CN116161674B - Hydrothermal preparation method of nano Ti-Beta molecular sieve - Google Patents
Hydrothermal preparation method of nano Ti-Beta molecular sieve Download PDFInfo
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- 239000002808 molecular sieve Substances 0.000 title claims abstract description 61
- 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 61
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- 238000000034 method Methods 0.000 claims abstract description 32
- 239000010936 titanium Substances 0.000 claims abstract description 31
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 27
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 27
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 39
- 239000000843 powder Substances 0.000 claims description 24
- 229910001868 water Inorganic materials 0.000 claims description 23
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 21
- 229910052710 silicon Inorganic materials 0.000 claims description 21
- 239000010703 silicon Substances 0.000 claims description 21
- 239000007788 liquid Substances 0.000 claims description 15
- 239000008367 deionised water Substances 0.000 claims description 13
- 229910021641 deionized water Inorganic materials 0.000 claims description 13
- 239000000443 aerosol Substances 0.000 claims description 11
- 239000013078 crystal Substances 0.000 claims description 11
- 239000007787 solid Substances 0.000 claims description 11
- UGACIEPFGXRWCH-UHFFFAOYSA-N [Si].[Ti] Chemical compound [Si].[Ti] UGACIEPFGXRWCH-UHFFFAOYSA-N 0.000 claims description 10
- 238000001354 calcination Methods 0.000 claims description 10
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 9
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 8
- 239000012686 silicon precursor Substances 0.000 claims description 8
- 238000001704 evaporation Methods 0.000 claims description 7
- 229940073455 tetraethylammonium hydroxide Drugs 0.000 claims description 7
- LRGJRHZIDJQFCL-UHFFFAOYSA-M tetraethylazanium;hydroxide Chemical compound [OH-].CC[N+](CC)(CC)CC LRGJRHZIDJQFCL-UHFFFAOYSA-M 0.000 claims description 7
- 238000005406 washing Methods 0.000 claims description 7
- 238000003756 stirring Methods 0.000 claims description 6
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical group CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 5
- 238000002156 mixing Methods 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- 229910010413 TiO 2 Inorganic materials 0.000 claims description 3
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims description 3
- 239000002243 precursor Substances 0.000 abstract description 16
- 238000001027 hydrothermal synthesis Methods 0.000 abstract description 12
- 230000015572 biosynthetic process Effects 0.000 abstract description 10
- 239000003795 chemical substances by application Substances 0.000 abstract description 10
- 238000003786 synthesis reaction Methods 0.000 abstract description 9
- 238000001308 synthesis method Methods 0.000 abstract description 8
- 230000002194 synthesizing effect Effects 0.000 abstract description 7
- 238000009826 distribution Methods 0.000 abstract description 5
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 abstract description 2
- 238000003912 environmental pollution Methods 0.000 abstract description 2
- 238000005265 energy consumption Methods 0.000 abstract 1
- 238000002425 crystallisation Methods 0.000 description 24
- 230000008025 crystallization Effects 0.000 description 24
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 19
- 229910052681 coesite Inorganic materials 0.000 description 10
- 229910052906 cristobalite Inorganic materials 0.000 description 10
- 239000000377 silicon dioxide Substances 0.000 description 10
- 229910052682 stishovite Inorganic materials 0.000 description 10
- 229910052905 tridymite Inorganic materials 0.000 description 10
- 235000012239 silicon dioxide Nutrition 0.000 description 9
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 8
- 229910052782 aluminium Inorganic materials 0.000 description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 8
- 239000000047 product Substances 0.000 description 6
- 239000002253 acid Substances 0.000 description 4
- 239000002699 waste material Substances 0.000 description 4
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 3
- 238000012512 characterization method Methods 0.000 description 3
- 229910052731 fluorine Inorganic materials 0.000 description 3
- 239000011737 fluorine Substances 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- 239000011734 sodium Substances 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- 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 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 2
