A PURIFICATION METHOD OF IONIC LIQUIDS TO OBTAIN THEIR HIGH PURITY Technica ! Fietd The present invention rotates to an ionic liquid purification method for preparing high purity ionic liquids which can be used as solvents for organic, inorganic and biochemical reactions or as electrolytic solutions of storage batteries, secondary batteries, or fuel batteries, by removing organic halide sails, organic sails, haiide residues, acid residues or excess alkali metals from unpurified ionic liquids using liquid/liquid continuous extraction.

Background Art 1, 3-dialkylimidazolium cation based ionic liquids, which are liquid at room temperature, were first reported by Wilkes et al. in 1982. Although these ionic liquids having chloroaluminate anions, have been found to have various advantages, including existence in a liquid phase over a wide range of temperature, thermal stability and wide chemical window, they were proven to be reactive with specific substances and very sensitive to water. As ionic liquids which are stable in air and water, tetrafluoroborate anion based ionic liquids were developed by Wolkes and Zaworotko in 1992. Since then, numerous kinds of ionic liquids having different anions have been reported.

Ionic liquids are salts composed of cations and anions, and the most commonly available ionic liquids exist in the form of salts having alkylammonium, alkylphosphonium, N-alkylpyridinium, N, N'-dialkylimidazolium cations. To offer a low melting point, these cations are usually large molecules.

Examples of the anion useful in ionic liquids include hexafluor phosphate (PF6), hexafluoro antimonite (SbF6), tetrafluoro borate (BF4), triflate (OTf), <BR> <BR> <BR> <BR> nonatriflate (NTfO), trifluoroacetate (TA), bis (trifluorosulfonyl) imide ( Tf2), and the like. Recent research has demonstrated that ionic liquids can be used under room temperature as solvents for a wide range of chemical reactions

including polymerization, hydrogenation, Friedel-Craft acylation and Diels-Alder reaction.

Ionic liquids can serve as substitutes for conventional organic solvents used in chemical reactions for several reasons. Low vapor pressure of the ionic liquid$ is one very important feature. That is, the ionic liquid has negligible vapor pressure and is capable of solving several problems of conventional organic solvents. Although the ionic liquids are very highly polar, they are a very weakly coordinating solvent. Also, some ionic liquids are immiscible with water or organic solvents, and may have a two-phase structure. Owning to their excellent properties as solvents, the ionic liquids can take heterogeneous materials into the same phase. More recently, studies on features and uses of ionic liquids have been available.

Synthesis of ionic liquids is generally achieved by preparing organic halide salts using amine or phosphine and haloalkane and substituting the halides by quantitatively treating the prepared organic halide salt with metallic salts or acid. A method for synthesizing 1, 3-dialkylimidazolium ionic liquid, for example, which has been recently used, is shown in Fig. 3. In detail, 1,3- dialkylimidazolium halide salt is first prepared using 1-alkylimidazole and haloalkane, and then halide is substituted with metallic salt or acid. The substitution is achieved by removing hydrogen-halogen using metallic salt or acid or precipitating in the form of metal-halogen. Alternatively, 1,3- dialkylimidazolium sulfonate or triflate salt may be synthesized using 1- alkylimidazole and alkyl sulfonate or alkyl triflate, followed by substituting with acid. This substitution is performed by distilling and removing hydrogen- sulfonate or hydrogen-triflate using acid.

Major impurities produced during synthesis of ionic liquids are organic halide salts, organic salts, halide residues, acid residues, excess alkali metal or the like. In particular, the halide ions are easily bonded with ionic liquid constituents, making it difficult to completely remove the same from the ionic liquids. Typical examples of the halide include fluoride, chloride, bromide,

and iodine. Examples of the acid residues include hydrogen sulfonate, hydrogen carbonate, trifluoroacetate (triflate), and hydrogen halide, and examples of the alkali metal include potassium, and sodium. In a case where ionic liquids are synthesized using low-priced acid or alkali metal salts, the amount of the organic haiide sa ! ts, organic sails, haiide residues, acid residues, or excess alkali metal, increases.

In order for ionic liquids to be used as solvents for large scale reactions, a contamination problem due to impurities should be solved. For example, when the ionic liquid is used as a solvent in a transition metal catalytic reaction, a halogen ion having a high covalent bonding capability reduces the activity of a catalyst. The halogen ion is oxidized into halogen by reactants, and a reaction device may be eroded by the produced halogen. Also, residual halogen ions have an affect not only intrinsic physical properties but also density, flowability and electrical properties of ionic liquids. Further, when ionic liquids used as solvents of reactions, the halogen ions affect reactivity (Pure appl. chem. (2000). 72 (12), 2275-2287). In a reaction that is very sensitive to halide ions, the amount of halide residues ions in the ionic liquid must be controlled to be not greater than 1,000 ppm, and preferably not greater than 100 ppm. Under a more sensitive reaction condition, the amount of halide residues ions in the ionic liquid must be controlled to be not greater than 30 ppm, most preferably not greater than 5 ppm, and precipitation in the AgNO3 reaction should be avoided.

