A method for preparing a zsm-5 molecular sieve

Abstract

The application belongs to the technical field of molecular sieve, and particularly relates to a preparation method of ZSM-5 molecular sieve. The preparation method of ZSM-5 molecular sieve provided by the application comprises the following steps: first mixing alcohol amine, an alkali source and water to obtain solution A; second mixing the solution A and an aluminum source to obtain solution B; third mixing the solution B and a silicon source to obtain solution C; performing a crystallization reaction on the solution C to obtain a solid; and performing calcination on the solid to obtain the ZSM-5 molecular sieve. The ZSM-5 molecular sieve with an average particle size range of 0.05-16 microns and a silicon-aluminum ratio range of 20-150 is prepared by using alcohol amine as a structure directing agent and other inorganic raw materials, which greatly reduces the production cost of the ZSM-5 molecular sieve and also provides a new structure directing agent for the synthesis of the molecular sieve.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve technology, specifically relating to a method for preparing ZSM-5 molecular sieve. Background Technology

[0002] Molecular sieves possess characteristics such as high specific surface area, abundant pore structure, controllable framework composition, and good thermal stability, making them widely used in chemical processes such as catalysis and separation. Among them, high-silica ZSM-5 molecular sieves, due to their unique three-dimensional ten-membered ring pore structure, tunable acidity, shape selectivity, and high-temperature hydrothermal stability, are widely used in industrial processes such as catalytic cracking, alkylation, methanol-to-olefins, olefin cracking, and isomerization.

[0003] In the industrial production of ZSM-5 molecular sieves, without the addition of structure-directing agents to the inorganic system, only ZSM-5 molecular sieves with a low silica-to-alumina ratio can be obtained. These low-silica-to-alumina ratio ZSM-5 molecular sieves exhibit low crystallinity and poor hydrothermal stability. The synthesis of high-silica-to-alumina ratio ZSM-5 molecular sieves requires the addition of structure-directing agents. The choice of structure-directing agent often plays a crucial role in the physical and chemical properties of the prepared molecular sieve and is a key factor affecting its synthesis. Currently, the main structure-directing agents that can be used to synthesize ZSM-5 molecular sieves include tetrapropylammonium hydroxide, hexamethylenediamine, diethylamine, or propylamine. These suitable structure-directing agents for ZSM-5 molecular sieve synthesis are relatively expensive, increasing the production cost of ZSM-5 molecular sieves. Summary of the Invention

[0004] In view of this, the present invention provides a ZSM-5 molecular sieve and its preparation method. The present invention uses inexpensive alkanolamines as structure directing agents to prepare ZSM-5 molecular sieves with adjustable particle size and silica-alumina ratio, which greatly reduces the production cost of ZSM-5 molecular sieves.

[0005] To address the aforementioned technical problems, this invention provides a method for preparing ZSM-5 molecular sieves, comprising the following steps:

[0006] The alcohol amine, the alkali source, and water are first mixed to obtain solution A;

[0007] Solution A is mixed with the second aluminum source to obtain solution B;

[0008] Solution B is mixed with silicon source 3 to obtain solution C;

[0009] The solution C was subjected to a crystallization reaction to obtain a solid.

[0010] The solid was calcined to obtain the ZSM-5 molecular sieve.

[0011] Preferably, the alkanolamine is one or more of 5-amino-1-pentanol, 6-amino-1-hexanol, 7-amino-1-heptanol, and 8-amino-1-octanol;

[0012] The molar ratio of the alkanolamine to water is 0.3–2:10–100.

[0013] Preferably, the crystallization reaction further includes: mixing the solution C and the seed crystal fourth;

[0014] The mass ratio of the seed crystal to the silicon source is 1 to 20:100, based on the Si element content.

[0015] Preferably, the method for preparing the seed crystal includes the following steps:

[0016] Tetrapropylammonium hydroxide is dissolved in water to obtain a tetrapropylammonium hydroxide solution;

[0017] Tetraethyl orthosilicate was added dropwise to the tetrapropylammonium hydroxide solution and subjected to a hydrothermal reaction to obtain the seed crystals.

