A pure silicon AlPO-16 molecular sieve and its preparation method
By employing novel structure-directing agents and crystallization methods, pure silicon AlPO-16 molecular sieves with octahedral morphology were successfully prepared, solving the problem of insufficient research in existing technologies and realizing high-yield and applicable molecular sieve applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2022-10-20
- Publication Date
- 2026-06-30
AI Technical Summary
There is limited research on pure silicon AlPO-16 molecular sieves in the existing technology, especially on its structure directing agents, which limits the understanding of its synthesis mechanism and the expansion of its synthesis routes.
A novel structure-directing agent was used to prepare pure silicon AlPO-16 molecular sieves by crystallizing a mixture of silicon source, fluorine source, water and structure-directing agent. The specific steps included uniform mixing, evaporation of excess water, static crystallization and solid-liquid separation, resulting in pure silicon AlPO-16 molecular sieves with an octahedral morphology.
A high-yield preparation of pure silicon AlPO-16 molecular sieves was achieved, which is suitable for adsorption and separation. The preparation method is simple and has good prospects for industrial application.
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Figure CN117917376B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of molecular sieve preparation, specifically to a pure silicon AlPO-16 molecular sieve and its preparation method. Background Technology
[0002] Octadecasil, a pure silicon AlPO-16 molecular sieve, was initially synthesized hydrothermally in a fluoride medium by Caullet using tetramethyl quaternary ammonium or quinine as structure directing agents and fumed silica as the silicon source. The required pH for synthesis was 6–9, and the crystallization temperature was 443 K (P. Caullet, J. L. Guth, J. Hazm, J. M. L. Amblin, H. Gies, Eur. J. Solid State Inorg. Chem. 28 (1991) 345.). Octadecasil is an isomorphous molecular sieve of AlPO-16, and the International Molecular Sieve Association has given Octadecasil the structural code AST. The topological structure of Octadecasil consists of rhombic dodecahedrons [4]. 6 6 12 The cage is constructed using a hexahedral cage [4]. 6 The molecular sieve is formed by the stacking of interconnected rings, and the hexahedral cage is usually called a double four-membered ring (D4R). Octadecasil belongs to the cage-like silicon family. Its large cage-like space can only be entered through small rings (not larger than a six-membered ring with a shared angle of silicon-oxygen tetrahedron), and cannot enter the internal voids of the molecular sieve through windows of rings not smaller than an eight-membered ring.
[0003] Since its discovery, Octadecasil has been the subject of limited research, particularly regarding its structure-directing agents. The structure-directing agents used by scientists in its synthesis are mostly tetramethylammonium cations (TMA). +Luis A et al. synthesized Octadecasil using n-butyltrimethylammonium hydroxide as a structure-directing agent (LA Villaescusa, PA Barrett, MA Amblor, Chem. Mater. 1998, 1012, 3966-3973). Javier et al. also synthesized Octadecasil using n-butyltrimethylammonium hydroxide as a structure-directing agent. An aluminum source was added to the synthesis system, resulting in an Octadecasil with a Si / Al ratio of 30. Desilication yielded Octadecasil nanocrystals, which were then applied to the cracking of high-density polyethylene, showing good catalytic performance (Javier Perez-Ramrez, Sonia Abello, Luis A. Villaescusa, and Adriana Bonilla, Angew. Chem. 2008, 120, 8031-8035).
[0004] Developing novel structure-directing agents to guide the synthesis of pure silicon AlPO-16 molecular sieves is of great practical significance for understanding the synthetic mechanism of Octadecasil and expanding its synthetic routes. Summary of the Invention
[0005] This invention provides a pure silicon AlPO-16 molecular sieve and its preparation method. The preparation method uses a novel structure-directing agent to synthesize a pure silicon AlPO-16 molecular sieve, suitable for adsorption and separation.
[0006] The first aspect of this invention provides a method for preparing pure silicon AlPO-16 molecular sieve, comprising the following steps: crystallizing a mixture of a silicon source, a fluorine source, water, and a structure-directing agent to obtain a pure silicon AlPO-16 molecular sieve; wherein the structure-directing agent has the following structure:
[0007]
[0008] According to the present invention, the preparation method of the pure silicon AlPO-16 molecular sieve is further described in the following steps: a silicon source is added to an aqueous solution of a structure-directing agent, and a fluorine source is added after uniform mixing; excess water is evaporated at 20-90°C to obtain a gel mixture, and the mixture is subjected to crystallization treatment to obtain the pure silicon AlPO-16 molecular sieve.
