JPS6029645B2 - Method for producing acicular zinc oxide particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing acicular zinc oxide particles, and particularly to a method for producing acicular zinc oxide particles having a uniform particle size.

Conventionally, the method for producing acicular zinc oxide was to oxidize the zinc vapor produced by heating metal zinc.However, this method requires the heating conditions to be kept constant because the process is carried out at high temperatures. However, it was difficult to keep the shape and size of the particles constant, as the resulting particles would cause burnt silk.

For this reason, there have been drawbacks such as limited application to catalysts where particle properties have a subtle effect. Furthermore, since high-temperature equipment, carrier gas, etc. are required, the device also has the disadvantage of being complicated and expensive. The present invention was made with the aim of solving these problems, and it is possible to produce acicular zinc oxide particles in an aqueous solution with a uniform particle size compared to conventional ones, and to change the particle size by adjusting the reaction conditions. The present invention provides a method for producing acicular zinc oxide particles whose diameter can be controlled.

That is, acicular zinc oxide particles are obtained by adding an organic compound that generates a base through hydrolysis to an aqueous zinc salt solution, or adding an organic compound that generates an acid through hydrolysis to an aqueous zinc salt solution. .

The outline of this reaction is as follows. That is, when an organic compound that generates a base upon hydrolysis is added to an aqueous zinc salt solution and heated, hydrolysis proceeds, and the base is gradually and uniformly generated in the aqueous zinc salt solution.

This generated base reacts with the zinc salt to produce zinc oxide. Furthermore, when an organic compound that generates an acid upon hydrolysis is added to an aqueous zincate solution and heated, hydrolysis proceeds, and the acid is gradually and uniformly generated in the aqueous zincate solution.
This generated acid reacts with zincate to form zinc oxide. The organic compound used here that generates a base upon hydrolysis may be any organic compound that gradually generates a base upon hydrolysis, is water-soluble, and can be easily removed after the reaction. In particular, organic compounds containing nitrogen atoms can be used, among which hexamethylenetetramine gives particularly good results. In addition to this, urea can also be used. Further, the organic compound used here that generates an acid upon hydrolysis may be any organic compound that gradually generates an acid upon hydrolysis, is water-soluble, and can be easily removed after the reaction.

In particular, esters can be used, of which ethylene chlorohydrin gives particularly good results. Besides, ethyl acetate can also be used.

The reaction temperature is 2000 to 10000, more preferably 6000 when hexamethylenetetramine is used.
o to 10,000, or 4,000 to 10,000 when ethylene chlorohydrin is used.

If it is less than 20 qo, the reaction will be extremely slow and it will be difficult to control the particle size.

Regarding the relationship between the reaction temperature and the particle size and particle size distribution, generally speaking, the higher the reaction temperature, the smaller the particle size and the narrower the particle size distribution. The reaction time is between 5 minutes and more preferably 6 minutes.

If the reaction time is 5 minutes or less, the reaction will proceed sufficiently and no precipitation will occur.

Furthermore, no further precipitation occurs even if the reaction is continued for 60 minutes or more. The molar ratio between the zinc salt and the organic compound that produces a base upon hydrolysis, or the molar ratio between the zinc salt and the organic compound that yields an acid upon hydrolysis, varies depending on the type of zinc salt or zincate used, but the molar ratio In general, the larger the molar ratio, the smaller the particle size and the narrower the particle size distribution. By changing reaction conditions such as reaction temperature and molar ratio, the long axis can be adjusted to 0.1 to 1.
Desired acicular zinc oxide particles having a size of about 5 mm can be obtained.

The reaction method is as follows.

That is, in an aqueous solution, a zinc salt and an organic compound that produces a base when hydrolyzed, or a zinc salt and an organic compound that produces an acid when hydrolyzed are reacted at a predetermined temperature for a predetermined period of time, and the resulting precipitate is filtered and dissolved in water. The white powder can be obtained by washing and drying.

This white powder is thermally stable up to 1000 qo, and is confirmed to be zinc oxide by X-ray diffraction.

Furthermore, the electron micrograph confirms that the particles are acicular particles with a uniform particle size. When the acicular zinc oxide obtained in the present invention was used as a catalyst for the reaction of propylene oxidation to synthesize benzene, the benzene selectivity reached over 40%. When used, for example, the selectivity of spherical zinc oxide is about 10%.
, showed a high catalytic ability compared to the selectivity of plate zinc oxide, which was about 5%.

In the present invention, the reaction is carried out in the presence of an organic compound that generates a base or acid through hydrolysis without directly adding a base or acid, so as the base or acid is generated in the aqueous solution, zinc salt or It is thought that since zinc oxide is produced by reacting with zincate, particles with a uniform particle size can be obtained.

