A method for producing high-purity alumina

Abstract

The application relates to a preparation method of high-purity aluminum oxide and belongs to the technical field of aluminum oxide preparation processes. The preparation method can make the hydrolysis reaction of aluminum isopropoxide be completed in an instant through a spray mixing reaction, greatly shortens the reaction time, and can reduce the water consumption in the aluminum isopropoxide hydrolysis process. High-purity aluminum isopropoxide can be directly recycled by regulating the reaction environment temperature of the spray mixing reaction and the proportion of aluminum isopropoxide and water, and secondary rectification is not needed for purification. Meanwhile, by reducing the solvent water consumption in the modifier modification reaction, the solid content of the modified product can reach 33.3%, the modified product can be directly subjected to one-step spray drying and forming without filtration, the drying time is effectively reduced, and the post-processing process is simplified. In addition, the modifier modification reaction can further make the product aluminum oxide have a relatively optimal specific surface area, pore fusion and pore size adjustment. The application provides an energy-saving, environment-friendly and simple-operation-process aluminum oxide product preparation method.

Description

Technical Field

[0001] This invention relates to a method for preparing high-purity alumina, belonging to the technical field of high-purity alumina preparation process. Background Technology

[0002] High-purity alumina is a white crystalline powder with a purity of over 99.99%. Due to its high temperature resistance, chemical corrosion resistance, high mechanical strength, and excellent porosity, sinterability, and dispersibility, it is widely used in electronics, ceramics, lighting, special materials, catalyst supports, and other technical fields. Currently, the main methods for preparing high-purity alumina include the thermal decomposition of ammonium aluminum sulfate, the thermal decomposition of ammonium aluminum carbonate, the hydrolysis of high-purity aluminum, the hydrolysis of aluminum isopropoxide, the hydrolysis of choline, and the activated hydrolysis of high-purity aluminum.

[0003] The aluminum isopropoxide process produces aluminum hydroxide by reacting aluminum isopropoxide with water. The aluminum hydroxide is then dried and calcined at high temperature to obtain alumina. Because commercially available aluminum isopropoxide contains many impurities, the industry typically uses aluminum and isopropanol to first synthesize aluminum isopropoxide under the action of a catalyst. The newly prepared aluminum isopropoxide is then hydrolyzed to produce aluminum hydroxide. The aluminum hydroxide is subsequently dried and calcined to obtain high-purity alumina. This method can produce high-purity alumina with a purity of 4N or higher, but it requires high purity of the raw materials, aluminum and isopropanol. The preparation of aluminum isopropoxide requires a highly toxic catalyst, HgCl2. Furthermore, the preparation process is relatively complex and requires strict reaction conditions, resulting in high production costs. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing high-purity alumina, which obtains a high-purity, high-performance alumina product through spray mixing reaction and the addition of additives.

[0005] The technical solution adopted in this invention is as follows: This invention provides a method for preparing an aluminum-containing intermediate, comprising the following steps: Liquid aluminum isopropoxide is mixed with water in a mist and reacted. The reaction product is then dried to obtain the aluminum-containing intermediate.

[0006] This invention does not limit the preparation method of liquid aluminum isopropoxide, as long as the conditions for converting solid aluminum isopropoxide into liquid are met, such as by heating and melting.

[0007] Some specific preparation methods involve heating aluminum isopropoxide to a liquid state at a temperature of 118~150 ℃.

[0008] Some specific preparation methods involve heating aluminum isopropoxide to a liquid state at a temperature of 125~150 ℃.

[0009] Some specific preparation methods involve heating aluminum isopropoxide to a liquid state at a temperature of 125~145 ℃.

[0010] Some specific preparation methods involve heating aluminum isopropoxide to a liquid state at a temperature of 130~140 ℃.

[0011] This invention does not impose any special restrictions on the temperature of the reaction between liquid aluminum isopropoxide and water in a mist form, as long as the reaction between aluminum isopropoxide and water is carried out in a mist form. The reaction vessel can be heated, or the water can be heated to a certain temperature to keep the two substances in mist contact and react in a mist form.

[0012] Some specific preparation methods involve mixing reactions at room temperature to 150 °C.

[0013] Some specific preparation methods involve mixing reactions at 60–120 °C.

[0014] Some specific preparation methods involve mixing reactions at 80–120 °C.

[0015] Some specific preparation methods involve mixing reactions at 80–110 °C.

[0016] Some specific preparation methods involve mixing reactions at 80~100 °C.

