Self-supporting SAPO-11 molecular sieve, its preparation method and application

Abstract

This invention relates to the field of molecular sieve synthesis, specifically to a self-supporting SAPO-11 molecular sieve, its preparation method, and its applications. The molecular sieve is a loose, spherical aggregate with a diameter of 2-80 μm, formed by the aggregation of primary thin-film crystals with a thickness of 15-50 nm. The average pore size of the molecular sieve is 30-55 nm, and the median pore size is 40-65 nm. This molecular sieve has a smaller scale in a certain direction, which is beneficial for the diffusion of small organic molecules and reduces the probability of carbon deposition during reactions, thus resulting in a longer service life in reactions compared to general crystals with the same structure.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve synthesis, specifically to a self-supporting SAPO-11 molecular sieve, its preparation method, and its applications. Background Technology

[0002] Molecular sieves are substances with uniform micropores, the size of which is comparable to that of ordinary molecules. They are widely used in petrochemicals, agriculture, environmental protection, and high-tech fields. While some molecular sieves can be obtained from nature, most molecular sieves used in catalysis are synthesized artificially. Hydrothermal synthesis is the most commonly used method for synthesizing molecular sieves, and some industrially important molecular sieves, such as type A, type X, type Y, and ZSM-5, can be obtained through hydrothermal synthesis. With advancements in synthesis technology and the diversification of synthesis methods, microwave and supercritical technologies have been applied to the synthesis of molecular sieves. SAPO-11 molecular sieve, due to its unique pore structure and acidity, exhibits excellent performance in carbon chain skeletal isomerization reactions, and has therefore been extensively studied.

[0003] US20180264447A1 used ethylene glycol as a solvent, and crystallized the product in a reactor at 200°C for 144 h with carbon dioxide to obtain small-crystal SAPO-11 molecular sieves; (Materials Letters 228(2018)61–64; https: / / doi.org / 10.1016 / j.matlet.2018.05.118) prepared SAPO-11 molecular sieves with a special screw morphology using ultrasonic pretreatment of the crystallization solution, di-n-propylamine as a template agent, and ethanol as a solvent; (Fuel 255(2019)115821; https: / / doi.org / 10.1016 / j.fuel.2019.115821) used complex polymers (F127, EO... 106 PO 70 EO 106 Using a mesoporous pore-forming agent, hierarchical SAPO-11 molecular sieves were obtained in a supercritical carbon dioxide system. Patent CN108996518A describes the preparation of SAPO-11 molecular sieves with hierarchical pores by post-treating them with solid acid under different conditions.

[0004] In addition, RyongRyoo's research group published an article (Nature, 2009, 461(10):246-250) that first reported the use of long-chain biheaded quaternary ammonium salts as template agents to obtain self-supporting nanosheet MFI crystals, which significantly extended the lifetime of the product in the catalytic reaction due to the shortened diffusion path. Our research group discovered in our experiments that self-supporting SAPO-11 molecular sieves can also be obtained using monoheaded quaternary ammonium salts with the assistance of imidazole compounds. To date, no SAPO-11 molecular sieves with this morphology have been reported.

[0005] Existing technologies and research have revealed that diethylamine, dipropylamine, or diisopropylamine are commonly used template agents for synthesizing SAPO-11. However, the resulting molecular sieves generally have relatively large crystal sizes. To reduce crystal size, expensive surfactants (such as hexadecyltrimethylammonium bromide) and special additives like HF(aq) are typically added, which is not conducive to industrial scale-up, and the crystal size (thickness) is still not small enough. While the microwave method offers significant advantages in terms of time and cost, it is prone to crystal transformation during crystallization, generating impurity phases, which is detrimental to the preparation of pure-phase SAPO-11 molecular sieves. Furthermore, the microwave method is not suitable for large-scale industrial production.

[0006] In view of the shortcomings of existing technologies, this invention aims to propose a preparation method not covered by existing technologies, which does not require the addition of additional surfactants or the use of environmentally harmful substances. The raw materials are inexpensive and readily available, the operation is simple, the reproducibility is good, and it is easy to scale up for industrial production. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of large size and high preparation cost of self-supporting SAPO-11 molecular sieves in the prior art, and to provide a self-supporting SAPO-11 molecular sieve, its preparation method and application, which has the characteristics of small size and low preparation cost.

