Aluminum alcohol salt and preparation method thereof

Abstract

The invention belongs to the field of chemical technology, and in particular to a kind of aluminum alcoholate and preparation method thereof. The present invention uses argon non-thermal plasma to bombard the surface of aluminum foil, peels off the oxide film on the surface of aluminum foil and forms active aluminum radicals, reduces the reaction energy barrier of aluminum alcoholate, enables aluminum alcoholate to be carried out under the conditions of no catalyst, realizes the green and efficient synthesis of aluminum alcoholate;Use thiosemicarbazide carboxylic acid bidentate ligand to complex the impurity iron in aluminum alcoholate, by the sulfur and nitrogen double coordination site in thiosemicarbazide unit, coordinate the oxygen coordination site in carboxylic acid group, form higher complexing ability to impurity iron, improve complex stability;Crystallization is regulated by the pH response characteristic of carboxylic acid group, realizes the efficient removal of impurity iron in aluminum alcoholate.

Description

Technical Field

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

[0002] High-purity alumina refers to aluminum oxide with a purity of 4N (99.99% by mass) or higher. Due to its exceptional thermal, optical, magnetic, electrical, and mechanical properties, it is widely used in cutting-edge materials such as catalyst supports, lithium battery separator coatings, sapphire, specialty ceramics, and phosphors. Currently, the primary preparation technology for high-purity alumina is aluminum alkoxide hydrolysis. Aluminum alkoxides are a class of metal organic compounds formed by the bond of aluminum and an alcoholic hydroxyl group (-OH) through an oxygen atom. The preparation of aluminum alkoxides requires a catalyst to react with the alumina or directly dissolve the oxide film on the aluminum metal surface, exposing the fresh aluminum surface and forming an active intermediate, enabling the aluminum-alcohol reaction at a lower temperature. Aluminum chloride (AlCl3) is currently the most commonly used catalyst. However, the use of catalysts carries the risk of catalyst residues introducing impurities such as chlorine and iron.

[0003] Raw aluminum is the primary source of impurities in high-purity alumina. The main impurity elements in aluminum include silicon, iron, sodium, calcium, magnesium, and zinc. Silicon, iron, and zinc are difficult to react with alcohols, and most can be removed by filtration. Calcium, sodium, and magnesium are relatively reactive impurities, and while they readily react with alcohols, their content in aluminum is relatively low. Although iron also has poor reactivity with alcohols, it is a major associated impurity in aluminum and presents at high levels. Furthermore, in the production of high-purity alumina, reactors and pipelines are prone to introducing iron impurities into the product. Removing iron impurities from high-purity alumina is difficult, and their presence significantly impacts the purity, crystal structure, and physicochemical properties of the resulting high-purity alumina. Summary of the Invention

[0004] The object of the present invention is to provide an aluminum alcoholate and a preparation method thereof to solve the above-mentioned technical problems.

[0005] In order to achieve the above technical objectives, the technical solution of the present invention is:

[0006] A method for preparing an aluminum alcoholate, characterized in that it comprises the following steps:

[0007] S1. Soak the cleaned aluminum foil in 15 wt % sulfuric acid solution and 8 wt % sodium hydroxide solution to remove impurities, then wash with deionized water, dry until the surface of the aluminum foil is free of water, and activate it using argon non-thermal plasma;

[0008] S2. Under a nitrogen atmosphere, place 20-40 g of activated aluminum foil and 200-400 mL of isopropanol with a water content of less than 0.2 wt % in a three-necked flask and heat to boiling for reaction. Continue the reaction for 5 h after the isopropanol refluxes smoothly.

[0009] S3. After the reaction is carried out for 5 hours, a semicarbazide-carboxylic acid bidentate ligand is added to a three-necked flask, the pH is adjusted to 3.5-5.5, and the reaction is continued in a water bath at 45° C. for 2 hours. After extraction, crystallization, centrifugation, filtration, and washing, an alkoxide aluminum salt mixture is obtained. The alkoxide aluminum salt mixture is subjected to reduced pressure distillation, and the distillate above 135° C. is collected to obtain an alkoxide aluminum salt; wherein the addition amount of the semicarbazide-carboxylic acid bidentate ligand is 0.6-1.0 wt % of the aluminum foil.

