JP2010037284A - Method for producing amidinium hexafluorophosphoric acid salt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an industrially suitable method for producing an amidinium hexafluorophosphoric acid salt in high purity and in high yield. <P>SOLUTION: The method for producing the amidinium hexafluorophosphoric acid salt (A) comprises the process wherein a crude reaction mixture (Ac) obtained by conducting a reaction between an amidinium halogenide (A1) and potassium hexafluorophosphate (A2) in an aqueous solvent followed by dehydration is added with a solvent (B), whose solubility of potassium chloride is 100 ppm or less at 20°C, to extract an amidinium hexafluorophosphoric acid salt followed by refining it. In this method, the amidinium cation as a constituent of the amidinium halogenide (A1) is preferably an imidazolium cation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a method for producing amidinium hexafluorophosphate, and more particularly to a method for producing amidinium hexafluorophosphate including a purification step using a specific extraction solvent.

  Among the conventionally known methods for producing amidinium group-containing cations and hexafluorophosphate anions, such as imidazolium hexafluorophosphate, the imidazolium halide salt is a particularly active production method. And an alkali metal salt containing the target anion (for example, sodium hexafluorophosphate), and then washed with a hydrocarbon solvent and then washed with water (for example, patents). Literature-1). However, this production method is unsuitable from the viewpoint of an industrial production method such that removal of by-product salts is not sufficient and it is difficult to obtain a high-purity target product or the yield is low.

JP 2003-313171 A

  An object of the present invention is to provide a method for producing amidinium hexafluorophosphate which is small in residual amount of by-product salt, has high purity and high yield, and is industrially suitable.

  The present invention relates to a crude reaction mixture (Ac) obtained by reacting an amidinium halide salt (A1) and potassium hexafluorophosphate (A2) in an aqueous solvent and then dehydrating [hereinafter, simply (Ac) And a solvent (B) having a solubility of potassium chloride at 20 ° C. of 100 ppm or less [hereinafter sometimes simply referred to as (B)], and amidinium hexafluoro This is a method for producing amidinium hexafluorophosphate (A) [hereinafter sometimes simply referred to as (A)], wherein the phosphate is extracted and purified.

  According to the production method of the present invention, the residual amount of a by-product salt of amidinium hexafluorophosphate (A) is small, high purity and high yield, and it is suitable for industrial production.

The crude reaction mixture (Ac) in the present invention comprises an amidinium halogen salt (A1) [hereinafter sometimes referred to simply as (A1)] and potassium hexafluorophosphate (A2) [hereinafter referred to simply as (A2). )] In a water solvent, followed by dehydration. The amidinium halogen salt (A1) in the present invention is a salt composed of an amidinium cation and a halogen anion.

Examples of the amidinium cation constituting the (A1) include a chain amidinium cation and a cyclic amidinium cation.

  Compounds capable of forming a chain amidinium cation include N, N-dimethyl-N′-benzylformamidine, N-methyl-N, N′-dibenzylformamidine, N, N-dimethyl-N ′. -Benzylacetamidine, N, N-dimethyl-N′-phenylacetamidine, N-methyl-N, N′-dibenzylacetamidine and the like.

Examples of the compound capable of forming a cyclic amidinium cation include a compound having an imidazole ring, a 2-imidazoline ring or a tetrahydroimidazoline ring.

Examples of the compound having an imidazole ring include 1-ethylimidazole, 1-ethyl-2-methylimidazole, 1,2-dimethylimidazole, 1,2,4-trimethylimidazole, 1-phenylimidazole, 1-benzylimidazole, 1, Examples include 2-dimethylimidazole and 1-methylbenzimidazole.

Examples of the compound having a 2-imidazoline ring include 1-methylimidazoline, 1,2-dimethylimidazoline, 1,2,4-trimethylimidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-phenylimidazoline, and Examples include 1-methyl-2-benzylimidazoline.

  Examples of the compound having a tetrahydroimidazoline ring include 1-methyl-1,4,5,6-tetrahydropyrimidine, 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1,8-diazabicyclo [5,4, 0] undecene-7 and 1,5-diazabicyclo [4,3,0] nonene-5.

Of the amidinium cations, from the viewpoint of easy availability, a cyclic one is preferable, and an imidazolium cation (= a cation having an imidazole ring) is more preferable. Preferred is the imidazolium cation.

