Liquid-phase xylene isomerization method, catalyst for liquid-phase non-hydroxylene isomerization reaction and preparation method

Abstract

The invention relates to a liquid-phase xylene isomerization method, a catalyst for a liquid-phase non-hydroxylene isomerization reaction and a preparation method, and the liquid-phase xylene isomerization method comprises the following steps: enabling alkyl aromatic hydrocarbon to be in contact with the catalyst for the liquid-phase non-hydroxylene isomerization reaction to carry out isomerization reaction under the reaction pressure of keeping the liquid state, the catalyst comprises 10-80% of a hydrogen-type silicon-aluminum molecular sieve and 20-90% of a binder based on the total mass of the catalyst, the hydrogen type silicon-aluminum molecular sieve comprises the following components in percentage by total mass of the hydrogen type silicon-aluminum molecular sieve: 10-80% of a Beta molecular sieve, 10-80% of a ZSM-5 molecular sieve and 10-80% of a ZSM-12 molecular sieve. According to the liquid-phase xylene isomerization method, the active components of the catalyst are prepared by compounding the Beta molecular sieve, the ZSM-5 molecular sieve and the ZSM-12 molecular sieve according to a certain proportion, precious metal loading and activation reduction are not needed, and the activity of the catalyst is greatly improved through synergistic interaction of the three molecular sieves.

Description

Technical Field

[0001] The invention relates to the field of xylene isomerization, and in particular to a liquid phase xylene isomerization method, a catalyst for liquid phase non-hydrogen xylene isomerization reaction and a preparation method thereof. Background Art

[0002] Paraxylene (PX) is an important chemical raw material, mainly used to produce terephthalic acid, ethylene glycol terephthalate, butanediol esters and other products. In addition, it can also be used in coatings, dyes, pesticides and medicines. With the continuous development of these industries in my country, the demand for PX has grown rapidly. In order to meet market needs, the construction scale of aromatics complex units mainly producing PX, which consists of technical units including C8 aromatics isomerization, xylene distillation and adsorption or crystallization separation, has been continuously expanded. Among them, the xylene isomerization unit technology for increasing the production of PX is the key means to convert ethylbenzene, meta-xylene and o-xylene into PX. Under normal circumstances, the aromatics complex uses traditional crystallization or molecular sieve adsorption to separate pure para-xylene, and the deheptane tower and the xylene tower remove a small amount of light non-aromatics, benzene, toluene and C9+ heavy aromatics respectively. The remaining C8 aromatic materials can be used as isomerization raw materials. After the xylene isomerization unit, the three xylene isomers in the C8 aromatics can reach or approach the thermodynamic equilibrium composition, namely 52-54% by mass of meta-xylene, 23-24% by mass of para-xylene and 23-24% by mass of ortho-xylene, and are recycled back to the separation unit to purify para-xylene. However, ethylbenzene in the C8 aromatics material requires a higher isomerization temperature and conditions such as hydrogenation to be converted into xylene or deethylated to generate benzene. In recent years, with the continuous advancement of combined processes, there are a variety of means to make the mixed C8 aromatics of the isomerization feed substantially free of ethylbenzene, so that it is possible to catalyze the isomerization of ortho-xylene and meta-xylene at a lower temperature and in a liquid phase without hydrogenation or relying only on dissolved hydrogen to maintain the stability of the catalyst, thereby greatly reducing the energy consumption and material consumption of PX production.

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

[0004] CN108423688A discloses a method for synthesizing a ZSM-12 molecular sieve, which can be used for acid-catalyzed reactions such as methane aromatization, methanol conversion, alkane dehydrogenation to olefins, olefin disproportionation, xylene isomerization, and toluene alkylation.

[0005] In patent US20170297977A1, the molecular sieve used in the liquid phase non-hydrogenated xylene isomerization catalyst is UZM-54, preferably 70% molecular sieve content, and the binder is alumina, and no metal loading is required. Under non-hydrogenated conditions, the xylene isomerization reaction can reach thermodynamic equilibrium.

[0006] US20110263918 A1 introduces a xylene isomerization process, which uses HZSM-5 or MCM-49 as a catalyst for the acidic component. Under the conditions of a temperature below 295°C and a pressure that ensures that the reactants are liquid, a xylene component with a composition close to equilibrium can be obtained. The process can be operated continuously when the feed only contains ppm-level dissolved hydrogen. It can also be cyclically applied to non-hydrogen-containing feeds, but the catalyst needs to be periodically regenerated with low-ppm-level hydrogen.

[0007] The document "Study on the Catalyst for Liquid-Phase Isomerization of Xylene" (Petrochemical Industry, Vol. 7, No. 3, 1978) studied the performance of liquid-phase isomerization of xylene on a ZSM-5 catalyst synthesized from water glass, aluminum sulfate, sulfuric acid and ethylamine. The experimental results showed that the ZSM-5 zeolite catalyst has high activity and selectivity for liquid-phase isomerization of xylene and is applicable to mixed xylene feedstocks containing ethylbenzene.

[0008] In the above patents and documents, the liquid phase xylene isomerization reaction has high activity, but requires a trace amount of dissolved hydrogen to maintain catalyst stability, and at the same time as achieving high activity, it usually means a decrease in reaction selectivity. How to carry out the liquid phase xylene isomerization reaction under the conditions of reducing energy consumption and catalyst cost, and what kind of xylene isomerization catalyst to use in the reaction to have both high isomerization activity of p-xylene and xylene yield are technical problems that need to be solved urgently. Summary of the invention

[0009] The present invention provides a liquid phase xylene isomerization method, a catalyst for liquid phase non-hydrogen xylene isomerization reaction and a preparation method, the purpose of which is to enable alkyl aromatics to be better converted into p-xylene under a reaction pressure that keeps the alkyl aromatics in a liquid state, thereby increasing the production of p-xylene.

