Modified Y-type molecular sieve, preparation method thereof and hydrocracking catalyst

Abstract

The invention provides a modified Y-type molecular sieve, a preparation method thereof and a hydrocracking catalyst. The preparation method comprises the following steps: in a liquid phase system, carrying out first reaction on an organic matter and a Y-type molecular sieve to obtain a modified Y-type molecular sieve A; wherein the organic matter has one or a combination of more than two of amidino functional groups, benzyl functional groups and sulfydryl functional groups; carrying out a second reaction on the modified Y-type molecular sieve A in an acidic liquid phase system, and then carrying out roasting treatment to obtain the modified Y-type molecular sieve, wherein the mass ratio of the Y-type molecular sieve to the organic matter is (3-12.5): 1. The preparation method disclosed by the invention is safe and harmless, the surface of the obtained molecular sieve has a tunnel structure, and the molecular sieve has good catalytic activity.

Description

Technical Field

[0001] The present invention belongs to the field of molecular sieve modification, and particularly relates to a modified Y-type molecular sieve, a preparation method thereof, and a hydrocracking catalyst. Background Art

[0002] Y-type molecular sieve is a synthetic molecular sieve with a supercage surrounded by β-cages and hexagonal prismatic cages, consisting of 18 four-membered rings, 4 six-membered rings, and 4 twelve-membered rings, forming a structural pore orifice diameter of 0.74 nm and an inner diameter of 1.2 nm. Due to its rich pore structure and a large number of cracking active centers required for solid acid catalysts. Since the hydrothermal stability of Y-type molecular sieve with a low silicon-aluminum ratio affects the subsequent use effect, the high silicon-aluminum ratio Y-type molecular sieve obtained by modification has good hydrothermal stability and acid stability. Therefore, the modified Y-type molecular sieve plays an irreplaceable role as a catalytic material in oil refining processes such as catalytic cracking and hydrocracking. There are mainly three methods for modifying Y-type molecular sieve: high-temperature hydrothermal method, chemical method, and a combined method of high-temperature hydrothermal and chemical methods. The high-temperature hydrothermal method is simple and feasible, and can generate some secondary pores. The aluminum removed from the framework does not leave the molecular sieve but exists in various forms in the molecular sieve pores, resulting in an unreasonable pore distribution of the molecular sieve and a large loss of crystallinity. The chemical method is to treat it with chemical reagents to partially remove aluminum from the framework. This method can be divided into two categories: one is dealumination and silicon supplementation, that is, while removing aluminum by the chemical reagent method, silicon atoms are filled in the positions where aluminum has been removed, and a relatively high crystallinity can be maintained. The typical methods are gas-phase dealumination and silicon supplementation with SiCl 4 vapor-phase dealumination and silicon supplementation and (NH 4 ) 2 SiF 6 liquid-phase dealumination and silicon supplementation; the other is to use inorganic acids or organic acids to act on the molecular sieve for simple dealumination. Inorganic acid dealumination with HCl, HNO 3 , H 2 SO 4 , citric acid, etc. only relies on H + for dealumination, so the crystallinity decreases greatly.

[0003] CN106608643B aims at the deficiency that the total acid amount of zeolite decreases during the hydrothermal ultrastabilization process of zeolite, which affects the cracking activity or selectivity, and provides a modification method for Y-type zeolite with a high framework silicon-aluminum ratio, good stability, and an appropriate increase in the number of acid centers. Specifically, it includes: (1) activating NaY-type zeolite with polyhydric alcohol at 80-200°C for 1-10 h to obtain slurry A; (2) cooling slurry A and mixing it with an organic base to obtain slurry B; (3) adding a silicon source and an aluminum source in the order of adding the silicon source first and then the aluminum source, and subjecting the mixture to aging treatment to obtain slurry C; (4) subjecting slurry C to hydrothermal crystallization and recovering the product. This technology activates the zeolite with polyhydric alcohol to Si-OH and Al-OH, and then adds a silicon source and an aluminum source to re-perform hydrothermal crystallization, aiming to increase the initial silicon-aluminum ratio and acid amount of NaY-type zeolite, without achieving external modification of the zeolite pores.

