A method for preparing chloroplatinic acid based on waste platinum catalyst

Abstract

The application provides a method for preparing chloroplatinic acid based on waste platinum catalyst, comprising the following steps: pretreating the waste platinum catalyst to obtain crude metal platinum; dissolving the crude metal platinum in aqua regia to obtain a mixed solution; adjusting the pH of the mixed solution to 2.0-3.0, adding a first batch of reducing agent and dispersant, and reacting at 70-80 DEG C for 8-20 min to perform the first step reduction; adjusting the pH to 3.0-4.0, adding a second batch of reducing agent and dispersant, and continuing to react at 70-80 DEG C for 8-20 min to perform the second step reduction, so as to obtain a nano platinum system; separating to obtain monodisperse nano platinum; dissolving the monodisperse nano platinum in a hydrochloric acid-hydrogen peroxide system, the molar ratio of hydrochloric acid to hydrogen peroxide being 4:1-6:1, the dissolving temperature being 130-140 DEG C, and the dissolving time being 20-30 min, so as to obtain a chloroplatinic acid solution; and evaporating and crystallizing the chloroplatinic acid solution to obtain chloroplatinic acid crystals.

Description

Technical Field

[0001] This application relates to the field of chloroplatinic acid preparation, specifically to a method for preparing chloroplatinic acid based on waste platinum catalyst. Background Technology

[0002] Chloroplatinic acid, an important platinum compound, is widely used in catalyst preparation, electroplating, and pharmaceuticals. Current industrial preparations of chloroplatinic acid primarily involve dissolving metallic platinum in aqua regia, followed by multiple denitration steps to obtain the final product. While this process is mature, it has several shortcomings in practical production.

[0003] First, traditional methods struggle to effectively control nitrogen content, resulting in low platinum content, poor crystallinity, and high impurity levels in the product, thus affecting the application performance and subsequent processing of chloroplatinic acid. Second, with increasing platinum resource scarcity, the recycling of spent platinum catalysts has become a key focus in the industry. However, existing recycling and reuse processes generally suffer from low platinum recovery rates and incomplete impurity removal, limiting the preparation of high-purity chloroplatinic acid.

[0004] In the production process, how to improve the platinum content and crystallinity of chloroplatinic acid, optimize the size distribution of nano-platinum particles, and achieve efficient recovery of platinum from waste platinum catalysts are current challenges that need to be addressed. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a method for preparing chloroplatinic acid based on waste platinum catalyst.

[0006] The first aspect of this application provides a method for preparing chloroplatinic acid based on waste platinum catalyst, comprising the following steps: pretreating the waste platinum catalyst to obtain crude platinum metal; dissolving the crude platinum metal in aqua regia to obtain a mixed solution; adjusting the pH of the mixed solution to 2.0-3.0, adding the first batch of reducing agent and dispersant, and reacting at 70-80℃ for 8-20 min for the first step of reduction; adjusting the pH to 3.0-4.0, adding the second batch of reducing agent and dispersant, and continuing to react at 70-80℃ for 8-20 min for the second step of reduction to obtain a nano-platinum system; separating monodisperse nano-platinum; and placing the monodisperse nano-platinum in a hydrochloric acid-hydrogen peroxide system. The solution is dissolved in a solution of hydrochloric acid and hydrogen peroxide at a molar ratio of 4:1 to 6:1, at a temperature of 130-140℃, and for 20-30 minutes to obtain a chloroplatinic acid solution. The chloroplatinic acid solution is then evaporated and crystallized to obtain chloroplatinic acid crystals. The mass ratio of crude platinum, reducing agent, and dispersant is 1:(0.5-0.9):(0.69-1.6). The first and second batches of reducing agents are independently selected from one or a combination of two of hydrazine hydrate and ascorbic acid. The dispersant is a mixture of polyethylene glycol and sodium dodecyl sulfate, with a mass ratio of polyethylene glycol to sodium dodecyl sulfate of (3:0.8)-(5:1.2).

