Preparation of Metal-Organic Framework Materials and Their Application in Flue Gas Desulfurization and Dehumidification

Abstract

The present invention discloses the preparation of a metal-organic framework material and its application in flue gas desulfurization and dehumidification, belonging to the technical field of adsorption separation materials. The material is prepared by mixing an organic ligand 4,4',4",4"',4"",4""'-(9,10-dihydro-9,10-[1,2]benzanthracene-2,3,6,7,14,15-hexayl)hexabenzoic acid, yttrium nitrate, and o-fluorobenzoic acid, and then performing a solvent thermal reaction using N,N-dimethylformamide and water or nitric acid as solvents. The material is filtered, washed, and dried to obtain the product. The desulfurization performance of the material is substantially unaffected by humidity changes and exhibits stable and good performance even under high humidity conditions. The material is also capable of dehumidification, and its performance is substantially unaffected by the presence of sulfur dioxide gas.

Description

Technical Field

[0001] The present invention belongs to the technical field of adsorption separation materials, and in particular relates to the preparation of a metal organic framework material and its application in flue gas desulfurization and dehumidification. Background Art

[0002] Large amounts of sulfur dioxide (SO2) emitted in flue gas pose a serious threat to human health and the ecological environment. On the other hand, SO2 is also a key raw material for the synthesis of sulfuric acid and various fine chemicals. Therefore, the effective removal and reversible recovery of SO2 from flue gas has become a pressing issue in the industrial sector.

[0003] Traditional dry and wet desulfurization technologies have drawbacks such as low desulfurization efficiency (<95%), high energy consumption and non-recyclability. The solid waste generated also causes secondary pollution. In contrast, physical adsorption separation technology based on porous materials has become a research hotspot due to its high efficiency, energy saving and economic separation, and is considered to be an effective alternative to traditional desulfurization technology. Metal-Organic Frameworks (MOFs), as a new type of porous material, have become ideal materials for gas adsorption separation due to their adjustable composition, diverse structure, designability and modifiability.

[0004] At present, the research on MOF-based adsorbents is mainly aimed at the adsorption and separation of dry SO2, while the flue gas produced by the combustion of fossil fuels inevitably contains a large amount of water vapor. Therefore, flue gas desulfurization under high humidity conditions is of great significance, and there are two key problems that need to be solved urgently: First, the adsorbent requires extremely high water stability. This not only means that the material can maintain its structural integrity, crystallinity and porosity when immersed in water or exposed to humid air, but more importantly, it can withstand the destruction of the framework by the capillary tension of water vapor during the cyclic adsorption-desorption process. Secondly, the competitive adsorption of water vapor has a great influence on the desulfurization effect of the material. H2O will occupy the original adsorption sites of SO2, resulting in a decrease in desulfurization performance.

[0005] Hydrophobic MOFs offer a promising solution to these challenges. However, the extremely low water adsorption capacity of fully hydrophobic materials also compromises their dehumidification capabilities. Unremoved moisture not only impacts subsequent flue gas treatment (such as CO2 removal) but also hinders pipeline transport. Therefore, designing and developing new material platforms for efficient flue gas desulfurization and dehumidification presents a significant technical challenge. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned problems existing in the prior art and to provide a preparation method of a metal organic framework material and its application in flue gas desulfurization and dehumidification.

