Y-type molecular sieve nanocluster, synthesis method and application thereof

Abstract

The application discloses Y-type molecular sieve nanoclusters, a synthesis method and application thereof. The Y-type molecular sieve nanoclusters have a particle size of 1-4 microns, preferably 2-3 microns; the nanocluster particles are composed of nanomolecular sieves with a crystal grain size of 30-60 nm, preferably 35-50 nm; and a silicon-aluminum ratio (SiO2 / Al2O3) of 5.0-6.5, preferably 5.8-6.3. The Y-type molecular sieve nanoclusters have the advantages of high specific surface area, high silicon-aluminum ratio, high pore volume, high hydrothermal stability and the like; and the preparation method does not need to use a template agent, has low cost and is easy to be applied in industry.

Description

TECHNICAL FIELD

[0001] The present application relates to a Y-type molecular sieve nanocluster and a synthesis method and application thereof, in particular to a Y-type molecular sieve nanocluster with high hydrothermal stability and a synthesis method and application thereof. BACKGROUND

[0002] Y-type molecular sieve is widely used in the industry in the fields of catalytic cracking, hydrocracking, etc., is an important active component of catalyst, and has very high cracking reaction activity. Due to its special pore structure and acid property, Y-type molecular sieve has incomparable advantages in the field of hydrocracking, and the 0.74 nm pore opening diameter forms a unique three-dimensional pore structure, which provides an ideal reaction site for reactants, and the eight-membered zeolite cage inside the molecular sieve has good conversion capacity for cyclic hydrocarbons.

[0003] However, due to the limitation of Y molecular sieve micropores, many large molecule reactants cannot enter the pore channel, which limits the application effect, and the traditional Y molecular sieve crystal grain size is about 1 μm, and the long pore channel also makes the reactant molecules easy to be cracked multiple times, and the liquid yield is reduced. Therefore, reducing the size of the molecular sieve and nanocrystallizing the molecular sieve have become an important research direction in recent years. Nanocrystallization of Y molecular sieve can not only expose more surface acid centers, solve the problem of insufficient conversion capacity of molecular sieve for large molecules in heavy oil, but also can reduce the generation of coke caused by diffusion to a certain extent, and prolong the service life of the catalyst.

[0004] CN1296915A discloses a preparation method of nano Y zeolite. The method uses a conventional method to prepare a silica-alumina gel solution, ages at a certain temperature, then adds an acidified aluminum salt solution and an unacidified aluminum salt solution to the silica-alumina gel, and crystallizes the mixture at a certain temperature to obtain a nano NaY molecular sieve with a size of 30-250 nm, but the silica-alumina ratio is low.

[0005] Although the nano Y-type molecular sieve solves the problem of accessibility of large molecule reactants, it also has some shortcomings: it is difficult to separate from the reaction system after synthesis, the silica-alumina ratio is low, and the stability is not good, which limits its further application. The nano self-assembled Y-type molecular sieve not only retains the advantages of nano zeolite, but also solves the problem of difficult separation after synthesis, and some documents have been reported at present.

[0006] Ting Tang et al. in RSC Advances, vol. 7, issue 13, pages 7711-7717, "Organic template-free synthesis of zeolite Y nanoparticle assemblies and their application in the catalysis of the Ritter reaction" reported that a nanoparticle self-assembled Y zeolite was prepared by heating a silica-alumina gel with a molar ratio of Al2O3: 14.4Na2O: 9.8SiO2: 590H2O at 75°C for 16 h without using an organic template, and the external surface area reached 111 m 2 / g. Shuling Xu et al. in RSC Advances, vol. 6, issue 74, pages 69822-69827, "Zeolite Y nanoparticle assemblies with high activity in the direct hydration of terminal alkynes" reported that a nanoparticle self-assembled Y zeolite was synthesized by using TMOAC as an additive, the crystal grain size of the zeolite was 60-100 nm, and the external surface area reached 158 m 2 / g. Yu Jiao et al. in Chemical Physics Letters, vol. 749, "Nanocrystal zeolite Y assembly synthesized with CTAB under low gelling and aging temperature" reported that a nanoparticle self-assembled Y zeolite with a mesoporous structure was synthesized by using CTAB as a mesoporous template, the external specific surface area of the zeolite was 163 m 2 / g, and the silica-alumina ratio was 4.4. The nanoparticle self-assembled Y zeolites disclosed in the prior art have a low silica-alumina ratio, and have poor stability in practical applications. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application provides a Y-type zeolite, a synthesis method thereof and an application thereof. The zeolite has the advantages of high specific surface area, high silica-alumina ratio, high pore volume and high hydrothermal stability. The preparation method does not require the use of a template, has low cost and is easy to apply in industry.