- 239000012153 distilled water Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000003292 glue Substances 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 239000004005 microsphere Substances 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000002371 ultraviolet--visible spectrum Methods 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 229910021536 Zeolite Inorganic materials 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000006735 epoxidation reaction Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000000634 powder X-ray diffraction Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000001694 spray drying Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
- 231100000419 toxicity Toxicity 0.000 description 1
- 239000010457 zeolite Substances 0.000 description 1
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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
- C01B39/06—Preparation of isomorphous zeolites characterised by measures to replace the aluminium or silicon atoms in the lattice framework by atoms of other elements, i.e. by direct or secondary synthesis
- C01B39/08—Preparation of isomorphous zeolites characterised by measures to replace the aluminium or silicon atoms in the lattice framework by atoms of other elements, i.e. by direct or secondary synthesis the aluminium atoms being wholly replaced
- C01B39/085—Group IVB- metallosilicates
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- 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
- 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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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
- C01P2002/84—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by UV- or VIS- data
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- C—CHEMISTRY; METALLURGY
- 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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- General Life Sciences & Earth Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Nanotechnology (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Crystallography & Structural Chemistry (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Inorganic Chemistry (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Silicates, Zeolites, And Molecular Sieves (AREA)
Abstract
The invention discloses a hydrothermal preparation method of a nano Ti-Beta molecular sieve. The method provided by the invention is used for directly and rapidly synthesizing the Ti-Beta molecular sieve with excellent performance through one-step hydrothermal reaction by preparing the precursor, and compared with the traditional method for directly synthesizing the Ti-Beta molecular sieve, the method is small in template agent consumption, short in synthesis time, free of fluoride addition, and capable of effectively reducing energy consumption and environmental pollution. In addition, the obtained Ti-Beta molecular sieve has good titanium distribution. The synthesis method provided by the invention is quick and simple, has strong repeatability, and has obvious technical advancement compared with the existing method.
Description
Technical Field
The invention relates to a novel method for preparing a Ti-Beta molecular sieve, in particular to a Ti-Beta molecular sieve with excellent performance, which is directly and rapidly synthesized by one-step hydrothermal method through preparing a precursor.
Background
Ti-Beta is a molecular sieve with a twelve-membered ring straight-through channel structure with a pore diameter of 0.77x0.67nm, and has wide application prospect in the fields of epoxidation, alcohol selective oxidation, oxidative desulfurization and the like due to the characteristics of large silicon-aluminum ratio range, large pore channel, rich acid sites, good stability and the like. The preparation method of Ti-Beta molecular sieve mainly comprises hydrothermal synthesis method, gel synthesis method and post synthesis method.
Blasco T et al hydrothermally synthesized Ti-Beta molecular sieves under seeded (chem. Commun,1996,20,2367-368.) and non-seeded (J. Phys. Chem. B,1998,102 (1): 75-88), respectively: adding a silicon source, a titanium source, deionized water, a template agent and the like into a crystallization system, and crystallizing for a certain time at a certain temperature to obtain a final product. In the hydrothermal synthesis of Ti-Beta, the crystallization system can be roughly classified into a fluorine-containing system and a hydroxyl system (high pH). The neutral environment crystallization using fluorine-containing compound as mineralizer does not need seed crystal guiding and does not need adding of aluminum-containing substance. However, the synthesized molecular sieve has larger crystal grains, and the toxicity of the mineralizer can cause great burden to the environment. The hydrothermal synthesis under the strong alkaline condition of the hydroxyl system takes at least one of the seed crystal and the aluminum-containing substance, and aluminum can introduce acid site B to affect the catalytic performance. In addition, the traditional hydrothermal method has the defects of large template dosage, large crystallization waste liquid discharge amount, long crystallization time and the like, and needs to be further improved.
