JP2003246686A - Method of producing spinel porous body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for inexpensively producing a spinel porous body which has excellent heat resistance, corrosion resistance and thermal shock resistance. <P>SOLUTION: The method of producing a spinel porous body includes a stage where a mixture of tervalent metal oxide (M<SP>3</SP><SB>2</SB>O<SB>3</SB>) powder and bivalent metal sulfate (M<SP>2</SP>SO<SB>4</SB>) powder is made into a molding, and a stage where the molding is sintered to produce spinel in the sintered compact. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a porous ceramic body substantially composed of spinel, and more particularly to a method for producing a spinel porous body suitable for use in a ceramic filter or the like.

[0002]

2. Description of the Related Art Porous ceramics are excellent in heat resistance and corrosion resistance and are therefore used as filtration filters or catalyst carriers used under high temperatures where organic materials cannot be used or under conditions of strong acidity and alkalinity.

Examples of the material actually used as the ceramic porous body include cordierite, alumina, and mullite. It is also reported that a ceramic porous body made of these materials is further prepared with a film of silica, zeolite or the like and applied. The above-mentioned ceramic porous bodies are all made of oxides, but in addition to these, porous bodies of silicon carbide and silicon nitride have been developed.

As a method for producing a porous body, there have hitherto been used a method of mixing a foamable or combustible substance with a ceramic powder or a slurry thereof and firing it, a method of adhering ceramics to a foam itself such as urethane and firing it. Are known. In JP-A-5-238848 and JP-A-6-24859, sludge is adhered to a synthetic resin foam having a three-dimensional network skeleton structure to remove excess sludge, followed by drying and firing to non-oxidize. A method of forming a green ceramic is disclosed.

Further, in JP-A-1-188479, powders having different particle diameters are mixed and then fired,
A method of forming pores between particles is disclosed, and a silicon powder having a specific particle diameter and a silicon nitride powder having a specific particle diameter are mixed at a specific ratio and then fired in a nitrogen atmosphere to obtain a silicon nitride material. A porous body is formed. On the other hand, there is also known a method of manufacturing a cordierite-based or alumina-based porous body having a honeycomb structure by using an extrusion molding method.

The above-mentioned ceramic porous body physically removes and separates solids from a gas or a liquid as a filter or a catalyst carrier, separates and concentrates a target specific gas from a mixed gas, and produces sound insulation ( It has applicability in a wide range of fields, such as being used as a soundproofing material or a heat insulating material.

[0007]

As described above, the ceramic porous body is excellent in heat resistance and corrosion resistance and therefore cannot be used as an organic filter under high temperature conditions or under acidic or alkaline strong conditions. It has excellent properties as a catalyst carrier.

Among the above-mentioned ceramic porous bodies, as a cordierite porous body, for example, a honeycomb type is often used, but it cannot be said that the heat resistance is sufficient.
For this reason, it has not reached widespread use. Further, although the alumina porous body is widely used as a separation filter for solid-liquid or solid-gas separation, its thermal shock resistance is not yet sufficient and it cannot be used in an environment involving a sudden temperature change. There is an inconvenience. Further, the above cordierite-based porous body and the alumina-based porous body are generally used in a honeycomb form, but in order to obtain such a honeycomb form, there is a disadvantage that it is costly. is there. Further, porous bodies of silicon carbide and silicon nitride, which are often proposed in order to solve such inconvenience, have high cost of raw materials, high production cost, and sufficient oxidation resistance at high temperature. However, there are inconveniences such as not being said, and it is currently used only for some applications.

On the other hand, spinel has the property of being excellent in heat resistance. Furthermore, among oxides,
It has the characteristics of excellent corrosion resistance and good thermal shock resistance. Utilizing these characteristics, spinel is used as a dense refractory material, but it has been difficult to easily produce a uniform porous body, and a porous body having a higher porosity is prepared. It's not easy and not fully utilized.

From the viewpoint of the method for producing a porous ceramic body, it is difficult to control the particle diameter and the particle size distribution by a method of mixing a foamable or combustible substance with ceramic powder or its slurry and firing the mixture. There is a risk. Further, in the method in which the ceramic raw material is adhered to the foam itself and then fired, the ceramic porous body has a hollow structure, and there is a possibility that sufficient strength cannot be obtained.