[0010] In a first aspect, the present invention relates to a liquid phase xylene isomerization method, the liquid phase xylene isomerization method comprising:

[0011] The alkyl aromatic hydrocarbon is brought into contact with a catalyst for a liquid-phase non-hydrogenated xylene isomerization reaction under a reaction pressure that maintains the liquid state to carry out an isomerization reaction;

[0012] Wherein, the alkyl aromatic hydrocarbons include m-xylene, o-xylene, ethylbenzene and optionally p-xylene; the catalyst includes 10-80% hydrogen-type silica-alumina molecular sieve and 20-90% binder, based on the total mass of the catalyst;

[0013] The hydrogen-type silicon-aluminum molecular sieve includes the following components in proportion based on the total mass of the hydrogen-type silicon-aluminum molecular sieve:

[0014] Beta molecular sieve 10~80%,

[0015] ZSM-5 molecular sieve 10~80%,

[0016] ZSM-12 molecular sieve 10~80%.

[0017] In a second aspect, the present invention relates to a catalyst for liquid-phase non-hydrogenated xylene isomerization reaction, the catalyst comprising 10 to 80% hydrogen-type silica-alumina molecular sieve and 20 to 90% binder, based on the total mass of the catalyst;

[0018] Wherein, the hydrogen-type silicon-aluminum molecular sieve includes the following components in proportion based on the total mass of the hydrogen-type silicon-aluminum molecular sieve:

[0019] Beta molecular sieve 10~80%,

[0020] ZSM-5 molecular sieve 10~80%,

[0021] ZSM-12 molecular sieve 10~80%.

[0022] In a third aspect, the present invention relates to a method for preparing the catalyst for the liquid-phase non-hydrogen xylene isomerization reaction described in the second aspect, the preparation method comprising the following steps:

[0023] (1) subjecting a first silicon source, a first aluminum source, a first template, a first inorganic base and water to a first crystallization to obtain a metal cation type Beta molecular sieve;

[0024] (2) subjecting a second silicon source, a second aluminum source, a second template, a second inorganic base and water to a second crystallization to obtain a metal cation type ZSM-5 molecular sieve;

[0025] (3) subjecting a third silicon source, a third aluminum source, a third template, a third inorganic base and water to a third crystallization to obtain a metal cation type ZSM-12 molecular sieve;

[0026] (4) mixing the metal cation type Beta molecular sieve, the metal cation type ZSM-5 molecular sieve and the metal cation type ZSM-12 molecular sieve with a binder, adding an inorganic acid solution for kneading, and extruding into strips to obtain a strip;

[0027] The strips are subjected to a first drying, pelletizing and a first roasting to obtain pellets;

[0028] The granules are contacted with an ammonium salt solution to carry out ion exchange, washing, second drying and second calcination to obtain the liquid-phase non-hydrogenated xylene isomerization reaction catalyst.

[0029] Beneficial effects:

[0030] In the liquid-phase xylene isomerization method of the present invention, a catalyst based on a liquid-phase non-hydrogen xylene isomerization reaction is used for catalytic reaction, wherein the active components are Beta molecular sieve, ZSM-5 molecular sieve and ZSM-12 molecular sieve compounded in a certain ratio, and the catalyst preparation process does not need to load precious metals and does not need to be activated and reduced. When alkyl aromatic hydrocarbons contact the catalyst for liquid-phase xylene isomerization reaction, the three molecular sieves synergistically enhance the activity of the catalyst, significantly improve the isomerization activity of para-xylene and the xylene yield, and can effectively increase the production of para-xylene. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is the XRD diffraction spectrum of the Beta molecular sieve prepared in Example 1-3;

[0032] Figure 2 is the XRD diffraction spectrum of the ZSM-5 molecular sieve prepared in Example 1-3;

[0033] Figure 3 is the XRD diffraction spectrum of the ZSM-12 molecular sieve prepared in Example 1-3;

[0034] Figure 4 is a SEM photograph of the Beta molecular sieve prepared in Example 1;

[0035] Figure 5 is a SEM photo of the ZSM-5 molecular sieve prepared in Example 1;

[0036] Figure 6 is a SEM photo of the ZSM-12 molecular sieve prepared in Example 1;

[0037] Figure 7 is a SEM photograph of the Beta molecular sieve prepared in Example 2;

[0038] Figure 8 is a SEM photo of the ZSM-5 molecular sieve prepared in Example 2;

[0039] Fig. 9 is a SEM photo of the ZSM-12 molecular sieve prepared in Example 2;

[0040] Fig.10 is a SEM photograph of the Beta molecular sieve prepared in Example 3;

[0041] Fig.11 is a SEM photo of the ZSM-5 molecular sieve prepared in Example 3;

[0042] Fig.12 This is a SEM photograph of the ZSM-12 molecular sieve prepared in Example 3. DETAILED DESCRIPTION

[0043] The present application is further described in detail below through the accompanying drawings and embodiments. Through these descriptions, the characteristics and advantages of the present application will become clearer and more specific.

[0044] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0045] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0046] In a first aspect, the present invention relates to a liquid phase xylene isomerization method, the liquid phase xylene isomerization method comprising:

[0047] The alkyl aromatic hydrocarbon is brought into contact with a catalyst for a liquid-phase non-hydrogenated xylene isomerization reaction under a reaction pressure that maintains the liquid state to carry out an isomerization reaction;

[0048] Wherein, the alkyl aromatic hydrocarbons include m-xylene, o-xylene, ethylbenzene and optionally p-xylene; the catalyst includes 10-80% hydrogen-type silica-alumina molecular sieve and 20-90% binder, based on the total mass of the catalyst;

[0049] The hydrogen-type silicon-aluminum molecular sieve includes the following components in proportion based on the total mass of the hydrogen-type silicon-aluminum molecular sieve:

[0050] Beta molecular sieve 10~80%,

[0051] ZSM-5 molecular sieve 10~80%,

[0052] ZSM-12 molecular sieve 10~80%.

[0053] It should be noted that, keeping the alkyl aromatic hydrocarbons under a reaction pressure that keeps them in a liquid state 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; and carrying out the catalytic reaction under a reaction pressure that keeps the alkyl aromatic hydrocarbons in a liquid state. Therefore, the isomerization method of the present invention is a liquid phase xylene isomerization method. Optional p-xylene means that the alkyl aromatic hydrocarbons may not contain p-xylene, or may contain p-xylene in any proportion.

