CN116239786A - Metal-organic framework material for separation of carbon dioxide mixed gas and its preparation method and application - Google Patents

Abstract

The invention discloses a metal organic framework material for separating carbon dioxide mixed gas, a preparation method and application thereof. Weigh an appropriate amount of metal salt, add deionized water, add formic acid after ultrasonication for 5-10min, stir the resulting mixed solution at 600rpm for 10min, add fumaric acid, stir the resulting mixed solution at room temperature for 12h, centrifuge, wash with water and ethanol Washing and drying to obtain MOF-801 for the separation of carbon dioxide mixed gas; the metal salt is zirconium salt, cerium salt or hafnium salt. The preparation method of the present invention is simple, low in cost, environment-friendly, good in repeatability, and can be scaled up. The raw materials and solvents synthesized are green and non-toxic. In terms of application, they can match the gas separation performance of MOFs synthesized by high-temperature solvothermal synthesis. The sustainable separation of CO ₂ /N ₂ or CO ₂ /CH ₄ under pressure is an excellent candidate for the application of MOFs in industrial fields.

Description

Metal-organic framework material and its preparation method for the separation of carbon dioxide mixed gas law and application

technical field

The invention belongs to the technical field of gas separation, and in particular relates to a metal organic framework material for the separation of carbon dioxide mixed gas and a green synthesis method thereof. The material has high thermal stability and separation cycle stability.

Background technique

With the development of society and the progress of science and technology, the global energy situation is becoming increasingly tense. It is undeniable that gas separation has played a pivotal role as an important purification method in the energy industry. Currently, separation technologies such as traditional cryogenic distillation account for 10-15% of the world's energy consumption. Non-thermally driven adsorption separation is considered as a low-cost, efficient and environmentally friendly separation technology.

Since the two industrial revolutions, the excessive emission of carbon dioxide produced by the extensive use of fossil fuels is the main cause of "greenhouse gases". The greenhouse effect will lead to global warming, ice melting, sea level rise and other hazards, which greatly affect people's daily life. The traditional method of treating carbon dioxide is to use amine solution to chemically absorb it. However, due to its high requirements for production equipment and high regeneration costs of the adsorbent, it is urgent to develop a high-efficiency, low-cost and strong regeneration capacity carbon dioxide adsorbent. Metal-organic frameworks (MOFs) often exhibit excellent gas adsorption and separation properties due to their high porosity, tunable pore channels, and surface chemistry. However, how to design MOFs with high selectivity and high gas adsorption capacity is still a challenging problem.

Early developed adsorbents such as zeolites and activated carbons have shown some application in gas separation. Although these materials are inexpensive, their separation efficiency is poor due to the limitations of height tunability and structural diversity, which cannot meet practical industrial applications. Currently, a feasible approach is to separate industrial gases by designing porous adsorbents with adjustable structures. High and diverse functions, not only can reduce energy consumption, but also can maximize separation efficiency by design.

Traditional methods of synthesizing MOFs, such as solvothermal and hydrothermal synthesis, consume a certain amount of energy, and most organic ligands are expensive. Even if a certain separation performance has been achieved, it is still difficult to achieve large-scale industrial applications due to cost constraints. Therefore, it is very necessary to prepare novel adsorbents with high adsorption capacity and separation selectivity through green synthesis methods.

Contents of the invention

The purpose of the present invention is to provide a green synthesis method of metal organic framework materials for the separation of carbon dioxide mixed gas, to solve the problems of huge energy consumption and high cost in the synthesis process of MOFs materials, and to promote the industrialization of MOFs materials in the field of gas separation process.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows: a metal organic framework material for the separation of carbon dioxide mixed gas, the metal organic framework material for the separation of carbon dioxide mixed gas is MOF-801, and the preparation method includes the following steps : Weigh an appropriate amount of metal salt, add deionized water, add formic acid after ultrasonication for 5-10min, stir the resulting mixed solution at 600rpm for 10min, add fumaric acid, stir the resulting mixed solution at room temperature for 12h, centrifuge, water and Washing with ethanol and drying to obtain MOF-801 for the separation of carbon dioxide mixed gas; the metal salt is zirconium salt, cerium salt or hafnium salt.

Further, in the aforementioned metal organic framework material for the separation of carbon dioxide mixed gas, the zirconium salt is zirconium chloride.

