JP2011219387A - Method for producing ionic liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an ionic liquid that achieves low halogen concentration while reducing the production cost.SOLUTION: In the method for producing an ionic liquid having a carboxylate anion, a cation exchange resin is used. The cation of the ionic liquid is at least one selected from the group consisting of an ammonium ion, an imidazolium ion, an imidazolinium ion, a pyridinium ion, a pyrrolidinium ion, a pyrrolinium ion, a pyrazinium ion, a pyrimidinium ion, a triazonium ion, a triazinium ion, etc., and derivatives thereof.

Description

  The present invention relates to a method for producing an ionic liquid.

  An ionic liquid is a compound composed of a combination of a cation such as imidazolium and an appropriate anion, and has excellent functions such as high ionic conductivity, flame retardancy, non-volatility, and high thermal stability. Recently, it has been suitably applied to electrochemical device applications such as electrolytic capacitors, secondary battery electrolytes, and dye-sensitized solar cells. High specifications are required for items such as these. Among them, very strict specifications are required for the halogen concentration.

  Hydrophilic ionic liquids, like hydrophobic ionic liquids, cannot perform halide removal by washing with water. Therefore, if a halide is mixed in, it is very difficult to remove it. Therefore, in order to obtain a hydrophilic ionic liquid having a low halogen concentration, it must be synthesized by a prescription that does not contain halogen other than the salt exchange method that is generally used. Examples of such a synthesis method include an acid ester method, a carbonate method, and an acid-base neutralization method.

  The acid ester method is a method in which an organic acid ester is directly reacted with a tertiary amine to onium salt and simultaneously supply a counter anion (Non-patent Document 1). However, if the reaction does not proceed 100%, the raw material is ionized as an impurity. There is a problem that it remains in the liquid, and in particular, when an ester of a carboxylic acid that is a weak acid is used, the reaction often does not proceed 100%, so this is a useful synthesis method in terms of obtaining a high-purity ionic liquid. There is no such thing.

The carbonate method is a method for obtaining a quaternary ammonium salt via an alkyl carbonate as an intermediate, and is a reaction comprising two steps of a quaternization reaction and a neutralization decarboxylation reaction. The first step is, for example, a step of methylating a tertiary amine with dimethyl carbonate to obtain a methyl ammonium carbonate salt, and the second step is to generate CO ₂ by causing various organic acids to act on the methyl ammonium carbonate salt. This is a process of allowing the anion exchange reaction to proceed (Patent Document 1). However, in the first step of this synthesis method, high temperature and high pressure are required to advance the quaternization reaction, and it is expensive to prepare equipment for carrying out the reaction. There is a problem that costs are also increased. In addition, as a useful synthesis tool in that the carbonate method can be easily performed, a methanol solution of methyl ammonium salt “CBILS (Carbonated Based Ionic Liquids Synthesis)” (manufactured by Sigma-Aldrich) is commercially available. However, since it is a very expensive reagent, it is not suitable for mass synthesis in consideration of production costs.

  The acid-base neutralization method is a method of neutralizing a base that is an onium cation with an acid. For example, a method of producing an ionic liquid by dissolving an alkyl imidazolium bromide salt in an aqueous solvent, then converting the alkyl imidazolium bromide salt into an alkyl imidazolium hydroxide salt by passing it through an anion exchange resin, and reacting this with a specific amino acid Is disclosed (Patent Document 2). However, in addition to the ion-exchange resin tower for the reaction to obtain the alkyl imidazolium hydroxide salt, a reaction kettle for reacting the alkyl imidazolium hydroxide salt with an amino acid is required, which increases the production cost. . Further, the onium hydroxide salt that is an intermediate is unstable depending on the cation, and the applicable cation is limited. Therefore, it cannot be said that it is a technique that can synthesize a wide variety of ionic liquids.

Japanese Patent Laid-Open No. 10-17554 Japanese Patent No. 4261223

Hiroyuki Ohno et al., 27 others, "Ionic liquids-the forefront and future of development"

  The objective of this invention is providing the manufacturing method of the ionic liquid which implement | achieved low halogen concentration while reducing manufacturing cost.

  As a result of intensive studies in view of the above, the present inventors have produced an ionic liquid having a carboxylate anion using a cation exchange resin, and compared with the conventional acid ester method, carbonate method, and acid-base neutralization method. Thus, it is possible to reduce the manufacturing cost and the number of reaction steps, and it has been found that an ionic liquid having a low halogen concentration that satisfies the specifications of an electrolyte for electrochemical devices can be produced without performing special purification, and the present invention is completed. It came.

