust gas-purifying catalyst according to any one of <1> to <3>, which is 60% by mass.

<5> The supported on the surface of the base particles, Fe ₂ O _{3-δ (where,} [delta] represents the amount of oxygen deficiency is a number satisfying 0 ≦ δ ≦ 1.) Further above containing < The catalyst for exhaust gas purification according to any one of 1> to <4>.
<6> The above-mentioned <1> to <1>, wherein the rare earth solid solution zirconia oxide is a zirconia oxide in which at least one rare earth element selected from the group consisting of Y, Ce, Nd, and Nd is solid solution. The exhaust gas purifying catalyst according to any one of 5>.
<7> The exhaust gas-purifying catalyst according to any one of <1> to <6>, wherein the composite particle does not substantially contain a noble metal element.

<8> A catalyst carrier and a catalyst layer provided on at least one surface side of the catalyst carrier, and the catalyst layer includes the exhaust gas according to any one of the above items <1> to <7>. A monolithic exhaust gas purification catalyst comprising at least a purification catalyst.
<9> The integral structure exhaust gas purification catalyst according to <8>, wherein the amount of the exhaust gas purification catalyst supported is 3 to 450 g / L per unit volume of the catalyst carrier.

<10> on the surface of the base particles having an average particle diameter D ₅₀ of 1μm or 30μm or less and containing a rare earth solid solution of zirconia-based oxide, applying a solution containing at least strontium ions and iron ions, and after treatment wherein the base particles 500 ° C. or higher 1490 ° C. and heat-treated below, SrFeO ₃ is a perovskite type catalyst activity particles supported on the surface of the base particles and the base particles containing a rare earth solid solution of zirconia-based oxide _-δ (where δ represents the amount of oxygen deficiency, and is a number satisfying 0 ≦ δ ≦ 0.5). Production method.
<11> The method for producing an exhaust gas purifying catalyst according to <10>, wherein a content ratio of Fe to Sr (Fe / Sr) is 0.5 or more and 1.5 or less in the aqueous solution.
<12> The method for producing an exhaust gas purifying catalyst according to <10> or <11>, wherein the aqueous solution does not substantially contain a rare earth metal element other than Sr and a transition metal element other than Fe.
<13> The method for producing an exhaust gas purifying catalyst according to any one of the above <10> to <12>, wherein the composite particle does not substantially contain a noble metal element.

  According to the present invention, it is possible to realize an exhaust gas purifying catalyst, a manufacturing method thereof, an exhaust gas purifying catalyst, and the like that have excellent heat resistance and excellent catalytic performance even after high temperature exposure. The exhaust gas purifying catalyst of the present invention is a catalyst particle having a composite structure in which minute catalytically active sites are supported on base material particles, and NOx, CO, HC, etc. in exhaust gas are reduced based on the composition and structure. As a three-way catalyst (TWC), it can be particularly preferably used. Moreover, since the exhaust gas purifying catalyst of the present invention does not need to use a noble metal element (PM) as an essential component, it is excellent in economic efficiency. Moreover, unlike conventional catalysts using inferior heat resistance such as zeolite, the exhaust gas purifying catalyst of the present invention can be mounted on an engine direct catalytic converter or a tandem direct catalytic converter. Reduction of canning cost can be achieved.

1 is a schematic diagram illustrating a schematic configuration of an exhaust gas purifying catalyst 100 according to an embodiment. It is a chart which shows the result of the powder X-ray-diffraction measurement of the powder catalyst of Example 1 after a baking process.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The positional relationship such as up, down, left, and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios. However, the following embodiments are examples for explaining the present invention, and the present invention is not limited to these. In other words, the present invention can be implemented with any modifications without departing from the scope of the invention. In this specification, for example, the description of a numerical range of “1 to 100” includes both the upper limit value “100” and the lower limit value “1”. This also applies to other numerical range notations.

FIG. 1 is a schematic diagram showing a schematic configuration of an exhaust gas purifying catalyst 100 according to an embodiment of the present invention. The exhaust gas-purifying catalyst 100 includes a base material particle 11 containing a rare earth solid solution zirconia-based oxide and having an average particle diameter D ₅₀ of 1 μm or more and 30 μm or less, and a perovskite type supported on the surface 11 a of the base material particle 11. SrFeO _3-δ that is the catalytically active particles 21 (where δ represents the amount of oxygen deficiency and is a number that satisfies 0 ≦ δ ≦ 0.5. Hereinafter, it may be simply referred to as “SrFeO _3-δ ”. ) And at least composite particles.

The base material particles 11 are core particles that carry perovskite-type catalytically active particles 21 on the surface 11a in a highly dispersed manner. As the base material particle 11, a rare earth solid solution zirconia-based oxide is preferably used from the viewpoint of imparting a carrier effect and improving the catalytic activity. Here, in the present specification, the “rare earth solid solution zirconia oxide” means a zirconia composite oxide in which a rare earth element is dissolved, specifically, zirconia in which a rare earth element is dissolved, and It is used as a concept including a complex oxide or a solid solution doped with other elements such as transition elements. 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%. As the zirconia-based oxide, those having a mass ratio of Zr of 50% by mass or more and 80% by mass or less in terms of oxide (ZrO ₂ ) based on the total amount are preferably used.

  Rare earth elements include cerium, scandium, yttrium, lanthanum, praseodymium, neodymium, promethium, samarium, eurobium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. , Sometimes referred to as “other rare earth elements”). These rare earth elements can be used individually by 1 type or in combination of 2 or more types as appropriate. Among these, yttrium, cerium, praseodymium, and neodymium are preferable, yttrium, cerium, and neodymium are more preferable, and yttrium and neodymium are more preferable from the viewpoints of crystal structure stability, heat resistance, and the like. A zirconia-based composite oxide in which yttrium and / or neodymium is dissolved is particularly preferably used from the viewpoint of heat resistance and the like while suppressing the formation of by-products with the perovskite-type catalytically active particles 21 supported on the surface.

