Preparation method of ZSM-22 molecular sieve

Abstract

The invention provides a preparation method of a ZSM-22 molecular sieve. The preparation method of the ZSM-22 molecular sieve comprises the following steps: uniformly mixing an aluminum source, an alkali source, water, an organic template agent and a silicon source to obtain a gel mixed solution; at least crystallizing and roasting the gel mixed solution to obtain a ZSM-22 molecular sieve; wherein the organic template agent comprises an alcohol amine compound with the carbon number of 5-6. According to the preparation method of the ZSM-22 molecular sieve, the low-cost organic template agent is adopted, and the pure-phase ZSM-22 molecular sieve can be prepared.

Description

Technical Field

[0001] The invention relates to a method for preparing a ZSM-22 molecular sieve, and belongs to the technical field of molecular sieves. Background Art

[0002] ZSM-22 molecular sieve is a TON topological structure molecular sieve first developed by Mobil in the early 1980s. It is a zeolite molecular sieve with a pore kinetic diameter of 0.45nm×0.55nm, with five-membered rings, six-membered rings and ten-membered rings. Its five-membered rings and six-membered rings are side cages, and the main pores are one-dimensional ten-membered ring pores. Because ZSM-22 molecular sieve has suitable acid strength, thermal stability and hydrothermal stability and an adjustable higher silicon-aluminum ratio range, it shows excellent catalytic performance in reactions such as shape-selective catalysis and hydrogenation isomerization.

[0003] Hydrothermal synthesis is the most commonly used method for preparing ZSM-22 molecular sieves. Due to the metastable structure of ZSM-22, it is easy to produce impurities such as ZSM-5 and white quartz during the preparation process, or form a eutectic with ZSM-23. At present, in the prior art, 1,6-hexanediamine or ethylenediamine is generally used as a template when synthesizing ZSM-22 molecular sieves. These templates are expensive, and are prone to produce a large amount of harmful gases during processing. In addition, the crystallization temperature is high and the time is long, making industrialization difficult.

[0004] CN113307287A discloses a dynamic synthesis method of high crystallinity ZSM-22 molecular sieve. In this method, a synthesis aid is added during the synthesis process to improve the crystallinity of the product, which reduces the amount of template, thereby reducing costs and reducing environmental pollution, and the synthesis process is more environmentally friendly. Although the technology introduces a synthesis aid to reduce the amount of template, the template still uses 1,6-hexanediamine, diethylamine, and n-butylamine, which are more polluting.

[0005] CN107285332A discloses a method for synthesizing a ZSM-22 molecular sieve and the synthesized ZSM-22 molecular sieve. The ZSM-22 molecular sieve crystal synthesized by the method is flaky, the crystal thickness is less than 20 nanometers, and the template agent used is 1-ethylpyridinium bromide. The template agent used in the method is high in cost and highly polluting.

[0006] CN113233472A discloses a method for synthesizing a nano-sized small-grain ZSM-22 molecular sieve. The method uses natural diatomite as all the silicon and aluminum sources required for synthesizing the molecular sieve, and in-situ crystallization is performed to obtain a nano-sized small-grain ZSM-22 molecular sieve without a template. Although the method does not use a template, it requires the addition of seed crystals, which is costly and has a complicated preparation process.

[0007] Therefore, developing a new method for synthesizing ZSM-22 molecular sieves using a low-cost organic template has become one of the urgent problems to be solved in this field.

[0008] CN103864097A discloses a SAPO-34 molecular sieve using diglycolamine as a template and a synthesis method thereof. The method comprises the following steps: a) mixing deionized water, a silicon source, an aluminum source, a phosphorus source and diglycolamine in a certain proportion to obtain an initial gel mixture; b) placing the initial gel mixture obtained in step a) into a high-pressure synthesis reactor, sealing it, heating it to 150-220°C, and crystallizing it under autogenous pressure for 5-72 hours; c) after the crystallization is completed, the solid product is separated, washed with deionized water until neutral, and dried to obtain the SAPO-34 molecular sieve.

