High-purity aluminum sol and preparation method thereof

Abstract

The invention belongs to the technical field of aluminum sol preparation, and provides high-purity aluminum sol and a preparation method thereof. According to the method, an aluminum hydroxide solution and a sodium bicarbonate solution serve as starting raw materials and are converted into dihydroxy aluminum sodium carbonate crystals under the heating condition, the dihydroxy aluminum sodium carbonate crystals are prepared after filtering and washing and acidification replacement of an inorganic acid solution, and finally the dihydroxy aluminum sodium carbonate crystals are obtained after filtering and washing and conversion of a hydrochloric acid solution. And preparing to obtain a high-purity aluminum sol product. The preparation cost is low, the production process is mild, safe and controllable, the aluminum sol product with high purity, high aluminum oxide content and high aluminum-chlorine ratio can be prepared, and the aluminum sol product has high adhesive property; besides, aluminum sol products with different aluminum-to-chlorine ratios can be produced only by regulating and controlling the heating condition and the raw material input proportion, the chemical and physical properties of the aluminum sol can completely reach the same level of commercially available liquid aluminum sol, and the aluminum sol can be widely applied to various fields.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum sol preparation, and in particular to a high-purity aluminum sol and a preparation method thereof. Background Art

[0002] Aluminum sol, scientifically known as basic polyaluminum chloride, is an acidic inorganic polymer material with a molecular formula of Al2(OH) n Cl 6-n . Aluminum sol has the characteristics of adhesiveness, thixotropy, easy dispersibility, water-soluble reversibility, suspension, positive charge, adsorption and stability. It is widely used in petrochemical catalysts, aluminum silicate fibers and ceramics and other high-temperature resistant materials forming binders, ceramic enamel glaze additives, antistatic agents for velveting and electrostatic flocking, film-forming agents and antistatic agents for textile and fiber treatment, precision casting alumina casting materials, emulsifiers and stabilizers for pigments and coatings, surface treatment agents for photographic paper, greenhouse antifogging agents, waterproofing agents, etc. At the same time, aluminum sol can also be used in various fields such as inorganic fibers, activated alumina, high-purity alumina, enamel, daily necessities, papermaking, etc. In recent years, with the rapid growth of the domestic emerging industry MTO (methanol to olefins) catalyst market demand, it has greatly driven the strong demand for aluminum sol with a high aluminum-chlorine ratio. In current commercial applications, aluminum sol is mainly presented in liquid form. According to the needs of different customers, the content of alumina in liquid aluminum sol ranges from 18% to 24%. Another important indicator is that the aluminum-chlorine ratio in the aluminum sol is between 1.3 and 2.1. The higher the aluminum-chlorine ratio, the stronger its bonding performance is usually.

[0003] The most widely used method for preparing liquid aluminum sol in China is: under the catalytic action of acid, metal aluminum and water react to form aluminum sol. The reaction formula of this reaction is Al+HCl+H2O→Al2(OH) n Cl 6-n +H2(n=1~5). Since a large amount of hydrogen will be produced during the reaction, and hydrogen has a wide explosion limit and is very easy to explode, the explosion-proof level of the production site is required to be extremely high. Moreover, the reaction of this preparation method is violent and difficult to control. In addition, this process technology is usually based on the production of aluminum sol with a low aluminum-chlorine ratio. When molecular sieve catalyst manufacturers use aluminum sol as a binder, more chlorine will be introduced. Its high acidity can easily destroy the specific surface area of ​​the molecular sieve catalyst, resulting in a decrease in catalyst performance. Foreign countries usually use the technology of direct reaction of aluminum chloride aqueous solution and aluminum ingot to moderate the reaction. The reaction formula of this reaction is Al+AlCl3+H2O→Al2(OH) n Cl 6-n+H2 (n=1-5). This reaction can produce aluminum sols with different aluminum-chlorine ratios or high aluminum-chlorine ratios for use as catalyst binders to enhance the hydrothermal aging performance of the catalyst. However, this preparation method is the same as the reaction of metal aluminum and water under acid catalysis to produce aluminum sol, and it will inevitably produce a large amount of hydrogen during the reaction, which brings great safety hazards to production; in addition, the aluminum ingot method produces aluminum sol in the liquid phase, and the product cannot be purified and often contains impurities, such as iron, nickel or other metal impurities brought from the production equipment.

