A metal organic framework-molecular sieve composite material, a preparation method and application thereof

Abstract

This invention relates to a metal-organic framework-molecular sieve composite material, its preparation method, and its applications. The metal-organic framework-molecular sieve composite material has a core-shell structure, with the core layer comprising a molecular sieve and the shell layer comprising a metal-organic framework material. The molecular sieve includes a FAU-type molecular sieve. The pore size range of the metal-organic framework material is 2.8 Å to 3.2 Å. In this invention, the negatively charged framework and the balancing cations of the FAU-type molecular sieve can form a strong electric field, and N2 is adsorbed through a quadrupole-electrostatic interaction with the FAU-type molecular sieve, achieving N2 / O2 separation. The pore size range of the metal-organic framework material, 2.8 Å to 3.2 Å, matches the de Broglie wavelength of water molecules (approximately 3.0 Å) and triggers a kinetic quantum sieve effect, causing water molecules to diffuse and separate. The core-shell structure enables the diffusion separation of water in the shell layer and the adsorption of N2 in the core layer, ensuring the N2 / O2 separation capability of the FAU-type molecular sieve and preventing structural collapse, thus improving separation stability.

Description

Technical Field

[0001] This invention belongs to the field of gas separation materials, and relates to a molecular sieve material, particularly a metal-organic framework-molecular sieve composite material, its preparation method and application. Background Technology

[0002] In industrial gas separation applications such as air-to-nitrogen production and oxygen-enriched combustion, FAU-type molecular sieves are the core material for separating nitrogen (N2) and oxygen (O2). However, when the feed gas contains water vapor, such as when the humidity is >30%, the FAU-type molecular sieve will adsorb some water molecules, leading to framework hydrolysis, pore blockage, and even water-induced structural collapse, thereby reducing the separation performance by more than 50%.

[0003] There are currently two main solutions to this problem. One is a pre-installed desiccant drying device, but this solution will increase energy consumption by at least 30% and requires frequent replacement of the desiccant. The other is to use hydrophobic modified molecular sieves, but this will significantly reduce their adsorption performance and N2 / O2 separation capacity, or even reduce them irreversibly.

[0004] Metal-organic frameworks (MOFs) possess large specific surface areas, tunable pore sizes, and ease of functionalization, exhibiting excellent adsorption properties and promising broad application prospects in gas separation. CN106861634A discloses a metal-organic framework compound@mesoporous material composite material, its preparation method, and its applications. This material utilizes the promoting effect of mesoporous material pores on CO2 diffusion and the adsorption performance of the metal-organic framework compound on CO2 to achieve CO2 capture. Furthermore, the mesoporous material effectively mitigates the decomposition and denaturation of the metal-organic framework compound in flue gas environments, giving it excellent water resistance. However, it does not address the selective adsorption of water vapor in flue gas environments or the structural stability of the metal-organic framework compound under high humidity conditions. CN114259888A discloses a molecular sieve-metal-organic framework composite membrane, its preparation method and application. The molecular sieve-metal-organic framework composite membrane includes a support layer, a molecular sieve layer and a metal-organic framework layer stacked sequentially. The support layer provides support for the composite membrane to ensure its strength. The combination of the molecular sieve layer and the metal-organic framework layer improves the hydrophilicity and water vapor permeation efficiency of the composite membrane. The matching and combination of the two membrane layers improves the water vapor separation efficiency in the dehumidification process. However, it does not address the selective adsorption of water vapor in the mixed gas and the structural stability of the molecular sieve layer and the metal-organic framework layer under high humidity conditions.

[0005] Therefore, developing a novel metal-organic framework-molecular sieve composite material that ensures excellent N2 / O2 separation capability while also exhibiting good water vapor separation performance, and avoiding water-induced structural collapse of FAU-type molecular sieves due to water molecule adsorption, thereby improving their separation stability, is an urgent problem to be solved in the current field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a metal-organic framework-molecular sieve composite material, its preparation method, and its applications. The metal-organic framework-molecular sieve composite material provided by this invention utilizes the negatively charged framework of the FAU-type molecular sieve and the balanced cations to form a strong electric field. Based on the quadrupole moment difference between N2 and O2, N2 can preferentially adsorb through a strong quadrupole-electrostatic interaction with the cations / framework, thereby achieving N2 / O2 separation. The pore size range of the metal-organic framework material is 2.8 Å to 3.2 Å, and the de Broglie wavelength of water molecules is approximately 3.0 Å. Matching these two parameters triggers a kinetic quantum sieve effect, significantly improving the kinetic diffusion selectivity of water molecules and achieving highly efficient selective diffusion separation of water molecules. Furthermore, water molecule removal from the metal-organic framework material can be achieved simply by increasing the temperature. Constructing a core-shell structure enables shell-layer diffusion separation of water vapor and core-layer adsorption of nitrogen, ensuring excellent N2 / O2 separation capability while preventing water-induced structural collapse of the FAU-type molecular sieve, significantly improving its separation stability.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a metal-organic framework-molecular sieve composite material, wherein the metal-organic framework-molecular sieve composite material has a core-shell structure, the core layer includes a molecular sieve, and the shell layer includes a metal-organic framework material; the molecular sieve includes an FAU type molecular sieve; and the pore size range of the metal-organic framework material is 2.8 Å to 3.2 Å.