Further, in the aforementioned metal organic framework material for the separation of carbon dioxide mixed gas, the cerium salt is cerium ammonium nitrate.

Further, in the aforementioned metal organic framework material for the separation of carbon dioxide mixed gas, the hafnium salt is hafnium chloride.

的笼型孔。Further, the above metal organic framework material for the separation of carbon dioxide mixed gas, the specific surface area of MOF-801 for the separation of carbon dioxide mixed gas is 573.0234-817.8636m ² /g, with

cage hole.

Further, the metal-organic framework material for the separation of carbon dioxide mixed gas mentioned above has a molar ratio of metal salt:fumaric acid=1:1.

The metal organic framework material used for the separation of carbon dioxide mixed gas provided by the invention is used as an adsorbent in the separation of carbon dioxide from carbon dioxide mixed gas.

Further, the carbon dioxide mixed gas includes a mixed gas of CO ₂ and N ₂ and/or CH ₄ .

Further, the method is as follows: a metal organic framework material for separating the carbon dioxide mixed gas is added to the carbon dioxide mixed gas.

Further, the metal organic framework material used for the separation of the carbon dioxide mixed gas is activated before adsorption, and the activation method includes the following steps: placing the metal organic framework material used for the separation of the carbon dioxide mixed gas in methanol for 36 hours, performing solvent exchange, During this period, fresh methanol was changed every 6 hours. After the exchange was completed, the activated product was separated by centrifugation and dried under vacuum at 60°C.

The beneficial effects of the present invention are:

1, the organic ligand fumaric acid used in the present invention is a kind of green cheap organic ligand, and the μ-OH site in the conjugated maleic group in the structure and metal cluster can produce polarizing action to _CO , thus To achieve the purpose of efficiently adsorbing _CO2 .

2. The metal-organic framework material synthesized in the present invention relies on the polarization of the μ-OH binding site and double bond in the metal cluster to CO ₂ to realize the selective physical adsorption of CO ₂ /N ₂ and CO ₂ /CH ₄ , so its isothermal adsorption enthalpy (28.50kJ·mol ^-1 ) is much smaller than that of other MOFs materials. This feature greatly reduces the regeneration cost of adsorbent recycling, which has important practical significance.

3. The penetration experiments of the MOF-801 series materials prepared by the present invention in the dual-component gas (CO ₂ /N ₂ , 15:85; v:v) simulating the actual gas engine exhaust gas show that the material can be used for as long as 100 Complete separation of CO ₂ and N ₂ within minutes. This shows that the material can actually and effectively realize the highly selective separation of CO ₂ /N ₂ .

4. The MOF-801 series materials synthesized by the present invention have excellent chemical stability and thermal stability. Both thermogravimetric test and XRD after adsorption separation show that the material has good stability and renewable performance.

5. The present invention prepares a series of metal-organic framework materials with mild reaction conditions, large output and high stability through the method of green synthesis. The metal-organic framework materials selectively separate and adsorb CO ₂ /N ₂ and CO ₂ /CH ₄ It has great application prospects in the field and in mitigating the greenhouse effect.

6. The MOFs preparation method of the present invention is simple to operate, has good repeatability, and has good thermal stability and separation cycle stability.

Description of drawings

Fig. 1 is the single-component adsorption curve and pore size distribution diagram of _N2 at 77K for the metal organic framework material MOF-801 (Zr) synthesized by the present invention.

Fig. 2 is the single-component adsorption curve and pore size distribution diagram of the metal organic framework material MOF-801(Ce) synthesized by the present invention under _N2 at 77K.

Fig. 3 is the single-component adsorption curve and pore size distribution diagram of _N2 at 77K for the metal organic framework material MOF-801(Hf) synthesized by the present invention.

Fig. 4 is an X-ray powder diffraction (PXRD) pattern of the metal organic framework material synthesized in the present invention.

Fig. 5 is a single-component adsorption curve of CO ₂ and N ₂ at 298K for the metal organic framework material synthesized by the present invention.

Fig. 6 is a single-component adsorption curve of CO ₂ and CH ₄ at 298K for the metal organic framework material synthesized in the present invention.

Fig. 7 is a graph showing the CO ₂ isothermal adsorption enthalpy curve of the metal organic framework material synthesized in the present invention.

