KR20040012817A - Method for producing nitrogen fluorides - Google Patents

Abstract

The present invention relates to the field of inorganic chemistry, the production of nitrogen fluoride, namely nitrogen trifluoride (NF ₃ ), tetrafluorohydrazine (N ₂ F ₄ ), difluorohydrazine (N ₂ F ₂ ), difluoro It relates to a process for preparing an amine (NF ₂ H). The gist of the method is a method for producing nitrogen fluoride by fluorinating a melt of ammonium hydrogen fluoride of the formula NH ₄ H _(x-1) F _x (x = 2.1-3.0) with gaseous fluorine while stirring. It introduces a reagent that binds to the hydrogen fluoride produced in the melt and also splits and washes the product. This is accomplished by aligning and moving the active cycle of the reagent in a vertical direction, and the method is carried out on the fluoride produced at a temperature of 80-153 ° C. The method improves the agitation of the reactants and determines the specific parameters of the reaction, thereby improving the composition of the resulting product, producing more of one of the products, increasing the yield of the target product and ensuring the stability of the process.

Description

Method for producing nitrogen fluorides

Nitrogen fluoride has been applied in many chemical and electronics industries, ie in the chemical industry, as fluorinating agents for the synthesis of fluorinated olefins, ammonium fluoride salts; It is applied as a very effective fuel oxidant in rocket technology; The electronics industry is used for semiconductor microcrystal cleaning and dry etching of large scale integrated circuits.

Difluoroamine and tetrafluorohydrazine (N ₂ F ₄ ) are applied as difluoroamine agents in organofluorine material synthesis; Difluorodiazine (N ₂ F ₂ ) is used as a catalyst for the polymerization of monomers, styrene methylmethacrylate and cyclopentadiene.

Tetrafluorohydrazine (N ₂ F ₄ ) interacts with nitrogen trifluoride with the fluorine acceptor, with carbon (at 440 ° C.) or with metals (copper, bismuth, cobalt, uranium (at 320 to 375 ° C.)). Pankratov, Journal of Physical Chemistry, No 3, 398, 1969], reacting fluorine and ammonia at 0-50 ° C. in the presence of a catalyst [G. Ellenrieder et al., Z. Phys. Chem., NF, N 55, 144, 1967] to fluorinate NH ₄ F in the mixture using sodium fluoride [LM Brown et al., J Chem. Phys., N 42.2158, 1965].

Difluorodiazine can be obtained by decomposing fluoride azide, fluorinating sodium azide, or pyrolyzing nitrogen trifluoride or tetrafluorohydrazine [A.V. Pankratov, O.M. Sokolov, J. Phys. Chem., No 11, 1497, 1966; A.V. Pankratov, O.M. Sokolov, J. Phys. Chem., No 13, 2881, 1968 and the like].

Currently, two major techniques for producing nitrogen trifluoride are used in industry. These are described by electrolysis of acidic ammonium fluoride [US Pat. No. 5,084,156, cl. C25 B 1/24, published June 14, 1991, US Pat. No. 5,085,752, cl.25 B 9/00, 1992; February 4, FRG Application 377722163, cl. C25 G 1/00, February 14, 1989] or directly fluorination of ammonia in a melt of acidic ammonium fluoride [US Pat. No. 4,001,380, cl. C01 B21 / 00, published Jan. 4, 1977, US Pat. No. 4,091,081, cl. C01 B 21/52, May 23, 1978, etc.] to produce nitrogen trifluoride.

Attempts to fluorine gaseous ammonia at ammonia / fluorine (1.01-2.0) / 1 (molar) ratio [J. Amer. Chem. Soc., 1960, p. 5301-5304 are known; The NF ₃ yield calculated for fluorine is then 10-25%:

2NH ₃ + 3F ₂ → NF ₃ + 3HF

In this reaction, side reactions occur and the reaction in which NF ₃ is fluorinated with N ₂ and HF is dominant.

Individual ammonium fluorides are decomposed at fluorination temperatures and their use is not suitable.

In the fluorination of the melt of the ammonium acid salt, the process for forming nitrogen fluoride proceeds according to the following scheme:

NH ₄ FHF + 3F ₂ → NF ₃ + ₃ NH ₄ F + 8 HF

A negligible amount (trace) of other nitrogen trifluoride is formed in the mixture.

