A catalyst and its preparation method for a liquid-phase xylene isomerization reaction, and a liquid-phase xylene isomerization method.

Abstract

This invention relates to a catalyst and its preparation method for a liquid-phase xylene isomerization reaction, as well as a liquid-phase xylene isomerization method. The catalyst comprises 10-80% hydrogen-form silica-alumina molecular sieves and 20-90% binder, based on the total mass of the catalyst. The hydrogen-form silica-alumina molecular sieves comprise the following components in the following proportions based on the total mass of the hydrogen-form silica-alumina molecular sieves: 10-80% Beta molecular sieve, 10-80% ZSM-5 molecular sieve, and 10-80% MCM-22 molecular sieve. In the catalyst for the liquid-phase xylene isomerization reaction of this invention, the active components are composed of Beta molecular sieve, ZSM-5 molecular sieve, and MCM-22 molecular sieve in a certain ratio. When alkyl aromatic hydrocarbons contact the catalyst to carry out the liquid-phase xylene isomerization reaction, the three molecular sieves synergistically enhance the effect, significantly improving the isomerization activity and xylene yield of p-xylene, and effectively increasing the production of p-xylene.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a catalyst and preparation method for a liquid-phase xylene isomerization reaction, and a liquid-phase xylene isomerization method. Background Technology

[0002] Para-xylene (PX) is an important chemical raw material, mainly used in the production of terephthalic acid, ethylene terephthalate, and butylene glycol ester. In addition, it can be used in coatings, dyes, pesticides, and pharmaceuticals. With the continuous development of these industries in my country, the demand for PX is growing rapidly. To meet market demand, the construction scale of aromatic hydrocarbon complexes, mainly producing PX, is constantly expanding. These complexes consist of C8 aromatic hydrocarbon isomerization, xylene distillation, and adsorption or crystallization separation technologies. Among them, the xylene isomerization unit technology for increasing PX production is a key means to convert ethylbenzene, m-xylene, and o-xylene into PX. Typically, aromatic hydrocarbon complexes use traditional methods such as crystallization or molecular sieve adsorption to separate pure para-xylene. A heptane removal tower and a xylene tower remove small amounts of light non-aromatic hydrocarbons, benzene, toluene, and C9+ heavy aromatic hydrocarbons, respectively. The remaining C8 aromatic hydrocarbon material can be used as isomerization feedstock. After passing through the xylene isomerization unit, the three xylene isomers in the C8 aromatics can reach or approach thermodynamic equilibrium composition, namely 52-54% by mass of m-xylene, 23-24% by mass of p-xylene, and 23-24% by mass of o-xylene, which are then recycled back to the separation unit for purification of p-xylene. However, ethylbenzene in the C8 aromatic feed requires higher isomerization temperatures and conditions such as hydrogenation to be converted into xylene or deethylated to produce benzene. In recent years, with the continuous advancement of combined processes, various methods have been developed to ensure that the mixed C8 aromatics in the isomerization feed are essentially free of ethylbenzene. This allows for the catalytic isomerization of o-xylene and m-xylene at lower temperatures and in the liquid phase under conditions of non-hydrogenation or relying solely on dissolved hydrogen to maintain catalyst stability, thereby significantly reducing energy and material consumption in PX production.

[0003] Taking into account the process design and power consumption of the device, selecting non-hydrogen-contaminated liquid phase conditions for the isomerization reaction unit is a technical solution with unique advantages.

[0004] CN114314607A discloses an MCM-22 molecular sieve and its preparation method, as well as a method for alkylation reaction of benzene catalyzed by molecular sieve. By controlling the order of addition of aluminum source and silicon-aluminum, NaMCM-22 molecular sieve raw powder with controllable crystal size and acidity is obtained, thereby realizing its large-scale production and further improving the effect of MCM-22 molecular sieve catalyzing the alkylation reaction of benzene.

[0005] CN109399660A discloses a hierarchical porous molecular sieve and a catalyst prepared from the molecular sieve, specifically a hierarchical porous Beta molecular sieve and its Ca-Ni type catalyst, as well as a preparation method. It provides a bifunctional template agent to meet the needs of preparing hierarchical porous molecular sieves, and further modifies it to prepare a catalyst for ethanol reforming to produce hydrogen.

[0006] The liquid-phase non-hydrogen-dependent xylene isomerization catalyst disclosed in patent US20170297977A1 ​​uses UZM-54 molecular sieve, preferably with a molecular sieve content of 70%, and alumina as the binder, without requiring a supported metal. Under non-hydrogen-dependent conditions, the xylene isomerization reaction can reach thermodynamic equilibrium.

[0007] US20110263918A1 describes a xylene isomerization process using HZSM-5 or MCM-49 as the acidic catalyst. Under conditions of below 295°C and pressure ensuring the reactants remain liquid, a xylene fraction with a near-equilibrium composition can be obtained. This process can operate continuously when the feed only requires ppm-level dissolved hydrogen. It can also be recycled with non-hydrogen-dependent feeds, but the catalyst needs periodic regeneration with low-ppm-level hydrogen.

[0008] The literature "A Study on Xylene Liquid-Phase Isomerization Catalysts" (Petrochemical Technology, Vol. 7, No. 3, 1978) investigated the performance of xylene liquid-phase isomerization reaction on the ZSM-5 catalyst, synthesized from water glass, aluminum sulfate, sulfuric acid, and ethylamine. Experimental results showed that the ZSM-5 zeolite catalyst exhibits high activity and selectivity for xylene liquid-phase isomerization and is suitable for mixed xylene feedstocks containing ethylbenzene.

[0009] In the aforementioned patents and literature, the xylene liquid-phase isomerization reaction exhibits high activity, but requires trace amounts of dissolved hydrogen to maintain catalyst stability. Furthermore, achieving high activity typically implies a decrease in reaction selectivity. Therefore, obtaining a xylene isomerization catalyst that simultaneously possesses high p-xylene isomerization activity and xylene yield, while minimizing energy consumption and reducing catalyst costs, is a pressing technical problem that needs to be solved. Summary of the Invention

[0010] This invention provides a catalyst and preparation method for a liquid-phase xylene isomerization reaction, as well as a liquid-phase xylene isomerization method, with the aim of better converting C8 aromatics into para-xylene and increasing the production of para-xylene.

[0011] In a first aspect, the present invention relates to a catalyst for a liquid-phase xylene isomerization reaction, the catalyst comprising 10-80% hydrogen-type silica-alumina molecular sieve and 20-90% binder, based on the total mass of the catalyst;

[0012] The hydrogen-form silica-alumina molecular sieve comprises the following components in the following proportions based on the total mass of the hydrogen-form silica-alumina molecular sieve:

[0013] Beta molecular sieve 10-80%

[0014] ZSM-5 molecular sieve 10-80%

[0015] MCM-22 molecular sieve content: 10-80%.

