A method for preparing γ-alumina

Abstract

This application relates to a method for preparing γ-alumina, the method comprising: neutralizing an acidic aluminum salt with a basic salt to obtain a γ-alumina precursor; wherein the γ-alumina precursor contains a plurality of micelles in its structure, and the micelles interact with each other; aging the γ-alumina precursor with an ammonium salt to fully utilize each micelle, to obtain an aluminum ammonium salt; and pyrolyzing the aluminum ammonium salt to obtain γ-alumina. This application controls the growth behavior of alumina particles through the above three stages to prepare γ-alumina with a large specific surface area, producing a rich porous structure, with a specific surface area reaching 700 m². 2 / g.

Description

Technical Field

[0001] This application relates to the field of alumina production technology, and more particularly to a method for preparing γ-alumina. Background Technology

[0002] γ-alumina is used in high-end transparent ceramics, fine polishing, and spraying, with a specific surface area of ​​20–200 m². 2 / It has a particle size of approximately g / cm³, and a relatively small specific surface area. Currently, some γ-alumina products require the addition of high-purity γ-alumina with a large specific surface area.

[0003] Therefore, there is an urgent need to produce a type of γ-alumina with a large specific surface area to meet user requirements. Summary of the Invention

[0004] This application provides a method for preparing γ-alumina to solve the technical problem of small specific surface area of ​​existing γ-alumina.

[0005] In a first aspect, this application provides a method for preparing γ-alumina, the method comprising:

[0006] Acidic aluminum salt and basic salt are neutralized to obtain γ-alumina precursor; wherein, the structure of the γ-alumina precursor contains several micelles, and there are forces between the several micelles;

[0007] The γ-alumina precursor is subjected to an aging reaction with an ammonium salt to fully utilize each micelle, thereby obtaining an aluminum ammonium salt.

[0008] The aluminum ammonium salt was subjected to a pyrolysis reaction to obtain γ-alumina.

[0009] Optionally, the acidic aluminum salt includes at least one of the following: aluminum sulfate, aluminum chloride, and aluminum nitrate.

[0010] Optionally, the basic salt includes at least one of the following: sodium aluminate, sodium carbonate, and sodium bicarbonate.

[0011] Optionally, the acidic aluminum salt is aluminum sulfate, and the basic salt is sodium aluminate; wherein the concentration of the aluminum sulfate is 50 g / L to 100 g / L, and the concentration of the sodium aluminate is 50 g / L to 120 g / L.

[0012] Optionally, the process parameters for the neutralization reaction include: a neutralization reaction temperature of 15℃ to 40℃ and a neutralization reaction endpoint pH value of 5 to 7.

[0013] Optionally, the ammonium salt includes at least one of the following: ammonium bicarbonate, ammonium sulfate, and ammonium carbonate.

[0014] Optionally, the ammonium salt is ammonium bicarbonate, and the amount of ammonium bicarbonate used is 20 kg / m³. 3 ~60KG / M 3 .

[0015] Optionally, the initial pH value of the aging reaction system is 7.5 to 10.0.

[0016] Optionally, the process parameters of the aging reaction include: an aging temperature of 100℃~150℃ and an aging time of 1h~6h.

[0017] Optionally, the process parameters of the pyrolysis reaction include: a pyrolysis temperature of 500℃ to 850℃ and a pyrolysis time of 2h to 8h.

[0018] The technical solutions provided in this application have the following advantages compared with the prior art:

[0019] The method for preparing γ-alumina provided in this application first utilizes a neutralization reaction between an acidic aluminum salt and a basic salt to prepare high-purity amorphous alumina as a precursor for γ-alumina powder. This precursor contains several micelles with inter-molecular forces, ensuring the stability of the γ-alumina powder precursor and increasing the specific surface area of ​​the product. The γ-alumina powder precursor is then aged with ammonium salt to generate aluminum ammonium salt. This stage ensures that each micelle is fully utilized, maintaining the stability of the product's specific surface area. Finally, pyrolysis maximizes the specific surface area, yielding γ-alumina powder. In summary, by controlling the growth behavior of alumina particles through the above three stages, γ-alumina with a large specific surface area and abundant pore structure is prepared, achieving a specific surface area of ​​up to 700 m². 2 / g. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic flowchart illustrating a method for preparing γ-alumina according to an embodiment of this application. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0025] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0026] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0027] Firstly, this application provides a method for preparing γ-alumina; please refer to [link to relevant documentation]. Figure 1 The method includes:

