Preparation method of high-purity hydroxyplatinic acid

Abstract

The invention discloses a purification preparation method of high-purity hydroxyplatinic acid, and belongs to the field of synthesis and purification of metal compounds, the method comprises the following steps: (1) mixing a crude hydroxyplatinic acid solid with ethanolamine in a solution according to a certain proportion; (2) heating the mixed solution to enable the mixed solution to become a uniform and transparent faint yellow solution; (3) adding a certain amount of acid into the obtained faint yellow solution to adjust the solution to be acidic, so as to obtain faint yellow hydroxyplatinic acid precipitate; and (4) filtering and separating a product, and washing to obtain pure hydroxyplatinic acid. According to the purification method disclosed by the invention, the metal ions and the content can be reduced to be less than 100ppm only by washing for 2-4 times in the purification process, and the yield is greater than 93%. The manpower and time cost in the purification process is reduced, meanwhile, the wastewater generation amount is reduced, and the method has the advantages of being simple, more environmentally friendly and the like and is convenient for large-scale purification.

Description

Technical Field

[0001] The invention relates to the field of synthesis and purification of metal compounds, and relates to a method for preparing high-purity hydroxyplatinic acid. Background Art

[0002] Hydroxyplatinic acid, also known as hexahydroxyplatinic acid (H2Pt(OH)6), is a common platinum precursor, mainly used as a precursor in the fields of supported platinum catalysts, platinum-based electroplating solutions and fine platinum compound processing (such as platinum nitrate).

[0003] Hydroxyplatinic acid is generally prepared by reacting chloroplatinic acid with hydroxide (sodium hydroxide, potassium hydroxide, etc.) in water, and then filtering and washing to obtain a relatively pure product. In this method, excessive addition of hydroxide often introduces excessive impurity metal ions (sodium ions / potassium ions), but insufficient addition will cause a surge in chloride ion content. Therefore, no matter how the process is fine-tuned, high-purity hydroxyplatinic acid must be obtained through multiple washings, which results in its synthesis and purification process not only generating a large amount of waste liquid but also being quite time-consuming and labor-intensive.

[0004] CN106391139A discloses a method for preparing a hexahydroxyplatinic acid di(ethanolamine) aqueous solution by electrodialysis. After preparing a crude hydroxyplatinic acid product, the product is washed three times with acetic acid, purified water and acetone respectively. After further reaction and dilution, the purified hydroxyplatinic acid has a sodium ion content of 83-97 ppm and a chlorine content of 95-98 ppm. It can be estimated that the sodium ion and chloride ion contents of the hydroxyplatinic acid after multiple washings and purification are both higher than 500 ppm.

[0005] CN117303469A discloses a method for synthesizing platinum nitrate, wherein the prepared crude hydroxyplatinic acid is fully washed with a dilute acid reagent, but the final Na ion content can only be guaranteed to be below 5000 ppm.

[0006] CN110422893A discloses a method for preparing platinum nitrate solution by ultrasonic synergy of molten salt method, wherein the prepared crude hydroxyplatinic acid is subjected to ultrasonic method for impurity removal, and purified hydroxyplatinic acid is obtained after repeated "adding ultrapure water for slurrying - ultrasonic oscillation - filtering" operation for 6-8 times. After further reaction and dilution, the sodium ion and chloride ion contents of the hydroxyplatinic acid are both about 20ppm, from which it can be estimated that the sodium ion and chloride ion contents of the hydroxyplatinic acid are both about 100ppm. Although this method can remove impurity ions well, the operation is extremely complicated, time-consuming and labor-intensive, and generates a large amount of wastewater and noise pollution.

[0007] In summary, the hydroxyplatinic acid prepared by these existing methods needs to be repeatedly washed more than 6 times, and the sodium ion and chloride ion content in the product is between 100ppm and 5000ppm. Not only is the operation complicated and a lot of waste liquid is generated, but there is also the problem that impurities such as sodium ions and chloride ions limit the removal rate. Summary of the invention

[0008] The technical problem to be solved by the present invention is to overcome the above-mentioned shortcomings and provide a method for preparing high-purity hydroxyplatinic acid with less impurity content and simpler operation. The present invention effectively destroys the particle structure of hydroxyplatinic acid and weakens the coordination effect of chloride ions and platinum by mixing ethanolamine into the solvent during the washing and purification process, thereby greatly increasing the washing efficiency. The method provided by the present invention can reduce the content of metal ions and chloride ions to less than 100 ppm under the condition of washing 2-4 times, and the yield is greater than 93%.

[0009] The technical solution of the present invention is:

[0010] A method for preparing high-purity hydroxyplatinic acid comprises the following steps:

[0011] (1) mixing crude hydroxyplatinic acid solid with ethanolamine in a solution in a certain ratio;

[0012] (2) heating the mixed solution to make it a uniform, transparent, light yellow solution;

[0013] (3) adding a certain amount of acid to the obtained light yellow solution to adjust the solution to acidity, thereby obtaining a light yellow hydroxyplatinic acid precipitate;

[0014] (4) The product is separated by filtration and washed to obtain pure hydroxyplatinic acid.