[0007] This process combines stepwise reduction with pH control to form uniform crystal nuclei from platinum nanoparticles in the first reduction step, and further controls the crystal growth rate in the second reduction step, thus obtaining platinum nanoparticles with uniform size distribution. A composite dispersion system of PEG (polyethylene glycol) and SDS (sodium dodecyl sulfate) effectively prevents platinum nanoparticle agglomeration and improves dispersion stability. The uniform platinum nanoparticles dissolve fully in the hydrochloric acid-hydrogen peroxide system, promoting the formation of high-purity, highly crystalline chloroplatinic acid. This process not only improves the platinum content and crystallinity of chloroplatinic acid but also includes pretreatment processes for different types of spent platinum catalysts, effectively removing support materials and impurity metals, laying the foundation for the subsequent preparation of high-purity chloroplatinic acid, and achieving efficient resource utilization and high-quality product production.

[0008] Furthermore, when the spent platinum catalyst is a carbon-based catalyst, the pretreatment includes oxidative dissolution, resin desorption, and electrodeposition. This method effectively removes the carbon support and impurities, improves the purity of the crude platinum, and enhances the purity and performance of the final product.

[0009] Furthermore, when the spent platinum catalyst is a γ-alumina supported catalyst, the pretreatment includes sulfuric acid dissolution of the support, oxidative dissolution, resin desorption, and electrodeposition. This process can efficiently remove the alumina support and impurity metals, significantly improving the purity of the crude platinum.

[0010] Furthermore, the current density of the electrodeposition is 200 A / m. 2 Using 200A / m 2 Electrowinning at a specific current density helps to ensure sufficient reduction of platinum ions while suppressing the co-deposition of impurity metals and improving the purity of crude platinum.

[0011] Furthermore, the evaporation and crystallization temperature of the chloroplatinic acid solution is 60°C. Controlling the evaporation and crystallization temperature at 60°C helps the chloroplatinic acid to precipitate and crystallize, thereby improving the crystallinity and purity of the product.

[0012] Furthermore, the dispersant is a mixture of PEG-4000 and sodium dodecyl sulfate. PEG-4000 has good dispersing and stabilizing effects, and when combined with sodium dodecyl sulfate, it can effectively prevent the agglomeration of platinum nanoparticles.

[0013] Furthermore, in the reduction step, the reaction temperatures for the first and second reduction steps are 70°C and 80°C, respectively. This step-by-step temperature control further optimizes the formation process of platinum nanoparticles.

[0014] Furthermore, in the reduction step, the reaction times for the first and second reduction steps are 10 min and 15 min, respectively. By controlling the reaction time, it is helpful to obtain platinum nanoparticles with a more uniform particle size distribution.

[0015] Furthermore, in the hydrochloric acid-hydrogen peroxide system, the mass of crude platinum added per 100 ml of system is 14 g-20 g. This ratio helps to achieve complete dissolution of nano-platinum, improving the yield and purity of chloroplatinic acid.

[0016] The second aspect of this application provides an application of the above-described process in the recovery of waste platinum catalysts and the preparation of chloroplatinic acid.

[0017] This application not only achieves efficient recycling of precious metal resources, but also improves the product quality of chloroplatinic acid, which has significant economic value and environmental significance.

[0018] The present invention has the following beneficial effects:

[0019] This method combines stepwise reduction with pH control to form uniform crystal nuclei in the first reduction step and further control the crystal growth rate in the second reduction step, thereby obtaining uniformly sized platinum nanoparticles and improving the platinum content and crystallinity of chloroplatinic acid.

[0020] This solution employs a composite dispersion system of polyethylene glycol and sodium dodecyl sulfate, which effectively prevents the agglomeration of platinum nanoparticles, improves dispersion stability, and solves the problem of easy agglomeration of platinum nanoparticles in traditional processes.

[0021] The synergistic effect of the stepwise reduction process and the composite dispersion system in this scheme can optimize the size distribution of nano-platinum particles, reduce the impurity content, and achieve efficient recovery of waste platinum catalyst and preparation of high-purity chloroplatinic acid. Detailed Implementation

[0022] To facilitate understanding of this application, a more complete description will be provided below. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0026] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0027] Unless otherwise specified, the percentage content mentioned in this application refers to mass percentage for solid-liquid mixtures and solid-phase-solid mixtures, and volume percentage for liquid-phase-liquid mixtures.

