WO2019044596A1 - Hydrogen carrier and method for producing same - Google Patents

Hydrogen carrier and method for producing same Download PDF

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Publication number
WO2019044596A1
WO2019044596A1 PCT/JP2018/030849 JP2018030849W WO2019044596A1 WO 2019044596 A1 WO2019044596 A1 WO 2019044596A1 JP 2018030849 W JP2018030849 W JP 2018030849W WO 2019044596 A1 WO2019044596 A1 WO 2019044596A1
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Prior art keywords
hydrogen
hydrate
hollow particles
cage
particles
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PCT/JP2018/030849
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French (fr)
Japanese (ja)
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洋 鈴木
悦之 菰田
るり 日出間
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国立大学法人神戸大学
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Priority to JP2019539399A priority Critical patent/JP7161778B2/en
Publication of WO2019044596A1 publication Critical patent/WO2019044596A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
    • B01J20/16—Alumino-silicates
    • B01J20/18—Synthetic zeolitic molecular sieves
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
    • C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C11/00—Use of gas-solvents or gas-sorbents in vessels
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/32—Hydrogen storage

Definitions

  • the present invention relates to a hydrogen carrier useful as a hydrogen terminal carrier for delivering hydrogen from a hydrogen station to an end user, and to a method for producing the same, because it is excellent and safe in storage and release characteristics of hydrogen.
  • a high pressure hydrogen cylinder is the simplest as a means to enhance the transport efficiency of hydrogen.
  • the high pressure hydrogen cylinder has problems such as leakage and explosion, so its safety is low. Therefore, organic hydrides are being studied as hydrogen carriers.
  • the organic hydride include methylcyclohexane and decalin obtained by reducing toluene and naphthalene with hydrogen. Methylcyclohexane and decalin are safer than hydrogen and are excellent in handleability because they are liquid at normal temperature and pressure.
  • a special catalyst and high temperature conditions are required.
  • Organic hydrides are therefore not suitable as hydrogen terminal carriers, for example for delivering hydrogen from hydrogen stations to end users.
  • hydrogen hydrate is expected as a hydrogen carrier, particularly as a hydrogen terminal carrier.
  • Hydrogen hydrate is very safe and releases hydrogen easily only by standing at normal temperature and pressure.
  • the formation of hydrogen hydrate requires low temperature and high pressure conditions such as 100 MPa at -24 ° C, for example. Therefore, in Patent Document 1, an aqueous solution of a hydrate forming aid which shifts the phase equilibrium pressure and temperature of hydrogen hydrate, such as tetrahydrofuran, to normal pressure and normal temperature side, for example, 5 MPa at less than 7 ° C.
  • a process for producing hydrogen hydrate is disclosed, which is characterized in that The ease of formation of hydrates varies depending on the type of guest molecule to be included.
  • Patent Document 2 describes a method for producing hydrogen hydrate under high temperature and low temperature of ⁇ 30 ° C. to ⁇ 1 ° C. and 3 to 20 MPa using an aqueous solution such as acetone.
  • Patent Document 3 discloses a method in which an aqueous solution of tetrahydrofuran or acetone is absorbed in a void in a carbon nanotube bead, and hydrogen at 120 to 200 atm is occluded in a hydrate cage at a temperature below the freezing point.
  • the present invention can be produced using normal pressure or relatively near normal pressure hydrogen, is excellent in storage characteristics of hydrogen, and is also excellent and safe in releasing characteristics of hydrogen, and in particular, is particularly hydrogen.
  • An object of the present invention is to provide a hydrogen carrier useful as a terminal carrier and a method for producing the same.
  • the present inventors have intensively studied to solve the above problems. As a result, it has been found that if hollow particles having pores in the outer shell are used, a large amount of hydrogen can be easily stored in a hydrate cage at normal pressure or a pressure relatively close to normal pressure, and the present invention is completed. did. Hereinafter, the present invention is described.
  • the hollow particle which has a pore in an outer shell may be abbreviated as a "porous hollow particle.”
  • the shell of the hollow particle has pores,
  • the hydrogen carrier of the present invention can store a large amount of hydrogen, and the main components are only inorganic porous hollow particles and hydrogen hydrate, so it is safe and has a small environmental load, and it can be stored at about normal temperature. Particularly, it is useful as a hydrogen terminal carrier because hydrogen can be easily released by raising the temperature. In addition, the hydrogen carrier of the present invention can be efficiently produced without the need for extremely low temperature or high pressure hydrogen. Thus, it is also possible to produce at the hydrogen station for supplying hydrogen to the end users, for example, since they do not require extensive equipment for their production. Therefore, the present invention is very useful industrially as promoting practical use of a renewable energy source that uses hydrogen as a main raw material such as a fuel cell.
  • FIG. 1 is an enlarged photograph of the perforated hollow particle according to the present invention.
  • FIG. 2 is a schematic view of an apparatus used to produce a hydrogen carrier according to the present invention.
  • FIG. 3 is a graph showing a cooling curve of the temperature in the vicinity of hollow particles when the hydrogen carrier according to the present invention is produced.
  • the hydrogen carrier of the present invention comprises perforated hollow particles and hydrogen hydrate.
  • the material of the porous hollow particles is safe, and is not particularly limited as long as the particles are sufficiently small and hollow, and examples thereof include silica (SiO 2 ) and zeolite.
  • silica SiO 2
  • zeolite has silicon dioxide as a main skeleton, it has a crystal structure in which a part of silicon is replaced by aluminum or the like.
  • the porous hollow silica particles can be easily produced by a conventional method, for example, the method described in WO 2015/025259 or JP-A-2017-3148. That is, a lipophilic organic solvent such as n-hexane and a surfactant are added to an aqueous solution of a silicate or silane coupling agent and a pore-forming material such as poly (meth) acrylate, and the solution is vigorously stirred. / O emulsion is obtained. By adjusting the size of droplets in the emulsion, the size of hollow particles can be adjusted. The size of the droplets can be adjusted, for example, by the type and amount of surfactant, stirring power, and the like.
  • the pore area ratio to the surface area of the hollow particles can be adjusted by the use ratio of the pore forming material to the hollow particle raw material.
  • a W / O / W emulsion is prepared by adding the above W / O emulsion to an aqueous phase such as an aqueous solution of ammonium hydrogen carbonate and vigorously stirring.
  • polysiloxane or silica containing a pore-forming material is formed in the oil phase.
  • the formed particles are separated from the liquid phase, dried, and fired at about 350 ° C. or more and 800 ° C. or less, whereby porous hollow silica particles can be produced.
  • the porous hollow zeolite particles can be easily produced by a conventional method, for example, the method described in JP-A-2009-269788. That is, a core zeolite containing a metal such as aluminum is formed, crystals of the metal-free zeolite are grown to form a shell, the metal is removed, and the core zeolite is further decomposed by a silica decomposition agent. Pore hollow zeolite particles can be made.
  • the size of the perforated hollow particles is an important parameter for the present invention.
  • the present invention has been made in consideration of the fact that hydrogen is occluded in a hydrate cage existing in a place where hydrogen has diffused by the diffusion phenomenon of hydrogen in water. That is, in the case of hollow particles having a diameter exceeding the diffusion distance of hydrogen, the present invention encloses water in a perforated hollow particle having an appropriate diameter in view of the presence of a waste water region where hydrogen absorption does not occur in the first place.
  • efficient hydrogen storage is realized by disposing the water including the hydrate cage without waste at a distance where hydrogen entering from the pores of the outer shell can diffuse.
  • Time Hydrogen diffusion distance 1 minute 94 ⁇ m 10 minutes 298 ⁇ m 30 minutes 517 ⁇ m That is, since it diffuses to about 517 ⁇ m in about 30 minutes, it becomes about 1000 ⁇ m in diameter.
  • the size of the porous hollow particle may be appropriately adjusted in consideration of the time for hydrogen diffusion, but can be, for example, 3 ⁇ m or more and 1000 ⁇ m or less in diameter.
  • the size of the hollow hollow particles is smaller, the storage of hydrogen in the hydrate cage can be performed in a short time, and if the diameter is 1000 ⁇ m or less, it can be said that the time efficiency of hydrogen storage is sufficiently high.
  • the production of hollow particles that are too small may be difficult, and the hydrogen storage amount per weight of hydrogen carrier may be rather small, so the diameter is preferably 3 ⁇ m or more.
  • hollow particles As said diameter, 10 micrometers or more are more preferable, and 500 micrometers or less or 100 micrometers or less are more preferable, 50 micrometers or less or 30 micrometers or less are still more preferable, and 25 micrometers or less are especially preferable.
  • the diameter of the hollow particles can be measured by a laser diffraction type particle size distribution measuring device or a scanning electron microscope.
  • hollow particles to be used may include hollow particles exceeding the above range as long as the problems of the present invention can be solved.
  • the hollow particles used in the present invention have pores in their outer shell. Hydrogen can be absorbed into the hydrate cage contained in the hollow particles through such pores.
  • the size of the pore diameter can be, for example, 10 nm or more and 500 nm or less in equivalent circle diameter. If the circle equivalent diameter is 500 nm or less, the strength of the hollow particles can be sufficiently maintained regardless of the presence of pores, and if 10 nm or more, the hydrogen storage efficiency can be sufficiently secured.
  • As the said diameter 50 nm or more is preferable, 100 nm or more is more preferable, and 400 nm or less is preferable.
  • a ratio of the sum total of the aperture area part of the pore with respect to the surface area (a pore part is included) of a hollow particle 0.5% or more and 10% or less are preferable. If the ratio is 0.5% or more, the storage efficiency of hydrogen can be sufficiently ensured, and if 10% or less, the strength of the hollow particles can be sufficiently maintained.
