A method for continuously preparing octahedral copper powder based on a dynamic tube solvent hot synthesis method

Abstract

The application discloses a kind of octahedral copper powder based on the continuous preparation method of dynamic tube solvent synthesis, after mixing copper source, surfactant and solvent, it is placed on magnetic stirrer and is fully dissolved stirring;Then sodium hydroxide is dissolved in solvent and added to the system, after stirring dispersion is uniform, it is injected into dynamic tube reactor by plunger pump, and octahedral copper powder is synthesized by solvent thermal reaction.The application realizes the continuous preparation of material by combining plunger pump with dynamic tube reactor, so that the scale-up production of solvent thermal condition becomes possible.Due to the small reaction cavity, combined with strong convection, the mass transfer and heat transfer of the material can be effectively improved, the consistency of the environment in the synthesis process of the material is improved, and the uniformity of the material itself is improved.The application is prepared by using the solvent thermal method, which avoids the use of strong reducing agent, further reduces the preparation cost, and realizes the preparation of octahedral nanometer copper powder.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of noble metal materials, and particularly relates to a method for continuously preparing octahedral copper powder based on a dynamic tube solvothermal synthesis method. BACKGROUND

[0002] Copper powder is a common metal material and is widely used in people's daily life and actual production. Compared with noble metals such as Au, Ag, Pd and Pt, Cu is rich in reserves and low in price. It has superior electrical conductivity in metals, second only to Ag, and is often used as a conductive material, electrode material, solid lubricant, high-efficiency catalyst, engineering material, etc., and is widely used in the fields of electronic information, energy and power, petroleum and chemical industry, light industry and textile, industrial engineering, etc.

[0003] Copper octahedron, as a copper structure with a specific geometric shape, has a larger specific surface area than other shapes (such as cubes), which means that it can provide more active sites for catalytic reactions. Cu(111) crystal plane is a unique crystal plane in copper octahedron structure, which exhibits significant advantages in many applications, mainly in terms of catalytic activity, oxidation resistance, surface oxygen species characteristics, and electrical and thermal conductivity. Angew. Chem. Int. Ed. 2024, Vol. 63, No. 11, pointed out that Cu(111) crystal plane performs well in the reaction of electrocatalytic reduction of NO to synthesize ammonia. Compared with Cu(100) crystal plane, Cu(111) crystal plane achieves higher yield (371.89 μmol cm -2 h -1 ) and Faraday efficiency (93.19%), indicating that Cu(111) crystal plane is the dominant crystal plane for electrocatalytic reduction of NO to synthesize ammonia. Nature 2022, page 434, pointed out that Cu(111) crystal plane has excellent oxidation resistance, which is due to its flat surface structure that can effectively prevent the diffusion of oxygen atoms and the progress of oxidation reactions. In addition, first-principles calculation simulation also shows that step edge sites are beneficial to the oxidation resistance of Cu.

[0004] The stability and dispersibility of copper powder in the medium affect its performance. Surfactants have multiple effects in the preparation of copper powder, such as improving dispersibility, controlling particle size, increasing stability, affecting morphology, and improving performance. By selecting the appropriate surfactant and its dosage, copper powder products with excellent performance can be prepared. Chem. - Eur. J. 2012, 18, 44 reported that during the synthesis of Ni and Pd nanoparticles, metal (II) acetylacetone complexes (M(acac)2 or M(C5H7O2)2) and oleylamine had a rich reactivity, in which oleylamine played the role of reducing agent by oxidative dehydrogenation. Regarding the synthesis of Cu nanoparticles by reducing Cu(acac)2 with oleylamine, it was found that oleylamine was not the ligand of the nanoparticles. On the contrary, the ligand was a substance formed during the reaction: N-oleylacetamide. And oleylamine was also difficult to remove in the subsequent washing process. Colloid Polym Sci. 2024, 302, 362 reported the RSH and particle size of copper powder dispersed in SDS, SDBS, CTAB, and PVP. The results showed that PVP was the most effective surfactant for dispersing Cu in water medium. Materials Development and Application (22, 1) pointed out that when preparing ultrafine copper powder, adding an appropriate amount of PVP can make the ultrafine copper powder particles have higher sphericity, better uniformity, and effectively eliminate the agglomeration phenomenon of copper powder.

