JP2005232034A - Polymer metal complex, use as gas adsorbent, gas separation apparatus and gas storage apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a new polymer metal complex useful as a gas adsorbent and to provide a gas separation apparatus and a gas storage apparatus using the same. <P>SOLUTION: The polymer metal complex has a unit structure represented by the formula: [NiY<SB>2</SB>L<SB>2</SB>]<SB>n</SB>(Y is a counter ion; L is an organic ligand). BF<SB>4</SB><SP>-</SP>ion is cited as the Y. 1,4-Bis(4-pyridyl)benzene is cited as the organic ligand L. The gas adsorbent comprising the polymer metal complex is applied to the gas separation apparatus and the gas storage apparatus. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polymer metal complex, use of the polymer metal complex as a gas adsorbent, and a gas separation device and a gas storage device using the gas adsorbent.

  The gas adsorbent has characteristics that can store a large amount of gas at a low pressure as compared with pressurized storage and liquefied storage. For this reason, in recent years, development of a gas storage device and a gas separation device using a gas adsorbent has been active. As the gas adsorbent, activated carbon, zeolite and the like are known. Recently, a method of occluding gas in a porous polymer metal complex has also been proposed (see Patent Document 1 and Non-Patent Document 1).

  However, these conventionally proposed gas adsorbents cannot be said to be sufficiently satisfactory in terms of gas adsorption amount, workability, etc., and development of gas adsorbents with better properties is desired. . In particular, an increase in the amount of gas adsorption is an important issue.

On the other hand, polymer metal complexes that cause a dynamic structural change due to an external stimulus have been reported (see Non-Patent Document 2 and Non-Patent Document 3). Among these new dynamic structural change metal complexes, when a polymer metal complex having a polymer structure and having a void in the interior is used as a gas adsorbent, gas is not adsorbed up to a certain pressure. However, a peculiar phenomenon that gas adsorption starts when a certain pressure is exceeded has been observed. As for gas release, gas is not released up to a certain pressure, but a phenomenon in which gas is suddenly released when the pressure falls below a certain pressure is simultaneously observed, and its use as a gas storage material is increasing (Non-Patent Documents). 4, non-patent document 5). These polymer metal complexes with dynamic structural changes include sites with weak interactions such as hydrogen bonds and π-π interactions in the molecule, which are considered to cause structural changes. However, details are unknown.
JP 2000-109493 A Susumu Kitagawa, Integrated Metal Complex, Kodansha Scientific, 2001, 214-218 Kazuhiro Uemura, Susumu Kitagawa, Future Materials, December, 44, (2002) Ryotaro Matsuda, Susumu Kitagawa, Petrotec, Vol. 26, No. 2, pp. 97-104 (2003) Kitagawa, S .; et al. , Angelwandte Chem. Int. Ed. (2003) 428 Seki, K .; et al. Phys. Chem. Chem. Phys. , (2002) 4, 1968

  An object of the present invention is to provide a novel polymer metal complex and to provide a gas adsorbent having excellent characteristics using the same. It is another object of the present invention to provide a gas storage device and a gas separation device each containing a gas adsorbent having the above characteristics, and a vehicle equipped with the gas storage device.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a polymer metal complex containing nickel ions has a gas storage capacity under specific conditions, and further, by external stimulation. It has been found that it has the ability to absorb and release gas rapidly, and has completed the present invention.

  That is, the present invention relates to a nickel-based polymer metal complex composed of nickel ions and an organic ligand. The present invention also relates to the use of the polymer metal complex as a gas storage material, a gas storage device and gas separation device in which the gas adsorbent is housed, and a vehicle on which the gas storage device is mounted.

Specifically, the present invention provides:
(1) a polymer metal complex having a unit structure of the following formula (1),

(In the formula, Y represents a counter ion and L represents an organic ligand.)
(2) the counter-ion Y is BF ₄ ^- is an ion, polymer metal complex according to (1),
(3) The polymer metal complex according to (1) or (2), wherein the organic ligand L is 1,4-bis (4-pyridyl) benzene.
(4) The polymer metal complex according to any one of (1) to (3), wherein an adsorption / desorption isotherm regarding at least one gas shows a hysteresis loop,
(5) The polymer metal complex according to (4), wherein the gas is at least one gas selected from the group consisting of hydrogen, hydrocarbon, carbon monoxide, carbon dioxide, oxygen, and nitrogen,
(6) The polymer metal complex according to (4), wherein the gas is at least one gas selected from the group consisting of hydrogen sulfide, sulfur oxide, nitrogen oxide, and ammonia,
(7) A gas adsorbent comprising the polymer metal complex according to any one of (1) to (6),
(8) A pressure swing adsorption type gas separation device using the gas adsorbent according to (7),
(9) A gas storage device containing the gas adsorbent according to (7) inside,
(10) A vehicle equipped with the gas storage device according to (9),
It is.

