Structure-directing agent for synthesizing MSE molecular sieve, preparation method of structure-directing agent and preparation method of MSE molecular sieve

Abstract

The invention provides a structure-directing agent capable of being used for synthesizing an MSE molecular sieve and a preparation method thereof, and a preparation method of the MSE molecular sieve, the structure-directing agent comprises a compound represented by a formula (1): in the formula (1), X <-> is a halide ion or a hydroxide ion; r1 and R2 form a ring or do not form a ring; and R3 and R4 form a ring or do not form a ring. The novel structure-directing agent provided by the invention is controllable in cost, easy to prepare, capable of being used for hydro-thermal synthesis of the MSE molecular sieve, adjustable in silica-alumina ratio and small in crystal grain, and the molecular sieve catalyst can be used for catalytic cracking and other reactions.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis, and in particular to a class of structure-directing agents for the synthesis of MSE molecular sieves and their preparation methods, as well as methods for preparing MSE molecular sieves. Background Technology

[0002] ZSM-5 molecular sieves with a three-dimensional 10-membered ring channel structure and β molecular sieves with a three-dimensional 12-membered ring channel structure are mainstream catalysts for naphtha catalytic cracking to olefins, and their channel structure plays a role in regulating shape selectivity. Recently, MSE molecular sieves with multiple three-dimensional channel structures containing both 10-membered and 12-membered rings have attracted widespread attention due to their channel structure being between that of ZSM-5 and β molecular sieves, exhibiting high propylene selectivity in catalytic cracking reactions.

[0003] In the synthesis of MSE molecular sieves, structure-directing agents and / or seed crystals are often required. However, the synthesis conditions of conventional structure-directing agents are currently harsh, resulting in MSE molecular sieves with narrow silica-to-alumina ratio windows, a tendency to form impurities, and insufficient thermal stability, which greatly limits their industrial applications. For example, US Patent 6049018A discloses a method for synthesizing an MSE molecular sieve (MCM-68) using N,N,N',N'-tetraethyl-exo,exo-bicyclo[2.2.2]oct-7-ene-2,3,5,6-bitetrahydropyrrole diiodoammonium salt (TEBOP). 2+ (I - 2) As a structure-directing agent, this molecular sieve can be synthesized via a hydrothermal method. This method is still in use today and is considered the most classic synthetic route. (TEBOP) 2+ (I - The second method requires starting from bis(2.2.2)oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BOTD) and proceeding through a three-step reaction involving amidation, carbonyl reduction, and quaternization. This method involves expensive raw materials, a complex process, and a long workflow. Furthermore, the silica-to-alumina ratio window of the synthesized MCM-68 molecular sieve is relatively narrow, ranging from 9 to 12. International patent WO2011162741A1 discloses a structure-directing agent, dimethyl dipropyl hydroxide (DMDPAOH), which produces a UZM-35 molecular sieve with a narrow silica-to-alumina window of 7 to 9. This synthesis requires strict composition control and is prone to generating competing impurities such as MFI. Other synthetic routes also present similar problems. Summary of the Invention

[0004] This invention provides a type of structure-directing agent for the synthesis of MSE molecular sieves. This type of structure-directing agent has advantages such as high synthesis yield and wide silicon-to-aluminum ratio window (10-25) in the preparation of MSE molecular sieves.

[0005] This invention also provides a method for preparing a type of structure directing agent for synthesizing MSE molecular sieves, which has the advantages of controllable cost and simple process.

[0006] The present invention also provides a method for preparing MSE molecular sieves by using the above-mentioned structure-directing agent. Since the method uses a specific structure-directing agent, the synthesized MSE molecular sieve has the advantage of a wider silicon-to-aluminum ratio window.

[0007] In a first aspect, the present invention provides a class of structure-directing agents for the synthesis of MSE molecular sieves, comprising compounds of formula (1):

[0008]

[0009] In equation (1), X - The components are halide ions or hydroxide ions; R1 and R2 may be cyclic or non-cyclic. When R1 and R2 are non-cyclic, they are independently C1-C6 straight-chain alkyl or branched alkyl, or C3-C6 cycloalkyl. When R1 and R2 are cyclic, the cyclic structure of R1 and R2 is a five-membered ring, a six-membered ring, a branched five-membered ring, or a branched six-membered ring. R3 and R4 may be cyclic or non-cyclic. When R3 and R4 are non-cyclic, they are independently C1-C6 straight-chain alkyl or branched alkyl, or C3-C6 cycloalkyl. When R3 and R4 are cyclic, the cyclic structure of R3 and R4 is a five-membered ring, a six-membered ring, a branched five-membered ring, or a branched six-membered ring.

