Process for the preparation of high surface area, high conversion pseudo-boehmite by attrition hydrolysis

Abstract

This invention discloses a method for preparing pseudoboehmite with high specific surface area and high conversion rate by sand milling and hydrolysis, belonging to the field of materials chemistry. The method involves using high-purity aluminum isopropoxide purified by vacuum distillation as a dispersant, and sand milling and stirring under specific pH, temperature, and vacuum conditions to complete the hydrolysis and aging process. Microwave drying is then employed to obtain a sample with a specific surface area >350 cm². 2 Boehmite powder with an alumina conversion rate of ≥76% per g can be used for the production of laser crystal-grade alumina and gem-grade alumina, and is also suitable for use as a catalyst support; moreover, the preparation method is simple to operate, easy to control, and easy to industrialize.

Description

Technical Field

[0001] This invention relates to a method for preparing pseudoboehmite with high specific surface area and high conversion rate by sand milling and hydrolysis, belonging to the field of materials chemistry. Background Technology

[0002] Materials with a purity ≥ 99.9% can be classified as high-purity materials. For boehmite, a purity ≥ 99.9% is considered high-purity boehmite. Materials with a purity between 99.994% and 99.999% are considered gem-grade boehmite; alumina powder prepared from boehmite of this purity can be used for sapphire material growth. Boehmite with a purity exceeding 99.999% can be classified as laser crystal grade, as it minimizes the influence of impurities. Alumina powder prepared from boehmite of this purity can be used as a raw material powder for synthesizing laser crystals, such as YAG powder. Furthermore, reducing the particle size of the powder will result in a larger specific surface area.

[0003] High-specific-surface-area and high-conversion-rate pseudoboehmite has broad market prospects at home and abroad. For example, high-purity pseudoboehmite with high specific-surface-area can be used to prepare activated alumina as a catalyst carrier material in petrochemical and fine chemical industries, and can also be used as a binder for molecular sieves and high-performance refractory materials.

[0004] Although the traditional aluminum alkoxide hydrolysis method can prepare high-purity boehmite, its specific surface area is generally ≤250 cm². 2 / g, and the conversion rate of alumina is ≤70%. To obtain a higher specific surface area, pore expanders need to be added, which reduces the purity; to improve the conversion rate, the temperature needs to exceed 150℃ and hydrothermal treatment is required under certain pressure, which increases energy consumption and may result in incomplete hydrolysis, leading to excessively high carbon content in the pseudoboehmite, which is not conducive to later use.

[0005] It should be noted that the above content falls within the inventor's technical knowledge and does not necessarily constitute prior art. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for preparing pseudoboehmite with high specific surface area and high conversion rate through sand milling and hydrolysis. The obtained pseudoboehmite can achieve a particle size of nanometer scale, with controllable purity and a specific surface area greater than 350 cm². 2 / g, alumina conversion rate ≥76%.

[0007] The present invention achieves the above objectives by adopting the following technical solutions:

[0008] A method for preparing pseudoboehmite with high specific surface area and high conversion rate by sand milling and hydrolysis includes the following steps:

[0009] (1) Add high-purity aluminum alkoxide and dispersant to a grinding mill and stir to mix. The dispersant is a low-carbon alcohol with 2 to 4 carbon atoms. The mass ratio of dispersant to aluminum alkoxide is 1:1 to 1:1.5.

[0010] (2) Add high-purity water to the solution obtained in step (1), the amount of high-purity water added is 35% to 50% of the weight of aluminum alkoxide;

[0011] (3) Add pH adjuster to the solution obtained in step (2) to adjust the pH value of the solution to 4-6;

[0012] (4) The solution obtained in step (3) is subjected to sand milling hydrolysis and aging reaction in two stages: the solution temperature in the first stage is 60-75℃, the sand milling speed is 200-250r / min, and the sand milling time is 0.5-2h; the solution temperature in the second stage is 85-100℃, the sand milling speed is 300-500r / min, the sand milling time is 5-6h, and the vacuum degree is -0.08--0.04MPa.

[0013] (5) The hydrolyzed and aged product obtained in step (4) is dried to obtain pseudoboehmite powder.