Camblor M A et al (analysis. A, general,1995,133 (2): L185-L189) use a "wet" gel to prepare Ti-Beta molecular sieves: firstly preparing TiO 2-SiO2 gel, then soaking by using a template guiding agent, and finally crystallizing to synthesize the Ti-Beta molecular sieve. The crystallization process of the method also needs the addition of aluminum or aluminum-containing seed crystal, still discharges a large amount of waste liquid, and needs more than one week of crystallization time. Jappar N et al (Journal of catalysis,1998,180 (2): 132-141.) A dry gel process was used for the first time to prepare Ti-Beta molecular sieves. The gel powder is not in direct contact with water, but is transferred into a special crystallization kettle, and the Ti-Beta molecular sieve is synthesized by utilizing the auxiliary action of water vapor. The dry gel method needs not only aluminum but also a small amount of sodium, and the sodium content can influence the crystallinity of the molecular sieve and the doping amount of Ti. Although the template agent dosage and the waste liquid yield of the dry glue method are less than those of the hydrothermal method, the synthetic grain size is larger (micron level), the repeatability is poor, and the dry glue method has no industrial application. .
The post synthesis method is to synthesize the Ti-Beta molecular sieve by dealuminating Beta zeolite and doping titanium in two steps, and is prepared by gas-solid, solid-solid and liquid-solid isomorphous substitution modes at present. The post synthesis method has short synthesis time generally, and the Ti-Beta molecular sieve can be prepared basically within 1-2 days.
The difficulty of doping Ti into the zeolite skeleton of Beta is far higher than that of TS-1, so the crystallization of Ti-Beta and the doping amount of skeleton titanium are two key problems faced by industrial production. The crystallization time of the hydrothermal method and the gel method is 7-14 days, and the doping amount of the framework titanium is limited. The post synthesis method has the advantages of short time and high titanium doping amount, but no matter which post synthesis method is adopted, the coordination state of titanium is difficult to control, and a large amount of non-framework titanium and anatase exist; in addition, the defective sites cannot be fully occupied, resulting in the formation of B acid, affecting catalytic performance.
Therefore, the novel Ti-Beta preparation method can be researched aiming at the defects of the prior art, and has important practical significance.
Disclosure of Invention
The invention aims to provide the preparation method for hydrothermally synthesizing the nano Ti-Beta molecular sieve, which has the advantages of simple steps, short time consumption, no need of adding fluoride and aluminum source, and good titanium species distribution.
A hydrothermal preparation method of a nano Ti-Beta molecular sieve, which comprises the following steps:
(1) Silicon source is calculated as SiO 2, titanium source is calculated as TiO 2, and the silicon source is calculated as SiO 2：TiO2：H2 O: hcl=1: 0.01 to 0.05: 20-80: mixing the mixture fully according to the molar ratio of 0.033-0.135, and stirring the mixture for 20min at room temperature; then using an aerosol generator to spray-dry the solution at 220 ℃ to obtain titanium-silicon precursor powder;
(2) Roasting the titanium silicon precursor powder at 550 ℃ for 3-6 hours to obtain solid powder; adding template tetraethylammonium hydroxide, then adding Beta molecular sieve seed crystal accounting for 2-5% of the mass of the silicon source, evaporating water and concentrating the mixed liquid in a water bath kettle at 60-80 ℃ to obtain a molar ratio of SiO 2：TiO2：H2 O: teaoh=1: 0.01 to 0.05: 3-10: 0.2 to 0.55;
(3) Transferring the obtained turbid liquid into an autoclave, crystallizing for 3-7 d at 130-150 ℃, washing with deionized water, drying, and calcining to obtain the Ti-Beta molecular sieve.
In the step 1, the silicon source is tetraethyl orthosilicate or silica sol. The titanium source used was tetra-n-butyl titanate.
In the step3, the drying temperature is 110 ℃, the roasting temperature is 550 ℃, and the roasting time is 6 hours.
The invention has the beneficial effects that:
Compared with the existing Ti-Beta molecular sieve preparation technology, the method has the following remarkable advantages:
a. The preparation method of the special precursor comprises the following steps: the silicon source and the titanium source are hydrolyzed under the acidic condition, and the titanium-silicon microsphere precursor is prepared by combining aerosol spray drying and high-temperature roasting, so that the coordination state of titanium species is effectively regulated and controlled before crystallization, and the primary problem of Ti-Beta molecular sieve synthesis is solved; the titanium-silicon microsphere precursor is dissolved by a template agent, and the proper proportion is the key point of synthesis. In addition, in the step 2, the concentration of the commercially available tetraethylammonium hydroxide is 25% -35%, and the proportioning requirement of the method cannot be met, so that additional evaporation water is needed; the industrialization can adopt more than ninety percent of template agent, the reasonable proportion can be found by the method, the step of evaporating water and concentrating is omitted, and the synthesis path can be further simplified. The aerosol precursor is roasted at high temperature to reduce the amount of synthetic water, eliminate the influence of acid in the precursor and optimize the distribution of titanium.
