Preparation method of platinum oxide powder

Abstract

The invention relates to a preparation method of platinum oxide powder, which comprises the following steps: uniformly mixing platinum powder with a polymeric dispersant polyvinylpyrrolidone (PVP), treating at 600-1000 DEG C, thermally decomposing the PVP in the high-temperature treatment process to generate oxygen active free radicals, and oxidizing high-temperature active platinum particles into platinum oxide. Platinum oxide powder is prepared by controlling the temperature and adjusting the dispersion and mixing state of platinum powder and PVP. According to the method, the platinum oxide powder is directly prepared from the platinum powder, and the method has the advantages of being short in working procedure and simple in process.

Description

Technical Field

[0001] The invention belongs to the technical field of metal powder materials, and in particular relates to a method for preparing platinum oxide powder. Background Art

[0002] Platinum oxide powder, as a high-performance hydrogenation catalyst, excellent hydrogen absorption material, high-temperature structural material and key material for electronic paste, plays an important role in automobile exhaust purification, chemical synthesis, fuel cell electrodes and aerospace high-temperature resistant components.

[0003] Platinum is chemically stable, making it difficult to directly oxidize it to produce platinum oxide. Currently, a high-temperature melting method is commonly used to prepare platinum oxide, in which chloroplatinate and sodium nitrate are melted at 500°C. While this method is simple and suitable for mass production, it suffers from long melting times, high energy consumption, and the release of large amounts of nitrogen oxides during the reaction, posing new challenges to production safety and environmental protection. Furthermore, the platinum oxide particles generated during the melting process are highly reactive and prone to agglomeration upon contact between particles, necessitating subsequent ball milling and grading. The liquid-phase method involves boiling an aqueous solution of platinum chloride in an alkaline solution and then adding acetic acid to produce a platinum oxide colloid. Alternatively, chloroplatinic acid is converted to platinum hydroxide, which is dispersed in highly substituted hydroxypropyl cellulose to form a gel. The dry gel is then ultrasonically washed in an ethanol solution, where the heat generated by the ultrasound converts the platinum hydroxide to platinum oxide. The liquid-phase method for preparing platinum oxide involves numerous processing steps and produces large amounts of wastewater. Residual chemical reagents affect the properties of platinum oxide, limiting its mass production and polluting the environment. Summary of the Invention

[0004] The present invention aims to provide a method for preparing platinum oxide powder, which directly uses platinum powder to prepare platinum oxide powder and has the advantages of short process and simple technology.

[0005] The technical solution of the present invention is to uniformly mix platinum powder with a polymer dispersant, polyvinylpyrrolidone (PVP), and treat it at a temperature range of 600-1000°C. During the high-temperature treatment, the PVP thermally decomposes to produce oxygen-active free radicals, which oxidize the high-temperature active platinum particles into platinum oxide. Platinum oxide powder is prepared by controlling the temperature and adjusting the dispersed mixing state of the platinum powder and PVP. The specific preparation method of the method of the present invention includes the following steps:

[0006] 1) Mixing platinum powder, PVP and CaO uniformly to obtain a uniform mixed powder;

[0007] 2) The mixed powder obtained in step 1) is treated at a temperature of 600-1000° C., cooled to room temperature, and then added to dilute acid to remove CaO;

[0008] The dilute acid is dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid;

[0009] 3) The powder after removing CaO is dried to obtain platinum and platinum oxide powder with a particle size of less than 1.65 μm.

[0010] In step 1), the platinum powder, PVP, and CaO are mixed by dry ball milling or wet ball milling. The dry ball milled mixed powder is directly heated. In the wet ball milling method, ethyl acetate is added in an amount of 1 / 4-1 / 2 of the total mass of the mixed powder, mixed uniformly, and then heated to dry the ethyl acetate dispersant. After volatilization and removal, the heating temperature is 80-100°C for 2-4 hours. The mixed powder is then heated for 2-8 hours at a heating rate of 5-15°C / min. After heating, the mixed powder is cooled to room temperature. If wet ball milling is used, the ethyl acetate must be volatilized before heating. This avoids the loss of precious metal platinum powder caused by rapid volatilization of ethyl acetate and overflow of solid powder due to direct heating. The heating time and heating rate are conducive to the full decomposition of PVP into platinum oxide particles. This is because PVP generates reactive oxygen free radicals during thermal decomposition, which can oxidize platinum particles that are also in a high-temperature active state.

