JP2008201703A - Method for producing imidazolium salt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an imidazolium salt giving an imidazolium salt having high purity in high yield. <P>SOLUTION: The method for producing an imidazolium salt (D) from a crude imidazolium salt (C) containing an impurity (e) comprises the extraction and removal of the impurity (e) with a solvent (d) having solubility of the imidazolium salt (D) of 0.2-20 g in 100 g of the solvent at 25°C. Preferably, the crude imidazolium salt (C) has a powdery form having a volume-average particle diameter of 0.01-10 mm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a method for purifying an imidazolium salt by removing impurities by extraction using a solvent.

Imidazolium salts have uses that are used in pharmaceuticals, agricultural chemicals, electrolytes, etc., but particularly when used as electrolytes for electrochemical capacitors such as electric double layer capacitors, high purity (for example, 99% by weight or more) It is required to be. As a method of purifying imidazolium salt with high purity, a method of precision distillation of imidazole compound as a precursor, a method of purifying imidazolium salt by recrystallization method, etc., methanol and ethanol are added and distilled by distillation. Along with this, there is a method of removing moisture. (See Patent Documents 1 and 2).
However, the precision distillation method has a problem that it is difficult to separate impurities having a small boiling point difference generated during the synthesis of the imidazole compound, and even if the impurities can be separated, the yield is lowered.
Further, the recrystallization method has a problem that a reaction product of a solvent and an imidazolium salt used at the time of dissolution by heating is generated, and the resulting crystal has low purity, high moisture, and low yield.
From the above viewpoint, there is no known industrial method for obtaining an imidazolium salt that requires a particularly high purity in a high yield.
JP2003-335739 JP 2000-277125 A

That is, the objective of this invention is providing the manufacturing method of the imidazolium salt which can obtain a highly purified imidazolium salt with a high yield.

The present invention extracts from a crude imidazolium salt (C) containing an impurity (e) using a solvent (d) in which the solubility of the imidazolium salt (D) in 100 g of the solvent at the extraction temperature is 0.2 to 20 g. The method for producing an imidazolium salt (D), wherein the impurity (e) is removed and purified by the method.

According to the production method of the present invention, a high-purity imidazolium salt can be obtained in a high yield.

As for the solvent (d) used for this invention, the solubility of the imidazolium salt (D) with respect to the solvent 100g at 25 degreeC is 0.2-20g. Preferably it is 0.3-10g, Most preferably, it is 0.5-5g. When the solubility is less than 0.2 g, the extraction effect cannot be sufficiently obtained, and a high-purity imidazolium salt (D) cannot be obtained. Moreover, when solubility is larger than 20 g, a yield will worsen or it will melt | dissolve completely and a high purity imidazolium salt (D) will not be obtained. Examples of the solvent (d) include monohydric alcohol (d1) having 2 to 8 carbon atoms, ketone (d2) having 4 to 10 carbon atoms, dialkyl carbonate ester (d3) having 4 to 10 carbon atoms, and 4 to 4 carbon atoms. 10 ethers (d4), C3-C9 monocarboxylic acid alkyl esters (d5) and the like are preferable. At least one solvent (d) can be used.

Examples of the monohydric alcohol (d1) having 2 to 8 carbon atoms include ethanol, isopropyl alcohol, n-propyl alcohol, t-butyl alcohol, i-butyl alcohol, n-butyl alcohol, s-butyl alcohol, and t-amyl. Examples include alcohol, 2-ethylhexanol, cyclopentanol, and cyclohexanemethanol. From the viewpoint of the purity and yield of the imidazolium salt (D) after extraction, a monohydric alcohol having 2 to 4 carbon atoms is more preferable. Particularly preferred are ethanol and isopropyl alcohol.

Examples of the ketone (d2) having 4 to 10 carbon atoms include ethyl methyl ketone, diethyl ketone, di n-propyl ketone, diisopropyl ketone, methyl isobutyl ketone, acetophenone, cyclopentanone, and cyclohexanone. From the viewpoint of the purity and yield of the imidazolium salt (D) after extraction, a dialkyl ketone having 4 to 6 carbon atoms is more preferable. Particularly preferred is ethyl methyl ketone.

Examples of the dialkyl carbonate (d3) having 4 to 10 carbon atoms include ethyl methyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, and di-n-butyl carbonate. From the viewpoint of the purity and yield of the imidazolium salt (D) after extraction, a C 4-6 dialkyl carbonate is more preferred. Particularly preferred is ethyl methyl carbonate.

