Ammonium Paratungstate Decomposition Under Non-oxidizing Atmosphere

Decomposition of ammonium paratungstate under non-oxidizing atmosphere:

The first stage： 90~180℃，lose crystal water：
5(NH4)2O·12WO3·5H2O=5(NH4)2O·12WO3·H2O+4H2O↑

The second stage: 180 ~ 260 ℃, ammonia loss:
5(NH4)2O·12WO3·H2O=3(NH4)2O·12WO3·3H2O+4NH3↑
Ammonium metatungstate（AMT）

The third stage, 260 ~ 350 ℃, further of lose water and ammonia, ammonium tungsten bronze occurred (ATB):
3(NH4)2O·12WO3·3H2O＝(NH4)2O·12WO3+4NH3↑+5H2O↑

Fourth stage: 350 ~ 450 ℃, ammonia begins to decompose to generate hydrogen and nitrogen:
2NH3 =N2 ↑ + 3H2 ↑
This phase chemical reactions may be
(NH4)2O·12WO3 + H2＝12(NH4)xWO3+H2O+(2-x)NH3↑
(NH4)xWO2.8~3.0

Fifth stage: 450 ~ 550 ℃, ATB decomposition output WO3 and WO2.9

Sixth stage: 550 ~ 650 ℃, decomposition products in addition to small amounts of ATB, there are WO3, WO2.9 and tungsten oxide WO2.72 etc., even WO2.



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