Production method for phosphorus trifluoride

Abstract

The purpose of the present invention is to provide a production method for phosphorus trifluoride in which the reaction can be carried out using readily available materials at a temperature equal to or lower than atmospheric temperature, said method being suitable for use on an industrial scale.　The production method for phosphorus trifluoride involves reacting phosphorus trichloride with a complex of an organic base and hydrogen fluoride.

Description

Method for producing phosphorus trifluoride

[0001] The present invention relates to a method for producing phosphorus trifluoride.

[0002] Phosphorus trifluoride (PF ３ ) is a transition metal ligand, LIB electrolyte LiPF ６ It is used as a raw material for semiconductor etching gases, etc. Phosphorus trifluoride can be produced by phosphorus trichloride (PCl ３ ) to trialkyltin fluoride (R ３ a method of reacting with a fluorinating agent such as SnF (Non-Patent Document 1), a method of reacting with phosphorus trichloride (PCl ３ ) together with hydrogen fluoride (HF) in an activated carbon packed column (Patent Document 1), ３ ) and antimony fluoride (SbF ３ ), a method of reacting phosphorus trichloride (PCl) (Non-Patent Documents 2 and 3), ３ and a method of reacting a fluoride compound (e.g., NaF or KF-HF) with an alkali metal fluoride (e.g., NaF, KF-HF) (Non-Patent Documents 4 and 5).

[0003] International Publication No. 2023 / 168597

[0004] Z. Naturforsch. 49b, 981-982 (1994)Inorganic Syntheses,26,12-17,1989Inorganic Syntheses,26,310-15,1990Indian Journal of Chemistry, Section A : Inorganic, Physical, Theoretical & Analytical 20A, 1, 83-84, 1981Indian Journal of Chemistry, Section A: Inorganic, Physical, Theoretical & Analytical 23A, 12, 990-991, 1984

[0005] However, PCl ３The reaction between fluorination and HF has low reactivity, requires heating at 100°C or higher and an excess amount of hydrogen fluoride, and requires a lot of time and effort to maintain the equipment and recover the raw materials. ３ Although the fluorination of phosphorus trifluoride (SnF) has been reported in Non-Patent Document 1, the fluorinating agent is expensive and its use on an industrial scale is difficult. Therefore, an object of the present invention is to provide a method for producing phosphorus trifluoride that is suitable for industrial scale operation and that can carry out the reaction at a low temperature below room temperature using readily available materials.

[0006] The present invention provides the following inventions. [1] A method for producing phosphorus trifluoride, comprising reacting phosphorus trichloride with an organic base-hydrogen fluoride complex. [2] The method according to [1], wherein the organic base is at least one selected from the group consisting of pyridine, pyrimidine, tertiary alkylamine, and strong organic base. [3] The method according to [1] or [2], wherein the reaction is carried out at a temperature of 25°C to -40°C. [4] The method according to [1] or [2], wherein the organic base is in excess relative to the hydrogen chloride produced, and the hydrogen chloride produced forms a complex with the organic base and remains in the reactor. [5] The method according to [4], wherein all of the hydrogen chloride produced forms a complex with the organic base, the hydrogen chloride remains in the reactor as a complex, and no hydrogen chloride is contained in the product gas. In particular, when all of the hydrogen chloride produced forms a complex with the excess organic base in a 1:1 molar ratio, all of the hydrogen chloride remains in the reactor as a complex, and no hydrogen chloride is mixed into the product gas.