[0010] Furthermore, in formula (1), when R1 and R2 do not form a ring, they are each independently methyl, ethyl, propyl, or isopropyl; when R1 and R2 form a ring, the ring formed by R1 and R2 is a five-membered ring with at least one C1-C6 alkyl branch or a six-membered ring with at least one C1-C6 alkyl branch.

[0011] And / or, when R3 and R4 are not cyclic, they are each independently methyl, ethyl, propyl, or isopropyl; when R3 and R4 are cyclic, R1 and R2 are cyclic to form a five-membered ring with at least one C1-C6 alkyl branch or a six-membered ring with at least one C1-C6 alkyl branch.

[0012] Furthermore, the cyclization of R1 and R2 is a five-membered or six-membered ring with a methyl group;

[0013] And / or, the R3 and R4 rings are five-membered or six-membered rings with methyl groups.

[0014] Furthermore, the cationic portion of the compound of formula (1) includes at least one of the following structures:

[0015]

[0016] Secondly, the present invention provides a method for preparing the above-mentioned structure-directing agents for synthesizing MSE molecular sieves, comprising the following steps:

[0017] A mixture comprising a first raw material, a second raw material, and a solvent is subjected to a reflux reaction, followed by separation and purification to obtain the structure-directing agent;

[0018] The first raw material is 1,2,4,5-tetrabromotoluene or 1,2,4,5-tetrachlorotoluene; the second raw material is one of an amine compound or its derivative, pyrrole or its derivative, and piperidine or its derivative.

[0019] Furthermore, the molar ratio of the first raw material to the second raw material is 1:4-5;

[0020] And / or, the reflux reaction is carried out at a temperature of 60-100°C for a time of 12-36 hours.

[0021] Furthermore, the separation and purification include the following processes: the liquid product obtained from the reflux reaction is subjected to rotary evaporation to obtain a solid product, the solid product is washed with an organic solvent, and the product is obtained by filtration and vacuum drying to obtain the structure-directing agent.

[0022] Thirdly, the present invention provides a method for preparing a class of MSE molecular sieves, including the step of using the structure-directing agent described in the first aspect.

[0023] Furthermore, the specific steps include:

[0024] 1) The structure-directing agent is optionally ion-exchanged, dispersed in a solvent, and an alkali source, an aluminum source, and a silicon source are added. After stirring, a gel product is obtained.

[0025] 2) The gel product is subjected to hydrothermal crystallization treatment at 120-200℃ for 48-384h.

[0026] Furthermore, it also includes the following processes:

[0027] The gel product and MSE molecular sieve seed crystals are mixed and then subjected to the hydrothermal crystallization treatment.

[0028] The novel structure-directing agent provided by this invention is cost-controllable, easy to synthesize, and can directly synthesize MSE molecular sieves with adjustable silicon-to-aluminum ratio and small crystal size in one step by hydrothermal method, which is beneficial to improving the diffusion of reactants in catalysts and the activity of acidic sites in catalytic reactions. Attached Figure Description

[0029] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0030] Figure 1 The structure-directing agent prepared in Example 1 1 H NMR and 13 C NMR spectrum;

[0031] Figure 2 The structure-directing agent prepared in Example 2 1 H NMR and 13 C NMR spectrum;

[0032] Figure 3 The structure-directing agent prepared in Example 3 1 H NMR and 13 C NMR spectrum;

[0033] Figure 4 For Comparative Example 1, TEBOP 2+ (I - )2. XRD pattern of MCM-68 molecular sieve prepared with structure-directing agent;

[0034] Figure 5 The XRD pattern of the MCM-68 molecular sieve prepared in Experimental Example 1;

[0035] Figure 6 The XRD pattern of the MCM-68 molecular sieve prepared in Experimental Example 2;

[0036] Figure 7 The XRD pattern of the MCM-68 molecular sieve prepared in Experimental Example 3;

[0037] Figure 8 The XRD pattern of the MCM-68 molecular sieve prepared in Experimental Example 4;

[0038] Figure 9 SEM images of the MCM-68 molecular sieve prepared in Experimental Example 1 at different magnifications;

[0039] Figure 10 SEM images of the MCM-68 molecular sieve prepared in Experimental Example 4 at different magnifications;

