JPH05105411A - Production of nitrogen trifluoride - Google Patents

Abstract

PURPOSE:To improve reaction efficiency, yield or the like by allowing a gaseous starting material to flow along the inner wall of a reactor in helical form to mix and allow to react when producing nitrogen trifluoride by reacting fluorine gas with ammonia gas in vapor phase. CONSTITUTION:The raw material blowing pipes 1 and 2 are connected to the reactor 6 so as to enable the gaseous starting material to blow in tangential direction of the cylindrical part of the reactor 6, and ammonia gas and fluorine gas, if necessary adjusted their conc. with a dilution gas, are injected into the reactor 6 from the raw material blowing pipes 1 and 2, are allowed to flow along the inner wall of the reactor 6 in helical form in the inside of the reactor 6 and are sufficiently mixed to allow to react. Next, the reacted gas is drawn out from the formed gas draw-out pipe 3 and is introduced into the gas scrubber 4 to clean, and then, formed nitrogen trifluoride is recovered by the recovering device 5. A solid part of the by-product is stored in the storage vessel 7. As a result, the gaseous starting material is sufficiently mixed and clogging of the reactor and pipe line is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a production method for producing nitrogen trifluoride by reacting fluorine gas and ammonia gas in a gas phase.

[0002]

2. Description of the Related Art Nitrogen trifluoride has a boiling point of -129 ° C and a melting point of-
It is a compound at 208 ° C and is a stable gas at room temperature and atmospheric pressure. Applications include a fluorine source in a fluorination reaction, an oxidizer for high-energy fuel, or a dry etching agent.

Conventionally, the following methods are known as manufacturing methods. Ruff et al. Reacted nitrogen gas in a gaseous state with fluorine gas and ammonia gas to produce nitrogen trifluoride in a yield of 6
%, But succeeded in synthesis [Z.anorg.u.allge
n. Chem., 197, 32 (1931)]. Morrow et al. Also reported that nitrogen trifluoride was successfully synthesized by a similar method with a yield of 24.3% [JACS, Vol. 82,530.
1/4 (1960)].

[0004]

In general, when fluorine gas and ammonia gas are reacted in a gas phase to synthesize nitrogen trifluoride, ammonium fluoride, particularly solid components such as ammonium acid fluoride are produced. There is a problem in that the reactor and the piping are clogged by the solidification of this ammonium acid fluoride. Further, this reaction is accompanied by a large amount of heat generation, and an increase in the reaction temperature due to this heat generation cannot be effectively suppressed, so that nitrogen trifluoride once generated is decomposed and it is difficult to increase the yield.

Among these problems, regarding the clogging of the reactor and the piping, JP-A-2-255511 and JP-A-2-25512
In the publication, a thin rectangular parallelepiped-like reactor having an ammonia gas blow-in pipe above and a fluorine gas blow-in pipe on its side is used, or a reactor having a thickness of 80 to 250 is used.
It has been shown that it can be improved by installing in a heat medium bath kept at ℃. However, the yield is as low as about 17% (based on NH ₃ ) by either method. In addition, JP-A-2-255
Japanese Patent No. 513 discloses that the yield can be improved up to 59.5% (based on NH ₃ ) when a large amount of a specific diluent gas is used as compared with the raw material gas. However, the result is not necessarily industrially satisfactory, for example, a device for recovering the used diluent gas is required.

Therefore, the object of the present invention is to solve the problems of the conventional production method, such as clogging of the reactor and piping and low yield due to solid contents such as by-produced acidic ammonium fluoride,
It intends to develop a method for producing nitrogen trifluoride that does not necessarily require a diluent gas.

[0007]

DISCLOSURE OF THE INVENTION As a result of intensive studies for achieving the above-mentioned objects, the present inventors have found that these objects can be achieved by improving the mixing method of raw material gases. ..

That is, according to the present invention, when the fluorine gas and the ammonia gas are reacted in a gas phase to produce nitrogen trifluoride, the raw material gas is made to spirally flow along the inner wall of the reactor inside the reactor. The present invention provides a method for producing nitrogen trifluoride, which comprises mixing and reacting raw material gases.

[0009]

In the method of the present invention, the flow inside the reactor for synthesizing nitrogen trifluoride is similar to the flow inside the cyclone separator and forms a spiral flow along the inner wall of the reactor. From this, it is considered that the following advantages are occurring.

