CN115818663B - Amine-free high-silicon ZSM-5 molecular sieve and preparation method and application thereof - Google Patents
Amine-free high-silicon ZSM-5 molecular sieve and preparation method and application thereof Download PDFInfo
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- 239000002808 molecular sieve Substances 0.000 title claims abstract description 100
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 title claims abstract description 100
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 78
- 239000010703 silicon Substances 0.000 title claims abstract description 78
- 238000002360 preparation method Methods 0.000 title description 8
- 239000013078 crystal Substances 0.000 claims abstract description 69
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 67
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 59
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 50
- 238000000034 method Methods 0.000 claims abstract description 42
- 239000003513 alkali Substances 0.000 claims abstract description 40
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 26
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 26
- 239000007795 chemical reaction product Substances 0.000 claims abstract description 22
- 238000002156 mixing Methods 0.000 claims abstract description 9
- 239000000203 mixture Substances 0.000 claims abstract description 8
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 78
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 63
- 239000011734 sodium Substances 0.000 claims description 32
- 239000000741 silica gel Substances 0.000 claims description 30
- 229910002027 silica gel Inorganic materials 0.000 claims description 30
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 28
- 238000006243 chemical reaction Methods 0.000 claims description 24
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 17
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 17
- 229910052708 sodium Inorganic materials 0.000 claims description 17
- 239000000377 silicon dioxide Substances 0.000 claims description 15
- 238000004523 catalytic cracking Methods 0.000 claims description 14
- QGZKDVFQNNGYKY-UHFFFAOYSA-O ammonium group Chemical group [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims description 12
- 150000002430 hydrocarbons Chemical class 0.000 claims description 12
- 239000004215 Carbon black (E152) Substances 0.000 claims description 11
- 229930195733 hydrocarbon Natural products 0.000 claims description 11
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 9
- 239000012265 solid product Substances 0.000 claims description 9
- 229910000272 alkali metal oxide Inorganic materials 0.000 claims description 6
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims description 6
- 239000004115 Sodium Silicate Substances 0.000 claims description 3
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 claims description 3
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 claims description 3
- 238000010304 firing Methods 0.000 claims description 3
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 3
- 235000019353 potassium silicate Nutrition 0.000 claims description 3
- 239000000843 powder Substances 0.000 claims description 3
- 230000008569 process Effects 0.000 claims description 3
- 229910052911 sodium silicate Inorganic materials 0.000 claims description 3
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 abstract description 13
- 238000003756 stirring Methods 0.000 description 28
- 239000008367 deionised water Substances 0.000 description 24
- 229910021641 deionized water Inorganic materials 0.000 description 24
- 229910001220 stainless steel Inorganic materials 0.000 description 14
- 239000010935 stainless steel Substances 0.000 description 14
- 238000002441 X-ray diffraction Methods 0.000 description 13
- 239000003795 chemical substances by application Substances 0.000 description 13
- 230000000052 comparative effect Effects 0.000 description 10
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- 229910052593 corundum Inorganic materials 0.000 description 9
- 238000001914 filtration Methods 0.000 description 9
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- 230000015572 biosynthetic process Effects 0.000 description 8
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- BGHCVCJVXZWKCC-UHFFFAOYSA-N tetradecane Chemical compound CCCCCCCCCCCCCC BGHCVCJVXZWKCC-UHFFFAOYSA-N 0.000 description 8
- 238000002425 crystallisation Methods 0.000 description 7
- 230000008025 crystallization Effects 0.000 description 7
- 238000001878 scanning electron micrograph Methods 0.000 description 6
- 230000002194 synthesizing effect Effects 0.000 description 6
- 150000001412 amines Chemical class 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- -1 catalytic cracking Chemical class 0.000 description 4
- 238000001514 detection method Methods 0.000 description 4
- YCOZIPAWZNQLMR-UHFFFAOYSA-N heptane - octane Natural products CCCCCCCCCCCCCCC YCOZIPAWZNQLMR-UHFFFAOYSA-N 0.000 description 4
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 229910021536 Zeolite Inorganic materials 0.000 description 3
- 230000004913 activation Effects 0.000 description 3
- 150000001298 alcohols Chemical class 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 239000007791 liquid phase Substances 0.000 description 3
- 230000006911 nucleation Effects 0.000 description 3
- 238000010899 nucleation Methods 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- 239000010457 zeolite Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 238000004220 aggregation Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 238000001354 calcination Methods 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 239000006229 carbon black Substances 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 2
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 239000002351 wastewater Substances 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- 230000029936 alkylation Effects 0.000 description 1
- 238000005804 alkylation reaction Methods 0.000 description 1
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 description 1
- 238000005899 aromatization reaction Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 231100000086 high toxicity Toxicity 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- 238000006317 isomerization reaction Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000000877 morphologic effect Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000004626 scanning electron microscopy Methods 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000006276 transfer reaction Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 238000004876 x-ray fluorescence Methods 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
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- Silicates, Zeolites, And Molecular Sieves (AREA)
Abstract
The present disclosure relates to a method for preparing an amine-free high silicon ZSM-5 molecular sieve, the method comprises S1, mixing a first silicon source, an aluminum source, a first alkali source, water and a first seed crystal, and then carrying out a first hydrothermal reaction on the obtained first mixture to obtain a first hydrothermal reaction product; wherein, the mole ratio of the first silicon source, the aluminum source, the first alkali source and the water is (20-45): 1: (1-5): (140-440) the amount of the first seed crystal is 1-10 wt% of the amount of the first silicon source; s2, mixing the first hydrothermal reaction product with a second silicon source, a second alkali source, water and a second crystal, and then carrying out a second hydrothermal reaction on the obtained second mixture; wherein the mole ratio of the total amount of the second silicon source to the first silicon source, the amount of the aluminum source, the total amount of the first alkali source to the second alkali source and the total amount of water is (50-70): 1: (2-8): (600-1000), the total amount of the first seed crystal and the second seed crystal being 1-10% by weight of the total amount of the first silicon source and the second silicon source. The method can prepare the ZSM-5 molecular sieve with higher silicon-aluminum molar ratio and crystallinity.