[0011] The ball milling speed is 300-500 rpm, the ball milling time is 1-3 hours, the mass ratio of grinding balls to the mixture is 3:1, and the ball material is agate grinding balls.

[0012] The purpose of using dry ball milling or wet ball milling is to ensure that the platinum powder, PVP and CaO are evenly mixed. In the subsequent heating process, CaO acts as a good physical barrier to prevent the platinum particles from sintering and agglomerating, so that the platinum powder remains in a well-dispersed state and in full contact with the PVP, ensuring that the platinum powder is oxidized by the oxygen active free radicals generated by the thermal decomposition of the PVP, ensuring that the redox reaction occurs evenly.

[0013] In step 1), the mass ratio of the platinum powder, PVP and CaO is 1:(0.05-0.5):(10-20).

[0014] Step 2) The CaO removal method comprises converting the CaO into a water-soluble calcium salt using a dilute acid having a mass concentration of less than 2%, repeatedly washing with deionized water, and precipitating to remove excess acid and the water-soluble calcium salt. Washing is stopped when the pH of the washing solution reaches 7±0.3. The dilute acid reacts with the CaO to form a soluble calcium salt, which is then repeatedly washed with deionized water and precipitated to separate the CaO from the platinum oxide particles.

[0015] Step 3) The drying temperature is 100±5°C and the drying time is 2-4 hours. ， The water in the washed platinum oxide particles can be removed by volatilization.

[0016] The method of the present invention uses platinum powder as a raw material, uniformly mixes the platinum powder with a polymer dispersant, PVP, and heats the mixture at 500-1000°C. The active oxygen free radicals generated by the thermal decomposition of PVP at high temperature oxidize the high-temperature, highly active platinum particles, converting the platinum powder into platinum oxide particles. CaO, which has excellent thermal stability, is added during the mixing process of the platinum powder and PVP. The physical isolation effect of CaO prevents thermal sintering and agglomeration of the platinum powder during the heating process, and the CaO mixes uniformly with the PVP, effectively increasing the contact area between the PVP and the platinum powder, reducing the volatilization rate of the PVP thermal decomposition products, and extending the reaction time between the active free radicals generated by the thermal decomposition of PVP and the platinum particles, thereby achieving more thorough oxidation of the platinum particles and maintaining a well-dispersed state of the prepared platinum oxide particles.

[0017] The reagents described in the present invention are all commercially available products. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 XRD of platinum and platinum oxide powders treated at 600℃;

[0019] Figure 2 The microstructure of platinum and platinum oxide powders treated at 600°C (magnification 10,000 times);

[0020] Figure 3 XRD of platinum and platinum oxide powders treated at 800℃;

[0021] Figure 4 The microstructure of platinum and platinum oxide powders treated at 800°C (magnification 10,000 times);

[0022] Figure 5 XRD of platinum and platinum oxide powders treated at 900℃;

[0023] Figure 6 The microstructure of platinum and platinum oxide powders treated at 900°C (magnification 10,000 times);

[0024] Figure 7 XRD of platinum powder treated at 1000℃;

[0025] Figure 8 This is the microscopic morphology of platinum powder treated at 1000℃ (magnification 10,000 times). DETAILED DESCRIPTION

[0026] Example 1:

[0027] The preparation method of platinum oxide powder specifically comprises the following steps:

[0028] S1. Mix platinum powder and PVP evenly. In order to prevent platinum powder from sintering and agglomerating during high-temperature treatment, mix platinum powder, PVP and CaO evenly. Use ethyl acetate as a dispersing solution to wet-ball-mill the three materials, wherein the mass ratio of platinum powder, PVP and CaO is 1:0.1:10, the amount of ethyl acetate is 1 / 3 of the total amount of the three materials, the ball milling speed is 360 rpm, the ball milling time is 1 h, the mass ratio of grinding balls: platinum powder, PVP and CaO mixture is 3:1 (ball-to-material ratio 3:1), and the ball material is agate grinding balls.

[0029] S2. The wet-mixed materials were volatilized at 80°C to remove ethyl acetate. The mixed powder of platinum powder, PVP, and CaO was subjected to a high-temperature treatment at a temperature range of 600°C. The treatment time was 2 hours, the heating rate was 10°C / min, and the mixed powder was cooled to room temperature in the furnace.