[0010] As a further improvement, in step S3, the preparation method of the semicarbazide-carboxylic acid bidentate ligand is as follows: under a nitrogen atmosphere, 50~70mLγ-(2, 3-epoxypropoxy)propyltrimethoxysilane, 0.1~0.2mol semicarbazide, 150mL anhydrous ethanol, and 0.12~0.24mol acetic acid are mixed and placed in a three-necked flask, cooled to 0~5°C in an ice bath, and 20wt% sodium hydroxide solution is slowly added dropwise to adjust the pH to 8~9. After stirring for 30 minutes, the mixture is heated to 75°C and refluxed for 8 hours. After the reaction is completed, the pH is adjusted to 2~3, and the precipitated white precipitate is filtered, washed, and dried to obtain a semicarbazide-carboxylic acid bidentate ligand.

[0011] As a further improvement, in step S3, the thiosemicarbazide-carboxylic acid bidentate ligand is added in a pulsed manner at a concentration of 0.5 mol / L into a three-necked flask at 10 MPa using supercritical CO2 as a carrier, with a pulse frequency of 2 Hz.

[0012] As a further improvement, in step S1, the conditions for the argon non-thermal plasma activation of the aluminum foil are: chamber pressure 10 Pa, power 1.5 kW, frequency 13.56 MHz, and argon non-thermal plasma activation treatment for 10 minutes.

[0013] As a further improvement, in step S3, the extraction method of the aluminum alcohol salt mixture is: reducing the pressure of the supercritical CO2 from 10 MPa to 6 MPa at a pressure reduction rate of 0.5 MPa / min.

[0014] As a further improvement, in step S3, the alcohol aluminum salt mixture is crystallized by adjusting the pH to 8.0 using aqueous ammonia and cooling the reaction temperature from 45°C to -10°C at a cooling rate of 0.2°C / min.

[0015] The present invention also provides an aluminum alcoholate.

[0016] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0017] 1. A semicarbazide-carboxylic acid bidentate ligand is used to complex the impurity iron in the aluminum alkoxide. The semicarbazide unit provides dual coordination sites for sulfur and nitrogen. The strong lone pair electrons of the sulfur atom and the alkalinity of the nitrogen atom enhance the complexing ability and improve the stability of the complex. The carboxylic acid group provides an oxygen atom coordination site, cooperating with the semicarbazide unit to form a stable iron complex. Furthermore, the carboxylic acid group can be protonated in an acidic environment, strengthening the binding force between the thiourea unit and the impurity iron. Under alkaline conditions, the carboxylic acid group dissociates, allowing the iron complex to crystallize in the aluminum alkoxide, making it easier to separate.

[0018] 2. The surface of the aluminum foil is bombarded with argon non-thermal plasma to peel off the oxide film on the surface of the aluminum foil and form active aluminum free radicals, which significantly reduces the reaction energy barrier of aluminum alcohol salts and enables the production of aluminum alcohol salts in the absence of catalysts. This eliminates the risk of the product containing exogenous impurities such as chlorine and iron brought by the catalyst, thus achieving green and efficient synthesis of aluminum alcohol salts. DETAILED DESCRIPTION

[0019] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0020] Example 1 A method for preparing an aluminum alkoxide comprises the following steps:

[0021] 1. Under nitrogen atmosphere, 50 mL of γ-(2, 3-epoxypropoxy)propyltrimethoxysilane, 0.1 mol of thiosemicarbazide, 150 mL of anhydrous ethanol, and 0.12 mol of acetic acid were mixed and placed in a three-necked flask. The mixture was cooled to 0°C in an ice bath. 20 wt% sodium hydroxide solution was slowly added dropwise. The pH was adjusted to 8 with aqueous ammonia. The mixture was stirred at 800 rpm for 30 min, then the temperature was raised to 75°C and refluxed for 8 h.