B. The Ti-Beta molecular sieve is hydrothermally synthesized by the method, no additional treatment is needed for a titanium source silicon source, the synthesis process is simple and convenient, no harsh requirements are imposed on conditions in each link, and the repeatability is very strong. In addition, the crystallization time of the method is obviously shorter than that of the traditional hydrothermal method.
C. The synthesis method does not additionally add fluorine source, aluminum source and alkali metal (Na), and reduces resource waste and environmental pollution to the maximum extent.
Drawings
FIGS. 1 and 3 show XRD characterization results of the synthesized Ti-Beta molecular sieves of the invention in the examples.
FIG. 2 is a UV-vis diagram of a regulatory contrast of Ti-Beta molecular sieve titanium species synthesized in accordance with the present invention.
FIG. 4 is an SEM image of a synthesized Ti-Beta molecular sieve of the present invention.
Detailed Description
The present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.
The crystallization process in the following examples is a crystallization process known in the art, and the crystallization process is a static crystallization process.
The washing, drying, and calcination methods described in the examples below are well known to those skilled in the art. For example, deionized water is used to wash to neutral pH and the mixture is dried at 110℃for 3 to 10 hours.
In the following examples, the molar mass of the silicon source was calculated as SiO 2, the molar mass of the titanium source was calculated as TiO 2, the molar mass of the template was calculated as TEA +, and the mass of the silicon source was calculated as SiO 2 contained.
Example 1
The embodiment is used for explaining a preparation method of the nano Ti-Beta molecular sieve.
Titanium source, silicon source (tetraethyl orthosilicate), deionized water and hydrochloric acid are mixed according to SiO2: tiO2: H2O: hcl=1: 0.016:20: mixing the components in a molar ratio of 0.135, and stirring the components at room temperature for 20min; then using an aerosol generator to spray-dry the solution at 220 ℃ to obtain titanium-silicon precursor powder; roasting the precursor powder at 550 ℃ for 6 hours to obtain solid powder, adding the solid powder into 11.61g of tetraethylammonium hydroxide, then adding Beta molecular sieve seed crystals which are 5% of the mass of a silicon source, evaporating water and concentrating the mixed liquid in a water bath kettle at 70 ℃ to obtain a molar ratio of SiO2: tiO2: H2O: teaoh=1: 0.016:3.4:0.55; and finally, transferring the obtained turbid liquid into an autoclave, crystallizing for 5 days at 140 ℃, washing with deionized water, drying, and calcining to obtain the Ti-Beta molecular sieve, wherein the product is named as sample 1. The XRD spectrum is shown in figure 1; the UV-vis spectrum is shown as 'regulated' in figure 2, namely the prepared aerosol powder is roasted at high temperature; the SEM is shown in fig. 3.
Example 2
Comparative example 1 of this example: for further explaining the regulation of the coordination state of the titanium species
Titanium source, silicon source, deionized water and hydrochloric acid are mixed according to SiO2: tiO2: H2O: hcl=1: 0.016:20: mixing the components in a molar ratio of 0.135, and stirring the components at room temperature for 20min; then using an aerosol generator to spray-dry the solution at 220 ℃ to obtain titanium-silicon precursor powder; directly adding the obtained precursor powder into 11.61g of tetraethylammonium hydroxide without treatment, then adding Beta molecular sieve seed crystal which is equivalent to 5% of the mass of a silicon source, evaporating water and concentrating the mixed liquid in a water bath kettle at 70 ℃ to obtain a molar ratio of SiO2: tiO2: H2O: teaoh=1: 0.016:3.4:0.55; and finally, transferring the obtained turbid liquid into an autoclave, crystallizing for 5 days at 140 ℃, washing with deionized water, drying, and calcining to obtain the Ti-Beta molecular sieve. The UV-vis spectrum is shown as "before regulation" in figure 2, i.e. the prepared aerosol powder is directly fed for crystallization without roasting treatment.
