JPS6065725A - Preparation of spherical particles of titania - Google Patents

Abstract

PURPOSE:To obtain spherical particles of titania having high strength, approximately spherical state, and smooth surface, by dispersing titanium oxide into hydrosol of titanium (IV) salt, forming hydrogel in a hot solvent immiscilbe with water. CONSTITUTION:An aqueous solution of titanium (IV) salt is adjusted to 0.6- 2.0pH to give hydrosol, which is dissolved in an ammonia precursor decomposable into ammonia by raising the temperature, if necessary. Particles of titanium oxide or titanic acid are finely dispered into the solution. Hydrogel is formed in a hot solvent immiscible with water, aged, washed with water, dried, and, if necessary, calcined. The hydrosol can contain an ammonia precursor such as urea, hexamethylenetetramine, etc. decomposable into ammonia by rise in temperature. The precursor is effective for shortening the time required to gelatinize it in the hot solvent, and forming spherical hydrogel having high strength.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing titania spherical particles having a diameter of α08 to 2% and a pore size suitable for adsorbents, catalysts, and catalyst supports. Titanium molded bodies are used for various purposes such as adsorbents, catalysts, catalyst carriers, enzyme immobilization carriers, and ceramic thermal spray materials. In particular, spherical particles with a diameter smaller than about 2% 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 fluid granulation are known methods for producing spherical particles with a diameter of less than 2% using fine powder raw materials, but in both methods, the strength of the particles is low;
It is difficult to obtain products with high wear resistance. Metal hydroxide, a method in which hydrosils of substances are dispersed in the form of droplets in a water-immiscible medium and heated and dehydrated to form spherical hydrogels, produces spherical particles with a true spherical shape and a smooth surface. be able to.

The present inventors added an alkali to an aqueous solution of titanium sulfate, chloride, etc. to adjust the pH to α6~zO, and heated the resulting sol in a water-immiscible heating medium to form a spherical hydrogel. Although we succeeded in producing spherical particles with excellent strength and wear resistance using a method of forming δ, when using them for adsorbents, catalysts, and catalyst supports, it is difficult to use them because the pore diameter and pore volume are small. It was found that the performance could not be fully demonstrated.

As a method for increasing the pore size, it is known to disperse in a sol water-insoluble organic substances such as crystalline cellulose, crushed natural fibers, or substances that generate water-insoluble polymers by heating. In this case, the strength of the spherical hydrogel decreases, and macropores with a pore diameter of approximately Looffi are formed in the fired particles.
Undesirable.

The present inventors found that when titanium oxide or titanic acid particles were finely dispersed in the hydrosil 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.

A similar effect is observed when powders of alumina-based materials, alumina-based materials, alumina-based materials, etc. are dispersed in a sol, but these materials have a unique adsorption ability of titanium oxide, titanic acid, etc. If the catalyst is still present, it may impede its performance as a carrier or be mixed as an impurity, which is undesirable. The titanic acid obtained by combining the titanic acid and the calcined product thereof are used, but the particle size is dl.

Is the specific surface area (BF>T method) 2OfTV? The above is desirable.

The proportion of titanium oxide or titanic acid added to the hydrosil is 20 to 60 times TiO2 in terms of Ti0z. When it is less than 20%, no substantial increase in pore diameter is observed, and when it exceeds 60%, it becomes difficult to form a spherical hydrogel or the strength of the gel decreases, so it is preferable &t7-1゜Titanium oxide Alternatively, it is desirable to finely disperse titanic acid in hydrosil, and if necessary, a dispersant is added and sufficient stirring is performed.

That is, the present invention adjusts the pH of the titanium salt aqueous solution to 0.6
After finely dispersing titanium oxide or titanium particles into the obtained hydrosil adjusted to ~zO, a spherical hydrogel is formed in a water-immiscible heating medium, followed by aging, washing with water,
The present invention provides a method for producing titania spherical particles with increased pore diameter and pore volume, which is characterized by drying.