Examples of the ether having 4 to 10 carbon atoms (d4) include diethyl ether, di-n-propyl ether, diisopropyl ether, tetrahydrofuran and the like. From the viewpoint of the purity and yield of the imidazolium salt (D) after extraction, an alkyl ether having 4 to 6 carbon atoms is more preferable. Particularly preferred is diethyl ether.

Examples of the monocarboxylic acid alkyl ester (d5) having 3 to 9 carbon atoms include ethyl formate, n-propyl formate, isopropyl formate, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate and the like. From the viewpoint of the purity and yield of the imidazolium salt (D) after extraction, a C 3-5 monocarboxylic acid alkyl ester is more preferable. Particularly preferred are ethyl formate and methyl acetate.

In the method for producing the imidazolium salt (D) of the present invention, the method for synthesizing the imidazolium salt is not particularly limited, but the imidazolium salt is synthesized in the following steps, and the crude imidazolium is extracted by extraction using the solvent (d). A production method for removing the impurity (e) from the lithium salt (C) is preferred.
Step (1): A step of obtaining imidazole (A) by cyclization reaction of glyoxal, aldehyde, ammonia and, if necessary, primary amine.
Step (2): A step of quaternizing the imidazole (A) to obtain an imidazolium salt (B).
Step (3): A step of replacing the counter anion with the acid anion by adding an acid to the imidazolium salt (B) to obtain a crude imidazolium salt (C).
Step (4): A step of removing the impurity (e) from the crude imidazolium salt (C) by extraction using the solvent (d) and then distilling off the solvent to obtain the imidazolium salt (D).
The details of the production method can be performed in accordance with, for example, the method described in JP-A-2004-207451.

The imidazolium salt (D) in the present invention is preferably a compound represented by the following general formula (1). .

[R ¹ , R ² and R ³ are alkyl groups having 1 to 6 carbon atoms, and may be the same or different. R ⁴ and R ⁵ are each an alkyl group having 1 to 6 carbon atoms or a hydrogen atom, and may be the same or different. X ⁻ is a counter anion. ]

Examples of the cation of the imidazolium salt (D) include the following cations.

(1) 1,2,3-position-substituted 1,2,3-trimethylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-methyl-2-ethyl-3-methylimidazolium, 1,2 -Diethyl-3-methylimidazolium, 1,3-diethyl-2-methylimidazolium, 1,2,3-triethylimidazolium, 1-propyl-2,3-dimethylimidazolium and 1-isopropyl-2,3 -Dimethylimidazolium and the like.

(2) 1,2,3,4-position substituted 1,2,3,4-tetramethylimidazolium, 1-ethyl-2,3,4-trimethylimidazolium, 2-ethyl-1,3,4 Trimethylimidazolium, 1,2-diethyl-3,4-dimethylimidazolium, 1,3-diethyl-2,4-dimethylimidazolium, 1,2,3-triethyl-4-methylimidazolium, 1,2, 3-trimethyl-
4-ethylimidazolium, 1,4-diethyl-2,3-dimethylimidazolium, 2,
4-diethyl-1,3-dimethylimidazolium, 1,2,4-triethyl-3-methylimidazolium, 1,3,4-triethyl-2-methylimidazolium, 1,2,3,4
-Tetraethylimidazolium, 1-propyl-2,3,4-trimethylimidazolium, 1-isopropyl-2,3,4-trimethylimidazolium and the like.

(3) 1,2,3,5-position substitution product 1,2,3,5-tetramethylimidazolium, 1-ethyl-2,3,5-trimethylimidazolium, 1,2-diethyl-3,5- Dimethylimidazolium, 1,5-diethyl-2,3-dimethylimidazolium, 1,2,5-triethyl-3-methylimidazolium, 1-propyl-2,3,5-trimethylimidazolium and 1-isopropyl- 2,3,5-trimethylimidazolium and the like.

(4) 1,2,3,4,5-position substitution product 1,2,3,4,5-pentamethylimidazolium, 1-ethyl-2,3,4,5-tetramethylimidazolium, 2-ethyl -1,3,4,5-tetramethylimidazolium, 3-ethyl-1,2,4,5-tetramethylimidazolium, 4-ethyl-1,2,3,5-tetramethylimidazolium, 1, 2,3,4,5-pentaethylimidazolium, 1-propyl-2,3,4,5-tetramethylimidazolium, 1-isopropyl-2,3,4,5-tetramethylimidazolium and the like. 1,2,3-trimethylimidazolium, 1,3-dimethyl-2-ethylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1,2,3-triethylimidazolium, 1,2-dimethyl- 3-propylimidazolium, 1,2,3,4-tetramethylimidazolium, 1,3,4-trimethyl-2-ethylimidazolium, 1,3-dimethyl-2,4-diethylimidazolium, 1,2 -Dimethyl-3,4-diethylimidazolium, 1-methyl-2,3,4-triethylimidazolium, 1,2,3,4-tetraethylimidazolium and the like.

