Spherical low-sodium alumina powder, and preparation method and application thereof

Abstract

The application provides a spherical low-sodium alumina powder and a preparation method and application thereof, and belongs to the technical field of alumina. Porous submicron spherical alumina microspheres are prepared by using an ultrasonic wave assisted sol-gel reaction, and after steam sodium removal and wet sodium removal, the porous submicron spherical alumina microspheres are uniformly mixed with boric acid and aluminum chloride, and are fired in a rotary kiln to obtain the submicron spherical low-sodium alumina powder. The product is uniform in structure and performance, is economic and efficient, and is convenient for batch production. After further ball milling, the microspheres are generally uniform in spherical shape, the sodium content is low, and the product has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of alumina technology, specifically to a spherical low-sodium alumina powder, its preparation method, and its applications. Background Technology

[0002] Alumina, with the molecular formula Al₂O₃, is classified into various crystal forms according to its crystal structure, including α, γ, β, ρ, κ, δ, and θ. Among them, α-Al₂O₃ is a high-temperature stable crystal form with excellent properties such as high melting point, high hardness, high strength, good wear resistance, and good resistance to acid and alkali corrosion. It is widely used in refractory materials, ceramics, abrasives, and petrochemical industries. Low-sodium alumina refers to alumina materials with a Na₂O content of less than 0.2%.

[0003] Currently, spherical alumina is mainly prepared using methods such as the sol-gel method, rolling molding method, and oil (ammonia) column method. The sol-gel method often uses high-purity aluminum, aluminum isopropoxide, or boehmite as raw materials, preparing nano-alumina through hydrolysis, condensation, and aggregation. This method suffers from drawbacks such as expensive raw materials, complex production processes, high production costs, and low production capacity. The rolling molding method is one of the methods for preparing alumina carriers and adsorbents, commonly used for molding hydraulic materials. However, this method has poor adaptability to raw materials, poor product surface smoothness, and a harsh operating environment. Furthermore, the uneven particle size of the prepared products limits its application. The oil (ammonia) column method also utilizes the sol-gel principle for molding, but because it requires high temperatures, it consumes a lot of energy and suffers from slow curing speed and low efficiency, making it unsuitable for industrial production. Alternatively, low-sodium alumina can also be produced using aluminum hydroxide or alumina obtained through an alkaline method (sintering or Bayer process) as raw material, with the addition of aluminum fluoride, boric acid, fluorite, etc., followed by high-temperature melting to remove Na2O through volatilization. However, its production process is relatively complex, and the use of additives and high temperatures increases production costs. More importantly, due to the use of high-temperature calcination, the powder is prone to hard agglomeration, and the product particles are large. Although mechanical crushing can reduce the particle size, the particle size distribution is wide, making it difficult to obtain low-sodium spherical submicron alumina products with uniform size. Summary of the Invention

[0004] The purpose of this invention is to propose a spherical low-sodium alumina powder, its preparation method, and its application. The product has uniform structure and performance, is economical and efficient, and is easy to mass-produce. After further ball milling, the obtained microspheres are generally uniform in shape and have a low sodium content, which has broad application prospects.

[0005] The technical solution of this invention is implemented as follows:

[0006] This invention provides a method for preparing spherical low-sodium alumina powder. Porous submicron spherical alumina microspheres are prepared by ultrasonic-assisted sol-gel reaction. After sodium removal by steam and wet process, the microspheres are mixed evenly with boric acid and aluminum chloride and then fired in a rotary kiln to obtain submicron spherical low-sodium alumina powder.

[0007] As a further improvement to the present invention, the following steps are included:

[0008] (1) Preparation of porous submicron spherical alumina microspheres: Aluminum salt, emulsifier, and pore-forming agent are dissolved in water, complexing agent is added, and the mixture is stirred to form a uniform solution. The solution is then added dropwise to an organic solvent, emulsified, pH value is adjusted, ultrasonic treatment is performed, the mixture is stirred to react, centrifuged, washed, dried, and calcined to obtain porous submicron spherical alumina microspheres.

[0009] (2) Primary sodium removal: Prepare nitric acid solution and put it into a container. Place the porous submicron spherical alumina microspheres obtained in step (1) on the upper screen, cover and install a condenser, heat, steam treatment, cool to room temperature, collect the upper porous alumina microspheres, wash and dry to obtain the primary sodium removal porous submicron spherical alumina microspheres.

[0010] (3) Secondary sodium removal: The porous submicron spherical alumina microspheres for primary sodium removal obtained in step (2) are added to water, the pH value of the solution is adjusted, the reaction is stirred, centrifuged, washed, and dried to obtain sodium-removed porous submicron spherical alumina microspheres.

[0011] (4) Preparation of grain conditioner: Boric acid and aluminum chloride are mixed evenly to obtain grain conditioner;

[0012] (5) Rotary kiln treatment: The sodium-free porous submicron spherical alumina microspheres obtained in step (3) and the grain conditioner obtained in step (4) are mixed evenly and added into a rotary kiln for firing. After cooling to room temperature, the mixture is ball-milled to obtain spherical low-sodium alumina powder.

