JP6359678B2 - Composite particle dispersion and method for producing the same - Google Patents

Description

  The present invention relates to a dispersion of composite particles containing a plurality of types of metals and a method for producing the same.

  Metal particles, particularly metal nanoparticles, have specific properties derived from their sizes, and thus are used in various applications. For example, metal nanoparticles are used as catalysts, electronic materials, magnetic materials, optical materials, and the like.

  Metal particles have been produced by various methods so far. As an example, a method for producing metal particles using a reduction reaction can be mentioned.

  For example, Patent Document 1 discloses a method of producing a dispersion of metal particles by adding a metal to a non-aqueous solvent containing a high molecular weight pigment dispersant and a reducing agent and reducing the metal. Patent Document 2 discloses a method for producing a dispersion of metal particles by adding a metal and a reducing agent to a dispersion containing a polymer compound and reducing the dispersion. Patent Document 3 discloses a method for producing a dispersion of metal particles by reducing a solution containing polyethyleneimine and a metal with a reducing agent.

  A dispersion of catalytic metal particles such as platinum and palladium can be used for producing an exhaust gas purification catalyst for purifying exhaust gas discharged from an internal combustion engine such as an engine. The exhaust gas purifying catalyst is generally composed of a base material and a catalyst layer disposed on the base material, and the catalyst layer includes a support and a catalyst metal supported on the support (for example, Patent Documents 4 to 10).

JP 2006-257517 A JP 2008-37949 A JP 2010-209455 A JP 2001-46870 A JP 2003-117398 A JP 2003-290658 A JP 2005-161109 A JP 2005-288307 A JP 2006-255610 A JP 2007-289913 A

  The method for producing a dispersion of metal particles using a reduction reaction described in Patent Documents 1 to 3 is complicated in operation. In particular, when forming metal particles composed of a plurality of types of metals, it is necessary to first reduce the first metal and then reduce the second metal. In order to perform such a multistage reduction reaction, the operation is further complicated.

  Further, when an exhaust gas purifying catalyst produced using a dispersion of metal particles is used for a long period of time, the catalyst metal is agglomerated, resulting in a problem that the catalyst performance is lowered. In order to suppress agglomeration of the catalyst metal, for example, Patent Document 9 covers the periphery of the catalyst metal particles generated using the gas evaporation method with another metal particle generated using the gas evaporation method. A method is disclosed. Patent Document 6 discloses a method in which tungsten or molybdenum is supported on an oxide carrier, and catalytic metal is reduced and deposited on the supported tungsten or molybdenum. However, each method has a problem of high cost and low productivity.

  Therefore, an object of the present invention is to provide a dispersion of metal particles for producing an exhaust gas purification catalyst that suppresses aggregation of catalyst metal during high temperature durability, and a simple method for producing the dispersion. .

  As a result of intensive studies by the present inventors, it is for exhaust gas purification using a dispersion of composite particles of a first metal as a catalyst metal and a second metal having a melting point higher than that of the first metal. It has been found that the catalyst metal can be prevented from agglomerating during high temperature aggregation by producing the catalyst. Moreover, it discovered that the said dispersion liquid can be easily manufactured by utilizing the neutralization reaction by an organic base, without utilizing a reduction reaction.

That is, the present invention includes the following.
[1] A dispersion containing a dispersion medium, an organic base having a molecular weight of 30 to 500, and composite particles containing the first metal and the second metal, which are dispersed in the dispersion medium,
The first metal is palladium and / or platinum;
The dispersion, wherein the second metal is a metal having a melting point higher than that of the first metal.
[2] The dispersion liquid according to [1], wherein the particle diameter of the composite particles is 1 to 10 nm.
[3] The organic base is diazabicycloundecene, diazabicyclononene, propylamine, methylamine, ethylamine, dimethylamine, triethylamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, hydroxylated [1] or [2], which is at least one selected from the group consisting of tetrabutylammonium, monoethanolamine, N, N-dimethyl-2-aminoethanol, 3-amino-1-propanol, and cyclohexylamine The dispersion liquid described in 1.
[4] The second metal is selected from the group consisting of zirconium, molybdenum, ruthenium, rhodium, rhenium, iridium, osmium, chromium, tungsten, tantalum, titanium, technetium, thorium, niobium, vanadium, hafnium, and lutetium. The dispersion according to any one of [1] to [3], which is at least one kind.
[5] The dispersion according to any one of [1] to [4], wherein the composite particles have a peak in a range of 550 to 700 cm ⁻¹ in a spectrum obtained by Raman spectroscopy.
[6] A fired product of composite particles, comprising a base material and a catalyst layer disposed on the base material, wherein the catalyst layer is contained in the dispersion liquid according to any one of [1] to [5] And an exhaust gas purifying catalyst comprising a carrier carrying the calcined product.

