CN113184871A - Method for preparing oriented molecular sieve membrane by liquid level vortex lifting technology - Google Patents

Method for preparing oriented molecular sieve membrane by liquid level vortex lifting technology Download PDF

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CN113184871A
CN113184871A CN202110535221.9A CN202110535221A CN113184871A CN 113184871 A CN113184871 A CN 113184871A CN 202110535221 A CN202110535221 A CN 202110535221A CN 113184871 A CN113184871 A CN 113184871A
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molecular sieve
liquid level
preparing
vortex
oriented
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CN113184871B (en
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王政
黄锐
周有慧
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Ningxia University
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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
    • C01B39/04—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 using at least one organic template directing agent, e.g. an ionic quaternary ammonium compound or an aminated compound
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B37/00—Compounds having molecular sieve properties but not having base-exchange properties
    • C01B37/005—Silicates, i.e. so-called metallosilicalites or metallozeosilites
    • 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
    • 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
    • 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
    • C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM

Abstract

The invention belongs to the technical field of molecular sieve membrane preparation, and provides a method for preparing an oriented molecular sieve membrane by using a liquid level vortex lifting technology. The method comprises the following specific steps: (1) preparing molecular sieve crystal grains and carrying out first hydrothermal crystallization; (2) modifying molecular sieve grains; (3) assembling a molecular sieve crystal grain layer by liquid level vortex lifting; (4) preparing an oriented molecular sieve membrane and carrying out second hydrothermal crystallization. The molecular sieve crystal grains are subjected to hydrophobic modification, so that the molecular sieve crystal grains can be applied to a liquid level vortex pulling technology to prepare the oriented molecular sieve membrane, and the blank that the liquid level vortex pulling technology is not adopted to prepare the oriented molecular sieve membrane in the prior art is filled. The preparation method provided by the invention has the advantages of simplicity, convenience, practicability, low cost, wide applicability, excellent performance and the like.

Description

Method for preparing oriented molecular sieve membrane by liquid level vortex lifting technology
Technical Field
The invention relates to the field of molecular sieve membrane preparation, in particular to a method for preparing an oriented molecular sieve membrane by using a liquid level vortex lifting technology.
Background
The assembly of the single-layer ordered molecular sieve crystal grain layer is a research hotspot in the field of molecular sieve membranes in recent years. As is well known, a molecular sieve membrane has been used in many disciplinary fields such as a material field of substance separation, a sensor material field, an anticorrosive material field, an optical material field, and the like, as a novel material. With the development of science and technology, the technology is applied to more fields.
Research shows that the preferentially oriented molecular sieve membrane has better performance in the aspects of material separation and the like than a non-oriented molecular sieve membrane. The continuity, compactness and orientation of the grain layer are the standards for measuring the quality of the grain layer, and the quality of the grain layer directly determines the quality of the molecular sieve membrane. If the crystal grain layer is not dense, the obtained molecular sieve membrane is likely to generate defects; if the orientation of the crystal grain layer is not good, a target oriented molecular sieve film cannot be obtained; if the seed layer has multiple layers, the resulting molecular sieve membrane will be very thick, which will affect its separation performance.
Therefore, the assembling effect of the molecular sieve crystal grain layer directly affects the preparation of the oriented molecular sieve membrane, and the obtained single-layer, compact and target oriented crystal grain layer becomes a bottleneck restricting the preparation of the high-quality molecular sieve membrane.
At present, the commonly used methods for preparing the grain layer comprise a Langmuir-Blodgett method, an adsorbed grain method and a spin coating method, and in addition, an in-situ hydrothermal method, an electric field induction method, a convection method, an organic bonding method and the like. Although these methods can assemble the molecular sieve crystal layer, they have disadvantages such as harsh experimental conditions, complicated process, and long preparation time. Therefore, the grain layer assembling method which is simple, convenient and easy to implement, low in cost, wide in applicability and excellent in performance is particularly important for preparing the oriented molecular sieve membrane.
Pan et al (Langmuir.2006, 22 (17): 7101-7104.) assemble monolayer colloidal grains on a carrier using a level vortex pulling method. Qihongfei et al (functional materials 2008, 10 (39): 1912-. The patent (CN101497067, published: 087/2009) discloses a preparation method for assembling a large-area ordered microsphere template by a liquid level vortex method. Zhou et al (journal of materials chemistry.2012, 22 (8): 3307-. Rodrigues et al (JPhysChemB.2013, 117 (21): 6524-. Xie et al (nanoscale.2014, 6 (6): 3064-. At present, no document or patent for orderly assembling molecular sieve crystal grains by using a liquid level vortex pulling technology is reported.
