A nanosheet-layered structure zsm-5 type molecular sieve and preparation and application thereof

Abstract

The application discloses a kind of nanosheet layer structure ZSM-5 type molecular sieve and preparation method thereof, the surface nanocrystalline size of the ZSM-5 molecular sieve is 100nm, sheet layer structure long axis length 80~160nm, b axis width 2~50nm.Its synthesis method is, under stirring condition, template agent is added to distilled water and dissolved, then aluminum source, alkali source are sequentially added, then gradually add silica source to obtain initial gel, then add a certain amount of high carbon alcohol, heat treatment in certain molar concentration sodium hydrogen phosphate saturated hydrothermal atmosphere for a period of time to carry out crystallization reaction, after crystallization reaction, drying, calcination, obtain nanosheet layer structure ZSM-5 molecular sieve.The ZSM-5 type molecular sieve of nanosheet layer structure provided by the application, b axis width is appropriate, hydrothermal stability is high, after being applied to heavy oil catalytic cracking reaction, can reduce the diffusion resistance of reactant and intermediate product in catalyst, improve the contact of reactant and catalyst active site, catalyst usage is less, catalytic efficiency and activity are high.

Description

TECHNICAL FIELD

[0001] The present application relates to a ZSM-5 type molecular sieve and a preparation method and application thereof, and belongs to the technical field of molecular sieve synthesis. BACKGROUND

[0002] Hierarchical porous molecular sieve refers to a molecular sieve containing two or more than two pore sizes (micropore, mesopore and macropore). The synthesis method of hierarchical porous molecular sieve can be divided into two categories. One takes the "top-down" route, starting from the existing microporous molecular sieve to obtain hierarchical pores through post-processing, mainly including dealumination method and alkali treatment desilication method. One takes the "bottom-up" route, introducing mesopores during the crystallization process of the molecular sieve, including template method, secondary crystallization method, dry condensation conversion method, etc. The bottom-up method has the advantages of convenient operation and controllability. It is generally believed that the mesoporous surface of hierarchical porous zeolite is not affected by steric hindrance, so it can catalyze macromolecular reactions in mesopores, which also opens up a path for the application of zeolite in other fields, such as fine chemical synthesis. The existence of mesopores in hierarchical zeolite makes the active sites distributed in micropores and mesopores.

[0003] Short-b-axis ZSM-5 molecular sieve has many advantages such as ultra-thin molecular sieve framework, high specific surface area, accessible acid sites and adjustable mesopore size, and has more superior catalytic performance for specific reactions. It is of great significance to explore its synthesis method and application field.

[0004] Chinese patent CN 113184875 B invents a preparation method of full-silicon type short-b-axis ZSM-5 zeolite molecular sieve, which comprises the following steps: (1) preparing a reaction solution: adding tetraethyl orthosilicate drop by drop in a mixed solution of sodium hydroxide, tetrapropylammonium hydroxide, isopropyl alcohol and urea in ultrapure water, and stirring thoroughly; the addition amount of sodium hydroxide, tetrapropylammonium hydroxide, isopropyl alcohol, urea and tetraethyl orthosilicate is 0.05 g: 7.785-9.575 mmol: 0.0636 ml: 1.0 g: 5.957 ml; (2) carrying out homogeneous reaction on the reaction solution after stirring in step (1), the reaction temperature is 140-190 DEG C, and the reaction time is 48 hours; (3) washing the solution after reaction in step (2), and drying the precipitate; (4) taking the dried product in step (3), and calcining to obtain full-silicon type short-b-axis ZSM-5 zeolite molecular sieve. The shortcomings of this method are that on the one hand, a high proportion of urea is used, which increases the emission of nitrogen-containing compounds, and on the other hand, the growth of the long axis of the obtained molecular sieve is not inhibited, and the molecular sieve still has difficulties in macromolecular cracking reactions. In addition, in industrial production, it is difficult to filter such strip-shaped materials, and a large amount of ethanol and water need to be used for alternative filtration.