[0022] 2. After the reflux reaction is completed, acetic acid is added dropwise to adjust the pH to 2 until a white precipitate is precipitated; the precipitated white precipitate is filtered using a Buchner funnel for 30 minutes, transferred to a Soxhlet extractor, and refluxed with anhydrous ethanol for 12 hours. After vacuum drying at 40°C and 0.1 kPa for 6 hours, a thiosemicarbazide-carboxylic acid bidentate ligand is obtained.

[0023] 3. Use deionized water to clean impurities on the surface of the aluminum foil, then soak the aluminum foil in a 15wt% sulfuric acid solution for 30s and then in an 8wt% sodium hydroxide solution for 20s to remove impurities. After soaking, wash it again with deionized water and place it in a ventilated and dry place until there is no water on the surface of the aluminum foil. Then use argon non-thermal plasma sputtering to activate the aluminum foil for 10 minutes at a chamber pressure of 10Pa, a power of 1.5kW, and a frequency of 13.56MHz.

[0024] 4. Under nitrogen atmosphere, place 20 g of activated aluminum foil and 200 mL of isopropanol with a water content of less than 0.2 wt% in a three-necked flask and heat until the isopropanol boils to react. Continue the reaction for 5 h after the isopropanol refluxes smoothly.

[0025] 5. After the reaction has been carried out for 5 hours, 0.5 mol / L of thiosemicarbazide-carboxylic acid bidentate ligand is added to the three-necked flask in a pulsed manner at a frequency of 2 Hz using supercritical CO2 at 10 MPa. The pH is adjusted to 3.5 using acetic acid. The reaction is continued in a water bath at 45°C for 2 hours. The pressure is then reduced from 10 MPa to 6 MPa at a rate of 0.5 MPa / min. The resulting solution is filtered and taken. The amount of thiosemicarbazide-carboxylic acid bidentate ligand added is 0.6 wt% of the aluminum foil.

[0026] 6. Adjust the pH of the filtered solution to 8.0 with aqueous ammonia, 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, and wash the resulting 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 alcohol aluminum salt.

[0027] Example 2 A method for preparing an aluminum alkoxide comprises the following steps:

[0028] 1. Under nitrogen atmosphere, 60 mL of γ-(2, 3-epoxypropoxy)propyltrimethoxysilane, 0.15 mol of thiosemicarbazide, 150 mL of anhydrous ethanol, and 0.18 mol of acetic acid were mixed and placed in a three-necked flask. The mixture was cooled to 3 °C in an ice bath. 20 wt% sodium hydroxide solution was slowly added dropwise. The pH was adjusted to 8.5 with aqueous ammonia. The mixture was stirred at 800 rpm for 30 min, then the temperature was raised to 75 °C and refluxed for 8 h.

[0029] 2. After the reflux reaction is completed, acetic acid is added dropwise to adjust the pH to 3 until a white precipitate is precipitated; the precipitated white precipitate is filtered using a Buchner funnel for 30 minutes, transferred to a Soxhlet extractor, and refluxed with anhydrous ethanol for 12 hours. After vacuum drying at 40°C and 0.1 kPa for 6 hours, a thiosemicarbazide-carboxylic acid bidentate ligand is obtained.

[0030] 3. Use deionized water to clean impurities on the surface of the aluminum foil, then soak the aluminum foil in a 15wt% sulfuric acid solution for 30s and then in an 8wt% sodium hydroxide solution for 20s to remove impurities. After soaking, wash it again with deionized water and place it in a ventilated and dry place until there is no water on the surface of the aluminum foil. Then use argon non-thermal plasma sputtering to activate the aluminum foil for 10 minutes at a chamber pressure of 10Pa, a power of 1.5kW, and a frequency of 13.56MHz.