[0009] CN107074571A discloses a method for synthesizing silicoaluminophosphate-34 molecular sieve using monoisopropanolamine. The method comprises the following steps: forming a slurry, the slurry comprising monoisopropanolamine; aging the slurry to form an aged slurry; and inducing crystallization of a silicoaluminophosphate molecular sieve comprising the SAPO-34 molecular sieve from the aged slurry.

[0010] Alcoholamine compounds are considered to be one of the more ideal organic templates because they have high boiling point, high flash point and relatively less toxicity. It can be seen from the contents disclosed in CN103864097A and CN107074571A that alcoholamine compounds have been applied to the synthesis of SAPO-34 molecular sieves as templates. And the selection of templates has a crucial impact on the crystal form, element composition, morphology, surface area and pore volume of synthetic molecular sieves. Exploring new templates that can synthesize ZSM-22 molecular sieves is one of the research hotspots in this field. Summary of the invention

[0011] In order to solve the above technical problems, the purpose of the present invention is to provide a method for preparing ZSM-22 molecular sieve. The method for preparing ZSM-22 molecular sieve of the present invention adopts a low-cost organic template agent and can prepare a pure phase ZSM-22 molecular sieve.

[0012] In order to achieve the above object, the present invention provides a method for preparing a ZSM-22 molecular sieve, which comprises the following steps:

[0013] (1) mixing an aluminum source, an alkali source, water, an organic template, and a silicon source to obtain a gel mixture;

[0014] (2) subjecting the gel mixture to at least crystallization and calcination to obtain the ZSM-22 molecular sieve;

[0015] Wherein, the organic template comprises an alcoholamine compound having 5 to 6 carbon atoms.

[0016] In the above preparation method, preferably, the organic template comprises 5-amino-1-pentanol and / or 6-amino-1-hexanol.

[0017] The inventors of this case have found through extensive research and experiments that pure phase ZSM-22 molecular sieves can be synthesized by using alcohol amine compounds with carbon numbers of 5 to 6, especially 5-amino-1-pentanol and / or 6-amino-1-hexanol as organic templates. The present invention creatively uses a new type of organic template to successfully synthesize pure phase ZSM-22 molecular sieves, and the organic template used in the present invention is cheap and easy to obtain, which reduces the synthesis cost.

[0018] In the above preparation method, preferably, the aluminum source includes one or a combination of aluminum sulfate, aluminum hydroxide and pseudo-boehmite.

[0019] In the above preparation method, preferably, the alkali source includes potassium hydroxide or the like.

[0020] The inventors of this case have found through research that pure phase ZSM-22 molecular sieve can be synthesized by using potassium hydroxide as an alkali source in combination with the aluminum source, organic template and silicon source used in the present invention. However, using sodium hydroxide as an alkali source will lead to the appearance of ZSM-11 crystal phase, and pure phase ZSM-22 molecular sieve cannot be synthesized.

[0021] In the above preparation method, preferably, the silicon source includes silica sol and / or fumed silica and the like.

[0022] In the above-mentioned preparation method, preferably, in the gel mixture, the molar ratio of the silicon source calculated as SiO2, the aluminum source calculated as Al2O3, the alkali source calculated as oxide (i.e., K2O), the organic template and H2O is 1: (0.006-0.03): (0.05-0.3): (0.3-2.0): (20-80).

[0023] In the above preparation method, preferably, step (1) specifically comprises: mixing an aluminum source, an alkali source and water evenly, then adding an organic template and mixing evenly, and then adding a silicon source and mixing evenly to obtain a gel mixture.

[0024] In some specific embodiments of the present invention, step (1) can be carried out at room temperature, and the mixing of the raw materials can be carried out under stirring conditions, and the stirring speed can be conventionally adjusted by those skilled in the art.

[0025] In the above-mentioned preparation method, preferably, step (2) specifically comprises: crystallizing the gel mixture, and then at least washing, drying and calcining to obtain the ZSM-22 molecular sieve.

