CN112807930B - Application of metal organic framework compound MFM-520 in adsorption, separation and conversion of acidic gas pollutants in air - Google Patents

Application of metal organic framework compound MFM-520 in adsorption, separation and conversion of acidic gas pollutants in air Download PDF

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CN112807930B
CN112807930B CN201911117093.5A CN201911117093A CN112807930B CN 112807930 B CN112807930 B CN 112807930B CN 201911117093 A CN201911117093 A CN 201911117093A CN 112807930 B CN112807930 B CN 112807930B
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杨四海
马丁·施罗德
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Ma DingShiluode
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
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    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/223—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material containing metals, e.g. organo-metallic compounds, coordination complexes
    • B01J20/226—Coordination polymers, e.g. metal-organic frameworks [MOF], zeolitic imidazolate frameworks [ZIF]
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/20—Organic adsorbents
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
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    • B01D2257/302—Sulfur oxides
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
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    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
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    • Y02C20/40—Capture or disposal of greenhouse gases of CO2

Abstract

The invention discloses a new application of a metal organic framework compound MFM-520. The application is the application of the composite material in the adsorption separation of acidic gas pollutants in air; or the application in the adsorption separation and the conversion of the acidic gas pollutants in the air. The acid gas contaminants in the air may be selected from at least one of: nitrogen dioxide, sulfur dioxide and carbon dioxide. Experiments show that the metal organic framework compound MFM-520 has good adsorption selectivity on acidic gas pollutants (especially nitrogen dioxide, sulfur dioxide and carbon dioxide) in the air under normal pressure and low pressure (10 ppm-1.0 of atmospheric pressure), and can be used for gas adsorption, separation and conversion.

Description

Application of metal organic framework compound MFM-520 in adsorption, separation and conversion of acidic gas pollutants in air
Technical Field
The invention belongs to the technical field of utilization of inorganic-organic hybrid materials, and particularly relates to application of a metal organic framework compound (MFM-520) in adsorption, separation and conversion of acidic gas pollutants in air.
Background
Air pollution is one of the major problems facing the world today. The World Health Organization (WHO) 2016 states that atmospheric pollution directly accounts for about one-eighth of the world population deaths, with about 7 million deaths per year being caused by direct or indirect air pollution (http:// www. WHO. Int/media/news/releases/2014/air-polarization/en/April 2016). Nitrogen dioxide and sulfur dioxide are acidic gases in atmospheric pollutants, mainly caused by the use of fuels such as petroleum, coal, diesel, biomass, etc. These gases are present in very high concentrations in large urban and heavy industrial areas where populations, vehicles are dense and the health risks to the relevant population are particularly severe. The biological pathological toxicity of nitrogen dioxide and sulfur dioxide is very high, which is the cause of many respiratory diseases. In recent years, the development and exploration of materials capable of efficiently capturing nitrogen dioxide and sulfur dioxide have become one of the research hotspots in the field of high-tech and new materials. However, this is a significant challenge to scientists because nitrogen dioxide and sulfur dioxide are corrosive, chemically very reactive, and can cause decomposition, failure and system corrosion of many materials in short contact times.
The adsorption materials most commonly used at present mainly comprise porous activated carbon materials and molecular sieves, however, the activated carbon has weak selective adsorption capacity for low-concentration acidic gas pollutants (nitrogen dioxide and sulfur dioxide) in the air, the total adsorption capacity of the molecular sieve materials is low, and the activated carbon and the molecular sieve materials are extremely easy to be oxidized and decomposed to lose effectiveness when being contacted with high-concentration nitrogen dioxide and sulfur dioxide.
At present, the main method for eliminating nitrogen oxides is carried out by a selective catalytic conversion method, ammonia gas is used as a reducing agent, and noble metal and transition metal oxides are used as catalysts under the condition of high temperature. The selective catalytic conversion process does not remove all the nitrogen oxides and the concentration of nitrogen oxides emitted from the treated exhaust gas can still reach between 1000 and 2000 ppm, thus causing a series of negative effects on the environment and human health.
Metal-organic framework (MOF) materials are a new type of porous functional materials constructed by metal ions or metal cluster units and organic ligands. The MOF material has super-large surface area and porous property, high crystallinity, and regularly and densely arranged adsorption active sites in the pore channels, so that the MOF material has many excellent properties in the aspect of gas adsorption. Currently, MOF materials are widely studied and paid attention to the adsorption properties of methane, carbon dioxide, nitrogen, hydrogen and small molecular hydrocarbons. However, MOF materials that are highly efficient and stable for the adsorption of nitrogen dioxide and sulfur dioxide are also very rare, especially the former. Most MOF compounds do not have sufficient stability to nitrogen dioxide and sulfur dioxide. Therefore, it is required to develop a metal organic framework compound having very high structural stability and high selectivity for pollutants and to apply it to the adsorption, separation and conversion of acidic gas pollutants in the air.
