PL240103B1 - Ionic mixture containing choline cations and application of this mixture as a medium in electrochemical processes - Google Patents

Abstract

The subject of the application is an ionic mixture containing choline cations and an admixture of an organic component, characterized in that it is liquid at room temperature and contains only non-toxic components, i.e. choline acetate and an additional organic component. According to the invention, the content of choline acetate in the mixture is less than 75% by mole, preferably less than 50% by mole, and the content of water in the mixture is more than 0.5% by mole. According to the invention, the content of the additional organic component in the mixture is more than 25% by mole, preferably more than 50% by mole. Alternatively, the mixture contains more than one organic component, and their total content in the mixture is more than 25% by mole, preferably more than 50% by mole. According to the invention, the additional organic component is formic acid, acetic acid, urea, oxalic acid, malonic acid, citric acid or mixtures thereof. The application also covers the use of the above-mentioned mixture as a medium in electrochemical measurements and tests, preferably as a medium for the reaction of separation of metals or metal oxides, as a medium for conducting the electrophoresis process of organic compounds, as a medium during the electrochemical characterization of unstable systems in aqueous solutions.

Description

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Description of the invention

The subject of the invention is an ionic mixture containing choline cations and the use of this mixture as a medium for conducting electrochemical processes.

Ionic liquids (IL) are a class of ionic chemicals that have a melting point below 100 ° C. Most often, ionic liquids contain large cations and organic or inorganic anions with high steric hindrance, which makes their crystallization at low temperatures difficult. Their physico-chemical properties, such as conductivity, viscosity and miscibility with water, are determined by the properties of the cation and anion, their composition and the presence of various admixtures.

Ionic liquids have found numerous applications in chemistry. For example, they are used as enzymatic reaction medium, as cellulose solvents [CA2462460], or as solvents for use in the electrodeposition of active metals [Electrochemical aspects of ionic liquids, Wiley (2005)]. For example, it is known to use aqueous solutions of choline acetate as a medium for the electrodeposition of a Cu-Zn alloy [Electrochim. Acta, 108 (2013) 788].

The use of ionic liquids as electrolytes in electrochemical processes is particularly advantageous because it provides the possibility of conducting electrochemical studies in a non-aqueous environment and is an alternative to organic electrolytes using standard organic solvents.

Ionic liquids are much more viscous than salt water solutions. However, an increase in viscosity causes a decrease in electrolytic conductivity, in accordance with the Walden rule, which says that the product of viscosity and boundary molar conductivity is a constant value [Electrochemistry. Jonika, WNT (2000) 125; Modern Electrochemistry 1. lonics, Springer (1998) 461-463]. This rule is approximate, but it illustrates the general tendency observed in electrolyte systems, also among ionic liquids. Unfortunately, the high viscosity of the solution is a disadvantageous feature from the point of view of electrochemical processes due to the low conductivity of such electrolytes. The viscosity of the solution can be lowered by heating the system, but this often leads to the degradation of the organic substances contained in the mixture.

Ionic liquids characterized by high ionic conductivity at the level of 10-20 mS cm ^-1 are usually characterized by a viscosity of 20-50 mPa s (Table 1). For example, chloride-based ionic liquids, which are very viscous, have low conductivity (eg [C1C8Mim] [CI] at 30 ° C: η = 3690 mPa s; κ = 0.09 mS cm ^-1 ). It is worth noting that the viscosity of ionic liquids does not correlate with their density, which is usually in the range of 1.0-1.5 gem ^-3 , and is slightly higher than that of water, with ionic liquids with chloride anions usually having the lowest densities. .

Table 1. Physicochemical properties of selected ionic liquids analyzed in scientific literature in terms of their potential use in electrochemical cells, T = 25 ° C (if different, its value is given in brackets), (-) no literature values.

