ZSM-5 molecular sieve and its preparation method and application

Abstract

The present invention relates to the field of molecular sieve technology, and discloses a ZSM-5 molecular sieve and a preparation method thereof. The method includes: after mixing a silicon source, an aluminum source, an alkali source and the template, the resulting mixture is sequentially subjected to solid phase crystallization and roasting; wherein the template contains at least one of the compounds shown in formula (1). After the template prepared by the present invention is mixed with a silicon source, an aluminum source and an alkali source, a multi-level pore ZSM-5 molecular sieve is prepared without adding a solvent and a mesoporous template, and the molecular sieve grain size is between 50-150nm. When the multi-level pore ZSM-5 molecular sieve of the present invention is used for methanol to olefins, it has a higher methanol conversion rate and a longer service life.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieves, and in particular to a ZSM-5 molecular sieve and a preparation method and application thereof. Background Art

[0002] Molecular sieves are a class of materials with three-dimensional, four-connected frameworks formed by shared vertices between phosphorus-oxygen tetrahedra or aluminum-oxygen tetrahedra. Due to their high thermal and hydrothermal stability, variable topology, and adjustable pore size, molecular sieves have broad and in-depth applications in catalysis, adsorption, and ion exchange.

[0003] ZSM-5 zeolite is a type of mesoporous molecular sieve with ten-membered ring cross-linked channels (straight channels with a pore size of 0.51×0.55nm along the B-axis and zigzag channels with a pore size of 0.53×0.56nm along the A-axis) and an MFI topology. ZSM-5 zeolite can be used in reactions such as alkylation, aromatization, and methanol to olefins (MTO). However, due to the limitations of the zeolite's nanopore structure, the diffusion rate of reactants and products in catalytic reactions is limited, resulting in severe carbon deposition on the catalyst. Constructing a multi-level pore structure in ZSM-5 zeolite is considered an effective way to improve the material's catalytic performance.

[0004] At present, multi-level pore ZSM-5 molecular sieves are usually prepared by post-treatment method and template method. The post-treatment method is to use acid or alkali to treat the microporous ZSM-5 molecular sieve to obtain a ZSM-5 molecular sieve with a multi-level pore structure. However, the post-treatment method will reduce the crystallinity of the ZSM-5 molecular sieve, produce a large amount of salt-containing wastewater, increase energy consumption, and become a limitation in its industrial application of molecular sieves. The preparation of multi-level pore ZSM-5 molecular sieves usually requires the addition of expensive mesoporous templates, and the mesoporous templates need to be calcined and removed later, which also increases the preparation cost of multi-level pore molecular sieves. At the same time, the traditional hydrothermal method for synthesizing molecular sieves often requires the consumption of a large amount of water solvent, producing a large amount of high-COD wastewater.

[0005] CN106185979A discloses a method for preparing a multi-level pore ZSM-5 molecular sieve. The method uses non-metallic mineral diatomite with a macroporous structure as a silicon source and utilizes a solid-phase solvent-free method to synthesize a ZSM-5 molecular sieve with a multi-level pore structure. However, since the non-metallic mineral diatomite contains a large amount of impurities, the crystallinity of the ZSM-5 molecular sieve is reduced. As a result, the prepared ZSM-5 molecular sieve has a large particle size and a long crystallization time. Summary of the Invention

[0006] In order to overcome the above technical problems, the present invention provides a ZSM-5 molecular sieve and a preparation method thereof. The ZSM-5 molecular sieve has a rich multi-level pore structure and a grain size between 50-150 nm.

[0007] During the synthesis of ZSM-5 molecular sieves, tetrapropyl quaternary ammonium salt (or tetrapropyl quaternary ammonium base) is usually introduced as a template. It is located in the pores or cages of the molecular sieve and plays the following roles in the formation of specific pores or cage structures (MFI structures): (1) space filling; (2) structural guidance. However, the ZSM-5 molecular sieve synthesized from tetrapropyl quaternary ammonium salt and inorganic substances only has a microporous structure, not a mesoporous structure. In the synthesis of mesoporous materials, the mesoporous template is usually used in conjunction with the raw materials to synthesize mesoporous materials, but conventional surfactants cannot guide the formation of MFI structures. Conventional understanding of those skilled in the art is, if the molecular size of template agent changes, unpredictable to the structural influence of the molecular sieve finally obtained, sometimes even can't obtain the molecular sieve (RRXu, WQPang, JHYu, QSHuo and JSChen, Chemistry of Zeolites and Related Porous Materials, Wiley, Singapore, 2007.), be difficult to realize in prior art and adopt a kind of template agent to synthesize the ZSM-5 molecular sieve with MFI structure, with micropore and mesoporous structure simultaneously.Yet the inventor finds in research process, when the molecular size synthesized by the present invention is combined with solid phase method greater than the template agent of tetrapropyl quaternary ammonium salt, the molecular sieve prepared not only has MFI structure, and contains micropore and mesoporous structure simultaneously, namely prepared the ZSM-5 molecular sieve with multi-level pore structure.