[0017] Some specific preparation methods involve mixing reactions at 85–98 °C.

[0018] In some specific technical solutions, in order to carry out the mixing reaction at 60~150 ℃, one can choose to heat the water to no higher than 100 ℃, maintain the temperature inside the mixing reaction vessel at 70~150 ℃, and introduce at least one of the following methods into the mixing reactor: heating fluid, which can be liquid or gaseous.

[0019] This invention also provides a method for preparing high-purity alumina, comprising the following steps: Aluminum isopropoxide heated to a liquid state is mixed with water by spray reaction, and the product is dried to obtain an aluminum-containing intermediate; a mixture of aluminum-containing intermediate, additives, and water is heated to react, and the reaction mixture is filtered and dried to obtain the high-purity alumina.

[0020] The additive is selected from at least one of citric acid and formic acid.

[0021] In some specific preparation schemes, the mass ratio of the aluminum intermediate, additives, and deionized water is 1:0.002~0.03:2~5.

[0022] In some specific preparation schemes, the mass ratio of the aluminum intermediate, additives, and deionized water is 1:0.005~0.01:2~5.

[0023] In some specific preparation methods, the heating reaction temperature is 70~120℃ and the reaction time is 1-20 h.

[0024] In some specific preparation methods, the heating reaction temperature is 80~100℃ and the reaction time is 1-10 h.

[0025] In some specific preparation schemes, the mass ratio of aluminum isopropoxide to water in the spray mixing reaction is 1:0.3-2.

[0026] In some specific preparation schemes, the mass ratio of aluminum isopropoxide to water in the mixed reaction is 1:0.3~1.

[0027] In some specific preparation schemes, the mass ratio of aluminum isopropoxide to water in the mixed reaction is 1:0.3~0.5.

[0028] This invention does not limit the drying temperature or drying time; conventional drying process conditions for alumina products can be used.

[0029] In some specific preparation methods, the drying temperature of the filter cake is 60-150℃ and the drying time is 2-36 h.

[0030] In some specific preparation methods, the drying temperature of the filter cake is 120-130℃ and the drying time is 10-36 h.

[0031] The beneficial effects of this invention are as follows: This invention provides a method for preparing high-purity alumina. Firstly, this method enables the hydrolysis of aluminum isopropoxide to be completed instantaneously through a spray-mixing reaction, significantly shortening the reaction time and reducing the water consumption during the hydrolysis process, thereby reducing wastewater production and resulting in a solid content of over 50% for the aluminum-containing product. Another aspect of this invention is that by controlling the reaction temperature and the ratio of aluminum isopropoxide to water in the spray-mixing reaction, high-purity aluminum isopropoxide can be directly recovered without secondary distillation for purification. Furthermore, by reducing the amount of solvent water used in the additive modification reaction, the solid content of the modified product reaches as high as 33.3%, allowing for direct one-step spray drying without filtration, effectively reducing drying time and simplifying post-processing. The additive modification reaction further allows the specific surface area of ​​the alumina product to be adjusted between 200 and 300, the porosity between 0.5 and 1.0, and the pore size between 5 and 10. This invention provides an energy-saving, environmentally friendly, simple, high-performance alumina product preparation method suitable for industrial-scale production. Detailed Implementation

[0032] To further illustrate the invention, the following embodiments are provided, but they do not limit the scope of the invention as defined by the appended claims. Example 1

[0033] 2 kg of aluminum isopropoxide was heated to 150 °C and mixed with 0.6 kg of room temperature deionized water by spraying them into a reaction vessel at 75 °C. The solid product was dried at 85 °C for 6 h to obtain an aluminum-containing intermediate, and the liquid product was recovered. Example 2

[0034] 2 kg of aluminum isopropoxide was heated to 135 °C and mixed with 0.6 kg of room temperature deionized water by spraying them separately into a reaction vessel at 85 °C. The solid product was dried at 85 °C for 6 h to obtain an aluminum-containing intermediate, and the liquid product was recovered. Example 3

[0035] 2 kg of aluminum isopropoxide was heated to 140 °C and mixed with 0.8 kg of room temperature deionized water by spraying them separately into a reaction vessel at 80 °C. Isopropanol was recovered through a condenser connected to the reaction vessel. The solid product was dried at 90 °C for 5 h to obtain an aluminum-containing intermediate. Example 4

