JPH0134929B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention has excellent mechanical strength, large specific surface area, and relatively fine pores (micropores).
The invention relates to a highly porous activated alumina molded body having a large amount of both mesopores and medium-sized pores (mesopores), and which is particularly suitable as an adsorbent, a catalyst support, or a catalyst. Alumina is used for various purposes such as a desiccant, an adsorbent, a catalyst, and a catalyst carrier. In particular, it is well known that alumina-supported catalysts are used in various reactions. The important qualities that these catalysts or supports are required to have are the crystal type of alumina,
Specific surface area, pore distribution range and amount, etc.
These give good results for certain reactions in which alumina is used. In particular, the adjustment of pores is considered to be an extremely important factor for the desired reaction, and it is important to create molded bodies that maintain physical properties such as mechanical strength and abrasion resistance, and have desired pores, or to manufacture them. Various laws have been proposed. Relatively high surface area activated alumina has a radius of 100
It has a considerable number of pores, and sometimes most of them, in the area around or below Å, and this is thought to be basically caused by the primary particles that make up alumina, but the micropores The distribution itself can be adjusted by selecting manufacturing raw materials or manufacturing methods. In addition, activated alumina that has been provided with pores with a larger pore radius by means of different manufacturing methods or the use of various additives is available, for example, activated alumina ACP-1 (100~
2000Å, 10000Å or more) or JP-A-1988-
Examples include activated alumina (10,000 Å or more) using rehydratable alumina, the manufacturing method of which is shown in No. 158397. The presence of these mesopores and macropores is an extremely important factor in specific reactions because of the advantages of facilitating intrapore diffusion and being able to control the reaction sequence. However, such molded bodies containing mesopores and macropores often have problems with properties such as strength, which are practically essential conditions, or have a pore distribution that is wider than desired. In view of these circumstances, the inventors of the present invention have developed a material that does not impair physical properties such as mechanical strength and abrasion resistance.
As a result of extensive research in order to obtain an excellent activated alumina molded body with extremely porous characteristics, it has a large specific surface area and a large number of concentrated pores (mesopores) with a radius of 100 Å to 600 Å. This invention has been achieved. The present invention will be explained in detail below. A remarkable feature of the activated alumina compact of the present invention is the distribution of pores and their capacity. It is well known that the mercury intrusion method is most suitable for measuring pore distribution and quantity over a wide range, and all descriptions regarding pores in the present invention are based on the results of this measurement. The porous activated alumina molded body of the present invention has a specific surface area of 100~
A porous activated alumina compact of 350 m ² /g, with a total volume of pores with a radius of 37.5 Å to 75000 Å of 0.6
~1.5 cc/g, preferably 0.7-1.3 cc/g, with at least 90% of the total pore volume having a radius of 37.5 Å
occupied by pores with a radius of 40 Å to 100 Å and a radius of 100 Å to 500 Å
Shows a pore distribution with one clear peak in each Å, and has a pore volume of at least 37.5 Å to 100 Å in radius.
0.45cc/g, preferably 0.5-1.1cc/g,
Pore volume with radius between 100 Å and 600 Å is at least 0.1
cc/g, preferably 0.15 to 0.8 cc/g. That is, the porous activated alumina molded article of the present invention is a porous activated alumina molded article having a large number of pores in two limited pore regions. In addition, this molded body has excellent mechanical strength and wear resistance, so it is extremely suitable for use in adsorbents, catalysts, catalyst carriers, and the like. The shape of the activated alumina molded article is usually granular, for example, spherical, cylindrical, or tablet-like, but it can also be molded into a plate-like shape or a honeycomb-like shape. The particle size in granular form is approximately 50 μ or more when used as a packing material for fluidized bed seromatosis, and generally 1 to 10 mm.
It is normal to have a degree of Next, a method for producing the porous activated alumina will be explained below. The alumina raw materials for producing the porous activated alumina molded body of the present invention include γ-alumina, η
- Activated alumina such as alumina, or alumina or alumina hydrate that becomes activated alumina by calcination, such as boehmite, pseudoboehmite, gypsite, etc., or rehydrating transition alumina, etc. is used. Particularly preferred raw materials include boehmite and pseudoboehmite. The porous activated alumina molded body of the present invention is produced by mixing carbon black with the above alumina raw material, adding water and a molding aid if necessary, kneading and molding, and then firing in an oxygen-containing air stream to form carbon black. It can be produced by burning and removing. The carbon black to be mixed with the alumina raw material has a particle size ranging from 150 to 3000 A units. Carbon blank generally has individual particles that aggregate to form a large chain-like higher-order structure (hereinafter referred to as "structure"), and the position and width of the mesopore distribution in the molded product obtained by the method of the present invention depend on the particle size of the carbon black. and the size of the structure. The size of the structure is expressed by the oil absorption capacity of the carbon black (for example, DBP absorption capacity; capacity of dibutyl phthalate absorbed by 100 g of carbon black, unit: ml/100 g).
And in normal carbon black, its DBP
Absorption amount is about 60-300ml/100g, special type
