Pore size concentrated high-purity pseudo-boehmite and preparation method thereof

Abstract

This invention belongs to the field of petrochemical technology, specifically relating to a high-purity pseudoboehmite with concentrated pore size and its preparation method. The preparation method includes: mixing aluminum sulfate solution with ammonia water for a primary neutralization reaction; adding ammonia water and a pore-expanding agent to the resulting slurry for a secondary neutralization reaction; subsequently heating and allowing it to age; filtering, washing, drying, and pulverizing the aged product to obtain high-purity pseudoboehmite. The preparation method of this invention employs co-current and overflow neutralization, reducing the process flow and simplifying operation. It solves the problems of high synthesis cost, complex operation, and environmental pollution in existing pseudoboehmite synthesis methods. The generated byproduct, ammonium sulfate, has certain industrial application value. The pseudoboehmite obtained by this invention has the advantages of large specific surface area, large pore volume, and uniform and concentrated pore size distribution.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, specifically relating to a high-purity pseudoboehmite with concentrated pore size and its preparation method. Background Technology

[0002] Boehmite is an inorganic non-metallic material with high specific surface area, large pore volume and excellent catalytic activity. It is widely used in the petrochemical field and is the core raw material for catalyst supports in hydrotreating, refining, cracking and reforming. Its purity, pore size distribution and structural stability directly determine the efficiency and service life of the catalyst.

[0003] Currently, the main methods for preparing high-purity boehmite include aluminum alkoxide hydrolysis, carbonization, acid methods, and aluminum salt neutralization. Each method has its own advantages and disadvantages. Aluminum alkoxide hydrolysis produces high-purity products, but the cost of organic alcohol recovery is high and the product has small pore volume. The carbonization method is a mature process, but it suffers from problems such as difficulty in controlling pore size, easy inclusion of sodium ions, and high acidity of the product. The acid method uses aluminum salts and ammonia water for neutralization. The ammonia method is simple, has stable pH, does not introduce sodium ions, and produces products with good purity and catalytic activity, making it one of the mainstream routes in the industry.

[0004] However, existing ammonia and aluminum salt neutralization methods still have technical shortcomings, which seriously restrict the stability of products and industrialization benefits. Traditional single-flow dropwise neutralization methods are difficult to control pH precisely, resulting in uneven crystal nucleus growth, diffuse pore size distribution, and large batch quality fluctuations, which cannot meet the requirements of high-end catalysts; moreover, most of them are intermittent production, with cumbersome processes, complex operations, low production efficiency, and difficulty in large-scale continuous operation.

[0005] To address these issues, researchers in the industry have made numerous attempts, but none have fundamentally overcome the technical bottlenecks. For example, patent CN103332716B discloses a method for preparing pseudoboehmite by adding ammonia to an aluminum nitrate solution. This method also suffers from problems such as difficulty in controlling pH and unstable product quality. Furthermore, the washing process requires 2-6 washes with an alcohol-water solution, necessitating a separate organic alcohol recovery process, which further increases production costs. The use and emission of organic alcohols also pose environmental pollution risks. Patent CN115974115B discloses a process for preparing pseudoboehmite through a neutralization reaction using an alkali-acid solution, followed by crystallization and aging. However, this method still suffers from localized pH fluctuations, leading to significant batch-to-batch phase differences. Moreover, the process is cumbersome and cannot achieve continuous industrial production. Patent CN107720792B discloses a method for preparing pseudoboehmite by dripping ammonia water into an aluminum salt solution to obtain a precipitate, which is then mixed with an aluminum sulfate solution for a hydrothermal reaction. This process requires two filtration operations, is lengthy, has low production efficiency, and lacks continuous production capability. Patent application CN109956488A discloses a method for preparing pseudoboehmite by co-current titration precipitation of aluminum nitrate nonahydrate solution and ammonia water under water bath conditions. However, it places the neutralization and aging processes in the same reactor, still a batch reaction mode, and requires extremely high precision in pH control. The problem of diffuse pore size distribution of the product is not effectively solved, resulting in poor batch-to-batch quality stability.

