Molecular sieve as well as preparation method and application thereof

Abstract

The invention provides a molecular sieve as well as a preparation method and application thereof. The molecular sieve is flaky, the length of the molecular sieve is not more than 1 [mu] m, and the thickness of the molecular sieve is not more than 300 nm. By adding the mixed additive, the self-polymerization behavior among particles can be effectively prevented, the growth or aggregation of crystals is inhibited, and the crystal grains of the molecular sieve are reduced; meanwhile, the structural orientation is changed, a flaky structure is generated, and the molecular sieve provided by the invention has flaky small grains with the grain size of not more than 1 [mu] m and the thickness of not more than 300 nm, and can be applied to the fields of petrochemical engineering, fine chemical engineering and the like as a catalyst. As a catalyst, the small-grain molecular sieve can shorten the residence time of molecules in pore channels, improve the connectivity rate of the pore channels and the outer surface, and contribute to improving the catalytic activity of the catalyst.

Description

Technical Field

[0001] The invention belongs to the field of catalysts, and specifically relates to a molecular sieve and a preparation method and application thereof. Background Art

[0002] In 1982, the Union Carbide Corporation (UCC) of the United States first introduced AlPO4 molecular sieves. The framework of this type of molecular sieve is neutral, without exchangeable cations, lacking the proton acid required for the catalytic activity of positive carbon ions, and showing weak acid catalytic performance. In 1984, Lok et al. introduced Si into the AlPO4 series of molecular sieves and synthesized a series of silicoaluminophosphate (SAPO) molecular sieves with small, medium or large pores composed of AlO4, PO4 and SiO4 tetrahedral units. The pore structure of SAPO-n molecular sieves ranges from six-membered rings to twelve-membered rings, with a pore size between 0.3 and 0.8nm, and has different strengths of acidity, which can adapt to the requirements of adsorption, diffusion and reaction of molecules of different sizes. As a member of the SAPO-n molecular sieve family, SAPO-11 molecular sieve is a medium-pore molecular sieve with a one-dimensional ten-membered ring elliptical pore and a pore size of 0.39×0.64nm. It has been studied and applied in various oil refining and chemical industries such as catalytic cracking, alkylation of branched aromatics, olefin isomerization, isodewaxing and light olefin polymerization.

[0003] CN201010262187.4 discloses a method for synthesizing SAPO-11 molecular sieve using long-chain alkyl silane as a silicon source, wherein a mixture of long-chain alkyl silane or a long-chain alkyl silane quaternary ammonium salt and ethyl orthosilicate or acidic silica sol is pre-hydrolyzed and then mixed with phosphoric acid, an aluminum source and a template agent for crystallization. The synthesized molecular sieve has a spherical structure formed by aggregation of smaller crystals, and a particle diameter of more than 5 μm.

[0004] CN201310130903.7 discloses a method for synthesizing a small-particle SAPO-11 molecular sieve and its use, which is obtained by adding an alkylated organosilane to a conventional SAPO-11 molecular sieve synthesis gel, and then dispersing it in an organic solvent medium for crystallization. The particle size of the SAPO-11 molecular sieve synthesized by the traditional method is 5 to 10 μm, while the particle size synthesized by this method is small, at 0.5 to 1.2 μm, and is a square or spherical particle.

[0005] CN201310548587.5 discloses a method for preparing SAPO-11 molecular sieve, which comprises preparing phosphoric acid, pseudo-boehmite, di-n-butylamine, silica sol and deionized water into an initial gel, and then crystallizing the gel to obtain the synthesized molecular sieve, which is an aggregate of regularly arranged rod-shaped crystals with a particle size of about 3 μm.

[0006] CN201410850689.7 discloses a small-grain gradient pore SAPO-11 molecular sieve and a hydrocarbon isomerization catalyst and a preparation method, which are obtained by adding 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 for mixed crystallization. The synthesized molecular sieve is a spherical particle, and each spherical particle is formed by stacking a large number of microcrystals, and the particle size is above 2μm.

[0007] The traditional morphology of SAPO-11 molecular sieve is a spherical structure with a 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 to occur. On the other hand, the larger particle size will cause a portion of the internal pores to be unable to connect with the outer surface, making it unable to play a role in the catalytic reaction and the acid centers unable to be utilized.

[0008] In view of the problems in the prior art that SAPO-11 molecular sieve has a large particle size and a single morphology, the present invention provides a molecular sieve and a preparation method and application thereof. Summary of the invention

[0009] In view of the problems existing in the prior art, the present invention provides a molecular sieve and its preparation method and application. The present invention can shorten the residence time of molecules in the pores by synthesizing small-grain molecular sieves, improve the connectivity between the pores and the outer surface, and help improve the catalytic activity of the catalyst.

