JP5055520B2 - Porous structure and method for producing the same - Google Patents
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- 238000004519 manufacturing process Methods 0.000 title claims description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 61
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 47
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- 238000001179 sorption measurement Methods 0.000 claims description 26
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 25
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- 238000000034 method Methods 0.000 claims description 15
- 239000000377 silicon dioxide Substances 0.000 claims description 15
- 238000009826 distribution Methods 0.000 claims description 12
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- 238000001816 cooling Methods 0.000 claims description 10
- 238000000352 supercritical drying Methods 0.000 claims description 10
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- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 19
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- MYWQGROTKMBNKN-UHFFFAOYSA-N tributoxyalumane Chemical compound [Al+3].CCCC[O-].CCCC[O-].CCCC[O-] MYWQGROTKMBNKN-UHFFFAOYSA-N 0.000 description 5
- 239000002244 precipitate Substances 0.000 description 4
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- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 3
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- 229910052751 metal Inorganic materials 0.000 description 3
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 2
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
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- OBROYCQXICMORW-UHFFFAOYSA-N tripropoxyalumane Chemical compound [Al+3].CCC[O-].CCC[O-].CCC[O-] OBROYCQXICMORW-UHFFFAOYSA-N 0.000 description 2
- 230000010718 Oxidation Activity Effects 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
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- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- OSQPUMRCKZAIOZ-UHFFFAOYSA-N carbon dioxide;ethanol Chemical compound CCO.O=C=O OSQPUMRCKZAIOZ-UHFFFAOYSA-N 0.000 description 1
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Description
本発明は、多孔質構造体及びその製造方法に関する。 The present invention relates to a porous structure and a method for producing the same.
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から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、ＮＯＸ吸蔵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ＮＯＸ、ＨＣ、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。 In recent years, there has been an increasing need to remove particulates and harmful substances in exhaust gas from internal combustion engines, boilers, and the like from the exhaust gas in consideration of environmental effects, and various exhaust gas purification technologies have been proposed. For example, the exhaust system of an automobile, an oxidation catalyst, three-way catalyst, NO X storage reduction catalyst and the like are arranged, to purify NO X in the exhaust gas, HC, harmful components such as CO mainly by the catalytic action of the noble metal Yes. In particular, as an oxidation catalyst, for example, a catalyst in which Pt having a high oxidation activity is supported on a carrier such as alumina or silica is known.
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。 Conventionally, when a catalyst component such as platinum is supported on an alumina or silica porous carrier, the alumina or silica porous carrier is usually immersed in a solution containing the catalyst component, for example, a salt solution of the catalyst component and dried. And the method of baking is employ | adopted if necessary.
最近では、多孔質担体として、アルミナ系エアロ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ロゲルを製造する方法としては、例えば、アルミニウム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ロゲルは、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。 Recently, alumina-based airgel is suitably used as the porous carrier. As a method for producing such an alumina airgel, for example, a wet alumina gel (wet gel) obtained by hydrolysis from aluminum alkoxide or the like is filled with an organic solvent and dried under supercritical conditions ( Supercritical drying) has been proposed, and the airgel obtained by this method is known to have a high surface area, a high porosity, and a high heat resistance.
しかしながら、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、水やアルコール等との混合物の液相を有するウエットゲルである。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、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等をアルコールで置換することが必要不可欠であるが、その製造工程や設備に大幅なコストを要し、また可燃性・毒性等の安全性に問題があった。 However, in the case of a wet gel prepared by a method such as hydrolysis and gelation of an alkoxide, it is a wet gel having a liquid phase of a mixture with water, alcohol or the like. In order to avoid structural destruction due to shrinkage during drying by the supercritical drying method, it is indispensable to replace water in the liquid phase of the wet gel with alcohol as a step before supercritical drying of the wet gel. However, the manufacturing process and equipment required significant costs, and there were problems with safety such as flammability and toxicity.
また、現在使用されているエアロゲルは、耐液体性に劣り、水等の液体にエアロ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、また使用用途も大幅に限定されてしまうという問題点があった。 In addition, the airgel currently used is inferior in liquid resistance, and the structure is destroyed at the moment when the airgel is immersed in a liquid such as water. Therefore, the metal is supported by the conventional impregnation method using an aqueous solution containing metal ions. However, there is a problem in that the usage is greatly limited.
更に、超臨界乾燥法は、臨界点以上の高温・高圧プロセスのため、高エネルギー消費型の製造方法であり、高製造コストに繋がると同時に、製造プロセス上安全性の問題も誘発する。また高エネルギー消費型プロセスであるがために二酸化炭素の排出も顕著となり、地球温暖化防止に向けた京都議定書の精神にも反するという問題点があった。 Furthermore, the supercritical drying method is a high energy consumption type manufacturing method because of a high temperature / high pressure process above the critical point, leading to high manufacturing costs and at the same time inducing safety problems in the manufacturing process. In addition, because it is a high energy consumption process, carbon dioxide emissions have become prominent, and this is contrary to the spirit of the Kyoto Protocol for the prevention of global warming.
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く、耐液体性であり、且つ液体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及びその製造方法を提供することにある。 The present invention has been made in view of the above-mentioned problems of the prior art, and its object is not only to have a high surface area, high porosity and high heat resistance, but also to be liquid resistant, and An object of the present invention is to provide a porous structure capable of obtaining a porous structure that does not cause structural destruction by contact with a liquid and contributing to safety and cost reduction, and a method for manufacturing the same.
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及びそ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 porous structure and a method for producing the same.
［１］ シリカが全質量ベースで２．５〜１０質量％添加されたシリカ−アルミナ系化合物で、アルミニウムアルコキシドから得られたベーマイトゾルに、シリコンアルコキシドを加えた水系での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、多孔質構造体を得る多孔質構造体の製造方法であって、前記ゲル化物から前記多孔質構造体を得る工程のいずれの段階にも触媒物質の担持工程および溶媒置換工程および超臨界乾燥工程を含まないことを特徴とする多孔質構造体の製造方法。 [1] A silica-alumina compound in which silica is added in an amount of 2.5 to 10% by mass based on the total mass, and gelled by an aqueous gelation reaction in which silicon alkoxide is added to boehmite sol obtained from aluminum alkoxide. And producing the porous structure by freeze-drying the gelled product, and a catalytic substance at any stage of the step of obtaining the porous structure from the gelled product. The method for producing a porous structure does not include a supporting step, a solvent replacement step, and a supercritical drying step.
