Tungsten Hexafluoride Purification Process

Tungsten hexafluoride, chemical formula for WF6, is a colorless gas, condensation, light yellow liquid, molar mass 297.83 g/mol, is one of the densest gases. Tungsten hexafluoride is mainly used for chemical vapor deposition of tungsten. It is also used to fabricate interconnects with low resistance and high melting point, large integrated circuit electronic components, protective shields against X-ray or gamma-ray, and high-efficiency solar absorbers.

Accordingly, the European Center for research on gas has developed a number of six tungsten fluoride purification technologies, such as the following processes:

1.The tungsten powder and metal fluoride are loaded into the reactor and mixed by stirring.

2.The raw material fluorine gas is fed into the reactor under the conditions of reaction temperature and pressure. The gas discharged after the reaction is a mixture of fluorine gas from unreacted raw material and tungsten hexafluoride.

3.After removing the solid particles from the filter, the mixed gas is put into a cryogenic collection tank to collect tungsten hexafluoride crude products, and the uncooled fluorine gas is pressurized by a compressor and returned to the reactor for reactions.

4.The amount of fluorine added to the raw materials can be determined by the pressure change in the reaction system.

5.The collected crude tungsten hexafluoride products were transported to the purification system, and the high purity tungsten hexafluoride products were prepared by drying, adsorption and distillation.

The results show that the utilization rate of fluorine in this process is 95%. The crude product of tungsten hexafluoride can be purified into 5N tungsten hexafluoride gas by subsequent purification process (drying, adsorption, rectification). The advantage of the process is that the reaction of the recycled raw material fluorine and tungsten powder in the presence of metal fluoride can effectively improve the efficiency of the reaction, reduce the waste of raw material fluorine gas, and effectively reduce the volume required by the reactor.

Tungsten powder can regenerate high-valent fluoride with fluorine gas, which effectively improves the reaction efficiency, reduces the influence of fluorine concentration on the reaction, and the reaction temperature is low, thus reducing energy consumption.

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