[0008] The first aspect of the present invention provides a method for preparing a ZSM-5 molecular sieve, comprising: mixing a silicon source, an aluminum source, an alkali source and a template, and then sequentially subjecting the resulting mixture to solid phase crystallization and calcination; wherein the template comprises at least one of the compounds represented by formula (1),

[0009]

[0010] Among them, R1 is a C2-C6 alkylene group, preferably a straight-chain alkylene group, and R2 is a C3-C5 straight-chain alkyl group, preferably a propyl group.

[0011] The "solid phase crystallization" mentioned in the present invention is relative to the "hydrothermal crystallization" in the hydrothermal synthesis of molecular sieves. The "solid phase crystallization" mentioned in the present invention refers to the preparation of ZSM-5 molecular sieves using a solid phase method, that is, the present invention does not require additional water to be added during the preparation of ZSM-5 molecular sieves.

[0012] The second aspect of the present invention provides a ZSM-5 molecular sieve prepared by the above method.

[0013] A third aspect of the present invention provides an application of the above-mentioned ZSM-5 molecular sieve in methanol to olefins.

[0014] Through the above technical solution, the present invention achieves the following beneficial effects:

[0015] After the template prepared by the present invention is mixed with a silicon source, an aluminum source, and an alkali source, a multi-level pore ZSM-5 molecular sieve is prepared without adding a solvent or a mesoporous template. The molecular sieve has an average grain size of 50-150 nm, an average mesopore diameter of 8-20 nm, and a specific surface area of ​​300-500 m 2 / g, the total pore volume is 0.2-0.4mL / g, the mesopore volume is 0.1-0.25mL / g, and the micropore volume is 0.09-0.15mL / g.

[0016] The multi-level pore ZSM-5 molecular sieve of the present invention does not require the addition of water during its preparation, resulting in a simple preparation method, a short crystallization time, low energy consumption, and reduced environmental pollution (less discharge of high-salt wastewater). Furthermore, the multi-level pore ZSM-5 molecular sieve does not require the addition of expensive mesoporous template agents (such as hexadecyltrimethylammonium bromide), thereby reducing the production cost of the multi-level pore ZSM-5 molecular sieve.

[0017] When the multi-level pore ZSM-5 molecular sieve of the present invention is used in methanol to olefins, it has a higher conversion rate and a longer service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the XRD pattern of the hierarchical pore ZSM-5 molecular sieve prepared in Example 1;

[0019] Figure 2 is a SEM image of the hierarchical pore ZSM-5 molecular sieve prepared in Example 1;

[0020] Figure 3 is a SEM image of the hierarchical pore ZSM-5 molecular sieve prepared in Example 1;

[0021] Figure 4 This is a TEM image of the hierarchical pore ZSM-5 molecular sieve prepared in Example 1. DETAILED DESCRIPTION

[0022] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0023] The first aspect of the present invention provides a method for preparing a ZSM-5 molecular sieve, comprising: mixing a silicon source, an aluminum source, an alkali source and a template, and then sequentially subjecting the resulting mixture to solid phase crystallization and calcination; wherein the template comprises at least one of the compounds represented by formula (1),

[0024]

[0025] Among them, R1 is a C2-C6 alkylene group, preferably a straight-chain alkylene group, and R2 is a C3-C5 straight-chain alkyl group, preferably a propyl group.

[0026] In the present invention, the C2-C6 alkylene group may be, for example, ethylene, propylene, isopropylene, butylene, isopropylene, pentylene, or hexylene.

[0027] In the present invention, the C3-C5 straight-chain alkyl group may be, for example, n-propyl, n-butyl, or n-pentyl.

[0028] According to a preferred embodiment of the present invention, the template is only at least one of the compounds represented by formula (1).

[0029] According to the present invention, preferably, the template is prepared by contacting an organic amine and a halogenated hydrocarbon in a solvent under nucleophilic substitution reaction conditions, and then subjecting the reaction product obtained by the contact to OH - That is, the method may further include the step of preparing the template as described above.

[0030] According to the present invention, preferably, the template does not include tetrapropyl quaternary ammonium salt, tetrapropyl quaternary ammonium base, or hexadecyl trimethyl quaternary ammonium salt.

[0031] According to the present invention, the types of the organic amine and the halogenated hydrocarbon are not particularly limited. Preferably, the organic amine is a monobasic fatty amine and the halogenated hydrocarbon is a dihalogenated hydrocarbon; more preferably, the monobasic fatty amine is C6-C 12 The monobasic fatty amine is a dihalogenated hydrocarbon of C2-C6; further preferably, the monobasic fatty amine is tri-n-propylamine, and the dihalogenated hydrocarbon is at least one of 1,6-dibromohexane, 1,4-dibromobutane and 1,6-diiodohexane.