[0004] CN110498424B aims at the problem of uneven dealumination existing in the chemical dealumination method, and provides a modification method for Y-type zeolite with a uniform aluminum distribution. Specifically, it includes: performing ammonium exchange treatment on NaY-type zeolite to obtain NH 4 Y-type zeolite, contacting the obtained NH 4 Y-type zeolite with a salt solution containing alkali metal ions and / or a salt solution containing alkaline earth metal ions, filtering, washing, and drying, then contacting the obtained product with an acid solution, and recovering the product to obtain the modified Y-type zeolite; this technical solution mainly utilizes the steric hindrance generated by NH 4 + ions to promote the enrichment of alkali metals on the outside of the zeolite and stabilize the framework, and then uniformly dealuminate with an acid solution. Its purpose is mainly to enhance the degree of bulk dealumination of the zeolite, without involving the modification of the surface morphology of the zeolite.

[0005] CN105498686B aims at the problems of poor adsorption effect and desorption and reuse of zeolite, and provides a zeolite modification method. Specifically, it includes: loading or exchanging the zeolite with a soluble metal salt or heteropolyacid, etc., and adsorbing 2-heptanone in cyclohexanone finished product with the modified zeolite; this technology aims to enhance the adsorption and desorption performance of the zeolite, without directionally modulating the pore structure of the zeolite, and thus changing its surface structure. Summary of the Invention

[0006] In order to solve the above problems in the prior art, the purpose of the present invention is to provide a modified Y-type zeolite and its preparation method. The preparation method is safe and harmless, the obtained zeolite has a tunnel structure on the surface, and the zeolite has good catalytic activity.

[0007] To achieve the above purpose, according to one aspect, the present invention provides a preparation method for a modified Y-type zeolite, which includes:

[0008] In a liquid-phase system, a first reaction is carried out between an organic substance and a Y-type molecular sieve to obtain a modified Y-type molecular sieve A; wherein, the organic substance has one or a combination of two or more of amidino, benzyl, and mercapto functional groups;

[0009] In an acidic liquid-phase system, a second reaction is carried out on the modified Y-type molecular sieve A, and then a calcination treatment is carried out to obtain the modified Y-type molecular sieve;

[0010] Wherein, the mass ratio of the Y-type molecular sieve to the organic substance is 3 to 12.5:1.

[0011] In the first reaction, the preparation method of the present invention completes the first-step modification of the modified Y-type molecular sieve. Specific functional groups in the organic substance (one or a combination of two or more of amidino, benzyl, and mercapto functional groups) react with the surface structure of the molecular sieve to form a stable organic substance-Y-type molecular sieve structure, thereby being able to have a positive impact on the subsequent chemical treatment process.

[0012] For the pore structure of the Y-type molecular sieve, it can be divided into a microporous structure formed by its crystal configuration and a mesoporous structure formed by the accumulation of molecular sieve particles. In terms of the microporous structure, the pore size in the Y-type molecular sieve crystal is 0.74 nm, which is about the length of 5 C-C bonds. During the reaction of the organic substance with the surface structure of the molecular sieve, the microporous channels in the Y-type molecular sieve will be significantly blocked, resulting in a significant reduction in the mass transfer performance of the original microporous structure. In terms of the mesoporous structure, the pore size of the accumulated pores formed by the Y-type molecular sieve is usually about 10 to 15 nm, and the reaction of the organic substance with the surface of the molecular sieve has almost no impact on the mass transfer performance of the mesoporous structure. Thus, by adsorbing the organic substance on the Y-type molecular sieve, the subsequent acid treatment process can more easily occur at the mesoporous channel position of the Y-type molecular sieve.

