JP4624905B2 - Method for producing nitrogen trifluoride - Google Patents

Description

The present invention efficiently reacts nitrogen gas trifluoride (NF ₃ ) by reacting fluorine gas (F ₂ gas) and ammonia gas (NH ₃ gas) in the gas phase in the presence of a diluent gas under non-catalytic conditions. It relates to a manufacturing method.

NF ₃ is used, for example, as a dry etching gas or a cleaning gas in a semiconductor device manufacturing process. In general, the production method is roughly classified into a chemical method and an electrolytic method. As the chemical method, for example, (1) a method of blowing F ₂ gas and NH ₃ gas into molten ammonium acid fluoride (see Japanese Patent Publication No. 55-8926 (Patent Document 1)), (2) F ₂
A method of directly reacting a gas and NH ₃ gas (Japanese Patent Laid-Open No. 2-255513 (Patent Document 2)
JP, 5-105411, A (patent documents 3)) etc. are known.

On the other hand, as an electrolytic method, for example, (3) a method of electrolysis using graphite ammonium as an anode, (4) a method of electrolysis using nickel as an anode, etc. are known. . Ruff et al. Reacted F ₂ and NH ₃ in the gas phase and synthesized NF ₃ by a chemical method with a yield of 6% or less (Z. anorg.allg.chem).
. 197, 395 (1931) (see Non-Patent Document 1), Morrow et al. Also reported that NF ₃ was synthesized in the gas phase in a yield of 24.3% (J. Amer. Chem. So).
c. 82.5301 (1960) (see Non-Patent Document 2)).

Direct fluorination reaction to synthesize NF ₃ by reacting conventional F ₂ gas and NH _3, since the use of F ₂ gas rich in highly reactive, there is a risk of explosion or corrosion, also these reactions reaction heat And the temperature in the reactor rises, causing side reactions and decomposition or side reactions of the produced NF ₃ , resulting in N ₂ , HF, N ₂ F ₂ , N ₂ O, NH ₄ F (ammonium fluoride) and NH ₄ HF ₂ (acidic ammonium fluoride) and the like are produced, resulting in a decrease in yield, and there is a problem that the reactor and piping are blocked due to the solid content of NH ₄ F and NH ₄ HF ₂ .

Among these problems, the reactor and piping clogging, etc., are described in JP-A-2-255511 (Patent Document 4) and JP-A-2-255512 (Patent Document 5). Therefore, it can be improved by using a reactor having an ammonia gas blowing tube above it and a fluorine gas blowing tube on the side, and installing the reactor in a heat medium tank maintained at 80 to 250 ° C. It is shown. However, the yield is as low as 17% (NH ₃ basis) by either method. JP-A-2-255513 (Patent Document 2) discloses that the yield can be improved to 59.5% (based on NH ₃ ) by using ₃ to 20 times as much F ₂ gas as NH ₃ gas. As shown, the yield based on F ₂ is poor and not economical.

In Japanese Patent Laid-Open No. 5-105411 (Patent Document 3), the reactor gas and the piping are blocked by mixing and reacting the source gas by flowing the source gas spirally along the inner wall of the reactor inside the reactor. It shows that the yield is improved to 63% (NH ₃ standard). However, since expensive F ₂ gas is used as a raw material, further improvement in yield is a problem.

Japanese Patent Application Laid-Open No. 2001-322806 (Patent Document 6) shows that the yield is improved to about 76% (F ₂ basis) by carrying out the reaction at 80 ° C. or lower in the presence of a diluent gas.
There are problems with reactor clogging and yield improvement.
Japanese Patent Publication No.55-8926 JP-A-2-255513 JP-A-5-105411 JP-A-2-255511 JP-A-2-255512 JP 2001-322806 A Z. anorg. allg. chem. 197, 395 (1931) J. et al. Amer. Chem. Soc. 82.5301 (1960)

The present invention is intended to solve the problems associated with the prior art as described above, and reacts F ₂ gas and NH ₃ gas to produce NF ₃ directly by an industrial fluorination method. It is an object of the present invention to provide a method capable of continuously producing with high yield.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have supplied F ₂ gas and NH ₃ gas to a tubular reactor, and reacted in the presence of a diluent gas in the gas phase in a non-catalytic condition. In the method for producing nitrogen trifluoride, wherein a gas product mainly composed of NF ₃ and a solid product (solid product) mainly composed of ammonium fluoride and / or acidic ammonium fluoride are produced, the tubular reactor and It has been found that NF ₃ can be continuously produced in good yield by removing the solid product adhering to the inner wall of the pipe by heat treatment in the presence of an inert gas.

In addition, when one hydrogen atom in NH ₃ is replaced with one fluorine atom in the reaction between F ₂ and NH ₃ , a large reaction heat of about −110 Kcal / mol is generated. Therefore, when NF ₃ is produced by direct fluorination reaction in which F ₂ gas and NH ₃ gas are reacted, a large reaction heat of about −330 Kcal / mol is generated, and the temperature is locally increased. When the temperature in the reactor increases, a side reaction [the following formula (2)] occurs predominantly in addition to the target NF ₃ production reaction [the following formula (1)].