[0008] To achieve the above objectives, the first aspect of the present invention provides a self-supporting SAPO-11 molecular sieve, which is a fluffy spherical aggregate with a diameter of 2-80 μm. The spherical aggregate is formed by the aggregation of primary thin-film crystals with a thickness of 15-50 nm. The average pore size of the molecular sieve is 30-55 nm, and the median pore size is 40-65 nm.

[0009] A second aspect of the present invention provides a method for preparing the molecular sieve described herein, the method comprising: preparing a hydrothermal reaction mixture using a phosphorus source, an aluminum source, a silicon source, a structure directing agent R1, and an additive R2; aging and crystallizing the reaction mixture; wherein the molar ratio of each substance is: (0.01-0.5)SiO2:(0.8-1.2)Al2O3:1P2O5:(0.2-0.95)R1:(0.3-1.0)R2:(45-110)H2O; the structure directing agent R1 is selected to have the structure shown in formula (I); the additive R2 is an imidazole compound;

[0010]

[0011] In formula (I), n = 5-6; R1, R2, R3, R4, and R5 are each independently selected from straight-chain alkyl groups with 1-3 carbon atoms or straight-chain alkyl groups substituted with hydroxyl groups, and may be the same or different.

[0012] A third aspect of the present invention provides an application of the molecular sieve described above in catalyst preparation.

[0013] Through the above technical solution, the present invention has the following beneficial effects:

[0014] This invention provides a self-supporting SAPO-11 molecular sieve with small crystal size. The molecular sieve has a small size in a certain direction, which is conducive to the diffusion of small organic molecules and reduces the probability of carbon deposition in the reaction. Therefore, it has a longer service life in the reaction than ordinary crystals with the same structure.

[0015] The catalyst described in this invention is prepared using a method that eliminates the need for ultrasonic or microwave treatment during synthesis, and avoids the addition of complex organic surfactants and environmentally harmful substances such as HF, making the preparation process simple, economical, and environmentally friendly. The raw materials are inexpensive and readily available, offering significant advantages in practical industrial applications.

[0016] Using the molecular sieve described in this invention for catalyst preparation can significantly improve catalyst lifespan. Attached Figure Description

[0017] Figure 1 The XRD pattern of the molecular sieve in Example 1;

[0018] Figure 2 This is a SEM image of the molecular sieve from Example 1, magnified 20,000 times.

[0019] Figure 3 This is a 2,000x magnified SEM image of the molecular sieve from Example 1.

[0020] Figure 4 The XRD pattern of the molecular sieve in Comparative Example 1 is shown.

[0021] Figure 5 The image is a SEM image of the molecular sieve from Comparative Example 1, magnified 20,000 times.

[0022] Figure 6 This is the XRD plot of Comparative Example 2. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] The first aspect of the present invention provides a self-supporting SAPO-11 molecular sieve, which is a fluffy spherical aggregate with a diameter of 2-60 μm. The spherical aggregate is formed by the aggregation of primary thin-film crystals with a thickness of 15-50 nm. The average pore size of the molecular sieve is 30-55 nm, and the median pore size is 40-65 nm.

[0025] This invention provides a self-supporting SAPO-11 molecular sieve with small grain size. This molecular sieve has a small size in a certain direction, which is conducive to the diffusion of small organic molecules and reduces the probability of carbon deposition in the reaction. Therefore, it should have a longer service life in the reaction than ordinary grains with the same structure.

[0026] According to a preferred embodiment of the present invention, the molecular sieve is a fluffy spherical aggregate with a diameter of 2-60 μm, wherein the spherical aggregate is formed by the aggregation of primary thin-film crystals with a thickness of 20-50 nm, and the average pore size of the molecular sieve is 40-50 nm, and the median pore size is 45-55 nm.

