JPH11228131A - Activated alumina and method for producing activated alumina having a micropore diameter distribution with a dual peak distribution curve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active alumina capable of simultaneously adsorbing 2 kinds of materials different in molecular size. SOLUTION: In the porous active alumina having many fine pores inside, the type of crystal form of the active alumina is a mixed type of γ-alumina with α-alumina and a distribution curve expressing the distribution of fine pore diameter formed in the active alumina becomes the double peak distribution curve exhibiting 2 peaks. In the double peak distribution curve, the fine pore diameter of the peak exhibited in the larger fine pore diameter side is preferably <=50 nm and the fine pore diameter of the peak exhibited in the smaller fine pore diameter side is preferably >=3 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an activated alumina and a method for producing the same, and more particularly, to a porous activated alumina having a large number of micropores formed therein and an active alumina having a micropore diameter distribution having a bipeak distribution curve. The present invention relates to a method for producing alumina.

[0002]

2. Description of the Related Art Alumina has high heat resistance, excellent chemical stability and chemical resistance, and is used for various industrial applications. In particular, porous activated alumina having a large number of micropores formed inside has a large specific surface area, and therefore has an adsorption ability to adsorb various gases and liquids, and supports catalysts, filters, and adsorbents. Or, it is used in many fields such as drying materials. Conventionally, such activated alumina has been produced by calcining raw materials such as aluminum hydroxide (such as bayerite, boehmite, and gibbsite), aluminum alkoxide, and alum.

[0003]

When activated alumina is used in the various fields described above, activated alumina having a fine pore diameter, a specific surface area, a pore volume, etc., which is suitable for molecules such as a gas to be adsorbed is used. There is a need. For this reason, conventionally, in the production process of activated alumina, it is possible to obtain activated alumina whose specific surface area or the like is adjusted by adjusting the mother salt crystals, the precursor, or the production conditions. However, the activated alumina obtained by the conventional production method has a single peak distribution curve representing the distribution of the fine pore diameter, and it is extremely difficult to simultaneously adsorb two kinds of substances having different molecular sizes. . Therefore, an object of the present invention is to provide an activated alumina capable of simultaneously adsorbing two kinds of substances having different molecular sizes and a method for producing the same.

[0004]

In order to solve the above-mentioned problems, the present inventor has found that activated alumina in which two types of micropore groups having different peak values of a distribution curve representing the distribution of micropore diameters coexist is effective. Considering that, first, two kinds of activated aluminas having different peak values of the distribution curve of the fine pore diameter were obtained separately, and then an attempt was made to mix both activated aluminas. However, the distribution curve of the fine pore diameter of the obtained mixed activated alumina was a single peak distribution curve, and was broader than the distribution curve of each fine pore diameter of the activated alumina before mixing. For this reason, the present inventors have repeatedly examined whether activated alumina having a bi-peak distribution curve can be obtained by calcining an aluminum compound as a raw material,
By gelling an aqueous basic aluminum chloride solution without adding an additive such as an organic compound, and sintering the obtained gelled product, it is possible to obtain activated alumina having a distribution curve of fine pore diameters having a bi-peak distribution curve. Know and arrived at the present invention.

That is, the present invention relates to a porous activated alumina having a large number of fine pores formed therein, wherein the crystal form of the activated alumina is a mixed type of γ-alumina and χ-alumina. Activated alumina is characterized in that the formed pore size distribution curve is a bi-peak distribution curve in which two peaks appear. Further, the present invention, when producing a porous activated alumina having a number of fine terms formed therein by firing an aluminum compound, the basic aluminum chloride aqueous solution used as the aluminum compound, such as an organic compound Gelling without adding additives, and then calcining the obtained gelled product so as to obtain an activated alumina having a mixture of a crystal form of γ-alumina and a crystal form of χ-alumina; The distribution lies in the method for producing activated alumina having a dual peak distribution curve.

