CN116081635A - Lamellar TS-1 molecular sieve and preparation method and application thereof - Google Patents

Lamellar TS-1 molecular sieve and preparation method and application thereof Download PDF

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CN116081635A
CN116081635A CN202310028814.5A CN202310028814A CN116081635A CN 116081635 A CN116081635 A CN 116081635A CN 202310028814 A CN202310028814 A CN 202310028814A CN 116081635 A CN116081635 A CN 116081635A
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molecular sieve
mixed solution
flaky
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liquid
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任申勇
陈尧
张敏
申宝剑
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China University of Petroleum Beijing
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    • C—CHEMISTRY; METALLURGY
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    • 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
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/89—Silicates, aluminosilicates or borosilicates of titanium, zirconium or hafnium
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D301/00—Preparation of oxiranes
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    • C07D301/03—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds
    • C07D301/12—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with hydrogen peroxide or inorganic peroxides or peracids
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    • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
    • B01J2229/10—After treatment, characterised by the effect to be obtained
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Abstract

The invention relates to the technical field of catalysts, and discloses a flaky TS-1 molecular sieve, a preparation method and application thereof. The flaky TS-1 molecular sieve has an MFI topological structure, the b axis is shorter than the a axis and the c axis, and the thickness of the flaky TS-1 molecular sieve is 50nm-100nm. Because the size of the flaky TS-1 molecular sieve in the b-axis direction is smaller, the diffusion path of the product in zeolite is shortened to a certain extent, the steric hindrance of the zeolite is weakened, and the zeolite has excellent catalytic activity. Meanwhile, when the flaky TS-1 molecular sieve prepared by the preparation method disclosed by the invention is used for catalyzing high-carbon alpha-olefin, the flaky TS-1 molecular sieve has excellent catalytic activity and high selectivity to alkylene oxide.

Description

Lamellar TS-1 molecular sieve and preparation method and application thereof
Technical Field
The invention relates to the technical field of catalysts, in particular to a flaky TS-1 molecular sieve and a preparation method and application thereof.
Background
The epoxy compound is a very critical organic synthesis intermediate and is widely applied to organic synthesis and fineThe fields of various chemical industry production such as fine chemical industry and the like. The epoxy compound is easy to generate ring-opening reaction under various conditions, can react with various functional groups such as amine, alcohol and the like to generate fine chemical products and intermediates with high added value, is a chemical raw material with wide application and extremely important, and is widely applied to various chemical and chemical production fields such as organic synthesis, fine chemical industry and the like. The traditional production process such as chlorohydrin method, co-oxidation method and the like has the problems of environmental pollution, equipment corrosion or large construction investment. In recent years, H is 2 O 2 The titanium-silicon molecular sieve TS-1 is taken as an oxidant, and the production process of the catalyst is emphasized by the characteristics of environmental friendliness and simple flow, and the key of the process is to improve the performance of the catalyst TS-1 molecular sieve.
The TS-1 molecular sieve is a typical MFI structure molecular sieve, and two pore structures exist in the molecular sieve, namely a Z-shaped cross-ring pore canal parallel to the a-axis direction and a cross-ring straight channel parallel to the b-axis direction. The diameter of the straight channel is larger, the mass transfer of the macromolecule in the interior is smoother, and the mass transfer in the Z-shaped pore canal is relatively difficult. Therefore, the thickness in the direction of the b axis is shortened, the diffusion path of the product in the zeolite can be shortened to a certain extent, the steric hindrance of the zeolite is weakened, and the adsorption and catalytic performance of the TS-1 molecular sieve are effectively improved.
The growth of the b-axis can be inhibited by adding a template agent or a mineralizer into the synthesis system, so that the MFI-type zeolite with relatively thin thickness is obtained. Choi et al (Nature. 20099,461 (7261): 246-249) are modified from C by addition of 22 Long carbon chain alkyl and two C 6 The surfactant composed of quaternary ammonium salt groups with alkyl intervals is used for successfully synthesizing the 2nm thick ultrathin platy MFI-type zeolite. Ji et al (Applied Catalysis A: general.2017, 533:90-98) synthesized ultra-thin nano-layered molecular sieves with the aid of ethanol by adding a surfactant of a bisquaternary ammonium salt. Liu et al (ChemCatChem.2012 (5): 1517-1523) synthesized thinner MFI-type zeolite by using urea. However, the surfactants used in the above methods are expensive and still have a certain distance from industrial applications.