In 2018, a research team of the inventor publishes the first MOF material [ named as MFM-300 (Al), nature Materials, 2018, 17, 691-696], capable of adsorbing nitrogen dioxide efficiently and stably in a circulating way in the world, so that the progress of related research is promoted to a great extent. However, while the MFM-300 (Al) material exhibits a high adsorption amount of nitrogen dioxide (14.1 mmol/g) at room temperature and one atmosphere pressure, the adsorption amount of this material in the low pressure region is not ideal, such as the MFM-300 (Al) material having an adsorption amount of 1.4 mmol/g at room temperature and a nitrogen dioxide partial pressure of 0.01 atm and an adsorption amount of only 0.1 mmol/g at a nitrogen dioxide partial pressure of 0.001 atm, which limits its application to some extent.
Disclosure of Invention
The invention aims to provide a new application of a metal-organic framework compound MFM-520.
The novel application of the metal-organic framework compound MFM-520 provided by the invention is the application of the metal-organic framework compound MFM-520 in adsorption separation of acidic gas pollutants in air; or the application in the adsorption separation and the conversion of acid gas pollutants in the air.
The acid gas contaminants in the air may be selected from at least one of: nitrogen dioxide, sulfur dioxide and carbon dioxide.
The pressure of the acid gas contaminants in the air may be between 10ppm and 1 atmosphere (1 ppm = parts per million).
The temperature of the adsorption separation is 273-393K.
The adsorptive separation may be carried out in the absence of water vapor or in the presence of water vapor.
When the adsorbed acid gas is nitrogen dioxide, the adsorbed nitrogen dioxide can be converted into nitric acid by the following specific method: putting the MFM-520 adsorbed with saturated nitrogen dioxide into water, stirring at room temperature, filtering to obtain filtrate (the nitrogen dioxide adsorbed in the pore channels of the MFM-520 is completely converted into nitric acid and dissolved in water), and activating the filtered MFM-520 again under the condition of reduced pressure and heating for adsorbing the nitrogen dioxide in a new round.
When the adsorbed acid gas is sulfur dioxide, the adsorbed sulfur dioxide can be converted into a sulfonamidation product (a compound shown as formula I).
Figure 794338DEST_PATH_IMAGE001
Formula I
The specific method comprises the following steps: MFM-520, 4-amino morpholine and 4-methoxy-boron p-phenyl tetrafluoride diazonium salt which are adsorbed with saturated sulfur dioxide react in acetonitrile solution, and after the reaction is finished, filtrate obtained by suction filtration is concentrated under vacuum to obtain a sulfonamidated product (a compound shown in a formula I). The filter cake obtained by suction filtration (MFM-520 material) was used for a new round of sulfur dioxide adsorption after heating to 100 ℃ under vacuum and holding for 1 hour.
The metal-organic framework compound MFM-520 of the present invention can be prepared by a method comprising the steps of: 1) Adding 4, 4' -bipyridine-2, 6', 2, 6' -tetracarboxylic acid, zinc chloride and 2, 6-lutidine into water, and carrying out hydrothermal reaction to obtain MFM-520;
2) And (3) heating the MFM-520 in an anhydrous environment for activation to obtain the activated MFM-520.
In the step 1) of the method, the molar ratio of the 4, 4' -bipyridine-2, 6', 2, 6' -tetracarboxylic acid to the zinc chloride to the 2, 6-lutidine is 1 (2.0-5.0) to 4.0-20.0, and the molar ratio of the 1.0:2.0:4.0 The product is superior.
The reaction temperature of the hydrothermal reaction is 110-130 ℃, and the reaction time is 3-6 days.
In the step 2) of the method, the activation temperature is 100-150 ℃ and the activation time is 1-5 hours.
The preparation can be carried out by referring to the following methods:
X. Lin, A. J. Blake, C. Wilson, X. Sun, N. R. Champness, M. W. George, P. Hubberstey, R. Mokaya and M. Schrӧder. Journal of the American Chemical Society. 2006, 128, 10745-10753。
MFM-520 (not activated) in this document is named "compound I"; the activated MFM-520 is named "compound II".
