CN115818663A - 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 117
- 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 117
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 80
- 239000010703 silicon Substances 0.000 title claims abstract description 80
- 238000002360 preparation method Methods 0.000 title description 8
- 239000013078 crystal Substances 0.000 claims abstract description 78
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 68
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 61
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 50
- 239000003513 alkali Substances 0.000 claims abstract description 43
- 238000000034 method Methods 0.000 claims abstract description 42
- 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
- 239000000203 mixture Substances 0.000 claims abstract description 22
- 238000002156 mixing Methods 0.000 claims abstract description 9
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 70
- 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
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 24
- 238000006243 chemical reaction Methods 0.000 claims description 23
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 21
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 21
- 239000000377 silicon dioxide Substances 0.000 claims description 20
- 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 18
- 229910052708 sodium Inorganic materials 0.000 claims description 18
- 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
- 229930195733 hydrocarbon Natural products 0.000 claims description 12
- 150000002430 hydrocarbons Chemical class 0.000 claims description 12
- 239000004215 Carbon black (E152) Substances 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
- 235000019353 potassium silicate Nutrition 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
- 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
- 239000000843 powder Substances 0.000 claims description 3
- 238000010304 firing Methods 0.000 claims 1
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 abstract description 3
- 239000008367 deionised water Substances 0.000 description 23
- 229910021641 deionized water Inorganic materials 0.000 description 23
- 238000003756 stirring Methods 0.000 description 23
- 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
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- BGHCVCJVXZWKCC-UHFFFAOYSA-N tetradecane Chemical compound CCCCCCCCCCCCCC BGHCVCJVXZWKCC-UHFFFAOYSA-N 0.000 description 8
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- 238000001878 scanning electron micrograph Methods 0.000 description 7
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- 230000002194 synthesizing effect Effects 0.000 description 5
- 150000001412 amines Chemical class 0.000 description 4
- 229910052799 carbon Inorganic materials 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
- 229910021536 Zeolite Inorganic materials 0.000 description 3
- 230000004913 activation Effects 0.000 description 3
- 238000001354 calcination Methods 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- -1 catalytic cracking Chemical class 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
- 230000000694 effects Effects 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 239000007791 liquid phase Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000011160 research 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
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- 150000001298 alcohols Chemical class 0.000 description 2
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- 239000003921 oil Substances 0.000 description 2
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- 239000011148 porous material 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
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- 238000003915 air pollution Methods 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
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- 208000012839 conversion disease Diseases 0.000 description 1
- 239000002283 diesel fuel Substances 0.000 description 1
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- 230000005496 eutectics Effects 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
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- 238000004626 scanning electron microscopy Methods 0.000 description 1
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- 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 disclosure relates to a method for preparing an amine-free high-silicon ZSM-5 molecular sieve, which comprises S1, mixing a first silicon source, an aluminum source, a first alkali source, water and a first crystal seed, and then carrying out 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 to the aluminum source to the first alkali source to 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 seed, and carrying out a second hydrothermal reaction on an obtained second mixture; wherein the molar ratio of the total dosage of the second silicon source and the first silicon source, the dosage of the aluminum source, the total dosage of the first alkali source and the second alkali source and the total dosage of water is (50-70): 1: (2-8): (600-1000), the total dosage of the first seed crystal and the second seed crystal is 1-10 wt% of the total dosage of the first silicon source and the second silicon source. The method disclosed by the invention can be used for preparing the ZSM-5 molecular sieve with higher silicon-aluminum molar ratio and crystallinity.
Description
Technical Field
The disclosure relates to the field of molecular sieve preparation, 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 channel system, high-silicon zeolite with an MFI topological structure and two cross-linked ten-membered ring channels. The catalyst has strong selective adsorption performance, good thermal stability and hydrothermal stability and moderate acidity, so that the catalyst is suitable for catalytic reactions of various hydrocarbons, such as catalytic cracking, isomerization, aromatization, alkylation reaction and the like, and is widely applied to the fields of petrochemical industry and industrial catalysis.