  Among rare earth solid solution zirconia-based oxides, Y solid solution zirconia-based oxides are particularly suitable as a base material for exhaust gas purification catalysts used in high-temperature environments because of their excellent heat resistance. In addition, the Y solid solution zirconia-based oxide has relatively fast mobility of surface oxygen at a high temperature of 600 ° C. or higher, and is excellent in response to switching of the exhaust gas treatment atmosphere. Therefore, by using the Y solid solution zirconia-based oxide for the base material particle 11, oxygen on the surface 11a of the base material particle 11 is easily activated, and as a result, the catalytic reaction is promoted and high exhaust gas purification performance is obtained. . Further, in the present catalyst system, there is an advantage that the solid solution of Sr or Fe is suppressed by using the Y solid solution zirconia oxide, compared with alumina, for example. The Y solid solution zirconia oxide may be a solid solution of rare earth elements other than Y. Y solid solution zirconia oxide in which other rare earth elements are further dissolved is easy to adjust lattice oxygen vacancies (δ). By using this, for example, exhaust gas purification performance and heat resistance can be improved or supported. The dispersibility of the perovskite-type catalytically active particles 21 can be improved.

In the rare earth solid solution zirconia-based oxide, the content ratio of the rare earth element is not particularly limited, but the total amount of the rare earth element in terms of oxide relative to the total amount of the rare earth solid solution zirconia oxide (for example, Y ₂ O ₃ , CeO _2). , Nd ₂ O ₃ , Pr ₅ O _11, etc.) is preferably 0.01% by mass or more and 50% by mass or less, and more preferably 0.1% by mass or more and 20% by mass or less.

In addition, the rare earth solid solution zirconia oxide may contain transition elements such as chromium, cobalt, iron, nickel, titanium, manganese, and copper. A transition element can be used individually by 1 type or in combination of 2 or more types as appropriate. When the transition element is contained, the content ratio is not particularly limited, but the total amount of the transition element described above in terms of oxide of the transition element (for example, Fe ₂ O ₃ , TiO _2, etc.) is not limited. Is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, further preferably 0.5% by mass or more, more preferably 10% by mass or less, and even more preferably 5% by mass or less. A mass% or less is more preferable.

  In addition, in the above rare earth solid solution zirconia oxide, a part of zirconium and rare earth elements are alkali metal elements such as lithium, sodium and potassium, alkaline earth metal elements such as beryllium, magnesium, calcium, strontium and barium. May be substituted. Each of the alkali metal element and the alkaline earth metal element can be used alone or in any combination and proportion of two or more. The rare earth solid-solution zirconia oxide may contain hafnium (Hf), which is usually contained in the zirconia ore in an amount of about 1 to 2% by mass, as an inevitable impurity. The total amount of inevitable impurities excluding hafnium is preferably 0.3% by mass or less.

  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, 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-Pr-Zr-Ce-Ox, Y-Nd-La-Zr-Ce-Ox, Y-Nd-Pr-Zr-Ce-Ox, Y-La-Pr-Zr-Ce-Ox, etc. Although melted zirconia is mentioned, it is not specifically limited to these. Y solid solution zirconia type oxide can be used individually by 1 type or in combination of 2 or more types as appropriate. In these exemplifications, the display is focused on the combination of constituent elements contained in each oxide, and the stoichiometric ratio of each constituent element is not displayed. That is, the stoichiometric ratio of each constituent element can be arbitrarily adjusted.

Here, from the viewpoint of maintaining a large specific surface area and increasing the amount of the perovskite-type catalytically active particles 21 supported, and increasing the number of the catalytically active sites by increasing the heat resistance, the base material particles 11 are: The average particle diameter D ₅₀ is preferably 1 μm or more and 30 μm or less, more preferably 1 μm or more and 15 μm or less, and still more preferably 1 μm or more and 10 μm or less. In the present specification, the average particle diameter D ₅₀ means the median size measured by a laser diffraction type particle size distribution measuring device (for example, manufactured by Shimadzu Corporation, a laser diffraction type particle size distribution measuring apparatus SALD-3100 etc.) .

  As the base material 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-type oxide is not specifically limited, A coprecipitation method and an alkoxide method are preferable.

  As the coprecipitation method, for example, an alkali substance is added to an aqueous solution in which a zirconium salt, an yttrium salt, and a rare earth metal element or a transition metal element salt to be blended as necessary are mixed at a predetermined stoichiometric ratio, and then added with water. A production method in which decomposition or coprecipitation of the precursor is performed and the hydrolysis product or coprecipitate is fired is preferable. The kind of various salt used here is not specifically limited. In general, hydrochloride, oxyhydrochloride, nitrate, oxynitrate, carbonate, phosphate, acetate, oxalate, citrate and the like are preferable. Moreover, the kind of alkaline substance is not particularly limited. In general, an aqueous ammonia solution is preferred. As the alkoxide method, for example, a production method is preferred in which a mixture obtained by mixing zirconium alkoxide, yttrium, and a rare earth metal element to be blended as necessary at a predetermined stoichiometric ratio is hydrolyzed and then fired. The kind of alkoxide used here is not particularly limited. In general, methoxide, ethoxide, propoxide, isopropoxide, butoxide, and these ethylene oxide adducts are preferable. Further, the rare earth metal element may be blended as a metal alkoxide or as the various salts described above.

  The firing conditions may be in accordance with conventional methods and are not particularly limited. The firing atmosphere may be any of an oxidizing atmosphere, a reducing atmosphere, and an air atmosphere. The firing temperature and treatment time vary depending on the desired composition of the Y-solute zirconia oxide and its stoichiometric ratio. However, from the viewpoint of productivity and the like, the firing temperature and the treatment time are generally from 150 ° C. to 1300 ° C. -12 hours are preferred, more preferably 350 ° C or higher and 800 ° C or lower for 2 to 4 hours. Prior to the high temperature firing, it is preferable to perform drying under reduced pressure using a vacuum dryer or the like, and to perform a drying treatment at about 50 ° C. to 200 ° C. for about 1 to 48 hours.