In the formula, R ¹ and R ³ are each an alkyl group having 1 to 6 carbon atoms, and may be the same or different. R ² , R ⁴ and R ⁵ are each a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and may be the same or different.

  Examples of the alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, ter-butyl group, n-pentyl group and isopentyl group. , N-hexyl group, isohexyl group and the like.

  Among the imidazolium cations represented by the general formula (1), 1-ethyl-3-methylimidazolium cation and 1-ethyl-2,3-dimethylimidazolium are preferable from the viewpoint of the usefulness of the purified product. Cations, 1,2,3-trimethylimidazolium cation and 1,2,3,4-tetramethylimidazolium cation.

Examples of the halogen anion constituting the (A1) include a chloro anion, a bromo anion, an iodo anion, and a fluorine anion. Of these, chloroanions are preferred from the viewpoint of raw material costs.

  The amidinium halogen salt (A1) is preferably a cyclic amidinium halogen salt from the viewpoint of easy availability, more preferably an imidazolium halogen salt, and particularly preferably the above general formula. The halogen salt of the imidazolium cation represented by (1), particularly preferred is 1-ethyl-3-methylimidazolium chloro salt, 1-ethyl-2,3-dimethylimidazolium chlor salt, 1,2 1,3-trimethylimidazolium chloro salt and 1,2,3,4-tetramethylimidazolium chlor salt.

The crude reaction mixture (Ac) in the present invention is obtained by reacting (A1) with potassium hexafluorophosphate (A2) in an aqueous solvent and then dehydrating. From the viewpoint of the purity of (A), The reaction conditions and dehydration conditions are preferably as follows.

An aqueous solution (A1) and an aqueous solution (A2) are prepared in advance, and then both are mixed. By making both into aqueous solution, reaction becomes easy to advance. In this case, a method of dropping one of them on the other is preferable. The concentration of the aqueous solution is preferably 5 to 95% by weight, more preferably 10 to 90% by weight in both cases (A1) and (A2).

  The charged molar ratio (A1: A2) of (A1) to (A2) is preferably 1: 0.50 to 1: 1.5, more preferably 1: 0.90 to 1: 1.1, particularly 1: 0. .95 to 1: 1.05 is preferred. The reaction temperature is usually 0 to 100 ° C, preferably 10 to 90 ° C, more preferably 20 to 80 ° C. The reaction time is usually 10 minutes to 20 hours, preferably 20 minutes to 10 hours.

The crude reaction mixture (Ac) in the present invention needs to dehydrate the product after the reaction. Without dehydration, purification is difficult and a large amount of potassium halide remains.

  The dehydration conditions applied in the present invention are preferably 25 ° C. to 150 ° C. under reduced pressure, and more preferably 60 ° C. to 120 ° C. at a pressure of 50 kPa or less. The end point of dehydration is when the water content is 0.5% by weight or less, preferably 0.1% by weight or less, particularly preferably 0.01% by weight. The moisture content can be measured with a Karl Fischer moisture measuring device (Hiranuma Sangyo Co., Ltd., AQ-7).

The crude reaction mixture (Ac) obtained as described above usually contains potassium halide in addition to the target amidinium hexafluorophosphate.

In the present invention, the method of extracting and purifying only the target product from (Ac) is such that the solubility of potassium chloride at 20 ° C. (hereinafter abbreviated as KCl solubility) is 100 ppm or less, preferably 50 ppm or less, more preferably In this method, a solvent having a concentration of 10 ppm or less is used as the extraction solvent. Even if the by-product potassium halide is not potassium chloride but potassium bromide, potassium iodide or potassium fluoride, the object of the present invention can be achieved if the KCl solubility of the solvent is in the above range.