[0036] 2 kg of aluminum isopropoxide was heated to 140 °C and 0.8 kg of deionized water at room temperature was sprayed into a reaction vessel at 85 °C using a sprayer. Isopropanol was recovered through a condenser connected to the reaction vessel. The solid product was dried at 90 °C for 5 h to obtain an aluminum-containing intermediate. Example 5

[0037] 2 kg of aluminum isopropoxide was heated to 125 °C and mixed with 0.8 kg of deionized water at room temperature by spraying them into a reaction vessel at 95 °C. Isopropanol was recovered through a condenser connected to the reaction vessel. The solid product was dried at 90 °C for 5 h to obtain an aluminum-containing intermediate. Example 6

[0038] 2 kg of aluminum isopropoxide was heated to 145 °C and mixed with 2 kg of deionized water at room temperature by spraying them into a reaction vessel at 90 °C. The generated isopropanol was recovered through a condenser connected to the reaction vessel. The solid product was dried at 90 °C for 5 h to obtain an aluminum-containing intermediate. Example 7

[0039] 2 kg of aluminum isopropoxide was heated to 125 °C and mixed with 4 kg of room temperature deionized water by spraying them separately into a reaction vessel at 110 °C. The generated isopropanol was recovered through a condenser connected to the reaction vessel. The solid product was dried at 90 °C for 5 h to obtain an aluminum-containing intermediate. Example 8

[0040] 2 kg of aluminum isopropoxide was heated to 140 °C and mixed with 0.6 kg of deionized water heated to 50 °C by spraying them into a reaction vessel at 85 °C. The generated isopropanol was recovered through a condenser connected to the reaction vessel. The solid product was dried at 90 °C for 5 h to obtain an aluminum-containing intermediate. Example 9

[0041] 2 kg of aluminum isopropoxide was heated to 140 °C and mixed with 0.6 kg of deionized water heated to 80 °C by spraying them into a reaction vessel at 95 °C. The generated isopropanol was recovered through a condenser connected to the reaction vessel. The solid product was dried at 90 °C for 5 h to obtain an aluminum-containing intermediate, and the liquid product was recovered. Example 10

[0042] 2 kg of aluminum isopropoxide was heated to 140 °C and mixed with 0.6 kg of deionized water heated to 90 °C by spraying them into a reaction vessel at 65 °C. The generated isopropanol was recovered through a condenser connected to the reaction vessel. The solid product was dried at 90 °C for 5 h to obtain an aluminum-containing intermediate, and the liquid product was recovered. Example 11

[0043] The product of Example 1 was added to 4 kg of deionized water along with 25 g of citric acid. The mixture was heated to 80 °C and reacted for 6 h. The reaction was then cooled to room temperature, filtered, and dried at 125 °C for 20 h. Example 12

[0044] The product of Example 1 was added to 6 kg of deionized water along with 25 g of formic acid. The mixture was heated to 90 °C and reacted for 6 h. The reaction was cooled to room temperature, and the mixture was filtered and dried at 130 °C for 15 h. Example 13

[0045] The product of Example 2 was added to 8 kg of deionized water along with 30 g of formic acid. The mixture was heated to 95 °C and reacted for 5 h. The reaction was then cooled to room temperature, filtered, and dried at 130 °C for 15 h. Example 14

[0046] The product of Example 3 and 35 g of citric acid were added to 10 kg of deionized water. The mixture was heated to 90 °C and reacted for 8 h. The reaction was cooled to room temperature, and the mixture was filtered and dried at 140 °C for 13 h. Example 15

[0047] The product of Example 4 was added to 6 kg of deionized water along with 25 g of citric acid. The mixture was heated to 100 °C and reacted for 5 h. The reaction was then cooled to room temperature, filtered, and dried at 130 °C for 15 h. Example 16

[0048] The product of Example 5 and 30 g of formic acid were added to 8 kg of deionized water. The mixture was heated to 100 °C and reacted for 6 h. The reaction was cooled to room temperature, and the mixture was filtered and dried at 130 °C for 15 h. Example 17

[0049] The product of Example 6 and 25 g of formic acid were added to 6 kg of deionized water. The mixture was heated to 110 °C and reacted for 3 h. The reaction was cooled to room temperature, and the mixture was filtered and dried at 130 °C for 15 h. Example 18

[0050] The product of Example 7 and 25g of urea were added to 4kg of deionized water. The mixture was heated to 95°C and reacted for 4 hours. The reaction was cooled to room temperature, and the mixture was filtered and dried at 130°C for 15 hours. Example 19

[0051] The product of Example 7 and 25 g of formic acid were added to 6 kg of deionized water. The mixture was heated to 100 °C and reacted for 4 h. The reaction was cooled to room temperature, and the mixture was filtered and dried at 150 °C for 12 h.

