Hierarchical pore Y molecular sieve, preparation method thereof, catalyst and application of catalyst

Abstract

The invention discloses a preparation method of a hierarchical pore Y molecular sieve, which comprises the following steps: a, mixing an aluminum source, a silicon source, an alkali source and deionized water, then adding poly (diallyldimethylammonium chloride), uniformly mixing, and aging to obtain a modified seed crystal guiding agent; b, mixing and stirring a heteroatom source, an aluminum source, a silicon source, an alkali source and deionized water to obtain a mother solution; c, adding the modified seed crystal guiding agent into the mother liquor, and stirring to obtain gel; and d, carrying out crystallization treatment on the gel obtained in the step c, and separating, washing and drying a solid product obtained after crystallization treatment to obtain the high-silicon hierarchical-pore Y molecular sieve. According to the method disclosed by the invention, the damage to a molecular sieve framework is small, the relative crystallinity of the Y molecular sieve is ensured, the silica-alumina ratio is high, and meanwhile, the prepared molecular sieve has a hierarchical porous structure and can be used as a carrier material of a catalyst for hydrocracking Fischer-Tropsch synthesis wax to prepare aviation kerosene.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a hierarchical porous Y molecular sieve and its preparation method, and particularly to a catalyst including the hierarchical porous Y molecular sieve and its application. Background Technology

[0002] In biomass-to-oil technology, Fischer-Tropsch synthesis involves gasifying biomass into syngas under high temperature and pressure, which is then converted into fuel oil and chemicals under different catalysts and process conditions. This entire technology route offers advantages such as cleanliness, environmental friendliness, and high added value. However, the products also contain over 40% solid Fischer-Tropsch waxes. These waxes are mostly long-chain n-alkanes with a carbon number distribution between C16 and C70 and a wide distillation range (370–800℃). Although Fischer-Tropsch waxes have high cetane numbers, they have poor low-temperature fluidity and easily solidify at low temperatures, making them unsuitable for direct use as fuel oil. Therefore, how to efficiently utilize Fischer-Tropsch waxes has become one of the key breakthroughs for improving the economic benefits of biomass-to-oil technology.

[0003] With the depletion of fossil fuels, the development of alternative fuels, especially green aviation kerosene, is receiving increasing attention. As the economy develops and residents' incomes rise, the demand and consumption of aviation kerosene in China's aviation industry have increased significantly, making it the world's second-largest consumer of aviation kerosene. Looking at development trends, the pressure to reduce emissions is increasing in the "dual-carbon" era, making the development of biofuels, primarily bio-jet kerosene, an inevitable trend. Aviation kerosene is a complex mixture with a carbon number distribution between C9 and C15, mainly consisting of n-alkanes and isoalkanes. Fischer-Tropsch wax has high molecular weight n-alkanes and extremely low aromatic content, making it very suitable for producing aviation kerosene through hydrocracking.

[0004] Silicate-aluminate molecular sieves are widely used in hydrocracking, especially γ-ray molecular sieves. Compared with other molecular sieve supports, they have become the most widely used support for hydrocracking catalysts due to their advantages such as low cost, high catalytic activity, and easily tunable acid properties. γ-ray molecular sieves belong to the FAU family, with an n(Si / Al) ratio greater than 3.0. They possess 3D 12-membered ring (MR) channels and spherical supercages (approximately 1.12 nm in diameter), and their micropores are narrow and elongated. The silica-to-alumina ratio of the γ-ray molecular sieve framework plays a decisive role in its hydrocracking performance. γ-ray molecular sieves with a silica-to-alumina ratio of 3.0-3.5 have a large number of acidic sites, resulting in excessively high hydrocracking activity and over-cracking. Therefore, preparing high-silica γ-ray molecular sieves can effectively improve the cracking performance of the catalyst. A higher silica-to-alumina ratio results in better catalytic activity and stability. The micropore structure of γ-ray molecular sieves is relatively small, typically less than 1 nm, which limits the contact between large molecular reactants and active sites, as well as product diffusion. Therefore, it is necessary to synthesize mesoporous-microporous hierarchical Y molecular sieves that possess both the microporous structure and surface acidity of microporous molecular sieve materials and the good pore structure of mesoporous materials.

[0005] High-silicon-to-alumina ratio hierarchical porous Y-zeolites can be obtained through direct synthesis and post-processing modification. Currently, industrially, post-processing methods such as dealumination or dealumination with silicon replenishment are used. The advantages of these methods are ease of industrialization, but the disadvantages include complex processes, significant loss of zeolite crystallinity, low product yield, and environmental pollution. Therefore, it is necessary to conduct in-depth research and improvement on the synthesis methods of Y-zeolites. Summary of the Invention

[0006] This invention is based on the inventors' discovery and understanding of the following facts and problems: the direct hydrothermal synthesis of Y-type molecular sieves can effectively avoid the various drawbacks of post-processing and maintain the stability of the crystal structure. In the direct synthesis method, high-silica hierarchical porous Y-type molecular sieves can be obtained by adjusting the feed ratio, adding a template agent, and modifying the process steps. However, the current method still suffers from the problem of expensive template agents, which increases production costs. Moreover, the removal of the template agent affects the relative crystallinity of the molecular sieve and causes environmental pollution. Therefore, developing a simple, low-pollution, and low-cost synthesis method for high-silica Y-type molecular sieves remains one of the urgent problems to be solved in this field.

[0007] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a hierarchical porous Y-type molecular sieve and its preparation method. By introducing a low-cost, non-toxic mesoporous template agent, PDDA, whose large steric hindrance and positive charge result in high nucleus dispersion, intergranular mesopores are introduced after calcination, forming a rich hierarchical pore structure. The resulting Y-type molecular sieve exhibits minimal damage to the molecular sieve framework, ensuring relative crystallinity and a high silicon-to-aluminum ratio, making it suitable as a carrier material for the Fischer-Tropsch synthesis wax hydrocracking catalyst for producing jet fuel.

[0008] The method for preparing hierarchical porous Y molecular sieve according to an embodiment of the present invention includes:

[0009] a. Mix aluminum source, silicon source, alkali source and deionized water, then add polydiallyldimethylammonium chloride and mix evenly. After aging, a modified seed crystal directing agent is obtained.

