With the promotion of the petroleum refining industry, research and development of tungsten catalyst have gained widespread attention. The active component of this catalyst - tungsten trioxide, is used as a catalyst carrier, as spherical silica, aluminum oxide prepared by dipping and  pyrolysis ammonium metatungstate (AMT). This is a direct power in recent years to promote the development of AMT. There are many processes of AMT production, such as thermal degradation, liquid - liquid extraction, ion exchange, electrodialysis, neutralization, acid hydrolysis alcohol precipitation method, etc.. These methods have some limitations. Nanofiltration technology is a membrane separation technology that separated from the reverse osmosis technology, which is a continuation and development of ultra-low pressure reverse osmosis technology branch.

 

Now, nanofiltration technique has been separated from the reverse osmosis technology between ultrafiltration and reverse osmosis technology and it has been widely used in water desalination, ultra-pure water manufacturing, food industry, environmental protection and many other fields, which has become an important branch of the membrane separation technique. The integration process of eutralization - nanofiltration - crystallization consists of the following three consecutive sessions: 1) AMT mixed solution preparation by acid neutralization; 2) Nanofiltration of AMT mixed solution; 3) Evaporation and crystallization of the AMT solution after nanofiltration. In this paper, coupling processes of neutralization - crystallization for preparing high purity AMT solution is the focus, that is the first two steps of the process described above, of which effects of temperature, pH, stirring speed, pressure and other factors on membrane processes were discussed, so that the conditions of neutralization nanofiltration coupling process for producing high purity crystals of ammonium metatungstate were determined.

 

Preparation: The dilute nitric acid was added into ammonium paratungstate (referred APT) solution at the appropriate reaction conditions of pH and temperature, and ammonium paratungstate gradually transformed into ammonium metatungstate.