[0009] It should be noted that the pore size range of the metal-organic framework material is 2.8 Å to 3.2 Å, indicating that the minimum pore size of the metal-organic framework material is 2.8 Å and the maximum pore size is 3.2 Å. Specifically, the pore size of the metal-organic framework material can be 2.8 Å, 2.9 Å, 3.0 Å, 3.1 Å or 3.2 Å, etc.

[0010] The metal-organic framework-molecular sieve composite material provided by this invention utilizes the negatively charged framework and balanced cations of the FAU-type molecular sieve to form a strong electric field. Based on the quadrupole moment difference between N2 and O2, N2 can preferentially adsorb through a strong quadrupole-electrostatic interaction with the cations / framework, thereby achieving N2 / O2 separation. The pore size range of the metal-organic framework material is 2.8 Å to 3.2 Å, and the de Broglie wavelength of water molecules is approximately 3.0 Å. The matching of these two can trigger a kinetic quantum sieve effect, thereby significantly improving the kinetic diffusion selectivity of water molecules and achieving highly efficient selective diffusion separation of water molecules. Moreover, the removal of water molecules from the metal-organic framework material can be achieved simply by increasing the temperature. Constructing a core-shell structure enables the diffusion separation of water vapor in the shell layer and the adsorption of nitrogen in the core layer, which not only ensures excellent N2 / O2 separation capability but also avoids water-induced structural collapse of the FAU-type molecular sieve, significantly improving its separation stability.

[0011] Preferably, the mass of the metal-organic framework material is 10wt% to 15wt% of the mass of the molecular sieve, for example, it can be 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, or 15wt%.

[0012] This invention improves the separation selectivity and stability of the metal-organic framework-molecular sieve composite material by adjusting the mass of the metal-organic framework material to 10wt%~15wt% of the molecular sieve mass. If the mass of the metal-organic framework material is too high, although it is beneficial to enhance water adsorption and thus protect the structural stability of the FAU-type molecular sieve, it will reduce the effective mass of the FAU-type molecular sieve in the material, or cover / block some channels / pores of the FAU-type molecular sieve, thereby affecting the adsorption of nitrogen and the N2 / O2 separation selectivity. If the mass of the metal-organic framework material is too low, the shell formed by the metal-organic framework material is too thin, or even some of the FAU-type molecular sieve surface is exposed, causing water molecules to be simultaneously diffused and separated by the metal-organic framework material and adsorbed by the FAU-type molecular sieve. The water molecules adsorbed by the FAU-type molecular sieve are difficult to desorb by increasing the temperature, thus affecting the structural stability and separation stability of the FAU-type molecular sieve.

[0013] Preferably, the metal-organic framework-molecular sieve composite material further includes a binder.

[0014] Preferably, the adhesive is located inside the shell and / or between the core and the shell.

[0015] Preferably, the binder comprises any one or a combination of at least two of sodium carboxymethyl cellulose, hydroxypropyl cellulose, or polyvinyl alcohol. Typical but non-limiting combinations include combinations of sodium carboxymethyl cellulose and hydroxypropyl cellulose, combinations of hydroxypropyl cellulose and polyvinyl alcohol, combinations of sodium carboxymethyl cellulose and polyvinyl alcohol, and combinations of sodium carboxymethyl cellulose, hydroxypropyl cellulose, and polyvinyl alcohol.

[0016] Preferably, the mass of the binder is 1 wt% to 3 wt% of the total mass of the molecular sieve and the metal-organic framework material, for example, it can be 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt% or 3 wt%.

[0017] The binder in this invention does not participate in the adsorption of water molecules or the separation of N2 / O2; its main function is to shape the material and prevent pulverization. By controlling the mass of the binder to 1wt%~3wt% of the total mass of the molecular sieve and metal-organic framework material, this invention can further improve the N2 / O2 separation capacity and separation stability of the metal-organic framework-molecular sieve composite material. If the binder quality is too high, on the one hand, the binder will cover the channels / pores of the metal-organic framework material and the FAU molecular sieve, which will reduce the N2 / O2 separation capacity of the FAU molecular sieve and reduce the diffusion separation of water molecules by the metal-organic framework material. This will lead to the FAU molecular sieve adsorbing some water molecules and making it difficult to desorb them by raising the temperature, thus reducing the structural stability and separation stability of the FAU molecular sieve. On the other hand, since the binder does not participate in the adsorption of water molecules and the separation of N2 / O2, it will also reduce the adsorption capacity per unit mass of the metal-organic framework-molecular sieve composite material. If the binder quality is too low, the bonding force between the metal-organic framework material and the FAU molecular sieve will be weak, making molding difficult. In addition, the bonding force between the metal-organic framework shell layer and the molecular sieve core layer will be low, and both will easily detach. This will lead to some water molecules being adsorbed by the FAU molecular sieve and making it difficult to desorb them by raising the temperature, thus affecting the structural stability and separation stability of the FAU molecular sieve.

