Preparation method of nano cobalt hydroxide with large specific surface area

Abstract

A preparation method of nano cobalt hydroxide with large specific surface area comprises the following steps: rapidly adding a sodium hydroxide solution into a mixed solution of a cobalt solution and L-ascorbic acid to prepare alpha-phase cobalt hydroxide with large specific surface area, and then aging for a long time under low stirring intensity to obtain the nano cobalt hydroxide with large specific surface area. Alpha-phase cobalt hydroxide is slowly converted into beta-phase cobalt hydroxide with a large specific surface area, the large specific surface area of the alpha-phase cobalt hydroxide is inherited, and then the large-specific-surface-area nano cobalt hydroxide product is prepared through washing, low-temperature vacuum drying and high-pressure airflow crushing.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation, and specifically relates to the preparation technology of nano cobalt hydroxide with a large specific surface area. Background Art

[0002] As an important metal binder, cobalt powder plays an irreplaceable role in the preparation of tungsten-cobalt alloys, the manufacturing of cemented carbide tools, and the production of diamond drill bits by virtue of its excellent physical and chemical properties. As a key precursor material for preparing metallic cobalt, the physical and chemical properties of cobalt hydroxide directly determine the performance of downstream cobalt powder products. In industrial production, cobalt hydroxide can be converted into high-purity metallic cobalt through high-temperature reduction or chemical conversion processes, and then used in the preparation of cemented carbide tools, tungsten-cobalt alloys, etc. Compared with ordinary crystalline products, nano cobalt hydroxide with a large specific surface area exhibits unique advantages: its abundant surface active sites can significantly enhance the reaction activity during the reduction process, which can not only promote the rapid diffusion and deep reduction of cobalt ions in the solid phase, generating cobalt powder particles with smaller particle sizes and larger specific surface areas; but also effectively reduce the residual of impurity phases by lowering the reduction reaction temperature threshold, ensuring the high purity and excellent reaction activity of cobalt powder from the source, and providing key material property support for subsequent high-end applications.

[0003] In addition, the high specific surface area and layered structure of nano cobalt hydroxide may be partially retained in the cobalt powder after reduction, forming a porous or loose structure, further increasing the specific surface area of the cobalt powder, which is beneficial to improving the application performance of the cobalt powder in the fields of catalysts, batteries, and biosensors.

[0004] Existing preparation methods still have deficiencies in preparing nano cobalt hydroxide with a large specific surface area. For example, the invention patent with the authorization announcement number CN115849459B discloses a preparation method and application of cobalt hydroxide. The preparation method includes mixing and reacting a cobalt solution, an alkali solution, and an additive; the additive includes ascorbic acid and hydrazine hydrate; by weight, the alkali solution is 340-350 g, and the ascorbic acid is 1-2 parts. In the cobalt hydroxide preparation method of this invention, the control of the specific surface area of cobalt hydroxide is achieved by adjusting the addition amounts of each component, and the specific surface area of the prepared cobalt hydroxide is 35 m 2 / g - 45 m 2 / g, which is significantly lower than the specific surface area (≥90 m 2 / g) of cobalt hydroxide prepared by the method of the present invention. Summary of the Invention

[0005] To overcome the deficiencies of the existing production process, the purpose of the present invention is to provide a preparation method of nano cobalt hydroxide with a large specific surface area that is easy to control in the production process and easy to industrialize. The purpose of the present invention can be achieved through the following technical solutions: The present invention relates to a method for preparing nano cobalt hydroxide with a large specific surface area, and the steps are as follows: Step (a) Solution preparation: Using soluble cobalt salt and L-ascorbic acid as raw materials, prepare a mixed solution with a cobalt concentration of 1.8 - 2.0 mol / L and an L-ascorbic acid concentration of 0.01 - 0.02 mol / L as solution A; prepare a sodium hydroxide solution with a concentration of 8 - 10 mol / L as solution B. Step (b) Synthesis reaction: Add 50 - 60% of the volume of solution A in the reaction kettle as the bottom liquid, and then quickly add solution B into the reaction kettle at a preset flow rate for the synthesis reaction. When the pH value of the slurry in the reaction kettle rises to a preset value, stop adding solution B. During the reaction process, strictly control the flow rate of solution B, the reaction temperature, and the stirring intensity. Step (c) Aging: After the synthesis reaction is completed, stop adding liquid and start aging under certain conditions. Step (d) Washing: After aging, wash the prepared material. Step (e) Drying: Dry the washed material. Step (f) Crushing: Crush the dried cobalt hydroxide to obtain a nano cobalt hydroxide product with a specific surface area ≥ 90 m 2 / g.