[0007] Technical solution of the present invention

[0008] A metal-organic framework material [Y9(μ3-O)2(μ3-OH) 12 (H2O)9(O2C-) 12 The preparation method of ]·[(CH3)2NH2](NKU-201-Y) comprises the following steps:

[0009] (1) Preparation of organic ligand 4,4',4",4"',4"",4""'-(9,10-dihydro-9,10-[1,2]benzanthracene-2,3,6,7,14,15-hexayl)hexabenzoic acid (H6PET)

[0010] Hexabromotriazine, 4-methoxycarbonylphenylboronic acid, cesium carbonate, and PdCl2(PPh3)2 were added to a tetrahydrofuran solution and heated to reflux under a nitrogen atmosphere. After the reaction, the mixture was cooled to room temperature and the tetrahydrofuran was removed by rotary evaporation. The resulting precipitate was dissolved in dichloromethane and extracted with water. The organic phase was collected and the dichloromethane was removed by rotary evaporation. The crude product was purified by silica gel chromatography to obtain methyl 4,4',4",4"',4"",4""'-(9,10-dihydro-9,10-[1,2]benzanthracene-2,3,6,7,14,15-hexayl)hexabenzoate (Me6PET).

[0011] Me6PET was dissolved in tetrahydrofuran and sodium hydroxide aqueous solution, heated to reflux, cooled to room temperature, and then the tetrahydrofuran was removed by rotary evaporation. The remaining aqueous solution was acidified with HCl aqueous solution, and the white precipitate was collected by filtration, washed with water, and vacuum dried to obtain the organic ligand H6PET.

[0012] Furthermore, the molar ratio of hexabromotriazine, 4-methoxycarbonylphenylboronic acid, cesium carbonate, and PdCl2(PPh3)2 is 1:9:9:0.1;

[0013] Furthermore, the ratio of tetrahydrofuran to sodium hydroxide aqueous solution is 1:1, the concentration of sodium hydroxide aqueous solution is preferably 1 mol / L, and the concentration of HCl aqueous solution is preferably 2 mol / L;

[0014] (2) Preparation of metal-organic framework material NKU-201-Y

[0015] The organic ligand H6PET, the metal salt Y(NO3)3·6H2O and the template agent o-fluorobenzoic acid are added to a mixed solvent of N,N-dimethylformamide (DMF) and water or nitric acid; the mixture is placed in a constant temperature oven for a solvothermal reaction, and after the reaction is completed, it is cooled to room temperature to obtain colorless hexagonal crystals. The material is washed with DMF and dried to obtain the crystalline material NKU-201-Y.

[0016] Furthermore, if the solvent system is DMF and water, the molar ratio of H6PET, Y(NO3)3·6H2O, and o-fluorobenzoic acid is 1:4:450 to 1:4:550, and the volume ratio of DMF and water is 10:3 to 10:4; if the solvent system is DMF and nitric acid, the molar ratio of H6PET, Y(NO3)3·6H2O, and o-fluorobenzoic acid is 1:4:250 to 1:4:350, and the volume ratio of DMF and nitric acid is 10:0.5 to 10:1.5, and the nitric acid is concentrated nitric acid diluted with DMF to 3.5 mol / L;

[0017] Furthermore, if the solvent system is DMF and water, the reaction temperature is 95°C to 110°C; if the solvent system is DMF and nitric acid, the reaction temperature is 110°C to 120°C;

[0018] Furthermore, the reaction time is 48 to 96 hours;

[0019] (3) Activation of material NKU-201-Y: The MOF material obtained in step (2) was collected and transferred to a DMF solution for soaking for one day, during which the solution was exchanged three times; the material was then transferred to an acetone solvent for soaking for three days, and the solvent was exchanged more than three times a day, preferably multiple times, and then activated at 130-160° C. on a degassing station for 8-12 hours to obtain the activated NKU-201-Y material.

[0020] The present invention also provides application of the metal organic framework material in flue gas desulfurization and dehumidification.

[0021] The activated NKU-201-Y material can simultaneously perform desulfurization and dehumidification in simulated flue gas under high humidity conditions.

[0022] Advantages and beneficial effects of the present invention:

[0023] (1) Compared with the reported synthesis methods of NKU-201-Y adsorbent materials, the method provided by the present invention does not involve highly toxic solvents such as chlorobenzene and is simple to synthesize;

[0024] (2) The present invention fully considers the gas composition in the flue gas, and the synthesized NKU-201-Y adsorbent material successfully avoids the competitive adsorption of SO2 and water molecules, achieving desulfurization and dehydration of flue gas under high humidity conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a synthetic route for the organic ligand H6PET involved in the present invention.