4NH ₃ + 3F ₂ → NF ₃ + 3NH ₄ F (1)
2NH ₃ + 3F ₂ → N ₂ + 6HF (2)
As a result of intensive studies to selectively advance the reaction of the above formula (1), the present inventors have found that the linear velocity increases due to adhesion of the solid product, gas turbulence, reduction of cooling efficiency, etc. We found that the rate drop was also closely related to the reaction temperature.

As a result, the present invention has been completed.
That is, the present invention is a method for producing NF ₃ shown in the following [1] to [29].
[1] Fluorine gas and ammonia gas are supplied to a tubular reactor and reacted in the gas phase in the presence of a diluent gas in a non-catalytic condition to produce a gas product mainly composed of nitrogen trifluoride and mainly fluorinated. A method for producing nitrogen trifluoride for producing a solid product comprising ammonium and / or ammonium acid fluoride, wherein the solid product adhering to the inner wall of the tubular reactor and / or piping is treated with an inert gas. A method for producing nitrogen trifluoride, which is removed by heat treatment in the presence.

  [2] The method for producing nitrogen trifluoride according to the above [1], wherein the reaction is carried out using two or more tubular reactors and switching between the two or more tubular reactors. .

[3] The method for producing nitrogen trifluoride according to the above [1] or [2], wherein the tubular reactor is installed so that a length direction thereof is a vertical direction.
[4] The method for producing nitrogen trifluoride according to any one of the above [1] to [3], wherein the gas flow inside the tubular reactor is vertically downward.

  [5] Fluorine gas and ammonia gas are supplied from the upper part of the tubular reactor installed so that the length direction is the vertical direction, and the reaction is performed in the gas phase in the presence of a diluent gas under non-catalytic conditions. A method for producing nitrogen trifluoride that produces a gas product mainly composed of nitrogen trifluoride and a solid product mainly composed of ammonium fluoride and / or ammonium acid fluoride, wherein two tubular reactors are provided. Using the above, and performing the above reaction while switching these two or more tubular reactors,
  A part of the solid product adhering to the inner wall of the tubular reactor is removed by the vibration generator and / or scraper attached to the tubular reactor, and remains on the inner wall of the tubular reactor. A method for producing nitrogen trifluoride, comprising removing the solid product and / or the solid product adhering to the inner wall of the pipe by heat treatment in the presence of an inert gas.

  [6] The vibration generator is an air knocker and / or an air-type piston vibrator attached to the outside of the reactor, and the solid product is removed by the vibration generator and removed. The method for producing nitrogen trifluoride according to [5].

[7] The production of nitrogen trifluoride according to [5], wherein the scraper drives the inside of the tubular reactor freely in the vertical and vertical directions to scrape and remove the solid product. Method
.

[8] The scraper is configured to scrape and remove the solid product by freely rotating the inside of the reactor around a vertical axis passing through the center of the radial cross section of the tubular reactor as a central axis. The method for producing nitrogen trifluoride according to [5] or [7].

[9] The fluorine gas is a high-purity fluorine gas having a total content of oxygen and an oxygen-containing compound of 0.1 vol% or less and a content of tetrafluoromethane of 50 vol ppm or less. 8] The method for producing nitrogen trifluoride according to any one of the above .

[10] The [1] to [9], wherein the ammonia gas is a high-purity ammonia gas having a total content of oxygen and an oxygen-containing compound of 10 volppm or less and an oil content of 2 massppm or less. The manufacturing method of nitrogen trifluoride in any one.

[11] The oxygen-containing compound contained in the high-purity fluorine gas is NO, NO ₂ , N ₂ O, CO, CO ₂ , H ₂ O, OF ₂ And O ₂ F ₂ At least one compound selected from the group consisting of
The method for producing nitrogen trifluoride according to [9], wherein the method is a product.

[12] The oxygen-containing compound contained in the high-purity ammonia gas is NO, NO ₂ , N ₂ O, CO, CO ₂ And H ₂ Be at least one compound selected from the group consisting of O
[10] The method for producing nitrogen trifluoride according to [10].

[13] The method for producing nitrogen trifluoride according to any one of [1] to [12], wherein fluorine gas and ammonia gas are reacted at a temperature of 60 ° C. or lower.

[14] The method for producing nitrogen trifluoride according to any one of [1] to [13], wherein the tubular reactor has a cooling structure.

[15] The method according to any one of [1] to [14], wherein the fluorine gas and the ammonia gas are supplied in a molar ratio (fluorine gas: ammonia gas) range of 1: 1 to 1: 2. Of manufacturing nitrogen trifluoride.

[16] The dilution gas is at least one gas selected from the group consisting of nitrogen, helium, argon, sulfur hexafluoride, hexafluoroethane, octafluoropropane, and nitrogen trifluoride. 1]-[15] The manufacturing method of the nitrogen trifluoride in any one of.

[17] The method for producing nitrogen trifluoride according to any one of [1] to [16], wherein a dilution gas is used in a circulating manner.

[18] The method for producing nitrogen trifluoride according to any one of [1] to [17], wherein after the reaction, unreacted fluorine gas is treated with an alkaline aqueous solution and / or alumina.

[19] The nitrogen trifluoride according to any one of [1] to [18], wherein the inert gas is at least one gas selected from the group consisting of nitrogen, helium, and argon. Production method.

[20] The method for producing nitrogen trifluoride according to any one of [1] to [19], wherein the heat treatment is performed at 135 ° C. or higher.

