JPH1017321A - Small alumna sphere and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a small prove volume and to enhance a mechanism strength by firing small spheres obtd. by granulating specified dry alumina powder. SOLUTION: Pseudo-boehmite alumina hydrogel obtd. by allowing an aq. soln. of a soluble aluminum salt to react with a basic aq. soln. in the presence of 2-15wt.% soluble carboxylic acid based on the amt. of alumina is washed to remove a salt as a by-product and to reduce the amt. of an alkali metal in the alumina to <=1.0wt.% (expressed in terms of oxide). The washed alumina hydrogel is spray-dried, water is added to the resultant dry alumina powder having 25-35wt.% water content so that the water content is regulated to 35-55wt.% and the powder is granulated to obtain small spheres each having 4-13mm diameter. These small spheres are dried under such conditions as to attain 1-26wt.%/hr rate of evaporating of water and the dried spheres are fired at 400-900 deg.C to obtain the objective small almina spheres each having 3-10mm diameter and >=10kg mechanical strength. The total pore volume of pores each having <100Å pore diameter in the spheres is 0.30-0.70ml/g and that of pores each having <=100 Å pore diameter is <=0.10ml/g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to alumina small spheres suitable for a catalyst carrier, an adsorbent, a filler and the like, having good mechanical strength and a controlled pore distribution, and a method for producing the same.

[0002]

2. Description of the Related Art Alumina small spheres are used in many fields such as various catalyst carriers, adsorbents and fillers. in this case,
A surface area, a pore volume, a pore diameter, and the like that are suitable for each purpose of use are required, and good mechanical strength is required. However, the mechanical strength of alumina small spheres tends to decrease in inverse proportion to the size of the pore diameter and the size of the pore volume. Alumina small spheres formed by granulation using dry alumina powder obtained by various known methods all have a pore diameter of 100 ° or more and a pore volume of at least 0.1 m.
1 / g or more.

With respect to an alumina molded body having relatively few macropores, for example, Japanese Patent Publication No. 6-104568 describes a method for producing an alumina carrier having a pore volume of 350 mm or more and a pore volume of 0.18 ml / g. Tokuhei 2-4
No. 8485 describes a method for producing an alumina carrier having a pore diameter of 500 ° or more and a pore volume of 0.1 ml / g. Further, Japanese Patent Application Laid-Open No. 52-59094 describes a process for producing alumina having a pore volume of 100 to 50,000 ° and a pore volume of less than 10% of the total pore volume. However, these are all based on the pressure extrusion molding method.

[0004] Conventionally, an alumina compact formed using dried alumina powder is formed by micropores of primary particles of alumina, mesopores generated in primary particle gaps, and secondary particle gaps formed by aggregation of primary particles. It has macropores that occur and has a wide pore size distribution at all times. The pores generated in the primary particle gap and the secondary particle gap decrease the mechanical strength. Among them, there is a problem that the mechanical strength is remarkably reduced particularly when there is a pore having a pore diameter of about 1,000 mm or more. is there.

It is known that the mechanical strength varies depending on the molding method. One of the typical molding methods is a method in which appropriate moisture is added to alumina powder and the mixture is kneaded and pressure-extruded. In this method, a molded article having a relatively high strength can be obtained by reducing macropores. Could not be spherical.

[0006] Therefore, in general, a rotary granulation method is employed to obtain a small spherical molded body. In this method, the alumina particles whose water content has been adjusted are seeded with a rotary granulator as necessary. In this method, granulation is performed by the cohesive force of alumina powder. In this method, since a strong external pressure was not applied, the alumina powder particles were not tightly packed, so that a material having few macropores could not be obtained, and a material having a high particle strength could not be obtained.

[0007]

DISCLOSURE OF THE INVENTION The present invention relates to an alumina small sphere having substantially no macropores and having a high mechanical strength by a rotary granulation method which does not have macropores and cannot obtain a high mechanical strength. An object of the present invention is to provide a manufacturing method thereof.

[0008]

The first aspect of the present invention relates to alumina small spheres having the following characteristics. The pore volume of the pore having a pore diameter of less than 100 ° is 0.30 to 0.7.
0 ml / g 0.10 ml / g pore volume with a pore diameter of 100 mm or more
The particle diameter is 3 to 10 mm and the mechanical particle strength is 10 kg or more.

