JP2001270783A - Alumina porous body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alumina porous body excellent in crushing strength and properties concerning shapes. SOLUTION: This alumina porous body having 1-10 mm particle diameter and >=10 kgf crushing strength is obtained by compacting two kinds of alumina powders consisting of (A) a powder having larger particle diameters and (B) a powder having smaller particle diameters, and regulated so that the relative ratio of the mutual particle diameters may be >=3, and firing the resultant compact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a porous alumina material. More specifically, the present invention relates to a porous alumina body having excellent crushing strength and shape, which is effectively used as a catalyst carrier in fuel reforming for reforming a reforming raw material such as hydrocarbon and water into a gas rich in hydrogen.

[0002]

2. Description of the Related Art In recent years, a reformer used in a fuel cell power generator or the like includes a reformer having a multi-cylindrical reactor in which a catalyst layer portion is disposed around a burner for miniaturization and high performance. Many are used. In such a multi-tubular reactor, the burner has an annular catalyst layer disposed around the inner center of the inner cylinder, so that the heat transfer area can be increased and the size can be reduced. At times, a temperature difference occurs between the inside and outside of the catalyst layer, so that a displacement due to a difference in thermal expansion between the inside and outside wall cylinders of the catalyst layer exerts a compressive force on the catalyst layer, and the catalyst is crushed. The generation of the powder by the crushing causes clogging of the catalyst layer and the downstream pipes, and as a result, the fluid resistance increases, and the operation may become impossible. Therefore, in order to prevent crushing of the catalyst, the catalyst carrier to be used is excellent in shape (the closer to a true sphere, the greater the resistance to compressive force as a catalyst layer), and the crushing strength as a physical property of the carrier itself. It needs to be excellent.

On the other hand, a catalyst used in such a reformer uses, for example, an alumina porous material as a catalyst carrier, and a noble metal such as nickel or ruthenium and a co-catalyst component as a catalytically active main component in pores of the porous material. Is used.

[0004]

The alumina porous body can be produced by molding and firing a raw material alumina powder, for example, by a rolling granulation method. If the diameter is large, the sinterability is poor, so the resulting alumina porous material must have a low crushing strength. Excessively stuck,
It became impossible to form into a sphere by tumbling granulation, and it was difficult to secure pores.

[0005] The present invention has been made in view of the above problems, and has as its object to provide an alumina porous body having excellent crushing strength and shape.

[0006]

According to the present invention, in order to attain the above object, according to the present invention, in an alumina porous body obtained by molding and firing an alumina powder, the alumina powder is a mixture of two kinds of powders. (A powder having a large particle diameter (A) and a powder having a small particle diameter (B)), and the two kinds of powder have a relative ratio of particle diameters to each other (particle diameter of (A) / (B) A) having a particle diameter of 3 or more is provided.

In a preferred embodiment, at least one of the two types of powders ((A) and (B)) in the mixture comprises an aggregate of fine primary particles, and has a primary particle diameter or When the powder is not an aggregate of the primary particles, the particle diameter of the powder itself and the relative ratio of each other ((A) the primary particle diameter or the particle diameter of the powder itself / (B))
(A primary particle diameter or a particle diameter of the powder itself) is 10 or less.

In a preferred embodiment, the mixing ratio of the two types of powder in the mixture is such that the powder (B) having a small particle diameter is mixed with 100 parts by weight of the powder (A) having a large particle diameter. There is provided an alumina porous material characterized by being 10 to 500 parts by weight.

In a preferred embodiment, the powder (A) having a large particle diameter has a particle diameter of 3 μm or more, and the powder (B) having a small particle diameter has a particle diameter of 10 μm or less. 2. An alumina porous body according to item 1 is provided.

In a preferred embodiment, the porous body has a particle size of 1 to 10 mm and a crushing strength of 10 to 10 mm.
The present invention provides a spherical alumina porous body having a weight of not less than kgf.

In a preferred embodiment, the porous material has a particle size of 1 mm to less than 4 mm and a crushing strength of 10 kgf or more, or the porous material has a particle size of 4 mm to 10 mm and a crushing strength of 20 kgf or more. Is provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the porous alumina of the present invention will be specifically described. Since the alumina porous body of the present invention is used as, for example, a catalyst carrier, the porous alumina body of the present invention has voids communicating with each other so as to sufficiently support a catalytically active main component, and has excellent crushing strength and shape. . The particle size of the porous alumina obtained in the present invention is usually 1 to 10 mm.