In the exhaust gas purifying catalyst 100 of the present embodiment, SrFeO _3−δ (where δ represents the amount of oxygen deficiency and 0 ≦ δ ≦) is formed on the surface 11a of the base material particle 11 as the perovskite-type catalytic active particles 21. It is a number satisfying 0.5.) It has one feature in that it has a particle structure of composite particles on which is supported. Typically, the exhaust gas purification catalyst 100 is a composite in which fine particles of SrFeO ₃ -δ having an average particle diameter of about 1 to 90 nm, preferably 10 to 80 nm, adhere to the surface 11 a of the base material particle 11 in a highly dispersed manner. It has a structure. By adopting such a composite particle structure, in this exhaust gas purifying catalyst 100, the deterioration of the catalyst performance after high temperature exposure is greatly suppressed. The reason for this is not clear, but SrFeO _3-δ having a perovskite crystal structure is relatively excellent in heat resistance, and on the surface 11 a of the base material particle 11, SrFeO _3-δ and the base material particle 11 Fine particles of various derivatives (for example, reduced products such as SrZrO _3-δ , iron oxide (FeO or Fe ₂ O ₃ ), and simple iron (Fe)) generated from contained elements are generated, and these fine particles are formed into SrFeO _3- distributed between _[delta] of the particulate, such as by contact opportunities between SrFeO _3-[delta] is allowed reduced, sintering and grain growth of SrFeO _3-[delta] due to high temperature exposure is presumably because it is inhibited. Therefore, the exhaust gas purifying catalyst 100 of the present embodiment has various derivatives (for example, SrZrO _3-δ , iron oxide (FeO or Fe ₂ O ₃ ), iron, etc. generated from elements contained in SrFeO _3-δ and base material particles 11. A reduction product such as simple substance (Fe) may be included.

Here, the perovskite structure of _{SrFeO 3-δ, brownmillerite, cubic} , tetragonal, and orthorhombic like are known, as these stoichiometric _{ratio, SrFeO 3, SrFeO 2.875, SrFeO} 2.75, SrFeO 2.5 Hitoshigachi It has been. In the exhaust gas purifying catalyst 100 of the present embodiment, any of these may be included as the perovskite-type catalytically active particles 21. The presence of SrFeO _3-δ on the base material particle 11 is observed by a scanning transmission electron microscope (STEM), powder X-ray diffraction (XRD), for example, 2θ = 32.6. ± 0.5 ° SrFeO ₃ peak, various types of electron probe microanalyzer (EPMA), X-ray photoelectron spectroscopy (XPS), or ESCA (electron spectroscopy for chemical analysis) The average particle diameter of SrFeO _{3 -δ} on the base material particle 11 is usually about 10 to 150 nm, preferably 10 to 120 nm, more preferably 20 to 110 nm. .

Further, the catalytic action of exhaust gas purification by SrFeO _{3 -δ} exhibits catalytic activity over the entire range from lean environment to stoichiometric environment to rich environment. The reason for this is not clear, but SrFeO _3-δ itself not only functions as a catalytically active component, but the various derivatives described above also function as a catalytically active component. The presence of active active species is presumed to exhibit particularly strong catalytic activity in stoichiometric to rich environments. Whatever the reason, the exhaust gas purifying catalyst 100 of the present embodiment has the exhaust gas purifying catalytic action reinforced over the entire range of lean environment, stoichiometric environment, and rich environment. As a result, noble metal elements (PM) and platinum group elements ( Even though PGM) is not used as an essential component, excellent exhaust gas purification performance is exhibited.

Here, from the viewpoint of further enhancing the catalytic activity and inhibiting sintering and grain growth, SrFeO _3-δ preferably has an average crystallite diameter of 1 nm to 80 nm, more preferably 10 nm to 70 nm, Preferably they are 20 nm or more and 65 nm or less. The average crystallite of SrFeO _3-δ can be calculated from, for example, the XRD diffraction pattern of the exhaust gas purifying catalyst 100 after the endurance treatment. By making SrFeO _3-δ having such a fine particle size present on the surface 11a of the base material particle 11, the surface area tends to be maintained higher and more catalytically active sites tend to be maintained.

The crystallite means the largest group that can generally be regarded as a single crystal, and the size of the crystallite is called the crystallite diameter. Further, in this specification, the average crystallite diameter means a value calculated from a Scherrer equation represented by the following equation (1) based on a measurement result obtained by measuring a diffraction pattern using an X-ray diffractometer. To do.
Crystallite diameter D (Å) = K · λ / (β · cos θ) (1)
In Equation (1), K is a Scherrer constant, and here, K = 0.9. Also, λ is the wavelength of the X-ray tube used, β is the half width, and θ is the diffraction angle (rad).

Further, the content (supported amount) of SrFeO _{3-δ in} the exhaust gas purification catalyst 100 is not particularly limited, but it has been described above from the viewpoint of improving the catalyst performance over the entire range of lean environment, stoichiometric environment, and rich environment. 1 mass% or more and 60 mass% or less are preferable with respect to the total mass of a composite particle, More preferably, they are 2 mass% or more and 55 mass% or less, More preferably, they are 3 mass% or more and 50 mass% or less.

In the exhaust gas purifying catalyst 100 of the present embodiment, in addition to the above-described (FeO and Fe ₂ O ₃ ) and the various derivatives described above, rare earth elements or transition metal elements other than Sr and Fe (hereinafter referred to as “others”). May be referred to as “rare earth element” or “other transition metal element”)) or the like. Examples of other rare earth elements include, but are not limited to, cerium, scandium, neodymium, promethium, samarium, eurobium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Other transition metal elements include, but are not limited to, chromium, cobalt, nickel, titanium, manganese, tungsten, and copper.

On the other hand, when the exhaust gas purifying 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 purifying catalyst 100 is from the viewpoint of improving the catalyst performance and low temperature activity. On the other hand, it is preferably 0.001% by mass or more and 3% by mass or less, more preferably 0.01% by mass or more in terms of the total of Fe ₂ O _{3 of} Fe ₂ O ₃ , Fe ₃ O ₄ and FeO. 2% by mass or less.