Description
Technical Field
The present disclosure relates to the field of molecular sieve preparation, and in particular, to an amine-free high-silicon ZSM-5 molecular sieve, and a preparation method and application thereof.
Background
The ZSM-5 molecular sieve has a unique three-dimensional cross pore system and high-silicon zeolite with an MFI topological structure, and has two cross-linked ten-membered ring pore channels. The catalyst has strong selective adsorption performance, good thermal stability, good hydrothermal stability and moderate acidity, so that the catalyst is suitable for catalytic reactions of various hydrocarbon compounds, such as catalytic cracking, isomerization, aromatization, alkylation and the like, and is widely applied to the fields of petrochemical industry and industrial catalysis.
The traditional hydrothermal synthesis method has the advantages that quaternary ammonium cations or other organic amine molecules are needed to be added as a template agent, the existing synthesis of ZSM-5 molecular sieves is mostly synthesized by adopting an organic amine template agent hydrothermal method, and although the ZSM-5 molecular sieves with uniform particle size, regular pore channels and crystal forms can be synthesized under wider conditions by taking organic amine with strong structure guiding effect as the template agent, the synthesized ZSM-5 molecular sieves have smaller crystal grains and lower stability in a reaction environment with severe catalytic cracking. In addition, the organic amine template agent has high toxicity, a large amount of organic wastewater can be generated in the synthesis process, and the air pollution can be caused when the template agent is roasted and decomposed, so that the performance of the molecular sieve can be influenced. In addition, the price of the template agent is high, and the large-scale use of the template agent greatly increases the production cost of the molecular sieve. Therefore, the research on synthesizing the ZSM-5 molecular sieve without the template has high environmental protection significance and economic value.
The template-free system for synthesizing the ZSM-5 molecular sieve has the characteristics of environmental friendliness, low cost and the like, is popular with vast researchers in recent years, and more template-free ZSM-5 molecular sieve synthesis processes emerge. Compared with the traditional synthesis method, the synthesis of ZSM-5 molecular sieve in the template-free system needs longer time, because the nucleation activation energy and the growth activation energy of the ZSM-5 molecular sieve are high due to the lack of the guiding function of the template agent; in addition, the phase region of the ZSM-5 molecular sieve synthesized by the template-free method is narrower, and the crystallization nucleus is difficult to form due to the lack of the guiding function of the template agent, so that the crystallization phenomenon is extremely easy to occur. If seed crystal containing formed crystal nucleus is added into synthetic liquid, a great amount of specific crystal nucleus can be induced to form in short time, so that the crystallization time is shortened, the synthetic phase area is widened, and the phenomena of eutectic and crystal transformation are avoided to a great extent, namely the seed crystal method.
The seed crystal method for preparing the ZSM-5 molecular sieve with the silicon-aluminum ratio of about 25 has been applied industrially, but the ZSM-5 molecular sieve with the silicon-aluminum ratio of 25 has higher acidity and brings higher hydrogen transfer reaction degree, and researches show that the ZSM-5 molecular sieve with the silicon-aluminum ratio of 40-50 is more suitable for catalytic cracking to produce more low-carbon olefin. However, the amine-free synthesis of ZSM-5 molecular sieves with higher silica-alumina ratios is a difficult problem, and even if seed crystals are added to synthesize ZSM-5 molecular sieves with higher silica-alumina ratios, the crystallinity is still lower. This is because the seed crystal guiding action can guide the ZSM-5 molecular sieve with low silica-alumina ratio, but the activation energy of nucleation growth is higher and the nucleation is difficult to form in a short time when the ZSM-5 molecular sieve with high silica-alumina ratio is synthesized.
Regarding the synthesis of ZSM-5 molecular sieve by amine-free method, chinese patent CN 105621451A, CN105692652B discloses a preparation method for synthesizing ZSM-5 molecular sieve without using template agent. Firstly, mixing a silicon source, an alkali source, an aluminum source, a seed crystal and deionized water, and preparing the ZSM-5 molecular sieve through two-stage crystallization. The preparation method synthesizes the molecular sieve under the conditions of no template agent, low water-silicon ratio, temperature rising speed control and two-stage crystallization. Although the method has higher crystallinity when synthesizing ZSM-5 molecular sieves with a silica-alumina ratio of 20 to 25 and has been realized for industrial application, the crystallinity of molecular sieves with a silica-alumina ratio of 40 to 60 or higher is lower.