[0006] In summary, current methods for preparing pseudoboehmite powder struggle to simultaneously achieve high purity, large pore volume, and concentrated pore size, while also enabling continuous and low-cost production. Existing technologies cannot address these core issues concurrently. The industry urgently needs high-performance, cost-effective continuous preparation technologies, and their development is of great significance for technological upgrading in the petrochemical catalyst field. Summary of the Invention

[0007] Based on the above technical background, the main objective of this invention is to provide a high-purity pseudoboehmite with concentrated pore size and its preparation method, so as to overcome the shortcomings of the prior art.

[0008] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0009] This invention provides a method for preparing high-purity pseudoboehmite with concentrated pore size, the method comprising the following steps: Step 1: Mix aluminum sulfate solution with ammonia water to carry out a neutralization reaction and obtain a slurry. Step 2: Add ammonia and a pore-expanding agent to the primary slurry obtained in Step 1 to carry out a secondary neutralization reaction and obtain a secondary slurry; Step 3: Heat the secondary slurry obtained in Step 2 and let it stand for aging. Step 4: Filter, wash, dry and pulverize the aging product obtained in Step 3 to obtain high-purity pseudoboehmite.

[0010] The steps described above are described in detail below.

[0011] In step 1, the concentration of the aluminum sulfate solution is 60–170 g / L.

[0012] Preferably, the concentration of the aluminum sulfate solution is 100 g / L.

[0013] The volume ratio of the aluminum sulfate solution to the ammonia solution is (10-1):1.

[0014] Preferably, the volume ratio of the aluminum sulfate solution to the ammonia solution is 5:1.

[0015] The temperature of the first neutralization reaction is 30–70°C, the pH of the reaction solution of aluminum sulfate solution and ammonia water is 4.5–7, and the time of the first neutralization reaction is 5–20 min.

[0016] Preferably, the temperature of the first neutralization reaction is 50°C, the pH of the reaction solution of aluminum sulfate solution and ammonia water is 4.5-7, and the time of the first neutralization reaction is 10 min.

[0017] In step 2, aluminum sulfate solution is mixed with ammonia water and a neutralization reaction is carried out. The resulting slurry overflows into a secondary neutralization reactor, and ammonia water and a pore-expanding agent are added to the secondary neutralization reactor for a secondary neutralization reaction.

[0018] The pore-expanding agent is selected from one or more of ammonium carbonate, urea, and PEG 600-800.

[0019] Preferably, the pore-expanding agent is a mixture of ammonium carbonate and urea, wherein the mass ratio of ammonium carbonate to urea is (1-3):1.

[0020] More preferably, the mass ratio of ammonium carbonate to urea is 2:1.

[0021] The pore-expanding agent is selected from easily degradable and residue-free substances such as ammonium carbonate, urea, and PEG 600-800, and the amount added can be adjusted within the range of 0%-1%. The pore-expanding agent used in this invention can not only optimize the pore structure, but also flexibly adjust the pore characteristics of the product according to the subsequent application scenario of the catalyst support, adapting to the catalyst preparation needs of different fields such as hydrotreating, hydrorefining, hydrocracking, and reforming, and has wide applicability.

[0022] The amount of the expanding agent added is 0% to 1% of the mass of the slurry.

[0023] Preferably, the amount of the pore-expanding agent added is 0.5% of the mass of the slurry.

[0024] The temperature of the secondary neutralization reaction is 40–90°C, the time of the secondary neutralization reaction is 5–20 min, and the pH value of the reaction solution of the secondary neutralization reaction is 7–10.

[0025] Preferably, the temperature of the secondary neutralization reaction is 60°C, the time of the secondary neutralization reaction is 10 min, and the pH value of the reaction solution of the secondary neutralization reaction is 7-10.

[0026] In step 3, after the secondary neutralization reaction is completed, the slurry after the secondary neutralization reaction in step 2 overflows into the aging reactor for aging reaction.

[0027] The aging temperature is 70–90°C, and the aging time is 30–200 min.

[0028] Preferably, the aging temperature is 80°C and the aging time is 100 min.