[0014] Optionally, the dispersant in step (1) may be one or more of ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and tert-butanol.

[0015] Optionally, in step (1), the stirring speed is 100-200 r / min and the stirring time is 0.5-1.5 h.

[0016] Optionally, the high-purity aluminum alkoxide in step (1) has a purity of ≥99.99%; the aluminum alkoxide is aluminum isopropoxide, aluminum ethoxide, aluminum n-butoxide, or aluminum sec-butoxide.

[0017] Optionally, the high-purity aluminum alkoxide in step (1) is obtained by catalytic synthesis of high-purity aluminum sheets and anhydrous isopropanol followed by purification by vacuum distillation.

[0018] Optionally, the resistivity of the high-purity water in step (2) is >12MΩ, and distilled water, deionized water or ion-exchange water is used.

[0019] Optionally, in step (3), the pH adjuster may be 98% sulfuric acid or 65% nitric acid.

[0020] Optionally, the drying method in step (4) is microwave drying, with a temperature of 80 to 160°C and a time of 8 to 20 hours.

[0021] Optionally, the grinding balls of the sand mill are alumina grinding balls with a purity >99.9% and a diameter of 2-8 mm.

[0022] The beneficial effects of this application include, but are not limited to:

[0023] This invention provides a method for preparing pseudoboehmite with high specific surface area and high conversion rate through sand milling and hydrolysis. The resulting pseudoboehmite particle size can reach the nanoscale, and the purity of aluminum isopropoxide does not decrease during the hydrolysis process. By controlling the pH value, sand milling and hydrolysis temperature, time, pressure, and microwave drying processes, laser crystal-grade powder with a purity exceeding 99.99% can be prepared for the production of laser crystal-grade alumina and gem-grade alumina. Simultaneously, the specific surface area of ​​the prepared pseudoboehmite is >350 cm². 2 / g, high activity, alumina conversion rate ≥76%, suitable for use as a catalyst support;

[0024] The preparation method provided by this invention is simple to operate, easy to control, easy to industrialize, and environmentally friendly. Detailed Implementation

[0025] The present invention will be further described in detail below. However, it should be noted that the following specific embodiments are merely exemplary examples of the invention, and the scope of protection of the invention is not limited thereto. The scope of protection of the invention is defined only by the claims. It will be apparent to those skilled in the art that various other modifications and substitutions can be made to the embodiments of the invention within the scope of protection defined by the claims, and the same technical effects can still be achieved, thus achieving the ultimate technical objective of the invention.

[0026] Unless otherwise specified, all raw materials in this manual were obtained through commercial channels.

[0027] The method for preparing pseudoboehmite with high specific surface area and high conversion rate by sand milling and hydrolysis provided by the present invention includes the following steps:

[0028] (1) Add high-purity aluminum alkoxide and dispersant to a grinding mill and stir to mix. The dispersant is a low-carbon alcohol with 2 to 4 carbon atoms. The mass ratio of dispersant to aluminum alkoxide is 1:1 to 1:1.5.

[0029] (2) Add high-purity water to the solution obtained in step (1), the amount of high-purity water added is 35% to 50% of the weight of aluminum alkoxide;

[0030] (3) Add pH adjuster to the solution obtained in step (2) to adjust the pH value of the solution to 4-6;

[0031] (4) The solution obtained in step (3) is subjected to sand milling hydrolysis and aging reaction in two stages: the solution temperature in the first stage is 60-75℃, the sand milling speed is 200-250r / min, and the sand milling time is 0.5-2h; the solution temperature in the second stage is 85-100℃, the sand milling speed is 300-500r / min, the sand milling time is 5-6h, and the vacuum degree is -0.08--0.04MPa.

[0032] (5) The hydrolyzed and aged product obtained in step (4) is dried to obtain the pseudo-boehmite powder.

[0033] In step (1), the dispersant is one or more of ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and tert-butanol.

[0034] In step (1), the stirring speed is 200-250 r / min and the stirring time is 0.5-1.5 h.