[0018] Preferably, the temperature of the crystallization reaction is 110–200°C, and the time of the crystallization reaction is 24–96 h.

[0019] Preferably, the alkali source is one or more of sodium hydroxide, ammonia, urea, and ammonium carbonate;

[0020] The molar ratio of the alkali source to water is 0.01–0.35:10–100.

[0021] Preferably, the aluminum source is one or more of aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum hydroxide, sodium aluminate, boehmite, and aluminum isopropoxide.

[0022] Based on aluminum oxide, the molar ratio of the aluminum source to water is 0.003–0.025:10–100.

[0023] Preferably, the silicon source is one or more of water glass, silica sol, fumed silica, silica fume and tetraethyl orthosilicate;

[0024] The molar ratio of the silicon source to water, calculated as silicon dioxide, is 1:10 to 100.

[0025] Preferably, the roasting temperature is 500-600℃ and the roasting time is 5-8h.

[0026] This invention provides a method for preparing ZSM-5 molecular sieves, comprising the following steps: first, mixing an alkanolamine, an alkaline source, and water to obtain solution A; second, mixing solution A with an aluminum source to obtain solution B; third, mixing solution B with a silicon source to obtain solution C; subjecting solution C to a crystallization reaction to obtain a solid; and calcining the solid to obtain the ZSM-5 molecular sieve. This invention uses inexpensive alkanolamines as structure-directing agents and other inorganic raw materials to prepare ZSM-5 molecular sieves with adjustable particle size and silicon-to-aluminum ratio, significantly reducing the production cost of ZSM-5 molecular sieves. The preparation method provided by this invention has a simple synthesis process, is easy to control, and is suitable for industrial production; using the preparation method provided by this invention, ZSM-5 molecular sieves with an average particle size range of 0.05–16 μm and a silicon-to-aluminum ratio range of 20–150 can be obtained. Attached Figure Description

[0027] Figure 1 The XRD pattern of the ZSM-5 molecular sieve prepared in Example 1 is shown below.

[0028] Figure 2 SEM image of the ZSM-5 molecular sieve prepared in Example 1;

[0029] Figure 3 The XRD pattern of the ZSM-5 molecular sieve prepared in Example 2 is shown below.

[0030] Figure 4 SEM image of the ZSM-5 molecular sieve prepared in Example 2;

[0031] Figure 5 The XRD pattern of the ZSM-5 molecular sieve prepared in Example 3 is shown below.

[0032] Figure 6 SEM image of the ZSM-5 molecular sieve prepared in Example 3;

[0033] Figure 7 The XRD pattern of the ZSM-5 molecular sieve prepared in Example 4 is shown below.

[0034] Figure 8 Here is a SEM image of the ZSM-5 molecular sieve prepared in Example 4;

[0035] Figure 9 The XRD pattern of the ZSM-5 molecular sieve prepared in Example 5;

[0036] Figure 10 SEM image of the ZSM-5 molecular sieve prepared in Example 5;

[0037] Figure 11 The XRD pattern of the ZSM-5 molecular sieve prepared in Example 6 is shown below.

[0038] Figure 12 The image shows a SEM image of the ZSM-5 molecular sieve prepared in Example 6. Detailed Implementation

[0039] This invention provides a method for preparing ZSM-5 molecular sieves, comprising the following steps:

[0040] The alcohol amine, the alkali source, and water are first mixed to obtain solution A;

[0041] Solution A is mixed with the second aluminum source to obtain solution B;

[0042] Solution B is mixed with silicon source 3 to obtain solution C;

[0043] The solution C was subjected to a crystallization reaction to obtain a solid.

[0044] The solid was calcined to obtain the ZSM-5 molecular sieve.