[0006] Preferably, in step (a), the soluble cobalt salt is cobalt sulfate, or cobalt chloride, or cobalt nitrate, or a mixture of several.

[0007] Preferably, in step (b), the flow rate of solution B is 100 - 120% of the volume of the reaction kettle per hour. When the pH value of the slurry in the reaction kettle rises to 13.0 - 13.2, stop adding solution B. During the reaction process, strictly control the reaction temperature at 20 - 25 °C and the stirring frequency of the reaction kettle at 50 Hz.

[0008] Preferably, in step (c), the aging process is as follows: the aging time is 8 - 10 h, the aging temperature is 20 - 25 °C, and the stirring frequency during aging is 25 - 30 Hz.

[0009] Preferably, in step (d), the washing equipment is a filter press, the filter cloth specification is 8000 - mesh filter cloth, and the washing liquids are a 1.0 - 1.2 mol / L sodium hydroxide solution at a temperature of 40 - 50 °C and a 0.05 - 0.1 mol / L L-ascorbic acid solution at a temperature of 40 - 50 °C.

[0010] Preferably, in step (e), the drying equipment is a vacuum drying oven, the drying temperature is 50 - 60 °C, and the moisture content of the dried material is ≤ 0.5%.

[0011] Preferably, in the step (f), the crushing device is a high-pressure air flow crusher, and the crushing pressure is 1.2~1.5 MPa.

[0012] Preferably, in the step (f), the indexes of the nano cobalt hydroxide with large specific surface area are as follows: D 50 ≤0.2 μm, the apparent density (AD) = 0.1~0.2 g / cm 3 , the specific surface area (BET) ≥ 90 m 2 / g, and the microscopic morphology is lamellar.

[0013] The beneficial effect of the present invention is that during the experiment of preparing cobalt hydroxide, the project personnel unexpectedly found that a small amount of L-ascorbic acid can significantly increase the specific surface area of cobalt hydroxide. Based on this discovery, by quickly adding a sodium hydroxide solution to a mixed solution of a cobalt solution and L-ascorbic acid, cobalt hydroxide with a large specific surface area can be prepared. α Then, through long-term aging under low stirring intensity, α the cobalt hydroxide phase slowly transforms into cobalt hydroxide with a large specific surface area β phase, and inherits the large specific surface area of α the cobalt hydroxide phase. Then, through washing, low-temperature vacuum drying, and high-pressure air flow crushing, a nano cobalt hydroxide product with a large specific surface area is prepared. Description of the Drawings

[0014] Figure 1 is the microscopic morphology of the cobalt hydroxide prepared in Example 1, Figure 2 is the microscopic morphology of the cobalt hydroxide prepared in Example 2, Figure 3 is the microscopic morphology of the cobalt hydroxide prepared in Example 3. Figure 4 is the process flow chart. Detailed Embodiments

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all 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. Embodiment

[0016] This embodiment provides a method for preparing cobalt hydroxide with a large specific surface area, and the preparation method includes the following steps: Using cobalt sulfate and L-ascorbic acid as raw materials, a mixed solution with a cobalt concentration of 1.8 mol / L and an L-ascorbic acid concentration of 0.01 mol / L is prepared as solution A; a sodium hydroxide solution with a concentration of 10 mol / L is prepared as solution B; The synthesis reaction is carried out in a 5L reactor. Add 2.5L of solution A into the reactor as the bottom liquid, and then quickly add solution B into the reactor at a flow rate of 5L / h for the synthesis reaction. When the reaction lasts for about 12 min, the pH value of the slurry in the reactor rises to 13.0 - 13.2, and the addition of solution B is stopped. During the reaction process, strictly control the flow rate of solution B at 5L / h, the reaction temperature at 20 - 22 °C, and the stirring frequency of the reactor at 50Hz; When the pH value of the slurry in the reactor reaches 13.0 - 13.2, the synthesis is completed, the feeding is stopped, and aging begins. The aging time is 8h, the aging temperature is 20 - 22 °C, and the stirring frequency during aging is 30Hz.