[0016] In a second aspect, the present invention relates to a liquid-phase xylene isomerization method, the liquid-phase xylene isomerization method comprising:

[0017] The alkyl aromatic hydrocarbon is brought into contact with the catalyst of the liquid-phase xylene isomerization reaction described in the first aspect under a reaction pressure that maintains a liquid state to carry out the isomerization reaction;

[0018] The alkyl aromatic hydrocarbons include m-xylene, o-xylene, ethylbenzene, and optionally p-xylene.

[0019] Thirdly, the present invention relates to a method for preparing a catalyst for the liquid-phase xylene isomerization reaction described in the first aspect, the method comprising the following steps:

[0020] (1) The first silicon source, the first aluminum source, the first template agent, the first inorganic base and water are subjected to first crystallization to obtain metal cation type Beta molecular sieve;

[0021] (2) The second silicon source, the second aluminum source, the second template agent, the second inorganic base and water are subjected to a second crystallization to obtain metal cation type ZSM-5 molecular sieve;

[0022] (3) The third silicon source, the third aluminum source, the third template agent, the third inorganic base and water are subjected to third crystallization to obtain metal cation type MCM-22 molecular sieve;

[0023] (4) Mix the metal cation type Beta molecular sieve, the metal cation type ZSM-5 molecular sieve and the metal cation type MCM-22 molecular sieve with the binder, add an inorganic acid solution to knead, and extrude to form strips to obtain strips;

[0024] The strip-shaped material is subjected to a first drying, pelletizing, and a first calcination to obtain granules.

[0025] The granular material is brought into contact with an ammonium salt solution for ion exchange, followed by washing, a second drying, and a second calcination to obtain the catalyst for the liquid-phase xylene isomerization reaction.

[0026] Beneficial effects:

[0027] In the catalyst for the liquid-phase xylene isomerization reaction of the present invention, the active components are composed of Beta molecular sieve, ZSM-5 molecular sieve and MCM-22 molecular sieve in a certain ratio. When alkyl aromatic hydrocarbons are in contact with the catalyst to carry out the liquid-phase xylene isomerization reaction, the three molecular sieves work synergistically to significantly improve the isomerization activity of p-xylene and the xylene yield, and can effectively increase the production of p-xylene. Attached Figure Description

[0028] Figure 1-1 The XRD diffraction patterns are those of Beta molecular sieve B-1 prepared in Example 1, Beta molecular sieve B-2 prepared in Example 2, and Beta molecular sieve B-3 prepared in Example 3.

[0029] Figure 1-2 The XRD diffraction patterns are those of ZSM-5 molecular sieve Z-1 prepared in Example 1, ZSM-5 molecular sieve Z-2 prepared in Example 2, and ZSM-5 molecular sieve Z-3 prepared in Example 3.

[0030] Figure 1-3 The XRD diffraction patterns are those of MCM-22 molecular sieve M-1 prepared in Example 1, MCM-22 molecular sieve M-2 prepared in Example 2, and MCM-22 molecular sieve M-3 prepared in Example 3.

[0031] Figure 2-1 These are SEM images of Beta molecular sieve B-1 prepared in Example 1;

[0032] Figure 2-2 These are SEM images of ZSM-5 molecular sieve Z-1 prepared in Example 1;

[0033] Figure 2-3 This is an SEM image of MCM-22 molecular sieve M-1 prepared in Example 1;

[0034] Figure 2-4 This is an SEM image of Beta molecular sieve B-2 prepared in Example 2;

[0035] Figure 2-5 This is an SEM image of ZSM-5 molecular sieve Z-2 prepared in Example 2;

[0036] Figure 2-6 These are SEM images of MCM-22 molecular sieve M-2 prepared in Example 2;

[0037] Figure 2-7 This is an SEM image of Beta molecular sieve B-3 prepared in Example 3;

[0038] Figure 2-8 This is an SEM image of ZSM-5 molecular sieve Z-3 prepared in Example 3;

[0039] Figure 2-9 This is an SEM image of MCM-22 molecular sieve M-3 prepared in Example 3. Detailed Implementation

[0040] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.

[0041] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0042] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0043] In a first aspect, the present invention relates to a catalyst for a liquid-phase xylene isomerization reaction, the catalyst comprising 10-80% hydrogen-type silica-alumina molecular sieve and 20-90% binder, based on the total mass of the catalyst;

[0044] The hydrogen-form silica-alumina molecular sieve comprises the following components in the following proportions based on the total mass of the hydrogen-form silica-alumina molecular sieve:

[0045] Beta molecular sieve 10-80%

[0046] ZSM-5 molecular sieve 10-80%

[0047] MCM-22 molecular sieve content: 10-80%.

[0048] It should be noted that in the catalyst of this invention, a mixture of Beta molecular sieve, ZSM-5 molecular sieve, and MCM-22 molecular sieve serves as the active component. The three molecular sieves are compounded according to the above-mentioned ratio, resulting in a catalyst with excellent catalytic activity during xylene isomerization, effectively increasing the production of para-xylene. This catalyst is used in liquid-phase xylene isomerization reactions. Compared to gas-phase xylene isomerization reactions, this catalyst does not contain precious metals, making it more cost-effective. It also exhibits excellent catalytic activity even in non-hydrogen-dependent conditions, achieving high isomerization activity and xylene yield while maintaining a lower reaction temperature and significantly reduced energy consumption.

[0049] In a more preferred embodiment, the mass percentage of Beta molecular sieve in the total mass of the hydrogen-form silica-alumina molecular sieve can be 13%-75%, specifically 14%, 20%, 30%, 45%, 58%, 60%, 72%, etc.; the mass percentage of ZSM-5 molecular sieve can be 13%-45%, specifically 14%, 14.5%, 20%, 30%, 40%, 43%, etc.; and the mass percentage of MCM-22 molecular sieve can be 13%-45%, specifically 14%, 14.5%, 20%, 30%, 40%, 43%, etc. In the catalyst for the liquid-phase xylene isomerization reaction, the mass percentage of hydrogen-form silica-alumina molecular sieve can be 60-80%, specifically 65%, 70%, 75%, etc., and the mass percentage of binder can be 20%-40%, specifically 25%, 30%, 35%, etc. In this preferred embodiment, the catalyst activity is further improved, and the isomerization activity and xylene yield can be further enhanced.

[0050] In one specific embodiment of the catalyst according to the present invention, the binder is alumina.