[0008] A Y-type zeolite nanoparticle cluster, the particle size of the Y-type zeolite nanoparticle cluster is 1-4 μm, preferably 2-3 μm; the nanoparticle cluster particle is composed of a nanomolecular sieve with a crystal grain size of 30-60 nm, preferably 35-50 nm; and the silica-alumina ratio (SiO2 / Al2O3) is 5.0-6.5, preferably 5.8-6.3.

[0009] The specific surface area of the Y-type molecular sieve nanocluster is 800-950 m 2 / g, preferably 830-900 m 2 / g, and the external specific surface area is 130-200 m 2 / g, preferably 140-180 m 2 / g; the pore volume is 0.50-0.66 ml / g, preferably 0.55-0.63 ml / g.

[0010] The Y-type molecular sieve nanocluster is treated with ammonium exchange at 700°C and 0.1 MPa of high-temperature water vapor for 2h, and the crystallinity retention rate of the Y-type molecular sieve after the treatment is 86-95%, preferably 89-93%, compared with the crystallinity of the Y-type molecular sieve before the hydrothermal treatment.

[0011] A synthesis method of a Y-type molecular sieve nanocluster, the method comprising the following contents:

[0012] The silicon source, the aluminum source and the alkali source are mixed and then crystallized, and the obtained solution after crystallization is recorded as solution A;

[0013] The silicon source is added to the solution A, and then crystallization is performed, and the obtained solution is recorded as solution B;

[0014] The silicon source is added to the solution B, and then crystallization is performed, and the material after crystallization is washed and dried to obtain the final Y-type molecular sieve nanocluster product.

[0015] In the synthesis method of the Y-type molecular sieve nanocluster, the silicon source is one or more of silica sol, silicon dioxide, water glass and sodium silicate; the aluminum source is one or more of sodium aluminate, aluminum powder and aluminum hydroxide; and the alkali source is one or more of sodium hydroxide, tetraethylammonium bromide and tetrapropylammonium bromide.

[0016] In the synthesis method of the Y-type molecular sieve nanocluster, the molar ratio of the silicon source, the aluminum source and the alkali source after mixing and crystallization is: Al2O3: (8-15) SiO2: (10-18) Na2O: (150-400) H2O, preferably Al2O3: (10-13) SiO2: (13-16) Na2O: (250-350) H2O, and the water-silicon ratio of the crystallization system is 20-35, preferably 23-30.

[0017] In the synthesis method of the Y-type molecular sieve nanocluster, the crystallization temperature after mixing the silicon source, the aluminum source and the alkali source for crystallization is 5-25°C, preferably 10-20°C; and the crystallization time is 8-15 d, preferably 8-12 d.

[0018] In the synthesis method of the Y-type molecular sieve nanocluster, the molar ratio of the materials after adding the silicon source to solution A for crystallization is Al2O3: (15-23) SiO2: (10-18) Na2O: (450-850) H2O, preferably Al2O3: (17-20) SiO2: (13-16) Na2O: (500-750) H2O, and the water-to-silicon ratio of the crystallization system is 27-40, preferably 30-37.

[0019] In the synthesis method of the Y-type molecular sieve nanocluster, the crystallization temperature after adding the silicon source to solution A for crystallization is 30-60°C, preferably 40-50°C; and the crystallization time is 4-7d, preferably 5-6d.

[0020] In the synthesis method of the Y-type molecular sieve nanocluster, the molar ratio of the materials after adding the silicon source to solution B for crystallization is Al2O3: (25-40) SiO2: (10-18) Na2O: (600-950) H2O, preferably Al2O3: (30-35) SiO2: (13-16) Na2O: (650-800) H2O.