CN112978757a discloses a method for preparing a flaky titanium silicalite molecular sieve TS-1, which comprises the following steps: 1) Preparing titanium silicagel I containing a silicon source, a titanium source, a template agent, a crystallization aid and water; 2) And after crystallizing the titanium silicagel I, separating, drying and roasting to obtain the flaky titanium silicalite molecular sieve TS-1. The flaky titanium silicon molecular sieve TS-1 prepared by the method has an MFI topological structure, the b axis is shorter than the a axis and the c axis, the grain size of the flaky molecular sieve TS-1 is 1-10 mu m multiplied by 0.05-0.8 mu m multiplied by 0.1-2 mu m, and the TS-1 molecular sieve prepared by the method has the characteristics of high hydrogen peroxide conversion rate and high propylene oxide selectivity in the epoxidation reaction of propylene. However, the crystallization aids sodium persulfate, potassium persulfate and ammonium persulfate used in the method have certain pollution and harm.
CN112978756a discloses a method for preparing a lamellar TS-1 molecular sieve, which comprises the following steps: adding the titanium dioxide/silicon compound into a mixed solution containing organic amine, urea and water, mixing, and drying to obtain a mixture; 2) And crystallizing the mixture by adopting a steam-assisted crystallization method, and then separating, drying and roasting to obtain the flaky TS-1 molecular sieve. The b-axis of the TS-1 molecular sieve prepared by the method is shorter than the a-axis and the c-axis, and the thickness of the flaky TS-1 molecular sieve is 50-500 nm. The flaky TS-1 molecular sieve has smaller size in the b axis direction, is more favorable for the diffusion of guest molecules, and has excellent catalytic performance. The straight pore channel direction (b axis) of the TS-1 molecular sieve is a main molecular diffusion path, and the diffusion efficiency of the product is improved due to the thinner thickness of the b axis. However, this method requires the use of an alkali source and an organic directing agent during the synthesis of the spherical titanium dioxide/silicon composite, and the added alkali and organic amine structure directing agent is expensive and has a certain environmental hazard.
Disclosure of Invention
The invention aims to provide a synthesis method of a flaky TS-1 molecular sieve on the premise of not using a surfactant, so as to obtain the TS-1 molecular sieve with good catalytic activity on high-carbon alpha-olefin and high alkylene oxide selectivity.
The inventor finds that in the research process, after mixing a silicon source and tetrapropylammonium hydroxide by adopting the method provided by the invention, the silicon source and the tetrapropylammonium hydroxide are mixed with a mixed solution of a titanium source and alcohol (namely, the titanium source and the silicon source are added step by step) and are matched with a pre-crystallization liquid prepared from the silicon source and the tetrapropylammonium hydroxide and an inorganic ammonium salt, the relative crystallinity of the obtained TS-1 molecular sieve is more than 90%, and the dimension in the direction of a b axis is 50-100nm, which is shorter than the a axis and the c axis; shortens the diffusion path of the product in zeolite to a certain extent, weakens the steric hindrance of the zeolite, and effectively improves the adsorption performance and catalytic activity of the TS-1 molecular sieve. Based on the foregoing, the inventors have provided the solution of the present invention.
In order to achieve the above object, a first aspect of the present invention provides a flaky TS-1 molecular sieve, the flaky TS-1 molecular sieve having an MFI topology, a b-axis being shorter than an a-axis and a c-axis, and the flaky TS-1 molecular sieve having a thickness of 50nm to 100nm.
In a second aspect, the present invention provides a method for preparing the flaky TS-1 molecular sieve according to the first aspect, the method comprising the steps of:
(1) Firstly mixing tetrapropylammonium hydroxide with a silicon source I to obtain a mixed solution I; the method comprises the steps of,
performing second mixing on the alcohol solvent and the titanium source to obtain a mixed solution II;
(2) Thirdly, mixing the mixed solution I and the mixed solution II in the presence of water to obtain a mixed solution III;
(3) Fourth mixing the pre-crystallized liquid and the mixed liquid III to obtain a mixed liquid IV;
(4) Fifth mixing ammonium salt with the mixed solution IV to obtain solid gel;
(5) Sequentially aging, crystallizing and separating solid from liquid to obtain a solid material;
(6) Drying and roasting the solid materials in sequence to obtain the TS-1 molecular sieve;
the pre-crystallization liquid is obtained by sequentially contacting tetrapropylammonium hydroxide with a silicon source II and pre-crystallizing.