[0010] b. Mix and stir the aluminum source, silicon source, alkali source and deionized water to obtain the mother liquor;

[0011] c. Add the modified seed crystal guiding agent to the mother liquor and stir to obtain a gel;

[0012] d. The gel obtained in step c is subjected to crystallization treatment. The solid product after crystallization treatment is separated, washed and dried to obtain a multi-level porous Y molecular sieve.

[0013] The advantages and technical effects of the preparation method of hierarchical porous Y molecular sieve in this invention are as follows: 1. In this invention, polydiallyldimethylammonium chloride (PDDA) is introduced as a template agent during the preparation of the seed crystal guiding agent. The solution system is highly alkaline during the synthesis of Y molecular sieve. PDDA is a cationic polymer with large steric hindrance. Therefore, the quaternary ammonium part of PDDA can guide the growth of crystals, and the polymer chain can play the role of a "porogen" in the formation of mesopores. At the beginning of the synthesis process, the negatively charged aluminosilicate seed crystals are adsorbed on the surface of the positively charged PDDA through electrostatic interaction. At the same time, the polymer PDDA macromolecules... Surrounded by amorphous aluminosilicate clusters, PDDA acts as a structure-directing agent in the growth of Y molecular sieves, guiding the growth of seed crystals. Furthermore, the large steric hindrance and positive charge of PDDA result in high dispersion of crystal nuclei, which can be introduced into intergranular mesopores after subsequent calcination, forming a rich hierarchical channel structure. 2. In the embodiments of the present invention, the template agent PDDA used is low in cost and has little environmental pollution. Moreover, the synthesis process is simple and easy to operate. The resulting Y molecular sieve causes little damage to the molecular sieve framework, ensuring the relative crystallinity of the Y molecular sieve and a high silica-to-alumina ratio. It can be used as a carrier material for the catalyst of Fischer-Tropsch synthesis wax hydrocracking to produce jet fuel, exhibiting excellent cracking performance.

[0014] In some embodiments, in step a and / or step b, the aluminum source includes at least one of sodium aluminate, aluminum sulfate, boehmite, aluminum isopropoxide, and aluminum nitrate, preferably at least one of boehmite or aluminum sulfate; the silicon source includes at least one of water glass, silica sol, tetraethyl orthosilicate, and sodium silicate, preferably at least one of water glass or silica sol; the alkali source includes at least one of sodium hydroxide, potassium hydroxide, sodium oxide, or potassium oxide.

[0015] In some embodiments, in step a, the molar ratio of polydiallyldimethylammonium chloride to the aluminum source is (0.02-1.2):1.

[0016] In some embodiments, in step a, the aging temperature is 5-50°C and the aging time is 16-48h. Preferably, the aging temperature is 20-40°C and the aging time is 18-36h.

[0017] In some embodiments, in step b, the molar ratio of the alkali source, aluminum source, and silicon source is (2-20):1:(10-20); and / or, the stirring speed is 400-800 rpm.

[0018] In some embodiments, step b includes: mixing an alkali source, a silicon source, a heteroatom source, and deionized water to obtain a first mixed solution; mixing an alkali source, an aluminum source, and deionized water to obtain a second mixed solution; and mixing the first mixed solution and the second mixed solution and stirring until homogeneous to obtain a mother liquor.

[0019] Preferably, the heteroatom source includes at least one of cobalt source, nickel source, iron source, zirconium source, and titanium source. More preferably, the cobalt source is selected from at least one of cobalt nitrate, cobalt sulfate, cobalt chloride, and cobalt hydroxide; the nickel source is selected from at least one of nickel nitrate, nickel sulfate, nickel chloride, and nickel hydroxide; the iron source is selected from at least one of ferric nitrate, ferric chloride, ferric sulfate, and hydrated ferric oxide (III); the zirconium source is selected from at least one of zirconium nitrate, zirconium sulfate, zirconium chloride, zirconium oxynitrate, zirconium ammonium carbonate, and zirconium oxyhydroxide; and the titanium source is selected from at least one of titanium oxysulfate, titanium sulfate, and titanium tetrachloride.

[0020] Preferably, the molar ratio of alkali source, aluminum source, silicon source and heteroatom source in the mother liquor is (2-20):1:(10-20):(0.05-0.6).

[0021] Preferably, the stirring time is 15-30 minutes.

[0022] In some embodiments, in step c, the stirring time is 1-3 hours and the stirring speed is 400-800 rpm.

[0023] In some embodiments, in step c, the ratio of the total mass of aluminum source, silicon source, and alkali source in the mother liquor to the total mass of aluminum source, silicon source, alkali source, and polydiallyldimethylammonium chloride in the modified seed crystal guide is 1:(0.05-0.12).

[0024] In some embodiments, in step d, the crystallization treatment is a variable-temperature segmented crystallization treatment, preferably including the following steps: the first stage pre-crystallization temperature is 15-30℃, and the crystallization time is 1-2 days; the second stage crystallization temperature is 30-60℃, and the crystallization time is 1-2 days; the third stage crystallization temperature is 60-120℃, and the crystallization time is 1-3 days; more preferably, the first stage pre-crystallization temperature is 30℃, and the crystallization time is 1 day; the second stage crystallization temperature is 60℃, and the crystallization time is 1 day; the third stage crystallization temperature is 95℃, and the crystallization time is 1 day.

[0025] In some embodiments, in step d, the drying temperature is 60-120°C and the drying time is 12-24 hours.

[0026] This invention also provides a hierarchical porous Y molecular sieve, which is prepared using the method described in this invention. The hierarchical porous Y molecular sieve of this invention has a high silica-to-alumina ratio and high relative crystallinity, and can be used as a support material for the catalyst in the hydrocracking of waxes to produce jet fuel in Fischer-Tropsch synthesis, exhibiting excellent cracking performance.

[0027] This invention also provides a catalyst, wherein the catalyst support comprises a HY molecular sieve, and Pt is loaded on the support. The HY molecular sieve is a Y molecular sieve prepared by the method of this invention, or a Y molecular sieve prepared by ammonium exchange treatment. The catalyst of this invention can be used for the hydrocracking of Fischer-Tropsch synthesis wax to produce jet fuel, exhibiting excellent cracking performance.

[0028] In some embodiments, the ammonium exchange treatment includes: mixing the Y molecular sieve with an ammonium-containing solution for ion exchange treatment, followed by separation, washing, drying, and calcination to complete the ammonium exchange treatment. Preferably, the ammonium-containing solution includes at least one of ammonium nitrate, ammonium sulfate, and ammonium chloride; the concentration of the ammonium-containing solution is 0.5-1.5 mol / L; the temperature of the ion exchange treatment is 60-90℃; the drying temperature is 60-120℃, and the drying time is 12-24 h; the calcination temperature is 500-700℃, and the calcination time is 4-8 h.

