JP5974631B2 - Exhaust gas purification catalyst and method for producing the same - Google Patents

Description

  The present invention relates to an exhaust gas purifying catalyst and a method for producing the same.

  Conventionally, various catalysts have been used to purify components such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) contained in a gas discharged from an internal combustion engine of an automobile. It was. As such an exhaust gas purifying catalyst, a catalyst having a transition metal supported on a carrier as an active component is known. For example, JP-A-7-171394 (Patent Document 1) carries at least one selected from Cu, Co, Fe, Cr, Zn, Ni and V on a support made of alumina or silica alumina. An exhaust gas purifying catalyst is disclosed. Further, JP-A-9-276700 (Patent Document 2) discloses a catalyst in which copper and iron are supported on a titania carrier as a catalyst for removing ammonia in exhaust gas in the column of Example 1. ing.

JP 7-171394 A JP 9-276700 A

  However, Patent Document 1 does not disclose a specific combination of two or more metal species as the transition metal. Further, the conventional exhaust gas purification catalyst as described in Patent Document 1 is not necessarily sufficient in terms of purification performance of carbon monoxide (CO), hydrocarbon (HC), nitrogen oxide (NOx) and the like. It was. Further, Patent Document 2 discloses an example of a catalyst supported by combining copper and iron, but the exhaust gas purifying catalyst as described in Patent Document 2 is composed of carbon monoxide (CO), hydrocarbons. (HC), nitrogen oxides (NOx), etc. were not necessarily sufficient in terms of purification performance.

  The present invention has been made in view of the above-described problems of the prior art, and an exhaust gas purifying catalyst capable of exhibiting sufficiently high catalytic activity while utilizing copper and iron as active components, and the catalyst. It is an object of the present invention to provide a method for producing an exhaust gas purifying catalyst capable of producing a gas efficiently and reliably.

  The present inventors first examined the reason why a sufficiently high catalytic activity could not be obtained in the above-described conventional technology. In the above-mentioned conventional technology, an impregnation method using a transition metal salt was used. Because the transition metal (copper, iron, etc.) was supported on the support, the transition metal could not be supported in a sufficiently fine state, and due to this, a sufficiently high catalytic activity was not obtained. I guessed. In addition, in the conventional methods such as the impregnation method, the present inventors have selected a combination of two types of metals from transition metals, and one of the metals covers the other of the core-shell type. In addition to being able to fully utilize the characteristics of the two types of metal, the two types of metal particles may be supported separately from each other by phase separation. The metal composite) is coarsened and cannot support each metal in a sufficiently fine state, so that even when iron and copper are selected as transition metals, the catalytic activity is not necessarily sufficient. I guessed it was not. Based on the results of such studies, the present inventors have conducted extensive research to achieve the above object, and as a result, provided a catalyst for exhaust gas purification and a composite of copper and iron supported on the carrier. Surprisingly, a sufficiently high catalytic activity can be exhibited by forming a CuFe composite cluster having a particle diameter of 0.5 to 1.5 nm while at least a part of the composite is formed. As a result, the present invention has been completed.

That is, the exhaust gas purifying catalyst of the present invention comprises a carrier and a composite of copper and iron supported on the carrier, and
At least a part of the composite is a CuFe composite cluster having a particle diameter of 0.5 to 1.5 nm.

  In the exhaust gas purifying catalyst of the present invention, it is preferable that 50 at% or more of the total number of atoms of copper and iron supported on the carrier as the composite form the CuFe composite cluster.

  The method for producing an exhaust gas purifying catalyst of the present invention comprises contacting a carrier with a complex-containing liquid containing a CuFe multinuclear complex containing copper atoms and iron atoms in the nucleus of the complex, and carrying the CuFe multinuclear complex on the carrier. And calcining to obtain the exhaust gas purifying catalyst of the present invention.

The CuFe multinuclear complex according to the present invention is preferably a CuFe multinuclear complex having one selected from the group consisting of Cu ₃ Fe ₃ , Cu ₅ Fe ₄ and Cu ₆ Fe _{4 at the} core of the complex. In addition, the CuFe polynuclear complex according to the present invention is selected from the group consisting of a tetramethylammonium ion, a tetraethylammonium ion, a tetrapropylammonium ion, and a tetrabutylammonium ion having a carbonyl ligand as a ligand and a counter cation. It is preferable to have at least one kind of ion.

  In the method for producing an exhaust gas purifying catalyst of the present invention, the solvent of the complex-containing liquid is preferably an organic solvent having polarity.

The reason why the above object is achieved by the automobile exhaust gas purification catalyst of the present invention and the manufacturing method thereof is not necessarily clear, but the present inventors speculate as follows. That is, first, in the method for producing an automobile exhaust gas purification catalyst of the present invention, copper and iron are supported on the carrier using the CuFe multinuclear complex. Salts (such as nitrates) that have been used to support copper and iron in conventional catalyst production processes are exposed on the surface of the support by a weak electrostatic interaction with the support. The salt is decomposed by firing and the metal is supported on the carrier. As described above, when copper and iron are supported on a support using a copper salt and an iron salt other than the CuFe multinuclear complex, the state of the salt before firing adheres to the support due to weak interaction due to electrostatic force. Or even adherence, the aggregation or scattering due to the movement of the salt is easily caused by firing. In addition, when copper and iron are supported on a carrier using a copper salt and an iron salt, there is no bond between copper and iron (a bond between metals or a bond via a ligand). Since these metals are supported, the supported metal may be a core-shell type aggregate, or may be supported as a phase-separated state for each metal, and may be supported in a sufficiently fine state. could not. On the other hand, the CuFe multinuclear complex used in the present invention forms a coordinate bond with a metal atom or oxygen atom on the support and is supported on the support in a sufficiently stable state. In order to explain the loading state of such a complex on the carrier, a suitable example of the CuFe multinuclear complex according to the present invention is a CuFe multinuclear complex having a core of Cu ₃ Fe ₃ and a carbonyl ligand (binuclear complex). ) Is taken as an example, and a process of supporting copper and iron on a carrier using a complex is schematically shown with reference to FIG. Here, FIG. 1A is a diagram conceptually showing a state in which the CuFe multinuclear complex 11 is supported on the support 10, and FIG. 1B shows a state in which the composite cluster 12 is supported on the support 10. It is a figure shown notionally. In FIG. 1, the carrier 10 includes a metal atom M, the complex 11 includes three iron atoms 11a and three copper atoms 11b in its nucleus, and the ligand L is a carbonyl. It is a ligand. Moreover, in the complex 11 described in FIG. 1, a part of the ligand L couple | bonded with the iron atom 11a and the copper atom 11b is abbreviate | omitted. In the present invention, first, a complex-containing liquid containing the CuFe multinuclear complex 11 is brought into contact with the carrier 10. As described above, when the complex-containing liquid containing the CuFe multinuclear complex 11 is brought into contact with the support 10, as illustrated in FIG. 1A, the complex 11 includes the oxygen atom in the carbonyl ligand L, the support metal M, and (In some cases, it can be adsorbed and supported also by hydrogen bonding between the ligand and the hydroxyl group present on the surface of the carrier, and depending on the metal species of the carrier, the oxygen atom of the CuFe multinuclear complex It is also conceivable that a bond can be formed and adsorbed on the metal ions in the carrier. When a bond is formed in this way, the complex 11 is supported on the support 10 in a state of excellent stability due to its strong binding force (note that the type of the ligand L is changed to the type of the metal M of the support). The carrier and the complex can be sufficiently bonded by appropriately selecting them accordingly. When the complex 11 is supported on the carrier 10 and then baked, since the thermal stability of the bond between the carrier 10 and the complex 11 is high, the nucleus of the complex (the nucleus formed by the iron atom 11a and the copper atom 11b) Since the ligand is removed while sufficiently preventing aggregation and scattering due to movement, the metal cluster molecules forming the nucleus of the complex (Cu ₃ Fe _{3 in the} example shown in FIG. 1) have a sufficient form. It is carried on the carrier while maintaining the same. Therefore, when the complex 11 is baked after being supported on the carrier 10, the iron atoms 11a and the copper atoms 11b are sufficiently dispersed as a composite cluster of copper and iron while maintaining a sufficient form (state) in the nucleus of the complex. It is carried on the carrier in a state of being. As described above, since the movement and scattering of the complex nuclei are sufficiently suppressed during firing, the aggregation of the metals forming the nuclei of one complex and the other complex is also sufficiently suppressed, and sufficiently fine. The present inventors infer that the composite cluster 12 in such a state can be supported on the carrier. In addition, when the nucleus of the complex 11 is a heterogeneous metal cluster molecule having a bond between metals in Cu and Fe as in the example shown in FIG. Scattering of metal atoms constituting the nucleus during firing is suppressed, and a composite cluster of copper and iron is supported on the support while maintaining the state of the complex nucleus sufficiently. Further, the composite cluster supported using the complex 11 in this way is more aggregated due to the stability of the cluster than the particles supported by an impregnation method using a metal salt other than the complex. Because of its difficult nature, it tends to maintain a sufficiently fine particle state even during calcination or use as a catalyst. As described above, in the exhaust gas purifying catalyst of the present invention that can be suitably manufactured by using the method of manufacturing the exhaust gas purifying catalyst of the present invention, the CuFe composite cluster is supported in a sufficiently fine state on the carrier. Thus, there is no inconvenience that one type of metal coats the other type of metal to reduce the activity, and aggregation is sufficiently prevented so that the catalyst has a sufficient amount of active points. Therefore, the present inventors speculate that a sufficiently high catalytic activity can be exhibited.