[0005] Chinese patent CN 117142484A discloses a synthesis method of multi-level hole ZSM-5 molecular sieve nanosheet with controllable b-axis thickness, comprising: first, preparing seed crystals with tetrapropylammonium hydroxide and tetrabutylammonium hydroxide, and the crystallization temperature is 50-70 DEG C; second, mixing the tetrapropylammonium hydroxide solution with the tetrabutylammonium hydroxide solution, then mixing with water, tetraethyl orthosilicate and the seed crystals, stirring, then adding an aluminum source solution, stirring overnight at room temperature to obtain a mixed solution II; dissolving ammonium fluoride in water and adding it into the mixed solution II, stirring vigorously, then loading into a hydrothermal crystallization kettle, crystallizing at 170 DEG C for 60h, centrifugal separation after water cooling, washing with water for multiple times to neutralize, drying and calcining to obtain multi-level hole ZSM-5 molecular sieve nanosheet. The method has the defects that both tetrabutylammonium hydroxide and tetrapropylammonium hydroxide, which are expensive, are used in the preparation process, the discharge of ammonium nitrogen wastewater and tail gas is increased, and the obtained material also has the problem of long long axis length. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a method for synthesizing ZSM-5 molecular sieve with nanosheet layer structure by self-assembly of high-carbon alcohol and phosphorus, which, compared with the existing b-axis ZSM-5 molecular sieve, not only significantly reduces the amount of ammonium template, but also presents a nanoscale sheet layer stacking structure, improves the hydrothermal stability, and has a long axis length of less than 100 nm, a more accessible area and more accessible active sites. At the same time, the application uses saturated steam containing phosphorus for treatment, and the phosphorus is not easily lost to the environment, and is distributed in the molecular sieve channel. The preparation of propylene by cracking of the obtained small crystal stacking sheet ZSM-5 molecular sieve macromolecule is significantly improved.

[0007] The technical scheme adopted by the present application to achieve the above-mentioned purposes is as follows.

[0008] A ZSM-5 molecular sieve with nanosheet layer structure, wherein the nanocrystal size on the surface of the sheet layer structure ZSM-5 molecular sieve is 100 nm, the long axis length of the sheet layer structure is 80-160 nm, and the b-axis width is 2-50 nm.

[0009] Further, the specific surface area of the nanosheet layer structure molecular sieve is greater than 600 m 2 / g, and the external surface area is greater than 300 m 2 / g; and the molar ratio of silicon-aluminum oxide in the molecular sieve is 100-300.

[0010] The method for self-assembly and synthesis of ZSM-5 molecular sieve with nanosheet layer structure according to the present application comprises the following steps:

[0011] Under stirring condition, the template agent is added into distilled water to be dissolved, then the aluminum source, the alkali source are added in sequence, then the silicon source is added gradually to obtain an initial gel, then a certain amount of high carbon alcohol is added, and the crystallization reaction is carried out in a saturated sodium hydrogen phosphate water heat atmosphere with a certain molar concentration for a period of time, after the crystallization reaction is completed, drying and calcination are carried out to obtain the ZSM-5 molecular sieve with a sheet structure.

[0012] Further, the composition of the molecular sieve synthesis solution is SiO2:Al2O3:M:Na:H2O:S:P=1:(0.001-0.1):(0.001-0.01):(0.001-0.2):(10-500):(0.01-0.5):(0.01-1) in terms of molar fraction; wherein the silicon source is represented by SiO2, the aluminum source is represented by Al2O3, the template agent is represented by M, Na is sodium element, H2O is distilled water, the high carbon alcohol is represented by S, and P is phosphorus element.

[0013] Further, the template agent is one of tetrapropylammonium hydroxide and tetraethylammonium hydroxide.

[0014] Further, the high carbon alcohol is one of butanol, amyl alcohol or cyclohexanol.

[0015] Further, the crystallization reaction process is that the synthesis solution is heat treated in a saturated sodium hydrogen phosphate water heat atmosphere with a molar concentration of 0.01-1 mol / L at 30-260℃ for 0.2-12 hours.

[0016] Further, the crystallization reaction temperature is 50-200℃, and the crystallization time is 2-48h.

