Preparation Method and Application of Platinum Oxide Nanopowder

Abstract

The present invention provides a method for preparing platinum oxide nanopowder and its application. In the present invention, an inorganic compound is used instead of a polymer surfactant as a stabilizer for nanoparticles. By adding a precursor solution containing sulfite to an aqueous solution of a Pt precursor, the strong coordination effect of sulfite is used to complex with Pt to obtain [Pt(SO3)3] 2‑ complex. This complex reacts with hydrogen peroxide to obtain platinum oxide nanopowder. The method of the present invention avoids the adsorption and poisoning of organic impurities on the surface of the powder, and the catalyst has high activity. In addition, the reaction temperature of the present invention is relatively low and the steps are simple, which can solve the problems of complex preparation process, harsh conditions and difficult batch preparation in the existing preparation of platinum oxide nanopowder.

Description

Technical Field

[0001] The present invention belongs to the field of catalytic technology, and particularly relates to a preparation method and application of platinum oxide nanopowder. Background Art

[0002] Nano platinum oxide is a highly active hydrogenation catalyst and can be used in the hydrogenation or hydrogenolysis reactions of olefins, alkynes, aromatic hydrocarbons, hydroxyl groups, aldehyde groups, imino groups, aromatic nitro groups, and benzene rings. Platinum oxide catalysts have the advantages of excellent catalytic performance, high activity, high selectivity, long service life, and convenient recovery, and play an important role in hydrogenation catalytic reactions in organic synthesis. In 1922, Adams et al. prepared platinum oxide nano-catalysts by the molten decomposition reaction of chloroplatinic acid and sodium nitrate at high temperature (reaction temperature ~ 450 °C), so nano platinum oxide catalysts are often referred to as Adams catalysts (Platinum Metals Rev., 1962, 6, 150). To obtain highly active platinum oxide catalysts with smaller particle sizes, Reetz et al. used betaine or quaternary ammonium salts with long carbon chains as surfactants and protective agents, and prepared platinum oxide catalysts by hydrolyzing platinum tetrachloride (PtCl4) or chloroplatinic acid solution in an alkaline solution at 50 °C for 7 days. The platinum oxide nano-catalysts prepared by this method can also be deposited on an alumina support to form a supported catalyst (J. Am. Chem. Soc. 1999, 121, 34, 7933). In 2004, Chen Yixian et al. used polyvinylpyrrolidone (PVP) as a stabilizer, boiled an aqueous solution of platinum tetrachloride under alkaline conditions, and then added acetic acid and reacted for a period of time to obtain platinum oxide colloid, and the particle size of the catalyst was about 51.7 nm (CN103265085A). CN108821352A discloses a preparation method of nano platinum oxide powder, which uses the framework structure of crown ether to stabilize platinum hydroxide colloid, and at the same time uses ultrasound to convert platinum hydroxide into platinum oxide and passivates the surface of platinum oxide, alleviating the agglomeration phenomenon of nano platinum oxide.

[0003] At present, the preparation process of existing platinum oxide nano-catalysts is relatively complex, and the reaction temperature is relatively high or the reaction time is relatively long, which is difficult to scale up and the preparation cost is relatively high; in addition, the polymer surfactants used in the preparation process are easily adsorbed on the surface of platinum oxide catalysts, affecting their catalytic activity. Summary of the Invention

[0004] Aiming at the problems in the prior art, the present invention provides a platinum oxide nano-catalyst and a preparation method. The present invention uses inorganic compounds instead of polymer surfactants as stabilizers for nanoparticles, avoiding the adsorption poisoning of organic impurities on the surface of the catalyst, and the catalyst has high activity; in addition, the reaction temperature of the present invention is relatively low and the steps are simple, which can solve the problems of complex preparation process, harsh conditions, and difficult batch preparation of existing platinum oxide nano-catalysts.

[0005] To achieve the above technical objectives, the technical solution of the present invention is as follows:

[0006] A method for preparing platinum oxide nanoparticles, comprising the following steps:

[0007] Step 1. Add an aqueous solution containing sulfite ions to an aqueous solution of a Pt precursor, and perform a complexation reaction to obtain [Pt(SO3)3] 2- complex;

[0008] Step 2. Add an alkaline aqueous solution to the reaction system in Step 1 to adjust the pH value, so that the complex precipitates in the form of a white precipitate;

[0009] Step 3. Wash the white precipitate precipitated in Step 2 and react it with hydrogen peroxide. After the reaction, centrifuge, wash, and dry to obtain platinum oxide nanoparticles.

