This procedure is exactly the same as the preparation of tungsten tetrachloride, but the product cannot contact with air due to its strong hygroscopicity, so it should be fully dried and preserved. Under this reaction condition, there is no protective atmosphere, so it is difficult to ensure that tungsten pentachloride is not decomposed. During refining, the product is put into a hard glass tube and placed in the air of vacuum or nitrogen and carbon dioxide. The glass tube is placed in an electric furnace and a temperature gradient is formed. As a result, the most sublimable tungsten pentachloride will be precipitated first, while tungsten tetrachloride will turn black and finally remain.
In addition, a preparation method of tungsten pentachloride was developed, including the following steps:
1) The reactor and the auxiliary collector, raw material sampling equipment, analytical balance, connecting pipeline, glass container and other equipment shall be dried overnight, and be purged with high-purity nitrogen for 2 hours. Exhaust gas shall be detected by chromatography to ensure that there is no moisture or air;
2) In the glove box under nitrogen atmosphere, grind the raw material tungsten hexachloride to a particle size of 40 m, weigh 1kg of raw material tungsten hexachloride with a balance, and transfer it to the reactor for continuous nitrogen protection;
3) The reactor was heated to 280℃ at a rate of 5-20℃/min. When the temperature was raised to 100℃, the reactor was kept warm for 2 hours.
4) High-purity hydrogen was fed into the reactor. The flow rate of high-purity hydrogen was 100mL/min. The internal pressure range of the reactor was 0.01mpa.
5) The gas whose main product is tungsten pentachloride enters the purifier I from the reactor, and the temperature rises to 280℃ in purifier I. Tungsten pentachloride and the light component impurities are gasified and transferred to purifier II, which rises to 230℃ in purifier II, and the light component impurities are gasified and transferred to the exhaust gas cleaning bottle.
(6) When the temperature of purifier II rises to 300℃, tungsten pentachloride will be gasified and transferred to the collector. Among them, the reactor, purifier, collector, accessory pipe fittings and sampling utensils are all high temperature-resistant, reduction-resistant and corrosion-resistant materials, such as glass, enamel and quartz, of which quartz is preferred. The inert gas can be high-purity nitrogen, helium, neon, argon, etc., among which argon is preferred, and the purity of tungsten pentachloride is analyzed by X-ray fluorescence spectroscopy. The purity of crude tungsten pentachloride after the first-order reaction is 99.1%, the purity of high-purity tungsten pentachloride after purification is 99.9991%, and the yield of tungsten hexachloride is 82.1%.