[0017] Further, the drying temperature is 60-120℃, the drying time is 8-24h, the calcination temperature is 400-650℃, and the calcination time is 4-10h.

[0018] The nanosheet structure molecular sieve provided by the application can be used as a catalyst and applied to the field of catalytic cracking, especially in the field of heavy oil catalytic cracking in petroleum refining industry.

[0019] Compared with the prior art, the application has the following beneficial effects:

[0020] (1) In the existing conventional synthesis method of the laminar ZSM-5 molecular sieve, tetrabutylammonium hydroxide is used as a laminar structure directing agent / template agent in the conventional synthesis of the laminar molecular sieve, and there are the defects of large amount of template agent, complex synthesis process and high cost. It is accidentally found in the present application that the laminar ZSM-5 molecular sieve can be synthesized by self-assembly through high-carbon alcohol and phosphorus modification. In the synthesis process, the ratio of the amount of high-carbon alcohol and phosphorus is controlled to regulate the hydrolysis and polymerization rate of the silicon source from the source, promote the interaction between the phosphorus species and the aluminum element, thereby inhibit the hydrolysis rate of the aluminum species, guide the growth of the silicon-aluminum oxide framework along a specific direction, realize the controllable b-axis thickness of the molecular sieve, and achieve the purpose of self-assembly into a nanosheet structure.

[0021] (2) The method of the present application can greatly reduce the amount of ammonium-containing template agent, realize the low-cost and simple synthesis of the laminar structure molecular sieve. And the laminar ZSM-5 molecular sieve prepared by the method of the present application has a phosphorus-stable laminar diffusion channel, excellent hydrothermal stability, is beneficial to the diffusion of large molecules in catalytic cracking, reduces the amount of catalyst under the premise of realizing high-efficiency catalysis, thereby reducing the generation of hazardous waste catalysts and waste liquid, and is beneficial to realizing energy saving and emission reduction in the catalytic process.

[0022] (3) In the existing conventional synthesis process of the laminar ZSM-5 molecular sieve, a large amount of n-butylammonium hydroxide template agent is used, and the method of the present application avoids the use of a large amount of n-butylammonium hydroxide template agent by regulating the crystallization of the silicon-aluminum source, thereby greatly reducing the amount of ammonium-containing template agent. In addition, the process of introducing phosphorus elements in the existing ZSM-5 molecular sieve has the problem of low phosphorus element doping efficiency, and the method of the present application uses the technical means of sodium hydrogen phosphate saturated steam treatment to make the phosphorus element directly doped and dispersed on the inner pore structure surface of the molecular sieve, thereby greatly improving the doping rate of the phosphorus element and the hydrothermal stability of the molecular sieve.

[0023] (4) The present application reduces the diffusion resistance of reactants and intermediate products in the catalyst through the coordination of nanocrystalline and laminar structure, improves the accessibility of the active sites of the catalyst, and has high catalytic cracking activity. The catalytic cracking results show that the heavy oil conversion efficiency and propylene yield of the molecular sieve of the present application are at least 21.8% and 17.8% higher than those of the molecular sieve prepared by the conventional method, respectively. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The XRD spectrum of the ZSM-5 molecular sieve prepared in Example 2.

[0025] Figure 2 The TEM image of the laminar structure contained in the ZSM-5 molecular sieve prepared in Example 2. DETAILED DESCRIPTION

[0026] The following examples are merely preferred embodiments of this application and are not intended to limit the application in any way. Various changes and modifications can be suggested to one skilled in the art and it is intended that the application encompass such changes and modifications as fall within the scope of the appended claims.

[0027] Example 1

[0028] (1) 0.43 g of Al2(SO4)3-18H2O, 0.1 g of NaOH were dissolved in 0.03 g of TPAOH (tetrapropylammonium hydroxide) and stirred for 5 min, then 17.5 g of silica sol was added dropwise to the initial gel while stirring, 0.5 g of butanol was added and stirred at room temperature for 48 h, and then the mixture was heated at 40°C for 0.5 h in a saturated sodium hydrogen phosphate water vapor atmosphere, and then was loaded into an autoclave and crystallized at 120°C for 48 h, the obtained product was stirred for 5 min, then was centrifuged at 9000 r / min until neutral, and then was dried in an oven at 100°C for 12 h, and finally the obtained solid powder was calcined at 550°C in an air atmosphere at a temperature increasing rate of 2°C / min for 6 h to obtain NaZSM-5.

