Preparation method of high-dispersion spherical palladium powder

Abstract

The invention belongs to the technical field of powder material preparation, and particularly relates to a preparation method of high-dispersion spherical palladium powder. The method comprises the following steps: mixing a palladium-containing solution and a reduction solution, and carrying out reduction reaction to obtain a palladium suspension; the reducing liquid comprises a surfactant, a reducing agent and water; the surfactant is Arabic gum; the reducing agent is ferrite; and the palladium suspension is subjected to solid-liquid separation, obtained solids are sequentially washed and dried, and the obtained spherical palladium powder is controllable in particle size, high in dispersion, good in sphericity degree, smooth in surface, uniform in size and narrow in particle size distribution. The preparation method of the palladium powder is simple in production process, short in period and suitable for mass production.

Description

Technical Field

[0001] The invention belongs to the technical field of powder material preparation, and particularly relates to a method for preparing highly dispersed spherical palladium powder. Background Art

[0002] Palladium has excellent physical and chemical properties. It is not only a good catalytic material and hydrogen storage material, but also one of the indispensable important materials in thick film conductive slurry. Palladium powder as an added phase in thick film conductive slurry can inhibit the migration of silver ions in the conductive film in high temperature and high humidity electric field, and can also play a role in improving the corrosion resistance of the slurry. At present, the preparation methods of palladium powder mainly include chemical reduction method, template method and electrochemical method. The process flow involved in the template method and electrochemical method is relatively complicated and not easy to operate. The liquid phase chemical reduction method has a simple technical route, low cost and is suitable for mass production.

[0003] The currently disclosed palladium powder has problems such as poor powder dispersibility, uneven size, and poor sphericity. These problems greatly affect the sintering characteristics of the slurry printing film layer, the rheological properties of the slurry, the fineness, and the dispersion effect of the powder in the organic carrier. In addition, polyvinyl pyrrolidone (PVP) is often used as a surfactant and dispersant in the existing process flow of preparing palladium powder by chemical reduction to reduce the agglomeration of palladium powder, but the sphericity of the prepared palladium powder is not high, and PVP is not easy to wash and remove, which affects the use of the final product. Therefore, improving the dispersibility of the powder and preparing spherical palladium powder with uniform size are current problems that need to be solved urgently. Summary of the invention

[0004] In view of this, an object of the present invention is to provide a method for preparing highly dispersed spherical palladium powder, wherein the spherical palladium powder prepared by the preparation method has high dispersibility and uniform size.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention also provides a method for preparing highly dispersed spherical palladium powder, comprising the following steps:

[0007] The palladium-containing solution and the reducing solution are mixed to perform a reduction reaction to obtain a palladium suspension;

[0008] The reducing liquid comprises a surfactant, a reducing agent and water;

[0009] The surfactant is gum arabic;

[0010] The reducing agent is a ferrous salt;

[0011] The palladium suspension is separated into solid and liquid, and the obtained solid is washed and dried in sequence to obtain highly dispersed spherical palladium powder.

[0012] Preferably, the ferrous salt is at least one of ferrous chloride and its hydrate, ferrous sulfate and its hydrate, and ferrous nitrate and its hydrate.

[0013] Preferably, the mass ratio of the surfactant to palladium in the palladium-containing solution is 0.1 to 10:10.

[0014] Preferably, the mass ratio of the surfactant to the reducing agent is 0.1 to 10:65.

[0015] Preferably, the reduction reaction is carried out at room temperature; the reduction reaction time is 1 to 4 hours.

[0016] Preferably, the method for preparing the palladium-containing solution is: dissolving raw palladium in an acid solution to obtain the palladium-containing solution.

[0017] Preferably, the acid solution is a nitric acid solution, or a mixed solution of nitric acid and hydrochloric acid.

[0018] Preferably, the raw palladium is fine palladium powder or sponge palladium.

[0019] Preferably, the palladium-containing solution and the reducing solution are mixed by: dropping the palladium-containing solution into the reducing solution.

