CN110143602B - Preparation method of beta molecular sieve - Google Patents
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- CN110143602B CN110143602B CN201810148721.5A CN201810148721A CN110143602B CN 110143602 B CN110143602 B CN 110143602B CN 201810148721 A CN201810148721 A CN 201810148721A CN 110143602 B CN110143602 B CN 110143602B
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- 239000002808 molecular sieve Substances 0.000 title claims abstract description 118
- 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 118
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 84
- 239000013078 crystal Substances 0.000 claims abstract description 63
- 238000006243 chemical reaction Methods 0.000 claims abstract description 60
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 60
- 238000010438 heat treatment Methods 0.000 claims abstract description 54
- 238000003756 stirring Methods 0.000 claims abstract description 48
- 229910001868 water Inorganic materials 0.000 claims abstract description 42
- 238000002425 crystallisation Methods 0.000 claims abstract description 40
- 230000008025 crystallization Effects 0.000 claims abstract description 39
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 34
- 229910052681 coesite Inorganic materials 0.000 claims abstract description 33
- 229910052906 cristobalite Inorganic materials 0.000 claims abstract description 33
- 229910052682 stishovite Inorganic materials 0.000 claims abstract description 33
- 229910052905 tridymite Inorganic materials 0.000 claims abstract description 33
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 28
- 239000010703 silicon Substances 0.000 claims abstract description 28
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000002243 precursor Substances 0.000 claims abstract description 24
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 23
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 23
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 22
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 21
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 21
- 238000000034 method Methods 0.000 claims abstract description 21
- 230000035484 reaction time Effects 0.000 claims abstract description 21
- 229910052593 corundum Inorganic materials 0.000 claims abstract description 18
- 229910001845 yogo sapphire Inorganic materials 0.000 claims abstract description 18
- 230000002194 synthesizing effect Effects 0.000 claims abstract description 15
- 229910052783 alkali metal Inorganic materials 0.000 claims abstract description 9
- 150000001340 alkali metals Chemical class 0.000 claims abstract description 9
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229910052751 metal Inorganic materials 0.000 claims abstract description 9
- 239000002184 metal Substances 0.000 claims abstract description 9
- 238000002156 mixing Methods 0.000 claims abstract description 9
- 239000002994 raw material Substances 0.000 claims abstract description 9
- KKCBUQHMOMHUOY-UHFFFAOYSA-N Na2O Inorganic materials [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000000499 gel Substances 0.000 claims description 90
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 72
- 239000011734 sodium Substances 0.000 claims description 29
- 229910052708 sodium Inorganic materials 0.000 claims description 23
- 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 22
- 229910002027 silica gel Inorganic materials 0.000 claims description 22
- 239000000741 silica gel Substances 0.000 claims description 22
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims description 5
- 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 4
- VXAUWWUXCIMFIM-UHFFFAOYSA-M aluminum;oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Al+3] VXAUWWUXCIMFIM-UHFFFAOYSA-M 0.000 claims description 3
- 239000011148 porous material Substances 0.000 abstract description 12
- 230000009286 beneficial effect Effects 0.000 abstract description 6
- 238000006317 isomerization reaction Methods 0.000 abstract description 4
- 238000004523 catalytic cracking Methods 0.000 abstract description 3
- 230000001737 promoting effect Effects 0.000 abstract description 2
- 239000002245 particle Substances 0.000 abstract 1
- 238000002441 X-ray diffraction Methods 0.000 description 33
- 230000001276 controlling effect Effects 0.000 description 33
- 239000008367 deionised water Substances 0.000 description 21
- 229910021641 deionized water Inorganic materials 0.000 description 21
- 238000012512 characterization method Methods 0.000 description 19
- 238000001035 drying Methods 0.000 description 19
- 238000005406 washing Methods 0.000 description 19
- 239000003795 chemical substances by application Substances 0.000 description 16
- 239000000463 material Substances 0.000 description 14
- 238000001228 spectrum Methods 0.000 description 13
- 230000000052 comparative effect Effects 0.000 description 10
- 238000001027 hydrothermal synthesis Methods 0.000 description 9
- 229910021536 Zeolite Inorganic materials 0.000 description 8
- 238000004458 analytical method Methods 0.000 description 8
- 238000004519 manufacturing process Methods 0.000 description 8
- 239000010457 zeolite Substances 0.000 description 8
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 229920002994 synthetic fiber Polymers 0.000 description 5
- 230000003197 catalytic effect Effects 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 230000009471 action Effects 0.000 description 3
- 239000006229 carbon black Substances 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 230000005672 electromagnetic field Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000006698 induction Effects 0.000 description 2
- 239000013081 microcrystal Substances 0.000 description 2
- 229910052680 mordenite Inorganic materials 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 229940073455 tetraethylammonium hydroxide Drugs 0.000 description 2
- LRGJRHZIDJQFCL-UHFFFAOYSA-M tetraethylazanium;hydroxide Chemical compound [OH-].CC[N+](CC)(CC)CC LRGJRHZIDJQFCL-UHFFFAOYSA-M 0.000 description 2
- KEAYESYHFKHZAL-UHFFFAOYSA-N Sodium Chemical compound [Na] KEAYESYHFKHZAL-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- 230000029936 alkylation Effects 0.000 description 1
- 238000005804 alkylation reaction Methods 0.000 description 1
