JP2002293657A - Method of manufacturing inorganic porous composite containing dispersed particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an inorganic porous composite whose energy cost to be raised by burning a binder and whose environmental load to be increased by discharging carbon dioxide, can be cut down and whose pore shape and pore size distribution are made uniform. SOLUTION: This inorganic porous composite is manufactured by forming the gel having the pores of >=100 nm diameter by reacting a fine particle component with a precursor of a mesh forming component in the fine particle component-dispersed solvent or mixing the fine particle-dispersed liquid in the mesh forming component-dissolved reaction solution to react them so that phase separation and sol-gel transition are caused at the same time, cleaning the wet gel with a new solvent or displacing the solvent of the wet gel with the new solvent, removing the new solvent and heat-treating the solvent-removed gel at the adequate temperature, if necessary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing an inorganic porous composite containing dispersed particles. The porous material produced according to the present invention is used as a filter or a carrier material.

[0002]

2. Description of the Related Art In general, an inorganic porous material represented by ceramics is obtained by sintering a compact formed of raw material fine particles bound by a resin component called a binder or a pore-forming agent with the combustion of the binder. It is manufactured by. The pores are formed by burning out the binder and leaving the space occupied by the sintered particles. The energy cost of burning the binder having a volume almost equal to the pore volume and the environmental load due to carbon dioxide emission are extremely high. In addition, since the connection structure of the particles necessarily has a neck portion, the shape of the pores is non-uniform and the size distribution is often wide. On the other hand, it is known that an inorganic porous material such as silica is produced with good reproducibility by a sol-gel method utilizing phase separation. In this method, a porous structure is formed by evaporating the solvent-rich phase, so that the environmental load can be dramatically reduced as compared with the conventional method. Further, the shape of the pores and the size distribution thereof are extremely uniform, and there is a high possibility that the separation and purification processes can be performed with higher efficiency than before.

[0003]

Accordingly, the present inventor has studied and found that a dispersed particle component was previously allowed to coexist in a sol-gel reaction solution containing silica as a main component under conditions that do not cause sedimentation or aggregation of the particles. It has been clarified that by causing a sol-gel transition accompanied by phase separation, a porous composite having dispersed particles incorporated in a gel phase can be obtained.

That is, the present invention includes an open pore and a dispersed particle by causing a dispersed particle component to coexist in a sol-gel reaction solution and causing a sol-gel transition accompanied by a phase transition. A method for producing an inorganic porous composite, which comprises producing an inorganic porous composite comprising a skeleton component. Here, the open pores have a diameter of 100 nm or more,
Preferably it is 200 to 10,000 nm. Macropores with a diameter of 100 nm or more are formed as areas occupied by the solvent phase generated during phase separation, so they are formed by ordinary drying operations without burning or thermal decomposition, and the solvent phase and the gel phase are each separated. When forming a so-called co-continuous structure that is entangled and continuous, an extremely sharp size distribution can be obtained.

The method includes reacting a precursor of a network-forming component in a solvent in which fine-particle components are dispersed in advance, or mixing and reacting a fine-particle dispersion with a reaction solution in which the network-forming component is dissolved in advance. By
Causes phase separation and sol-gel transition simultaneously, 100n diameter
The method is characterized in that a gel having pores of m or more is formed, the solvent is removed after the subsequent washing or solvent replacement treatment of the wet gel, and heat treatment is performed at an appropriate temperature if necessary.

[0005] Phase separation is an important part of the material manufacturing process.
This is a widespread phenomenon in which a region having a component different from the starting component is generated by precipitation or precipitation. In a sol-gel reaction system, a phase rich in a network-forming component causing gel formation (gel phase)
And a phase rich in solvent components that does not cause gel formation (solvent phase)
Then, separation occurs. In forming each phase region, diffusion of components against the concentration gradient occurs using the difference in chemical potential as the driving force, and mass transfer continues until each phase region reaches the equilibrium composition at the given temperature and pressure. I do. At this time, if the dispersed particle component is made to coexist in the starting composition and conditions are selected so that the dispersed particle component does not significantly affect the phase separation or the sol-gel reaction, the gel phase or the solvent phase may be selected according to the properties of the dispersed particles. In addition, it is possible to preferentially distribute the dispersed particles. That is, when dispersed particles having a high affinity for the component forming the gel phase and a low affinity for the component forming the solvent phase coexist, the dispersed particles are preferentially distributed to the gel phase. In the opposite case, the dispersed particles are preferentially distributed in the solvent phase.However, when the solvent phase is removed after gel formation to produce a porous body, the dispersed particles satisfying the former condition are selected. It becomes important.