[0004] The Chinese invention patent application with application number CN201911011501.9 discloses a method for preparing aluminum sol and the aluminum sol prepared therefrom. The hydrochloric acid solution is subjected to a two-stage cyclic aging reaction with an excess of aluminum source in a reactor and a buffer tank, which can effectively improve the uniformity of the reaction and aging of the aluminum sol, improve the aluminum-chlorine ratio of the product, and reduce the influence of different batches of hydrochloric acid on the product quality; the Chinese invention patent application with application number CN202311331515.5 discloses a method for preparing aluminum sol. The aluminum source is added to deionized water, hydrochloric acid is added to adjust the pH value to 2-6, stirred evenly at room temperature, placed in a hydrothermal reactor for hydrothermal reaction, and the initial product of aluminum sol is obtained; phosphorus compounds and modified mineral powder are added to the initial product of aluminum sol, and the aluminum sol product is prepared after heating reaction. The aluminum sol has an outer layer structure and an internal structure within the outer layer structure, has a larger grain size, has good adhesion and high stability; the Chinese invention patent application with application number CN202310444877.9 discloses a modified aluminum sol and its preparation method and application. An intermediate product is prepared by dripping an ammonia solution into an aluminum chloride solution, which is dripped into a re-prepared aluminum chloride solution, and after heating treatment, an auxiliary component is added and further aged to obtain a modified aluminum sol, thereby improving the stability and adhesion of the aluminum sol. As mentioned above, the preparation method of aluminum sol mainly focuses on using hydrochloric acid as a catalyst, through process improvement or component modification, to prepare aluminum sol or modified aluminum sol by reacting metallic aluminum and water; or using aluminum chloride solution as a starting raw material, and carrying out precipitation reaction with alkaline solutions such as ammonia water or sodium hydroxide, and obtaining an aluminum sol product after a series of aging treatments.

[0005] Therefore, it is of great significance to provide a method for preparing aluminum sol with mild process, safety and reliability, high product purity and high quality. Summary of the invention

[0006] The purpose of the present invention is to provide a high-purity aluminum sol and a preparation method thereof, in view of the fact that a large amount of explosive hydrogen will inevitably be produced when preparing liquid aluminum sol by the existing metal aluminum method, which brings great safety hazards to the production process, and the existing aluminum ingot method for producing aluminum sol has the disadvantage of low purity.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing high-purity aluminum sol, comprising the following reaction steps:

[0009] (1) mixing an aluminum hydroxide solution and a sodium bicarbonate solution, reacting the mixture, and obtaining dihydroxyaluminum sodium carbonate;

[0010] (2) mixing sodium dihydroxyaluminum carbonate and an inorganic acid solution to carry out a replacement reaction to obtain dihydroxyaluminum bicarbonate;

[0011] (3) Mixing dihydroxyaluminum bicarbonate and hydrochloric acid solution and reacting them to obtain the high-purity aluminum sol.

[0012] Preferably, the concentration of the aluminum hydroxide solution in step (1) is 0.1 to 5 mol / L, and the concentration of the sodium bicarbonate solution is 0.1 to 5 mol / L;

[0013] The molar ratio of aluminum hydroxide in the aluminum hydroxide solution to sodium bicarbonate in the sodium bicarbonate solution is 1:0.5-3.5.

[0014] Preferably, the reaction temperature in step (1) is 100-250° C., and the reaction time is 0.5-5 h.

[0015] Preferably, the inorganic acid solution in step (2) is a hydrochloric acid solution, a nitric acid solution or a sulfuric acid solution; the concentration of the inorganic acid solution is 0.01 to 0.5 mol / L;

[0016] The molar ratio of the solute to the sodium dihydroxyaluminum carbonate in the inorganic acid solution is 1 to 5:1.

[0017] Preferably, the reaction temperature in step (2) is 20-90° C., and the reaction time is 0.5-5 h.

