Alcohol aluminum salt and preparation method thereof

Abstract

The invention belongs to the technical field of chemical engineering, and particularly relates to an aluminum alkoxide salt and a preparation method thereof. According to the method, argon non-thermal plasma is adopted for bombarding the surface of the aluminum foil, an oxidation film on the surface of the aluminum foil is stripped, active aluminum free radicals are formed, the reaction energy barrier of the aluminum alkoxide salt is reduced, the aluminum alkoxide salt can be synthesized under the catalyst-free condition, and green and efficient synthesis of the aluminum alkoxide salt is achieved; a thiosemicarbazide-carboxylic acid bidentate ligand is adopted for complexing impurity iron in alkoxide aluminum salt, sulfur and nitrogen double coordination sites in a thiosemicarbazide unit are matched with oxygen coordination sites in a carboxylic acid group, higher complexing capacity is formed for the impurity iron, and the stability of the complex is improved; the crystallization is regulated and controlled through the pH response characteristic of the carboxylic acid group, so that the impurity iron in the aluminum alkoxide salt is efficiently removed.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical engineering, and particularly relates to an aluminum alkoxide and a preparation method thereof. Background Art

[0002] High-purity alumina refers to alumina with a purity above 4N (mass fraction 99.99%). Due to its special thermal, optical, magnetic, electrical, and mechanical properties, it is widely used in advanced material fields such as catalyst carriers, lithium battery separator coatings, sapphires, special ceramics, and phosphors. Currently, the hydrolysis method of aluminum alkoxide is the main preparation technology for high-purity alumina. Aluminum alkoxides are a class of metal-organic compounds formed by bonding aluminum elements with alcohol hydroxyl groups (-OH) through oxygen atoms. The preparation of aluminum alkoxides requires a catalyst to react with alumina or directly dissolve the oxide film on the surface of metallic aluminum, exposing the fresh aluminum surface, and at the same time forming active intermediates, enabling the reaction of aluminum-alcohol at a lower temperature. Currently, the commonly used catalyst is aluminum chloride (AlCl3). However, the use of the catalyst poses a risk of introducing impurities such as chlorine and iron due to catalyst residues.

[0003] The raw material metallic aluminum is the main source of impurities in high-purity alumina. The impurity elements in metallic aluminum mainly include silicon, iron, sodium, calcium, magnesium, zinc, etc. Among them, impurities such as silicon, iron, and zinc are difficult to react with alcohol, and most of them can be removed by filtration; impurities such as calcium, sodium, and magnesium are more active in nature. Although they are easy to react with alcohol, their content in metallic aluminum is small; although the reaction activity of iron with alcohol is also poor, iron is the main associated impurity in metallic aluminum, with a high content, and in the production of high-purity alumina, reactors, pipelines, etc. are prone to input iron impurities into the product. The removal of iron impurities in high-purity alumina is relatively difficult, and the presence of iron impurities has a great impact on the purity, crystal structure, physical and chemical properties, etc. of high-purity alumina products. Summary of the Invention

[0004] The purpose of the present invention is to provide an aluminum alkoxide and a preparation method thereof to solve the above technical problems.

[0005] To achieve the above technical purpose, the technical solution of the present invention is as follows: A preparation method of an aluminum alkoxide, characterized by comprising the following steps: S1. After the cleaned aluminum foil is successively soaked in a 15wt% sulfuric acid solution and an 8wt% sodium hydroxide solution for impurity removal, it is washed with deionized water, dried until the surface of the aluminum foil is anhydrous, and then activated by argon non-thermal plasma; S2. Under a nitrogen atmosphere, 20 - 40 g of the activated aluminum foil and 200 - 400 mL of isopropanol with a water content less than 0.2wt% are mixed and placed in a three-necked flask, and heated to boiling for reaction. After the isopropanol reflux is stable, the reaction continues for 5 h; S3. After the reaction proceeds for 5 h, add the thiosemicarbazide-carboxylic acid bidentate ligand to the three-necked flask, adjust the pH to 3.5 - 5.5, continue the reaction in a water bath at 45 °C for 2 h, and then obtain the alcohol aluminum salt mixture after extraction, crystallization, centrifugation, filtration, and washing. Distill the alcohol aluminum salt mixture under reduced pressure and collect the distillate at a temperature above 135 °C to obtain the alcohol aluminum salt; wherein, the addition amount of the thiosemicarbazide-carboxylic acid bidentate ligand is 0.6 - 1.0 wt% of the aluminum foil.

