A self-supporting mfi nanosheet molecular sieve, and a preparation method and use thereof

Abstract

The present application relates to the technical field of molecular sieve, in particular to a kind of self-supporting MFI nanosheet molecular sieve and its preparation method and purposes, the preparation method of the self-supporting MFI nanosheet molecular sieve includes the following steps: 1) after mixing silicon source, aluminium source, alkali source, template agent and water, obtain gel mixture;2) the gel mixture obtained in step 1) is crystallized, i.e. the self-supporting MFI nanosheet molecular sieve is obtained;Wherein, the template agent is imidazolyl quaternary ammonium salt compound.The self-supporting MFI nanosheet molecular sieve prepared in the present application does not need expensive surfactant, no phosphorus species is left in channel after calcination, the range of silicon-aluminum ratio is wide, and it is simple and easy to repeat.

Description

A self-supporting MFI nanosheet molecular sieve, its preparation method and applications Technical Field

[0001] This invention relates to the field of molecular sieve technology, and in particular to a self-supporting MFI nanosheet molecular sieve, its preparation method, and its applications. Background Technology

[0002] Since Argauer and Landelt et al. first synthesized ZSM-5 molecular sieves (MFI topology) using tetrapropylammonium hydroxide in 1972, MFI molecular sieves have been widely used in many fields such as petrochemicals, environmental catalysis, fine chemicals, and adsorption separation, making them one of the most important and widely used molecular sieves. With the increasing demand for deep processing of heavy oil and fine chemical products, the requirements for the mass transfer and diffusion efficiency of molecular sieve catalysts are also increasing. Nanosheet molecular sieves have attracted significant attention from researchers due to their advantages such as shortened mass transfer paths, improved diffusion capacity, and increased exposure of active sites.

[0003] In recent years, reports on MFI nanosheet molecular sieves have gradually increased. For example, in 2009, Ryoo et al. designed quaternary ammonium salt surfactant template agents [C 22 H 45 -N + (CH3)2-C6H 12 -N + (CH3)2-C6H 13 ·Br2 2- [The text appears to be a fragmented and incomplete sentence, possibly due to OCR errors. A more accurate translation would require the full context.] 10 H 20 -N + (CH3)2-C6H 13 ·Br -The growth of MFI nanosheet molecular sieves was restricted by the π-π interaction between the hydrophobic benzene rings at the tail of the template agent (Nat. Commun. 2014, 5, 4262.). However, due to the high synthesis cost of surfactant template agents, the MFI nanosheet molecular sieves synthesized by this method are difficult to promote to industrial applications. In 2012, Tsapatsis et al. first synthesized a self-supporting five-membered ring chain molecular sieve with a house-of-cards morphology and a thickness of 2 nm, abbreviated as SPP, using the small molecule template agent tetrabutylphosphine hydroxide (Science 2012, 336, 1684.). However, the phosphorus species remaining in the pores after calcination affected the catalytic reaction performance, and only high-silica SPP could be synthesized. Rimer et al. synthesized self-supporting MFI nanosheet molecular sieves without a template (Adv. Mater. 2021, 33, 2100897.), but only low-silica molecular sieves could be synthesized, which limited its application to a certain extent. The synthesis of self-supporting MFI nanosheet molecular sieves needs further optimization. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a self-supporting MFI nanosheet molecular sieve, its preparation method and uses, to solve the problems in the prior art.

[0005] To achieve the above and other related objectives, the present invention provides a method for preparing self-supporting MFI nanosheet molecular sieves, the method comprising the following steps:

[0006] 1) A gel mixture is obtained by mixing a silicon source, an aluminum source, an alkali source, a template agent and water, wherein the template agent is an imidazolium quaternary ammonium salt;

[0007] 2) Crystallize the gel mixture obtained in step 1) to obtain the self-supporting MFI nanosheet molecular sieve.

[0008] The present invention also provides a self-supporting MFI nanosheet molecular sieve, wherein the self-supporting MFI nanosheet molecular sieve is prepared by the preparation method described above.

[0009] The present invention also provides the use of the self-supporting MFI nanosheet molecular sieve as a catalyst.

[0010] As described above, the self-supporting MFI nanosheet molecular sieve of the present invention, its preparation method, and its uses have the following beneficial effects:

[0011] 1) This invention uses R1: 1,1-(hexane-1,6-diyl)bis(3-ethyl-1H-imidazol-3-onthium)ammonium hydroxide or R2: 1,1-(pentane-1,5-diyl)bis(3-ethyl-1H-imidazol-3-onthium)ammonium hydroxide or R3: 1,1-(hexane-1,6-diyl)bis(3-propyl)ammonium hydroxide.

