JPH0455377A - Production of inorganic porous body - Google Patents

Abstract

PURPOSE:To obtain an inorganic porous body which is large in pore volume and small in heat conductivity by extracting an absorbed solvent by liquid carbon oxide or carbon oxide being in a critical state in the case of drying a swelling laminar compd. being in a swelled state. CONSTITUTION:A swelling laminar compd. A such as Na-montmorillonite and synthetic mica is made to a swelling state by incorporating a solvent into this swelling laminar compd. A. Pillar materials 4 are inserted between the layers 1, 1 thereof and the large gaps 2 are formed between the layers 1, 1. Then the swelling laminar compd. A is dried by extracting the solvent absorbed into this compd. A being in the swelling state by liquid carbon dioxide or carbon dioxide in a critical state and then an inorganic porous body is obtained. Thereby the compd. is dried while intactly maintaining a porous structure before drying. The obtained inorganic porous body is preferably utilized as heat insulating material and a catalytic carrier.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing an inorganic porous body.

[Conventional technology]

By impregnating a swellable layered compound with a solvent to make it swell, and inserting a pillar material between the layers, large voids are formed between the layers, and these voids are utilized to provide excellent heat insulation and catalytic performance. It is known how to obtain the material (
Japanese Patent Publication No. 61-10130, Japanese Patent Publication No. 60-1378
(See Publication No. 12) [Problems to be Solved by the Invention] However, the pore area (specific volume) of the inorganic layered porous material obtained by these methods is at most 0°8 cc/
g or less, and it cannot be said that the latent functions originally possessed by the inorganic layered compound are fully brought out.

According to the inventors' findings, this is because even if the pillar material is inserted between the layers, the surface energy of the interlayer particles is taken away when the solvent evaporates during the drying stage. This is because the layer spacing of the swellable layered compound in the swollen state cannot be maintained as it is due to aggregation occurring between the inorganic layered compounds, and the structure of the porous body changes.

For this reason, for example, even if an inorganic layered porous material is used to obtain an insulating material with a thermal conductivity equivalent to or lower than that of air by utilizing the porous structure of the inorganic layered porous material, heat leaks from the solid part. was predominant, and it was not possible to obtain a heat insulating material with the desired physical properties.

This invention was made in view of the above circumstances, and reduces the aggregation of the particles constituting the pillars and the inorganic layered compounds that occur when the solvent contained between the layers evaporates during drying. An object of the present invention is to provide a method for producing an inorganic porous body having an extremely large pore volume.

[Means for Solving the Problems] In order to solve the above problems, the method for producing an inorganic porous body according to the present invention is to replace the solvent absorbed by the swellable layered compound in a swollen state with liquid carbon dioxide or a critical state. It is characterized by drying by extraction with carbon dioxide.

In the method for producing an inorganic porous body according to the present invention, a pillar material may be inserted between the layers of the swellable layered compound in the swollen state.

Furthermore, in the method for producing an inorganic porous body according to the present invention, an inorganic pillar material whose surface is modified with at least one compound selected from a cationic inorganic compound and an alcoholate may be used as the pillar material. good.

Further, in the method for producing an inorganic porous body according to the present invention, the pillar material inserted between the layers of the swellable layered compound in the swollen state is an organic pillar material, and when drying, the pillar material inserted between the layers of the swellable layered compound is an organic pillar material. may be removed at the same time.

[For production]

When drying a layered compound in a swollen state to obtain an inorganic porous body, the solvent absorbed by the layered compound is extracted with carbon dioxide in a liquid state or a critical state, and then dried. The surface energy of the particles constituting the pillar material used for this purpose is not taken away or is difficult to be taken away. Since there is no or little reduction in surface energy, agglomeration is less likely to occur. For this reason, the layered compound particles are dried in a manner that maintains their state in the solvent, and there are gaps between the particles, such as a card house structure (for example, a structure in which layered compound particles are adjacent to each other in different orientations). is successfully formed, and a sufficiently wide interlayer distance is maintained by preventing condensation of the solvent between the layers of the layered compound and aggregation of the pillar material.

