Synthesis method, shaping method and application of a metal-organic framework material

Abstract

The present invention provides a synthesis method, a forming method and an application of a metal-organic framework material. The synthesis method of the present invention includes: reacting a calcium salt with squaric acid to obtain calcium squarate, wherein the calcium salt is a weak acid salt of calcium ions. The synthesis method of the present invention does not require the additional use of an alkaline additive to promote the dissolution of squaric acid, and can achieve the large-scale synthesis of the metal-organic framework material at room temperature. The reaction conditions are mild, the process is simple and easy to operate, the reaction yield is high, and the product purity is high. The present invention also avoids pore blockage by adding a suitable binder during the forming process of the metal-organic framework, and the formed material has excellent adsorption and separation effects on propyne and propylene gases.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorption materials, and particularly relates to a synthesis method, a forming method and an application of a metal-organic framework material. Background Art

[0002] Propylene (C3H6), as the most basic chemical raw material, has been widely used in the production of various chemicals. For example, the total production volume of polypropylene reached 85 million tons in 2013, second only to the production volume of polyethylene. At present, propylene is generally obtained by cracking petroleum and multi-carbon hydrocarbons. However, the cracking products often have complex compositions and usually contain trace amounts (1000 - 2000 ppm) of propyne (C3H4), etc. In order to obtain polymer-grade propylene for production, the amount of propyne must be reduced to 5 ppm or even 1 ppm. However, due to the similar structures, similar molecular kinetic sizes and extremely trace contents of propylene / propyne, the separation of propylene / propyne is extremely challenging.

[0003] Compared with the partial hydrogenation method for purifying and separating propylene and propyne, the adsorption separation method has the characteristics of simple operation, low energy consumption, low cost, etc. However, the most crucial thing for the adsorption separation of propylene and propyne is to select an adsorbent with a considerable adsorption capacity and high adsorption selectivity. Commonly used adsorbents include activated carbon, clay, molecular sieve, silica gel, etc. However, due to the non-uniform internal pore structure of such materials, the adsorption capacity and selectivity cannot reach the industrial application level. Metal-organic frameworks (MOFs) have made progress and expansion in the fields of gas separation and storage due to their chemical diversity, which enables them to be used as both active substances and adsorbents, and their many advantages such as high specific surface area, strong structural tunability, and rich coordinatively unsaturated metal sites.

[0004] In the prior art, the use of MOF materials such as calcium squarate for the adsorption separation of propylene and propyne gases has been reported. However, the preparation of the calcium squarate adsorption material either promotes the dissolution of squaric acid by adding an alkali to the reaction system of calcium salt and squaric acid, or reacts under heating at high temperature. The process is cumbersome, the reaction period is long, and the reaction yield is low, which is not conducive to the efficient and batch synthesis of the calcium squarate adsorbent. For example, the research group of Professor Banglin Chen published a research paper on calcium squarate in Nature Materials. When a large amount of calcium squarate was prepared in the report, sodium squarate was used as the raw material, and sodium squarate dissolved slowly in water. According to the synthesis description in the literature, when NaOH was first used to dissolve squaric acid, a large amount of NaOH and squaric acid were difficult to dissolve simultaneously, had limited solubility in water, and dissolved slowly, and the dissolution degree was difficult to control. Therefore, when using NaOH to regulate the dissolution of squaric acid and its coordination with calcium, the operation is inconvenient, it is difficult to control the dissolution degree, and finally the crystallinity of the obtained product is not high.