[0051] In a second aspect, the present invention relates to a liquid-phase xylene isomerization method, the liquid-phase xylene isomerization method comprising:

[0052] The alkyl aromatic hydrocarbon is brought into contact with the catalyst of the liquid-phase xylene isomerization reaction described in the first aspect of the present invention under a reaction pressure that maintains a liquid state to carry out the isomerization reaction;

[0053] The alkyl aromatic hydrocarbons include m-xylene, o-xylene, ethylbenzene, and optionally p-xylene.

[0054] It should be noted that maintaining the alkyl aromatic hydrocarbons in a liquid state under reaction pressure means adjusting the pressure of the reaction system under different temperatures or different alkyl aromatic hydrocarbon compositions to keep the alkyl aromatic hydrocarbons in a liquid state. Since the catalytic reaction is carried out under this liquid-state reaction pressure, the isomerization method of this invention is a liquid-phase xylene isomerization method. Optional p-xylene indicates that the alkyl aromatic hydrocarbons may or may not contain p-xylene, or may contain p-xylene in any proportion.

[0055] In the liquid-phase xylene isomerization method of the present invention, the alkyl aromatic hydrocarbon is brought into contact with the catalyst of the liquid-phase xylene isomerization reaction described in the first aspect of the present invention to carry out the isomerization reaction. The catalyst of the liquid-phase xylene isomerization reaction can effectively catalyze the isomerization of C8 aromatic hydrocarbons, and better convert m-xylene, o-xylene, etc. into para-xylene, which can effectively increase the production of para-xylene and maintain good selectivity.

[0056] According to a specific embodiment of the liquid-phase xylene isomerization method of the present invention, the conditions for the isomerization reaction include:

[0057] The reaction temperature was 240–310 °C, and the weight hourly space velocity was 1–10 h⁻¹. -1 .

[0058] It should be noted that by controlling the temperature and weight hourly space velocity of the isomerization reaction as described above, when the alkyl aromatic hydrocarbon is contacted with the catalyst of the liquid-phase xylene isomerization reaction to carry out the isomerization reaction, the catalyst can exhibit better catalytic activity, thereby further improving the isomerization activity and xylene yield.

[0059] Thirdly, the present invention also relates to a method for preparing the catalyst for the liquid-phase xylene isomerization reaction described in the first aspect, the method comprising the following steps:

[0060] (1) The first silicon source, the first aluminum source, the first template agent, the first inorganic base and water are subjected to first crystallization to obtain metal cation type Beta molecular sieve;

[0061] (2) The second silicon source, the second aluminum source, the second template agent, the second inorganic base and water are subjected to a second crystallization to obtain metal cation type ZSM-5 molecular sieve;

[0062] (3) The third silicon source, the third aluminum source, the third template agent, the third inorganic base and water are subjected to third crystallization to obtain metal cation type MCM-22 molecular sieve;

[0063] (4) Mix the metal cation type Beta molecular sieve, the metal cation type ZSM-5 molecular sieve and the metal cation type MCM-22 molecular sieve with the binder, add an inorganic acid solution to knead, and extrude to form strips to obtain strips;

[0064] The strip-shaped material is subjected to a first drying, pelletizing, and a first calcination to obtain granules.

[0065] The granular material is brought into contact with an ammonium salt solution for ion exchange, followed by washing, a second drying, and a second calcination to obtain the catalyst for the liquid-phase xylene isomerization reaction.

[0066] It should be noted that in steps (1) to (3), when sodium hydroxide is used as the inorganic base in the preparation of the three molecular sieves, the molecular sieves prepared are Na-type Beta molecular sieve, Na-type ZSM-5 molecular sieve, and Na-type MCM-22 molecular sieve, respectively. After preparing three sodium-type molecular sieves in steps (1) to (3), the three sodium-type molecular sieves can be washed, dried, and then the catalyst for the liquid-phase xylene isomerization reaction can be prepared by the molding and ion exchange steps in step (4). The drying temperature can be 100-140℃ and the time can be 8-24h. The three Na-type molecular sieves prepared in steps (1) to (3) are ion exchanged with ammonium salt solution in step (4) and calcined. The resulting finished catalyst has a hydrogen-type molecular sieve.

[0067] The preparation method of the present invention is based on the three molecular sieves prepared in steps (1) to (3) to prepare catalysts. It does not require loading (such as impregnation) of noble metals or activation and reduction steps. It can prepare a catalyst for the liquid phase xylene isomerization reaction that can exhibit good catalytic activity under non-hydrogen conditions. It has high isomerization activity and xylene yield. At the same time, it is cheaper, simplifies the catalyst preparation process, shortens the preparation cycle, and improves the catalyst preparation efficiency.

[0068] According to a specific embodiment of the preparation method described in the third aspect of the present invention, in step (1):

[0069] The molar ratio of the first silicon source (calculated as SiO2), the first aluminum source (calculated as Al2O3), the first template agent, the first inorganic alkali, and water is 1:(0.005–0.05):(0.05–1.5):(0.02–0.5):(10–60); and / or,

[0070] In step (2):

[0071] The molar ratio of the second silicon source (calculated as SiO2), the second aluminum source (calculated as Al2O3), the second template agent, the second inorganic alkali, and water is 1:(0.005~0.05):(0.05~1):(0.02~1):(10~60); and / or,

[0072] In step (3):

[0073] The molar ratio of the third silicon source (calculated as SiO2), the third aluminum source (calculated as Al2O3), the third template agent, the third inorganic alkali, and water is 1:(0.005~0.05):(0.2~1):(0.1~1):(20~60).

[0074] It should be noted that in the preparation method of the present invention, the molar ratios of silicon source, aluminum source, template agent, inorganic base and water in each step (1) to (3) are controlled as above. The prepared metal cationic type, such as sodium type Beta molecular sieve, ZSM-5 molecular sieve and MCM-22 molecular sieve, can be used in subsequent step (4) to prepare a catalyst with better catalytic activity for liquid phase xylene isomerization reaction. When used in liquid phase xylene isomerization reaction, it can simultaneously obtain high target product isomerization activity for xylene and high xylene yield.

[0075] According to another specific embodiment of the preparation method described in the third aspect of the present invention, in step (1), the molar ratio of the first silicon source (based on SiO2) to the first aluminum source (based on Al2O3), in step (2), the molar ratio of the second silicon source (based on SiO2) to the second aluminum source (based on Al2O3), and in step (3), the molar ratio of the third silicon source (based on SiO2) to the third aluminum source (based on Al2O3), are each independently (25-150):1; and / or,

[0076] In step (1), the molar ratio of the first template agent to the first silicon source (based on SiO2) is (0.08 to 1.4):1;

[0077] In step (2), the molar ratio of the second template agent to the second silicon source (based on SiO2) is (0.06–0.9):1;

[0078] In step (3), the molar ratio of the third template agent to the third silicon source (calculated as SiO2) is (0.3 to 0.9):1.

