A molecular sieve, its preparation method and application

Abstract

This invention provides a molecular sieve, its preparation method, and its applications. The molecular sieve is plate-like, with a length not exceeding 1 μm and a thickness not exceeding 300 nm. By adding mixed additives, this invention effectively prevents self-aggregation between particles, inhibits crystal growth or aggregation, and reduces the size of the molecular sieve crystals. Simultaneously, it alters the structural orientation, generating a plate-like structure. The molecular sieve of this invention, with crystal sizes not exceeding 1 μm and thicknesses not exceeding 300 nm, consists of thin, plate-like crystals that can be used as catalysts in petrochemical, fine chemical, and other fields. As a catalyst, the small-crystal molecular sieve can shorten the residence time of molecules in the pores, increase the connectivity between the pores and the outer surface, and thus help improve the catalytic activity of the catalyst.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, specifically relating to a molecular sieve, its preparation method, and its application. Background Technology

[0002] In 1982, Union Carbide Corporation (UCC) first introduced AlPO4 molecular sieves. These sieves have a neutral framework, lack exchangeable cations, and lack the protonic acid required for catalytic activity against carbocations, exhibiting weak acid catalytic properties. In 1984, Lok et al. introduced Si into the AlPO4 series of molecular sieves, synthesizing a series of aluminosilicate phosphate (SAPO) molecular sieves with small, medium, or large pores, composed of AlO4, PO4, and SiO4 tetrahedral units. SAPO-n molecular sieves have pore structures ranging from six-membered to twelve-membered rings, with pore sizes between 0.3 and 0.8 nm, and exhibit varying degrees of acidity to accommodate the adsorption, diffusion, and reaction requirements of molecules of different sizes. SAPO-11 molecular sieve, as a member of the SAPO-n type molecular sieve family, is a mesoporous molecular sieve with one-dimensional ten-membered ring elliptical channels and a pore size of 0.39 × 0.64 nm. It has been studied and applied in various oil refining and chemical industries, including catalytic cracking, alkylation of branched aromatics, olefin isomerization, isomer dewaxing, and light olefin polymerization.

[0003] CN201010262187.4 discloses a method for synthesizing SAPO-11 molecular sieves using long-chain alkylsilanes as silicon sources. The method involves pre-hydrolyzing a mixture of long-chain alkylsilanes or long-chain alkylsilane quaternary ammonium salts with tetraethyl orthosilicate or acidic silica sol, followed by mixing and crystallizing with phosphoric acid, an aluminum source, and a template agent. The synthesized molecular sieve has a spherical structure formed by the aggregation of smaller crystallites, with a particle diameter exceeding 5 μm.

[0004] CN201310130903.7 discloses a method for synthesizing small-particle-size SAPO-11 molecular sieves and their applications. The method involves adding alkylated organosilanes to a conventional SAPO-11 molecular sieve synthesis gel, followed by dispersion and crystallization in an organic solvent medium. While conventional methods produce SAPO-11 molecular sieves with particle sizes of 5–10 μm, this method produces smaller particles, ranging from 0.5 to 1.2 μm, which are square or spherical.

[0005] CN201310548587.5 discloses a method for preparing SAPO-11 molecular sieves, which involves preparing an initial gel from phosphoric acid, boehmite, di-n-butylamine, silica sol, and deionized water, followed by crystallization. The synthesized molecular sieve is an aggregate of regularly arranged rod-shaped crystals with a particle size of approximately 3 μm.

[0006] CN201410850689.7 discloses a small-crystal-grained gradient-pore SAPO-11 molecular sieve and a hydrocarbon isomerization catalyst, as well as their preparation method. The method involves mixing and crystallizing a phosphorus source, deionized water, at least one aluminum source, at least one silicon source, at least one template agent, at least one cationic surfactant, and at least one co-solvent. The synthesized molecular sieve consists of spherical particles, each composed of numerous microcrystals stacked together, with a particle size greater than 2 μm.

