Preparation method of platinum nitrate solution

Abstract

The invention relates to the field of platinum nitrate solution production, and discloses a platinum nitrate solution preparation method, which comprises: S1, carrying out a reaction on platinum metal and concentrated nitric acid to form platinum ions; s2, an ammonium chloride solution is added to serve as a compounding agent, and the oxidation state of platinum ions is controlled; s3, adding a copper chloride solution as a stabilizer to prevent platinum ions from reducing and precipitating; s4, a catalyst is added in the reaction process, the catalyst is palladium powder or copper powder, and the mass of the catalyst is 1%-5% of the mass of platinum metal; and S5, controlling the reaction temperature to be 100 DEG C to 150 DEG C, and keeping the reaction pressure to be 0.1 MPa to 0.2 MPa. The technical scheme of heterogeneous catalysis and accurate preparation is adopted, and the effects of efficiently dissolving platinum metal and keeping the solution stable are achieved. By optimizing the use of the catalyst and controlling the dissolving process, the problems of too violent reaction and platinum ion reduction precipitation are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of platinum nitrate solution production, and particularly to a preparation method of platinum nitrate solution. Background Art

[0002] Platinum nitrate solution is widely used in the fields of catalyst preparation, precious metal extraction, electronic materials, and chemical synthesis. Especially in catalytic reactions, platinum nitrate, as an important catalyst component, plays a key role. Its applications include hydrogenation reactions, petroleum cracking, fuel cells, and many other industrial fields. Due to the excellent catalytic performance and high-temperature resistance of platinum, it is widely used in efficient catalytic reactions. However, with the increasing demand for high-purity and low-cost platinum solutions, there are still some inevitable technical bottlenecks in the existing preparation methods.

[0003] The existing methods for preparing platinum nitrate solution usually directly dissolve platinum metal with high-concentration nitric acid at high temperature. However, the dissolution efficiency of this process is often limited by reaction temperature, reaction pressure, and solvent conditions. Higher temperatures and concentrated nitric acid concentrations can increase the dissolution rate of platinum metal, but they are prone to cause the reduction and precipitation of platinum ions, thereby affecting the stability of the solution and ultimately reducing the dissolution efficiency. In addition, common dissolution methods also face interference from side reactions during the dissolution process, and the generated NO2 gas has a negative impact on the stability of the solution. Existing technologies often ignore the comprehensive influence of temperature, pressure, and solvent conditions on the dissolution of platinum metal during the reaction process, so it is difficult to achieve the best balance between dissolution rate and platinum ion stability. These problems greatly restrict the preparation of high-efficiency and stable platinum nitrate solution. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention provides a preparation method of platinum nitrate solution, which solves the problems of reduction and precipitation of platinum metal, low dissolution efficiency, and unstable solution caused by too high reaction temperature in the existing technology.

[0005] To achieve the above object, the present invention is realized through the following technical solutions: A preparation method of platinum nitrate solution, comprising the following steps: S1. React platinum metal with concentrated nitric acid to form platinum ions; in this step, platinum metal reacts with concentrated nitric acid, and platinum metal is oxidized to platinum ions. Nitric acid, as a strong oxidant, can quickly oxidize platinum metal to platinum ions (Pt 2+ or Pt 4+ ), and this process is the basis for the preparation of platinum nitrate solution. The reaction formula can be expressed as: Pt + 4HNO3 → Pt(NO3)2 + 2H2O + 2NO2 Mechanistically, the reaction of platinum metal with nitric acid releases nitrogen dioxide gas (NO2), while the platinum metal is oxidized to platinum ions. The rate of this process is affected by temperature, nitric acid concentration, and the form of platinum metal (platinum black, platinum powder). Under high temperature or concentrated nitric acid conditions, platinum metal can dissolve more easily to form platinum ions, but too high a temperature also accelerates side reactions, such as the reduction precipitation of platinum.

[0006] S2. Add ammonium chloride solution as a complexing agent to control the oxidation state of platinum ions; in this step, ammonium chloride is added as a complexing agent, which can help stabilize the oxidation state of platinum ions. Chloride ions in the ammonium chloride solution form a coordination complex with platinum ions, reducing the risk of platinum ion reduction. The role of ammonium chloride is mainly through the coordination effect to form [PtCl4] 2- a stable platinum complex, thus preventing further reduction precipitation of platinum ions. Mechanistically, the chloride ions provided by ammonium chloride interact with platinum ions, inhibiting the reduction reaction of platinum and helping platinum ions remain in the solution, ensuring the efficiency of the reaction and the stability of platinum.

[0007] S3. Add copper chloride solution as a stabilizer to prevent the reduction precipitation of platinum ions; the addition of copper chloride plays a role in further stabilizing the platinum solution. There is a strong interaction between copper ions in copper chloride and platinum ions, which can prevent platinum ions from being reduced back to metallic platinum in the solution. The role of copper chloride is to inhibit the reduction reaction of platinum ions and prevent them from precipitating out of the solution. Mechanistically, copper ions can interact with platinum ions in the solution, reducing the risk of platinum ion reduction precipitation through complexation reactions and improving the stability of the solution.

[0008] S4. Add a catalyst during the reaction. The catalyst is palladium powder or copper powder, and its mass is 1% - 5% of the mass of platinum metal; the addition of the catalyst (palladium powder or copper powder) helps accelerate the dissolution reaction of platinum metal. Palladium and copper, as catalysts, can promote the reaction of platinum metal with nitric acid and increase the dissolution efficiency. Palladium and copper participate in the reaction as catalysts, effectively reducing the activation energy of platinum dissolution and accelerating the oxidation and dissolution of platinum metal. Mechanistically, palladium or copper promotes the dissolution of platinum metal by providing electrons or changing the electronic environment on the platinum surface, thus increasing the dissolution rate. The introduction of these metal catalysts ensures that platinum metal can dissolve quickly while preventing the precipitation of platinum ions in the solution and maintaining an efficient reaction process.