[0079] It should be noted that, as a preferred embodiment, by controlling the feeding ratio of the above materials in the three steps as described above, and then proceeding to step (4), a catalyst for the liquid-phase xylene isomerization reaction with further improved catalytic activity can be prepared. When the prepared catalyst is used in the liquid-phase xylene isomerization reaction, the catalytic activity is further improved.

[0080] According to a specific embodiment of the preparation method according to the third aspect of the present invention, the first silicon source in step (1), the second silicon source in step (2) and the third silicon source in step (3) are each independently selected from liquid silica sol and / or solid silica gel;

[0081] Wherein, the concentration of the liquid silica sol is 10-40% by mass, preferably 30-40% by mass; the particle size of the solid silica gel is 0.005μm-0.5mm, preferably 0.01μm-0.3mm; and / or,

[0082] In step (1), the first aluminum source is aluminum chloride; in step (2), the second aluminum source is aluminum nitrate; and in step (3), the third aluminum source is aluminum nitrate and / or aluminum chloride; and / or...

[0083] The first inorganic base in step (1), the second inorganic base in step (2), and the third inorganic base in step (3) are each independently selected from sodium hydroxide and / or potassium hydroxide.

[0084] It should be noted that in the preparation method of the present invention, in steps (1) to (3), if silicon source, aluminum source and inorganic base are controlled or selected as above, sodium-type or potassium-type Beta molecular sieve, ZSM-5 molecular sieve and MCM-22 molecular sieve with excellent stability and activity can be prepared. Then, in the subsequent step (4), a catalyst for the liquid phase xylene isomerization reaction with excellent performance can be prepared.

[0085] According to a specific embodiment of the preparation method described in the third aspect of the present invention, the first template agent in step (1) and the second template agent in step (2) are each independently selected from N(R)4. + X - ;

[0086] Wherein, N is a nitrogen atom, R is selected from alkyl groups having 1 to 4 carbon atoms, and X... - Selected from hydroxide ions and / or halide anions;

[0087] The halide anion is selected from chloride ions and / or bromide ions;

[0088] In step (1), R in the first template agent is preferably ethyl; and / or,

[0089] In step (2), R in the second template agent is preferably propyl; and / or,

[0090] The X of the first template agent in step (1) and the second template agent in step (2) - Preferably, hydroxide ions; and / or,

[0091] The third template agent mentioned in step (3) is selected from one or more combinations of hexamethyleneimine, piperidine and cyclohexylamine, preferably hexamethyleneimine.

[0092] It should be noted that the first template agent in step (1) and the second template agent in step (2) are each independently selected from the quaternary ammonium salts or quaternary ammonium bases mentioned above. Simultaneously, the third template agent in step (3) is controlled or selected as described above, thereby enabling the preparation of metal cation-type catalysts with superior stability and catalytic activity, such as sodium-type Beta molecular sieves, ZSM-5 molecular sieves, and MCM-22 molecular sieves. Continuing with the molding, ammonium ion exchange, and calcination steps in step (4), a catalyst for the liquid-phase xylene isomerization reaction with significantly improved isomerization activity can be prepared.

[0093] According to a specific embodiment of the preparation method described in the third aspect of the present invention, the conditions for the first crystallization in step (1) include:

[0094] The temperature is 120–180°C, preferably 135–175°C; the time is 60–140 hours, preferably 96–120 hours; and / or,

[0095] The crystallite size of the metal cation type Beta molecular sieve obtained from step (1) is 30–600 nm, preferably 50–300 nm; and / or,

[0096] The conditions for the second crystallization in step (2) include:

[0097] The temperature is 140–190°C, preferably 175–185°C; the time is 40–140 hours, preferably 96–120 hours; and / or,

[0098] The crystallite size of the metal cation-type ZSM-5 molecular sieve obtained from step (2) is 0.05–10 μm, preferably 0.6–5 μm; and / or,

[0099] The conditions for the third crystallization in step (3) include:

[0100] The temperature is 120–180°C, preferably 150–180°C; the time is 80–150 hours, preferably 96–150 hours; and / or,

[0101] The crystal size of the metal cation-type MCM-22 molecular sieve obtained from step (3) is 100–1000 nm, preferably 150–500 nm; and / or,

[0102] The pressures during crystallization in steps (1), (2), and (3) are the self-generated pressures, respectively.

[0103] It should be noted that, by controlling the crystallization conditions as described above in steps (1) to (3), the prepared metal cation type, such as sodium-type Beta molecular sieve, ZSM-5 molecular sieve, and MCM-22 molecular sieve, completed a good crystallization process. The prepared molecular sieves have high crystallinity and uniform and complete crystal morphology. Based on these three molecular sieves, after molding, ammonium ion exchange, and calcination in step (4), the three H-type molecular sieves in the prepared finished catalyst exhibit good catalytic activity in synergy. When used to catalyze the liquid-phase xylene isomerization of alkyl aromatics, they can better isomerize C8 aromatics such as m-xylene and o-xylene to p-xylene, and the isomerization activity and xylene yield of p-xylene are significantly improved.

[0104] It should be noted that during ion exchange in step (4), the ammonium salt solution can be ammonium chloride solution, etc. For example, the intermediate formed by the mixture of three sodium-type molecular sieves after molding with the binder can be placed in ammonium chloride solution for ion exchange, and then washed until the mother liquor is free of chloride ions; or the intermediate formed by the mixture of three sodium-type molecular sieves after molding with the binder can be washed with ammonium chloride solution until the washing liquid is neutral, with a pH range of 6-8. After the ion exchange is completed, it is dried at a temperature of 100-140℃ for 4-24 hours. Then, it is calcined in an air atmosphere at a temperature of 520℃-550℃ for 2-24 hours; calcination can be carried out in a static atmosphere without air flow, or at a volume hourly space velocity of 50-500 h⁻¹. -1 The process is carried out in a dynamic atmosphere. The calcined catalyst does not require metal impregnation or activation / reduction steps to obtain the catalyst product described in this invention.

[0105] The present invention will be further described in detail below through examples, but these examples are not intended to limit the invention. In the following examples, unless otherwise specified, the experimental instruments and raw materials involved are all commercially available products.