Hereinafter, the present invention will be explained in more detail based on examples.

Example 1 A mixed aqueous solution prepared by dissolving 0.5 mol of hydrochloric acid, 1 mol of zinc chloride, and 2 mol of hexamethylenetetramine in 2,800 mol of water was heated at about 100 oo for 6 hours to produce a free-flowing white precipitate.

This was filtered, washed and dried. The electron micrograph shows that the particles are acicular zinc oxide particles with uniform particle size, as shown in the drawing. The particle size is about 4 meters, and the particle size distribution is 3 to 5 meters.
The yield was 80% of theory. Example 2 A mixed aqueous solution of 0.5 mol of nitric acid, 5 mol of zinc nitrate, and 5 mol of hexamethylenetetramine dissolved in 2,800 mol of water was heated at about 100 am for 60 minutes to form acicular zinc oxide particles of uniform particle size. Obtained.

The particle size was about 3 mm, the particle size distribution was 1 to 5 Am, and the yield was 80% of theory. Example 3 A mixed aqueous solution prepared by dissolving 50 moles of sodium hydroxide, 5 moles of zinc acetate, and 5 moles of ethylene chlorohydrin in 2800 moles of water was heated at about 100 oo for 60 minutes to obtain acicular zinc oxide particles of uniform particle size. .

The particle size was about 8 m, the particle size distribution was 8 to 12 m, and the yield was 90% of the theoretical value. Example 4 A mixed aqueous solution of 25 moles of sodium hydroxide, 25 moles of zinc chloride, and 15 moles of ethylene chlorohydrin dissolved in 2800 moles of water is
When heated for 60 minutes at 0oo, acicular zinc oxide particles with uniform particle size were obtained.

The particle size was about 1 mm, the particle size distribution was 1-2 mm, and the yield was 90% of theory. Example 5 A mixed aqueous solution prepared by dissolving 25 moles of sodium hydroxide, 25 moles of zinc nitrate, and 15 moles of ethylene chlorohydrin in 2800 moles of water was heated at about 1000° for 60 minutes to obtain acicular zinc oxide particles of uniform particle size. Ta.

The particle size was about 2 mm, the particle size distribution was 1 to 5 mm, and the yield was 90% of theory. Example 6 A mixed aqueous solution of 50 moles of sodium hydroxide, 5 moles of zinc acetate, and 5 moles of ethyl acetate dissolved in 2800 moles of water is
When heated at 00oo for 60 minutes, acicular zinc oxide particles of uniform particle size were obtained.

The particle size was about 9 rm, the particle size distribution was 8 to 12 m, and the yield was 90% of theory. Example 7 A mixed aqueous solution prepared by dissolving 25 moles of sodium hydroxide, 25 moles of zinc chloride, and 15 moles of ethyl acetate in 2800 moles of water was heated at about 100 q0 for 60 minutes to obtain acicular zinc oxide particles of uniform particle size.

The particle size was about 1 m, the particle size distribution was 1 to 2 m, and the yield was 90% of theory. Example 8 A mixed aqueous solution prepared by dissolving 25 moles of sodium hydroxide, 25 moles of zinc nitrate, and 15 moles of ethyl acetate in 2800 moles of water was heated at about 100 oo for 6 minutes to obtain acicular zinc oxide particles of uniform particle size.

The particle size was 2 meters, the particle size distribution was 1 to 54 meters, and the yield was 90% of theory. FIG. 2 shows an electron micrograph of zinc oxide particles obtained using an alkali.

This is the case in Example 8. As is clear from what has been described in detail above, the present invention produces acicular zinc oxide particles having a uniform particle size without using a high-temperature device or a carrier gas unlike the conventional production method by oxidizing zinc vapor. Furthermore, since it does not contain irregular shapes such as spherical or plate-like shapes as in conventional examples, it is an extremely useful catalyst when used as a catalyst, and will greatly contribute to the catalytic reaction industry.

[Brief explanation of the drawing]

1 and 2 are electron micrographs of acicular zinc oxide particles obtained in Examples 1 and 8. Figure 1 Figure 2

Claims (1)

[Claims] 1. At least one of zinc chloride, zinc nitrate, zinc sulfate, and zinc acetate aqueous solution to which an acid has been added is used as a starting material, and to this, an organic compound hexamethylenetetramine is added, or zinc chloride, zinc nitrate, zinc sulfate, At least one type of zinc acetate is used as a starting material, and an alkali is added to the aqueous solution of the starting material. To the resulting zinc acid aqueous solution, one type of organic compound, ethylene chlorohydrin or ethyl acetate, is added to form a needle-shaped A method for producing acicular zinc oxide particles, characterized by obtaining zinc oxide particles.