[0013] The organic substance modification in the present invention can produce beneficial effects in three aspects: the micropores, mesopores, and outer surface of the Y-type molecular sieve. First, in terms of the micropores, the adsorption of the organic substance can protect the microporous structure of the Y-type molecular sieve, reduce the loss of crystallinity caused by chemical modification, and further prevent the long-cycle operation life of the catalyst from being guaranteed. Second, in terms of the mesopores, it can achieve directional regulation of the mesoporous channel structure of the molecular sieve and enhance the connectivity of the channel structure. Third, in terms of the outer surface of the molecular sieve, it can directionally damage the framework structure of the outer surface of the molecular sieve, thereby generating a certain pit structure. The generation of this pit structure is beneficial for the preparation of the catalyst, enabling the near-spherical non-supported active phase to fall into the pits, thereby enhancing the binding degree between the non-supported active phase and the Y-type molecular sieve and achieving the purpose of improving the activity and selectivity of the non-supported catalyst.

[0014] The mass ratio of the Y-type molecular sieve to the organic matter is 3 to 12.5:1. Carrying out the first reaction according to this ratio is beneficial to achieving the beneficial effects brought about by the organic matter modification.

[0015] Further preferably, the mass ratio of the Y-type molecular sieve to the organic matter is 5 to 10:1.

[0016] In some preferred embodiments of the present invention, the temperature of the first reaction is 20 to 50 °C, and the time is 0.5 to 3 h.

[0017] More advantageously, the temperature of the first reaction is 20 to 45 °C.

[0018] In some embodiments of the present invention, in the liquid phase system of the first reaction, the solvent is water. Preferably, the solid-liquid mass ratio is 1:5 to 10. Preferably, the solid-liquid mass ratio is 1:10.

[0019] In some embodiments of the present invention, after the first reaction, the preparation method further includes:

[0020] Performing solid-liquid separation, washing, and drying on the reaction product obtained from the first reaction to obtain the modified Y-type molecular sieve A.

[0021] Preferably, the method for solid-liquid separation is filtration.

[0022] In the preparation method of the present invention, the methods for solid-liquid separation, washing, and drying can be conventional in the art.

[0023] It should be noted that after the first reaction, the above-mentioned solid-liquid separation, washing, and drying treatments are optional. In some embodiments of the present invention, the system obtained after the first reaction can be directly used for the second reaction, further simplifying the process and reducing costs.

[0024] In some embodiments of the present invention, after the first reaction, a washing treatment is performed. Preferably, a water washing treatment is performed. In the first reaction of the present invention, specific functional groups in the amino acid react with the surface structure of the molecular sieve to form a stable organic matter-Y-type molecular sieve structure. Therefore, water washing will not cause a change in the amino acid content adsorbed on the modified Y-type molecular sieve A.

[0025] In some embodiments of the present invention, preferably, the temperature of the second reaction is 35 to 60 °C, and the time is 0.5 to 4 h.

[0026] In some embodiments of the present invention, in the second reaction, the pH of the acidic liquid phase system is ≤1.

[0027] In some embodiments of the present invention, the organic acid and / or inorganic acid can provide the acidic environment in the second reaction. For example, it can be oxalic acid, hydrochloric acid, citric acid, etc. Preferably, the concentration of the added acid is 0.1 - 1 mol / L. Since molecular sieves are oxides of silicon and aluminum, they are unstable in both acidic and alkaline media. In an acidic medium, the Si and Al elements in the molecular sieve framework will react to form Al 3+ ions and Si 4+ ions (the reactivity of Al element detaching from the framework under acidic conditions is higher than that of Si element). Through this etching effect, pits are formed on the surface of the molecular sieve.

[0028] It should be noted that in the second reaction, the structure of the acid is not the main factor and it is not immobilized on the molecular sieve.

[0029] In some embodiments of the present invention, preferably, after the second reaction, the slurry is filtered, washed, and dried. Preferably, the drying temperature is 80 - 120 °C and the time is 2 - 8 h.

