WO2018127783A1

WO2018127783A1 - Ionic liquid production method

Info

Publication number: WO2018127783A1
Application number: PCT/IB2018/000030
Authority: WO
Inventors: 植田健太郎; 杉山孝之
Original assignee: 大阪瓦斯株式会社
Priority date: 2016-12-02
Filing date: 2018-01-25
Publication date: 2018-07-12
Also published as: JP2018090527A

Abstract

Provided is an ionic liquid production method in which the time efficiency and the yield have been improved. Specifically provided is an ionic solution production method for producing an ionic solution that comprises a cation and an anion by reacting a first ionic substance comprising a cation and a halogen with a second ionic substance comprising an alkali metal and an anion, wherein the cation is a quaternary tetraalkyl phosphonium compound or a quaternary tetraalkyl ammonium compound, and the anion is a benzimidazole derivative, an imidazole derivative or a carbazole derivative.

Description

Ionic liquid manufacturing method

The present invention relates to an ionic liquid manufacturing method.

From previous studies (Non-Patent Documents 1 and 2), it has been clarified that the ionic liquid has a carbon dioxide absorption superior to that of the conventional physical absorption liquid. Patent Document 1 proposes a carbon dioxide separation and recovery method in which CO ₂ is separated and recovered from a multicomponent mixed gas by a physical absorption method using an ionic liquid absorbing liquid. Non-Patent Document 3 describes a carbon dioxide recovery method using tetraethylphosphonium benzimidazolide (P2Bn).

Japanese Patent No. 5467394

Non-Patent Document 3 describes a method of reacting tetraethylphosphonium hydroxide and benzimidazole as a method for synthesizing tetraethylphosphonium benzimidazolide (P2Bn). However, in this synthesis method, both substances need to be mixed in methanol and stirred overnight to react, and it takes a long time to obtain the target substance. In addition, the yield of the target substance is about 91%, and there is room for improvement in this respect.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide an ionic liquid production method improved in terms of time efficiency and yield.

The characteristic configuration of the ionic liquid production method for achieving the above object is that a first ionic substance composed of a cation and a halogen is reacted with a second ionic substance composed of an alkali metal and an anion, and the cation and the anion are reacted. The cation is a quaternary tetraalkylphosphonium or quaternary tetraalkylammonium, and the anion is a benzimidazole derivative, an imidazole derivative, or a carbazole derivative. In that point.

The inventors have conducted intensive experiments and examinations, and when the cation is quaternary tetraalkylphosphonium or quaternary tetraalkylammonium and the anion is a benzimidazole derivative, imidazole derivative, or carbazole derivative, the cation To make it possible to produce a ionic liquid consisting of a cation and an anion with high time efficiency and yield by reacting a first ionic substance consisting of alkenyl and a halogen with a second ionic substance consisting of an alkali metal and an anion. Completed the invention. In particular, the difference in solubility in solvents between the ionic liquid produced and the salt of the by-product (halogen and alkali metal salt) makes it easy to separate the two, resulting in high time efficiency and yield. It is thought that was realized.

Another characteristic configuration of the ionic liquid production method according to the present invention is that the reaction between the first ionic substance and the second ionic substance is performed in the presence of a solvent, and the solubility of the solvent in the ionic liquid. However, the solubility is higher than the solubility in the salt composed of the halogen and the alkali metal.

According to the above characteristic configuration, the produced ionic liquid is more dissolved in the solvent, and the salt composed of halogen and alkali metal is less dissolved in the solvent. Therefore, the separation of the salt from the ionic liquid is further facilitated, which is preferable. Specifically, it is preferable if the solvent contains at least one of t-butanol, 2-propanol, 2-butanol, 2-methoxyethanol, and acetone.

The present invention can be suitably applied when the cation is tetraethylphosphonium and the anion is benzimidazole.

The present invention can be suitably applied when the cation is tetraethylammonium and the anion is benzimidazole.

The present invention can be suitably applied when the cation is tetraethylammonium and the anion is imidazole.