  • the equivalent circle diameter of the pores and the ratio of the pore area of the pores can be determined by a conventional method. For example, representative hollow particles can be enlarged and photographed by a scanning electron microscope (SEM), and the obtained image data can be taken into image analysis software and determined by image analysis software.
  • the hydrogen carrier of the present invention is a porous hollow particle containing hydrogen hydrate inside.
  • the hydrogen hydrate is contained in the porous hollow particles, so that not only it can be produced under milder conditions, there is also the possibility that the hydrogen hydrate is stabilized.
  • Hydrogen hydrate is a hydrate cage in which hydrogen is clathrated.
  • Hydrate cages are solid crystals constructed of water molecules, and three types, structure I and structure II, which are cubic crystals, and structure H, which is hexagonal crystals, are known.
  • Each structure contains an S-cage, which is a dodecahedron containing 12 regular pentagons composed of 5 water molecules.
  • xy a regular x-gonal y-face
  • S-cage is represented by 5 12 .
  • Structure I includes, in addition to S-cage, M-cage (5 12 6 2 ), which is composed of 12 pentagons and 2 hexagons, and structure II in addition to S-cage L-cage (5 12 6 4 ), and the structure H type includes S'-cage (4 3 5 6 6 3 ) and U-cage (5 12 6 8 ) in addition to S-cage.
  • the crystal structure of the hydrate cage is mainly determined by the size and shape of the guest molecule to be included, and it is known that phase transition is caused by temperature or pressure. It has also been reported that two hydrogen molecules may be included in S-cage and four hydrogen molecules may be included in L-cage.
  • the hydrate formation adjuvant is not particularly limited, but, for example, tetrahydrofuran, tetrahydrofurfuryl alcohol, 1,3-dioxolane, 2,5-dihydrofuran, tetrahydrofuran sulfonic acid, etc., tetrahydrofuran and derivatives thereof; tetrabutyl ammonium bromide , Quaternary ammonium salts such as tetrabutylammonium chloride, tetrabutylammonium hydroxide, tetrabutylammonium fluoride, tetramethylammonium hydroxide and the like; phosphates such as tetraphenylphosphonium bromide; carbonization such as propane, methane and cycl
  • the use amount of the hydrate formation adjuvant may be appropriately adjusted, but may be, for example, 1% by mass or more and 40% by mass or less based on the total of water forming the hydrate cage and the hydrate formation adjuvant it can.
  • the proportion is 1% by mass or more, the action of the hydrate formation adjuvant is more reliably exhibited.
  • the said ratio is 40 mass% or less, hydrogen storage amount can be ensured more reliably.
  • the amount used may be determined in consideration of the solubility of the hydrate formation aid in water. For example, the solubility of tetrabutylammonium bromide in water at normal temperature is about 40% by mass, and the solubility of tetrahydrofuran is about 19%.
  • Step of Encapsulating Water or Aqueous Solution water or a hydrate cage formation aid aqueous solution is enclosed inside the perforated hollow particles.
  • concentration of the aqueous solution of hydrate cage formation adjuvant may be the same as the ratio of the hydrate formation adjuvant to the total of water forming the hydrate cage and the hydrate formation adjuvant. Good.
  • a conventional method can be used. For example, by immersing the porous hollow particles in water or the aqueous solution, water or the aqueous solution is introduced into the porous hollow particles by pressure reduction, stirring, ultrasonic irradiation, shaking, or a combination of these two or more operations. Can be conveniently enclosed. After water or the aqueous solution is sealed in the porous hollow particles, the porous hollow particles may be separated from excess water or the aqueous solution by filtration, centrifugation or the like.
  • Step of Forming Hydrate Cage inside the porous hollow particle is obtained by cooling the porous hollow particle in which the water or the aqueous solution of hydrate formation adjuvant is sealed, which is obtained by the above-mentioned sealing step of water or aqueous solution. Form a hydrate cage from water or an aqueous solution of hydrate formation aid.
  • the hydrate formation aid Without the hydrate formation aid, considerable low temperature and high pressure conditions are required. Specifically, for example, under 1 atmosphere of hydrogen, the temperature needs to be lowered to about ⁇ 100 ° C. or less, and at about ⁇ 70 ° C., the pressure of hydrogen needs to be increased to several hundred atmospheres.
  • the hydrate formation adjuvant when a hydrate formation adjuvant is used, the hydrate formation adjuvant is included in the hydrate cage to stabilize the hydrate cage, so the pressure closer to normal temperature and the pressure closer to normal pressure Hydrate cages can be formed.
  • the specific conditions for forming the hydrate cage in the case of using the hydrate formation adjuvant depend on the type and amount of the hydrate formation adjuvant to be used, and may be appropriately determined.
  • It may be cooled to about ⁇ 10 ° C. or more and 35 ° C. or less. More specifically, it may be cooled to about -10 ° C. or more and 33 ° C. or less in the case of tetrahydrofuran, and to about -10 ° C. or more and 35 ° C. or less in the case of tetrabutylammonium bromide.
  • the formation of the hydrate cage can be confirmed, for example, by the temperature change of the perforated hollow particles. Specifically, when the temperature of the porous hollow particles is measured while cooling the porous hollow particles in which water or a hydrate cage formation aid aqueous solution is enclosed, a temperature peak is observed due to the formation of the hydrate cage. The porous hollow particles in which water or a hydrate cage formation aid aqueous solution is sealed may be cooled until such a temperature peak is observed. If it is difficult to directly measure the temperature of the perforated hollow particles, a thermometer may be inserted between the perforated hollow particles to measure the temperature in the vicinity of the perforated hollow particles.
  • Hydrogen Storage Step In this step, hydrogen is brought into contact with the hydrate cage formed in the above-mentioned hydrate cage forming step, whereby hydrogen carriers are absorbed into the hydrate cage to produce a hydrogen carrier.
  • the hydrate cage is formed in the porous hollow particles, it is possible to absorb hydrogen in the hydrate cage at a relatively high temperature and a relatively low pressure.
  • hydrogen gas is allowed to flow between the perforated hollow particles containing the hydrate cage, hydrogen is diffused inside through the pores of the perforated hollow particles, and hydrogen is brought into contact with the hydrate cage. , Occlude hydrogen in the hydrate cage.
  • the pressure of hydrogen may be normal pressure or near normal pressure.
  • the hydrogen gas may be pressurized to such an extent that hydrogen can flow between the perforated hollow particles without problems.
  • the mode of hydrogen storage is not a single mode in which one hydrogen enters the hydrate cage but a double mode in which two hydrogens enter.
  • the pressure of the hydrogen gas may be adjusted to a normal pressure or more and less than 1000 kPa.
  • the upper limit value of the pressure of hydrogen is an absolute pressure.
  • hydrogen may be brought into contact while cooling the porous hollow particles containing the hydrate cage.
  • heat absorption is measured while cooling the perforated hollow particles in which water or hydrate cage formation aid aqueous solution is enclosed, a temperature peak is observed due to the formation of the hydrate cage, but the cooling is continued while continuing By contacting hydrogen, it is possible to occlude hydrogen in the hydrate cage.
  • the step of forming the hydrate cage and the step of storing hydrogen may be performed simultaneously. That is, the porous hollow particles may be cooled while blowing the cooled hydrogen gas into the above-mentioned porous hollow particles in which water or an aqueous solution of hydrate formation adjuvant is sealed. At this time, when the temperature of the perforated hollow particles is measured, an endothermic peak is observed when the hydrate cage is formed along with the cooling of the perforated hollow particles. Therefore, hydrogen is occluded by the hydrate cage in the above-mentioned porous hollow particles by contacting hydrogen while continuing cooling thereafter, and hydrogen hydrate is formed.
  • the hydrogen carrier according to the present invention can stably contain hydrogen at relatively low temperature, it can be used as a transport medium of hydrogen. That is, by carrying the hydrogen carrier of the present invention, it becomes possible to carry hydrogen.
  • the temperature of the hydrogen carrier during transportation is preferably cooled to ⁇ 10 ° C. or more and 10 ° C. or less, more preferably cooled to 5 ° C. or less, and still more preferably cooled to 0 ° C. or less.
  • the lower limit of the temperature is not particularly limited, for example, ⁇ 20 ° C. or higher is preferable, and ⁇ 15 ° C. or higher or ⁇ 10 ° C. or higher is more preferable.
  • the hydrogen carrier according to the present invention can be produced at relatively high temperature and relatively low concentration. Also, hydrogen hydrate releases hydrogen easily by bringing it to a slightly elevated temperature or low pressure from equilibrium conditions. Therefore, the hydrogen carrier according to the present invention is particularly useful as a hydrogen terminal carrier because it releases hydrogen easily, for example, by raising the temperature to 15 ° C. or more under normal pressure. As temperature at the time of hydrogen release, 20 ° C or more is preferred, and 25 ° C or more is more preferred. Although the upper limit in particular of the temperature concerned is not restricted, it can be 50 ° C or less, for example.
  • Example 1 Production of hydrogen carrier (1) Production of perforated hollow particles 10 g of sodium polymethacrylate (molecular weight: 9500) is added to 30 g of 30% by weight aqueous solution of sodium silicate (Na 2 SiO 3 ), and pure water is further added. The total volume was adjusted to 36 mL. Hereinafter, the obtained aqueous solution is referred to as "aqueous phase-1". Separately, 0.5 g of surfactant polyoxyethylene (20) sorbitan monooleate (trade name: Tween 80) and 0.25 g sorbitan mono oleate (trade name: Span 80) are added to 72 mL of n-hexane.
  • surfactant polyoxyethylene (20) sorbitan monooleate trade name: Tween 80
  • 0.25 g sorbitan mono oleate trade name: Span 80
  • a W / O emulsion was obtained by mixing with the above aqueous phase-1 and stirring for 1 minute at 8000 rpm using a homogenizer ("KHM-510S" manufactured by Kyoto Denshi Kogyo Co., Ltd.).