[0028] Unless otherwise specified, all percentage concentrations mentioned in this application refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.

[0029] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows for temperature fluctuations within the precision range controlled by the instrument.

[0030] The term "particle" as used in this application, or a substance with a defined particle size distribution, is not necessarily spherical in shape; it may be irregular and can be either primary or secondary particles. The particle size of irregular particles is calculated as the average of their maximum and minimum diameters.

[0031] In some preferred embodiments, the spent platinum catalyst may be selected from any one of carbon-based catalysts, γ-alumina supported catalysts, or other platinum-containing catalysts. For carbon-based catalysts, pretreatment may include oxidative dissolution, resin desorption, and electrodeposition; for γ-alumina supported catalysts, pretreatment may include sulfuric acid dissolution of the support, oxidative dissolution, resin desorption, and electrodeposition.

[0032] In some preferred embodiments, the reducing agent may be selected from any combination of hydrazine hydrate and ascorbic acid, or any combination of formaldehyde and oxalic acid. The concentration of hydrazine hydrate may be selected from any value among 10 g / L, 15 g / L, 20 g / L, 25 g / L, and 30 g / L; the concentration of ascorbic acid may be selected from any value among 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, and 40 g / L; the concentration of formaldehyde may be selected from any value among 15 g / L, 20 g / L, 25 g / L, 30 g / L, and 35 g / L; and the concentration of oxalic acid may be selected from any value among 10 g / L, 15 g / L, 20 g / L, 25 g / L, and 30 g / L.

[0033] In some preferred embodiments, the dispersant may be selected from a mixture of PEG-4000 and SDS, the concentration of PEG-4000 may be selected from any value among 20 g / L, 25 g / L, 30 g / L, 35 g / L, and 40 g / L, and the concentration of SDS may be selected from any value among 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, and 10 g / L.

[0034] In some preferred embodiments, the reaction temperatures of the first reduction step and the second reduction step can be selected from any value among 70℃, 72℃, 75℃, 78℃, and 80℃, respectively, and the reaction time can be selected from any value among 8min, 10min, 12min, 15min, 18min, and 20min, respectively.

[0035] In some preferred embodiments, in the hydrochloric acid-hydrogen peroxide system, the molar ratio of hydrochloric acid to hydrogen peroxide can be selected from any value among 4:1, 4.5:1, 5:1, 5.5:1, and 6:1; the dissolution temperature can be selected from any value among 130℃, 132℃, 135℃, 138℃, and 140℃; and the dissolution time can be selected from any value among 20min, 22min, 25min, 28min, and 30min.

[0036] Example 1: This example provides a method and process flow for preparing chloroplatinic acid based on waste platinum-carbon-based catalyst.

[0037] Preparation of crude platinum: 1000g of spent platinum-carbon-based catalyst was added to 5000ml of aqua regia and oxidized and dissolved at 80℃ for 4h. Insoluble matter was removed by filtration. The filtrate was adsorbed through an anion exchange resin and then eluted with a 5% thiourea solution to obtain a platinum-containing eluent. The eluent was then subjected to a current density of 200A / m². 2 Electrowinning was performed under certain conditions to obtain crude platinum powder.

