Synthesis method and application of Ni@S-1 molecular sieve membrane

Abstract

This invention discloses a method for synthesizing Ni@S-1 molecular sieve membranes and their applications. The synthesis method includes the following steps: First, a silicon source, a nickel metal complex, an organic template agent, and a solvent are mixed and reacted to obtain Ni@S-1 seed crystals. Then, these seed crystals are dispersed in a dispersant and subjected to an impregnation-pulling treatment on an alumina substrate. After drying, a Ni@S-1 molecular sieve membrane seed layer is obtained. Next, a silicon source, an organic template agent, and a solvent are mixed and aged to obtain a secondary growth solution. The Ni@S-1 molecular sieve membrane seed layer is then immersed in the preheated secondary growth solution for hydrothermal secondary growth. Finally, the membrane is dried, calcined, and reduced to obtain the final product. This synthesis method is simple, has a short cycle time, and produces a highly compact Ni@S-1 molecular sieve membrane with H0H-oriented molecular sieve crystals, showing broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve membrane synthesis technology, and in particular to a method for synthesizing Ni@S-1 molecular sieve membranes and their applications. Background Technology

[0002] Zeolite molecular sieve membranes are a new type of inorganic membrane material. Due to their regular pore structure, which is comparable in size to common gas and solvent molecules, as well as their advantages such as high temperature resistance and chemical corrosion resistance, they are widely used in chemical sensors, membrane catalysis, pervaporation separation, gas separation, and environmental protection.

[0003] Among various zeolite molecular sieve membranes, MFI zeolite molecular sieve membranes have attracted much attention from researchers due to their unique advantages, such as uniform pores that facilitate molecular-level sieving and enable cation exchange, as well as adjustable pore size, hydrophilicity / hydrophobicity, and acidity / basicity. However, in various applications of zeolite molecular sieve membranes, while utilizing the molecular sieving mechanism of zeolites can significantly enhance separation selectivity, precise separation remains an unsolved challenge. For example, it is very difficult to separate ethane and ethylene, whose molecular sizes differ by only about 0.053 nm, solely through physical sieving. Furthermore, for many industrial applications, effectively removing alkyne impurities used in the production of polymer-grade lower olefins is an important and challenging goal. Chai et al. introduced a strategy that amplifies Ni in Ni@FAU by confining atomically dispersed Ni(II) sites within the pores of FAU zeolite. 2+ The difference in binding ability between alkynes and alkenes was investigated. Utilizing the strong electrostatic attraction between divalent metal cations and alkynes, Ni@FAU exhibited a significant adsorption capacity for alkynes, effectively separating mixtures such as acetylene / ethylene and propyne / propylene, demonstrating the possibility and potential of constructing chemical separation centers in zeolite molecular sieves for adsorption separation. Cheng et al. reported a high-performance material that successfully distinguished ethylene and ethane through molecular recognition and sieving capabilities: by uniformly confining the metal within interlayer channels of graphene oxide with an average height of 10.44 nm, the transition metal cation Mg... 2+ Ag + Ni 2+ Pairing with ethylene anions to achieve high dissociation activity, the membrane forms a reversible complex with ethylene. This membrane material combines size sieving effects with molecular recognition capabilities for ethylene, stimulating the selective transport of ethylene over ethane, further demonstrating the importance of constructing chemical separation centers within the membrane material. Therefore, for zeolite molecular sieve membranes, the challenge of precise separation lies in the construction of efficient separation centers, and these centers must be chemically-based.

[0004] Among related technologies, the most commonly used methods for preparing zeolite molecular sieve membranes include in-situ crystallization and hydrothermal secondary growth. In-situ growth is the most traditional method, involving placing the support directly in the synthesis solution and synthesizing the molecular sieve membrane under autogenous pressure. It is the earliest and simplest method for molecular sieve membrane synthesis. Although the preparation process is simple, this method has high requirements for the support, produces membranes with many defects, and is difficult to produce oriented molecular sieve membranes. In contrast, the secondary growth method divides membrane preparation into two steps: crystal nucleation and secondary crystal growth. It can produce molecular sieves with better orientation, but the preparation process is complex, time-consuming, and often involves the formation of twins during the secondary growth process.

[0005] Therefore, there is an urgent need to find a new method for synthesizing Ni@S-1 molecular sieve membranes, which can produce Ni@S-1 molecular sieve membranes with H0H orientation, high density, and ideal molecular sieve crystal intergrowth. Summary of the Invention

[0006] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a method for synthesizing Ni@S-1 molecular sieve membranes. The synthesis method of Ni@S-1 molecular sieve membranes is simple and has a short cycle time. The Ni@S-1 molecular sieve membranes obtained have high density and ideal molecular sieve crystal intergrowth. Moreover, the molecular sieve crystals are arranged in an H0H orientation, which can reduce energy loss and improve separation efficiency during molecular transport compared to a random orientation structure.

[0007] The present invention also proposes a Ni@S-1 molecular sieve membrane.

[0008] This invention also proposes a method for synthesizing Ni@S-1 molecular sieve membranes and its application in the preparation of molecular sieve membranes.

[0009] In a first aspect, the present invention provides a method for synthesizing Ni@S-1 molecular sieve membranes, comprising the following steps:

[0010] S1. A silicon source, a nickel metal complex, an organic template agent, and a solvent are mixed, reacted, separated, and dried to obtain Ni@S-1 seed crystals.