[0035] The high-purity aluminum alkoxide in step (1) has a purity of ≥99.99%; the aluminum alkoxide is aluminum isopropoxide, aluminum ethoxide, aluminum n-butoxide or aluminum sec-butoxide; specifically, the high-purity aluminum alkoxide in step (1) is obtained by high-purity aluminum flakes and anhydrous isopropanol catalytic synthesis followed by purification by vacuum distillation.

[0036] The resistivity of the high-purity water in step (2) is >12MΩ. Specifically, distilled water, deionized water or ion-exchange water can be used.

[0037] In step (3), the pH adjuster is either 98% sulfuric acid or 65% nitric acid.

[0038] The drying method in step (4) is microwave drying, with a temperature of 80-160℃ and a time of 8-20h.

[0039] The grinding balls in the sand mill are alumina grinding balls with a purity of >99.9% and a diameter of 2-8 mm.

[0040] The following will provide a detailed description of the method for preparing pseudoboehmite with high specific surface area and high conversion rate by sand milling and hydrolysis provided by the present invention through specific embodiments and comparative examples.

[0041] Example 1:

[0042] (1) Place 1000g of aluminum isopropoxide (Al(OPriso)) purified by vacuum distillation into a sand mill, add 1500g of isopropanol as a dispersant, and stir at room temperature for 0.5h at a speed of 150r / min.

[0043] (2) Add 500g of high-purity water;

[0044] (3) Add 65% HNO3 to adjust the pH of the solution to 4;

[0045] (4) While grinding and heating, control the solution temperature to 70℃, and carry out the hydrolysis reaction by grinding and stirring at 230r / min for 2h.

[0046] Next, the solution temperature was raised to 90℃, the vacuum degree was -0.06MPa, the speed of the sand mill was controlled at 400r / min, and the sand milling hydrolysis aging was carried out for 5h.

[0047] (5) The hydrolyzed and aged product was microwave dried at a temperature of 100°C for 12 hours and then passed through two air jet mills to obtain pseudo-boehmite powder.

[0048] Example 2:

[0049] (1) Place 1000g of Al(OPriso) purified by vacuum distillation into a sand mill, add 1500g of isopropanol as a dispersant, and stir at room temperature for 1.5h at a speed of 150r / min.

[0050] (2) Add 500g of high-purity water;

[0051] (3) Add 98% H2SO4 to adjust the pH of the solution to 5;

[0052] (4) While grinding and heating, control the solution temperature to 50℃, and carry out the hydrolysis reaction by grinding and stirring at 200r / min for 2h.

[0053] Next, the solution temperature was raised to 80℃, the vacuum degree was -0.04MPa, the speed of the sand mill was controlled at 400r / min, and the sand milling hydrolysis aging was carried out for 5h.

[0054] (5) The hydrolyzed and aged product was microwave dried at a temperature of 100°C for 12 hours to obtain boehmite powder.

[0055] Example 3:

[0056] (1) Place 1000g of Al(OPriso) purified by vacuum distillation into a sand mill, add 1000g of ethanol as a dispersant, and stir at room temperature for 0.5h at a speed of 150r / min.

[0057] (2) Add 500g of high-purity water;

[0058] (3) Add 65% HNO3 to adjust the pH of the solution to 5;

[0059] (4) While grinding and heating, control the solution temperature to 70℃, and stir for 2 hours at 230r / min to carry out the hydrolysis reaction;

[0060] Next, the solution temperature was raised to 90℃, the vacuum degree was -0.06MPa, the speed of the sand mill was controlled at 350r / min, and the sand milling hydrolysis aging was carried out for 6 hours;

[0061] (5) The hydrolyzed and aged product was microwave dried at a temperature of 160°C for 10 hours to obtain boehmite powder.

[0062] Example 4:

[0063] (1) Place 1000g of Al(OPriso) purified by vacuum distillation into a sand mill, add 1500g of n-butanol as a dispersant, and stir at room temperature for 1.5h at a speed of 150r / min.

[0064] (2) Add 400g of high-purity water;

[0065] (3) Add 65% HNO3 to adjust the pH of the solution to 5;

[0066] (4) While grinding and heating, control the solution temperature to 60℃, and carry out the hydrolysis reaction by grinding and stirring at 250r / min for 2h.