In the traditional hydrothermal synthesis method, quaternary ammonium cations or other organic amine molecules are required to be added as a template, most of the existing ZSM-5 molecular sieves are synthesized by adopting an organic amine template hydrothermal method, and although the ZSM-5 molecular sieves with uniform particle size and regular pore canal and crystal form can be synthesized by taking the organic amine with strong structure-oriented action as the template under wider conditions, the synthesized ZSM-5 molecular sieves have smaller crystal grains and lower stability in a harsh catalytic cracking reaction environment. In addition, the organic amine template has high toxicity, a large amount of organic wastewater is generated in the synthesis process, and the performance of the molecular sieve is also influenced by air pollution caused by roasting and decomposing the template. In addition, the price of the template agent is expensive, and the large amount of the template agent can greatly increase the production cost of the molecular sieve. Therefore, the research of synthesizing the ZSM-5 molecular sieve without the template has high environmental protection significance and economic value.
The template-free system synthesized ZSM-5 molecular sieve has the characteristics of environmental friendliness, low cost and the like, is favored by researchers in recent years, and more template-free ZSM-5 molecular sieves have emerged in the synthesis process. The synthesis of the ZSM-5 molecular sieve in a template-free system needs longer time compared with the traditional synthesis method, because the nucleation activation energy and the growth activation energy of the molecular sieve are both higher due to the lack of the guiding effect of a template agent; in addition, the phase region for synthesizing the ZSM-5 molecular sieve by the template-free method is narrow, because the crystal nucleus formation is difficult due to the lack of the guiding effect of a template agent, and the crystal transformation phenomenon is easy to occur. If the seed crystal containing formed crystal nucleus is added into the synthetic liquid, a large number of specific crystal nuclei can be induced to form in a short time, so that the crystallization time is shortened, the synthetic phase region is widened, and the phenomena of eutectic crystallization and crystal transformation are avoided to the greatest extent, namely the seed crystal method.
The ZSM-5 molecular sieve with the silica-alumina ratio of about 25 prepared by the seed crystal method has been industrially applied, but the ZSM-5 molecular sieve with the silica-alumina ratio of about 25 has higher acidity, so the hydrogen transfer reaction degree is higher, and researches find that the ZSM-5 molecular sieve with the silica-alumina 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 ratio becomes difficult, and even if seed crystals are added to synthesize the ZSM-5 molecular sieves with high silica-alumina ratio, the crystallinity is still lower. This is because the crystal seed guiding effect can guide the ZSM-5 molecular sieve with low silica alumina ratio, but when the ZSM-5 molecular sieve with high silica alumina ratio is guided and synthesized, the activation energy of nucleation growth is higher, and the crystal nucleus is difficult to form in a short time.
Regarding the synthesis of amine-free ZSM-5 molecular sieve, chinese patents CN 105621451A and CN105692652B disclose 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 performing two-stage crystallization to obtain the ZSM-5 molecular sieve. The preparation method is to synthesize the molecular sieve under the conditions of no template agent, low water-silicon ratio, temperature rise speed control and two-stage crystallization. Although the method has higher crystallinity and has achieved industrial application when synthesizing the ZSM-5 molecular sieve with the silica alumina ratio of 20-25, the crystallinity of the molecular sieve is lower when the silica alumina ratio is 40-60 or higher.
Chinese patent CN 108190913A discloses a method for synthesizing a silicon-rich ZSM-5 zeolite molecular sieve by using a seed crystal guiding method, which introduces alcohols to prepare the silicon-rich ZSM-5 zeolite molecular sieve with higher crystallinity and high silica-alumina ratio, thereby avoiding the use of expensive organic template and greatly reducing the synthesis cost. However, the introduction of alcohols increases the reaction pressure, which brings about safety hazards, and in addition, the subsequent separation treatment also brings about higher cost.
Although many ZSM-5 template-free synthesis methods have been reported, the synthesis of ZSM-5 molecular sieves with a silica-alumina ratio of 40-60 in a template-free and alcohol-free system is rarely reported.