[0021] In the synthesis method of the Y-type molecular sieve nanocluster, the crystallization temperature after adding the silicon source to solution B for crystallization is 80-100°C, preferably 85-95°C; and the crystallization time is 10-40 h, preferably 20-30 h.

[0022] In the synthesis method of the Y-type molecular sieve nanocluster, the crystallization temperature after mixing the silicon source, the aluminum source, and the alkali source for crystallization is 20-35°C lower than the crystallization temperature after adding the silicon source to solution A for crystallization, preferably 24-30°C lower.

[0023] In the synthesis method of the Y-type molecular sieve nanocluster, the crystallization temperature after adding the silicon source to solution A for crystallization is 20-65°C lower than the crystallization temperature after adding the silicon source to solution B for crystallization, preferably 40-50°C lower.

[0024] In the synthesis method of the Y-type molecular sieve nanocluster, the water-to-silicon ratio (H2O / SiO2) of solution A is 4-12 lower than the water-to-silicon ratio of solution B, preferably 6-10.5 lower.

[0025] The synthesis method of the Y-type molecular sieve nanocluster in the embodiment of the application specifically includes the following steps:

[0026] (1) Under stirring, sodium aluminate is dissolved in a sodium hydroxide solution with a certain concentration, and then taken out and cooled at a certain temperature; a certain amount of silica sol is added to the sodium aluminate solution, and the solution after crystallization is recorded as solution A;

[0027] (2) under the state of stirring, a certain amount of silica and distilled water are added into solution A, crystallization is carried out at a certain temperature for a period of time, and the solution after crystallization is recorded as solution B;

[0028] (3) under the state of stirring, a certain amount of silica and distilled water are added into solution B, crystallization is carried out at a certain temperature for a period of time, and the obtained solution is dried after washing and filtration to obtain the final product.

[0029] In the method, the molar ratio of the material before crystallization in step (1) is: Al2O3: (8-15) SiO2: (10-18) Na2O: (150-400) H2O, preferably Al2O3: (10-13) SiO2: (13-16) Na2O: (250-350) H2O.

[0030] In the method, the crystallization temperature of step (1) is 5-25℃, preferably 10-20℃; and the crystallization time is 8-15 d, preferably 8-12 d.

[0031] In the method, the molar ratio of the material before crystallization in step (2) is: Al2O3: (15-23) SiO2: (10-18) Na2O: (450-850) H2O, preferably Al2O3: (17-20) SiO2: (13-16) Na2O: (500-750) H2O.

[0032] In the method, the crystallization temperature of step (2) is 30-60℃, preferably 40-50℃; and the crystallization time is 4-7 d, preferably 5-6 d.

[0033] In the method, the molar ratio of the material before crystallization in step (3) is: Al2O3: (25-40) SiO2: (10-18) Na2O: (600-950) H2O, preferably Al2O3: (30-35) SiO2: (13-16) Na2O: (650-800) H2O.

[0034] In the method, the crystallization temperature of step (3) is 80-100℃, preferably 85-95℃; and the crystallization time is 10-40 h, preferably 20-30 h.

[0035] The Y-type molecular sieve nanocluster described above is used as an acid cracking component of a hydrocracking catalyst.

[0036] The method of the present application adopts three-stage temperature control crystallization and twice supplement of silicon source in the crystallization process to prepare the nano self-assembled Y molecular sieve. The formation process of the molecular sieve can be divided into the following three stages: the first stage is to crystallize under low temperature and low water-silicon ratio, at this time a large number of crystal nuclei are formed in the solution, the small size crystal nuclei cannot grow rapidly and gather together to form a precursor. The second stage is to increase the crystallization temperature and the water-silicon ratio, and supplement the silicon source in the crystallization process, to increase the crystallinity of the molecular sieve and make it grow together, while keeping a high silicon-aluminum ratio. The third stage is to further increase the crystallization temperature and supplement the silicon source to perform the final crystallization. The product obtained after crystallization is a nano cluster structure formed by the growth of multiple nanoscale crystal grains together, and the molecular sieve has a high silicon-aluminum ratio and small crystal grain size.