  • the W / O / W emulsion was prepared by adding the obtained W / O emulsion to 500 mL of 2 M aqueous ammonium hydrogencarbonate solution (aqueous phase-2) and reacting at 35 ° C. and 400 rpm for 10 minutes. However, as the reaction progressed, the oil layer hardened and the emulsion state was dissolved. The obtained particles were separated by filtration, further dried at 100 ° C. for 12 hours, and calcined at 500 ° C.
  • FIG. 1 the SEM enlarged photograph of the produced perforated hollow particle is shown. According to analysis of the obtained enlarged photograph etc., the particle diameter is 18.29 ⁇ m, the shell thickness is 2.27 ⁇ m, the ratio of the total area of the opening to the surface area is 3.2%, and the average pore diameter is 0.34 ⁇ m. there were.
  • FIG. 3 shows a cooling curve measured by a thermometer inserted between the particles. According to FIG. 3, a hydrate cage is formed about 7 minutes after the start of cooling at -5.degree. C., and then it is considered that hydrogen is absorbed because the temperature is stabilized at about -5.degree.

Abstract

The purpose of the present invention is to provide: a hydrogen carrier which can be produced using hydrogen having ambient pressure or a pressure that is relatively close to ambient pressure, has excellent hydrogen storage properties, also has excellent hydrogen release properties, and is safe, and is therefore particularly useful as a hydrogen terminal carrier; and a method for producing the hydrogen carrier. The hydrogen carrier according to the present invention is characterized by comprising hollow particles and a hydrogen hydrate, wherein the outer shell of each of the hollow particles has pores, and the hydrogen hydrate is contained in the hollow particles.

Description

水素キャリアとその製造方法Hydrogen carrier and its manufacturing method
　本発明は、水素の貯蔵特性と放出特性に優れ、且つ安全であることから、特に水素ステーションから末端ユーザーへ水素を届けるための水素ターミナルキャリアとして有用な水素キャリアとその製造方法に関するものである。 The present invention relates to a hydrogen carrier useful as a hydrogen terminal carrier for delivering hydrogen from a hydrogen station to an end user, and to a method for producing the same, because it is excellent and safe in storage and release characteristics of hydrogen.
　近年、地球温暖化などの問題が顕在化したことにより、化石燃料に代わる再生エネルギーが注目されている。例えば、ガソリン車に代わって燃料電池車が開発されたり、家庭用の燃料電池が開発されている。 In recent years, with the emergence of problems such as global warming, attention has been focused on renewable energy replacing fossil fuels. For example, fuel cell vehicles have been developed in place of gasoline vehicles, and household fuel cells have been developed.
　ところが、燃料電池の燃料である水素は、反応性が極めて高く危険である上に、常温常圧で気体であるため、ガソリンや灯油など常温常圧で液体である化石燃料に比べて運搬効率が低いという問題がある。 However, hydrogen, which is a fuel for fuel cells, has high reactivity and is dangerous. In addition, since it is a gas at normal temperature and pressure, its transportation efficiency is higher than that of fossil fuel such as gasoline and kerosene which is liquid at normal temperature and pressure. There is a problem that it is low.
　水素の運搬効率を高める手段としては、高圧水素ボンベが最も簡単である。しかし高圧水素ボンベには漏洩や爆発などの問題があり、安全性が低い。そこで、水素キャリアとして有機ハイドライドが検討されている。有機ハイドライドとしては、例えば、トルエンやナフタレンを水素で還元して得られたメチルシクロヘキサンやデカリンを挙げることができる。メチルシクロヘキサンやデカリンは水素よりも安全であり、且つ常温常圧で液体であることから取扱性に優れている。しかし、有機ハイドライドを酸化して水素を取り出す場合には、特殊な触媒と高温条件が必要となる。よって有機ハイドライドは、例えば水素ステーションから末端ユーザーへ水素を届けるための水素ターミナルキャリアとしては適さない。 A high pressure hydrogen cylinder is the simplest as a means to enhance the transport efficiency of hydrogen. However, the high pressure hydrogen cylinder has problems such as leakage and explosion, so its safety is low. Therefore, organic hydrides are being studied as hydrogen carriers. Examples of the organic hydride include methylcyclohexane and decalin obtained by reducing toluene and naphthalene with hydrogen. Methylcyclohexane and decalin are safer than hydrogen and are excellent in handleability because they are liquid at normal temperature and pressure. However, when oxidizing organic hydride and taking out hydrogen, a special catalyst and high temperature conditions are required. Organic hydrides are therefore not suitable as hydrogen terminal carriers, for example for delivering hydrogen from hydrogen stations to end users.
　また、水素により窒素を還元してアンモニアを製造し、このアンモニアを運搬し、使用時にアンモニアを酸化して水素を取り出すことも検討されている。しかし、アンモニアから水素を取り出すには触媒や高エネルギーが必要であるし、アンモニアは決して安全なものではなく、また、常温常圧で気体であり蒸気圧が高いことから取扱性に優れるものでもない。 In addition, it is also studied to reduce nitrogen with hydrogen to produce ammonia, transport this ammonia, oxidize the ammonia at the time of use, and take out hydrogen. However, catalysts and high energy are required to extract hydrogen from ammonia, and ammonia is not safe at all, nor is it a gas at normal temperature and pressure, and because it has a high vapor pressure, it is not excellent in handleability. .
　そこで、水素キャリア、特に水素ターミナルキャリアとして、水素ハイドレートが期待されている。水素ハイドレートは非常に安全性が高く、常温常圧下で放置するのみで容易に水素を放出する。しかし一般的に、水素ハイドレートの形成には、例えば－２４℃で１００ＭＰａといった低温高圧条件が必要である。そこで特許文献１には、テトラヒドロフランなど、水素ハイドレートの相平衡圧力・温度を常圧・常温側にシフトさせるハイドレート形成補助剤の水溶液に、多孔質フィルタを介して、例えば７℃未満で５ＭＰａの水素を供給することを特徴とする水素ハイドレートの生成方法が開示されている。なお、ハイドレートの形成され易さは、包接されるゲスト分子の種類により異なる。 Therefore, hydrogen hydrate is expected as a hydrogen carrier, particularly as a hydrogen terminal carrier. Hydrogen hydrate is very safe and releases hydrogen easily only by standing at normal temperature and pressure. However, generally, the formation of hydrogen hydrate requires low temperature and high pressure conditions such as 100 MPa at -24 ° C, for example. Therefore, in Patent Document 1, an aqueous solution of a hydrate forming aid which shifts the phase equilibrium pressure and temperature of hydrogen hydrate, such as tetrahydrofuran, to normal pressure and normal temperature side, for example, 5 MPa at less than 7 ° C. A process for producing hydrogen hydrate is disclosed, which is characterized in that The ease of formation of hydrates varies depending on the type of guest molecule to be included.
　また、水素ハイドレートには、吸蔵すべき水素が常温常圧で気体であることから、水素の貯蔵量が少ないという欠点がある。そこで特許文献２には、アセトンなどの水溶液を用い、－３０℃～－１℃、３～２０ＭＰａという低温高圧下で水素ハイドレートを製造する方法が記載されている。特許文献３には、カーボンナノチューブビーズ内の空隙に、テトラヒドロフランまたはアセトンの水溶液を吸収させ、氷点以下の温度で１２０～２００気圧の水素をハイドレートケージに吸蔵させる方法が開示されている。 Further, hydrogen hydrate has a disadvantage that the storage amount of hydrogen is small because hydrogen to be stored is a gas at normal temperature and pressure. Therefore, Patent Document 2 describes a method for producing hydrogen hydrate under high temperature and low temperature of −30 ° C. to −1 ° C. and 3 to 20 MPa using an aqueous solution such as acetone. Patent Document 3 discloses a method in which an aqueous solution of tetrahydrofuran or acetone is absorbed in a void in a carbon nanotube bead, and hydrogen at 120 to 200 atm is occluded in a hydrate cage at a temperature below the freezing point.
特開２０１２－２３６７４０号公報JP 2012-236740 A 特開２００８－２８５３４１号公報JP 2008-285341 A 特開２００７－２７２７８１号公報JP 2007-272781 A
　上述したように、水素ハイドレートを製造する方法は種々開発されていたが、一般的に、数十気圧以上（数ＭＰａ以上）という高圧の水素をハイドレートケージに吸蔵させるものであった。
　そこで本発明は、常圧または比較的常圧に近い水素を用いて製造可能なものであり、水素の貯蔵特性に優れ、また、水素の放出特性にも優れ且つ安全であることから、特に水素ターミナルキャリアとして有用な水素キャリアとその製造方法を提供することを目的とする。 As described above, various methods for producing hydrogen hydrate have been developed, but in general, high-pressure hydrogen of several tens of atmosphere or more (several MPa or more) is occluded in a hydrate cage.
Therefore, the present invention can be produced using normal pressure or relatively near normal pressure hydrogen, is excellent in storage characteristics of hydrogen, and is also excellent and safe in releasing characteristics of hydrogen, and in particular, is particularly hydrogen. An object of the present invention is to provide a hydrogen carrier useful as a terminal carrier and a method for producing the same.
　本発明者らは、上記課題を解決するために鋭意研究を重ねた。その結果、外殻に細孔を有する中空粒子を用いれば、多量の水素を常圧または比較的常圧に近い圧力でハイドレートケージに容易に吸蔵させることができることを見出して、本発明を完成した。
　以下、本発明を示す。なお、以下では、外殻に細孔を有する中空粒子を「有孔中空粒子」と略記する場合がある。 The present inventors have intensively studied to solve the above problems. As a result, it has been found that if hollow particles having pores in the outer shell are used, a large amount of hydrogen can be easily stored in a hydrate cage at normal pressure or a pressure relatively close to normal pressure, and the present invention is completed. did.