  The polymer metal complex of the present invention can occlude a large amount of gas. In addition, it is possible to manufacture a gas storage device and gas separation device in which the gas storage material made of the polymer metal complex of the present invention is housed, and a vehicle on which the gas storage device is mounted.

  The polymer metal complex of the present invention can be applied to various uses by utilizing the special properties relating to gas adsorption and desorption. For example, when applied to an adsorbent in a pressure swing adsorption method (hereinafter abbreviated as “PSA method”) gas separation device, the gas adsorption material of the present invention can be used to achieve very efficient gas separation. Is possible. In addition, the time required for pressure change can be shortened, contributing to energy saving. Furthermore, since it can contribute to miniaturization of the gas separation device, it is possible to increase cost competitiveness when selling high-purity gas as a product, of course, even when high-purity gas is used inside its own factory Since the cost required for the equipment that requires high purity gas can be reduced, the manufacturing cost of the final product can be reduced.

  Another application of the polymer metal complex of the present invention is a gas storage device. When the gas adsorbent of the present invention is applied to a gas storage device (business gas tank, consumer gas tank, vehicle fuel tank, etc.), it is possible to dramatically reduce the pressure during transportation and storage. . As an effect resulting from the ability to reduce the gas pressure during transportation or storage, first, an improvement in the degree of freedom in shape can be mentioned. In a conventional gas storage device, the gas adsorption amount cannot be maintained high unless the pressure during storage is maintained. However, in the gas storage device of the present invention, a sufficient amount of gas adsorption can be maintained even if the pressure is reduced. For this reason, the pressure resistance of a container can be made low and the shape of a gas storage apparatus can be designed freely to some extent. This effect is enormous, for example, when the gas storage device of the present invention is used as a fuel gas tank for a vehicle such as an automobile. When the gas storage device of the present invention is used as a fuel tank, restrictions on pressure resistance are relaxed as described above, and the shape can be designed freely to some extent. Specifically, the shape of the gas storage device can be adjusted to fit the shape of wheels, seats, and the like in the vehicle. As a result, various benefits such as miniaturization of the vehicle, securing of luggage space, and improvement of fuel consumption due to weight reduction of the vehicle can be obtained.

  In addition, when applied to a gas separation device or a gas storage device, the container shape, the material of the container, the type of the gas valve, etc. do not have to be used, and are used in the gas separation device and the gas storage device. Can be used. However, improvement of various apparatuses is not excluded, and any apparatus is included in the technical scope of the present invention as long as the gas polymer metal complex of the present invention is used.

  Next, the present invention will be described in detail.

  The nickel-based polymer metal complex of the present invention is a compound having a unit structure represented by the following formula (1).

(In the formula, Y represents a counter ion and L represents an organic ligand.)
The raw material for synthesize | combining the compound represented by Formula (1) is illustrated.

One of the raw materials is a nickel (II) salt, and examples of the counter ion contained in the nickel (II) salt include monovalent anions. For example, BF ₄ ⁻ , CF ₃ CO ₂ ⁻ , NO ₃ ^-Ions such as, and the like. From the viewpoint of ease of making the complex, BF ₄ ⁻ is preferable. The divalent counter ion tends to have a strong interaction with the nickel ion. In addition, among monovalent ions, Cl ⁻ , Br ⁻ , CH ₃ CO ₂ ^{— and the} like tend to have strong interactions in the same way, so care must be taken when using them as counter ions. However, these ions may be used when the problem of interaction does not occur or when the interaction does not matter so much.

  L in Formula (1) is an organic ligand. Examples of the organic ligand include a ligand having two coordination sites at relatively distant positions in the molecule, that is, ABA (A = 4-pyridyl group or 3-pyridyl group and functional groups thereof. Group-substituted ligand). Here, as B, 1,4-phenylene and substituted 1,4-phenylene, 1,3-phenylene and substituted 1,3-phenylene, 2,5-thiophenyl and its substituted products, 2,7-fluorenyl and its Substituted products, 1,4-diethynylbenzene group, 4,4′-biphenylene and the like can be mentioned. As an A-B-A type organic ligand, 1,4-bis (4-pyridyl) benzene, 1,4-bis (4-pyridyl) thiophene, 1, 2-bis (4-pyridyl) acetylene and 4,4′-bis (4-pyridyl) biphenyl are preferred, and 1,4-bis (4-pyridyl) benzene is particularly preferred.

  The polymer metal complex of the present invention, which is a porous body, contains water or an organic solvent in the pores when it comes into contact with organic molecules such as water, alcohol and ether, or, in some cases, between a metal ion and a ligand. In some cases, water or an organic solvent is inserted into the complex complex, for example, a complex complex represented by the formula (2).

(Wherein, Y represents a counter ion, L represents an organic ligand, Z represents an organic molecule such as water, alcohol, or ether, and m is 0.5 or more.)
However, organic molecules such as water, alcohol, and ether in these complex complexes are only weakly bonded to the polymer metal complex and are removed by pretreatment such as vacuum drying when used as a gas adsorbent. Returning to the complex represented by the original formula (1). Therefore, even a complex represented by the formula (2) can be regarded as essentially the same as the polymer metal complex of the present invention.