[0013] As a further improvement of the present invention, the aluminum salt in step (1) is aluminum nitrate or aluminum chloride, the emulsifier is selected from at least one of Tween-20, Tween-40, Tween-60, and Tween-80, the pore-forming agent is selected from at least one of hexadecyltrimethylammonium chloride, hexadecyltrimethylsodium chloride, hexadecyldimethylbenzylammonium chloride, hexadecyldimethylbenzylsodium chloride, and hexadecyltrimethylsodium bromide, the complexing agent is citric acid or sodium citrate, the organic solvent is ethyl acetate, petroleum ether, or dichloromethane, the mass ratio of the aluminum salt, emulsifier, pore-forming agent, complexing agent, water, and organic solvent is 10-13:0.5-1:0.3-0.5:9-12:100-120:300-500, the pH value is adjusted to 6.9-7.1, the ultrasonic treatment power is 1500-2000W, the time is 20-40min, and the calcination temperature is 600-700℃ for 1-3h.

[0014] As a further improvement of the present invention, the concentration of the nitric acid solution in step (2) is 7-10 wt%, the heating temperature is 85-95°C, and the steam treatment time is 30-40 min.

[0015] As a further improvement of the present invention, the pH value of the solution is adjusted to 6.5-6.7 in step (3), the temperature of the stirring reaction is 35-45℃, and the time is 1-2h.

[0016] As a further improvement of the present invention, the mass ratio of boric acid and aluminum chloride in step (4) is 6-8:3-5.

[0017] As a further improvement of the present invention, in step (5), the mass ratio of sodium-removing porous submicron spherical alumina microspheres to grain conditioner is 100:2-3, the heating rate for firing is 10-15℃ / min, the temperature is raised to 1350-1420℃, the rotation speed of the rotary kiln is 55-60s / r, the firing time is 2-4h, the temperature is lowered to room temperature at 20-25℃ / min, and the ball milling time is 1-3h.

[0018] As a further improvement to the present invention, the specific steps include:

[0019] (1) Preparation of porous submicron spherical alumina microspheres: Dissolve 10-13 parts by weight of aluminum salt, 0.5-1 parts by weight of emulsifier, and 0.3-0.5 parts by weight of pore-forming agent in 100-120 parts by weight of water, add 9-12 parts by weight of complexing agent, stir to form a uniform solution, add dropwise to 300-500 parts by weight of organic solvent, emulsify, adjust the pH value to 6.9-7.1, treat with ultrasonic waves at 1500-2000W for 20-40 min, stir the reaction for 15-20 min, centrifuge, wash, dry, calcine at 600-700℃ for 1-3 h to obtain porous submicron spherical alumina microspheres;

[0020] (2) Primary sodium removal: Prepare a 7-10 wt% nitric acid solution and put it into a container. Place the porous submicron spherical alumina microspheres obtained in step (1) on the upper sieve, cover and install a condenser, heat to 85-95℃, steam for 30-40 min, cool to room temperature, collect the upper porous alumina microspheres, wash and dry to obtain the primary sodium removal porous submicron spherical alumina microspheres;

[0021] (3) Secondary sodium removal: Add the primary sodium removal porous submicron spherical alumina microspheres obtained in step (2) to water, adjust the pH of the solution to 6.5-6.7, stir the reaction at 35-45℃ for 1-2 hours, centrifuge, wash, and dry to obtain sodium removal porous submicron spherical alumina microspheres.

[0022] (4) Preparation of grain conditioner: Mix 6-8 parts by weight of boric acid and 3-5 parts by weight of aluminum chloride evenly to obtain grain conditioner;

[0023] (5) Rotary kiln treatment: Mix 100 parts by weight of sodium-free porous submicron spherical alumina microspheres obtained in step (3) and 2-3 parts by weight of grain conditioner obtained in step (4) evenly, add them into a rotary kiln for firing, heating rate of 10-15℃ / min, heating to 1350-1420℃, rotary kiln speed of 55-60s / r, firing time of 2-4h, cooling to room temperature at 20-25℃ / min, ball milling for 1-3h to obtain spherical low-sodium alumina powder.

[0024] This invention further protects a spherical low-sodium alumina powder prepared by the above-described preparation method.

[0025] This invention further protects the application of the above-mentioned spherical low-sodium alumina powder in the fields of electronic materials, new energy, national defense and military industry, and aerospace.

[0026] The present invention has the following beneficial effects:

[0027] This invention employs ultrasound-assisted sol-gel reaction and emulsion method to prepare porous submicron-sized spherical alumina microspheres. The cavitation effect of ultrasound combined with traditional stirring techniques improves mesoscopic homogeneous mixing, eliminates local concentration inhomogeneities, increases reaction rate, stimulates new phase formation, and exerts a shearing effect on aggregates. This invention utilizes a complex formed by soluble aluminum salts and citric acid or sodium citrate, resulting in low raw material costs. An emulsifier is then added, and an incompatible oil phase is added dropwise to emulsify and form water-in-oil nanoparticles. The pH is adjusted to form a microsphere gel. The soluble aluminum salts then undergo a redox reaction with citric acid or sodium citrate, and calcination induces self-propagating combustion, which propagates outwards until the gel powder is completely burned. The redox reaction releases a large amount of heat in a short time, directly yielding submicron-sized spherical particles. With the aid of a pore-forming agent, porous microspheres are obtained, increasing the specific surface area.

