Methods for producing phosphorus trifluoride and phosphorus pentafluoride

Abstract

The present invention provides a method for producing phosphorus trifluoride and a method for producing phosphorus pentafluoride, which have high reaction efficiency, low reaction temperature, and high energy efficiency. The method for producing phosphorus trifluoride includes a step of introducing phosphorus trichloride and hydrogen fluoride into a first reactor and a step of discharging phosphorus trifluoride from the first reactor, and includes a carbon material in the first reactor. The method for producing phosphorus dichloride trifluoride includes a step of introducing phosphorus trifluoride and chlorine obtained above into a second reactor and a step of discharging phosphorus dichloride trifluoride from the second reactor. The method for producing phosphorus pentafluoride includes a step of introducing phosphorus dichloride trifluoride and hydrogen fluoride obtained above into a third reactor and a step of discharging phosphorus pentafluoride from the third reactor. The method for producing lithium hexafluorophosphate includes a step of introducing phosphorus pentafluoride and lithium fluoride obtained above into a fourth reactor and a step of discharging lithium hexafluorophosphate from the fourth reactor.

Description

[Technical field]

[0001] The present invention relates to a method for producing phosphorus trifluoride, phosphorus trifluoride dichloride, phosphorus pentafluoride, and hexafluorophosphate, and more specifically, to a method for producing phosphorus trifluoride, phosphorus trifluoride dichloride, and phosphorus pentafluoride used as raw materials for hexafluorophosphate, and a method for producing hexafluorophosphate, particularly lithium hexafluorophosphate, which can be used as an electrolyte for lithium batteries, etc. [Background technology]

[0002] In recent years, lithium-ion batteries have become more and more widely used, and are used not only in portable devices such as mobile phones, but also in power systems such as electric bicycles and electric cars, and in storage systems for wind power generation, solar power generation, etc. With the emergence of various problems such as energy and the environment, many countries have begun to accelerate industrial deployment for new energy, smart grid, etc., and it is expected that the demand for lithium-ion batteries will increase rapidly in the future.

[0003] A solution obtained by dissolving hexafluorophosphate in a carbonate-based solvent is commonly used as an electrolyte for batteries due to its high electrical conductivity, stable electrochemical performance, and low temperature operation. In particular, lithium hexafluorophosphate has many advantages, such as being the most excellent in overall performance in terms of electrical conductivity, electrochemical stability, and oxidation resistance compared to other lithium salts, being environmentally friendly, passivating the positive electrode current collector to prevent electrode corrosion, helping to form an SEI film on the negative electrode, and having a wide window of electrochemical stability, and is currently the most widely used electrolyte in lithium-ion batteries, and its quality determines the charge / discharge performance, service life, and safety of the battery. Therefore, as the demand for lithium hexafluorophosphate increases day by day, research and development of LiPF6 carbonate solution (typically LiPF6 / EMC solution) and its manufacturing method are being actively carried out.

[0004] Existing methods for producing hexafluorophosphate include, for example, a conventional method for producing LiPF6 in which lithium chloride is dissolved in hydrogen fluoride and then phosphorus pentafluoride is added thereto, and a method in which phosphorus pentafluoride is produced by reacting a phosphorus compound with hydrofluoric acid, and the phosphorus pentafluoride is introduced into a solution of a fluorine compound in anhydrous hydrofluoric acid (AHF) to produce hexafluorophosphate (see Patent Document 1).

[0005] As a method for producing phosphorus pentafluoride, Patent Document 2 describes a method in which phosphorus trichloride is used as a raw material and reacted with a molecular halogen and hydrogen fluoride.

[0006] Thus, the production of phosphorus trifluoride and phosphorus pentafluoride, the raw materials for LiPF6 carbonate solution, has been widely studied. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 2987713 specification [Patent Document 2] JP 2012-126621 A Summary of the Invention [Problem to be solved by the invention]

[0008] The inventors have found that the production methods described in the above patent documents have room for improvement in production efficiency. The present invention provides a method for producing phosphorus trifluoride, a method for producing phosphorus dichloride trifluoride, a method for producing phosphorus pentafluoride, and a method for producing lithium hexafluorophosphate that achieve high energy efficiency by improving reaction efficiency and lowering reaction temperature. [Means for solving the problem]