[0038] Preparation of chloroplatinic acid: Take 100g of the above crude platinum powder and dissolve it in 1000ml of aqua regia at 80℃ for 60min. After the platinum powder is completely dissolved, adjust the pH to 2.5, add 25g of hydrazine hydrate (50% of the total amount), 28g of PEG-4000 (50% of the total amount), and 7g of SDS (50% of the total amount) to a beaker, and react at 75℃ for 10min with stirring at 360r / min to carry out the first step of reduction. Then adjust the pH to 3.5, add the remaining 25g of hydrazine hydrate, 28g of PEG-4000, and 7g of SDS, and continue to react at 75℃ for 15min to carry out the second step of reduction. After the reaction is complete, wash thoroughly with water and alcohol, and filter. Add the obtained nano-platinum to 500ml of hydrochloric acid (10mol / L, the same below) + 100ml of hydrogen peroxide (10mol / L, the same below), i.e., molar ratio 5:1, and react at 130℃ for 20min. Finally, the obtained chloroplatinic acid solution was evaporated and crystallized at 60℃ to obtain chloroplatinic acid crystals. The mass ratio of crude platinum, reducing agent, and dispersant was 100g : 50g : 70g, i.e., 1 : 0.5 : 0.7, and the mass ratio of polyethylene glycol (PEG-4000) and sodium dodecyl sulfate (SDS) was 56g : 14g = 4 : 1.

[0039] Example 2: This example provides a method for preparing chloroplatinic acid based on waste platinum γ-alumina catalyst.

[0040] Preparation of crude platinum: 1000g of waste platinum γ-alumina catalyst was added to 3000ml of 20% sulfuric acid solution, and the alumina support was dissolved by stirring at 80℃ for 2h. The dissolved aluminum salts were removed by filtration, and the filter residue was dissolved by oxidation with 5000ml of aqua regia at 80℃ for 4h. Insoluble matter was removed by filtration, and the filtrate was adsorbed through an anion exchange resin, then eluted with 5% thiourea solution to obtain a platinum-containing eluent. The eluent was then subjected to a current density of 200A / m². 2 Electrowinning was performed under certain conditions to obtain crude platinum powder.

[0041] Preparation of chloroplatinic acid: Take 100g of the above crude platinum powder and dissolve it in 1000ml of aqua regia at 80℃ for 60min. After the platinum powder is completely dissolved, adjust the pH to 2.5, add 30g of hydrazine hydrate (60% of the total amount), 34g of PEG-4000 (60% of the total amount), and 8g of SDS (60% of the total amount) to a beaker, and react at 75℃ for 10min with stirring at 360r / min to carry out the first step of reduction. Then adjust the pH to 3.5, add the remaining 20g of hydrazine hydrate, 22g of PEG-4000, and 5g of SDS, and continue to react at 75℃ for 15min to carry out the second step of reduction. After the reaction is complete, wash thoroughly with water and alcohol, and filter. Add the obtained nano-platinum to 500ml of hydrochloric acid + 100ml of hydrogen peroxide, and react at 135℃ for 25min. Finally, evaporate the obtained chloroplatinic acid solution at 60℃ to crystallize and obtain chloroplatinic acid crystals. The mass ratio of crude platinum, reducing agent, and dispersant is 100g : 50g : 69g, i.e., 1 : 0.5 : 0.69. The mass ratio of polyethylene glycol (PEG-4000) and sodium dodecyl sulfate (SDS) is 56g : 13g≈4.3:1.

[0042] Example 3: The difference between this example and Example 1 is that the first step of reduction uses a combination of ascorbic acid and hydrazine hydrate as a reducing agent.

[0043] Preparation of crude platinum: Same as in Example 1.

[0044] Preparation of chloroplatinic acid: Take 100g of crude platinum powder and dissolve it in 1000ml of aqua regia at 80℃ for 60min. Adjust the pH to 2.5, add 30g of ascorbic acid (60% of the total), 10g of hydrazine hydrate (20% of the total), 28g of PEG-4000 (50% of the total), and 7g of SDS (50% of the total). React at 75℃ for 10min with stirring at 360r / min to carry out the first reduction step. Adjust the pH to 3.5, add 20g of hydrazine hydrate, 28g of PEG-4000, and 7g of SDS, and continue reacting at 75℃ for 15min to carry out the second reduction step. Subsequent steps are the same as in Example 1. The mass ratio of crude platinum, reducing agent, and dispersant is 100g : 60g : 70g = 1 : 0.6 : 0.7, and the mass ratio of polyethylene glycol and SDS is 56g : 14g = 4 : 1.

[0045] Example 4: The difference between this example and Example 1 is that the reaction temperatures for the two reduction steps are 70°C and 80°C, respectively.