[0032] According to a particularly preferred embodiment of the present invention, the preparation method of the template is as follows: under nucleophilic substitution reaction conditions, tri-n-propylamine and 1,4-dibromobutane are contacted in a solvent, and the reaction product obtained by contact is subjected to OH - Ion exchange.

[0033] According to the present invention, the amount of the dihalogenated hydrocarbon and the monobasic fatty amine is not particularly limited, as long as it can meet the amount required for the template reaction. Preferably, the molar ratio of the dihalogenated hydrocarbon to the monobasic fatty amine is 0.29-0.59:1.

[0034] According to the present invention, the types of the organic amine and the halogenated hydrocarbon are not particularly limited. Preferably, the organic amine is a dibasic fatty amine, and the halogenated hydrocarbon is a monohalogenated hydrocarbon; more preferably, the dibasic fatty amine is a C2-C6 dibasic fatty amine, and the monohalogenated hydrocarbon is a C3-C5 monohalogenated hydrocarbon; further preferably, the monohalogenated hydrocarbon is bromopropane and / or iodopropane, and the dibasic fatty amine is at least one of ethylenediamine, pentamethylenediamine and hexamethylenediamine.

[0035] According to a particularly preferred embodiment of the present invention, the preparation method of the template is as follows: under nucleophilic substitution reaction conditions, bromopropane or iodopropane is contacted with hexamethylenediamine in a solvent, and the reaction product obtained by the contact is subjected to OH - Ion exchange.

[0036] According to the present invention, the amount of the monohalogenated hydrocarbon and the dibasic fatty amine is not particularly limited, as long as it can meet the amount required for the template reaction. Preferably, the molar ratio of the monohalogenated hydrocarbon to the dibasic fatty amine is 3.8-7.6:1.

[0037] According to the present invention, the amounts of the solvent and the organic amine used are not particularly limited, as long as they can meet the amount required for the template reaction.

[0038] According to the present invention, preferably, the solvent is a C1-C5 monohydric alcohol, more preferably methanol and / or ethanol.

[0039] According to the present invention, preferably, the solvent is an anhydrous alcohol solvent.

[0040] According to the present invention, in order to avoid the influence of water on the structure of the template, preferably, anhydrous potassium carbonate is added to the solvent when preparing the template to absorb water in the solvent.

[0041] According to the present invention, the reaction conditions of the contact are not particularly limited. Preferably, the temperature of the contact is 50-100° C., and the time is 12-24 h.

[0042] According to the present invention, to improve the purity of the template, the preparation process of the template further includes rotary evaporation and washing of the reaction product obtained by contacting the organic amine and the halogenated hydrocarbon. The solid product obtained after the rotary evaporation and washing is then vacuum dried in a vacuum dryer. The washing conditions are not particularly limited. Preferably, the washing solvent is ethyl acetate and / or diethyl ether, and the number of washings is 3-5 times.

[0043] According to the present invention, the OH - Ion exchange can be a commonly used method in the art. Preferably, the OH - The specific process of ion exchange is: mixing and dissolving the solid product with an appropriate amount of water, then performing ion exchange with a strong basic anion exchange resin, and concentrating by rotary evaporation to obtain a template agent, wherein the water content of the template agent is 50-85% by weight.

[0044] According to the present invention, preferably, the strong basic anion exchange resin is 717 strong basic anion exchange resin.

[0045] According to the present invention, the amount of the silicon source is not particularly limited, as long as it can meet the requirements for molecular sieve preparation. Preferably, the amount of the silicon source is 0.5-3 g, preferably 1-2 g, relative to 1 g of the template.

[0046] According to the present invention, the amount of the aluminum source is not particularly limited, as long as it can meet the requirements for molecular sieve preparation. Preferably, the amount of the aluminum source is 0.001-0.1 g relative to 1 g of the template.

[0047] According to the present invention, the amount of the alkali source is not particularly limited, as long as it can meet the requirements for molecular sieve preparation. Preferably, the amount of the alkali source is 0.03-0.8 g relative to 1 g of the template.

[0048] According to the present invention, the type of silicon source is not particularly limited and can be any silicon source commonly used in the art. Preferably, the silicon source is an organic silicon source and / or an inorganic silicon source, more preferably at least one of silica gel, white carbon black, quartz, and sodium silicate; further preferably, silica gel.

[0049] According to the present invention, in order to improve the performance of the prepared ZSM-5 molecular sieve, preferably, the average pore size of the silica gel is 5-10 nm, the specific surface area is 100-300 m 2 / g, more preferably, the specific surface area is 200-300m 2 / g.

