WO2016086362A1

WO2016086362A1 - Method for synthesizing multilevel pore zsm-5 zeolite

Info

Publication number: WO2016086362A1
Application number: PCT/CN2014/092836
Authority: WO
Inventors: 王林英; 田鹏; 刘中民; 杨虹熠; 袁扬扬; 王德花
Original assignee: 中国科学院大连化学物理研究所
Priority date: 2014-12-02
Filing date: 2014-12-02
Publication date: 2016-06-09

Abstract

The present application relates to a high-yield method for synthesizing multilevel pore ZSM-5 zeolite. Per the method, in which no hard templating agent is used, the multilevel pore ZSM-5 zeolite having a high crystallinity, strong acidity, and great hydrothermal stability is synthesized from a small amount of a microporous templating agent and a polyquaternium.

Description

Method for synthesizing multistage pore ZSM-5 molecular sieve

Technical field

The present application relates to a method for synthesizing a multi-stage pore ZSM-5 molecular sieve. The present application also relates to the use of the above multistage pore ZSM-5 molecular sieve as a solid acid catalyst.

Background technique

The United States Mobil Company first reported the synthesis of ZSM-5 molecular sieves in 1972. The material has one of the most important molecular sieve catalytic materials in industrial applications due to its pore structure, acid center strength and density, high stability and unique shape-selection properties.

However, due to the single pore structure and small pore size of ZSM-5 molecular sieve, the diffusion resistance of large-sized molecules in the pore channel is increased, which limits its application in the catalytic reaction involving macromolecules. In recent years, researchers have attempted to solve this problem by introducing mesopores into zeolites by various methods. One of them is the “post-treatment method”, which mainly includes high-temperature heat treatment, steam heat treatment, acid treatment, alkali treatment, and the like. However, the mesopores obtained by the post-treatment method are irregular, and often accompanied by the collapse of the skeleton structure, and the processing conditions of the post-treatment method are relatively harsh and complicated to operate. Later, the "template method" was gradually developed, that is, mesopores were generated during micropore synthesis, mainly including various hard template methods. [JACs 2000, 122(29)7116] reported the synthesis of mesoporous single crystal ZSM-5 zeolite using mesoporous carbon black as a template; [Chem. Mater., 2001, 13(12): 4416] reported the use of carbon nanotubes. Synthesis of mesoporous ZSM-5 single crystals for hard template; [Chem. Mater., 2007, 19(12): 2915] reported the preparation of carbon/silicon composites using sucrose and silica to synthesize microporous ZSM-5 Single crystal. Although the sample obtained by the above method is subjected to high-temperature baking, a molecular sieve containing both mesoporous and microporous structures can be obtained. However, the carbon template used in the above method is expensive, the synthesis operation process is complicated, and all involve a large amount of microporous guiding agent, so the cost is high and the environmental pollution is heavy, which is not suitable for large-scale industrial applications.

Therefore, it is of great practical significance to develop a low-cost environmentally friendly route with high hydrothermal stability and strong acid microporous ZSM-5 molecular sieve.

Summary of the invention

According to one aspect of the present application, a method of synthesizing a multistage pore ZSM-5 molecular sieve in high yield is provided. The method can synthesize a multi-stage pore ZSM-5 molecular sieve with high crystallinity, high acidity and good hydrothermal stability by using a small amount of microporous templating agent and polyquaternary ammonium salt without using a hard templating agent.

The method for synthesizing the multi-stage pore ZSM-5 molecular sieve is characterized in that it comprises at least the following steps:

a) mixing the silicon source, the aluminum source, the templating agent R and water to obtain the initial gel mixture A having the following molar ratio:

SiO ₂ :Al ₂ O ₃ =20～1000:1

R: Al ₂ O ₃ = 3.46 to 112.6: 1

H ₂ O: Al ₂ O ₃ = 160 to 9600:1;

b) the initial gel mixture A is dynamically crystallized at 120 ~ 200 ° C for 0.5 ~ 16h, to obtain a precursor I;

c) mixing a silicon source, an aluminum source, an alkali source, and water to form an initial gel mixture B having the following molar ratio:

