Hollow y-type molecular sieve, method for preparing same, and use thereof

Abstract

The application discloses hollow Y-type molecular sieves, a preparation method and application thereof. The hollow Y-type molecular sieve has a hollow structure, the wall thickness of the hollow Y-type molecular sieve is 10-80nm, and the average particle size of the hollow Y-type molecular sieve is 100-500nm. The hollow Y-type molecular sieve has high hydrothermal stability, can expose more reaction active centers, shorten the diffusion path of reactants, and improve the reaction performance of the molecular sieve.

Description

Technical Field

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

[0002] Y-type molecular sieves are the most widely used molecular sieves in industrial hydrocracking catalysts. They are composed of two types of cage-like structural units: hexagonal columnar cages and β-cages. The octahedral zeolite cages are connected by twelve-membered rings at the pore openings, forming a three-dimensional channel system of Y-type molecular sieves. Hydrocracking catalysts containing Y-type molecular sieves have advantages such as high cracking activity, good ring-opening performance, and good stability. Currently, industrially used Y-type molecular sieves are mostly micron-sized or nano-sized, while hollow Y-type molecular sieves are used less and have been less studied. However, hollow Y-type molecular sieves can expose more reactive centers, shorten the reactant diffusion path, and improve the molecular sieve's reactivity.

[0003] Currently, research on hollow molecular sieves is limited. CN106395856A discloses a method for preparing ZSM-5 hollow molecular sieves via hydrothermal recrystallization. This method first crystallizes the ZSM-5 molecular sieve using conventional methods, then performs a secondary crystallization to obtain the ZSM-5 hollow molecular sieve. This method has a long crystallization cycle, increasing the cost. CN106082257A discloses a hollow molecular sieve, its preparation method, and its applications. The hollow molecular sieve prepared using this method has an outer diameter of 50 nm-10 μm, an inner diameter of 20 nm-9 μm, and a specific surface area of ​​200-1000 m². 2 / g, its shell consists of three layers of isomorphous molecular sieves with different Si / Al ratios. The types of hollow molecular sieves include any one or more of ZSM-5 type hollow molecular sieves, β-type hollow molecular sieves, and Y-type hollow molecular sieves. This method also utilizes hydrothermal recrystallization to prepare hollow molecular sieves, which is a relatively complex process and increases the cost. CN105712374A discloses a method for preparing hollow USY molecular sieves. This method uses low Si / Al ratio NaY type molecular sieves as seed crystals to obtain YY composite molecular sieves, and then obtains hollow Y molecular sieves through post-treatment processes such as hydrothermal and acid treatment. The molecular sieves obtained by this method have poor hydrothermal stability and are prone to over-processing such as framework collapse, which is not conducive to industrial applications.

[0004] Preparing hollow Y molecular sieves with high hydrothermal stability and using them in hydrocracking catalysts is a current technical challenge in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a hollow Y-type molecular sieve, its preparation method, and its applications. The hollow Y-type molecular sieve of this invention exhibits high hydrothermal stability, exposes more reactive centers, shortens reactant diffusion paths, and improves the molecular sieve's reactivity.

[0006] The first aspect of the present invention provides a hollow Y-type molecular sieve, wherein the hollow Y-type molecular sieve has a hollow structure, the wall thickness of the hollow Y-type molecular sieve is 10-80 nm, preferably 20-65 nm, and the average particle size of the hollow Y-type molecular sieve is 100-500 nm, preferably 300-500 nm.

[0007] Furthermore, the total specific surface area of ​​the hollow Y-type molecular sieve is 400–950 m². 2 / g, preferably 600-900m 2 / g, with an external specific surface area of ​​200–850m² 2 / g, preferably 350-850m 2 / g; the total pore volume is 0.25-0.50 mL / g, preferably 0.30-0.45 mL / g.