[0020] Preferably, the dropping time is 5 to 60 minutes.

[0021] The invention provides a preparation method of highly dispersed spherical palladium powder, comprising the following steps: mixing a palladium-containing solution and a reducing solution, performing a reduction reaction, and obtaining a palladium suspension; the reducing solution comprises a surfactant, a reducing agent and water; the surfactant is gum arabic; the reducing agent is a ferrous salt; and the palladium suspension is solid-liquid separated, and the obtained solid is sequentially washed and dried to obtain highly dispersed spherical palladium powder.

[0022] The present invention uses a liquid phase chemical reduction method to add a surfactant to a reducing agent solution to control the morphology and particle size of the palladium powder, thereby preparing a spherical palladium powder with high dispersibility and no adhesion and agglomeration. The average particle size D 50 It is close to the size of a single particle, has good sphericity, uniform size, narrow particle size distribution and a smooth surface.

[0023] The reaction process of the present invention does not need to adjust the temperature and pH, the entire reaction can be carried out at room temperature, the materials can be directly added for reaction, and the reaction can be naturally precipitated and washed, which reduces the production cost, is simple to operate, has a short cycle, and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a SEM image of the highly dispersed spherical palladium powder prepared in Example 1;

[0025] Figure 2 This is the EDS image of the highly dispersed spherical palladium powder prepared in Example 1;

[0026] Figure 3 This is a SEM image of the highly dispersed spherical palladium powder prepared in Example 2;

[0027] Figure 4 This is a SEM image of the highly dispersed spherical palladium powder prepared in Example 3;

[0028] Figure 5 This is a SEM image of the highly dispersed spherical palladium powder prepared in Example 4;

[0029] Figure 6 This is a SEM image of the highly dispersed spherical palladium powder prepared in Example 5;

[0030] Figure 7 This is a SEM image of the highly dispersed spherical palladium powder prepared in Example 6;

[0031] Figure 8 This is a SEM image of the highly dispersed spherical palladium powder prepared in Example 7;

[0032] Fig. 9 This is a SEM image of the highly dispersed spherical palladium powder prepared in Example 8;

[0033] Fig.10 This is a SEM image of the highly dispersed spherical palladium powder prepared in Example 9;

[0034] Fig.11 This is a SEM image of the palladium powder prepared in Comparative Example 1;

[0035] Fig.12 This is a SEM image of the palladium powder prepared in Comparative Example 2;

[0036] Fig.13 This is a SEM image of the palladium powder prepared in Comparative Example 3;

[0037] Fig.14 This is a SEM image of the palladium powder prepared in Comparative Example 4;

[0038] Fig.15 This is a SEM image of the palladium powder prepared in Comparative Example 5;

[0039] Fig.16 This is a SEM image of the palladium powder prepared in Comparative Example 6;

[0040] Fig.17 This is the SEM image of the palladium powder prepared in Comparative Example 7. DETAILED DESCRIPTION

[0041] The present invention provides a method for preparing highly dispersed spherical palladium powder, comprising the following steps:

[0042] The palladium-containing solution and the reducing solution are mixed to perform a reduction reaction to obtain a palladium suspension;

[0043] The reducing liquid comprises a surfactant, a reducing agent and water;

[0044] The surfactant is gum arabic;

[0045] The reducing agent is a ferrous salt;

[0046] The palladium suspension is separated into solid and liquid, and the obtained solid is washed and dried in sequence to obtain highly dispersed spherical palladium powder.

[0047] Unless otherwise specified, the present invention has no special requirements on the sources of the raw materials used, and commercially available products known to those skilled in the art may be used.

[0048] The invention mixes a palladium-containing solution and a reducing solution, performs a reduction reaction, and obtains a palladium suspension.

[0049] As an embodiment, the reducing liquid includes a surfactant, a reducing agent and water; the water is deionized water; the mass ratio of the surfactant to the reducing agent is 0.1 to 10:65, and in a specific embodiment, it is 1 to 3:65; the mass ratio of the surfactant to water is 0.1 to 10:1500, and in a specific embodiment, it is 1 to 3:1500.