Tests show that the metal organic framework compound MFM-520 has good adsorption selectivity on acidic gas pollutants (especially nitrogen dioxide, sulfur dioxide and carbon dioxide) in the air under normal pressure and low pressure (10 ppm-1.0 atmospheric pressure), and can be used for gas adsorption, separation and conversion.
The invention has the following beneficial effects:
1) The MFM-520 material has excellent adsorption capacity for acid gas contaminants, particularly nitrogen dioxide, sulfur dioxide and carbon dioxide, with nitrogen dioxide and sulfur dioxide adsorption capacity and selectivity superior to existing materials. Particularly under low pressure conditions and in the presence of water vapor, still exhibit strong adsorption capacity for nitrogen dioxide and sulfur dioxide.
2) The metal-organic framework compound MFM-520 is easy to desorb with the adsorbed gas, and the desorbed MFM-520 can be recycled, and the original adsorption capacity can be maintained.
3) The nitrogen dioxide and sulfur dioxide gas desorbed from the MFM-520 can be efficiently converted into basic chemicals for practical use or used for synthesis of drug molecules.
Drawings
FIG. 1 shows nitrogen dioxide isothermal adsorption lines for a material MFM-520 at different temperatures (298K, 303K, 308K, 313K, 318K, 323K, 333K); the inner diagram is a nitrogen dioxide isothermal adsorption line with logarithmic pressure;
fig. 2 (a) is a dynamic adsorption curve of the material MFM-520 to nitrogen dioxide (b) is a dynamic desorption curve of the material MFM-520 to nitrogen dioxide (for a certain set adsorption-desorption pressure, the corresponding adsorption-desorption is completed within 10 minutes);
FIG. 3 shows the MFM-520 pair of materials for different gases (NO) 2 , SO 2 , CO 2 , CH 4 , N 2 , O 2 CO and H 2 ) Isothermal adsorption line at room temperature (298K);
FIG. 4 is a graph of the isothermal adsorption lines of nitrogen dioxide and water for the material MFM-520 at room temperature (298K);
FIG. 5 shows nitrogen isotherms for the MFM-520 at different temperatures (273K, 283K, 298K and 318K);
FIG. 6 shows the variation of nitrogen dioxide heat of adsorption and entropy for MFM-520;
FIG. 7 is a theoretical calculation of the MFM-520 versus the gas composition (NO) of the nitrogen dioxide mixture for the material 2 And N 2 , NO 2 And CO 2 , NO 2 And SO 2 ) The adsorption selectivity of (a);
FIG. 8 is a comparison curve of the adsorption capacity of MFM-520 for nitrogen dioxide over 125 cycles;
FIG. 9 shows a graph of the dynamic adsorptive separation of the material MFM-520 under dry and wet conditions for nitrogen dioxide and nitrogen gas, respectively, in a fluid bed experiment;
FIG. 10 is a graph of the dynamic adsorptive separation of the material on mixed gases (nitrogen dioxide and sulfur dioxide) in a fluidized bed experiment;
FIG. 11 is a graph of the dynamic adsorptive separation of the material on mixed gases (nitrogen dioxide and carbon dioxide) in a fluidized bed experiment;
FIG. 12 shows powder diffraction patterns of the material under different harsh conditions;
FIG. 13 shows the powder diffraction pattern of the material MFM-520 at different cycle numbers during the cyclic conversion of nitrogen dioxide to nitric acid;
FIG. 14 (a) is a plot of the temperature sorption curve for sulfur dioxide for this material MFM-520 at different temperatures (273K, 283K, 293K, 298K, 303K, 308K, 313K and 318K); (b) is a sulfur dioxide isothermal adsorption line taking logarithm of pressure;
fig. 15 (a) is a dynamic adsorption curve of the material MFM-520 for sulfur dioxide (b) is a dynamic desorption curve of the material MFM-520 for sulfur dioxide (for a certain set adsorption and desorption pressure, the corresponding adsorption and desorption is completed within 10 minutes);
FIG. 16 shows the variation of the heat of adsorption and entropy of sulfur dioxide for this material MFM-520;
FIG. 17 shows the carbon dioxide isothermal adsorption lines of the material MFM-5200 at different temperatures (273K, 283K, 293K, 298K, 303K, 308K and 318K);
FIG. 18 shows the variation of the heat of carbon dioxide adsorption and entropy of this material MFM-520;
FIG. 19 is a comparison curve of the sulfur dioxide adsorption of 75 times of the MFM-520 material;
FIG. 20 is a theoretical calculation of the MFM-520 of this material for different sulfur dioxide gas components (SO) 2 And N 2 , SO 2 And CO 2 ) The adsorption selectivity of (a);