[0067] Next, the solution temperature was raised to 80℃, the vacuum degree was -0.08MPa, the sand mill speed was controlled at 500r / min, and the sand milling hydrolysis aging was carried out for 6 hours;

[0068] (5) The hydrolyzed and aged product was microwave dried at a temperature of 120°C for 10 hours to obtain boehmite powder.

[0069] Comparative Example 1:

[0070] (1) Place 1000g of Al(OPriso) purified by vacuum distillation in a regular stirred tank, add 1500g of n-butanol as a dispersant, and stir at room temperature for 1.5h at a speed of 60r / min.

[0071] (2) Add 400g of high-purity water;

[0072] (3) Add 65% HNO3 to adjust the pH of the solution to 5;

[0073] (4) Stir and heat at the same time, control the solution temperature to 60℃, and stir for 2 hours at 100r / min to carry out the hydrolysis reaction;

[0074] Next, the temperature was raised to 90℃, the vacuum degree was -0.08MPa, and the hydrolysis and aging were carried out at 100r / min for 6 hours.

[0075] (5) Control the drying temperature at 120℃ for 10 hours to obtain pseudoboehmite powder.

[0076] Comparative Example 2:

[0077] (1) Place 1000g of Al(OPriso) purified by vacuum distillation in a stirred tank, add 1500g of isopropanol as a dispersant, and stir at room temperature for 0.5h at a speed of 60r / min.

[0078] (2) Add 500g of high-purity water;

[0079] (3) Add 65% HNO3 to adjust the pH of the solution to 4;

[0080] (4) Stir and heat at the same time, control the solution temperature to 70℃, and stir for 2 hours at 100r / min to carry out the hydrolysis reaction;

[0081] Next, the temperature was raised to 90℃, the vacuum degree was -0.06MPa, and the hydrolysis and aging were carried out at 100r / min for 5h.

[0082] (5) Control the microwave drying temperature to 100℃ and dry for 12 hours to obtain pseudoboehmite powder.

[0083] Comparative Example 3:

[0084] (1) Place 1000g of Al(OPriso) purified by vacuum distillation into a sand mill, add 1500g of isopropanol as a dispersant, and stir at room temperature for 0.5h at a speed of 150r / min.

[0085] (2) Add 500g of high-purity water;

[0086] (3) Add 65% HNO3 solution to adjust the pH of the solution to 4;

[0087] (4) While grinding and heating, control the solution temperature to 70℃, and grind for 2 hours at 200r / min to carry out the hydrolysis reaction;

[0088] Next, the temperature was raised to 90℃, and under normal pressure, the speed of the sand mill was controlled at 400r / min, and the sand mill was hydrolyzed and aged for 5 hours.

[0089] (5) Control the microwave drying temperature to 100℃ and dry for 12 hours to obtain pseudoboehmite powder.

[0090] Comparative Example 4:

[0091] (1) Place 1000g of Al(OPriso) purified by vacuum distillation into a sand mill, add 1500g of isopropanol as a dispersant, and stir at room temperature for 0.5h at a speed of 150r / min.

[0092] (2) Add 500g of high-purity water;

[0093] (3) Add 65% HNO3 to adjust the pH of the solution to 4;

[0094] (4) While grinding and heating, control the solution temperature to 70℃, and grind for 2 hours at 230r / min to carry out the hydrolysis reaction;

[0095] Next, the temperature was raised to 90℃, and under normal pressure, the speed of the sand mill was controlled at 400r / min, and the sand mill was hydrolyzed and aged for 5 hours.

[0096] (5) Control the vacuum drying temperature to 100℃ and dry for 12 hours to obtain pseudoboehmite powder.

[0097] Comparative Example 5:

[0098] (1) Place 1000g of Al(OPriso) purified by vacuum distillation into a sand mill, add 1500g of n-pentanol as a dispersant, and stir at room temperature for 0.5h at a speed of 150r / min.