[0010] Preferably, the above preparation method specifically comprises the following steps:

[0011] Step 1. Add a water-soluble Pt precursor to deionized water and ultrasonically dissolve it until completely dissolved to prepare an aqueous solution of the Pt precursor;

[0012] Step 2. Slowly dropwise add an aqueous solution containing sulfite ions to the aqueous solution of the Pt precursor while stirring. Stop dropping when the solution changes from orange-red to light yellow;

[0013] Step 3. Slowly add an alkaline aqueous solution to the reaction system in Step 2 to adjust the pH of the reaction system to 8-12. The reaction system gradually changes from light yellow to a colorless solution;

[0014] Step 4. Keep the pH value of the reaction system unchanged, and continue to dropwise add an aqueous solution containing sulfite ions to the colorless solution in Step 3 under stirring conditions. A large amount of white precipitate will form in the reaction system. Stop dropping when the white precipitate no longer continues to precipitate. After dropping, continue to react for 1-2 hours to ensure complete precipitation;

[0015] Step 5. Wash, filter, and dry the white precipitate generated in Step 4 with a large amount of deionized water to obtain a white platinum sulfite powder;

[0016] Step 6. Under stirring conditions, dissolve the white platinum sulfite powder in an aqueous solution, adjust the pH of the solution to 1-5, add an aqueous hydrogen peroxide solution, heat up and react for 2-3 hours, then cool down, and continue to add an acidic aqueous solution to promote the precipitation of platinum oxide nanoparticles;

[0017] Step 7. Centrifuge the reaction solution in Step 6 and wash it with a large amount of deionized water. After solid-liquid separation, dry it to obtain platinum oxide nanoparticles.

[0018] Preferably, the Pt precursor in step 1 is one or more of chloroplatinic acid, sodium chloroplatinate, potassium chloroplatinate, potassium chloroplatinate, sodium chloroplatinate, and platinum tetrachloride, and the Pt concentration in the aqueous solution of the Pt precursor is 10 - 50 g / L.

[0019] Preferably, the dropping rate in step 2 is 2 - 6 mL / min, the stirring speed is 200 - 1000 r / min, the aqueous solution containing sulfite ions is one or more of sulfurous acid, sodium sulfite, sodium bisulfite, potassium sulfite, and potassium bisulfite aqueous solutions, and the concentration of sulfite ions in the aqueous solution is 50 - 100 g / L; when the solution turns light yellow, the pH of the reaction system is 4 - 5.

[0020] Preferably, the dropping rate of the alkaline aqueous solution in step 3 is 2 - 6 mL / min, the stirring speed is 200 - 1000 r / min, and the alkaline aqueous solution is one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, or ammonia water solution.

[0021] Preferably, the pH of the reaction system in step 4 is 7.5 - 11, the stirring speed is 200 - 1000 rpm, and the reaction temperature is 0 - 30 °C.

[0022] Preferably, the dilute acid solution in step 6 is one or more of dilute sulfuric acid, dilute hydrochloric acid, and acetic acid aqueous solutions, with a concentration of 0.05 - 0.5 mol / L, and the pH of the reaction system is 2 - 4; the molar ratio of the amount of H2O2 added in step 6 to the platinous sulfite salt is 1:1 - 5:1; the reaction temperature is 60 - 90 °C.

[0023] Preferably, the solid-liquid separation method in step 7 is centrifugation or filtration; the drying temperature is 30 - 60 °C.

[0024] The particle size of the platinum oxide nanopowder prepared by the above method of the present invention is 1 - 4 nm.

[0025] The platinum oxide nanopowder prepared by the above method of the present invention can be used as a catalyst or a catalyst active component for hydrogenation reactions.

[0026] Preferably, the platinum oxide nanoparticles prepared by the present invention are supported on an Al2O3 support and used for the reductive amination reaction of n-propylamine and benzaldehyde with methanol as a solvent at room temperature and atmospheric pressure.

