A chemical synthesis method of high-dispersion spherical palladium powder
By using a slow-stirring liquid-phase reduction method and a specific dispersant, the problems of low sphericity and crystallinity of palladium powder were solved, and the preparation of highly dispersed spherical palladium powder with controllable particle size was achieved, thus improving product quality and application range.
Patent Information
- Application Number
- CN202510388515.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-31
- Publication Date
- 2025-12-26
- Estimated Expiration
- 2045-03-31
AI Technical Summary
Existing preparation methods struggle to simultaneously achieve high sphericity and high crystallinity in palladium powder, and it is difficult to precisely control particle size and distribution. The powder is prone to agglomeration, resulting in poor product consistency and repeatability, and a narrow range of applications.
A slow-stirring liquid-phase reduction method was adopted, in which a palladium-containing solution was slowly added to a reducing agent solution at room temperature, and a specific dispersant such as polyvinyl alcohol was used to regulate the reaction process, control the morphology and dispersibility of palladium powder, and obtain spherical palladium powder by drying and sieving.
Highly dispersed spherical palladium powder with a particle size of 120-400 nm was prepared, exhibiting good dispersibility and crystallinity, high product quality consistency, and wide applicability, thus improving the agglomeration problem of slurry.
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Figure CN119897476B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of palladium powder materials, and particularly relates to a chemical synthesis method of high-dispersion spherical palladium powder. BACKGROUND
[0002] Palladium powder is an important noble metal powder, which is widely used in the fields of electronic industry, catalyst and the like. Its main uses include the preparation of thick film paste for electronic industry, thick film silver-palladium conductor paste, and internal and external electrode materials of multilayer ceramic capacitors.
[0003] In the existing preparation method, it is difficult to simultaneously achieve high sphericity and high crystallinity. For example, the palladium powder prepared by patent CN105945298A has low sphericity and crystallinity, while the palladium powder prepared by patent CN105945298A has high sphericity and crystallinity, but the preparation process has high energy consumption and is not friendly to the environment.
[0004] In addition, it is difficult to accurately control the particle size and distribution in the preparation process, and small changes in conditions such as temperature, dosage and concentration of each raw material, and stirring speed will affect the nucleation and growth process. The particles are prone to agglomeration due to the increase in interparticle attraction caused by high surface energy, have low dispersibility, and the reaction conditions or impurities may cause irregular morphology and make it difficult to maintain spherical morphology.
[0005] The specification of Chinese patent CN115722677A describes a preparation method of high-dispersion sub-micron spherical palladium powder. First, palladium nitrate solid is weighed and dissolved in dilute nitric acid to prepare a palladium nitrate dilute solution. Then, a reducing agent is dissolved in deionized water to obtain a reducing solution. Separately, a dispersant and an additive are dissolved in deionized water to obtain a mixed bottom solution. Then, the three are mixed to obtain a reaction slurry containing palladium powder. Finally, the sub-micron spherical palladium powder particles are obtained by filtration, washing and drying. The application uses a liquid phase reduction method to reduce the palladium nitrate solution with ascorbic acid or hydrazine hydrate as the reducing agent to prepare sub-micron spherical palladium powder. By adding organic polymer dispersants and small molecule alcohol additives to the bottom solution in a symmetrical feeding mode, the growth process and dispersibility of the particles are well controlled under the premise of ensuring the yield of the palladium powder. The prepared palladium powder particles are spherical and highly dispersed, with a particle size of 100-600 nm.
[0006] The experimental reaction steps described in the patent are as follows: the palladium nitrate dilute solution and the reducing solution are simultaneously and quickly added to the mixed bottom solution, and then the reaction is continued for 20-30 min. There is no specific description of the dropping speed of the palladium nitrate solution and the reducing solution, only the word "quickly", which has a large error. Moreover, the particle size of the prepared palladium powder is between 100-600 nm, which is a relatively wide range, which may affect the consistency and repeatability of the product. In addition, additives are used, the amount of solvent is increased, the cost is high, and it is difficult to control the particle size and distribution of the palladium powder, and the application range is narrow. SUMMARY
[0007] To solve the above technical problems, the application provides a chemical synthesis method of high-dispersion spherical palladium powder, and a new preparation method is creatively proposed. 2 The prepared palladium powder is spherical and has good dispersity, a specific surface area of 1.5-2.5 m
[0008] The chemical synthesis method of high-dispersion spherical palladium powder in the application to solve the above technical problems comprises the following steps:
[0009] (1) Preparation of a palladium-containing solution: water and palladium nitrate solution are sequentially added into a container, ammonia water is added after stirring, the pH is adjusted to 9-10, and the palladium-containing solution A is prepared after sufficient stirring; in volume units, water:ammonia water=100:50-100;
[0010] The volume ratio of the water and the palladium nitrate solution is 2:1.
