Method and composition for producing trifluoroiodomethane

Abstract

To reduce a load on a distillation process by bringing trifluoroiodomethane into contact with an alkaline medium as a pretreatment when distilling the trifluoroiodomethane to remove hydrogen fluoride gas, carbon dioxide gas and the like contained in the trifluoroiodomethane.SOLUTION: In the method for producing high-purity trifluoroiodomethane, trifluoromethane is reacted with iodine to produce trifluoroiodomethane, and the obtained trifluoroiodomethane is brought into contact with an alkaline solvent so that the content ratios of (a) carbon dioxide (CO2) and (b) hydrogen fluoride (HF) on the basis of peak areas determined by gas chromatography and / or ion chromatography are (a) ≤ 0.0010% and (b) ≤ 0.0010%, respectively, and the content of trifluoroiodomethane is 99.7% or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] Trifluoroiodomethane is widely used in industry, including as a chemical raw material, refrigerant, fumigant, fire extinguisher, and cover gas for alloy casting. The present invention relates to a method for producing trifluoroiodomethane, which is used in many industries, and to a composition containing high-purity trifluoroiodomethane. [Background technology]

[0002] Trifluoroiodomethane is synthesized using trifluoromethane or trifluoroacetic acid as raw materials (Patent Document 1). However, after the reaction, impurities such as hydrogen fluoride and carbon dioxide are mixed in as by-products. In particular, when trifluoroacetic acid is used as the starting material, the purity of the product is extremely low because carbon dioxide gas is by-produced in an amount equivalent to the product upon decarboxylation.

[0003] Pressure distillation is generally used as a method for purifying these gases, but in order to remove impurities to a low level, it is very inefficient, requiring multiple columns and time-consuming reflux, etc. Thus, reducing impurities by distillation alone is extremely disadvantageous in terms of energy. Furthermore, when carbon dioxide gas gets mixed into the product, part of the trifluoroiodomethane decomposes to produce iodine, which can cause corrosion of piping and containers.

[0004] Therefore, there is a demand for a process for obtaining practically high-purity trifluoroiodomethane by further removing by-products or impurities that have not been completely removed in the production of trifluoroiodomethane.

[0005] Patent Document 2 lists organic impurities, acid impurities, and water as impurities that may be contained in the target product in some known processes for producing CF3I and compositions containing CF3I, and discloses that in order to remove these impurities, the reaction materials in the production process are reacted with 0.5% to 5% by weight of an alkali metal carbonate or 0.01% to 5% by weight of an alkali metal hydroxide. Patent Document 2 lists as organic impurities fluorohydrocarbons and iodinated hydrocarbons such as pentafluoroethane (HFC-125), hexafluoropropene (HFO-1216), 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), 1,1,3,3,3-pentafluoropropene (HFO-1225zc), 1,1,1,3,3,3-hexafluoropropane (HFC-236fa), and methyl iodide (CHI), as well as carbon dioxide (CO). Acid impurities include hydrogen fluoride (HF), hydrogen chloride (HCl), hydrogen iodide (HI), and trifluoroacetic acid (TFA). Patent Document 2 states that in order to improve defects such as corrosion caused by these impurities, the acid impurities must be kept to 1 ppm or less and the water content to 10 ppm or less, and that to produce high-purity CF3I, a purification process is required to sufficiently remove organic impurities (particularly CH3I), acid impurities, and water. As described above, it discloses that the reaction materials for the production process are reacted with 0.5% to 5% by weight of alkali metal carbonate or 0.01% to 5% by weight of alkali metal hydroxide.

[0006] However, even though trifluoroiodomethane is synthesized using trifluoromethane or trifluoroacetic acid as a raw material in the production process, the by-products and impurities generated in these processes can vary depending on various factors such as the reaction conditions and the purity of the raw materials. For example, when trifluoromethane is used as the raw material, there are the raw materials CF3H, iodine (I2), and by-products generated by the reaction. When trifluoroacetic acid is used as the raw material, there are the raw materials trifluoroacetic acid, iodine I2, and by-products generated by the reaction. In particular, when using trifluoroacetic acid as the raw material, carboxyl groups or carbon dioxide derived from acetic acid remain or are generated, which imposes a heavy burden on their removal. Therefore, depending on the raw materials and by-products, it is desirable to optimize the impurity removal process. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 4547133 [Patent Document 2] Patent No. 7451527 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above-mentioned background art, an object of the present invention is to provide a method for producing high-purity trifluoroiodomethane, which can reduce the burden of impurity removal in the distillation step by contacting trifluoroiodomethane obtained by reacting trifluoromethane with iodine with an alkaline medium as a pretreatment for the distillation step, thereby removing impurities such as hydrogen fluoride and carbon dioxide contained therein, and a composition containing trifluoroiodomethane. [Means for solving the problem]

[0009] As a result of intensive research to solve the above problems, the present inventors have found that hydrogen fluoride, carbon dioxide, and the like contained in trifluoroiodomethane can be removed by contacting trifluoroiodomethane with an alkaline medium as a pretreatment for the distillation step, and have thus completed the present invention.