[0027] The reason for using a water-soluble Pt precursor in step 1 is that the water-soluble Pt precursor is easy to prepare and relatively inexpensive, and the aqueous phase synthesis is conducive to subsequent batch amplification, has little environmental pollution, and low preparation cost;

[0028] In Step 2, the sulfite precursor solution is slowly added to the aqueous solution of the Pt precursor. By utilizing the strong coordination of sulfite ions, they are complexed with Pt to obtain [Pt(SO3)3]. 2- The complex, SO3 2- is an inorganic compound stabilizer, which can protect the subsequently formed platinum oxide nanoparticles and prevent agglomeration. The purpose of slowly adding sulfite is to control the amount of sulfite ions added, because sulfite ions have a certain reducing property. If added too quickly, it is easy to cause direct reduction of the Pt precursor and prevent the formation of [Pt(SO3)3]. 2- complex;

[0029] In Step 3, the alkaline aqueous solution is slowly added to adjust the pH value of the reaction system to weakly alkaline, because [Pt(SO3)3]. 2+ complex exists in the form of ions in both strong acid and strong alkaline solutions. Only when the pH is weakly alkaline will it precipitate from the solution in the form of a white precipitate;

[0030] In Step 4, the continued addition of the sulfite solution is to ensure complete precipitation and guarantee that 100% of the Pt species in the solution precipitate from the solution and are all converted into platinum sulfite salt;

[0031] In Step 5, a large amount of deionized water is used for washing to ensure that chloride ions are removed completely and to prevent the catalyst from being poisoned by chloride ions;

[0032] In Step 6, H2O2 is used as the oxidant because after the reaction of H2O2, the product is water and it will not bring pollution to the reaction system; after the reaction, dilute acid aqueous solution is added to destroy the stability of the platinum oxide colloid and obtain platinum oxide nanocatalyst by subsequent solid-liquid separation;

[0033] In Step 7, the drying temperature is maintained at 30 - 60 °C to avoid the agglomeration of platinum oxide nanoparticles caused by high-temperature drying.

[0034] From the above description, it can be seen that the present invention has the following advantages:

[0035] 1. In the present invention, inorganic compound sulfite ions are used instead of polymer surfactants as the stabilizer of nanoparticles, avoiding the adsorption poisoning of organic impurities on the surface of platinum oxide powder, and the catalyst has high activity;

[0036] 2. In the present invention, platinum oxide nanopowder with small size and good dispersibility can be prepared in an aqueous solution without adding a protective agent. The operation is simple, the reaction conditions are mild, the environment is friendly, the production cost is low, and it is easy to scale up the synthesis. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is the XRD pattern of the platinum oxide nanoparticles prepared in Comparative Example 1 of the present invention.

[0038] Figure 2 This is the XRD pattern of the platinum oxide nanoparticles prepared in Example 1 of the present invention. Detailed implementation manners

[0039] The present invention will be specifically described below in conjunction with examples. Unless otherwise specified, the raw materials used in the following examples and comparative examples are all commercially available conventional raw materials.

[0040] Comparative Example 1: Preparation of platinum oxide nanopowder (without using sulfite as a complexing stabilizer)

[0041] At room temperature, 1 g of chloroplatinic acid was ultrasonically dispersed and dissolved in 10 mL of deionized water. An aqueous sodium hydroxide alkaline solution with a concentration of 50 g / L was added dropwise at a rate of 2 mL / min. The addition was stopped when the pH of the reaction system rose to 13. After continuing to stand and react for five days, yellow platinum hydroxide precipitate was deposited at the bottom of the container. After centrifugal separation and drying, a solid powder was obtained. After oxidation treatment in an air atmosphere at 300 °C for 1 hour, platinum oxide powder was obtained. It was found by XRD characterization and TEM observation that the prepared platinum oxide particles were large in size and seriously agglomerated, and heat treatment in air would cause partial thermal decomposition of platinum oxide into reduced metal Pt and oxygen, resulting in low catalytic performance in subsequent activity evaluation.

[0042] Comparative Example 2: Preparation of platinum oxide nanopowder (using PVP as a polymer stabilizer)

[0043] At room temperature, 1 g of chloroplatinic acid and 100 mg of PVP (molecular weight 70000) were ultrasonically dispersed and dissolved in 10 mL of deionized water. An aqueous sodium hydroxide alkaline solution with a concentration of 50 g / L was added dropwise at a rate of 2 mL / min. The addition was stopped when the pH of the reaction system rose to 13. After standing and reacting for one day, centrifugal separation was carried out and drying was carried out overnight in a vacuum oven at 60 °C to obtain a solid powder. After heat treatment in an air atmosphere at 500 °C for 1 hour, platinum oxide powder was obtained (a relatively high temperature was used here to ensure the oxidative removal of PVP). It was found by thermogravimetric, XRD characterization and TEM observation that a large amount of PVP species still remained on the surface of the prepared platinum oxide particles, and the platinum oxide nanoparticles were relatively large in size, resulting in low catalytic performance in subsequent activity evaluation.