[0106] Example 1

[0107] Add 15g of silicon source (solid silica gel, particle size 150-250μm, pore size 6nm), 2.22g of aluminum source (aluminum chloride), and 4g of template agent N(C2H5) to a 200mL reactor. + OH - The molecular sieve consisted of 70.14 g of a 35% (w / w) aqueous solution, 1.33 g of NaOH, and 26.41 g of water. The molar ratio of the reactants was Al₂O₃:template:NaOH:H₂O:SiO₂ = 0.033:0.67:0.13:16:1. The synthesis temperature was 135℃, and the synthesis time was 115 hours. A homogeneous reactor dynamic synthesis method was used to synthesize the molecular sieve. The molecular sieve was washed and dried.

[0108] A Beta molecular sieve, designated B-1, was obtained with a silica-to-alumina ratio of 30 and an average grain size of 230 nm. The XRD pattern is attached. Figure 1-1 It can be seen that the synthesized molecular sieve is a pure phase sieve, which not only has high crystallinity and stable baseline, but also exhibits a series of characteristic peaks at 2θ of 7.6°, 13.2°, 14.6°, 21.2°, 22.4°, 25.2°, 26.8°, and 29.5°. These are characteristic diffraction peaks of Beta molecular sieve, corresponding to the characteristic peaks of the (330), (302), (304), (008), and (306) planes of Beta molecular sieve, respectively. No other impurity peaks are present in the XRD pattern, indicating that the synthesized Beta molecular sieve is a pure phase product. Its SEM characterization is shown in the appendix. Figure 2-1 .

[0109] Add 30g of silicon source (liquid silica sol, concentration 30% by mass), 3.75g of aluminum source (aluminum nitrate nonahydrate), and 4g of template agent N(C3H7) to a 200mL reactor. + OH - The molecular sieve consisted of 81.34 g of a 25% (w / w) aqueous solution, 0.8 g of NaOH, and 0.972 g of water. The molar ratio of the reactants was Al₂O₃:template:NaOH:H₂O:SiO₂ = 0.033:0.67:0.13:31.33:1. The synthesis temperature was 175℃, and the synthesis time was 120 hours. A homogeneous reactor dynamic synthesis method was used to synthesize the molecular sieve. The molecular sieve was washed and dried.

[0110] The obtained ZSM-5 molecular sieve, denoted as Z-1, has a silica-to-alumina ratio of 30 and an average grain size of 0.75 μm. The XRD diffraction pattern is attached. Figure 1-2 Strong diffraction peaks appeared at 2θ = 7.9°, 8.8°, 23.1°, and 23.3°, which are typical characteristic peaks of ZSM-5. These peaks represent the (011), (020), (332), and (051) crystal planes of H-type ZSM-5 molecular sieve, respectively, indicating that the catalyst has a typical MFI structure. Meanwhile, the XRD pattern showed a stable baseline with no impurity peaks, indicating that a well-crystallized ZSM-5 molecular sieve was synthesized. Its SEM characterization is shown in the appendix. Figure 2-2 .

[0111] In a 200 mL reactor, 22.5 g of silicon source (liquid silica sol, 40% by mass), 1.334 g of aluminum source (aluminum chloride), 5.009 g of template agent hexamethyleneimine (HMI) (99% by mass), 1.2 g of NaOH, and 58.450 g of water were added. The molar ratio of the added substances was Al₂O₃:template agent:NaOH:H₂O:SiO₂ = 0.033:0.333:0.2:26.67:1. The molecular sieve was synthesized using a dynamic synthesis method at 155℃ for 100 hours. The molecular sieve was then washed and dried.

[0112] The obtained MCM-22 molecular sieve, denoted as M-1, has a silica-to-alumina ratio of 30 and an average grain size of 180 nm. The XRD diffraction pattern is attached. Figure 1-3 Typical characteristic diffraction peaks of MCM-22 were observed at 2θ = 7.1°, 7.2°, 8.1°, 10.0°, 14.2°, 26.1°, and 28.1°. Simultaneously, the XRD pattern showed a stable baseline and no extraneous peaks, indicating the synthesis of well-crystallized MCM-22 molecular sieve. Its SEM characterization is shown in the appendix. Figure 2-3 .

[0113] Beta molecular sieves B-1, ZSM-5 molecular sieve Z-1, and MCM-22 molecular sieve M-1 were thoroughly mixed with alumina at a mass ratio of 5:1:1:3. A 5% (w / w) aqueous nitric acid solution was added and kneaded until homogeneous (the nitric acid solution accounted for 35% of the mass of the solid mixture). The mixture was then extruded into strips. The strips were dried at 120°C for 6 hours, then granulated and calcined at 540°C for 4 hours. The calcined sample was subjected to ion exchange with a 5% (w / w) ammonium chloride aqueous solution at 90°C for 2 hours, washed until no chloride ions were present in the mother liquor, dried at 120°C for 6 hours, and calcined at 540°C for 4 hours to obtain catalyst C-1.

[0114] Example 2

[0115] Add 15g of silicon source (solid silica gel, particle size 150-250μm, pore size 6nm), 1.11g of aluminum source (aluminum chloride), and 4g of template agent N(C2H5) to a 200mL reactor. + OH - The molecular sieve consisted of 52.61 g of a 35% (w / w) aqueous solution, 0.5 g of NaOH, and 46.81 g of water. The molar ratio of the additives was Al₂O₃:template:NaOH:H₂O:SiO₂ = 0.017:0.5:0.05:18:1. The synthesis temperature was 140℃, and the synthesis time was 115 hours. A homogeneous reactor dynamic synthesis method was used to synthesize the molecular sieve. The molecular sieve was washed and dried.

[0116] The obtained Beta molecular sieve, designated B-2, has a silica-to-alumina ratio of 60 and an average grain size of 180 nm. The XRD diffraction pattern is attached. Figure 1-1 It can be seen that the synthesized molecular sieve is a pure phase sieve, which not only has high crystallinity and stable baseline, but also exhibits a series of characteristic peaks at 2θ of 7.6°, 13.2°, 14.6°, 21.2°, 22.4°, 25.2°, 26.8°, and 29.5°. These are characteristic diffraction peaks of Beta molecular sieve, corresponding to the characteristic peaks of the (330), (302), (304), (008), and (306) planes of Beta molecular sieve, respectively. No other impurity peaks are present in the XRD pattern, indicating that the synthesized Beta molecular sieve is a pure phase product. Its SEM characterization is shown in the appendix. Figure 2-4 .

[0117] Add 30g of silicon source (liquid silica sol, concentration 30% by mass), 1.88g of aluminum source (aluminum nitrate nonahydrate), and N(C3H7)4 to a 200mL reactor. + OH - 61g (25% by mass aqueous solution), 0.6g NaOH, and 0.834g water were added. The molar ratio of the added substances was Al2O3:template:NaOH:H2O:SiO2 = 0.017:0.5:0.1:25.33:1. The synthesis temperature was 180℃, and the synthesis time was 96 hours. The molecular sieve was synthesized using a homogeneous reactor dynamic synthesis method. The molecular sieve was washed and dried.