SiO ₂ :Al ₂ O ₃ =20～1000:1

Alkali source: Al ₂ O ₃ = 2.26 ~ 118.8: 1

H ₂ O: Al ₂ O ₃ =380～24000:1

d) adding a polyquaternary ammonium salt to the initial gel mixture B, to obtain a mixture C of a polyquaternium content of 0.01 to 10% by mass;

The mixture C is maintained at 80 to 100 ° C for 2 to 5 hours to obtain a precursor II;

e) mixing precursor I and precursor II, obtaining a mixture D having a precursor I content of 0.1 to 10% by mass, and crystallization of the mixture D at 120 to 220 ° C for 0.5 to 48 hours;

f) After the crystallization is completed in step e), the solid product is separated, washed and dried to obtain the multi-stage pore ZSM-5 molecular sieve.

In the initial gel mixture A of the step a), the silicon source is added in an amount of SiO ₂ ; the aluminum source is added in a molar amount of Al ₂ O ₃ ; and the templating agent R is added in an amount of R itself. The number of moles; the amount of water added is based on the moles of water itself.

Preferably, the silicon source in step a) is selected from at least one of silica sol, silicone gel, methyl orthosilicate, tetraethyl orthosilicate, and silica.

Preferably, the aluminum source in step a) is selected from at least one of aluminum isopropoxide, aluminum oxide, aluminum hydroxide, aluminum chloride, aluminum sulfate, aluminum nitrate, and sodium aluminate.

Preferably, the organic amine R in step a) is selected from at least one of n-butylamine, ethylenediamine, and tetrapropylammonium hydroxide.

Preferably, the temperature of the dynamic crystallization in step b) is from 160 to 180 °C.

Preferably, the crystallization time of the dynamic crystallization in step b) is 1 to 10 h.

In the initial gel mixture B in the step c), the silicon source is added in an amount of SiO ₂ ; the aluminum source is added in a molar amount of Al ₂ O ₃ ; the alkali source is added in an alkali source itself. In terms of moles, if the alkali source is ammonia, the amount of moles of ammonia in the ammonia water is used; the amount of water added is based on the moles of water itself.

Preferably, the silicon source in step c) is selected from at least one of silica sol, silicone gel, methyl orthosilicate, tetraethyl orthosilicate, and white carbon.

Preferably, the aluminum source in step c) is selected from at least one of aluminum isopropoxide, aluminum oxide, aluminum hydroxide, aluminum chloride, aluminum sulfate, aluminum nitrate, and sodium aluminate.

Preferably, the source of alkali in step c) is selected from at least one of the inorganic bases. Further preferably, the alkali source in step c) is sodium hydroxide and/or potassium hydroxide and/or ammonia water. Further preferably, the alkali source in step c) is sodium hydroxide and/or potassium hydroxide.

Preferably, the polyquaternium in step d) is selected from the group consisting of polyquaternium-6, polyquaternium-7, polyquaternium-10, polyquaternium-22, polyquaternium-32, At least one of polyquaternium-37, polyquaternium-39, and polyquaternium 44.

The polyquaternium P of the present invention is a polymer having a degree of polymerization of from 10 to 100,000, and the degree of polymerization refers to an average degree of polymerization, that is, an average value of the number of repeating units contained on a polymer macromolecular chain.

Wherein the polyquaternium-6 is a copolymer of dimethyldiallylammonium chloride having a molecular formula of (C ₈ H ₁₆ ClN) _n and n is a positive integer; the structural formula is:

The polyquaternium-7 is a dimethyldiallyl ammonium chloride-acrylamide copolymer having a molecular formula of (C ₈ H ₁₆ ClN) _n ·(C ₃ H ₅ NO) _m , m and n being positive Integer; structure is:

The polyquaternium-10 is also known as JR-400 or chlorinated 2-hydroxy-3-(trimethylamino)propyl polyepoxy Alkyl cellulose ether, the structural formula is:

m and n are positive integers.