[0009] In the present invention, the following means are used to improve the reaction efficiency and lower the reaction temperature in the fluorination reaction of phosphorus trichloride, thereby solving the technical problem of improving the reaction efficiency in the oxidation reaction of phosphorus trifluoride. (Item 1) introducing phosphorus trichloride and hydrogen fluoride into a first reactor; and discharging phosphorus trifluoride from the first reactor; 2. A method for producing phosphorus trifluoride, comprising: (Item 2) 2. The method for producing phosphorus trifluoride according to item 1, wherein the carbon material acts as a reaction catalyst. (Item 3) 3. The method for producing phosphorus trifluoride according to item 1 or 2, wherein the carbon material does not support any of the group consisting of SbCl5, SbF5, SbCl3, SbF3, TiF4, TiCl4, FeCl3 and AlCl3. (Item 4) 4. The method for producing phosphorus trifluoride according to any one of items 1 to 3, wherein the carbon material is a non-supported carbon material. (Item 5) 5. The method for producing phosphorus trifluoride according to any one of items 1 to 4, wherein the carbon material is activated carbon. (Item 6) 6. The method for producing phosphorus trifluoride according to any one of items 1 to 5, wherein the temperature inside the first reactor is 100°C to 150°C. (Item 7) 7. The method for producing phosphorus trifluoride according to any one of items 1 to 6, wherein the inner wall of the first reactor comprises stainless steel. (Item 8) 7. The method for producing phosphorus trifluoride according to any one of items 1 to 6, wherein the inner wall of the first reactor comprises austenitic stainless steel. (Item 9) A step of introducing phosphorus trifluoride and chlorine obtained by the method for producing phosphorus trifluoride according to any one of items 1 to 8 into a second reactor; discharging phosphorus dichloride trifluoride from the second reactor; A method for producing phosphorus dichloride trifluoride, comprising the steps of: (Item 10) Item 10. The method for producing phosphorus dichloride trifluoride according to item 9, wherein the second reactor contains a filler. (Item 11) 10. The method for producing phosphorus dichloride trifluoride according to item 9, wherein the second reactor contains a carbon material. (Item 12) 10. The method for producing phosphorus dichloride trifluoride according to item 9, wherein the second reactor contains activated carbon. (Item 13) 13. The method for producing phosphorus trifluoride dichloride according to any one of items 9 to 12, wherein the inner wall of the second reactor contains a nickel-based alloy. (Item 14) 13. The method for producing phosphorus trifluoride dichloride according to any one of items 9 to 12, wherein the inner wall of the second reactor contains Hastelloy. (Item 15) A step of introducing phosphorus dichloride trifluoride and hydrogen fluoride obtained by the method for producing phosphorus dichloride trifluoride according to any one of items 9 to 14 into a third reactor; discharging phosphorus pentafluoride from the third reactor; A method for producing phosphorus pentafluoride, comprising the steps of: (Item 16) A step of introducing phosphorus trifluoride obtained by the method for producing phosphorus trifluoride according to any one of items 1 to 8 and hydrogen fluoride into a second reactor; discharging phosphorus pentafluoride from the second reactor; A method for producing phosphorus pentafluoride, comprising the steps of: (Item 17) Introducing phosphorus pentafluoride and lithium fluoride obtained by the method for producing phosphorus pentafluoride according to item 15 or 16 into a fourth reactor; discharging lithium hexafluorophosphate from the fourth reactor; A method for producing lithium hexafluorophosphate, comprising: Effect of the Invention

[0010] By implementing the above technical means of the present invention, the following beneficial effects can be obtained: the carbon material can act as a reaction catalyst to improve the reaction efficiency of the fluorination reaction of phosphorus trichloride and the oxidation reaction of phosphorus trifluoride, and at the same time, the reaction temperature can be reduced, thereby realizing high energy efficiency. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of an apparatus used in one embodiment of the present invention. [Diagram 2] 1 shows FT-IR measurement results of reaction gases discharged from the reaction tube 2 in Examples 6 and 7 and Comparative Examples 6 and 7. [Diagram 3] Photographs of the Cl2 inlet after testing in Comparative Examples 8 and 9. [Figure 4] 1 shows the analysis results of the LiPF6 / EMC concentrated liquid obtained in Example 10. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The contents of the present invention will be described in detail below. The following technical features will be described based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. In this specification, the numerical range indicated by "numerical value A to numerical value B" means a range including the end values ​​A and B.

[0013] The method for producing phosphorus trifluoride of the present invention includes the steps of introducing phosphorus trichloride and hydrogen fluoride into a first reactor, and discharging phosphorus trifluoride from the first reactor, the first reactor containing a carbon material.

[0014] The method for producing phosphorus trifluoride dichloride of the present invention includes the steps of introducing the phosphorus trifluoride and chlorine obtained above into a second reactor, and discharging phosphorus trifluoride dichloride from the second reactor.

[0015] The method for producing phosphorus pentafluoride of the present invention includes the steps of introducing the phosphorus trifluoride dichloride and hydrogen fluoride obtained above into a third reactor, and discharging phosphorus pentafluoride from the third reactor.

[0016] The method for producing lithium hexafluorophosphate of the present invention includes the steps of introducing the phosphorus pentafluoride and lithium fluoride obtained above into a fourth reactor, and discharging lithium hexafluorophosphate from the fourth reactor.

