Potassium tetranitroplatinate as well as preparation method and application thereof

Abstract

The invention relates to the technical field of precious metal compound preparation, in particular to potassium tetranitroplatinate and a preparation method and application thereof, and the preparation method comprises the following steps: adding a potassium chloride solution into a chloroplatinic acid solution to obtain a yellow potassium chloroplatinate solid; adding water into the potassium chloroplatinate solid for slurrying, and dropwise adding a saturated oxalic acid solution to obtain a potassium chloroplatinite solution; the method comprises the following steps: introducing nitric oxide into a potassium chloroplatinite solution for reaction, and cooling and crystallizing after the solution becomes yellow green from red to obtain a white needle-like crystal which is a potassium tetranitroplatinate crude product; and recrystallizing the potassium tetranitroplatinate crude product to obtain the high-purity potassium tetranitroplatinate crystal. By introducing the nitric oxide gas, the hydrolysis of the potassium tetranitroplatinate can be effectively inhibited, so that hydrolysis products of the potassium tetranitroplatinate are reduced, the purity and the yield of the obtained product are greatly improved, and the problem of inclusion of insoluble substances caused by hydrolysis of the potassium tetranitroplatinate in the reaction process is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of precious metal compound preparation, and in particular to potassium tetranitrosoplatinate, a preparation method thereof and an application thereof. Background Art

[0002] The platinum coating is bright silver-white. Due to its bright color, good corrosion resistance, extremely high hardness, low contact resistance and good conductivity, it is widely used in electronic electroplating fields such as electrical contact materials and sensitive resistors.

[0003] Potassium tetranitroplatinate, also known as potassium tetranitrosoplatinate and potassium tetranitroplatinate, has a molecular formula of K2[Pt(NO2)4] and a molecular weight of 457.32. It is a white, needle-shaped crystal that is readily soluble in water, dissolving 27 times as much water at 15°C. It is insoluble in alcohol and ether. Its aqueous solution is neutral and completely loses its water of crystallization after drying in air for 24 hours. Because it contains no chloride ions and its aqueous solution is very stable, with its structure remaining unchanged even when boiled, it is commonly used in the electroplating industry. Coatings prepared with it have low porosity, high brightness, and excellent coating quality.

[0004] The traditional preparation method of potassium tetranitrosoplatinate is to dissolve metallic platinum in aqua regia to prepare chloroplatinic acid, and then react with potassium chloride to generate a yellow precipitate of potassium chloroplatinate. The potassium chloroplatinate precipitate is dissolved in water to a paste and then heated in an oil bath. Potassium chloroplatinate is stirred into a slurry with water, potassium nitrite is dissolved in hot water and added to potassium chloroplatinate, and a small amount of insoluble matter is filtered out to obtain a potassium tetranitrosoplatinate solution. This method uses potassium nitrite to react, and the potassium ion particle size is large. The introduction of excess potassium ions will be coated in the product and difficult to remove during recrystallization and filtration and washing. The obtained product has a high content of impurity ions, and the product obtained has insoluble matter. The purity of potassium tetranitrosoplatinate is substandard, and the chloride ion content is high, which greatly reduces the internal stress, compactness and corrosion resistance of the coating. At the same time, in the traditional synthesis method, the synthesis process of potassium tetranitrosoplatinate contains four hydrolysis products in the aqueous solution, which can lead to a large number of by-products.

[0005] Previous platinum electroplating practices have shown that impurity ions other than alkali and alkaline earth metals significantly impact microcracks and surface pinholes in platinum coatings. High chloride ion content can lead to high stress and poor density in the resulting coating. Chloride ion levels at the ppm level significantly impact the corrosion resistance of the deposited platinum coating. Summary of the Invention

[0006] In response to the problems of low purity and high content of chloride ions and other impurity metal ions in the above-mentioned prior art, the present invention provides potassium tetranitrosoplatinate and a preparation method and application thereof.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] A method for preparing potassium tetranitrosoplatinate comprises the following steps:

[0009] S1: Add potassium chloride solution to chloroplatinic acid solution, stir, and filter to obtain yellow potassium chloroplatinate solid;

[0010] S2: Slurrying potassium chloroplatinate solid with water, adding saturated oxalic acid solution dropwise, and stopping the addition of saturated oxalic acid solution when the solution changes from orange-red to bright red to obtain potassium chloroplatinite solution;

[0011] S3: Add nitric oxide to the potassium chloroplatinite solution for reaction. When the solution changes from red to yellow-green, stop adding nitric oxide, cool and crystallize, filter and wash to obtain white needle-like crystals, which are crude potassium tetranitrosoplatinate.