[0018] Preferably, the concentration of the hydrochloric acid solution in step (3) is 0.5 to 5 mol / L;

[0019] The molar ratio of hydrogen chloride to dihydroxyaluminum bicarbonate in the hydrochloric acid solution is 0.5-2.5:1.

[0020] Preferably, the reaction temperature in step (3) is 20 to 90° C., and the reaction time is 0.5 to 5 h.

[0021] The invention also provides high-purity aluminum sol prepared by the preparation method of the high-purity aluminum sol.

[0022] Preferably, the mass fraction of aluminum oxide in the high-purity aluminum sol is 14.72-23.2%, and the molar ratio of aluminum to chlorine in the high-purity aluminum sol is 0.84-1.82.

[0023] The beneficial effects of the present invention are:

[0024] The present invention uses aluminum hydroxide solution and sodium bicarbonate solution as starting raw materials, converts them into dihydroxyaluminum sodium carbonate crystals under heating conditions, prepares dihydroxyaluminum bicarbonate crystals after filtering, washing and acidification replacement of inorganic acid solution, and finally prepares high-purity aluminum sol products after filtering, washing and conversion of hydrochloric acid solution. The present invention has low preparation cost, mild production process, safe and controllable production process, and avoids the lack of safety hazards of inevitably generating a large amount of explosive hydrogen in the production process of liquid aluminum sol using metallic aluminum as the starting raw material; the present invention removes impurities by filtering and washing to prepare high-purity aluminum sol; the present invention can prepare aluminum sol products with high aluminum oxide content and high aluminum-chlorine ratio, and the aluminum sol products have high bonding performance; in addition, the present invention can produce aluminum sol products with different aluminum-chlorine ratios only by regulating heating conditions and raw material input ratios, and the chemical and physical properties of the aluminum sol can fully reach the same level as commercially available liquid aluminum sol, and can be widely used in various fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the specific preparation process of the high-purity aluminum sol in the present invention. DETAILED DESCRIPTION

[0026] The present invention provides a method for preparing high-purity aluminum sol, comprising the following reaction steps:

[0027] (1) mixing an aluminum hydroxide solution and a sodium bicarbonate solution, reacting the mixture, and obtaining dihydroxyaluminum sodium carbonate;

[0028] (2) mixing sodium dihydroxyaluminum carbonate and an inorganic acid solution to carry out a replacement reaction to obtain dihydroxyaluminum bicarbonate;

[0029] (3) Mixing dihydroxyaluminum bicarbonate and hydrochloric acid solution and reacting them to obtain the high-purity aluminum sol.

[0030] In the present invention, the concentration of the aluminum hydroxide solution in step (1) is preferably 0.1 to 5 mol / L, more preferably 0.5 to 3.5 mol / L, and more preferably 1 to 2.5 mol / L; the concentration of the sodium bicarbonate solution is preferably 0.1 to 5 mol / L, more preferably 0.5 to 3.5 mol / L, and more preferably 1 to 2.5 mol / L.

[0031] In the present invention, the molar ratio of aluminum hydroxide in the aluminum hydroxide solution to sodium bicarbonate in the sodium bicarbonate solution is preferably 1:0.5-3.5, more preferably 1:0.8-3, and even more preferably 1:1.5-2.

[0032] In the present invention, the mixing method in step (1) is preferably stirring, the aluminum hydroxide solution and the sodium bicarbonate solution are stirred evenly, and then heated to the reaction temperature under stirring conditions to carry out the reaction; the present invention does not specifically limit the stirring speed, and it can be determined by conventional technical means in the field.

[0033] In the present invention, the chemical formula of step (1) reaction is:

[0034] NaHCO3+Al(OH)3→NaAl(OH)2CO3+H2O.

[0035] In the present invention, the reaction temperature in step (1) is preferably 100-250°C, more preferably 140-220°C, and more preferably 160-180°C; the reaction time is preferably 0.5-5h, more preferably 1-3h, and more preferably 2-2.5h.