The polyquaternium-22 is a dimethyldiallyl ammonium chloride-acrylic acid copolymer having a molecular formula of (C ₈ H ₁₆ ClN) n·(C ₃ H ₅ NO) _m ; m and n are positive integers The structural formula is:

The quaternary ammonium salt-32 is N,N,N-trimethyl-2-(2-methyl-1-oxo-2-propenyloxy)ethyl ammonium chloride-acrylamide copolymer, molecular formula Is (C ₉ H ₁₈ ClNO ₂ ) _n ·(C ₃ H ₅ NO) _m , m and n are positive integers; the structural formula is:

The quaternary ammonium salt-37 is a homopolymer of N,N,N-trimethyl-2-[(2-methyl-1-oxo-2-propenyl)oxy]ethylamine hydrochloride; Is (C ₉ H ₁₈ ClNO ₂ ) _n , n is a positive integer; the structural formula is:

The quaternary ammonium salt-39 is a dimethyl diallyl ammonium chloride-acrylamide-acrylic acid copolymer; the molecular formula is (C ₃ H ₄ O ₂ ) _p ·(C ₈ H ₁₆ ClN) _n ·(C ₃ H ₅ NO) _m ; p, m, n are positive integers; the structural formula is:

The polyquaternium-44 is N-vinylpyrrolidone and a quaternized ethylene imidazole copolymer; the molecular formula is (C ₆ H ₉ N ₂ ·C ₆ H ₉ NO·CH ₃ O ₄ S) _n , n is a positive integer The structural formula is:

Preferably, the crystallization temperature in step e) is from 160 to 200 °C.

Preferably, the crystallization time in step e) is from 1 to 24 h.

The crystallization in the step e) may be dynamic crystallization or static crystallization. Preferably, the crystallization in step e) is dynamic crystallization.

The separation method in the step f) is centrifugal separation or filtration separation.

According to still another aspect of the present application, there is provided a solid acid catalyst characterized in that the multistage pore ZSM-5 molecular sieve synthesized according to any of the above methods is obtained by ammonium exchange and calcination in air at 400 to 600 °C.

As a preferred embodiment, the solid acid catalyst is prepared by the following steps: impregnating a multi-stage pore ZSM-5 molecular sieve synthesized according to any of the above methods into a 1 mol/L NH ₄ NO ₃ solution, stirring not less than 2 After ammonium exchange for an hour, it is obtained by suction filtration, drying, and calcination in air at 400 to 600 °C. Further preferably, the above ammonium exchange step can be repeated 2 to 5 times.

The beneficial effects of the present application include at least:

(1) The yield of the method described in the present application is high, and the yield of the multistage pore ZSM-5 molecular sieve is higher than 95% by weight.

(2) The method described in the present application substantially reduces the amount of templating agent used in the synthesis of high purity ZSM-5 molecular sieves. In the synthesis process, the amount of the templating agent used in the precursor I was only 1/10 of that of the conventional synthesis method.

(3) The method described in the present application produces a multi-stage pore ZSM-5 molecular sieve without using a post-treatment method and without using a hard templating agent, thereby reducing the production cost.

(4) The method described in the present application can greatly shorten the crystallization time of the ZSM-5 molecular sieve, and the high-purity nano ZSM-5 molecular sieve can be obtained in as little as 30 minutes. In industrial production, production energy consumption can be significantly reduced, enabling dynamic continuous synthesis.

(5) The product of the method described in the present invention is easy to separate, simplifies the cumbersome steps of high-speed centrifugal separation of the product, reduces energy consumption, and is more conducive to large-scale synthesis and industrial application of the product.

(6) The multi-stage pore ZSM-5 molecular sieve synthesized by the method described in the present application has strong acidity and stability, and has important application value for some important catalytic reactions.

DRAWINGS

Figure 1 is an X-ray diffraction spectrum of Sample 1 ^# .

Figure 2 is a scanning electron micrograph of sample 1 ^# .

Figure 3 is a transmission electron micrograph of sample 1 ^# .

Figure 4 is a transmission electron diffraction pattern of sample 1 ^# .

Figure 5 is a N ₂ physisorption diagram of sample 1 ^# .

Figure 6 is a pore size distribution diagram of sample 1 ^# .

Figure 7 is a scanning electron micrograph of Comparative Sample 1 ^# .

Figure 8 is a scanning electron micrograph of Comparative Sample 2 ^# .