［２］ 前記ゲル化物を、トラップ部冷却温度が−８０℃以下、且つ乾燥完了時の真空度が１０Ｐａ以下で凍結乾燥する［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 [1], wherein the gelled product is freeze-dried at a trap part cooling temperature of −80 ° C. or lower and a degree of vacuum at the completion of drying of 10 Pa or lower.
［３］ ［１］又は［２］に記載の方法によって製造された多孔質構造体であって、かさ密度が０．１ｇ／ｃｍ ３ 以下で、且つ主な結晶相がγ−Ａｌ ２ Ｏ ３ 結晶相から構成された多孔質構造体。 [3] A porous structure produced by the method according to [1] or [2], wherein the bulk density is 0.1 g / cm 3 or less and the main crystal phase is γ-Al 2 O 3. A porous structure composed of a crystalline phase.
［４］ 耐液体性であり、且つ液体との接触で構造破壊が起きない［３］に記載の多孔質構造体。 [4] The porous structure according to [3], which is liquid-resistant and does not cause structural destruction upon contact with a liquid.
［５］ 液体に浸した後に乾燥しても、細孔容積の変化率が液濡前の±３０％以内である［３］又は［４］に記載の多孔質構造体。 [5] The porous structure according to [3] or [4], wherein the rate of change in the pore volume is within ± 30% before the liquid is wet even after being dipped in the liquid and dried.
［６］ 液体に浸した後に乾燥しても、液濡前と変化率が±２０％以内の水蒸気吸着等温線を示す［３］〜［５］のいずれかに記載の多孔質構造体。 [6] The porous structure according to any one of [3] to [5], which shows a water vapor adsorption isotherm having a rate of change within ± 20% even after being dipped in a liquid and then dried.
［７］ 液体に浸した後に乾燥しても、液濡前と極大ピーク位置の変化が±１ｎｍ以内の細孔分布曲線を示す［３］〜［６］のいずれかに記載の多孔質構造体。
［８］ １１００℃以下の仮焼時における前記多孔質構造体の結晶相が、γ−Ａｌ ２ Ｏ ３ 結晶相であり、且つ１２００℃の仮焼時における前記多孔質構造体の結晶相が、γ−Ａｌ ２ Ｏ ３ 結晶相又はθ−Ａｌ ２ Ｏ ３ 結晶相のいずれかである請求項［３］〜［７］のいずれかに記載の多孔質構造体。
[7] The porous structure according to any one of [3] to [6], wherein, even after being dipped in a liquid and dried, the change in maximum peak position shows a pore distribution curve within ± 1 nm before liquid wetting .
[8] The crystalline phase of the porous structure at the time of calcination at 1100 ° C. or lower is a γ-Al 2 O 3 crystal phase, and the crystalline phase of the porous structure at the time of calcination at 1200 ° C. The porous structure according to any one of claims [3] to [7], which is either a γ-Al 2 O 3 crystal phase or a θ-Al 2 O 3 crystal phase.
本発明の多孔質構造体及びその製造方法は、高表面積、高気孔率及び高耐熱性を有するだけでなく、耐液体性であり、且つ液体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。 The porous structure of the present invention and the production method thereof have not only high surface area, high porosity and high heat resistance, but also liquid resistance, and a porous structure that does not cause structural breakage upon contact with liquid. As well as contribute to safety and cost reduction.
以下、本発明の多孔質構造体及びそ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く、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。 Hereinafter, the porous structure of the present invention and the method for producing the same will be described in detail. However, the present invention should not be construed as being limited thereto, and the knowledge of those skilled in the art can be obtained without departing from the scope of the present invention. Various changes, modifications, and improvements can be added based on the above.
本発明に係る多孔質構造体の主な特徴は、かさ密度が０．１ｇ／ｃｍ３以下で、且つ主な結晶相がγ−Ａｌ２Ｏ３結晶相から構成されたものである。 The main features of the porous structure according to the present invention are that the bulk density is 0.1 g / cm 3 or less and the main crystal phase is composed of γ-Al 2 O 3 crystal phase.
このとき、本発明の多孔質構造体は、かさ密度が０．１ｇ／ｃｍ３以下、より好ましくは、０．０２〜０．１ｇ／ｃｍ３である。これは、かさ密度が０．０２ｇ／ｃｍ３未満である場合、構造的にもろくなり、機械的強度が低下するからである。一方、かさ密度が０．１ｇ／ｃｍ３を超過する場合、エアロゲルレベルの多孔質性あるいは気孔率が確保されず、高温下でのシンタリングによりかさ密度が増大しやすいからである。 At this time, the porous structure of the present invention has a bulk density of 0.1 g / cm 3 or less, more preferably 0.02~0.1g / cm 3. This is because when the bulk density is less than 0.02 g / cm 3 , the structure becomes brittle and the mechanical strength decreases. On the other hand, when the bulk density exceeds 0.1 g / cm 3 , the porous property or porosity at the airgel level is not ensured, and the bulk density tends to increase due to sintering at high temperature.