[0011] S2. The Ni@S-1 seed crystals are dispersed in a dispersant, and impregnation and pulling treatment is performed on an alumina substrate. After drying, a Ni@S-1 molecular sieve membrane seed layer is obtained.

[0012] S3. The silicon source, organic template agent and solvent are mixed and aged to obtain a secondary growth solution. Then, the Ni@S-1 molecular sieve membrane seed layer is immersed in the preheated secondary growth solution for hydrothermal secondary growth. The product is separated, dried, calcined and reduced to obtain the final product.

[0013] The preparation method according to embodiments of the present invention has at least the following beneficial effects:

[0014] The synthesis method of Ni@S-1 molecular sieve membrane of the present invention is based on the secondary growth method. The preparation method is simple, has a short cycle, and is highly controllable and reproducible. It can easily, controllably and at low cost prepare HOH-oriented Ni@S-1 molecular sieve membranes with completeness, continuity, density and high crystallinity, which is suitable for industrial production.

[0015] In some embodiments of the present invention, the silicon source includes at least one of tetraethyl silicate, silica sol, sodium silicate, and silicon powder.

[0016] In some embodiments of the present invention, the ligand of the nickel metal complex is selected from at least one of tetraethylenepentamine (TEPA), diethylenetriamine (DETA), ethylenediamine (EDA), β-diketone (II), or ethylenediaminetetraacetic acid (EDTA).

[0017] Metallic nickel itself possesses excellent catalytic properties and can participate in chemical reactions during the formation of zeolite seed crystals, facilitating the adsorption, transformation, and separation of molecules, thereby improving separation efficiency and potentially enhancing reaction kinetics. Secondly, metallic nickel can serve as a separation center during the growth of zeolite seed crystals. Through its specific crystal structure and surface active sites, it exhibits high selectivity for the substances to be separated, promoting the adsorption and growth of target molecules on the seed crystal surface. Furthermore, the separation process can be precisely controlled by adjusting factors such as the content, morphology, and seed crystal preparation conditions of metallic nickel, making the separation process more controllable and efficient.

[0018] In some embodiments of the present invention, the organic template agent includes one or more of tetramethylammonium hydroxide solution, tetraethylammonium hydroxide solution, and tetrapropylammonium hydroxide solution.

[0019] In some embodiments of the present invention, the solvent includes water.

[0020] In some embodiments of the present invention, step S1 includes mixing by stirring. Preferably, the stirring temperature is 25°C to 37°C, and the time is 6 hours to 24 hours.

[0021] In some embodiments of the present invention, in step S1, the molar ratio of SiO2, organic template agent, nickel metal complex and solvent in the reaction system is 1:(0.1-0.5):(0.0001-0.05):(30-50).

[0022] In some preferred embodiments of the present invention, the molar ratio of SiO2, organic template agent, nickel metal complex and solvent in the reaction system is 1:(0.2-0.3):(0.0001-0.005):(30-40).

[0023] In some embodiments of the present invention, in step S1, the reaction temperature is 120°C to 150°C, preferably 130°C.

[0024] In some embodiments of the present invention, in step S1, the reaction time is 5h to 24h.

[0025] In some embodiments of the present invention, step S1 further includes washing after the reaction products are separated.

[0026] The washing process involves rinsing with deionized water until the water becomes neutral.

[0027] In some embodiments of the present invention, in step S2, the alumina is a sheet material. Preferably, the thickness of the sheet material is 0.5–2 mm.

[0028] In some embodiments of the present invention, step S2 further includes a pretreatment before the alumina is subjected to the impregnation and lifting treatment. Preferably, the pretreatment refers to completely immersing the alumina substrate in a dispersant for 24–48 hours.

[0029] In some embodiments of the present invention, in step S2, the speed of the immersion lifting process is 1000 μm / s to 6000 μm / s.

[0030] In some embodiments of the present invention, the immersion time for the immersion lifting treatment is 5 to 30 seconds.

[0031] In some embodiments of the present invention, the dwell time of the immersion lifting treatment is 30 to 120 seconds.

[0032] In some embodiments of the present invention, the number of dip-lifting treatments is 10 to 50. Preferably, the number of dip-lifting treatments is 20 to 40.

[0033] In some embodiments of the present invention, in step S3, the dispersant comprises deionized water or an alcohol. Preferably, the alcohol comprises anhydrous ethanol or sec-butanol.

[0034] In some embodiments of the present invention, in step S3, the mass percentage of the Ni@S-1 seed crystal to the dispersant is 0.4:10-30, preferably 0.4:15-25.

[0035] In some embodiments of the present invention, in step S3, the molar ratio of SiO2, organic template agent and solvent in the reaction system is (1-10):1:(500-1000).

[0036] In some embodiments of the present invention, in step S3, the aging treatment refers to stirring the mixture under certain conditions until the solution is clear and then letting it stand for later use.

[0037] In some embodiments of the present invention, in step S3, the temperature of the aging treatment is 25 to 37°C.

[0038] In some embodiments of the present invention, in step S3, the aging treatment time is 1 to 12 hours.

[0039] In some embodiments of the present invention, the temperature of the hydrothermal secondary growth is 150°C to 180°C; preferably 160°C to 170°C.

[0040] In some embodiments of the present invention, the hydrothermal secondary growth time is 10h to 18h. Preferably, the hydrothermal secondary growth time is 10h to 12h.