[0009] S5. Control the reaction temperature at 100°C to 150°C and maintain the reaction pressure at 0.1 MPa to 0.2 MPa; in this step, the reaction temperature and pressure are strictly controlled to ensure the dissolution of platinum metal under optimal conditions. Too low a temperature will cause the dissolution reaction to be slow, while too high a temperature will lead to side reactions and even cause the reduction and precipitation of platinum ions. By controlling the temperature within the range of 100°C to 150°C, the efficient dissolution of platinum metal in nitric acid solution can be ensured, while avoiding the excessive release of NO2 gas. The control of pressure also helps to maintain the stability of the reaction. At a lower pressure, the precipitation of NO2 gas can be prevented, reducing the occurrence of side reactions. Mechanistically, the optimization of temperature and pressure ensures the smooth progress of the oxidation process of platinum metal and reduces the possibility of platinum ion reduction, further improving the dissolution rate.

[0010] S6. After the reaction is completed, cool the reaction solution, filter to remove the catalyst and unreacted substances to obtain a platinum nitrate solution. Through filtration and cooling, it is ensured that the residual solids in the reaction system are effectively removed, and only platinum ions are retained in the solution. Mechanistically, the filtration process removes insoluble substances, unreacted substances, and the catalyst. If these impurities are not removed, they will affect the purity of the solution and reduce the stability of platinum ions. In the filtered solution, platinum exists stably in the form of platinum ions, providing a pure platinum nitrate solution for subsequent applications.

[0011] Preferably, the platinum metal is platinum black or platinum powder, with a mass of 0.5 g to 5.0 g.

[0012] The high specific surface area of platinum black and platinum powder is the key to their excellent solubility in this reaction. Platinum black usually has a small particle size and a large surface area, which makes the reaction between platinum metal and concentrated nitric acid faster and more complete. On smaller particles, the dissolution rate of platinum metal is faster because nitric acid molecules can more easily contact the platinum surface and oxidize the platinum metal to platinum ions. In addition, platinum powder also has good dissolution performance, especially fine platinum powder particles, which can provide a higher reaction rate at a lower temperature.

[0013] By selecting a platinum metal mass range of 0.5 g to 5.0 g, the present invention ensures the full reaction of platinum metal without excessive residue, optimizes the use efficiency of raw materials, and meets the requirements of the dissolution process. Within this mass range, platinum metal can fully react with nitric acid in the reaction to produce platinum ions (Pt 2+ or Pt 4+ ) and maintain the stability and purity of the solution.

[0014] Specifically in terms of the reaction mechanism, nitric acid, as a strong oxidant, oxidizes platinum metal to platinum ions (Pt 2+ or Pt 4+), and the smaller the platinum particles, the larger the reaction surface area, the faster the oxidation rate, and the higher the rate of platinum ion formation. Therefore, the use of platinum black and platinum powder significantly accelerates the dissolution process of platinum, avoiding problems such as over-dissolution conditions or solution instability caused by slow reactions.

[0015] Preferably, the concentration of the concentrated nitric acid is 12M - 14M.

[0016] The nitrate ion (NO3 - ) in nitric acid is the main oxidant for the dissolution of platinum metal. Under the condition of high-concentration nitric acid (12M - 14M), the nitrate ion can provide sufficient oxidation ability to oxidize platinum metal into platinum ions (Pt 2+ or Pt 4+ ). The specific reaction mechanism is as follows: Pt + 4HNO3 → Pt(NO3)2 + 2H2O + 2NO2 In this process, platinum metal is oxidized into platinum ions by nitric acid, and the nitrate ion is also involved in the formation of nitrogen dioxide (NO2) gas at the same time. The oxidant provided by concentrated nitric acid can quickly oxidize platinum metal, and the dissolution rate and efficiency can be controlled by adjusting the concentration of nitric acid. When the nitric acid concentration is between 12M - 14M, the dissolution reaction can proceed smoothly without being too slow due to too low a concentration.

[0017] However, too high a nitric acid concentration will trigger some side reactions, such as the excessive precipitation of NO2 gas, affecting the stability of the solution. Therefore, the concentration range of 12M - 14M can provide sufficient oxidation ability while maintaining a stable reaction environment, avoiding side reactions, and making the dissolution of platinum more efficient and controllable. Nitric acid in this concentration range can ensure that the oxidation process of platinum metal is neither too fast to cause platinum reduction precipitation nor too slow to affect the yield.

[0018] Preferably, the concentration of the ammonium chloride solution is 0.5M - 2.0M.

[0019] The role of the ammonium chloride solution is mainly reflected in the chloride ions it provides. Within this concentration range, ammonium chloride can effectively coordinate with platinum ions to form a [PtCl4] 2- complex, and this complex can stabilize the oxidation state of platinum ions, preventing them from being reduced to metallic platinum or forming insoluble platinum precipitates. The specific mechanism is that when platinum metal is oxidized by nitric acid to form platinum ions, chloride ions combine with platinum ions through coordination to form a stable complex, which not only prevents the reduction precipitation of platinum but also improves the solubility of platinum ions and the stability of the solution.

[0020] In the concentration range of 0.5M to 2.0M, the chloride ion concentration provided by ammonium chloride is high enough to effectively stabilize the oxidation state of platinum ions and will not overly affect the equilibrium of the reaction system. When the concentration is too low, the coordination effect of chloride ions is insufficient, leading to the re-reduction of platinum ions. When the concentration is too high, excessive complexes will be generated, thus affecting the dissolution rate. Therefore, the ammonium chloride concentration of 0.5M to 2.0M can not only ensure the stability of platinum ions but also optimize the dissolution process of platinum, enabling it to dissolve efficiently under appropriate conditions.