[0018] Preferably, the FAU type molecular sieve includes X-type molecular sieve and / or Y-type molecular sieve.

[0019] Preferably, the X-type molecular sieve includes LiX molecular sieve and / or NaX molecular sieve.

[0020] Preferably, the Y-type molecular sieve includes NaY molecular sieve.

[0021] Preferably, the pore size range of the FAU type molecular sieve is 7.0 Å to 8.0 Å.

[0022] It should be noted that the pore size range of FAU type molecular sieve is 7.0 Å to 8.0 Å, indicating that the minimum pore size of the FAU type molecular sieve is 7.0 Å and the maximum pore size is 8.0 Å. Specifically, the pore size of FAU type molecular sieve can be 7.0 Å, 7.2 Å, 7.4 Å, 7.5 Å, 7.6 Å, 7.8 Å or 8.0 Å, etc.

[0023] Preferably, the silica-alumina ratio of the FAU-type molecular sieve is 1 to 1.5, for example, it can be 1, 1.1, 1.2, 1.3, 1.4 or 1.5.

[0024] Preferably, the metal-organic framework material includes any one or a combination of at least two of MOF-303, CAU-10-H, or MIL-160. Typical but non-limiting combinations include a combination of MOF-303 and CAU-10-H, a combination of CAU-10-H and MIL-160, a combination of MOF-303 and MIL-160, and a combination of MOF-303, CAU-10-H, and MIL-160.

[0025] Preferably, the particle size range of the molecular sieve is 40 mesh to 80 mesh.

[0026] Preferably, the particle size range of the metal-organic framework material is 500 mesh to 1000 mesh.

[0027] Preferably, the particle size range of the metal-organic framework-molecular sieve composite material is 15 mesh to 20 mesh.

[0028] It should be noted that the particle size range of molecular sieves is 40 mesh to 80 mesh, indicating that the molecular sieve can pass through a 40 mesh sieve but not an 80 mesh sieve; the particle size range of metal-organic framework materials is 500 mesh to 1000 mesh, indicating that the metal-organic framework material can pass through a 500 mesh sieve but not a 1000 mesh sieve; and the particle size range of metal-organic framework-molecular sieve composite materials is 15 mesh to 20 mesh, indicating that the metal-organic framework-molecular sieve composite material can pass through a 15 mesh sieve but not a 20 mesh sieve.

[0029] In a second aspect, the present invention provides a method for preparing a metal-organic framework-molecular sieve composite material as described in the first aspect, comprising the following steps: mixing molecular sieves and metal-organic framework materials, adding a binder solution, and performing rotary granulation to obtain the metal-organic framework-molecular sieve composite material.

[0030] The preparation method provided by this invention is simple and easy to implement, and does not require high temperature, high pressure and toxic or harmful reagents.

[0031] Preferably, the preparation method further includes pretreatment of the molecular sieve.

[0032] Preferably, the pretreatment includes crushing, granulation and sieving performed sequentially.

[0033] Preferably, the sieving process includes passing the granulated molecular sieve through a 40-mesh sieve, collecting the undersize material, and then passing it through an 80-mesh sieve to collect the oversize material, thereby obtaining a 40-80 mesh molecular sieve.

[0034] Preferably, the mass fraction of the adhesive in the adhesive solution is 3wt% to 8wt%, for example, it can be 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, or 8wt%, etc.

[0035] Preferably, the solvent in the adhesive solution includes water.

[0036] Preferably, the adhesive solution is added by spraying.

[0037] Preferably, the mixing is carried out in a mixer.

[0038] Preferably, the rotor speed of the mixer is 2000rpm~3000rpm, for example, it can be 2000rpm, 2200rpm, 2400rpm, 2500rpm, 2600rpm, 2800rpm or 3000rpm.

[0039] Preferably, the power of the mixer is 8kW to 10kW, for example, it can be 8kW, 8.5kW, 9kW, 9.5kW or 10kW.

[0040] Preferably, the mixing time is 5 min to 20 min, for example, it can be 5 min, 10 min, 15 min or 20 min.

[0041] Preferably, the rotary granulation is carried out in a granulation tray.

[0042] Preferably, the rotation speed of the granulation disc is 30 rpm to 40 rpm, for example, it can be 30 rpm, 32 rpm, 34 rpm, 35 rpm, 36 rpm, 38 rpm or 40 rpm.

[0043] This invention improves the N2 / O2 separation capacity and stability of metal-organic framework-molecular sieve composites by adjusting the rotation speed of the granulation disc to 30-40 rpm. Excessively high or low rotation speeds increase the molding difficulty and reduce the compositional uniformity of the metal-organic framework-molecular sieve composites, affecting both the N2 / O2 separation capacity of the FAU-type molecular sieve and the diffusion separation of water molecules by the metal-organic framework. This leads to the adsorption of some water molecules by the FAU-type molecular sieve, which is difficult to desorb by increasing the temperature, thus reducing the structural and separation stability of the FAU-type molecular sieve.