[0041] In some embodiments of the present invention, in step S4, the calcination temperature is 300-500°C and the time is 5-12 hours.

[0042] In some embodiments of the present invention, the calcination atmosphere is an air atmosphere.

[0043] In some embodiments of the present invention, the temperature of the reduction treatment is 300°C to 550°C; preferably, the temperature of the reduction treatment is 300°C to 400°C.

[0044] In some embodiments of the present invention, the atmosphere for the reduction treatment is a nitrogen-hydrogen mixed atmosphere.

[0045] In a second aspect, the present invention provides a Ni@S-1 molecular sieve membrane, which is prepared by the synthesis method described in any one of the first aspects.

[0046] The Ni@S-1 molecular sieve membrane according to embodiments of the present invention has at least the following beneficial effects:

[0047] (1) The molecular sieve membrane of the present invention is composed of an alumina substrate and a molecular sieve coating layer, and the molecular sieve coating layer is formed by stacking micron-sized "coffin-like" structures.

[0048] (2) The Ni@S-1 molecular sieve membrane prepared by the method of this invention has high density and ideal molecular sieve crystal intergrowth. Furthermore, its molecular sieve crystals are arranged in an H0H orientation. Since the molecular sieve channels in the H0H-oriented molecular sieve membrane are parallel to the direction of gas or liquid molecule movement, they can provide more direct transport channels. Moreover, the sinusoidal channels (0.51 × 0.55 nm) in the H0H direction are smaller than the straight channels (0.53 × 0.56 nm) in the b-axis direction, exhibiting better pore size sieving potential. Therefore, this helps improve the selectivity and permeability of the molecular sieve membrane. In addition, because the molecular sieve membrane with an H0H orientation structure is more ordered and stable than the randomly oriented molecular sieve membrane, it can provide more effective molecular sieving during the separation of gas or liquid molecules, and can reduce energy loss and improve transport efficiency during molecular transport, thereby reducing energy consumption.

[0049] In some embodiments of the present invention, the molecular sieve coating layer of the Ni@S-1 molecular sieve membrane is formed by stacking micron-sized "coffin-shaped" all-silicon molecular sieves.

[0050] A third aspect of the present invention provides the application of the method for synthesizing Ni@S-1 molecular sieve membranes as described in any one of the first aspects in the preparation of molecular sieve membranes.

[0051] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0052] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0053] Figure 1 This is a flowchart illustrating the preparation process of the Ni@S-1 molecular sieve membrane of the present invention.

[0054] Figure 2 The images show the X-ray diffraction patterns of the Ni@S-1 molecular sieve membranes prepared in Examples 1-3 of this invention.

[0055] Figure 3 This is a scanning electron microscope image of the Ni@S-1 molecular sieve membrane prepared in Example 1 of the present invention.

[0056] Figure 4 This is a scanning electron microscope image of the Ni@S-1 molecular sieve membrane prepared in Example 2 of the present invention.

[0057] Figure 5 This is a scanning electron microscope image of the Ni@S-1 molecular sieve membrane prepared in Example 3 of the present invention.

[0058] Figure 6This is a scanning electron microscope image of the Ni@S-1 molecular sieve membrane prepared in Comparative Example 1 of this invention.

[0059] Figure 7 This is a scanning electron microscope image of the Ni@S-1 molecular sieve membrane prepared in Comparative Example 2 of this invention.

[0060] Figure 8 This is a scanning electron microscope image of the Ni@S-1 molecular sieve membrane prepared in Comparative Example 3 of this invention.

[0061] Figure 9 This is a scanning electron microscope image of the Ni@S-1 molecular sieve membrane prepared in Comparative Example 4 of this invention.

[0062] Figure 10 This is a scanning electron microscope image of the Ni@S-1 molecular sieve membrane prepared in Comparative Example 5 of this invention. Detailed Implementation

[0063] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0064] The terms "preferred," "more preferably," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0065] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0066] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0067] Unless otherwise specified, "about" in this invention means that the allowable error is within ±2%.

[0068] Unless otherwise specified, "room temperature" in this invention means 25℃~37℃.

[0069] In the embodiments of the present invention, the substrate used to synthesize the molecular sieve membrane is alumina, which has a diameter of about 18 mm and a thickness of about 1 mm. Before use, the alumina substrate is ultrasonically washed with ethanol and sec-butanol and then dried for later use.

[0070] In an embodiment of the present invention, the nickel complex solution is Ni-TEPA, which is a Ni-TEPA complex solution obtained by mixing nickel nitrate hexahydrate with the complexing agent tetraethylenepentamine.

[0071] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0072] Inventive concept

[0073] This invention provides a method for preparing HOH-oriented Ni@S-1 molecular sieve membranes, the specific process of which is as follows: Figure 1 As shown, the process includes: first, a silicon source, a nickel metal complex solution, and an organic template are subjected to a crystallization reaction to obtain all-silicon molecular sieve seed crystals encapsulating the metal; then, the seed crystals are mixed with a dispersant, and an alumina substrate and the seed crystal solution are placed together in an immersion-pulling device to obtain a molecular sieve membrane seed layer; next, the molecular sieve membrane seed layer is vertically and completely immersed in an ultra-dilute secondary growth solution for a crystallization reaction; after the reaction, it is removed, washed with deionized water, and calcined to obtain an S-1 molecular sieve membrane with a specific orientation encapsulating the metal. This invention, through a hydrothermal secondary growth method, can simply, controllably, and cost-effectively prepare HOH-oriented Ni@S-1 molecular sieve membranes with completeness, continuity, density, and high crystallinity. The synthesis of this molecular sieve membrane has high reproducibility and is suitable for industrial scale-up.