If drying is performed by normal heating without inserting a pillar material between the layers of a swellable layered compound, the layer spacing that once opened due to swelling will narrow again, but drying using carbon dioxide in a liquid state or a critical state For example, since voids similar to the above-mentioned cardhouse structure are created between particles, a porous material with a large pore volume can be obtained despite a narrow layer spacing.

When the pillar material is inserted between the layers of the swellable layered compound in a swollen state, the spaces between the layers are expanded, so that an inorganic porous body having a sufficiently wide interlayer distance can be obtained.

When the inorganic pillar material is located between the layers of the swellable layered compound, the inorganic pillar material acts as a support and ensures a wider interlayer distance.
Moreover, if the surface of the inorganic pillar material is modified with a cationic inorganic compound or an alcoholate, the pillar material is likely to be fixed between the layers of the layered compound.

The organic pillar material is eventually removed from between the layers, but
When drying using carbon dioxide in a liquid state or critical state, if the organic pillar material is extracted into the carbon dioxide in the liquid state or critical state and dried so as to flow out together with the fluid, the organic pillar material will be removed from between the layers. It removes it. Therefore, the organic pillar material can be removed during drying without providing a step such as baking for removing the organic pillar material.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to the drawings showing embodiments thereof.

FIG. 2(b) shows the structure of inorganic layered porous particles A' obtained by a conventional manufacturing method. As shown in the figure, the inorganic layered porous particles A' have voids 2' formed by the pillar material 4 between the layers 1 and 1 of the inorganic layered compound.
has. However, in this inorganic layered porous particle A',
Because the agglomeration and condensation occur during the drying stage, undulations occur in J'il, and as a result, the gap between Fiil and 1 becomes narrower between the pillar materials 4 and 4, and the gap between layer 1 and pillar 1 becomes narrower. The contact area with material 4 is also larger,
This increase in contact area also increases the amount of heat transfer between solids.

FIG. 2(a) shows the structure of inorganic layered porous particles A obtained by an example of the method for producing an inorganic porous body according to the present invention. In this inorganic layered porous particle A, since aggregation and condensation do not occur during drying, unlike the structure of the conventional inorganic layered porous particle A', there is no undulation in the layer 1. The gap 2 between the pillar materials 4 and 1 is not narrowed even between the pillar materials 4 and 4, and the gap 2 between the layer 1
The contact area between the pillar material 4 and the pillar material 4 is smaller than that of the conventional one. Therefore, the amount of solid-solid heat transfer between the layer 1 and the pillar material 4 is small.

Examples of the swelling layered compound include Na-montmorillonite,
Ca-montmorillonite, 3-octahedral synthetic smectite (e.g., synthetic sabonite, Na-hectolite,
(Li-hectolite, Na-teniolite, Li-teniolite, etc.), acid clay, synthetic mica, etc.
The present invention is not limited to these as long as it is a swellable layered compound. In addition, when using a layered compound that is difficult to swell, such as Ca-montmorillonite or acid clay, it is necessary to apply a strong shearing force by crosstalk or the like during l11 wetting.

Unlike natural products such as the above-mentioned montmorillonites, 3-octahedral synthetic smectite is a synthetic product, so it contains extremely few impurities such as iron, and the resulting inorganic porous material is transparent (semi-transparent). It turns out. For example, 3-octahedral synthetic sabonite (hereinafter referred to as "synthetic sabonite") has a three-layer structure in which a so-called Mg octahedron is located in the center, and so-called St tetrahedrons are located on the front and back sides of the Mg octahedron. It is. Synthetic savonite is a very small particle, for example, 1/10 to 1/20 the size of Na-montmorillonite or synthetic mica. Therefore,
There are enough narrow gaps in the card house structure between the particles,
For example, an inorganic porous material with very good heat insulation properties can be obtained.

The inorganic pillar material inserted between the layers of the swellable layered compound is a colloidal inorganic compound, alcoholate (hereinafter, alcoholate for pillar material is referred to as "alcolate I").
A hydrolyzate of , etc. is used.

Colloidal inorganic compounds are not particularly limited, but include:
It is preferable to use a thermally stable oxide or one that expands when heated. Examples of such compounds include SiO2, SbxOs, Fex
Os, Alx Ox, Ti1t, zro! etc. These can be used alone or in combination. Although the particle size of such a colloidal inorganic compound is not particularly limited in the present invention, it is preferably about 50 to 150 particles.