FIG. 21 is a comparison of the dynamic adsorption separation cycle curve for sulfur dioxide in a water presaturation fluidized bed experiment with the dynamic adsorption separation curve for sulfur dioxide in a dry fluidized bed experiment;
FIG. 22 is a comparison of the dynamic adsorptive separation of mixed gases (sulfur dioxide and nitrogen) under dry and wet conditions in a fluidized bed experiment;
FIG. 23 is a graph of the dynamic adsorptive separation of a mixed gas at 298K (sulfur dioxide and carbon dioxide) in a fluidized bed experiment;
FIG. 24 is a graph of the dynamic adsorptive separation of a mixed gas at 318K (sulfur dioxide and carbon dioxide) in a fluidized bed experiment;
FIG. 25 is a reaction equation for conversion of captured sulfur dioxide to sulfanilamide;
FIG. 26 is a graph of experimental carbon dioxide adsorption heat for the material MFM-520;
FIG. 27 is a sulfur dioxide adsorption heat experimental curve of the material MFM-520;
FIG. 28 is a graph of dynamic adsorptive separation of mixed gases at 293K (carbon dioxide and nitrogen) in a fluidized bed experiment;
FIG. 29 is a graph of dynamic adsorptive separation of mixed gases at 323K (carbon dioxide and nitrogen) in a fluidized bed experiment.
Detailed Description
The present invention is described below with reference to specific embodiments, but the present invention is not limited thereto, and any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.
Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
In the quantitative tests in the following examples, three replicates were set up and the results averaged.
The metal-organic framework compounds MFM-520 used in the examples described below are all activated MFM-520 unless otherwise indicated.
The preparation method comprises the following steps:
the preparation method of the organic ligand molecule (4, 4' -bipyridine-2, 6', 2, 6' -tetracarboxylic acid) is prepared according to the following method in the literature: J.A. Berson& T. Cohen. Journal of Organic Chemistry.1955, 20, 1461-1468.
The preparation method comprises the following steps: 4-bromo-2, 6-lutidine (0.470 g, 2.5 mmol), niBr 2 (PPh 3 ) 2 (0.56 g, 0.75 mmol), zinc powder (0.245 g, 3.8 mmol) and Et 4 NI (0.64 g, 2.5 mmol) in dry tetrahydrofuran (15 ml) was refluxed for 18 hours under protection of dry nitrogen, after the reaction was completed, the reaction solution was cooled to room temperature, filtered with suction, and the obtained filtrate was concentrated under vacuum to obtain a crude product of 2, 2', 6, 6' -tetramethyl-4, 4' -bipyridine. The resulting crude product was dissolved in 10% aqueous ethylenediamine (100 ml) and extracted with chloroform (100 ml). The obtained organic layer was washed with aqueous hydrochloric acid (100 ml, 1 mol/l), aqueous sodium hydroxide (1 mol/l) was added to the obtained aqueous layer until the solution became alkaline, the obtained alkaline solution was extracted three times with chloroform (50 ml), the obtained extracts were combined and dried over magnesium sulfate, and concentrated under vacuum to obtain a solutionTo a white solid. Recrystallization from hexane gave pure 2, 2', 6, 6' -tetramethyl-4, 4' -bipyridine (0.193 g, 70% yield).
The pure 2, 2', 6, 6' -tetramethyl-4, 4' -bipyridine product obtained in the previous step (3.0 g, 14.1 mmol) was dissolved in concentrated sulfuric acid (50 ml), and then chromium trioxide (15 g, 0.15 mol) was added to the solution in portions, and the mixture was reacted at 75 ℃ for two hours. After the reaction is finished, cooling the reaction solution to room temperature, then pouring the reaction solution into ice water (200 g), separating out white solid, and performing suction filtration to obtain a crude product of the 4, 4' -bipyridine-2, 6', 2, 6' -tetracarboxylic acid. The crude product obtained was recrystallized from 35% nitric acid to give the ligand 4, 4' -bipyridine-2, 6', 2, 6' -tetracarboxylic acid (3.28 g, yield 70%).
The unactivated metal organic framework compound MFM-520 was prepared according to the following literature: x, lin, a.j. Blake, c, wilson, x, sun, n.r. Champness, m.w. George, p. Hubberstey, r. Mokaya and m. Schr 1255der.Journal of the American Chemical Society. 2006, 128, 10745-10753. MFM-520 (not activated) is named "compound I" in this document.