本発明の多孔質構造体は、主な結晶相がγ−Ａｌ２Ｏ３結晶相であるクリオゲルから構成されたものであることが好ましい。これにより、本発明の多孔質構造体は、多孔体のかさ密度をエアロゲルレベルの０．１ｇ／ｃｍ３以下に抑え、粒子成長の原因であるネックの数を減らすことができるからである。その結果、γ−Ａｌ２Ｏ３結晶相が１０００℃付近でα−Ａｌ２Ｏ３に転移することを抑制することができるため、耐熱性及び高温時（例えば、１０００℃以上）における熱安定性を確保することができる。尚、クリオゲルは、耐液体性であるとともに、液体との接触で構造破壊を起こすことなく、液体に浸した後に乾燥しても、液浸前の特性（例えば、ＢＥＴ比表面積、細孔容積、平均細孔径等）とほぼ不変的であるものである（耐液再現性に優れている）。 The porous structure of the present invention is preferably composed of a cryogel whose main crystal phase is a γ-Al 2 O 3 crystal phase. This is because the porous structure of the present invention can suppress the bulk density of the porous body to an airgel level of 0.1 g / cm 3 or less and reduce the number of necks that cause particle growth. As a result, it is possible to suppress the transition of the γ-Al 2 O 3 crystal phase to α-Al 2 O 3 around 1000 ° C., so that heat resistance and thermal stability at high temperatures (eg, 1000 ° C. or higher) are achieved. Can be secured. In addition, the cryogel is liquid-resistant and does not cause structural destruction by contact with the liquid. Even if the gel is dried after being immersed in the liquid, characteristics before the immersion (for example, BET specific surface area, pore volume, Average pore diameter etc.) and almost unchanged (excellent liquid reproducibility).
更に、本発明の多孔質構造体は、液体に浸した後に乾燥しても、液濡前と変化率が±３０％（より好ましくは、±２５％）以内の細孔容積を示すことが好ましい。これにより、本発明の多孔質構造体は、反応系内に存在する液体による細孔容積変化を最小限にくい止めることができる。 Further, even when the porous structure of the present invention is dipped in a liquid and then dried, it preferably has a pore volume within ± 30% (more preferably ± 25%) before the liquid is wet. . Thereby, the porous structure of the present invention can minimize the change in pore volume due to the liquid present in the reaction system.
本発明の多孔質構造体は、液体に浸した後に乾燥しても、液濡前と変化率が±２０％（より好ましくは、±１５％）以内の水蒸気吸着等温線を示すことが好ましい。これは、触媒反応系に存在する水による構造変化を最小限にくい止めることができるからである。 Even if the porous structure of the present invention is dipped in a liquid and then dried, it preferably exhibits a water vapor adsorption isotherm with a change rate within ± 20% (more preferably ± 15%). This is because the structural change due to water present in the catalytic reaction system can be minimized.
本発明の多孔質構造体は、液体に浸した後に乾燥しても、液濡前と極大ピーク位置の変化が±１ｎｍ（より好ましくは、±０．８ｎｍ）以内の細孔分布曲線を示すことが好ましい。これは、反応系中に存在する液体による細孔分布の変化を最小限にくい止めることができるからである。 Even if the porous structure of the present invention is dipped in a liquid and then dried, it exhibits a pore distribution curve within ± 1 nm (more preferably ± 0.8 nm) before the liquid is wet and the change in the maximum peak position. Is preferred. This is because the change in the pore distribution due to the liquid present in the reaction system can be kept to a minimum.
次に、本発明の多孔質構造体の製造方法は、シリカが全質量ベースで２．５〜１０質量％添加されたシリカ−アルミナ系化合物で、アルミニウムアルコキシドから得られたベーマイトゾルに、シリコンアルコキシドを加えた水系での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、多孔質構造体を得るものであって、前記ゲル化物から前記多孔質構造体を得る工程のいずれの段階にも触媒物質の担持工程および溶媒置換工程および超臨界乾燥工程を含まないことを特徴とするものである。 Next, the method for producing a porous structure of the present invention is a silica-alumina compound to which 2.5 to 10% by mass of silica is added based on the total mass , and a silicon alkoxide is added to a boehmite sol obtained from aluminum alkoxide. A gelled product is prepared by a gelation reaction in an aqueous system to which a gel is added, and the gelled product is freeze-dried to obtain a porous structure, and any of the steps of obtaining the porous structure from the gelled product This stage is also characterized in that it does not include a catalyst substance loading process, a solvent replacement process, and a supercritical drying process.
このとき、本発明の多孔質構造体の製造方法の主な特徴は、アルミナ（γ−Ａｌ２Ｏ３）の出発原料であるアルミニウムアルコキシドから得られたベーマイトゾルに、シリカ（ＳｉＯ２）の出発原料であるシリコンアルコキシドを添加することにある。シリカの添加量は、多孔質構造体の全質量ベースで２．５〜１０質量％、より好ましくは、２．５〜５質量％である。 At this time, the main feature of the method for producing the porous structure of the present invention is that the boehmite sol obtained from aluminum alkoxide, which is a starting material of alumina (γ-Al 2 O 3 ), is used to start silica (SiO 2 ). It is to add silicon alkoxide as a raw material. The addition amount of silica is 2.5 to 10% by mass, more preferably 2.5 to 5% by mass, based on the total mass of the porous structure.
これは、シリカの添加量が２．５質量％未満である場合、シリカの添加効果が現れないためである。一方、シリカの添加量が５質量％を超過する場合、アルミナよりもシリカの特徴が顕著になって、高温耐熱特性が低下するからである。 This is because the addition effect of silica does not appear when the addition amount of silica is less than 2.5% by mass. On the other hand, when the addition amount of silica exceeds 5% by mass, the characteristics of silica become more prominent than that of alumina, and the high-temperature heat resistance is deteriorated.
尚、本発明で用いるアルミナの出発原料であるアルミニウムアルコキシドは、特に限定されないが、例えば、アルミニウムトリブトキシド：ＡＳＢ（Ａｌ（ｓｅｃ−ＢｕＯ）３）またはアルミニウムトリプロポキシド：ＡＩＰ（Ａｌ（ｉｓｏ−Ｐｒｏ）３）を好適に用いることができる。また、本発明で用いるシリカの出発原料であるシリコンアルコキシドは、特に限定されないが、例えば、テトラエトキシシラン（Ｓｉ（ＯＣ２Ｈ５）４）を好適に用いることができる。 The aluminum alkoxide that is the starting material of alumina used in the present invention is not particularly limited. For example, aluminum tributoxide: ASB (Al (sec-BuO) 3 ) or aluminum tripropoxide: AIP (Al (iso-Pro) 3 ) can be suitably used. Moreover, the silicon alkoxide which is a starting material of silica used in the present invention is not particularly limited, but, for example, tetraethoxysilane (Si (OC 2 H 5 ) 4 ) can be suitably used.