[0021] Through this coordination effect, the ammonium chloride solution not only helps maintain a high concentration of platinum ions in the solution but also prevents unwanted reduction reactions, ensuring the high purity of the platinum solution and the efficiency of the reaction. This mechanism is consistent with the dissolution efficiency and stability required by the present invention, further optimizing the preparation process of platinum nitrate solution.

[0022] Preferably, the concentration of the copper chloride solution is 0.02M to 0.1M.

[0023] Copper ions (Cu 2+ ) in the copper chloride solution play a crucial role in the reaction. Through the interaction with platinum ions, copper ions can effectively stabilize the oxidation state of platinum ions and prevent the reduction reaction of platinum ions in the solution. After platinum metal reacts with nitric acid to form platinum ions, copper ions in copper chloride will reduce the chance of platinum ions being reduced to metallic platinum through a coordination reaction with platinum ions, thus effectively improving the stability of the solution.

[0024] In the copper chloride solution with a concentration of 0.02M to 0.1M, the concentration of copper ions is low enough to prevent excessive complexation while controlling the reaction rate. Copper ions coordinate with platinum ions to form platinum-copper complexes or stabilize the oxidation state of platinum ions through their electronic effects, reducing the precipitation and reduction processes of platinum metal. The lower concentration of copper chloride effectively avoids the influence of excessive copper ions on the solution while maintaining the dissolution stability of platinum metal.

[0025] The copper chloride solution within this concentration range not only enhances the stability of the platinum solution but also ensures the efficient dissolution of platinum metal and reduces the occurrence of side reactions to a certain extent. Through this mechanism, the present invention can effectively improve the dissolution efficiency of platinum and avoid the problem of reduction precipitation of platinum metal during the dissolution process with traditional high-concentration nitric acid.

[0026] Preferably, the catalyst is palladium powder or copper powder, the mass of the catalyst is 1% to 5% of the mass of platinum metal, and the particle size of the catalyst particles is 50μm to 100μm.

[0027] Palladium powder and copper powder are used as catalysts. Their main function is to increase the reaction surface area, provide more active sites, enabling platinum metal to react with nitric acid more rapidly. These metal catalysts can change the electronic state on the surface of platinum metal, lower the dissolution activation energy of platinum metal, thereby accelerating the oxidation process of platinum. Specifically, the metal surfaces of palladium and copper can interact with platinum metal, promoting the reaction of platinum with the oxidant in nitric acid to generate platinum ions. In this process, the catalyst not only improves the reaction efficiency but also prevents the reduction precipitation of platinum metal due to slow dissolution.

[0028] The particle size of the catalyst particles is controlled within the range of 50μm to 100μm. This particle size ensures the reaction activity and uniform distribution of the catalyst. Too small particles lead to excessive participation of the catalyst in the reaction, thereby affecting the reaction equilibrium, while too large particles cannot provide sufficient reaction surface, thus limiting the reaction efficiency. Within the range of 50μm to 100μm, the catalyst can maintain high catalytic activity and can be evenly distributed during the dissolution process, promoting the dissolution of platinum metal.

[0029] Preferably, the reaction temperature is controlled at 120°C, and the reaction pressure is 0.1MPa to 0.2MPa. During the reaction process, the reaction pressure is maintained stable by a pressure control device.

[0030] The reaction temperature and reaction pressure play a crucial role in the dissolution process of platinum metal. When the temperature is too low, the reaction rate is slow, and the dissolution efficiency of platinum metal is low. A reaction temperature of 120°C can not only provide sufficient oxidation energy to accelerate the oxidation reaction of platinum but also avoid side reactions (reduction precipitation of platinum ions or re-precipitation of platinum metal) caused by too high temperature. At this temperature, NO 3- ions in nitric acid can effectively oxidize platinum metal to generate platinum ions and moderately precipitate NO2 gas without excessive precipitation, ensuring the stability of the solution.

[0031] The control of the reaction pressure is equally crucial. Within the range of 0.1MPa to 0.2MPa, an appropriate pressure can increase the gas solubility in the reaction system, especially for the generated NO2 gas, and can avoid its excessive escape. The excessive precipitation of NO2 will affect the acidity of the solution and lead to incomplete dissolution of platinum metal. While controlling the pressure within the range of 0.1MPa to 0.2MPa helps to dissolve NO2, ensures the stability of platinum ions in the solution, and avoids the occurrence of side reactions. In addition, a stable reaction pressure can also improve the controllability of the reaction and avoid unstable dissolution efficiency caused by pressure fluctuations.

[0032] Preferably, the reaction time is controlled within 30 minutes to 45 minutes.

[0033] Reaction time plays a crucial role in the dissolution process of platinum. A short reaction time results in insufficient oxidation of platinum metal by nitric acid, a slow generation rate of platinum ions, and low dissolution efficiency. In the initial stage of the reaction, the oxidant in nitric acid can effectively oxidize platinum metal. However, if the reaction time is too short, the dissolution process is not fully carried out, leading to incomplete conversion of platinum metal into platinum ions.

[0034] As time extends, platinum metal gradually dissolves, and the concentration of platinum ions continuously increases. When the reaction continues for more than a certain time (45 minutes), the reaction rate begins to level off, and the dissolution of platinum metal approaches completion. During this process, the precipitation of NO2 gas affects the stability of the solution. An overly long reaction time also causes the reduction of platinum ions to metallic platinum precipitation or other unstable situations in the solution. Therefore, a reaction time of 30 to 45 minutes can ensure the end of the reaction on the premise of complete dissolution of platinum metal and effectively prevent side reactions from occurring, ensuring the stability of the solution.

[0035] Preferably, after the reaction ends, the pH value of the obtained solution is further adjusted to 4.5 - 5.5 with ammonia water, and centrifugation separation technology is used to remove trace impurities in the solution.

