KR101130793B1 - Ionic Liquid and Method for Preparing Other Ionic Liquid Using the Same - Google Patents

Abstract

The present invention relates to a novel ionic liquid and a method for producing another ionic liquid using the same. More specifically, the present invention provides a separate purification for separating impurities such as halogens by preparing ionic liquids containing various carboxylate anions and other ionic liquids which are commonly reacted with strong acids to produce these ionic liquids. It relates to an effective ionic liquid synthesis method that does not require a process. According to the present invention, the hydrophilic or hydrophobic ionic liquid can be obtained according to the selection of the carboxylic acid anion, and the ionic liquid can be economically prepared by using an acid having a low raw material cost instead of the expensive salt used in the conventional ionic liquid manufacturing. Can be synthesized.

Ionic Liquid, Carboxylic Acid, Ethylhexanoate, Butylmethylimidazolium

Description

Novel Ionic Liquid and Method for Preparing Ionic Liquid Using the Same

The present invention relates to a novel ionic liquid and a method for producing another ionic liquid using the same. More specifically, the present invention provides an effective method for synthesizing ionic liquids which does not require a separate purification process by preparing ionic liquids containing various carboxylate anions and other ionic liquids generally known using the ionic liquids. It is about.

Ionic liquids that maintain a liquid state over a wide range of temperatures, including room temperature, are drawing attention as a useful reaction medium for chemical processes in that they can be reused, including chemical and thermal stability.

Room temperature ionic liquids based on 1,3-dialkylimidazolium cations were first reported by Wilkes et al. In 1982. This ionic liquid has chloroaluminate anions and has many useful properties such as wide liquid range, thermal stability and wide electronic window, but it reacts with specific materials and is very sensitive to moisture. Air and water stable ionic liquids were developed by Wilkes and Zaworotko on the basis of tetrafluoroborate anions in 1992 (Wilkes, JS; Zaworotko, MJ J. Chem. Soc., Chem. Commun ., 1992, 965: Scheme 1).

Scheme 1

In addition, a wide range of ionic liquids with other anions have been reported. Various ionic liquid preparation methods described in the prior art literature can be summarized as in Schemes 2 to 5 below.

Scheme 2 : J. Electrochem. Soc ., Vol 144, 1997

Scheme 3 : Huddleston, JG; Willauer, HD; Swatloski, RP; Visser; AE; Rogers, RD Chem. Commun . 1998, 1765

Scheme 4 : KRSeddon et al., WO 01/40146, June 7, 2001

Scheme 5 : KRSeddon, et al., WO 01/77081, 2001

In the case of the reaction schemes 2 to 4, when a fluoroester compound or an alkylsulfonate is used as a synthesis method of an ionic liquid which does not generate impurities such as residual halogen ions and alkali metal impurities, the used acid remains May have undesired chemical reactivity.

In the case of Scheme 5, using carbene, there is a problem of productivity in the scale-up step and requires an expensive device.

Ionic liquids are salts of cations and anions. The most common ionic liquids are in the form of alkylimidazolium, alkylphosphonium, N-alkylpyridinium, N, N'-dialkylimidazolium cations, These cations usually use large molecules to have a low melting point. As anions, [PF ₆ ], [BF ₄ ], [SbF ₆ ], [TfO] (triplate), [NfO] (nona triplate), [TA] (trifluoroacetate), [Tf ₂ N] (Bis (tripleyl) amide) and the like are used. In general, the physical properties of ionic liquids are determined by the anions, and the choice of anions is a very important factor in changing the physical and chemical properties of ionic liquids. In addition, the price of the anion is very expensive, and most of the halogen is substituted, there is a problem to release the halide upon decomposition.