[0052] Comparative Example 1 2 kg of aluminum isopropoxide was added to 4 kg of deionized water, and the mixture was hydrolyzed at 90 °C for 8 h. The product was filtered and dried at 85 °C for 6 h to obtain the hydrolysis product.

[0053] Comparative Example 2 2 kg of aluminum isopropoxide was added to 2 kg of deionized water, and the mixture was hydrolyzed at 100 °C for 6 h. The product was filtered and dried at 85 °C for 6 h to obtain the hydrolysis product.

[0054] Comparative Example 3 2 kg of aluminum isopropoxide was added to 6 kg of deionized water, and the mixture was hydrolyzed at 90 °C for 8 h. The product was filtered and dried at 85 °C for 6 h to obtain the hydrolysis product. The hydrolysis product and 25 g of formic acid were added to 6 kg of deionized water, and the mixture was heated to 100 °C for 4 h. The reaction was cooled to room temperature, the mixture was filtered, and dried at 150 °C for 12 h.

[0055] Comparative Example 4 2 kg of aluminum isopropoxide was added to 2 kg of deionized water, and the mixture was hydrolyzed at 100 °C for 6 h. The product was filtered and dried at 85 °C for 6 h to obtain the hydrolysis product. The hydrolysis product and 25 g of citric acid were added to 6 kg of deionized water, and the mixture was heated to 100 °C for 4 h. The reaction was cooled to room temperature, the mixture was filtered, and dried at 150 °C for 12 h. Example 20

[0056] Determination of the colloidal index of the example and comparative samples: A 10% alumina suspension was prepared by mixing the sample (m1) with water. Nitric acid was added at an acid-to-alumina ratio of n(acid):n(Al) = 1:10, and the mixture was stirred for 15 min. After colloidal dissolution, the sample was centrifuged at 5000 r / min for 10 min. The bottom precipitate was dried, cooled, and weighed (m2). The fraction of alumina in the colloidal portion relative to the total alumina content in the sample [100% × (m1 - m2) / m1] is the colloidal index.

[0057] Table 1. Colloidal index of the samples

[0058] The specific surface area, pore size, pore volume, and purity of the samples prepared in the examples and comparative examples were determined. Specific surface area, pore size, and pore volume were determined using a McMurray Ticco ASAP2460 specific surface area and porosity analyzer via the BET method. Purity was determined using a PAN Analytical X-ray fluorescence spectrometer (X-ray fluorescence, XRF, excitation voltage 40 kV, current 50 mA).

[0059] Table 2 Sample Performance Indicators

[0060] As shown in Tables 1 and 2, the alumina prepared in the embodiments of the present invention has a higher colloidal index, and the colloidal index fluctuates little under different conditions. Furthermore, high-purity aluminum isopropoxide can be recovered. High-purity alumina products are obtained through spray reaction and secondary hydrolysis.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing high-purity alumina, characterized in that, Includes the following steps: Liquid aluminum isopropoxide is mixed with water in a mist and reacted. The product is dried to obtain an aluminum-containing intermediate. The mixture of the aluminum-containing intermediate, additives, and water is heated and reacted. The reaction mixture is filtered and dried to obtain the high-purity alumina. The auxiliary agent is selected from at least one of citric acid and formic acid; The mass ratio of the aluminum-containing intermediate, additives, and water is 1:0.002~0.02:2~5; In the mixed reaction, the mass ratio of aluminum isopropoxide to water is 1:0.3~2, and the mixed reaction is carried out at 60~150℃; The heating temperature for the reaction is 80~120 ℃, and the reaction time is 1~10 h.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the aluminum-containing intermediate, additives, and water is 1:0.002~0.01:2~5.

3. The preparation method according to claim 1, characterized in that, In the mixed reaction, the mass ratio of aluminum isopropoxide to water is 1:0.3~1.

4. The preparation method according to claim 1, characterized in that, Liquid aluminum isopropoxide is obtained by heating to 118~150℃.

5. The preparation method according to claim 1, characterized in that, Liquid aluminum isopropoxide is obtained by heating to 125~140℃.

6. The preparation method according to claim 1, characterized in that, The mixed reaction was carried out at 85~120℃.

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