[0028] S1. Acidic aluminum salt and basic salt are neutralized to obtain γ-alumina precursor; wherein, the structure of the γ-alumina precursor contains several micelles, and there are forces between the several micelles.

[0029] In this embodiment, to produce γ-alumina with a large specific surface area, it is necessary to ensure the presence of as many micelles as possible in the precursor preparation stage, while minimizing the interaction forces between the micelles to facilitate the subsequent reaction. Therefore, controlling the amount of micelles and the interaction forces between them is crucial for increasing the specific surface area. Specifically, the specific surface area is controlled by adjusting the concentration, pH, and temperature of the reaction system.

[0030] In some embodiments, the acidic aluminum salt includes at least one of the following: aluminum sulfate, aluminum chloride, and aluminum nitrate.

[0031] In the embodiments of this application, the above-mentioned acidic aluminum salt is used as a reactant in the neutralization reaction to provide Al. 3+ The acidic substance exists in the reaction system. At least one of aluminum sulfate, aluminum chloride, and aluminum nitrate can be selected as the acidic aluminum salt. Preferably, aluminum sulfate can be selected.

[0032] In some embodiments, the basic salt includes at least one of the following: sodium aluminate, sodium carbonate, and sodium bicarbonate.

[0033] In this embodiment, the aforementioned basic salt, as a reactant in the neutralization reaction, exists as an alkaline substance in the reaction system and can provide Al, increasing energy production. At least one of sodium aluminate, sodium carbonate, and sodium bicarbonate can be selected as the basic salt, since sodium carbonate and sodium bicarbonate only provide OH-. - Without Al-based salts, production capacity is halved. The preferred second aluminum salt is sodium aluminate, which can provide AlO2. - .

[0034] In some embodiments, the first aluminum salt is aluminum sulfate and the second aluminum salt is sodium aluminate; wherein the concentration of the aluminum sulfate is 50 g / L to 100 g / L and the concentration of the sodium aluminate is 50 g / L to 120 g / L.

[0035] In the embodiments of this application, controlling the concentrations of aluminum sulfate and sodium aluminate has the following positive effects: it allows for the rapid generation of a large number of micelles, preparing the body for the next reaction step. If the concentration of aluminum sulfate is too high, it will, to some extent, affect the formation of a large number of micelles, encapsulating the active centers and hindering micelle development; if the concentration of aluminum sulfate is too low, it will, to some extent, affect the rapid initial generation of a large number of micelles and inhibit the rapid development of the active centers. Similarly, if the concentration of sodium aluminate is too high, it will, to some extent, affect the formation of a large number of micelles, encapsulating the active centers and hindering micelle development; if the concentration of sodium aluminate is too low, it will, to some extent, slow down the reaction rate, affecting the rapid initial generation of a large number of micelles and slowing down micelle development. Specifically, the concentration of aluminum sulfate can be 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, etc., and the concentration of sodium aluminate can be 50 g / L, 60 g / L, 70 g / L, 80 g / L, 100 g / L, 110 g / L, 120 g / L, etc.; preferably, the concentrations of both aluminum sulfate and sodium aluminate can be 100 g / L.

[0036] In some embodiments, the process parameters of the neutralization reaction include: a neutralization reaction temperature of 15°C to 40°C, and a neutralization reaction endpoint pH value of 5 to 7.

