JPH1179719A - Reversible adsorbing and desorbing method of nitrogen gas by controlling potential of electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable repetition of reversible adsorption and desorption of nitrogen at a normal temp. and under normal pressure by bringing a pair of electrodes into contact with soln. of a ruthenium complex which can absorb and emit molecular nitrogen and controlling the electrode potential. SOLUTION: A ruthenium complex is expressed by formula I (wherein R is H, hydrocarbon group, fluorinated hydrocarbon group; X, Y are ligands) or formula II (wherein R is a hydrocarbon group; R' is H, hydrocarbon group; X, Y are ligands). The voltage to be applied is controlled to the potential which can reduce the complex to bivalent or lower valence when nitrogen is to be adsorbed to the ruthenium complex. On the other hand, the voltage is controlled to the potential which can oxidize the complex to tervalent or higher valence when nitrogen is to be desorbed. The reaction soln. to adsorb and desorb nitrogen gas is prepared by dissolving the complex in water, alcohol or a mixture liquid of water and alcohol. In this case, an electrolyte comprising a pair of cation and anion is added to the soln. As the working electrodes, porous carbon electrodes or the like are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for measuring the absorption and release of nitrogen gas at normal temperature and normal pressure by using a solution containing a ruthenium complex as an active substance by applying a voltage to a pair of electrodes brought into contact with the solution. Control freely by operation,
It also relates to a method for reversibly and repeatedly performing this.

[0002]

2. Description of the Related Art It goes without saying that many reactions for unilaterally releasing gas without recovery are known. Also,
Conversely, materials that exclusively perform gas sorption (eg, activated carbon, silica gel, iron powder, etc.) are often used, but reusing any of them requires a lot of labor and energy. As a general method for reversibly absorbing and releasing gas, there is a method based on heat control. However, this method has a limited use temperature and requires the use of a low-temperature heat source. As a method for reversibly adsorbing and desorbing gas with a relatively small temperature change, there is a method using a hydrogen storage alloy.
There is also a method of reversibly adsorbing and desorbing oxygen using heat.
It has been shown that a trans-dichlorotertiary tetraamine complex having a 2,3,2-tetraamine skeleton can immobilize dissolved nitrogen gas in water by reacting with titanium trichloride in an aqueous solution (T. Takahashi, K. et al. Hirat
ani, K .; Kimura, Chem. Lett. , 1
993, 1761). In addition, the present inventors have previously found that a ruthenium complex having a hydrocarbon substituent introduced on the coordinating nitrogen of the above complex has a nitrogen gas absorbing ability (Japanese Patent Application No. 7-262147). .

[0003] The reversible adsorption / desorption reaction of gas involves gas occlusion,
A wide variety of applications are possible, including separation, purification, and detection, as well as actuator applications. However, most of the conventional technologies use heat.
It always required two heat sources, high and low. In addition, flammable gas such as hydrogen,
A combustible gas such as oxygen was used.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method for reversibly adsorbing and desorbing a gas, comprising: (1) controlling the adsorption and desorption of gas at ordinary temperature and pressure without using heat; A method characterized in that desorption control is performed only by a potential operation, (3) gas adsorption / desorption can be performed reversibly and repeatedly, and (4) nitrogen gas is used as an active substance for realizing this. Is the task.

[0005]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above problems, and as a result, have completed the present invention.

That is, according to the present invention, a pair of electrodes are brought into contact with a solution in which a ruthenium complex capable of absorbing and releasing molecular nitrogen is dissolved, and the potential of the electrodes is manipulated, whereby nitrogen gas is reversibly formed. A method is provided for adsorbing and desorbing to and from a surface.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a solution in which a ruthenium complex that absorbs and releases molecular nitrogen is dissolved is used, and a voltage is applied to the ruthenium complex in the solution via a pair of electrodes. In this case, the potential at which nitrogen is adsorbed on the ruthenium complex is a potential at which the ruthenium complex can be reduced to divalent or lower, while the potential at which nitrogen is desorbed from the ruthenium complex is a potential at which the ruthenium complex can be oxidized to trivalent or higher. is there. Examples of ruthenium complexes that adsorb and desorb nitrogen gas by electrolytic reduction and oxidation include, for example, the following.