Figure 9 is a scanning electron micrograph of Comparative Sample 3 ^# .

Figure 10 shows the results of the reaction of methanol on the sample 1 ^# and the comparative sample 1 ^# on the dimethyl ether.

detailed description

The present application is described in detail below by way of examples, but the application is not limited thereto.

Unless otherwise specified, the test conditions of this application are as follows:

The elemental composition was measured using a Philips Magix-601 ray fluorescence analyzer (XRF).

X-ray powder diffraction phase analysis (XRD) was carried out using an X'Pert PRO X-ray diffractometer from the PANalytical Company of the Netherlands, a Cu target, a Kα radiation source (λ = 0.15418 nm), a voltage of 40 kV, and a current of 40 mA.

The SEM morphology analysis was performed using a SU8020 scanning electron microscope from the Scientific Instrument Factory of the Chinese Academy of Sciences.

TEM transmission electron microscopy and diffraction analysis were performed on a Philips Tecnai G220 transmission electron microscope with an acceleration voltage of 200 kV.

The N ₂ physical adsorption analysis was measured using a Micromeritics ASAP Model 2020 physical adsorption analyzer from Micron, USA.

Acidic samples Chembet-3000 type in the NH ₃ -TPD measurement instrument.

Example 1 Preparation of Sample 1 ^#

0.10 g of sodium metaaluminate was dissolved in 0.61 (25 wt%) g of n-butylamine aqueous solution, and then 5.25 g of silica sol (SiO ₂ : 30.54 wt%) was added dropwise to the above obtained solution under rapid stirring (300 rpm). In the middle, stirring was continued for 2 hours at room temperature until the mixture was uniformly mixed to obtain the initial gel mixture A. The molar ratio of each raw material in the initial gel mixture A is as follows: 50 SiO ₂ : 2.0 NaAlO ₂ : 3.9 C ₄ H ₁₁ N: 427H ₂ O. The initial gel mixture A was transferred to a stainless steel reactor equipped with a polytetrafluoro liner, and was dynamically crystallized at 160 ° C for 5 hours, and then cooled to room temperature to obtain a precursor I.

First, 0.62g sodium metaaluminate and 0.40g sodium hydroxide were dissolved in 20g of deionized water, then 10.00g of white carbon black was gradually added to the above obtained clear solution under rapid stirring (300rmp), and 44.8g was added. Ionic water was continued to stir at room temperature until it was mixed uniformly to obtain the initial gel mixture B. The molar ratio of each raw material in the initial gel mixture B is as follows: 50 SiO ₂ : 2.0 NaAlO ₂ : 3.9 C ₄ H ₁₁ N: 427 H ₂ O.

9.45 g of polyquaternium-6 was added to the initial gel mixture B, and stirred for 2 hours until the mixture was homogeneous to obtain a mixture C. The mixture C was placed in a closed vessel and heated to 80 ° C for 2 hours under stirring, and then cooled to room temperature to obtain a precursor II.

4.0 g of the precursor I was added to the precursor II, and stirring was continued for 0.5 h to obtain a mixture D. The mixture D was transferred to a stainless steel reaction vessel with a polytetrafluoro liner, and was spin-crystallized at 180 ° C for 4 h. The obtained solid product was centrifuged and dried at 120 ° C to obtain the multi-stage pore ZSM-5 molecular sieve. Record as sample 1 ^# .

Example 2 Preparation of Sample 2 ^# ～20 ^#

Sample ^# 2 - ^# 20 type materials, ratio of raw materials, the crystallization conditions shown in Table 1, Sample ^# 1 was prepared in the same procedure as in Example 1 Ingredients embodiment.

Table 1 molecular sieve synthesis ingredients and crystallization conditions

^a : In the initial gel mixture A, the silicon source is added in an amount of SiO ₂ ; the aluminum source is added in a molar amount of Al ₂ O ₃ ; and the templating agent R is added in a molar amount of the templating agent R itself. The amount of water added is based on the moles of water itself.

^b : in the initial gel mixture B, the silicon source is added in an amount of SiO ₂ ; the aluminum source is added in moles of Al ₂ O ₃ ; the alkali source is added in an amount of the base source itself. In the case of the number of moles of ammonia in the ammonia water, the amount of water added is based on the moles of water itself.

