WO2006041170A1 - Method for producing porous structure - Google Patents

Method for producing porous structure Download PDF

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Publication number
WO2006041170A1
WO2006041170A1 PCT/JP2005/018984 JP2005018984W WO2006041170A1 WO 2006041170 A1 WO2006041170 A1 WO 2006041170A1 JP 2005018984 W JP2005018984 W JP 2005018984W WO 2006041170 A1 WO2006041170 A1 WO 2006041170A1
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WO
WIPO (PCT)
Prior art keywords
porous structure
producing
metal
catalyst
cryogel
Prior art date
Application number
PCT/JP2005/018984
Other languages
French (fr)
Japanese (ja)
Inventor
Michihiro Asai
Toshihiko Osaki
Koji Watari
Kimiyasu Sato
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Ngk Insulators, Ltd.
National Institute Of Advanced Industrial Science And Technology
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Application filed by Ngk Insulators, Ltd., National Institute Of Advanced Industrial Science And Technology filed Critical Ngk Insulators, Ltd.
Priority to JP2006540989A priority Critical patent/JP5098333B2/en
Publication of WO2006041170A1 publication Critical patent/WO2006041170A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • 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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/42—Platinum
    • B01J35/56—
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/03—Precipitation; Co-precipitation
    • B01J37/036—Precipitation; Co-precipitation to form a gel or a cogel
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/32—Freeze drying, i.e. lyophilisation
    • 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
    • C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
    • C01B33/157—After-treatment of gels
    • C01B33/158—Purification; Drying; Dehydrating
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/14—Pore volume

Definitions

  • the present invention relates to a method for producing a porous structure.
  • Reduction type catalyst is arranged, and NO, H in exhaust gas mainly by catalytic action of noble metal
  • oxidation catalyst for example, a catalyst in which Pt having a high oxidation activity is supported on a support such as alumina or silica is known.
  • a catalyst component such as platinum is supported on a porous support of alumina or silica
  • the alumina or silica porous support is usually placed in a solution containing the catalyst component, for example, a salt solution of the catalyst component.
  • a method of dipping, drying, and firing if necessary is employed.
  • a wet gel produced by a method such as hydrolysis and gelation of alkoxide it is a wet gel having a liquid phase of a mixture of water and an alcohol such as ethanol.
  • an alcohol such as ethanol.
  • water in the liquid phase of the wet gel is replaced with alcohol, and then the organic solvent is further removed. It was essential to replace
  • the air mouth gel currently used is inferior in water resistance and breaks down in the moment when the air mouth gel is immersed in water. Therefore, the conventional metal impregnation method using an aqueous solution containing metal ions is used. Since it is impossible to carry the support, there is a problem in that the metal ion must be added at the gel synthesis stage, and the usage is greatly limited.
  • the supercritical drying method requires a high temperature and high pressure above the critical point, and thus has a problem of safety and high cost.
  • the present invention has been made in view of the above-mentioned problems of the prior art, and the object thereof is water resistance not only having high surface area, high porosity, and high heat resistance.
  • An object of the present invention is to provide a method for producing a porous structure that can obtain a porous structure that does not cause structural destruction by contact with water and that can contribute to safety and cost reduction.
  • the present invention provides the following method for producing a porous structure.
  • a method for producing a porous structure in which a gel is produced from a raw material by a gel reaction, the gelled product is freeze-dried, and then fired to obtain a porous structure.
  • the porous structure is water-resistant and does not cause structural destruction when contacted with water.
  • the method for producing a porous structure according to any one of [1] to [6].
  • [8] [8]
  • the porous structure has a three-dimensional network skeleton structure, and metal fine particles or metal oxide fine particles or both are dispersed in a base material constituting the skeleton.
  • FIG. 1 (a) is an image diagram showing a dispersion state of silica nanoparticles (sol) in the gelation process of the method for producing a porous structure of the present invention.
  • FIG. 1 (b) is an image diagram showing a state in which silica nanoparticles (sol) are bound in a network form in the gelling process of the method for producing a porous structure of the present invention.
  • FIG. 1 (c) is an image diagram showing a gel skeleton structure in the gelation process of the method for producing a porous structure of the present invention.
  • FIG. 2 is an image diagram showing an example of a cryogel catalyst obtained by the method for producing a porous structure of the present invention.
  • the main feature of the method for producing a porous structure according to the present invention is that a gelled product is produced from a raw material by a gelation reaction, and the gelled product is freeze-dried and then fired to obtain a porous structure ( Is to obtain taliogel).
  • the gelled product is preferably freeze-dried at a trap part cooling temperature of _80 ° C or lower and a vacuum degree of lOPa or lower.
  • a trap part cooling temperature exceeds 80 ° C
  • freeze-drying of the wet gel becomes incomplete and the microstructure is destroyed by drying shrinkage.
  • the degree of vacuum at the completion of drying exceeds lOPa
  • freeze-drying is not completed, and microstructural destruction occurs due to drying shrinkage. .
  • the gelled product (wet gel) is cooled to -80 ° C or lower, and after confirming that the gely product (wet gel) is frozen, the gel is evacuated.
  • the trap part cooling temperature it is preferable to hold the trap part cooling temperature at 80 ° C or lower for about! ⁇ 3 days. At this time, the holding time varies depending on the size, density and shape of the target gelled product (wet gel), but at least the holding time at which the degree of vacuum is less than lOPa is desirable.
  • a freezer may be used for the initial cooling of the gelled product (wet gel), but it is possible to reduce the freezing time and to reduce the gelled product (wet) by cooling it as quickly as possible with a refrigerant such as dry ice ethanol or liquid nitrogen.
  • a refrigerant such as dry ice ethanol or liquid nitrogen.
  • Wet gel is preferable because it can suppress structural destruction during freezing.
  • the main composition of the raw material used in the present invention is preferably composed of at least one of silica, alumina, zirconia, and titania, and more preferably composed of alumina and silica. .
  • a solution containing metal ions, metal fine particles, metal oxide fine particles, or any one metal species may be added to the raw material in advance.
  • the porous structure obtained by the present invention has a three-dimensional network skeleton structure, and a metal fine particle, a metal oxide fine particle, a metal oxide fine particle, or both are formed on a base material constituting the skeleton.
  • a dispersed porous structure (cryogel), It can be used as it is as a catalyst.
  • the catalyst fine particles exposed on the surface of the base material are highly active, so the reaction rate per active point of the catalyst fine particles is also the catalyst by the conventional impregnation method. Faster (about 2 times), excellent in catalytic ability, and metal fine particles are almost buried in the base material, so it has excellent high-temperature heat resistance compared to conventional impregnated catalysts. .
  • the metal species used in the present invention is not particularly limited, but is preferably a noble metal such as gold, silver, platinum or palladium or a transition metal such as iron or cobalt from the viewpoint of catalytic activity. Les.
  • the particle diameter of the metal fine particles is not particularly limited, but is preferably 5 nm or less because the catalytic ability can be improved.
  • a gelled product (wet gel) is freeze-dried and then fired in an air atmosphere.
  • the metal compound derived from the metal fine particles carried by the obtained porous structure (cryogel) is reduced to metal fine particles, thereby exhibiting catalytic activity.
  • a protective molecule is used.
  • the obtained porous structure (cryogel) has a three-dimensional network skeleton structure, and the metal fine particles are dispersed in the base material constituting the skeleton.
  • the degree of exposure of the metal fine particles can be appropriately adjusted by firing in an atmosphere and then firing in a hydrogen atmosphere.
  • the method for producing a porous structure of the present invention employs freeze-drying instead of supercritical drying, thereby providing high surface area, high porosity, high
  • it is water resistant and can produce a porous structure (cryogel) that does not cause structural breakdown like air gel when contacted with water.
  • the method for producing a porous structure of the present invention does not perform supercritical drying using a high temperature 'high pressure above the critical point, so that it is excellent in safety and freeze-dried at low temperature' low pressure.
  • it is more energy-saving than supercritical drying, and the water in the liquid phase of the wet gel can be dried as it is without replacing it with alcohol (freeze drying), which simplifies the process and equipment. Because it is possible, the cost can be greatly reduced.
  • the method for producing a porous structure of the present invention has a structure that is water-resistant and can be immersed in water and re-dried as long as it does not cause structural breakdown like airgel when contacted with water.
  • porous structure (cryogel) that does not break, so conventional metal ions can be obtained simply by adding metal ions at the gel synthesis stage.
  • Metal loading can also be performed by an impregnation method using an aqueous solution containing the solution.
  • a porous structure in which the main composition is composed of silica (SiO) and platinum (Pt) is dispersed.
  • the manufacturing method of the above PtZsi 0 cryogel is as follows: (1) Gelation process
  • silica nanoparticles (sol) 10 This progresses in the liquid phase and repeats the bonding to produce silica nanoparticles (sol) 10 as an intermediate process, as shown in FIG. 1 (a).
  • the silica nanoparticle (sol) 10 continues to grow in both number and size, and is bonded in a network shape to form a gel skeleton structure 20 shown in FIG. 1 (c). .
  • the gelation time tends to be faster as the amount of HO is smaller and the amount of HPCA is smaller.
  • the increase in the amount of HO and the longer gelation time increase the gel volume as the amount of HO increases.
  • the amount of HPCA is linked to pH, which is thought to be due to the effect of pH on the gelling process.
  • the prepared gel (wet gel) is frozen at _80 ° C. or lower, and after confirmation of freezing, the trap portion cooling temperature is kept at a vacuum of ⁇ 80 ° C. or lower for a predetermined time and freeze-dried.
  • the fine network formed during the gelation process is responsible for the surface tension during drying. It will be destroyed more.
  • the air mouth gel has been dried using a supercritical fluid.
  • the surface tension is canceled by using the freeze drying method, and a fine network is maintained.
  • a dry gel (cryogel) can be obtained as it is.
