A bimodal high crystallinity alpo-18 molecular sieve and a method for preparing the same

Abstract

The application discloses a kind of double-template method high crystallinity AlPO-18 molecular sieve and preparation method thereof.Step includes: phosphorus source, deionized water, aluminium source, tetraethylammonium hydroxide, tetraethylammonium chloride and seed crystal are sequentially added in hydrothermal reactor with stirring uniformity, and after aging certain time at room temperature, hydrothermal reactor is sealed, and placed in reactor high-temperature static crystallization;The hydrothermal crystallization product is washed, dried and calcined, and then high-crystallinity quadrilateral AlPO-18 molecular sieve is obtained.Compared with prior art, its significant features are simple operation, low water aluminum ratio, high crystallinity, high yield;And using double-template method, to a certain extent, reduce the amount of expensive template agent tetraethylammonium hydroxide, effectively reduce the cost, with the wide prospect of industrial production and application.

Description

Technical Field

[0001] This invention relates to the preparation of molecular sieve materials, specifically to a dual-template method for preparing a highly crystalline AlPO-18 molecular sieve and its preparation method. Background Technology

[0002] AlPO-18 molecular sieve with an AEI topology is a typical aluminum phosphate molecular sieve. AlPO-18 molecular sieve has eight-membered ring channels that are vertically interconnected along the x, y, and z axes, with a pore size of 0.38 nm × 0.38 nm. Due to its unique channel structure (size, dimensions, etc.), it is widely used in industrial fields, playing a crucial role in the adsorption and separation of gases such as CO2, N2, H2, CH4, and C2H6.

[0003] The literature [Anbealagan LD, Chew TL, Yeong YF, et al. Synthesis and characterization of (3-aminopropyl)triethoxysilane (APTES) functionalized zeolite AlPO-18[J]. IOP Conference Series: Materials Science and Engineering, 2021, 1195(1): 012047] synthesized an irregularly shaped plate-like AlPO-18 molecular sieve by static crystallization at 150℃ for 20 h with a gel ratio of 1.0Al2O3:3.16P2O5:6.32TEAOH:186H2O.

[0004] The literature [Su J, Zhou H, Liu S, et al. Syngas to light olefins conversion with high olefin / paraffin ratio using ZnCrOx / AlPO-18 bifunctional catalysts[J]. Nature Communications, 2019, 10(1): 1297.] describes the preparation of AlPO-18 molecular sieves by hydrothermal synthesis with a gel ratio of 1Al2O3:1P2O5:0.67(TEA)2O:0.33HCl:40H2O and a crystallization temperature of 170℃ for 3 days of static crystallization.

[0005] Chinese patent (CN 109806729 A) discloses a method for preparing AlPO-18 molecular sieve membranes using N,N-diisopropylethylamine as a template agent.

[0006] Chinese patent (CN 109354035 B) discloses a method for synthesizing AlPO-18 molecular sieves using N,N-diisopropylethylamine and tetraethylammonium hydroxide (TEAOH) as mixed template agents, aluminum isopropoxide as the aluminum source, and phosphoric acid as the phosphorus source.

[0007] The commonly used template agents in the synthesis of AlPO-18 are tetraethylammonium hydroxide and N,N-diisopropylethylamine. However, the use of the expensive template agent TEAOH results in drawbacks such as high synthesis cost and low crystallinity.

[0008] Currently, although pure-phase AlPO-18 can be synthesized, the content of the template agent tetraethylammonium hydroxide is high, and the synthesized AlPO-18 has relatively low crystallinity.

[0009] Based on this, this patent, by introducing the template agent tetraethylammonium chloride (TEACl), synthesizes AlPO-18, which not only effectively reduces the content of the template agent compared to that in the literature, but also greatly improves its relative crystallinity. Summary of the Invention

[0010] The purpose of this invention is to provide a dual-template method for preparing highly crystallinity AlPO-18 molecular sieves, thereby solving the problems of low crystallinity and high production costs in the synthesis of AlPO-18 molecular sieves.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] A method for preparing highly crystalline AlPO-18 molecular sieve using a dual-template method is characterized by the following steps: placing a phosphorus source, deionized water, an aluminum source, a template agent, and seed crystals in a hydrothermal reactor in sequence and stirring until homogeneous; aging the mixture at room temperature for a certain period of time; sealing the hydrothermal reactor and placing it in a reactor for static crystallization at high temperature; washing, drying, and calcining the hydrothermal crystallization product to obtain a highly crystalline tetrahedral AlPO-18 molecular sieve.