[0050] As an embodiment, the surfactant is gum arabic.

[0051] As an embodiment, the reducing agent is a ferrous salt; the ferrous salt is at least one of ferrous chloride and its hydrate, ferrous sulfate and its hydrate, and ferrous nitrate and its hydrate. As another embodiment, the ferrous salt is ferrous sulfate or ferrous sulfate hydrate.

[0052] As an embodiment, the preparation method of the palladium-containing solution is: dissolving raw palladium in acid solution to obtain a palladium-containing solution; the raw palladium is fine palladium powder or sponge palladium; the acid solution is a nitric acid solution, or a mixed solution of nitric acid and hydrochloric acid; the mass ratio of the raw palladium to the acid solution is 1:10. The present invention does not specifically limit the concentration of nitric acid and hydrochloric acid, and nitric acid and hydrochloric acid with concentrations well known in the art can be used to dissolve the raw palladium.

[0053] As an implementation mode, the mass ratio of the surfactant to palladium in the palladium-containing solution is 0.1 to 10:10, and in a specific embodiment, it is 1 to 3:10.

[0054] As an embodiment, the palladium-containing solution and the reducing solution are mixed as follows: the palladium-containing solution is added dropwise to the reducing solution, and the adding time is 5 to 60 minutes, and in a specific embodiment, it is 25 to 45 minutes.

[0055] As an embodiment, the reduction reaction is carried out at room temperature; the reduction reaction time is 1 to 4 hours, and in a specific embodiment, it is 2 hours; the reduction reaction is carried out under stirring conditions; the stirring rate is 100 to 300 rpm, and in a specific embodiment, it is 100 to 200 rpm.

[0056] After obtaining the palladium suspension, the present invention separates the palladium suspension into solid and liquid, and sequentially washes and dries the obtained solid to obtain highly dispersed spherical palladium powder.

[0057] As an embodiment, the solid-liquid separation is static sedimentation; the static sedimentation time is 3 hours; the washing liquid used for washing is deionized water; the washing is performed until the conductivity of the solution after washing is close to the conductivity of deionized water; the drying temperature is 65°C; and the drying time is 24 hours.

[0058] As an embodiment, the particle size of the highly dispersed spherical palladium powder is ≥300 nm, and in a specific embodiment, it is 400 nm to 1 μm.

[0059] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, but they should not be construed as limiting the protection scope of the present invention.

[0060] Example 1

[0061] Dissolve 1.5 g of gum arabic in 1500 mL of deionized water, then add 65 g of ferrous sulfate, and stir at 100 rpm at room temperature to dissolve to obtain a reducing solution;

[0062] Dissolve 10 g of palladium in 100 mL of concentrated nitric acid to obtain a palladium nitrate solution, dilute the palladium nitrate solution to 300 mL, and uniformly dropwise add the solution to the reducing solution over a period of 30 minutes; perform a reduction reaction at room temperature with stirring at 200 rpm for 2 hours to obtain a palladium suspension;

[0063] The palladium suspension was allowed to settle for 3 hours, the upper liquid was poured off, and the obtained solid was washed with deionized water until the conductivity of the washed solution was close to that of deionized water, and dried at 65° C. for 24 hours to obtain highly dispersed spherical palladium powder.

[0064] Example 2

[0065] The difference from Example 1 is that the amount of gum arabic is 1 g.

[0066] Example 3

[0067] The difference from Example 1 is that the amount of gum arabic is 2 g.

[0068] Example 4

[0069] The difference from Example 1 is that the amount of gum arabic is 3 g.

[0070] Example 5

[0071] The difference from Example 1 is that nitric acid is replaced by a mixture of nitric acid and hydrochloric acid, and the dropping time is 25 min.

[0072] Example 6

[0073] The difference from Example 1 is that nitric acid is replaced by a mixture of nitric acid and hydrochloric acid, and the dropping time is 35 minutes.