[0012] Using 1H-imidazol-3-onium)ammonium hydroxide or R4: 1,1-(hexane-1,6-diyl)bis(3-butyl-1H-imidazol-3-onium)ammonium hydroxide as a template agent, compared with surfactant template agents, tetrabutylphosphine hydroxide or template-free methods, the single template agent of this application can synthesize all-silicon and silicon-aluminum controllable self-supporting MFI nanosheet molecular sieves in one step, without the need for expensive surfactants, without phosphorus species remaining in the pores after calcination, with a wide silicon-aluminum ratio range, and simple and reproducible operation;

[0013] 2) The self-supporting MFI nanosheet molecular sieve prepared by the method of the present invention has a larger silicon-to-aluminum ratio, which is not less than 15. The controllable aluminum content makes the number of Bronsted acids in the self-supporting MFI nanosheet molecular sieve controllable. Therefore, the self-supporting MFI nanosheet molecular sieve obtained in this application has a wider range of applications.

[0014] 3) The self-supporting MFI nanosheet molecular sieve prepared by the method of the present invention has excellent activity in methanol to propylene (MTP), Beckmann rearrangement, and 1-hexene catalytic cracking reaction;

[0015] 4) The self-supporting MFI nanosheet molecular sieve prepared by the method of the present invention has a shorter b-axis and a shorter diffusion path, which gives it a longer lifetime and propylene selectivity in the methanol-to-propylene reaction. Attached Figure Description

[0016] Figure 1 shows the XRD pattern of the self-supporting MFI nanosheet molecular sieve obtained in Example 3 of the present invention.

[0017] Figure 2 shows a SEM image of the self-supporting MFI nanosheet molecular sieve obtained in Example 3 of the present invention.

[0018] Figure 3 shows a TEM image of the self-supporting MFI nanosheet molecular sieve obtained in Example 3 of the present invention.

[0019] Figure 4 shows the N2 adsorption curve of the self-supporting MFI nanosheet molecular sieve obtained in Example 3 of the present invention.

[0020] Figure 5 shows the solid aluminum NMR spectrum of the self-supporting MFI nanosheet molecular sieve obtained in Example 3 of the present invention.

[0021] Figure 6 shows the MTP reactivity of the self-supporting MFI nanosheet molecular sieve obtained in Example 3 of the present invention. Detailed Implementation

[0022] This invention first provides a method for preparing self-supporting MFI nanosheet molecular sieves, the method comprising the following steps:

[0023] 1) A gel mixture is obtained by mixing a silicon source, an aluminum source, an alkali source, a template agent and water, wherein the template agent is an imidazolium quaternary ammonium salt compound;

[0024] 2) Crystallize the gel mixture obtained in step 1) to obtain the self-supporting MFI nanosheet molecular sieve.

[0025] In some embodiments of the present invention, in step 1), the imidazolium quaternary ammonium salt compound is selected from:

[0026] 1,1-(hexane-1,6-diyl)bis(3-ethyl-1H-imidazol-3-onium) hydroxide,

[0027] Or 1,1-(pentane-1,5-diyl)bis(3-ethyl-1H-imidazol-3-onium) hydroxide,

[0028] Or 1,1-(hexane-1,6-diyl)bis(3-propyl-1H-imidazol-3-onium) hydroxide,

[0029] Or one or more of 1,1-(hexane-1,6-diyl)bis(3-butyl-1H-imidazol-3-onium) hydroxides.

[0030] In some embodiments of the present invention, the 1,1-(hexane-1,6-diyl)bis(3-ethyl-1H-imidazol-3-onthium) hydroxide is 1,1-(hexane-1,6-diyl)bis(3-ethyl-1H-imidazol-3-onthium)ammonium hydroxide. The structural formula of the 1,1-(hexane-1,6-diyl)bis(3-ethyl-1H-imidazol-3-onthium)ammonium hydroxide is as follows:

[0031]

[0032] In some embodiments of the present invention, the 1,1-(pentane-1,5-diyl)bis(3-ethyl-1H-imidazol-3-onium) hydroxide is 1,1-(pentane-1,5-diyl)bis(3-ethyl-1H-imidazol-3-onium)ammonium hydroxide. The structural formula of the 1,1-(pentane-1,5-diyl)bis(3-ethyl-1H-imidazol-3-onium)ammonium hydroxide is as follows:

[0033]

[0034] In some embodiments of the present invention, the 1,1-(hexane-1,6-diyl)bis(3-propyl-1H-imidazol-3-onium) hydroxide is 1,1-(hexane-1,6-diyl)bis(3-propyl-1H-imidazol-3-onium)ammonium hydroxide, and the structural formula of the 1,1-(hexane-1,6-diyl)bis(3-propyl-1H-imidazol-3-onium)ammonium hydroxide is as follows:

[0035]

[0036] In some embodiments of the present invention, the 1,1-(hexane-1,6-diyl)bis(3-butyl-1H-imidazol-3-onium) hydroxide is 1,1-(hexane-1,6-diyl)bis(3-butyl-1H-imidazol-3-onium)ammonium hydroxide, and the structural formula of the 1,1-(hexane-1,6-diyl)bis(3-butyl-1H-imidazol-3-onium)ammonium hydroxide is as follows:

[0037]

[0038] In some embodiments of the present invention, in step 1), the mass of the silicon source is converted to the molar number of SiO2 based on the molar number of silicon elements; the mass of the aluminum source is converted to the molar number of Al2O3 based on the molar number of aluminum elements, and the silicon source, aluminum source, alkali source, template agent and water are mixed according to a molar ratio of 1:(0~0.033):(0.1~0.3):(0.15~0.25):(20~40).

[0039] In some embodiments of the present invention, in step 1), the molar ratio of the silicon source, aluminum source, alkali source, template agent, and water is selected from any of the following ranges: 1:(0~0.01):(0.1~0.3):(0.15~0.25):(20~40), 1:(0.01~0.02):(0.1~0.3):(0.15~0.25):(20~40), 1:(0.02~0.033):(0.1~0.033). 3): (0.15~0.25): (20~40), 1: (0~0.033): (0.1~0.15): (0.15~0.25): (20~40), 1: (0~0.033): (0.15~0.2): (0.15-0.25): (20~40), 1: (0~0.033): (0.2~0.25): (0.15~0.25): (20~40), 1: ( 0~0.033):(0.25~0.3):(0.15~0.25):(20~40), 1:(0~0.033):(0.1~0.3):(0.15~0.2):(20~40), 1:(0~0.033):(0.1~0.3):(0.2~0.25):(20~40), 1:(0~0.033):(0.1~0.3):(0.15~0.25) :(20~30), 1:(0~0.033):(0.1~0.3):(0.15~0.25):(30~40), 1:0:(0.1~0.15):(0.15~0.25):(20~40), 1:0:(0.15~0.2):(0.2~0.25):(20~40), 1:0:(0.2~0.25):(0.15~0.25):(20~40).

[0040] In some embodiments of the present invention, in step 1), the molar ratio of the silicon source, aluminum source, alkali source, template agent and water is selected from any of the following ranges: 1:0.033:0.1:0.15:20, 1:0.017:0.15:0.20:30, 1:0.005:0.10:0.20:26, 1:0.005:0.25:0.25:40, 1:0.033:0.10:0.15:20, 1:0.10:0.20:0.25:40, 1:0:0.10:0.20:26, 1:0:0.15:0.20:30, 1:0:0.25:0.25:40, 1:0:0.25:0.25:40.

[0041] For example, in some embodiments of the present invention, the silicon source is 10g of tetraethyl orthosilicate (TEOS). The chemical formula of TEOS is known to be Si(OC2H5)4, and its molar mass is 208.33g / mol. Therefore, the number of moles of TEOS is 0.048mol. Since one TEOS molecule and one SiO2 molecule both contain one silicon atom, each mole of TEOS can be converted into each mole of SiO2. Therefore, 10g of TEOS is equivalent to 0.048mol of SiO2.

[0042] For example, in some embodiments of the present invention, the aluminum source is 10g of aluminum sulfate octahydrate [Al2(SO4)3·18H2O]. It is known that the molar mass of Al2(SO4)3·18H2O is 666.43g / mol, so the number of moles of Al2(SO4)3·18H2O is 0.015mol. Since one Al2(SO4)3·18H2O and one Al2O3 molecule both contain two aluminum atoms, each mole of Al2(SO4)3·18H2O can be converted into each mole of aluminum oxide. Therefore, 10g of Al2(SO4)3·18H2O is equivalent to 0.015mol of Al2O3.

[0043] In some embodiments of the present invention, in step 1), the silicon source is selected from one or more of silica, silica sol, tetramethyl orthosilicate (TMOS) or tetraethyl orthosilicate (TEOS).

[0044] In a preferred embodiment of the present invention, in step 1), the silica sol is selected from 40 wt.% silica sol or 30.5 wt.% silica sol.

[0045] In this invention, the 40 wt.% silica sol or 30.5 wt.% silica sol refers to silica sol with a SiO2 solid content of 40% (weight percentage) or 30.5% (weight percentage).

[0046] In some embodiments of the present invention, in step 1), the aluminum source is selected from one or more of sodium aluminate, boehmite, aluminum nitrate, aluminum sulfate octahydrate, or aluminum isopropoxide.

