Nano self-assembled y-type molecular sieve, preparation method and application thereof

Abstract

The application discloses a kind of nano self-assembly Y type molecular sieve and its preparation method and application.The nano self-assembly molecular sieve is the aggregate formed by nano crystalline grain cluster, and the size of nano crystalline grain is 40-100 nm;Aggregate size is 1.3 μm-3.5 μm;Skeleton silicon aluminum ratio (SiO­2 / Al­2O3) is 8.0-13.0.The preparation method of the nano self-assembly Y type molecular sieve, the method comprises the following steps: (1) the mixture material containing alkali source, sodium source, aluminum source, tetramethylammonium template agent, cationic surfactant, silicon source is obtained by aging, crystallization after crystallization material;(2) after crystallization material is mixed with tetramethylammonium fluoride (TMA) F, silicon source and water, after crystallization, washing, filtration, drying is prepared final nano self-assembly Y type molecular sieve.The molecular sieve has higher crystallinity, higher skeleton silicon aluminum ratio, higher external specific surface area, and good stability in high-temperature hydrothermal environment and acidic environment.

Description

Technical Field

[0001] The invention belongs to the field of molecular sieve synthesis and relates to a Y-type molecular sieve and a preparation method and application thereof, in particular to a nano self-assembled Y-type molecular sieve and a preparation method and application thereof. Background Art

[0002] As a large-pore molecular sieve, Y-type molecular sieve has been widely used in oil refining applications such as catalytic cracking, hydrocracking, and isomerization due to its unique acidic properties and pore structure, and has been used for over 50 years. The pores of Y-type molecular sieves are composed of twelve-membered rings with an effective pore diameter of 0.74 nm and an internal cavity volume of up to 50%, making them ideal as active components in cracking reactions. In recent years, the trend toward heavier and inferior crude oil has become increasingly pronounced. The limited pore size of traditional Y-type molecular sieves prevents large molecular reactants from entering the interior of the molecular sieve, forcing them to react only on the limited external surface, significantly reducing catalytic efficiency. Furthermore, due to the large grain size and long pores of traditional Y-type molecular sieves, carbon deposits are easily formed during the reaction, which also shortens the catalyst life to a certain extent. Nanosizing Y-type molecular sieves can expose more acidic sites and is an effective means of improving the diffusion efficiency of large molecules. Although nano Y molecular sieves solve the diffusion problem, there are still separation difficulties in actual industrial production. Self-assembling nano molecular sieves to form aggregates with cluster morphology not only retains the advantages of nano zeolites, but also overcomes the separation difficulties after synthesis. It has become a research direction in this field and has been reported in the literature.

[0003] Yu Jiao et al. reported a method for synthesizing nano self-assembled Y-type molecular sieves in "Nanocrystal zeolite Y assembly synthesized with CTAB under low gelling and aging temperature" in Volume 749 of Chemical Physics Letters. This paper used CTAB as a template to synthesize molecular sieves with a specific surface area of ​​824 m 2 / g, and the external specific surface area is 163 m 2 / g, the grain size is 40nm, and the framework silicon-aluminum ratio is 4.4.

[0004] Ting Tang et al. reported a method for synthesizing nano-self-assembled Y molecular sieves under template-free conditions in RSC Advances Vol. 7, No. 13, P 7711-7717, “Organic template-free synthesis of zeolite Y nanoparticle assemblies and their application in the catalysis of the Ritter reaction”. This method was synthesized under high alkalinity, and the molecular sieve particles could be controlled at the nanoscale with a specific surface area of ​​647 m 2 / g, external specific surface area is 111m 2 / g, compared with traditional Y molecular sieve, it has better catalytic activity.

[0005] Patent CN 107055567 A discloses a method for preparing nano Y zeolite aggregates. The method uses water glass as a silicon source, dissolves it in a sodium hydroxide solution, then adds an aluminum source solution to the silicon source, stirs it evenly, and crystallizes it at 60-100°C for 12-36 hours to obtain nano Y zeolite aggregates. The specific surface area is 650-780m 2 / g, micropore volume 0.23-0.27ml / g, mesopore volume 0.16-0.25ml / g.