  The polymer metal complex of the present invention is a polymer having a structure in which the unit structure represented by the formula (1) is repeated. In the formula (1) and the formula (2), n merely indicates that the unit structure of the formula (1) or the formula (2) is repeated as in the case of the general polymer compound notation, The range of n is not particularly limited. The molecular weight of the polymer compound is not particularly limited. For example, it has a number average molecular weight of 1000 or more.

  In the gas adsorbent of the present invention, the adsorption / desorption isotherm relating to at least one gas preferably exhibits a hysteresis loop. That is, as shown in FIG. 1, the gas pressure-gas adsorption amount curve at the time of adsorption is different from the gas pressure-gas adsorption amount curve at the time of desorption.

  The peculiarity of the gas adsorbent in which the gas pressure-gas adsorption amount curve of the present invention exhibits a hysteresis loop will be described with reference to the drawings. FIG. 1 is a graph showing the relationship between gas pressure and gas adsorption amount in the gas adsorbent of the present invention. FIG. 2 is a graph showing the relationship between gas pressure and gas adsorption amount in a conventional adsorbent. In the figure, the horizontal axis indicates the gas pressure, and the vertical axis indicates the gas adsorption amount per unit mass of the adsorbent.

In the conventional gas adsorbent, the gas adsorption amount increases as the gas pressure increases, and the pressure-adsorption amount curve during adsorption coincides with the pressure-adsorption amount curve during desorption (FIG. 2). For example, the amount of adsorption adsorbed to conventional gas adsorbent when the A _1, it is necessary to pressurize the gas pressure to the P _1, the pressure to hold the adsorption amount to the A ₁ to P ₁ Need to hold. In contrast, in the gas adsorbent of the present invention, the pressure-adsorption amount curve during gas adsorption shows a hysteresis loop (FIG. 1).

  The mechanism by which such a hysteresis loop appears has not yet been fully understood. As a possible mechanism, it is considered that a lattice layer of a 2D square grid composed of metal ions and a ligand is stacked, and that these layers have an important function (Zawarotoko, M. et al. J., Crystal Engineering, 2 (1999), 37). As shown in FIG. 3, when the layers are shifted and stacked, there is no substantial void in the compound, and no gas adsorption occurs. On the other hand, when the layers are stacked as shown in FIG. 4, vacancies are generated and gas adsorption occurs. That is, the mechanism of rapid gas adsorption can be estimated as follows. When there is no gas or at a low pressure, the layers are laminated as shown in FIG. 3, and when the gas pressure is increased, phase transition occurs in the laminated structure of FIG. 4, and the gas is rapidly adsorbed in the pores. Stabilized within the pores. On the other hand, the mechanism of rapid gas release becomes unstable due to a decrease in gas pressure, and a phase transition from FIG. 4 to FIG. 3 opposite to the above occurs, and gas is considered to be released. In gas adsorption and outgassing, the pore structure of the complex is changed, resulting in a hysteresis loop (Seiichi Kondo, Tatsuo Ishikawa, Ikuo Abe, Adsorption Chemistry, Maruzen Co., Ltd., pages 53-57) .

  According to this estimation, the interaction between the layers has a great influence on the likelihood of misalignment. In fact, many polymer metal complexes in which a so-called 2D square grid lattice layer is laminated are known. However, almost all of them do not absorb gas, or even if they are absorbed, a rapid gas such as the compound of the present invention is generated. It does not show a hysteresis loop of gas adsorption / desorption accompanied by absorption and release (Kitagawa, S., Chemistry-A European Journal (2002), 8 (16), 3586-3600, Zawortko, MJ, Chem. Commun. (1999) 1327, Roye, H.-C., Angelwandte Chem. Int. Ed. (2002) 583, Kitagawa, S., J. Am. Chem. Soc., (2002) 2568). For this reason, it is considered that metal ions and counter ions play an important role as a control factor for the displacement between layers for the gas adsorption ability expression as in the present invention, but the detailed mechanism is unknown. .

  In the present invention, the nature of the ligand is also important. In the present invention, the ligand functions to form a skeleton of the polymer metal complex by coordinating to nickel ions at both ends of the molecule. Based on such principles, a number of synthesis examples of polymer metal complexes have been reported. Here, when copper ions are used, a very diverse molecule is used as a ligand. For example, the distance between nitrogen atoms at both ends, such as pyrazine and 4,4′-bipyridyl, is 0.75 nm or less. Many synthetic examples using relatively short ligands have also been reported (Munakata, M., Advances in Inorganic Chemistry, 46 (1999) 173-303).