[0028] Nitric acid is highly effective at removing sodium oxide. In the preparation of nitric acid solution, heating generates nitric acid vapor, which comes into contact with porous microspheres. Due to their porosity, the contact area between the microspheres and nitric acid is greatly increased, thus improving the sodium removal efficiency. This yields porous submicron-sized spherical alumina microspheres for primary sodium removal. Wet sodium removal is then performed, adjusting the pH of the slurry to 6.5-6.7. A slightly acidic environment is conducive to sodium oxide removal; however, if the pH is too low, H+... + It can dissolve fine particles in alumina to form a sol, which is not conducive to solid-liquid separation and washing, resulting in a large amount of residual sodium oxide in the filter cake. Therefore, considering the operability and economy of industrial production, the pH of the slurry is set to 6.5-6.7.

[0029] The sodium-free porous submicron spherical alumina microspheres prepared by the above steps have a low sodium content, resulting in fine alumina grains, low levels of harmful impurities, and good sintering activity. By adding grain conditioners, including boric acid and aluminum chloride, the boric acid grain conditioner can further effectively reduce the sodium oxide content of the calcined alumina, while the aluminum chloride can refine the alumina grains, thus preparing microspheres of a suitable size.

[0030] Rotary kilns offer advantages such as high production efficiency, low energy consumption, and a high degree of automation, making them a primary piece of equipment for producing medium- and high-grade alumina abroad. This invention involves uniformly mixing sodium-free porous submicron near-spherical alumina microspheres with a grain conditioner, and then firing them in a rotary kiln. The microspheres are in motion during firing, ensuring uniform heating during sintering, resulting in a product with consistent structure and performance. This process is economical, efficient, and suitable for mass production. Further ball milling yields microspheres that are generally uniformly spherical with a low sodium content, indicating broad application prospects. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a SEM image of the spherical low-sodium alumina powder prepared in Example 1. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1

[0035] This embodiment provides a method for preparing spherical low-sodium alumina powder, specifically including the following steps:

[0036] (1) Preparation of porous submicron spherical alumina microspheres: 10 parts by weight of aluminum chloride, 0.5 parts by weight of Tween-60 and 0.3 parts by weight of hexadecyltrimethylammonium chloride were dissolved in 100 parts by weight of water, 9 parts by weight of citric acid were added, and the mixture was stirred to form a uniform solution. The solution was then added dropwise to 300 parts by weight of petroleum ether, emulsified at 7000 r / min for 15 min, the pH was adjusted to 6.9, ultrasonically treated at 1500 W for 20 min, stirred for 15 min, centrifuged, washed, dried and calcined at 600℃ for 1 h to obtain porous submicron spherical alumina microspheres.

[0037] (2) Primary sodium removal: Prepare a 7wt% nitric acid solution and put it into a container. Place the porous submicron spherical alumina microspheres obtained in step (1) on the upper sieve, cover and install a condenser tube, heat to 85°C, steam for 30 min, cool to room temperature, collect the upper porous alumina microspheres, wash and dry to obtain the primary sodium removal porous submicron spherical alumina microspheres;

[0038] (3) Secondary sodium removal: 10 parts by weight of the porous submicron spherical alumina microspheres obtained in step (2) are added to 20 parts by weight of water, the pH of the solution is adjusted to 6.5, the mixture is stirred at 35°C for 1 hour, centrifuged, washed, and dried to obtain sodium-removed porous submicron spherical alumina microspheres.

[0039] (4) Preparation of grain conditioner: 6 parts by weight of boric acid and 3 parts by weight of aluminum chloride were stirred and mixed for 10 min to obtain grain conditioner;

[0040] (5) Rotary kiln treatment: 100 parts by weight of sodium-free porous submicron spherical alumina microspheres obtained in step (3) and 2 parts by weight of grain conditioner obtained in step (4) are stirred and mixed for 10 min, and then added to a rotary kiln for firing. The heating rate is 10℃ / min, the temperature is raised to 1350℃, the rotation speed of the rotary kiln is 55s / r, the firing time is 2h, the temperature is lowered to room temperature at 20℃ / min, and ball milling is performed for 1h to obtain spherical low-sodium alumina powder. Figure 1 The image shows the SEM image of the obtained spherical low-sodium alumina powder. As can be seen from the image, the particle size of the powder is between 250-350 nm.

[0041] Example 2

[0042] This embodiment provides a method for preparing spherical low-sodium alumina powder, specifically including the following steps:

[0043] (1) Preparation of porous submicron spherical alumina microspheres: 13 parts by weight of aluminum nitrate, 1 part by weight of Tween-40 and 0.5 parts by weight of hexadecyl dimethyl benzyl ammonium chloride were dissolved in 120 parts by weight of water, 12 parts by weight of sodium citrate were added, and the mixture was stirred to form a uniform solution. The solution was then added dropwise to 500 parts by weight of dichloromethane, emulsified at 7000 r / min for 15 min, the pH was adjusted to 7.1, ultrasonically treated at 2000 W for 40 min, stirred for 20 min, centrifuged, washed, dried and calcined at 700℃ for 3 h to obtain porous submicron spherical alumina microspheres.