[0007] SAPO-11 molecular sieves traditionally have a spherical structure and relatively large particle size. In catalytic reactions, the larger size increases the residence time of reactants and products in the pores, making side reactions more likely. On the other hand, the larger particle size also means that some of the internal pores cannot connect with the external surface, thus failing to play a role in the catalytic reaction and the acid centers cannot be utilized.

[0008] To address the issues of large particle size and uniform morphology in existing SAPO-11 molecular sieves, this invention provides a molecular sieve, its preparation method, and its applications. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a molecular sieve, its preparation method, and its applications. This invention, by synthesizing small-crystal molecular sieves, can shorten the residence time of molecules in the pores, increase the connectivity between the pores and the outer surface, and thus help improve the catalytic activity of the catalyst.

[0010] In a first aspect, the present invention provides a molecular sieve, wherein the molecular sieve is in the form of a sheet, and the length of the molecular sieve does not exceed 1 μm and the thickness does not exceed 300 nm.

[0011] In some embodiments, the molecular sieve is a SAPO molecular sieve.

[0012] In some embodiments, the molecular sieve is SAPO-11 molecular sieve.

[0013] In a second aspect, the present invention provides a method for preparing a molecular sieve, comprising the following steps:

[0014] The molecular sieve is obtained by mixing aluminum source, phosphorus source, silicon source, template agent, additive and solvent, crystallizing and then calcining.

[0015] In some embodiments, the additives include mineralizers and high molecular weight organic compounds.

[0016] In some embodiments, the mineralizing agent is selected from any one or more of hydrofluoric acid, ammonium fluoride, sodium fluoride, or potassium fluoride.

[0017] In some embodiments, the high molecular weight organic compound is polyethylene glycol and / or polyhexamethylene biguanide hydrochloride (PHMB).

[0018] In some embodiments, the average molecular weight of the polyethylene glycol is 400 to 1000, and the average molecular weight of the polyhexamethylene biguanide hydrochloride is 1000 to 4000.

[0019] In some embodiments, the additive is a combination of hydrofluoric acid and polyethylene glycol or a combination of ammonium fluoride and polyhexamethylene biguanide hydrochloride.

[0020] In some embodiments, the aluminum source is selected from at least one of aluminum salts, aluminates, activated alumina, pseudoboehmite, or pseudoboehmite.

[0021] In some embodiments, the phosphorus source is at least one of orthophosphoric acid, metaphosphoric acid, phosphate, or phosphorus oxide.

[0022] In some embodiments, the silicon source is selected from at least one of silica sol, water glass, activated silica, or orthosilicate.

[0023] In some embodiments, the template agent is an organic amine template agent.

[0024] In some embodiments, the template agent is selected from at least one of di-n-propylamine, diisopropylamine, or diethylamine.

[0025] In some embodiments, the solvent is at least one of water, C1-C6 alcohols, ethers, or ketones.

[0026] In some embodiments, the solvent is water.

[0027] In some embodiments, the molar ratio of the additive to the aluminum source, calculated as Al2O3, is (0.101-2.5):1, for example, 0.101:1, 0.2:1, 0.5:1, 0.8:1, 1.1:1, 1.3:1, 1.5:1, 1.7:1, 1.9:1, 2.1:1, 2.3:1, 2.5:1.

[0028] In some embodiments, the molar ratio of the additive to the aluminum source, calculated as Al2O3, is (0.15-1.25):1.

[0029] In some embodiments, the molar ratio of the mineralizer to the high molecular weight organic compound in the additive is (0.2-600):1, for example, 0.2:1, 2:1, 5:1, 10:1, 15:1, 20:1, 25:1, 100:1, 150:1, 200:1, 300:1, 400:1, 500:1, or 600:1.

[0030] In some embodiments, the molar ratio of mineralizer to high molecular weight organic compound in the additive is (15-450):1.

