JP2003342260A - Three-dimensional metal complex, adsorbing material and separating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a adsorbing material capable of selectively adsorbing a substance such as gas and a separating material having high separation performance. <P>SOLUTION: In a porous metal complex adsorbing gases or liquids, an accumulation structure of the basic skeleton of the metal complex is changed and the size of the pores is changed by kinds of substances to be adsorbed, adsorption pressure or adsorption temperature. The adsorbing material or the separating material are each composed of the metal complex. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a three-dimensional metal complex, an adsorbent and a separating material comprising the complex.

[0002]

2. Description of the Related Art When separating a gas from a mixed gas by a pressure swing method or a temperature swing method, generally, activated carbon, zeolite or the like is used as a separation adsorbent, and its equilibrium adsorption amount is used. Alternatively, separation has been performed by the difference in adsorption rate.

However, in the case of separating by the difference in the equilibrium adsorption amount, the conventional adsorbent cannot selectively adsorb only one substance (gas), so that the separation coefficient becomes small and the apparatus becomes large. I was invited. On the other hand, in the case of separation based on the difference in adsorption rate, only one substance (gas) can be adsorbed depending on the type of gas, but it is necessary to alternate adsorption and desorption in a short time, leading to an increase in the size of the device. .

An object of the present invention is to provide an adsorbent capable of selectively adsorbing a substance such as gas, and a separator having a high separation performance.

[0005]

[Means for Solving the Problems] Types of substances to be adsorbed,
By using a novel external field-responsive metal complex whose pore size changes depending on the adsorption pressure or adsorption temperature, it is possible to selectively adsorb a substance by either the pressure swing method or the temperature swing method. Heading out, the present invention has been completed.

That is, the present invention provides a three-dimensional metal complex, an adsorbent and a separator as shown below. Item 1. A porous metal complex that adsorbs gas or liquid, in which the integrated structure of the basic skeleton of the metal complex changes and the size of the pores changes depending on the type of substance to be adsorbed, the adsorption pressure or the adsorption temperature. Complex. Item 2. Item 2. The metal complex according to Item 1, wherein the integrated structure of the basic skeleton is an interpenetrating type. Item 3. Item 1 or 2 containing terephthalic acid, at least one divalent metal selected from copper, rhodium, chromium, molybdenum, palladium, zinc and tungsten, and 4,4′-bipyridyl as an organic ligand The metal complex described. Item 4. Terephthalic acid and at least one metal salt selected from copper salts, rhodium salts, chromium salts, molybdenum salts, palladium salts, zinc salts and tungsten salts,
Item 4. The method according to any one of Items 1 to 3, which is obtained by dissolving in an organic solvent to cause a reaction, and further reacting the reaction product with 4,4'-bipyridyl as an organic ligand to precipitate a metal dicarboxylic acid complex. Metal complex of. Item 5. Item 4. An adsorbent comprising the metal complex according to any one of items 1 to 4. Item 6. Item 4. A separating material comprising the metal complex according to any one of items 1 to 4. Item 7. Carbon dioxide, hydrogen, carbon monoxide, oxygen, nitrogen,
Item 7. The separating material according to item 6 for separating a hydrocarbon having 1 to 4 carbon atoms or steam. Item 8. Carbon dioxide in methane, carbon dioxide in nitrogen,
Item 7. The separation material according to Item 6 for separating oxygen in air or methane in natural gas.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Unlike the structure of a conventional three-dimensional type metal complex (FIG. 2), the three-dimensional type metal complex of the present invention has three-dimensional basic skeletons doubly interconnected as shown in FIG. It penetrates and the pore diameter (b) is small. Here, the basic skeleton means a group of n basic unit lattices. In FIG. 1, terephthalic acid, copper (II), and
1 schematically shows the structure of a three-dimensional metal complex containing 4,4'-bipyridyl as an organic ligand. In FIG. 1, "bip
"y" means 4,4'-bipyridyl.

The basic skeleton of the three-dimensional metal complex accumulates at the most energetically stable place, but the three-dimensional metal complex of the present invention has a center of pores of one basic skeleton as shown in FIG. They are accumulated in a structure (interpenetration type) in which another basic skeleton penetrates at a position slightly offset. Further, the three-dimensional metal complex of the present invention has a three-dimensional channel structure.