Among imidazolium salts (D), an imidazolium cation, for example, 1-ethyl-2,3, in which at least one of R ₁ , R ₂ and R ₃ is a different alkyl group in general formula (1) It is more preferable to apply the production method of the present invention to dimethylimidazolium and cations which are 1,2,3-trimethylimidazolium and 1,2,3,4-tetramethylimidazolium.

Further, the counter anion X ^{− of} the imidazolium salt (D) is PF ₆ ⁻ , BF ₄ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , N (RfSO ₃ ) ₂ ⁻ , C (RfSO ₃ ) ₃ ⁻ and RfSO ₃ ^−. (Rf is a fluoroalkyl group having 1 to 12 carbon atoms) in the imidazolium salt (D) is at least one selected from the group consisting of, it is preferable to apply the production method of the present invention, the counter anion wherein X ^-, More preferably, it is applied to an imidazolium salt (D) which is PF ₆ ⁻ or BF ₄ ^— .

The crude imidazolium salt (C) in the present invention is an imidazolium salt (D) containing an impurity (e). The impurity (e) mainly includes impurities (e1) to (e3) and the like.

The impurity (e1) is represented by the general formula (2), and is the step (1) described above in which the glyoxal, aldehyde, and ammonia, and if necessary, the primary amine is cyclized to obtain the imidazole (A). The by-produced imidazole compound having hydrogen at the 2-position is a compound reacted in step (2) and step (3).

[Wherein, R ¹ , R ³ , R ⁴ , R ⁵ and X ⁻ are the same as those in the general formula (1). ]

Impurities (e2) and (e3) are imidazolium compounds represented by the general formulas (3) and (4), respectively, and having a carboxyl group by-produced from the imidazole (A) in the step (2) described above.

[Wherein, R ⁶ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Y ¹ is a carboxy (—CO ₂ H) group or a carboxyoxy (—OCO ₂ H) group, and Y ² is a carboxylate (—CO ₂ ⁻ ) group or a carboxylateoxy (—OCO ₂ ⁻ ) group. R ¹ , R ³ , R ⁴ and X ⁻ are the same as those in the general formula (1). ]

[Wherein R ¹ , R ⁶ , R ³ , X ⁻ , Y ¹ , Y ² are the same as those in the general formula (3). ]

The crude imidazolium salt (C) may be solid or liquid, but is preferably solid. In addition, even if the extraction process is a solid-liquid extraction in which extraction is performed in a solid state (C), the extraction is performed in a state where (C) is in a liquid state or (C) is melted from a solid into a liquid state. Liquid-liquid extraction may be performed, but solid-liquid extraction is preferred.

When the crude imidazolium (C) is a solid, it is preferable to use a pulverizer as a pretreatment to form a powder. Examples of the pulverizer include a mesh mill, a turbo mill, a cutter mill, a roll crusher, a wheely pulverizer, a roller mill, a ball mill, a bin mill, a hammer mill, and a centrifugal pulverizer. Among these, a mesh mill, a turbo mill, a cutter mill, a roll crusher, a Wiley grinder, etc., which are shear type grinders are preferable.

From the viewpoint of the purity and productivity of the imidazolium salt (D), the crude imidazolium (C) powder preferably has a volume average particle size of 0.01 to 10 mm. More preferably, the volume average particle diameter is 0.05 to 5 mm, particularly preferably 0.1 to 1 mm.

From the viewpoint of the yield and purity of the imidazolium salt (D), the weight ratio of the solvent (d) to the crude imidazolium salt (C), [weight of the solvent (d)] / [weight of the crude imidazolium salt (C) ] Is preferably 2-20. More preferably, [weight of solvent (d)] / [weight of crude imidazolium salt (C)] is 3 to 15, particularly preferably 4 to 10.

For extraction, an ordinary stainless steel autoclave with a condenser can be used. The crude imidazolium (C) and the solvent (d) are charged, followed by extraction with stirring, followed by filtration, and the solvent is dried under reduced pressure to obtain the imidazolium salt (D). The extraction temperature is usually −10 to 150 ° C., preferably 10 to 130 ° C. The treatment time is usually 0.1 to 50 hours, preferably 0.2 to 30 hours, particularly preferably 0.3 to 10 hours.