  According to the present invention, an exhaust gas purification catalyst capable of exhibiting a sufficiently high catalytic activity while using copper and iron as active components, and an exhaust gas purification capable of efficiently and reliably producing the catalyst. It is possible to provide a method for producing an industrial catalyst.

FIG. 1A is a conceptual diagram schematically showing a continuous process of supporting copper and iron on a carrier using a complex, and FIG. 1A is a conceptual diagram showing a state where a polynuclear complex is supported on the carrier. 1 (b) is a conceptual diagram showing a state in which a composite cluster is supported on a carrier. 4 is an ORTEP diagram showing a molecular structure of a CuFe complex obtained in Preparation Example 1. FIG. FIG. 6 is a packing diagram (Packing diagram) showing an integrated structure of the CuFe complex obtained in Preparation Example 1. It is a graph of the mass spectrum (mass-to-charge ratio (m / z) of 600-1500 range) of the CuFe complex obtained in Preparation Example 1. FIG. 5 is an enlarged view of a portion where the mass-to-charge ratio (m / z) in the mass spectrum graph shown in FIG. FIG. 6 is an enlarged view of a portion where the mass-to-charge ratio (m / z) in the mass spectrum graph shown in FIG. ₃ is a graph of a theoretical mass spectrum of a complex represented by the formula: Cu ₃ Fe ₃ (CO) ₁₂ . 2 is a scanning transmission electron microscope (STEM) photograph of the exhaust gas purifying catalyst obtained in Example 1. FIG. 3 is a scanning transmission electron microscope (STEM) photograph of an exhaust gas purifying catalyst obtained in Example 2. FIG. 3 is a scanning transmission electron microscope (STEM) photograph of an exhaust gas purifying catalyst obtained in Example 2. FIG. 2 is a scanning transmission electron microscope (STEM) photograph of an exhaust gas purifying catalyst obtained in Comparative Example 1. It is a scanning transmission electron microscope (STEM) photograph of the sample of the exhaust gas purifying catalyst obtained in Example 2 in which EDS analysis was performed. It is an X-ray photograph which shows the mapping data of aluminum (Al) of the catalyst for exhaust gas purification obtained in Example 2 by EDS analysis. It is an X-ray photograph which shows the mapping data of iron (Fe) of the catalyst for exhaust gas purification obtained in Example 2 by EDS analysis. It is a X-ray photograph which shows the mapping data of the copper (Cu) of the catalyst for exhaust gas purification obtained in Example 2 by EDS analysis. 3 is a graph of an EDS spectrum of an exhaust gas purifying catalyst obtained in Example 2. 3 is a scanning transmission electron microscope (STEM) photograph of an exhaust gas purifying catalyst obtained in Example 2. FIG. 18 is a graph of EDS spectra at arbitrary four points (001 to 004) of the exhaust gas purifying catalyst obtained in Example 2 shown in FIG. It is a graph of CO conversion rate of the exhaust gas purifying catalyst obtained in Example 1 and Comparative Examples 1 to 3 under the condition of 500 ° C. Is a graph of C ₃ H ₆ conversion of the resultant catalyst in Example 1 and Comparative Examples 1 to 3 under the conditions of 500 ° C.. It is a graph of NO conversion rate of the exhaust gas purifying catalyst obtained in Example 1 and Comparative Examples 1 to 3 under the condition of 500 ° C. It is a graph of NO conversion rate of the exhaust gas purifying catalyst obtained in Example 1 and Comparative Examples 1 to 3 in a temperature range of 200 ° C to 600 ° C.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

[Exhaust gas purification catalyst]
The exhaust gas purifying catalyst of the present invention comprises a carrier and a composite of copper and iron supported on the carrier, and
At least a part of the composite is a CuFe composite cluster having a particle diameter of 0.5 to 1.5 nm.

The carrier according to the present invention is not particularly limited, and a known carrier that can be used as a catalyst for exhaust gas purification can be appropriately used. For example, a carrier made of a metal oxide can be appropriately used. Examples of the metal oxide used for such a carrier include activated alumina, alumina-ceria-zirconia, ceria-zirconia, zirconia, lanthanum stabilized activated alumina, and the like. Lanthanum (La), cerium (Ce) , Praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er) , Oxides of thulium (Tm), ytterbium (Yb), lutetium (Lu), yttrium (Y), zirconium (Zr), aluminum (Al), magnesium (Mg) and vanadium (V), solid solutions thereof, and these At least selected from the group consisting of complex oxides of Seed is preferred. Among such metal oxides, CeO ₂ , ZrO ₂ , Y ₂ O ₃ , TiO ₂ , Al ₂ O ₃ , solid solutions thereof, and composite oxides thereof are obtained from the viewpoint that higher catalytic activity can be obtained. What contains at least 1 type selected from the group which consists of a thing is more preferable.

In addition, the shape of such a carrier is not particularly limited, but is preferably a powder from the viewpoint of obtaining a sufficient specific surface area. Further, when such a carrier is in the form of powder, the average primary particle diameter of the carrier is preferably 5 to 200 nm, more preferably 5 to 100 nm, from the viewpoint of obtaining higher catalytic activity. . Further, the specific surface area of such a carrier is not particularly limited, but from the viewpoint of obtaining higher catalytic activity, it is more preferably 30 m ² / g or more, and further preferably 50 to ²⁰⁰ m ² / g. .

  In the exhaust gas purifying catalyst of the present invention, a composite of copper and iron is supported on the carrier. The "composite" here contains copper atoms and iron atoms, and refers to an aggregate of copper and iron atoms ("aggregates" described later and "copper and iron composite clusters"). (CuFe composite cluster) ”. In the present invention, at least a part of the composite is a composite cluster of iron and copper having a particle diameter of 0.5 to 1.5 nm (CuFe composite cluster: a composite of copper atoms and iron atoms). Cluster).

  Thus, the CuFe composite cluster according to the present invention satisfies the condition that the particle diameter is 0.5 to 1.5 nm (more preferably 0.5 to 1.3 nm). If the particle size is less than the lower limit, the interaction between the cluster and the carrier becomes too strong and sufficient activity cannot be expressed. On the other hand, if the upper limit is exceeded, the composite particles of copper and iron as active ingredients As a result of this coarsening, the amount of active sites in the catalyst is reduced, and sufficient catalytic activity cannot be obtained. In the present specification, in the following, the condition of the CuFe composite cluster according to the present invention (the condition that the particle diameter is 0.5 to 1.5 nm) is not satisfied, and the particle diameter is 1.5 nm. The excess composite particles are simply referred to as “aggregates” for convenience.

  Further, such a CuFe composite cluster is preferably a cluster in which the total number of iron and copper atoms is 100 atoms or less, more preferably a cluster in which the total number of iron and copper atoms is 6 to 50 atoms, More preferably, the total number of iron and copper atoms is a cluster of 6 to 30 atoms. When the total number of atoms in such a CuFe composite cluster exceeds the above upper limit, the particle diameter of the composite becomes larger than 1.5 nm, and the condition of the CuFe composite cluster is not satisfied. On the other hand, if it is less than the lower limit, the interaction between the cluster and the support becomes too strong, and there is a tendency that sufficient activity cannot be expressed. The particle diameter of such a CuFe composite cluster and the number of atoms in the cluster are determined by measuring the composite of copper and iron supported on the support by a scanning transmission electron microscope (Cs-STEM). Can be obtained by measuring the number of. In addition, the particle diameter here means the maximum diameter of the circumscribed circle when the CuFe composite cluster is not spherical.