The present invention can be suitably applied when the cation is tetrabutylammonium and the anion is carbazole.

The present invention can be suitably applied when the halogen is fluorine, chlorine, bromine or iodine.

The present invention can be suitably applied when the alkali metal is lithium, sodium or potassium.

FIG. 1 is a graph showing 1H-NMR measurement results of the reaction intermediate of Example 1.
FIG. 2 is a graph showing 1H-NMR measurement results of benzimidazole.
FIG. 3 is a graph showing 1H-NMR measurement results of the reaction intermediate of Example 2.
FIG. 4 is a graph showing the results of 1H-NMR measurement of the reaction product of Example 2.

In the ionic liquid manufacturing method according to this embodiment, at least two ionic substances are mixed and reacted to generate an ionic liquid. One ionic substance is a first ionic substance composed of a cation and a halogen, and the other ionic substance is a second ionic substance composed of an alkali metal and an anion.

The cation of the first ionic substance is quaternary tetraalkylphosphonium or quaternary tetraalkylammonium, and is represented by the chemical formula 1 below. A is phosphonium or ammonium, and R1 to R4 are alkyl groups having 2 to 4 carbon atoms. R1 to R4 may have different carbon numbers.

The cation of the first ionic material, specifically, tetraethyl phosphonium _{(tetraethylphosphonium, P 2222,} of 2), tetraethylammonium _{(tetraethylammonium, N 2222,} of 3), tetrabutylammonium _{(tetrabuthylammonium, N 4444,} of 4 ) Is preferably used.

Fluorine, chlorine, bromine, iodine or the like can be used as the halogen of the first ionic substance, but bromine is preferably used.

As the alkali metal of the second ionic substance, lithium, sodium, potassium and the like can be used, but potassium is preferably used.

As the anion of the second ionic substance, a benzimidazole derivative, an imidazole derivative, or a carbazole derivative can be used. In particular, benzimidazole (benzimidazole, BnIm, Chemical formula 5), imidazole (imidazole, Im, Chemical formula 6), and carbazole (carbazole, Cz, chemical formula 7) are preferably used.

In the ionic liquid production method according to this embodiment, the reaction between the first ionic substance and the second ionic substance is performed in the presence of a solvent. As the solvent, a solvent whose solubility in the generated ionic liquid is larger than the solubility in the salt (by-product salt) composed of the halogen of the first ionic substance and the alkali metal of the second ionic substance is preferably used. It is done. Specifically, it is preferable that the solvent contains at least one of t-butanol, 2-propanol, 2-butanol, 2-methoxyethanol, and acetone.

<Example 1: Tetraethylphosphonium benzimidazolide (P2Bn)>
Hereinafter, examples in which tetraethylphosphonium benzimidazolide (P2Bn) was synthesized will be described. The first ionic substance, second ionic substance and solvent used are as follows.
First ionic substance Cation: Tetraethylphosphonium Halogen: Bromine Second ionic substance Alkali metal: Potassium Anion: Benzimidazole Solvent: t-Butanol

To a three-necked flask, add 1.0012 g of benzimidazole (8.31 mmol for 98% product) and 5 ml of t-butanol, and heat and stir in an oil bath at 60 ° C. to obtain 1.0428 g of potassium t-butoxide (95% product). Therefore, 8.83 mmol) was added. The solvent was distilled off to obtain an intermediate product.

The intermediate product was dissolved in d6-DMSO, and 1H-NMR (400 MHz NMR) was measured. The results are shown in FIG. Compared with the result of 1H-NMR of benzimidazole in FIG. 2, the peak (σ˜12.5) corresponding to the NH proton of benzimidazole seen in FIG. 2 disappears in FIG. Since the peak of the benzene ring proton is shifted to the high magnetic field side in FIG. 2, the benzimidazole is a potassium salt, that is, a second ionic substance comprising an alkali metal (potassium) and an anion (benzimidazole). Was confirmed to be generated.