Halogenized impurities and alkali metal impurities are generated when synthesizing known ionic liquids. In particular, halogen ions are not easily solvent-bonded with components of the ionic liquid and are not easily removed from the ionic liquid. Such halogenic impurities and alkali metal impurities are increased in the amount of inexpensive acids or metal salts in the synthesis of the ionic liquid. Contamination by halogen impurities and alkali metal impurities in the ionic liquid is a problem that must be solved when attempting to use the ionic liquid as a reaction solvent on a large scale. For example, when using ionic liquids as solvents in transition metal catalysis, halogen ions with strong covalent forces resulted in decreased catalyst activity. In many reactions, halogen ions are oxidized to halogens by the reactants, which in turn can cause corrosion of the reactor. Residual halogen ions affect the intrinsic physical properties of ionic liquids, affect the density, flowability, and electrical properties of ionic liquids and, if used as solvents, affect the reactivity ( Pure appl. Chem . (2000). 72 (12), 2275-2287).

The solubility of water in ionic liquids is determined by the anion: ionic liquids having [PF ₆ ], [Ntf ₂ ] and [SbF ₆ ] as anions are fat-soluble, [BF ₄ ], [OTf] (tree Plates), ionic liquids having acetate, lactate, borate compounds, sulfonate compounds as anions are water soluble ( J. Phys. Chem B , vol 105, No. 44, 2001). Fat-soluble ionic liquids are not soluble in water and can be washed with water to remove halogenic impurities effectively.However, water-soluble ionic liquids can be washed with water simply because they are soluble in water (JOC 1999. 2133-2139). It is difficult to remove.

Conventionally, silver tetrafluoroborate was used or reacted with propanone to remove residual halogen ions and alkali metal ions from a water-soluble ionic liquid. However, this method is expensive and scale-up process. Is difficult to effectively remove halogen ions ( J. Electrochem. Soc. , 1997. 144. 3881).

In addition, as described above, a fluoroester compound or an alkylsulfonate and a carbene may be used as a method of synthesizing an ionic liquid which does not generate impurities such as residual halogen ions and alkali metal impurities. The acid can be used to retain the unwanted chemical reactivity and the latter has the disadvantage of productivity in the scale-up step and requires expensive equipment.

Accordingly, the present inventors have tried to solve these shortcomings, and have thus prepared an ionic liquid composed of an anion which is a general cation and a carboxylic acid derivative. By varying the substituents of the carboxylic acid derivatives, the properties of the ionic liquid may be adjusted to be hydrophilic or hydrophobic. In addition, when the ionic liquid developed by the present inventors is used as an intermediate and reacted with a strong acid, an ionic liquid generally known as an economic method can be synthesized with high purity. The synthesis method not only generates halogen impurities, but also uses a low-cost acid as a synthetic raw material, and the acid formed as a by-product has the property of not mixing with water and an ionic liquid, and thus can be easily removed by separation or washing. In this paper, we propose an economical method for synthesizing ionic liquids.

It is an object of the present invention to provide an ionic liquid comprising a carboxylic acid derivative anion.

Another object of the present invention is to provide a method for preparing a known ionic liquid by reacting an ionic liquid with an acid.

The present invention relates to a novel ionic liquid consisting of cations and anions of carboxylic acid derivatives. An ionic liquid according to the present invention is represented by the following formula (1).

Formula 1

[Q] ⁺ _n A ^n-

Wherein Q ⁺ is a cation as pyridinium, pyridazinium, pyrimidinium, pyrazinium, imidazolium, pyrazolium, thiazolium, oxazolium, triazium, pyrrolidinium, ammonium, phosphonium or derivatives thereof Cations, including, but not limited to. Most preferably Q is butylmethylimidazolium. The cations include a wide range of cations of generally known ionic liquids. Examples of cations are as follows.

Wherein R, R ', R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ are the same as or different from each other, H; F; An alkyl group having 1 to 18 carbon atoms; An alkyl group which is converging with N (nitrogen) and alkylene having 2 to 4 carbon atoms to form a ring;

Yes:                     

Phenyl group; And an electron-withdrawing group substituted with the alkyl group, the alkylene group, and the phenyl group.

A ^n- is an anion of the carboxylic acid derivative represented by the following formula (2):

Formula 2

Wherein R is a C ₅ -C ₁₇ alkyl group or a C ₅ -C ₁₇ aryl group, preferably a linear alkyl group in which R is C ₅ -C ₁₇ , and most preferably R is a 2-alkyl substituted C _5- It is a C ₁₇ alkyl group. Most preferably A is 2-ethylhexanoate.