Hereinafter, the present invention is described. In addition, below, the hollow particle which has a pore in an outer shell may be abbreviated as a "porous hollow particle."
　［１］　中空粒子と水素ハイドレートを含み、
　前記中空粒子の外殻が細孔を有し、
　前記中空粒子中に前記水素ハイドレートが含まれることを特徴とする水素キャリア。 [1] containing hollow particles and hydrogen hydrate,
The shell of the hollow particle has pores,
A hydrogen carrier characterized in that the hydrogen hydrate is contained in the hollow particles.
　［２］　前記中空粒子の粒子径が１０００μｍ以下である上記［１］に記載の水素キャリア。 [2] The hydrogen carrier according to the above [1], wherein the particle diameter of the hollow particles is 1000 μm or less.
　［３］　前記中空粒子の表面積に対する前記細孔の開孔部面積の合計の割合が０．５％以上、１０％以下である上記［１］または［２］に記載の水素キャリア。 [3] The hydrogen carrier according to the above [1] or [2], wherein the ratio of the total of the pore area of the pores to the surface area of the hollow particles is 0.5% or more and 10% or less.
　［４］　前記中空粒子が中空シリカ粒子または中空ゼオライト粒子である上記［１］～［３］のいずれかに記載の水素キャリア。 [4] The hydrogen carrier according to any one of the above [1] to [3], wherein the hollow particles are hollow silica particles or hollow zeolite particles.
　［５］　前記水素ハイドレートが、水と水素に加えてハイドレート形成補助剤を含む上記［１］～［４］のいずれかに記載の水素キャリア。 [5] The hydrogen carrier according to any one of the above [1] to [4], wherein the hydrogen hydrate contains a hydrate formation aid in addition to water and hydrogen.
　［６］　水素キャリアを製造するための方法であって、
　外殻が細孔を有する中空粒子の内部に水またはハイドレート形成補助剤の水溶液を封入する工程、
　前記水またはハイドレート形成補助剤水溶液を封入した前記中空粒子を冷却してハイドレートケージを形成する工程、および、
　前記ハイドレートケージに水素を接触させることにより前記ハイドレートケージ中に水素を吸蔵させる工程を含む方法。 [6] A method for producing a hydrogen carrier,
Encapsulating water or an aqueous solution of hydrate formation aid inside the hollow particle whose outer shell has pores,
Cooling the hollow particles enclosing the water or the aqueous solution of hydrate formation adjuvant to form a hydrate cage;
Storing hydrogen in the hydrate cage by contacting the hydrate cage with hydrogen.
　［７］　前記水素の圧力を常圧以上、１０００ｋＰａ未満とする上記［６］に記載の方法。 [7] The method according to the above-mentioned [6], wherein the pressure of the hydrogen is at a normal pressure or more and less than 1000 kPa.
　［８］　上記［６］または［７］に記載の方法により水素キャリアを製造する工程、および、
　前記水素キャリアを運搬する工程を含む水素の運搬方法。 [8] A process for producing a hydrogen carrier by the method according to the above [6] or [7], and
A method of transporting hydrogen comprising the step of transporting the hydrogen carrier.
　本発明の水素キャリアは、多量の水素を貯蔵することができ、主な構成成分は無機の有孔中空粒子と水素ハイドレートのみであるので、安全であり且つ環境負荷が小さい上に、常温程度に昇温することにより水素を容易に放出することができるので、特に水素ターミナルキャリアとして有用である。また、本発明の水素キャリアは、極端な低温や高圧の水素を必要とせず、効率的に製造することができる。よって、例えばその製造のために大規模な設備を必要としないため、末端ユーザーに水素を供給するための水素ステーションで製造することも可能である。よって本発明は、燃料電池など水素を主な原料とする再生エネルギー源の実用化を促進するものとして、産業上非常に有用である。 The hydrogen carrier of the present invention can store a large amount of hydrogen, and the main components are only inorganic porous hollow particles and hydrogen hydrate, so it is safe and has a small environmental load, and it can be stored at about normal temperature. Particularly, it is useful as a hydrogen terminal carrier because hydrogen can be easily released by raising the temperature. In addition, the hydrogen carrier of the present invention can be efficiently produced without the need for extremely low temperature or high pressure hydrogen. Thus, it is also possible to produce at the hydrogen station for supplying hydrogen to the end users, for example, since they do not require extensive equipment for their production. Therefore, the present invention is very useful industrially as promoting practical use of a renewable energy source that uses hydrogen as a main raw material such as a fuel cell.
図１は、本発明に係る有孔中空粒子の拡大写真である。FIG. 1 is an enlarged photograph of the perforated hollow particle according to the present invention. 図２は、本発明に係る水素キャリアを製造するために用いた装置の概略図である。FIG. 2 is a schematic view of an apparatus used to produce a hydrogen carrier according to the present invention. 図３は、本発明に係る水素キャリアを製造した際の中空粒子の近傍の温度の冷却曲線を示すグラフである。FIG. 3 is a graph showing a cooling curve of the temperature in the vicinity of hollow particles when the hydrogen carrier according to the present invention is produced.
　本発明の水素キャリアは、有孔中空粒子と水素ハイドレートを含む。有孔中空粒子の材質は、安全なものであり、また、粒子が十分に小さく且つ中空のものであれば特に制限されないが、例えばシリカ（ＳｉＯ2）やゼオライトを挙げることができる。なお、ゼオライトは二酸化ケイ素を主骨格とするものの、一部のケイ素がアルミニウムなどに置換されている結晶構造を有する。 The hydrogen carrier of the present invention comprises perforated hollow particles and hydrogen hydrate. The material of the porous hollow particles is safe, and is not particularly limited as long as the particles are sufficiently small and hollow, and examples thereof include silica (SiO 2 ) and zeolite. In addition, although zeolite has silicon dioxide as a main skeleton, it has a crystal structure in which a part of silicon is replaced by aluminum or the like.
　有孔中空シリカ粒子は、常法、例えばＷＯ２０１５／０２５５２９号や特開２０１７－３１４８号公報に記載の方法により容易に製造することができる。即ち、ケイ酸塩やシランカップリング剤と、ポリ（メタ）アクリル酸塩などの孔形成材の水溶液に、ｎ－ヘキサンなどの親油性有機溶媒と界面活性剤を加え、激しく攪拌することによりＷ／Ｏエマルジョンを得る。当該エマルジョン中における液滴の大きさを調整することにより、中空粒子の大きさを調整することができる。液滴の大きさは、例えば、界面活性剤の種類や量、攪拌動力などにより調整可能である。また、中空粒子の表面積に対する孔面積比は、中空粒子原料に対する孔形成材の使用割合により調整することができる。次に、上記Ｗ／Ｏエマルジョンを、炭酸水素アンモニウム水溶液などの水相に加えて激しく攪拌することにより、Ｗ／Ｏ／Ｗエマルジョンを調製する。この際、油相において、孔形成材を含むポリシロキサンやシリカが形成される。形成された粒子を液相から分離し、乾燥した後、３５０℃以上、８００℃以下程度で焼成することにより、有孔中空シリカ粒子を製造することができる。 The porous hollow silica particles can be easily produced by a conventional method, for example, the method described in WO 2015/025259 or JP-A-2017-3148. That is, a lipophilic organic solvent such as n-hexane and a surfactant are added to an aqueous solution of a silicate or silane coupling agent and a pore-forming material such as poly (meth) acrylate, and the solution is vigorously stirred. / O emulsion is obtained. By adjusting the size of droplets in the emulsion, the size of hollow particles can be adjusted. The size of the droplets can be adjusted, for example, by the type and amount of surfactant, stirring power, and the like. The pore area ratio to the surface area of the hollow particles can be adjusted by the use ratio of the pore forming material to the hollow particle raw material. Next, a W / O / W emulsion is prepared by adding the above W / O emulsion to an aqueous phase such as an aqueous solution of ammonium hydrogen carbonate and vigorously stirring. At this time, polysiloxane or silica containing a pore-forming material is formed in the oil phase. The formed particles are separated from the liquid phase, dried, and fired at about 350 ° C. or more and 800 ° C. or less, whereby porous hollow silica particles can be produced.
　有孔中空ゼオライト粒子は、常法、例えば特開２００９－２６９７８８号公報に記載の方法により容易に製造することができる。即ち、アルミニウムなどの金属を含むコアゼオライトを形成し、前記金属を含まないゼオライトの結晶を成長させてシェルを形成し、前記金属を除去し、更にシリカ分解剤によりコアゼアライトを分解することにより、有孔中空ゼオライト粒子を作製することができる。 The porous hollow zeolite particles can be easily produced by a conventional method, for example, the method described in JP-A-2009-269788. That is, a core zeolite containing a metal such as aluminum is formed, crystals of the metal-free zeolite are grown to form a shell, the metal is removed, and the core zeolite is further decomposed by a silica decomposition agent. Pore hollow zeolite particles can be made.