[0006] As a further improvement, in step S3, the preparation method of the thiosemicarbazide-carboxylic acid bidentate ligand is as follows: Under a nitrogen atmosphere, mix 50 - 70 mL of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 0.1 - 0.2 mol of thiosemicarbazide, 150 mL of absolute ethanol, and 0.12 - 0.24 mol of acetic acid in a three-necked flask, cool it to 0 - 5 °C in an ice bath, slowly dropwise add 20 wt% sodium hydroxide solution, adjust the pH to 8 - 9, stir and react for 30 min, then raise the temperature to 75 °C and reflux and react for 8 h. After the reaction ends, adjust the pH to 2 - 3, and after filtering, washing, and drying the precipitated white precipitate, obtain the thiosemicarbazide-carboxylic acid bidentate ligand.

[0007] As a further improvement, in step S3, the addition method of the thiosemicarbazide-carboxylic acid bidentate ligand is as follows: Using supercritical CO2 as the carrier, at 10 Mpa, add the thiosemicarbazide-carboxylic acid bidentate ligand into the three-necked flask in a pulsed manner at a concentration of 0.5 mol / L, and the pulse frequency is 2 Hz.

[0008] As a further improvement, in step S1, the conditions for activating the aluminum foil with argon non-thermal plasma are as follows: Under a chamber pressure of 10 Pa, a power of 1.5 kW, and a frequency of 13.56 MHz, use argon non-thermal plasma to activate and treat for 10 min.

[0009] As a further improvement, in step S3, the extraction method of the alcohol aluminum salt mixture is as follows: At a pressure reduction rate of 0.5 MPa / min, reduce the pressure of supercritical CO2 from 10 MPa to 6 MPa.

[0010] As a further improvement, in step S3, the crystallization method of the alcohol aluminum salt mixture is as follows: Use ammonia water to adjust the pH to 8.0, and at a temperature reduction rate of 0.2 °C / min, reduce the reaction temperature from 45 °C to -10 °C.

[0011] The present invention also provides an alcohol aluminum salt.

[0012] Due to the adoption of the above technical solutions, the beneficial effects of the present invention are: 1. Chelate the impurity iron in the aluminum alkoxide with a thiosemicarbazide-carboxylic acid bidentate ligand. The thiosemicarbazide unit provides sulfur and nitrogen double coordination sites. Through the strong lone pair electrons of the sulfur atom and the basicity of the nitrogen atom, it forms a higher complexing ability for the impurity iron, improving the stability of the complex; on the one hand, the carboxylic acid group can provide an oxygen atom coordination site to cooperate with the thiosemicarbazide unit to form a stable iron complex; on the other hand, the carboxylic acid group can be protonated in an acidic environment, enhancing the binding force between the thiourea unit and the impurity iron, and dissociating under alkaline conditions to achieve the crystallization of the iron complex in the aluminum alkoxide, making it easier to separate.

[0013] 2. Bombard the surface of the aluminum foil with argon non-thermal plasma to strip the oxide film on the surface of the aluminum foil and form active aluminum radicals, significantly reducing the reaction energy barrier of the aluminum alkoxide, enabling the generation of aluminum alkoxide without a catalyst, eliminating the risk of exogenous impurities chlorine and iron brought by the catalyst in the product, and realizing the green and efficient synthesis of aluminum alkoxide. Detailed implementation mode

[0014] The technical solutions of the present invention will be clearly and completely described below in conjunction with the specific implementation modes. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. Those not specified in the embodiments are carried out under conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0015] Example 1 A method for preparing an aluminum alkoxide, comprising the following steps: 1. Under a nitrogen atmosphere, 50 mL of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 0.1 mol of thiosemicarbazide, 150 mL of absolute ethanol, and 0.12 mol of acetic acid were mixed and placed in a three-necked flask. The temperature was lowered to 0 °C in an ice bath, and a 20 wt% sodium hydroxide solution was slowly added dropwise. The pH was adjusted to 8 with ammonia water, and after stirring and reacting at 800 rpm for 30 min, the temperature was raised to 75 °C and refluxed for 8 h.