[21] The method for producing nitrogen trifluoride according to any one of [1] to [20], wherein the supply concentration of the fluorine gas is 3 mol% or less.

[22] The method for producing nitrogen trifluoride according to any one of [1] to [21], wherein the supply concentration of the ammonia gas is 6 mol% or less.

[23] The method for producing nitrogen trifluoride according to any one of [1] to [22], wherein fluorine gas and ammonia gas are reacted at a pressure of 0.05 to 1.0 MPa.
  [24] The solid product remaining on the inner wall of the remaining tubular reactor not used for the reaction by reacting fluorine gas and ammonia gas using at least one of the two or more tubular reactors [2] and [5] to [23], wherein the solid product adhering to the inner wall of the product and / or the piping is removed by heat treatment in the presence of an inert gas. A method for producing nitrogen trifluoride.

According to the present invention, an inner wall of a tubular reactor or piping is used to solve problems and problems such as a decrease in yield due to blockage of the reactor and piping in the NF ₃ manufacturing method in which F ₂ gas and NH ₃ gas are reacted. Provided a method for producing NF ₃ continuously and in a good yield economically by heat-treating a solid product mainly composed of ammonium fluoride and / or acid ammonium fluoride adhering to the surface in the presence of an inert gas. it can.

In addition, in order to suppress the content of difficult-to-separate substances such as CF ₄ and trace impurities contained in NF ₃ , it is possible to continuously and economically react with high purity F ₂ gas and high purity NH ₃ gas. In particular, a method capable of producing NF ₃ can be provided.

Hereinafter, preferred embodiments of the present invention will be described in detail.
First, the apparatus for producing nitrogen trifluoride used in the present invention will be described. This manufacturing apparatus has a fluorine gas supply means, an ammonia gas supply means, and a reactor.

  The reactor preferably has a reaction temperature control means (for example, a cooling structure), and examples thereof include a jacket-type tubular reactor. Moreover, it is preferable that the reactor is equipped with an apparatus for removing the solid product adhering to the inner wall of the reactor. Such devices include vibration generators and scrapers. Either one of the vibration generator and the scraper may be used, but is preferably used in combination.

  Examples of the vibration generator include an air knocker and an air type piston vibrator. One or more, preferably two or more air knockers are provided outside the reactor, and the solid product adhering to the inner wall of the reactor is periodically impacted by a timer or the like to drop off the solid product. It is a device that prevents blockage. The pneumatic piston vibrator is composed of, for example, a muffler, a web cover, an O-ring, a piston, a cylinder, a taper spring, and the like. There are effects such as blocking prevention and sliding promotion. That is, one or more, preferably two or more, air-type piston vibrator devices are provided outside the reactor, and the solid product attached to the inner wall of the reactor is impacted to drop off the solid product. It is a device that prevents the blockage of the.

  The scraper is not particularly limited as long as it has the same shape as the cross section of the reactor and does not hinder the passage of gas, but a ring-shaped thin plate provided with a support rod is preferably used. Further, when the tubular reactor is installed so that its longitudinal direction is the vertical direction, the scraper can freely drive the inside of the reactor in the vertical vertical direction and / or the radial cross section of the reactor. It is preferable that the inside of the reactor can be freely rotated about a vertical axis passing through the center of the reactor.

Moreover, it is preferable that the manufacturing apparatus used for this invention has a means to store the solid product removed from the said reactor, and a means to isolate | separate a solid product and a gas component. Specifically, it is preferable that an apparatus for separating and discharging a solid content (hereinafter referred to as “solid separation / discharge apparatus”) is installed at the lower part of the reactor. The solid separation / discharge device preferably has a cross section larger than that of the reactor. More specifically, a solid storage tank that can be exchanged periodically is preferable, and two tanks are provided in series, and two tanks and tanks that can be separated from each other by a rotary valve are provided and switched. It is preferable to have a structure capable of Moreover, it is preferable that the solid separation / discharge device is provided with a gas discharge line through a filter at the upper part for introducing the target NF ₃ and dilution gas to the next step. This filter can remove a small amount of solids accompanying the gas. Furthermore, it is more preferable that two gas discharge lines are provided, for example, and the gas flow is switched periodically to operate continuously.

A conventionally well-known thing can be used for a fluorine gas supply means, an ammonia gas supply means, and the means to switch the reactor to be used.
Of the above-described constituent devices and parts, the material of the devices and parts other than the filter is preferably SUS316.

Next, the manufacturing method of the nitrogen trifluoride of this invention is demonstrated. In the present invention, two or more reactors as described above are used, and the reaction is performed while switching these two or more reactors. The raw material F ₂ gas and NH ₃ gas need to be supplied into the reactor through different pipes and contacted and mixed for the first time in the reactor. When F ₂ gas and NH ₃ gas are mixed at the reactor inlet and supplied to the reactor, the reaction proceeds in the mixing section, solids are generated and the piping is blocked, which is not preferable.