A second aspect of the present invention relates to a method for producing alumina small spheres, comprising the following steps (a) to (f). (A) reacting a soluble aluminum salt aqueous solution with a basic aqueous solution in the presence of 2 to 15 wt% of soluble carboxylic acid based on alumina to form pseudo-boehmite alumina hydrogel, and (b) washing the alumina hydrogel Removing by-product salts to reduce the alkali metal in alumina to 1.0 wt% or less as an oxide; (c) spray-drying the washed alumina hydrogel to dry alumina powder having a water content in the range of 25 wt% to 35 wt% (D) adding water to the dried alumina powder to adjust the water content to a range of 35 to 55 wt%, (e) granulating the dried alumina powder having adjusted moisture into small spheres, (f) A) a step of drying the granulated and formed small spheres, followed by firing to form alumina small spheres, and the above-mentioned alumina small spheres can be obtained by this method.

In the step (f), the granulated and formed small spheres have a water evaporation rate per alumina of 26 wt%.
It is preferable to dry at a rate of not more than / hr and then calcinate at 400 ° C to 900 ° C.

The alumina small spheres of the present invention have a pore volume (PVm) having a pore diameter of 100 ° or more as measured by a mercury intrusion method of 0.10 ml / g or less, preferably 0 to 0.05 ml.
/ G, and the total pore volume (PVt, value at relative pressure P / P ₀ = 0.976) determined by the nitrogen adsorption method is in the range of 0.30 ml / g to 0.80 ml / g. hand,
The pore volume (PVs, value at a relative pressure P / P ₀ = 0.780) of pore diameter less than 100 ° determined by the nitrogen adsorption method is in the range of 0.30 to 0.70 ml / g, and the Kiya type hardness It has a mechanical strength of at least 10 kg, preferably 11 to 20 kg, and a particle diameter of 3 to 10 mm.

When the pore volume of the pore having a pore diameter of less than 100 ° is 0.3
When the amount is less than 0 ml / g, the performance as a catalyst carrier, an adsorbent, etc. is insufficient, and when the amount is more than 0.70 ml / g, the pore volume having a pore diameter of 100 mm or more tends to increase. The target strength may be weak.

[0013] The volume of pores having a pore diameter of 100 ° or more is 0.1
If it is more than 0 ml / g, the mechanical strength becomes weak, which is not preferable.

Further, the mechanical strength becomes weak, for example, 10
If the weight is less than Kg, it is not preferable because the powder is broken or broken when used as a catalyst carrier, an adsorbent or the like, and cannot be used for a long time or repeatedly.

As the soluble carboxylic acid of the present invention, gluconic acid, succinic acid, oxalic acid, citric acid, malonic acid, tartaric acid, adipic acid and the like can be suitably used.

As the aqueous solution of the soluble aluminum salt, an aqueous solution of aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum acetate or the like can be used. As the basic aqueous solution, an aqueous solution of aluminate such as sodium aluminate or potassium aluminate can be used. An aqueous solution of an alkali metal, caustic soda, ammonia or the like can be used.

Examples of the basic aqueous solution include an aqueous solution of an alkali metal salt of aluminate, an aqueous solution of an alkali metal hydroxide and an aqueous solution of ammonia.

The pseudo-boehmite alumina hydrogel of the present invention is obtained by adding the above-mentioned soluble carboxylic acid to the above-mentioned basic aqueous solution, for example, an aqueous solution of an alkali metal aluminate or an aqueous ammonia solution having a concentration of 0.1 to 5.0% by weight in terms of alumina. It is prepared by dissolving and supplying it to a soluble aluminum salt aqueous solution having a concentration of 0.2 to 10.0 wt% when converted to alumina, with stirring.

Next, the alumina hydrogel is filtered and washed, for example, while applying aqueous ammonia to remove by-product salts and the like.

The washed pseudo-boehmite alumina hydrogel is spray-dried under conditions such that the water content is 25 to 35% by weight to prepare a dry alumina powder. Water is added to the dried alumina powder to adjust the water content to 35 to 55% by weight, and granulated by a rotary granulator to obtain a diameter of about 4 to 1%.
3 mm spherical alumina particles are obtained, and the spherical alumina particles are dried and fired to produce spherical alumina small spheres having a mechanical particle strength of 10 kg or more and a diameter of about 3 to 10 mm.