[0040] Figure 11 The graph shows the change in the conversion rate of n-heptane over time when deAl-TEBOP-MSE(50) and deAl-OSDA3-MSE(50) are used for catalytic cracking of n-heptane. Detailed Implementation

[0041] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] In this application, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0043] In a first aspect, the present invention provides a class of structure-directing agents for the synthesis of MSE molecular sieves, comprising compounds of formula (1):

[0044]

[0045] In formula (1), X- is a halide ion or hydroxide ion; R1 and R2 are either cyclic or non-cyclic. When R1 and R2 are not cyclic, they are each independently a C1-C6 straight-chain alkyl or branched alkyl, or a C3-C6 cycloalkyl. When R1 and R2 are cyclic, the cyclic structure of R1 and R2 is a five-membered ring, a six-membered ring, a branched five-membered ring, or a branched six-membered ring. R3 and R4 are either cyclic or non-cyclic. When R3 and R4 are not cyclic, they are each independently a C1-C6 straight-chain alkyl or branched alkyl, or a C3-C6 cycloalkyl. When R3 and R4 are cyclic, the cyclic structure of R3 and R4 is a five-membered ring, a six-membered ring, a branched five-membered ring, or a branched six-membered ring.

[0046] In this invention, by defining a specific rigid cyclic framework for the structure-directing agent, it is possible to induce and regulate the silica-alumina ratio window of the MSE molecular sieve, and synthesize MSE molecular sieves with small crystallites, which helps to improve the catalytic performance and stability of the MSE molecular sieve.

[0047] It can be understood that when R1 and R2 form a ring, it means that together with N they form one of the following: a five-membered heterocycle, a six-membered heterocycle, a five-membered heterocycle with branches, or a six-membered heterocycle with branches. The same applies to R3 and R4.

[0048] In one specific embodiment, when R1 and R2 are not cyclic, they are each independently methyl, ethyl, propyl, or isopropyl; when R1 and R2 are cyclic, the cyclic R1 and R2 are a five-membered ring with at least one C1-C6 alkyl branch or a six-membered ring with at least one C1-C6 alkyl branch.

[0049] And / or, when R3 and R4 are not cyclic, they are each independently methyl, ethyl, propyl, or isopropyl; when R3 and R4 are cyclic, the cyclic formation of R3 and R4 is a five-membered ring with at least one C1-C6 alkyl branch or a six-membered ring with at least one C1-C6 alkyl branch.

[0050] In one specific embodiment, the cyclization of R1 and R2 is a five-membered or six-membered ring with a methyl group;

[0051] And / or, the R3 and R4 rings are five-membered or six-membered rings with methyl groups.

[0052] To further improve the catalytic performance and stability of MSE molecular sieves, in one specific embodiment, the cationic moiety of the compound of formula (1) includes at least one of the following structures:

[0053]

[0054]

[0055] In the above embodiments, there is a structure-directing agent in which R1, R2, R3 and R4 are short-chain alkyl groups. This type of structure-directing agent, due to its suitable molecular chain length, can appropriately induce and regulate the silica-alumina ratio window of the MSE molecular sieve. Another type is a structure-directing agent in which R1 and R2 form rings and R3 and R4 form rings. This type of structure-directing agent has a more rigid cyclic framework, which can not only induce and regulate the silica-alumina ratio window of the MSE molecular sieve, but also is more conducive to inducing the formation of MSE molecular sieves with better stability.

[0056] Secondly, the present invention provides a method for preparing the above-mentioned structure-directing agents for synthesizing MSE molecular sieves, comprising the following steps:

[0057] A mixture comprising a first raw material, a second raw material, and a solvent is subjected to a reflux reaction, followed by separation and purification to obtain the structure-directing agent;

[0058] The first raw material is 1,2,4,5-tetrabromotoluene or 1,2,4,5-tetrachlorotoluene; the second raw material is one of an amine compound or its derivative, pyrrole or its derivative, and piperidine or its derivative.

[0059] It is understood that the second raw material is the source of the R1-R4 groups, so the specific type of the second raw material can be adjusted according to the specific structure of the desired R1-R4 groups; for example, the second raw material is diethylamine, pyrrole or piperidine.

[0060] The above separation and purification generally includes the following steps: the liquid product obtained by reflux is evaporated to dryness in a vacuum rotary evaporator to obtain a solid product, which is then washed with an organic solvent, filtered, and vacuum dried overnight to obtain the precursor compound.

