Hollow structured zsm-12 molecular sieve and method for making same

Abstract

The application provides a hollow-structure ZSM-12 molecular sieve and a preparation method thereof, the crystal form is a ZSM-12 molecular sieve structure, the crystal is a single-crystal particle hollow-structure crystal characterized by a transmission electron microscope, the central part of the crystal is hollow, and the crystal presents a hollow structure. The preparation method comprises the following steps: firstly, ZSM-12 molecular sieve is contacted with water vapor for treatment, then the material obtained after washing, separation and drying is mixed with inorganic alkali, an aluminum source, a silicon source and water for reaction, and finally the ZSM-12 molecular sieve obtained after washing, separation, drying and calcination. The application provides a novel method for synthesizing ZSM-12 molecular sieve with a hollow structure, overcomes the problem that the existing synthesis and preparation method of hollow zeolite in the prior art cannot obtain ZSM-12 molecular sieve with a hollow structure, and the preparation method provided by the application has a simple process route and is suitable for large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of inorganic synthesis, and relates to a zeolite material and a preparation method thereof, in particular to a ZSM-12 molecular sieve and a preparation method thereof. BACKGROUND

[0002] Zeolite molecular sieve is a kind of microporous crystalline material with framework structure, has a specific pore size and a large specific surface area, and is widely used in the fields of catalysis and separation, especially in the aspects of petroleum refining and processing, coal chemical industry, biomass industry and natural gas chemical industry.

[0003] ZSM-12 zeolite molecular sieve is a kind of molecular sieve with twelve-membered ring pore structure, and has a one-dimensional linear non-crossing twelve-membered ring elliptical straight pore structure. The ZSM-12 zeolite molecular sieve can exhibit excellent catalytic performance in the reaction processes of catalytic cracking, catalytic dewaxing, hydrocracking, reforming, aromatization, isomerization and alkylation.

[0004] CN104437606A discloses a ZSM-12 molecular sieve with a multi-layer structure and a preparation method thereof. The preparation process is that a silicon source, an aluminum source, an alkali source, water and a template agent are uniformly mixed and stirred according to a certain proportion, then ZSM-12 molecular sieve is added and uniformly stirred, and a mixture is obtained; the mixture is put into a reaction kettle for crystallization, and the ZSM-12 molecular sieve with the multi-layer structure is obtained.

[0005] CN106966408A discloses a bifunctional template for oriented synthesis of hierarchical pore ZSM-12 type zeolite molecular sieve, a preparation method thereof and a molecular sieve based on the same. The bifunctional template is prepared first, and then a mesopore-micropore dual-pore hierarchical pore ZSM-12 zeolite is prepared by using the bifunctional template in a one-step hydrothermal crystallization method.

[0006] At present, the zeolite molecular sieve material with a hollow structure is a kind of special functional material. The research on the related material has become a research hotspot in the fields of chemistry and new materials. The hollow zeolite molecular sieve has a multi-level structure and a large specific surface area, and has unique physical and chemical properties, and therefore has a broad application prospect in shape-selective adsorbents, catalysts, drug sustained-release agents and micro-reactors, and has attracted more and more attention.

[0007] CN102491366A discloses a preparation method of a hollow ZSM-5 nano zeolite. The ZSM-5 nano zeolite is treated with a mixture of a quaternary ammonium salt and sodium hydroxide in a molar ratio of 1:1, a mixture of a quaternary ammonium salt and potassium hydroxide in a molar ratio of 1:1, n-butylamine and a quaternary ammonium base at 80-200℃ for 10-200h, and finally the hollow ZSM-5 zeolite is obtained.

[0008] CN104591220A discloses a kind of hollow beta zeolite and its preparation method, first water, inorganic alkali, aluminium source and beta zeolite are mixed in turn stirring;Then be loaded into airtight reactor constant temperature processing certain time, hollow beta zeolite is obtained.

[0009] At present, there is no mature hollow structure ZSM-12 molecular sieve technology disclosed, and it is urgent to develop the preparation technology of hollow structure ZSM-12 molecular sieve and expand the application field of ZSM-12 molecular sieve. SUMMARY

[0010] In view of the deficiencies in the prior art, the present application provides a hollow structure ZSM-12 molecular sieve and its preparation method, providing a novel method for synthesizing ZSM-12 molecular sieve with hollow structure, overcoming the problem that the existing synthesis and preparation method of hollow zeolite cannot obtain ZSM-12 molecular sieve with hollow structure, and the preparation method provided by the present application has a simple process route, does not increase additional equipment and use expensive reagents, is easy to operate, and is especially suitable for large-scale industrial production.

[0011] The present application first provides a ZSM-12 molecular sieve with hollow structure, which has the following characteristics: the molecular sieve crystal form is ZSM-12 molecular sieve structure characterized by X-ray diffractometer, and the crystal is a single crystal particle with hollow structure characterized by transmission electron microscope, the center part of the crystal is hollow, and the crystal presents a hollow structure.

[0012] Further, as a specific embodiment, the particle diameter of the ZSM-12 molecular sieve crystal with hollow structure is 50-800 nm, preferably 80-700 nm.