  That is, the present invention provides the following general formula (1):

(Wherein R ¹ and R ² are each independently a hydrogen atom, a protected or unprotected hydroxyl group, a protected or unprotected amino group, an alkoxy group, a nitro group, a cyano group, a carboxyl group, a halogen atom, C _1- alkyl C _20, C ₂ ~C ₂₀ alkenyl group, C ₂ -C ₂₀ alkynyl group, an aryl group of C ₆ -C _20, heteroaryl group of C ₄ -C _20, aralkyl C ₇ -C ₂₀ Or a C _{4 to} C ₂₀ heteroaralkyl group, wherein the alkyl group, alkenyl group, alkynyl group, aryl group, aralkyl group, heteroaryl group and heteroaralkyl group may have a substituent, A method of producing an ionic liquid having an anion represented by the following formula, which uses a cation exchange resin.

  In the method for producing an ionic liquid of the present invention, the cation of the ionic liquid is ammonium ion, imidazolium ion, imidazolinium ion, pyridinium ion, pyrrolidinium ion, pyrrolium ion, pyrazinium ion, pyrimidinium ion, triazo Nium ion, triazinium ion, triazine ion, quinolinium ion, isoquinolinium ion, indolinium ion, quinoxalinium ion, piperazinium ion, oxazolinium ion, thiazolinium ion, morpholinium ion, It is preferably at least one selected from the group consisting of piperazine ions and derivatives thereof.

  In the method for producing an ionic liquid of the present invention, it is preferable to ion-exchange the compound having an anion represented by the general formula (1) and the compound having a cation in the presence of a cation exchange resin.

  According to the method for producing an ionic liquid of the present invention, an ionic liquid having a low halogen concentration can be produced economically.

  Hereinafter, embodiments of the present invention will be described in detail.

  The production method of the present invention is a method for producing an ionic liquid having an anion represented by the general formula (1).

  An ionic liquid, which is also referred to as a room temperature molten salt, refers to a liquid that is liquid at room temperature despite being composed only of ions. For example, it is composed of a combination of a cation such as imidazolium and an appropriate anion. In general, it is considered that the ionic liquid is formed only from ions and is 100% ionized.

In the general formula (1), R ¹ and R ² are each independently a hydrogen atom, a protected or unprotected hydroxyl group, a protected or unprotected amino group, an alkoxy group, a nitro group, a cyano group, a carboxyl group, a halogen atom, C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl group, C ₂ -C ₂₀ alkynyl group, an aryl group of C ₆ -C _20, heteroaryl group of C ₄ ~C _20, C ₇ ~C _{20 represents} an aralkyl group or a C _{4 to} C ₂₀ heteroaralkyl group. The alkyl group, alkenyl group, alkynyl group, aryl group, aralkyl group, heteroaryl group and heteroaralkyl group may have a substituent, and may form a straight chain, a branch or a ring. “It may have a substituent” means that it may be substituted with another atom or substituent. The “substituent” is not particularly limited as long as it does not adversely affect the reaction. Specifically, the hydroxyl group, alkyl group, alkoxy group, alkylthio group, nitro group, amino group, cyano group, carboxyl group, A halogen atom etc. are mentioned.

  As the hydroxyl-protecting group, a general protecting group can be used, and examples thereof include those described in “PROTECTIVE GROUPS in ORGANIC SYNTHESIS THIRD EDITION” (page 17 WILEY-INTERSCIENCE). Specifically, alkyl group such as methyl group and ethyl group, ether type protective group such as methoxymethyl group, methylthiomethyl group, trimethylsilyl group and triethylsilyl group, and ester type protective group such as acetyl group and chloroacetyl group are included. Can be mentioned.

  As the protecting group for the amino group, a general protecting group can be used, and examples include those described in “PROTECTIVE GROUPS in ORGANIC SYNTHESIS THIRD EDITION” (page 494, WILEY-INTERSCIENCE). Specifically, benzyl group, trityl group, formyl group, acetyl group, chloroacetyl group, tetrachloroacetyl group, tetrafluoroacetyl group, benzoyl group, phenylacetoxy group, methoxycarbonyl group, ethoxycarbonyl group, 9-fluorene group. Examples thereof include a nylmethoxycarbonyl group and a t-butoxycarbonyl group. From the viewpoint of ease of introduction and deprotection, benzyl group, trityl group, formyl group, acetyl group, chloroacetyl group, tetrachloroacetyl group, tetrafluoroacetyl group, benzoyl group, phenylacetoxy group, 9-fluorenylmethoxy A carbonyl group or a t-butoxycarbonyl group is preferred.

