1. TiC1 4 produced similar principles silica oxyhydrogen flame hydrolysis method and the vapor phase method, a gas is TiC1 4 leaders oxyhydrogen flame (700 a 1000 ℃) carried out vapor phase hydrolysis, chemical reaction formula:
TiC1 4 hydrogen flame hydrolysis method first developed by Degussa (Degussa) successfully, and produce ultra-fine titanium white powder nano powder of one of the famous brands. In addition, Cabot Corporation of the United States and Aerosil Corporation of Japan use this method to produce ultrafine titanium dioxide powder. This powder preparation process is generally used in smaller anatase and rutile hybrid, high purity (99.5%), small particle size (21 nm), large surface area, good dispersion, degree of agglomeration, Mainly used in electronic materials, catalysts and functional ceramics. This preparation process has matured and there have been few patent applications in this area for more than two decades. The process is characterized by a short process and a high degree of automation. However, due to its high process temperature, severe corrosion, strict material requirements, and precise control of process parameters, the product cost is high and it is difficult for general manufacturers to bear.
2. TiCl 4 gas phase oxidation method This method is similar to the principle of chlorination for the manufacture of ordinary rutile type, except that the process control conditions are more complicated and precise, and its basic chemical reaction formula:
Shi Liyi, Li Chunzhong, etc. carried TiC1 4 vapor with N 2 , preheated to 435 ° C and then entered the high temperature tubular reactor through the inner tube of the casing nozzle. O 2 was preheated to 870 ° C and then passed through the outer tube of the casing nozzle. Also entering the reactor, TiC1 4 and O 2 are reacted at 900-1400 ° C, and the nano TiO 2 particles formed by the reaction are subjected to gas-solid separation through a particle trapping system. This process is still in the laboratory test phase. The key to the process is to solve the structural design of the nozzle and reactor and the problem of titanium dioxide particles in the cold wall. The advantage of this process is the high degree of automation and the ability to produce high quality powders.
3. Titanium alkoxide gas phase hydrolysis method This process was first developed by the Massachusetts Institute of Technology, and can be used to produce monodisperse spherical nano titanium dioxide with chemical reaction formula:
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Japan's Caoda Corporation and Idemitsu Kosan Co., Ltd. use nitrogen, helium or air as carrier gas to introduce titanium alkoxide vapor and water vapor into the reaction zone of the reactor for instantaneous mixing and rapid hydrolysis; The residence time, molar ratio, flow rate, concentration, and reaction temperature of the vapor are used to adjust the particle size and particle shape of the nano titanium dioxide. This preparation process can obtain an amorphous nano titanium white powder having an average primary particle diameter of 10 to 150 nm and a specific surface area of ​​50 to 300 m 2 /g. This process is characterized by low operating temperatures, low energy consumption, low production requirements, and continuous production.
4. Titanium alkoxide gas phase decomposition method This process uses titanium alkoxide as raw material, heats and vaporizes it, and uses nitrogen, helium or oxygen as carrier gas to preheat the titanium alkoxide vapor into the thermal decomposition furnace for thermal decomposition. reaction. Take butyl titanate as an example:
Japan Idemitsu Kosan Co., Ltd. uses the titanium alkoxide gas phase decomposition method to produce spherical amorphous nano titanium dioxide, which can be used as adsorbent, photocatalyst, catalyst carrier and cosmetics. It is said that in order to increase the decomposition reaction rate, the carrier gas preferably contains water vapor, the decomposition temperature is suitably 250-350 ° C, the residence time of the titanium alkoxide vapor in the thermal decomposition furnace is 0.1-l0 s, and the flow rate is 10-1000 mm. /s, the volume fraction is 0.1%-10%; in order to improve the weather resistance of the produced nano titanium dioxide, the vapor of the volatile metallization (such as aluminum , wrong alkoxide) can be simultaneously introduced into the thermal decomposition furnace to make the nano titanium powder Powder preparation and inorganic surface treatment are carried out simultaneously.
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