　有孔中空粒子の大きさ、例えば直径は、本発明にとって重要なパラメータである。本発明は、水素の水中での拡散現象により、水素が拡散していった場所に存在するハイドレートケージに吸蔵されることを考慮してなされたものである。即ち、水素の拡散距離を超える直径の中空粒子では、水素吸蔵がそもそも生じない無駄な水の領域があることに鑑みて、本発明は、適切な直径の有孔中空粒子に水を封入することによって、外殻の細孔から進入した水素が拡散可能な距離にハイドレートケージを含む水を無駄なく配置することで効率的な水素吸蔵を実現したものである。水素の水中での拡散係数は、約７．４４×１０-9ｍ2／秒であるので、その拡散距離は時間の関数として、具体的に以下のような関係となることが略計算される。
　　時間　　　　水素拡散距離
　　１分　　　　　　９４μｍ
　　１０分　　　　２９８μｍ
　　３０分　　　　５１７μｍ
　即ち、３０分程度で５１７μｍ程度に拡散するので、直径に換算すると約１０００μｍとなる。 The size of the perforated hollow particles, eg the diameter, is an important parameter for the present invention. The present invention has been made in consideration of the fact that hydrogen is occluded in a hydrate cage existing in a place where hydrogen has diffused by the diffusion phenomenon of hydrogen in water. That is, in the case of hollow particles having a diameter exceeding the diffusion distance of hydrogen, the present invention encloses water in a perforated hollow particle having an appropriate diameter in view of the presence of a waste water region where hydrogen absorption does not occur in the first place. Thus, efficient hydrogen storage is realized by disposing the water including the hydrate cage without waste at a distance where hydrogen entering from the pores of the outer shell can diffuse. Since the diffusion coefficient of hydrogen in water is about 7.44 × 10 −9 m 2 / sec, it is roughly calculated that the diffusion distance as a function of time has the following relationship: .
Time Hydrogen diffusion distance 1 minute 94μm
10 minutes 298 μm
30 minutes 517 μm
That is, since it diffuses to about 517 μm in about 30 minutes, it becomes about 1000 μm in diameter.
　従って、有孔中空粒子の大きさは、水素拡散のための時間を考慮して適宜調整すればよいが、例えば、直径で３μｍ以上、１０００μｍ以下とすることができる。有孔中空粒子が小さいほどハイドレートケージへの水素の吸蔵が短時間で行えることになり、直径が１０００μｍ以下であれば、水素吸蔵の時間効率は十分に高いといえる。一方、過剰に小さい中空粒子の製造は難しくなる場合があり、また、水素キャリアの重量当たりの水素吸蔵量がかえって小さくなる可能性があり得るため、上記直径としては３μｍ以上が好ましい。上記直径としては、１０μｍ以上がより好ましく、また、５００μｍ以下または１００μｍ以下がより好ましく、５０μｍ以下または３０μｍ以下がよりさらに好ましく、２５μｍ以下が特に好ましい。なお、中空粒子の直径は、レーザ回折式粒度分布測定装置や走査型電子顕微鏡などにより測定することができる。また、本発明の課題が解決できる範囲であれば、使用する中空粒子に上記の範囲を超える中空粒子が含まれていてもよい。 Therefore, the size of the porous hollow particle may be appropriately adjusted in consideration of the time for hydrogen diffusion, but can be, for example, 3 μm or more and 1000 μm or less in diameter. As the size of the hollow hollow particles is smaller, the storage of hydrogen in the hydrate cage can be performed in a short time, and if the diameter is 1000 μm or less, it can be said that the time efficiency of hydrogen storage is sufficiently high. On the other hand, the production of hollow particles that are too small may be difficult, and the hydrogen storage amount per weight of hydrogen carrier may be rather small, so the diameter is preferably 3 μm or more. As said diameter, 10 micrometers or more are more preferable, and 500 micrometers or less or 100 micrometers or less are more preferable, 50 micrometers or less or 30 micrometers or less are still more preferable, and 25 micrometers or less are especially preferable. The diameter of the hollow particles can be measured by a laser diffraction type particle size distribution measuring device or a scanning electron microscope. In addition, hollow particles to be used may include hollow particles exceeding the above range as long as the problems of the present invention can be solved.
　本発明で用いる中空粒子は、その外殻に細孔を有する。かかる細孔を介して、中空粒子内に含まれるハイドレートケージに水素を吸蔵させることができる。かかる細孔径の大きさとしては、例えば、円相当径で１０ｎｍ以上、５００ｎｍ以下とすることができる。当該円相当径が５００ｎｍ以下であれば、細孔の存在にかかわらず中空粒子の強度を十分に保つことができ、１０ｎｍ以上であれば、水素の吸蔵効率を十分に確保することができる。当該径としては、５０ｎｍ以上が好ましく、１００ｎｍ以上がより好ましく、また、４００ｎｍ以下が好ましい。また、中空粒子の表面積（細孔部分を含む）に対する細孔の開孔部面積の合計の割合としては、０．５％以上、１０％以下が好ましい。当該割合が０．５％以上であれば、水素の吸蔵効率を十分に確保することができ、１０％以下であれば、中空粒子の強度を十分に保つことができる。上記の細孔の円相当径や細孔の開孔部面積の割合は、常法により求めることができる。例えば、代表的な中空粒子を走査型電子顕微鏡（ＳＥＭ）で拡大撮影し、得られた画像データを画像解析ソフトに取り込み、画像解析ソフトにより求めることが可能である。 The hollow particles used in the present invention have pores in their outer shell. Hydrogen can be absorbed into the hydrate cage contained in the hollow particles through such pores. The size of the pore diameter can be, for example, 10 nm or more and 500 nm or less in equivalent circle diameter. If the circle equivalent diameter is 500 nm or less, the strength of the hollow particles can be sufficiently maintained regardless of the presence of pores, and if 10 nm or more, the hydrogen storage efficiency can be sufficiently secured. As the said diameter, 50 nm or more is preferable, 100 nm or more is more preferable, and 400 nm or less is preferable. Moreover, as a ratio of the sum total of the aperture area part of the pore with respect to the surface area (a pore part is included) of a hollow particle, 0.5% or more and 10% or less are preferable. If the ratio is 0.5% or more, the storage efficiency of hydrogen can be sufficiently ensured, and if 10% or less, the strength of the hollow particles can be sufficiently maintained. The equivalent circle diameter of the pores and the ratio of the pore area of the pores can be determined by a conventional method. For example, representative hollow particles can be enlarged and photographed by a scanning electron microscope (SEM), and the obtained image data can be taken into image analysis software and determined by image analysis software.
　本発明の水素キャリアは、内部に水素ハイドレートを含む有孔中空粒子である。本発明の水素キャリアでは、水素ハイドレートが有孔中空粒子中に内包されていることにより、より穏和な条件で製造できるのみでなく、水素ハイドレートが安定化されている可能性もある。 The hydrogen carrier of the present invention is a porous hollow particle containing hydrogen hydrate inside. In the hydrogen carrier of the present invention, the hydrogen hydrate is contained in the porous hollow particles, so that not only it can be produced under milder conditions, there is also the possibility that the hydrogen hydrate is stabilized.
　水素ハイドレートは、ハイドレートケージに水素が包接されたものをいう。ハイドレートケージは、水分子によって構築された固体結晶であり、立方晶である構造Ｉ型と構造ＩＩ型、および、六方晶である構造Ｈ型の３種類が知られている。各構造にはＳ－ｃａｇｅが含まれており、Ｓ－ｃａｇｅは水分子５個で構成されている正五角形１２個を含む１２面体である。以下、正ｘ角形のｙ面体をｘyで表す。例えば、Ｓ－ｃａｇｅは５12で表される。構造Ｉ型は、Ｓ－ｃａｇｅに加えて、１２面の五角形と２面の六角形で構成されているＭ－ｃａｇｅ（５12６2）を含み、構造ＩＩ型は、Ｓ－ｃａｇｅに加えて、Ｌ－ｃａｇｅ（５12６4）を含み、構造Ｈ型は、Ｓ－ｃａｇｅに加えて、Ｓ’－ｃａｇｅ（４3５6６3）とＵ－ｃａｇｅ（５12６8）を含む。ハイドレートケージの結晶構造は、主に包接されるゲスト分子のサイズや形状などで決定される他、温度や圧力などによって相転移することが知られている。また、Ｓ－ｃａｇｅに２つの水素分子が包接される場合や、Ｌ－ｃａｇｅに４つの水素分子が包接される場合があることが報告されている。 Hydrogen hydrate is a hydrate cage in which hydrogen is clathrated. Hydrate cages are solid crystals constructed of water molecules, and three types, structure I and structure II, which are cubic crystals, and structure H, which is hexagonal crystals, are known. Each structure contains an S-cage, which is a dodecahedron containing 12 regular pentagons composed of 5 water molecules. Hereinafter, a regular x-gonal y-face is represented by xy. For example, S-cage is represented by 5 12 . Structure I includes, in addition to S-cage, M-cage (5 12 6 2 ), which is composed of 12 pentagons and 2 hexagons, and structure II in addition to S-cage L-cage (5 12 6 4 ), and the structure H type includes S'-cage (4 3 5 6 6 3 ) and U-cage (5 12 6 8 ) in addition to S-cage. The crystal structure of the hydrate cage is mainly determined by the size and shape of the guest molecule to be included, and it is known that phase transition is caused by temperature or pressure. It has also been reported that two hydrogen molecules may be included in S-cage and four hydrogen molecules may be included in L-cage.
　水素ハイドレートを安定に保持するためには、極低温や１００ＭＰａ以上といった高圧が必要である。しかし、ハイドレート形成補助剤を用いることにより、ハイドレートケージの形成条件をより比較的高温で且つ比較的低圧にすることが可能になる。ハイドレート形成補助剤としては、特に制限されないが、例えば、テトラヒドロフラン、テトラヒドロフルフリルアルコール、１，３－ジオキソラン、２，５－ジヒドロフラン、テトラヒドロフランスルホン酸など、テトラヒドロフランおよびその誘導体；臭化テトラブチルアンモニウム、塩化テトラブチルアンモニウム、水酸化テトラブチルアンモニウム、フッ化テトラブチルアンモニウム、水酸化テトラメチルアンモニウムなどの第四級アンモニウム塩；テトラフェニルホスホニウムブロマイドなどのリン酸塩；プロパン、メタン、シクロペンタンなどの炭化水素類；アセトンなどのケトン類；プロピレンオキシドなどのエポキシ類などを挙げることができる。 In order to keep hydrogen hydrate stable, high temperature such as cryogenic temperature or 100 MPa or more is required. However, the use of a hydrate formation aid allows the hydrate cage formation conditions to be relatively hot and relatively low pressure. The hydrate formation adjuvant is not particularly limited, but, for example, tetrahydrofuran, tetrahydrofurfuryl alcohol, 1,3-dioxolane, 2,5-dihydrofuran, tetrahydrofuran sulfonic acid, etc., tetrahydrofuran and derivatives thereof; tetrabutyl ammonium bromide , Quaternary ammonium salts such as tetrabutylammonium chloride, tetrabutylammonium hydroxide, tetrabutylammonium fluoride, tetramethylammonium hydroxide and the like; phosphates such as tetraphenylphosphonium bromide; carbonization such as propane, methane and cyclopentane Hydrogens; ketones such as acetone; epoxys such as propylene oxide; and the like.