[0005] In addition, MOFs are usually microcrystalline powders industrially, which are not conducive to processing in practical applications. Moreover, in the form of dust, they are difficult to transport, load and unload, recycle and reuse, and may even cause dust pollution. In the process, it will lead to problems such as excessive pressure drop and pipeline blockage. To promote industrial applications, forming MOFs is an essential step. In the actual industrial process, forming can not only avoid the above-mentioned problems, but also facilitate repeated use and recycling, and can further expand its application scope. Although in recent years, relatively in-depth research has been carried out on the synthesis, structure regulation and application of MOF materials, the research on the forming and practical application of MOFs is relatively less. Different from organic polymers, metal-organic framework materials are non-thermoplastic and insoluble crystal powders in solvents, which means that traditional solvent or melt processing technologies are not applicable to MOFs, and more suitable forming methods for MOFs need to be explored. Summary of the Invention

[0006] To solve the above technical problems existing in the prior art, the present invention provides a synthesis method and a forming method for metal-organic framework materials. The synthesis method of the present invention can achieve the large-scale synthesis of metal-organic framework materials at room temperature, and no alkaline additives are required during the whole reaction process. The operation is simple, the reaction yield is high, the product purity is high, the cycle is short, the equipment requirements are low, the cost is low, and it is suitable for industrial production. The present invention also adds a suitable binder during the forming process of the metal-organic framework material to prevent pore blockage during the forming process and improve the adsorption performance of the metal-organic framework material.

[0007] The technical solution of the present invention is as follows:

[0008] In the first aspect, the present invention provides a synthesis method for a metal-organic framework material, comprising: reacting a calcium salt with squaric acid to obtain calcium squarate, wherein the calcium salt is a weak acid salt of calcium ions.

[0009] The solubility of squaric acid in water at 20 °C is 20 g / L, and it is difficult to directly dissolve to achieve the purpose of large-scale synthesis of calcium squarate. The present invention uses a weak acid salt of calcium for the reaction, making the solution alkaline. During the reaction process, it is beneficial to the dissolution of squaric acid, thereby realizing the coordination of squarate ions and calcium ions. Without other additives such as alkali, the problem of squaric acid dissolution is solved. The dissolution of squaric acid consumes calcium ions, and the remaining weak acid root promotes the ionization of ions in water, making the solution alkaline enhanced, so that squaric acid can continue to dissolve.

[0010] In some embodiments, the weak acid is selected from at least one of inorganic weak acids, monobasic or polybasic organic weak acids having 1-12 carbon atoms. The inorganic weak acids include but are not limited to carbonic acid, oxalic acid, etc. The monobasic or polybasic organic weak acids having 1-12 carbon atoms include but are not limited to formic acid, acetic acid, lactic acid, citric acid, etc.

[0011] In some specific embodiments, the calcium salt is selected from at least one of calcium formate, calcium acetate, calcium lactate, calcium citrate, calcium carbonate, and calcium oxalate.

[0012] The calcium salt in the present invention is preferably calcium acetate.

[0013] In some embodiments, the temperature of the reaction is 15 - 40 °C, such as 15 °C, 18 °C, 20 °C, 25 °C, 30 °C, 35 °C, 38 °C, 40 °C or any value therebetween, preferably 20 - 35 °C.

[0014] In some embodiments, the reaction is carried out in a first solvent. Preferably, the first solvent is water. In the present invention, the calcium salt and squaric acid preferably participate in the reaction in the form of a solution. When the squaric acid solution and the calcium salt solution are mixed, rapid and thorough stirring can promote the full contact of squaric acid and calcium ions in an environment of high-concentration reactants, so as to rapidly form a calcium squarate product with high crystallinity.

[0015] In terms of theoretical analysis, the squaric acid ligand may not completely coordinate with calcium to form a product, but there is a tendency of reversible conversion. In order to increase the reaction conversion rate, increasing the proportion of the calcium salt that is more soluble in water than squaric acid can improve the reaction efficiency and yield. In some embodiments, the molar ratio of squaric acid to calcium salt is 1:(1 - 3), such as 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.5, 1:2.8, 1:3 or any value therebetween.

[0016] In some embodiments, the method further includes a post-treatment step, and the post-treatment includes washing and drying the reaction product calcium squarate. Preferably, the solvent used for washing is water and / or alcohol, preferably water and / or methanol. Preferably, the drying temperature is 15 - 40 °C.

[0017] In some embodiments, the method further includes: mixing the obtained calcium squarate, a second solvent, and a binder, and then molding and granulating to obtain a molded metal-organic framework material.