Chinese patent CN 108190913A discloses a method for synthesizing a silicon-rich ZSM-5 zeolite molecular sieve by adopting a seed crystal guiding method, which introduces alcohols to prepare the silicon-rich ZSM-5 zeolite molecular sieve with higher crystallinity and high silicon-aluminum ratio, avoids using an expensive organic template agent, and greatly reduces the synthesis cost. However, the introduction of alcohols increases the reaction pressure, which brings about a safety hazard, and the subsequent separation treatment brings about higher cost.
Although many methods for synthesizing ZSM-5 without template exist, the synthesis of ZSM-5 molecular sieve with 40-60 of silicon-aluminum ratio in a system without template and alcohol is still reported.
Disclosure of Invention
The purpose of the present disclosure is to provide an amine-free high-silicon ZSM-5 molecular sieve, a preparation method and an application thereof, wherein the method can prepare the ZSM-5 molecular sieve with high crystallinity and high silicon-aluminum ratio.
To achieve the above object, a first aspect of the present disclosure provides a method for preparing an amine-free high silica ZSM-5 molecular sieve, the method comprising:
s1, mixing a first silicon source, an aluminum source, a first alkali source, water and a first seed crystal, and performing a first hydrothermal reaction on the obtained first mixture to obtain a first hydrothermal reaction product;
Wherein the molar ratio of the first silicon source, the aluminum source, the first alkali source and the water is (20-45): 1: (1-5): (140-440), the amount of the first seed crystal being 1-10 wt% of the amount of the first silicon source, the first silicon source being calculated as SiO 2, the aluminum source being calculated as Al 2O3, the first alkali source being calculated as alkali metal oxide, the first seed crystal being calculated as SiO 2;
S2, mixing the first hydrothermal reaction product with a second silicon source, a second alkali source, water and a second crystal seed, and then carrying out a second hydrothermal reaction on the obtained second mixture;
Wherein the molar ratio of the total amount of the second silicon source and the first silicon source, the amount of the aluminum source, the total amount of the first alkali source and the second alkali source, and the total amount of the water is (50-70): 1: (2-8): (600-1000), the total amount of the first seed crystal and the second seed crystal being 1-10 wt% of the total amount of the first silicon source and the second silicon source, the second silicon source being calculated as SiO 2, the second alkali source being calculated as alkali metal oxide, the second seed crystal being calculated as SiO 2.
Optionally, the conditions of the first hydrothermal reaction include: the temperature is 180-220 ℃ and the time is 1-5 hours; in step S2, the conditions of the second hydrothermal reaction include: the temperature is 150-180 ℃ and the time is 8-20h.
Optionally, in step S1, the molar ratio of the first silicon source, the aluminum source, the first alkali source and the water is (20-35): 1: (3-4): (320-360) the first seed is present in an amount of 8-10 wt% of the first silicon source.
Optionally, the molar ratio of the total amount of the first and second silicon sources, the total amount of the aluminum source, the first and second alkali sources, the amount of water is (55-65): 1: (4-8): (600-700), the total amount of the first seed crystal and the second seed crystal being 8-10 wt% of the total amount of the first silicon source and the second silicon source.
Optionally, the first silicon source and the second silicon source are each independently selected from one or more of silica gel, water glass, silica and white carbon black;
the aluminum source is selected from one or more of sodium metaaluminate, SB powder, aluminum oxide, aluminum hydroxide and aluminum sulfate;
The first alkali source and the second alkali source are respectively and independently selected from one or more of sodium hydroxide, sodium silicate and potassium hydroxide;
the first seed crystal and the second seed crystal are each independently an industrial ZSM-5 molecular sieve having a silica to alumina ratio of 20 to 50.
Optionally, the method further comprises step S3: and collecting a solid product of the second hydrothermal reaction, and sequentially carrying out ammonium exchange and roasting treatment on the solid product.
Optionally, the conditions of the firing treatment include: the temperature is 400-800 ℃, the time is 0.5-8h, and the atmosphere is air atmosphere or water vapor atmosphere.
A second aspect of the present disclosure provides an amine-free high silica ZSM-5 molecular sieve prepared by the method provided in the first aspect of the present disclosure.
Optionally, the molar ratio of SiO 2 to Al 2O3 of the amine-free high-silicon ZSM-5 molecular sieve is 40-60, the relative crystallinity is 80-95%, the specific surface area is 240-300m 2/g, and the particle size is 1-2 mu m.
A third aspect of the present disclosure provides an application of the amine-free high-silicon ZSM-5 molecular sieve provided in the second aspect of the present disclosure in a light hydrocarbon catalytic cracking reaction.