The activated alumina according to the present invention gels an aqueous solution of basic aluminum chloride without adding an additive such as an organic compound, and converts the obtained gel to a crystal form of γ-alumina and a crystal form of χ-alumina. Is obtained by sintering so as to obtain activated alumina mixed with. For this reason, in the obtained activated alumina, the distribution curve of the micropore diameter becomes a bi-peak distribution curve in which two peaks appear, and two types of micropore groups coexist. Thus, according to the activated alumina according to the present invention in which two types of micropores coexist, a substance having a molecular size suitable for the micropore diameter of each micropore group can be adsorbed, and two substances having different molecular sizes can be used. At the same time, adsorption can be made possible.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The activated alumina according to the present invention has a crystal form of a mixture of γ-alumina and χ-alumina, and has fine pore diameter distribution curves different from each other as shown in FIG. It is important to have a bi-peak distribution curve in which two peaks appear at the pore size. Here, when the crystal form of activated alumina is a single crystal form of γ-alumina or χ-alumina, the distribution curve of the fine pore size distribution tends to be a single-peak distribution curve. The micropore size distribution shown in FIG. 1 was measured by a nitrogen gas adsorption method. That is, the nitrogen gas is applied to the sample at the temperature of liquid nitrogen while changing the relative pressure between the saturation pressure of the nitrogen gas (vapor pressure of the liquid nitrogen bath) and the pressure of the nitrogen gas brought into equilibrium with the sample. After the adsorption, the relationship between the relative pressure and the adsorption amount was measured, and the obtained measured values were analyzed by the BJH method to calculate the fine pore size distribution. The BJH method is based on the fact that when the relative pressure is low, nitrogen gas is adsorbed on small pores, and as the relative pressure increases, adsorption on large pores is caused.

In the dual peak distribution curve shown in FIG.
The peak P that appears on the side with the larger micropore diameter₁Micropore
The diameter is 50 nm or less (particularly preferably 50 to 5 nm).
And the peak P that appears on the side where the micropore diameter is smaller_TwoFine
The pore size is 3 nm or more (particularly preferably 3 to 4 nm)
Is a zeolite that is widely used as a porous material
Micropore group with a slightly larger pore size than
A group of fine pores having a large pore diameter can coexist.
In the dual peak distribution curve shown in FIG.₁Height H
₁Is the peak P_TwoHeight H_TwoIs higher than. This
Peak P₁, P_TwoHeight H of each distribution curve₁, H_TwoIs
As shown in FIG. 1, the baselines 10 and 12 of each distribution curve
From each peak P ₁, P_TwoUp to the height.

As described above, in the activated alumina according to the present invention having a bipeak distribution curve, the specific surface area is 50 to 1
In the range of 10 m ² / g, pore volume 0.2-0.25 cm
^In the range of ³ / g. The value of the specific surface area is determined by a BET method in which nitrogen gas is adsorbed on a sample under liquid nitrogen temperature, and the specific surface area is measured from the amount of adsorption and the occupied area of the nitrogen gas molecules. Further, the value of the pore volume is in the range of pores having a pore diameter of 1.7 to 300 nm obtained by nitrogen gas adsorption.

The activated alumina according to the present invention, which has a mixed crystal form of γ-alumina and χ-alumina and has a bipeak distribution curve shown in FIG. 1, is obtained by adding a basic aqueous solution of aluminum chloride to an additive such as an organic compound. Can be obtained by calcining the obtained gelled product after gelation without adding the compound. Here, when an additive such as an organic compound, for example, a water-soluble organic compound such as polyethylene glycol is added to the basic aluminum chloride aqueous solution to form a gel, the activated alumina finally obtained has a crystal form of γ.
It is difficult to obtain activated alumina which tends to be one of alumina and χ-alumina, and the distribution curve of the fine pore diameter becomes a very sharp single peak distribution curve, and exhibits a dual peak distribution curve. The basic aluminum chloride aqueous solution used in the present invention has an OH / Al molar ratio of 1.
A basic aluminum chloride aqueous solution in the range of 5 to 2.7, specifically, a basic aluminum chloride aqueous solution shown in the following [Chemical Formula 2] is preferable.

Embedded image

In the present invention, the basic aqueous aluminum chloride solution is gelled. The gelation temperature is between room temperature and 70
It is preferable to set the temperature to about ° C. Next, the obtained gel is calcined so as to obtain activated alumina in which a crystal form of γ-alumina and a crystal form of χ-alumina are mixed. As the firing conditions, the heating rate up to the firing temperature is 50 to 50.
It is preferable that the firing temperature is 0 ° C / Hr and the firing temperature is 600 to 1100 ° C (particularly preferably 700 to 950 ° C).
If the firing temperature exceeds 1100 ° C., the crystal form of the obtained alumina tends to be α-alumina. The activated alumina thus obtained is in the form of powder, granules, or flakes, and its crystal form is a mixture of γ-alumina and χ-alumina, and the fine pore size distribution is as shown in FIG. A bi-peak distribution curve results.

