JPH06247890A - Production of acetylacetone iridium salt solution - Google Patents

Abstract

PURPOSE:To produce an acetylacetone iridium salt solution in high yield and to enable the storage of the solution in high stability. CONSTITUTION:An aqueous solution containing iridium(IV) ion and/or iridium(IV) complex ion, a reducing agent and an acetylacetone alkali salt is heated, a solution composed of an acetylacetone iridium salt and acetylacetone is separated and extracted from the heat-treated aqueous solution by salting-out and the acetylacetone solution of the extracted acetylacetone iridium salt is dissolved in dimethylformamide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a solution of acetylacetone iridium salt used for a catalyst for purifying nitrogen oxides, an organic metal ink as an electronic material and the like.

[0002]

2. Description of the Related Art Most acetylacetone salts are produced by a metathesis method in which an acetylacetone alkali salt such as sodium acetylacetone is mixed with an aqueous solution of another metal salt to precipitate the acetylacetone metal salt. But,
When an aqueous solution of iridium salt such as hexachloroiridium (IV) salt is used as the aqueous solution of metal salt, hydrolysis of alkali acetylacetone causes precipitation of a hydroxide that is not soluble in an organic solvent, and an acetylacetone iridium salt solution cannot be obtained.

Further, while mixing acetylacetone and an iridium metal ion aqueous solution, the pH is made neutral or slightly acidic,
There is a solvent extraction method in which an acetylacetone iridium salt is synthesized by extracting iridium metal ions into an organic solvent. However, in this method, since the iridium ion is a highly hydrophilic complex salt in the aqueous phase in all pH ranges, the iridium ion is hardly extracted.

A metal such as indium which forms an acetylacetone salt having an extremely high complex stability easily reacts with acetylacetone, and there is a direct reaction method in which the metal simple substance or the metal oxide is directly reacted with acetylacetone by heating (Japanese Patent Laid-Open No. 2000-242242). JP-A-59-70690, JP-A-3-5895
No. 1). However, since iridium metal has a very high redox potential and low complex stability, and the iridium compound is also inactive, iridium metal alone, iridium oxide
Iridium compounds such as (IV) and iridium (IV) hydroxide hardly react with acetylacetone even when heated. It was not possible to produce an acetylacetone iridium salt with an iridium content in a yield of 5% by weight or more by the above direct reaction method.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to produce an acetylacetone iridium salt solution in high yield and to store it stably.

In the present invention, an aqueous solution containing an iridium (IV) ion and / or an iridium (IV) complex ion, a reducing agent, and an acetylacetone alkali salt is heated, and the acetylacetone iridium salt and acetylacetone are heated from the heated aqueous solution. It is characterized in that the resulting solution is separated and extracted by a salting out method. Another solution is to dissolve a separated solution of acetylacetone iridium salt and acetylacetone in dimethylformamide to enable long-term storage.

The iridium (IV) ion and / or iridium (IV) complex ion used in the present invention include iridium (IV) chloride dissolved in water, iridium (IV) sulfate, and hexachloroiridium (IV) such as sodium hexachloroiridate. IV) Acid salts, etc. The concentration of these aqueous solutions is arbitrary and may be a suspension of solids.

In the present invention, a reducing agent having a standard redox potential of -1 to +0.2 V such as hydrazine, sulfurous acid and oxalic acid is used. If the standard redox agent potential exceeds +0.2 V, the reducing power is insufficient. Hydrazine is most suitable because it does not accumulate ions in the liquid and does not form a precipitate. The amount of reducing agent added is, of course, iridium (IV) ion and / or iridium (IV)
By adjusting the amount of the complex ion to an amount necessary for reducing the iridium (III) ion and / or the iridium (III) complex ion to prevent the iridium (IV) ion and / or the iridium (IV) complex ion from remaining. , Prevent the formation of precipitates and improve the yield.

As the acetylacetone alkali salt solution, ammonia water, lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, or another alkali is added to acetylacetone. Made. Ammonia water is preferred because the mixture of acetylacetone and acetylacetone ammonium salt has a pH buffering action. By adding alkali to acetylacetone, ionization is carried out to form free acetylacetone, and iridium (III) ions and / or iridium (II)
I) It will react with complex ions. For the same reason as described above, the concentration of this solution is arbitrary and may be a suspension of solids.