[0029] This invention also provides an application of a catalyst in the hydrocracking of Fischer-Tropsch synthetic waxes to jet fuel. The catalyst of this invention exhibits excellent cracking performance in the hydrocracking of Fischer-Tropsch synthetic waxes to jet fuel.

[0030] In some embodiments, the reaction conditions for the hydrocracking of the Fischer-Tropsch synthetic wax are: a reaction temperature of 240-380°C, a reaction pressure of 2-4 MPa, a hydrogen-to-oil ratio of 400-600:1, and a liquid hourly space velocity of 2-10 h⁻¹. -1 In this embodiment of the invention, the hydrogen-to-oil ratio refers to the volume ratio of hydrogen to Fischer-Tropsch wax. Attached Figure Description

[0031] Figure 1 This is a scanning electron microscope image of the Y molecular sieve prepared in Example 5;

[0032] Figure 2 This is a scanning electron microscope image of the Y molecular sieve prepared in Example 6;

[0033] Figure 3 The XRD patterns of Examples 1-10 and Comparative Example 1 are shown below.

[0034] Figure 4 The XRD patterns are those of Example 1 and Comparative Examples 1-4;

[0035] Figure 5 The N2 adsorption-desorption isotherms are for Example 1 and Comparative Examples 1-4;

[0036] Figure 6 The N2 adsorption-desorption isotherms are for Examples 1-10 and Comparative Example 1. Detailed Implementation

[0037] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0038] The method for preparing hierarchical porous Y molecular sieve according to an embodiment of the present invention includes:

[0039] a. Mix aluminum source, silicon source, alkali source and deionized water, then add polydiallyldimethylammonium chloride and mix evenly. After aging, a modified seed crystal directing agent is obtained.

[0040] b. Mix and stir the aluminum source, silicon source, alkali source and deionized water to obtain the mother liquor;

[0041] c. Add the modified seed crystal guiding agent to the mother liquor and stir to obtain a gel;

[0042] d. The gel obtained in step c is subjected to crystallization treatment. The solid product after crystallization treatment is separated, washed and dried to obtain a multi-level porous Y molecular sieve.

[0043] In the preparation method of the hierarchical porous Y-zeolite of this invention, polydiallyldimethylammonium chloride (PDDA) is introduced as a template agent during the preparation of the seed crystal guiding agent. The solution system is highly alkaline during the synthesis of the Y-zeolite. PDDA is a cationic polymer with large steric hindrance; therefore, the quaternary ammonium portion of PDDA can guide crystal growth, and the polymer chain can act as a "porogen" in the formation of mesopores. At the beginning of the synthesis process, negatively charged aluminosilicate seed crystals are adsorbed onto the surface of positively charged PDDA through electrostatic interactions. Simultaneously, the polymer PDDA macromolecules are adsorbed onto the surface of the amorphous aluminosilicate... The clusters surrounding the Y molecular sieve act as structure-directing agents, guiding the growth of the seed crystals. Furthermore, the large steric hindrance and positive charge of PDDA result in high dispersion of the crystal nuclei, which can be introduced into the intercrystalline mesopores after subsequent calcination, forming a rich hierarchical pore structure. In the embodiments of this invention, the template agent PDDA is low in cost and has little environmental pollution. Moreover, the synthesis process is simple and easy to operate. The resulting Y molecular sieve causes little damage to the molecular sieve framework, ensuring the relative crystallinity of the Y molecular sieve and a high silicon-to-aluminum ratio. It can be used as a carrier material for the catalyst of Fischer-Tropsch synthesis wax hydrocracking to produce jet fuel, exhibiting excellent cracking performance.

[0044] In some embodiments, in step a and / or step b, the aluminum source includes at least one of sodium aluminate, aluminum sulfate, boehmite, aluminum isopropoxide, and aluminum nitrate, preferably at least one of boehmite or aluminum sulfate; the silicon source includes at least one of water glass, silica sol, tetraethyl orthosilicate, and sodium silicate, preferably at least one of water glass or silica sol; the alkali source includes at least one of sodium hydroxide, potassium hydroxide, sodium oxide, or potassium oxide. In these embodiments, there are no particular limitations on the aluminum, silicon, and alkali sources used in the seed crystal guide and mother liquor; commonly used aluminum, silicon, and alkali sources in the prior art for preparing Y-molecular sieves are all applicable to this invention.

[0045] In some embodiments, in step a, the molar ratio of polydiallyldimethylammonium chloride to the aluminum source is (0.02-1.2):1. In this embodiment of the invention, the preferred amounts of each substance used in the preparation of the modified seed crystal directing agent are beneficial for seed crystal growth and the formation of hierarchical channels during synthesis, thereby improving the performance of the Y molecular sieve. If the amount of polydiallyldimethylammonium chloride is too small, it cannot function effectively; if too much polydiallyldimethylammonium chloride is added, it leads to an increase in amorphous substances in the Y molecular sieve, a decrease in crystallinity, and even the introduction of impurity phases.

[0046] In some embodiments, in step a, the aging temperature is 5-50°C and the aging time is 16-48h. Preferably, the aging temperature is 20-40°C and the aging time is 18-36h.

[0047] In some embodiments, in step b, the molar ratio of the alkali source, aluminum source, and silicon source is (2-20):1:(10-20); and the stirring speed is 400-800 rpm.