　ハイドレート形成補助剤の使用量は、適宜調整すればよいが、例えば、ハイドレートケージを形成する水とハイドレート形成補助剤の合計に対して１質量％以上、４０質量％以下とすることができる。当該割合が１質量％以上であれば、ハイドレート形成補助剤の作用がより確実に発揮される。一方、当該割合が４０質量％以下であれば、水素吸蔵量をより確実に確保することができる。当該割合としては、２質量％以上がより好ましく、５質量％以上がよりさらに好ましく、また、１５質量％以下がより好ましい。より具体的には、ハイドレート形成補助剤の水に対する溶解度も考慮して使用量を決定すればよい。例えば、常温における臭化テトラブチルアンモニウムの水に対する溶解度は約４０質量％であり、テトラヒドロフランの同溶解度は約１９％である。 The use amount of the hydrate formation adjuvant may be appropriately adjusted, but may be, for example, 1% by mass or more and 40% by mass or less based on the total of water forming the hydrate cage and the hydrate formation adjuvant it can. When the proportion is 1% by mass or more, the action of the hydrate formation adjuvant is more reliably exhibited. On the other hand, if the said ratio is 40 mass% or less, hydrogen storage amount can be ensured more reliably. As the said ratio, 2 mass% or more is more preferable, 5 mass% or more is further more preferable, and 15 mass% or less is more preferable. More specifically, the amount used may be determined in consideration of the solubility of the hydrate formation aid in water. For example, the solubility of tetrabutylammonium bromide in water at normal temperature is about 40% by mass, and the solubility of tetrahydrofuran is about 19%.
　水素ハイドレートにおいては、ハイドレート形成補助剤を用いた場合にはその分だけ水素吸蔵量は減るし、また、全てのハイドレートケージに水素が吸蔵される訳ではない。実際には、１００気圧の水素下で得られる水素ハイドレートの水素吸蔵量は０．１０質量％程度であった。しかし、本発明者らによる実験的知見によれば、常圧の水素を用いたにもかかわらず約０．６０質量％の水素吸蔵量が達成できた。このように本発明では、常圧または比較的常圧に近い水素を用いているにもかかわらず、１００気圧の水素を用いて得られた場合の６倍以上の水素吸蔵量が達成された。 In hydrogen hydrate, when a hydrate formation aid is used, the amount of stored hydrogen decreases accordingly, and not all the hydrate cage stores hydrogen. In fact, the hydrogen storage capacity of hydrogen hydrate obtained under hydrogen at 100 atm was about 0.10 mass%. However, according to experimental findings by the present inventors, a hydrogen storage capacity of about 0.60 mass% could be achieved despite the use of hydrogen at normal pressure. As described above, in the present invention, although hydrogen is used at or near normal pressure, a hydrogen storage capacity of 6 or more times that obtained when using 100 atm of hydrogen was achieved.
　以下、本発明に係る水素キャリアの製造方法につき説明する。
　１．水または水溶液の封入工程
　本工程では、上記有孔中空粒子の内部に水またはハイドレートケージ形成補助剤水溶液を封入する。ハイドレートケージ形成補助剤水溶液を用いる場合、ハイドレートケージ形成補助剤水溶液の濃度は、ハイドレートケージを形成する水とハイドレート形成補助剤の合計に対するハイドレート形成補助剤の割合と同様にすればよい。 Hereinafter, the method for producing a hydrogen carrier according to the present invention will be described.
1. Step of Encapsulating Water or Aqueous Solution In this step, water or a hydrate cage formation aid aqueous solution is enclosed inside the perforated hollow particles. When using an aqueous solution of hydrate cage formation adjuvant, the concentration of the aqueous solution of hydrate cage formation adjuvant may be the same as the ratio of the hydrate formation adjuvant to the total of water forming the hydrate cage and the hydrate formation adjuvant. Good.
　上記有孔中空粒子への水または上記水溶液の具体的な封入方法としては、常法を用いることができる。例えば、上記有孔中空粒子を水または上記水溶液に浸漬した上で、減圧、攪拌、超音波照射、振盪、またはこれら２以上の操作を組み合わせることにより、上記有孔中空粒子内へ水または上記水溶液を簡便に封入することができる。
　上記有孔中空粒子内へ水または上記水溶液を封入した後は、濾過や遠心分離などにより、有孔中空粒子を過剰の水または上記水溶液から分離してもよい。 As a specific method for enclosing water or the above aqueous solution in the above-mentioned perforated hollow particles, a conventional method can be used. For example, by immersing the porous hollow particles in water or the aqueous solution, water or the aqueous solution is introduced into the porous hollow particles by pressure reduction, stirring, ultrasonic irradiation, shaking, or a combination of these two or more operations. Can be conveniently enclosed.
After water or the aqueous solution is sealed in the porous hollow particles, the porous hollow particles may be separated from excess water or the aqueous solution by filtration, centrifugation or the like.
　２．ハイドレートケージの形成工程
　本工程では、上記水または水溶液の封入工程により得られた、水またはハイドレート形成補助剤水溶液が封入された有孔中空粒子を冷却することにより、有孔中空粒子内で水またはハイドレート形成補助剤水溶液からハイドレートケージを形成する。 2. Step of Forming Hydrate Cage In this step, inside the porous hollow particle is obtained by cooling the porous hollow particle in which the water or the aqueous solution of hydrate formation adjuvant is sealed, which is obtained by the above-mentioned sealing step of water or aqueous solution. Form a hydrate cage from water or an aqueous solution of hydrate formation aid.
　ハイドレート形成補助剤を用いない場合、かなりの低温高圧条件が必要である。具体的には、例えば１気圧の水素下では、約－１００℃以下まで温度を下げる必要があり、約－７０℃では、水素の圧力を数百気圧まで高める必要がある。一方、ハイドレート形成補助剤を用いた場合には、ハイドレート形成補助剤がハイドレートケージに包接されてハイドレートケージを安定化するため、より常温に近い温度で且つより常圧に近い圧力でハイドレートケージが形成され得る。ハイドレート形成補助剤を用いた場合のハイドレートケージの具体的な形成条件は、使用するハイドレート形成補助剤の種類や量などに依存するので、適宜決定すればよいが、例えば常圧の場合、－１０℃以上、３５℃以下程度に冷却すればよい。より具体的には、テトラヒドロフランの場合は－１０℃以上、３３℃以下程度に、臭化テトラブチルアンモニウムの場合は－１０℃以上、３５℃以下程度に冷却すればよい。 Without the hydrate formation aid, considerable low temperature and high pressure conditions are required. Specifically, for example, under 1 atmosphere of hydrogen, the temperature needs to be lowered to about −100 ° C. or less, and at about −70 ° C., the pressure of hydrogen needs to be increased to several hundred atmospheres. On the other hand, when a hydrate formation adjuvant is used, the hydrate formation adjuvant is included in the hydrate cage to stabilize the hydrate cage, so the pressure closer to normal temperature and the pressure closer to normal pressure Hydrate cages can be formed. The specific conditions for forming the hydrate cage in the case of using the hydrate formation adjuvant depend on the type and amount of the hydrate formation adjuvant to be used, and may be appropriately determined. For example, in the case of normal pressure It may be cooled to about −10 ° C. or more and 35 ° C. or less. More specifically, it may be cooled to about -10 ° C. or more and 33 ° C. or less in the case of tetrahydrofuran, and to about -10 ° C. or more and 35 ° C. or less in the case of tetrabutylammonium bromide.
　ハイドレートケージの形成は、例えば、有孔中空粒子の温度変化により確認することができる。具体的には、水またはハイドレートケージ形成補助剤水溶液が封入された有孔中空粒子を冷却しつつ、有孔中空粒子の温度を測定すると、ハイドレートケージの形成により温度ピークが認められる。かかる温度ピークが認められるまで、水またはハイドレートケージ形成補助剤水溶液が封入された有孔中空粒子を冷却すればよい。なお、有孔中空粒子の温度を直接測定することが難しい場合には、有孔中空粒子間に温度計を挿入し、有孔中空粒子近傍の温度を測定すればよい。 The formation of the hydrate cage can be confirmed, for example, by the temperature change of the perforated hollow particles. Specifically, when the temperature of the porous hollow particles is measured while cooling the porous hollow particles in which water or a hydrate cage formation aid aqueous solution is enclosed, a temperature peak is observed due to the formation of the hydrate cage. The porous hollow particles in which water or a hydrate cage formation aid aqueous solution is sealed may be cooled until such a temperature peak is observed. If it is difficult to directly measure the temperature of the perforated hollow particles, a thermometer may be inserted between the perforated hollow particles to measure the temperature in the vicinity of the perforated hollow particles.