There are also over 300ml/100g. In the method of the present invention, carbon black
If the DBP absorption amount is the same, generally if carbon black with a smaller particle size is used, the average pore radius of the mesopores of the obtained molded body will be smaller.
On the other hand, if particles with a large particle size are used, the average pore radius will become large. Furthermore, if carbon black having a wide particle size distribution is used, a molded article having a slightly wide pore distribution can be obtained. The particle size of carbon black is appropriately determined by taking into account its DBP absorption amount and mesopore distribution of the molded product. There are no particular restrictions on the type of carbon black that can be used, and commercially available carbon blacks such as channel blacks such as Mitsubishi Carbon Black #100 and #600 (manufactured by Mitsubishi Chemical Industries, Ltd.), Diablack A, and Diablack H ( Mitsubishi Chemical Industries
Furnace black (manufactured by Co., Ltd.), Asahi Thermal
Examples include FT (manufactured by Asahi Carbon Co., Ltd.), Denka Acetylene (manufactured by Denki Kagaku Kogyo Co., Ltd.), and Ketsutien Black EC (manufactured by Akzochemy Co., Ltd.). During molding, the alumina raw material and carbon black should be mixed as uniformly as possible to obtain better physical properties. The amount of carbon black added to the alumina raw material is 5 to 120
% by weight, preferably 10 to 100% by weight. When using additives that disappear upon firing, the upper limit of the amount of additives is approximately 10% by weight to avoid impairing the strength and other physical properties of the resulting molded product. Compared to the usual case, when producing the porous activated alumina molded article of the present invention, the amount of carbon black added is extremely large. Moreover, it is quite surprising that the addition of such a large amount imparts mesopores in a controlled location and amount, yet does not impair the required physical properties. The raw material alumina and carbon black that have been uniformly mixed in this way are further mixed and kneaded by adding water and other forming aids if necessary.
Molded into desired shape. Well-known molding methods include tableting, extrusion, and extrusion.
There are methods such as the Marmo method, rolling granulation method, and briquetting method, among which extrusion molding method is easy and versatile. The molding method will be explained by taking as an example a case where pseudoboehmite (monohydrated alumina whose X-ray analysis shows a broad boehmite structure) is used as a raw material. For example, 30 to 100 parts of pseudoboehmite
After adding 50% of carbon black and mixing uniformly with a mixer, transfer to a kneader, add water and auxiliary agents, and knead. Preferred auxiliaries include inorganic acids,
Examples include organic acids or basic nitrogen compounds such as ammonia, hydrazine, aliphatic amines, aromatic amines, and heterocyclic amines, and organic substances such as polyvinyl alcohol. The kneaded material thus obtained is then extruded using an extruder through a die hole of a desired size. The molded product can also be aged in a closed container if desired. The alumina molded bodies formed by various methods as described above are then dried and fired, and finally become porous activated alumina molded bodies. In this firing step, alumina becomes activated alumina and has properties as a carrier or catalyst. In order to obtain the porous activated alumina compact of the present invention, it is necessary to burn off the carbon black during the firing step.
However, oxidative calcination must be accomplished with great care. This is because carbon black is flammable and the amount added is relatively large.
This is because if the removal of combustion heat is insufficient, the desired temperature cannot be controlled and there is a strong possibility that the temperature will become high. A rapid temperature rise is not desirable even if the temperature is below the upper limit temperature. The final firing temperature to obtain activated alumina, including the combustion removal of carbon black as described above, is approximately 500°C or higher. The upper limit temperature for firing is about 800°C if the activated alumina is in the γ- or η-form, and about 1200°C if it is in the θ-form. Further, the firing time is not particularly limited, but is usually about 1 hour to 1 day. Thus, it has excellent mechanical strength, abrasion resistance, and physical properties such as large surface area and large pore volume, and in addition to the micropores derived from the alumina primary particles, the carbon black is also derived from the addition of carbon black and its removal. An activated alumina molded body having mesopores with controlled distribution and amount can be obtained. The amount of mesopores depends mainly on the amount of carbon black added. Moreover, the distribution can be controlled by the type of carbon black used, ie, the diameter and structure of its unit particles. Specific examples thereof will be shown in the Examples below. Due to the unique properties of the activated alumina thus obtained, it is understood that it can be expected to have excellent performance in a variety of applications such as catalysts, catalyst supports, and even adsorbents. Hereinafter, the content of the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples unless the gist thereof is exceeded. The pore distribution and amount in the examples were measured using a mercury intrusion porosimeter. The machine used is Carlo Erba Porosimeter Series 2000 with a maximum pressure of 2000 kg/
^cm2 gauge. Therefore, the measurement range of the pore is the radius
The range is from 37.5 Å to 75000 Å. The surface area was calculated using the BET method using the nitrogen adsorption method.
The machine used is Carlo Erba Soap Tomatics 1800.
It is. For the compressive strength, the radial breaking load (Kg/piece) of the extrusion molded product was measured using a Kiya hardness tester, and the average value of 20 pieces was adopted. Further, Table 1 shows the physical properties of carbon black used in the following examples.

