JPH08104526A - Production of rhodium nitrate solution - Google Patents

Abstract

PURPOSE: To provide a method for producing a rhodium nitrate solution enabling to increase the yield of dissolution into nitric acid and reduce chloride ion concentration. CONSTITUTION: The production of a rhodium nitrate solution consists of a process adding a potassium hydroxide solution to a rhodium chloride solution and neutralizing, a process filtering a formed rhodium hydroxide and then washing, a process adding nitric acid to the rhodium hydroxide and dissolving under heat at a temp. not forming insoluble oxide of rhodium, while the solution is stirred, and then a process adding excess silver nitrate or silver oxide more than mol equivalent of chlorine and heating, and subsequently hydrochloric acid being an equal quantity to mol equivalent of silver is added and heated and formed silver chloride is filtered, thus the rhodium nitrate solution containing less chloride ions, is obtained at a high yield.

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 rhodium nitrate solution as a starting material for a catalyst or a starting material for synthesizing a rhodium compound by utilizing the characteristics of rhodium.

[0002]

2. Description of the Related Art Conventionally, as a method of producing a rhodium nitrate (Rh (NO ₃ ) ₃ ) solution, a step of adding an alkaline solution to a rhodium chloride (RhCl ₃ ) solution to neutralize it and a rhodium hydroxide (Rh (NO ₃ ) ₃ ) solution produced (OH) ₃ ) is separated by a gradient method and washed, and nitric acid (HN ₃ ) is added to the washed rhodium hydroxide.
O ₃ ), and heating and dissolving in a hot water bath, and a step of filtering and separating undissolved substances after heating and dissolving, or instead of the rhodium chloride solution, the rhodium nitrate solution obtained by the above method is used. There are known methods of performing the above method using the same.

[0003]

However, in the conventional method for producing a rhodium nitrate solution, the yield is poor, and the concentration of chlorine ions, which hinders the catalyst performance, is high, and the number of steps for reducing the concentration of chlorine ions increases. There is a problem called.

[0004]

In order to solve the above-mentioned problems, a method for producing a rhodium nitrate solution of the present invention comprises a step of neutralizing a rhodium chloride solution in the method for producing a rhodium nitrate solution, and a step of producing the generated hydroxide. After the rhodium is filtered off and washed, the nitric acid is added to the washed rhodium hydroxide to dissolve it by heating, and after heating and dissolving, the silver nitrate or silver oxide solution is added in excess of the chloride ion equivalent in the solution and heated. And a step of adding hydrochloric acid by a molar equivalent amount of silver ions remaining in the liquid after the heating and heating, and a step of separating the produced silver chloride by filtration.

Each of the neutralizing steps is preferably carried out using a potassium hydroxide solution. In each of the washing steps, the operation of decanting the rhodium hydroxide generated after neutralization after standing still and / or the operation of decanting after adding pure water and standing still is repeated 2-3 times. Is preferred. Further, it is preferable that each of the heating and melting steps is performed at a temperature of 80 ° C. or higher. More preferably, the temperature is 85 to 95 ° C. On the other hand, the amount of silver nitrate or silver oxide added is preferably 1.1 to 2 times the molar equivalent of chloride ion. The heating after the addition of the silver nitrate or silver oxide solution is preferably performed at a temperature of 85 ° C. or higher. The heating after the addition of hydrochloric acid is preferably performed at a temperature of 90 ° C to 95 ° C.

[0006]

In the method for producing a rhodium nitrate solution of the present invention, since silver nitrate or silver oxide is added in excess of the molar equivalent of chloride ions in the solution, silver chloride is completely produced and chloride ions can be completely removed. .

If each of the above-mentioned washing steps is performed once, the effect of removing chlorine ions is not sufficiently exerted. If the heating and melting steps are carried out at a temperature lower than 80 ° C., the reaction rate becomes slow. On the other hand, when the amount of the silver nitrate or silver oxide solution added is less than 1.1 times the molar equivalent of chlorine, the formation of silver chloride is not complete and the removal of chlorine is incomplete, while the amount of chlorine is twice the molar equivalent. If the amount is larger, wasteful silver nitrate or silver oxide is increased, which is uneconomical. If the heating after the addition of the silver nitrate or silver oxide solution is performed at a temperature lower than 85 ° C., the reaction rate becomes slow and chlorine cannot be sufficiently removed. The heating after the addition of hydrochloric acid is set to 50 ° C. or higher because the heating in this range promotes the aggregation of silver chloride and improves the filterability thereafter.

[0008]

EXAMPLES Examples of the present invention will be described below together with comparative examples.