[0007] By using an organic base complex of hydrogen fluoride as the fluorinating agent, the reaction proceeds instantly at room temperature, and phosphorus trifluoride can be obtained in high yield using an almost stoichiometric amount of hydrogen fluoride. More specifically, the present invention provides the following effects: (1) The PCl of the present invention ３ According to the reaction of hydrogen fluoride-organic base complex with PF, a nearly stoichiometric amount of hydrogen fluoride can be produced at temperatures below room temperature. ３can be obtained. Because the reaction can proceed at room temperature, in a short time, and with a theoretical amount of hydrogen fluoride, the method of the present invention can be carried out with simpler production equipment and is excellent in productivity. (2) The higher the degree of association of hydrogen fluoride with the organic base (the number n in nHF in the above reaction formula), the more effectively by-products can be suppressed, and therefore phosphorus trifluoride can be produced in high yield. In particular, when pyridine-8HF is used as the organic base-hydrogen fluoride complex, HF is in large excess relative to the pyridine base, but the raw material PCl ３ By adding an equivalent amount of pyridine-8HF so that almost all of the HF reacts with the product PF, no unreacted HF remains, and the remaining pyridine forms a complex with the by-product HCl in a 1:1 ratio. The by-product HCl that did not form a complex is converted into the product PF. ３ It is discharged out of the system together with PCl. ３ When an equivalent amount of pyridine-8HF is charged so that HF ​​is in excess relative to the amount of HF, the remaining HF remains as a complex with pyridine, and HCl cannot form a complex with pyridine and escapes to the outside of the system as PF ３ and is discharged together with the organic base. (3) In a specific embodiment, HCl produced as a result of the reaction forms a complex with the organic base and remains in the reaction system as a salt. When the number of moles of the organic base is equal to or greater than the number of moles of hydrogen chloride produced, the organic base is supplied in excess of the hydrogen chloride produced, so that hydrochloride is preferentially produced after the reaction. In this case, phosphorus trifluoride is the main gas species produced, and hydrogen chloride remains in the reactor as a salt and is recovered. Therefore, phosphorus trifluoride can be easily purified without having to consider separation of phosphorus trifluoride and hydrogen chloride in the gas state, and the obtained phosphorus trifluoride is highly pure. (4) A complex in which the number of equivalents of an organic base and HF is approximately the same becomes a solid, so the reaction system becomes a slurry, making stirring difficult. However, it has been found that this problem can be solved by adding an organic solvent, which disperses the complex of the organic base and HF in the organic solvent and allows the fluorination reaction to proceed smoothly.

[0008] [Action] Phosphorus trichloride, the raw material, has an unshared electron pair and is therefore not expected to react easily with nucleophilic species. In fact, prior art techniques using hydrogen fluoride are generally carried out under heated conditions. On the other hand, selecting a fluorinating agent with stronger nucleophilicity increases costs and makes handling difficult. Therefore, the present inventors focused on the leaving group side of phosphorus trichloride and used an environment in which hydrogen chloride is easily eliminated, i.e., an organic base complex of hydrogen fluoride to which an organic base has been added, as the fluorinating agent. As a result, the reaction proceeded at room temperature in a short time and phosphorus trifluoride was successfully obtained in high yield. As will be seen from the comparative examples described below, simply stirring and mixing phosphorus trichloride and hydrogen fluoride at temperatures below room temperature results in separation of the mixture into two layers, making it impossible to efficiently fluorinate phosphorus trichloride to phosphorus trifluoride.

[0009] [Raw Material] In the present invention, phosphorus trichloride (PCl) is used as the raw material. ３ ) is used. ３ is the cheapest and most readily available trivalent phosphorus source, is liquid at room temperature, and is easier to handle than elemental phosphorus.

[0010] [Organic Base] The organic base is a base containing a proton (H ＋ )-accepting nitrogen-containing compounds can be used, and examples of compounds that provide a good yield of the target product, phosphorus trifluoride, include pyridine, pyrimidine, tertiary alkylamines, and strong organic bases. Examples of tertiary alkylamines include amines formed by bonding three alkyl groups having 1 to 4 carbon atoms to a nitrogen atom, and more specific examples include trimethylamine, methyldiethylamine, dimethylethylamine, triethylamine, tri-n-propylamine, triisopropylamine, and tributylamine. Examples of strong organic bases include diazabicycloundecene (1,8-diazabicyclo[5.4.0]undec-7-ene), DBN (1,5-diazabicyclo[4.3.0]non-5-ene), and MTBD (7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene).

[0011] [Organic Base-Hydrogen Fluoride Complex] The organic base-hydrogen fluoride complex used in the present invention can be easily prepared by mixing an organic base with hydrogen fluoride. The degree of association of hydrogen fluoride with the organic base in the complex can be adjusted by the mixing ratio of the two. Examples of organic base-hydrogen fluoride complexes include pyridine-8HF obtained by mixing pyridine and hydrogen fluoride in a molar ratio of 1:8, triethylamine (Et ３ N) and hydrogen fluoride in a molar ratio of 1:3 to obtain Et ３ N-3HF, triethylamine (Et ３ N) and hydrogen fluoride in a molar ratio of 1:0.8 to obtain a solid Et ３ N-0.8HF, and diazabicycloundecene-3HF obtained by mixing diazabicycloundecene and hydrogen fluoride in a molar ratio of 1:3.

