A method for synthesizing platinum nitrate

Abstract

The application provides a synthesis method of platinum nitrate, comprising the following steps: step (A), uniformly mixing sponge platinum, an oxidizing agent and a flux, heating to complete melting, and obtaining a product after cooling; step (B), heating and dissolving the product obtained in step (A) with a sodium hydroxide solution, filtering and washing to obtain a sodium hexahydroxyplatinate solution; step (C), precipitating the sodium hexahydroxyplatinate solution obtained in step (B) with an acid reagent, filtering to obtain platinous hydroxide, sufficiently washing the platinous hydroxide until the Na content is qualified, and grinding into a powder after vacuum drying. The application has a reasonable structure, can effectively avoid the negative influence of nitrogen oxide pollution and chloride ion residue from the root, greatly improves the synthesis efficiency of the platinum nitrate product, effectively solves the colloid precipitation problem in the synthesis process of the platinum nitrate, and the direct yield of the platinum nitrate reaches more than 99%.

Description

TECHNICAL FIELD

[0001] The present application relates to the preparation of platinum nitrate, in particular, to a synthesis method of platinum nitrate. BACKGROUND

[0002] Platinum nitrate is an important compound for the preparation of other platinum-containing compounds, various platinum catalysts and material surface coatings, and has a very broad market application prospect. At present, there are few reports on the synthesis method of platinum nitrate.

[0003] In the prior art, Chinese invention patent (CN104310498B) discloses a preparation method of platinum nitrate. Sponge platinum is dissolved with aqua regia to obtain chloroplatinic acid by chasing nitration, and then reduced by oxalic acid, neutralized by alkali to obtain platinum hydroxide, and finally dissolved with concentrated nitric acid to obtain platinum nitrate. This method has the problems of long concentration and chasing nitration time and nitrogen oxide pollution hazards, and the yield of platinum hydroxide is not high, resulting in low direct yield of final platinum nitrate.

[0004] Chinese invention patent (CN110482619B) discloses a synthesis method of platinum nitrate solution. Chloroplatinic acid is prepared by dissolving with aqua regia, neutralizing with alkali, reducing with hydrazine hydrate, dissolving with hydrochloric acid and hydrogen peroxide, avoiding the chasing nitration process, and then obtaining platinum nitrate solution by subsequent alkali complexation, neutralization precipitation and nitric acid dissolution. This method uses hydrochloric acid and hydrogen peroxide to dissolve platinum twice, introduces a large amount of chloride ions, causes long time consumption of alkali complexation and high platinum content in neutralization tail liquid, resulting in low direct yield of final platinum nitrate.

[0005] It can be seen that the existing synthesis methods of platinum nitrate generally have problems such as nitrogen oxide pollution, chloride ion residue, long production cycle and low direct yield, which seriously restricts the development of the industry. In addition, in the process of dissolving hydroxyl platinum with nitric acid to synthesize platinum nitrate, there is a "polymerization" behavior of platinum complex monomers, about 8% of the platinum is precipitated in colloidal state, which greatly reduces the direct yield of platinum nitrate. Therefore, there is an urgent need for a synthesis method of platinum nitrate to solve the above problems. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application aims to provide a synthesis method of platinum nitrate to solve the problems raised in the background art.

[0007] In order to achieve the above-mentioned purpose, the present application provides a synthesis method of platinum nitrate, comprising the following steps:

[0008] Step (A) uniformly mixing sponge platinum, an oxidizing agent and a flux in a crucible, heating and reacting to complete melting, cooling to room temperature after reaction to obtain a product;

[0009] Step (B) dissolving the product obtained in step (A) with sodium hydroxide solution, filtering and washing after cooling to obtain a bright yellow sodium hexahydroxyplatinic acid solution;

[0010] Step (C) The sodium hexahydroxyplatinate solution obtained in step (B) is neutralized with an acid reagent and precipitated, and the light yellow hydroxyplatinate is obtained by filtration. The hydroxyplatinate is washed with a dilute acid reagent until the Na content is qualified, and then vacuum dried and ground into powder;

[0011] Step (D) The powdered hydroxyplatinate obtained in step (C) is slowly added to concentrated nitric acid, a dispersing agent is added, and the reaction is stirred until completely dissolved, to obtain a platinum nitrate solution.