The direct fluorination reaction using F ₂ gas uses an extremely reactive F ₂ gas. Therefore, reacting NH ₃ containing hydrogen with F ₂ at a high concentration causes a risk of combustion and explosion, and is even greater. This is not preferred because the temperature rises due to the heat of reaction and the yield of the target product, NF ₃ , decreases. For this reason, it is necessary to dilute the F ₂ gas and the NH ₃ gas to react in a low concentration region. The F ₂ gas is preferably diluted with a diluent gas and supplied at 3 mol% or less of the total amount of the supply gas, and the NH ₃ gas is preferably diluted with a dilution gas and supplied at 6 mol% or less of the total amount of the supply gas. That is, it is preferable that the raw material gases (NH ₃ gas and F ₂ gas) are 9 mol% or less in total and the dilution gas is 91 mol% or more. If the NH ₃ gas concentration exceeds 6 mol% and the fluorine gas exceeds 3 mol%, there is a risk of a sudden rise in temperature such as an increase in reaction heat, combustion, or explosion, which is not preferable. Examples of the dilution gas include inert gases such as nitrogen, helium, argon, sulfur hexafluoride, hexafluoroethane, octafluoropropane, and nitrogen trifluoride. These diluent gases can be used alone or in admixture of two or more. Of these dilution gases, sulfur hexafluoride, hexafluoroethane, and octafluoropropane are preferred in consideration of the specific heat of the dilution gas, separation / purification in the distillation step, and the like.

Further, F ₂ gas and NH ₃ gas molar ratio (F ₂ gas: NH ₃ gas) 1: 1 to 1: are preferably fed to the reactor at 2 range. Supplying an excessive amount of F ₂ gas is not preferable because it may cause a sudden rise in temperature, such as an increase in heat of reaction, combustion or explosion. Moreover, it is not preferable to supply NH ₃ gas in excess of twice the mole of F ₂ gas because the yield of NF ₃ with respect to NH ₃ decreases.

F ₂ gas and NH ₃ gas diluted in this way are supplied from the upper part of one reactor, mixed and contacted in the reactor, and reacted in the gas phase under non-catalytic conditions. As described above, the reaction temperature is closely related to the main reaction of the above formula (1) and the side reaction of the above formula (2). The temperature is preferably 60 ° C. or less, more preferably −20 to 60 ° C., and still more preferably in the range of −20 to 50 ° C. As a method for controlling the reaction temperature, for example, a method of controlling the temperature in the reactor by a heat medium circulation external cooling system using a jacket type reactor, or cooling before introducing raw materials and / or dilution gas into the reactor in advance. Thus, a method of supplying them is preferable. The reaction pressure is preferably in the range of 0.05 to 1.0 MPa. If it exceeds 1.0 MPa, it is not economically preferable because it is necessary to increase the pressure resistance of the apparatus. The gas inside the reactor is preferably flowing vertically downward.

The F ₂ gas and NH ₃ gas may contain oxygen or an oxygen-containing compound. Examples of oxygen-containing compounds contained in F ₂ gas include NO, NO ₂ , N ₂ O, CO, CO ₂ , H ₂ O.
, OF ₂ and O ₂ F ₂ , which are used alone or in combination of two or more. N
Examples of the oxygen-containing compound contained in the H ₃ gas include NO, NO ₂ , N ₂ O, CO, CO ₂ and H ₂ O, and these are used alone or in combination of two or more. In addition, F ₂ gas
Further, tetrafluoromethane (CF ₄ ) may be contained, and the NH ₃ gas may further contain methane, hydrogen, a hydrogen-containing compound, and oil. The oxygen and oxygen-containing compounds by-produce impurities such as N ₂ O and N ₂ F ₂ or react with F ₂ gas to react with CF ₄ , COF, C
OF ₂ and OF ₂ are produced as by-products. Methane contained in the NH ₃ gas reacts with the F ₂ gas to produce CF ₄ as a by-product. CF ₄ contained in the by-product CF ₄ or F ₂ gas, the boiling point of -128 ° C., close to the boiling point of NF ₃ as the target compound, there are problems such separation is very difficult. N
Hydrogen or a hydrogen-containing compound contained in the H ₃ gas reacts with the F ₂ gas to produce hydrogen fluoride (HF), which reacts with the NH ₃ gas to form NH ₄ F, which is not preferable. The oil contained in the NH ₃ gas reacts with the F ₂ gas to produce CF ₄ , COF, COF ₂ , OF _2, etc. as a by-product. As described above, since the trace impurities contained in the source gas produce many impurities as by-products, the F ₂ gas and the NH ₃ gas are preferably high-purity gases, and it is necessary to reduce the impurities as much as possible.

The F ₂ gas utilizes a difference in boiling point between F ₂ gas (boiling point: −188 ° C.) and CF ₄ (boiling point: −128 ° C.), and is, for example, liquid nitrogen or the like and is −150 to −160 ° C. It can be purified by low-temperature distillation at a temperature to remove CF ₄ contained in the F ₂ gas, and at the same time, oxygen and oxygen-containing compounds are also removed. The CF ₄ content in the purified F ₂ gas is preferably 50 vol ppm or less, and the total content of oxygen and oxygen-containing compounds is preferably 0.1 vol% or less.

On the other hand, the NH ₃ gas is obtained by evaporating liquid ammonia with a heat exchanger or the like, and repeating cooling and recovery to remove oil, or repeating distillation purification and adsorption operations, etc. to generate hydrogen, hydrogen-containing compounds, methane, oxygen, oxygen Purification can be achieved by removing the contained compound. The content of oil in the NH ₃ gas after purification is preferably 2 mass ppm or less, and the total content of oxygen and oxygen-containing compounds is preferably 10 volppm or less.