[0031] 4. Under nitrogen atmosphere, mix 30 g of activated aluminum foil and 300 mL of isopropanol with a water content of less than 0.2 wt% in a three-necked flask and heat until the isopropanol boils to react. After the isopropanol refluxes smoothly, continue the reaction for 5 h.

[0032] 5. After the reaction has been carried out for 5 hours, 0.5 mol / L of thiosemicarbazide-carboxylic acid bidentate ligand is added to the three-necked flask in a pulsed manner at a frequency of 2 Hz using supercritical CO2 at 10 MPa. The pH is adjusted to 4.0 using acetic acid. The reaction is continued in a water bath at 45°C for 2 hours. The pressure is then reduced from 10 MPa to 6 MPa at a rate of 0.5 MPa / min. The resulting solution is filtered and taken. The amount of thiosemicarbazide-carboxylic acid bidentate ligand added is 0.8 wt% of the aluminum foil.

[0033] 6. Adjust the pH of the filtered solution to 8.0 with aqueous ammonia, 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, and wash the resulting 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 alcohol aluminum salt.

[0034] Example 3 A method for preparing an aluminum alkoxide comprises the following steps:

[0035] 1. Under nitrogen atmosphere, 70 mL of γ-(2, 3-epoxypropoxy)propyltrimethoxysilane, 0.2 mol of thiosemicarbazide, 150 mL of anhydrous ethanol, and 0.24 mol of acetic acid were mixed and placed in a three-necked flask. The mixture was cooled to 5 °C in an ice bath. 20 wt% sodium hydroxide solution was slowly added dropwise. The pH was adjusted to 9 with aqueous ammonia. The mixture was stirred at 800 rpm for 30 min, then the temperature was raised to 75 °C and refluxed for 8 h.

[0036] 2. After the reflux reaction is completed, acetic acid is added dropwise to adjust the pH to 2 until a white precipitate is precipitated; the precipitated white precipitate is filtered using a Buchner funnel for 30 minutes, transferred to a Soxhlet extractor, and refluxed with anhydrous ethanol for 12 hours. After vacuum drying at 40°C and 0.1 kPa for 6 hours, a thiosemicarbazide-carboxylic acid bidentate ligand is obtained.

[0037] 3. Use deionized water to clean impurities on the surface of the aluminum foil, then soak the aluminum foil in a 15wt% sulfuric acid solution for 30s and then in an 8wt% sodium hydroxide solution for 20s to remove impurities. After soaking, wash it again with deionized water and place it in a ventilated and dry place until there is no water on the surface of the aluminum foil. Then use argon non-thermal plasma sputtering to activate the aluminum foil for 10 minutes at a chamber pressure of 10Pa, a power of 1.5kW, and a frequency of 13.56MHz.

[0038] 4. Under nitrogen atmosphere, place 40 g of activated aluminum foil and 400 mL of isopropanol with a water content of less than 0.2 wt% in a three-necked flask and heat until the isopropanol boils to react. Continue the reaction for 5 h after the isopropanol refluxes smoothly.

[0039] 5. After the reaction has been carried out for 5 hours, 0.5 mol / L of thiosemicarbazide-carboxylic acid bidentate ligand is added to the three-necked flask in a pulsed manner at a frequency of 2 Hz using supercritical CO2 at 10 MPa. The pH is adjusted to 5.5 using acetic acid. The reaction is continued in a water bath at 45°C for 2 hours. The pressure is then reduced from 10 MPa to 6 MPa at a rate of 0.5 MPa / min. The resulting solution is filtered and taken. The amount of thiosemicarbazide-carboxylic acid bidentate ligand added is 1.0 wt% of the aluminum foil.

[0040] 6. Adjust the pH of the filtered solution to 8.0 with aqueous ammonia, 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, and wash the resulting 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 alcohol aluminum salt.

