Preparation method of spherical magnesium oxide

Abstract

The invention discloses a preparation method of spherical magnesium oxide, which comprises the following steps: dissolving magnesium sulfate heptahydrate in water to prepare a magnesium sulfate solution, and adding ammonia water into the magnesium sulfate solution while stirring the magnesium sulfate solution to obtain magnesium hydroxide precursor slurry; stirring the magnesium hydroxide precursor slurry, and then spraying the magnesium hydroxide precursor slurry into a drying box by using a spray dryer to obtain spherical magnesium hydroxide; and calcining the spherical magnesium hydroxide to obtain spherical magnesium oxide. The method comprises the following steps: preparing spherical magnesium hydroxide by combining precipitation reaction and spray drying, and calcining the spherical magnesium hydroxide to obtain spherical magnesium oxide particles with uniform particle size distribution and particle diameter of 15-20 microns; the method for preparing the spherical magnesium oxide is high in efficiency and controllable in shape and granularity; the prepared magnesium oxide particles are spherical, have the characteristics of high filling density and good fluidity, and can meet the performance requirements of electrical grade magnesium oxide.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic chemical industry, and particularly relates to a preparation method of spherical magnesium oxide. Background Art

[0002] In recent years, with the rapid development and technological advancement of electric heating elements, higher performance requirements have been placed on electrical-grade magnesium oxide. To ensure rapid heat transfer at high temperatures and good insulation resistance at operating temperatures, magnesium oxide particles are generally required to be spherical, which allows for high packing density and good fluidity.

[0003] Currently, the main methods for preparing spherical magnesium oxide include hydrothermal method, precipitation method, aerosol-assisted ammonia method, and carbonization method. Although spherical magnesium oxide can be prepared using these methods, they have a series of disadvantages, such as complex preparation process, low efficiency, and uncontrollable particle size and shape, which make it difficult to meet the rapid development needs of electric heating elements in my country. For example, Reference I (Zhang Z, Zheng Y, Zhang J, et al. Magnesium oxide microspheres as a packing material forthese paration of basic compounds in normal-phase liquid chromatography [J]. Journal of Chromatography A, 2007, 1165 (1-2): 116-121.) uses a hydrothermal method to prepare flower-shaped magnesium oxide microspheres with a three-dimensional structure using magnesium chloride hexahydrate and sodium carbonate as raw materials. The average particle size is about 10 μm. However, this method requires high temperature, high pressure, and a closed environment, which results in high energy consumption, high requirements for sintering equipment, and high production costs. Reference II (Xia Yongliang, Liu Jiaxiang, Ou Long, et al. Preparation of high-purity spherical magnesium oxide by adding sodium oxalate to heavy magnesium water [J]. Journal of the Chinese Ceramic Society, 2013, 41(05): 650-655.) uses light-burned dolomite as raw material, prepares heavy magnesium water by carbonization, separation and filtration, and then obtains high-purity spherical magnesium oxide with an average particle size of 9 μm by calcining the heavy magnesium water; however, this method has a complicated preparation process and low efficiency.

[0004] Literature III (Ye Junwei, Chai Zhengze, Ning Guiling. A preparation method, device and application of spherical magnesium oxide [P]. Liaoning Province: CN108975360B, 2020-12-11.) A magnesium salt (magnesium nitrate hexahydrate, magnesium chloride hexahydrate or magnesium sulfate heptahydrate) and an additive (triblock copolymer: poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), hexadecyltrimethyl, ammonium bromide, polyvinylpyrrolidone, polyethylene glycol, urea, triammonium citrate, ammonium acetate, ammonium carbonate, ammonium oxalate, ammonium bicarbonate or glucose) are mixed and stirred to form a precursor solution or dilution, and then the precursor solution or emulsion is passed through a tubular pyrolysis furnace together with a carrier gas (air, nitrogen or helium), and the solid powder is collected and calcined to produce a spherical magnesium oxide product. However, this method relies on chemical reagents and the morphology of magnesium oxide is difficult to control.