In Formula 1, n is an integer of 1 or more.

The ionic liquid according to the present invention may have various physical and chemical properties by changing the substituent of the carboxylic acid derivative which is an anion, and the synthesized ionic liquid has high thermal stability and wide liquid phase range (66 to 250 ° C). ).

In addition, the ionic liquid according to the present invention is a high-purity product having no halogen atoms in the molecule, and thus is a new use of the ionic liquid, which has recently been spotlighted as a secondary battery, a lithium secondary battery, a lithium polymer battery, a storage battery, a special battery, a solar cell. It can be applied as an electrolyte and the like, and there is no halide involved in the reaction in the molecule, so it can be used as a solvent of various chemical reactions.

Another embodiment of the present invention is a method for producing another ionic liquid using the ionic liquid represented by Chemical Formula 1.

In the present invention, the ionic liquid of Formula 1 is reacted with a strong acid to prepare an ionic liquid in which a carboxylic acid derivative anion is substituted with a strong acid. Strong acids are HPF ₆ , HBF ₄ , CF ₃ SO ₃ H, HNO ₃ , CH ₃ COOH and the like, of which HPF ₆ and HBF ₄ are most preferred.

Therefore, the production method according to the present invention provides a method for industrially mass production of ionic liquids using carboxylic acid derivatives which are inexpensive and can be easily separated after the reaction is completed.

One embodiment according to the invention is shown in Scheme 6 below.                     

Scheme 6

According to the known art, a separate purification process is required to remove residual halogen from the ionic liquid, but according to the present invention, since no halogen is generated from the synthesis step, a separate purification process is not necessary. Therefore, an economical and high purity ionic liquid can be obtained.

In order to illustrate the advantages of the present invention, two kinds of ionic liquid ethylmethylimidazolium tetrafluoroborate ([emim] [BF ₄ ]) and butylmethylimidazolium prepared by the known technique are shown in Table 1 below. In order to remove the halogen remaining in the tetrafluoroborate ([(bmim)] [BF ₄ ]), the content of residual chlorine and the yield of the ionic liquid by the number of purification was shown.

[emim] [BF ₄ ] [bmim] [BF ₄ ] Number of times Residual Cl (ppm) Yield (%) Number of times Residual Cl (ppm) Yield (%) One 1220 85 One 604 95 2 505 72 2 152 89 3 214 60 3 47 83 4 84 52 4 18 71 5 42 43 5 10 62 6 28 36 6 7 58 7 14 31 7 4 55 8 7 27 9 5 23

As shown in Table 1, the ionic liquids obtained according to the known technology require 9 cleaning cycles and 7 cleaning cycles to reduce the residual chlorine content to 5 ppm or less, respectively, and the yield of the product decreases as the cleaning process is repeated. It can be seen that. The present invention can obtain an ionic liquid with high purity and high yield in an economical way that does not require such a purification process.

Hereinafter, the present invention will be described in more detail with reference to Examples.

The following examples are intended to illustrate the subject matter of the present invention, and the present invention is not limited thereto.

Example

Example 1: Synthesis of [butylmethylimidazolium] [2-ethylhexanoate]

A salt consisting of 1-butyl-3-methyl-imidazolium and chlorine ([bmim] [Cl]) (82.5 g, 0.47 mol) was added to acetone (700 ml) and stirred. SEH (sodium 2-ethyl-hexanoate) (78.5 g, 0.47 mol) was added to the acid and stirred. The salt formed was removed by filtration and the solvent was removed by distillation. The yield of [1-butyl-3-methyl-imidazolium] [2-ethylhexanoate] as the obtained ionic liquid was 126 g (yield: 95%). The NMR analysis results of the obtained ionic liquid are as follows.