For example, when the three-dimensional metal complex of the present invention contains terephthalic acid, copper (II) and 4,4'-bipyridyl as an organic ligand, the pore size (b ) Is about 3Å, and in general, molecules larger than this pore size cannot be adsorbed. However, since the position of penetration in the integrated state in which the basic skeleton is doubly interpenetrated like the three-dimensional metal complex of the present invention changes under certain conditions,
With the change, the structure of the pore also changes. That is,
As a result of adsorbing the substance, it is possible to change to a pore structure having a structurally more stable energy state. The conditions under which this structure changes depend on the type of substance to be adsorbed, the adsorption pressure, and the adsorption temperature. In this way, the position of penetration in the accumulated state changes in the direction of increasing the pore diameter, and molecules larger than 3Å are adsorbed in the enlarged pores. After the adsorbed substance is desorbed, it returns to the original integrated structure, so that the pore diameter also returns to the original. FIG. 3 schematically shows the mechanism in which the integrated structure of the basic skeleton and the pore size change due to adsorption and desorption.

The three-dimensional metal complex of the present invention includes, for example, terephthalic acid, at least one divalent metal selected from copper, rhodium, chromium, molybdenum, palladium, zinc and tungsten, and a bidentate. Examples of the positionable organic ligand include those containing 4,4′-bipyridyl.

[0011] Such metal complexes has the formula (1): {M (OOC -C 6 H 4 -COO) · 1/2 (4,4'- bipyridyl)} n (1) wherein, M is Cu ²⁺ , Rh ²⁺ , Cr ²⁺ , Mo ²⁺ , P
d ²⁺ , Zn ²⁺ or W ²⁺ is shown. ] It can be represented by. Here, n the complex is _{M (OOC-C 6 H 4} -COO)
-It means that the crystal has 1/2 (4,4'-bipyridyl) as a repeating unit.

Accordingly, the present invention has the formula (1): {M (OOC -C 6 H 4 -COO) · 1/2 (4,4'- bipyridyl)} n (1) wherein, M is Cu ²⁺ , Rh ²⁺ , Cr ²⁺ , Mo ²⁺ , P
d ²⁺ , Zn ²⁺ or W ²⁺ is shown. n means an arbitrary natural number. ] It also relates to a dicarboxylic acid metal complex represented by

[0013] For example, in the chemical formula (1), {M (OO
_{C-C 6 H 4 -COO)} · 1/2 (4,4'- bipyridyl)} n
Corresponds to the basic skeleton described in the explanation of FIG.

The structure of the metal complex of the present invention can be confirmed by a powder X-ray pattern, a change in magnetic susceptibility with temperature, and an elemental analysis result.

To produce the three-dimensional metal complex of the present invention, for example, a mixed solution of terephthalic acid and a metal salt is reacted for several hours to several days, and the resulting metal complex is capable of bidentate coordination. By mixing a solution containing 4'-bipyridyl and reacting for several hours to several days, a dicarboxylic acid complex as an objective adsorbent or separating material can be produced. Crystals of the external field-responsive dicarboxylic acid complex can be produced by collecting the precipitate from the obtained mixed solution by suction filtration, washing with methanol, and vacuum drying at about 100 ° C. for several hours.

The concentration of terephthalic acid is 0.003 to 0.
1 mol / l is preferable, 0.005-0.05 mol
/ L is more preferable.

As the metal salt, a metal salt selected from copper salts, rhodium salts, chromium salts, molybdenum salts, palladium salts, zinc salts and tungsten salts can be used. Further, as these metal salts, organic acid salts such as acetate and formate, and inorganic acid salts such as sulfate, nitrate and carbonate can be used. The concentration of the metal salt is an equimolar amount with the terephthalic acid, preferably 0.003 to 0.1 mol / l, more preferably 0.005 to 0.05 mol / l.

The concentration of 4,4'-bipyridyl capable of bidentate coordination is preferably 0.5 to 1 molar equivalent, and more preferably 0.5 to 1 molar equivalent to the metal complex formed from the terephthalic acid and the metal salt.
0.6 molar equivalent is more preferable.