- AMVQGJHFDJVOOB-UHFFFAOYSA-H aluminium sulfate octadecahydrate Chemical compound O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.[Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O AMVQGJHFDJVOOB-UHFFFAOYSA-H 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000036571 hydration Effects 0.000 description 1
- 238000006703 hydration reaction Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 238000005984 hydrogenation reaction Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000007783 nanoporous material Substances 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 1
- 238000005504 petroleum refining Methods 0.000 description 1
- 238000007146 photocatalysis Methods 0.000 description 1
- 230000001699 photocatalysis Effects 0.000 description 1
- 235000019353 potassium silicate Nutrition 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000000634 powder X-ray diffraction Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 229910001388 sodium aluminate Inorganic materials 0.000 description 1
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
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- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
- C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
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- C01—INORGANIC CHEMISTRY
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- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/12—Surface area
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/14—Pore volume
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- General Physics & Mathematics (AREA)
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Abstract
The invention discloses a preparation method of a beta molecular sieve. Step 1, synthesis of initial gel: mixing a silicon source, an aluminum source, an alkaline metal source and water, uniformly stirring, and synthesizing initial gel; silicon source of SiO2Calculated by Al as the aluminum source2O3Calculated as Na, the alkali metal source2Calculated by O, the molar ratio of the raw materials for synthesizing the initial gel is as follows: SiO 22/Al2O3＝30～150:1，Na2O/SiO2＝0.03～0.35:1，H2O/SiO23.0-50.0: 1; step 2, microwave treatment of the initial gel: adding beta molecular sieve seed crystal into the initial gel prepared in the step 1, wherein the seed crystal has a silicon-aluminum ratio of SiO2/Al2O320-100: 1, and the addition amount is SiO by mass23-25% of the mass, uniformly mixing, and then heating by microwave to prepare crystallized precursor gel; step 3, crystallization reaction: and (3) carrying out crystallization reaction on the crystallized precursor gel obtained in the step (2) by microwave heating, wherein the reaction temperature is 140-180 ℃, and the reaction time is 4-20 h, so as to obtain a beta molecular sieve product. The molecular sieve obtained by the method has smaller particle size, abundant pore structure and more smooth channels, and is beneficial to promoting the catalytic cracking and isomerization.
Description
Technical Field
The invention belongs to the technical field of catalytic chemistry, and particularly relates to a synthesis method of a beta molecular sieve.
Background
Beta molecular sieves were developed by Mobil oil company, usa in 1967 as the patent product USP 3308069. Earlier reports of superior catalytic performance of beta molecular sieves were made by Mobil corporation in subsequent patents EP0159846, EP0159847 which developed beta molecular sieves, disclosing that beta molecular sieves have excellent activity for cracking and isomerization of hydrocarbons. With the understanding of the crystal structure of the beta-zeolite, the research on the synthesis and catalytic performance of the beta-zeolite has been rapidly developed in the past 90 years, and the excellent catalytic performance of the beta-zeolite in numerous catalytic reactions of petroleum refining and petrochemical processes such as hydrogenation, cracking, isomerization, alkylation, olefin hydration, dewaxing, photocatalysis and the like is reported at document. As the high-silicon zeolite is the only high-silicon zeolite with a three-dimensional twelve-membered ring pore channel system in the world at present, the pore diameter is similar to that of a Y molecular sieve, the pore structure is more superior than that of a ZMS-5 molecular sieve, the advantages of Y and ZSM-5 are integrated, and the silica-alumina ratio can be adjusted in a very large range, so that the acid property and the stability of the high-silicon zeolite are controlled to a certain extent, thereby providing a prerequisite for the application of the high-silicon zeolite in a functionalized catalytic cracking catalyst.
The microwave is an electromagnetic wave with extremely short wavelength and extremely high frequency, the wavelength is 1mm-1m, the frequency is 300MHz-300GHz, and the microwave is positioned between infrared light and radio wave. The microwave frequency for heating is typically fixed at 2450MHz or 915 MHz. The basic principle of microwave heating is as follows: under the action of the external alternating electromagnetic field, polar molecules in the material are polarized and frequently turn to friction along with the change of the polarity of the external alternating electromagnetic field, so that electromagnetic energy is converted into heat energy. The microwave heating has the characteristics of high and uniform heating speed, high energy utilization rate, environmental protection and the like. Most notably, microwaves have shown the ability to influence reaction kinetics and selectivity in the synthesis of nanoporous materials.
The conventional hydrothermal synthesis of the beta molecular sieve generally uses an organic template, for example, under the condition of using tetraethylammonium hydroxide as the template, the synthesis time is generally more than 40 hours, the production time is longer, and the production efficiency is lower. Particularly, the production cost is very high due to the large consumption of the template agent, and the molecular sieve product needs to be roasted and subjected to template agent stripping treatment at the later stage, so that the structure of the product is damaged, and the removed template agent also seriously pollutes the environment. The molecular sieve synthesis technology without the template has important practical significance.