[0005] Document IV (Zhao Y, Zhu G. Synthesis of MgO microspheres with nanosheets in a mechanical force reactor and its optical property [J]. Materials Science & Engineering B, 2007, 142 (2-3): 93-97.) uses Mg (NO 3 ) 2 · 6H 2 O, NH 4 HCO 3 and NH 4 OH as raw materials and prepares them into solutions of different pH values. The various solutions are kept in a reflux state and stirred continuously until a gel is obtained. The obtained product is dried at 70 ° C for 12 hours and then heat-treated at high temperature for 72 hours. 10 nm porous magnesium oxide microspheres are prepared by this method. However, the prepared magnesium oxide particles have too many voids, the spheres are easy to break, and are difficult to control. Summary of the Invention

[0006] In order to overcome the above-mentioned defects in the prior art, the present invention aims to provide a method for preparing spherical magnesium oxide by combining precipitation reaction and spray drying.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides a method for preparing spherical magnesium oxide, which comprises the following steps:

[0008] ① Dissolve magnesium sulfate heptahydrate in water to prepare a magnesium sulfate solution, and add ammonia water to the magnesium sulfate solution while stirring the magnesium sulfate solution to obtain a magnesium hydroxide precursor slurry.

[0009] ② Stir the magnesium hydroxide precursor slurry obtained in step ①, and then use a spray dryer to spray the magnesium hydroxide precursor slurry into a drying oven to obtain spherical magnesium hydroxide.

[0010] ③ calcining the spherical magnesium hydroxide obtained in step ② to obtain spherical magnesium oxide with uniform particle size distribution.

[0011] Spray drying, as a specialized material preparation technology, can complete material synthesis in just a few minutes, significantly improving production efficiency. Furthermore, a magnesium hydroxide solution is obtained through a precipitation reaction rather than directly using a magnesium sulfate solution as a precursor. This is because sulfate ions are difficult to volatilize during calcination, while sulfate ions in the solution after the precipitation reaction can be removed by washing. Furthermore, the introduced ammonia ions are volatile and easily removed.

[0012] In the above technical solution, further, the concentration of the magnesium sulfate solution prepared in step ① is 10-30 ml / L.

[0013] Furthermore, the stirring rate of the magnesium sulfate solution in step ① is 50-70 rpm.

[0014] Furthermore, in step ①, the ammonia solution is added to the magnesium sulfate solution by dripping the ammonia solution using a peristaltic pump or spraying the ammonia solution into the solution in an atomized form.

[0015] Furthermore, the magnesium hydroxide precursor slurry obtained in step ① contains Mg 2+ / OH - The molar ratio is 1:1~3.

[0016] Furthermore, in step ②, the stirring speed of the magnesium hydroxide precursor slurry is 200-600 rpm, and the stirring time is 10-20 min.

[0017] Furthermore, the temperature of the drying oven in step ② is set to 85°C to 95°C.

[0018] Furthermore, the calcination temperature in step ③ is 700° C. to 900° C., and the calcination time is 55 to 65 minutes.

[0019] Furthermore, the particle diameter of the spherical magnesium oxide obtained in step ③ is 15 to 20 μm.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] ① The preparation process of spherical magnesium oxide provided by the present invention only has the steps of heating, spray drying, calcination, etc., and has the advantages of simple operation, low experimental cost, mild reaction conditions, and low requirements for equipment and operators. Therefore, it is suitable for large-scale promotion and application.

[0022] ② The spherical magnesium oxide obtained by the preparation method provided by the present invention has a regular spherical morphology and a uniform particle size, and the spherical magnesium oxide has good dispersibility and no agglomeration phenomenon.

[0023] ③ The present invention uses magnesium sulfate heptahydrate and ammonia water as raw materials to prepare spherical magnesium hydroxide by a method combining precipitation reaction and spray drying. After calcining the spherical magnesium hydroxide, spherical magnesium oxide particles with uniform particle size distribution and a particle diameter of 15 to 20 μm are obtained. This technical solution has high efficiency in preparing spherical magnesium oxide, and the shape and particle size are controllable. The prepared magnesium oxide particles are spherical, have the characteristics of high packing density and good fluidity, and can meet the performance requirements of electrical grade magnesium oxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The figure is a schematic diagram of a process flow device for preparing spherical magnesium oxide according to the present invention;

[0025] Figure 2 This is an electron micrograph of the spherical magnesium oxide prepared in Example 1;

[0026] Figure 3 is a particle size distribution curve of the spherical magnesium oxide prepared in Example 1;

[0027] Figure 4 This is a particle size distribution curve of the spherical magnesium oxide prepared in Example 2;

[0028] Figure 5 This is a particle size distribution curve of the spherical magnesium oxide prepared in Example 3. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to specific examples, but the present invention is not limited in any way. To avoid redundancy, the raw materials in the following examples are all commercially available products unless otherwise specified, and the methods used are all conventional methods unless otherwise specified.

