JP2017205702A - Dispersion of fine particle containing nobble metal and manufacturing method therefor, and manufacturing method of fine particle carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dispersion of fine particles suitable for carrying fine particles containing noble metal such as platinum on a carrier uniformly.SOLUTION: There is provided a dispersion by dispersing fine particles containing noble metal in a dispersant and containing further a carrier homogenization agent for homogenizing fine particle carried by the carrier. The carrier homogenization agent is at least one kind selected from hydroxy acid, amino acid, or a salt thereof. Percentage content of the fine particles dispersed in the dispersion is 4000 ppm or more based on mass. The hydroxy acid is for example glycol acid and/or 3-hydroxy propone acid, amino acid is for example glycine and/or alanine. A reductant used for reducing a noble metal compound to be fine particles is preferably gallic acid and/or a salt thereof, and preferably ascorbic acid and/or a salt thereof is used together with the same.SELECTED DRAWING: None

Description

  The present invention relates to a dispersion liquid in which fine particles containing a noble metal are dispersed in a dispersion medium, and further relates to a fine particle carrier in which fine particles containing a noble metal are supported on a carrier.

  Precious metals such as gold and platinum are sometimes used in the form of fine particles supported on a carrier as a catalyst, a diagnostic agent or the like. As the carrier, oxide, metal, resin, carbon or the like is used. By making the particles fine, the surface area per unit mass is increased, thereby improving the activity per unit mass of the noble metal (for example, catalytic activity). Core / shell fine particles in which a noble metal shell is attached to the core particles are also known, and core / shell type fine particles in which the core particles are made of a material other than the noble metal have also been proposed. The following two methods are known as methods for obtaining a fine particle support by supporting fine particles containing a noble metal on a carrier.

(1) The carrier is impregnated with a solution in which the noble metal compound is dissolved, and the impregnated noble metal compound is reduced to deposit fine particles containing the noble metal on the surface of the carrier (for example, Patent Document 1).
(2) A dispersion liquid in which fine particles containing a noble metal are dispersed is brought into contact with the carrier to carry the fine particles on the surface of the carrier (for example, Patent Document 2).

JP 2007-324092 A JP 2005-199204 A

  The fine particle carrier obtained by the method (1) has a problem that fine particles deposited in a portion that is difficult to come into contact with an external reactive species, for example, in a deep hole portion on the surface of the carrier, do not function sufficiently. This problem is basically solved by using the method (2). However, the method (2) has a problem that it is difficult to uniformly support fine particles. Sufficient activity cannot be obtained from a carrier that supports fine particles in an aggregated state.

  In order to uniformly support the fine particles in the method (2), it is desirable to carry out an operation of gradually removing the dispersion medium using an evaporator or the like while stirring the dispersion charged with the carrier. However, while the excess dispersion medium is removed by this operation, the carrier is exposed to a risk of being damaged by colliding with the inner wall of the container holding the dispersion or colliding with each other. Since the desorbed material from the carrier may impair the dispersion stability of the fine particles in the dispersion, and a new surface may be formed on the carrier due to the breakage. It can be a factor that reduces uniformity.

  In view of the above, an object of the present invention is to provide a dispersion of fine particles suitable for uniformly supporting fine particles containing a noble metal on a carrier. Another object of the present invention is to provide a new method for producing a fine particle carrier using a dispersion in which fine particles containing a noble metal are dispersed.

The present invention
A dispersion of fine particles in which fine particles containing a noble metal are dispersed in a dispersion medium,
A supporting and homogenizing agent that is at least one selected from hydroxy acids, amino acids and salts thereof;
Dispersion liquid in which the fine particles of 4000 ppm or more are dispersed on a mass basis.

The present invention also provides:
A method for producing a fine particle carrier, in which a fine particle containing a noble metal is dispersed in a dispersion medium and a carrier is brought into contact with the fine particle dispersion to carry the fine particle on the carrier.
The dispersion is a dispersion according to the invention,
A method for producing a fine particle carrier is provided.

