JP2002053532A - Method for purifying quaternary ammonium salt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for simply and efficiently purifying a quaternary ammonium salt. SOLUTION: This method for purifying the quaternary ammonium salt is characterized by recrystallizing the quaternary ammonium salt in a mixed solvent containing at least one kind of alcohol and at least one kind of chain carbonate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for purifying a quaternary ammonium salt, and more particularly to a method for recrystallizing a quaternary ammonium salt using a specific solvent in combination.

[0002]

2. Description of the Related Art Quaternary ammonium salts are widely used as electrolytes for electronic components such as electric double layer capacitors and aluminum electrolytic capacitors. In this application, the quaternary ammonium salt is required to have a high purity, and in particular, to have a low impurity water content. Therefore, a method for producing a quaternary ammonium salt having a small amount of by-products such as water, or
There is a need for a purification method for efficiently removing the by-products.

[0003] The purification of quaternary ammonium salts is mainly carried out by recrystallization from alcohol. However, in the case of alcohol, it is difficult to isolate crystals and remove impurity moisture, and the recrystallization efficiency (crystal weight / charged weight × 100%) is poor.

[0004]

Accordingly, an object of the present invention is to provide a method for purifying a quaternary ammonium salt simply and efficiently.

[0005]

SUMMARY OF THE INVENTION Surprisingly, it has been found that the above object can be achieved by using a specific solvent in combination as a recrystallization solvent. That is, the present invention is a method for purifying a quaternary ammonium salt, comprising recrystallizing a quaternary ammonium salt in a mixed solvent containing at least one alcohol and at least one chain carbonate.

Preferred embodiments of the present invention further include the following. (1) The alcohol is methanol, ethanol, n-propanol, i-propanol, n-butanol, sec
-The method for purifying a quaternary ammonium salt, wherein the method is at least one selected from the group consisting of butanol. (2) The method for purifying a quaternary ammonium salt, wherein the chain carbonate is at least one selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. (3) The method for purifying the quaternary ammonium salt, wherein the alcohol and the chain carbonate are used in a weight ratio of 2:98 to 98: 2.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The quaternary ammonium salt used in the method of the present invention is represented by the general formula [R ₁ R ₂ R ₃ R ₄ N] ⁺ X ⁻ . The type and manufacturing method are not particularly limited. Preferably, in the above formula, R _{1 to} R ₄ independently of one another have 1 to 1 carbon atoms.
It is an aliphatic, alicyclic or aromatic hydrocarbon group having 20 and more preferably an alkyl group having 1 to 6 carbon atoms.
Also, any two of R _{1 to} R ₄ may form a ring. Examples of these compounds include triethylmethylammonium, tetraethylammonium, diethyldimethylammonium, ethyltrimethylammonium, dimethylpyrrolidinium, diethylpyrrolidinium, ethylmethylpiperidinium, N-methylpiperidinium.

X in the above equation^-As BF_Four ^-, PF₆ ^-, CF
_ThreeSO_Three ^-, SiF₆ ^2-, SiF_Five ^-, ClO_Four ^-, SO _ThreeF^-, Acetic acid, propylene
Aliphatic monocarboxylic acid ions such as on-acid and butyric acid, malon
Acid, maleic acid, succinic acid, glutaric acid, adipic acid, etc.
Of aliphatic dicarboxylic acid ions, benzoic acid, phthalic acid, etc.
Examples thereof include aromatic carboxylate ions. Above all, B
F _Four ^-, PF₆ ^-, ClO_Four ^-, Maleate ion, or phthalic acid
Ions are preferred for electrolyte applications.

The process according to the invention is characterized in that a combination of at least one alcohol and at least one linear carbonate is used as a recrystallization solvent. The alcohol and the chain carbonate may be used so as to finally become a mixed solvent. That is, first, a mixed solvent of an alcohol and a chain carbonate is prepared, and then a quaternary ammonium salt is dissolved in the mixed solvent, or a quaternary ammonium salt is first added to the alcohol, and a predetermined amount of The carbonates may be added or vice versa. By using a combination of an alcohol and a chain carbonate as a recrystallization solvent, crystals having a low water content and which can be easily isolated by filtration or decantation are 90% or more, preferably 94% or more.
With a recrystallization efficiency of

The alcohol preferably used in the present invention includes an alcohol having a hydrocarbon residue having 1 to 12 carbon atoms, preferably an alkyl group, and more preferably methanol, ethanol, n-propanol, i-propanol. -At least one selected from the group consisting of propanol, n-butanol and sec-butanol.

The chain carbonate preferably used in the present invention is a compound represented by the following formula: R ₁ O— (C ＝ O) —OR ₂ (where R ₁ and R ₂ are independently of each other) A hydrocarbon residue having 1 to 6 carbon atoms), and more preferably at least one selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0012] A plurality of types of alcohols and chain carbonates may be used respectively. The mixing ratio of all alcohols and all chain carbonates can be appropriately optimized depending on the type of the quaternary ammonium salt, but is usually 2: 2 by weight.
98-98: 2, preferably 5: 95-95: 5, more preferably 50:
50-95: 5.

Furthermore, conventional solvents other than alcohols and chain carbonates may be added in amounts which do not impair the object of the invention. For example, halogenated hydrocarbons, aliphatic hydrocarbons, aromatic hydrocarbons, ethers, esters, ketones, amides, amines, nitriles, nitros,
Examples include sulfite-based, sulfoxide-based, sulfone-based, and phosphate-based solvents and water.

