Method for directly synthesizing and molding SAPO-5 molecular sieve and application of SAPO-5 molecular sieve

Abstract

The invention belongs to the technical field of molecular sieve preparation, and discloses a method for directly synthesizing a molded SAPO-5 molecular sieve and application, and the molded molecular sieve can be directly used as a carrier in aromatic compound reaction. The method is mainly characterized by comprising the following steps: mixing an aluminum source, a phosphorus source, a silicon source, a fluorine source, organic amine, an ionic liquid and water according to a certain proportion to prepare gel, then processing and molding the obtained gel according to an expected shape, and crystallizing the molded gel under a certain condition to obtain a molded body completely composed of a molecular sieve. The molded SAPO-5 molecular sieve is prepared in one step and can be directly used as a catalyst carrier, and the catalyst preparation process is simplified. Compared with a traditional method, the method is simple in preparation process, high in raw material utilization rate, low in waste liquid discharge amount and wide in application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of molecular sieve preparation, and provides a preforming method for synthesizing SAPO-5 subsieves, in particular to a method for directly synthesizing and forming SAPO-5 molecular sieves and applications thereof. Background Art

[0002] Since the 21st century, the economy has developed rapidly, and the demand for gasoline and diesel has increased, but the world's high-quality crude oil reserves are becoming increasingly depleted. Low-quality diesel with high aromatic content has become a problem faced by clean production. At present, my country's automotive diesel standards are becoming more and more stringent, and the diesel VI standard will be implemented in 2019. The published sixth phase GB 19147-2016 "Automotive Diesel" standard is escorting my country's environmental development. Among them, the content of polycyclic aromatic hydrocarbons in automotive diesel is required to be reduced from ≤11 w% to ≤7 w%. The implementation of this current standard is more stringent than the technical requirements for the mass fraction of polycyclic aromatic hydrocarbons in the EU automotive diesel standard. Aromatic hydrocarbons are a carcinogen that has a great impact on human health. Therefore, reducing the content of aromatic hydrocarbons in diesel has become one of the important research topics for scientific researchers. At present, the catalytic hydrodearomatization (HDA) process is one of the necessary means to reduce aromatic compounds in oil products, and the research on high-performance and efficient hydrodearomatization catalysts has become a hot topic.

[0003] SAPO-n molecular sieve is a new type of silicoaluminophosphate series molecular sieve (US4440871, USP 4499327) developed by Union Carbide Corporation (UCC) in 1984. It uses organic amine as a template, hydrated alumina, phosphoric acid, and silica sol as aluminum sources, phosphorus sources, and silicon sources, respectively. First, an organic amine / aluminophosphate / silicon complex with a microporous phase is obtained by hydrothermal crystallization, and then the template organic amine is removed by calcination. At present, 13 three-dimensional microporous skeleton structures of SAPO molecular sieves have been reported, and SAPO-5 is one of them. SAPO-5 molecular sieve belongs to the AFI type molecular sieve, with a one-dimensional 12-membered ring channel parallel to the

[001] direction, a channel size of 7.3×7.3 Å, and a channel wall composed entirely of 6-membered rings. It belongs to the hexagonal crystal system and has a space group of P 6 cc , unit cell parameters a=13.726 Å, c=8.484 Å, skeleton density 17.3 T / 1000 Å, pore size about 0.80nm, belongs to large pore size molecular sieve, is formed by Si isomorphous substitution of phosphorus atoms in a single aluminum phosphate skeleton or two silicon atoms simultaneously replacing a pair of phosphorus aluminum atoms, a kind of high-efficiency molecular sieve with acidic skeleton. Due to its unique pore structure and acidity, SAPO-5 has good catalytic performance in catalytic hydrogenation and dearomatization reactions.

[0004] Conventional hydrothermal synthesis method (US4440871, US4499327, US6680278) is to prepare a mixture of template, aluminum source, phosphorus source and silicon source respectively, and perform constant temperature crystallization reaction under autogenous pressure under suitable temperature conditions. After the crystallization is complete, the solid product is filtered, washed and dried to obtain the original molecular sieve powder, and then the template is removed by roasting to obtain SAPO-5 molecular sieve powder. To apply SAPO-5 molecular sieve to catalytic reaction, it needs to be formed first, which requires mixing the molecular sieve powder with additives such as binder, plasticizer, extrusion aid, pore-forming agent to obtain a plastic body, and then kneading, curing, drying and roasting to obtain the finished product.