[0026] Figure 2 This is a structural diagram of the NKU-201-Y material prepared in the present invention.

[0027] Figure 3 1 is the PXRD pattern of the NKU-201-Y material prepared in the present invention immersed in different solvents (a) and pH (b).

[0028] Figure 4 1. The temperature-varying PXRD pattern (a) and thermogravimetric curve (b) of the NKU-201-Y material prepared in the present invention.

[0029] Figure 5 1. The nitrogen adsorption-desorption isotherm diagram (a) and pore size distribution diagram (b) of the NKU-201-Y material prepared by the present invention.

[0030] Figure 6 1. The water adsorption isotherm diagram (a) and 60-cycle diagram (b) of the NKU-201-Y material prepared by the present invention.

[0031] Figure 7 The single-component adsorption isotherm diagram (a) of SO2 / CO2 / N2 / O2 of the NKU-201-Y material prepared by the present invention at 298K, the single-component adsorption isotherm diagram (b) of SO2, and the adsorption heat Q of SO2 / CO2. st Figure (c), SO2 / CO2 separation ratio figure (d).

[0032] Figure 8 These are the simulated flue gas fixed bed penetration curves of the NKU-201-Y material prepared by the present invention at 298K, including SO2 / N2 binary mixture (a), SO2 / CO2 / N2 ternary mixture (b), SO2 / CO2 / N2 / O2 quaternary mixture (c) and in-situ desorption curve (d).

[0033] Figure 9 The figures are the fixed-bed penetration curve (a) and in-situ desorption curve (b) of the SO2 / N2 binary mixed gas of the NKU-201-Y material prepared by the present invention under different humidity conditions, as well as the time dependence graph (c) of the SO2 and H2O vapor adsorption kinetics.

[0034] Figure 10 It is a penetration curve diagram (a) of water vapor of the NKU-201-Y material prepared by the present invention in the presence and absence of SO2 and a penetration curve cycle diagram (b) of the SO2 / CO2 / O2 / N2 mixed gas at 70% relative humidity. DETAILED DESCRIPTION

[0035] Example 1:

[0036] Preparation of organic ligand 4,4',4",4"',4"",4""'-(9,10-dihydro-9,10-[1,2]benzanthracene-2,3,6,7,14,15-hexayl)hexabenzoic acid (H6PET). The synthetic route is as follows: Figure 1

[0037] Hexabromotriazine (3.00 g, 4.12 mmol), 4-methoxycarbonylphenylboronic acid (6.68 g, 37.1 mmol), Cs2CO3 (12.1 g, 37.2 mmol), and PdCl2(PPh3)2 (0.29 g, 0.412 mmol) were added to a tetrahydrofuran (40 mL) solution and heated to reflux at 75°C under a N2 atmosphere for 72 hours. After cooling to room temperature, the tetrahydrofuran was removed by rotary evaporation, and the resulting precipitate was dissolved in 200 mL of dichloromethane and extracted with water (100 mL x 3). The organic phase was collected and the dichloromethane was removed by rotary evaporation. The crude product was purified by silica gel chromatography (eluent: 0%-2% ethyl acetate in dichloromethane) to obtain the obtained Me6PET product (3.28 g, 75.2% yield).

[0038] Me6PET (1.7 g, 1.61 mmol) was dissolved in tetrahydrofuran (20 mL) and aqueous sodium hydroxide solution (1 mol / L, 20 mL), heated under reflux at 75°C for 24 hours, and then cooled to room temperature. The tetrahydrofuran was removed by rotary evaporation, and the remaining aqueous solution was acidified with aqueous HCl solution (pH = 1). The white precipitate was collected by filtration, washed with water, and dried in vacuo to obtain the organic ligand H6PET (1.46 g, yield 85.8%).