[0013] Further, as a specific embodiment, the shell thickness of the ZSM-12 molecular sieve crystal particle with hollow structure is 20-350 nm, preferably 30-300 nm.

[0014] Further, as a specific embodiment, the silicon-aluminum oxide ratio of the ZSM-12 molecular sieve with hollow structure is 8-110, preferably 10-100.

[0015] Further, as a specific embodiment, the surface area of the ZSM-12 molecular sieve with hollow structure is 280-640 m 2 / g, preferably 300-600 m 2 / g.

[0016] Further, as a specific embodiment, the pore volume of the ZSM-12 molecular sieve with hollow structure is 0.08-0.32 cm 3 / g, preferably 0.1-0.3 cm 3 / g.

[0017] Further, as a specific embodiment, the ZSM-12 molecular sieve with hollow structure has an acid amount of 0.045-0.21 mmol / g, preferably 0.05-0.2 mmol / g.

[0018] The present application also provides a preparation method of the ZSM-12 molecular sieve with hollow structure, comprising the following steps:

[0019] (1) treating the ZSM-12 molecular sieve by contacting with water vapor, then washing, separating and drying;

[0020] (2) mixing the material obtained after drying in step (1), inorganic base, aluminum source, silicon source, methyl triethyl ammonium chloride and water under mixing condition to react, then washing, separating and drying the reacted material;

[0021] (3) obtaining the ZSM-12 molecular sieve by calcining the solid-phase material obtained after drying in step (2).

[0022] The present application also provides a preparation method of the H-ZSM-12 molecular sieve with hollow structure, comprising the following steps:

[0023] S1, preparing a ZSM-12 molecular sieve precursor, comprising the following steps:

[0024] (1) treating the ZSM-12 molecular sieve by contacting with water vapor, then washing, separating and drying;

[0025] (2) mixing the material obtained after drying in step (1), inorganic base, aluminum source, silicon source, methyl triethyl ammonium chloride and water under mixing condition to react, then washing, separating and drying the reacted material;

[0026] S2, ammonium exchanging the solid-phase material obtained after drying in step (2);

[0027] S3, obtaining the H-ZSM-12 molecular sieve by further washing, separating, drying and calcining the material after the ammonium exchanging in step S2.

[0028] As a specific embodiment, in the above preparation method, the ZSM-12 molecular sieve in step (1) can be selected from commercially available ZSM-12 molecular sieves in the art, or synthesized by using the existing method for synthesizing ZSM-12 molecular sieves. More specifically, the ZSM-12 molecular sieve zeolite generally has the following properties: the particle diameter of the ZSM-12 molecular sieve crystal is 50-800 nm, the surface area is 300-740 m 2 / g, and the pore volume is 0.08-0.38 cm 3 / g.

[0029] As a specific embodiment, in the preparation method, the treatment temperature in step (1) is 350-730°C, preferably 400-700°C, and the treatment time is 2-8h, preferably 3-6h.

[0030] As a specific embodiment, in the preparation method, the treatment of ZSM-12 molecular sieve with water vapor in step (1) is a gas-solid two-phase reaction, and the ZSM-12 molecular sieve is treated by being fully contacted with water vapor. Specifically, the following operation mode can be used: a support is placed in the reactor, the ZSM-12 molecular sieve is placed on the support, and a certain amount of water is added to the lower part of the reactor; the ZSM-12 molecular sieve is prevented from directly contacting with the liquid water, the water vapor fills the entire reactor during the treatment, and the water vapor and the ZSM-12 molecular sieve interact with each other; further, the weight ratio of the ZSM-12 molecular sieve to water is 0.08-0.25, preferably 0.1-0.2.

[0031] As a specific embodiment, in the preparation method, the washing, separation and drying in step (1) can be selected from the existing operation modes in the art, and preferably in the present application, the washing is washing with deionized water until the filtrate is neutral, which can be washed several times, and usually needs to be washed multiple times. The separation is liquid-solid two-phase separation of the stream obtained after washing, which can be any one of the modes capable of realizing liquid-solid two-phase separation such as filtration and centrifugal separation, and the drying is generally drying treatment at 100-140°C for 5-15h.

[0032] As a specific embodiment, in the preparation method, the inorganic base in step (2) is an alkali metal hydroxide, and the alkali metal can be at least one of lithium, sodium and potassium, and specifically can be selected from one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide.

[0033] As a specific embodiment, in the preparation method, the aluminum source in step (2) is an aluminum salt, preferably an inorganic salt containing aluminum, and the acid radical ion of the aluminum salt can be one or more of sulfate, metavanadate, nitrate and chloride. Specifically, it can be selected from one or more of sodium aluminate, aluminum sulfate, aluminum chloride and aluminum nitrate.

[0034] As a specific embodiment, in the preparation method, the silicon source in step (2) is a silicon-containing compound, and specifically can be selected from one or more of white carbon black, silica gel and silica sol.