[0012] S4: Dissolve the crude potassium tetranitrosoplatinate in hot water, then cool it down for recrystallization, filter, wash, and dry it to obtain high-purity potassium tetranitrosoplatinate crystals.

[0013] Furthermore, in S1, the reaction temperature is 50-100° C., the pH value of the reaction solution is 5-6; the platinum content in the chloroplatinic acid solution is 15-22%, and the pH value is 0.5; the concentration of the potassium chloride solution is 2-3 mol / L, and the molar ratio of potassium chloride to platinum is 2-3.

[0014] Furthermore, in S2, the reaction temperature is 70-90°C, the pH value of the solution after the reaction is 9-10; and the pH value of the saturated oxalic acid solution is 1-2.

[0015] Furthermore, in S3, the reaction temperature is 90-100°C; the temperature of the cooling crystallization is 5-10°C; and washing is performed with 5-10°C water and ethanol solution.

[0016] Furthermore, in S4, the hot water temperature is 80-95°C, the drying temperature is 50-90°C, and the drying time is 5-10 hours.

[0017] The present invention also includes the following technical solutions:

[0018] Disclosed is potassium tetranitrosoplatinate prepared by a preparation method of potassium tetranitrosoplatinate.

[0019] Furthermore, the total content of other metal impurities in the potassium tetranitrosoplatinate is less than 0.1%, and the chloride ion content is less than 0.01 ppm.

[0020] The present invention also includes the following technical solutions:

[0021] An application of potassium tetranitrosoplatinate in electroplating.

[0022] The reaction mechanism of the present invention is as follows:

[0023] H2PtCl6+KCl=K2PtCl6↓+HCl

[0024] H2PtCl6+H2C2O4=K2PtCl4+2HCl+2CO2↑

[0025] K2PtCl4+4NO+2H2O=K2[Pt(NO2)4]+4HCl

[0026] The hydrolysis reaction equation of potassium tetranitrosoplatinate is as follows

[0027]

[0028] The introduction of nitric oxide gas can effectively inhibit the hydrolysis of potassium tetranitrosoplatinate, thereby reducing the hydrolysis products of potassium tetranitrosoplatinate.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention provides potassium tetranitrosoplatinate and its preparation method and application. Compared with the traditional method, the present invention reduces the impurity ion content and chloride ion content by recrystallizing the crude product and filtering and washing. No chloride ions or other metal impurity ions are introduced into the reaction system during the synthesis process, effectively reducing the impurity content and chloride ion content. By introducing nitric oxide gas, the hydrolysis of potassium tetranitrosoplatinate is effectively inhibited, so that the hydrolysis products of potassium tetranitrosoplatinate are reduced, the purity and yield of the obtained product are greatly improved, and the problem of insoluble inclusion caused by the hydrolysis of potassium tetranitrosoplatinate during the reaction process is solved. The potassium tetranitrosoplatinate prepared by the present invention is high in purity for electroplating and does not introduce impurity metal ions. When used to prepare a coating, it will not affect the properties of the electroplating solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The embodiments of the present invention are further described below with reference to the accompanying drawings, in which:

[0032] Figure 1 The process flow chart of the preparation method of potassium tetranitrosoplatinate is shown. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] Example 1

[0035] A method for preparing potassium tetranitrosoplatinate comprises the following steps:

[0036] S1: Add chloroplatinic acid solution containing 1 mol of platinum into a 5 L three-necked flask, stir and mix with 2 mol / L potassium chloride aqueous solution, the molar ratio of potassium chloride to platinum is 2, heat to 50°C, adjust the pH to 5, and produce yellow granular precipitate of potassium chloroplatinate, which is filtered to obtain yellow potassium chloroplatinate solid;

[0037] S2: The potassium chloroplatinate solid obtained in S1 is slurried with water, heated to 70°C, and a saturated oxalic acid solution is added dropwise. When the solution changes from orange-red to bright red, the addition of the saturated oxalic acid solution is stopped, and the pH of the solution is adjusted to 10 to obtain a potassium chloroplatinite solution;

[0038] S3: Heat the potassium chloroplatinite solution obtained in S2 to 90°C, introduce nitric oxide into the solution for reaction, and continue bubbling. When the solution changes from red to yellow-green, stop introducing nitric oxide, cool to 10°C for crystallization, filter, and wash with 500ml each of 10°C cold pure water and ethanol solution to obtain white needle-like crystals. The obtained white needle-like crystals are crude potassium tetranitrosoplatinate.