  Further, as such a CuFe composite cluster, a composite cluster having 3 to 50 atoms of iron and 3 to 50 atoms of copper is preferable, and 3 to 20 atoms of iron and copper. A composite cluster having 3 to 20 atoms is more preferable, a composite cluster having 3 to 4 atoms of iron and 3 to 6 atoms of copper is further preferable, and the number of iron atoms is 3 A composite cluster having 3 atoms and copper atoms is particularly preferred. If the number of iron atoms is less than the lower limit, the interaction between the composite cluster and the support becomes too strong, and there is a tendency that sufficient activity cannot be expressed. It tends to decrease.

  Moreover, the average particle diameter of the composite (including the CuFe composite cluster and the aggregate) supported on such a carrier is preferably 0.5 to 5.0 nm, and 0.5 to 3 More preferably, it is 0.0 nm. If the average particle size is less than the lower limit, the interaction between the complex and the carrier becomes too strong, and there is a tendency that sufficient activity cannot be expressed. On the other hand, if the upper limit is exceeded, the number of active sites decreases. Tend to. In addition, such an average particle diameter measures a particle diameter about the arbitrary 10 or more composites currently carry | supported on the support | carrier with the scanning transmission electron microscope (Cs-STEM), and averages the calculated | required particle diameter. This can be calculated.

  In the present invention, 50 at% or more (more preferably 60 at% or more, particularly preferably 70 at% or more) of the total number of atoms of copper and iron supported as a complex on the carrier, and the particle size is 0.00. It is preferable to form a CuFe composite cluster of 5 to 1.5 nm. When the existing ratio (at%) of such CuFe composite clusters is less than the lower limit, the catalytic activity tends to decrease. The existence ratio (at%) of such CuFe composite cluster is determined by scanning an electron microscope having a spherical aberration correction device on a converging lens in an arbitrary region of 10 nm in the vertical direction and 10 nm in the horizontal direction on the support for the exhaust gas purification catalyst. Measured by (Cs-STEM), based on the obtained STEM image, the total number of atoms of copper and iron present in the region, and iron present as a CuFe composite cluster having a particle diameter of 0.5 to 1.5 nm And the number of copper atoms, respectively, and the ratio of the number of copper and iron atoms present as a CuFe composite cluster with respect to the total number of copper and iron atoms is calculated. It is obtained by imitating the existence ratio (at%) of the composite cluster. In addition, as a scanning transmission electron microscope (STEM) used when measuring the particle diameter, the number of atoms, and the existence ratio of such a CuFe composite cluster, for example, a trade name “JEM-2100F” manufactured by JEOL is used. it can.

  Further, the total amount of copper and iron supported on the support (the total supported amount of copper and iron supported as the composite (including the CuFe composite cluster)) is based on the total amount of the support and the composite. 0.05 to 3.5% by mass (more preferably 0.10 to 3.0% by mass, still more preferably 0.5 to 2.5% by mass, particularly preferably 1.0 to 2.0% by mass). Preferably there is. If the total amount of copper and iron is less than the lower limit, sufficient catalytic activity tends not to be obtained. On the other hand, if the upper limit is exceeded, sintering tends to occur, and a sufficiently fine CuFe composite cluster is sufficient. It tends to be difficult to disperse and carry the material, and sufficient activity cannot be obtained. The ratio of copper and iron supported on the carrier is preferably 1: 1 to 2: 1 by mass ratio (copper: iron), and is 1.1: 1 to 1.9: 1. It is more preferable. If the content ratio of iron is less than the lower limit, the activity tends to decrease.

  In the present invention, the average value of the distance between the particles of the CuFe composite cluster and the particles of the composite adjacent to the CuFe composite cluster (including the CuFe composite cluster) is 0.2 nm or more (more preferably 0.2 to 5 nm) is preferable. If the average value of the distance between the particles is less than the lower limit, the dispersibility of the active ingredient tends to be lowered, and a sufficiently high catalytic activity tends to be not obtained. When the surface area is small, the number of active sites tends to decrease and a sufficiently high catalytic activity tends not to be obtained. The “distance between the particles of the CuFe composite cluster and the composite particles adjacent to the CuFe composite cluster (distance between the particles)” referred to in the present invention is the abundance ratio (at%) of the aforementioned CuFe composite cluster. The Cs-STEM measurement can be performed in the same manner as the method for obtaining the value and obtained based on the obtained STEM image. That is, in the present invention, the “distance between the CuFe composite cluster and the particles of the composite adjacent to the CuFe composite cluster (distance between the particles)” refers to the adjacent composite viewed from the particles of each CuFe composite cluster. The length of the line segment obtained by selecting the particle with the shortest distance between the particles of the "CuFe composite cluster and the average value of the distances between the composite particles adjacent to the CuFe composite cluster" "Means an average value of the lengths of the line segments. Here, the “length of the line segment” means the length of the line segment when the closest contacts of each particle are connected. The average value of such distances is determined by selecting at least any five or more CuFe composite clusters as measurement particles, and measuring the composite particles having the shortest line segment length for each particle, It can obtain | require by calculating | requiring the length of the line segment, respectively, and calculating the average value. Note that the average value of such distances (average value of the length of the line segment) is, for example, an STEM image of an arbitrary region of 10 nm in length and 10 nm in width, and any five or more in the image It can be determined by using CuFe composite clusters as the particles for measurement.

Further, as the CuFe composite cluster, since a higher degree of catalytic activity can be obtained, it is preferable that the CuFe composite cluster is supported on the carrier by using a CuFe multinuclear complex containing a copper atom and an iron atom in the nucleus of the complex. It is more preferable to use a CuFe multinuclear complex comprising one kind selected from the group consisting of Cu ₃ Fe ₃ , Cu ₅ Fe ₄ and Cu ₆ Fe ₄ as the core of the above, and supported on the carrier. As a method for supporting a CuFe composite cluster on a carrier using such a CuFe multinuclear complex, the method for producing an exhaust gas purifying catalyst of the present invention described later can be suitably employed.

  Further, the form of the exhaust gas purifying catalyst of the present invention is not particularly limited. For example, a honeycomb-shaped monolith catalyst in which a catalyst including a carrier and a composite of copper and iron supported on the carrier is supported on a substrate. Alternatively, it may be in the form of a pellet-shaped pellet catalyst. The base material used here is not particularly limited, and a particulate filter base material (DPF base material), a monolithic base material, a pellet base material, a plate base material, and the like can be suitably used. Also, the material of such a base material is not particularly limited, but a base material made of a ceramic such as cordierite, silicon carbide, mullite, or a base material made of a metal such as stainless steel including chrome and aluminum is preferably used. can do.

  Further, the method for supporting the catalyst on such a substrate is not particularly limited, and a known method can be appropriately employed. In addition, in such an exhaust gas purification catalyst, other components (for example, NOx occlusion material) that can be used for the exhaust gas purification catalyst as long as the effects of the present invention are not impaired may be supported as appropriate. Further, the exhaust gas purifying catalyst of the present invention can be efficiently manufactured by adopting the method for manufacturing the exhaust gas purifying catalyst of the present invention described later.

[Method for producing exhaust gas-purifying catalyst]
In the method for producing an exhaust gas purifying catalyst of the present invention, a complex-containing liquid containing a CuFe multinuclear complex containing copper atoms and iron atoms in the nucleus of a complex is brought into contact with a carrier, and the CuFe multinuclear complex is supported on the carrier, By calcining, the exhaust gas purifying catalyst of the present invention is obtained.

  Such a carrier is the same as the carrier used in the exhaust gas purifying catalyst of the present invention.