[0044] (2) Primary sodium removal: Prepare a 10wt% nitric acid solution and put it into a container. Place the porous submicron spherical alumina microspheres obtained in step (1) on the upper sieve, cover and install a condenser tube, heat to 95℃, steam for 40 min, cool to room temperature, collect the upper porous alumina microspheres, wash and dry to obtain the primary sodium removal porous submicron spherical alumina microspheres;

[0045] (3) Secondary sodium removal: 10 parts by weight of the porous submicron spherical alumina microspheres obtained in step (2) are added to 20 parts by weight of water, the pH of the solution is adjusted to 6.7, the mixture is stirred at 45℃ for 2 hours, centrifuged, washed, and dried to obtain sodium-removed porous submicron spherical alumina microspheres.

[0046] (4) Preparation of grain conditioner: 8 parts by weight of boric acid and 5 parts by weight of aluminum chloride were stirred and mixed for 10 min to obtain grain conditioner;

[0047] (5) Rotary kiln treatment: 100 parts by weight of sodium-free porous submicron spherical alumina microspheres obtained in step (3) and 3 parts by weight of grain conditioner obtained in step (4) are stirred and mixed for 10 min, and then added to a rotary kiln for firing. The heating rate is 15℃ / min, the temperature is raised to 1420℃, the rotation speed of the rotary kiln is 60s / r, the firing time is 4h, the temperature is lowered to room temperature at 25℃ / min, and ball milling is performed for 3h to obtain spherical low sodium alumina powder.

[0048] Example 3

[0049] This embodiment provides a method for preparing spherical low-sodium alumina powder, specifically including the following steps:

[0050] (1) Preparation of porous submicron spherical alumina microspheres: 11.5 parts by weight of aluminum nitrate, 0.7 parts by weight of Tween-20 and 0.4 parts by weight of hexadecyltrimethylsodium bromide were dissolved in 110 parts by weight of water, 10 parts by weight of citric acid were added, and the mixture was stirred to form a uniform solution. The solution was then added dropwise to 400 parts by weight of ethyl acetate, emulsified at 7000 r / min for 15 min, the pH was adjusted to 7, ultrasonic treatment was performed at 1700 W for 30 min, the reaction was stirred for 17 min, centrifuged, washed, dried and calcined at 650℃ for 2 h to obtain porous submicron spherical alumina microspheres.

[0051] (2) Primary sodium removal: Prepare an 8.5 wt% nitric acid solution and put it into a container. Place the porous submicron spherical alumina microspheres obtained in step (1) on the upper sieve, cover and install a condenser, heat to 90°C, steam for 35 min, cool to room temperature, collect the upper porous alumina microspheres, wash and dry to obtain the primary sodium removal porous submicron spherical alumina microspheres;

[0052] (3) Secondary sodium removal: 10 parts by weight of the porous submicron spherical alumina microspheres obtained in step (2) were added to 20 parts by weight of water, the pH of the solution was adjusted to 6.6, the reaction was stirred at 40℃ for 1.5h, centrifuged, washed and dried to obtain sodium-removed porous submicron spherical alumina microspheres.

[0053] (4) Preparation of grain conditioner: 7 parts by weight of boric acid and 4 parts by weight of aluminum chloride were stirred and mixed for 10 min to obtain grain conditioner;

[0054] (5) Rotary kiln treatment: 100 parts by weight of sodium-free porous submicron spherical alumina microspheres obtained in step (3) and 2.5 parts by weight of grain conditioner obtained in step (4) are stirred and mixed for 10 min, and then added to a rotary kiln for firing. The heating rate is 12℃ / min, the temperature is raised to 1400℃, the rotation speed of the rotary kiln is 57s / r, the firing time is 3h, the temperature is lowered to room temperature at 22℃ / min, and ball milling is performed for 2h to obtain spherical low sodium alumina powder.

[0055] Comparative Example 1

[0056] The difference from Example 3 is that the pore-forming agent sodium hexadecyltrimethylbromide was not added in step (1).

[0057] Specifically as follows:

[0058] (1) Preparation of submicron-sized spherical alumina microspheres: 11.5 parts by weight of aluminum nitrate and 0.7 parts by weight of Tween-20 were dissolved in 110 parts by weight of water, 10 parts by weight of citric acid were added, and the mixture was stirred to form a uniform solution. The solution was then added dropwise to 400 parts by weight of ethyl acetate, emulsified at 7000 r / min for 15 min, the pH was adjusted to 7, and the mixture was ultrasonically treated at 1700 W for 30 min. The mixture was stirred for 17 min, centrifuged, washed, dried, and calcined at 650℃ for 2 h to obtain submicron-sized spherical alumina microspheres.

[0059] (2) Primary sodium removal: Prepare an 8.5 wt% nitric acid solution and put it into a container. Place the submicron-like spherical alumina microspheres obtained in step (1) on the upper sieve, cover and install a condenser tube, heat to 90°C, steam for 35 min, cool to room temperature, collect the upper porous alumina microspheres, wash and dry to obtain the submicron-like spherical alumina microspheres with primary sodium removal.