As described above, a method for producing a ceramic porous body by an inexpensive method while balancing various required characteristics, particularly a ceramic porous body having excellent properties including a spinel phase and a production method therefor are provided. Was desired.

Therefore, the present invention has been made to solve the above problems, and the present invention provides corrosion resistance, heat resistance,
An object of the present invention is to provide a spinel-containing porous body having excellent thermal shock resistance and which can be manufactured at low cost, and a manufacturing method thereof.

[0013]

Means for Solving the Problems As a result of intensive studies by the present inventors in order to solve the above object, the present inventors achieved the above object by providing a method for producing a spinel porous body of the present invention. The inventors of the present invention have found out what can be done and have reached the present invention.

Therefore, according to the present invention, trivalent metal oxide (M ³ ₂ O ₃ ) powder and divalent metal sulfate (M ² SO ₃ ) are used.
₄ ) A method for producing a spinel porous body is provided, which includes a step of forming a mixture with powder into a compact, and a step of firing the compact to generate spinel in the sintered body. The ^M ₃ 2 O
₃ is at least one selected from the group consisting of Al ₂ O ₃ , Fe ₂ O ₃ and Cr ₂ O _3;
² SO ₄ is preferably at least one selected from the group consisting of MgSO ₄ , FeSO ₄ , NiSO ₄ and ZnSO ₄ .

Further, M ³ ₂ O ₃ and M ² used in the present invention
SO ₄ is preferably Al ₂ O ₃ and MgSO ₄ . In the molded body, the Al ₂ O ₃ content is 35.0 mass% to
77.0 mass% (hereinafter, simply abbreviated as%), the MgSO
₄ is preferably contained in an amount of 23.0% to 65.0%.

In the present invention, it is preferable to further include a step of leaching a substance other than the spinel from the sintered body. Specifically, it is preferable to wash with an acid, water or a mixture thereof to dissolve out the acid-soluble substance or the water-soluble substance from the sintered body.

Further, it is preferable to use ultrasonic waves together with the leaching of the acid-soluble substance or the water-soluble substance.

In the present invention, the firing temperature is 120.
It is preferably 0 ° C. or higher and 1800 ° C. or lower.

Further, in the present invention, it is preferable that the porous body substantially comprises a spinel phase.

Here, the spinel has the chemical formula M ² O · M.
³ ₂ O ₃ , M ³ is Al ^{3 +} , Fe ³⁺ , Cr ^3+, etc., M ² is Mg ²⁺ , Fe ²⁺ , N
Examples thereof include i ²⁺ , Zn ^{2+, and the} like, but are not limited thereto.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a spinel porous body according to the present invention comprises the step of preparing a mixture of trivalent metal oxide (M ³ ₂ O ₃ ) powder and divalent metal sulfate (M ² SO ₄ ) powder. A method for producing a spinel-like porous body, comprising: a step of forming a compact, and a step of firing the compact to generate spinel in a sintered body.

M ³ ₂ O ₃ used in the present invention is Al
₂ O ₃ , at least one selected from the group consisting of Fe ₂ O ₃ and Cr ₂ O ₃ , and M ² SO ₄ is
MgSO ₄ , FeSO ₄ , NiSO ₄ and ZnSO ₄
It is preferably at least one selected from the group consisting of These compounds have a purity of 99% excluding H ₂ O.
The above is preferable. The particle size is not particularly limited, but powder is preferred.

Further, M ³ ₂ O ₃ and M used in the present invention
² SO ₄ includes Al ₂ O ₃ and MgSO ₄ , respectively.
Is more preferable.

In the present invention, the mechanism of pore formation of the porous body is that the reaction of the following formula (1) occurs during sintering, that is, it is due to the SO ₃ gas produced, that is due to the change in volume before and after the reaction, and Porosity is also considered to be generated by substantially leaching out substances that do not participate in the reaction.