　３．水素吸蔵工程
　本工程では、上記ハイドレートケージ形成工程で形成されたハイドレートケージに水素を接触させることにより、ハイドレートケージ中に水素を吸蔵させることにより水素キャリアを製造する。本発明では、有孔中空粒子中にハイドレートケージを形成しているため、比較的高温で且つ比較的低圧でハイドレートケージに水素を吸蔵させることが可能になる。 3. Hydrogen Storage Step In this step, hydrogen is brought into contact with the hydrate cage formed in the above-mentioned hydrate cage forming step, whereby hydrogen carriers are absorbed into the hydrate cage to produce a hydrogen carrier. In the present invention, since the hydrate cage is formed in the porous hollow particles, it is possible to absorb hydrogen in the hydrate cage at a relatively high temperature and a relatively low pressure.
　具体的には、本工程では、ハイドレートケージを内包する有孔中空粒子間に水素ガスを流通させ、有孔中空粒子の細孔を通じて水素を内部に拡散させてハイドレートケージに水素を接触させ、水素をハイドレートケージ内に吸蔵させる。この際、ハイドレートケージの安定化のため、有孔中空粒子を低温に維持し、且つ水素ガスも低温に冷却することが好ましい。有孔中空粒子と水素ガスは、ハイドレートケージの形成温度の±５℃の範囲に調整することが好ましい。より具体的には、有孔中空粒子と水素ガスを－１０℃以上、１０℃以下に冷却することが好ましく、５℃以下に冷却することがより好ましく、０℃以下に冷却することがより更に好ましい。 Specifically, in this step, hydrogen gas is allowed to flow between the perforated hollow particles containing the hydrate cage, hydrogen is diffused inside through the pores of the perforated hollow particles, and hydrogen is brought into contact with the hydrate cage. , Occlude hydrogen in the hydrate cage. At this time, in order to stabilize the hydrate cage, it is preferable to maintain the porous hollow particles at a low temperature and also cool the hydrogen gas to a low temperature. It is preferable to adjust the porous hollow particles and the hydrogen gas in the range of ± 5 ° C. of the formation temperature of the hydrate cage. More specifically, it is preferable to cool the porous hollow particles and the hydrogen gas to -10 ° C. or more and 10 ° C. or less, more preferably to 5 ° C. or less, and even more preferably to 0 ° C. or less preferable.
　従来、水素ハイドレートの製造には低温高圧条件が一般的に必要であったが、本発明では、有孔中空粒子の使用により上述したように比較的常温に近い温度でハイドレートケージに水素を吸蔵させることができるし、その際の水素の圧力も常圧または略常圧でよい。但し、有孔中空粒子間に水素を問題無く流通できる程度に水素ガスを加圧してもよい。加圧すると、水素吸蔵のモードがハイドレートケージに１個の水素が入るシングルモードではなく、２個の水素が入るダブルモードになることも期待される。具体的には、水素ガスの圧力を常圧以上、１０００ｋＰａ未満に調整してもよい。当該圧力としては、５００ｋＰａ以下が好ましく、２００ｋＰａ以下がより好ましく、１５０ｋＰａ以下または１２０ｋＰａ以下がより更に好ましい。なお、ここでの水素の圧力の上限値は、絶体圧である。 In the past, low temperature and high pressure conditions were generally required for the production of hydrogen hydrate, but in the present invention, as described above, use of porous hollow particles allows hydrogen to be added to the hydrate cage at a temperature relatively close to normal temperature. The pressure of hydrogen may be normal pressure or near normal pressure. However, the hydrogen gas may be pressurized to such an extent that hydrogen can flow between the perforated hollow particles without problems. When pressurized, it is also expected that the mode of hydrogen storage is not a single mode in which one hydrogen enters the hydrate cage but a double mode in which two hydrogens enter. Specifically, the pressure of the hydrogen gas may be adjusted to a normal pressure or more and less than 1000 kPa. As the said pressure, 500 kPa or less is preferable, 200 kPa or less is more preferable, 150 kPa or less or 120 kPa or less is still more preferable. Here, the upper limit value of the pressure of hydrogen is an absolute pressure.
　ハイドレートケージへ水素を吸蔵させるには、例えば、ハイドレートケージを内包する有孔中空粒子を冷却しつつ水素を接触させればよい。上述した様に、水またはハイドレートケージ形成補助剤水溶液が封入された有孔中空粒子を冷却しつつ吸熱量を測定すると、ハイドレートケージの形成により温度ピークが認められるが、冷却を継続しつつ水素を接触させることにより、ハイドレートケージ内に水素を吸蔵させることができる。 In order to occlude hydrogen in the hydrate cage, for example, hydrogen may be brought into contact while cooling the porous hollow particles containing the hydrate cage. As described above, when heat absorption is measured while cooling the perforated hollow particles in which water or hydrate cage formation aid aqueous solution is enclosed, a temperature peak is observed due to the formation of the hydrate cage, but the cooling is continued while continuing By contacting hydrogen, it is possible to occlude hydrogen in the hydrate cage.
　上記ハイドレートケージの形成工程と水素吸蔵工程は、同時に実施してもよい。即ち、水またはハイドレート形成補助剤水溶液が封入された上記有孔中空粒子に冷却した水素ガスを吹き込みつつ、有孔中空粒子を冷却してもよい。この際、上記有孔中空粒子の温度を測定すると、有孔中空粒子の冷却に伴って、ハイドレートケージの形成の際に吸熱ピークが観察される。よって、その後も冷却を継続しつつ水素を接触させることにより、水素が上記有孔中空粒子内のハイドレートケージに吸蔵され、水素ハイドレートが形成される。 The step of forming the hydrate cage and the step of storing hydrogen may be performed simultaneously. That is, the porous hollow particles may be cooled while blowing the cooled hydrogen gas into the above-mentioned porous hollow particles in which water or an aqueous solution of hydrate formation adjuvant is sealed. At this time, when the temperature of the perforated hollow particles is measured, an endothermic peak is observed when the hydrate cage is formed along with the cooling of the perforated hollow particles. Therefore, hydrogen is occluded by the hydrate cage in the above-mentioned porous hollow particles by contacting hydrogen while continuing cooling thereafter, and hydrogen hydrate is formed.
　本発明に係る水素キャリアは、比較的低温で水素を安定的に内包できるため、水素の運搬媒体として利用することができる。即ち、本発明の水素キャリアを運搬することにより、水素を運搬することが可能になる。運搬時における水素キャリアの温度としては、－１０℃以上、１０℃以下に冷却することが好ましく、５℃以下に冷却することがより好ましく、０℃以下に冷却することがより更に好ましい。当該温度の下限は特に制限されないが、例えば、－２０℃以上が好ましく、－１５℃以上または－１０℃以上がより好ましい。 Since the hydrogen carrier according to the present invention can stably contain hydrogen at relatively low temperature, it can be used as a transport medium of hydrogen. That is, by carrying the hydrogen carrier of the present invention, it becomes possible to carry hydrogen. The temperature of the hydrogen carrier during transportation is preferably cooled to −10 ° C. or more and 10 ° C. or less, more preferably cooled to 5 ° C. or less, and still more preferably cooled to 0 ° C. or less. Although the lower limit of the temperature is not particularly limited, for example, −20 ° C. or higher is preferable, and −15 ° C. or higher or −10 ° C. or higher is more preferable.
　上述したように、本発明に係る水素キャリアは、比較的高温で且つ比較的低濃度で製造することができる。また、水素ハイドレートは、平衡条件から僅かに高温または低圧にすることにより、容易に水素を放出する。よって本発明に係る水素キャリアは、例えば常圧で１５℃以上にすることにより容易に水素を放出するため、特に水素ターミナルキャリアとして非常に有用である。水素放出時の温度としては、２０℃以上が好ましく、２５℃以上がより好ましい。当該温度の上限は特に制限されないが、例えば５０℃以下とすることができる。 As mentioned above, the hydrogen carrier according to the present invention can be produced at relatively high temperature and relatively low concentration. Also, hydrogen hydrate releases hydrogen easily by bringing it to a slightly elevated temperature or low pressure from equilibrium conditions. Therefore, the hydrogen carrier according to the present invention is particularly useful as a hydrogen terminal carrier because it releases hydrogen easily, for example, by raising the temperature to 15 ° C. or more under normal pressure. As temperature at the time of hydrogen release, 20 ° C or more is preferred, and 25 ° C or more is more preferred. Although the upper limit in particular of the temperature concerned is not restricted, it can be 50 ° C or less, for example.
　本願は、２０１７年８月３０日に出願された日本国特許出願第２０１７－１６５７８３号に基づく優先権の利益を主張するものである。２０１７年８月３０日に出願された日本国特許出願第２０１７－１６５７８３号の明細書の全内容が、本願に参考のため援用される。 The present application claims the benefit of priority based on Japanese Patent Application No. 2017-165783, filed on Aug. 30, 2017. The entire content of the specification of Japanese Patent Application No. 2017-165783, filed on August 30, 2017, is incorporated herein by reference.
　以下、実施例を挙げて本発明をより具体的に説明するが、本発明はもとより下記実施例によって制限を受けるものではなく、前・後記の趣旨に適合し得る範囲で適当に変更を加えて実施することも勿論可能であり、それらはいずれも本発明の技術的範囲に包含される。 EXAMPLES Hereinafter, the present invention will be more specifically described by way of examples. However, the present invention is of course not limited by the following examples, and appropriate modifications may be made as long as the present invention can be applied to the purpose. Of course, implementation is also possible, and all of them are included in the technical scope of the present invention.