[0017] Fig. 1 is a schematic diagram of an apparatus used in one embodiment of the present invention. The apparatus includes a reaction tube 1 for reacting phosphorus trichloride (PCl3) vaporized by heating with hydrogen fluoride (HF) in the gas phase (fluorination reaction), a relay pipe for transferring a reaction gas containing phosphorus trifluoride (PF3) to the reaction tube 2, the reaction tube 2 for generating a reaction (oxidation reaction) between the reaction gas and introduced chlorine gas (Cl2), an analyzer that is arranged immediately after the reaction tube 1 or immediately after the reaction tube 2 via the pipe and valve, and is arranged as necessary to sample the reaction gas and perform composition analysis, and an abatement device that is arranged as necessary to abatement the exhaust gas.

[0018] The reactor 1 shown in FIG. 1 corresponds to the first reactor of the present application, and the reactor 2 corresponds to the second reactor of the present application. The reactor shown in FIG. 1 is an apparatus used in a continuous reaction for producing phosphorus trifluoride through a fluorination reaction from phosphorus trichloride, and producing phosphorus dichloride trifluoride through an oxidation reaction. However, it is clear that the reactor may be designed as a stage-type reactor for carrying out a method of producing phosphorus trifluoride by fluorinating phosphorus trichloride and a method of producing phosphorus dichloride trifluoride by oxidizing phosphorus trifluoride. Alternatively, a reactor 3 (not shown) for carrying out a method of producing phosphorus pentafluoride by fluorinating phosphorus dichloride trifluoride and a reactor 4 (not shown) for carrying out a method of producing lithium hexafluorophosphate from phosphorus pentafluoride may be installed in a continuous or stage-type manner at the rear of the reactor. The reactor 3 corresponds to the third reactor of the present application, and the reactor 4 corresponds to the fourth reactor of the present application.

[0019] In one embodiment of the present invention, phosphorus trichloride and hydrogen fluoride are introduced into a first reactor to carry out a fluorination reaction, and then phosphorus trifluoride is discharged from the first reactor, where the first reactor contains a carbon material.

[0020] The method of introducing phosphorus trichloride and hydrogen fluoride into the first reactor may be a method of heating phosphorus trichloride and hydrogen fluoride, respectively, to vaporize them, and introducing the gaseous phosphorus trichloride and hydrogen fluoride into the first reactor, respectively. The supply amounts of phosphorus trichloride gas and hydrogen fluoride gas can be easily controlled by a mass flow controller. Alternatively, an inert gas such as nitrogen or argon may be used as a carrier gas as necessary. From the viewpoint of preventing a decrease in yield due to hydrolysis of the product phosphorus trifluoride, the hydrogen fluoride is preferably anhydrous hydrogen fluoride.

[0021] The first reactor may be provided with a heating jacket, which controls the temperature of the fluorination reaction. In conventional manufacturing methods, the yield could be improved by extending the reaction tube or gas residence time, but a practical yield could only be obtained by adopting a high reaction temperature of 220°C or higher, particularly 250°C or higher. Such a high reaction temperature may lead to an increase in energy costs. On the other hand, in the present application, a carbon material is provided in the first reactor, and the carbon material acts as a catalyst, thereby realizing a high yield at a reaction temperature that is clearly lower than the conventional one.

[0022] The temperature of the fluorination reaction of the present invention can be 85°C to 170°C, preferably 100°C to 150°C, more preferably 105°C to 135°C. If the reaction temperature is lower than 85°C, some of the phosphorus trichloride may liquefy. If some of the PCl3 liquefies, when the fluorination reaction in the first reactor, the oxidation reaction in the second reactor, the fluorination reaction in the third reactor, and the lithium hexafluorophosphate production reaction in the fourth reactor are continuously carried out to produce a LiPF6 / carbonate solution, it is difficult to control the charge ratio of PF3>Cl2 in the oxidation reaction, and the unreacted Cl2 causes the solvent to become colored. On the other hand, if the reaction temperature exceeds 170°C, the effect of lowering the reaction temperature realized by the catalytic action of the carbon material of the present invention becomes insignificant.

[0023] The temperatures used for the heating and vaporization of phosphorus trichloride and hydrogen fluoride may be set as necessary, and are not particularly limited as long as the vaporization of phosphorus trichloride and hydrogen fluoride can be ensured. It is preferable that phosphorus trichloride is maintained in a gaseous state when mixed with hydrogen fluoride in the first reactor. From the viewpoint of preventing liquefaction of PCl3, it is more preferable that the temperatures of phosphorus trichloride gas and hydrogen fluoride gas are each in the same range as the preferred range of the reaction temperature, or that the temperature of the mixed gas after mixing phosphorus trichloride gas and hydrogen fluoride gas is in the same range as the preferred range of the reaction temperature.