[0029] In step 4, the washing temperature is 60-90°C, preferably 80°C.

[0030] The detergent is one or more of water, ethanol, methanol and acetone.

[0031] Preferably, the detergent is water.

[0032] The drying method is flash drying or spray drying.

[0033] The drying temperature is 70–150°C, and the drying time is 3–30 seconds.

[0034] Preferably, the drying temperature is 110°C and the drying time is 10 seconds.

[0035] The preparation method described in this invention employs a stepwise reaction. First, aluminum sulfate solution and ammonia are neutralized at a low pH to partially precipitate and form specific precursor crystal nuclei with good uniformity. Then, the pH is adjusted to the final level for a second neutralization, completing the precipitation and crystal transformation. By adjusting the pH, temperature, and time of the two neutralization reactions, the formation and growth of crystal nuclei can be precisely controlled, resulting in a more concentrated pore size in the obtained boehmite precursor, thus reducing the amount of pore-expanding agents such as ammonium carbonate and urea required. Furthermore, the preparation method described in this invention, through a co-current primary neutralization + overflow secondary neutralization + overflow aging process, enables continuous production, resulting in more stable batch product quality.

[0036] A second aspect of the present invention is to provide a high-purity pseudoboehmite with concentrated pore size obtained by the preparation method described in the first aspect of the present invention.

[0037] The pseudoboehmite prepared by this invention has a specific surface area of ​​260 m². 2 With a pore volume of ≥1.0 mL / g and a pore size distribution of 9.0–20.0 nm, this pseudoboehmite exhibits good pore distribution concentration, stable product quality, and low content of impurity crystals and ions. It can be used to prepare hydrogenation catalyst supports, enabling the catalyst to have high activity and high selectivity, effectively improving hydrogenation efficiency. This pseudoboehmite can be used in fields such as hydrogenation treatment, hydrogenation refining, hydrocracking, and reforming catalysts.

[0038] The beneficial effects of this invention are as follows: (1) The preparation method of the present invention, through precise control of two-stage neutralization reaction, combined with a specific pore-expanding agent and aging process, enables the prepared pseudoboehmite to achieve a stable specific surface area of ​​260 m². 2 The pore volume reaches 1.0 mL / g or higher, and the pore size is strictly distributed within the range of 9.0–20.0 nm, exhibiting high concentration. The excellent pore structure of this pseudoboehmite provides ample loading sites and diffusion channels for the active components of the catalyst. The preparation method described in this invention solves the problem of limited catalyst activity caused by insufficient specific surface area, small pore volume, and scattered pore size distribution of traditional pseudoboehmite.

[0039] (2) The preparation method described in this invention can effectively suppress the formation of impurity crystals by precisely controlling the volume ratio of aluminum sulfate to ammonia, the pH and temperature range of the neutralization reaction. Simultaneously, the high-temperature water washing process can efficiently remove impurity ions, significantly reducing the content of impurity crystals and ions in the product. The high purity of the pseudoboehmite obtained by this invention avoids the poisoning effect of impurities on the active components of the catalyst, ensuring the stability of the catalyst's catalytic performance and solving the shortcomings of existing technologies where impurities affect the selectivity and lifespan of the catalyst.

[0040] (3) The entire preparation process of the method adopts a continuous operation mode of parallel feeding and overflow neutralization, and strictly sets the parameters such as temperature, pH, reaction time, and pore-expanding agent dosage in each step within a certain range. The parameters can be precisely adjusted according to actual production needs, so that the preparation method has high process stability and is easy to achieve large-scale and industrialized production. Compared with batch production processes, this method has good batch stability, avoids the problem of performance fluctuation between batches, and reduces the difficulty of quality control in industrialized production.

[0041] (4) The preparation method described in this invention has a short overall reaction cycle and high production efficiency; the drying process adopts flash drying or spray drying, which consumes less energy than traditional drying processes, and the application of belt filter improves the solid-liquid separation efficiency, further reducing production energy consumption and cost.