[0041] Comparative Example 1 A method for preparing an aluminum alkoxide, which differs from Example 1 in that the aluminum foil is not activated and the aluminum alkoxide reaction is catalyzed by aluminum chloride, comprises the following steps:

[0042] 1. Under nitrogen atmosphere, 50 mL of γ-(2, 3-epoxypropoxy)propyltrimethoxysilane, 0.1 mol of thiosemicarbazide, 150 mL of anhydrous ethanol, and 0.12 mol of acetic acid were mixed and placed in a three-necked flask. The mixture was cooled to 0°C in an ice bath. 20 wt% sodium hydroxide solution was slowly added dropwise. The pH was adjusted to 8 with aqueous ammonia. The mixture was stirred at 800 rpm for 30 min, then the temperature was raised to 75°C and refluxed for 8 h.

[0043] 2. After the reflux reaction is completed, acetic acid is added dropwise to adjust the pH to 2 until a white precipitate is precipitated; the precipitated white precipitate is filtered using a Buchner funnel for 30 minutes, transferred to a Soxhlet extractor, and refluxed with anhydrous ethanol for 12 hours. After vacuum drying at 40°C and 0.1 kPa for 6 hours, a thiosemicarbazide-carboxylic acid bidentate ligand is obtained.

[0044] 3. Use deionized water to clean the impurities on the surface of the aluminum foil, then soak the aluminum foil in 15wt% sulfuric acid solution for 30s and 8wt% sodium hydroxide solution for 20s to remove impurities. After soaking, wash it again with deionized water and place it in a ventilated and dry place until there is no water on the surface of the aluminum foil.

[0045] 4. Under a nitrogen atmosphere, place 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 and heat until the isopropanol boils to react. Continue the reaction for 5 h after the isopropanol refluxes smoothly.

[0046] 5. After the reaction has been carried out for 5 hours, 0.5 mol / L of thiosemicarbazide-carboxylic acid bidentate ligand is added to the three-necked flask in a pulsed manner at a frequency of 2 Hz using supercritical CO2 at 10 MPa. The pH is adjusted to 3.5 using acetic acid. The reaction is continued in a water bath at 45°C for 2 hours. The pressure is then reduced from 10 MPa to 6 MPa at a rate of 0.5 MPa / min. The resulting solution is filtered and taken. The amount of thiosemicarbazide-carboxylic acid bidentate ligand added is 0.6 wt% of the aluminum foil.

[0047] 6. Adjust the pH of the filtered solution to 8.0 with aqueous ammonia, 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, and wash the resulting 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 alcohol aluminum salt.

[0048] Comparative Example 2 A method for preparing an aluminum alkoxide, which differs from Example 1 in that no thiosemicarbazide-carboxylic acid bidentate ligand is used to complex the impurity iron, comprises the following steps:

[0049] 1. Use deionized water to clean impurities on the surface of the aluminum foil, then soak the aluminum foil in 15wt% sulfuric acid solution for 30s and 8wt% sodium hydroxide solution for 20s to remove impurities. After soaking, wash it again with deionized water and place it in a ventilated and dry place until there is no water on the surface of the aluminum foil. Use argon non-thermal plasma sputtering to activate the aluminum foil for 10 minutes at a chamber pressure of 10Pa, a power of 1.5kW, and a frequency of 13.56MHz.

[0050] 2. Under nitrogen atmosphere, place 20 g of activated aluminum foil and 200 mL of isopropanol with a water content of less than 0.2 wt% in a three-necked flask and heat until the isopropanol boils to react. Continue the reaction for 5 h after the isopropanol refluxes smoothly.

[0051] 5. After the reaction has been carried out for 5 hours, 10 MPa of supercritical CO2 was introduced, and the reaction was continued in a water bath at 45°C for 2 hours. Then, the pressure was reduced from 10 MPa to 6 MPa at a rate of 0.5 MPa / min, and the resulting solution was filtered.

[0052] 6. Adjust the pH of the filtered solution to 8.0 with aqueous ammonia, 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, and wash the resulting 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 alcohol aluminum salt.