CN101249968 discloses a method for synthesizing beta zeolite without an organic template, which comprises the steps of mixing a silicon source, an aluminum source, a sodium source and water to prepare initial gel, adding beta molecular sieve seed crystals, and carrying out hydrothermal reaction to finally obtain a beta molecular sieve product. However, since no organic template agent is added into the system, the stability of the reaction system is difficult to maintain only by the structure-oriented action of the seed crystal, and as a result, the phase zone for synthesizing the beta molecular sieve is very narrow, the actual reaction condition is difficult to control, and the mixed crystals are easy to generate.
In conclusion, the conventional hydrothermal synthesis of the beta molecular sieve generally uses an organic template agent, the production time is long, particularly, the use amount of the template agent is large, so that the production cost is very high, the molecular sieve product needs to be treated by a roasting and stripping agent at the later stage, the product structure is damaged, and the removed template agent can seriously pollute the environment. At present, the technology of synthesizing the beta molecular sieve without additionally adding an organic template is disclosed, but the stability of a reaction system is difficult to maintain only by the structure guiding action of crystal seeds due to the adoption of a conventional hydrothermal synthesis mode, so that the phase region of the synthesized beta molecular sieve is very narrow, the actual reaction condition control difficulty is high, and mixed crystals are easy to generate.
Therefore, the synthesis of the beta molecular sieve without the template agent is a good research idea, but how to control the stability of a reaction system and relax the requirements of actual synthesis conditions has more important significance on subsequent actual production.
Disclosure of Invention
The invention mainly aims to provide a preparation method of a beta molecular sieve, and the beta molecular sieve obtained by the preparation method has smaller grain size, higher crystallinity and richer pore structure, and has more unobstructed pore channels.
In order to achieve the above object, the present invention provides a method for preparing a beta molecular sieve, comprising:
step 1, synthesis of initial gel: mixing a silicon source, an aluminum source, an alkaline metal source and water, uniformly stirring, and synthesizing initial gel; silicon source of SiO2Calculated by Al as the aluminum source2O3Calculated as Na, the alkali metal source2Calculated by O, the molar ratio of the raw materials for synthesizing the initial gel is as follows: SiO 22/Al2O3＝30～150:1，Na2O/SiO2＝0.03～0.35:1，H2O/SiO2＝3.0～50.0:1；
Step 2, microwave treatment of the initial gel: adding beta molecular sieve seed crystal into the initial gel prepared in the step 1, wherein the seed crystal has a silicon-aluminum ratio of SiO2/Al2O320-100: 1, and the addition amount is SiO by mass23-25% of the mass, uniformly mixing, and then heating by microwave at the temperature of 80-120 ℃ for 0.1-10 h to prepare crystallized precursor gel;
step 3, crystallization reaction: and (3) carrying out crystallization reaction on the crystallized precursor gel obtained in the step (2) by microwave heating, wherein the reaction temperature is 140-180 ℃, and the reaction time is 4-20 h, so as to obtain a beta molecular sieve product.
The preparation method of the beta molecular sieve, disclosed by the invention, comprises the following step of selecting a silicon source as a silicon source, wherein the silicon source is preferably one or more of the group consisting of coarse silica gel, white carbon black and silica sol.
In the preparation method of the beta molecular sieve, the aluminum source is preferably one or more selected from the group consisting of sodium metaaluminate, aluminum sulfate and pseudoboehmite.
In the method for preparing the beta molecular sieve, the alkali metal source is preferably sodium hydroxide.
The preparation method of the beta molecular sieve, provided by the invention, is characterized in that the silicon-aluminum ratio of the beta molecular sieve seed crystal is preferably SiO2/Al2O322-80 by massPreferably SiO25 to 20 percent of the mass.
The preparation method of the beta molecular sieve, provided by the invention, is characterized in that the beta molecular sieve seed crystal is more preferably SiO in a silicon-aluminum ratio2/Al2O3＝23.5:1。
The preparation method of the beta molecular sieve comprises the following step 2, wherein the heating temperature is preferably 100-120 ℃, and the heating time is preferably 4-6 h.
In the preparation method of the beta molecular sieve, in the step 3, the reaction temperature is preferably 140-170 ℃, and the reaction time is preferably 6-15 h.
The preparation method of the beta molecular sieve comprises the following steps of (1) dissolving an alkaline metal source in water, heating to 50-80 ℃, adding an aluminum source, stirring until the aluminum source is completely dissolved, finally adding a silicon source, and continuously and uniformly stirring to obtain the initial gel.
The preparation method of the beta molecular sieve comprises the steps of using SiO as a silicon source2Calculated by Al as the aluminum source2O3Calculated as Na, the alkali metal source2The molar ratio of the raw materials for synthesizing the initial gel is preferably: SiO 22/Al2O3＝30～95:1，Na2O/SiO2＝0.07～0.30:1，H2O/SiO2＝3.5～22:1。
The invention has the beneficial effects that:
the conventional hydro-thermal synthesis of the beta molecular sieve has the problems of long production time, large template agent dosage, higher system water content and low product yield. By adopting the method, the synthesis time of the beta molecular sieve is greatly shortened and the yield and the crystallinity of the beta molecular sieve are improved through the extremely high thermal efficiency of the microwave.
More importantly, the invention discovers that the microwave shows the property of influencing the reaction kinetics and the molecular sieve structure in the process of synthesizing the beta molecular sieve, and the molecular sieve obtained by the method has smaller grain diameter, rich pore structure and more unobstructed channels, thereby being beneficial to promoting the catalytic cracking and the isomerization.