[0039] Synthesis of NKU-201-Y material

[0040] 9.75 mg of H6PET, 17.8 mg of Y(NO3)3·6H2O, 700 mg of o-fluorobenzoic acid, 2 mL of DMF, and 0.7 mL of deionized water were added to a 10 mL glass vial. After ultrasonic treatment for 20 minutes, the mixture was heated in a 100°C oven for 72 hours. After the reaction, the mixture was cooled to room temperature to obtain colorless hexagonal crystals. After filtration and drying, the crystalline material was initially obtained.

[0041] Activation of NKU-201-Y material

[0042] The MOF material obtained in Example 2 was transferred to a DMF solution and soaked for one day, during which the solution was exchanged three times, 10 mL each time; the material was then transferred to an acetone solvent and soaked for three days, with the solvent exchanged 3-5 times a day, and then activated at 150°C for 12 hours on a degassing station to obtain activated NKU-201-Y.

[0043] Example 2:

[0044] Synthesis of NKU-201-Y material

[0045] 9.75mg H6PET, 17.8mg Y(NO3)3·6H2O, 630mg o-fluorobenzoic acid, 2mL DMF, 0.6mL

[0046] Deionized water was added to a 10 mL glass vial, ultrasonically treated for 20 min, and then placed in a 100 °C oven for constant heating for 72 h.

[0047] After the reaction is completed, the mixture is cooled to room temperature to obtain colorless hexagonal crystals, which are filtered and dried to preliminarily obtain the crystalline material.

[0048] The remaining steps are the same as in Example 1.

[0049] Example 3:

[0050] Synthesis of NKU-201-Y material

[0051] 9.75 mg of H6PET, 17.8 mg of Y(NO3)3·6H2O, 770 mg of o-fluorobenzoic acid, 2 mL of DMF, and 0.8 mL of deionized water were added to a 10 mL glass vial. The mixture was ultrasonically treated for 20 minutes and then heated in a 100°C oven for 72 hours. After the reaction, the mixture was cooled to room temperature to obtain colorless hexagonal crystals. After filtration and drying, the crystalline material was initially obtained.

[0052] The remaining steps are the same as in Example 1.

[0053] Example 4:

[0054] Synthesis of NKU-201-Y material

[0055] 9.75 mg of H6PET, 17.8 mg of Y(NO3)3·6H2O, 350 mg of o-fluorobenzoic acid, 2 mL of DMF, and 0.1 mL of nitric acid (3.5 mol / L, diluted in DMF) were added to a 10 mL glass vial. The mixture was ultrasonically treated for 20 minutes and then heated in a 120°C oven for 72 hours. After the reaction, the mixture was cooled to room temperature to obtain colorless hexagonal crystals. After filtration and drying, the crystalline material was initially obtained.

[0056] The remaining steps are the same as in Example 1.

[0057] Example 5:

[0058] Synthesis of NKU-201-Y material

[0059] 9.75 mg of H6PET, 17.8 mg of Y(NO3)3·6H2O, 490 mg of o-fluorobenzoic acid, 2 mL of DMF, and 0.3 mL of nitric acid (3.5 mol / L, diluted in DMF) were added to a 10 mL glass vial. The mixture was ultrasonically treated for 20 minutes and then heated in a 120°C oven for 72 hours. After the reaction, the mixture was cooled to room temperature to obtain colorless hexagonal crystals. After filtration and drying, the crystalline material was initially obtained.

[0060] The remaining steps are the same as in Example 1.

[0061] Example 6:

[0062] Characterization and performance testing of NKU-201-Y material

[0063] The crystal structure diagram of the obtained NKU-201-Y material is as follows: Figure 2 As shown, the material is a (6,12)-connected alb topology network with The diamond channel has a size of and The cage provides a suitable confined space for the adsorption of SO2 and H2O molecules. The three coordinated water molecules at the equatorial position of the metal cluster can be removed by thermal activation, which also provides a strong binding site for SO2 and H2O.