[0012] Preferably, 1-5 grams of the oxidizing agent, 0.5-3 grams of the fluxing agent, 2-3 grams of the sodium hydroxide solution, 3-5 milliliters of the concentrated nitric acid, and 0.2-1 gram of the dispersing agent are added per gram of the sponge platinum.

[0013] Preferably, the oxidizing agent in step (A) includes one or more of sodium peroxide, potassium peroxide, barium peroxide, calcium peroxide, magnesium peroxide, and zinc peroxide; and the fluxing agent includes one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, and sodium acetate.

[0014] Preferably, the heating reaction melting temperature in step (A) is 650-750°C, and the melting time is 0.5-2 hours.

[0015] Preferably, the product in step (B) is dissolved with a 5-15% mass fraction sodium hydroxide solution, the dissolution temperature is 100-110°C, and the dissolution time is 30-50 minutes.

[0016] Preferably, the vacuum drying temperature of the hydroxyplatinate in step (C) is 50-80°C.

[0017] Preferably, the end point pH value of the acid neutralization and precipitation in step (C) is 4.5-4.9, and the acid reagent used in the neutralization and precipitation and the washing process is the same.

[0018] Preferably, the acid reagent includes one or more of sulfuric acid, nitric acid, phosphoric acid, acetic acid, butyric acid, citric acid, and oxalic acid, and the pH value of the dilute acid is 4.5-4.9.

[0019] Preferably, the dispersing agent is one or more of ammonium nitrate, ammonium sulfate, ammonium bisulfate, ammonium carbonate, ammonium bicarbonate, ammonium formate, and ammonium acetate.

[0020] Preferably, the dissolution temperature in step (D) is 45-70°C, the dissolution time is 1-5 hours, and the mass fraction of the concentrated nitric acid is 30-68%.

[0021] According to the synthesis method of the platinum nitrate, the negative effects of nitrogen oxide pollution and chloride ion residue are effectively solved from the root. Since no chloride ion is introduced, on the one hand, the hydroxyl ions do not need to replace the chloride ions in the platinum chloride complex in the alkaline complexing process, the conversion time of platinum is shortened, the preparation efficiency of the intermediate product sodium hexahydroxyplatinic acid solution is greatly improved, on the other hand, in the acid neutralization process, the platinum will not be left in the form of soluble chloride complex in the tail liquid, the platinum residue in the acid neutralization tail liquid is reduced, and at the same time, through the measures of vacuum drying, grinding and powdering, adding a dispersing agent and the like, the problem of colloid precipitation in the synthesis process of the platinum nitrate is effectively solved, so that the direct yield of the platinum nitrate is increased by 10% and reaches more than 99%. BRIEF DESCRIPTION OF DRAWINGS

[0022] Other features, objects, and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments, when read in conjunction with the accompanying drawings:

[0023] Figure 1 A flow chart of the synthesis method of the platinum nitrate according to an embodiment of the application. DETAILED DESCRIPTION

[0024] In order to make the technical means, creative features, purposes and effects achieved by the application easy to understand, the application will be further described below in conjunction with specific embodiments.

[0025] As shown in the drawings, Figure 1 The application provides a technical solution: a synthesis method of platinum nitrate, comprising the following steps:

[0026] Step (A) uniformly mixing sponge platinum, an oxidizing agent and a flux in a crucible, heating and reacting until complete melting, and cooling to room temperature to obtain a product;

[0027] Step (B) dissolving the product obtained in step (A) with a sodium hydroxide solution, filtering and washing after cooling to obtain a bright yellow sodium hexahydroxyplatinic acid solution;

[0028] Step (C) precipitating the sodium hexahydroxyplatinic acid solution obtained in step (B) with an acid reagent, filtering to obtain a light yellow hydroxyplatinic acid, washing the hydroxyplatinic acid with a dilute acid reagent until the Na content is less than 0.5%, and then grinding into a powder after vacuum drying;

[0029] Step (D) slowly adding the powdered hydroxyplatinic acid obtained in step (C) to concentrated nitric acid, adding a dispersing agent, and stirring until complete dissolution to obtain a platinum nitrate solution.