[0016] 2. After the reflux reaction was completed, acetic acid was added dropwise to adjust the pH to 2 until a white precipitate was formed; the precipitated white precipitate was filtered with a Buchner funnel for 30 min and transferred to a Soxhlet extractor for reflux washing with absolute ethanol for 12 h, and then dried under vacuum at 40 °C and 0.1 kPa for 6 h to obtain the thiosemicarbazide-carboxylic acid bidentate ligand.

[0017] 3. Wash the impurities on the surface of the aluminum foil with deionized water, and then soak the aluminum foil in a 15 wt% sulfuric acid solution for 30 s and an 8 wt% sodium hydroxide solution for 20 s in sequence for impurity removal. After soaking, wash it again with deionized water. Place it in a ventilated and dry place until the surface of the aluminum foil is free of water, and then use argon non-thermal plasma sputtering to activate the aluminum foil for 10 min at a chamber pressure of 10 Pa, a power of 1.5 kW, and a frequency of 13.56 MHz.

[0018] 4. Under a nitrogen atmosphere, mix 20 g of the activated aluminum foil and 200 mL of isopropanol with a water content of less than 0.2 wt% in a three-necked flask, heat it to the boiling point of isopropanol, and carry out the reaction. After the reflux of isopropanol is stable, continue the reaction for 5 h.

[0019] 5. After the reaction proceeds for 5 h, use supercritical CO2 at 10 MPa as the carrier, and pulse-add a 0.5 mol / L thiosemicarbazide-carboxylic acid bidentate ligand to the three-necked flask at a frequency of 2 Hz. Adjust the pH to 3.5 with acetic acid, continue the reaction in a water bath at 45 °C for 2 h, then decrease the pressure from 10 MPa to 6 MPa at a pressure reduction rate of 0.5 MPa / min, filter, and take the obtained solution. Among them, the addition amount of the thiosemicarbazide-carboxylic acid bidentate ligand is 0.6 wt% of the aluminum foil.

[0020] 6. Adjust the pH of the solution obtained after filtration to 8.0 with ammonia water, cool the reaction temperature from 45 °C to -10 °C at a cooling rate of 0.2 °C / min, centrifuge at 5000 rpm for 15 min, filter, wash the obtained product with supercritical CO2 at 35 °C and 8 MPa to obtain an alcohol aluminum salt mixture. Distill the alcohol aluminum salt mixture under reduced pressure at 0.5 kPa, and collect the distillate above 135 °C to obtain the alcohol aluminum salt.

[0021] Example 2 A method for preparing an alcohol aluminum salt, comprising the following steps: 1. Under a nitrogen atmosphere, mix 60 mL of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 0.15 mol of thiosemicarbazide, 150 mL of absolute ethanol, and 0.18 mol of acetic acid in a three-necked flask, cool it to 3 °C in an ice bath, slowly add a 20 wt% sodium hydroxide solution dropwise, adjust the pH to 8.5 with ammonia water, stir and react at 800 rpm for 30 min, then raise the temperature to 75 °C and reflux for 8 h.

[0022] 2. After the reflux reaction is completed, add acetic acid dropwise to adjust the pH to 3 until a white precipitate appears. Filter the precipitated white precipitate with a Buchner funnel for 30 min, transfer it to a Soxhlet extractor, and reflux and wash it with absolute ethanol for 12 h. After vacuum drying at 40 °C and 0.1 kPa for 6 h, a thiosemicarbazide-carboxylic acid bidentate ligand is obtained.

[0023] 3. Wash the impurities on the surface of the aluminum foil with deionized water, and then soak the aluminum foil in a 15 wt% sulfuric acid solution for 30 s and an 8 wt% sodium hydroxide solution for 20 s in sequence to remove impurities. After soaking, wash it with deionized water again. Place it in a ventilated and dry place until the surface of the aluminum foil is anhydrous, and then use argon non-thermal plasma sputtering to activate the aluminum foil for 10 min at a chamber pressure of 10 Pa, a power of 1.5 kW, and a frequency of 13.56 MHz.

[0024] 4. Under a nitrogen atmosphere, place 30 g of the activated aluminum foil and 300 mL of isopropanol with a water content of less than 0.2 wt% in a three-necked flask, heat it to the boiling point of isopropanol, and carry out the reaction. After the isopropanol reflux is stable, continue the reaction for 5 h.