Embedded image (Wherein, R represents hydrogen, a hydrocarbon group or a fluorinated hydrocarbon group, and X and Y represent ligands)

Embedded image (Wherein R represents a hydrocarbon group, R ′ represents hydrogen or a hydrocarbon group, and X and Y represent ligands)

[0008] The hydrocarbon group includes an aliphatic hydrocarbon group and an aromatic hydrocarbon group. Aliphatic hydrocarbon groups include linear and cyclic alkyl groups. Examples of the chain alkyl group include an alkyl group having 1 to 12, preferably 2 to 4 carbon atoms. Examples of the cyclic alkyl group include cyclohexyl. Examples of the aromatic group include an aryl group such as phenyl, tolyl, and naphthyl, and an arylalkyl group such as benzyl, phenethyl, and naphthylmethyl. Examples of the fluorinated hydrocarbon group include fluorinated compounds of the various hydrocarbon groups described above.
A 2,2-trifluoroethyl group and the like. Examples of the ligand include various ligands that can be complexed with ruthenium such as chlorine, a hydroxyl group, water, or oxygen.

In order to prepare the reaction solution for adsorbing and desorbing nitrogen gas according to the present invention, the ruthenium complex of the above (1) or (2) is mixed with water, alcohol or water in order to increase the rate of adsorption and desorption of nitrogen gas. Dissolve in a mixed solution of alcohol.
In this case, it is preferable to add an electrolyte composed of a pair of cations and anions to the solution containing the ruthenium complex. In this electrolyte, examples of the cation include a hydrogen ion, a lithium ion, a sodium ion, a potassium ion, a beryllium ion, a magnesium ion, a calcium ion, an ammonium ion, and a quaternary ammonium. On the other hand, as the anion, fluoride ion, chloride ion, bromide ion, iodide ion,
Hydroxide ion, carbonate ion, hydrogen carbonate ion, borate ion, hydrogen borate ion, dihydrogen borate ion, phosphate ion, hydrogen phosphate ion, dihydrogen phosphate ion, sulfate ion, hydrogen sulfate ion, acetic acid Ion, trifluoroacetate ion, methanesulfonate ion, trifluoromethanesulfonate ion, and alkyl and aryl sulfonate ions such as toluenesulfonate ion. When dissolving the ruthenium complex in water, a moderator solution is preferably used to keep the pH of the solution constant, and the pH is more preferably 7 or more and around 12 is most preferably used. As the solution in this case, a conventional solution containing a phosphate ion or a hydrogen phosphate ion is used.

To perform adsorption and desorption of nitrogen using the reaction solution, a pair of electrodes are brought into contact with the solution to perform electrolytic reduction and oxidation. Working electrodes for this purpose are platinum, gold, silver,
A metal such as copper or mercury, or a carbon electrode is used. Preferably, a porous carbon electrode (manufactured by BAS) having a large surface area and a large potential window is used. Further, it is desirable to use a reference electrode for controlling the potential of the electrode to be constant. As the reference electrode, a hydrogen electrode, a calomel electrode, an Ag / AgCl electrode, or the like is used. Metals such as platinum, gold, silver, copper, and mercury, or carbon electrodes are used for the counter electrode. Films, salt bridges, porous glass, etc. are used to prevent oxidation and reduction of the complex on the counter electrode. It is desirable to keep the reaction solution away from the reaction solution.

The potential of the reduction is a potential at which ruthenium, which is the central metal of the ruthenium complexes (1) and (2), is reduced to divalent or lower, and is more two potentials than the divalent / trivalent half-wave potential.
It is desirable that the voltage is lower than 00 mV. However, if an attempt is made to reduce at an extremely low potential, the solvent may be reduced. Specifically, for example, the solvent is -1000 to -1200 mV (vs Ag / AgCl) in an aqueous solution having a pH of 12.
It is preferred that it is about. By applying the reduction potential, the solution absorbs nitrogen.