[0006] Patent CN 108046287 A discloses a method for synthesizing nano self-assembled zeolites using a long-chain alkyl trimethylammonium bromide surfactant as a template. This patent uses a relatively concentrated formulation system for gelation. By controlling the gelation, aging, and crystallization temperatures at low temperatures, the grain size can be reduced. However, the silicon and aluminum content of the product synthesized by this method is relatively low.

[0007] The nanometer Y molecular sieve self-assembly synthesized by the prior art has the problem of relatively low silicon-aluminum skeleton and poor stability in practical applications. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention provides a nano-self-assembled Y-type molecular sieve, its preparation method, and application. The Y-type molecular sieve is an aggregate formed by clustering multiple small nano-sized Y-type molecular sieve crystals. The molecular sieve has high crystallinity, a high framework silicon-to-aluminum ratio, and a high external specific surface area. It also exhibits excellent stability in high-temperature hydrothermal and acidic environments.

[0009] A nano self-assembled Y-type molecular sieve, which is an aggregate formed by clustering nanocrystals, with a nanocrystal size of 40-100 nm, preferably 60-85 nm; an aggregate size of 1.3 μm-3.5 μm, preferably 1.8 μm-2.8 μm; and a framework silicon-aluminum ratio (SiO2 / Al2O3) of 8.0-13.0, preferably 10.0-12.0.

[0010] In the nano self-assembled Y-type molecular sieve of the present invention, the specific surface area of ​​the molecular sieve is 800-930m 2 / g, preferably 840-900m 2 / g, external specific surface area is 100-170m 2 / g, preferably 140-160m 2 / g.

[0011] In the nano self-assembled Y-type molecular sieve of the present invention, the molecular sieve is firstly subjected to ammonium exchange after synthesis, then calcined at 500°C, and finally hydrothermally treated at 650°C for 7h. The crystallinity of the Y molecular sieve after hydrothermal treatment is 83-96%, preferably 86-93%.

[0012] In the nano self-assembled Y-type molecular sieve of the present invention, after the synthesized molecular sieve is treated with a 0.4M nitric acid solution at 90°C for 1 hour, the resulting Y molecular sieve has a crystallinity of 80-93%, preferably 83-88%.

[0013] A method for preparing a nano self-assembled Y-type molecular sieve, comprising the following steps:

[0014] (1) A mixture containing an alkali source, a sodium source, an aluminum source, a tetramethylammonium template, a cationic surfactant, and a silicon source is aged and crystallized to obtain a crystallized material;

[0015] (2) The crystallized material is mixed with tetramethylammonium fluoride (TMA)F, a silicon source, and water, and then crystallized, washed, filtered, and dried to obtain the final nano self-assembled Y-type molecular sieve.

[0016] In step (1) of the method of the present invention, the concentration of the cationic surfactant in the mixed material is 0.040-0.072 mol / L, preferably 0.045-0.067 mol / L, and more preferably 0.050-0.061 mol / L; the molar ratio of the tetramethylammonium template to the cationic surfactant is 50-110, preferably 60-90, and more preferably 65-85. By controlling the molar ratio of the cationic surfactant to the tetramethylammonium template in the solution, a nano-Y-type molecular sieve with a high silicon-to-aluminum ratio can be prepared.

[0017] In step (1) of the method of the present invention, the molar ratio of the materials in the mixture is: Al2O3: (6.5-12.5)SiO2: (0.1-1.0)Na2O: (6.0-10.0)(TMA)2O: (160-310)H2O: (0.1-0.4) CTAB; preferably Al2O3: (7.2-10.0)SiO2: (0.3-0.7)Na2O: (7.7-9.0)(TMA)2O: (180-270)H2O: (0.15-0.30) CTAB.

[0018] In step (1) of the method of the present invention, the alkali source is one or more of sodium hydroxide, tetramethylammonium hydroxide aqueous solution (TMAOH), and tetramethylammonium hydroxide pentahydrate.

[0019] In step (1) of the method of the present invention, the aluminum source is one or more of aluminum isopropoxide, aluminum powder, sodium metaaluminate, and aluminum sulfate 18hydrate.

