JP4681449B2 - Method for producing hydrogen adsorbent - Google Patents

Description

The present invention relates to a method of manufacturing the hydrogen adsorbent to adsorb the hydrogen gas.

  In recent years, a fuel cell vehicle equipped with a fuel cell has attracted attention due to the growing interest in environmental protection. This is because the fuel cell vehicle uses the fuel cell as a travel drive source, so there is no need to burn gasoline or light oil, and therefore no hydrocarbon gas, NOx, SOx, or the like is discharged.

  When operating the fuel cell, it is necessary to supply a fuel gas, for example, hydrogen gas. For this reason, a hydrogen storage tank is attached to the fuel cell. As the amount of hydrogen stored in the hydrogen storage tank increases, the operation time of the fuel cell can be extended. Therefore, various studies have been made on the construction of a hydrogen storage tank by containing a hydrogen adsorbent in the container. In this case, since the hydrogen adsorbent adsorbs and holds hydrogen, more hydrogen can be stored as compared with the case where the hydrogen adsorbent is not accommodated.

  Recently, as this type of hydrogen adsorbent, a metal-organic framework has attracted particular attention (see, for example, Patent Document 1). The metal-organic skeleton structure is a kind of a complex in which a metal atom or a metal ion is coordinated so that an organic molecule or an organic ion surrounds it, and a stable porous skeleton even in the absence of a guest molecule. Maintain structure. Hydrogen gas is adsorbed in the porous skeleton structure.

  As described in Patent Document 2, the metal-organic skeleton structure is brought into contact with a base material, and is compressed into a pellet, for example, and used as a hydrogen adsorbent.

US Patent Application Publication No. 2003/0148165 US Patent Application Publication No. 2003/0222023

  As described above, the metal-organic framework structure has a porous framework structure. For this reason, when compression molding is performed by applying an excessively large molding pressure to the powder, the porous skeleton structure may be crushed. When such a situation occurs, it becomes difficult to adsorb and hold hydrogen gas. In other words, the hydrogen gas adsorption amount decreases.

  Moreover, in the prior art described in Patent Document 2, a large amount of a binder or thickener that does not contribute to the adsorption action of hydrogen gas is added. For this reason, even if the volume of the pellet is increased, it is not easy to increase the amount of hydrogen gas that can be adsorbed.

  Thus, in the prior art, the problem that it is not easy to obtain a hydrogen adsorbent having a large hydrogen gas adsorption amount per unit volume has become apparent.

The present invention has been made to solve the problems described above, the hydrogen gas adsorption amount per unit volume is large and, for the purpose of the volume to provide a method for manufacturing a large hydrogen adsorbent.

  In order to achieve the above object, a hydrogen adsorbent according to the present invention comprises a base material and a complex-bonded base material comprising a plurality of complexes that can be deposited on the surface of the base material and adsorb hydrogen gas. It is formed.

  In this complex-bonded substrate, a plurality of complex particles are bonded to the substrate to increase the particle size. For this reason, a complex conjugate or aggregate having a large volume, that is, a hydrogen adsorbent can be produced without going through a compression molding step. Therefore, the adsorption site for adsorbing hydrogen gas is not crushed. Moreover, in the present invention, since the base material also functions as a binder, it is not particularly necessary to add a binder separately. Therefore, it is not necessary to use a large amount of a binder that does not contribute to the hydrogen gas adsorption capacity.

  For the reasons described above, a hydrogen adsorbent excellent in hydrogen gas adsorbing capacity per unit volume can be configured.

  As a preferable example of the substrate, a substance having a linear molecule formed by binding molecules in a linear form can be exemplified. In this case, a hydrogen adsorbent having a larger volume can be obtained by entanglement or bonding of the complex-bonded substrates.

  As another suitable example of the substrate, a sheet material made of either a polymer or a carbon material can be exemplified. In this case, there is an advantage that the hydrogen adsorbent can be deformed into an arbitrary shape.

Further, the present invention is a method for producing a hydrogen adsorbent having a complex-bonded substrate in which a plurality of complexes capable of adsorbing hydrogen gas are deposited on the surface of the substrate,
Preparing a solvent containing the base material, metal salt and organic compound;
Reacting the metal salt with the organic compound in the solvent to deposit a complex on the surface of the base material to form a complex-bonded base material;
Separating the complex-binding substrate and the solvent;
It is characterized by having.

  By going through such a process, it is possible to easily produce a hydrogen adsorbent having a large particle size without going through a compression molding process and without adding a large amount of a binder or the like. Therefore, in the obtained hydrogen adsorbent, the hydrogen gas adsorption amount per unit volume is increased.