[0048] In some embodiments, step b includes: mixing an alkali source, a silicon source, a heteroatom source, and deionized water to obtain a first mixed solution; mixing an alkali source, an aluminum source, and deionized water to obtain a second mixed solution; and mixing the first mixed solution and the second mixed solution and stirring until homogeneous to obtain a mother liquor. Preferably, the heteroatom source includes at least one of a cobalt source, a nickel source, an iron source, a zirconium source, and a titanium source. More preferably, the cobalt source is selected from at least one of cobalt nitrate, cobalt sulfate, cobalt chloride, and cobalt hydroxide; the nickel source is selected from at least one of nickel nitrate, nickel sulfate, nickel chloride, and nickel hydroxide; the iron source is selected from at least one of ferric nitrate, ferric chloride, ferric sulfate, and hydrated ferric oxide (III); the zirconium source is selected from at least one of zirconium nitrate, zirconium sulfate, zirconium chloride, zirconium oxynitrate, ammonium zirconium carbonate, and zirconium oxyhydroxide; and the titanium source is selected from at least one of titanium oxysulfate, titanium sulfate, and titanium tetrachloride. In this embodiment of the invention, introducing a heteroatom source during the preparation of the mother liquor can reduce the nucleation free energy and promote nucleation. Furthermore, mixing the heteroatom source with a silicon source first, and then mixing it with an aluminum source to prepare the mother liquor, facilitates the introduction of silicon into the molecular sieve framework during hydrothermal synthesis, thereby increasing the silicon-to-aluminum ratio of the molecular sieve. This may be because mixing the heteroatom source with the silicon source first, due to the lower nucleation free energy of heteroatoms, allows for the formation of more intermediate products M–O–Si, increasing the Si content around the heteroatom source M. Subsequently, introducing the Al source, since the stability of heteroatom M–O–Si is weaker than that of Al–O–Si, allows Al to replace M, thus increasing the silicon-to-aluminum ratio of the Y molecular sieve.

[0049] Preferably, the molar ratio of the alkali source, aluminum source, silicon source, and heteroatom source in the mother liquor is (2-20):1:(10-20):(0.05-0.6). In this embodiment of the invention, the ratio of each substance in the mother liquor when introducing heteroatoms is further optimized, which is beneficial to increasing the silicon-to-aluminum ratio of the Y molecular sieve. If too few heteroatom sources are introduced, it will not be conducive to improving the silicon-to-aluminum ratio. If too many heteroatom sources are introduced, it will lead to a decrease in crystallinity and reduce the structural order of the Y molecular sieve.

[0050] Preferably, the stirring time is 15-30 minutes.

[0051] In some embodiments, in step c, the stirring time is 1-3 hours and the stirring speed is 400-800 rpm. In this embodiment of the invention, the preferred stirring parameters for preparing the mother liquor are beneficial for the thorough and uniform mixing of the various substances and for the synthesis of Y molecular sieves.

[0052] In some embodiments, in step c, the ratio of the total mass of the aluminum source, silicon source, and alkali source in the mother liquor to the total mass of the aluminum source, silicon source, alkali source, and polydiallyldimethylammonium chloride in the modified seed crystal guide is 1:(0.05-0.12). In this embodiment of the invention, the preferred ratio of mother liquor to modified seed crystal guide is beneficial for crystal growth, thereby improving the synthesis quality and performance of the Y molecular sieve. If the amount of modified seed crystal guide is too low, it cannot fully exert its function, which is detrimental to the formation of hierarchical channels and crystal growth. If the amount of modified seed crystal guide is too high, it disrupts the pH of the silica-alumina gel, affecting the nucleation and depolymerization of the silica-alumina gel and damaging the crystallinity of the Y molecular sieve.

[0053] In some embodiments, step d, the crystallization treatment is a variable-temperature segmented crystallization treatment, preferably including the following steps: the first stage pre-crystallization temperature is 15-30℃, and the crystallization time is 1-2 days; the second stage crystallization temperature is 30-60℃, and the crystallization time is 1-2 days; the third stage crystallization temperature is 60-120℃, and the crystallization time is 1-3 days; more preferably, the first stage pre-crystallization temperature is 30℃, and the crystallization time is 1 day; the second stage crystallization temperature is 60℃, and the crystallization time is 1 day; the third stage crystallization temperature is 95℃, and the crystallization time is 1 day. In this embodiment of the invention, variable-temperature segmented crystallization is used, and a lower crystallization temperature is used in the first two stages of crystallization, which is conducive to the formation of crystal nuclei and slows down the crystal growth rate, which is beneficial to the synthesis of molecular sieves with smaller crystal sizes.

[0054] In some embodiments, in step d, the drying temperature is 60-120°C and the drying time is 12-24 hours.

[0055] This invention also provides a hierarchical porous Y molecular sieve, which is prepared using the method described in this invention. The hierarchical porous Y molecular sieve of this invention has a high silica-to-alumina ratio and high relative crystallinity, and can be used as a support material for the catalyst in the hydrocracking of waxes to produce jet fuel in Fischer-Tropsch synthesis, exhibiting excellent cracking performance.

[0056] This invention also provides a catalyst, wherein the catalyst support comprises a HY molecular sieve, and Pt is loaded on the support. The HY molecular sieve is a Y molecular sieve prepared by the method of this invention, or a Y molecular sieve prepared by ammonium exchange treatment. The catalyst of this invention can be used for the hydrocracking of Fischer-Tropsch synthesis wax to produce jet fuel, exhibiting excellent cracking performance.

[0057] In some embodiments, the ammonium exchange treatment includes: mixing the Y molecular sieve with an ammonium-containing solution for ion exchange treatment, followed by separation, washing, drying, and calcination to complete the ammonium exchange treatment. Preferably, the ammonium-containing solution includes at least one of ammonium nitrate, ammonium sulfate, and ammonium chloride; the concentration of the ammonium-containing solution is 0.5-1.5 mol / L; the temperature of the ion exchange treatment is 60-90℃; the drying temperature is 60-120℃, and the drying time is 12-24 h; the calcination temperature is 500-700℃, and the calcination time is 4-8 h.

[0058] This invention also provides an application of a catalyst in the hydrocracking of Fischer-Tropsch synthetic waxes to jet fuel. The catalyst of this invention exhibits excellent cracking performance in the hydrocracking of Fischer-Tropsch synthetic waxes to jet fuel.

[0059] In some embodiments, the reaction conditions for the hydrocracking of the Fischer-Tropsch synthetic wax are: a reaction temperature of 240-380°C, a reaction pressure of 2-4 MPa, a hydrogen-to-oil ratio of 400-600:1, and a liquid hourly space velocity of 2-10 h⁻¹. -1 .

[0060] The present invention will now be described in detail with reference to the embodiments and accompanying drawings.

[0061] Example 1

[0062] I. Preparation of Y-zeolite

[0063] 1. Preparation of seed crystal directing agent: At a temperature of 25℃, 2.67g of alkaline source sodium hydroxide, 0.368g of aluminum source sodium aluminate, and 6.5g of silicon source silica sol (silica mass percentage of 30%) were added to deionized water and stirred for 1h. Then, 0.2mol of PDDA was added to obtain a mixed solution. After stirring for another 1h, the solution was sealed and aged for 24h to obtain a modified seed crystal directing agent. The molar ratio of alkaline source (calculated as Na2O, including sodium ions from sodium hydroxide and sodium aluminate), aluminum source (calculated as Al2O3), silicon source (calculated as SiO2), PDDA, and deionized water in the mixed solution was 16:1:16:0.2:320.