Examples of titanium salts used in the present invention include sulfates and chlorides. In addition, the alkali used to neutralize the aqueous solution of these salts includes alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, carbonates such as sodium carbonate, potassium carbonate, hydrogen carbonate, etc. and ammonium hydroxide.

Using the above alkali, the pH of the aqueous solution of titanium salt is partially neutralized to 06 to zO to prepare hydrosil. P.H.
If it is lower than 06, the strength of the produced spherical hydrogel will be low, which is not preferable. Furthermore, when the pH is higher than zo 2 , the amount of precipitates increases, and peptization is insufficient even when heated or left overnight, and the strength of the spherical hydrogel also decreases in this case.

In the present invention, the titanium oxide or titanic acid particles described above are finely dispersed in the hydrosil prepared in this manner.

The hydrosil is then dispersed in 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 allowed to gel 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 is based on the diameter. The latter method 11 (suitable for producing fine particles of 108 to 2X) is suitable for producing particles of about 5 to 2X.

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, an ammonia precursor such as urea, hexamethylenetetramine, etc., which can be decomposed into ammonia by increasing the temperature, can be incorporated into the above-mentioned hydrosil. These ammonia precursors are effective in shortening the time required for gelation in a heating medium and forming a strong spherical hydrogel. In addition, 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.

Aging the spherical hydrogel formed by the above operation;
Wash with water and dry. 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 alone, but it may be forced-dried or baked depending on the application.

When used as an adsorbent, it is desirable to dry it at a temperature of 800°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 L Ti02 (titanyl sulfate aqueous solution I L K ta2N-' aqueous solution with 11 degrees of 200 f/1 partially neutralized to Pf (L7) and left overnight to form translucent titania sol Hexamethylene lenticin)=ly:y40fk was dissolved in this sol, and sol (7) T
The i0z concentration was adjusted to ft8oVt. Next, the semi-average particle size (
116μm1 specific surface 37% titanium oxide powder 60gr
, was added and stirred to finely disperse it. This sol was mixed with a mixed medium of trichlorobenzene and gelosin (SG 1.
The mixture is press-fitted through a nozzle from the bottom of a granulation tower with a height of 80 cm and filled with a temperature of 257° C.). By medium sehito 1
It is kept at 20°C. While rising in the medium, the sol becomes a spherical hydrogel with a diameter of about 2 to 8 yen. The hydrogel was separated from the medium and left in a 20% by weight aqueous ammonium nitrate solution for 4 hours. Thereafter, the sample was 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 Titanium tetrachloride was reacted with water.
Gradually add ammonia water to partially neutralize to PH08,
- A translucent titanya sol was obtained by leaving it overnight.

40 r of hexamethylenetetramine was dissolved in this sol, and the Tiozftl degree of the sol was adjusted to 80 VL. Next, T obtained by thermally hydrolyzing a titanyl sulfate aqueous solution
iO□ content 86 cm, average particle size α18 μm 1 specific surface area 1
86 powder of titanic acid powder 702 was added and stirred to finely disperse it. 4 tons of trichlorobenzene in which 1% of unrubitan monooleate was dissolved was heated to about 120° C., and the above-mentioned sol lt was added dropwise with strong stirring to disperse it in the form of 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 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 have a shape close to a true sphere, and the surface V
i is smooth and t is -).

Comparative Example 2 A hydrogel was obtained in the same manner as in Example 2 except that titanic acid powder was not added to the sol in Example 2, and the surface was smooth and flat.

Examples & 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.

The method for measuring the wood surface is as follows.OL Specific surface area
BET method 2 Pore volume Mercury intrusion method a Average pore diameter Determined by the following formula using the above specific surface area and pore volume values.

Average pore diameter - pore volume per area Patent applicant: Fuji Titanium Industry Co., Ltd.

Claims (1)

[Claims] If necessary, an ammonia precursor that can be decomposed into ammonia by increasing the temperature is dissolved in the hydrosil obtained by adjusting the pH of the titanium (he) salt aqueous solution to α6-20, and titanium oxide or titanic acid particles are finely dispersed. After that, a spherical hydrogel is formed in a water-immiscible heating medium, followed by aging, washing with water, drying, and optionally firing.