Disclosure of Invention
In view of the above, in order to fill up the blank in the prior art, the invention provides a method for preparing an oriented molecular sieve membrane by using a liquid level vortex pulling technology, and the oriented molecular sieve membrane which is single-layer, compact and has a target oriented molecular sieve crystal grain layer can be prepared.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for preparing an oriented molecular sieve membrane by using a liquid level vortex pulling technology comprises the following steps:
(1) preparing molecular sieve crystal grains: mixing a silicon source, a template agent a and water to prepare gel A, and carrying out first hydrothermal crystallization on the gel to prepare molecular sieve grains;
(2) modification of molecular sieve crystal grains: dispersing the molecular sieve crystal grains in a dispersing agent to prepare a suspension, and stirring at room temperature to complete modification;
(3) assembling a molecular sieve crystal layer by liquid level vortex lifting: placing the open container on a magnetic stirrer, adding a piece of clean magneton and deionized water into the open container, starting the magnetic stirrer to enable the open container to generate a stable vortex, dripping the modified molecular sieve crystal grains onto the liquid level of the vortex by using an injector, stopping dripping the modified molecular sieve crystal grains after the molecular sieve crystal grain layer on the liquid level of the vortex is compact, reducing the rotating speed of the magnetic stirrer until the stopping, immersing and pulling out the carrier by using a pulling machine after the liquid level of the vortex is reduced to a horizontal plane, and drying the carrier in an oven to obtain the carrier loaded with the molecular sieve crystal grain layer;
(4) preparing an oriented molecular sieve membrane: and (3) contacting the carrier carrying the molecular sieve crystal grain layer with gel B prepared by mixing a silicon source, a template agent B, KOH and water, and carrying out second hydrothermal crystallization in an oven together to prepare the oriented molecular sieve membrane.
Further, the preparation process of the gel A in the step (1) is as follows:
and mixing Tetraethoxysilane (TEOS) serving as a silicon source and tetrapropylammonium hydroxide (TPAOH) serving as a template agent a with water according to a certain molar ratio, and stirring at room temperature for 24 hours to obtain the gel A.
Further, the prepared gel a exhibited a milky translucent appearance.
Further, the first hydrothermal crystallization process in step (1) is as follows:
pouring the gel A into a polytetrafluoroethylene lining, covering and sealing, and statically crystallizing in an oven at 150-165 ℃ for 2-5 hours.
Further, the step (1) further comprises a cleaning process of the molecular sieve crystal grains after the first hydrothermal crystallization is completed:
and taking out the polytetrafluoroethylene lining after the first hydrothermal crystallization is finished, quickly putting the polytetrafluoroethylene lining into water for cooling, then washing the polytetrafluoroethylene lining for a plurality of times by using distilled water and ammonia water respectively, and then putting the polytetrafluoroethylene lining into a drying oven at 110 ℃ for drying overnight to obtain the molecular sieve crystal grains.
Further, the concentration of ammonia water was 0.1 mol/L.
Further, the dispersant in the step (2) is an alcohol solution, and comprises one or more of methanol, ethanol, sec-butyl alcohol, n-butyl alcohol and dibutyl alcohol.
Further, the stirring time of the suspension in the step (2) is 48-60 hours.
Furthermore, the concentration of the molecular sieve crystal grains in the suspension liquid in the step (2) is 0.1-0.3 wt%.
Further, the deionized water is added in the step (3) in an amount of 50% of the volume of the open container.
Further, the rotating speed of the magnetic stirrer in the step (3) is 300-400 r/min.
Further, the speed of carrier pulling in the step (3) is 1-3000 μm/s.
Further, the set temperature of the oven in the step (3) is 80-100 ℃, and the drying time is 2-4 h.
Further, the preparation process of the gel B in the step (4) is as follows:
and (2) mixing Tetraethoxysilane (TEOS) serving as a silicon source and tetrapropylammonium bromide dimer (dimer-TPABr) serving as a template B with water and KOH according to a certain molar ratio, and stirring at room temperature for 5 hours to obtain gel B.
Further, the obtained gel B exhibited a milky translucent appearance, and the mass of the gel B was 30 g.
Further, the second hydrothermal crystallization process in the step (4) is as follows:
and contacting the gel B with a carrier carrying a molecular sieve crystal grain layer, putting the gel B and the carrier into a hydrothermal crystallization reaction kettle, putting the hydrothermal crystallization reaction kettle into an oven at 170-180 ℃, and statically crystallizing for 2-3 hours.
Further, the mode of contacting the carrier loaded with the molecular sieve crystal grain layer in the step (4) with the gel B is as follows: the carrier carrying the molecular sieve grain layer is placed horizontally, and the molecular sieve grain layer contacts the gel B downwards.
Further, the step (4) further comprises a cleaning process of the molecular sieve crystal grains after the second hydrothermal crystallization is completed:
and taking out the hydrothermal crystallization reaction kettle after the second hydrothermal crystallization, quickly putting the hydrothermal crystallization reaction kettle into water for cooling, washing the hydrothermal crystallization reaction kettle for a plurality of times by using ammonia water, and then putting the hydrothermal crystallization reaction kettle into an oven at 80 ℃ for drying overnight to obtain the oriented molecular sieve membrane.