[0030] S3. Add 1% dilute hydrochloric acid to the mixed powder cooled to room temperature to convert CaO into water-soluble CaCl2. Repeatedly wash with deionized water to remove excess hydrochloric acid and CaCl2. Detect the pH of the washing solution at 6.8 and stop washing.

[0031] S4. The powder after removing CaO was dried at 100℃ for 2h to obtain platinum and platinum oxide (CaPt2O4) powder. XRD data showed that CaPt2O4 was obtained after the mixture of platinum powder, PVP and CaO was treated at 600℃. The XRD diffraction peak intensity indicated that the content of platinum oxide (CaPt2O4) was less than that of platinum powder (see Figure 1 ), and there is obvious agglomeration between the powders, and the particle size distribution is less than 0.5μm (see Figure 2 ).

[0032] Example 2:

[0033] The preparation method of platinum oxide powder specifically comprises the following steps:

[0034] S1. Platinum powder and PVP are mixed evenly. To prevent sintering and agglomeration of platinum powder during high-temperature treatment, platinum powder, PVP and CaO are mixed evenly. Platinum powder, PVP and CaO are wet-milled using ethyl acetate as a dispersing solvent. The mass ratio of platinum powder, PVP and CaO is 1:0.1:10, and the amount of ethyl acetate is 1 / 3 of the total amount of the three materials. The ball milling speed is 360 rpm, the ball milling time is 1 h, and the ball-to-material ratio is 3:1. The balls are made of agate grinding balls.

[0035] S2. The wet-mixed materials were volatilized at 80°C to remove ethyl acetate. The mixed powder of platinum powder, PVP, and CaO was subjected to a high-temperature treatment at a temperature range of 800°C for 2 hours at a heating rate of 10°C / min. After treatment, the mixed powder was furnace-cooled to room temperature.

[0036] S3. Add 1% dilute hydrochloric acid to the mixed powder cooled to room temperature to convert CaO into water-soluble CaCl2. Repeatedly wash with deionized water to remove excess hydrochloric acid and CaCl2. Detect the pH of the washing solution at 6.8 and stop washing.

[0037] S4. The powder after removing CaO was dried at 100℃ for 2h to obtain platinum and platinum oxide (CaPt2O4) powder. XRD data showed that the mixture of platinum powder, PVP and CaO was treated at 800℃ to obtain CaPt2O4, in which the content of platinum oxide (CaPt2O4) was higher than that of platinum powder (see Figure 3 ), the powder has various shapes, small particles are agglomerated, and the particle size is less than 1.1 μm (see Figure 4 ).

[0038] Example 3:

[0039] The preparation method of platinum oxide powder specifically comprises the following steps:

[0040] S1. Platinum powder and PVP are mixed evenly. To prevent sintering and agglomeration of platinum powder during high-temperature treatment, platinum powder, PVP and CaO are mixed evenly. Platinum powder, PVP and CaO are wet-milled using ethyl acetate as a dispersing solvent. The mass ratio of platinum powder, PVP and CaO is 1:0.1:10, and the amount of ethyl acetate is 1 / 3 of the total amount of the three materials. The ball milling speed is 360 rpm, the ball milling time is 1 h, and the ball-to-material ratio is 3:1. The balls are made of agate grinding balls.

[0041] S2. The wet-mixed materials were volatilized at 80°C to remove ethyl acetate. The mixed powder of platinum powder, PVP, and CaO was subjected to a high-temperature treatment at a temperature range of 900°C. The treatment time was 2 hours, the heating rate was 10°C / min, and the mixed powder was cooled to room temperature in the furnace.

[0042] S3. Add 1% dilute hydrochloric acid to the mixed powder cooled to room temperature to convert CaO into water-soluble CaCl2. Repeatedly wash with deionized water to remove excess hydrochloric acid and CaCl2. Detect the pH of the washing solution to 7.1 and stop washing.

[0043] S4. The powder after removing CaO was dried at 100℃ for 2h to obtain platinum and platinum oxide (CaPt2O4) powder. XRD data showed that the mixture of platinum powder, PVP and CaO was treated at 900℃ to obtain CaPt2O4, in which the content of platinum oxide (CaPt2O4) was significantly lower than that of platinum powder (see Figure 5 ), the powder particle morphology changes to spherical or quasi-spherical, and the particle size becomes significantly larger (<1.6μm) (ref. Figure 6 ).