[7] Formation in which an acidic solution containing the first metal and the second metal is mixed with an organic base having a molecular weight of 30 to 500 to form composite particles containing the first metal and the second metal. A process for producing a dispersion of composite particles comprising the steps of:
The first metal is palladium and / or platinum;
The method, wherein the second metal is a metal having a melting point higher than that of the first metal.
[8] The method according to [7], wherein the particle diameter of the composite particles is 1 to 10 nm.
[9] The organic base is diazabicycloundecene, diazabicyclononene, propylamine, methylamine, ethylamine, dimethylamine, triethylamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, hydroxylated [7] or [8], which is at least one selected from the group consisting of tetrabutylammonium, monoethanolamine, N, N-dimethyl-2-aminoethanol, 3-amino-1-propanol, and cyclohexylamine. The method described in 1.
[10] The second metal is selected from the group consisting of zirconium, molybdenum, ruthenium, rhodium, rhenium, iridium, osmium, chromium, tungsten, tantalum, titanium, technetium, thorium, niobium, vanadium, hafnium, and lutetium. The method according to any one of [7] to [9], which is at least one kind.
[11] The method according to any one of [7] to [10], wherein the composite particles have a peak in a range of 550 to 700 cm ⁻¹ in a spectrum obtained by Raman spectroscopy.

ADVANTAGE OF THE INVENTION According to this invention, the dispersion liquid of the composite particle for manufacturing the exhaust gas purification catalyst which suppressed aggregation of the catalyst metal at the time of high temperature aggregation, and its simple manufacturing method can be provided.
This specification includes the contents described in the specification, claims and drawings of Japanese Patent Application No. 2014-204224 which is the basis of the priority of the present application.

Hereinafter, the present invention will be described in detail.
<Composite particle dispersion>
The present invention relates to a dispersion liquid comprising a dispersion medium, an organic base having a molecular weight of 30 to 500, and composite particles containing a first metal and a second metal dispersed in the dispersion medium. The dispersion according to the present invention is characterized in that the first metal is palladium and / or platinum, and the second metal is a metal having a melting point higher than that of the first metal.

  When the exhaust gas purifying catalyst is used for a long period of time, the catalyst metal (palladium, platinum, etc.) agglomerates and the particle size becomes large. Thereby, the specific surface area of a catalyst metal becomes small, and the problem that catalyst performance falls arises. When an exhaust gas purification catalyst is produced using the dispersion according to the present invention, in addition to the catalyst metal (first metal), an additional metal (second metal) having a higher melting point than the catalyst metal. Will exist. When the second metal having a relatively high melting point is present in the vicinity of the first metal, aggregation of the first metal during high temperature aggregation can be suppressed. Further, due to the presence of the second metal, poisoning of the first metal due to the sulfur component contained in the exhaust gas can be suppressed.

  By the way, a dispersion produced by a conventional method utilizing a reduction reaction contains an organic polymer dispersant in order to prevent aggregation of the generated metal particles. However, since the organic polymer coats the adsorption point of the carrier for supporting the metal particles, there is a problem that the efficiency of supporting the metal particles on the carrier is low when a dispersion containing the organic polymer is used. As a result, when using a dispersion containing an organic polymer, it is necessary to repeatedly carry metal particles on the carrier.

  On the other hand, since the dispersion according to the present invention does not need to contain an organic polymer, the efficiency of supporting the composite particles on the carrier can be improved. For example, the composite particles can be supported on the carrier with a supporting efficiency of 60% or more, preferably 70% or more, more preferably 80% or more, and still more preferably 90% or more.

  In addition, when using a dispersion liquid containing an organic polymer, there is a problem that the supported metal particles are easily detached from the carrier, but this problem can be solved by using the dispersion liquid according to the present invention. Can do.

  Examples of the organic polymer include organic polymers having a molecular weight of 10,000 or more, 5,000 or more, 2,500 or more, 1,000 or more, or 750 or more.

  Since the dispersion according to the present invention can prevent the aggregation of the composite particles without using an organic polymer, the composite particles can be contained at a high concentration. For example, the metal concentration of the dispersion can be 0.1 to 20% by weight, 0.1 to 15% by weight, or the like with respect to the dispersion.

  Further, since the dispersion according to the present invention does not need to contain an organic polymer, the manufacturing cost can be reduced.

  Further, when using a dispersion liquid containing an organic polymer, a large amount of carbon compounds derived from the organic polymer is generated when the metal particles are adsorbed on a carrier and baked and fixed. The generated carbon compounds adhere to the furnace and cause damage to the furnace body. On the other hand, this problem can be avoided by using the dispersion according to the present invention.

  The first metal contained in the dispersion according to the present invention is palladium (melting point: 1552 ° C.) and / or platinum (melting point: 1772 ° C.) used as a catalyst metal.