[0031] In some embodiments, the aluminum source is calculated as Al2O3, the phosphorus source as P2O5, the silicon source as SiO2, the template agent as R-NH2, the mineralizer in the mixed additives as T1, and the polymeric organic matter as T2. The molar ratio of each substance is: Al2O3:P2O5:SiO2:R-NH2:T1:T2:H2O = 1.0:(0.5~1.5):(0.02~2.0):(0.5~2.0):(0.1~2.0):(0.001~0.5):(10~120), for example, Al2O3:P2O5:SiO2:R-NH2: T1:T2:H2O=1.0:(0.5, 0.6, 0.7, 0.8, 0.9, 1.1, 1.3 or 1.5):(0.02, 0.1, 0.45, 0.7, 0.95, 1.2, 1.45, 1.7, 2.0):(0.5, 0.8, 1.1, 1.3, 1.6, 1.9, 2.0):(0.1, 0.5, 0.9, 1.3, 1.7, 2.0):(0.001, 0.01, 0.1, 0.2, 0.3, 0.4, 0.5):(10, 50, 70, 90, 100, 110, 120).

[0032] In some embodiments, the crystallization is a single-stage crystallization or a two-stage crystallization.

[0033] In some embodiments, the crystallization is a two-stage crystallization.

[0034] In some embodiments, when the crystallization is a single-stage crystallization, the temperature of the single-stage crystallization is 170-200°C (e.g., 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, 200°C), and the crystallization time is 12h-120h (e.g., 12h, 20h, 30h, 40h, 50h, 60h, 70h, 80h, 90h, 100h, 110h, 120h).

[0035] In some embodiments, when the crystallization is a two-stage crystallization, the two-stage crystallization includes a first crystallization and a second crystallization. The temperature of the first crystallization is 100–160°C (e.g., 100°C, 107°C, 110°C, 115°C, 120°C, 123°C, 130°C, 136°C, 140°C, 148°C, 150°C, 154°C, 160°C), and the time of the first crystallization is 2–48 hours (e.g., 2 hours, 10 hours, 20 hours, 30 hours, 40 hours, 48 ​​hours). The second crystallization… The temperature is 120–260℃ (e.g., 120℃, 128℃, 135℃, 145℃, 150℃, 156℃, 165℃, 173℃, 180℃, 188℃, 195℃, 201℃, 210℃, 219℃, 225℃, 234℃, 240℃, 251℃, 255℃), and the second crystallization time is 2–96h (e.g., 2h, 10h, 20h, 30h, 40h, 48h, 60h, 70h, 80h, 90h, 96h).

[0036] In some embodiments, the temperature of the second crystallization is 20 to 100°C higher than the temperature of the first crystallization, for example, the temperature of the second crystallization is 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C higher than the temperature of the first crystallization.

[0037] In some embodiments, the calcination temperature is 500–600°C (e.g., 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C), and the calcination time is 5–8 hours (e.g., 5 hours, 5.2 hours, 5.4 hours, 5.6 hours, 5.8 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours).

[0038] In some embodiments, the preparation method includes:

[0039] (1) Mix the aluminum source, phosphorus source, silicon source, template agent and solvent evenly to obtain a mixed solution;

[0040] (2) Add additives to the mixed solution and mix evenly. Then crystallize, separate solid and liquid to obtain a solid product, wash with deionized water until neutral, and dry.

[0041] (3) The solid product dried in step (2) is calcined to obtain the molecular sieve.

[0042] In some embodiments, aging is performed before crystallization, and the aging time is 1 to 24 hours, for example, 1 hour, 5 hours, 10 hours, 15 hours, 20 hours, or 24 hours.

[0043] In some embodiments, the drying can be carried out at 100–150°C, for example, 100°C, 120°C, 140°C, or 150°C.

[0044] In some embodiments, the solid-liquid separation can be achieved by centrifugation or filtration.