In the present invention, the fine pore size distribution of the obtained activated alumina can be changed by adjusting the OH / Al molar ratio of the basic aluminum chloride aqueous solution, the firing temperature, and the partial pressure of water vapor during firing. In particular, factors such as the OH / Al molar ratio of the basic aluminum chloride aqueous solution and the calcination temperature have a great influence on the distribution of the fine pore diameter of the obtained activated alumina. That, along with increasing the OH / Al molar ratio of basic aluminum chloride aqueous solution, in the distribution curve of fine pore diameter of the resulting activated alumina, a peak P ₁ of the distribution curve appearing on the side made small fine pore size, its position Are substantially the same value, and the height H ₁ of the peak P ₁ gradually increases. On the other hand, the peak P ₂ of the distribution curve appearing on the side of the larger pore diameter gradually shifts in the direction of smaller pore diameter while its height H ₂ gradually decreases. Further, with the firing temperature to heating, in the distribution curve of fine pore diameter of the resulting activated alumina, a peak P ₂ of the distribution curve appearing in large consisting side of the fine pore size, becoming gradually increases its height H ₂ It gradually shifts in the direction of larger micropore diameter. On the other hand, the peak P of the distribution curve that appears on the side where the micropore diameter is smaller
The position ₁ has substantially the same value, and the height H ₁ of the peak P ₁ gradually decreases. Therefore, in the activated alumina according to the present invention, the OH of the basic aluminum chloride aqueous solution
By adjusting the / Al molar ratio or the firing temperature, the fine pore size distribution of the obtained activated alumina can be adjusted.

The reason why the distribution curve of the fine pore diameter of the activated alumina obtained by the present invention becomes a bi-peak distribution curve is considered as follows. That is, since the micropores formed in the activated alumina are gaps between the generated crystal grains,
It is determined by the crystal type and the size of the crystal grains and their distribution. In this regard, since the activated alumina according to the present invention has a mixed crystal type in which γ-alumina and χ-alumina are mixed, a fine pore size based on the size and distribution of both crystal types and crystal particles is formed, and the activated alumina is activated. The fine pore size distribution of alumina becomes a bi-peak distribution curve. Further, in the present invention, OH /
The distribution of the fine pore diameter of the obtained activated alumina also changes depending on the Al molar ratio. For this reason, it is considered that the content ratio of the aluminum monomer, oligomer, and polymer present in the basic aluminum chloride aqueous solution affects the fine pore size distribution of the obtained activated alumina.

That is, an aqueous solution having a high polymer content ratio
A basic aluminum chloride having a high OH / Al molar ratio
When using an aqueous solution of alumina
Appears on the smaller side of the micropore diameter in the diameter distribution curve
Distribution curve peak P₁Height H₁Is a monomer or oligo
OH / Al molar ratio, which is an aqueous solution having a high content of
Activity obtained using low basic aluminum chloride aqueous solution
Is higher than that of crystalline alumina. On the other hand, large pores
P of the distribution curve that appears on the side_TwoHeight H _TwoIs
OH, which is an aqueous solution with a high content of nomers and oligomers
Uses basic aluminum chloride aqueous solution with low / Al molar ratio
Lower than the activated alumina obtained by the method. Like this
In the present invention, a basic aluminum chloride aqueous solution
Of monomers, oligomers and polymers contained in
Since the fine pore size based on the content ratio is formed,
Micropore size based on crystal form and crystal particle size and their distribution
Along with the distribution curve of the fine pore size of activated alumina.
Curve distribution curve.

In the present invention, it is also possible to obtain a molded article formed of activated alumina into a predetermined shape. Such a molded article can be obtained by heating a gel molded article formed into a predetermined shape at a temperature increasing rate of 6 to 120 ° C./Hr while adjusting the dehydration rate, and firing at a temperature of 600 to 1100 ° C. it can. Here, the gel molded body molded into a predetermined shape may be obtained by pulverizing the obtained gelled material and compression-molding a powdery material, and after gelling a basic aluminum chloride aqueous solution placed in a container of a predetermined shape. Alternatively, it can also be obtained by taking out a gel molded body molded into a container shape.
The basic aluminum chloride aqueous solution is a solution containing aluminum at a high concentration, but has a lower solution viscosity than other solutions containing aluminum at the same concentration. For this reason, a basic aluminum chloride aqueous solution is impregnated under reduced pressure into the porous body, so that the basic aluminum chloride aqueous solution enters the pores of the porous body. Then, after gelling the basic aluminum chloride aqueous solution that has entered the pores, the gelled material is calcined, so that the activated alumina whose distribution curve of the fine pore diameter becomes a distribution curve of the dual peak is placed in the pores of the porous body. Can be formed.