[0011] (2) Preparation of a reducing agent solution: water, a dispersant and hydrazine hydrate are sequentially added into a container, and the solution B is prepared after sufficient stirring; in mass volume units, water:dispersant:hydrazine hydrate=100-300:0.1-0.6:20-40.
[0012] (3) Solution A is poured into solution B, slowly stirred, washed with water and alcohol in sequence after precipitation, dried in an oven, and screened to obtain the product.
[0013] The above reaction is performed at room temperature except drying.
[0014] The molar concentration of the palladium nitrate solution is 0.5-1.0 mol / L.
[0015] The water is deionized water.
[0016] The dispersant is one of PVP, polyvinyl alcohol and gum arabic powder. The dispersant raw material type greatly affects whether the palladium powder can be spherical, and some dispersants cannot form a spherical shape. In the application, a specific dispersant is added to control the morphology and sphericity.
[0017] In a further optimization scheme, the dispersant is polyvinyl alcohol.
[0018] The slow stirring in step (3) is 200 rpm / min for 20-30 min.
[0019] In the present application, the stirring time is determined by color change. When palladium is generated, the solution gradually changes from white to dark gray. The time for the solution to completely change to dark gray is 20 min. Stirring for 10 min more is to ensure complete reaction. Therefore, the reaction is complete when the solution changes to dark gray and no longer changes color.
[0020] In step (3), the solution is dried in an oven at 58-62 DEG C for 6-9 h, and in the optimization, the solution is dried at 60 DEG C for 8 h.
[0021] In the present application, the role of ammonia water is to adjust the pH to alkaline. Hydrazine hydrate has strong reducing property only under alkaline conditions, and can reduce palladium nitrate to palladium.
[0022] In step (2), the ratio of water: dispersant: hydrazine hydrate is 100-300:0.5:20. Hydrazine hydrate is a reducing agent, and the amount of hydrazine hydrate has a minimum limit. The optimal amount is 20 mL, which is verified by experiments. When the amount is less than 20 mL, the reaction is not complete (0.5 is calculated). At the same time, too much reducing agent has little effect on the morphology and yield.
[0023] In the present application, 50 ml of palladium nitrate solution is taken as an example. The 50 ml of palladium nitrate solution contains 4 g of palladium. 0.5 g of dispersant and 20 g of hydrazine hydrate are needed. The mass concentration ratio of palladium: dispersant: hydrazine hydrate is 4:0.5:20.
[0024] In the present application, the particle size of palladium powder is 120-400 nm, and in the optimization, the particle size of palladium powder is 129-280 nm.
[0025] In the present application, each batch of experiment inputs 4 g of palladium nitrate solution containing 4 g of palladium, and 3.90-3.98 g of palladium powder can be obtained, with a yield of 97.5%-99.5%.
[0026] In the present application, the palladium powder obtained from the electron microscope image is spherical and smooth in surface, with high crystallinity and good sphericity. The palladium powder is not formed by aggregation of many small particles. Hydrazine hydrate has reducing property and can reduce palladium nitrate to palladium under alkaline conditions. The addition of a suitable dispersant can adjust the morphology of the generated palladium powder.