[0010] That is, the present invention relates to the following inventions. [1] Reacting trifluoromethane with iodine to produce trifluoroiodomethane; The resulting trifluoroiodomethane is contacted with an alkaline medium to The trifluoroiodomethane may contain major impurities, (a) carbon dioxide (CO2) and (b) hydrogen fluoride (HF), whose peak area content is determined by gas chromatography and / or ion chromatography is (a) ≦0.0010% and (b) ≦0.0.0010%, respectively, and the trifluoroiodomethane content is 99.7% or more (provided that the sum of the peak areas of trifluoroiodomethane and (a) to (b) is 100%, excluding trifluoromethane (CF3H)). A method for producing high-purity trifluoroiodomethane. [2] a step of reacting trifluoromethane with iodine to produce trifluoroiodomethane; contacting the obtained trifluoroiodomethane with an alkaline medium; separating the trifluoroiodomethane after contact with the alkaline medium from trifluoromethane (CF3H) by distillation; A method for producing high-purity trifluoroiodomethane, comprising: The high-purity trifluoroiodomethane is characterized in that the peak area content ratios of the major impurities that may be contained in the high-purity trifluoroiodomethane, namely (a) carbon dioxide (CO2), (b) hydrogen fluoride (HF), and (c) trifluoromethane (CF3H), determined by gas chromatography and / or ion chromatography, are (a) ≦0.0005%, (b) ≦0.0005%, and (c) ≦0.08%, respectively, and the trifluoroiodomethane content is 99.7% or more (provided that the sum of the peak areas of trifluoroiodomethane and (a) to (c) is 100%). A method for producing high-purity trifluoroiodomethane. [3] The method according to item [1] or [2], wherein the alkaline medium is an aqueous potassium hydroxide solution. [4] The method according to item [3], wherein the concentration of the aqueous potassium hydroxide solution is 5% by weight to 50% by weight. [5] A trifluoroiodomethane composition, characterized in that the peak area-based content ratios of the major impurities that may be contained in trifluoroiodomethane, namely (a) carbon dioxide (CO2), (b) hydrogen fluoride (HF), and (c) trifluoromethane (CF3H), determined by gas chromatography and / or ion chromatography, are (a) ≦0.0005%, (b) ≦0.0005%, and (c) ≦0.08%, respectively, and the trifluoroiodomethane content is 99.7% or more (provided that the sum of the peak areas of trifluoroiodomethane and (a) to (c) is 100%). [Effects of the Invention]

[0011] According to the present invention, trifluoroiodomethane is brought into contact with an alkaline medium as a pretreatment for the distillation step to remove contained hydrogen fluoride, carbon dioxide, etc., thereby reducing the burden of removing impurities in the distillation step. INDUSTRIAL APPLICABILITY The present invention provides a method for producing high-purity trifluoroiodomethane and a composition containing trifluoroiodomethane, which are industrially useful. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing a reaction vessel for contacting a raw material reaction gas with an alkaline medium, and the flow of the reaction gas and the alkaline medium, for producing high-purity trifluoroiodomethane according to the present invention. [Figure 2] FIG. 1 shows a schematic diagram of a distillation column in which the reaction gas is brought into contact with an alkaline medium, and the treated reaction gas is removed from the top of the reaction vessel, and then the reaction gas is pressurized and distilled to obtain the CF3I product. [Figure 3] 1 is a schematic diagram showing a reaction vessel for contacting a raw material reaction gas with an alkaline medium, and the flow of the reaction gas and the alkaline medium, for producing high-purity trifluoroiodomethane according to the present invention. [Figure 4]1 is a schematic diagram showing a reaction vessel for contacting a raw material reaction gas with an alkaline medium, and the flow of the reaction gas and the alkaline medium, for producing high-purity trifluoroiodomethane according to the present invention. [Figure 5] FIG. 1 is a schematic diagram showing a reaction vessel for contacting the raw reaction gas with zeolite (granular) as an alkaline medium for the production of high-purity trifluoroiodomethane of the present invention, and the flow of the reaction gas and the alkaline medium. [Figure 6] FIG. 1 is a schematic diagram showing a reaction vessel for contacting the raw material reaction gas with an alkaline medium for the production of high-purity trifluoroiodomethane of the present invention, and the flow of the reaction gas and alkaline medium flowing in a spiral shape in the reaction vessel. [Figure 7] 1 is a schematic diagram showing a flow-type reactor for contacting a raw material reaction gas with an alkaline medium for producing high-purity trifluoroiodomethane of the present invention, and the flow of the reaction gas and the alkaline medium. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below with reference to the accompanying drawings.

[0014] <Method of producing high-purity trifluoroiodomethane> The method for producing high-purity trifluoroiodomethane of the present invention comprises the steps of: reacting trifluoromethane with iodine to produce trifluoroiodomethane; The resulting trifluoroiodomethane is contacted with an alkaline medium to The trifluoroiodomethane is characterized in that the content ratios of the major impurities that may be contained in the trifluoroiodomethane, (a) carbon dioxide (CO2) and (b) hydrogen fluoride (HF), based on the peak area determined by gas chromatography and / or ion chromatography, are (a) ≦0.0010% and (b) ≦0.0010%, respectively, and the trifluoroiodomethane content is 99.7% or more (however, excluding trifluoromethane (CF3H), the sum of the peak areas of trifluoroiodomethane and (a) to (b) is 100%).

[0015] In the present invention, a method for producing high purity trifluoroiodomethane is provided. This method produces trifluoroiodomethane, including impurities derived from the raw materials and by-products of the reaction. These impurities are removed by contacting them with an alkaline medium and reacting them. The remaining impurities are then removed through a subsequent distillation process to produce high-purity trifluoroiodomethane. In the present invention, the conditions for contacting the gaseous reactant with an alkaline medium to remove impurities present in the reactant can be appropriately selected based on the purpose, application and other conditions.

[0016] In the present invention, high-purity trifluoroiodomethane is a compound identified as CF3I. It is synthesized using trifluoromethane, trifluoroacetic acid, or the like as raw materials. The types and amounts of impurities contained in the resulting trifluoroiodomethane vary depending on the raw materials and manufacturing recipe used. In the present invention, trifluoromethane is reacted with iodine to produce trifluoroiodomethane, and then an alkaline medium is contacted with a reaction gas containing trifluoroiodomethane to remove impurities by reaction.

[0017] The main impurities and unreacted raw materials are: (a) Carbon dioxide (CO2), (b) hydrogen fluoride (HF), and (c) Trifluoroiodomethane (CF3H) These can be quantified together with trifluoroiodomethane (CF3I) by gas chromatography (GC) and / or ion chromatography (IC). Impurities include tetrafluoromethane (CF4) and carbon monoxide (CO), which cannot be removed by reaction in an alkaline medium, but can be separated from trifluoroiodomethane (CF3I) and removed in a subsequent distillation step.