[0010] In a first aspect, the present invention provides a molecular sieve, which is in the form of a sheet, and has a length not exceeding 1 μm and a thickness not exceeding 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] An aluminum source, a phosphorus source, a silicon source, a template, an additive and a solvent are mixed, crystallized and then calcined to obtain the molecular sieve.

[0015] In some embodiments, the additives include a mineralizer and a high molecular weight organic matter.

[0016] In some embodiments, the mineralizer 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 substance is polyethylene glycol and / or polyhexamethylene biguanide hydrochloride (PHMB).

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

[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, phosphates, or phosphorus oxides.

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

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

[0024] In some embodiments, the template 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, in the additive, the molar ratio of the mineralizer to the high molecular organic matter 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, 600:1.

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

[0031] In some embodiments, the aluminum source is calculated as Al2O3, the phosphorus source is calculated as P2O5, the silicon source is calculated as SiO2, the template is calculated as R-NH2, the mineralizer in the mixed additive is calculated as T1, and the high molecular organic matter is calculated 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 one-stage crystallization or two-stage crystallization.

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

[0034] In some embodiments, when the crystallization is a one-stage crystallization, the temperature of the one-stage crystallization is 170-200°C (for example, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, 200°C), and the crystallization time is 12h-120h (for example, 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 (for example, 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), the time of the first crystallization is 2-48h (for example, 2h, 10h, 20h, 30h, 40h, 48h), and the time of the second crystallization is 2-48h. The temperature is 120-260°C (for example, 120°C, 128°C, 135°C, 145°C, 150°C, 156°C, 165°C, 173°C, 180°C, 188°C, 195°C, 201°C, 210°C, 219°C, 225°C, 234°C, 240°C, 251°C, 255°C), and the time for the second crystallization is 2-96h (for example, 2h, 10h, 20h, 30h, 40h, 48h, 60h, 70h, 80h, 90h, 96h).

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

[0037] In some embodiments, the calcination temperature is 500-600°C (for example, 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 5-8h (for example, 5h, 5.2h, 5.4h, 5.6h, 5.8h, 6h, 6.5h, 7h, 7.5h, 8h).

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

[0039] (1) mixing an aluminum source, a phosphorus source, a silicon source, a template and a solvent to obtain a mixed solution;

[0040] (2) adding additives to the mixed solution and mixing them evenly, performing crystallization, solid-liquid separation, obtaining a solid product, washing it with deionized water until it is neutral, and drying it;

[0041] (3) calcining the solid product after drying in step (2) 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 may be performed 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 performed by centrifugation or filtration.

[0045] In a third aspect, the present invention provides a use 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 sieve described in the first aspect or the molecular sieve prepared by the preparation method described in the second aspect is applied to the fields of petrochemical industry and / or fine chemical industry.

[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 a methanol to olefin reaction.

[0048] The present invention can effectively prevent the self-aggregation behavior between particles by adding mixed additives, inhibit the growth or aggregation of crystals, and reduce the molecular sieve grain size; at the same time, the structural orientation is changed to generate a flaky structure. The molecular sieve of the present invention has a flaky small grain size of no more than 1 μm and a thickness of no more than 300 nm, which can be used as a catalyst in the fields of petrochemical industry, fine chemical industry, etc. Small-grain molecular sieve can shorten the residence time of molecules in the pores as a catalyst, improve the connectivity between the pores and the outer surface, and help improve the catalytic activity of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a scanning electron microscope photograph of Example 1;

[0050] Figure 2 This is a scanning electron microscope photograph of Example 7;

[0051] Figure 3 This is a scanning electron microscope photograph of Comparative Example 1. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and drawings. The specific embodiments described herein are only used to explain the present invention and are not intended to constitute any limitation to the present invention. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concepts of the present disclosure. Such structures and technologies are also described in many publications.

[0053] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

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

[0055] In the present invention, the morphology of the molecular sieve product is determined by scanning electron microscopy (SEM). The SEM photo of the molecular sieve is measured by 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 tested under high vacuum, with the microscope emission voltage of 300kV.