Comparative Example 1 Preparation of Comparative Sample 1 ^#

Sample ^# 11 was prepared in a specific ratio of ingredients, the blending process and the crystallization conditions being the same, but it was not added to the initial gel mixture polyquaternium-B, referred to as comparative sample resulting sample ^# 1.

Comparative Example 2 Preparation of Comparative Sample 2 ^#

The specific batch ratio, batching process and crystallization conditions were the same as those of the sample 1 ^# in Example 1, except that the activation temperature of the mixture C was changed to 25 ° C, and the obtained sample was recorded as Comparative Sample 2 ^# .

Comparative Example 3 Preparation of Comparative Sample 3 ^#

The specific proportion of ingredients, the batching process and the crystallization conditions were the same as those of the sample 1 ^# in Example 1, except that the time of initial crystallization of the initial gel mixture A was changed to 12 h, and the obtained sample was recorded as Comparative Sample 3 ^# .

Example 3 XRD analysis of sample 1 ^# ～20 ^# and comparative sample 1 ^# ～3 ^#

The phases of the samples 1 ^# to 20 ^# and the comparative samples 1 ^# to 3 ^# were analyzed by an X-ray diffraction method.

The results showed that the samples 1 ^# to 20 ^# and the comparative samples 1 ^# to 3 ^# prepared in Examples 1 and 2 were both high purity and high crystallinity ZSM-5 molecular sieves, and typically represented XRD of sample 1 ^# in Fig. 1. Spectrum. The XRD spectrum results of sample 2 ^# ～20 ^# and comparison sample 1 ^# ～3 ^# are close to those of Fig. 1, that is, the position and shape of the diffraction peak are basically the same, and the relative peak intensity fluctuates within ±5% according to the change of the synthesis condition, indicating Sample 1 ^# ～ 20 ^# and Comparative Sample 1 ^# ～3 ^# have the characteristics of the ZSM-5 structure and are free of crystals.

Example 4 SEM analysis of sample 1 ^# ～20 ^# and comparative sample 1 ^# ～3 ^#

The morphology of the obtained samples 1 ^# to 20 ^# and the comparative samples 1 ^# to 3 ^# were analyzed by scanning electron microscopy (SEM).

The results show that Example 12 and the resulting sample ^# 1 ~ ^# 20 is about 1μm grains, the grain surface is not smooth. Taking sample 1 ^# as a typical representative, the scanning electron micrograph is shown in Fig. 2 ^, and the SEM results of sample 2 ^# ～20 ^# are close to those in Fig. 2.

The SEM photograph of Comparative Sample 1 ^# is shown in FIG. It can be seen that Comparative Sample 1 ^# is a solid crystal whose surface is relatively smooth.

The SEM photograph of Comparative Sample 2 ^# is shown in FIG. It can be seen that Comparative Sample 2 ^# is a solid crystal with a slightly pleated surface.

The SEM photograph of Comparative Sample 3 ^# is shown in FIG. It can be seen that the comparative sample 3 ^# is a nanoparticle agglomerate of about 100 to 300 nm.

Example 5 Transmission electron microscopy analysis of sample 1 ^#

Sample ^# 1 is a transmission electron microscope is shown in Figure 3 and Figure 4, it can be seen, the sample ^# 1 with a cavity in the pore structure, crystal structure and individual particles remain.

Example 6 Sample 1 ^# ～ 20 ^# and Comparative Sample 1 ^# ～3 ^# Yield Calculation

The weights of the obtained sample 1 ^# to 20 ^# and the comparative sample 1 ^# to 3 ^# were measured, and the yield of the product was calculated. The results are shown in Table 2. The calculation formula is:

Yield = product mass / (dry basis mass in initial gel mixture A + dry basis weight in mixture C) x 100%.

Example 7 Sample 1 ^# ～ 20 ^# and Comparative Sample 1 ^# ～3 ^#的孔分析分析

The pore size distributions of the obtained samples 1 ^# to 20 ^# and the comparative samples 1 ^# to 3 ^# were analyzed by N ₂ physical adsorption, and the results are shown in Table 2.