  The second metal contained in the dispersion according to the present invention is not particularly limited as long as it has a higher melting point than the melting point of the first metal. For example, zirconium (melting point: 1852 ° C.), molybdenum (melting point: 2617 ° C.), ruthenium (melting point: 2310 ° C.), rhodium (melting point: 1966 ° C.), rhenium (melting point: 3180 ° C.), iridium (melting point: 2410 ° C.), Osmium (melting point: 3054 ° C), chromium (melting point: 1860 ° C), tungsten (melting point: 3410 ° C), tantalum (melting point: 2996 ° C), titanium (melting point: 1660 ° C), technetium (melting point: 2172 ° C), thorium ( Melting point: 1750 ° C., niobium (melting point: 2468 ° C.), vanadium (melting point: 1887 ° C.), hafnium (melting point: 2230 ° C.), lutetium (melting point: 1652 ° C.), and the like.

  Preferred examples of the second metal include zirconium, molybdenum, titanium, rhodium, and iridium.

  Examples of the combination of the first metal and the second metal include palladium / zirconium, palladium / molybdenum, palladium / titanium, palladium / rhodium, palladium / iridium, platinum / zirconium, platinum / molybdenum, platinum / titanium, and platinum. / Rhodium, platinum / iridium, palladium + platinum / zirconium, palladium + platinum / molybdenum, palladium + platinum / titanium, palladium + platinum / rhodium, palladium + platinum / iridium, and the like. The combination of the first metal and the second metal is not limited to these, and the specific first metal and second metal can be appropriately combined. Each of the first metal and the second metal may be used alone or in combination of two or more.

  The dispersion medium contained in the dispersion liquid is preferably a hydrophilic solvent, and particularly preferably water.

  The organic base contained in the dispersion is not particularly limited as long as the molecular weight is 30 to 500. Since such a low molecular weight organic base is used, the composite particles can be contained at a high concentration. The molecular weight of the organic base is preferably 30 to 400, more preferably 30 to 300.

  The organic base is preferably hydrophilic. More specifically, it is preferably an organic base that dissolves at least 0.1 g in 100 g of water at 25 ° C. The number of carbons contained in the main chain of the organic base is preferably 20 or less. Furthermore, the organic base preferably contains no halogen and no aromatic ring in its structure.

  Specifically, examples of the organic base include cyclic amines, alkyl amines, tetraalkyl ammonium hydroxides, amino alcohols, cycloalkyl amines, and the like.

  More specifically, as the organic base, diazabicycloundecene (DBU), diazabicyclononene (DBN), propylamine, methylamine, ethylamine, dimethylamine, triethylamine, tetramethylammonium hydroxide (TMAH), water Tetraethylammonium oxide (TEAH), tetrapropylammonium hydroxide (TPAH), tetrabutylammonium hydroxide (TBAH), monoethanolamine, N, N-dimethyl-2-aminoethanol, 3-amino-1-propanol, cyclohexylamine Etc.

  Preferred organic bases include DBU, DBN, propylamine, TMAH, TEAH, TPAH, TBAH, monoethanolamine, N, N-dimethyl-2-aminoethanol, 3-amino-1-propanol, and cyclohexylamine. Can do.

  Particularly preferred organic bases include TMAH, TEAH, TPAH, TBAH, monoethanolamine, N, N-dimethyl-2-aminoethanol, 3-amino-1-propanol, and cyclohexylamine.

  The ratio between the total number of moles of the first metal and the second metal and the number of moles of the organic base is not particularly limited, and is, for example, 1: 0.1-40, 1: 1-20, 1: 2-20. Etc.

  The dispersion preferably contains 0.1% by weight or more of an organic base. Although content of an organic base is not specifically limited, For example, 0.1-50 weight%, 0.3-50 weight%, 0.3-30 weight% etc. can be mentioned.

  The kind and ratio of the first metal and the second metal can be appropriately determined according to the application of the composite particles. Although not particularly limited, the ratio of the weight of the first metal to the weight of the second metal is 1: 0.01-20, 1: 0.1-10, 1: 0.2-9, etc. It can be.

The composite particles contained in the dispersion have a peak in the range of 550 to 700 cm ⁻¹ in the spectrum obtained by Raman spectroscopy. “Having a peak in the range of 550 to 700 cm ⁻¹ ” means that the top of the peak is located in the range of 550 to 700 cm ⁻¹ . This peak corresponds to the form of palladium or platinum hydroxide or the hydrated form of the oxide.

  The dispersion liquid can contain composite particles having a particle size of 1 to 10 nm, 1 to 4.5 nm, and the like, for example. The particle diameter of the composite particles can be determined by a dynamic light scattering method.

  Since the first metal and the second metal are compounded as composite particles in the dispersion, they can be uniformly supported on the carrier. In addition, the composite particles contained in the dispersion are not alloyed, but the first metal and the second metal exist in close proximity, so that the composite particles are easily supported at a low temperature after being supported on the carrier. Can be alloyed.

