JP2863574B2 - Method for producing nitrogen trifluoride - Google Patents

Description

The present invention relates to a method for producing nitrogen trifluoride (NF ₃ ).

Nitrogen trifluoride is a colorless gas with a boiling point of -129 ° C,
Gas for plasma cleaning of equipment, dry etching gas such as silicon, polysilicon, Si ₂ N ₃ .WSi ₂ .MoSi ₃ and gas for excimer laser, and NF ₃ as a fluorine source which is moderately less active than fluorine Due to its low toxicity, it is an industrially important gas conventionally used especially as a fluorine source in the preparation of fluoroolefins and as an oxidizer for high energy fuels.

[Conventional technology and its problems]

Various methods have been proposed as a method for producing NF ₃ conventionally. For example, U.S. Pat.
How to obtain NF ₃ discloses by passed through a plasma arc, also introducing a gas fluorine post-arc zone close to the anode at a temperature above.

A method of producing NF ₃ by gas-solid reaction at room temperature or a solid ammonium complex and elemental fluorine of metal fluoride is disclosed in Japanese Patent Publication Sho 62-21724.

Patent Publication 55-8926 discloses that NF ₃ is produced by reacting gas phase fluorine with a liquid phase ammonium oxyfluoride maintained at a temperature from the melting temperature to substantially 400 ° F. or less. How to do is described.

Journal of the American Chemical Society (J. Am. Chem. Soc), vol. 82 , p. 5301 (1960), uses ammonia in a molar ratio of ammonia to fluorine, about 1: 1 to 2: 1. Discloses the synthesis of NF ₃ by direct gas phase fluorination of

Although the details of the reaction conditions are not described, a yield of NF ₃ of about 10 to 25% based on fluorine is reported.

U.S. Pat. No. 325,474 describes a molten salt electrolysis method of ammonium acid fluoride. All of these use elemental fluorine, which is primarily at risk of explosion and requires measures to prevent explosion. Nothing is possible, and implementing such measures has resulted in reduced yields.

In the electrolysis method, NH ₄ F.HF using ammonium oxygen fluoride or ammonium fluoride and hydrogen fluoride as raw materials
NF ₃ gas is generated from the anode of the electrolytic cell when NF ₃ is produced by performing molten salt electrolysis with a KF / NH ₄ F / HF system containing potassium acid fluoride or potassium fluoride as a raw material. Then, H ₂ gas is generated from the cathode. The NH ₃ and H ₂ cause an explosion when mixed. Therefore, various measures need to be taken for the operation method.

[Object of the invention]

An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional methods, to produce NF ₃ efficiently without danger of explosion, without requiring special equipment.

[Content of the invention]

The present invention provides a method for producing nitrogen trifluoride, comprising dissolving ammonia in a perfluorocarbon liquid and then introducing fluorine gas; or dissolving fluorine gas in the perfluorocarbon liquid and then introducing ammonia gas. It is. That is, in the method of the present invention, either ammonia or fluorine gas is dissolved in a perfluorocarbon liquid, and then fluorine gas or ammonia is introduced by introducing either fluorine gas or ammonia to cause a reaction in a liquid phase without the simultaneous presence of fluorine and ammonia in the gas phase. By doing so,
The removal of heat of reaction is facilitated, and NF ₃ can be produced safely and in good yield without runaway or explosion of the reaction.

"Perfluorocarbon liquid" used in the present invention
Is a chain or cyclic perfluoro compound having 6 to 14 carbon atoms which is liquid at room temperature, such as perfluorohexane, perfluorooctane, perfluorocyclohexane, perfluoromethylcyclohexane, perfluoronaphthalene, and perfluoroanthracene. And the like, and a mixture thereof may be used.

The reaction temperature is preferably in the range of −30 ° C. to the boiling point of the solvent, and the amount of ammonia and fluorine dissolved is preferably a little excessive from the theoretical amount in consideration of the subsequent treatment.

〔Example〕

 Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1 An experiment was performed by the apparatus shown in FIG. A perfluorocarbon liquid (carbon number: 11, melting point: 160 ° C) of the trademark “KPF-112” manufactured by Kanto Denka Kogyo Co., Ltd. was pumped at a flow rate of 5 / min by pump (B) at the top of the fluorine dissolution tower (1) Then, fluorine gas was charged at a flow rate of 1 / min from the lower part of the tower. A perfluorocarbon solution in which fluorine gas is dissolved accumulates in a liquid reservoir at the bottom of the tower, and ammonia gas is introduced into the lower portion of the reaction tower (2) at a flow rate of 0.4 / min while being sent to the top of the reaction tower (2) by a pump (A). did. When the perfluorocarbon liquid in which almost no fluorine gas was dissolved was accumulated in the liquid reservoir of the reaction tower (2), this was sent to the fluorine dissolution tower (1) by the pump (B), and the fluorine gas was dissolved again. During this circulation, NF ₃ , HF, N ₂ and some unreacted ammonia come out from the top of the reaction tower (2). It was sent to (3) to remove HF and unreacted ammonia. The composition of the gas emerging from the top of the washing tower (3) during the reaction for two consecutive hours was analyzed every 20 minutes. The average of the gas composition was as follows.

N ₂ 2.1% NF ₃ 97.7% Other 0.2% Example 2 300 ml of a perfluorocarbon liquid (carbon number 8, boiling point 102 ° C.) of the trademark “KPF-82” manufactured by Kanto Denka Kogyo KK was placed in a Teflon bottle, Ammonia gas was blown in while stirring with a magnetic stirrer. Next, ammonia in the blowing tube was replaced by nitrogen gas, and fluorine gas was blown to cause a reaction. The reaction gas was washed with water, and the gas composition was analyzed by gas chromatography.

N ₂ 3.9% NF ₃ 90.4% Others 5.7%

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an example of an apparatus for performing the method of the present invention. 1 Fluorine gas dissolving tower 2 Reaction tower 3 Gas washing tower (A), (B), (C): Pump

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Shiro Sato 425 Kanai, Shibukawa-shi, Gunma Kanto Denka Kogyo Co., Ltd. Research and Development Center (56) References JP-A-2-255513 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) C01B 21/083

Claims (1)

(57) [Claims] 1. A process for producing nitrogen trifluoride, comprising dissolving ammonia in a perfluorocarbon liquid and then introducing fluorine gas; or dissolving fluorine gas in the perfluorocarbon liquid and then introducing ammonia gas. Method.