[0056] Example 1

[0057] Hydrofluoric acid (T1) and polyethylene glycol (T2) are mixed additives, pseudo-boehmite, phosphoric acid, tetraethyl orthosilicate, and di-n-propylamine are aluminum source, phosphorus source, silicon source, and template (R-NH2), respectively, and the molar ratio is T1:T2:Al2O3:P2O5:SiO2:R-NH2:H2O=0.5:0.006:1.0:0.9:0.45:1.2:55. The ingredients are weighed, the pseudo-boehmite and deionized water are mixed evenly, and then phosphorus is added. Acid is stirred, tetraethyl orthosilicate is added and stirred continuously, and finally cyclohexylamine and mixed additives are added and stirred evenly, and the above reaction mixture is placed in a crystallization kettle with a polytetrafluoroethylene liner, and first crystallized at 150℃ under autogenous pressure for 18 hours, and then crystallized at 180℃ under autogenous pressure for 24 hours, and the crystallized product is washed with deionized water until neutral, and the separated solid is dried in an oven at 100℃, and calcined in a muffle furnace at 550℃ for 6 hours to obtain SAPO-11 molecular sieve, which is recorded as A1. The scanning electron microscope photo is shown in Figure 1 As shown in Table 1, it is a plate-like crystal with a grain length of about 800nm ​​and a thickness of about 100nm.

[0058] Example 2

[0059] Ammonium fluoride (T1) and polyhexamethylene biguanide hydrochloride (T2) are mixed additives, aluminum isopropoxide, metaphosphoric acid, silica sol and diisopropylamine are aluminum source, phosphorus source, silicon source and template (R-NH2) respectively, and the molar ratio is T1:T2:Al2O3:P2O5:SiO2:R-NH2:H2O=0.2:0.005:1.0:0.8:0.28:1.5:55. The ingredients are weighed, aluminum isopropoxide and deionized water are mixed evenly, and then added Stir the metaphosphoric acid, then add silica sol and continue stirring, finally add diisopropylamine and mixed additives and stir evenly, then put the above reaction mixture into a crystallization kettle with a polytetrafluoroethylene liner, first crystallize at 145℃ under autogenous pressure for 20h, then crystallize at 175℃ under autogenous pressure for 36h, wash the crystallized product with deionized water until neutral, separate the solid and dry it in a 100℃ oven, and calcine it at 550℃ in a muffle furnace for 6 hours to obtain SAPO-11 molecular sieve, recorded as A2. Scanning electron microscope photos and Figure 1 similar.

[0060] Example 3

[0061] Hydrofluoric acid (T1) and polyethylene glycol (T2) are mixed additives, pseudo-boehmite, phosphoric acid, tetraethyl orthosilicate, and di-n-propylamine are aluminum source, phosphorus source, silicon source, and template (R-NH2), respectively, and the molar ratio is T1:T2:Al2O3:P2O5:SiO2:R-NH2:H2O=0.1:0.006:1.0:0.9:0.45:1.2:55. The ingredients are weighed, the pseudo-boehmite and deionized water are mixed evenly, and then added Phosphoric acid is added and stirred, and then tetraethyl orthosilicate is added and continued to be stirred. Finally, cyclohexylamine and mixed additives are added and stirred evenly. The reaction mixture is charged into a crystallization kettle with a polytetrafluoroethylene liner, 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 is washed with deionized water until neutral, and the separated solid is 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.

[0062] Example 4

[0063] Hydrofluoric acid (T1) and polyethylene glycol (T2) are mixed additives, pseudo-boehmite, phosphoric acid, tetraethyl orthosilicate, and di-n-propylamine are aluminum source, phosphorus source, silicon source, and template (R-NH2), respectively, and the molar ratio is T1:T2:Al2O3:P2O5:SiO2:R-NH2:H2O=2:0.006:1.0:0.9:0.45:1.2:55. The ingredients are weighed, the pseudo-boehmite and deionized water are mixed evenly, and then added Phosphoric acid is stirred, and then tetraethyl orthosilicate is added and continued to be stirred. Finally, cyclohexylamine and mixed additives are added and stirred evenly. The reaction mixture is charged into a crystallization kettle with a polytetrafluoroethylene liner, 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 is washed with deionized water until neutral, and the separated solid is 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.

[0064] Example 5

[0065] Hydrofluoric acid (T1) and polyhexamethylene biguanide hydrochloride (T2) are mixed additives, pseudo-boehmite, phosphoric acid, tetraethyl orthosilicate, and di-n-propylamine are aluminum source, phosphorus source, silicon source, and template (R-NH2), respectively, and the molar ratio is T1:T2:Al2O3:P2O5:SiO2:R-NH2:H2O=0.5:0.006:1.0:0.9:0.45:1.2:55. The ingredients are weighed, and the pseudo-boehmite and deionized water are mixed evenly. After homogenizing, add phosphoric acid and stir, then add tetraethyl orthosilicate and continue stirring, finally add cyclohexylamine and mixed additives and stir evenly, charge the above reaction mixture into a crystallization kettle with a polytetrafluoroethylene liner, first crystallize at 150°C under autogenous pressure for 18 hours, 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.

