A metal organic framework material with ethylene and propylene adsorption separation and preparation method

Abstract

The present invention provides a metal-organic framework material capable of ethylene and propylene adsorption separation and a preparation method. The metal-organic framework material has the chemical formula [Co2(OATA)(DPA)]·4DMF and is prepared using a solvothermal synthesis method using cobalt nitrate hexahydrate, organic ligands N,N'-bis(isophthalic acid)oxamide, and di(pyridin-4-yl)amine as raw materials. The metal-organic framework material prepared by the method of the present invention has a porosity of 56.3%, contains a throat-like pore structure, and has a minimum pore size of only 0.5 nm. The obtained metal-organic framework material exhibits significant preferential adsorption for propylene and weak adsorption for ethylene, resulting in high propylene / ethylene adsorption selectivity and potential application as an adsorption separation material in the field of ethylene and propylene adsorption separation. The present invention also provides a simple process, mild reaction conditions, and uses ligand raw materials from a wide range of sources.

Description

Technical Field

[0001] The present invention belongs to the field of inorganic and material chemistry sciences; in particular, it relates to a metal organic framework material with ethylene and propylene adsorption separation function and a preparation method thereof. Background Art

[0002] Ethylene is a key feedstock for the petrochemical industry. By 2022, global ethylene production capacity had reached nearly 220 million tons per year, with my country producing nearly 40 million tons. Mature processes exist for coal-to-olefins (CTO) and methanol-to-olefins (MTO), but both produce low-carbon mixed olefins primarily composed of propylene and ethylene. However, chemical production typically requires high-purity ethylene (99.5%), and ethylene purification is crucial to ensuring its efficient use. Removing excess impurities from the ethylene product is the most critical and challenging task in the ethylene purification process.

[0003] Adsorption separation is a new technology with low energy consumption, simple processes, and high efficiency. It achieves separation by exploiting the differences in adsorption of different substances by adsorbents, with the adsorbent being the key. Metal-organic frameworks, or MOFs (metal-organic frameworks), are porous crystalline materials formed by the coordination assembly of organic ligands and metal centers. Isophthalic acid ligands easily coordinate with multiple metal centers via carboxylic acids to form multinuclear cluster building blocks, thus forming MOFs with the desired structure. Introducing pyridine ligands (DPA) into MOFs, the -NH- groups in the DPA linkers not only form densely electronegative binding sites to increase gas adsorption, but also further create a throat-like "restricted entrance" for adsorbing propylene and rejecting ethylene, significantly improving the adsorption separation performance of MOFs. Compared with traditional porous materials, MOFs offer significant advantages as adsorbents for producing high-purity ethylene. The design and synthesis of MOFs for the adsorption separation of ethylene and propylene is of great significance. Summary of the Invention

[0004] The purpose of the present invention is to provide a metal organic framework material with ethylene and propylene adsorption separation and a preparation method.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention relates to a metal organic framework material with ethylene and propylene adsorption and separation functions. The chemical formula of the metal organic framework material is [Co2(OATA)(DPA)]·4DMF;

[0007] In the chemical formula, OATA is deprotonated N, N'-bis(isophthalic acid) oxamide, DPA is di(pyridin-4-yl)amine, and DMF is N, N-dimethylformamide;

[0008] Preferably, the crystal of the metal organic framework material belongs to the tetragonal system I422 space group, and the asymmetric unit consists of a Co 2+ ions, an OATA 4- ligand and a DPA ligand.

[0009] Preferably, the metal organic framework material contains a throat-shaped pore structure and a BET specific surface area of ​​823.2 m 2 g -1 At 298K and 0.05 atm, the adsorption capacity of propylene and ethylene is 97.8 cm 3 ·g -1 and 20.0cm 3 ·g -1 , which is almost four times the difference; the separation selectivity of the material for propylene and ethylene mixture reaches 21.7-23.1, and has good adsorption separation function.

[0010] Preferably, the structural formula of the ligand H4OATA of the metal organic framework material is as shown in formula (I):

[0011]

[0012] The structural formula of the DPA is shown in formula (II):

[0013]

[0014] The present invention also relates to a method for preparing the aforementioned metal organic framework material capable of ethylene and propylene adsorption separation, comprising the following steps:

[0015] The present invention adopts a solvent thermal synthesis method, using cobalt nitrate hexahydrate, organic ligand N, N'-bis(isophthalic acid) oxamide and di(pyridin-4-yl)amine as raw materials, and the specific steps are as follows:

[0016] Step 1: adding 0.09-0.11 mmol of cobalt nitrate hexahydrate, 0.04-0.05 mmol of N,N'-bis(isophthalic acid)oxamide ligand, and 0.04-0.05 mmol of di(pyridin-4-yl)amine ligand to a mixed solvent consisting of N,N-dimethylformamide and concentrated nitric acid to obtain a mixture;

[0017] Step 2: Place the mixture in a 15 ml autoclave, heat and keep it sealed, and then cool it to room temperature at a rate of 20-30° C. per hour;

[0018] Step 3, taking out the reaction product, filtering it to obtain cyan flaky crystals, and obtaining a preliminary metal-organic framework material;

[0019] Step 4: exchanging the preliminary metal organic framework material with acetone and heating it in vacuum to obtain a metal organic framework material with ethylene and propylene adsorption and separation functions.