[0020] In step (1) of the method of the present invention, the silicon source is one or more of silica sol, sodium silicate, ethyl orthosilicate, nano-silica, and water glass.

[0021] In step (1) of the method of the present invention, the sodium source is one or more of sodium hydroxide, sodium chloride, and sodium bromide.

[0022] In step (1) of the method of the present invention, the tetramethylammonium template agent is one or more of tetramethylammonium hydroxide aqueous solution, tetramethylammonium hydroxide pentahydrate, tetramethylammonium bromide, and tetramethylammonium chloride.

[0023] In step (1) of the method of the present invention, the cationic surfactant is one or more of dodecyltrimethylammonium bromide (DTAB), hexadecyltrimethylammonium bromide (CTAB), and octadecyltrimethylammonium bromide (STAB).

[0024] In step (1) of the method of the present invention, the aging temperature is 25-35°C, preferably 28-31°C; the aging time is 20-40h, preferably 25-35h; the crystallization temperature is 80-100°C, preferably 85-95°C; and the crystallization time is 60-100h, preferably 70-90h.

[0025] In step (2) of the method of the present invention, after tetramethylammonium fluoride, silicon source and water are added to the crystallized material, the molar ratio of the materials in the solution is Al2O3:(14-20)SiO2:(0.1-1.0)Na2O:(6-10)(TMA)2O:(4-8)(TMA)F:(320-540)H2O:(0.1-0.4)CTAB; preferably Al2O3:(15-18)SiO2:(0.30-0.7)Na2O:(7.7-9.0)(TMA)2O:(5.2-6.6)(TMA)F:(380-430)H2O:(0.15-0.30)CTAB.

[0026] In step (2) of the method of the present invention, the crystallization temperature is 85-105°C, preferably 90-101°C; the crystallization time is 30-70h, preferably 40-60h.

[0027] In step (2) of the method of the present invention, the molecular sieve is dried at a temperature of 80-120°C for 7-13 hours, and calcined at a temperature of 450-550°C for 3-5 hours.

[0028] A specific method for preparing a nano self-assembled Y-type molecular sieve comprises the following steps:

[0029] 1) Under stirring, dissolve the alkali source, sodium source and tetramethylammonium template in a certain amount of distilled water, then add surfactant to the solution and stir until the surfactant is completely dissolved. Then, under stirring, add silicon source to the above aluminum source solution to form gel at room temperature, age at room temperature for a period of time, and then crystallize at a certain temperature for a period of time;

[0030] 2) Take out the crystallized solution, add tetramethylammonium fluoride (TMA)F, silicon source and water to the solution under stirring conditions, stir evenly and continue to crystallize at a certain temperature for a period of time, take out, wash, filter, dry and calcine to obtain the final nano self-assembled Y-type molecular sieve product.

[0031] The nano self-assembled Y-type molecular sieve is used to prepare a hydrocracking catalyst.

[0032] Compared with the prior art, the nano self-assembled Y-type molecular sieve and its preparation method and application in the present invention have the following advantages:

[0033] 1. In the presence of cationic surfactants and tetramethylammonium ions (TMA + ) in a dual-template system to synthesize Y molecular sieve nanocluster precursors. + There is an electrostatic repulsive force between the two, and by controlling the molar ratio of tetramethylammonium template and cationic surfactant in the solution, TMA +It will be easier to enter the framework of the molecular sieve and prepare a nanocluster Y-type molecular sieve precursor with a high silicon-aluminum ratio.

[0034] 2. Wrapped with TMA + The sodalite cage structure is more stable, but not TMA + The stability of the sodalite cage is poor. Under the action of fluoride ions, the Si-O-Al bond is opened, and the silicon atoms and aluminum atoms form fluorine complexes. + 、TMA + Under the joint action of silicon and aluminum, a part of TMA is recombined. + Enclosed in sodalite cages, the Si-Al ratio of the molecular sieve framework is further increased;

[0035] 3. The molecular sieve has a high framework silicon-aluminum ratio, a small grain size and a high crystallinity, good hydrothermal stability and acid stability, and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the XRD diffraction pattern of the Y-type molecular sieve prepared in Example 1. DETAILED DESCRIPTION

[0037] The characterization method of the nano Y-type molecular sieve self-assembly in the present invention is as follows:

[0038] To test hydrothermal stability, the sample was first subjected to ammonium exchange three times with a 1.5 mol / L ammonium chloride solution at 90°C, with a solid-to-liquid ratio of 1:10 for each exchange. The sample was then calcined at 500°C for 3 hours and finally hydrothermally treated at 650°C in a 0.1 MPa water vapor atmosphere for 5 hours. The crystallinity of the sample after hydrothermal treatment was determined using X-ray diffraction.