The results showed that the samples 1 ^# to 20 ^# obtained in Examples 1 and 2 were ZSM-5 molecular sieves having a multi-stage pore size. Taking sample 1 ^# as a typical representative, the N ₂ physical adsorption and the pore size distribution map obtained from the adsorption branch data are shown in Fig. 4 and Fig. 5 respectively. As can be seen from the figure, it can be seen that the sample is at p/p ₀ = 0.4. The left and right intermediate pressure regions have obvious hysteresis loops, and have obvious pore size distributions at 4 nm and 10 to 35 nm, indicating that sample 1 ^# has both microporous and double mesoporous multi-stage pore structures. The N ₂ physical adsorption and pore size distribution of sample 2 ^# to 20 ^# are close to sample 1 ^# , and the specific results are shown in Table 2.

Comparative Sample N ₂ adsorption results ^# 1 ~ ^# 3 are displayed, Comparative Sample ^# 1 ~ ^# 3 having only micropores, mesopores have not.

Table 2

Example 8 Determination of Acid Performance of Sample 1 ^#

The acid center strength and acid center number of sample 1 ^# and commercially purchased ZSM-5 molecular sieve (20-50 nm, purchased from Nankai University Catalyst Factory) were determined by NH ₃ -TPD method. The results are shown in Table 3. The results show that the samples synthesized by the technical scheme described in the present application have more strong acid centers and total acid amounts.

Table 3 sample acid properties and silicon to aluminum ratio

^a : NH ₃ -TPD results, the weak acid is 100-300 ° C, and the strong acid is 300-600 ° C.

^b : Determined by XRF.

Example 9 Hydrothermal Stability

Sample 1 ^# and commercially available ZSM-5 molecular sieves (20-50 nm, purchased from Nankai University Catalyst Plant) were tested for hydrothermal stability. The test conditions were as follows: Sample 1 ^# and commercially purchased ZSM-5 molecular sieves were respectively placed at 100% steam at 800 ° C for 24 h. XRD and N ₂ adsorption were used to determine the change in crystallinity and pore structure.

The results show that the sample 1 ^# relative crystallinity after hydrothermal treatment (the ratio of the diffraction peak area at 2θ=7.8, 8.7, 23-25° before and after treatment in the XRD results) is 96%; the BET specific surface area is 450 cm ³ / g (464 cm ³ /g before treatment). After the commercial samples after hydrothermal treatment relative crystallinity was 73%, a specific surface area of 220cm ³ / g (pre-treatment of 355cm ³ / g).

Example 10 Evaluation of Methanol to Dimethyl Ether

Respectively obtained in Example 1 and the sample ^# 1 was evaluated for catalytic performance ^# 1 Comparative Example 1 Comparative sample obtained in methanol to dimethyl ether reactions.

Sample 1 ^# and comparative sample 1 ^# were ion exchanged by NH ₄ NO _{3 to} remove sodium ions, and calcined in air at 400 to 600 ° C for 4 hours, and then compressed and crushed to 20 to 40 mesh. 0.5 g of the sample was weighed into a fixed bed reactor, and at the beginning of the reaction, the catalyst was activated by nitrogen at 500 ° C for 2 hours, and then cooled to 260 ° C for reaction. The raw material methanol N ₂ is carried by the carrier gas, and the liquid hourly space velocity (LHSV) of methanol is 0.6 h ^-1 . The reaction was carried out under normal pressure and the product was tested on-line on an Agilent 7890A gas chromatograph equipped with a hydrogen flame detector (FID) and an HP-5 capillary column.

The results showed that the methanol conversion rate of sample 1 ^# was always above 95% within the reaction period of 0.5~5h, and the selectivity of dimethyl ether was always above 99.2%; the conversion rate of the comparison sample 1 ^# was from the original 94.6. % decreased to 89.1%, and the selectivity of dimethyl ether decreased from the initial 98.6% to 62.9%. After 5 h of reaction, the selectivity of methane on the sample 1 ^# was 0.3%, and the selectivity of ethane was 0.5%. The selectivity of methane on the sample 1 ^# was 15.2%, and the selectivity of ethane was 21.9. %. Figure 10 shows the results of the reaction at 5 h of the reaction. It can be seen that the multi-stage pore ZSM-5 molecular sieve prepared by the method of the present invention exhibits excellent catalytic activity and stability in the reaction of methanol to produce dimethyl ether.