[0061] As for organic solvents, they can be matched according to the solubility of impurities, for example, a mixed solution of ethanol and tetrahydrofuran in a volume ratio of (1:1).

[0062] In one specific embodiment, the molar ratio of the first raw material and the second raw material is 1:4-5;

[0063] And / or, the reflux reaction temperature is 60-100℃, and the time is 12-36h. If the reflux temperature is too high or too low, the structure-directing agent of the target structure cannot be synthesized.

[0064] Thirdly, the present invention provides a method for preparing a class of MSE molecular sieves, including the step of using the structure-directing agent described in the first aspect.

[0065] The MSE molecular sieves prepared using the structure-directing agent provided by this invention do not require the addition of seed crystals and can be synthesized directly in a single step under hydrothermal conditions, which are relatively mild.

[0066] In one specific implementation, the following steps are included:

[0067] 1) The structure-directing agent is optionally ion-exchanged, dispersed in a solvent, and then an alkali source, an aluminum source, and a silicon source are added. After stirring, a gel product is obtained.

[0068] 2) The gel product is subjected to hydrothermal crystallization at 120-200℃ for 48-384h to obtain the MSE molecular sieve.

[0069] If the anionic portion of the structure-directing agent is a halide ion, it needs to undergo ion exchange to become hydroxide ions, for example, using 717 anion exchange resin for ion exchange.

[0070] The above-mentioned ion exchange generally includes the following process: soaking neutral resin in 2-4% NaOH solution for 8-24 hours to obtain OH... - Type-3 resin, containing structure-directing agents, deionized water and OH... -The resins were mixed in a certain proportion and stirred for 8-24 hours, with multiple exchanges to ensure complete exchange. The water was then removed by rotary evaporation to obtain the OH- type structure-directing agent. The concentration of OH- in the structure-directing agent could then be confirmed by titration with a 0.10M HCl standard solution.

[0071] It is understood that when the MSE molecular sieve is used in a catalytic cracking reaction, the following steps are also included:

[0072] MSE molecular sieves are ion-exchanged to form hydrogen-type molecular sieves, and then dealuminized using nitric acid to obtain MSE molecular sieves for catalytic cracking reactions.

[0073] For example, the solvents mentioned above include, but are not limited to, deionized water or toluene; the alkali sources mentioned above include, but are not limited to, sodium hydroxide, potassium hydroxide, and ammonium hydroxide; the aluminum sources mentioned above include, but are not limited to, one or more of H-FAU, aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum hydroxide, sodium aluminate, boehmite, and aluminum isopropoxide. The silicon sources mentioned above include, but are not limited to, one or more of sodium silicate, silica sol, fumed silica, silica, and tetraethyl orthosilicate. The hydrothermal synthesis conditions mentioned above include static hydrothermal synthesis and dynamic hydrothermal synthesis.

[0074] For example, the Si / Al ratio of the aluminum source and the silicon source is 9-30, and the OH- / Si ratio of the alkali source and the silicon source is 0.375-0.775.

[0075] Furthermore, when the alkali source is potassium hydroxide, the K / Si ratio of the alkali source and the silicon source is 0.375.

[0076] After hydrothermal crystallization, the process includes centrifugation, washing, drying, and calcination. Washing typically uses deionized water, and the purpose of calcination is to remove the structure-directing agent and moisture, generally at 1°C / min. -1 The heating rate was increased from room temperature to 550℃, and the temperature was calcined for 6-10 hours.

[0077] Although the preparation of MSE molecular sieves using the structure-directing agent provided by the present invention does not require the addition of seed crystals, in some embodiments, in order to further shorten the crystallization time and induce nucleation, the following process is also included:

[0078] The gel product and MSE molecular sieve seed crystals are mixed and then subjected to the hydrothermal crystallization treatment.

[0079] The technical solution of the present invention will be further illustrated below with reference to specific embodiments. All parts, percentages and ratios recorded in the following embodiments are based on weight. All reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing. The instruments used in the embodiments are also commercially available.

[0080] The structures of the cationic portions of the structure-directing agents prepared in the examples are shown in Table 1;

[0081] Table 1:

[0082]

[0083] Example 1

[0084] OSDA1 preparation process

[0085] 1) Add 1,2,4,5-tetrabromotoluene and diethylamine to a mixed solution (180 mL) of ethanol and tetrahydrofuran (volume ratio 1:1) at a molar ratio of 1:4.2 and mix thoroughly.