[0010]

In general, since the iridium salt is a soluble salt, it is formed as a tetravalent salt by strongly oxidizing the raw material. The iridium (IV) ion and / or the iridium (IV) complex ion has low basicity and is easily converted into a hydroxide by the addition of alkali. That is, when there is an acetylacetonato ion generated from acetylacetone and alkali, the iridium (IV) ion and / or the iridium (IV) complex ion does not react with acetylacetone and becomes a hydroxide. Even if an acetylacetone iridium salt is produced, the tetravalent salt will be hydrolyzed to a hydroxide. On the other hand, the iridium (III) ion and / or the iridium (III) complex ion is resistant to hydrolysis and is stable, and a stable acetylacetone iridium salt can be produced.

In the present invention, without using acetylacetone,
The reason for using acetylacetone alkali is that acetylacetone alkali is ionized into acetylacetone and alkali in an aqueous solution, and iridium (IV) ions and / or iridium (IV) complex ions are reduced by a reducing agent to generate iridium (III) ions and / or Alternatively, it is easy to react with the iridium (III) complex ion, so that an acetylacetone iridium salt can be easily produced.

The reaction is carried out by mixing an aqueous solution containing iridium (IV) ions and / or iridium (IV) complex ions, a reducing agent, and an acetylacetone alkali salt solution. Prior to the addition of the reducing agent, iridium (IV) ) Ions and / or iridium (IV) complex ions and an aqueous solution of an acetylacetone alkali salt are mixed, a precipitate is likely to be formed. Therefore, an aqueous solution containing iridium (IV) ions and / or iridium (IV) complex ions , It is preferable to mix the reducing agent and then the acetylacetone alkali salt solution, or to mix the three simultaneously.

The reaction is carried out by stirring the mixed solution at 70-
Perform at a temperature of 140 ° C. If the temperature is lower than 70 ° C, the reaction is slow and takes too long, and if the temperature exceeds 140 ° C, acetylacetone boils. The liquids may be heated by heating and mixing the respective liquids, or may be heated after being mixed.

By heating, in the mixed solution, ionization of salts in the aqueous solution is promoted, the ionic strength of the solution is increased, the hydrophilicity of acetylacetone is lowered, and acetylacetone in a free state is precipitated in the form of oil droplets, and at the same time, it is dissolved in water. Slightly soluble and easily soluble in acetylacetone acetylacetone iridium (III)
A salt forms and dissolves in the acetylacetone oil droplets. Once
Acetylacetone iridium (III) to acetylacetone
When the salt dissolves, the hydrophilicity of acetylacetone decreases,
Acetylacetone does not dissolve in an aqueous solution even if the temperature decreases and the ionic strength of the liquid decreases.

In the presence of acetylacetone, when the iridium (IV) ion and / or the iridium (IV) complex ion is reduced, a chelate complex salt of acetylacetoneiridium (III) salt is produced, and the reduction potential to the metal is greatly lowered. , Even at high temperature and alkaline, metal is not reduced. Therefore, by using the iridium (IV) ion and / or the iridium (IV) complex ion as a raw material and simultaneously reducing the iridium (III) ion and / or the iridium (III) complex ion to produce an acetylacetone iridium (III) salt, A stable and high quality acetylacetone iridium (III) salt solution is obtained.

It has been found that even with acetylacetone iridium salts, acetylacetone iridium salts having low hydrophilicity can be deposited by increasing the ionic strength of the aqueous phase. As the salt to be added, acetylacetone iridium salt, iridium (III) salt, iridium (III) complex salt,
Any substance that does not react with acetylacetone and is soluble in water may be used. In addition to ammonium chloride, ammonium nitrate, ammonium sulfate, potassium sulfate, and sodium sulfate, sodium acetylacetone, potassium acetylacetone, ammonium acetylacetone, and the like, which can be dissolved in the organic phase, can be preferably used. The concentration of the added salt is optional, but if it is added at a concentration higher than the saturation concentration, it is not preferable because a sparingly soluble iridium inorganic compound such as iridium (III) sulfate ammonium and iridium sulfate may precipitate.

The acetylacetone iridium salt dissolved in the aqueous phase can be recovered by a solvent extraction method in which acetylacetone is added. Any organic solvent for extraction may be used as long as it dissolves the acetylacetone iridium salt, does not dissolve other added salts, and is hardly soluble in water. For example, a polyhalogenated alkyl such as chloroform, bromoform or a solution of carbon tetrabromide in bromoform can be used. Does not generate corrosive gas when heated,
Acetylacetone that can be used repeatedly is preferred.