[0035] As a specific embodiment, in the preparation method, the ratio of the inorganic base, the aluminum source, the silicon source, the material obtained after drying in step (1), MTEA, and water in step (2) is 0.8-2.5:1.2-2.7:2.5-6:8-25:0.8-2.2:100, preferably 1-2:1.5-2.5:2-4:10-20:1-2:100.

[0036] As a specific embodiment, in the preparation method, the reaction in step (2) is carried out at a temperature of 70-150°C, preferably 80-120°C, and the reaction time is generally controlled to be 13-22h, preferably 15-20h.

[0037] As a specific embodiment, in the preparation method, the washing, separation, and drying in step (2) can be selected from the existing operation modes in the art, and preferably in the present application, the washing is washing with deionized water until the filtrate is neutral, which can be washed for several times, and generally needs to be washed for multiple times, and specifically can be controlled to be 1-10 times. The separation is liquid-solid two-phase separation of the stream obtained after washing, and any one of the modes capable of realizing liquid-solid two-phase separation such as filtration and centrifugal separation can be used, and the drying is generally drying treatment at 80-150°C for 1-20h.

[0038] As a specific embodiment, in the preparation method, the ammonium exchange treatment in step S2 can use any one of the existing ammonium exchange modes in the art; and the ammonium exchange treatment is carried out at least once, preferably 3-5 times.

[0039] As a specific embodiment, in the preparation method, the ammonium exchange treatment in step S2 is ion exchange treatment of the solid-phase material obtained after drying in step (2), an ammonium salt, and water, wherein the mass ratio of the solid-phase material obtained after drying in step (2), the ammonium salt, and water is 8-25:8-25:100, preferably 10-20:10-20:100.

[0040] As a specific embodiment, in the preparation method, the ammonium salt can be one or more of ammonium nitrate and ammonium chloride, and preferably is ammonium nitrate.

[0041] As a specific embodiment, in the preparation method, the ion exchange treatment temperature is 70-100°C, preferably 80-90°C, and the ion exchange treatment time is 1-5h, preferably 2-4h.

[0042] As a specific embodiment, in the preparation method, the washing, separation, drying and calcination in step S3 can be selected from the existing operation modes in the art, and preferably in the scheme of the present application, the washing is washing with deionized water until the filtrate is neutral, which can be washed for several times, and usually needs to be washed for multiple times, and specifically can be controlled to 1-10 times. The separation is liquid-solid two-phase separation of the stream obtained after washing, and any one of the liquid-solid two-phase separation modes such as filtration and centrifugal separation can be used, the drying is generally drying treatment at 80-150 DEG C for 1-20 h. The calcination is high-temperature calcination treatment at 400-600 DEG C for 1-10 h, and the calcination is carried out in the presence of an oxygen-containing atmosphere (such as air or oxygen).

[0043] The hollow-structured ZSM-12 molecular sieve and the preparation method thereof provided by the present application have the following technical effects and advantages:

[0044] Based on the research and experiments on the preparation process of the existing hollow-structured molecular sieve, the existing method for preparing the hollow-structured molecular sieve cannot be applied to the preparation of the hollow-structured ZSM-12 molecular sieve, which may be because different types of molecular sieves have different crystal structures, and thus the physical and chemical properties are also quite different. As we all know, the synthesis methods of different types of zeolites cannot be completely universal, and the preparation method of the hollow-structured molecular sieve cannot be directly used for different types of zeolites, and different hollow-structured molecular sieves cannot be obtained by directly replacing the raw material types. For example, treating a conventional zeolite with an inorganic base can produce a mesoporous structure in the zeolite crystal to obtain a mesoporous zeolite, but CN104591220A can prepare a hollow Beta zeolite under the joint action of an inorganic base and an aluminum source. Since the ZSM-12 molecular sieve has special properties, the existing method cannot treat the ZSM-12 molecular sieve to obtain the hollow-structured ZSM-12 molecular sieve.

[0045] In the preparation method, the ZSM-12 molecular sieve is first pretreated by high-temperature steam, and the silicon and aluminum in the ZSM-12 molecular sieve crystal will rearrange positions during the pretreatment process. After analysis, it is believed that the main reason may be that the aluminum element migrates to the outside of the crystal, and the aluminum element forms a gradient distribution inside and outside the crystal, the aluminum content of the outside of the crystal increases, and the aluminum content of the inside decreases, which is beneficial to the formation of the hollow structure.

[0046] In this invention, the ZSM-12 molecular sieve treated with high-temperature steam is reacted with other raw materials for synthesizing molecular sieves, such as inorganic alkali, aluminum source, and silicon source. The ratio of each material is controlled within a certain range (significantly different from the existing raw material ratios for ZSM-12 molecular sieve preparation, and not within the effective range of material ratios in conventional hydrothermal synthesis reactions). During the reaction, the inorganic alkali, aluminum source, and silicon source react with the treated ZSM-12 molecular sieve. Aluminum enters the exterior of the ZSM-12 molecular sieve crystal, while a dissolution reaction occurs inside the ZSM-12 molecular sieve crystal, thus forming a hollow structure. The secondary crystallization reaction in this method differs from the existing hydrothermal synthesis reaction of zeolites. In this method, the silicon source basically does not enter the ZSM-12 molecular sieve crystal framework during the reaction. The template agent, such as methyltriethylammonium chloride, can stabilize the crystal structure and prevent crystal collapse. Analysis suggests that in this preparation method, the silicon source only plays a stabilizing role in the system; without a silicon source, the zeolite cannot effectively transform into a hollow structure. Attached Figure Description

[0047] Figure 1 The image shown is a transmission electron microscope image of the sample obtained in Example 1.

