A microporous material SDMOF-1 and its preparation method and application

Abstract

The present invention belongs to the field of metal organic framework materials, and specifically relates to a microporous material SDMOF-1, a preparation method thereof, and an application thereof. According to the difference in the sizes of C2H2 and C2H4 molecules, a microporous MOFs with a suitable size is designed to capture C2H2 molecules, thereby achieving the purpose of separating a mixture of C2H2 and C2H4 and purifying C2H4. The present invention selects H2bodc and bpy ligands and copper nitrate to construct a microporous material SDMOF-1 with a pore size of #imgabs0#. The Cu2(COO)4 paddle wheel secondary building unit is connected to four H2bodc ligands to form a twisted lattice-shaped two-dimensional layer. The bpy ligand coordinates with copper along the c-axis direction and supports each layer to form a complete three-dimensional structure. The pore size of the framework is very compatible with the size of the C2H2 molecule, but cannot accommodate the C2H4 molecule, thereby achieving a molecular sieving effect.

Description

Technical Field

[0001] The present invention belongs to the field of metal organic framework materials, and in particular relates to a microporous material SDMOF-1 and a preparation method and application thereof. Background Art

[0002] Ethylene (C2H4) is a raw material for the production of polymers and organic compounds. Currently, approximately 98% of global ethylene production is achieved through tubular furnace steam cracking, with an additional 2% utilizing technologies such as methanol-to-olefins and catalytic cracking. In tubular furnace steam cracking, raw materials such as ethane, light hydrocarbons, and naphtha are mixed with steam and then introduced into furnace tubes, where they undergo thermal cracking reactions at high temperatures to produce olefins such as ethylene and products such as pyrolysis gasoline. However, this cracking process produces trace amounts of acetylene (C2H2), which can poison catalysts in the production of polyethylene (one of the most important and widely used plastics), thereby hindering ethylene polymerization. Furthermore, C2H2 is explosive above 29 kPa (40 psi) and can form solid metal, which can block the ruptured gas flow and pose a greater safety risk. Therefore, separation and purification of C2H4 and C2H2 mixtures is necessary. Traditional separation methods primarily include solvent absorption, catalytic hydrogenation, and adsorption separation.

[0003] Solvent absorption technology achieves separation through the difference in solubility of solvents in the various components of cracked gas. Solvents are divided into low-temperature type and normal-temperature type. Normal-temperature solvents include N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), etc., and low-temperature adsorbents include acetone, methanol, etc. Among them, DMF and NMP show high solubility for C2H2. Under the conditions of room temperature, 0.8-1.2MPa, and C2H2 content below 5ppm, C2H4 product can be obtained. This method has good stability and safety, but it consumes a large amount of solvent and is not environmentally friendly.

[0004] Catalytic hydrogenation technology refers to the precise introduction of hydrogen into the reaction system according to the acetylene content. The reaction temperature and pressure are low, and it is easy to operate and adjust. However, the catalyst needs to be regenerated repeatedly, resulting in a short catalyst life and high energy consumption.

[0005] Adsorption separation technology mainly uses the difference in affinity of adsorbents to different components in a mixture to achieve the purpose of separation.

[0006] As a non-thermal alternative to distillation, separation using porous adsorbents is considered to be more energy-efficient, with simple operation, regenerable adsorbents, and no pollution to the environment.

[0007] In summary, adsorption separation technology is easy to operate and will have great potential in the adsorption separation of C2H2 / C2H4 mixtures.

[0008] With the rapid development of separation technologies, the requirements for adsorbents in terms of environmental friendliness and efficiency are becoming increasingly stringent. Traditional porous materials such as activated carbon, mesoporous silica, and zeolites cannot meet the requirements for gas separation due to their inability to easily adjust their pore size and lack of specific functional groups that interact with gas molecules. Furthermore, the similar molecular sizes make the separation of C2H2 and C2H4 mixtures extremely challenging. Metal-organic frameworks (MOFs) are emerging crystalline porous materials assembled from metal units and organic linkers. Due to the tunable structural characteristics of MOFs, researchers have conducted extensive research on the adsorption separation of C2H2 / C2H4 mixtures. Utilizing this feature, pore size can be precisely controlled, leading to the synthesis of MOFs suitable for C2H4 separation and purification. This paper provides a design strategy for separating C2H2 and C2H4 using MOFs constructed based on bicyclo[2.2.2]octane-1,4-dicarboxylic acid ligands (H2bodc) and 4,4-bipyridine (bpy) ligands.

[0009] The three technical solutions used in the prior art for separating C2H2 and C2H4 have the following problems:

[0010] Solvent absorption technology uses a liquid solvent as the absorbent. Based on the principle that like dissolves like in organic matter, the liquid adsorbent absorbs gaseous impurities, achieving separation. However, due to the high investment required for post-processing of the absorbent and its high selectivity for organic components, this increases costs and technical complexity, and is prone to secondary contamination.