Further, a mold formed from a material such as paper which disappears by burning or pyrolysis during firing is immersed in a basic aluminum chloride aqueous solution, so that the basic aluminum chloride is formed on the surface and inside of the mold. After adhering the aqueous solution, the basic aluminum chloride aqueous solution adhering to the surface and inside of the mold is gelled, and then the gelled product is fired together with the mold. Although the mold material disappears by such sintering, an activated alumina molded body maintaining the shape of the mold material can be obtained. As described above, the activated alumina according to the present invention is capable of simultaneously adsorbing two kinds of substances having different molecular sizes, and from a mixture of homologous series including molecules of plural sizes such as crude oil, a plurality of homologous series. It can be used as an adsorbent to simultaneously adsorb species components. The activated alumina according to the present invention can also be used as a catalyst. That is,
In general, in a porous material, large micropores control the adsorption speed through the passage of molecules to be adsorbed, and small micropores mainly act as adsorption sites. Therefore, in the activated alumina of the present invention in which two types of micropore groups having different micropore diameters coexist,
A group of micropores having a large micropore diameter is used as a high-speed diffusion field, and a group of micropores having a small micropore diameter is used as a reaction field for molecules matching the micropore diameter.

[0017]

The present invention will be described in more detail with reference to the following examples. Here, the structural analysis of the activated alumina was performed using X-ray diffraction (CuKα), and the specific surface area was determined by the aforementioned B
It was measured by the ET method, and the micropore size distribution was also measured by the BJH method described above. Further, the pore volume is a pore volume in a range of pores having a pore diameter of 1.7 to 300 nm obtained by nitrogen gas adsorption.

Example 1 An OH / Al ratio was 2.46 and aluminum oxide (Al
_TwoO_ThreeAluminum whose converted concentration is equivalent to 22.5% by weight
60 parts of basic aluminum chloride aqueous solution containing
Drying at 0 ° C. yielded a clear gel. The resulting gel
Aluminum content of aluminum oxide (Al_TwoO_Three)
Was 42.1% by weight. Then the resulting gelation
The sintering temperature was 900 ° C at a heating rate of 100 ° C / Hr.
Temperature, and then hold at a firing temperature of 900 ° C for 1 hour.
Was. Activated alumina consisting mainly of granular particles is obtained
Was. About the obtained granular particles of activated alumina, etc., X
According to structural diffraction by X-ray diffraction, the crystal type is
χIt was a mixed type with alumina. In addition, its fine pore size
As a result of measuring the distribution, the distribution curves shown in FIG.
Where two peaks appear at different micropore diameters
It becomes a peak distribution curve. In such a bipeak distribution curve
The peak P of the distribution curve appearing on the side with the larger micropore diameter.
_TwoHeight H_TwoIs the distribution curve that appears on the smaller side of the micropore diameter.
Line peak P₁Height H₁Lower and peak
P₁Is located near 3.4 nm, and the peak P _TwoIs 5-9n
m. Furthermore, the ratio table of the obtained activated alumina
The area is 108.6m^Two/ G and a pore volume of 0.20
3cm^Three/ G. In addition, when firing the gelled material,
By setting the temperature rate to 60 ° C./Hr, the particle size is 5 mm.
Approximately granular activated alumina could be obtained.

Example 2 An OH / Al ratio of 2.00 and aluminum oxide (Al
60 a basic aluminum chloride aqueous solution containing ₂ O ₃₎ in terms of the converted concentration of 19.3 wt% equivalent aluminum component
Drying at 0 ° C. yielded a clear gel. The amount of aluminum in the obtained gel was 36.8% by weight in terms of aluminum oxide (Al ₂ O ₃ ). Next, the obtained gel was calcined under the same conditions as in Example 1 to obtain an activated alumina mainly composed of granular particles. According to the structural diffraction by X-ray diffraction of the obtained granular particles of activated alumina, the crystal type was a mixed type of γ-alumina and χ-alumina. However, in the activated alumina obtained in this example, the ratio of χalumina increased compared to the activated alumina obtained in Example 1. In addition, as a result of measuring the distribution of the fine pore diameters, as shown in FIG. 2, a double peak distribution curve in which two peaks appeared at different micropore diameter locations was obtained. Such in twin peak distribution curve, height H ₂ of the peak P ₂ appearing on the side comprising a large fine pore size is larger than the height H ₁ of the peak P ₁ appearing in small consisting side of the fine pore size, and Peak P ₁ is located near 3.4 nm, and peak P ₂ is located near 12 nm.