Further, the concentration of ammonia water was 0.1 mol/L.
The invention has the following beneficial effects:
1. according to the invention, the molecular sieve crystal grains are modified, and hydrophobic groups are attached to the surfaces of the molecular sieve crystal grains, so that the molecular sieve crystal grains can float on the liquid level of the vortex, the vortex can enable the molecular sieve crystal grains to be orderly and tightly arranged, and the loading of the molecular sieve crystal grain layer is completed after the operation of a pulling machine.
2. The oriented molecular sieve membrane prepared by twice hydrothermal crystallization has excellent performance highly consistent with the target orientation, and can be prepared by adjusting various parameters in the preparation method according to actual orientation requirements.
3. The method for preparing the oriented molecular sieve membrane by using the liquid level vortex pulling technology has the advantages of simplicity, convenience, practicability, low cost, wide applicability, excellent performance and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a flow chart of the present invention for preparing an oriented molecular sieve membrane by using a liquid level vortex pulling technique;
FIG. 2 is a schematic diagram of the modification of the molecular sieve grains of the present invention;
FIG. 3 is an SEM image of the silicalite-1 molecular sieve grain layer obtained in step (3) of example 1 of the present invention;
FIG. 4 is an AFM of the silicalite-1 molecular sieve grain layer obtained in step (3) of example 1 of the present invention;
FIG. 5 is an XRD pattern of the silicalite-1 molecular sieve grain layer obtained in step (3) of example 1 of the present invention;
FIG. 6 is an SEM photograph of an a-axis oriented silicalite-1 molecular sieve membrane prepared in example 1 of the present invention;
FIG. 7 is an AFM image of an a-axis oriented silicalite-1 molecular sieve membrane prepared in example 1 of the present invention;
FIG. 8 is an SEM image of the silicalite-1 molecular sieve grain layer obtained in step (3) of example 2 of the present invention;
FIG. 9 is an XRD pattern of the silicalite-1 molecular sieve grain layer obtained in step (3) of example 2 of the present invention;
FIG. 10 is an SEM photograph of a b-axis oriented silicalite-1 molecular sieve membrane prepared in example 2 of the present invention;
FIG. 11 is an XRD pattern of a b-axis oriented silicalite-1 molecular sieve membrane prepared in example 2 of the present invention;
FIG. 12 is an SEM image of the silicalite-1 molecular sieve grain layer obtained in step (3) of example 3 of the present invention;
FIG. 13 is an SEM photograph of an a, c-axis oriented silicalite-1 molecular sieve membrane obtained in example 3 of the present invention;
FIG. 14 is an SEM photograph of an a, c-axis oriented silicalite-1 molecular sieve membrane prepared in comparative example 1 of the present invention;
FIG. 15 is an XRD pattern of an a, c-axis oriented silicalite-1 molecular sieve membrane obtained in example 3 of the present invention and an a, c-axis oriented silicalite-1 molecular sieve membrane obtained in comparative example 1.
Detailed Description
The invention provides a method for preparing an oriented molecular sieve membrane by using a liquid level vortex pulling technology, which comprises the following steps:
(1) preparing molecular sieve crystal grains: mixing a silicon source, a template agent a and water to prepare gel A, and carrying out first hydrothermal crystallization on the gel to prepare molecular sieve grains;
(2) modification of molecular sieve crystal grains: dispersing the molecular sieve crystal grains in a dispersing agent to prepare a suspension, and stirring at room temperature to complete modification;
(3) assembling a molecular sieve crystal layer by liquid level vortex lifting: placing the open container on a magnetic stirrer, adding a piece of clean magneton and deionized water into the open container, starting the magnetic stirrer to enable the open container to generate a stable vortex, dripping the modified molecular sieve crystal grains onto the liquid level of the vortex by using an injector, stopping dripping the modified molecular sieve crystal grains after the molecular sieve crystal grain layer on the liquid level of the vortex is compact, reducing the rotating speed of the magnetic stirrer until the stopping, immersing and pulling out the carrier by using a pulling machine after the liquid level of the vortex is reduced to a horizontal plane, and drying the carrier in an oven to obtain the carrier loaded with the molecular sieve crystal grain layer;
(4) preparing an oriented molecular sieve membrane: and (3) contacting the carrier carrying the molecular sieve crystal grain layer with gel B prepared by mixing a silicon source, a template agent B, KOH and water, and carrying out second hydrothermal crystallization in an oven together to prepare the oriented molecular sieve membrane.
Further, the flow chart of the invention for preparing the oriented molecular sieve membrane by using the liquid level vortex pulling technology is shown in figure 1.
Further, the preparation process of the gel A in the step (1) is as follows:
and mixing Tetraethoxysilane (TEOS) serving as a silicon source and tetrapropylammonium hydroxide (TPAOH) serving as a template agent a with water according to a certain molar ratio, and stirring at room temperature for 24 hours to obtain the gel A.