[0013] The molar ratio of phosphorus source, aluminum source, primary template agent one (TEAOH), secondary template agent two (TEACl), and water is 0.7–1:1:0.938–1.34:1.34–2.34:40–45; wherein, the phosphorus source, aluminum source, and template agent are selected according to the ratio of P2O5, Al2O3, and TEA. + count;

[0014] The phosphorus source is an 80%–90% phosphoric acid solution.

[0015] The aluminum source is either boehmite or liquid sodium.

[0016] The seed crystals are self-made, and their specific preparation method is as follows: phosphorus source, water, aluminum source, hydrochloric acid, and template agent are placed in a hydrothermal reactor in sequence and stirred evenly. After aging at room temperature for a certain period of time, the hydrothermal reactor is sealed and placed in a reactor for static crystallization at 150-180℃. After washing and drying the hydrothermal crystallization product, AlPO-18 molecular sieve seed crystals can be obtained. The amount of seed crystals added is 5% of the mass fraction of aluminum oxide in the raw material aluminum source.

[0017] The aging time is 8 to 16 hours.

[0018] The crystallization temperature is 150–180℃, and the crystallization time is 60–80 h.

[0019] The roasting temperature is 450–600℃, and the roasting time is 4–12 hours.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. This invention uses tetraethylammonium hydroxide and tetraethylammonium chloride as template agents. Some of the expensive tetraethylammonium hydroxide template agent is replaced by tetraethylammonium chloride, which greatly reduces the production cost and provides certain conditions for subsequent industrial production, thereby solving the problem of high production cost in the synthesis of AlPO-18 molecular sieve.

[0022] 2. The AlPO-18 molecular sieve synthesized in this invention has a relatively regular quadrilateral thin-plate morphology and a crystallinity 1.5 times that of the single-template method. Compared with other AlPO-18 molecular sieves, it has a more regular morphology and a higher relative crystallinity, effectively solving the problem of low crystallinity in the current industrial production of AlPO-18 molecular sieves.

[0023] 3. The synthesis method of AlPO-18 molecular sieve of the present invention is simple to operate, low in cost, and has relatively high crystallinity, and has broad prospects for industrial production and application. Attached Figure Description

[0024] Figure 1 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Example 1.

[0025] Figure 2 This is the SEM spectrum of the AlPO-18 molecular sieve prepared in Example 1.

[0026] Figure 3 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Example 2.

[0027] Figure 4 This is the SEM image of the AlPO-18 molecular sieve prepared in Example 2.

[0028] Figure 5 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Example 3.

[0029] Figure 6 This is the SEM spectrum of the AlPO-18 molecular sieve prepared in Example 3.

[0030] Figure 7 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Example 4.

[0031] Figure 8 This is the SEM spectrum of the AlPO-18 molecular sieve prepared in Example 4.

[0032] Figure 9 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Example 5.

[0033] Figure 10 This is the SEM image of the AlPO-18 molecular sieve prepared in Example 5.

[0034] Figure 11 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Example 6.

[0035] Figure 12 This is the SEM image of the AlPO-18 molecular sieve prepared in Example 6.

[0036] Figure 13 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Example 7.

[0037] Figure 14 This is the SEM image of the AlPO-18 molecular sieve prepared in Example 7.

[0038] Figure 15 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Example 8.

[0039] Figure 16 This is the SEM image of the AlPO-18 molecular sieve prepared in Example 8.

[0040] Figure 17 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Comparative Example 1.

[0041] Figure 18 This is the SEM spectrum of the AlPO-18 molecular sieve prepared in Comparative Example 1.

[0042] Figure 19 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Comparative Example 2.

[0043] Figure 20 This is the SEM image of the AlPO-18 molecular sieve prepared in Comparative Example 2.

[0044] Figure 21 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Comparative Example 3.

[0045] Figure 22 This is the SEM image of the AlPO-18 molecular sieve prepared in Comparative Example 3.