A third aspect of the present invention provides the use of the flaky TS-1 molecular sieve according to the first aspect for catalyzing the epoxidation of a higher alpha-olefin.
The TS-1 molecular sieve obtained by the method provided by the invention has the advantages of high relative crystallinity of more than 90%, size of 50-100nm in the direction of the b axis, shorter than the a axis and the c axis, good catalytic activity and high selectivity to alkylene oxide.
Drawings
FIG. 1 is an XRD pattern of the flaky TS-1 molecular sieves prepared in examples 1-6 and comparative examples 1-4.
FIG. 2 is a scanning electron microscope image of the flaky TS-1 molecular sieve prepared in examples 1-6.
FIG. 3 is a scanning electron microscope image of the flaky TS-1 molecular sieve prepared in comparative examples 1-4.
Detailed Description
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
As described above, the first aspect of the present invention provides a flaky TS-1 molecular sieve having an MFI topology, the b-axis being shorter than the a-axis and the c-axis, and the flaky TS-1 molecular sieve having a thickness of 50nm to 100nm.
Preferably, the thickness of the flaky TS-1 molecular sieve is 50nm to 65nm.
As previously described, the second aspect of the present invention provides a process for preparing the flaky TS-1 molecular sieve of the first aspect, the process comprising the steps of:
(1) Firstly mixing tetrapropylammonium hydroxide with a silicon source I to obtain a mixed solution I; the method comprises the steps of,
performing second mixing on the alcohol solvent and the titanium source to obtain a mixed solution II;
(2) Thirdly, mixing the mixed solution I and the mixed solution II in the presence of water to obtain a mixed solution III;
(3) Fourth mixing the pre-crystallized liquid and the mixed liquid III to obtain a mixed liquid IV;
(4) Fifth mixing ammonium salt with the mixed solution IV to obtain solid gel;
(5) Sequentially aging, crystallizing and separating solid from liquid to obtain a solid material;
(6) Drying and roasting the solid materials in sequence to obtain the TS-1 molecular sieve;
the pre-crystallization liquid is obtained by sequentially contacting tetrapropylammonium hydroxide with a silicon source II and pre-crystallizing.
Preferably, the preparation step of the pre-crystallization liquid comprises the following steps:
s1: tetrapropylammonium hydroxide is contacted with a silicon source II to obtain a contact liquid I; the conditions of the contacting include: the temperature is 20-30 ℃, the time is 1-5h, and the stirring rotation speed is 300-700rpm;
s2: pre-crystallizing the contact liquid I; obtaining the pre-crystallization liquid.
Preferably, the pre-crystallization conditions include: the temperature is 50-200 ℃ and the time is 24-96h.
More preferably, the conditions for the pre-crystallization include: the temperature is 60-100deg.C, and the time is 36-54h. The inventors found that in this preferred case, the average thickness of the prepared flaky TS-1 molecular sieve is thinner and the catalytic activity is better.
Preferably, in the pre-crystallization liquid, the tetrapropylammonium hydroxide is mixed with SiO 2 The content mole ratio of the silicon source II is 0.2-0.8:1. more preferably, in the pre-crystallization liquid, the tetrapropylammonium hydroxide is mixed with SiO 2 The content mole ratio of the silicon source II is 0.4-0.7:1. the inventors found that in this preferred case, the average thickness of the prepared flaky TS-1 molecular sieve is thinner and the catalytic activity is better.
In the present invention, the tetrapropylammonium hydroxide is added in the form of an aqueous solution. The mass fraction of the aqueous solution of tetrapropylammonium hydroxide is 20-30wt%, preferably 25wt%.
Preferably, in step (1), the tetrapropylammonium hydroxide is added toSiO 2 The mole ratio of the silicon source I is 0.2-0.4:1.
preferably, the alcohol solvent and the catalyst are in the form of TiO 2 The molar ratio of the titanium source is 20-70:1. more preferably, the alcohol solvent and the catalyst are in the form of TiO 2 The molar ratio of the titanium source is 40-60:1.
preferably, the alcohol solvent is at least one selected from isopropanol, ethanol and n-butanol.