The preparation method comprises the following steps: and (3) synthesizing the metal organic framework material by a hydrothermal reaction. A predetermined amount of 4, 4' -bipyridine-2, 6', 2, 6' -tetracarboxylic acid (0.166 g, 0.5 mmol), zinc chloride (0.317 g, 1.0 mmol) and 2, 6-lutidine were mixed well in 30 ml of water and then charged into a 45 ml reaction vessel. The autoclave was placed in an oven at a rate of 1 degree celsius/minute to 130 degrees celsius and the reaction was continued at this temperature for 6 days. After the reaction is finished, the temperature is reduced to room temperature, and white solid is obtained by suction filtration. The white solid was washed with deionized water, ethanol, and ether in this order, and then dried in air to give MFM-520 (76% yield). The average particle size is 10-200 microns.
The activated MFM-520 material is prepared according to the following literature: x, lin, a.j. Blake, c, wilson, x, sun, n.r. Champness, m.w. George, p. Hubberstey, r. Mokaya and m. Schr 1255der.Journal of the American Chemical Society. 2006, 128, 10745-10753In this document, the activated MFM-520 is named "compound II".
The specific activation method is as follows: the unactivated MFM-520 produced by the reaction is placed in an anhydrous environment (vacuum or dry nitrogen stream) and heated to 100 degrees celsius for 1 hour to yield desolventized MFM-520.
Example 1 static adsorption Capacity examination of MFM-520 Material on Nitrogen dioxide
The isothermal adsorption experiment studies the static adsorption capacity of the MFM-520 material on nitrogen dioxide. In the temperature range of 0-60 ℃, under the constant temperature condition, the activated MFM-520 material is placed in a vacuum closed reactor, the adsorption and desorption are balanced under different nitrogen dioxide pressures (0-1 atmospheric pressure), and the static nitrogen dioxide saturation absorption curve of the MFM-520 at the temperature is measured.
Taking 25 degrees celsius and one atmosphere pressure as an example, the adsorption amount of the MFM-520 to nitrogen dioxide is 4.53 mmol/g, which is significantly higher than that of other types of porous materials, such as common activated carbon, which has an adsorption amount of only 1.70-2.96 mmol/g to nitrogen dioxide under the same conditions, porous silica (SBA-15), which has an adsorption amount of only 0.64 mmol/g to nitrogen dioxide under the same conditions, amino-modified silica material, which has an adsorption amount of only 0.98-2.17 mmol/g to nitrogen dioxide under the same conditions, and metal oxide, such as ceria-zirconia, which has an adsorption amount of only 0.48-0.87 mmol/g to nitrogen dioxide under the same conditions. Although the Y-type molecular sieve shows a high adsorption capacity (9.78 mmol/g) for nitrogen dioxide, experiments prove that the material can adsorb nitrogen dioxide and simultaneously reduce the nitrogen dioxide into nitric oxide, and the molecular sieve material is partially oxidized to cause partial decomposition of the material.
The MFM-520 still exhibits a strong capability of adsorbing nitrogen dioxide under low pressure conditions. For example, when the pressure of nitrogen dioxide in the reaction is 0.1% atmospheric pressure and 1% atmospheric pressure, the adsorption amounts of MFM-520 for nitrogen dioxide are 1.3 mmol/g and 4.2 mmol/g, respectively. The high adsorption efficiency of the MFM-520 on nitrogen dioxide, which is due mainly to the relatively fast adsorption kinetics of the adsorption process of the MFM-520 on nitrogen dioxide, generally requires only 3-20 minutes to reach equilibrium, makes the material of great practical value, since the concentration of nitrogen dioxide pollutants in air is generally not more than 0.1% under practical conditions.
From 7 isothermal adsorption curves (see fig. 1) in the interval of 25 to 60 degrees celsius, we can calculate the adsorption heat of the MFM-520 for nitrogen dioxide at different adsorption amounts of nitrogen dioxide. This value is 70 to 65 kj/mole, demonstrating a strong interaction force of MFM-520 with nitrogen dioxide.