After purification by extraction, a method of removing water by adding methanol or a mixed solvent of methanol and ethanol to the imidazole salt (D) and distilling off the methanol or the mixed solvent of methanol and ethanol is preferable. . In this case, the imidazole salt (D) is preferably liquid. By this method, an imidazolium salt (D) having a lower moisture content and higher purity can be obtained.
The mixing ratio (wt%) of the mixed solvent of methanol and ethanol is preferably methanol: ethanol = 100: 0 to 20:80.
The conditions for distilling off methanol or a mixed solvent of methanol and ethanol are preferably a temperature of 65 to 150 ° C. and a pressure of normal pressure to 0 KPa.

  The contents of impurities (e1) to (e3) can be quantified by high performance liquid chromatography (HPLC). The HPLC conditions were: column: packed with polymer-coated filler, mobile phase: phosphate buffer (pH 2-3), flow rate: 0.5 ml / min, detector: UV, temperature: 40 ° C. ( For example, apparatus: 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, perchlorine Sodium acid aqueous solution having a concentration of 100 mmol / l, flow rate: 0.8 ml / min, detector: UV (210 nm), injection amount: 20 μl, column temperature: 40 ° C.). A calibration curve can be prepared using (e1) to (e3) fractionated by preparative HPLC. Further, (e2) and (e3) may be synthesized by reacting (C) with carbon dioxide in an autoclave (Henkel & Cie: D.A.S 1033667 (1958)).

The content of the impurity (e) in the imidazolium salt (D), that is, the total content of the impurities (e1) to (e3) is preferably 2.5% by weight or less, more preferably 1.5% by weight. And particularly preferably 0.5% by weight or less.

In addition, the chemical structure of the imidazolium salt can be specified by a normal organic chemical method, for example, ¹ H-NMR (for example, instrument: AVANCE300 (manufactured by Nippon Bruker), solvent: deuterated dimethyl sulfoxide, Frequency: 300 MHz), ¹⁹ F-NMR (for example, instrument: XL-300 (manufactured by Varian), solvent: deuterated dimethyl sulfoxide, frequency: 300 MHz) and ¹³ C-NMR (for example, instrument: AL-300 (manufactured by JEOL)) , Solvent: deuterated dimethyl sulfoxide, frequency: 300 MHz) and the like.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to this. Hereinafter, unless otherwise specified, “parts” means “parts by weight” and% means% by weight.
The purity of the imidazolium salt in the present invention is defined as 100%-[total content of impurities (e1) + impurities (e2) + impurities (e3)]. For the content of (e1) and the total content of (e2) and (e3), values measured by the following high performance liquid chromatography (HPLC) were used.
In the following production examples and examples, the purity of the imidazolium salt was measured by high performance liquid chromatography (HPLC). The 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 , An 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.
The measurement limit of this measurement method is that the content of (e1) is 0.005% by weight, and the total content of (e2) and (e3) is 0.005% by weight.
The volume average particle diameter was measured with Microtrac HRA9320-X100 (manufactured by Nikkiso Co., Ltd.). The volume average particle diameter is an average value of D50 measured values twice.
Water content was measured by Karl Fischer coulometric titration.
¹ H-NMR was measured with an instrument: AVANCE 300 (manufactured by Nippon Bruker Co., Ltd.), solvent: deuterated dimethyl sulfoxide, frequency: 300 MHz.

Production Example 1
A reaction flask equipped with a stirrer, thermometer, dropping funnel, reflux condenser, and nitrogen gas inlet tube was charged with a mixture of 31 parts of methylamine (70% aqueous solution) and 32 parts of ammonia (28% aqueous solution) and stirred. To a homogeneous solution. While maintaining the temperature at 45 ° C. or lower, a mixture of 69 parts of glyoxal (40% aqueous solution) and 107 parts of acetaldehyde (30% aqueous solution) was dropped from the dropping funnel. The dropwise addition of the mixed solution of glioxal and acetaldehyde was added dropwise over 5 hours, and after completion of the addition, the mixture was reacted at 40 ° C. for 1 hour. Next, dehydration was performed by gradually reducing the pressure from 80 ° C. and normal pressure to 5.0 kPa, followed by rough purification by simple distillation at a temperature of 105 ° C. and a pressure of 1.0 kPa to obtain 1,2-dimethylimidazole. Obtained. The purity was 94.2%.
Next, 100 parts of 1,2-dimethylimidazole obtained in a stainless steel autoclave with a reflux condenser, 135 parts of dimethyl carbonate, and 192 parts of methanol were charged and uniformly dissolved. Next, the temperature was raised to 130 ° C. The reaction was performed at a pressure of 0.8 MPa for 80 hours. ¹ H-NMR analysis of the reaction product revealed that 1,2,3-trimethylimidazolium monomethyl carbonate was produced. 395 parts of the resulting reaction mixture was placed in a flask, and 207 parts of a borohydrofluoric acid aqueous solution (purity 42% by weight) was gradually added dropwise over about 30 minutes at room temperature with stirring. Carbon dioxide gas was generated along with the dripping. After generation | occurrence | production of foam | bubble was stopped, the reaction liquid was moved to the rotary evaporator and the whole quantity of solvent was removed. In the flask, 81 parts of a tan transparent liquid remained. As a result of ¹ H-NMR analysis of this solution, the main component was 1,2,3-trimethylimidazolium tetrafluoroborate (hereinafter abbreviated as TMI · BF ₄ ), and the purity was 91.1% from HPLC analysis. there were.