[0045] This invention involves first mixing an alkanolamine, an alkaline source, and water to obtain solution A. In this invention, the alkanolamine is preferably one or more of 5-amino-1-pentanol, 6-amino-1-hexanol, 7-amino-1-heptanol, and 8-amino-1-octanol, more preferably 6-amino-1-hexanol. In this invention, when the alkanolamine comprises two or more of the above-mentioned substances, the proportions of the substances are not particularly important and any proportion can be used. In this invention, the alkanolamine serves as a structure-directing agent. In this invention, the alkaline source is preferably one or more of sodium hydroxide, ammonia, urea, and ammonium carbonate, more preferably sodium hydroxide or urea, and even more preferably urea. In this invention, when the alkaline source is sodium hydroxide, it is preferable to dissolve the sodium hydroxide in a portion of the water before the first mixing to obtain a sodium hydroxide solution; the mass concentration of the sodium hydroxide solution is preferably 28-32%, more preferably 30%. In this invention, the water is preferably deionized water. In this invention, the molar ratio of the alkanolamine to water is preferably 0.3–2:10–100, more preferably 0.3–1.67:20–90, even more preferably 0.35–0.9:20–35, and most preferably 0.5–0.9:20. In this invention, the molar ratio of the alkali source to water is preferably 0.01–0.35:10–100, more preferably 0.1–0.25:20–35, and even more preferably 0.15–0.2:20.

[0046] In this invention, molecular sieves are prepared in a sodium-free system when urea is used as the alkali source, which shortens the synthesis process and avoids the ion exchange process and the generation of a large amount of wastewater.

[0047] In this invention, the first mixing is preferably carried out under stirring conditions, the stirring temperature is preferably room temperature, preferably 20-35°C, more preferably 25-30°C; the stirring speed is preferably 100-500 r / min, more preferably 250-300 r / min; and the stirring time is preferably 10-60 min, more preferably 20-30 min.

[0048] After obtaining solution A, the present invention mixes solution A with a second aluminum source to obtain solution B. In the present invention, the aluminum source is preferably one or more of aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum hydroxide, sodium aluminate, boehmite, and aluminum isopropoxide, more preferably aluminum sulfate, and the aluminum sulfate is preferably aluminum sulfate octadechydrate. In the present invention, when the aluminum source is two or more of the above-mentioned specific substances, the present invention has no special requirements on the ratio of the specific substances, and any ratio can be used. In the present invention, based on aluminum oxide, the molar ratio of the aluminum source to water is preferably 0.003–0.025:10–100, more preferably 0.01–0.017:20–35, and even more preferably 0.014–0.017:20.

[0049] In this invention, the second mixing is preferably carried out under stirring conditions, wherein the stirring temperature is preferably room temperature, preferably 20–35°C, more preferably 25–30°C; the stirring speed is preferably 100–500 r / min, more preferably 250–300 r / min; and the stirring time is preferably 10–60 min, more preferably 20–30 min.

[0050] After obtaining solution B, the present invention mixes solution B with a third silicon source to obtain solution C. In the present invention, the silicon source is preferably one or more of water glass, silica sol, fumed silica, silica, and tetraethyl orthosilicate, more preferably silica sol. In the present invention, the silica sol is preferably a neutral silica sol. In the present invention, the silica content in the silica sol is preferably 28-32%, more preferably 30%. In the present invention, based on silica, the molar ratio of the silicon source to water is preferably 1:10-100, more preferably 1:20-35.

[0051] In this invention, the third mixing is preferably achieved by adding a silicon source dropwise to solution B. The dropping rate is preferably 1–5 mL / min, more preferably 3–4 mL / min. The dropping is preferably accompanied by stirring, with a stirring speed preferably 100–500 r / min, more preferably 250–300 r / min; the stirring time is preferably 10–60 min, more preferably 20–30 min.

[0052] In this invention, solution C is a gel.

[0053] After obtaining solution C, the present invention performs a crystallization reaction on solution C to obtain a solid. In the present invention, the crystallization reaction preferably further includes: mixing solution C and seed crystals in a fourth step. In the present invention, based on the Si element content, the mass ratio of the seed crystal to the silicon source is preferably 1-20:100, more preferably 5-10:100. In the present invention, the mass ratio of the seed crystal to the silicon source is preferably the mass ratio of silicon element in the seed crystal to silicon element in the silicon source. In the present invention, the seed crystal is preferably an all-silicon seed crystal. In the present invention, the method for preparing the seed crystal preferably includes the following steps:

[0054] Tetrapropylammonium hydroxide is dissolved in water to obtain a tetrapropylammonium hydroxide solution;

[0055] Tetraethyl orthosilicate was added dropwise to the tetrapropylammonium hydroxide solution and subjected to a hydrothermal reaction to obtain the seed crystals.

