JP3781694B2 - Method for producing trivalent ruthenium chloride - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing trivalent ruthenium chloride, characterized by electrolytic reduction of a ruthenium chloride aqueous solution in which trivalent ruthenium ions and tetravalent ruthenium ions are mixed.
[0002]
[Prior art]
Ruthenium is used in various synthetic reaction catalysts because it exhibits an excellent catalytic activity as a metal, oxide, complex or the like. Further, ruthenium dioxide is attracting attention in the fields of automobiles and electronic components because it is effective as a resistance material, various sensor materials, capacitor electrode materials, electromagnetic wave shielding materials, and the like. The ruthenium chloride salt (RuCl ₃ · nH ₂ O) or the aqueous ruthenium chloride solution (H ₃ RuCl ₆ ), which are generally produced as the above-mentioned catalyst and ruthenium dioxide raw material, have trivalent ruthenium ions 60 to 70 in the production process. %, Tetravalent ruthenium ions in a mixture of 30 to 40%.
When ruthenium chloride in which trivalent ruthenium ions and tetravalent ruthenium ions are mixed is used as a catalyst material or an electronic component material, it causes variations in catalyst characteristics, electrical characteristics, electromagnetic wave shielding effects, and the like.
It was also found that the yield of reaction products was poor when ruthenium chloride containing trivalent and tetravalent ruthenium ions was used in synthesizing an organic complex from ruthenium chloride.
[0003]
A method of reducing the above tetravalent ruthenium ion to a trivalent ruthenium ion with a reducing agent such as hydrazine, SBH, SO ₂ and oxalic acid has also been tried. However, residual salts produced after charging the reducing agent are ruthenium chloride as impurities. Since it remained in the salt, there was a defect that the purity of the ruthenium chloride salt was lowered.
[0004]
[Problems to be solved by the invention]
The present invention has been made paying attention to such a situation, and its purpose is to form tetravalent ruthenium ions with hydrogen ions by electrolysis of an aqueous solution of ruthenium chloride mixed with trivalent ruthenium ions and tetravalent ruthenium ions. It is an object of the present invention to provide a method for producing trivalent ruthenium chloride which is reduced to trivalent ruthenium ions, avoids contamination by impurities such as a reducing agent, and is purified only to trivalent ruthenium ions.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention
A ruthenium chloride aqueous solution in which trivalent ruthenium ions and tetravalent ruthenium ions are mixed is brought into contact with a hydrochloric acid solution through a fluororesin cation exchange membrane, a cathode is placed in the ruthenium chloride aqueous solution, and the hydrochloric acid solution The anode is inserted and a direct current is passed between the electrodes to reduce the tetravalent ruthenium ion to the trivalent ruthenium ion on the cathode side, and the reduction current of the obtained trivalent ruthenium chloride is obtained by a voltammetric measurement method. The present invention provides a method for producing trivalent ruthenium chloride, characterized in that reduction is carried out until almost no potential difference occurs in the potential range of +0.3 to +0.8 .
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In practicing the present invention, a ruthenium chloride aqueous solution is prepared by dissolving a ruthenium chloride salt (RuCl ₃ .nH ₂ O) containing trivalent ruthenium ions and tetravalent ruthenium ions in water. Alternatively, a ruthenium chloride aqueous solution produced from metal ruthenium is prepared. Trivalent ruthenium chloride purified by reducing tetravalent ruthenium ions to trivalent ruthenium ions by using an electrolytic reduction tank 1 as shown in FIG. 1 is produced. That is, in FIG. 1, the electrolytic reduction tank 1 is divided into two chambers by a cation exchange membrane 6, the ruthenium chloride aqueous solution 5 in which the trivalent ruthenium ion and the tetravalent ruthenium ion are mixed is put in one chamber, and the other 1 to 3M dilute hydrochloric acid is placed in the chamber. Examples of the cation exchange membrane 6 include a fluororesin cation exchange membrane and a styrene-vinylbenzene cation exchange membrane. Then, a platinum-plated titanium cathode is inserted into the ruthenium chloride aqueous solution 5, and a platinum-plated titanium anode is inserted into the other dilute hydrochloric acid solution, and 11 to 14 mA / cm ² between the cathode and the anode. Electrolysis is carried out by flowing a direct current.
When the current density is 11 mA / cm ² or less, the electrolysis time becomes long, which is not preferable. On the other hand, if it is 14 mA / cm ² or more, the electrolysis efficiency does not increase, and a load is applied to the cation exchange membrane.