Further, TEOS, TPAOH and H in gel A2The molar ratio of O to TEOS: TPAOH: h2O＝20～30：5～10：1300～1600。
Preferably, gel A contains TEOS, TPAOH and H2The molar ratio of O to TEOS: TPAOH: h2O＝25：6：1450。
Further, the prepared gel a exhibited a milky translucent appearance.
Further, the first hydrothermal crystallization process in step (1) is as follows:
pouring the gel A into a polytetrafluoroethylene lining, covering and sealing, and statically crystallizing in an oven at 150-165 ℃ for 2-5 hours.
Preferably, the polytetrafluoroethylene liner has a volume of 50 mL.
Preferably, the oven temperature is 150 ℃ or 165 ℃.
Preferably, the static crystallization time is 2h or 5 h.
Further, the step (1) further comprises a cleaning process of the molecular sieve crystal grains after the first hydrothermal crystallization is completed:
and taking out the polytetrafluoroethylene lining after the first hydrothermal crystallization is finished, quickly putting the polytetrafluoroethylene lining into water for cooling, then washing the polytetrafluoroethylene lining for a plurality of times by using distilled water and ammonia water respectively, and then putting the polytetrafluoroethylene lining into a drying oven at 110 ℃ for drying overnight to obtain the molecular sieve crystal grains.
Further, the concentration of ammonia water was 0.1 mol/L.
Further, the dispersant in the step (2) is an alcohol solution, and comprises one or more of methanol, ethanol, sec-butyl alcohol, n-butyl alcohol and dibutyl alcohol.
Furthermore, the molecular sieve crystal grains modified by the dispersant can be suspended on the water surface. The molecular sieve crystal grains which are not treated by the dispersing agent are miscible after contacting with water and cannot be suspended above the water surface because the surfaces of the molecular sieve crystal grains are provided with hydrophilic groups.
Further, the stirring time of the suspension in the step (2) is 48-60 hours.
Preferably, the stirring time is 48h or 60 h.
Furthermore, the concentration of the molecular sieve crystal grains in the suspension liquid in the step (2) is 0.1-0.3 wt%.
Preferably, the concentration of molecular sieve crystallites in the suspension of step (2) is 0.2 wt%.
Further, the modification schematic diagram of the molecular sieve crystal grains in the step (2) is shown in fig. 2.
Preferably, the open container used in step (3) is made of polytetrafluoroethylene.
Further, the deionized water is added in the step (3) in an amount of 50% of the volume of the open container.
Further, the rotating speed of the magnetic stirrer in the step (3) is 300-400 r/min.
Preferably, the rotation speed of the magnetic stirrer in the step (3) is 300r/min or 400 r/min.
Further, after the magnetic stirrer is turned on, the rotation of the magnetons can enable the water surface to generate stable vortex.
Further, the support material provides a surface for supporting the grains, which form a dense film layer as they grow. The carrier material may be any material from which the seed layer is deposited. The surface area, thickness of the carrier material can be selected according to the size of the open container and can provide the desired strength without affecting its application. The shape of the carrier may be any geometric configuration, such as circular, square, and polygonal.
Preferably, the support coated with the layer of oriented grains is a metal sheet, a dense substrate, a porous substrate and an oxide substrate, which may be of any geometric shape. Further preferably, the support is stainless steel, quartz or graphite with a smooth surface and a porous inorganic porous material or alloy.
Furthermore, different types of carrier pretreatment methods are different, specifically as follows:
(1) a metal carrier: such as stainless steel, alloy, etc., is put into a beaker filled with ethanol solution, taken out after 30min of ultrasonic treatment, and dried. Then, the carrier is placed in a muffle furnace at 550 ℃ for roasting for 6 hours, and after the roasting is finished, the carrier is placed in a mixed solution [ V (H) of sulfuric acid and hydrogen peroxide2SO4)：V(H2O2)＝2：1]Treating for a certain time, taking out immediately when the surface of the carrier has bright metal color, and placingAdding into ethanol solution and storing for use.
(2) Porous alumina support: polishing the surface with 1500, 3000, 5000 mesh sand paper, and ultrasonic cleaning in deionized water for 15 min. Then respectively adding 0.1mol/L NH3And H2O and HCl are statically soaked for 15min, taken out and placed in deionized water for ultrasonic washing for 3 times, and stored for later use.
Further, the speed of carrier pulling in the step (3) is 1-3000 μm/s.
Further, the set temperature of the oven in the step (3) is 80-100 ℃, and the drying time is 2-4 h.
Preferably, the set temperature of the oven in the step (3) is 90 ℃, and the drying time is 3 h.
Further, the preparation process of the gel B in the step (4) is as follows:
and (2) mixing Tetraethoxysilane (TEOS) serving as a silicon source and tetrapropylammonium bromide dimer (dimer-TPABr) serving as a template B with water and KOH according to a certain molar ratio, and stirring at room temperature for 5 hours to obtain gel B.