[0074] Example 7

[0075] The difference from Example 1 is that nitric acid is replaced by a mixture of nitric acid and hydrochloric acid, and the dropping time is 40 minutes.

[0076] Example 8

[0077] The difference from Example 1 is that nitric acid is replaced by a mixture of nitric acid and hydrochloric acid, and the dropping time is 45 minutes.

[0078] Example 9

[0079] The difference from Example 1 is that nitric acid is replaced by a mixture of nitric acid and hydrochloric acid, and the dropping time is 30 minutes.

[0080] Comparative Example 1

[0081] The difference from Example 1 is that the surfactant-gum arabic is removed.

[0082] Comparative Example 2

[0083] The difference from Example 1 is that gum arabic is replaced by polyethylene glycol.

[0084] Comparative Example 3

[0085] The difference from Example 1 is that gum arabic is replaced by polyvinyl pyrrolidone.

[0086] Comparative Example 4

[0087] The difference from Example 1 is that gum arabic is replaced by gelatin.

[0088] Comparative Example 5

[0089] The difference from Example 1 is that 65 g of ferrous sulfate is replaced by 40 g of ascorbic acid.

[0090] Comparative Example 6

[0091] The difference from Example 1 is that 65 g of ferrous sulfate is replaced by 20 g of hydrazine hydrate.

[0092] Comparative Example 7

[0093] The difference from Example 1 is that the surfactant-gum arabic is removed, and 65 g of ferrous sulfate is replaced by 40 g of glucose.

[0094] Performance Testing

[0095] (1) Figure 1 This is a SEM image of the highly dispersed spherical palladium powder prepared in Example 1. Figure 2 This is the EDS image of the highly dispersed spherical palladium powder prepared in Example 1.

[0096] Depend on Figure 1 and 2 It can be seen that the highly dispersed spherical palladium powder prepared in Example 1 of the present invention is spherical, with a smooth surface, no irregular shapes such as flakes and dendrites, excellent dispersibility, uniform size, and the particle size is mostly around 400nm. EDS results show that the palladium powder has no other impurities and high purity. The particle size distribution test shows that the palladium powder D10, D50, D90, and D100 (referring to the particle size corresponding to the cumulative particle size distribution number of the palladium powder sample reaching 10%, 50%, 90%, and 100%, respectively) are 231nm, 447nm, 998nm, and 1792nm, respectively, and D50 (average particle size) is relatively close to the size measured by electron microscopy, which further illustrates that the palladium powder is highly dispersed, has no agglomeration phenomenon, is uniform in size, and has a narrow particle size distribution. The specific surface area is tested to be 2.3211m 2 / g, further indicating that the palladium powder has high sphericity and a smooth surface.

[0097] (2) Figure 3 This is a SEM image of the highly dispersed spherical palladium powder prepared in Example 2. Figure 4 This is a SEM image of the highly dispersed spherical palladium powder prepared in Example 3. Figure 5 This is the SEM image of the highly dispersed spherical palladium powder prepared in Example 4.

[0098] Depend on Figures 3 to 5 It can be seen that the morphology, dispersion, smoothness, etc. of the palladium powder prepared in Examples 2 to 4 of the present invention are similar to those of the palladium powder obtained in Example 1.

[0099] (3) Figure 6 This is a SEM image of the highly dispersed spherical palladium powder prepared in Example 5. Figure 7 This is a SEM image of the highly dispersed spherical palladium powder prepared in Example 6. Figure 8 This is a SEM image of the highly dispersed spherical palladium powder prepared in Example 7. Fig. 9 This is the SEM image of the highly dispersed spherical palladium powder prepared in Example 8.

[0100] Depend on Figures 6 to 9It can be seen that the morphology, dispersion, smoothness, etc. of the palladium powder prepared in Examples 5 to 8 of the present invention are similar to those of the palladium powder obtained in Example 1, but there is a difference in size. The longer the feeding time, the larger the particle size.