[0037] The Y type molecular sieve is formed by the growth of multiple nanoscale Y type molecular sieve small crystal grains together, and is easy to separate after synthesis. The molecular sieve has a high silicon-aluminum ratio while ensuring a small crystal grain size, has good hydrothermal stability, and has industrial application value. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 XRD diffraction pattern of the Y type molecular sieve prepared in Example 1.

[0039] Figure 2 SEM image of the Y type molecular sieve prepared in Example 1 at a magnification of 50k.

[0040] Figure 3 SEM image of the Y type molecular sieve prepared in Example 1 at a magnification of 5k. DETAILED DESCRIPTION

[0041] The characterization method of the nano self-assembled Y type molecular sieve in the present application is as follows: the hydrothermal stability test is to first perform ammonium exchange on the sample three times with 1.5 mol / L, 70℃ ammonium chloride solution, and the solid-liquid ratio is controlled at 1:10 each time. Then the sample is placed in a water vapor atmosphere at 700℃ and 0.1 MPa for hydrothermal treatment for 2 hours, and the crystallinity of the sample after hydrothermal treatment is determined by X-ray diffraction. The specific surface area and pore volume of the molecular sieve are measured by N2 physical adsorption under low pressure. The silicon-aluminum ratio of the molecular sieve is measured by X-ray fluorescence (XRF), and is expressed as the molar ratio of SiO2 / Al2O3. The crystal grain size of the molecular sieve is measured by scanning electron microscopy (SEM).

[0042] The role and effect of the method of the present application will be further illustrated by combining the following examples and comparative examples, but the following examples do not constitute a limitation on the method of the present application, and the following examples and comparative examples are mass percentages unless otherwise specified. The water-silicon ratio in the method of the present application is a molar ratio.

[0043] Example 1

[0044] (1) Sodium aluminate, sodium hydroxide and distilled water were mixed uniformly under stirring and placed at the crystallization temperature, then silica sol was added and stirred uniformly, the solution composition was Al203: 11.5 Si02: 17 Na20: 400 H20. The obtained solution was crystallized at 20°C for 14 days, and was recorded as solution A. The water to silica ratio of solution A was 35.

[0045] (2) Silica and distilled water were added to solution A under stirring and stirred uniformly, the obtained solution composition was Al203: 21 Si02: 17 Na20: 850 H20. The obtained solution was crystallized at 40°C for 6 days, and was recorded as solution B. The water to silica ratio of solution B was 40, which was 5 lower than that of solution A.

[0046] (3) Silica and distilled water were added to solution B under stirring and stirred uniformly, the final composition of the obtained solution was Al203: 35 Si02: 17 Na20: 850 H20. The obtained solution was crystallized at 100°C for 24 hours, and after being taken out, it was washed, filtered and dried to obtain the final product.

[0047] Example 2

[0048] (1) Sodium aluminate, sodium hydroxide and distilled water were mixed uniformly under stirring and placed at the crystallization temperature, then silica sol was added and stirred uniformly, the solution composition was Al203: 15 Si02: 18 Na20: 400 H20. The obtained solution was crystallized at 25°C for 12 days, and was recorded as solution A. The water to silica ratio of solution A was 27.

[0049] (2) Silica and distilled water were added to solution A under stirring and stirred uniformly, the obtained solution composition was Al203: 23 Si02: 18 Na20: 713 H20. The obtained solution was crystallized at 60°C for 4 days, and was recorded as solution B. The water to silica ratio of solution B was 31, which was 4 lower than that of solution A.

[0050] (3) Silica and distilled water were added to solution B under stirring and stirred uniformly, the final composition of the obtained solution was Al203: 39 Si02: 18 Na20: 950 H20. The obtained solution was crystallized at 80°C for 10 hours, and after being taken out, it was washed, filtered and dried to obtain the final product. The water to silica ratio of the final solution was 24.

[0051] Example 3

[0052] (1) Under stirring, sodium aluminate, sodium hydroxide and distilled water were mixed uniformly and placed at a crystallization temperature, then silica sol was added and stirred uniformly, the solution composition was Al203: 8 Si02: 10 Na20: 160 H20. The obtained solution was crystallized at 5°C for 15 days, and was recorded as solution A. The water to silica ratio of solution A was 20.