[0039] The stability test under acidic conditions is to add the sample to a 0.4M nitric acid solution with a solid-liquid ratio of 1:10, and stir at 90°C for 1 hour. The treated molecular sieve is washed and dried, and then the crystallinity is tested.

[0040] The specific surface area and pore volume of the molecular sieve were measured by N2-adsorption desorption method. Before the measurement, the sample was first heat treated at 300℃ for 3h, and then tested by nitrogen adsorption at 77K. The specific surface area of ​​the molecular sieve was calculated by BET method, and the total pore volume was calculated by p / p 0 =0.98, and the external specific surface area was obtained by t-Plot method.

[0041] The silicon-to-aluminum ratio of the molecular sieve framework was measured using X-ray diffraction. The unit cell parameter a0 was measured using the Chinese petrochemical industry standard SH / T0339-92 and then substituted into the Breck formula (Si / Al = ((192 × 0.00868) / (a0 − 24.191))–1) for calculation. The resulting silicon-to-aluminum ratio is expressed as the molar ratio SiO2 / Al2O3.

[0042] The particle size of the nano Y-type molecular sieve was measured using a scanning electron microscope (SEM).

[0043] The following examples and comparative examples further illustrate the effects and benefits of the method of the present invention, but the following examples do not limit the method of the present invention. In the preparation process of the nano self-assembled Y-type molecular sieve of the present invention, the drying temperature is 100°C for 10 hours and the calcination temperature is 500°C for 4 hours.

[0044] Example 1

[0045] (1) Under stirring, sodium hydroxide and tetramethylammonium hydroxide were added to water. After stirring evenly, aluminum isopropoxide was added, followed by hexadecyltrimethylammonium bromide. The mixture was stirred for a period of time until completely dissolved. Silica sol was added to the above solution and gelled at room temperature. The solution composition was Al2O3: 9.5SiO2: 0.5Na2O: 8.3(TMA)2O: 230H2O: 0.26CTAB. The concentration of the cationic surfactant in the mixture was 0.063 mol / L. The molar ratio of the tetramethylammonium template to the cationic surfactant was 64. The mixture was statically aged at 27°C for 22 h. The aged solution was crystallized at 90°C for 80 h.

[0046] (2) The crystallized solution was removed and, under stirring, tetramethylammonium fluoride, nano-silica, and water were added to the solution. After uniform stirring, the solution composition became Al2O3: 16.8SiO2: 0.5Na2O: 8.3(TMA)2O: 5.8(TMA)F: 410H2O: 0.26CTAB. The solution was crystallized at 96°C for 46 hours, removed, washed, filtered, dried, and calcined to obtain the product.

[0047] Further examples are given according to Example 1.

[0048] Example 2

[0049] (1) Under stirring, sodium hydroxide and tetramethylammonium hydroxide were added to water. After stirring evenly, aluminum isopropoxide was added, followed by hexadecyltrimethylammonium bromide. The mixture was stirred for a period of time until completely dissolved. Silica sol was added to the above solution and gelled at room temperature. The solution composition was Al2O3: 7.2SiO2: 0.3Na2O: 7.8(TMA)2O: 185H2O: 0.15STAB. The concentration of the cationic surfactant in the mixture was 0.045 mol / L. The molar ratio of the tetramethylammonium template to the cationic surfactant was 104. The mixture was statically aged at 24°C for 25 h. The aged solution was crystallized at 82°C for 88 h.