[0018] For quantification, the elution position (elution time) of a peak detected in an analytical chart by gas chromatography and / or ion chromatography, the area of ​​the peak, etc. can be determined, and then converted into a weight equivalent value, for example.

[0019] In gas chromatography (GC) analysis, the peak areas provided by the GC analysis for each compound may be combined with integration by an information processing means built into or external to the GC analysis to provide the GC area percentage (GC area %) of all compounds relative to each of the analyte compounds as a measure of the relative concentration of the compound in the reaction gas. A mass spectrometer may also be used to identify the analyte compounds, if desired. For quantitative analysis, the GC peak area may be regarded as a weight and used as a relative weight conversion value.

[0020] When a compound contains halogens such as fluorine, they can be liberated by dissolving them in water and then quantified by ion chromatography. Ion chromatography (IC) analysis calculates the concentration of specific ions, especially fluorine (F) ions, in the target compound. By combining this with gas chromatography (GC) analysis, the composition of trifluoroiodomethane (CF3I) and impurities can be quantified.

[0021] Although it is preferable to have a small amount of impurities, it is also preferable to avoid excessive purification treatment, which would significantly reduce the yield of the desired high-purity trifluoroiodomethane. Although excessive purification, for example, purification using multiple distillation steps, is possible, in consideration of equipment costs, operation management, and a reduction in the yield of the desired product, it is preferable to minimize the burden of the distillation steps.

[0022] The amount of impurities in trifluoromethane is expressed as the content ratio based on the peak area determined by gas chromatography and / or ion chromatography. (1) Reacting trifluoromethane with iodine to produce trifluoroiodomethane; When the resulting trifluoroiodomethane is contacted with an alkaline medium; (a) Carbon dioxide (CO2) is preferably 0.0010% or less (≦0.0010%), more preferably 0.0005% or less (≦0.0005%), and particularly preferably 0.0002% or less (≦0.0002%). (b) Hydrogen fluoride (HF) is preferably 0.0010% or less (≦0.0010%), more preferably 0.0005% or less (≦0.0005%), and particularly preferably 0.0002% or less (≦0.0002%). However, except for trifluoromethane (CF3H), the sum of the peak areas of trifluoroiodomethane and (a) to (b) is set to 100%. (2) When trifluoroiodomethane after contact with an alkaline medium is separated from trifluoromethane (CF3H) by distillation; (a) Carbon dioxide (CO2) is preferably 0.0005% or less (≦0.0005%), more preferably 0.0003% or less (≦0.0003%), and particularly preferably 0.0001% or less (≦0.0001%). (b) Hydrogen fluoride (HF) is preferably 0.0005% or less (≦0.0005%), more preferably 0.0003% or less (≦0.0003%), and particularly preferably 0.0001% or less (≦0.0001%). (c) Trifluoroiodomethane (CF3H) is preferably 0.08% or less (≦0.08%), more preferably 0.04% or less (≦0.04%), and particularly preferably 0.02% or less (≦0.02%). It is also preferable that the trifluoroiodomethane content is 99.7% or more. However, the sum of the peak areas of trifluoroiodomethane and (a) to (c) is set to 100%.

[0023] In the present invention, trifluoroiodomethane is produced by reacting trifluoromethane with iodine. There are other methods for producing trifluoroiodomethane, such as a method using trifluoroacetic acid as a raw material. As described above, there are various methods for producing trifluoroiodomethane, and depending on the production method and the raw materials used, compounds other than the target trifluoroiodomethane may be present in the reaction medium due to various factors such as impurities contained in the raw materials, side reactions during production, and unreacted components. Therefore, the method for removing impurities present in the trifluoroiodomethane may vary depending on the method for producing the trifluoroiodomethane and the raw materials used. Of course, it would be ideal if the impurities could be removed uniformly using the same method, but depending on the production method, impurity removal may be insufficient or excessive removal treatment equipment may be required. Therefore, in the present invention, in the method for producing trifluoroiodomethane by reacting trifluoromethane with iodine, the amount of trifluoroiodomethane generated by the raw materials used and the production recipe is reduced. (a) Carbon dioxide (CO2), (b) hydrogen fluoride (HF), and (c) Trifluoroiodomethane (CF3H) This paper proposes a prescription to remove the In particular, by using a method of reactive removal using an alkaline medium, it is possible to quantitatively remove the impurities (a) carbon dioxide (CO2) and (b) hydrogen fluoride (HF), and the main residue, trifluoroiodomethane (CF3H), can also be removed by subsequent distillation. Moreover, since most of the major impurities have been removed, there is the advantage that the burden on the distillation process is reduced.

[0024] In the present invention, the alkaline medium refers to an agent for removing impurities present in a container containing trifluoroiodomethane, and removes the major impurities (a) carbon dioxide (CO) and (b) hydrogen fluoride (HF) by reacting them with the impurities.

[0025] Specifically, alkali metal hydroxides such as potassium hydroxide (KOH), sodium hydroxide (NaOH), and lithium hydroxide (LiOH) are examples of bases, with potassium hydroxide (KOH) being preferred. These may be used alone or in combination, and may be dissolved in water to form an aqueous solution.

[0026] In the present invention, the concentration of the alkaline medium used is 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, or 50 wt%, or, for example, 5 wt% to 50 wt%, 10 wt% to 50 wt%, 15 wt% to 50 wt%, 20 wt% to 50 wt%, 25 wt% to 50 wt%, 30 wt% to 45 wt%, or 35 wt% to 40 wt%, etc., and the reaction step containing the alkali metal hydroxide within any range defined between any two of the above values ​​is preferably a concentration that can remove impurities in the reaction gas and can particularly reduce the burden on the subsequent distillation step.