[0053] (2) Under stirring, silica and distilled water were added to solution A, and stirred uniformly, the obtained solution composition was Al203: 15 Si02: 10 Na20: 480 H20. The obtained solution was crystallized at 30°C for 7 days, and was recorded as solution B. The water to silica ratio of solution B was 32, which was 12 lower than that of solution A.

[0054] (3) Under stirring, silica and distilled water were added to solution B, and stirred uniformly, the obtained solution final composition was Al203: 25 Si02: 10 Na20: 600 H20. The obtained solution was crystallized at 80°C for 40 h, and after being taken out, was washed, filtered and dried to obtain the final product. The water to silica ratio of the final solution was 24.

[0055] Example 4

[0056] (1) Under stirring, sodium aluminate, sodium hydroxide and distilled water were mixed uniformly and placed at a crystallization temperature, then silica sol was added and stirred uniformly, the solution composition was Al203: 10 Si02: 16 Na20: 300 H20. The obtained solution was crystallized at 20°C for 10 days, and was recorded as solution A. The water to silica ratio of solution A was 30.

[0057] (2) Under stirring, silica and distilled water were added to solution A, and stirred uniformly, the obtained solution composition was Al203: 18 Si02: 16 Na20: 650 H20. The obtained solution was crystallized at 45°C for 5 days, and was recorded as solution B. The water to silica ratio of solution B was 36, which was 6 lower than that of solution A.

[0058] (3) Under stirring, silica and distilled water were added to solution B, and stirred uniformly, the obtained solution final composition was Al203: 33 Si02: 16 Na20: 800 H20. The obtained solution was crystallized at 95°C for 20 h, and after being taken out, was washed, filtered and dried to obtain the final product.

[0059] Example 5

[0060] (1) The sodium aluminate, sodium hydroxide and distilled water were mixed under stirring and placed at the crystallization temperature, then the silica sol was added and stirred uniformly. The solution composition was Al203: 13 Si02: 15 Na20: 350 H20. The resulting solution was crystallized at 10°C for 12 days and was labeled as solution A. The water to silica ratio of solution A was 27.

[0061] (2) The silica and distilled water were added to solution A under stirring and stirred uniformly. The resulting solution composition was Al203: 20 Si02: 15 Na20: 750 H20. The resulting solution was crystallized at 40°C for 6 days and was labeled as solution B. The water to silica ratio of solution B was 37.5, which was 10.5 lower than that of solution A.

[0062] (3) The silica and distilled water were added to solution B under stirring and stirred uniformly. The resulting solution composition was Al203: 35 Si02: 15 Na20: 800 H20. The resulting solution was crystallized at 85°C for 30 hours, then washed, filtered and dried to obtain the final product.

[0063] Example 6

[0064] (1) The sodium aluminate, sodium hydroxide and distilled water were mixed under stirring and placed at the crystallization temperature, then the silica sol was added and stirred uniformly. The solution composition was Al203: 11 Si02: 13 Na20: 250 H20. The resulting solution was crystallized at 20°C for 8 days and was labeled as solution A. The water to silica ratio of solution A was 23.

[0065] (2) The silica and distilled water were added to solution A under stirring and stirred uniformly. The resulting solution composition was Al203: 17 Si02: 13 Na20: 510 H20. The resulting solution was crystallized at 50°C for 6 days and was labeled as solution B. The water to silica ratio of solution B was 30, which was 7 lower than that of solution A.

[0066] (3) The silica and distilled water were added to solution B under stirring and stirred uniformly. The resulting solution composition was Al203: 31 Si02: 13 Na20: 650 H20. The resulting solution was crystallized at 90°C for 26 hours, then washed, filtered and dried to obtain the final product.

[0067] Comparative Example 1

[0068] (1) The sodium aluminate, sodium hydroxide and distilled water were mixed under stirring and placed at the crystallization temperature, then the silica sol was added and stirred uniformly. The solution composition was Al203: 11 Si02: 13 Na20: 250 H20. The resulting solution was crystallized at 20°C for 8 days and was labeled as solution A.

[0069] (2) Silica and distilled water were added to solution A under stirring, and the resulting solution was stirred uniformly. The final composition of the resulting solution was Al203: 31 Si02: 13 Na20: 650 H20. The resulting solution was crystallized at 90°C for 26 h, and after being taken out, it was washed, filtered, and dried to obtain the final product.