[0008] Furthermore, the relative crystallinity of the hollow Y-type molecular sieve is 80% to 98%, preferably 85% to 95%; and / or, after the hollow Y-type molecular sieve is hydrothermally treated at 500 to 700°C for 1 to 3 hours, the relative crystallinity of the resulting hollow Y-type molecular sieve is 70% to 95%, preferably 75% to 90%.

[0009] A second aspect of the present invention provides a method for preparing the above-mentioned hollow Y-type molecular sieve, comprising:

[0010] (1) Acid treatment was performed on NaY molecular sieve, then an organic template agent was added and stirred for the first time, then a silicon-containing compound was added and stirred for the second time, washed, filtered, and dried to obtain modified Y molecular sieve;

[0011] (2) The modified Y molecular sieve obtained in step (1) is mixed with aluminum source, silicon source, alkali source and surfactant, and crystallization reaction is carried out;

[0012] (3) The product obtained in step (2) is filtered, dried and calcined to obtain a hollow Y-type molecular sieve.

[0013] Further, in step (1), the properties of the NaY molecular sieve include: a SiO2 / Al2O3 molar ratio of 5 to 6, and a total specific surface area of ​​600 to 900 m². 2 / g, with a pore volume of 0.35~0.45mL / g.

[0014] Furthermore, in step (1), the specific process of acid treatment includes: mixing the NaY molecular sieve with water, and then adding an acidic solution for treatment.

[0015] Furthermore, when NaY molecular sieve is mixed with water, the solid-liquid mass-to-volume ratio is 1g / 5mL to 1g / 10mL.

[0016] Further, the acidic solution is one or more of the following: inorganic acid solution, organic acid solution, and strong acid-weak base salt solution; preferably, it is one or more of the following: hydrochloric acid solution, sulfuric acid solution, nitric acid solution, phosphoric acid solution, citric acid solution, stearic acid solution, oxalic acid solution, tartaric acid solution, aluminum sulfate solution, aluminum nitrate solution, aluminum phosphate solution, aluminum chloride solution, and ammonium chloride solution. The concentration of the acidic solution is 0.5–4.0 mol / L, preferably 0.8–3.5 mol / L. After adding the acidic solution, the pH value of the system is 1.0–5.0.

[0017] Further, in step (1), the acid treatment temperature is 50-100℃, preferably 60-95℃, and the time is 1.0-5.0h, preferably 1.5-4.0h.

[0018] Further, in step (1), the organic template agent is one or more of tetraethylammonium hydroxide (TEAOH), tetramethylammonium hydroxide (TMAOH), tetrapropylammonium hydroxide (TPAOH), pyrrolidine, ethylenediamine, and n-butylamine. The mass ratio of the organic template agent to the NaY molecular sieve is 0.5–5.0:1, preferably 0.5–4.0:1.

[0019] Furthermore, in step (1), the first stirring time is 1 to 5 hours and the temperature is 15 to 60°C.

[0020] Further, in step (1), the silicon-containing compound is one or more of tetraethyl orthosilicate, acidic silica sol, aluminum silicate, sodium silicate, ammonium silicate, silicon tetrachloride, fluorosilicic acid, silicon tetrafluoride, silicon trifluoride and silicon pentafluoride.

[0021] Furthermore, in step (1), the second stirring time is 1 to 5 hours and the temperature is 60 to 100°C.

[0022] Furthermore, in step (1), the washing and filtering are carried out using conventional methods in the art. The drying conditions are: drying temperature of 90–200°C and drying time of 10–48 hours.

[0023] Further, in step (1), the SiO2 / Al2O3 molar ratio of the modified Y molecular sieve is 60.0–100.0, preferably 65.0–95.0, and the specific surface area is 650–1000 m². 2 / g, with a pore volume of 0.45~0.65mL / g.

[0024] Further, in step (2), the aluminum source is one or more of sodium aluminate, aluminum isopropoxide, aluminum hydroxide, aluminum sulfate, aluminum nitrate, and aluminum chloride. The silicon source is one or more of water glass, silica, and alkaline silica sol. The alkali source is one or more of sodium hydroxide, sodium bicarbonate, sodium carbonate, potassium hydroxide, potassium bicarbonate, and potassium carbonate.