[0030] 1-5 grams of the oxidizing agent, 0.5-3 grams of the flux, 2-3 grams of the sodium hydroxide, 3-5 milliliters of the concentrated nitric acid and 0.2-1 gram of the dispersing agent are added to each gram of the sponge platinum.

[0031] The oxidizing agent in step (A) includes one or more of sodium peroxide, potassium peroxide, barium peroxide, calcium peroxide, magnesium peroxide and zinc peroxide; and the flux includes one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate and sodium acetate.

[0032] The heating reaction melting temperature in step (A) is 650-750°C, and the melting time is 0.5-2 hours.

[0033] The product in step (B) is dissolved with a sodium hydroxide solution having a mass fraction of 5-15%, the dissolving temperature is 100-110°C, and the dissolving time is 30-50 minutes.

[0034] The vacuum drying temperature of the hydroxyplatinic acid in step (C) is 50-80°C.

[0035] The end point pH value of the acid neutralization precipitation in step (C) is 4.5-4.9, and the acid reagent used in the neutralization precipitation and the washing process is the same.

[0036] The acid reagent includes one or more of sulfuric acid, nitric acid, phosphoric acid, acetic acid, butyric acid, citric acid and oxalic acid, and the pH value of the dilute acid is 4.5-4.9.

[0037] The dispersing agent is one or more of ammonium nitrate, ammonium sulfate, ammonium bisulfate, ammonium carbonate, ammonium bicarbonate, ammonium formate and ammonium acetate.

[0038] The dissolving temperature in step (D) is 45-70°C, the dissolving time is 1-5 hours, and the mass fraction of the concentrated nitric acid is 30-68%.

[0039] The following describes a specific embodiment according to a synthesis method of platinum nitrate according to the present application,

[0040] Embodiment 1

[0041] Step (A1) 10 grams of sponge platinum, 50 grams of potassium peroxide and 15 grams of sodium carbonate are placed in a crucible and uniformly mixed, heated and reacted at 650°C for 1 hour until completely melted, and cooled to room temperature after the reaction to obtain the product;

[0042] Step (B1) the product obtained in step (A1) is dissolved with a sodium hydroxide solution having a mass fraction of 8% at 103°C for 50 minutes, the amount of sodium hydroxide is 25 grams, the amount of sodium hydroxide here is the amount of sodium hydroxide in the sodium hydroxide solution, and after cooling, filtration and washing, a bright yellow sodium hexahydroxyplatinic acid solution is obtained;

[0043] Step (C1) The sodium hexahydroxyplatinate solution obtained in step (B1) was precipitated by neutralization with acetic acid, and the end point pH was 4.8. A yellowish hydroxyplatinate was obtained by filtration, and the hydroxyplatinate was washed with dilute acetic acid having a pH of 4.8 until the Na content was less than 0.5%, and then the hydroxyplatinate was ground into powder after vacuum drying at 50°C;

[0044] Step (D1) The powdered hydroxyplatinate obtained in step (C1) was slowly added to 45 ml of concentrated nitric acid having a mass fraction of 60%, and 5 g of ammonium acetate was added. The reaction was stirred at 60°C for 5 hours until complete dissolution, and a platinum nitrate solution was obtained.

[0045] Example 2

[0046] Step (A2) 10 g of sponge platinum, 10 g of sodium peroxide, and 25 g of sodium hydroxide were uniformly mixed in a crucible, and the mixture was heated at 750°C for 0.5 hours until complete melting. After the reaction was completed, the product was cooled to room temperature.