[0027] A second aspect of the present invention provides a method for preparing the molecular sieve described herein, the method comprising: preparing a hydrothermal reaction mixture using a phosphorus source, an aluminum source, a silicon source, a structure directing agent R1, and an additive R2; aging and crystallizing the reaction mixture; wherein the molar ratio of each substance is: (0.01-0.5)SiO2:(0.8-1.2)Al2O3:1P2O5:(0.2-0.95)R1:(0.3-1.0)R2:(45-110)H2O; the structure directing agent R1 is selected to have the structure shown in formula (I); the additive R2 is an imidazole compound;

[0028]

[0029] In formula (I), n = 5-6; R1, R2, R3, R4, and R5 are each independently selected from straight-chain alkyl groups with 1-3 carbon atoms or straight-chain alkyl groups substituted with hydroxyl groups, and may be the same or different.

[0030] The catalyst described in this invention is prepared using a method that eliminates the need for ultrasonic or microwave treatment during synthesis, and avoids the addition of complex organic surfactants and environmentally harmful substances such as HF, making the preparation process simple, economical, and environmentally friendly. The raw materials are inexpensive and readily available, offering significant advantages in practical industrial applications.

[0031] In this invention, the silicon source can be a silicon-containing compound commonly used in the art. According to a preferred embodiment of this invention, the silicon source is selected from at least one of silica sol and fumed silica.

[0032] In this invention, the aluminum source can be a common aluminum-containing compound in the art. According to a preferred embodiment of this invention, the aluminum source is selected from at least one of boehmite, aluminum isopropoxide, aluminum sulfate, aluminum chloride, and aluminum hydroxide.

[0033] In this invention, the phosphorus source can be a phosphorus-containing compound commonly used in the art. According to a preferred embodiment of this invention, the phosphorus source is selected from at least one of phosphoric acid, phosphorous acid, ammonium hydrogen phosphate, and ammonium dihydrogen phosphate.

[0034] According to a preferred embodiment of the present invention, the method further includes cooling, separating, washing, drying and calcining the crystallized product.

[0035] According to a preferred embodiment of the present invention, the conditions for cooling, separation and washing can be conventional choices in the art, and are not particularly limited in the present invention.

[0036] In this invention, the drying conditions can be conventionally selected in the art. According to a preferred embodiment of the invention, the drying conditions include: a drying temperature of 50-200°C, preferably 80-120°C, and / or a drying time of 5-30 hours, preferably 8-15 hours.

[0037] In this invention, the calcination conditions can be conventionally selected in the art. According to a preferred embodiment of this invention, the calcination conditions include: a calcination temperature of 350-700℃, preferably 450-600℃; and / or a calcination time of 1-15h, preferably 5-8h.

[0038] According to a preferred embodiment of the present invention, the crystallized product is cooled, separated, and washed before drying. The conditions for cooling, separation, and washing can be conventional choices in the art, as long as they can achieve the purpose of the present invention.

[0039] In this invention, the aging conditions can be conventionally selected in the art. According to a preferred embodiment of this invention, the aging conditions include: an aging temperature of 20-40°C and an aging time of 2-15 hours.

[0040] In this invention, the crystallization conditions can be conventionally selected in the art. According to a preferred embodiment of this invention, the crystallization conditions include: a crystallization temperature of 180-210℃, preferably 190-205℃; and / or a crystallization time of 2-24h, preferably 4-18h.

[0041] According to a preferred embodiment of the present invention, the aging and crystallization can be carried out in a crystallization kettle lined with polytetrafluoroethylene, preferably using dynamic aging and crystallization, and more preferably aging and crystallization under stirring conditions.

[0042] According to a preferred embodiment of the present invention, the molar ratio of each substance in the reaction mixture is: (0.05-0.3)SiO2:(0.8-1.0)Al2O3:1P2O5:(0.2-0.5)R1:(0.3-0.8)R2:(60-90)H2O.

[0043] According to a preferred embodiment of the present invention, the imidazole compound is selected from at least one of imidazole, 1-methylimidazolium, 1-ethylimidazolium, 1-propylimidazolium, 1-butylimidazolium, 1-(2-aminoethyl)imidazolium, and 1-(3-aminopropyl)imidazolium.