Furthermore, the present invention provides
(I) preparing a dispersion A in which fine particles containing a noble metal produced by reduction of the noble metal compound are dispersed by heating a solution containing the noble metal compound and a reducing agent;
The step (ii) of obtaining the dispersion B by concentrating the dispersion A so that the dispersed fine particles are 4000 ppm or more on a mass basis;
Adding a supporting and homogenizing agent to the dispersion A and / or the dispersion B (iii),
The supported homogenizing agent includes at least one selected from hydroxy acids, amino acids and salts thereof.
A method for producing a dispersion of fine particles.

Still further, the present invention provides:
(I) preparing a dispersion A in which fine particles containing a noble metal produced by reduction of the noble metal compound are dispersed by heating a solution containing the noble metal compound and a reducing agent;
The step (ii) of obtaining the dispersion B by concentrating the dispersion A so that the dispersed fine particles are 4000 ppm or more on a mass basis;
A step (iii) of adding a supporting and homogenizing agent to the dispersion A and / or the dispersion B;
And (iv) obtaining a fine particle carrier by bringing the carrier B into contact with the dispersion B containing the carrier homogenizing agent to carry the fine particles on the carrier.
The supported homogenizing agent includes at least one selected from hydroxy acids, amino acids and salts thereof.
A method for producing a fine particle carrier is provided.

  In the dispersion according to the present invention, fine particles containing a noble metal are dispersed so as to have a content of 4000 ppm or more on a mass basis. For this reason, the dispersion according to the present invention can reduce the time required for the operation of gradually removing the dispersion medium while stirring the support, and suppress damage to the support that inhibits the uniformity of the fine particles on the support. Or it makes it easy to carry | support a microparticles | fine-particles on a support | carrier uniformly by operation which makes a support | carrier soak a dispersion liquid.

  When a dispersion having a high content rate of fine particles as described above is used, the fine particles are likely to be aggregated and nonuniformly supported when the fine particles are supported on the carrier. However, in the dispersion according to the present invention, the predetermined supporting and homogenizing agent facilitates uniform supporting of the fine particles.

  Hereinafter, embodiments of the present invention will be described, but the following description is not intended to limit the present invention to specific embodiments. Hereinafter, “%” and “ppm” indicating the content and concentration are all based on mass.

[Dispersion]
The dispersion of this embodiment contains at least one selected from hydroxy acids, amino acids, and salts thereof as a supporting homogenizer together with fine particles containing a noble metal.

(Fine particles)
The fine particles are made of at least one noble metal, that is, gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), and osmium (Os). It contains at least one selected from The noble metal may be a noble metal excluding silver, for example, platinum. The fine particles only have to have a structure in which the noble metal is exposed on at least a part of the surface thereof, and the whole of the fine particles may be constituted by the same noble metal or may be constituted by two or more kinds of noble metals. The fine particles may have a so-called core-shell structure. In the core / shell structure, both the core and the shell may be made of a noble metal, and are made up of a core made of a material other than the noble metal (for example, oxide, base metal, carbon, resin) and a shell made of a noble metal. Also good.

  The average particle size of the fine particles in the dispersion is, for example, 5 nm or less, preferably 3 nm or less, more preferably 2.5 nm or less, and particularly preferably 2 nm or less. The smaller the particle size, the larger the surface area per unit mass of the fine particles, and it can be expected that the activity of the fine particles containing the noble metal is improved. The average particle size of the fine particles in the dispersion is not particularly limited as to the lower limit, but may be, for example, 0.5 nm or more, particularly 1 nm or more. The average particle size can be determined by a simple average of the particle sizes of 10 or more arbitrarily selected fine particles. The particle size can be measured using a transmission electron microscope (TEM). In the dispersion, it is preferable that the particle diameters of substantially all the fine particles are in a range determined by any combination of the above upper limit and lower limit. In the present specification, “substantially all” means 90% or more, preferably 95% or more, more preferably 99% or more. With respect to the average particle diameter of the fine particles, it is determined whether or not “substantially all” is met on the basis of the number.

