JP5288026B2 - Method for producing carbonyl fluoride - Google Patents

Description

  The present invention relates to a method for producing carbonyl fluoride, and more particularly to a method for obtaining carbonyl fluoride by reacting tetrafluoroethylene with oxygen.

Carbonyl fluoride (COF ₂ ) is used as a substitute for a gas having a high global warming potential, which has been conventionally used as a cleaning gas for a CVD (chemical vapor deposition) apparatus used in the semiconductor industry and the like. That demand is expanding.

As a method for producing carbonyl fluoride, the following method is known (see Patent Document 1).
1. 1. A method using carbon monoxide or carbon dioxide as a raw material. 2. A method using phosgene as a raw material. 3. Method using trifluoromethane as a raw material Method using tetrafluoroethylene as a raw material

  The above methods 1 to 3 require expensive equipment such as an electrolytic cell, the toxicity of the raw materials used is high, the ignitability of the raw materials and the reaction mixture is high, and the reaction temperature of 500 ° C. or higher is required. However, it is not suitable for industrial production of carbonyl fluoride.

  As for the above method 4, there is a method of obtaining carbonyl fluoride by oxidizing tetrafluoroethylene with oxygen, but there is a risk of explosion when tetrafluoroethylene is directly reacted with oxygen. Thus, diluents such as fluorinated compounds can be used to safely produce carbonyl fluoride.

International Publication No. 2007/037468 Pamphlet

H. Teranishi, “Studies on the Explosions under High Pressures (IV) The Explosions of Tetrafluoroethylene Mixed with Oxygen or Air” The Review of Physical Chemistry of Japan, 1958, 28, p. 9

  As described above, the method for obtaining carbonyl fluoride by reacting tetrafluoroethylene with oxygen has a risk of explosion, but a method capable of efficiently producing carbonyl fluoride is required while ensuring safety. ing.

  An object of the present invention is to provide a novel method for producing carbonyl fluoride, which is capable of obtaining carbonyl fluoride safely and efficiently by reacting tetrafluoroethylene with oxygen.

  In Patent Document 1, when tetrafluoroethylene is reacted with oxygen to generate carbonyl fluoride, the presence of nitrogen gas hinders the progress of the oxidation reaction of tetrafluoroethylene. It describes that the yield of carbonyl is improved, and teaches removing nitrogen gas mixed in as air in the reactor.

  However, the present inventors have found that carbonyl fluoride can be produced in high yield from tetrafluoroethylene even when air is used as an oxygen source, and as a result of intensive studies, the present invention has been completed.

  According to one aspect of the present invention, tetrafluoroethylene is reacted with oxygen by heating in the presence of tetrafluoroethylene gas and 8 times mole or more of air with respect to tetrafluoroethylene to obtain carbonyl fluoride. A method for producing carbonyl fluoride is provided.

  According to the production method of the present invention, the danger of explosion can be avoided by using air of 8 times mol or more with respect to tetrafluoroethylene. Furthermore, in the above method of the present invention, air is used as an oxygen source, so that carbonyl fluoride can be obtained in a high yield despite the presence of a considerable proportion of nitrogen in the reactor. It has been confirmed by the present inventors.

  In the present invention, the term “air” is used in a general sense. More specifically, air is usually composed of about 78 mol% nitrogen, about 21 mol% oxygen, and the remainder (argon, carbon dioxide, etc.), but in some cases there may be slight differences for each nitrogen and oxygen content. Note that can occur.

  In the production method of the present invention, the tetrafluoroethylene gas preferably has a tetrafluoroethylene purity of 90 mol% or more. By using such a highly pure (or purified) tetrafluoroethylene gas, carbonyl fluoride can be obtained in high yield even when air is used as the oxygen source.

  In the present invention, the tetrafluoroethylene gas preferably has a chlorodifluoromethane content of 1 mol% or less. Thus, by using tetrafluoroethylene gas that contains only a small amount, preferably substantially no chlorodifluoromethane, carbonyl fluoride can be obtained in high yield even when air is used as the oxygen source. it can.