NMR analysis: ¹ H NMR (300 MHz, acetone- d6 ) 0.74 (m, 9H), 1.19 (m, 8H), 1.44 (m, 2H), 1.78 (m, 3H), 1.94 (m, 4H), 3.96 (s, 3H), 4.30 (t, J = 7.4 Hz, 2H), 7.78 (s, 1H), 7.79 (s, 1H)

Example 2: Synthesis of [dimethylethylimidazolium] [2-ethylhexanoate]

Dimethylethylimidazolium bromide ([edmim] [Br]) (50.0 g, 0.23 mol) was added to acetone (700 ml) and stirred. SEH (38.1 g, 0.23 mol) was added thereto and stirred. The salt formed was removed by filtration and the solvent was removed by distillation. The yield of [dimethylethylimidazolium] [2-ethylhexanoate] as the obtained ionic liquid was 62 g (yield: 95%). The NMR analysis results of the obtained ionic liquid are as follows.

NMR analysis: ¹ H NMR (300 MHz, acetone- d6 ) 0.89 (m, 6H), 1.24 (m, 7H), 1.58 (m, 4H), 2.04 (s, 3H), 2.27 (m, 1H), 3.96 (s, 3H), 4.34 (q, J = 5.3 Hz, 2H), 7.73 (s, 1H), 7.76 (s, 1H)

Example 3: Synthesis of [butylmethylpyridium] [2-ethylhexanoate]

Butylmethylpyridium bromide ([Bmpy] [Br]) (50.0 g, 0.23 mol) was added to acetone (700 ml) and stirred. SEH (38.1 g, 0.23 mol) was added thereto and stirred. The salt formed was removed by filtration and the solvent was removed by distillation. The yield of [butyl methyl pyridium] [2-ethylhexanoate] as the obtained ionic liquid was 62 g (yield: 95%). The NMR analysis results of the obtained ionic liquid are as follows.

NMR analysis: ¹ H NMR (300 MHz, acetone- d6 ) 0.90 (m, 6H), 1.24 (m, 4H), 1.46 (m, 3H), 1.60 (m, 4H), 1.94 (m, 4H), 2.29 (s, 4H), 2.27 (m, 1H), 3.21 (s, 3H), 3.69 (m, 6H).

Example 4: Synthesis of [butylmethylimidazolium] [2-ethyl-octanoate]

Butylmethylimidazolium chloride ([bmim] [Cl]) (50.0 g, 0.28 mol) was added to acetone (400 ml) and stirred. SEO (sodium 2-ethyl-octanoate) (55.3 g, 0.28 mol) was added thereto and stirred. The salt formed was removed by filtration and the solvent was removed by distillation. The yield of [butyl methyl imidazolium] [2-ethyloctanoate] as the obtained ionic liquid was 81 g (yield: 93%).

Examples 5 and 6 below relate to a method for preparing another ionic liquid by reacting an ionic liquid containing a carboxylic acid derivative anion with an acid, and a schematic reaction process is as follows. As can be seen below, according to the present invention, the carboxylic acid derivative (ethylhexanoate) which is not mixed with water is obtained as a by-product, which is advantageous in that it is easy to separate from the ionic liquid and can be reused.

Example 5: [Butylmethylimidazolium] [hexafluorophosphate] ([bmim] [PF ₆ Synthesis of

[1-butyl-3-methyl-imidazolium] [2-ethylhexanoate] (17 g, 0.060 mol) obtained in Example 1 was dissolved in water and 60% HPF ₆ (7.97 ml, 0.054 mol) was dissolved. Put in. After stirring the reaction solution for 30 minutes, the lower layer [bmim] [PF ₆ ] (density> 1) was separated. The yield of [butyl methyl imidazolium] [hexafluorophosphate] obtained was 16 g (yield: 95%). The NMR analysis results of the obtained ionic liquid are as follows.