[0048] Figure 2 Transmission electron microscope images of the sample obtained for comparison example 1.

[0049] Figure 3 The XRD pattern of the sample obtained in Example 1 is shown.

[0050] Figure 4 The XRD pattern of the sample was obtained for comparison example 1. Detailed Implementation

[0051] The technical solutions and effects of the present invention will be further illustrated below with reference to the embodiments, but the invention is not limited to the following embodiments.

[0052] In this paper, the pore structure of the zeolite material was characterized by N2 adsorption-desorption using a physical adsorption instrument from Micron Technology (USA). Prior to measurement, the samples were vacuum-treated at 300℃ for at least 4 hours. Parameters such as specific surface area and pore size were calculated using the BET and BJH formulas.

[0053] In this paper, the phase structure and crystallinity of zeolite materials were characterized by X-ray diffraction. The tests were performed using a Rigaku D / max2500 X-ray diffractometer with a Cu target, Kα radiation source, graphite monochromator, tube voltage of 40 kV, tube current of 80 mA, scanning range of 5° to 40°, step size of 0.1°, and scanning speed of 1° / min.

[0054] In the present text, the acid amount of the zeolitic material is measured by ammonia temperature programmed desorption, and the ammonia temperature programmed desorption test is carried out by using an AutoChem II 2920 chemisorption instrument manufactured by the Micromeritics Company of the United States, first heated to 550℃ at a rate of 10℃ / min under the protection of helium and kept for 1h; then reduced to room temperature (25℃) at a rate of 10℃ / min, changed to ammonia and adsorbed for 1h; then changed to helium and heated to 600℃ at a rate of 10℃ / min.

[0055] In the present text, the crystal morphology of the zeolitic material is characterized by transmission electron microscopy, and a high-resolution transmission electron microscope manufactured by the JEOL Company of Japan is used, the instrument model is JEM-2200FS field emission ultra-high resolution transmission electron microscope, the acceleration voltage is 200KV, and the point resolution is 0.19nm.

[0056] In the present text, the chemical reagents used are all analytical pure chemical reagents, which can be obtained by purchasing commercially available goods.

[0057] Example 1

[0058] ZSM-12 molecular sieve and water were weighed according to the mass ratio of 15.5:100. Then the ZSM-12 molecular sieve and water were respectively placed above and below the support of the reaction kettle, and the two did not directly contact, then the reaction kettle was sealed for reaction, the reaction temperature was 550℃, and the reaction time was 8h. The reaction product was washed, filtered and dried to obtain a first material, the drying temperature was 120℃, and the drying time was 10h. Sodium hydroxide, aluminum nitrate, white carbon black, the obtained first material, methyl triethyl ammonium chloride, and deionized water were mixed according to the mass ratio of 1.6:1.8:4:12:1.5:100, and then were continuously loaded into a sealed reaction kettle for reaction, the reaction temperature was 110℃, and the reaction time was 23h. The reaction product was washed, filtered and dried to obtain a second material, the drying temperature was 120℃, and the drying time was 10h. Then ammonium nitrate, the second material, and water were mixed according to the mass ratio of 16:15:100 for ammonium exchange treatment, the treatment temperature was 87℃, the treatment time was 3h, and the treatment was repeated for 3 times. After the end, the obtained solid sample was filtered for several times, and then was dried at 120℃ for 10h. Finally, the sample was calcined in air at 500℃ for 10h, and the obtained sample was numbered as C1. The crystal structure of the prepared sample belongs to ZSM-12 zeolite, and the crystal morphology is a hollow structure.

[0059] Example 2

[0060] ZSM-12 molecular sieve and water were weighed according to a mass ratio of 10:100. Then the ZSM-12 molecular sieve and water were respectively placed above and below the support of the reaction kettle, without direct contact, and then the reaction kettle was closed for reaction, with a reaction temperature of 400 ℃ and a reaction time of 4 h. The reaction product was washed, filtered and dried to obtain a first material, with a drying temperature of 120 ℃ and a drying time of 6 h. Sodium hydroxide, aluminum nitrate, white carbon black, the obtained first material, methyl triethyl ammonium chloride and deionized water were uniformly mixed according to a mass ratio of 1:1.5:2:10:1:100, and then were continuously loaded into the closed reaction kettle for reaction, with a reaction temperature of 80 ℃ and a reaction time of 20 h. The reaction product was washed, filtered and dried to obtain a second material, with a drying temperature of 120 ℃ and a drying time of 10 h. Ammonium nitrate, the second material and water were mixed according to a mass ratio of 10:10:100 for ammonium exchange treatment, with a treatment temperature of 90 ℃ and a treatment time of 2 h, and the treatment was repeated for 3 times. Then the obtained solid sample was filtered for multiple times, and then was dried at 120 ℃ for 10 h. Finally, the sample was calcined in air at 500 ℃ for 10 h, and the obtained sample was numbered as C2. The crystal structure of the prepared sample belongs to ZSM-12 zeolite, and the crystal morphology is a hollow structure.