. Acid residues of the ionic liquid are unnecessary impurities that may participate in the reaction and act as a catalyst. One way of measuring acid residues is to check the pH level of ionic water produced after washing ionic liquids with the ionic water.

The residual metal ions may affect physical, chemical properties of the ionic liquid, and traces of metal ions can be analyzed by elemental analysis or ion chromatography.

The residual impurities make it difficult to use ionic liquids in practice.

Thus, in order to obtain pure ionic liquids to be used as appropriate reaction solvents or additives, purification of ionic liquids is essentially necessary.

One factor making it difficult to purify ionic liquids by a general technique is due to the physical properties of the ionic liquid. The ionic liquid has negligible vapor pressure and exists as a liquid at room temperature due to its low melting point. Also, the ionic liquid is very highly polar, it is dissolved in water very well. In detail, since the ionic liquid has negligible vapor pressure, it cannot be purified by a general purification method. Also, since the ionic liquid has a low melting point, it exists in a liquid phase at room temperature or low temperature, making it difficult to purify the same by recrystallization.

The water solubility of the ionic liquid is determined by anions contained therein. Such anions as hexafluor phosphate (PF6), bis (trifluorosulfonylimide (NTf2), or hexafluor antimonite (SbF6), make the ionic liquid oil-soluble, and such anions as tetrafluoro borate (BF4), triflate (OTf), or acetate (Oac), sulfonate (S03CH3) make the ionic liquid water- soluble (J. Phys. Chem B, vol 105, No. 44,2001). Since the oil-soluble ionic liquid is synthesized using acid or salt and is not dissolved in water, washing the ionic liquids with water can applied to remove halide impurities, alkali metal impurities, or acid residues. This method, however, has a limitation in completely removing acid residues remaining in the ionic liquid to obtain high purity ionic liquids. Since the water-soluble ionic liquid is dissolved in water (JOC 1999.2133-2139), removing impurities by washing with water is disadvantageous in efficacy and yield.

Other conventional attempts to remove halide residues, alkali metal ion, acid residues produced in the course of synthesizing ionic liquids include using silver tetrafluoroborate or reacting in propanone. However, these techniques are not effective and economic because they are costly and several problems may be presented during a scale-up process. Also, trace impurities may remain even aft : er the purification process, disabling attainment of high purity ionic liquids (J. Electrochem. Soc. , 1997.144. 3881). In order to synthesize

ionic liquids without impurities such as halide residues or alkali metal impurity, use of fluoroester compounds or alkylsulfonates, or use of carbene have been proposed. In the former case, however, there is a problem in that the acid residues used may bring undesired chemical readion$. In th@ latter case, a <BR> <BR> <BR> <BR> productivity problem may be presented during a cale-up process and expensive equipment is required.

In order to solve the various problems with conventional purification, the present inventors carried out earnest and constant research into highly efficient and economically effective purification method of ionic liquids. As a result, they developed a commercially large-scale, economically effective and highly efficient purification method for ionic liquids, in which impurities such as organic halide salts, organic salts, halide residues, acid residues, excess alkali metals and so on, are removed using liquid/liquid continuous extraction, thereby completing the present invention.

Disclosure of the Invention It is an object of the present invention to provide a method of economically and efficiently purifying ionic liquids by removing impurities such as organic halide salts, organic salts, halide residues, acid residues, excess alkali metals and so on from unpurified ionic liquids.

It is another object of the present invention to provide a method of preparing ionic liquids with high purity of 95% or greater, which can be used as solvents for organic, inorganic and biochemical reactions or as electrolytic solutions of storage batteries, secondary batteries, or fuel batteries.

In accordance with an aspect of the present invention, there is provided a purification method of ionic liquids, comprising the steps of: preparing a mixed ionic liquid solution by dissolving unpurified ionic liquid in a solvent with ionic water alone or in combination with a cosolvens capable of forming the same phase with water and adding the prepared mixed ionic iiquid solution to a continuous distillation extraction apparatus; adding an extracting organic

solvent to the continuous distillation extraction apparatus; extracting ionic liquids by continuously refluxing the extracting organic solvent in the continuous distillation extraction apparatus at an appropriate temperature for an appropriate time ; and removing an organic solvent by distilling ionic liquid organic solvent mixed solution recovered in a receiver of the continuous distillation eAraction apparatus, and removing water by drying under reduced pressure.

In the above-described method, the mixed ionic liquid solution is adjusted to have a concentration sufficient to dissolve the ionic liquid and to effectively separate impurities, that is, the solution comprising about 10% to 90% (w/w) to the solvent according to the solubility of the ionic liquid. In order to effectively remove impurities and purify an ionic liquid, the purification efficiency may be affected by the concentration of a mixed ionic liquid solution to be extracted. That is, when the mixed ionic liquid solution is highly concentrated, residual impurities may also be extracted with the target ionic liquid, thereby lowering the extraction efficiency. When the mixed ionic liquid solution is lightly concentrated, the removal efficiency of residual impurities increased but the amount of the residual impurities extracted per hour may be reduced. To achieve effective extraction, the concentration of the mixed ionic liquid solution that meets requirements of both impurity purification efficiency and yield must be determined in consideration of the solubility of the ionic liquid.