  The fine particle content (dispersion concentration) in the dispersion is 4000 ppm or more, preferably 5000 ppm or more, more preferably 6000 ppm or more, still more preferably 6500 ppm or more, and particularly preferably 7000 ppm or more. The upper limit of the content of fine particles in the dispersion is not limited as long as dispersion is possible, and is, for example, 5% or less. However, in particular, when it does not contain a water-soluble polymer for stably dispersing the fine particles, it is preferably adjusted to 3% or less, more preferably 2% or less, and particularly preferably about 1% or less.

(Supporting homogenizing agent)
The hydroxy acid, amino acid and salts thereof contained in the dispersion contribute to uniformly supporting the fine particles on the carrier as a supporting and homogenizing agent. Hydroxy acid is an organic compound having a hydroxyl group and a carboxyl group, and is sometimes referred to as hydroxycarboxylic acid. As is well known, an amino acid is an organic compound having an amino group and a carboxyl group.

  The molecular weight of the support homogenizer is preferably small. The organic compound adhering to the fine particles of the carrier can cause a decrease in the activity of the noble metal. However, the carrier homogenizing agent having a small molecular weight is usually relatively easy to remove from the carrier by heating. The molecular weight of the support homogenizer is preferably 150 or less, more preferably 120 or less, and particularly preferably 100 or less.

  The supported homogenizing agent is preferably a compound in which one of the hydrogen atoms of the aliphatic chain hydrocarbon is substituted with a hydroxyl group or an amino group and one of the terminal methyl groups is substituted with a carboxyl group. The carbon number is not particularly limited, but is preferably 6 or less, more preferably 5 or less, for example 2 to 4. As the supporting homogenizing agent, a compound having such a number of carbon atoms, a molecular weight that is not too large, and an excellent balance between hydrophilicity and hydrophobicity is suitable.

  The hydroxy acid as the supporting homogenizing agent is preferably glycolic acid and / or 3-hydroxypropionic acid, particularly preferably glycolic acid. Glycine and / or alanine is preferable as the amino acid as the loading homogenizer, and glycine is particularly preferable. These compounds have the lowest molecular weight among the compounds corresponding to hydroxy acids or amino acids. That is, the support homogenizing agent preferably includes at least one selected from glycolic acid, 3-hydroxypropionic acid, glycine and alanine, and more preferably includes glycolic acid and / or glycine. The counter ion constituting the salt of hydroxy acid and amino acid is not particularly limited, but is, for example, an alkali metal ion, particularly sodium ion, potassium ion, and, for example, ammonium ion.

  The concentration of the supporting and homogenizing agent in the dispersion is preferably 1 to 10,000 ppm. The concentration of the supporting and homogenizing agent may be 3 ppm or more, particularly 5 ppm or more, 5000 ppm or less, further 3000 ppm or less, particularly 1000 ppm or less, especially 500 ppm or less. A supported homogenizing agent included at an appropriate concentration significantly improves the uniformity of the fine particles on the carrier. A suitable concentration from this point of view is 80 ppm or less, in particular 50 ppm or less, for example 1-80 ppm.

(Compound derived from reducing agent)
The dispersion may further contain a product A produced by a chemical reaction involving oxidation of gallic acid, and may contain a product B produced by a chemical reaction involving oxidation of ascorbic acid together with the product A. Products A and B are compounds that remain in the dispersion when gallic acid and ascorbic acid are used as the reducing agent for the noble metal compound, respectively. These products may be compounds derived from the corresponding reducing agent, and may be not only an oxidized form of the reducing agent but also a derivative produced by a chemical reaction such as esterification of the oxidized form. As will be described later, the combination of gallic acid and ascorbic acid enables both the concentration of the dispersion and the control of the particle size of the fine particles to be small. However, since the concentrations of the products A and B can be reduced by ion exchange or the like and can be removed in some cases, even if the corresponding reducing agent is used, all of the products produced from the reducing agent are dispersed. It does not always remain.