  • platinum acid or the like added as a platinum source is self-decomposed by heating and reduced to platinum (including oxides). Since the reduction temperature requires a temperature higher than the autolysis temperature of the platinum compound (for example, 400 to 430 ° C for hexachloroplatinic acid), it is usually treated in an atmosphere at 500 ° C for 1 hour. I do. Further, immediately after calcination, the platinum surface is partially made of platinum oxide. Therefore, Pt / SiO cryogel (catalyst) can be obtained by performing hydrogen reduction treatment and reducing to complete metal platinum. Note that the Pt / SiO2 crystal obtained in the present invention.
  • the main form of 2 2 liogel (catalyst) has a skeleton structure 30 of a three-dimensional network, and metal fine particles 1 are dispersed in a base material 2 constituting the skeleton.
  • the force hydrogen reduction treatment in which platinum as 1 is almost absorbed in silica as the base material 2, the degree of exposure of platinum as the metal fine particles 1 can be appropriately adjusted.
  • the main composition is alumina (A1
  • the solubilization process is performed using ASB (Al (sec—BuO)) or AIP (Al (iso—PrO), which is an alumina source.
  • Boehmite sol (AIOOH) is produced by holding for a while.
  • the boehmite sol (AIOOH) obtained in the solubilization process is converted to platinum acid (HCPA: hexaclonal platinum acid hexahydrate [H (PtCl)), a platinum source protected with a chelating agent
  • the HCPA / boehmite gel (AIOOH) obtained in the gelation process is frozen at 80 ° C or lower, and after freezing is confirmed, it is kept at a trap cooling temperature of 80 ° C or lower for a specified time. And freeze-dried.
  • the fine network formed in the gelation process is destroyed by the surface tension during drying.
  • the air-mouthed gel has been dried using a supercritical fluid, but in the present invention, the surface tension is canceled and a fine network is maintained by using a freeze-drying method.
  • a dried gel (cryogel) can be obtained as it is.
  • platinum acid or the like added as a platinum source is self-decomposed by heating and reduced to platinum (including oxides). Since the reduction temperature requires a temperature higher than the autolysis temperature of the platinum compound (for example, 400 to 430 ° C for hexachloroplatinic acid), it is usually treated in an atmosphere at 500 ° C for 1 hour. By performing this, a Pt / Al 2 O cryogel (catalyst) can be obtained.
  • the evaluation was performed with FID (flame ion detector) and TCD (thermal conductivity detector).
  • the CH ⁇ CO conversion efficiency was calculated from the FID results. Since TCD has low detection sensitivity, it was used to confirm the generated gas composition (CH, CO 2) and to backup the conversion efficiency calculation.
  • urea was added to 22 g of deionized water and stirred for 15 minutes to dissolve.
  • HCPA Kisakuro port chloroplatinic acid hexahydrate to
  • TMOS tetramethoxysilane
  • the obtained lyophilized gel was placed in an alumina crucible and baked in an electric furnace at 500 ° C for 1 hour in an air atmosphere. Next, the obtained PtZSiO cryogel was treated with hydrogen (H atmosphere [3
  • spherical silica powder (SP-03B manufactured by Fuso Science Co., Ltd.) having an average particle size of 300 nm was used as a support for the catalyst by the conventional impregnation method.
  • Hydrogen reduction Pt / SiO cryogel catalyst is H
  • a material prepared with O22ml / Ptfi0.075g was prepared by hydrogen reduction treatment at each temperature (500.C, 700.C, 900 ° C). The amount of metal Pt in each catalyst was constant at 0.5%.
  • the SiO cryogel catalyst In the case of the SiO cryogel catalyst, it was 16.80%. On the other hand, in the case of the catalyst by the conventional impregnation method (hydrogen reduction 500 ° C), the exposure degree of the metal Pt was 10.84%.
  • the methane oxidation rate at 700 ° C is about 68% in the case of the 500 ° C hydrogen reduction catalyst by the conventional impregnation method, whereas in the case of the 500 ° C hydrogen reduction PtZSiO cryogel catalyst About 56%, 700 ° C Hydrogen reduction About 50 for Pt / SiO cryogel catalyst. / o, 9
  • the 500 ° C hydrogen reduction Pt / SiO cryogel catalyst was obtained by the conventional impregnation method.
  • the exposure of metal Pt is less than half, but CH oxidation performance evaluation (oxidation catalytic performance evaluation) is a catalyst approaching 500 ° C hydrogen reduction catalyst by conventional impregnation method. Have the ability. This suggests that the active sites of metal Pt functioning as a catalyst are equally high.
  • the hydrogen-reduced Pt / SiO cryogel catalyst has a high density of active sites present on the metal Pt surface, that is, it may give more active sites to the slightly exposed Pt metal surface. I found out.
  • the high temperature hydrogen treatment caused damage to the surface of the cryogel substrate, and the metal Pt was sintered and deactivated due to heat. Conceivable.
  • HCPA / boehmite sol (AIOOH) was prepared.
  • platinum source add hexaclonal platinum acid hexahydrate [H (PtCl) ⁇ 6 ⁇ ] 0 ⁇ 0749g to 0 ⁇ 5 ml of hexylene glycol in a working environment of 60 ° C and hold for 20 minutes. This was produced.
  • the obtained lyophilized gel was placed in an alumina crucible and 500% in an air atmosphere in an electric furnace.
  • Pt / Al 2 O cryogel catalyst was obtained by calcination at ° C for 1 hour.
  • the 1 O air-mouth gel catalyst was immersed in water, and the state change at that time was observed.
  • cryogel catalyst PtZAl O cryogel catalyst
  • conventional catalyst catalyst by impregnation method
  • the power of reduction at 800 ° C over the reduction at 500 ° C is a force that improves the exposure of metal Pt.
  • the exposure of metal Pt The degree is decreasing. That is, although it cannot be generally stated, it was suggested that the cryogel catalyst has higher temperature and heat resistance than the conventional catalyst.
  • the method for producing a porous structure of the present invention can be suitably used, for example, for producing a catalyst for exhaust gas treatment.

Abstract

Disclosed is a method for producing a porous structure wherein a gelated material is produced from a raw material through a gelation reaction, and the gelated material is freeze-dried and then fired, thereby obtaining a porous structure. By such a method for producing a porous structure, there can be obtained a porous structure which has not only a large surface area, high porosity and high heat resistance but also water resistance, while being prevented from structural damage which may be caused when it is in contact with water. The method also contributes to safety and reduction of cost. This method for producing a porous structure can be suitably used as, for example, a method for producing a catalyst for processing exhaust gases.

Description

明 細 書  Specification
多孔質構造体の製造方法  Method for producing porous structure
技術分野  Technical field
[0001] 本発明は、多孔質構造体の製造方法に関する。  [0001] The present invention relates to a method for producing a porous structure.
背景技術  Background art
[0002] 近年、内燃機関、ボイラー等の排気ガス中の微粒子や有害物質は、環境への影響 を考慮して排気ガス中力 除去する必要性が高まりつつあり、各種排ガス浄化技術 が提案されている。例えば、 自動車の排気系には、酸化触媒、三元触媒、 NO吸蔵  In recent years, there is an increasing need to remove particulates and harmful substances in exhaust gas from internal combustion engines, boilers, etc. in consideration of environmental effects, and various exhaust gas purification technologies have been proposed. Yes. For example, in automobile exhaust systems, oxidation catalysts, three-way catalysts, NO storage
X  X
還元型触媒等が配置され、主として貴金属の触媒作用によって排ガス中の NO 、 H  Reduction type catalyst is arranged, and NO, H in exhaust gas mainly by catalytic action of noble metal
X  X
C、 CO等の有害成分を浄化している。特に、酸化触媒としては、例えば、アルミナや シリカ等の担体に酸化活性の高い Ptを担持したものが知られている。  Purifies harmful components such as C and CO. In particular, as an oxidation catalyst, for example, a catalyst in which Pt having a high oxidation activity is supported on a support such as alumina or silica is known.
[0003] 従来、アルミナやシリカの多孔質担体に白金等の触媒成分を担持させる場合、通 常、アルミナやシリカの多孔質担体を触媒成分を含有する溶液、例えば、触媒成分 の塩の溶液に浸漬し、乾燥し、必要により焼成する方法が採用されている。  [0003] Conventionally, when a catalyst component such as platinum is supported on a porous support of alumina or silica, the alumina or silica porous support is usually placed in a solution containing the catalyst component, for example, a salt solution of the catalyst component. A method of dipping, drying, and firing if necessary is employed.
[0004] 最近では、多孔質担体として、アルミナ系エア口ゲルが好適に用いられている。この ようなアルミナ系エア口ゲルを製造する方法としては、例えば、アルミナアルコキシド 等から加水分解して得られた湿潤なアルミナ系ゲル (ウエットゲル）を有機溶媒で満 たし、超臨界条件下で乾燥する方法 (超臨界乾燥)が提案されており、この方法で得 られたエア口ゲルは、高表面積、高気孔率及び高耐熱性を有することが知られている  [0004] Recently, alumina-based air-mouth gel is suitably used as the porous carrier. As a method for producing such an alumina-based air-opening gel, for example, a wet alumina-based gel (wet gel) obtained by hydrolysis from alumina alkoxide or the like is filled with an organic solvent, and is subjected to supercritical conditions. A drying method (supercritical drying) has been proposed, and the air-mouthed gel obtained by this method is known to have a high surface area, a high porosity, and a high heat resistance.