[0037] In the embodiments of this application, the positive effects of controlling the process parameters of the neutralization reaction are as follows: A large number of reactive micelles with a favorable specific surface area are prepared, which are precursors that readily react with ammonium salts during the aging stage. If the neutralization reaction temperature is too high, it will reduce the amount of micelles in the precursor to a certain extent, causing the micelles to become larger, which is detrimental to the reaction during the aging stage and will result in impurities, reducing the specific surface area of ​​the product. If the neutralization reaction temperature is too low, it will increase the interaction forces between the micelles to a certain extent, slowing down the reaction and reducing efficiency. If the pH value at the end of the neutralization reaction is too high, it will increase the crystallinity of the precursor to a certain extent, which is detrimental to the subsequent aging stage reaction and will greatly generate another substance, boehmite impurity, affecting the specific surface area of ​​the product. If the pH value at the end of the neutralization reaction is too low, it will consume more ammonium salts during the aging stage to a certain extent, reducing the specific surface area of ​​the product. Specifically, the neutralization reaction temperature can be 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, etc., and the final pH value of the neutralization reaction can be 5, 6, 7, etc.; preferably, the neutralization reaction temperature can be 25℃, and the final pH value of the neutralization reaction can be 6.2. In addition, after the neutralization reaction is completed, the resulting slurry needs to be separated and washed. The washing temperature is controlled at 15℃~50℃, preferably around 40℃, and the washing water volume is 1~5 times the volume of the precursor slurry, preferably 3 times, with a water content of 15%~60%, preferably 40%, to prepare a high-purity amorphous alumina γ-alumina powder precursor.

[0038] S2. The γ-alumina precursor is subjected to an aging reaction with an ammonium salt to ensure that each micelle is fully utilized, thereby obtaining aluminum ammonium salt;

[0039] In the embodiments of this application, the aging stage aims to fully utilize each micelle to generate pure-phase aluminum ammonium salt, thereby ensuring the stability of the product's specific surface area.

[0040] In some embodiments, the ammonium salt includes at least one of the following: ammonium bicarbonate, ammonium sulfate, and ammonium carbonate.

[0041] In the embodiments of this application, the above-mentioned ammonium salt plays a role in increasing the activity of the product during the aging process. As a reactant, it participates in the reaction to obtain the precursor aluminum ammonium salt. At least one of ammonium bicarbonate, ammonium sulfate, and ammonium carbonate can be selected as the ammonium salt. Since ammonium bicarbonate has both bicarbonate and ammonium ions, both of which can increase the activity of the product, ammonium bicarbonate is preferred.

[0042] In some embodiments, the ammonium salt is ammonium bicarbonate, and the amount of ammonium bicarbonate used is 20 kg / m³. 3 ~60KG / M 3 .

[0043] In this embodiment, if the amount of ammonium bicarbonate is too high, it will promote the growth of impurities to a certain extent and inhibit the formation of pure phase ammonium aluminum carbonate; if the amount is too low, it will lead to the passivation reaction to a certain extent, and the alumina micelles will not develop completely, affecting the purity. Specifically, the amount of ammonium bicarbonate can be 20 kg / m³. 3 25KG / M 3 30KG / M 3 35KG / M 3 40KG / M 3 45KG / M 3 50KG / M 3 55KG / M 3 60KG / M 3 Preferably, the amount of ammonium bicarbonate used is 50 kg / m³. 3 Furthermore, ammonium salts can be added either as a solid or as a solution.

[0044] In some embodiments, the initial pH of the aging reaction system is 7.5 to 10.0.

[0045] In this embodiment, the initial pH value of the aging reaction system is controlled to promote the formation of pure-phase ammonium aluminum carbonate and avoid excessive impurities in other phases, which could affect the product's activity and specific surface area. If the initial pH value of the aging reaction system is too high, it can lead to the generation of impurities, resulting in low activity and a small specific surface area. If the initial pH value of the aging reaction system is too low, it can lead to a large number of micelles being difficult to fully utilize, resulting in insufficient kinetics and incomplete reaction, thus affecting various product indicators. Specifically, the initial pH value of the aging reaction system can be 7.5, 8, 8.5, 9.0, 9.5, 10.0, etc.; preferably, the initial pH value of the aging reaction system is 9.0.

[0046] In some embodiments, the process parameters of the aging reaction include: an aging temperature of 100℃~150℃ and an aging time of 1h~6h.