[0012] When the organic base-hydrogen fluoride complex is a solid, it is desirable to add an organic solvent to the reaction system to disperse the organic base-hydrogen fluoride complex in the organic solvent, thereby smoothly carrying out the reaction. Such organic solvents are preferably aprotic organic solvents, and specific examples include carbonate compounds such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), etc.; ester compounds such as ethyl acetate, butyl acetate, etc.; ether compounds such as tetrahydrofuran (THF), diethyl ether, etc.; nitrile compounds such as acetonitrile, N-methylpyrrolidone, N,N'-dimethylpropylene urea, dimethyl sulfoxide, dimethylformamide, etc. It is believed that the organic base-hydrogen fluoride complex is insoluble in organic solvents. For this reason, the purpose (amount) of the organic solvent is to make the reaction solution a suspension state, making it easier to stir, and to reduce the amount of PF generated. ３ Prevents gas from being trapped in the voids of the solid, making it difficult to separate from the reaction liquid, and reduces the amount of PF generated. ３The purpose of this method is to facilitate the transfer of gas to the gas phase by stirring the suspension. The amount of organic solvent used for this purpose is usually about 1 to 10 times by volume relative to the amount of the organic base-hydrogen fluoride complex. It has been found that a higher degree of association of hydrogen fluoride with the organic base can suppress by-products and result in a higher yield. Therefore, it is preferable to use an organic base that can form a complex with a high degree of association of hydrogen fluoride.

[0013] [Reaction Conditions] The reaction of the present invention can be carried out under atmospheric pressure at a temperature equal to or lower than room temperature. Because the phosphorus trifluoride and hydrogen chloride produced are gases under the reaction conditions, the reaction temperature is preferably around 0°C, for example, 25°C to -40°C, preferably 20°C to -20°C, more preferably 10°C to -10°C, more preferably 5°C to -5°C, and more preferably 5°C to 0°C. It is desirable that the reaction liquid be a homogeneous solution in terms of evaporation of the reaction product gas and recovery by cooling. When the reaction liquid contains a solid and is in a slurry state, it is desirable to add an organic solvent to maintain a homogeneous solution.

[0014] [Recovery of Reaction Product] In the present invention, phosphorus trifluoride and hydrogen chloride are generated as gases. These gases are then passed through a condenser installed in the reactor and liquefied in a collection vessel downstream of the condenser, where they are recovered as a mixture of phosphorus trifluoride and hydrogen chloride. The recovered mixture of phosphorus trifluoride and hydrogen chloride can be purified by precision distillation due to the difference in boiling points. The generated hydrogen chloride reacts with an organic base in the reaction system to form a complex. The generated organic base-hydrogen chloride complex remains in the reaction system as a solid, so the mixture ratio of phosphorus trifluoride and hydrogen chloride recovered as a gas outside the reaction system is affected by the degree of association of hydrogen fluoride in the organic base-hydrogen fluoride complex used in the reaction. When an excess amount of organic base is present in the reaction system relative to hydrogen chloride, all of the generated hydrogen chloride forms a complex with the organic base and remains in the reaction solution, and the reaction product gas is recovered as high-purity phosphorus trifluoride that does not contain hydrogen chloride. The reason why the generated hydrogen chloride remains in the reaction system is related not only to the relationship between the number of moles of organic base and the number of moles of hydrogen chloride, but also to the number of moles of hydrogen fluoride (HF). When the number of moles of organic base is equal to or greater than (the total number of moles of hydrogen chloride generated and the number of moles of unreacted hydrogen fluoride), the generated hydrogen chloride reacts with the organic base and remains in the reaction system. Here, (the total number of moles of hydrogen chloride generated and the number of moles of unreacted hydrogen fluoride) = the number of moles of hydrogen fluoride in the raw organic base-hydrogen fluoride complex. Therefore, when the number of moles of organic base in the raw organic base-hydrogen fluoride complex is equal to or greater than the number of moles of HF, the by-product HCl forms a complex with the organic base at a molar ratio of 1:1 and remains in the reaction system as a solid. For example, as described in Example 3 below, solid Et ３ 40.6 g of N-0.8HF (HF content 0.28 mol) was added to PCl ３ When reacted with 12.5 g (0.09 mol) of PCl ３ All of the reactants react to produce 0.27 mol of HCl, but the organic base Et ３ Since 0.35 mol (= 0.28 / 0.8) of N is present in excess, all of the HCl is ３ It remains in the reaction system as an N-HCl complex.

