JPH05287325A - Composite porous body of activated alumina and metal - Google Patents

Abstract

PURPOSE:To produce a composite porous body of activated alumina and metal with the alumina capable of being utilized for a catalyst carrier or an adsorbent. CONSTITUTION:Fine particles of alumina are deposited on the surface of a three-dimensional reticular metallic porous body as a carrier to obtain a porous body of the activated alumina and metal. The porous body is dipped in aq. aluminum hydroxide to deposit the aluminum hydroxide on the porous body surface, and the coated porous body is dried and calcined to remove the water of crystallization. The metallic porous body has a three-dimensional reticular structure and is obtained by compacting a superfine metal powder and then calcining the compact. The compact is calcined at a temp. 100-500 deg.C lower than the m.p. of the metal.

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 composite porous body of activated alumina and a metal for efficiently utilizing activated alumina utilized as a catalyst carrier or an adsorbent.

The composite porous material of the present invention is suitable as a material for a catalyst carrier for purifying automobile exhaust gas, a filter for removing and removing harmful substances in water, a deodorizing filter, and the like.

[0003]

2. Description of the Related Art A method for producing activated alumina is generally produced by heating aluminum hydroxide and separating water of crystallization.

Among them, according to the method of heating aluminum hydroxide produced by neutralization of aluminum salt to separate the water of crystallization, activated alumina having an ultrafine crystal structure is produced, and therefore the specific surface area is large and the activity is high. You get something.

However, there is a drawback that handling is difficult because the produced powder is fine.

[0006] For example, in order to make efficient contact with a gas fluid, the gas permeability cannot be maintained unless it is processed into granules or molded into a honeycomb shape.

This fine activated alumina can also be processed in accordance with a usual ceramic processing method, for example, a method of extrusion molding and firing, but if it is firmly sintered to obtain strength, the specific surface area becomes small and the activity becomes small. I lose my degree.

On the contrary, if the sintering is weakened in order to maintain the activity, the strength cannot be maintained, and when it comes into contact with water, problems such as cracking and pulverization occur, and it is difficult to completely solve the problem.

Further, in general, the catalyst and the adsorption reaction are diffusion-controlled, so that the activated alumina inside the molded body of the activated alumina processed into the molded body hardly contributes to the reaction.

[0010]

SUMMARY OF THE INVENTION In order to fully utilize the activity of fine activated alumina, an activated alumina material that exhibits breathability, thermal shock resistance, and vibration resistance strength over a long period of time is desired. The object is to provide a material that makes full use of the activity of fine activated alumina, secures air permeability, and enhances the strength of the structure for ensuring air permeability so that it can be used stably, and a manufacturing method thereof.

[0011]

DISCLOSURE OF THE INVENTION The present invention is a composite porous body of activated alumina and metal, characterized in that a three-dimensional mesh-like metal porous body is used as a carrier and alumina fine particles are supported on the surface of the carrier. ..

Further, in the present invention, the porous metal body is immersed in an aluminum hydroxide solution to deposit aluminum hydroxide on the surface of the porous metal body, dried, and then baked in a non-oxidizing atmosphere and treated with decrystallization water. A method for producing a composite porous body of activated alumina and a metal, comprising:

The present invention also provides a method for producing a composite porous body of activated alumina and a metal, wherein the porous metal body has a three-dimensional network structure obtained by molding and firing ultrafine metal powder having a size of 40 μm or less.

The present invention is also a method for producing a composite porous body of activated alumina and metal, which comprises firing the above-mentioned ultrafine metal powder at a temperature 100 to 500 ° C. lower than the melting point of the metal.

[0015]

The applicant of the present invention has previously disclosed Japanese Patent Application Laid-Open No. 02-019405,
Japanese Unexamined Patent Publication No. 02-254106 has proposed a method for producing a metal porous body by applying a kneaded product of a metal powder such as iron and a binder onto a resin foam and then firing the mixture.

This porous metal body has characteristics such as air permeability, thermal shock resistance, and vibration strength performance because it is a sintered metal particle body.

