阅读说明：本技术 一种zsm-5沸石及其制备方法和用途 (ZSM-5 zeolite, and preparation method and application thereof ) 是由 杨世和 洪梅 董磊 于 2021-06-30 设计创作，主要内容包括：本发明提供了一种ZSM-5沸石及其制备方法,并提供了ZSM-5沸石用作化学反应催化剂或催化剂载体的用途。本发明使用的原料简单,廉价易得,与沸石结晶兼容性好,不会破坏沸石的结晶,可以对沸石结晶过程进行灵活的调控,改变沸石的结晶行为,提高沸石结晶度,提高骨架硅铝比,减少骨架缺陷,提高了催化剂的活性和稳定性,有利于催化反应,制备工艺简单,利于工业化规模生产。另外,本发明制备的ZSM-5沸石还可作为半导体复合材料催化剂的载体材料,具有极高的兼容性,提高了其光催化反应效率。(The invention provides a ZSM-5 zeolite and a preparation method thereof, and provides an application of the ZSM-5 zeolite as a chemical reaction catalyst or a catalyst carrier. The invention has the advantages of simple raw materials, low price, easy obtainment, good compatibility with zeolite crystals, no damage to the zeolite crystals, flexible regulation and control of the zeolite crystallization process, change of the crystallization behavior of the zeolite, improvement of the crystallinity of the zeolite, improvement of the framework silica-alumina ratio, reduction of framework defects, improvement of the activity and stability of the catalyst, contribution to catalytic reaction, simple preparation process and contribution to industrial scale production. In addition, the ZSM-5 zeolite prepared by the invention can also be used as a carrier material of a semiconductor composite material catalyst, has extremely high compatibility and improves the photocatalytic reaction efficiency.)

1. A method for preparing ZSM-5 zeolite is characterized by comprising the following steps:

s1: according to the aluminum source: silicon source: quaternary ammonium cation templating agent: organic small molecule compound containing active hydrogen: the water molar ratio is (0.1-0.5): (1-10): (0.15-3): (0-3.5): (50-1000), slowly dissolving raw materials of an aluminum source, a silicon source, a quaternary ammonium cation template agent and an organic micromolecular compound containing active hydrogen in deionized water, and continuously stirring until a synthetic liquid is formed;

s2: aging the synthetic liquid for 1-5 days to obtain an aging liquid, then crystallizing the aging liquid at 100-200 ℃ for 24-72 hours, centrifugally washing for 2-4 times after crystallization is finished, and then drying at 50-70 ℃ overnight to obtain a dried substance; preferably, the aging temperature is 0-30 ℃; preferably, the crystallization time is 120-170 ℃;

s3: and calcining the dried substance obtained in the step S2 at 500-800 ℃ for 4-8 h to obtain the catalyst.

2. The method of preparing a ZSM-5 zeolite as claimed in claim 1, wherein the S1 specifically includes:

s11: according to the aluminum source: silicon source: quaternary ammonium cation templating agent: organic small molecule compound containing active hydrogen: the water molar ratio is 0.1: 10: 3: (0-3.5): weighing the raw materials according to the proportion of 1000;

s12: uniformly mixing an aluminum source and a silicon source to obtain stock solution;

s13: dissolving a quaternary ammonium cation template and an organic micromolecular compound containing active hydrogen in deionized water, and continuously stirring until a solution is formed;

s14: the stock solution obtained in S12 was slowly added to the solution obtained in S13 while stirring, and mixed uniformly to obtain a synthetic solution.

3. The method of preparing a ZSM-5 zeolite as claimed in claim 1, wherein the S1 specifically includes:

s11: according to the aluminum source: silicon source: quaternary ammonium cation templating agent: organic small molecule compound containing active hydrogen: the water molar ratio is 0.1: 10: 3: (0-3.5): weighing the raw materials according to the proportion of 1000;

s12: under the condition of continuous stirring, adding an aluminum source, a quaternary ammonium cation template and an organic small molecular compound containing active hydrogen into deionized water until the aluminum source, the quaternary ammonium cation template and the organic small molecular compound are completely dissolved to form a solution;

s13: the silicon source solution was slowly added to the solution formed in step S12 with vigorous stirring to form a synthetic solution.

4. The method for preparing ZSM-5 zeolite of any one of claims 1 to 3, wherein the aluminum source in S1 is selected from the group consisting of aluminum isopropoxide and Al₂(SO₄)₃Any one or more of pseudo-boehmite, aluminum sec-butoxide, aluminum hydroxide, aluminum oxide and aluminum simple substance.