[0036] Adjusting the pH value of the solution to 4.5 - 5.5 with ammonia water is a key step to ensure the stable existence of platinum ions in the solution. Platinum ions are prone to reducing into metallic platinum precipitation in an acidic environment (low pH value), which affects the purity of the solution. By adding ammonia water and adjusting the solution to an appropriate weakly acidic or neutral range, the stable state of platinum ions can be effectively maintained, and their reduction to platinum metal or precipitation can be avoided. In addition, the addition of ammonia water can also neutralize the excessive acidic substances in the solution, reducing the impact on the stability of platinum ions.

[0037] During the centrifugation separation process, trace impurities, unreacted solid substances, and catalyst particles in the solution will precipitate to the bottom of the test tube due to density differences. The centrifugation technology accelerates through rotation, separating these impurities from the solution to obtain a purer platinum nitrate solution. Centrifugation separation can not only remove larger particle impurities but also effectively remove the tiny solid particles generated due to the use of the catalyst, thereby improving the purity of the solution.

[0038] Preferably, after the reaction ends, the catalyst and unreacted substances are removed by filtration through filter paper or a filter screen to obtain a clear platinum nitrate solution with a volume of 250 mL to 500 mL, and a microfiltration membrane is used for fine filtration during the filtration process.

[0039] After the reaction is completed, the dissolution of platinum metal will produce some unreacted solid substances and catalyst particles, which have a negative impact on the purity and stability of the solution. Coarse filtration through filter paper or a filter screen can remove these larger particulate matters, but these traditional filtration methods have limited effectiveness in removing tiny particles. Therefore, the present invention uses a microfiltration membrane for fine filtration. Its pore size is usually less than 1 μm, which can effectively remove tiny impurities and residual catalyst particles in the solution.

[0040] The function of the microfiltration membrane is to utilize the physical sieving effect of the membrane. Through its fine pore size, impurities or undissolved substances (catalyst particles, residues from incomplete reactions) with larger particle sizes in the solution are filtered out. In this way, a more pure and stable platinum nitrate solution can be obtained, avoiding the influence of impurities in the solution on the stability of platinum ions, thereby reducing precipitation and reduction reactions.

[0041] The present invention provides a method for preparing a platinum nitrate solution. It has the following beneficial effects: 1. The present invention adopts the technical scheme of heterogeneous catalysis and precise formulation, achieving the effect of efficiently dissolving platinum metal and maintaining the stability of the solution. Compared with the common high-temperature and high-concentration nitric acid dissolution methods in the prior art, the present invention solves the problems of overly violent reactions and reduction precipitation of platinum ions by optimizing the use of catalysts and the control of the dissolution process.

[0042] 2. The present invention adds copper chloride and ammonium chloride as formulating agents and stabilizers during the dissolution process, achieving the technical effect of preventing the reduction precipitation of platinum ions. Different from the traditional methods for preparing platinum nitrate solutions, the existing methods are easily interfered by impurities. The present invention effectively avoids the pollution of the solution by impurities by stabilizing platinum ions, ensuring the high purity of the product.

[0043] 3. The present invention realizes the efficient preparation of platinum nitrate solution by precisely controlling the reaction temperature and pressure. Compared with the prior art processes with unstable reaction conditions, the present invention solves the technical bottlenecks of low platinum dissolution efficiency and incomplete reactions during the reaction process through precise regulation of temperature and pressure, significantly improving the yield.

[0044] 4. The present invention uses a microfiltration membrane for fine filtration in the post-reaction treatment stage, effectively removing impurities and unreacted substances in the solution. Different from the traditional methods that only use simple filtration or centrifugal separation, the fine filtration technology of the present invention further improves the purity and stability of the platinum nitrate solution, reducing precipitation problems during subsequent use. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic flow chart of the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0046] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0047] Example 1: Preparation of platinum nitrate solution under standard reaction conditions.

[0048] Steps: Add 1.5 g of platinum black into the reaction kettle.

[0049] Add 40 mL of concentrated nitric acid (concentration 12 M) into the reaction kettle.

[0050] Add 10 mL of ammonium chloride solution (concentration 1 M) as a complexing agent.

[0051] Add 5 mL of copper chloride solution (concentration 0.05 M) as a stabilizer.

[0052] Heat the reaction kettle to 120 °C and maintain the reaction pressure at 0.15 MPa.

[0053] React under this condition for 30 minutes and observe the dissolution during the reaction process.

[0054] After the reaction is completed, cool the reaction solution to room temperature and filter to remove unreacted substances and catalysts.

[0055] Adjust the pH of the solution to 4.8 using ammonia water, and then perform fine filtration through a microfiltration membrane to obtain a clear platinum nitrate solution.

[0056] Example 2: Low reaction temperature conditions for efficient dissolution of platinum metal.

[0057] Steps: Take 1 g of platinum powder and add it to the reaction vessel.

[0058] Add 15 mL of concentrated nitric acid (concentration 13 M) into the container.

[0059] Add 5 mL of ammonium chloride solution (concentration 1.5 M) as a complexing agent.

[0060] Add 3 mL of copper chloride solution (concentration 0.02 M) as a stabilizer.

[0061] Set the reaction temperature to 100 °C and keep the reaction pressure at 0.12 MPa.

[0062] React under this condition for 50 minutes and monitor the dissolution process in real time.

[0063] After the reaction is completed, quickly cool the reaction solution and filter off the catalyst.

[0064] Use centrifugation to remove trace impurities in the solution, and finally obtain a high-purity platinum nitrate solution.

[0065] Example 3: Rapid dissolution with optimized temperature and pressure.

[0066] Steps: Add 2.0 g of platinum black to a 500 mL reaction kettle.

[0067] Add 50 mL of concentrated nitric acid (concentration 12 M).

[0068] Add 20 mL of ammonium chloride solution (concentration 2 M) to the reaction kettle.

[0069] Add 10 mL of copper chloride solution (concentration 0.1 M) as a stabilizer.

