KR100974890B1 - A recycling process of ionic liquids using microwave irradiation - Google Patents

Abstract

The present invention relates to a method for recovering an ionic liquid using microwaves. An ionic liquid used as a reaction medium or an ionic liquid mixed or formed with another solvent including water through formation of a reaction medium or an ideal system By selectively heating and evaporating water or other solvents through microwaves, it is possible to efficiently separate, recover and reuse expensive ionic liquids, which is useful for cost reduction and productivity improvement of processes using ionic liquids. Can be.

Microwave, ionic liquid, recovery process, evaporation

Description

A recycling process of ionic liquids using microwave irradiation

The present invention relates to a method for separating and recovering an ionic liquid using microwaves.

As volatile organic compounds (VOCs), widely used in chemical and petrochemical processes, have been found to be a major contributor to air pollution, regulations on the use of these materials are increasingly being enforced around the world. As a way to solve the VOCs problem, there is an active research on the next generation green solvent that can replace volatile organic compounds.

The most ideal clean solvent should be nontoxic and volatile, chemically and physically stable, soluble in a wide range of materials and easy to separate and reuse. From this point of view, ionic liquids (ILs), which are emerging in recent years, may be regarded as clean solvents that best meet these conditions.

Unlike ionic salts or salt compounds consisting of metal cations and non-metal anions, such as salts, usually melting at high temperatures above 800 ° C, salts or salt compounds with melting points at temperatures below 100 ° C are called ionic liquids. In particular, ionic liquids present as liquids at room temperature are called room temperature ionic liquids (RTILs). The ionic liquid is an organic salt composed of an organic cation and an anion, and the cations include dialkylimidazolium, alkylpyridinium, quaternary ammonium and quaternary phosphonium. a is _{^{NO 3 -, BF 4 -,}} AlCl 4 -, Al 2 Cl 7 -, AcO -, PF 6 -, TfO - (trifluoromethanesufonate, CF 3 SO 3 -), Tf 2 N - (trifluoromethanesulfonylamide, (CF 3 SO and the like ^{_{- 2) 2 N), CH}} 3 CH (OH) CO 2 - (L-lactate), and SbF.

Room temperature ionic liquids (RTILs) are non-volatile, non-toxic, non-flammable, have excellent thermal stability, ionic conductivity, and are large in polarity to dissolve inorganic and organometallic compounds. It has high value as a potential green solvent. It can be applied to a wide range of chemical fields such as catalysts, separations, and electrochemistry. The chemical and physical properties of ionic liquids such as melting point, viscosity, density, hydrophobicity, and polarity can be controlled by changing the structure of the cations and anions constituting the ionic liquid. Because of its ease of synthesis, ionic liquids are often referred to as designer solvents. Therefore, ionic liquids, which are eco-friendly solvents that can replace organic solvents, which are used throughout the industry, are applied in various fields such as chemical process, biological process, chemical synthesis, new material synthesis, electrochemistry, analytical chemistry, and energy environment. Technology is possible.

However, although ionic liquids have this advantage, their low price competitiveness poses a big problem for industrialization. Therefore, when an ionic liquid is used as a solvent in the reaction medium, as a solvent for forming a liquid-liquid equilibrium, or as an additive in various reaction systems, development of a process for separating and reusing an expensive ionic liquid after the reaction system is difficult. It's urgent. In the conventional method of separating an ionic liquid, a method of evaporating water or an organic solvent, which is a reaction medium, has been reported almost exclusively, and this process requires a lot of energy, and another environmental pollution problem occurs.

Microwaves, on the other hand, have a frequency of 30 MHz to 3 GHz and strong energy of 124 neV to 12.4 μeV, which makes it easy to transfer energy to other media through the medium.

The principle that microwaves heat materials is by using dipole polarization and by ionic conduction.

The first principle of heating materials using microwaves is heating through dipole polarization. In polar materials with high dielectric constants, dipoles are self-aligned by rotation by electric fields formed by microwaves. If the frequency is low, all dipoles can be aligned in the direction of the electric field and then rearranged in the direction of the next formed electric field. At higher frequencies, however, before all dipoles are aligned in the direction of the electric field, some dipoles are rearranged along the direction of the next electric field, creating phase differences in the same solution. This phase difference between dipoles causes intermolecular friction and collapse, resulting in energy loss of molecules. The energy loss of the molecules can be converted to thermal energy to heat the polar material.

The second method of transferring heat is ionic conduction. The electric field changes rapidly and causes ionic motion of these materials to generate energy, resulting in local ignition of the solution, which can heat the solution.

Using this principle, microwaves are used to irradiate materials with only microwaves without a separate heating device and catalyst, heating them in a short time, and binding or cleaving specific compounds.

Microwaves can rapidly heat solutions or change the structure of compounds through dipole polarization and ionic conduction as described above. It is stable and cannot be decomposed or modified by microwaves.