[0047] Step (B2) The product obtained in step (A2) was dissolved by heating at 109°C for 30 minutes using a sodium hydroxide solution having a mass fraction of 15%, and the amount of sodium hydroxide used was 22 g. Here, the amount of sodium hydroxide used refers to the amount of sodium hydroxide in the sodium hydroxide solution. After cooling, filtration and washing were performed, and a bright yellow sodium hexahydroxyplatinate solution was obtained.

[0048] Step (C2) The sodium hexahydroxyplatinate solution obtained in step (B2) was precipitated by neutralization with phosphoric acid, and the end point pH was 4.5. A yellowish hydroxyplatinate was obtained by filtration, and the hydroxyplatinate was washed with dilute phosphoric acid having a pH of 4.5 until the Na content was less than 0.5%, and then the hydroxyplatinate was ground into powder after vacuum drying at 70°C.

[0049] Step (D2) The powdered hydroxyplatinate obtained in step (C2) was slowly added to 35 ml of concentrated nitric acid having a mass fraction of 50%, and 8 g of ammonium nitrate was added. The reaction was stirred at 50°C for 2 hours until complete dissolution, and a platinum nitrate solution was obtained.

[0050] Example 3

[0051] Step (A3) 10 g of sponge platinum, 30 g of calcium peroxide, and 10 g of sodium acetate were uniformly mixed in a crucible, and the mixture was heated at 700°C for 2 hours until complete melting. After the reaction was completed, the product was cooled to room temperature.

[0052] Step (B3) The product obtained in step (A3) was dissolved by heating at 106°C for 40 minutes using a sodium hydroxide solution having a mass fraction of 12%, and the amount of sodium hydroxide used was 30 g. Here, the amount of sodium hydroxide used refers to the amount of sodium hydroxide in the sodium hydroxide solution. After cooling, filtration and washing were performed, and a bright yellow sodium hexahydroxyplatinate solution was obtained.

[0053] Step (C3) The sodium hexahydroxoplatinate solution obtained in step (B3) was precipitated by neutralization with nitric acid, and the end point pH was 4.9. A yellowish hydroxypalladic acid was obtained by filtration. The hydroxypalladic acid was washed with dilute nitric acid having a pH of 4.9 until the Na content was less than 0.5%, and then was dried at 80°C under vacuum and ground into powder;

[0054] Step (D3) The powdered hydroxypalladic acid obtained in step (C3) was slowly added to 40 mL of concentrated nitric acid having a mass fraction of 40%, and 10 g of ammonium formate was added. The reaction was stirred at 70°C for 1 hour until complete dissolution, and a platinum nitrate solution was obtained.

[0055] Example 4

[0056] Step (A4) 10 g of sponge platinum, 40 g of sodium peroxide, and 20 g of sodium hydroxide were uniformly mixed in a crucible, heated at 710°C for 1 hour until complete melting, and then cooled to room temperature to obtain a product;

[0057] Step (B4) The product obtained in step (A4) was dissolved at 105°C for 40 minutes with 30 g of a 10% sodium hydroxide solution. After cooling, filtration and washing were performed, and a bright yellow sodium hexahydroxoplatinate solution was obtained;

[0058] Step (C4) The sodium hexahydroxoplatinate solution obtained in step (B4) was precipitated by neutralization with acetic acid, and the end point pH was 4.8. A yellowish hydroxypalladic acid was obtained by filtration. The hydroxypalladic acid was washed with dilute acetic acid having a pH of 4.8 until the Na content was less than 0.5%, and then was dried at 50°C under vacuum and ground into powder;

[0059] Step (D4) The powdered hydroxypalladic acid obtained in step (C4) was slowly added to 30 mL of concentrated nitric acid having a mass fraction of 66%, and 5 g of ammonium acetate was added. The reaction was stirred at 50°C for 2 hours until complete dissolution, and a platinum nitrate solution was obtained.