Preferably, the silicon source I and the silicon source II are respectively and independently selected from at least one of methyl orthosilicate, silica sol and ethyl orthosilicate. More preferably, the silicon source I, the silicon source II are the same, and the silicon source I, the silicon source II are tetraethyl orthosilicate.
Preferably, the titanium source is at least one selected from tetrabutyl titanate, titanium sulfate and titanium tetrachloride. More preferably, the titanium source is tetrabutyl titanate.
According to a preferred embodiment, the silicon source I, II is ethyl orthosilicate, the titanium source is tetrabutyl titanate, and the alcoholic solvent is isopropanol. The inventors found that in this preferred case, the average thickness of the prepared flaky TS-1 molecular sieve is thinner and the catalytic activity is better.
Preferably, in step (2), siO is used in an amount of 1mol 2 The water content of the mixed liquid I is 10-80mol.
According to a preferred embodiment, in step (2), the operation of third mixing comprises:
mixing the mixed solution I and the mixed solution II under a first condition in the presence of water, and heating to obtain a mixed solution III; the heating conditions include: the stirring speed is 300-800rpm, the temperature is 40-100 ℃, and the time is 2-45h.
More preferably, the heating conditions include: the stirring speed is 300-500rpm, the temperature is 80-100 ℃, and the time is 8-16h.
Preferably, the first condition includes: the temperature is 20-100 ℃, and the stirring speed is 300-500rpm for 1-7h.
Preferably, in the step (3), the mass ratio of the mixed solution III to the pre-crystallization solution calculated as the silicon source I is 1:0.2-0.8.
Preferably, in step (4), the ammonium salt is selected from at least one of ammonium carbonate, ammonium bicarbonate, ammonium acetate, and diammonium phosphate.
More preferably, the ammonium salt is ammonium carbonate. In this preferred case, the inventors have found that the TS-1 molecular sieve produced has a thinner average thickness and better catalytic activity.
Preferably, in step (4), the amount of the ammonium salt and the mixed solution IV is controlled so that the ammonium salt and SiO in the solid gel 2 The molar ratio of the silicon source I is 0.1-0.5:1.
The mode of the solid-liquid separation in the step (5) is not particularly limited, and the present invention can be carried out by those skilled in the art using known techniques, such as suction filtration.
Preferably, in step (1), the conditions of the first mixing include: the temperature is 20-30 ℃; the time is 1-5h, and the stirring speed is 300-500rpm.
According to a preferred embodiment, in step (1), the conditions of the second mixing comprise: the temperature is 20-30 ℃; the time is 1-2h, and the stirring speed is 300-500rpm.
Preferably, in step (3), the fourth mixing condition includes: the temperature is 20-30 ℃; the time is 1-5h, and the stirring speed is 300-500rpm.
Preferably, in step (4), the fifth mixing condition includes: the temperature is 20-40 ℃; the stirring speed is 1500-2500rpm. The stirring time of the fifth mixing is not particularly limited in the present invention, as long as the ammonium salt and the mixed solution IV can be mixed and stirred until a solid gel is formed. If gel is not formed in the fifth mixing process, mixing and stirring are carried out for 2 hours.
Preferably, in step (5), the aging conditions include: the temperature is 20-40 ℃ and the time is 3-7h.
Preferably, in step (5), the crystallization conditions include: the temperature is 100-200 ℃; the time is 12-96h. More preferably, the crystallization conditions include: the temperature is 140-180 ℃; the time is 36-54h.
Preferably, in step (6), the drying conditions include: the temperature is 100-120 ℃ and the time is 5-10h.
Preferably, in step (6), the roasting conditions include: the temperature is 500-600 ℃; the time is 2-8h.
As previously described, a third aspect of the present invention provides the use of the flaky TS-1 molecular sieve according to the first aspect for catalyzing the epoxidation of a higher alpha-olefin.
Preferably, the higher alpha-olefin is 1-hexene.
The invention will be described in detail below by way of examples. In the following examples, the instruments, reagents, materials and the like are those conventionally known in the art and are commercially available, unless otherwise specified. In the invention, the room temperature is 20+/-3 ℃.
The main materials used in the examples are all commercially available, and are specified below.