Further, TEOS, dimer-TPABr, KOH and H in gel B2The molar ratio of O is TEOS: dimer-TPABr: KOH: h2O＝70～90：10～20：40～60：19000～20000。
Preferably, gel B contains TEOS, dimer-TPABr, KOH and H2The molar ratio of O is TEOS: dimer-TPABr: KOH: h2O＝80：15：50：19500。
Further, the prepared gel B exhibited a milky translucent appearance.
Further, the second hydrothermal crystallization process in the step (4) is as follows:
and contacting the gel B with a carrier carrying a molecular sieve crystal grain layer, putting the gel B and the carrier into a hydrothermal crystallization reaction kettle, putting the hydrothermal crystallization reaction kettle into an oven at 170-180 ℃, and statically crystallizing for 2-3 hours.
Preferably, the temperature of the second hydrothermal crystallization is 175 ℃, and the static crystallization time is 3 h.
Further, the mode of contacting the carrier loaded with the molecular sieve crystal grain layer in the step (4) with the gel B is as follows: the carrier carrying the molecular sieve grain layer is placed horizontally, and the molecular sieve grain layer contacts the gel B downwards.
Further, the step (4) further comprises a cleaning process of the molecular sieve crystal grains after the second hydrothermal crystallization is completed:
and taking out the hydrothermal crystallization reaction kettle after the second hydrothermal crystallization, quickly putting the hydrothermal crystallization reaction kettle into water for cooling, washing the hydrothermal crystallization reaction kettle for a plurality of times by using ammonia water, and then putting the hydrothermal crystallization reaction kettle into an oven at 80 ℃ for drying overnight to obtain the oriented molecular sieve membrane.
Further, the concentration of ammonia water was 0.1 mol/L.
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The preparation method of the a-axis oriented silicalite-1 molecular sieve membrane comprises the following steps:
(1) preparing molecular sieve crystal grains: TEOS, TPAOH and H2O is according to TEOS: TPAOH: h2O20: 5: 1300, and stirring at room temperature for 24h to obtain milky translucent gel A with a mass of 30 g. Slowly pouring the gel A into a 50mL polytetrafluoroethylene lining, covering and sealing, placing in a 150 ℃ oven, and statically crystallizing for 5 hours to carry out first hydrothermal crystallization. After the first hydrothermal crystallization is finished, the lining is quickly taken out and put into cold water, and then the obtained product is washed for a plurality of times by distilled water and 0.1mol/L ammonia water respectively. Drying the washed product in an oven at 110 ℃ overnight to obtain silicalite-1 molecular sieve grains.
(2) Modification of molecular sieve crystal grains: dispersing silicalite-1 molecular sieve crystal grains into a dibutanol solution, stirring for 48 hours at room temperature to prepare a suspension with the concentration of the molecular sieve crystal grains being 0.1 wt%, and obtaining the modified molecular sieve crystal grains.
(3) Assembling a molecular sieve crystal layer by liquid level vortex lifting: and placing the open container on a magnetic stirrer, adding a piece of clean magneton and deionized water with the volume of 50% of the container into the open container, starting the magnetic stirrer, and setting the rotating speed to be 300r/min to generate stable vortex in the open container. Dropping the modified molecular sieve crystal grains onto the vortex liquid surface by using an injector, stopping dropping the modified molecular sieve crystal grains after a molecular sieve crystal grain layer on the vortex liquid surface is compact, increasing the rotating speed to 400r/min at the moment, enabling a gap to appear on the liquid surface, continuing dropping the modified molecular sieve crystal grains by using the injector, stopping dropping and reducing the rotating speed of a magnetic stirrer until stirring is stopped when the crystal grain layer on the liquid surface is compact again, immersing a smooth quartz carrier into the vortex liquid surface by using a pulling machine after the vortex liquid surface is reduced to a horizontal plane, pulling out the smooth quartz carrier at the speed of 1 mu m/s, and drying the smooth quartz carrier in an oven at the temperature of 80 ℃ for 4 hours to obtain the smooth quartz carrier loaded with the silicalite-1 molecular sieve crystal grain layer.
(4) Preparing an oriented molecular sieve membrane: TEOS, dimer-TPABr, KOH and H2O is according to TEOS: dimer-TPABr: KOH: h2O70: 10: 40: 19000 and stirred at room temperature for 5 hours to obtain milky translucent gel B, the mass of which was 30 g.
And (3) contacting the gel B with a smooth quartz carrier carrying a silicalite-1 molecular sieve crystal grain layer, horizontally placing the carrier, contacting the molecular sieve crystal grain layer with the gel B downwards, placing the gel B and the molecular sieve crystal grain layer in a hydrothermal crystallization reaction kettle, placing the hydrothermal crystallization reaction kettle in an oven at 170 ℃, and statically crystallizing for 3 hours to perform second hydrothermal crystallization. And after the second hydrothermal crystallization is finished, quickly taking out the lining, putting the lining into cold water, and washing the obtained product for several times by using distilled water and 0.1mol/L ammonia water respectively. The washed product was dried overnight in an oven at 80 ℃ to give an a-axis oriented silicalite-1 molecular sieve membrane.