  The exhaust gas purifying catalyst 100 of this embodiment includes gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), and osmium (Os). Even if noble metal element (PM) such as platinum or platinum group element (PGM) is not used as an essential component, it has excellent heat resistance and excellent catalytic performance even after high temperature exposure. Therefore, from the viewpoint of economy and stable supply, one preferred embodiment is an exhaust gas purifying catalyst 100 that substantially does not contain a noble metal element (PM) and a platinum group element (PGM). Here, “substantially not contained” means that the total amount of the noble metal element (PM) and the platinum group element (PGM) is in the range of 0% by mass or more and less than 1.0% by mass with respect to the total amount of the exhaust gas purification catalyst 100. More preferably, it is 0 mass% or more and less than 0.5 mass%, More preferably, it is 0 mass% or more and less than 0.3 mass%.

The shape of the exhaust gas purifying catalyst 100 is not particularly limited. The catalyst powder, which is an aggregate of catalyst particles in which SrFeO _3-δ is supported on the base material particles 11, can be used as it is. Also, for example, the catalyst powder can be formed into an arbitrary shape to form a granular or pellet shaped catalyst. Further, the exhaust gas purification catalyst 100 can be held (supported) on a catalyst carrier and used as an integral structure type exhaust gas purification catalyst. As the catalyst carrier used here, those known in the art can be appropriately selected. Typical examples include ceramic monolith carriers such as cordierite, silicon carbide, silicon nitride, metal honeycomb carriers such as stainless steel, wire mesh carriers such as stainless steel, and steel wool knit wire carriers. There is no particular limitation. In addition, the shape is not particularly limited, and any 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 individually by 1 type or in combination of 2 or more types as appropriate.

  The exhaust gas purification catalyst 100 described above can be used as a catalyst for purifying exhaust gas from diesel engines, gasoline engines, jet engines, boilers, gas turbines, etc., for example, exhaust gas purification catalysts for internal combustion engines, especially automobile exhaust gas. 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 a method in which SrFeO _3-δ is supported on the base material particles 11 as described above can be obtained. From the viewpoint of manufacturing the exhaust gas-purifying catalyst 100 having the above-described structure with good reproducibility and at low cost, the evaporation to dry method (impregnation method) or the like is preferable.

  As the evaporation to dryness method, a manufacturing method in which the base material particle 11 described above is impregnated with an aqueous solution containing at least strontium ions and iron ions and then fired is preferable. By this impregnation treatment, strontium ions and iron ions are adsorbed (attached) to the surfaces 11a of the base material particles 11 in a highly dispersed state. Here, strontium ions and iron ions can be blended in the aqueous solution as various salts. The kind of various salt used here is not specifically limited. In general, sulfate, hydrochloride, oxyhydrochloride, nitrate, oxynitrate, carbonate, phosphate, chloride, oxide, complex oxide, complex salt, acetate, oxalate, citrate, etc. Is preferred.

  After the impregnation treatment, a solid-liquid separation treatment, a water washing treatment, for example, a drying treatment for removing moisture 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. The drying treatment may be natural drying, or a drying apparatus such as a drum dryer, a vacuum dryer, or spray drying may be used. The atmosphere during the drying treatment may be any of air, vacuum, and inert gas atmosphere such as nitrogen gas. In addition, you may perform a grinding | pulverization process, a classification process, etc. further before and after drying as needed.

The firing conditions may be in accordance with conventional methods and are not particularly limited. 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 treatment time vary depending on the desired composition and the stoichiometric ratio, but from the viewpoint of the production and productivity of SrFeO _{3 -δ} , the firing temperature and treatment time are generally from 0.5 to 1490 ° C. 1-12 hours are preferable, More preferably, it is 550 degreeC or more and 800 degrees C or less for 0.5 to 6 hours. Prior to high-temperature firing, drying under reduced pressure using a vacuum dryer or the like may be performed, and a drying treatment may be performed at 50 ° C. or higher and 200 ° C. or lower for about 1 to 48 hours. By this firing treatment, SrFeO _{3 -δ} highly dispersed in a nano-order size and, depending on the treatment conditions, fine particles of various derivatives described above are generated (synthesized) on the surface 11 a of the base material particle 11.

The content ratio of Fe to Sr in the aqueous solution (Fe / Sr) can be adjusted as appropriate and is not particularly limited. However, from the viewpoint of the catalytic activity of the obtained exhaust gas purification catalyst 100, the molar ratio of Fe and Sr is 0. 0.5 or more and 1.5 or less is preferable, and from the viewpoint of suppressing generation other than SrFeO _3-δ and Fe ₂ O _3-δ , more preferably 0.9 or more and 1.5 or less, and even more preferably 1.0. It is 1.45 or less.

In addition, the aqueous solution, if necessary, rare earth elements such as cerium, scandium, lanthanum, praseodymium, neodymium, promethium, samarium, eurobium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, lithium, Alkali metal elements such as sodium and potassium, alkaline earth metal elements such as beryllium, magnesium, calcium, strontium and barium, and transition metal elements such as cobalt, nickel, titanium and copper may be contained. In addition, these can be used individually by 1 type or in combination of 2 or more types as appropriate. These rare earth elements, alkali metal elements, alkaline earth metal elements, and transition metal elements are supplied to aqueous solutions as inorganic acid salts, such as sulfates, nitrates, acetates, chlorides, oxides, complex oxides, and complex salts. can do. At this time, it is preferable that the aqueous solution does not substantially contain a rare earth metal element other than strontium and a transition metal element other than iron from the viewpoint of suppressing the by-production of complex oxides other than SrFeO _{3 -δ} . Here, “substantially not contained” means that the total molar amount of the rare earth metal element other than strontium and the transition metal element other than iron is 1/20 or less with respect to the total molar amount of Sr and Fe in the aqueous solution. More preferably, it is 1/40 or less, more preferably 1/50 or less, and particularly preferably 1/100 or less. For example, by making an aqueous solution substantially free of La, unintentional by-products such as derivatives other than SrFeO _3-δ and Fe ₂ O _3-δ , such as LaFeO ₃ and LaSrFeO _3, can be suppressed.