[0046] Figure 23 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Comparative Example 4.

[0047] Figure 24 This is the SEM image of the AlPO-18 molecular sieve prepared in Comparative Example 4.

[0048] Figure 25 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Comparative Example 5.

[0049] Figure 26 This is the SEM image of the AlPO-18 molecular sieve prepared in Comparative Example 5.

[0050] Figure 27 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Comparative Example 6.

[0051] Figure 28 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Comparative Example 7.

[0052] Figure 29 This is the SEM image of the AlPO-18 molecular sieve prepared in Comparative Example 7.

[0053] Figure 30 shows the XRD pattern of the AlPO-18 molecular sieve prepared in Comparative Example 8.

[0054] Figure 31 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Comparative Example 9.

[0055] Figure 32 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Comparative Example 10.

[0056] Figure 33 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Comparative Example 11.

[0057] Figure 34 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Comparative Example 12.

[0058] Figure 35 This is the XRD pattern of the AlPO-18 molecular sieve prepared in Comparative Example 13. Detailed Implementation

[0059] The present invention will be further described in detail below with reference to embodiments, in order to better understand the content of the present invention, rather than to limit the present invention.

[0060] Example 1:

[0061] 4.57 g of distilled water, 7.89 g of boehmite, and 11.84 g of phosphoric acid were added to a 100 ml hydrothermal reactor and stirred until homogeneous. While stirring, 0.4 g of 37.5% hydrochloric acid and 40.54 g of 25% tetraethylammonium hydroxide were added sequentially. The mixture was aged at room temperature for 4 hours, then sealed and placed in a static reactor. Static hydrothermal crystallization was carried out at 170℃ for 72 hours. The hydrothermal crystallization product was washed, dried, and calcined at 550℃ for 4 hours to synthesize highly crystalline pure-phase AlPO-18 molecular sieve seed crystals. The XRD and SEM images of the sample are shown below. Figure 1 , Figure 2 As shown in the figure, the obtained molecular sieve exhibits characteristic peaks of the AEI structure at approximately 2θ values ​​of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, indicating the synthesis of a pure-phase AlPO-18 molecular sieve with a relative crystallinity of 100%. Its morphology consists of small hexagonal crystals with relatively uniform dispersion.

[0062] Example 2:

[0063] 13.93 g of distilled water, 7.89 g of boehmite, and 11.84 g of phosphoric acid were added to a 100 ml hydrothermal reactor and stirred until homogeneous. While stirring, 28.38 g of tetraethylammonium hydroxide (25% by mass) was slowly added, and stirring continued until homogeneous. Then, 11.4 g of tetraethylammonium chloride and 0.26 g of AlPO-18 seed crystals prepared in Example 1 were added. The mixture was aged at room temperature for 8 hours, then sealed and placed in a static reactor. Static hydrothermal crystallization was performed at 170 °C for 72 hours. The hydrothermal crystallization product was washed, dried, and calcined at 550 °C for 5 hours to synthesize a highly crystalline pure-phase AlPO-18 molecular sieve. The mass of the obtained molecular sieve was measured to be 9.81 g. The XRD and SEM images of the sample are shown below. Figure 3 , Figure 4 As shown in the XRD and SEM images, the obtained molecular sieve exhibits characteristic peaks of the AEI structure at approximately 2θ values ​​of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, indicating the synthesis of a pure-phase AlPO-18 molecular sieve with a relative crystallinity as high as 167.2%. Its morphology consists of quadrilateral crystals with relatively large particle sizes (0.6–1.3 μm).

[0064] Example 3

[0065] Example 3 differs from Example 2 only in the phosphoric acid content; the phosphoric acid content is 8.29 g. All other conditions are the same as in Example 2, resulting in the synthesis of a highly crystalline pure-phase AlPO-18 molecular sieve. The mass of the obtained molecular sieve was measured to be 8.49 g. The XRD and SEM images of the sample are shown below. Figure 5 , Figure 6 As shown in the XRD and SEM images, the obtained molecular sieve exhibits characteristic peaks of the AEI structure at approximately 2θ values ​​of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, indicating the synthesis of a pure-phase AlPO-18 molecular sieve with a relative crystallinity of 99.09%. Compared to Example 2, the decrease in the phosphorus-aluminum ratio resulted in a lower relative crystallinity. Most of its morphology is quadrilateral, but it is less regular than that of Example 2.