5 ml of t-butanol was added to the intermediate product and heated and stirred at 60 ° C. in an oil bath to dissolve the potassium salt (intermediate product). From the dropping funnel, 1.9260 g of tetraethylphosphonium bromide (8.31 mmol because it is a 98% product) and 20 ml of t-butanol were added to the reaction system, and the mixture was stirred at 60 ° C. for 1 hour. The reaction mixture was filtered through a PTFE filter (pore size 0.45 μm), and the filtrate was washed with 10 ml of t-butanol. The solvent was distilled off from the obtained filtrate and dried under reduced pressure (60 ° C., 17 hours) to obtain 2.17 g of a white solid reaction product.

The reaction product was dissolved in d6-DMSO, and 1H-NMR (400 MHz NMR) was measured. The results are shown in FIG. From the results of FIG. 3, the peaks (σ˜12.5) corresponding to the NH protons of benzimidazole seen in FIG. 2 disappear, and the positions of each peak are the literature values [σ of tetraethylphosphonium benzimidazolide [σ = 1.09-1.15 (dt, 12H), 2.18-2.24 (dq, 8H), 6.64-6.66 (dd, 2H), 7.27-7.28 (broad, 2H), 7.59 (s, 1H). ], And the ratio of the peak integration value of the cation to the anion is approximately 1: 1, so that the reaction product is tetraethylphosphonium benzimidazolide, that is, the cation and the second ionicity of the first ionic substance. It was confirmed that an ionic liquid composed of the anion of the substance was generated.

When the purity of the product was calculated from the peak integrated value of 1H-NMR in FIG. 3, the purity of the reaction product was estimated to be 99% or more.

When the molar amount of the obtained reaction product is calculated, it is calculated as 8.13 mmol from the mass 2.17 g, the molecular weight 264.35, and the purity 99%. Since 8.13 mmol of tetraethylphosphonium benzimidazolide was obtained from 8.31 mmol of benzimidazole and 8.31 mmol of tetraethylphosphonium bromide, the yield was 8.13 / 8.31 = 97.8%. Thus, according to the ionic liquid production method of the present embodiment, tetraethylphosphonium benzimidazolide was obtained in a high yield in a short reaction time.

<Example 2: Tetraethylammonium benzimidazolide (N2Bn)>
Hereinafter, examples in which tetraethylammonium benzimidazolide (N2Bn) was synthesized will be described. The first ionic substance, second ionic substance and solvent used are as follows.
First ionic substance Cation: Tetraethylammonium Halogen: Bromine Second ionic substance Alkali metal: Potassium Anion: Benzimidazole Solvent: t-Butanol

To a three-necked flask, add 9.96 g of benzimidazole (83.5 mmol for 99% product) and 50 ml of t-butanol, and heat and stir in an oil bath at 60 ° C. Therefore, 153.9 mmol) was added.

From the dropping funnel, 17.90 g of tetraethylammonium bromide (83.5 mmol for 98% product) and 200 ml of t-butanol were added to the reaction system, and the mixture was stirred at 60 ° C. for 1 hour. The reaction mixture was filtered through a PTFE filter (pore size 0.50 μm), and the filtrate was washed with t-butanol. The solvent was distilled off from the obtained filtrate and dried under reduced pressure (60 ° C., 18 hours) to obtain 22.05 g of a white solid reaction product.

The reaction product was dissolved in d6-DMSO, and 1H-NMR (400 MHz NMR) was measured. The results are shown in FIG. From the results of FIG. 4, the peaks (σ˜12.5) corresponding to the NH protons of benzimidazole seen in FIG. 2 disappeared, and the position of each peak was estimated from the structural formula of tetraethylammonium benzimidazolide. [The peak near σ = 1.12-1.18 is attributed to hydrogen (12H) of the methyl group at the end of the ethyl group on the nitrogen atom in the cation. The peak around σ = 3.14-3.56 is attributed to hydrogen (8H) of the methylene group of the same ethyl group. The peak groups of 6.65-6.70 (2H), 7.27-7.32 (2H)), and 7.62 (1H) belong to hydrogen of benzimidazole. ] Since the ratio of the peak integral value of the cation and the anion is approximately 1: 1, the reaction product is tetraethylammonium benzimidazolide, that is, an ion composed of the cation of the first ionic substance and the anion of the second ionic substance. It was confirmed that liquid was generated.