The present invention uses a pseudo-boehmite alumina hydrogel obtained as a precipitate in a known manner in the presence of 2 to 15 wt%, preferably 3 to 10 wt%, of carboxylic acid based on alumina. If the content is less than 2 wt%, the primary particles become too large, and the pore volume of the final alumina small spheres having a pore diameter of 100 ° or more as measured by the mercury intrusion method is 0.10.
It is not preferable because it is larger than ml / g and the strength becomes weak. Further, even if gluconic acid is used in an amount exceeding 15% by weight, the effect of suppressing the growth of particles does not increase, which is not preferable from the economical viewpoint.

The pseudo-boehmite alumina hydrogel of the present invention has a specific surface area of 200 to 200 as measured by the BET method.
400 m ² / g, pore volume (value at relative pressure P / P ₀ = 0.976) measured by nitrogen adsorption method is 0.35
Pseudo-boehmite alumina hydrogel having properties of ~ 0.60 ml / g is preferred. The specific surface area and the pore volume are measured by firing pseudo-boehmite alumina hydrogel at 600 ° C. for 2 hours.

A pseudo-boehmite alumina hydrogel having a specific surface area of less than 200 m ² / g is not preferred because alumina primary particles are overgrown and it is difficult to obtain strong alumina small spheres. 400m ² specific surface area
In the case of / g or more, primary alumina particles do not grow and are very fine primary particles, so that the shrinkage in the drying and firing steps is too large to obtain strong alumina small spheres.

When the pore volume of the pseudo-boehmite alumina hydrogel is less than 0.35 ml / g, the pore volume of the final alumina microspheres having a pore diameter of less than 100 ° is 0.30 ml.
/ G, which is not preferred because the performance as a catalyst and an adsorbent is reduced. If it is 0.60 ml / g or more, the pore volume of the obtained alumina small spheres having a pore diameter of 100 ° or more as measured by the mercury porosimetry tends to increase, and the mechanical strength may be weak, which is not preferable. .

Next, the pseudo-boehmite alumina hydrogel is filtered and washed with pure water, a low-concentration aqueous solution of mineral acid or aqueous ammonia to remove by-product salts and the like. %, Preferably 0.5% by weight or less.

When pure water is used for washing, it may be difficult to reduce the alkali metal content to 1.0 wt% or less. When a low-concentration aqueous solution of mineral acid is used, the removal of the alkali metal is easy, It is not preferable because anions derived from mineral acids may remain or a part of the alumina hydrogel may be dissolved. The use of ammonia water is preferred because the alkali metal ion is replaced with ammonium ion to remove the alkali metal, and since it is basic, the ammonium ion reacts with the anion to remove it.

The ammonia concentration of the aqueous ammonia used for cleaning is preferably 0.05 to 1.0 wt%. The amount of the aqueous ammonia is preferably 5 to 100 times the weight of the hydrogel.

When the content of alkali metal in alumina exceeds 1.0 wt% as an oxide, the performance as a catalyst and an adsorbent decreases, and the thermal stability also decreases.

Next, the pseudo-boehmite alumina hydrogel is spray-dried with a spray drier so that the water content of the spray-dried alumina powder is 25 to 35% by weight. If the water content of the spray-dried alumina powder is higher than 35% by weight, the degree of drying is insufficient, so that the alumina powder adheres to each other and the powder state is not maintained. If the water content is less than 25% by weight, the alumina powder is too hard because it is too dry, and does not shrink so as to be densely packed, which causes the formation of macropores in the granulated product and lowers the mechanical strength. Is not preferred.

The average particle size of the spray-dried alumina powder is preferably from 10 to 100 μm as measured by a micromesh method. Particularly preferably, it is 20 to 70 μm. Dry alumina powder having an average particle size of less than 10 μm may have difficulty in handling the powder, and if the average particle size is more than 100 μm, a large pore size of the granulated product may be generated, resulting in poor mechanical strength. It is not preferable because it lowers.

Water is added to the dried alumina powder to reduce the water content to 35 to 55 wt%, preferably 40 to 50 watts.
After adjusting the water content to t%, the mixture is formed into spherical particles by a rotary granulator. Even if the water content is less than 35 wt% or more than 55 wt%, granulation cannot be performed. The water content per unit weight of the dried alumina powder whose water content was adjusted was 1.2 to 1.5 times the pore volume of the alumina powder measured by separately calcining the dried alumina powder at 600 ° C. for 2 hours on a volume basis. It is preferred that Granulation cannot be performed if the water content is higher or lower than the range of the water content calculated from the pore volume of the dried alumina powder. When the water content of the dried alumina powder is lower than 35 wt%, the water content is almost in the pores and is small outside the particles, so that the adhesion force and pseudo-collection force of the particles are low and granulation cannot be performed, and when the water content is higher than 55 wt%. Cannot be granulated because it becomes a slurry. The dried alumina powder used in the present invention has a pore volume (relative pressure P / P ₀ = 0.9) measured by a nitrogen adsorption method.
(Value at 76) of about 0.45 to 0.80 ml / g are preferably used. Therefore, the moisture content of the dried alumina powder whose water content has been adjusted is 35 to 55 wt%.