In order to increase the extraction efficiency, when necessary, a solvent may be further added, and examples of the solvent useful in the present invention include solvents capable of forming the same phase with water, for example, methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, acetone, dioxan, or acetonitrile.

The extracting organic solvent is used for the purpose of maximizing the extraction efficiency during extraction and circulation processes, the extracting organic solvent shoutd be capable of selectively extracting ionic liquids during extraction and removing impurities. Also, the organic solvent

used is a solvent capable of forming two phases together with the mixed ionic liquid solution. Preferred examples of the organic solvent include methylene chloride, ethyl acetate, ethyl ethanoate, tetrahydrofuran, toluene, or azeotropic mixed solvent thereof. Preferably, the extracting organic solvent is used in an amount of 1% to 3% (v/w) to the ionic liquid and continuously used for circulation.

The continuous disti ! ! ation extraction apparatus can be selectively used depending on the property of the extracting organic solvent used. In other words, when an extracting organic solvent which is lighter than the ionic liquid solution is used, a distilled extraction convertible liquid/liquid continuous extractor can be used. When an extracting organic solvent which is heavier than the ionic liquid solution is used, a liquid/liquid extraction apparatus can be used. Also, any continuous distillation extractor that can be appreciated by one skilled in the art can be used compatibly with the two types of continuous distillation extractors.

According to the purification method of the present invention, in the extracting step, the temperature of the mixed ionic liquid solution is adjusted to selectively extract ionic liquids only by increasing the solubility of impurities in the solvent. Generally, the mixed ionic liquid solution to be purified by the extractor is kept at room temperature in the extracting step. However, when necessary, the mixed ionic liquid solution may be cooled or heated within the temperature range in which it may not be frozen or distilled. Also, in the extracting step, the extracting organic solvent is boiled at a boiling point to then be refluxed. The reflux termination time is 1 to 72 hours, preferably 2 to 24 hours, after the extracting step started.

After the extracting step is completed, the mixed solution of the extracted ionic liquid and the organic solvent is distilled to remove the extracting organic solvent, and dried under reduced pressure at 25-300'C to remove residual water.

The water-soluble or oil-soluble ionic liquid that can be purified by the purification method according to the present invention includes organic cations and anions, and are organic salts represented by formulas :

wherein R, R', and R"are each independently a Ci-Ci2 primary alkyl, secondary alkyl, or tertiary alkyl group.

X-represents an anion capable of forming salts, e. g., MAn-, or RO-.

Here, M represents elements of group VIII, IB, 2B, IIIA, or VA of Periodic Table of the Elements (CAS version), and A represents a halide, more preferably fluorine. RO-is an alkylsulfonyl, haloalkylsulfonyl, phosphoryl, imide or carbonyl group.

Specific examples of the ionic liquid useful in the present invention include imidazolium salts containing cations such as 1-ethyl-3-methyl- imidazolium (EMIM), 1-methyl-3-propyl-imidazolium (PMIM), 1-butyl-3-methyl- imidazolium (BMiM), 1-methyl-3-pentyl-imidazolium, PnMIM), 1-hexyl-3-methyl- imidazolium, HMIM), 1-heptyl-3-methyl-imidazolium (HpMI i), and an anion

group of hexafluoroantimonate (SbF6), hexafluorophosphate (PF6), tetrafluoroborate (BF4), bis (trifluorosulfonyl) imide (NTf2), trifluoromethanesulfonate (OTf , acetate (OAc), or nitrate (N03).

To increase purifying effects, the entire process of the purification method according to the present invention may be repeated) y performed, preferably 1 to 3 times.

According to the purification method of the present invention, only ionic liquids can be selectively extracted while removing impurities such as organic halide salts, organic salts, halide residues, acid residues, or excess alkali metal impurities, thereby synthesizing high purity ionic liquids in an economically effective, highly efficient manner. In the ionic liquid prepared according to the purification method, impurities such as halide residues, alkali metal impurity, and so on, are present in an amount of not greater than 1,000 ppm, more preferably not greater than 100 ppm, and most preferably not greater than 5 ppm. Also, the ionic liquids have high purity of not less than 95%, more preferably not less than 99%, and most preferably not less than 99.9%.

Therefore, the ionic liquid according to the present invention can be used as solvents for organic, inorganic and biochemical reactions and can be used as electrolytic solutions for storage batteries, secondary batteries and fuel batteries.

Also, according to the purification method of the present invention, a small amount of the extracting organic solvent is used and only the organic solvent is subjected to distillation and circulation, thereby extracting and purifying ionic liquids having negligible vapor pressure in an environmentally friendly, economic manner.

Brief Description of the Drawings FIG 1 is a sketch view of a liquid/liquid continuous extraction apparatus that is useful in the present invention ; FIG. 2 is a sketch view of a distilled extraction convertible liquid/liquid

continuous extractor that is useful in the present invention; and FIG. 3 is a schematic diagram illustrating a general synthesis method and purification method of 1,3-dialkylimidazolium ionic liquid.

