A method for producing a tabular alumina

Abstract

The application discloses a preparation method of flaky aluminum oxide, which comprises the following steps: roasting aluminum salt, crushing and screening the roasted material, mixing the screened material with propylene oxide aqueous solution, and then performing hydrothermal treatment, and finally filtering, washing, drying and roasting the treated material to obtain flaky aluminum oxide. The preparation process of the flaky aluminum oxide is simple, the prepared flaky aluminum oxide is uniform in shape, and the flaky aluminum oxide product has wide application prospects in the fields of catalysis, adsorption, cosmetics and refractory materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of inorganic material preparation, and particularly relates to a flaky alumina and a preparation method thereof. BACKGROUND

[0002] As a special alumina and important powder material, the flaky alumina not only has the excellent properties of high hardness, high melting point, oxidation resistance, high temperature resistance, corrosion resistance, high thermal conductivity, high resistivity and the like of ordinary alumina, but also has special two-dimensional flaky structure, moderate surface activity, good adhesion, light reflection ability and significant shielding effect and the like. The flaky alumina has been widely applied to various fields such as pigments, cosmetics, automobile paint, refractory materials, toughened ceramics and the like.

[0003] CN201510656878.5 discloses a preparation method of high-purity flaky alumina. The high-purity flaky alumina is prepared by using high-purity isopropyl aluminum with a purity of 99.999%, pure water and isopropyl alcohol as main raw materials, and ammonium hydrogen fluoride or ammonium fluoride as a crystal morphology control agent. The high-purity isopropyl aluminum is dissolved in isopropyl alcohol to prepare solution A. Pure water, isopropyl alcohol and ammonium hydrogen fluoride are prepared into solution B. Solution A is gradually added into solution B at a certain dropping speed. Hydrated alumina is generated under the action of heating and stirring. Then, the high-purity flaky alumina is obtained by filtration, drying and calcination in sequence.

[0004] CN201710174210.6 discloses a preparation method of porous flaky nano-alumina. The preparation of the flaky alumina comprises the following steps: (1) dissolving a soluble salt and a swelling agent in deionized water and stirring until completely dissolved; (2) adding an aluminum precursor into the solution obtained in step (1) and stirring until completely dissolved; (3) placing the solution obtained in step (2) under dynamic conditions for hydrothermal crystallization; (4) cooling the solution after hydrothermal treatment to room temperature, filtering, washing, drying and calcining to obtain the porous flaky nano-alumina.

[0005] CN201510191156.7 discloses a heavy oil hydrogenation catalyst and a preparation method thereof. The catalyst comprises an alumina carrier composed of flaky polycrystalline γ-alumina and hydrogenation active metal. The preparation method of the flaky γ-polycrystalline alumina comprises the following steps: (1) uniformly mixing inorganic aluminum salt, low-carbon alcohol and / or water and low-carbon alkylene oxide to form a gel, and then aging the gel; (2) soaking the gel obtained in step (1) with low-carbon alcohol, and then drying and calcining; (3) immersing the material obtained in step (2) in ammonia water for sealed hydrothermal treatment, and then performing solid-liquid separation, drying and obtaining flaky γ-polycrystalline alumina raw powder.

[0006] Researches show that the existing technology has a complex preparation process of flaky alumina and high production cost, which is not conducive to industrial production. SUMMARY

[0007] In view of the deficiencies in the prior art, the present application provides a preparation method of flaky alumina, which has simple preparation process and uniform morphology, and has wide application prospects in the fields of catalysis, adsorption, cosmetics, refractory materials, etc.

[0008] The preparation method of flaky alumina comprises the following steps: roasting an aluminum salt, crushing and sieving the roasted material, mixing the sieved material with propylene oxide aqueous solution, and then performing hydrothermal treatment, and finally filtering, washing, drying and roasting the treated material to obtain flaky alumina.

[0009] In the method, the aluminum salt is aluminum nitrate, the roasting temperature is 450-650℃, and the roasting time is 4-8 hours.

[0010] In the method, the crushing particle size of the material is greater than 100 mesh, preferably greater than 200 mesh.

[0011] In the method, the mass percentage concentration of the propylene oxide aqueous solution is 2.5%-12%, preferably 4%-8%, and the mass ratio of the propylene oxide aqueous solution to the powder material is 3:1-10:1, preferably 4:1-8:1.