Disclosure of Invention
The invention aims to provide an amine-free high-silicon ZSM-5 molecular sieve, and a preparation method and application thereof, and the ZSM-5 molecular sieve with higher crystallinity and higher silica-alumina ratio can be prepared by the method.
To achieve the above object, the present disclosure provides, in a first aspect, 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 first crystal seeds, and carrying out a first hydrothermal reaction on an 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 dosage of the first seed crystal is 1-10 wt% of the dosage of the first silicon source, and the first silicon source is SiO 2 The aluminum source is calculated as Al 2 O 3 The first alkali source is calculated by alkali metal oxide, and the first seed crystal is calculated by SiO 2 Counting;
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 an 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 dosage of the first seed crystal and the second seed crystal is 1-10 wt% of the total dosage of the first silicon source and the second silicon source,the second silicon source is made of SiO 2 The second alkali source is calculated by alkali metal oxide, and the second seed crystal is calculated by SiO 2 And (6) counting.
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), wherein the dosage of the first seed crystal is 8-10 wt% of the dosage of the first silicon source.
Optionally, the molar ratio of the total amount of the first silicon source and the second silicon source, the total amount of the aluminum source, the first alkali source and the second alkali source, and the 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 is 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, alumina, 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, water glass 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 the 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 roasting treatment include: the temperature is 400-800 deg.C, the time is 0.5-8h, and the atmosphere is air atmosphere or water vapor atmosphere.
In a second aspect, the present disclosure provides an amine-free high-silicon ZSM-5 molecular sieve prepared by the method provided in the first aspect of the present disclosure.
Optionally, siO of the amine-free high-silicon ZSM-5 molecular sieve 2 With Al 2 O 3 Has a molar ratio of 40-60, a relative crystallinity of 80-95%, and a specific surface area of 240-300m 2 (iii) per gram, particle size 1-2 μm.
In a third aspect of the present disclosure, there is provided an application of the amine-free high-silicon ZSM-5 molecular sieve provided in the second aspect of the present disclosure in light hydrocarbon catalytic cracking reaction.
The method disclosed has the following advantages:
(1) The method disclosed by the invention adopts a method of supplementing silicon after two-stage crystallization combination to prepare the ZSM-5 molecular sieve, can prepare the ZSM-5 molecular sieve with the silica-alumina ratio of 40-60, has higher relative crystallinity, has better yield of low-carbon olefin when being used in a light hydrocarbon catalytic cracking reaction, and is beneficial to more propylene production.
(2) The method is simple to operate, the ZSM-5 molecular sieve with the silicon-aluminum ratio of 40-60 is synthesized by adopting a template-free and alcohol-free system, ammonia nitrogen wastewater is not discharged in the preparation process, and the method 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, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure without limiting the disclosure. In the drawings:
FIG. 1 is an X-ray diffraction pattern of a ZSM-5 molecular sieve sample 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 ZSM-5 molecular sieve sample 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 ZSM-5 molecular sieve sample prepared in example 3 of the present disclosure;
FIG. 6 is an X-ray diffraction pattern of a ZSM-5 molecular sieve sample prepared in examples 4, 5 of the present 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 ZSM-5 molecular sieve sample 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 a 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 according to comparative example 3 of the present disclosure.
Detailed Description
The following detailed description of specific embodiments of the present disclosure is provided in connection with the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present disclosure, are given by way of illustration and explanation only, not limitation.
In a first aspect of the disclosure, there is provided a process for preparing an amine-free high silica ZSM-5 molecular sieve, the process comprising:
s1, mixing a first silicon source, an aluminum source, a first alkali source, water and first crystal seeds, and carrying out a first hydrothermal reaction on an 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 dosage of the first seed crystal is 1-10 wt% of the dosage of the first silicon source, and the first silicon source is SiO 2 The aluminum source is calculated as Al 2 O 3 The first alkali source is calculated by alkali metal oxide, and the first seed crystal is calculated by SiO 2 Counting;
s2, mixing the first hydrothermal reaction product with a second silicon source, a second alkali source, water and a second crystal seed, and carrying out a second hydrothermal reaction on an obtained second mixture;
wherein the second silicon sourceAnd the molar ratio of the total amount of 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 dosage of the first seed crystal and the second seed crystal is 1-10 wt% of the total dosage of the first silicon source and the second silicon source, and the second silicon source is SiO 2 The second alkali source is calculated by alkali metal oxide, and the second seed crystal is calculated by SiO 2 And (6) counting.