[0025] 5. After the reaction proceeds for 5 h, use supercritical CO2 at 10 MPa as the carrier, and pulse-add a 0.5 mol / L thiosemicarbazide-carboxylic acid bidentate ligand to the three-necked flask at a frequency of 2 Hz. Adjust the pH to 4.0 with acetic acid, continue the reaction in a water bath at 45 °C for 2 h, then reduce the pressure from 10 MPa to 6 MPa at a pressure reduction rate of 0.5 MPa / min, filter, and take the obtained solution. Among them, the addition amount of the thiosemicarbazide-carboxylic acid bidentate ligand is 0.8 wt% of the aluminum foil.

[0026] 6. Adjust the pH of the solution obtained after filtration to 8.0 with ammonia water, lower the reaction temperature from 45 °C to -10 °C at a cooling rate of 0.2 °C / min, centrifuge at 5000 rpm for 15 min, filter, wash the obtained product with supercritical CO2 at 35 °C and 8 MPa to obtain an alcohol aluminum salt mixture. Distill the alcohol aluminum salt mixture under reduced pressure at 0.5 kPa, and collect the distillate above 135 °C to obtain the alcohol aluminum salt.

[0027] Example 3 A method for preparing an alcohol aluminum salt, comprising the following steps: 1. Under a nitrogen atmosphere, mix 70 mL of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 0.2 mol of thiosemicarbazide, 150 mL of absolute ethanol, and 0.24 mol of acetic acid in a three-necked flask, cool it to 5 °C in an ice bath, slowly add a 20 wt% sodium hydroxide solution dropwise, adjust the pH to 9 with ammonia water, stir and react at 800 rpm for 30 min, then raise the temperature to 75 °C and reflux for 8 h.

[0028] 2. After the reflux reaction is completed, add acetic acid dropwise to adjust the pH to 2 until a white precipitate appears. Filter the precipitated white precipitate with a Buchner funnel for 30 min, transfer it to a Soxhlet extractor, and reflux and wash it with absolute ethanol for 12 h. After vacuum drying at 40 °C and 0.1 kPa for 6 h, a thiosemicarbazide-carboxylic acid bidentate ligand is obtained.

[0029] 3. Wash the impurities on the surface of the aluminum foil with deionized water, and then soak the aluminum foil in a 15 wt% sulfuric acid solution for 30 s and an 8 wt% sodium hydroxide solution for 20 s in sequence for impurity removal. After soaking, wash it with deionized water again. Place it in a ventilated and dry place until the surface of the aluminum foil is free of water, and then use argon non-thermal plasma sputtering to activate the aluminum foil for 10 min at a chamber pressure of 10 Pa, a power of 1.5 kW, and a frequency of 13.56 MHz.

[0030] 4. Under a nitrogen atmosphere, place 40 g of the activated aluminum foil and 400 mL of isopropanol with a water content of less than 0.2 wt% in a three-necked flask, heat it to the boiling point of isopropanol, and carry out the reaction. After the reflux of isopropanol is stable, continue the reaction for 5 h.

[0031] 5. After the reaction proceeds for 5 h, use supercritical CO2 at 10 MPa as the carrier, and pulse-add a 0.5 mol / L thiosemicarbazide-carboxylic acid bidentate ligand to the three-necked flask at a frequency of 2 Hz. Adjust the pH to 5.5 with acetic acid, and continue the reaction in a water bath at 45 °C for 2 h. Then, reduce the pressure from 10 MPa to 6 MPa at a pressure reduction rate of 0.5 MPa / min, filter, and take the obtained solution. Among them, the addition amount of the thiosemicarbazide-carboxylic acid bidentate ligand is 1.0 wt% of the aluminum foil.

[0032] 6. Adjust the pH of the solution obtained after filtration to 8.0 with ammonia water, cool the reaction temperature from 45 °C to -10 °C at a cooling rate of 0.2 °C / min, centrifuge at 5000 rpm for 15 min, filter, wash the obtained product with supercritical CO2 at 35 °C and 8 MPa to obtain an alcohol aluminum salt mixture. Distill the alcohol aluminum salt mixture under reduced pressure at 0.5 kPa, and collect the distillate above 135 °C to obtain the alcohol aluminum salt.

[0033] Comparative Example 1 A method for preparing an alcohol aluminum salt, which is different from Example 1 in that the aluminum foil is not activated, and aluminum chloride is used to catalyze the reaction of the alcohol aluminum salt, including the following steps: 1. Under a nitrogen atmosphere, mix 50 mL of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 0.1 mol of thiosemicarbazide, 150 mL of absolute ethanol, and 0.12 mol of acetic acid in a three-necked flask, cool it to 0 °C in an ice bath, slowly add a 20 wt% sodium hydroxide solution, adjust the pH to 8 with ammonia water, stir and react at 800 rpm for 30 min, then raise the temperature to 75 °C and reflux for 8 h.