[0047] In a preferred embodiment of the present invention, in step 1), the aluminum source is selected from aluminum sulfate octadecahydrate.

[0048] In some embodiments of the present invention, in step 1), the alkali source is selected from one or more of sodium hydroxide, potassium hydroxide, or cesium hydroxide.

[0049] In some embodiments of the invention, in step 2), the crystallization is performed in a closed reactor, such as a sealed reactor.

[0050] In some embodiments of the present invention, in step 2), the crystallization temperature is 110–180°C. The crystallization temperature is selected from any of the following ranges: 110–120°C, 120–140°C, 140–160°C, or 160–180°C.

[0051] In a preferred embodiment of the present invention, in step 2), the crystallization temperature is 120°C or 160°C.

[0052] In this invention, the crystallization temperature cannot be too high or too low. If it is too high (e.g., above 180°C), the template agent will decompose and form heterogeneous zeolite; if it is too low (e.g., 100°C), amorphous powder will be produced and molecular sieves cannot be formed.

[0053] In some embodiments of the present invention, in step 2), the crystallization time is 24 to 168 hours. The crystallization time is selected from any of the following ranges: 24 to 50 hours, 50 to 80 hours, 80 to 110 hours, 110 to 140 hours, and 140 to 168 hours.

[0054] In a preferred embodiment of the present invention, in step 2), the crystallization time is 48h, 96h or 168h.

[0055] In this invention, the crystallization time cannot be too short or too long. If it is too long (e.g., 180h), a dense phase without a pore structure may be formed; if it is too short (e.g., 12h), a product of coexistence of self-supporting MFI nanosheet molecular sieve and amorphous material will be formed.

[0056] In some embodiments of the present invention, in step 2), the crystallization state is dynamic crystallization or static crystallization.

[0057] In a preferred embodiment of the present invention, in step 2), the dynamic crystallization is rotational dynamic crystallization.

[0058] In some embodiments of the present invention, step 2) further includes post-processing of the obtained product after crystallization.

[0059] The post-processing includes washing, drying, and calcination. The washing, drying, and calcination are conventional techniques in this field.

[0060] The drying temperature is 80–120°C. The drying temperature is selected from any of the following ranges: 80–90°C, 90–100°C, 100–110°C, and 110–120°C.

[0061] The roasting temperature is 550–600°C. The roasting temperature is selected from any of the following ranges: 550–560°C, 560–570°C, 570–580°C, 580–590°C, or 590–600°C.

[0062] The present invention also provides a self-supporting MFI nanosheet molecular sieve, wherein the self-supporting MFI nanosheet molecular sieve is prepared by the preparation method described above.

[0063] In some embodiments of the present invention, the self-supporting MFI nanosheet molecular sieve is an all-silica molecular sieve.

[0064] In some embodiments of the present invention, the silicon-to-aluminum ratio of the self-supporting MFI nanosheet molecular sieve is ≥15.

[0065] In a preferred embodiment of the present invention, the silicon-to-aluminum ratio of the self-supporting MFI nanosheet molecular sieve is ≥30.

[0066] In a preferred embodiment of the present invention, the silicon-to-aluminum ratio of the self-supporting MFI nanosheet molecular sieve is 30, 50 or 100.

[0067] The present invention also provides the use of the self-supporting MFI nanosheet molecular sieve as a catalyst.

[0068] In some embodiments of the present invention, the catalyst is a catalyst used in one or more of the following chemical reactions: methanol to propylene, hydrogenation of nitrobenzene, Beckmann rearrangement, or catalytic cracking of 1-hexene.

[0069] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0070] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention; in the specification and claims of the present invention, unless otherwise expressly stated in the text, the singular forms "a", "an" and "this" include the plural forms.

[0071] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0072] Example 1

[0073] In Example 1, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0074] 1) A gel mixture was obtained by mixing 40 wt.% silica sol, aluminum nitrate, sodium hydroxide, and R1: 1,1-(hexane-1,6-diyl)bis(3-ethyl-1H-imidazol-3-onium)ammonium hydroxide as the silicon source, aluminum source, alkali source, and template agent, respectively. The molar ratios of silicon source, aluminum source, alkali source, template agent, and water were as follows: SiO2:Al2O3:Na2O:R1:H2O = 1.0:0.033:0.1:0.15:20;

[0075] 2) Transfer to a reaction vessel and crystallize at 110℃ for 168h. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 550℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0076] Example 2