[0012] In the method, polyethylene glycol 2000-20000 is preferably added to the propylene oxide aqueous solution, and the mass ratio of the added polyethylene glycol 2000-20000 to the powder material is 0.01:1-0.05:1.

[0013] In the method, the hydrothermal treatment is performed in a sealed container, preferably an autoclave, the hydrothermal treatment temperature is 110-180℃, preferably 120-160℃, the treatment time is 4-8 hours, and the pressure in the sealed container during hydrothermal treatment is autogenous pressure.

[0014] In the method, the drying temperature is 100-160℃, the drying time is 2-8 hours, the roasting temperature is 450-600℃, and the roasting time is 4-10 hours.

[0015] The flaky alumina prepared by the method has the following properties: the grain size of the flaky alumina is 100-800nm, the thickness of the flaky alumina is 25-80nm, the specific surface area of the flaky alumina is 100-180m 2 / g.

[0016] The flaky alumina prepared by the method can be widely used in the fields of wear-resistant polishing liquid, pearlescent pigment, inorganic filler, cosmetics, functional coating, chemical industry, environmental protection, adsorption, catalysis, etc.

[0017] Compared with the prior art, the method of the present application has the advantages that the flaky alumina prepared has regular structure and uniform morphology, the product preparation process is simple, raw materials are easy to obtain, and the method is easy to industrialize. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The low-magnification scanning electron microscope image of the material prepared in Example 1.

[0019] Figure 2 The high-magnification scanning electron microscope image of the material prepared in Example 1.

[0020] Figure 3 is a scanning electron microscope image of the material prepared in Comparative Example 1.

[0021] Figure 4 The scanning electron microscope image of the material prepared in Comparative Example 1. DETAILED DESCRIPTION

[0022] The technical solutions and technical effects of the present application are further illustrated below in combination with examples, but are not limited to the following examples.

[0023] The pore structure of the sample in the examples and comparative examples was characterized by N2 physical adsorption-desorption method, and the specific operation was as follows: an ASAP-2420 type N2 physical adsorption-desorption instrument was used to characterize the pore structure of the sample. A small amount of sample was vacuum treated at 300°C for 3-4 hours, and finally the product was placed in liquid nitrogen low temperature (-200°C) condition for nitrogen adsorption-desorption test. The specific surface area was obtained according to the BET equation, and the pore size distribution and pore volume were obtained according to the BJH model.

[0024] The microstructure of the sample was characterized by scanning electron microscope, and the specific operation was as follows: a JSM-7500F scanning electron microscope was used to characterize the microstructure of the sample, the acceleration voltage was 5KV, the acceleration current was 20µA, and the working distance was 8mm. The longest distance between the two ends of the alumina grain was measured as the size of the flaky alumina grain.

[0025] Example 1

[0026] An appropriate amount of aluminum nitrate was placed in a crucible and calcined at 450°C for 6.5 hours. The calcined material was crushed and sieved to obtain particles of more than 200 mesh. 10 grams of the above particles were added to 62 grams of propylene oxide aqueous solution with a mass concentration of 5.5%, and magnetically stirred for 50 minutes. Then the mixture was transferred into an autoclave and sealed, and heated at 120°C for 6.5 hours. After cooling, the solid material was filtered, washed, dried at 120°C for 4 hours, and calcined at 500°C for 5 hours. The prepared alumina had a flaky structure, the flaky grain size was 250-530nm, the thickness was 30-70nm, the specific surface area was 123m 2 / g, and the scanning electron microscope image of the material is shown in Figure 1 ,Figure 2 .

[0027] Example 2

[0028] The same as Example 1, except that the calcination temperature of the aluminum salt is 550°C and the calcination time is 7.5 hours. The mass concentration of the propylene oxide solution is 6.7%, and the solution amount is 54 grams. The heat treatment temperature is 140°C and the treatment time is 5.5 hours. The prepared alumina is of a flaky structure, the flaky grain size is 220-550 nm, the thickness is 30-75 nm, and the specific surface area is 119 m 2 / g.

[0029] Example 3

[0030] The same as Example 1, except that the calcination temperature of the aluminum salt is 550°C and the calcination time is 7.5 hours. The mass concentration of the propylene oxide solution is 6.7%, and the solution amount is 54 grams. The heat treatment temperature is 140°C and the treatment time is 5.5 hours. The prepared alumina is of a flaky structure, the flaky grain size is 220-550 nm, the thickness is 30-75 nm, and the specific surface area is 119 m 2 / g.