[0024] The reaction pressure may be atmospheric pressure, or may be carried out under pressurized or reduced pressure conditions. From the viewpoint of convenience of operation and simplification of equipment, it is preferable to carry out the reaction under atmospheric pressure. The carbon material may be activated carbon, carbon black, graphite, graphene, carbon nanotubes, or carbon nanofibers, and activated carbon is preferably used.

[0025] The activated carbon has a specific surface area of ​​500 to 2000 m 2 / g activated carbon is preferred, and the specific surface area is 800 to 1000 m 2 By setting the specific surface area within the above range, it is possible to effectively promote the mixing of phosphorus trichloride and hydrogen fluoride and provide a reaction site.

[0026] The shape of the activated carbon is not particularly limited, and may be, for example, pellet-shaped, granular, powdery, or spherical. Granular activated carbon is preferred. Molded carbon, microbead carbon, pulverized carbon, or granulated carbon can be used as the granular activated carbon. From the viewpoint of the loading of the activated carbon in the reactor and the action as a catalyst, the particle size of the granular activated carbon is preferably 0.1 to 40 mm, more preferably 0.2 to 25 mm, and even more preferably 0.3 to 10 mm.

[0027] The type of activated carbon is not particularly limited, and a commercially available product may be used, or activated carbon that has been activated in advance may be used. Examples of the activated carbon activation method include a gas activation method and a chemical activation method. Examples of commercially available activated carbon include Shirasagi (trademark) manufactured by Osaka Gas Chemicals Co., Ltd., Filtrasorb (trademark) CAL, Diahope (trademark), Diasorb (trademark) manufactured by Calgon Carbon Japan Co., Ltd., Evadia (trademark) series manufactured by Suing Co., Ltd., Kuraray Coal (trademark) series and BPL manufactured by Kuraray Co., Ltd., Krikol (trademark) series manufactured by Kurita Water Industries Ltd., and PL series, PG series, PGN series, and PGD series manufactured by Dainen Co., Ltd.

[0028] Since the carbon material of the present invention exerts catalytic action by itself, it is preferable to use a non-supported carbon material in terms of ensuring the catalytic action of the carbon material and reducing costs. Compared with a supported carbon material in which a part of the pores is clogged due to the catalyst being supported, a non-supported carbon material may have a larger specific surface area, and therefore the catalytic action of the carbon material can be more effectively ensured. The non-supported carbon material is, for example, a carbon material that does not support SbCl5, SbF5, SbCl3, SbF3, TiF4, TiCl4, FeCl3 and / or AlCl3, and non-supported activated carbon is more preferable, for example, activated carbon that does not support SbCl5, SbF5, SbCl3, SbF3, TiF4, TiCl4, FeCl3 and / or AlCl3.

[0029] The shape of the first reactor is not particularly limited, and typical examples include a reaction tube, a reaction kettle, a reaction tower, and the like. The material of the reactor can be selected from materials resistant to HF, and examples thereof include nickel, nickel alloys, and stainless steel. Examples of nickel alloys include Monel (registered trademark) alloys and Hastelloy (registered trademark) alloys, which mainly contain nickel and copper and further contain iron, manganese, sulfur, and the like. Examples of stainless steels include austenitic stainless steels such as SUS304 and SUS316.

[0030] From the viewpoint of achieving both cost and corrosion resistance, the first reactor is preferably a stainless steel reaction tube. The first reactor may be entirely made of stainless steel, or only the inner wall may be made of stainless steel.

[0031] In the present invention, the product gas discharged from the first reactor is a mixed gas of phosphorus trifluoride, hydrogen chloride, hydrogen fluoride, etc., but when impurity gases such as hydrogen chloride and hydrogen fluoride are not a problem, the product gas may be used as it is, for example, the product gas may be directly supplied to the oxidation reaction in the second reactor. In addition, the impurity gases may be removed to provide high-purity phosphorus trifluoride.

[0032] In one embodiment of the present invention, the phosphorus trifluoride-containing reaction gas discharged from the first reactor and chlorine gas are introduced into a second reactor, and phosphorus trifluoride dichloride is discharged from the second reactor.

[0033] The inventors have found that when the oxidation reaction in the second reactor is carried out using the reaction gas discharged from the first reactor, the oxidation reaction rate is improved when the fluorination reaction rate of the reaction gas is low. This is believed to be because, when the fluorination reaction rate in the first reactor is low, the high boiling point components such as unreacted PCl3 remaining in the reaction gas are liquefied in the second reactor at a low temperature and react with Cl2 in the liquid phase for a sufficient time, thereby improving the oxidation reaction rate. However, when a reaction gas with a low fluorination reaction rate is actually used, solids such as PCl5 are likely to precipitate at the chlorine gas injection port, and in serious cases, they will clog the gas flow path. Therefore, it is not realistic to lower the fluorination reaction rate in order to improve the oxidation reaction rate.