[0050] According to the present invention, in order to improve the performance of the prepared ZSM-5 molecular sieve, preferably, the average pore size of the white carbon black is 5-10 nm, the specific surface area is 50-300 m 2 / g, more preferably, the specific surface area is 100-200m 2 / g.

[0051] According to the present invention, the type of the aluminum source is not particularly limited and can be any aluminum source commonly used in the art. Preferably, the aluminum source is an organic aluminum source and / or an inorganic aluminum source, more preferably at least one of boehmite, sodium metaaluminate, elemental aluminum, aluminum oxide, and aluminum isopropoxide, and further preferably pseudo-boehmite and / or sodium metaaluminate.

[0052] According to the present invention, preferably, the alumina is γ-alumina.

[0053] According to the present invention, the type of the alkali source is not particularly limited, and can be any alkali source commonly used in the art. Preferably, the alkali source is an inorganic base, preferably sodium hydroxide and / or potassium hydroxide.

[0054] According to the present invention, the conditions for the solid phase crystallization can be selected within a wide range. Preferably, the temperature of the solid phase crystallization is 100-200°C, preferably 160-180°C, and the time is 1-8 hours, preferably 3-8 hours. The present invention does not require additional water to be added during the preparation of the ZSM-5 molecular sieve, that is, the solid phase crystallization process in the method of the present invention is carried out under substantially anhydrous conditions (the water content in the crystallization system is less than 50% by weight).

[0055] According to the present invention, the drying conditions can be selected within a wide range. Preferably, the drying temperature is 80-150° C. and the drying time is 5-10 hours.

[0056] According to the present invention, the calcination conditions can be selected within a wide range. Preferably, the calcination temperature is 500-600°C and the calcination time is 3-7 hours.

[0057] According to the present invention, in order to ensure that the raw materials are fully and evenly mixed, the method of the present invention further comprises the step of grinding the silicon source, aluminum source, alkali source and the template after mixing. Preferably, the grinding time is 5-20 minutes.

[0058] According to the present invention, the grinding method is not particularly limited, and can be manual grinding or mechanical grinding, as long as the silicon source, aluminum source, alkali source and the template are fully mixed.

[0059] According to the most preferred embodiment of the present invention, the preparation method of the ZSM-5 molecular sieve comprises the following steps:

[0060] (1) Anhydrous potassium carbonate and anhydrous ethanol are added to a flask, and then iodine propane and hexamethylenediamine are added to the flask, wherein the molar ratio of iodine propane to hexamethylenediamine is 4-4.5:1, and then the mixture is stirred at 50-60°C for 20-24 hours. After the reaction is completed, the mixture is rotary evaporated to a semi-solid state, and then washed with ether 3-5 times, and then freeze-dried in a vacuum to obtain a solid product. Water is then added to the solid product to dissolve it, and then ion exchange is carried out with 717 strong basic anion exchange resin, and then concentrated by rotary evaporation to obtain a template agent, wherein the template agent contains the compound represented by formula (I).

[0061] (2) The solid raw materials: fine silica gel, template, pseudo-boehmite and sodium hydroxide are then ground in a mortar for 15-20 minutes to fully mix, and then transferred to a stainless steel reactor lined with polytetrafluoroethylene, crystallized at 160-170°C for 5-6 hours, cooled to room temperature after crystallization, washed with deionized water until neutral, then dried at 100-105°C for 2.5-3 hours, and finally calcined at 500-510°C in an air atmosphere for 6-7 hours to obtain a ZSM-5 molecular sieve. In the most preferred embodiment of the present invention, the amount of fine silica gel used is 1-1.2g, the amount of pseudo-boehmite used is 0.01-0.02g, and the amount of sodium hydroxide used is 0.1-0.12g relative to 1g of template.

[0062] The second aspect of the present invention provides a ZSM-5 molecular sieve prepared by the above method.

[0063] According to the present invention, preferably, the average crystal size of the ZSM-5 molecular sieve is 50-150 nm; the average pore size of the mesopores of the ZSM-5 molecular sieve is 8-20 nm, and the specific surface area is 300-500 m 2 / g, and the total pore volume is 0.2-0.4mL / g.

[0064] A third aspect of the present invention provides an application of the above-mentioned ZSM-5 molecular sieve in methanol to olefins.

[0065] According to the present invention, the reaction conditions of methanol to olefins can be the reaction conditions commonly used in the art. Preferably, the reaction conditions of methanol to olefins include: temperature of 350-500°C, methanol mass space velocity of 0.5-10h -1 .

[0066] According to the present invention, preferably, the olefin is at least one of ethylene, propylene and butene.

[0067] The present invention will be described in detail below by way of examples.