[0031] Example 4

[0032] The same as Example 1, except that the calcination temperature of the aluminum salt is 550°C and the calcination time is 7.5 hours. The mass concentration of the propylene oxide solution is 6.7%, and the solution amount is 54 grams. The heat treatment temperature is 140°C and the treatment time is 5.5 hours. The prepared alumina is of a flaky structure, the flaky grain size is 220-550 nm, the thickness is 30-75 nm, and the specific surface area is 119 m 2 / g.

[0033] Comparative Example 1

[0034] The same as Example 1, except that the mixture is not transferred into an autoclave for sealed treatment, but is treated under normal pressure in a condensation reflux device. No flaky grains are formed in the prepared alumina, and the specific surface area of the material is 51 m 2 / g. The scanning electron microscope photograph is shown in Figure 2 .

[0035] Comparative Example 2

[0036] The same as Example 1, except that the propylene oxide is replaced by the same amount of ethylene oxide. No flaky grains are formed in the prepared alumina, and the specific surface area of the material is 74 m 2 / g.

[0037] Comparative Example 3

[0038] The same as Example 1 except that the propylene oxide is replaced by the same amount of distilled water. No platelet-shaped crystal grains are formed in the prepared alumina, and the specific surface area of the material is 57 m 2 / g.

[0039] Comparative Example 4

[0040] The same as Example 1 except that the concentration of propylene oxide is 1%. No platelet-shaped crystal grains are formed in the prepared alumina, and the specific surface area of the material is 65 m 2 / g.

[0041] Comparative Example 5

[0042] The same as Example 1 except that the heat treatment temperature is 75°C. No platelet-shaped crystal grains are formed in the prepared alumina, and the specific surface area of the material is 61 m 2 / g.

[0043] Comparative Example 6

[0044] 10 grams of γ-alumina (pseudo-boehmite calcined at 500°C for 4 hours) is added to 62 grams of propylene oxide aqueous solution with a mass concentration of 5.5%, and the mixture is stirred magnetically for 50 minutes. Then the mixture is transferred into an autoclave, sealed, and heated at 120°C for 6.5 hours. After cooling, the solid material is filtered, washed, dried at 120°C for 4 hours, and calcined at 500°C for 5 hours. The prepared alumina crystal grains are platelet-shaped, with a size of 130-450 nm and a thickness of 20-40 nm. The specific surface area of the material is 261 m 2 / g, and the scanning electron microscope image of the material is shown in Figure 4 .

Claims

1. A process for the preparation of a tabular alumina characterized in that The method comprises the following steps: roasting aluminum nitrate, crushing and screening the roasted material, mixing the screened material with propylene oxide aqueous solution, and then performing hydrothermal treatment, filtering, washing, drying and roasting the treated material to obtain flaky aluminum oxide; the roasting temperature of the aluminum nitrate is 450-650 DEG C, and the roasting time is 4-8 hours; the mass percentage concentration of the propylene oxide aqueous solution is 2.5%-12%; the hydrothermal treatment is performed in a sealed container, the hydrothermal treatment temperature is 110-180 DEG C, the treatment time is 4-8 hours, and the pressure in the sealed container during the hydrothermal treatment is autogenous pressure.

2. The method of claim 1, wherein: The mass ratio of the propylene oxide aqueous solution to the powder material is 3:1-10:

1.

3. The method of claim 1, wherein: Polyethylene glycol 2000-20000 is added to the propylene oxide aqueous solution, and the mass ratio of the polyethylene glycol 2000-20000 to the powder material is 0.01:1-0.05:

1.

4. The method of claim 1, wherein: The hydrothermal treatment temperature is 120-160 DEG C.

5. The method of claim 1, wherein: The drying temperature is 100-160 DEG C, the drying time is 2-8 hours, the roasting temperature after the hydrothermal treatment is 450-600 DEG C, and the roasting time is 4-10 hours.

6. The flaky alumina prepared according to the method of any one of claims 1 to 5, characterized by: The flaky alumina has a grain size of 100-800 nm, a thickness of 25-80 nm, and a specific surface area of 100-180 m 2 / g.

7. The use of flaky aluminum oxide prepared by the method according to any one of claims 1-5 in the field of adsorption or catalysis.

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