[0009] According to the present invention, the crystal morphology of the pure silicon AlPO-16 molecular sieve is octahedral. The octahedral surface is smooth.
[0010] According to the present invention, the particle size range of the pure silicon AlPO-16 molecular sieve is 50 to 100 micrometers.
[0011] According to the present invention, the silicon source is one or more selected from tetraethyl orthosilicate, silica, and silica sol. The fluorine source is ammonium fluoride.
[0012] According to the present invention, further, in the mixture, the silicon source is calculated as SiO2, the fluorine source is calculated as NH4F, and the molar ratio of NH4F:structure directing agent:SiO2:H2O is (0.3~0.6):(0.2~0.5):(0.7~1.5):(4~15). Wherein, H2O represents all the water content in the preparation method.
[0013] According to the present invention, the method for preparing the structure-directing agent further includes:
[0014] (1) Place the dimethylamine methanol solution in an ice bath, adjust the pH to 7-8, add 1,4-cyclohexanedione and sodium cyanoborohydride, stir at 10-35℃ for 60-85 hours, adjust the pH to 1.5-2.5, remove excess methanol by rotary evaporation, adjust the pH to 11.5-13.0, add sodium chloride to saturate, extract with dichloromethane 3-5 times, remove dichloromethane by rotary evaporation, and obtain product 1, with the following chemical formula:
[0015]
[0016] (2) Dissolve product 1 obtained in step (1) in methanol, place in an ice bath, add iodomethane methanol solution dropwise, stir at 10-35℃ for 60-85 hours, filter to obtain solid, which is product 2, with the following chemical formula:
[0017]
[0018] (3) The product 2 obtained in step (2) is subjected to ion exchange with an anion exchange resin to obtain an aqueous solution of the structure directing agent, as shown in the following chemical formula:
[0019]
[0020] According to the present invention, in step (1), the concentration of the dimethylamine methanol solution is 0.7 to 1.5 mol / L.
[0021] According to the present invention, further, in step (1), a hydrochloric acid (methanol) solution can be used to adjust the pH value to 7-8, wherein the concentration of the hydrochloric acid (methanol) solution is 0.5-3.0 mol / L; a hydrochloric acid (methanol) solution can be used to adjust the pH value to 1.5-2.5, wherein the concentration of the hydrochloric acid (methanol) solution is 0.5-7.0 mol / L; a potassium hydroxide solution can be used to adjust the pH value to 11.5-13.0, wherein the concentration of the potassium hydroxide solution is 1.0-3.0 mol / L.
[0022] According to the present invention, in step (1), the molar ratio of 1,4-cyclohexanedione to dimethylamine is 1:3 to 5; the molar ratio of 1,4-cyclohexanedione to sodium cyanoborohydride is 1:1.2 to 3.
[0023] According to the present invention, in step (2), the concentration of product 1 is: 1 g product 1 / 2 to 5 mL methanol; the volume ratio of iodomethane to methanol is: 1:(0.8 to 1.5).
[0024] According to the present invention, in step (3), the mass ratio of product 2 to anion exchange resin is 1:(7-12).
[0025] According to the present invention, in step (3), the anion exchange resin is any one of a strong basic type I anion exchange resin, a strong basic styrene-based anion exchange resin, and a macroporous strong basic anion exchange resin.
[0026] According to the present invention, the crystallization conditions are further as follows: the crystallization temperature is 140-190°C, and the crystallization time is 100-300 hours.
[0027] According to the present invention, the crystallization is further described as static crystallization.
[0028] According to the present invention, further, after the crystallization treatment is completed, the solid, namely the pure silicon AlPO-16 molecular sieve, can be separated from the obtained mixture by any conventionally known solid-liquid separation method. After solid-liquid separation, washing and drying can be performed. The solid-liquid separation, washing, and drying can be carried out in any manner conventionally known in the art. Specifically, the solid-liquid separation can be performed, for example, by centrifugation. The washing can be performed, for example, using deionized water. The drying temperature is 40–150°C, and the drying time is 8–30 hours.
[0029] A second aspect of the present invention provides a pure silicon AlPO-16 molecular sieve, which is prepared by the above-described preparation method.
[0030] A third aspect of the present invention also provides a molecular sieve composition comprising a pure silicon AlPO-16 molecular sieve prepared according to the method described in the first aspect above, or a pure silicon AlPO-16 molecular sieve prepared according to the method described in the second aspect above, and a binder.