Complex salts containing HF and NH ₃ in an HF: NH ₃ 2: 1 or greater ratio and methods for fluorinating the complex are also known [US Pat. No. 4,091,081, cl. C01 B 21/52, May 78 23]. Day publication]. This method consists in fluorinating a melt of acidic ammonium fluoride (heavy fluoride) NH ₄ F HF. Elemental fluorine bubbling through the NH ₄ F HF melt was carried out according to the above method at a bath temperature of 130-160 ° C. and a pressure of 200-445 kPa.

As a result, 5 moles of HF per 4 moles of the initial heavy fluoride are formed as by-products. The formed NF ₃ consumes 1 mole of NH ₃ per mole, so that ammonia or its gaseous derivatives, fluorinated in order to carry out the operation in continuous mode, There is a need to continuously supply ammonium or ammonium bifluoride. The outflowing gaseous mixture contains up to 10-15% by volume of HF.

The temperature is maintained in the range from the melting temperature of the initial fluoride (127 ° C.) to the product decomposition temperature. The formation of NF ₃ takes place 370 kcal and the heat needs to be removed to avoid promoting side reactions that reduce the yield of the desired product:

2NH ₄ F + 3F ₂ → N ₂ + 10HF

NF ₃ + NH ₄ F HF → N ₂ + 5HF

The following ammonia compounds may also be fluorinated: NH ₄ Cl, NH ₄ Br, NH ₄ I, NH ₄ NO ₃ , (NH ₄ ) ₂ SO ₄ and NH _4, NH ₄ H _x-1 F _x Polyfluoride and (NH ₄ ) _y MF _z nHF (wherein M is an element of groups IA-VA, IB-VIIB and VIII of the periodic table, ie Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Double salts of Ba, Al, Ga, In, TI, Si, Ge, Sn, Pb and the like.

Methods of preparing nitrogen trifluoride are also known [US Pat. No. 5,637,285, cl. C 01 B 21/06, issued June 10, 1997], according to this method, a mixture of (traces) of different fluorides The desired product containing is prepared from elemental fluorine and ammonium in a melt of acidic bifluoride of the ammonia salt of formula NH ₄ H _1-x F _x (x ≧ 2.55).

Fluorination of the compound with vigorous stirring in the formula NH ₄ H _1-x F _x with x> 2.5 can increase the yield of NF ₃ to 90% with 80% selectivity. The fluorination reaction can be carried out in a continuous working mode under a pressure of 200-445 kPa and a contact time of 5 seconds to 2 minutes at a temperature of 121-160 ° C.

In a manner similar to the method described above (US Pat. No. 4,091,081), ammonium is additionally introduced to convert the HF formed into the initial compound:

NH ₃ + xHF → NH ₄ H _x-1 F _x .

When the HF content is high in the melt, the yield of NH ₃ depends on the stirring force. Up to 5000 W / m ³ and is mixed with the reagent intensity indicated by the ratio (P / N), the stirrer power for the melt volume to be the optimum value 35000W / m ^3. In other words, vigorous stirring improves the contact of the reagents and increases the conversion reaction.

However, the process is not possible with other nitrogen fluorides, some of which are made in negligible amounts.

The present invention relates to the field of inorganic chemistry, the production of nitrogen fluoride, namely nitrogen trifluoride (NF ₃ ), tetrafluorohydrazine (N ₂ F ₄ ), difluorohydrazine (N ₂ F ₂ ), difluoro It relates to a process for preparing an amine (NF ₂ H).

1 is a flow chart of a method for synthesizing nitrogen fluoride according to the present invention.

Explanation of symbols on the main parts of the drawings

I: fluorinated liquid phase reactor

II: Expander-Phase Separator

III: fluorinated gas phase reactor

1.1 ^a : fluorine supply line

2: composition of hydrogen fluoride, such as ammonia, fluorine, and bifluoroammonia

Of reagents associated with

3: reverse reaction channel

4: fluorinated products (tetrafluorohydrazine, difluorodiazine,

Partial extraction to units for separation and cleaning of difluoroamines)

5: yield of washed nitrogen trifluoride

An object of the present invention is to provide a method for changing the composition of a product to be produced with a main yield of one of the compounds described above, and the following commercially available products, nitrogen trifluoride (NF ₃ ), tetrafluorohydrazine, depending on market conditions. It was to develop a method for preparing (N ₂ F ₄ ), difluorodiazine (N ₂ F ₂ ), difluorodiamine (NF ₂ H).

This object is solved by improving the process of mixing reagents which provide circulation in the reactor and by determining the reaction parameters to obtain the desired product.