[0070] Adjust the reaction temperature to 130 °C and the pressure to 0.18 MPa.

[0071] Under these conditions, the reaction lasts for 40 minutes.

[0072] After the reaction is completed, cool the solution to room temperature and filter off the catalyst.

[0073] Use a microfiltration membrane to finely filter the solution, and finally obtain a pure platinum nitrate solution.

[0074] Example 4: Catalytic effect under low-temperature conditions.

[0075] Steps: Weigh 1.8 g of platinum powder and add it to the reaction kettle.

[0076] Add 25 mL of concentrated nitric acid (concentration 12 M).

[0077] Add 8 mL of ammonium chloride solution (concentration 1 M) as a complexing agent.

[0078] Add 4 mL of copper chloride solution (concentration 0.03 M) as a stabilizer.

[0079] Set the reaction temperature to 110 °C and control the reaction pressure at 0.14 MPa.

[0080] The reaction duration is 35 minutes, and the catalyst is added at the start of the reaction.

[0081] After the reaction ends, cool the reaction solution and use filter paper to filter off the catalyst and impurities.

[0082] Adjust the pH value of the solution to 4.7 with ammonia water to obtain a high-purity platinum nitrate solution.

[0083] Example 5: Enhanced dissolution efficiency with high-concentration ammonium chloride.

[0084] Steps: Add 2.5 g of platinum black to the reaction vessel.

[0085] Add 60 mL of concentrated nitric acid (concentration 13 M).

[0086] Prepare 10 mL of ammonium chloride solution (concentration 2.0 M) and add it as a reagent.

[0087] Add 7 mL of copper chloride solution (concentration 0.05 M) as a stabilizer.

[0088] Set the reaction temperature to 125 °C and the pressure to 0.16 MPa.

[0089] React for 45 minutes under these conditions to ensure complete dissolution of the platinum metal.

[0090] After the reaction, cool to room temperature and filter to remove the catalyst and impurities.

[0091] Further filter the solution using a fine filter membrane to obtain a pure platinum nitrate solution.

[0092] Comparative Example 1: Traditional high-temperature and high-concentration nitric acid dissolution method.

[0093] Steps: Add 1.5 g of platinum black to the reaction vessel.

[0094] Add 40 mL of concentrated nitric acid (concentration 14 M) to the vessel.

[0095] Do not add any reagents or stabilizers.

[0096] Set the reaction temperature to 150 °C and control the reaction pressure at atmospheric pressure.

[0097] The reaction time is 60 minutes, and no catalyst is added during the reaction.

[0098] After the reaction, cool to room temperature and filter using ordinary filter paper to remove the unreacted substances.

[0099] Adjust the pH of the solution to 4.5 by simple ammonia water to obtain a platinum nitrate solution.

[0100] Comparative Example 2: Dissolution method using a single reagent.

[0101] Steps: Take 1 g of platinum powder and add it to the reaction kettle.

[0102] Add 30 mL of concentrated nitric acid (concentration 12 M) to the reaction kettle.

[0103] Only 10 mL of ammonium chloride solution (concentration 1 M) was added as a reagent, and no stabilizer was used.

[0104] The reaction temperature was set at 120 °C, and the reaction pressure was maintained at 0.15 MPa.

[0105] The reaction time was set to 40 minutes.

[0106] After the reaction, it was cooled to room temperature, and the catalyst and impurities were removed by filtration.

[0107] The pH value of the solution was adjusted to 4.8 to obtain a platinum nitrate solution.

[0108] Comparative Example 3: A reaction without temperature and pressure control.

[0109] Steps: 2 g of platinum black was added to the reaction vessel.

[0110] 50 mL of concentrated nitric acid (concentration 13 M) was added to the vessel.

[0111] 5 mL of ammonium chloride solution (concentration 1.5 M) was added as a reagent, but no copper chloride was added as a stabilizer.

[0112] The reaction temperature was not controlled, and the reaction was carried out at room temperature (ambient temperature), and the reaction pressure was set at atmospheric pressure.

[0113] The reaction time was set to 60 minutes.

[0114] After the reaction, it was cooled to room temperature, and the catalyst and unreacted substances were removed by filtration using ordinary filter paper.

[0115] The pH value of the solution was adjusted to 4.7 to finally obtain a platinum nitrate solution.

[0116] Comparative Example 4: A reaction method without fine filtration.

[0117] Steps: 2 g of platinum powder was taken and added to the reaction vessel.

[0118] 40 mL of concentrated nitric acid (concentration 12 M) was added to the vessel.

[0119] 10 mL of ammonium chloride solution (concentration 2 M) was added as a reagent, and at the same time, 10 mL of copper chloride solution (concentration 0.05 M) was added as a stabilizer.

[0120] The reaction temperature was set at 120 °C, the reaction pressure was 0.18 MPa, and the reaction continued for 45 minutes.

[0121] After the reaction, it was cooled to room temperature, and the catalyst and impurities were removed by filtration using ordinary filter paper.

[0122] Adjust the pH value of the solution to 4.6, and directly obtain the solution without further fine filtration.

[0123] Comparative Example 5: A reaction method with an excessively low dosage of the traditional catalyst.

[0124] Steps: Take 1.8 g of platinum black and add it to the reaction vessel.

[0125] Add 45 mL of concentrated nitric acid (concentration 12 M) to the vessel.

[0126] Add 5 mL of ammonium chloride solution (concentration 1 M) as a complexing agent and 5 mL of copper chloride solution (concentration 0.02 M) as a stabilizer.

[0127] Set the reaction temperature at 130 °C, maintain the reaction pressure at 0.17 MPa, and set the reaction time at 50 minutes.

[0128] After the reaction, cool to room temperature and filter off the catalyst using ordinary filter paper.

[0129] Adjust the pH of the solution to 4.8 using ammonia water to obtain a platinum nitrate solution.