[0018] The calcium squarate synthesized in large quantities in the present invention is a calcium squarate crystal with high crystallinity in the shape of a strip, which is a metal-organic framework material with a one-dimensional pore structure. However, this material is prone to pore blockage during the molding process, resulting in a decrease in adsorption performance. Therefore, in the present invention, by using a suitable binder, the metal-organic framework material can reduce pore blockage during the molding process and improve the adsorption performance.

[0019] In some embodiments, the binder is selected from at least one of kaolin, hydroxypropyl cellulose, hydroxyethyl cellulose, diatomite, sucrose, polymethyl methacrylate, polyvinyl butyral, alumina, and pseudo-boehmite.

[0020] In some embodiments, the mass ratio of the binder to calcium squarate is (3 - 25):(75 - 97).

[0021] In some embodiments, the binder accounts for 3 - 25% of the mass of the metal-organic framework material, such as 3%, 5%, 10%, 15%, 20%, 25% or any value therebetween.

[0022] In some embodiments, the second solvent is selected from water, ester solvents, and alcohol solvents, preferably at least one of water, ethyl acetate, and ethanol.

[0023] In the present invention, an extrusion aid and / or an acidic sol can also be added during the process of forming and granulating. The extrusion aid includes but is not limited to sesbania powder. The acidic sol includes but is not limited to nitric acid, oxalic acid, succinic acid, etc.

[0024] In some embodiments, the metal-organic framework material after forming and granulating is in the shape of a cube, rod, granule, or column.

[0025] In some specific embodiments, the method includes the following steps:

[0026] (1) Mix a calcium salt, squaric acid, and deionized water, and react at 15 - 40 °C to obtain a reaction product;

[0027] (2) Wash the reaction product with deionized water and an organic solvent several times in sequence, and dry naturally to obtain calcium squarate powder;

[0028] (3) Mix the calcium squarate powder, binder, and solvent and grind them into a paste, then dry, form, and granulate.

[0029] In a second aspect, the present invention provides a method for forming a metal-organic framework material, including the following steps:

[0030] Mix calcium squarate, a solvent, a binder, an optional extrusion aid, and an optional acidic sol, and then form and granulate to obtain a formed metal-organic framework material; wherein, the binder is selected from at least one of kaolin, hydroxypropyl cellulose, hydroxyethyl cellulose, diatomaceous earth, sucrose, polymethyl methacrylate, polyvinyl butyral, alumina, and pseudo-boehmite.

[0031] In some embodiments, the mass ratio of the binder to calcium squarate is (3 - 25):(75 - 97).

[0032] In some embodiments, the binder accounts for 3 - 25% of the mass of the metal-organic framework material, such as 3%, 5%, 10%, 15%, 20%, 25% or any value therebetween.

[0033] In some embodiments, the solvent is selected from water, ester solvents, and alcohol solvents, preferably at least one of water, ethyl acetate, and ethanol.

[0034] In the present invention, the extrusion aid includes but is not limited to sesbania powder. The acidic sol includes but is not limited to nitric acid, oxalic acid, succinic acid, etc.

[0035] In some embodiments, the metal-organic framework material after molding and granulation is cubic, rod-shaped, granular, or columnar.

[0036] In a third aspect, the present invention provides a metal-organic framework material obtained by the synthesis method described in the first aspect.

[0037] Preferably, the metal-organic framework material is cubic, rod-shaped, granular, or columnar. The metal-organic framework material of the present invention can be used as an adsorbent for the separation of gases such as alkanes, alkenes, and alkynes, and has excellent effects especially in the adsorption and separation of propyne and propylene.

[0038] In a fourth aspect, the present invention provides an application of the metal-organic framework material described in the third aspect in the separation of propylene and propyne.

[0039] In some preferred embodiments, the application includes: using the metal-organic framework material described in the third aspect of the present invention as an adsorbent to separate and purify propylene gas and propyne gas from a mixed gas containing propylene and propyne.

[0040] The metal-organic framework material prepared by the synthesis method of the present invention has excellent separation effects on propyne and propylene, and still shows good separation effects on propyne and propylene gases even after being formed with a binder.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] 1. The method of the present invention directly synthesizes calcium squarate of metal-organic framework material through one-step stirring, with a simple process, mild reaction conditions, convenient operation, environmental friendliness, and easy popularization and application.