[0005] Copper powder preparation according to the state of aggregation of the reactants is divided into gas phase method, liquid phase method and solid phase method. The powder prepared by gas phase method and solid phase method has respective corresponding difficult-to-overcome shortcomings. It is pointed out in Hunan Nonferrous Metals (2015, Vol. 3, page 62) that gas phase evaporation method is the most direct and effective method for preparing metal powder. The copper ultrafine powder is prepared by using the improved gas phase evaporation method powder preparation technology of inductive heating method of Lairliqusd Company in France, and the yield is 0.5 kg / h. The copper powder prepared by gas phase method is usually regular spherical, and the equipment requirement is higher, and the investment is larger. The copper powder prepared by solid phase method has wide particle size distribution, and impurities are easily introduced; because of the above shortcomings, the application and popularization of these preparation methods are limited. The liquid phase method has its unique advantages for preparing nano copper powder, such as easy control of components, simple equipment, low production cost, easy industrial production and the like. Among them, the traditional solvothermal synthesis method is widely used, which is a wet chemical method completed in a closed container, using water, ethanol and other solutions as reaction medium, by heating the reaction container, a high temperature and high pressure reaction environment is formed, so that the usually difficultly soluble or insoluble substances are dissolved and recrystallized. However, the output is very small, and it is limited in large-scale industrial production. At present, the main shortcomings of the reaction kettle are that the yield of single preparation is small due to the closed system; at the same time, due to the existence of high temperature and high pressure environment, if the volume is simply enlarged in the amplification process, it is relatively dangerous in efficiency, in addition, copper powder and cuprous oxide exist in the reaction kettle, the existence of copper powder will accelerate the decomposition of reducing agent, that is, the amount of reducing agent is increased, and the particle size uniformity of copper powder is relatively poor, therefore, through the improvement of process to realize the uniformity synthesis of copper powder, not only the particle size can be effectively controlled, but also the use amount of reducing agent can be reduced, the quality of copper powder can be improved and the cost can be reduced. The patent CN118218603A provides a method for preparing ultrafine copper powder by using traditional solvothermal method, which has simple process, excellent dispersity, oxidation resistance and controllable morphology, but cannot realize continuous preparation, which hinders its large-scale industrial production, and the morphology and uniformity of the powder material are poor, and there is no octahedral copper powder in the various morphologies. SUMMARY

[0006] The present application provides a method for continuously preparing octahedral copper powder based on dynamic tube solvothermal synthesis.

[0007] The application realizes continuous preparation of materials by combining a dynamic tube reactor with a plunger pump, so that the production of materials under solvothermal conditions is possible. Due to the small reaction cavity and strong convection, the mass transfer and heat transfer of the materials can be effectively improved, the consistency of the environment in the synthesis process of the materials is improved, and the uniformity of the materials is improved. At the same time, although the cavity of the dynamic tube is small, the production efficiency and speed can be effectively improved due to the use of the continuous production process, and the preparation cost of the materials is significantly reduced. The use of the solvothermal method avoids the use of strong reducing agents, further reduces the preparation cost, and realizes the preparation of octahedral copper powder.

[0008] The application discloses a method for continuously preparing octahedral copper powder based on a dynamic tube solvothermal synthesis method, which comprises the following steps:

[0009] The copper source, the surfactant and the solvent are mixed and then placed on a magnetic stirrer for sufficient dissolution and stirring. Then, sodium hydroxide is dissolved in the solvent and added to the system, and after uniform stirring and dispersion, the system is injected into a dynamic tube reactor through a plunger pump, and octahedral copper powder is synthesized through a solvothermal reaction.

[0010] The copper source is selected from one or more of copper sulfate, copper nitrate, copper phosphate and copper acetate.

[0011] The surfactant is selected from one or more of sodium dodecylbenzenesulfonate, urea, ammonium sulfate, polyvinylpyrrolidone, triton X100 and benzotriazole.

[0012] The solvent is selected from one or more of methanol, ethanol, ethylene glycol, formaldehyde, acetaldehyde and isopropyl alcohol.

[0013] Further, the total volume of the above reaction system is controlled to be 30 mL. In the reaction system, the concentration of the copper source is 0.25 mol / L, the concentration of the surfactant is 10-20 g / L, and the concentration of sodium hydroxide is 1.2 mol / L.

[0014] The temperature of the dynamic tube reactor is set to 200 DEG C, the reaction is carried out for 15 min after pumping, and the rotation speed of the dynamic tube is kept at 50-300 r / min. The reaction time is controlled by the pumping speed of the plunger pump, and the greater the pumping speed, the shorter the residence time.

[0015] The application adopts a dynamic tube reactor, due to the small reaction cavity, and the strong convection effect, the mass transfer and heat transfer of the material can be effectively improved, the uniformity of the environment in the synthesis process of the material is improved, and the uniformity of the material itself is improved; due to the full contact of the solvent and the copper source in the dynamic flow process, the reducing effect of the solvent itself can be maximized, and the amount of reducing agent can be maximized. At the same time, although the cavity of the dynamic tube itself is small, due to the use of continuous production process, the production efficiency and speed can be effectively improved, and the preparation cost of the material can be significantly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The preparation process flowchart of the application.