[0015] The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to these examples. In the following description, the following abbreviations may be used: PFA: perfluoroalkoxyalkane Et ３ N: Triethylamine DMC: Dimethyl carbonate

[0016] Example 1 A 100 ml PFA reactor, the air of which had been thoroughly purged with dry nitrogen in advance, was equipped with a thermometer, a −5° C. chiller circulation condenser, and an inlet tube, and 33.1 g of pyridine-8HF (HF content: 1.11 mol) was charged as an organic base hydrogen fluoride complex and cooled to 5° C. in an ice bath. While stirring the pyridine-8HF in the reactor, PC1 ３　 50.0 g (0.36 mol) of the reaction mixture was added dropwise from the introduction tube over 1 hour. Simultaneously with the addition, the generation of gas was visually confirmed. After the addition was completed, the ice bath was removed, and the reaction mixture was stirred and aged for 1 hour while the temperature was returned to room temperature. 49.3 g of the generated gas was collected in a SUS cylinder cooled with pentane / liquid nitrogen via a trap cooled to around -100°C. The composition of the collected gas was determined from the area % of GC analysis to be PF ３ NMR analysis of the reaction mixture showed that PF ３ , PCl ３ The collected gas was subjected to a general distillation process to obtain a product with a purity of 98% or more, containing PF ３ (27.8 g / 31.68 g (theoretical yield) × 100 = 88%). In this example, the number of moles of hydrogen chloride produced (1.08 mol) is in excess of the number of moles of organic base used (0.14 mol), so hydrogen chloride is contaminated in the product gas.

[0017] Example 2 A 250 ml PFA reactor, which had been thoroughly purged with dry nitrogen in advance, was equipped with a thermometer, a −5° C. chiller circulation condenser, and an inlet tube, and Et ３ 59.6 g of N-3HF (HF content: 1.11 mol) was charged and cooled to 5° C. in an ice bath. ３ While stirring N-3HF, PCl ３50.0 g (0.36 mol) of the mixture was added dropwise from the introduction tube over 1 hour. At the same time as the addition, the generation of gas was visually confirmed, and FT-IR analysis showed that the generated gas was PF ３ and hydrogen chloride. After the dropwise addition was completed, the ice bath was removed, and the reaction solution was stirred and aged for 1 hour while the temperature of the reaction solution was returned to room temperature. 40.0 g of the generated gas was collected in a SUS cylinder cooled with pentane / liquid nitrogen via a trap cooled to around -100°C. The composition of the collected gas was determined from the area % of GC analysis to be PF ３ The reaction mixture was a viscous liquid with some solids present. ３ is dissolved at 1%, and a small amount of by-products is confirmed. ３ Furthermore, ion chromatography showed that HCl was not detected in the Et ３ Approximately the same equivalent amount as N was detected. In this example, the number of moles of hydrogen chloride produced (1.08 mol) was in excess of the number of moles of organic base used (0.37 mol), so hydrogen chloride was mixed into the product gas.