<Exhaust gas purification catalyst>
The present invention also relates to an exhaust gas purifying catalyst. Specifically, the present invention relates to an exhaust gas purifying catalyst including a base material and a catalyst layer disposed on the base material. Here, the catalyst layer contains a fired product of the composite particles contained in the dispersion and a carrier carrying the fired product.

  The type of the carrier is not particularly limited, and examples thereof include alumina, titania, zirconia, silica, ceria, cerium-zirconium composite oxide and the like.

  Examples of the substrate include a straight flow type or wall flow type monolith substrate generally used in an exhaust gas purification catalyst. The material of the base material is not particularly limited, and examples thereof include base materials such as ceramic, silicon carbide, and metal.

<Method for producing dispersion of composite particles>
The present invention also relates to a method for producing the dispersion. Specifically, this invention mixes the acidic solution containing a 1st metal and a 2nd metal, and the organic base whose molecular weight is 30-500, and contains a 1st metal and a 2nd metal. The present invention relates to a method for producing a dispersion of composite particles, including a forming step of forming composite particles. The method according to the present invention is characterized in that the first metal is palladium and / or platinum, and the second metal is a metal having a melting point higher than that of the first metal.

  In the method according to the present invention, the first metal and the second metal contained in the acidic solution are neutralized and precipitated by the organic base. As a result, the first metal and the second metal are combined in close proximity. Thereafter, the metal composite is dispersed again to form composite particles. According to the method of the present invention, since a reduction reaction is not used, a dispersion of composite particles can be easily produced.

  In the conventional method using a reduction reaction, as described above, an organic polymer dispersant is used to prevent aggregation of the generated metal particles. However, due to the presence of the organic polymer, it has been difficult to produce a dispersion containing metal particles at a high concentration. On the other hand, in the method according to the present invention, aggregation of composite particles can be prevented without using an organic polymer. Therefore, a dispersion containing the composite particles at a high concentration can be produced. For example, it is possible to produce a dispersion in which the metal concentration of the dispersion is 0.1 to 20% by weight, 0.1 to 15% by weight, or the like with respect to the dispersion. Further, since no organic polymer is used, the manufacturing cost can be reduced.

  Examples of the organic polymer include organic molecules having a molecular weight of 10,000 or more, 5,000 or more, 2,500 or more, 1,000 or more, 750 or more.

  The first metal used in the method according to the present invention is palladium and / or platinum used as the catalyst metal.

  The second metal used in the method according to the present invention is not particularly limited as long as it has a higher melting point than the melting point of the first metal. For example, zirconium, molybdenum, ruthenium, rhodium, rhenium, iridium, osmium, chromium, tungsten, tantalum, titanium, technetium, thorium, niobium, vanadium, hafnium, lutetium, and the like can be given.

  Preferred examples of the second metal include zirconium, molybdenum, titanium, rhodium, and iridium.

  Examples of the combination of the first metal and the second metal include palladium / zirconium, palladium / molybdenum, palladium / titanium, palladium / rhodium, palladium / iridium, platinum / zirconium, platinum / molybdenum, platinum / titanium, and platinum. / Rhodium, platinum / iridium, palladium + platinum / zirconium, palladium + platinum / molybdenum, palladium + platinum / titanium, palladium + platinum / rhodium, palladium + platinum / iridium, and the like. The combination of the first metal and the second metal is not limited to these, and the specific first metal and second metal can be appropriately combined. Each of the first metal and the second metal may be used alone or in combination of two or more.

  In the method according to the present invention, composite particles are formed by using a neutralization reaction by mixing an acidic solution containing a first metal and a second metal and an organic base. Therefore, the acid is used to acidify the solution before mixing with the organic base. Examples of the acid used for this purpose include inorganic acids, organic acids and the like. Specifically, the inorganic acids can include nitric acid, hydrochloric acid, sulfuric acid and the like, and the organic acids include acetic acid, formic acid, citric acid. Oxalic acid, maleic acid, malic acid, lactic acid, tartaric acid, malonic acid, succinic acid and the like.

  The solvent constituting the acidic solution is preferably a hydrophilic solvent, and particularly preferably water.

  The first metal and the second metal contained in the acidic solution are preferably dissolved in the solvent. When the solvent is a hydrophilic solvent, the metal contained in the acidic solution is preferably present in an ion, complex, or salt state. The metal salt is not particularly limited as long as the salt can be dissolved in a hydrophilic solvent. For example, metal nitrates, sulfates, hydrochlorides and the like can be mentioned.

  The organic base used in the method according to the present invention is not particularly limited as long as the molecular weight is 30 to 500. By using such a low molecular weight organic base, a dispersion containing a high concentration of composite particles can be produced. The molecular weight of the organic base is preferably 30 to 400, more preferably 30 to 300.

  The organic base is preferably hydrophilic. More specifically, it is preferably an organic base that dissolves at least 0.1 g in 100 g of water at 25 ° C. The number of carbons contained in the main chain of the organic base is preferably 20 or less. By using a hydrophilic organic base, the first metal and the second metal can be uniformly neutralized and precipitated in a hydrophilic solvent that is preferably used, and can be combined.