[0061] Example 3

[0062] ZSM-12 molecular sieve and water were weighed according to a mass ratio of 20:100. Then the ZSM-12 molecular sieve and water were respectively placed above and below the support of the reaction kettle, without direct contact, and then the reaction kettle was closed for reaction, with a reaction temperature of 700 ℃ and a reaction time of 3 h. The reaction product was washed, filtered and dried to obtain a first material, with a drying temperature of 120 ℃ and a drying time of 10 h. Sodium hydroxide, aluminum nitrate, white carbon black, the obtained first material, methyl triethyl ammonium chloride and deionized water were uniformly mixed according to a mass ratio of 2:2.5:4:20:2:100, and then were continuously loaded into the closed reaction kettle for reaction, with a reaction temperature of 120 ℃ and a reaction time of 15 h. The reaction product was washed, filtered and dried to obtain a second material, with a drying temperature of 120 ℃ and a drying time of 10 h. Ammonium nitrate, the second material and water were mixed according to a mass ratio of 20:20:100 for ammonium exchange treatment, with a treatment temperature of 80 ℃ and a treatment time of 4 h, and the treatment was repeated for 3 times. Then the obtained solid sample was filtered for multiple times, and then was dried at 120 ℃ for 10 h. Finally, the sample was calcined in air at 500 ℃ for 10 h, and the obtained sample was numbered as C3. The crystal structure of the prepared sample belongs to ZSM-12 zeolite, and the crystal morphology is a hollow structure.

[0063] Example 4

[0064] ZSM-12 molecular sieve and water were weighed according to the mass ratio of 13.2:100 respectively. Then the ZSM-12 molecular sieve and water were placed above and below the support of the reaction kettle respectively, and the two did not directly contact, then the reaction kettle was sealed for reaction, the reaction temperature was 570℃, and the reaction time was 5h. The reaction product was washed, filtered and dried to obtain a first material, the drying temperature was 120℃, and the drying time was 10h. Sodium hydroxide, aluminum sulfate, silica gel, the obtained first material, methyl triethyl ammonium chloride and deionized water were uniformly mixed according to the mass ratio of 1.2:2.1:3.2:12.5:1.2:100, and then were continuously loaded into a sealed reaction kettle for reaction, the reaction temperature was 110℃, and the reaction time was 22h. The reaction product was washed, filtered and dried to obtain a second material, the drying temperature was 120℃, and the drying time was 10h. Ammonium nitrate, the second material and water were mixed according to the mass ratio of 17.2:16.3:100 for ammonium exchange treatment, the treatment temperature was 85℃, the treatment time was 3h, and the treatment was recycled for 3 times. Then the obtained solid sample was filtered for multiple times, and then was dried at 120℃ for 10h. Finally, the sample was calcined in air at 500℃ for 10h, and the obtained sample was numbered as C4. The crystal structure of the prepared sample belongs to ZSM-12 zeolite, and the crystal morphology is a hollow structure.

[0065] Example 5

[0066] ZSM-12 molecular sieve and water were weighed according to the mass ratio of 17.4:100 respectively. Then the ZSM-12 molecular sieve and water were placed above and below the support of the reaction kettle respectively, and the two did not directly contact, then the reaction kettle was sealed for reaction, the reaction temperature was 670℃, and the reaction time was 7h. The reaction product was washed, filtered and dried to obtain a first material, the drying temperature was 120℃, and the drying time was 10h. Sodium hydroxide, aluminum chloride, silica sol, the obtained first material, methyl triethyl ammonium chloride and deionized water were uniformly mixed according to the mass ratio of 1.3:2.4:3.5:13.5:1.3:100, and then were continuously loaded into a sealed reaction kettle for reaction, the reaction temperature was 90℃, and the reaction time was 25h. The reaction product was washed, filtered and dried to obtain a second material, the drying temperature was 120℃, and the drying time was 10h. Ammonium nitrate, the second material and water were mixed according to the mass ratio of 16.5:11:100 for ammonium exchange treatment, the treatment temperature was 80℃, the treatment time was 3h, and the treatment was recycled for 3 times. Then the obtained solid sample was filtered for multiple times, and then was dried at 120℃ for 10h. Finally, the sample was calcined in air at 500℃ for 10h, and the obtained sample was numbered as C5. The crystal structure of the prepared sample belongs to ZSM-12 zeolite, and the crystal morphology is a hollow structure.

[0067] Comparative Example 1

[0068] The ZSM-12 molecular sieve was not pretreated.