  In the present invention, from the viewpoint of reducing impurities after the reaction, a high-purity gas in which the diluent gas contains as little impurities as possible, such as sulfur hexafluoride having a purity of 99.999% or more, is more preferably used.

The above reaction produces a gas product mainly composed of nitrogen trifluoride. Further, as the above reaction proceeds, a solid product mainly composed of ammonium fluoride and / or ammonium acid fluoride is generated and adheres to the inner wall of the reactor. The attached solid product, for example, causes a decrease in the yield and selectivity of the target NF ₃ due to a rise in temperature, turbulence of gas flow, an increase in linear velocity, etc. due to a decrease in cooling efficiency. It is necessary to remove it as a deduction. For this reason, the solid product is removed from the inner wall of the reactor using the vibration generator attached to the reactor, or scraped off using the scraper attached to the inside of the reactor. . It is preferable to use this combination of scraping and scraping.

  The removed solid product is collected in the solid separation and discharge device installed at the lower part of the reactor. In order to facilitate this recovery, as described above, the reactor is preferably installed so that its length direction is vertical.

By further separating and purifying the solid product recovered in the solid separation / discharge device, the obtained ammonium fluoride and ammonium acid fluoride can be used for other purposes.
On the other hand, the gas product contains a trace amount of unreacted F ₂ gas and the like in addition to the target NF ₃ and diluent gas. For this reason, it is preferable to remove unreacted F ₂ gas from the gas product that has passed through the filter provided at the top of the solid separation / discharge device. As a method of removing unreacted F ₂ gas, for example, a dry removal method of removing by reacting with alumina (aluminum oxide) or a wet removal method of removing by contacting with an alkaline aqueous solution is preferably applied. Depending on the case, both methods may be used in combination. As the alkaline aqueous solution, a sodium hydroxide aqueous solution and a potassium hydroxide aqueous solution are preferable.

Since water is contained in the mixed gas of NF ₃ and diluent gas from which unreacted F ₂ gas has been removed, it is preferable to dehydrate using molecular sieve or the like. The molecular sieve is preferably 3A, 4A, or 5A. These molecular sieves may be used alone or in combination of two or more.

The dehydrated gas is separated into NF ₃ and a diluent gas in a distillation / separation process, and NF ₃ is recovered to become a product, and the diluent gas can be reused as a raw material or a diluent gas for a reaction system.
As described above, NF ₃ can be produced efficiently and continuously by reacting F ₂ gas and NH ₃ gas while removing the solid product adhering to the inner wall of the reaction tube. As a result, the yield of NF ₃ may decrease. Therefore, in the present invention, the reactor used in combination of two or more, to produce a NF ₃ while switching these reactors. Specifically, after producing NF ₃ for a certain period of time using at least one of the two or more reactors (hereinafter referred to as “reactor A”), the remaining reactors ( Hereinafter, this reactor is referred to as “reactor B”), and a reaction is started by supplying a raw material gas. Next, the supply of the raw material gas to the reactor A is stopped, and NF ₃ is produced only in the reactor B. During the production in the reactor B, an inert gas is introduced into the reactor A to heat the reactor A. By this heat treatment, the solid product remaining on the inner wall of the reactor A and / or the solid product adhering to the inner wall of the pipe can be removed. Specifically, ammonium fluoride which is a solid product can be decomposed and removed into hydrogen fluoride and ammonia. Hydrogen fluoride and ammonia can be detoxified by a known method, for example, an acid or alkali aqueous solution.

  The temperature during the heat treatment is preferably 135 ° C. or higher, more preferably 135 to 300 ° C. Moreover, nitrogen, helium, and argon are mentioned as said inert gas, These can be used 1 type or in mixture of 2 or more types.

After producing NF ₃ in the reactor B for a certain period of time, the reactor is switched in the same manner as above, and again,
NF ₃ is produced in reactor A, during which reactor B is heat treated to remove the solid product. By repeating this series of operations, NF ₃ can be stably produced in high yield without stopping the production line.

[Example]
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited at all by this Example.

<Preparation of F ₂ gas>
[Preparation Example 1]
A composition of KF · 1.8HF to KF · 2.5HF is subjected to molten salt electrolysis at about 100 ° C., and F ₂ is generated and collected at the anode, and HF in the obtained crude F ₂ gas is liquid nitrogen. After separation and purification using F2, the F ₂ gas was subjected to low-temperature distillation using liquid nitrogen to obtain high-purity fluorine gas. Results of analyzing oxygen, oxygen-containing compound, and tetrafluoromethane contained in the high-purity fluorine gas by using TCD method and FID method of gas chromatography (GC) and gas chromatography mass spectrometer (GC-MS) Is shown below.