[0029] (2) The NaZSM-5 was mixed with 1M aqueous ammonium chloride solution at a solid-liquid ratio of 1 g:20 mL for ammonium exchange treatment, and after repeating 3 times, was washed with deionized water 3 times, dried at 100°C overnight, and calcined at 550°C for 6 h to obtain catalyst 1.

[0030] Example 2

[0031] (1) 0.28 g of Al2(SO4)3-18H2O, 0.2 g of NaOH were dissolved in 0.01 g of TPAOH (tetrapropylammonium hydroxide) and stirred for 5 min, then 17.5 g of TEOS (tetraethyl orthosilicate) was added dropwise to the initial gel while stirring, and finally 2 g of butanol was added and stirred at 40°C for 48 h, and then the mixture was heated at 80°C for 0.5 h in a saturated sodium hydrogen phosphate water vapor atmosphere, and then was loaded into an autoclave and crystallized at 120°C for 48 h, the obtained product was stirred for 10 min, then was centrifuged at 9000 r / min until neutral, and then was dried in an oven at 80°C for 12 h, and finally the obtained solid powder was calcined at 550°C in an air atmosphere at a temperature increasing rate of 5°C / min for 6 h to obtain NaZSM-5.

[0032] (2) The NaZSM-5 was mixed with 1M aqueous ammonium chloride solution at a solid-liquid ratio of 1 g:20 mL for ammonium exchange treatment, and after repeating 3 times, was washed with deionized water 3 times, dried at 100°C overnight, and calcined at 550°C for 6 h to obtain catalyst 2.

[0033] In the accompanying Figure 1The TEM image of the HZSM-5 molecular sieve prepared in the present example is shown in Figure 1, which shows that the surface of the HZSM-5 is highly rough, and each crystal grain is composed of self-pillared nanosheets arranged repeatedly, and the width of the b axis is about 6 nm.

[0034] Example 3

[0035] (1) 0.222 g of pseudoboehmite, 0.07 g of NaOH and 0.02 g of TPAOH (tetrapropylammonium hydroxide) were stirred for 5 min, and then 17.34 g of TEOS (tetraethyl orthosilicate) was added dropwise while stirring to obtain an initial gel, 5 g of cyclohexanol was finally added, and stirring was performed at room temperature for 48 h, and then the mixture was placed in a hydrothermal kettle and crystallized at 120 °C for 48 h, the obtained product was stirred for 5 min, and then centrifuged at 9000 r / min until neutral, and then dried in an oven at 100 °C for 12 h, and finally the obtained solid powder was calcined in a muffle furnace at 550 °C in an air atmosphere at a temperature increasing rate of 2 °C / min for 6 h to obtain NaZSM-5.

[0036] (2) The NaZSM-5 was mixed with 1M aqueous ammonium chloride solution at a solid-liquid ratio of 1 g:20 mL for ammonium exchange treatment, and after repeated 3 times, deionized water washing was performed 3 times, and then dried at 100 °C overnight, and finally calcined at 550 °C for 6 h to obtain catalyst 3.

[0037] Example 4

[0038] (1) 0.45 g of Al2(SO4)3·18H2O, 0.1 g of NaOH and 0.02 g of TPAOH (tetrapropylammonium hydroxide) were stirred for 5 min, and then 18.3 g of TEOS (tetraethyl orthosilicate) was added dropwise while stirring to obtain an initial gel, 0.5 g of cyclohexanol was finally added, and stirring was performed at room temperature for 48 h, and then the mixture was placed in a hydrothermal kettle and crystallized at 120 °C for 48 h, the obtained product was stirred for 15 min, and then centrifuged at 9000 r / min until neutral, and then dried in an oven at 100 °C for 12 h, and finally the obtained solid powder was calcined in a muffle furnace at 550 °C in an air atmosphere at a temperature increasing rate of 2 °C / min for 6 h to obtain NaZSM-5.