[0069] The sodium hydroxide, aluminum nitrate, white carbon black, ZSM-12 molecular sieve, methyl triethyl ammonium chloride, and deionized water were mixed in a ratio of 1.6:1.8:4:12:1.5:100 by mass, and then were continuously charged into a closed reaction kettle for reaction. The reaction temperature was 110°C, and the reaction time was 23h. The reaction product was washed, filtered, and then was dried to obtain a second material. The drying temperature was 120°C, and the drying time was 10h. The ammonium nitrate, the second material, and water were mixed in a ratio of 16:15:100 by mass, and then were subjected to ammonium exchange treatment. The treatment temperature was 87°C, the treatment time was 3h, and the treatment was repeated three times. The obtained solid sample was filtered multiple times, and then was dried at 120°C for 10h. Finally, the sample was calcined in air at 500°C for 10h. The obtained sample was numbered as C6. The crystal structure of the prepared sample belonged to ZSM-12 zeolite, but was not a hollow structure.

[0070] Comparative Example 2

[0071] The ZSM-12 molecular sieve and water were weighed in a ratio of 15.5:100 by mass, respectively. Then, the ZSM-12 molecular sieve and water were respectively placed above and below the support of a reaction kettle, and were not in direct contact with each other. Then, the reaction kettle was closed for reaction. The reaction temperature was 550°C, and the reaction time was 8h. The reaction product was washed, filtered, and then was dried to obtain a first material. The drying temperature was 120°C, and the drying time was 10h. The sodium hydroxide, white carbon black, the obtained first material, methyl triethyl ammonium chloride, and deionized water were mixed in a ratio of 1.6:4:12:1.5:100 by mass, and then were continuously charged into a closed reaction kettle for reaction. The reaction temperature was 110°C, and the reaction time was 23h. The reaction product was washed, filtered, and then was dried to obtain a second material. The drying temperature was 120°C, and the drying time was 10h. The ammonium nitrate, the second material, and water were mixed in a ratio of 16:15:100 by mass, and then were subjected to ammonium exchange treatment. The treatment temperature was 87°C, the treatment time was 3h, and the treatment was repeated three times. The obtained solid sample was filtered multiple times, and then was dried at 120°C for 10h. Finally, the sample was calcined in air at 500°C for 10h. The obtained sample was numbered as C7. The crystal structure of the prepared sample belonged to ZSM-12 zeolite, but was not a hollow structure.

[0072] Comparative Example 3

[0073] ZSM-12 molecular sieve and water were weighed according to a mass ratio of 15.5:100, respectively. Then the ZSM-12 molecular sieve and water were respectively placed above and below the support of the reaction kettle, without direct contact, and then the reaction kettle was closed for reaction, with a reaction temperature of 550°C and a reaction time of 8h. The reaction product was washed, filtered and dried to obtain a first material, with a drying temperature of 120°C and a drying time of 10h. Sodium hydroxide, aluminum nitrate, the obtained first material, methyl triethyl ammonium chloride, deionized water were uniformly mixed according to a mass ratio of 1.6:1.8:12:1.5:10, and then were continuously loaded into the closed reaction kettle for reaction, with a reaction temperature of 110°C and a reaction time of 23h. The reaction product was washed, filtered and dried to obtain a second material, with a drying temperature of 120°C and a drying time of 10h. Ammonium nitrate, the second material, water were mixed according to a mass ratio of 16:15:100 for ammonium exchange treatment, with a treatment temperature of 87°C and a treatment time of 3h, and the treatment was repeated for 3 times. Then the obtained solid sample was filtered for multiple times, and then was dried at 120°C for 10h. Finally, the sample was calcined in air at 500°C for 10h, and the obtained sample was numbered as C8. The prepared sample has a crystal structure of ZSM-12 zeolite, and the crystal morphology is not a hollow structure.

[0074] Comparative Example 4

[0075] ZSM-12 molecular sieve and water were weighed according to a mass ratio of 15.5:100, respectively. Then the ZSM-12 molecular sieve and water were respectively placed above and below the support of the reaction kettle, without direct contact, and then the reaction kettle was closed for reaction, with a reaction temperature of 550°C and a reaction time of 8h. The reaction product was washed, filtered and dried to obtain a first material, with a drying temperature of 120°C and a drying time of 10h. Sodium hydroxide, aluminum nitrate, white carbon black, the obtained first material, deionized water were uniformly mixed according to a mass ratio of 1.6:1.8:4:12:100, and then were continuously loaded into the closed reaction kettle for reaction, with a reaction temperature of 110°C and a reaction time of 23h. The reaction product was washed, filtered and dried to obtain a second material, with a drying temperature of 120°C and a drying time of 10h. Ammonium nitrate, the second material, water were mixed according to a mass ratio of 16:15:100 for ammonium exchange treatment, with a treatment temperature of 87°C and a treatment time of 3h, and the treatment was repeated for 3 times. Then the obtained solid sample was filtered for multiple times, and then was dried at 120°C for 10h. Finally, the sample was calcined in air at 500°C for 10h, and the obtained sample was numbered as C9. The prepared sample has an amorphous structure, and does not belong to a crystal.