The above description is only a few examples of the present application, and is not intended to limit the scope of the application. However, the present application is disclosed in the preferred embodiments, but is not intended to limit the application, any person skilled in the art, It is within the scope of the technical solution to make a slight change or modification equivalent to the equivalent embodiment when the technical content of the above disclosure is made without departing from the scope of the technical solution of the present application.

Claims

A method for synthesizing a multi-stage pore ZSM-5 molecular sieve, characterized in that it comprises at least the following steps:

a) mixing the silicon source, the aluminum source, the templating agent R and water to obtain the initial gel mixture A having the following molar ratio:

SiO 2 :Al 2 O 3 =20～1000:1

R: Al 2 O 3 = 3.46 to 112.6: 1

H 2 O: Al 2 O 3 = 160 to 9600:1;

b) the initial gel mixture A is dynamically crystallized at 120 ~ 200 ° C for 0.5 ~ 16h, to obtain a precursor I;

c) mixing a silicon source, an aluminum source, an alkali source, and water to form an initial gel mixture B having the following molar ratio:

SiO 2 :Al 2 O 3 =20～1000:1

Alkali source: Al 2 O 3 = 2.26 ~ 118.8: 1

H 2 O: Al 2 O 3 =380～24000:1

d) adding a polyquaternary ammonium salt to the initial gel mixture B, to obtain a mixture C of a polyquaternium content of 0.01 to 10% by mass;

The mixture C is maintained at 80 to 100 ° C for 2 to 5 hours to obtain a precursor II;

e) mixing precursor I and precursor II, obtaining a mixture D having a precursor I content of 0.1 to 10% by mass, and crystallization of the mixture D at 120 to 220 ° C for 0.5 to 48 hours;

f) after the crystallization is completed in step e), the solid product is separated, washed, and dried. Multistage pore ZSM-5 molecular sieves are described.
The method according to claim 1, wherein said silicon source in step a) is selected from at least one of silica sol, silicone gel, methyl orthosilicate, tetraethyl orthosilicate, and silica. The aluminum source is selected from at least one of aluminum isopropoxide, aluminum oxide, aluminum hydroxide, aluminum chloride, aluminum sulfate, aluminum nitrate, and sodium aluminate; the template R is selected from the group consisting of n-butylamine and ethylene At least one of an amine and tetrapropylammonium hydroxide.
The method according to claim 1, wherein the temperature of the dynamic crystallization in the step b) is 160 to 180 °C.
The method according to claim 1, wherein the crystallization time of the dynamic crystallization in the step b) is 1 to 10 h.
The method according to claim 1, wherein the silicon source in step c) is at least one selected from the group consisting of silica sol, silicone gel, methyl orthosilicate, tetraethyl orthosilicate, and white carbon black. The aluminum source is at least one selected from the group consisting of aluminum isopropoxide, aluminum oxide, aluminum hydroxide, aluminum chloride, aluminum sulfate, aluminum nitrate, and sodium aluminate; and the alkali source is at least one selected from the group consisting of inorganic bases. Kind.
The method of claim 1 wherein said source of alkali in step c) is sodium hydroxide and/or ammonia.
The method according to claim 1, wherein said polyquaternium in step d) is selected from the group consisting of polyquaternium-6, polyquaternium-7, polyquaternium-10, polyquaternium -22. At least one of polyquaternium-32, polyquaternium-37, polyquaternium-39, and polyquaternium-44.
The method of claim 1 wherein said crystallization in step e) is dynamic crystallization.
The method according to claim 1, wherein the crystallization temperature in the step e) is from 160 to 200 ° C for a period of from 1 to 24 hours.
A solid acid catalyst characterized in that the multistage pore ZSM-5 molecular sieve synthesized by the method according to any one of claims 1 to 9 is obtained by ammonium exchange and calcination in air at 400 to 600 °C.