  The exhaust gas-purifying catalyst 100 thus obtained can be used as a powder that is an aggregate of catalyst particles, and is mixed with a catalyst, a co-catalyst, a catalyst carrier, and an additive known in the art. Can be used. At this time, the exhaust gas-purifying catalyst 100 can be used as a co-catalyst with another catalyst (main catalyst), or another catalyst (co-catalyst) can be used in combination with the exhaust gas-purifying catalyst 100. Furthermore, the exhaust gas-purifying catalyst 100 can be prepared as a granular or pellet shaped body (molded catalyst) by preparing a composition containing the catalyst in advance and molding the composition into an arbitrary predetermined shape. Various known dispersing devices, kneading devices, and molding devices can be used for producing the molded body. When used as a molded body, the content of the exhaust gas-purifying catalyst 100 in the molded body is not particularly limited, but is preferably 10% by mass or more and 99% by mass or less, more preferably 20% by mass or more and 99% by mass with respect to the total amount. % Or less, more preferably 30% by mass or more and 99% by mass or less.

Examples of known catalysts, cocatalysts, and catalyst carriers that can be used in combination include metal oxides or metal composite oxides such as silica, alumina, ceria, zirconia, ceria-zirconia, lanthanum oxide, neodymium oxide, praseodymium oxide; Complex oxides such as zirconia and ceria-zirconia doped with elements and / or transition elements; perovskite oxides other than SrFeO _3-δ ; alumina such as silica-alumina, silica-alumina-zirconia, silica-alumina-boria Complex oxides containing: barium compounds, zeolites and the like, but not limited thereto. The ratio of the catalyst, cocatalyst and catalyst carrier used in combination can be appropriately set according to the required performance and the like, and is not particularly limited, but is preferably 0.01% by mass or more and 50% by mass or less in total with respect to the total amount, The total is more preferably 0.05% by mass or more and 20% by mass or less, and the total is more preferably 0.1% by mass or more and 8% by mass or less.

  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, and the like, but are not particularly limited thereto. . Examples of the binder include various sols such as alumina sol, titania sol, silica sol, and zirconia sol, but are not particularly limited thereto. 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 a quantity required for maintenance of a molded object. In addition, although the usage-amount of the additive mentioned above can be suitably set according to required performance etc., it is not specifically limited, 0.01-20 mass% in total is preferable with respect to the total amount, and 0.05-10 mass in total % Is more preferable, and 0.1 to 8% by mass in total is more preferable.

  The exhaust gas purifying catalyst 100 obtained as described above may further carry a noble metal element or a platinum group element as necessary. The method for supporting the noble metal element or the platinum group element is not particularly limited, and a known method can be applied. For example, a noble metal element or a platinum group element can be supported by preparing a solution of a salt containing a noble metal element or a platinum group element, impregnating the exhaust gas-purifying catalyst 100 with the salt-containing solution, and then firing the solution. it can. The salt-containing solution is not particularly limited, but an aqueous nitrate solution, dinitrodiammine nitrate solution, aqueous chloride solution and the like are preferable. Also, the baking treatment is not particularly limited, but is preferably 350 ° C. or more and 1000 ° C. or less for about 1 to 12 hours. Prior to the high temperature firing, it is preferable to perform drying under reduced pressure using a vacuum dryer or the like, and to perform a drying treatment at about 50 ° C. to 200 ° C. for about 1 to 48 hours.

  The monolithic structure type catalyst described above is a catalyst member (laminated catalyst member) having a laminated structure including at least a catalyst carrier and a catalyst layer provided on at least one surface side of the catalyst carrier. By adopting such a configuration, the applicability to various uses such as easy incorporation into the apparatus increases. For example, in an exhaust gas purification application, a honeycomb structure carrier or the like is used as a catalyst carrier, the integrated structure type catalyst is installed in a flow path through which the gas flow passes, and the gas flow is passed through the cells of the honeycomb structure carrier. The exhaust gas purification can be performed with high efficiency.

  Here, in this specification, “provided on at least one surface side of the catalyst carrier” means any other layer (for example, primer layer, adhesive layer) between the one surface of the catalyst carrier and the catalyst layer. Etc.) is included. That is, in this specification, “provided on one side” means an aspect in which the catalyst carrier and the catalyst layer are directly placed, and the catalyst carrier and the catalyst layer are separated via any other layer. It is used in the meaning including both arranged modes. In addition, the catalyst layer may be provided on only one surface of the catalyst carrier, or may be provided on a plurality of surfaces (for example, one main surface and the other main surface).

  The monolithic structure type catalyst having the above-described layer structure can be manufactured according to a conventional method. For example, it can be obtained by coating (supporting) the above-described exhaust gas-purifying catalyst on the surface of the catalyst carrier. Specifically, the above-described exhaust gas-purifying catalyst, an aqueous medium, and a binder, other catalyst, co-catalyst, OSC material, base material particle, additive, and the like known in the art as required at a desired blending ratio. A method of preparing a slurry mixture by mixing, applying the obtained slurry mixture to the surface of a catalyst carrier such as a honeycomb structure carrier, drying and firing is preferably used. At this time, it is preferable to use the above-described binder or the like in order to firmly attach or bind the above-described exhaust gas purification catalyst to the support.

  What is necessary is just to use the quantity which the catalyst for exhaust gas purification can disperse | distribute uniformly in a slurry for the aqueous medium used at the time of preparation of a slurry-like mixture. At this time, if necessary, an acid or a base for adjusting the pH can be blended, or a surfactant, a dispersing resin or the like can be blended for adjusting the viscosity or improving the slurry dispersibility. As a method for mixing the slurry, a known pulverization method or mixing method such as pulverization and mixing using a ball mill or the like can be applied. When the slurry-like mixture is applied on the catalyst support, various known coating methods, wash coat methods, and zone coat methods can be applied according to conventional methods.