[0056] This invention involves dissolving tetrapropylammonium hydroxide in water to obtain a tetrapropylammonium hydroxide solution. In this invention, the water is preferably deionized water; the mass concentration of the tetrapropylammonium hydroxide solution is preferably 38-42%, more preferably 40%. In this invention, the dissolution is preferably carried out under stirring conditions; the stirring temperature is preferably room temperature, preferably 20-35°C, more preferably 25-30°C; the stirring speed is preferably 100-500 r / min, more preferably 250-300 r / min; and the stirring time is preferably 10-60 min, more preferably 20-30 min.

[0057] After obtaining a tetrapropylammonium hydroxide solution, the present invention adds tetraethyl orthosilicate dropwise to the tetrapropylammonium hydroxide solution and then performs a hydrothermal reaction to obtain the seed crystals. In the present invention, the dropping rate of tetraethyl orthosilicate is preferably 1-5 mL / min, more preferably 3-4 mL / min. In the present invention, the dropping is preferably accompanied by stirring; the present invention has no special requirements for the stirring, as long as it can achieve uniform mixing.

[0058] In this invention, the temperature of the hydrothermal reaction is preferably 85-95°C, more preferably 90°C; the time of the hydrothermal reaction is preferably 70-74 hours, more preferably 72 hours.

[0059] In this invention, the hydrothermal reaction preferably further includes: cooling the system after the hydrothermal reaction to separate the solid and liquid phases. In this invention, the cooling temperature is preferably room temperature, preferably 20–35°C, more preferably 25–30°C. This invention does not have special requirements for the cooling method, as long as the desired temperature can be achieved. This invention also does not have special limitations on the solid-liquid separation, as long as the solid can be separated.

[0060] In this invention, the temperature of the crystallization reaction is preferably 110–200°C, more preferably 165–180°C; the time of the crystallization reaction is preferably 24–96 h, more preferably 48–72 h. In this invention, the crystallization reaction is preferably a static crystallization reaction or a dynamic crystallization reaction, more preferably a dynamic crystallization reaction. In this invention, the rotational speed of the dynamic crystallization reaction is preferably 10–500 r / min, more preferably 65–120 r / min, and even more preferably 70–80 r / min.

[0061] In this invention, the crystallization reaction preferably further includes: solid-liquid separation of the crystallization reaction system, and washing and drying the solid obtained from the solid-liquid separation to obtain the solid. In this invention, the solid-liquid separation is preferably centrifugation. This invention has no special requirements for the centrifugation, as long as solid-liquid separation can be achieved. In this invention, the washing is preferably water washing, and the water used for washing is preferably deionized water; the number of water washings is preferably 2 to 4 times, more preferably 3 times. This invention has no special requirements for the drying, as long as the surface moisture of the solid can be removed.

[0062] After obtaining the solid, the present invention calcines the solid to obtain the ZSM-5 molecular sieve. In the present invention, the calcination temperature is preferably 500-600℃, more preferably 530-580℃; the calcination time is preferably 5-8h, more preferably 6-7h.

[0063] In this invention, the average particle size of the ZSM-5 molecular sieve is preferably 0.05-16 μm, more preferably 0.1-13 μm; the silicon-to-aluminum ratio of the ZSM-5 molecular sieve is preferably 20-150, more preferably 28-47.

[0064] This invention uses alkanolamines as structure-directing agents to prepare ZSM-5 molecular sieves, which not only achieves sodium-free synthesis but also modulates the size and morphology of the molecular sieves, making it suitable for the synthesis of nano- and short b-axis ZSM-5 molecular sieves.