  Furthermore, the organic base preferably contains no halogen and no aromatic ring in its structure. If halogen is contained, the function of the composite particles may be adversely affected. In addition, when an aromatic ring is contained, an undesirable substance such as a nitro compound may be generated when the composite particles are supported on a carrier and fired.

  Specifically, examples of the organic base include cyclic amines, alkyl amines, tetraalkyl ammonium hydroxides, amino alcohols, cycloalkyl amines, and the like.

  More specifically, as the organic base, diazabicycloundecene (DBU), diazabicyclononene (DBN), propylamine, methylamine, ethylamine, dimethylamine, triethylamine, tetramethylammonium hydroxide (TMAH), water Tetraethylammonium oxide (TEAH), tetrapropylammonium hydroxide (TPAH), tetrabutylammonium hydroxide (TBAH), monoethanolamine, N, N-dimethyl-2-aminoethanol, 3-amino-1-propanol, cyclohexylamine Etc.

  DBU, DBN, propylamine, TMAH, TEAH, TPAH, TBAH, monoethanolamine, N, N-dimethyl-2-aminoethanol, 3-amino-1-propanol, and cyclohexylamine may be used as the organic base. preferable. Since these organic bases have a boiling point of 25 to 100 ° C., they can be used without volatilization at room temperature.

  It is particularly preferable to use TMAH, TEAH, TPAH, TBAH, monoethanolamine, N, N-dimethyl-2-aminoethanol, 3-amino-1-propanol, and cyclohexylamine as the organic base. Since these organic bases have a boiling point of 100 ° C. or higher, they do not volatilize even when heated when the neutralized precipitates of the first metal and the second metal are dispersed. Therefore, composite particles can be formed stably.

  In the forming step of the method according to the present invention, a metal composite is formed by neutralization precipitation, and then composite particles are formed by dispersing the metal composite. Although the reaction temperature in a formation process is not specifically limited, It is preferable to carry out at normal temperature.

  The ratio of the total number of moles of the first metal and the second metal contained in the acidic solution and the number of moles of the organic base is not particularly limited, but for example, 1: 0.1-40, 1: 1-20, 1: 2 to 20 etc. The pH of the acidic solution to which the organic base has been added in the forming step may be changed to neutral or basic, or may remain acidic.

  The kind and ratio of the first metal and the second metal can be appropriately determined according to the application of the composite particles. Although not particularly limited, the ratio of the weight of the first metal to the weight of the second metal is 1: 0.01-20, 1: 0.1-10, 1: 0.2-9, etc. It can be.

  From the viewpoint of more efficiently complexing the first metal and the second metal, it is preferable to use the organic base in an amount of 0.1% by weight or more based on the dispersion. Although the usage-amount of an organic base is not specifically limited, For example, 0.1-50 weight%, 0.3-50 weight%, 0.3-30 weight% etc. can be mentioned.

The composite particles formed according to the method of the present invention have a peak in the range of 550 to 700 cm ⁻¹ in the spectrum obtained by Raman spectroscopy. “Having a peak in the range of 550 to 700 cm ⁻¹ ” means that the top of the peak is located in the range of 550 to 700 cm ⁻¹ . This peak corresponds to the form of palladium or platinum hydroxide or the hydrated form of the oxide.

  According to the method according to the invention. For example, composite particles having a particle size of 1 to 10 nm, 1 to 4.5 nm, and the like can be formed. The particle diameter of the composite particles can be determined by a dynamic light scattering method.

  The organic base has a function as a dispersant in addition to a function as a neutralizer. Therefore, the particle diameter of the composite particles can be adjusted as appropriate by changing the type of the organic base.

  The particle diameter of the composite particles can also be adjusted by changing the type of metal salt. When neutralizing with an organic base, the metal salt forms a hydroxide or oxide hydrate, and the formation process varies depending on the type of metal salt. For example, when nitrates and hydrochlorides are compared, chloride ions have higher coordination power to metals than nitrate ions and are less likely to desorb, making it difficult for hydroxides or oxide hydrates to form and grow. As a result, when metal hydrochloride is used, the particle diameter of the composite particles tends to be smaller than when metal nitrate is used.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example and a comparative example, the technical scope of this invention is not limited to this.

<Preparation of dispersion>
[Example 1]
31.25 g of palladium nitrate solution (Pd concentration: 16% by weight, Pd amount: 5 g, manufactured by Cataler, Inc.) was charged into a beaker. Furthermore, 6.00 g of molybdenum oxide (manufactured by Nacalai Tesque) was put into a beaker. A nitric acid solution containing two kinds of metals was stirred for 1 hour or more. Next, DBU (manufactured by Wako Pure Chemical Industries, Ltd.) was added until the pH reached 10.0 or higher. Thereafter, the concentration was adjusted with pure water so that the metal concentration was 0.1% by weight.