[0066] Example 4

[0067] Example 4 differs from Example 2 only in the content of phosphoric acid; the phosphoric acid content is 10.66 g. All other conditions are the same as in Example 2, resulting in the synthesis of a highly crystalline pure-phase AlPO-18 molecular sieve. The mass of the obtained molecular sieve was measured to be 8.41 g. The XRD and SEM images of the sample are shown below. Figure 7 , Figure 8 As shown in the XRD and SEM images, the obtained molecular sieve exhibits characteristic peaks of the AEI structure at approximately 2θ values ​​of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, indicating the synthesis of a pure-phase AlPO-18 molecular sieve with a relative crystallinity as high as 162.09%, which is significantly higher than that of Example 3. Its morphology consists of small-sized (0.2–0.6 μm) quadrilateral crystals, which are more regular in shape and more uniformly dispersed than those in Example 3.

[0068] Example 5

[0069] Example 5 differs from Example 2 only in the content of tetraethylammonium chloride; the content of tetraethylammonium chloride is 19.93 g. All other conditions are the same as in Example 2, resulting in the synthesis of a highly crystalline pure-phase AlPO-18 molecular sieve. The mass of the obtained molecular sieve was measured to be 8.24 g. The XRD and SEM images of the sample are shown below. Figure 9 , Figure 10 As shown in the XRD and SEM images, the obtained molecular sieve exhibits characteristic peaks of the AEI structure at approximately 2θ values ​​of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, indicating the synthesis of a pure-phase AlPO-18 molecular sieve with a relative crystallinity of 88.67%, which is significantly lower than that of Example 2. Its morphology is quadrilateral, and the grain size (0.2–0.4 μm) is smaller than that of Example 2.

[0070] Example 6

[0071] Example 6 differs from Example 2 only in the content of tetraethylammonium chloride; the content of tetraethylammonium chloride is 15.96 g. All other conditions are the same as in Example 2, resulting in the synthesis of a highly crystalline pure-phase AlPO-18 molecular sieve. The mass of the obtained molecular sieve was measured to be 8.54 g. The XRD pattern and SEM image of the sample are shown below. Figure 11 , Figure 12 As shown in the XRD and SEM images, the obtained molecular sieve exhibits characteristic peaks of the AEI structure at approximately 2θ values ​​of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, indicating the synthesis of a pure-phase AlPO-18 molecular sieve with a relative crystallinity as high as 149.42%, which is significantly higher than that of Example 5. The morphology is a quadrilateral crystal with a larger grain size (1–2 μm) compared to Example 5.

[0072] Example 7

[0073] Example 7 differs from Example 2 only in the water content; the water content is 9.08 g. All other conditions are the same as in Example 2, resulting in the synthesis of a highly crystalline pure-phase AlPO-18 molecular sieve. The mass of the obtained molecular sieve was measured to be 8.43 g. The XRD and SEM images of the sample are shown below. Figure 13 , Figure 14 As shown in the XRD and SEM images, the obtained molecular sieve exhibits characteristic peaks of the AEI structure at approximately 2θ values ​​of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, indicating the synthesis of a pure-phase AlPO-18 molecular sieve with a relative crystallinity as high as 121.8%, which is slightly lower than that of Example 2. The morphology consists of quadrilateral crystals with a relatively uniform particle size distribution (0.8–1.2 μm).

[0074] Example 8

[0075] Example 8 differs from Example 2 only in the water content; the water content is 15g. All other conditions are the same as in Example 2, resulting in the synthesis of a highly crystalline pure-phase AlPO-18 molecular sieve. The mass of the obtained molecular sieve was measured to be 9.21g. The XRD and SEM images of the sample are shown below. Figure 15 , Figure 16 As shown in the XRD and SEM images, the obtained molecular sieve exhibits characteristic peaks of the AEI structure at approximately 2θ values ​​of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, indicating the synthesis of a pure-phase AlPO-18 molecular sieve with a relative crystallinity as high as 120.94%, which is slightly lower than that of Example 2. The morphology consists of quadrilateral crystals with a grain size of approximately 0.5–1.5 μm.