[0036] In the present invention, after the reaction in step (1) is completed, the obtained system is naturally cooled and then filtered, and the obtained filter cake is washed and filtered in sequence, and the steps of washing and filtering are repeated to remove the by-product, that is, the sodium carbonate filtrate, to obtain dihydroxyaluminum sodium carbonate (labeled as DASC); the target temperature for natural cooling is preferably 20 to 30°C, more preferably 22 to 28°C, and more preferably 25°C; the washing temperature is preferably 20 to 90°C, more preferably 25 to 70°C, and more preferably 30 to 50°C; and the washing and filtering are repeated until the pH value of the filtrate is preferably 7 to 10, more preferably 7.5 to 9.5, and more preferably 8 to 9.

[0037] In the present invention, the inorganic acid solution in step (2) is preferably hydrochloric acid solution, nitric acid solution or sulfuric acid solution; the concentration of the inorganic acid solution is preferably 0.01 to 0.5 mol / L, more preferably 0.02 to 0.25 mol / L, and more preferably 0.05 to 0.1 mol / L.

[0038] In the present invention, the molar ratio of the solute to the sodium dihydroxyaluminum carbonate in the inorganic acid solution is preferably 1 to 5:1, more preferably 1.5 to 4:1, and even more preferably 2 to 3:1.

[0039] In the present invention, the purpose of the reaction in step (2) is to acidify and replace the Na-type DASC crystals with H-type DAHC crystals. The chemical formula of the reaction in step (2) is:

[0040] NaAl(OH)2CO3+H + →HAl(OH)2CO3+Na + .

[0041] In the present invention, the reaction temperature in step (2) is preferably 20 to 90°C, more preferably 25 to 70°C, and more preferably 30 to 50°C; the reaction time is preferably 0.5 to 5h, more preferably 1 to 3h, and more preferably 2 to 2.5h.

[0042] In the present invention, after the reaction in step (2) is completed, the obtained system is filtered, and then the obtained filter cake is washed and filtered in sequence, and the washing and filtering steps are repeated to remove by-products to obtain dihydroxyaluminum hydrogen carbonate (labeled as DAHC); the washing temperature is preferably 20 to 90° C., more preferably 25 to 70° C., and more preferably 30 to 50° C.; the washing and filtering are repeated until the pH value of the filtrate is preferably 3 to 7, more preferably 4 to 6, and more preferably 5.

[0043] In the present invention, the concentration of the hydrochloric acid solution in step (3) is preferably 0.5 to 5 mol / L, more preferably 1 to 4 mol / L, and even more preferably 2 to 3 mol / L.

[0044] In the present invention, the molar ratio of hydrogen chloride to dihydroxyaluminum hydrogen carbonate in the hydrochloric acid solution is preferably 0.5 to 2.5:1, more preferably 0.75 to 2:1, and even more preferably 1 to 1.5:1.

[0045] In the present invention, the purpose of step (3) is to convert carbonate ions (CO3 2- ) is acidified and converted into CO2 gas for release, and the DAHC crystals are acidified and converted into aluminum sol (Al2(OH)5Cl). The chemical formula of step (3) is:

[0046] 2HAl(OH)2CO3+HCl→Al2(OH)5Cl+2CO2.

[0047] In the present invention, the reaction temperature in step (3) is preferably 20 to 90°C, more preferably 25 to 70°C, and more preferably 30 to 50°C; the reaction time is preferably 0.5 to 5h, more preferably 1 to 3h, and more preferably 2 to 2.5h.

[0048] When the inorganic acid solution used in step (2) is a hydrochloric acid solution, the specific preparation process diagram of the aluminum sol in the present invention is as follows: Figure 1 As shown. Figure 1It can be seen that the present invention uses aluminum hydroxide solution and sodium bicarbonate solution as starting raw materials, which are converted into dihydroxyaluminum sodium carbonate crystals (NaAl(OH)2CO3, DASC) under heating conditions, and then prepared into dihydroxyaluminum hydrogen carbonate crystals (HAl(OH)2CO3, DAHC) after filtering, washing and acidification replacement with hydrochloric acid solution. Finally, DAHC crystals are filtered, washed and converted into hydrochloric acid solution again to prepare a liquid product (basic polyaluminum chloride, Al2(OH)5Cl) with the same performance as commercially available aluminum sol. The overall reaction formula for preparing aluminum sol in the present invention is 2Al(OH)3+2NaHCO3+3HCl→Al2(OH)5Cl+2NaCl+2CO2+3H2O.

