New Method for Electronic Grade Tungsten Hexafluoride

Tungsten hexafluoride is a colorless gas at room temperature and its density is the largest among known gases. WF6 has a relative molecular mass of 297.84, and its molecule has a symmetrical regular octahedral structure at room temperature and is diamagnetic. At present, the industry mainly adopts a method in which metal tungsten is directly reacted with fluorine gas or NF₃ to prepare WF₆, and the reaction is usually carried out at a temperature higher than 350 °C.

In order to reduce the production of by-products, dehydration and deoxidization should be carried out prior to the use of traditional tungsten metals. Therefore, inadequate contact between fluorine and tungsten powder and low reactor efficiency become a problem in practical operation. In order to overcome the shortcomings of the existing technology, some scholars have proposed a preparation method of six tungsten fluoride. Include the following steps:

Step (1): preparation of tungsten composition
Polypropylene resin with 5-10% stearic acid and 100-200% tungsten powder was stirred at 100-130 ℃ for 0.5-2 h. The tungsten powder was extruded and pelleted at 50-80 ℃ for 20-60 h in acetone with 5-10% tungsten powder. Stearic acid was dissolved and dried at 60-100 ℃ for 5-10 h, the particles with microporous structure are obtained. Aminopropyl-3-methylimidazolium hexafluorophosphate with the content of 0.1-1% of tungsten powder and 5-15% of tungsten powder were added to the complex. The complex reacted at 25-60 ℃ for 5-10 h and then dried at 100-200 ℃ for 5-10 H. Tungsten composition is obtained.

Step (2): synthesis reaction
The crude tungsten hexafluoride is prepared by reaction of fluorine with tungsten in a reactor equipped with the tungsten composition. The molar ratio of fluorine to tungsten is 3-5:1, the reaction temperature is 300-500 ℃, and the space velocity is 1-5 BV/h.

Step (3): refinement
Tungsten hexafluoride gas through well-known purification technology, including distillation separation technology, remove low boiling matter, then remove high boiling matter, and then into the adsorption tower with adsorbents, temperature - 40 ~ - 10 C, flow rate of 1 ~ 5BV / h; after adsorption, high-purity tungsten hexafluoride gas is obtained.

In the scheme, the tungsten composition, as a granular, has a microporous structure, can be stacked in a fixed bed, and has a large contact area with fluorine gas. The addition of aminopropyl-3-methylimidazolium hexafluorophosphate and hydropyridine fluoride complexes makes the tungsten composition more easily react with fluorine gas, and the electronic grade tungsten hexafluoride can be obtained after further refining the product.

• < Prev
• Next >