[0027] Impurities can be removed from the reaction gas by passing the reaction gas containing the impurities and trifluoroiodomethane (CF3I) through a reaction vessel for contacting the reaction gas with an alkaline medium. The reaction vessel and reaction conditions used in the present invention allow for effective removal of impurities from the reaction gas without significant decomposition of trifluoroiodomethane (CF3I).

[0028] Zeolite, for example, basic zeolite, can also be used. Zeolite with a large pore volume is preferred in terms of reaction efficiency, and synthetic zeolites such as X-type and A-type zeolites, or natural zeolites can be used. Furthermore, since the zeolite is expected to be used by being filled into a reaction vessel or the like, not only powdered zeolite but also granulated zeolite containing an extender or other binder can be used. Granulated zeolite can be prepared by appropriately using known techniques. Alternatively, zeolite, synthetic polymers or other agents may be used as a carrier, which may be coated with an alkaline medium such as an alkali metal hydroxide or alkali metal, and then packed in a reaction vessel as a solid. As these alkaline media, alkali metal hydroxides, particularly potassium hydroxide (KOH), are preferably used in view of impurity removal performance, economy, ease of use, and burden on production facilities.

[0029] FIG. 1 is a schematic diagram showing a reaction vessel (1) for contacting a raw material reaction gas (11) with an alkaline medium (10) for the production of high-purity trifluoroiodomethane according to the present invention, and the flow of the reaction gas (11) and the alkaline medium (10). The reaction gas (11) is supplied from the bottom of the reaction vessel (1), and the alkaline medium (10) is supplied from the top of the reaction vessel (1). After the reaction, the treated reaction gas (11) is removed from the top of the reaction vessel (1). Although not shown, the alkaline medium (10) that has come into contact with the reaction gas (11) is discharged from the reaction vessel (1) through an outlet (not shown) provided at the bottom of the reaction vessel (1) or at an appropriate location.

[0030] 1, there are various variations depending on the type of alkaline medium used and the method of contacting the reaction gas with the alkaline medium in the reaction vessel, and these can be selected appropriately. Examples are shown below, but the present invention is not limited to these examples.

[0031] 2 shows a schematic diagram of the distillation column (2) in which the reaction gas (11) is contacted with the alkaline medium (10) in FIG. 1, and the treated reaction gas (12) is then removed from the top of the reaction vessel (1), and the treated reaction gas (12) is then distilled under pressure to produce a CF3I product (13). After distillation, the treated reaction gas (12) is removed from the top of the distillation column (2) and produced as a CF3I product (13). Although not shown, when the treated reaction gas (12) is distilled under pressure, components other than CF3I in the treated reaction gas (12) are discharged from the distillation column (2) through an outlet (not shown) provided at the bottom of the distillation column (2) or at an appropriate position. The CF3I product (13) is transferred to the next process, such as filling into a cylinder or a storage tank.

[0032] 3 is a schematic diagram of a reaction vessel (1) for contacting a raw material reaction gas (11) with an alkaline medium (10) for producing high-purity trifluoroiodomethane according to the present invention, in which the reaction gas (11) is supplied from the bottom of the reaction vessel (1) and the alkaline medium (10) is supplied from the top of the reaction vessel (1). Although not shown, the top or bottom of the reaction vessel (1) may be provided with stirring equipment such as a stirring spring (not shown) and its control mechanism (not shown), which can mix the reaction gas (11) with the alkaline medium (10) to improve contact efficiency.

[0033] 4 is a schematic diagram of a reaction vessel (1) for contacting a raw material reaction gas (11) with an alkaline medium (10) for producing high-purity trifluoroiodomethane according to the present invention. The reaction gas (11) is flowed from the bottom of the reaction vessel (1) at an angle inclined toward the reaction vessel (1), forming a spiral vortex flow within the reaction vessel (1), and the alkaline medium (10) is supplied from the top of the reaction vessel (1) in a countercurrent direction to the flow of the reaction gas (11). Although not shown, the top or bottom of the reaction vessel (1) may be provided with stirring equipment such as a stirring spring (not shown) and its control mechanism (not shown), which mixes the reaction gas (11) with the alkaline medium (10) to further improve the contact efficiency.

[0034] 5 is a schematic diagram of a reaction vessel (1) for contacting a raw material reaction gas (11) with an alkaline medium (10) for producing high-purity trifluoroiodomethane according to the present invention. The lower part of the reaction vessel (1) is provided with a packed bed (14) pre-filled with basic granular zeolite, the top of which is open. A reaction gas (11) is supplied from the bottom of the reaction vessel (1). When the reaction gas (11) is supplied, it comes into contact with the packed bed (14) filled with granular zeolite. Since the top of the packed bed (14) is open, some of the packed granular zeolite rises and diffuses upward, improving the contact efficiency.

[0035] FIG. 6 is a schematic diagram of a reaction vessel (1) for contacting a raw material reaction gas (11) with an alkaline medium (10) for producing high-purity trifluoroiodomethane according to the present invention. A mist generator (15) having fine holes is installed at the top of the reaction vessel (1). The reaction gas (11) is supplied from the bottom of the reaction vessel (1), and the alkaline medium (10) is supplied from the top of the reaction vessel (1). When the alkaline medium (10) passes through the mist generator (15), the liquid alkaline medium (10) turns into small droplets in a mist and comes into contact with the reaction gas (11). Although not shown, the alkaline medium (10) that has come into contact with the reaction gas (11) is discharged from the reaction vessel (1) through an outlet (not shown) provided below the mist generator (15) or at an appropriate position.

[0036] FIG. 7 is a schematic diagram of a Y-shaped microreactor (3) for producing high-purity trifluoroiodomethane according to the present invention, in which a raw material reaction gas (11) is brought into contact with an alkaline medium (10). The alkaline medium (10) is supplied from one side of the Y-shaped left side of the microreactor (3), and the reaction gas (11) is supplied from the other side. The two gases are brought into contact and mixed at the point where they meet. After mixing, the gas is transferred to the right side of the Y-shaped part. After transfer, the reaction gas (11) and the alkaline medium (10) are separated, and the reaction gas (11) is transferred to the next step, such as a distillation column (2). The alkaline medium (10) is discharged, but can be regenerated by removing components derived from the reaction gas (11) contained in the alkaline medium (10) and reused for contact with the reaction gas (11) as needed.