[0074] Example 1

[0075] This embodiment provides a method for preparing an HOH-oriented Ni@S-1 molecular sieve membrane, which follows the same procedure as in Example 1, except that the number of dip-coating cycles is changed. Specifically, the method includes the following steps:

[0076] S1. Add 5.5g of 40wt% tetrapropylammonium hydroxide solution and 5g of nickel complex solution to 20g of deionized water, and slowly add 8.32g of tetraethyl silicate dropwise while stirring. Stir at room temperature for 9h to obtain a clear Ni@S-1 seed sol, wherein the molar ratio of SiO2:tetrapropylammonium hydroxide:water:nickel complex is 1:0.27:34.72:0.000877.

[0077] S2. Transfer the clarified seed solution to the reaction vessel, heat the reaction vessel to 130°C and maintain it for 12 hours. After the reaction vessel cools to room temperature, wash with deionized water, centrifuge and dry to obtain Ni@S-1 seed powder.

[0078] S3. Add 0.4g of seed crystal powder to 20g of sec-butanol and stir at room temperature for 12h to obtain seed crystal solution. Place the pretreated alumina substrate and seed crystal solution together in an immersion and pulling device. The immersion and pulling speed is set to 1500μm / s, the immersion time is 10s, the residence time is 60s, the number of cycles is 40, and after drying, Ni@S-1 molecular sieve membrane seed layer is obtained.

[0079] S4. Add 0.875g of 40wt% tetrapropylammonium hydroxide solution to 30g of deionized water, stir at room temperature for 1h, then slowly add 1.735g of tetraethyl silicate dropwise while stirring, stir at room temperature for 3h, and let stand for later use to obtain ultra-dilute secondary growth solution.

[0080] S5. Transfer the ultra-dilute secondary growth solution to the reactor, heat the reactor to 160℃, maintain for 2 hours, then quickly remove the preheated ultra-dilute secondary growth solution and centrifuge. Transfer the supernatant obtained after centrifugation back to the reactor. Vertically immerse the Ni@S-1 molecular sieve membrane seed layer in the preheated and centrifuged ultra-dilute secondary growth solution. Heat the reactor to 160℃, maintain for 12 hours, then remove it, wash with deionized water until neutral, dry, calcine with dry air at 400℃ for 6 hours, and then reduce with a nitrogen-hydrogen mixture at 350℃ for 3 hours to obtain the Ni@S-1 molecular sieve membrane.

[0081] The obtained Ni@S-1 molecular sieve membrane was subjected to X-ray diffraction, and the results are as follows: Figure 2As shown, the 2θ (unit: °) of the characteristic peaks are: 7.97±0.2; 8.82±0.2; 23.08±0.2; 23.92±0.2; 24.41±0.2, indicating that the molecular sieve crystals constituting the molecular sieve membrane have an S-1 structure. Further observation of the Ni@S-1 molecular sieve membrane structure using scanning electron microscopy yielded the following results: Figure 3 As shown, the Ni@S-1 molecular sieve membrane prepared by this method has high density, ideal molecular sieve crystal intergrowth, and the molecular sieve crystals are arranged in an H0H orientation.

[0082] Example 2

[0083] This embodiment provides a method for preparing an HOH-oriented Ni@S-1 molecular sieve membrane, following the same procedures as in Example 1, except that the synthesis temperature of the Ni@S-1 molecular sieve membrane in step S5 is changed. Specifically, the method includes the following steps:

[0084] S1. Add 5.5g of 40wt% tetrapropylammonium hydroxide solution and 5g of nickel complex solution to 20g of deionized water, and slowly add 8.32g of tetraethyl silicate dropwise while stirring. Stir at room temperature for 9h to obtain a clear Ni@S-1 seed sol, wherein the molar ratio of SiO2:tetrapropylammonium hydroxide:water:nickel complex is 1:0.27:34.72:0.000877.

[0085] S2. Transfer the clarified seed solution to the reaction vessel, heat the reaction vessel to 130°C and maintain it for 12 hours. After the reaction vessel cools to room temperature, wash with deionized water, centrifuge and dry to obtain Ni@S-1 seed powder.

[0086] S3. Add 0.4g of seed crystal powder to 20g of sec-butanol and stir at room temperature for 12h to obtain seed crystal solution. Place the pretreated alumina substrate and seed crystal solution together in an immersion and pulling device. The immersion and pulling speed is set to 1500μm / s, the immersion time is 10s, the residence time is 60s, the number of cycles is 40, and after drying, Ni@S-1 molecular sieve membrane seed layer is obtained.

[0087] S4. Add 0.875g of 40wt% tetrapropylammonium hydroxide solution to 30g of deionized water, stir at room temperature for 1h, then slowly add 1.735g of tetraethyl silicate dropwise while stirring, stir at room temperature for 3h, and let stand for later use to obtain ultra-dilute secondary growth solution.