[0030] A method for preparing spherical magnesium oxide comprises the following steps:

[0031] ① Dissolve magnesium sulfate heptahydrate in water to prepare a magnesium sulfate solution, and add ammonia water to the magnesium sulfate solution while stirring the magnesium sulfate solution to obtain a magnesium hydroxide precursor slurry;

[0032] ② Stirring the magnesium hydroxide precursor slurry obtained in step ①, and then spraying the magnesium hydroxide precursor slurry into a drying oven using a spray dryer to obtain spherical magnesium hydroxide;

[0033] ③ calcining the spherical magnesium hydroxide obtained in step ② to obtain spherical magnesium oxide.

[0034] The process flow diagram of the spherical magnesium oxide preparation method is as follows: Figure 1As shown, ammonia water is added to a stirred magnesium sulfate solution, and the water bath temperature of the water bath is adjusted to 50°C; after the stirring rate is adjusted to 200-600 rpm, the precursor is placed in the water bath and stirred for 10-20 minutes; the spray dryer operation panel is adjusted: the red start button of the equipment is turned to start the fan and the heater; the inlet temperature and outlet temperature values ​​are set, and the material to be dried is prepared; water is first added, and the atomization and temperature changes of the material are observed, and the fan, inlet temperature, or outlet temperature are reset, and the material is added after stabilization; when the material is used up, water is added to spray all the material in the hose, and the peristaltic pump is turned off; the air compressor and the heater are turned off, and the fan is turned off when the inlet temperature drops below 30-40°C; the spray-dried material is collected and placed in a muffle furnace, and the calcination temperature is set to 700-900°C and the calcination time is 55-65 minutes; finally, magnesium oxide powder is obtained.

[0035] The samples in the following examples are made from industrial pure magnesium sulfate heptahydrate and ammonia water.

[0036] Any matters not described in the following embodiments are the same as those described in the above specific implementation methods.

[0037] Example 1

[0038] A method for preparing spherical magnesium oxide, comprising the following steps:

[0039] ① Take magnesium sulfate heptahydrate and dissolve it in water to prepare a magnesium sulfate solution with a concentration of 20ml / L. While stirring the magnesium sulfate solution, use a peristaltic pump to drop ammonia water into the magnesium sulfate solution at a rate of 100ml / min to obtain a magnesium hydroxide precursor slurry. The stirring rate of the magnesium sulfate solution is 60rpm. The magnesium hydroxide precursor slurry obtained has Mg 2+ / OH - The molar ratio is 1:1.

[0040] ② The magnesium hydroxide precursor slurry obtained in step ① was fully stirred at a stirring speed of 400 rpm for 15 min; the magnesium hydroxide precursor slurry was then sprayed into a drying oven using a spray dryer, and the temperature of the drying oven was set to 90° C. to obtain spherical magnesium hydroxide.

[0041] ③ calcining the spherical magnesium hydroxide obtained in step ② at a calcination temperature of 800° C. for 60 min to obtain spherical magnesium oxide particles.

[0042] The spherical magnesium oxide particles obtained in Example 1 were tested. Figure 2 The electron micrograph shown in FIG. 3 shows that the morphology of the spherical magnesium oxide particles is regular spherical; the particle size distribution is as follows: Figure 3 As shown, the particle size distribution is uniform, the concentration is high, and the particle diameter is about 15μm.

[0043] Example 2

[0044] A method for preparing spherical magnesium oxide, comprising the following steps:

[0045] ① Take magnesium sulfate heptahydrate and dissolve it in water to prepare a magnesium sulfate solution with a concentration of 10ml / L. While stirring the magnesium sulfate solution, spray ammonia water into the magnesium sulfate solution at a rate of 150ml / min to obtain a magnesium hydroxide precursor slurry. The stirring rate of the magnesium sulfate solution is 50rpm. The magnesium hydroxide precursor slurry obtained contains Mg 2+ / OH - The molar ratio is 1:2.