[0064] 2. Preparation of Mother Liquor: At 25℃, 1g of sodium hydroxide and 77g of water glass were slowly added to 35g of deionized water at 400rpm. After stirring for 20min, a silicon source mixed solution was obtained. 3.25g of sodium aluminate and 3.5g of aluminum sulfate were slowly added to 70g of deionized water at 650rpm. After stirring for 20min, an aluminum source mixed solution was obtained. The silicon source mixed solution and the aluminum source mixed solution were stirred at 650rpm for 20min to obtain a sol, i.e., the mother liquor. The molar ratio of the alkali source (calculated as Na2O, including sodium ions from sodium hydroxide and sodium aluminate), aluminum source (calculated as Al2O3), silicon source (calculated as SiO2) and water used in preparing the mother liquor was 6:1:12:300.

[0065] 3. At a temperature of 16℃, under stirring conditions of 700 rpm, a modified seed crystal guiding agent was slowly added dropwise to the mother liquor, and stirring was continued for 2 hours to obtain a gel. The ratio of the total mass of aluminum source, silicon source, and alkali source in the mother liquor to the total mass of aluminum source, silicon source, alkali source, and polydiallyldimethylammonium chloride in the added modified seed crystal guiding agent was 1:0.08.

[0066] 4. Place the gel in a crystallization vessel and crystallize at 30℃ for one day; at 60℃ for one day; and at 95℃ for one day. After crystallization, separate and wash the solid product, and then dry it at 110℃ for 16 hours to obtain Y molecular sieve, denoted as 0.2PDDA-Y molecular sieve.

[0067] II. Catalyst Preparation

[0068] The synthesized 0.2PDDA-Y molecular sieve was exchanged with a 0.5 mol / L ammonium sulfate aqueous solution at 60 °C for 2 h. The mixture was then transferred to a stainless steel autoclave and crystallized at 90 °C for 3 h. After crystallization, it was filtered, washed, and calcined at 500 °C for 4 h. The ion exchange process was repeated three times to obtain the 0.2PDDA-HY molecular sieve.

[0069] A composite support was prepared by mixing 0.2 PDDA-HY molecular sieve with amorphous aluminosilicate (ASA) at a mass ratio of 3:7, and then pressing it into 20-40 mesh particles. Pt (wherein the mass of PtO was 0.3 wt% of the composite support) was loaded using an equal-volume impregnation method, allowed to stand at room temperature for 12 h, dried at 110 °C for 12 h, and calcined at 500 °C for 4 h to obtain the catalyst.

[0070] Example 2

[0071] The method is the same as in Example 1, except that the amount of PDDA used in step 1 of the Y molecular sieve preparation is different. Specifically, the molar ratio of alkali source (calculated as Na2O), aluminum source (calculated as Al2O3), silicon source (calculated as SiO2), PDDA and deionized water is 16:1:16:0.05:320.

[0072] The Y molecular sieve prepared in this embodiment is designated as 0.05PDDA-Y molecular sieve.

[0073] Example 3

[0074] The method is the same as in Example 1, except that the amount of PDDA used in step 1 of the Y molecular sieve preparation is different. Specifically, the molar ratio of alkali source (calculated as Na2O), aluminum source (calculated as Al2O3), silicon source (calculated as SiO2), PDDA and deionized water is 16:1:16:0.1:320.

[0075] The Y molecular sieve prepared in this embodiment is designated as 0.1PDDA-Y molecular sieve.

[0076] Example 4

[0077] The method is the same as in Example 1, except that the amount of PDDA used in step 1 of the Y molecular sieve preparation is different. Specifically, the molar ratio of alkali source (calculated as Na2O), aluminum source (calculated as Al2O3), silicon source (calculated as SiO2), PDDA and deionized water is 16:1:16:0.6:320.

[0078] The Y molecular sieve prepared in this embodiment is designated as 0.6PDDA-Y molecular sieve.

[0079] Example 5

[0080] The method is the same as in Example 3, except that a Co source is introduced into the mother liquor in step 2 of the Y molecular sieve preparation, as detailed below:

[0081] At 25°C, 1g of sodium hydroxide and 77g of water glass were slowly added to 35g of deionized water at 400rpm and stirred for 20min. Then, 0.2 moles of cobalt nitrate were added and stirred for another 30min to obtain the first mixed solution. 3.25g of sodium aluminate and 3.5g of aluminum sulfate were slowly added to 70g of deionized water at 650rpm and stirred for 20min to obtain the second mixed solution. The first and second mixed solutions were stirred at 650rpm for 20min to obtain a sol, i.e., the mother liquor. The molar ratio of the alkali source (calculated as Na2O), aluminum source (calculated as Al2O3), silicon source (calculated as SiO2), cobalt source (calculated as Co) and water used to prepare the mother liquor was 6:1:12:0.2:300.

[0082] The Y molecular sieve prepared in this embodiment is denoted as (0.1PDDA+0.2Co)-Y molecular sieve.

[0083] The scanning electron microscope image of the Y molecular sieve prepared in this embodiment is shown below. Figure 1 ,from Figure 1 It can be seen that there are intercrystalline mesopores in the Y molecular sieve, and the synthesized Y molecular sieve has a meso-micro hierarchical pore structure, indicating that the incorporation of Co is beneficial to the growth of Y molecular sieve crystals and promotes the growth of soluble silicates and aluminates around the crystal nuclei in the molecular sieve synthesis gel.

[0084] Example 6

[0085] The method is the same as in Example 4, except that a Co source is introduced into the mother liquor in step 2 of the Y molecular sieve preparation. The method for introducing the cobalt source is the same as in Example 5. In this example, the molar ratio of alkali source (calculated as Na2O), aluminum source (calculated as Al2O3), silicon source (calculated as SiO2), cobalt source (calculated as Co element) and water used in the preparation of the mother liquor is 6:1:12:0.3:300.

[0086] The Y molecular sieve prepared in this embodiment is denoted as (0.6DDA+0.3Co)-Y molecular sieve.