[0050] (2) The crystallized solution was removed and, under stirring, tetramethylammonium fluoride, nano-silica, and water were added to the solution. After uniform stirring, the solution composition became Al2O3: 15.2SiO2: 0.3Na2O: 7.8(TMA)2O: 5.3(TMA)F: 383H2O: 0.15STAB. The solution was crystallized at 90°C for 60 h, removed, washed, filtered, dried, and calcined to obtain the product.

[0051] Example 3

[0052] (1) Under stirring, sodium hydroxide and tetramethylammonium hydroxide were added to water. After stirring evenly, aluminum isopropoxide was added, followed by hexadecyltrimethylammonium bromide. The mixture was stirred for a period of time until completely dissolved. Silica sol was added to the above solution and gelled at room temperature. The solution composition was Al2O3: 9.8SiO2: 0.7Na2O: 8.8(TMA)2O: 270H2O: 0.29DTAB. The concentration of the cationic surfactant in the mixture was 0.060 mol / L. The molar ratio of the tetramethylammonium template to the cationic surfactant was 6:1. The mixture was statically aged at 31°C for 18 h. The aged solution was crystallized at 95°C for 70 h.

[0053] (2) The crystallized solution was removed and, under stirring, tetramethylammonium fluoride, nano-silica, and water were added to the solution. After uniform stirring, the solution composition became Al2O3: 18.0% SiO2: 0.7% Na2O: 8.8% (TMA)2O: 6.6% (TMA)F: 430% H2O: 0.29% DTAB. The solution was crystallized at 101°C for 40 hours, removed, washed, filtered, dried, and calcined to obtain the product.

[0054] Example 4

[0055] (1) Under stirring, sodium hydroxide and tetramethylammonium hydroxide were added to water. After stirring evenly, aluminum isopropoxide was added, followed by hexadecyltrimethylammonium bromide. The mixture was stirred for a period of time until completely dissolved. Silica sol was added to the above solution and gelled at room temperature. The solution composition was Al2O3: 6.8SiO2: 0.2Na2O: 6.0(TMA)2O: 160H2O: 0.13CTAB. The concentration of the cationic surfactant in the mixture was 0.045 mol / L. The molar ratio of the tetramethylammonium template to the cationic surfactant was 92. The mixture was statically aged at 20°C for 30 h. The aged solution was crystallized at 80°C for 100 h.

[0056] (2) The crystallized solution was removed and, under stirring, tetramethylammonium fluoride, nano-silica, and water were added to the solution. After uniform stirring, the solution composition became Al2O3:14.0SiO2:0.2Na2O:6.0(TMA)2O:4.0(TMA)F:320H2O:0.13CTAB. The solution was crystallized at 86°C for 70 h, removed, washed, filtered, dried, and calcined to obtain the product.

[0057] Example 5

[0058] (1) Under stirring, sodium hydroxide and tetramethylammonium hydroxide were added to water. After stirring evenly, aluminum isopropoxide was added, followed by hexadecyltrimethylammonium bromide. The mixture was stirred for a period of time until completely dissolved. Silica sol was added to the above solution and gelled at room temperature. The solution composition was Al2O3: 12.2SiO2: 0.95Na2O: 10.0(TMA)2O: 310H2O: 0.4CTAB. The concentration of the cationic surfactant in the mixture was 0.072 mol / L. The molar ratio of the tetramethylammonium template to the cationic surfactant was 50. The mixture was statically aged at 35°C for 10 h. The aged solution was crystallized at 100°C for 63 h.

[0059] (2) The crystallized solution was removed and, under stirring, tetramethylammonium fluoride, nano-silica, and water were added to the solution. After uniform stirring, the solution composition became Al2O3: 20.0SiO2: 0.95Na2O: 10.0(TMA)2O: 7.8(TMA)F: 537H2O: 0.4CTAB. The solution was crystallized at 105°C for 30 h, removed, washed, filtered, dried, and calcined to obtain the product.

[0060] Comparative Example 1

[0061] (1) While stirring, add sodium hydroxide and tetramethylammonium hydroxide to water. After stirring evenly, add aluminum isopropoxide and then cetyltrimethylammonium bromide. Stir for a while until completely dissolved. Add silica sol to the above solution and form a gel at room temperature. The solution composition is Al2O3: 9.5SiO2: 0.5Na2O: 8.3(TMA)2O: 230H2O: 0.26CTAB. Static aging is carried out at 27℃ for 22 hours. The aged solution is then crystallized at 90℃ for 80 hours.