[0070] Comparative Example 2

[0071] (1) Sodium aluminate, sodium hydroxide, and distilled water were mixed uniformly and placed at a crystallization temperature under stirring, and then silica sol was added and stirred uniformly. The composition of the solution was Al203: 11 Si02: 13 Na20: 250 H20. The resulting solution was crystallized at 20°C for 8 d, and was designated as solution A.

[0072] (2) Silica and distilled water were added to solution A under stirring, and the resulting solution was stirred uniformly. The composition of the resulting solution was Al203: 17 Si02: 13 Na20: 510 H20. The resulting solution was crystallized at 50°C for 6 d, and after being taken out, it was washed, filtered, and dried to obtain the final product.

[0073] Comparative Example 3

[0074] (1) Sodium aluminate, sodium hydroxide, and distilled water were mixed uniformly and placed at a crystallization temperature under stirring, and then silica sol was added and stirred uniformly. The composition of the solution was Al203: 11 Si02: 13 Na20: 250 H20. The resulting solution was crystallized at 20°C for 8 d, and was designated as solution A.

[0075] (2) Silica and distilled water were added to solution A under stirring, and the resulting solution was stirred uniformly. The composition of the resulting solution was Al203: 31 Si02: 13 Na20: 650 H20. The resulting solution was crystallized at 100°C for 65 h, and after being taken out, it was washed, filtered, and dried to obtain the final product.

[0076] Table 1 Structural properties of products in Examples and Comparative Examples

[0077]

Claims

1. A method for synthesizing Y-type molecular sieve nanoclusters, characterized in that: The method includes the following: The silicon source, aluminum source, and alkali source are mixed and crystallized. The resulting solution is denoted as solution A. The molar ratio of the materials for crystallization after mixing the silicon source, aluminum source, and alkali source is: Al2O3∶(8-15)SiO2∶(10-18)Na2O∶(150-400)H2O. The water-to-silicon ratio of the crystallization system is 20-35. After adding a silicon source to solution A, crystallization was carried out, and the resulting solution was denoted as solution B. The molar ratio of materials for crystallization after adding a silicon source to solution A was: Al2O3∶(15-23)SiO2∶(10-18)Na2O∶(450-850)H2O, and the water-silicon ratio of the crystallization system was 27-40. After adding a silicon source to solution B, crystallization was carried out. After washing and drying, the final Y-type molecular sieve nanocluster product was obtained. The molar ratio of the materials crystallized after adding a silicon source to solution B was: Al2O3∶(25-40)SiO2∶(10-18)Na2O∶(600-950)H2O. The crystallization temperature of crystallizing by mixing silicon source, aluminum source and alkali source is 20-35°C lower than the crystallization temperature of crystallizing by adding silicon source to solution A. The crystallization temperature after adding a silicon source to solution A is 20-65°C lower than the crystallization temperature after adding a silicon source to solution B. The water-to-silicon ratio is the molar ratio of H2O / SiO2.

2. The method according to claim 1, characterized in that: The silicon source is one or more of silica sol, silicon dioxide, water glass, and sodium silicate; the aluminum source is one or more of sodium aluminate, aluminum powder, and aluminum hydroxide; and the alkali source is one or more of sodium hydroxide, tetraethylammonium bromide, and tetrapropylammonium bromide.

3. The method according to claim 1, characterized in that: The molar ratio of the materials for crystallization after mixing silicon source, aluminum source and alkali source is Al2O3∶(10-13)SiO2∶(13-16)Na2O∶(250-350)H2O.

4. The method according to claim 1, characterized in that: The water-to-silicon ratio of the crystallization system, which is formed by mixing silicon, aluminum, and alkali sources, is 23-30, where the water-to-silicon ratio is the molar ratio of H2O / SiO2.

5. The method according to claim 1, characterized in that: The crystallization temperature for mixing silicon, aluminum, and alkali sources is 5-25℃; the crystallization time is 8-15 days.

6. The method according to claim 5, characterized in that: The crystallization temperature for mixing silicon, aluminum, and alkali sources is 10-20℃; the crystallization time is 8-12 days.