Oxygen and oxygen-containing compound 0.0610 vol%
Tetrafluoromethane 0.0013 vol%
[Preparation Example 2]
A composition of KF · 1.8HF to KF · 2.5HF is subjected to molten salt electrolysis at about 100 ° C., and F ₂ is generated and collected at the anode, and HF in the obtained crude F ₂ gas is liquid nitrogen. Separation and purification were performed to obtain fluorine gas. The results of analysis of oxygen, oxygen-containing compounds and tetrafluoromethane contained in the fluorine gas using the TCD method and FID method of gas chromatography (GC) and a gas chromatography mass spectrometer (GC-MS) are as follows: Shown in

Oxygen and oxygen-containing compound 0.3320 vol%
Tetrafluoromethane 0.0108vol%
<Preparation of NH ₃ gas>
[Preparation Example 3]
Liquid ammonia produced by the high-pressure catalyst method, which is an industrial production method, was evaporated and recovered by cooling with a heat exchanger, and further purified by distillation to obtain high-purity ammonia. The results of analysis of oxygen and oxygen-containing compounds, methane, and oil contained in this high-purity ammonia using the TCD method and FID method of gas chromatography (GC) and a gas chromatography mass spectrometer (GC-MS) are as follows: Shown in

Oxygen and oxygen-containing compounds <0.5 volppm
Methane <0.1 volppm
Oil content <0.1 mass ppm
[Preparation Example 4]
Gas chromatography (GC) TCD method and FID method, gas chromatography mass spectrometer (GC) for oxygen and oxygen-containing compounds, methane, and oil contained in liquid ammonia produced by the high-pressure catalyst method that is an industrial production method The results of analysis using -MS) are shown below.

Oxygen and oxygen-containing compound 0.0110 vol%
Methane 0.0008vol%
Oil content 0.0006% by mass

  The apparatus shown in FIG. 1 was used. As shown in FIG. 1, SUS316L tubular reactors (with a jacket 4, with refrigerant circulation cooling) 11 and 21 having two inner gas supply lines and having an inner diameter of 54.9 mm and a length of 700 mm are connected in parallel. ing. Each of these tubular reactors 11 and 21 has an automatic vertical drive type scraper 2 in which a shaft (bar) and a handle are mounted on a ring-shaped thin plate having an outer diameter of 53.9 mm and an inner diameter of 53.1 mm, respectively. The air knocker 3 (made by Seishin Co., Ltd., air knocker SK / 30 type) is provided outside. Further, a solid storage tank 5 made of SUS316L having an inner diameter of 109.8 mm and a length of 350 mm is attached to the lower part of each of the tubular reactors 11 and 21, and a gas is passed through a filter 6 to the upper part of the solid storage tank 5. A discharge line 7 is connected.

High purity F ₂ gas 2.3 obtained in Preparation Example 1 from one of the raw material gas supply lines of the tubular reactor 11
A mixed gas of NL / hr and sulfur hexafluoride (purity:> 99.999%) 59.64 NL / hr was mixed with the high purity NH obtained in Preparation Example 3 from the other raw material gas supply line of the tubular reactor 11. _Three
A mixed gas of gas 3.06 NL / hr and sulfur hexafluoride (purity:> 99.999%) 50 NL / hr was supplied into the tubular reactor 11, and F ₂ gas and NH ₃ were fed into the reactor 11. The gas was mixed and reacted. During the reaction, the scraper 2 was moved up and down in the reactor 11 every 30 minutes by a timer, and the air knocker 3 was operated at a knocker strike interval of 30 minutes by the timer. Moreover, it reacted, cooling the reactor 11 with a refrigerant | coolant. Ten hours after the start of the reaction, the peak temperature in the reactor 11 was 15.8 ° C.

The gas recovered from the gas discharge line was treated with an aqueous potassium iodide solution to remove unreacted fluorine gas and produced hydrogen fluoride, and then gas components were analyzed by gas chromatography. The results are shown below.

NF ₃ yield: 97.6% (F ₂ basis)
CF _4: 0.0012vol%
COF ₂ : not detected
COF: not detected
OF ₂ : not detected
N ₂ O: not detected When the reaction in the reactor 11 was further continued, the peak temperature in the reactor 11 after 48 hours from the start of the reaction was 16.1 ° C. The gas recovered from the gas discharge line was analyzed in the same manner as described above. The results are shown below.

NF ₃ Yield: 97.2% (F ₂ basis)
When the reaction in the reactor 11 was further continued, the peak temperature in the reactor 11 72 hours after the start of the reaction was 15.9 ° C. The gas recovered from the gas discharge line was analyzed in the same manner as described above. The results are shown below.

NF ₃ Yield: 97.2% (F ₂ basis)
As is clear from this result, by using high-purity fluorine gas and high-purity ammonia gas, it is possible to suppress trace impurities, particularly CF ₄ by-product, and supply raw material gas at a low concentration, The target product, NF _3, was continuously obtained in a high yield (97% or more) by controlling the temperature of the reactor and further removing the solid product from the reactor.

Next, the mixed gas of the high purity F ₂ gas obtained in Preparation Example 1 and sulfur hexafluoride (purity:> 99.999%) obtained from one of the raw material gas supply lines of the tubular reactor 21 is used as the tubular reactor 21. High purity NH ₃ gas and sulfur hexafluoride (purity:> 9) obtained in Preparation Example 3 from the other raw material gas supply line
9.999%) is supplied to the tubular reactor 21 under the same conditions as described above, and the solid product adhering to the inside of the reactor 21 is removed under the same conditions as described above, and the reaction is performed. While the reactor 21 was cooled, F ₂ gas and NH ₃ gas were mixed and reacted in the reactor 21.

Thereafter, the supply of the raw material gas and the dilution gas to the tubular reactor 11 was stopped, and the reaction was performed only in the tubular reactor 21. During this reaction, the reactor 11 was heat-treated according to the procedure described later.
One hour after the start of the reaction in the tubular reactor 21, the peak temperature in the reactor 21 was 16.4 ° C.