When the purity of the product was calculated from the peak integrated value of 1H-NMR in FIG. 4, the purity of the reaction product was estimated to be 90% or more.

When the molar amount of the obtained reaction product is calculated, it is calculated as 80.22 mmol from a mass of 22.05 g, a molecular weight of 247.38, and a purity of 90%. Since 80.22 mmol of tetraethylammonium benzimidazolide was obtained from 83.5 mmol of benzimidazole and 83.5 mmol of tetraethylammonium bromide, the yield was 80.22 / 83.5 = 96.1%. Thus, according to the ionic liquid production method of the present embodiment, tetraethylammonium benzimidazolide was obtained in a high yield in a short reaction time.

<Solubility test>
A test was conducted to confirm the solubility of N2Bn, P2Bn and potassium bromide in t-butanol, 2-propanol, 2-butanol, 2-methoxyethanol and acetone.

An ionic liquid was added to the above five solvents so as to have a concentration of 12% by mass, followed by stirring at 30 ° C. for 3 hours. After completion of the stirring, the presence or absence of undissolved residue in the solution was visually confirmed. If the confirmation was difficult, vacuum filtration was performed to confirm the presence of residue on the filter paper. When the residue could be confirmed, the solubility was low (× in the table), and when the residue could not be confirmed, the solubility was high (◯ in the table). The results are shown in Table 1.
Potassium bromide was added to the above five solvents so that the concentration was 5% by mass and stirred sufficiently. The supernatant was subjected to ion chromatographic analysis to determine the bromine concentration. The results are shown in Table 1.

As shown in Table 1, all five solvents are soluble in ionic liquids. Moreover, the solubility with respect to potassium bromide of five solvents is small. Since 2-methoxyethanol has higher solubility than other solvents, the efficiency of separation between the salt and the ionic liquid and the purity of the purified ionic liquid may be slightly deteriorated. Separation is possible.

Note that the configurations disclosed in the above-described embodiments (including the other embodiments, the same applies hereinafter) can be applied in combination with the configurations disclosed in the other embodiments unless there is a contradiction. The embodiments disclosed in this specification are exemplifications, and the embodiments of the present invention are not limited thereto, and can be appropriately modified without departing from the object of the present invention.

Claims

An ionic liquid production method for producing an ionic liquid comprising the cation and the anion by reacting a first ionic substance comprising a cation and a halogen with a second ionic substance comprising an alkali metal and an anion,
The cation is quaternary tetraalkylphosphonium or quaternary tetraalkylammonium;
An ionic liquid production method, wherein the anion is a benzimidazole derivative, an imidazole derivative, or a carbazole derivative.
The reaction between the first ionic substance and the second ionic substance is performed in the presence of a solvent, and the solubility of the solvent in the ionic liquid is greater than the solubility in the salt composed of the halogen and the alkali metal. The method for producing an ionic liquid according to claim 1, which is larger.
The method for producing an ionic liquid according to claim 2, wherein the solvent contains at least one of t-butanol, 2-propanol, 2-butanol, 2-methoxyethanol, and acetone.
The method for producing an ionic liquid according to any one of claims 1 to 3, wherein the cation is tetraethylphosphonium and the anion is benzimidazole.
The method for producing an ionic liquid according to any one of claims 1 to 3, wherein the cation is tetraethylammonium and the anion is benzimidazole.
The method for producing an ionic liquid according to any one of claims 1 to 3, wherein the cation is tetraethylammonium and the anion is imidazole.
The cation is tetrabutylammonium. The method for producing an ionic liquid according to any one of claims 1 to 3, wherein the anion is carbazole.
The method for producing an ionic liquid according to any one of claims 1 to 7, wherein the halogen is fluorine, chlorine, bromine or iodine.
The method for producing an ionic liquid according to any one of claims 1 to 8, wherein the alkali metal is lithium, sodium or potassium.