[0025] Further, the mass ratio of the silicon source (calculated as SiO2), aluminum source (calculated as Al2O3) and the modified Y-type molecular sieve in step (2) is SiO2:Al2O3:modified Y-type molecular sieve = (0.2~20.8):(0.15~3.5):1.

[0026] Furthermore, the amount of alkali source added in step (2) is sufficient to make the pH of the system 9 to 14, preferably 10 to 14.

[0027] Further, in step (2), the surfactant is one or more of cationic surfactants, anionic surfactants, nonionic surfactants, and amphoteric surfactants; preferably a cationic surfactant, and more preferably one or more of tetraethylammonium bromide (TEAB), hexadecyltrimethylammonium bromide (CTAB), hexadecyltrimethylammonium chloride, dodecyldimethylbenzylammonium chloride, polyquaternium-16, tetraethylammonium hydroxide (TEAOH), tetramethylammonium bromide (TMAB), tetrapropylammonium bromide (TPAB), tetramethylammonium hydroxide (TMAOH), and tetrapropylammonium hydroxide (TPAOH). The mass ratio of the surfactant to the modified Y molecular sieve is 0.1–3.0:1, preferably 0.15–3.0:1.

[0028] Furthermore, in step (2), the mixing is carried out under stirring until the mixture is homogeneous.

[0029] Further, in step (2), the conditions for the crystallization reaction are: crystallization temperature of 50-150℃, preferably 60-120℃, and crystallization time of 6-48h, preferably 12-30h.

[0030] Further, in step (3), the drying temperature is 90–200°C, and the drying time is 10–48 h. The calcination temperature is 400–800°C, preferably 450–700°C, and the calcination time is 1–7 h, preferably 2–5 h.

[0031] A third aspect of the present invention provides a hydrocracking catalyst comprising the above-mentioned hollow Y-type molecular sieve, alumina, and a hydrocracking active metal component.

[0032] Furthermore, the active metal component for hydrogenation includes Group VIB metals and Group VIII metals. Group VIB metals are preferably tungsten (W) and / or molybdenum (Mo), and Group VIII metals are preferably cobalt (Co) and / or nickel (Ni).

[0033] Furthermore, based on the weight of the hydrocracking catalyst, the hollow Y-type molecular sieve content is 5%–65%, preferably 10%–60%; the alumina content is 5%–90%, preferably 8%–80%; the group VIB metal content is 5%–35%, preferably 10%–28%, based on oxides; and the group VIII metal content is 2%–15%, preferably 3%–12%, based on oxides.

[0034] The fourth aspect of this invention provides the application of the above-mentioned hydrocracking catalyst in the hydrocracking process.

[0035] Furthermore, the specific application involves using the hydrocracking catalyst in the hydrocracking reaction of wax oil feedstock to produce light oil fractions such as heavy naphtha and jet fuel. The reaction conditions are as follows: under a hydrogen atmosphere, a reaction pressure of 4–20 MPa, a reaction temperature of 300–430 °C, a hydrogen-to-oil volume ratio of 500–1800:1, and a liquid hourly space velocity of 0.5–5.0 h⁻¹. -1 .

[0036] Furthermore, the wax oil feedstock can be a conventional vacuum wax oil fraction.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] The hollow Y-type molecular sieve of the present invention has a specific hollow structural morphology, which can expose more reactive centers, shorten the diffusion path of reactants, improve the reaction performance of molecular sieve, and exhibit higher reactivity.

[0039] In the preparation method of hollow Y-type molecular sieve of the present invention, NaY molecular sieve is first modified to obtain modified Y molecular sieve, so that its outer surface is more conducive to the integration of silicon source and aluminum source in the synthesis environment in the subsequent process, forming hollow Y molecular sieve with high hydrothermal stability.