[0054] In the liquid-phase xylene isomerization method of the present invention, the alkyl aromatic hydrocarbon is brought into contact with a liquid-phase non-hydrogenated xylene isomerization reaction catalyst to carry out an isomerization reaction. The liquid-phase non-hydrogenated xylene isomerization reaction catalyst can well catalyze the isomerization of C8 aromatic hydrocarbons, better convert meta-xylene, ortho-xylene, etc. into para-xylene, can effectively increase the production of para-xylene, and maintain good selectivity.

[0055] According to a specific embodiment of the liquid phase xylene isomerization method according to the first aspect of the present invention, the conditions of the isomerization reaction include:

[0056] The reaction temperature is 240-310°C, and the weight hourly space velocity is 1-10h -1 .

[0057] It should be noted that by controlling the temperature and weight hourly space velocity of the isomerization reaction as above, when the alkyl aromatic hydrocarbon contacts the catalyst for the liquid phase non-hydrogenated xylene isomerization reaction for isomerization reaction, the catalyst can exhibit better catalytic activity, so that the isomerization activity and xylene yield are further improved.

[0058] It should be noted that the catalyst used in the liquid-phase xylene isomerization method of the first aspect of the present invention may be the catalyst for the liquid-phase non-hydrogen xylene isomerization reaction of the second aspect of the present invention, or may be the catalyst prepared by the preparation method of the third aspect of the present invention.

[0059] In a second aspect, the present invention relates to a catalyst for liquid-phase non-hydrogenated xylene isomerization reaction, the catalyst comprising 10 to 80% hydrogen-type silica-alumina molecular sieve and 20 to 90% binder, based on the total mass of the catalyst;

[0060] Wherein, the hydrogen-type silicon-aluminum molecular sieve includes the following components in proportion based on the total mass of the hydrogen-type silicon-aluminum molecular sieve:

[0061] Beta molecular sieve 10~80%,

[0062] ZSM-5 molecular sieve 10~80%,

[0063] ZSM-12 molecular sieve 10~80%.

[0064] It should be noted that the ZSM-12 molecular sieve belongs to the mordenite class, has an MTW-type structure, and has a one-dimensional linear non-intersecting channel composed of twelve-membered rings. In the catalyst of the present invention, a mixture of Beta molecular sieve, ZSM-5 molecular sieve and ZSM-12 molecular sieve is used as an active component, and the three molecular sieves are compounded according to the above ratio, so that the catalyst has very good catalytic activity when performing xylene isomerization, and can effectively increase the production of paraxylene. The catalyst of the present invention is used for liquid-phase xylene isomerization reaction. Compared with the gas-phase xylene isomerization reaction, the catalyst of the present invention does not contain precious metals and has a lower cost; it can also exert good catalytic activity in the absence of hydrogen, and while obtaining a higher isomerization activity and xylene yield, the reaction temperature is lower and the energy consumption is greatly reduced.

[0065] In a more preferred embodiment, in the total mass of the hydrogen-type silicon-aluminum molecular sieve, the mass proportion of Beta molecular sieve can be 13%-75%, specifically 14%, 20%, 30%, 45%, 58%, 60%, 72%, etc.; the mass proportion of ZSM-5 molecular sieve can be 13%-45%, specifically 14%, 14.5%, 20%, 30%, 40%, 43%, etc.; the mass proportion of ZSM-12 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 proportion of hydrogen-type silicon-aluminum molecular sieve can be 60-80%, specifically 65%, 70%, 75%, etc., and the mass proportion of binder can be 20%-40%, specifically 25%, 30%, 35%, etc. In this preferred embodiment, the activity of the catalyst is further improved, and the isomerization activity and the xylene yield can be further improved.

[0066] According to a specific implementation of the catalyst according to the second aspect of the present invention, the binder is aluminum oxide.

[0067] In a third aspect, the present invention relates to a method for preparing the catalyst for the liquid-phase non-hydrogen xylene isomerization reaction described in the second aspect, the preparation method comprising the following steps:

[0068] (1) subjecting a first silicon source, a first aluminum source, a first template, a first inorganic base and water to a first crystallization to obtain a metal cation type Beta molecular sieve;

[0069] (2) subjecting a second silicon source, a second aluminum source, a second template, a second inorganic base and water to a second crystallization to obtain a metal cation type ZSM-5 molecular sieve;

[0070] (3) subjecting a third silicon source, a third aluminum source, a third template, a third inorganic base and water to a third crystallization to obtain a metal cation type ZSM-12 molecular sieve;

[0071] (4) mixing the metal cation type Beta molecular sieve, the metal cation type ZSM-5 molecular sieve and the metal cation type ZSM-12 molecular sieve with a binder, adding an inorganic acid solution for kneading, and extruding into strips to obtain a strip;

[0072] The strips are subjected to a first drying, pelletizing and a first roasting to obtain pellets;

[0073] The granules are contacted with an ammonium salt solution to carry out ion exchange, washing, second drying and second calcination to obtain the liquid-phase non-hydrogenated xylene isomerization reaction catalyst.

[0074] It should be noted that in the process of preparing three molecular sieves in steps (1) to (3), when the inorganic base used is sodium hydroxide, the prepared molecular sieves are Na-type Beta molecular sieve, Na-type ZSM-5 molecular sieve and Na-type ZSM-12 molecular sieve respectively. After preparing three sodium-type molecular sieves, for example, by steps (1) to (3), the three sodium-type molecular sieves can be washed and dried, and then the steps of molding, ion exchange and the like in step (4) are performed to prepare the catalyst for the liquid-phase non-hydrogen xylene isomerization reaction. The drying temperature can be 100 to 140° C., and the time can be 8 to 24 hours. The three types of molecular sieves, for example, Na-type molecular sieves prepared in steps (1) to (3) are contacted with an ammonium salt solution for ion exchange and calcined in step (4). In the obtained finished catalyst, the molecular sieve is a hydrogen-type molecular sieve.

[0075] 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 the loading (such as impregnation) of precious metals and does not require activation and reduction steps. That is, it can prepare a liquid-phase non-hydrogen xylene isomerization reaction catalyst that can show good catalytic activity in the absence of hydrogen, has high isomerization activity and xylene yield; while the cost is lower, the catalyst preparation process is simplified, the preparation cycle is shortened, and the catalyst preparation efficiency is improved.