  After the slurry-like mixture is applied on the catalyst carrier, the integral structure-type catalyst of the present embodiment can be obtained by drying and firing according to a conventional method. In addition, although 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 above-mentioned integrated structure type catalyst, the layer structure of the catalyst layer may be either a single layer or multiple layers. However, in the case of automotive exhaust gas applications, the catalyst performance is considered in consideration of the trend of stricter exhaust gas regulations. 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 3 to 450 g / L, and more preferably 50 to 350 g / L, from the viewpoint of catalyst performance and pressure loss balance.

  In automotive exhaust gas applications, the exhaust gas purifying catalyst and the integral structure type catalyst described above can be arranged in exhaust systems of various engines. The number and location of the installation can be appropriately designed according to the exhaust gas regulations. For example, when exhaust gas regulations are strict, the number of installation locations can be two or more, and the installation location can be arranged at the lower floor position behind the catalyst directly under the exhaust system.

  Hereinafter, the features of the present invention will be described more specifically with reference to test examples, examples and comparative examples, but the present invention is not limited thereto. That is, the materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. In addition, various production conditions and evaluation result values in the following examples have a meaning as a preferable upper limit value or a preferable lower limit value in the embodiment of the present invention, and a preferable range is the above-described upper limit or lower limit value. And a range defined by a combination of values of the following examples or values of the examples.

Example 1
As a base material particle, 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 this specification, the BET specific surface area refers to a specific surface area / pore distribution measuring device (trade name: BELSORP-mini II, manufactured by Microtrack Bell Co., Ltd.) and analysis software (trade name: BEL_Master, Microtrack Means a value determined by the BET single point method.
Next, strontium nitrate and iron nitrate nonahydrate are dissolved in water, and 0.094 mol / L Sr and 0.047 mol / L in terms of the molar ratio of each oxide (SrO, Fe ₂ O ₃ ). An aqueous solution 1 containing L Fe was prepared.
By impregnating the base material particles with the aqueous solution 1 and performing a baking treatment at 700 ° C. for 1 hour, SrFeO _3-δ having an average particle diameter D ₅₀ of 20 nm is supported on the surface of the Y-ZrO ₂ base material particles. The powder catalyst of Example 1 after the calcination treatment (Yr-ZrO ₂ powder catalyst supporting 11.95% by mass of SrFeO _{3 -δ} , Sr content in terms of SrO: 6.47% by mass, Fe ₂ O ₃ conversion Fe content: 5.00 mass%) was obtained.
The obtained powder catalyst of Example 1 was dispersed in water, milled with a pot mill, and pulverized until D ₅₀ = 4.1 μm to obtain a catalyst slurry. The catalyst slurry was coated on a 600 cpsi, 3.5 mil cordierite honeycomb carrier by a wash coat method and then dried to provide a catalyst layer, thereby supporting 150 g of catalyst per liter of honeycomb carrier. 1 honeycomb catalyst (exhaust gas purification catalyst, integral structure type catalyst) was obtained.
Thereafter, the obtained honeycomb catalyst was subjected to high-temperature exposure treatment (endurance treatment) in an endurance furnace. Note that as the high temperature exposure treatment, heat treatment was performed at 980 ° C. for 6 hours while sequentially switching the external atmosphere to A / F = 12.8 and an oxygen atmosphere.

(Comparative Example 1)
Lanthanum nitrate hexahydrate and iron nitrate nonahydrate are dissolved in water, 0.033 mol / L La in terms of molar ratio of each oxide (La ₂ O ₃ , Fe ₂ O ₃ ), and An aqueous solution 2 containing 0.047 mol / L Fe was prepared.
The same procedure as in Example 1 was conducted except that this aqueous solution 2 was used instead of the aqueous solution 1, and the powder catalyst and exhaust gas purification catalyst of Comparative Example 1 (Y-ZrO on which 10.63% by mass of LaFeO _3-δ was supported). ₂ powder catalyst, La ₂ O ₃ equivalent La content: 7.13 mass%, Fe ₂ O ₃ equivalent Fe content: 5.00 mass%).

(Comparative Example 2)
As base material particles, γ-alumina (D ₅₀ = 28.1 μm, BET specific surface area: 141 m ² / g) was used.
The same procedure as in Example 1 was performed except that this γ-alumina was used in place of the above Y—ZrO ₂ , and the powder catalyst and exhaust gas purification catalyst of Comparative Example 2 (supporting 11.95% by mass of SrFeO _{3 -δ)} Γ-alumina powder catalyst, Sr content in terms of SrO: 6.47% by mass, Fe content in terms of Fe ₂ O ₃ : 5.00% by mass) were obtained.

(Comparative Example 3)
The same procedure as in Comparative Example 2 was performed except that the above aqueous solution 2 was used in place of the above aqueous solution 1, and the powder catalyst and exhaust gas purifying catalyst of Comparative Example 3 (LaFeO _3-δ was supported at 10.63% by mass). A γ-alumina powder catalyst, La content in terms of La ₂ O ₃ : 7.13 mass%, Fe content in terms of Fe ₂ O ₃ : 5.00 mass%) were obtained.

<Preparation of exhaust gas purification catalyst sample (integrated structure type catalyst)>
The obtained powder catalysts of Examples and Comparative Examples 1 to 3 after the firing treatment were each coated on a honeycomb carrier by a wash coat method and dried to provide a catalyst layer, and then subjected to a high temperature exposure treatment (durability) in a durability furnace. The exhaust gas purification catalyst sample (integrated structure type catalyst) was produced. Note that as the high temperature exposure treatment, heat treatment was performed at 980 ° C. for 6 hours while sequentially switching the external atmosphere to A / F = 12.8 and an oxygen atmosphere.
[Production conditions]
Honeycomb carrier: Corning International, φ1 inch x 50 mmL (25 cc), 600 cpsi / 3.5mil
Catalyst loading: 150 g / L

<Powder X-ray diffraction measurement>
The powder catalyst of Example 1 after the firing treatment was subjected to powder X-ray diffraction measurement under the following conditions using an X-ray diffractometer (trade name: X'Pert PRO MPD, manufactured by Yamato Scientific Co., Ltd.). = Inherent peak (221) of SrFeO _3-δ crystal was confirmed around 32.6 °. FIG. 2 shows the measurement result of the powder X-ray diffraction measurement.
Target: Cu
K-Alpha1 [A]: 1.5406
X-ray output setting: 40 mA, 45 kV

<Measurement of average crystallite size>
Furthermore, when the average crystallite size of the SrFeO _3-δ particles was calculated based on the above formula (1), the average crystallite size of the SrFeO _3-δ particles of the powder catalyst of Example 1 was 20 nm. Note that the calculation by the Scherrer method was performed using commercially available software (Spectres, PANalytical X'Pert High Score Plus 3.0) based on the strong peak (221) near 2θ = 32.6 ° described above. .