Best mode for carrying out the invention The present invention will now be described in more detail through embodiments.

EXAMPLES Example 1: Synthesis of 1-butyl-3-methylimidazolium hexafluorophosphate 57 g of 1-butyl-3-methylimidazolium chloride was added to 150 ml of acetone, and 79 g (1.1 eq. ) of potassium hexafluorophosphate was added thereto and reacted for 24 hours, followed by filtering the reactant solution to remove salts. The resulting filtrate was distilled to remove acetone, giving an unpurified 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid.

To the unpurified 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid was added a mixed solution of ionic water and methyl alcohol (1v/3v) to prepare a product having a concentration of about 50%, followed by transferring to a reflux device of the continuous distillation extraction apparatus.

Then, methylene chloride was added to a receiver (3v/w) and refluxed at 39- 40 °C for about 12 hours. Then, the methylene chloride solution was collected from the receiver of the continuous distillation extraction apparatus and methylene chloride was distilled to be removed, followed by drying under reduced pressure at 60 °C for 76 hours to remove water, thereby acquiring a desired ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate.

Yield : 100 g (90%), halide residues ions : 2-20 ppm (before purification : 1000 ppm), residua ! sodium ions : 1-5 ppm (before purification : 30 ppm), water : 200 ppm.

To achieve high purity ionic liquids, the obtained 1-butyl-3- methylimidazolium hexafluorophosphate ionic liquid was repeatedly purified.

Yield : 99 g (99%), residual chloride ions: 1-5 ppm (before repeated cycles of purification: 2-20 ppm), residual sodium ions < 3 ppm (before repeated cycles of purification : 1 # 5 ppm), water: 200 ppm.

Example 2 : Synthesis of 1-butyl-3-methMlimidazoXium hexafiuoroantimonate 50 g of 1-butyl-3-methylimidazolium chloride was added to 150 ml of acetone, and 81 g (1. 1 eq.) of potassium hexafluorophosphate was added thereto and reacted for 24 hours, followed by filtering the reactant solution to remove salts. The resulting filtrate was distilled to remove acetone, giving an unpurified 1-butyl-3-methylimidazolium hexafluoroantimonate ionic liquid.

To the unpurified 1-butyl-3-methylimidazolium hexafluoroantimonate ionic liquid was added a mixed solution of ionic water and methyl alcohol (1v/3v) to prepare a product having a concentration of about 50%, followed by transferring to a reflux device of the continuous distillation extraction apparatus.

Then, methylene chloride was added to a receiver (3v/w) and refluxed at 39- 40°C for about 12 hours. Then, the methylene chloride solution was collected from the receiver of the continuous distillation extraction apparatus and methylene chloride was distilled to be removed, followed by drying under reduced pressure at 60°C for 76 hours to remove water, thereby acquiring a desired ionic liquid, 1-butyl-3-methylimidazolium hexafluoroantimonate.

Yield : 100 g (93%), residual chloride ions: 2-20 ppm (before purification: 500 ppm), residual sodium ions: 1 # 5 ppm (before purification: 7 ppm), water: 200 ppm.

To achieve high purity ionic liquids, the obtained 1-butyl-3- methylimidazolium hexafluoroantimonate ionic liquid was repeatedly purified.

Yield : 99 g (99%), residual chloride ions : 1-5 ppm (before repeated cycles of purification : 2 ppm), residual sodium ion < 3ppm (before repeated cycles of purification : 1 ppm), water : 200 ppm.

Example 3: Synthesis of 1-butvl-3-methylimidazolium bis (trifluorosulfonvl) imide 54 g of 1-butyl-3-methylimidazolium chloride was added to 150 ml of acetone, and 68 g (1. 1 eq.) of lithium bis (trifluorosulfonyl)imide was added thereto and reacted for 24 hours, followed by filtering the reactant solution to remove sails. The resulting filtrate was distilled to remove acetone, giving an unpurified 1-butyl-3-methylimic3azolium bis (trifluorosulfonly) imide ionic liquid.

To the unpurified 1-butyl-3-methylimidazolium bis(trifluorosulfonyl)imide ionic liquid was added a mixed solution of ionic water and methyl alcohol (1v/3v) to prepare a product having a concentration of about 50%, followed by transferring to a reflux device of the continuous distillation extraction apparatus.

Then, methylene chloride was added to a receiver (3v/w) and refluxed at 39- 40°C for about 12 hours. Then, the methylene chloride solution was recovered from the receiver of the continuous distillation extraction apparatus and methylene chloride was distilled to be removed, followed by drying under reduced pressure at 60°C for 76 hours to remove water, thereby acquiring a desired ionic liquid, 1-butyl-3-methylimidazolium bis (trifluorosulfonyl) imide ionic liquid.

Yield : 100 g (95%), residual chloride ions: 2-20 ppm (before purification: 100 ppm), residual sodium ions: 1 # 5 ppm (before purification: 30 ppm), water: 200 ppm.