[0034] 2. After the reflux reaction is completed, add acetic acid to adjust the pH to 2 until a white precipitate is formed. Filter the precipitated white precipitate with a Buchner funnel for 30 min, transfer it to a Soxhlet extractor, and reflux and wash it with absolute ethanol for 12 h. After vacuum drying at 40 °C and 0.1 kPa for 6 h, obtain the thiosemicarbazide-carboxylic acid bidentate ligand.

[0035] 3. Wash the impurities on the surface of the aluminum foil with deionized water, and then soak the aluminum foil in a 15 wt% sulfuric acid solution for 30 s and an 8 wt% sodium hydroxide solution for 20 s in sequence to remove impurities. After soaking, wash it with deionized water again, and place it in a ventilated and dry place until the surface of the aluminum foil is free of water.

[0036] 4. Under a nitrogen atmosphere, mix 20 g of aluminum foil, 0.3 g of anhydrous aluminum chloride, and 200 mL of isopropanol with a water content of less than 0.2 wt% in a three-necked flask, heat it to the boiling point of isopropanol, and carry out the reaction; after the isopropanol reflux is stable, continue the reaction for 5 h.

[0037] 5. After the reaction proceeds for 5 h, use supercritical CO2 at 10 MPa as the carrier, and pulse-adding a 0.5 mol / L thiosemicarbazide-carboxylic acid bidentate ligand into the three-necked flask at a frequency of 2 Hz. Adjust the pH to 3.5 with acetic acid, continue the reaction in a water bath at 45 °C for 2 h, then reduce the pressure from 10 MPa to 6 MPa at a pressure reduction rate of 0.5 MPa / min, filter, and take the obtained solution; among them, the addition amount of the thiosemicarbazide-carboxylic acid bidentate ligand is 0.6 wt% of the aluminum foil.

[0038] 6. Adjust the pH of the solution obtained after filtration to 8.0 with ammonia water, reduce the reaction temperature from 45 °C to -10 °C at a cooling rate of 0.2 °C / min, centrifuge at 5000 rpm for 15 min, filter, wash the obtained product with supercritical CO2 at 35 °C and 8 MPa to obtain an alcohol aluminum salt mixture; distill the alcohol aluminum salt mixture under reduced pressure at 0.5 kPa, and collect the distillate above 135 °C to obtain the alcohol aluminum salt.

[0039] Comparative Example 2 A method for preparing an alcohol aluminum salt, which is different from Example 1 in that a thiosemicarbazide-carboxylic acid bidentate ligand is not used to complex impurity iron, and includes the following steps: 1. Wash the impurities on the surface of the aluminum foil with deionized water, and then soak the aluminum foil in a 15 wt% sulfuric acid solution for 30 s and an 8 wt% sodium hydroxide solution for 20 s in sequence to remove impurities. After soaking, wash it with deionized water again, and place it in a ventilated and dry place until the surface of the aluminum foil is free of water. Then, use argon non-thermal plasma sputtering to activate the aluminum foil for 10 min at a chamber pressure of 10 Pa, a power of 1.5 kW, and a frequency of 13.56 MHz.

[0040] 2. Under a nitrogen atmosphere, mix 20 g of the activated aluminum foil and 200 mL of isopropanol with a water content of less than 0.2 wt% in a three-necked flask, heat it to the boiling point of isopropanol, and carry out the reaction; after the isopropanol reflux is stable, continue the reaction for 5 h.

[0041] 5. After the reaction proceeds for 5 h, supercritical CO2 at 10 MPa is introduced. After continuing the reaction for 2 h in a water bath at 45 °C, the pressure is decreased from 10 MPa to 6 MPa at a pressure reduction rate of 0.5 MPa / min, followed by filtration, and the resulting solution is taken.

[0042] 6. The pH of the solution obtained after filtration is adjusted to 8.0 using ammonia water. The reaction temperature is decreased from 45 °C to -10 °C at a temperature reduction rate of 0.2 °C / min, followed by centrifugation at 5000 rpm for 15 min and then filtration. The resulting product is washed with supercritical CO2 at 35 °C and 8 MPa to obtain an alcohol aluminum salt mixture; the alcohol aluminum salt mixture is subjected to vacuum distillation at 0.5 kPa, and the distillate at a temperature above 135 °C is collected to obtain the alcohol aluminum salt.