[0060] Comparative Example 1

[0061] Step (A5) 10 g of sponge platinum was placed in a 150 mL beaker, and 50 mL of hydrochloric acid having a mass fraction of 36% and 10 mL of nitric acid having a mass fraction of 68% were added. The solution was heated on an electric stove until the sponge platinum was completely dissolved. Then, the volume of the solution was concentrated to 20 mL, 20 mL of hydrochloric acid having a mass fraction of 36% was added, and the volume of the solution was concentrated to 20 mL to perform nitrate chasing. This was repeated three times. After the nitrate chasing was completed, 20 mL of pure water was added, and the volume of the solution was concentrated to 20 mL to chase free hydrochloric acid. This was repeated three times. After the hydrochloric acid chasing was completed, the beaker was removed and cooled;

[0062] Step (B5) The solution obtained in step (A5) was added to a 12% by mass sodium hydroxide solution, and then heated at 103°C for 15 hours, the amount of sodium hydroxide used was 30 g, after cooling, filtration and washing, a bright yellow sodium hexahydroxyplatinic acid solution was obtained;

[0063] Step (C5) The sodium hexahydroxyplatinic acid solution obtained in step (B5) was precipitated by neutralization with acetic acid, the end point pH was 4.9, filtration gave a light yellow hydroxyplatinic acid, which was washed with dilute acetic acid having a pH of 4.9 until the Na content was less than 0.5%;

[0064] Step (D5) The hydroxyplatinic acid obtained in step (C5) was slowly added to 50 ml of 68% by mass concentrated nitric acid, and the reaction was stirred at 45°C for 6 hours, filtration gave a platinum nitrate solution and insoluble colloid.

[0065] According to the synthesis method of platinum nitrate of the present application, the platinum nitrate prepared in the above examples 1-4 and comparative example 1 was tested as follows: the yield was measured with reference to Table 1 below, wherein "-" means that it could not be weighed, and was detected after aqua regia dissolution, wherein the alkali dissolution residue was the product obtained by dissolving with a sodium hydroxide solution, the acid neutralization tail liquid was obtained by neutralization and precipitation, and the platinum nitrate solution and insoluble colloid were obtained by dissolving the hydroxyplatinic acid with concentrated nitric acid.

[0066] Table 1 Test results of the synthesis of platinum nitrate

[0067]

[0068]

[0069] According to Table 1, the new method for synthesizing platinum nitrate in the application adopts the way of high-temperature oxidation-alkali complexation to prepare sodium hexahydroxy platinate solution, the elemental platinum forms an oxidation layer of platinum dioxide on the surface under the action of high temperature and oxidizing agent, the oxidation layer can be melted by flux one by one and form a platinum salt soluble in alkali solution, and the melting product is cooled, and then sodium hydroxide solution is used for heating and dissolving to prepare sodium hexahydroxy platinate solution, which effectively solves the pollution hidden danger of nitrogen oxides from the root compared with aqua regia dissolution. Since no chloride ion is introduced, on the one hand, the hydroxyl ion does not need to replace the chloride ion in the platinum chloride complex in the alkali complexation process, which shortens the conversion time of platinum and greatly improves the preparation efficiency of the intermediate product sodium hexahydroxy platinate solution, on the other hand, in the acid neutralization process, platinum will not remain in the form of soluble chloride complex in the tail liquid, which reduces the platinum residual amount in the acid neutralization tail liquid. The colloid is an oligomer formed by nucleation of the hydroxyl complex of Pt(IV) through bridging -OH groups, and the colloid precipitation problem in the synthesis process of platinum nitrate is effectively solved by low-temperature vacuum drying, grinding and powdering and adding dispersing agent, on the one hand, the hydroxyplatinum is subjected to low-temperature vacuum drying, grinding and powdering, which can increase the contact area of hydroxyplatinum acid and nitric acid and weaken the formation of platinum oligomers to a certain extent, on the other hand, the coordination ability of Pt(IV) and NH3 is very strong, and the addition of ammonium dispersant can directly destroy the bridging -OH groups in the platinum oligomer, so that the platinum oligomer is dispersed into platinum hydroxyl complex monomer, so that it is completely dissolved in the nitric acid solution, and no insoluble colloid appears in Examples 1-4 of the application. Therefore, the application reduces the loss of platinum in the acid neutralization tail liquid and colloid, and according to Table 1, the direct yield of platinum nitrate in Comparative Examples 1-4 of the application is more than 99%, while the direct yield of platinum nitrate in Comparative Example 1 of the prior art is 89%, therefore, the new method for synthesizing platinum nitrate in the application can increase the direct yield of platinum nitrate by 10% to more than 99%.