7. The method according to claim 1, characterized in that: The molar ratio of materials added to solution A for crystallization after adding silicon source is: Al2O3∶(17-20)SiO2∶(13-16)Na2O∶(500-750)H2O.

8. The method according to claim 1, characterized in that: The water-to-silicon ratio of the crystallization system after adding a silicon source to solution A is 30-37, where the water-to-silicon ratio is the molar ratio of H2O / SiO2.

9. The method according to claim 1, characterized in that: The crystallization temperature for adding a silicon source to solution A is 30-60℃; the crystallization time is 4-7 days.

10. The method according to claim 9, characterized in that: The crystallization temperature for adding a silicon source to solution A is 40-50℃; the crystallization time is 5-6 days.

11. The method according to claim 1, characterized in that: The molar ratio of materials added to solution B for crystallization after adding silicon source is: Al2O3∶(30-35)SiO2∶(13-16)Na2O∶(650-800)H2O.

12. The method according to claim 1, characterized in that: The crystallization temperature for adding a silicon source to solution B is 80-100℃; the crystallization time is 10-40h.

13. The method according to claim 12, characterized in that: The crystallization temperature for adding a silicon source to solution B is 85-95℃; the crystallization time is 20-30h.

14. The method according to claim 1, characterized in that: The crystallization temperature of crystallizing by mixing silicon source, aluminum source and alkali source is 24-30℃ lower than the crystallization temperature of crystallizing by adding silicon source to solution A.

15. The method according to claim 1, characterized in that: The crystallization temperature after adding a silicon source to solution A is 40-50°C lower than the crystallization temperature after adding a silicon source to solution B.

16. The method according to claim 1, characterized in that: The water-to-silicon ratio of solution A is 4-12 lower than that of solution B, and the water-to-silicon ratio is the molar ratio of H2O / SiO2.

17. The method according to claim 16, characterized in that: The water-to-silicon ratio of solution A is 6-10.5 lower than that of solution B, and the water-to-silicon ratio is the molar ratio of H2O / SiO2.

18. A Y-type molecular sieve nanocluster prepared by the method according to any one of claims 1-17, characterized in that: The Y-type molecular sieve nanoclusters have a particle size of 1-4 μm; the nanoclusters are composed of molecular sieves with a grain size of 30-60 nm and a silicon-to-aluminum ratio of 5.0-6.5, and the specific surface area of ​​the Y-type molecular sieve nanoclusters is 800-950 m². 2 / g, with an external specific surface area of ​​130-200m² 2 / g, with a pore volume of 0.50-0.66ml / g, and the silicon-to-aluminum ratio is the molar ratio of SiO2 / Al2O3.

19. The Y-type molecular sieve nanoclusters according to claim 18, characterized in that: The Y-type molecular sieve nanocluster particles have a size of 2-3 μm; the nanocluster particles are composed of nanomolecular sieves with a grain size of 35-50 nm and a silicon-to-aluminum ratio of 5.8-6.3, wherein the silicon-to-aluminum ratio is the molar ratio of SiO2 / Al2O3.

20. The Y-type molecular sieve nanoclusters according to claim 18, characterized in that: The specific surface area of ​​the Y-type molecular sieve nanoclusters is 830-900 m². 2 / g, with an external specific surface area of ​​140-180m² 2 / g; pore volume is 0.55-0.63ml / g.

21. The Y-type molecular sieve nanoclusters according to claim 18, characterized in that: After ammonium exchange, the Y-type molecular sieve nanoclusters were treated with high-temperature steam at 700℃ and 0.1MPa for 2 hours. The crystallinity of the Y-type molecular sieve was maintained at 86-95% compared with that of the Y-type molecular sieve before hydrothermal treatment.

22. The Y-type molecular sieve nanoclusters according to claim 18, characterized in that: After ammonium exchange, the Y-type molecular sieve nanoclusters were treated with high-temperature steam at 700℃ and 0.1MPa for 2 hours. The crystallinity retention rate of the Y-type molecular sieve was 89-93% compared with that of the Y-type molecular sieve before hydrothermal treatment.

23. The Y-type molecular sieve nanoclusters according to any one of claims 18-22 as an acid cracking component of a hydrocracking catalyst.

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