  As described above, as the base material, a substance having linear molecules formed by bonding molecules in a straight line can be used. In this case, it is preferable to stir the complex-binding substrate in a solvent. As a result, the complex-bonding base materials are entangled with each other, so that it is easy to increase the particle size.

  The solvent may be the solvent used when the complex is precipitated, or may be another solvent.

  Or you may make it use the sheet | seat material which consists of either a polymer or a carbon material as a base material.

  According to the present invention, since a plurality of complex particles are deposited on the surface of the substrate, it is easy to increase the particle size of the particles, and eventually, a large volume of hydrogen adsorption without going through a compression molding process. A material can be produced. Further, in the present invention, it is not particularly necessary to use a large amount of binder or the like, so that the relative proportion of the complex that acts to adsorb hydrogen gas can be remarkably increased.

  That is, the effect that a hydrogen adsorbent with a large hydrogen gas adsorption amount per unit volume can be obtained is achieved.

  Hereinafter, preferred embodiments of the hydrogen adsorbent and the method for producing the same according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic structural explanatory view schematically showing the structure of a complex-bonding substrate 10 constituting the hydrogen adsorbent according to the present embodiment. In this complex-bonded substrate 10, a plurality of complex particles 14 are deposited on the surface of a substrate 12 made of linear molecules. In other words, the particles 14 are bonded to the surface of the substrate 12.

  The linear molecules that are the material of the base material 12 are made of a substance in which the molecules are linearly bonded and extend. Suitable examples of this type of material include linear polymers, and more specifically, polyethylene, vinyl chloride, polytetrafluoroethylene, thermoplastic elastomers and the like are exemplified. Or a carbon nanotube, a vapor growth carbon fiber, etc. may be sufficient.

In this case, the complex constituting the particle 14 is composed of a metal-organic skeleton structure in which a metal atom or a metal ion is surrounded by an organic molecule or an organic ion and coordinated. Preferable examples of this type of metal-organic framework structure include [M ₂ (4,4′-bipyridine) ₃ (NO ₃ ) ₄ ] (where M is any one of Co, Ni, and Zn), [ M ₂ (1,4-benzenedicarboxylate anion) ₂ ] (where M is either Cu or Zn), [Fe ₂ (trans-4,4′-azopyridine) ₄ (NCS) ₄ ] and the like. It is done.

Alternatively, the general formula may be M ₄ O (aromatic dicarboxylate anion) ₃ . Preferable examples of M include Zn, Mg, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al, Ru, Rh, Pd, Ag, and Pt. Further, instead of the aromatic dicarboxylate anion, the aromatic dicarboxylate anion is composed of an aromatic dicarboxylate anion derivative in which at least one of H present in the aromatic ring of the aromatic dicarboxylate anion is substituted with a functional group. Also good.

  Preferable examples of the aromatic dicarboxylate anion or a derivative thereof include 1,4-benzenedicarboxylate anion, 2-bromo-1,4-benzenedicarboxylate anion, 2-amino-1,4-benzenedi Carboxylate anion, 2,5-propyl-1,4-benzenedicarboxylate anion, 2,5-pentyl-1,4-benzenedicarboxylate anion, cyclobutene-1,4-benzenedicarboxylate anion, 1, 4-naphthalenedicarboxylate anion, 2,6-naphthalenedicarboxylate anion, 4,4′-biphenyldicarboxylate anion, 4,5,9,10-tetrahydropyrene-2,7-dicarboxylate anion, pyrene -2,7-dicarboxylate anion, 4, "-. Terphenyl dicarboxylate anion, etc. Each structural formula is as follows.

  FIG. 2 is a schematic structural explanatory view schematically showing the structure of the hydrogen adsorbent 20 according to the present embodiment. As can be understood from FIG. 2, the hydrogen adsorbent 20 is configured by a plurality of complex-bonding base materials 10 (see FIG. 1) contacting or bonding to each other. That is, the complex bond base materials 10 may be in a so-called entangled state, or a state in which the complexes (particles 14) deposited on the separate complex bond base materials 10 and 10 are connected by physical or chemical bonding. It may be.

  That is, according to the present embodiment, the hydrogen adsorbent 20 having a large volume can be formed without performing compression molding by bonding or assembling the complex binding base materials 10 together. In the complex-bonded base material 10 which is a basic structural unit of the hydrogen adsorbent 20, the porous skeleton structure of the complex (metal-organic skeleton structure) constituting the particles 14 is not crushed, and thus excellent hydrogen gas adsorption. It becomes a hydrogen adsorbent exhibiting performance.