[Example 2]
3.125 g of palladium nitrate solution (Pd concentration: 16 wt%, Pd amount: 0.5 g, manufactured by Cataler, Inc.) was charged into a beaker. Further, 178.57 g of a rhodium nitrate solution (Rh concentration: 2.8 wt%, Rh amount: 5 g, manufactured by Cataler Co., Ltd.) was put into a beaker. A nitric acid solution containing two kinds of metals was stirred for 1 hour or more. Next, monoethanolamine (manufactured by Wako Pure Chemical Industries, Ltd.) was added until the pH reached 10.0 or higher. Thereafter, the concentration was adjusted with pure water so that the metal concentration was 5% by weight.

[Example 3]
31.25 g of palladium nitrate solution (Pd concentration: 16% by weight, Pd amount: 5 g, manufactured by Cataler, Inc.) was charged into a beaker. Further, 150.05 g of molybdenum oxide (manufactured by Nacalai Tesque Co., Ltd.) was charged into the beaker. A nitric acid solution containing two kinds of metals was stirred for 1 hour or more. Next, a 15% by weight TMAH solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added until the pH reached 10.0 or higher. Thereafter, the concentration was adjusted with pure water so that the metal concentration was 6.6% by weight.

[Example 4]
31.25 g of palladium nitrate solution (Pd concentration: 16% by weight, Pd amount: 5 g, manufactured by Cataler, Inc.) was charged into a beaker. Further, a solution in which 1.54 g of zirconium oxynitrate (95%, manufactured by Nacalai Tesque, Inc.) was dissolved was put into a beaker, and 1.93 g of citric acid / anhydrous (Nacalai Tesque, Inc.) was added. A nitric acid solution containing two kinds of metals was stirred for 1 hour or more. Next, a 15% by weight TMAH solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added until the pH reached 10.0 or higher. Thereafter, the concentration was adjusted with pure water so that the metal concentration was 5.5% by weight.

[Example 5]
31.25 g of palladium nitrate solution (Pd concentration: 16% by weight, Pd amount: 5 g, manufactured by Cataler, Inc.) was charged into a beaker. Furthermore, 0.38 g of molybdenum oxide (manufactured by Nacalai Tesque Co., Ltd.) was put into a beaker, and 1.25 g of nitric acid (60% by weight, manufactured by Nacalai Tesque Co., Ltd.) was added. A nitric acid solution containing two kinds of metals was stirred for 1 hour or more. Next, DBN (manufactured by Wako Pure Chemical Industries, Ltd.) was charged until the pH reached 10.0 or higher. Thereafter, the concentration was adjusted with pure water so that the metal concentration was 15% by weight.

[Example 6]
31.25 g of palladium nitrate solution (Pd concentration: 16% by weight, Pd amount: 5 g, manufactured by Cataler, Inc.) was charged into a beaker. Further, 16.1 g of titanium trichloride (about 20% by weight solution, manufactured by Nacalai Tesque) was put into a beaker. A nitric acid solution containing two kinds of metals was stirred for 1 hour or more. Next, monoethanolamine (manufactured by Wako Pure Chemical Industries, Ltd.) was added until the pH reached 10.0 or higher. Thereafter, the concentration was adjusted with pure water so that the metal concentration was 3.8% by weight.

[Example 7]
31.25 g of palladium nitrate solution (Pd concentration: 16% by weight, Pd amount: 5 g, manufactured by Cataler, Inc.) was charged into a beaker. Further, 40.25 g of titanium trichloride (about 20% by weight solution, manufactured by Nacalai Tesque) was charged into the beaker. A nitric acid solution containing two kinds of metals was stirred for 1 hour or more. Next, a 15% by weight TMAH solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added until the pH reached 10.0 or higher. Thereafter, the concentration was adjusted with pure water so that the metal concentration was 4.1% by weight.

[Example 8]
31.25 g of palladium nitrate solution (Pd concentration: 16% by weight, Pd amount: 5 g, manufactured by Cataler, Inc.) was charged into a beaker. Further, 17.85 g of a rhodium nitrate solution (Rh concentration: 2.8 wt%, Rh amount: 0.5 g, manufactured by Cataler Co., Ltd.) was put into a beaker. A nitric acid solution containing two kinds of metals was stirred for 1 hour or more. Next, a 15% by weight TMAH solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added until the pH reached 10.0 or higher. Thereafter, the concentration was adjusted with pure water so that the metal concentration was 3.0% by weight.