[0088] S5. Transfer the ultra-dilute secondary growth solution to the reactor, heat the reactor to 150°C, maintain for 2 hours, then quickly remove the preheated ultra-dilute secondary growth solution and centrifuge. Transfer the supernatant obtained after centrifugation back to the reactor. Vertically immerse the Ni@S-1 molecular sieve membrane seed layer in the preheated and centrifuged ultra-dilute secondary growth solution. Heat the reactor to 150°C, maintain for 12 hours, then remove it, wash with deionized water until neutral, dry, calcine with dry air at 400°C for 6 hours, and then reduce with a nitrogen-hydrogen mixture at 350°C for 3 hours to obtain the Ni@S-1 molecular sieve membrane.

[0089] The obtained Ni@S-1 molecular sieve membrane was subjected to X-ray diffraction, and the results are as follows: Figure 2 As shown in Example 2, the structure of its Ni@S-1 molecular sieve membrane was further observed using scanning electron microscopy, and the results are as follows. Figure 4 As shown, the Ni@S-1 molecular sieve membrane prepared by this method has high density, ideal molecular sieve crystal intergrowth, and the molecular sieve crystals are arranged in an H0H orientation.

[0090] Example 3

[0091] This embodiment provides a method for preparing an HOH-oriented Ni@S-1 molecular sieve membrane, following the same procedures as in Example 1, except that the synthesis temperature of the Ni@S-1 molecular sieve membrane in step S5 is changed. Specifically, the method includes the following steps:

[0092] S1. Add 5.5g of 40wt% tetrapropylammonium hydroxide solution and 5g of nickel complex solution to 20g of deionized water, and slowly add 8.32g of tetraethyl silicate dropwise while stirring. Stir at room temperature for 9h to obtain a clear Ni@S-1 seed sol, wherein the molar ratio of SiO2:tetrapropylammonium hydroxide:water:nickel complex is 1:0.27:34.72:0.000877.

[0093] S2. Transfer the clarified seed solution to the reaction vessel, heat the reaction vessel to 130°C and maintain it for 12 hours. After the reaction vessel cools to room temperature, wash with deionized water, centrifuge and dry to obtain Ni@S-1 seed powder.

[0094] S3. Add 0.4g of seed crystal powder to 20g of sec-butanol and stir at room temperature for 12h to obtain seed crystal solution. Place the pretreated alumina substrate and seed crystal solution together in an immersion and pulling device. The immersion and pulling speed is set to 1500μm / s, the immersion time is 10s, the residence time is 60s, the number of cycles is 40, and after drying, Ni@S-1 molecular sieve membrane seed layer is obtained.

[0095] S4. Add 0.875g of 40wt% tetrapropylammonium hydroxide solution to 30g of deionized water, stir at room temperature for 1h, then slowly add 1.735g of tetraethyl silicate dropwise while stirring, stir at room temperature for 3h, and let stand for later use to obtain ultra-dilute secondary growth solution.

[0096] S5. Transfer the ultra-dilute secondary growth solution to the reactor, heat the reactor to 170℃, maintain for 2 hours, then quickly remove the preheated ultra-dilute secondary growth solution and centrifuge. Transfer the supernatant obtained after centrifugation back to the reactor. Vertically immerse the Ni@S-1 molecular sieve membrane seed layer in the preheated and centrifuged ultra-dilute secondary growth solution. Heat the reactor to 170℃, maintain for 12 hours, then remove it, wash with deionized water until neutral, dry, calcine with dry air at 400℃ for 6 hours, and then reduce with a nitrogen-hydrogen mixture at 350℃ for 3 hours to obtain the Ni@S-1 molecular sieve membrane.

[0097] The obtained Ni@S-1 molecular sieve membrane was subjected to X-ray diffraction, and the results are as follows: Figure 2 As shown in Example 3, the structure of its Ni@S-1 molecular sieve membrane was further observed using scanning electron microscopy, and the results are as follows. Figure 5 As shown, the Ni@S-1 molecular sieve membrane prepared by this method has high density, ideal molecular sieve crystal intergrowth, and the molecular sieve crystals are arranged in an H0H orientation.

[0098] Comparative Example 1

[0099] This comparative example provides a method for preparing Ni@S-1 molecular sieve membranes, following the same procedures as in Example 1, except that the preheating and aging time of the ultra-dilute secondary growth solution is changed. Specifically, the method includes the following steps:

[0100] S1. Add 5.5g of 40wt% tetrapropylammonium hydroxide solution and 5g of nickel complex solution to 20g of deionized water, and slowly add 8.32g of tetraethyl silicate dropwise while stirring. Stir at room temperature for 9h to obtain a clear Ni@S-1 seed sol, wherein the molar ratio of SiO2:tetrapropylammonium hydroxide:water:nickel complex is 1:0.27:34.72:0.000877.

[0101] S2. Transfer the clarified seed solution to the reaction vessel, heat the reaction vessel to 130°C and maintain it for 12 hours. After the reaction vessel cools to room temperature, wash with deionized water, centrifuge and dry to obtain Ni@S-1 seed powder.

[0102] S3. Add 0.4g of seed crystal powder to 20g of sec-butanol and stir at room temperature for 12h to obtain seed crystal solution. Place the pretreated alumina substrate and seed crystal solution together in an immersion and pulling device. The immersion and pulling speed is set to 1500μm / s, the immersion time is 10s, the residence time is 60s, the number of cycles is 40, and after drying, Ni@S-1 molecular sieve membrane seed layer is obtained.

