Under the push of petroleum industry, research and development of tungsten catalyst has been greatly taken into account. The active ingredients – tungsten trioxide is used as carrier of catalyst. Silica, aluminum oxide are all dipped and pyrolysis by ammonium metatungstate which accelerate the production of AMT in recent years.

Nano-filter technology is a membrane separating technology originates from anti-seepage technology, it is the branch of low pressure anti-seepage technology. Nowadays, nano-filter technology has been separated from anti-seepage technology and is widely used in sea water desalination, food industry and environment protection.

Neutralization – nanofiltration – crystallization producing high purity ammonium metatungstate steps:

1) Acid neutralization produces ammonium metatungstate mix solution: add dilute nitric acid into ammonium paratungstate solution. Under proper acidity and temperature condition, ammonium paratungstate gradually turns into ammonium metatungstate.

2) Nanofiltration of AMT mixed solution. Filter AMT solution by filtration device, after concentration and wash, pure ammonium metatungstate solution can be obtained.

3) Evaporation and crystallization of AMT solution.

Neutralization process is an effective way to produce high purity ammonium metatungstate crystalline, it can produce high purity AMT solution, reduce cost for subsequent crystalline process and impurity content.