[0077] In Example 2, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0078] 1) A gel mixture was obtained by mixing 40 wt.% silica sol, aluminum isopropoxide, cesium hydroxide, and 1,1-(hexane-1,6-diyl)bis(3-ethyl-1H-imidazol-3-onium)ammonium hydroxide as the silicon source, aluminum source, alkali source, and template agent, respectively. The molar ratios of silicon source, aluminum source, alkali source, template agent, and water were as follows: SiO2:Al2O3:Cs2O:R1:H2O=1.0:0.017:0.15:0.20:30;

[0079] 2) Transfer to a reaction vessel and crystallize at 160℃ for 24 hours. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 600℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0080] Example 3

[0081] In this Example 3, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0082] 1) Using 40 wt.% silica sol, aluminum sulfate octadecyl water, potassium hydroxide and 1,1-(hexane-1,6-diyl)bis(3-ethyl-1H-imidazolium)

[0083] -3-Onium)ammonium hydroxide was mixed with silicon source, aluminum source, alkali source, and template agent to obtain a gel mixture. The molar ratio of silicon source, aluminum source, alkali source, template agent, and water was as follows: SiO2:Al2O3:K2O:R1:H2O=1.0:0.005:0.10:0.20:26;

[0084] 2) Transfer to a reaction vessel and crystallize at 120℃ for 144h. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 550℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0085] The prepared self-supporting MFI nanosheet molecular sieve was characterized by XRD, SEM, TEM, N2 adsorption and solid aluminum NMR. The results are shown in Figures 1, 2, 3, 4 and 5.

[0086] XRD characterization results showed that the self-supported MFI nanosheet molecular sieve obtained in this application possesses the characteristic diffraction peaks of MFI molecular sieves; SEM results indicated that the crystal size obtained in this application is below 200 nm; TEM results showed that the self-supported MFI nanosheet molecular sieve is a "house of cards" morphology nanocrystal with a nanosheet thickness below 30 nm, and nitrogen adsorption results showed that its BET value is 380.9 nm. 2 / g, micropore volume is 0.11cm 3 / g. Solid aluminum NMR results indicate that the prepared self-supported MFI nanosheet molecular sieve mainly contains 4-coordinated framework aluminum species. In summary, the characterization results demonstrate that the method described in this application can prepare highly crystalline self-supported MFI nanosheet molecular sieves.

[0087] Example 4

[0088] In Example 4, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0089] 1) Using 40 wt.% silica sol, aluminum sulfate octadecyl water, potassium hydroxide and 1,1-(hexane-1,6-diyl)bis(3-ethyl-1H-imidazolium)

[0090] -3-Onium)ammonium hydroxide was mixed with silicon source, aluminum source, alkali source, and template agent to obtain a gel mixture. The molar ratio of silicon source, aluminum source, alkali source, template agent, and water was as follows: SiO2:Al2O3:K2O:R1:H2O=1.0:0.005:0.10:0.25:40;

[0091] 2) Transfer to a reaction vessel and crystallize at 140℃ for 96 hours. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 550℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0092] Example 5

[0093] In Example 5, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0094] 1) Using tetraethyl silicate, boehmite, sodium hydroxide and 1,1-(pentane-1,5-diyl)bis(3-ethyl-1H-imidazol-3-onium)

[0095] Ammonium hydroxide was mixed with silicon source, aluminum source, alkali source, and template agent to obtain a gel mixture. The molar ratios of silicon source, aluminum source, alkali source, template agent, and water were as follows: SiO2:Al2O3:Na2O:R2:H2O = 1.0:0.033:0.10:0.15:20;

[0096] 2) Transfer to a reaction vessel and crystallize at 110℃ for 168h. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 550℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0097] Example 6

[0098] In Example 6, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0099] 1) A gel mixture was obtained by mixing silica, aluminum isopropoxide, cesium hydroxide, and 1,1-(pentane-1,5-diyl)bis(3-ethyl-1H-imidazol-3-onium)ammonium hydroxide as the silicon source, aluminum source, alkali source, and template agent, respectively. The molar ratios of silicon source, aluminum source, alkali source, template agent, and water were as follows: SiO2:Al2O3:Cs2O:R2:H2O=1.0:0.017:0.15:0.20:30;

[0100] 2) Transfer to a reaction vessel and crystallize at 160℃ for 24 hours. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 600℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0101] Example 7

[0102] In Example 7, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0103] 1) A gel mixture was obtained by mixing 40 wt.% silica sol, aluminum sulfate octadecylhydrate, potassium hydroxide, and 1,1-(pentane-1,5-diyl)bis(3-ethyl-1H-imidazol-3-onium)ammonium hydroxide as the silicon source, aluminum source, alkali source, and template agent, respectively. The molar ratios of silicon source, aluminum source, alkali source, template agent, and water were as follows: SiO2:Al2O3:K2O:R2:H2O = 1.0:0.01:0.10:0.25:40;