5. The method for preparing ZSM-5 zeolite of any one of claims 1 to 3, wherein the silicon source in S1 is selected from SiO with an effective material content of 20-60% by mass₂Any one or more of sol, gas phase silicon dioxide, sodium silicate and ethyl orthosilicate.

6. The method for preparing ZSM-5 zeolite of any one of claims 1 to 3, wherein the quaternary ammonium cationic template in S1 is a tetrapropylammonium hydroxide (TPAOH) aqueous solution with a mass percent concentration of 10% to 40%.

7. The ZSM-5 zeolite of any one of claims 1-3, wherein in S1, the organic small molecule compound containing active hydrogen is selected from any one or more of phenol, alanine, lysine, 1,2, 4-triazole, trifluoroacetic acid, isobutyric acid or derivatives thereof.

8. The method for preparing ZSM-5 zeolite according to claim 1, wherein in S2, the crystallization is performed in a polytetrafluoroethylene-lined stainless steel autoclave, and the polytetrafluoroethylene-lined stainless steel autoclave is heated in a rotary oven with a rotation speed of 10-30 rpm.

9. A ZSM-5 zeolite, characterized in that it is obtained by the process of any one of claims 1 to 8.

10. The ZSM-5 zeolite according to claim 9, wherein the ZSM-5 zeolite has an ellipsoidal morphology with a particle size of 2 to 3 μm, and a molar ratio of the elements to silicon: aluminum is 50-150: 1; and the inner diameter of the inner mesopore is 8-20 nm.

11. Use of a ZSM-5 zeolite according to any of claims 9 to 10 as a catalyst or catalyst support.

12. Use according to claim 11, characterized in that the catalyst is used in the reaction of propylene from methanol.

13. Use according to claim 11, wherein the ZSM-5 zeolite is used as a catalyst support for the preparation of composite semiconductor photocatalysts.

14. Use according to claim 13, wherein the preparation of the composite semiconductor photocatalyst comprises the steps of:

mixing tetrabutyl titanate, ethanol and nitric acid according to a volume ratio of 5-8: 20-30: 1-5, stirring for 15-60 min at room temperature to form a solution, adding the ZSM-5 zeolite into the solution, stirring for 0.5-2 h to form a mixture, slowly adding 0.5-5 mL deionized water into the mixture, stirring, keeping the stirring speed at 40-80 rpm, controlling the reaction temperature at 60-80 ℃, hydrolyzing tetrabutyl titanate to enable tetrabutyl titanate to be adsorbed on the surfaces of ZSM-5 particles to form gel, drying at 90-110 ℃ for 10-15 h to remove the solvent, washing the ZSM-5 particles with water, and calcining at 300-500 ℃ for 1-3 h to obtain the composite semiconductor photocatalyst, wherein TiO in the composite semiconductor photocatalyst is TiO₂The ZSM-5 accounts for 5-50% of the mass of the ZSM-5.

Technical Field

The invention belongs to the technical field of catalyst preparation, and particularly relates to ZSM-5 zeolite and a preparation method and application thereof.

Background

The ZSM-5 zeolite catalyst is a catalyst for catalyzing the reaction of preparing propylene from methanol, but because the natural microporous ZSM-5 zeolite is not beneficial to macromolecular diffusion due to smaller micropore size, the problem of serious diffusion limitation is caused, and meanwhile, the intrinsic structure of the zeolite catalyst has poorer catalytic performance, so the structure of the zeolite needs to be optimized and improved.

Since zeolite materials have great application potential in the fields of energy and health, it is important to reasonably design and synthesize zeolite molecular sieves with target structures and properties. Although researchers have put great efforts on the controllable preparation of zeolite, including the adjustment of crystallization parameters and the use of some hard and soft templates, the crystallization mechanism is still poorly understood, and the rational control of nucleation and growth in the crystallization process of zeolite remains a great challenge. The prior zeolite crystallization theory is mainly divided into a classical crystallization theory and a non-classical crystallization theory, wherein the two theories are based on the addition process of nutrients, and the difference is that the nutrients in the classical crystallization theory are monomers of precursors, and the nutrients in the non-classical crystallization theory are oligomers, compounds, nanoparticles and the like of the precursors.

In the prior art, in order to realize the regulation and control of the specific functions of the microporous zeolite, the post-treatment method is greatly developed. In these post-treatment strategies, the use of high temperature steam, acid-base etching or hydrogen peroxide and microwave radiation to remove framework elements is often devastating to the structure of the zeolitic material, which can lead to the creation of secondary channels and the collapse of part of the framework structure, thereby reducing its crystallinity. The current commonly used post-treatment methods in the prior art include: steam treatment, acid treatment, desilication.