[0053] Comparative Example 3 A method for preparing an aluminum alkoxide is different from that of Example 1 in that the impurity iron in the aluminum alkoxide is complexed using a common complexing agent ethylenediaminetetraacetic acid (EDTA), and the method comprises the following steps:

[0054] 1. Use deionized water to clean impurities on the surface of the aluminum foil, then soak the aluminum foil in 15wt% sulfuric acid solution for 30s and 8wt% sodium hydroxide solution for 20s to remove impurities. After soaking, wash it again with deionized water and place it in a ventilated and dry place until there is no water on the surface of the aluminum foil. Use argon non-thermal plasma sputtering to activate the aluminum foil for 10 minutes at a chamber pressure of 10Pa, a power of 1.5kW, and a frequency of 13.56MHz.

[0055] 2. Under a nitrogen atmosphere, 20 g of activated aluminum foil and 200 mL of isopropanol with a water content of less than 0.2 wt% were mixed in a three-necked flask and heated to boiling of the isopropanol to carry out the reaction. After the isopropanol refluxed steadily, the reaction was continued for 5 h until a white precipitate appeared in the three-necked flask. The mixture was centrifuged at 5000 rpm for 15 min, filtered, and washed with anhydrous ethanol to obtain an alcohol aluminum salt mixture.

[0056] 3. Dissolve the obtained aluminum alcohol salt mixture in anhydrous ethanol at a mass ratio of 1:150, mix well, add 0.005 g / L EDTA solution under a nitrogen atmosphere, stir at 300 rpm and 70°C for 3 h, then cool from 70°C to room temperature at a cooling rate of 5°C / min, let stand for 10 h, filter, and then distill under reduced pressure at 0.5 kPa, collect the distillate above 135°C, and obtain the aluminum alcohol salt after impurity removal; wherein the mass ratio of EDTA to the aluminum alcohol salt mixture is 3:1.

[0057] The yield of aluminum alkoxide and the content of impurity iron in aluminum alkoxide were measured for each embodiment and comparative example.

[0058] 1. Determination of aluminum alcoholate yield

[0059] The aluminum alkoxides obtained in the above different examples and comparative examples were compared with the theoretical yields to calculate the yields of aluminum alkoxides. The calculation results are shown in Table 1.

[0060] Table 1 Test results of aluminum alcohol salt yield

[0061]

[0062] As can be seen from Table 1, the yields of aluminum alkoxides in Examples 1-3 were all higher than those in Comparative Examples 1-3, particularly in Comparative Example 1, where the yield of aluminum alkoxides decreased by more than 22% relative to that in Example 2. Argon non-thermal plasma bombarding the aluminum foil surface generates activated aluminum radicals, significantly reducing the energy barrier for aluminum alkoxide synthesis, increasing the yield of aluminum alkoxides, and achieving efficient synthesis of aluminum alkoxides. The thiosemicarbazide-carboxylic acid bidentate ligand and EDTA primarily complex the impurity iron ions in the aluminum alkoxides, having little effect on the yield of the aluminum alkoxides. Therefore, the yields of aluminum alkoxides in Comparative Examples 2-3 were not significantly reduced relative to those in Examples 1-3.

[0063] 2. Test results of impurity iron content in aluminum alcohol salt

[0064] Weigh 5 g of aluminum alcoholate 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 scale. The impurity iron content is determined using the o-phenanthroline method. The test results are shown in Table 2.

[0065] Table 2 Impurity iron content in aluminum alkoxide

[0066]

[0067] As shown in Table 2, the impurity iron content in the aluminum alcohol salt of Examples 1 to 3 is significantly lower than that in Comparative Examples 1 to 3. The impurity iron in the aluminum alcohol salt is complexed using thiosemicarbazide-carboxylic acid bidentate ligand, and the content of impurity iron in the aluminum alcohol salt can be reduced by more than 70.6%. Comparative Example 1 differs from Example 1 in that the aluminum foil is not activated, but is carried out using aluminum chloride catalysis, and the iron ions brought by aluminum chloride itself cause the impurity iron content in the aluminum alcohol salt to increase; Comparative Example 2 differs from Example 1 in that the impurity iron in the aluminum alcohol salt is not complexed using thiosemicarbazide-carboxylic acid bidentate ligand, and impurity iron is removed only by physical filtration, so the impurity iron content in Comparative Example 2 is the highest; Comparative Example 3 uses traditional iron removal reagent EDTA to complex the impurity iron in the aluminum alcohol salt, and although the impurity iron content is reduced relative to Comparative Example 2, it is still much higher than that in Examples 1 to 3.