[0031] The fourth aspect of the present invention also provides a pure silicon AlPO-16 molecular sieve prepared according to the method described in the first aspect above, or a pure silicon AlPO-16 molecular sieve according to the second aspect above, or a molecular sieve composition according to the third aspect above, as an adsorbent or separating agent.
[0032] Compared with the prior art, the present invention has the following advantages:
[0033] 1. In the preparation method of pure silicon AlPO-16 molecular sieve of this invention, the structure-directing agent used is a novel structure-directing agent, and no related reports have been found to date. The preparation method of pure silicon AlPO-16 molecular sieve of this invention is simple, has low equipment requirements, and produces high product yield; therefore, this invention has excellent prospects for industrial application.
[0034] 2. The pure silicon AlPO-16 molecular sieve prepared according to the preparation method of the present invention is suitable for adsorption and separation. Attached Figure Description
[0035] Figure 1 These are the XRD patterns of the pure silicon AlPO-16 molecular sieves obtained in Examples 2-4 of this invention;
[0036] Figure 2 This is a scanning electron microscope image of the pure silicon AlPO-16 molecular sieve obtained in Example 2 of the present invention;
[0037] Figure 3 This is a scanning electron microscope image of the pure silicon AlPO-16 molecular sieve obtained in Example 3 of the present invention;
[0038] Figure 4 This is a scanning electron microscope image of the pure silicon AlPO-16 molecular sieve obtained in Example 4 of the present invention;
[0039] Figure 5 This is the XRD pattern of the material obtained in Comparative Example 1 of this invention;
[0040] Figure 6 This is a scanning electron microscope image of the material obtained in Comparative Example 1 of the present invention;
[0041] Figure 7 This is the XRD pattern of the material obtained in Comparative Example 2 of the present invention;
[0042] Figure 8 This is a scanning electron microscope image of the material obtained in Comparative Example 2 of the present invention.
[0043] Figure 9 This is the XRD pattern of the material obtained in Comparative Example 3 of the present invention;
[0044] Figure 10 This is a scanning electron microscope image of the material obtained in Comparative Example 3 of the present invention. Detailed Implementation
[0045] The technical solution of the present invention will be further illustrated below with reference to the embodiments, but it is not limited to the following embodiments.
[0046] In the method of this invention, XRD data were obtained using a Bruker AXS D8 Advance X-ray diffractometer (Germany), under the following conditions: voltage 40 kV, current 80 mA, CuKα target, and scanning speed 15°·min⁻¹. 1 The scanning range 2θ is 5–50°.
[0047] In the method of this invention, images 2 and 6 were obtained using a Zeiss Gemini 2 field emission scanning electron microscope (FE-SEM) from Germany, under the following test conditions: voltage 1.5 kV and current 30 mA. Images 3, 4, 8, and 10 were obtained using a Hitachi S4800 field emission scanning electron microscope (FE-SEM) from Japan, under the following test conditions: voltage 3 kV and current 10 μA.
[0048] Example 1
[0049] A 1.0 mol / L dimethylamine methanol solution was placed in an ice bath. The pH of the solution was adjusted to 7 using a 1.0 mol / L hydrochloric acid (methanol) solution. Then, 1,4-cyclohexanedione (n...) was added. 1,4-环己二酮 :n 二甲胺 =1:3.5), add sodium cyanoborohydride (n 1,4-环己二酮 The reaction mixture was stirred at room temperature (20℃) for 72 hours with sodium cyanoborohydride (1:1.5). The pH of the reaction system was adjusted to 2 with 3.0 mol / L hydrochloric acid (methanol) solution. Excess methanol was removed by rotary evaporation. The pH was adjusted to 12 with 2.0 mol / L potassium hydroxide solution, and sodium chloride was added to achieve saturation. The mixture was extracted four times with dichloromethane, and the dichloromethane was removed by rotary evaporation to obtain product 1, with the following chemical formula:
[0050]
[0051] Product 1 was dissolved in a small amount of methanol (1g product 1 / 5mL methanol), placed in an ice bath, and then an iodomethane methanol solution (1mL iodomethane / 1mL methanol) was added dropwise to the methanol solution of product 1. The mixture was stirred at room temperature (20℃) for 72 hours, and the solid was obtained by filtration, which is product 2, with the following chemical formula:
[0052]
[0053] Product 2 was subjected to ion exchange with an anion exchange resin (1g product 2 / 9g strongly basic styrene-based anion exchange resin) to obtain an aqueous solution of the structure-directing agent, as shown in the following chemical formula:
[0054]
[0055] Example 2
[0056] The silica sol (containing 40% by weight SiO2) was added to the aqueous solution of the structure directing agent prepared in Example 1 and stirred until homogeneous. Then, ammonium fluoride was added to the mixture and stirred for 1.5 hours. The excess water was evaporated by stirring in a 60°C water bath to obtain a gel mixture. The molar ratio of each substance in the gel mixture was: H2O:NH4F:SiO2:structure directing agent = 5:0.5:1:0.25.