NMR: ¹ H NMR (300 MHz, acetone- d6 ) 0.59 (t, J = 7.3 Hz, 3H), 1.05 (m, 2H), 1.58 (m, 2H), 3.69 (s, 3H), 3.99 (t, J = 7.3 Hz, 2H), 7.32 (s, 1H), 7.38 (s, 1H), 8.58 (s, 1H)

Example 6: [butylmethylimidazolium] [tetrafluoroborate] ([bmim] [BF ₄ Synthesis of

[1-butyl-3-methyl-imidazolium] [2-ethylhexanoate] (42.4 g, 0.15 mol) obtained in Example 1 was dissolved in 1/3 to 1 (V / W) of water and 54 % HBF ₄ (18.6 ml, 0.13 mol) was added. After the reaction solution was stirred for 30 minutes, the aqueous layer and the [bmim] [BF ₄ ] mixed solution were separated from the resulting EHA layer. The aqueous layer was washed three times with EA (50 ml) to remove residual EHA. The aqueous layer was treated at 150 ° C./high vacuum to completely remove water and residual EHA. The yield of [butyl methyl imidazolium] [tetrafluoroborate] obtained was 32 g (yield: 94%). The NMR analysis results of the obtained ionic liquid are as follows.

NMR: ¹ H NMR (300 MHz, acetone- d6 ) 0.92 (t, J = 7.3 Hz, 3H), 1.37 (m, 2H), 1.89 (m, 2H), 4.00 (s, 3H), 4.31 (t, J = 7.3 Hz, 2H), 7.66 (s, 1H), 7.72 (s, 1H), 8.94 (s, 1H)

The present invention provides a novel ionic liquid containing a carboxylic acid derivative anion and a known method of preparing an ionic liquid using the same. According to the present invention, an ionic liquid having various physical and chemical properties can be synthesized by changing substituents of an anionic carboxylic acid derivative, and the synthesized ionic liquid has high thermal stability and a wide liquid phase range (66 to 250). ℃). The carboxylic acid anion constituting the ionic liquid of the present invention is easy to purchase and very inexpensive, thereby providing an economical ionic liquid.

In addition, the ionic liquid according to the present invention is a high-purity product having no halogen atoms in the molecule, and thus is a new use of the ionic liquid, which has recently been spotlighted as a secondary battery, a lithium secondary battery, a lithium polymer battery, a storage battery, a special battery, a solar cell. It can be applied as an electrolyte and the like, there is no halide involved in the reaction in the molecule can be applied as a solvent in various chemical reactions.

When the ionic liquid according to the present invention is reacted with a strong acid, an ionic liquid including a known halide can be easily prepared. Since a carboxylic acid derivative is obtained as a by-product after the reaction, it is not mixed with water and washed with an organic solvent if necessary. It can be easily removed by using a high-temperature decompression device. It is very weak acid, so it is environmentally friendly in that there is no harm in use and no special facilities or neutralization facilities are required in the process.

Claims (6)

An ionic liquid of formula Formula 1 [Q] ⁺ _n A ^n- Wherein Q ⁺ is a cation of imidazolium or pyridium, A ^n- is an anion of the carboxylic acid derivative represented by the following formula (2), and Formula 2

Wherein R is a C ₅ -C ₁₇ alkyl group or a C ₅ -C ₁₇ aryl group n is an integer of 1 or more. The ionic liquid of claim 1, wherein Q is 1-butyl-3-methylimidazolium and A is a carboxylic acid derivative wherein R is a linear alkyl group having C ₅ -C ₁₇ . The ionic liquid of claim 1, wherein Q is 1-butyl-3-methylimidazolium and A is 2-ethylhexanoate.

The ionic liquid of claim 1, wherein Q is 1-butyl-3-methylpyridium and A is 2-ethylhexanoate.

A method of preparing 1-butyl-3-methylimidazolium hexafluorophosphate by reacting an ionic liquid of Formula 1 with a strong acid: Formula 1 [Q] ⁺ _n A ^n- Wherein Q ⁺ is a cation of imidazolium or pyridium, A ^n- is an anion of a carboxylic acid derivative represented by the following formula,

Wherein said strong acid is HPF ₆ . A method for preparing 1-butyl-3-methylimidazolium tetrafluoroborate by reacting an ionic liquid of Formula 1 with a strong acid: Formula 1 [Q] ⁺ _n A ^n- Wherein Q ⁺ is a cation of imidazolium or pyridium, A ^n- is an anion of a carboxylic acid derivative represented by the following formula,

Wherein said strong acid is HBF ₄ .