The reduction rate from tetravalent ruthenium ions to trivalent ruthenium ions by electrolysis is determined by the voltammetric method of the generation of reduction current and the color of the solution (the ruthenium chlorate aqueous solution in which trivalent ruthenium ions and tetravalent ruthenium ions are mixed is brownish brown) However, when it was purified to trivalent ruthenium ions, it turned blue-black, and thus it was evaluated.
[0007]
【Example】
Next, the present invention will be described specifically by way of examples. The present invention is not limited to the examples described below.
[0008]
[Example 1]
A crude ruthenium chloride salt (RuCl ₃ · nH ₂ O) containing trivalent ruthenium ions and tetravalent ruthenium ions was dissolved in water to prepare a 40 g / l aqueous ruthenium chloride solution. Next, using the electrolytic reduction tank 1 shown in FIG. 1, 20 g / l of the above-mentioned aqueous ruthenium chloride solution is put into one cathode side chamber partitioned by the fluororesin cation exchange membrane 6, and 2M hydrochloric acid 4 is put into the other anode side chamber. Is placed in the same manner as the liquid level of the aqueous ruthenium chloride solution in the cathode side chamber. Next, a platinum-plated titanium cathode plate 3 is placed in an aqueous ruthenium chloride solution 5, the platinum-plated titanium anode plate 2 is inserted into 2M hydrochloric acid, and a current of 2-3V and 12A is passed between the electrodes by a rectifier. did.
Activate the circulation pump for agitation. After 23 hours, the rectifier was stopped, the aqueous ruthenium chloride solution in the cathode side chamber was taken out, filtered to remove insoluble unreacted substances and dust, and the aqueous ruthenic acid chloride solution 5 was charged into the rotary evaporator. The mixture was heated to 105 ° C. and evaporated to dryness to obtain trivalent ruthenium chloride crystals .
[0009]
The resulting trivalent ruthenium chloride crystal and the crude ruthenium chloride salt (RuCl ₃ · nH ₂ O) used as raw materials were each applied to a voltammetric measuring instrument to measure the state of reduction current generation. The results are shown in FIGS.
[0010]
As is apparent from FIG. 2, the trivalent ruthenium chloride obtained by the production method of the present invention has a potential difference of almost zero in the potential range of +0.3 to +0.8, and the tetravalent ruthenium ion is It can be seen that the trivalent ruthenium ion is a specially priced trivalent ruthenium chloride crystal that is specially sold. On the other hand, as is apparent from FIG. 3, the crude ruthenium chloride salt used as a raw material has a potential difference of about +300 in the range of potential +0.3 to +0.8. This is because trivalent ruthenium ions and tetravalent ruthenium ions are mixed.
[0011]
【The invention's effect】
The present invention is configured as described above. By electrolytic reduction of a crude ruthenium chloride salt (RuCl ₃ .nH ₂ O) in which tetravalent ruthenium ions and trivalent ruthenium ions are mixed, the crude ruthenium chloride salt is incorporated into the crude ruthenium chloride salt. Tetravalent ruthenium ions contained therein can be efficiently converted into trivalent ruthenium ions, and high-purity trivalent ruthenium chloride crystals purified only to trivalent ruthenium ions can be easily produced.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an electrolytic reduction tank used for production of the present invention.
FIG. 2 is a graph showing the results of measuring the reduction rate of the trivalent ruthenium chloride crystal obtained in Example 1 of the present invention by a voltammetric measurement method.
FIG. 3 is a graph showing the results of measuring a ruthenium chloride crystal by a voltammetric measurement method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electrolytic reduction tank 2 Anode plate 3 Cathode plate 4 Dilute hydrochloric acid 5 Chlorine ruthenium acid aqueous solution 6 Cation exchange membrane

Claims (1)

A ruthenium chloride aqueous solution in which trivalent ruthenium ions and tetravalent ruthenium ions are mixed is brought into contact with a hydrochloric acid solution through a fluororesin cation exchange membrane, a cathode is placed in the ruthenium chloride aqueous solution, and the hydrochloric acid solution The anode is inserted and a direct current is passed between the electrodes to reduce the tetravalent ruthenium ion to the trivalent ruthenium ion on the cathode side, and the reduction current of the obtained trivalent ruthenium chloride is obtained by a voltammetric measurement method. A method for producing trivalent ruthenium chloride, characterized in that the reduction is carried out until almost no potential difference occurs in the range of potential +0.3 to +0.8.

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