In the present invention, recrystallization can be carried out according to a known method, for example, a method utilizing a difference in solubility of a quaternary ammonium salt due to a temperature difference. That is, the quaternary ammonium salt is added to the mixed solvent if necessary.
Heat to about 40-50 ° C to dissolve and leave to cool to room temperature. After the crystals have grown sufficiently, the crystals are isolated by filtration or decantation and dried under vacuum. According to the method of the present invention, the amount of water initially contained in about 100 ppm is reduced to less than 20 ppm.

The quaternary ammonium salt obtained in the present invention is
At a concentration of about 0.2 to 2.5 mol / l, for example, ethylene carbonate, propylene carbonate, γ-butyrolactone, sulfolane, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, It is dissolved in a solvent such as 1,2-dibutoxyethane and ethoxymethoxyethane, and is suitable for use as an electrolyte for electronic components.

The present invention also relates to a method for using the above electrolyte as an electrolyte for a capacitor. The configuration of the capacitor, for example, the positive electrode, the negative electrode, and the separator is not particularly limited, and may be a known configuration. As the positive electrode and the negative electrode, for example, a sheet obtained by mixing activated carbon into a sheet and an aluminum foil collector electrode can be used.As the separator, cellulose, or a microporous nonwoven fabric such as glass can be used. Can be used. The capacitor in the present invention, a separator sandwiched between the positive electrode and the negative electrode, stacked in the case of a square cell, or wound in the case of a cylindrical cell, then impregnated with the electrolytic solution, and finally Can be made by sealing. As the capacitor, an electric double layer capacitor and an aluminum electrolytic capacitor are preferable.

[0017]

The present invention will be described below with reference to examples. In the examples, the water content was measured by the Karl Fischer method. Example 1 100 g of triethylmethylammonium tetrafluoroborate (initial water content: 150 ppm) was added to dimethyl carbonate /
The mixture was dissolved by heating and stirring in 300 g of a mixed solvent of ethyl alcohol (weight ratio: 93/7). The resulting solution was left at room temperature. After 5 hours, the solvent was removed by decantation,
The isolated crystals are dried in a vacuum dryer at 50 ° C. and 0.1 mmHg.
And dried for 5 hours. The amount of the obtained crystals was 94.4 g (recovery rate 94.4%), and the water content in the crystals measured by the Karl Fischer method was 14 ppm.

Example 2 As a recrystallization solvent, a mixed solvent of dimethyl carbonate / ethyl alcohol / i-propyl alcohol (weight ratio: 85 /
Example 1 was repeated, except that 5/10) was used.
The amount of crystals obtained was 95.1 g (recovery 95.1%),
The water content in the crystals was 13 ppm.

Example 3 Example 1 was repeated except that a mixed solvent of ethyl methyl carbonate / ethyl alcohol (50/50 by weight) was used as a recrystallization solvent. The amount of crystals obtained was 94.2
g (recovery rate 94.2%), and the water content in the crystals is 14 ppm.
Met.

Example 4 100 g of triethylmethylammonium perchlorate was dissolved in 240 g of a mixed solvent of dimethyl carbonate / i-propyl alcohol (weight ratio 50/50) by heating and stirring. The resulting solution was left at room temperature. After 5 hours, the solvent isolated by decantation of the solvent was dried in a vacuum dryer.
It was dried at 50 ° C. and 0.1 mmHg for 5 hours. The amount of the obtained crystals was 98.1 g (recovery rate 98.1%), and the water content in the crystals was 12 ppm.

Comparative Example 1 100 g of triethylmethylammonium tetrafluoroborate was dissolved in 400 g of ethyl alcohol by heating and stirring. The resulting solution was left at room temperature for 5 hours. The precipitated crystals were flocculent and could not be isolated by decantation, so they were isolated by filtration under reduced pressure. The isolated crystals were dried in a vacuum dryer at 50 ° C. and 0.1 mmHg for 5 hours. The amount of crystals obtained is 96.1 g (recovery rate 96.1%)
And the water content in the crystals was 85 ppm.

Comparative Example 2 The same procedure as in Comparative Example 1 was tried except that dimethyl carbonate was used in place of ethyl alcohol, but the ammonium salt was hardly dissolved and recrystallization could not be performed.

Comparative Example 3 100 g of triethylmethylammonium perchlorate was dissolved in 350 g of ethyl alcohol by heating and stirring. The resulting solution was left at room temperature for 5 hours. The precipitated crystals were flocculent and could not be isolated by decantation, so they were isolated by filtration under reduced pressure. The isolated crystals were dried in a vacuum dryer at 50 ° C. and 0.1 mmHg for 5 hours. The amount of the obtained crystals was 97.7 g (recovery rate 97.7%), and the water content in the crystals was 65 ppm.

According to the method of the present invention, a quaternary ammonium salt can be efficiently purified by a simple method. The quaternary ammonium salt obtained by the method of the present invention has a low water content and is suitable as an electrolyte for capacitors and the like.

Claims (1)

[Claims] 1. A method for purifying a quaternary ammonium salt, comprising recrystallizing a quaternary ammonium salt in a mixed solvent containing at least one alcohol and at least one chain carbonate.