[0037] Among the major impurities mentioned above, unreacted CF3H can be effectively removed from the reaction gas by distillation. However, CF3H can also be separated from CF3I by distillation and reused as a raw material.

[0038] As the solid alkaline medium, zeolites, particularly basic zeolites, can be used. In the present invention, the removal of impurities by reacting zeolite with a reaction gas containing CF3I and small amounts of impurities such as CF3H, CO2, and HF is believed to depend not only on the reactivity with basic zeolite but also on its adsorption characteristics. For this reason, zeolites with relatively large pores are preferably used, such as synthetic zeolites of type X, type Y, and type L, or equivalent natural zeolites.

[0039] The contact time between the reaction gas and the alkaline medium can vary depending on various factors, such as the size and shape of the reaction vessel, the flow rate of the reaction gas, and the pressure during the reaction. For example, in Example 1 of this specification, the reaction gas was introduced from the bottom of a reaction vessel with an inner diameter of 105 mm and a height of 3 m (internal volume: 26.0 liters) at a gas introduction rate of 37 L / min. The residence time in this case was 42 seconds. By shortening this residence time, that is, by increasing the flow rate of the reaction gas, the efficiency of removing impurities in the reaction gas by reaction with the alkaline medium increases, but there is a possibility that the reaction may become insufficient. On the other hand, although the efficiency of reactive removal increases if there is sufficient residence time, depending on the type of alkaline medium used, for example, when a base such as sodium hydroxide (NaOH) or potassium hydroxide (KOH) is used, alcohol may be produced as an impurity due to the decomposition of CF3I.

[0040] In this way, the process of removing impurities in the reaction vessel should be designed in relation to the load on the subsequent distillation process. As mentioned above, there are various methods for contacting the reaction gas with the alkaline medium, and an efficient method can be selected depending on the settings. For example, when a solid catalyst such as basic zeolite is used, the impurities are likely to be removed by the adsorption properties of the zeolite, making the decomposition of CF3I less likely to occur. However, the efficiency of impurity removal will need to be further investigated. On the other hand, when high concentrations of sodium hydroxide (NaOH) or potassium hydroxide (KOH) are used, it is expected that the efficiency of reactive removal of CO2 and HF will increase, but care must be taken to prevent the decomposition of CF3I. As described above, there may be conditions that conflict with the removal of impurities from the reaction gas and the production efficiency of high-purity CF3I. Therefore, it is preferable to set optimal conditions while taking into consideration the effects, as seen in the examples of this specification.

[0041] When the reactant gas and alkaline medium come into contact in the reaction vessel, if the alkaline medium is a base such as aqueous sodium hydroxide, a gas-liquid reaction occurs between the gaseous reactant gas and the liquid alkaline medium. In this case, the reaction occurs at the gas-liquid interface, or in the liquid if the reactant gas is dissolved in the liquid alkaline medium. Therefore, assuming the reaction is more efficient, By breaking the liquid into small droplets and increasing the surface area per unit volume, the opportunity for contact with the reactant gas can be increased. For example, a mist generator can be used to atomize the liquid, or the liquid can be passed through a solid object with tiny pores to create a microfluidic solution, or the liquid can be pressurized and sprayed onto a solid object with tiny cavities. In order to increase the density of CF3I in the reaction gas, the reaction vessel is pressurized to increase the gas density. - To increase the contact efficiency of the reactant gas, the gas movement is accelerated. To achieve this, it is advisable to increase the reaction temperature. However, increasing the reaction temperature may accelerate the decomposition of CF3I, and high temperature control is required to control the temperature of the reaction vessel, which increases the equipment cost. - To increase the contact efficiency of the reactant gas, the gas movement is accelerated. To achieve this, the reactant gas supply rate to the reaction vessel is increased. In this case, equipment to increase the supply rate is required, which increases the equipment cost. It is advisable to design the equipment with the above points in mind and install appropriate facilities.

[0042] When the reactant gas and alkaline medium come into contact in the reaction vessel, if the alkaline medium is a solid such as basic zeolite, a gas-solid reaction occurs between the gaseous reactant gas and the solid basic zeolite. In this case, the reaction occurs at the interface between the gas and the solid, or when the reactant gas penetrates into the pores of the solid basic zeolite. Therefore, assuming the reaction is more efficient, To reduce the size of solids, it is advisable to powder them or to pulverize granular materials to make them finer. However, care must be taken when filling small powders into equipment, as they may become pressurized or the density may increase, causing problems. When the particle size is small, such as in powders, increasing the surface area per unit volume increases the chance of contact with the reaction gas. In order to increase the density of CF3I in the reaction gas, the reaction vessel is pressurized to increase the gas density. In this case, it is necessary to set conditions so that the liquid zeolite is packed densely and is not crushed by the pressure. - To increase the contact efficiency of the reactant gas, the gas movement is accelerated. To achieve this, it is advisable to increase the reaction temperature. However, increasing the reaction temperature may accelerate the decomposition of CF3I, and high temperature control is required to control the temperature of the reaction vessel, which increases the equipment cost. - To increase the contact efficiency of the reactant gas, the gas movement is accelerated. To achieve this, the reactant gas supply rate to the reaction vessel is increased. In this case, equipment to increase the supply rate is required, which increases the equipment cost. It is advisable to design the equipment with the above points in mind and install appropriate facilities.