  The CuFe polynuclear complex is not particularly limited as long as it contains a copper atom and an iron atom in the nucleus of the complex, but the total number of iron and copper atoms is 6 to 50 atoms (more preferably 6 atoms). 11 atoms, more preferably 6 atoms) and an intermetallic compound having a bond between copper and iron metal atoms (a heterometallic cluster molecule of copper and iron) forms the nucleus of the complex preferable. If the number of atoms is less than the lower limit, the function as an active point tends to be reduced, and sufficient activity tends not to be obtained. On the other hand, if the upper limit is exceeded, the active point is decreased (reduction in the surface area of the active point). There is a tendency that sufficient activity cannot be obtained. In addition, when the heterogeneous metal cluster molecule having a bond between copper and iron metal atoms is used as the nucleus of the complex in this way, when compared with a complex in which a copper atom and an iron atom are bonded via a ligand , Since the bond between metals is more fully maintained during pyrolysis of the ligand during firing, it is possible to suppress metal atoms from scattering due to pyrolysis of the ligand at a higher level. In addition, it is possible to support the copper and iron on the support while maintaining the state of the cluster molecules forming the nucleus more sufficiently. Furthermore, as the nucleus of the CuFe multinuclear complex, the number of iron atoms is 3 to 20 atoms (more preferably 3 to 4 atoms, particularly preferably 3 atoms), and the number of copper atoms is 3 to 30 atoms (more preferably). Is more preferably 3 to 6 atoms, particularly preferably 3 atoms), and an intermetallic compound (a heterometallic cluster molecule of copper and iron) having a bond between copper and iron metal atoms is more preferable. When the number of iron atoms is less than the lower limit, the function as the active point is lowered, and there is a tendency that sufficient activity cannot be obtained. On the other hand, when the upper limit is exceeded, the active point is decreased (the surface area of the active point is decreased) ), Sufficient activity tends not to be obtained.

Further, the core of such a CuFe multinuclear complex is selected from the group consisting of Cu ₃ Fe ₃ , Cu ₅ Fe ₄ and Cu ₆ Fe ₄ since the activity of the resulting catalyst is higher. More preferred are intermetallic compounds (heterogeneous metal cluster molecules of copper and iron), and Cu ₃ Fe ₃ is particularly preferred.

  In addition, such a ligand of the CuFe multinuclear complex has a bond between transition metals constituting the complex and can be supported on the support according to the type of metal of the support. The carbonyl ligand is particularly preferable, although it is not particularly limited. In addition, such a ligand may contain 1 type individually or in mixture of 2 or more types.

  Further, as such a CuFe polynuclear complex, a metal that forms a nucleus by preventing the complexes from contacting each other due to the presence of a counter cation, and supporting the complex on a carrier while maintaining a sufficient distance between the complexes. Since it is possible to support copper and iron on the support while maintaining the form of the intermetallic compound sufficiently (copper and iron can be efficiently supported as a CuFe composite cluster), tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium as counter cations Those having at least one ion selected from the group consisting of ions and tetrabutylammonium ions are preferred, and those having tetramethylammonium ions as counter cations are particularly preferred because higher loading efficiency can be obtained.

While such is not a specific restriction on the CuFe polynuclear complex, for example, the chemical formula _{Cu 3 Fe 3 (CO) 12} · [N (CH 3) 4] 3, Cu 3 Fe 3 (CO) 12 · [N (C 2 H ₅ ) ₄ ] ₃ , Cu ₃ Fe ₃ (CO) ₁₂ · [N (C ₃ H ₇ ) ₄ ] ₃ , Cu ₃ Fe ₃ (CO) ₁₂ · [N (C ₄ H ₉ ) ₄ ] ₃ etc. And the complex. Moreover, it does not restrict | limit especially as a manufacturing method of such a CuFe multinuclear complex, The well-known method which can manufacture the polynuclear complex (binuclear complex) which contains copper and iron in a nucleus can be employ | adopted suitably. (For example, methods described in documents such as J. Am. Chem. Soc., Vol. 108, No. 3, 1986, P. 445-451 may be used as appropriate).

  Moreover, it does not restrict | limit especially as a solvent of the said complex containing liquid, The water which can dissolve the said CuFe polynuclear complex, an organic solvent, etc. can be used suitably. In addition, the solvent of the complex-containing liquid is preferably an organic solvent having polarity from the viewpoint that the CuFe composite cluster can be more efficiently supported while maintaining the state of the complex more sufficiently. Examples of the organic solvent having such polarity include tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), dichloromethane, chloroform, ethyl acetate, propanol, acetone, and the like. Moreover, as such a solvent, you may utilize 1 type individually or in combination of 2 or more types.

  The organic solvent having a polarity suitable as the solvent is preferably one having a dielectric constant (unit: F / m) of 20 or less (more preferably 15 or less, still more preferably 4 to 9). When such a dielectric constant exceeds the upper limit, the complex tends not to be efficiently dispersed (dissolvable) in the solvent. Further, as the solvent of the complex-containing liquid, an organic solvent having a dielectric constant of 20 or less and a polarity is preferable, and tetrahydrofuran (THF), dimethyl is particularly preferable from the viewpoint that it can be supported while maintaining the state of the complex more sufficiently. More preferred are sulfoxide (DMSO), dichloromethane, chloroform and ethyl acetate. Examples of such dielectric constant values include values described in “Organic Solvents: Physical Properties and Methods of Purification”, 4th ed., Wiley, 1986, and free encyclopedias on the Internet. The values described in the “solvent” page of “Wikipedia” can be used.

  Moreover, as content of the CuFe polynuclear complex in such a complex containing liquid, it is preferable that it is 0.01-0.5 mass%, and it is more preferable that it is 0.02-0.3 mass%. If such a content is less than the lower limit, the loading efficiency tends to decrease, and if it exceeds the upper limit, the dispersion of the complex in the solvent tends to be insufficient.

  Furthermore, although the total amount of copper and iron contained in such a complex-containing liquid is not particularly limited, it is preferably 0.005 to 0.5% by mass in terms of metal, and 0.01 to 0.25. More preferably, it is mass%. When the total amount of copper and iron is less than the lower limit, not only the amount of the supporting solution is increased, but also it tends to be difficult to efficiently support the complex on the support. On the other hand, when the upper limit is exceeded, the complex Further, since the dispersibility of both the supports decreases, it tends to be difficult to uniformly support the CuFe multinuclear complex.

  Moreover, as a ratio of copper and iron contained in such a complex containing liquid, it is preferable that it is 1: 1-2: 1 by mass ratio (copper: iron), 1.1: 1-1 More preferably, it is 9: 1. If the content ratio of iron is less than the lower limit, the activity tends to decrease.

  Moreover, the preparation method of such a complex containing liquid is not restrict | limited, What is necessary is just to employ | adopt suitably the method which can melt | dissolve the said complex in the said solvent.

Furthermore, the method of bringing the complex-containing liquid into contact with the carrier and supporting the CuFe multinuclear complex on the carrier is not particularly limited, and depends on the type of metal species of the carrier, the type of ligand of the complex, and the like. A known method capable of supporting the complex on the carrier can be appropriately employed. For example, the CuFe multinuclear complex is supported on the carrier by immersing the carrier in the complex-containing liquid. A method or the like may be adopted. For example, when the ligand of the complex is a carbonyl ligand and the support is alumina, etc., by adopting a method of immersing the support in the complex-containing liquid as described above, The complex can be coordinated and bonded to an aluminum ion (Al ³⁺ ) atom via the oxygen atom of the child, whereby the CuFe multinuclear complex can be bonded and supported on the metal atom on the carrier. In the present invention, since the aggregation and scattering of the complex can be more sufficiently suppressed even during firing, the CuFe polynuclear complex is preferably supported by being bonded (for example, coordinated) to the metal atom on the carrier. .

  In addition, when the CuFe polynuclear complex is supported on the surface of the carrier by immersing the carrier in the complex-containing liquid, the pressure is 1 to 10 atm, the melting point of the solvent of the complex-containing liquid is not higher than the boiling point (more It is preferable to stir for about 0.5 to 24 hours under the temperature condition of preferably about 10 to 100 ° C., particularly preferably about 10 to 30 ° C. If the pressure and temperature conditions for supporting the CuFe multinuclear complex on the surface of the support are less than the lower limit, the supporting efficiency tends to decrease.On the other hand, if the upper limit is exceeded, production costs are reduced by continuing excessive stirring. It tends to increase.

  In addition, as a method of firing after supporting the CuFe multinuclear complex on the carrier, it is preferable to employ a method of firing for about 1 to 5 hours at a temperature of 200 to 800 ° C. (more preferably 300 to 600 ° C.). . If the calcination temperature and time are less than the lower limit, it tends to be difficult to remove the ligand efficiently and sufficiently, and if the upper limit is exceeded, the ligand is decomposed on the support. At this time, metal atoms in adjacent complexes tend to aggregate easily.