[0040] The hydrocracking catalyst prepared using the hollow Y-type molecular sieve of this invention is used in the hydrocracking of wax oil feedstock to produce light oil fractions such as heavy naphtha and jet fuel, exhibiting high catalytic activity and selectivity. Attached Figure Description

[0041] Figure 1 The image shows a TEM image of the Y molecular sieve modified in step (2) of Example 1.

[0042] Figure 2 The image shows the TEM image of the hollow Y molecular sieve obtained in Example 1.

[0043] Figure 3 TEM image of the product obtained in Comparative Example 1;

[0044] Figure 4 TEM images of the product obtained in Comparative Example 2;

[0045] Figure 5 For comparison, see the TEM image of the product obtained in Example 3;

[0046] Figure 6 For comparison, see the TEM image of the product obtained in Example 4;

[0047] Figure 7 The TEM image of the product obtained in Comparative Example 5 is shown. Detailed Implementation

[0048] The present invention and its effects will be further described in detail below with reference to embodiments and comparative examples, but the following embodiments do not constitute a limitation on the scope of protection of the present invention. Unless otherwise specified, % in the context of the present invention should be understood as a percentage by mass.

[0049] In this invention, the TEM images of the samples were obtained using a Tecnai G2-F20 high-resolution transmission electron microscope to analyze the microstructure of the catalyst, with an accelerating voltage of 200 kV.

[0050] In this invention, the N2 adsorption-desorption characterization of the samples was determined using an ASAP2420 micrometer from Microlithics, Inc. (USA). Specific surface area and pore volume were calculated using the DFT model and the t-plot model, respectively.

[0051] In this invention, the relative crystallinity of the synthesized (hollow) Y-type molecular sieve was measured using XRD diffraction, following the method specified in the Chinese petrochemical industry standard SH / T 0340-92 (《Compilation of Chemical Industry Standards》, China Standards Press, 2000). The relative crystallinity of the hydrothermally treated molecular sieve was calculated based on the synthesized (hollow) Y-type molecular sieve. Quantitative analysis was performed using XRD based on the principle that the X-ray diffraction intensity of a crystalline phase is proportional to its content.

[0052] Example 1

[0053] (1) Weigh 10.0g of NaY molecular sieve (SiO2 / Al2O3 molar ratio = 5.3, total specific surface area is 834m²). 2 / g (pore volume of 0.43mL / g), add deionized water at a solid-liquid ratio of 1g / 10mL, then add 2.0mol / L citric acid to adjust the pH to 2.0, treat at 80℃ for 2h, add 10g TEAOH, stir at 25℃ for 2h, then add 0.5mol / L silicon tetrachloride, set the temperature to 90℃, react for 2h with stirring, wash, filter, and dry at 120℃ for 12h to obtain modified Y molecular sieve.

[0054] (2) Weigh 5g of the modified Y molecular sieve obtained in step (1), add 5.0g of NaAlO2 (41% by mass of Al2O3) and 25g of water glass (26% by mass of SiO2), then add sodium hydroxide to make the pH of the system 14, add 5.0g of hexadecyltrimethylamine bromide (CTAB) during stirring, continue stirring for 4h until homogeneous, and then crystallize at 100℃ for 24h.

[0055] (3) The crystallized product is filtered, dried at 150℃ for 15 hours, and then calcined at 600℃ for 3 hours to obtain the final product, which is a Y-type molecular sieve with a hollow structure. See details below. Figure 2 .

[0056] Example 2

[0057] (1) Weigh 10.0g of NaY molecular sieve (same as in Example 1), add deionized water at a solid-liquid ratio of 1g / 5mL, add 2.0mol / L hydrochloric acid to adjust the pH to 1.0, treat at 60℃ for 2h, add 20g of ethylenediamine, stir at 25℃ for 3h, add 1.2mol / L tetraethyl orthosilicate, set the temperature to 60℃, react under stirring for 2h, wash, filter, and dry at 150℃ for 10h to obtain modified Y molecular sieve.