[0042] (5) The pseudoboehmite prepared by the present invention can be used as a hydrogenation catalyst support. When used as a hydrogenation catalyst support, it can significantly improve the activity and selectivity of the catalyst, effectively improve the hydrogenation efficiency, provide high-performance support materials for petrochemical processes such as hydrogenation treatment and hydrogenation refining, help improve the quality of petroleum products, reduce production energy consumption, and has good industrial application prospects and economic value. Attached Figure Description

[0043] Figure 1 The BET curves of the high-purity boehmite prepared in Examples 1, 5 and Comparative Example 5 are shown. Detailed Implementation

[0044] The present invention will now be described in detail, and its features and advantages will become clearer and more apparent from these descriptions.

[0045] A method for preparing high-purity pseudoboehmite with concentrated pore size, the method comprising the following steps: Step 1: Add aluminum sulfate solution and ammonia water in parallel to a stirred reactor to carry out a neutralization reaction to obtain a slurry. The concentration of the aluminum sulfate solution is 60-170 g / L, the volume ratio of aluminum sulfate solution to ammonia water is (10-1):1, the temperature of the neutralization reaction is 30-70℃, the pH of the reaction solution is 4.5-7, and the time of the neutralization reaction is 5-20 min.

[0046] Step 2: The primary slurry from Step 1 overflows into the secondary neutralization reactor. Ammonia and a pore-expanding agent solution are added to the secondary neutralization reactor to control the pH of the reaction solution. The reaction continues until it is complete, yielding a secondary slurry. The temperature of the secondary neutralization reaction is 40–90°C, the reaction time is 5–20 min, and the pH of the reaction solution is 7–10. The pore-expanding agent is a mixture of ammonium carbonate and urea at a mass ratio of (1–3):1, and the amount of pore-expanding agent added is 0.1%–1% of the mass of the primary slurry.

[0047] In step 3, the secondary slurry from step 2 overflows into the aging reactor, is heated, and then allowed to stand for aging. The aging temperature is 70-90℃, and the aging time is 30-200 min.

[0048] Step 4: Filter, wash, dry and pulverize the product from Step 3 to obtain high-purity pseudoboehmite powder. The filtration is carried out using a belt filter. The washing temperature is 60-90℃. The drying is spray drying at a temperature of 70-150℃ for 3-30 seconds.

[0049] Example The present invention is further illustrated below with specific examples. These embodiments are merely illustrative and not intended to limit the scope of the invention. All raw materials used in the embodiments of the present invention are commercially available.

[0050] Example 1 Step 1: Add aluminum sulfate solution and ammonia water in parallel to a stirred reactor to start a first neutralization reaction; the concentration of the aluminum sulfate solution is 100 g / L; the volume ratio of aluminum sulfate solution to ammonia water is 5:1; the temperature of the first neutralization reaction is 70℃; the pH of the reaction solution is 4.5-7; the time of the first neutralization reaction is 10 min, and a first slurry is obtained.

[0051] Step 2: The primary slurry from Step 1 overflows into the secondary neutralization reactor. Ammonia and a pore-expanding agent solution are added to control the pH of the reaction solution, and the reaction continues until completion. The pH of the reaction solution in the secondary neutralization reaction is 7-10, the temperature of the secondary neutralization reaction is 90℃, and the time of the secondary neutralization reaction is 10 min. The pore-expanding agent is obtained by mixing ammonium carbonate and urea at a mass ratio of 2:1. The amount of pore-expanding agent added is 0.5% of the mass of the primary slurry, thus obtaining the secondary slurry.

[0052] In step 3, the secondary slurry from step 2 overflows into the aging reactor, is heated, and then allowed to stand for aging. The aging temperature is 80°C and the aging time is 100 min.

[0053] Step 4: The product from Step 3 is filtered, washed, dried, and pulverized to obtain high-purity boehmite powder. Filtration is performed using a belt filter, the washing temperature is 80℃, and drying is done by spray drying at 110℃ for 10 seconds. The purity of the boehmite was tested to be 99.9%, indicating that the boehmite obtained by this invention has high purity.