[0045] In a third aspect, the present invention provides an application of the molecular sieve described in the first aspect or the molecular sieve prepared by the preparation method described in the second aspect as a catalyst.

[0046] In some embodiments, the molecular sieves described in the first aspect or prepared by the preparation method described in the second aspect are applied in the petrochemical and / or fine chemical industries.

[0047] In some embodiments, the molecular sieve described in the first aspect or the molecular sieve prepared by the preparation method described in the second aspect is applied to the methanol-to-olefins reaction.

[0048] This invention, by adding mixed additives, effectively prevents the self-aggregation of particles, inhibits crystal growth or aggregation, and reduces the size of molecular sieve crystals. Simultaneously, it alters the structural orientation, generating a plate-like structure. The molecular sieve crystals of this invention are thin, plate-like crystals with a size not exceeding 1 μm and a thickness not exceeding 300 nm, which can be used as catalysts in petrochemical, fine chemical, and other fields. As a catalyst, the small-crystal molecular sieve can shorten the residence time of molecules in the pores, increase the connectivity between the pores and the outer surface, and help improve the catalytic activity of the catalyst. Attached Figure Description

[0049] Figure 1 Here is a scanning electron microscope image of Example 1;

[0050] Figure 2 Here is a scanning electron microscope image of Example 7;

[0051] Figure 3 This is a scanning electron microscope image of Comparative Example 1. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0053] 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.

[0054] The present invention will be described in detail below through embodiments.

[0055] In this invention, the morphology of the molecular sieve product is determined by scanning electron microscopy (SEM). The SEM images of the molecular sieve are determined using a Nova NanoSEM 450 scanning electron microscope. The sample is first ground into a powder of 200-400 mesh, fixed with double-sided conductive adhesive, and then tested under high vacuum conditions. The microscope emission voltage is 300kV.

[0056] Example 1

[0057] Hydrofluoric acid (T1) and polyethylene glycol (T2) were used as mixed additives. Boehmite, phosphoric acid, tetraethyl orthosilicate, and di-n-propylamine were used as the aluminum source, phosphorus source, silicon source, and template agent (R-NH2), respectively. The ingredients were weighed and mixed in a molar ratio of T1:T2:Al2O3:P2O5:SiO2:R-NH2:H2O = 0.5:0.006:1.0:0.9:0.45:1.2:55. After the boehmite and deionized water were thoroughly mixed, phosphoric acid was added. The mixture was stirred with acid, then tetraethyl orthosilicate was added and stirring continued. Finally, cyclohexylamine and mixed additives were added and stirred until homogeneous. The reaction mixture was then placed in a crystallization vessel lined with polytetrafluoroethylene. Crystallization was first carried out at 150°C under autogenous pressure for 18 hours, followed by crystallization at 180°C under autogenous pressure for 24 hours. The crystallized product was washed with deionized water until neutral, and the solid was separated and dried in an oven at 100°C. It was then calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-11 molecular sieve, denoted as A1. Scanning electron microscopy images are shown below. Figure 1 As shown, the crystals are plate-like with a grain length of about 800 nm and a thickness of about 100 nm, as shown in Table 1.

[0058] Example 2

[0059] Ammonium fluoride (T1) and polyhexamethylene biguanide hydrochloride (T2) were used as mixed additives. Aluminum isopropoxide, metaphosphoric acid, silica sol, and diisopropylamine were used as the aluminum source, phosphorus source, silicon source, and template agent (R-NH2), respectively. The ingredients were weighed out in a molar ratio of T1:T2:Al2O3:P2O5:SiO2:R-NH2:H2O = 0.2:0.005:1.0:0.8:0.28:1.5:55. Aluminum isopropoxide and deionized water were mixed evenly and then added to the mixture. Phosphoric acid was stirred, then silica sol was added and stirring continued. Finally, diisopropylamine and mixed additives were added and stirred until homogeneous. The reaction mixture was then placed in a crystallization vessel lined with polytetrafluoroethylene. Crystallization was first carried out at 145°C under autogenous pressure for 20 hours, followed by crystallization at 175°C under autogenous pressure for 36 hours. The crystallized product was washed with deionized water until neutral, and the solid was separated and dried in an oven at 100°C. It was then calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-11 molecular sieve, denoted as A2. Scanning electron microscope images and... Figure 1 similar.