[0043] Comparative Example 3 A method for preparing an alcohol aluminum salt, which is different from Example 1 in that the common complexing agent ethylenediaminetetraacetic acid (EDTA) is used to complex the impurity iron in the alcohol aluminum salt, and the method includes the following steps: 1. The impurities on the surface of the aluminum foil are washed off using deionized water, and then the aluminum foil is successively immersed in a 15 wt% sulfuric acid solution for 30 s and an 8 wt% sodium hydroxide solution for 20 s for impurity removal. After immersion, it is washed again with deionized water and placed in a ventilated and dry place until the surface of the aluminum foil is free of water. Then, argon non-thermal plasma sputtering is used to perform activation treatment on the aluminum foil at a chamber pressure of 10 Pa, a power of 1.5 kW, and a frequency of 13.56 MHz for 10 min.

[0044] 2. Under a nitrogen atmosphere, 20 g of the activated aluminum foil and 200 mL of isopropyl alcohol with a water content of less than 0.2 wt% are mixed and placed in a three-necked flask, and the mixture is heated to the boiling point of isopropyl alcohol for reaction; after the isopropyl alcohol reflux is stable, the reaction continues for 5 h until white precipitate appears in the three-necked flask. Then, it is centrifuged at 5000 rpm for 15 min and filtered, and washed with absolute ethanol to obtain an alcohol aluminum salt mixture.

[0045] 3. According to a mass ratio of 1:150, the obtained alcohol aluminum salt mixture is dissolved in absolute ethanol. After mixing evenly, under a nitrogen atmosphere, an EDTA solution with a concentration of 0.005 g / L is added, and the mixture is stirred at 300 rpm and 70 °C for 3 h. Then, the temperature is decreased from 70 °C to room temperature at a temperature reduction rate of 5 °C / min, allowed to stand for 10 h, followed by suction filtration, and then vacuum distillation at 0.5 kPa to collect the distillate at a temperature above 135 °C to obtain the impurity-removed alcohol aluminum salt; among them, the mass ratio of EDTA to the alcohol aluminum salt mixture is 3:1.

[0046] The alcohol aluminum salt yield and the content of impurity iron in the alcohol aluminum salt are measured for each example and comparative example.

[0047] 1. Determination of the alcohol aluminum salt yield The aluminate obtained from the above different examples and comparative examples was compared with the theoretical yield, and the yield of aluminate was calculated. The calculation results are shown in Table 1.

[0048] Table 1 Test results of the yield of aluminate

[0049] As can be seen from Table 1, the yields of aluminate in Examples 1-3 are all higher than those in Comparative Examples 1-3. In particular, the yield of aluminate in Comparative Example 1 decreased by more than 22% compared with that in Example 2. Bombarding the aluminum foil surface with argon non-thermal plasma can generate activated aluminum radicals, significantly reducing the energy barrier of the aluminate synthesis reaction, increasing the yield of aluminate, and realizing the efficient synthesis of aluminate; while the aminothiourea-carboxylic acid bidentate ligand and EDTA mainly complex the impurity iron ions in the aluminate, and have little effect on the yield of aluminate. Therefore, the yields of aluminate in Comparative Examples 2-3 did not decrease significantly compared with those in Examples 1-3.

[0050] 2. Test results of the iron content of impurities in aluminate Weigh 5 g of aluminate into a small beaker, add 30 mL of 6 mol / L hydrochloric acid, stir and dissolve until a clear solution is obtained. Transfer the obtained clear solution to a 50 mL volumetric flask and finally dilute to the mark. The iron content of impurities was determined by the phenanthroline method. The test results are shown in Table 2.