The dried alumina powder whose water content has been adjusted is granulated by a rotary granulator. At this time, the granulated product preferably has a particle diameter of about 4 to 13 mm. When the particle diameter is in this range, the particle diameter of the final alumina small spheres is reduced by drying and firing to 3 mm to 10 mm, and alumina small spheres having a particle diameter useful as a catalyst, a catalyst carrier and the like can be obtained.

Next, the alumina granulated product is dried and fired to obtain alumina small spheres. The drying rate at this time is preferably such that the water evaporation rate per alumina is 26 wt% / hr or less. The firing temperature is preferably from 400 to 900C.

The spherical alumina particles obtained in the present invention have small primary particles in the pseudo-boehmite alumina hydrogel stage, and have very large shrinkage during drying and firing because the water content of the dried alumina powder is adjusted. There is a feature.
The shrinkage ratio of the granulated alumina particles after drying and firing is about 40 to 50% by volume. Therefore, the drying and firing conditions are very important, and the drying and firing at this time must be performed very slowly.

Drying is carried out by air drying at room temperature until the water content becomes about 30% by weight, or preferably at a relative humidity of 40 to 70%.
% To 3 to 48 wt.
It is desirable to dry in time.

The drying rate at this time varies depending on the size of the pore volume of the spray-dried alumina powder or the moisture content after moisture adjustment, but the moisture evaporation rate (per hour,
(Weight ratio of evaporated water to alumina)
26 wt% / hr, preferably in the range of 2 to 20 wt% / hr. If the drying rate is less than 1 wt% / hr, it takes too much time to lower the production efficiency. If the drying is too long, there is a problem that if the time is too long, the particles may be powdered by abrasion before the strength of the particles is developed. The drying speed is 2
When the content is higher than 6 wt% / hr, the spherical particles are densely packed and the particle gap is extremely small, so that there is almost no water evaporation path at the time of drying, and the particles are destroyed by the pressure of steam generated by rapid evaporation of water. In addition, even if not broken, a large evaporation path is formed to form macropores, or the primary particles are not shrunk in a close-packed manner, and as a result, the particle strength is undesirably reduced.

Next, the temperature is raised before firing,
Preferably, the temperature is raised to a temperature of 20 ° C./hr at a rate of 20 to 40 ° C./hr. If the rate of temperature rise up to 200 ° C. is less than 20 ° C./hr, the effect of the slow rate of temperature rise does not increase, and it takes time from the viewpoint of productivity, which is not preferable. If the temperature is higher than 40 ° C./hr, shrinkage in the form of densely packed primary particles and secondary particles hardly occurs, macropores are generated, and bonding between particles does not sufficiently occur. Is difficult to obtain, which is not preferable.

The firing temperature is preferably in the range of 400 ° C. to 900 ° C. If the sintering temperature is lower than 400 ° C, the spray-dried alumina particles may not be sufficiently bonded due to insufficient binding of alumina particles, and if the sintering temperature is higher than 900 ° C, crystal transition and reduction of the surface area due to sintering may occur. Good performance as a carrier or adsorbent may not be obtained.

The firing time is not particularly limited, but is preferably in the range of about 1 hour to 10 hours. If the sintering time is less than 1 hour, the particle strength may not be sufficiently developed, and if the sintering time is 10 hours or more, the particle strength does not further increase. It is not preferable because there is a case where a product having a good performance cannot be obtained.