[0087] The scanning electron microscope image of the Y molecular sieve prepared in this embodiment is shown below. Figure 2 ,from Figure 2 It can be seen that the synthesized Y molecular sieve has a meso-micro hierarchical porous structure, with more intercrystalline mesopores than in Example 5. This indicates that the incorporation of Co is beneficial to the growth of Y molecular sieve crystals and promotes the growth of soluble silicates and aluminates around the crystal nuclei in the molecular sieve synthesis gel.

[0088] Example 7

[0089] The method is the same as in Example 5, except that an iron source is introduced into the mother liquor in step 2 of the Y molecular sieve preparation. The molar ratio of the alkali source (calculated as Na2O), aluminum source (calculated as Al2O3), silicon source (calculated as SiO2), iron source (calculated as Fe element) and water used to prepare the mother liquor is 6:1:12:0.1:300.

[0090] The Y molecular sieve prepared in this embodiment is denoted as (0.1PDDA+0.1Fe)-Y molecular sieve.

[0091] Example 8

[0092] The method is the same as in Example 5, except that the mother liquor introduced in step 2 of the Y molecular sieve preparation is a zirconium source, and the molar ratio of the alkali source (calculated as Na2O), aluminum source (calculated as Al2O3), silicon source (calculated as SiO2), zirconium source (calculated as Zr element) and water used to prepare the mother liquor is 6:1:12:0.2:300.

[0093] The Y molecular sieve prepared in this embodiment is denoted as (0.1PDDA+0.2Zr)-Y molecular sieve.

[0094] Example 9

[0095] The method is the same as in Example 5, except that a nickel source is introduced into the mother liquor in step 2 of the Y molecular sieve preparation. The molar ratio of the alkali source (calculated as Na2O), aluminum source (calculated as Al2O3), silicon source (calculated as SiO2), nickel source (calculated as Ni element) and water used to prepare the mother liquor is 6:1:12:0.2:300.

[0096] The Y molecular sieve prepared in this embodiment is denoted as (0.1PDDA+0.2Ni)-Y molecular sieve.

[0097] Example 10

[0098] The method is the same as in Example 5, except that the mother liquor introduced in step 2 of the Y molecular sieve preparation is a Ti source, and the molar ratio of the alkali source (calculated as Na2O), aluminum source (calculated as Al2O3), silicon source (calculated as SiO2), titanium source (calculated as Ti element) and water used to prepare the mother liquor is 6:1:12:0.1:300.

[0099] The Y molecular sieve prepared in this embodiment is denoted as (0.1PDDA+0.1Ti)-Y molecular sieve.

[0100] Comparative Example 1

[0101] The method is the same as in Example 1, except that PDDA is not added in step 1 of the preparation of Y molecular sieve.

[0102] Comparative Example 2

[0103] The method is the same as in Example 1, except that PDDA is not added in step 1 of the Y molecular sieve preparation, but is added in the preparation of the mother liquor in step 2. The specific method for preparing the mother liquor is as follows: at 25°C, 1g of sodium hydroxide and 77g of water glass are slowly added to 35g of deionized water at 400rpm, and stirred for 20min to obtain a silicon source mixed solution; 3.25g of sodium aluminate and 3.5g of aluminum sulfate are slowly added to 70g of deionized water at 650rpm, and stirred for 20min to obtain an aluminum source mixed solution; the silicon source mixed solution and the aluminum source mixed solution are stirred at 650rpm for 20min, then 0.2 moles of PDDA are added, and stirring is continued for 20min to obtain a sol, i.e., the mother liquor. The molar ratio of alkali source (calculated as Na2O), aluminum source (calculated as Al2O3), silicon source (calculated as SiO2), PDDA and water used in preparing the mother liquor is 6:1:12:0.2:300.

[0104] The Y molecular sieve prepared in this comparative example is denoted as (0.2PDDA)Y molecular sieve.

[0105] Comparative Example 3

[0106] The method is the same as in Example 1, except that PDDA is not added in step 1 of the preparation of Y molecular sieve, but instead the same molar amount of hexadecyltrimethylammonium bromide (CTAB) is introduced.

[0107] The Y molecular sieve prepared in this comparative example is denoted as 0.2CTAB-Y molecular sieve.

[0108] Comparative Example 4

[0109] The method is the same as in Example 5, except that PDDA is not added in step 1 of the Y molecular sieve preparation, and the mother liquor introduced in step 2 of the Y molecular sieve preparation is a Co source. The molar ratio of the alkali source (calculated as Na2O), aluminum source (calculated as Al2O3), silicon source (calculated as SiO2), cobalt source (calculated as Co element) and water used to prepare the mother liquor is 6:1:12:0.2:300.

[0110] The Y molecular sieve prepared in this embodiment is designated as 0.2Co-Y molecular sieve.

[0111] The performance of the Y molecular sieves prepared in each embodiment and comparative example was tested, and the test results are shown in the figure. Figure 3-6 See Table 1.

[0112] Table 1

[0113]

[0114] Note: The relative crystallinity is calculated based on the crystallinity of Comparative Example 1 being normalized to 100%.

[0115] Figure 3 The XRD spectra of Examples 1-10 and Comparative Example 1 are shown below. Figure 3 It can be seen that the Y zeolite with added PDDA and different heteroatom sources still has the same crystal structure as the Y zeolite, indicating that the crystal structure of FAU is still preserved. Combined with Table 1, it can be seen that the crystallinity is maintained above 90%, indicating that the introduction of PDDA has little impact on the crystal structure of the Y zeolite.

[0116] Figure 4 The XRD spectra of Example 1 and Comparative Examples 1-4 are obtained by... Figure 4 It can be seen that, compared with the conventional Y-zeolite in Comparative Example 1, the addition of PDDA and CTAB still results in the same crystal structure as the Y-zeolite, with a crystallinity maintained above 94%. Figure 4As shown in Table 1, comparing the addition of PDDA to the seed crystal and mother liquor in Example 1 and Comparative Example 2, it can be seen that adding PDDA to the directing agent in Example 1 resulted in better retention of the crystallinity of the Y molecular sieve, reaching 98.65%, while adding PDDA to the mother liquor in Comparative Example 2 caused the crystallinity to decrease to 94.52%. Comparing the addition of PDDA and CTAB to the seed crystal in Example 1 and Comparative Example 3, it can be seen that adding PDDA to the seed crystal resulted in better retention of the crystallinity of the Y molecular sieve. This is related to the properties of PDDA and CTAB; PDDA is a cationic polymer, and CTAB is a cationic surfactant. PDDA can better bind to the surface of the negatively charged Y crystal nucleus precursor.