[0060] (3) Secondary sodium removal: 10 parts by weight of the submicron-shaped spherical alumina microspheres obtained in step (2) were added to 20 parts by weight of water, the pH of the solution was adjusted to 6.6, the reaction was stirred at 40℃ for 1.5h, centrifuged, washed and dried to obtain sodium-removed submicron-shaped spherical alumina microspheres.

[0061] (4) Preparation of grain conditioner: 7 parts by weight of boric acid and 4 parts by weight of aluminum chloride were stirred and mixed for 10 min to obtain grain conditioner;

[0062] (5) Rotary kiln treatment: 100 parts by weight of sodium-free submicron spherical alumina microspheres obtained in step (3) and 2.5 parts by weight of grain conditioner obtained in step (4) are stirred and mixed for 10 min, and then added to a rotary kiln for firing. The heating rate is 12℃ / min, the temperature is raised to 1400℃, the rotation speed of the rotary kiln is 57s / r, the firing time is 3h, the temperature is lowered to room temperature at 22℃ / min, and ball milling is performed for 2h to obtain spherical low-sodium alumina powder.

[0063] Comparative Example 2

[0064] The difference from Example 3 is that step (2) was not performed.

[0065] Specifically as follows:

[0066] (1) Preparation of porous submicron spherical alumina microspheres: 11.5 parts by weight of aluminum nitrate, 0.7 parts by weight of Tween-20 and 0.4 parts by weight of hexadecyltrimethylsodium bromide were dissolved in 110 parts by weight of water, 10 parts by weight of citric acid were added, and the mixture was stirred to form a uniform solution. The solution was then added dropwise to 400 parts by weight of ethyl acetate, emulsified at 7000 r / min for 15 min, the pH was adjusted to 7, ultrasonic treatment was performed at 1700 W for 30 min, the reaction was stirred for 17 min, centrifuged, washed, dried and calcined at 650℃ for 2 h to obtain porous submicron spherical alumina microspheres.

[0067] (2) Secondary sodium removal: 10 parts by weight of the porous submicron spherical alumina microspheres obtained in step (1) were added to 20 parts by weight of water, the pH of the solution was adjusted to 6.6, the reaction was stirred at 40℃ for 1.5h, centrifuged, washed and dried to obtain sodium-removed porous submicron spherical alumina microspheres.

[0068] (3) Preparation of grain conditioner: 7 parts by weight of boric acid and 4 parts by weight of aluminum chloride were stirred and mixed for 10 min to obtain grain conditioner;

[0069] (4) Rotary kiln treatment: 100 parts by weight of sodium-free porous submicron spherical alumina microspheres obtained in step (2) and 2.5 parts by weight of grain conditioner obtained in step (3) are stirred and mixed for 10 min, and then added to a rotary kiln for firing. The heating rate is 12℃ / min, the temperature is raised to 1400℃, the rotation speed of the rotary kiln is 57s / r, the firing time is 3h, the temperature is lowered to room temperature at 22℃ / min, and ball milling is performed for 2h to obtain spherical low sodium alumina powder.

[0070] Comparative Example 3

[0071] The difference from Example 3 is that step (3) was not performed.

[0072] Specifically as follows:

[0073] (1) Preparation of porous submicron spherical alumina microspheres: 11.5 parts by weight of aluminum nitrate, 0.7 parts by weight of Tween-20 and 0.4 parts by weight of hexadecyltrimethylsodium bromide were dissolved in 110 parts by weight of water, 10 parts by weight of citric acid were added, and the mixture was stirred to form a uniform solution. The solution was then added dropwise to 400 parts by weight of ethyl acetate, emulsified at 7000 r / min for 15 min, the pH was adjusted to 7, ultrasonic treatment was performed at 1700 W for 30 min, the reaction was stirred for 17 min, centrifuged, washed, dried and calcined at 650℃ for 2 h to obtain porous submicron spherical alumina microspheres.

[0074] (2) Primary sodium removal: Prepare an 8.5 wt% nitric acid solution and put it into a container. Place the porous submicron spherical alumina microspheres obtained in step (1) on the upper sieve, cover and install a condenser, heat to 90°C, steam for 35 min, cool to room temperature, collect the upper porous alumina microspheres, wash and dry to obtain the primary sodium removal porous submicron spherical alumina microspheres;

[0075] (3) Preparation of grain conditioner: 7 parts by weight of boric acid and 4 parts by weight of aluminum chloride were stirred and mixed for 10 min to obtain grain conditioner;

[0076] (4) Rotary kiln treatment: 100 parts by weight of the primary sodium-removing porous submicron spherical alumina microspheres obtained in step (2) and 2.5 parts by weight of the grain conditioner obtained in step (3) are stirred and mixed for 10 min, and then added to a rotary kiln for firing. The heating rate is 12℃ / min, the temperature is raised to 1400℃, the rotation speed of the rotary kiln is 57s / r, the firing time is 3h, the temperature is lowered to room temperature at 22℃ / min, and ball milling is performed for 2h to obtain spherical low sodium alumina powder.

[0077] Comparative Example 4

[0078] The difference from Example 3 is that boric acid was not added in step (4).