Tetrapropylammonium hydroxide: 25% by weight aqueous solution, available from Beijing Inocan technologies Co., ltd., model A64568;
ethyl orthosilicate: reagent grade, purchased from Shanghai Ala Biochemical technologies Co., ltd;
methyl orthosilicate: reagent grade, purchased from Shanghai Ala Biochemical technologies Co., ltd;
isopropyl alcohol: analytical grade, purchased from beijing enokio technologies limited;
tetrabutyl titanate: analytical grade, purchased from Shanghai microphone Biochemical technologies Co., ltd;
titanium tetrachloride: analytical grade, purchased from Shanghai microphone Biochemical technologies Co., ltd;
urea: purchased from Tianjin Fuchen chemical Co., ltd;
ammonium carbonate: analytical grade, purchased from Tianjin Fuchen chemical reagent Co., ltd;
ammonium bicarbonate: analytical grade, purchased from Tianjin Fuchen chemical reagent Co., ltd;
1-hexene: 99%, purchased from beijing enoki technologies limited.
Preparation example 1: preparation of Pre-crystallized liquid A1
S1: at room temperature, 20.0g of tetrapropylammonium hydroxide and 10.00g of ethyl orthosilicate are stirred for 5 hours at 400rpm to obtain a contact liquid I;
s2: transferring the contact liquid I into a 200mL reaction kettle, and placing the reaction kettle in a 60 ℃ oven for static pre-crystallization for 48 hours; the pre-crystallized liquid A1 is obtained.
Preparation example 2: preparation of Pre-crystallized liquid A2
The preparation example is similar to the preparation example 1, except that in the step S2, the contact liquid I is transferred into a 200mL reaction kettle and placed in an oven at 80 ℃ for static pre-crystallization for 48 hours; the pre-crystallized liquid A2 is obtained.
Preparation example 3: preparation of Pre-crystallized liquid A3
The preparation example is similar to the preparation example 1, except that in the step S2, the contact liquid I is transferred into a 200mL reaction kettle and placed in a 100 ℃ oven for static pre-crystallization for 48 hours; the pre-crystallized liquid A3 is obtained.
Preparation example 4: preparation of Pre-crystallized liquid A4
This preparation is similar to the process of preparation 1 except that in step S1, the amount of tetrapropylammonium hydroxide is 12g and the amount of ethyl orthosilicate is 10g and stirred at 400rpm for 5 hours; the pre-crystallized liquid A4 is obtained.
Example 1
(1) 15.00g of tetraethyl orthosilicate and 16.96g of tetrapropylammonium hydroxide are stirred at 400rpm for 3 hours at room temperature to obtain a mixed solution I; and
6.90g of isopropanol and 0.80g of tetrabutyl titanate are stirred for 1h at the room temperature at 300rpm to obtain a mixed solution II;
(2) Stirring the obtained mixed solution I and mixed solution II at 400rpm for 3 hours at room temperature, then adding 28.80g of deionized water, continuously stirring for 3 hours, and then heating and stirring for 12 hours under the condition of condensing and refluxing, wherein the heating temperature is 90 ℃, and the stirring speed is 300rpm to obtain mixed solution III;
(3) At room temperature, adding 4.0g of pre-crystallization liquid A1 into the mixed liquid III, and stirring at 500rpm for 5 hours to obtain a mixed liquid IV;
(4) Adding 2.60g of ammonium carbonate into the mixed solution IV at room temperature and 2500rpm, and stirring for 1h to obtain solid gel;
(5) Aging the solid gel for 5 hours at room temperature, transferring the solid gel into a 200mL reaction kettle, placing the solid gel in a rotary oven at 160 ℃ for dynamic crystallization for 48 hours, and then carrying out solid-liquid separation to obtain a solid material;
(6) And (3) drying the solid material in an oven at 120 ℃ for 5 hours, and roasting the dried solid material in a muffle furnace at 550 ℃ for 6 hours to obtain the flaky TS-1 molecular sieve S1.
Example 2
This example is similar to the preparation of example 1, except that in step (3), the pre-crystallization liquid A1 of example 1 is replaced by a pre-crystallization liquid A2 in equal amount;
the remaining steps were the same as in example 1 to obtain a flaky TS-1 molecular sieve S2.