[0043] 2. The method of the present invention can achieve the large-scale synthesis of calcium squarate of metal-organic framework material at room temperature without adding alkaline additives, and has a high reaction yield and high product purity.

[0044] 3. By selecting a suitable binder, the present invention effectively prevents the pore blockage caused by calcium squarate of metal-organic framework material during the molding process, not only solves the problems of difficult transportation and handling of MOFs powder materials and the resulting dust pollution, but also improves the adsorption performance of the formed material.

[0045] 4. The adsorption capacity of the metal-organic framework material synthesized by the present invention for propyne is significantly higher than that for propylene under equilibrium conditions, realizing the effective separation of propyne and propylene.

[0046] 5. The raw materials used in the aspects of the present invention are widely sourced, low in cost, cheap and easily available, having important economic and environmental benefits. Description of the Drawings

[0047] Figure 1 It is the PXRD pattern of calcium squarate synthesized in Example 3.

[0048] Figure 2 It is the adsorption performance diagram of calcium squarate@10% Kaolin formed particles prepared in Example 5 for propylene and propyne.

[0049] Figure 3 It is the adsorption performance diagram of calcium squarate@10% SB formed particles prepared in Example 11 for propylene and propyne.

[0050] Figure 4 It is the adsorption performance diagram of calcium squarate@10% PMMA formed particles prepared in Example 12 for propylene and propyne.

[0051] Figure 5 It is the adsorption performance diagram of calcium squarate@10% CS formed particles prepared in Example 13 for propylene and propyne. Detailed Embodiments

[0052] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and the drawings. The specific embodiments described herein are only used to explain the present invention and do not constitute any limitation to the present invention.

[0053] The binder alumina used in the following examples is the SB powder produced by Condean Company, Germany.

[0054] Example 1

[0055] (1) Add 50 mmol of calcium acetate to 250 mL of distilled water and stir well to form a calcium acetate solution.

[0056] (2) Add 50 mmol of squaric acid to the above calcium acetate solution under stirring and mix well.

[0057] (3) After stirring and reacting for 5 h at room temperature in step (2), filter to obtain a precipitate, wash the precipitate three times with distilled water and then three times with methanol, and dry naturally to obtain 6.9590 g of calcium squarate product, with a yield of 82% (based on squaric acid).

[0058] Example 2

[0059] In terms of theoretical analysis, the ligand may not be able to fully coordinate with calcium to form a product, but there is a tendency for reversible conversion. To increase the reaction conversion rate, the proportion of calcium acetate that is easily soluble in water is increased so that the ratio of calcium acetate to squaric acid is 1.1:1.

[0060] (1) Add 55 mmol of calcium acetate to 250 mL of distilled water and stir well to form a calcium acetate solution.

[0061] (2) Add 50 mmol of squaric acid to the above calcium acetate solution under stirring and mix well by stirring.

[0062] (3) After reacting for 5 h at room temperature in step (2), filter to obtain a precipitate. Wash the precipitate three times with distilled water and then three times with methanol, and dry it naturally to obtain 7.6407 g of calcium squarate product, with a yield of 90% (based on squaric acid).

[0063] Example 3: Large-scale synthesis of calcium squarate

[0064] To further discuss the industrial application value of the one-step stirring synthesis method for synthesizing calcium squarate, the reaction batch is enlarged.

[0065] (1) Add 1100 mmol of calcium acetate to 5 L of distilled water and stir well to form a calcium acetate solution.

[0066] (2) Add 1000 mmol of squaric acid to the above calcium acetate solution under stirring and mix well by stirring.

[0067] (3) After reacting for 5 h at room temperature in step (2), filter to obtain a precipitate. Wash the precipitate three times with distilled water and then three times with methanol, and dry it naturally to obtain 148.8958 g of calcium squarate product, with a yield of 88% (based on squaric acid).

[0068] Example 4: Large-scale synthesis of calcium squarate

[0069] The difference from Example 3 is only that: calcium carbonate is used instead of calcium acetate.