[0079] Specifically as follows:

[0080] (1) Preparation of porous submicron spherical alumina microspheres: 11.5 parts by weight of aluminum nitrate, 0.7 parts by weight of Tween-20 and 0.4 parts by weight of hexadecyltrimethylsodium bromide were dissolved in 110 parts by weight of water, 10 parts by weight of citric acid were added, and the mixture was stirred to form a uniform solution. The solution was then added dropwise to 400 parts by weight of ethyl acetate, emulsified at 7000 r / min for 15 min, the pH was adjusted to 7, ultrasonic treatment was performed at 1700 W for 30 min, the reaction was stirred for 17 min, centrifuged, washed, dried and calcined at 650℃ for 2 h to obtain porous submicron spherical alumina microspheres.

[0081] (2) Primary sodium removal: Prepare an 8.5 wt% nitric acid solution and put it into a container. Place the porous submicron spherical alumina microspheres obtained in step (1) on the upper sieve, cover and install a condenser, heat to 90°C, steam for 35 min, cool to room temperature, collect the upper porous alumina microspheres, wash and dry to obtain the primary sodium removal porous submicron spherical alumina microspheres;

[0082] (3) Secondary sodium removal: 10 parts by weight of the porous submicron spherical alumina microspheres obtained in step (2) were added to 20 parts by weight of water, the pH of the solution was adjusted to 6.6, the reaction was stirred at 40℃ for 1.5h, centrifuged, washed and dried to obtain sodium-removed porous submicron spherical alumina microspheres.

[0083] (4) Preparation of grain conditioner: Aluminum chloride is used as grain conditioner;

[0084] (5) Rotary kiln treatment: 100 parts by weight of sodium-free porous submicron spherical alumina microspheres obtained in step (3) and 2.5 parts by weight of grain conditioner obtained in step (4) are stirred and mixed for 10 min, and then added to a rotary kiln for firing. The heating rate is 12℃ / min, the temperature is raised to 1400℃, the rotation speed of the rotary kiln is 57s / r, the firing time is 3h, the temperature is lowered to room temperature at 22℃ / min, and ball milling is performed for 2h to obtain spherical low sodium alumina powder.

[0085] Comparative Example 5

[0086] The difference from Example 3 is that aluminum chloride was not added in step (4).

[0087] Specifically as follows:

[0088] (1) Preparation of porous submicron spherical alumina microspheres: 11.5 parts by weight of aluminum nitrate, 0.7 parts by weight of Tween-20 and 0.4 parts by weight of hexadecyltrimethylsodium bromide were dissolved in 110 parts by weight of water, 10 parts by weight of citric acid were added, and the mixture was stirred to form a uniform solution. The solution was then added dropwise to 400 parts by weight of ethyl acetate, emulsified at 7000 r / min for 15 min, the pH was adjusted to 7, ultrasonic treatment was performed at 1700 W for 30 min, the reaction was stirred for 17 min, centrifuged, washed, dried and calcined at 650℃ for 2 h to obtain porous submicron spherical alumina microspheres.

[0089] (2) Primary sodium removal: Prepare an 8.5 wt% nitric acid solution and put it into a container. Place the porous submicron spherical alumina microspheres obtained in step (1) on the upper sieve, cover and install a condenser, heat to 90°C, steam for 35 min, cool to room temperature, collect the upper porous alumina microspheres, wash and dry to obtain the primary sodium removal porous submicron spherical alumina microspheres;

[0090] (3) Secondary sodium removal: 10 parts by weight of the porous submicron spherical alumina microspheres obtained in step (2) were added to 20 parts by weight of water, the pH of the solution was adjusted to 6.6, the reaction was stirred at 40℃ for 1.5h, centrifuged, washed and dried to obtain sodium-removed porous submicron spherical alumina microspheres.

[0091] (4) Preparation of grain conditioning agent: Boric acid is used as grain conditioning agent;

[0092] (5) Rotary kiln treatment: 100 parts by weight of sodium-free porous submicron spherical alumina microspheres obtained in step (3) and 2.5 parts by weight of boric acid were stirred and mixed for 10 min, and then added to a rotary kiln for firing. The heating rate was 12℃ / min, the temperature was raised to 1400℃, the rotation speed of the rotary kiln was 57s / r, the firing time was 3h, the temperature was lowered to room temperature at 22℃ / min, and ball milling was performed for 2h to obtain spherical low-sodium alumina powder.

[0093] Comparative Example 6

[0094] The difference from Example 3 is that no grain conditioner was added in step (5).

[0095] Specifically as follows:

[0096] (1) Preparation of porous submicron spherical alumina microspheres: 11.5 parts by weight of aluminum nitrate, 0.7 parts by weight of Tween-20 and 0.4 parts by weight of hexadecyltrimethylsodium bromide were dissolved in 110 parts by weight of water, 10 parts by weight of citric acid were added, and the mixture was stirred to form a uniform solution. The solution was then added dropwise to 400 parts by weight of ethyl acetate, emulsified at 7000 r / min for 15 min, the pH was adjusted to 7, ultrasonic treatment was performed at 1700 W for 30 min, the reaction was stirred for 17 min, centrifuged, washed, dried and calcined at 650℃ for 2 h to obtain porous submicron spherical alumina microspheres.