  Moreover, according to the present embodiment, the hydrogen adsorbent can be produced without using a large amount of binder or the like that does not contribute to the expression of the hydrogen gas adsorption ability. For this reason, it can be set as the hydrogen adsorbent with a large hydrogen gas adsorption amount per unit volume.

  This hydrogen adsorbent 20 can be produced as follows. First, as a base material 12, for forming a complex (metal-organic framework structure) with linear molecules such as polyethylene, vinyl chloride, polytetrafluoroethylene, thermoplastic elastomer, carbon nanotube, and vapor-grown carbon fiber. A metal ion source and an organic ligand source are added to the solvent.

What is necessary is just to select a metal salt and an organic compound as a metal ion source and an organic ligand source, respectively. Specific metal salts include, for example, zinc nitrate tetrahydrate: Zn (NO ₃ ) ₂ .4H ₂ O, which is a Zn salt, while specific examples of organic compounds include 2,6-naphthalene. Dicarboxylic acid is mentioned.

As the solvent, a liquid that can dissolve both the metal salt and the organic compound is selected. Preferable examples include N, N′-diethylformamide, dimethylformamide, and N-methylpyrrolidone. As both the metal salt and the organic compound are dissolved in the solvent, as shown in FIG. 3, the metal ion M ⁺ and the organic ligand L ⁻ are liberated, and in this state, the substrate 12 (linear molecules ) To surround the surroundings.

Thereafter, the reaction between the metal ion M ⁺ and the organic ligand L ⁻ proceeds, and the complex particles 14 start to be deposited from the surface of the substrate 12 as shown in FIG. By proceeding the precipitation, the complex-bonding substrate 10 is obtained. As the precipitation progresses, the particles 14 and 14 are bonded to each other to cause grain growth, resulting in large particles.

  Here, the reaction time may be set depending on the temperature. That is, it is allowed to stand for several days to several weeks at room temperature, and 20 to 72 hours at 85 to 105 ° C. Of course, after standing at room temperature for several days, it may be held at 85 to 105 ° C. for several hours to several tens of hours. In any case, it is preferable to use a sealed vessel when heating.

  The complex binding substrate 10 thus obtained may be separated from the solvent by filtration or the like, and the solvent contained in the filtration residue may be removed by volatilization to obtain a hydrogen adsorbent. The material 10 may be stirred in a solvent. This stirring can be carried out by stirring the solvent before separation, or stirring another solvent to which the complex-binding substrate 10 after being separated from the solvent is added.

  By this stirring, the entanglement or bonding between the complex bonded substrates 10 and 10 easily proceeds. Here, the size of the particles 14 deposited and grown on the surface of the base material 12 is not uniform. Therefore, the surface of the base material 12 to which a large number of particles 14 are bonded is uneven. Yes. The complex bonded substrates 10 and 10 are easily entangled with each other by the engagement of the irregularities.

  The aggregated structure in which a plurality of complex-bonding substrates 10 are entangled or bonded to each other is separated from the solvent by filtration or the like, and the solvent contained in the filtration residue is removed by volatilization. The hydrogen adsorbent 20 to be obtained is obtained.

  As understood from the above, in the present embodiment, the compression molding process is not obtained when the hydrogen adsorbent 20 is produced. Therefore, the porous skeleton structure of the metal-organic skeleton structure constituting the complex bonding substrate 10 is not crushed. In addition, since it is not particularly necessary to add a large amount of binder or the like, the hydrogen adsorbent can be constituted by only the base material 12 and the particles 14.

  Here, the particles 14 precipitate and grow so as to cover substantially the entire surface of the substrate 12. Therefore, the ratio of the base material 12 in the hydrogen adsorbent 20 is significantly smaller than the ratio occupied by the particles 14. In other words, most of the hydrogen adsorbing material 20 is particles 14 that act to adsorb hydrogen gas, and the ratio of the base material 12 is very small. The hydrogen gas adsorption amount per volume does not become excessively small.

  For the above reasons, the hydrogen adsorbent 20 having excellent hydrogen gas adsorption ability can be obtained.

  Further, since the complex particles 14 are precipitated starting from the nuclei present on the surface of the substrate 12, the bonding force between the particles 14 and the substrate 12 is large. Therefore, the complex-bonding substrate 10 is mechanically stable.