  In the present invention, the reaction is preferably carried out at a temperature of 272 ° C. or higher and 350 ° C. or lower. By selecting such a temperature range, carbonyl fluoride can be obtained in high yield.

  ADVANTAGE OF THE INVENTION According to this invention, it is a manufacturing method of carbonyl fluoride, Comprising: The novel method which can react a tetrafluoroethylene with oxygen and can obtain carbonyl fluoride safely and efficiently is provided.

It is a graph showing the temperature dependence of carbonyl fluoride (COF ₂₎ yield.

  Hereafter, the manufacturing method of carbonyl fluoride of this invention is explained in full detail.

  First, tetrafluoroethylene gas is prepared as a raw material. The tetrafluoroethylene gas may be any gas that contains tetrafluoroethylene (also referred to as TFE in this specification) with relatively high purity.

  The tetrafluoroethylene purity in the tetrafluoroethylene gas is preferably 90 mol% or more, more preferably about 98 mol% or more (however, the theoretical maximum value is 100 mol%).

  Such tetrafluoroethylene gas may be obtained by any method. For example, a tetrafluoroethylene-containing composition obtained by thermal decomposition of chlorodifluoromethane (also referred to as HCFC-22 in this specification) may be purified.

  The tetrafluoroethylene gas may contain other components as impurities, but preferably has a low chlorodifluoromethane content, and more preferably contains as little chlorodifluoromethane as possible. The chlorodifluoromethane content in the tetrafluoroethylene gas is preferably 1 mol% or less, more preferably about 0.1 mol% or less (however, the theoretical minimum value is 0 mol%).

  Next, this tetrafluoroethylene gas is introduced into the reactor together with air.

  If a tubular reactor is used as the reactor, carbonyl fluoride can be produced continuously. As the tubular reactor, for example, one having an inner diameter of 10 mm or less, preferably 2 mm or less can be used, and if a tubular reactor having such dimensions is used, high heat transfer efficiency can be obtained. However, the present invention is not limited to this, and any appropriate reaction vessel may be used, and carbonyl fluoride may be produced batchwise.

  The amount of air introduced into the reactor is 8 times mol or more, preferably 9 times mol or more, for example, 9 to 19 times mol, relative to tetrafluoroethylene contained in the tetrafluoroethylene gas introduced together. Tetrafluoroethylene and oxygen can explode if there is an ignition source, but in the case of a two-component system of tetrafluoroethylene and air, the explosion range is reported to be a tetrafluoroethylene concentration of 11 to 60%. (See Non-Patent Document 1). Therefore, if air of 8 times mole or more with respect to tetrafluoroethylene is present, it can be removed from the explosion range of tetrafluoroethylene and air, and even if there is an ignition source, no explosion occurs.

  The temperature in the reactor (that is, the reaction temperature) can be in the range of 200 ° C. or more and 400 ° C. or less, for example. If it is less than 200 degreeC, the tetrafluoroethylene gas will be in a chemically stable state with respect to air, and reaction does not advance. If the temperature exceeds 400 ° C., energy (heat) is excessively supplied, which is not efficient, and is disadvantageous because the thermal load on the material constituting the reactor or the like increases. The appropriate temperature range may vary depending on the specific conditions (reactor shape and dimensions, tetrafluoroethylene gas and air supply flow rate, other reaction conditions such as pressure), but not less than 200 ° C. and not more than 400 ° C. Among the ranges, the present inventors have confirmed that a high yield can be obtained particularly at a temperature exceeding 250 ° C., for example, at a temperature range of 272 ° C. to 350 ° C. The pressure in the reactor is not particularly limited, but may be, for example, 0.1013 to 0.3 MPaA (absolute pressure). The reaction time (residence time) can be appropriately set to such an extent that the carbonyl fluoride formation reaction proceeds sufficiently, but may be, for example, 0.1 to 30 seconds, and preferably 1 to 10 seconds.