  Solvents (B) include aromatic hydrocarbon solvents such as toluene (KCl solubility = insoluble), xylene, ethylbenzene and tetralin; fats such as n-hexane (KCl solubility = insoluble), n-heptane, mineral spirits and cyclohexane Aromatic or alicyclic hydrocarbon solvents; halogen solvents such as methyl chloride, methyl bromide, methyl iodide, methylene dichloride, carbon tetrachloride, trichloroethylene and perchloroethylene; ethyl acetate, butyl acetate, methoxybutyl acetate, methyl Ester or ester ether solvents such as cellosolve acetate and ethyl cellosolve acetate; ether solvents such as diethyl ether, tetrahydrofuran, dioxane, ethyl cellosolve, butyl cellosolve and propylene glycol monomethyl ether Ketone ketone solvents such as acetone (KCl solubility = 0.9 ppm), methyl ethyl ketone, methyl isobutyl ketone, di-n-butyl ketone and cyclohexanone; n-propanol (KCl solubility = 61 ppm), isopropanol, n-butanol (KCl solubility = 30 ppm); ), Alcohol solvents such as isobutanol, t-butanol, 2-ethylhexyl alcohol and benzyl alcohol; amide solvents such as dimethylformamide and dimethylacetamide; sulfoxide solvents such as dimethyl sulfoxide, and heterocyclic groups such as N-methylpyrrolidone Compound solvents and mixed solvents of two or more of these may be mentioned.

  Among these, from the viewpoint of the yield and purity of the target product, a ketone solvent is preferable, and acetone is more preferable.

  When the reaction mixture (Ac) is mixed with the solvent (B) for extraction and purification, the weight ratio (Ac) :( B) is 95: 5 to 5:95 from the viewpoint of yield and purity. More preferably, it is 85: 15-15: 85. The time for extraction and purification is preferably 1 to 60 hours, more preferably 2 to 50 hours, and it may be appropriately adjusted according to the scale. The temperature for extraction and purification is preferably 0 to 100 ° C, more preferably 10 to 90 ° C. After extraction and purification, the solvent (B) solution of amidinium hexafluorophosphate (A) is obtained by separating the precipitated potassium halide with a device such as a filter or a centrifuge. The target amidinium hexafluorophosphate (A) is obtained by removing the solvent (B) from this solution.

  The solvent (B) is usually removed by heating under reduced pressure, the temperature is usually 25 to 150 ° C., preferably 60 to 120 ° C., and the degree of vacuum is usually 50 kPa or less. In addition, if necessary, the above-described extraction / purification operation may be repeated twice or more. From the viewpoint of process time, one extraction / purification is preferable.

  Among the amidinium hexafluorophosphates (A) obtained by the production method of the present invention, preferred are the aforementioned preferred ones of (A1) and the aforementioned preferred ones of (A2). A cyclic amidinium hexafluorophosphate, more preferably an imidazolium hexafluorophosphate, and particularly preferably hexafluoro of an imidazolium cation represented by the general formula (1). Particularly preferred are phosphates, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-2,3-dimethylimidazolium hexafluorophosphate, 1,2,3-trimethyl With imidazolium hexafluorophosphate and 1,2,3,4-tetramethylimidazolium hexafluorophosphate is there.

  The amidinium hexafluorophosphate (A) obtained by the production method of the present invention has a small residual amount of by-product salt (potassium halide), and (A) contains potassium ions (hereinafter abbreviated as K ions). ) Is usually 200 ppm or less, preferably 20 ppm or less, and halogen ions are usually 200 ppm or less, preferably 20 ppm or less. K ion can be measured by the atomic absorption method of the flame method. Halogen ions can be measured by ion chromatography.

  The amidinium hexafluorophosphate (A) obtained by the production method of the present invention has a high purity and is usually 96% or more, preferably 99% or more, more preferably 99.5% or more. Purity can be measured by liquid high performance chromatography (HPLC).

  Furthermore, according to the production method of the present invention, the yield of amidinium hexafluorophosphate (A) is high, usually 90% or more, preferably 95% or more. The yield is a yield calculated based on the number of moles of the charged amidinium halogen salt.

  Since the amidinium hexafluorophosphate (A) obtained by the production method of the present invention is low in potassium halide and high in purity, it is an intermediate for producing electrolytes for electrochemical devices, pharmaceuticals, agricultural chemicals or dyes. It is useful as a curing agent for a resin such as an epoxy resin or a polyurethane resin.

  In the following, the present invention will be further described with reference to examples, but the present invention is not limited thereto. Hereinafter, unless otherwise specified,% means% by weight.