[0026] In some specific embodiments of the present invention, before washing and drying, cooling, solid-liquid separation and other steps may be performed. These steps may be performed in a conventional manner in the art, and the present invention does not specifically limit them.

[0027] In the above preparation method, preferably, the crystallization temperature in step (2) is 140-160° C. and the time is 36-72 h.

[0028] In the above preparation method, preferably, the crystallization in step (2) is dynamic crystallization, and the rotation speed is 35-50 rpm.

[0029] In the above preparation method, preferably, the drying temperature in step (2) is 80-120° C. and the drying time is 8-15 h.

[0030] In the above preparation method, preferably, the calcination temperature in step (2) is 450-600° C. and the calcination time is 8-15 h.

[0031] In addition, the present invention also provides the use of 5-amino-1-pentanol and / or 6-amino-1-hexanol as an organic template in the synthesis of ZSM-22 molecular sieve.

[0032] In addition, the present invention also provides a ZSM-22 molecular sieve prepared by the above-mentioned preparation method of the ZSM-22 molecular sieve.

[0033] According to a specific embodiment of the present invention, the ZSM-22 molecular sieve is a pure phase ZSM-22 molecular sieve.

[0034] According to a specific embodiment of the present invention, preferably, the BET specific surface area of ​​the ZSM-22 molecular sieve is 276-292 m 2 / g, with a total pore volume of 0.210-0.225cm 3 / g, and the mesopore volume is 0.121-0.126cm 3 / g.

[0035] The present invention provides a method for preparing a ZSM-22 molecular sieve. The preparation process and post-treatment process of the ZSM-22 molecular sieve of the present invention are simple, a new type of structure directing agent (i.e., an organic template agent) is used, and the structure directing agent used is cheap and easily available, which reduces the synthesis cost, is easy to realize industrial scale-up production, and the prepared ZSM-22 molecular sieve has the advantages of pure phase, stable pore window, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 XRD patterns of the ZSM-22 molecular sieves provided in Example 1, Comparative Example 1 and Comparative Example 2.

[0037] Figure 2a and Figure 2b The following are SEM photos of the ZSM-22 molecular sieve provided in Example 1 and Comparative Example 1 respectively. DETAILED DESCRIPTION

[0038] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0039] Example 1

[0040] This embodiment provides a method for preparing a ZSM-22 molecular sieve, which comprises the following steps:

[0041] (1) 0.24 g of aluminum sulfate, 0.33 g of potassium hydroxide and 15.75 g of deionized water were stirred and mixed at room temperature, 3.36 g of 6-amino-1-hexanol was added to the resulting solution, and the mixture was stirred and mixed again, followed by the addition of 3.75 g of silica sol (SiO2 mass concentration of 40%), and the mixture was stirred and mixed to form a uniform gel mixture;

[0042] (2) The obtained gel mixture was transferred to a high-pressure reactor lined with polytetrafluoroethylene, and dynamically crystallized at 160°C and 50 rpm for 48 hours. After that, it was cooled and washed, dried at 80°C for 12 hours, and calcined in a muffle furnace at 550°C for 15 hours to obtain the product ZSM-22 molecular sieve.

[0043] The X-ray diffraction (XRD) pattern of the product ZSM-22 molecular sieve is as follows Figure 1 The scanning electron microscope (SEM) photo of the product ZSM-22 molecular sieve is shown as follows Figure 2a As shown. Figure 1 It can be seen that the product prepared in this example has characteristic diffraction peaks at 2θ=8.2°, 20.5°, 24.3°, 24.7° and 25.8°, which are typical TON topological structure characteristic diffraction peaks, and no other structural characteristic diffraction peaks appear, indicating that the synthesized sample is a pure phase ZSM-22 molecular sieve. Figure 2a It can be seen that the morphology of the product is one-dimensional tubular, with a grain length of 1 μm and an outer diameter of 0.15 μm.