[0039] (2) The NaZSM-5 was mixed with 1M aqueous ammonium chloride solution at a solid-liquid ratio of 1 g:20 mL for ammonium exchange treatment, and after repeated 3 times, deionized water washing was performed 3 times, and then dried at 80 °C overnight, and finally calcined at 550 °C for 6 h to obtain catalyst 4.

[0040] Example 5

[0041] (1) 0.427 g of Al2(SO4)3-18H2O, 0.139 g of NaOH were dissolved in 0.01 g of TPAOH (tetrapropylammonium hydroxide) and stirred for 5 min, then 17.34 g of TEOS (tetraethyl orthosilicate) was added dropwise while stirring to obtain an initial gel, 0.2 g of cyclohexanol was finally added, stirred at room temperature for 48 h, treated at 100°C for 0.5 h in a saturated aqueous sodium hydrogen phosphate atmosphere, then loaded into an autoclave and crystallized at 120°C for 48 h, the obtained product was stirred for 5 min, then centrifuged at 9000 r / min to neutral, dried in an oven at 100°C for 12 h, and finally the obtained solid powder was calcined at 550°C in an air atmosphere at a heating rate of 2°C / min for 6 h to obtain NaZSM-5.

[0042] (2) The NaZSM-5 was mixed with 1M aqueous ammonium chloride solution at a solid-liquid ratio of 1 g:20 mL for ammonium exchange treatment, repeated 3 times, then washed with deionized water 3 times, dried at 100°C overnight, and calcined at 550°C for 6 h to obtain catalyst 5.

[0043]

Example 6

[0044] (1) 0.427 g of Al2(SO4)3-18H2O, 0.139 g of NaOH were dissolved in 0.01 g of TPAOH (tetrapropylammonium hydroxide) and stirred for 5 min, then 17.34 g of TEOS (tetraethyl orthosilicate) was added dropwise while stirring to obtain an initial gel, 0.2 g of cyclohexanol was finally added, stirred at room temperature for 48 h, treated at 100°C for 0.5 h in a saturated aqueous sodium hydrogen phosphate atmosphere, then loaded into an autoclave and crystallized at 120°C for 48 h, the obtained product was stirred for 5 min, then centrifuged at 9000 r / min to neutral, dried in an oven at 100°C for 12 h, and finally the obtained solid powder was calcined at 550°C in an air atmosphere at a heating rate of 2°C / min for 6 h to obtain NaZSM-5.

[0045] (2) The NaZSM-5 was mixed with 1M aqueous ammonium chloride solution at a solid-liquid ratio of 1 g:20 mL for ammonium exchange treatment, repeated 3 times, then washed with deionized water 3 times, dried at 100°C overnight, and calcined at 550°C for 6 h to obtain catalyst 6.

[0046]

Example 7

[0047] (1) 0.427 g of Al2(SO4)3-18H2O, 0.07 g of NaOH were dissolved in 10.35 g of deionized water and stirred for 5 min, 0.009 g of TPAOH (tetrapropylammonium hydroxide) was added and stirred for 5 min, then 17.34 g of TEOS (tetraethyl orthosilicate) was added dropwise while stirring to obtain an initial gel, finally 2 g of cyclohexanol was added, stirred at room temperature for 24 h, treated at 120 °C for 3 h in a saturated aqueous sodium hydrogen phosphate hydrothermal atmosphere, then loaded into a hydrothermal kettle and crystallized at 120 °C for 48 h, the obtained product was stirred for 5 min, then centrifuged at 9000 r / min to neutral, dried in an oven at 100 °C for 12 h, finally the obtained solid powder was calcined at 550 °C in an air atmosphere at a heating rate of 2 °C / min for 6 h to obtain NaZSM-5.

[0048] (2) The NaZSM-5 was mixed with 1M aqueous ammonium chloride solution at a solid-liquid ratio of 1 g:20 mL for ammonium exchange treatment, repeated 3 times, then washed with deionized water 3 times, dried at 100 °C overnight, and calcined at 550 °C for 6 h to obtain catalyst 7.

