JP2820289B2 - Method for producing potassium tetrachloroplatinate - Google Patents

Description

The present invention relates to a method for producing potassium tetrachloroplatinate.

(Prior art and its problems) Conventionally, a method for producing potassium tetrachloroplatinate is a reaction in which potassium chloride is added to a hexachloroplatinic acid solution and reacted.
After cooling in an ice bath to form a precipitate of potassium hexachloroplatinate, the mixture was filtered, hot ethanol was added to dissolve the precipitate, and the mixture was quickly filtered while hot, and dioxane was added to the filtrate.
Cooling in an ice bath produces a precipitate of crude potassium hexachloroplatinate, which is filtered, dissolved in a small amount of water, and left in a vacuum desiccator at room temperature to obtain potassium hexachloroplatinate crystals of high purity.

Next, the crystals are suspended in a small amount of water, and a reduction reaction is performed by adding a small amount of sulfurous acid solution little by little, and concentrated on a steam bath until crystals start to be formed, and then cooled to room temperature to completely form crystals. After filtration, the crystals were separated, and the crystals were dissolved in cold water. If there was any undissolved material, the crystals were filtered.If an equal volume mixed solution of acetone / ether was added to the filtrate, the mixture was rapidly stirred to obtain tetrachloroplatinic acid. The potassium precipitates.

Then, the mixture was allowed to stand and the supernatant was decanted off.
The precipitate is washed with a mixed solution of acetone and ether, then washed with ether, and then the crystals are air-dried on filter paper. There is a drawback that labor is required.

As another method, potassium oxalate is reduced by changing to the sulfite aqueous solution used for the reduction reaction, and then heated to such an extent that the solution is not boiled by adding approximately the same volume of hydrochloric acid, and about half volume of ethanol is added. The method of forming crystals of potassium tetrachloroplatinate by allowing to cool is disadvantageous in that impurities easily coexist and the production yield is low.

In addition, the reaction was heated to 50 to 65 ° C. while adding little by little hydrazine dihydrochloride to the reduction reaction and stirring to keep potassium hexachloroplatinate slightly insoluble, and then the temperature was maintained for about 2 hours. The reaction was completed by raising the temperature to 80-90 ° C, cooling in an ice bath, filtering out unreacted potassium hexachloroplatinate and obtaining a mixed solution of potassium tetrachloroplatinate and hydrochloric acid. There is a disadvantage that crystals of potassium acid cannot be obtained.

(Object of the Invention) The present invention has been made in order to solve the above-mentioned drawbacks of the conventional method, and a method for producing a crystal of potassium tetrachloroplatinate with high production yield and high purity by a simple method. It is intended to provide.

(Means for Solving the Problems) The present invention provides a method for producing potassium tetrachloroplatinate, in which a potassium chloride aqueous solution is added to a hexachloroplatinate solution to precipitate potassium hexachloroplatinate crystals,
(A) a step of obtaining crystals of potassium hexachloroplatinate by filtration and washing and drying at 60 to 80 ° C .; and measuring the crystals of potassium hexachloroplatinate to calculate the amount of platinum, suspending the crystals in dilute hydrochloric acid to adjust the platinum concentration. It is adjusted to 40-60 g /, the amount of hydrazine dihydrochloride required for the reduction reaction is calculated and measured from the calculated amount of platinum, and the hydrazine dihydrochloride is stirred at a reduction reaction temperature of 70 to 90 ° C. under stirring at 10 g / min to 20 g. After the addition at a rate of 2 min / min, maintaining the reduction reaction temperature, continuing stirring and aging for 2 to 3 hours (b), and subjecting the aged solution to a platinum concentration of 35 to 45 g /
And measuring the volume of the solution, adding concentrated hydrochloric acid in an amount corresponding to half the volume of the solution, stirring the mixture, allowing it to stand overnight, and then filtering to obtain a filtrate (c). An equal amount of ethanol was added to the amount of the filtrate, and the mixture was stirred to precipitate crystals of potassium tetrachloroplatinate, filtered, washed with ethanol, and washed with ethanol.
A method for producing potassium tetrachloroplatinate, comprising a step (d) of drying at 100 ° C. and then increasing the temperature to 100 ° C. and drying.

Hereinafter, the production method of the present invention will be described in more detail.

In precipitating potassium hexachloroplatinate crystals, the reaction is carried out promptly by adding it as an aqueous solution of potassium chloride. In addition, an excess amount of potassium chloride is added as an aqueous solution in excess of the amount of potassium chloride required for the reaction, followed by filtration. After drying thoroughly, dry overnight at 60-80 ° C.