[0070] Finally, 126.8998 g of calcium squarate product is obtained, with a yield of 75% (based on squaric acid).

[0071] Example 5: Shaping of calcium squarate

[0072] After obtaining calcium squarate through a large - batch synthesis method, a forming technique using kaolin binder was adopted to form calcium squarate: Weigh 0.95 g of non - degassed calcium squarate powder and 50 mg of kaolin, mix them evenly in a mortar, and use a syringe to add a small amount of deionized water (the solvent) multiple times, and continuously grind the mixture until it becomes a paste. After the mixture is semi - dry, roll it into a strip of appropriate size and cut it into spherical particles with a particle size of 1 - 2 mm. After air - drying, calcium squarate @ 5% kaolin formed particles (the binder content accounts for about 5% of the mass of the formed particles) are obtained. The formed products have guaranteed thermal stability and water stability, which are sufficient to meet the requirements of general adsorption environments.

[0073] Using the same method, weigh 0.9 g of calcium squarate powder and 0.1 g of kaolin respectively to obtain calcium squarate @ 10% kaolin formed particles.

[0074] Using the same method, weigh 0.85 g of calcium squarate powder and 0.15 g of kaolin respectively to obtain calcium squarate @ 15% kaolin formed particles.

[0075] Using the same method, weigh 0.80 g of calcium squarate powder and 0.2 g of kaolin respectively to obtain calcium squarate @ 20% kaolin formed particles.

[0076] Example 6: Forming of Calcium Squarate

[0077] Using hydroxypropyl cellulose (HPC) as the binder and adopting the same method as in Example 4, calcium squarate @ 5% HPC formed particles, calcium squarate @ 10% HPC formed particles, and calcium squarate @ 15% HPC formed particles are obtained.

[0078] Example 7: Forming of Calcium Squarate

[0079] Using hydroxyethyl cellulose (HEC) as the binder and adopting the same method as in Example 4, calcium squarate @ 5% HEC formed particles, calcium squarate @ 10% HEC formed particles, and calcium squarate @ 15% HEC formed particles are obtained.

[0080] Example 8: Forming of Calcium Squarate

[0081] Using diatomite as the binder and adopting the same method as in Example 4, calcium squarate @ 5% diatomite formed particles, calcium squarate @ 10% diatomite formed particles, and calcium squarate @ 15% diatomite formed particles are obtained.

[0082] Example 9: Forming of Calcium Squarate

[0083] Using polyvinyl butyral (PVB) as the binder and ethanol as the solvent, the other processes were the same as in Example 4. Calcium squarate@5% PVB formed particles, calcium squarate@10% PVB formed particles, and calcium squarate@15% PVB formed particles were obtained.

[0084] Example 10: Molding of Calcium Squarate

[0085] Using carboxymethyl cellulose (CMC) as the binder and adopting the same method as in Example 4, calcium squarate@5% CMC formed particles, calcium squarate@10% CMC formed particles, and calcium squarate@15% CMC formed particles were obtained.

[0086] Example 11: Molding of Calcium Squarate

[0087] Using alumina as the binder and adopting the same method as in Example 4, calcium squarate@5% SB formed particles, calcium squarate@10% SB formed particles, and calcium squarate@15% SB formed particles were obtained.

[0088] Example 12: Molding of Calcium Squarate

[0089] Using polymethyl methacrylate (PMMA) as the binder and adopting the same method as in Example 4, calcium squarate@5% PMMA formed particles, calcium squarate@10% PMMA formed particles, and calcium squarate@15% PMMA formed particles were obtained.

[0090] Example 13: Molding of Calcium Squarate

[0091] Using cane sugar as the binder and adopting the same method as in Example 4, calcium squarate@5% CS formed particles, calcium squarate@10% CS formed particles, and calcium squarate@15% CS formed particles were obtained.

[0092] Example 14: Molding of Calcium Squarate

[0093] Using pseudoboehmite as the binder and adopting the same method as in Example 4, calcium squarate@5% pseudoboehmite formed particles, calcium squarate@10% pseudoboehmite formed particles, and calcium squarate@15% pseudoboehmite formed particles were obtained.