As a solvent, a metal complex formed from terephthalic acid and a metal salt and 4,4'-bipyridyl which is a bidentate-coordinating organic ligand are easily dissolved, and a target three-dimensional metal complex is obtained. It is possible to use an organic solvent that is difficult to dissolve. Specifically, alcohols such as methanol, ethanol and propanol, benzene, toluene, acetonitrile, tetrahydrofuran, dimethylformamide (DMF), hexane, acetone or a mixed solvent thereof can be used. It is preferable to add a small amount of an organic acid such as formic acid to the organic solvent.

The reaction temperature is preferably about -20 to 100 ° C., and the reaction is possible even at room temperature.

The three-dimensional metal complex of the present invention has a constant size because the integrated structure of the basic skeleton of the metal complex and the size of the pores change depending on the type of the substance to be adsorbed, the adsorption pressure or the adsorption temperature. Adsorption pressure suddenly starts to reach the maximum adsorption amount. The adsorption start pressure varies depending on the type of substance to be adsorbed or the adsorption temperature.

Therefore, the adsorbent comprising the three-dimensional metal complex of the present invention can selectively adsorb substances such as gas. Moreover, the separating material comprising the three-dimensional metal complex of the present invention has excellent separating performance.

The separation material of the present invention can efficiently separate carbon dioxide, hydrogen, carbon monoxide, oxygen, nitrogen, hydrocarbons having 1 to 4 carbon atoms (methane, ethane, ethylene, etc.) or water vapor. . In particular, it is suitable for separating carbon dioxide in methane, carbon dioxide in nitrogen, oxygen in air, methane in natural gas, etc. by a pressure swing method or a temperature swing method.

[0024]

The adsorbent comprising the three-dimensional metal complex of the present invention can selectively adsorb substances such as gas.

The separating material comprising the three-dimensional type metal complex of the present invention has excellent separating performance. In particular, it is suitable for separation by a pressure swing method or a temperature swing method.

[0026]

EXAMPLES The present invention will be described in detail below with reference to examples. The present invention is not limited to the examples.

Example 1 [[Cu (OOCC ₆ H ₄ COO) · 1
Synthesis of / 2 (4,4'-bipyridyl)] n] 10 ml of a solution of copper sulfate pentahydrate 0.31 g in methanol
Was added to 200 ml of a methanol solution of 0.21 g of terephthalic acid and 1.50 ml of formic acid and stirred at room temperature.
The reaction was carried out at 0 ° C for 3 days. Then, the supernatant of the reaction solution was removed, and 30 ml of a methanol solution containing 0.10 g of 4,4′-bipyridyl was added to the precipitate, and the mixture was stirred at room temperature and reacted for 2 days. Then, the precipitate was suction filtered, washed with methanol three times, and dried by heating under vacuum at 100 ° C. for about 2 hours to obtain 0.31 g of the desired product. The BET specific surface area of the obtained complex determined by adsorption of argon at 87 K was 700 m ² / g, and the pore volume was 0.26 ml / g.

This complex has a binuclear structure in which terephthalic acid is coordinated around copper ions as shown in FIG. 4 based on powder X-rays, magnetic susceptibility and elemental analysis results. The bridged two-dimensional lattice structure is converted into 4,4'-
Bipyridyl forms a three-dimensional structure in which it is crosslinked as an axial ligand. Then, as shown in FIG. 5, the three-dimensional structure (basic skeleton) is a structure in which two mutually penetrate each other.

Example 2 With respect to the complex obtained in Example 1, adsorption isotherms of various gases were measured by a gravimetric method. The result is shown in FIG.
As is clear from FIG. 6, the start of adsorption depends on the adsorption pressure, the adsorption suddenly starts at a predetermined pressure, and the maximum adsorption amount is instantaneously reached. This pressure varied depending on the type of gas.

By utilizing this feature, it is possible to perform gas separation having a high separation performance as compared with the case of using a conventional separation material.

Example 3 With respect to the complex obtained in Example 1, adsorption isotherms of methane gas at various temperatures were measured by a gravimetric method. The result is shown in FIG. 7. From FIG. 7, it was found that the starting point of adsorption (pressure at which adsorption starts) depends on temperature and can be controlled.

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.

Example 4 For the complex obtained in Example 1, the adsorption isotherm of a binary gas mixture of 65% methane and 35% carbon dioxide was calculated.
It was measured by a gravimetric method and a volume method. The result is shown in FIG. As is clear from FIG. 8, since this complex can selectively adsorb only carbon dioxide, it can be used as a gas separating material.