[0076] According to a specific implementation of the preparation method according to the third aspect of the present invention, in step (1):

[0077] The molar ratio of the first silicon source calculated as SiO2, the first aluminum source calculated as Al2O3, the first template, the first inorganic base and water is 1:(0.005-0.05):(0.05-1.5):(0.02-0.5):(10-60); and / or,

[0078] In step (2):

[0079] The molar ratio of the second silicon source calculated as SiO2, the second aluminum source calculated as Al2O3, the second template, the second inorganic base and water is 1:(0.005-0.05):(0.05-1):(0.02-1):(10-60); and / or,

[0080] In step (3):

[0081] The molar ratio of the third silicon source calculated as SiO2, the third aluminum source calculated as Al2O3, the third template, the third inorganic base and water is 1:(0.005-0.05):(0.05-1.5):(0.1-1):(10-60).

[0082] It should be noted that in the preparation method of the present invention, the molar ratios of the silicon source, aluminum source, template, inorganic base and water in each step are controlled in steps (1) to (3) as described above, and the prepared metal cation type, such as sodium-type Beta molecular sieve, ZSM-5 molecular sieve and ZSM-12 molecular sieve, can be used to prepare a catalyst with better catalytic activity for liquid-phase non-hydrogen xylene isomerization reaction through the subsequent step (4). When used for liquid-phase xylene isomerization reaction, high isomerization activity of the target product p-xylene and high xylene yield can be obtained simultaneously.

[0083] According to a specific embodiment of the preparation method of the third aspect of the present invention, in step (1), the molar ratio of the first silicon source calculated as SiO2 to the first aluminum source calculated as Al2O3, in step (2), the molar ratio of the second silicon source calculated as SiO2 to the second aluminum source calculated as Al2O3, in step (3), the molar ratio of the third silicon source calculated as SiO2 to the third aluminum source calculated as Al2O3, are each independently (25-150):1; and / or,

[0084] In step (1), the molar ratio of the first template to the first silicon source calculated as SiO2 is (0.08-1.4):1;

[0085] In step (2), the molar ratio of the second template to the second silicon source calculated as SiO2 is (0.06-0.9):1;

[0086] In step (3), the molar ratio of the third template to the third silicon source calculated as SiO2 is (0.1-1):1.

[0087] It should be noted that, as a preferred embodiment, by controlling the feed ratio between the above-mentioned materials in the three steps as described above, and then carrying out step (4), a catalyst for liquid-phase non-hydrogenated xylene isomerization reaction with further improved catalytic activity can be prepared. When the prepared catalyst is used for liquid-phase xylene isomerization reaction, the catalytic activity is further improved.

[0088] According to another specific embodiment of the preparation method described in 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;

[0089] 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 0.005 μm-0.5 mm, preferably 0.01 μm-0.3 mm; and / or,

[0090] 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 sulfate and / or sodium aluminate; and / or,

[0091] 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.

[0092] It should be noted that in the preparation method of the present invention, in steps (1) to (3), by controlling or selecting the silicon source, aluminum source and inorganic base as described above, sodium-type or potassium-type Beta molecular sieve, ZSM-5 molecular sieve and ZSM-12 molecular sieve with excellent stability, activity and other aspects can be prepared, and then through the subsequent step (4), a liquid-phase non-hydrogenated xylene isomerization reaction catalyst with excellent performance can be prepared.

[0093] According to a specific embodiment of the preparation method of the third aspect of the present invention, the first template in step (1), the second template in step (2) and the third template in step (3) are each independently selected from N(R)4 + X - ;

[0094] Wherein, N is a nitrogen atom, R is selected from an alkyl group having 1 to 4 carbon atoms, and X - selected from hydroxide ions and / or halogen anions;

[0095] The halogen anion is selected from chloride ion and / or bromide ion;

[0096] In step (1), R of the first template is preferably ethyl; and / or,

[0097] In step (2), R of the second template is preferably a propyl group; and / or,

[0098] In step (3), R of the third template is preferably ethyl.

[0099] It should be noted that the first template in step (1), the second template in step (2) and the third template in step (3) are independently selected from the quaternary ammonium salt or quaternary ammonium base as described above, so that metal cations with better stability and catalytic activity can be prepared, such as sodium-type Beta molecular sieve, ZSM-5 molecular sieve and ZSM-12 molecular sieve. Continuing through the steps of shaping, ammonium ion exchange and roasting in step (4), the sodium-type molecular sieve is converted into an H-type molecular sieve and then shaped and roasted, so as to prepare a catalyst for liquid-phase xylene isomerization reaction with significantly improved isomerization activity.

[0100] According to another specific implementation of the preparation method according to the third aspect of the present invention, the conditions for the first crystallization in step (1) include:

[0101] The temperature is 120 to 180° C., preferably 135 to 175° C.; the time is 60 to 140 hours, preferably 96 to 120 hours; and / or,

[0102] The crystal size of the metal cation type Beta molecular sieve obtained in step (1) is 30 to 600 nm, preferably 50 to 300 nm; and / or,

[0103] The conditions for the second crystallization in step (2) include:

[0104] The temperature is 140 to 190° C., preferably 175 to 185° C.; the time is 40 to 140 hours, preferably 96 to 120 hours; and / or,

[0105] The crystal size of the metal cation type ZSM-5 molecular sieve obtained in step (2) is 0.05 to 10 μm, preferably 0.6 to 5 μm; and / or,

[0106] The conditions for performing the third crystallization in step (3) include:

[0107] The temperature is 140 to 180° C., preferably 150 to 180° C.; the time is 60 to 140 hours, preferably 90 to 140 hours; and / or,

[0108] The crystal size of the metal cation type ZSM-12 molecular sieve obtained in step (3) is 300 to 1500 nm, preferably 400 to 600 nm; and / or,

[0109] The pressures during crystallization in step (1), step (2) and step (3) are respectively autogenous pressures.

[0110] It should be noted that, in steps (1) to (3), the conditions in the crystallization process are controlled as above, and the prepared metal cation type, such as sodium type Beta molecular sieve, ZSM-5 molecular sieve and ZSM-12 molecular sieve, completes a good crystallization process, and the prepared molecular sieve has high crystallinity, uniform and complete grain morphology. Based on these three molecular sieves, after forming, ammonium ion exchange and roasting in step (4), the three H-type molecular sieves in the prepared finished catalyst synergistically show good catalytic activity. When used to catalyze the liquid phase xylene isomerization of alkyl aromatics, it can better isomerize C8 aromatics such as m-xylene and o-xylene into p-xylene, and the isomerization activity of p-xylene and the xylene yield are significantly improved.