[0015] Further:

[0016] In step (1), the ratio of the crude hydroxyplatinic acid solid to ethanolamine is between 1:0.1-10 (mass ratio, the same below), preferably 1:1-3; the solvent used in the solution is water or a mixture of water and an organic solvent, such as pure water, a mixture of water and ethanol, etc.; the ratio of the crude hydroxyplatinic acid solid to the solvent used is between 1:3-20, preferably 1:5-10.

[0017] In step (2), the heating temperature is between 20 and 100 degrees Celsius.

[0018] The acid in step (3) is an acid with no coordination or low coordination ability, such as acetic acid, nitric acid, etc. After the acid is added, the solution becomes acidic, and the pH should be between 1-6.5, preferably 4-6.

[0019] The washing process described in step (4) uses water or a mixture of water and other organic solvents for washing, such as pure water, a mixture of water and ethanol, or a mixture of water and ethanolamine. The washing process needs to be repeated 0-6 times, preferably 2-4 times.

[0020] Compared with the prior art, the present invention can effectively destroy the particle structure of hydroxyplatinic acid and weaken the coordination effect of chloride ions and platinum by adding ethanolamine in the purification stage, so as to greatly increase the efficiency of washing and impurity removal. Its beneficial effects include:

[0021] (1) High-purity hydroxyplatinic acid can be obtained more stably, and the metal ions (sodium, potassium) and chloride ions in hydroxyplatinic acid can be reduced to below 100 ppm;

[0022] (2) The number of washing times required is only 2-4 times, which is more than 50% lower than the previous report, greatly reducing labor and time costs;

[0023] (3) Less pollutant emissions: Since the number of washing times during the purification process is reduced, the amount of wastewater generated will be greatly reduced, making it more environmentally friendly.

[0024] Therefore, the method has the advantages of simpler operation, lower cost, less pollutant emission, etc., and is more suitable for large-scale synthesis of high-purity hydroxyplatinic acid. DETAILED DESCRIPTION

[0025] For ease of understanding, the present invention will be described in detail below through specific embodiments. It should be particularly noted that these descriptions are merely exemplary descriptions and do not constitute limitations on the scope of the present invention. Based on the discussion of this specification, many variations and changes of the present invention are obvious to those skilled in the art.

[0026] Example 1

[0027] 119.4 g crude hydroxyplatinic acid (sodium ion content 1300 ppm, chloride ion content 691 ppm) was mixed with 60.04 g ethanolamine in 1.5 L water, and the mixture changed from milky white to light yellow clear liquid after stirring. Acetic acid was gradually added dropwise to the solution until no more precipitation occurred, and the pH value was 5.2 at this time. The precipitate was collected by filtration, and the filter cake was washed twice with 1 L of pure water. After drying the filter cake, 114.5 g of purified hydroxyplatinic acid was obtained, with a yield of 96%.

[0028] The elemental analysis results are:

[0029] Theoretical value: platinum 65.21%, sodium 0ppm, chlorine 0ppm;

[0030] Detection values: platinum 64.84%, sodium 80ppm, chlorine 107ppm.

[0031] Example 2

[0032] 119.4 g crude hydroxyplatinic acid (sodium ion content 1300 ppm, chloride ion content 691 ppm) was mixed with 60.04 g ethanolamine in 1.5 L water, and the mixture changed from milky white to light yellow clear liquid after stirring. Acetic acid was gradually added dropwise to the solution until no more precipitation occurred, and the pH value was 5.2 at this time. The precipitate was collected by filtration, and the filter cake was washed 4 times with 1 L of pure water. After drying the filter cake, 111.2 g of purified hydroxyplatinic acid was obtained, with a yield of 93%.

[0033] The elemental analysis results are:

[0034] Theoretical value: platinum 65.21%, sodium 0ppm, chlorine 0ppm;

[0035] Detection values: platinum 64.77%, sodium 42ppm, chlorine 87ppm.

[0036] Example 3

[0037] 119.4 g crude hydroxyplatinic acid (sodium ion content 3000 ppm, chloride ion content 307 ppm) was mixed with 60.04 g ethanolamine in 1.5 L water, and the mixture changed from milky white to light yellow clear liquid after stirring. Acetic acid was gradually added dropwise to the solution until no more precipitation occurred, and the pH value was 5.2 at this time. The precipitate was collected by filtration, and the filter cake was washed twice with 1 L of pure water. After drying the filter cake, 114.7 g of purified hydroxyplatinic acid was obtained, with a yield of 96%.

[0038] The elemental analysis results are:

[0039] Theoretical value: platinum 65.21%, sodium 0ppm, chlorine 0ppm;

[0040] Detection values: platinum 64.87%, sodium 89ppm, chlorine 64ppm.