The steam treatment process is a hydrothermal treatment process, and generally needs to be carried out at a temperature of 500 ℃ or higher, and Si-O-Al bonds in zeolite are broken, resulting in loss of aluminum from the zeolite framework to prepare a secondary pore structure. While some less stable and mobile silicon may migrate elsewhere and condense with silanol at the defect healing process may result moreComplex hierarchical pore structures. Van Bokhoven et Al found that steam-induced structural changes did not occur at the highest temperatures when water entered the pores at relatively low temperatures using X-ray diffraction (XRD) and X-ray absorption Spectroscopy (XAS) in situ testing by Van Bokhoven et Al³⁺Migration to a position outside the frame is also most evident. And typically a mild acid treatment may be required after the steam treatment. According to this mechanism, the formation of mesopores is highly dependent on the Al concentration in the zeolite and the degree of hydrolysis of Al sites. Therefore, most of the steaming work is carried out on zeolites having a low initial Si/Al ratio.

Acid treatment is also a commonly used dealumination method, and the mechanism of secondary pore formation is the same as in steaming. Tromp et al performance tests in the hydroisomerization of n-hexane catalyzed by zeolite compared the activity of the acid-leached Pt/mordenite catalyst with the untreated Pt/mordenite catalyst; it was found that the activity of the acid-treated zeolite in the hydroisomerization of n-hexane was significantly increased, which may be attributed to the reduction of molecular diffusion paths and the exposure of more acidic sites.

Desilication is also a method for preparing hierarchical pore zeolite molecular sieves, generally by means of an alkaline treatment. In 1967, Young d.a. first synthesized mordenite which showed high crystallinity and had enhanced benzene adsorption capacity using a base treatment process.Et al studied the framework element profile in the alkali treatment of ZSM-5. Ogura et al prepared for the first time ZSM-5 crystals with a mesoporous structure treated with sodium hydroxide. Groen et al subsequently explored in detail the alkali treatment optimization conditions for mesopore formation; it has been found that for ZSM-5 crystals, a parent zeolite Si/Al ratio (50-100) is most suitable, producing a zeolite with a specific surface area of up to 235 m²·g^-1Meanwhile, the original crystallinity and acidity are kept; the mesopores produced are typically about 10nm with a relatively broad size distribution. When the Si/Al ratio is low, the formation of mesopores is limited by the repulsive force between OH-and the negatively charged lattice, whereas when it is lowWhen the Si/Al ratio is higher, more secondary pores are produced, but there is a severe loss of crystallinity. In addition to the Si/Al ratio, the morphology of the original zeolite (including large single crystals or intergrown small particles with large specific surface area) also has a strong influence on the dissolution process of desilication, where the boundaries and defect parts of the zeolite crystals are more easily dissolved and etched. Then, researchers introduced inorganic additives (e.g., Al (OH)) during the desilication process^4-And Ga (OH)^4-) Or organic additives (such as tetrapropylammonium and tetrabutylammonium) to adjust the secondary pore structure of the crystals. The studies by Perrez-Ramfirez et al show that the specific interaction of these additives with the zeolite surface under alkaline conditions provides protection against excessive dissolution of the zeolite, which enables the preparation of zeolites with smaller mesoporous structures. And by the zeolite retaining a better microporous structure than by standard alkali treatment, wherein the affinity of the additive to the zeolite surface is believed to play a critical role. Studies on different USY and Beta zeolites (Si/Al ═ 15-385) show that highly effective additives are positively charged organic molecules with about 10-20 carbon atoms. The use of external additives allows to extend the process to all-silica zeolites and to prevent excessive desilication phenomena, maintaining to a certain extent the Si/Al ratio of the zeolite crystals.

In addition to the above methods, calcination and chemical treatment with ammonium hexafluorosilicate, silicon tetrachloride or ethylenediaminetetraacetic acid have also been reported as dealumination methods for producing a hierarchical pore zeolite. This approach has not solved the diffusion limitation problem of microporous zeolites because the number of acid sites in the zeolite is reduced during dealumination due to the removal of aluminum atoms from the framework and it has also been found that the zeolite prepared by dealumination contains many independent cavities rather than an interconnected pore structure.