[0025]

[Chemical 1]

As Al ₂ O ₃ used in the present invention, α-
Alumina (corundum) may be mentioned, but in the present invention, γ represented by AlO (OH) in addition to α-alumina.
-Alumina or aluminum hydroxide (Al (OH)
₃ ) can be used. These compounds change to α-alumina at a temperature of 1100 ° C. or lower, generate H ₂ O in the process of this change, and can obtain higher porosity. Further, by changing the particle size of these powders, the pore diameter and porosity of the spinel porous body can be controlled. The particle size of the powder used in the present invention is not particularly limited, and any particle size can be used as long as the desired pore size and porosity can be appropriately obtained.

As MgSO ₄ used in the present invention, commercially available magnesium sulfate can be used, and a hydrated salt may be used. When magnesium sulfate is a hydrous salt, it is convenient because dehydration leads to pore formation. Further, the particle size of magnesium sulfate is not particularly limited in the present invention, and may be any particle size as long as a desired pore size and porosity can be appropriately obtained.

The composition ratio of M ³ ₂ O ₃ and M ² SO ₄ used in the present invention can be appropriately set by the combination of M ² and M ³ . In the present invention, the composition ratio of M ³ ₂ O ₃ and M ² SO ₄ is such that the content of M ³ ₂ O ₃ is 40 mol% to 70 mol.
%, M ² SO ₄ content of 30 mol% to 60 mol%
It is preferable that

Further, M used in the present invention^Three _TwoO_ThreeIs Al_Two
O_ThreeAnd M^TwoSO_FourIs MgSO_FourIf
In the molded body, Al_TwoO_Three35.0% to 77.0%,
MgSO_Four23.0% to 65.0%, respectively
Is preferable. Molded Al _TwoO_ThreeAnd MgSO_FourIncluding
If the content is in the above range, high porosity, high specific surface area,
A porous body having high strength can be obtained. However, the molded body
Al_TwoO_ThreeContent exceeds 77.0% and MgSO
_FourWhen the content is less than 23.0%, the porosity is high.
It becomes difficult to obtain the pores. On the other hand, the Al_TwoO
_ThreeContent less than 35.0% and MgSO_FourContent is
If it exceeds 65.0%, it becomes difficult to obtain a porous body.
The tendency is that the strength is insufficient when formed as a sintered body.
Becomes

Various kinds of mixing / grinding means such as a ball mill and a planetary mill can be used for mixing these powders, and the mixing / grinding can be carried out in dry or wet using these mixing / grinding means. When wet mixing,
Since M ² SO ₄ is water-insoluble, water (H 2
₂ O) can be used. Therefore, the manufacturing cost of the spinel porous body of the present invention can be reduced.

In the method for producing a spinel porous body of the present invention, a mixed powder of M ³ ₂ O ₃ powder and M ² SO ₄ powder is then molded. A mold uniaxial compression method or a cold isostatic press (CIP) can be used for the molding, but a method other than these, for example, a slurry casting method, an extrusion molding method or the like may be used. The shape of the spinel porous body of the present invention is not particularly limited, but it is preferably disk-shaped or hollow cylindrical.

In the method for producing a spinel porous body of the present invention, the molded body obtained is then fired to form a spinel phase. An electric furnace equipped with a heating element such as molybdenum silicide can be used for the firing, and the firing temperature is 12
00 ° C or higher and 1800 ° C or lower, more preferably 1400 ° C
The above is performed at 1600 ° C. or less. Calcination temperature is 1800 ℃
If it exceeds, sintering tends to proceed, and it tends to be difficult to obtain a porous body. The time for the above-mentioned firing can be appropriately set depending on the shape and size of the target spinel porous body,
In the present invention, specifically, a firing time of about 4 hours can be adopted.

Then, in the method for producing a spinel porous body of the present invention, it is preferable that substances other than spinel are substantially leached. Specifically, the obtained calcined product was washed with an acid, water or a mixture thereof to decompose M ² SO ₄ into M.
Leach out acid-soluble substances or water-soluble substances such as ² O. Acids that can be used in the present invention include inorganic acids, organic acids, or mixtures thereof. Specifically, hydrochloric acid (HCl) can be used. When hydrochloric acid is used, its concentration is 0.1 mol / L to 1.0 mol / L
It is preferable that the range is However, other concentrations may be used.