  In the above-described embodiment, linear molecules are selected as the material of the substrate 12, but a sheet material made of a polymer or a carbon material may be used. Preferable examples of the polymer include polyethylene, vinyl chloride, polytetrafluoroethylene, thermoplastic elastomer and the like. Specific examples of the sheet material made of carbon material include carbon paper, carbon mat, carbon nonwoven fabric, and carbon woven fabric.

  When a sheet material is used as a base material, a sheet-like hydrogen adsorbent is obtained. Such a hydrogen adsorbent is, for example, wound in a roll shape and accommodated in a cylindrical container, or accommodated in the container after being cut to match the inner shape of the container. There is an advantage that it can be easily deformed according to the shape of the container. Accordingly, the housing is significantly easier than when the powdery metal-organic framework structure is housed in the container.

  1 mg of single-walled carbon nanotubes having a purity of 90% or more was added to 1000 ml of N, N′-diethylformamide (DEF). The added solution was evacuated and degassed to release air from the carbon nanotubes and to allow DEF to enter the gaps between the carbon nanotubes. During this operation, the carbon nanotubes were dispersed throughout the DEF by ultrasonic vibration and stirring using a stirrer.

1.2 g of 2,6-naphthalenedicarboxylic acid and 11 g of Zn (NO ₃ ) ₂ .4H ₂ O were added to and dissolved in the above additive solution that had been evacuated. After this solution was sealed in a sealed container, it was kept at 95 ° C. for 20 hours. As a result, a complex-bonded substrate in which particles of Zn ₄ O (2,6-naphthalenedicarboxylate anion) _3. (DEF) ₆ were deposited on the surface of the carbon nanotube was obtained.

  The sealed container was allowed to stand until the room temperature and the equilibrium temperature were reached, and the complex-binding substrate was separated from DEF by filtration. After the filtration residue was added to another DEF, the DEF was stirred. By this stirring, the complex bonded substrates gathered to increase the particle size, and a bulk body of the complex bonded substrates was obtained.

This bulk was immersed in chloroform (CHCl ₃ ) for 24 hours, and DEF, which is a guest molecule of Zn ₄ O (2,6-naphthalenedicarboxylate anion) _3. (DEF) ₆ , was replaced with CHCl ₃ .

Thereafter, the bulk material and chloroform were separated by filtration, and the filtration residue was left at room temperature for 12 hours to volatilize and remove chloroform. Thereby, the bulk body of the complex bond base material in which Zn ₄ O (2,6-naphthalenedicarboxylate anion) ₃ was deposited on the surface of the single-walled carbon nanotube was generated.

  The above operation was repeated to obtain 50 g of the bulk body. This is Example 1.

The average particle diameter of this bulk body was determined by an electron microscope and an image processing method, and was 500 μm. Moreover, it was 1455 m < ² > / g when the specific surface area was measured from the nitrogen adsorption amount in 77K.

  A carbon paper of 50 mm × 50 mm × thickness 0.3 mm was positioned and fixed in a container storing 1000 ml of DEF. In this state, vacuuming was performed to release air from the carbon paper, and DEF was allowed to enter the gaps of the carbon paper.

1.2 g of 2,6-naphthalenedicarboxylic acid and 11 g of Zn (NO ₃ ) ₂ .4H ₂ O were added to the DEF that had been vacuumed while carbon paper was immersed. Dissolved. After this solution was sealed in a sealed container, it was kept at 95 ° C. for 20 hours. As a result, a complex-bonded substrate in which particles of Zn ₄ O (2,6-naphthalenedicarboxylate anion) _3. (DEF) ₆ were deposited on the surface of the carbon paper was obtained.

  The sealed container was allowed to stand until the room temperature and the equilibrium temperature were reached, and the complex-binding substrate was separated from DEF by filtration. The filtration residue was added to another DEF and washed by stirring the DEF.

The filtration residue, ie the complex binding substrate, is added to another DEF, and further to this DEF, 1.2 g 2,6-naphthalenedicarboxylic acid and 11 g Zn (NO ₃ ) ₂ .4H ₂ O Was added and dissolved. After this solution was sealed in a sealed container, it was kept at 95 ° C. for 20 hours.

  Thereafter, the sealed container was allowed to stand until it reached room temperature and an equilibrium temperature, and the complex-bound substrate was separated from DEF by filtration. After the filtration residue was added to another DEF, the DEF was stirred.