[0118] The obtained ZSM-5 molecular sieve, designated Z-2, has a silica-to-alumina ratio of 60 and an average grain size of 0.8 μm. The XRD diffraction pattern is attached. Figure 1-2 Strong diffraction peaks appeared at 2θ = 7.9°, 8.8°, 23.1°, and 23.3°, which are typical characteristic peaks of ZSM-5. These peaks represent the (011), (020), (332), and (051) crystal planes of H-type ZSM-5 molecular sieve, respectively, indicating that the catalyst has a typical MFI structure. Meanwhile, the XRD pattern showed a stable baseline with no impurity peaks, indicating that a well-crystallized ZSM-5 molecular sieve was synthesized. Its SEM characterization is shown in the appendix. Figure 2-5 .

[0119] 30 g of silicon source (liquid silica sol, concentration 30% by mass), 0.667 g of aluminum source (aluminum chloride), 6.01 g of hexamethyleneimine (HMI), 1.2 g of NaOH, and 59.940 g of water were added to a 200 mL reactor. The molar ratio of the added substances was Al2O3:template:NaOH:H2O:SiO2 = 0.0167:0.4:0.2:30:1. The molecular sieve was synthesized using a dynamic synthesis method at 160℃ for 110 hours. The molecular sieve was then washed and dried.

[0120] The obtained MCM-22 molecular sieve, denoted as M-2, has a silica-to-alumina ratio of 60 and an average grain size of 220 nm. The XRD diffraction pattern is attached. Figure 1-3 Typical characteristic diffraction peaks of MCM-22 were observed at 2θ = 7.1°, 7.2°, 8.1°, 10.0°, 14.2°, 26.1°, and 28.1°. Simultaneously, the XRD pattern showed a stable baseline and no extraneous peaks, indicating the synthesis of well-crystallized MCM-22 molecular sieve. Its SEM characterization is shown in the appendix. Figure 2-6 .

[0121] Beta molecular sieve B-2, ZSM-5 molecular sieve Z-2, MCM-22 molecular sieve M-2, and alumina were thoroughly mixed at a mass ratio of 4:2:1:3. Catalyst C-2 was then obtained according to the catalyst preparation method described in Example 1.

[0122] Example 3

[0123] Add 15g of silicon source (solid silica gel, particle size 150-250μm, pore size 6nm), 0.833g of aluminum source (aluminum chloride), and 4g of template agent N(C2H5) to a 200mL reactor. + OH - The molecular sieve consisted of 39.46 g of a 35% (w / w) aqueous solution, 0.375 g of NaOH, and 41.85 g of water. The molar ratio of the additives was Al₂O₃:template:NaOH:H₂O:SiO₂ = 0.0125:0.375:0.0375:15:1. The synthesis temperature was 155℃, and the synthesis time was 105 hours. A homogeneous reactor dynamic synthesis method was used to synthesize the molecular sieve. The molecular sieve was washed and dried.

[0124] The obtained Beta molecular sieve, designated B-3, has a silica-to-alumina ratio of 80 and an average grain size of 260 nm. The XRD diffraction pattern is attached. Figure 1-1 It can be seen that the synthesized molecular sieve is a pure phase sieve, which not only has high crystallinity and stable baseline, but also exhibits a series of characteristic peaks at 2θ of 7.6°, 13.2°, 14.6°, 21.2°, 22.4°, 25.2°, 26.8°, and 29.5°. These are characteristic diffraction peaks of Beta molecular sieve, corresponding to the characteristic peaks of the (330), (302), (304), (008), and (306) planes of Beta molecular sieve, respectively. No other impurity peaks are present in the XRD pattern, indicating that the synthesized Beta molecular sieve is a pure phase product. Its SEM characterization is shown in the appendix. Figure 2-7 .

[0125] Add 22.5 g of silicon source (liquid silica sol, concentration 40% by mass), 1.406 g of aluminum source (aluminum nitrate nonahydrate), and 4 g of template agent N(C3H7) to a 200 mL reactor. +OH - The molecular sieve consisted of 30.504 g of a 25% (w / w) aqueous solution, 0.45 g of NaOH, and 0.814 g of water. The molar ratio of the reactants was Al₂O₃:template:NaOH:H₂O:SiO₂ = 0.0125:0.25:0.075:14:1. The synthesis temperature was 180℃, and the synthesis time was 100 hours. A homogeneous reactor dynamic synthesis method was used to synthesize the molecular sieve. The molecular sieve was washed and dried.

[0126] The obtained ZSM-5 molecular sieve, designated Z-3, has a silica-to-alumina ratio of 80 and an average grain size of 1.0 μm. The XRD diffraction pattern is attached. Figure 1-2 Strong diffraction peaks appeared at 2θ = 7.9°, 8.8°, 23.1°, and 23.3°, which are typical characteristic peaks of ZSM-5. These peaks represent the (011), (020), (332), and (051) crystal planes of H-type ZSM-5 molecular sieve, respectively, indicating that the catalyst has a typical MFI structure. Meanwhile, the XRD pattern showed a stable baseline with no impurity peaks, indicating that a well-crystallized ZSM-5 molecular sieve was synthesized. Its SEM characterization is shown in the appendix. Figure 2-8 .

[0127] 15g of silicon source (solid silica gel, particle size 150-250μm, pore size 6nm), 2.345g of aluminum source (aluminum nitrate nonahydrate), 12.521g of template agent hexamethyleneimine (HMI), 3.75g of NaOH, and 111.362g of water were added to a 200mL reactor. The molar ratio of the added substances was Al2O3:template agent:NaOH:H2O:SiO2 = 0.0125:0.5:0.375:25:1. The molecular sieve was synthesized using a dynamic synthesis method at 150℃ for 110 hours. The molecular sieve was then washed and dried.

[0128] The obtained MCM-22 molecular sieve, designated M-3, has a silica-to-alumina ratio of 80 and an average grain size of 350 nm. The XRD diffraction pattern is attached. Figure 1-3 Typical characteristic diffraction peaks of MCM-22 were observed at 2θ = 7.1°, 7.2°, 8.1°, 10.0°, 14.2°, 26.1°, and 28.1°. Simultaneously, the XRD pattern showed a stable baseline and no extraneous peaks, indicating the synthesis of well-crystallized MCM-22 molecular sieve. Its SEM characterization is shown in the appendix. Figure 2-9 .

[0129] Beta molecular sieve B-3, ZSM-5 molecular sieve Z-3, MCM-22 molecular sieve M-3, and alumina were thoroughly mixed at a mass ratio of 3:2:2:3. Catalyst C-3 was then obtained according to the catalyst preparation method described in Example 1.