The method of the present disclosure has the following advantages:
(1) The method adopts a method of supplementing silicon after two sections of crystallization are combined to prepare the ZSM-5 molecular sieve, can prepare the ZSM-5 molecular sieve with the silicon-aluminum ratio of 40-60, has higher relative crystallinity, has better yield of low-carbon olefin when being used in light hydrocarbon catalytic cracking reaction, and is beneficial to the production of more propylene.
(2) The operation is simple, the ZSM-5 molecular sieve with the silicon-aluminum ratio of 40-60 is synthesized by adopting a system without template agent and alcohols, and the preparation process has no ammonia nitrogen wastewater discharge, and is clean and environment-friendly.
Additional features and advantages of the present disclosure will be set forth in the detailed description which follows.
Drawings
The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification, illustrate the disclosure and together with the description serve to explain, but do not limit the disclosure. In the drawings:
FIG. 1 is an X-ray diffraction pattern of a sample ZSM-5 molecular sieve prepared in example 1 of the present disclosure;
FIG. 2 is a scanning electron micrograph of a ZSM-5 molecular sieve sample prepared in example 1 of the present disclosure;
FIG. 3 is an X-ray diffraction pattern of a sample ZSM-5 molecular sieve prepared in example 2 of the present disclosure;
FIG. 4 is a scanning electron micrograph of a ZSM-5 molecular sieve sample prepared in example 2 of the present disclosure;
FIG. 5 is an X-ray diffraction pattern of a sample ZSM-5 molecular sieve prepared in example 3 of the present disclosure;
FIG. 6 is an X-ray diffraction pattern of a sample ZSM-5 molecular sieve prepared in examples 4, 5 of the disclosure;
FIG. 7 is a scanning electron micrograph of a ZSM-5 molecular sieve sample prepared in example 4 of the present disclosure;
FIG. 8 is a scanning electron micrograph of a ZSM-5 molecular sieve sample prepared in example 5 of the present disclosure;
FIG. 9 is an X-ray diffraction pattern of a sample ZSM-5 molecular sieve prepared in comparative example 1 of the present disclosure;
FIG. 10 is a scanning electron micrograph of a ZSM-5 molecular sieve sample prepared in comparative example 2 of the present disclosure;
FIG. 11 is an X-ray diffraction pattern of the ZSM-5 molecular sieve prepared in comparative example 3 of the present disclosure;
fig. 12 is a scanning electron micrograph of a ZSM-5 molecular sieve sample prepared in comparative example 3 of the present disclosure.
Detailed Description
Specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the disclosure, are not intended to limit the disclosure.
A first aspect of the present disclosure provides a method of preparing an amine-free high silica ZSM-5 molecular sieve, the method comprising:
s1, mixing a first silicon source, an aluminum source, a first alkali source, water and a first seed crystal, and performing a first hydrothermal reaction on the obtained first mixture to obtain a first hydrothermal reaction product;
Wherein the molar ratio of the first silicon source, the aluminum source, the first alkali source and the water is (20-35): 1: (1-5): (140-440), the amount of the first seed crystal being 1-10 wt% of the amount of the first silicon source, the first silicon source being calculated as SiO 2, the aluminum source being calculated as Al 2O3, the first alkali source being calculated as alkali metal oxide, the first seed crystal being calculated as SiO 2;
S2, mixing the first hydrothermal reaction product with a second silicon source, a second alkali source, water and a second crystal seed, and then carrying out a second hydrothermal reaction on the obtained second mixture;
Wherein the molar ratio of the total amount of the second silicon source and the first silicon source, the amount of the aluminum source, the total amount of the first alkali source and the second alkali source, and the total amount of the water is (50-70): 1: (2-8): (600-1000), the total amount of the first seed crystal and the second seed crystal being 1-10 wt% of the total amount of the first silicon source and the second silicon source, the second silicon source being calculated as SiO 2, the second alkali source being calculated as alkali metal oxide, the second seed crystal being calculated as SiO 2.
Compared with the method of one-step feeding and one-step crystallization in the prior art, the method can enable the ZSM-5 molecular sieve prepared to have higher silicon-aluminum ratio and higher relative crystallinity, and is particularly suitable for catalytic cracking reaction of light hydrocarbon.
In one embodiment of the present disclosure, the conditions of the first hydrothermal reaction include: the temperature is 180-220 ℃ for 1-5 hours, preferably 190-200 ℃ for 2-4 hours, more preferably 195-200 ℃ for 2-4 hours.
In a specific embodiment of the present disclosure, in step S2, the conditions of the second hydrothermal reaction include: the temperature is 150-180 ℃ and the time is 8-20h; preferably, the temperature is 165-175℃for a period of 10-17 hours. The first and second hydrothermal reactions may be carried out in devices conventionally employed by those skilled in the art, for example, in heat-resistant closed vessels, preferably autoclaves, as is well known to those skilled in the art in light of the present disclosure. The reaction pressure of the first hydrothermal reaction and the second hydrothermal reaction is not particularly limited, and may be, for example, the autogenous pressure of the reaction system or an applied pressure, preferably the autogenous pressure of the reaction system.