As alcoholate I, for example, 5i (OC! H
s)i, S i (OCHs)4, Ge (QCs
H? )41. Ge (QC! Hz) + etc. can be used, but other than these can also be used.

The above-mentioned inorganic pillar material may be inserted between the layers of the swellable layered compound as it is, but its surface may be a cationic inorganic compound, an alcoholate other than the alcoholate I (hereinafter referred to as modification of the pillar material). The alcoholate used for
The polymer may be modified with at least one of alcoholate 'II J) and ester before being inserted between the layers.

Cationic inorganic compounds used to modify the surface of inorganic pillar materials include titanium compounds, zirconium compounds, hafnium compounds, iron compounds, copper compounds, chromium compounds, nickel compounds, and zinc compounds. compounds, aluminum compounds, manganese compounds, phosphorus compounds, boron compounds, etc., for example, T
There are metal chlorides such as i Cl m, metal oxychlorides such as Zr0C1, and other nitrate compounds, etc.
Other materials may also be used. In addition, as alcoholate ■, T i (OR) 4 , Z r
(OR), , PO(OR), , B (OR)1, etc. can be used, and specifically, for example, Ti(Q
Cs Ht ), , Zr (QCs Ht ), ,
PO(QCHl)s, PO(OCtHs)*
, B (QCHl), , B (oc, H,)4, etc., but other than these may also be used. Note that these can be used alone or in combination.

Further, in this invention, an organic pillar material consisting of at least one selected from a water-soluble polymer compound, a quaternary ammonium salt, a higher fatty acid, an amphoteric surfactant, and a choline compound is used alone or together with an inorganic pillar material. , can also be inserted between layers 1 and 1 of the swellable layered compound.

Various water-soluble polymer compounds can be considered, including polyvinyl alcohol, polyethylene glycol, polyethylene oxide, methylcellulose, carboxymethylcellulose, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinylpyrrolidone, etc. .

Furthermore, various types of quaternary ammonium salts and higher fatty acids can be considered, but among them, those having groups such as octadecyl group, hexadecyl group, tetradecyl group, and dodecyl group are particularly preferable. Such quaternary ammonium salts include octadecyltrimethylammonium salt, diotadecyldimethylammonium salt, hexadecyltrimethylammonium salt, diotadecyldimethylammonium salt, tetradecyltrimethylammonium salt, diotadecyldimethylammonium salt, etc. Higher fatty acids include valmitic acid,
These include stearic acid, oleic acid, and linoleic acid.

Various choline compounds can be considered, but for example, (HOCH,C)(,N(CHI),)"0H-
Cs H14c l N O.

Ci HI4N OC4Hs O4, Cs Hl 4 N OC-Ht Ot, Cs Hl
4N OC-Ht*Ot is preferred.

In addition, various types of amphoteric surfactants can be considered, but among them, the cation part is an aliphatic amine type, and the anion part is a carboxyl group, sulfate ester group, sulfone group, or phosphate ester group. Those having at least one group selected from these are preferred.

In the present invention, as the organic material and the lar material, materials other than those mentioned above can be used as long as they can be inserted between the layers of the swellable layered compound.

Next, the method for manufacturing an inorganic porous body according to the present invention will be described in detail based on a schematic diagram representing one embodiment thereof.

Substances such as swelling clay minerals, as shown in Figure 3,
It is made of a collection of swellable inorganic layered compounds A. This compound A1, which is the main material, is mixed with a solvent such as water, and further,
If necessary, the mixture is kneaded and, as shown in FIG. 4, solvent 3 is included between r@1 and 1 to swell the mixture in advance. Water is generally used as a solvent, but other polar solvents such as methanol, ethanol, DM
F, DMSO, acetone, etc. may be used alone or in combination. Alternatively, a mixed solvent of at least one of these and water may be used.