[0011] Catalytic hydrogenation technology involves the catalytic reaction of hydrogen with organic matter. Excessive hydrogen can easily lead to side reactions and even temperature fluctuations. Furthermore, catalyst deactivation can lead to raw material loss and high energy consumption.

[0012] Adsorption separation technology: According to the different operation modes, it can be divided into temperature swing adsorption (TSA) and pressure swing adsorption (PSA). Temperature swing adsorption mainly performs adsorption based on the difference in the adsorption capacity of the adsorbent for the adsorbate at different temperatures. The adsorbent is regenerative and the product yield is high, but the heat transfer rate is slow, the regeneration cycle is long, and it is very energy-consuming. Pressure swing adsorption mainly performs adsorption based on the difference in the adsorption capacity of the adsorbent for the adsorbate at different pressures. The operation cycle is short, the product purity is high, the energy consumption is low, and it is suitable for the production of large-scale equipment, but the yield is low. Molecular sieves have uniform pore size, mature synthesis process and ultra-high stability. Many scholars have applied them to the adsorption separation research of C2H2 / C2H4 mixtures. However, because C2H2 and C2H4 exhibit similar physical properties such as molecular size and boiling point, the separation effect using molecular sieves is not ideal. Therefore, further development of porous adsorption materials is needed. Summary of the Invention

[0013] Solvent absorption technology requires significant investment in post-processing of the absorbent and is highly selective for organic components, increasing costs and technical complexity, and is prone to secondary pollution. Catalytic hydrogenation technology, however, is susceptible to side reactions and even temperature fluctuations due to excess hydrogen. Furthermore, catalyst deactivation is prone to cause raw material loss and high energy consumption. Adsorption separation technology, on the other hand, has slow heat transfer, long regeneration cycles, and is very energy-intensive.

[0014] In order to solve the above-mentioned technical problems, this application provides the following technical solutions:

[0015] The present invention provides a method for preparing a microporous material SDMOF-1, comprising the following steps:

[0016] S1: preparing an organic mixed solution and a copper salt aqueous solution respectively; the solutes in the organic mixed solution are bicyclo[2.2.2]octane-1,4-dicarboxylic acid (H2bodc) and 4,4'-bipyridine (bpy);

[0017] S2: mixing the organic mixed solution and the copper ion solution, and heating the mixture at 80-120° C. for reaction for 10-48 hours to obtain the microporous material SDMOF-1.

[0018] Preferably, the solvent in the organic mixed solution is N,N-dimethylformamide.

[0019] Preferably, the copper salt is copper nitrate.

[0020] Preferably, the molar ratio of bicyclo[2.2.2]octane-1,4-dicarboxylic acid to 4,4'-bipyridine is 1:1-3.

[0021] Preferably, the molar ratio of the bicyclo[2.2.2]octane-1,4-dicarboxylic acid to the copper salt is 1:1-5.

[0022] Preferably, the mass ratio of the solvent in the organic mixed solution to the solvent in the copper salt aqueous solution is 1:1-6.

[0023] The present invention also provides a microporous material SDMOF-1 prepared by the above preparation method.

[0024] Furthermore, the specific surface area of ​​the microporous material SDMOF-1 is 190-350m 2 g -1 .

[0025] The present invention also provides the use of the microporous material SDMOF-1 in separating C2H2 and C2H4.

[0026] Ideal molecular sieves can block larger gas molecules from entering the pores while showing high adsorption capacity for smaller gas molecules, thus significantly reducing the energy cost of gas separation and purification. C2H4: ), design a microporous MOFs with suitable size to capture C2H2 molecules to achieve the purpose of C2H4 separation and purification.

[0027] H2bodc and bpy ligands and copper nitrate [Cu(NO3)2·3H2O] were used to design and construct a pore size The microporous material SDMOF-1. Figure 1 As shown, (a) shows a two-dimensional layered structure; (b) shows a three-dimensional network structure. A Cu2(COO)4 paddlewheel secondary building unit (SBU) is connected to four H2bodc ligands, forming a twisted, two-dimensional grid of layers. The bpy ligands coordinate with the copper of the SBU along the c-axis, supporting each layer and forming a complete three-dimensional structure. This pore size is more compatible with the size of a C2H2 molecule, and the minimum pore size cannot accommodate a C2H4 molecule, thus achieving separation.

[0028] Furthermore, the microporous material SDMOF-1 was degassed at 100-120° C. for 12 h before separating C 2 H 2 and C 2 H 4 .

[0029] The technical solution of the present invention has the following advantages over the prior art:

[0030] This paper proposes a method for synthesizing the microporous material SDMOF-1 and applies it to the separation of C2H2 and C2H4. Experimental data confirms that the material has excellent separation performance and is simple to operate, making it a low-energy, environmentally friendly material. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the structure of microporous material SDMOF-1.

[0032] Figure 2 This is the adsorption performance diagram of SDMOF-1 for C2H2 and C2H4.

[0033] Figure 3 This is the N2 adsorption curve of SDMOF-1 measured at 77K.