FIGS. 3, 4 and 5 are the SEM, AFM and XRD patterns, respectively, of the silicalite-1 molecular sieve grain layer obtained in step (3) of example 1 of the present invention. As can be seen from FIGS. 3 and 4, the crystal grains have high coverage, are continuously arranged, are dense and ordered, and have flat surfaces. As is clear from fig. 5, the presence of characteristic diffraction peaks of (200), (400) and (600) indicates that the resulting silicalite-1 molecular sieve crystal grain layer is a-axis oriented and the orientation of the crystal grain layer is good.
FIGS. 6 and 7 are an SEM photograph and an AFM photograph, respectively, of an a-axis oriented silicalite-1 molecular sieve membrane obtained in example 1 of the present invention. As shown in FIGS. 6 and 7, when the time of the second hydrothermal crystallization is 3h, the crystal grains of the a-axis oriented Sicalate-1 molecular sieve film grow along the original orientation, the gaps among the crystal grains are gradually filled, and the molecular sieve crystal grains are crosslinked and compacted to form the compact molecular sieve film.
Example 2
The preparation method of the silicalite-1 molecular sieve membrane with the b-axis orientation comprises the following steps:
(1) preparing molecular sieve crystal grains: TEOS, TPAOH and H2O is according to TEOS: TPAOH: h2O-30: 10: 1600, stirring at room temperature for 24h to obtain milk-like translucent gel A, the mass of the obtained gel A is 30 g. Slowly pouring the gel A into a 50mL polytetrafluoroethylene lining, covering and sealing, placing in a 150 ℃ oven, and statically crystallizing for 5 hours to carry out first hydrothermal crystallization. After the first hydrothermal crystallization is finished, the lining is quickly taken out and put into cold water, and then the obtained product is washed for a plurality of times by distilled water and 0.1mol/L ammonia water respectively. Drying the washed product in an oven at 110 ℃ overnight to obtain silicalite-1 molecular sieve grains.
(2) Modification of molecular sieve crystal grains: dispersing silicalite-1 molecular sieve grains in an ethanol solution, stirring at room temperature for 60 hours to prepare a suspension with the concentration of the molecular sieve grains being 0.3 wt%, and obtaining the modified molecular sieve grains.
(3) Assembling a molecular sieve crystal layer by liquid level vortex lifting: and placing the open container on a magnetic stirrer, adding a piece of clean magneton and deionized water with the volume of 50% of the container into the open container, starting the magnetic stirrer, and setting the rotating speed to be 360r/min to generate stable vortex in the open container. Dropping the modified molecular sieve crystal grains onto the vortex liquid level by using an injector, stopping dropping the modified molecular sieve crystal grains after the molecular sieve crystal grain layer on the vortex liquid level is compact, reducing the rotating speed of a magnetic stirrer until stirring is stopped, immersing the stainless steel carrier by using a lifting machine after the vortex liquid level is reduced to a horizontal plane, pulling out the stainless steel carrier at the speed of 1000 mu m/s, and drying the stainless steel carrier in a drying oven at the temperature of 90 ℃ for 3 hours to obtain the stainless steel carrier loaded with the silicalite-1 molecular sieve crystal grain layer.
(4) Preparing an oriented molecular sieve membrane: TEOS, dimer-TPABr, KOH and H2O is according to TEOS: dimer-TPABr: KOH: h2O-90: 20: 60: 20000, stirring at room temperature for 5h to obtain milk-like translucent gel B with a mass of 30 g.
And (3) contacting the gel B with a stainless steel carrier carrying a silicalite-1 molecular sieve crystal grain layer, horizontally placing the carrier, contacting the molecular sieve crystal grain layer with the gel B downwards, placing the gel B and the molecular sieve crystal grain layer in a hydrothermal crystallization reaction kettle, placing the hydrothermal crystallization reaction kettle in an oven at 180 ℃, and statically crystallizing for 2 hours to perform second hydrothermal crystallization. And after the second hydrothermal crystallization is finished, quickly taking out the lining, putting the lining into cold water, and washing the obtained product for several times by using distilled water and 0.1mol/L ammonia water respectively. The washed product was dried overnight in an oven at 80 ℃ to obtain a silicalite-1 molecular sieve membrane having b-axis orientation.
FIGS. 8 and 9 are an SEM photograph and an XRD photograph, respectively, of a crystalline layer of the silicalite-1 molecular sieve obtained in step (3) of example 2 of the present invention. As can be seen from fig. 8, when stainless steel is used as the carrier, the molecular sieve crystal layer is dense, almost every crystal grain is close to the substrate at the largest surface, the arrangement among the crystal grains is compact, the coverage and the continuity are high, and the molecular sieve crystal layer is in a single-layer arrangement, and is an ideal molecular sieve crystal layer. As can be seen from fig. 9, the molecular sieve grain layer has characteristic diffraction peaks of (020), (040), (080), and (0100), indicating that it is b-axis oriented, and the (501) peak other than b-axis oriented is weak, indicating that the grain layer has excellent orientation.