[0043] When the reaction gas and alkaline medium come into contact with each other in the reaction vessel, the reaction temperature is 15°C, 20°C, 25°C, 30°C, 40°C, or 50°C, or a temperature in any range defined between any two of the above temperatures, such as 15°C to 50°C, 20°C to 50°C, 25°C to 40°C, or 20°C to 40°C. Preferably, the reaction temperature is 20°C to 40°C.

[0044] The method for producing high-purity trifluoroiodomethane of the present invention comprises a step of contacting trifluoroiodomethane containing impurities with an alkaline medium to remove them by reaction, and a step of purifying the obtained trifluoroiodomethane by pressure distillation.

[0045] Impurities such as CF3H contained in the reaction gas can be removed by a distillation step following the reaction step. In particular, pressure distillation is preferably carried out to remove impurities with a boiling point lower than that of the target product, CF3I. The distillation step may include not only a first distillation but also a second distillation, if necessary. The first distillation can remove impurities having a boiling point lower than that of CF3I from the treated reaction gas after the reaction step. Such low boiling point impurities can include, for example, CF3H, CO2, CF4, CO, etc. The second distillation can remove impurities from the reaction gas that have a boiling point higher than that of CF3I, such as HF.

[0046] The distillation of the reaction gas in the distillation step following the reaction step can be carried out either as a continuous process or a batch process. A single distillation may be more suitable for a batch process, while a distillation process comprising a first distillation and a second distillation may be more suitable for a continuous process.

[0047] Of course, the first distillation and the second distillation can be carried out in a single distillation column, but impurities with higher and lower boiling points than the boiling point of the target product, CF3I, may be present, requiring more precise distillation operations.

[0048] <Trifluoroiodomethane composition>

[0049] The trifluoroiodomethane composition of the present invention is characterized in that the content ratios of the major impurities that may be contained in trifluoroiodomethane, namely (a) carbon dioxide (CO), (b) hydrogen fluoride (HF), and (c) trifluoromethane (CFH), based on peak areas determined by gas chromatography and / or ion chromatography, are (a) ≦0.0005%, (b) ≦0.0005%, and (c) ≦0.08%, respectively, and that trifluoroiodomethane accounts for 99.7% or more (with the proviso that the sum of the peak areas of trifluoroiodomethane and (a) to (c) is 100%).

[0050] By the above-described method for producing high-purity trifluoroiodomethane, a composition containing trifluoroiodomethane can be obtained. The trifluoroiodomethane composition preferably has the following specifications based on peak areas determined by gas chromatography and / or ion chromatography: (a) Carbon dioxide (CO2) is preferably 0.0005% or less (≦0.0005%), more preferably 0.0003% or less (≦0.0003%), and particularly preferably 0.0001% or less (≦0.0001%). (b) Hydrogen fluoride (HF) is preferably 0.0005% or less (≦0.0005%), more preferably 0.0003% or less (≦0.0003%), and particularly preferably 0.0001% or less (≦0.0001%). (c) Trifluoroiodomethane (CF3H) is preferably 0.08% or less (≦0.08%), more preferably 0.04% or less (≦0.04%), and particularly preferably 0.02% or less (≦0.02%). It is preferable that the trifluoroiodomethane content is 99.7% or more. However, the sum of the peak areas of trifluoroiodomethane and the above (a) to (c) is set to 100%. [Example]

[0051] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0052] The conditions of the apparatus used for the analysis were as follows: <Materials used> The materials used to carry out this example are as follows: Helium gas Dry air carbon dioxide Sodium hydroxide (NaOH) Potassium hydroxide (KOH) Zeolite (X-type zeolite)

[0053] <Analysis by gas chromatography (GC)> A sample was injected, and the GC purity (based on area %) was calculated based on the peaks in the analysis chart. <Analysis by ion chromatography (IC)> A sample was injected and the fluorine content in the reaction gas was analyzed.

[0054] Synthesis Example 1 A 105mm diameter Hastelloy C vertical reactor equipped with a stirring blade and thermometer was filled with 1 kg of alkali metal-supported solid catalyst. The temperature of the catalyst layer in the reactor was then raised to 440°C while the stirring blade was rotating. A mixed gas of CHF3 = 6.1 kg / hr and I2 = 11 kg / hr was supplied from the top of the reactor to react, and the reaction gas was continuously withdrawn from the bottom of the reactor. The linear velocity was 84 cm / min. Iodine was prepared by bubbling trifluoromethane (CF3H) into liquid iodine to generate a mixed gas of CF3H and iodine (I2), which was then supplied to the reaction system.

[0055] After the reaction, the reaction gas was cooled through a cooler and separated into gas and solid. The gas was washed with water and analyzed by gas chromatography and ion chromatography. Analysis of the reaction gas 10 hours after the start of the reaction revealed that the proportions of the gas excluding CHF were CF3I = 75.8 wt% (wt%), CF4 = 11.5 wt%, CO2 = 12.5 wt%, and HF = 0.2 wt%. The analysis results are also shown in Table 1.

[0056] Example 1 The reaction gas obtained in Synthesis Example 1 was introduced into a reaction vessel having an inner diameter of 105 mm and a height of 3 m (internal volume: 26.0 L) from the bottom of the column. The gas introduction rate was 37 L / min. The residence time in this case was 42 seconds. On the other hand, a 10 wt % (wt %) aqueous solution of sodium hydroxide was introduced from the top of the tower at a rate of 0.18 kg / min, and after sufficient gas-liquid contact had occurred inside the tower, the washed gas was extracted from the top of the tower and analyzed by gas chromatography and ion chromatography.

[0057] Analysis of the resulting reaction gas revealed that the proportions of the gas excluding CF3H were CF3I = 84.6 wt%, CO2 = 0.0007 wt%, and HF = 0.0007 wt%. The results are also shown in Table 1. Of the remainder, CF4 = 12.7 wt%, and CO = 2.7 wt%. The resulting gas was further purified by pressure distillation to obtain the trifluoroiodomethane product. Analysis of the product by gas chromatography and ion chromatography revealed that the product's composition was 99.7 wt% CF3I, 0.08 wt% CF3H, 0.0004 wt% CO2, and 0.0004 wt% HF. The composition of the resulting CF3I product is also shown in Table 2.

