JPS629532B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing titania spherical particles having a diameter of 0.03 to 5 m/m and a pore size suitable for adsorbents, catalysts, and catalyst supports. The titanium molded body is
It is used for a variety of purposes, including adsorbents, catalysts, catalyst carriers, enzyme immobilization carriers, and ceramic spray materials. In particular, spherical particles with a diameter smaller than about 2 m/m are suitable for use in a fluidized or suspended state.
In this case, it is important that particles do not collapse or wear out due to mutual collisions and vibrations. For this purpose, it is desirable that the particles have high strength, have a shape close to a true sphere, and have a smooth surface. Spray granulation and flow granulation are known methods for producing spherical particles with a diameter of less than 2 m/m using fine powder raw materials, but in both methods, the strength of the particles is low and wear resistance is poor. It is difficult to obtain something with high quality. According to a method in which a metal hydroxide hydrosol is dispersed in droplets in a water-immiscible medium and heated and dehydrated to form a spherical hydrogel,
Spherical particles having a true spherical shape and a smooth surface can be produced. The present inventors added an alkali to an aqueous solution of titanium () sulfate, chloride, etc. to adjust the pH to 0.6 to 2.0, and formed a spherical hydrogel with the resulting sol in a heating medium that is immiscible with water. We succeeded in producing spherical particles with excellent strength and wear resistance using a method of It was found that the performance could not be achieved. A known method for increasing the pore size is to disperse in a sol water-insoluble organic substances such as crystalline cellulose, crushed natural fibers, or substances that generate water-insoluble polymers when heated. However, in this case, the strength of the spherical hydrogel is low, and the pore size is 1000 Å in the calcined particles.
Some macropores are formed, which is not preferable. The present inventors found that when titanium oxide or titanic acid particles were finely dispersed in the hydrosol to form a spherical hydrogel in a water-immiscible heating medium, the pores of the added titanium oxide or titanic acid It was discovered that the pore diameter of the resulting spherical hydrogel increases regardless of the degree of increase, and the present invention was completed. Alumina-based materials, alumina-silica-based materials,
A similar effect is also observed when powders such as lyca-based substances are dispersed in a sol, but these substances may inhibit the unique adsorption performance of titanium oxide or titanic acid, or their performance as a catalyst or carrier. Otherwise, it is undesirable because it is mixed as an impurity. As the titanium oxide or titanic acid to be dispersed in the hydrosol, titanic acid obtained by heating or neutralizing an aqueous solution of titanium sulfate, chloride, etc., and a calcined version of this are used, but the particle size is 10
μm or less, and the specific surface area (BET
It is desirable that the surface area is 20 m ² /g or more. The ratio of titanium oxide or titanic acid added to the hydrosol is the TiO ₂ contained in the sol _.
In terms of conversion, it is usually 10 to 100% by weight. When it is less than 10%, no substantial increase in pore diameter is observed, and when it exceeds 100%, the number of macropores increases, which may be undesirable depending on the application. It is desirable to finely disperse titanium oxide or titanic acid in the hydrosol, and if necessary, a dispersant is added and sufficient stirring is performed. That is, the present invention aims to improve the pH of titanium () salt aqueous solution.
After finely dispersing titanium oxide or titanic acid particles in the hydrosol obtained by adjusting the ratio of The present invention provides a method for producing titanium spherical particles with characteristically increased pore diameter and pore volume. Examples of titanium salts used in the present invention include sulfates and chlorides. In addition, alkalis used to neutralize aqueous solutions of these salts include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, carbonates such as sodium carbonate, potassium carbonate, and sodium hydrogen carbonate, and hydroxides. Examples include ammonium. A hydrosol is prepared by partially neutralizing the pH of an aqueous solution of titanium salt to 0.6 to 2.0 using the above alkali. If the pH is lower than 0.6, the strength of the resulting spherical hydrogel will be low, which is not preferable. In addition, when the pH is higher than 2.0, the amount of precipitate increases, and peptization is insufficient even if heated or left overnight.
In this case as well, the strength of the spherical hydrogel decreases. In the present invention, the titanium oxide or titanic acid particles described above are finely dispersed in the hydrosol prepared in this manner. The hydrosol is then dispersed into droplets in a water-immiscible heating medium to form a spherical hydrogel. Specific methods include, for example, a method in which the sol is dropped into a heating medium and gelled while falling through the heating medium, a method in which the sol is added while stirring the heating medium, and the like. The former method has a diameter of 0.5~