That is, the method of blowing the raw material gas in the conventional nitrogen trifluoride reactor is the method of blowing the two raw material gases in parallel into the reactor, or the two raw material gases are blown at a certain angle and the raw material gas is contacted. It was one of the methods. At this time, when the two source gases are blown in parallel, the source gases are mixed at a certain angle in the gas diffusion rate.
When the raw material gas of the seed was blown in, it was due to the turbulent flow generated at the gas contact surface. For this reason, the mixing of the raw material gases was either very slow or, conversely, very fast for the reaction of the fluorine gas and the ammonia gas to proceed smoothly.

However, when the flow in the reactor is mixed by the spiral flow along the inner surface of the reactor as in the present invention, the flow is a parallel flow immediately after the raw material gas is blown into the reactor. , The mixing was due to the diffusion rate of the gas. However, thereafter, a secondary flow is generated around the main spiral flow due to the pressure difference between the inside and the outside of the spiral flow caused by the spiral flow inside the reactor.
This secondary flow allows sufficient mixing of the source gases. Therefore, a mixed state of the raw material gas suitable for the production of nitrogen trifluoride, which cannot be obtained by the conventional method of blowing the raw material gas, can be obtained.

[0012] Further, since such a spiral flow provides a residence time of the raw material gas in the reactor required for completion of the reaction even if the size of the reactor is small, the raw material gas can be obtained. The amount of gas blown in can be increased. In addition, since the flow velocity in the reactor is faster than the reaction rate of the fluorine gas and the ammonia gas, the reaction is dispersed in the entire reaction tank without being concentrated at one point in the reactor, resulting in localized heat generation. Suppressed. Therefore, it became possible to remove heat efficiently. Therefore, nitrogen trifluoride can be obtained with a good yield, and the production amount per unit volume of the reactor can be increased.

The solid content such as ammonium acid fluoride produced as a by-product is caused by a cyclone separator-like effect, that is, the centrifugal force generated by the spiral flow in the reactor and the free fall of the solid particles due to their own weight. It is efficiently collected in the lower part of the reactor and can be discharged by an appropriate method, for example, by installing a replaceable solid storage tank in the lower part of the reactor or continuously discharging it by a rotary valve. Therefore, the problem of blockage of the reactor and the pipe can be solved.

Next, a preferable manufacturing apparatus and manufacturing method for carrying out the method of the present invention will be described. Manufacturing equipment is shown in Figure 1.
There is no problem as long as the conditions of a general fluorine gas vapor phase reaction as shown in (3) are satisfied. However, regarding the reactor, a reactor having the following features is preferable. The shape of the reactor will be described with reference to the schematic view of the reactor of FIG. 2 and the top view of the reactor of FIG.

The shape of the reactor is such that the flow of the feed gas in the reactor is effectively a spiral flow along the inner surface of the reactor similar to the flow in the cyclone separator. There must be. Therefore, the reaction-related part of the reactor must be cylindrical.

Further, at least one of the raw material gas blowing pipes is arranged so that the raw material gas can be blown in the tangential direction of the cylindrical portion. However, the arrangement of the other raw material gas blowing pipe is not particularly limited as long as the raw material gas can be blown into the cylindrical portion of the reactor as long as the generated spiral flow is not hindered.

In order to efficiently generate a spiral flow in the reactor, a guide plate may be provided near the outlet of the raw material gas blowing pipe. At this time, the arrangement of the source gas blowing pipe is
It is not necessary to limit the arrangement of the raw material gas blowing pipes so that the raw material gas can be blown in the tangential direction of the cylindrical portion of the reactor, and it may be arranged on the upper surface or the lower surface of the cylindrical portion.

The portion of the reactor not directly involved in the reaction is not particularly limited, but the by-produced ammonium acid fluoride is liable to settle in the lower portion of the reactor, for example, the lower portion of the reactor has a conical shape. That is preferable. Further, it is preferable to have a device for continuously discharging a space sufficient to temporarily store ammonium acid fluoride in the reactor. For example, discharging the solid content storage tank by a rotary valve connected to the lower part of the reactor.

Regarding the ratio of the amount of raw material gas blown into the reactor, the ratio of fluorine gas to ammonia gas is 1 to 3.
About 0 times is preferable. Particularly, about 2 to 4 times is preferable.

The concentration of the amount of raw material gas blown into the reactor is not particularly limited. That is, both ammonia gas and fluorine gas may or may not be diluted with a diluent gas. The type of diluent gas is not particularly limited as long as it does not inhibit this reaction.

The flow rate of the raw material gas blown into the reactor is not particularly limited, but if the flow rate of the blown gas is 0.01 m / sec or more, there is no problem.