[0049] The invention also provides high-purity aluminum sol prepared by the preparation method of the high-purity aluminum sol.

[0050] In the present invention, the mass fraction of aluminum oxide in the high-purity aluminum sol is preferably 14.72-23.2%, more preferably 18-23%, and more preferably 19-20%; the molar ratio of aluminum to chlorine in the high-purity aluminum sol is preferably 0.84-1.82, more preferably 0.90-1.60, and more preferably 1.20-1.50.

[0051] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0052] Example 1

[0053] A 1 mol / L aluminum hydroxide solution and a 1 mol / L sodium bicarbonate solution were added to a high-pressure reactor respectively, the molar ratio of aluminum hydroxide in the aluminum hydroxide solution to sodium bicarbonate in the sodium bicarbonate solution was 1:1.5, and the mixture was stirred evenly at a rotation speed of 250 r / min, and then heated to 160°C at a stirring speed of 250 r / min, and reacted for 1 hour. After the reaction, the obtained system was naturally cooled to 25°C, and then filtered. The obtained filter cake was washed with 25°C water, and then filtered. The washing and filtering steps were repeated until the pH value of the filtrate was 7 to obtain dihydroxyaluminum sodium carbonate;

[0054] Sodium dihydroxyaluminum carbonate was mixed with a hydrochloric acid solution having a concentration of 0.05 mol / L, wherein the molar ratio of hydrogen chloride to sodium dihydroxyaluminum carbonate in the hydrochloric acid solution was 1.5:1, and the mixture was reacted at 25°C for 1 hour. After the reaction was completed, the obtained system was filtered, and then the obtained filter cake was washed with water at 25°C, and then filtered. The steps of washing and filtering were repeated until the pH value of the filtrate reached 7, thereby obtaining dihydroxyaluminum bicarbonate.

[0055] Dihydroxyaluminum bicarbonate is mixed with a hydrochloric acid solution with a concentration of 1 mol / L, wherein the molar ratio of hydrogen chloride to dihydroxyaluminum bicarbonate in the hydrochloric acid solution is 1:1, and the mixture is reacted at 25°C for 1 hour to obtain a high-purity aluminum sol.

[0056] Example 2

[0057] The preparation method described in Example 1 is followed, except that the molar ratio of aluminum hydroxide in the aluminum hydroxide solution to sodium bicarbonate in the sodium bicarbonate solution is 1:2, to obtain a high-purity aluminum sol.

[0058] Example 3

[0059] The preparation method described in Example 1 was followed, except that the reaction of the aluminum hydroxide solution and the sodium bicarbonate solution was carried out at 140° C. to obtain a high-purity aluminum sol.

[0060] Example 4

[0061] The preparation method described in Example 1 is followed, except that the reaction of the aluminum hydroxide solution and the sodium bicarbonate solution is carried out at 180° C. to obtain a high-purity aluminum sol.

[0062] Example 5

[0063] The preparation method described in Example 1 was followed, except that the molar ratio of hydrogen chloride to sodium dihydroxyaluminum carbonate in the hydrochloric acid solution was 2:1, to obtain a high-purity aluminum sol.

[0064] Example 6

[0065] The preparation method described in Example 1 was followed, except that the molar ratio of hydrogen chloride to dihydroxyaluminum bicarbonate in the hydrochloric acid solution was 0.75:1, to obtain a high-purity aluminum sol.

[0066] Example 7

[0067] The preparation method described in Example 6 is followed, except that the preparation process of dihydroxyaluminum bicarbonate is as follows: sodium dihydroxyaluminum carbonate is mixed with a nitric acid solution with a concentration of 0.05 mol / L, the molar ratio of the solute to sodium dihydroxyaluminum carbonate in the nitric acid solution is 1.25:1, and the mixture is reacted at 25°C for 1 hour. After the reaction is completed, the obtained system is filtered, and then the obtained filter cake is washed with water at 25°C and then filtered. The washing and filtering steps are repeated until the pH value of the filtrate is 7 to obtain dihydroxyaluminum bicarbonate; and finally a high-purity aluminum sol is obtained.