[0070] The basic principles, main features and advantages of the application are shown and described above. It should be understood by those skilled in the art that the application is not limited by the above examples, the above examples and descriptions in the specification are only to illustrate the principles of the application, and various changes and improvements can be made without departing from the spirit and scope of the application, and these changes and improvements all fall within the scope of the claimed application. The scope of protection of the application is defined by the appended claims and their equivalents.

Claims

1. A method for synthesizing platinum nitrate, characterized in that, Includes the following steps: Step (A) Place the sponge platinum, oxidant and flux in a crucible and mix them evenly. Heat the mixture until it is completely melted. After the reaction is complete, cool it to room temperature to obtain the product. Step (B) The product obtained in step (A) is dissolved by heating with sodium hydroxide solution, cooled, filtered and washed to obtain a bright yellow sodium hexahydroxyplatinate solution; Step (C) The sodium hexahydroxyplatinate solution obtained in step (B) is neutralized and precipitated with an acid reagent, filtered to obtain pale yellow hydroxyplatinic acid, which is then thoroughly washed with dilute acid reagent until the Na content is qualified, and then vacuum dried and ground into powder. Step (D) Slowly add the powdered hydroxyplatinic acid obtained in step (C) into concentrated nitric acid, add a dispersant, and stir until completely dissolved to obtain a platinum nitrate solution; Relative to 1 gram of platinum sponge, the amount of the oxidant is 1-5 grams, the amount of the flux is 0.5-3 grams, the amount of sodium hydroxide in the sodium hydroxide solution is 2-3 grams, the amount of concentrated nitric acid is 3-5 milliliters, and the amount of the dispersant is 0.2-1 gram. The oxidizing agent in step (A) includes one or more of sodium peroxide, potassium peroxide, barium peroxide, calcium peroxide, magnesium peroxide, and zinc peroxide; the flux includes one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, and sodium acetate. The dispersant is one or more selected from ammonium nitrate, ammonium sulfate, ammonium bisulfate, ammonium carbonate, ammonium bicarbonate, ammonium formate, and ammonium acetate. The dissolution temperature in step (D) is 45-70°C, and the mass fraction of the concentrated nitric acid is 30-68%.

2. The method for synthesizing platinum nitrate according to claim 1, characterized in that, The heating reaction melting temperature in step (A) is 650-750℃, and the melting time is 0.5-2 hours.

3. The method for synthesizing platinum nitrate according to claim 1, characterized in that, The product in step (B) is dissolved in a sodium hydroxide solution with a mass fraction of 5-15% at a dissolution temperature of 100-110℃ for 30-50 minutes.

4. The method for synthesizing platinum nitrate according to claim 1, characterized in that, The vacuum drying temperature of hydroxyplatinic acid in step (C) is 50-80℃.

5. The method for synthesizing platinum nitrate according to claim 1, characterized in that, The endpoint pH value of acid neutralization precipitation in step (C) is 4.5-4.9, and the acid reagent used in the neutralization precipitation and washing processes is the same.

6. The method for synthesizing platinum nitrate according to claim 5, characterized in that, The acid reagent includes one or more of sulfuric acid, nitric acid, phosphoric acid, acetic acid, butyric acid, citric acid, and oxalic acid, and the pH value of the dilute acid is 4.5-4.

9.

7. The method for synthesizing platinum nitrate according to claim 1, characterized in that, The dissolution time in step (D) is 1-5 hours.

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