[0044] Preferably, the rotary granulation time is 30 min to 60 min, for example, it can be 30 min, 40 min, 45 min, 50 min or 60 min.

[0045] Preferably, after rotary granulation, the process further includes drying to obtain the metal-organic framework-molecular sieve composite material.

[0046] Preferably, the drying temperature is 80℃~120℃, for example, it can be 80℃, 90℃, 100℃, 110℃ or 120℃.

[0047] Preferably, the drying time is 8h to 16h, for example, it can be 8h, 10h, 12h, 14h or 16h.

[0048] Thirdly, the present invention provides an application of the metal-organic framework-molecular sieve composite material as described in the first aspect, wherein the metal-organic framework-molecular sieve composite material is used for gas separation; wherein the gas to be separated is a mixture of nitrogen, oxygen and water vapor.

[0049] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The metal-organic framework-molecular sieve composite material provided by this invention utilizes the negatively charged framework and balanced cations of the FAU-type molecular sieve to form a strong electric field. Based on the quadrupole moment difference between N2 and O2, N2 can preferentially adsorb through a strong quadrupole-electrostatic interaction with the cations / framework, thereby achieving N2 / O2 separation. The pore size range of the metal-organic framework material is 2.8 Å to 3.2 Å, and the de Broglie wavelength of water molecules is approximately 3.0 Å. The matching of these two can trigger a kinetic quantum sieve effect, thereby significantly improving the kinetic diffusion selectivity of water molecules and achieving highly efficient selective diffusion separation of water molecules. Moreover, the removal of water molecules from the metal-organic framework material can be achieved simply by increasing the temperature. Constructing a core-shell structure enables the diffusion separation of water vapor in the shell layer and the adsorption of nitrogen in the core layer, which not only ensures excellent N2 / O2 separation capability but also avoids water-induced structural collapse of the FAU-type molecular sieve, significantly improving its separation stability. Detailed Implementation

[0052] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0053] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0054] Unless otherwise specified, the term "at least two combinations" in this invention refers to a quantity greater than or equal to 2. For example, "any one or at least two combinations" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention.

[0055] In this invention, unless otherwise specified, the feature or solution corresponding to "and / or" covers any one of two or more related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a set consisting of A, B, and combinations of A and B. "Including A and / or B" can be understood, depending on the context of the statement, as including A, including B, or simultaneously including both A and B. In this invention, "optional" means that the corresponding feature, component, step, or solution is not essential, i.e., selected from either "present" or "absent" parallel solutions. If multiple "optional" limitations appear in a technical solution, unless otherwise specified and without technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0056] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A may consist only of a1, a2, and a3, or it may include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements."

[0057] All embodiments and optional embodiments of the present invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of the present invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment or implementation of the present invention. The appearance of this phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art can explicitly and implicitly understand that the embodiments described in this invention can be combined with other embodiments without technical conflict.

[0058] In this invention, the ordinal numbers “first,” “second,” “third,” and “fourth” used in expressions such as “first aspect,” “second aspect,” “third aspect,” and “fourth aspect” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0059] In this invention, the order in which the steps are written in the methods described in each embodiment does not imply a strict execution order. The actual execution order of each step should be determined based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any order without conflict, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0060] Example 1

[0061] This embodiment provides a metal-organic framework-molecular sieve composite material. The metal-organic framework-molecular sieve composite material has a core-shell structure, with a core layer of spherical NaX molecular sieve and a shell layer of CAU-10-H. The pore size range of CAU-10-H is 3.0 Å to 3.1 Å. The mass of CAU-10-H is 15 wt% of the mass of the spherical NaX molecular sieve. The metal-organic framework-molecular sieve composite material also includes a binder, sodium carboxymethyl cellulose, which is located between the core and shell layers. The mass of sodium carboxymethyl cellulose is 3 wt% of the total mass of the spherical NaX molecular sieve and CAU-10-H. The particle size range of the spherical NaX molecular sieve is 40 mesh to 80 mesh, the particle size range of CAU-10-H is 500 mesh to 1000 mesh, and the particle size range of the metal-organic framework-molecular sieve composite material is 15 mesh to 20 mesh.

[0062] The preparation method of the metal-organic framework-molecular sieve composite material provided in this embodiment includes the following steps:

[0063] (1) The spherical NaX molecular sieve is crushed, granulated and sieved. The sieve sieve includes passing through a 40-mesh sieve and collecting the undersize material, and then passing through an 80-mesh sieve and collecting the oversize material to obtain a 40-80 mesh spherical NaX molecular sieve.

[0064] (2) Add the pretreated spherical NaX molecular sieve and CAU-10-H to the mixer and mix for 10 min at a rotor speed of 2500 rpm and a power of 9 kW.