[0076] Comparative Example 1:

[0077] Using the exact same conditions and procedures as in Example 2, the difference was that when the content of tetraethylammonium hydroxide, i.e., the amount of tetraethylammonium hydroxide, was 24.36 g, the AlPO-18 molecular sieve obtained had a relative crystallinity of less than 60% and contained impurities, with a purity of less than 50%. The XRD and SEM images of the sample are shown below. Figure 17 , Figure 18 As shown in the XRD and SEM images, it can be found that the obtained sample not only shows the characteristic peaks of the AEI structure at approximately 2θ of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, but also the characteristic peaks of the AFI configuration at approximately 2θ of 7.5°, 19.8°, 21.13°, and 22.5°, indicating that the synthesized sample contains a certain amount of heterocrystalline phase AlPO-5; its morphology consists of spherical AlPO-5 and quadrilateral AlPO-18 molecular sieve crystals.

[0078] Comparative Example 2

[0079] Using the exact same conditions and procedures as in Example 4, the difference was that when the phosphoric acid content, i.e., the mass of phosphoric acid, was 14.21 g, the relative crystallinity of the obtained AlPO-18 molecular sieve was less than 60%, and the purity was less than 50%. The XRD and SEM images of the samples are shown below. Figure 19 , Figure 20 As shown in the XRD and SEM images, it can be found that the obtained sample not only shows the characteristic peaks of the AEI structure at approximately 2θ of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, but also the characteristic peaks of the AFI configuration at approximately 2θ of 7.5°, 19.8°, 21.13°, and 22.5°, indicating that the synthesized sample contains a certain amount of heterocrystalline phase AlPO-5; its morphology consists of spherical AlPO-5 and quadrilateral AlPO-18 molecular sieve crystals.

[0080] Comparative Example 3

[0081] Using the exact same conditions and procedures as in Example 6, the difference was that when the content of tetraethylammonium chloride, i.e., the amount of tetraethylammonium chloride, was 8.87 g, the relative crystallinity of the obtained AlPO-18 molecular sieve was less than 60% and impurities were present, resulting in a purity of less than 50%. The XRD and SEM images of the sample are shown below. Figure 21 , Figure 22As shown in the XRD and SEM images, it can be found that the obtained sample not only shows the characteristic peaks of the AEI structure at approximately 2θ of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, but also the characteristic peaks of the AFI configuration at approximately 2θ of 7.5°, 19.8°, 21.13°, and 22.5°, indicating that the synthesized sample contains a certain amount of heterocrystalline phase AlPO-5; its morphology consists of spherical AlPO-5 and quadrilateral AlPO-18 molecular sieve crystals.

[0082] Comparative Example 4

[0083] Using the exact same conditions and procedures as in Example 7, the difference was that when the water content, specifically the mass of water, was 16.5 g, the relative crystallinity of the obtained AlPO-18 molecules was less than 60%, and the purity was less than 50%. The XRD and SEM images of the samples are shown below. Figure 23 , Figure 24 As shown in the XRD and SEM images, it can be found that the obtained sample not only shows the characteristic peaks of the AEI structure at approximately 2θ of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, but also the characteristic peaks of the AFI configuration at approximately 2θ of 7.5°, 19.8°, 21.13°, and 22.5°. This indicates that the synthesized sample contains a large amount of heterocrystalline AlPO-5, and its morphology is mainly spherical AlPO-5 crystals.

[0084] Comparative Example 5

[0085] Using the exact same conditions and procedures as in Example 8, except that the water content (i.e., the mass of water) was 10.37 g, the crystallinity of the resulting AlPO-18 molecular sieve was as low as 55.42%. The XRD and SEM images of the sample are shown below. Figure 25 , Figure 26 As shown in the XRD and SEM images, it can be seen that the obtained sample not only shows the characteristic peaks of the AEI structure at 2θ of approximately 9.6°, 12.8°, 16.8°, 21°, and 23.6°, indicating that the synthesized sample is an AlPO-18 crystal phase; its morphology is a quadrilateral crystal with a particle size of 100–600 nm.