According to the present disclosure, in step S1, the molar ratio of the first silicon source, the aluminum source, the first alkali source and the water amount may vary within a wide range. In a specific embodiment of the present disclosure, in step S1, the molar ratio of the first silicon source, the aluminum source, the first alkali source, and the water is 20 to 35): 1: (1-5): (140-440), more preferably (20-35): 1: (3-4): (320-360) the first seed is present in an amount of 8-10 wt% of the first silicon source.
In one embodiment of the present disclosure, the molar ratio of the total amount of the first and second silicon sources, the total amount of the aluminum source, the first and second alkali sources, and the amount of water is (55-65): 1: (4-8): (600-700), the total amount of the first seed crystal and the second seed crystal being 8-10 wt% of the total amount of the first silicon source and the second silicon source.
The first silicon source and the second silicon source are well known to those skilled in the art in light of the present disclosure, and preferably, the first silicon source and the second silicon source are each independently selected from one or more of silica gel, water glass, silica and white carbon black; the first alkali source and the second alkali source are respectively and independently selected from one or more of sodium hydroxide, sodium silicate and potassium hydroxide, preferably sodium hydroxide; the aluminum source can be one or more selected from sodium metaaluminate, SB powder, aluminum oxide, aluminum hydroxide and aluminum sulfate; the seed crystal can be an industrial ZSM-5 molecular sieve with a silicon-aluminum ratio of 20-50.
In one embodiment of the present disclosure, the method further comprises step S3: and collecting a solid product of the second hydrothermal reaction, and sequentially carrying out ammonium exchange and roasting treatment on the solid product. Preferably, the solid product is washed to neutrality and then subjected to ammonium exchange, and the liquid used for washing may be any kind of liquid which does not react with the solid product, for example, deionized water. The method for collecting the solid product is not particularly limited in the present disclosure, and filtration, centrifugal separation, etc. may be employed. The calcination treatment is well known to those skilled in the art and may be performed, for example, in a tube furnace, a muffle furnace, or the like. Preferably, the conditions of firing may include: the temperature is 400-800 ℃ and the time is 0.5-8 hours, and the roasting can be carried out in an air atmosphere or a water vapor atmosphere.
A second aspect of the present disclosure provides an amine-free high silica ZSM-5 molecular sieve prepared by the method provided in the first aspect of the present disclosure. The ZSM-5 molecular sieve disclosed by the invention has the advantages of higher silicon-aluminum molar ratio and relative crystallinity, smooth surface and low molecular sieve aggregation degree.
In one specific embodiment of the present disclosure, the amine-free high silica ZSM-5 molecular sieve has a molar ratio of SiO 2 to Al 2O3 of 40-60, a relative crystallinity of 80-95%, a specific surface area of 240-300m 2/g, and a particle size of 1-2. Mu.m. The molar ratio of SiO 2 to Al 2O3 can be detected by adopting an X-ray fluorescence spectrum. The relative crystallinity is detected by a Siemens D5005 type X-ray diffractometer by taking a ZSM-5 molecular sieve standard sample of the Shike's institute as a reference, namely the relative crystallinity of the ZSM-5 molecular sieve standard sample of the China petrochemical Co., ltd. The specific surface area can be determined by adopting a specific surface area tester according to the N 2 adsorption principle and a BJH calculation method (see petrochemical analysis method (RIPP test method), RIPP-90, scientific press, 1990 publication), and the particle size can be estimated by carrying out SEM analysis on a molecular sieve and arbitrarily selecting 50 particles in an SEM picture to measure the particle size and calculate the average value.
A third aspect of the present disclosure provides an application of the amine-free high-silicon ZSM-5 molecular sieve provided in the second aspect of the present disclosure in a light hydrocarbon catalytic cracking reaction.
According to the present disclosure, the light hydrocarbon catalytic cracking reaction may be performed in a fixed bed reactor, and reaction conditions of the light hydrocarbon catalytic cracking reaction may include: the temperature is 600-650 ℃, the reaction mass airspeed is 20-40h -1, and the reaction pressure is 0.8-1.2MPa.
The present disclosure is further illustrated by the following examples, but the present disclosure is not limited thereby. The raw materials used in the following examples and comparative examples are commercially available unless otherwise specified.
Example 1
S1, adding 21.8g of silica gel, 11.97g of sodium metaaluminate (Na 2O:156.3g/L,Al2O3:103.8 g/L), 0.63g of sodium hydroxide, 49.3g of deionized water and 1.75gZSM-5 seed crystal (wherein the molar amount of the silica gel calculated as SiO 2 is equal to the molar amount of the sodium metaaluminate calculated as Al 2O3, the molar amount of the sodium hydroxide calculated as Na 2 O is equal to the molar amount of the deionized water=32:1:3.27:350, and the amount of the ZSM-5 seed crystal calculated as SiO 2 is 10 percent by weight of the silica gel calculated as SiO 2) in sequence under stirring, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 3 hours to obtain a first hydrothermal reaction product;
S2, transferring the first hydrothermal reaction product into a beaker, sequentially adding 18.2g of silica gel, 2.18g of sodium hydroxide, 48.9g of deionized water and 2.26gZSM-5 seed crystals under stirring (wherein the total molar amount of the silica gel calculated as SiO 2 is 10 percent by weight of the total amount of the silica gel calculated as SiO 2, the total molar amount of the sodium metaaluminate calculated as Al 2O3 is Na 2 O, the total molar amount of the sodium hydroxide calculated as Na 2 O is deionized water=60:1:6:642, and the total amount of the ZSM-5 seed crystals calculated as SiO 2 is fully and uniformly stirred; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 170 ℃ for 12h, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12h, and roasting at 550 ℃ in air atmosphere for 4h to obtain a ZSM-5 molecular sieve, wherein the molecular sieve is denoted as A, an X-ray diffraction spectrum of the molecular sieve is shown in figure 1, and a scanning electron microscope picture is shown in figure 2.