[0057] The resulting gel mixture was subjected to static crystallization at a temperature of 170°C for 240 hours. The resulting sample was centrifuged, washed, and dried at 100°C for 10 hours to obtain pure silicon AlPO-16 molecular sieve with an octahedral morphology.
[0058] The XRD pattern of the pure silicon AlPO-16 molecular sieve obtained in Example 2 is as follows: Figure 1 As shown in the figure, the diffraction peaks of the synthesized pure silicon AlPO-16 molecular sieve are relatively sharp and have obvious intensity.
[0059] Scanning electron microscope images of the AlPO-16 molecular sieve obtained in Example 2 are shown below. Figure 2 As shown in the figure, the molecular sieve has an octahedral morphology with a smooth surface and a size range of 50–100 micrometers.
[0060] Example 3
[0061] Tetraethyl orthosilicate (TEOS) was added to the aqueous solution of the structure-directing agent prepared in Example 1 and stirred until homogeneous. Then, ammonium fluoride was added to the mixture and stirred for 1.5 hours. The excess water was evaporated by stirring in a water bath at 20°C to obtain a gel mixture. The molar ratio of each substance in the gel mixture was: H2O:NH4F:TEOS:structure-directing agent = 13:0.6:1.4:0.5.
[0062] The resulting gel mixture was subjected to static crystallization at a temperature of 170°C for 240 hours. The resulting sample was centrifuged, washed, and dried at 100°C for 10 hours to obtain pure silicon AlPO-16 molecular sieve with an octahedral morphology.
[0063] The XRD pattern of the pure silicon AlPO-16 molecular sieve obtained in Example 3 is as follows: Figure 1 As shown, the diffraction peaks of the synthesized pure silicon AlPO-16 molecular sieve are relatively sharp and have obvious intensity.
[0064] Scanning electron microscope images of the AlPO-16 molecular sieve obtained in Example 3 are shown below. Figure 3As shown, the molecular sieve has an octahedral morphology with a smooth surface and a size range of 50–100 micrometers.
[0065] Example 4
[0066] Add silica to the aqueous solution of the structure directing agent prepared in Example 1 and stir until homogeneous; then add ammonium fluoride to the mixture and stir for 1.5 hours; continue stirring in a 20°C water bath to evaporate excess water and obtain a gel mixture; the molar ratio of each substance in the gel mixture is: H2O:NH4F:SiO2:structure directing agent = 12:0.5:1.4:0.3.
[0067] The resulting gel mixture was subjected to static crystallization at a temperature of 170°C for 240 hours. The resulting sample was centrifuged, washed, and dried at 100°C for 10 hours to obtain pure silicon AlPO-16 molecular sieve with an octahedral morphology.
[0068] The XRD pattern of the pure silicon AlPO-16 molecular sieve obtained in Example 4 is as follows: Figure 1 As shown, the diffraction peaks of the synthesized pure silicon AlPO-16 molecular sieve are relatively sharp and have obvious intensity.
[0069] Scanning electron microscope images of the AlPO-16 molecular sieve obtained in Example 4 are as follows: Figure 4 As shown, the molecular sieve has an octahedral morphology with a smooth surface and a size range of 50–100 micrometers.
[0070] Comparative Example 1
[0071] The silica sol (containing 40% by weight SiO2) was added to the aqueous solution of the structure directing agent prepared in Example 1 and stirred until homogeneous. Then, ammonium fluoride was added to the mixture and stirred for 1.5 hours. The excess water was evaporated by stirring in a water bath at 20°C to obtain a gel mixture. The molar ratio of each substance in the gel mixture was: H2O:NH4F:SiO2:structure directing agent = 20:0.6:1:0.25.
[0072] The resulting gel mixture was subjected to static crystallization at 170°C for 240 hours. The resulting sample was then centrifuged, washed, and dried at 100°C for 10 hours to obtain the product.
[0073] The XRD pattern of the product obtained in Comparative Example 1 is shown below. Figure 5 As shown in the figure, the synthesized product is an amorphous product.