The adsorption selectivity and the mechanism for selectivity are described below. By further measuring the isothermal adsorption curves of MFM-520 for other major components in air and other common gases (see fig. 3), it can be seen that the adsorption amounts of the material for nitrogen, oxygen, carbon dioxide, hydrogen, methane, and carbon monoxide at 25 degrees celsius and one atmosphere pressure are: 0.18 0.19, 2.14, 0.22, 0.71 and 0.36 mmol/g. Further, it was confirmed that the material had an extremely weak adsorption capacity for the main component harmless to the air and a relatively weak adsorption capacity for carbon dioxide. The selective adsorption is derived from the fact that the pore channel of the MFM-520 has a unique three-dimensional shape, so that the dimer of the nitrogen dioxide molecule can be stably enriched in the pore channel of the MFM-520. In situ synchrotron radiation X-ray crystallography accurately characterizes the location of nitrogen dioxide in the MFM-520 pore channels and the formation of dimers. The strong interaction between nitrogen dioxide and MFM-520 is further determined by in situ electron paramagnetic resonance and inelastic neutron scattering. This strong interaction directly results in very high adsorption selectivity.
The nitrogen dioxide adsorbed in the MFM-520 pore canal can be completely desorbed by a constant-temperature reduced-pressure vacuumizing method. 125 cycles of nitrogen dioxide adsorption-desorption tests prove that the MFM-520 always maintains high-efficiency adsorption capacity for nitrogen dioxide during the cycle, and the single nitrogen dioxide adsorption amount does not show any observable attenuation (see figure 8). The characterization of X-ray crystal diffraction proves that the MFM-520 subjected to 125-cycle nitrogen dioxide adsorption-desorption tests completely maintains the original crystal structure (see figure 12), and proves the excellent structural stability and strong adsorption to nitrogen dioxide of the material.
Example 2 dynamic adsorption Capacity examination of MFM-520 Material on Nitrogen dioxide
In the dynamic nitrogen dioxide adsorption separation experiment, 1 g of unactivated MFM-520 powder (average particle size of about 1 μm) was packed in a cylindrical fluidized bed reactor having an inner diameter of 7 mm, a total length of 120 mm, and a sample packing thickness of 20 mm. Helium or nitrogen was passed through the reactor at a flow rate of 50 ml/min and the reactor was heated to 150 degrees celsius, so that the MFM-520 filled therein was sufficiently activated.
The bed was then cooled to 25 degrees celsius, a nitrogen test gas containing 0.25% nitrogen dioxide was passed through the reactor at a flow rate of 16-50 ml/min, and the evolved gas composition was detected at the gas outlet with a mass spectrometer. Since the MFM-520 has an extremely weak adsorption capacity and an extremely low adsorption amount for nitrogen, the nitrogen component in the test gas rapidly passes through the reactor, and instantaneously escapes from the outlet. In contrast, the MFM-520 has a strong adsorption capacity and a high adsorption amount for nitrogen dioxide in the test gas, and thus nitrogen dioxide in the test gas can be selectively retained in the reactor filled with the MFM-520 until the MFM-520 in the reactor is fully saturated with nitrogen dioxide, and nitrogen dioxide is not detected at the gas outlet. This experiment effectively demonstrates that MFM-520 can still preferentially capture and adsorb nitrogen dioxide from nitrogen gas under flow conditions in a simulated reality (see fig. 9).
In a test using a nitrogen gas mixture containing 0.25% of nitrogen dioxide and 3% of water vapor, the MFM-520 still maintains good adsorption capacity to the nitrogen dioxide (see figure 9), and further embodies the objective application prospect of the material in cleaning acidic gas pollutants in the air.
The nitrogen dioxide adsorbed in the MFM-520 material can be recycled for conversion to nitric acid by interaction with air and water, as follows. In the above-mentioned fluidized bed experiment, MFM-520 powder (100 mg) having adsorbed saturated nitrogen dioxide was stirred in 5 ml of pure water at room temperature for 30 minutes, filtered with suction, and the pH of the filtrate was measured (pH = 1.06). The filtrate was calculated to be 0.09 mol/l nitric acid, i.e., nitrogen dioxide adsorbed in the pores of the MFM-520 had been completely converted to nitric acid and dissolved in water. The filtered MFM-520 may be reactivated under reduced pressure and heat and used in a new round of nitrogen dioxide adsorption experiments. The process (MFM-520 adsorbs saturated nitrogen dioxide, the material is washed by water to convert the nitrogen dioxide into nitric acid, and the MFM-520 after the water washing is heated and activated again) can be cycled for at least ten times, and the MFM-520 always keeps the original crystal structure and the same adsorption quantity of the nitrogen dioxide. The results of the element analysis of the material MFM-520 at different cycle times during the conversion of nitrogen dioxide to nitric acid are shown in Table 1.