[0046] Preparation of crude platinum: Same as in Example 1.

[0047] Preparation of chloroplatinic acid: Take 100g of crude platinum powder and dissolve it in 1000ml of aqua regia at 80℃ for 60min. Adjust the pH to 2.5, add 25g of hydrazine hydrate, 28g of PEG-4000, and 7g of SDS, and react at 70℃ for 10min with stirring at 360r / min for the first step of reduction. Adjust the pH to 3.5, add the remaining 25g of hydrazine hydrate, 28g of PEG-4000, and 7g of SDS, and continue to react at 80℃ for 15min for the second step of reduction. Subsequent steps are the same as in Example 1. The mass ratio of crude platinum, reducing agent, and dispersant is 100g : 50g : 70g = 1 : 0.5 : 0.7, and the mass ratio of polyethylene glycol and SDS is 56g : 14g = 4 : 1.

[0048] Example 5: The difference between this example and Example 1 is that the reaction times for the two reduction steps are 15 min and 10 min, respectively.

[0049] Preparation of crude platinum: Same as in Example 1.

[0050] Preparation of chloroplatinic acid: Take 100g of crude platinum powder and dissolve it in 1000ml of aqua regia at 80℃ for 60min. Adjust the pH to 2.5, add 25g of hydrazine hydrate, 28g of PEG-4000, and 7g of SDS, and react at 75℃ for 15min with stirring at 360r / min to carry out the first step of reduction. Adjust the pH to 3.5, add the remaining 25g of hydrazine hydrate, 28g of PEG-4000, and 7g of SDS, and continue to react at 75℃ for 10min to carry out the second step of reduction. Subsequent steps are the same as in Example 1. The mass ratio of crude platinum, reducing agent, and dispersant is 120g : 60g : 84g = 1 : 0.5 : 0.7, and the mass ratio of polyethylene glycol and SDS is 67.2g : 16.8g = 4 : 1.

[0051] Example 6: The difference between this example and Example 1 is that in the hydrochloric acid-hydrogen peroxide system, the mass of crude platinum added per 100ml of system is 18g.

[0052] Preparation of crude platinum: Same as in Example 1.

[0053] Preparation of chloroplatinic acid: 100g of crude platinum powder was dissolved in 1000ml of aqua regia at 80℃ for 60min. The pH was adjusted to 2.5, and 25g of hydrazine hydrate, 28g of PEG-4000, and 7g of SDS were added. The reaction was carried out at 75℃ for 10min with stirring at 360r / min for the first reduction step. The pH was adjusted to 3.5, and the remaining 25g of hydrazine hydrate, 28g of PEG-4000, and 7g of SDS were added. The reaction was continued at 75℃ for 15min for the second reduction step. The resulting nano-platinum was added to 555ml of hydrochloric acid + 111ml of hydrogen peroxide (total system 666ml, crude platinum 120g), and reacted at 130℃ for 20min. Subsequent steps were the same as in Example 1. The mass ratio of crude platinum, reducing agent, and dispersant is 120g : 60g : 84g = 1 : 0.5 : 0.7, and the mass ratio of polyethylene glycol and SDS is 67.2g : 16.8g = 4 : 1.

[0054] Example 7: The difference between this example and Example 1 is that the amount of crude platinum powder used is 120g (i.e., 20g of crude platinum metal is added to 100ml of hydrochloric acid-hydrogen peroxide system). In the first reduction step, the pH is adjusted to 2.0, the temperature is 80℃, and the reaction time is 8min. In the second reduction step, the pH is adjusted to 3.0, the temperature is 80℃, and the reaction time is 8min. The ratio of reducing agent to dispersant is adjusted to a mass ratio of crude platinum metal, reducing agent, and dispersant of 1:0.9:1.6. The mass ratio of polyethylene glycol to sodium dodecyl sulfate in the dispersant is 3:0.8. The ratio of the amount of reducing agent to dispersant added in the first and second reduction steps is the same as in Example 1. When dissolving the nano-platinum, the molar ratio of hydrochloric acid to hydrogen peroxide is 4:1, the dissolution temperature is 130℃, and the dissolution time is 20min.