[0005] し力、しながら、アルコキシドの加水分解とゲル化等の方法により作製されたウエット ゲルの場合、水とエタノール等のアルコールとの混合物の液相を有するウエットゲル であり、乾燥時の収縮による構造破壊を超臨界乾燥法で回避させるためには、前記 ウエットゲルを超臨界乾燥する前段階として、まず、ウエットゲルの液相中の水をアル コールで置換した後、更に前記有機溶媒に置換することが必要不可欠であった。 However, in the case of a wet gel produced by a method such as hydrolysis and gelation of alkoxide, it is a wet gel having a liquid phase of a mixture of water and an alcohol such as ethanol. In order to avoid structural destruction due to shrinkage by the supercritical drying method, as a step before supercritical drying of the wet gel, first, water in the liquid phase of the wet gel is replaced with alcohol, and then the organic solvent is further removed. It was essential to replace
[0006] また、現在使用されているエア口ゲルは、耐水性に劣り、水にエア口ゲルを浸した瞬 間に構造破壊してしまうため、従来の金属イオンを含む水溶液による含浸法で金属 担持を行うことが不可能であるため、ゲル合成段階で金属イオンを添加するしかなく 、また使用用途も大幅に限定されしまうという問題点があった。 [0006] Furthermore, the air mouth gel currently used is inferior in water resistance and breaks down in the moment when the air mouth gel is immersed in water. Therefore, the conventional metal impregnation method using an aqueous solution containing metal ions is used. Since it is impossible to carry the support, there is a problem in that the metal ion must be added at the gel synthesis stage, and the usage is greatly limited.
[0007] 更に、超臨界乾燥法は、臨界点以上の高温'高圧を必要とするため、安全性の問 題や高コストであるという問題点があった。  [0007] Further, the supercritical drying method requires a high temperature and high pressure above the critical point, and thus has a problem of safety and high cost.
[0008] 本発明は、上述した従来技術の問題点に鑑みてなされたものであり、その目的とす るところは、高表面積、高気孔率及び高耐熱性を有するだけでなぐ耐水性であり、 且つ水との接触で構造破壊を起こさない多孔質構造体を得ることができるとともに、 安全性やコストの削減に寄与することができる多孔質構造体の製造方法を提供する ことにある。  [0008] The present invention has been made in view of the above-mentioned problems of the prior art, and the object thereof is water resistance not only having high surface area, high porosity, and high heat resistance. An object of the present invention is to provide a method for producing a porous structure that can obtain a porous structure that does not cause structural destruction by contact with water and that can contribute to safety and cost reduction.
発明の開示  Disclosure of the invention
[0009] 上述の目的を達成するため、本発明は、以下の多孔質構造体の製造方法を提供 するものである。  In order to achieve the above object, the present invention provides the following method for producing a porous structure.
[0010] [1] 原材料からゲルィヒ反応によりゲルィヒ物を作製し、前記ゲル化物を凍結乾燥した 後、焼成し、多孔質体構造体を得る多孔質構造体の製造方法。  [0010] [1] A method for producing a porous structure, in which a gel is produced from a raw material by a gel reaction, the gelled product is freeze-dried, and then fired to obtain a porous structure.
[0011] [2] 前記ゲル化物を、トラップ部冷却温度が— 80°C以下、且つ真空度が lOPa以 下で凍結乾燥する [1]に記載の多孔質構造体の焼成方法。  [0011] [2] The method for firing a porous structure according to [1], wherein the gelled product is freeze-dried at a trap portion cooling temperature of −80 ° C. or lower and a vacuum degree of lOPa or lower.
[0012] [3] 前記原材料の主組成が、シリカ、アルミナ、ジルコユア、チタニアを生成する金 属アルコキシドの少なくとも 1種以上力も構成される [1]又は [2]に記載の多孔質構 造体の製造方法。 [3] The porous structure according to [1] or [2], wherein the main composition of the raw material is composed of at least one kind of metal alkoxide that generates silica, alumina, zirconia, and titania. Manufacturing method.
[0013] [4] 前記原材料に、金属イオン、金属微粒子、金属酸化物微粒子のいずれか 1種 以上の金属種を含む溶液を添加する [1]〜 [3]のレ、ずれかに記載の多孔質構造体 の製造方法。  [4] The solution according to any one of [1] to [3], wherein a solution containing one or more metal species of metal ions, metal fine particles, and metal oxide fine particles is added to the raw material. A method for producing a porous structure.
[0014] [5] 前記金属種が、貴金属又は遷移金属である [1]〜 [4]のいずれかに記載の多 孔質構造体の製造方法。  [5] The method for producing a porous structure according to any one of [1] to [4], wherein the metal species is a noble metal or a transition metal.
[0015] [6] 前記ゲル化物が、凍結乾燥後、大気雰囲気下及び/又は水素雰囲気下で焼 成される [ 1]〜 [5]のレ、ずれかに記載の多孔質構造体の製造方法。 [6] [6] The porous structure according to any one of [1] to [5], wherein the gelled product is lyophilized and then baked in an air atmosphere and / or a hydrogen atmosphere. Method.
[0016] [7] 前記多孔質構造体が、耐水性であり、且つ水との接触で構造破壊が起きなレ、 [[7] The porous structure is water-resistant and does not cause structural destruction when contacted with water.
1]〜 [6]のレ、ずれかに記載の多孔質構造体の製造方法。 [0017] [8] 前記多孔質構造体が、三次元網目の骨格構造を有し、且つ前記骨格を構成 する基材に金属微粒子又は金属酸化物微粒子もしくはそれら両方が分散されているThe method for producing a porous structure according to any one of [1] to [6]. [8] [8] The porous structure has a three-dimensional network skeleton structure, and metal fine particles or metal oxide fine particles or both are dispersed in a base material constituting the skeleton.
[4]〜 [7]のレ、ずれかに記載の多孔質構造体の製造方法。 The method for producing a porous structure according to any one of [4] to [7].
[0018] [9] 前記金属微粒子又は金属酸化物微粒子もしくはそれら両方が、前記基材にほ とんど埋没してレ、る [4]〜 [8]に記載の多孔質構造体の製造方法。 [0018] [9] The method for producing a porous structure according to any one of [4] to [8], wherein the metal fine particles and / or metal oxide fine particles are almost buried in the substrate. .
[0019] [10] 前記多孔質構造体が、触媒である [4]〜 [9]のいずれかに記載の多孔質構 造体の製造方法。 [10] The method for producing a porous structure according to any one of [4] to [9], wherein the porous structure is a catalyst.
図面の簡単な説明  Brief Description of Drawings
[0020] [図 1(a)]本発明の多孔質構造体の製造方法のゲル化過程におけるシリカナノ粒子（ ゾル）の分散状態を示すイメージ図である。  [0020] FIG. 1 (a) is an image diagram showing a dispersion state of silica nanoparticles (sol) in the gelation process of the method for producing a porous structure of the present invention.
[図 1(b)]本発明の多孔質構造体の製造方法のゲルィ匕過程におけるシリカナノ粒子（ ゾル）がネットワーク状に結合する状態を示すイメージ図である。  FIG. 1 (b) is an image diagram showing a state in which silica nanoparticles (sol) are bound in a network form in the gelling process of the method for producing a porous structure of the present invention.
[図 1(c)]本発明の多孔質構造体の製造方法のゲル化過程におけるゲル骨格構造を 示すイメージ図である。  FIG. 1 (c) is an image diagram showing a gel skeleton structure in the gelation process of the method for producing a porous structure of the present invention.
[図 2]本発明の多孔質構造体の製造方法で得られるクリオゲル触媒の一例を示すィ メージ図である。  FIG. 2 is an image diagram showing an example of a cryogel catalyst obtained by the method for producing a porous structure of the present invention.
[図 3]クリオゲル触媒 (PtZAl Oクリオゲル触媒)と、従来法触媒 (含浸法による触媒  [Figure 3] Cryogel catalyst (PtZAl O cryogel catalyst) and conventional catalyst (catalyst by impregnation method)
2 3  twenty three
)における CH酸化能評価 (メタン転化率）を示すグラフである。  It is a graph which shows CH oxidation ability evaluation (methane conversion rate) in).
4  Four
[図 4]クリオゲル触媒 (PtZAl Oクリオゲル触媒)と、従来法触媒 (含浸法による触媒  [Figure 4] Cryogel catalyst (PtZAl O cryogel catalyst) and conventional catalyst (catalyst by impregnation method)
2 3  twenty three
)における CH酸化能評価 (活性点当たりの反応速度）を示すグラフである。  Is a graph showing the CH oxidation ability evaluation (reaction rate per active site).
4  Four
[図 5]クリオゲル触媒 (PtZAl Oクリオゲル触媒)と、従来法触媒 (含浸法による触媒  [Fig.5] Cryogel catalyst (PtZAl O cryogel catalyst) and conventional catalyst (catalyst by impregnation method)
2 3  twenty three
)について、 500°C還元及び 800°C還元したときにおける金属 Ptの露出度を示すグ ラフである。  Is a graph showing the exposure degree of metal Pt when reduced at 500 ° C and 800 ° C.
符号の説明  Explanation of symbols
[0021] 1 :金属微粒子、 2 :基材、 10 :シリカナノ粒子（ゾル）、 20 :ゲル骨格構造、 30 :三次元 網目の骨格構造。  [0021] 1: metal fine particles, 2: substrate, 10: silica nanoparticles (sol), 20: gel skeleton structure, 30: skeleton structure of 3D network.
発明を実施するための最良の形態  BEST MODE FOR CARRYING OUT THE INVENTION
[0022] 以下、多孔質構造体の製造方法について詳細に説明するが、本発明は、これに限 定されて解釈されるものではなぐ本発明の範囲を逸脱しない限りにおいて、当業者 の知識に基づいて、種々の変更、修正、改良を加え得るものである。 [0022] Hereinafter, the method for producing a porous structure will be described in detail, but the present invention is not limited thereto. Various changes, modifications, and improvements can be made based on the knowledge of those skilled in the art without departing from the scope of the present invention, which is not intended to be construed.
[0023] 本発明に係る多孔質構造体の製造方法の主な特徴は、原材料からゲル化反応に よりゲル化物を作製し、ゲル化物を凍結乾燥した後、焼成し、多孔質体構造体 (タリ ォゲル)を得ることにある。  [0023] The main feature of the method for producing a porous structure according to the present invention is that a gelled product is produced from a raw material by a gelation reaction, and the gelled product is freeze-dried and then fired to obtain a porous structure ( Is to obtain taliogel).