  However, as in the present invention, in order to synthesize a polymer metal complex using nickel ions and develop a gas adsorption function, the distance between nitrogen atoms at both ends exceeds 4,4′-bipyridyl. It is preferable to use a ligand having a certain length, such as 1,4-bis (4-pyridyl) benzene. I don't know the detailed reason for this, but as the ligand length increases, the interaction between the ligands becomes stronger, so the interaction between the metal and the nitrogen of the ligand corresponding to their strength is required. It is considered that a ligand having a long ligand molecular length and a strong interaction between ligands is necessary for the coordination between nickel and nitrogen atoms. In the polymer metal complex containing nickel ions of the present invention, the property that a ligand having a long molecular length can be suitably used is a very preferable property when used as a material adsorbing material. The adsorption ability of the polymer metal complex is considered to be because the substance is adsorbed in the voids of the lattice composed of the ligand and the metal ion. Therefore, when the molecular length of the ligand is increased, the length of one side of the lattice is also increased, the void volume of the lattice is increased, and as a result, a large amount of substance can be adsorbed. However, these are only estimates. In other words, even if the estimation is not followed, it is included in the technical scope of the present invention as long as the requirements defined in the present invention are satisfied and a hysteresis loop is exhibited with respect to a predetermined gas.

  The production process of the polymer complex of the present invention is preferably carried out in a solution state by dissolving a raw material nickel salt and an organic ligand in a solvent in order to produce the compound represented by the formula (1). As a solvent for dissolving the nickel salt, good results can be obtained by using a proton solvent such as water or alcohol. Protonic solvents such as water and alcohol dissolve nickel salts well, stabilize nickel salts by coordinating and hydrogen bonding to nickel ions and counter ions, and suppress rapid reactions with ligands. This suppresses side reactions. Examples of the alcohol include aliphatic monohydric alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol and 2-butanol, and aliphatic dihydric alcohols such as ethylene glycol. Methanol, ethanol, 1-propanol, 2-propanol, and ethylene glycol are preferred because they are inexpensive and have high solubility of nickel salts. These alcohols may be used alone or in combination.

  It is also preferable to use a mixture of water and the alcohol as a solvent. The mixing ratio is arbitrary from 1: 100 to 100: 1 (volume ratio). When a ligand having a long ligand length, for example, a length of 4,4′-bis (4-pyridyl) biphenyl or more, is used, the mixing ratio of alcohols may be 30% or more. From the viewpoint of improving the property.

  Moreover, it is also possible to mix and use organic solvents other than alcohol with water, alcohol, or the mixed solvent of water-alcohol. The organic solvent to be mixed is a solvent miscible with water, and examples thereof include acetonitrile, tetrahydrofuran, acetone, 1,4-dioxane, dimethylformamide, dimethyl sulfoxide and the like. These may be used singly or in combination of two or more. Of these, acetone, 1,4-dioxane, dimethylformamide, dimethyl sulfoxide and acetonitrile give good results. The mixing ratio of the organic solvent is 50 mol% or less, preferably 30 mol% or less.

  On the other hand, as a solvent for dissolving the organic ligand, alcohol solvents such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol and ethylene glycol, acyclic and cyclic such as ether and tetrahydrofuran Aliphatic ethers, ketones such as acetone, esters such as ethyl acetate, aliphatic nitriles such as acetonitrile, halogenated solvents such as dichloromethane, aromatic solvents such as benzene and toluene, formamides such as dimethylformamide, dimethyl sulfoxide The sulfoxides such as can be widely exemplified. These may be used singly or in combination of two or more. In terms of cost and solubility, methanol, ethanol, 2-propanol, acetonitrile, acetone and the like are preferable.

  The mixing method of the nickel salt solution and the organic ligand system solution may be the addition of the ligand solution to the nickel salt solution or vice versa. In addition, it is not always necessary to carry out mixing in a solution. For example, a method of adding a solid ligand to a nickel salt solution and simultaneously adding a solvent, or after charging a reaction vessel with nickel salt, Alternatively, various methods are possible as long as the reaction finally occurs substantially in a solvent, such as injecting a solution and further injecting a solution for dissolving the nickel salt. However, the method of dropping and mixing the nickel salt solution and the ligand solution is industrially the most convenient and preferable.

  The concentration of the solution is 40 mmol / L to 4 mol / L, preferably 80 mmol / L to 2 mol / L for the nickel salt solution, and 40 mmol / L to 3 mol / L, preferably 80 mmol / L to the organic solution of the ligand. 1.8 mol / L. Even if the reaction is carried out at a lower concentration, the target product can be obtained, but the production efficiency may be lowered. Further, at a concentration higher than this, there is a possibility that the adsorption capacity is lowered.

  The reaction temperature is -20 to 120 ° C, preferably 25 to 90 ° C. If it is carried out at a temperature lower than this, the solubility of the raw material may be lowered. Although it is possible to carry out the reaction at a higher temperature using an autoclave or the like, the yield is difficult to improve for the energy cost such as heating.

  The mixing ratio of the nickel salt and the organic ligand used in the reaction of the present invention is in the range of 3: 1 to 1: 5, preferably 1.5: 1 to 1: 3. In other ranges, the yield of the target product decreases, and unreacted raw materials remain, making it difficult to take out the target product.