[0044] According to a preferred embodiment of the present invention, the structure directing agent R1 is selected from at least one of N,N-dimethylaminohexyl-2-hydroxyethyldimethylammonium bromide, N,N-dimethylaminohexyl-2-ethyldimethylammonium bromide, and hexamethyldiammonium.

[0045] In this invention, the preparation steps of the hydrothermal reaction mixture can be conventional choices in the art. According to a preferred embodiment of this invention, the preparation steps of the hydrothermal reaction mixture are as follows:

[0046] 1) Dissolve the aluminum source and phosphorus source in water to obtain mixed solution I;

[0047] 2) Add a mixture of template agent R1, additive R2 and water to mixture I to obtain mixture II;

[0048] 3) Add a silicon source to mixture II to obtain a hydrothermal reaction mixture.

[0049] A third aspect of the present invention provides an application of the molecular sieve described above in catalyst preparation.

[0050] Using the molecular sieve described in this invention for catalyst preparation can significantly improve catalyst lifespan.

[0051] The present invention will be described in detail below through embodiments. In the following embodiments, the structure of the molecular sieve is determined by X-ray diffraction (XRD), which is measured by X-ray powder diffraction (XRD) using a Cu-Kα ray source with a Kα1 wavelength λ = 1.5405980 angstroms. A nickel filter was used, operating at 40 kV and 40 mA, with a scanning range of 3–50°. Product morphology was captured using a Japanese emission scanning electron microscope (Fe-SEM). Average and median pore sizes were determined using a mercury porosimeter, with the following specifications: Pascal 140 low-pressure mercury porosimeter: pore size: 116–3.8 μm, pressure range: 0.1–400 kPa; Pascal 240 high-pressure mercury porosimeter: pore size: 15–0.0074 μm, maximum pressure: 200 MPa.

[0052] Unless otherwise specified, all raw materials are commercially available products.

[0053] Example 1

[0054] Weigh 1.9 g of boehmite (containing 70 wt% alumina, the same below), add 9 g of water, then add 3.45 g of 85% phosphoric acid, and stir at room temperature for 3 h to obtain mixture I; then add a mixture of 1.32 g of 1-(3-aminopropyl)imidazolium and 3.8 g of water, and a mixture of 1.5 g of 6-N,N-dimethylaminohexyl-2-hydroxyethyldimethylammonium bromide and 10 g of water to mixture I, and stir at room temperature for 4 h to obtain mixture II; then add 0.09 g of nano-silica to mixture II and stir overnight. Crystallize at 200 °C for 7 h. Cool to room temperature, centrifuge, and wash. The obtained solid material is dried at 110 °C overnight and calcined at 550 °C for 5 h to obtain molecular sieve. Figure 1 The XRD pattern of the obtained molecular sieve shows that it is SAPO-11 molecular sieve. Figure 2 (Magnified 20,000 times) Figure 3 (Magnified 2000x) These are SEM images of the molecular sieve obtained by scanning electron microscopy at different magnifications. It can be seen that the molecular sieve is a self-supporting, loose, spherical aggregate formed by the aggregation of primary thin-film crystals. High-magnification SEM images show that the thickness of the nanosheets ranges from 20-50 nm, and the diameter of the spherical aggregates ranges from 20-50 μm. Mercury porosimetry pore size analysis determined that the average pore size of this molecular sieve is 41.76 nm, and the median pore size is 51.28 nm.