[0104] 2) Transfer to a reaction vessel and crystallize at 120℃ for 120h. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 550℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0105] Example 8

[0106] In Example 8, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0107] 1) A gel mixture was obtained by mixing 30.5 wt.% silica sol, aluminum sulfate octadecylhydrate, potassium hydroxide, and 1,1-(hexane-1,5-diyl)bis(3-ethyl-1H-imidazol-3-onium)ammonium hydroxide as the silicon source, aluminum source, alkali source, and template agent, respectively. The molar ratios of silicon source, aluminum source, alkali source, template agent, and water were as follows: SiO2:Al2O3:K2O:R2:H2O = 1.0:0.005:0.10:0.25:40;

[0108] 2) Transfer to a reaction vessel and crystallize at 140℃ for 96 hours. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 550℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0109] Example 9

[0110] In Example 9, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0111] 1) Using 40 wt.% silica sol, aluminum nitrate, sodium hydroxide and 1,1-(hexane-1,6-diyl)bis(3-propyl-1H-imidazol-3-onium)

[0112] Ammonium hydroxide was mixed with silicon source, aluminum source, alkali source, and template agent to obtain a gel mixture. The molar ratios of silicon source, aluminum source, alkali source, template agent, and water were as follows: SiO2:Al2O3:Na2O:R3:H2O = 1.0:0.033:0.1:0.15:20;

[0113] 2) Transfer to a reaction vessel and crystallize at 110℃ for 168h. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 550℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0114] Example 10

[0115] In this Example 10, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0116] 1) A gel mixture was obtained by mixing 40 wt.% silica sol, aluminum isopropoxide, cesium hydroxide, and 1,1-(hexane-1,6-diyl)bis(3-propyl-1H-imidazol-3-onium)ammonium hydroxide as the silicon source, aluminum source, alkali source, and template agent, respectively. The molar ratios of silicon source, aluminum source, alkali source, template agent, and water were as follows: SiO2:Al2O3:Cs2O:R3:H2O=1.0:0.017:0.15:0.20:30;

[0117] 2) Transfer to a reaction vessel and crystallize at 160℃ for 24 hours. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 600℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0118] Example 11

[0119] In Example 11, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0120] 1) A gel mixture was obtained by mixing 40 wt.% silica sol, aluminum sulfate octadecylhydrate, potassium hydroxide, and 1,1-(hexane-1,6-diyl)bis(3-propyl-1H-imidazol-3-onium)ammonium hydroxide as the silicon source, aluminum source, alkali source, and template agent, respectively. The molar ratios of silicon source, aluminum source, alkali source, template agent, and water were as follows: SiO2:Al2O3:K2O:R3:H2O = 1.0:0.01:0.10:0.25:40;

[0121] 2) Transfer to a reaction vessel and crystallize at 120℃ for 120h. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 550℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0122] Example 12

[0123] In Example 5, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0124] 1) Using 30.5 wt.% silica sol, aluminum sulfate octadecylhydrate, potassium hydroxide, and 1,1-(hexane-1,6-diyl)bis(3-propyl-1H-

[0125] Imidazole-3-onium (IMO)ammonium hydroxide was mixed with silicon, aluminum, alkali, and template agent to obtain a gel mixture. The molar ratios of silicon, aluminum, alkali, template agent, and water were as follows: SiO2:Al2O3:K2O:R3:H2O

[0126] = 1.0:0.005:0.10:0.25:40;

[0127] 2) Transfer to a reaction vessel and crystallize at 140℃ for 96 hours. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 550℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0128] Example 13

[0129] In this Example 13, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0130] 1) Using 40 wt.% silica sol, aluminum nitrate, sodium hydroxide and 1,1-(hexane-1,6-diyl)bis(3-butyl-1H-imidazol-3-onium)

[0131] Ammonium hydroxide was mixed with silicon source, aluminum source, alkali source, and template agent to obtain a gel mixture. The molar ratios of silicon source, aluminum source, alkali source, template agent, and water were as follows: SiO2:Al2O3:Na2O:R4:H2O = 1.0:0.033:0.10:0.15:20;

[0132] 2) Transfer to a reaction vessel and crystallize at 110℃ for 168h. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 550℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0133] Example 14

[0134] In this Example 14, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0135] 1) Using tetramethyl orthosilicate, aluminum isopropoxide, cesium hydroxide and 1,1-(hexane-1,6-diyl)bis(3-butyl-1H-imidazol-3-onium)