Compared with the method of one-time feeding and one-section crystallization in the prior art, the method disclosed by the invention can ensure that the prepared ZSM-5 molecular sieve has 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 deg.C and the time is 1-5 hours, preferably 190-200 deg.C and the time is 2-4 hours, more preferably 195-200 deg.C and the time is 2-4 hours.
In one 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 ℃ and the time is 10-17 hours. The hydrothermal reaction is well known to those skilled in the art in light of the present disclosure, and the first hydrothermal reaction and the second hydrothermal reaction may be carried out in an apparatus conventionally employed by those skilled in the art, for example, in a heat-resistant closed vessel, preferably an autoclave. The reaction pressure of the first hydrothermal reaction and the second hydrothermal reaction is not particularly limited in the present disclosure, and may be, for example, the autogenous pressure of the reaction system, or may be performed under an applied pressure, and is preferably performed under the autogenous pressure of the reaction system.
According to the present disclosure, in step S1, the molar ratio of the amounts of the first silicon source, the aluminum source, the first alkali source and the water may vary within a wide range. In one 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), wherein the dosage of the first seed crystal is 8-10 wt% of the dosage 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 alkali source and the second alkali source, and the 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 is 8-10 wt% of the total amount of the first silicon source and the second silicon source.
According to the present disclosure, the first silicon source and the second silicon source are well known to those skilled in the art, 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, water glass and potassium hydroxide, and preferably are sodium hydroxide; the aluminum source can be one or more selected from sodium metaaluminate, SB powder, alumina, aluminum hydroxide and aluminum sulfate; the seed crystal can be industrial ZSM-5 molecular sieve with the silica-alumina ratio of 20-50.
In a specific embodiment of the present disclosure, the method further includes step S3: and collecting the 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 that does not react with the solid product, and may be, for example, deionized water. The method for collecting the solid product is not particularly limited in the present disclosure, and methods such as filtration, centrifugation and the like may be employed. The calcination treatment is well known to those skilled in the art and may be carried out, for example, in a tube furnace, a muffle furnace, or the like. Preferably, the conditions of the calcination may include: the temperature is 400-800 deg.C, the time is 0.5-8 hr, and the calcination can be carried out in air atmosphere or water vapor atmosphere.
In a second aspect, the present disclosure provides an amine-free high-silicon 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 silica-alumina molar ratio and relative crystallinity, smooth surface and low molecular sieve aggregation degree.
In one embodiment of the present disclosure, the amine-free high silica ZSM-5 molecular sieve is SiO 2 With Al 2 O 3 Has a molar ratio of 40-60, a relative crystallinity of 80-95%, and a specific surface area of 240-300m 2 (iii) per gram, particle size 1-2 μm. Wherein, siO 2 With Al 2 O 3 The molar ratio of (A) to (B) can be detected by X-ray fluorescence spectroscopy. The relative crystallinity is obtained by taking a ZSM-5 molecular sieve standard sample of a Shikeji (namely the relative crystallinity of the ZSM-5 molecular sieve standard sample of the petrochemical engineering science research institute of the China petrochemical company, inc. is 100%) and detecting the relative crystallinity by using a Siemens D5005 type X-ray diffractometer. The specific surface area can be measured according to N by using a specific surface area tester 2 The adsorption principle is determined by a BJH calculation method (see petrochemical analysis method (RIPP test method), RIPP151-90, scientific Press, 1990) and the particle size can be estimated by performing SEM analysis on the molecular sieve and arbitrarily selecting 50 particles in the SEM picture to measure the particle size and averaging the particle size.