To achieve high purity ionic liquids, the obtained 1-butyl-3- methylimidazolium bis (trifluorosulfonyl) imide ionic liquid was repeatedly purified Yield : 99 g (99%), residual chloride ions: 1 # 5 ppm (before repeated cycles of purification: 2-20 ppm), residual sodium ions > 3 ppm (before repeated cycles of purification : 1 # 5 ppm), water : 200 ppm.

Example 4: Synthesis of 1-butyl-3-methylimidazolium tetrafluoroborate 70 g of 1-butyl-3-methylimidazolium chloride was added to 150 ml of acetone, and 57 g (1.1 eq. ) of sodium tetrafluoroborate was added thereto and

reacted for 24 hours, followed by filtering the reactant solution to remove salts.

The resulting filtrate was distilled to remove acetone, giving an unpurified 1- butyl-3-methylimidazolium tetrafluoroborate ionic liquid.

To the unpurified 1-butl-3-methylimidazolium tetraftuoroborate ionic liquid was added ionic water to prepare a product having a concentration of about 50%, followed by transferring to a reflux device of the continuous distillation extraction apparatus. Then, methylene chloride was added to a receiver (3v/w) and refluxed at 39 ~ 40°C for about 24 hours. Then, the methylene chloride solution was collected from the receiver of the continuous distillation extraction apparatus and methylene chloride was distilled to be removed, followed by drying under reduced pressure at 60°C for 76 hours to remove water, thereby acquiring a desired ionic liquid, 1-butyl-3- methylimidazolium tetrafluoroborate ionic liquid.

Yield : 100 g (93%), residual chloride ions: 2-20 ppm (before purification: 3500 ppm), residual sodium ions: 1-5 ppm (before purification: 300 ppm), water: 500 ppm.

To achieve high purity ionic liquids, the obtained 1-butyl-3- methylimidazolium tetrafluoroborate ionic liquid was repeatedly purified.

Yield : 95 g (95%), residual chloride ions: 1-5 ppm (before repeated cycles of purification: 2-20 ppm), residual sodium ions < 3 ppm (before repeated cycles of purification: 1 # 5 ppm), water: 500 ppm.

Example 5: Synthesis of 1-butyl-3-methylimidazolium trifluoromethanesulfonate 65 g of 1-butyl-3-methylimidazolium trifluoromethanesulfonate was added to 150 ml of acetone, and 70 g (1.1 eq. ) of potassium trifluoromethanesulfonate was added thereto and reacted for 24 hours, followed by filtering the reactant solution to remove salts. The resulting filtrate was <BR> <BR> <BR> <BR> distilled to remove acetone, giving an unpurified 1-butyl-3-methylimidazolium trifiuoromethanesuifonate ionic liquid.

To the unpurified 1-butyl-3-methylimidazolium trifluoromethanesulfonate

ionic liquid was added ionic water to prepare a product having a concentration of about 50%, followed by transferring to a reflux device of the continuous distillation extraction apparatus. Then, methylene chloride was added to a <BR> <BR> <BR> <BR> receiver (3v/w) and refluxed at 39 # 40°C for about 36 hours. Then, the methylene chloride solution was collected from the receiver of the continuous distillation extraction apparatus and methylene chloride was distilled to be removed, followed by drying under reduced pressure at 60 C for 76 hours to remove water, thereby acquiring 1-butyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid.

Yield : 100 g (93%), residual chloride ions: 2 ~ 20 ppm (before purification: 3,500 ppm), residual potassium ions: 1 ~ 5 ppm (before purification: 300 ppm), water: 300 ppm.

To achieve high purity ionic liquids, the obtained 1-butyl-3- methylimidazolium trifluoromethanesulfonate ionic liquid was repeatedly purified.

Yield : 95 g (95%), residual chloride ions: 1-5 ppm (before repeated cycles of purification: 2-20 ppm), residual potassium ions < 3 ppm (before repeated cycles of purification: 1 # 5 ppm), water: 300 ppm.

Example 6: Synthesis of 1-butyl-3-methylimidazolium methanesulfonate 70 g of 1-butyl-3-methylimidazolium chloride was added to 150 ml of acetone, and 71 g (1.1 eq. ) of potassium methanesulfonate was added thereto and reacted for 24 hours, followed by filtering the reactant solution to remove salts. The resulting filtrate was distilled to remove acetone, giving an unpurified 1-butyl-3-methylimidazolium methanesulfonate ionic liquid.

To the unpurified 1-butyl-3-methylimidazolium methanesulfonate ionic liquid was added ionic water to prepare a product having a concentration of about 75%, followed by transferring to a reflux device of the continuous distillation extraction apparatus. Then, methylene chloride was added to a receiver (3v/w) and refluxed at 39 ~ 40oC for about 48 hours. Then, the

methylene chloride solution was collected from the receiver of the continuous distillation extraction apparatus and methylene chloride was distilled to be removed, followed by drying under reduced pressure at 60'C for 76 hours to remove water, thereby acquiring 1-butyl-3-methylimidazolium methanesulfonate ionic liquid.