The above operation was repeated to densely deposit Zn ₄ O (2,6-naphthalenedicarboxylate anion) _3. (DEF) ₆ particles on the surface of the carbon paper. Then, this complex-bonded substrate is immersed in chloroform (CHCl ₃ ) for 24 hours, and DEF which is a guest molecule of Zn ₄ O (2,6-naphthalenedicarboxylate anion) _3. (DEF) ₆ is added to CHCl ₃ . Replaced.

Both were separated by removing the complex-bound substrate from chloroform, and the complex-bound substrate was left at room temperature for 12 hours to volatilize and remove the chloroform. As a result, a complex-bonded substrate in which 50 g of Zn ₄ O (2,6-naphthalenedicarboxylate anion) ₃ was precipitated on the surface of the carbon paper was obtained. This is Example 2.

It was 1430 m < ² > / g when the specific surface area was calculated | required like Example 1 about this sheet-like complex bonding base material.

For comparison, powdery Zn ₄ O (2,6-naphthalenedicarboxylate anion) ₃ was synthesized. That is, 1.2 g of 2,6-naphthalenedicarboxylic acid and 11 g of Zn (NO ₃ ) ₂ .4H ₂ O were dissolved in 1000 ml of DEF. After this solution was sealed in a sealed container, it was kept at 95 ° C. for 20 hours. Thereby, particles of Zn ₄ O (2,6-naphthalenedicarboxylate anion) _3. (DEF) ₆ were precipitated in DEF.

  Thereafter, the sealed container was allowed to stand at room temperature (25 ° C.) and an equilibrium temperature, and the particles were separated from DEF by filtration. The filtration residue was washed with DEF to obtain an aggregate of the particles.

This aggregate was immersed in chloroform (CHCl ₃ ) at room temperature for 24 hours, and DEF, which is a guest molecule of Zn ₄ O (2,6-naphthalenedicarboxylate anion) _3. (DEF) ₆ , was replaced with CHCl ₃ . . Furthermore, it was left to stand at room temperature for 12 hours to volatilize and remove chloroform to obtain Zn ₄ O (2,6-naphthalenedicarboxylate anion) ₃ .

The above operation was repeated individually to obtain a total of 50 g of powdery Zn ₄ O (2,6-naphthalenedicarboxylate anion) ₃ . The powdery Zn ₄ O (2,6-naphthalenedicarboxylate anion) ₃ was subjected to compression molding with a press molding machine to obtain pellets. The applied pressure was 300 kgf / m ² . This is a comparative example.

For Zn ₄ O (2,6-naphthalenedicarboxylate anion) ₃ as a comparative example, the average particle size was determined by an electron microscope and an image processing method in the same manner as in the example. The result was 20 μm, which was only 1/25 of Example 1. Moreover, when the specific surface area was measured from the nitrogen adsorption amount at 77 K, it was 203 m ² / g, which was about 1/7 of that of Examples 1 and 2.

  From the above results, it is possible to obtain a complex-bonded base material having a large particle size, that is, a volume, by depositing and growing a complex on the surface of the base material. It is clear that the hydrogen gas adsorption ability is excellent.

It is a schematic structure explanatory drawing which shows typically the structure of the complex bond substrate which constitutes the hydrogen adsorption material concerning this embodiment. It is a schematic structure explanatory drawing which shows typically the structure of the hydrogen adsorption material concerning this embodiment. It is a schematic diagram which shows typically the state which a metal ion and an organic ligand exist freely around the base material. It is a schematic diagram which shows typically the state where the particle | grains precipitated on the surface of the base material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Complex-bonding base material 12 ... Base material 14 ... Particle 20 ... Hydrogen adsorbent

Claims (1)

A method for producing a hydrogen adsorbent comprising an aggregate formed by a plurality of complex-bonded carbon nanotubes in which a plurality of complexes capable of adsorbing hydrogen gas are deposited on the surface of carbon nanotubes,
The carbon nanotube, N containing zinc nitrate tetrahydrate and 2,6-naphthalene dicarboxylic acid, preparing a N'- diethyl formamide as a first solvent,
Reacting the zinc nitrate tetrahydrate and the 2,6-naphthalenedicarboxylic acid in the first solvent to precipitate as a complex on the surface of the carbon nanotubes to form complex-bonded carbon nanotubes;
Separating the complex-bonded carbon nanotube and the first solvent;
N containing separate the complex bound carbon nanotubes, the method comprising the steps of: preparing a N'- diethyl formamide as a second solvent,
Stirring the complex-bonded carbon nanotubes in the second solvent to obtain an aggregate of a plurality of the complex-bonded carbon nanotubes;
Separating the aggregate and the second solvent;
A method for producing a hydrogen adsorbent characterized by comprising:

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