Preparation of Tungsten Trioxide

By drying, calcination tungstate and ammonium paratungstate can be prepared from tungsten trioxide. Drying temperatures around 100℃, the main material is physically adsorbed water vapor but only at higher temperatures the material is calcined to remove ammonium paratungstate and tungstic acid molecule of water and ammonia compounds.

Acid usually calcination in air, 180 ℃ starts dehydration at 500 ℃ for complete dehydration, tungsten oxide formation: H2WO4 = WO3 + H2O ↑

Ammonium paratungstate calcined by heating in air at different temperatures will produce different phase, when the temperature is raised to about 500 ℃, can be completely converted to tungsten trioxide.

Shao-Yi, who used differential thermal analysis and X-ray diffraction observation during calcination of APT and analysis, that the heating APT in the air phase change its course as follows: at a temperature of not less than 240 ℃, APT converted to ammonium metatungstate (AMT), continue heating to 300 ~ 350C, the conversion of the amorphous material (ammonium tungsten bronze ATB), temperature was raised to 400C, into a hexagonal type W03, temperature reached 500 ℃, to obtain a three triclinic crystal tungsten oxide. The purity determined APT purity tungsten trioxide, APT crystal form of the crystal tungsten trioxide hereditary, calcination temperature and the rate of thermal decomposition of the product physical properties of tungsten trioxide has a significant impact.

Calcined at different temperatures with a number of APT, WO3 products vary greatly surface area and particle size, the higher the calcination temperature, the more coarse particle size of the obtained WO3.


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