Regarding crystallization control, the current zeolite crystallization theory is mainly divided into a classical crystallization theory and a non-classical crystallization theory, and the two theories are based on the addition process of nutrients, and the difference is that the nutrients in the classical crystallization theory are monomers of precursors, and the nutrients in the non-classical crystallization theory are oligomers, compounds, nanoparticles and the like of the precursors. The specific mechanism of action of these crystallization mechanisms is not clear and is not flexible enough to control the zeolite structure and physicochemical properties. In addition, the zeolite with a core-shell structure can be synthesized by a crystal inverse growth theory which appears recently, but a plurality of additives are required to be added in the synthesis process, the synthesis steps are complicated, and the repeatability is poor.

Aluminosilicate zeolites, on the other hand, are effective supports for semiconductor photocatalysts and are commonly used to remove organic compounds from wastewater and air. The dispersing action of the aluminosilicate zeolite not only inhibits the growth and aggregation of the crystallite size of the semiconductor particles, but also facilitates the separation and recovery of the photocatalyst from the bulk medium. The zeolite carrier can be used as an adsorbent to pre-adsorb and condense organic compounds on the surface of the catalyst, which is beneficial to promoting the photocatalytic activity. The improvement of the photocatalytic performance of zeolite-based composite materials is mainly determined by the enhanced adsorption performance and the separation and transfer efficiency of photon-generated carriers. However, the existing zeolite carrier has the defects of low specific surface area, limited accessible catalytic sites, poor compatibility with semiconductor materials and the like.

Therefore, it is highly desirable to provide a zeolite catalyst with excellent catalytic performance, which is prepared by a simple preparation process, improves the crystallinity of zeolite, changes the framework silica-alumina ratio of zeolite, and optimizes the acid sites of zeolite, and is used as a carrier of a composite catalytic material.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides the following technical scheme:

the first aspect of the present invention provides a method for preparing a ZSM-5 zeolite, comprising the steps of:

s1: according to the aluminum source: silicon source: quaternary ammonium cation templating agent: organic small molecule compound containing active hydrogen: the water molar ratio is (0.1-0.5): (1-10): (0.15-3): (0-3.5): (50-1000), slowly dissolving raw materials of an aluminum source, a silicon source, a quaternary ammonium cation template agent and an organic micromolecular compound containing active hydrogen in deionized water, and continuously stirring until a synthetic liquid is formed;

s2: aging the synthetic liquid for 1-5 days at room temperature to obtain an aging liquid, then crystallizing the aging liquid at 100-200 ℃ for 24-72 hours, centrifugally washing for 2-4 times after crystallization is finished, and then drying at 50-70 ℃ overnight to obtain a dried substance; preferably, the aging time is 2 days; preferably, the aging temperature is 0-30 ℃; preferably, the crystallization time is 120-170 ℃; preferably, the centrifugal water washing times are 3; preferably, the drying temperature is 60 ℃;

s3: calcining the dried substance obtained in the step S2 at 500-800 ℃ for 4-8 h to obtain the catalyst; preferably, the calcination temperature is 550 ℃; preferably, the calcination time is 6 h;

further, the S1 specifically includes:

s11: according to the aluminum source: silicon source: quaternary ammonium cation templating agent: organic small molecule compound containing active hydrogen: the water molar ratio is 0.1: 10: 3: (0-3.5): weighing the raw materials according to the proportion of 1000;

s12: uniformly mixing an aluminum source and a silicon source to obtain stock solution;

s13: dissolving a quaternary ammonium cation template and an organic micromolecular compound containing active hydrogen in deionized water, and continuously stirring until a solution is formed;

s14: slowly adding the stock solution prepared in the step S12 into the solution prepared in the step S13 while stirring, and uniformly mixing to obtain a synthetic solution;

or further, the S1 specifically includes:

s11: according to the aluminum source: silicon source: quaternary ammonium cation templating agent: organic small molecule compound containing active hydrogen: the water molar ratio is 0.1: 10: 3: (0-3.5): weighing the raw materials according to the proportion of 1000;

s12: under the condition of continuous stirring, adding an aluminum source, a quaternary ammonium cation template and an organic small molecular compound containing active hydrogen into deionized water until the aluminum source, the quaternary ammonium cation template and the organic small molecular compound are completely dissolved to form a solution;

s13: slowly adding the silicon source solution into the solution formed in the step S21 while stirring vigorously to form a synthetic solution;

further, in S1, the aluminum source is selected from aluminum isopropoxide and Al₂(SO₄)₃Pseudo-boehmite, aluminum sec-butoxide, aluminum hydroxide, aluminum oxide,Any one or more of simple aluminum substances; preferably, the aluminum source is aluminum tri-sec-butoxide or Al₂(SO₄)₃；