[0066] Example 6

[0067] Ammonium fluoride (T1) and polyethylene glycol (T2) are mixed additives, pseudo-boehmite, phosphoric acid, tetraethyl orthosilicate, and di-n-propylamine are aluminum source, phosphorus source, silicon source, and template (R-NH2), respectively, and the molar ratio is T1:T2:Al2O3:P2O5:SiO2:R-NH2:H2O=0.5:0.006:1.0:0.9:0.45:1.2:55. The ingredients are weighed, the pseudo-boehmite and deionized water are mixed evenly, and then added Phosphoric acid is added and stirred, and then tetraethyl orthosilicate is added and continued to be stirred. Finally, cyclohexylamine and mixed additives are added and stirred evenly. The reaction mixture is charged into a crystallization kettle with a polytetrafluoroethylene liner, 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 is washed with deionized water until neutral, and the separated solid is 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.

[0068] Example 7

[0069] Hydrofluoric acid (T1) is used as an additive, pseudo-boehmite, phosphoric acid, tetraethyl orthosilicate, and di-n-propylamine are used as aluminum source, phosphorus source, silicon source, and template (R-NH2) respectively, and the molar ratio is T1:Al2O3:P2O5:SiO2:R-NH2:H2O=0.506:1.0:0.9:0.45:1.2:55. The ingredients are weighed, the pseudo-boehmite and deionized water are mixed evenly, phosphoric acid is added, and then orthosilicic acid is added. The tetraethyl ester was stirred continuously, and finally cyclohexylamine and mixed additives were added and stirred evenly. The reaction mixture was placed in a crystallization kettle with a polytetrafluoroethylene liner, and 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 separated solid was 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. The scanning electron microscope photo is shown as follows: Figure 2 shown.

[0070] Example 8

[0071] Polyethylene glycol (T2) was used as an additive, pseudo-boehmite, phosphoric acid, tetraethyl orthosilicate, and di-n-propylamine were used as aluminum source, phosphorus source, silicon source, and template (R-NH2) respectively, and the molar ratio was T2:Al2O3:P2O5:SiO2:R-NH2:H2O=0.506:1.0:0.9:0.45:1.2:55. The ingredients were weighed, the pseudo-boehmite and deionized water were mixed evenly, phosphoric acid was added, and stirred, and then added Add tetraethyl orthosilicate and continue stirring. Finally, add cyclohexylamine and mixed additives and stir evenly. Then, charge the reaction mixture into a crystallization kettle with a polytetrafluoroethylene liner, first crystallize at 150°C under autogenous pressure for 18 hours, then crystallize at 180°C under autogenous pressure for 24 hours. Wash the crystallized product with deionized water until it is neutral. The separated solid is 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.

[0072] Example 9

[0073] Hydrofluoric acid (T1) and polyethylene glycol (T2) are mixed additives, pseudo-boehmite, phosphoric acid, tetraethyl orthosilicate, and di-n-propylamine are aluminum source, phosphorus source, silicon source, and template (R-NH2), respectively, and the molar ratio is T1:T2:Al2O3:P2O5:SiO2:R-NH2:H2O=0.496:0.01:1.0:0.9:0.45:1.2:55. The ingredients are weighed, and the pseudo-boehmite and deionized water are mixed evenly. Phosphoric acid was added and stirred, and then tetraethyl orthosilicate was added and continued to be stirred. Finally, cyclohexylamine and mixed additives were added and stirred evenly. The reaction mixture was charged into a crystallization kettle with a polytetrafluoroethylene liner, and 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 separated solid was 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.

[0074] Comparative Example 1

[0075] Preparation of conventional SAPO-11 molecular sieve

[0076] Pseudo-boehmite, phosphoric acid, silica sol, and di-n-propylamine are respectively aluminum source, phosphorus source, silicon source, and template (R), and the molar ratio is Al2O3:P2O5:SiO2:R:H2O=1.0:1.0:0.5:1.0:35. Weigh the ingredients, mix the pseudo-boehmite and deionized water evenly, add phosphoric acid and stir, then add silica sol and continue stirring, finally add di-n-propylamine and stir evenly, then put the above reaction mixture into a crystallization kettle with a polytetrafluoroethylene liner, crystallize at 185°C under autogenous pressure for 36 hours, wash the crystallized product with deionized water until neutral, separate the solid, dry it in an oven at 100°C, and roast it in a muffle furnace at 550°C for 6 hours to obtain SAPO-11 molecular sieve, recorded as B1. Scanning electron microscope photos are shown in Figure 3 As shown, it is a spherical structure with a grain size of 10 to 15 μm.