また、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℃以下、且つ真空度が１０Ｐａ以下で凍結乾燥することが重要である。これは、トラップ部冷却温度が−８０℃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１０Ｐａ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。 In the method for producing a porous structure of the present invention, it is important that the gelled product be freeze-dried at a trap portion cooling temperature of −80 ° C. or lower and a vacuum degree of 10 Pa or lower. This is because when the trap portion cooling temperature exceeds −80 ° C., freeze-drying of the wet gel becomes incomplete, and the microstructure is destroyed due to drying shrinkage. Further, the vacuum degree is better as it is closer to the vacuum. However, when the degree of vacuum at the time of completion of drying exceeds 10 Pa, freeze-drying is not completed, and the microstructure is destroyed due to drying shrinkage.
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℃以下で冷却し、ゲル化物（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℃以下にて、１〜３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１０Ｐａ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−エタノールや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い。 More specifically, in the lyophilization, first, the gelled product (wet gel) is cooled at −80 ° C. or lower, and after the gelled product (wet gel) is confirmed to be frozen, it is evacuated to cool the trap portion cooling temperature. Is preferably maintained at -80 ° C or lower for about 1 to 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 10 Pa or less is desirable. In addition, a freezer may be used for the initial cooling of the gelled product (wet gel). However, cooling as quickly as possible with a refrigerant such as dry ice-ethanol or liquid nitrogen shortens the freezing time and reduces the gelled product (wet gel). Gel) is preferable because structural destruction during freezing can be suppressed.
このように、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、エアロ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く、耐液体性であり、且つ液体との接触でエアロゲルのように構造破壊を起こさない多孔質構造体（クリオゲル）を得ることができる。 As described above, the manufacturing method of the porous structure of the present invention only has high surface area, high porosity and high heat resistance, which are excellent characteristics of airgel, by adopting freeze drying instead of supercritical drying. In addition, it is possible to obtain a porous structure (cryogel) that is liquid resistant and that does not cause structural breakdown like aerogel when in contact with a liquid.
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。 In addition, the method for producing a porous structure of the present invention does not perform supercritical drying using a high temperature and high pressure above the critical point, and thus is excellent in safety and employs freeze drying at a low temperature and low pressure. Therefore, it is more energy-saving than supercritical drying, and it can be directly dried (freeze-dried) without replacing the water in the liquid phase of the wet gel with alcohol, so that the process and equipment can be simplified. Therefore, the cost can be greatly reduced.
以上のことから、本発明の多孔質構造体の製造方法は、アルミニウムとシリコンの金属アルコキシドを用いることにより、アルミニウムの金属アルコキシドだけを用いて得られたものと比較して、クリオゲルのγ−Ａｌ２Ｏ３結晶相が１０００℃付近でα−Ａｌ２Ｏ３に転移することをより抑制することができるため、耐熱性及び高温時（例えば、１０００℃以上）における熱安定性を新たに確保することができる。 From the above, the method for producing the porous structure of the present invention is obtained by using the metal alkoxide of aluminum and silicon, compared with that obtained using only the metal alkoxide of aluminum, and γ-Al of cryogel. Since it is possible to further suppress the transition of the 2 O 3 crystal phase to α-Al 2 O 3 in the vicinity of 1000 ° C., heat resistance and thermal stability at a high temperature (for example, 1000 ° C. or higher) are newly secured. be able to.
また、本発明の多孔質構造体の製造方法は、耐液体性であるとともに、液体との接触で構造破壊を起こすことなく、液浸した後に乾燥しても、液浸前の特性（例えば、ＢＥＴ比表面積、細孔容積、平均細孔径等）とほぼ不変的な、即ち、耐液再現性に優れたクリオゲルを得ることができる。 In addition, the method for producing a porous structure of the present invention is liquid-resistant, and does not cause structural destruction by contact with a liquid. It is possible to obtain a cryogel that is substantially invariant with the BET specific surface area, pore volume, average pore diameter, etc., that is, excellent in liquid reproducibility.
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。 The present invention will be described in more detail based on examples, but the present invention is not limited to these examples.
（実施例１〜３、参照例１）
アルミナ源としてアルミニウムトリブトキシド（Ａｌ（ｓｅｃ−ＢｕＯ）３）０．０２８６ｍｏｌを８６℃の温水２０ｍＬに投入して加水分解し、ＨＮＯ３を加えて邂逅させた後、シリカ源としてテトラエトキシシラン（Ｓｉ（ＯＣ２Ｈ５）４）を加えた。シリカ添加量は、０質量％（参照例１）、２．５質量％（実施例１）、５質量％（実施例２）、１０質量％（実施例３）とした。ゲル化後、トラップ温度−８０℃以下、真空度１０Ｐａ以下の条件で凍結乾燥し、乾燥ゲル（クリオゲル）のサンプルをそれぞれ得た。
(Examples 1-3, Reference Example 1)
After aluminum tri-butoxide (Al (sec-BuO) 3 ) 0.0286mol a was put into hot water 20mL of 86 ° C. to hydrolyze the alumina source, were Encounter by adding HNO 3, tetraethoxysilane as the silica source (Si (OC 2 H 5 ) 4 ) was added. The amount of silica added was 0% by mass (Reference Example 1), 2.5% by mass (Example 1), 5% by mass (Example 2), and 10% by mass (Example 3). After gelation, the sample was freeze-dried under conditions of a trap temperature of −80 ° C. or lower and a vacuum of 10 Pa or lower to obtain dry gel (cryogel) samples.
得られたサンプル（実施例１〜３及び参照例１）を、１０００〜１４００℃にて５時間焼成後、ＸＲＤ分析及びＴＥＭ写真により、高温耐熱性の評価を行った。 The obtained samples (Examples 1 to 3 and Reference Example 1) were fired at 1000 to 1400 ° C. for 5 hours, and then evaluated for high-temperature heat resistance by XRD analysis and TEM photographs.