[0117] Figure 5 The N2 adsorption-desorption isotherms for Example 1 and Comparative Examples 1-4 are obtained by... Figure 5 It can be seen that although both PDDA and CTAB can introduce mesopores into Y molecular sieves, according to Table 1, adding PDDA provides a larger specific surface area, pore volume, and pore size compared to adding CTAB. In Example 1, the largest specific surface area of ​​769 m² was obtained by adding PDDA to the seed crystals. 2 / g, maximum pore volume is 0.68cm³ 3 With a maximum pore size of 4.51 nm, it has the best effect in introducing mesopores.

[0118] Figure 6 The N2 adsorption-desorption isotherms for Examples 1-10 and Comparative Example 1 are obtained by... Figure 6 It can be seen that the N2 adsorption-desorption isotherm curve of the conventional Y molecular sieve is a type I isotherm, indicating that the synthesized Y molecular sieve is a typical microporous structure. Referring to Table 1, in Examples 1-4, compared with Comparative Example 1, it can be seen that adding PDDA to the seed crystals introduces mesopores into the Y molecular sieve, and the specific surface area, pore volume, and pore size all increase. In Examples 5-10, after adding PDDA and introducing heteroatom sources, compared with the conventional Y molecular sieve of Comparative Example 1, the specific surface area, pore volume, and pore size significantly increase, and the number of introduced mesopores increases. In Comparative Example 4, no PDDA was added, only a heteroatom source was added. Due to the different ionic radii of each heteroatom, when incorporated into the Y molecular sieve framework, it drives the migration of adjacent Si and Al atoms, forming framework defects, and also assists in the formation of some mesopores. Therefore, the pore size of Comparative Example 4 is slightly increased compared with the conventional molecular sieve of Comparative Example 1. In Examples 5-10, the introduction of heteroatom sources occupies a certain amount of pores. Therefore, compared with Examples 3 and 4, which did not introduce heteroatoms, the specific surface area, pore volume, and pore size of Examples 5-10 decreased, but the silicon-to-aluminum ratio was effectively improved.

[0119] As shown in Table 1, the molecular sieves prepared in Examples 1-10 of this invention have large pore volume and pore size, and large specific surface area. This indicates that the mesoporous template agent PDDA has large steric hindrance and positive charge, which guides crystal nucleus growth, slows down crystal growth rate, and reduces crystal size. The large steric hindrance of PDDA results in high crystal nucleus dispersion. After calcination, mesopores are introduced, which is beneficial to increasing the specific surface area and pore volume and pore size, providing more reaction surface. Furthermore, in the preparation process of the molecular sieves in Examples 5-10, heteroatom sources were introduced, due to the microcrystalline M(OH)... n The presence of [agents] provides a good attachment surface for nucleation, reduces the nucleation free energy, and promotes nucleation. Simultaneously, the substitution of framework Al ions by M ions induces the synthesis of high-silicon Y molecular sieves, further increasing the silicon-to-aluminum ratio. This results in Examples 5-10 exhibiting both large pore volume, pore size, and specific surface area, while also possessing a higher silicon-to-aluminum ratio. In this invention, by introducing the mesoporous template agent PDDA into the seed crystal guide and heteroatoms into the mother liquor, high-silicon molecular sieves with a hierarchical porous structure were prepared, effectively improving the performance of the molecular sieves.

[0120] Unlike Comparative Example 1, which did not introduce PDDA, Comparative Example 2 and Example 1 respectively added PDDA to the mother liquor and seed crystals. The molecular sieve prepared by adding PDDA to the seed crystals in Example 1 had a larger specific surface area, pore volume, and pore size. This is because the cationic polymer PDDA added to the seed crystals adsorbs onto the precursor surface of the Y crystal nuclei, guiding nucleus growth and improving nucleus dispersion. In Comparative Example 2, PDDA was added to the mother liquor. Although this resulted in the formation of mesopores and an increase in specific surface area after calcination compared to Comparative Example 1 without PDDA, the addition of PDDA to the mother liquor caused uneven dispersion of PDDA, which adsorbed onto the nucleus surface. This uneven dispersion and agglomeration of PDDA in the mother liquor led to poor crystallinity of the formed molecular sieve and limited mesopore formation. Compared to Example 1, the pore volume, pore size, and specific surface area were significantly reduced.

[0121] In Comparative Example 3, PDDA was not added to the seed crystals; instead, the cationic surfactant CTAB was introduced. The specific surface area, pore volume, pore size, and silicon-to-aluminum ratio of the resulting molecular sieve were significantly lower than those in Example 1. This is mainly because the PDDA introduced in this invention has greater steric hindrance, introduces more mesopores, and these are disordered mesopores. At the same time, PDDA attracts more silicon into the framework of the Y molecular sieve, thus increasing the silicon-to-aluminum ratio.

[0122] The catalytic performance of the catalysts prepared in each embodiment and comparative example was tested, and the test results are shown in Table 2.

[0123] 1. Reduction treatment: The catalysts prepared in each example and comparative example were reduced at 550°C for 6 hours and then set aside for later use.

[0124] 2. Using Fischer-Tropsch synthetic wax as raw material, the reaction temperature was 340℃, the H2 pressure was 4MPa, the hydrogen-to-oil ratio was 400:1, and the liquid hourly space velocity was 6h. -1 .

[0125] Table 2

[0126] Serial Number Catalysts (named after the support) C9-C15 selectivity, % Example 1 0.2PDDA-Y 29.66 Example 2 0.05PDDA-Y 27.33 Example 3 0.1PDDA-Y 28.86 Example 4 0.6PDDA-Y 36.80 Example 5 (0.1PDDA+0.2Co)-Y 34.40 Example 6 (0.6PDDA+0.3Co)-Y 47.35 Example 7 (0.1PDDA+0.1Fe)-Y 32.59 Example 8 (0.1PDDA+0.2Zr)-Y 34.29 Example 9 (0.1PDDA+0.2Ni)-Y 31.09 Example 10 (0.1PDDA+0.1Ti)-Y 32.98 Comparative Example 1 Y 25.42 Comparative Example 2 (0.2PDDA)Y 26.71 Comparative Example 3 0.2CTAB-Y 26.74 Comparative Example 4 0.2Co-Y 28.01

[0127] As shown in Table 2, the catalysts prepared in the embodiments of the present invention exhibit cracking selectivity of over 27% when used in the hydrocracking of Fischer-Tropsch synthesis wax to produce jet fuel. In particular, Examples 5-10 show cracking selectivity of over 31%, demonstrating excellent cracking performance. This is mainly because the Y molecular sieve prepared in the embodiments of the present invention has a rich hierarchical porous structure and a high silica-to-alumina ratio. Using it as a support for catalyst preparation effectively improves the cracking performance of the catalyst.