[0077] Table 1

[0078]

[0079]

[0080] Application Examples

[0081] Application Examples 1-9

[0082] The molecular sieves prepared in Examples 1-9 are used to catalyze the methanol to olefin reaction. The specific steps include: the samples obtained in the examples and comparative examples are respectively tableted and crushed, and then sieved to obtain the particle size portion of 20 to 40 mesh. A fixed bed catalytic reaction device is used to conduct catalyst evaluation experiments. The experimental conditions are: the catalyst loading is 2.0g, the reaction temperature is 450℃, the reaction pressure is normal pressure, the reaction raw material is 75% methanol aqueous solution, and the methanol weight space velocity is 4h -1 .

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

[0084] Application Comparative Example 1

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

[0086] The methanol conversion rate and the distribution of main hydrocarbon products in the application examples and comparative examples are shown in Table 2.

[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 flaky molecular sieve of the present invention has higher reaction activity, 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 are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A molecular sieve, which is in sheet form, has a length not exceeding 1 μm and a thickness not exceeding 300 nm.

2. The molecular sieve according to claim 1, characterized in that The molecular sieve is a SAPO molecular sieve, and preferably the molecular sieve is a SAPO-11 molecular sieve.

3. A method for preparing a molecular sieve, comprising the following steps: An aluminum source, a phosphorus source, a silicon source, a template, an additive and a solvent are mixed, crystallized and then calcined to obtain the molecular sieve.

4. The preparation method according to claim 3, characterized in that: The additives include mineralizers and high molecular organic matter. Preferably, the mineralizer is selected from any one or more of hydrofluoric acid, ammonium fluoride, sodium fluoride or potassium fluoride; and / or The macromolecular organic substance is polyethylene glycol and / or polyhexamethylene biguanide hydrochloride; Preferably, 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; Preferably, 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 3, characterized in that: The aluminum source is selected from at least one of aluminum salts, aluminates, activated alumina, pseudoboehmite or pseudoboehmite; and / or The phosphorus source is at least one of orthophosphoric acid, metaphosphoric acid, phosphate or phosphorus oxide; and / or The silicon source is selected from at least one of silica sol, water glass, active silicon dioxide or orthosilicate; and / or The template agent is an organic amine template agent, preferably the template agent is at least one selected from di-n-propylamine, diisopropylamine or diethylamine; and / or The solvent is at least one of water, C1-C6 alcohols, ethers or ketones; Preferably the solvent is water.

6. The preparation method according to any one of claims 3 to 5, characterized in that: The molar ratio of the additive to the aluminum source in terms of Al2O3 is (0.101-2.5):1, preferably (0.15-1.25):1; In the additive, the molar ratio of the mineralizer to the high molecular organic matter is (0.2-600):1, preferably (15-450):1; The aluminum source is calculated as Al2O3, the phosphorus source is calculated as P2O5, the silicon source is calculated as SiO2, the template is calculated as R-NH2, the mineralizer in the additive is calculated as T1, and the high molecular organic matter is calculated 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).

7. The preparation method according to any one of claims 3 to 6, characterized in that: The crystallization is one-stage crystallization or two-stage crystallization, preferably two-stage crystallization.

8. The preparation method according to any one of claims 3 to 7, characterized in that: When the crystallization is a one-stage crystallization, the temperature of the one-stage crystallization is 170 to 200° C., and the crystallization time is 12 to 120 hours; 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., the time of the first crystallization is 2-48 hours, the temperature of the second crystallization is 120-260° C., and the time of the second crystallization is 2-96 hours; Preferably, the temperature of the second crystallization is 20-100° C. higher than the temperature of the first crystallization.

9. The preparation method according to any one of claims 3 to 8, characterized in that: The calcination temperature is 500-600° C., and the calcination time is 5-8 hours.

10. Use of the molecular sieve according to claim 1 or 2 or the molecular sieve prepared by the preparation method according to any one of claims 3 to 9 as a catalyst; Preferably, the molecular sieve according to claim 1 or 2 or the molecular sieve prepared by the preparation method according to any one of claims 3 to 9 is applied to the field of petrochemical industry and / or fine chemical industry; Preferably, the molecular sieve according to claim 1 or 2 or the molecular sieve prepared by the preparation method of any one of claims 3 to 9 is applied to the methanol to olefins reaction.

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