TABLE 1
Figure 139869DEST_PATH_IMAGE002
Example 3 evaluation of the adsorption Capacity of MFM-520 Material for Sulfur dioxide
The adsorption of sulfur dioxide by MFM-520 was 3.38 mmol/g at room temperature under 1 atm. However, MFM-520 exhibits a superior ability to adsorb sulfur dioxide over other metal organic framework compounds under low pressure conditions. For example, when the pressure of sulfur dioxide in the reaction is 0.1% atm, the adsorption of sulfur dioxide by MFM-520 is 1.66 mmol/g, respectively, which is higher than the adsorption of sulfur dioxide by most of the reported metal-organic framework compounds under the conditions. The high-efficiency adsorption of the low-pressure area is mainly due to the relatively fast adsorption kinetics of the MFM-520 on the sulfur dioxide adsorption process.
From 7 isothermal adsorption curves (see fig. 14) in the interval of 25 to 60 degrees celsius we can calculate the heat of adsorption of MFM-520 for sulfur dioxide at different amounts of sulfur dioxide adsorption. This value is 60-120 kj/mol, demonstrating a very strong interaction force of MFM-520 with sulfur dioxide.
The mechanism of sulfur dioxide adsorption is explained below. In situ synchrotron radiation X-ray crystallography accurately characterizes the location of sulfur dioxide in the MFM-520 pore channels. In situ inelastic neutron scattering and infrared spectral patterns further confirm the strong interaction between sulfur dioxide and MFM-520. This strong interaction directly results in very high adsorption selectivity.
The sulfur dioxide adsorbed in the pore channels of the MFM-520 can be completely desorbed by constant-temperature reduced-pressure vacuumizing. The 75-cycle nitrogen dioxide adsorption-desorption test proves that the MFM-520 always maintains the efficient adsorption capacity for the sulfur dioxide in the cycle process, and the single sulfur dioxide adsorption amount does not have any observable attenuation (see figure 19). The characterization of X-ray crystal diffraction proves that the MFM-520 subjected to 75-cycle sulfur dioxide adsorption-desorption tests completely maintains the original crystal structure, and the excellent structural stability and the strong adsorption to sulfur dioxide of the material are proved.
In the dynamic sulfur dioxide absorption separation experiment, 1 g of an unactivated MFM-520 powder (average particle size of about 1 μm) was packed in a cylindrical fluidized bed reactor having an inner diameter of 7 mm, an overall length of 120 mm, and a sample packing thickness of 20 mm. Helium or nitrogen was passed through the reactor at a flow rate of 50 ml/min and the reactor was heated to 150 degrees celsius, so that the MFM-520 filled therein was sufficiently activated.
The reaction bed was then cooled to 25 degrees celsius, and a nitrogen test gas containing 0.25% sulfur dioxide was passed through the reactor at a flow rate of 50 ml/min and the evolved gas composition was detected at the gas outlet with a mass spectrometer. Sulfur dioxide can be selectively retained in the reactor filled with MFM-520 while nitrogen in the test gas escapes rapidly at the beginning of the reaction. This experiment effectively demonstrates that MFM-520 can still preferentially capture and adsorb sulfur dioxide from nitrogen under flow conditions in a simulated reality (see fig. 22).
The MFM-520 still maintains good adsorption capacity to sulfur dioxide in a test using a nitrogen mixed gas containing 0.25 percent of sulfur dioxide and 1.5 percent of water vapor (see figure 22), and further embodies the objective application prospect of the material in cleaning acidic gas pollutants in the air.
In the above fluidized bed experiment, MFM-520 powder (0.357 g, equivalent to 1.18 mmol SO) saturated with sulfur dioxide was adsorbed 2 ) 4-Aminomorpholine (2) (0.128 g, 1.25 mmol) in acetonitrile (3 ml) was added and stirred at room temperature for 1 hour. A solution of 4-methoxy-p-phenyl boron tetrafluoride diazonium salt (1) (0.055 g, 0.25 mmol) in acetonitrile (1 ml) was added dropwise to the suspension (see fig. 25 for the reaction equation for the above reaction). The reaction was continued for 1 hour with stirring at room temperature, after completion of the reaction, the filtrate obtained by suction filtration was concentrated under vacuum to give the sulfonamidated product (3) (0.054 g, 99% conversion, 80% yield). The filter cake obtained by suction filtration (material MFM-520) is heated to 100 ℃ under vacuum and kept for 1 hour, and then the process is continued (the fluidized bed experiment adsorbs sulfur dioxide, and sulfanilation converts sulfur dioxide). The process can be cycled at least three times, and the MFM-520 maintains the original crystal structure and the same amount of sulfur dioxide adsorbed throughout the process. The results of the element analysis of the material MFM-520 at different cycle times during the process of converting sulfur dioxide into sulfanilamide are shown in FIG. 2.