[0062] Comparative Example 2

[0063] (1) While stirring, add sodium hydroxide and tetramethylammonium hydroxide to water. After stirring evenly, add aluminum isopropoxide and then cetyltrimethylammonium bromide. Stir for a period of time until completely dissolved. Then, add an aqueous solution of nano-silica and tetramethylammonium fluoride to the above solution. The solution forms a gel at room temperature. The solution composition is Al2O3:16.8SiO2:0.5Na2O:8.3(TMA)2O:5.8(TMA)F:410H2O:0.26CTAB. The solution is crystallized at 96°C for 46 hours, washed, filtered, dried, and calcined to obtain the product.

[0064] Comparative Example 3

[0065] (1) Under stirring, sodium hydroxide and tetramethylammonium hydroxide were added to water. After stirring evenly, aluminum isopropoxide was added, followed by hexadecyltrimethylammonium bromide. The mixture was stirred for a period of time until completely dissolved. Silica sol was added to the above solution and gelled at room temperature. The solution composition was Al2O3: 9.5SiO2: 0.5Na2O: 3.9(TMA)2O: 230H2O: 0.26CTAB. The concentration of the cationic surfactant in the mixture was 0.063 mol / L. The molar ratio of the tetramethylammonium template to the cationic surfactant was 30. The mixture was statically aged at 27°C for 22 h. The aged solution was crystallized at 90°C for 80 h.

[0066] (2) The crystallized solution was removed and, under stirring, tetramethylammonium fluoride, nano-silica, and water were added to the solution. After uniform stirring, the solution composition became Al2O3: 16.8SiO2: 0.5Na2O: 3.9(TMA)2O: 5.8(TMA)F: 410H2O: 0.26CTAB. The solution was crystallized at 96°C for 46 hours, removed, washed, filtered, dried, and calcined to obtain the product.

[0067] The product properties of the above examples and comparative examples are shown in Table 1

[0068] Table 1 Structural properties of products in Examples and Comparative Examples

[0069]

Claims

1. A method for preparing a nano self-assembled Y-type molecular sieve, wherein: The nano self-assembled molecular sieve is an aggregate formed by clustering nanocrystals, the nanocrystal size is 40-100 nm; the aggregate size is 1.3 μm-3.5 μm; the framework SiO2 / Al2O3 molar ratio is 8.0-13.0, and the method comprises the following steps: (1) A mixture containing an alkali source, a sodium source, an aluminum source, a tetramethylammonium template, a cationic surfactant, and a silicon source is aged and crystallized to obtain a crystallized material; (2) The crystallized material is mixed with tetramethylammonium fluoride, a silicon source, and water, and then crystallized, washed, filtered, and dried to obtain the final nano self-assembled Y-type molecular sieve; The tetramethylammonium template is one or more of tetramethylammonium hydroxide aqueous solution, tetramethylammonium hydroxide pentahydrate, tetramethylammonium bromide, and tetramethylammonium chloride; The cationic surfactant is one or more of dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide; Wherein, the molar ratio of the tetramethylammonium template agent to the cationic surfactant is 50-110.

2. The method according to claim 1, wherein: In step (1), the concentration of the cationic surfactant in the mixed material is 0.040-0.072 mol / L.

3. The method according to claim 2, wherein: In step (1), the concentration of the cationic surfactant in the mixed material is 0.045-0.067 mol / L; and the molar ratio of the tetramethylammonium template to the cationic surfactant is 60-90.

4. The method according to claim 2, wherein: In step (1), the concentration of the cationic surfactant in the mixed material is 0.050-0.061 mol / L; and the molar ratio of the tetramethylammonium template to the cationic surfactant is 65-85.

5. The method according to claim 1, wherein: In step (1), the molar ratio of the materials in the mixture is: Al2O3: (6.5-12.5)SiO2: (0.1-1.0)Na2O: (6.0-10.0)(TMA)2O: (160-310)H2O: (0.1-0.4) CTAB.