[0068] The morphology and particle size of the molecular sieve were characterized by SEM, the instrument model was Hitachi SU1510;

[0069] The pore structure of the molecular sieve was characterized by BET and TEM. The instrument used for BET test was ASAP2020 model from Micromeritics; the instrument used for TEM test was JEM-2100F model.

[0070] The BET test method is as follows: take a certain amount of sample (about 0.1g), degas under 200℃ and 1mmHg vacuum conditions for 6 hours, and measure the nitrogen adsorption and desorption curve of the sample in liquid nitrogen (-196℃); then use NLDFT to calculate the pore size distribution and distribution of mesopores. The specific surface area test method is as follows: take a certain amount of sample (about 0.1g), vacuumize at 30℃ for 10 hours, and the vacuum degree is <6.67×10 2 Pa, and then the adsorption line data in the BET equation was used to calculate the specific surface area of ​​the sample.

[0071] TEM testing conditions were: an accelerating voltage of 200 kV, a point resolution of 0.23 nm, and a line resolution of 0.14 nm. Before testing, the sample was crushed and ground to 300 mesh, then suspended in ethanol. After ultrasonic dispersion at room temperature for 5-10 minutes, the upper suspension was pipetted onto a copper grid. After evaporation of the ethanol, HRTEM (high-resolution transmission electron microscopy) characterization was performed.

[0072] The crystal form of the molecular sieve was characterized by XRD, and the instrument used for the XRD test was a Smartlab X-ray diffractometer from Rigaku Corporation of Japan;

[0073] The average pore size of fine silica gel is 8nm and the specific surface area is 200m 2 / g;

[0074] The average pore size of white carbon black is 8nm and the specific surface area is 150m 2 / g;

[0075] Pseudoboehmite was purchased from Aladdin Reagent Company;

[0076] Tetrapropylammonium hydroxide was purchased from Aladdin Reagent Company;

[0077] The calculation formula for the conversion rate of methanol is Conv.(methanol)=(100-Sel. 未反应甲醇 ) / 100;

[0078] The calculation formula of silicon source conversion rate is: silicon element content in molecular sieve ÷ silicon element content in silicon source × 100%.

[0079] Preparation Example 1

[0080] 30 g of anhydrous potassium carbonate and 200 mL of anhydrous ethanol were added to a flask and stirred thoroughly. 200 g of bromopropane and 25 g of hexamethylenediamine were then added to the flask, and the mixture was stirred at 90° C. for 24 h. After the reaction, the mixture was rotary evaporated to a semi-solid state, washed three times with ethyl acetate, and then freeze-dried in a vacuum to obtain a solid product. Water was then added to the solid product to dissolve it, and ion exchange was performed with 717 strong basic anion exchange resin. After rotary evaporation and concentration, a template was obtained, wherein the template contained a compound represented by formula (I) (wherein R1 is hexamethylene and R2 is n-propyl); the water content in the template was 80% by weight.

[0081] Preparation Example 2

[0082] 30 g of anhydrous potassium carbonate and 150 mL of anhydrous ethanol were added to a flask and stirred thoroughly. 160 g of iodopropane and 25 g of hexamethylenediamine were then added to the flask, and the mixture was stirred at 50° C. for 24 h. After the reaction, the mixture was rotary evaporated to a semi-solid state, washed with ether five times, and then freeze-dried in a vacuum to obtain a solid product. Water was then added to the solid product to dissolve it, and ion exchange was performed with 717 strong basic anion exchange resin. After rotary evaporation and concentration, a template was obtained, wherein the template contained a compound represented by formula (I) (wherein R1 is hexamethylene and R2 is n-propyl); the water content in the template was 70% by weight.

[0083] Preparation Example 3

[0084] 30 g of anhydrous potassium carbonate and 150 mL of anhydrous ethanol were added to a flask and stirred thoroughly. 160 g of iodopropane and 25 g of pentamethylenediamine were then added to the flask, and the mixture was stirred at 80° C. for 12 h. After the reaction, the mixture was rotary evaporated until semi-solid, washed five times with ethyl acetate, and then freeze-dried in a vacuum to obtain a solid product. Water was then added to the solid product to dissolve it, and ion exchange was performed with 717 strong basic anion exchange resin. After rotary evaporation and concentration, a template was obtained, wherein the template contained a compound represented by formula (I) (wherein R1 is pentylene and R2 is n-propyl); the water content in the template was 70% by weight.

[0085] Preparation Example 4

[0086] 30 g of anhydrous potassium carbonate and 200 mL of anhydrous ethanol were added to a flask and stirred thoroughly. 90 g of 1,6-dibromohexane and 90 g of tri-n-propylamine were then added to the flask and reacted at 80° C. under stirring for 12 h. After the reaction, the material was rotary evaporated until semi-solid, washed three times with ethyl acetate, and then freeze-dried in a vacuum to obtain a solid product. Water was then added to the solid product to dissolve it, and ion exchange was performed with 717 strong basic anion exchange resin. After rotary evaporation and concentration, a template was obtained, wherein the template contained a compound represented by formula (I) (wherein R1 is hexamethylene and R2 is n-propyl); the water content in the template was 80% by weight.