[0054] Example 2 Step 1: Add aluminum sulfate solution and ammonia water in parallel to a stirred reactor to start a first neutralization reaction; the concentration of the aluminum sulfate solution is 60 g / L; the volume ratio of aluminum sulfate solution to ammonia water is 10:1; the temperature of the first neutralization reaction is 60℃; the pH of the reaction solution is 4.5-7; the time of the first neutralization reaction is 20 min, and a first slurry is obtained.

[0055] Step 2: The primary slurry from Step 1 overflows into the secondary neutralization reactor. The pH of the reaction solution is controlled by ammonia and a pore-expanding agent solution, and the reaction continues until completion. The pH of the reaction solution in the secondary neutralization reaction is 7-10, the temperature of the secondary neutralization reaction is 80℃, and the time of the secondary neutralization reaction is 20 minutes. The pore-expanding agent is obtained by mixing ammonium carbonate and urea in a mass ratio of 1:1. The amount of pore-expanding agent added is 0.5% of the mass of the primary slurry, thus obtaining the secondary slurry.

[0056] In step 3, the secondary slurry from step 2 overflows into the aging reactor, is heated, and then allowed to stand for aging. The aging temperature is 70°C and the aging time is 200 min.

[0057] Step 4: Filter, wash, dry and pulverize the product from step 3 to obtain high-purity pseudoboehmite powder. The filtration is carried out using a belt filter, the washing temperature is 60℃, and the drying is spray drying at 70℃ for 30 seconds.

[0058] Example 3 Step 1: Add aluminum sulfate solution and ammonia water in parallel to a stirred reactor to start a first neutralization reaction; the concentration of the aluminum sulfate solution is 170 g / L; the volume ratio of aluminum sulfate solution to ammonia water is 1:1; the temperature of the first neutralization reaction is 45℃; the pH of the reaction solution is 4.5-7; the time of the first neutralization reaction is 5 min, and a first slurry is obtained.

[0059] Step 2: The primary slurry from Step 1 overflows into the secondary neutralization reactor. The pH of the reaction solution is controlled by ammonia and a pore-expanding agent solution, and the reaction continues until completion. The pH of the reaction solution in the secondary neutralization reaction is 7-10, the temperature of the secondary neutralization reaction is 70℃, the time of the secondary neutralization reaction is 5 min, and the pore-expanding agent is obtained by mixing ammonium carbonate and urea at a mass ratio of 3:1. The amount of pore-expanding agent added is 0.5% of the mass of the primary slurry, thus obtaining the secondary slurry.

[0060] In step 3, the secondary slurry from step 2 overflows into the aging reactor, is heated, and then allowed to stand for aging. The aging temperature is 90°C and the aging time is 30 min.

[0061] Step 4: Filter, wash, dry and pulverize the product from step 3 to obtain high-purity pseudoboehmite powder. The filtration is carried out using a belt filter, the washing temperature is 90℃, and the drying is flash drying at 150℃ for 3 seconds.

[0062] Example 4 The high-purity boehmite was prepared in a manner similar to that in Example 1, except that the amount of pore expander added was 0.1% of the mass of the slurry.

[0063] Example 5 The high-purity boehmite was prepared in a manner similar to that in Example 1, except that the amount of pore-expanding agent added was 1.0% of the mass of the slurry.

[0064] Example 6 The high-purity boehmite was prepared in a manner similar to that in Example 1, except that the pore-expanding agent was ammonium carbonate.

[0065] Example 7 The high-purity boehmite was prepared in a manner similar to that in Example 1, except that the pore-expanding agent was urea.

[0066] Comparative Example Comparative Example 1 The high-purity boehmite was prepared in a manner similar to that in Example 1, with the main difference being that a neutralization reaction was not performed first; instead, ammonia and a pore-expanding agent solution were directly added to the aluminum sulfate solution for a one-step neutralization reaction. The specific preparation steps are as follows: Step 1: Add ammonia and a pore-expanding agent solution to the aluminum sulfate solution, control the pH of the reaction solution, and neutralize the reaction until the reaction is complete; the pH of the reaction solution of aluminum sulfate solution and ammonia is 7-10, the temperature of the neutralization reaction is 90℃, the neutralization reaction time is 5 min, the pore-expanding agent is obtained by mixing ammonium carbonate and urea at a mass ratio of 3:1, and the amount of pore-expanding agent added is 0.5% of the mass of the slurry.