[0065] (3) The mixed spherical NaX molecular sieve and CAU-10-H were transferred to the granulation tray, and a sodium carboxymethyl cellulose aqueous solution with a mass fraction of 5wt% was sprayed. The mixture was granulated by rotating at a speed of 35rpm for 45min, and then dried at 100℃ for 12h to obtain the metal-organic framework-molecular sieve composite material.

[0066] Example 2

[0067] This embodiment provides a metal-organic framework-molecular sieve composite material. The metal-organic framework-molecular sieve composite material has a core-shell structure, with a spherical LiX molecular sieve as the core layer and MOF-303 as the shell layer. The pore size of MOF-303 ranges from 3.0 Å to 3.2 Å. The mass of MOF-303 is 10 wt% of the mass of the spherical LiX molecular sieve. The metal-organic framework-molecular sieve composite material also includes a binder, hydroxypropyl cellulose, which is located between the core and shell layers. The mass of hydroxypropyl cellulose is 1 wt% of the total mass of the spherical LiX molecular sieve and MOF-303. The particle size range of the spherical LiX molecular sieve is 40 mesh to 80 mesh, the particle size range of MOF-303 is 500 mesh to 800 mesh, and the particle size range of the metal-organic framework-molecular sieve composite material is 15 mesh to 18 mesh.

[0068] The preparation method of the metal-organic framework-molecular sieve composite material provided in this embodiment includes the following steps:

[0069] (1) The spherical LiX molecular sieve is crushed, granulated and sieved. The sieve sieve includes passing it through a 40-mesh sieve and collecting the undersize material, and then passing it through an 80-mesh sieve and collecting the oversize material to obtain a 40-80 mesh spherical LiX molecular sieve.

[0070] (2) Add the pretreated spherical LiX molecular sieve and MOF-303 to the mixer and mix for 5 minutes at a rotor speed of 2000 rpm and a power of 8 kW.

[0071] (3) The mixed spherical LiX molecular sieve and MOF-303 were transferred to the granulation tray, and a 3wt% hydroxypropyl cellulose aqueous solution was sprayed on it. The granulation was carried out by rotating the tray at 30 rpm for 30 min, and then dried at 80℃ for 16 h to obtain the metal-organic framework-molecular sieve composite material.

[0072] Example 3

[0073] This embodiment provides a metal-organic framework-molecular sieve composite material. The metal-organic framework-molecular sieve composite material has a core-shell structure, with a core layer of spherical NaY molecular sieve and a shell layer of MIL-160. The pore size range of MIL-160 is 2.8 Å to 3.0 Å. The mass of MIL-160 is 12 wt% of the mass of the spherical NaY molecular sieve. The metal-organic framework-molecular sieve composite material also includes a binder, polyvinyl alcohol, which is located inside the shell layer. The mass of polyvinyl alcohol is 2 wt% of the total mass of the spherical NaY molecular sieve and MIL-160. The particle size range of the spherical NaY molecular sieve is 40 mesh to 80 mesh, the particle size range of MIL-160 is 800 mesh to 1000 mesh, and the particle size range of the metal-organic framework-molecular sieve composite material is 18 mesh to 20 mesh.

[0074] The preparation method of the metal-organic framework-molecular sieve composite material provided in this embodiment includes the following steps:

[0075] (1) The spherical NaY molecular sieve is crushed, granulated and sieved. The sieve sieve includes passing it through a 40-mesh sieve and collecting the undersize material, and then passing it through an 80-mesh sieve and collecting the oversize material to obtain 40-80 mesh spherical NaY molecular sieve.

[0076] (2) Add the pretreated spherical NaY molecular sieve and MIL-160 to the mixer and mix for 20 minutes at a rotor speed of 3000 rpm and a power of 10 kW.

[0077] (3) The mixed spherical NaY molecular sieve and MIL-160 were transferred to the granulation tray, and a polyvinyl alcohol aqueous solution with a mass fraction of 8wt% was sprayed. The mixture was rotated and granulated for 60 min at a rotation speed of 40 rpm, and then dried at 120℃ for 8 h to obtain the metal-organic framework-molecular sieve composite material.

[0078] Example 4

[0079] This embodiment provides a metal-organic framework-molecular sieve composite material, which is the same as that in Example 1 except that the mass of CAU-10-H is 5wt% of the mass of the spherical NaX molecular sieve.

[0080] Example 5

[0081] This embodiment provides a metal-organic framework-molecular sieve composite material, which is the same as that in Example 1 except that the mass of CAU-10-H is 20wt% of the mass of the spherical NaX molecular sieve.

[0082] Example 6

[0083] This embodiment provides a metal-organic framework-molecular sieve composite material, which is the same as that in Example 1, except that the mass of sodium carboxymethyl cellulose is 0.5 wt% of the total mass of spherical NaX molecular sieve and CAU-10-H.

[0084] Example 7

[0085] This embodiment provides a metal-organic framework-molecular sieve composite material, except that the mass of sodium carboxymethyl cellulose is 5 wt% of the total mass of spherical NaX molecular sieve and CAU-10-H, and everything else is the same as in Example 1.