[0034] Furthermore, the inventors have found that it is important to stably maintain the PCl3 concentration higher than Cl2 in the second reactor. If the fluorination of PCl3 is sufficient in the first reactor, the subsequent liquefaction of PCl3 and clogging of the reaction tube by solid PCl5 can be suppressed, and the conditions for making the PCl3 concentration higher than Cl2 can be easily stabilized. In an ideal embodiment, the raw material is 100% converted to low-boiling point PCl3 in the first reactor. Improving the fluorination efficiency as in the present application brings about advantages such as a smaller reactor and improved energy efficiency.

[0035] On the other hand, when the fluorination reaction rate in the first reactor is high, the phosphorus component in the reaction gas is mainly PF3, which has a low boiling point, and therefore the reaction with Cl2 in the second reactor becomes a completely gas-phase system, and the effect of the gas stirring efficiency becomes significant, resulting in a decrease in the oxidation reaction rate.

[0036] In order to prevent clogging in the second reactor and improve the oxidation reaction rate, it is preferable to fill the second reactor with a filler, such as Berl Saddle, McMahon packing, Dixon packing, Raschig Ring, Pall Ring, Heilex Ring, Teller Rosette, IMPAC filler, Helipack filler, carbon material, etc.

[0037] From the viewpoint of further improving the oxidation reaction rate, it is more preferable to use a carbon material or a metal filler such as Helipack filler as the filler. Suitable forms and examples of the carbon material can be referred to those of the carbon material used in the first reactor.

[0038] The shape and material of the second reactor are not particularly limited, and suitable forms and examples thereof can be referred to the suitable forms and examples of the shape and material of the first reactor.

[0039] The temperature of the oxidation reaction in the second reactor is not particularly limited, and the reaction can be carried out at any temperature within the range of, for example, 15°C to 60°C, preferably 20°C to 50°C. From the viewpoint of convenience of operation and simplification of equipment, it is preferable to carry out the reaction at room temperature. Furthermore, the temperature of the oxidation reaction can be controlled by providing a heating jacket or a cooling device.

[0040] The reaction pressure may be atmospheric pressure, or may be under increased or reduced pressure, but it is preferable to carry out the reaction under atmospheric pressure from the viewpoints of ease of operation and simplification of equipment.

[0041] When LiPF6 / carbonate solution is produced using phosphorus trifluoride-containing reaction gas discharged from the second reactor, and further phosphorus pentafluoride produced by reacting the reaction gas with hydrogen fluoride, it is preferable to strictly control the charge ratio of PF3>Cl2 during the oxidation reaction in order to prevent the solvent coloring of the final product due to unreacted Cl2. Since the Cl2 charge equivalent is directly related to the yield, it is preferable to make it as close as possible to 1.0eq. (equivalent). In order to ensure that the yield does not decrease, the Cl2 charge equivalent is usually 0.85eq. or more, preferably 0.90eq. or more, relative to PF3. On the other hand, the charge ratio is also affected by the accuracy of the feed gas, so in order to ensure the charge ratio of PF3>Cl2, the Cl2 charge equivalent is preferably 0.97eq. or less relative to PF3, and it is preferable to carry out the oxidation reaction in the second reactor under conditions of 0.95eq. or less.

[0042] In the present invention, the product gas discharged from the second reactor is a mixed gas of phosphorus dichloride trifluoride, phosphorus trifluoride, hydrogen chloride, etc., but when impurity gases such as phosphorus trifluoride and hydrogen chloride are not a problem, the product gas may be used as it is, for example, the product gas may be directly supplied to the fluorination reaction in the third reactor. In addition, the impurity gases may be removed to provide high-purity phosphorus dichloride trifluoride.

[0043] In one embodiment of the present invention, the phosphorus dichloride trifluoride-containing reaction gas discharged from the second reactor and hydrogen fluoride are introduced into a third reactor, and phosphorus pentafluoride is discharged from the third reactor.

[0044] The shape and material of the third reactor are not particularly limited, and it is sufficient that the phosphorus dichloride trifluoride-containing reaction gas discharged from the second reactor can be contacted with hydrogen fluoride to cause a reaction. For suitable forms and examples of the third reactor, the suitable forms and examples of the shape and material of the first reactor can be referred to. Furthermore, the third reactor may use an AHF cleaning device.

[0045] The reaction conditions such as the temperature of the fluorination reaction in the third reactor can be determined by referring to known methods. The hydrogen fluoride may be in any form of gas, liquid, or solution, and is not particularly limited.