Production Example 2
The same operation was performed except that 235 parts of HPF ₆ aqueous solution (purity 62%) was used in place of 207 parts (purity 42% by weight) of the aqueous borofluoric acid solution of Example 1. 83 parts of a yellowish brown transparent liquid substance was obtained, and this liquid was analyzed by ¹ H-NMR. As a result, the main component was 1,2,3-trimethylimidazolium hexafluorophosphate (hereinafter abbreviated as TMI · PF ₆ ). Yes, purity was 91.1% by HPLC analysis.

Production Example 3
A reaction flask equipped with a stirrer, thermometer, dropping funnel, reflux condenser, and nitrogen gas inlet tube was charged with a mixture of 31 parts of ethylamine (70% aqueous solution) and 32 parts of ammonia (28% aqueous solution) while stirring. A homogeneous solution was obtained. While maintaining the temperature at 45 ° C. or lower, a mixed solution of 69 parts of glyoxal (40% aqueous solution) and 71 parts of acetaldehyde (30% aqueous solution) was dropped from the dropping funnel. The dropwise addition of the mixed solution of glioxal and acetaldehyde was added dropwise over 5 hours, and after completion of the addition, the mixture was reacted at 40 ° C. for 1 hour. Next, dehydration was performed by gradually reducing the pressure from 80 ° C. and normal pressure to 5.0 kPa, followed by rough purification by simple distillation under the conditions of 105 ° C. and 1.0 kPa, and 1-ethyl-2-methyl Imidazole was obtained. The purity was 95.0%.
Next, 100 parts of 1-ethyl-2-methylimidazole obtained in a stainless steel autoclave with a reflux condenser, 135 parts of dimethyl carbonate, and 192 parts of methanol were charged and uniformly dissolved. Next, the temperature was raised to 130 ° C. The reaction was performed at a pressure of 0.8 MPa for 80 hours. ¹ H-NMR analysis of the reaction product revealed that 1-ethyl-2,3-dimethylimidazolium monomethyl carbonate was produced. 427 parts of the resulting reaction mixture was placed in a flask, and 207 parts of a borohydrofluoric acid aqueous solution (purity 42% by weight) was gradually added dropwise over about 30 minutes at room temperature with stirring. Carbon dioxide gas was generated along with the dripping. After generation | occurrence | production of foam | bubble was stopped, the reaction liquid was moved to the rotary evaporator and the whole quantity of solvent was removed. In the flask, 82 parts of a yellowish brown transparent liquid remained. As a result of ¹ H-NMR analysis of this liquid, the main component was 1-ethyl-2,3-dimethylimidazolium tetrafluoroborate (hereinafter abbreviated as EDMI · BF ₄ ), and the purity was 91.7 from HPLC analysis. %Met.

Example 1
TMI · BF ₄ prepared in Production Example 1 was pulverized with a turbo mill. The volume average particle diameter of the powder was 0.32 mm. 10 parts of this powder and 50 parts of ethanol were placed in a SUS autoclave and extracted at 25 ° C. with stirring for 2 hours. After filtration under an atmosphere of a dew point of -35 ° C. to prevent this process was a hygroscopic powder was removed under reduced pressure at 120 ° C., to obtain a TMI · BF ₄ in ethanol was distilled off. The yield was 79%. According to HPLC analysis, the purity was 99.7% and the water content was 130 ppm. The solubility of TMI · BF _{4 in} 100 g of ethanol at 25 ° C. was 3.9 g, and [weight of solvent (d)] / [weight of crude imidazolium salt (C)] was 5.