1. Raw Material (Alumina Powder) (1) Type The type of the raw material (alumina powder) used in the present invention is not particularly limited, and may be α-alumina powder, β-alumina powder, γ-alumina powder, or the like. Any of them can be used, but α-alumina powder which is inexpensive and easy to handle is preferable.

(2) Mixture ((A) + (B)) In the present invention, as the particle size of the alumina powder, a powder (A) having a large particle size (for example, preferably 3 μm or more, more preferably 3 μm or less) And the sphericity of the molded body is deteriorated.) And the powder (B) having a small particle diameter (for example, preferably 10 μm or less, and if it exceeds 10 μm, the strength after firing is reduced). And a mixture of two types of powder.

Here, the particle diameter means the particle diameter of the powder as an aggregate formed by assembling individual powders having a small primary particle diameter, and the aggregate having a primary particle diameter. If not, it means the particle size of the powder itself. In addition, the particle diameter in this case means an average particle diameter.

When only the powder (A) having a large particle diameter is used, the moldability is excellent and sufficient pores can be formed. However, sintering is difficult due to insufficient contact surface area between the powders and heat conductivity. It is difficult to perform sufficiently, and the crushing strength must be low.

Conversely, when only the powder (B) having a small particle size is used, the crushing strength due to sintering is not a problem, but the particles are excessively adhered to each other at the time of granulation and formed into a fine spherical shape. And it is also difficult to form sufficient pores.

In the present invention, the use of a mixture of the powders (A) and (B) makes use of the advantages of these two and makes up for the disadvantages.

(3) Relative ratio of particle diameter of mixture ((A) and (B)) In the present invention, the powder (A) having a large particle diameter in the mixture ((A) and (B)) When the relative ratio of the particle diameter to the powder (B) having a small particle diameter (the particle diameter of (A) / the particle diameter of (B)) is 3 or more, both in the crushing strength and the shape, It is preferable to make it excellent. For example, when (A) has a particle diameter of a μm, and as (B), the secondary particle diameter is (１ ／) aμ
m or less is preferably used. When the secondary particle diameter of (B) exceeds (１ ／) a μm, the effect of improving the crushing strength is relatively reduced.

In the present invention, the mixture ((A)
And at least one of (B)) may be composed of an aggregate of fine primary particles. In this case, the relative ratio of the primary particle diameter (the particle diameter of the powder if the powder is not an aggregate of the primary particles) (the primary particle diameter of the (A) or the particle diameter of the powder itself / (B)) (The primary particle diameter or the particle diameter of the powder itself) is preferably 10 or less. If it exceeds 10, the crushing strength after sintering decreases.

(4) Mixing ratio of mixture ((A) and (B)) In the present invention, the mixing ratio of mixture ((A) and (B)) is based on 100 parts by weight of powder (A). On the other hand, powder (B)
It is preferably from 10 to 500 parts by weight, more preferably from 20 to 200 parts by weight. Among them, 30 to 150 parts by weight is most preferable. If the amount of the powder (B) is less than 10 parts by weight, the desired effect of improving the crushing strength may not be obtained, and if it exceeds 500 parts by weight, the desired spherical shape may not be obtained.

2. Alumina Porous Body (1) Preparation Method There are no particular restrictions on the preparation of the alumina porous body of the present invention. For example, a rolling granulation method, a wet extrusion round method, a press molding method, and a CIP molding method are used. Can be. Among them,
In order to economically form a spherical porous body, a rolling granulation method capable of treating many raw materials per hour is preferable. In addition, the tumbling granulation method refers to a method of granulating (forming) a spherical shape while spraying a small amount of water in a rotating cylinder of a raw material alumina powder. The granulated granules are classified and 1,100 ° C.
It is fired in a gas furnace at 1,400 ° C. to prepare an alumina porous body as a final product.

Molding conditions While spraying water or an aqueous solution in which a binder is dissolved so that the water content is 10 to 20%, the peripheral speed is 30 to 100 m / m.
Granulate with a min pan type granulator or mixer. If granulation is difficult, add water to the raw material and adjust the peripheral speed to 50-120.
Rotate using a mixer at a high speed of m / min
After producing particles serving as seeds of about mm, the above-mentioned granulation is performed using these particles.

Firing conditions After drying at 85-105 ° C., a gas furnace or an electric furnace is used at 20-200 ° C./h for 1,100-1,400.
C. and cooled to room temperature at 20-200.degree. C./h.