The present invention provides a method for producing nitrogen fluoride by fluorination of an acidic ammonium fluoride of formula NH ₄ H _(x-1) F _x (x = 2.1-3.0) with gaseous fluorine, wherein ammonia, fluorine Agitating with the melt of hydrogen fluoride, such as ammonia bifluoride, to provide an active circulation of the reagents by constructing the melt flow in a vertical direction, and under a temperature change of 80-153 ° C. depending on the fluorine produced. It is characterized by performing a process.

In a preferred embodiment, the interaction product obtained as a result of fluorination in the melt is subjected to further gaseous fluorination.

In a preferred embodiment, said further gas phase fluorination reaction is carried out at 200-450 ° C.

In a preferred embodiment, difluorodiazine (N ₂ F ₂ ) is obtained at 80-100 ° C.

In a preferred embodiment, tetrafluorohydrazine (N ₂ F ₄ ) is obtained at 110-125 ° C.

In a preferred embodiment, difluoroamine (NF ₂ H) is obtained at 125-135 ° C.

In a preferred embodiment, nitrogen trifluoride (NF ₃ ) is obtained at 138-153 ° C.

In a preferred embodiment, the pressure is maintained at 0.5 to 3.0 atmospheres to increase the safety of liquid phase fluorination.

Typical method for the acquisition of nitrogen fluoride containing experimental data (Table 1: Preparation of reaction product (nitrogen fluoride) according to temperature in liquid phase reactor) and preparation example of mixture with predominant content of nitrogen trifluoride (Table 2 : Dependence of nitrogen trifluoride yield on liquid phase reactor temperature and gas phase reactor temperature).

Summary of the Invention The gist of the present invention is that the synthesis of nitrogen fluoride is carried out by fluorination of an acidic ammonium fluoride of formula NH ₄ H _(x-1) F _x (x = 2.1-3.0) with gaseous fluorine. Is carried out under agitation to provide circulation of the reagents at atmospheric temperatures at 80-153 ° C.

The process is carried out at 80-100 ° C. to obtain the maximum difluorodiazine if necessary, at 110-125 ° C. to produce tetrafluorohydrazine, and 125-135 ° C. to produce difluoroamine. To be carried out in Nitrogen trifluoride is obtained at 138-153 ° C. Interaction products obtained as a result of fluorination in the melt are subjected to further gaseous fluorination at 200-450 ° C. This method is carried out according to the scheme shown in FIG. 1 below. Gaseous fluorine is fed to reactor location (I) along line (1), filled with a melt of ammonium acidity 2.1 to 3.0 and ammonia or ammonium bifluoride is fed to reactor along line (2). This reaction can utilize a reactor with an agitator, such as an impeller mixer, a jet bubbler, a liquid flow circuit or a circulation pipe. Hydrochloric acid in the synthesis reactor is automatically maintained within the ranges described above (2.1-3.0), for example by feeding ammonia or ammonium fluoride (or ammonium bifluoride) to the reaction volume. The amount of nitrogen in the gas of the composite increases with an acidity of 2.1 or less, ie the consumption coefficient of fluoride increases. If the acidity is 3.0 or more, fluorine does not react with the salt. The synthesis of nitrogen fluoride is carried out at a fluorine specific flow rate of 0.05-0.15 cm ³ / min per volume unit (cm ³ ) of the melt. The temperature for preparing difluorodiazine (N ₂ F ₂ ) in 70 volume% yield is 80-100 ° C., and the temperature for preparing tetrafluorohydrazine (N ₂ F ₄ ) in 40 volume% yield is 100-. 125 ° C., and the temperature for preparing difluoroamine (NF ₂ H) in 30% by volume yield is 125-135 ° C. Nitrogen trifluoride is prepared in 65 vol% yield at a temperature of 138-153 ° C.

A predominant amount of compound and nitrogen fluoride mixture obtained from the reactor (position I) is fed to a phase-separator (position II) to purify and separate the compound according to line (4). These steps are carried out by known methods.