[0058] (2) Weigh 5g of the modified Y molecular sieve obtained in step (1), add 50.0g of aluminum isopropoxide (13% by mass of Al2O3) and 20g of silica sol (40% by mass of SiO2), add sodium hydroxide to make the solution pH=12, add 15g of TMAB during stirring, continue stirring for 4h until uniform, and then crystallize at 150℃ for 12h.

[0059] (3) The crystallized product is filtered, dried at 180°C for 10 hours, and then calcined at 550°C for 4 hours to obtain the final product, which is a Y-type molecular sieve with a hollow structure.

[0060] Example 3

[0061] (1) Weigh 10.0g of NaY molecular sieve (same as in Example 1), add deionized water at a solid-liquid ratio of 1g / 10mL, adjust the pH to 2.0 with 1.5mol / L sulfuric acid, treat at 80℃ for 2h, add 15g of n-butylamine, stir at 25℃ for 3h, add 1.0mol / L fluorosilicic acid, set the temperature to 80℃, react under stirring for 4h, wash, filter, and dry at 100℃ for 24h to obtain modified Y molecular sieve.

[0062] (2) Weigh 5g of the modified Y molecular sieve obtained in step (1), add 10.0g of NaAlO2 and 20g of silica sol, add ammonia water to make the solution pH=10, add 10g of TEAB during stirring, continue stirring for 4h until uniform, and then crystallize at 100℃ for 24h.

[0063] (3) The crystallized product is filtered, dried at 120°C for 24 hours, and then calcined at 600°C for 3 hours to obtain the final product, which is a Y-type molecular sieve with a hollow structure.

[0064] Example 4

[0065] (1) Weigh 10.0g of NaY molecular sieve (same as in Example 1), add deionized water at a solid-liquid ratio of 1g / 8mL, adjust the pH to 3.5 with 2.0mol / L oxalic acid, treat at 80℃ for 2h, add 35g of TEAOH, stir at 25℃ for 3h, add 3.5mol / L ammonium silicate, set the temperature to 95℃, react for 4h with stirring, wash, filter, and dry at 120℃ for 24h to obtain modified Y molecular sieve.

[0066] (2) Weigh 5g of the modified Y molecular sieve obtained in step (1), add 45.0g of aluminum sulfate and 45g of silica, add sodium hydroxide to make the pH of the system 14, add 15g of TPAB during stirring, continue stirring for 4h until uniform, and then crystallize at 90℃ for 36h.

[0067] (3) The crystallized product is filtered, dried at 90°C for 48 hours, and calcined at 700°C for 2 hours to obtain the final product, which is a Y-type molecular sieve with a hollow structure.

[0068] Example 5

[0069] (1) Weigh 10.0g of NaY molecular sieve (SiO2 / Al2O3 molar ratio = 5.3, total specific surface area is 834m²). 2 / g (pore volume of 0.43mL / g), add deionized water at a solid-liquid ratio of 1g / 10mL, adjust the pH to 3.5 with 4.0mol / L aluminum sulfate, treat at 95℃ for 4h, add 10g TEAOH, stir at 25℃ for 2h, add 0.5mol / L silicon tetrachloride, set the temperature to 90℃, react for 2h with stirring, wash, filter, and dry at 120℃ for 12h to obtain modified Y molecular sieve.

[0070] (2) Weigh 5g of the modified Y molecular sieve obtained in step (1), add 5.0g of NaAlO2 (41% by mass of Al2O3) and 25g of water glass (26% by mass of SiO2), then add sodium hydroxide to make the pH of the system 14, add 5.0g of hexadecyltrimethylamine bromide (CTAB) during stirring, continue stirring for 4h until homogeneous, and then crystallize at 100℃ for 24h.

[0071] (3) The crystallized product is filtered, dried at 150℃ for 15 hours, and then calcined at 600℃ for 3 hours to obtain the final product, which is a Y-type molecular sieve with a hollow structure. See details below. Figure 2 .