Yield : 100 g (93%), residual chloride ions : 2-50 ppm (before purification : 8000 ppm), residual potassium ions: 1 # 5 ppm (before purification : 300 ppm), water : 50 ppm.

To achieve high purity ionic liquids, the obtained 1-butyl-3- methylimidazolium methanesulfonate ionic liquid was repeatedly purified.

Yield : 90 g (90%), residual chloride ions: 2-5 ppm (before repeated cycles of purification: 2-50 ppm), residual potassium ions < 3 ppm (before repeated cycles of purification: 1 # 5 ppm), water: 200 ppm.

Example 7: Synthesis of 1-ethyl-3-methylimidazolium bis (trifluorosulfonyl) imide 79 g of 1-ethyl-3-methylimidazolium bromide was added to 250 ml of acetone, and 76 g (1.1 eq. ) of lithium bis (trifluorosulfonyl) imide was added thereto and reacted for 24 hours, followed by filtering the reactant solution to remove salts. The resulting filtrate was distilled to remove acetone, giving an unpurified 1-ethyl-3-methylimidazolium bis (trifluorosulfonyl) imide ionic liquid.

To the unpurified 1-ethyl-3-methylimidazolium bis (trifluorosulfonyl) imide ionic liquid was added a mixed solution of ionic water and methyl alcohol (1v/3v) to prepare a product having a concentration of about 50%, followed by transferring to a reflux device of the continuous distillation extraction apparatus.

Then, methylene chloride was added to a receiver (3v/w) and refluxed at 39 # 40 °C for about 12 hours. Then, the methylene chloride solution was collected from the receiver of the continuous distillation e) draction apparatus and <BR> <BR> <BR> methylene chloride was distilled to be removed, followea'by drying under reduced pressure at 60°C for 76 hours to remove water, thereby acquiring 1-

ethyl-3-methylimidazolium bis (trifluorosulfonyl) imide ionic liquid.

Yield : 100 g (95%), residual bromide ions: 2-100 ppm (before purification : 100 ppm), residual ! sodium ions : 1-5 ppm (before purification : 30 ppm), , water: 200 ppm.

To achieve high purity ionic liquids, the obtained 1-ethyl-3- methylimidazolium bis (trifluoro$ulfonyl) imide ionic liquid was repeaUdly purified.

Yield : 99 g (99%), residual chloride ion : 1 ppm (before repeated cycles of purification: 2 # 20 ppm), residual sodium ions > 3 ppm (before repeated cycles of purification : 1-5 ppm), water : 200 ppm.

Example 8: Synthesis of 1-ethyl-3-methylimidazolium tetrafluoroborate 114 g of 1-ethyl-3-methylimidazolium bromide was added to 250 ml of acetone, and 72 g (1.1 eq. ) of sodium tetrafluoroborate was added thereto and reacted for 24 hours, followed by filtering the reactant solution to remove salts.

The resulting filtrate was distilled to remove acetone, giving an unpurified 1- ethyl-3-methylimidazolium tetrafluoroborate ionic liquid.

To the unpurified 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid was added ionic water to prepare a product having a concentration of about 20%, followed by transferring to a reflux device of the continuous distillation extraction apparatus. Then, methylene chloride was added to a receiver (3v/w) and refluxed at 39 ~ 40°C for about 24 hours. Then, the methylene chloride solution was collected from the receiver of the continuous distillation extraction apparatus and methylene chloride was distilled to be removed, followed by drying under reduced pressure at 60oC for 76 hours to remove water, thereby acquiring 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid.

Yield : 100 g (85%), residual chloride ions : 2 ppm (before purification : 3500 ppm), residual ! sodium ions : 1-5 ppm (before purification : 300 ppm), water : 500 ppm.

To achieve high purity ionic liquids, the obtained 1-ethyl-3-

methylimidazolium tetrafluoroborate ionic liquid was repeatedly purified.

Yield : 95 g (95 %), residual chloride ions: 1 # 5 ppm (before repeated cycles of purification: 2 # 20 ppm), residual sodium ions < 3 ppm (before repeated cycles of purification: 1 # 5 ppm), water : 500 ppm.

Example 9: Synthesis of 1-ethyl-3-methylimic azolium trifluoromethanesulknate 85 g of 1-ethyl-3-methylimidazolium bromide was added to 250 ml of acetone, and 84 g (1. 1 eq.) of potassium trifluoromethanesulfonate was added thereto and reacted for 24 hours, followed by filtering the reactant solution to remove salts. The resulting filtrate was distilled to remove acetone, giving an unpurified 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid.

To the unpurified 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid was added ionic water to prepare a product having a concentration of about 30%, followed by transferring to a reflux device of the continuous distillation extraction apparatus. Then, methylene chloride was added to a receiver (3v/w) and refluxed at 39-40 °C for about 36 hours. Then, the methylene chloride solution was collected from the receiver of the continuous distillation extraction apparatus and methylene chloride was distilled to be removed, followed by drying under reduced pressure at 60 C for 76 hours to remove water, thereby acquiring 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid.

Yield : 100 g (86%), residual chloride ions: 2 ~ 20 ppm (before purification: 2,500 ppm), residual potassium ions: 1 ~ 5 ppm (before purification: 300 ppm), water: 300 ppm.