Next, when using, for example, a polymer of alcoholate as the inorganic pillar material, a solvent such as ethanol or isopropanol is added to the alcoholate to dissolve it, and water and a reaction catalyst such as hydrochloric acid (hydrolysis (catalyst) and mix to cause a hydrolysis reaction. This hydrolysis reaction is preferably carried out at a temperature of about 70°C, although it is not particularly limited. In addition, at the stage where the hydrolysis reaction of the inorganic pillar material has progressed to a certain extent and the nucleus 41 has grown (see Fig. 5 (C1)), alcoholate ■ or a cationic inorganic compound is added to the reaction solution. When the compound is subjected to an addition reaction on the surface of the nucleus, a reactant 42 whose surface is positively charged is obtained as shown in FIG. 5(b).The inorganic pillar material made in this way 42, an organic pillar material 51 made of a water-soluble polymer compound, a quaternary ammonium salt, or the like is used in combination, if necessary.

When a colloidal inorganic compound is used as the inorganic pillar material, it may be used as it is as shown in FIG. A reactant may also be obtained in the same manner by adding alcoholate (2) or a cationic inorganic compound and causing an addition reaction with these compounds on the surface of the core 41 made of the inorganic pillar material as in the previous case.

Further, when the organic pillar material 51 is used in combination with the unmodified core 41, the result is as shown in FIG. 5(a).

A liquid mixture containing the above components is mixed with the swelling layered compound which has been swollen in advance, and the mixture is intercalated between layers 1 and 1 of the layered compound. Although the temperature during mixing is not particularly limited in the present invention, it is preferably around 60 to 70°C.

In addition, when a water-soluble polymer compound or a quaternary ammonium salt is blended as an organic pillar material, as shown in FIGS. 6(a) and (b), this organic pillar material 5 is At the same time, it acts to slow down the movement of the inorganic pillar material 4 and to hold it between the layers 1 and 1. When no organic pillar material is added, as shown in Fig. 6 (C) The retained inorganic pillar material 4 is as follows.
Thereby, the space between layers 1 and 1 is kept spread apart. In addition, when this inorganic pillar material is a reactant 4' whose surface is modified, the positive charge on its surface is electrically connected to the negative part on the surface of layer 1, as shown in FIG. 6(b). In order to bond to the inorganic pillar material 4', the wide layer 1
It will be held and fixed between 1 and 1.

Furthermore, as shown in FIG. 7, an inorganic porous body can be made by inserting an organic pillar material 5 between N1 and 1 of the swellable layered compound, but not inserting an inorganic pillar material.

After the reaction solution as described above is centrifuged to turn the sample into a gel state, it is oriented into, for example, a plate shape using a spatula or the like. Carbon dioxide (carbonic acid) is in a liquid or critical state when the plate-shaped body is oriented (in Fig. (critical point CP)]. For example, the solvent of the swollen layered compound is extracted and dried by flowing liquid carbon dioxide or carbon dioxide in a critical state. Methods for producing carbon dioxide in a liquid state include, for example, directly using a liquefied carbon dioxide gas cylinder, or vaporizing the carbon dioxide gas, compressing it with a pump, and liquefying it again (see Figure 1). Drying is completed by allowing liquids and fluids in this state to escape from the system.

In addition, if the solvent used for swelling is a solvent that is not or is difficult to be extracted by carbon dioxide in a liquid state or critical state, if necessary, such a solvent may be added to a solvent that is compatible with carbon dioxide in the above-mentioned state. This solvent can be extracted from the system with carbon dioxide in the above-mentioned state and dried. For example, when the inorganic porous material is swollen with water, the water is replaced with ethanol, etc., and the ethanol is extracted with carbon dioxide in a liquid or critical state and dried. The porous structure is maintained as it is before drying, so the pore volume (specific volume) is extremely large compared to conventional hot air drying or freeze drying, and it has extremely high heat insulation properties.

Specific examples and comparative examples of the present invention are shown below, but the present invention is not limited to the following examples.

Example 1 - Alcoholate I S i (QCs Hs )
Ethanol (special grade reagent manufactured by Hanai Chemicals ■) was added to 4 (manufactured by Hirai Chemicals ■) and thoroughly mixed to form a solution.

Approximately 50% of 2N hydrochloric acid was added to this solution, and the solution was heated to 70°C to carry out a hydrolysis reaction to form the core of the inorganic pillar material.