The oxidation potential is a potential at which ruthenium, which is the central metal of ruthenium complexes (1) and (2), is oxidized to trivalent or higher, preferably pentavalent or higher, and is higher than the nitrogen desorption potential of the nitrogen complex. Further, it is desirable that the voltage is higher by 200 mV or more. However, if you try to oxidize at too high a potential,
Since the solvent may be oxidized, specifically, for example, the solvent is 500 to 600 mV (vs.
(Ag / AgCl). By applying this oxidation potential, nitrogen is released from the solution.

[0013]

Next, the present invention will be described in more detail with reference to examples.

Example 1 Trans- [Ru (III) (OH) (2,5,9,12
-Tetramethyl-2,5,9,12-tetraazatridecane) (OH ₂ )] (CF ₃ SO ₃ ) ₂ 48.2 mg was dissolved in phosphate buffer (pH 12) 120 ml to prepare a nitrogen gas adsorption / desorption solution. . Incidentally, the ruthenium complex,
Toshikazu Takahashi et al., Proceedings of the 67th Annual Meeting of the Chemical Society of Japan 1p59
(1994), Toshikazu Takahashi, doctoral dissertation "Ruthenium (II)
Scavenging of Molecular Nitrogen by Polyamine Complex and Isolation of Nitrogen Complex "(1993).

The solution was placed in a container equipped with a constant temperature water circulation jacket, and a porous carbon electrode (manufactured by BAS) and Ag /
An AgCl reference electrode (manufactured by BAS) and a stirrer chip were put in, and the lid was rubbed together with glass.
1 through a salt bridge, a wiring for a porous carbon electrode, a wiring for a reference electrode, and a glass tube of a resistance temperature detector, and solidified with an epoxy adhesive. In addition, a joint was attached to the glass tube attached to the lid, and a nitrogen gas adsorption / desorption cell was produced. The other end of the salt bridge is immersed in an aqueous solution of potassium ferrocyanide, into which a platinum wire electrode is inserted as a counter electrode.

This cell is connected to a pressure gauge and a gas tight syringe for pressure control, a pipe that connects them, a pipe that can be hermetically sealed, a device that can move the syringe up and down by an electric signal, and a pressure gauge from the pressure gauge to keep the pressure constant. It consists of a computer that controls the syringe by input and its software, and is connected to an automatic gas adsorption / desorption measuring device that can automatically control the inside of the system to the set pressure input to the computer by operating the syringe automatically, and perform electrochemical reduction. An automatic measuring device for gas adsorption and desorption by oxidation was completed. (Fig. 1)

The gas adsorption / desorption automatic measuring apparatus shown in FIG. 1 is filled with nitrogen gas containing saturated moisture, placed in a thermostatic chamber adjusted to 25 ° C., and placed in a nitrogen gas adsorption / desorption cell jacket at 25 ° C. Circulate the water and increase the pressure inside the device to 760
Control was started to be mmHg. Until the temperature inside the device and system becomes constant and the syringe becomes constant,
It took about one hour.

-1100 mV (vs. Ag / AgC) was applied to the porous carbon electrode serving as the working electrode of the nitrogen gas adsorption / desorption cell.
The voltage of 1) was applied for reduction for 273 minutes. 41.0-0.
At a current of 89 mA, 54 coulombs of electricity flowed, and the nitrogen gas adsorption / desorption solution absorbed 1.6 ml of nitrogen gas, which was about 94% of the amount of the complex. (Fig. 2)

Next, the porous carbon electrode, which is the working electrode of the nitrogen gas adsorption / desorption cell, was charged with 500 mV (vs. Ag / A).
gCl) and oxidized for 170 minutes. 95-1
At a current of 1 mA, 112 coulombs of electricity flowed, and the nitrogen gas adsorption / desorption solution released almost all of the absorbed nitrogen gas. (Fig. 2)

Again, the porous carbon electrode, which is the working electrode of the nitrogen gas adsorption / desorption cell, was applied at -1100 mV (vs. A
g / AgCl) and reduced for 273 minutes. 5
At a current of 2.0 to 0.62 mA, 48 coulombs of electricity flow, and the nitrogen gas adsorption / desorption solution contains 1.5% of about 88% of the complex amount.
ml of nitrogen gas was absorbed. (Fig. 2)

Next, the porous carbon electrode, which is the working electrode of the nitrogen gas adsorption / desorption cell, was charged with 500 mV (vs. Ag / A
gCl) and oxidized for 170 minutes. 97-1
At a current of 0 mA, 107 coulombs of electricity flowed, and the nitrogen gas adsorption / desorption solution released almost all the absorbed nitrogen gas. (Fig. 2)

[Brief description of the drawings]

FIG. 1 is a structural explanatory view of a gas adsorption / desorption amount automatic measuring device.