[0111] It should be noted that when ion exchange is performed in step (4), the ammonium salt solution can be an ammonium chloride solution, etc. For example, the intermediate formed by the mixture of the three sodium-type molecular sieves after forming with the binder can be placed in an 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 the three sodium-type molecular sieves after forming with the binder is washed with an ammonium chloride solution until the eluate is neutral with a pH range of 6 to 8. After the ion exchange is completed, dry at a temperature of 100 to 140°C for 4 to 24 hours. Then roast in an air atmosphere at a temperature of 520°C to 550°C for 2 to 24 hours; roasting can be carried out in a static atmosphere without air flow, or at a volume space velocity of 50 to 500h / s. -1 The calcined catalyst does not need to be impregnated with metal and activated and reduced to obtain the finished catalyst of the present invention.

[0112] The present invention is further described in detail by way of examples below, but the present invention is not limited thereto. The reagents used in the following examples, etc., except for those specifically stated, can be commercially available products.

[0113] Example 1

[0114] In a 200 mL reactor, add 15 g of silicon source (solid silica gel, particle size 150-250 μm, pore size 6 nm), 2.22 g of aluminum source (aluminum chloride), and template agent N (C2H5) 4 + OH -(35 mass % aqueous solution) 70.14g, NaOH 1.33g, water 26.41g. The molar ratio of each material is Al2O3: template: NaOH: H2O: SiO2 = 0.033: 0.67: 0.13: 16: 1. The synthesis temperature is 135°C, the synthesis time is 115 hours, and the molecular sieve is synthesized by a homogeneous reactor dynamic synthesis method. The molecular sieve is washed and dried.

[0115] The obtained Beta molecular sieve is denoted as B-1, with a silicon-aluminum ratio of 30 and an average grain size of 230nm. The XRD diffraction spectrum is shown in the attached Figure 1 It can be seen that the synthesized molecular sieve is a pure phase molecular sieve, which not only has a high degree of crystallinity and a stable baseline, but also has 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°, which are the characteristic peaks of Beta molecular sieve, corresponding to the characteristic peaks of Beta molecular sieve (330), (302), (304), (008), and (306) surfaces. There are no other impurity peaks in the XRD graph, which means that the synthesized Beta molecular sieve is a pure phase product. Its SEM electron microscope characterization is attached Figure 4 .

[0116] In a 200 mL reactor, 30 g of a silicon source (liquid silica sol, concentration 30% by mass), 3.75 g of an aluminum source (aluminum nitrate nonahydrate), and a template agent N(C3H7)4 were added. + OH - (25 mass % aqueous solution) 81.34g, NaOH 0.8g, water 0.972g. The molar ratio of each material is Al2O3: template: NaOH: H2O: SiO2 = 0.033: 0.67: 0.13: 31.33: 1. The synthesis temperature is 175°C, the synthesis time is 120 hours, and the molecular sieve is synthesized by a homogeneous reactor dynamic synthesis method. The molecular sieve is washed and dried.

[0117] The obtained ZSM-5 molecular sieve is denoted as Z-1, with a silicon-aluminum ratio of 30 and an average grain size of 0.75 μm. The XRD diffraction spectrum is shown in the attached Figure 2 , strong diffraction peaks appear at 2θ=7.9°, 8.8°, 23.1° and 23.3°. These diffraction peaks are typical characteristic peaks of ZSM-5, which represent the (011), (020), (332), (051) crystal planes of H-type ZSM-5 molecular sieve, respectively, indicating that the catalyst has a typical MFI structure. At the same time, the baseline in the XRD spectrum is stable and no impurity peaks are generated, indicating that a ZSM-5 molecular sieve with good crystallinity has been synthesized. Its SEM electron microscopy characterization is shown in the attached Figure 5 .

[0118] Add 10g of silicon source (solid silica gel, particle size 150-250μm, pore size 6nm), 3.701g of aluminum source (aluminum sulfate 18hydrate), 17.690g of template agent tetraethylammonium bromide (concentration 99 mass%), 0.888g of NaOH, and 88.023g of water into a 200mL reactor. The molar ratio of each material is Al2O3: template agent: NaOH: H2O: SiO2 = 0.033: 0.5: 0.133: 30: 1. The synthesis temperature is 155°C, the synthesis time is 100 hours, and the molecular sieve is synthesized by dynamic synthesis method. The molecular sieve is washed and dried.

[0119] The obtained ZSM-12 molecular sieve is denoted as S-1, with a silicon-aluminum ratio of 30 and an average grain size of 450 nm. The XRD diffraction spectrum is shown in the attached Figure 3 The typical characteristic diffraction peaks of ZSM-12 appear at 2θ=8.7°, 20.8° and 22.8°. At the same time, the baseline in the XRD spectrum is stable and no impurity peaks are generated, indicating that a ZSM-12 molecular sieve with good crystallinity has been synthesized. Its SEM electron microscopy characterization is shown in the attached Figure 6 .

[0120] Prepare Beta molecular sieve B-1, ZSM-5 molecular sieve Z-1, ZSM-12 molecular sieve S-1 and alumina in a mass ratio of 5:1:1:3 and mix them evenly. Add 5% by mass nitric acid aqueous solution and knead them evenly, the nitric acid aqueous solution used accounts for 35% by mass of the solid mixture, and then extrude them into strips. Dry the strips at 120°C for 6 hours, then cut into pellets and calcine at 540°C for 4 hours. The calcined sample is ion exchanged with 5% by mass ammonium chloride aqueous solution at 90°C for 2 hours, washed until there is no chloride ion in the mother liquor, dried at 120°C for 6 hours, and calcined at 540°C for 4 hours to obtain catalyst C-1.