Further, in S1, the silicon source is selected from SiO containing 20-60% of effective substances by mass₂Any one or more of sol, gas-phase silicon dioxide, sodium silicate and ethyl orthosilicate; preferably, the silicon source is sodium silicate or ethyl orthosilicate;

further, in S1, the quaternary ammonium cation template is a tetrapropyl ammonium hydroxide (i.e., TPAOH) aqueous solution with a mass percentage concentration of 10% to 40%; preferably, the mass concentration of the tetrapropylammonium hydroxide (namely TPAOH) aqueous solution is 40%;

further, in S1, the organic small molecule compound containing active hydrogen is selected from any one or more of phenol, alanine, lysine, 1,2, 4-triazole, trifluoroacetic acid, isobutyric acid or derivatives thereof; preferably, the small molecular compound containing active hydrogen is phenol;

further, in S2, the crystallization is performed in a polytetrafluoroethylene-lined stainless steel autoclave, and the polytetrafluoroethylene-lined stainless steel autoclave is heated in a rotary oven, wherein the rotation speed of the oven is 10-30 rpm;

the second aspect of the invention provides a ZSM-5 zeolite prepared by the above method;

further, the ZSM-5 zeolite has an oval shape, the particle size of the zeolite is 2-3 μm, and the molar weight ratio of the elements is silicon: aluminum is 50-150: 1; the inner diameter of the inner mesopore is 8-20 nm; preferably, the molar ratio of the elements silicon: the aluminum content is 80-140: 1; preferably, the ZSM-5 zeolite has a mesoporous inner diameter of 10 nm;

a third aspect of the invention provides the use of a ZSM-5 zeolite as described above as a catalyst or catalyst support;

further, the catalyst is used in the reaction of preparing propylene from methanol;

or further, the carrier used as the catalyst is used as a carrier for preparing the composite semiconductor photocatalyst; further, the preparation of the composite semiconductor photocatalyst comprises the following steps:

mixing tetrabutyl titanate, ethanol and nitric acid according to a volume ratio of 5-8: 20-30: 1-5, stirring for 15-60 min at room temperature to form a solution, adding ZSM-5 into the solution, stirring for 0.5-2 h to form a mixture, slowly adding 0.5-5 mL deionized water into the mixture, stirring, keeping the stirring speed at 40-80 rpm, controlling the reaction temperature at 60-80 ℃, hydrolyzing tetrabutyl titanate to enable tetrabutyl titanate to be adsorbed on the surfaces of ZSM-5 particles to form gel, drying at 90-110 ℃ for 10-15 h to remove the solvent, washing the ZSM-5 particles with water, and calcining at 300-500 ℃ for 1-3 h to obtain the composite semiconductor photocatalyst, wherein TiO in the composite semiconductor photocatalyst is TiO₂The ZSM-5 accounts for 5-50% of the mass of the ZSM-5.

Drawings

FIG. 1 is an evolution diagram of the etched time-varying structure of the crystal growth behavior of the ZSM-5 zeolite of example 1

FIG. 2 is a graph of the crystal crystallization time correlation spectrum of the ZSM-5 zeolite of example 1

FIG. 3 is a graph of the size, composition and crystallinity of the ZSM-5 zeolite of example 1

FIG. 4 is a control diagram of the mesoporosity of the ZSM-5 zeolite of example 1

FIG. 5 shows the catalytic performance reaction of ZSM-5 zeolite prepared in example 1 and 2 in MTP

FIG. 6 is a graph of the protocol and range study of nucleophilic etching growth in example 3

Advantageous effects

1. The organic micromolecule with active hydrogen contained in the raw material used by the invention has flexible and simple structure, low price and easy obtaining, good compatibility with zeolite crystal, no damage to the zeolite crystal, flexible regulation and control on the zeolite crystallization process, change of the crystallization behavior of the zeolite, further improve various physical and chemical properties of the zeolite, such as simultaneously improving the zeolite crystallinity, improving the framework silicon-aluminum ratio, enlarging the size and generating mesopores, the synthesized zeolite has a single crystal structure, the increase of the silicon-aluminum ratio is favorable for improving the catalyst stability, the acidity is moderate, and the catalytic reaction is favorable.

2. The synthesis method of the ZSM-5 zeolite is simple, convenient and feasible, low in synthesis temperature and low in cost. Because the reaction solution is not added with sodium hydroxide, ion exchange in the finished product is avoided; after the calcination, the preparation cost of the catalyst is obviously reduced, and the preparation procedure of the zeolite is simplified.