Example 2
TMI · BF ₄ prepared in Production Example 1 was pulverized with a turbo mill. The volume average particle diameter of the powder was 0.32 mm. 10 parts of this powder and 80 parts of methyl ethyl ketone were charged into a SUS autoclave and extracted with stirring at 25 ° C. for 2 hours. The treated product was filtered under an atmosphere with a dew point of −35 ° C. to prevent moisture absorption, and then the powder was taken out and methyl ethyl ketone was distilled off under reduced pressure at 120 ° C. to obtain TMI · BF ₄ . The yield was 83%. According to HPLC analysis, the purity was 99.2% and the water content was 150 ppm. The solubility of TMI · BF _{4 in} 100 g of methyl ethyl ketone at 25 ° C. was 2.1 g, and [weight of solvent (d)] / [weight of crude imidazolium salt (C)] was 8.

Example 3
TMI · BF ₄ prepared in Production Example 1 was pulverized with a turbo mill. The volume average particle diameter of the powder was 0.21 mm. 10 parts of this powder and 80 parts of ethyl methyl carbonate were charged into a SUS autoclave and extracted with stirring at 25 ° C. for 2 hours. The treated product was filtered under an atmosphere having a dew point of -35 ° C. to prevent moisture absorption, and then the powder was taken out, and ethyl methyl carbonate was distilled off under reduced pressure at 120 ° C. to obtain TMI · BF ₄ . The yield was 75%. According to HPLC analysis, the purity was 99.0% and the water content was 180 ppm. The solubility of TMI · BF _{4 in} 100 g of ethyl methyl carbonate at 25 ° C. was 3.0 g, and [weight of solvent (d)] / [weight of crude imidazolium salt (C)] was 8.

Example 4
TMI · BF ₄ prepared in Production Example 1 was pulverized with a turbo mill. The volume average particle diameter of the powder was 0.21 mm. 10 parts of this powder and 60 parts of isopropyl alcohol were charged into a SUS autoclave and extracted with stirring at 25 ° C. for 2 hours. The treated product was filtered under an atmosphere with a dew point of −35 ° C. to prevent moisture absorption, and then the powder was taken out and isopropyl alcohol was distilled off under reduced pressure at 120 ° C. to obtain TMI · BF ₄ . The yield was 81%. According to HPLC analysis, the purity was 99.3% and the water content was 200 ppm. The solubility of TMI · BF _{4 in} 100 g of isopropyl alcohol at 25 ° C. was 3.0 g, and [weight of solvent (d)] / [weight of crude imidazolium salt (C)] was 6.

Example 5
The TMI · PF ₆ prepared in Production Example 2 was pulverized with a turbo mill. The volume average particle diameter of the powder was 0.45 mm. 10 parts of this powder and 60 parts of ethanol were placed in a SUS autoclave and extracted with stirring at 25 ° C. for 2 hours. The treated product was filtered under an atmosphere having a dew point of −35 ° C. to prevent moisture absorption, and then the powder was taken out, and ethanol was distilled off under reduced pressure at 120 ° C. to obtain TMI · PF ₆ . The yield was 71%. According to HPLC analysis, the purity was 99.6% and the water content was 140 ppm. The solubility of TMI · PF _{6 in} 100 g of ethanol at 25 ° C. was 4.5 g, and [weight of solvent (d)] / [weight of crude imidazolium salt (C)] was 6.

Example 6
The EDMI · BF ₄ prepared in Production Example 3 was pulverized with a turbo mill. The volume average particle diameter of the powder was 0.61 mm. 10 parts of this powder and 60 parts of ethanol were placed in a SUS autoclave and extracted with stirring at 25 ° C. for 2 hours. After filtration under an atmosphere of a dew point of -35 ° C. to prevent this process was a hygroscopic powder was removed under reduced pressure at 120 ° C., to obtain a EDMI · BF ₄ in ethanol was distilled off. The yield was 70%. According to HPLC analysis, the purity was 99.6% and the water content was 140 ppm. The solubility of EDMI · BF _{4 in} 100 g of ethanol at 25 ° C. was 4.8 g, and [weight of solvent (d)] / [weight of crude imidazolium salt (C)] was 6.

Example 7
The EDMI · BF ₄ prepared in Production Example 3 was pulverized with a turbo mill. The volume average particle diameter of the powder was 0.61 mm. 10 parts of this powder and 60 parts of isopropyl alcohol were charged into a SUS autoclave and extracted with stirring at 25 ° C. for 2 hours. After filtration under an atmosphere of a dew point of -35 ° C. to prevent this process was a hygroscopic powder was removed under reduced pressure at 120 ° C., to obtain a EDMI · BF ₄ and evaporated isopropyl alcohol. The yield was 75%. According to HPLC analysis, the purity was 99.1% and the water content was 180 ppm. The solubility of EDMI · BF _{4 in} 100 g of isopropyl alcohol at 25 ° C. was 4.0 g, and [weight of solvent (d)] / [weight of crude imidazolium salt (C)] was 6.