When the bi-peak distribution curve shown in FIG. 2 is compared with the bi-peak distribution curve shown in FIG. 1, the peak P ₁ of the distribution curve appearing on the side with the smaller pore diameter is substantially at the same position. but the peak P ₂ of the distribution curve appearing in large consisting side of the fine hole diameter is shifted in the direction of larger fine hole diameter. Thus, the OH /
By adjusting the Al ratio, the fine pore size distribution of the obtained activated alumina can be adjusted. Further, the specific surface area of the obtained activated alumina was 76.9 m ² / g, and the pore volume was 0.247 cm ³ / g.

Example 3 The transparent gelled product obtained in Example 1 was crushed and crushed to a particle size of 43 μm or less.
Into a mold, and molded at a pressure of 30 MPa to form a diameter of 13
mm was obtained. Next, the activated alumina molded body can be obtained by firing the gel molded body. Here, when firing the obtained gel molded body,
The gel molded body was heated to a firing temperature of 850 ° C. at a heating rate of 60 ° C./Hr, and further kept at a firing temperature of 850 ° C. for 1 hour. The obtained activated alumina molded body has a bulk density of 1.95.
g / cm ³ , and the anti-bending strength was 22 MN / m ² . The activated alumina molded body has a diameter of 9.8.
5 mm, shrinking to 75.8% of the gel compact. The activated alumina shaved from the activated alumina molded body was measured for structural diffraction and fine pore size distribution by X-ray diffraction. As a result, the crystal form of the activated alumina was a mixed type of γ-alumina and χ-alumina. The distribution curve of the fine pore diameter was a bi-peak distribution curve in which two peaks appeared at different locations of the fine pore diameter.

Example 4 An OH / Al ratio was 2.53, and aluminum oxide (Al
A basic aluminum chloride aqueous solution containing an aluminum component having a converted concentration of 22.3% by weight in terms of ₂ O ₃ ) was placed in a fluororesin dish having an inner diameter of 6.2 cm to gel. The gelation conditions were as follows: in an atmosphere where the relative humidity was maintained at 70% or more, the basic aluminum chloride aqueous solution was heated from normal temperature to 60 ° C. and gradually dried.
The obtained transparent and gelled molded article having a diameter of 6.2 cm is
After heating to 120 ° C. at a heating rate of 30 ° C./Hr, then 850 ° C. (firing temperature) at a heating rate of 60 ° C./Hr
And heated at 850 ° C. for 1 hour to obtain an activated alumina molded body. The obtained activated alumina molded body has a diameter of 4.3 cm and shrinks in the diameter direction to approximately 69% of the gel molded body. The activated alumina shaved from the activated alumina molded body was measured for structural diffraction and fine pore size distribution by X-ray diffraction. As a result, the crystal form of the activated alumina was a mixed type of γ-alumina and χ-alumina. The distribution curve of the fine pore diameter was a bi-peak distribution curve in which two peaks appeared at different locations of the fine pore diameter.

Example 5 A cylindrical filter paper having a diameter of 25 mm and a length of 90 mm was immersed in the basic aluminum chloride aqueous solution used in Example 1 under reduced pressure, and the filter paper was dried at 35 ° C. and adhered thereto. The aqueous solution gelled. Next, the temperature of the filter paper to which the gel was adhered was raised to 350 ° C. at a rate of 100 ° C./Hr, held for 30 minutes, and then raised to 600 ° C. at a rate of 150 ° C./Hr. The temperature was raised to 850 ° C. (calcination temperature) at a temperature increase rate of ° C./Hr. It was kept at the firing temperature (850 ° C.) for 1 hour to obtain an activated alumina molded body. The obtained activated alumina molded body has a cylindrical shape substantially the same shape as the cylindrical filter paper, but the filter paper has disappeared. The activated alumina compact has a diameter of 19 mm and a length of 69 mm, and has shrunk to about 76% of the thimble.
The activated alumina shaved from the activated alumina molded body was measured for structural diffraction and fine pore size distribution by X-ray diffraction. As a result, the crystal form of the activated alumina was a mixed type of γ-alumina and χ-alumina. The distribution curve of the fine pore diameter was a bi-peak distribution curve in which two peaks appeared at different locations of the fine pore diameter. When the surface state of the activated alumina molded article was observed by an electron microscope, it was confirmed that the activated alumina molded article had a microstructure in which the shape of the cellulose fiber forming the cylindrical filter paper was reduced and transferred as it was. The firing temperature is 1150 ° C.
As a result, the obtained molded product had a cylindrical shape substantially the same shape as the cylindrical filter paper and had a dense structure, but the crystal type was α-alumina.