Next, Ti, which is a cationic inorganic compound, is added to this solution.
Cj! A 4 mol/l aqueous solution of No. 4 (manufactured by Hirai Chemical Co., Ltd.) was added and thoroughly mixed to cause a reaction, thereby obtaining a reaction solution in which the reactants were dispersed. This reaction solution was mixed with a 0.8% aqueous solution of Na-montmorillonite (Nipia F manufactured by Kunimine Industries), which is a swelling layered compound, which had been swollen with water in advance, and the mixture was heated at 60°C for 1.5 hours. An insertion reaction was performed.

After the reaction, washing and centrifugation are repeated several times with ethanol, oriented into a plate shape with a spatula, and liquid carbon dioxide (
It was dried for 48 hours at 20° C. and 150 atm).

The blending ratio of each component is 5i (QC, Hi,
: Ethanol: 2N hydrochloric acid: T i Cj! 4=17
= 18:65:1.7, and the blending ratio of Na-montmorillonite and SiOt was 1:0.6 in terms of weight ratio.

Example 2 - TiC, a cationic inorganic compound, as an inorganic biller material
j! a (manufactured by Hirai Chemical Co., Ltd.), and a 4 mol/1 aqueous solution thereof was swollen with water in advance to create Na-montmorillonite (Kunimine Kogyo Co., Ltd.), which is a swellable layered compound.
The mixture was mixed with a 0.8% aqueous solution of Kunipia F (trade name: Kunipia F), and an insertion reaction was carried out at 60°C for 1.5 hours. Except for this, an inorganic porous material sample was obtained in the same manner as in Example 1.

Example 3 - As an inorganic pillar material, a colloidal inorganic compound, Lucitania Zirconia coated silica soil (manufactured by Nissan Chemical Industries, Ltd., trade name: Snowtex TZK) was used. Except for this, an inorganic porous material sample was obtained in the same manner as in Example 1.

Example 4 - T i (OCm Hv
) 4 was used in the same manner as in Example 1,
An inorganic porous material sample was obtained.

Example 5 - Alcoholate I S i (OCt Hs ) 4
(manufactured by Hirai Chemicals) and ethanol (manufactured by Hirai Chemicals)
(manufactured special grade reagent) was added and mixed thoroughly to form a solution. 2N hydrochloric acid was added to this solution, and it was heated to 70°C to perform a hydrolysis reaction to form the core of the inorganic pillar material.

Next, Ti, which is a cationic inorganic compound, is added to this solution.
CJ! A 4 mol/l aqueous solution of a (manufactured by Hirai Chemicals ■) was added and thoroughly mixed, and a reaction was carried out to obtain a reaction liquid in which the reactants were dispersed.

Octadecyltrimethylammonium chloride (Cation AB, manufactured by NOF Corporation), which is a quaternary ammonium salt, was sufficiently mixed with the reaction solution thus obtained to obtain a mixed solution.

The resulting mixed solution was mixed with a 0.8% by weight aqueous solution of Na-montmorillonite (NIVIA F manufactured by Kunimine Kogyo ■), which is a swelling layered compound that had been swollen with water in advance, and heated to 60°C for 1. The insertion reaction was carried out for 5 hours.

After the reaction, washing with ethanol and centrifugation are repeated several times, followed by liquid carbon dioxide (20°C, 150 atm).
was extracted and dried for 24 hours to obtain an inorganic porous material sample.

The blending ratio of each component is 5i (QCsHs) in molar ratio.
4: Ethanol: 2N hydrochloric acid: T i Cj! a=
The weight ratio of Na-montmorillonite, 5ins and octadecyltrimethylammonium chloride was 1F0.6:1.

Example 6 In Example 1, instead of drying with liquid carbon dioxide for 48 hours, critical state carbon dioxide [temperature 31°C (
An inorganic porous material sample was obtained in exactly the same manner as in Example 1 except that it was dried at 31.1° C.) and 72.8 atm) for 48 hours.

In the above examples, a supercritical fluid extraction device (type 2I!) manufactured by Pressure Instruments was used for drying with carbon dioxide in a liquid or critical state.

- Comparative Example 1 - After the insertion reaction in Example 1, without washing with ethanol, in the swollen state, under atmospheric pressure, at a temperature of 60 ° C.
The sample was dried for 12 hours to obtain an inorganic porous material sample.