[0005] For example, patent CN101244393A discloses a method for preparing AFI type cerium aluminum molecular sieve. In this method, aluminum source, phosphorus source, cerium source, template and water are mixed in the ratio of P2O5: CeO2: Al2O3: template: H2O = 1: (0.03~1): (0.92~1.1): (1.3~2.2), and crystallized at 155~190°C for 1-10 days. After the crystallization is completed, the AFI type cerium aluminum molecular sieve powder is obtained by filtration, washing, drying and roasting. CN102872908A discloses a method for preparing a catalyst for hydrofining of inferior diesel. In this method, AlPO4-5 and metal-substituted molecular sieve MeAPO4-5 powder are mixed with a binder, a pore-forming agent, an extrusion aid, etc. in a certain proportion, and the AFI type catalyst product is obtained by extrusion molding and roasting. The catalyst is used in the hydrofining reaction of inferior diesel.

[0006] The above method first prepares the molecular sieve powder, and then mixes it with additives such as binders to form, dry and roast it to obtain the finished catalyst and adsorbent. The process is long and complicated. In addition, the hydrothermal crystallization process of the molecular sieve is carried out under high pressure, which poses a safety hazard; the filtration and washing process of the molecular sieve powder produces a large amount of wastewater, causing environmental pollution; due to the introduction of binders, the content of molecular sieves in the finished catalysts and adsorbents is generally 60~80%, and cannot reach 100%, which affects the performance of the molecular sieve.

[0007] In order to solve the above problems, people have done a lot of research on simplifying the preparation process of molecular sieve catalysts and adsorbents and increasing the content of molecular sieves in the molded body.

[0008] Researchers use raw materials with a certain shape to directly produce molecular sieves with the same shape as the raw materials without the need for reshaping, which can simplify the preparation process of molecular sieve catalysts and adsorbents.

[0009] For example, Barg, S. et al. prepared a molded X-type molecular sieve adsorbent using aluminum foam monolithic material as raw material. This method placed the aluminum foam monolithic material at 820°C in an air atmosphere for 2 h to convert part of the Al into Al3O2, and then placed it in a solution with a molar ratio of Na2O: K2O: SiO2: H2O = 70: 20: 10: 1500 and crystallized it at 80°C. The resulting molded adsorbent was composed of X-type molecular sieve and Al2O3 (J. Porous Mat., 2011, 18(1): 89-98).

[0010] The above methods crystallize part of the raw materials in the form of integral materials under hydrothermal conditions, and obtain integral catalysts and adsorbents in one step, simplifying the preparation process. However, other raw materials still exist in the aqueous solution, and crystallization is still a hydrothermal process, which poses a safety hazard; the reaction raw materials are divided into solid and liquid phases, the reaction process is limited by mass transfer, the finished product contains unconverted raw materials, and the molecular sieve content is not high. In addition, these methods use raw materials in the shape of integral materials, which are limited by the raw material material and have a single shape. At present, the actual finished products of molded catalysts and adsorbents are rich in shapes, including spheres, strips, cylinders, honeycombs, four-leaf clover shapes, three-leaf clover shapes, external gear shapes, non-porous external gear shapes, plum blossom shapes, porous plum blossom shapes, seven-hole spheres, non-porous spheres, seven-rib wheel shapes, four-hole shapes, four-leaf butterfly shapes, etc.

[0011] In order to increase the content of molecular sieves in molecular sieve catalysts and adsorbent products, researchers have done a lot of work to crystallize additives such as binders added during the molding process into molecular sieves.

[0012] For example, patent CN1105906A discloses a method for preparing a zeolite catalyst, which comprises mixing ZSM-5 powder and a silica binder, and then subjecting the mixture to a hydrothermal treatment in an organic amine or organic quaternary ammonium base aqueous solution or steam to obtain an integrated molecular sieve, and then calcining the mixture to obtain a finished catalyst.