6. The method according to claim 5, wherein: In step (1), the molar ratio of the materials in the mixture is: Al2O3: (7.2-10.0)SiO2: (0.3-0.7)Na2O: (7.7-9.0)(TMA)2O: (180-270)H2O: (0.15-0.30) CTAB.

7. The method according to claim 1, wherein: In step (2), after tetramethylammonium fluoride, silicon source and water are added to the crystallized material, the molar ratio of the materials in the solution is Al2O3:(14-20)SiO2:(0.1-1.0)Na2O:(6-10)(TMA)2O:(4-8)(TMA)F:(320-540)H2O:(0.1-0.4)CTAB.

8. The method according to claim 7, wherein: In step (2), the molar ratio of the materials in the solution is Al2O3:(15-18)SiO2:(0.30-0.7)Na2O:(7.7-9.0)(TMA)2O:(5.2-6.6)(TMA)F:(380-430)H2O:(0.15-0.30)CTAB.

9. The method according to claim 1, wherein: In step (2), the crystallization temperature is 85-105°C; and the crystallization time is 30-70h.

10. The method according to claim 9, characterized in that: In step (2), the crystallization temperature is 90-101°C; and the crystallization time is 40-60h.

11. The method according to claim 1, wherein: The method comprises the steps of: 1) Under stirring, dissolve the alkali source, sodium source and tetramethylammonium template in a certain amount of distilled water, then add the aluminum source and surfactant to the solution in sequence, stir until the surfactant is completely dissolved, then add the silicon source to the above solution under stirring, form a gel at room temperature, age at room temperature for a period of time, and then crystallize at a certain temperature for a period of time; 2) Take out the crystallized solution, add tetramethylammonium fluoride (TMA)F, silicon source and water to the solution under stirring conditions, stir evenly and continue to crystallize at a certain temperature for a period of time, take out, wash, filter and dry to obtain the final nano self-assembled Y-type molecular sieve product.

12. Nano self-assembled Y-type molecular sieve prepared by the method according to any one of claims 1 to 11.

13. The nano self-assembled Y-type molecular sieve according to claim 12, characterized in that: The nano self-assembled molecular sieve is an aggregate formed by clustering nanocrystals, the nanocrystal size is 60-85 nm, the aggregate size is 1.8 μm-2.8 μm, and the framework SiO2 / Al2O3 molar ratio is 10.0-12.

0.

14. The nano self-assembled Y-type molecular sieve according to claim 12, characterized in that: The specific surface area of ​​the molecular sieve is 800-930m 2 / g, external specific surface area is 100-170m 2 / g.

15. The nano self-assembled Y-type molecular sieve according to claim 12, characterized in that: The specific surface area of ​​the molecular sieve is 840-900m 2 / g, external specific surface area is 140-160m 2 / g.

16. The nano self-assembled Y-type molecular sieve according to claim 12, characterized in that: After synthesis, the molecular sieve was first subjected to ammonium exchange, then calcined at 500°C, and finally hydrothermally treated at 650°C for 7 hours. The crystallinity of the Y molecular sieve after hydrothermal treatment was 83-96%.

17. The nano self-assembled Y-type molecular sieve according to claim 12, characterized in that: After synthesis, the molecular sieve was first subjected to ammonium exchange, then calcined at 500°C, and finally hydrothermally treated at 650°C for 7 hours. The crystallinity of the Y molecular sieve after hydrothermal treatment was 86-93%.

18. The nano self-assembled Y-type molecular sieve according to claim 12, characterized in that: After the synthesized molecular sieve was treated with a 0.4M nitric acid solution at 90°C for 1 hour, the crystallinity of the obtained Y molecular sieve was 80-93%.

19. The nano self-assembled Y-type molecular sieve according to claim 12, characterized in that: After the synthesized molecular sieve was treated with a 0.4M nitric acid solution at 90°C for 1 hour, the crystallinity of the obtained Y molecular sieve was 83-88%.

20. Use of the nano self-assembled Y-type molecular sieve according to any one of claims 12 to 19 in the preparation of a hydrocracking catalyst.

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