[0055] Example 8: The difference between this example and Example 1 is that the amount of crude platinum powder used is 84g (i.e., the mass of crude platinum metal added to 100ml hydrochloric acid-hydrogen peroxide system is 14g). In the first reduction step, the pH is adjusted to 3.0, the temperature is 70℃, and the reaction time is 20min. In the second reduction step, the pH is adjusted to 4.0, the temperature is 70℃, and the reaction time is 20min. The amount of reducing agent and dispersant is adjusted to a mass ratio of crude platinum metal, reducing agent, and dispersant of 1:0.5:1.4, and the mass ratio of polyethylene glycol to sodium dodecyl sulfate in the dispersant is 5:1.2. The ratio of the amount of reducing agent and dispersant added in the first and second reduction steps is the same as in Example 1. When dissolving the nano-platinum, the molar ratio of hydrochloric acid to hydrogen peroxide is 6:1, the dissolution temperature is 140℃, and the dissolution time is 30min.

[0056] Comparative Example 1: The difference between this comparative example and Example 1 is that the pH control is not performed during the preparation of chloroplatinic acid, and a one-time reduction is used.

[0057] Preparation of crude platinum: Same as in Example 1.

[0058] Preparation of chloroplatinic acid: Take 100g of crude platinum powder and dissolve it in 1000ml of aqua regia at 80℃ for 60min. Add 50g of hydrazine hydrate, 56g of PEG-4000, and 14g of SDS to a beaker at once, and react at 75℃ for 25min with stirring at 360r / min. Subsequent steps are the same as in Example 1. The mass ratio of crude platinum, reducing agent, and dispersant is 100g : 50g : 70g = 1 : 0.5 : 0.7, and the mass ratio of polyethylene glycol and SDS is 56g : 14g = 4 : 1.

[0059] Comparative Example 2: The difference between this comparative example and Example 1 is that only PEG-4000 is used as the dispersant, and SDS is not included.

[0060] Preparation of crude platinum: Same as in Example 1.

[0061] Preparation of chloroplatinic acid: Take 100g of crude platinum powder and dissolve it in 1000ml of aqua regia at 80℃ for 60min. Adjust the pH to 2.5, add 25g of hydrazine hydrate and 56g of PEG-4000, and react at 75℃ for 10min with stirring at 360r / min to carry out the first step of reduction. Adjust the pH to 3.5, add the remaining 25g of hydrazine hydrate and 56g of PEG-4000, and continue to react at 75℃ for 15min to carry out the second step of reduction. Subsequent steps are the same as in Example 1. The mass ratio of crude platinum, reducing agent, and dispersant is 100g : 50g : 56g = 1 : 0.5 : 0.56.

[0062] Comparative Example 3: This comparative example differs from Example 1 in that only SDS is used as the dispersant, PEG is not included. The mass ratio of crude platinum, reducing agent, and dispersant is 100g : 50g : 14g = 1 : 0.5 : 0.14

[0063] Preparation of crude platinum: Same as in Example 1.

[0064] Preparation of chloroplatinic acid: Take 100g of crude platinum powder and dissolve it in 1000ml of aqua regia at 80℃ for 60min. Adjust the pH to 2.5, add 25g of hydrazine hydrate and 14g of SDS, and react at 75℃ for 10min with stirring at 360r / min to carry out the first step of reduction. Adjust the pH to 3.5, add the remaining 25g of hydrazine hydrate and 14g of SDS, and continue to react at 75℃ for 15min to carry out the second step of reduction. Subsequent steps are the same as in Example 1.

[0065] Performance testing methods

[0066] Platinum chloroplatinate content: determined according to GB / T 15072.1-2008.

[0067] Size distribution of platinum nanoparticles: TEM measurements of 200 particles, statistical standard deviation.

[0068] Impurity content: Total impurities were determined by ICP-MS.

[0069] Nano-platinum conversion rate and solubility: calculated as the ratio of actual product to theoretical value.

[0070] Table 1. Performance test results of the examples and comparative examples.