[0006] The precursor of the network component causing gel formation used in the sol-gel reaction includes metal alkoxides, complexes, metal salts, organically modified metal alkoxides, organic cross-linked metal alkoxides, and partial hydrolysis products and partial products thereof. A polymer which is a polymerization product can be used. The sol-gel transition by changing the pH of water glass or an aqueous silicate solution can be used as well.

Further, in a specific production method of the present invention, a water-soluble polymer is dissolved in an acidic aqueous solution, fine particle components are dispersed therein, and a metal compound having a hydrolyzable functional group is added thereto to carry out a hydrolysis reaction. After the product has solidified, it is then dried and heated. Here, the water-soluble polymer is a water-soluble organic polymer that can theoretically be formed into an aqueous solution having an appropriate concentration, and is used in a reaction system containing an alcohol generated by a metal compound having a hydrolyzable functional group. As long as it can be uniformly dissolved in water, specifically, a sodium or potassium salt of polystyrene sulfonic acid which is a polymer metal salt, polyacrylic acid which is a polymer acid and dissociates into a polyanion, Preferred are polyallylamine and polyethyleneimine, which are molecular bases and generate polycations in an aqueous solution, or polyethylene oxide, which is a neutral polymer having an ether bond in the main chain, or polyvinylpyrrolidone. Further, formamide, polyhydric alcohol, a surfactant may be used instead of the organic polymer,
In that case, glycerin is optimal as the polyhydric alcohol, and polyoxyethylene alkyl ethers are optimal as the surfactant.

As the metal compound having a hydrolyzable functional group, a metal alkoxide or an oligomer thereof can be used. For example, those having a small number of carbon atoms such as a methoxy group, an ethoxy group and a propoxy group are preferable. . As the metal, a metal of an oxide finally formed, for example, Si, Ti, Zr, or Al is used. One or more of these metals may be used.
On the other hand, any oligomer can be used as long as it can be uniformly dissolved and dispersed in alcohol, and specifically, up to about 10-mers can be used. Alkoxyalkoxysilanes, in which some of the alkoxy groups of these silicon alkoxides are substituted with alkyl groups, and oligomers of up to about 10-mers thereof are preferably used. Alkyl-substituted metal alkoxides in which the central metal element is replaced with titanium, zirconium, aluminum or the like instead of silicon can also be used.

The acidic aqueous solution is usually a mineral acid such as hydrochloric acid or nitric acid having a concentration of 0.001 N or more, or formic acid,
Organic acids such as acetic acid having a concentration of 0.1N or more are preferred. In the hydrolysis, the solution was heated at room temperature 40-80 ° C for 0.5-
This can be achieved by storing for 5 hours.

[0010] Currently, industrially produced and marketed dispersed particles are mainly composed of an organic polymer, a metal oxide or a metal, and their particle diameters (average diameters) range from about 5 nm to about 100 μm in a very wide range. I have. The chemical affinity between these fine particles and the network component that causes gel formation,
It is known that it can be freely controlled in many cases by chemical modification of the particle surface, etc., and if the particle satisfies conditions that do not cause aggregation or sedimentation during the sol-gel reaction, it can be applied to the present production method regardless of the chemical composition. be able to. Therefore, in the present invention, the dispersed particles are a metal oxide, a metal,
Organic polymers and their complexes can be used,
Preferred average diameters are between 5 nm and 100 μm. Specifically, silicon oxide, titanium oxide, zirconium oxide, aluminum oxide, calcium oxide, magnesium oxide, iron oxide, transition metal oxides, yttrium oxide, lanthanum oxide, and rare earth oxides are suitable. Further, carbonates, nitrates, sulfates, phosphates, halides, inorganic salts, and the like, which are stable in the reaction solution, can also be used. An organic salt, a complex, a protected metal colloid, a polymer latex, and a particulate organic polymer can also be used for preparing the inorganic porous composite according to the present invention by controlling the dispersibility in the reaction solution. The amount of the dispersed particles to be added is 90% by weight or less, preferably 80% by weight or less. The pore size decreases as the amount of the dispersed particles increases.