[0130] Experiment 1: Comparison of platinum dissolution efficiency (temperature comparison) The experimental steps are as follows: Preparation of reactants: Take 1.5 g of platinum black and place it in a 250 mL reaction vessel.

[0131] Addition of nitric acid solution: Add 40 mL of concentrated nitric acid (concentration 12 M) to the reaction vessel to ensure that the platinum metal is completely immersed in the solution.

[0132] Addition of complexing agent: Add 10 mL of ammonium chloride solution (concentration 1 M) as a complexing agent and 10 mL of copper chloride solution (concentration 0.05 M) as a stabilizer to the reaction kettle.

[0133] Set temperature and pressure: In Example 1, set the temperature at 120 °C and maintain the reaction pressure at 0.15 MPa; in Comparative Example 1, set the temperature at 150 °C and the reaction pressure at atmospheric pressure.

[0134] Carry out the reaction: Start the reaction. Example 1 reacts for 30 minutes continuously, and Comparative Example 1 reacts for 60 minutes continuously. Record the dissolution situation regularly during the reaction.

[0135] Sampling and dissolution analysis: Take samples every 10 minutes, analyze the dissolved amount of platinum using atomic absorption spectrometry (AAS), and evaluate the dissolution rate.

[0136] Cooling and treatment: After the reaction is completed, quickly cool the solution to room temperature, filter off the unreacted substances through ordinary filter paper. Then, further analyze the platinum concentration in the solution by AAS.

[0137] The experimental data table comparing the finally measured platinum solubility with the reaction temperature is as follows: It can be seen from the experimental data that at a reaction temperature of 120 °C, the solubility of platinum gradually increases, but the reaction rate is slightly slower than that at 150 °C. Under high-temperature conditions, although the solubility increases significantly, due to the too high temperature, side reactions will occur, resulting in a decrease in the stability of some platinum ions in the solution. This phenomenon is related to the dissolution mechanism given previously. At higher temperatures, the oxidation ability provided by nitric acid increases, and the dissolution rate of platinum metal also increases accordingly. However, the too high temperature also leads to the precipitation of NO2 gas, accelerating the reduction and precipitation of platinum, thus affecting the stability of the reaction. For 120 °C, although the reaction is relatively slow, the stability is good, and the solubility of platinum metal remains at a relatively high level.

[0138] In Example 1, due to the more suitable temperature, the platinum metal can continuously dissolve, and the reaction process is relatively stable. Therefore, within the same time, the solubility does not show the problems caused by unstable or too fast reactions. On the contrary, in Comparative Example 1, although the dissolution rate is fast, the occurrence of side reactions will make the final dissolution effect of platinum metal relatively unstable, and even precipitation will occur in the subsequent process. Generally speaking, the reaction temperature of 120 °C provides a relatively balanced dissolution condition, avoiding the side effects caused by too high temperature.

[0139] This experiment not only reveals the dual effects of temperature on the reaction rate and dissolution efficiency, but also shows that at lower temperatures, the reaction can better control side reactions and maintain the stability of the solution. This result is consistent with the temperature optimization scheme proposed in the present invention, indicating that 120 °C can provide sufficient oxidation ability during the platinum dissolution process and effectively avoid side reactions caused by too high temperature, thus achieving high efficiency and stability in platinum dissolution.

[0140] Experiment 2: Comparison of reaction pressure: Experimental procedure: Prepare reactants: Take 2 g of platinum black and place it in a 500 mL reaction vessel.

[0141] Add concentrated nitric acid: Add 50 mL of concentrated nitric acid (concentration 13 M) to the reaction vessel.

[0142] Add complexing agent and stabilizer: Add 20 mL of ammonium chloride solution (concentration 1.5 M) and add 10 mL of copper chloride solution (concentration 0.05 M).

[0143] Temperature and pressure setting: In Example 3, the temperature is set to 130 °C and the reaction pressure is 0.18 MPa; in Comparative Example 3, the temperature is set to 130 °C and the reaction pressure is normal pressure (1 atm).

[0144] Reaction time: The reaction time was set to 40 minutes (Example 3) and 60 minutes (Comparative Example 3) to observe the effect of pressure difference on the dissolution efficiency.

[0145] Sampling and analysis: Samples were taken every 10 minutes during the reaction, and the solubility of platinum was detected using atomic absorption spectroscopy (AAS).

[0146] Cooling and treatment: After the reaction, it was quickly cooled to room temperature, and the catalyst and unreacted substances were removed by filtration.

[0147] Determination of platinum solubility: The concentration of platinum in the solution was measured by AAS to calculate the dissolution efficiency.

[0148] The experimental data table of the effect of the finally measured reaction pressure on the solubility of platinum is shown as follows: The experimental data shows that the reaction pressure has a significant effect on the dissolution efficiency of platinum. In Example 3, the reaction pressure of 0.18 MPa significantly increased the solubility of platinum, and the dissolution rate was faster than that under atmospheric pressure conditions. At higher pressures, the oxidation ability of nitric acid was further enhanced, and the dissolution rate of platinum metal increased significantly. This phenomenon is consistent with the reaction mechanism given previously. The increase in reaction temperature and pressure accelerates the oxidation process of platinum metal, generates platinum ions and promotes their dissolution, while the increased pressure helps to keep the generated NO2 gas dissolved in the reaction system and prevents its escape, thus ensuring the stable existence of platinum ions.

[0149] Compared with the atmospheric pressure condition in Comparative Experiment 3, the solubility of platinum is lower and the reaction process is relatively slower. This indicates that the release of gas and side reactions under atmospheric pressure reduce the dissolution efficiency of platinum and also result in unstable concentration of platinum ions in the solution. By applying pressure, the nitrogen oxides in the reaction environment are inhibited, and thus the dissolution effect of platinum is improved. This further proves the coupling effect of temperature and pressure in the reaction, and the efficient progress of the dissolution reaction can be promoted by appropriate pressurization.