The alkyl group of C ₁ -C _20, for example a methyl group, a hydroxymethyl group, an ethyl group, n- propyl group, an isopropyl group, a cyclopropyl group, n- butyl group, sec- butyl group, tert- butyl group, cyclobutyl Group, n-pentyl group, cyclopentyl group, n-hexyl group, cyclohexyl group, n-heptyl group, n-octyl group, n-decyl group, etc., and these alkyl groups such as trifluoromethyl group Examples include those in which any number of hydrogen atoms are substituted with fluorine atoms.

The alkenyl group of C ₂ -C _20, for example, vinyl group, propenyl group, a styryl group, an isopropenyl group, a cyclopropenyl group, a butenyl group, a cyclobutenyl group, cyclopentenyl group, cyclohexenyl group, and cyclohexenyl group .

The alkynyl groups of C ₂ -C _20, for example, ethynyl group, propynyl group, phenylethynyl group, a cyclopropyl ethynyl, butynyl group, pentynyl group, cyclobutyl ethynyl group, a hexynyl group.

Examples of the C _{6 to} C ₂₀ aryl group include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, a terphenyl group, and a 3,4,5-trifluorophenyl group.

Examples of the C _{4 to} C ₂₀ heteroaryl group include a pyrrolinyl group, a pyridyl group, a quinolyl group, an imidazolyl group, a furyl group, an indolyl group, a thienyl group, an oxazolyl group, a thiazolyl group, 2-phenylthiazolyl, 2- And anisyl thiazolyl group.

Examples of the C ₇ -C ₂₀ aralkyl group include benzyl group, chlorobenzyl group, bromobenzyl group, salicyl group, α-hydroxybenzyl group, phenethyl group, α-hydroxyphenethyl group, naphthylmethyl group, anthracenylmethyl. Group, 3,5-difluorobenzyl group, trityl group and the like.

Examples of the C _{4 to} C ₂₀ heteroaralkyl group include a pyridylmethyl group, a difluoropyridylmethyl group, a quinolylmethyl group, an indolylmethyl group, a furfuryl group, and a thienylmethyl group.

  The anion represented by the general formula (1) is paired with a cation to form an ionic liquid.

  Cations include ammonium and its derivatives, imidazolium and its derivatives, pyridinium and its derivatives, pyrrolidinium and its derivatives, pyrrolinium and its derivatives, pyrazinium and its derivatives, pyrimidinium and its derivatives, triazonium and its derivatives, triazinium and its derivatives, Triazine and its derivatives, quinolinium and its derivatives, isoquinolinium and its derivatives, indolinium and its derivatives, quinoxalinium and its derivatives, piperazinium and its derivatives, oxazolinium and its derivatives, thiazolinium and its derivatives, morpholinium and its derivatives, piperazine and its And derivatives thereof.

  The method for producing an ionic liquid according to the present invention is characterized by using a cation exchange resin. This makes it possible to reduce manufacturing costs and the number of reaction steps compared to conventional methods, and ions with a carboxylate anion with a low halogen concentration that meet the specifications of electrolytes for electrochemical devices without special purification. Liquid can be easily obtained.

  The cation exchange resin generally used can be used for the cation exchange resin used for the manufacturing method of this invention. For example, Amberlite IR120B (H) and Amberjet 1020H (trade name, manufactured by Organo Corporation) can be used.

  In the production method of the present invention, a compound having a cation paired with an anion represented by the general formula (1) (hereinafter sometimes simply referred to as “compound having an anion”) and a cation exchange resin are reacted. It is preferable that the process (henceforth "process (A)") may be included. In this step (A), it is preferable to combine the cation-containing compound with the cation exchange resin, and a form including such a step is one of the preferred forms of the present invention. The term “bond” as used herein means a state in which bonds are formed by covalent bonds, ionic bonds, coordination bonds, bonds between molecules, interactions between molecules, and the like. preferable.

