JP4258608B2 - Three-dimensional metal complex, adsorbent and separation material - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a three-dimensional metal complex, an adsorbent comprising the complex, and a separating material.
[0002]
[Prior art]
When separating a gas from a mixed gas by a pressure swing method or a temperature swing method, in general, activated carbon, zeolite, or the like is used as a separation adsorbent, and the separation has been performed by the difference in the equilibrium adsorption amount or adsorption rate (for example, Non-Patent Document 1).
[0003]
However, when separation is performed due to the difference in the amount of equilibrium adsorption, conventional adsorbents cannot selectively adsorb only one substance (gas), resulting in a small separation factor and an increase in the size of the apparatus. . On the other hand, when separating by the difference in adsorption speed, depending on the type of gas, only one substance (gas) can be adsorbed, but it is necessary to perform adsorption and desorption alternately in a short time, leading to an increase in the size of the apparatus. .
[0004]
[Non-Patent Document 1]
Supervised by Satoshi Takeuchi, "Handbook of latest adsorption technology", 1st edition, NTS Corporation, January 11, 1999, p. 84-163
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide an adsorbent capable of selectively adsorbing a substance such as a gas or a separation material having high separation performance.
[0006]
[Means for Solving the Problems]
By using a novel external field-responsive metal complex whose pore size (structure) changes depending on the type of substance to be adsorbed, adsorption pressure, adsorption temperature, etc., in either pressure swing method or temperature swing method, The inventors have found that substances can be selectively adsorbed and have completed the present invention.
[0007]
That is, the present invention provides a three-dimensional metal complex, an adsorbent, a separation material, an adsorption storage device, and a separation device as shown below.
Item 1. A metal comprising 2,5-dihydroxybenzoic acid, at least one metal selected from copper, rhodium, chromium, molybdenum, palladium, zinc and tungsten, and an organic ligand capable of bidentate coordination with the metal Complex.
Item 2. 2,5-dihydroxybenzoic acid, at least one metal salt selected from copper salt, rhodium salt, chromium salt, molybdenum salt, palladium salt, zinc salt and tungsten salt, and organic coordination capable of bidentate coordination Item 2. The metal complex according to Item 1, which is obtained by reacting a child in a solvent and precipitating it.
Item 3. Organic ligands include pyrazine, 4,4'-bipyridyl, trans-1,2-bis (4-pyridyl) ethylene, 4,4'-azopyridine, 4,4'-bipyridylethane, 4,4'-bis Item 3. The metal complex according to Item 1 or 2, which is at least one selected from bipyridylphenylene and N- (4-pyridyl) isonicotinamide.
Item 4. Item 4. The metal complex according to Item 3, wherein the organic ligand is 4,4'-bipyridyl.
Item 5. Item 5. The metal complex according to any one of Items 1 to 4, wherein the metal is copper and the organic ligand is 4,4′-bipyridyl.
Item 6. Item 1-5, which is a porous metal complex that adsorbs a gas or a liquid, wherein the integrated structure of the metal complex changes and the pore size changes depending on the type of adsorbed substance, the adsorption pressure, or the adsorption temperature. The metal complex in any one of.
Item 7. The adsorbent which consists of a metal complex in any one of claim | item 1 -6.
Item 8. Item 7. A separating material comprising the metal complex according to any one of Items 1 to 6.
Item 9. Item 9. The separation material according to Item 8, for separating carbon dioxide, hydrogen, carbon monoxide, oxygen, nitrogen, hydrocarbons having 1 to 4 carbon atoms, ammonia, water vapor, or organic vapor.
Item 10. Item 9. The separation material according to Item 8, for separating carbon dioxide in methane, carbon dioxide in nitrogen, oxygen in air, or methane in natural gas.
Item 11. An adsorption storage device using the adsorbent according to Item 7.
Item 12. Item 11. A separation device using the separation material according to any one of Items 8 to 10.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The metal complex of the present invention includes 2,5-dihydroxybenzoic acid, at least one metal selected from copper, rhodium, chromium, molybdenum, palladium, zinc and tungsten, and an organic compound capable of bidentate coordination with the metal. Consisting of a ligand.
[0009]
[Production of metal complexes]
In order to produce the metal complex of the present invention, 2,5-dihydroxybenzoic acid and at least one metal salt selected from a copper salt, a rhodium salt, a chromium salt, a molybdenum salt, a palladium salt, a zinc salt, and a tungsten salt are used. And an organic ligand capable of bidentate coordination are allowed to react in a solvent for several hours to several days to be precipitated.
[0010]
For example, when an aqueous solution or an organic solution of a metal salt and an organic solution containing 2,5-dihydroxybenzoic acid and an organic ligand capable of bidentate coordination are mixed and reacted, good crystallinity (purity A metal complex having a high adsorption performance and high adsorption performance.