<Measurement of exhaust gas purification rate (HC, CO, NOx)>
The obtained exhaust gas purification catalyst samples of Example 1 and Comparative Examples 1 to 3 were set in a model gas reactor. The exhaust gas purification rate is calculated by analyzing the gas at the catalyst outlet side using a model gas with the following composition, and the formula “Purification rate (%) = 100 * (INLET gas concentration−catalyst OUT gas concentration) ÷ INLET gas concentration” Calculated based on
[Model gas evaluation conditions]
Model gas equipment: SIGU4012 HORIBA analyzer Analyzer: MEXA-7100 HORIBA catalyst inlet temperature: 600 ℃
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, 1Hz (Adjusted with Rich = CO, Lean = O ₂ )

Table 1 shows the measurement results of the exhaust gas purification rate. The monolithic structure type catalyst of Example 1 corresponding to the present invention uses SrFeO _3, which is more susceptible to oxygen deficiency than LaFeO _3, as the perovskite type catalyst active particles. In comparison, it was confirmed that the CO purification rate, the HC purification rate, and the NOx purification rate showed high purification performance. This suggests that when perovskite-type catalytically active particles are used, the catalytic activity increases depending on the type of compound in which oxygen deficiency is likely to occur and the amount of oxygen deficiency. Further, in the integrated structure type catalysts of Comparative Examples 2 to 3, the improvement effect of the CO purification rate and the HC purification rate was recognized as compared with the integrated structure type catalyst of Comparative Example 1, but the NOx purification rate was improved. From the comparison with the integrated structure type catalyst of Example 1, it is understood that there is still room for improvement in the CO purification rate.

(Example 2)
As a base material particle, 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 this specification, the BET specific surface area refers to a specific surface area / pore distribution measuring device (trade name: BELSORP-mini II, manufactured by Microtrack Bell Co., Ltd.) and analysis software (trade name: BEL_Master, Microtrack Means a value determined by the BET single point method.
Next, strontium nitrate and iron nitrate nonahydrate are dissolved in water, and 0.047 mol / L Sr and 0.023 mol / L in terms of molar ratio of each oxide (SrO, Fe ₂ O ₃ ). An aqueous solution A containing L Fe was prepared.
By impregnating the base material particles with the aqueous solution A and firing at 700 ° C. for 1 hour, SrFeO _3-δ having an average particle diameter D ₅₀ of 20 nm is supported on the surface of the Y-ZrO ₂ base material particles. Thus, the powder catalyst of Example 2 after firing was obtained (Y-ZrO ₂ powder catalyst supporting 5.73% by mass of SrFeO _3-δ and 0.01% by mass of Fe ₂ O _3-δ ). .

Example 3
Strontium nitrate and iron nitrate nonahydrate are dissolved in water, and 0.094 mol / L of Sr and 0.047 mol / L of Fe in terms of molar ratio of each oxide (SrO, Fe ₂ O ₃ ). An aqueous solution B containing was prepared.
Except that this aqueous solution B is used in place of the aqueous solution A, the same procedure as in Example 2 is carried, whereby SrFeO _3-δ having an average particle diameter D ₅₀ of 20 nm is supported on the surface of the Y-ZrO ₂ base material particles. Thus, the powder catalyst of Example 3 after the firing treatment (Y-ZrO ₂ powder catalyst carrying 11.95% by mass of SrFeO _3-δ and 0.02% by mass of Fe ₂ O _3-δ ) was obtained. .

Example 4
Strontium nitrate and iron nitrate nonahydrate are dissolved in water, and 0.187 mol / L Sr and 0.094 mol / L Fe in terms of molar ratio of each oxide (SrO, Fe ₂ O ₃ ). An aqueous solution C containing was prepared.
Except that this aqueous solution C is used in place of the aqueous solution A, the same procedure as in Example 2 is performed, so that SrFeO _3-δ having an average particle diameter D ₅₀ of 20 nm is supported on the surface of the Y-ZrO ₂ base material particles. Thus, a powder catalyst of Example 4 (Y-ZrO ₂ powder catalyst on which 23.90% by mass of SrFeO _3-δ and 0.03% by mass of Fe ₂ O _3-δ were supported) after firing was obtained. .

(Example 5)
Strontium nitrate and iron nitrate nonahydrate are dissolved in water and converted into a molar ratio of each oxide (SrO, Fe ₂ O ₃ ), 0.374 mol / L Sr, and 0.188 mol / L Fe. An aqueous solution D containing was prepared.
Except for using this aqueous solution D in place of the aqueous solution A, the same procedure as in Example 2 was carried out to support SrFeO _3-δ having an average particle diameter D ₅₀ of 20 nm on the surface of the Y-ZrO ₂ base material particles. Thus, the powder catalyst of Example 5 after firing was obtained (Y-ZrO ₂ powder catalyst carrying 47.80 mass% of SrFeO _3-δ and 0.07 mass% of Fe ₂ O _3-δ ). .

(Example 6)
Strontium nitrate and iron nitrate nonahydrate are dissolved in water, and 0.066 mol / L of Sr and 0.047 mol / L of Fe in terms of molar ratio of each oxide (SrO, Fe ₂ O ₃ ) are converted. An aqueous solution E containing was prepared.
Except for using the aqueous solution E instead of the aqueous solution A, the same procedure as in Example 2 was carried out, whereby SrFeO _3-δ and Fe having an average particle diameter D ₅₀ of 20 nm on the surface of the Y-ZrO ₂ base material particles. The powder catalyst of Example 6 after the calcination treatment on which ₂ O _3-δ was supported (Y-ZrO on which 8.38 mass% of SrFeO _3-δ and 1.51 mass% of Fe ₂ O _3-δ were supported) ₂ powder catalysts) were obtained.