Example 3
This example is similar to the preparation of example 1, except that in step (3), the pre-crystallization liquid A1 of example 1 is replaced by a pre-crystallization liquid A3 in equal amount;
the remaining steps were the same as in example 1 to obtain a flaky TS-1 molecular sieve S3.
Example 4
(1) 15.22g of methyl orthosilicate and 16.26g of tetrapropylammonium hydroxide are stirred at 500rpm for 3 hours at room temperature to obtain a mixed solution I; and
25.3g of ethanol and 1.89g of titanium tetrachloride are stirred at 300rpm for 1 hour at room temperature to obtain a mixed solution II;
(2) Stirring the obtained mixed solution I and mixed solution II at 500rpm for 3 hours at room temperature, then adding 54g of deionized water, continuously stirring for 3 hours, and then heating and stirring for 10 hours under the condition of condensing and refluxing, wherein the heating temperature is 100 ℃, and the stirring speed is 500rpm to obtain mixed solution III;
(3) 10.0g of pre-crystallization liquid A1 is added into the mixed liquid III at room temperature, and stirred for 5 hours at 300rpm to obtain mixed liquid IV;
(4) At room temperature and 1500rpm, adding 1.97g of ammonium bicarbonate into the mixed solution IV, and stirring for 2 hours to obtain solid gel;
(5) Aging the solid gel for 5 hours at room temperature, transferring the solid gel into a reaction kettle, placing the reaction kettle in a rotary oven at 180 ℃ for dynamic crystallization for 48 hours, and then carrying out solid-liquid separation to obtain a solid material;
(6) And (3) drying the solid material in a drying oven at 100 ℃ for 7 hours, and roasting the dried solid material in a muffle furnace at 500 ℃ for 8 hours to obtain the flaky TS-1 molecular sieve S4.
Example 5
This example is similar to the preparation of example 1, except that in step (3), the pre-crystallization liquid A1 of example 1 is replaced by a pre-crystallization liquid A4 in equal amount;
the remaining steps were the same as in example 1 to obtain a flaky TS-1 molecular sieve S5.
Example 6
This example is similar to the preparation of example 1, except that in step (4), 2.60g of ammonium carbonate from example 1 is replaced with 1.60g of urea;
the remaining steps were the same as in example 1 to obtain a flaky TS-1 molecular sieve S6.
Comparative example 1
This comparative example was similar to the preparation method of example 1, except that in this comparative example, the pre-crystallization liquid A1 and ammonium carbonate were not added;
the remaining procedure was the same as in example 1 to obtain a flaky TS-1 molecular sieve DS1.
Comparative example 2
This comparative example is similar to the preparation of example 1, except that in step (4), no ammonium carbonate is added;
the remaining procedure was the same as in example 1 to obtain a flaky TS-1 molecular sieve DS2.
Comparative example 3
This comparative example is similar to the preparation method of example 1, except that in step (3), the pre-crystallization liquid A1 is not added;
the remaining procedure was the same as in example 1 to obtain a flaky TS-1 molecular sieve DS3.
Comparative example 4
This comparative example was similar to the preparation of example 1, except that,
in the step (1), 15.00g of tetraethoxysilane, 16.96g of tetrapropylammonium hydroxide, 6.90g of isopropanol and 0.80g of tetrabutyl titanate are stirred at 400rpm for 3 hours at room temperature to obtain a mixed solution I;
in the step (2), 28.80g of deionized water is added into the mixed solution I, stirring is continued for 3 hours, heating and stirring are carried out for 12 hours under the condition of condensing and refluxing, the heating temperature is 90 ℃, and the stirring speed is 300rpm, so that mixed solution III is obtained;
the remaining steps (3) to (6) were the same as in example 1, to obtain a flaky TS-1 molecular sieve DS4.
Test example 1
The morphology, grain size and relative crystallinity of the flake-like TS-1 molecular sieves prepared in examples and comparative examples were measured, wherein the results of the relative crystallinity and average flake thickness measurements are shown in Table 1.
XRD characterization was performed on the prepared flaky TS-1 molecular sieve by using an X-ray diffractometer (model: PA Nalytial X' Pert Powder).
The calculation method of the relative crystallinity comprises the following steps: calculated according to the comparison of the sum of peak intensities of diffraction angles 7.8 degrees, 8.8 degrees, 23.2 degrees, 23.8 degrees and 24 degrees and 3 degrees in XRD analysis and a standard sample;
the method for detecting the crystal morphology and the grain size comprises the following steps: and analyzing by adopting a Quanta F20 type scanning electron microscope, counting the thickness of the molecular sieve, and calculating the average value.