　実施例１：　水素キャリアの製造
　（１）　有孔中空粒子の製造
　３０質量％ケイ酸ナトリウム（Ｎａ2ＳｉＯ3）水溶液３０ｇにポリメタクリル酸ナトリウム（分子量：９５００）を１０ｇ加え、更に純水を加えて総量を３６ｍＬに調整した。以下、得られた水溶液を「水相－１」という。別途、ｎ－ヘキサン７２ｍＬに、界面活性剤であるポリオキシエチレン（２０）ソルビタンモノオレアート（商品名：Ｔｗｅｅｎ８０）０．５ｇと、ソルビタンモノオレアート（商品名：Ｓｐａｎ８０）０．２５ｇを添加し、上記水相－１と混合し、ホモジナイザー（「ＫＨＭ－５１０Ｓ」京都電子工業社製）を用いて８０００ｒｐｍで１分間撹拌することにより、Ｗ／Ｏエマルジョンを得た。得られたＷ／Ｏエマルジョンを２Ｍ炭酸水素アンモニウム水溶液５００ｍＬ（水相－２）に加え、３５℃、４００ｒｐｍで１０分間反応させることにより、Ｗ／Ｏ／Ｗエマルジョンを作製した。但し、反応の進行に伴って油層は硬化し、エマルジョン状態は解消された。得られた粒子を濾別し、更に１００℃で１２時間乾燥し、５００℃で５時間焼成することにより、ナノサイズの孔を有する中空粒子を作製した。
　図１に、作製された有孔中空粒子のＳＥＭ拡大写真を示す。得られた拡大写真などを解析したところ、粒子径は１８．２９μｍ、外殻厚は２．２７μｍ、表面積に対する開孔部面積の合計の割合は３．２％、平均細孔径は０．３４μｍであった。 Example 1: Production of hydrogen carrier (1) Production of perforated hollow particles 10 g of sodium polymethacrylate (molecular weight: 9500) is added to 30 g of 30% by weight aqueous solution of sodium silicate (Na 2 SiO 3 ), and pure water is further added. The total volume was adjusted to 36 mL. Hereinafter, the obtained aqueous solution is referred to as "aqueous phase-1". Separately, 0.5 g of surfactant polyoxyethylene (20) sorbitan monooleate (trade name: Tween 80) and 0.25 g sorbitan mono oleate (trade name: Span 80) are added to 72 mL of n-hexane. A W / O emulsion was obtained by mixing with the above aqueous phase-1 and stirring for 1 minute at 8000 rpm using a homogenizer ("KHM-510S" manufactured by Kyoto Denshi Kogyo Co., Ltd.). The W / O / W emulsion was prepared by adding the obtained W / O emulsion to 500 mL of 2 M aqueous ammonium hydrogencarbonate solution (aqueous phase-2) and reacting at 35 ° C. and 400 rpm for 10 minutes. However, as the reaction progressed, the oil layer hardened and the emulsion state was dissolved. The obtained particles were separated by filtration, further dried at 100 ° C. for 12 hours, and calcined at 500 ° C. for 5 hours to produce hollow particles having nano-sized pores.
In FIG. 1, the SEM enlarged photograph of the produced perforated hollow particle is shown. According to analysis of the obtained enlarged photograph etc., the particle diameter is 18.29 μm, the shell thickness is 2.27 μm, the ratio of the total area of the opening to the surface area is 3.2%, and the average pore diameter is 0.34 μm. there were.
　（２）　水素キャリアの製造
　得られた有孔中空粒子を臭化テトラ－ｎ－ブチルアンモニウム（ＴＢＡＢ）の１０質量％水溶液に加え、１００ｈＰａに減圧して３０分間脱泡し、ＴＢＡＢ１０質量％水溶液を中空粒子に内包させた。粒子を吸引ろ過にて分離した。図２に示す装置を用いて、得られた粒子中のＴＢＡＢ水溶液を冷却してハイドレートケージを形成させつつ、水素を吸蔵させた。詳しくは、上記粒子１．０ｇを１０ｍＬ容量容器に入れ、－２℃に冷却した常圧の水素ガスを１０ｍＬ／ｍｉｎで吹き込みながら、氷水を用いて冷却した。４０分後、氷水を－５℃に調整した氷冷塩水に代えて引き続き冷却することで、水素ハイドレートを作製した。図３に、上記粒子間に挿入した温度計で測定した冷却曲線を示す。図３によれば、－５℃での冷却開始から約７分後にハイドレートケージが形成され、その後、約－５℃で温度が安定化していることから、水素が吸蔵されたと考えられる。 (2) Production of hydrogen carrier The obtained porous hollow particles are added to a 10% by mass aqueous solution of tetra-n-butylammonium bromide (TBAB), decompressed to 100 hPa and degassed for 30 minutes, and a 10% by mass aqueous solution of TBAB It was included in hollow particles. The particles were separated by suction filtration. Using the apparatus shown in FIG. 2, hydrogen was absorbed while cooling the TBAB aqueous solution in the obtained particles to form a hydrate cage. Specifically, 1.0 g of the above particles were placed in a 10 mL volumetric container and cooled with ice water while blowing hydrogen gas at normal pressure cooled to −2 ° C. at 10 mL / min. After 40 minutes, the hydrogen hydrate was prepared by replacing the ice water with ice cold brine adjusted to −5 ° C. and subsequently cooling. FIG. 3 shows a cooling curve measured by a thermometer inserted between the particles. According to FIG. 3, a hydrate cage is formed about 7 minutes after the start of cooling at -5.degree. C., and then it is considered that hydrogen is absorbed because the temperature is stabilized at about -5.degree.
　（３）　水素吸蔵量の算出
　上記水素キャリアを別のセルへ移して密閉し、室温（２５℃）で１時間放置して水素ハイドレートを融解させた。その後、セル内の気体５００μＬを採取し、ガスクロマトグラフィーで気体試料中の水素濃度を測定したところ、気体試料の０．６４４ｖｏｌ％が水素ガスであった。また、水素ハイドレートを融解させたセルの空隙体積が２ｍＬであったので、セル内に存在していた水素ガスの体積は２×０．６４４／１００＝０．０１２９ｍＬと算出され、その質量は、［１×０．０１２９／（０．０８２１×２９８）］×２＝０．００１０５ｇと算出された。ここで，有孔中空粒子内に内包されたＴＢＡＢ水溶液の総質量は０．１７４ｇなので、ＴＢＡＢ／水素ハイドレート中の水素ガスの質量割合は、０．００１０５／０．１７４×１００＝０．６０質量％と算出された。 (3) Calculation of the amount of absorbed hydrogen The above-mentioned hydrogen carrier was transferred to another cell, sealed, and allowed to stand at room temperature (25 ° C.) for 1 hour to melt hydrogen hydrate. Thereafter, 500 μL of the gas in the cell was collected, and the hydrogen concentration in the gas sample was measured by gas chromatography. As a result, 0.644 vol% of the gas sample was hydrogen gas. Further, since the void volume of the cell in which the hydrogen hydrate was melted was 2 mL, the volume of hydrogen gas present in the cell was calculated to be 2 × 0.644 / 100 = 0.0129 mL, and the mass was , [1 × 0.0129 / (0.0821 × 298)] × 2 = 0.00105 g. Here, since the total mass of the TBAB aqueous solution contained in the porous hollow particles is 0.174 g, the mass ratio of hydrogen gas in TBAB / hydrogen hydrate is 0.00105 / 0.174 × 100 = 0.60. It was calculated as mass%.

Claims (8)

  1. 　中空粒子と水素ハイドレートを含み、
    　前記中空粒子の外殻が細孔を有し、
    　前記中空粒子中に前記水素ハイドレートが含まれることを特徴とする水素キャリア。     Containing hollow particles and hydrogen hydrate,
    The shell of the hollow particle has pores,
    A hydrogen carrier characterized in that the hydrogen hydrate is contained in the hollow particles.
  2. 　前記中空粒子の粒子径が１０００μｍ以下である請求項１に記載の水素キャリア。 The hydrogen carrier according to claim 1, wherein the particle diameter of the hollow particles is 1000 μm or less.
  3. 　前記中空粒子の表面積に対する前記細孔の開孔部面積の合計の割合が０．５％以上、１０％以下である請求項１または２に記載の水素キャリア。 The hydrogen carrier according to claim 1 or 2, wherein the ratio of the total of the pore area of the pores to the surface area of the hollow particles is 0.5% or more and 10% or less.
  4. 　前記中空粒子が中空シリカ粒子または中空ゼオライト粒子である請求項１～３のいずれかに記載の水素キャリア。 The hydrogen carrier according to any one of claims 1 to 3, wherein the hollow particles are hollow silica particles or hollow zeolite particles.
  5. 　前記水素ハイドレートが、水と水素に加えてハイドレート形成補助剤を含む請求項１～４のいずれかに記載の水素キャリア。 The hydrogen carrier according to any one of claims 1 to 4, wherein the hydrogen hydrate contains a hydrate formation aid in addition to water and hydrogen.
  6. 　水素キャリアを製造するための方法であって、
    　外殻が細孔を有する中空粒子の内部に水またはハイドレート形成補助剤の水溶液を封入する工程、
    　前記水またはハイドレート形成補助剤水溶液を封入した前記中空粒子を冷却してハイドレートケージを形成する工程、および、
    　前記ハイドレートケージに水素を接触させることにより前記ハイドレートケージ中に水素を吸蔵させる工程を含む方法。     A method for producing a hydrogen carrier,
    Encapsulating water or an aqueous solution of hydrate formation aid inside the hollow particle whose outer shell has pores,
    Cooling the hollow particles enclosing the water or the aqueous solution of hydrate formation adjuvant to form a hydrate cage;
    Storing hydrogen in the hydrate cage by contacting the hydrate cage with hydrogen.
  7. 　前記水素の圧力を常圧以上、１０００ｋＰａ未満とする請求項６に記載の方法。 The method according to claim 6, wherein the pressure of the hydrogen is set to a normal pressure or more and less than 1000 kPa.
  8. 　請求項６または７に記載の方法により水素キャリアを製造する工程、および、
    　前記水素キャリアを運搬する工程を含む水素の運搬方法。     A process for producing a hydrogen carrier by the method according to claim 6 or 7, and
    A method of transporting hydrogen comprising the step of transporting the hydrogen carrier.
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