In a third aspect of the present disclosure, there is provided an application of the amine-free high-silicon ZSM-5 molecular sieve provided in the second aspect of the present disclosure in light hydrocarbon catalytic cracking reaction.
According to this disclosure, light hydrocarbon catalytic cracking reaction can go on in fixed bed reactor, and light hydrocarbon catalytic cracking reaction's reaction condition can include: the temperature is 600-650 ℃, and the reaction mass space velocity is 20-40h -1 The reaction pressure is 0.8-1.2MPa.
The present disclosure is further illustrated by the following examples, but is not to be construed as being limited thereby. The raw materials used in the following examples and comparative examples were all commercially available unless otherwise specified.
Example 1
S1, adding 21.8g of silica gel and 11.97g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.63g sodium hydroxide, 49.3g deionized water, 1.75g ZSM-5 seed crystal (wherein, siO is used 2 Calculated molar amount of silica gel: with Al 2 O 3 Calculated molar amount of sodium metaaluminate: with Na 2 Molar amount of sodium hydroxide calculated as O: deionized water molar =32:1:3.27:350 in SiO 2 The dosage of the ZSM-5 crystal seeds is calculated by SiO 2 10 percent by weight of the silica gel) and fully and uniformly stirring; transferring the mixture into a stainless steel kettle, and carrying out a first hydrothermal reaction for 3h at 190 ℃ to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, and adding 18.2g of silica gel, 2.18g of sodium hydroxide, 48.9g of deionized water and 2.26g of ZSM-5 seed crystal (wherein SiO is used as the seed crystal) in turn under stirring 2 Total molar amount of silica gel: with Al 2 O 3 Calculated molar amount of sodium metaaluminate: with Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water =60:1:6:642 of SiO 2 The total dosage of ZSM-5 seed crystal is SiO 2 10 percent by weight of the total amount of the silica gel) and fully and uniformly stirring; and transferring the mixture into a stainless steel kettle again, carrying out a second hydrothermal reaction at 170 ℃ for 12h, filtering, washing to pH =7-8, carrying out ammonium exchange, drying at 120 ℃ for 12h, and then roasting at 550 ℃ for 4h in an air atmosphere to obtain the ZSM-5 molecular sieve, wherein the molecular sieve is marked as A, and the X-ray diffraction spectrum of the molecular sieve is shown in figure 1, and the scanning electron microscope picture of the molecular sieve is shown in figure 2.
Example 2
S1, adding 21.8g of silica gel and 11.97g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.63g of sodium hydroxide, 49.3g of deionized water and 1.75g of ZSM-5 seed crystal are fully and uniformly stirred; transferring the mixture into a stainless steel kettle, and carrying out a first hydrothermal reaction for 3h at 190 ℃ to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, adding 18.2g of silica gel, 2.18g of sodium hydroxide, 48.9g of deionized water and 2.26g of ZSM-5 seed crystal in sequence under stirring, and fully and uniformly stirring; and transferring the mixture into a stainless steel kettle again, carrying out a second hydrothermal reaction at 165 ℃ for 17h, filtering, washing to pH =7-8, carrying out ammonium exchange, drying at 120 ℃ for 12h, and then roasting at 550 ℃ for 4h in an air atmosphere to obtain the ZSM-5 molecular sieve, wherein the molecular sieve is marked as B, and the X-ray diffraction spectrum and the scanning electron microscope photo are respectively shown in FIG. 3 and FIG. 4.