TABLE 1
TS-1 molecular sieve numbering Type of pre-crystallization liquid Ammonium salt species Relative crystallinity Average thickness of sheet (nm)
S1 A1 Ammonium carbonate 98 61
S2 A2 Ammonium carbonate 99 63
S3 A3 Ammonium carbonate 99 51
S4 A1 Ammonium bicarbonate 95 74
S5 A4 Ammonium carbonate 92 74
S6 A1 Urea 94 97
DS1 - - 90 750
DS2 - Ammonium carbonate 92 78
DS3 A1 - 95 360
DS4 A1 Ammonium carbonate 80 75
As can be seen from Table 1, the TS-1 molecular sieve prepared by the method of the invention has good crystallinity, and the average thickness of the flake is 50-100nm.
Among them, FIG. 1 is XRD patterns of molecular sieves S1 to S6, DS1 to DS4 prepared in the examples. As can be seen from FIG. 1, the XRD patterns of the molecular sieves S1-S6 and DS1-DS4 are consistent with the characteristic patterns of the standard MFI molecular sieve, and the diffraction peak intensity is high and the crystallization is good.
FIG. 2 is a scanning electron microscope image of molecular sieves S1-S6 prepared in the examples. It can be seen from FIG. 2 that the synthesized sample is a typical lamellar morphology with an average thickness of 50-100nm.
FIG. 3 is a scanning electron microscope image of the molecular sieves DS1 to DS4 prepared in the comparative example. As can be seen from fig. 3, the synthesized sample DS1 is typically spherical and has a large particle size; DS2 is in the form of flakes, but because no pre-crystallization liquid is added, the molecular sieve is thicker. DS3 is also typically spherical because no ammonium salt is added, and because a pre-crystallization liquid is added, the particle size is much smaller than DS1. As can be seen from the figure, DS4 has a poor crystallinity and is more mixed with amorphous material.
Test example 2
0.05g of the platelet-shaped TS-1 molecular sieve prepared in the example or comparative example, 0.86g of 1-hexene, 1.5 g of H 2 O 2 (30 wt%) and 7.90g of methanol were sequentially added to a round bottom flask, an oil bath was maintained at constant temperature (60 ℃) for 24 hours, cyclohexanone as an internal standard was added after the completion of the reaction, stirred for 2 minutes, the obtained product was centrifugally separated to obtain a clear solution, and the composition of the product in the clear solution was analyzed by gas chromatography to calculate 1-hexene conversion and 1, 2-epoxyhexane selectivity, and specific results are shown in Table 2.
Wherein, the gas chromatography analysis method comprises the following steps: and (3) injecting the clear liquid from a gas chromatograph injection port, flowing through a chromatographic column, detecting by using a flame ionization detector, and quantitatively analyzing by an external standard method. The gas chromatograph used was 7890A gas chromatograph manufactured by Agilent technologies, inc. of America, and the analytical column used was HP-5 column.
The calculation formula of the olefin conversion rate is as follows: [ (n) 1 -n 2 )/n 1 ]x100%, formula (1);
in formula (1), n 1 Represents the initial number of moles of 1-hexene; n is n 2 The number of moles of 1-hexene after the reaction is shown.
The calculation formula of the selectivity of the 1, 2-epoxyhexane comprises the following formula: (n) 3 /n Total (S) ) x100%, formula (2);
in formula (2), n 3 Represents the mole of 1, 2-epoxyhexaneA mole number; n is n Total (S) Represents the sum of the moles of all products.
TABLE 2
TS-1 molecular sieve numbering 1-hexene conversion/% 1, 2-epoxyhexane selectivity/%
S1 69.2 67.2
S2 68.8 66.4
S3 70.2 68.5
S4 63.8 64.8
S5 60.5 64.6
S6 52.6 58.6
DS1 50.0 34.0
DS2 55.7 54.4
DS3 51.2 42.8
DS4 42.5 44.1
As can be seen from Table 2, the flaky TS-1 molecular sieve provided by the application has the advantages of high olefin conversion rate and high target product selectivity in the olefin epoxidation reaction.
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.