[Table] Example 1 Boehmite powder Pural SB manufactured by Condea (Al ₂ O ₃
75%) 225g and carbon black
After dry mixing 67.5 g of A (30% by weight based on boehmite) in a mixer for 60 minutes, transfer it to a batch kneader (inner capacity 2) and add 220 g of a 4.3% nitric acid aqueous solution.
g was added while kneading over about 5 minutes, and kneading was continued for an additional 25 minutes. Next, 128 g of 2.1% ammonia water was added to the mixture, kneaded for 25 minutes, and then extruded to a diameter of 1.5 mm using a screw extruder.
After drying the molded product at 120℃ for 3 hours, the temperature was gradually raised in an electric furnace with drying air flowing through it, and finally
An activated alumina molded body was obtained by firing at a temperature of 600°C for 3 hours. The diameter of the extruded product after firing was approximately 1.2 mm, and the average compressive strength was 2.5 kg/piece. Further, the specific surface area was 274 m ² /g. The pore volume and pore distribution of this molded body were as follows. Pore capacity from radius 37.5 Å to 100 Å 0.728 cc/g Pore capacity from radius 100 Å to 600 Å 0.233 cc/g Total pore volume (37.5 Å to 75000 Å) 0.965 cc/g Modest pore radius (distribution is maximum) radius)
64 Å and 200 Å The pore distribution curves of these molded bodies are shown in FIG. Comparative Example 1 An activated alumina molded body was produced in exactly the same manner as in Example 1 except that carbon black was not used. The diameter of the obtained molded body was about 1.2 mm, the compressive strength was 2.6 Kg/ke, and the specific surface area was 195 m ² /g. The pore volume and pore distribution were as follows. Pore capacity from radius 37.5Å to 100Å 0.680cc/g Pore capacity from radius 100Å to 600Å 0.049cc/g Total pore capacity (37.5Å to 75000Å) 0.729cc/g Modest pore radius 62Å The pore distribution curve of the molded body is shown in FIG. Example 2 This example shows that the pore distribution can be adjusted by selecting the type of carbon black. Various alumina molded bodies were obtained in exactly the same manner as in Example 1 except that the type of carbon black was changed as shown in Table 2. The compressive strength of each of these was approximately 2 kg/kg. The pore distribution and pore capacity are shown in Table-2.