Example 3
S1, adding 21.8g of silica gel and 11.97g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.63g of sodium hydroxide, 49.3g of deionized water and 1.75g of ZSM-5 seed crystal are fully and uniformly stirred; transferring the mixture into a stainless steel kettle, and carrying out a first hydrothermal reaction for 3h at 190 ℃ to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, adding 18.2g of silica gel, 2.18g of sodium hydroxide, 48.9g of deionized water and 2.26g of ZSM-5 seed crystal in sequence under stirring, and fully and uniformly stirring; and transferring the mixture into a stainless steel kettle again, carrying out a second hydrothermal reaction at 160 ℃ for 17h, filtering, washing to pH =7-8, carrying out ammonium exchange, drying at 120 ℃ for 12h, and then roasting at 550 ℃ for 4h in an air atmosphere to obtain the ZSM-5 molecular sieve, wherein the molecular sieve is marked as C, and the X-ray diffraction spectrum of the molecular sieve is shown in figure 5.
Example 4
S1, adding 21.8g of silica gel and 11.97g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.63g of sodium hydroxide, 49.3g of deionized water and 1.75g of ZSM-5 seed crystal are fully and uniformly stirred; transferring the mixture into a stainless steel kettle, and carrying out 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, adding 18.2g of silica gel, 1.5g of sodium hydroxide, 48.9g of deionized water and 2.26g of ZSM-5 seed crystal in sequence under stirring, and fully and uniformly stirring; and transferring the mixture to a stainless steel kettle again, carrying out a second hydrothermal reaction at 165 ℃ for 10h, filtering, washing to pH =7-8, carrying out ammonium exchange, drying at 120 ℃ for 12h, and then roasting at 550 ℃ in an air atmosphere for 5h to obtain the ZSM-5 molecular sieve, wherein the molecular sieve is marked as D, and the X-ray diffraction spectrum of the molecular sieve is shown in figure 6, and the scanning electron micrograph of the molecular sieve is shown in figure 7.
Example 5
S1, adding 21.8g of silica gel and 11.97g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.63g sodium hydroxide and 49.3g sodium hydroxideThe ionized water and 1.75g of ZSM-5 seed crystal are fully and uniformly stirred; transferring the mixture into a stainless steel kettle, and carrying out a first hydrothermal reaction for 3 hours at 200 ℃ to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, adding 18.2g of silica gel, 1.5g of sodium hydroxide, 48.9g of deionized water and 2.26g of ZSM-5 seed crystal in sequence under stirring, and fully and uniformly stirring; and transferring the mixture into a stainless steel kettle again, carrying out a second hydrothermal reaction at 170 ℃ for 10h, filtering, washing to pH =7-8, carrying out ammonium exchange, drying at 120 ℃ for 12h, and then roasting at 550 ℃ for 4h in an air atmosphere to obtain the ZSM-5 molecular sieve, wherein the molecular sieve is marked as E, and the X-ray diffraction spectrum of the molecular sieve is shown in figure 6, and the scanning electron microscope picture of the molecular sieve is shown in figure 8.
Example 6
S1, adding 21.8g of silica gel and 11.97g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.63g of sodium hydroxide, 49.3g of deionized water and 1.75g of ZSM-5 seed crystal are fully and uniformly stirred; transferring the mixture into a stainless steel kettle, and carrying out 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, adding 18.2g of silica gel, 1.5g of sodium hydroxide, 48.9g of deionized water and 2.26g of ZSM-5 seed crystal in sequence under stirring, and fully and uniformly stirring; and transferring the mixture to a stainless steel kettle again, carrying out a second hydrothermal reaction at 170 ℃ for 12h, filtering, washing until the pH is =7-8, carrying out ammonium exchange, drying at 120 ℃ for 12h, then roasting at 550 ℃ for 4h in an air atmosphere to obtain the ZSM-5 molecular sieve, wherein the molecular sieve is marked as F, and the prepared ZSM-5 molecular sieve is known through XRD detection, and a specific spectrogram is not shown.
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 and 8.7g of sodium metaaluminate (Na) were sequentially added under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 1.17g sodium hydroxide, 51.8g deionized water, 1.75g ZSM-5 seed crystal.