  The reaction can be carried out using an ordinary glass-lined SUS reaction vessel and a mechanical stirrer. After completion of the reaction, the target substance and raw material can be separated by filtration and drying to produce a target substance with high purity.

  The gas adsorbent using the nickel-based polymer metal complex of the present invention is a material in which the adsorption / desorption isotherm relating to the gas exhibits a hysteresis loop, but it is sufficient that the hysteresis loop is expressed with respect to at least one kind of gas. However, a hysteresis loop may not be shown.

The gas that the gas adsorbent of the present invention needs to exhibit a hysteresis loop varies depending on the application of the gas adsorbent of the present invention. For example, when the gas adsorbent of the present invention is used in a methane gas storage device, it is necessary to show a hysteresis loop for methane gas. When the gas adsorbent of the present invention is used in a gas separation device that separates hydrogen gas from a mixed gas of hydrogen and oxygen, it is preferable to show a hysteresis loop for each gas. Generally speaking, if the gas adsorbent of the present invention is used for storage or separation of a gas used for various applications, the gas in which the gas adsorbent of the present invention exhibits a hysteresis loop is hydrogen, hydrocarbon (methane Ethane, propane, butane, isobutane, etc.), carbon monoxide, carbon dioxide, oxygen, nitrogen and the like. Of course, a hysteresis loop may be shown for these two or more gases so that a mixture of a plurality of hydrocarbon gases such as LNG can be stored. In addition, if the gas adsorbent of the present invention is used for gas removal, the gas in which the gas adsorbent of the present invention exhibits a hysteresis loop includes hydrogen sulfide, sulfur oxide (SO _x ), and nitrogen oxide (NO _x ). Ammonia is preferred. Of course, a hysteresis loop may be shown for these two or more gases. A hysteresis loop may be shown for gases other than those exemplified above.

The material used as the gas adsorbent of the present invention may be selected according to the gas to be stored and the pressure required during adsorption. Although not particularly limited, [Ni (BF ₄ ) ₂ (bp1p) ₂ ] _n (wherein bp1p represents 1,4-bis (4-pyridyl) benzene) is exemplified as a specific example. it can.

[Combination of adsorbents]
The gas adsorbent of the present invention (hereinafter referred to as adsorbent (A)) may be used alone as an adsorbent, or may be used in combination with other adsorbents. When combined and used, the gas adsorbent having very excellent adsorption characteristics when used in combination with the adsorbent (B) exhibiting a behavior in which the adsorption isotherm and desorption isotherm coincide with each other. It can be.

  Here, the adsorbent (B) is a material that exhibits a behavior in which an adsorption isotherm and a desorption isotherm relating to gas coincide with each other. That is, as shown in FIG. 2, the gas pressure-gas adsorption amount curve at the time of adsorption is substantially the same as the gas pressure-gas adsorption amount curve at the time of desorption. The adsorbent (B) is not particularly limited as long as it has such characteristics, and a physical adsorbent, a chemical adsorbent, and a physicochemical adsorbent formed by combining them can be used.

  A physical adsorbent is an adsorbent that adsorbs molecules to be adsorbed using a weak force such as the interaction between molecules. Examples of the physical adsorbent include activated carbon, silica gel, activated alumina, zeolite, clay, super adsorbent fiber, and metal complex. A chemical adsorbent refers to an adsorbent that adsorbs molecules to be adsorbed by chemical bonds. Examples of the chemical adsorbent include calcium carbonate, calcium sulfate, potassium permanganate, sodium carbonate, potassium carbonate, sodium phosphate, and activated metal. The physicochemical adsorbent refers to an adsorbent that includes both physical adsorbent and chemical adsorbent adsorption mechanisms. Two or more of these may be used in combination. However, the technical scope of the present invention is not limited to these specific examples. The shape of the adsorbent (B) is not particularly limited, but generally a powdery material having an average particle size of 500 to 5000 μm is used.

As the adsorbent (B), activated carbon is preferable in consideration of production cost and gas adsorption performance. Activated carbon is relatively inexpensive and has a large amount of gas adsorption per mass. In addition, activated carbon has poor cycle characteristics related to gas adsorption / desorption, and when adsorption / desorption is repeated, the amount of gas adsorption tends to be remarkably reduced. For this reason, in the past, it was difficult to use in gas storage devices and gas separation devices despite the large amount of gas adsorption per mass. In this regard, when used as the adsorbent (B) of the present invention, the excellent gas adsorption performance of the activated carbon can be sufficiently extracted. Moreover, since activated carbon has the tendency for an adsorption amount to increase, so that a specific surface area is large, it is preferable that the specific surface area of activated carbon is 1000 m < ² > / g or more.