[0064] The PXRD test showed that the material was successfully synthesized, had good crystallinity and could be successfully activated. Figure 3 a; Solvent stability, water and acid-base stability tests show that the material can maintain good crystal stability in common organic solvents (ethanol, acetone, dichloromethane, ether), pH = 2-12 and boiling water, such as Figure 3 ab.

[0065] The temperature-dependent PXRD and thermogravimetric tests showed that the thermal stability of the material was as high as 500 °C. Figure 4 The BET specific surface area of ​​the material tested in nitrogen at 77K is 1239 m 2 / g, the pore size is mainly distributed in like Figure 5 ab.

[0066] In order to test the water adsorption performance of the prepared NKU-201-Y material, the water adsorption isotherm at 298K was tested, as shown in Figure 6 a. The material exhibits an S-type adsorption curve. Before the inflection point of 50% RH, the water absorption of the material is less than 0.1 g / g. Above 60% RH, the water absorption reaches 0.56 g / g. Figure 6 b, The material still maintains a stable working capacity after 60 cycles of adsorption and desorption.

[0067] In order to test the desulfurization performance of the prepared NKU-201-Y material, the adsorption isotherms of flue gas components (SO2, CO2, N2, O2) at 298K were first tested, as shown in Figure 2. Figure 7 a. The adsorption capacity of SO2 at 1 bar is 10.8 times that of CO2, while N2 and O2 are hardly adsorbed; Figure 7 b. After 5 cycles of SO2 adsorption and desorption, the performance of the material remains stable; Figure 7 c, SO at 1 bar 2 / The separation selectivities of CO2 (50 / 50, 90 / 10, v / v) were 105 and 33 respectively, and the separation selectivities of SO2 / N2 and SO2 / O2 were greater than 1.0×10 6 ;like Figure 7 d. The material's near-zero coverage adsorption heat for SO2 is 46.55 kJ / mo1, and the near-zero coverage adsorption heat for CO2 is 16.16 kJ / mo1, which is consistent with the calculated trend of the adsorption isotherm and separation selectivity. Figure 8 The material's actual separation performance for SO2 / N2 binary gas mixture, SO2 / CO2 / N2 ternary gas mixture, and SO2 / CO2 / N2 / O2 quaternary gas mixture was demonstrated. The results showed that SO2 can maintain a stable breakthrough time and can desorb adsorbed SO2 in situ with a purity of up to 96.4%.

[0068] In order to test the desulfurization and water removal performance of the material under different humidity, the fixed bed penetration experiment of SO2 / N2 was tested at 10% RH, 30% RH, 50% RH and 70% RH, such as Figure 9 a. The results show that the breakthrough time of SO2 is almost unaffected by humidity changes; Figure 9 b. The adsorption kinetics experiments of SO2 and water vapor at different humidity levels show that the adsorption rate of SO2 is significantly faster than that of water; Figure 9 c. The fixed bed in-situ desorption experiment shows that when adsorbing the same amount of SO2, the number of H2O molecules adsorbed at 70% RH is significantly greater than that at 30% RH and 50% RH, so there is almost no competitive adsorption between SO2 and H2O; Figure 10 a. Regardless of the presence of SO2, the dehydration property of the material remains unchanged, and the breakthrough time of H2O does not change significantly; Figure 10 b. At 70% relative humidity, the breakthrough time of simulated flue gas SO2 / CO2 / O2 / N2 is still as high as 52 min / g, and the performance does not decrease after two cycles.