(Other)
In order to prevent aggregation of fine particles in the dispersion, it is known to add a colloid protective agent to the dispersion. A typical colloid protective agent is a water-soluble polymer, and examples of the water-soluble polymer include polyvinylpyrrolidone, polyvinyl alcohol, polyacrylic acid, and gelatin. The water-soluble polymer stabilizes the dispersibility of the fine particles dispersed as a colloid, but the surface of the fine particles supported on the carrier is bulky to reduce the activity of the noble metal, or the fine particles are dense on the carrier. It becomes a factor that makes it difficult to be carried on the surface. For this reason, it is preferable that a dispersion liquid does not contain water-soluble polymer substantially. In this specification, “substantially free” means that the content is less than 5%, preferably less than 1%, more preferably less than 0.1%. In addition, here, the term “polymer” is used in the usual sense, that is, as a term indicating a molecule having a molecular weight of 10,000 or more.

  As the colloid protective agent, a compound other than the water-soluble polymer, for example, tetramethylammonium may be used. However, in any case, conventionally, the colloid protective agent has been added in an amount exceeding the fine particles to be dispersed on a mass basis for the expression of its function. Even if the dispersion liquid of this embodiment does not contain an amount of colloid protective agent that exceeds the amount of dispersed fine particles on a mass basis, the amount of fine particles as illustrated above can be held in a dispersed state. it can.

  The carrier for supporting the fine particles and the dispersion liquid are usually stored individually until the operation of carrying the fine particles on the carrier (step (iv) described later) is performed. The dispersion is preferably stored in a state that does not substantially contain the carrier, that is, in a state where it is not in contact with the carrier.

(Dispersion medium)
The dispersion medium of the dispersion liquid of this embodiment is not particularly limited, but is preferably water and / or a polar organic solvent. When used together with water, the polar organic solvent is suitably a solvent miscible with water typified by an alcohol having 1 to 3 carbon atoms.

[Method for producing dispersion]
The method for producing a dispersion according to this embodiment is a step (i) of preparing a dispersion A of fine particles in which fine particles generated by reduction of a noble metal compound are dispersed by heating a solution containing a noble metal compound and a reducing agent. And step (ii) of preparing the dispersion B by concentrating the dispersion A so that the content of the fine particles is not less than a predetermined value, and adding a supporting homogenizing agent to the dispersion A and / or the dispersion B. Step (iii). Hereinafter, each step will be described.

(Process (i))
In step (i), the noble metal compound is reduced using a reducing agent. Examples of the noble metal compound include chlorides, nitrates, sulfates and metal complexes of the noble metals exemplified above.

  Examples of the reducing agent include citric acids, alcohols, carboxylic acids, ketones, ethers, aldehydes, and esters. Examples of citric acids include citric acid and citrates such as sodium citrate, potassium citrate and ammonium citrate. Examples of alcohols include methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, glycerin and the like. Examples of carboxylic acids include formic acid, acetic acid, fumaric acid, malic acid, succinic acid, aspartic acid, gallic acid, ascorbic acid, and salts thereof. Examples of ketones include acetone and methyl ethyl ketone. Examples of ethers include diethyl ether. Examples of aldehydes include formaldehyde and acetaldehyde. Examples of esters include methyl formate, methyl acetate, and ethyl acetate.

  The type of reducing agent used affects the limit at which the dispersion can be concentrated. Therefore, an appropriate reducing agent should be selected, particularly when the dispersion is concentrated without resorting to stabilization with a colloid protectant. A gallic acid can be mentioned as a suitable reducing agent from this viewpoint. In order to facilitate the implementation of step (ii), the reducing agent preferably contains gallic acid and / or a salt thereof.

  The type of reducing agent used also affects the particle size of the fine particles produced. When gallic acid is used as the reducing agent, the reducing agent that facilitates obtaining fine particles in combination with this is ascorbic acid. The reducing agent preferably contains ascorbic acid and / or a salt thereof. Examples of the counter ion constituting the salt of gallic acid and ascorbic acid are as described above.

  The gallic acid and / or salt thereof is preferably contained in the solution so as to be 2 to 40 mol, preferably 5 to 28 mol, per mol of the noble metal to be reduced contained in the noble metal compound. In this case, the ascorbate and / or salt thereof added to the solution together with gallic acid and / or its salt is 0.1 to 0.9 mol per mol of the noble metal to be reduced contained in the noble metal compound. It is preferably contained in the solution. When these reducing agents are contained in an appropriate amount, it is easy to control the particle size of the fine particles to be small.