１１００℃の仮焼時、参照例１（シリカ無添加クリオゲル）では、α−θ混合相となるのに対し、実施例１〜３（シリカ添加クリオゲル）は、全てγ相のままであった。１２００℃の仮焼時、参照例１（シリカ無添加クリオゲル）は、α相となるのに対し、実施例１及び実施例２では、θ−Ａｌ２Ｏ３結晶相であり、実施例３では、γ−Ａｌ２Ｏ３結晶相が維持されていた（図１参照）。即ち、実施例１〜３では、１２００℃における耐熱性及び熱安定性を確保していることを確認した。 At the time of calcination at 1100 ° C., Reference Example 1 (silica-free cryogel) was an α-θ mixed phase, whereas Examples 1 to 3 (silica-added cryogel) were all in the γ phase. At the time of calcination at 1200 ° C., Reference Example 1 (silica-free cryogel) becomes an α phase, whereas in Example 1 and Example 2, it is a θ-Al 2 O 3 crystal phase, and in Example 3, , Γ-Al 2 O 3 crystal phase was maintained (see FIG. 1). That is, in Examples 1 to 3, it was confirmed that heat resistance and thermal stability at 1200 ° C. were secured.
次に、得られたサンプル（実施例１〜３及び参照例１）を、１０００〜１４００℃で５時間仮焼した後のＢＥＴ比表面積のグラフを図２に示す。 Next, the graph of the BET specific surface area after calcining the obtained sample (Examples 1-3 and Reference Example 1) at 1000-1400 degreeC for 5 hours is shown in FIG.
図２に示すように、１２００℃仮焼時におけるＢＥＴ比表面積が、参照例１では、３．３ｍ２／ｇ、実施例１では、２５．７ｍ２／ｇ、実施例２では、３９．０ｍ２／ｇ、実施例３では、４６．７ｍ２／ｇであった。これにより、実施例１〜３では、シリカを添加することにより、耐熱性及び高温時における熱安定性を飛躍的に向上させることができた。また、実施例１〜３では、従来のアルミナエアロゲルの同温度焼成時における比表面積（通常、２０ｍ２／ｇ程度）と遜色無かった。 As shown in FIG. 2, the BET specific surface area during calcination at 1200 ° C. was 3.3 m 2 / g in Reference Example 1, 25.7 m 2 / g in Example 1, and 39.0 m in Example 2. 2 / g, in Example 3, it was 46.7 m 2 / g. Thereby, in Examples 1-3, the heat resistance and the thermal stability at the time of high temperature could be improved dramatically by adding silica. Moreover, in Examples 1-3, the specific surface area (usually about 20 m < 2 > / g) at the time of the same temperature baking of the conventional alumina airgel was not inferior.
尚、実施例１〜３では、１２００℃焼成時におけるＴＥＭ写真観察により、高温焼成後も微細な粒子が多数存在しており、高温時における熱安定性に優れていることを確認した。 In Examples 1 to 3, it was confirmed by observation of a TEM photograph during firing at 1200 ° C. that many fine particles were present even after firing at high temperature, and the thermal stability at high temperature was excellent.
液体が構造に及ぼす影響を調べるため、実施例１〜３のサンプルを５００℃で仮焼したものを蒸留水に浸漬した後に、水を乾燥・除去する処理を行った。５００℃仮焼により実施例１〜３のサンプルは全てγ−Ａｌ２Ｏ３結晶相を示した。水処理による多孔体の構造変化は観察されず、水処理後も水処理前と全く同一の見かけ構造を示した。水処理前後の窒素吸着等温線を測定したところ、等温線は同型を示し、細孔容積の変化率は±２５％以内であった。細孔分布曲線のピーク位置も±１ｎｍの変化範囲内にあった。また水処理前後の水蒸気吸着等温線の変化率は±１５％以内であった。 In order to investigate the influence of the liquid on the structure, the samples of Examples 1 to 3 were calcined at 500 ° C. and immersed in distilled water, and then the water was dried and removed. All samples of Examples 1 to 3 exhibited a γ-Al 2 O 3 crystal phase by calcining at 500 ° C. The structural change of the porous body due to the water treatment was not observed, and the same apparent structure as that before the water treatment was exhibited after the water treatment. When nitrogen adsorption isotherms before and after water treatment were measured, the isotherms showed the same type, and the change rate of the pore volume was within ± 25%. The peak position of the pore distribution curve was also within a change range of ± 1 nm. The change rate of the water vapor adsorption isotherm before and after the water treatment was within ± 15%.
（参照例２、比較例１〜３）
アルミナ源としてアルミニウムトリブトキシド：ＡＳＢ（Ａｌ（ｓｅｃ−ＢｕＯ）３）を用いた。８６℃の水２０ｍＬに対し、このアルミナ源を０．０２８６ｍｏｌ加えて加水分解した後、ＨＮＯ３を加えてゾルを邂逅した。邂逅後、透明ゾルが調製されたら０．２ｇの尿素を添加し、同温度で一晩放置してゲル化を促した。作製されたゲルを液体窒素で急冷凍結した後、―８０℃のトラップ冷却温度で２４時間真空凍結乾燥を施し、アルミナクリオゲルを得た（参照例２）。比較のため、参照例２と同じ出発原料でありながら凍結乾燥を施さないアルミナキセロゲル（比較例１）と、ゾルゲル反応を施さないアルミナ沈殿物（比較例２）のサンプルを作製し、更に市販アルミナ（大明化学工業株式会社製：ＴＭ−３００Ｄ）（比較例３）のサンプルと共に、ＸＲＤ分析及びＴＥＭ写真により、高温耐熱性を評価した。
(Reference Example 2, Comparative Examples 1 to 3)
Aluminum tributoxide: ASB (Al (sec-BuO) 3 ) was used as the alumina source. After 0.0286 mol of this alumina source was added to 20 mL of water at 86 ° C. for hydrolysis, HNO 3 was added to dissolve the sol. After that, when a transparent sol was prepared, 0.2 g of urea was added and allowed to stand overnight at the same temperature to promote gelation. The prepared gel was quenched and frozen with liquid nitrogen, and then vacuum freeze-dried for 24 hours at a trap cooling temperature of −80 ° C. to obtain an alumina cryogel (Reference Example 2). For comparison, a sample of an alumina xerogel (Comparative Example 1) that is the same starting material as Reference Example 2 but is not lyophilized and an alumina precipitate (Comparative Example 2) that is not subjected to a sol-gel reaction are prepared. High temperature heat resistance was evaluated by an XRD analysis and a TEM photograph together with a sample (Daimei Chemical Industry Co., Ltd .: TM-300D) (Comparative Example 3).