In addition, the initial gel is heated by microwaves at a lower temperature, so that the beta molecular sieve seed crystals can be rapidly dispersed into beta molecular sieve microcrystals with higher structure induction performance under an alkaline condition, molecular sieve crystal nuclei are preliminarily generated, then the crystallization reaction is carried out by microwave heating at a higher temperature, the rapid growth of the crystals is realized, and the finally obtained beta molecular sieve has high crystallinity and rich pore structures.
Drawings
FIG. 1 is an XRD spectrum of a beta molecular sieve seed crystal;
FIG. 2 is a scanning electron micrograph of the synthetic material of example 1;
FIG. 3 is an XRD spectrum of the synthesized material in example 1
FIG. 4 is an XRD spectrum of the synthesized material of example 2;
FIG. 5 is an XRD spectrum of the as-synthesized material of example 3;
FIG. 6 is an XRD spectrum of the as-synthesized material of example 4;
FIG. 7 is an XRD spectrum of the as-synthesized material of example 5;
FIG. 8 is an XRD spectrum of the as-synthesized material of example 6;
FIG. 9 is an XRD spectrum of the as-synthesized material of example 8;
FIG. 10 is an XRD spectrum of the synthesized material of example 13;
FIG. 11 is an XRD spectrum of the synthetic material of comparative example 1;
FIG. 12 is an XRD spectrum of the synthetic material of comparative example 2;
FIG. 13 is a scanning electron micrograph of the synthetic material of comparative example 4;
FIG. 14 is an XRD spectrum of the synthetic material of comparative example 4;
figure 15 is an XRD spectrum of the standard.
Detailed Description
The following examples illustrate the invention in detail: the present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and process are given, but the scope of the present invention is not limited to the following embodiments, and any other known variations within the scope of the present invention should be included. The experimental methods in the following examples, which are not specified under specific conditions, are generally performed under conventional conditions.
The invention mainly aims to provide a preparation method of a beta molecular sieve, which is characterized in that an organic template agent is not additionally added, a synthesis system is more stable and controllable, a high-crystallinity beta molecular sieve product is easier to synthesize, the synthesis time can be further shortened, and the environmental pollution is reduced.
The invention provides a preparation method of a beta molecular sieve, which comprises the following steps:
(1) synthesis of the initial gel: mixing a silicon source, an aluminum source, an alkaline metal source and water, uniformly stirring, and synthesizing initial gel; silicon source of SiO2Calculated by Al as the aluminum source2O3Calculated as Na, the alkali metal source2Calculated by O, the molar ratio of the raw materials for synthesizing the initial gel is as follows: SiO 22/Al2O3＝30～150，Na2O/SiO2＝0.03～0.35，H2O/SiO23.0-50.0 percent; preferably: SiO 22/Al2O3＝30～95:1，Na2O/SiO2＝0.07～0.30:1，H2O/SiO2＝3.5～22:1；
(2) Microwave treatment of the initial gel: adding beta molecular sieve seed crystals into the initial gel prepared in the step (1), wherein the seed crystals have the silicon-aluminum ratio to SiO2/Al2O320-100 percent of SiO in the silicon source according to the mass23% -25% of the effective mass, uniformly mixing, and then heating by microwave at 80-120 ℃ for 0-10 h to prepare crystallized precursor gel;
(3) and (3) crystallization reaction: and (3) continuously carrying out microwave heating on the crystallized precursor gel obtained in the step (2) for crystallization reaction at the temperature of 140-180 ℃ for 4-20 h to obtain a beta molecular sieve product.
The silicon source can be coarse-pore silica gel, white carbon black or silica sol, and other common raw materials such as water glass and the like can also be selected. The aluminum source can be sodium metaaluminate, aluminum sulfate or pseudo-boehmite, and other common raw materials such as alumina and the like can also be selected. The alkali metal source may be sodium hydroxide. The water may be deionized water.
The preparation method of the initial gel comprises the steps of dissolving an alkaline metal source in water, heating to 50-80 ℃, adding an aluminum source, stirring until the alkaline metal source is completely dissolved, finally adding a silicon source into the solution, and continuously stirring until the initial gel is uniform. The material ratio of the initial gel, SiO2/Al2O3The aim can be selected in a larger range to synthesize products with different silicon-aluminum ratios; na (Na)2O/SiO2、H2O/SiO2The water content can be selected in a larger range, the viscosity degree of the gel can be regulated and controlled, and meanwhile, the addition amount of the alkaline metal source needs to be properly regulated to ensure that the pH value of the gel is basically stable.
The source of the beta molecular sieve seed crystal is not specially required, and the beta molecular sieve provided by the institute of petrochemical engineering can be selected as the seed crystal, and the silicon-aluminum ratio of the beta molecular sieve seed crystal is SiO2/Al2O3XRD is shown in figure 1 as 23.5. Or the beta molecular sieve of other sources can be selected as the seed crystal, and the silicon-aluminum ratio of the seed crystal is SiO2/Al2O320-100 percent of SiO in the silicon source23 to 25 percent of the mass. Preferred seeds have a silicon to aluminum ratio of SiO2/Al2O3The addition amount of the SiO in the silicon source is preferably 22-80 by mass25 to 20 percent of the mass. In the step of microwave treatment of the initial gel, the temperature of the microwave treatment is 80-120 ℃, and the heating time is 0.1-10 h, so as to prepare crystallized precursor gel; the optimal microwave treatment temperature is 100-120 ℃, and the heating time is 4-6 h. In the crystallization reaction step, the microwave heating temperature is 140-180 ℃, and the heating time is 4-20 h, so that a beta molecular sieve product is obtained; the preferable microwave heating temperature is 140-170 ℃, and the heating time is 6-15 h.