[0017] After aging is completed, pump the slurry into a filter press for washing. First, wash with sodium hydroxide with a concentration of 1.2mol / L at 40 - 50 °C, and then wash with an L - ascorbic acid solution with a concentration of 0.05mol / L at 40 - 50 °C. When S% ≤ 0.05% and Na% ≤ 0.01% in the sodium hydroxide, the washing is completed; After washing is completed, dry the material in a vacuum drying oven at a drying temperature of 50 - 60 °C. When the moisture content in the material ≤ 0.5%, the drying is completed; Then crush the material with a high - pressure air crusher at a crushing pressure of 1.2MPa to obtain a cobalt hydroxide product with no agglomeration and nanoscale.

[0018] The cobalt hydroxide slurry prepared in this example is pink. The specific surface area of the final product cobalt hydroxide is 98.4m 2 / g, the particle size is 0.170μm. The microscopic morphology of the prepared cobalt hydroxide is shown in the appendix Figure 1 . Example

[0019] Using cobalt chloride and L - ascorbic acid as raw materials, prepare a mixed solution with a cobalt concentration of 1.9mol / L and an L - ascorbic acid concentration of 0.015mol / L as solution A; prepare a sodium hydroxide solution with a concentration of 9mol / L as solution B; The synthesis reaction is carried out in a 5L reactor. Add 2.8L of solution A into the reactor as the bottom liquid, and then quickly add solution B into the reactor at a flow rate of 5.5L / h for the synthesis reaction. When the reaction lasts for about 14 min, the pH value of the slurry in the reactor rises to 13.0 - 13.2, and the addition of solution B is stopped. During the reaction process, strictly control the flow rate of solution B at 5.5L / h, the reaction temperature at 22 - 24 °C, and the stirring frequency of the reactor at 50Hz; When the pH value of the slurry in the reactor reaches 13.0 - 13.2, the synthesis is completed, the feeding is stopped, and aging begins. The aging time is 9h, the aging temperature is 22 - 24 °C, and the stirring frequency during aging is 28Hz.

[0020] After the aging is completed, the slurry is pumped into a filter press for washing. First, it is washed with sodium hydroxide at a concentration of 1.1 mol / L at 40 - 50 °C, and then with an L - ascorbic acid solution at 40 - 50 °C and a concentration of 0.08 mol / L. The washing ends when the Cl% in sodium hydroxide ≤ 0.05% and Na% ≤ 0.01%. After the washing is completed, the material is dried in a vacuum drying oven at a drying temperature of 50 - 60 °C. The drying ends when the moisture content in the material ≤ 0.5%. Then the material is crushed by a high - pressure air - flow crusher at a crushing pressure of 1.4 MPa to obtain a cobalt hydroxide product in nano - scale without agglomeration.

[0021] The cobalt hydroxide slurry prepared in this example is pink. The specific surface area of the final cobalt hydroxide product is 95.8 m 2 / g, the particle size is 0.12 μm. The microscopic morphology of the prepared cobalt hydroxide is shown in the appendix Figure 2 . Example

[0022] Using cobalt nitrate and L - ascorbic acid as raw materials, a mixed solution with a cobalt concentration of 2.0 mol / L and an L - ascorbic acid concentration of 0.02 mol / L is prepared as solution A; a sodium hydroxide solution with a concentration of 8 mol / L is prepared as solution B; The synthesis reaction is carried out in a 5 - L reaction kettle. 3 L of solution A is added to the reaction kettle as the bottom liquid, and then solution B is rapidly added to the reaction kettle at a flow rate of 6 L / h for the synthesis reaction. When the reaction lasts for about 16 min, the pH value of the slurry in the reaction kettle rises to 13.0 - 13.2, and the addition of solution B is stopped. During the reaction process, the flow rate of solution B is strictly controlled at 6 L / h, the reaction temperature is 23 - 25 °C, and the stirring frequency of the reaction kettle is 50 Hz; When the pH value of the slurry in the reaction kettle reaches 13.0 - 13.2, the synthesis ends, the feeding is stopped, and aging starts. The aging time is 10 h, the aging temperature is 23 - 25 °C, and the stirring frequency during aging is 25 Hz.