[0072] Comparative Example 1

[0073] Compared with Example 1, the only difference is that in step (1), no organic template agent (TEAOH) is added, and the final product is a Y-type molecular sieve with a non-hollow structure.

[0074] Comparative Example 2

[0075] Compared with Example 1, the only difference is that silicon tetrachloride is not added in step (1), and the final product is a Y-type molecular sieve with a non-hollow structure.

[0076] Comparative Example 3

[0077] Compared with Example 1, only the surfactant (CTAB) was not added in step (2), and the final product was a Y-type molecular sieve with a non-hollow structure.

[0078] Comparative Example 4

[0079] Compared with Example 1, in step (1), the pH value was adjusted to 5.5 with 0.1 mol / L citric acid to obtain the final product, which is a Y-type molecular sieve with a non-hollow structure.

[0080] Comparative Example 5

[0081] Compared with Example 1, in step (1), the pH value was adjusted to 0.5 with 5.0 mol / L citric acid to obtain the final product, which is a Y-type molecular sieve with a non-hollow structure.

[0082] Comparative Example 6

[0083] Hollow USY molecular sieves were prepared according to Example 8 of CN105712374A.

[0084] Table 1. Properties of the modified Y molecular sieves in the examples.

[0085]

[0086] Table 2. Physicochemical properties of the samples obtained from the examples and comparative examples.

[0087] Example 1 Example 2 Example 3 Example 4 Example 5 <![CDATA[Total specific surface area, m 2 / g]]> 892 872 815 781 803 Total pore volume, mL / g 0.37 0.37 0.35 0.34 0.35 <![CDATA[External surface area, m 2 / g]]> 822 803 729 673 691 Wall thickness, nm 35 30 45 65 50 Average particle size, nm 300 300 350 500 400 Relative crystallinity, % 95 91 88 85 86

[0088] Continued from Table 2

[0089] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 <![CDATA[Total specific surface area, m 2 / g]]> 275 386 653 685 362 607 Total pore volume, mL / g 0.23 0.25 0.30 0.32 0.25 0.42 <![CDATA[External surface area, m 2 / g]]> 138 155 143 250 143 243 Wall thickness, nm - - - - - 100 Average particle size, nm - - - - - 1000 Relative crystallinity, % 21 48 71 73 46 78

[0090] Table 3. Physicochemical properties of the molecular sieve samples after hydrothermal treatment obtained from each embodiment and comparative example.

[0091]

[0092]

[0093] Experimental evaluation of cracking performance of hollow Y-type molecular sieves:

[0094] Catalyst preparation method: The hollow Y molecular sieve obtained in Example 1, the non-hollow Y molecular sieve obtained in Comparative Example 4, and the hollow USY molecular sieve obtained in Comparative Example 6 were mixed with alumina, molybdenum oxide, and nickel nitrate (based on NiO content) in a mass ratio of 30:50:17:3, respectively, and then rolled to prepare catalysts. After drying for 24 hours, the catalysts were placed in a muffle furnace and calcined at 500°C for 4 hours to obtain catalysts, which were designated as catalyst 1, catalyst 2, and catalyst 3.

[0095] Catalyst evaluation conditions: The properties of the feedstock oil used in the experiment are shown in Table 3. The evaluation process conditions were: reaction pressure 14.0 MPa, liquid hourly space velocity (R1 / R2) 1.0 / 1.5 h⁻¹. -1 The hydrogen-to-oil volume ratio was 1000:1, the reaction temperature was 375℃, and the organic nitrogen content of the feed oil in the hydrorefining catalyst bed needed to be controlled at 5ppm. The comparison results are shown in Table 4.