According to the production method of the present invention, an inorganic porous composite containing dispersed particles in a skeletal phase and having pores of 100 nm or more can be obtained.

[0012]

Example First, 0.90 g of polyethylene oxide (product number 85,645-2, manufactured by Aldrich), which is a water-soluble polymer, was added to 0.01 parts.
The solution was dissolved in 10 g of a normal acetic acid aqueous solution, and alumina powder (average particle size: 0.5 μm, easily sinterable alumina powder AES-12 # 00601 manufactured by Sumitomo Chemical Co., Ltd.) was added to the solution under stirring and dispersed. . Then, 5 ml of tetramethoxysilane was added under stirring to carry out a hydrolysis reaction. After stirring for a few minutes, transfer the resulting clear solution to a closed container and add
When it was kept in a constant temperature bath at 0 ° C., it solidified after about 40 minutes. The obtained gel is aged at the same temperature for 3 days,
Thereafter, the solvent was removed by evaporation to obtain a massive porous composite. The amount of alumina powder was 0.25, 0.50, 1.0
0, 2.00 g (about 1.5, 3.0, 5.9, 11.1
%), A porous composite having continuous through-holes was obtained at any amount. However, the pore diameter became smaller with the increase in the amount of alumina powder added, and the pore shape was changed by adding alumina. From the smooth thing you see when you don't have
The surface changed to a rough shape. FIG. 1 shows the results obtained by determining the pore size distribution of the porous composite having an alumina addition amount of 0.25 g by the mercury porosimetry. It can be seen that a sharp pore distribution centering on a diameter of 1.0 micron is obtained. FIG. 2 shows the result of the pore size distribution of the porous composite having an alumina content of 0.50 g determined by the mercury porosimetry. It can be seen that a sharp pore distribution centering on a diameter of 0.7 micron is obtained. The pore size becomes smaller as the amount of alumina powder added increases.

[0013]

According to the present invention, it is possible to reduce the energy cost of burning a binder and the environmental load due to carbon dioxide emission as in the conventional method, and furthermore, the inorganic porous composite having a uniform pore shape and size distribution. Body can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing the pore size distribution of a porous composite containing 0.25 g of alumina added by a mercury intrusion method.

FIG. 2 is a diagram showing the pore size distribution of a porous composite containing 0.50 g of alumina added by a mercury intrusion method.

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[Procedure amendment]

[Submission date] May 31, 2001 (2001.5.3)
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0003

[Correction method] Change

[Correction contents]

[0003]

Accordingly, the present inventor has studied and found that a dispersed particle component was previously allowed to coexist in a sol-gel reaction solution containing silica as a main component under conditions that do not cause sedimentation or aggregation of the particles. It has been clarified that by causing a sol-gel transition accompanied by phase separation, a porous composite having dispersed particles incorporated in a gel phase can be obtained.

That is, the present invention includes an open pore and a dispersed particle by causing a dispersed particle component to coexist in a sol-gel reaction solution and causing a sol-gel transition accompanied by phase separation. A method for producing an inorganic porous composite, which comprises producing an inorganic porous composite comprising a skeleton component. Here, the open pores have a diameter of 100 nm or more,
Preferably it is 200 to 10,000 nm. Macropores with a diameter of 100 nm or more are formed as areas occupied by the solvent phase generated during phase separation, so they are formed by ordinary drying operations without burning or thermal decomposition, and the solvent phase and the gel phase are each separated. When forming a so-called co-continuous structure that is entangled and continuous, an extremely sharp size distribution can be obtained.

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Claims (5)

[Claims] An inorganic porous composite comprising a skeleton component containing open pores and dispersed particles by causing a dispersed particle component to coexist in a sol-gel reaction solution and causing a sol-gel transition accompanied by a phase transition. And a method for producing an inorganic porous composite. 2. The method for producing an inorganic porous composite according to claim 1, wherein the open pores have a diameter of 100 nm or more. 3. The method for producing an inorganic porous composite according to claim 1, wherein the dispersed particles are a metal oxide, a metal, an organic polymer and a composite thereof. 4. The method for producing an inorganic porous composite according to claim 1, wherein the dispersed particles have an average diameter of 5 nm to 100 μm. 5. An inorganic porous composite containing dispersed particles in a skeletal phase and having pores of 100 nm or more.