Fig. 8 is a breakthrough curve of the metal organic framework material MOF-801(Zr) synthesized in the present invention.

Fig. 9 is a breakthrough curve of the metal organic framework material MOF-801(Ce) synthesized in the present invention.

Fig. 10 is the breakthrough curve of the metal organic framework material MOF-801(Hf) synthesized in the present invention.

Fig. 11 is a three-time breakthrough curve of the metal organic framework material MOF-801(Zr) synthesized in the present invention under the mixed gas condition of CO ₂ /N ₂ volume ratio of 1:1.

Fig. 12 is a powder X-ray diffraction (PXRD) pattern of the metal organic framework material MOF-801 (Zr) synthesized in the present invention after 7 cycles of adsorption separation.

Fig. 13 is a powder X-ray diffraction (PXRD) pattern of the metal organic framework material MOF-801 (Ce) synthesized in the present invention after 7 cycles of adsorption separation.

Fig. 14 is a powder X-ray diffraction (PXRD) pattern of the metal organic framework material MOF-801(Hf) synthesized in the present invention after 7 cycles of adsorption separation.

Detailed ways

In order to make the technical means, creative features and realization effects of the invention easy to understand, the content of the present invention will be further elucidated below in conjunction with the embodiments. However, this does not limit the implementation scope of the present invention, that is, equivalent modifications made according to the scope of patents of the present invention and the contents of the description shall all fall within the scope of the present invention.

Example 1 Metal-organic framework material for separation of carbon dioxide mixed gas (1) Preparation of metal-organic framework material (MOF-801(Zr)) for separation of carbon dioxide mixed gas

The preparation method is as follows: weigh zirconium chloride (350mg, 1.5mmol) and place it in a 100mL round bottom flask, add 8mL deionized water, ultrasonicate for 5-10min, add 2mL formic acid after it is completely dissolved, and stir the resulting mixed solution at 600rpm for 10min , then added fumaric acid (174mg, 1.5mmol), and the resulting mixed solution was stirred at room temperature for 12h again to produce a white solid, which was collected by centrifugation, washed three times with water and ethanol, and finally dried in a constant temperature drying oven to obtain The MOF-801 separated from carbon dioxide mixed gas is labeled as MOF-801(Zr).

(2) Preparation of metal organic framework material (MOF-801(Ce)) for the separation of carbon dioxide mixed gas

The preparation method is as follows: Weigh cerium ammonium nitrate (822mg, 1.5mmol) into a 100mL round bottom flask, add 8mL deionized water, ultrasonicate for 5-10min, add 2mL formic acid after all dissolved, and stir the resulting mixed solution at 600rpm for 10min , then added fumaric acid (174mg, 1.5mmol), and the resulting mixed solution was stirred at room temperature for 12h again to produce a white solid, which was collected by centrifugation, washed three times with water and ethanol, and finally dried in a constant temperature drying oven to obtain The MOF-801 separated from carbon dioxide mixed gas is labeled as MOF-801(Ce).

(3) Preparation of metal organic framework material (MOF-801(Hf)) for the separation of carbon dioxide mixed gas

The preparation method is as follows: Weigh hafnium chloride (480mg, 1.5mmol) into a 100mL round-bottomed flask, add 8mL deionized water, ultrasonicate for 5-10min, add 2mL formic acid after it is completely dissolved, and stir the resulting mixed solution at 600rpm for 10min , then added fumaric acid (174mg, 1.5mmol), and the resulting mixed solution was stirred at room temperature for 12h again to produce a white solid, which was collected by centrifugation, washed three times with water and ethanol, and finally dried in a constant temperature drying oven to obtain The MOF-801 separated from carbon dioxide mixed gas is labeled as MOF-801(Hf).

(4) Representation

Activation: In order to remove the solvent molecules in the pores of the material to obtain an activated crystal material, the metal-organic framework material is first activated by solvent exchange. Soak 300mg of MOF-801, a metal-organic framework material used for the separation of carbon dioxide mixed gas, in dry methanol for 36 hours, and perform solvent exchange. During this period, fresh methanol was changed every 6 hours. Vacuum-dried for 6 hours, and then vacuum-activated at 120°C for 12 hours to finally obtain about 250 mg of crystal material of the activated metal-organic framework material MOF-801.