Specific surface area, pore volume, interlayer distance, apparent density, and thermal conductivity were measured for the plate-shaped inorganic porous body samples obtained in the above Examples and Comparative Examples. The results are shown in Table 1.

Note that the specific surface area and pore volume are B in the nitrogen adsorption method.
In the ET method, the interlayer distance (interlayer spacing) was determined by dIII measurement in X-ray diffraction. Also, the thermal conductivity is AS
It was measured by a heat flow meter method based on TM-C-518.

The product name of each measuring device is as follows.

Nitrogen adsorption method: Manufactured by Quantachrome Co., Ltd., trade name: Autosorb 6 The pore volume and interlayer distance were larger, and the apparent density and thermal conductivity were smaller than that of the 200% carbon nanotube. This is considered to be because the above-mentioned phenomenon occurred due to the difference in the drying method.

The specific surface area of Kunipia F used in the examples and comparative examples is In-r/g, and the interlayer distance d0. was 9.6 people, and the pore volume was very small.

The manufacturing method of the present invention has the advantage that it can be performed at lower pressure and/or lower temperature than drying in a supercritical state.

In the porous body of the example, as shown in FIG. 8, the particles A are dried without being aggregated, and a large number of voids are formed between the particles A. Particle A″ where pillar material is not inserted
Since the voids between the particles A'' are formed in the same way, the thermal conductivity becomes low.

〔Effect of the invention〕

As described above, in the method for producing an inorganic porous body according to the present invention, drying is performed using carbon dioxide in a liquid state or a critical state. A porous body with extremely large pore volume and sufficiently low thermal conductivity can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a phase diagram showing the relationship between pressure P-temperature T-density ρ of carbon dioxide, and FIG. Structure explanatory diagram of inorganic layered porous particles A in the body, Figure 2 (b
) is a structural explanatory diagram of inorganic layered porous particles A' in an inorganic layered porous material obtained by a conventional method for producing an inorganic porous material,
Figure 3 is a schematic side view of a swellable layered compound, Figure 4 is an explanatory diagram of the state leading to swelling, and Figure 5 (al is a compound formed by hydrolyzing a colloidal inorganic compound or an alcoholate. An explanatory diagram of a state in which an organic pillar material is blended with an inorganic pillar material, Fig. 5. Figure 10) is an explanatory diagram of the state of the inorganic pillar material formed from a colloidal inorganic compound or alcoholate I, and the mixture of Figure 6 (al is Ta in Figure 5) is inserted between the layers of the swellable inorganic layered compound. Figure 6 tb+ is an explanatory diagram of the state in which the mixture of Figure 5 (bl) is inserted between the layers of the swellable inorganic layered compound, and Figure 6 (C) is the diagram of Figure 5 (C). Figure 7 is a schematic diagram showing the state in which the mixture is inserted between the layers of the swellable inorganic layered compound, and Figure 8 is a schematic diagram showing the state in which the organic pillar material is inserted between the layers of the swellable layered compound. It is a schematic diagram showing one example of a porous body obtained by the manufacturing method. A, A'... Inorganic layered porous body A,... Swellable inorganic layered compound 1... Layer 2.2'. ...Gap 3...
・Solvent 4...Inorganic pillar material 4'...Modified inorganic pillar material 5...Organic pillar material @ 1 Illustration agent Patent attorney Takehiko Matsumoto (c) Figure 3

Claims (1)

[Claims] 1. A method for producing an inorganic porous body by drying a swellable layered compound in a swollen state, in which the solvent absorbed by the swellable layered compound is replaced with liquid carbon dioxide or carbon dioxide in a critical state. 1. A method for producing an inorganic porous material, which comprises drying by extraction. 2. The method for producing an inorganic porous body according to claim 1, wherein the swellable layered compound in a swollen state has a pillar material inserted between its layers. 3. The method for producing an inorganic porous body according to claim 2, wherein the pillar material is an inorganic pillar material whose surface is modified with at least one compound selected from cationic inorganic compounds and alcoholates. 4. The method for producing an inorganic porous body according to claim 2, wherein the pillar material is an organic pillar material, and the organic pillar material is simultaneously removed from between the layers during drying.