The reason for adding the potassium chloride aqueous solution is that when crystals are added, potassium hexachloroplatinate precipitates on the surface of the crystals, which causes a decrease in purity. The purpose of preventing dissolution of potassium platinate is to wash thoroughly with a 2 wt% aqueous potassium chloride solution to remove impurities and prevent dissolution of potassium hexachloroplatinate. The reason for performing the treatment overnight is that if the temperature is high, the composition is easily decomposed, and if the temperature is low, the drying time is long.

Further, to reduce potassium hexachloroplatinate to potassium tetrachloroplatinate, weigh out crystals of potassium hexachloroplatinate, and determine the amount of platinum as a platinum content of 40.14w.
Calculate as t%, dissolve in diluted hydrochloric acid and adjust the platinum concentration to 40 to 60 g
The reason why hydrazine dihydrochloride is used as the reducing agent is that the substances generated in the reduction reaction are nitrogen and hydrochloric acid, which hardly affect the purity of potassium tetrachloroplatinate crystals, and the amount of platinum added is The reason why the addition speed was set to 10 g / min to 20 g / min in terms of the chemical reaction equivalent is that at 20 g / min or more, hydrazine dihydrochloride would be decomposed and wasteful, and at 10 g / min or less, the reduction time would be long. This is because it lacks workability.

As a condition for performing the above-mentioned reduction reaction, potassium hexachloroplatinate crystals are dissolved in dilute hydrochloric acid (0.5 to 1.0 N) so that the reduction reaction can be carried out promptly in a stable state. After the reaction at 9090 ° C. and the addition of hydrazine dihydrochloride is completed, the reaction temperature is maintained, stirring is continued, and the mixture is aged for 2 to 3 hours.

Dilute hydrochloric acid is used to accelerate the reduction reaction.Hydrazine dihydrochloride is easily decomposed in a hydrochloric acid solution of 1.0 N or more and is wasted, and a reduction reaction of 0.5 N or less makes the reduction reaction unstable. The reason why the temperature is set to 70 to 90 ° C. is that platinum black easily forms at 90 ° C. or higher, and 70 ° C.
This is because the reaction time becomes longer in the following.

Next, the concentrated hydrochloric acid is reduced, half the volume of the matured solution is added thereto, and the mixture is stirred and left standing overnight.

Thereafter, the mixture was filtered without using water, an equal amount of ethanol was added to the filtrate, and the mixture was stirred to precipitate crystals of potassium tetrachloroplatinate, filtered, washed with ethanol, and then washed with ethanol.
After sufficiently drying at 100 ° C., drying at 100 ° C. or lower gives potassium tetrachloroplatinate crystals.

Ethanol is added to precipitate crystals by using the solubility of potassium tetrachloroplatinate, and the amount thereof is sufficient as described above.

Hereinafter, examples according to the present invention will be described, but the examples do not measure the present invention.

(Example 1) A potassium chloride aqueous solution (KCl 230 g /) 2.3 was added to hexachloroplatinic acid solution (Pt50 g /) 1 and stirred to precipitate potassium hexachloroplatinate crystals, and then allowed to stand.
Filter using 3μ filter paper and crystallize the crystals in 70 ° C air dryer.
Dried for 12 hours.

Then, 50 g of the crystal was weighed and dissolved in a 0.7N diluted hydrochloric acid solution to prepare a platinum concentration of 50 g /, heated to 70 ° C. in a hot water bath, and stirred under agitation with an amount of hydrazine dihydrochloride equivalent to platinum amount of 6.0 g.
Was added at a rate of 20 g / min, and the mixture was aged for 3 hours while maintaining the heating temperature and stirring to obtain a potassium tetrachloroplatinate solution.

Next, water was added to the solution to adjust the platinum concentration to 40 g /, concentrated hydrochloric acid of 1/2 of the volume was added, stirred, and allowed to stand overnight.

After standing, the mixture was filtered through a dry filter paper, an equal amount of ethanol to the filtrate was added, and the mixture was stirred to precipitate crystals of potassium tetrachloroplatinate. The crystals were filtered using dry filter paper and washed four times with ethanol. Then, after drying in an air dryer set at 30 ° C. for 5 hours, the temperature was raised to 100 ° C. and dried for 10 hours to obtain 42.5 g of potassium tetrachloroplatinate crystals.

When the crystals were analyzed by X-ray diffraction, no compound other than potassium tetrachloroplatinate was detected, and the production yield was 60% based on the amount of platinum charged.

(Example 2) 2.3 Potassium chloride aqueous solution (KCl 230 g /) 2.3 was added to hexachloroplatinic acid solution (Pt50 g /) 1 and stirred to precipitate potassium hexachloroplatinate crystals, and then allowed to stand.
Filter using 3μ filter paper and crystallize the crystals in 70 ° C air dryer.
Dried for 12 hours.