[0086] 2) The solution obtained in step 1) was refluxed at 70°C for 24 hours;

[0087] 3) The solution obtained in step 2) was evaporated to dryness in a vacuum rotary evaporator to obtain a solid product, which was then washed with a mixed solution of ethanol and tetrahydrofuran (volume ratio 1:1) and filtered to obtain a white solid.

[0088] 4) The white solid obtained in step 3) was vacuum dried overnight to obtain OSDA1 structure directing agent with a yield of 85%;

[0089] NMR was measured when OSDA1 structure-directing agent was dissolved in heavy water (see attached diagram). Figure 1 .

[0090] Example 2

[0091] OSDA2 preparation process

[0092] 1) Add 1,2,4,5-tetrabromotoluene and pyrrolidine in a molar ratio of 1:4.4 to a mixed solution (156 mL) of ethanol and tetrahydrofuran (volume ratio 1:1) and mix thoroughly.

[0093] 2) The solution obtained in step 1) was refluxed at 70°C for 24 hours;

[0094] 3) The solution obtained in step 2) was evaporated to dryness in a vacuum rotary evaporator to obtain a solid product, which was then washed with a mixed solution of ethanol and tetrahydrofuran (volume ratio 1:1) and filtered to obtain a white solid.

[0095] 4) The white solid obtained in step 3) was vacuum dried overnight to obtain OSDA2 structure directing agent with a yield of 91%;

[0096] NMR was measured when OSDA2 structure-directing agent was dissolved in heavy water (see attached diagram). Figure 2 .

[0097] Example 3

[0098] Preparation process of OSDA3:

[0099] 1) Add 1,2,4,5-tetrabromotoluene and piperidine in a molar ratio of 1:4.2 to a mixed solution (100 mL) of ethanol and tetrahydrofuran (volume ratio 1:1) and mix thoroughly.

[0100] 2) The solution obtained in step 1) was refluxed at 70°C for 24 hours;

[0101] 3) The solution obtained in step 2) was evaporated to dryness in a vacuum rotary evaporator to obtain a solid product, which was then washed with a mixed solution of dichloromethane and filtered to obtain a white solid.

[0102] 4) The white solid obtained in step 3) was vacuum dried overnight to obtain OSDA3 structure directing agent with a yield of 88%;

[0103] NMR was measured when OSDA3 structure-directing agent was dissolved in heavy water (see attached diagram). Figure 3 .

[0104] Comparative Example 1

[0105] With TEBOP 2+ (I - )2 was used as a structure directing agent to synthesize MSE molecular sieves (silicon-to-aluminum ratio of 10).

[0106] 1) Weigh 1.86g TEBOP 2+ (I - 2. Stir 14.87g of deionized water until homogeneous at room temperature;

[0107] 2) Add 0.83g of potassium hydroxide (purity: 85%) to the solution obtained in step 1) and stir again until homogeneous;

[0108] 3) Add 0.263g of aluminum hydroxide powder (purity: 99.9%) to the solution obtained in step 2), stir to form a homogeneous solution, and let it stand statically for 12h at 120℃.

[0109] 4) Slowly add 5.00g of silica sol (Ludox-HS-40) to the solution obtained in step 3) and stir at room temperature for 24h. Transfer the resulting solution to a 100mL hydrothermal reactor and perform dynamic hydrothermal crystallization at 160℃ for 384h.

[0110] 5) Centrifuge, wash, and dry the solid obtained in step 4) at 1℃·min -1 The temperature was increased from room temperature to 550℃ and held for 6 hours to obtain pure-phase MCM-68 molecular sieve (particle size distribution in the range of 70-170 nm), with a yield of 50%. XRD test results are shown in the appendix. Figure 4 .

[0111] Experimental Example 1

[0112] MSE molecular sieves (silicon-to-aluminum ratio of 10) were synthesized using OSDA1 as a structure directing agent.

[0113] 1) The OSDA1 prepared in Example 1 was dispersed in deionized water, and then a certain amount of OH was added. - Type resin, in which OSDA1, deionized water and OH - The resin ratio was 1:3:5, exchanged 3 times, and the water was removed by rotary evaporation to obtain OH. - OSDA1 type; weigh 0.462g OH - Mix OSDA1 and 4.5g of deionized water at room temperature until homogeneous;

[0114] 2) Add 0.247g of potassium hydroxide (purity: 85%) to the solution obtained in step 1) and stir again until homogeneous;

[0115] 3) Add 0.104g of aluminum hydroxide powder (purity: 78%) to the solution obtained in step 2), stir to form a homogeneous solution, and let it stand statically for 12h at 120℃.