[0047] In this embodiment, the aging process parameters are controlled to generate pure-phase aluminum ammonium salt, prevent the generation of impurities, and ensure the maximum specific surface area of ​​the final product. If the aging temperature is too high, impurities will be generated to some extent, affecting product purity and resulting in a lower specific surface area. If the aging temperature is too low, the aging reaction will be insufficient to some extent, also generating boehmite impurities, affecting product purity and resulting in a lower specific surface area. If the aging time is too long, boehmite impurities will be generated to some extent, affecting product purity and resulting in a smaller specific surface area. If the aging time is too short, impurities will be generated to some extent, affecting product purity and resulting in a smaller specific surface area. Specifically, the aging temperature can be 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, etc., and the aging time can be 1h, 2h, 3h, 4h, 5h, etc.; preferably, the aging temperature can be 120℃ and the aging time can be 3h. In addition, after the aluminum ammonium salt is prepared, it needs to be filtered and washed. The temperature of the washing water is 40℃~100℃, preferably 70℃, the amount of washing water is 1~5 times the volume of the slurry, preferably 3 times, and the moisture content is 10%~60%, preferably 10%.

[0048] S3. The aluminum ammonium salt is subjected to a pyrolysis reaction to obtain γ-alumina.

[0049] In some embodiments, the process parameters of the pyrolysis reaction include: a pyrolysis temperature of 500℃ to 850℃ and a pyrolysis time of 2h to 8h.

[0050] In this embodiment, to maximize the specific surface area of ​​the product, the pyrolysis process parameters are controlled. If the pyrolysis temperature is too high, the specific surface area will decrease significantly; if the pyrolysis temperature is too low, incomplete pyrolysis will also result in a smaller specific surface area; if the pyrolysis time is too long, the specific surface area will decrease significantly; if the pyrolysis time is too short, incomplete pyrolysis will also result in a smaller specific surface area. Specifically, the pyrolysis temperature can be 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, etc., and the pyrolysis time can be 2h, 3h, 4h, 5h, 6h, 7h, 8h, etc.; preferably, the pyrolysis temperature can be 700℃, and the pyrolysis time can be 3h. In addition, after the aluminum ammonium salt is prepared, it needs to be filtered and washed. The temperature of the washing water is 40℃~100℃, preferably 70℃, the amount of washing water is 1~5 times the volume of the slurry, preferably 3 times, and the moisture content is 10%~60%, preferably 10%.

[0051] In the embodiments of this application, the purity of the first aluminum salt, the second aluminum salt, and the ammonium salt is ≥99.99% to ensure the high purity of the final product and to minimize the introduction of new impurities throughout the entire process.

[0052] The γ-alumina prepared by the method described in this application yields high-purity γ-alumina with a large specific surface area, exhibiting a rich porous structure. This results in a product that combines the flowability of large particles with a porous crystalline morphology, meeting market demands for high purity, flowability, and a large specific surface area. Furthermore, the chemical composition of the γ-alumina is as follows: Na ≤ 100 ppm, Si ≤ 10 ppm, Fe ≤ 3 ppm, Ca ≤ 3 ppm, and total impurities ≤ 200 ppm, achieving high purity. The product has applications in optical glass, gemstone crystals, high-purity aluminum salts, high-purity catalysts, advanced ceramics, ruby ​​crystals, structural ceramics, aerospace catalysts, and 5G communication alumina substrates. The high activity of the product from this application is primarily evident in later-stage applications, such as catalysis. This product provides more acidic sites, enhancing the activation performance of the catalyst and extending its lifespan.

[0053] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0054] In a first aspect, embodiments of this application provide a method for preparing γ-alumina, the method comprising:

[0055] S31. Acidic aluminum salt and basic salt are neutralized to obtain γ-alumina precursor; wherein, the structure of the γ-alumina precursor contains several micelles, and there are forces between the several micelles.

[0056] S21. The γ-alumina precursor is subjected to an aging reaction with an ammonium salt to ensure that each micelle is fully utilized, thereby obtaining aluminum ammonium salt;

[0057] S31. The aluminum ammonium salt is subjected to a pyrolysis reaction to obtain γ-alumina. For specific process steps, please refer to Examples 1-3 below.