[0055] Example 2

[0056] Weigh 1.9g of boehmite, add 9g of water, then add 3.45g of 85% phosphoric acid, and stir at room temperature for 3h to obtain mixture I; then add a mixture of 1.32g of 1-(3-aminopropyl)imidazolium and 3.8g of water, and a mixture of 1.8g of 6-N,N-dimethylaminohexyl-dimethyl-propylammonium bromide and 10g of water to mixture I, and stir at room temperature for 3h to obtain mixture II; then add 0.09g of nano-silica to mixture II and stir overnight. Crystallize at 200℃ for 7h. Cool to room temperature, centrifuge, and wash. The obtained solid material is dried at 110℃ overnight and calcined at 550℃ for 5h to obtain a molecular sieve. The XRD and SEM images of the prepared molecular sieve are the same as in Example 1, showing that the molecular sieve is SAPO-11 molecular sieve, which is a self-supporting, fluffy, spherical aggregate obtained by the aggregation of primary thin-plate crystals. High-magnification scanning electron microscopy revealed that the thickness of the nanosheets ranged from 20 to 50 nm, and the diameter of the spheroidal aggregates ranged from 20 to 50 μm. Mercury intrusion porosimetry determined the molecular sieve to have an average pore size of 40.95 nm and a median pore size of 53.768 nm.

[0057] Example 3

[0058] Weigh 1.9g of boehmite, add 9g of water, then add 3.45g of 85% phosphoric acid, and stir at room temperature for 3h to obtain mixture I; then add a mixture of 1.32g of 1-(3-aminopropyl)imidazolium and 10g of water, and a mixture of 1.5g of 6-N,N-dimethylaminohexyl-dimethyl-ethylammonium bromide and 7.5g of water to mixture I, and stir at room temperature for 4h to obtain mixture II; then add 0.09g of nano-silica to mixture II and stir overnight. Crystallize at 200℃ for 7h. Cool to room temperature, centrifuge, and wash. The obtained solid material is dried at 110℃ overnight and calcined at 550℃ for 5h to obtain a molecular sieve. The XRD and SEM images of the prepared molecular sieve are the same as in Example 1, showing that the molecular sieve is SAPO-11 molecular sieve, which is a self-supporting, fluffy, spherical aggregate obtained by the aggregation of primary thin-plate crystals. High-magnification scanning electron microscopy revealed that the thickness of the nanosheets ranged from 20 to 50 nm, and the diameter of the spheroidal aggregates ranged from 20 to 50 μm. Mercury intrusion porosimetry determined the molecular sieve to have an average pore size of 41.16 nm and a median pore size of 52.17 nm.

[0059] Example 4

[0060] Weigh 1.9g of boehmite, add 9g of water, then add 3.45g of 85% phosphoric acid, and stir at room temperature for 3h to obtain mixture I; then add a mixture of 1.1g of 1-(3-aminopropyl)imidazolium and 3.8g of water, and a mixture of 1.5g of 6-N,N-dimethylaminohexyl-2-hydroxyethyldimethylammonium bromide and 3.8g of water to mixture I, and stir at room temperature for 5h to obtain mixture II; then add 0.23g of 40% silica sol to mixture II and stir overnight. Crystallize at 185℃ for 20h. Cool to room temperature, centrifuge, and wash. The obtained solid material is dried at 110℃ overnight and calcined at 550℃ for 5h to obtain a molecular sieve. The XRD and SEM images of the prepared molecular sieve are the same as in Example 1, showing that the molecular sieve is SAPO-11 molecular sieve, which is a self-supporting, fluffy, spherical aggregate obtained by the aggregation of primary thin-plate crystals. High-magnification scanning electron microscopy revealed that the thickness of the nanosheets ranged from 20 to 50 nm, and the diameter of the spheroidal aggregates ranged from 20 to 50 μm. Mercury intrusion porosimetry determined the molecular sieve to have an average pore size of 41.99 nm and a median pore size of 53.64 nm.

[0061] Example 5

[0062] Weigh 1.9g of boehmite, add 9g of water, then add 3.45g of 85% phosphoric acid, and stir at room temperature for 3h to obtain mixture I. Then add a mixture of 1.32g of 1-(3-aminopropyl)imidazolium and 3.8g of water, and a mixture of 1.5g of 5-N,N-dimethylaminohexyl-2-hydroxyethyldimethylammonium bromide and 10g of water to mixture I, and stir at room temperature for 4h to obtain mixture II. Then add 0.23g of 40% silica sol to mixture II and stir overnight. Crystallize at 205℃ for 5h. Cool to room temperature, centrifuge, and wash. The obtained solid material is dried at 110℃ overnight and calcined at 550℃ for 5h to obtain a molecular sieve. The XRD and SEM images of the prepared molecular sieve are the same as in Example 1. It can be seen that the molecular sieve is SAPO-11 molecular sieve, which is a self-supported, fluffy, spherical aggregate obtained by the aggregation of primary thin-plate crystals. High-magnification scanning electron microscopy revealed that the thickness of the nanosheets ranged from 20 to 50 nm, and the diameter of the spheroidal aggregates ranged from 20 to 50 μm. Mercury intrusion porosimetry determined the average pore size of the molecular sieve to be 43.39 nm, with a median pore size of 56.08 nm.