[0011]
A precipitate is collected from the obtained mixed solution by suction filtration, washed with methanol, and then vacuum-dried at about 100 ° C. for several hours to produce an external-field-responsive metal complex crystal.
[0012]
The molar concentration of 2,5-dihydroxybenzoic acid is preferably 0.01 to 0.5 mol / l, more preferably 0.05 to 0.3 mol / l.
[0013]
As the metal salt, a metal salt selected from a copper salt, a rhodium salt, a chromium salt, a molybdenum salt, a palladium salt, a zinc salt and a tungsten salt can be used, and a copper salt is preferable. As these metal salts, organic acid salts such as acetates and formates, and inorganic acid salts such as sulfates, nitrates and carbonates can be used. The molar concentration of the metal salt is about ½ of 2,5-dihydroxybenzoic acid, preferably 0.002 to 0.25 mol / l, and more preferably 0.02 to 0.15 mol / l.
[0014]
Organic ligands capable of bidentate coordination include pyrazine, 4,4'-bipyridyl, trans-1,2-bis (4-pyridyl) ethylene, 4,4'-azopyridine, 4,4'-bipyridylethane , 4,4′-bisbipyridylphenylene and N- (4-pyridyl) isonicotinamide can be used, with 4,4′-bipyridyl being preferred. The molar concentration of the organic ligand capable of bidentate coordination is about the same as that of the metal salt, preferably 0.002 to 0.25 mol / l, and more preferably 0.02 to 0.15 mol / l.
[0015]
As the solvent, an organic solvent, water, or a mixed solvent thereof can be used. Specifically, alcohols such as methanol, ethanol, and propanol, diethyl ether, benzene, toluene, acetonitrile, tetrahydrofuran, dimethylformamide, hexane, acetone, water, or a mixed solvent thereof can be used.
[0016]
As reaction temperature, about -20-100 degreeC is preferable, and it reacts also at normal temperature.
[0017]
[Metal complex structure]
In the metal complex of the present invention obtained as described above, as shown in FIG. 1, two oxygens in the carboxyl group and two oxygens in the dihydroxy group of 2,5-dihydroxybenzoic acid are converted into metal ions (for example, , A copper ion), a two-dimensional sheet is formed in which a one-dimensional chain formed by coordination with a bidentate organic ligand (for example, 4,4′-bipyridyl) is formed. These two-dimensional sheets are accumulated to form a packing structure. In the a-axis direction, pores (channels) are generated. For convenience, FIG. 1 schematically shows the structure of a metal complex composed of 2,5-dihydroxybenzoic acid, copper ions, and 4,4′-bipyridyl as an organic ligand.
[0018]
[Adsorption / desorption mechanism]
The metal complex of the present invention has a pillared layer structure with a π stack such that two-dimensional sheets are engaged with each other, and has pores (channels) in the a-axis direction.
[0019]
For example, when the metal complex of the present invention comprises 2,5-dihydroxybenzoic acid, copper, and 4,4′-bipyridyl as an organic ligand, the pore size of this structure is about 3 0.0 × 3.6 cm, and in general, molecules larger than these pores cannot be adsorbed. However, since the packing structure in which these two-dimensional sheets in the metal complex of the present invention are integrated can be changed in the synthesized crystal, the structure and size of the pores change with the change. That is, as a result of adsorbing the substance, it can be changed to a pore structure having a structurally more stable energy state. The conditions for changing the structure depend on the type of substance to be adsorbed, the adsorption pressure, and the adsorption temperature. In this way, the pores become large, and large molecules are adsorbed in the enlarged pores. After the adsorbed substance is desorbed, it returns to its original structure, so the pore size also returns. FIG. 2 schematically shows the mechanism by which the accumulation structure and the pore size change due to adsorption and desorption.
[0020]
In the metal complex of the present invention, the accumulation structure of the metal complex and the size of the pores change depending on the kind of the substance to be adsorbed, the adsorption pressure or the adsorption temperature. It starts and reaches the maximum amount of adsorption instantly. The starting pressure of adsorption varies depending on the type of substance to be adsorbed or the adsorption temperature.
[0021]
Therefore, the adsorbent comprising the metal complex of the present invention can selectively adsorb substances such as gas. Moreover, the separation material comprising the metal complex of the present invention has excellent separation performance.