[0130] Example 4

[0131] Catalyst C-4 was obtained according to the catalyst preparation method in Example 1, except that the mass ratio of Beta molecular sieve B-1, ZSM-5 molecular sieve Z-1, MCM-22 molecular sieve M-1 to alumina was 3:1:3:3.

[0132] Example 5

[0133] Catalyst C-5 was obtained according to the catalyst preparation method in Example 2, except that the mass ratio of Beta molecular sieve B-2, ZSM-5 molecular sieve Z-2, MCM-22 molecular sieve M-2 to alumina was 2:3:2:3.

[0134] Example 6

[0135] Catalyst C-6 was obtained according to the catalyst preparation method in Example 3, except that the mass ratio of Beta molecular sieve B-3, ZSM-5 molecular sieve Z-3, MCM-22 molecular sieve M-3 to alumina was 1:3:3:3.

[0136] Comparative Example 1

[0137] Catalyst D-1 was obtained according to the catalyst preparation method in Example 1, except that ZSM-5 molecular sieve and MCM-22 molecular sieve were not added to the catalyst, and the mass ratio of Beta molecular sieve B-1 to alumina was 7:3.

[0138] Comparative Example 2

[0139] Catalyst D-2 was obtained according to the catalyst preparation method in Example 1, except that Beta molecular sieve and MCM-22 molecular sieve were not added to the catalyst, and the mass ratio of ZSM-5 molecular sieve Z-1 to alumina was 7:3.

[0140] Comparative Example 3

[0141] Catalyst D-3 was obtained according to the catalyst preparation method in Example 1, except that Beta molecular sieve and ZSM-5 molecular sieve were not added to the catalyst, and the mass ratio of MCM-22 molecular sieve M-1 to alumina was 7:3.

[0142] Comparative Example 4

[0143] Catalyst D-4 was obtained according to the catalyst preparation method in Example 3, except that Beta molecular sieve was not added to the catalyst, and the mass ratio of ZSM-5 molecular sieve Z-3, MCM-22 molecular sieve M-3 to alumina was 3:4:3.

[0144] Comparative Example 5

[0145] Catalyst D-5 was obtained according to the catalyst preparation method in Example 3, except that ZSM-5 molecular sieve was not added to the catalyst, and the mass ratio of Beta molecular sieve B-3, MCM-22 molecular sieve M-3 to alumina was 2:5:3.

[0146] Comparative Example 6

[0147] Catalyst D-6 was obtained according to the catalyst preparation method in Example 3, except that MCM-22 molecular sieve was not added to the catalyst, and the mass ratio of Beta molecular sieve B-3, ZSM-5 molecular sieve Z-3 to alumina was 1:6:3.

[0148] Test Implementation Examples

[0149] In a small, continuously flowing fixed-bed apparatus, 3 grams of catalyst were loaded, and the catalyst performance was evaluated using feedstocks with the compositions described in Table 1. The evaluation conditions were: 250°C, 2 MPa, and a feed mass hourly space velocity (WHSV) of 2 h⁻¹. -1 The alkyl aromatic hydrocarbon feedstocks in Table 1 are brought into contact with the catalyst in a liquid state to undergo an isomerization reaction.

[0150] The catalysts used in each embodiment and comparative example and the reaction results are shown in Tables 2 and 3.

[0151] The catalyst performance was evaluated using the following calculation method:

[0152] Isomerization activity indicators:

[0153] Xylene yield:

[0154] Table 1 Raw Material Composition

[0155] <![CDATA[C8NA]]> B T EB PX MX OX <![CDATA[C9 + ]]> 0.355 0.000 0.000 4.760 0.085 65.194 29.531 0.000

[0156] Table 2 Catalysts and Reaction Performance in Examples

[0157]

[0158] Table 3 Comparative examples and their reaction performance

[0159]

[0160] As shown in Tables 2 and 3, the catalysts prepared by the methods of Examples 1-6 of this invention have higher isomerization activity (PX / ∑X) and higher xylene yield than the catalysts of Comparative Examples 1-6. This indicates that the method of this invention, which combines three molecular sieves in a certain proportion as the active component of the catalyst, has better isomerization activity and selectivity than using only one or two molecular sieves as the active component of the catalyst.

[0161] In addition, through the long-term research and development process of the inventors of this application, it was found that the above three molecular sieves were prepared according to the methods of steps (1) to (3) of this application, and various conditions were controlled. The three molecular sieves were prepared in a certain ratio relationship. According to step (4) and various conditions were controlled, the catalyst was obtained. It can have good catalytic activity when used for liquid phase xylene isomerization. The isomerization activity of the target product on xylene (PX / ∑X) and the xylene yield were significantly improved at the same time.

[0162] In the description of this application, it should be noted that the terms "upper", "lower", "inner", "outer", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship in the working state of this application. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0163] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0164] The present application has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.

Claims

1. A catalyst for a liquid-phase xylene isomerization reaction, characterized in that, The catalyst comprises 10-80% hydrogen-type silica-alumina molecular sieve and 20-90% binder, based on the total mass of the catalyst; The hydrogen-form silica-alumina molecular sieve comprises the following components in the following proportions based on the total mass of the hydrogen-form silica-alumina molecular sieve: Beta molecular sieve 10-80% ZSM-5 molecular sieve 10~80% MCM-22 molecular sieve content: 10-80%; The method for preparing the catalyst includes the following steps: (1) The first silicon source, the first aluminum source, the first template agent, the first inorganic base and water are subjected to first crystallization to obtain metal cation type Beta molecular sieve; (2) The second silicon source, the second aluminum source, the second template agent, the second inorganic base and water are subjected to a second crystallization to obtain metal cation type ZSM-5 molecular sieve; (3) The third silicon source, the third aluminum source, the third template agent, the third inorganic base and water are subjected to third crystallization to obtain metal cation type MCM-22 molecular sieve; (4) Mix the metal cationic Beta molecular sieve, the metal cationic ZSM-5 molecular sieve and the metal cationic MCM-22 molecular sieve with the binder, add an inorganic acid solution to knead, and extrude to form strips to obtain strips; The strip-shaped material is subjected to a first drying, pelletizing, and a first calcination to obtain granules. The granular material is contacted with an ammonium salt solution for ion exchange, washed, dried a second time, and then calcined a second time to obtain the catalyst for the liquid-phase xylene isomerization reaction. The conditions for the first crystallization in step (1) include: a temperature of 120~180℃ and a time of 60~140 hours; The conditions for the second crystallization in step (2) include: a temperature of 140~190℃ and a time of 40~140 hours; The conditions for the third crystallization in step (3) include: a temperature of 120~180℃ and a time of 80~150 hours.