[0101] (4) Fig.10 This is the SEM image of the highly dispersed spherical palladium powder prepared in Example 9.

[0102] Depend on Fig.10 It can be seen that the palladium powder prepared in Example 9 is a highly dispersed smooth sphere with a size of about 1 μm.

[0103] (5) Fig.11 This is the SEM image of the palladium powder prepared in Comparative Example 1.

[0104] Depend on Fig.11 It can be seen that the palladium powder prepared in Comparative Example 1 is in the shape of a flower formed by stacking small pieces, has good dispersibility, and has a size of about 1.3 μm.

[0105] (6) Fig.12 This is the SEM image of the palladium powder prepared in Comparative Example 2.

[0106] Depend on Fig.12 It can be seen that the palladium powder prepared in Comparative Example 2 is in the shape of a sea urchin, slightly agglomerated, and has a size of about 1.3 μm.

[0107] (7) Fig.13 This is the SEM image of the palladium powder prepared in Comparative Example 3.

[0108] Depend on Fig.13 It can be seen that the palladium powder prepared in Comparative Example 3 is spherical, severely agglomerated, and has a size of 300 to 600 nm.

[0109] (8) Fig.14 This is the SEM image of the palladium powder prepared in Comparative Example 4.

[0110] Depend on Fig.14 It can be seen that the palladium powder prepared in Comparative Example 4 is spherical and has a size of 150 to 350 nm.

[0111] (9) Fig.15 This is the SEM image of the palladium powder prepared in Comparative Example 5.

[0112] Depend on Fig.15 It can be seen that the palladium powder prepared in Comparative Example 5 is spherical and has a size of 100 to 200 nm.

[0113] (10) Fig.16 This is the SEM image of the palladium powder prepared in Comparative Example 6.

[0114] Depend on Fig.16 It can be seen that the palladium powder prepared in Comparative Example 6 is in the form of small particles with a size of several nanometers, and these small particles aggregate together to form large agglomerates.

[0115] (11) Fig.17 This is the SEM image of the palladium powder prepared in Comparative Example 7.

[0116] Depend on Fig.17 It can be seen that the palladium powder prepared in Comparative Example 7 is in large chunks.

[0117] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing highly dispersed spherical palladium powder, characterized in that: The following steps are involved: The palladium-containing solution and the reducing solution are mixed to perform a reduction reaction to obtain a palladium suspension; The reducing liquid comprises a surfactant, a reducing agent and water; The surfactant is gum arabic; The reducing agent is a ferrous salt; The palladium suspension is separated into solid and liquid, and the obtained solid is washed and dried in sequence to obtain highly dispersed spherical palladium powder.

2. The preparation method according to claim 1, characterized in that: The ferrous salt is at least one of ferrous chloride and its hydrate, ferrous sulfate and its hydrate, and ferrous nitrate and its hydrate.

3. The preparation method according to claim 1, characterized in that: The mass ratio of the surfactant to palladium in the palladium-containing solution is 0.1 to 10:

10.

4. The preparation method according to claim 1, characterized in that: The mass ratio of the surfactant to the reducing agent is 0.1 to 10:

65.

5. The preparation method according to claim 1, characterized in that: The reduction reaction is carried out at room temperature; the reduction reaction time is 1 to 4 hours.

6. The preparation method according to claim 1, characterized in that: The preparation method of the palladium-containing solution is: dissolving raw material palladium in acid solution to obtain the palladium-containing solution.

7. The preparation method according to claim 6, characterized in that: The acid solution is a nitric acid solution, or a mixed solution of nitric acid and hydrochloric acid.

8. The preparation method according to claim 6, characterized in that: The raw material palladium is fine palladium powder or sponge palladium.

9. The preparation method according to claim 1, characterized in that: The palladium-containing solution and the reducing solution are mixed by dropping the palladium-containing solution into the reducing solution.

10. The preparation method according to claim 9, characterized in that: The dropping time is 5 to 60 minutes.

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