JPH0215485B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to highly porous, especially adsorbent, catalyst supports or The present invention relates to a theta-alumina molded body suitable as 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 methods have been proposed, but so far no porous molded body having sufficient mechanical strength has been obtained for theta alumina. 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.
The present invention was achieved as a result of intensive research to obtain an excellent theta-alumina molded body having a large specific surface area and porous properties. The present invention will be explained in detail below. A remarkable feature of the theta-alumina molded body 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 the distribution and amount of pores over a wide range, and all descriptions regarding pores in this explanation are based on the results of this measurement. The porous theta alumina molded body of the present invention has a specific surface area of 30
~150m ² /g theta alumina compact with a total volume of pores with a radius of 37.5 Å to 75000 Å of 0.4
~1.0cc/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 200 Å and a radius of 100 Å to 3000 Å
Shows a pore distribution with one clear peak in each angstrom, and has a pore volume of 0.45 cc/cm with a radius of 37.5 angstroms to 100 angstroms.
37.5 Å to 150 Å in radius, the pore volume is 0.1 to 0.5 cc/g, and the radius is 150 Å to 150 Å.
Characterized by a 3000 Å pore volume of at least 0.1 cc/g. That is, the porous theta-alumina molded body of the present invention is a porous theta-alumina molded body 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 theta-alumina molded product is usually granular, for example, spherical, cylindrical, or tablet-like, but it can also be molded into a plate or honeycomb shape. The particle size in granular form is approximately 50 μ or more when used as a packing material for fluidized beds or chromatography, and generally 1 to 10 mm.
It is normal to have a degree of Next, a method for manufacturing the porous theta alumina will be described below. The alumina raw materials for producing the porous theta alumina molded body of the present invention include γ-alumina,
Activated alumina such as η-alumina or alumina hydrate, such as boehmite, pseudoboehmite, gypsite, etc., or rehydrated transition alumina, etc. are used. Particularly preferred raw materials include boehmite and pseudoboehmite. The porous theta-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 flow 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 angstroms. Generally, individual particles of carbon black aggregate to form a large chain-like higher order structure (hereinafter referred to as "structure"), and the position and width of the pore 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 (eg, 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. 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, Ltd.
), Asahi Thermal FT, etc.
(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 theta-alumina molded body 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 pores of controlled location and quantity, 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 pseudopemite (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 theta-alumina molded bodies. In this firing step, alumina becomes theta alumina and has properties as a carrier or catalyst. In order to obtain the porous theta-alumina compact of the present invention, it is necessary to burn off 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, so if the removal of combustion heat is insufficient, the desired temperature cannot be controlled and there is a great 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 firing temperature required to burn off the carbon black as described above is approximately 500°C or higher, and the final firing temperature to obtain theta alumina is 1000°C or higher.
The temperature is 1250℃. Further, the firing time is not particularly limited, but is usually about 1 hour to 1 day. Thus, a theta-alumina compact is obtained which has excellent mechanical strength, abrasion resistance and physical properties such as large surface area, large pore volume, and characteristic pore distribution. 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 as long as the gist thereof is not 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/unit) of the extruded product was measured using a Kiya hardness tester, and the average value of 20 samples 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 ) content 75%) and 67.5 g of carbon black A (30% by weight based on boehmite) were dry mixed in a mixer for 60 minutes, then transferred to a batch kneader (inner capacity 2), and 4.3 % nitric acid aqueous solution was added over about 5 minutes while kneading, 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 3.5 mm using a screw extruder. After drying the molded product at 120℃ for 3 hours,
Gradually raise the temperature under dry air circulation in an electric furnace.
Baked at 600℃ for 3 hours, then at a temperature of 1100℃ for 3 hours.
An alumina molded body was obtained by firing for a period of time. The diameter of the extruded product after firing is approximately 2.4 mm, and the compressive strength is average
It was 2.5Kg/ke. Further, the specific surface area was 100 m ² /g. The analysis results of this alumina compact by X-ray diffraction are published in Catalysis Society of Japan's Handbook of Catalysts by Element (Jijinshokan) 27-28.
This was consistent with the data for theta alumina described on page 7. The pore volume and pore distribution of this molded body were as follows. Pore capacity from radius 37.5Å to 100Å 0.355cc/g Pore capacity from radius 37.5Å to 150Å 0.471cc/g Pore capacity from radius 150Å to 3000Å 0.205cc/g Pore volume from radius 37.5Å to 3000Å Capacity 0.676 cc/g Total pore capacity (37.5 Å to 75000 Å) 0.685 cc/g Modest pore radius (radius at which the distribution is maximum) 90 Å and 230 Å The pore distribution curve of this molded body is shown in FIG. Comparative Example 1 A theta-alumina molded body was produced in exactly the same manner as in Example 1 except that carbon black was not used. The specific surface area was 82 m ² /g. The pore volume and pore distribution were as follows. Pore capacity from radius 37.5Å to 100Å 0.399cc/g Pore capacity from radius 37.5Å to 150Å 0.400cc/g Pore capacity from radius 150Å to 3000Å 0.004cc/g Pore volume from radius 37.5Å to 3000Å Capacity: 0.404 cc/g Total pore volume (37.5 Å to 75000 Å) 0.404 cc/g Modest pore radius 82 Å The pore distribution curve of this molded body is shown in FIG. Example 2 An experiment was carried out in the same manner as in Example 1, except that the final firing temperature was changed to 1200°C, and an alumina molded body containing θ-type and α-type crystal forms was obtained. Various physical property values of the obtained alumina molded body were as follows. Compressive strength 3.1Kg/ke Specific surface area 63m ² /g Pore capacity (37.5~100Å) 0.085cc/g 〃 (37.5~150Å) 0.160 〃 〃 (150~3000Å) 0.300 〃 〃 (37.5~3000Å) 0.460 〃 〃( 37.5 to 75000 Å) 0.465 〃 Modest pore radius 93 Å and 920 Å Examples 3 and 4 Same as Example 1 except that the type or amount of carbon black added was changed and an extrusion molding machine with a die hole diameter of 1.5 mmφ was used. A theta alumina molded body was produced. Table 2 shows the physical properties of the molded product obtained.