[0018] (Example 3) A 250 ml PFA reactor, which had been thoroughly purged with dry nitrogen in advance, was equipped with a thermometer, a −5° C. chiller circulation condenser, and an inlet tube, and 100 ml of DMC and solid Et ３ 40.6 g of N-0.8HF (HF content: 0.28 mol) was charged and cooled to 5° C. in an ice bath. While stirring the slurry in the reactor, PC1 ３ 12.5 g (0.09 mol) of the mixture was added dropwise from the introduction tube over 1 hour. At the same time as the addition, the generation of gas was visually confirmed, and FT-IR analysis showed that the generated gas was PF ３ After the dropwise addition, the ice bath was removed, and the reaction solution was stirred and aged for 1 hour while the temperature of the reaction solution was returned to room temperature. 4.0 g of the generated gas was collected in a SUS cylinder cooled with pentane / liquid nitrogen via a trap cooled to around -100°C. The composition of the collected gas was determined from the area % of GC analysis to be PF ３ NMR analysis of the reaction solution revealed that PF ３ The same by-products as in Example 2 were confirmed, and the raw material PCl ３Furthermore, ion chromatography detected almost the theoretical amount of HCl, and Et ３ It was suggested that a salt was formed with N. In this example, the number of moles of hydrogen chloride produced (0.27 mol) was too small compared to the number of moles of organic base used (0.35 mol), so hydrogen chloride formed a complex with the organic base and remained in the reactor as a solid. Therefore, hydrogen chloride was not contained in the product gas.

[0019] Example 4 A 100 ml PFA reactor, the air of which had been thoroughly purged with dry nitrogen in advance, was equipped with a thermometer, a −5° C. chiller circulation condenser, and an inlet tube, and 39.0 g (HF content: 0.55 mol) of diazabicycloundecene-3HF was charged as an organic base hydrogen fluoride complex and cooled to 5° C. in an ice bath. While stirring the diazabicycloundecene-3HF in the reactor, PC1 ３ 25.0 g (0.18 mol) of the mixture was added dropwise from the introduction tube over 1 hour. Simultaneously with the addition, the generation of gas was visually confirmed. After the addition was completed, the ice bath was removed and the mixture was stirred and aged for 1 hour while returning to room temperature. 13.9 g of the generated gas was collected in a SUS cylinder cooled with pentane / liquid nitrogen via a trap cooled to around -100°C. The composition of the collected gas was determined from the area % of GC analysis to be PF ３ NMR analysis of the reaction mixture revealed that PF ３ The same by-products as in Example 2 were confirmed. ３ In this example, the number of moles of hydrogen chloride produced (0.54 mol) was in excess relative to the number of moles of organic base used (0.18 mol), so hydrogen chloride was mixed into the product gas.

[0020] (Comparative Example 1) A 50 ml PFA reactor, which had been thoroughly purged with dry nitrogen in advance, was equipped with a thermometer, a −5° C. chiller circulation condenser, and an inlet tube. ３ The reaction mixture was cooled to 5°C in an ice bath. 2.2 g (110 mmol) of HF was added while stirring. No gas generation was visually confirmed, and the reaction mixture was stirred and aged for 1 hour after the HF introduction. The reaction mixture separated into two layers. NMR analysis revealed that the upper layer was unreacted PCl ３ The lower layer is unreacted HF, and the lower layer is PF ３was not generated.

[0021] As can be seen from the above examples, the method for producing phosphorus trifluoride of the present invention can produce phosphorus trifluoride as a product with a purity of 98% or more at low temperatures below room temperature using readily available materials, with a reaction yield exceeding 80%, making the method suitable for industrial-scale operation. Comparative Example 1 demonstrates that simply mixing phosphorus trichloride and hydrogen fluoride at temperatures below room temperature does not result in a reaction. Furthermore, in Example 3, in which the organic base is supplied in excess of the hydrogen chloride produced, all of the produced hydrogen chloride remains in the reactor as an organic base-hydrogen chloride complex (solid), and therefore only the target phosphorus trifluoride is obtained as a highly pure product gas.

Claims

1. A method for producing phosphorus trifluoride which comprises reacting phosphorus trichloride with an organic base-hydrogen fluoride complex.

2. The method according to claim 1, wherein the organic base is at least one selected from the group consisting of pyridine, pyrimidine, tertiary alkylamine, and strong organic base.

3. The method according to claim 1 or 2, wherein the reaction is carried out at a temperature of 25°C to -40°C.

4. The method according to claim 1 or 2, wherein the organic base is in excess relative to the hydrogen chloride produced, and the hydrogen chloride produced remains in the reactor in the form of a complex with the organic base.

5. The process of claim 4, wherein all of the hydrogen chloride produced is complexed with the organic base, the hydrogen chloride remaining as a complex in the reactor, and the product gas is free of hydrogen chloride.

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