[0044] Example 1

[0045] Step 1, at room temperature, 0.27 g of chloroplatinic acid was ultrasonically dispersed and dissolved in 10 mL of deionized water to obtain a precursor solution with a Pt concentration of 10 g Pt / L;

[0046] Step 2: Slowly add an aqueous solution of sodium bisulfite with a concentration of 50 g / L drop by drop at a rate of 2 mL / min. Stop adding when the reaction system changes from orange-yellow to light yellow. At this time, the pH of the solution is about 4.2.

[0047] Step 3: Maintain a stirring speed of 300 rpm. Use an aqueous solution of sodium carbonate to adjust the pH of the reaction system to 12, then stop adding. At this time, the solution color becomes colorless and a small amount of white precipitate appears.

[0048] Step 4: Continue to add the aqueous solution of sodium bisulfite, and the amount of white precipitate increases. During the addition of sodium bisulfite, the pH of the solution will slightly decrease. During the reaction process, it is necessary to continuously add an aqueous solution of sodium carbonate to maintain the pH of the reaction system above 7.5. Stop adding the sodium bisulfite solution when the white precipitate no longer appears, and continue to stir the reaction at room temperature for 1 hour.

[0049] Step 5: Use a centrifuge to separate the white precipitate from the supernatant, and wash the white precipitate with a large amount of deionized water until no chloride ions are detected in the centrifugate by 1 mol / L AgNO3.

[0050] Step 6: Dissolve the washed white precipitate with a 0.2 mol / L dilute sulfuric acid solution to obtain a colorless and transparent liquid, and add an excessive amount of aqueous H2O2 solution (30 wt% aqueous H2O2 solution, where the molar ratio of H2O2 to Pt is 2:1). Control the reaction temperature of the reaction system at 80 °C. During the heating process and the reaction, install a condenser to prevent excessive volatilization and loss of water. Continue to stir the reaction for 3 hours. After cooling, add 20 mL of 0.52 mol / L sulfuric acid solution to the reaction system, let it stand for 1 hour, then centrifuge and wash with a large amount of deionized water.

[0051] Step 7: Place the solid obtained after centrifugation in a vacuum oven, dry it at 40 °C for 4 hours, and then take it out to obtain platinum oxide nanoparticles.

[0052] Figure 2 XRD pattern of the prepared platinum oxide nanoparticles. From the broadening degree of the corresponding XRD diffraction peaks, it can be seen that the prepared platinum oxide particles are relatively small. Calculated using the Scherrer formula, the average grain size is about 1.0 nm.

[0053] The platinum oxide nanoparticles prepared in Example 1, Comparative Example 1 and Comparative Example 2 were ultrasonically dispersed in an aqueous solution and then supported on an Al2O3 support respectively to obtain a PtO2 / Al2O3 (5 wt%) catalyst. At room temperature and atmospheric pressure, using methanol as a solvent, the reductive amination reaction of n-propylamine and benzaldehyde was investigated at a substrate-to-Pt ratio of 1000:1. The catalyst activity was compared by measuring the amount of H2 absorbed per gram of Pt per minute. The results showed that the activity of the PtO2 / Al2O3 catalyst prepared in Example 1 (1200 mL H2 g -1 min -1 ) was 5-6 times that of the Al2O3 catalysts prepared in Comparative Example 1 and 2 (the hydrogen absorption amounts in Comparative Example 1 and 2 were 200 and 180 mL H2 g - 1 min -1 ) and 6-7 times that amount.

[0054] Example 2

[0055] Step 1, at room temperature, 1.05 grams of potassium chloroplatinate was dispersed and dissolved in 10 mL of deionized water to obtain a precursor solution with a Pt concentration of 50 g Pt / L.

[0056] Step 2, an aqueous solution of sodium bisulfite with a concentration of 90 g / L was added dropwise at a dropping rate of 5 mL / minute. The dropping was stopped when the reaction system changed from orange-yellow to light yellow. At this time, the pH of the solution was about 4.5.