[0040]

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

Example 1 Step (a): The concentration when converted to alumina was 2.5 w
22.5 g of gluconic acid is dissolved in 10 kg of an aqueous solution of sodium aluminate having a concentration of 5.0 wt% as an alumina solution.
Kg was fed with stirring to prepare a precipitate of alumina hydrogel (the amount of gluconic acid at this time was 3.0 wt% per alumina). Step (b): This precipitate was filtered and washed while pouring ammonia water having an ammonia concentration of 0.3 wt% to prepare pseudo-boehmite alumina hydrogel. Analysis of the salt after washing revealed that 0.15 wt% of Na ₂ O was
0.75 wt% of O ₄ remained. Part of the pseudo-boehmite alumina hydrogel is dried and then 600
C., and the specific surface area, pore volume and pore diameter were measured. Specific surface area is 323 m ² / g, pore volume is 0.37 m
1 / g. Step (c): This pseudo-boehmite alumina hydrogel is
Spray dryer inlet temperature 260 ° C, outlet temperature 1
Spray drying was performed at 10 ° C. and a temperature difference of 150 ° C. to obtain a dried alumina powder. The water content of this dried alumina powder is 32 wt%
Met. Further, the pore volume measured by calcining the dried alumina powder at 600 ° C. was 0.55 ml / g. Steps (d) and (e): Water was added to the dried alumina powder to adjust the water content to 46 wt%, and then spherical alumina particles having an average particle diameter of 7 mm were prepared using a rotary granulator. Step (f): The spherical alumina particles were dried at room temperature while supplying air at a relative humidity of 50%, and the average drying rate was about 7 wt% /
After rotating and drying at 60 ° C. for 6 hours, the temperature was raised to 200 ° C. at a heating rate of 20 ° C./hr, followed by rotary firing at 600 ° C. for 2 hours. Table 1 shows the properties of the obtained alumina small spheres (S-1).
FIG. 1 shows the pore distribution by the mercury intrusion method.

Example 2 Spray dryer inlet temperature 285 ° C., outlet temperature 1
Spray-dried at 10 ° C, temperature difference 175 ° C and water content 30
Alumina small spheres (S-2) were obtained in exactly the same manner as in Example 1, except that dry alumina powder of wt% was used. The properties of the small spheres are shown in Table 1, and the pore distribution is shown in FIG. S-1
And the pore distribution of S-2 showed almost the same curve.

Example 3 Spray dryer inlet temperature 205 ° C., outlet temperature 1
Spray-dried at a temperature of 05 ° C, a temperature difference of 100 ° C and a water content of 35
Alumina small spheres (S-3) were obtained in exactly the same manner as in Example 1 except that the dried alumina powder of wt% was used. The properties of the small spheres are shown in Table 1, and the pore distribution is shown in FIG.

Comparative Example 1 Inlet temperature 400 ° C., outlet temperature 1 of spray dryer
Spray-dried at 20 ° C, temperature difference 280 ° C, water content 23
Except for using wt% of dry alumina powder, alumina small spheres (R-1) were obtained in exactly the same manner as in Example 1. The properties of the small spheres are shown in Table 1, and the pore distribution is shown in FIG.

Comparative Example 2 Inlet temperature 170 ° C., outlet temperature 9 of spray dryer
Spray-dried at 0 ° C, temperature difference 80 ° C, water content 38wt
% Water by adding water to dry alumina powder of 46%
However, since spray-dried particles adhere to each other, it is difficult to handle the powder, and uniform water adjustment suitable for granulation molding cannot be performed, and subsequent granulation by a rotary granulator must be performed. Became difficult.

Comparative Example 3 An aqueous solution of 10 kg of sodium aluminate having a concentration of 2.5 wt% when converted to alumina was converted to an aqueous solution of aluminum sulfate having a concentration of 5.0 wt% when converted to alumina.
The precipitate was supplied with stirring to 0 kg to prepare a precipitate of alumina hydrogel, and the precipitate was filtered and washed while applying ammonia water having an ammonia concentration of 0.3 wt% to prepare pseudo-boehmite alumina hydrogel. This example is a case where gluconic acid is not used at all. A part of the pseudo-boehmite alumina hydrogel was dried and then calcined at 600 ° C. to measure the specific surface area, pore volume and pore diameter. The specific surface area was 195 m ² / g, and the pore volume was 0.37 ml / g. This pseudo-boehmite alumina hydrogel was sprayed at an inlet temperature of 260 ° C. and an outlet temperature of 110 ° C.
Spray drying was performed at a temperature difference of 150 ° C. to obtain a dried alumina powder. The water content of the dried alumina powder was 32% by weight. Water is added to the dried alumina powder to obtain a water content of 46 w
The water content was adjusted to t%, and spherical alumina particles having an average particle diameter of 7 mm were prepared using a rotary granulator. The spherical alumina particles are dried at room temperature while supplying air at a relative humidity of 50% at an average drying rate of about 7 wt% / hr for 6 hours, and then heated to 200 ° C. at a heating rate of 20 ° C./hr. Rotary firing was performed at 600 ° C. for 2 hours. Table 2 shows the properties of the obtained alumina small spheres (R-2).