Under such conditions, when heated in the reactor, tetrafluoroethylene reacts with oxygen to produce carbonyl fluoride. The produced carbonyl fluoride (COF ₂ ) is removed from the reactor as a reaction mixture (gaseous material) together with other remaining components (including nitrogen derived from air, and unreacted TFE, if present). Extracted.

  Thus, the method for producing carbonyl fluoride of the present invention is carried out.

  According to the present invention, tetrafluoroethylene and air are present at a ratio outside the explosion range, and the carbonyl fluoride production reaction can be carried out outside the explosion range, so that carbonyl fluoride can be produced safely.

  In addition, according to the present invention, air can be used as an oxygen source, and nitrogen in the air functions as a diluent. Therefore, it is possible to use high-purity oxygen or an expensive diluent such as a fluorinated compound. Therefore, carbonyl fluoride can be produced at a low cost.

  Although not limiting the present invention, according to such a production method, even at a relatively low temperature (for example, 272 ° C.), carbonyl fluoride can be obtained in a high yield, for example, 95% or more, preferably about 100%. It can be produced in a yield.

  Although the present invention is not bound by any theory, it is understood that the presence of nitrogen gas does not substantially hinder the progress of the oxidation reaction of tetrafluoroethylene when high purity tetrafluoroethylene gas is used. In Patent Document 1, since low-purity tetrafluoroethylene gas (which contains a relatively large amount of HCFC-22 in addition to TFE) is used, if the reaction is performed using air as an oxygen source, the oxidation reaction of tetrafluoroethylene is performed. (See the comparative example of Patent Document 1).

  EXAMPLES Hereinafter, although this invention is demonstrated in detail through an Example, this invention is not limited to these Examples.

  Tetrafluoroethylene gas (hereinafter also referred to as TFE gas) having a tetrafluoroethylene purity of 99 mol% and a chlorodifluoromethane content of 0.1 mol% or less (substantially 0 mol%) is used as the raw material tetrafluoroethylene gas. It was.

  As the reactor, a straight tube reactor (“Toray Engineering Co., Ltd.,“ Microreactor for high-temperature reaction ”) having an inner diameter of 1.78 mm and a length of 20 m that can be adjusted with an external heater was used.

  The reactor was set to a predetermined temperature in advance, and nitrogen gas was circulated from an inlet located at one end of the reactor to an outlet located at the other end to purge the inside of the reactor.

  A TFE gas and air were introduced into a reactor set at a set temperature of 300 ° C. by mixing with a mixer installed immediately before the reactor inlet, and circulated through the reactor to obtain a reaction mixture from the outlet. The supply flow rate of TFE gas was 14.9 NmL / min (5 mol%), and the supply flow rate of air was 283.5 NmL / min (95 mol%). The residence time was about 5 seconds. In addition, a flow rate is shown by the flow rate (NmL / min) in a standard state (0 degreeC, 1 atm).

The composition of the reaction mixture obtained above was analyzed by gas chromatography to determine TFE conversion, COF ₂ selectivity, and COF ₂ yield. The results are shown in Table 1 (No. 1). The measured values of the reactor inlet temperature and outlet temperature are also shown in Table 1.

  As shown in Table 1, a reaction mixture was obtained in the same manner as above except that the set temperature of the reactor was variously changed. These results are shown in Table 1 (Nos. 2 to 6).

From the data in Table 1 (5 mol% TFE gas, 95 mol% air, air / TFE = 19 (mol / mol), thus oxygen / TFE = about 4 (mol / mol)), the reactor inlet temperature (° C. 1 is a graph plotting COF ₂ yield (%) against). As understood from FIG. 1 and Table 1, the COF ₂ yield was 0% at a temperature of 250 ° C. or lower, whereas in the temperature range of 272 ° C. to 350 ° C. (272 ° C. to 352 ° C. at the inlet temperature). A 100% COF ₂ yield was obtained.