[0030] In some embodiments of the present invention, preferably, the organic matter is one or a combination of two or more of arginine, phenylalanine, methionine, acetamidine hydrochloride, benzamidine hydrochloride, and 3-(formamidothio)-1-propanesulfonic acid. When the carbon chain length of the organic matter is greater than 5, it is easier to use the organic matter to occupy the micropores and complete the pore blocking.

[0031] Similarly, through the experiments in the technical development of the present invention, it is found that if amino acids with larger molecular weight and steric hindrance are used to modify the molecular sieve, the larger molecular weight molecules are difficult to enter the micropore channels, and the modification process is relatively difficult to occur.

[0032] In some embodiments of the present invention, preferably, the temperature of the calcination treatment is 470 - 560 °C and the time is 3 - 6 h. Here, the temperature of the calcination treatment only needs to be able to burn all the modified amino acids. Generally, a treatment temperature greater than 500 °C can ensure that all organic matters are burned. However, for some organic matters with low decomposition temperature, there are also instances where the treatment before 500 °C can also be achieved.

[0033] In the preparation method of the present invention, there is no additional limitation on the specific model of the Y-type molecular sieve. Common Y-type molecular sieves on the market, regardless of their silicon-aluminum ratio, can be applicable to the modification method provided by the present invention.

[0034] According to another aspect of the present invention, there is provided a modified Y-type molecular sieve obtained by the above-mentioned preparation method, the surface of which has a tunnel structure. In the preparation of the catalyst, the formation of this tunnel structure is beneficial to making near-spherical cluster pellets (non-supported active phase) fall into the tunnels, thereby enhancing the binding degree between the non-supported active phase and the Y-type molecular sieve, achieving the purpose of enhancing the activity and selectivity of the non-supported catalyst. The cluster pellets can function as the active phase of a hydrocracking catalyst after sulfidation.

[0035] In the present invention, the design goal of the tunnels on the surface of the molecular sieve is to form a tunnel structure with a size of not less than 20 nm on the surface of the molecular sieve, preferably between 20 and 40 nm. According to another aspect of the present invention, there is provided a hydrocracking catalyst, the raw materials of which include the above-mentioned modified Y-type molecular sieve.

[0036] In some embodiments of the present invention, preferably, the hydrocracking catalyst further includes a non-supported active phase, alumina, and optionally amorphous silica-alumina. Through mixing, shaping, drying, and calcination, a non-supported hydrocracking catalyst is obtained.

[0037] Compared with the prior art, the molecular sieve synthesized in the present invention has the following beneficial effects: The hydrocracking catalyst prepared from the modified Y-type molecular sieve of the present invention has a higher conversion rate, which means that the molecular sieve synthesized by the present invention has higher performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The scanning electron micrograph of the modified Y1 molecular sieve in Example 1 of the present invention is shown.

[0039] Figure 2 The scanning electron micrograph of the Y molecular sieve before modification in Example 1 of the present invention is shown.

[0040] Figure 3 The scanning electron micrograph of the modified Y molecular sieve in Comparative Example 1 of the present invention is shown.

[0041] Figure 4 The ultraviolet spectrum of the washing solution of the arginine solution and the Y-A2 molecular sieve in Example 2 of the present invention is shown. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] In order to have a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below, but it should not be construed as a limitation on the scope of implementation of the present invention.

[0043] The Y-type molecular sieve used in the embodiments of the present invention is the HY molecular sieve produced by Nankai Catalyst Factory (SiO 2 、Al 2 O 3Molar ratio 10.7), hereinafter referred to as Y-type molecular sieve.