Example 4 A part of the dried alumina powder having an average particle diameter of 55 μm obtained in Example 1 was classified by a sieve to prepare a dried alumina powder having an average particle diameter of about 10 μm. Water was added thereto to adjust the water content so that the water content became 46 wt%, and then spherical alumina particles having an average particle diameter of 7 mm were prepared using a rotary granulator. The spherical alumina particles were dried at room temperature with an average drying speed of about 7 wt% / hr while supplying air at a relative humidity of 50%.
After rotation drying for 200 hours, 200 ° C at a heating rate of 20 ° C / hr
The temperature was raised to 600 ° C., and then rotary firing was performed for 2 hours at 600 ° C. The properties of each of the obtained alumina small spheres (S-4) are shown in Table 2.

Comparative Example 4 The dry alumina powder having a water content of 32% obtained in Example 1 was granulated by a rotary granulator as it was, but the dried alumina powder did not aggregate and adhere, and did not become spherical alumina particles. .

Example 5 Water was added to the dried alumina powder having a water content of 32% obtained in Example 1 to adjust the water content to 40% by weight, and then a spherical particle having an average particle diameter of 7 mm was obtained by a rotary granulator. Alumina particles were used. Then, the spherical alumina particles were dried at room temperature with an average drying speed of about 7 watts while supplying air at a relative humidity of 50%.
After rotating and drying at t% / hr for 6 hours, the temperature was raised at a rate of 20 ° C./hr.
The temperature was raised to 200 ° C. for hr, and then rotary firing was performed at 600 ° C. for 2 hours. Table 3 shows the properties of each of the obtained alumina small spheres (S-5).

Comparative Example 5 Water was added to the dried alumina powder having a water content of 32% obtained in Example 1 so that the water content became 60 wt%, but it became a paste and was granulated by a rotary granulator. Could not be performed.

Example 6 The spherical alumina particles having an average particle diameter of 7 mm prepared in Example 1 were dried at 50.degree.
After rotating and drying at 4 wt% / hr for about 3 hours,
The temperature was raised to 200 ° C. at 0 ° C./hr, and then rotary firing was performed at 600 ° C. for 2 hours. Table 3 shows the properties of the obtained alumina small spheres (S-6).

Example 7 The spherical alumina particles having an average particle diameter of 7 mm prepared in Example 1 were dried at 80.degree.
After spin-drying at 5 wt% / hr for about 1.5 hours, the temperature is raised to 200 ° C. at a temperature rising rate of 20 ° C./hr, and then 2 hours at 600 ° C.
Rotary firing for hours. The obtained alumina small spheres (S-7)
Table 4 shows the properties.

Example 8 The spherical alumina particles having an average particle diameter of 7 mm prepared in Example 1 were spin-dried at room temperature for 6 hours at an average drying rate of about 7 wt% / hr while supplying air at a relative humidity of 50%. ,
The temperature is raised to 200 ° C. at a rate of 20 ° C./hr and then 500
C. for 2 hours. The obtained alumina microspheres (S
Table 4 shows the properties of -8).

[0054]

[Table 1] ○: Satisfies the requirements of the present invention ×: Does not satisfy the requirements of the present invention

[0055]

[Table 2]

[0056]

[Table 3]

[0057]

[Table 4]