Example 2
S1, adding 21.8g of silica gel, 11.97g of sodium metaaluminate (Na 2O:156.3g/L,Al2O3:103.8 g/L), 0.63g of sodium hydroxide, 49.3g of deionized water and 1.75gZSM-5 seed crystals in sequence under stirring, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 3 hours to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, sequentially adding 18.2g of silica gel, 2.18g of sodium hydroxide, 48.9g of deionized water and 2.26gZSM-5 seed crystals under stirring, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 165 ℃ for 17h, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12h, and roasting at 550 ℃ in air for 4h to obtain a ZSM-5 molecular sieve, denoted as B, wherein an X-ray diffraction pattern is shown in FIG. 3, and a scanning electron microscope is shown in FIG. 4.
Example 3
S1, adding 21.8g of silica gel, 11.97g of sodium metaaluminate (Na 2O:156.3g/L,Al2O3:103.8 g/L), 0.63g of sodium hydroxide, 49.3g of deionized water and 1.75gZSM-5 seed crystals in sequence under stirring, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 3 hours to obtain a first hydrothermal reaction product;
S2, transferring the first hydrothermal reaction product into a beaker, sequentially adding 18.2g of silica gel, 2.18g of sodium hydroxide, 48.9g of deionized water and 2.26gZSM-5 seed crystals under stirring, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 160 ℃ for 17 hours, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12 hours, and roasting at 550 ℃ in air for 4 hours to obtain a ZSM-5 molecular sieve, which is marked as C, wherein an X-ray diffraction diagram is shown in figure 5.
Example 4
S1, adding 21.8g of silica gel, 11.97g of sodium metaaluminate (Na 2O:156.3g/L,Al2O3:103.8 g/L), 0.63g of sodium hydroxide, 49.3g of deionized water and 1.75gZSM-5 seed crystals in sequence under stirring, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 200 ℃ for 1h to obtain a first hydrothermal reaction product;
S2, transferring the first hydrothermal reaction product into a beaker, sequentially adding 18.2g of silica gel, 1.5g of sodium hydroxide, 48.9g of deionized water and 2.26gZSM-5 seed crystals under stirring, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 165 ℃ for 10 hours, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12 hours, and roasting at 550 ℃ in air for 5 hours to obtain a ZSM-5 molecular sieve, which is denoted by D, wherein an X-ray diffraction pattern is shown in FIG. 6, and a scanning electron microscope is shown in FIG. 7.
Example 5
S1, adding 21.8g of silica gel, 11.97g of sodium metaaluminate (Na 2O:156.3g/L,Al2O3:103.8 g/L), 0.63g of sodium hydroxide, 49.3g of deionized water and 1.75gZSM-5 seed crystals in sequence under stirring, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 200 ℃ for 3 hours to obtain a first hydrothermal reaction product;
S2, transferring the first hydrothermal reaction product into a beaker, sequentially adding 18.2g of silica gel, 1.5g of sodium hydroxide, 48.9g of deionized water and 2.26gZSM-5 seed crystals under stirring, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 170 ℃ for 10 hours, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12 hours, and roasting at 550 ℃ in air for 4 hours to obtain a ZSM-5 molecular sieve, denoted as E, wherein an X-ray diffraction pattern is shown in FIG. 6, and a scanning electron microscope is shown in FIG. 8.
Example 6
S1, adding 21.8g of silica gel, 11.97g of sodium metaaluminate (Na 2O:156.3g/L,Al2O3:103.8 g/L), 0.63g of sodium hydroxide, 49.3g of deionized water and 1.75gZSM-5 seed crystals in sequence under stirring, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 200 ℃ for 4 hours to obtain a first hydrothermal reaction product;
S2, transferring the first hydrothermal reaction product into a beaker, sequentially adding 18.2g of silica gel, 1.5g of sodium hydroxide, 48.9g of deionized water and 2.26gZSM-5 seed crystals under stirring, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 170 ℃ for 12 hours, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12 hours, and roasting at 550 ℃ in air atmosphere for 4 hours to obtain a ZSM-5 molecular sieve, which is marked as F, wherein the XRD detection shows that the prepared ZSM-5 molecular sieve is not shown any more.