In the following examples, the purity was measured by liquid high performance chromatography (HPLC). HPLC conditions were as follows: instrument: model name (LC-10A), manufacturer (Shimadzu Corporation), column: Develosil C30-UG (4.6 mmφ × 25 cm) manufacturer (Nomura Chemical), mobile phase: phosphoric acid concentration 10 mmol / L , Aqueous solution of sodium perchlorate at a concentration of 100 mmol / L, flow rate: 0.8 mL / min, detector: UV (210 nm), injection amount: 20 μL, column temperature: 40 ° C. The purity can be calculated from the total area and the area of the main component.

K ions were measured by flame atomic absorption. Equipment: Model name (AA-6700F), manufacturer (Shimadzu Corporation), gas: Air-C ₂ H ₂ , wavelength: 766.5 nm.

  Halogen ions (here, chloro ions, hereinafter abbreviated as Cl ions) were measured by ion chromatography. The conditions for ion chromatography are as follows: instrument: model name (HIC-NS system), manufacturer (Shimadzu Corporation), column: Shim-pack IC-A1 (4.6 mmφ × 100 mm) manufacturer (Shimadzu Corporation), mobile phase: phthalic acid Concentration 2.5 mmol / L, aqueous solution of tris (hydroxylmethyl) aminomethane concentration 2.4 mmol / L, flow rate: 1.2 mL / min, detector: conductivity detector, injection volume: 20 μL, column temperature: 40 ° C. The concentration was calculated from a comparison with the Cl ion peak area of a Cl ion aqueous solution having a known concentration.

Example 1
Using a 1 L four-necked flask, 93.9 g (0.51 mol) of potassium hexafluorophosphate (manufactured by Aldrich, grade: 99 +%) was added to 600 g of water, and an aqueous solution 1 was prepared while stirring at 50 ° C. Using a 300 mL beaker, 73.3 g (0.50 mol) of 1-ethyl-3-methylimidazolium chlorate (synthesized according to the method described in JP-A-2006-089379) was added to 20 g of water, and 25 Aqueous solution 2 was obtained with stirring at ° C. Aqueous solution 2 was placed in a 200 mL dropping funnel and added dropwise to aqueous solution 1 at 50 ° C. over 30 minutes. After further stirring for 30 minutes at 50 ° C., the product was put into a 1 L eggplant flask, dehydrated with an evaporator at 70 ° C. and 15 kPa for 1 hour (water content = 0.06%), and the crude reaction mixture was taken out. It was. To 165.5 g of the crude reaction mixture taken out, 250 mL (197.5 g) of acetone was added with stirring at 25 ° C., and the mixture was stirred at 25 ° C. for 3 hours, and then insoluble matters were removed by filtration under reduced pressure. The mother liquor was placed in a 500 mL eggplant flask, and acetone was removed with an evaporator at 70 ° C. and 15 kPa for 3 hours to give 1-ethyl-3-methylimidazolium hexafluorophosphate (hereinafter abbreviated as EMI · PF ₆ ) 122. .9 g was obtained. Table 1 shows the K ion, Cl ion, purity and yield of the obtained EMI · PF ₆ .

Example 2
Using a 1 L four-necked flask, 93.9 g (0.51 mol) of potassium hexafluorophosphate (manufactured by Aldrich, grade: 99 +%) was added to 600 g of water, and an aqueous solution 3 was prepared while stirring at 50 ° C. Using a 300 mL beaker, 80.3 g (0.50 mol) of 1-ethyl-2,3-methylimidazolium chlorate (synthesized according to the method described in JP 2006-089379 A) was added to 20 g of water. In addition, while stirring at 25 ° C., an aqueous solution 4 was prepared. Aqueous solution 4 was placed in a 200 mL dropping funnel and added dropwise to aqueous solution 3 at 50 ° C. over 30 minutes. After further stirring for 30 minutes at 50 ° C., the product was put into a 1 L eggplant flask, dehydrated with an evaporator at 70 ° C. and 15 kPa for 1 hour (water content = 0.06%), and the crude reaction mixture was taken out. It was. Acetone 250 mL (197.5 g) was added to 172.5 g of the taken out crude reaction mixture at 25 ° C. with stirring, and the mixture was stirred at 25 ° C. for 3 hours. Then, insoluble matters were removed by filtration under reduced pressure. The mother liquor was placed in a 500 mL eggplant flask, and acetone was removed with an evaporator at 70 ° C. and 15 kPa for 3 hours, and 1-ethyl-2,3-methylimidazolium hexafluorophosphate (hereinafter abbreviated as EDMI · PF ₆ ). ) 128.3 g was obtained. Table 1 shows the K ion, Cl ion, purity and yield of the obtained EDMI · PF ₆ .