[0136] Ammonium hydroxide was mixed with silicon source, aluminum source, alkali source, and template agent to obtain a gel mixture. The molar ratios of silicon source, aluminum source, alkali source, template agent, and water were as follows: SiO2:Al2O3:Cs2O:R4:H2O = 1.0:0.017:0.15:0.20:30;

[0137] 2) Transfer to a reaction vessel and crystallize at 160℃ for 24 hours. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 600℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0138] Example 15

[0139] In this Example 15, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0140] 1) A gel mixture was obtained by mixing 40 wt.% silica sol, aluminum sulfate octadecylhydrate, potassium hydroxide, and 1,1-(hexane-1,6-diyl)bis(3-butyl-1H-imidazol-3-onium)ammonium hydroxide as the silicon source, aluminum source, alkali source, and template agent, respectively. The molar ratios of silicon source, aluminum source, alkali source, template agent, and water were as follows: SiO2:Al2O3:K2O:R4:H2O = 1.0:0.01:0.15:0.25:40;

[0141] 2) Transfer to a reaction vessel and crystallize at 120℃ for 120h. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 550℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0142] Example 16

[0143] In this Example 16, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0144] 1) A gel mixture was obtained by mixing 30.5 wt.% silica sol, aluminum sulfate octadecylhydrate, potassium hydroxide, and 1,1-(hexane-1,6-diyl)bis(3-butyl-1H-imidazol-3-onium)ammonium hydroxide as the silicon source, aluminum source, alkali source, and template agent, respectively. The molar ratios of silicon source, aluminum source, alkali source, template agent, and water were as follows: SiO2:Al2O3:K2O:R4:H2O = 1.0:0.005:0.10:0.25:40;

[0145] 2) Transfer to a reaction vessel and crystallize at 140℃ for 96 hours. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 550℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0146] Example 17

[0147] In this Example 17, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0148] 1) A gel mixture was obtained by mixing 40 wt.% silica sol, potassium hydroxide, and 1,1-(hexane-1,6-diyl)bis(3-ethyl-1H-imidazol-3-onium)ammonium hydroxide as the silicon source, alkali source, and template agent, respectively. The molar ratios of silicon source, alkali source, template agent, and water were as follows: SiO2:K2O:R1:H2O=1.0:0.10:0.20:26;

[0149] 2) Transfer to a reaction vessel and crystallize at 120℃ for 168h. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 550℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0150] Example 18

[0151] In this Example 18, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0152] 1) Using tetramethyl orthosilicate, aluminum isopropoxide, cesium hydroxide, and 1,1-(pentane-1,5-diyl)bis(3-ethyl-1H-imidazol-3-onium)

[0153] Ammonium hydroxide was mixed with the silicon source, alkali source, and template agent to obtain a gel mixture. The molar ratio of silicon source, alkali source, template agent, and water was as follows: SiO2:Cs2O:R2:H2O = 1.0:0.15:0.20:30;

[0154] 2) Transfer to a reaction vessel and crystallize at 160℃ for 24 hours. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 600℃ to obtain self-supporting MFI nanosheet molecular sieve.

[0155] Example 19

[0156] In this Example 19, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0157] 1) A gel mixture was obtained by mixing 30.5 wt.% silica sol, potassium hydroxide, and 1,1-(hexane-1,6-diyl)bis(3-propyl-1H-imidazol-3-onium)ammonium hydroxide as the silicon source, alkali source, and template agent, respectively. The molar ratios of silicon source, alkali source, template agent, and water were as follows: SiO2:K2O:R3:H2O = 1.0:0.15:0.25:40;

[0158] 2) Transfer to a reaction vessel and crystallize at 140℃ for 96 hours. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 550℃ to obtain the all-silicon self-supporting MFI nanosheet molecular sieve.

[0159] Example 20

[0160] In this Example 20, the preparation of self-supporting MFI nanosheet molecular sieves includes the following steps:

[0161] 1) A gel mixture was obtained by mixing tetraethyl silicate, potassium hydroxide, and 1,1-(hexane-1,6-diyl)bis(3-butyl-1H-imidazol-3-onium)ammonium hydroxide as the silicon source, base source, and template agent, respectively. The molar ratio of silicon source, base source, template agent, and water was as follows: SiO2:K2O:R4:H2O=1.0:0.25:0.25:40;

[0162] 2) Transfer to a reaction vessel and crystallize at 120℃ for 96 hours. After crystallization, cool, filter, wash, dry at 80℃, and calcine at 550℃ to obtain the all-silicon self-supporting MFI nanosheet molecular sieve.

[0163] Application Example 1

[0164] In this application example 1, the self-supporting MFI nanosheet molecular sieve obtained in example 3 was used to test the catalytic performance of methanol to propylene (MTP) using a fixed-bed catalytic reactor line analyzer.