2. The catalyst according to claim 1, characterized in that, The adhesive is aluminum oxide.

3. A liquid-phase xylene isomerization method, characterized in that, The liquid-phase xylene isomerization method includes: The alkyl aromatic hydrocarbon is brought into contact with the catalyst of the liquid-phase xylene isomerization reaction as described in claim 1 or 2 under a reaction pressure that maintains a liquid state to carry out the isomerization reaction; The alkyl aromatic hydrocarbons include m-xylene, o-xylene, ethylbenzene, and optionally p-xylene.

4. The liquid-phase xylene isomerization method according to claim 3, characterized in that, The conditions for the isomerization reaction include: The reaction temperature is 240~310℃, and the weight hourly space velocity is 1~10h. -1 .

5. A method for preparing the catalyst for the liquid-phase xylene isomerization reaction according to claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) The first silicon source, the first aluminum source, the first template agent, the first inorganic base and water are subjected to first crystallization to obtain metal cation type Beta molecular sieve; (2) The second silicon source, the second aluminum source, the second template agent, the second inorganic base and water are subjected to a second crystallization to obtain metal cation type ZSM-5 molecular sieve; (3) The third silicon source, the third aluminum source, the third template agent, the third inorganic base and water are subjected to third crystallization to obtain metal cation type MCM-22 molecular sieve; (4) Mix the metal cationic Beta molecular sieve, the metal cationic ZSM-5 molecular sieve and the metal cationic MCM-22 molecular sieve with the binder, add an inorganic acid solution to knead, and extrude to form strips to obtain strips; The strip-shaped material is subjected to a first drying, pelletizing, and a first calcination to obtain granules. The granular material is contacted with an ammonium salt solution for ion exchange, washed, dried a second time, and then calcined a second time to obtain the catalyst for the liquid-phase xylene isomerization reaction. The conditions for the first crystallization in step (1) include: a temperature of 120~180℃ and a time of 60~140 hours; The conditions for the second crystallization in step (2) include: a temperature of 140~190℃ and a time of 40~140 hours; The conditions for the third crystallization in step (3) include: a temperature of 120~180℃ and a time of 80~150 hours.

6. The preparation method according to claim 5, characterized in that, In step (1): The molar ratio of the first silicon source (calculated as SiO2), the first aluminum source (calculated as Al2O3), the first template agent, the first inorganic alkali, and water is 1:(0.005~0.05):(0.05~1.5):(0.02~0.5):(10~60); and / or, In step (2): The molar ratio of the second silicon source (calculated as SiO2), the second aluminum source (calculated as Al2O3), the second template agent, the second inorganic alkali, and water is 1:(0.005~0.05):(0.05~1):(0.02~1):(10~60); and / or, In step (3): The molar ratio of the third silicon source (calculated as SiO2), the third aluminum source (calculated as Al2O3), the third template agent, the third inorganic alkali, and water is 1:(0.005~0.05):(0.2~1):(0.1~1):(20~60).

7. The preparation method according to claim 5, characterized in that, In step (1), the molar ratio of the first silicon source (based on SiO2) to the first aluminum source (based on Al2O3), in step (2), the molar ratio of the second silicon source (based on SiO2) to the second aluminum source (based on Al2O3), and in step (3), the molar ratio of the third silicon source (based on SiO2) to the third aluminum source (based on Al2O3) are each independently (25~150):1; and / or, In step (1), the molar ratio of the first template agent to the first silicon source (based on SiO2) is (0.08~1.4):1; In step (2), the molar ratio of the second template agent to the second silicon source (based on SiO2) is (0.06~0.9):1; In step (3), the molar ratio of the third template agent to the third silicon source (calculated as SiO2) is (0.3~0.9):

1.

8. The preparation method according to claim 5, characterized in that, The first silicon source in step (1), the second silicon source in step (2), and the third silicon source in step (3) are each independently selected from liquid silica sol and / or solid silica gel; Wherein, the concentration of the liquid silica sol is 10-40% by mass; the particle size of the solid silica gel is 0.005μm-0.5mm; and / or, In step (1), the first aluminum source is aluminum chloride; in step (2), the second aluminum source is aluminum nitrate; and in step (3), the third aluminum source is aluminum nitrate and / or aluminum chloride; and / or, The first inorganic base in step (1), the second inorganic base in step (2), and the third inorganic base in step (3) are each independently selected from sodium hydroxide and / or potassium hydroxide.

9. The preparation method according to claim 8, characterized in that, The concentration of the liquid silica sol is 30-40% by mass, and the particle size of the solid silica gel is 0.01μm-0.3mm.

10. The preparation method according to claim 5, characterized in that, The first template agent in step (1) and the second template agent in step (2) are each independently selected from N(R)4. + X - ; Wherein, N is a nitrogen atom, R is selected from alkyl groups having 1 to 4 carbon atoms, and X... - Selected from hydroxide ions and / or halide anions; The halide anion is selected from chloride ions and / or bromide ions; The third template agent mentioned in step (3) is selected from one or more combinations of hexamethyleneimine, piperidine and cyclohexylamine.

11. The preparation method according to claim 10, characterized in that, In step (1), R in the first template agent is ethyl; In step (2), the R of the second template agent is propyl; The X of the first template agent in step (1) and the second template agent in step (2) - It is a hydroxide ion; and / or, The third template agent mentioned in step (3) is hexamethyleneimine.

12. The preparation method according to claim 5, characterized in that, The conditions for the first crystallization in step (1) include: Temperature 135~175℃; time 96~120 hours; and / or, The crystallite size of the metal cation type Beta molecular sieve obtained from step (1) is 30~600 nm; and / or, The conditions for the second crystallization in step (2) include: Temperature 175~185℃; time 96~120 hours; and / or, The crystallite size of the metal cation-type ZSM-5 molecular sieve obtained from step (2) is 0.05~10 μm; and / or, The conditions for the third crystallization in step (3) include: Temperature 150~180℃; time 96~150 hours; and / or, The crystallite size of the metal cation-type MCM-22 molecular sieve obtained from step (3) is 100~1000 nm; and / or, The pressures during crystallization in steps (1), (2), and (3) are the self-generated pressures, respectively.

13. The preparation method according to claim 12, characterized in that, The crystal size of the metal cation type Beta molecular sieve obtained from step (1) is 50~300 nm; The crystallite size of the metal cation-type ZSM-5 molecular sieve obtained from step (2) is 0.6~5 μm; and / or, The crystal size of the metal cation type MCM-22 molecular sieve obtained from step (3) is 150~500nm.

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