[0076] Comparative Example 5

[0077] ZSM-12 molecular sieve and water were weighed according to a mass ratio of 15.5:100. Then the ZSM-12 molecular sieve and water were respectively placed above and below the support of the reaction kettle, without direct contact, and then the reaction kettle was sealed for reaction. The reaction temperature was 150°C, and the reaction time was 8h. The reaction product was washed, filtered, and then dried to obtain a first material. The drying temperature was 120°C, and the drying time was 10h. Sodium hydroxide, aluminum nitrate, white carbon black, the obtained first material, methyl triethyl ammonium chloride, and deionized water were uniformly mixed according to a mass ratio of 1:0.5:0.2:10:0.5:100, and then were continuously loaded into the sealed reaction kettle for reaction. The reaction temperature was 80°C, and the reaction time was 23h. The reaction product was washed, filtered, and then dried to obtain a second material. The drying temperature was 120°C, and the drying time was 10h. Ammonium nitrate, the second material, and water were mixed according to a mass ratio of 16:15:100 for ammonium exchange treatment. The treatment temperature was 87°C, the treatment time was 3h, and the cycle treatment was 3 times. Then the obtained solid sample was filtered for multiple times, and then was dried at 120°C for 10h. Finally, the sample was calcined in air at 500°C for 10h, and the obtained sample was numbered as C10.

[0078] The physicochemical properties of the samples obtained in each example and comparative example are shown in Table 1.

[0079]

[0080] Note: The sample obtained in Example 1 is used as a reference, and the crystallinity thereof is set as 100%. The relative crystallinity of all other samples is obtained by comparison with the crystallinity of the reference. The original acid amount of the ZSM-12 zeolite is 0.152mmol / g.

Claims

1. A ZSM-12 molecular sieve with a hollow structure, wherein the ZSM-12 molecular sieve has the following characteristics: X-ray diffraction instrumentation shows that the molecular sieve crystal form is a ZSM-12 molecular sieve structure; transmission electron microscopy characterizes it as a hollow crystal structure with a single crystal particle, the central part of the crystal being hollow, exhibiting a hollow structure; the preparation method of the ZSM-12 molecular sieve with a hollow structure includes the following steps: (1) The ZSM-12 molecular sieve is treated by contacting water vapor, and then washed, separated and dried; the treatment temperature is 350-730℃ and the treatment time is 2-8h; (2) Under mixed conditions, the material obtained after drying in step (1), inorganic alkali, aluminum source, silicon source, methyltriethylammonium chloride, and water are mixed and reacted. The reacted material is washed, separated, and dried. The ratio of inorganic alkali, aluminum source, silicon source, material obtained after drying in step (1), MTEA, and water is 0.8-2.5:1.2-2.7:2.5-6:8-25:0.8-2.2:100 based on the weight ratio of each material. The reaction is carried out at a temperature of 70-150℃ and the reaction time is controlled at 13-22h. (3) The ZSM-12 molecular sieve is obtained by calcining the solid material obtained after drying in step (2).

2. The ZSM-12 molecular sieve with a hollow structure according to claim 1, wherein, The ZSM-12 molecular sieve crystals with hollow structure have a particle diameter of 50–800 nm and a shell thickness of 20–350 nm.

3. The ZSM-12 molecular sieve with a hollow structure according to claim 1, wherein, The ZSM-12 molecular sieve crystals with a hollow structure have a particle diameter of 80–700 nm and a shell thickness of 30–300 nm.

4. The ZSM-12 molecular sieve with a hollow structure according to claim 1, wherein, The ZSM-12 molecular sieve with a hollow structure has an oxide silica-alumina ratio of 8–110 and an acidity of 0.045–0.21 mmol / g.

5. The ZSM-12 molecular sieve with a hollow structure according to claim 1, wherein, The ZSM-12 molecular sieve with a hollow structure has an oxide silica-alumina ratio of 10–100 and an acidity of 0.05–0.2 mmol / g.

6. The ZSM-12 molecular sieve with a hollow structure according to claim 1, wherein, The surface area of ​​ZSM-12 molecular sieves with hollow structures is 280–640 m². 2 / g; pore volume is 0.08~0.32cm³ 3 / g.

7. The ZSM-12 molecular sieve with a hollow structure according to claim 1, wherein, The surface area of ​​ZSM-12 molecular sieves with hollow structures is 300–600 m². 2 / g; pore volume is 0.1~0.3cm 3 / g.

8. A method for preparing the ZSM-12 molecular sieve with a hollow structure according to any one of claims 1-7, comprising the following steps: (1) The ZSM-12 molecular sieve is treated by contacting water vapor, and then washed, separated and dried; the treatment temperature is 350-730℃ and the treatment time is 2-8h; (2) Under mixed conditions, the material obtained after drying in step (1), inorganic alkali, aluminum source, silicon source, methyltriethylammonium chloride, and water are mixed and reacted. The reacted material is washed, separated, and dried. The ratio of inorganic alkali, aluminum source, silicon source, material obtained after drying in step (1), MTEA, and water is 0.8-2.5:1.2-2.7:2.5-6:8-25:0.8-2.2:100 based on the weight ratio of each material. The reaction is carried out at a temperature of 70-150℃ and the reaction time is controlled at 13-22h. (3) The ZSM-12 molecular sieve is obtained by calcining the solid material obtained after drying in step (2).