[0017] Figure 2 The preparation process principle diagram of the application.

[0018] Figure 3 In the case of the same proportion of copper source, surfactant and reducing agent, the material morphology (A) of the kettle type reaction and the copper powder morphology (B) synthesized by the dynamic tube.

[0019] Figure 4 The XRD diagram of the copper powder synthesized by the dynamic tube of the application.

[0020] Figure 5 The influence of the surfactant on the morphology (urea).

[0021] Figure 6 The influence of the surfactant on the morphology (sodium dodecyl sulfonate).

[0022] Figure 7 The influence of the surfactant concentration on the morphology when the surfactant concentration is low.

[0023] Figure 8 The influence of the copper salt concentration on the morphology when the copper salt concentration is high. DETAILED DESCRIPTION

[0024] The technical scheme of the application is further analyzed and explained through specific examples.

[0025] The specific process is:

[0026] 0.25 mol / L copper salt, 10 ml solvent, 10 g / L~20 g / L surfactant were mixed and placed on a magnetic stirrer for sufficient dissolution and stirring for 10 min. Then 1.2 mol / L sodium hydroxide and 20 mL solvent were added and stirring was continued for 30 min. Subsequently, it was injected into a dynamic tubular reactor through a plunger pump. The temperature of the reactor was set to 200℃, and after pumping, the reaction was maintained for 15 min at a dynamic tube speed of 50-300 r / min. From the discharge, the obtained powder was washed, dried, and octahedral copper powder was obtained Figure 1 and 2 ).

[0027] It can be seen from the scanning electron microscope and XRD analysis that the dynamic tube synthesis method can effectively improve the reduction effect of the solvent, and at the same time, the octahedral copper powder can be obtained, and the material is more uniform Figure 3 and Figure 4 ); By adjusting the types of different surfactants, the coordination between the surfactant and copper can make the morphology closer to the octahedron Figure 5 and Figure 6 ); When the content of the surfactant is too low, the copper powder does not form an octahedron and is not uniformly dispersed Figure 7 ); When the content of the surfactant is too high, it will cause the product to foam and cannot stably prepare the material; When the content of the copper salt is too high, the copper powder also does not form an octahedron Figure 8 ), which is mainly due to the fact that the copper powder cannot be fully protected by the surfactant.

[0028] The copper source is selected from one or more of copper sulfate, copper nitrate, copper phosphate, and copper acetate.

[0029] The solvent is selected from one or more of methanol, ethanol, ethylene glycol, formaldehyde, acetaldehyde, and isopropyl alcohol.

[0030] The surfactant is selected from one or more of sodium dodecylbenzene sulfate, urea, ammonium sulfate, polyvinylpyrrolidone, triton X100, and benzotriazole.

[0031] Comparative Example 1:

[0032] Ethanol was used as a solvent to prepare a mixed solution of 0.25 mol / L copper nitrate and 14 g / L polyvinylpyrrolidone with a total volume of 30 mL. The mixed solution was added to the reaction kettle, stirred at a rate of 100 rpm / min, and heated to 200℃. After reaching the reaction temperature (200℃), the obtained powder was washed and dried after 5h of reaction to obtain octahedral copper powder 1.

[0033] Example 1:

[0034] A mixture solution of 0.25 mol / L copper nitrate and 14 g / L surfactant polyvinylpyrrolidone with a total volume of 30 mL was prepared by using ethanol as solvent. Then, the dynamic tube was started and the stirring paddle was kept rotating at a speed of 100 r / min. The reaction temperature in the dynamic tube was 200℃. Subsequently, the mixture solution was pumped into the cavity of the dynamic tube at a rate of 5 mL / min by using a syringe pump for reduction reaction. After 5-20 min of reaction in the dynamic tube, the powder discharged through the product outlet was washed and dried to obtain octahedral copper powder 2.

[0035] The octahedral copper powder in Comparative Example 1 and Example 1 was characterized by using a scanning electron microscope, and Example 1 was analyzed by using an X-ray diffractometer, as shown in Figure 3 、 4

[0036] Figure 3 A is a scanning electron microscope (SEM) image of octahedral copper powder 1 prepared in the reaction kettle in Comparative Example 1 of the present application; Figure 3 B is a scanning electron microscope (SEM) image of octahedral copper powder 2 prepared by the dynamic tube solvothermal synthesis method in Example 1 of the present application. As shown in Figure 3 A, the surface of the octahedral copper powder 1 prepared by using the reaction kettle (Comparative Example 1) is rough, has agglomeration phenomenon and uneven morphology. In contrast, the octahedral copper powder 2 prepared by the dynamic tube solvothermal synthesis method has a smooth surface, a very clear octahedral morphology, and uniform particle size without agglomeration phenomenon, as shown in Figure 3 B.