Although microwave has been used as a heating means for molecular sieve synthesis in the prior art, the microwave only has the effect of improving the heating efficiency and shortening the crystallization time. Experiments show that the microwave can influence the reaction kinetics in the synthesis process of the beta molecular sieve and the pore structure of the synthesized beta molecular sieve to a certain extent. In addition, a microwave method is adopted for crystallization, and the crystallization method has complementary relevance with the material ratio of the synthesized molecular sieve, for example, the water content of a synthesis system can influence reaction mass transfer and further influence the quality of a product due to too low water content; too high water content can cause too much microwave to be absorbed by the water medium, thereby affecting the effect of microwave on other materials and causing the failure of molecular sieve synthesis. Meanwhile, the microwave has the characteristics of concentrated instantaneous energy, difficultly controlled propagation path and limited penetrability, so that the difficulty of temperature control under microwave heating is higher. The synthesis phase area of the beta molecular sieve is wide, and the product selectivity is not influenced by temperature fluctuation, dynamic or static crystallization state, so the fitting degree of microwave heating and beta molecular sieve synthesis is good, and the difficulty of microwave heating synthesis can be greatly improved by other molecular sieves with narrow synthesis phase areas and strict requirements on crystallization temperature and crystallization state.
Furthermore, in the process of the research on the synthesis of the beta molecular sieve, the effect of directly performing microwave heating crystallization on the initial gel is not particularly ideal. The method treats the initial gel by microwave heating at a lower temperature, is favorable for quickly dispersing beta molecular sieve crystal seeds into beta molecular sieve microcrystals with higher structure induction performance under an alkaline condition, preliminarily generates molecular sieve crystal nuclei, and then carries out crystallization reaction by microwave heating at a higher temperature to realize quick growth of the crystals, and finally the obtained beta molecular sieve has high crystallinity and rich pore structure.
The raw materials used in the invention are:
silicon source: coarse silica gel, silica sol (solid content 30%), white carbon black;
an aluminum source: NaAlO2Sodium metaaluminate, Al2(SO4)2·18H2O (aluminum sulfate octadecahydrate);
seed crystal: beta molecular sieves, supplied by the institute of petrochemical engineering;
and others: deionized water, NaOH (sodium hydroxide).
Phase analysis method: the relative crystallinity of each sample is determined by the relative ratio of the characteristic diffraction peak areas by using a beta molecular sieve (a product of the commercially available Nankai catalyst factory beta molecular sieve) standard sample with known relative crystallinity as an external standard through phase analysis of the sample by adopting a powder X-ray diffraction (XRD) technology.
Phase analysis instrument: dutch Pasnake X-Pert Pro type X-ray powder diffractometer.
Phase analysis measurement conditions: and (3) CuK rays, wherein the tube voltage is 40kV, the tube current is 40mA, the scanning range of the measured crystalline phase is 5-40 degrees, and the scanning speed is 4 degrees/min.
Scanning electron microscope: field emission scanning electron microscope FEI NanoSEM 450.
BET analysis: mike 2460MP type full-automatic analyzer for specific surface area and porosity.
The technical solution of the present invention will be further illustrated by the following specific examples.
Example 1
In a vessel in a 70 ℃ water bath, 28.43g of deionized water and 0.42g of sodium hydroxide were added and dissolved with stirring. 1.65g of sodium metaaluminate is added, stirred and dissolved. 15.00g of coarse silica gel is added and stirred uniformly. Adding 1.80g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And (3) carrying out microwave treatment on the initial gel, controlling the temperature to be 120 ℃, and treating for 4 hours to obtain the crystallized precursor gel. Then carrying out microwave heating to carry out crystallization reaction, controlling the temperature to be 170 ℃ and the reaction time to be 10 h. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the crystallinity of the product is shown in Table 1. Scanning electron microscope and BET analysis were carried out, and the results are shown in Table 2.
Example 2
In a vessel in a 70 ℃ water bath, 28.43g of deionized water and 0.42g of sodium hydroxide were added and dissolved with stirring. 1.65g of sodium metaaluminate is added, stirred and dissolved. 15.00g of coarse silica gel is added and stirred uniformly. Adding 0.75g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And (3) carrying out microwave treatment on the initial gel, controlling the temperature to be 120 ℃, and treating for 4 hours to obtain the crystallized precursor gel. Then carrying out microwave heating to carry out crystallization reaction, controlling the temperature to be 170 ℃ and the reaction time to be 10 h. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the crystallinity of the product is shown in Table 1.