In order to increase the NF ₃ yield to 90% by volume or more, nitrogen fluoride (NF ₂ H, N ₂ F ₂ , N ₂ F ₄ ) formed in the liquid phase reactor in the first process step was subjected to elemental fluorine at 200-450 ° C. Additionally fluorinated. This additional fluorination step is realized in the reactor of gas phase fluorination (position III). Depending on the fluorine flow rate in the first stage, in the second stage, partially unreacted fluorine or fresh gaseous fluorine obtained from the liquid phase reactor along line 1 ^a can be used. When the specific flow rate of fluorine in the two stages is in the range of 0.05 -0.1 cm ³ / min per cm ³ of the melt, the new fluorine has a total value of fluorine flow rate in the second stage of less than 0.15 cm ³ / min F ₂ per cm ³ of the melt It is supplied to the gas phase reactor at a flow rate such that

The reactor of the gas phase fluorination reaction is an empty vessel whose walls are incubated at 200-450 ° C. and filled with a mixture of nitrogen fluoride and fluorine. Nitrogen trifluoride taken along line 5 from the gas phase reactor is purified from the mixture.

The temperature is measured by a thermocell mounted on the reactor wall. The following are examples of practicing the present invention.

Nitrogen Fluoride

A 350 mm long and 70 mm diameter cylindrical reactor (position 1) (D / d-1.5) with a circulation pipe of about 47 mm diameter is equipped with a flat-blade turbine-type mixer and an electric heater on the outer wall. The reactor is charged with a melt of acidic salt of ammonium fluoride (acidity x = 2.1-3.0). The gaseous fluorine (F ₂ ), which is fed to the melt under the mixer at a flow rate of 0.05 -0.15 cm ³ / min per cm ³ of melt (along line 1), is distributed in volume by the mixer. The gaseous reaction product is removed from the reactor via a phase-separator (position II) and sent to a separation and purification step along line 4 in a closed valve on the line leading to the reactor (position III). The composition of the reaction product according to the melting temperature in the range of 80-155 ° C. is shown in Table 1 below. The further rise in reaction temperature leads to the formation of large amounts of nitrogen with the reaction product and therefore this method is ineffective for the synthesis of nitrogen fluoride. Therefore, the above-described temperature interval is most appropriate. Method variables and the results accordingly are shown in Table 1 below (Examples 1-7).

Preparation of Mixtures with Predominant Nitrogen Trifluoride Content

This method is carried out according to the scheme shown in the flowchart. In this case, however, the mixture of products removed from the reactor (position 1) after the phase separator (position II) is further fluorinated. In a closed valve on line 4 the mixture from the phase separator (position II) flows along an open valve on the line and enters the gas phase fluorination reactor (position III). The outer surface of the reactor is equipped with an electric heater. Gaseous fluorine is fed along line 1 ^a to the reactor (position III) filled with reagents obtained from the phase separator. When fluorine is the melt flow rate of 1 cm 0.05 -0.1cm in particular ³ / minute feed (in the reactor (position I)) per ^3, new fluorine is the total flow rate of the fluorine 0.15cm ³ / (cm ³ * min in two steps It is supplied to the gas phase reactor so as not to be higher than). In the reactor (position III) the fluorination reaction is carried out at a temperature of 200-450 ° C. The temperature is measured by a thermocell installed on the reactor wall.

The nitrogen trifluoride values obtained according to the melting temperature in the first step and the reactor wall temperature in the second process step are shown in Table 2 (Examples 8-18).

Claims (8)

In a process for producing nitrogen fluoride by fluorinating an acidic ammonium fluoride of formula NH ₄ H _(x-1) F _x (x = 2.1-3.0) with gaseous fluorine, Agitating associated with a melt of hydrogen fluoride such as ammonia, fluorine, bifluor ammonia, etc., and providing an activated circulation of the reagents in a way that constitutes the flow of the melt in a vertical direction, and at 80-153 ° C. depending on the fluorine produced. Characterized in that the process is carried out under temperature changes. The process of claim 1, wherein the reaction product obtained as a result of the fluorination reaction in the melt is subjected to a gas phase fluorination treatment. 3. The process of claim 2, wherein said further gas phase fluorination is carried out at 200-450 ° C. The method according to claim 1, wherein difluorodiazine (N ₂ F ₂ ) is obtained at 80-100 ° C. A process according to claim 1, wherein tetrafluorohydrazine (N ₂ F ₄ ) is obtained at 110-125 ° C. A process according to claim 1, wherein difluoroamine (NF ₂ H) is obtained at 125-135 ° C. A process according to claim 1, wherein nitrogen trifluoride (NF ₃ ) is obtained at 138-153 ° C. 8. Process according to any one of the preceding claims, characterized in that it maintains 0.5-3.0 atmospheres in order to increase the safety of the liquid fluorination reaction.