[0046] In the present invention, the product gas discharged from the third reactor is a mixed gas of phosphorus pentafluoride, hydrogen fluoride, hydrogen chloride, chlorine gas, etc., but if impurity gases such as hydrogen fluoride, hydrogen chloride, chlorine gas, etc. are not a problem, it may be used as it is, for example, the product gas may be directly supplied to the reaction in the fourth reactor. In addition, the above impurity gases may be removed to provide high-purity phosphorus pentafluoride.

[0047] In one embodiment of the present invention, the phosphorus pentafluoride-containing reaction gas discharged from the third reactor and lithium fluoride are introduced into a fourth reactor, and lithium hexafluorophosphate is discharged from the fourth reactor.

[0048] Known methods can be referred to for conditions such as the reaction temperature in the fourth reactor. The lithium fluoride introduced into the fourth reactor may be in any form of powder, dispersion, or suspension. When a carbonate solvent is further introduced into the fourth reactor, the lithium hexafluorophosphate can be discharged from the fourth reactor in the form of a carbonate solution of lithium hexafluorophosphate. In particular, when methyl ethyl carbonate (EMC) is used, the product obtained from the fourth reactor may be a lithium hexafluorophosphate / EMC solution.

[0049] The carbonate solution of lithium hexafluorophosphate discharged from the fourth reactor may be degassed as necessary. The lithium hexafluorophosphate / EMC solution after degassing may be directly used for preparing an electrolyte solution for a lithium battery, or may be concentrated as necessary to provide a lithium hexafluorophosphate / EMC concentrated solution. Here, in order to satisfy the free acid index, the solution may be diluted once or several times as necessary before being concentrated. For the operation and conditions of degassing and concentration, known methods may be referred to.

[0050] In the above, the reactions in the first, second, third and fourth reactors have been described separately. However, it is clear that, if necessary, a plurality of reactions carried out in successive reactors may be integrated into one reactor. For example, the product gas, chlorine gas and hydrogen fluoride discharged from the first reactor may be introduced together into the second reactor, which not only carries out the oxidation reaction of phosphorus trifluoride, but also at least a part of the fluorination reaction of pentavalent phosphorus fluoride chloride.

[0051] When a lithium hexafluorophosphate / EMC concentrate is produced by the method of the present invention, the yield of lithium hexafluorophosphate is high, and the coloring of the solvent caused by unreacted chlorine is suppressed, so that a lithium hexafluorophosphate / EMC concentrate that meets industrial standards can be obtained. EXAMPLES

[0052] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0053] The reactor used in the examples was arranged as shown in Figure 1. Here, a SUS316L BA tube (φ=1 / 4 inch) was used as the reaction tube, which was heated to a predetermined temperature using a heating belt during the reaction. A Fourier transform infrared spectrometer (FT-IR) was used as the analyzer, and quantitative analysis was performed based on peak height. The specific measurement conditions were as follows:

[0054] FT-IR measurement conditions Equipment: Shimadzu Prestige-21 Gas sample cell length: 10cm Sample cell window material: ZnSe Measurement mode: Absorbance Total number of times: 100 Measured peaks: HF:4037.01cm -1 (Measurement range: 2054.37~4021.58cm -1 ) HCl: 2819.93 cm -1 (Measurement range: 2810.28~2829.57cm-1 ) PF3: 904.61cm -1 (Measurement range: 740.67~1099.43cm -1 )

[0055] Example 1

[0056] Phosphorus trichloride gas and anhydrous hydrogen fluoride gas heated to 120°C were supplied to reaction tube 1 (first reactor) at rates of 11.9 sccm and 52.3 sccm, respectively [equivalent ratio (AHF / PCl3) = 3.9], and reacted. The reaction conditions are as shown in Table 1 below, and 2 g of granular Shirasagi LH2c (Osaka Gas Chemicals Co., Ltd.) was packed into reaction tube 1 as activated carbon. The reaction gas discharged from reaction tube 1 was quantitatively analyzed using FT-IR. 60 minutes after the start of the reaction, the PF3 yield stabilized, and at this time, this value was recorded in Table 1 as the PF3 yield.

[0057] Examples 2 to 5 and Comparative Examples 1 to 5

[0058] The reaction was carried out in the same manner as in Example 1 except that the charging conditions and reaction conditions were changed as shown in Table 1, and the PF3 yield was quantitatively analyzed. The results are shown in Table 1 below.

[0059] [Table 1]

[0060] Information on the fillers used in each example is shown in Table 2 below.