3. Because the catalyst has larger size, the tablet can carry out catalytic reaction, the pressure drop is small, and the catalytic conversion number (TON) and the conversion frequency (TOF) are also very high.

4. The ZSM-5 zeolite is used as a semiconductor photocatalyst carrier, has high specific area, high stability, good compatibility with semiconductor materials, capability of effectively separating photon-generated carriers, strong adsorption affinity with degraded reactants and remarkably improved photocatalytic efficiency.

Detailed Description

1.1 Experimental materials

All reagents were commercially available and used without purification. Aluminum tri-sec-butoxide and 2-amino-1-propanol were purchased from Aldrich (Aldrich). Tetrapropylammonium hydroxide (40%), phenol, trifluoroacetic acid, L-lysine, isobutyric acid, 1H-1,2, 4-triazole were purchased from Hadamard (Adamas). Ethyl orthosilicate is purchased from Aladdin. Methanol was purchased from general purpose reagent (great).

1.2 examples

Example 1: synthesis of ZSM-5 zeolite-ethyl orthosilicate as silicon source

A preparation method of ZSM-5 zeolite comprises the following steps of S1-S2:

the step of S1 includes: s11: 0.16g of aluminum tri-sec-butoxide (C)₁₂H₂₇AlO₃Molecular weight 246, purity (mass percent) 97%) and 6.97g of tetraethoxysilane (C)₈H₂₀O₄Si with the molecular weight of 208) are uniformly mixed to be used as stock solutions of an aluminum source and a silicon source; s12: 5g of TPAOH (40% by weight aqueous TPAOH solution) and 0.9255g of phenol were dissolved in 56g of deionized water and continuously stirred until a solution was formed; s13: slowly adding the stock solution prepared in the step S11 into the solution prepared in the step S12 while stirring, and uniformly mixing to obtain a synthetic solution; s2: aging the synthetic solution at room temperature for 2 days, and finishing agingThen, placing the synthetic solution into a 100mL polytetrafluoroethylene-lined stainless steel autoclave, heating the polytetrafluoroethylene-lined stainless steel autoclave in a rotary oven at the rotation speed of 10rpm and at the temperature of 120 ℃ for crystallization for 36 hours, after the reaction is finished, centrifugally washing the product for three times, and drying at the temperature of 60 ℃ overnight to obtain a dried substance; s3: and calcining the dried substance obtained in the step S2 at 550 ℃ for 6 hours to remove TPAOH, thus obtaining the TPAOH.

EXAMPLE 2 Synthesis of ZSM-5 Zeolite sodium silicate as silicon source

A method for preparing ZSM-5 zeolite comprises the following steps:

the step of S1 includes: s11: adding Al to deionized water under continuous stirring₂(SO₄)₃0.45g of TPAOH (40% strength by mass of an aqueous TPAOH solution) and 5g of phenol were added until they were completely dissolved to prepare a solution; s12: while stirring vigorously, 15g of Na was added₂SiO₃(containing SiO)₂26.5 percent by mass of Na₂O accounts for 10.6 percent by mass), and slowly adding the solution into the solution of S11 to form a synthetic solution; s2: aging the synthetic liquid for 2 days at room temperature, after the aging is finished, placing the synthetic liquid into a 100mL polytetrafluoroethylene-lined stainless steel high-pressure kettle, heating the polytetrafluoroethylene-lined stainless steel high-pressure kettle in a rotary oven, crystallizing at 170 ℃ for 72 hours at the rotating speed of 30rpm, after the reaction is finished, washing the product by centrifugal water for three times, and drying at 60 ℃ overnight to obtain a dried product; s3: and calcining the dried substance obtained from the S2 at 550 ℃ for 6 hours to obtain the catalyst.

Example 3

A preparation method of ZSM-5 zeolite comprises the following steps of S1-S2:

the step of S1 includes: s11: 0.16g of aluminum tri-sec-butoxide (C)₁₂H₂₇AlO₃Molecular weight 246, purity (mass percent) 97%) and 6.97g of tetraethoxysilane (C)₈H₂₀O₄Si with the molecular weight of 208) are uniformly mixed to be used as stock solutions of an aluminum source and a silicon source; s12: 5g of TPAOH (40% by weight aqueous TPAOH solution) and 0.58g of alanine were dissolved in 56g of deionized water and continuously stirred until a solution was formed; s13: storage prepared from S11Stirring the prepared solution, slowly adding the prepared solution into the solution prepared in the S12, and uniformly mixing to obtain a synthetic solution; s2: aging the synthetic liquid for 2 days at room temperature, after the aging is finished, placing the synthetic liquid into a 100mL polytetrafluoroethylene-lined stainless steel high-pressure kettle, heating the polytetrafluoroethylene-lined stainless steel high-pressure kettle in a rotary oven, crystallizing at 120 ℃ for 36 hours at the rotating speed of 10rpm, after the reaction is finished, washing the product by centrifugal water for three times, and drying at 60 ℃ overnight to obtain a dried product; s3: and calcining the dried substance obtained in the step S2 at 550 ℃ for 6 hours to remove TPAOH, thus obtaining the TPAOH.