[0024] このとき、本発明の多孔質構造体の製造方法は、ゲル化物を、トラップ部冷却温度 が _80°C以下、且つ真空度が lOPa以下で凍結乾燥することが好ましい。これは、ト ラップ部冷却温度が一 80°Cを超過する場合、湿潤ゲルの凍結乾燥が不完全となり、 乾燥収縮による微構造の破壊が発生するためである。また、真空度は、真空に近け れば近いほど良いが、乾燥完了時の真空度が lOPaを超過すると、凍結乾燥が完了 しておらず、乾燥収縮による微構造の破壊が発生してしまう。  [0024] At this time, in the method for producing a porous structure of the present invention, the gelled product is preferably freeze-dried at a trap part cooling temperature of _80 ° C or lower and a vacuum degree of lOPa or lower. This is because when the trap cooling temperature exceeds 80 ° C, freeze-drying of the wet gel becomes incomplete and the microstructure is destroyed by drying shrinkage. In addition, the closer the vacuum is, the better the degree of vacuum is. However, if the degree of vacuum at the completion of drying exceeds lOPa, freeze-drying is not completed, and microstructural destruction occurs due to drying shrinkage. .
[0025] 更に詳細には、上記凍結乾燥は、初めに、ゲル化物（ウエットゲル）を、 _ 80°C以 下で冷却し、ゲルィ匕物（ウエットゲル）の凍結を確認した後、真空に引き、トラップ部冷 却温度を 80°C以下にて、：!〜 3日程度保持することが好ましい。このとき、上記保 持時間は、対象となるゲル化物（ウエットゲル）の大きさ、密度や形状によって様々で あるが、少なくとも真空度が lOPa以下になる保持時間が望ましい。また、ゲル化物（ ウエットゲル）の初期冷却には、フリーザーを用いてもよいが、ドライアイス エタノー ルゃ液体窒素等の冷媒で、できるだけ瞬間冷却する方が、凍結時間の短縮及びゲ ル化物（ウエットゲル）の凍結時における構造破壊を抑制することができるため好まし レ、。  [0025] More specifically, in the lyophilization, first, the gelled product (wet gel) is cooled to -80 ° C or lower, and after confirming that the gely product (wet gel) is frozen, the gel is evacuated. In addition, it is preferable to hold the trap part cooling temperature at 80 ° C or lower for about! ~ 3 days. At this time, the holding time varies depending on the size, density and shape of the target gelled product (wet gel), but at least the holding time at which the degree of vacuum is less than lOPa is desirable. In addition, a freezer may be used for the initial cooling of the gelled product (wet gel), but it is possible to reduce the freezing time and to reduce the gelled product (wet) by cooling it as quickly as possible with a refrigerant such as dry ice ethanol or liquid nitrogen. (Wet gel) is preferable because it can suppress structural destruction during freezing.
[0026] 尚、本発明で用いる原材料の主組成は、シリカ、アルミナ、ジルコニァ、チタニアの 少なくとも 1種以上から構成されることが好ましぐ特に、アルミナ及びシリカから構成 されていることがより好ましい。  [0026] The main composition of the raw material used in the present invention is preferably composed of at least one of silica, alumina, zirconia, and titania, and more preferably composed of alumina and silica. .
[0027] また、本発明の多孔質構造体の製造方法は、予め、原材料に、金属イオン、金属 微粒子、金属酸化物微粒子のレ、ずれか 1種の金属種を含む溶液を添加してもよレヽ。 これにより、本発明で得られる多孔質構造体は、三次元網目の骨格構造を有し、且 つ骨格を構成する基材に金属微粒子または金属酸化物微粒子又は金属酸化物微 粒子もしくはそれら両方が分散された多孔質構造体 (クリオゲル）にすることができ、 そのまま触媒として使用することができる。このように得られた多孔質構造体 (クリオゲ ノレ）は、基材表面に露出している触媒微粒子が高活性であるため、触媒微粒子の活 性点当たりの反応速度も従来の含浸法による触媒より速く（約 2倍）、触媒能に優れて レ、るとともに、金属微粒子が基材にほとんど埋没しているため、従来の含浸法による 触媒と比較して高温耐熱性に優れてレ、る。 [0027] Further, in the method for producing a porous structure of the present invention, a solution containing metal ions, metal fine particles, metal oxide fine particles, or any one metal species may be added to the raw material in advance. Yo! As a result, the porous structure obtained by the present invention has a three-dimensional network skeleton structure, and a metal fine particle, a metal oxide fine particle, a metal oxide fine particle, or both are formed on a base material constituting the skeleton. A dispersed porous structure (cryogel), It can be used as it is as a catalyst. In the porous structure (cryogenore) thus obtained, the catalyst fine particles exposed on the surface of the base material are highly active, so the reaction rate per active point of the catalyst fine particles is also the catalyst by the conventional impregnation method. Faster (about 2 times), excellent in catalytic ability, and metal fine particles are almost buried in the base material, so it has excellent high-temperature heat resistance compared to conventional impregnated catalysts. .
[0028] 尚、本発明で用いる金属種は、特に限定されないが、特に金、銀、白金、パラジゥ ム等の貴金属又は鉄、コバルト等の遷移金属であることが、触媒活性の面から好まし レ、。また、上記金属微粒子の粒径は、特に限定されないが、 5nm以下であることが、 触媒能を向上できるため好ましい。  [0028] The metal species used in the present invention is not particularly limited, but is preferably a noble metal such as gold, silver, platinum or palladium or a transition metal such as iron or cobalt from the viewpoint of catalytic activity. Les. The particle diameter of the metal fine particles is not particularly limited, but is preferably 5 nm or less because the catalytic ability can be improved.
[0029] 更に、本発明の多孔質構造体の製造方法は、ゲル化物（ウエットゲル)を凍結乾燥 後、大気雰囲気下で焼成する。これにより、得られた多孔質構造体 (クリオゲル）に担 持された金属微粒子に由来する金属化合物から金属微粒子へ還元し、触媒活性を 発現させる。易還元性の金属イオンを用いる場合、保護分子を用いるが、保護してい る保護分子を加熱により自己分解させることで、金属微粒子に還元し、本来の触媒 活性を発現させることもできる。また、得られた多孔質構造体 (クリオゲル）は、三次元 網目の骨格構造を有し、且つ前記骨格を構成する基材に金属微粒子が分散されて いる力 金属微粒子の基材表面に露出する面積 (露出度）を向上させたい場合、大 気雰囲気下で焼成後、更に水素雰囲気下で焼成することにより、金属微粒子の露出 度を適宜調節することができる。  [0029] Further, in the method for producing a porous structure of the present invention, a gelled product (wet gel) is freeze-dried and then fired in an air atmosphere. As a result, the metal compound derived from the metal fine particles carried by the obtained porous structure (cryogel) is reduced to metal fine particles, thereby exhibiting catalytic activity. In the case of using an easily reducible metal ion, a protective molecule is used. However, by protecting the protected protective molecule by self-decomposition by heating, it can be reduced to fine metal particles to exhibit the original catalytic activity. Further, the obtained porous structure (cryogel) has a three-dimensional network skeleton structure, and the metal fine particles are dispersed in the base material constituting the skeleton. When it is desired to improve the area (degree of exposure), the degree of exposure of the metal fine particles can be appropriately adjusted by firing in an atmosphere and then firing in a hydrogen atmosphere.
[0030] 以上のことから、本発明の多孔質構造体の製造方法は、超臨界乾燥に代わり凍結 乾燥を採用することにより、エア口ゲルの優れた特性である高表面積、高気孔率及び 高耐熱性を有するだけでなぐ耐水性であり、且つ水との接触でエア口ゲルのように 構造破壊を起こさなレ、多孔質構造体 (クリオゲル)を得ること力できる。  [0030] From the above, the method for producing a porous structure of the present invention employs freeze-drying instead of supercritical drying, thereby providing high surface area, high porosity, high In addition to having heat resistance, it is water resistant and can produce a porous structure (cryogel) that does not cause structural breakdown like air gel when contacted with water.
[0031] また、本発明の多孔質構造体の製造方法は、臨界点以上の高温'高圧を用いる超 臨界乾燥を行わないため、安全性に優れているとともに、低温'低圧下での凍結乾燥 を採用することにより、超臨界乾燥よりも省エネであり、且つウエットゲルの液相中の 水をアルコールで置換することなくそのまま乾燥 (凍結乾燥)することができるため、 工程や設備の簡略化が可能であるため、コストを大幅に削減することができる。 [0032] 更に、本発明の多孔質構造体の製造方法は、耐水性であり、且つ水との接触でェ ァロゲルのように構造破壊を起こさないだけでなぐ水に浸し再乾燥させても構造 (例 えば、表面積、細孔容積、平均細孔径）が壊れない多孔質構造体 (クリオゲル)を得 ること力 Sできるので、ゲル合成段階で金属イオンを添加するだけでなぐ従来の金属 イオンを含む水溶液による含浸法で金属担持を行うこともできる。 [0031] In addition, the method for producing a porous structure of the present invention does not perform supercritical drying using a high temperature 'high pressure above the critical point, so that it is excellent in safety and freeze-dried at low temperature' low pressure. By adopting, it is more energy-saving than supercritical drying, and the water in the liquid phase of the wet gel can be dried as it is without replacing it with alcohol (freeze drying), which simplifies the process and equipment. Because it is possible, the cost can be greatly reduced. [0032] Further, the method for producing a porous structure of the present invention has a structure that is water-resistant and can be immersed in water and re-dried as long as it does not cause structural breakdown like airgel when contacted with water. (For example, surface area, pore volume, average pore diameter) can obtain a porous structure (cryogel) that does not break, so conventional metal ions can be obtained simply by adding metal ions at the gel synthesis stage. Metal loading can also be performed by an impregnation method using an aqueous solution containing the solution.
[0033] 次に、本発明の多孔質構造体の製造方法を更に具体的に説明する。 [0033] Next, the method for producing a porous structure of the present invention will be described more specifically.