[0087] Preparation Example 5

[0088] 30g of anhydrous potassium carbonate and 300mL of anhydrous ethanol were added to a flask and stirred thoroughly. 50g of 1,6-dibromohexane and 100g of tri-n-propylamine were then added to the flask and reacted at 60°C with stirring for 24h. After the reaction, the material was rotary evaporated to a semi-solid state, washed with ether three times, and then freeze-dried in a vacuum to obtain a solid product. Water was then added to the solid product to dissolve it, and ion exchange was performed with 717 strong basic anion exchange resin. After rotary evaporation and concentration, a template was obtained, wherein the template contained a compound represented by formula (I) (wherein R1 is hexamethylene and R2 is n-propyl); the water content in the template was 70% by weight.

[0089] Preparation Example 6

[0090] 30g of anhydrous potassium carbonate and 300mL of anhydrous ethanol were added to a flask and stirred thoroughly. 45g of 1,4-dibromobutane and 100g of tri-n-propylamine were then added to the flask and reacted at 80°C with stirring for 24h. After the reaction, the material was rotary evaporated to a semi-solid state, washed with ether three times, and then freeze-dried in a vacuum to obtain a solid product. Water was then added to the solid product to dissolve it, and then ion exchange was performed with 717 strong basic anion exchange resin. After rotary evaporation and concentration, a template was obtained, wherein the template contained a compound represented by formula (I) (wherein R1 is butylene and R2 is n-propyl); the water content in the template was 70% by weight.

[0091] Example 1

[0092] First, the solid raw materials: 1.5g fine silica gel, 1g template obtained in Preparation Example 1, 0.05g pseudo-boehmite, and 0.1g sodium hydroxide were placed in a mortar and ground for 5 minutes to fully mix them. Then, they were transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 180°C for 3 hours. After crystallization, they were cooled to room temperature, washed with deionized water until neutral, and then dried at 100°C for 5 hours. Finally, they were calcined at 550°C for 5 hours in an air atmosphere to obtain a hierarchical pore ZSM-5 molecular sieve.

[0093] XRD detection showed that ( Figure 1 ), there are characteristic peaks at 8° and 24°, etc., which proves that the molecular sieve prepared in Example 1 is ZSM-5 molecular sieve, and the peak shape is relatively sharp, indicating that the crystallinity of ZSM-5 molecular sieve is high. Figure 2 and Figure 3 )Observe the ZSM-5 molecular sieve obtained in Example 1, and it can be seen that the average crystallite size of the ZSM-5 molecular sieve is 105nm. Figure 4 ) It can be seen that there are many mesopores inside the crystal of ZSM-5 molecular sieve. Figure 4 The white circles in the middle are relatively clear mesopores with a pore size range of 8-20 nm. The silicon source conversion rate is 80% by weight.

[0094] Example 2

[0095] First, the solid raw materials: 1g fine silica gel, 1g template obtained in Preparation Example 2, 0.01g pseudo-boehmite, 0.1g sodium hydroxide were placed in a mortar and ground for 20min to fully mix them. Then, they were transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 160°C for 5h. After crystallization, they were cooled to room temperature, washed with deionized water until neutral, and then dried at 100°C for 3h. Finally, they were calcined at 500°C for 7h in an air atmosphere to obtain ZSM-5 molecular sieve. XRD characterization results are consistent with those of the ZSM-5 molecular sieve. Figure 1 The conversion rate of the silicon source was 80 wt %.

[0096] Example 3

[0097] First, the solid raw materials: 2g fine silica gel, 1g template obtained in Preparation Example 3, 0.01g pseudo-boehmite, 0.05g sodium hydroxide were placed in a mortar and ground for 10min to fully mix them. Then, they were transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 150°C for 8h. After crystallization, they were cooled to room temperature, washed with deionized water until neutral, and then dried at 100°C for 10h. Finally, they were calcined at 600°C in an air atmosphere for 3h to obtain ZSM-5 molecular sieve. XRD characterization results are consistent with Figure 1 The conversion rate of the silicon source was 90 wt %.

[0098] Example 4

[0099] First, the solid raw materials: 0.5g fine silica gel, 1g template obtained in Preparation Example 4, 0.1g pseudo-boehmite, 0.2g sodium hydroxide were placed in a mortar and ground for 5min to fully mix them. Then, they were transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 200℃ for 2h. After the crystallization was completed, they were cooled to room temperature, washed with deionized water until neutral, and then dried at 100℃ for 5h. Finally, they were calcined at 550℃ in an air atmosphere for 5h to obtain a multi-level porous ZSM-5 molecular sieve. XRD characterization results are consistent with Figure 1 The conversion rate of the silicon source was 70 wt %.