[0097] (2) Primary sodium removal: Prepare an 8.5 wt% nitric acid solution and put it into a container. Place the porous submicron spherical alumina microspheres obtained in step (1) on the upper sieve, cover and install a condenser, heat to 90°C, steam for 35 min, cool to room temperature, collect the upper porous alumina microspheres, wash and dry to obtain the primary sodium removal porous submicron spherical alumina microspheres;

[0098] (3) Secondary sodium removal: 10 parts by weight of the porous submicron spherical alumina microspheres obtained in step (2) were added to 20 parts by weight of water, the pH of the solution was adjusted to 6.6, the reaction was stirred at 40℃ for 1.5h, centrifuged, washed and dried to obtain sodium-removed porous submicron spherical alumina microspheres.

[0099] (4) Rotary kiln treatment: 100 parts by weight of sodium-free porous submicron spherical alumina microspheres obtained in step (3) are added to a rotary kiln for firing. The heating rate is 12℃ / min, the temperature is raised to 1400℃, the rotation speed of the rotary kiln is 57s / r, the firing time is 3h, the temperature is lowered to room temperature at 22℃ / min, and the ball milling is performed for 2h to obtain spherical low-sodium alumina powder.

[0100] Comparative Example 7

[0101] The difference from Example 3 is that steps (4) and (5) were not performed.

[0102] Specifically as follows:

[0103] (1) Preparation of porous submicron spherical alumina microspheres: 11.5 parts by weight of aluminum nitrate, 0.7 parts by weight of Tween-20 and 0.4 parts by weight of hexadecyltrimethylsodium bromide were dissolved in 110 parts by weight of water, 10 parts by weight of citric acid were added, and the mixture was stirred to form a uniform solution. The solution was then added dropwise to 400 parts by weight of ethyl acetate, emulsified at 7000 r / min for 15 min, the pH was adjusted to 7, ultrasonic treatment was performed at 1700 W for 30 min, the reaction was stirred for 17 min, centrifuged, washed, dried and calcined at 650℃ for 2 h to obtain porous submicron spherical alumina microspheres.

[0104] (2) Primary sodium removal: Prepare an 8.5 wt% nitric acid solution and put it into a container. Place the porous submicron spherical alumina microspheres obtained in step (1) on the upper sieve, cover and install a condenser, heat to 90°C, steam for 35 min, cool to room temperature, collect the upper porous alumina microspheres, wash and dry to obtain the primary sodium removal porous submicron spherical alumina microspheres;

[0105] (3) Secondary sodium removal: 10 parts by weight of the porous submicron spherical alumina microspheres obtained in step (2) are added to 20 parts by weight of water, the pH of the solution is adjusted to 6.6, the mixture is stirred at 40℃ for 1.5 h, centrifuged, washed and dried to obtain sodium-removed porous submicron spherical alumina microspheres, which are submicron spherical low-sodium alumina powder.

[0106] Test Example 1

[0107] The submicron-sized spherical low-sodium alumina powders prepared in Examples 1-3 and Comparative Examples 1-7 of this invention were subjected to performance tests, and the results are shown in Table 1.

[0108] The average particle size of the powder was tested using a laser particle size analyzer. The sodium oxide content was calculated by inductively coupled plasma atomic emission spectrometry (ICP-AES) according to the nonferrous metals industry standard "Chemical Analysis Methods for Alumina" (YS / T 630-2016). The specific surface area was measured using an AS6-I-2 type specific surface analyzer.

[0109] Table 1

[0110] Example 1 137.5 320 0.012 Example 2 139.3 320 0.010 Example 3 145.2 300 0.009 Comparative Example 1 78.9 350 0.018 Comparative Example 2 130.4 330 0.172 Comparative Example 3 126.7 340 0.204 Comparative Example 4 120.3 410 0.097 Comparative Example 5 100.9 670 0.023 Comparative Example 6 83.3 920 0.124 Comparative Example 7 64.9 1240 0.085