[0034] 本発明の多孔質構造体の製造方法の一例として、主組成がシリカ（Si〇 )で構成さ れ、且つ白金 (Pt)が分散された多孔質構造体 (Pt/SiOクリオゲル）について説明 する。上記 PtZsi〇クリオゲルの製造方法は、大まかな工程として、（1)ゲル化工程[0034] As an example of the method for producing a porous structure according to the present invention, a porous structure (Pt / SiO cryogel) in which the main composition is composed of silica (SiO) and platinum (Pt) is dispersed. explain. The manufacturing method of the above PtZsi 0 cryogel is as follows: (1) Gelation process
、（2)乾燥工程、（3)焼成工程から構成される。 (2) Drying step and (3) Firing step.
[0035] (1)ゲル化工程 [0035] (1) Gelation process
ゲル化工程では、尿素、白金源である白金酸（HCPA:へキサクロ口白金酸六水和 物 (PtCl ) · 6Η Ο] )やシリカ源である TMOS (テトラメトキシシラン)等の各材料 を溶媒である水に溶解する。シリカ源として TMOS (テトラメトキシシラン）を用い、カロ 水分解により Si〇をナノ粒子として発生させ、粒子間の結合とシリカ（SiO )の析出に より微細なネットワークを形成、ゲル化させる。ゲルィ匕反応 (TMOSと H Oとの反応） は、 TMOS2分子間を結合するものである。これが液相で進行し、結合を繰り返すこ とで、図 1 (a)に示すように、中間過程としてシリカナノ粒子（ゾル）10を生じる。このシ リカナノ粒子（ゾル） 10は、図 1 (b)に示すように、数 ·サイズ共に成長し続け、ネットヮ ーク状に結合し、図 1 (c)に示すゲル骨格構造 20を形成する。ゲル化時間は、 H〇 量が少ないほど、また、 HPCA量が少ないほど早い傾向があり、 H O量の増加とゲ ル化時間の長時間化は、 H〇量の増加とともに、ゲル体積が増えることで、ゲルのネ ットワーク構造が疎になり、強度が発現しにくいと考えられる。また、 HPCA量は pHと 連動しており、ゲルィ匕過程に pHが影響を与えるためと考えられる。  In the gelation process, urea, platinum source (platinum acid hexahydrate (PtCl) 6Η Η)) and platinum source TMOS (tetramethoxysilane) are used as solvents. Is dissolved in water. TMOS (tetramethoxysilane) is used as a silica source and SiO is generated as nanoparticles by calo-hydrolysis to form a fine network and gel by bonding between particles and precipitation of silica (SiO 2). The gely reaction (reaction between TMOS and H 2 O) is a bond between two TMOS molecules. This progresses in the liquid phase and repeats the bonding to produce silica nanoparticles (sol) 10 as an intermediate process, as shown in FIG. 1 (a). As shown in FIG. 1 (b), the silica nanoparticle (sol) 10 continues to grow in both number and size, and is bonded in a network shape to form a gel skeleton structure 20 shown in FIG. 1 (c). . The gelation time tends to be faster as the amount of HO is smaller and the amount of HPCA is smaller. The increase in the amount of HO and the longer gelation time increase the gel volume as the amount of HO increases. As a result, the network structure of the gel becomes sparse and it is considered that the strength is difficult to develop. The amount of HPCA is linked to pH, which is thought to be due to the effect of pH on the gelling process.
[0036] (2)乾燥工程 [0036] (2) Drying process
乾燥工程では、作製したゲル (ウエットゲル)を、 _80°C以下で凍結し、凍結確認後 、更にトラップ部冷却温度が— 80°C以下の真空下で所定時間保持し、凍結乾燥する 。通常乾燥では、ゲル化過程で形成した微細なネットワークが乾燥時の表面張力に より破壊されてしまう。これを防止するため、エア口ゲルでは超臨界流体を用いた乾 燥が行われてきたが、本発明では、凍結乾燥法を用いることにより、表面張力をキヤ ンセルさせ、微細なネットワークを維持したままで乾燥ゲル (クリオゲル)を得ることが できる。 In the drying step, the prepared gel (wet gel) is frozen at _80 ° C. or lower, and after confirmation of freezing, the trap portion cooling temperature is kept at a vacuum of −80 ° C. or lower for a predetermined time and freeze-dried. In normal drying, the fine network formed during the gelation process is responsible for the surface tension during drying. It will be destroyed more. In order to prevent this, the air mouth gel has been dried using a supercritical fluid. However, in the present invention, the surface tension is canceled by using the freeze drying method, and a fine network is maintained. A dry gel (cryogel) can be obtained as it is.
[0037] (3)焼成工程  [0037] (3) Firing step
焼成工程では、白金源として投入した白金酸等を加熱により自己分解させ、白金（ 酸化物を含む）に還元する。還元温度は、白金化合物の自己分解温度（例えば、へ キサクロ口白金酸では 400〜430°C)以上の温度を必要とするため、通常、大気雰囲 気下、 500°C、 1時間で処理を行う。また、焼成直後では、白金表面が部分的に酸化 白金になっているため、水素還元処理を施し、完全な金属白金に還元することにより 、 Pt/SiOクリオゲル (触媒）を得ることができる。尚、本発明で得られる Pt/SiOク  In the firing step, platinum acid or the like added as a platinum source is self-decomposed by heating and reduced to platinum (including oxides). Since the reduction temperature requires a temperature higher than the autolysis temperature of the platinum compound (for example, 400 to 430 ° C for hexachloroplatinic acid), it is usually treated in an atmosphere at 500 ° C for 1 hour. I do. Further, immediately after calcination, the platinum surface is partially made of platinum oxide. Therefore, Pt / SiO cryogel (catalyst) can be obtained by performing hydrogen reduction treatment and reducing to complete metal platinum. Note that the Pt / SiO2 crystal obtained in the present invention.
2 2 リオゲル (触媒)の主な形態は、図 2に示すように、三次元網目の骨格構造 30を有し 、且つ骨格を構成する基材 2に金属微粒子 1が分散されており、金属微粒子 1である 白金が、基材 2であるシリカにほとんど坦没しているものである力 水素還元処理を調 整することにより、金属微粒子 1である白金の露出度を適宜調整することができる。  As shown in FIG. 2, the main form of 2 2 liogel (catalyst) has a skeleton structure 30 of a three-dimensional network, and metal fine particles 1 are dispersed in a base material 2 constituting the skeleton. By adjusting the force hydrogen reduction treatment in which platinum as 1 is almost absorbed in silica as the base material 2, the degree of exposure of platinum as the metal fine particles 1 can be appropriately adjusted.
[0038] また、本発明の多孔質構造体の製造方法の他の例として、主組成がアルミナ (A1 [0038] As another example of the method for producing the porous structure of the present invention, the main composition is alumina (A1
2 2
O )で構成され、且つ白金 (Pt)が分散された多孔質構造体 (Pt/Al Oクリオゲル）O) and a porous structure in which platinum (Pt) is dispersed (Pt / Al O cryogel)
3 2 3 について説明する。上記 Pt/Al Oクリオゲルの製造方法は、大まかな工程として、 ( Explain 3 2 3. The above Pt / Al O cryogel manufacturing method is a rough process:
2 3  twenty three
1)ゾルイ匕工程、 （2)ゲル化工程、 （3)乾燥工程、（4)焼成工程から構成される。  It consists of 1) Zorii soot process, (2) Gelation process, (3) Drying process, and (4) Firing process.
[0039] (1)ゾル化工程 [0039] (1) Zolization process
ゾル化工程は、アルミナ源である ASB (Al (sec— BuO) )又は AIP (Al (iso— PrO  The solubilization process is performed using ASB (Al (sec—BuO)) or AIP (Al (iso—PrO), which is an alumina source.
3  Three
) )を溶媒である水に混合し、アルコキシド加水分解後、 HNO溶液をカ卩えて、所定 )) Is mixed with water as a solvent, and after alkoxide hydrolysis, the HNO solution is added and
3 3 3 3
時間保持することにより、ベーマイトゾル (AIOOH)を作製する。  Boehmite sol (AIOOH) is produced by holding for a while.
[0040] (2)ゲル化工程 [0040] (2) Gelation process
ゲル化工程は、ゾル化工程で得られたベーマイトゾル (AIOOH)に、キレート剤で 保護された白金源である白金酸 (HCPA:へキサクロ口白金酸六水和物 [H (PtCl )  In the gelation process, the boehmite sol (AIOOH) obtained in the solubilization process is converted to platinum acid (HCPA: hexaclonal platinum acid hexahydrate [H (PtCl)), a platinum source protected with a chelating agent
2 6 2 6
•6H〇] )力 構成された白金ソースを投入後、尿素を加えて、所定時間保持した後• 6H ○]) Power After adding the configured platinum source, add urea and hold for a specified time
2 2
、更に所定温度で所定時間保持することにより、 HCPA/ベーマイトゲル (AIOOH) を作製する。 HCPA / Boehmite gel (AIOOH) Is made.
[0041] (3)乾燥工程  [0041] (3) Drying process
乾燥工程は、ゲル化工程で得られた HCPA/ベーマイトゲル (AIOOH)を、 80 °C以下で凍結し、凍結確認後、更にトラップ部冷却温度— 80°C以下の真空下で所 定時間保持し、凍結乾燥する。通常乾燥では、ゲル化過程で形成した微細なネットヮ ークが乾燥時の表面張力により破壊されてしまう。これを防止するため、エア口ゲルで は超臨界流体を用いた乾燥が行われてきたが、本発明では、凍結乾燥法を用いるこ とにより、表面張力をキャンセルさせ、微細なネットワークを維持したままで乾燥ゲル（ クリオゲル)を得ることができる。  In the drying process, the HCPA / boehmite gel (AIOOH) obtained in the gelation process is frozen at 80 ° C or lower, and after freezing is confirmed, it is kept at a trap cooling temperature of 80 ° C or lower for a specified time. And freeze-dried. In normal drying, the fine network formed in the gelation process is destroyed by the surface tension during drying. In order to prevent this, the air-mouthed gel has been dried using a supercritical fluid, but in the present invention, the surface tension is canceled and a fine network is maintained by using a freeze-drying method. A dried gel (cryogel) can be obtained as it is.