  According to such a method for producing an exhaust gas purifying catalyst of the present invention, a CuFe composite cluster having a particle diameter of 0.5 to 1.5 nm can be efficiently supported on a carrier, and the exhaust gas purifying of the present invention is performed. It becomes possible to manufacture the catalyst for use efficiently.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

(Preparation Example 1: Preparation of CuFe complex)
Cu ₃ Fe ₃ (CO) _12. [N (CH ₃ ) ₄ ] ₃ was formed as follows using an autoclave manufactured by Buchgrass Woster. That is, first, in an argon (Ar) atmosphere, Na ₂ Fe (CO) ₄ complex (manufactured by Wako Pure Chemical Industries, Ltd .: Na ₂ Fe (CO) ₄ · 1.5-dioxane: 0.99 g) and CuBr (Trade name “Copper (I) bromide” of ALDRICH: 0.41 g) was dissolved in tetrahydrofuran (THF: manufactured by Wako Pure Chemical Industries, Ltd., dielectric constant: 7.58) and stirred at room temperature (25 ° C.) for 6 hours. To produce a Na salt of a Cu ₃ Fe ₃ (CO) ₁₂ complex containing 3 atoms of Cu and Fe, and a THF solution containing the salt was obtained. The chemical reaction formula of the step of obtaining the Na salt of such Cu ₃ Fe ₃ (CO) ₁₂ complex is the following formula (1):
3Na ₂ Fe (CO) ₄ + 3CuBr → Na ₃ Cu ₃ Fe ₃ (CO) ₁₂ + 3NaBr (1)
It is represented by

Next, tetramethylammonium chloride (Wako Pure Chemical Industries, Ltd .: [N (CH ₃ ) ₄ ] Cl) was added to the THF solution thus obtained, and the mixture was stirred at room temperature (25 ° C.) for 16 hours. _Cu 3 _Fe 3 _{(CO) 12} complex _{[N (CH 3) 4]} 3 generates a salt in a _{THF, [N (CH 3)} 4] of _{Cu 3 Fe 3 (CO) 12} 3 THF containing salt A solution was obtained. The chemical reaction formula of the process of producing such a [N (CH ₃ ) ₄ ] ₃ salt of Cu ₃ Fe ₃ (CO) ₁₂ is the following formula (2):
Na ₃ Cu ₃ Fe ₃ (CO) ₁₂ +3 [N (CH ₃ ) ₄ ] Cl → Cu ₃ Fe ₃ (CO) ₁₂・ [N (CH ₃ ) ₄ ] ₃ + 3NaCl (2)
It is represented by Next, a THF solution containing the [N (CH ₃ ) ₄ ] ₃ salt of Cu ₃ Fe ₃ (CO) ₁₂ obtained in this manner was subjected to pressure: 10 Pa or less, room temperature (25 ° C.), and 12 hours. After vacuum drying under conditions, the resulting dried product was extracted with acetone, concentrated, and then again vacuum-dried under conditions of pressure: 10 Pa or less, room temperature (25 ° C.), 12 hours to remove impurities, Cu ₃ Fe ₃ (CO) _12. [N (CH ₃ ) ₄ ] ₃ was purified. In this way, a single crystal of CuFe complex (Cu ₃ Fe ₃ (CO) _12. [N (CH ₃ ) ₄ ] ₃ ) was obtained.

[Evaluation of properties of complex obtained in Preparation Example 1]
<Single crystal X-ray structure analysis>
A single crystal X-ray structural analysis measuring device (trade name “Saturn CCD single crystal X-ray structural analysis device” manufactured by Rigaku Corporation) for the single crystal of the CuFe complex obtained in Preparation Example 1 is as follows. Was used for single crystal X-ray structural analysis. That is, first, a liquid paraffin was used as a protective medium, and after preparing a sample in which the surface of the single crystal of the CuFe complex obtained in Preparation Example 1 was protected with liquid paraffin, the sample was mounted on the measuring device, Single crystal X-ray structural analysis was performed at −100 ° C. using an apparatus. The single crystal used had a block shape of 0.1 mm in length, 0.1 mm in width, and 0.05 mm in thickness, and the color of the crystal was yellow. For such single crystal X-ray structure analysis, SHELX97 was used as software for crystal structure analysis, and the direct method was adopted (SHELX97 direct method). As a result of such analysis, the crystallographic data of the CuFe complex obtained in Preparation Example 1 is shown in Table 1, the ORTEP diagram showing the molecular structure of the CuFe complex is shown in FIG. FIG. 3 shows a packing diagram (Packing diagram) representing the integrated structure of the above.

As is apparent from the results shown in Table 1 and FIG. 2, the CuFe polynuclear complex obtained in Preparation Example 1 is represented by the formula: Cu ₃ Fe _{3 in} which the complex has a bond between the atoms of Cu and Fe. It was confirmed to have a nuclear structure. Further, as is clear from the results shown in FIG. 2, it was confirmed that the CuFe complex obtained in Preparation Example 1 had three molecules of “N (CH ₃ ) ₄ ” as counter cations. Was confirmed not to exist. Further, as apparent from the Packing diagram shown in FIG. 3, it was found that a counter cation was present between the molecules of the CuFe multinuclear complex obtained in Preparation Example 1 having Cu ₃ Fe ₃ as a nucleus. . In addition, from the results shown in FIG. 3, the charge balance is maintained by intercalating four molecules of counter cation “N (CH ₃ ) ₄ ” between the molecules of the CuFe multinuclear complex and the present invention. They guess. In addition, since the balance of charges between the complex molecules is maintained by the counter cation in this way, the present inventors believe that there is almost no interaction between the molecules of the CuFe multinuclear complex obtained in Preparation Example 1. I guess. Further, as is clear from the results shown in FIGS. 2 and 3, since there are always N (CH ₃ ) ₄ molecules around the Cu ₃ Fe ₃ nucleus of the CuFe multinuclear complex, the CuFe multinuclear complex is supported on the carrier. It can also be seen that a counter cation is present around the complex even in the process, and aggregation of Cu ₃ Fe ₃ nuclei is suppressed.

<Mass spectrometry (MALDI-MS)>
Mass analysis (MALDI-MS: Matrix-Assisted Laser Desorption / Ionization Mass Spectrometry analysis) was performed using the CuFe complex obtained in Preparation Example 1. In addition, for such mass analysis, a mass spectrometer manufactured by Bruker Daltonics (trade name “Autoflex”) is used as a measurement apparatus, and measurement conditions are laser wavelength: 337 nm (nitrogen gas laser), acceleration voltage: 19 kV. The conditions were employed and 2-[(E) -3- (4-tert-butylphenyl) -2-methyl-2-propenylidene] malononitrile was used as the matrix. Moreover, for such mass spectrometry, a solution containing a very small amount of the CuFe complex obtained in Preparation Example 1 and a matrix (DCTB) in THF was used as a sample for measurement. Graphs of measured data of mass spectra obtained as a result of such mass spectrometry (MALDI-MS) are shown in FIGS. 4 shows a mass spectrum having a mass-to-charge ratio (m / z value) in the range of 600 to 1500, and FIG. 5 shows a mass-to-mass ratio (m / z value) of the mass spectrum shown in FIG. FIG. 6 shows an enlarged view of the spectrum in which the mass-to-charge ratio (m / z value) of the mass spectrum shown in FIG. 4 is in the range of 1300 to 1325. For reference, a graph of a theoretical mass spectrum (calculated value) of a complex represented by the formula: Cu ₃ Fe ₃ (CO) ₁₂ is shown in FIG.

As apparent from the data shown in FIGS. 4 to 7, the measured data (spectrum) obtained in FIGS. 4 to 6 and the theoretical spectrum (calculation) of the complex represented by Cu ₃ Fe ₃ (CO) ₁₂ shown in FIG. Value), the spectrum pattern shown in the measured data is very similar to the isotope pattern of the theoretical spectrum of a molecule composed of 3 atoms of Cu and 3 atoms of Fe. In FIG. 5, it was found that Cu exists as a hexanuclear complex consisting of 3 atoms and 3 atoms of Fe. That is, from these results, the CuFe complex obtained in Preparation Example 1 may exist as a hexanuclear complex having a molecule represented by Cu ₃ Fe ₃ in the nucleus even in a solution using THF as a solvent. confirmed. Therefore, using the complex-containing liquid in which the CuFe polynuclear complex (Cu ₃ Fe ₃ (CO) _12. [N (CH ₃ ) ₄ ] ₃ ) obtained in Preparation Example 1 is contained in an organic solvent such as THF. When the complex is supported on the carrier, the structure of the molecule forming the nucleus (the structure of the molecule represented by Cu ₃ Fe ₃ ) is sufficiently maintained in the solvent. It can be seen that the complex can be supported on the support while the structure of Cu ₃ Fe ₃ is sufficiently maintained.