Example 3
In a vessel in a 70 ℃ water bath, 28.43g of deionized water and 0.42g of sodium hydroxide were added and dissolved with stirring. 1.65g of sodium metaaluminate is added, stirred and dissolved. 15.00g of coarse silica gel is added and stirred uniformly. Adding 3g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And (3) carrying out microwave treatment on the initial gel, controlling the temperature to be 120 ℃, and treating for 4 hours to obtain the crystallized precursor gel. Then carrying out microwave heating to carry out crystallization reaction, controlling the temperature to be 170 ℃ and the reaction time to be 10 h. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the crystallinity of the product is shown in Table 1.
Example 4
In a vessel in a 70 ℃ water bath, 28.43g of deionized water and 0.40g of sodium hydroxide were added and dissolved with stirring. 2.00g of sodium metaaluminate is added and stirred to dissolve. 15.00g of coarse silica gel is added and stirred uniformly. Adding 1.20g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And (3) carrying out microwave treatment on the initial gel, controlling the temperature to be 120 ℃, and treating for 4 hours to obtain the crystallized precursor gel. Then carrying out microwave heating to carry out crystallization reaction, controlling the temperature to be 170 ℃ and the reaction time to be 10 h. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the crystallinity of the product is shown in Table 1.
Example 5
In a vessel in a 70 ℃ water bath, 28.43g of deionized water and 0.54g of sodium hydroxide were added and dissolved with stirring. 0.86g of sodium metaaluminate is added, stirred and dissolved. 15.00g of coarse silica gel is added and stirred uniformly. Adding 3g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And (3) carrying out microwave treatment on the initial gel, controlling the temperature to be 120 ℃, and treating for 4 hours to obtain the crystallized precursor gel. Then carrying out microwave heating to carry out crystallization reaction, controlling the temperature to be 170 ℃ and the reaction time to be 10 h. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the crystallinity of the product is shown in Table 1.
Example 6
In a vessel in a 70 ℃ water bath, 28.43g of deionized water and 0.85g of sodium hydroxide were added and dissolved with stirring. 0.40g of sodium metaaluminate is added, stirred and dissolved. 15.00g of coarse silica gel is added and stirred uniformly. Adding 3.75g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And (3) carrying out microwave treatment on the initial gel, controlling the temperature to be 120 ℃, and treating for 4 hours to obtain the crystallized precursor gel. Then carrying out microwave heating to carry out crystallization reaction, controlling the temperature to be 170 ℃ and the reaction time to be 10 h. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the crystallinity of the product is shown in Table 1.
Example 7
In a vessel in a 70 ℃ water bath, 12.70g of deionized water and 0.44g of sodium hydroxide were added and dissolved with stirring. 1.84g of sodium metaaluminate is added and dissolved by stirring. 15.00g of coarse silica gel is added and stirred uniformly. Adding 1.80g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And (3) carrying out microwave treatment on the initial gel, controlling the temperature to be 120 ℃, and treating for 4 hours to obtain the crystallized precursor gel. Then carrying out microwave heating to carry out crystallization reaction, controlling the temperature to be 170 ℃ and the reaction time to be 10 h. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the crystallinity of the product is shown in Table 1.
Example 8
In a vessel of 70 ℃ water bath, 5g of silica sol, 17.50g of deionized water and 6.15g of sodium hydroxide were added and dissolved by stirring. 1.13g of aluminum sulfate was added and dissolved by stirring. 0.45g of beta molecular sieve seed crystal is added and stirred evenly to prepare initial gel. And (3) carrying out microwave treatment on the initial gel, controlling the temperature to be 120 ℃, and treating for 4 hours to obtain the crystallized precursor gel. Then carrying out microwave heating to carry out crystallization reaction, controlling the temperature to be 170 ℃ and the reaction time to be 20 h. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the crystallinity of the product is shown in Table 1.
Example 9
In a vessel in a 70 ℃ water bath, 28.43g of deionized water and 0.42g of sodium hydroxide were added and dissolved with stirring. 1.65g of sodium metaaluminate is added, stirred and dissolved. 15.00g of coarse silica gel is added and stirred uniformly. Adding 1.80g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And (3) carrying out microwave treatment on the initial gel, controlling the temperature to be 120 ℃, and treating for 10h to obtain the crystallized precursor gel. Then carrying out microwave heating to carry out crystallization reaction, controlling the temperature to be 170 ℃ and the reaction time to be 4 h. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the crystallinity of the product is shown in Table 1.
Example 10
In a vessel in a 70 ℃ water bath, 28.43g of deionized water and 0.42g of sodium hydroxide were added and dissolved with stirring. 1.65g of sodium metaaluminate is added, stirred and dissolved. 15.00g of coarse silica gel is added and stirred uniformly. Adding 1.80g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And (3) carrying out microwave treatment on the initial gel, controlling the temperature to be 120 ℃, and treating for 0.1h to obtain the crystallized precursor gel. Then carrying out microwave heating to carry out crystallization reaction, controlling the temperature to be 170 ℃ and the reaction time to be 20 h. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the crystallinity of the product is shown in Table 1.
Example 11
In a vessel in a 70 ℃ water bath, 28.43g of deionized water and 0.42g of sodium hydroxide were added and dissolved with stirring. 1.65g of sodium metaaluminate is added, stirred and dissolved. 15.00g of coarse silica gel is added and stirred uniformly. Adding 1.80g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And (3) carrying out microwave treatment on the initial gel, controlling the temperature to be 80 ℃, and treating for 10h to obtain the crystallized precursor gel. Then microwave heating is carried out to carry out crystallization reaction, the temperature is controlled at 160 ℃, and the reaction time is 20 hours. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the crystallinity of the product is shown in Table 1.