[0086] Example 8

[0087] This embodiment provides a method for preparing a metal-organic framework-molecular sieve composite material. Except for the rotation speed of the granulation disc in step (3) being 20 rpm, all other steps are the same as in Example 1.

[0088] Example 9

[0089] This embodiment provides a method for preparing a metal-organic framework-molecular sieve composite material. Except for the rotation speed of the granulation disc in step (3) being 50 rpm, all other steps are the same as in Example 1.

[0090] Comparative Example 1

[0091] This comparative example provides a metal-organic framework-molecular sieve composite material, which is the same as Example 1 except that CAU-10-H is replaced with MIL-101(Cr) and the pore size range of MIL-101(Cr) is 12Å~16Å.

[0092] Comparative Example 2

[0093] This comparative example provides a molecular sieve material that is identical to that of Example 1 except for the absence of the shell layer CAU-10-H and the binder sodium carboxymethyl cellulose.

[0094] The preparation method of the molecular sieve material provided in this comparative example is the same as that in Example 1, except that steps (2) and (3) are omitted.

[0095] This invention characterizes the water adsorption stability of metal-organic framework materials and their protective effect on FAU-type molecular sieves (preventing water-induced structural collapse of FAU-type molecular sieves) by measuring the water saturation adsorption retention rate. The test method for the water saturation adsorption retention rate is as follows:

[0096] The metal-organic framework-molecular sieve composite materials / molecular sieve materials provided in Examples 1-9 and Comparative Examples 1-2 were tested for their saturated water adsorption capacity using a smart gravimetric adsorption analyzer under conditions of 50% humidity and 25°C. Desorption was then performed at 70°C, and 10 adsorption-desorption tests were conducted under the same conditions. The water saturated adsorption capacity in the first test was recorded as Γ1, and the water saturated adsorption capacity in the tenth test was recorded as Γ2. The water saturated adsorption capacity retention rate for each material was calculated.

[0097] The formula for calculating the water saturated adsorption capacity retention rate is: Water saturated adsorption capacity retention rate = Γ2 / Γ1.

[0098] The test results are shown in Table 1.

[0099]

[0100] As shown in Table 1, the metal-organic framework-molecular sieve composite materials provided in Examples 1 to 3 exhibit a saturation adsorption retention rate of over 90% after 10 adsorption-desorption tests. This indicates that the pore size range of the metal-organic framework material in the shell is 2.8 Å to 3.2 Å, which can match the de Broglie wavelength of water molecules (approximately 3.0 Å), thereby triggering the kinetic quantum sieve effect. This significantly improves the kinetic diffusion selectivity of water molecules and achieves efficient selective diffusion separation of water molecules. Furthermore, water molecules in the metal-organic framework material can be removed simply by increasing the temperature, thus avoiding water-induced structural collapse of the FAU-type molecular sieve due to adsorption of water molecules and difficulty in desorption, which is beneficial for improving its separation stability.

[0101] Compared to Example 1, the metal-organic framework-molecular sieve composite materials provided in Examples 4 and 5 have a metal-organic framework material mass that is outside the range of 10wt% to 15wt% of the molecular sieve mass. While an excessively high metal-organic framework material mass is beneficial for enhancing water adsorption and thus protecting the structural stability of the FAU-type molecular sieve, it also reduces the effective mass of the FAU-type molecular sieve in the material, covering / blocking some of the channels / pores of the FAU-type molecular sieve, thereby affecting the adsorption capacity of nitrogen and the N2 / O2 separation selectivity. Conversely, an excessively low metal-organic framework material mass results in a thin shell, or even partial exposure of the FAU-type molecular sieve surface. This leads to water molecules being simultaneously diffused and separated by the metal-organic framework material and adsorbed by the FAU-type molecular sieve. Furthermore, the water molecules adsorbed by the FAU-type molecular sieve are difficult to desorb by increasing the temperature, thus affecting the structural and separation stability of the FAU-type molecular sieve.

[0102] Compared to Example 1, the metal-organic framework-molecular sieve composite materials provided in Examples 6 and 7 have a binder mass that is outside the total mass of the molecular sieve and metal-organic framework material (1wt%~3wt%), resulting in a decrease in the saturated adsorption capacity retention rate after 10 adsorption-desorption tests. This is because the binder does not participate in the adsorption of water molecules or the separation of N2 / O2; its main function is to shape the material and prevent pulverization. If the binder mass is too high, it will cover the channels / pores of the metal-organic framework material and the FAU-type molecular sieve, reducing the diffusion and separation of water molecules by the metal-organic framework material. This leads to the FAU-type molecular sieve adsorbing some water molecules, which are difficult to desorb by increasing the temperature, thus reducing the structural and separation stability of the FAU-type molecular sieve. If the binder mass is too low, the bonding force between the metal-organic framework material and the FAU-type molecular sieve is weak, making shaping difficult. Furthermore, the bonding force between the metal-organic framework shell layer and the molecular sieve core layer is low, making them prone to detachment. This results in some water molecules being adsorbed by the FAU-type molecular sieve and difficult to desorb by increasing the temperature, thus affecting the structural and separation stability of the FAU-type molecular sieve.