The embodiments of the present invention are listed below. (1) Alumina spheres having the following characteristics: The pore volume of the pore having a pore diameter of less than 100 ° is 0.30 to 0.7.
0 ml / g 0.10 ml / g pore volume with a pore diameter of 100 mm or more
The particle diameter is 3 to 10 mm. The mechanical particle strength is 10 kg or more. (2) The method for producing alumina small spheres according to the above (1), comprising the following steps (a) to (f). (A) a step of reacting a soluble aluminum salt aqueous solution with a basic aqueous solution in the presence of 2 to 15% by weight of a soluble carboxylic acid based on alumina to form a pseudo-baited alumina hydrogel, and (b) washing the alumina hydrogel. (C) spraying the washed alumina hydrogel onto a dry alumina powder having a water content in the range of 25 wt% to 35 wt% Drying, (d) adding water to the dried alumina powder to adjust the water content to a water content in the range of 35 to 55 wt%, (e) granulating the dried alumina powder having adjusted moisture into small spheres, f) drying the granulated and formed small spheres, followed by firing to form alumina small spheres; (3) removing the granulated and formed small spheres in step (f). The water evaporation rate per lumina is 26wt% / hr
(2) The method for producing alumina small spheres according to the above (2), wherein the alumina spheres are dried at a temperature of 400 ° C. to 900 ° C. (4) The pseudo-boehmite alumina hydrogel used in the step (a) has a specific surface area of 200 to 400 m ² / when measured by a BET method after calcination at 600 ° C. for 2 hours.
g, the pore volume as measured by the nitrogen adsorption method is 0.3
The method for producing alumina small spheres according to the above (2) or (3), wherein the amount is 5 to 0.60 ml / g. (5) The method for producing alumina small spheres according to the above (2), (3) or (4), wherein the washing in the step (b) uses ammonia water. (6) The ammonia concentration of the aqueous ammonia is 0.05 to
The method for producing alumina small spheres according to the above (5), which is 1.0 wt%. (7) The average particle diameter of the spray-dried alumina powder in the step (d) is 10 to 1 as measured by a micromesh method.
The method for producing alumina small spheres according to the above (2), (3), (4), (5) or (6), which is 00 μm. (8) The amount of water per unit weight of the dried alumina powder used in the water adjustment in the step (d) is determined by separately calcining the dried alumina powder on a volume basis at 600 ° C. for 2 hours. Of the pore volume of 1.2 to
The previous items (2), (3), (4), which are 1.5 times the amount,
(5) The method for producing alumina spheres according to (6) or (7). (9) The above items (2), (3), (4), wherein the particle diameter of the small spheres formed by granulation in the step (e) is 4 to 13 mm.
(5) The method for producing alumina small spheres according to (6), (7) or (8). (10) The drying in the step (f) is performed at a relative humidity of 40 to
(2), (3), (4), (5), (6), (7), and (7), which are performed while supplying 70% air.
(8) The method for producing alumina small spheres according to (9). (11) In the firing in the step (f), at 200 ° C.
(2), (3), (4), (5), (6), wherein the rate of temperature rise when the temperature is increased to 20 to 40 ° C./hr
(7) The method for producing alumina spheres according to (8), (9) or (10).

[0059]

The alumina small spheres according to the present invention have the excellent features that the pore volume of pores having a pore diameter of 100 ° or more is very small and the mechanical strength is strong. For this reason, the alumina small spheres obtained by the present invention are useful for various catalyst carriers, adsorbents, fillers and the like. The excellent alumina microspheres of the present invention can be produced only by the method of the present invention.

[Brief description of the drawings]

FIG. 1 shows pore distributions of the alumina microspheres S-1, S-2 and S-3 of Examples 1, 2 and 3 and the alumina microsphere R-1 of Comparative Example 1 by a mercury method. FIG.

Claims (3)

[Claims] 1. Alumina small spheres having the following characteristics: The pore volume of the pore having a pore diameter of less than 100 ° is 0.30 to 0.7.
0 ml / g 0.10 ml / g pore volume with a pore diameter of 100 mm or more
The particle diameter is 3 to 10 mm and the mechanical particle strength is 10 kg or more. 2. A method for producing alumina small spheres, comprising the following steps (a) to (f). (A) reacting a soluble aluminum salt aqueous solution with a basic aqueous solution in the presence of 2 to 15 wt% of soluble carboxylic acid based on alumina to form pseudo-boehmite alumina hydrogel, and (b) washing the alumina hydrogel Removing by-product salts to reduce the alkali metal in alumina to 1.0 wt% or less as an oxide; (c) spray-drying the washed alumina hydrogel to dry alumina powder having a water content in the range of 25 wt% to 35 wt% (D) adding water to the dried alumina powder to adjust the water content to a range of 35 to 55 wt%, (e) granulating the dried alumina powder having adjusted moisture into small spheres, (f) Drying the granulated and formed small spheres and then firing to form alumina small spheres; 3. In the step (f), the granulated and formed small spheres have a water evaporation rate per alumina of 26 wt.
The method for producing alumina small spheres according to claim 2, wherein the alumina small spheres are dried at a rate of not more than% / hr and then calcined at 400C to 900C.