参照例２及び比較例１〜３では、ＸＲＤ分析結果から、９００℃以下の仮焼時、γ−Ａｌ２Ｏ３結晶相のみが検出された。また、１０００℃仮焼時、比較例３（市販アルミナ）では、α−Ａｌ２Ｏ３結晶相とθ−Ａｌ２Ｏ３結晶相が検出され、参照例２、比較例１及び比較例２では、θ−Ａｌ２Ｏ３結晶相のみが検出された。更に、１１００℃仮焼時、比較例１〜３では、Ａｌ２Ｏ３の結晶相が、全てα−Ａｌ２Ｏ３結晶相に相変化しているのに対し、参照例２では、α−Ａｌ２Ｏ３結晶相とθ−Ａｌ２Ｏ３結晶相を維持していることを確認した。即ち、１１００℃の仮焼時では、参照例２のみが、１１００℃における耐熱性及び熱安定性を確保していることを確認した。 In Reference Example 2 and Comparative Examples 1 to 3, only the γ-Al 2 O 3 crystal phase was detected from the XRD analysis results during calcination at 900 ° C. or lower. Further, at the time of calcining at 1000 ° C., in Comparative Example 3 (commercially available alumina), an α-Al 2 O 3 crystal phase and a θ-Al 2 O 3 crystal phase were detected, and in Reference Example 2, Comparative Example 1 and Comparative Example 2, Only the θ-Al 2 O 3 crystal phase was detected. Furthermore, during 1100 ° C. calcination, Comparative Examples 1 to 3, the crystalline phase of Al 2 O 3 is, while being phase change to all α-Al 2 O 3 crystal phase, in Reference Example 2, alpha- It was confirmed that the Al 2 O 3 crystal phase and the θ-Al 2 O 3 crystal phase were maintained. That is, at the time of calcination at 1100 ° C., it was confirmed that only Reference Example 2 ensured heat resistance and thermal stability at 1100 ° C.
次に、参照例２及び比較例１〜３を、１１００℃で、５時間仮焼した後の窒素吸着等温線のグラフを図３に示すとともに、７００〜１２００℃で５時間仮焼した後のＢＥＴ比表面積のグラフを図４に示す。 Next, a graph of nitrogen adsorption isotherm after calcining Reference Example 2 and Comparative Examples 1 to 3 at 1100 ° C. for 5 hours is shown in FIG. 3, and after calcining at 700 to 1200 ° C. for 5 hours. A graph of the BET specific surface area is shown in FIG.
図３に示すように、１１００℃の仮焼では、参照例２のみ窒素吸着等温線にヒステリシスが認められた。また、図４に示すように、参照例２では、１１００℃仮焼時におけるＢＥＴ比表面積が比較例１〜３よりもはるかに優れていた。尚、このときの参照例２のＢＥＴ比表面積は２０ｍ２／ｇ、細孔容積が６１ｍｍ３／ｇ、平均細孔径が８ｎｍであった。 As shown in FIG. 3, in the calcining at 1100 ° C., hysteresis was recognized in the nitrogen adsorption isotherm only in Reference Example 2. As shown in FIG. 4, in Reference Example 2, the BET specific surface area at the time of calcining at 1100 ° C. was far superior to Comparative Examples 1 to 3. At this time, the BET specific surface area of Reference Example 2 was 20 m 2 / g, the pore volume was 61 mm 3 / g, and the average pore diameter was 8 nm.
１１００℃で５時間仮焼した時の表面積（対７００℃仮焼時の表面積）を比較した場合、参照例２（アルミナクリオゲル）では、９．２％、比較例１（アルミナキセロゲル）では、２．９％、比較例２（アルミナ沈殿物）では、４．５％、比較例３（市販アルミナ）では、３．９％であることから、参照例２（アルミナクリオゲル）の耐熱性及び高温時における熱安定性に優れていることを確認した。 When comparing the surface area when calcined at 1100 ° C. for 5 hours (vs. the surface area when calcined at 700 ° C.), in Reference Example 2 (alumina cryogel), in 9.2%, in Comparative Example 1 (alumina xerogel), Since 2.9%, Comparative Example 2 (alumina precipitate) is 4.5%, and Comparative Example 3 (commercial alumina) is 3.9%, the heat resistance of Reference Example 2 (alumina cryogel) and It was confirmed that the thermal stability at high temperature was excellent.
更に、７００℃で仮焼した参照例２及び比較例１〜３のＴＥＭ写真を比較すると、参照例２（アルミナクリオゲル）は、一次粒子同士の密集度が小さく、粒子間の隙間が大きいのに対し、比較例１（アルミナキセロゲル）、比較例２（アルミナ沈殿物）の順に従って粒子同士の密集度が大きくなった。尚、密集度が小さいと粒子成長の原因であるネック数を減少させることができる。従って、１１００℃の高温仮焼では、比較例１（アルミナキセロゲル）や比較例２（アルミナ沈殿物）、比較例３（市販アルミナ）では、α相転移により巨大なアルミナ粒子へと粒成長するのに対し、参照例２（アルミナクリオゲル）では、微細なアルミナ粒子が多数存在しており、高温時における熱安定性に優れていることを確認した。 Furthermore, when the TEM photographs of Reference Example 2 and Comparative Examples 1 to 3 calcined at 700 ° C. are compared, Reference Example 2 (alumina cryogel) has a small degree of compaction between primary particles and a large gap between particles. On the other hand, the density of particles increased in the order of Comparative Example 1 (alumina xerogel) and Comparative Example 2 (alumina precipitate). If the density is small, the number of necks that cause particle growth can be reduced. Therefore, in high-temperature calcining at 1100 ° C., comparative example 1 (alumina xerogel), comparative example 2 (alumina precipitate), and comparative example 3 (commercial alumina) grow into large alumina particles due to α phase transition. On the other hand, in Reference Example 2 (alumina cryogel), a large number of fine alumina particles were present, and it was confirmed that the thermal stability at high temperature was excellent.