Example 3
Using a 1 L four-necked flask, 93.9 g (0.51 mol) of potassium hexafluorophosphate (manufactured by Aldrich, grade: 99 +%) was added to 600 g of water, and an aqueous solution 5 was obtained while stirring at 50 ° C. Using a 300 mL beaker, 80.3 g (0.50 mol) of 1,2,3,4-tetramethylimidazolium chlorate (synthesized according to the method described in JP-A-2006-089379) was added to 20 g of water. In addition, the aqueous solution 6 was prepared with stirring at 25 ° C. Aqueous solution 4 was placed in a 200 mL dropping funnel and added dropwise to aqueous solution 3 at 50 ° C. over 30 minutes. After further stirring for 30 minutes at 50 ° C., the product was put into a 1 L eggplant flask, dehydrated with an evaporator at 70 ° C. and 15 kPa for 1 hour (water content = 0.05%), and the crude reaction mixture was taken out. It was. To 173.2 g of the crude reaction mixture taken out, 250 mL (197.5 g) of acetone was added with stirring at 25 ° C., and the mixture was stirred at 25 ° C. for 3 hours, and then insoluble matters were removed by filtration under reduced pressure. Put mother liquor 500mL eggplant flask, 70 ° C. with an evaporator, 3 hours under conditions of 15 kPa, to remove acetone, 1,2,3,4-tetramethyl imidazolium hexafluorophosphate (hereinafter abbreviated as TMI · PF ₆ 132.4 g was obtained. Table 1 shows the K ions, Cl ions, purity and yield of the obtained TMI · PF ₆ .

Comparative Example 1
92.0 g (0.5 mol) of potassium hexafluorophosphate (manufactured by Aldrich, grade: 99 +%), and 1-ethyl-3-methylimidazolium chlorate (the method described in JP-A-2006-089379) 73.3 g (0.5 mol) was added to 500 g of acetone and stirred at 27 ° C. for 24 hours. The obtained crude reaction mixture was filtered to remove precipitates, and then acetone was distilled off under reduced pressure. To the residue, 200 g of toluene was added and stirred for 15 minutes, and the operation of separating and removing toluene was performed twice. Next, 200 g of ion-exchanged water was added and stirred for 15 minutes, and water was separated and removed twice. By drying under reduced pressure of 1 Pa at 70 ° C., 106.3 g of 1-ethyl-3-methylimidazolium hexafluorophosphate (EMI · PF ₆ ) was obtained. Table 1 shows the K ion, Cl ion, purity and yield of the obtained EMI · PF ₆ .

From the results shown in Table 1, the amidinium hexafluorophosphate (A) to which the method for producing amidinium hexafluorophosphate of the present invention (Examples 1 to 3) was applied was compared with Comparative Example 1 in terms of K ion. It can be seen that the content of Cl and Cl ions is small, and the purity is high and the yield is high.

  The amidinium hexafluorophosphate obtained from the production method of the present invention is useful as an intermediate for producing an electrolytic solution for an electrochemical device, a medicine, an agricultural chemical, a dye, or the like. It is also useful as a curing agent for resins such as epoxy resins or polyurethane resins.

Claims (5)

  The solubility of potassium chloride at 20 ° C. is 100 ppm or less in the crude reaction mixture (Ac) obtained by reacting amidinium halogen salt (A1) and potassium hexafluorophosphate (A2) in an aqueous solvent and then dehydrating. A method for producing amidinium hexafluorophosphate (A), wherein the solvent (B) is used to extract and purify amidinium hexafluorophosphate.   The method according to claim 1, wherein the amidinium cation constituting the amidinium halogen salt (A1) is an imidazolium cation. The production method according to claim 2, wherein the imidazolium cation is a cation represented by the general formula (1).

[Wherein, R ¹ and R ³ are each an alkyl group having 1 to 6 carbon atoms, and may be the same or different. R ² , R ⁴ and R ⁵ are each a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and may be the same or different. ]   The production method according to claim 1, wherein the amidinium halogen salt (A1) is a chlor salt.   The production method according to claim 1, wherein the solvent (B) is acetone.