[0027] The innovative palladium powder formation method in the present application can make the application range of palladium powder wider by adjusting the size and crystallinity of the palladium powder, and can meet more application scenarios. The palladium powder with good sphericity and high crystallinity can greatly improve the agglomeration problem of the palladium-containing slurry, make the prepared slurry more smooth, and improve the product quality. BRIEF DESCRIPTION OF DRAWINGS
[0028] Figure 1The SEM scanning electron microscope image of the palladium powder obtained in the experimental example of the test one in the present application is shown in the following figure:
[0029] Figure 2 The SEM scanning electron microscope image of the palladium powder obtained in the experimental example of the test one in the present application is shown in the following figure:
[0030] Figure 3 The SEM scanning electron microscope image of the palladium powder obtained in the experimental example of the test one in the present application is shown in the following figure:
[0031] Figure 4 The low-magnification electron microscope image of the palladium powder obtained in the experimental example of the test one in the present application is shown in the following figure. Figure 3 The low-magnification electron microscope image of the palladium powder obtained in the experimental example of the test one in the present application is shown in the following figure. DETAILED DESCRIPTION
[0032] The present application is further described below in conjunction with specific embodiments:
[0033] Example 1
[0034] A chemical synthesis method of high-dispersion spherical palladium powder is provided, and the specific synthesis method and steps are as follows:
[0035] (1) Preparation of a palladium-containing solution: 100 mL of deionized water is added to a container, then 0.5 mol / L palladium nitrate solution is added, and after uniform stirring, 50 mL of ammonia water is added to adjust the pH to 9-10, and after sufficient stirring, a palladium-containing solution A is prepared; the volume ratio of water to palladium nitrate solution is 2:1;
[0036] (2) Preparation of a reducing agent solution: 100 mL of deionized water is added to a container, 0.1 g of a dispersant, which is polyvinyl alcohol, is added, then 20 mL of hydrazine hydrate is added, and after sufficient stirring, a solution B is prepared;
[0037] (3) Solution A is poured into solution B, slowly stirred for 30 min, then washed with deionized water three times after precipitation, washed with alcohol twice, then sent to an oven for drying at 60°C for 8 h, and finally screened to obtain a finished product.
[0038] Example 2
[0039] A chemical synthesis method of high-dispersion spherical palladium powder is provided, and the specific synthesis method and steps are as follows:
[0040] (1) Preparation of a palladium-containing solution: 100 mL of deionized water is added to a container, then 0.5 mol / L palladium nitrate solution is added, and after uniform stirring, 50 mL of ammonia water is added to adjust the pH to 9-10, and after sufficient stirring, a palladium-containing solution A is prepared; the volume ratio of water to palladium nitrate solution is 2:1;
[0041] (2) Preparation of reducing agent solution: add 300 mL of deionized water into a container, add 0.6 g of dispersant PVP, then add 40 mL of hydrazine hydrate, and prepare solution B after fully stirring;
[0042] (3) Pour solution A into solution B, slowly stir for 30 min, then wash the precipitate with deionized water for three times, and then wash with alcohol for two times, and then send into an oven for drying at 60°C for 8 h, and then sieve to obtain the finished product.
[0043] Example 3
[0044] A chemical synthesis method of high-dispersion spherical palladium powder, the specific synthesis method and steps are as follows:
[0045] (1) Preparation of palladium-containing solution: add 100 mL of deionized water into a container, then add 0.8 mol / L palladium nitrate solution, stir uniformly, then add 80 mL of ammonia water, adjust pH to 9-10, and prepare solution A after fully stirring; the volume ratio of water and palladium nitrate solution is 2:1;
[0046] (2) Preparation of reducing agent solution: add 150 mL of deionized water into a container, add 0.3 g of dispersant gum arabic powder, then add 30 mL of hydrazine hydrate, and prepare solution B after fully stirring;
[0047] (3) Pour solution A into solution B, slowly stir for 30 min, then wash the precipitate with deionized water for three times, and then wash with alcohol for two times, and then send into an oven for drying at 60°C for 8 h, and then sieve to obtain the finished product.
[0048] Example 4
[0049] A chemical synthesis method of high-dispersion spherical palladium powder, the specific synthesis method and steps are as follows:
[0050] (1) Preparation of palladium-containing solution: add 100 mL of deionized water into a container, then add 0.8 mol / L palladium nitrate solution, stir uniformly, then add 80 mL of ammonia water, adjust pH to 9-10, and prepare solution A after fully stirring; the volume ratio of water and palladium nitrate solution is 2:1;
[0051] (2) Preparation of reducing agent solution: add 150 mL of deionized water into a container, add 0.3 g of dispersant gum arabic powder, then add 30 mL of hydrazine hydrate, and prepare solution B after fully stirring;
[0052] (3) Pour solution A into solution B, slowly stir for 30 min, then wash the precipitate with deionized water for three times, and then wash with alcohol for two times, and then send into an oven for drying at 60°C for 8 h, and then sieve to obtain the finished product.