[0063] Example 6

[0064] Weigh 1.9g of boehmite, add 9g of water, then add 3.45g of 85% phosphoric acid, and stir at room temperature for 3h to obtain mixture I; then add a mixture of 0.57g of 1-(3-aminopropyl)imidazolium and 3.8g of water, and a mixture of 1.5g of 6-N,N-dimethylaminohexyl-2-hydroxyethyldimethylammonium bromide and 3.8g of water to mixture I, and stir at room temperature for 3h to obtain mixture II; then add 0.09g of nano-silica to mixture II and stir overnight. Crystallize at 190℃ for 16h. Cool to room temperature, centrifuge, and wash. The obtained solid material is dried at 110℃ overnight and calcined at 550℃ for 5h to obtain a molecular sieve. The XRD and SEM images of the prepared molecular sieve are the same as in Example 1, showing that the molecular sieve is SAPO-11 molecular sieve, which is a self-supporting, fluffy, spherical aggregate obtained by the aggregation of primary thin-plate crystals. High-magnification scanning electron microscopy revealed that the thickness of the nanosheets ranged from 20 to 50 nm, and the diameter of the spheroidal aggregates ranged from 20 to 50 μm. Mercury intrusion porosimetry determined the molecular sieve to have an average pore size of 42.79 nm and a median pore size of 53.98 nm.

[0065] Example 7

[0066] Weigh 7.2g of aluminum isopropoxide, add 9g of water, stir at room temperature for 2 hours to fully hydrolyze, then add 3.45g of 85% phosphoric acid, and stir at room temperature for another 2 hours to obtain mixture I; then add a mixture of 1.32g of 1-(3-aminopropyl)imidazolium and 3.8g of water, and a mixture of 1.5g of 5-N,N-dimethylaminopentyl-2-hydroxyethyldimethylammonium bromide and 10g of water to mixture I, and stir at room temperature for 3 hours to obtain mixture II; then add 0.36g of nano-silica to mixture II and stir overnight. Crystallize at 200℃ for 7 hours. Cool to room temperature, centrifuge, and wash. The obtained solid material is dried at 110℃ overnight and calcined at 550℃ for 5 hours to obtain a molecular sieve. The XRD and SEM images of the prepared molecular sieve are the same as in Example 1, showing that the molecular sieve is SAPO-11 molecular sieve, which is a self-supporting, fluffy, spherical aggregate obtained by the aggregation of primary thin-film crystals. High-magnification scanning electron microscopy revealed that the thickness of the nanosheets ranged from 20 to 50 nm, and the diameter of the spheroidal aggregates ranged from 20 to 50 μm. Mercury intrusion porosimetry determined the molecular sieve to have an average pore size of 41.96 nm and a median pore size of 52.36 nm.

[0067] Example 8

[0068] Weigh 1.9g of boehmite, add 9g of water, then add 3.45g of 85% phosphoric acid, and stir at room temperature for 3h to obtain mixture I; then add a mixture of 0.93g imidazole and 3.8g of water, and a mixture of 1.5g of 6-N,N-dimethylaminohexyl-2-hydroxyethyldimethylammonium bromide and 10g of water to mixture I, and stir at room temperature for 4h to obtain mixture II; then add 0.09g of nano-silica to mixture II and stir overnight. Crystallize at 200℃ for 8h. Cool to room temperature, centrifuge, and wash. The obtained solid material is dried at 110℃ overnight and calcined at 550℃ for 5h to obtain a molecular sieve. The XRD and SEM images of the prepared molecular sieve are the same as in Example 1, showing that the molecular sieve is SAPO-11 molecular sieve, which is a self-supporting, fluffy, spherical aggregate obtained by the aggregation of primary thin-plate crystals. High-magnification scanning electron microscopy revealed that the thickness of the nanosheets ranged from 20 to 50 nm, and the diameter of the spheroidal aggregates ranged from 20 to 50 μm. Mercury intrusion porosimetry determined the molecular sieve to have an average pore size of 42.66 nm and a median pore size of 55.28 nm.