Example 1
First, using the CuFe polynuclear complex (Cu ₃ Fe ₃ (CO) _12. [N (CH ₃ ) ₄ ] ₃ ) obtained in Preparation Example 1, γ-Al ₂ O ₃ (commercially available from Sumitomo Chemical Co., Ltd.) An exhaust gas purifying catalyst was obtained by supporting a composite of copper and iron on a carrier having the name “AKP-G015”, specific surface area: 150 m ² / g, average particle diameter:> 100 nm). That is, first, in an argon atmosphere, 303 mg of the CuFe polynuclear complex obtained in Preparation Example 1 was dissolved in THF (1000 mL, dielectric constant: 7.58) to obtain a complex-containing liquid. Next, 10 g of the γ-Al ₂ O ₃ was added to the complex-containing liquid in an Ar atmosphere, and the mixture was stirred at a temperature of 30 ° C. for 12 hours. Subsequently, solid content was taken out from the complex-containing liquid after stirring by filtration, and calcined in the atmosphere at a temperature condition of 500 ° C. for 3 hours to obtain an exhaust gas purifying catalyst. The obtained exhaust gas-purifying catalyst was molded by a cold isostatic pressure method (CIP: 1000 kg / cm ² ) and then pulverized into pellets having a diameter of 0.5 to 1 mm to obtain a pellet-shaped catalyst.

(Example 2)
Exhaust gas purification catalyst (pellet-shaped catalyst) was obtained in the same manner as in Example 1 except that the amount of CuFe polynuclear complex used was changed from 303 mg to 606 mg when obtaining the complex-containing liquid.

(Comparative Example 1)
Copper nitrate (trade name “Copper (II) Nitrate Trihydrate” manufactured by Wako Pure Chemical Industries, Ltd.) 220 mg and iron nitrate (trade name “Iron (III) Nitrate Nonhydrate” manufactured by Wako Pure Chemical Industries, Ltd.) 261 mg of ion-exchanged water ( 1 L) to obtain a solution containing copper and iron salts. Next, γ-Al ₂ O ₃ (trade name “AKP-G015” manufactured by Sumitomo Chemical Co., Ltd., specific surface area: 150 m ² / g, average particle size:> 100 nm) is added to the copper and iron salt-containing solution. 10g was added, and the mixture was heated and stirred in the atmosphere at 100 ° C for 12 hours to evaporate to dryness to obtain a solid content. Thereafter, the solid content was calcined in the atmosphere at a temperature of 300 ° C. for 3 hours to obtain an exhaust gas purifying catalyst for comparison in which iron and copper were supported on γ-Al ₂ O ₃ . In addition, the exhaust gas purifying catalyst for comparison obtained in this way was molded into a pellet having a diameter of 0.5 to 1 mm after being formed by a cold isostatic pressure method (CIP: 1000 kg / cm ² ) to form a pellet. This catalyst was used.

(Comparative Example 2)
Except for not using iron nitrate, an exhaust gas purifying catalyst (pellet-shaped catalyst) for comparison in which copper was supported on γ-Al ₂ O ₃ was obtained in the same manner as in Comparative Example 1.

(Comparative Example 3)
Except for not using copper nitrate, an exhaust gas purifying catalyst (pellet-shaped catalyst) for comparison in which iron was supported on γ-Al ₂ O ₃ was obtained in the same manner as in Comparative Example 1.

(Comparative Example 4)
Comparative example in which iron and copper were supported on γ-Al ₂ O ₃ in the same manner as in Comparative Example 1 except that the amount of copper nitrate used was changed from 220 mg to 525 mg and the amount of iron nitrate used was changed from 261 mg to 557 mg. An exhaust gas purifying catalyst (pellet-shaped catalyst) was obtained.

(Comparative Example 5)
Exhaust gas purification catalyst (pellet) for comparison, in which copper was supported on γ-Al ₂ O ₃ in the same manner as in Comparative Example 1 except that iron nitrate was not used and the amount of copper nitrate used was changed from 220 mg to 525 mg. Catalyst was obtained.

(Comparative Example 6)
Exhaust gas purifying catalyst (pellet) for comparison in which copper was supported on γ-Al ₂ O ₃ in the same manner as in Comparative Example 1 except that copper nitrate was not used and the amount of iron nitrate was changed from 261 mg to 557 mg. Catalyst was obtained.

[Evaluation of characteristics of catalysts obtained in Examples 1 and 2 and Comparative Examples 1 to 6]
<ICP analysis>
ICP (Inductively Coupled Plasma) analysis was performed using each of the exhaust gas purifying catalysts obtained in Examples 1-2 and Comparative Examples 1-6, and the supported amounts of copper and iron in each catalyst were measured. For such ICP analysis, a trade name “CIROS 120EOP” manufactured by Rigaku Corporation was used as an ICP analyzer. As a measurement sample, 0.2 g of catalyst was added to aqua regia ([HNO ₃ ]: [HCl] = 1: 3 (volume ratio)) for decomposition, and then an aqueous sulfuric acid solution was added to the decomposition solution. Then, a solution obtained by completely dissolving the catalyst was used. When measuring the amount of copper and iron supported, first, the measurement sample was introduced into argon plasma using the ICP analyzer, and the emission spectrum intensities of Cu and Fe were measured. Next, based on the obtained emission spectrum, Cu and Fe were quantified by a calibration curve method, and the concentrations of Cu and Fe were determined to calculate the supported amounts of copper and iron. The measurement wavelengths were Cu: 324.754 nm and Fe: 259.941 nm. Table 2 shows the amount of supported copper (wt%) and the amount of supported iron (wt%) in each catalyst determined based on the ICP analysis results. In order to clarify the structure of the exhaust gas purifying catalyst obtained in each example and each comparative example, the type of carrier used to form each catalyst and the support for copper and iron on the carrier. Table 2 also shows the types of solutions used.

  From the results of such ICP analysis, the supported amount of Cu and Fe in each catalyst is proportional to the charged amount of Cu and Fe in the supported solution regardless of the type of metal complex and metal salt used. It was found that the metal complex or metal salt used for supporting Cu and Fe on the support was supported on the support at a ratio of almost 100%, and Cu and Fe were supported on the support.

<Measurement by Scanning Transmission Electron Microscope (Cs-STEM) of Catalysts Obtained in Examples 1 and 2 and Comparative Example 4>
The powders of exhaust gas purifying catalysts obtained in Examples 1 and 2 and Comparative Example 4 were each subjected to a scanning transmission electron microscope with a spherical aberration correction device (trade name “JEM-2100F” manufactured by JEOL Ltd.) for X-ray analysis. ) To confirm the loading state of the loaded material and EDS attached to the above device (energy dispersive X-ray spectroscopic analysis: use the product name “EX-24063JGT” manufactured by JEOL for X-ray analysis) Went. In addition, as a measurement sample, what baked each catalyst in the air at 300 degreeC for 3 hours was utilized. The measurement conditions are shown below.

〔Measurement condition〕
Device: JEM-2100F (manufactured by JEOL)
Acceleration voltage: 200 kV
Lattice resolution (lattice image): 0.1 nm
Point resolution (particle image): 0.19 nm
STEM resolution: 0.2 nm
Magnification (STEM): ~ 150000000 times (measured by appropriately changing the magnification)
Electron gun: Hot cathode field emission X-ray detection solid angle: 0.24 sr (unit: sr indicates steradian. Solid angle with respect to the center of the portion on the sphere having an area equal to the square of the sphere radius).

  FIG. 8 shows a scanning transmission electron microscope (STEM) photograph of the exhaust gas purifying catalyst obtained in Example 1 obtained by such measurement, and FIG. 8 shows the scanning transmission type of the exhaust gas purifying catalyst obtained in Example 2. An electron microscope (STEM) photograph is shown in FIGS. 9 to 10, and a scanning transmission electron microscope (STEM) photograph of the exhaust gas purifying catalyst obtained in Comparative Example 1 is shown in FIG. In the figure, a region surrounded by a white line is a region where CuFe composite clusters or aggregates are confirmed.