[0037] Figure 4 X-ray diffraction (XRD) pattern of octahedral copper powder 2 prepared by the dynamic tube solvothermal synthesis method in Example 1 of the present application. As shown in Figure 4 , the dynamic tube solvothermal synthesis method can obtain octahedral copper powder with single composition.

[0038] Example 2:

[0039] Octahedral copper powder 3 was prepared by using the same method as in Example 1, the only difference being that urea was used as the surfactant. The scanning electron microscope (SEM) image of the prepared octahedral copper powder 3 is shown in Figure 5 .

[0040] Figure 5 B is a scanning electron microscope (SEM) image of octahedral copper powder 2 prepared by the dynamic tube solvothermal synthesis method in Example 1 of the present application. As shown in Figure 5 , the octahedral copper powder 3 prepared by the method in Example 2 has a slightly rough surface.

[0041] Example 3: ​

[0042] The same method as in Example 1 was used to prepare octahedral copper powder 4, the only difference being that the surfactant used was sodium dodecyl sulfonate, and the scanning electron microscope (SEM) image of the prepared octahedral copper powder 4 is shown in Figure 6 .

[0043] Figure 6 The scanning electron microscope (SEM) image of the octahedral copper powder 4 prepared by the dynamic tube solvent-thermal synthesis method in Example 3 of the present application is shown in Figure 6 . As shown, the octahedral copper powder 4 prepared by the method in Example 3 has a non-uniform morphology and a rough surface.

[0044] Comparative Example 2:

[0045] The same method as in Example 1 was used to prepare octahedral copper powder 5, the only difference being that the concentration of the surfactant polyvinylpyrrolidone was 5 g / L, and the scanning electron microscope (SEM) image of the prepared octahedral copper powder 4 is shown in Figure 7 .

[0046] Figure 7 The scanning electron microscope (SEM) image of the octahedral copper powder 5 prepared by the dynamic tube solvent-thermal synthesis method in Comparative Example 2 of the present application is shown in Figure 7 . As shown, when the concentration of the surfactant is relatively low (less than 10 g / L), it cannot better coordinate with copper ions, resulting in a relatively fast deposition rate of the copper salt; and when the concentration of the surfactant is relatively high, the surfactant will be adsorbed on the surface of the copper particles, affecting the further growth of the material.

[0047] Comparative Example 3:

[0048] The same method as in Example 1 was used to prepare octahedral copper powder 6, the only difference being that the concentration of the copper salt used was relatively high at 0.5 mol / L, and the scanning electron microscope (SEM) image of the prepared octahedral copper powder 6 is shown in Figure 8 .

[0049] Figure 8 The scanning electron microscope (SEM) image of the octahedral copper powder 6 prepared by the dynamic tube solvent-thermal synthesis method in Comparative Example 3 of the present application is shown in Figure 8 . As shown, the size of the copper powder is relatively large and very non-uniform, which is due to the relatively high concentration of the copper salt, which cannot gradually release a small amount of copper ions during the growth process, and the excess concentration of copper ions leads to non-uniform growth of the copper powder material.

Claims

1. A method for continuous preparation of octahedral copper powder based on dynamic tube solvothermal synthesis, characterized in that... Includes the following steps: The copper source, surfactant, and solvent were mixed and placed on a magnetic stirrer for thorough dissolution and stirring. Then, sodium hydroxide was dissolved in the solvent and added to the system. After being stirred and dispersed evenly, the mixture was injected into a dynamic tubular reactor through a plunger pump to synthesize octahedral copper powder through a solvothermal reaction. The copper source is selected from one or more of copper sulfate, copper nitrate, copper phosphate, and copper acetate; The surfactant is selected from one or more of sodium dodecylbenzene, urea, ammonium sulfate, polyvinylpyrrolidone, Triton X100, and benzotriazole; The solvent is selected from one or more of methanol, ethanol, ethylene glycol, formaldehyde, acetaldehyde, and isopropanol; The total volume of the reaction system was controlled at 30 mL; in the reaction system, the concentration of copper source was 0.25 mol / L, the concentration of surfactant was 10-20 g / L, and the concentration of sodium hydroxide was 1.2 mol / L. The temperature of the dynamic tubular reactor was set to 200℃. After pumping in the reactor, the reaction was carried out for 15 minutes, and the rotation speed of the dynamic tube was maintained at 50-300 r / min.

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