[0058] Example 1

[0059] Take 3000ml of aluminum sulfate solution containing 50g / l alumina and 3000ml of sodium aluminate solution containing 50g / l alumina, and add them to the reaction tank in parallel using a peristaltic pump. Add 300ml of high-purity water solution to the reaction tank. The entire process is controlled at 15℃, and the pH at the end of the reaction is controlled at 5.0 to carry out the metathesis neutralization reaction to generate the precursor amorphous alumina. After the reaction is completed, filter and wash.

[0060] The filter cake is washed statically with 6L of high-purity water at 15℃ to obtain a wet filter cake. The filter cake is then slurried with high-purity water to form a slurry of a certain concentration with a solid content controlled at 5%.

[0061] Add 240g of high-purity ammonium bicarbonate solid, adjust the pH of the slurry to 7.5, and pump the prepared slurry into a high-pressure autoclave for high-temperature and high-pressure aging. The autoclave temperature is 100℃, and the aging time is 1 hour. After filtration and washing, high-purity ammonium aluminum carbonate is obtained.

[0062] Finally, ammonium aluminum carbonate was placed in a pyrolysis furnace for high-temperature pyrolysis at 500℃ for 2 hours to obtain high-purity γ-alumina powder with a large specific surface area.

[0063] Example 2

[0064] Take 3000 ml of aluminum sulfate solution containing 100 g / L alumina and 3000 ml of sodium aluminate solution containing 100 g / L alumina, and add them to the reaction tank in parallel using a peristaltic pump. Add 300 ml of high-purity water solution to the reaction tank. The entire process is controlled at 25℃, and the pH at the end of the reaction is controlled at 6.2 to carry out the metathesis neutralization reaction to generate the precursor amorphous alumina. After the reaction is completed, filter and wash.

[0065] The filter cake is washed with 40℃ high-purity water, and the washing water volume is 18L of the precursor slurry volume to obtain a wet filter cake. The filter cake is then slurried with high-purity water to form a slurry of a certain concentration, with the solid content controlled at 20%.

[0066] Add 300g of high-purity ammonium bicarbonate solid, adjust the pH of the slurry to 9.0, and pump the prepared slurry into a high-pressure autoclave for high-temperature and high-pressure aging. The autoclave temperature is 120℃, and the aging time is 2 hours. After filtration and washing, high-purity ammonium aluminum carbonate is obtained.

[0067] Finally, ammonium aluminum carbonate was placed in a pyrolysis furnace for high-temperature pyrolysis at 700℃ for 3 hours to obtain high-purity γ-alumina powder with a large specific surface area.

[0068] Example 3

[0069] Take 3000 ml of aluminum sulfate solution containing 100 g / L alumina and 3000 ml of sodium aluminate solution containing 120 g / L alumina, and add them to the reaction tank in parallel using a peristaltic pump. Add 300 ml of high-purity water solution to the reaction tank. The entire process is controlled at 40℃, and the pH at the end of the reaction is controlled at 7.0 to carry out the metathesis neutralization reaction to generate the precursor amorphous alumina. After the reaction is completed, filter and wash.

[0070] The filter cake is washed with 50℃ high-purity water in a static wash, with the amount of water being 30L of the precursor slurry volume, to obtain a wet filter cake. The filter cake is then slurried with high-purity water to form a slurry of a certain concentration, with the solid content controlled at 40%.

[0071] Add 360g of high-purity ammonium bicarbonate solid, adjust the pH of the slurry to 10.0, and pump the prepared slurry into a high-pressure autoclave for high-temperature and high-pressure aging. The autoclave temperature is 150℃, and the aging time is 6 hours. After filtration and washing, high-purity ammonium aluminum carbonate is obtained.

[0072] Finally, ammonium aluminum carbonate was placed in a pyrolysis furnace for high-temperature pyrolysis, with the temperature controlled at 850℃ and the time at 8 hours, to obtain high-purity γ-alumina powder with a large specific surface area.