Example 8
The EDMI · BF ₄ prepared in Production Example 3 was pulverized with a turbo mill. The volume average particle diameter of the powder was 0.61 mm. 10 parts of this powder and 60 parts of methyl ethyl ketone were charged into a SUS autoclave and extracted with stirring at 25 ° C. for 2 hours. The treated product was filtered under an atmosphere with a dew point of −35 ° C. to prevent moisture absorption, and then the powder was taken out and methyl ethyl ketone was distilled off under reduced pressure at 120 ° C. to obtain EDMI · BF ₄ . The yield was 83%. According to HPLC analysis, the purity was 99.1% and the water content was 170 ppm. The solubility of EDMI · BF _{4 in} 100 g of methyl ethyl ketone at 25 ° C. was 2.5 g, and [weight of solvent (d)] / [weight of crude imidazolium salt (C)] was 6.

Example 9
The EDMI · BF ₄ prepared in Production Example 3 was pulverized with a turbo mill. The volume average particle diameter of the powder was 0.61 mm. 10 parts of this powder and 80 parts of n-butyl alcohol were placed in a SUS autoclave and extracted in a liquid-liquid state with stirring at 105 ° C. for 2 hours. The lower layer was taken out and n-butyl alcohol was distilled off under reduced pressure at 120 ° C. to obtain EDMI · BF ₄ . The yield was 72%. According to HPLC analysis, the purity was 99.0% and the water content was 170 ppm. The solubility of EDMI · BF _{4 in} 100 g of n-butyl alcohol at 25 ° C. was 0.5 g, and [weight of solvent (d)] / [weight of crude imidazolium salt (C)] was 8. .

Comparative Example 1
TMI · BF ₄ prepared in Production Example 1 was pulverized with a turbo mill. The volume average particle diameter of the powder was 0.21 mm. 10 parts of this powder and 80 parts of a mixed solvent of diethyl ether and acetone were charged into a SUS autoclave and stirred at 25 ° C. for 1 hour. The solvent weight% was 25% diethyl ether and 75% acetone. After becoming a uniform solution, the solution was cooled to −15 ° C. and allowed to stand for 10 hours, whereby crystals were precipitated. The crystals were filtered under an atmosphere having a dew point of −35 ° C. to prevent moisture absorption, and then the solvent was distilled off under reduced pressure at 120 ° C. to obtain TMI · BF ₄ . The yield was 52%. According to HPLC analysis, the purity was 96.9% and the water content was 350 ppm.

Comparative Example 2
The EDMI · BF ₄ prepared in Production Example 3 was pulverized with a turbo mill. The volume average particle diameter of the powder was 0.61 mm. 10 parts of this powder and 80 parts of a mixed solvent of ethyl acetate and acetone were charged into a SUS autoclave and stirred at 25 ° C. for 1 hour. The solvent weight% was 25% ethyl acetate and 75% acetone. After becoming a uniform solution, the solution was cooled to −15 ° C. and allowed to stand for 10 hours, whereby crystals were precipitated. The crystals were filtered under an atmosphere having a dew point of −35 ° C. to prevent moisture absorption, and then the solvent was distilled off under reduced pressure at 120 ° C. to obtain EDMI · BF ₄ . The yield was 52%. According to HPLC analysis, the purity was 97.3% and the water content was 320 ppm.

Comparative Example 3
TMI · BF ₄ prepared in Production Example 1 was pulverized with a turbo mill. The volume average particle diameter of the powder was 0.32 mm. 10 parts of this powder and 80 parts of methanol were charged into a SUS autoclave and stirred at 25 ° C. for 2 hours. The treated product was completely dissolved and became a solution. Methanol was distilled off from this treated product under reduced pressure at 120 ° C. to obtain TMI · BF ₄ . The yield was 98%. According to HPLC analysis, the purity was 91.8% and the water content was 360 ppm. The solubility of TMI · BF _{4 in} 100 g of methanol at 25 ° C. was 100 g or more, and [weight of solvent (d)] / [weight of crude imidazolium salt (C)] was 8.