FIGS. 10 and 11 are an SEM photograph and an XRD photograph, respectively, of a b-axis oriented silicalite-1 molecular sieve membrane obtained in example 2 of the present invention. As can be seen from FIG. 10, when the time for the second hydrothermal crystallization was 3 hours, the continuity of the b-axis oriented Sicalate-1 molecular sieve film was good, and the surface was flat, dense and defect-free. As can be seen from fig. 11, the characteristic peaks of (020), (040), (060), (080) appeared in the XRD patterns at θ ═ 8.86, 17.80, 26.88, and 36.10, indicating that the prepared Sicalite-1 molecular sieve membrane has a high degree of b-axis orientation.
Example 3
The preparation method of the a, c-axis oriented silicalite-1 molecular sieve membrane comprises the following steps:
(1) preparing molecular sieve crystal grains: TEOS, TPAOH and H2O is according to TEOS: TPAOH: h2O25: 6: 1450, stirring at room temperature for 24h to obtain milk-like translucent gel A with a mass of 20 g. Slowly pouring the gel A into a 50mL polytetrafluoroethylene lining, covering and sealing, placing in a 165 ℃ oven, and statically crystallizing for 2 hours to carry out first hydrothermal crystallization. After the first hydrothermal crystallization is finished, the lining is quickly taken out and put into cold water, and then the obtained product is washed for a plurality of times by distilled water and 0.1mol/L ammonia water respectively. Drying the washed product in an oven at 110 ℃ overnight to obtain silicalite-1 molecular sieve grains.
(2) Modification of molecular sieve crystal grains: dispersing silicalite-1 molecular sieve grains in a n-butyl alcohol solution, stirring at room temperature for 48 hours to prepare a suspension with the concentration of the molecular sieve grains being 0.2 wt%, and obtaining the modified molecular sieve grains.
(3) Assembling a molecular sieve crystal layer by liquid level vortex lifting: and placing the open container on a magnetic stirrer, adding a piece of clean magneton and deionized water with the volume of 50% of the container into the open container, starting the magnetic stirrer, and setting the rotating speed to be 300r/min to generate stable vortex in the open container. Dropping the modified molecular sieve crystal grains onto the vortex liquid level by using an injector, stopping dropping the modified molecular sieve crystal grains after the molecular sieve crystal grain layer on the vortex liquid level is compact, reducing the rotating speed of a magnetic stirrer until stirring is stopped, immersing the porous alumina carrier by using a lifting machine after the vortex liquid level is reduced to a horizontal plane, pulling out the porous alumina carrier at the speed of 3000 mu m/s, and drying the porous alumina carrier in a drying oven at the temperature of 100 ℃ for 2 hours to obtain the porous alumina carrier loaded with the silicalite-1 molecular sieve crystal grain layer.
(4) Preparing an oriented molecular sieve membrane: TEOS, dimer-TPABr, KOH and H2O is according to TEOS: dimer-TPABr: KOH: h2O80: 15: 50: 19500 mixing at room temperature under stirringStirring for 5h to obtain milky translucent gel B, the mass of which is 30 g.
And (3) contacting the gel B with a stainless steel carrier carrying a silicalite-1 molecular sieve crystal grain layer, horizontally placing the carrier, contacting the molecular sieve crystal grain layer with the gel B downwards, placing the gel B and the molecular sieve crystal grain layer in a hydrothermal crystallization reaction kettle, placing the hydrothermal crystallization reaction kettle in an oven at 175 ℃, and statically crystallizing for 3 hours to perform second hydrothermal crystallization. And after the second hydrothermal crystallization is finished, quickly taking out the lining, putting the lining into cold water, and washing the obtained product for several times by using distilled water and 0.1mol/L ammonia water respectively. The washed product was dried overnight in an oven at 80 ℃ to obtain an a, c-axis oriented silicalite-1 molecular sieve membrane.
Comparative example 1
An a, c-axis oriented silicalite-1 molecular sieve membrane was prepared, which differed from example 3 only in that the time for the second hydrothermal crystallization was 1 h.
FIG. 12 is an SEM picture of the silicalite-1 molecular sieve grain layer obtained in step (3) of example 3 of the present invention. As can be seen from fig. 12, the crystal grains are arranged in series, are densely ordered, are substantially a single layer, and are ideal crystal grain layers.
FIGS. 13 and 14 are SEM pictures of the a, c-axis oriented silicalite-1 molecular sieve membrane obtained in example 3 of the present invention and SEM pictures of the a, c-axis oriented silicalite-1 molecular sieve membrane obtained in comparative example 1, respectively.
