Preparation method of nano titanium dioxide---titanium alkoxide gas phase pyrolysis method and gas phase oxidation method

June 15, 2022

1. Titanium alkoxide gas phase pyrolysis

The process uses titanium alkoxide as a raw material, heats and vaporizes it, uses nitrogen gas, helium gas or oxygen as a carrier gas, and preheats the titanium alkoxide vapor into a decomposition furnace to carry out thermal decomposition reaction. Its reaction formula is as follows:

nTi(OC ₄ H ₉ ) ₄ (g)===nTiO ₂ (s)+2nH ₂ O(g)+4nC ₄ H ₈ (g)

Idemitsu Kosan Co., Ltd. vapor of titanium alkoxide spherical amorphous fumed production of TiO _2, TiO ₂ nanoparticles that can be used as adsorbents, photocatalysts, catalyst carriers, and the like of the shaped article. 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 0.1~10 s, and the flow rate is 10~ 1000mm / s, the volume fraction of 0.1% to 10%; weatherable TiO ₂ nanoparticles to improve the generated, while introducing a metal compound (such as aluminum, zirconium alkoxide) vapor volatile decomposes furnace to heat the Nano TiO ₂ powder preparation and inorganic surface treatment are carried out simultaneously. The biggest disadvantage of this process is high raw material cost, high residual carbon content in the product, and difficulty in synthesizing pure rutile nano TiO ₂ .

Second, titanium alkoxide gas phase oxidation

The titanium alkoxide vapor is introduced into the reactor to react with oxygen. Due to the saturated vapor pressure, the reaction precursor is generally selected from the group consisting of titanyl lactide (TTIP).

Arabi-Katbi et al. studied the effect of flame orientation and structure on the synthesis of nano-TiO ₂ using TTIP as raw material. The orientation of the premixed reactor mainly affects the residence time, and has a certain influence on the crystal form and particle size, but has little effect on the morphology of the particles. The mixing mode and flame structure of the nano-TiO ₂ reactor in the laminar diffusion flame counter can effectively control the average raw particle size (10~50mm) and crystal form of the product (the rutile type mass fraction is 6%~50). %). In order to increase the particle size and increase the rutile content of the product, it can be achieved by increasing the flow rate of the methane gas to increase the reaction temperature.

The gas phase synthesis method of nano TiO ₂ includes, in addition to the above, a low temperature plasma chemistry method, a laser chemical reaction method, a metal organic compound vapor deposition method, a strong photo ion beam evaporation method, an emulsion combustion method, etc., although these gas phase processes are used. The obtained nano TiO ₂ powder has high purity, narrow particle size distribution, good dispersibility, less agglomeration, large surface activity, fast reaction rate, and continuous production. However, the gas phase reaction is completed instantaneously at a high temperature, and the reactants are required to achieve uniform microscopic mixing in a very short period of time, and the reactor type, equipment material, heating method, and feeding mode are highly demanded, and High production costs. Therefore, the application value is not great. Among the above various methods, the TiCl ₄ gas phase oxidation method is most competitive due to economic, environmental protection and flexibility of the production process.

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