[0121] Example 2

[0122] In a 200 mL reactor, add 15 g of silicon source (solid silica gel, particle size 150-250 μm, pore size 6 nm), 1.11 g of aluminum source (aluminum chloride), and template agent N(C2H5)4 + OH - (35 mass % aqueous solution) 52.61g, NaOH 0.5g, water 46.81g. The molar ratio of each material is Al2O3: template: NaOH: H2O: SiO2 = 0.017: 0.5: 0.05: 18: 1. The synthesis temperature is 140 ° C, the synthesis time is 115 hours, and the molecular sieve is synthesized by a homogeneous reactor dynamic synthesis method. The molecular sieve is washed and dried.

[0123] The obtained Beta molecular sieve is denoted as B-2, with a silicon-aluminum ratio of 60 and an average grain size of 180 nm. The XRD diffraction spectrum is shown in the attached Figure 1 It can be seen that the synthesized molecular sieve is a pure phase molecular sieve, which not only has a high degree of crystallinity and a stable baseline, but also has 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°, which are the characteristic peaks of Beta molecular sieve, corresponding to the characteristic peaks of Beta molecular sieve (330), (302), (304), (008), and (306) surfaces. There are no other impurity peaks in the XRD graph, which means that the synthesized Beta molecular sieve is a pure phase product. Its SEM electron microscope characterization is attached Figure 7 .

[0124] In a 200 mL reactor, 30 g of a silicon source (liquid silica sol, concentration 30% by mass), 1.88 g of an aluminum source (aluminum nitrate nonahydrate), and N(C3H7)4 + OH - 61g (25 mass % aqueous solution), 0.6g NaOH addition, 0.834g water. The molar ratio of each material is Al2O3: template: NaOH: H2O: SiO2 = 0.017: 0.5: 0.1: 25.33: 1. The synthesis temperature is 180 ° C, the synthesis time is 96 hours, and the molecular sieve is synthesized by a homogeneous reactor dynamic synthesis method. The molecular sieve is washed and dried.

[0125] The obtained ZSM-5 molecular sieve is denoted as Z-2, with a silicon-aluminum ratio of 60 and an average grain size of 0.8 μm. The XRD diffraction spectrum is shown in the attached Figure 2 , strong diffraction peaks appear at 2θ=7.9°, 8.8°, 23.1° and 23.3°. These diffraction peaks are typical characteristic peaks of ZSM-5, which represent the (011), (020), (332), (051) crystal planes of H-type ZSM-5 molecular sieve, respectively, indicating that the catalyst has a typical MFI structure. At the same time, the baseline in the XRD spectrum is stable and no impurity peaks are generated, indicating that a ZSM-5 molecular sieve with good crystallinity has been synthesized. Its SEM electron microscopy characterization is shown in the attached Figure 8 .

[0126] Add 25g of silicon source (liquid silica sol, concentration 40% by mass), 1.850g of aluminum source (aluminum sulfate 18 hydrate), 14.742g of template agent tetraethylammonium bromide (concentration 99% by mass), 1.667g of NaOH, and 43.953g of water into a 200mL reactor. The molar ratio of each material is Al2O3: template agent: NaOH: H2O: SiO2 = 0.0167: 0.416: 0.25: 20: 1. The synthesis temperature is 160°C, the synthesis time is 95 hours, and the molecular sieve is synthesized by dynamic synthesis method. The molecular sieve is washed and dried.

[0127] The obtained ZSM-12 molecular sieve is denoted as S-2, with a silicon-aluminum ratio of 60 and an average grain size of 500 nm. The XRD diffraction spectrum is shown in the attached Figure 3 The typical characteristic diffraction peaks of ZSM-12 appear at 2θ=8.7°, 20.8° and 22.8°. At the same time, the baseline in the XRD spectrum is stable and no impurity peaks are generated, indicating that a ZSM-12 molecular sieve with good crystallinity has been synthesized. Its SEM electron microscopy characterization is shown in the attached Fig. 9 .

[0128] Beta molecular sieve B-2, ZSM-5 molecular sieve Z-2, ZSM-12 molecular sieve S-2 and alumina were mixed uniformly at a mass ratio of 4:2:1:3. Catalyst C-2 was then obtained according to the catalyst preparation method in Example 1.

[0129] Example 3

[0130] In a 200 mL reactor, add 15 g of silicon source (solid silica gel, particle size 150-250 μm, pore size 6 nm), 0.833 g of aluminum source (aluminum chloride), and template agent N(C2H5)4 + OH - (35 mass % aqueous solution) 39.46g, NaOH 0.375g, water 41.85g. The molar ratio of each material is Al2O3: template: NaOH: H2O: SiO2 = 0.0125: 0.375: 0.0375: 15: 1. The synthesis temperature is 155°C, the synthesis time is 105 hours, and the molecular sieve is synthesized by a homogeneous reactor dynamic synthesis method. The molecular sieve is washed and dried.

[0131] The obtained Beta molecular sieve is denoted as B-3, with a silicon-aluminum ratio of 80 and an average grain size of 260 nm. The XRD diffraction spectrum is shown in the attached Figure 1 It can be seen that the synthesized molecular sieve is a pure phase molecular sieve, which not only has a high degree of crystallinity and a stable baseline, but also has 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°, which are the characteristic peaks of Beta molecular sieve, corresponding to the characteristic peaks of Beta molecular sieve (330), (302), (304), (008), and (306) surfaces. There are no other impurity peaks in the XRD graph, which means that the synthesized Beta molecular sieve is a pure phase product. Its SEM electron microscope characterization is attached Fig.10 .

[0132] In a 200 mL reactor, 22.5 g of a silicon source (liquid silica sol, concentration 40% by mass), 1.406 g of an aluminum source (aluminum nitrate nonahydrate), and a template agent N(C3H7)4 were added. + OH- (25 mass % aqueous solution) 30.504g, NaOH 0.45g, water 0.814g. The molar ratio of each material is Al2O3: template: NaOH: H2O: SiO2 = 0.0125: 0.25: 0.075: 14: 1. The synthesis temperature is 180°C, the synthesis time is 100 hours, and the molecular sieve is synthesized by a homogeneous reactor dynamic synthesis method. The molecular sieve is washed and dried.