[0039] S4: Dissolve the crude potassium tetranitrosoplatinate in 80°C hot water, then cool to 10°C for recrystallization, filter and wash, and dry at 50°C for 10 hours to obtain high-purity potassium tetranitrosoplatinate crystals.

[0040] Example 2

[0041] A method for preparing potassium tetranitrosoplatinate comprises the following steps:

[0042] S1: Add chloroplatinic acid solution containing 1 mol of platinum into a 5 L three-necked flask, stir and mix with 3 mol / L potassium chloride aqueous solution, the molar ratio of potassium chloride to platinum is 3, heat to 100°C, adjust the pH to 6, and produce yellow granular precipitate of potassium chloroplatinate, which is filtered to obtain yellow potassium chloroplatinate solid;

[0043] S2: The potassium chloroplatinate solid obtained in S1 is slurried with water, heated to 90°C, and a saturated oxalic acid solution is added dropwise. When the solution changes from orange-red to bright red, the addition of the saturated oxalic acid solution is stopped, and the pH of the solution is adjusted to 9 to obtain a potassium chloroplatinite solution;

[0044] S3: Heat the potassium chloroplatinite solution obtained in S2 to 100°C, introduce nitric oxide into the solution for reaction, and continue bubbling. When the solution changes from red to yellow-green, stop introducing nitric oxide, cool to 5°C for crystallization, filter, and wash with 500ml each of 5°C cold pure water and ethanol solution to obtain white needle-like crystals. The obtained white needle-like crystals are crude potassium tetranitrosoplatinate.

[0045] S4: Dissolve the crude potassium tetranitrosoplatinate in 95°C hot water, then cool to 5°C for recrystallization, filter and wash, and dry at 90°C for 5 hours to obtain high-purity potassium tetranitrosoplatinate crystals.

[0046] Example 3

[0047] A method for preparing potassium tetranitrosoplatinate comprises the following steps:

[0048] S1: Add chloroplatinic acid solution containing 1 mol of platinum into a 5 L three-necked flask, stir and mix with 3 mol / L potassium chloride aqueous solution, the molar ratio of potassium chloride to platinum is 2.5, heat to 75°C, adjust the pH to 5.5, and produce yellow granular precipitate of potassium chloroplatinate, which is filtered to obtain yellow potassium chloroplatinate solid;

[0049] S2: The potassium chloroplatinate solid obtained in S1 is slurried with water, heated to 85°C, and a saturated oxalic acid solution is added dropwise. When the solution changes from orange-red to bright red, the addition of the saturated oxalic acid solution is stopped, and the pH of the solution is adjusted to 9 to obtain a potassium chloroplatinite solution;

[0050] S3: Heat the potassium chloroplatinite solution obtained in S2 to 95°C, introduce nitric oxide into the solution for reaction, and continue bubbling. When the solution changes from red to yellow-green, stop introducing nitric oxide, cool to 8°C for crystallization, filter, and wash with 500ml each of 5°C cold pure water and ethanol solution to obtain white needle-like crystals. The obtained white needle-like crystals are crude potassium tetranitrosoplatinate.

[0051] S4: Dissolve the crude potassium tetranitrosoplatinate in 85°C hot water, then cool to 5°C for recrystallization, filter and wash, and dry at 70°C for 8 hours to obtain high-purity potassium tetranitrosoplatinate crystals.

[0052] Comparative Example 1

[0053] A method for preparing potassium tetranitrosoplatinate comprises the following steps:

[0054] S1: Add chloroplatinic acid solution containing 1 mol of platinum into a 5 L three-necked flask, stir and mix with 2 mol / L potassium chloride aqueous solution, the molar ratio of potassium chloride to platinum is 2, heat to 50°C, adjust the pH to 5, and produce yellow granular precipitate of potassium chloroplatinate, which is filtered to obtain yellow potassium chloroplatinate solid;

[0055] S2: The potassium chloroplatinate solid obtained in S1 is slurried with water, heated to 70°C, and potassium nitrite solution is added. The insoluble matter is filtered to obtain a potassium tetranitrosoplatinate solution;

[0056] S3: Cool the potassium tetranitrosoplatinate solution obtained in S2 to 10°C for crystallization, filter, and add 500ml each of 10°C cold pure water and ethanol solution to wash to obtain white needle-like crystals. The obtained white needle-like crystals are crude potassium tetranitrosoplatinate;

[0057] S4: Dissolve the crude potassium tetranitrosoplatinate in 80°C hot water, then cool to 10°C for recrystallization, filter and wash, and dry at 50°C for 10 hours to obtain high-purity potassium tetranitrosoplatinate crystals.