[0096] Table 3 Properties of Feed Oil

[0097] <![CDATA[Density (20°C), g / cm 3 > 0.9003 Distillation range / ℃ IBP / EBP 295 / 525 Nitrogen content, ng / ul 573 Mass spectrometry composition, wt% Alkanes 21.1 Cycloalkanes 37.4 Aromatics 41.1 gelatin 0.4

[0098] Table 4 Catalyst Product Distribution

[0099]

[0100]

[0101] As shown in Table 4, when the same reaction temperature is controlled, the organic nitrogen content of the feed oil in the hydrorefining catalyst bed needs to be controlled at 5 ppm. The tail oil yield of catalyst 1 is significantly lower than that of catalyst 2 and catalyst 3, while the yields of light naphtha, heavy naphtha, and jet fuel are significantly higher than those of catalyst 2 and catalyst 3. This indicates that the hollow Y molecular sieve composite material prepared by the method of this invention has higher cracking activity.

Claims

1. A hollow Y-type molecular sieve, characterized in that, The hollow Y-type molecular sieve has a hollow structure, the wall thickness of the hollow Y-type molecular sieve is 10-80 nm, preferably 20-65 nm, and the average particle size of the hollow Y-type molecular sieve is 100-500 nm, preferably 300-500 nm.

2. The hollow Y-type molecular sieve according to claim 1, characterized in that, The total specific surface area of ​​the hollow Y-type molecular sieve is 400–950 m². 2 / g, preferably 600-900m 2 / g, with an external specific surface area of ​​200–850m² 2 / g, preferably 350-850m 2 / g; the total pore volume is 0.25-0.50 mL / g, preferably 0.30-0.45 mL / g.

3. The hollow Y-type molecular sieve according to claim 1, characterized in that, The hollow Y-type molecular sieve has a relative crystallinity of 80% to 98%, preferably 85% to 95%; And / or, after the hollow Y-type molecular sieve is hydrothermally treated at 500-700℃ for 1-3 hours, the relative crystallinity of the obtained hollow Y-type molecular sieve is 70%-95%, preferably 75%-90%.

4. A method for preparing the hollow Y-type molecular sieve according to any one of claims 1-3, comprising: (1) Acid treatment was performed on NaY molecular sieve, then an organic template agent was added and stirred for the first time, then a silicon-containing compound was added and stirred for the second time, washed, filtered, and dried to obtain modified Y molecular sieve; (2) The modified Y molecular sieve obtained in step (1) is mixed with aluminum source, silicon source, alkali source and surfactant, and crystallization reaction is carried out; (3) The product obtained in step (2) is filtered, dried and calcined to obtain a hollow Y-type molecular sieve.

5. The method according to claim 4, characterized in that, In step (1), the properties of the NaY molecular sieve include: a SiO2 / Al2O3 molar ratio of 5 to 6, and a total specific surface area of ​​600 to 900 m². 2 / g, with a pore volume of 0.35~0.45mL / g.

6. The method according to claim 4, characterized in that, In step (1), the specific process of acid treatment includes: mixing the NaY molecular sieve with water, and then adding an acidic solution for treatment; Preferably, when NaY molecular sieve is mixed with water, the solid-liquid mass-to-volume ratio is 1g / 5mL to 1g / 10mL; Preferably, the acidic solution is one or more of the following: inorganic acid solution, organic acid solution, and strong acid-weak base salt solution; more preferably, it is one or more of the following: hydrochloric acid solution, sulfuric acid solution, nitric acid solution, phosphoric acid solution, citric acid solution, stearic acid solution, oxalic acid solution, tartaric acid solution, aluminum sulfate solution, aluminum nitrate solution, aluminum phosphate solution, aluminum chloride solution, and ammonium chloride solution; the concentration of the acidic solution is 0.5–4.0 mol / L, preferably 0.8–3.5 mol / L; after adding the acidic solution, the pH value of the system is 0.5–5. Preferably, in step (1), the acid treatment temperature is 50-100℃, more preferably 60-95℃, and the time is 1.0-5.0h, more preferably 1.5-4.0h.