[0022]
The separation material of the present invention efficiently separates carbon dioxide, hydrogen, carbon monoxide, oxygen, nitrogen, hydrocarbons having 1 to 4 carbon atoms (methane, ethane, ethylene, etc.), ammonia, water vapor, or organic vapor. Can do. The organic vapor means a vaporized organic substance that is liquid at normal temperature and pressure. Examples of such organic substances include alcohols such as methanol and ethanol; amines such as trimethylamine; aldehydes such as acetaldehyde; aliphatic hydrocarbons having 5 to 16 carbon atoms; aromatic compounds such as benzene, toluene and aniline; acetone And ketones such as methyl ethyl ketone; fluorinated hydrocarbons; halogenated hydrocarbons such as methyl chloride and chloroform. The separation material of the present invention is particularly suitable for separating carbon dioxide in methane, carbon dioxide in nitrogen, oxygen in air, methane in natural gas, and the like by a pressure swing method or a temperature swing method.
[0023]
The adsorption storage device using the adsorbent of the present invention is excellent in adsorption efficiency. Moreover, the separation apparatus using the separation material of the present invention is excellent in separation efficiency.
[0024]
【The invention's effect】
The adsorbent comprising the metal complex of the present invention can selectively adsorb substances such as gas.
[0025]
Moreover, the separation material comprising the metal complex of the present invention has excellent separation performance. In particular, it is suitable for separation by a pressure swing method or a temperature swing method.
[0026]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples. The present invention is not limited to the examples.
[0027]
Example 1
0.13 g (0.56 mmol) of copper nitrate was dissolved in 20 ml of water, 0.50 g (3.2 mmol) of 2,5-dihydroxybenzoic acid and 0.13 g (0.8 mmol) of 4,4′-bipyridyl were dissolved in diethyl ether. Dissolved in 20 ml. The mixture was reacted at room temperature for 1 week while diffusing the diethyl ether solution into the copper nitrate aqueous solution. Thereafter, the precipitate was suction filtered, washed with methanol three times, and dried by heating at 100 ° C. for about 2 hours under vacuum to obtain 0.18 g of the target metal complex (single crystal).
[0028]
The structure of this metal complex obtained by X-ray analysis is shown in FIG. (A), (b), and (c) in FIG. 3 show the structure of the metal complex as seen from different directions.
[0029]
Example 2
For the metal complex obtained in Example 1, adsorption / desorption isotherms of various gases (nitrogen, oxygen, methane, carbon dioxide (carbon dioxide)) at room temperature (298 K) were measured by a gravimetric method. The results are shown in FIGS. As is apparent from the figure, the start of adsorption depends on the adsorption pressure, and the adsorption started suddenly at a predetermined pressure, and reached the maximum adsorption amount instantly. This pressure varied depending on the type of gas.
[0030]
By utilizing this feature, it is possible to perform gas separation with high separation performance as compared with the case of using a conventional separation material.
[0031]
Example 3
For the metal complex obtained in Example 1, adsorption / desorption isotherms at various temperatures of methane gas were measured by a gravimetric method. The result is shown in FIG. From FIG. 8, it was found that the starting point of adsorption (pressure at which adsorption begins) depends on temperature and can be controlled.
[0032]
By utilizing this feature, it is possible to perform gas separation with high separation performance by the temperature swing method as compared with the case of using a conventional separation material.
[Brief description of the drawings]
FIG. 1 is a schematic view showing the structure of a metal complex of the present invention.
FIG. 2 is a schematic view showing a mechanism of adsorption / desorption in the metal complex of the present invention.
FIG. 3 is a diagram showing the structure of the metal complex of the present invention obtained by X-ray analysis.
FIG. 4 is a graph showing an adsorption / desorption isotherm of nitrogen for the metal complex of the present invention.
FIG. 5 is a graph showing oxygen adsorption / desorption isotherms for the metal complexes of the present invention.
FIG. 6 is a graph showing an adsorption / desorption isotherm of methane for the metal complex of the present invention.
FIG. 7 is a graph showing carbon dioxide adsorption and desorption isotherms for the metal complex of the present invention.
FIG. 8 is a graph showing adsorption / desorption isotherms at various temperatures for the metal complex of the present invention.

Claims (8)

A metal complex composed of 2,5-dihydroxybenzoic acid, copper, and 4,4′- bipyridyl . And 2,5-dihydroxybenzoic acid, and a copper salt, 4,4' a bipyridyl, are reacted in a solvent, metal complex according to claim 1, obtained by precipitation. Adsorbent comprising a metal complex according to claim 1 or 2. Separation material comprising a metal complex according to claim 1 or 2. The separation material according to claim 4 , for separating carbon dioxide, hydrogen, carbon monoxide, oxygen, nitrogen, hydrocarbon having 1 to 4 carbon atoms, ammonia, water vapor or organic vapor. The separation material according to claim 4 for separating carbon dioxide in methane, carbon dioxide in nitrogen, oxygen in air, or methane in natural gas. An adsorption storage device using the adsorbent according to claim 3 . A separation apparatus using the separation material according to claim 4 .

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