图2为本实施例合成的金属有机框架材料MOF-801(Ce)在77K的N₂吸附-脱附曲线图。由图2可见，所制备的MOF-801(Ce)具有典型的微孔特征，其孔径大小约为/>

图3为本实施例合成的金属有机框架材料MOF-801(Hf)在77K的N₂吸附-脱附曲线图。由图3可见，所制备的MOF-801(Hf)具有典型的微孔特征，其孔径大小约为/>

The activated crystalline material was subjected to 77K-N ₂ adsorption experiments under liquid nitrogen conditions to obtain parameters such as the specific surface area of the crystalline material. Fig. 1 is the _N2 adsorption-desorption curve of the metal organic framework material MOF-801 (Zr) synthesized in this example at 77K. It can be seen from Figure 1 that the prepared MOF-801(Zr) has typical microporous characteristics, and its pore size is about

Fig. 2 is the _N2 adsorption-desorption curve of the metal organic framework material MOF-801 (Ce) synthesized in this example at 77K. As can be seen from Figure 2, the prepared MOF-801 (Ce) has typical microporous characteristics, and its pore size is about

Fig. 3 is the _N2 adsorption-desorption curve of the metal organic framework material MOF-801(Hf) synthesized in this example at 77K. As can be seen from Figure 3, the prepared MOF-801 (Hf) has typical microporous characteristics, and its pore size is about

Fig. 4 is an X powder ray diffraction (PXRD) pattern of the metal organic framework material synthesized in this example. It can be seen from Figure 4 that the prepared MOF-801 series materials are consistent with the diffraction peaks obtained by simulation, which proves that the materials have good crystallinity and high phase purity.

Then, under the temperature control conditions of 273K and 298K, the single-component adsorption curves of CO ₂ , N ₂ , and CH ₄ of the crystal materials at corresponding temperatures were completed. Fig. 5 is a single-component adsorption curve of CO ₂ and N ₂ at 298K for the metal organic framework material synthesized in this example. It can be seen from Fig. 5 that at 298K, the obtained materials have good _CO2 adsorption performance, among which MOF-801(Ce) exhibits the highest adsorption capacity, in contrast, the adsorption of _N2 is almost negligible, proving that The material has excellent separation potential for CO ₂ /N ₂ . Fig. 6 is a single-component adsorption curve of CO ₂ and CH ₄ at 298K for the metal organic framework material synthesized in this example. It can be seen from Figure 6 that the adsorption capacity of the material for CH ₄ is much lower than that of CO ₂ , indicating that the material has good CO ₂ /CH ₄ separation potential. Fig. 7 is the _CO2 isothermal adsorption enthalpy curve of the metal organic framework material synthesized in this example. It can be seen from Figure 7 that the adsorption enthalpy of the prepared materials for CO ₂ is between 22 and 30kJ mol ^-1 , among which the adsorption enthalpy of MOF-801(Ce) and CO ₂ is the highest, which is 28.4kJ mol ^-1 .

Example 2 Application of Metal Organic Framework Materials for Separation of Carbon Dioxide Mixed Gases

(1) The method is as follows:

Activation: In order to remove the solvent molecules in the pores of the material to obtain an activated crystal material, the metal-organic framework material is first activated by solvent exchange. Soak 300mg of MOF-801, a metal-organic framework material used for the separation of carbon dioxide mixed gas, in dry methanol for 36 hours, and perform solvent exchange. During this period, fresh methanol was changed every 6 hours. Vacuum-dried for 6 hours, and then vacuum-activated at 120°C for 12 hours to finally obtain about 250 mg of crystal material of the activated metal-organic framework material MOF-801.

Gas separation: Take 1.2g of activated MOF-801 material to complete the penetration simulation of simulated fuel engine exhaust on the dynamic adsorption gas penetration equipment. In the mixed gas atmosphere of CO ₂ and N ₂ with a volume ratio of 15:85 or 50:50, the separation performance of the material on the mixed gas and the stability of the separation cycle were tested. It is worth noting that after each breakthrough, only It needs to be purged with 10mL/min helium at 80°C to complete the regeneration, which proves the excellent regeneration performance of the material.

(2) Representation

Fig. 8 is a breakthrough curve of the metal organic framework material MOF-801(Zr) synthesized in the present invention. It can be seen from Figure 8 that MOF-801(Zr) has good CO ₂ /N ₂ separation ability, showing effective separation time of 30min (50/50, v/v) and 55min (15/85, v/v) respectively .