  As the step (A), it is preferable to use a cation exchange resin as a stationary phase, thereby enabling mass synthesis and reducing the halogen concentration of the ionic liquid obtained after the step (B) described later. . In this case, as the step (A), it is preferable that the compound having a cation is passed through a column having a cation exchange resin as a stationary phase and brought into contact with the cation exchange resin. When passing through the column, the compound having a cation is dissolved in pure water or an organic solvent such as an alcohol, but it is preferable to use pure water because of the solubility of the compound having a cation. In addition, the reaction temperature when the compound having a cation is allowed to flow is generally higher because the exchange rate with the cation exchange resin is improved, but the boiling point of the solvent to be used and the heat resistance temperature of the resin are preferred. In consideration, 0 to 100 ° C. is preferable, and 10 to 85 ° C. is more preferable.

  Thus, after the cation paired with the anion represented by the general formula (1) is bonded to the end of the side chain of the cation exchange resin, it is contained in the resin by thoroughly washing with pure water or the like. Impurities and halogens can be removed, and as a result, an ionic liquid with high purity and low halogen concentration can be obtained.

  Examples of the compound having a cation used in the step (A) include ammonium and derivatives thereof, imidazolium and derivatives thereof, pyridinium and derivatives thereof, pyrrolidinium and derivatives thereof, pyrrolium and derivatives thereof, pyrazinium and derivatives thereof, pyrimidinium and derivatives thereof. Derivatives, triazonium and derivatives thereof, triazinium and derivatives thereof, triazine and derivatives thereof, quinolinium and derivatives thereof, isoquinolinium and derivatives thereof, indolinium and derivatives thereof, quinoxalinium and derivatives thereof, piperazinium and derivatives thereof, oxazolinium and derivatives thereof, thiazolinium and derivatives thereof Its derivatives, morpholinium and its derivatives, piperazine and its salts used However, the form of the cation is preferably a halide, carbonate, alkyl sulfate, sulfate, or carboxylate, and a halide or carboxylate is preferable in view of the exchange rate with the cation exchange resin. .

  In the production method of the present invention, after the step (A), the compound having an anion represented by the general formula (1) is passed through the cation exchange resin prepared in the step (A), and the ionic liquid which is the target compound is obtained. It is preferable that the process (henceforth a process (B)) obtained is included. In the step (B), a cation exchange resin prepared by adjusting the “compound having an anion represented by the general formula (1)” (hereinafter sometimes simply referred to as “compound having an anion”) in the step (A) is fixed. The target ionic liquid can be obtained by passing the solution through a phase column. The anionic compound used is represented by the following general formula (2):

(X represents a hydrogen atom or a salt represented by at least one metal atom selected from an alkali metal atom, an alkaline earth metal atom, a transition metal atom, and a rare earth metal atom). X represents a hydrogen atom or at least one metal atom selected from an alkali metal atom, an alkaline earth metal atom, a transition metal atom, and a rare earth metal atom, and is bonded to the cation exchange resin prepared in the step (A). In view of the exchange rate with the cation moiety, Na, K, Mg, and Ca are preferable.

  In the step (B), the reaction is carried out by passing a compound having an anion through the one in which the cation moiety is bound to the cation exchange resin in the step (A). When the liquid is passed, the compound having an anion is dissolved in pure water or an organic solvent such as an alcohol, but it is preferable to use pure water because of the solubility of the compound having an anion. In addition, the reaction temperature at the time of passing the compound having an anion is generally higher because the exchange rate with the cation exchange resin is improved, but the boiling point of the solvent to be used and the heat resistance temperature of the resin are preferred. In consideration, 0 to 100 ° C. is preferable, and 10 to 85 ° C. is more preferable.

  Hereinafter, the present invention will be described more specifically with reference to examples.

(Measurement of ¹ H NMR)
The nuclear magnetic resonance spectrum ( ¹ H NMR) was measured with a deuterated chloroform solution using Gemini 300 (300 MHz for 1H) manufactured by VARIAN. The chemical shift was expressed as a δ value (ppm) with tetramethylsilane (TMS) as an internal standard. The following abbreviations were used for the signal division mode, and expressed as s = singlet, d = doublelet, t = triplet, q = quartet, m = multiplet.

(Halogen analysis method)
In the halogen analysis method, pretreatment was performed by a combustion tube combustion method using QF-02 made by Dia Instruments, and then ion chromatography using ICS-2000 made by Dionex (columns are IonPac AG18, AS18 (4 mmφ × 250 mm)). A graph measurement was performed, and the measurement was performed with a lower limit of 5 ppm.