  If necessary, a reaction accelerator may be added to the raw material liquid in order to promote the reduction. Examples of the reaction accelerator include alkali carbonates such as potassium carbonate, alkali hydrogen carbonates such as sodium hydrogen carbonate, and alkali hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide.

  Although the heating temperature in process (i) is not specifically limited, For example, it is 80-100 degreeC, Preferably it is 95-100 degreeC.

(Process (ii))
In the step (ii), the dispersion A is concentrated so that the content of the fine particles containing the noble metal becomes a predetermined value, and the dispersion B is obtained. A preferable content of the fine particles in the dispersion B is as described above, and is at least 4000 ppm. Step (ii) can be carried out by removing the dispersion medium of dispersion A. The method for removing the dispersion medium is not particularly limited, but it is preferable to carry out by evaporating the dispersion medium with reduced pressure, specifically, removing the dispersion medium using an evaporator.

  When adding at least a part of the supporting and homogenizing agent to the dispersion B in the step (iii) to be described later, the concentration in the step (ii) takes into account that the content of fine particles in the dispersion B slightly decreases. It is advisable to determine the degree to do. However, since the loaded homogenizing agent to be added is effective even in a trace amount as described above, in practice, it is sufficient to concentrate it, for example, about several ppm higher than the content to be finally achieved. There are many cases.

  In reality, it is difficult to prepare a dispersion having a high content of fine particles as described above only by the step (i). This is because aggregation of fine particles cannot be prevented. The content of fine particles in the dispersion A prepared in the step (i) may be limited to an appropriate range of less than 4000 ppm, for example, 3000 ppm or less, preferably 2000 ppm or less, more preferably 1000 ppm or less.

(Step (iii))
In the step (iii), a supporting and homogenizing agent is added to the dispersion A and / or the dispersion B. The support homogenizing agent contains at least one selected from hydroxy acids, amino acids, and salts thereof, and examples thereof are as described above.

  When adding the supporting homogenizer before concentrating the fine particle dispersion (that is, also in the dispersion A), depending on the type of the supporting homogenizer used and the method of concentration of the dispersion, Along with this, the carrying homogenizing agent may evaporate. Therefore, it is recommended to add at least a part, preferably all, of the support homogenizer to the dispersion B. In particular, when the method of removing the dispersion medium under reduced pressure is employed in step (ii) and the molecular weight of the supported homogenizing agent is as small as described above, substantially all of the supported homogenizing agent is added to the dispersion B. It is preferable to do. The meaning of “substantially all” is as described above, but here it is determined on a mass basis.

  When a supporting homogenizing agent is added to the dispersion A, the amount of the supporting homogenizing agent needs to be adjusted in consideration of the concentration of the dispersion. When adding a supporting and homogenizing agent to the dispersion B, it is necessary to pay attention to the fact that the content rate of the fine particles is slightly lowered.

[Production method of particulate carrier]
In the method for producing a fine particle carrier of the present embodiment, the step (iv) of carrying the fine particles on the carrier by bringing the fine particle dispersion (dispersion B) and the carrier into contact with each other is further performed. For example, step (iv) can be carried out while introducing the carrier into the dispersion and gradually removing the dispersion medium of the dispersion using an evaporator or the like as necessary. In the dispersion B, since the fine particles are already dispersed at a high content, the time for stirring the dispersion B in a state containing the carrier can be shortened. By shortening the stirring time, damage to the carrier can be suppressed. Step (iv) can also be carried out without introducing the carrier into the dispersion, for example, by allowing the dispersion to penetrate into the carrier. By allowing a dispersion having a high content of fine particles to permeate the carrier, it is possible to shorten the time required for the dispersion to reach the desired loading rate and to increase the amount of fine particles that can be carried. In the operation of infiltrating a “thin” dispersion having a low content of fine particles, an equilibrium state is reached when a small amount of fine particles are loaded, and thus it is difficult to load a large amount of fine particles.