[0086] Comparative Example 6

[0087] Using the exact same conditions and procedures as in Example 2, the difference was the crystallization time: when the crystallization time was 30 hours, the resulting AlPO-18 molecular sieve had a relative crystallinity of less than 60% and contained impurities, with a purity of less than 50%. The XRD pattern of the sample is shown below. Figure 27As shown in the XRD and SEM images, it can be found that the obtained sample not only shows the characteristic peaks of the AEI structure at approximately 2θ of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, but also shows a weak characteristic peak of the AFI configuration at approximately 2θ of 7.5°, indicating that the synthesized sample contains a certain amount of heterocrystalline phase AlPO-5.

[0088] Comparative Example 7

[0089] 3.95 g of distilled water, 7.89 g of boehmite, and 11.84 g of phosphoric acid were added to a 100 ml hydrothermal reactor and stirred until homogeneous. While stirring, 1.4 g of 37.5% hydrochloric acid and 40.54 g of 25% tetraethylammonium hydroxide were added sequentially. The mixture was aged at room temperature for 4–6 hours, then sealed and placed in a static reactor. Static hydrothermal crystallization was carried out at 170℃ for 72 hours. The hydrothermal crystallization product was washed, dried, and calcined at 550℃ for 4–12 hours. The resulting AlPO-18 molecular sieve had a relative crystallinity as low as 65.25% and contained impurities. The XRD and SEM images of the sample are shown below. Figure 28 , Figure 29 As shown in the figure, it can be seen that the obtained molecular sieve exhibits characteristic peaks of the AEI structure at approximately 2θ values ​​of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, and also shows characteristic peaks of the AFI configuration at approximately 2θ value of 7.5°, indicating that the synthesized sample contains a certain amount of heterocrystalline phase AlPO-5.

[0090] Comparative Example 8:

[0091] Using the exact same conditions and procedures as in Example 2, the difference was the amount of seed crystal added. Without seed crystals, the resulting AlPO-18 molecular sieve had a relative crystallinity of less than 70% and contained impurities, with a purity of less than 50%. The XRD pattern of the sample is shown in Figure 30. The XRD pattern reveals that the obtained sample not only exhibited characteristic peaks of the AEI structure at approximately 2θ values ​​of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, but also a characteristic peak of the AFI configuration at approximately 2θ value of 7.5°, indicating that the synthesized sample contained a certain amount of impurity AlPO-5 phase.

[0092] Comparative Example 9:

[0093] 41.92 g of distilled water, 3.94 g of boehmite, and 5.92 g of phosphoric acid were added to a 100 ml hydrothermal reactor and stirred until homogeneous. While stirring, 15.13 g of tetraethylammonium hydroxide (25% by mass) was slowly added, and stirring continued until homogeneous. Then, 2.69 g of N,N-diisopropylethylamine was added. The mixture was aged at room temperature for 8–16 h, then sealed and placed in a static reactor. Static hydrothermal crystallization was performed at 180 °C for 48 h. The hydrothermal crystallized product was washed, dried, and calcined at 550 °C for 5 h. The resulting AlPO-18 molecular sieve had a relative crystallinity of 89.89% but contained impurities. The XRD pattern of the sample is shown below. Figure 31 As shown in the XRD pattern, the obtained sample not only showed characteristic peaks of the AEI structure at approximately 2θ of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, but also characteristic peaks of the AFI configuration at approximately 2θ of 7.5°, indicating that the synthesized sample contains a certain amount of heterocrystalline phase AlPO-5.

[0094] Comparative Example 10:

[0095] Using the exact same conditions and procedures as in Example 2, the differences were: the type of template agent and the amount of seed crystals added, specifically, replacing tetraethylammonium chloride with N,N-diisopropylethylamine and not adding any seed crystals. The XRD pattern of the AlPO-18 molecular sieve sample is shown below. Figure 32 As shown in the XRD pattern, the obtained sample exhibits characteristic peaks of the AEI structure at approximately 2θ values ​​of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, but its relative crystallinity is as low as 23.85%.

