KR19980035031A - Process for producing large processed spherical alumina catalyst support - Google Patents

Abstract

The present invention relates to a method for producing a spherical alumina catalyst support having a pore structure of atmospheric pores having a diameter of 1 µm or more in the particles while maintaining sufficient mechanical strength.

According to the present invention, alumina hydrosol prepared by dissolving aluminum metal in an acid solution and a weak base are mixed, and then dropped in a suspension medium to form alumina hydrogel, followed by aging, washing, drying, and firing to prepare spherical alumina particles. In this process, the aging process consists of the first step in the suspension medium used for the dropping and the second step in the ammonium hydroxide.The suspension medium is a liquid paraffin having a specific gravity of 0.86-0.87 and a kinematic viscosity of 10cSt-30cSt. It is characterized by using.

Description

Method for preparing atmospheric sphere spherical alumina catalyst support

The present invention relates to a method for producing a spherical alumina catalyst support, and more particularly, to forming alumina particles into a spherical shape by an oil-dropping method, while maintaining the mechanical strength, a diameter of a predetermined size or more in the particle is maintained. Eggplant relates to a method of manufacturing to have atmospheric pores.

Alumina may serve as a catalyst or may be used as a catalyst support, and the performance of alumina depends greatly on reactivity, that is, activity, selectivity, reaction stability, as well as physical stability and pore structure. In particular, when used as a catalyst support, forming a spherical shape with sufficient physical stability results in less crushing or frictional loss during transportation and process operation, thereby preventing clogging in the reactor and the moving device, and smoothing the flow in a fluidized bed reactor. The effect can be obtained.

In addition, when the particles have a structure having air holes in the particles it is possible to smooth the flow of the reactants and products, as a result can have an excellent effect of improving the reactivity.

The preparation of spherical alumina particles by the oil-dropping method of known US Pat. No. 2,620,314 is briefly constructed as follows. Alumina hydrosol prepared by dissolving an aluminum metal in an acid solution and a weak base to be hydrolyzed with ammonia in the preparation process are mixed, and then dropped into a suitable non-aqueous liquid kerosene as a suspension medium to form a spherical alumina hydro. Form a gel. The spherical alumina particles are finally prepared by aging the spherical gel, followed by washing, drying and calcining.

In the above prior art, spherical alumina hydrogel particles produced while passing through a high temperature kerosene are subjected to a aging process in an aqueous ammonium hydroxide solution whose concentration is fixed at 1-5% by weight at 95-110 ° C. However, the alumina particles prepared by this aging method are brought into direct contact with a relatively high concentration of ammonium hydroxide solution, so that the apparent density can be obtained relatively excellent value, but the pore structure in the particles is difficult to be completely built. Accordingly, the mechanical strength is lowered, so that the fracture is easily broken and cracked on the surface, and air holes having a diameter of 1 μm or more in the particles cannot be formed.

In US Pat. No. 3,600,129, the alumina hydrogel is contacted with the aqueous solution of ammonium hydroxide during the aging process to improve the mechanical strength even at low apparent density. A method of aging by press was introduced.

British Patent No. 1,542,557 proposes a method of aging alumina hydrogel in aqueous ammonium hydroxide solution in order to improve the mechanical strength of spherical alumina particles in the oil-dropping method of US Patent No. 2,620,314. That is, the aging process consisted of a first aging step in which the concentration of ammonium hydroxide was fixed low, and a second aging step gradually increasing to a high concentration.

However, the two prior art methods improve the mechanical strength, that is, the lowering of the fracture strength due to the instability of the aging stage, among the disadvantages of US Pat. No. 2,620,314, but the pore structure of the air pores is 0.1 μm or less. Since it does not have the use as a catalyst support requiring a smooth flow of reactants and products has a problem that is disturbed.

The present invention is to solve the above problems of the prior art, while maintaining a sufficient mechanical strength when the spherical alumina particles are removed at the same time having a pore structure of air pores having a diameter of 1㎛ or more, when used as a catalyst support The purpose is to facilitate the flow of reactants and products so that they can have an excellent effect of improving the reactivity as a result.

According to the present invention, alumina hydrosol prepared by dissolving aluminum metal in an acid solution and a weak base are mixed, and then dropped in a suspension medium to form alumina hydrogel, followed by aging, washing, drying, and firing to prepare spherical alumina particles. In this case, the aging process consists of the first step in the suspension medium used for the dropping and the second step in the ammonium hydroxide of a certain concentration, and the use of liquid paraffin having a specific specific gravity and kinematic viscosity as the suspension medium. It features.

Hereinafter, the present invention will be described in detail.

In the present invention, first, a fluid paraffin having a specific specific gravity and kinematic viscosity is introduced as a suspension medium in which a mixture of alumina hydrosol and a weak base is dropped.

Then, the alumina hydrogel particles produced by dropping were subjected to the first aging process in the specific fluidized paraffin, and then subjected to the second aging process in an aqueous ammonium hydroxide solution having a concentration of 25% by weight, thereby providing mechanical strength. To produce spherical alumina particles that can obtain both a and a pore diameter by a predetermined value or more.