[0023] After the aging is completed, the slurry is pumped into a filter press for washing. First, it is washed with sodium hydroxide at a concentration of 1.2 mol / L at 40 - 50 °C, and then with an L - ascorbic acid solution at 40 - 50 °C and a concentration of 0.05 mol / L. The washing ends when the Na% in sodium hydroxide ≤ 0.01%. After the washing is completed, the material is dried in a vacuum drying oven at a drying temperature of 50 - 60 °C. The drying ends when the moisture content in the material ≤ 0.5%. Then the material is crushed by a high - pressure air - flow crusher at a crushing pressure of 1.5 MPa to obtain a cobalt hydroxide product in nano - scale without agglomeration.

[0024] The cobalt hydroxide slurry prepared in this example is pink. The specific surface area of the final product cobalt hydroxide is 102.5 m 2 / g, the particle size is 0.19 μm, and the microscopic morphology of the prepared cobalt hydroxide is shown in the appendix Figure 3 .

Claims

1. A preparation method of nano cobalt hydroxide with a large specific surface area, characterized in that, The steps are as follows: Step (a) Solution preparation: Using soluble cobalt salt and L-ascorbic acid as raw materials, prepare a mixed solution with a cobalt concentration of 1.8 - 2.0 mol / L and an L-ascorbic acid concentration of 0.01 - 0.02 mol / L as Solution A; prepare a sodium hydroxide solution with a concentration of 8 - 10 mol / L as Solution B; Step (b) Synthesis reaction: Add 50 - 60% of the volume of the reaction kettle of Solution A into the reaction kettle as the bottom liquid, and then quickly add Solution B into the reaction kettle at a preset flow rate for the synthesis reaction. When the pH value of the slurry in the reaction kettle rises to the preset value, stop adding Solution B; strictly control the flow rate of Solution B, the reaction temperature, and the stirring intensity during the reaction process; Step (c) Aging: After the synthesis reaction is completed, stop adding liquid and start aging under certain conditions; Step (d) Washing: After aging is completed, wash the prepared material; Step (e) Drying: Dry the washed material; Step (f) Crushing: Crush the dried cobalt hydroxide to obtain a nano cobalt hydroxide product with a specific surface area of ≥ 90 m 2 / g.

2. The preparation method of nano cobalt hydroxide with a large specific surface area according to claim 1, characterized in that: In the said step (a), the soluble cobalt salt is cobalt sulfate, or cobalt chloride, or cobalt nitrate, or a mixture of several kinds.

3. The preparation method of nano cobalt hydroxide with a large specific surface area according to claim 1, characterized in that: In the said step (b), the flow rate of Solution B is 100 - 120% of the volume of the reaction kettle per hour. When the pH value of the slurry in the reaction kettle rises to 13.0 - 13.2, stop adding Solution B. During the reaction process, strictly control the reaction temperature at 20 - 25 °C and the stirring frequency of the reaction kettle at 50 Hz.

4. The preparation method of nano cobalt hydroxide with a large specific surface area according to claim 1, characterized in that: In the said step (c), the aging process is that the aging time is: 8 - 10 h, the aging temperature is: 20 - 25 °C, and the stirring frequency during aging is: 25 - 30 Hz.

5. The preparation method of nano cobalt hydroxide with a large specific surface area according to claim 1, characterized in that: In the said step (d), the washing equipment is a filter press, the filter cloth specification is 8000-mesh filter cloth, and the washing liquids are a 1.0 - 1.2 mol / L sodium hydroxide solution at a temperature of 40 - 50 °C and a 0.05 - 0.1 mol / L L-ascorbic acid solution at a temperature of 40 - 50 °C.

6. The preparation method of nano cobalt hydroxide with large specific surface area according to claim 1, characterized in that: In the said step (e), the drying equipment is a vacuum drying oven, the drying temperature is 50 - 60 °C, and the moisture content of the dried material is ≤0.5%.

7. The preparation method of nano cobalt hydroxide with a large specific surface area according to claim 1, characterized in that: In the said step (f), the crushing equipment is a high-pressure air flow crusher, and the crushing pressure is 1.2 - 1.5 MPa.

8. The preparation method of nano cobalt hydroxide with a large specific surface area according to claim 1, characterized in that: In the step (f), the indexes of the nano cobalt hydroxide with large specific surface area are as follows: D 50 ≤0.2 μm, apparent density (AD) = 0.1 - 0.2 g / cm 3 , specific surface area (BET) ≥ 90 m 2 / g, and the microscopic morphology is lamellar.

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