[0013] The above method is to mix the molecular sieve powder and the binder to obtain a molded body, and then crystallize it again to convert the binder into the molecular sieve. Although this method can obtain a molded body composed entirely of molecular sieves, it still requires the synthesis of molecular sieve raw powder; the molding process adds a crystallization step, which increases the manufacturing cost. Summary of the invention

[0014] In order to make up for the shortcomings of the prior art, the present invention proposes a complete molecular sieve preforming synthesis method, which can simultaneously achieve the goals of simplifying the preparation process of molecular sieve catalysts and adsorbents and increasing the molecular sieve content in the molded body. Based on the wide application of SAPO-5 in catalytic hydrogenation and dearomatization reactions, the present invention specifically provides a preforming synthesis method for SAPO-5 molecular sieves.

[0015] The present invention aims to simplify the process of preparing molecular sieve catalysts, directly prepare pure molecular sieve materials with desired shapes, and provide a preforming method for synthesizing SAPO-5 subsieves.

[0016] The solution of the present invention to solve the above technical problems is as follows: A method for directly synthesizing a SAPO-5 molecular sieve, wherein the synthetic gel is processed and shaped into a desired shape, and recrystallized to obtain a shaped molecular sieve having the same shape as the shaped gel, comprising the following steps: (1) Aluminum source, phosphorus source, silicon source, fluorine source, organic amine, ionic liquid and water are mixed in the order of Al2O3:P2O5:SiO2:F - The gel is prepared by mixing organic amine: ionic liquid: H2O in a molar ratio of 1: 0.5-2.5: 0.1-2.0: 0-3: 0.05-2: 0.05-1.5: 35-50, and the reaction is carried out in a self-made ultrasonic oscillation high-pressure reactor; (2) processing the gel prepared in step (1) into a shaped gel having a desired shape; (3) placing the formed gel obtained in step (2) in a sealed container and crystallizing at 160-200° C. for 30 min-24 h to obtain a formed SAPO-5 molecular sieve; Step (2) and step (3) are carried out in a homemade ultrasonic oscillation microwave reactor.

[0017] Furthermore, a reactor ultrasonic oscillator is installed at the lower part of the shell of the ultrasonic oscillation high-pressure reactor, a feeding port is opened at the upper part, a discharging port is opened at the bottom, a middle agitator extends into the reactor, and the agitator is connected to the reactor motor.

[0018] Furthermore, the ultrasonic oscillation high-pressure reactor is also provided with a thermocouple and a pH meter.

[0019] Furthermore, the oscillation frequency of the ultrasonic oscillator of the reactor is: 120KHZ in the early stage, 60KHZ in the middle stage, and 30KHZ in the final stage. Each oscillation time is 10-30 minutes, and the interval period is 4-8 hours. Under the action of high-frequency ultrasonic oscillation, the gel can produce more crystal nuclei, which is conducive to crystal growth, shortens the synthesis time, and improves the crystallinity of the product. The production cost of the catalyst can be reduced by 24-38% compared with the traditional production process synthesis + molding energy consumption.

[0020] Furthermore, a plurality of microwave reaction ultrasonic oscillators are installed at the bottom of the cavity of the ultrasonic oscillation microwave reactor, the rear of which is connected to the receiving hopper, and the front of which is connected to the conveyor belt, and the microwave reaction motor provides power for the conveyor belt.

[0021] Furthermore, the microwave reaction motor is provided with an operation panel, and the cavity is supported by a plurality of brackets.

[0022] Furthermore, the oscillation frequency of the microwave reaction ultrasonic oscillator is 20 MHZ to 3000 MHZ to prevent adhesion between particles.

[0023] Furthermore, the gel molding described in the present invention can be extrusion molding, compression molding, oil column molding, rotation molding, spray molding or granulation; the shape of the obtained molded gel can be spherical, strip, cylindrical, honeycomb, four-leaf clover, three-leaf clover, external gear, non-porous external gear, plum blossom, porous plum blossom, seven-hole sphere, non-porous sphere, seven-rib wheel, four-hole or four-leaf butterfly, etc.; the specific shape and size used are selected and determined according to the actual use conditions.

[0024] Furthermore, the gel of the present invention may be pretreated in a certain form before the molding operation to improve its plasticity so as to ensure convenient operation of the molding process. For example, the gel may be aged at room temperature for 3 to 6 hours, and then treated at 50°C to 110°C for 5 to 12 hours to remove part of the water in the gel to obtain a plastic solid, which is then molded.

[0025] Furthermore, the silicon source described in the present invention is silica sol.