When an inorganic acid or organic acid other than HCl is used, the concentrations of these acids can be set appropriately. Further, in the present invention, water may be used alone depending on the powder to be mixed. The temperature for carrying out the leaching step with an acid, water or a mixture thereof can be appropriately set, but the temperature of the acid, water or a mixture thereof may be 50 ° C. to 80
C. is preferable because leaching is promoted.

When ultrasonic waves are used together during leaching, leaching can be further promoted. The ultrasonic wave means is not particularly limited as long as the ultrasonic wave can appropriately act on the fired body, but for example, a commercially available ultrasonic cleaning machine can be used. When leaching with water, M ² O can be recovered and reused.

The present invention will be described below with reference to examples, but the present invention is not limited to the examples described below.

【Example】

Example 1 Various trivalent metal oxide powders and divalent metal sulfate powders were mixed so that the trivalent metal oxide powder and the divalent metal sulfate powder were equimolar. Were weighed and mixed in the proportions shown in, and mixed with ethanol as a medium for 20 hours. After mixing, it was dried to obtain a raw material powder.

[0038]

[Table 1]

The raw material powder prepared as described above was used as 35
It was molded at a pressure of 10 MPa using a die of mm × 55 mm, and then CIP was performed at a pressure of 150 MPa to obtain a molded body. Next, the obtained molded body was heated at a temperature rising rate of 100 ° C./hour in an electric furnace using molybdenum silicide as a heating element to obtain 1
It was fired by heating to 600 ° C. and then holding it for 4 hours.

Further, the fired body was immersed in a 1M HCl aqueous solution heated to 70 ° C. for 20 hours to be leached. Then, it was further washed twice with water, and the steps from immersion to washing with water were repeated 5 times in total.

The obtained porous body was processed into 3 mm × 4 m
A m × 40 mm prism was obtained as a sample for evaluation. The porosity of this sample was measured by the mercury penetration method. Also,
According to JIS1601, the three-point bending strength was measured at room temperature. Table 2 shows the results of porosity measurement and three-point bending strength test.
Shown in. The crystal phase of the obtained porous body was analyzed by X-ray diffraction (C
uKα, 40 kV, 0.1 A, scanning speed 0.03 ° /
When identified in s), a spinel phase was confirmed.

[0042]

[Table 2]

From Tables 1 and 2, a spinel-like porous material having both high porosity and high strength was obtained by firing and leaching a mixed powder of trivalent metal oxide powder and divalent metal sulfate powder. You can see that

Example 2 MgSO ₄ powder and Al ₂ O ₃
The powder and the powder were weighed and mixed in the proportions shown in Table 3, and the mixture of Example 1
Mixing, firing and leaching treatment were carried out in the same manner as in 1. to obtain a porous body.
Further, the porosity and the three-point bending strength of the porous body obtained in the same manner as in Example 1 were measured. The results are shown in Table 3.

[0045]

[Table 3]

It can be seen from Table 3 that a spinel-like porous material having high strength can be obtained by firing a mixed powder of MgSO ₄ powder and Al ₂ O ₃ powder and subjecting it to leaching treatment. When the crystal phase of the porous body obtained in the same manner as in Example 1 was identified, in addition to spinel, corundum was also identified for Samples B1 and B2, but it was found to be a spinel single phase except for Samples B1 and B2. confirmed. Sample B shown in Table 3
The specific surface areas of 3, B5, and B7 were measured using the mercury penetration method. The specific surface areas (m ² / kg) of Samples B3, B5, and B7 are 7720, 7740, and 387.
It was 0. These values were high values for the sintered body, and particularly, the values of Samples B3 and B5 were extremely high.

Example 3 Sample B in Example 2
Porous bodies of Samples C1, C2, and C3 shown in Table 4 were obtained in the same manner as in Example 2 except that no leaching treatment was performed for 3, B5, and B7. The porosity of the obtained porous body was measured in the same manner as in Example 1. The results are shown in Table 4. When the crystal phase of the porous body obtained in the same manner as in Example 1 was identified, a spinel phase was confirmed.

[0048]

[Table 4]

From Table 4, it is possible to obtain a spinel porous body by heat-treating the mixed powder of MgSO ₄ powder and Al ₂ O ₃ powder, and from the comparison with Table 3, there is a change in porosity due to leaching treatment. Recognize.