[0071]

[0072] As shown in Table 1, the conversion and solubility of nano-platinum in all examples reached over 99.98%, the platinum content of the products was over 40.3%, the standard deviation of particle size distribution was less than 1.9 nm, and the impurity content was extremely low. In particular, Example 2 achieved a platinum content of 40.2% and a particle size distribution standard deviation of only 1.6 nm, indicating that this process can effectively improve the purity and crystallinity of chloroplatinic acid. In contrast, Comparative Example 1 did not use stepwise reduction and pH control, resulting in a particle size distribution standard deviation of 4.1 nm and a slightly lower platinum content. Comparative Example 2 used only PEG, resulting in severe particle agglomeration, a distribution standard deviation of 3.7 nm, and a decrease in both solubility and platinum content. Comparative Example 3 used only SDS, resulting in poor dispersion, a particle size distribution standard deviation of 4.8 nm, and a platinum content lower than the examples.

[0073] Examples 4 and 5 adjusted the reduction temperature and time, resulting in a slight increase in particle size distribution, but still significantly better than the comparative example. Example 3 used a combination of ascorbic acid and hydrazine hydrate, resulting in a slightly wider particle size distribution but excellent overall performance. In summary, the key to obtaining high-purity, highly crystalline chloroplatinic acid lies in using a PEG-SDS composite dispersion system, stepwise reduction and pH control, and appropriate dissolution conditions.

[0074] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0075] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing chloroplatinic acid based on spent platinum catalyst, characterized by, The method comprises the following steps: The waste platinum catalyst is pretreated to obtain metal crude platinum; the metal crude platinum is dissolved in aqua regia to obtain a mixed solution; the pH of the mixed solution is adjusted to 2.0-3.0, a first batch of reducing agent and dispersant are added, and the first-step reduction is carried out at 70-80 ℃ for 8-20 min; the pH is adjusted to 3.0-4.0, a second batch of reducing agent and dispersant are added, and the second-step reduction is continued at 70-80 ℃ for 8-20 min to obtain a nano platinum system; monodisperse nano platinum is separated; the monodisperse nano platinum is dissolved in a hydrochloric acid-hydrogen peroxide system, the molar ratio of hydrochloric acid to hydrogen peroxide is 4:1-6:1, the dissolution temperature is 130-140 ℃, and the dissolution time is 20-30 min to obtain a chloroplatinic acid solution; the chloroplatinic acid solution is evaporated and crystallized to obtain chloroplatinic acid crystals; wherein the mass ratio of the metal crude platinum, the reducing agent and the dispersant is 1:(0.5-0.9):(0.69-1.6), the first batch of reducing agent and the second batch of reducing agent are independently selected from one or a combination of the other of hydrazine hydrate and ascorbic acid, the dispersant is a mixture of PEG-4000 and sodium dodecyl sulfate, the mass ratio of polyethylene glycol to sodium dodecyl sulfate is (3:0.8)-(5:1.2), and the reaction temperatures of the first-step reduction and the second-step reduction are 70 ℃ and 80 ℃, respectively.

2. The method of claim 1, wherein, The waste platinum catalyst is a carbon-based catalyst, and the pretreatment comprises oxidation dissolution, resin resolution and electrodeposition.

3. The method of claim 1, wherein, The waste platinum catalyst is a γ-alumina carrier catalyst, and the pretreatment comprises sulfuric acid dissolution of the carrier, oxidation dissolution, resin resolution and electrodeposition.

4. The method of claim 3, wherein, The current density of the electrodeposition is 200 A / m 2 .

5. The method of claim 1, wherein, The evaporation and crystallization temperature of the chloroplatinic acid solution is 60 ℃.

6. The method of claim 1, wherein, The reaction times of the first-step reduction and the second-step reduction are 10 min and 15 min, respectively.

7. The method of claim 1, wherein, In the hydrochloric acid-hydrogen peroxide system, the mass of the metal crude platinum added per 100 ml of the system is 14 g-20 g.

8. Use of the method according to any one of claims 1-7 in recycling waste platinum catalysts and preparing chloroplatinic acid.

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