[0026] Furthermore, the synthetic gel of the present invention needs to add an ionic liquid, and the anion of the added ionic liquid is One or more of the following: the cation is an alkyl-substituted imidazolium ion , alkyl-substituted pyridinium ion , alkyl quaternary ammonium salt ion One or more of the following, R is a C1-C16 alkyl group.

[0027] Furthermore, the organic amine described in the present invention is one or both of tetraethylammonium chloride and triethylamine.

[0028] Furthermore, the aluminum source described in the present invention is one or both of pseudo-boehmite and activated alumina.

[0029] Furthermore, the phosphorus source described in the present invention is one or both of phosphoric acid and ammonium monohydrogen phosphate.

[0030] Furthermore, the fluorine source described in the present invention is one or both of hydrofluoric acid and ammonium fluoride.

[0031] The crystallization process can also be carried out by placing the formed gel in a conventional pressure container in the art, and a certain amount of water can be placed in the container in advance, but it is not necessary to directly contact the water with the formed gel. The crystallization process adopts a conventional heating method in the art, such as oil bath heating, oven heating and microwave heating.

[0032] After the crystallization is completed, the molded product prepared by the present invention does not need to be filtered or washed. The crystallized product maintains the same shape and size as the molded gel and is completely composed of molecular sieves. The molecular sieve skeleton structure of the sample of the present invention is the AFI structure confirmed by the International Zeolite Association.

[0033] The invention discloses an application of a directly synthesized SAPO-5 molecular sieve, which is mainly used in: alkylation reaction of toluene and isopropanol; synthesis reaction of p-aminophenol; isomerization reaction of xylene; cracking of alkanes; and hydrorefining of oil products.

[0034] In summary, the present invention provides a preforming method for synthesizing SAPO-5 subsieves, which has the following advantages: The one-step preparation of the molded molecular sieve simplifies the catalyst or adsorbent preparation process. The molded body is completely composed of molecular sieves, which increases the content of molecular sieves per unit volume of catalyst or adsorbent, and can improve its catalytic activity and adsorption capacity. The method directly obtains the molded molecular sieve, avoids the filtering and washing steps in the conventional molecular sieve production process, has low waste liquid discharge, and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the structure of an ultrasonic oscillation high-pressure reactor; Figure 2 It is a schematic diagram of the structure of an ultrasonic oscillation microwave reactor; Figure 3 is the XRD pattern of the sample in Example 1 of the present invention; Figure 4 This is a photo of a cylindrical SAPO-5 molecular sieve prepared by the preforming method of Example 1 of the present invention; Figure 5 This is a photo of the three-leaf clover strip SAPO-5 molecular sieve prepared by the preforming method of Example 2 of the present invention.

[0036] Among them, 1. discharge port, 2. agitator, 3. shell, 4. feeding port, 5. reactor motor, 6. thermocouple, 7. pH meter, 8. reactor ultrasonic oscillator, 9. conveyor belt, 10. microwave reaction motor, 11. operation panel, 12. microwave reaction ultrasonic oscillator, 13. bracket, 14. box shell, 15. hopper, 16. cavity. DETAILED DESCRIPTION

[0037] The present invention is described in detail below by way of examples, but the method of the present invention is not limited thereto and cannot limit the scope of protection of the present invention. To help understand the present invention, the term "preformed" is defined below. The term defined here has the meaning commonly understood by a person of ordinary skill in the art related to the present invention.

[0038] Unless otherwise specified, "preforming" herein refers to the process or step of processing the gel used for synthesizing molecular sieves into a shaped gel with a certain shape, size and mechanical strength by compression, extrusion, rotation, spraying, etc.

[0039] Table 1 Synthesis conditions of Examples 1 to 4 of the present invention . Example 1

[0040] 17.39g pseudo-boehmite (78.6wt% Al2O3) was placed in a 250mL beaker, 110.54g deionized water was added, and the mixture was stirred at room temperature for 30 minutes; 30.82g 85wt% phosphoric acid was added and stirred for 3 hours; 5.34g 30w% silica sol was added and stirred for 30 minutes; 2.34g 40wt% hydrofluoric acid was added and stirred for 30 minutes; 13.53g triethylamine was added and stirred for 30 minutes; finally 38.3g 1-ethyl-3-methyl imidazolium bromide ionic liquid was added. The mixture was stirred evenly into a gel state, and then baked at 90℃ for 30 minutes. The plastic gel mixture obtained by the above operation was extruded into a cylindrical strip using a twin-screw extruder. The obtained cylindrical strip gel was placed in a crystallization reactor with a polytetrafluoroethylene reactor liner and crystallized in a closed state at 195℃ for 20 hours.