[Example 9]
31.25 g of palladium nitrate solution (Pd concentration: 16% by weight, Pd amount: 5 g, manufactured by Cataler, Inc.) was charged into a beaker. Further, a solution in which 3.66 g of zirconium oxynitrate (95%, manufactured by Nacalai Tesque, Inc.) was dissolved was put into a beaker, and 1.93 g of citric acid / anhydrous (Nacalai Tesque, Inc.) was added. A nitric acid solution containing two kinds of metals was stirred for 1 hour or more. Next, DBU (manufactured by Wako Pure Chemical Industries, Ltd.) was added until the pH reached 10.0 or higher. Thereafter, the concentration was adjusted with pure water so that the metal concentration was 8.1% by weight.

[Example 10]
31.25 g of a palladium nitrate solution (Pd concentration: 16 wt%, Pd amount: 5 g, manufactured by Cataler, Inc.) was charged into a beaker. Furthermore, 15.01 g of molybdenum oxide (manufactured by Nacalai Tesque) was put into a beaker. A nitric acid solution containing two kinds of metals was stirred for 1 hour or more. Next, a 10% by weight TEAH solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added until the pH reached 10.0 or higher. Thereafter, the concentration was adjusted with pure water so that the metal concentration was 12% by weight.

[Example 11]
31.25 g of palladium nitrate solution (Pd concentration: 16% by weight, Pd amount: 5 g, manufactured by Cataler Co., Ltd.) was put into a beaker, and further, 0.85 g of nitric acid (60% by weight, manufactured by Nacalai Tesque Co., Ltd.) was added. . Furthermore, 300 g of iridium nitrate solution (Ir concentration: 5 wt%, Ir amount: 15 g, manufactured by Furuya Metal Co., Ltd.) was put into a beaker. A nitric acid solution containing two kinds of metals was stirred for 1 hour or more. Next, a 10% by weight TEAH solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added until the pH reached 10.0 or higher. Thereafter, the concentration was adjusted with pure water so that the metal concentration was 8.3% by weight.

[Example 12]
55.56 g of platinum nitrate solution (Pt concentration: 9% by weight, Pt amount: 5 g, manufactured by Cataler Co., Ltd.) was put into a beaker. Further, a solution in which 3.66 g of zirconium oxynitrate (95%, manufactured by Nacalai Tesque, Inc.) was dissolved was put into a beaker, and 1.93 g of citric acid / anhydrous (Nacalai Tesque, Inc.) was added. A nitric acid solution containing two kinds of metals was stirred for 1 hour or more. Next, a 15% by weight TMAH solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added until the pH reached 10.0 or higher. Thereafter, the concentration was adjusted with pure water so that the metal concentration was 4.5% by weight.

[Comparative Example 1]
A palladium nitrate solution manufactured by Cataler Co., Ltd. was used. No second metal was added.

[Comparative Example 2]
31.25 g of palladium nitrate solution (Pd concentration: 16% by weight, Pd amount: 5 g, manufactured by Cataler, Inc.) was charged into a beaker. Furthermore, a solution in which 1.54 g of zirconium oxynitrate (95%, manufactured by Nacalai Tesque, Inc.) was dissolved was put into a beaker, and the metal concentration was adjusted to 10% by weight with pure water.
In this comparative example, neutralization precipitation of two kinds of metals is not performed.

[Comparative Example 3]
31.25 g of a palladium nitrate solution (Pd concentration: 16 wt%, Pd amount: 5 g, manufactured by Cataler, Inc.) was charged into a beaker. Further, 0.75 g of molybdenum oxide (manufactured by Nacalai Tesque Co., Ltd.) was charged into the beaker. A nitric acid solution containing two kinds of metals was stirred for 1 hour or more. Next, a 28 wt% ammonia solution (manufactured by Nacalai Tesque, Inc.) was added until the pH reached 9.0 or higher. Thereafter, the concentration was adjusted with pure water so that the metal concentration was 5.5% by weight.
In this comparative example, NH ₃ was stably coordinated with palladium, and composite particles of palladium and molybdenum were not formed.

[Comparative Example 4]
31.25 g of a palladium nitrate solution (Pd concentration: 16 wt%, Pd amount: 5 g, manufactured by Cataler, Inc.) was charged into a beaker. Further, 1.90 g of copper nitrate trihydrate (manufactured by Nacalai Tesque Co., Ltd.) was charged into the beaker. A nitric acid solution containing two kinds of metals was stirred for 1 hour or more. Next, a 10% by weight TMAH solution (manufactured by Nacalai Tesque Co., Ltd.) was added until the pH reached 10.0 or higher. Thereafter, the concentration was adjusted with pure water so that the metal concentration was 5.5% by weight.
In this comparative example, copper having a melting point lower than that of palladium (melting point: 1084 ° C.) was used.

[Comparative Example 5]
31.25 g of palladium nitrate solution (Pd concentration: 16 wt%, Pd amount: 5 g, manufactured by Cataler) and 22.78 g of iridium nitrate solution (Ir concentration: 3 wt%, Ir amount: 0.5 g, stock) Made by Furuya Metal Co., Ltd.) and stirred for 1 hour. Next, after adding polyvinylpyrrolidone (PVP), 3.10 g of hydrazine (80%) was added as a reducing agent and stirred at 80 ° C. for 5 hours to obtain a colloidal solution.