[0042] (4)焼成工程  [0042] (4) Firing step
焼成工程では、白金源として投入した白金酸等を加熱により自己分解させ、白金（ 酸化物を含む）に還元する。還元温度は、白金化合物の自己分解温度（例えば、へ キサクロ口白金酸では 400〜430°C)以上の温度を必要とするため、通常、大気雰囲 気下、 500°C、 1時間で処理を行うことにより、 Pt/Al Oクリオゲル (触媒）を得ること ができる。  In the firing step, platinum acid or the like added as a platinum source is self-decomposed by heating and reduced to platinum (including oxides). Since the reduction temperature requires a temperature higher than the autolysis temperature of the platinum compound (for example, 400 to 430 ° C for hexachloroplatinic acid), it is usually treated in an atmosphere at 500 ° C for 1 hour. By performing this, a Pt / Al 2 O cryogel (catalyst) can be obtained.
[0043] 本発明を実施例に基づいて、更に詳細に説明するが、本発明はこれらの実施例に 限られるものではない。  [0043] The present invention will be described in more detail based on examples, but the present invention is not limited to these examples.
[0044] (評価方法）  [0044] (Evaluation method)
(1) CO吸着法による金属露出度評価  (1) Evaluation of metal exposure by CO adsorption method
ガスクロマトグラフ（GC)を用レ、、 0. 100g、カラム（φ 4mm)に充填したサンプルに 対し、 Heをキャリアとして CO (0. 5ml)を 5分毎に 6回流し、 COの総吸着量を GCプ ロットの結果より算出した。尚、サンプルは、一度、ペレット化 20mm, 20MPa/2 min保持）した後、粉砕'分級し、 300〜600 x mに調整したものである。 COl分子 は、金属白金 1原子に吸着する特性があるため、 COの総吸着量からサンプル表面 に存在する金属白金の量を算出することができる。また、サンプルに含まれる白金量 も組成から算出することができる。これらから、サンプル (触媒）に含まれる金属白金 原子の内、表面に露出している金属白金の割合 (露出度[%] )を算出した。  Using a gas chromatograph (GC) sample, 0.100 g, packed in a column (φ 4 mm), CO (0.5 ml) was flowed 6 times every 5 minutes using He as a carrier, and the total amount of CO adsorbed Was calculated from the results of the GC plot. The sample is once pelletized (20 mm, 20 MPa / 2 min hold), then pulverized and classified, and adjusted to 300 to 600 × m. Since COl molecules have the property of adsorbing to one atom of platinum metal, the amount of platinum metal present on the sample surface can be calculated from the total amount of CO adsorption. The amount of platinum contained in the sample can also be calculated from the composition. From these, the proportion of metal platinum exposed on the surface (exposure [%]) of the metal platinum atoms contained in the sample (catalyst) was calculated.
[0045] (2) CH酸化能評価 (酸化触媒能評価） Ar及び Oを 79 : 20 (疑似大気組成）で混合し、それに CHを 1 % (ν/ν)含むガス を作成した。これをサンプル (0. lg)に通じ、各温度でメタン酸化触媒活性を測定し た。測定温度は、 300〜700°Cの範囲で、 50°C亥 IJみとした。各温度で 25分流通させ た後、サンプリングした。尚、サンプルは、 H還元処理、 CO吸着測定を行ったものを 用レ、、実サンプノレ重量 (約 0. 10g)の 10倍重量の石英砂 (WAKO試薬）と混合'希 釈し、それをカラム 8mm)に充填して用いた。評価は、 FID (水素炎イオン検出器 )及び TCD (熱伝導度検出器）で行った。 FIDの結果から、 CH→COの変換効率を 算出した。 TCDは、検出感度が低いため、発生したガス組成の確認（CH、 CO )と、 変換効率算出のバックアップを目的として使用した。 [0045] (2) CH oxidation ability evaluation (oxidation catalytic ability evaluation) Ar and O were mixed at 79:20 (pseudo atmospheric composition), and a gas containing 1% (ν / ν) CH was created. This was passed through a sample (0. lg), and the methane oxidation catalyst activity was measured at each temperature. The measurement temperature was in the range of 300-700 ° C and 50 ° C IJ. The sample was sampled after 25 minutes at each temperature. In addition, the sample was used after being subjected to H reduction treatment and CO adsorption measurement, mixed and diluted with quartz sand (WAKO reagent) 10 times the actual sample weight (approximately 0.10 g). Column 8 mm) was used. The evaluation was performed with FID (flame ion detector) and TCD (thermal conductivity detector). The CH → CO conversion efficiency was calculated from the FID results. Since TCD has low detection sensitivity, it was used to confirm the generated gas composition (CH, CO 2) and to backup the conversion efficiency calculation.
[0046] (実施例 1：水素還元 Pt/SiOクリオゲル触媒の製造方法） (Example 1: Method for producing hydrogen reduction Pt / SiO cryogel catalyst)
脱イオン水 22gに対し、尿素 1. 5gをカ卩え、 15分間攪拌'溶解したことを目視で確 認した。この尿素水溶液に対し、へキサクロ口白金酸六水和物（以下、 HCPAと呼ぶ ) 50質量％水溶液を150111§加ぇ、混合し均一化させた。ここへシリカ源となるテトラメ トキシシラン（以下、 TMOSと呼ぶ）を 15· 2g加え、 20分混合した。反応熱でおおよ そ 40°Cまでサンプルが加熱された。これを室温（20°C)にて静置し、ゲル化させた。 It was visually confirmed that 1.5 g of urea was added to 22 g of deionized water and stirred for 15 minutes to dissolve. The urea solution to, Kisakuro port chloroplatinic acid hexahydrate to (hereinafter, referred to as HCPA) 50 wt% aqueous solution of one hundred fifty thousand one hundred eleven § pressurized tut, were mixed and homogenized. To this was added 15 · 2 g of tetramethoxysilane (hereinafter referred to as TMOS) as a silica source and mixed for 20 minutes. The sample was heated to approximately 40 ° C with the heat of reaction. This was left to stand at room temperature (20 ° C.) to gelate.
[0047] 得られたウエットゲルを、液体窒素を用いて初期冷却を行った。初期冷却は、液体 窒素中にウエットゲルを 5分以上保持し、凍結を目視で確認した。次に、得られた凍 結ゲルを、凍結乾燥機を用いて、 3日間、真空下でトラップ部冷却温度 80°Cで保 持した後、 6Paで取り出し、大気開放することにより、凍結乾燥ゲルを得た。尚、上記 凍結乾燥機には、 EYELA社製 FDU 810を用いた。この凍結乾燥機は、トラップ 部冷却温度 80°Cを維持可能で、凍結ゲルを収容したサンプルルームの大きさは、 φ 230mm, H = 200mmであった。また、サンプルルーム内を真空に引くために使 用した真空ポンプには、 ULVAC社製 GCD— 051Xを用いた。この真空ポンプの カタログ上の真空到達度は、 6. 7 X 10— 2Paであった。 [0047] The obtained wet gel was initially cooled with liquid nitrogen. For initial cooling, the wet gel was kept in liquid nitrogen for 5 minutes or more, and freezing was confirmed visually. Next, the obtained frozen gel was held at a trap part cooling temperature of 80 ° C under vacuum for 3 days using a freeze dryer, then taken out at 6 Pa and released into the atmosphere to freeze-dried gel. Got. For the freeze dryer, FDU 810 manufactured by EYELA was used. This freeze-dryer was able to maintain the trap section cooling temperature of 80 ° C, and the size of the sample room containing the frozen gel was φ 230 mm and H = 200 mm. ULVAC GCD-051X was used for the vacuum pump used to evacuate the sample room. Ultimate vacuum degree on the catalog of the vacuum pump was 6. 7 X 10- 2 Pa.
[0048] 得られた凍結乾燥ゲルを、アルミナルツボに収め、電気炉で大気雰囲気下で 500 °C、 1時間焼成を行った。次に、得られた PtZSiOクリオゲルを水素（H雰囲気下 [3 [0048] The obtained lyophilized gel was placed in an alumina crucible and baked in an electric furnace at 500 ° C for 1 hour in an air atmosphere. Next, the obtained PtZSiO cryogel was treated with hydrogen (H atmosphere [3
OmlZmin] )で、各温度（500°C、 700°C又は 900°C)まで昇温（10°C/min)した後 、各温度（500°C、 700°C、 900°C)、 1時間還元処理を行うことにより、水素還元 PtZ SiOクリオゲル触媒をそれぞれ得た。 OmlZmin]), each temperature (500 ° C, 700 ° C, 900 ° C), 1 ° C (500 ° C, 700 ° C, 900 ° C) By performing time reduction treatment, hydrogen reduction PtZ Each of the SiO cryogel catalysts was obtained.
[0049] (CO吸着法による金属露出度評価）  [0049] (Metal exposure evaluation by CO adsorption method)
得られた水素還元 Pt/SiOクリオゲル触媒 3種（500°C、 700°C、 900°C水素還元 Obtained hydrogen reduction 3 Pt / SiO cryogel catalysts (500 ° C, 700 ° C, 900 ° C hydrogen reduction)
)と、従来の含浸法による触媒（500°C水素還元）を調製し、金属 Ptの露出度を CO 吸着量より算出した。 ) And a conventional impregnation catalyst (500 ° C hydrogen reduction), and the degree of exposure of metal Pt was calculated from the amount of CO adsorption.