[0041] After the crystallization is completed, the crystallization kettle is cooled to room temperature to obtain a cylindrical strip-shaped molecular sieve. The shaped molecular sieve is ground into powder for XRD analysis. The molecular sieve is SAPO-5, such as Figure 3 As shown. The molded molecular sieve is in the shape of a cylindrical strip, such as Figure 4 shown. Example 2

[0042] 17.39g pseudo-boehmite (78.6wt% Al2O3) was placed in a 250mL beaker, 35.27g deionized water was added, and the mixture was stirred at room temperature for 30 minutes; 77g 85wt% phosphoric acid was added and stirred for 3 hours; 53.4g 30w% silica sol was added and stirred for 30 minutes; 13.53g triethylamine and 11.07g tetraethylammonium chloride were added and stirred for 30 minutes; finally, 1.3g 1-ethyl-3-methyl imidazolium bromide ionic liquid was added. The above mixture was stirred evenly into a gel state, and then baked at 100℃ for 30 minutes. The plastic gel mixture obtained by the above operation was extruded into a clover strip with a diameter of 2mm using a twin-screw extruder. The obtained clover strip gel was placed in a crystallization kettle with a polytetrafluoroethylene kettle liner and crystallized in a closed state at 230℃ for 30 minutes.

[0043] After the crystallization is completed, the crystallization kettle is cooled to room temperature to obtain a clover-shaped molecular sieve. The molded molecular sieve is ground into powder for XRD analysis, and the molecular sieve is SAPO-5. The molded molecular sieve is a clover-shaped strip. Figure 5 shown. Example 3

[0044] 17.35g pseudo-boehmite (78.6wt% Al2O3) was placed in a 250mL beaker, 56.55g deionized water was added, and the mixture was stirred at room temperature for 30 minutes; 15.41g 85wt% phosphoric acid was added and stirred for 3 hours; 53.4g 30w% silica sol was added and stirred for 30 minutes; 27.06g triethylamine was added and stirred for 30 minutes; finally, 2.1g 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid and 11g 1-ethyl-3-methylimidazolium bromide ionic liquid were added. The above mixture was stirred evenly into a gel state, and then baked at 75℃ for 30 minutes. The plastic gel mixture obtained by the above operation was rolled into a ball. The obtained spherical gel was placed in a crystallization kettle with a polytetrafluoroethylene kettle liner and crystallized at 160℃ for 24h.

[0045] After the crystallization is completed, the crystallization kettle is cooled to room temperature to obtain a spherical molecular sieve. The spherical molecular sieve is ground into powder for XRD analysis, and the molecular sieve is SAPO-5. Example 4

[0046] 17.39g pseudo-boehmite (78.6wt% Al2O3) was placed in a 250mL beaker, 92.06g deionized water was added, and stirred at room temperature for 30 minutes; 15.41g 85wt% phosphoric acid and 7.69g ammonium monohydrogen phosphate were added, and stirred for 3 hours; 2.67g 30w% silica sol was added, and stirred for 30 minutes; 20.06g 40wt% hydrofluoric acid was added, and stirring continued for 30 minutes; 0.18g triethylamine was added, and stirring continued for 30 minutes; finally, 20.4g 1-ethyl-3-methyl imidazolium bromide ionic liquid was added. The above mixture was stirred evenly into a gel state, and then baked at 75℃ for 30 minutes. The plastic gel mixture obtained by the above operation was extruded into a honeycomb shape using a single screw extruder. The obtained molded honeycomb gel was placed in a crystallization kettle with a polytetrafluoroethylene kettle liner and crystallized in a closed state at 200℃ for 12h.

[0047] After the crystallization is completed, the crystallization kettle is cooled to room temperature to obtain a honeycomb-shaped molecular sieve. The formed molecular sieve is ground into powder for XRD analysis, and the molecular sieve is SAPO-5.