（参照例３、比較例４）
アルミナ源としてアルミニウムトリブトキシド（Ａｌ（ｓｅｃ−ＢｕＯ）３）０．０２８６ｍｏｌを８６℃の温水２０ｍＬに投入して加水分解し、ＨＮＯ３を加えてゾルを邂逅した。邂逅後、透明ゾル（透明ベーマイトゾル）を得た。この透明ゾルに０．２ｇの尿素を添加し、同温度で一晩放置してゲル化を促した。
( Reference Example 3 , Comparative Example 4)
Aluminum tri-butoxide (Al (sec-BuO) 3 ) 0.0286mol a was put into hot water 20mL of 86 ° C. to hydrolyze the alumina source, it was encounter the sol by addition of HNO 3. After that, a transparent sol (transparent boehmite sol) was obtained. 0.2 g of urea was added to this transparent sol and allowed to stand overnight at the same temperature to promote gelation.
作製されたゲル（湿潤ベーマイトゲル）を溶媒置換することなく液体窒素で急冷凍結した後、−８０℃のトラップ冷却温度で２４時間真空凍結乾燥を施し、ベーマイトクリオゲルを得た。得られたクリオゲルを５００℃で３時間仮焼し、アルミナクリオゲルのサンプルを作製した（参照例３）。 The prepared gel (wet boehmite gel) was quenched and frozen with liquid nitrogen without solvent substitution, and then vacuum freeze-dried at a trap cooling temperature of −80 ° C. for 24 hours to obtain a boehmite cryogel. The obtained cryogel was calcined at 500 ° C. for 3 hours to prepare an alumina cryogel sample ( Reference Example 3 ).
一方、作製されたゲル（湿潤ベーマイトゲル）をエタノールに浸漬し、ゲル内の水などをエタノールに置換した後、エタノールの臨界点、即ち２４３℃、６４気圧以上の超臨界条件下でエタノールを除去し、ベーマイトエアロゲルを得た。得られたベーマイトエアロゲルを５００℃で３時間仮焼し、アルミナエアロゲルのサンプルを作製した（比較例４）。 On the other hand, after the prepared gel (wet boehmite gel) is immersed in ethanol and the water in the gel is replaced with ethanol, ethanol is removed under supercritical conditions of ethanol at the critical point, that is, 243 ° C., 64 atm or more. Boehmite airgel was obtained. The obtained boehmite airgel was calcined at 500 ° C. for 3 hours to prepare an alumina airgel sample (Comparative Example 4).
それぞれ得られたサンプル（参照例３及び比較例４）をシャーレに並べて水に浸漬させると、エアロゲル構造体（比較例４）の場合、水との接触で瞬時に構造破壊が起こり、パウダー状となってしまった。一方、クリオゲル構造体（参照例３）の場合、水との接触で何ら構造変化が起きず、再度、水を乾燥除去後も全く同一の見かけ構造を示した。 When the obtained samples ( Reference Example 3 and Comparative Example 4) were arranged in a petri dish and immersed in water, in the case of an airgel structure (Comparative Example 4), structural destruction occurred instantaneously upon contact with water, It is had. On the other hand, in the case of the cryogel structure ( Reference Example 3 ), no structural change occurred upon contact with water, and the same apparent structure was shown even after the water was removed by drying again.
（参照例４及び参照例５、比較例５及び比較例６）
アルミナ源としてアルミニウムトリブトキシド（Ａｌ（ｓｅｃ−ＢｕＯ）３）０．０２８６ｍｏｌを８６℃の温水２０ｍＬに投入して加水分解し、ＨＮＯ３を加えてゾルを邂逅した。邂逅後、透明ゾル（透明ベーマイトゾル）を得た。得られた透明ゾルに、０．２ｇの尿素を添加し、同温度で一晩放置してゲル化を促した。
( Reference Example 4 and Reference Example 5 , Comparative Example 5 and Comparative Example 6)
Aluminum tri-butoxide (Al (sec-BuO) 3 ) 0.0286mol a was put into hot water 20mL of 86 ° C. to hydrolyze the alumina source, it was encounter the sol by addition of HNO 3. After that, a transparent sol (transparent boehmite sol) was obtained. To the obtained transparent sol, 0.2 g of urea was added and allowed to stand overnight at the same temperature to promote gelation.
作製されたゲル（湿潤ベーマイトゲル）を溶媒置換することなく液体窒素で急冷凍結した後、−８０℃のトラップ冷却温度で２４時間真空凍結乾燥を施し、クリオゲル（ベーマイトクリオゲル）を得た。得られたベーマイトクリオゲルを５００℃で３時間仮焼し、アルミナクリオゲルのサンプルを作製した（参照例４）。同様の方法で、アルミナ源としてアルミニウムトリプロポキシド（Ａｌ（ｉｓｏ−Ｐｒｏ）３）を用いたアルミナクリオゲルのサンプルを作製した（参照例５）。 The prepared gel (wet boehmite gel) was quenched and frozen with liquid nitrogen without solvent substitution, and then subjected to vacuum lyophilization for 24 hours at a trap cooling temperature of −80 ° C. to obtain a cryogel (boehmite cryogel). The obtained boehmite cryogel was calcined at 500 ° C. for 3 hours to prepare an alumina cryogel sample ( Reference Example 4 ). In the same manner, an alumina cryogel sample using aluminum tripropoxide (Al (iso-Pro) 3 ) as an alumina source was prepared ( Reference Example 5 ).
一方、作製されたゲル（湿潤ベーマイトゲル）をエタノールに浸漬し、ゲル内の水などをエタノールに置換した後、エタノールの臨界点、即ち２４３℃、６４気圧以上の超臨界条件下でエタノールを除去し、エアロゲル（ベーマイトエアロゲル）を得た（比較例５）。得られたベーマイトエアロゲルを５００℃で３時間仮焼しアルミナエアロゲルのサンプルを作製した（比較例６）。 On the other hand, after the prepared gel (wet boehmite gel) is immersed in ethanol and the water in the gel is replaced with ethanol, ethanol is removed under supercritical conditions of ethanol at the critical point, that is, 243 ° C., 64 atm or more. Airgel (boehmite airgel) was obtained (Comparative Example 5). The obtained boehmite airgel was calcined at 500 ° C. for 3 hours to prepare a sample of alumina airgel (Comparative Example 6).