Example 3
Comparative example 1 of this example: for further verifying the uniqueness of the invention
Titanium source, silicon source (tetraethyl orthosilicate), deionized water and hydrochloric acid are mixed according to SiO2: tiO2: H2O: hcl=1: 0.016:20: mixing the components in a molar ratio of 0.135, and stirring the components at room temperature for 20min; then using an aerosol generator to spray-dry the solution at 220 ℃ to obtain titanium-silicon precursor powder; roasting the precursor powder at 550 ℃ for 6 hours to obtain solid powder, adding the solid powder into 11.61g of tetraethylammonium hydroxide, then adding Beta molecular sieve seed crystals which are 5% of the mass of a silicon source, and uniformly stirring the mixed liquid at room temperature; and finally, transferring the obtained turbid liquid into an autoclave, crystallizing for 5 days at 140 ℃, washing with deionized water, drying, and calcining to obtain the Ti-Beta molecular sieve, namely, the precursor template agent is not concentrated, the product is marked as 'sample 2', and the XRD spectrum of the product is shown in figure 1. By X-ray powder diffraction characterization, the relative crystallinity of sample 1 was taken as a reference, and sample 2 was only 46%, in addition, since Beta seed crystals were added in the synthesis route, only very little or no Ti-Beta molecular sieve synthesis was judged in combination with the yield obtained.
As can be seen from the mutual evidence of examples 1,2 and 3, the Ti-Beta molecular sieve prepared by the invention has the following distinct characteristics: the pure calcination by means of aerosol technology will deteriorate the distribution of titanium species, while the lack of concentration of the template agent will directly result in the inability to synthesize Ti-Beta molecular sieves. Each process of precursor preparation is complementary, and is indispensable.
Example 4
This example is illustrative of the method for synthesizing Ti-Beta molecular sieves using different amounts of templating agent
Example 1 was repeated, but in the final distilled water concentration step a molar ratio of SiO2 was reached: tiO2: H2O: teaoh=1: 0.016:4.5:0.2/0.3/0.4. The obtained products were designated as "sample 3", "sample 4", "sample 5", and the XRD spectra thereof are shown in FIG. 3. The relative crystallinity of samples 3-5 reached 70%, 90% and 115%, respectively, using the crystallinity of sample 1 as a reference. Therefore, the template agent dosage of the invention can reach the best when 0.4 and is less than that of the traditional hydrothermal method (0.55).
Example 5
The example is used for explaining that the method can synthesize the Ti-Beta molecular sieve through different crystallization time lengths.
Example 1 was repeated, but at 140℃for the final crystallization period, 3d, 4d, 6d, 7d were used. The obtained products were designated as "sample 6", "sample 7", "sample 8" and "sample 9", and the XRD spectra thereof are shown in FIG. 3. The relative crystallinity of samples 6-9 reached 80%, 89%, 114%, 102% respectively, using the crystallinity of sample 1 as a reference. The invention can reach the best crystallization state in 6 days of crystallization, but the relative crystallinity in 3 days of crystallization reaches 80 percent, and the crystallization time required for synthesizing the Ti-Beta molecular sieve by using the invention is far shorter than that of directly synthesizing the Ti-Beta molecular sieve by the traditional hydrothermal method.
Example 5
This example is intended to illustrate that different simultaneous long calcination of the spray powder precursors can be used to synthesize the Ti-Beta molecular sieves.
Example 1 was repeated, but the powder-sprayed precursors were calcined at 550℃for 3h, 4h, 5h. The characterization result of the obtained sample is not different from that of the example 1, and the calcining time is not greatly influenced in the preparation of the Ti-Beta molecular sieve.
Example 6
This example is intended to illustrate that Ti-Beta molecular sieves can be prepared with varying Ti content.