[0150] From a mechanistic perspective, a higher reaction pressure effectively promotes the reaction between platinum metal and nitric acid. Especially in the process of oxidizing platinum, the reaction pressure provides a higher solubility for NO2 gas in the solution, thus avoiding the side reaction of platinum reduction. This means that under pressurized conditions, the oxidation rate of platinum metal increases, the concentration of platinum ions is more stable, and the overall reaction process is more efficient. This discovery fully verifies that carrying out the dissolution reaction under high-pressure conditions can significantly improve the dissolution efficiency of platinum and improve the controllability of the reaction.

[0151] Experiment 3: Comparison of catalyst usage: Experimental procedure: Preparation of platinum metal: Take 2 g of platinum black and add it to the reaction vessel.

[0152] Preparation of nitric acid solution: Add 45 mL of concentrated nitric acid (concentration 12 M) to the reaction vessel to completely immerse the platinum metal.

[0153] Addition of complexing agent and stabilizer: Example 4: Add 10 mL of ammonium chloride solution (concentration 1.5 M) as the complexing agent and 5 mL of copper chloride solution (concentration 0.05 M) as the stabilizer.

[0154] Comparative Example 5: Only add 10 mL of ammonium chloride solution, without copper chloride solution as the stabilizer.

[0155] Set reaction conditions: The temperature is set at 120 °C, and the reaction pressure is maintained at 0.15 MPa. The reaction time is 40 minutes.

[0156] Sampling and analysis: Sample every 10 minutes and analyze the platinum concentration in the solution using atomic absorption spectroscopy (AAS).

[0157] End and treatment: After the reaction is completed, cool to room temperature and filter using ordinary filter paper to remove the catalyst and unreacted substances. Further analyze the solubility of platinum and the impurity level of the obtained solution using AAS.

[0158] The experimental data table of the influence of the finally measured catalyst on the platinum dissolution rate is shown as follows: Judging from the experimental results, adding copper chloride as a stabilizer significantly improves the dissolution efficiency of platinum. In Example 4, the addition of copper chloride accelerates the platinum dissolution process and reaches a relatively high platinum concentration in a shorter time. In contrast, the platinum dissolution efficiency in Comparative Example 5 is lower and the dissolution rate is significantly slowed down. This is consistent with the mechanism explanation given before. Copper chloride as a stabilizer can prevent the reduction precipitation of platinum ions, maintain the stable existence of platinum in the solution, and avoid the precipitation and reduction reactions that platinum undergoes under conventional reaction conditions, thereby increasing the solubility of platinum.

[0159] Mechanistically, copper chloride forms a complex with platinum ions, stabilizes the oxidation state of platinum, and reduces the reduction phenomenon of platinum metal. Platinum metal undergoes a coordination reaction with copper ions in the copper chloride solution to form a soluble complex, thereby increasing the platinum dissolution rate. This effect is not manifested when copper chloride is not added in Comparative Example 5, where the reaction rate is slower and the platinum solubility is much lower than that in Experiment 4.

[0160] It should be noted that although copper chloride helps to increase the solubility of platinum, an excessive amount of copper chloride will also cause the generation of copper ions in the solution, which will affect the subsequent reactions or product purity. Therefore, precisely controlling the addition amount of copper chloride is crucial for ensuring the stability and purity of the platinum solution. From a mechanistic perspective, an appropriate amount of copper chloride can effectively promote the dissolution reaction and accelerate the dissolution of platinum while preventing side reactions.

[0161] Experiment 4: Comparison of post-treatment steps: Experimental procedure: Preparation of platinum metal: Take 2 g of platinum powder and add it to a 500 mL reaction vessel.

[0162] Add concentrated nitric acid: Add 50 mL of concentrated nitric acid (concentration 13 M) to the vessel to ensure that the platinum powder is completely immersed.

[0163] Add complexing agent and stabilizer: Add 20 mL of ammonium chloride solution (concentration 1.5 M), and add 10 mL of copper chloride solution (concentration 0.05 M) as a stabilizer.

[0164] Set reaction conditions: Set the reaction temperature to 120 °C, maintain the reaction pressure at 0.15 MPa, and set the reaction time to 40 minutes.

[0165] Sampling and analysis: Take samples every 10 minutes and analyze the platinum solubility using atomic absorption spectroscopy (AAS).

[0166] Filtration step: Example 2: After the reaction is completed, cool the solution to room temperature and perform fine filtration using a microfiltration membrane to ensure better solution purity.

[0167] Comparative example 2: After the reaction ends, also cool to room temperature, but only filter using ordinary filter paper without performing fine filtration.

[0168] Determination of platinum solubility: Determine the platinum solubility by AAS and compare the effects of fine filtration and ordinary filtration on solution purity.

[0169] The experimental data table of the influence of fine filtration on platinum solubility finally measured is as follows: According to the experimental data, using a microfiltration membrane to filter the solution in Example 2 significantly improved the platinum solubility and solution purity. In contrast, the filtration effect of using ordinary filter paper in Comparative example 2 was poor, with relatively low solubility and more impurities remaining in the solution. The microfiltration membrane can effectively remove smaller particulate impurities during the filtration process, which is consistent with the aforementioned dissolution mechanism. As the impurities in the solution are removed, the solubility of the platinum metal is increased, and the platinum ions maintain a high stability.

[0170] From a mechanistic perspective, the microfiltration membrane can prevent tiny impurities and incompletely reacted platinum particles from entering the solution through its relatively small pore size filtration effect. This process reduces the influence of non-platinum substances in the solution, ensures the stability of platinum ions, and avoids the reduction phenomenon of unstable platinum ions in the solution. The filtration effect of ordinary filter paper is poor and it cannot effectively remove tiny impurities and insoluble substances, so the dissolution efficiency of platinum metal is relatively low.