Fig. 9 is a breakthrough curve of the metal organic framework material MOF-801(Ce) synthesized in the present invention. It can be seen from Figure 9 that MOF-801(Ce) has good CO ₂ /N ₂ separation ability, showing effective separation time of 70min (50/50, v/v) and 90min (15/85, v/v) respectively .

Fig. 10 is the breakthrough curve of the metal organic framework material MOF-801(Hf) synthesized in the present invention. It can be seen from Figure 10 that MOF-801(Ce) has a good CO ₂ /N ₂ separation ability, showing an effective separation time of 44min (50/50, v/v) and 56min (15/85, v/v) respectively .

Fig. 11 is a three-time breakthrough curve of the metal organic framework material MOF-801(Zr) synthesized in the present invention under the mixed gas condition of CO ₂ /N ₂ volume ratio of 1:1. It can be seen from Figure 11 that the prepared MOF-801(Zr) has stable performance in the three-cycle breakthrough test, and the separation effect has not changed significantly.

Fig. 12 is a powder X-ray diffraction (PXRD) pattern of the metal organic framework material MOF-801 (Zr) synthesized in the present invention after 7 cycles of adsorption separation. It can be seen from Figure 12 that the structure of the prepared MOF-801(Zr) remains intact after 7 adsorption cycle tests, which proves that the material has excellent structural stability in practical applications.

Fig. 13 is a powder X-ray diffraction (PXRD) pattern of the metal organic framework material MOF-801 (Ce) synthesized in the present invention after 7 cycles of adsorption separation. It can be seen from Figure 13 that the structure of the prepared MOF-801(Ce) remains intact after 7 adsorption cycle tests, which proves that the material has excellent structural stability in practical applications.

Fig. 14 is a powder X-ray diffraction (PXRD) pattern of the metal organic framework material MOF-801(Hf) synthesized in the present invention after 7 cycles of adsorption separation. It can be seen from Figure 14 that the structure of the prepared MOF-801(Hf) remains intact after 7 adsorption cycle tests, which proves that the material has excellent structural stability in practical applications.

Claims (8)

1. The metal organic framework material for separating the carbon dioxide mixed gas is MOF-801, and the preparation method comprises the following steps: weighing a proper amount of metal salt, adding deionized water, adding formic acid after ultrasonic treatment for 5-10 min, stirring the obtained mixed solution at 600rpm for 10min, adding fumaric acid, stirring the obtained mixed solution at room temperature for 12h again, centrifuging, washing with water and ethanol, and drying to obtain MOF-801 for carbon dioxide mixed gas separation; the metal salt is zirconium salt, cerium salt or hafnium salt.

2. A metal organic framework material for carbon dioxide mixed gas separation according to claim 1, characterized in that the zirconium salt is zirconium chloride; the cerium salt is ceric ammonium nitrate; the hafnium salt is hafnium chloride.

3. The metal organic framework material for carbon dioxide mixed gas separation according to claim 1, wherein the MOF-801 specific surface area for carbon dioxide mixed gas separation is 573.0234-817.8636 m ² /g, with

Is a cage-shaped hole.

4. A metal organic framework material for carbon dioxide mixed gas separation according to claim 1, characterized in that the metal salt is fumaric acid=1:1 in molar ratio.

5. Use of a metal organic framework material for carbon dioxide gas mixture separation as claimed in claim 1 as an adsorbent for separating carbon dioxide from carbon dioxide gas mixture.

6. The use according to claim 5, wherein the carbon dioxide gas mixture comprises CO ₂ And N ₂ And/or CH ₄ Is a mixed gas of (a) and (b).

7. The use according to claim 6, characterized in that the method is as follows: a metal organic framework material for carbon dioxide mixed gas separation as claimed in claim 1 is added to the carbon dioxide mixed gas.

8. Use according to claim 5, 6 or 7, characterized in that the metal organic framework material for carbon dioxide mixed gas separation is activated before adsorption, the activation method comprising the steps of: the metal organic framework material for carbon dioxide mixed gas separation was placed in methanol for 36h, solvent exchange was performed, fresh methanol was exchanged every 6h during the period, and after the exchange was completed, the activated product was centrifugally separated and dried under vacuum at 60 ℃.

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