Preparation method of porous alumina
The porous alumina is prepared using gibbsite and a coupling agent through the sol-gel method, which solves the problems of complex by-product treatment and high cost in the existing technology, and realizes simple and efficient porous alumina preparation. The product has high purity and low cost, and is suitable for large-scale production.
Patent Information
- Application Number
- CN202511076753.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-01
- Publication Date
- 2025-10-17
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
The existing porous alumina preparation methods have problems such as complex by-product treatment, high cost, and cumbersome process. In particular, the use of pore-forming agents brings difficulties in recovery and increased costs.
Using gibbsite as raw material and coupling agent as isolation agent, porous alumina is prepared under mild conditions through the sol-gel method. The coupling agent is used to self-assemble under alkaline conditions to form a micellar network, which simultaneously binds aluminum ions and guides pore formation, avoiding the addition of templates and high-temperature treatment.
The preparation process is simple, the product purity is high, the cost is low, and no additional treatment of by-products is required. The obtained porous alumina particles are uniform, have a large specific surface area and good stability, and are suitable for large-scale production.
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Figure CN120793980A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of alumina, in particular to a preparation method of porous alumina. BACKGROUND
[0002] As a key inorganic non-metallic material, alumina is widely used in refractory materials, polishing media, heat-conducting fillers, sapphire and LED substrates, ceramic substrates, and catalyst carriers, etc. due to its performance being highly related to crystal structure, size and morphology. Among them, porous alumina has become an ideal adsorbent, catalyst or carrier material due to its excellent high stability, large specific surface area and pore volume, and controllable surface acidity and alkalinity.
[0003] At present, the mainstream pore-forming technology for preparing porous alumina includes hard template method, soft template method and biological template method. This kind of method often produces by-products in the reaction process, which need to be treated additionally. More importantly, in order to build a porous structure, pore-forming agents (such as precipitating agents, template agents, etc.) need to be introduced. These additives either decompose in subsequent high-temperature treatment or need to be removed through complex steps, which is difficult to recover and significantly increases the cost. The pretreatment steps involved in some methods are also relatively complicated. SUMMARY
[0004] In view of the by-product problem of the above-mentioned aluminum salt raw material and the cost and process complexity brought by the use of pore-forming agents, the present application proposes a new scheme based on different raw materials and process paths: using gibbsite as raw material and coupling agent as isolating agent, porous alumina is prepared under relatively mild conditions by sol-gel method. The product has smaller size, uniform particles, larger specific surface area and better stability, and the cost is lower, the process is simple, and it is easy to mass produce.
[0005] A preparation method of porous alumina, comprising the following steps:
[0006] (1) Put the aluminum source into the mixed solution of deionized water and ethylene glycol, and add coupling agent and mineralizer to the above-mentioned solution under stirring, then heat and keep the reaction liquid for 6h-12h;
[0007] (2) After cooling, slowly add ammonia solution to the solution to obtain Al(OH)3 gel precursor;
[0008] (3) The Al(OH)3 gel precursor is freeze-dried and calcined at high temperature to prepare porous α-Al2O3.
[0009] In step (1), the aluminum source is one of aluminum nitrate, aluminum sulfate, aluminum chloride and isopropyl alcohol aluminum.
[0010] In step (1), the volume ratio of deionized water and ethylene glycol in the mixed solution is (5:1) to (1:1).
[0011] In step (1), the coupling agent is one of polyethylene glycol, polyethylene and polyethylene oxide, and the mass ratio of the coupling agent to the aluminum source is (1:5) to (1:100).
[0012] In step (1), the mineralizer is aluminum fluoride, and the mass ratio of the mineralizer to the aluminum salt is (1:5) to (1:20).
[0013] In step (1), the holding temperature is 40 DEG C to 80 DEG C.
[0014] In step (2), the ammonia solution is one of ammonia water and n-butylamine.
[0015] In step (3), the freeze-drying process is that the precursor is placed in a cold trap at -30 DEG C to -80 DEG C to be frozen to obtain a solid sample, the temperature is kept unchanged, and the solid sample is dried in a vacuum chamber; and the freeze-drying time is 2h to 24h.
[0016] In step (3), the high-temperature calcination temperature is 800 DEG C to 1200 DEG C, and the high-temperature calcination time is 2h to 24h.
[0017] The average particle size of the porous alumina is 100nm to 300nm, and the pore size is 0.2nm to 3nm.