The obtained powder catalysts of Examples 2 to 6 were dispersed in water, milled with a pot mill, and pulverized until D ₅₀ = 4.1 μm to obtain a catalyst slurry. The catalyst slurry was coated on the above cordierite honeycomb carrier of 600 cpsi, 3.5 mil by the wash coat method and then dried to provide a catalyst layer, thereby supporting 150 g of catalyst per liter of the honeycomb carrier. The honeycomb catalysts of Examples 2 to 6 (exhaust gas purification catalyst, integral structure type catalyst) were obtained. Thereafter, the obtained honeycomb catalyst was subjected to high-temperature exposure treatment (endurance treatment) in an endurance furnace. Note that as the high temperature exposure treatment, heat treatment was performed at 980 ° C. for 6 hours while sequentially switching the external atmosphere to A / F = 12.8 and an oxygen atmosphere.

<Measurement of exhaust gas purification rate (HC, CO, NOx)>
The obtained exhaust gas purification catalyst samples of Example 1 and Comparative Examples 1 to 3 were set in a model gas reactor. The exhaust gas purification rate is calculated by analyzing the gas at the catalyst outlet side using a model gas with the following composition, and the formula “Purification rate (%) = 100 * (INLET gas concentration−catalyst OUT gas concentration) ÷ INLET gas concentration” Calculated based on
[Model gas evaluation conditions]
Model gas equipment: SIGU4012 HORIBA analyzer Analyzer: MEXA-7100 HORIBA catalyst inlet temperature: 600 ℃
Gas composition: CO ₂ = 14.00%, O ₂ = 0.47%, NO = 0.05%, CO = 0.50%,
H ₂ = 0.17%, C ₃ H ₆ = 0.04%,
H ₂ O = 10.00%, N ₂ balance
No A / F perturbation
With A / F perturbation: 14.7 ± 0.6, 1Hz (Adjusted with Rich = CO, Lean = O ₂ )

  Table 2 shows the measurement results of the exhaust gas purification rate. It was confirmed that all of the integrated structure type catalysts of Examples 2 to 6 corresponding to the present invention showed high purification performance.

  The present invention can be widely and effectively used as a catalyst for reducing NOx, CO, HC, and the like in exhaust gas, such as an engine direct type catalytic converter in which heat resistance is particularly required, and a direct type catalytic converter in a tandem arrangement. It can be used particularly effectively as a three-way catalyst (TWC).

11: Base material particles 11a: Surface 21: SrFeO _3-δ
31... Derivative (eg Fe ₂ O ₃ )
100 ... Catalyst for exhaust gas purification

Claims (13)

Base material particles containing a rare earth solid solution zirconia-based oxide and having an average particle diameter D ₅₀ of 1 μm or more and 30 μm or less;
SrFeO _3−δ (where δ represents the amount of oxygen deficiency and satisfies 0 ≦ δ ≦ 0.5), which is a perovskite-type catalytically active particle supported on the surface of the base material particle.
Containing composite particles having at least
Exhaust gas purification catalyst. The exhaust gas purifying catalyst according to claim 1, wherein a diffraction peak of SrFeO ₃ is expressed at 2θ = 32.6 ± 0.5 ° in powder X-ray diffraction measurement. The average particle diameter of SrFeO _3-[delta] is the catalyst for purification of exhaust gas according to claim 1 or 2 is 1～90Nm. The content ratio of SrFeO _3−δ (where δ represents the amount of oxygen deficiency and satisfies 0 ≦ δ ≦ 0.5) is 1 to 60% by mass with respect to the total mass of the composite particles. The exhaust gas-purifying catalyst according to any one of claims 1 to 3. 5. The composition further contains Fe ₂ O _3−δ (where δ represents an oxygen deficiency and is a number satisfying 0 ≦ δ ≦ 1) supported on the surface of the base material particles. The exhaust gas-purifying catalyst according to any one of the above. 6. The rare earth solid solution zirconia oxide is a zirconia oxide in which at least one rare earth element selected from the group consisting of Y, Ce, Nd, and Nd is dissolved. The exhaust gas-purifying catalyst according to Item. The exhaust gas-purifying catalyst according to any one of claims 1 to 6, wherein the composite particles do not substantially contain a noble metal element. A catalyst support;
A catalyst layer provided on at least one surface side of the catalyst carrier,
The catalyst layer contains at least the exhaust gas-purifying catalyst according to any one of claims 1 to 7,
Monolithic exhaust gas purification catalyst. The monolithic exhaust gas purification catalyst according to claim 8, wherein an amount of the exhaust gas purification catalyst supported is 3 to 450 g / L per unit volume of the catalyst carrier. On the surface of the base particles having an average particle diameter D ₅₀ of 1μm or 30μm or less and containing a rare earth solid solution of zirconia-based oxide, applying a solution containing at least strontium ions and iron ions, and the mother after the treatment The base material particles are heat-treated at 500 ° C. or higher and 1490 ° C. or lower, and SrFeO _3-δ (perovskite-type catalytically active particles supported on the surface of the base material particles containing the rare earth solid solution zirconia-based oxide). However, δ represents the amount of oxygen deficiency, and is a number satisfying 0 ≦ δ ≦ 0.5.)
A method for producing an exhaust gas purifying catalyst. The method for producing an exhaust gas purifying catalyst according to claim 10, wherein a content ratio of Fe to Sr (Fe / Sr) in the aqueous solution is 0.5 to 1.5 in terms of molar ratio. The method for producing an exhaust gas purifying catalyst according to claim 10 or 11, wherein the aqueous solution does not substantially contain a rare earth metal element other than Sr and a transition metal element other than Fe. The method for producing an exhaust gas purifying catalyst according to any one of claims 10 to 12, wherein the composite particles contain substantially no precious metal element.