9. A method for preparing H-ZSM-12 molecular sieve with a hollow structure, wherein the ZSM-12 molecular sieve has the following characteristics: X-ray diffraction instrumentation shows that the molecular sieve crystal form is ZSM-12 molecular sieve structure; transmission electron microscopy characterizes it as a hollow crystal structure of single crystal particles, with the central part of the crystal being hollow, exhibiting a hollow structure; the preparation method includes the following steps: S1. Preparation of ZSM-12 molecular sieve precursor, including the following steps: (1) The ZSM-12 molecular sieve is treated by contacting water vapor, and then washed, separated and dried; (2) Under mixed conditions, the material obtained after drying in step (1), inorganic alkali, aluminum source, silicon source, methyltriethylammonium chloride, and water are mixed and reacted. The reacted material is washed, separated, and dried. The ratio of inorganic alkali, aluminum source, silicon source, material obtained after drying in step (1), MTEA, and water is 0.8-2.5:1.2-2.7:2.5-6:8-25:0.8-2.2:100 based on the weight ratio of each material. The reaction is carried out at a temperature of 70-150℃ and the reaction time is controlled at 13-22h. S2. The solid material obtained after drying in step (2) is subjected to ammonium exchange treatment. S3. The material after ammonium exchange treatment in step S2 is further washed, separated, dried and calcined to obtain H-ZSM-12 molecular sieve.

10. The preparation method according to claim 8 or 9, wherein, The processing temperature in step (1) is 400-700℃ and the processing time is 3-6 h.

11. The preparation method according to claim 8 or 9, wherein, The process of contacting ZSM-12 molecular sieve with water vapor in step (1) is a gas-solid two-phase reaction. The ZSM-12 molecular sieve is fully contacted in the presence of water vapor. The following operation method is adopted: a support is placed in the reactor, the ZSM-12 molecular sieve is placed on the support, and water is added to the reactor below the support. Ensure that the ZSM-12 molecular sieve does not come into direct contact with the liquid water. During the treatment, water vapor fills the entire reactor and interacts with the ZSM-12 molecular sieve. The weight ratio of ZSM-12 molecular sieve to water is 0.08 to 0.

25.

12. The preparation method according to claim 11, wherein, The weight ratio of ZSM-12 molecular sieve to water is 0.1 to 0.

2.

13. The preparation method according to claim 8 or 9, wherein, The inorganic base in step (2) is selected from one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

14. The preparation method according to claim 8 or 9, wherein, The aluminum source in step (2) is an aluminum salt, and the anions of the aluminum salt are one or more of sulfate, aluminate, nitrate and chloride ions.

15. The preparation method according to claim 8 or 9, wherein, The aluminum source in step (2) is selected from one or more of sodium aluminate, aluminum sulfate, aluminum chloride, and aluminum nitrate.

16. The preparation method according to claim 8 or 9, wherein, The silicon source in step (2) is selected from one or more of silica, silica gel, and silica sol.

17. The preparation method according to claim 8 or 9, wherein, Based on the weight ratio of each material, the ratio of inorganic alkali, aluminum source, silicon source, material obtained after drying in step (1), MTEA, and water in step (2) is 1~2:1.5~2.5:2~4:10~20:1~2:

100.

18. The preparation method according to claim 8 or 9, wherein, The reaction in step (2) is carried out at a temperature of 80-120℃ and the reaction time is controlled to be 15-20h.

19. The preparation method according to claim 9, wherein, The ammonium exchange treatment in step S2 is to mix the solid material obtained after drying in step (2), ammonium salt, and water for ion exchange treatment, wherein the mass ratio of the solid material obtained after drying in step (2), ammonium salt, and water is 8-25:8-25:

100.

20. The preparation method according to claim 9, wherein, The ammonium exchange treatment in step S2 is to mix the solid material obtained after drying in step (2), ammonium salt, and water for ion exchange treatment, wherein the mass ratio of the solid material obtained after drying in step (2), ammonium salt, and water is 10-20:10-20:

100.

21. The preparation method according to claim 19 or 20, wherein, The ammonium salt is one or more of ammonium nitrate and ammonium chloride.

22. The preparation method according to claim 19 or 20, wherein, The ammonium salt is ammonium nitrate.

23. The preparation method according to claim 19 or 20, wherein, The ion exchange treatment temperature is 70–100℃, and the ion exchange treatment time is 1–5 h.

24. The preparation method according to claim 19 or 20, wherein, The ion exchange treatment temperature is 80–90℃, and the ion exchange treatment time is 2–4 h.

25. The preparation method according to claim 9, wherein, The calcination in step S3 is a high-temperature calcination treatment at 400-600℃ for 1-10 hours, and the calcination is carried out in the presence of an oxygen-containing atmosphere.

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