  It is preferable that the structure of the adsorbent (B) to be used is appropriately controlled according to the gas to be adsorbed. For example, the pores contained in the activated carbon can be classified into super micropores (up to 0.8 nm), micropores (0.8 to 2 nm), mesopores (2 to 50 nm), and macropores (50 nm to) depending on the size of the pores. . Gases that are easily adsorbed differ depending on the size of the pores. For example, methane gas is easily adsorbed to micropores. Therefore, when it is desired to adsorb methane gas, the pore distribution of the activated carbon may be controlled so that the proportion of micropores is increased.

  When the adsorbent (A) and adsorbent (B) of the present invention are combined, the adsorbent (A) covers the adsorbent (B), but preferably has no cracks or incomplete coverage. It is preferable to completely cover the adsorbent (B) so that it does not come into contact with the outside air. However, even if there are some cracks or the like, the adsorbent (B) obstructs free gas adsorption, and the adsorbent (B) covered with the adsorbent (A) exhibits a hysteresis loop with respect to gas adsorption. If so, it is included in the technical scope of the present invention. Preferably, the adsorbent (B) is covered with 5 to 50% by volume of the adsorbent (A) with respect to the adsorbent (B). Further, the thickness of the adsorbent (A) covering the adsorbent (B) needs to be determined according to the type of the adsorbent (A), but if the adsorbent (A) is too thin, the adsorbent (B) ) May not be fully controlled. On the other hand, if the adsorbent (A) is too thick, gas adsorption to the adsorbent (B) is difficult to occur, and the gas adsorption amount as a whole may be reduced. Considering these, it is preferable that the average thickness of the adsorbent (A) is 10 to 100 μm. The thickness of the adsorbent (A) can be controlled by adjusting the amount of adsorbent (A) used. The thickness of the adsorbent (A) can be calculated from a cross-sectional photograph taken using an electron microscope.

  As a method of combining the adsorbents (A) and (B), (i) the adsorbent (B) that does not dissolve in the solution is added to the solution in which the adsorbent (A) is dissolved, and then A method of adsorbing the adsorbent (A) on the surface of the adsorbent (B) by crystal growth of the adsorbent (A); (ii) preparing a slurry containing the adsorbent (A); ) A method of attaching the adsorbent (A) to the surface of the adsorbent (B) by coating and drying the surface, etc. can be used.

[Application to gas separation equipment]
The gas adsorbent of the present invention can be used as an adsorbent in a pressure separating adsorption (hereinafter abbreviated as “PSA”) gas separation apparatus. PSA gas separation is based on the principle of utilizing the difference between the gas pressure on the adsorbent and the gas adsorption amount.

  In an adsorbent that exhibits a behavior in which the adsorption isotherm and desorption isotherm of a gas such as activated carbon and zeolite coincide with each other, the gas adsorbent has two or more kinds of gases (for example, A gas, B gas) often adsorbs. Therefore, when performing gas separation by the PSA method using such a conventional material, since both the A gas and the B gas are adsorbed, the off gas includes the A gas as well as the B gas. Therefore, when only A gas is separated, it is very inefficient, and in order to increase the purity of A gas as a product gas, there is a disadvantage that loss of A gas into off-gas increases.

On the other hand, in the gas adsorbent (A) of the present invention, there is a phenomenon that there is a clear gas adsorption start pressure and a desorption start pressure, and these differ depending on the gas type. As an example, a gas adsorption / desorption isotherm of oxygen and nitrogen of [Ni (BF ₄ ) ₂ (bp1p) ₂ ] _n (where bp1p represents 1,4-bis (4-pyridyl) benzene) As shown in FIG. In this case, oxygen begins to absorb at O ₁ MPa and desorbs at O ₂ MPa. On the other hand, nitrogen adsorbs at n ₁ MPa, but desorption does not start until n ₂ MPa. Therefore, a mixed gas of oxygen and nitrogen is exposed to the gas adsorbent (A) at n ₁ MPa or more to adsorb both oxygen and nitrogen, and then the gas pressure is controlled to n ₂ MPa or less and O ₁ MPa or more. By doing so, it is possible to separate only nitrogen gas without releasing oxygen gas. That is, the gas separation performance is dramatically improved, and it is possible to obtain extremely high purity gas without contamination by one PSA operation. However, it does not exclude performing a PSA operation of two cycles or more.

  Since the gas separation apparatus of the present invention requires a small pressure swing width as described above, it contributes to a significant downsizing of the gas separation apparatus. Moreover, since the pressure swing width is small, the time required for pressure change is shortened, energy saving, and further, the production running cost of high-purity gas and the fixed cost of equipment can be reduced. The cost competitiveness when selling high-purity gas as a product can be enhanced, and even when high-purity gas is used in its own factory, the cost required for facilities that require high-purity gas can be reduced. Therefore, it has the effect of reducing the manufacturing cost of the final product.

[Application to gas storage equipment]
By storing the adsorbent (A) in a container such as a tank, a gas storage device that is superior to the case where a conventional material is used can be obtained.