[0049]

Example 8

[0050] (1) 0.427 g of Al2(SO4)3-18H2O, 0.07 g of NaOH were dissolved in 10.35 g of deionized water and stirred for 5 min, 0.009 g of TPAOH (tetrapropylammonium hydroxide) was added and stirred for 5 min, then 17.34 g of TEOS (tetraethyl orthosilicate) was added dropwise while stirring to obtain an initial gel, finally 2 g of cyclohexanol was added, stirred at room temperature for 24 h, treated at 120 °C for 3 h in a saturated aqueous sodium hydrogen phosphate hydrothermal atmosphere, then loaded into a hydrothermal kettle and crystallized at 120 °C for 48 h, the obtained product was stirred for 5 min, then centrifuged at 9000 r / min to neutral, dried in an oven at 100 °C for 12 h, finally the obtained solid powder was calcined at 550 °C in an air atmosphere at a heating rate of 2 °C / min for 6 h to obtain NaZSM-5.

[0051] (2) The NaZSM-5 was mixed with 1M aqueous ammonium chloride solution at a solid-liquid ratio of 1 g:20 mL for ammonium exchange treatment, repeated 3 times, then washed with deionized water 3 times, dried at 100 °C overnight, and calcined at 550 °C for 6 h to obtain catalyst 7.

[0052]

Example 9

[0053] NaOH was dissolved in 25.35 g of deionized water and stirred for 5 min, 0.02 g of TEAOH (tetraethylammonium hydroxide) was added and stirred for 5 min, then 17.34 g of TEOS (tetraethyl orthosilicate) was added dropwise while stirring to obtain an initial gel, 0.2 g of cyclohexanol was finally added, and stirring was performed at room temperature for 48 h, and then the mixture was placed in a hydrothermal kettle and crystallized at 120°C for 48 h, the obtained product was stirred for 5 min, then centrifuged at 9000 r / min until neutral, dried in an oven at 100°C for 12 h, and finally the obtained solid powder was calcined at 550°C in an air atmosphere at a temperature increasing rate of 2°C / min for 6 h to obtain NaZSM-5. The NaZSM-5 was mixed with 1M ammonium chloride aqueous solution at a solid-liquid ratio of 1 g:20 mL for ammonium exchange treatment, and after repeating 3 times, centrifuged and washed with deionized water 3 times, dried at 100°C overnight, and calcined at 550°C for 6 h to obtain catalyst 9.

[0054] Comparative Example 1

[0055] NaOH was dissolved in 25.35 g of deionized water and stirred for 5 min, 0.02 g of TEAOH (tetraethylammonium hydroxide) was added and stirred for 5 min, then 17.34 g of TEOS (tetraethyl orthosilicate) was added dropwise while stirring to obtain an initial gel, 0.2 g of cyclohexanol was finally added, and stirring was performed at room temperature for 48 h, and then the mixture was placed in a hydrothermal kettle and crystallized at 120°C for 48 h, the obtained product was stirred for 5 min, then centrifuged at 9000 r / min until neutral, dried in an oven at 100°C for 12 h, and finally the obtained solid powder was calcined at 550°C in an air atmosphere at a temperature increasing rate of 2°C / min for 6 h to obtain NaZSM-5. The NaZSM-5 was mixed with 1M ammonium chloride aqueous solution at a solid-liquid ratio of 1 g:20 mL for ammonium exchange treatment, and after repeating 3 times, centrifuged and washed with deionized water 3 times, dried at 100°C overnight, and calcined at 550°C for 6 h to obtain catalyst 9.

[0056] Comparative Example 2

[0057] Compared with Example 1, butanol was not added in this example.

[0058] Comparative Example 3

[0059] Compared with Example 1, this example was not treated in a sodium hydrogen phosphate saturated hydrothermal atmosphere.