[0103] S4. Add 0.875g of 40wt% tetrapropylammonium hydroxide solution to 30g of deionized water, stir at room temperature for 1h, then slowly add 1.735g of tetraethyl silicate dropwise while stirring, stir at room temperature for 3h, and let stand for later use to obtain ultra-dilute secondary growth solution.

[0104] S5. Transfer the ultra-dilute secondary growth solution to the reactor, heat the reactor to 160℃, maintain for 30 min, then quickly remove the preheated ultra-dilute secondary growth solution and centrifuge. Transfer the supernatant obtained after centrifugation back to the reactor. Vertically immerse the Ni@S-1 molecular sieve membrane seed layer in the preheated and centrifuged ultra-dilute secondary growth solution. Heat the reactor to 160℃, maintain for 12 h, then remove it, wash with deionized water until neutral, dry, calcine with dry air at 400℃ for 6 h, and then reduce with a nitrogen-hydrogen mixture at 350℃ for 3 h to obtain the final product.

[0105] The structure of its Ni@S-1 molecular sieve membrane was observed using scanning electron microscopy, and the results are as follows: Figure 6 As shown, crystals grow on the alumina substrate, but the density is poor. The ultra-dilute secondary growth solution after preheating and centrifugation can provide a favorable environment for subsequent crystal growth. However, the preheating time is not sufficient, resulting in poor intergrowth of crystals, which is not conducive to the formation of a dense molecular sieve membrane. This illustrates the necessity of the preheating and aging time of the ultra-dilute secondary growth solution for crystal growth and membrane density.

[0106] Comparative Example 2

[0107] This comparative example provides a method for preparing Ni@S-1 molecular sieve membranes, following the same procedures as in Example 1, except that the hydrothermal secondary growth temperature is changed. Specifically, the method includes the following steps:

[0108] S1. Add 5.5g of 40wt% tetrapropylammonium hydroxide solution and 5g of nickel complex solution to 20g of deionized water, and slowly add 8.32g of tetraethyl silicate dropwise while stirring. Stir at room temperature for 9h to obtain a clear Ni@S-1 seed sol, wherein the molar ratio of SiO2:tetrapropylammonium hydroxide:water:nickel complex is 1:0.27:34.72:0.000877.

[0109] S2. Transfer the clarified seed solution to the reaction vessel, heat the reaction vessel to 130°C and maintain it for 12 hours. After the reaction vessel cools to room temperature, wash with deionized water, centrifuge and dry to obtain Ni@S-1 seed powder.

[0110] S3. Add 0.4g of seed crystal powder to 20g of sec-butanol and stir at room temperature for 12h to obtain seed crystal solution. Place the pretreated alumina substrate and seed crystal solution together in an immersion and pulling device. The immersion and pulling speed is set to 1500μm / s, the immersion time is 10s, the residence time is 60s, the number of cycles is 40, and after drying, Ni@S-1 molecular sieve membrane seed layer is obtained.

[0111] S4. Add 0.875g of 40wt% tetrapropylammonium hydroxide solution to 30g of deionized water, stir at room temperature for 1h, then slowly add 1.735g of tetraethyl silicate dropwise while stirring, stir at room temperature for 3h, and let stand for later use to obtain ultra-dilute secondary growth solution.

[0112] S5. Transfer the ultra-dilute secondary growth solution to the reactor, heat the reactor to 140℃, maintain for 2 hours, then quickly remove the preheated ultra-dilute secondary growth solution and centrifuge. Transfer the supernatant obtained after centrifugation back to the reactor. Vertically immerse the Ni@S-1 molecular sieve membrane seed layer in the preheated and centrifuged ultra-dilute secondary growth solution. Heat the reactor to 140℃, maintain for 12 hours, then remove it, wash with deionized water until neutral, dry, calcine with dry air at 400℃ for 6 hours, and then reduce with a nitrogen-hydrogen mixture at 350℃ for 3 hours to obtain the final product.

[0113] The structure of its Ni@S-1 molecular sieve membrane was observed using scanning electron microscopy, and the results are as follows: Figure 7 As shown, crystals grow on the alumina substrate, but the density is poor. This indicates that the growth of seed crystals is blocked to a certain extent under low temperature conditions, making it difficult to obtain large and uniformly shaped grains. At the same time, it cannot guarantee the formation of a film. This illustrates the necessity of secondary growth temperature for film density.

[0114] Comparative Example 3

[0115] This comparative example provides a method for preparing Ni@S-1 molecular sieve membranes, following the same procedures as in Example 1, except that the hydrothermal secondary growth time is changed. Specifically, the method includes the following steps:

[0116] S1. Add 5.5g of 40wt% tetrapropylammonium hydroxide solution and 5g of nickel complex solution to 20g of deionized water, and slowly add 8.32g of tetraethyl silicate dropwise while stirring. Stir at room temperature for 9h to obtain a clear Ni@S-1 seed sol, wherein the molar ratio of SiO2:tetrapropylammonium hydroxide:water:nickel complex is 1:0.27:34.72:0.000877.

[0117] S2. Transfer the clarified seed solution to the reaction vessel, heat the reaction vessel to 130°C and maintain it for 12 hours. After the reaction vessel cools to room temperature, wash with deionized water, centrifuge and dry to obtain Ni@S-1 seed powder.