[0116] 4) Add 1.50 g of silica sol (Ludox-AS-40) to the solution obtained in step 3) and stir at room temperature for 24 h. Transfer the resulting solution to a 50 mL hydrothermal reactor and add 0.10 g of MCM-68 molecular sieve from Comparative Example 1 as seed crystals. Perform dynamic hydrothermal crystallization at 160 °C for 240 h.

[0117] 5) Centrifuge, wash, and dry the solid obtained in step 4) at 1℃·min -1 The temperature was increased from room temperature to 550℃ and held for 6 hours to obtain pure-phase MCM-68 molecular sieve with a yield of 63%. XRD results are shown in the appendix. Figure 5 The SEM test results are attached. Figure 9 .Depend on Figure 9 It can be seen that the particle size distribution of the MCM-68 molecular sieve prepared in this example is in the range of 80-150 nm.

[0118] Experimental Example 2

[0119] MSE molecular sieves (silicon-to-aluminum ratio of 10) were synthesized using OSDA2 as a structure directing agent.

[0120] 1) The OSDA2 prepared in Example 2 was dispersed in deionized water, and then a certain amount of OH was added. -The resin was prepared in a ratio of 1:3:5, consisting of OSDA2, deionized water, and OH-type resin. The resin was exchanged three times, and the water was removed by rotary evaporation to obtain OH-type OSDA2. 0.456 g of OH-type OSDA2 and 4.5 g of deionized water were weighed and stirred evenly at room temperature.

[0121] 2) Add 0.247g of potassium hydroxide (purity: 85%) to the solution obtained in step 1) and stir again until homogeneous;

[0122] 3) Add 0.104g of aluminum hydroxide powder (purity: 78%) to the solution obtained in step 2), stir to form a homogeneous solution, and let it stand statically for 12h at 120℃.

[0123] 4) Add 1.50 g of silica sol (Ludox-AS-40) to the solution obtained in step 3) and stir at room temperature for 24 h. Transfer the resulting solution to a 50 mL hydrothermal reactor and add 0.10 g of MCM-68 molecular sieve from Comparative Example 1 as seed crystals. Perform dynamic hydrothermal crystallization at 160 °C for 240 h.

[0124] 5) Centrifuge, wash, and dry the solid obtained in step 4) at 1℃·min -1 The temperature was increased from room temperature to 550℃ and held for 6 hours to obtain pure-phase MCM-68 molecular sieve with a yield of 65%. XRD results are shown in the appendix. Figure 6 .

[0125] Experimental Example 3

[0126] MSE molecular sieves (silicon-to-aluminum ratio of 18) were synthesized using OSDA3 as a structure directing agent.

[0127] 1) The OSDA3 prepared in Example 3 was dispersed in deionized water, and then a certain amount of OH-type resin was added. The ratio of OSDA3, deionized water and OH-type resin was 1:3:5. The mixture was exchanged three times, and the water was removed by rotary evaporation to obtain OH-type resin. - Type OSDA3; Weigh 0.332g OH - Mix OSDA3 and 4.5g of deionized water at room temperature until homogeneous.

[0128] 2) Add 0.247g of potassium hydroxide (purity: 85%) to the solution obtained in step 1) and stir again until homogeneous;

[0129] 3) Add 0.055g of aluminum hydroxide powder (purity: 78%) to the solution obtained in step 2), stir to form a homogeneous solution, and let it stand statically for 12h at 120℃.

[0130] 4) Add 1.50 g of silica sol (Ludox-AS-40) to the solution obtained in step 3) and stir at room temperature for 24 h. Transfer the resulting solution to a 50 mL hydrothermal reactor and add 0.10 g of MCM-68 molecular sieve from Comparative Example 1 as seed crystals. Perform dynamic hydrothermal crystallization at 160 °C for 240 h.

[0131] 5) Centrifuge, wash, and dry the solid obtained in step 4) at 1℃·min -1 The temperature was increased from room temperature to 550℃ and held for 6 hours to obtain pure-phase MCM-68 molecular sieve with a yield of 67%. XRD results are shown in the appendix. Figure 7 .