  As the carrier, a known carrier, for example, a carrier made of oxide, metal, resin, carbon or the like can be used. As the carrier, it is preferable to use particles having a large surface area per unit mass. The particle size of a suitable carrier is, for example, 1 μm or more, preferably 1 mm or more, and for example, 10 mm or less, preferably 5 mm or less.

  If necessary, after the step (iv), a step (v) of heat-treating the fine particle support may be further performed. Step (v) is useful for decomposing an organic compound that is derived from the dispersion and adheres to the fine particles and may reduce the activity of the fine particles. Organic compounds include compounds derived from reducing agents, supported homogenizing agents and the like. The heat treatment temperature is preferably 100 ° C. or higher, more preferably 150 ° C. or higher, for example, 300 to 500 ° C.

  The following examples are also illustrative of the present invention and are not intended to limit the present invention.

[Production of platinum fine particle support]
Example 1
185.61 g of ultrapure water was weighed into a 200 mL two-necked flask, fitted with a Dimroth condenser, and boiled for 30 minutes using a mantle heater. Subsequently, 5.32 g of 4% hexachloroplatinic acid (IV) hexahydrate (manufactured by Oura Kikinzoku Kogyo) was added to the two-necked flask and boiled for 30 minutes. Subsequently, 1.38 g of 10% potassium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) aqueous solution was added to the two-necked flask, and 4.84 g and 17% of 1% L (+)-ascorbic acid (manufactured by Kanto Kagaku) mixed in advance. A 2.85 g aqueous solution of 5% gallic acid (manufactured by Nacalai Tesque) was added to a two-necked flask and boiled for 10 minutes to obtain a dispersion A of platinum fine particles.

  After boiling, the two-necked flask is cooled with water at 5 ° C. for 15 minutes, and 8 ml of ion exchange resin (manufactured by Organo; Amberlite MB-1) is used to remove the impurity ions in the dispersion. Velocity) The ion exchange of dispersion A was performed at a flow rate of 15. After ion exchange, using an evaporator, water was removed from the dispersion until the content of platinum fine particles reached 7000 ppm, and dispersion A was concentrated to obtain dispersion B.

  Thereafter, glycolic acid was added to Dispersion B so that the glycolic acid concentration was 10 ppm. Subsequently, 10 g of the carrier was placed in a 50 mL screw tube bottle, and the dispersion B to which glycolic acid had been added was added dropwise using a spoid. At this time, the dispersion B was dropped around the place where the dispersion B did not adhere while rotating the screw tube so that the dispersion B was uniformly dropped onto the carrier. Then, the screw tube bottle was shaken lightly so that the dispersion liquid B was adapted to the whole to obtain a platinum fine particle carrier. The support was dried at 100 ° C. and then heat-treated at 300 ° C. As the carrier, an alumina carrier (Sumitomo Chemical: KHO-12) was used.

(Example 2)
The amount of ultrapure water was 177.78 g, the amount of 10% potassium hydroxide was 1.54 g, the amount of 1% L (+)-ascorbic acid aqueous solution was 5.42 g, and the 17.5% gallic acid aqueous solution The amount is 9.94 g, the amount of the ion exchange resin is 18 ml, and the dispersion A is concentrated so that the content of platinum fine particles in the dispersion B is 5000 ppm. The concentration of glycine is 100 ppm instead of glycolic acid. A platinum fine particle carrier was obtained in the same manner as in Example 1 except that the addition was performed as described above.

(Example 3)
The amount of ultrapure water was 83.89 g, the amount of 1% L (+)-ascorbic acid aqueous solution was 5.42 g, the amount of 17.5% gallic acid aqueous solution was 3.99 g, and the amount of ion exchange resin was 18 ml, and the dispersion A was concentrated so that the content of platinum fine particles in the dispersion B was 10,000 ppm, and glycolic acid was added so that the concentration became 5 ppm. A platinum fine particle carrier was obtained.