[0065] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0066] Example 1

[0067] 1.80 g of 6-amino-1-hexanol, 6.27 g of deionized water and 0.61 g of 30 wt.% sodium hydroxide aqueous solution were stirred at 25 °C and 250 r / min to obtain solution A;

[0068] Solution A and 0.20 g of aluminum sulfate octadeca were stirred at 25°C and 250 r / min to obtain solution B;

[0069] 6.01 g of silica sol (neutral, silica content 30 wt.%) was added dropwise to solution B at a dropping rate of 4 mL / min (accompanied by a rotation speed of 250 r / min) to obtain solution C;

[0070] Solution C was statically crystallized at 165℃ for 48 hours, then cooled to room temperature and centrifuged. The solid obtained by centrifugation was washed with water three times and dried. It was then calcined at 550℃ for 6 hours to obtain ZSM-5 molecular sieve, which was designated as product 1. The silicon source was calculated as silicon dioxide and the aluminum source was calculated as aluminum oxide. The molar ratio of SiO2, Al2O3, 6-amino-1-hexanol, NaOH and H2O in solution C (parent gel) was 1:0.01:0.5:0.15:20.

[0071] Example 2

[0072] 1.80 g of 6-amino-1-hexanol, 6.16 g of deionized water and 0.81 g of 30 wt.% sodium hydroxide aqueous solution were stirred at 25 °C and 250 r / min to obtain solution A;

[0073] Solution A and 0.33g of aluminum sulfate octadeca were stirred at 25℃ and 250r / min to obtain solution B;

[0074] 5.97 g of silica sol (neutral, silica content 30 wt.%) was added dropwise to solution B at a dropping rate of 4 mL / min (accompanied by a rotation speed of 250 r / min) to obtain solution C;

[0075] Solution C was dynamically crystallized at 180℃ and 70 r / min for 48 h, then cooled to room temperature and centrifuged. The solid obtained by centrifugation was washed with water three times and dried. It was then calcined at 550℃ for 6 h to obtain ZSM-5 molecular sieve, which was designated as product 2. The silicon source was calculated as silicon dioxide and the aluminum source was calculated as aluminum oxide. The molar ratio of SiO2, Al2O3, 6-amino-1-hexanol, NaOH and H2O in solution C (parent gel) was 1:0.017:0.5:0.2:20.

[0076] Example 3

[0077] 2.72 g of 6-amino-1-hexanol, 5.24 g of deionized water and 0.50 g of 30 wt.% sodium hydroxide aqueous solution were stirred at 25 °C and 300 r / min to obtain solution A;

[0078] Solution A and 0.23g of aluminum sulfate octadeca were stirred at 25℃ and 300r / min to obtain solution B;

[0079] 4.87 g of silica sol (neutral, silica content 30 wt.%) was added dropwise to solution B at a dropping rate of 4 mL / min (accompanied by a rotation speed of 300 r / min) to obtain solution C;

[0080] Solution C was dynamically crystallized at 180℃ and 70 r / min for 72 h, then cooled to room temperature and centrifuged. The solid obtained by centrifugation was washed with water, dried, and calcined at 600℃ for 6 h to obtain ZSM-5 molecular sieve, designated as product 3. The silicon source was calculated as silicon dioxide, and the aluminum source was calculated as aluminum oxide. The molar ratio of SiO2, Al2O3, 6-amino-1-hexanol, NaOH, and H2O in solution C (parent gel) was 1:0.014:0.9:0.15:20.

[0081] Example 4

[0082] 1.51 g of 6-amino-1-hexanol, 5.33 g of deionized water and 0.33 g of 30 wt.% sodium hydroxide aqueous solution were stirred at 25 °C and 250 r / min to obtain solution A;

[0083] Solution A and 0.17g of aluminum sulfate octadeca were stirred at 25℃ and 250r / min to obtain solution B;

[0084] 4.91 g of silica sol (neutral, silica content 30 wt.%) was added dropwise to solution B at a dropping rate of 3 mL / min (accompanied by a rotation speed of 250 r / min) to obtain solution C;

[0085] Solution C was dynamically crystallized at 180℃ and 70 r / min for 72 h, then cooled to room temperature and centrifuged. The solid obtained by centrifugation was washed with water and dried, and then calcined at 530℃ for 7 h to obtain ZSM-5 molecular sieve, which was designated as product 4. The silicon source was calculated as silicon dioxide and the aluminum source was calculated as aluminum oxide. The molar ratio of SiO2, Al2O3, 6-amino-1-hexanol, NaOH and H2O in solution C (parent gel) was 1:0.01:0.5:0.1:20.