Example 1 was repeated, but the titanium source, silicon source (tetraethyl orthosilicate), deionized water, hydrochloric acid were prepared according to SiO2: tiO2: H2O: hcl=1: 0.05/0.025/0.0125/0.01:20: a molar ratio of 0.135 was thoroughly mixed; similarly, the molar ratio achieved in the final distilled water concentration step is SiO2: tiO2: H2O: teaoh=1: 0.05/0.025/0.0125/0.01:4.5:0.55, successfully preparing Ti-Beta molecular sieves with different Ti contents. It can be seen that Ti-Beta molecular sieves of different titanium loadings can be prepared as desired using the present invention.
Example 7
This example is intended to illustrate that Ti-Beta molecular sieves can be prepared with some changes or modifications without departing from the scope of the invention. The Ti-Beta molecular sieve is prepared by replacing a silicon source and adding no seed crystal.
After 0.386g of tetra-n-butyl titanate, 2.5g of deionized water and 1.0g of hydrogen peroxide (31 wt%) are stirred for 1h at room temperature to ensure that the solution is uniformly mixed without generating precipitate, 7.1g of silica sol is added and stirred for 1.5h until the solution is uniformly clarified; then using an aerosol generator to spray-dry the solution at 220 ℃ to obtain titanium-silicon precursor powder; roasting the precursor powder at 550 ℃ for 6 hours to obtain solid powder, adding the solid powder into 11.61g of tetraethylammonium hydroxide, and evaporating water and concentrating the mixed liquid in a water bath kettle at 70 ℃ to obtain a molar ratio of SiO2: tiO2: H2O: teaoh=1: 0.016:3.4:0.55; and finally, transferring the obtained turbid liquid into an autoclave, crystallizing for 5 days at 140 ℃, washing with deionized water, drying, and calcining to obtain the Ti-Beta molecular sieve. The product was designated as "sample 10" and its XRD spectrum is shown in FIG. 3.
The data obtained above shows that the method for directly synthesizing the Ti-Beta molecular sieve by the special precursor through hydrothermal reaction provided by the invention has the advantages of obtaining the nano Ti-Beta molecular sieve with higher crystallinity and good titanium species distribution state by using less crystallization time and has strong repeatability. By combining the analysis, the method provided by the invention has the characteristic of realizing large-scale industrialization of the Ti-Beta molecular sieve, greatly reduces the synthesis cost and the environmental load, and greatly improves the application field of the Ti-Beta molecular sieve.
Claims (4)
1. The hydrothermal preparation method of the nano Ti-Beta molecular sieve is characterized by comprising the following steps of:
(1) Silicon source is calculated as SiO 2, titanium source is calculated as TiO 2, and the silicon source is calculated as SiO 2：TiO2：H2 O: hcl=1: 0.01 to 0.05: 20-80: mixing the mixture fully according to the molar ratio of 0.033-0.135, and stirring the mixture for 20min at room temperature; then using an aerosol generator to spray-dry the solution at 220 ℃ to obtain titanium-silicon precursor powder;
(2) Roasting the titanium silicon precursor powder at 550 ℃ for 3-6 hours to obtain solid powder; adding template tetraethylammonium hydroxide, then adding Beta molecular sieve seed crystal accounting for 2-5% of the mass of the silicon source, evaporating water and concentrating the mixed liquid in a water bath kettle at 60-80 ℃ to obtain a molar ratio of SiO 2：TiO2：H2 O: teaoh=1: 0.01 to 0.05: 3-10: 0.2 to 0.55;
(3) Transferring the obtained turbid liquid into an autoclave, crystallizing for 3-7 d at 130-150 ℃, washing with deionized water, drying, and calcining to obtain the Ti-Beta molecular sieve.
2. The method for preparing nano Ti-Beta molecular sieve according to claim 1, wherein in the step 1, the silicon source is tetraethyl orthosilicate or silica sol.
3. The method for preparing nano Ti-Beta molecular sieve according to claim 1, wherein the titanium source is tetra-n-butyl titanate.
4. The method for preparing nano Ti-Beta molecular sieve according to claim 1, wherein in the step 3, the drying temperature is 110 ℃, the roasting temperature is 550 ℃, and the roasting time is 6 hours.
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