[0067] Step 2: Overflow the slurry from Step 1 into the aging reactor, heat it up, and let it stand for aging; the aging temperature is 90℃ and the aging time is 30 min.

[0068] Step 3: Wash, dry and pulverize the product from step 2 to obtain high-purity pseudoboehmite powder. The filtration is carried out using a belt filter, the washing temperature is 90℃, and the drying is flash drying at 150℃.

[0069] Comparative Example 2 The high-purity boehmite was prepared in a manner similar to that in Example 1, except that no static aging was performed.

[0070] Comparative Example 3 The high-purity boehmite was prepared in a manner similar to that in Example 1, except that the temperature of the first neutralization reaction was 25°C, the pH of the reaction solution was 4.5–7, and the time of the first neutralization reaction was 25 min.

[0071] Comparative Example 4 The high-purity boehmite was prepared in a manner similar to that in Example 1, except that the temperature of the first neutralization reaction was 95°C, the time of the first neutralization reaction was 4 min, and the pH value of the reaction solution for the first neutralization reaction was 7-10.

[0072] Comparative Example 5 The high-purity boehmite was prepared in a manner similar to that in Example 1, except that the aluminum sulfate solution was replaced with a mixed solution of aluminum sulfate solution and sodium aluminate solution, wherein the volume ratio of aluminum sulfate solution to sodium aluminate solution was 1:1.

[0073] Experimental Example Experiment Example 1 Performance Test The pore volume, specific surface area, and probable pore size of the high-purity boehmite prepared in Examples 1 to 8 and Comparative Examples 1 to 4 were tested respectively. The testing standard for pore volume, specific surface area, and probable pore size was YS / T 1161.3-2016. The test results are shown in Table 1.

[0074] The BET curves of the high-purity boehmite prepared in Examples 1, 5, and 5 are as follows: Figure 1 As shown.

[0075] Table 1. Results of pore structure testing of samples

[0076] from Figure 1 It can be seen that, compared with Example 5 and Comparative Example 5, the pore size distribution of the boehmite prepared in Example 1 is more concentrated, and the pore size distribution of the boehmite prepared in Example 5 is more concentrated than that in Comparative Example 5. These results indicate that the preparation method described in this invention can produce boehmite with a more concentrated pore size distribution and larger pore volume and specific surface area. Specifically, the boehmite prepared using the method described in Example 1 has a more concentrated pore size distribution and larger pore volume and specific surface area.

[0077] As can be seen from Table 1, the pseudoboehmite prepared in Examples 1-8 has a pore volume of 0.89 mL / g or higher and a specific surface area of ​​280 m². 2 / g or more.

[0078] Compared with Example 1, Examples 4 and 5 show that Example 4 reduced the amount of pore-expanding agent, while Example 5 increased the amount of pore-expanding agent. Test results show that the specific surface area, pore volume, and probable pore size of the pseudoboehmite obtained in Examples 4 and 5 were all reduced. These results indicate that the amount of pore-expanding agent affects the specific surface area, pore volume, and probable pore size of the pseudoboehmite product. Only when the amount of pore-expanding agent is within the range defined by this invention is it beneficial to improve the specific surface area, pore volume, and probable pore size of the pseudoboehmite.

[0079] Compared with Example 1, Examples 6 and 7 changed the type of pore-expanding agent. Test results showed that the pore volume and probable pore size of the boehmite prepared in Examples 6 and 7 were lower than those in Example 1. These results indicate that the type of pore-expanding agent affects the probable pore size and pore volume of boehmite. A mixture of ammonium carbonate and urea at a mass ratio of 2:1 is more beneficial for improving the probable pore size and pore volume of boehmite.

[0080] Compared to Example 1, Comparative Example 1 did not undergo two neutralization reactions, but instead used a single neutralization reaction. The specific surface area and pore volume of Comparative Example 1 were significantly reduced compared to Example 1. These results indicate that performing a two-step neutralization reaction is more beneficial for increasing the specific surface area and pore volume of boehmite.