[0165] The test conditions were as follows: 0.5 g of 20-40 mesh catalyst was weighed and loaded into the reaction tube. The mixture was pretreated for 120 min in a N2 atmosphere (30 ml / min) at 500℃ under normal pressure. After cooling to 480℃, methanol was pumped into the vaporization chamber using a high-pressure pump. The mixture was then mixed with nitrogen and introduced into the reaction tube. The methanol space velocity was 2 h⁻¹. -1 The products were analyzed using a gas chromatograph equipped with an FID detector and an HP-PLOT-Q gas chromatograph.

[0166] Figure 6 shows the methanol conversion rate and product selectivity in the MTP reaction. The self-supporting MFI nanosheet molecular sieve can maintain a high methanol conversion rate and propylene selectivity for a long time.

[0167] The above embodiments are for illustrating the implementation schemes disclosed in this invention and should not be construed as limiting the invention. Furthermore, various modifications and variations of the methods listed herein will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been specifically described in conjunction with various specific preferred embodiments, it should be understood that the invention should not be limited to these specific embodiments. In fact, various modifications as described above that are obvious to those skilled in the art to obtain the invention should be included within the scope of this invention.

Claims

1. A method for preparing a self-supporting MFI nanosheet molecular sieve, characterized in that, The preparation method includes the following steps: 1) mixing a silicon source, an aluminum source, an alkali source, a template agent, and water to obtain a gel mixture, wherein the template agent is an imidazolium quaternary ammonium salt compound; the imidazolium quaternary ammonium salt compound is selected from 1,1-(hexane-1,6-diyl)bis(3-ethyl-1H-imidazol-3-onium)ammonium hydroxide, 1,1-(pentane-1,5-diyl)bis(3-ethyl-1H-imidazol-3-onium)ammonium hydroxide, 1,1 1) One or more of 1,1-(hexane-1,6-diyl)bis(3-propyl-1H-imidazol-3-onium)ammonium hydroxide or 1,1-(hexane-1,6-diyl)bis(3-butyl-1H-imidazol-3-onium)ammonium hydroxide; the silicon source is selected from one or more of silica, silica sol, tetramethyl orthosilicate or tetraethyl orthosilicate; 2) Crystallize the gel mixture obtained in step 1) to obtain the self-supporting MFI nanosheet molecular sieve.

2. The preparation method according to claim 1, characterized in that, Step 1) includes any one or more of the following conditions: 11) The aluminum source is selected from one or more of sodium aluminate, boehmite, aluminum nitrate, aluminum sulfate octahydrate, or aluminum isopropoxide; 12) The alkali source is selected from one or more of sodium hydroxide, potassium hydroxide, and cesium hydroxide.

3. The preparation method according to claim 1, characterized in that, In step 1), the mass of the silicon source is converted to the molar number of SiO2 based on the molar number of silicon elements; the mass of the aluminum source is converted to the molar number of Al2O3 based on the molar number of aluminum elements, and the silicon source, aluminum source, alkali source, template agent and water are mixed according to a molar ratio of 1:0~0.033:0.1~0.3:0.15-0.25:20~40.

4. The preparation method according to claim 1, characterized in that, Step 2) includes any one or more of the following conditions: 1) the crystallization is completed in a reactor; 2) the crystallization temperature is 110~180 ℃; 3) the crystallization time is 24~168 h; 4) the crystallization state is dynamic crystallization or static crystallization.

5. The preparation method according to claim 1, characterized in that, Step 2) also includes post-processing of the obtained product after crystallization.

6. The preparation method according to claim 5, characterized in that, The post-processing includes washing, drying, and calcination.

7. The preparation method according to claim 6, characterized in that, The drying temperature is 80~120 ℃; and / or the calcination temperature is 550~600 ℃.

8. A self-supporting MFI nanosheet molecular sieve, characterized in that, The self-supporting MFI nanosheet molecular sieve is prepared by any of the preparation methods described in claims 1 to 7.

9. The self-supporting MFI nanosheet molecular sieve according to claim 8, characterized in that, The molecular sieve includes one or more of the following characteristics: I. The self-supporting MFI nanosheet molecular sieve is an all-silica molecular sieve; II. The silica-to-alumina ratio of the self-supporting MFI nanosheet molecular sieve is ≥15.

10. Use of the self-supporting MFI nanosheet molecular sieve as described in any one of claims 8 to 9 as a catalyst.

11. The use as described in claim 10, characterized in that, The catalyst is used in one or more of the following chemical reactions: methanol to propylene, hydrogenation of nitrobenzene, Beckmann rearrangement, or catalytic cracking of 1-hexene.

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