Next, 50 g of the crystal was weighed and dissolved in a 1.0 N diluted hydrochloric acid solution to prepare a platinum concentration of 45 g /.
Was added at a rate of 10 g / min, and the mixture was aged for 2 hours while maintaining the heating temperature and stirring to obtain a potassium tetrachloroplatinate solution.

Next, water was added to the solution to adjust the platinum concentration to 40 g /, concentrated hydrochloric acid of 1/2 of the volume was added, stirred, and allowed to stand overnight.

After standing, the mixture was filtered through a dry filter paper, an equal amount of ethanol to the filtrate was added, and the mixture was stirred to precipitate crystals of potassium tetrachloroplatinate. The crystals were filtered using dry filter paper and washed four times with ethanol. Then, after drying in an air dryer set at 30 ° C. for 5 hours, the temperature was raised to 100 ° C. and dried for 10 hours to obtain 43.2 g of potassium tetrachloroplatinate crystals.

When the crystals were analyzed by X-ray diffraction, no compound other than potassium tetrachloroplatinate was detected, and the production yield was 61% based on the amount of platinum charged.

(Conventional example) Crystals of hexachloroplatinic acid are dissolved in a small amount of water, potassium chloride crystals are added in excess, and the mixture is stirred and cooled in an ice bath to precipitate crystals of potassium hexachloroplatinate, filtered,
Dissolve the filtered crystals in ethanol heated to 60 ° C,
Filter quickly to separate the excess potassium chloride, add dioxane to the obtained filtrate, cool in an ice bath, precipitate potassium hexachloroplatinate crystals again, filter and dissolve the crystals again with a small amount of water. And a vacuum desiccator (0.5 Torr
In the following), crystals were obtained by standing at room temperature overnight.

Then, while suspending the crystals in a small amount of water and stirring at 85 ° C. on a steam bath, repeating the operation of adding 1 ml of sulfurous acid solution and adding sulfurous acid solution again after the smell of sulfurous acid gas disappeared to complete the reduction reaction. After that, 85 ℃ on steam bath
When the crystals begin to precipitate, stop and cool to room temperature, dissolve the filtered crystals in cold water, filter unreacted potassium hexachloroplatinate, and add about 10 times the volume of acetone / ether to the filtrate. An equal volume mixed solution was added and rapidly stirred to precipitate potassium tetrachloroplatinate crystals.After allowing to stand, the supernatant was removed by decantation, and the crystals were added with an acetone / ether equivalent mixed solution. The operation of stirring, standing, decanting, and removing the supernatant liquid was performed three times, and then similarly performed three times with ether. The crystals were transferred to filter paper, air-dried, and dried to give 35.1 g of potassium tetrachloroplatinate crystals.
I got

The production yield of potassium tetrachloroplatinate obtained from the charged crystals of hexachloroplatinic acid was calculated to be 33% for platinum.

(Effects of the Invention) As described above, according to the production method of the present invention, it is possible to shorten the production time by about 4 hours more easily than in the conventional method, and to reduce the production yield from the charged hexachloroplatinic acid. It can be said that the effect is improved by about two times, the purity of the produced potassium tetrachloroplatinate is high, and the effect is extremely large.

Claims (1)

(57) [Claims] In a method for producing potassium tetrachloroplatinate, an aqueous potassium chloride solution is added to a hexachloroplatinate solution to precipitate crystals of potassium hexachloroplatinate,
(A) a step of obtaining crystals of potassium hexachloroplatinate by filtration and washing and drying at 60 to 80 ° C .; and measuring the crystals of potassium hexachloroplatinate to calculate the amount of platinum, suspending the crystals in dilute hydrochloric acid to adjust the platinum concentration. It is adjusted to 40-60 g /, the amount of hydrazine dihydrochloride required for the reduction reaction is calculated and measured from the calculated amount of platinum, and the hydrazine dihydrochloride is stirred at a reduction reaction temperature of 70 to 90 ° C. under stirring at 10 g / min to 20 g. After the addition at a rate of 2 min / min, maintaining the reduction reaction temperature, continuing stirring and aging for 2 to 3 hours (b), and subjecting the aged solution to a platinum concentration of 35 to 45 g /
And measuring the volume of the solution, adding concentrated hydrochloric acid in an amount corresponding to half the volume of the solution, stirring the mixture, allowing it to stand overnight, and then filtering to obtain a filtrate (c). An equal amount of ethanol was added to the amount of the filtrate, and the mixture was stirred to precipitate crystals of potassium tetrachloroplatinate, filtered, washed with ethanol, and washed with ethanol.
A method for producing potassium tetrachloroplatinate, comprising a step (d) of drying at 100 ° C. and then increasing the temperature to 100 ° C. and drying.