[0133] The obtained ZSM-5 molecular sieve is denoted as Z-3, with a silicon-aluminum ratio of 80 and an average grain size of 1.0 μm. The XRD diffraction spectrum is shown in the attached Figure 2 , strong diffraction peaks appear at 2θ=7.9°, 8.8°, 23.1° and 23.3°. These diffraction peaks are typical characteristic peaks of ZSM-5, which represent the (011), (020), (332), (051) crystal planes of H-type ZSM-5 molecular sieve, respectively, indicating that the catalyst has a typical MFI structure. At the same time, the baseline in the XRD spectrum is stable and no impurity peaks are generated, indicating that a ZSM-5 molecular sieve with good crystallinity has been synthesized. Its SEM electron microscopy characterization is shown in the attached Fig.11 .

[0134] Add 33.33g of silicon source (liquid silica sol, concentration 30% by mass), 1.3878g of aluminum source (aluminum sulfate 18 hydrate), 17.690g of template agent tetraethylammonium bromide (concentration 99% by mass), 2.5g of NaOH, and 50.81g of water into a 200mL reactor. The molar ratio of each material is Al2O3: template agent: NaOH: H2O: SiO2 = 0.0125: 0.5: 0.375: 25: 1. The synthesis temperature is 170°C, the synthesis time is 100 hours, and the molecular sieve is synthesized by dynamic synthesis method. The molecular sieve is washed and dried.

[0135] The obtained ZSM-12 molecular sieve is denoted as S-3, with a silicon-aluminum ratio of 80 and an average grain size of 550 nm. The XRD diffraction spectrum is shown in the attached Figure 3 The typical characteristic diffraction peaks of ZSM-12 appear at 2θ=8.7°, 20.8° and 22.8°. At the same time, the baseline in the XRD spectrum is stable and no impurity peaks are generated, indicating that a ZSM-12 molecular sieve with good crystallinity has been synthesized. Its SEM electron microscopy characterization is shown in the attached Fig.12 .

[0136] Beta molecular sieve B-3, ZSM-5 molecular sieve Z-3, ZSM-12 molecular sieve S-3 and alumina were mixed uniformly at a mass ratio of 3:2:2:3. Catalyst C-3 was then obtained according to the catalyst preparation method in Example 1.

[0137] Example 4

[0138] Catalyst C-4 was obtained according to the preparation method of the catalyst in Example 1, except that the mass ratio of Beta molecular sieve B-1, ZSM-5 molecular sieve Z-1, ZSM-12 molecular sieve S-1 and alumina was 3:1:3:3.

[0139] Example 5

[0140] Catalyst C-5 was obtained according to the preparation method of the catalyst in Example 2, except that the mass ratio of Beta molecular sieve B-2, ZSM-5 molecular sieve Z-2, ZSM-12 molecular sieve S-2 and alumina was 2:3:2:3.

[0141] Example 6

[0142] Catalyst C-6 was obtained according to the preparation method of the catalyst in Example 3, except that the mass ratio of Beta molecular sieve B-3, ZSM-5 molecular sieve Z-3, ZSM-12 molecular sieve S-3 and alumina was 1:3:3:3.

[0143] Comparative Example 1

[0144] Catalyst D-1 was obtained according to the catalyst preparation method in Example 1, except that ZSM-5 molecular sieve and ZSM-12 molecular sieve were not added to the catalyst, and the mass ratio of Beta molecular sieve B-1 to alumina was 7:3.

[0145] Comparative Example 2

[0146] Catalyst D-2 was obtained according to the catalyst preparation method in Example 1, except that Beta molecular sieve and ZSM-12 molecular sieve were not added to the catalyst, and the mass ratio of ZSM-5 molecular sieve Z-1 to alumina was 7:3.

[0147] Comparative Example 3

[0148] Catalyst D-3 was obtained according to the preparation method of the catalyst in Example 1, except that Beta molecular sieve and ZSM-5 molecular sieve were not added to the catalyst, and the mass ratio of ZSM-12 molecular sieve S-1 to alumina was 7:3.

[0149] Comparative Example 4

[0150] Catalyst D-4 was obtained according to the preparation method of the catalyst 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, ZSM-12 molecular sieve S-3 and alumina was 3:4:3.

[0151] Comparative Example 5

[0152] Catalyst D-5 was obtained according to the preparation method of the catalyst 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, ZSM-12 molecular sieve S-3 and alumina was 2:5:3.

[0153] Comparative Example 6

[0154] Catalyst D-6 was obtained according to the preparation method of the catalyst in Example 3, except that ZSM-12 molecular sieve was not added to the catalyst, and the mass ratio of Beta molecular sieve B-3, ZSM-5 molecular sieve Z-3 and alumina was 1:6:3.

[0155] Test Example

[0156] In a small-scale continuous flow fixed bed device, 3 grams of catalyst were loaded, and the catalyst performance was evaluated using the raw materials of the composition described in Table 1. The evaluation conditions were: 250°C, 2MPa, feed mass space velocity 2h -1 .

[0157] The alkyl aromatic hydrocarbon feedstock in Table 1 is contacted with a catalyst in a liquid state to carry out an isomerization reaction without the presence of hydrogen.

[0158] The catalysts used in the examples and comparative examples and the reaction results are shown in Tables 2 and 3.

[0159] The catalyst performance is evaluated according to the following calculation method:

[0160] Isomerization activity index:

[0161] Xylene yield:

[0162] Table 1 Raw material composition

[0163] <![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

[0164] Table 2 Catalysts and reaction performances described in Examples

[0165]

[0166] Table 3 Comparative Examples of Catalysts and Reaction Performance

[0167]

[0168]

[0169] It can be seen from Tables 2 and 3 that the catalysts prepared by the methods of Examples 1 to 6 of the present invention have higher isomerization activity (PX / ∑X) index for the target product p-xylene and higher xylene yield than the catalysts of Comparative Examples 1 to 6, indicating that the method of the present invention, using a combination of three molecular sieves as active components of the catalyst, has better isomerization activity and selectivity than using only one or two molecular sieves as active components.

[0170] In addition, after a long period of research and development, the inventors of the present application discovered that the above three molecular sieves are prepared according to the methods of steps (1) to (3) of the present application, respectively, and various conditions are controlled, and the three prepared molecular sieves are made in a certain ratio, and various conditions are controlled according to step (4), so that the catalyst can be obtained. When used for liquid phase xylene isomerization, it has good catalytic activity, and the isomerization activity (PX / ∑X) of the target product xylene and the xylene yield are significantly improved.