The adsorbent (A) of the present invention has a gas adsorption start pressure and a desorption start pressure. At a pressure higher than the adsorption start pressure, the gas is abruptly occluded to the full capacity of the adsorbent and below the desorption start pressure, almost all of the adsorbed gas is released at the desorption start pressure. As an example, adsorption / desorption of an adsorbent having a unit structure represented by [Ni (BF ₄ ) ₂ (bp1p) ₂ ] _n (wherein bp1p represents 1,4-bis (4-pyridyl) benzene) FIG. 6 shows an isotherm and an adsorption / desorption isotherm of a conventional material such as activated carbon. The adsorbent (A) has a characteristic that a gas storage amount is large at a low pressure as compared with a conventional material, and can be suitably used when storing gas at a low pressure.

  Furthermore, the pressure of the gas discharged from the conventional material decreases as the gas is desorbed. However, when gas is used in an actual apparatus, for example, a gas engine, a problem occurs in the operability of the engine at an extremely low pressure, for example, 0.5 MPa or less. For this reason, in the conventional material, the storage gas having a gas pressure of 0.5 MPa or less (the portion on the left side of the line) cannot be practically used, resulting in a decrease in the storage gas pressure. On the other hand, since the adsorbent (A) releases almost the entire amount of gas at a pressure higher than 0.5 MPa, the gas loss phenomenon does not occur, and when used in a gas storage device, it is preferable that the effective capacity is large. Characteristics occur.

  When manufacturing containers, such as a tank using an adsorbent (A), those structures and materials can use a conventionally well-known technique and are not specifically limited. For example, it is possible to use a metal container or the like that can control the entry and exit of gas by valve control. For example, it is possible to use a metal thin-walled container wrapped around a carbon fiber reinforced plastic material having excellent strength per unit density. If the container is provided with a regulating valve for controlling the internal pressure of the gas storage device, the regulating valve can be utilized when gas is released from the gas storage device.

  The accommodation method of the adsorbent (A) can be a known method such as filling in a pressure resistant container, and is not particularly limited. The capacity of the gas adsorbent may be determined according to the gas storage capacity required for the gas storage device. The shape and material of the pressure vessel are not particularly limited. The gas storage device of the present invention does not need to be provided with a special pressure-resistant structure because it may be at a lower pressure in order to ensure the same storage amount as compared with the conventional type. In this respect, it can be said that there is an advantage in cost.

  When the gas adsorbent is in a powder form, there is a possibility that it cannot be filled well if it is stored in a container constituting the gas storage device. When using a tank having a high degree of freedom in shape, this problem may be particularly noticeable. In this case, the powder may be stored in a tablet shape. In the case of using a tablet-shaped product, it is excellent in handleability and is very convenient when replacing an aged compound.

  The gas storage device of the present invention has various applications such as, but not limited to, commercial gas tanks, consumer gas tanks, and vehicle fuel tanks. As an effect resulting from the ability to reduce the gas pressure at the time of conveyance or storage, firstly, improvement in the degree of freedom of shape can be mentioned. In the conventional gas storage device, the gas adsorption amount cannot be maintained high unless the pressure during storage is maintained. However, in the gas storage device of the present invention, a sufficient amount of gas adsorption can be maintained even if the pressure is reduced. For this reason, the pressure resistance of a container can be made low and the shape of a gas storage apparatus can be designed freely to some extent. This effect is enormous, for example, when the gas storage device of the present invention is used as a fuel gas tank for a vehicle such as an automobile. In the conventional fuel gas tank, the shape of the fuel gas tank is determined regardless of the shape of the vehicle. This inevitably results in a considerable amount of dead space. In addition, a special device is required to maintain a high pressure. In this regard, when the gas storage device of the present invention is used as a fuel gas tank, the restrictions on pressure resistance are relaxed as described above, so that the shape can be designed to some extent freely. Specifically, the shape of the gas storage device can be adjusted to fit the shape of wheels, seats, and the like in the vehicle. As a result, various benefits such as miniaturization of the vehicle, securing of luggage space, and improvement of fuel consumption due to weight reduction of the vehicle can be obtained.

The method for preparing the polymer metal complex varies depending on the type of the gas adsorbent and cannot be uniquely determined. Here, [Ni (BF ₄ ) ₂ (bp1p) ₂ ] _n (wherein bp1p represents 1,4-bis (4-pyridyl) benzene.) An example of the synthesis will be described.

(Example 1)
An ethanol solution (80 mmol / L) of 1,4-bis (4-pyridyl) benzene is slowly laminated on an ethanol solution (80 mmol / L) of nickel (II) borofluoride, sealed, and left for 10 days. did. The precipitated powder was filtered under reduced pressure and dried under reduced pressure to obtain whiteish blue polymer metal complex crystals.