Comparing fig. 13 and 14, it can be seen that the silicalite-1 molecular sieve membrane exhibits significant advantages in the directions of the a and c axes as the time for the second hydrothermal crystallization is prolonged. After crystallization for 3h, the molecular sieve crystals become willow-leaf shaped, and the orientation of the a and c axes can be judged.
FIG. 15 is an XRD pattern of an a, c-axis oriented silicalite-1 molecular sieve membrane obtained in example 3 of the present invention and an a, c-axis oriented silicalite-1 molecular sieve membrane obtained in comparative example 1. As can be seen from fig. 15, as the second hydrothermal crystallization time was prolonged, the diffraction peaks of the (101), (002), (102), (103) and (104) crystal planes were enhanced, and when the crystallization was carried out for 3 hours, the molecular sieve film had good a, c-axis orientation.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A method for preparing an oriented molecular sieve membrane by using a liquid level vortex pulling technology is characterized by comprising the following steps:
(1) preparing molecular sieve crystal grains: mixing and stirring a silicon source, a template agent a and water to prepare gel A, and carrying out first hydrothermal crystallization on the gel A to prepare molecular sieve crystal grains;
(2) modification of molecular sieve crystal grains: dispersing the molecular sieve crystal grains in a dispersing agent to prepare a suspension, and stirring at room temperature to complete modification;
(3) assembling a molecular sieve crystal layer by liquid level vortex lifting: opening a magnetic stirrer to form a vortex liquid level, dropwise adding the modified molecular sieve crystal grains onto the vortex liquid level, stopping dropwise adding after a molecular sieve crystal grain layer on the vortex liquid level is compact, reducing the rotating speed of the magnetic stirrer until the dripping is stopped, immersing and pulling out the carrier after the vortex liquid level is reduced to a horizontal plane, and drying to obtain the carrier loaded with the molecular sieve crystal grain layer;
(4) preparing an oriented molecular sieve membrane: and (3) contacting the carrier carrying the molecular sieve crystal grain layer with gel B prepared by mixing a silicon source, a template agent B, KOH and water, and carrying out second hydrothermal crystallization to obtain the oriented molecular sieve membrane.
2. The method for preparing an oriented molecular sieve membrane by using the liquid level vortex pulling technology as claimed in claim 1, wherein the silicon source in step (1) is TEOS, and the template a is TPAOH.
3. The method for preparing the oriented molecular sieve membrane by using the liquid level vortex pulling technology as claimed in claim 1, wherein the first hydrothermal crystallization time in the step (1) is 2-5 h, and the temperature is 150-165 ℃.
4. The method for preparing the oriented molecular sieve membrane by using the liquid level vortex pulling technology as claimed in claim 1, wherein the dispersant in the step (2) is an alcohol solution.
5. The method for preparing an oriented molecular sieve membrane by using a liquid level vortex pulling technology as claimed in claim 1, wherein the concentration of the suspension in the step (2) is 0.1-0.3 wt%, and the stirring time is 48-60 h.
6. The method for preparing the oriented molecular sieve membrane by using the liquid level vortex pulling technology as claimed in claim 1, wherein the rotating speed of the magnetic stirrer in the step (3) is 300-400 r/min.
7. The method for preparing the oriented molecular sieve membrane by using the liquid level vortex pulling technology as claimed in claim 1, wherein the carrier pulling speed in the step (3) is 1-3000 μm/s.
8. The method for preparing an oriented molecular sieve membrane by using the liquid level vortex pulling technology as claimed in claim 1, wherein the silicon source is TEOS and the template b is dimer-TPABr in the step (4).
9. The method for preparing the oriented molecular sieve membrane by using the liquid level vortex pulling technology as claimed in claim 1, wherein the contact mode in the step (4) is as follows: the carrier carrying the molecular sieve grain layer is placed horizontally, and the molecular sieve grain layer contacts the gel B downwards.
10. The method for preparing the oriented molecular sieve membrane by using the liquid level vortex pulling technology as claimed in claim 1, wherein the second hydrothermal crystallization time in the step (4) is 2-3 h, and the temperature is 170-180 ℃.
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CN105727757A (en) * 2016-03-18 2016-07-06 宁夏大学 Preparation method of orientation LTL type molecular sieving membrane for gas separation
CN109569316A (en) * 2018-12-05 2019-04-05 广西大学 A kind of preparation method of Silicalite-1 molecular screen membrane

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101497067A (en) * 2009-01-16 2009-08-05 北京航空航天大学 Preparation method for assembling large-area ordered microsphere template by liquid level swirl method
CN101544379A (en) * 2009-04-30 2009-09-30 浙江大学 Method for synthesizing molecular sieve membrane by dip coating-rubbing crystal-coating method
WO2012010069A1 (en) * 2010-07-19 2012-01-26 大连理工大学 Synthesis method of naa zeolite molecular sieve membrane on macropore carrier
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