[0061] [Table 2]

[0062] As can be seen from Table 1, all of Examples 1 to 5 using activated carbon achieved a high PF3 yield of about 100%, while Comparative Example 4, in which no filler was used in the reaction tube, had a low PF3 yield. Furthermore, in Comparative Examples 1 to 3 in which activated carbon was not used as the filler, the PF3 yield was low even when the reaction temperature was raised to 220°C to provide more favorable conditions for the production of PF3. Compared to Comparative Example 1 in which no filler was used, Comparative Example 2 in which a filler other than a carbon material (activated carbon) was used did not show a significant improvement in the PF3 yield. Compared to Comparative Example 1, Comparative Example 3 in which the residence time was extended by lengthening the reaction tube showed a slight improvement in the PF3 yield, but did not achieve a high yield at the level of the Examples. In Comparative Example 5, the residence time was extended by lengthening the reaction tube, and the reaction temperature was further raised to 240°C, and the PF3 yield increased to 62.0%, but a high yield at the level of the Examples was still not achieved.

[0063] Example 6

[0064] Phosphorus trichloride gas and anhydrous hydrogen fluoride gas were reacted in a reaction tube 1 (first reactor), and the reaction gas containing unreacted hydrogen fluoride gas with a PF3 yield of 100% was discharged from the reaction tube 1 and introduced into a reaction tube 2 (second reactor), while chlorine gas was introduced into the reaction tube 2, and the reaction gas was subjected to an oxidation reaction and a fluorination reaction. The composition of the reaction gas discharged from the reaction tube 2 was analyzed using FT-IR, and the results are shown in FIG. 2B. Here, the reaction tube 2 was filled with Helipak No. 2.

[0065] Example 7

[0066] The same operation as in Example 6 was carried out except that the reaction tube 2 was filled with activated carbon instead of Helipack No. 2. The composition analysis results of the reaction gas discharged from the reaction tube 2 are shown in FIG. 2D.

[0067] Comparative Example 6

[0068] The same operation as in Example 6 was performed except that the PF3 yield was changed to 60% and no packing material was packed into the reaction tube 2. The composition analysis result of the reaction gas discharged from the reaction tube 2 is shown in FIG. 2A.

[0069] Comparative Example 7

[0070] The same procedure as in Example 6 was carried out except that the reaction tube 2 was not filled with any packing material. The composition analysis result of the reaction gas discharged from the reaction tube 2 is shown in FIG.

[0071] As can be seen from Fig. 2, phosphorus pentafluoride was significantly produced in Examples 6 and 7, in which the reaction gas with a PF3 yield of 100% was used as the raw material and the reaction tube 2 was filled with a filler. Compared with Example 6, in which Helipack No. 2 was used, the conversion rate of phosphorus trifluoride was higher in Example 7, and the yield of phosphorus pentafluoride was improved.

[0072] On the other hand, in Comparative Example 6, in which a reaction gas with a PF3 yield of 60% was used as the raw material and no packing material was used, phosphorus pentafluoride was significantly produced, but clogging occurred within a certain time after the start of the reaction, and a stable reaction over a long period of time was not possible. Also, in Comparative Example 7, in which a reaction gas with a PF3 yield of 100% was used as the raw material and no packing material was used, the amount of phosphorus pentafluoride produced was small.

[0073] Examples 8 and 9, Comparative Examples 8 and 9

[0074] Phosphorus trichloride gas and anhydrous hydrogen fluoride gas were reacted in the reaction tube 1 under the fluorination reaction conditions shown in Table 3, and the PF3 yield of the reaction gas discharged from the reaction tube 1 was measured and shown in Table 3. The reaction gas containing unreacted hydrogen fluoride gas and chlorine gas were introduced into the reaction tube 2 (second reactor) and reacted under the oxidation reaction conditions shown in Table 4. The presence or absence of precipitates at the chlorine gas inlet was observed, and the results are shown in Table 4.

[0075] [Table 3]

[0076] [Table 4]

[0077] As can be seen from Tables 3 and 4, in Examples 8 and 9 in which the fluorination reaction was 100% and the reaction tube 2 was filled with activated carbon, no precipitate was observed near the Cl2 inlet. On the other hand, as shown in FIG. 3, in Comparative Example 8 in which the fluorination reaction rate was low, clogging occurred during the reaction, and when the test was stopped and the tube was opened for inspection, white crystals were observed near the Cl2 inlet. The crystals were hygroscopic and acidic, and therefore were considered to be PCl5 produced by unreacted PCl3 and Cl2. In Comparative Example 9 in which the fluorination reaction rate was about 60%, clogging of the reaction tube 2 did not occur, but some crystal precipitation was observed near the Cl2 inlet.