Example 4
Example 1 except that the amount of ultrapure water was 184.59 g, the amount of 1% L (+)-ascorbic acid aqueous solution was 5.86 g, and glycolic acid was added to a concentration of 200 ppm. In the same manner, a platinum fine particle support was obtained.

(Example 5)
Example 1 except that the amount of ultrapure water was 186.11 g, the amount of 1% L (+)-ascorbic acid aqueous solution was 4.34 g, and glycolic acid was added to a concentration of 800 ppm. In the same manner, a platinum fine particle support was obtained.

(Example 6)
Except that the amount of ultrapure water was 185.27 g, the amount of 10% potassium hydroxide was 1.71 g, and glycolic acid was added to a concentration of 50 ppm, the same as in Example 1, A platinum fine particle carrier was obtained.

(Example 7)
A platinum fine particle support was obtained in the same manner as in Example 1 except that the amount of ultrapure water was 183.58 g and the amount of 1% L (+)-ascorbic acid aqueous solution was 6.87 g. .

(Example 8)
A platinum fine particle carrier was obtained in the same manner as in Example 1 except that the amount of ultrapure water was 190.45 g and the 1% L (+)-ascorbic acid aqueous solution was not added.

Example 9
The amount of ultrapure water was 175.27 g, the amount of 10% potassium hydroxide was 2.21 g, the amount of 1% L (+)-ascorbic acid aqueous solution was 5.42 g, and the 17.5% gallic acid aqueous solution A platinum fine particle carrier was obtained in the same manner as in Example 1 except that the amount was 11.78 g.

(Comparative Example 1)
185.04 g of ultrapure water was weighed into a 200 mL two-necked flask, fitted with a Dimroth condenser, and boiled for 30 minutes using a mantle heater. Subsequently, 5.32 g of 4% hexachloroplatinic acid (IV) hexahydrate (manufactured by Oura Kikinzoku Kogyo) was added to the two-necked flask and boiled for 30 minutes. Subsequently, 9.64 g of 10% aqueous sodium citrate (manufactured by Wako Pure Chemical Industries) was added to the two-necked flask and boiled for 60 minutes to obtain a dispersion A of platinum fine particles.

  After boiling, the 2-necked flask is cooled with water at 5 ° C. for 15 minutes, and 8 ml of ion exchange resin (manufactured by Organo; Amberlite MB-1) is used to remove impurity ions in the dispersion. The ion exchange of dispersion A was performed at a flow rate of 15. When water was removed from the dispersion A in the same manner as in Example 1, when the platinum fine particle content was about 2000 ppm, the platinum fine particles were condensed and precipitated, and could not be further concentrated.

(Comparative Example 2)
A platinum fine particle carrier was obtained in the same manner as in Example 1 except that glycolic acid was not added.

[Evaluation]
(Uniformity of platinum particles in the carrier)
The uniformity of the platinum fine particles supported on the platinum fine particle support was visually evaluated based on the following criteria. Since the portion where the platinum fine particles are supported can be observed in black, the relative evaluation of uniformity can be made visually.
A: Fine particles are uniformly supported on the surface of 80% or more of the carrier.
○: The fine particles are almost uniformly supported on the surface of the carrier, but the surface uniformly supported is less than 80% of the whole.
X: Aggregation of fine particles on the surface of the carrier is remarkable.

(Particle diameter of dispersion B)
Observation was performed using a transmission electron microscope (TEM). The number of fine particles whose particle size was measured is 10 to 20 for each dispersion.

  The above results are summarized in Table 1. In the column of “concentration” in Table 1, the case where the dispersion can be concentrated to the extent that the fine particle content is 5000 ppm or more is indicated as “◯”, and the case where the dispersion is not possible is indicated as “X”. However, as is clear from the above, the numerical value of the content ratio of the dispersion B does not indicate a limit value at which concentration is possible.

  The particle size of the fine particles in the dispersion was 90% or more, that is, substantially all were within the range shown in Table 1. In Table 1, the amount of addition of the reducing agent is indicated by the number of moles per mole of platinum.