[0009]

Example 1 Rhodium chloride solution (50 g / l as Rh)
While stirring 1 l, 4N potassium hydroxide solution was added, and p
It was neutralized to H7 to produce rhodium hydroxide. Then, the rhodium hydroxide was collected by filtration, and the rhodium hydroxide was washed to remove chlorine ions. For washing, 1000 ml of pure water was added to the rhodium hydroxide collected by filtration, and the mixture was stirred, allowed to stand, and decanted three times. Next, 850 ml of 25% nitric acid was added to the washed rhodium hydroxide, and the mixture was heated and dissolved in a hot water bath at a temperature of 85 to 95 ° C for 7 hours with stirring, and then the silver nitrate solution was added at 1.1 times the molar equivalent of chloride ion in the solution. 90-95 ℃
The mixture was heated in a water bath at the temperature of 7 hours with stirring. Next, after the above heating, the silver concentration in the supernatant was measured, hydrochloric acid was added in an amount equivalent to the molar equivalent of the remaining silver ions in the liquid, and the mixture was heated for 30 minutes while stirring in a water bath at a temperature of 60 ° C. Silver chloride was separated by filtration to obtain 1000 ml of a rhodium nitrate solution.

The rhodium in the rhodium nitrate solution after heating and dissolution with the above nitric acid added was 48 g / l, and the yield was 98% or more. The rhodium nitrate solution thus obtained had a chloride ion concentration of 0.05 g / l or less and a silver ion concentration of 5 ppm or less with respect to Rh of 50 g / l. Similar effects were obtained even when silver oxide was used instead of silver nitrate.

[0011]

[Comparative Example 1] Rhodium chloride solution (Rh: 20 g / l)
While stirring 1 liter, add 14% aqueous ammonia, 50-60 ℃
Was neutralized to pH 7 at the temperature of 1 to produce rhodium hydroxide. Then, the rhodium hydroxide separated by decantation was washed in the same manner as in Example 1 to remove chlorine ions. Then, wash the rhodium hydroxide with 20% nitric acid 500
ml was added and dissolved by heating in a water bath at a temperature of 100 ° C. for 8 hours while stirring, and after cooling, the undissolved substance was separated by filtration using a membrane filter to obtain 250 ml of a rhodium nitrate solution.

The amount of rhodium in the rhodium nitrate solution after heating and dissolution with the above nitric acid added was 56 g / l, and the yield was 70%. The chloride ion concentration of the obtained rhodium nitrate solution was 2 g / l with respect to Rh 50 g / l.

[0013]

As described above, according to the method for producing a rhodium nitrate solution of the present invention, the yield is high, and by adding silver nitrate or silver oxide solution in excess of the molar equivalent of chlorine, chlorine Is almost completely removed, the chloride ion concentration in the rhodium nitrate solution can be 0.05 g / l or less with respect to Rh 50 g / l. Therefore, when used as a catalyst raw material, a rhodium nitrate solution can be obtained in which the catalytic activity does not decrease.

Claims (7)

[Claims] 1. A method for producing a rhodium nitrate solution, which comprises a step of neutralizing the rhodium chloride solution, a step of filtering the produced rhodium hydroxide and then washing, and heating the washed rhodium hydroxide with nitric acid. A step of dissolving, a step of heating after adding silver nitrate or silver oxide solution in excess of the molar equivalent of chloride ions in the solution after heating and dissolving, and hydrochloric acid after the heating, a molar equivalent of silver ions remaining in the solution A method for producing a rhodium nitrate solution, which comprises a step of adding and heating minute amounts and a step of separating the produced silver chloride by filtration. 2. The method for producing a rhodium nitrate solution according to claim 1, wherein the step of neutralizing the rhodium chloride is performed using a potassium hydroxide solution. 3. Each of the washing steps includes an operation of decanting the rhodium hydroxide formed after neutralization after standing still and / or an operation of decanting after adding pure water and standing still 2-3 times. The method for producing a rhodium nitrate solution according to claim 1 or 2, wherein the method is repeated. 4. The method for producing a rhodium nitrate solution according to claim 1, wherein the heating and melting step is performed at a temperature of 80 ° C. or higher. 5. The method according to claim 1, wherein the silver nitrate or silver oxide solution is added in an amount of 1.1 to 2 times the molar equivalent of chloride ion in the solution. Four
A method for producing the rhodium nitrate solution described. 6. The heating method after the addition of the silver nitrate or silver oxide solution is performed at a temperature of 85 ° C. or higher, claim 1, claim 2, claim 3, claim 4 or claim 5. Method for producing rhodium nitrate solution of. 7. The heating after the addition of hydrochloric acid is performed at a temperature of 50 ° C. or higher, claim 1, claim 2, claim 3, claim 4, claim 5, or claim 6. Method for producing rhodium nitrate solution of.