[0100] Example 5

[0101] First, the solid raw materials: 3g fine silica gel, 1g template obtained in Preparation Example 5, 0.001g pseudo-boehmite, 0.1g sodium hydroxide were placed in a mortar and ground for 5min to fully mix them. Then, they were transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 100℃ for 5h. After the crystallization was completed, they were cooled to room temperature, washed with deionized water until neutral, and then dried at 100℃ for 5h. Finally, they were calcined at 550℃ in an air atmosphere for 5h to obtain a multi-level porous ZSM-5 molecular sieve. XRD characterization results are consistent with Figure 1 The conversion rate of the silicon source was 90 wt %.

[0102] Example 6

[0103] First, the solid raw materials: 2g of white carbon black, 1g of the template obtained in Preparation Example 6, 0.05g of pseudo-boehmite, and 0.15g of sodium hydroxide were placed in a mortar and ground for 10 minutes to fully mix them. Then, they were transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 200°C for 2 hours. After crystallization, they were cooled to room temperature, washed with deionized water until neutral, and then dried at 100°C for 10 hours. Finally, they were calcined at 600°C in an air atmosphere for 3 hours to obtain ZSM-5 molecular sieve. XRD characterization results are consistent with those of the embodiment of the present invention. Figure 1 The conversion rate of the silicon source was 90 wt %.

[0104] Example 7

[0105] First, the solid raw materials: 2.5g of white carbon black, 1g of the template obtained in Preparation Example 1, 0.025g of sodium aluminate, and 0.01g of sodium hydroxide were placed in a mortar and ground for 15 minutes to fully mix them. Then, they were transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 180°C for 5 hours. After crystallization, they were cooled to room temperature and washed with deionized water until neutral. Then, they were dried at 100°C for 10 hours and finally calcined at 600°C for 3 hours in an air atmosphere to obtain ZSM-5 molecular sieve. XRD characterization results are consistent with those of the above. Figure 1 The conversion rate of the silicon source was 80 wt %.

[0106] Example 8

[0107] First, the solid raw materials: 0.67g white carbon black, 1g template obtained in Preparation Example 1, 0.003g sodium aluminate, 0.03g sodium hydroxide were placed in a mortar and ground for 15min to fully mix them. Then, they were transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 150°C for 5h. After crystallization, they were cooled to room temperature, washed with deionized water until neutral, and then dried at 100°C for 10h. Finally, they were calcined at 600°C for 3h in an air atmosphere to obtain ZSM-5 molecular sieve. XRD characterization results are consistent with Figure 1 The conversion rate of the silicon source was 90 wt %.

[0108] Example 9

[0109] The molecular sieve was prepared according to the method of Example 1, except that the silicon source used was coarse-porous silica gel with an average pore size of 30 nm and a specific surface area of ​​120 m 2 / g, pore volume 0.45mL / g. XRD characterization results and Figure 1 The conversion rate of the silicon source was 80 wt %.

[0110] Example 10

[0111] Molecular sieves were prepared according to the method of Example 1, except that the amount of fine silica gel used was 5 g, the amount of pseudoboehmite used was 1.5 g, and the amount of sodium hydroxide used was 2 g. XRD characterization results showed that no molecular sieve sample with an MFI topology was obtained.

[0112] Comparative Example 1

[0113] The molecular sieve was synthesized by hydrothermal method: 1.5g of fine silica gel, 1g of the template obtained in Preparation Example 1, 0.05g of pseudo-boehmite, 0.1g of sodium hydroxide and 100mL of deionized water were stirred and mixed at room temperature, and then transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 180℃ for 24h, cooled at room temperature, washed with deionized water until neutral, and then dried at 100℃ for 5h. Finally, it was calcined at 550℃ for 5h in air atmosphere to obtain the molecular sieve product. XRD characterization results are consistent with Figure 1 The conversion rate of the silicon source was 50 wt %.

[0114] Comparative Example 2

[0115] Under hydrothermal conditions, tetrapropylammonium hydroxide was used as a template to synthesize ZSM-5 molecular sieves. 0.05g of pseudo-boehmite and 40g of tetrapropylammonium hydroxide aqueous solution (the mass fraction of the tetrapropylammonium hydroxide aqueous solution was 20wt.%) were added to 30g of deionized water. After dissolution, 5g of fine silica gel was added. After stirring at room temperature for 2h, the synthesized gel was transferred to a stainless steel reactor lined with polytetrafluoroethylene and crystallized at 180℃ for 48h, then dried at 100℃ for 5h, and finally calcined at 550℃ in an air atmosphere for 5h to obtain a molecular sieve product to prepare a microporous ZSM-5 molecular sieve. XRD characterization results are consistent with those of the above. Figure 1 The conversion rate of the silicon source was 60 wt %.