Example 7
An amine-free high silica ZSM-5 molecular sieve was prepared in the same manner as in example 1 except that in step S1, 21.8g of silica gel, 8.7g of sodium metaaluminate (Na 2O:156.3g/L,Al2O3: 103.8 g/L), 1.17g of sodium hydroxide, 51.8g of deionized water and 1.75gZSM-5 seed crystals were sequentially added with stirring.
Wherein, the mole amount of silica gel is calculated by SiO 2: molar amount of sodium metaaluminate calculated as Al 2O3: molar amount of sodium hydroxide in terms of Na 2 O: molar amount of deionized water = 45:1:4.5:482, the amount of ZSM-5 seed crystals calculated as Al 2O3 was 10% by weight of silica gel calculated as SiO 2. The obtained product is marked as G, and XRD detection shows that the prepared ZSM-5 molecular sieve is prepared, and a specific spectrogram is not shown.
Example 8
An amine-free high silica ZSM-5 molecular sieve was prepared in the same manner as in example 1 except that in step S2, the first hydrothermal reaction product was transferred to a beaker, and 2.97g of silica gel, 28.2g of sodium hydroxide, 66.68g of deionized water, and 2.93gZSM-5 seed crystals were sequentially added with stirring.
Wherein, the total mole of the silica gel is calculated as SiO 2: molar amount of sodium metaaluminate calculated as Al 2O3: total molar weight of sodium hydroxide in Na 2 O: total molar amount of deionized water = 70:1:7:749 the total amount of ZSM-5 seeds calculated as Al 2O3 is 10% by weight of the total amount of silica gel calculated as SiO 2. The obtained product is marked as H, and XRD detection shows that the prepared ZSM-5 molecular sieve is prepared, and a specific spectrogram is not shown any more.
Comparative example 1
An amine-free high silica ZSM-5 molecular sieve was prepared in the same manner as in example 1 except that in step S2, the first hydrothermal reaction product was transferred to a beaker, and 28.2g of silica gel, 3.38g of sodium hydroxide, 75.82g of deionized water, and 3.27gZSM-5 seed crystals were sequentially added with stirring.
Wherein, the total mole of the silica gel is calculated as SiO 2: molar amount of sodium metaaluminate calculated as Al 2O3: total molar weight of sodium hydroxide in Na 2 O: total molar amount of deionized water = 75:1:7.5:803, the total amount of ZSM-5 seeds calculated as Al 2O3 was 10% by weight of the total amount of silica gel calculated as SiO 2. The obtained product is marked as D1, and XRD detection shows that the prepared ZSM-5 molecular sieve is prepared, and a specific spectrogram is not shown any more.
Comparative example 2
40G of silica gel, 11.97g of sodium metaaluminate (Na 2O:156.3g/L,Al2O3:103.8 g/L), 2.81g of sodium hydroxide, 98.2g of deionized water and 4.01gZSM-5 seed crystal are added in sequence under stirring, and fully and uniformly stirred; transferring to a stainless steel kettle, performing hydrothermal reaction at 180deg.C for 20h, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120deg.C for 12h, and calcining at 550deg.C in air atmosphere for 4h to obtain ZSM-5 molecular sieve, denoted as D2, with X-ray diffraction pattern shown in figure 9 and scanning electron microscope picture shown in figure 10.
Comparative example 3
40G of silica gel, 11.97g of sodium metaaluminate (Na 2O:156.3g/L,Al2O3:103.8 g/L), 2.81g of sodium hydroxide, 98.2g of deionized water and 4.01gZSM-5 seed crystal are added in sequence under stirring, and fully and uniformly stirred; transferring to a stainless steel kettle, performing a first hydrothermal reaction at 190 ℃ for 3h, then performing a second hydrothermal reaction at 170 ℃ for 12h, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12h, and roasting in air at 550 ℃ for 4h to obtain a ZSM-5 molecular sieve, denoted as D3, wherein an X-ray diffraction spectrum is shown in figure 11, and a scanning electron microscope photo is shown in figure 12.
Test case
The molecular sieves prepared in the examples and the comparative examples are used as catalysts in the light hydrocarbon catalytic cracking reaction to carry out the catalytic cracking reaction of n-tetradecane, and the specific method is as follows: the influence of the molecular sieve on the yield and conversion rate of the low-carbon olefin in the light hydrocarbon catalytic cracking is evaluated by adopting pure hydrocarbon micro-reaction. The reaction is carried out in a fixed bed reactor, raw oil is n-tetradecane, carrier gas is nitrogen, the flow is 30mL/min, the reaction temperature is 650 ℃, the regeneration temperature is 600 ℃, the weight airspeed is 20h -1, the molecular sieve is sieved to 20-40 meshes of particles after tabletting, the filling amount is 2.0g, the catalyst-oil volume ratio is 1.28, the sample analysis is carried out after the reaction for 900s, the material balance calculation is carried out, and the product distribution is shown in Table 1.
Wherein, the micro-inverse conversion rate X of the raw material and the yield Y i of the product are calculated by adopting the following formulas:
X=100% - (yield of liquid phase product X content of n-tetradecane in liquid phase product) ×100%, liquid phase product refers to gasoline and diesel;
Y i = mass of component i in the product/mass of converted n-tetradecane x 100%, i representing ethylene, propylene, butene.