[0057] Step 3, while maintaining a stirring speed of 300 rpm, the pH of the reaction system was adjusted to 12 with an aqueous solution of sodium bicarbonate and then the addition was stopped. At this time, the solution color became colorless and a small amount of white precipitate was precipitated.

[0058] Step 4, continue to add the aqueous solution of sodium bisulfite, and the amount of white precipitate precipitated increased. During the addition of sodium bisulfite, the pH of the solution would slightly decrease. During the reaction process, an aqueous solution of sodium carbonate needed to be continuously added to maintain the pH of the reaction system above 8. After the white precipitate no longer continued to precipitate, the addition of the sodium bisulfite solution was stopped, and the reaction was continued to stir at room temperature for 2 hours.

[0059] Step 5, the white precipitate was separated from the supernatant by a centrifuge, and the white precipitate was washed with a large amount of deionized water until no chloride ions were detected in the centrifugate.

[0060] Step 6: Dissolve the washed white precipitate in a 0.2 mol / L dilute sulfuric acid solution to obtain a colorless and transparent liquid, and add an excessive amount of aqueous hydrogen peroxide solution (30 wt% aqueous hydrogen peroxide solution, where the molar ratio of H2O2 to Pt is 1:1). Control the reaction temperature of the reaction system at 70 °C. A condenser should be installed during the heating process and the reaction to prevent excessive volatilization and loss of water. Continue to stir and react for 5 hours. After cooling, add 20 mL of 0.05 mol / L sulfuric acid solution to the reaction system, let it stand for 1 hour, and then perform centrifugal separation and wash with a large amount of deionized water;

[0061] Step 7: Place the solid obtained after centrifugation in a vacuum oven, dry it at 50 °C for 6 hours, and then take it out to obtain platinum oxide nanoparticles.

[0062] It was found through XRD and electron microscopy characterization that the average particle size of the platinum oxide nanoparticles prepared by the above steps was about 2.6 nm, and there was no obvious agglomeration phenomenon. The platinum oxide nanoparticles prepared in Example 2 were ultrasonically dispersed in an aqueous solution and then supported on an Al2O3 support respectively to obtain a PtO2 / Al2O3 (10 wt%) catalyst. At room temperature and atmospheric pressure, using methanol as a solvent, the reductive amination reaction of n-propylamine and benzaldehyde was investigated with a substrate-to-Pt ratio of 1000:1. The catalytic activity was compared by measuring the amount of H2 absorbed per gram of Pt per minute. The results showed that the activity of the PtO2 / Al2O3 catalyst prepared in Example 2 (1000 mL H2 g -1 min -1 ) was 5-6 times that of the Al2O3 catalysts prepared in Comparative Examples 1 and 2 (the hydrogen absorption amounts of Comparative Examples 1 and 2 were 200 and 180 mL H2 g - 1 min -1 ) and 4-5 times that of them.

[0063] Example 3

[0064] The specific experimental steps of this example are similar to those of Example 1, except that the Pt precursor used is an aqueous solution of platinum tetrachloride at 40 g Pt / L, and the sulfite precursor solution is an aqueous solution of potassium sulfite at 100 g / L. The dropping rate of sulfite into the Pt precursor is 5 ml / min. When the solution changes from orange to light yellow, the pH is about 4.8. Keep the stirring speed at 1500 rpm, and use an aqueous sodium hydroxide solution to adjust the pH of the reaction system to rise to 12 and then stop dropping. At this time, the solution color becomes colorless and a small amount of white precipitate precipitates out; continue to drop the aqueous potassium sulfite solution into the reaction system until the white precipitate no longer increases; the subsequent steps are the same as those in Example 1.

[0065] It was found by XRD and electron microscopy characterization that the average particle size of the platinum oxide nanocatalyst prepared by the above steps was about 3.0 nm, and there was no obvious agglomeration phenomenon.

[0066] The platinum oxide nanoparticles prepared in Example 3 were ultrasonically dispersed in an aqueous solution and then supported on an Al2O3 support respectively to obtain a PtO2 / Al2O3 (2 wt%) catalyst. At room temperature and atmospheric pressure, using methanol as the solvent, the reductive amination reaction of n-propylamine and benzaldehyde was investigated at a substrate-to-Pt ratio of 1000:1. The catalytic activity was compared by measuring the amount of H2 absorbed per gram of Pt per minute.