[0069] Example 9

[0070] Weigh 1.9g of boehmite, add 9g of water, then add 3.45g of 85% phosphoric acid, and stir at room temperature for 3h to obtain mixture I; then add a mixture of 1.5g of 1-propylimidazolium and 3.8g of water, and a mixture of 1.5g of 6-N,N-dimethylaminohexyl-2-hydroxyethyldimethylammonium bromide and 10g of water to mixture I, and stir at room temperature for 3h to obtain mixture II; then add 0.09g of nano-silica to mixture II and stir overnight. Crystallize at 200℃ for 8h. Cool to room temperature, centrifuge, and wash. The obtained solid material is dried at 110℃ overnight and calcined at 550℃ for 5h to obtain a molecular sieve. The XRD and SEM images of the prepared molecular sieve are the same as in Example 1, showing that the molecular sieve is SAPO-11 molecular sieve, which is a self-supporting, fluffy, spherical aggregate obtained by the aggregation of primary thin-plate crystals. High-magnification scanning electron microscopy revealed that the thickness of the nanosheets ranged from 20 to 50 nm, and the diameter of the spheroidal aggregates ranged from 20 to 50 μm. Mercury intrusion porosimetry determined the molecular sieve to have an average pore size of 43.47 nm and a median pore size of 54.73 nm.

[0071] Example 10

[0072] Weigh 1.9g of boehmite, add 9g of water, then add 3.45g of 85% phosphoric acid, and stir at room temperature for 3h to obtain mixture I. Then add a mixture of 1.11g of 1-methylimidazole and 3.8g of water, and a mixture of 1.5g of 6-N,N-dimethylaminohexyl-2-hydroxyethyldimethylammonium bromide and 10g of water to mixture I, and stir at room temperature for 5h to obtain mixture II. Then add 0.09g of nano-silica to mixture II and stir overnight. Crystallize at 200℃ for 8h. Cool to room temperature, centrifuge, and wash. The obtained solid material is dried at 110℃ overnight and calcined at 550℃ for 5h to obtain a molecular sieve. The XRD and SEM images of the prepared molecular sieve are the same as in Example 1. It can be seen that the molecular sieve is SAPO-11 molecular sieve, which is a self-supported, fluffy, spherical aggregate obtained by the aggregation of primary thin-plate crystals. High-magnification scanning electron microscopy revealed that the thickness of the nanosheets ranged from 20 to 50 nm, and the diameter of the spheroidal aggregates ranged from 20 to 50 μm. Mercury intrusion porosimetry determined the molecular sieve to have an average pore size of 44.76 nm and a median pore size of 55.46 nm.

[0073] Comparative Example 1

[0074] Same as Example 1, except that 1-(3-aminopropyl)imidazole is not added, while the ratio of other raw materials remains unchanged, to obtain a molecular sieve. Figure 4 The XRD pattern of the obtained molecular sieve shows that it is SAPO-11 molecular sieve. Figure 5 The image shows a SEM image of the molecular sieve obtained by scanning electron microscopy at 20,000x magnification. It can be seen that the molecular sieve is a non-spherical aggregate.

[0075] Comparative Example 2

[0076] Same as Example 1, except that 6-N,N-dimethylaminohexyl-2-hydroxyethyldimethylammonium bromide was not added, while the other raw material ratios remained unchanged, to obtain a molecular sieve. Figure 6 The XRD pattern of the obtained molecular sieve shows that the molecular sieve is not SAPO-11 molecular sieve.

[0077] The results of the embodiments show that the molecular sieve of the present invention has a small size and a long service life.