To achieve high purity ionic liquids, the obtained 1-ethyl-3- methyiimidazoiium trifluoromethanesulfonate ionic liquid was repeatedly purified.

Yield : 95 g (95%), residual chloride ions : 1 # 5 ppm (before repeated cycles of purification: 2 # 20 ppm), residual potassium ions < 3 ppm (before

repeated cycles of purification: 1-5 ppm), water: 300 ppm.

Example 10: Synthesis of 1-ethyl-3-methylimidazolium methanesulfonate 101 g g of 1-ethyl-3-methylimidazolium bromide was added to 250 ml of acetone, and 79 g (1. 1 eq.) of potassium methanesuifonate was added thereto and reacted for 24 hours, followed by filtering the reactant solution to remove salts. The resulting filtrate was distilled to remove acetone, giving an unpurified 1-ethyl-3-methylimidazolium methanesulfonate ionic liquid.

To the unpurified 1-ethyl-3-methylimidazolium methanesulfonate ionic liquid was added ionic water to prepare a product having a concentration of about 75%, followed by transferring to a reflux device of the continuous distillation extraction apparatus. Then, methylene chloride was added to a receiver (3v/w) and refluxed at 39-40 °C for about 48 hours. Then, the methylene chloride solution was collected from the receiver of the continuous distillation extraction apparatus and methylene chloride was distilled to be removed, followed by drying under reduced pressure at 60°C for 76 hours to remove water, thereby acquiring 1-ethyl-3-methylimidazolium methanesulfonate ionic liquid.

Yield : 100 g (85%), residual chloride ions: 2-50 ppm (before purification : 8000 ppm), residual potassium ions: 1-5ppm (before purification: 300 ppm), water: 50 ppm.

To achieve high purity ionic liquids, the obtained 1-ethyl-3- methylimidazolium methanesulfonate ionic liquid was repeatedly purified.

Yield : 90 g (90%), residual chloride ions: 2-5 ppm (before repeated cycles of purification : 2 ~ 50 ppm), residual potassium ions < 3 ppm (before repeated cycles of purification : 1-5 ppm), water : 200 ppm.

Example 11 : Synthesis of N,N'-butyl,methyl pyrolidinium trifluoromethanesulfonate

71 g of N, N'-butyl, methyl pyrolidinium chloride was added to 250 ml of acetone, and 75 g (1.1 eq. ) of potassium trifluoromethanesulfonate was added thereto and reacted for 24 hours, followed by filtering the reactant solution to remove sails. The resulting was distilled to remove acetone, giving an unpurified N, N'-butyl, methyl pyrolidinium trifluoromethanesulfonate ionic liquid.

To the unpurified N, N'-butyl, methyl pyrolidinium trifluoromethanesulfonate ionic liquid was added a mixed solution of ionic water and methyl alcohol (1v/5v) to prepare a product having a concentration of about 30%, followed by transferring to a reflux device of the continuous distillation extraction apparatus. Then, methylene chloride was added to a receiver (3v/w) and refluxed at 39 # 40°C for about 48 hours. Then, the methylene chloride solution was collected from the receiver of the continuous distillation extraction apparatus and methylene chloride was distilled to be removed, followed by drying under reduced pressure at 60°C for 76 hours to remove water, thereby acquiring N, N'-butyl, methyl pyrolidinium trifluoromethanesulfonate ionic liquid.

Yield : 100 g (86%), residual chloride ions: 5 ~ 100 ppm (before purification: 15,000 ppm), residual potassium ions 1 # 5 ppm (before purification: 300 ppm), water: 500 ppm.

To achieve high purity ionic liquids, the obtained N, N'-butyl, methyl pyrolidinium trifluoromethanesulfonate ionic liquid was repeatedly purified.

Yield : 95 g (95%), residual chloride ions : 2-5 ppm (before repeated cycles of purification: 5-100 ppm), residual potassium ions < 3 ppm (before repeated cycles of purification: 1 # 5 ppm), water: 500 ppm.

Example 12 : Synthesis of lis N'-but yl, evroiidinium methanesulfonate 78 g of IM, N'-butyl, methyl pyrolidinium chloride was added to 250 ml of acetone, and 66 g (1. 1 eq.) of potassium methanesulfonate was added thereto and reacted for 24 hours, followed by filtering the reactant solution to remove

salts. The resulting filtrate was distilled to remove acetone, giving an unpurified N, N'-butyl, methyl pyrolidinium methanesulfonate ionic liquid.

To the unpurified N, N'-butyl, methyl pyrolidinium methanesutfonate ionic liquid was was added a mixed solution of ionic water and methyl alcohol (1v/5v) to prepare a product having a concentration of about 30%, followed by transferring to a reflux device of the continuous distittation extraction apparatus.

Then, methylene chloride was added to a receiver (3v/w) and refluxed at 3 - <BR> <BR> <BR> <BR> <BR> 40 C for about 48 hours. Then, the methylene chloride solution was collected from the receiver of the continuous distillation apparatus and methylene chloride was distilled to be removed, followed by drying under reduced pressure at 60 °C for 76 hours to remove water, thereby acquiring N, N'-butyl, methyl pyrolidinium methanesulfonate ionic liquid.