[0044] Example 2

[0045] This embodiment provides a method for preparing a ZSM-22 molecular sieve, which comprises the following steps:

[0046] (1) 0.084 g of aluminum sulfate, 0.14 g of potassium hydroxide and 6.75 g of deionized water were stirred and mixed at room temperature, 5 g of 6-amino-1-hexanol was added to the resulting solution, and the mixture was stirred and mixed again, followed by the addition of 3.75 g of silica sol (SiO2 mass concentration of 40%), and the mixture was stirred and mixed to form a uniform gel mixture;

[0047] (2) The obtained gel mixture was transferred to a high-pressure reactor lined with polytetrafluoroethylene, and dynamically crystallized at 150°C and 40 rpm for 36 hours. After that, it was cooled and washed, dried at 100°C for 10 hours, and then calcined at 500°C in a muffle furnace for 12 hours to obtain the product ZSM-22 molecular sieve.

[0048] Example 3

[0049] This embodiment provides a method for preparing a ZSM-22 molecular sieve, which comprises the following steps:

[0050] (1) 0.044 g of pseudo-boehmite (with an Al2O3 mass fraction of 70%), 0.84 g of potassium hydroxide and 22.5 g of deionized water were stirred and mixed at room temperature, 2.58 g of 5-amino-1-pentanol was added to the resulting solution, and the mixture was stirred and mixed again, and then 1.5 g of fumed silica was added, and the mixture was stirred and mixed to form a uniform gel mixture;

[0051] (2) The obtained gel mixture was transferred to a high-pressure reactor lined with polytetrafluoroethylene, and dynamically crystallized at 160°C and 35 rpm for 36 hours. After that, it was cooled and washed, dried at 120°C for 8 hours, and calcined in a muffle furnace at 600°C for 8 hours to obtain the product ZSM-22 molecular sieve.

[0052] Example 4

[0053] This embodiment provides a method for preparing a ZSM-22 molecular sieve, which comprises the following steps:

[0054] (1) 0.023 g of aluminum hydroxide, 0.56 g of potassium hydroxide and 27 g of deionized water were stirred and mixed at room temperature, 5.15 g of 5-amino-1-pentanol was added to the resulting solution, and the mixture was stirred and mixed again, and then 1.5 g of fumed silica was added, and the mixture was stirred and mixed to form a uniform gel mixture;

[0055] (2) The obtained gel mixture was transferred to a high-pressure reactor lined with polytetrafluoroethylene, and dynamically crystallized at 140°C and 45 rpm for 72 hours. After that, it was cooled, washed, dried at 80°C for 15 hours, and calcined in a muffle furnace at 450°C for 15 hours to obtain the product ZSM-22 molecular sieve.

[0056] Example 5

[0057] This embodiment provides a method for preparing a ZSM-22 molecular sieve, which comprises the following steps:

[0058] (1) 0.08 g of aluminum hydroxide, 0.6 g of potassium hydroxide and 36 g of deionized water were stirred and mixed at room temperature, 0.44 g of 5-amino-1-pentanol and 0.5 g of 6-amino-1-hexanol were added to the resulting solution, and the mixture was stirred and mixed again, followed by addition of 4 g of silica sol (SiO2 mass concentration of 40%), and the mixture was stirred and mixed to form a uniform gel mixture;

[0059] (2) The obtained gel mixture was transferred to a high-pressure reactor lined with polytetrafluoroethylene, and dynamically crystallized at 160°C and 50 rpm for 72 hours. After that, it was cooled and washed, dried at 100°C for 10 hours, and calcined in a muffle furnace at 550°C for 10 hours to obtain the product ZSM-22 molecular sieve.

[0060] Example 6

[0061] This embodiment provides a method for preparing a ZSM-22 molecular sieve, which comprises the following steps:

[0062] (1) 0.031 g of aluminum hydroxide, 0.19 g of potassium hydroxide and 12 g of deionized water were stirred and mixed at room temperature, 1.03 g of 5-amino-1-pentanol was added to the resulting solution, and the mixture was stirred and mixed again, followed by the addition of 5 g of silica sol (SiO2 mass concentration of 40%), and the mixture was stirred and mixed to form a uniform gel mixture;

[0063] (2) The obtained gel mixture was transferred to a high-pressure reactor lined with polytetrafluoroethylene, and dynamically crystallized at 160°C and 50 rpm for 72 hours. After that, it was cooled and washed, dried at 80°C for 10 hours, and calcined in a muffle furnace at 500°C for 12 hours to obtain the product ZSM-22 molecular sieve.