[0078] The preferred 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 combinations of 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 a self-supporting SAPO-11 molecular sieve, characterized in that, The method comprises: using a hydrothermal reaction mixture liquid prepared by mixing a phosphorus source, an aluminum source, a silicon source, a structure directing agent R1 and an additive R2, aging and crystallizing the reaction mixture liquid, wherein the molar ratio of each substance is (0.01-0.5) SiO2:(0.8-1.2) Al2O3:1 P2O5:(0.2-0.95) R1:(0.3-1.0) R2:(45-110) H2O; the structure directing agent R1 is selected from the group consisting of compounds having the structure shown in formula (I); and the additive R2 is an imidazole compound. Formula (I) In formula (I), n=5-6; R1, R2, R3, R4 and R5 are each independently selected from linear alkyl groups with 1-3 carbon atoms or linear alkyl groups substituted with a hydroxyl group, and can be the same or different.

2. The production method according to claim 1, wherein The method further comprises cooling, separating, washing, drying and calcining the crystallized product.

3. The preparation method according to claim 2, wherein, the drying conditions comprise a drying temperature of 50-200°C and / or a drying time of 5-30h; and / or the calcining conditions comprise a calcining temperature of 350-700°C and / or a calcining time of 1-15h.

4. The preparation method according to claim 3, wherein, the drying conditions comprise a drying temperature of 80-120°C and / or a drying time of 8-15h; and / or the calcining conditions comprise a calcining temperature of 450-600°C and / or a calcining time of 5-8h.

5. The preparation method according to claim 1, wherein, the aging conditions comprise an aging temperature of 20-40°C and an aging time of 2-15h; and / or the crystallization conditions comprise a crystallization temperature of 180-210°C and / or a crystallization time of 2-24h.

6. The preparation method according to claim 5, wherein, the crystallization conditions comprise a crystallization temperature of 190-205°C and / or a crystallization time of 4-18h.

7. The preparation method according to claim 1, wherein, the molar ratio of each substance in the reaction mixture liquid is (0.05-0.3) SiO2:(0.8-1.0) Al2O3:1 P2O5:(0.2-0.5) R1:(0.3-0.8) R2:(60-90) H2O.

8. The preparation method according to claim 1, wherein, the imidazole compound is at least one selected from the group consisting of imidazole, 1-methylimidazole, 1-ethylimidazole, 1-propylimidazole, 1-butylimidazole, 1-(2-aminoethyl)imidazole and 1-(3-aminopropyl)imidazole; and / or the structure directing agent R1 is at least one selected from the group consisting of N,N-dimethylamino hexyl-2-hydroxyethyl dimethyl ammonium bromide, N,N-dimethylamino hexyl-2-ethyl dimethyl ammonium bromide and hexamethonium.

9. The production process according to any one of claims 1 to 8, wherein The preparation steps of the hydrothermal reaction mixture liquid are as follows: 1) dissolving the aluminum source and the phosphorus source in water to obtain a mixture I; 2) adding a mixture of the template agent R1, the additive R2 and water to the mixture I to obtain a mixture II; 3) adding the silicon source to the mixture II to obtain the hydrothermal reaction mixture liquid.

10. The self-supporting SAPO-11 molecular sieve prepared by the preparation method of any one of claims 1-8, characterized in that, The molecular sieve is a fluffy, spheroid-like aggregate having a diameter of 2-80 μm, the spheroid-like aggregate is aggregated into a shape by primary lamellar crystal grains having a thickness of 15-60 nm, the average pore diameter of the molecular sieve is 30-55 nm, and the median pore diameter is 40-65 nm.

11. The molecular sieve of claim 10, wherein, The molecular sieve is a fluffy, spheroid-like aggregate having a diameter of 2-60 μm, the spheroid-like aggregate is aggregated into a shape by primary lamellar crystal grains having a thickness of 20-50 nm, the average pore diameter of the molecular sieve is 40-50 nm, and the median pore diameter is 45-55 nm.

12. Use of the molecular sieve according to claim 10 or 11 in catalyst preparation.

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