[0018] The coupling agent is self-assembled into a micellar network under alkaline conditions in the application, which synchronously binds aluminum ions and guides pore formation; meanwhile, the coupling agent effectively separates alumina molecular agglomeration, realizes solvent thermal in-situ pore formation, additive-free and low-temperature phase inversion three-in-one innovation, breaks through the dependence on templates and high temperature in the prior art, and has significant progress in simplifying the process, improving the purity and reducing the cost.
[0019] Compared with other prior art, the application has the following beneficial effects:
[0020] (1) The alumina sol precursor can be prepared in one step by the solvothermal method, and the preparation process is very simple.
[0021] (2) The raw materials used in the application do not need to add template agents, pore-forming agents and other materials, which avoids introducing other impurities, inorganic salt by-products and the like in the preparation process, greatly reduces the artificial time consumption, material cost and impurity content of the product. BRIEF DESCRIPTION OF DRAWINGS
[0022] Figure 1 X-ray diffraction patterns of Examples 1-2;
[0023] Figure 2is a scanning electron microscope image of Example 1;
[0024] Figure 3 This is a scanning electron microscope image of Example 3;
[0025] Figure 4 This is a scanning electron microscope image of Example 4;
[0026] Figure 5 This is a scanning electron microscope image of Example 5;
[0027] Figure 6 This is a scanning electron microscope image of Example 6;
[0028] Figure 7 This is a scanning electron microscope image of Example 7;
[0029] Figure 8 is a scanning electron microscope image of Example 8;
[0030] Figure 9 This is the nitrogen adsorption-desorption isotherm diagram of Example 1. DETAILED DESCRIPTION
[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0032] Example 1:
[0033] 5 g of aluminum sulfate and 60 mL of water-ethylene glycol solution (5:1) were placed in a polytetrafluoroethylene liner. After sufficient magnetic stirring for 20 min, 0.5 g of polyethylene glycol and 1 g of aluminum fluoride were added. After complete dissolution, the liner was placed in a stainless steel jacket and sealed to obtain an autoclave; the autoclave was placed in a heating box, kept at 80 ° C for 6 h, and then naturally cooled; then 1 g of ammonia water was slowly dripped into the reaction solution. After standing for 30 minutes, a yellow gel precipitated; the wet gel was placed in a cold trap at a temperature of -80 ° C and frozen for 4 h, and then the temperature was kept constant. The solid sample was placed in a vacuum chamber for vacuum freeze drying for 12 h, and then the dried precursor was fully ground in an agate mortar and placed in a corundum crucible. It was calcined at high temperature in a muffle furnace, heated to 1200 ° C at a rate of 5 ° C / min and kept warm for 3 h. After the insulation ended, it was naturally cooled to room temperature to obtain the product, which was porous alumina. Figure 1 The XRD spectrum of the porous alumina obtained in Example 1 is given, indicating that the product is α-A12O3 crystalline alumina; Figure 2 The microscopic morphology of porous alumina is shown in Figure 2. The alumina is a nanosphere with a particle size of 200 nm. Figure 9 The nitrogen adsorption-desorption isotherm of alumina shows that alumina has a porous structure (pore size 0.2-3nm) and a high specific surface area (87m 2 / g).
[0034] Example 2:
[0035] The preparation process and parameters are the same as those in Example 1, except that the calcination temperature is 800°C. Figure 1 The curve shows the XRD spectrum of the calcined material prepared in Example 2, and its diffraction peaks correspond to those in Example 1. This shows that α-Al2O3 can be obtained at a lower calcination temperature.
[0036] Example 3:
[0037] 5 g of aluminum isopropoxide and 60 mL of water-ethylene glycol solution (1:1) were placed in a polytetrafluoroethylene liner. After sufficient magnetic stirring for 20 min, 0.1 g of polyethylene glycol and 0.5 g of aluminum fluoride were added. After complete dissolution, the liner was placed in a stainless steel jacket and sealed to obtain an autoclave. The autoclave was placed in a heating box, kept at 40 ° C for 6 h, and then naturally cooled. Then 1 g of ammonia water was slowly dripped into the reaction solution. After standing for 30 minutes, a yellow gel precipitated. The wet gel was placed in a cold trap at a temperature of -50 ° C and frozen for 1 h. Then, the temperature was kept constant and the solid sample was placed in a vacuum chamber for vacuum freeze drying for 1 h. The dried precursor was then fully ground in an agate mortar and placed in a corundum crucible. It was calcined at high temperature in a muffle furnace and heated to 1200 ° C at a rate of 5 ° C / min and kept warm for 24 h. After the insulation, it was naturally cooled to room temperature. The product obtained was porous α-A12O3, and its micromorphology is as follows Figure 3 As shown in the figure, the alumina particles obtained in this embodiment have a uniform particle size of about 150 nm.