[Comparative Example 6]
A nitric acid solution of dinitrodiamine platinum manufactured by Cataler Co., Ltd. was used. No second metal was added.
Table 1 shows the contents of Examples and Comparative Examples.

<Various tests>
(1) Particle diameter in dispersion The dispersion whose metal concentration was adjusted to 0.5% by weight was measured by a dynamic light scattering method using Zetasizer S (manufactured by Malvern), and the particle diameter was measured.

(2) Compounding in dispersion A dispersion containing 0.3 g of palladium or platinum and an alumina support (9.7 g) were mixed to form a slurry, which was stirred for 30 minutes. Thereafter, the slurry was dried at 100 ° C. overnight, ground in a mortar, and then fired at 500 ° C. for 3 hours. The fired product was observed with a transmission electron microscope (TEM) to confirm whether the first metal and the second metal were present in the same particle on the carrier.

(3) Activity evaluation after endurance test (T50-HC)
The fired product obtained in the above test (2) was pressed at 1.5 kN for 1 minute using a manual press machine to obtain a molded body. The molded body was pulverized to about 0.5 mm with a mortar to prepare pellets. As an endurance test, the pellets were heated to 1000 ° C. while flowing a predetermined gas (N ₂ : 450 cc / min, CO: 50 cc / min) in a gas flow furnace and treated for 10 hours (a pretreatment simulating a rich atmosphere). ). Alternatively, the pellet is heated to 1000 ° C. while flowing a gas (N ₂ : 450 cc / min, CO: 50 cc / min or O ₂ : 25 cc / min) in which CO and O ₂ are switched at intervals of 1 minute in a gas flow furnace. The temperature was raised and treated for 10 hours.

  The sample after the durability test was evaluated with a model gas evaluation apparatus (manufactured by Best Sokki Co., Ltd.) having a gas composition shown in Table 2, and the temperature at which the purification rate of the HC component was 50% was measured.

  For Example 12 and Comparative Example 6, an endurance test was performed at 700 ° C. for 10 hours using an electric furnace (FO810, manufactured by Yamato Scientific Co., Ltd.), and measurement was performed using a model gas evaluation device (manufactured by Best Instrument Co., Ltd.). It was.

(4) Particle size after endurance test A 0.2 g endurance test sample was treated at 300 ° C. for 15 minutes in an oxygen atmosphere, and then treated at 400 ° C. for 15 minutes in a reducing atmosphere. The obtained sample was measured using a CO gas adsorption device (manufactured by Henmi Kakusha Co., Ltd.).
Table 3 shows the results of various tests.

  The dispersions of Comparative Examples 1 to 4 had low activity after the durability test and large particle diameters after the durability test in the fired products obtained using them. Moreover, about the dispersion liquid of Comparative Examples 2-4, composite formation of the 1st metal and the 2nd metal was not able to be confirmed. Therefore, Comparative Examples 2 and 3 contain an element having a high melting point but are not close to the noble metal, so that the aggregation suppressing effect is not exhibited. It was also inferred that the addition of an element having a low melting point does not exert the aggregation suppressing effect. The dispersion of Comparative Example 5 is active because the first metal and the second metal are alloyed in the colloidal solution, the particle diameter in the dispersion is large, the particle diameter after durability is large, and the active point is small. Was estimated to be lower. About the dispersion liquid of the comparative example 6, since the 2nd metal was not added, the activity after an endurance test was low in the baked product obtained using it.

  All publications, patents and patent applications cited herein are incorporated herein by reference in their entirety.

Claims (5)

An organic base having a molecular weight of 30 to 500 is mixed with an acidic solution containing the first metal and the second metal until the pH becomes 10 or more, and a composite containing the first metal and the second metal. A method for producing a dispersion of composite particles, comprising a forming step of forming particles,
The first metal is palladium and / or platinum;
The method, wherein the second metal is a metal having a melting point higher than that of the first metal. The method according to claim 1 , wherein the composite particles have a particle size of 1 to 10 nm. Organic base is diazabicycloundecene, diazabicyclononene, propylamine, methylamine, ethylamine, dimethylamine, triethylamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide The method according to claim 1 or 2 , which is at least one selected from the group consisting of, monoethanolamine, N, N-dimethyl-2-aminoethanol, 3-amino-1-propanol, and cyclohexylamine. The second metal is at least one selected from the group consisting of zirconium, molybdenum, ruthenium, rhodium, rhenium, iridium, osmium, chromium, tungsten, tantalum, titanium, technetium, thorium, niobium, vanadium, hafnium, and lutetium. The method according to any one of claims 1 to 3 , wherein The method according to any one of claims 1 to 4 , wherein the composite particles have a peak in a range of 550 to 700 cm ^-1 in a spectrum obtained by Raman spectroscopy.