There is no problem with the reaction temperature as long as it is lower than the decomposition temperature of nitrogen trifluoride, but it is preferable to maintain the reaction temperature from room temperature to 120 ° C, particularly 30 to 70 ° C. Therefore, if necessary, a cooling device may be attached to the outer surface of the reactor or other portion in order to remove the heat of reaction.

[0023]

The following is a description of preferred examples of the method of the present invention, but this does not limit the scope of the method of the present invention. Example 1 Using the reactor shown in FIG. 1, ammonia gas and fluorine gas were reacted in a gas phase to synthesize nitrogen trifluoride. In this reactor, the reactor (6) is installed so that both the raw material injection pipes (1, 2) can blow the raw material in the tangential direction of the cylindrical portion of the reactor. Further, an inner cylinder (8) is installed in the reactor. A solid by-product storage tank (7) is connected to the bottom of the reactor. Also, this reactor (6) does not have a device for cooling or heating the reactor.

In this apparatus, ammonia gas and fluorine gas adjusted to a predetermined concentration were injected into the reactor through the raw material blowing pipes (1, 2). Then, the gas after the reaction was extracted from the generated gas extracting pipe (3). This gas is introduced into the gas scrubber (4) by a pipe, washed, and then recovered by the recovery device (5).

The reactor was diluted with helium to a concentration of 3
Fluorine gas adjusted to 6% and helium were diluted, and ammonia gas adjusted to a concentration of 20% was injected at a ratio of 2.4: 1. The blowing velocity at this time was 0.19 each.
m / sec and 0.13 m / sec. Although the reactor was not particularly cooled, the internal temperature of the reactor became stable in the range of 35 to 45 ° C. As a result, nitrogen trifluoride was obtained with a yield of 43.7% (based on ammonia gas).

The yield based on ammonia gas can be determined as follows:

## EQU1 ## Yield = (number of moles of NF ₃ formed / N blown in)
H number of moles of ₃₎ × 100

Example 2 The reaction was carried out in the same reactor as in Example 1. At this time, the concentration of fluorine gas injected into the reactor was 20%, the concentration of ammonia gas was 100%, and the ratio was 3.0: 1.
And the blowing velocity is 2.1 m / sec and 0.47 m, respectively.
/ Sec. The temperature inside the reactor was maintained at 50 to 70 ° C. As a result, nitrogen trifluoride was obtained with a yield of 63% (based on ammonia gas). Moreover, the reactor and the pipe were not blocked.

Example 3 The reaction was carried out in the same reactor as in Example 1. At this time, the concentration of fluorine gas injected into the reactor was 50%, the concentration of ammonia gas was 100%, and the ratio was 2.8: 1.
And the blowing velocity was 0.06 m / sec and 0.01, respectively.
m / sec. As a result, the reactor internal temperature is 80 to 100 ° C.
And nitrogen trifluoride was obtained with a yield of 40.1% (based on ammonia gas).

Example 4 The reaction was carried out in the same reactor as in Example 1. At this time, the concentration of fluorine gas injected into the reactor was 100%, the concentration of ammonia gas was also 100%, and the ratio was 20: 1.
And the blowing velocity was 0.16m / sec and 0.02m, respectively.
m / sec. As a result, the reactor internal temperature is 100 to 120.
Stable at 0 ° C., and nitrogen trifluoride was obtained with a yield of 20% (based on ammonia gas).

[0030]

When fluorine gas and ammonia gas are reacted in the gas phase by the method of the present invention to produce nitrogen trifluoride,
Since the solid content by-produced in the reactor can be separated and discharged, the clogging of the reactor and the piping due to the solid content can be eliminated. Moreover, since the heat of reaction can be removed efficiently, the yield could be increased without using a diluent gas.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus used in the method of the present invention.

FIG. 2 is a schematic view of a reactor used in the method of the present invention.

FIG. 3 is a top view of a reactor used in the method of the present invention.

[Explanation of symbols]

 1 Raw material injection pipe 2 Raw material injection pipe 3 Product gas outlet 4 Gas scrubber 5 Nitrogen trifluoride recovery device 6 Reactor 7 Solids storage tank

Front page continuation (72) Inventor Takeshi Kuroda 1-7 Toyosu, Koto-ku, Tokyo Onoda Cement Co., Ltd.

Claims (1)

[Claims] 1. When reacting fluorine gas and ammonia gas in a gas phase to produce nitrogen trifluoride, the raw material gas is caused to flow spirally along the inner wall of the reactor inside the reactor to produce the raw material gas. A method for producing nitrogen trifluoride, which comprises mixing and reacting.