Thus, the inventors have found a method of separating from a mixture by irradiating microwaves to a mixture of ionic liquids and water or other solvents to selectively heat and evaporate water or other solvents, and completed the present invention.

It is an object of the present invention to provide a method for heating separation and recovery of water or organic solvents other than ionic liquids by ultrasonic irradiation in a mixture containing an ionic liquid used as an additive in the formation of an ideal system or as a reaction medium.

In order to achieve the above object, the present invention provides a method for separating an ionic liquid using microwaves.

In the method for recovering an ionic liquid according to the present invention, an ionic liquid used as a reaction medium or an ionic liquid mixed with other solvents including water through the formation of a reaction medium or an ideal system or forming an ideal system through microwaves, By selectively heating and evaporating water or other solvents, expensive ionic liquids can be efficiently separated, recovered and reused, which can be useful for cost reduction and productivity improvement of processes using ionic liquids.

Hereinafter, the present invention will be described in detail.

The present invention provides a method for recovering an ionic liquid using microwaves to recover an ionic liquid used as an additive in the formation of an ideal system or a reaction medium.

Specifically, the present invention includes a solvent, a cosolvent, a co-solvent, or an additive to form an ionic liquid which is present in the reaction medium and does not dissolve, and a liquid-liquid equilibrium ideal system formed by an organic solvent or water. And separating and recovering the ionic liquid from the mixture using microwaves.

The ionic liquid recovered in the present invention uses dialkylimidazolium, alkylpyridinium, quaternary ammonium or quaternary phosphonium as the cation, and NO ₃ ⁻ , BF ₄ ⁻ as the anion. ^{_{, AlCl 4 -, Al 2 Cl}} 7 -, AcO -, PF 6 -, TfO - (trifluoromethanesufonate, CF 3 SO 3 -), Tf 2 N - (trifluoromethanesulfonylamide, (CF 3 SO 2) 2 N), CH 3 CH ^{_{(OH) CO 2 - (L}} -lactate), SbF - can be synthesized using, for example, is changed by variously combining them.

The method for recovering an ionic liquid according to the present invention includes a method of separating an organic solvent or water by heating and evaporating by microwave.

In the mixture containing microwave irradiated ionic liquid, except for high boiling point ionic liquid, only low boiling water or organic solvent is selectively heated and evaporated, so it can be efficiently recovered by irradiating microwave only. Can be.

According to the present invention, the frequency range of the microwave for separating the ionic liquid is preferably 30 MHz to 300 GHz. The frequency of the region uses the frequency of metric wave, decimeter wave, centimeter wave, and can selectively heat and evaporate water or organic solvent.

At this time, if the frequency is less than 30 MHz, there is a problem that the heating of water or the organic solvent does not occur sufficiently, and evaporation does not occur. When the frequency is higher than 300 GHz, the energy consumption is greater than that of the water or organic solvent, and the ionic liquid evaporates. There is a problem.

Microwaves for separating ionic liquids according to the invention can be irradiated continuously or discontinuously. If the microwave is irradiated discontinuously, the microwave may be irradiated for 20 to 30 seconds, and the irradiation may be repeated for 1 to 2 seconds.

The microwave irradiation time for separating the ionic liquid according to the present invention is irradiated until all contained water or organic solvent is discharged, and the microwave irradiation time may be shortened as the frequency is increased.

In addition, the recovery process using the microwave for separating the ionic liquid according to the present invention further includes ultracentrifugation, filtration, absorption, adsorption and desorption process using a carrier.

The recovery process uses the properties such as large molecular weight, density and conductivity of the ionic liquid, and the ultracentrifugation, filtration or absorption, adsorption and desorption using a carrier together with microwaves can further separate the ionic liquid. Can be increased.

The ultracentrifugation is a method of separating liquid states having different specific gravity that do not dissolve with each other by using a large molecular weight of the mixture, and the filtration is a method of separating a fluidic solid-liquid mixture through a porous filtration membrane, and the absorption Is a method of separating solutes by moving them from one phase to another through the interface of two phases, and adsorption and desorption using the carrier are ionic using polymer resin, activated carbon, carbon nanoparticles, etc. It is a method of selectively adsorbing liquid and inducing desorption by change of temperature, concentration and the like.

Hereinafter, the present invention will be described in detail with reference to Examples. However, the following examples are merely to illustrate the invention, the present invention is not limited by the examples.

Preparation Example 1 Preparation of Mixture of Ionic Liquid and Water 1

Prepare a mixture of [Bmim] [BF ₄ ] (C-Tri) at 5% by volume with water.

Preparation Example 2 Preparation of Mixture of Ionic Liquid and Water 2

Prepare a mixture of [Bmim] [BF ₄ ] at 10% by volume of water.