[0074] The scanning electron microscope image of the product obtained in Comparative Example 1 is shown below. Figure 6As shown in the figure, the morphology of the product is amorphous nanoparticles with a particle size range of 20 to 200 nanometers.
[0075] Comparative Example 2
[0076] Silica sol (containing 40% by weight SiO2) was added to the aqueous solution of the structure-directing agent prepared in Example 1 and stirred until homogeneous. Ammonium fluoride was then added to the mixture and stirred for 1.5 hours. Excess water was evaporated by stirring in a 20°C water bath to obtain a gel mixture. The molar ratio of the substances in the gel mixture was: H2O:NH4F:SiO2:structure-directing agent = 15:0.2:1.4:0.5
[0077] The resulting gel mixture was subjected to static crystallization at 170°C for 240 hours. The resulting sample was then centrifuged, washed, and dried at 100°C for 10 hours to obtain the product.
[0078] The XRD pattern of the product obtained in Comparative Example 1 is shown below. Figure 7 As shown in the figure, the synthesized product is a different product, mostly amorphous, with some weak peaks that do not belong to AlPO-16 molecular sieve.
[0079] The scanning electron microscope image of the product obtained in Comparative Example 1 is shown below. Figure 8 As shown in the figure, the morphology of the product is amorphous nanoparticles with a particle size range of 0.5 to 2 micrometers.
[0080] Comparative Example 3
[0081] Add silica sol (containing 40% by weight SiO2) to water and stir until homogeneous; then add ammonium fluoride and stir for 1.5 hours; continue stirring in a 60°C water bath to evaporate excess water and obtain a gel mixture; the molar ratio of each substance in the gel mixture is: H2O:NH4F:SiO2=5:0.5:1.
[0082] The resulting gel mixture was subjected to static crystallization at a temperature of 170°C for 240 hours. The resulting sample was centrifuged, washed, and dried at 100°C for 10 hours to obtain the product.
[0083] XRD pattern of the product obtained in Comparative Example 3 ( Figure 9 This indicates that the obtained product is an amorphous substance.
[0084] The SEM images of the product obtained in Comparative Example 3 prove that the morphology of the obtained sample is amorphous.
[0085] The specific embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A method for preparing pure silicon AlPO-16 molecular sieve, comprising the following steps: crystallizing a mixture of silicon source, fluorine source, water, and structure directing agent to obtain the pure silicon AlPO-16 molecular sieve, wherein the silicon source is calculated as SiO2, the fluorine source is calculated as NH4F, and the molar ratio of NH4F:structure directing agent:SiO2:H2O is (0.3~0.6):(0.2~0.5):(0.7~1.5):(4~15); wherein, The structure-directing agent has the following structure: 。 2. The preparation method according to claim 1, characterized in that, The preparation method of the pure silicon AlPO-16 molecular sieve is as follows: a silicon source is added to an aqueous solution of a structure-directing agent, and a fluorine source is added after uniform mixing; excess water is evaporated at 20~90℃ to obtain a gel mixture, which is then subjected to crystallization treatment to obtain the pure silicon AlPO-16 molecular sieve.
3. The preparation method according to claim 1 or 2, characterized in that, The silicon source is one or more of silica sol, silica fume, and tetraethyl orthosilicate.
4. The preparation method according to claim 1 or 2, characterized in that, The fluorine source is ammonium fluoride.
5. The preparation method according to claim 1 or 2, characterized in that, The crystallization conditions are as follows: crystallization temperature is 140~190℃, and crystallization time is 100~300 hours.
6. The preparation method according to claim 1 or 2, characterized in that, The crystallization is static crystallization.
7. The preparation method according to claim 1 or 2, characterized in that, The particle size range of the pure silicon AlPO-16 molecular sieve is 50~100μm.
8. The preparation method according to claim 1 or 2, characterized in that, The pure silicon AlPO-16 molecular sieve has an octahedral morphology.
9. A pure silicon AlPO-16 molecular sieve, characterized in that, It is prepared by any one of the preparation methods described in claims 1-8.
10. A molecular sieve composition comprising a pure silica AlPO-16 molecular sieve prepared by the method of any one of claims 1-8 or the pure silica AlPO-16 molecular sieve according to claim 9, and a binder.
11. The pure silicon AlPO-16 molecular sieve prepared by any of the methods described in claims 1-8, or the pure silicon AlPO-16 molecular sieve according to claim 9, or the molecular sieve composition according to claim 10, as an adsorbent or separating agent.