[0116] Test Example 1

[0117] The structures of the ZSM-5 molecular sieves prepared in Examples 1-9 and Comparative Examples 1-2 were characterized, and the results are shown in Table 1.

[0118] Table 1

[0119]

[0120] Test Example 2

[0121] The ZSM-5 molecular sieves prepared in Examples 1-9 and Comparative Examples 1-2 were used as catalysts for methanol to olefins. The reaction conditions for methanol to olefins included: a temperature of 480° C., a pressure of atmospheric pressure, a mass space velocity of methanol of 1 h -1 The catalyst lifespan was investigated. Catalyst lifespan is characterized by the time it takes for the catalyst to deactivate. Catalyst deactivation is defined as the time it takes for the catalyst conversion rate to fall below 90% of the initial conversion rate of 100% in a single catalytic reaction. The results are shown in Table 2.

[0122] Table 2

[0123] Time (h) Lifespan (h) Example 1 178 Example 2 187 Example 3 178 Example 4 165 Example 5 147 Example 6 145 Example 7 126 Example 8 125 Example 9 126 Comparative Example 1 70 Comparative Example 2 35

[0124] It can be seen from the results in Table 2 that the ZSM-5 molecular sieve with multi-level pores prepared by the present invention has a long catalyst life when used in methanol to olefins.

[0125] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing ZSM-5 molecular sieve, characterized in that: The method comprises: mixing a silicon source, an aluminum source, an alkali source and a template, and then subjecting the obtained mixture to solid phase crystallization and calcination; wherein the template contains at least one of the compounds represented by formula (1), Formula (1) wherein R1 is one of hexylene, pentylene and butylene, and R2 is n-propyl; Relative to 1g of template, the amount of silicon source used is 0.5-3g, and the amount of aluminum source used is 0.001-0.1g; The silicon source is at least one of silica gel, white carbon black, quartz and sodium silicate; The aluminum source is at least one of boehmite, sodium metaaluminate, aluminum, aluminum oxide, and aluminum isopropoxide; Wherein, relative to 1g of template agent, the amount of alkali source used is 0.03-0.8g; Wherein, the temperature of the solid phase crystallization is 100-200° C., and the time is 1-8 hours.

2. The method according to claim 1, wherein the template is prepared by contacting an organic amine and a halogenated hydrocarbon in a solvent under nucleophilic substitution reaction conditions, and then subjecting the reaction product obtained by the contact to OH - ion exchange; Alternatively, the templating agent does not include tetrapropylammonium salt, tetrapropylammonium base, and cetyltrimethylammonium salt.

3. The method according to claim 2, wherein: The organic amine is a monobasic fatty amine, and the halogenated hydrocarbon is a dihalogenated hydrocarbon; the molar ratio of the dihalogenated hydrocarbon to the monobasic fatty amine is 0.29-0.59:

1.

4. The method according to claim 3, wherein: The monobasic fatty amine is tri-n-propylamine, and the dihalogenated hydrocarbon is at least one of 1,6-dibromohexane, 1,4-dibromobutane and 1,6-diiodohexane.

5. The method according to claim 2, wherein: The organic amine is a dibasic fatty amine, and the halogenated hydrocarbon is a monohalogenated hydrocarbon; the molar ratio of the monohalogenated hydrocarbon to the dibasic fatty amine is 3.8-7.6:

1.

6. The method according to claim 5, wherein: The monohalogenated hydrocarbon is bromopropane and / or iodopropane, and the dibasic fatty amine is at least one of ethylenediamine, pentamethylenediamine and hexamethylenediamine.

7. The method according to claim 2, wherein: The contact temperature is 50-100°C and the contact time is 12-24h; And / or, the solvent is a C1-C5 monohydric alcohol.

8. The method according to claim 7, wherein: The solvent is methanol and / or ethanol.

9. The method according to claim 1, wherein: The alkaline source is an inorganic base; And / or, the average pore size of the silica gel is 5-10 nm, the specific surface area is 100-300 m 2 / g.

10. The method according to claim 9, wherein: The alkali source is sodium hydroxide and / or potassium hydroxide.

11. The method according to claim 1, wherein The calcination temperature is 500-600° C. and the calcination time is 3-7 hours.

12. A ZSM-5 molecular sieve, characterized in that The ZSM-5 molecular sieve is prepared by the method according to any one of claims 1 to 11.

13. Application of ZSM-5 molecular sieve in methanol to olefins, characterized in that: The ZSM-5 molecular sieve is prepared by the method according to any one of claims 1 to 11.

14. The use according to claim 13, wherein: The reaction conditions of methanol to olefins include: temperature of 350-500°C, methanol mass space velocity of 0.5-10h -1 .

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