[0067] The results showed that the activity of the PtO2 / Al2O3 catalyst prepared in Example 1 (800 mL H2 g -1 min -1 ) was 3-4 times that of the Al2O3 catalysts prepared in Comparative Examples 1 and 2 (the hydrogen absorption amounts of Comparative Examples 1 and 2 were 200 and 180 mL H2 g -1 min -1 ), respectively.

[0068] It can be understood that the above specific description of the present invention is only for explaining the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced to achieve the same technical effects; as long as the use requirements are met, they are all within the protection scope of the present invention.

Claims

1. Use of platinum oxide nanopowder as a catalyst or a catalyst active component in a hydrogenation reaction, characterized in that, Supported platinum oxide nanopowder on an Al2O3 support and used it for the reductive amination reaction of n-propylamine and benzaldehyde at room temperature and atmospheric pressure with methanol as the solvent. The preparation method of the platinum oxide nanopowder includes the following steps: Step 1: Dissolve a water-soluble Pt precursor in deionized water to obtain an aqueous Pt precursor solution. Step 2: Gradually add an aqueous solution containing sulfite ions dropwise to the aqueous Pt precursor solution while stirring. Stop adding when the solution changes from orange-red to light yellow. Step 3: Gradually add an alkaline aqueous solution dropwise to the reaction system in Step 2 while stirring, and adjust the pH of the reaction system to 8 - 12. The reaction system changes from light yellow to a colorless solution. Step 4: Keep the pH value of the reaction system unchanged. While stirring, continue to add an aqueous solution containing sulfite ions dropwise to the colorless solution in Step 3. White precipitate forms in the reaction system. Stop adding when no more white precipitate precipitates, and then continue to react for 1 - 2 hours to ensure complete precipitation. Step 5: Wash, filter, and dry the white precipitate formed in Step 4 with water to obtain white platinum sulfite powder. Step 6: Under stirring conditions, dissolve the white platinum sulfite powder in an aqueous solution, adjust the pH of the solution to 1 - 5, add an aqueous hydrogen peroxide solution, heat up and react for 2 - 3 hours, then cool down, and continue to add an acidic aqueous solution to promote the sedimentation of platinum oxide nanoparticles. Step 7: Centrifuge the reaction solution in Step 6 and wash it with deionized water. After solid-liquid separation, dry it to obtain the platinum oxide nanopowder. In Step 2, the dropping rate is 2 - 6 mL / min, and the concentration of sulfite in the aqueous solution containing sulfite ions is 50 - 100 g / L. In Step 4, the reaction temperature is 0 - 30 °C. In Step 7, the drying temperature is 30 - 60 °C. The particle size of the platinum oxide nanopowder is 1 - 4 nm.

2. The application according to claim 1, characterized in that, In Step 1, the Pt precursor is one or more of chloroplatinic acid, sodium chloroplatinate, potassium chloroplatinate, potassium chloroplatinate, sodium chloroplatinate, and platinum tetrachloride. The Pt concentration in the aqueous Pt precursor solution is 10 - 50 g / L.

3. The application according to claim 1, characterized in that, In Step 2, the stirring speed is 200 - 1000 r / min. The aqueous solution containing sulfite ions is one or more of sulfurous acid, sodium sulfite, sodium bisulfite, potassium sulfite, and potassium bisulfite aqueous solutions. When the solution turns light yellow, the pH of the reaction system is 4 - 5.

4. The application according to claim 1, wherein In Step 3, the dropping rate is 2 - 6 mL / min, the stirring speed is 200 - 1000 r / min. The alkaline aqueous solution is one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, ammonia water, and potassium hydroxide aqueous solutions. In Step 4, the pH of the reaction system is 7.5 - 11, and the stirring speed is 200 - 1000 rpm.

5. The application according to claim 1, characterized in that, In the said step 6, the acidic aqueous solution is one or more of dilute sulfuric acid, dilute hydrochloric acid, and acetic acid aqueous solution, and the concentration of the acidic aqueous solution is 0.05 - 0.5 mol / L; the molar ratio of the addition amount of H2O2 to the platinous sulfite salt is 1:1 - 5:1; the reaction temperature is 60 - 90 o °C; in the said step 7, the solid-liquid separation method is centrifugation or filtration.

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