[0064] Example 7

[0065] This embodiment provides a method for preparing a ZSM-22 molecular sieve, which comprises the following steps:

[0066] (1) 0.146 g of pseudo-boehmite (with an Al2O3 mass fraction of 70%), 1.12 g of potassium hydroxide and 48 g of deionized water were stirred and mixed at room temperature, 7.81 g of 6-amino-1-hexanol was added to the resulting solution, and the mixture was stirred and mixed again, and then 2 g of fumed silica was added, and the mixture was stirred and mixed to form a uniform gel mixture;

[0067] (2) The obtained gel mixture was transferred to a high-pressure reactor lined with polytetrafluoroethylene, and dynamically crystallized at 160°C and 35 rpm for 48 hours. After that, it was cooled and washed, dried at 120°C for 8 hours, and calcined in a muffle furnace at 450°C for 12 hours to obtain the product ZSM-22 molecular sieve.

[0068] Example 8

[0069] This embodiment provides a method for preparing a ZSM-22 molecular sieve, which comprises the following steps:

[0070] (1) 0.062 g of aluminum hydroxide, 0.45 g of potassium hydroxide and 24 g of deionized water were stirred and mixed at room temperature, 3.59 g of 6-amino-1-hexanol was added to the resulting solution, and the mixture was stirred and mixed again, followed by the addition of 4 g of silica sol (SiO2 mass concentration of 40%), and the mixture was stirred and mixed to form a uniform gel mixture;

[0071] (2) The obtained gel mixture was transferred to a high-pressure reactor lined with polytetrafluoroethylene, and dynamically crystallized at 140°C and 40 rpm for 72 hours. After that, it was cooled and washed, dried at 120°C for 8 hours, and calcined in a muffle furnace at 550°C for 8 hours to obtain the product ZSM-22 molecular sieve.

[0072] Comparative Example 1

[0073] This comparative example provides a method for preparing a ZSM-22 molecular sieve, which is substantially the same as that of Example 1, except that the organic template 6-amino-1-hexanol in Example 1 is replaced by 1,6-hexanediamine.

[0074] The preparation method comprises the following steps:

[0075] (1) 0.24 g of aluminum sulfate, 0.33 g of potassium hydroxide and 15.75 g of deionized water were stirred and mixed at room temperature, 3.36 g of 1,6-hexanediamine was added to the resulting solution, and the mixture was stirred and mixed again, followed by the addition of 3.75 g of silica sol (SiO2 mass concentration of 40%), and the mixture was stirred and mixed to form a uniform gel mixture;

[0076] (2) The obtained gel mixture was transferred to a high-pressure reactor lined with polytetrafluoroethylene, and dynamically crystallized at 160°C and 50 rpm for 48 hours. After that, it was cooled and washed, dried at 80°C for 12 hours, and calcined in a muffle furnace at 550°C for 15 hours to obtain the product ZSM-22 molecular sieve.

[0077] The X-ray diffraction (XRD) pattern of the product ZSM-22 molecular sieve is as follows Figure 1The scanning electron microscope (SEM) photo of the product ZSM-22 molecular sieve is shown as follows Figure 2b As shown. Figure 1 and Figure 2b It can be seen that the ZSM-22 molecular sieve prepared by conventional template in this comparative example also shows the crystal phase of ZSM-22, and its morphology is one-dimensional tubular. However, the crystal length of the ZSM-22 molecular sieve product is 2.5 μm, the outer diameter is 0.25 μm, and the crystal size is larger than that of Example 1.

