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AssigneeMitsui Toatsu Chemicals, Inc.
InventorsHiroyuki Hyakutake, Isao Harada, Naruyuki Iwanaga, Toshihiko Nishitsuji
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The present invention has as its technical theme to provide a liquefactive and condensable method that enables the reaction step of forming NF.sub.3 to be operated safely and continuously and purifying method that eliminates O.sub.2, N.sub.2, etc. in NF.sub.3. The present invention is directed to a method wherein liquefaction and condensation of NF.sub.3 is carried out with an additive gas such as He, and Ne introduced in order to prevent H.sub.2 from mixing. The present invention is also directed to a purifying method wherein deeply cooled distillation of liquefied NF.sub.3 is carried out with one or more of He, He, and Ar introduced as a third component gas. According to the present invention, a safe long-term continuous operation has been made possible. Since O.sub.2, N.sub.2, etc. in NF.sub.3 can be eliminated efficiently, highly pure NF.sub.3 can be obtained.
A method of liquefying and condensing nitrogen fluoride, which method comprises leading a mixed gas of nitrogen trifluoride and a carrier gas to a cooling step, cooling said mixed gas in the copresence of a gas whose boiling point is lower than that of nitrogen gas and that is not dissolved in liquid nitrogen trifluoride to obtain liquefied nitrogen trifluoride mainly comprising nitrogen trifluoride, and recovering the obtained liquefied nitrogen trifluoride.
The method as claimed in claim I, wherein the carrier gas comprises one or more gases selected from the group consisting of nitrogen, argon, helium, and neon.
The method of purifying nitrogen trifluoride, wherein nitrogen trifluoride gas mixed with impurity gases is cooled to be liquefied and is subjected to, or liquefied nitrogen trifluoride is subjected to deeply cooled distillation in the copresence of a third component gas whose boiling point is lower than that of nitrogen trifluoride, the deeply cooled distillation being carried out at a temperature ranging between up to the liquefying temperature of NF.sub.3 and down to the solidifying temperature of NF.sub.3 and at which the copresent third component will not liquefy, and that is not dissolved in liquid nitrogen trifluoride.
Dependencies are inferred from the claim text.