[0068] Comparative Example 1

[0069] The commercially available aluminum sol was purchased from Yueyang Delong Packaging Materials Co., Ltd., and the model number was aluminum sol-12%.

[0070] The aluminum sols obtained in Examples 1 to 7 and Comparative Example 1 were subjected to performance tests, and the performance test results of the aluminum sols obtained in Examples 1 to 7 and Comparative Example 1 were obtained, as shown in Table 1.

[0071] Table 1 Performance test results of aluminum sol obtained in Examples 1 to 7 and Comparative Example 1

[0072]

[0073] As can be seen from the above embodiments, the present invention uses aluminum hydroxide solution and sodium bicarbonate solution as starting raw materials, which are converted into dihydroxyaluminum sodium carbonate crystals under heating conditions, and dihydroxyaluminum bicarbonate crystals are prepared after filtering, washing and acidification replacement with hydrochloric acid solution, and finally filtered, washed and converted with hydrochloric acid solution to prepare aluminum sol products. The present invention has low preparation cost, mild production process, safe and controllable production process, and avoids the lack of safety hazards of inevitably producing a large amount of explosive hydrogen in the production process of liquid aluminum sol using metallic aluminum as the starting raw material; the present invention can prepare aluminum sol products with high purity, high alumina content and high aluminum-chlorine ratio, and the aluminum sol products have high bonding properties; in addition, the present invention can produce aluminum sol products with different aluminum-chlorine ratios only by regulating the heating conditions and the input ratio of raw materials, and the chemical and physical properties of the aluminum sol can fully reach the same level as the commercially available liquid aluminum sol, and can be widely used in various fields.

[0074] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing high-purity aluminum sol, characterized in that: The reaction steps include: (1) mixing an aluminum hydroxide solution and a sodium bicarbonate solution, reacting to obtain dihydroxyaluminum sodium carbonate; (2) mixing sodium dihydroxyaluminum carbonate and an inorganic acid solution to carry out a replacement reaction to obtain dihydroxyaluminum bicarbonate; (3) Mixing dihydroxyaluminum bicarbonate and hydrochloric acid solution and reacting them to obtain the high-purity aluminum sol.

2. The method for preparing high-purity aluminum sol according to claim 1, characterized in that: The concentration of the aluminum hydroxide solution in step (1) is 0.1 to 5 mol / L, and the concentration of the sodium bicarbonate solution is 0.1 to 5 mol / L; The molar ratio of aluminum hydroxide in the aluminum hydroxide solution to sodium bicarbonate in the sodium bicarbonate solution is 1:0.5-3.

5.

3. The method for preparing high-purity aluminum sol according to claim 1 or 2, characterized in that: The reaction temperature of step (1) is 100-250° C., and the reaction time is 0.5-5 h.

4. The method for preparing high-purity aluminum sol according to claim 3, characterized in that: The inorganic acid solution in step (2) is hydrochloric acid solution, nitric acid solution or sulfuric acid solution; the concentration of the inorganic acid solution is 0.01 to 0.5 mol / L; The molar ratio of the solute to the sodium dihydroxyaluminum carbonate in the inorganic acid solution is 1 to 5:

1.

5. The method for preparing high-purity aluminum sol according to claim 4, characterized in that: The reaction temperature in step (2) is 20-90° C., and the reaction time is 0.5-5 h.

6. The method for preparing high-purity aluminum sol according to claim 5, characterized in that: The concentration of the hydrochloric acid solution in step (3) is 0.5 to 5 mol / L; The molar ratio of hydrogen chloride to dihydroxyaluminum bicarbonate in the hydrochloric acid solution is 0.5-2.5:

1.

7. The method for preparing high-purity aluminum sol according to claim 5 or 6, characterized in that: The reaction temperature in step (3) is 20-90° C., and the reaction time is 0.5-5 h.

8. The high-purity aluminum sol prepared by the method for preparing high-purity aluminum sol according to any one of claims 1 to 7.

9. The high purity aluminum sol according to claim 8, characterized in that The mass fraction of aluminum oxide in the high-purity aluminum sol is 14.72-23.2%, and the molar ratio of aluminum to chlorine in the high-purity aluminum sol is 0.84-1.82.

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