[0053] Example 5
[0054] A chemical synthesis method of high-dispersion spherical palladium powder, the specific synthesis method and steps are as follows:
[0055] (1) Preparation of palladium-containing solution: 100 mL of deionized water is added to a container, then 0.2 mol / L palladium nitrate solution is added, after stirring uniformly, 60 mL of ammonia water is added, the pH is adjusted to 9-10, and after sufficient stirring, a palladium-containing solution A is prepared; the volume ratio of water and palladium nitrate solution is 2:1;
[0056] (2) Preparation of reducing agent solution: 250 mL of deionized water is added to a container, 0.2 g of dispersant, which is gum arabic powder, is added, then 25 mL of hydrazine hydrate is added, and after sufficient stirring, solution B is prepared;
[0057] (3) Pour solution A into solution B, slowly stir for 30 min, then wash the precipitate with deionized water three times, then wash with alcohol twice, then send into an oven to dry at 60°C for 8 h, and then sieve to obtain the finished product.
[0058] The SEM scanning electron microscope graph of the palladium powder obtained in the application is shown in Figures 1-4 , Figure 4 is Figure 3 Another low-magnification electron microscope graph, which can observe the uniform morphology of the spherical powder in a larger range.
[0059] Test one when the dispersant dosage is different
[0060] Set experimental examples and comparative examples 1 and 2, as follows:
[0061] The synthesis method and steps in the experimental examples are as follows:
[0062] (1) Preparation of palladium-containing solution: 100 mL of deionized water is added to a container, then 0.2 mol / L palladium nitrate solution is added, after stirring uniformly, 60 mL of ammonia water is added, the pH is adjusted to 9-10, and after sufficient stirring, a palladium-containing solution A is prepared; the volume ratio of water and palladium nitrate solution is 2:1;
[0063] (2) Preparation of reducing agent solution: 250 mL of deionized water is added to a container, 0.2 g of dispersant, which is gum arabic powder, is added, then 25 mL of hydrazine hydrate is added, and after sufficient stirring, solution B is prepared;
[0064] (3) Pour solution A into solution B, slowly stir for 30 min, then wash the precipitate with deionized water three times, then wash with alcohol twice, then send into an oven to dry at 60°C for 8 h, and then sieve to obtain the finished product, the SEM scanning electron microscope graph of the palladium powder obtained is shown in Figure 1 .
[0065] The other contents in the comparative example 1 are the same as those in the experimental example, wherein the dispersant 0.6 g is added in step (2), and the SEM scanning electron micrograph of the obtained palladium powder is as follows Figure 2 .
[0066] The other contents in the comparative example 1 are the same as those in the experimental example, wherein the dispersant 0.6 g is added in step (2), and the SEM scanning electron micrograph of the obtained palladium powder is as follows Figure 3 .
[0067] From the above comparative test, it can be seen that in the present application, the dispersity and crystallinity of the obtained palladium powder are improved by adding a dispersant, and the size of the palladium powder is precisely controlled by changing the amount of the dispersant. For example, in the experimental example, after increasing the amount of the dispersant by 20%, the obtained electron micrograph is Figure 1 , and the average particle size is reduced from ~200 nm to ~100 nm. On the contrary, when the amount of the dispersant is reduced by 20%, the obtained electron micrograph is Figure 2 , and the average particle size is increased to ~300 nm. Figure 3
[0068] In the present application, by controlling the size and crystallinity of the palladium powder, the application range of the palladium powder is wider, and more application scenarios can be met. Palladium powder of different sizes can be prepared to meet the needs of customers. For example, in the above test, less dispersant is added for larger powder, and more dispersant is added for smaller powder. The spherical degree and crystallinity of the palladium powder can greatly improve the agglomeration problem of the palladium-containing slurry, and the prepared slurry is more smooth.
[0069] Test two: different conditions when the dispersant and other raw materials are different
[0070] Set experimental example and comparative examples 1-3. Comparative example 1 is to add the additive methanol in the patent document 202211567554.0, comparative example 2 is to add polyvinylpyrrolidone in the patent document 202211567554.0, and comparative example 3 is without ammonia water.
[0071] The synthesis method and steps of the experimental example are as follows:
[0072] (1) Preparation of palladium-containing solution: 100 mL of deionized water is added to a container, then 0.5 mol / L palladium nitrate solution is added, and after stirring uniformly, 70 mL of ammonia water is added, and the pH is adjusted to 9-10. After stirring thoroughly, a palladium-containing solution A is prepared. The volume ratio of water to palladium nitrate solution is 2:1;
[0073] (2) Preparation of reducing agent solution: 200 mL of deionized water is added to a container, 0.5 g of dispersant is added, the dispersant is polyvinyl alcohol, 20 mL of hydrazine hydrate is added, and after stirring thoroughly, a solution B is prepared;
[0074] (3) Pour solution A into solution B, slowly stir for 30 min, then wash the precipitate with deionized water three times, and then wash with alcohol twice, and then put into an oven and dry at 60°C for 8 h, and then sieve to obtain the finished product.