In the above embodiment, if case of a temperature of 250 ° C. or less in (No.3~4) next to COF ₂ yield 0%, which was temperature 272 ℃ ~350 ℃ (No.1~2,5~6) The COF ₂ yield was 100%, and the COF ₂ yield rose remarkably between 250 ° C. and 272 ° C. In the present invention, although the COF ₂ yield tends to change significantly depending on the temperature, the lower limit of the temperature at which a high COF ₂ yield is obtained depends on the specific conditions (reactor shape and dimensions, tetrafluoro Other reaction conditions such as ethylene gas and air feed flow rates and pressures) may vary. Therefore, an appropriate temperature range can be individually selected according to specific conditions based on the disclosure of the present invention.

  Next, the set temperature of the reactor was set to 272 ° C., the TFE gas supply flow rate was set to 29.8 NmL / min (10 mol%), and the air supply flow rate was set to 268.6 NmL / min (90 mol%). The residence time was 5 seconds (No. 7), the TFE gas supply flow rate was 59.7 NmL / min (10 mol%), the air supply flow rate was 537.1 NmL / min (90 mol%), The residence time was 2.5 seconds (No. 8), the TFE gas supply flow rate was 120.3 NmL / min (10 mol%), and the air supply flow rate was 1082.7 NmL / min (90 mol%). A reaction mixture was obtained in the same manner as above except that the residence time was 1.2 seconds (No. 9). These results are shown in Table 2 (Nos. 7 to 9).

  In addition, the set temperature of the reactor was 272 ° C., the TFE gas supply flow rate was 120.3 NmL / min (10 mol%), the air supply flow rate was 1082.7 NmL / min (90 mol%), and the residence time Was set to 1.2 seconds, and a reaction mixture was obtained in the same manner as above except that mixing was not performed with a mixer. The results are shown in Table 2 (No. 10).

As can be seen from the data in Table 2 (TFE gas 10 mol%, air 90 mol%, air / TFE = 9 (mol / mol), thus oxygen / TFE = about 2 (mol / mol)), the temperature 272 A COF ₂ yield of 99% or more was obtained at ℃.

  In these examples, TFE gas having a tetrafluoroethylene purity of 99 mol% and a chlorodifluoromethane content of 0.1 mol% or less (substantially 0 mol%) was used as the raw material tetrafluoroethylene gas. The invention is not limited to this. In general, in the present invention, it is preferable that the tetrafluoroethylene purity is high and the chlorodifluoromethane content is low, but an appropriate numerical range of the tetrafluoroethylene purity and chlorodifluoromethane content of the tetrafluoroethylene gas is determined according to specific conditions ( Other reactor conditions such as reactor geometry and dimensions, tetrafluoroethylene gas and air feed flow rates, pressure, etc.) may vary.

  According to the present invention, carbonyl fluoride can be produced safely and efficiently, and the present invention can be suitably used for industrially producing carbonyl fluoride. The carbonyl fluoride produced according to the present invention can be used for various applications in addition to the cleaning gas for the CVD apparatus in the semiconductor industry and the like.

Claims (6)

  A process for producing carbonyl fluoride, which comprises reacting tetrafluoroethylene with oxygen by heating in the presence of tetrafluoroethylene gas and air at least 8 moles relative to tetrafluoroethylene.   The method for producing carbonyl fluoride according to claim 1, wherein the tetrafluoroethylene gas has a tetrafluoroethylene purity of 90 mol% or more.   The method for producing carbonyl fluoride according to claim 1 or 2, wherein the tetrafluoroethylene gas has a chlorodifluoromethane content of 1 mol% or less.   The method for producing carbonyl fluoride according to any one of claims 1 to 3, wherein the reaction is carried out at a temperature of 200 ° C or higher and 400 ° C or lower.   The method for producing carbonyl fluoride according to claim 4, wherein the reaction is carried out at a temperature exceeding 250 ° C and not more than 400 ° C.   The method for producing carbonyl fluoride according to claim 5, wherein the reaction is carried out at a temperature of 272 ° C or higher and 350 ° C or lower.

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