[0103] Compared to Example 1, the metal-organic framework-molecular sieve composite materials provided in Examples 8-9, when the rotational speed of the granulation disc during rotary granulation was outside the range of 30-40 rpm, showed a decrease in the saturated adsorption capacity retention rate after 10 adsorption-desorption tests. This is because excessively high or low rotational speeds increase the molding difficulty of the metal-organic framework-molecular sieve composite material and reduce its compositional uniformity, affecting the diffusion and separation of water molecules by the metal-organic framework material. Consequently, the FAU-type molecular sieve adsorbs some water molecules and is difficult to desorb by increasing the temperature, reducing the structural stability and separation stability of the FAU-type molecular sieve.

[0104] Compared to Example 1, the metal-organic framework-molecular sieve composite material provided in Comparative Example 1 has a pore size range of 12 Å to 16 Å, which is much larger than the de Broglie wavelength of water molecules, making it impossible to trigger the kinetic quantum sieve effect to improve the kinetic diffusion selectivity of water molecules and achieve efficient selective diffusion separation of water molecules. It is also much larger than the kinetic diameter of water molecules, making it impossible to retain water molecules through size sieving. Therefore, water molecules mainly rely on spherical NaX molecular sieves for adsorption and are difficult to desorb by increasing the temperature. Water molecules can cause spherical NaX molecular sieves to undergo framework hydrolysis and pore blockage, and even structural collapse, resulting in a significant decrease in the saturated adsorption capacity retention rate after 10 adsorption-desorption tests.

[0105] Compared with Example 1, the molecular sieve material provided in Comparative Example 2 does not have a metal-organic framework shell layer on its surface. Water molecules rely entirely on the spherical NaX molecular sieve for adsorption and are difficult to desorb by increasing the temperature. Water molecules can cause the spherical NaX molecular sieve to undergo framework hydrolysis and pore blockage, and even structural collapse. As a result, its saturated adsorption capacity retention rate after 10 adsorption-desorption tests is significantly reduced.

[0106] This invention characterizes the effect of introducing metal-organic framework materials and binders on the nitrogen adsorption capacity of the bulk FAU-type molecular sieve by measuring the nitrogen saturation adsorption retention rate. The test method for the nitrogen saturation adsorption retention rate is as follows:

[0107] The metal-organic framework-molecular sieve composite materials / molecular sieve materials provided in Examples 1-9 and Comparative Examples 1-2, along with their corresponding bulk FAU-type molecular sieves, were degassed under vacuum at 200°C for 24 hours. Then, under conditions of 25°C and 101.3 kPa absolute pressure, their saturated nitrogen adsorption capacity was tested using a physical adsorption analyzer. The nitrogen saturated adsorption capacity of the FAU-type molecular sieve in the metal-organic framework-molecular sieve composite material / molecular sieve material was denoted as Γ3, and the nitrogen saturated adsorption capacity of the bulk FAU-type molecular sieve was denoted as Γ4. The nitrogen saturated adsorption capacity retention rate for each material was calculated.

[0108] The formula for calculating the nitrogen saturated adsorption capacity retention rate is: Nitrogen saturated adsorption capacity retention rate = Γ3 / Γ4.

[0109] The test results are shown in Table 2.

[0110]

[0111] As can be seen from Table 2, the nitrogen saturation adsorption retention rate of the metal-organic framework-molecular sieve composite materials provided in Examples 1 to 3 is higher than 85%, which indicates that the metal-organic framework material and binder in the shell have little effect on the adsorption of nitrogen by the FAU-type molecular sieve.

[0112] Compared with Example 1, the adsorption of nitrogen by the FAU-type molecular sieve was basically unaffected in the metal-organic framework-molecular sieve composite materials provided in Examples 4 and 6 due to the low quality of the metal-organic framework material and binder.

[0113] Compared with Example 1, the metal-organic framework-molecular sieve composite materials provided in Examples 5 and 7 have a reduced nitrogen adsorption capacity due to the excessively high quality of the metal-organic framework material and binder, which covers / blocks some of the channels / pores of the FAU molecular sieve and affects the N2 / O2 separation capacity of the FAU molecular sieve.

[0114] Compared with Example 1, the metal-organic framework-molecular sieve composite materials provided in Examples 8 to 9 have a lower compositional uniformity due to the rotational speed of the granulation disc being outside the range of 30 rpm to 40 rpm during rotary granulation. This reduces the nitrogen adsorption capacity of the FAU-type molecular sieve and affects its N2 / O2 separation capability.

[0115] Compared with Example 1, the metal-organic framework-molecular sieve composite material provided in Comparative Example 1 has virtually no impact on the adsorption of nitrogen by the FAU-type molecular sieve because the pore size range of MIL-101(Cr) is 12Å~16Å, which is much larger than the kinetic diameter of nitrogen molecules.