[0044] Example 4:

[0045] The preparation method of platinum oxide powder specifically comprises the following steps:

[0046] S1. Mix platinum powder and PVP evenly. To prevent sintering and agglomeration of platinum powder during high-temperature treatment, mix platinum powder, PVP, and CaO evenly. Use ethyl acetate as a dispersing solvent to wet-ball-mill the three materials, wherein the mass ratio of platinum powder, PVP, and CaO is 1:0.1:10, the amount of ethyl acetate is 1 / 3 of the total amount of the three materials, the ball mill speed is 360 rpm, the ball milling time is 1 h, and the ball-to-material ratio is 3:1.

[0047] S2. The wet-mixed materials were volatilized at 80-100°C to remove ethyl acetate. The mixed powder of platinum powder, PVP, and CaO was subjected to a high-temperature treatment in the temperature range of 1000°C. The treatment time was 2 hours, the heating rate was 10°C / min, and the mixed powder was cooled to room temperature in the furnace.

[0048] S3. Add 1% dilute hydrochloric acid to the mixed powder cooled to room temperature to convert CaO into water-soluble CaCl2. Repeatedly wash with deionized water to remove excess hydrochloric acid and CaCl2. Detect the pH of the washing solution at 6.9 and stop washing.

[0049] S4. The powder after removing CaO was dried at 100°C for 2 hours to obtain platinum powder. XRD data showed that during the high temperature treatment of the platinum powder, PVP and CaO mixture at 1000°C, PVP decomposed rapidly due to the high temperature, and oxidation was not achieved, resulting in complete platinum powder. The XRD test data only showed the diffraction peak of platinum, but no diffraction peak of platinum oxide (CaPt2O4) (see Figure 7 ), the morphology of platinum powder particles has all changed to spherical or quasi-spherical, the dispersion between particles has been improved, there is no obvious agglomeration, and the particle size is less than 1.0 μm (see Figure 8 ).

[0050] The applicant's experiments show that treatment temperature significantly affects the products and their content after high-temperature treatment of a mixture of platinum powder, PVP, and CaO. Lower treatment temperatures produce platinum oxide (CaPt2O4), but the content is low. As the temperature rises to 800°C, the content of CaPt2O4 reaches its highest level. However, further increases in temperature reduce the content, ultimately converting the entire mixture to platinum powder after treatment at 1000°C.

Claims

1. A method for preparing platinum oxide powder, characterized in that: The following steps are involved: 1) Mixing platinum powder, PVP and CaO uniformly to obtain a uniform mixed powder; 2) The mixed powder obtained in step 1) is treated at a temperature of 600-1000° C., cooled to room temperature, and then added to dilute acid to remove CaO; 3) The powder after removing CaO is dried to obtain platinum and platinum oxide powder with a particle size of less than 1.65 μm.

2. The preparation method according to claim 1, wherein: The method of mixing the platinum powder, PVP and CaO in step 1) includes dry ball milling or wet ball milling.

3. The preparation method according to claim 2, wherein: The ball milling speed is 300-500 rpm, the ball milling time is 1-3 hours, and the mass ratio of grinding balls to mixture is 3:

1.

4. The preparation method according to claim 1, wherein: The dry ball milled mixed powder is directly heated; Wet ball milling is performed, and 1 / 4-1 / 2 of the total mass of the mixed powder is added with ethyl acetate. After mixing evenly, heating is performed to volatilize and remove the ethyl acetate dispersant. The heating treatment time is 2-8 hours, and the heating rate is 5-15°C / min. After treatment, the mixed powder is cooled to room temperature.

5. The preparation method according to claim 4, characterized in that: The heating temperature is 80-100° C. and the heating time is 2-4 hours.

6. The preparation method according to claim 1, wherein: In step 1), the mass ratio of the platinum powder, PVP and CaO is 1:(0.05-0.5):(10-20).

7. The preparation method according to claim 1, wherein: Step 2) The method for removing CaO is to convert CaO into a water-soluble calcium salt using a dilute acid with a mass concentration of less than 2%, and repeatedly wash and precipitate with deionized water to remove excess acid and water-soluble calcium salt; and stop washing when the pH of the washing solution is detected to be 7±0.

3.

8. The preparation method according to claim 1, wherein: Step 3) The drying temperature is 100±5°C and the drying time is 2-4 hours.

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