[0060] Example 3

[0061] Hydrofluoric acid (T1) and polyethylene glycol (T2) were used as mixed additives. Boehmite, phosphoric acid, tetraethyl orthosilicate, and di-n-propylamine were used as the aluminum source, phosphorus source, silicon source, and template agent (R-NH2), respectively. The ingredients were weighed out in a molar ratio of T1:T2:Al2O3:P2O5:SiO2:R-NH2:H2O = 0.1:0.006:1.0:0.9:0.45:1.2:55. The boehmite and deionized water were mixed thoroughly and then added... Phosphoric acid was added and stirred, then tetraethyl orthosilicate was added and stirred again. Finally, cyclohexylamine and mixed additives were added and stirred evenly. The above reaction mixture was then loaded into a crystallization vessel with a polytetrafluoroethylene liner. It was first crystallized at 150°C under autogenous pressure for 18 hours, and then crystallized at 180°C under autogenous pressure for 24 hours. The crystallized product was washed with deionized water until neutral, and the solid was separated and dried in an oven at 100°C. It was then calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-11 molecular sieve.

[0062] Example 4

[0063] Hydrofluoric acid (T1) and polyethylene glycol (T2) were used as mixed additives. Boehmite, phosphoric acid, tetraethyl orthosilicate, and di-n-propylamine were used as the aluminum source, phosphorus source, silicon source, and template agent (R-NH2), respectively. The ingredients were weighed out in a molar ratio of T1:T2:Al2O3:P2O5:SiO2:R-NH2:H2O = 2:0.006:1.0:0.9:0.45:1.2:55. The boehmite and deionized water were mixed thoroughly and then added... Phosphoric acid was stirred, then tetraethyl orthosilicate was added and stirring continued. Finally, cyclohexylamine and mixed additives were added and stirred evenly. The above reaction mixture was then loaded into a crystallization vessel with a polytetrafluoroethylene liner. It was first crystallized at 150°C under autogenous pressure for 18 hours, and then crystallized at 180°C under autogenous pressure for 24 hours. The crystallized product was washed with deionized water until neutral, and the solid was separated and dried in an oven at 100°C. It was then calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-11 molecular sieve.

[0064] Example 5

[0065] Hydrofluoric acid (T1) and polyhexamethylene biguanide hydrochloride (T2) were used as mixed additives. Boehmite, phosphoric acid, tetraethyl orthosilicate, and di-n-propylamine were used as the aluminum source, phosphorus source, silicon source, and template agent (R-NH2), respectively. The ingredients were weighed and mixed in a molar ratio of T1:T2:Al2O3:P2O5:SiO2:R-NH2:H2O = 0.5:0.006:1.0:0.9:0.45:1.2:55. The boehmite and deionized water were then thoroughly mixed. After mixing, phosphoric acid was added and stirred, followed by tetraethyl orthosilicate and stirring. Finally, cyclohexylamine and mixed additives were added and stirred until homogeneous. The reaction mixture was then placed in a crystallization vessel with a polytetrafluoroethylene liner and crystallized at 150°C under autogenous pressure for 18 hours, followed by crystallization at 180°C under autogenous pressure for 24 hours. The crystallized product was washed with deionized water until neutral, and the solid was separated and dried in an oven at 100°C. The solid was then calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-11 molecular sieve.