[0044] Example 1

[0045] Weigh 10 g of Y-type molecular sieve and add it to 100 g of deionized water, stir evenly, then add 1 g of 3-(formamidinothio)-1-propanesulfonic acid and 1 g of benzamidine hydrochloride, and carry out the first reaction at 20 °C for 3 h. Then, filter and wash the formed slurry, and dry it at 120 °C for 3 h to obtain modified Y-type molecular sieve A, denoted as Y-A1.

[0046] Weigh 9 g of Y-A1 and add it to 90 g of deionized water, stir evenly; then add 4 g of oxalic acid, adjust the pH < 1, and raise the temperature to 50 °C for reaction for 3 h. Then, filter and wash the slurry, dry it at 120 °C for 3 h, and calcine it at 550 °C to obtain modified Y-type molecular sieve, denoted as Y1 molecular sieve.

[0047] Characterize the molecular sieve before and after modification by scanning electron microscopy. The scanning electron micrographs of the modified Y1 and the unmodified Y molecular sieve are shown in Figure 1 and Figure 2 respectively. It can be clearly recognized that compared with the unmodified Y molecular sieve, a certain pit structure has been generated on the surface of the molecular sieve modified by the method of this example.

[0048] Example 2

[0049] Weigh 10 g of Y-type molecular sieve and add it to 80 g of deionized water, stir evenly, then add 1.5 g of arginine, and carry out the reaction at 25 °C for 2 h. Then, filter and wash the formed slurry, and dry it at 120 °C for 3 h to obtain modified Y-type molecular sieve A, denoted as Y-A2.

[0050] Characterize the ability of water-washed Y-A2 molecular sieve not to cause changes in its organic matter content by ultraviolet-visible spectroscopy. As shown in Figure 4 , there is an obvious ultraviolet-visible absorption spectrum when 1.5 g of arginine is dissolved in 80 g of water at the initial stage of preparation; add Y-A2 to 80 g of water, stir and then filter to take the water-washed solution, which does not have a significant ultraviolet-visible absorption spectrum (as shown in Figure 4 ), indicating that the modified organic matter has chemically reacted with the molecular sieve to form a stable organic matter-Y-type molecular sieve structure. Therefore, it can be used for subsequent modification treatment in an aqueous solution environment.

[0051] Weigh 9 g of Y-A2 and add it to 90 g of deionized water, stir evenly; then add 14.0 g of citric acid, and raise the temperature to 60 °C for reaction for 2 h. Then, filter and wash the slurry, dry it at 120 °C for 3 h, and calcine it at 550 °C to obtain modified Y-type molecular sieve, denoted as Y2 molecular sieve.

[0052] Example 3

[0053] Weigh 10 g of Y-type molecular sieve and add it to 50 g of deionized water. Stir evenly, then add 0.6 g of methionine and 0.6 g of acetamidine hydrochloride, and carry out the reaction at 35 °C for 1 h. Then filter and wash the formed slurry, and dry it at 120 °C for 3 h to obtain modified Y-type molecular sieve A, denoted as Y-A3.

[0054] Weigh 9 g of Y-A3 and add it to 90 g of deionized water. Stir evenly; then add 1.87 g of hydrochloric acid (concentration 36%), with pH < 1, and raise the temperature to 55 °C for reaction for 1 h. Then filter and wash the slurry, and dry it at 120 °C for 3 h, and calcine it at 550 °C to obtain modified Y-type molecular sieve, denoted as Y3 molecular sieve.

[0055] Example 4

[0056] Weigh 10 g of Y-type molecular sieve and add it to 100 g of deionized water. Stir evenly, then add 0.83 g of phenylalanine, and carry out the reaction at 45 °C for 2 h. Then filter and wash the formed slurry, and dry it at 120 °C for 3 h to obtain modified Y-type molecular sieve A, denoted as Y-A4.

[0057] Weigh 9 g of Y-A4 and add it to 90 g of deionized water. Stir evenly; then add 8.6 g of citric acid, with pH < 1, and raise the temperature to 45 °C for reaction for 4 h. Then filter and wash the slurry, and dry it at 120 °C for 3 h, and calcine it at 550 °C to obtain modified Y-type molecular sieve, denoted as Y4 molecular sieve.