Example 12
In a vessel in a 70 ℃ water bath, 28.43g of deionized water and 0.42g of sodium hydroxide were added and dissolved with stirring. 1.65g of sodium metaaluminate is added, stirred and dissolved. 15.00g of coarse silica gel is added and stirred uniformly. Adding 1.80g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And (3) carrying out microwave treatment on the initial gel, controlling the temperature to be 120 ℃, and treating for 2h to obtain the crystallized precursor gel. Then carrying out microwave heating to carry out crystallization reaction, controlling the temperature to be 170 ℃ and the reaction time to be 10 h. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the crystallinity of the product is shown in Table 1.
Example 13
In a vessel in a 70 ℃ water bath, 28.43g of deionized water and 0.42g of sodium hydroxide were added and dissolved with stirring. 1.65g of sodium metaaluminate is added, stirred and dissolved. 15.00g of coarse silica gel is added and stirred uniformly. Adding 1.80g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And (3) carrying out microwave treatment on the initial gel, controlling the temperature to be 120 ℃, and treating for 6h to obtain the crystallized precursor gel. Then microwave heating is carried out to carry out crystallization reaction, the temperature is controlled at 140 ℃, and the reaction time is 20 hours. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the crystallinity of the product is shown in Table 1.
Example 14
In a vessel in a 70 ℃ water bath, 28.43g of deionized water and 0.42g of sodium hydroxide were added and dissolved with stirring. 1.65g of sodium metaaluminate is added, stirred and dissolved. 15.00g of coarse silica gel is added and stirred uniformly. Adding 1.80g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And (3) carrying out microwave treatment on the initial gel, controlling the temperature to be 80 ℃, and treating for 6 hours to obtain the crystallized precursor gel. Then carrying out microwave heating to carry out crystallization reaction, controlling the temperature at 180 ℃ and the reaction time to be 8 h. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the crystallinity of the product is shown in Table 1.
Example 15
In a vessel in a 70 ℃ water bath, 28.43g of deionized water and 0.42g of sodium hydroxide were added and dissolved with stirring. 1.65g of sodium metaaluminate is added, stirred and dissolved. 15.00g of coarse silica gel is added and stirred uniformly. Adding 1.80g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And (3) carrying out microwave treatment on the initial gel, controlling the temperature to be 100 ℃, and treating for 3h to obtain the crystallized precursor gel. Then microwave heating is carried out to carry out crystallization reaction, the temperature is controlled at 140 ℃, and the reaction time is 15 h. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the crystallinity of the product is shown in Table 1.
Comparative example 1
In a vessel in a 70 ℃ water bath, 28.43g of deionized water and 0.42g of sodium hydroxide were added and dissolved with stirring. 1.65g of sodium metaaluminate is added, stirred and dissolved. 15.00g of coarse silica gel is added and stirred uniformly. Adding 3.00g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And carrying out conventional hydrothermal synthesis on the initial gel, controlling the temperature to be 120 ℃, reacting for 4 hours, then controlling the temperature to be 170 ℃, and reacting for 10 hours. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the result shows that the product has more mordenite. Compared with the example 3, it can be seen that under the condition of the same material proportion, crystallization temperature and crystallization time, the microwave heating is more beneficial to the selectivity of the beta molecular sieve product and the improvement of the crystallinity of the molecular sieve.
Comparative example 2
In a vessel in a 70 ℃ water bath, 28.43g of deionized water and 0.42g of sodium hydroxide were added and dissolved with stirring. 1.65g of sodium metaaluminate is added, stirred and dissolved. 15.00g of coarse silica gel is added and stirred uniformly. Adding 1.80g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And carrying out conventional hydrothermal synthesis on the initial gel, controlling the temperature to be 120 ℃, reacting for 4 hours, then controlling the temperature to be 170 ℃, and reacting for 10 hours. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the result shows that the product contains a large amount of mordenite. Compared with example 1, it can be seen that under the condition of the same material ratio, crystallization temperature and crystallization time, microwave heating is more beneficial to selectivity of the beta molecular sieve product (especially when the addition amount of the directing agent-seed crystal of the system structure is less) and is also more beneficial to improvement of the crystallinity of the molecular sieve.
Comparative example 3
In a vessel in a 70 ℃ water bath, 28.43g of deionized water and 0.42g of sodium hydroxide were added and dissolved with stirring. 1.65g of sodium metaaluminate is added, stirred and dissolved. 15.00g of coarse silica gel is added and stirred uniformly. Adding 1.80g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And (3) directly carrying out microwave heating on the initial gel to carry out crystallization reaction, controlling the temperature to be 170 ℃ and the reaction time to be 10 h. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the result shows that the product is an amorphous product.
Under the condition of the template agent, the pre-crystallization stage is not very necessary, the beta molecular sieve can be synthesized, but under the condition of no template agent, the structure guiding function is exerted only by the seed crystal, the seed crystal is basically the beta molecular sieve with a more complete crystal structure, the structure guiding function of the seed crystal is not high, the seed crystal is further decomposed and dispersed in the pre-crystallization stage under the microwave heating, so that the structure guiding function is improved, and finally the beta molecular sieve with higher crystallinity can be obtained.