The suspending medium used in the dropping process is insoluble in water-soluble mixtures of alumina hydrosol and weak base and has a higher surface tension than water so that the dropped mixture is formed into a spherical structure having the smallest surface area in its volume. It should be able to play a role to make it possible.

In the aging process, the alumina hydrogel stays in the suspension medium at a temperature of 100-110 ° C. for 24-48 hours. At this time, the suspension medium should gradually form pore structure as the weak base in the alumina hydrogel is hydrolyzed.

In the present invention, as a suspending medium that can perform the above roles in the dropping and aging process, it uses a liquid paraffin having a specific gravity of 0.86-0.87 and a kinematic viscosity of 10cSt-30cSt.

If the specific gravity of the liquid paraffin is out of the above range, it is not good because it cannot be completely spherical in the dropping process. When the kinematic viscosity is less than 10 cSt, the mechanical strength is lowered due to the excessive formation of pores, and when the kinematic viscosity exceeds 30 cSt, the mechanical strength is excellent, but atmospheric pores having a diameter of 1 μm or more are not formed.

Hereinafter, the present invention will be described in detail through Examples and Comparative Examples.

First, the measurement method of the physical property is as follows.

* Crushing strength measurement

20-50 representative particle samples were selected and dried at 200 ° C. for 3 hours, and then cooled to room temperature in a desiccator. In order to prevent moisture in the analysis, only the sample which can be measured for 10 minutes was taken out and measured.The measuring method is to put the particles on a plate and apply the force with a piston to record the force when the particles are broken as breaking strength. Repeat 20 times to average these values.

* Determination of the presence of atmospheric air diameter

Determination was made by photographic reading of a sample magnified 1,000 times using an electron microscope (SEM).

* Specific gravity and kinematic viscosity measurement

The measurements were made in accordance with Korean Industrial Standards 2002 (KS M 2002) and Korean Industrial Standards 2014 (KS M 2014), respectively.

EXAMPLE

10 g of purity 99.7% granol-type aluminum metal was administered to a reactor containing 45.3 ml of pure water and mixed at room temperature. 22.6 ml of 35% sulfuric acid was administered very slowly over 12 hours into the reactor.

The generated hydrogen gas was cooled to not exceed 90 ° C. using a water jacket while continuing to discharge. After 3 hours, the heating using the mantle was properly adjusted to maintain 90 ° C., and about 50 ml of aluminum aqueous solution was prepared after 24 hours.

After preparing a weak base solution in which 9.3 g of diallylamine was dissolved in 23.9 ml of pure water, it was administered to a reactor cooled to room temperature and mixed with vigorous stirring to prepare about 90 ml of alumina hydrosol.

As a suspension medium, a liquid paraffin having a specific gravity of 0.8627 and a kinematic viscosity of 14.5 cSt was filled in a glass tube 5 cm in diameter and 100 cm in length, and the temperature was maintained at 95 ° C. while dropping the alumina hydrosol prepared above through a nozzle from 4 cm above the liquid level. To give a spherical alumina hydrogel.

The alumina hydrogel accumulated at the bottom of the glass tube was extracted and transferred to a container filled with the same liquid paraffin, and aged first at 107 ° C. for 15 hours. The first aged alumina hydrogel was extracted from the vessel and transferred to 400 ml of 25% by weight aqueous ammonium hydroxide solution at 93 ° C., followed by secondary aging for 8 hours.

After drying at 120 ° C. for 12 hours, and calcining at 630 ° C. for 3 hours to finally form spherical alumina particles, the fracture strength was measured and the pore having a diameter of 1 μm or more was measured by electron microscopy of the shear surface of the particles. The presence or absence was confirmed, and the results are shown in Table 1 below.

Comparative Example 1

Spherical alumina particles were prepared and analyzed in the same manner as in Example, except that the suspending medium for dropping and kerosene instead of liquid paraffin were used for the first aging, and the results are shown in Table 1 below.

Comparative Example 2

Spherical alumina particles were prepared and analyzed in the same manner as in Example, except that the suspending medium for dropping and the liquid paraffin having a specific gravity of 0.8699 and a kinematic viscosity of 77.02cSt were used for the first aging, and the results are shown in Table 1 below. It was.

TABLE 1

Spherical alumina particles prepared by dropping using a liquid paraffin as a suspending medium and also subjected to a secondary aging process, as in the present invention, since the pore structure can be sufficiently built, the breaking strength, which is a measure of mechanical strength, is not less than 2.2 kgf. While retaining, it has pores with a diameter of 1 μm or more, and thus has sufficient physical stability and atmospheric pore structure to be used as a catalyst support.

Claims (3)

In the manufacture of spherical alumina particles by mixing alumina hydrosol and weak base prepared by dissolving aluminum metal in acid solution, dropping in suspension medium to form alumina hydrogel, and then aging, washing, drying and firing A process for producing an atmospheric sphere alumina catalyst support, characterized in that the aging process consists of a first step in a suspension medium used for dropping and a second step in ammonium hydroxide. The method of claim 1, wherein the suspension medium used in the dropping and the first aging step is a fluidized paraffin having a specific gravity of 0.86-0.87 and a kinematic viscosity of 10 cSt-30 cSt. . The method of claim 1, wherein the air spherical alumina catalyst support has a fracture strength of 2.2 kgf or more and a diameter of 1 µm or more.