  Moreover, the EDS analysis result of the exhaust gas purification catalyst obtained in Example 2 is shown in FIGS. That is, a scanning transmission electron microscope (STEM) photograph of the sample of the exhaust gas purifying catalyst obtained in Example 2 used for EDS analysis is shown in FIG. 12, and X-rays showing the mapping data of aluminum (Al) of the sample A photograph is shown in FIG. 13, an X-ray photograph showing mapping data of iron (Fe) of the sample is shown in FIG. 14, an X-ray photograph showing mapping data of copper (Cu) of the sample is shown in FIG. The graph of the EDS spectrum as an analysis result is shown in FIG. In FIG. 16, the peak P1 of the spectrum shows the peak of Fe (FeKa), and the peak P2 shows the peak of Cu (CuKa). Further, a scanning transmission electron microscope (STEM) photograph of the exhaust gas purifying catalyst obtained in Example 2 is shown in FIG. 17, and any four points (001 to 004) of EDS on the exhaust gas purifying catalyst shown in FIG. The spectrum graph is summarized in FIG. 18A to 18D show EDS spectra at points 001 to 004, respectively, peak P3 shows the peak of Fe (FeKa), and peak P4 shows the peak of Cu (CuKa).

  As is clear from the results shown in FIG. 8, in the exhaust gas purifying catalyst obtained in Example 1, a composite cluster of iron and copper (CuFe) having a particle diameter of 0.5 to 1.5 nm is formed on alumina (support). It was confirmed that the composite cluster) was supported (in FIG. 8, the particles confirmed as CuFe composite clusters were the largest and the particle diameter was 1 nm). Further, in such a scanning transmission electron microscope, an arbitrary region of 10 nm in length and 10 nm in width is measured, and copper atoms and iron supported as CuFe composite clusters having a particle diameter of 0.5 to 1.5 nm are measured. When the proportion of atoms was determined, in the exhaust gas purifying catalyst obtained in Example 1, the particle diameter was 70 at% with respect to the total number of copper atoms and iron atoms carried on the carrier in the region. Is supported as a CuFe composite cluster of 0.5 to 1.5 nm. Further, in such a scanning transmission electron microscope measurement, an arbitrary region of 10 nm in length and 10 nm in width is measured, and the “CuFe composite cluster and the adjacent iron and copper composite of the exhaust gas purifying catalyst obtained in Example 1” are obtained. Average distance between bodies (hereinafter, in each example and comparative example, when viewed from five clusters, the average value of distances between adjacent complexes (including the case of clusters)) The average distance was 0.5 nm. Furthermore, it was found that all the supports (CuFe composite clusters) having a particle diameter of 0.5 to 1.5 nm existing in the region are clusters having a total number of metal atoms of 6 to 12. In addition, the particle diameter data of any 10 supported materials were obtained from such a scanning transmission electron microscope measurement, and the average particle diameter was determined based on such data. It was 0 nm.

  As is clear from the results shown in FIGS. 9 to 10, in the exhaust gas purifying catalyst obtained in Example 2, the alumina (support) is made of iron and copper having a particle diameter of 0.5 to 1.5 nm. It was confirmed that the composite cluster (CuFe composite cluster) was supported (in FIG. 9 and FIG. 10, the particles confirmed as the CuFe composite cluster were the largest and the particle diameter was 1.5 nm). Further, in such a scanning transmission electron microscope measurement, an arbitrary region of 10 nm in length and 10 nm in width is measured, and copper atoms and iron supported as CuFe composite clusters having a particle diameter of 0.5 to 1.5 nm are measured. In the exhaust gas purifying catalyst obtained in Example 2, 70 at% of the total number of copper atoms and iron atoms carried on the carrier in the region was 70% by particle. It was confirmed that it was supported as a CuFe composite cluster having a diameter of 0.5 to 1.5 nm. Further, in such a scanning transmission electron microscope measurement, an arbitrary region of 10 nm in length and 10 nm in width is measured, and the “CuFe composite cluster and the adjacent iron-copper composite of the exhaust gas purifying catalyst obtained in Example 2” are obtained. As a result of confirming the “average distance to the body”, the average distance was 4 nm. Furthermore, it was found that all the supports (CuFe composite clusters) having a particle diameter of 0.5 to 1.5 nm existing in the region are clusters having a total number of metal atoms of 6 to 24. In addition, the particle diameter data of any 10 supported materials were obtained from such a scanning transmission electron microscope measurement, and the average particle diameter was determined based on such data. It was 3 nm.

  On the other hand, as is clear from the results shown in FIG. 11, the support on the carrier shown in FIG. 11 (support in the figure surrounded by the white line) has a particle diameter of 4 nm, It was confirmed that an aggregate in which a large number of metal atoms aggregated was supported on the support. Further, in the exhaust gas purifying catalyst obtained in Comparative Example 4, in the measurement of an arbitrary region of 10 nm in length and 10 nm in width, the particle size is 0.5 to 1.5 nm as a supported material supported on the carrier. Particles could not be confirmed, and the ratio of copper atoms and iron atoms supported as CuFe composite clusters having a particle diameter of 0.5 to 1.5 nm was 0 at%. From such a scanning transmission electron microscope measurement, the particle diameter data of any 10 supported materials was obtained, and the average particle diameter was obtained based on the data. As a result, the exhaust gas purifying catalyst obtained in Comparative Example 4 was obtained. The average particle size of the support was 4 nm. In addition, from such a scanning transmission electron microscope measurement, the catalyst for exhaust gas purification obtained in Comparative Example 4 has low uniformity in the size of the support (the size varies), and clusters of a fixed size were confirmed. could not.

  Further, as is apparent from the results shown in FIGS. 12 to 18, in the exhaust gas purifying catalyst of the present invention (Example 2) obtained by adopting the method of manufacturing the exhaust gas purifying catalyst of the present invention, copper It is confirmed that atoms and iron atoms are sufficiently dispersed without being biased and supported on an alumina carrier, and the strengths of Cu and Fe are almost equal in any four-point EDS spectrum. From this, it was confirmed that the cluster supported on the carrier was a composite of Cu and Fe. In addition, the exhaust gas purification catalyst obtained in Example 1 was similarly measured for arbitrary four points of EDS spectra. As a result, the strengths of Cu and Fe were almost equal and no deviation was observed. From the results of such EDS analysis, the cluster supported on the carrier of the exhaust gas purification catalyst obtained in Examples 1 and 2 confirmed by scanning transmission electron microscope measurement is composed of a composite of Cu and Fe, It can be seen that the support (cluster) as shown in the STEM images of FIGS. 8 to 10 is a CuFe composite cluster.

  As is clear from the results of measurement by such a scanning transmission electron microscope, the results of EDS analysis and ICP analysis, etc., the method for producing an exhaust gas purifying catalyst of the present invention (Examples 1 and 2) is adopted. In each of the catalysts obtained, it was confirmed that copper and iron can be supported in a fine cluster state, and copper and iron are supported on the support using a CuFe polynuclear complex. It can be seen that the CuFe composite cluster can be uniformly supported. On the other hand, in the conventional loading method using the salt employed in Comparative Example 4, it was confirmed that copper and iron could not be loaded in a fine cluster state even if copper and iron were loaded on the carrier. It was. In particular, if the catalyst obtained in Example 2 and the catalyst obtained in Comparative Example 4 in which the supported amounts of copper and iron are the same amount are compared (particularly, FIGS. 9 to 10 and FIG. 11 are compared). In the exhaust gas purifying catalyst obtained in Example 2, it is clear that the agglomeration of the support is sufficiently suppressed. From the results as described above, according to the method for producing an exhaust gas purifying catalyst of the present invention (Examples 1 and 2), while maintaining the structure of the cluster molecules forming the nuclei of the used CuFe multinuclear complex sufficiently, It can be seen that copper and iron can be supported, and aggregation is sufficiently suppressed in the firing step. In addition, such a result shows that, by supporting copper and iron using a CuFe polynuclear complex, scattering of cluster molecules that form the nucleus of the complex is suppressed even when the ligand is decomposed, and the nucleus is formed. The present inventors infer that this is because copper and iron are supported on the carrier while maintaining the state of the molecules to be sufficiently maintained.