[0068] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an aluminum alkoxide, characterized in that: The following steps are involved: S1. Soak the cleaned aluminum foil in 15 wt % sulfuric acid solution and 8 wt % sodium hydroxide solution to remove impurities, then wash with deionized water, dry until the surface of the aluminum foil is free of water, and activate it using argon non-thermal plasma; S2. Under a nitrogen atmosphere, place 20-40 g of activated aluminum foil and 200-400 mL of isopropanol with a water content of less than 0.2 wt % in a three-necked flask and heat to boiling for reaction. Continue the reaction for 5 h after the isopropanol refluxes smoothly. S3. After the reaction is carried out for 5 hours, a semicarbazide-carboxylic acid bidentate ligand is added to a three-necked flask, the pH is adjusted to 3.5-5.5, and the reaction is continued in a water bath at 45° C. for 2 hours. After extraction, crystallization, centrifugation, filtration, and washing, an alkoxide aluminum salt mixture is obtained. The alkoxide aluminum salt mixture is subjected to reduced pressure distillation, and a distillate above 135° C. is collected to obtain an alkoxide aluminum salt; wherein the amount of the semicarbazide-carboxylic acid bidentate ligand added is 0.6-1.0 wt % of the aluminum foil; The preparation method of the semicarbazide-carboxylic acid bidentate ligand is as follows: under a nitrogen atmosphere, 50-70 mL of γ-(2, 3-epoxypropyloxy)propyltrimethoxysilane, 0.1-0.2 mol of semicarbazide, 150 mL of anhydrous ethanol, and 0.12-0.24 mol of acetic acid are mixed and placed in a three-necked flask, the mixture is cooled to 0-5° C. in an ice bath, 20 wt % sodium hydroxide solution is slowly added dropwise, the pH is adjusted to 8-9, the mixture is stirred for reaction for 30 minutes, the temperature is raised to 75° C., and the mixture is refluxed for reaction for 8 hours. After the reaction is completed, the pH is adjusted to 2-3, and the precipitated white precipitate is filtered, washed, and dried to obtain the semicarbazide-carboxylic acid bidentate ligand; In step S3, the thiosemicarbazide-carboxylic acid bidentate ligand is added by pulse-adding the thiosemicarbazide-carboxylic acid bidentate ligand at a concentration of 0.5 mol / L into a three-necked flask using supercritical CO2 at 10 MPa as a carrier, with a pulse frequency of 2 Hz; In step S3, the extraction method of the alcohol aluminum salt mixture is: reducing the pressure of supercritical CO2 from 10MPa to 6MPa at a pressure reduction rate of 0.5MPa / min; the washing method is: using supercritical CO2 at 35°C and 8MPa for washing.

2. The method for preparing an aluminum alcoholate according to claim 1, wherein In step S1 , the conditions for argon non-thermal plasma activation of the aluminum foil are: chamber pressure 10 Pa, power 1.5 kW, frequency 13.56 MHz, and argon non-thermal plasma activation treatment for 10 minutes.

3. The method for preparing an aluminum alcoholate according to claim 1, wherein In step S3, the aluminum alcohol salt mixture is crystallized by adjusting the pH to 8.0 using aqueous ammonia and cooling the reaction temperature from 45°C to -10°C at a cooling rate of 0.2°C / min.

4. The aluminum alcoholate obtained by the preparation method of the aluminum alcoholate according to claim 1.

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