  When the reaction in the reactor 21 was further continued, the peak temperature in the reactor 21 after 24 hours from the start of the reaction in the reactor 21 was 16.0 ° C. The gas recovered from the gas discharge line was treated with an aqueous potassium iodide solution to remove unreacted fluorine gas and produced hydrogen fluoride, and then gas components were analyzed by gas chromatography. The results are shown below.

NF ₃ yield: 98.1% (F ₂ basis)
CF _4: 0.0012vol%
COF ₂ : not detected
COF: not detected
OF ₂ : not detected
N ₂ O: not detected When the reaction in the reactor 21 was further continued, the peak temperature in the reactor 21 72 hours after the start of the reaction in the reactor 21 was 15.8 ° C. The gas recovered from the gas discharge line was analyzed in the same manner as described above. The results are shown below.

NF ₃ yield: 97.6% (F ₂ basis)
As is clear from this result, even when the reaction was carried out by switching to the reactor 21, the target NF ₃ was continuously obtained in a high yield (97% or more) as in the case of using the reactor 11. Could get in.

(Heat treatment of reactor 11)
After the gas supply to the reactor 11 is stopped, the solid product mainly made of ammonium fluoride collected (deposited) in the solid storage tank 5 is removed, and the refrigerant circulation to the jacket 4 of the reactor 11 is stopped. After that, while introducing steam at about 169 ° C. into the jacket 4, nitrogen gas previously heated to about 350 ° C. was introduced into the reactor 11 at 100 NL / hr from the source gas supply line. At this time, when the gas recovered from the gas discharge line 7 (gas temperature after passing through the filter 6: 148 ° C.) was analyzed, it was confirmed that hydrogen fluoride and ammonia gas were generated. After this heat treatment was continued for 10 hours, the introduction of nitrogen gas and steam was stopped. When the inside of the reactor 11, the solid storage tank 5, the filter 6, and the piping were observed with the naked eye, no solid matter was observed.

[Reference Example 1]
The apparatus shown in FIG. 2 was used. As shown in FIG. 2, a SUS316L tubular reactor 31 (with a jacket 4 and a refrigerant circulation cooling type) having an inner diameter of 54.9 mm and a length of 700 mm, which has two source gas supply lines, It is equipped with an automatic vertical drive type scraper 2 in which a shaft (rod) and handle are mounted on a ring-shaped thin plate having a diameter of 53.9 mm and an inner diameter of 53.1 mm. Air knocker SK / 30 type). In addition, a solid storage tank 5 made of SUS316L having an inner diameter of 109.8 mm and a length of 350 mm is attached to the lower part of the tubular reactor 31, and a gas discharge line 7 is connected to the upper part of the solid storage tank 5 through a filter 6. Is connected.

A mixed gas of 2.3 NL / hr of F ₂ gas obtained in Preparation Example 2 and sulfur hexafluoride (purity:> 99.999%) 59.64 NL / hr from one of the source gas supply lines is used as the other source material. NH ₃ gas 3.06NL / hr obtained in Preparation Example 4 from the gas supply line and sulfur hexafluoride (purity:
> 99.999%) A mixed gas of 50 NL / hr was supplied into the tubular reactor 31, and F ₂ gas and NH ₃ gas were mixed and reacted in the reactor 31. The scraper 2 was moved up and down in the reactor 31 every 30 minutes by a timer, and the air knocker 3 was operated at a knocker hitting interval of 30 minutes by the timer. Moreover, it reacted, cooling the reactor 31 with a refrigerant | coolant. 24 hours after the start of the reaction, the peak temperature in the reactor 31 was 15.8 ° C.

  The gas recovered from the gas discharge line was treated with an aqueous potassium iodide solution to remove unreacted fluorine gas and produced hydrogen fluoride, and then gas components were analyzed by gas chromatography. The results are shown below.

NF ₃ yield: 97.3% (F ₂ basis)
CF _4: 0.0115vol%
COF ₂ : 0.0002 vol%
COF: 0.0001 vol%
OF ₂ : 0.0001 vol%
N ₂ O: 0.0002 vol%
Thereafter, the supply of the raw material gas and the dilution gas was stopped, and the inside of the reactor and the solid storage tank were visually observed. As a result, no adhesion of solid product was observed inside the reactor.

The method for producing nitrogen trifluoride according to the present invention utilizes a direct fluorination reaction in which F ₂ gas and NH ₃ are reacted in the gas phase in the presence of a diluent gas under non-catalytic conditions. By using this, it is possible to overcome conventional problems and problems, and to produce NF ₃ economically in an industrially safe, continuous and high yield.

FIG. 1 is a schematic view showing an example of a production apparatus used in the method for producing nitrogen trifluoride according to the present invention. FIG. 2 is a schematic view showing an example of a production apparatus used in the method for producing nitrogen trifluoride of the reference example.