[0066] Example 6

[0067] Ammonium fluoride (T1) and polyethylene glycol (T2) were used as mixed additives. Boehmite, phosphoric acid, tetraethyl orthosilicate, and di-n-propylamine were used as the aluminum source, phosphorus source, silicon source, and template agent (R-NH2), respectively. The ingredients were weighed out in a molar ratio of T1:T2:Al2O3:P2O5:SiO2:R-NH2:H2O = 0.5:0.006:1.0:0.9:0.45:1.2:55. The boehmite and deionized water were mixed thoroughly and then added... Phosphoric acid was added and stirred, then tetraethyl orthosilicate was added and stirred again. Finally, cyclohexylamine and mixed additives were added and stirred evenly. The above reaction mixture was then loaded into a crystallization vessel with a polytetrafluoroethylene liner. It was first crystallized at 150°C under autogenous pressure for 18 hours, and then crystallized at 180°C under autogenous pressure for 24 hours. The crystallized product was washed with deionized water until neutral, and the solid was separated and dried in an oven at 100°C. It was then calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-11 molecular sieve.

[0068] Example 7

[0069] Using hydrofluoric acid (T1) as an additive, and boehmite, phosphoric acid, tetraethyl orthosilicate, and di-n-propylamine as the aluminum source, phosphorus source, silicon source, and template agent (R-NH2) respectively, the ingredients were weighed out in a molar ratio of T1:Al2O3:P2O5:SiO2:R-NH2:H2O = 0.506:1.0:0.9:0.45:1.2:55. Boehmite and deionized water were mixed evenly, then phosphoric acid was added and stirred, followed by the addition of orthosilicate. The tetraethyl ester was stirred continuously, and finally cyclohexylamine and mixed additives were added and stirred evenly. The above reaction mixture was then loaded into a crystallization vessel with a polytetrafluoroethylene liner. Crystallization was first carried out at 150°C under autogenous pressure for 18 hours, and then at 180°C under autogenous pressure for 24 hours. The crystallized product was washed with deionized water until neutral, and the solid was separated and dried in an oven at 100°C. It was then calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-11 molecular sieve. Scanning electron microscopy images are shown below. Figure 2 As shown.

[0070] Example 8

[0071] Using polyethylene glycol (T2) as an additive, and boehmite, phosphoric acid, tetraethyl orthosilicate, and di-n-propylamine as the aluminum source, phosphorus source, silicon source, and template agent (R-NH2) respectively, the ingredients were weighed out in a molar ratio of T2:Al2O3:P2O5:SiO2:R-NH2:H2O = 0.506:1.0:0.9:0.45:1.2:55. After the boehmite and deionized water were mixed evenly, phosphoric acid was added and stirred, followed by... Add tetraethyl orthosilicate and continue stirring. Finally, add cyclohexylamine and mixed additives and stir evenly. Then, put the above reaction mixture into a crystallization vessel with a polytetrafluoroethylene liner. First, crystallize at 150°C under autogenous pressure for 18 hours, and then crystallize at 180°C under autogenous pressure for 24 hours. Wash the crystallized product with deionized water until neutral, separate the solid, dry it in an oven at 100°C, and calcine it in a muffle furnace at 550°C for 6 hours to obtain SAPO-11 molecular sieve.

[0072] Example 9

[0073] Hydrofluoric acid (T1) and polyethylene glycol (T2) were used as mixed additives. Boehmite, phosphoric acid, tetraethyl orthosilicate, and di-n-propylamine were used as the aluminum source, phosphorus source, silicon source, and template agent (R-NH2), respectively. The ingredients were weighed out in a molar ratio of T1:T2:Al2O3:P2O5:SiO2:R-NH2:H2O = 0.496:0.01:1.0:0.9:0.45:1.2:55. The boehmite and deionized water were then mixed thoroughly. Phosphoric acid was added and stirred, followed by tetraethyl orthosilicate and stirring. Finally, cyclohexylamine and mixed additives were added and stirred until homogeneous. The reaction mixture was then placed in a crystallization vessel lined with polytetrafluoroethylene. Crystallization was carried out at 150°C under autogenous pressure for 18 hours, followed by crystallization at 180°C under autogenous pressure for 24 hours. The crystallized product was washed with deionized water until neutral, and the solid was separated and dried in an oven at 100°C. The solid was then calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-11 molecular sieve.