[0132] Test Example 4

[0133] MSE molecular sieves (silicon-to-aluminum ratio of 22) were synthesized using OSDA3 as a structure directing agent.

[0134] 1) Weigh out 0.332g of OH - Mix OSDA3 and 4.5g of deionized water at room temperature until homogeneous.

[0135] 2) Add 0.247g of potassium hydroxide (purity: 85%) to the solution obtained in step 1) and stir again until homogeneous;

[0136] 3) Add 0.045g of aluminum hydroxide powder (purity: 78%) to the solution obtained in step 2), stir to form a homogeneous solution, and let it stand statically for 12h at 120℃.

[0137] 4) Add 1.50g of silica sol (Ludox-AS-40) to the solution obtained in step 3) and stir at room temperature for 24h. Transfer the resulting solution to a 50mL hydrothermal reactor without adding any seed crystals and perform dynamic hydrothermal crystallization at 160℃ for 336h.

[0138] 5) Centrifuge, wash, and dry the solid obtained in step 4) at 1℃·min -1 The temperature was increased from room temperature to 550℃ and held for 6 hours to obtain pure-phase MCM-68 molecular sieve with a yield of 68%. XRD results are shown in the appendix. Figure 8 The SEM test results are attached. Figure 10 .Depend on Figure 10 It can be seen that the particle size distribution of the MCM-68 molecular sieve prepared in this example is in the range of 50-120 nm.

[0139] Catalytic evaluation

[0140] Using the MCM-68 molecular sieves from the above experimental examples and comparative examples as catalysts in the catalytic cracking reaction of n-heptane, the specific steps include:

[0141] 1) Exchange treatment: The MCM-68 molecular sieves of each experimental example and comparative example were mixed with NH4Cl solution (0.5-1M) in a certain proportion, refluxed at 80℃ for 12h, and the exchange was repeated at least 3 times. After centrifugation, washing and drying, NH4-type molecular sieves were obtained. -1 The heating rate was increased from room temperature to 550℃, and after holding at that temperature for 6 hours, H-type molecular sieve was obtained.

[0142] 2) Dealuminization treatment: Each H-type MCM-68 molecular sieve undergoes the following dealuminization treatment: The H-type MCM-68 molecular sieve is mixed with 0.5-6M HNO3 solution at a liquid-to-solid ratio of 100ml:1g, stirred and refluxed at 25-120℃ for 5-24h, centrifuged, washed, and dried, and then discharged at 1℃·min. -1 The heating rate was increased from room temperature to 550℃, and after holding at that temperature for 6 hours, the dealuminized MCM-68 molecular sieve was obtained.

[0143] Among them, the silicon-aluminum ratio of the MCM-68 molecular sieves in the experimental example and the comparative example after dealuminization was 50. The MCM-68 molecular sieves in experimental example 4 and the comparative example 1 after dealuminization were denoted as deAl-OSDA3-MSE(50) and deAl-TEBOP-MSE(50), respectively.

[0144] 3) Catalytic reaction of n-heptane: reaction temperature 640℃, catalyst loading 0.20g, weight hourly space velocity = 15h -1 g 正庚烷 g 催化剂. -1 Nitrogen flow rate 20 mL·min -1 .

[0145] The initial conversion rate and the conversion rate after 12 h of n-heptane are shown in Table 2. The conversion rates of n-heptane catalyzed by deAl-OSDA3-MSE(50) and deAl-TEBOP-MSE(50) change with time are shown in Table 2. Figure 11 As shown.

[0146] Table 2:

[0147] catalyst Initial conversion rate Conversion rate after 12 hours Experimental Example 1 96.4％ 52.3％ Experimental Example 2 96.7％ 49.6％ Experimental Example 3 97.1％ 56.8％ Test Example 4 97.4％ 57.5％ Comparative Example 1 96.2％ 42.5％

[0148] As can be seen from Table 2, the molecular sieves used in Comparative Example 1 and each experimental example were used to catalyze the cracking of n-heptane. The initial conversion rate of n-heptane was relatively high. However, after 12 hours, the molecular sieves in each experimental example showed significantly better catalytic stability.