Yield : 100 g (90%), residual chloride ions: 5-200 ppm (before purification: 8000 ppm), residual sodium ions: 1-5ppm (before purification : 100 ppm), water: 500 ppm.

To achieve high purity ionic liquids, the obtained N, N'-butyl, methyl pyrolidinium methanesulfonate ionic liquid was repeatedly purified.

Yield : 90 g (90%), residual chloride ions: 2-5 ppm (before repeated cycles of purification: 5-200 ppm), residual potassium ions < 3 ppm (before repeated cycles of purification: 1 # 5 ppm), water: 500 ppm.

Example 13: Synthesis of N-butyl pyridinium trifluoromethanesulfonate 70 g of N-butyl pyridinium chloride was added to 200 ml of acetone, and 77 g (1.1 eq. ) of potassium trifluoromethanesulfonate was added thereto and reacted for 24 hours, followed by filtering the reactant solution to remove salts.

The resulting fi) trate was distiiied to remove acetone, giving an unpurified N- butyl pyridinium trifluoromethanesulfonate ionic liquid.

To the unpurified N-butyl pyridinium trifluoromethanesulfonate ionic liquid was added a mixed solution of ionic water and methyl alcohol (1v/5v to prepare a product having a concentration of about 30%, followed by

transferring to a reflux device of the continuous distillation extraction apparatus.

Then, methylene chloride was added to a receiver (3v/w) and refluxed at 39- 40 °C for about 36 hours. Then, the methylene chloride solution was collected from the receiver of the continuous distillation extraction apparatus and methylene chloride was distilled to be removed, followed by drying under reduced pressure at 60°C for 76 hours to remove water, thereby acquiring N- butyl pyridinium trifiuoromethanesuifonate ionic liquid.

Yield : 100 g (95%), residual chloride ions : 5-200 ppm (before purification : 15, 000 ppm), residual potassium ions : 5ppm (before purification: 300 ppm), water: 500 ppm.

To achieve high purity ionic liquids, the obtained N-butyl pyridinium trifluoromethanesulfonate ionic liquid was repeatedly purified.

Yield : 95 g (95%), residual chloride ions: 2-5 ppm (before repeated cycles of purification: 5-200 ppm), residual potassium ion: < 3 ppm (before repeated cycles of purification : 1-5ppm), water: 500 ppm.

Example 14: Synthesis of N-butyl pyridinium methanesulfonate 73 g of N-butyl pyridinium chloride was added to 200 mi of acetone, and 64 g (1.1 eq. ) of potassium methanesulfonate was added thereto and reacted for 24 hours, followed by filtering the reactant solution to remove salts. The resulting filtrate was distilled to remove acetone, giving an unpurified N-butyl pyridinium methanesulfonate ionic liquid.

To the unpurified N-butyl pyridinium methanesulfonate ionic liquid was added a mixed solution of ionic water and methyl alcohol (1v/5v) to prepare a product having a concentration of about 30%, followed by transferring to a reflux device of the continuous distillation extraction apparatus. Then, methylene chloride was added to a receiver (3v/w) and refiuxed at 39-40 °C for about 48 hours. Then, the methylene chloride solution was collected from the receiver of the continuous distillation extraction apprratus and methylene chloride was distilled to be removed, followed by drying under reduced

pressure at 60 °C for 76 hours to remove water, thereby acquiring N-butyl pyridinium methanesulfonate ionic liquid.

Yield : 100 g (95%), residual chloride ions : 5-200 ppm (before purification : 15,000 ppm), residual potassium ions: 1 # 5ppm (before purification : 300 ppm), water : 50 ppm.

To achieve high purity ionic liquids, the obtained 19-butyl pyridinium methanesulfonate ionic liquid was repeatedly purified.

Yield : 90 g (90%), residual chloride ions : 2-5 ppm (before repeated cycles of purification : 5-200 ppm), residual ! potassium ions < 3 ppm (before repeated cycles of purification: 1-5 ppm), water: 200 ppm.

Industrial Applicability According to the purification method of the present invention, impurities such as organic halide salts, organic salts, halide residues, acid residues, or excess alkali metals can be effectively removed from ionic liquids using liquid/liquid continuous extraction. In the ionic liquid prepared according to the purification method, impurities such as halide residues, alkali metal impurity, and so on, are present in an amount of not greater than 1,000 ppm, more preferably not greater than 100 ppm, and most preferably not greater than 5 ppm. Also, the ionic liquid has high purity of not less than 95%, more preferably not less than 99%, and most preferably not less than 99.9%.

Therefore, the ionic liquid according to the present invention can be used as solvents for organic, inorganic and biochemical reactions and can used as electrolytic solutions for storage batteries, secondary batteries and fuel batteries.

Further, the purification method according to the present invention enables mass production of high purity ionic liquids in an industrial scale effectively and economically using liquid/liquid continuous extraction.