The inventors of the present invention have incorporated pores of several tens of μ or less in the structure of the metal porous body by stopping the sintering in the middle of sintering when producing the metal fine powder compact by sintering. A porous metal body is obtained, and the air permeability of the porous metal body is
It was confirmed that the properties such as the thermal shock resistance and the vibration resistance performance were comparable to those of the above-mentioned conventional porous metal body.

Metal powder and a binder such as polyvinyl alcohol are mixed and coated on urethane foam, or a honeycomb structure is molded by an extrusion molding method at a temperature 100 to 500 ° C. lower than the melting point of the metal in a non-oxidizing atmosphere. When sintered, it is possible to manufacture a metal porous body which is a structure having large pores of 0.1 mm or more, but the structure itself is a porous body having pores of tens of μm or less.

These metal porous bodies are generally superior in thermal shock resistance and vibration resistance as compared with ceramic sintered bodies.

The sintering temperature of the above-mentioned metal powder compact is set to a temperature which is 100 to 500 ° C. lower than the melting point of the metal, because the metal particles are completely melt-bonded to each other during the sintering process to form between the metal particles. The fine gap that had been created disappears.

When sintered at a temperature 100 to 500 ° C. lower than the melting point of the metal, the metal particles are fused only to the surface layer of the metal, so that fine gaps remain.

On the other hand, the finer the metal particles, the more quickly the melting point of the metal particles melts.

Therefore, a temperature lower than the melting point by 100 to 500 ° C. is selected depending on the kind of metal used and the particle size.

Examples of the metal for the carrier include Fe, Ni,
There are Cr, Cu, Zn, Al and the like, and these metals can be used alone or in combination.

The particle size of the above-mentioned metal particles is set to 40 μm or less because the number of contacts for fusing only the surface layers of the fine metal particles to each other is increased, and the thermal shock resistance and the vibration resistance strength in the state where the fine gaps remain. This is to express.

By using these metal porous bodies as a carrier and adhering the fine particles of activated alumina to the surface layer thereof, it is possible to impart thermal shock resistance and vibration resistance without deteriorating the characteristics of activated alumina.

As a method for adhering fine particles of activated alumina to the surface layer of the metal porous body produced as described above,
Neutralize the aluminum salt solution with an alkaline solution,
An aluminum hydroxide aqueous solution is produced.

When the metal is easily oxidized, a solution prepared by dissolving a small amount of an aluminum hydroxide aqueous solution in an alcohol solution may be used.

By immersing the porous metal body therein or by spraying an aluminum hydroxide solution on the porous metal body, aluminum hydroxide is deposited on the surface and the pores of the porous metal body.

After that, the solvent is rapidly dried by a drier or the like and baked at a temperature of 250 ° C. or higher in a non-oxidizing atmosphere to decompose and separate the water of crystallization so that the surface layer of the porous metal is coated with fine particles of activated alumina. The composite porous body can be produced.

The firing in a non-oxidizing atmosphere is for preventing the oxidization of the porous metal body, and in particular, when the specific surface area of the porous metal body is large, the oxidization reaction is likely to occur even at a low temperature, so caution is required.

Since the activated alumina fine particles are sintered in a structure in which the pores of the metal porous body are rooted, the activated alumina fine particles are not destroyed as easily as the activated alumina alone, but have a large air permeability as a structure. Can be kept.

In this way, a method for producing a material having resistance to thermal shock and vibration and having characteristics that could not be achieved conventionally as a material maintaining the activity of activated alumina could be established.

Next, examples of the present invention will be described.

[0035]

Example 1 A fine iron powder having a particle size of 20 μP and a fine iron powder of 20 μ under was mixed and applied to an urethane foam, and the mixture was fired in a non-oxidizing atmosphere at 1150 ° C. for 2 hours to produce a porous iron body. ..

The size of one piece is about 90 mm × 80 mm × 1
At 0 mm, the weight was about 40 g.

Similarly, SUS of 40 μ under
Powder, 10μ under copper powder 1250 ℃ ×
The porous metal was manufactured by firing at 800 ° C. for 2 hours for 2 hours.