Preparation Example 3 Preparation of Mixture of Ionic Liquid and Water 3

Prepare a mixture of [Bmim] [BF ₄ ] at 20% by volume of water.

Preparation Example 4 Preparation of Mixture of Ionic Liquid and Water 4

Prepare a mixture of [Bmim] [BF ₄ ] at 30% by volume with water.

Preparation Example 5 Preparation of Mixture of Ionic Liquid and Water 5

Prepare a mixture of [Bmim] [BF ₄ ] at 40% by volume of water.

Preparation Example 6 Preparation of Mixture of Ionic Liquid and Water 6

Prepare a mixture of [Bmim] [BF ₄ ] at 50% by volume of water.

Example 1 Separation and Recovery of Ionic Liquid 1

0.5 ml of the mixture prepared in Preparation Example 1 was placed in a reaction vessel of a monomode microwave generator (CEM dicover, USA) (see FIG. 1 (a)), irradiated with microwave at 2450 MHz for 30 seconds, and irradiated for 2 seconds. Was stopped and irradiated for 30 seconds again to separate and recover the ionic liquid.

In the microwave generator, since the microwave generating vibrator is installed perpendicular to the center of the reaction vessel (see FIG. 1 (b)), the microwave can be irradiated evenly over the entire mixture, thereby increasing the recovery rate.

Example 2 Separation and Recovery of Ionic Liquid 2

In Example 1, except that Preparation Example 2 was used instead of Preparation Example 1 was carried out in the same manner.

Example 3 Separation and Recovery of an Ionic Liquid 3

In Example 1, except that Preparation Example 3 was used instead of Preparation Example 1 was carried out in the same manner.

Example 4 Separation and Recovery of Ionic Liquid 4

In Example 1, except for using Preparation Example 4 instead of Preparation Example 1 was carried out in the same manner.

Example 5 Separation and Recovery of Ionic Liquid 5

In Example 1, except for using Preparation Example 5 instead of Preparation Example 1 was carried out in the same manner.

Example 6 Separation and Recovery of an Ionic Liquid 6

In Example 1, except that Preparation Example 6 was used instead of Preparation Example 1 was carried out in the same manner.

Experimental Example 1 Recovery Efficiency According to the Concentration of the Ionic Liquid

In order to determine the recovery efficiency of the method according to the present invention according to the concentration of the ionic liquid, the recovery rate of the ionic liquid recovered by Examples 1 to 6 are summarized in Table 1 below.

Before the investigation Total survey time
(minute) After investigation % Recovery
Amount of mixture (g) Amount of Ionic Liquid (g) Amount of mixture (g) Amount of Ionic Liquid (g) Example 1 0.5072 0.020 13 0.0245 0.020 100.39 Example 2 0.5123 0.077 17 0.0790 0.078 101.39 Example 3 0.5193 0.090 20 0.1020 0.090 100.34 Example 4 0.5311 0.15 30 0.1702 0.15 100.50 Example 5 0.5416 0.22 22 0.2307 0.22 100.47 Example 6 0.5448 0.26 27 0.2877 0.27 100.68

As shown in Table 1, the recoveries of Examples 1 to 6 irradiated with microwaves were 100%, and all the mixed water was discharged and only pure ionic liquid was recovered.

1 is a microwave generator (a) and its internal schematic diagram (b).

Claims (8)

Ionic liquids used to form liquid-liquid equilibrium systems in which ionic liquids and organic solvents that do not dissolve with each other or ionic liquids and water that do not dissolve together form water or ionic liquids used as additives in the reaction medium Recovering an ionic liquid by heating and evaporating an organic solvent or water to recover only an ionic liquid. delete delete The method of claim 1, wherein the ionic liquid used to form the liquid-liquid equilibrium ideal system is included as a solvent, cosolvent or cosolvent in the reaction medium. The method of claim 1, wherein the ionic liquid uses dialkylimidazolium, alkylpyridinium, quaternary ammonium or quaternary phosphonium as the cation, and NO ₃ ⁻ , BF as the anion. ^{_{4 -, AlCl 4 -, Al}} 2 Cl 7 -, AcO -, PF 6 -, TfO - (trifluoromethanesufonate, CF 3 SO 3 -), Tf 2 N - (trifluoromethanesulfonylamide, (CF 3 SO 2) 2 N), CH ^{_{3 CH (OH) CO 2 -}} (L-lactate) or SbF ^- a method for recovering an ionic liquid characterized by using. The method of claim 1, wherein the microwave is 30 MHz ~ 300 GHz recovery method of the ionic liquid. The method of claim 1, wherein the microwave is irradiated continuously or discontinuously. The method of claim 1, wherein the recovery method further comprises any one selected from the group consisting of ultracentrifugation, filtration, absorption and adsorption and desorption using a carrier. .

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