It is suitable for producing particles of about 2 m/m, and the latter method is suitable for producing fine particles of 0.03 to 2 m/m. In either method, it is important to shorten the time required for gelation and to form a gel with high strength in order to produce particles with uniform particle size and close to true spheres. In the present invention, the above hydrosol can contain an ammonia precursor that can be decomposed into ammonia by increasing the temperature, such as urea and hexamethylenetetramine. These ammonia precursors are effective in shortening the time required for gelation in a heating medium and forming a strong spherical hydrogel. Further, in the present invention, a small amount of surfactant may be dissolved in the heating medium in order to prevent mutual adhesion and deformation of the spherical hydrogels. The spherical hydrogel formed by the above operations is aged, washed with water, and dried. Aging is performed by leaving the spherical hydrogel in a maturing solution for several hours or more. The ripening solution is an aqueous solution of ammonium nitrate, ammonium sulfate, ammonium chloride, etc., and its concentration is about 20%. Next, the aged spherical hydrogel is sufficiently washed with water to flush out sulfate ions, chloride ions, ammonium ions, sodium ions, etc. coexisting in the hydrogel. The spherical hydrogel washed with water has sufficient strength and abrasion resistance even when air-dried, but it may be forced-dried or fired depending on the application. When used as an adsorbent, it is desirable to dry at a temperature of 300°C or lower, but when used as a catalyst or catalyst carrier, it is usually calcined at a temperature of 500°C or higher. The strength and pore size of the particles increase as they are processed at higher temperatures. EXAMPLES The present invention will be specifically explained below with reference to Examples. Example 1 Titanyl sulfate water with a TiO ₂ concentration of 200 g/
Gradually add 13.2N ammonia water to solution 1.
It was partially neutralized to pH 1.7 and left overnight to obtain a translucent titanium sol. Dissolve 40g of hexamethylenetetramine in this sol and bring the _TiO2 concentration of the sol to 80.
g/. Next, 60 gr. of titanium oxide powder with an average particle size of 0.16 μm and a specific surface of 37 m ² /g was added.
Stir to finely disperse. This sol was mixed with a mixed medium of trichlorobenzene and kerosene (SG1.25/
It is press-fitted through a nozzle from the bottom of an 80cm-high granulation tower filled with 20°C. The medium is heated to 120
It is kept at ℃. While rising in the medium, the sol becomes a spherical hydrogel with a diameter of about 2 to 3 m/m.
The hydrogel was separated from the medium and left in a 20% by weight aqueous ammonium nitrate solution for 4 hours. Thereafter, it was thoroughly washed with water to remove coexisting soluble ions, and dried at 50°C. The obtained spherical particles had a shape close to a true sphere and had a smooth surface. Example 2 Aqueous solution of titanium chloride obtained by reacting titanium tetrachloride with water (TiO ₂ 200g/) 1 to 12.8N
of ammonium water was gradually added to partially neutralize the pH to 0.8, and the mixture was left overnight to obtain a translucent titanium sol. 40g of hexamethylenetetramine in this sol
was dissolved and the TiO ₂ concentration of the sol was adjusted to 80 g/. Next, a TiO ₂ content of 86% and an average particle size of 0.18μ were obtained by thermally hydrolyzing a titanyl sulfate aqueous solution.
70 g of titanic acid powder having a specific surface area of 186 m ² /g was added and stirred to be finely dispersed. Trichlorobenzene 4 in which 1% sorbitan monooleate was dissolved was heated to about 120°C, and the above-mentioned Sol 1 was added dropwise to the mixture while stirring vigorously to disperse it into fine droplets. After being held at 120°C for 2 minutes to transform it into a fine spherical hydrogel, it was aged, washed with water, and dried in the same manner as in Example 1. The obtained spherical particles had a shape close to a true sphere and had a smooth surface. Comparative Example 1 A hydrogel was formed in exactly the same manner as in Example 1 except that titanium oxide powder was not added to the sol. The obtained spherical particles had a shape close to a true sphere and had a smooth surface. Comparative Example 2 A hydrogel was formed in the same manner as in Example 2 except that titanic acid powder was not added to the sol. The obtained spherical particles had a shape close to a true sphere and had a smooth surface. Example 3 Table 1 shows the physical properties of the spherical particles obtained in Examples 1 and 2 and Comparative Examples 1 and 2, which were calcined at 600°C for 2 hours.

[Table] 〓〓〓〓

Claims (1)

[Claims] 1. If necessary, an ammonia precursor that can be decomposed into ammonia by increasing the temperature is dissolved in the hydrosol obtained by adjusting the pH of the titanium () salt aqueous solution to 0.6 to 2.0, and fine titanium oxide or titanic acid particles are dissolved. A method for producing titanium spherical particles, which comprises dispersing the titanium particles into a water-immiscible heating medium, forming a spherical hydrogel in a water-immiscible heating medium, aging, washing with water, drying, and optionally firing.