[0149] from Figure 11 As can be seen from the blank test without catalyst ( Figure 11(In the dashed section), the conversion rate of n-heptane thermal cracking was 25.2%; the initial conversion rates of deAl-TEBOP-MSE(50) and deAl-OSDA3-MSE(50) were both high, reaching 96.2% and 97.4% respectively, which is attributed to their high acid density, which greatly promoted the conversion of raw materials. After 12 hours of reaction, the n-heptane conversion rate of deAl-TEBOP-MSE(50) decreased from 96.2% to 42.5%; while the n-heptane conversion rate of deAl-OSDA3-MSE(50) decreased from 97.4% to 57.5%, which is attributed to the high rigidity of the structure-directing agent of the present invention, the high carbon-nitrogen ratio, the small crystal size of the synthesized molecular sieve, and the good diffusion performance and catalyst stability.

[0150] In summary, the MSE molecular sieve synthesized by the structure-directing agent of this invention exhibits good catalytic performance and enhances catalyst stability during the catalytic cracking of n-heptane.

[0151] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A type of structure-directing agent for the synthesis of MSE molecular sieves, characterized in that, Including the compound shown in formula (1): In equation (1), X - The components are halide ions or hydroxide ions; R1 and R2 may be cyclic or non-cyclic. When R1 and R2 are non-cyclic, they are independently C1-C6 straight-chain alkyl or branched alkyl, or C3-C6 cycloalkyl. When R1 and R2 are cyclic, the cyclic structure of R1 and R2 is a five-membered ring, a six-membered ring, a branched five-membered ring, or a branched six-membered ring. R3 and R4 may be cyclic or non-cyclic. When R3 and R4 are non-cyclic, they are independently C1-C6 straight-chain alkyl or branched alkyl, or C3-C6 cycloalkyl. When R3 and R4 are cyclic, the cyclic structure of R3 and R4 is a five-membered ring, a six-membered ring, a branched five-membered ring, or a branched six-membered ring.

2. The structure-directing agent for synthesizing MSE molecular sieves according to claim 1, characterized in that, In formula (1), when R1 and R2 do not form a ring, they are each independently methyl, ethyl, propyl, or isopropyl; when R1 and R2 form a ring, the ring formed by R1 and R2 is a five-membered ring with at least one C1-C6 alkyl branch or a six-membered ring with at least one C1-C6 alkyl branch. And / or, when R3 and R4 are not cyclic, they are each independently methyl, ethyl, propyl, or isopropyl; when R3 and R4 are cyclic, the cyclic formation of R3 and R4 is a five-membered ring with at least one C1-C6 alkyl branch or a six-membered ring with at least one C1-C6 alkyl branch.

3. The structure-directing agent for synthesizing MSE molecular sieves according to claim 2, characterized in that, The rings R1 and R2 are either five-membered or six-membered rings with methyl groups; And / or, the R3 and R4 rings are five-membered or six-membered rings with methyl groups.

4. The structure-directing agent for synthesizing MSE molecular sieves according to claim 1 or 2, characterized in that, The cationic moiety of the compound of formula (1) includes one of the following structures:

5. A method for preparing a structure-directing agent for synthesizing MSE molecular sieves as described in any one of claims 1-4, characterized in that, Includes the following steps: A mixture comprising a first raw material, a second raw material, and a solvent is subjected to a reflux reaction, followed by separation and purification to obtain the structure-directing agent; The first raw material is 1,2,4,5-tetrabromotoluene or 1,2,4,5-tetrachlorotoluene; the second raw material is one of an amine compound or its derivative, pyrrole or its derivative, and piperidine or its derivative.

6. The preparation method according to claim 5, characterized in that, The molar ratio of the first raw material to the second raw material is 1:4-5; And / or, the reflux reaction is carried out at a temperature of 60-100°C for a time of 12-36 hours.

7. The preparation method according to claim 5, characterized in that, The separation and purification process includes the following steps: the liquid product obtained by reflux reaction is subjected to rotary evaporation to obtain a solid product, the solid product is washed with an organic solvent, and the product is obtained by filtration and vacuum drying to obtain the structure-directing agent.

8. A method for preparing a type of MSE molecular sieve, characterized in that, The step includes using the structure-directing agent as described in any one of claims 1-4.

9. The preparation method according to claim 8, characterized in that, Specifically, the following steps are included: 1) The structure-directing agent is optionally ion-exchanged, dispersed in a solvent, and an alkali source, an aluminum source, and a silicon source are added. After stirring, a gel product is obtained. 2) The gel product is subjected to hydrothermal crystallization treatment at 120-200℃ for 48-384h.

10. The preparation method according to claim 9, characterized in that, It also includes the following processes: The gel product and MSE molecular sieve seed crystals are mixed and then subjected to the hydrothermal crystallization treatment.

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