Wherein, siO is used 2 Calculated molar amount of silica gel: with Al 2 O 3 Calculated sodium metaaluminateMolar weight: with Na 2 Molar amount of sodium hydroxide calculated as O: deionized water molar weight =45:1:4.5:482, with Al 2 O 3 The dosage of the ZSM-5 crystal seeds is calculated by SiO 2 Calculated as 10 wt% of silica gel. The obtained product is marked as G, and the prepared ZSM-5 molecular sieve can be known by XRD detection, 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 into a beaker, and 2.97g of silica gel, 28.2g of sodium hydroxide, 66.68g of deionized water, and 2.93g of ZSM-5 seed crystal were sequentially added with stirring.
Wherein, siO is used 2 Total molar amount of silica gel: with Al 2 O 3 Calculated molar amount of sodium metaaluminate: with Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water =70:1:7:749 use Al 2 O 3 The total dosage of ZSM-5 seed crystal is SiO 2 Calculated as 10 wt% of the total amount of silica gel used. The obtained product is marked as H, and the prepared ZSM-5 molecular sieve can be known by XRD detection, and a specific spectrogram is not shown.
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 3.27g of ZSM-5 seed crystal were sequentially added with stirring.
Wherein, siO is used 2 Total molar amount of silica gel: with Al 2 O 3 Calculated molar amount of sodium metaaluminate: with Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water =75:1:7.5:803 of Al 2 O 3 The total dosage of ZSM-5 seed crystal is SiO 2 Calculated as 10 wt% of the total amount of silica gel used. The obtained product is marked as D1, and the prepared ZSM-5 molecular sieve can be known by XRD detection, and a specific spectrogram is not shown.
Comparative example 2
Adding the components in turn under stirring40g of silica gel, 11.97g of sodium metaaluminate (Na) 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 2.81g of sodium hydroxide, 98.2g of deionized water and 4.01g of ZSM-5 seed crystal are fully and uniformly stirred; and transferring the mixture into a stainless steel kettle, carrying out hydrothermal reaction at 180 ℃ for 20h, filtering, washing until the pH is =7-8, carrying out ammonium exchange, drying at 120 ℃ for 12h, and then roasting at 550 ℃ for 4h in an air atmosphere to obtain the ZSM-5 molecular sieve which is marked as D2, wherein an X-ray diffraction spectrum of the ZSM-5 molecular sieve is shown in figure 9, and a scanning electron microscope picture of the ZSM-5 molecular sieve is shown in figure 10.
Comparative example 3
40g of silica gel and 11.97g of sodium metaaluminate (Na) are added in turn with stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 2.81g of sodium hydroxide, 98.2g of deionized water and 4.01g of ZSM-5 seed crystal are fully and uniformly stirred; and transferring the mixture into a stainless steel kettle, carrying out a first hydrothermal reaction at 190 ℃ for 3h, then carrying out a second hydrothermal reaction at 170 ℃ for 12h, filtering, washing to pH =7-8, carrying out ammonium exchange, drying at 120 ℃ for 12h, and then roasting at 550 ℃ for 4h in an air atmosphere to obtain the ZSM-5 molecular sieve, wherein the molecular sieve is marked as D3, the X-ray diffraction spectrum of the molecular sieve is shown in figure 11, and the scanning electron microscope picture of the molecular sieve is shown in figure 12.
Test example
The molecular sieves prepared in the examples and the comparative examples are used as catalysts in light hydrocarbon catalytic cracking reaction to carry out catalytic cracking reaction of n-tetradecane, and the specific method is as follows: the influence of the molecular sieve on the yield and the conversion rate of the low-carbon olefin in the catalytic cracking of the light hydrocarbon is evaluated by adopting a 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 rate is 30mL/min, the reaction temperature is 650 ℃, the regeneration temperature is 600 ℃, and the weight space velocity is 20h -1 After the molecular sieve is tabletted, the particles are sieved into 20-40 meshes, the loading is 2.0g, the volume ratio of the agent to the oil is 1.28, sampling analysis is carried out after 900s of reaction, material balance calculation is carried out, and the product distribution is shown in table 1.