7. The method according to claim 4, characterized in that, In step (1), the organic template agent is one or more of tetraethylammonium hydroxide, tetramethylammonium hydroxide, tetrapropylammonium hydroxide, pyrrolidine, ethylenediamine, and n-butylamine; the mass ratio of the organic template agent to the NaY molecular sieve is 0.5-5.0:1, preferably 0.5-4.0:1; And / or, in step (1), the first stirring time is 1 to 5 hours and the temperature is 15 to 60°C; And / or, the second stirring time is 1 to 5 hours, and the temperature is 60 to 100°C; And / or, in step (1), the silicon-containing compound is one or more of tetraethyl orthosilicate, acidic silica sol, aluminum silicate, sodium silicate, ammonium silicate, silicon tetrachloride, fluorosilicic acid, silicon tetrafluoride, silicon trifluoride and silicon pentafluoride; And / or, in step (1), the SiO2 / Al2O3 molar ratio of the modified Y molecular sieve is 60.0–100.0, preferably 65.0–95.0, and the specific surface area is 650–1000 m². 2 / g, with a pore volume of 0.45~0.65mL / g.

8. The method according to claim 4, characterized in that, In step (2), the aluminum source is one or more of sodium aluminate, aluminum isopropoxide, aluminum hydroxide, aluminum sulfate, aluminum nitrate, and aluminum chloride; the silicon source is one or more of water glass, silica, and alkaline silica sol; and the alkali source is one or more of sodium hydroxide, sodium bicarbonate, sodium carbonate, potassium hydroxide, potassium bicarbonate, and potassium carbonate.

9. The method according to claim 4, characterized in that, The mass ratio of the silicon source (SiO2), the aluminum source (Al2O3), and the modified Y-type molecular sieve in step (2) is SiO2:Al2O3:modified Y-type molecular sieve = (0.2~20.8):(0.15~3.5):1; And / or, the amount of alkali source added in step (2) is sufficient to make the pH of the system 9 to 14, preferably 10 to 14; And / or, in step (2), the surfactant is one or more of cationic surfactants, anionic surfactants, nonionic surfactants, and amphoteric surfactants; preferably a cationic surfactant, and more preferably one or more of tetraethylammonium bromide (TEAB), hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, dodecyldimethylbenzylammonium chloride, polyquaternium-16, tetraethylammonium hydroxide, tetramethylammonium bromide, tetrapropylammonium bromide, tetramethylammonium hydroxide, and tetrapropylammonium hydroxide; the mass ratio of the surfactant to the modified Y molecular sieve is 0.1 to 3.0:1, preferably 0.15 to 3.0:1; And / or, in step (2), the conditions for the crystallization reaction are: crystallization temperature of 50 to 150°C, preferably 60 to 120°C, and crystallization time of 6 to 48 hours, preferably 12 to 30 hours.

10. The method according to claim 4, characterized in that, In step (3), the drying temperature is 90-200℃ and the drying time is 10-48h; the calcination temperature is 400-800℃, preferably 450-700℃, and the calcination time is 1-7h, preferably 2-5h.

11. A hydrocracking catalyst comprising the hollow Y-type molecular sieve of any one of claims 1-3 or the hollow Y-type molecular sieve prepared by any one of claims 4-10, alumina, and a hydrocracking active metal component.

12. The hydrocracking catalyst according to claim 11, characterized in that, The hydrocracking catalyst, based on its weight, comprises: 5%–65% hollow Y-type molecular sieve, preferably 10%–60%; 5%–90% alumina, preferably 8%–80%; 5%–35% Group VIB metals (based on oxides), preferably 10%–28%; and 2%–15% Group VIII metals (based on oxides), preferably 3%–12%.

13. The application of the hydrocracking catalyst according to any one of claims 11-12 in the hydrocracking process.

14. The application according to claim 13, characterized in that, The specific application is as follows: the hydrocracking catalyst is used in the hydrocracking reaction of wax oil feedstock to produce heavy naphtha and jet fuel.

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