Example 4 ZSM-5 Zeolite-semiconductor composite

TiO₂the/ZSM-5 composite semiconductor photocatalyst is prepared according to a sol-gel method. Mixing tetrabutyl titanate, ethanol and nitric acid according to a volume ratio of 6:24:1, stirring for 30min at room temperature to form a solution, adding ZSM-5 into the solution, stirring for 1 hour to form a mixture, slowly adding 1mL of deionized water into the mixture, stirring, keeping the stirring speed at 60rpm, controlling the reaction temperature at 70 ℃, hydrolyzing tetrabutyl titanate to be adsorbed on the surface of ZSM-5 particles to form gel, drying for 12 hours at 100 ℃ to remove the solvent, washing ZSM-5 particles for three times, calcining for 2 hours at 400 ℃ in a muffle furnace to obtain the composite semiconductor photocatalyst, wherein TiO in the composite semiconductor photocatalyst is TiO₂Accounting for 40 percent of the ZSM-5 by mass.

Comparative example 1

A preparation method of ZSM-5 zeolite comprises the following steps of S1-S2:

the step of S1 includes: s11: 0.16g of aluminum tri-sec-butoxide (C)₁₂H₂₇AlO₃Molecular weight 246, purity (mass percent) 97%) and 6.97g of tetraethoxysilane (C)₈H₂₀O₄Si with the molecular weight of 208) are uniformly mixed to be used as stock solutions of an aluminum source and a silicon source; s12: 5g of TPAOH (40% by mass aqueous TPAOH solution) is dissolved in 56g of deionized water and continuously stirred until a solution is formed; s13: slowly adding the stock solution prepared in the step S11 into the solution prepared in the step S12 while stirring, and uniformly mixing to obtain a synthetic solution; s2: at the room temperature, the reaction kettle is used for heating,aging the synthetic liquid for 2 days, after the aging is finished, placing the synthetic liquid into a 100mL polytetrafluoroethylene-lined stainless steel high-pressure kettle, heating the polytetrafluoroethylene-lined stainless steel high-pressure kettle in a rotary oven, wherein the rotation speed of the oven is 10rpm, crystallizing the polytetrafluoroethylene-lined stainless steel high-pressure kettle at 120 ℃ for 36 hours, after the reaction is finished, centrifugally washing the product for three times, and drying the product at 60 ℃ overnight to obtain a dried product; s3: and calcining the dried substance obtained in the step S2 at 550 ℃ for 6 hours to remove TPAOH, thus obtaining the TPAOH.

1.3 Experimental example

Experimental example 1

XRD, SEM, TEM, IR spectrum, and the like were performed on the ZSM-5 zeolite synthesized in example 1,²⁷Al and²⁹si solid MAS nuclear magnetic resonance experiments reflect the in-situ etching in the zeolite crystallization process and show the crystallization process of nucleation-dissolution-recrystallization, and the results are as follows:

FIG. 1: the evolution diagram of the etched time-varying structure of the crystal growth behavior of the "example 1ZSM-5 zeolite": (a) testing the XRD patterns of the zeolite obtained at different crystallization times (intercepting the sample before the crystallization time is 32 h); (b) normalizing the time distribution of crystallinity; (c-e) SEM images of solid samples at (c)0h, (d)4h and (e)24h, inset magnifies the view of individual particles; (f-h) TEM images of solid samples at (f)0h, (g)4h, and (h)24h, magnified inset shows high resolution TEM images showing expected lattice fringes of the zeolite.

FIG. 2: time dependent spectral plots. Demonstration of the etching Process in the crystallization of the ZSM-5 Zeolite of example 1 (a) the IR Spectroscopy, (b)²⁷Al-MAS nuclear magnetic resonance spectroscopy in which the inset shows the variation of the half-peak width with time, (c)²⁹Si-MAS NMR spectra, inset shows Q4/(Q2+ Q3) as a function of time.

FIG. 3: size, composition and crystallinity of "example 1ZSM-5 zeolite". The size, composition and crystallinity of ZSM-5 zeolite were controlled by varying the amount of phenol in the synthesis mixture, (a) XRD patterns with different molar amounts of phenol, (b) silica to alumina ratio, (c) crystal size, (d-i) SEM images.