[0074] Comparative Example 1

[0075] Preparation of conventional SAPO-11 molecular sieves

[0076] Boehmite, phosphoric acid, silica sol, and di-n-propylamine were weighed and mixed as aluminum source, phosphorus source, silicon source, and template agent (R), respectively, in a molar ratio of Al2O3:P2O5:SiO2:R:H2O = 1.0:1.0:0.5:1.0:35. Boehmite and deionized water were mixed thoroughly, then phosphoric acid was added and stirred. Silica sol was added and stirring continued. Finally, di-n-propylamine was added and stirred thoroughly. The reaction mixture was then placed in a crystallization vessel lined with polytetrafluoroethylene (PTFE) and crystallized at 185°C under autogenous pressure for 36 hours. The crystallized product was washed with deionized water until neutral, and the solid was separated, dried in an oven at 100°C, and calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-11 molecular sieve, denoted as B1. Scanning electron microscopy images are shown below. Figure 3 As shown, it has a spherical structure with a grain size of 10–15 μm.

[0077] Table 1

[0078]

[0079]

[0080] Application Examples

[0081] Application Examples 1-9

[0082] The molecular sieves prepared in Examples 1-9 were used to catalyze the methanol-to-olefins reaction. The specific steps included: pressing the samples obtained in the examples and comparative examples into tablets, crushing them, and sieving to obtain a particle size fraction of 20-40 mesh. A fixed-bed catalytic reactor was used to conduct catalyst evaluation experiments. The experimental conditions were: catalyst loading of 2.0 g, reaction temperature of 450 °C, reaction pressure at atmospheric pressure, reactant of 75% methanol aqueous solution, and methanol weight hourly space velocity (WHSV) of 4 h⁻¹. -1 .

[0083] The conversion rate of methanol and the distribution of major hydrocarbon products are shown in Table 2.

[0084] Application Comparative Example 1

[0085] Unlike Application Example 1, the conventional SAPO-11 molecular sieve used in Comparative Example 1 was employed to catalyze the methanol-to-olefins reaction.

[0086] Table 2 shows the methanol conversion rate and the distribution of major hydrocarbon products in the application examples and comparative examples.

[0087] Table 2

[0088]

[0089] As can be seen from Table 2, compared with the conventional SAPO-11 molecular sieve catalyzing the methanol-to-olefins reaction, the plate-like molecular sieve of the present invention has higher reactivity, which can not only effectively improve the conversion rate of methanol, but also improve the selectivity of ethylene in the product.

[0090] 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 molecular sieve, wherein the molecular sieve is in the form of a sheet, and the length of the molecular sieve does not exceed 1 μm and the thickness does not exceed 300 nm; The molecular sieve is SAPO-11 molecular sieve; The method for preparing the molecular sieve includes the following steps: An aluminum source, a phosphorus source, a silicon source, a template agent, an additive, and a solvent are mixed, crystallized, and then calcined to obtain the molecular sieve. The additives include mineralizers and high molecular weight organic compounds; The mineralizing agent is selected from any one or more of hydrofluoric acid, ammonium fluoride, sodium fluoride or potassium fluoride; The high molecular weight organic compound is polyethylene glycol and / or polyhexamethylene biguanide hydrochloride; The template agent is selected from at least one of di-n-propylamine, diisopropylamine, or diethylamine; The crystallization is a two-stage crystallization; the two-stage crystallization includes a first crystallization and a second crystallization, the temperature of the first crystallization is 100-160℃, the time of the first crystallization is 2-48h, the temperature of the second crystallization is 120-260℃, and the time of the second crystallization is 2-96h. The temperature of the second crystallization is 20 to 100°C higher than that of the first crystallization.