<Evaluation test of purification performance of CO, C ₃ H ₆ , NO (I)>
Using the exhaust gas purifying catalyst (pellet catalyst) obtained in Example 1 and Comparative Examples 1 to 3, the air-fuel ratio (λ: A / F) is in the range of 0.96 to 1.04. The exhaust gas purification catalysts obtained in Example 1 and Comparative Examples 1 to ₃ were evaluated for CO, C ₃ H ₆ , and NO purification performance. That is, first, 1.5 g of the catalyst was placed in an atmospheric pressure fixed bed flow type reaction apparatus (manufactured by Vest Sokki). Next, to the catalyst, CO (0.45 _{volume%), H} 2 (0 volume%), NO (0.12 _{volume%), C 3 H 6 (} 0.146 volume% _{C 1} (carbon equivalent Concentration)), O ₂ (1.213% by volume), CO ₂ (8.0% by volume), H ₂ O (5.0% by volume) and N ₂ (remainder) mixed gas at 7 L / min. While supplying at a gas flow rate, the concentration of carbon monoxide (CO), propylene (C ₃ H ₆ ) and oxygen concentration (O ₂ ) in the mixed gas is changed, and the air-fuel ratio (λ) becomes 0.96. (CO concentration in gas: 1.5 vol%, C ₃ H ₆ concentration: 0.185 vol% C ₁ , O ₂ concentration: 0.406 vol%) to 1.04 (CO concentration in gas: 0. 45 _volume%, C 3 _{H 6} concentration: _0.146% by volume C 1, _{O 2} concentration: 1.213 touch when a value in the range of volume%) CO incoming gas (gas prior to contacting the catalyst) to, C _{3 H} 6, and the concentration of _{NO, CO} outgoing from the catalyst in the gas (gas after contact with the catalyst), C _{3 H} 6, The concentration of NO is measured, and the CO and C ₃ H of each catalyst when the air-fuel ratio (λ: A / F) is in the range of 0.96 to 1.04 under the condition of the input gas temperature: 500 ° C. _6. The conversion rate of NO was measured. When the air-fuel ratio (λ) is 1.00, the concentrations of CO, C ₃ H ₆ and O _{2 in} the gas are as follows: CO concentration: 0.6998 volume%, C ₃ H ₆ concentration: 0.16 volume % C ₁ , O ₂ concentration: 0.646% by volume. The obtained results are shown in FIG. 19 (CO conversion), FIG. 20 (C ₃ H ₆ conversion), and FIG. 21 (NO conversion).

As is clear from the results shown in FIGS. 19 to 21, the exhaust gas-purifying catalyst obtained in Example 1 has comparative examples 1 to 1 when the air-fuel ratio (λ) is in the range of 0.96 to 1.04. Compared with the exhaust gas purifying catalyst obtained in No. 3, the conversion rate of CO and C ₃ H ₆ was always high, and it was confirmed that the purification performance of CO and C ₃ H ₆ was sufficiently high. Further, the exhaust gas purifying catalyst obtained in Example 1 has a sufficiently high NO purification performance at a stoichiometric to rich air-fuel ratio (an air-fuel ratio such that λ is between 0.98 and 1). It was confirmed that Thus, since the NO conversion rate is very high in the atmosphere in the vicinity of stoichiometric, the exhaust gas purification catalyst obtained in Example 1 is the exhaust gas purification catalyst obtained in Comparative Examples 1 to 3. It was found that the performance was sufficiently high as a so-called three-way catalyst used under stoichiometric conditions. From these results, the exhaust gas purifying catalyst obtained in Example 1 is sufficiently higher in CO, C ₃ H ₆ and NO than the exhaust gas purifying catalyst obtained in Comparative Examples 1 to _3. It was confirmed that the catalyst can be purified in a well-balanced manner at a standard level and is highly practical.

<Evaluation test of NO purification performance (II)>
Using the exhaust gas purifying catalysts (pellet-shaped catalyst) obtained in Example 1 and Comparative Examples 1 to 3, the NO purification performance of each catalyst was evaluated. That is, first, 1.5 g of the catalyst was placed in an atmospheric pressure fixed bed flow type reaction apparatus (manufactured by Vest Sokki). Next, with respect to the catalyst, CO (0.6998 volume%), H ₂ (0 volume%), NO (0.12 volume%), C ₃ H ₆ (0.16 volume% C ₁ (carbon conversion) Concentration)), O ₂ (0.646% by volume), CO ₂ (8.0% by volume), H ₂ O (5.0% by volume) and N ₂ (remainder) stoichiometric gas of 7 L / min. It was supplied at a flow rate and adjusted so that the temperature of the gas with catalyst was 200 ° C. Thereafter, the temperature of the gas containing the catalyst is increased to 700 ° C. at a rate of temperature increase of 15 ° C./min, and the NO concentration in the gas entering the catalyst and the gas exiting from the catalyst is changed between 200 ° C. and 600 ° C. Each measurement was performed, and the NO conversion rate of each exhaust gas purification catalyst was calculated from the difference between the measured values of the catalyst-containing gas and the catalyst output gas. As a result, the NO conversion curve is shown in FIG.

  As is apparent from the results shown in FIG. 22, in the exhaust gas purifying catalyst (Example 1) of the present invention, the 30% conversion temperature of NO (the temperature at which the NO conversion rate reaches 30% during the temperature rising process) is Among the exhaust gas purifying catalysts for comparison (Comparative Examples 1 to 3), the 30% conversion temperature of NO was 490 ° C. even in the highest performance. Further, in the exhaust gas purifying catalyst of the present invention (Example 1), it cannot be achieved with a comparative catalyst in a temperature range of 460 ° C. or more, compared with a comparative exhaust gas purifying catalyst (Comparative Examples 1 to 3). It was found that higher catalytic activity was obtained. Thus, it was confirmed that the exhaust gas purifying catalyst (Example 1) of the present invention has sufficient catalytic activity for NO.

From above results, the exhaust gas purifying catalyst of the present invention (Example 1), compared with the catalyst for purification of exhaust gas for comparison (Comparative Examples 1 to 3), CO in the exhaust gas, NO, C ₃ It was confirmed that H ₆ can be purified in a balanced manner at a higher level.

  As described above, according to the present invention, an exhaust gas purifying catalyst capable of exhibiting sufficiently high catalytic activity while using copper and iron as active components and the catalyst are efficiently and reliably produced. It is possible to provide a method for producing an exhaust gas purifying catalyst that can be used.

Therefore, the exhaust gas purifying catalyst of the present invention is useful, for example, as a catalyst for purifying CO, NO, C ₃ H ₆ contained in exhaust gas from automobiles.

  DESCRIPTION OF SYMBOLS 10 ... Support | carrier, 11 ... Complex, 11a ... Iron atom, 11b ... Copper atom, 12 ... Composite cluster, M ... Metal atom, L ... Ligand.

Claims (6)

A carrier and a composite of copper and iron supported on the carrier; and
At least a part of the composite is a CuFe composite cluster having a particle diameter of 0.5 to 1.5 nm.   2. The exhaust gas purifying catalyst according to claim 1, wherein 50 at% or more of the total number of atoms of copper and iron supported as the composite on the carrier forms the CuFe composite cluster. By the complex-containing solution containing a CuFe polynuclear complexes in the nucleus of the complex, including a copper atom and iron atom brought into contact with the carrier, carrying the CuFe multinuclear complex on the support and calcined, according to claim 1 or 2 A method for producing an exhaust gas purifying catalyst, comprising obtaining an exhaust gas purifying catalyst. According to claim 3, wherein CuFe polynuclear complex, characterized in that it is a CuFe polynuclear complex comprising one selected from the group consisting of _{Cu 3 Fe 3, Cu 5 Fe} 4 and _Cu 6 Fe ₄ nuclear complex Of manufacturing exhaust gas purification catalyst. The CuFe polynuclear complex has a carbonyl ligand as a ligand and at least one ion selected from the group consisting of tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion and tetrabutylammonium ion as a counter cation The method for producing an exhaust gas purifying catalyst according to claim 3 or 4 , wherein the exhaust gas purifying catalyst is provided. The method for producing an exhaust gas purifying catalyst according to any one of claims 3 to 5 , wherein a solvent of the complex-containing liquid is an organic solvent having polarity.