[0058] Comparative Example 1

[0059] Weigh 9 g of Y-type molecular sieve and add it to 90 g of deionized water. Stir evenly, then add 14 g of citric acid, with pH < 1, and raise the temperature to 60 °C for constant temperature for 2 h. Then filter and wash the slurry, and dry it at 120 °C for 3 h, and calcine it at 550 °C to obtain modified D1 molecular sieve.

[0060] Use scanning electron microscopy to characterize the differences of the molecular sieves modified by the technical solutions of the present invention. The scanning electron micrographs of the modified Y1 and D1 molecular sieves are respectively as Figure 1 、 Figure 3 shown. It can be clearly identified from the figure that a certain pit structure has been generated on the surface of the molecular sieve Y1 modified by the method of this example. For the molecular sieve D1 not modified by this method, since the acidic solution can enter the micropores of the molecular sieve, it is impossible to achieve targeted etching of the acidic solution on the surface of the molecular sieve. Therefore, a modified molecular sieve with no characteristic morphology is formed.

[0061] Comparative Example 2

[0062] Weigh 9 g of Y-type molecular sieve and add it to 90 g of deionized water. Stir evenly, then add 1.87 g of hydrochloric acid (concentration 36%), with the pH < 1, and heat up to 55 °C for constant temperature. After reacting for 1 h, filter and wash the slurry, and dry it at 120 °C for 3 h, then calcine it at 550 °C to obtain the modified D2 molecular sieve.

[0063] Comparative Example 3

[0064] Weigh 10 g of Y-type molecular sieve and add it to 100 g of deionized water. Stir evenly, then add 2 g of glucose, and carry out the reaction at 20 °C for 2 h. Then filter and wash the formed slurry, and dry it at 120 °C for 3 h to obtain Y-D3 molecular sieve; conduct the same water washing test as in Example 2 on the Y-D3 obtained in the previous step. Take 10 mL of the filtrate after water washing and add 10 mL of 0.05 mol / L iodine standard solution, then slowly add 0.2 mol / L sodium hydroxide solution until the solution turns light yellow. Use pH test paper to detect and find that the solution is weakly acidic, indicating that the washing solution contains glucose. Therefore, a modified Y molecular sieve with stable adsorption cannot be obtained in this process.

[0065] The physical adsorption characterization results of Y, Y1, Y2, Y3, Y4, D1, and D2 molecular sieves are shown in Table 1. Among them, the total specific surface area is calculated by the BET method. In order to make the BET equation hold, select no less than 3 points in the p / p0 range of 0.01 - 0.30, and obtain the BET specific surface area under the condition that the C value satisfying the BET equation is greater than 0. The characterization of the mesoporous and microporous specific surface areas is based on the BET specific surface area and calculated by the t-Plot method.

[0066] As can be seen from the data in Table 1, the mesoporous specific surface areas of Y1, Y2, Y3, and Y4 molecular sieves have all increased to a certain extent compared with that of Y molecular sieve, indicating that the method of the present invention can achieve the directional regulation of the mesoporous channel structure of the molecular sieve and enhance the connectivity of the channel structure. The microporous specific surface areas of Y1, Y2, Y3, and Y4 molecular sieves have little difference compared with that of Y molecular sieve, but the microporous specific surface areas of D1 and D2 molecular sieves have decreased to a large extent, indicating that the adsorption of amino acid organic matter in the method of the present invention can protect the microporous structure of Y-type molecular sieve.

[0067] Table 1

[0068]

[0069] The relative crystallinity results of Y, Y1, Y2, Y3, Y4, D1, and D2 molecular sieves are shown in Table 2. It can be seen from the data in Table 2 that the relative crystallinity of Y1, Y2, Y3, and Y4 molecular sieves is higher than that of D1 and D2 molecular sieves. This shows that the method of the present invention can protect the structure of Y-type molecular sieves by adsorbing amino acid organic substances, reducing the loss of crystallinity caused by chemical modification.