Claims

1. A method for directly synthesizing a formed SAPO-5 molecular sieve, characterized in that: The following steps are involved: S1. Mix aluminum source, phosphorus source, silicon source, fluorine source, organic amine, ionic liquid and water according to the formula of Al2O3:P2O5:SiO2:F - The gel is prepared by mixing organic amine: ionic liquid: H2O in a molar ratio of 1: 0.5-2.5: 0.1-2.0: 0-3: 0.05-2: 0.05-1.5: 35-50, and the reaction is carried out in a self-made ultrasonic oscillation high-pressure reactor; S2. Processing the gel obtained in step S1 into a shaped gel having a desired shape; S3. placing the formed gel obtained in step S2 in a sealed container and crystallizing at 160-200 °C for 30 min-24 h to obtain a formed SAPO-5 molecular sieve; Step S2 and step S3 are carried out in a self-made ultrasonic oscillation microwave reactor. A reactor ultrasonic oscillator (8) is installed at the lower part of the shell (3) of the ultrasonic oscillation high-pressure reactor.

2. The method for directly synthesizing a SAPO-5 molecular sieve according to claim 1, characterized in that: The upper part of the ultrasonic oscillation high-pressure reactor is provided with a feeding port (4), the lower part is provided with a discharging port (1), the middle part of the agitator (2) extends into the reactor, and the agitator (2) is connected to the reactor motor (5); the oscillation frequency of the reactor ultrasonic oscillator (8) is: 120KHZ in the early stage, 60KHZ in the middle stage, and 30KHZ in the final stage, each oscillation time is 10-30 minutes, and the interval period is 4-8 hours.

3. The method for directly synthesizing a SAPO-5 molecular sieve according to claim 2, characterized in that: The ultrasonic oscillation high-pressure reactor is also provided with a thermocouple (6) and a pH meter (7).

4. The method for directly synthesizing SAPO-5 molecular sieve according to claim 1, characterized in that: A plurality of microwave reaction ultrasonic oscillators (12) are installed at the bottom of the cavity (16) of the ultrasonic oscillation microwave reactor, the rear of which is connected to a material receiving hopper (15) and the front of which is connected to a conveyor belt (9). A microwave reaction motor (10) provides power for the conveyor belt (9); the oscillation frequency of the microwave reaction ultrasonic oscillators (12) is 20 MHZ to 3000 MHZ.

5. The method for directly synthesizing SAPO-5 molecular sieve according to claim 4, characterized in that: The microwave reaction motor (10) is provided with an operation panel (11), and the cavity (16) is supported by a plurality of brackets (13).

6. The method for directly synthesizing SAPO-5 molecular sieve according to claim 1, characterized in that: The method of molding the gel in step S2 is extrusion molding, compression molding, oil column molding, rotation molding, spray molding or granulation; the shape of the molded gel is spherical, strip, cylindrical, honeycomb, four-leaf clover, three-leaf clover, external gear, non-porous external gear, plum blossom, porous plum blossom, seven-hole sphere, non-porous sphere, seven-rib wheel, four-hole or four-leaf butterfly.

7. The method for directly synthesizing a SAPO-5 molecular sieve according to claim 1, characterized in that: Step S2: The molded gel is pretreated before the molding operation: the gel is aged at room temperature for 3 to 6 hours, and then treated at 50°C to 110°C for 5 to 12 hours to remove part of the water in the gel to obtain a plastic solid, which is then molded.

8. The method for directly synthesizing SAPO-5 molecular sieve according to claim 1, characterized in that: The silicon source in step S1 is silica sol; the anion of the ionic liquid is One or more of the following: the cation is an alkyl-substituted imidazolium ion , alkyl-substituted pyridinium ion , alkyl quaternary ammonium salt ion One or more of the above, R is a C1-C16 alkyl group; the organic amine is one or both of tetraethylammonium chloride and triethylamine; the aluminum source is one or both of pseudo-boehmite and activated alumina; the phosphorus source is one or both of phosphoric acid and ammonium monohydrogen phosphate; the fluorine source is one or both of hydrofluoric acid and ammonium fluoride.

9. The method for directly synthesizing a SAPO-5 molecular sieve according to claim 1, characterized in that: In step S3, the crystallization process can also be carried out by placing the formed gel in a pressure container, in which a certain amount of water is placed in advance, and the water is not in direct contact with the formed gel; heating is performed during the crystallization process.

10. An application of directly synthesized SAPO-5 molecular sieve, characterized in that: It is used in the alkylation reaction of toluene and isopropanol; the synthesis reaction of p-aminophenol; the isomerization reaction of xylene; the cracking of alkanes; and the hydrorefining of oil products.

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