Example 4 MgSO ₄ powder and Al ₂ O ₃ powder were weighed and mixed in the proportion shown in sample C2 of Table 4,
A raw material powder was obtained by mixing in the same manner as in Example 1. The raw material powder was fired under the conditions shown in Table 5 and leached in the same manner as in Example 1 to obtain a porous body. The porosity of the obtained porous body was measured in the same manner as in Example 1. The results are shown in Table 5.

[0051]

[Table 5]

From Table 5, it can be seen that the porous body obtained from the mixed powder of sample C2 in Table 4 can stably obtain the spinel porous body under a wide range of firing conditions.

Comparative Example 1 Commercially available MgO.Al ₂ O
₃ (spinel MgO = 28.3%, Al ₂ O ₃ = 71.
7%) powder (sample R1) and MgO powder and Al ₂ O ₃ powder were weighed in the proportions shown in Table 6 (samples R2 to R5),
Mixing and firing were carried out in the same manner as in Example 1 to obtain a porous body.
The porosity of the obtained porous body was measured in the same manner as in Example 1. The results are shown in Table 6.

[0054]

[Table 6]

From Table 6, it can be seen that the MgO.Al ₂ O ₃ (spinel) powder and the mixed powder of MgO powder and Al ₂ O ₃ powder cannot provide a spinel-like porous material having a high porosity.

[0056]

As described above, according to the present invention, a mixed powder of a trivalent metal oxide powder and a divalent metal sulfate powder is molded and fired, so that a pore-forming agent is not particularly added. A spinel-like porous material is obtained by the spinel-forming reaction. The spinel porous body obtained by the method for producing a spinel porous body of the present invention has high porosity, specific surface area and strength,
Furthermore, it is possible to inexpensively provide a filter, a catalyst carrier, a soundproofing material, and a heat insulating material that can be used in a high temperature environment or a strong acid or alkaline environment. Therefore, the spinel porous body produced by the method for producing a spinel porous body of the present invention is useful as a filter, a catalyst carrier, a soundproofing material, and a heat insulating material having excellent heat resistance, thermal shock resistance, and corrosion resistance.

Continued front page    (72) Inventor Shinji Kondo             1150 Hazawa-machi, Kanagawa-ku, Yokohama-shi, Kanagawa             Asahi Glass Co., Ltd. F-term (reference) 4G019 GA04                 4G031 AA03 AA16 AA21 AA29 BA21                       BA23 BA26 CA01 CA09 GA11                       GA19

Claims (7)

[Claims] 1. A trivalent metal oxide (M ³ ₂ O ₃ ) powder and 2
A method for producing a spinel porous body, comprising: a step of forming a mixture with a valent metal sulfate (M ² SO ₄ ) powder into a compact; and a step of firing the compact to generate spinel in a sintered body. 2. The M^Three _TwoO_ThreeIs Al_TwoO_Three, Fe_TwoO_Three
And Cr_TwoO_ThreeAt least 1 selected from the group consisting of
More than one species, and said M^TwoSO_FourIs MgSO_Four, Fe
SO _Four, NiSO_FourAnd ZnSO_FourSelected from the group consisting of
The spin according to claim 1, wherein at least one kind of the spice is present.
A method for producing a flaky porous body. 3. The method for producing a spinel porous body according to claim 2, wherein the M ³ ₂ O ₃ is Al ₂ O ₃ and the M ² SO ₄ is MgSO ₄ . 4. The Al ₂ O ₃ in the molded body is adjusted to 35.0.
The manufacturing method of the spinel porous body according to claim 3, wherein the spinel-like porous body contains mass% to 77.0 mass% and MgSO ₄ of 23.0 mass% to 65.0 mass%, respectively. 5. The method for producing a spinel porous body according to claim 1, further comprising the step of leaching a substance other than the spinel from the sintered body. 6. The firing temperature is 1200 ° C. or higher and 1800 ° C.
It is the following, The manufacturing method of the spinel porous body of any one of Claims 1-5. 7. The porous body comprises a spinel phase.
7. The method for producing a spinel porous body according to any one of items 1 to 6.