[0034] Figure 4 This is the PXRD pattern diffraction pattern of SDMOF-1. DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0036] Example 1

[0037] H2bodc and bpy were dissolved in DMF solution, and Cu(NO3)2·3H2O was dissolved in H2O. After mixing, the mixture was transferred to a water heat pipe and maintained in an oven at 80°C for 10 hours. Finally, green crystals were obtained. The molar ratio of H2bodc to bpy was 1:1, the molar ratio of H2bodc to Cu(NO3)2·3H2O was 1:1, and the ratio of DMF to H2O was 1:1. The yield was 64%. The specific surface area measured at 77K was 190m 2 g -1 .

[0038] Example 2

[0039] H2bodc and bpy were dissolved in DMF solution, and Cu(NO3)2·3H2O was dissolved in H2O. After mixing, the mixture was transferred to a water heat pipe and maintained in an oven at 100°C for 16 hours. Finally, green crystals were obtained. The molar ratio of H2bodc to bpy was 1:2, the molar ratio of H2bodc to Cu(NO3)2·3H2O was 1:5, and the ratio of DMF to H2O was 1:3. The yield was 58%. The specific surface area measured at 77K was 348m 2 g -1 .

[0040] Example 3

[0041] H2bodc and bpy were dissolved in DMF solution, and Cu(NO3)2·3H2O was dissolved in H2O. After mixing, the mixture was transferred to a water heat pipe and maintained in an oven at 120°C for 25 hours. Finally, green crystals were obtained. The molar ratio of H2bodc to bpy was 1:1, the molar ratio of H2bodc to Cu(NO3)2·3H2O was 1:3, and the ratio of DMF to H2O was 1:5. The yield was 50%. The specific surface area measured at 77K was 204m 2 g -1 .

[0042] Example 4

[0043] H2bodc and bpy were dissolved in DMF solution, and Cu(NO3)2·3H2O was dissolved in H2O. After mixing, the mixture was transferred to a water heat pipe and maintained in an oven at 120°C for 48 hours. Finally, green crystals were obtained. The molar ratio of H2bodc to bpy was 1:3, the molar ratio of H2bodc to Cu(NO3)2·3H2O was 1:3, and the ratio of DMF to H2O was 1:6. The yield was 68%. The specific surface area measured at 77K was 336m 2 g -1 .

[0044] Example 5

[0045] Before testing single-component adsorption, the samples were degassed (i.e., activated) for 12 hours under a high vacuum environment (less than 5 μmHg) at 120°C. After activation, single-component adsorption isotherms for the two gases were collected for each SDMOF-1 sample in Examples 1-4 using an adsorption analyzer (Micromeritics ASAP2020Plus). Figure 2 In the figure, (a) is the adsorption isotherm of SDMOF-1 for C2H2 and C2H4 at 298K; (b) is the IAST of SDMOF-1 for C2H2 and C2H4.

[0046] Effect evaluation 1

[0047] The single component adsorption isotherms of SDMOF-1 for C2H2 and C2H4 are shown in Figure 2. Figure 2 As shown in a, at 298 K, SDMOF-1 exhibits very different adsorption properties for C2H2 and C2H4. The ideal adsorption solution theory (IAST) calculation shows that the selectivity of SDMOF-1 for a mixture of C2H2 and C2H4 (volume ratio: 50 / 50) at 298 K and 1 bar is 26 ( Figure 2 b). Compared with many MOFs, SDMOF-1 is a porous material with a relatively high separation effect.

[0048] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a microporous material SDMOF-1, characterized in that: The steps include: S1: preparing an organic mixed solution and a copper salt aqueous solution respectively; the solutes in the organic mixed solution are bicyclo[2.2.2]octane-1,4-dicarboxylic acid and 4,4'-bipyridine; S2: The organic mixed solution and the copper salt aqueous solution are mixed and heated at 80-120° C. for 8-48 hours to obtain the microporous material SDMOF-1; the solvent in the organic mixed solution is N,N-dimethylformamide; the molar ratio of the bicyclo[2.2.2]octane-1,4-dicarboxylic acid and 4,4'-bipyridine is 1:1-3; the molar ratio of the bicyclo[2.2.2]octane-1,4-dicarboxylic acid and copper salt is 1:1-5.

2. The preparation method according to claim 1, wherein The copper salt is copper nitrate.

3. The preparation method according to claim 1, wherein The mass ratio of the solvent in the organic mixed solution to the solvent in the copper salt aqueous solution is 1:1-6.

4. A microporous material SDMOF-1 prepared by the preparation method according to any one of claims 1 to 3.

5. The microporous material SDMOF-1 according to claim 4, characterized in that The specific surface area of ​​the microporous material SDMOF-1 is 190-350 m 2 g -1 .

6. Use of the microporous material SDMOF-1 according to claim 4 or 5 in separating C2H2 and C2H4.

7. The use according to claim 6, characterized in that The microporous material SDMOF-1 was degassed at 100-120 °C for 12 h before separating C2H2 and C2H4.

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