[0051] Table 2 Iron content of impurities in aluminate

[0052] As can be seen from Table 2, the iron content of impurities in the aluminate of Examples 1-3 is significantly lower than that in Comparative Examples 1-3. Using the aminothiourea-carboxylic acid bidentate ligand to complex the iron impurities in the aluminate can reduce the iron content of impurities in the aluminate by more than 70.6%. The difference between Comparative Example 1 and Example 1 is that the aluminum foil was not activated, but aluminum chloride was used to catalyze the reaction. Due to the iron ions brought by aluminum chloride itself, the iron content of impurities in the aluminate increased; the difference between Comparative Example 2 and Example 1 is that the aminothiourea-carboxylic acid bidentate ligand was not used to complex the iron impurities in the aluminate, and the iron impurities were only removed by physical filtration. Therefore, the iron content of impurities in Comparative Example 2 is the highest; Comparative Example 3 used the traditional iron removal reagent EDTA to complex the iron impurities in the aluminate. Although the iron content of impurities decreased compared with that in Comparative Example 2, it is still much higher than that in Examples 1-3.

[0053] The specific embodiments of the present invention described above do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and deformations made according to the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing an aluminum alkoxide, characterized in that, It includes the following steps: S1. After the cleaned aluminum foil is soaked in a 15wt% sulfuric acid solution and an 8wt% sodium hydroxide solution in sequence for impurity removal, it is washed with deionized water and dried until there is no water on the surface of the aluminum foil, and then activated with argon non-thermal plasma; S2. Under a nitrogen atmosphere, 20 - 40 g of the activated aluminum foil and 200 - 400 mL of isopropanol with a water content less than 0.2wt% are mixed and placed in a three-necked flask, and heated to boiling for reaction. After the isopropanol reflux is stable, the reaction continues for 5 h; S3. After the reaction proceeds for 5 h, a thiosemicarbazide-carboxylic acid bidentate ligand is added to the three-necked flask, the pH is adjusted to 3.5 - 5.5, and the reaction continues for 2 h in a water bath at 45°C. After extraction, crystallization, centrifugation, filtration, and washing, an alcohol aluminum salt mixture is obtained. The alcohol aluminum salt mixture is subjected to vacuum distillation, and the distillate above 135°C is collected to obtain the alcohol aluminum salt; wherein, the addition amount of the thiosemicarbazide-carboxylic acid bidentate ligand is 0.6 - 1.0wt% of the aluminum foil.

2. The preparation method of an aluminum alkoxide according to claim 1, wherein, In step S3, the preparation method of the thiosemicarbazide-carboxylic acid bidentate ligand is as follows: Under a nitrogen atmosphere, 50 - 70 mL of γ-(2, 3-epoxypropoxy)propyltrimethoxysilane, 0.1 - 0.2 mol of thiosemicarbazide, 150 mL of absolute ethanol, and 0.12 - 0.24 mol of acetic acid are mixed and placed in a three-necked flask. The temperature is lowered to 0 - 5°C in an ice bath, and a 20wt% sodium hydroxide solution is slowly added dropwise to adjust the pH to 8 - 9. After stirring and reacting for 30 min, the temperature is raised to 75°C and the reflux reaction is carried out for 8 h. After the reaction is completed, the pH is adjusted to 2 - 3. The precipitated white precipitate is subjected to suction filtration, washing, and drying to obtain the thiosemicarbazide-carboxylic acid bidentate ligand.

3. The preparation method of an aluminum alkoxide according to claim 1, wherein, In step S3, the addition method of the thiosemicarbazide-carboxylic acid bidentate ligand is as follows: Using supercritical CO2 as a carrier, at 10 Mpa, the thiosemicarbazide-carboxylic acid bidentate ligand is added to the three-necked flask in a pulsed manner at a concentration of 0.5 mol / L, and the pulse frequency is 2 Hz.

4. The preparation method of an aluminum alkoxide according to claim 1, characterized in that In step S1, the conditions for activating the aluminum foil with argon non-thermal plasma are: under a chamber pressure of 10 Pa, a power of 1.5 kW, and a frequency of 13.56 MHz, the aluminum foil is activated with argon non-thermal plasma for 10 min.

5. The preparation method of an aluminum alkoxide according to claim 1, characterized in that, In step S3, the extraction method of the alcohol aluminum salt mixture is: at a pressure reduction rate of 0.5 MPa / min, the pressure of supercritical CO2 is reduced from 10 MPa to 6 MPa.

6. The preparation method of an aluminum alkoxide according to claim 1, characterized in that In step S3, the crystallization method of the alcohol aluminum salt mixture is: using ammonia water to adjust the pH to 8.0, and at a temperature reduction rate of 0.2°C / min, the reaction temperature is reduced from 45°C to -10°C.

7. The alcohol aluminum salt obtained by the preparation method of an alcohol aluminum salt as described in claim 1.

Images