[0116] In summary, the metal-organic framework-molecular sieve composite material provided by this invention utilizes the strong electric field formed by the negatively charged framework and balanced cations of the FAU-type molecular sieve. Based on the difference in quadrupole moments between N2 and O2, N2 can preferentially adsorb through a strong quadrupole-electrostatic interaction with the cations / framework, thereby achieving N2 / O2 separation. The pore size range of the metal-organic framework material is 2.8 Å to 3.2 Å, and the de Broglie wavelength of water molecules is approximately 3.0 Å. The matching of these two factors can trigger a kinetic quantum sieve effect, thereby significantly improving the kinetic diffusion selectivity of water molecules and achieving highly efficient selective diffusion separation of water molecules. Moreover, the removal of water molecules from the metal-organic framework material can be achieved simply by increasing the temperature. Constructing a core-shell structure enables the diffusion separation of water vapor in the shell layer and the adsorption of nitrogen in the core layer, ensuring excellent N2 / O2 separation capability while preventing water-induced structural collapse of the FAU-type molecular sieve, significantly improving its separation stability.

[0117] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A metal-organic framework-molecular sieve composite material, characterized in that, The metal-organic framework-molecular sieve composite material has a core-shell structure, with the core layer including a molecular sieve and the shell layer including a metal-organic framework material. The molecular sieve includes FAU type molecular sieve; The pore size range of the metal-organic framework material is 2.8 Å to 3.2 Å.

2. The metal-organic framework-molecular sieve composite material according to claim 1, characterized in that, The mass of the metal-organic framework material is 10wt% to 15wt% of the mass of the molecular sieve.

3. The metal-organic framework-molecular sieve composite material according to claim 1 or 2, characterized in that, The metal-organic framework-molecular sieve composite material also includes a binder; Preferably, the adhesive is located inside the shell and / or between the core and the shell; Preferably, the binder comprises any one or a combination of at least two of sodium carboxymethyl cellulose, hydroxypropyl cellulose, or polyvinyl alcohol; Preferably, the mass of the binder is 1 wt% to 3 wt% of the total mass of the molecular sieve and the metal-organic framework material.

4. The metal-organic framework-molecular sieve composite material according to any one of claims 1 to 3, characterized in that, The FAU type molecular sieve includes X-type molecular sieve and / or Y-type molecular sieve; Preferably, the X-type molecular sieve includes LiX molecular sieve and / or NaX molecular sieve; Preferably, the Y-type molecular sieve includes NaY molecular sieve; Preferably, the pore size range of the FAU type molecular sieve is 7.0 Å to 8.0 Å; Preferably, the metal-organic framework material includes any one or a combination of at least two of MOF-303, CAU-10-H, or MIL-160.

5. The metal-organic framework-molecular sieve composite material according to any one of claims 1 to 4, characterized in that, The particle size range of the molecular sieve is 40 mesh to 80 mesh; Preferably, the particle size range of the metal-organic framework material is 500 mesh to 1000 mesh; Preferably, the particle size range of the metal-organic framework-molecular sieve composite material is 15 mesh to 20 mesh.

6. A method for preparing a metal-organic framework-molecular sieve composite material as described in any one of claims 1 to 5, characterized in that, Includes the following steps: The metal-organic framework-molecular sieve composite material is obtained by mixing molecular sieves and metal-organic framework materials, adding a binder solution, and then performing rotary granulation.

7. The preparation method according to claim 6, characterized in that, The preparation method further includes pretreatment of the molecular sieve; Preferably, the pretreatment includes crushing, granulation, and sieving performed sequentially; Preferably, the sieving process includes passing the granulated molecular sieve through a 40-mesh sieve, collecting the undersize material, and then passing it through an 80-mesh sieve to collect the oversize material, thereby obtaining a 40-80 mesh molecular sieve.

8. The preparation method according to claim 6 or 7, characterized in that, The adhesive solution contains 3 wt% to 8 wt% of the adhesive by mass. Preferably, the solvent in the adhesive solution includes water; Preferably, the adhesive solution is added by spraying.

9. The preparation method according to any one of claims 6 to 8, characterized in that, The mixing is carried out in a mixer; Preferably, the rotor speed of the mixer is 2000 rpm to 3000 rpm; Preferably, the power of the mixer is 8kW~10kW; Preferably, the mixing time is 5 min to 20 min; Preferably, the rotary granulation is carried out in a granulation tray; Preferably, the rotation speed of the granulation disc is 30 rpm to 40 rpm; Preferably, the rotary granulation time is 30 min to 60 min; Preferably, after rotary granulation, the process further includes drying to obtain the metal-organic framework-molecular sieve composite material; Preferably, the drying temperature is 80℃~120℃; Preferably, the drying time is 8h to 16h.

10. An application of the metal-organic framework-molecular sieve composite material as described in any one of claims 1 to 5, characterized in that, The metal-organic framework-molecular sieve composite material is used for gas separation; The gas mixture separated by the gas separation includes nitrogen, oxygen and water vapor.

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