[0081] Compared with Example 1, Comparative Example 2 did not undergo static aging. The test results showed that the specific surface area and pore volume of the pseudoboehmite prepared in Comparative Example 2 were significantly reduced compared with Example 1. The above results indicate that static aging is beneficial to improving the pore volume and specific surface area of ​​the prepared pseudoboehmite.

[0082] Compared with Example 1, Comparative Examples 3 and 4 lowered the temperature of the first neutralization reaction to 25°C, while Comparative Example 4 raised the temperature to 95°C. Test results showed that the specific surface area and pore volume of the pseudoboehmite prepared in Comparative Examples 3 and 4 were significantly lower than those in Example 1, and the probable pore size of the pseudoboehmite prepared in Comparative Example 3 was also lower than that in Example 1. These results indicate that the temperature of the first neutralization reaction has a significant impact on the performance of the final product, pseudoboehmite. Only when the neutralization reaction temperature is within a suitable range (30–70°C) is it beneficial to increase the pore volume and specific surface area of ​​the pseudoboehmite and to make the pore size distribution more concentrated.

[0083] Compared to Example 1, Comparative Example 5 changed the raw materials for preparing boehmite, replacing the aluminum sulfate solution with a mixed solution of aluminum sulfate and sodium aluminate. Test results showed that the specific surface area, pore volume, and probable pore size of the boehmite prepared in Comparative Example 5 were lower than those in Example 1. These results indicate that the raw materials used in preparation affect the specific surface area, pore volume, and probable pore size of the final boehmite, and using a single aluminum sulfate solution is more beneficial for improving these parameters.

[0084] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for preparing high-purity pseudoboehmite with concentrated pore size, characterized in that, The preparation method includes the following steps: Step 1: Mix aluminum sulfate solution with ammonia water to carry out a neutralization reaction and obtain a slurry. Step 2: Add ammonia and a pore-expanding agent to the primary slurry obtained in Step 1 to carry out a secondary neutralization reaction and obtain a secondary slurry; Step 3: Heat the secondary slurry obtained in Step 2 and let it stand for aging. Step 4: Filter, wash, dry and pulverize the aging product obtained in Step 3 to obtain high-purity pseudoboehmite.

2. The preparation method according to claim 1, characterized in that, In step 1, The concentration of the aluminum sulfate solution is 60–170 g / L; The volume ratio of the aluminum sulfate solution to the ammonia solution is (10-1):

1.

3. The preparation method according to claim 1, characterized in that, In step 1, The temperature of the first neutralization reaction is 30–70°C, the pH of the reaction solution of aluminum sulfate solution and ammonia water is 4.5–7, and the time of the first neutralization reaction is 5–20 min.

4. The preparation method according to claim 1, characterized in that, In step 2, The pore-expanding agent is selected from one or more of ammonium carbonate, urea, and PEG 600-800.

5. The preparation method according to claim 4, characterized in that, In step 2, The pore-expanding agent is a mixture of ammonium carbonate and urea, wherein the mass ratio of ammonium carbonate to urea is (1-3):

1.

6. The preparation method according to claim 1, characterized in that, In step 2, The amount of the expanding agent added is 0% to 1% of the mass of the slurry.

7. The preparation method according to claim 1, characterized in that, In step 2, The temperature of the secondary neutralization reaction is 40–90°C, the time of the secondary neutralization reaction is 5–20 min, and the pH value of the reaction solution of the secondary neutralization reaction is 7–10.

8. The preparation method according to claim 1, characterized in that, In step 3, The aging temperature is 70–90°C, and the aging time is 30–200 min.

9. The preparation method according to claim 1, characterized in that, In step 4, The washing temperature is 60–90°C; The drying method is flash drying or spray drying, the drying temperature is 70-150℃, and the drying time is 3-30 seconds.

10. A high-purity pseudoboehmite with concentrated pore size prepared by the preparation method according to any one of claims 1 to 9.

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