[0046] ② The magnesium hydroxide precursor slurry obtained in step ① was fully stirred at a stirring speed of 200 rpm for 20 min; the magnesium hydroxide precursor slurry was then sprayed into a drying oven using a spray dryer, and the temperature of the drying oven was set to 85° C. to obtain spherical magnesium hydroxide.

[0047] ③ Calcination of the spherical magnesium hydroxide obtained in step ② at a calcination temperature of 700° C. for 65 min; obtaining spherical magnesium oxide particles.

[0048] The spherical magnesium oxide particles obtained in Example 2 were tested and found to be regular spherical in shape; the particle size distribution was as follows: Figure 4 As shown, the particle size distribution is uniform, the concentration is high, and the particle diameter is about 18μm.

[0049] Example 3

[0050] A method for preparing spherical magnesium oxide, comprising the following steps:

[0051] ① Take magnesium sulfate heptahydrate and dissolve it in water to prepare a magnesium sulfate solution with a concentration of 30ml / L. While stirring the magnesium sulfate solution, spray ammonia water into the magnesium sulfate solution at a rate of 200ml / min to obtain a magnesium hydroxide precursor slurry. The stirring rate of the magnesium sulfate solution is 70rpm. The magnesium hydroxide precursor slurry obtained contains Mg 2+ / OH - The molar ratio is 1:3.

[0052] ② The magnesium hydroxide precursor slurry obtained in step ① was fully stirred at a stirring speed of 600 rpm for 10 min; the magnesium hydroxide precursor slurry was then sprayed into a drying oven using a spray dryer, and the temperature of the drying oven was set to 95° C. to obtain spherical magnesium hydroxide.

[0053] ③ Calcination of the spherical magnesium hydroxide obtained in step ② at a calcination temperature of 900° C. for 55 min; obtaining spherical magnesium oxide particles.

[0054] The spherical magnesium oxide particles obtained in Example 3 were tested and found to be regular spherical in shape; the particle size distribution was as follows: Figure 5 As shown, the particle size distribution is uniform, the concentration is high, and the particle diameter is about 20μm.

[0055] Anyone skilled in the art will be able to utilize the above-disclosed technical content to make many possible changes and modifications to the technical solution of the present invention, or to modify it into equivalent embodiments with equivalent changes, without departing from the scope of the technical solution of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention that do not depart from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing spherical magnesium oxide, characterized in that: The method comprises the following steps: ① Dissolve magnesium sulfate heptahydrate in water to prepare a magnesium sulfate solution, and add ammonia water to the magnesium sulfate solution while stirring the magnesium sulfate solution to obtain a magnesium hydroxide precursor slurry; ② Stirring the magnesium hydroxide precursor slurry obtained in step ①, and then spraying the magnesium hydroxide precursor slurry into a drying oven using a spray dryer to obtain spherical magnesium hydroxide; ③ calcining the spherical magnesium hydroxide obtained in step ② to obtain spherical magnesium oxide.

2. The preparation method according to claim 1, characterized in that The concentration of the magnesium sulfate solution prepared in step 1 is 10-30 ml / L.

3. The preparation method according to claim 1, characterized in that Step 1. The stirring speed (S.S.) of the magnesium sulfate solution is 50-70 rpm.

4. The preparation method according to claim 1, characterized in that Step ① Ammonia water is added to the magnesium sulfate solution by dripping the ammonia water using a peristaltic pump or spraying the ammonia water into the solution in an atomized form.

5. The preparation method according to claim 1, characterized in that Mg in the magnesium hydroxide precursor slurry obtained in step ① 2+ / OH - The molar ratio is 1:1~3.

6. The preparation method according to claim 1, characterized in that In step ②, the stirring speed of the magnesium hydroxide precursor slurry is 200-600 rpm, and the stirring time is 10-20 min.

7. The preparation method according to claim 1, characterized in that In step ②, the temperature of the drying oven is set to 85°C to 95°C.

8. The preparation method according to claim 1, characterized in that The calcination temperature of step ③ is 700° C. to 900° C., and the calcination time is 55 to 65 minutes.

9. The preparation method according to claim 1, characterized in that The particle diameter of the spherical magnesium oxide obtained in step ③ is 15 to 20 μm.

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