Example 5 With respect to the complex obtained in Example 1, adsorption isotherms of vapors of various liquids were measured by the volume method. The result is shown in FIG. As is clear from FIG. 9, the start of adsorption depends on the relative pressure, and the adsorption suddenly starts at a predetermined relative pressure (pressure), and the maximum adsorption amount is instantaneously reached. This point (relative pressure) varied depending on the type of steam. In the case of water, only surface adsorption is performed, and adsorption into pores does not occur.

By utilizing this feature, it is possible to perform liquid vapor separation having a high separation performance as compared with the case where a conventional separating material is used.

Example 6 With respect to the complex obtained in Example 1, methanol vapor was used as the substance to be adsorbed, and before and after the adsorption and after desorption in order to study the change in the structure (pore size) of the complex due to adsorption. The X-ray diffraction pattern was measured at. The result is shown in FIG. In FIG. 10, a) shows before adsorption, b) shows after adsorption, and c) shows after desorption. As is clear from FIG. 10, the peak of the interplanar distance corresponding to the pore diameter is shifted by the adsorption, indicating that the pore diameter is expanded. X
The pore diameter expanded from 3.33Å to 3.85Å when calculated from the 2θ value of the line. In addition, the fact that the other peaks do not change suggests that the basic skeleton is maintained and only the mode of mutual penetration changes. Furthermore, it can be seen that after complete desorption of the methanol vapor, the original structure before adsorption is restored.

Further, when the adsorption isotherm of methanol vapor was measured, the same isotherm was shown even after repeated adsorption and desorption.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an interpenetrating structure of a three-dimensional metal complex of the present invention.

FIG. 2 is a schematic diagram showing the structure of a conventional three-dimensional metal complex.

FIG. 3 is a schematic diagram showing a mechanism of adsorption / desorption in the three-dimensional metal complex of the present invention.

FIG. 4 is a schematic view showing a part of the structure of the three-dimensional metal complex of the present invention.

FIG. 5 is a schematic view showing an interpenetrating structure of the three-dimensional metal complex of the present invention.

FIG. 6 is a graph showing adsorption isotherms of various gases for the three-dimensional metal complex of the present invention.

FIG. 7 is a graph showing adsorption isotherms at various temperatures for the three-dimensional metal complex of the present invention.

FIG. 8 is a graph showing adsorption isotherms of a mixed gas for the three-dimensional metal complex of the present invention.

FIG. 9 is a graph showing vapor adsorption isotherms of various liquids for the three-dimensional metal complex of the present invention.

FIG. 10 is a diagram showing an X-ray diffraction pattern of the three-dimensional metal complex of the present invention.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4C055 AA01 BA01 CA01 DA25 EA01                       GA02                 4G066 AB24B BA31 BA36 CA27                       CA35 CA37 CA51 CA56 GA14                 4H048 AA01 AB90 AC90 VA20 VA56                       VB10 VB80

Claims (8)

[Claims] 1. A porous metal complex which adsorbs a gas or a liquid, wherein the integrated structure of the basic skeleton of the metal complex is changed and the size of the pores is changed depending on the type of the substance to be adsorbed, the adsorption pressure or the adsorption temperature. A metal complex that changes in shape. 2. The metal complex according to claim 1, wherein the integrated structure of the basic skeleton is an interpenetrating type. 3. Containing terephthalic acid, at least one divalent metal selected from copper, rhodium, chromium, molybdenum, palladium, zinc and tungsten, and 4,4′-bipyridyl as an organic ligand. Claim 1 or 2
The metal complex according to. 4. Terephthalic acid and at least one metal salt selected from copper salts, rhodium salts, chromium salts, molybdenum salts, palladium salts, zinc salts and tungsten salts are dissolved in an organic solvent and reacted. The metal complex according to claim 1, which is obtained by further reacting the reaction product with 4,4′-bipyridyl as an organic ligand to precipitate a dicarboxylic acid metal complex. 5. An adsorbent comprising the metal complex according to claim 1. 6. A separating material comprising the metal complex according to claim 1. 7. Carbon dioxide, hydrogen, carbon monoxide, oxygen,
The separation material according to claim 6 for separating nitrogen, hydrocarbon having 1 to 4 carbon atoms, or steam. 8. The separating material according to claim 6, for separating carbon dioxide in methane, carbon dioxide in nitrogen, oxygen in air or methane in natural gas.