[0099] (2) Add 500g of high-purity water;

[0100] (3) Add 65% HNO3 to adjust the pH of the solution to 4;

[0101] (4) While grinding and heating, control the solution temperature to 70℃, and carry out the hydrolysis reaction by grinding and stirring at 230r / min for 2h.

[0102] Next, the solution temperature was raised to 90℃, the vacuum degree was -0.06MPa, the speed of the sand mill was controlled at 400r / min, and the sand milling hydrolysis aging was carried out for 5h.

[0103] (5) The hydrolyzed and aged product was microwave dried at a temperature of 100°C for 12 hours to obtain boehmite powder.

[0104] The results of testing the properties of the pseudoboehmite powder prepared in each embodiment and comparative example using conventional experimental methods are as follows.

[0105] Table 1

[0106]

[0107] As can be seen from the results in Table 1, changing the process parameters such as stirring method, vacuum degree, pH value, and dispersant used in the reaction will have a significant impact on the various properties of pseudoboehmite powder.

[0108] The above specific embodiments should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, any alternative improvements or modifications made to the embodiments of the present invention shall fall within the scope of protection of the present invention.

[0109] Any aspects of this invention not described in detail are well-known to those skilled in the art.

Claims

1. A process for the production of high surface area, high conversion pseudoboehmite by attrition hydrolysis, characterized in that, Includes the following steps: (1) Add high-purity aluminum alkoxide and dispersant to a sand mill and stir to mix. The dispersant is a low-carbon alcohol with 2 to 4 carbon atoms. The mass ratio of dispersant to aluminum alkoxide is 1:1 to 1:1.

5. The dispersant is one or more of ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and tert-butanol. The purity of high-purity aluminum alkoxide is ≥99.99%. (2) Add high-purity water to the solution obtained in step (1), wherein the amount of high-purity water added is 35% to 50% of the weight of aluminum alkoxide; (3) Add pH adjuster to the solution obtained in step (2) to adjust the pH value of the solution to 4-6; (4) The solution obtained in step (3) is subjected to sand milling hydrolysis and aging reaction in two stages: the solution temperature in the first stage is 60-75℃, the sand milling speed is 200-250r / min, and the sand milling time is 0.5-2h; the solution temperature in the second stage is 85-100℃, the sand milling speed is 300-500r / min, and the sand milling time is 5-6h. The second stage is vacuumed with a vacuum degree of -0.08--0.04MPa. (5) The hydrolyzed and aged product obtained in step (4) is dried to obtain pseudo-boehmite powder; the drying method is microwave drying, the temperature of microwave drying is 80-160℃, and the time is 8-20h.

2. The method for preparing pseudoboehmite with high specific surface area and high conversion rate by sand milling and hydrolysis according to claim 1, characterized in that, In step (1), the stirring speed is 100-200 r / min and the stirring time is 0.5-1.5 h.

3. The method for preparing pseudoboehmite with high specific surface area and high conversion rate by sand milling and hydrolysis according to claim 1, characterized in that, The aluminum alkoxide is aluminum isopropoxide, aluminum ethoxide, aluminum n-butoxide, or aluminum sec-butoxide.

4. The method for preparing pseudoboehmite with high specific surface area and high conversion rate by sand milling and hydrolysis according to claim 1, characterized in that, The high-purity aluminum alkoxide in step (1) is obtained by catalytic synthesis of high-purity aluminum sheets and anhydrous isopropanol followed by purification by vacuum distillation.

5. The method for preparing pseudoboehmite with high specific surface area and high conversion rate by sand milling and hydrolysis according to claim 1, characterized in that, The resistivity of the high-purity water in step (2) is >12MΩ, and distilled water, deionized water or ion-exchange water is used.

6. The method for preparing pseudoboehmite with high specific surface area and high conversion rate by sand milling and hydrolysis according to claim 1, characterized in that, In step (3), the pH adjuster is either 98% sulfuric acid or 65% nitric acid.

7. The method for preparing pseudoboehmite with high specific surface area and high conversion rate by sand milling and hydrolysis according to claim 1, characterized in that, The grinding balls in the sand mill are alumina grinding balls with a purity of >99.9% and a diameter of 2-8mm.

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