Example 1
A chromatography column tube was filled with Amberjet 1020 (H) (trade name, manufactured by Organo Corporation) to prepare a column, and the column was heated to 83 ° C., and then 5 wt% 1-butyl-3-methylimidazolium chloride aqueous solution ( 330 g, 90 mmol) was passed through SV3.5. The resin was washed with pure water until the pH of the filtrate reached 7 while maintaining the column temperature at 83 ° C., and then a 10 wt% sodium mandelate aqueous solution (155 g, 90 mmol) was passed through SV3.5. The obtained filtrate was concentrated to obtain a pale yellow oily substance with a yield of 84%.

The obtained oil was analyzed for halogen to find Cl: 23 ppm and Br: ND. Further, when analyzed by ¹ H NMR, it was confirmed to be 1-butyl-3-methylimidazolium mandelate of the following formula (hereinafter abbreviated as [BMIm] [Mandelate]).

¹ H NMR (CDCl ₃ , 300 MHz) δ 0.93 (t, 3H), 1.29-1.34 (m, 2H), 1.74-1.79 (m, 2H), 3.84 (s, 3H), 4.10 (t, 2H), 4.92 (s, 1H), 7.04 (s, 1H), 7.14-7.26 (m, 1H), 7.23-7.26 (M, 3H), 7.54 (d, 2H), 10.74 (s, 1H)
Since the sodium mandelate used was Cl: 9.4 ppm, it is considered possible to obtain [BMIm] [Mandelate] having a lower halogen by using halogen-free sodium mandelate.

(Comparative Example 1)
A chromatographic column tube was filled with IRA400 (OH) AG (trade name, manufactured by Organo) (50 mL) to prepare a column, and a 5 wt% 1-butyl-3-methylimidazolium bromide aqueous solution (60 g, 14 mmol) was brought to room temperature. After passing through SV3.5, pure water (60 mL) was further passed to obtain a 1-butyl-3-methylimidazolium hydroxide aqueous solution. A part of the obtained aqueous solution was sampled and subjected to halogen analysis of the residue obtained by concentration. As a result, Cl: 3900 ppm and Br: ND were obtained. After adding pure water (60 mL) to mandelic acid (2.1 g, 14.0 mmol) to make a homogeneous solution, the above 1-butyl-3-methylimidazolium hydroxide aqueous solution was slowly added dropwise thereto at 0 ° C. Stir for 12 hours. The reaction solution was concentrated as it was and dried by heating under reduced pressure to obtain a pale yellow oil with a yield of 98%.

The obtained oil was analyzed for halogen to find Cl: 2300 ppm and Br: ND. Furthermore, was analyzed by ¹ H NMR, was confirmed to be [BMIm] [Mandelate].

  The mandelic acid used was Cl: 25 ppm.

Claims (3)

The following general formula (1):

(Wherein R ¹ and R ² are each independently a hydrogen atom, a protected or unprotected hydroxyl group, a protected or unprotected amino group, an alkoxy group, a nitro group, a cyano group, a carboxyl group, a halogen atom, C _1- alkyl C _20, C ₂ ~C ₂₀ alkenyl group, C ₂ -C ₂₀ alkynyl group, an aryl group of C ₆ -C _20, heteroaryl group of C ₄ -C _20, aralkyl C ₇ -C ₂₀ Or a C _{4 to} C ₂₀ heteroaralkyl group, wherein the alkyl group, alkenyl group, alkynyl group, aryl group, aralkyl group, heteroaryl group and heteroaralkyl group may have a substituent, A method of producing an ionic liquid having an anion represented by the following formula, which uses a cation exchange resin.   The cation of the ionic liquid is ammonium ion, imidazolium ion, imidazolinium ion, pyridinium ion, pyrrolidinium ion, pyrrolinium ion, pyrazinium ion, pyrimidinium ion, triazonium ion, triazinium ion, triazine ion, From the group consisting of quinolinium ion, isoquinolinium ion, indolinium ion, quinoxalinium ion, piperazinium ion, oxazolinium ion, thiazolinium ion, morpholinium ion, piperazine ion and their derivatives The manufacturing method of the ionic liquid of Claim 1 which is at least 1 type selected.   The method for producing an ionic liquid according to claim 1 or 2, wherein the compound having an anion represented by the general formula (1) and the compound having a cation are ion-exchanged in the presence of a cation exchange resin.