得られたサンプル（参照例４及び参照例５、比較例５及び比較例６）を、蒸留水に浸漬した後、水を乾燥・除去する水処理を行った。このとき、水処理前後の液体窒素温度における窒素吸着等温線（図５〜８）、細孔分布（図９〜１２）、２５℃における水蒸気吸着等温線（図１３〜１６）を、それぞれのサンプルについて測定した。 The obtained samples ( Reference Example 4 and Reference Example 5 , Comparative Example 5 and Comparative Example 6) were immersed in distilled water, and then subjected to water treatment for drying and removing the water. At this time, the nitrogen adsorption isotherm (FIGS. 5-8), the pore distribution (FIGS. 9-12) at the liquid nitrogen temperature before and after the water treatment, and the water vapor adsorption isotherm (FIGS. 13-16) at 25 ° C. Was measured.
参照例４及び参照例５（アルミナクリオゲル）では、図５及び図６に示すように、水処理前後の液体窒素温度における窒素吸着等温線に変化が無く、細孔容積の変化率は±０．３５％以内であった。細孔分布曲線では、図９及び図１０に示すように、２〜３ｎｍにピークを示し、ピーク位置の変化は±１ｎｍ以内であった。 In Reference Example 4 and Reference Example 5 (alumina cryogel), as shown in FIGS. 5 and 6, there is no change in the nitrogen adsorption isotherm at the liquid nitrogen temperature before and after the water treatment, and the rate of change of the pore volume is ± 0. Within 35%. In the pore distribution curve, as shown in FIGS. 9 and 10, a peak was observed at 2 to 3 nm, and the change in the peak position was within ± 1 nm.
一方、比較例５（ベーマイトエアロゲル）及び比較例６（アルミナエアロゲル）では、図１１及び図１２に示すように、水処理前、ミクロ孔からマクロ孔まで幅広い細孔分布を示していたが、水処理後、３ｎｍ前後のメソ孔が相対的に増大していることを確認した。尚、水処理後には、図７及び図８に示すように、窒素吸着等温線にヒステリシスが出現し、アルミナエアロゲルの細孔容積変化率は３２％以上に達した。 On the other hand, Comparative Example 5 (boehmite aerogel) and Comparative Example 6 (alumina aerogel) showed a wide pore distribution from micropores to macropores before water treatment, as shown in FIGS. After the treatment, it was confirmed that the mesopores around 3 nm were relatively increased. After water treatment, as shown in FIGS. 7 and 8, hysteresis appeared in the nitrogen adsorption isotherm, and the pore volume change rate of the alumina airgel reached 32% or more.
また、参照例４及び参照例５（アルミナクリオゲル）では、図１３及び図１４に示すように、２５℃における水蒸気吸着等温線に変化が無く、算出される比表面積も、相対圧０．９０での水吸着量も水処理前後でほとんど変化が無かった。 In Reference Example 4 and Reference Example 5 (alumina cryogel), as shown in FIGS. 13 and 14, there is no change in the water vapor adsorption isotherm at 25 ° C., and the calculated specific surface area also has a relative pressure of 0.90. The amount of water adsorbed on the basin was almost unchanged before and after water treatment.
一方、比較例５（ベーマイトエアロゲル）及び比較例６（アルミナエアロゲル）では、図１５及び図１６に示すように、水処理前後で形の全く異なる水蒸気吸着等温線を示した。また窒素吸着等温線（図７及び図８）と比較すると、水蒸気吸着等温線では、水処理前のサンプルでも等温線に大きなヒステリシスが現れた。水処理前のエアロゲルサンプルを水蒸気吸着測定した後に目視・観察すると、測定前にセル内に投入したエアロゲルの様子とは明らかに異なり、いわゆる体積収縮が観察された。これは水蒸気吸着測定中にエアロゲルが水と接触し、徐々に構造破壊を起こしたことによるものと考えられた。 On the other hand, in Comparative Example 5 (boehmite aerogel) and Comparative Example 6 (alumina aerogel), as shown in FIGS. 15 and 16, water vapor adsorption isotherms having completely different shapes before and after water treatment were shown. In addition, compared with the nitrogen adsorption isotherm (FIGS. 7 and 8), the water vapor adsorption isotherm showed a large hysteresis in the isotherm even in the sample before water treatment. When the airgel sample before water treatment was visually observed and observed after water vapor adsorption measurement, the so-called volume shrinkage was observed, which was clearly different from the state of the airgel put into the cell before the measurement. This was thought to be due to the fact that the airgel contacted water during the water vapor adsorption measurement and gradually caused structural destruction.
本発明の多孔質構造体及びその製造方法は、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。 The porous structure and the method for producing the same according to the present invention can be suitably used for producing a catalyst for treating exhaust gas, for example.
Claims (8)
前記ゲル化物から前記多孔質構造体を得る工程のいずれの段階にも触媒物質の担持工程および溶媒置換工程および超臨界乾燥工程を含まないことを特徴とする多孔質構造体の製造方法。 A silica-alumina compound with 2.5 to 10% by mass of silica added based on the total mass, and a gelled product is produced by a gelation reaction in an aqueous system in which silicon alkoxide is added to boehmite sol obtained from aluminum alkoxide. , A method for producing a porous structure obtained by freeze-drying the gelled product to obtain a porous structure,
A method for producing a porous structure characterized in that any step of obtaining the porous structure from the gelled product does not include a catalyst substance supporting step, a solvent replacement step, and a supercritical drying step.
かさ密度が０．１ｇ／ｃｍ３以下で、且つ主な結晶相がγ−Ａｌ２Ｏ３結晶相から構成された多孔質構造体。 A porous structure produced by the method according to claim 1 or 2,
A porous structure having a bulk density of 0.1 g / cm 3 or less and a main crystal phase composed of a γ-Al 2 O 3 crystal phase.
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