[0038] Example 4:
[0039] 5 g of aluminum chloride and 60 mL of water-ethylene glycol solution (1:1) were placed in a polytetrafluoroethylene liner. After sufficient magnetic stirring for 20 min, 0.1 g of polyethylene glycol and 0.25 g of aluminum fluoride were added. After complete dissolution, the liner was placed in a stainless steel jacket and sealed to obtain an autoclave. The autoclave was placed in a heating box, kept at 50 ° C for 6 h, and then naturally cooled. Then 1 g of ammonia water was slowly dripped into the reaction solution. After standing for 30 minutes, a yellow gel precipitated. The wet gel was placed in a cold trap at a temperature of -50 ° C and frozen for 2 h. Then, the temperature was kept constant and the solid sample was placed in a vacuum chamber for vacuum freeze drying for 2 h. The dried precursor was then fully ground in an agate mortar and placed in a corundum crucible. It was calcined at high temperature in a muffle furnace, heated to 1200 ° C at a rate of 5 ° C / min and kept warm for 12 h. After the insulation, it was naturally cooled to room temperature. The product obtained was porous α-A12O3, and its micromorphology is as follows Figure 4 As shown in the figure, it can be seen that the aluminum oxide obtained in this embodiment has a uniform particle size of about 100 nm.
[0040] Example 5:
[0041] 5 g of aluminum nitrate and 60 mL of water-ethylene glycol solution (1:1) were placed in a polytetrafluoroethylene liner. After sufficient magnetic stirring for 20 min, 0.1 g of polyethylene glycol and 0.3 g of aluminum fluoride were added. After complete dissolution, the liner was placed in a stainless steel jacket and sealed to obtain an autoclave. The autoclave was placed in a heating box, kept at 60 ° C for 6 h, and then naturally cooled. Then 1 g of ammonia water was slowly dripped into the reaction solution. After standing for 30 minutes, a yellow gel precipitated. The wet gel was placed in a cold trap at a temperature of -50 ° C and frozen for 3 h. Then, the temperature was kept constant and the solid sample was placed in a vacuum chamber for vacuum freeze drying for 1 h. The dried precursor was then fully ground in an agate mortar and placed in a corundum crucible. It was calcined at high temperature in a muffle furnace, heated to 1200 ° C at a rate of 5 ° C / min and kept warm for 2 h. After the insulation, it was naturally cooled to room temperature. The product obtained was porous α-A12O3, and its micromorphology is as follows Figure 5 As can be seen from the figure, the alumina particles obtained in this embodiment have a uniform particle size of about 250 nm.
[0042] Example 6:
[0043] 5 g of aluminum sulfate and 60 mL of water-ethylene glycol solution (5:1) were placed in a polytetrafluoroethylene liner. After sufficient magnetic stirring for 20 min, 0.5 g of polyethylene and 0.4 g of aluminum fluoride were added. After complete dissolution, the liner was placed in a stainless steel jacket and sealed to obtain an autoclave. The autoclave was placed in a heating box, kept at 80 ° C for 6 h, and then naturally cooled. Then 2 g of n-butylamine was slowly dripped into the reaction solution. After standing for 30 minutes, a yellow gel precipitated. The wet gel was placed in a cold trap at a temperature of -80 ° C and frozen for 0.5 h. Then, the temperature was kept constant and the solid sample was placed in a vacuum chamber for vacuum freeze drying for 3.5 h. The dried precursor was then fully ground in an agate mortar and placed in a corundum crucible. It was calcined at high temperature in a muffle furnace, heated to 1200 ° C at a rate of 5 ° C / min and kept warm for 8 h. After the insulation, it was naturally cooled to room temperature. The product obtained was porous α-A12O3, and its micromorphology is as follows Figure 6 As shown in the figure, it can be seen that the alumina obtained in this embodiment has a uniform particle size, and the particle size is about 250nm of uniform α-A12O3.