【table】

[Table] Example 3 This example shows the effect of varying the amount of carbon black added. An alumina molded body was obtained in exactly the same manner as in Example 1 except that the amount of carbon black added was changed as shown in Table 3. However, due to the capacity of the kneader, the total amount of boehmite and carbon black was set to 300 g. 4.3% HNO ₃ aqueous solution and 2.1 accordingly
% ammonia aqueous solution addition amount is 100g of boehmite
They were 97.7g and 56.9g, respectively. The results are shown in Table-3.

[Table] Figure 3 shows the pore distribution curve of an alumina molded body produced with an added amount of carbon black A of 50% by weight. Example 4 In the same manner as in Example 1, 225 g of boehmite and 67.5 g of carbon black A were mixed and then kneaded in a kneader. At this time, instead of nitric acid, 225 g of a 3.75% acetic acid aqueous solution was added and kneaded for 30 minutes, and then 112.5 g of 1.30% aqueous ammonia was added and kneaded for 25 minutes. below,
Drying and firing were carried out in exactly the same manner as in Example 1 to obtain an activated alumina molded body. strength is average
The specific surface area was 283 m ² /g. The pore volume and distribution of this material were as follows.
The pore distribution curve is shown in FIG. Pore capacity 37.5 Å to 100 Å (radius) 0.585 cc/g Pore capacity 100 Å to 600 Å (radius) 0.248 cc/g Total drilling capacity (37.5 to 75000 Å) 0.838 cc/g Modest pore radius 50 Å 200 Å Example 5 After mixing and kneading in exactly the same manner as in Example 1, extrusion molding was performed using an extruder with a die hole diameter of 3.5 mmφ. Next, the molded products were dried at 120°C for 3 hours, and then the temperature was gradually raised in an electric furnace with drying air flowing.Finally, one part was baked at 600°C for 3 hours, and the other at 1000°C for 3 hours. An alumina molded body was obtained. The physical properties of the obtained molded product are shown in Table 4.

[Table] Example 6 An alumina molded body was produced in the same manner as in Example 3 except that the amount of carbon black A added was changed to 70% by weight based on the boehmite. The physical properties of the obtained alumina molded body are as follows. Compressive strength 1.8Kg/ke Pore capacity (37.5~100Å) 0.497cc/g Pore capacity (100~600Å) 0.587〃 Total pore volume (37.5~75000Å) 1.091〃 Modest pore radius 46Å and 310Å

[Brief explanation of drawings]

Figures 1, 2, 3 and 4 are Example 1, Comparative Example 1, Example 3 and Example 4, respectively.
FIG. 3 is a pore distribution state diagram of an activated alumina molded body manufactured in FIG. Curves 1, 3, 5 and 7 are curves showing the state of pore distribution, and curves 2, 4, 6 and 8 are cumulative curves of pore volume.

Claims (1)

[Claims] 1. A porous activated alumina molded body having a specific surface area of 100 to 350 m ² /g, wherein the total volume of pores with a radius of 37.5 Å to 75000 Å is 0.6.
~1.5cc/g, at least 90% of the total pore volume above with a radius of 37.5Å
occupied by pores with a radius of 40 Å to 100 Å and a radius of 100 Å to 500 Å
Shows a pore distribution with one clear peak in each Å, and has a pore volume of at least 37.5 Å to 100 Å in radius.
0.45 cc/g, and a porous activated alumina molded body characterized in that the pore volume with a radius of 100 Å to 600 Å is at least 0.1 cc/g.