[0060] Table 1: Structural parameter results list of catalysts of Examples 1-9 and Comparative Example 1

[0061]

[0062] The ZSM-5 molecular sieves prepared in the above Examples 1-9 and Comparative Examples 1-3 were subjected to ammonium exchange treatment to make the sodium oxide content less than 0.08 wt%, to obtain hydrogen type molecular sieves. The ammonium exchange conditions were: molecular sieve: ammonium chloride: deionized water = 1:0.6:10, ammonium exchange temperature 60°C, and reaction time 2h. After ammonium exchange, the molecular sieves were filtered, washed, dried, and calcined at 550°C for 4h. The obtained hydrogen type molecular sieve samples were evaluated on a normal pressure fixed bed micro-reactor device, with industrial naphtha as the raw oil, and the evaluation conditions were: reaction temperature 650°C, catalyst / oil ratio (by weight) 0.6, and oil feeding time 70s. The results are shown in Table 2.

[0063] Table 2 Evaluation results of naphtha catalytic cracking of Examples 1-9 and Comparative Examples 1-3

[0064] Reaction temperature / °C Reaction pressure / MPa Conversion / wt% Propylene yield / wt% Example 1 650 0.1 65.1 23.2 Example 2 650 0.1 85.2 37.3 Example 3 650 0.1 79.5 31.3 Example 4 650 0.1 72.8 28.8 Example 5 650 0.1 61.6 24.9 Example 6 650 0.1 68.2 27.8 Example 7 650 0.1 66.7 28.6 Example 8 650 0.1 52.3 26.9 Example 9 650 0.1 55.9 27.8 Comparative Example 1 650 0.1 30.5 5.4

Claims

1. A method for self-assembly of a ZSM-5 molecular sieve with a synthetic nanosheet layer structure, characterized by: The template agent is dissolved in distilled water under stirring, and then the aluminum source, the alkali source and the silicon source are sequentially added to obtain an initial gel, and then a certain amount of high-carbon alcohol is added, and the initial gel is heat-treated in a saturated sodium hydrogen phosphate water heat atmosphere at a certain molar concentration for a period of time to perform a crystallization reaction, and after the crystallization reaction is completed, drying and calcination are performed to obtain the ZSM-5 molecular sieve with a sheet structure. According to the molar fraction, the composition of the molecular sieve synthesis solution is SiO2:Al2O3:M:Na:H2O:S:P=1:(0.001-0.1):(0.001-0.01):(0.001-0.2):(10-500):(0.01-0.5):(0.01-1); wherein the silicon source is represented by SiO2, the aluminum source is represented by Al2O3, the template agent is represented by M, Na is sodium, H2O is distilled water, the high-carbon alcohol is represented by S, and P is the phosphorus element. The nanosheet layer structure ZSM-5 molecular sieve has a surface nanocrystal grain size of 100 nm, a long axis length of 80-160 nm of the nanosheet layer structure, a b-axis width of 2-50 nm, a specific surface area greater than 600 m 2 / g, and an external surface area greater than 300 m 2 / g; and a molar ratio of silicon-aluminum oxides in the molecular sieve is 100-300.

2. The method for self-assembling and synthesizing ZSM-5 molecular sieves with nanosheet structures according to claim 1, characterized in that: The template agent is one of tetrapropylammonium hydroxide and tetraethylammonium hydroxide.

3. The method of self-assembling ZSM-5 molecular sieves of nanosheet layer structure according to claim 1, characterized by: The high-carbon alcohol is one of butanol, pentanol or cyclohexanol.

4. The method of claim 1, wherein the ZSM-5 molecular sieve self-assembled synthetic nanosheet layer structure is characterized by: The process of the crystallization reaction is that the synthesis solution is heat-treated in a saturated sodium hydrogen phosphate water heat atmosphere at a molar concentration of 0.01-1 mol / L at 30-260°C for 0.2-12 hours.

5. The method of self-assembling ZSM-5 molecular sieves of nanosheet layer structure according to claim 1, characterized by: The crystallization temperature is 50-200°C, and the crystallization time is 2-48h.

6. The method of self-assembling ZSM-5 molecular sieves of nanosheet layer structure according to claim 1, characterized by: The drying temperature is 60-120°C, the drying time is 8-24h, the calcination temperature is 400-650°C, and the calcination time is 4-10h.

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