Wherein the micro-reaction conversion rate X of the raw material and the yield Y of the product are calculated by the following formula i ：
X =100% - (yield of liquid-phase product X content of n-tetradecane in liquid-phase product) X100%, liquid-phase product refers to gasoline and diesel oil;
Y i = mass of component i in the product/mass of converted n-tetradecane × 100%, i denotes ethylene, propylene, butene.
TABLE 1
As can be seen from Table 1, the ZSM-5 molecular sieve prepared by the method of the present disclosure has a silica-alumina ratio of 40-60 and a relatively high crystallinity (up to 86.1%). Meanwhile, when the scanning electron microscope photos of the ZSM-5 molecular sieves prepared in the examples 1, 2, 4 and 5 are compared with the scanning electron microscope photos of the ZSM-5 molecular sieves prepared in the comparative examples 2 and 3, the ZSM-5 molecular sieves prepared by the method have complete particles, smooth surfaces and low aggregation degree, 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 specific surface area and the pore volume of the ZSM-5 molecular sieve disclosed by the invention are higher than those of a one-stage method, and when the ZSM-5 molecular sieve is used in a light hydrocarbon catalytic cracking reaction, the yield of low-carbon olefins is relatively high, and the propylene can be produced in a large amount.
The preferred embodiments of the present disclosure are described in detail with reference to the accompanying drawings, however, the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present disclosure within the technical idea of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.
It should be noted that, in the foregoing embodiments, various features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various combinations that are possible in the present disclosure are not described again.
In addition, any combination of various embodiments of the present disclosure may be made, and the same should be considered as the disclosure of the present disclosure, as long as it does not depart from the spirit of the present disclosure.
Claims (10)
1. A method of preparing an amine-free high silicon ZSM-5 molecular sieve, the method comprising:
s1, mixing a first silicon source, an aluminum source, a first alkali source, water and first crystal seeds, and carrying out a first hydrothermal reaction on an 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 dosage of the first seed crystal is 1-10 wt% of the dosage of the first silicon source, and the first silicon source is SiO 2 The aluminum source is calculated as Al 2 O 3 The first alkali source is counted by alkali metal oxide, and the first seed crystal is counted by SiO 2 Counting;
s2, mixing the first hydrothermal reaction product with a second silicon source, a second alkali source, water and a second crystal seed, and carrying out a second hydrothermal reaction on an 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 dosage of the first seed crystal and the second seed crystal is 1-10 wt% of the total dosage of the first silicon source and the second silicon source, and the second silicon source is SiO 2 The second alkali source is calculated by alkali metal oxide, and the second seed crystal is calculated by SiO 2 And (6) counting.
2. The method of claim 1, wherein 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.
3. 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 is (20-35): 1: (3-4): (320-360), wherein the dosage of the first seed crystal is 8-10 wt% of the dosage of the first silicon source.
4. The method of claim 3, wherein the molar ratio of the total amount of the first and second silicon sources, the total amount of the aluminum source, the first alkali source, and the second alkali source, 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 is 8-10 wt% of the total amount of the first silicon source and the second silicon source.
5. The method according to 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 silica white;
the aluminum source is selected from one or more of sodium metaaluminate, SB powder, alumina, 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, water glass 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.
6. The method according to claim 1, wherein the method further comprises step S3: and collecting the solid product of the second hydrothermal reaction, and sequentially carrying out ammonium exchange and roasting treatment on the solid product.
7. The method of claim 6, wherein the conditions of the firing treatment include: the temperature is 400-800 deg.C, the time is 0.5-8h, and the atmosphere is air atmosphere or water vapor atmosphere.
8. The amine-free high silica ZSM-5 molecular sieve produced by the method of any one of claims 1 to 7.
9. The amine-free, high silica ZSM-5 molecular sieve of claim 8, wherein the amine-free, high silica ZSM-5 molecular sieve has a SiO 2 With Al 2 O 3 Has a molar ratio of 40-60, a relative crystallinity of 80-95%, and a specific surface area of 240-300m 2 /g。
10. Use of the amine-free, high silica ZSM-5 molecular sieve as defined in any of claims 8 and 9 in light hydrocarbon catalytic cracking reactions.
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