[0096] Comparative Example 11:

[0097] Using the exact same conditions and procedures as in Example 2, the difference lies in the type of template agent. Specifically, N,N-diisopropylethylamine was used instead of tetraethylammonium chloride. The resulting AlPO-18 molecular sieve exhibited a relative crystallinity of less than 50% and contained impurities. The XRD pattern of the sample is shown below. Figure 33 As shown in the XRD pattern, the obtained sample not only showed characteristic peaks of the AEI structure at approximately 2θ of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, but also characteristic peaks of the AFI configuration at approximately 2θ of 7.5°, indicating that the synthesized sample contains a certain amount of heterocrystalline phase AlPO-5.

[0098] Comparative Example 12:

[0099] Using the exact same conditions and procedures as in Example 2, the differences were: the type of aluminum source and template agent, and the amount of seed crystals added. Specifically, aluminum isopropoxide was used as the aluminum source, N,N-diisopropylethylamine was used instead of tetraethylammonium chloride, and no seed crystals were added. The resulting AlPO-18 molecular sieve had a relative crystallinity of less than 50% and contained impurities, with a purity of less than 50%. The XRD pattern of the sample is shown below. Figure 34 As shown in the XRD pattern, the obtained sample not only showed characteristic peaks of the AEI structure at approximately 2θ of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, but also characteristic peaks of the AFI configuration at approximately 2θ of 7.5°, indicating that the synthesized sample contains a certain amount of heterocrystalline phase AlPO-5.

[0100] Comparative Example 13:

[0101] Using the exact same conditions and procedures as in Example 2, the difference lies in the type of aluminum source and template agent. Specifically, when aluminum isopropoxide is used as the aluminum source and N,N-diisopropylethylamine is used instead of tetraethylammonium chloride, the resulting AlPO-18 molecular sieve has a relative crystallinity of less than 50% and contains impurities. The XRD pattern of the sample is shown below. Figure 35 As shown in the XRD pattern, the obtained sample not only showed characteristic peaks of the AEI structure at approximately 2θ of 9.6°, 12.8°, 16.8°, 21°, and 23.6°, but also characteristic peaks of the AFI configuration at approximately 2θ of 7.5°, indicating that the synthesized sample contains a certain amount of heterocrystalline phase AlPO-5.

[0102] Table 1. Crystal phases of AlPO-18 molecular sieves synthesized by different methods

[0103]

Claims

1. A method for preparing highly crystallinity AlPO-18 molecular sieve using a dual-template method, characterized in that, The process includes the following steps: Phosphorus source, deionized water, aluminum source, template agent and seed crystals are placed in a hydrothermal reactor in sequence and stirred evenly. After aging at room temperature for a certain period of time, the hydrothermal reactor is sealed and placed in a reactor for static crystallization at high temperature. The hydrothermal crystallization product is washed, dried and calcined to obtain a highly crystalline tetrahedral AlPO-18 molecular sieve. The molar ratio of phosphorus source, aluminum source, template agent 1 (TEAOH), template agent 2 (TEACl), and water is 0.7–1:1:0.938–1.34:1.34–2.34:40–45; wherein, the phosphorus source, aluminum source, and template agent are selected according to the ratio of P2O5, Al2O3, and TEA... + count; The aluminum source is boehmite; The preparation method of the seed crystal is as follows: phosphorus source, water, aluminum source, hydrochloric acid and template agent are placed in a hydrothermal reactor in sequence and stirred evenly. After aging at room temperature for a certain period of time, the hydrothermal reactor is sealed and placed in a reactor for static crystallization at 150-180℃. After washing and drying the hydrothermal crystallization product, AlPO-18 molecular sieve seed crystals can be obtained. The amount of seed crystal added is 5% of the mass fraction of aluminum oxide in the raw material aluminum source.

2. The preparation method according to claim 1, characterized in that, The phosphorus source is an 80%–90% phosphoric acid solution.

3. The preparation method according to claim 1, characterized in that, The aging time is 8 to 16 hours.

4. The preparation method according to claim 1, characterized in that, The crystallization temperature is 150–180℃, and the crystallization time is 60–80 h.

5. The preparation method according to claim 1, characterized in that, The roasting temperature is 450–600℃, and the roasting time is 4–12 hours.

6. The highly crystallinity AlPO-18 molecular sieve prepared by any one of the methods described in claims 1-5.

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