[0094] Figure 1 It is the PXRD pattern of the calcium squarate product synthesized in Example 3. From Figure 1 it can be seen that the PXRD of the synthesized powder crystal is consistent with the PXRD pattern obtained by simulation analysis. The diffraction peaks have high intensity and no extra diffraction peaks, indicating that the material prepared by the method of the present invention has a uniform structure, good crystallinity, and high purity.

[0095] Adsorption and separation performance test of calcium squarate for propyne and propylene:

[0096] To test the adsorption and separation performance of sample particles for propyne and propylene, static adsorption tests were carried out using the calcium squarate@10% Kaolin shaped particles prepared in Example 5, the calcium squarate@10% SB shaped particles prepared in Example 11, the calcium squarate@10% PMMA shaped particles prepared in Example 12, and the calcium squarate@10% CS shaped particles prepared in Example 13. The test method is as follows:

[0097] The single-component static adsorption isotherms were all collected on an ASAP2460 instrument. The test pressure was 0 - 100 kPa, and the test temperature was 298 K. Before analysis, the sample needs to be degassed and activated under high vacuum at 120 °C for 24 h to remove the solvent water molecules in the pores. After activation, it was transferred to the analysis port of the ASAP2460 gas adsorption instrument for static experiments of single-component gases. When the relative error range within 10 seconds after the test pressure balances with the set pressure is within 0.001%, it is considered that the adsorbate reaches dynamic equilibrium at this pressure.

[0098] The adsorption performance results of the calcium squarate products prepared in Example 5, Example 11, Example 12, and Example 13 for propyne and propylene are respectively as Figure 2 , Figure 3 , Figure 4 , Figure 5 shown. As can be seen from the figure, the shaped particles have excellent separation performance for propyne and propylene.

[0099] The technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention falls within the protection scope of the present invention.

Claims

1. A method for synthesizing a metal-organic framework material, comprising: React calcium salt with squaric acid to obtain calcium squarate, wherein the calcium salt is calcium acetate; the temperature of the reaction is 15 - 40 °C; The method further includes mixing the obtained calcium squarate, a solvent, a binder, an optional extrusion aid, and an optional acidic sol, and then forming and granulating to obtain a formed metal-organic framework material; the binder is selected from alumina, and the solvent is selected from at least one of water, ester solvents, or alcohol solvents.

2. The synthesis method according to claim 1, characterized in that, The reaction is carried out in a solvent, and the solvent is water; and / or the temperature of the reaction is 20 - 35 °C.

3. The synthesis method according to claim 1, characterized in that, The molar ratio of squaric acid to calcium salt is 1:(1 - 5).

4. The synthesis method according to claim 1, wherein The molar ratio of squaric acid to calcium salt is 1:(1 - 3).

5. The synthesis method according to any one of claims 1-4, characterized in that, The method further includes the steps of washing and drying the calcium squarate.

6. The synthesis method according to claim 5, wherein, The solvent used for washing is water and / or alcohol.

7. The synthesis method according to claim 5, characterized in that The temperature of the drying is 15 - 40 °C.

8. The synthesis method according to claim 1, characterized in that, The solvent is selected from at least one of water, ethyl acetate, and ethanol; and / or, the extrusion aid is sassafras powder, and the acidic sol is selected from at least one of nitric acid, oxalic acid, and succinic acid; and / or, the mass ratio of the binder to calcium squarate is (3 - 25):(75 - 97).

9. The metal-organic framework material obtained by the synthesis method according to any one of claims 1 - 8.

10. The metal-organic framework material according to claim 9, characterized in that, The metal-organic framework material is cubic, rod-shaped, granular, or columnar.

11. The application of the metal-organic framework material according to claim 9 or 10 in separating propylene and propyne.

12. The application according to claim 11, wherein The application includes using the metal-organic framework material according to claim 9 or 10 as an adsorbent to separate and purify propylene gas and propyne gas from a mixed gas containing propylene and propyne.

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