[0073] Comparative Example 1

[0074] Take 3000 ml of aluminum sulfate solution containing 100 g / L alumina and 3000 ml of sodium aluminate solution containing 100 g / L alumina, and add them to the reaction tank in parallel using a peristaltic pump. Add 300 ml of high-purity water solution to the reaction tank. The entire process is controlled at 50℃, and the pH at the end of the reaction is controlled at 7.5 to carry out the metathesis neutralization reaction to generate the precursor amorphous alumina. After the reaction is completed, filter and wash.

[0075] The filter cake is washed with 30℃ high-purity water, and the washing water volume is 18L of the precursor slurry volume to obtain a wet filter cake. The filter cake is then slurried with high-purity water to form a slurry of a certain concentration, with the solid content controlled at 25%.

[0076] Add 400g of high-purity ammonium bicarbonate solid, adjust the pH of the slurry to 10.0, and pump the prepared slurry into a high-pressure autoclave for high-temperature and high-pressure aging. The autoclave temperature is 160℃, and the aging time is 4 hours. After filtration and washing, high-purity ammonium aluminum carbonate is obtained.

[0077] Finally, ammonium aluminum carbonate was placed in a pyrolysis furnace for high-temperature pyrolysis at 900℃ for 4 hours to obtain high-purity γ-alumina powder with a large specific surface area.

[0078] Comparative Example 2

[0079] Under stirring conditions at 50℃, high-purity ammonium bicarbonate solution was added to 1L of 1.3mol / L high-purity ammonium aluminum sulfate solution at a rate of 25g / min. A white flocculent precipitate formed, which disappeared upon re-dissolution with stirring. The amount of ammonium bicarbonate solution added was controlled to adjust the pH of the solution to 4, forming a metastable solution. The solution was then filtered to obtain the alumina precursor. The prepared alumina precursor was dried in air at 80℃ for 5 hours, then calcined in a high-temperature furnace at 900℃ for 4 hours. After natural cooling, it was removed to obtain high-purity γ-alumina.

[0080] The performance of the γ-alumina prepared in Examples 1-3 and Comparative Examples 1-2 was tested, and the test results are shown in Table 1.

[0081] Table 1. Performance test results of γ-alumina

[0082]

[0083] As shown in Table 1, through Examples 1-3, γ-alumina with a large specific surface area can be prepared, producing a rich porous structure, with a specific surface area reaching 700 m². 2 The specific surface area was approximately 1 / g, and the purity was relatively high. However, the process parameters for neutralization, aging, and pyrolysis in Comparative Example 1 were not within the scope of the embodiments of this application, resulting in a significant reduction in specific surface area and a higher Na concentration. The specific surface area of ​​γ-alumina prepared by Comparative Example 2 using another conventional technical solution was also relatively low.

[0084] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing γ-alumina, characterized in that, The method includes: Acidic aluminum salt and basic salt are neutralized to obtain γ-alumina precursor; wherein, the structure of the γ-alumina precursor contains several micelles, and there are forces between the several micelles; the neutralization reaction temperature is 15℃~40℃. The γ-alumina precursor is subjected to an aging reaction with an ammonium salt to ensure that each micelle is fully utilized, thereby obtaining an aluminum ammonium salt. The aluminum ammonium salt was subjected to a pyrolysis reaction to obtain γ-alumina; The ammonium salt is ammonium bicarbonate, and the amount of ammonium bicarbonate used is 20 kg / m³. 3 ~60kg / m 3 ; The initial pH value of the aging reaction system is 7.5~10.0; The aging temperature is 100℃~150℃, and the aging time is 1h~6h; The acidic aluminum salt is aluminum sulfate, and the basic salt is sodium aluminate; wherein the concentration of the aluminum sulfate is 50 g / L to 100 g / L, and the concentration of the sodium aluminate is 50 g / L to 120 g / L. The endpoint pH value of the neutralization reaction is 5-7; The process parameters for the pyrolysis reaction include: The pyrolysis temperature is 500℃~850℃, and the pyrolysis time is 2h~8h.

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