Comparative Example Aluminum hydroxide (gibbsite) was heated at 100 ° C./Hr
At a heating rate of 900 ° C. to a firing temperature of 900 ° C.
It was kept at a firing temperature of 0 ° C. for one hour. An activated alumina consisting of powdery particles was obtained. According to the structural diffraction of the obtained activated alumina powder particles by X-ray diffraction, the crystal form was
It was only alumina. In addition, as a result of measuring the fine pore size distribution, a single peak distribution curve shown in FIG. 3 was obtained.
In this distribution curve, the peak value is a fine pore diameter of 5 nm.
Nearby. Further, the specific surface area of the obtained activated alumina was 102.5 m ² / g, and the pore volume was 0.232 cm ³ / g.

[0025]

According to the activated alumina of the present invention, two types of micropores coexist and a substance having a molecular size suitable for each of the micropores can be adsorbed. Can be made adsorbable. Therefore, two kinds of substances in a solution or a gas can be simultaneously adsorbed, and can be used as an adsorbent for preventing pollution. In the activated alumina according to the present invention, a group of micropores having a large micropore diameter can be used as a high-speed diffusion field, and a group of micropores having a small micropore diameter can be used as a reaction field for molecules matching the micropore diameter. Therefore, it can be used as a catalyst.

[Brief description of the drawings]

FIG. 1 shows an example of a distribution curve representing a fine pore size distribution of activated alumina according to the present invention.

FIG. 2 shows another example of a distribution curve representing the distribution of fine pore sizes of activated alumina according to the present invention.

FIG. 3 shows a distribution polarity representing a fine pore size distribution of activated alumina as a comparative example with respect to activated alumina according to the present invention.

[Explanation of symbols]

P ₁ Peak of distribution curve of fine pore diameter group with small fine pore diameter P ₂ Peak of distribution curve of fine pore diameter group with large fine pore diameter H ₁ Peak height of distribution curve of fine pore diameter group with small fine pore diameter H ₂ fine Peak height of the distribution curve of the group of micropores with large pore size

Claims (6)

[Claims] 1. A porous activated alumina having a large number of fine pores formed therein, wherein the crystal form of the activated alumina is a mixed type of γ-alumina and χ-alumina, and Activated alumina characterized in that a distribution curve representing a distribution of pore diameters is a bi-peak distribution curve in which two peaks appear at locations having mutually different fine pore diameters. 2. In the dual peak distribution curve, the peak having a larger pore diameter on the larger side has a fine pore diameter of 50 nm or less, and the peak on the smaller side of the fine pore diameter has a fine pore diameter of 3 nm or more. The activated alumina according to claim 1. 3. Activated alumina obtained by using a basic aluminum chloride aqueous solution as a raw material, wherein activated alumina in said raw material is
When the H / Al ratio is changed, the positions of the peaks appearing on the side where the fine pore diameter is smaller are substantially the same in the bipeak curve of the fine pore diameters of the activated alumina, 3. The activated alumina according to claim 1, wherein the position of the appearing peak varies. 4. When a porous activated alumina having a large number of fine pores formed therein is produced by firing an aluminum compound, the basic aluminum chloride aqueous solution used as the aluminum compound is added with an organic compound or the like. The gelled product was then added with the crystal form of γ-alumina
A method for producing activated alumina having a bi-peak distribution curve with a fine pore size distribution, characterized by firing to obtain activated alumina mixed with the crystal form of alumina. 5. As a basic aluminum chloride aqueous solution,
The method for producing activated alumina according to claim 4, wherein a basic aluminum chloride aqueous solution represented by the following formula (1) is used. Embedded image 6. The sintering temperature of the obtained gelled product is 600
The method for producing activated alumina according to claim 4 or 5, wherein the fine pore size distribution has a dual peak distribution curve.