[0171] This experiment verified the influence of the purity of the solution on the dissolution of platinum metal. Through fine filtration, platinum ions can be better stabilized in the solution, reducing the reduction precipitation caused by impurity interference. Overall, the microfiltration membrane provides higher filtration accuracy, significantly improves the dissolution efficiency, and ensures the quality of the solution.

[0172] Experiment 5: Reaction time comparison: Experimental procedure: Prepare reactants: Take 2 g of platinum black and add it to a 500 mL reaction vessel.

[0173] Add concentrated nitric acid: Add 50 mL of concentrated nitric acid (concentration 13 M) to the reaction vessel to ensure that the platinum metal is completely immersed.

[0174] Add complexing agent and stabilizer: Add 20 mL of ammonium chloride solution (concentration 1.5 M) to the reaction kettle, and add 10 mL of copper chloride solution (concentration 0.05 M) as a stabilizer.

[0175] Set reaction conditions: Set the reaction temperature to 125 °C and keep the reaction pressure at 0.16 MPa.

[0176] Reaction time comparison: Example 5: Set the reaction time to 45 minutes.

[0177] Comparative example 4: Set the reaction time to 60 minutes.

[0178] Sampling and analysis: Take samples every 10 minutes and analyze the platinum solubility using atomic absorption spectrometry (AAS).

[0179] Cooling and treatment: After the reaction, quickly cool to room temperature and use ordinary filter paper to filter out unreacted substances.

[0180] Determination of platinum solubility: Determine the platinum concentration in the solution by AAS to evaluate the dissolution efficiency.

[0181] The experimental data table of the influence of the finally measured reaction time on platinum solubility is shown as follows: The experimental data reveals a significant effect of reaction time on the dissolution efficiency of platinum. At a reaction time of 45 minutes, the platinum solubility in Example 5 is significantly higher than that in Comparative Example 4. Although the reaction time in Comparative Example 4 is longer, the solubility of platinum does not ultimately reach the level of Example 5 because the rate of the dissolution reaction begins to gradually slow down. The experimental results show that a longer reaction time does not always lead to a higher dissolution efficiency. An overly long reaction time causes the dissolution rate of platinum to gradually level off, while within a shorter time of 45 minutes, the reaction already achieves a relatively high platinum solubility.

[0182] From a mechanistic perspective, at the initial stage of the reaction, the oxidizing ability provided by nitric acid can rapidly dissolve platinum metal, generating platinum ions and releasing NO2 gas. Within 45 minutes, the dissolution process of platinum proceeds rapidly. As time extends, the concentration of platinum ions in the solution gradually reaches an equilibrium state. After a certain time, the dissolution rate decreases, and the release of NO2 gas affects the stability of the solution, causing platinum ions to be reduced back to platinum metal precipitate. Therefore, the best dissolution effect can be achieved within an appropriate reaction time.

[0183] In contrast, although the reaction time of 60 minutes is longer, the dissolution rate of platinum metal has already started to slow down, resulting in a less significant increase in solubility compared to Example 5. The reaction kinetics during the dissolution process is more efficient within a certain time. An overly long time leads to the occurrence of other side reactions during the dissolution process, thereby affecting the stability and dissolution efficiency of platinum. Therefore, within an appropriate reaction time (45 minutes), the dissolution effect of platinum metal is the best, which can avoid unnecessary side effects and time waste.

[0184] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a platinum nitrate solution, characterized in that, It includes the following steps: S1. React platinum metal with concentrated nitric acid to form platinum ions; S2. Add ammonium chloride solution as a complexing agent to control the oxidation state of platinum ions; S3. Add copper chloride solution as a stabilizer to prevent the reduction and precipitation of platinum ions; S4. Add a catalyst during the reaction. The catalyst is palladium powder or copper powder, and its mass is 1% - 5% of the mass of platinum metal; S5. Control the reaction temperature at 100°C - 150°C and maintain the reaction pressure at 0.1 MPa - 0.2 MPa; S6. After the reaction, cool the reaction solution, filter to remove the catalyst and unreacted substances to obtain a platinum nitrate solution.

2. The preparation method of a platinum nitrate solution according to claim 1, characterized in that, The platinum metal is platinum black or platinum powder, and its mass is 0.5 g - 5.0 g.

3. A method for preparing a platinum nitrate solution according to claim 1, characterized in that, The concentration of the concentrated nitric acid is 12 M - 14 M.

4. The preparation method of a platinum nitrate solution according to claim 1, wherein, The concentration of the ammonium chloride solution is 0.5 M - 2.0 M.

5. A method for preparing a platinum nitrate solution according to claim 1, characterized in that, The concentration of the copper chloride solution is 0.02 M - 0.1 M.

6. The preparation method of a platinum nitrate solution according to claim 1, characterized in that, The catalyst is palladium powder or copper powder. The mass of the catalyst is 1% - 5% of the mass of platinum metal, and the particle size of the catalyst is 50 μm - 100 μm.

7. A method for preparing a platinum nitrate solution according to claim 1, characterized in that, The reaction temperature is controlled at 120°C, and the reaction pressure is 0.1 MPa - 0.2 MPa. During the reaction, the reaction pressure is maintained stable by a pressure control device.

8. A method for preparing a platinum nitrate solution according to claim 1, characterized in that, The reaction time is controlled within 30 minutes to 45 minutes.

9. A method for preparing a platinum nitrate solution according to claim 1, characterized in that, After the reaction, further adjust the pH value of the obtained solution to 4.5 - 5.5 with ammonia water, and use centrifugal separation technology to remove trace impurities in the solution.

10. The preparation method of a platinum nitrate solution according to claim 1, wherein, After the reaction, filter to remove the catalyst and unreacted substances through filter paper or a filter screen to obtain a clear platinum nitrate solution. The volume of the solution is 250 mL to 500 mL, and a microfiltration membrane is used for fine filtration during the filtration process.

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