FIG. 4: the mesoporosity of ZSM-5 is controlled by varying the molar amount of phenol in the synthesis mixture. (a) N is a radical of₂Adsorption-desorption isotherms and (b) BJH poresThe diameter distribution chart shows the structural property of the ZSM-5 molecular sieve synthesized by different phenol dosages, when the feeding ratio of silicon materials to phenol reaches 10SiO₂3Phe, a mesoporous structure of about 10nm is generated; (c) low resolution TEM images of the samples of example 1; (d) magnified TEM images are shown in box (c); (d) the inset therein is an electron diffraction image of selected areas, revealing in situ etching during crystallization of the zeolite.

Experimental example 2 catalytic test of ZSM-5 zeolite for propylene (MTP) with methanol

The atmospheric pressure MTP catalytic performance of the ZSM-5 zeolite obtained in example 1 was evaluated using a quartz fixed bed reactor. The method comprises the following specific steps: first, 0.3g of a catalyst (20-40 mesh) was placed in the center of a quartz tube (8mm inner diameter) and placed on a reaction apparatus. The nitrogen flow rate was set at 100 mL/min, the reaction temperature was set at 472 ℃, and the starting material methanol (95 v/v%) was added to the reaction system by a peristaltic pump and vaporized at 150 ℃. The space velocity (WHSV) of the reaction was 11.56g_MeOH g_{Catalyst and process for preparing same} ^-1 h^-1. The reaction products were detected by gas chromatography equipped with an ionic flame detector and an HP-PLOT Q column. The methanol conversion and propylene selectivity were calculated according to the area normalization method, with 80% conversion as the catalytic conversion end point. Has extremely long service life and high propylene selectivity at high space velocity (WHSV), and the calculated active site conversion number (TON) and conversion frequency (TOF) are 1.47 x 10⁶And 1.63X 10⁴h^-1。

FIG. 5 shows the catalytic performance of the zeolites prepared separately in examples 1 and 2 compared to comparative example 1 (without phenol) in MTP by (a) methanol conversion in MTP and (b) C₃H₆Selective reaction of (2). Reaction conditions are as follows: t472 ℃ and WHSV 12g_MeOH g_{Catalyst and process for preparing same} ^-1h^-1。

FIG. 6: nucleophilic etching growth mechanism and etchant species research: (a) the zeolite nucleation growth and the nucleophilic etching process compete with each other, (b) the expansion of ZSM-5 zeolite organic nucleophile: (b1) and various developed organic matters. In the boxes are the molecular structure (top), pKa1 value (bottom left) and the abbreviation symbol (bottom right), the solid boxes represent etchants with etching capability, while the dashed boxes represent organic molecules without etching capability; (b2) alanine is added to control the crystal size of the ZSM-5, and (b3) alanine is added to control the mesopores of the ZSM-5.

Experimental example 3 ZSM-5 Zeolite-semiconductor Material composite and photocatalysis

The ZSM-5 zeolite synthesized in the example 1 is compounded with the semiconductor material titanium oxide, and the advantage of the zeolite as a hierarchical pore solid acid carrier for synthesizing the photocatalyst is reflected. Composite photocatalyst TiO₂ZSM-5 was prepared according to the sol-gel method. N-butyl titanate, ethanol and nitric acid were mixed at a volume ratio of 6:24:1, respectively, and after stirring at room temperature for 30 minutes, ZSM-5 was added to the solution. After stirring for an additional 1 hour, about 1mL of deionized water was slowly added to the mixture. The stirring speed was maintained at 60rpm, and the temperature was controlled at 70 ℃ to hydrolyze the butyl titanate to adsorb it on the surface of the ZSM-5 particles. After gel formation, the gel was dried at 100 ℃ for 12 hours to remove the solvent. And after washing for three times, calcining for 2 hours in a muffle furnace at 400 ℃ to obtain the composite photocatalyst. TiO using the composite photocatalyst₂The research on the photocatalytic degradation of acetaminophen in an aqueous solution by the aid of the/ZSM-5 material shows that the initial acetaminophen concentration is 15mg/L, and the low illumination intensity is 1mW/cm²In the case of 3 hours of light irradiation, the degradation rate of acetaminophen by the photocatalyst prepared using the zeolite of example 1 was 96.8%, whereas the degradation rate of acetaminophen by the photocatalyst prepared using the zeolite of comparative example 1 was only 79.4%.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.