[0041] Example 4

[0042] 119.4 g crude hydroxyplatinic acid (sodium ion content 1300 ppm, chloride ion content 691 ppm) was mixed with 40.04 g ethanolamine in 1.0 L water, heated to 95 degrees Celsius, and stirred to change from a milky white mixed liquid to a light yellow clear liquid. Acetic acid was gradually added dropwise to the solution until no more precipitation occurred, and the pH value was 5.0 at this time. After returning to room temperature, the precipitate was collected by filtration, and the filter cake was washed twice with 1 L of pure water. After drying the filter cake, 117.2 g of purified hydroxyplatinic acid was obtained, with a yield of 98%.

[0043] The elemental analysis results are:

[0044] Theoretical value: platinum 65.21%, sodium 0ppm, chlorine 0ppm;

[0045] Detection values: platinum 65.03%, sodium 79ppm, chlorine 305ppm.

[0046] Example 5

[0047] 119.4 g crude hydroxyplatinic acid (sodium ion content 1300 ppm, chloride ion content 691 ppm) was mixed with 60.04 g ethanolamine in 1.5 L water, and the mixture changed from milky white to light yellow clear liquid after stirring. Dilute nitric acid was gradually added dropwise to the solution until the pH value was 5.8. The precipitate was collected by filtration, and the filter cake was washed twice with 1 L of pure water. After drying the filter cake, 108.6 g of purified hydroxyplatinic acid was obtained, with a yield of 91%.

[0048] The elemental analysis results are:

[0049] Theoretical value: platinum 65.21%, sodium 0ppm, chlorine 0ppm;

[0050] Detection values: platinum 64.96%, sodium 141ppm, chlorine 124ppm.

[0051] Example 6

[0052] 119.4 g crude hydroxyplatinic acid (potassium ion content 1400 ppm, chloride ion content 723 ppm) was mixed with 60.04 g ethanolamine in 1.5 L water, and the mixture changed from milky white to light yellow clear liquid after stirring. Acetic acid was gradually added dropwise to the solution until no more precipitation occurred, and the pH value was 5.3 at this time. The precipitate was collected by filtration, and the filter cake was washed twice with 1 L of pure water. After drying the filter cake, 114.4 g of purified hydroxyplatinic acid was obtained, with a yield of 96%.

[0053] The elemental analysis results are:

[0054] Theoretical value: platinum 65.21%, potassium 0ppm, chlorine 0ppm;

[0055] Detection values: platinum 64.81%, potassium 85ppm, chlorine 178ppm.

[0056] It can be seen from Examples 1-6 that the present method can reduce metal ions (sodium or potassium) and chloride ions to less than 100 ppm after washing 2-4 times in the purification stage mainly by adding ethanolamine. Therefore, the embodiments of the present invention have fewer washing times and lower impurity ion content than the methods disclosed in the prior art.

Claims

1. A method for preparing high-purity hydroxyplatinic acid, characterized in that: The following steps are involved: Step (1), mixing crude hydroxyplatinic acid solid with ethanolamine in a solution in a certain ratio to form a mixed solution; Step (2), heating the mixed solution to make the mixed solution become a uniform and transparent light yellow solution; Step (3), adding a certain amount of acid to the obtained light yellow solution to adjust the solution to acidity, thereby obtaining a light yellow hydroxyplatinic acid precipitate; Step (4), separating the product by filtration and washing to obtain pure hydroxyplatinic acid.

2. The method for preparing high-purity hydroxyplatinic acid according to claim 1, characterized in that: In step (1), the mass ratio of crude hydroxyplatinic acid solid to ethanolamine is between 1:0.1-10.

3. The method for preparing high-purity hydroxyplatinic acid according to claim 1, characterized in that: In step (1), the solvent used in the solution is water or a mixture of water and an organic solvent.

4. The method for preparing high-purity hydroxyplatinic acid according to claim 3, characterized in that: In step (1), the mass ratio of the crude hydroxyplatinic acid solid to the solvent used is between 1:3-20.

5. The method for preparing high-purity hydroxyplatinic acid according to claim 1, characterized in that: In step (2), the heating temperature is between 20-100°C.

6. The method for preparing high-purity hydroxyplatinic acid according to claim 1, characterized in that: In step (3), the acid includes an acid having no coordination ability or low coordination ability.

7. The method for preparing high-purity hydroxyplatinic acid according to claim 1, characterized in that: In step (3), the pH of the solution is controlled between 1 and 6.5 after the acid is added.

8. The method for preparing high-purity hydroxyplatinic acid according to any one of claims 1 to 7, characterized in that: In step (4), the washing process includes washing with water or a mixture of water and an organic solvent.

9. The method for preparing high-purity hydroxyplatinic acid according to any one of claims 1 to 7, characterized in that: In step (4), washing includes repeating washing 6 times.

10. The method for preparing high-purity hydroxyplatinic acid according to claim 6, characterized in that: The acid includes acetic acid or nitric acid.