2. A method for preparing the molecular sieve according to claim 1, comprising the following steps: An aluminum source, a phosphorus source, a silicon source, a template agent, an additive, and a solvent are mixed, crystallized, and then calcined to obtain the molecular sieve. The additives include mineralizers and high molecular weight organic compounds. The mineralizing agent is selected from any one or more of hydrofluoric acid, ammonium fluoride, sodium fluoride or potassium fluoride; The high molecular weight organic compound is polyethylene glycol and / or polyhexamethylene biguanide hydrochloride; The template agent is selected from at least one of di-n-propylamine, diisopropylamine, or diethylamine; The crystallization is a two-stage crystallization; The two-stage crystallization includes a first crystallization and a second crystallization. The temperature of the first crystallization is 100-160℃ and the time of the first crystallization is 2-48h. The temperature of the second crystallization is 120-260℃ and the time of the second crystallization is 2-96h. The temperature of the second crystallization is 20 to 100°C higher than that of the first crystallization.

3. The preparation method according to claim 2, characterized in that, The average molecular weight of the polyethylene glycol is 400-1000, and the average molecular weight of the polyhexamethylene biguanide hydrochloride is 1000-4000.

4. The preparation method according to claim 2, characterized in that, The additive is a combination of hydrofluoric acid and polyethylene glycol or a combination of ammonium fluoride and polyhexamethylene biguanide hydrochloride.

5. The preparation method according to claim 2, characterized in that, The aluminum source is selected from at least one of aluminum salts, aluminates, activated alumina, pseudoboehmite, or pseudoboehmite.

6. The preparation method according to claim 2, characterized in that, The phosphorus source is selected from at least one of orthophosphoric acid, metaphosphoric acid, phosphate, or phosphorus oxide.

7. The preparation method according to claim 2, characterized in that, The silicon source is selected from at least one of silica sol, water glass, active silica, or orthosilicate.

8. The preparation method according to claim 2, characterized in that, The solvent is at least one of water, C1-C6 alcohols, ethers, or ketones.

9. The preparation method according to claim 2, characterized in that, The solvent is water.

10. The preparation method according to claim 2, characterized in that, The molar ratio of additives to aluminum source (calculated as Al2O3) is (0.101-2.5):

1.

11. The preparation method according to claim 2, characterized in that, The molar ratio of additives to aluminum source (calculated as Al2O3) is (0.15-1.25):

1.

12. The preparation method according to claim 2, characterized in that, In the additives, the molar ratio of mineralizer to high molecular weight organic matter is (0.2-600):

1.

13. The preparation method according to claim 2, characterized in that, In the additives, the molar ratio of mineralizer to high molecular weight organic matter is (15-450):

1.

14. The preparation method according to claim 2, characterized in that, The aluminum source is calculated as Al2O3, the phosphorus source as P2O5, the silicon source as SiO2, the template agent as R-NH2, the mineralizer in the additives as T1, and the high molecular weight organic matter as T2. The molar ratio of each substance is: Al2O3:P2O5:SiO2:R-NH2:T1:T2:H2O=1.0:(0.5~1.5):(0.02~2.0):(0.5~2.0):(0.1~2.0):(0.001~0.5):(10~120).

15. The preparation method according to claim 2, characterized in that, The roasting temperature is 500-600℃, and the roasting time is 5-8 hours.

16. The use of the molecular sieve of claim 1 or the molecular sieve prepared by any one of claims 2 to 15 as a catalyst.

17. The molecular sieve of claim 1 or the molecular sieve prepared by any one of claims 2 to 15 is applied in the petrochemical and / or fine chemical industries.

18. The molecular sieve of claim 1 or the molecular sieve prepared by any one of claims 2 to 15 is applied to the methanol-to-olefins reaction.

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