[0078] Example 10

[0079] Phosphorus trichloride gas and anhydrous hydrogen fluoride gas were reacted in the reaction tube 1 under the same fluorination reaction conditions as in Example 9. The reaction gas containing unreacted hydrogen fluoride gas and chlorine gas discharged from the reaction tube 1 were introduced into the reaction tube 2 (second reactor), and oxidation and fluorination reactions were carried out under the same conditions as in Example 9 to produce phosphorus pentachloride. The reaction product discharged from the reaction tube 2 was introduced into a gas collection vessel (fourth reactor) containing a 2.4 wt% lithium fluoride EMC solution. Here, the 2.4 wt% lithium fluoride EMC solution was a mixture of 200 g EMC and 5 g (1.9 eq.) LiF, and gas collection was carried out for 210 minutes under ice-cooling conditions. After completion of gas collection, the solution in the gas collector was degassed under ice-cooling conditions for 1 hour, left to stand to recover to room temperature, and then degassed for 0.5 hours to obtain 216.01 g of degassed solution. The degassed solution was concentrated under reduced pressure at 60°C for 0.5 hours to obtain 40.23g of a concentrated solution. The concentrated solution was pressure filtered using a 0.5μm PTFE membrane, the filter residue was washed with EMC, the filtrates were combined, and finally a 33% LiPF6 / EMC concentrated solution was obtained. The analytical results of the 33% LiPF6 / EMC concentrated solution are shown in Table 5.

[0080] [Table 5]

[0081] In Example 10, the yield of LiPF6 was as good as 97.8%, and the coloring of the solvent due to unreacted Cl2 was also suppressed. 19 F NMR results showed 0.7% LiPO2F2, likely due to residual moisture in the gas collection vessel. [Industrial Applicability]

[0082] According to the present invention, a method for producing phosphorus trifluoride and a method for producing phosphorus pentafluoride, which have high reaction efficiency, low reaction temperature, and can avoid clogging of a reactor, are provided, and are applicable to the industrial production of LiPF6 / EMC concentrated solution.

[0083] Although the embodiments of the present invention have been described above, the above description is illustrative and not exhaustive, and is not limited to the disclosed embodiments. Various modifications and changes will be obvious to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. introducing phosphorus trichloride and hydrogen fluoride into a first reactor; and discharging phosphorus trifluoride from the first reactor; Containing a carbon material in the first reactor. Method for producing phosphorus trifluoride.

2. The method for producing phosphorus trifluoride according to claim 1 , wherein the carbon material acts as a reaction catalyst.

3. The carbon material is SbCl ５ , SbF ５ , SbCl ３ , SbF ３ , TiF ４ , TiCl ４ , FeCl ３ and AlCl ３ The method for producing phosphorus trifluoride according to claim 1 or 2, wherein none of the group consisting of:

4. The method for producing phosphorus trifluoride according to any one of claims 1 to 3, wherein the carbon material is a non-supported carbon material.

5. The method for producing phosphorus trifluoride according to any one of claims 1 to 4, wherein the carbon material is activated carbon.

6. The method for producing phosphorus trifluoride according to any one of claims 1 to 5, wherein a temperature in the first reactor is 100°C to 150°C.

7. The method for producing phosphorus trifluoride according to any one of claims 1 to 6, wherein an inner wall of the first reactor comprises stainless steel.

8. The method for producing phosphorus trifluoride according to any one of claims 1 to 6, wherein an inner wall of the first reactor comprises austenitic stainless steel.

9. A step of introducing phosphorus trifluoride and chlorine obtained by the method for producing phosphorus trifluoride according to any one of claims 1 to 8 into a second reactor; discharging phosphorus dichloride trifluoride from the second reactor; A method for producing phosphorus dichloride trifluoride comprising the steps of:

10. 10. The method for producing phosphorus trifluoride dichloride according to claim 9, further comprising the step of:

11. 10. The method for producing phosphorus trifluoride dichloride according to claim 9, further comprising the step of:

12. 10. The method of claim 9, further comprising the step of:

13. The method for producing phosphorus dichloride trifluoride according to any one of claims 9 to 12, wherein the inner wall of the second reactor comprises a nickel-based alloy.

14. The method for producing phosphorus trifluoride dichloride according to any one of claims 9 to 12, wherein an inner wall of the second reactor comprises Hastelloy.

15. A step of introducing phosphorus dichloride trifluoride and hydrogen fluoride obtained by the method for producing phosphorus dichloride trifluoride according to any one of claims 9 to 14 into a third reactor; discharging phosphorus pentafluoride from the third reactor; A method for producing phosphorus pentafluoride comprising the steps of:

16. A step of introducing phosphorus trifluoride obtained by the method for producing phosphorus trifluoride according to any one of claims 1 to 8 and hydrogen fluoride into a second reactor; discharging phosphorus pentafluoride from the second reactor; A method for producing phosphorus pentafluoride comprising the steps of:

17. A step of introducing phosphorus pentafluoride and lithium fluoride obtained by the method for producing phosphorus pentafluoride according to claim 15 or 16 into a fourth reactor; discharging lithium hexafluorophosphate from the fourth reactor; The method for producing lithium hexafluorophosphate comprises the steps of:

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