[0118] S3. Add 0.4g of seed crystal powder to 20g of sec-butanol and stir at room temperature for 12h to obtain seed crystal solution. Place the pretreated alumina substrate and seed crystal solution together in an immersion and pulling device. Set the immersion and pulling speed to 1500μm / s, the immersion time to 10s, the residence time to 60s, and the number of cycles to 30. After drying, obtain Ni@S-1 molecular sieve membrane seed layer.

[0119] S4. Add 0.875g of 40wt% tetrapropylammonium hydroxide solution to 30g of deionized water, stir at room temperature for 1h, then slowly add 1.735g of tetraethyl silicate dropwise while stirring, stir at room temperature for 3h, and let stand for later use to obtain ultra-dilute secondary growth solution.

[0120] S5. Transfer the ultra-dilute secondary growth solution to the reactor, heat the reactor to 160℃, maintain for 2 hours, then quickly remove the preheated ultra-dilute secondary growth solution and centrifuge. Transfer the supernatant obtained after centrifugation back to the reactor. Vertically immerse the Ni@S-1 molecular sieve membrane seed layer in the preheated and centrifuged ultra-dilute secondary growth solution. Heat the reactor to 160℃, maintain for 8 hours, then remove it, wash with deionized water until neutral, dry, calcine with dry air at 400℃ for 6 hours, and then reduce with a nitrogen-hydrogen mixture at 350℃ for 3 hours to obtain the final product.

[0121] The structure of its Ni@S-1 molecular sieve membrane was observed using scanning electron microscopy, and the results are as follows: Figure 8 As shown, crystals grow on the alumina substrate, but the density is poor. Under suitable crystallization temperature, crystals begin to grow as the crystallization time increases, but a large number of intergranular defects appear, indicating that 8 hours is insufficient for the crystals to form a film. Continuing to extend the synthesis time is expected to improve the intergranular defects. This shows the necessity of secondary growth time for the crystal growth shape, size and film density.

[0122] Comparative Example 4

[0123] This comparative example provides a method for preparing Ni@S-1 molecular sieve membranes, following the same procedures as in Example 1, except that the preheating step of the secondary growth solution is omitted. Specifically, the method includes the following steps:

[0124] S1. Add 5.5g of 40wt% tetrapropylammonium hydroxide solution and 5g of nickel complex solution to 20g of deionized water, and slowly add 8.32g of tetraethyl silicate dropwise while stirring. Stir at room temperature for 9h to obtain a clear Ni@S-1 seed sol, wherein the molar ratio of SiO2:tetrapropylammonium hydroxide:water:nickel complex is 1:0.27:34.72:0.000877.

[0125] S2. Transfer the clarified seed solution to the reaction vessel, heat the reaction vessel to 130°C and maintain it for 12 hours. After the reaction vessel cools to room temperature, wash with deionized water, centrifuge and dry to obtain Ni@S-1 seed powder.

[0126] S3. Add 0.4g of seed crystal powder to 20g of sec-butanol and stir at room temperature for 12h to obtain seed crystal solution. Place the pretreated alumina substrate and seed crystal solution together in an immersion and pulling device. Set the immersion and pulling speed to 1500μm / s, the immersion time to 10s, the residence time to 60s, and the number of cycles to 30. After drying, obtain Ni@S-1 molecular sieve membrane seed layer.

[0127] S4. Add 0.875g of 40wt% tetrapropylammonium hydroxide solution to 30g of deionized water, stir at room temperature for 1h, then slowly add 1.735g of tetraethyl silicate dropwise while stirring, stir at room temperature for 3h, and let stand for later use to obtain ultra-dilute secondary growth solution.

[0128] S5. Transfer the ultra-dilute secondary growth solution to the reactor. Vertically immerse the Ni@S-1 molecular sieve membrane seed layer in the ultra-dilute secondary growth solution. Heat the reactor to 160℃ and maintain for 12 hours. Remove the reactor, wash it with deionized water until neutral, dry it, calcine it with dry air at 400℃ for 6 hours, and then reduce it with a nitrogen-hydrogen mixture at 350℃ for 3 hours to obtain the final product.

[0129] The structure of its Ni@S-1 molecular sieve membrane was observed using scanning electron microscopy, and the results are as follows: Figure 9 As shown, crystals grow on the alumina substrate, but the density is poor. This is because the ultra-dilute secondary growth solution after preheating and centrifugation provides a favorable environment for subsequent crystal growth. Centrifugation of the preheated growth solution can effectively remove excess crystal nuclei, which is beneficial to suppressing the generation of twins and controlling the overall film thickness. Without the above operations, it is not conducive to the formation of a dense and thin molecular sieve film, indicating the necessity of preheating and aging treatment of ultra-dilute secondary growth solution for crystal growth and film density and thickness.

[0130] Comparative Example 5

[0131] This comparative example provides a method for preparing Ni@S-1 molecular sieve membranes, following the same procedures as in Example 1, except that the number of impregnation-lift cycles is changed. Specifically, the method includes the following steps:

[0132] S1. Add 5.5g of 40wt% tetrapropylammonium hydroxide solution and 5g of nickel complex solution to 20g of deionized water, and slowly add 8.32g of tetraethyl silicate dropwise while stirring. Stir at room temperature for 9h to obtain a clear Ni@S-1 seed sol, wherein the molar ratio of SiO2:tetrapropylammonium hydroxide:water:nickel complex is 1:0.27:34.72:0.000877.