substance density [g-ęm * ⁹ ] conductivity [mS-cm * ¹ ] viscosity [mPa-s] Miscibility and water (N (HO-Et) H3] [CHOj] 1.20 4.40 (25 * C) 188 (25'C) very good [C2Mim] [AcO] 1.10 2.50 (25 * C) 93 (25 * C) very good [CZMimjjBFł] 1.28 14.1 (25 "C) 33.8 (25 * C) very good [EtNHj] [NOa] 1.21 25.4 (25 * C) 36.5 (25 * C) very good [PrC2MIM] [Tf ₂ N] 1.45 1.9S (25'C) 91.9 (25 * C) weak (HO-C2Mim] (reF *] 1.34 3.42 (20'C) 137 (25 * C) very good (C4Mim] [PF ₆ ) 1.37 1.92 (25 * C) 267 (25 * C) weak [C4Mim] [[BF ₄ ] 1.30 3.15 (25 * 0) 1O4 (25'C) very good [C4Mim] | SCN] 1.07 8.98 (30 * C) 35.9 (30C) very good (C4Mim] (TCMJ - 8.83 (30 * C) 25.7 (25 * 0 very good (C4Mim] | TfO] 1.30 3.05 (25 * C) 80 (25'0 very good [C10Mlm] [CI] 0.99 0.02 (30 * C) 8570 (30 * 0 very good | C10Mim] [TfO] 1.15 0.41 (24 * C) 298 (25 * 0 very good [ClC8Mlm] [CI | ________ 1.01 0.09 (30'C) 3690 (35 * 0 very good

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Nowadays, great emphasis is placed on the safety of solvents. In the case of ionic liquids, the toxicity of their anions and cations decreases in the following series [Crit. Rev. Env. Sci. Tec., 48 (2018) 859; Arh. Hig. Advice. Toksikol., 68 (2017) 171 *]:

[CN] -> [Tf2N] -, [PFe] ', [SbF6] -> [BF4] -, [SCN] -, [C8PO4] -> [Cl] -, [NO3] ·, [C1SO4]^-, [CH3COO] [CnMim]⁺(n> 11)> (P66614]⁺> [C4Mim]⁺> [N1888]⁺> [C4pyr]⁺> [N111 (2 (O) OH)]⁺, [Ch]⁺However, it should be remembered that the toxicity of the ionic liquid is mainly caused by its cation [Water Res., 44 (2010) 352]. The above list shows that the safest are those ionic liquids that contain simple cations with unbranched aliphatic chains and anions that do not contain fluorine or cyanide groups.

Examples of non-toxic ionic systems are compounds containing a protonated choline cation and a halide anion or a simple organic acid residue (e.g., acetic acid). Unfortunately, such ion systems are usually solids at room temperature. For example, choline chloride melts with decomposition at about 300 ° C, unlike choline acetate, which, although solid at room temperature, melts at about 85 ° C. What's more, choline salts show high biotransformity.

It is possible to obtain liquid ionic solutions containing non-toxic choline acetate or choline chloride at room temperature by adding a natural organic compound, e.g. oxalic acid or citric acid. In this way, systems which are liquids at room temperatures are obtained [Chem. Rev. 2014, 114, 11060-11082]. Recent literature reports indicate that choline in systems containing organic acids undergoes esterification reaction, but the process is slow [ACS Sustainable Chem. Eng., 7 (2019) 11521], therefore the change of the physico-chemical properties of the analyzed systems is also slow.

Choline has a wide industrial application, for example for the synthesis of its derivatives [US2731493A, US2013536A]. Choline is also used to nourish and stimulate development

[BE1024170B1], incl. as a component of the herbicide [US2019142006A1].

Choline chloride with urea and methyl urea is also used to prepare the epoxy hardener [PL227299B1]. Literature reports indicate the possibility of using ionic liquids based on choline also as anti-inflammatory substances [J. Moth. Liquids, 232 (2017) 20]. They are also analyzed in the context of organic synthesis [J. Moth. Liquids, 227 (2017) 234]. Choline acetate in mixtures with DMSO and water was also investigated in the context of dissolving cellulose [J. Chem. Eng. Date, 64 (2019) 2923]. It is known to use systems containing choline chloride and urea or ethylene glycol as an extraction medium [J. Water Process Eng., 21 (2018) 163].

Chloride or choline acetate in combination with urea, glycerol or ethylene glycol (1: 1) show stronger bacterial inhibitory properties than single components [Chemosphere, 132 (2015) 63], and at the same time their toxicity is lower than the toxicity of single components. Choline acetate has been shown to be less toxic than choline chloride [Chemosphere, 132 (2015) 63], and a mixture of choline chloride and acetic acid is more toxic than choline acetate alone [ACS Sustainable Chem. Eng., 3 (2015) 3398].

