Tungsten Hexafluoride High Purity Method

Tungsten hexafluoride, a chemical formula of WF₆, is a colorless gas. When condensed, it is a pale yellow liquid with a molar mass of 297.83 g/mol, which is one of the most dense gases. Among tungsten tungsten fluorides, tungsten hexafluoride is the only stable and industrially produced variety.

In order to overcome the shortcomings of the existing technology, some enterprises adopt a more efficient synthesis method of tungsten hexafluoride, which can reduce the influence of fluorine concentration on the reaction, avoid waste of raw materials and reduce the difficulty of subsequent treatment of harmful gas emissions.

The 30 kg tungsten powder with 100 mesh raw material was added into the reactor with silver difluoride (powder). The reactor was heated to the reaction temperature after dehydration and drying (heating and vacuum, water content less than 3 ppm) with the equipment pipeline. During the reaction, fluorine gas is increased to 1.5 bar by compressor and then reacted in the reactor through adsorbent. The reaction temperature is 280 ℃ and the intake flow rate is set at about 120L/min. The tail gas discharged from the reactor is condensed into the cryogenic collector to collect WF₆ at - 5 ℃. The function of the filter is mainly to remove the solid substances such as dust and particles in the tail gas and enter the cryogenic temperature. WF₆ in the tail gas of the collection tank gradually condenses into liquid at low temperature (below its boiling point temperature), and the unconsolidated gas in the tail gas is beaten back to the reactor by compressor pressurization for reaction. High purity tungsten hexafluoride was prepared from WF₆ collected by refining system.

The raw material fluorine gas and tungsten powder are selected as 5N fluorine gas and 3N tungsten powder respectively. Tungsten hexafluoride products are mainly used in semiconductor manufacturing process, which requires high purity. As raw materials of tungsten hexafluoride, fluorine and tungsten powder should also be higher and better in purity, avoiding excessive impurities entering the products, increasing the difficulty of subsequent purification. The utilization rate of raw material fluorine is 95%, and the crude products of tungsten hexafluoride are subsequently obtained. The 5N tungsten hexafluoride gas can be prepared by the purification process (drying, adsorption and distillation).

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