Explanation of symbols

1 Thermocouple insertion tube 2 Scraper 3 Air knocker 4 Jacket (refrigerant or steam circulation type)
5 Solid storage tank 6 Filter 7 Gas exhaust line 8 Exhaust gas (mainly NF ₃ and dilution gas)
9 Refrigerant or steam 10 Exhaust gas (mainly HF and NH ₃ gas)
11, 21, 31 Tubular reactor

Claims (21)

Fluorine gas and ammonia gas are supplied to a tubular reactor and reacted in the gas phase in the gas phase in a non-catalytic condition at a temperature of 60 ° C. or lower to produce a gas product mainly composed of nitrogen trifluoride, A method for producing nitrogen trifluoride that produces a solid product mainly composed of ammonium fluoride and / or ammonium acid fluoride, wherein two or more tubular reactors are used, and the two or more tubular tubes are used. Perform the reaction while switching the reactor,
After the use in the reaction, the solid product adhering to the inner wall of the tubular reactor and / or the pipe not used in the reaction, in which the supply of the fluorine gas and the ammonia gas is stopped , is present in the presence of an inert gas. A method for producing nitrogen trifluoride, characterized in that it is removed by heat treatment in a step. 2. The method for producing nitrogen trifluoride according to claim 1 , wherein the tubular reactor is installed such that a length direction thereof is a vertical direction. The method for producing nitrogen trifluoride according to claim 1 or 2 , wherein the gas flow inside the tubular reactor is vertically downward. Fluorine gas and ammonia gas are supplied from the upper part of the tubular reactor installed so that the length direction is the vertical direction, and in the presence of a dilution gas, in the gas phase, at a temperature of 60 ° C. or less under non-catalytic conditions. A method for producing nitrogen trifluoride, which reacts to produce a gas product mainly composed of nitrogen trifluoride and a solid product mainly composed of ammonium fluoride and / or acidic ammonium fluoride, the tubular reactor the use of two or more, and performs the reaction while switching the two or more tubular reactors,
A part of the solid product adhering to the inner wall of the tubular reactor is removed by a vibration generator and / or a scraper attached to the tubular reactor, and after being used for the reaction, The presence of an inert gas in the solid product remaining on the inner wall of the tubular reactor not used for the reaction and / or the solid product adhering to the inner wall of the pipe, in which the supply of fluorine gas and ammonia gas is stopped A method for producing nitrogen trifluoride, which is removed by heat treatment under the following conditions. The vibration generator is an air knocker and / or an air piston vibrator attached to the outside of the reactor, and the solid generator is removed by the vibration generator to remove the solid product. 4. The method for producing nitrogen trifluoride according to 4 . 5. The method for producing nitrogen trifluoride according to claim 4 , wherein the scraper is driven freely in a vertical vertical direction inside the tubular reactor to scrape and remove the solid product. The scraper removes the solid product by rotating the scraper freely around the vertical axis passing through the center of the radial cross section of the tubular reactor as a central axis. The method for producing nitrogen trifluoride according to 4 or 6 . The fluorine gas, claim 1-7, wherein the amount of oxygen and the total content of less 0.1 vol% and tetrafluoromethane oxygen-containing compound is less pure fluorine gas 50volppm The manufacturing method of nitrogen trifluoride as described in any one of. Said ammonia gas is, the total content of oxygen and oxygen-containing compound according to any one of claims 1-8, wherein the content of the following and oil 10volppm is high-purity ammonia gas of 2 mass ppm A method for producing nitrogen trifluoride. The oxygen-containing compound contained in the high purity fluorine gas is at least one compound selected from the group consisting of NO, NO ₂ , N ₂ O, CO, CO ₂ , H ₂ O, OF ₂ and O ₂ F ₂ . The method for producing nitrogen trifluoride according to claim 8 , wherein: The oxygen-containing compound contained in the high-purity ammonia gas is at least one compound selected from the group consisting of NO, NO ₂ , N ₂ O, CO, CO ₂ and H ₂ O. Item 10. The method for producing nitrogen trifluoride according to Item 9 . The method for producing nitrogen trifluoride according to any one of claims 1 to 11 , wherein the tubular reactor has a cooling structure. The nitrogen trifluoride according to any one of claims 1 to 12 , wherein fluorine gas and ammonia gas are supplied in a molar ratio (fluorine gas: ammonia gas) range of 1: 1 to 1: 2. Manufacturing method. The dilution gas is at least one gas selected from the group consisting of nitrogen, helium, argon, sulfur hexafluoride, hexafluoroethane, octafluoropropane, and nitrogen trifluoride. 14. The method for producing nitrogen trifluoride according to any one of 13 above. The method for producing nitrogen trifluoride according to any one of claims 1 to 14 , wherein a dilution gas is circulated and used. The method for producing nitrogen trifluoride according to any one of claims 1 to 15 , wherein after the reaction, unreacted fluorine gas is treated with an alkaline aqueous solution and / or alumina. The method for producing nitrogen trifluoride according to any one of claims 1 to 16 , wherein the inert gas is at least one gas selected from the group consisting of nitrogen, helium, and argon. The method for producing nitrogen trifluoride according to any one of claims 1 to 17 , wherein the heat treatment is performed at 135 ° C or higher. The method for producing nitrogen trifluoride according to any one of claims 1 to 18 , wherein a supply concentration of the fluorine gas is 3 mol% or less. The method for producing nitrogen trifluoride according to any one of claims 1 to 19 , wherein a supply concentration of the ammonia gas is 6 mol% or less. The method for producing nitrogen trifluoride according to any one of claims 1 to 20 , wherein fluorine gas and ammonia gas are reacted at a pressure of 0.05 to 1.0 MPa.

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