[Table] The pore distribution curve of the theta alumina molded body obtained in Example 3 is shown in FIG. Example 5 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 3 to obtain a theta alumina molded body. strength is average
The specific surface area was 2.3 kg/g and 115 m ² /g. The pore volume and distribution of this material were as follows. Pore capacity (37.5Å to 100Å) 0.366cc/g 〃 (37.5Å to 150Å) 0.485 〃 〃 (150Å to 3000Å) 0.238 〃 〃 (37.5Å to 3000Å) 0.723 〃 Total pore volume (37.5Å to 75000Å) 0.730 〃 Modest pore radius 73 Å 250 Å Example 6 Same as Example 1 except that ammonia water was not added during kneading, except that the die pore diameter was 1.5 mm.
A theta alumina molded body was produced by changing the diameter to φ. The physical properties of the obtained theta alumina molded body are shown below.

【table】

【table】 [Brief explanation of drawings]

Figures 1, 2, and 3 are pore distribution diagrams of the theta alumina molded bodies produced in Example 1, Comparative Example 1, and Example 3, respectively, and curves 1, 3, and 5 are pore distribution diagrams. Curves 2, 4 and 6 are cumulative pore volume curves.

Claims (1)

[Claims] 1. A theta alumina molded body having a specific surface area of 30 to 150 m ² /g, the total volume of pores with a radius of 37.5 Å to 75000 Å being 0.4
~1.0cc/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 200 Å and a radius of 100 Å to 3000 Å
Shows a pore distribution with one clear peak in each angstrom, and has a pore volume of 0.45 cc/cm with a radius of 37.5 angstroms to 100 angstroms.
37.5 Å to 150 Å in radius, the pore volume is 0.1 to 0.5 cc/g, and the radius is 150 Å to 150 Å.
A porous theta-alumina compact characterized in that the 3000 Å pore volume is at least 0.1 cc/g.