Since the extraction suppresses volatilization, it is preferable to carry out the extraction by cooling to room temperature. When extracting with acetylacetone, the extraction can be carried out almost completely by extracting about three times with a volume of about 1/2 of the aqueous phase.

Iridium remaining in the aqueous phase after salting out and extraction
(III) ion and / or iridium (III) complex ion is obtained by adding iridium (III) ion and / or iridium (III) complex ion and acetylacetone alkali salt and mixing with heat, and then adding acetylacetone to form acetylacetone iridium salt. An acetylacetone iridium salt solution consisting of and acetylacetone can be extracted.

When dimethylformamide is added to the organic phase after extraction, not only the solubility of acetylacetone increases, but also it can be stored for a long period of time without forming a precipitate.

[0021]

【Example】

Example Metal iridium powder and sodium chloride in an amount twice that of the metal iridium powder were mixed and heated at 600 ° C. for 1 hour in a chlorine gas stream to obtain sodium hexachloroiridate (Na).
₂ [IrCl ₆ ]) was obtained. This was dissolved in water to prepare an aqueous sodium hexachloroiridate solution having an iridium metal content of 90.5 g / l. Next, 140 g of special grade acetylacetone and 70% ammonia water with a concentration of 25% by weight.
4 ml was mixed to prepare an acetylacetone ammonium aqueous solution. 21 ml of the iridium solution, 17.8 ml of the acetylacetone ammonium aqueous solution, and 1 ml of a 90 wt% aqueous solution of hydrazine hydrate (N ₂ H ₄ · H ₂ O) were mixed.

While stirring this mixed solution, the mixture was stirred at a temperature of 95 ° C. for 1 hour.
Reaction was carried out for 0 minutes to generate an acetylacetone iridium salt solution. This solution was cooled to 25 ° C., and as a salting-out agent, reagent grade ammonium sulfate [(NH ₄ ) ₂ SO ₄ ] 20
15 g of the above acetylacetone solution after dissolving g
The addition of 1 and extraction of the acetylacetone iridium salt solution was repeated 3 times. The extraction ratio of pure iridium to the added amount of iridium was 83% by weight.

Further, to the iridium solution after extraction, the above sodium hexachloroiridate aqueous solution containing 1.5 g of iridium metal was added, the acetylacetone iridium salt solution was separated again in the same manner as described above, and acetylacetone iridium was prepared in the same manner as described above. The salt solution was extracted. The extraction ratio of pure iridium to the amount of added iridium is 105.
% By weight.

The arithmetic average extraction rate of pure iridium by the above-mentioned two extraction treatments is 94% by weight, and the arithmetic average impurity ion concentration of pure iridium in the extract is less than 0.3% by weight of Na and SO. It was ₄ 0.3% by weight.

Each of the two extracted organic phases was diluted 5 times with dimethylformamide, sealed and left at room temperature for 6 months, but no precipitate was formed at all.

Comparative Example 1 An acetylacetone iridium salt solution was obtained in the same manner as in Example 1 except that ammonium sulfate as a salting-out agent was not used. The arithmetic average extraction rate of pure iridium was 28% by weight, and most of iridium remained in the aqueous phase.

Comparative Example 2 When the extracted organic phase of the above Example was diluted 5 times with acetylacetone, sealed and left at room temperature, the formation of precipitates was observed after about 1 week. Further, when the extracted organic phase of the above-mentioned Example was sealed as it was and left at room temperature, a precipitate was formed after 1 day.

[0028]

According to the present invention, an acetylacetone iridium salt solution can be obtained in high yield and can be stored for a long period of time.

Claims (3)

[Claims] 1. A solution consisting of an iridium (IV) ion and / or an iridium (IV) complex ion, a reducing agent, and an acetylacetone alkali salt, which is heated, and the solution after heating is composed of an acetylacetone iridium salt and acetylacetone. A method for producing an acetylacetone iridium salt solution, which comprises separating the salt by a salting-out method. 2. The solution of acetylacetone iridium salt and acetylacetone is extracted from the aqueous solution obtained by separating the solution of acetylacetone iridium salt and acetylacetone by a salting-out method using acetylacetone as a solvent. Method for producing acetylacetone iridium salt solution. 3. A method for producing an acetylacetone iridium salt solution, which comprises dissolving acetylacetone containing an acetylacetone iridium salt in dimethylformamide.