Sieving (classification) In order to classify into a target particle size, dry (or /
And) After sintering, sieving is performed using a continuous or intermittent classifier.

(2) Evaluation of Physical Properties The crushing strength of the obtained spherical porous alumina was measured using a Kiya type crushing strength measuring device.

[0027]

EXAMPLES The present invention will be described more specifically with reference to the following examples. [Example 1] α-alumina powder having a particle diameter of 7 µm (alumina A) which is an aggregate having a primary particle diameter of 3 to 5 µm
While spraying a small amount of water in a cylinder rotating 100 parts by weight and 43 parts by weight of α-alumina powder (alumina B) having a particle diameter of 0.6 μm, which is an aggregate having a primary particle diameter of 0.4 μm. The sphere was formed into a sphere by a granulation method (rolling granulation method). This was classified and a sphere of 4.5 mm or more was taken out. This was dried using the residual heat of a gas furnace for firing, and fired in a gas furnace at 1,280 ° C. for 26 hours. Among the alumina porous bodies thus obtained, 4.5 to 5.5
The one having a diameter of mm was taken out by sieving.

Comparative Example 1 The procedure of Example 1 was repeated except that alumina B was not mixed.

Comparative Example 2 Alumina A in Example 1
Was performed in the same manner as in Example 1 except that was not mixed.

Example 2 100 parts by weight of α-alumina powder (alumina A) having a particle diameter of 7 μm, which is an aggregate having a primary particle diameter of 3 to 5 μm, and a primary particle diameter of 0.4 μm
43 parts by weight of α-alumina powder (alumina B) having a particle diameter of 0.6 μm, which is an aggregate of the above, was mixed with a kneader to prepare a raw material alumina. A part of the raw material alumina and a small amount of water are placed in an Erich mixer and the pan is rotated at a peripheral speed of 62 m / mi while rotating the agitator (up to 1800 rpm).
n for 2 to 3 minutes to granulate. Particles having a size of 1 mm or less were classified from the obtained spherical alumina particles. The particles were placed in a pan-type granulator, rotated at a peripheral speed of 30 m / min, and formed into a sphere while spraying water and adding the remainder of the raw material alumina as needed. This is classified and 4.5
A sphere of not less than mm was taken out. This was dried using the residual heat of the gas furnace for firing, and fired in a gas furnace at 1280 ° C. for 26 hours. Among the alumina porous bodies thus obtained, those having a diameter of 4.5 to 5.5 mm were taken out by sieving.

Table 1 shows the crushing strength and shape of the obtained alumina porous body.

[0032]

[Table 1]

[0033]

As described above, according to the present invention, an alumina porous body excellent in both crushing strength and shape can be provided.

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Claims (7)

[Claims] In an alumina porous body obtained by molding and firing alumina powder, the alumina powder is a mixture of two kinds of powders (a powder (A) having a large particle diameter and a powder having a small particle diameter). Powder (B)).
An alumina porous material, wherein a relative ratio of particle diameters (particle diameter of (A) / particle diameter of (B)) is 3 or more. 2. At least one of the two kinds of powders ((A) and (B)) in the mixture is an aggregate of fine primary particles, and the primary particle diameter or the powder is primary particles. When the particles are not aggregates, the particle diameter of the powder itself and the relative ratio of each other ((A) primary particle diameter or powder itself particle diameter / (B) primary particle diameter or powder itself particle diameter) are 2. The method according to claim 1, wherein the number is not more than 10.
The porous alumina according to the above. 3. The mixing ratio of the two kinds of powders in the mixture is such that the powder (B) having a small particle diameter is 10 to 500 parts by weight based on 100 parts by weight of the powder (A) having a large particle diameter. The alumina porous body according to claim 1 or 2, wherein: 4. The powder (A) having a large particle diameter has a particle diameter of 3
powder (B) having a particle diameter of at least
The alumina porous body according to any one of claims 1 to 3, wherein the thickness is not more than μm. 5. The particle size of the obtained alumina porous body is:
The alumina porous body according to any one of claims 1 to 4, wherein the alumina porous body has a crushing strength of 10 kgf or more. 6. The particle size of the obtained alumina porous body is as follows:
The alumina porous body according to any one of claims 1 to 4, wherein the crushing strength is 1 kg to less than 4 mm and the crushing strength is 10 kgf or more. 7. The particle size of the obtained porous alumina body is as follows:
The alumina porous body according to any one of claims 1 to 4, wherein the crushing strength is 4 kg or more and 10 mm or more and the crushing strength is 20 kgf or more.