[0050] 尚、従来の含浸法による触媒には、担体として、平均粒径 300nmの球状シリカ粉 末 (扶桑科学社製 SP— 03B)を用いた。水素還元 Pt/SiOクリオゲル触媒は、 H [0050] In addition, spherical silica powder (SP-03B manufactured by Fuso Science Co., Ltd.) having an average particle size of 300 nm was used as a support for the catalyst by the conventional impregnation method. Hydrogen reduction Pt / SiO cryogel catalyst is H
O22ml/Ptfi0. 075gで調製したものを、各温度（500。C、 700。C、 900°C)で水素 還元処理して作製した。各触媒の金属 Pt量は、 0. 5%で一定であった。 A material prepared with O22ml / Ptfi0.075g was prepared by hydrogen reduction treatment at each temperature (500.C, 700.C, 900 ° C). The amount of metal Pt in each catalyst was constant at 0.5%.
[0051] 金属 Ptの露出度は、 500°C水素還元 Pt/SiOクリオゲル触媒の場合、 3. 92%、 [0051] The exposure of metal Pt is 3.92% in the case of 500 ° C hydrogen reduction Pt / SiO cryogel catalyst,
700°C水素還元 Pt/SiOクリオゲル触媒の場合、 12. 68%、 900°C水素還元 Pt/ In the case of 700 ° C hydrogen reduction Pt / SiO cryogel catalyst, 12. 68%, 900 ° C hydrogen reduction Pt /
SiOクリオゲル触媒の場合、 16. 80%であった。一方、従来の含浸法による触媒 (水 素還元 500°C)の場合、金属 Ptの露出度が 10. 84%であった。 In the case of the SiO cryogel catalyst, it was 16.80%. On the other hand, in the case of the catalyst by the conventional impregnation method (hydrogen reduction 500 ° C), the exposure degree of the metal Pt was 10.84%.
[0052] これは、 Pt/Si〇クリオゲル触媒の場合、その製造方法の性質上、クリオゲル内部 に金属 Ptが坦没し、外表面への露出が少ないからである。しかしながら、還元温度を 高めることにより、 Pt/SiOクリオゲル触媒の金属 Ptの露出度を向上させることがで きた。これは、高温水素処理により、クリオゲルの基材の表面にダメージを与え、金属 Ptが露出したためである。 [0052] This is because, in the case of a Pt / Si Cryogel catalyst, the metal Pt is buried inside the cryogel due to the nature of the production method, and the exposure to the outer surface is small. However, by increasing the reduction temperature, the exposure of the metal Pt in the Pt / SiO cryogel catalyst could be improved. This is because the surface of the cryogel base material was damaged by the high-temperature hydrogen treatment, and the metal Pt was exposed.
[0053] (CH酸化能評価） [0053] (CH oxidation ability evaluation)
次に、得られた水素還元 Pt/Si〇クリオゲル触媒 3種（500°C、 700°C、 900°C水 素還元）と、従来の含浸法による 500°C水素還元触媒について、 CH酸化能評価（ 酸化触媒能評価)を行った。  Next, the obtained hydrogen-reduced Pt / Si 0 cryogel catalyst (500 ° C, 700 ° C, 900 ° C hydrogen reduction) and the 500 ° C hydrogen reduction catalyst by the conventional impregnation method were used for CH oxidation ability. Evaluation (oxidation catalytic ability evaluation) was performed.
[0054] その結果、特に、 700°Cにおけるメタン酸化率力 従来の含浸法による 500°C水素 還元触媒の場合、約 68%であるのに対して、 500°C水素還元 PtZSiOクリオゲル 触媒の場合、約 56%、 700°C水素還元 Pt/SiOクリオゲル触媒の場合、約 50。/o、 9[0054] As a result, in particular, the methane oxidation rate at 700 ° C is about 68% in the case of the 500 ° C hydrogen reduction catalyst by the conventional impregnation method, whereas in the case of the 500 ° C hydrogen reduction PtZSiO cryogel catalyst About 56%, 700 ° C Hydrogen reduction About 50 for Pt / SiO cryogel catalyst. / o, 9
00°C水素還元 Pt/SiOクリオゲル触媒の場合、失活していた (約 6%)。 In the case of 00 ° C hydrogen reduction Pt / SiO cryogel catalyst, it was deactivated (about 6%).
[0055] ここで、得られた CH酸化能評価 (酸化触媒能評価）と先程の金属 Ptの露出度とを 比較検討すると、 500°C水素還元 Pt/SiOクリオゲル触媒は、従来の含浸法による 500°C水素還元触媒と比較して、金属 Ptの露出度が半分以下であるが、 CH酸化 能評価 (酸化触媒能評価)では、従来の含浸法による 500°C水素還元触媒に迫る触 媒能を有している。これは、触媒として機能する金属 Ptの活性点が同等に多いことを 示唆している。以上のことから、水素還元 Pt/SiOクリオゲル触媒は、金属 Pt表面 上に存在する活性点の密度が大きい、即ち、僅かに露出する Pt金属表面への活性 点をより多く付与している可能性を見い出した。尚、 900°C水素還元 PtZSiOクリオ ゲル触媒の場合、高温水素処理により、クリオゲルの基材の表面にダメージを与えす ぎてしまい、熱により金属 Ptがシンタリング等を起こして、失活したと考えられる。 [0055] Here, when comparing the obtained CH oxidation ability evaluation (oxidation catalytic ability evaluation) and the exposure degree of the metal Pt, the 500 ° C hydrogen reduction Pt / SiO cryogel catalyst was obtained by the conventional impregnation method. Compared to 500 ° C hydrogen reduction catalyst, the exposure of metal Pt is less than half, but CH oxidation performance evaluation (oxidation catalytic performance evaluation) is a catalyst approaching 500 ° C hydrogen reduction catalyst by conventional impregnation method. Have the ability. This suggests that the active sites of metal Pt functioning as a catalyst are equally high. Based on the above, the hydrogen-reduced Pt / SiO cryogel catalyst has a high density of active sites present on the metal Pt surface, that is, it may give more active sites to the slightly exposed Pt metal surface. I found out. In the case of a 900 ° C hydrogen reduction PtZSiO cryogel catalyst, the high temperature hydrogen treatment caused damage to the surface of the cryogel substrate, and the metal Pt was sintered and deactivated due to heat. Conceivable.
[0056] (実施例 2： Pt/Al Oクリオゲル触媒の製造方法） (Example 2: Method for producing Pt / Al 2 O cryogel catalyst)
80°C下での作業環境で、アルミナ源である ASB (Al (sec Bu〇） ) 26. 2mlを溶 媒である水 80mlに混合し、アルコキシド加水分解後、 HN〇溶液（1. ON)を 12ml カロえて、 2時間保持することにより、ベーマイトゾル (A1〇〇H)を作製した。  In a work environment at 80 ° C, 2 ml of ASB (Al (sec BuO)), which is an alumina source, is mixed with 80 ml of water, which is a solvent, and after alkoxide hydrolysis, HNO solution (1. ON) Boehmite sol (A1OOH) was prepared by holding 12 ml of this and holding for 2 hours.
[0057] 50°C下での作業環境で、得られたベーマイトゾノレ (AIOOH)に、キレート剤で保護 された白金源である白金酸（HCPA :へキサクロ口白金酸六水和物 [H (PtCl ) · 6Η[0057] In the working environment at 50 ° C, the resulting boehmite zonore (AIOOH) was converted to a platinum source (HCPA: hexaclonal platinic acid hexahydrate) that was a platinum source protected with a chelating agent [H (PtCl) 6Η
Ο] )から構成された白金ソースを 50°Cで投入後、尿素をカ卩えて、 50°Cで 12時間保 持した後、更に 80°C下での作業環境で、 24時間保持することにより、 HCPA/ベー マイトゾル (AIOOH)を作製した。尚、白金ソースは、 60°Cの作業環境で、へキシレ ングリコール 0· 5mlにへキサクロ口白金酸六水和物 [H (PtCl ) · 6Η〇] 0· 0749g を加え、 20分間保持することにより作製した。 Ο])) is added at 50 ° C, urea is added, and held at 50 ° C for 12 hours, and then kept at 80 ° C for 24 hours. As a result, HCPA / boehmite sol (AIOOH) was prepared. For the platinum source, add hexaclonal platinum acid hexahydrate [H (PtCl) · 6Η〇] 0 · 0749g to 0 · 5 ml of hexylene glycol in a working environment of 60 ° C and hold for 20 minutes. This was produced.
[0058] 得られた HCPA/ベーマイトゲル (AIOOH)を、 80°Cで凍結した後、得られた凍 結ゲルを更にトラップ部冷却温度 80°Cの真空下 (真空度:!〜 2Pa)で 24時間凍結 乾燥した。尚、使用した凍結法及び乾燥法は、実施例 1と同様の方法を用いた。 [0058] After freezing the obtained HCPA / boehmite gel (AIOOH) at 80 ° C, the obtained frozen gel was further subjected to a trap part cooling temperature of 80 ° C under vacuum (degree of vacuum:! ~ 2Pa). Freeze-dried for 24 hours. The freezing method and the drying method used were the same as in Example 1.
[0059] 得られた凍結乾燥ゲルを、アルミナルツボに収め、電気炉で大気雰囲気下で 500[0059] The obtained lyophilized gel was placed in an alumina crucible and 500% in an air atmosphere in an electric furnace.
°C、 1時間焼成を行うことにより、 Pt/Al Oクリオゲル触媒を得た。 Pt / Al 2 O cryogel catalyst was obtained by calcination at ° C for 1 hour.
[0060] (耐水性試験）  [0060] (Water resistance test)
得られた Pt/Al Oクリオゲル触媒と、従来の超臨界乾燥方法で作製された Pt/A The obtained Pt / Al O cryogel catalyst and Pt / A produced by the conventional supercritical drying method
1 Oエア口ゲル触媒を水に浸し、そのときの状態変化を観察した。 The 1 O air-mouth gel catalyst was immersed in water, and the state change at that time was observed.
[0061] 上記 Pt/Al〇エア口ゲル触媒の場合、水との接触により瞬時に構造破壊を起こし てしまうが、 Pt/Al Oクリオゲル触媒の場合、水に接しても構造破壊は起こらず、原 [0061] In the case of the above-mentioned Pt / Al 0 air-mouth gel catalyst, the structure is instantly destroyed by contact with water. However, in the case of the Pt / Al O cryogel catalyst, structural destruction does not occur even when in contact with water.