[0058] Example 2 An experiment was carried out in the same manner as in Example 1, except that the 10% aqueous sodium hydroxide solution in Example 1 was replaced with a 5% aqueous potassium hydroxide solution. Analysis of the resulting reaction gas revealed that the proportions of the gas excluding CF3H were CF3I = 84.6 wt%, CO2 = 0.0005 wt%, and HF = 0.0005 wt%. The results are also shown in Table 1. Of the remainder, CF4 = 12.7 wt%, and CO = 2.7 wt%. Furthermore, the obtained product was analyzed by gas chromatography and ion chromatography, and the composition of the product was found to be CF3I = 99.7 wt%, CF3H = 0.08 wt%, CO2 = 0.0003 wt%, and HF = 0.0003 wt%. The composition of the obtained product, CF3I, is also shown in Table 2.

[0059] Example 3 An experiment was carried out in the same manner as in Example 1, except that the 10% aqueous solution of sodium hydroxide in Example 1 was replaced with a 10% aqueous solution of potassium hydroxide. Analysis of the resulting reaction gas revealed that the proportions of the gas excluding CF3H were CF3I = 84.6 wt%, CO2 = 0.00025 wt%, and HF = 0.00025 wt%. The results are also shown in Table 1. Of the remainder, CF4 = 12.7 wt%, and CO = 2.7 wt%. Furthermore, the resulting product was analyzed by gas chromatography and ion chromatography, and the product composition was found to be CF3I = 99.7 wt%, CF3H = 0.08 wt%, CO2 = less than 0.0001 wt% (<0.0001 wt%), and HF = less than 0.0001 wt% (<0.0001 wt%). The composition of the resulting product, CF3I, is also shown in Table 2.

[0060] Example 4 An experiment was carried out in the same manner as in Example 1, except that the 10% aqueous sodium hydroxide solution in Example 1 was replaced with a 30% aqueous potassium hydroxide solution. Analysis of the resulting reaction gas revealed that the proportions of the gas excluding CF3H were CF3I = 84.6 wt%, CO2 = 0.00025 wt%, and HF = 0.00025 wt%. The results are also shown in Table 1. Of the remainder, CF4 = 12.7 wt%, and CO = 2.7 wt%. Furthermore, the resulting product was analyzed by gas chromatography and ion chromatography, and the product composition was found to be CF3I = 99.7 wt%, CF3H = 0.08 wt%, CO2 = less than 0.0001 wt% (<0.0001 wt%), and HF = less than 0.0001 wt% (<0.0001 wt%). The composition of the resulting product, CF3I, is also shown in Table 2.

[0061] Example 5 The 10% aqueous sodium hydroxide solution used in Example 1 was replaced with basic zeolite (granular X-type zeolite, average particle size 100 μm, manufactured by Tosoh Corporation), which was previously packed into the tower in a volume equivalent to 1 / 10 of the internal volume. The reaction gas was introduced into the tower from the bottom at a gas introduction rate of 37 L / min. The reaction gas was brought into contact with the basic zeolite previously packed into the tower, and the reaction gas was stirred by bringing the two into contact so that the reaction gas would spray up the zeolite. The gas was then extracted from the top of the tower and analyzed by gas chromatography and ion chromatography.

[0062] Analysis of the resulting reaction gas revealed that the proportions of the gas excluding CF3H were CF3I = 84.6 wt%, CO2 = 0.0010 wt%, and HF = 0.0010 wt%. The results are also shown in Table 1. Of the remainder, CF4 = 12.7 wt%, and CO = 2.7 wt%. Furthermore, the obtained product was analyzed by gas chromatography and ion chromatography, and the composition of the product was found to be CF3I = 99.7 wt%, CF3H = 0.08 wt%, CO2 = 0.0005 wt%, and HF = 0.0005 wt%. The composition of the obtained product, CF3I, is also shown in Table 2.

[0063] Comparative Example 1 The 10 wt % aqueous sodium hydroxide solution used in Example 1 was not used. Therefore, the reaction gas was introduced from the bottom of the tower at a gas introduction rate of 37 L / min. After stirring the reaction gas introduced inside the tower, the gas was extracted from the top of the tower and analyzed by gas chromatography and ion chromatography. Analysis of the resulting reaction gas revealed that the proportions of the gas excluding CF3H were CF3I = 65.5 wt%, CO2 = 10.7 wt%, and HF = 11.8 wt%. The results are also shown in Table 1. Of the remainder, CF4 = 9.9 wt%, and CO = 2.1 wt%. Furthermore, the reaction gas obtained was analyzed by gas chromatography and ion chromatography, and the composition of the reaction gas was found to be CF3I = 89.7 wt%, CF3H = 0.08 wt%, CO2 = 9.4 wt%, and HF = 0.6 wt%. The composition of the obtained CF3I product is also shown in Table 2.

[0064] Comparative Example 2 An experiment was carried out in the same manner as in Example 1, except that the 10 wt % aqueous sodium hydroxide solution in Example 1 was replaced with a 2 wt % aqueous sodium hydroxide solution. Analysis of the resulting reaction gas revealed that the proportions of the gas excluding CF3H were CF3I = 84.6 wt%, CO2 = 0.0050 wt%, and HF = 0.0025 wt%. The results are also shown in Table 1. Of the remainder, CF4 = 12.7 wt%, and CO = 2.7 wt%. Furthermore, the obtained CF3I product was analyzed by gas chromatography and ion chromatography, and the composition of the CF3I product was found to be CF3I = 99.7 wt%, CF3H = 0.08 wt%, CO2 = 0.0010 wt%, and HF = 0.0010 wt%. The composition of the obtained CF3I product is also shown in Table 2.