Comparative Example 4
TMI · BF ₄ prepared in Production Example 1 was pulverized with a turbo mill. The volume average particle diameter of the powder was 0.32 mm. 10 parts of this powder and 80 parts of n-octane were charged into a SUS autoclave and stirred at 25 ° C. for 2 hours. The treated product was filtered under an atmosphere having a dew point of −35 ° C. to prevent moisture absorption, and then the powder was taken out and n-octane was distilled off under reduced pressure at 120 ° C. to obtain TMI · BF ₄ . The yield was 98%. According to HPLC analysis, the purity was 93.1% and the water content was 490 ppm. The solubility of TMI · BF _{4 in} 100 g of n-octane at 25 ° C. was 0.1 g or less, and [weight of solvent (d)] / [weight of crude imidazolium salt (C)] was 8. .

The imidazolium salts (D) of Examples 1 to 9 and Comparative Examples 1 to 4 of the present invention were diluted to 1 mol / l with propion carbonate to prepare electrolytic solutions 1 to 9 and comparative electrolytic solutions 1 to 4. Using these various electrolytes, coin-type electrochemical capacitors were produced and the rate of change in equivalent series resistance was evaluated.

Rate of change in equivalent series resistance When an electrochemical capacitor is applied with a voltage of 2.5 V at 80 ° C. for 1000 hours, the equivalent series resistance (RE1000) of the electrochemical capacitor at 1 kHz and the equivalent series resistance at 1 kHz before voltage application ( The ratio with respect to RE0) was calculated by the following equation, and this was defined as the rate of change of the equivalent series resistance. The equivalent series resistance was measured at 25 ° C. using an impedance analyzer (Solartron SI1253, SI1286). This rate of change means that the smaller the value, the smaller the deterioration of performance over time, and the better charge / discharge characteristics can be maintained.
(Equivalent Series Resistance Change Rate) (%) = [(RE1000) / (RE0)] × 100

  Table 1 shows the experimental results of the purity and yield of the imidazolium salts (D) of Examples 1 to 9 and Comparative Examples 1 to 4, and the equivalent series resistance change rate of the electrochemical capacitors. From Table 1, it was found that according to the present invention, a high-purity imidazolium salt (D) can be obtained in a high yield. In addition, since the imidazolium salt (D) obtained by this production method has high purity, it is possible to produce an electrolytic solution for an electrochemical element having a small equivalent series resistance change rate, that is, extremely little deterioration in performance over time. all right.

Since the imidazolium salt obtained by the production method of the present invention has a high yield and high purity, it is used as an intermediate for producing an electrolytic solution for electrochemical elements, particularly an electrolytic solution for electrochemical capacitors, pharmaceuticals, agricultural chemicals, and dyes. It is useful as a resin curing agent such as epoxy resin and polyurethane resin.

Claims (6)

Impurities (e) are extracted by extraction from crude imidazolium salt (C) containing impurities (e) using solvent (d) having a solubility of imidazolium salt (D) of 0.2 to 20 g in 100 g of solvent at 25 ° C. ) Is removed and purified, and a method for producing an imidazolium salt (D). The production method according to claim 1, wherein the crude imidazolium salt (C) is a powder and the volume average particle diameter thereof is 0.01 to 10 mm. The weight ratio of the solvent (d) to the crude imidazolium salt (C), [Weight of the solvent (d)] / [Weight of the crude imidazolium salt (C)] is 2 to 20, 3. Production method. The manufacturing method of any one of Claims 1-3 which consists of a process including the following processes.
Step (1): A step of obtaining imidazole (A) by cyclization reaction of glyoxal, aldehyde, ammonia and, if necessary, primary amine.
Step (2): A step of quaternizing the imidazole (A) to obtain an imidazolium salt (B).
Step (3): A step of replacing the counter anion with the acid anion by adding an acid to the imidazolium salt (B) to obtain a crude imidazolium salt (C).
Step (4): A step of removing the impurity (e) from the crude imidazolium salt (C) by extraction using the solvent (d) and then distilling off the solvent to obtain the imidazolium salt (D). The solvent (d) is a monohydric alcohol (d1) having 2 to 8 carbon atoms, a ketone (d2) having 4 to 10 carbon atoms, a dialkyl carbonate (d3) having 4 to 10 carbon atoms, or an ether having 4 to 10 carbon atoms. The production method according to any one of claims 1 to 4, which is at least one selected from the group consisting of (d4) and a C3-9 monocarboxylic acid alkyl ester (d5). At least the cation of the imidazolium salt (D) is selected from the group consisting of 1-ethyl-2,3dimethylimidazolium, 1,2,3-trimethylimidazolium, and 1,2,3,4-tetramethylimidazolium It is 1 type, The manufacturing method of any one of Claims 1-5.