[0044] Example 7:
[0045] Take 5 g of aluminum sulfate and 60 mL of water-glycol solution (5:1) into a polytetrafluoroethylene liner, after 20 min of sufficient magnetic stirring, add 0.5 g of polyethylene oxide and 0.25 g of aluminum fluoride, after complete dissolution, put the liner into a stainless steel jacket for sealing to obtain an autoclave; the autoclave is placed in a heating box, and after being kept at 80℃ for 6 h, it is naturally cooled; then 2 g of n-butylamine is slowly dropped into the reaction solution, and after standing for 30 min, yellow gel is precipitated; the wet gel is frozen in a cold trap at a temperature of-80℃ for 4 h, then the temperature is kept unchanged, the solid sample is put into a vacuum chamber for vacuum freeze-drying for 12 h, and then the dried precursor is ground in a corundum crucible in a muffle furnace, heated to 1200℃ at a rate of 5℃ / min, kept for 3 h, and then naturally cooled to room temperature to obtain the product, which is porous α-A12O3, and the micro-morphology is shown in Figure 7 As can be seen from the figure, the aluminum oxide obtained in this embodiment has uniform particle size, and the particle size is about 300 nm.
[0046] Example 8:
[0047] Take 5 g of aluminum sulfate and 60 mL of water-glycol solution (5:1) into a polytetrafluoroethylene liner, after 20 min of sufficient magnetic stirring, add 0.5 g of polyethylene oxide and 0.25 g of aluminum fluoride, after complete dissolution, put the liner into a stainless steel jacket for sealing to obtain an autoclave; the autoclave is placed in a heating box, and after being kept at 80℃ for 6 h, it is naturally cooled; then 2 g of n-butylamine is slowly dropped into the reaction solution, and after standing for 30 min, yellow gel is precipitated; the wet gel is frozen in a cold trap at a temperature of-80℃ for 4 h, then the temperature is kept unchanged, the solid sample is put into a vacuum chamber for vacuum freeze-drying for 12 h, and then the dried precursor is ground in a corundum crucible in a muffle furnace, heated to 1200℃ at a rate of 5℃ / min, kept for 3 h, and then naturally cooled to room temperature to obtain the product, which is porous α-A12O3, and the micro-morphology is shown in Figure 8 As can be seen from the figure, the aluminum oxide obtained in this embodiment has uniform particle size, and the particle size is about 300 nm.
Claims
1. A method for preparing porous alumina, characterized in that: The following steps are involved: (1) Adding an aluminum source to a mixed solution of deionized water and ethylene glycol, adding a coupling agent and a mineralizer to the solution while stirring, and then heating the reaction solution and keeping it warm for 6 to 12 hours; (2) After cooling, ammonia solution is added to the solution to obtain an Al(OH)3 gel precursor; (3) The Al(OH)3 gel precursor was freeze-dried and calcined at high temperature to prepare porous α-A12O3.
2. The method for preparing porous alumina according to claim 1, wherein: In step (1), the aluminum source is one of aluminum nitrate, aluminum sulfate, aluminum chloride and aluminum isopropoxide.
3. The method for preparing porous alumina according to claim 1, wherein: In step (1), the volume ratio of deionized water to ethylene glycol in the mixed solution is (5:1) to (1:1).
4. The method for preparing porous alumina according to claim 1, wherein: In step (1), the coupling agent is one of polyethylene glycol, polyethylene and polyethylene oxide; The mass ratio of the coupling agent to the aluminum source is (1:5) to (1:100).
5. The method for preparing porous alumina according to claim 1, wherein: In step (1), the mineralizer is aluminum fluoride; The mass ratio of the mineralizer to the aluminum source is (1:5) to (1:20).
6. The method for preparing porous alumina according to claim 1, wherein: In step (1), the insulation temperature is 40°C to 80°C.
7. The method for preparing porous alumina according to claim 1, wherein: In step (2), the ammonia solution is one of aqueous ammonia and n-butylamine.
8. The method for preparing porous alumina according to claim 1, wherein: In step (3), the freeze-drying process is to place the precursor in a cold trap at -30°C to -80°C to freeze the solid sample, keep the temperature constant, and dry the solid sample in a vacuum chamber; The freeze-drying time is 2 hours to 24 hours.
9. The method for preparing porous alumina according to claim 1, wherein: In step (3), the high-temperature calcination temperature is 800° C. to 1200° C., and the high-temperature calcination time is 2 h to 24 h.
10. The method for preparing porous alumina according to claim 1, wherein: The average particle size of the porous alumina is 100 nm to 300 nm, and the pore size is 0.2 nm to 3 nm.