TABLE 2
Figure 493490DEST_PATH_IMAGE003
Example 4 examination of the adsorption Capacity of MFM-520 Material for carbon dioxide
From 6 isothermal adsorption curves (see fig. 14) in the interval of 0 to 45 degrees celsius we can calculate the heat of adsorption of the MFM-520 for carbon dioxide at different amounts of carbon dioxide adsorption to be 32-50 kj/mole. At room temperature, under 1 atmosphere, the adsorption amount of MFM-520 to carbon dioxide is 2.15 mmol/g, while under the same conditions, the adsorption amount of MFM-520 to nitrogen is only 0.21 mmol/g.
In the dynamic sulfur dioxide absorption separation experiment, 1 g of unactivated MFM-520 powder (average particle size of about 1 micron) was packed in a cylindrical fluidized bed reactor with an inner diameter of 7 mm, an overall length of 120 mm, and a sample packing thickness of 20 mm. Helium or nitrogen was passed through the reactor at a flow rate of 50 ml/min and the reactor was heated to 150 degrees celsius, so that the MFM-520 filled therein was sufficiently activated.
After cooling the reaction bed to 20 degrees celsius, we selected a mixed gas representing the ratio of carbon dioxide and nitrogen in the flue gas (15% carbon dioxide and 85% nitrogen) under realistic conditions to be passed through the reactor at a flow rate of 50 ml/min and the evolved gas composition detected at the gas outlet with a mass spectrometer. Carbon dioxide may be selectively retained in the reactor filled with MFM-520 while nitrogen in the test gas escapes rapidly at the beginning of the reaction. This experiment effectively demonstrates that MFM-520 can still preferentially capture and adsorb carbon dioxide from nitrogen under flow conditions in a simulated reality (see fig. 28).
When the temperature of the dynamic separation experiment is increased to be closer to the temperature (50 ℃) of the tail gas of the flue gas in practical production, the MFM-520 can still efficiently and selectively capture carbon dioxide from nitrogen (see figure 29), and the objective application prospect of the material in cleaning acid gas pollutants in the air is further reflected.

Claims (7)

1. The use of a metal organic framework compound MFM-520 for the adsorptive separation of acid gas contaminants from air; the pressure of the acid gas pollutants in the air is 10ppm-1.0 atmosphere;
the acidic gas contaminants in the air are selected from at least one of: nitrogen dioxide, sulfur dioxide and carbon dioxide;
the metal-organic framework compound MFM-520 is prepared according to a method comprising the steps of:
1) Adding 4, 4' -bipyridine-2, 6', 2, 6' -tetracarboxylic acid, zinc chloride and 2, 6-dimethylpyridine into water, and carrying out hydrothermal reaction to obtain unactivated MFM-520;
2) And (3) heating the unactivated MFM-520 in a water-free environment for activation to obtain activated MFM-520.
2. Use according to claim 1, characterized in that: the temperature of the adsorption separation is 273-333K.
3. Use according to claim 1, characterized in that: the adsorptive separation is carried out in the absence of water vapor or water vapor.
4. Use according to claim 1, characterized in that: the acidic gas pollutant which is adsorbed and separated is nitrogen dioxide, and the adsorbed nitrogen dioxide is converted into nitric acid.
5. Use according to claim 1, characterized in that: the acidic gas pollutant which is absorbed and separated is sulfur dioxide, and the absorbed sulfur dioxide is converted into a sulfonamide.
6. Use according to claim 1, characterized in that: in the step 1), the mol ratio of the 4, 4' -bipyridine-2, 6', 2, 6' -tetracarboxylic acid, the zinc chloride and the 2, 6-dimethylpyridine is 1 (2.0-5.0) to (4.0-20.0);
the reaction temperature of the hydrothermal reaction is 110-150 ℃, and the reaction time is 3-6 days;
in the step 2), the activation temperature is 100-150 ℃ and the activation time is 1-5 hours.
7. Use according to claim 6, characterized in that: in the step 1), the molar ratio of 4, 4' -bipyridine-2, 6', 2, 6' -tetracarboxylic acid to zinc chloride to 2, 6-lutidine is 1.0:2.0:4.0.
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