[0058] The yields and analytical results of the products obtained in the above examples and comparative examples are shown in Table 1.

[0059] Table 1 Product yield and test analysis results

[0060] Yield (%) Platinum content (%) Potassium content (%) Chlorine content (ppm) Example 1 89.2 42.14 17.12 <0.01ppm Example 2 89.5 42.19 17.10 <0.01ppm Example 3 89.1 42.45 17.06 <0.01ppm Comparative Example 1 75.2 40.25 25.64 0.05ppm

[0061] The present invention provides potassium tetranitrosoplatinate and its preparation method and application. Compared with the traditional method, the present invention reduces the impurity ion content and chloride ion content by recrystallizing the crude product and filtering and washing. No chloride ions or other metal impurity ions are introduced into the reaction system during the synthesis process, effectively reducing the impurity content and chloride ion content. By introducing nitric oxide gas, the hydrolysis of potassium tetranitrosoplatinate is effectively inhibited, so that the hydrolysis products of potassium tetranitrosoplatinate are reduced, the purity and yield of the obtained product are greatly improved, and the problem of insoluble inclusion caused by the hydrolysis of potassium tetranitrosoplatinate during the reaction process is solved. The potassium tetranitrosoplatinate prepared by the present invention is high in purity for electroplating and does not introduce impurity metal ions. When used to prepare a coating, it will not affect the properties of the electroplating solution.

[0062] Some exemplary embodiments of the present invention are described above. It will be understood that the above embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention. The features in these embodiments can be recombined in an appropriate manner, and the solutions obtained thereby are still within the scope of protection claimed by the present invention. Based on the above embodiments, all other embodiments obtained by those skilled in the art without making creative work, that is, all modifications, equivalent substitutions and improvements made within the spirit and principles of this application, fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing potassium tetranitrosoplatinate, characterized in that: The following steps are involved: S1: Add potassium chloride solution to chloroplatinic acid solution, stir, and filter to obtain yellow potassium chloroplatinate solid; S2: Slurrying potassium chloroplatinate solid with water, adding saturated oxalic acid solution dropwise, and stopping the addition of saturated oxalic acid solution when the solution changes from orange-red to bright red to obtain potassium chloroplatinite solution; S3: Add nitric oxide to the potassium chloroplatinite solution for reaction. When the solution changes from red to yellow-green, stop adding nitric oxide, cool and crystallize, filter and wash to obtain white needle-like crystals, which are crude potassium tetranitrosoplatinate. S4: Dissolve the crude potassium tetranitrosoplatinate in hot water, then cool it down for recrystallization, filter, wash, and dry it to obtain high-purity potassium tetranitrosoplatinate crystals.

2. The method for preparing potassium tetranitrosoplatinate according to claim 1, wherein: In S1, the reaction temperature is 50-100° C., the pH value of the reaction solution is 5-6; the platinum content in the chloroplatinic acid solution is 15-22%, and the pH value is 0.5; the concentration of the potassium chloride solution is 2-3 mol / L, and the molar ratio of potassium chloride to platinum is 2-3.

3. The method for preparing potassium tetranitrosoplatinate according to claim 2, wherein: In S2, the reaction temperature is 70-90° C., the pH value of the solution after the reaction is 9-10; and the pH value of the saturated oxalic acid solution is 1-2.

4. The method for preparing potassium tetranitrosoplatinate according to claim 1, wherein: In S3, the reaction temperature is 90-100°C; the temperature of the cooling crystallization is 5-10°C; and washing is performed with water and ethanol solution at 5-10°C.

5. The method for preparing potassium tetranitrosoplatinate according to claim 1, wherein: In S4, the hot water temperature is 80-95°C, the drying temperature is 50-90°C, and the drying time is 5-10 hours.

6. Potassium tetranitrosoplatinate prepared by the method for preparing potassium tetranitrosoplatinate according to any one of claims 1 to 5.

7. The potassium tetranitrosoplatinate according to claim 6, characterized in that The total content of other metal impurities in the potassium tetranitrosoplatinate is less than 0.1%, and the chloride ion content is less than 0.01 ppm.

8. Use of the potassium tetranitrosoplatinate according to claims 6-7 in electroplating.

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