  In the same manner as in the above examples, further experiments were conducted in which the concentration of glycolic acid was changed. As a result, it was confirmed that glycolic acid had an effect of improving the uniformity of loading of fine particles even when the concentration was about 1 ppm. did it. However, in the dispersion having a low dispersion concentration of the fine particles as in Comparative Example 1, the effect of improving the uniformity of the fine particles is limited because the risk of the carrier being damaged cannot be reduced even when glycolic acid is added. Become.

Claims (19)

A dispersion of fine particles in which fine particles containing a noble metal are dispersed in a dispersion medium,
A supporting and homogenizing agent that is at least one selected from hydroxy acids, amino acids and salts thereof;
A dispersion in which the fine particles of 4000 ppm or more are dispersed on a mass basis.   2. The supported homogenizing agent is a compound in which one of hydrogen atoms of an aliphatic chain hydrocarbon is substituted with a hydroxyl group or an amino group, and one of terminal methyl groups is substituted with a carboxyl group. Dispersion.   The dispersion according to claim 1 or 2, wherein the carrying homogenizing agent has a molecular weight of 150 or less.   The dispersion according to claim 2 or 3, wherein the hydroxy acid is glycolic acid and / or 3-hydroxypropionic acid.   The dispersion according to claim 2 or 3, wherein the amino acid is glycine and / or alanine.   The dispersion according to any one of claims 1 to 5, wherein the concentration of the supporting and homogenizing agent is 1 to 1000 ppm on a mass basis.   The dispersion according to claim 6, wherein the concentration of the supporting and homogenizing agent is 1 to 80 ppm on a mass basis.   The dispersion liquid according to any one of claims 1 to 7, wherein an average particle diameter of the fine particles is 5 nm or less.   The dispersion liquid according to any one of claims 1 to 8, further comprising a product A produced by a chemical reaction involving oxidation of gallic acid.   The dispersion according to claim 9, further comprising a product B produced by a chemical reaction involving oxidation of ascorbic acid.   The dispersion liquid of any one of Claims 1-10 which does not contain water-soluble polymer substantially.   The dispersion according to any one of claims 1 to 11, which does not substantially contain a carrier for supporting the fine particles. A method for producing a fine particle carrier, in which a fine particle containing a noble metal is dispersed in a dispersion medium and a carrier is brought into contact with the fine particle dispersion to carry the fine particle on the carrier.
The dispersion is the dispersion according to any one of claims 1 to 12.
A method for producing a particulate carrier. (I) preparing a dispersion A in which fine particles containing a noble metal produced by reduction of the noble metal compound are dispersed by heating a solution containing the noble metal compound and a reducing agent;
The step (ii) of obtaining the dispersion B by concentrating the dispersion A so that the dispersed fine particles are 4000 ppm or more on a mass basis;
Adding a supporting and homogenizing agent to the dispersion A and / or the dispersion B (iii),
The supported homogenizing agent includes at least one selected from hydroxy acids, amino acids and salts thereof.
A method for producing a dispersion of fine particles.   The said reducing agent is a manufacturing method of Claim 14 containing a gallic acid and / or its salt.   The said reducing agent is a manufacturing method of Claim 15 which further contains ascorbic acid and / or its salt. (I) preparing a dispersion liquid A of fine particles in which fine particles containing noble metal produced by reduction of the noble metal compound are dispersed by heating a solution containing the noble metal compound and a reducing agent;
The step (ii) of obtaining the dispersion B by concentrating the dispersion A so that the dispersed fine particles are 4000 ppm or more on a mass basis;
A step (iii) of adding a supporting and homogenizing agent to the dispersion A and / or the dispersion B;
And (iv) obtaining a fine particle carrier by bringing the carrier B into contact with the dispersion B containing the carrier homogenizing agent to carry the fine particles on the carrier.
The supported homogenizing agent includes at least one selected from hydroxy acids, amino acids and salts thereof.
A method for producing a particulate carrier.   The said reducing agent is a manufacturing method of Claim 17 containing a gallic acid and / or its salt.   The said reducing agent is a manufacturing method of Claim 18 which further contains ascorbic acid and / or its salt.