Claims (10)

1. A flaky TS-1 molecular sieve, characterized in that the flaky TS-1 molecular sieve has an MFI topology, the b-axis is shorter than the a-axis and the c-axis, and the flaky TS-1 molecular sieve has a thickness of 50nm to 100nm.
2. A process for preparing the flaky TS-1 molecular sieve according to claim 1, comprising the steps of:
(1) Firstly mixing tetrapropylammonium hydroxide with a silicon source I to obtain a mixed solution I; the method comprises the steps of,
performing second mixing on the alcohol solvent and the titanium source to obtain a mixed solution II;
(2) Thirdly, mixing the mixed solution I and the mixed solution II in the presence of water to obtain a mixed solution III;
(3) Fourth mixing the pre-crystallized liquid and the mixed liquid III to obtain a mixed liquid IV;
(4) Fifth mixing ammonium salt with the mixed solution IV to obtain solid gel;
(5) Sequentially aging, crystallizing and separating solid from liquid to obtain a solid material;
(6) Drying and roasting the solid materials in sequence to obtain the TS-1 molecular sieve;
the pre-crystallization liquid is obtained by sequentially contacting tetrapropylammonium hydroxide with a silicon source II and pre-crystallizing.
3. The method of claim 2, wherein in step (1), the tetrapropylammonium hydroxide is combined with SiO 2 The mole ratio of the silicon source I is 0.2-0.4:1, a step of; and/or
In step (1), the alcoholic solvent and the TiO-based solvent 2 The molar ratio of the titanium source is 20-70:1 and/or
In step (2), siO is used in terms of 1mol 2 The water content of the mixed liquid I is 10-80mol.
4. A method according to claim 2 or 3, wherein in step (2) the operation of third mixing comprises:
mixing the mixed solution I and the mixed solution II under a first condition in the presence of water, and heating to obtain a mixed solution III; the heating conditions include: the stirring speed is 300-800rpm, the temperature is 40-100 ℃, and the time is 2-45h.
5. The method according to any one of claims 2-4, wherein in the pre-crystallization liquid the tetrapropylammonium hydroxide is mixed with SiO 2 Calculated as the content mole of the silicon source IIThe molar ratio is 0.2-0.8:1, and/or
In the step (3), the dosage mass ratio of the mixed solution III to the pre-crystallization solution calculated by the silicon source I is 1:0.2-0.8.
6. The method according to any one of claims 2 to 5, wherein in step (4), the ammonium salt is selected from at least one of ammonium carbonate, ammonium bicarbonate, ammonium acetate, and diammonium phosphate; and/or
In step (4), the amount of the ammonium salt and the mixed solution IV is controlled so that the ammonium salt and SiO in the solid gel 2 The molar ratio of the silicon source I is 0.1-0.5:1.
7. The method of any one of claims 2-6, wherein in step (1), the first mixing conditions comprise: the temperature is 20-30 ℃; the time is 1-5h, and the stirring speed is 300-500rpm; and/or
In step (1), the conditions of the second mixing include: the temperature is 20-30 ℃; the time is 1-2h, and the stirring speed is 300-500rpm; and/or
In step (3), the fourth mixing conditions include: the temperature is 20-30 ℃; the time is 1-5h, and the stirring speed is 300-500rpm; and/or
In step (4), the fifth mixing conditions include: the temperature is 20-40 ℃; the stirring speed is 1500-2500rpm; and/or
In step (5), the crystallization conditions include: the temperature is 100-200 ℃; the time is 12-96h; and/or
In step (6), the firing conditions include: the temperature is 500-600 ℃; the time is 2-8h.
8. The method of any of claims 2-7, wherein the pre-crystallization conditions comprise: the temperature is 50-200 ℃ and the time is 24-96h.
9. The method of any of claims 2-8, wherein the silicon source I, silicon source II are each independently selected from at least one of methyl orthosilicate, silica sol, ethyl orthosilicate; and/or
The titanium source is at least one selected from tetrabutyl titanate, titanium sulfate and titanium tetrachloride.
10. Use of the flaky TS-1 molecular sieve according to claim 1 for catalyzing epoxidation of higher alpha-olefins.
CN202310028814.5A 2023-01-09 2023-01-09 Lamellar TS-1 molecular sieve and preparation method and application thereof Pending CN116081635A (en)

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