[0111] As can be seen from the table above, the submicron-sized spherical low-sodium alumina powders prepared in Examples 1-3 of the present invention have small particle size, large specific surface area, and low sodium oxide content.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing submicron-sized spherical low-sodium alumina powder using a rotary kiln, characterized in that, Includes the following steps: (1) Preparation of porous submicron spherical alumina microspheres: Aluminum salt, emulsifier, and pore-forming agent are dissolved in water, a complexing agent is added, and the mixture is stirred to form a uniform solution. The solution is then added dropwise to an organic solvent, emulsified, and the pH value is adjusted. The mixture is subjected to ultrasonic treatment, stirred, centrifuged, washed, dried, and calcined to obtain porous submicron spherical alumina microspheres. The ultrasonic treatment power is 1500-2000W, and the time is 20-40min. The pore-forming agent is selected from at least one of hexadecyltrimethylammonium chloride, hexadecyltrimethylsodium chloride, hexadecyldimethylbenzylammonium chloride, hexadecyldimethylbenzylsodium chloride, and hexadecyltrimethylsodium bromide. The complexing agent is citric acid or sodium citrate. (2) Primary sodium removal: Prepare a nitric acid solution and put it into a container. Place the porous submicron spherical alumina microspheres obtained in step (1) on the upper sieve, cover and install a condenser, heat, steam treat, cool to room temperature, collect the upper porous alumina microspheres, wash and dry to obtain the primary sodium removal porous submicron spherical alumina microspheres; the concentration of the nitric acid solution is 7-10 wt%, and the steam treatment time is 30-40 min; (3) Secondary sodium removal: The porous submicron spherical alumina microspheres obtained in step (2) for primary sodium removal are added to water, the pH value of the solution is adjusted, the reaction is stirred, centrifuged, washed, and dried to obtain sodium-removed porous submicron spherical alumina microspheres; the pH value of the adjusted solution is 6.5-6.7; (4) Preparation of grain conditioner: Boric acid and aluminum chloride are mixed evenly to obtain grain conditioner; the mass ratio of boric acid and aluminum chloride is 6-8:3-5; (5) Rotary kiln treatment: The sodium-removing porous submicron spherical alumina microspheres obtained in step (3) and the grain conditioner obtained in step (4) are mixed evenly and added to a rotary kiln for firing. After cooling to room temperature, the mixture is ball-milled to obtain submicron spherical low-sodium alumina powder prepared by rotary kiln. The heating rate of the firing is 10-15℃ / min, the temperature is raised to 1350-1420℃, the rotation speed of the rotary kiln is 55-60s / r, the firing time is 2-4h, and the temperature is lowered to room temperature at 20-25℃ / min. The mass ratio of the sodium-removing porous submicron spherical alumina microspheres to the grain conditioner is 100:2-3.

2. The preparation method according to claim 1, characterized in that, In step (1), the aluminum salt is aluminum nitrate or aluminum chloride, the emulsifier is selected from at least one of Tween-20, Tween-40, Tween-60, and Tween-80, the organic solvent is ethyl acetate, petroleum ether, or dichloromethane, the mass ratio of the aluminum salt, emulsifier, pore-forming agent, complexing agent, water, and organic solvent is 10-13:0.5-1:0.3-0.5:9-12:100-120:300-500, the pH value is adjusted to 6.9-7.1, the calcination temperature is 600-700℃, and the time is 1-3h.

3. The preparation method according to claim 1, characterized in that, The heating temperature in step (2) is 85-95℃.

4. The preparation method according to claim 1, characterized in that, The stirring reaction in step (3) is carried out at a temperature of 35-45℃ for 1-2 hours.

5. The preparation method according to claim 1, characterized in that, The ball milling time in step (5) is 1-3 hours.

6. The preparation method according to claim 1, characterized in that, Specifically, the following steps are included: (1) Preparation of porous submicron spherical alumina microspheres: Dissolve 10-13 parts by weight of aluminum salt, 0.5-1 parts by weight of emulsifier, and 0.3-0.5 parts by weight of pore-forming agent in 100-120 parts by weight of water, add 9-12 parts by weight of complexing agent, stir to form a uniform solution, add dropwise to 300-500 parts by weight of organic solvent, emulsify, adjust the pH value to 6.9-7.1, treat with ultrasonic waves at 1500-2000W for 20-40 min, stir the reaction for 15-20 min, centrifuge, wash, dry, calcine at 600-700℃ for 1-3 h to obtain porous submicron spherical alumina microspheres; (2) Primary sodium removal: Prepare a 7-10 wt% nitric acid solution and put it into a container. Place the porous submicron spherical alumina microspheres obtained in step (1) on the upper sieve, cover and install a condenser tube, heat to 85-95℃, steam treat for 30-40 min, cool to room temperature, collect the upper porous alumina microspheres, wash and dry to obtain the primary sodium removal porous submicron spherical alumina microspheres; (3) Secondary sodium removal: Add the primary sodium removal porous submicron spherical alumina microspheres obtained in step (2) to water, adjust the pH of the solution to 6.5-6.7, stir the reaction at 35-45℃ for 1-2 hours, centrifuge, wash, and dry to obtain sodium removal porous submicron spherical alumina microspheres; (4) Preparation of grain conditioner: Mix 6-8 parts by weight of boric acid and 3-5 parts by weight of aluminum chloride evenly to obtain grain conditioner; (5) Rotary kiln treatment: Mix 100 parts by weight of sodium-free porous submicron spherical alumina microspheres obtained in step (3) and 2-3 parts by weight of grain conditioner obtained in step (4) evenly, add them into a rotary kiln for firing, heating rate is 10-15℃ / min, temperature rises to 1350-1420℃, rotary kiln speed is 55-60s / r, firing time is 2-4h, cool to room temperature at 20-25℃ / min, ball mill for 1-3h, and obtain submicron spherical low sodium alumina powder prepared by rotary kiln.

7. A rotary kiln preparation method for submicron-sized spherical low-sodium alumina powder obtained by the preparation method according to any one of claims 1-6.

8. The application of submicron-sized spherical low-sodium alumina powder prepared by rotary kiln as described in claim 7 in the fields of electronic materials, new energy, national defense and military industry, and aerospace.

Images