[0086] Example 5

[0087] 10.62 g of deionized water and 18.30 g of tetrapropylammonium hydroxide were stirred evenly at 25 °C and 300 r / min to obtain a tetrapropylammonium hydroxide solution with a mass concentration of 40 wt.%. 21.48 g of tetraethyl orthosilicate was added dropwise to the tetrapropylammonium hydroxide solution at a dropping rate of 3 mL / min (with stirring), and the solution was subjected to a hydrothermal reaction at 90 °C for 72 h. After cooling to room temperature, the solution was filtered to obtain all-silicon seed crystals.

[0088] 1.51 g of 6-amino-1-hexanol, 5.50 g of deionized water and 0.30 g of urea were stirred at 25 °C and 300 r / min to obtain solution A;

[0089] Solution A and 0.17g of aluminum sulfate octadeca were stirred at 25℃ and 300r / min to obtain solution B;

[0090] 4.91 g of silica sol (neutral, silica content 30 wt.%) was added dropwise to solution B at a dropping rate of 3 mL / min (accompanied by a rotation speed of 300 r / min) to obtain solution C;

[0091] 0.84 g of all-silicon seed crystals (based on silicon element, the mass ratio of seed crystals to silica sol is 5:100) were added to solution C and mixed evenly. After static crystallization at 180℃ for 72 h, the mixture was cooled to room temperature and centrifuged. The solid obtained by centrifugation was washed with water and dried. It was then calcined at 500℃ for 6 h to obtain ZSM-5 molecular sieve, which was designated as product 5. The silicon source was calculated as silicon dioxide and the aluminum source was calculated as aluminum oxide. The molar ratio of SiO2, Al2O3, 6-amino-1-hexanol, Urea and H2O in solution C (parent gel) was 1:0.014:0.5:0.2:20.

[0092] Example 6

[0093] All-silicon seed crystals were prepared according to the method in Example 5;

[0094] 0.66 g of 6-amino-1-hexanol, 8.16 g of deionized water and 0.25 g of urea were stirred at 25 °C and 550 r / min to obtain solution A;

[0095] Solution A and 0.11g of aluminum sulfate octadeca were stirred at 25℃ and 250r / min to obtain solution B;

[0096] 3.34 g of silica sol (neutral, silica content 30 wt.%) was added dropwise to solution B at a dropping rate of 4 mL / min (accompanied by a rotation speed of 250 r / min) to obtain solution C;

[0097] 0.84 g of all-silicon seed crystals (based on silicon element, the mass ratio of seed crystals to silica sol is 10:100) were added to solution C and mixed evenly. After dynamic crystallization at 180℃ and 70 r / min for 72 h, the mixture was cooled to room temperature and centrifuged. The solid obtained by centrifugation was washed with water and dried. It was then calcined at 550℃ for 6 h to obtain ZSM-5 molecular sieve, which was designated as product 6. The silicon source was calculated as silicon dioxide and the aluminum source was calculated as aluminum oxide. The molar ratio of SiO2, Al2O3, 6-amino-1-hexanol, NaOH and H2O in solution C (parent gel) was 1:0.01:0.33:0.25:35.

[0098] The ZSM-5 molecular sieves prepared in Examples 1-6 were subjected to XRD and scanning electron microscopy analysis, respectively, to obtain XRD patterns and SEM images, as shown below. Figures 1-12 As shown; where Figure 1 The image shows the XRD pattern of the ZSM-5 molecular sieve prepared in Example 1. Figure 2 SEM image of the ZSM-5 molecular sieve prepared in Example 1; Figure 3 The image shows the XRD pattern of the ZSM-5 molecular sieve prepared in Example 2. Figure 4 SEM image of the ZSM-5 molecular sieve prepared in Example 2; Figure 5 The image shows the XRD pattern of the ZSM-5 molecular sieve prepared in Example 3. Figure 6 SEM image of the ZSM-5 molecular sieve prepared in Example 3; Figure 7 The image shows the XRD pattern of the ZSM-5 molecular sieve prepared in Example 4. Figure 8 Here is a SEM image of the ZSM-5 molecular sieve prepared in Example 4; Figure 9 The image shows the XRD pattern of the ZSM-5 molecular sieve prepared in Example 5. Figure 10 SEM image of the ZSM-5 molecular sieve prepared in Example 5; Figure 11 The image shows the XRD pattern of the ZSM-5 molecular sieve prepared in Example 6. Figure 12 The image shows a SEM image of the ZSM-5 molecular sieve prepared in Example 6.