[0128] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0129] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a hierarchical porous Y molecular sieve, characterized in that, include: a. Mix aluminum source, silicon source, alkali source and deionized water, then add polydiallyldimethylammonium chloride and mix evenly. After aging, a modified seed crystal directing agent is obtained. b. Mix and stir the aluminum source, silicon source, alkali source and deionized water to obtain the mother liquor; c. Add the modified seed crystal guiding agent to the mother liquor and stir to obtain a gel; d. The gel obtained in step c is subjected to crystallization treatment. The solid product after crystallization treatment is separated, washed and dried to obtain a multi-level porous Y molecular sieve.

2. The method for preparing hierarchical porous Y molecular sieve according to claim 1, characterized in that, In step a and / or step b, the aluminum source includes at least one of sodium aluminate, aluminum sulfate, boehmite, aluminum isopropoxide, and aluminum nitrate, preferably at least one of boehmite or aluminum sulfate. And / or, the silicon source includes at least one of water glass, silica sol, tetraethyl orthosilicate, and sodium silicate, preferably at least one of water glass or silica sol; And / or, the alkali source includes at least one of sodium hydroxide, potassium hydroxide, sodium oxide, or potassium oxide.

3. The method for preparing hierarchical porous Y molecular sieve according to claim 1 or 2, characterized in that, In step a, the molar ratio of polydiallyldimethylammonium chloride to the aluminum source is (0.02-1.2):1; And / or, in step a, the aging temperature is 5-50℃ and the aging time is 16-48h, preferably, the aging temperature is 20-40℃ and the aging time is 18-36h.

4. The method for preparing hierarchical porous Y molecular sieve according to claim 1 or 2, characterized in that, In step b, the molar ratio of the alkali source, aluminum source, and silicon source is (2-20):1:(10-20); and / or, the stirring speed is 400-800 rpm.

5. The method for preparing hierarchical porous Y molecular sieve according to claim 1 or 2, characterized in that, Step b includes: mixing an alkali source, a silicon source, a heteroatom source, and deionized water to obtain a first mixed solution; mixing an alkali source, an aluminum source, and deionized water to obtain a second mixed solution; and mixing the first mixed solution and the second mixed solution and stirring until homogeneous to obtain a mother liquor. Preferably, the heteroatom source includes at least one of a cobalt source, a nickel source, an iron source, a zirconium source, and a titanium source. More preferably, the cobalt source is selected from at least one of cobalt nitrate, cobalt sulfate, cobalt chloride, and cobalt hydroxide; the nickel source is selected from at least one of nickel nitrate, nickel sulfate, nickel chloride, and nickel hydroxide; the iron source is selected from at least one of ferric nitrate, ferric chloride, ferric sulfate, and hydrated ferric oxide (III); the zirconium source is selected from at least one of zirconium nitrate, zirconium sulfate, zirconium chloride, zirconium oxynitrate, zirconium ammonium carbonate, and zirconium oxyhydroxide; and the titanium source is selected from at least one of titanium oxysulfate, titanium sulfate, and titanium tetrachloride. Preferably, the molar ratio of the alkali source, aluminum source, silicon source, and heteroatom source in the mother liquor is (2-20):1:(10-20):(0.05-0.6); Preferably, the stirring time is 15-30 minutes.

6. The method for preparing hierarchical porous Y molecular sieve according to claim 1 or 2, characterized in that, In step c, the stirring time is 1-3 hours and the stirring speed is 400-800 rpm; And / or, in step c, the ratio of the total mass of aluminum source, silicon source, and alkali source in the mother liquor to the total mass of aluminum source, silicon source, alkali source, and polydiallyldimethylammonium chloride in the modified seed crystal guide agent is 1:(0.05-0.12); And / or, in step d, the crystallization treatment is a variable-temperature segmented crystallization treatment, preferably including the following steps: the first stage pre-crystallization temperature is 15-30℃, and the crystallization time is 1-2 days; the second stage crystallization temperature is 30-60℃, and the crystallization time is 1-2 days; the third stage crystallization temperature is 60-120℃, and the crystallization time is 1-3 days; more preferably, the first stage pre-crystallization temperature is 30℃, and the crystallization time is 1 day; the second stage crystallization temperature is 60℃, and the crystallization time is 1 day; the third stage crystallization temperature is 95℃, and the crystallization time is 1 day; And / or, in step d, the drying temperature is 60-120℃ and the drying time is 12-24h.

7. A hierarchical porous Y molecular sieve, characterized in that, It is made by any one of claims 1-6.

8. A catalyst, characterized in that, The catalyst support includes a HY molecular sieve, on which Pt is loaded, wherein the HY molecular sieve is obtained by the method of any one of claims 1-6 or by the HY molecular sieve of claim 7 through ammonium exchange treatment.

9. The catalyst according to claim 8, characterized in that, The ammonium exchange treatment includes: mixing the Y molecular sieve with an ammonium-containing solution for ion exchange treatment, and then completing the ammonium exchange treatment after separation, washing, drying, and calcination; Preferably, the ammonium-containing solution includes at least one of ammonium nitrate, ammonium sulfate, and ammonium chloride; Preferably, the concentration of the ammonium-containing solution is 0.5-1.5 mol / L; Preferably, the temperature of the ion exchange treatment is 60-90°C; Preferably, the drying temperature is 60-120℃ and the drying time is 12-24h; Preferably, the calcination temperature is 500-700℃ and the calcination time is 4-8 hours.

10. The application of the catalyst according to claim 8 or 9 in the hydrocracking of Fischer-Tropsch synthetic wax to produce jet fuel; preferably, the reaction conditions for the hydrocracking of Fischer-Tropsch synthetic wax are: reaction temperature of 240-380℃, reaction pressure of 2-4 MPa, hydrogen-to-oil ratio of 400-600:1, and liquid hourly space velocity of 2-10 h⁻¹. -1 .

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