Each size is about 90 mm × 8
The size was 0 mm × 10 mm, and the weight was about 50 g.

Aluminum chloride 0.005 mol / l ~
The pH was adjusted to 7 to 8 by adding a 0.01 mol / l potassium hydroxide aqueous solution or a 0.7 mol / l ammonia aqueous solution to the 0.05 mol / l aqueous solution.

In part, the aqueous solution was further diluted 6 to 11 times with ethanol. After immersing the porous metal body in the aqueous solution and ethanol / water mixed solution and leaving it for 30 minutes, the solution was cut and immediately put in a dryer set at 120 ° C. for drying for 2 hours.

Further, the aluminum hydroxide was activated by holding it at a temperature of 250 ° C. to 1000 ° C. for 2 hours in a weak reducing atmosphere of 3% hydrogen and 97% nitrogen.

As a result, activated alumina was produced in the surface layer, and it was confirmed by SEM observation and X-ray diffraction that activated alumina was produced. An example of the investigation is shown in FIG.

FIG. 1 shows a result of X-ray diffraction analysis of the active alumina portion scraped from the surface of the composite porous body of activated alumina and SUS produced by precipitating aluminum hydroxide on the SUS porous body and firing at 750 ° C. for 2 hours. And the diffraction angle with a circle in the peak indicates the formation of activated alumina.

Almost no generation of powder was observed on the low-tap vibrating screen over 3 hours, and the strength against vibration could be confirmed.

Further, in order to evaluate the activity of the produced activated alumina, the adsorption performance of acetaldehyde was examined.

The investigation method is the evaluation device having the structure shown in FIG. 2, the inner volume of the device is 40 l, and the circulation capacity of the fan is 400 l.
/ Min. Initial concentration of acetaldehyde is 100pp
The removal rate after 30 minutes was evaluated as the deodorization rate.

The weight of the evaluation sample was about 40 g for the iron porous system, and about 50 g for the SUS porous body and the copper porous body. The activated alumina evaluated for comparison was powdered with a particle size of about 1 mm or less and granular with a particle size of about 5 mm.
The test was performed by spreading 0 g each on a non-woven fabric.

The weight of activated alumina adhering to the porous metal is about 1 g, which is 1/100 of that of commercially available activated alumina powder.
Despite using only 40 weights, the deodorizing rate was almost the same. Typical measurement examples are shown in Table 1.

[0049]

[Table 1]

[0050]

INDUSTRIAL APPLICABILITY According to the present invention, a composite porous body of activated alumina and a metal having high activity of activated alumina and excellent in air permeability, heat shock resistance and vibration resistance can be obtained, and these materials can be economically produced. Because it is possible, its industrial effect is great.

[Brief description of drawings]

FIG. 1 is a diagram showing an X-ray diffraction intensity of activated alumina powder.

FIG. 2 is an explanatory view showing the structure of a test device for evaluating deodorizing performance.

[Explanation of symbols]

 1 Airtight container 2 Circulation fan 3 Deodorant evaluation sample 4 Gas inlet 5 Gas sample collection port 6 Gas circulation direction

Claims (4)

[Claims] 1. A three-dimensional mesh metal porous body as a carrier,
A composite porous body of activated alumina and a metal, characterized in that fine alumina particles are supported on the surface of the carrier. 2. A method of immersing a porous metal body in an aluminum hydroxide solution to deposit aluminum hydroxide on the surface of the porous metal body, followed by drying, firing in a non-oxidizing atmosphere, and decrystallization water treatment. A method for producing a composite porous body of activated alumina and a metal. 3. The method for producing a composite porous body of activated alumina and a metal according to claim 2, wherein the metal porous body has a three-dimensional network structure formed by molding ultrafine metal powder of 40 μm or less and firing. .. 4. The activated alumina-metal composite porous body according to claim 2, wherein the metal ultrafine powder is fired at a temperature of 100 to 500 ° C. lower than the melting point of the metal. Production method.