[0099] As can be seen from the XRD spectra of Examples 1 to 6, the products prepared in Examples 1 to 6 have the crystal phase structure of ZSM-5 molecular sieve, indicating that ZSM-5 molecular sieve was prepared according to the preparation method provided by the present invention.

[0100] The particle size of ZSM-5 molecular sieves was obtained from the SEM images of Examples 1-6, and the results are listed in Table 1. It can be seen that the average particle size of the ZSM-5 molecular sieves prepared in Examples 1-6 is 0.07-12.5 μm, indicating that ZSM-5 molecular sieves with adjustable particle size within a certain range were prepared according to the preparation method provided by the present invention.

[0101] The silicon-to-aluminum ratio of the ZSM-5 molecular sieves prepared in Examples 1-6 was tested by inductively coupled plasma atomic emission spectrometry, and the results are listed in Table 1.

[0102] Table 1. Si / aluminum ratio and average particle size of ZSM-5 molecular sieves prepared in Examples 1-6

[0103] Example The silica-alumina ratio of the parent gel Actual Si / Al Ratio of Molecular Sieves Average particle size of molecular sieves (μm) Example 1 50 47 12.5 Example 2 30 28 3.5 Example 3 35 37 0.12 Example 4 50 48 9 Example 5 35 34 0.07 Example 6 50 48 0.75

[0104] As can be seen from the data in Table 1, the actual silica-alumina ratio of the molecular sieves prepared in Examples 1 to 6 is basically consistent with the ratio in the parent gel formulation. The slight discrepancies should be attributed to losses in the synthesis mother liquor and experimental operation errors.

[0105] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing ZSM-5 zeolite, comprising the following steps: mixing an alcohol amine, an alkali source and water first to obtain solution A; the alcohol amine is one or more of 5-amino-1-pentanol, 6-amino-1-hexanol, 7-amino-1-heptanol and 8-amino-1-octanol; the molar ratio of the alcohol amine to water is 0.3-2:10-100; mixing the solution A and an aluminum source second to obtain solution B; mixing the solution B and a silicon source third to obtain solution C; performing a crystallization reaction on the solution C to obtain a solid; performing calcination on the solid to obtain the ZSM-5 zeolite. The method further comprises the following step before the crystallization reaction: mixing the solution C and seeds fourth. The mass ratio of the seeds to the silicon source is 1-20:100 in terms of Si element content. The method for preparing the seeds comprises the following steps: dissolving tetrapropylammonium hydroxide in water to obtain a tetrapropylammonium hydroxide solution; and adding tetraethyl orthosilicate dropwise to the tetrapropylammonium hydroxide solution and then performing a hydrothermal reaction to obtain the seeds. The temperature of the crystallization reaction is 110-200℃, and the time of the crystallization reaction is 24-96h. The alkali source is one or more of sodium hydroxide, ammonia, urea and ammonium carbonate.

2. The method of claim 1, wherein, The molar ratio of the alkali source to water is 0.01-0.35:10-100. The aluminum source is one or more of aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum hydroxide, sodium metaaluminate, pseudo-boehmite and aluminum isopropoxide.

3. The preparation method according to claim 2, characterized in that, The molar ratio of the aluminum source to water is 0.003-0.025:10-100 in terms of aluminum trioxide. The silicon source is one or more of water glass, silica sol, fumed silica, white carbon black and tetraethyl orthosilicate. The molar ratio of the silicon source to water is 1:10-100 in terms of silicon dioxide.

4. The method of claim 1, 2 or 3, wherein, The calcination temperature is 500-600℃, and the calcination time is 5-8h.

5. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. ​ ​ 6. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. ​ ​ 7. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. ​ ​ 8. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. ​

Images