[0065] Comparative Example 3 An experiment was carried out in the same manner as in Example 1, except that the 10 wt % aqueous sodium hydroxide solution in Example 1 was replaced with a 2 wt % aqueous potassium hydroxide solution. Analysis of the resulting reaction gas revealed that the proportions of the gas excluding CF3H were CF3I = 93.2 wt%, CO2 = 0.002 wt%, and HF = less than 0.0001 wt% (<0.0001 wt%). The results are also shown in Table 1. Of the remainder, CF4 = 12.7 wt%, and CO = 2.7 wt%. Furthermore, the obtained CF3I product was analyzed by gas chromatography and ion chromatography, and the composition of the CF3I product was found to be CF3I = 99.7 wt%, CF3H = 0.08 wt%, CO2 = 0.0008 wt%, and HF = 0.0005 wt%. The composition of the obtained product is also shown in Table 2.

[0066] [Table 1]

[0067] [Table 2]

[0068] The results shown in Tables 1 and 2 reveal the following. 1) From the results of Examples 1 to 4, by contacting an alkaline medium with a reaction gas containing CF3I, the carbon dioxide (CO2) and hydrogen fluoride (HF) contained in the reaction gas were reduced to 0.0005 wt% or less, and impurities that react with the alkaline medium were removed. This reduced the burden on the subsequent distillation process. 2) From the results of Example 5, it was found that by contacting the alkaline medium in the form of a solid substance called zeolite with the reaction gas containing CF3I, the impurities contained in the reaction gas were both reduced to 0.0010 wt%, reducing the burden on the subsequent distillation process. It is presumed that the impurities in CF3I could be removed by using zeolite because these impurities were adsorbed onto the zeolite. 3) Furthermore, according to the results shown in Table 2, carbon dioxide (CO2) and hydrogen fluoride (HF) were almost completely removed in all of Examples 1 to 5, and tetrafluoromethane (CF4) and carbon monoxide (CO) were also removed to approximately 0.1 wt%. This shows that these impurities were removed by reaction in an alkaline medium, and that other impurities were also separated by distillation. 4) From the results of Comparative Example 1, it can be seen that without using an alkaline medium, the reaction gas containing CF3I is transferred essentially as is to the distillation step, which results in a heavy burden on the distillation step and makes it impossible to sufficiently reduce impurities. 5) The results of Comparative Examples 2 and 3 show that the concentrations of the alkaline medium are insufficient compared to the 10 wt% NaOH in Example 1, the 5 wt% KOH in Example 2, and the 10 wt% KOH in Example 3. This shows that, particularly when producing CF3I, it is important to remove carbon dioxide (CO2) and hydrogen fluoride (HF) as much as possible to further increase the purity of CF3I. 6) When the product CF3I contains carbon dioxide (CO2), iodine (I) released from CF3I can react with metals and accelerate corrosion, and hydrogen fluoride (HF) itself can corrode metals, so its removal is important. In either case, it is important to remove as many impurities from the CF3I as possible before distillation to avoid putting a strain on plant equipment, especially the distillation equipment used to produce high-purity CF3I. [Industrial Applicability]

[0069] INDUSTRIAL APPLICABILITY The present invention provides a method for producing high-purity trifluoroiodomethane and a composition containing trifluoroiodomethane, which are useful for industrial applications. [Explanation of symbols]

[0070] 1. Alkaline medium treatment tank 2. Distillation tower 3. Reaction gas reservoir 10 Alkaline medium 11 Reactive gas 12. Reaction gas after treatment 13 CF3I Products

Claims

1. reacting trifluoromethane with iodine to produce trifluoroiodomethane; The resulting trifluoroiodomethane is contacted with an alkaline medium to The main impurities that may be contained in the trifluoroiodomethane are: (a) carbon dioxide (CO ２ ), and (b) hydrogen fluoride (HF), the peak area-based content ratios determined by gas chromatography and / or ion chromatography are (a) ≦0.0010% and (b) ≦0.0010%, respectively, and trifluoroiodomethane is 99.7% or more (provided that trifluoromethane (CF ３ (H) except for the sum of the peak areas of trifluoroiodomethane and (a) to (b) is 100%), A method for producing high-purity trifluoroiodomethane.

2. reacting trifluoromethane with iodine to produce trifluoroiodomethane; contacting the obtained trifluoroiodomethane with an alkaline medium; After contact with the alkaline medium, trifluoroiodomethane is distilled to give trifluoromethane (CF ３ H) and separating the A method for producing high-purity trifluoroiodomethane, comprising: The major impurities that may be contained in the high-purity trifluoroiodomethane are: (a) carbon dioxide (CO ２ ) and (b) hydrogen fluoride (HF), and (c) trifluoromethane (CF ３ H) are each contained in a ratio based on the peak area as determined by gas chromatography and / or ion chromatography of (a)≦0.0005%, (b)≦0.0005%, and (c)≦0.08%, respectively, and trifluoroiodomethane is contained in an amount of 99.7% or more (provided that the sum of the peak areas of trifluoroiodomethane and (a) to (c) is 100%), A method for producing high-purity trifluoroiodomethane.

3. 3. The method according to claim 1, wherein the alkaline medium is an aqueous potassium hydroxide solution.

4. The method according to claim 3, wherein the concentration of the aqueous potassium hydroxide solution is 5% by weight to 50% by weight.

5. The main impurities that can be contained in trifluoroiodomethane are (a) carbon dioxide (CO ２ ) and (b) hydrogen fluoride (HF), and (c) trifluoromethane (CF ３ The trifluoroiodomethane composition according to claim 1, wherein the content ratios of the trifluoroiodomethane compounds (A) and (B) based on the peak areas determined by gas chromatography and / or ion chromatography are (a) ≦0.0.0005%, (b) ≦0.0.0005%, and (c) ≦0.08%, respectively, and the content of trifluoroiodomethane is 99.7% or more (provided that the sum of the peak areas of trifluoroiodomethane and (a) to (c) is 100%).

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