Comparative example 4
In a water bath at 70 ℃, 11.00g of deionized water is added, 13.00g of tetraethylammonium hydroxide solution is added, and the mixture is stirred uniformly. 0.31g of sodium hydroxide and 1.85g of sodium metaaluminate are added and stirred to dissolve. 15.00g of coarse silica gel is added and stirred uniformly. Adding 0.30g of beta molecular sieve seed crystal, and uniformly stirring to obtain initial gel. And carrying out conventional hydrothermal synthesis on the initial gel, controlling the temperature to be 160 ℃, and reacting for 40 h. And (3) after the reaction is finished, washing and drying the product, and performing X-ray diffraction characterization, wherein the result shows that the product is a beta molecular sieve product with higher crystallinity. Scanning electron microscope and BET analysis were carried out, and the results are shown in Table 2. As can be seen, the average crystal grain size of the beta molecular sieve synthesized by the conventional hydrothermal method is 500nm, which is far larger than 50nm of that synthesized by microwave, and the specific surface area and pore volume of micropores are both smaller than those synthesized by microwave.
Table 1 shows the calculation results of relative crystallinity of the examples and comparative examples
Table 2 shows the results of the crystal grain size comparison and BET analysis of example 1 and comparative example 4
The invention relates to a technology for synthesizing a molecular sieve without adding a template agent, wherein crystal seeds have a certain structure guiding function, but the molecular sieve is synthesized by completely replacing the template agent with the crystal seeds, so that the method has higher difficulty, particularly, mixed crystals are easy to generate, and the product has poorer crystallinity. The invention aims to improve the guiding effect of the seed crystal structure after microwave heating treatment and realize the purposes of no mixed crystal and higher crystallinity of the product. The standard sample used for calculating the relative crystallinity has higher crystallinity, but the sample is synthesized by adding an organic template agent, so the production cost is high. Although the relative crystallinity of the result obtained by some embodiments of the invention is slightly lower than that of the standard sample, the synthesis cost per se is far lower than that of the standard sample, and therefore, the result still has certain application value.
The present invention is capable of other embodiments, and various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A preparation method of a beta molecular sieve is characterized by comprising the following steps:
step 1, synthesis of initial gel: mixing a silicon source, an aluminum source, an alkaline metal source and water, uniformly stirring, and synthesizing initial gel; silicon source of SiO2Calculated by Al as the aluminum source2O3Calculated as Na, the alkali metal source2Calculated by O, the molar ratio of the raw materials for synthesizing the initial gel is as follows: SiO 22/Al2O3＝30～150:1，Na2O/SiO2＝0.03～0.35:1，H2O/SiO2＝3.0～50.0:1；
Step 2, microwave treatment of the initial gel: adding beta molecular sieve seed crystal into the initial gel prepared in the step 1, wherein the seed crystal has a silicon-aluminum ratio of SiO2/Al2O320-100: 1, and the addition amount is SiO by mass23-25% of the mass, uniformly mixing, and then heating by microwave at the temperature of 80-120 ℃ for 0.1-10 h to prepare crystallized precursor gel;
step 3, crystallization reaction: and (3) carrying out crystallization reaction on the crystallized precursor gel obtained in the step (2) by microwave heating, wherein the reaction temperature is 140-180 ℃, and the reaction time is 4-20 h, so as to obtain a beta molecular sieve product.
2. The method for preparing beta-molecular sieve according to claim 1, wherein the silicon source is one or more selected from the group consisting of coarse silica gel, silica white and silica sol.
3. The method for preparing beta molecular sieve according to claim 1, wherein the aluminum source is one or more selected from the group consisting of sodium metaaluminate, aluminum sulfate and pseudo-boehmite.
4. The method of claim 1, wherein the source of the alkaline metal is sodium hydroxide.
5. The method for preparing the beta molecular sieve of claim 1, wherein the beta molecular sieve seed crystal has a silica-alumina ratio of SiO2/Al2O322-80 parts by mass of SiO25 to 20 percent of the mass.
6. The method for preparing the beta molecular sieve of claim 5, wherein the beta molecular sieve seed crystal has a silica-alumina ratio of SiO2/Al2O3＝23.5:1。
7. The preparation method of the beta molecular sieve according to claim 1, wherein the heating temperature in the step 2 is 100-120 ℃ and the heating time is 4-6 h.
8. The preparation method of the beta molecular sieve of claim 1, wherein in the step 3, the reaction temperature is 140-170 ℃ and the reaction time is 6-15 h.
9. The method for preparing the beta molecular sieve according to claim 1, wherein the initial gel in the step 1 is prepared by dissolving an alkali metal source in water, heating to 50-80 ℃, adding an aluminum source, stirring until the aluminum source is completely dissolved, finally adding a silicon source, and continuously and uniformly stirring to obtain the initial gel.
10. Root of herbaceous plantThe method of claim 1, wherein the silicon source is SiO2Calculated by Al as the aluminum source2O3Calculated as Na, the alkali metal source2Calculated by O, the molar ratio of the raw materials for synthesizing the initial gel is as follows: SiO 22/Al2O3＝30～95:1，Na2O/SiO2＝0.07～0.30:1，H2O/SiO2＝3.5～22:1。
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