[0070] Table 2

[0071] Name Relative crystallinity Y zeolite / Y1 zeolite 98％ Y2 zeolite 98％ Y3 zeolite 96％ Y4 zeolite 97％ D1 zeolite 87％ D2 zeolite 84％

[0072] Weigh 10 g of Y1, Y2, Y3, Y4, D1, and D2 molecular sieves respectively, mix them evenly with 60 g of alumina, 30 g of non-supported active phase, and 2 g of talc powder, and perform wet mixing with nitric acid aqueous solution. Then extrude them into pellets. After the formed products are dried at 120 °C for 4 h and calcined at 500 °C for 3 h, hydrocracking catalysts CAT-Y1, CAT-Y2, CAT-Y3, CAT-Y4, CAT-D1, and CAT-D2 are obtained respectively. Using the prepared catalysts with straight-run diesel as the raw material, under the conditions of 340 °C, 8.0 MPa, hydrogen-oil ratio of 800, and space velocity of 4.5 h -1 carry out the catalyst evaluation experiment, and the test results are shown in Table 3 below. Among them, the conversion rate is the mass fraction of the fraction product with a boiling point less than 180 °C in all products.

[0073] Table 3

[0074] Catalyst name Conversion rate CAT-Y1 38.5％ CAT-Y2 37.8％ CAT-Y3 36.9％ CAT-Y4 37.7％ CAT-D1 29.8％ CAT-D2 31.5％

[0075] It can be seen from the evaluation results of each catalyst in Table 3 that compared with the comparative technology, the hydrocracking catalysts prepared using the molecular sieves synthesized by the present invention have a higher conversion rate, indicating that the molecular sieves synthesized by the present invention have higher performance.

[0076] Of course, the present invention can also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes and deformations should all fall within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a modified Y-type molecular sieve, characterized in that, it includes: In a liquid phase system, a first reaction occurs between an organic substance and a Y-type molecular sieve to obtain a modified Y-type molecular sieve A; wherein, the organic substance has one or a combination of two or more of amidino, benzyl, and mercapto functional groups; In an acidic liquid phase system, a second reaction occurs for the modified Y-type molecular sieve A, and then a calcination treatment is carried out to obtain the modified Y-type molecular sieve; wherein, the mass ratio of the Y-type molecular sieve to the organic substance is 3 to 12.5:

1.

2. The preparation method according to claim 1, characterized in that, the mass ratio of the Y-type molecular sieve to the organic substance is 5 to 10:

1.

3. The preparation method according to claim 1, characterized in that, the temperature of the first reaction is 20 to 50 °C, and the time is 0.5 to 3 h.

4. The preparation method according to claim 1, characterized in that, after the first reaction ends, the preparation method further includes: performing solid-liquid separation, washing, and drying on the reaction product obtained from the first reaction to obtain the modified Y-type molecular sieve A.

5. The preparation method according to claim 1, characterized in that, the temperature of the second reaction is 35 to 60 °C, and the time is 0.5 to 4 h.

6. The preparation method according to claim 1, characterized in that, in the second reaction, the pH of the acidic liquid phase system is ≤1.

7. The preparation method according to claim 1, characterized in that, the organic substance is one or a combination of two or more of arginine, phenylalanine, methionine, ethylamidine hydrochloride, benzamidine hydrochloride, and 3-(amidinosulfanyl)-1-propanesulfonic acid.

8. The preparation method according to claim 1, characterized in that, the temperature of the calcination treatment is 470 to 560 °C, and the time is 3 to 6 h.

9. A modified Y-type molecular sieve obtained by the preparation method according to any one of claims 1 to 8.

10. A hydrocracking catalyst, characterized in that, its raw material contains the modified Y-type molecular sieve according to claim 9.

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