2 3  twenty three
形を留めてレヽることを確認した。  It was confirmed that the shape was retained and the label was restored.
[0062] (CH酸化能評価） [0062] (CH oxidation ability evaluation)
4  Four
500°C還元したクリオゲル触媒（Pt/Al Oクリオゲル触媒）と、 500°C還元した従  500 ° C reduced cryogel catalyst (Pt / Al O cryogel catalyst) and 500 ° C reduced slave
2 3  twenty three
来法触媒 (含浸法による触媒）について、 CH酸化能評価 (酸化触媒能評価)を行つ  Perform CH oxidation ability evaluation (oxidation catalyst ability evaluation) for conventional catalyst (catalyst by impregnation method)
4  Four
た。その結果を図 3及び図 4に示す。  It was. The results are shown in Figs.
[0063] 図 3に示すように、クリオゲル触媒の場合、その製造方法の性質上、クリオゲル内部 に金属 Ptが坦没し、外表面への露出が少ないため、従来法触媒よりもメタンの酸化 活性が低かったが、図 4に示すように、金属 Ptの活性点当たりの反応速度では、タリ ォゲル触媒が従来法触媒の約 2倍の触媒能を有することを確認した。  [0063] As shown in Fig. 3, in the case of a cryogel catalyst, the metal Pt is buried inside the cryogel due to the nature of its production method, and the exposure to the outer surface is less. Therefore, the oxidation activity of methane is lower than that of the conventional catalyst. However, as shown in Fig. 4, it was confirmed that the taliogel catalyst had about twice the catalytic capacity of the conventional catalyst at the reaction rate per active point of metal Pt.
[0064] (耐熱性試験）  [0064] (Heat resistance test)
クリオゲル触媒 (PtZAl Oクリオゲル触媒)と、従来法触媒 (含浸法による触媒）に  For cryogel catalyst (PtZAl O cryogel catalyst) and conventional catalyst (catalyst by impregnation method)
2 3  twenty three
ついて、 500°C還元及び 800°C還元したときにおける金属 Ptの露出度を CO吸着量 よりそれぞれ算出した。その結果を図 5に示す。  The degree of exposure of metal Pt when reduced at 500 ° C and 800 ° C was calculated from the amount of CO adsorption. The results are shown in Fig. 5.
[0065] 図 5に示すように、クリオゲル触媒の場合、 500°C還元よりも 800°C還元の方力 金 属 Ptの露出度は向上している力 従来法触媒の場合、金属 Ptの露出度が低下して いる。即ち、一概には言えないが、クリオゲル触媒の方が、従来法触媒よりも高温耐 熱性を有してレ、ることが示唆された。 [0065] As shown in Fig. 5, in the case of a cryogel catalyst, the power of reduction at 800 ° C over the reduction at 500 ° C is a force that improves the exposure of metal Pt. In the case of a conventional catalyst, the exposure of metal Pt The degree is decreasing. That is, although it cannot be generally stated, it was suggested that the cryogel catalyst has higher temperature and heat resistance than the conventional catalyst.
[0066] (実施例 3：クリオゲルの耐水再現性試験） [0066] (Example 3: Water reproducibility test of cryogel)
予め白金ソースを加えないで作製した A1〇クリオゲル (ASB)と A1〇クリオゲル（  A10 Cryogel (ASB) and A10 Cryogel (ASB) prepared without adding platinum source in advance
2 3 2 3  2 3 2 3
AIP)を、水に浸し常温乾燥させた。水に浸し常温乾燥の前後における BET表面積（ m2/g)、細孔容積 (mm3Zg)及び平均細孔径 (nm)をそれぞれ測定し、耐水再現 性を評価した。その結果を表 1に示す。 AIP) was immersed in water and dried at room temperature. The BET surface area (m 2 / g), pore volume (mm 3 Zg), and average pore diameter (nm) before and after drying at room temperature were measured to evaluate water reproducibility. The results are shown in Table 1.
[0067] [表 1] BET表面積 細孔容積 平均細孔径 [0067] [Table 1] BET surface area Pore volume Average pore diameter
(m2/g) (m s/g) mm) (m 2 / g) (m s / g) mm)
A 1203クリオゲル （AB S) 2 8 6. 9 43 3. 6 2. 6 7 [初期値] A 1 2 0 3 Cryogel (AB S) 2 8 6. 9 43 3. 6 2. 6 7 [Initial value]
A 1203クリオゲル （AB S) 3 3 8. 1 43 0. 6 2. 40 を水に浸し乾燥させたもの A 1 2 0 3 Cryogel (AB S) 3 3 8. 1 43 0. 6 2. 40 soaked in water and dried
A 1203クリオゲル （A I P) 2 6 1. 7 3 1 3. 4 2. 0 6 [初期値] A 1 2 0 3 Cryogel (AIP) 2 6 1. 7 3 1 3. 4 2. 0 6 [Initial value]
A 1203クリオゲル （A I P) 3 0 0. 3 3 1 9. 4 2. 0 6 を水に浸し乾燥させたもの A 1 2 0 3 Cryogel (AIP) 3 0 0. 3 3 1 9. 4 2. 0 6 soaked in water and dried
[0068] 表 1の結果から、 Al Oクリオゲル (ASB)及び Al Oクリオゲル (AIP)は、 BET表面 [0068] From the results in Table 1, Al O cryogel (ASB) and Al O cryogel (AIP)
2 3 2 3  2 3 2 3
積 (m2/g)がやや増大するものの、細孔容積 (mm3/g)及び平均細孔径 (nm)はほ ぼ不変であった。以上のことから、本発明で得られるクリオゲルは、耐水再現性に優 れていることを確認した。 Although the product (m 2 / g) increased slightly, the pore volume (mm 3 / g) and the average pore diameter (nm) were almost unchanged. From the above, it was confirmed that the cryogel obtained in the present invention was excellent in water reproducibility.
産業上の利用可能性  Industrial applicability
[0069] 本発明の多孔質構造体の製造方法は、例えば、排ガス処理用の触媒の製造に好 適に用いることができる。 [0069] The method for producing a porous structure of the present invention can be suitably used, for example, for producing a catalyst for exhaust gas treatment.

Claims

請求の範囲 The scope of the claims
[1] 原材料からゲル化反応によりゲル化物を作製し、前記ゲル化物を凍結乾燥した後 [1] After producing a gelled material from a raw material by a gelation reaction and freeze-drying the gelled material
、焼成し、多孔質構造体を得る多孔質構造体の製造方法。 The manufacturing method of the porous structure which bakes and obtains a porous structure.
[2] 前記ゲル化物を、トラップ部冷却温度が— 80°C以下、且つ乾燥完了時の真空度が lOPa以下で凍結乾燥する請求項 1に記載の多孔質構造体の製造方法。  [2] The method for producing a porous structure according to claim 1, wherein the gelled product is freeze-dried at a trap portion cooling temperature of −80 ° C. or lower and a degree of vacuum at the completion of drying of lOPa or lower.
[3] 前記原材料の主組成が、シリカ、アルミナ、ジルコユア、チタニアを生成する金属ァ ルコキシドの少なくとも 1種以上から構成される請求項 1又は 2に記載の多孔質構造 体の製造方法。  [3] The method for producing a porous structure according to claim 1 or 2, wherein the main composition of the raw material is composed of at least one of metal alkoxides that produce silica, alumina, zirconia, and titania.
[4] 前記原材料に、金属イオン、金属微粒子、金属酸化物微粒子のレ、ずれか 1種以上 の金属種を含む溶液を添加する請求項：!〜 3のいずれか 1項に記載の多孔質構造 体の製造方法。  [4] The porous material according to any one of [1] to [3] above, wherein a solution containing at least one metal species, metal ions, metal fine particles, and metal oxide fine particles is added to the raw material. Manufacturing method of structure.
[5] 前記金属種が、貴金属又は遷移金属である請求項 1〜4のいずれ力 1項に記載の 多孔質構造体の製造方法。  [5] The method for producing a porous structure according to any one of claims 1 to 4, wherein the metal species is a noble metal or a transition metal.
[6] 前記ゲル化物が、凍結乾燥後、大気雰囲気下及び/又は水素雰囲気下で焼成さ れる請求項 1〜5のいずれ力 1項に記載の多孔質構造体の製造方法。 6. The method for producing a porous structure according to any one of claims 1 to 5, wherein the gelled product is baked in an air atmosphere and / or a hydrogen atmosphere after freeze-drying.
[7] 前記多孔質構造体が、耐水性であり、且つ水との接触で構造破壊が起きない請求 項：!〜 6のいずれか 1項に記載の多孔質構造体の製造方法。 [7] The method for producing a porous structure according to any one of [6] to [6], wherein the porous structure is water-resistant and structural destruction does not occur upon contact with water.
[8] 前記多孔質構造体が、三次元網目の骨格構造を有し、且つ前記骨格を構成する 基材に金属微粒子又は金属酸化物微粒子もしくはそれら両方が分散されている請 求項 4〜7のいずれか 1項に記載の多孔質構造体の製造方法。 [8] Claims 4-7, wherein the porous structure has a three-dimensional network skeleton structure, and metal fine particles and / or metal oxide fine particles are dispersed in a base material constituting the skeleton. The method for producing a porous structure according to any one of the above.
[9] 前記金属微粒子又は金属酸化物微粒子もしくはそれら両方が、前記基材にほとん ど坦没している請求項 4〜8のいずれか 1項に記載の多孔質構造体の製造方法。 [9] The method for producing a porous structure according to any one of [4] to [8], wherein the metal fine particles or the metal oxide fine particles or both of them are substantially immersed in the base material.
[10] 前記多孔質構造体が、触媒である請求項 4〜9のいずれか 1項に記載の多孔質構 造体の製造方法。 [10] The method for producing a porous structure according to any one of claims 4 to 9, wherein the porous structure is a catalyst.
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