[0020] Preferably, the mixed solvent is composed of 5-6 ml of N,N-dimethylformamide and 0.08-0.1 ml of concentrated nitric acid.

[0021] Preferably, in step 2, the temperature of the sealed heating is 115-125° C., and the insulation time is 70 to 80 hours.

[0022] Preferably, in step 4, the exchange time is 2 to 3 days.

[0023] Preferably, in step 4, the vacuum heating temperature is 150-160° C. and the time is 4-6 hours.

[0024] The present invention has the following advantages:

[0025] (1) The metal organic framework material for the adsorption separation of ethylene and propylene involved in the present invention has a simple preparation process, mild reaction conditions, and the ligand raw materials used are widely available;

[0026] (2) The porosity of the metal-organic framework material prepared by the method of the present invention is 56.3%, and it contains a throat-shaped pore structure. At the same time, the minimum pore size is only 0.5 nm. The obtained metal-organic framework material shows obvious preferential adsorption for propylene and weak adsorption for ethylene. Therefore, it has a high propylene / ethylene adsorption selectivity and can be used as a potential adsorption separation material in the field of adsorption separation of ethylene and propylene. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The Co in the metal organic framework material of the present invention 2+ Coordination environment diagram of the ion;

[0028] Figure 2 is a three-dimensional structural diagram of the metal organic framework material of the present invention;

[0029] Figure 3 is a powder X-ray diffraction pattern of the metal organic framework material of the present invention;

[0030] Figure 4 is a nitrogen adsorption isotherm diagram of the metal organic framework material of the present invention at 77K;

[0031] Figure 5 is an adsorption isotherm diagram of ethylene and propylene at room temperature for the metal organic framework material of the present invention;

[0032] Figure 6This is a comparison chart of the selectivity of metal-organic framework materials for ethylene / propylene mixtures with different mixing ratios at 298K and 1atm calculated using ideal adsorption solution theory. DETAILED DESCRIPTION

[0033] The present invention will be described in detail below with reference to specific embodiments. It should be noted that the following embodiments are only for further explanation of the present invention, but the protection scope of the present invention is not limited to the following embodiments.

[0034] Example

[0035] This embodiment relates to a method for preparing a metal organic framework material capable of adsorption separation of ethylene and propylene, and the specific steps are as follows:

[0036] Step 1: 0.029 g of cobalt nitrate hexahydrate (0.10 mmol), 0.021 g of N,N'-bis(isophthalic acid)oxamide (0.05 mmol), and 0.008 g of di(pyridin-4-yl)amine (0.05 mmol) were uniformly mixed with 5 mL of N,N-dimethylformamide (DMF) to obtain a mixture;

[0037] Step 2: Place the mixed solution in a 15 mL autoclave, heat to 120° C. for 72 hours, and then cool to room temperature;

[0038] Step 3, taking out the reaction product, filtering it to obtain cyan flaky crystals, and obtaining a preliminary metal-organic framework material;

[0039] Step 4: exchanging the solvent of the preliminary metal organic framework material with acetone every 12 hours for 6 times, and heating it at 160° C. in vacuum for 6 hours to obtain a metal organic framework material with ethylene and propylene adsorption and separation functions.

[0040] (1) Structural description of the obtained metal-organic framework material with ethylene and propylene adsorption separation

[0041] The crystal structure of the metal organic framework material was characterized and analyzed to determine its unit cell and spatial structure. The crystal belongs to the tetragonal system I422 space group, and the asymmetric unit consists of a Co 2+ ions, an OATA 4- ligand and a DPA ligand, see Figure 1 As shown. Two Co 2+ ions and four carboxyl groups form a [Co2(COO)4] paddle wheel SBU, and each Co 2+ ions form a complex consisting of four different OATA 4- The O atom of the ligand and the N atom of one DPA form a pyramidal coordination configuration. 4-Interconnecting SBUs in a four-way connection manner produces a three-dimensional framework, see Figure 2 As shown. The DPA ligands occupying the vertices of SBUs support the framework and divide the pore space, giving the framework narrow pores and high stability. The pore surface is modified by -CONH- and -NH- groups. It is worth noting that in addition to the straight channel modified with oxalamide (0.68nm), the imine in the DPA ligand forms a "restrictive entrance" in the original channel, resulting in the formation of a throat-like channel in the framework. The narrow pore diameter is only 0.5nm, which is an ultramicropore. At the same time, the metal organic framework material has a high porosity of 56.3%, which ensures a higher adsorption capacity.