FIG. 2 shows a change over time in a nitrogen gas absorption volume.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshikazu Takahashi 1-1-1, Higashi, Tsukuba, Ibaraki Pref., National Institute of Advanced Industrial Science and Technology (72) Inventor Kazuhisa Hiratani 1-1-1, Higashi, Tsukuba, Ibaraki Pref. Within the Institute of Engineering Technology (72) Inventor Kazuyuki Kazuga 1-1-1, Higashi, Tsukuba City, Ibaraki Prefecture Within the Institute of Materials Science and Technology, Institute of Industrial Science and Technology (72) Inventor Takayoshi Adachi 2-4-1, Utsuhoncho, Nishi-ku, Osaka-shi, Osaka Inside Taiyo Toyo Oxygen Co., Ltd. (72) Inventor Makoto Uchino 2-4-1-11 Utsuhoncho, Nishi-ku, Osaka, Osaka Prefecture Inside Taiyo Toyo Oxygen Co., Ltd. (72) Taizo Ichida, Utsubocho, Nishi-ku, Osaka, Osaka Chome 4-11 Inside Taiyo Toyo Oxygen Co., Ltd. (72) Inventor Riichi Nakatsuji 1-16-7 Nishishinbashi, Minato-ku, Tokyo (72) Inventor Ayumu Okamoto 1-16-7 Nishi-Shimbashi, Minato-ku, Tokyo Inside Nippon Oxide Co., Ltd. (72) Inventor Ichiro Nakayama 1-16-17 Nishi-Shimbashi, Minato-ku, Tokyo Inside Nippon Oxide Co., Ltd. (72) Inventor Nobuyoshi Ito 1-16-7 Nishishinbashi, Minato-ku, Tokyo Inside Nippon Oxide Corporation

Claims (11)

[Claims] 1. A method for bringing a pair of electrodes into contact with a solution in which a ruthenium complex capable of absorbing and releasing molecular nitrogen is dissolved, and adsorbing and desorbing nitrogen gas by controlling the electrode potential. 2. The ruthenium complex according to claim 1, wherein the ruthenium complex is a ruthenium complex represented by the following general formula (1).
Nitrogen gas adsorption and desorption method. Embedded image (Wherein, R represents hydrogen, a hydrocarbon group or a fluorinated hydrocarbon group, and X and Y represent ligands) 3. The ruthenium complex according to claim 1, wherein the ruthenium complex is a ruthenium complex represented by the following general formula (2).
Nitrogen gas adsorption and desorption method. Embedded image (Wherein, R represents a hydrocarbon group, R ′ represents hydrogen or a hydrocarbon group, and X and Y represent ligands) 4. The method according to claim 2, wherein the solvent is water, alcohol or a mixture of water and alcohol. 5. The method for adsorbing and desorbing nitrogen gas according to claim 2, wherein the solvent is a solution obtained by dissolving an electrolyte in water, alcohol or a mixture of water and alcohol. 6. The method for adsorbing and desorbing nitrogen gas according to claim 5, wherein the electrolyte comprises a cation and an anion. 7. The combination according to claim 6, wherein the electrolyte is a combination capable of acting as a buffer for keeping the pH constant.
Nitrogen gas adsorption and desorption method. 8. The method for adsorbing and desorbing nitrogen gas according to claim 7, wherein the buffer solution is alkaline. 9. The method for adsorbing and desorbing nitrogen gas according to claim 8, wherein the pH of the buffer solution is 10 or more. 10. The method for adsorbing and desorbing nitrogen gas according to claim 1, wherein the potential for adsorbing nitrogen is a potential capable of reducing a ruthenium complex to divalent or lower. 11. The method for adsorbing and desorbing nitrogen gas according to claim 1, wherein the potential for desorbing nitrogen is a potential capable of oxidizing a ruthenium complex to three or more valences.