Claims

1. A method for preparing a metal organic framework material, wherein the material is [Y9(μ3-O)2(μ3-OH) 12 (H2O)9(O2C−) 12 ]·[(CH3)2NH2](NKU-201-Y), the specific steps are as follows: (1) Preparation of organic ligand 4,4',4'',4''',4'''',4'''''-(9,10-dihydro-9,10-[1,2]benzanthracene-2,3,6,7,14,15-hexayl)hexabenzoic acid (H6PET) Hexabromotriazine, 4-methoxycarbonylphenylboronic acid, cesium carbonate, and PdCl2(PPh3)2 were added to a tetrahydrofuran solution, and the mixture was heated to reflux under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature and the tetrahydrofuran was removed by rotary evaporation. The resulting precipitate was dissolved in dichloromethane, extracted with water, and the organic phase was collected. The dichloromethane was removed by rotary evaporation. The crude product was purified by silica gel chromatography to obtain methyl 4,4',4'',4''',4''',4'''',4''''-(9,10-dihydro-9,10-[1,2]benzanthracene-2,3,6,7,14,15-hexayl)hexabenzoate (Me6PET) product; Me6PET was dissolved in tetrahydrofuran and sodium hydroxide aqueous solution, heated to reflux, cooled to room temperature, and then the tetrahydrofuran was removed by rotary evaporation. The remaining aqueous solution was acidified with HCl aqueous solution, and the white precipitate was collected by filtration, washed with water, and vacuum dried to obtain the organic ligand H6PET; (2) Preparation of metal-organic framework material NKU-201-Y The organic ligand H6PET, metal salt Y(NO3)3·6H2O and template agent o-fluorobenzoic acid were added to N,N - a mixed solvent of dimethylformamide (DMF) and water or nitric acid; the mixture is placed in a constant temperature oven for solvothermal reaction, and after the reaction is completed, it is cooled to room temperature to obtain colorless hexagonal crystals, which are washed with DMF and dried to obtain the crystalline material NKU-201-Y; (3) Activation of metal-organic framework material NKU-201-Y The obtained material NKU-201-Y was collected and transferred to a DMF solution for soaking for one day, during which the solution was exchanged more than three times; the material was then transferred to an acetone solvent for soaking for three days, during which the solvent was exchanged more than three times a day, and then activated at 130-160 °C on a degassing station for 8-12 h to obtain the activated NKU-201-Y material.

2. The preparation method according to claim 1, characterized in that In step (1), the molar ratio of hexabromotriazine, 4-methoxycarbonylphenylboronic acid, cesium carbonate, and PdCl2(PPh3)2 is 1:9:9:0.1; and the volume ratio of tetrahydrofuran and sodium hydroxide aqueous solution is 1:

1.

3. The preparation method according to claim 1, characterized in that In step (1), the concentration of the sodium hydroxide aqueous solution is 1 mol / L, and the concentration of the HCl aqueous solution is 2 mol / L.

4. The preparation method according to claim 1, characterized in that In step (2), when the solvent system is DMF and water, the molar ratio of H6PET, Y(NO3)3·6H2O, and o-fluorobenzoic acid is 1:4:450 to 1:4:550, and the volume ratio of DMF and water is 10:3 to 10:4; when the solvent system is DMF and nitric acid, the molar ratio of H6PET, Y(NO3)3·6H2O, and o-fluorobenzoic acid is 1:4:250 to 1:4:350, and the volume ratio of DMF and nitric acid is 10:0.5 to 10:1.5, and the nitric acid is concentrated nitric acid diluted with DMF to 3.5 mol / L.

5. The preparation method according to claim 1, characterized in that In step (2), when the solvent system is DMF and water, the reaction temperature is 95°C to 110°C; when the solvent system is DMF and nitric acid, the reaction temperature is 110°C to 120°C.

6. The preparation method according to claim 1, characterized in that In step (2), the reaction time is 48 to 96 hours.

7. The metal organic framework material NKU-201-Y prepared by the method according to any one of claims 1 to 6.

8. Use of the material NKU-201-Y according to claim 7 in flue gas desulfurization and dehumidification.

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