[0171] In the description of the present application, it should be noted that the terms "upper", "lower", "inside", "outside", "front", "back", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships in the working state of the present application. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limitations on the present application.

[0172] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "install", "connect" and "connect" should be understood in a broad sense. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0173] The present application has been described above in conjunction with preferred embodiments, but these embodiments are only exemplary and serve only as an illustration. On this basis, various replacements and improvements may be made to the present application, all of which fall within the scope of protection of the present application.

Claims

1. A liquid phase xylene isomerization method, characterized in that: The liquid phase xylene isomerization method comprises: The alkyl aromatic hydrocarbon is brought into contact with a catalyst for a liquid-phase non-hydrogenated xylene isomerization reaction under a reaction pressure that maintains the liquid state to carry out an isomerization reaction; Wherein, the alkyl aromatic hydrocarbons include m-xylene, o-xylene, ethylbenzene and optionally p-xylene; the catalyst includes 10-80% hydrogen-type silica-alumina molecular sieve and 20-90% binder, based on the total mass of the catalyst; The hydrogen-type silicon-aluminum molecular sieve includes the following components in proportion based on the total mass of the hydrogen-type silicon-aluminum molecular sieve: Beta molecular sieve 10~80%, ZSM-5 molecular sieve 10~80%, ZSM-12 molecular sieve 10~80%.

2. The liquid phase xylene isomerization method according to claim 1, characterized in that: The conditions of the isomerization reaction include: The reaction temperature is 240-310°C, and the weight hourly space velocity is 1-10h -1 .

3. A catalyst for liquid phase non-hydrogenated xylene isomerization reaction, characterized in that: The catalyst comprises 10-80% hydrogen-type silicon-aluminum molecular sieve and 20-90% binder, based on the total mass of the catalyst; Wherein, the hydrogen-type silicon-aluminum molecular sieve includes the following components in proportion based on the total mass of the hydrogen-type silicon-aluminum molecular sieve: Beta molecular sieve 10~80%, ZSM-5 molecular sieve 10~80%, ZSM-12 molecular sieve 10~80%.

4. The catalyst according to claim 3, characterized in that The binder is aluminum oxide.

5. The method for preparing the catalyst for liquid phase non-hydrogen xylene isomerization reaction according to claim 3 or 4, characterized in that: The preparation method comprises the following steps: (1) subjecting a first silicon source, a first aluminum source, a first template, a first inorganic base and water to a first crystallization to obtain a metal cation type Beta molecular sieve; (2) subjecting a second silicon source, a second aluminum source, a second template, a second inorganic base and water to a second crystallization to obtain a metal cation type ZSM-5 molecular sieve; (3) subjecting a third silicon source, a third aluminum source, a third template, a third inorganic base and water to a third crystallization to obtain a metal cation type ZSM-12 molecular sieve; (4) mixing the metal cation type Beta molecular sieve, the metal cation type ZSM-5 molecular sieve and the metal cation type ZSM-12 molecular sieve with a binder, adding an inorganic acid solution for kneading, and extruding to obtain a strip; The strips are subjected to a first drying, pelletizing and a first roasting to obtain pellets; The granules are contacted with an ammonium salt solution to carry out ion exchange, washing, second drying and second calcination to obtain the liquid-phase non-hydrogenated xylene isomerization reaction catalyst.

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, the first inorganic base 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, the second inorganic base 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, the third inorganic base and water is 1:(0.005-0.05):(0.05-1.5):(0.1-1):(10-60).

7. The preparation method according to claim 5, characterized in that: In step (1), the molar ratio of the first silicon source calculated as SiO2 to the first aluminum source calculated as Al2O3, in step (2), the molar ratio of the second silicon source calculated as SiO2 to the second aluminum source calculated as Al2O3, and in step (3), the molar ratio of the third silicon source calculated as SiO2 to the third aluminum source calculated as Al2O3 are each independently (25-150):1; and / or, In step (1), the molar ratio of the first template to the first silicon source calculated as SiO2 is (0.08-1.4):1; In step (2), the molar ratio of the second template to the second silicon source calculated as SiO2 is (0.06-0.9):1; In step (3), the molar ratio of the third template to the third silicon source calculated as SiO2 is (0.1-1):

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, preferably 30-40% by mass; the particle size of the solid silica gel is 0.005 μm-0.5 mm, preferably 0.01 μm-0.3 mm; 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 sulfate and / or sodium aluminate; 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 5, characterized in that: The first template in step (1), the second template in step (2) and the third template in step (3) are each independently selected from N(R)4 + X - ; Wherein, N is a nitrogen atom, R is selected from an alkyl group having 1 to 4 carbon atoms, and X - selected from hydroxide ions and / or halogen anions; The halogen anion is selected from chloride ion and / or bromide ion; In step (1), R of the first template is preferably ethyl; and / or, In step (2), R of the second template is preferably a propyl group; and / or, In step (3), R of the third template is preferably ethyl.

10. The preparation method according to claim 5, characterized in that: The first crystallization conditions in step (1) include: The temperature is 120 to 180° C., preferably 135 to 175° C.; the time is 60 to 140 hours, preferably 96 to 120 hours; and / or, The crystal size of the metal cation type Beta molecular sieve obtained in step (1) is 30 to 600 nm, preferably 50 to 300 nm; and / or, The conditions for the second crystallization in step (2) include: The temperature is 140 to 190° C., preferably 175 to 185° C.; the time is 40 to 140 hours, preferably 96 to 120 hours; and / or, The crystal size of the metal cation type ZSM-5 molecular sieve obtained in step (2) is 0.05 to 10 μm, preferably 0.6 to 5 μm; and / or, The conditions for performing the third crystallization in step (3) include: The temperature is 140 to 180° C., preferably 150 to 180° C.; the time is 60 to 140 hours, preferably 90 to 140 hours; and / or, The crystal size of the metal cation type ZSM-12 molecular sieve obtained in step (3) is 300 to 1500 nm, preferably 400 to 600 nm; and / or, The pressures during crystallization in step (1), step (2) and step (3) are respectively autogenous pressures.

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