In order to determine the composition of the obtained crystal, the following experiment was conducted. The obtained crystals were dried at 100 ° C. for 3 hours under reduced pressure of 3 Pa, 1.00 g was weighed under an argon stream, and the powder was dissolved in 1 mol / L aqueous ammonia and extracted with dichloromethane. Dichloromethane was distilled off using a rotary evaporator, and 662 mg of the obtained solid was analyzed using a gas chromatograph mass spectrometer (Shimadzu QP5050A). As a result, it was 1,4-bis (4-pyridyl) benzene, Was found to be contained at 66.2% by mass. Further, the content of nickel in the aqueous ammonia layer was examined by ICP emission method, and as a result, it was 8.13% by mass. Further, the content of fluorine atoms in the aqueous ammonia layer was examined by distillation separation spectrophotometry, and as a result, it was found to be 22.4% by mass. Furthermore, the content of boron atoms in the aqueous ammonia layer was examined by ICP emission method, and as a result, it was found to be 3.02% by mass. Together, it was found that the composition of the obtained crystal was [Ni (BF ₄ ) ₂ (bp1p) ₂ ] _n .

The obtained crystals were dried at 100 ° C. under reduced pressure of 3 Pa for 3 hours, and analyzed by infrared spectroscopy using a Perkin Elmer infrared spectrometer system 2000 and ATR attachment under a nitrogen stream. As a result of the measurement has an absorption of less, BP1P molecules and BF ₄ ^- was found to be a complex containing an ion: 3503,1618,1555,1489,1432,1334,1224,1137,1070,1023,1012 , 981, 945, 865, 842, 813, 763, 726 cm ⁻¹ .

  The nitrogen adsorption characteristic at 77K of the obtained gas adsorbent was investigated. For the measurement, a BET automatic adsorption device (Bell Soap 36 manufactured by Nippon Bell Co., Ltd.) was used. Prior to the measurement, the sample was vacuum-dried at 383 K for 3 hours to remove solvent molecules that may remain in a trace amount. Nitrogen adsorption was not observed until the relative pressure was about 0.4, and a phenomenon was observed in which the amount of adsorption rapidly increased when the relative pressure exceeded 0.4. The adsorption amount of nitrogen gas was 350 mL / g.

Furthermore, the methane adsorption property at room temperature of the obtained gas adsorbent was investigated. Prior to measurement, the sample was vacuum-dried at 383 K for 3 hours to remove solvent molecules and the like that may remain in trace amounts. The measurement was carried out by methane high-pressure adsorption isotherm measurement by mass method at 303K (the electronic balance uses a cahn balance 1100 manufactured by Cahn, Inc. The purity of methane is 99.5%, passed through a dry ice-ethanol trap. Use what you did). No adsorption of methane was observed up to about 8 MPa, and a sudden increase in the amount of adsorption was confirmed around 8 MPa. In addition, during the desorption, the desorption amount up to about 3.5 MPa was slight, but a sudden decrease in the adsorption amount was confirmed around 3.5 MPa. The maximum value of the adsorption amount of methane gas was 158 cm ³ (Normal) per 1 cm ^{3 of} the gas adsorbent.

  In the polymer metal complex of the present invention, a large number of micropores formed by alignment of ligands are present inside the substance. Taking advantage of this porosity, it can be used for adsorption and removal of various substances. For example, removal of toxic substances in the air, purification of water by removing unnecessary substances such as inorganic and organic substances in the water, or adsorption of useful substances in the air and water and taking them out, the useful substances air and water Can be recovered.

It is a gas adsorption / desorption curve in the gas adsorbent of the present invention. It is a gas adsorption-desorption curve in the conventional gas adsorbent. It is a conceptual diagram which shows the aspect of lamination | stacking of a polymeric metal complex in which the substantial void | hole is not formed. It is a conceptual diagram which shows the aspect of lamination | stacking of a polymer metal complex in which the void | hole was formed. It is an oxygen and nitrogen gas adsorption-desorption curve (-196 degreeC) in the gas adsorbent of this invention. It is a graph which compares the gas adsorption / desorption curve of the gas adsorbent of the present invention and the conventional adsorbent.

Claims (10)

A polymer metal complex having a unit structure of the following formula (1).

(In the formula, Y represents a counter ion and L represents an organic ligand.) The counterion Y is BF ₄ ^- is an ion, polymer metal complex according to claim 1.   The polymer metal complex according to claim 1 or 2, wherein the organic ligand L is 1,4-bis (4-pyridyl) benzene.   The polymer metal complex according to any one of claims 1 to 3, wherein an adsorption / desorption isotherm relating to at least one gas exhibits a hysteresis loop.   The polymer metal complex according to claim 4, wherein the gas is at least one gas selected from the group consisting of hydrogen, hydrocarbon, carbon monoxide, carbon dioxide, oxygen, and nitrogen.   The polymer metal complex according to claim 4, wherein the gas is at least one gas selected from the group consisting of hydrogen sulfide, sulfur oxide, nitrogen oxide, and ammonia.   A gas adsorbent comprising the polymer metal complex according to claim 1.   A pressure swing adsorption type gas separation apparatus using the gas adsorbent according to claim 7.   A gas storage device in which the gas adsorbent according to claim 7 is accommodated.   A vehicle comprising the gas storage device according to claim 9.

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