[0042] (2) Adsorption test of the obtained metal organic framework material with ethylene and propylene adsorption separation

[0043] The obtained metal organic framework material was solvent exchanged with acetone, and the solvent was exchanged every 12 hours for 6 times, and then activated under vacuum conditions at 160°C for 6 hours to obtain the activated metal organic framework material. The results of powder X-ray diffraction showed that the activated metal organic framework material had a high phase purity. Figure 3 The nitrogen gas adsorption test was carried out using the ASAP 2020M specific surface area meter from the American company Micromeritics. The BET specific surface area of ​​the metal organic framework material was 823.2 m 2 g -1 ,See Figure 4 The adsorption and separation performance of the metal organic framework material for propylene and ethylene was further tested. At 298K and 1 bar, the adsorption capacity of the material for propylene was 121.3 cm 3 g -1 , significantly higher than ethylene (94.5cm 3 g -1 ),like Figure 5 Moreover, at high temperatures of 313K and 333K, the adsorption capacity of propylene by the material at 1 bar still remained at 111.9 cm 3 g -1 and 101.9cm 3 g -1 The above test results show that the material still has good adsorption capacity in industrial processes with relatively high temperatures.

[0044] Through Figure 5 Further study of the adsorption curves in the figure shows that the adsorption curve of propylene at low pressure increases rapidly, especially at 0.05 bar, the adsorption amount reaches 97.8 cm 3 g -1, which is 80.6% of the adsorption capacity at 1 bar pressure and about 5 times that of ethylene, which makes the metal organic framework material show significant propylene / ethylene selectivity. Figure 6 As shown, at 0.1 bar and 1 bar, for propylene / ethylene mixtures with different mixing ratios: for propylene / ethylene = 50 / 50 mixture, the selectivity reaches 21.9 and 23.1 respectively; for propylene / ethylene = 25 / 75 mixture, the selectivity reaches 21.7 and 22.7 respectively; for propylene / ethylene = 25 / 75 mixture, the selectivity reaches 21.6 and 22.3 respectively, showing excellent ethylene / propylene separation potential.

[0045] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A metal organic framework material with the ability to separate ethylene and propylene by adsorption, characterized in that: The chemical formula of the metal-organic framework material is [Co2(OATA)(DPA)]·4DMF; In the chemical formula, OATA is deprotonated N,N'-bis(isophthalic acid)oxalamide, DPA is di(pyridin-4-yl)amine, and DMF is N,N-dimethylformamide.

2. The metal organic framework material with ethylene and propylene adsorption separation according to claim 1, characterized in that: The crystal of the metal organic framework material belongs to the tetragonal I422 space group, and the asymmetric unit consists of a Co 2+ ions, an OATA 4- ligand and a DPA ligand.

3. The metal organic framework material with ethylene and propylene adsorption separation according to claim 1, characterized in that: The metal organic framework material contains a throat-shaped pore structure and a BET specific surface area of ​​823.2 m 2 g -1 At 298K and 0.05 atm, the adsorption capacity of propylene and ethylene is 97.8 cm 3 ·g -1 and 20.0cm 3 ·g -1 The separation selectivity of the material for the mixture of propylene and ethylene is 21.7-23.

1.

4. The metal organic framework material capable of adsorption separation of ethylene and propylene according to claim 2, characterized in that: The structural formula of the ligand H4OATA of the metal organic framework material is shown in formula (I): The structural formula of the DPA is shown in formula (II):

5. A method for preparing a metal organic framework material capable of adsorption separation of ethylene and propylene as claimed in claim 1, characterized in that: The following steps are involved: Step 1: adding cobalt nitrate hexahydrate, N,N'-bis(isophthalic acid)oxamide ligand and di(pyridin-4-yl)amine ligand to a mixed solvent consisting of N,N-dimethylformamide and concentrated nitric acid to obtain a mixture; Step 2: Place the mixture in a 15 ml autoclave, heat and keep it sealed, and cool it to room temperature at a rate of 20-30° C. per hour; Step 3, taking out the reaction product, filtering it to obtain cyan flaky crystals, and obtaining a preliminary metal-organic framework material; Step 4: exchanging the preliminary metal organic framework material with acetone and heating it in vacuum to obtain a metal organic framework material with ethylene and propylene adsorption and separation functions.

6. The method for preparing a metal organic framework material capable of adsorption separation of ethylene and propylene according to claim 5, wherein: In step 1, the ratio of the cobalt nitrate hexahydrate, N,N'-bis(isophthalic acid)oxamide ligand, and di(pyridin-4-yl)amine ligand is 0.09-0.11: 0.04-0.05: 0.04-0.05; and the mixed solvent is composed of 5-6 ml of N,N-dimethylformamide and 0.08-0.1 ml of concentrated nitric acid.

7. The method for preparing a metal organic framework material capable of adsorption separation of ethylene and propylene according to claim 5, wherein: In step 2, the temperature of the sealed heating is 115-125° C., and the insulation time is 70 to 80 hours.

8. The method for preparing a metal organic framework material capable of adsorption separation of ethylene and propylene according to claim 5, wherein: In step 4, the exchange time is 2 to 3 days.

9. The method for preparing a metal organic framework material capable of adsorption separation of ethylene and propylene according to claim 5, wherein: In step 4, the vacuum heating temperature is 150-160° C. and the time is 4-6 hours.

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