[0133] S2. Transfer the clarified seed solution to the reaction vessel, heat the reaction vessel to 130°C and maintain it for 12 hours. After the reaction vessel cools to room temperature, wash with deionized water, centrifuge and dry to obtain Ni@S-1 seed powder.

[0134] S3. Add 0.4g of seed crystal powder to 20g of sec-butanol and stir at room temperature for 12h to obtain seed crystal solution. Place the pretreated alumina substrate and seed crystal solution together in an immersion and pulling device. The immersion and pulling speed is set to 1500μm / s, the immersion time is 10s, the residence time is 60s, the number of cycles is 40, and after drying, Ni@S-1 molecular sieve membrane seed layer is obtained.

[0135] S4. Add 0.875g of 40wt% tetrapropylammonium hydroxide solution to 30g of deionized water, stir at room temperature for 1h, then slowly add 1.735g of tetraethyl silicate dropwise while stirring, stir at room temperature for 3h, and let stand for later use to obtain ultra-dilute secondary growth solution.

[0136] S5. Transfer the ultra-dilute secondary growth solution to the reactor, heat the reactor to 160℃, maintain for 2 hours, then quickly remove the preheated ultra-dilute secondary growth solution and centrifuge. Transfer the supernatant obtained after centrifugation back to the reactor. Vertically immerse the Ni@S-1 molecular sieve membrane seed layer in the preheated and centrifuged ultra-dilute secondary growth solution. Heat the reactor to 160℃, maintain for 12 hours, then remove it, wash with deionized water until neutral, dry, and calcine with dry air at 400℃ for 9 hours to obtain the final product.

[0137] The structure of its Ni@S-1 molecular sieve membrane was observed using scanning electron microscopy, and the results are as follows: Figure 10 As shown, crystals grow on the alumina substrate, but the crystal stacking problem is serious, resulting in a large film thickness.

[0138] In summary, this invention provides a method for preparing a Ni@S-1 molecular sieve membrane with HOH orientation. The method can significantly shorten the preparation time, and the resulting molecular sieve membrane has good integrity, high density, and ideal molecular sieve crystal aggregation. The molecular sieve crystals are arranged in an HOH orientation, and the molecular sieve channels are parallel to the direction of gas or liquid molecule movement, which can provide a more direct transport channel, thereby improving selectivity and permeability.

[0139] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for synthesizing Ni@S-1 molecular sieve membranes, characterized in that, Includes the following steps: S1. A silicon source, a nickel metal complex, an organic template agent, and a solvent are mixed, reacted, separated, and dried to obtain Ni@S-1 seed crystals. S2. The Ni@S-1 seed crystals are dispersed in a dispersant, and impregnation and pulling treatment is performed on an alumina substrate. After drying, a Ni@S-1 molecular sieve membrane seed layer is obtained. S3. A secondary growth solution is obtained by mixing a silicon source, an organic template agent, and a solvent and then aging the mixture. The Ni@S-1 molecular sieve membrane seed layer is then immersed in the preheated secondary growth solution for hydrothermal secondary growth. The product is separated, dried, calcined, and reduced to obtain the final product. In step S1, the molar ratio of SiO2, organic template agent, nickel metal complex and solvent in the reaction system is 1:(0.1-0.5):(0.0001-0.05):(30-50). In step S3, the molar ratio of SiO2, organic template agent and solvent during the aging process is (1-10):1:(500-1000). The silicon source includes at least one of tetraethyl silicate, silica sol, sodium silicate, and silicon powder; the ligand of the nickel metal complex is selected from at least one of tetraethylenepentamine, diethylenetriamine, ethylenediamine, β-diketone, or ethylenediaminetetraacetic acid; the organic template agent includes one or more of tetramethylammonium hydroxide solution, tetraethylammonium hydroxide solution, and tetrapropylammonium hydroxide solution.

2. The synthesis method according to claim 1, characterized in that, The solvent includes water; And / or, the dispersant comprises deionized water or alcohol.

3. The synthesis method according to claim 2, characterized in that, In step S1, the molar ratio of SiO2, organic template agent, nickel metal complex and solvent in the reaction system is 1:(0.2-0.3):(0.0001-0.005):(30-40).

4. The synthesis method according to claim 1, characterized in that, In step S1, the reaction temperature is 120℃~150℃, and the reaction time is 5h~24h.

5. The synthesis method according to claim 1, characterized in that, In step S2, the speed of the immersion lifting treatment is 1000 μm / s to 6000 μm / s; And / or, the immersion time for the immersion lifting treatment is 5~30s; And / or, the dwell time of the immersion lifting treatment is 30~120s; And / or, the number of dip-lifting treatments is 10 to 50.

6. The synthesis method according to claim 1, characterized in that, In step S3, the aging treatment temperature is 25℃~37℃, and the time is 1~12h; And / or, the preheating temperature is 150℃~170℃; And / or, the temperature of the hydrothermal secondary growth is 150℃~180℃, and the time is 3h~18h.

7. The synthesis method according to any one of claims 1 to 6, characterized in that, In step S4, the calcination temperature is 300~500℃ and the time is 5~12h; And / or, the calcination atmosphere is a nitrogen-hydrogen mixed atmosphere.

8. A Ni@S-1 molecular sieve membrane, characterized in that, It is prepared by the synthesis method described in any one of claims 1 to 7.

9. The application of the method for synthesizing Ni@S-1 molecular sieve membrane as described in any one of claims 1 to 7 in the preparation of molecular sieve membranes.

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