[0075] Comparative Example 1 is based on the content of the experimental example, and a dispersing agent of polyvinyl alcohol and an additive of methanol are added in step (2), and the methanol is 1-10% of the mass of palladium.
[0076] Comparative Example 2 is based on the content of the experimental example, and a dispersing agent of polyvinylpyrrolidone is added in step (2).
[0077] Comparative Example 3 is based on the content of the experimental example, and no ammonia water is added in step (1).
[0078] In the above Comparative Example 1, Comparative Example 2 and Comparative Example 3, Comparative Example 1 and Comparative Example 3 cannot form spherical palladium powder, and Comparative Example 2 can form spherical palladium powder, but the spherical rate is not high and it is easy to form a group. In the experimental example, the powder has a high spherical rate, good shape and high dispersibility.
[0079] Test 3: When the concentration of palladium nitrate solution is different
[0080] Assuming that the experimental example and Comparative Example 1-Comparative Example 2, the experimental example is synthesized by the following method and steps:
[0081] (1) Preparation of palladium-containing solution: add 100 mL of deionized water to a container, then add 0.5 mol / L of palladium nitrate solution, stir uniformly, then add 70 mL of ammonia water, adjust the pH to 9-10, and fully stir to prepare solution A containing palladium; the volume ratio of water to palladium nitrate solution is 2:1;
[0082] (2) Preparation of reducing agent solution: add 200 mL of deionized water to a container, add 0.5 g of dispersing agent polyvinyl alcohol, then add 20 mL of hydrazine hydrate, and fully stir to prepare solution B;
[0083] (3) Pour solution A into solution B, slowly stir for 30 min, then wash the precipitate with deionized water three times, and then wash with alcohol twice, and then put into an oven and dry at 60°C for 8 h, and then sieve to obtain the finished product.
[0084] Comparative Example 1 is based on the content of the experimental example, and the palladium nitrate solution in step (1) is 0.4 mol / L.
[0085] Comparative Example 2 is based on the content of the experimental example, and the palladium nitrate solution in step (2) is 1 mol / L.
[0086] In the above Comparative Example 1 and Comparative Example 2, the particle size of the palladium powder in Comparative Example 1 is smaller than that in the Experimental Example, but the dispersion is smaller and the powder is easily agglomerated; the particle size of the palladium powder in Comparative Example 2 is larger than that in the Experimental Example. Under the same conditions, the smaller the concentration of the palladium nitrate solution, the smaller the particle size of the palladium powder to be reduced.
[0087] The above described embodiments and experimental examples are merely examples for clearly illustrating the present application, and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, it is not necessary and impossible to exhaust all the embodiments. The changes or variations derived therefrom are still within the protection scope of the present application.
Claims
1. A method for the chemical synthesis of a highly dispersed spherical palladium powder, characterized in that: The method comprises the following steps: (1) preparing a solution containing palladium: adding water and palladium nitrate solution into a container in sequence, stirring until uniform, then adding ammonia water to adjust the pH to 9-10, and preparing solution A containing palladium after sufficient stirring; water:ammonia water=100:50-100 by volume; (2) preparing a reducing agent solution: adding water, dispersant and hydrazine hydrate into a container in sequence, and preparing solution B after sufficient stirring; water:dispersant:hydrazine hydrate=100-300:0.1-0.5:20-40 by mass volume; the dispersant is one of PVP, polyvinyl alcohol and gum arabic powder; (3) pouring solution A into solution B, slowly stirring for 30 min, then sequentially cleaning with water and alcohol after precipitation, and drying in an oven for 8 h at 60℃, and then sieving to obtain the product.
2. A chemical synthesis process for high dispersion spherical palladium powder as claimed in claim 1, wherein: The molar concentration of the palladium nitrate solution is 0.5-1.0 mol / L.
3. A chemical synthesis process for high dispersion spherical palladium powder as claimed in claim 1, wherein: The water is deionized water.
4. The method of claim 1, wherein the method is characterized by: In step (2), water:dispersant:hydrazine hydrate=100-300:0.5:
20.
5. The method of claim 1, wherein the method is characterized by: The particle size of the palladium powder is 120-400 nm.
6. The method of claim 5, wherein the method further comprises the step of: The particle size of the palladium powder is 129-280 nm.
Citation Information
Patent Citations
Preparation method for hollow palladium nanospheres
CN105945298A
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CN115722677B
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