TABLE 1
As can be seen from Table 1, the ZSM-5 molecular sieve prepared by the method has a silicon-aluminum ratio of 40-60 and a relatively high degree of crystallinity (the relatively high degree of crystallinity can reach 86.1%). Meanwhile, as can be seen by comparing the scanning electron microscope photographs of the ZSM-5 molecular sieves prepared in examples 1, 2, 4 and 5 with the scanning electron microscope photographs of the ZSM-5 molecular sieves prepared in comparative examples 2 and 3, the ZSM-5 molecular sieves prepared by the method of the application have complete particles, smooth surfaces and low aggregation degree of molecular sieves, and the particle size of the ZSM-5 molecular sieves is about 1-2 mu m, and the ZSM-5 molecular sieves have proper particle sizes and better morphological structures. The ZSM-5 molecular sieve disclosed by the application has the specific surface area and the pore volume higher than those of a one-stage method, has better low-carbon olefin yield when being used in a light hydrocarbon catalytic cracking reaction, and can produce more propylene.
The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, but the present disclosure is not limited to the specific details of the embodiments described above, and various simple modifications may be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure, and all the simple modifications belong to the protection scope of the present disclosure.
In addition, the specific features described in the foregoing embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, the present disclosure does not further describe various possible combinations.
Moreover, any combination between the various embodiments of the present disclosure is possible as long as it does not depart from the spirit of the present disclosure, which should also be construed as the disclosure of the present disclosure.
Claims (8)
1. A method for preparing an amine-free high-silicon ZSM-5 molecular sieve, which comprises the following steps:
s1, mixing a first silicon source, an aluminum source, a first alkali source, water and a first seed crystal, and performing a first hydrothermal reaction on the obtained first mixture to obtain a first hydrothermal reaction product;
wherein the molar ratio of the first silicon source, the aluminum source, the first alkali source and the water is (20-45): 1: (1-5): (140-440), the amount of the first seed crystal being 1-10 wt% of the amount of the first silicon source, the first silicon source being calculated as SiO 2, the aluminum source being calculated as Al 2O3, the first alkali source being calculated as alkali metal oxide, the first seed crystal being calculated as SiO 2; the conditions of the first hydrothermal reaction include: the temperature is 180-220 ℃ and the time is 1-5 hours;
S2, mixing the first hydrothermal reaction product with a second silicon source, a second alkali source, water and a second crystal seed, and then carrying out a second hydrothermal reaction on the obtained second mixture;
Wherein the molar ratio of the total amount of the second silicon source and the first silicon source, the amount of the aluminum source, the total amount of the first alkali source and the second alkali source, and the total amount of the water is (50-70): 1: (2-8): (600-1000), the total amount of the first seed crystal and the second seed crystal being 1-10 wt% of the total amount of the first silicon source and the second silicon source, the second silicon source being calculated as SiO 2, the second alkali source being calculated as alkali metal oxide, the second seed crystal being calculated as SiO 2; the first seed crystal and the second seed crystal are each independently an industrial ZSM-5 molecular sieve having a silica to alumina ratio of 20 to 50; the conditions of the second hydrothermal reaction include: the temperature is 150-180 ℃ and the time is 8-20h;
The molar ratio of SiO 2 to Al 2O3 of the amine-free high-silicon ZSM-5 molecular sieve is 40-60, the relative crystallinity is 80-95%, and the specific surface area is 240-300m 2/g.
2. The method of claim 1, wherein in step S1, the molar ratio of the first silicon source, the aluminum source, the first alkali source, and the water usage is (20-35): 1: (3-4): (320-360) the first seed is present in an amount of 8-10 wt% of the first silicon source.
3. The method of claim 2, wherein a molar ratio of a total amount of the first and second silicon sources, a total amount of the aluminum source, the first and second alkali sources, and an amount of the water is (55-65): 1: (4-8): (600-700), the total amount of the first seed crystal and the second seed crystal being 8-10 wt% of the total amount of the first silicon source and the second silicon source.
4. The method of claim 1, wherein the first silicon source and the second silicon source are each independently selected from one or more of silica gel, water glass, silica and white carbon;
the aluminum source is selected from one or more of sodium metaaluminate, SB powder, aluminum oxide, aluminum hydroxide and aluminum sulfate;
the first alkali source and the second alkali source are respectively and independently selected from one or more of sodium hydroxide, sodium silicate and potassium hydroxide.
5. The method according to claim 1, wherein the method further comprises step S3: and collecting a solid product of the second hydrothermal reaction, and sequentially carrying out ammonium exchange and roasting treatment on the solid product.
6. The method of claim 5, wherein the conditions of the firing process include: the temperature is 400-800 ℃, the time is 0.5-8h, and the atmosphere is air atmosphere or water vapor atmosphere.
7. The amine-free high silica ZSM-5 molecular sieve prepared by the method of any one of claims 1-6.
8. The use of the amine-free high silica ZSM-5 molecular sieve of claim 7 in a light hydrocarbon catalytic cracking reaction.
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