Thermal Decomposition of Ammonium Paratungstate

Ammonium paratungstate crystals were white and transparent, is a loose and fluidity are better powder material. Ammonium paratungstate English name Ammonium paratungstate, commonly referred to as APT. As a middle product in the production of tungsten products, ammonium paratungstate is one of the main raw materials for the production of tungsten products such as tungsten oxide, tungsten wire, tungsten powder and tungsten carbide powder.

Ammonium paratungstate as a raw material for the production of tungsten products in the military, electric power, metallurgy, aerospace, machining and other fields play a crucial role, so the application of ammonium paratungstate prospects are very broad.

The thermal decomposition of ammonium paratungstate directly affects the quality of tungsten products, and its thermal decomposition process will be affected by factors such as APT structure, temperature, atmosphere, analysis methods and other factors. When ammonium paratungstate is heated in an air atmosphere, ammonia starts to be lost when the temperature reaches 60 ° C, and de-crystallization begins at 100 ° C. At 450 ℃ began to decompose, the final formation of WO3. The total chemical reaction of ammonium paratungstate thermal decomposition process is:

5(NH₄) ₂O·12 WO₃·n H₂O = 12WO₃ + 10NH₃↑+ n H₂O↑

Paratungstate thermal decomposition process can be divided into the following stages:
(1) The first step is ammonium paratungstate to dew crystal water at 50-180 ° C to form anhydrous APT.
(2) The second step is to form an amorphous compound after dehydration of ammonia at 190-280 ° C. There are two kinds of amorphous compounds, one is speculation of AMT and the other is speculation of ATB.
(3) The third step is to release H2O and NH3 from 250 to 380 ° C amorphous compound, finally forming the ATB product of (NH4) x WO3 series;
  (4) In the fourth step, the ATB product starts to decompose when the temperature is raised to over 400 ° C, and further product NH 3 is finally released to produce tungsten trioxide.

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