[0078] Comparative Example 2

[0079] This comparative example provides a method for preparing a ZSM-22 molecular sieve, which is substantially the same as that of Example 1, except that the organic template 6-amino-1-hexanol in Example 1 is replaced by ethanolamine.

[0080] The preparation method comprises the following steps:

[0081] (1) 0.24 g of aluminum sulfate, 0.33 g of potassium hydroxide and 15.75 g of deionized water were stirred and mixed at room temperature, 3.36 g of ethanolamine was added to the resulting solution, and the mixture was stirred and mixed again, followed by the addition of 3.75 g of silica sol (SiO2 mass concentration of 40%), and the mixture was stirred and mixed to form a uniform gel mixture;

[0082] (2) The obtained gel mixture was transferred to a high-pressure reactor lined with polytetrafluoroethylene, and dynamically crystallized at 160°C and 50 rpm for 48 hours. After that, it was cooled and washed, dried at 80°C for 12 hours, and calcined in a muffle furnace at 550°C for 15 hours to obtain the product ZSM-22 molecular sieve.

[0083] The X-ray diffraction (XRD) pattern of the product ZSM-22 molecular sieve is as follows Figure 1 As shown. Figure 1 It can be seen that the ZSM-22 molecular sieve prepared in this comparative example using ethanolamine as a template also shows a ZSM-22 crystal phase. However, the relative crystallinity of the ZSM-22 molecular sieve is lower than that of Example 1.

[0084] Test Case

[0085] In this test example, the nitrogen physical adsorption and desorption isotherms of the molecular sieves prepared in Examples 1 to 8 and Comparative Examples 1 to 2 were measured and characterized by conventional methods such as the BET method (including the BJH method). The obtained specific surface area and pore structure data are shown in Table 1.

[0086] Table 1 Specific surface area and pore structure data of each product ZSM-22 molecular sieve

[0087]

[0088] It can be seen from the data in Table 1 that compared with the preparation method using conventional 1,6-hexanediamine as a template and using ethanolamine as a template, the method of the present invention uses 5-amino-1-pentanol and / or 6-amino-1-hexanol as a template, and the prepared ZSM-22 molecular sieve has a larger specific surface area, total pore volume and mesopore volume.

[0089] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing a ZSM-22 molecular sieve, comprising the following steps: (1) mixing an aluminum source, an alkali source, water, an organic template, and a silicon source to obtain a gel mixture; (2) subjecting the gel mixture to at least crystallization and calcination to obtain the ZSM-22 molecular sieve; Wherein, the organic template comprises an alcoholamine compound having a carbon number of 5 to 6.

2. The preparation method according to claim 1, wherein The organic template includes 5-amino-1-pentanol and / or 6-amino-1-hexanol.

3. The preparation method according to claim 1, wherein The aluminum source includes one or a combination of aluminum sulfate, aluminum hydroxide and pseudo-boehmite.

4. The preparation method according to claim 1, wherein The alkaline source includes potassium hydroxide.

5. The preparation method according to claim 1, wherein The silicon source includes silica sol and / or fumed silica.

6. The preparation method according to claim 1, wherein In the gel mixture, the molar ratio of the silicon source calculated as SiO2, the aluminum source calculated as Al2O3, the alkali source calculated as oxide, the organic template and H2O is 1: (0.006-0.03): (0.05-0.3): (0.3-2.0): (20-80).

7. The preparation method according to claim 1, wherein Step (1) specifically comprises: mixing an aluminum source, an alkali source and water evenly, then adding an organic template and mixing evenly, and then adding a silicon source and mixing evenly to obtain a gel mixture.

8. The preparation method according to claim 1, wherein Step (2) specifically includes: crystallizing the gel mixture, and then at least washing, drying and calcining to obtain the ZSM-22 molecular sieve.

9. The preparation method according to claim 1 or 8, wherein: The crystallization temperature in step (2) is 140-160° C. and the crystallization time is 36-72 hours.

10. The preparation method according to claim 1 or 8, wherein: The crystallization in step (2) is dynamic crystallization, and the rotation speed is 35-50 rpm.

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