Taking into account the low toxicity of choline and its mixtures with natural, organic compounds, it is attractive to use this type of mixtures as a medium during electrochemical measurements in relation to systems that can be used in the production of biologically active compounds. In the literature, there are individual reports on the electrochemical studies of non-aqueous choline-based systems, but they are practically limited to its halide forms.

The electrochemical characterization of mixtures containing choline halides as hydrogen bond acceptors (HBA) in the presence of appropriate hydrogen bond donors (HBD) is known [Chem. Soc. Rev., 41 (2012) 7108]. Based on the analysis of the results of these tests (Table 2), it can be seen that the electrochemical stability of the choline halides decreases in the Cl> Br> I series. Mixtures containing fluorides, as very toxic, were not included in the analysis. The individual results described in the above-mentioned publication also concerned nitrates (V) and chlorates (VII).

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Table 2. Selected physicochemical properties of choline-based systems. Potentials vs. Ag | AgCl (10 mM) in acetonitrile. [Chem. Soc. Rev., 41 (2012) 7108].

system EiM EaM Potential window [V] ChCi + oxalic acid -0.92 1.24 2.16 ChCl + glkerol -2.21 1.38 3.59 ChCl + urea -2.75 1.54 4.29 ChCi + malonic acid -2.55 1.70 4.25 ChBr + glycerol -2.36 1.16 3.52 ChBr * urea -2.09 1.23 3.32 ChBr * malonic acid -2.38 1.03 2.41 CN + oxalic acid -0.92 1.24 2.16 Chl * glycerol -2.32 0.44 2.76 Chi * urea -0.89 0.36 1.25 Chi * malonic acid -2.32 0.44 2.76

The systems containing choline chloride as well as urea and malonic acid were also tested electrochemically, but due to the high viscosity of these systems, the potential windows had to be registered at a temperature of 70 ° C [U.P.B. Sci. Bull. Series B, 76 (2014) 21]

There is a known mixture of choline chloride and ethylene glycol (1: 2) characterized by low viscosity coefficients at room temperature (37 mPa s at 25 ° C) [Green Chem., 13 (2011) 82], but due to the poisonous properties of glycol and high temperature boiling point, its use in electrochemical synthesis and the study of biological systems is not preferred.

The viscosity and conductivity of systems based on choline chloride with other substances, including organic acids, were also tested. For example, at a temperature of 25 ° C, a mixture of choline chloride with urea has a high viscosity of 259 mPa s, and in a mixture with malonic acid as much as 1124 mPa s [J. Am. Chem. Soc., 126 (2004) 788]. The conductivity of the mixture of choline chloride with urea at 40 ° C is about 0.2 mS-cm- ¹ [Sc /. China Chem., 59 (2016) 571],

The high viscosity of ionic mixtures (low conductivity) based on choline chloride and organic acids means that their use in electrochemistry is not frequent, and the use of ionic mixtures containing other choline salts is unknown.

There is an unmet need to develop new choline-based liquid ionic mixtures that exhibit low viscosity and high ionic conductivity, while having low toxicity, bioreutrality and biodegradability, which could serve as a medium for electrochemical processes.

The essence of the invention.

The ionic mixture containing choline cations and an admixture of an organic component is liquid at room temperature and contains only non-toxic components, i.e. choline acetate and an additional organic component, which is formic acid, acetic acid, urea, oxalic acid, and malonic acid. , citric acid or mixtures thereof.

According to the invention, the content of choline acetate in the mixture is less than 75 mol%, preferably less than 50 mol%. According to the invention, the water content of the mixture is more than 0.5 mol%. According to the invention, the content of the organic component in the mixture is more than 25% by mol, preferably more than 50% by mol. Alternatively, the mixture contains more than one organic component and the total content of the mixture is more than 25 mole%, preferably more than 50 mole%.

The use of the ionic mixture described above as a medium in electrochemical measurements and studies, preferably as a medium for the precipitation of metals or metal oxides, as a medium for electrophoresis of organic compounds, as a medium during the electrochemical characterization of unstable systems in aqueous solutions.

The invention will now be described in detail by way of example with reference to the accompanying drawing. Figures 1-3 show the appearance of the obtained choline acetate ionic mixtures with selected organic compounds, i.e .:

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Fig. 1 1: 2 mixture of choline acetate and urea (Ch + U);

1: 2 mixture of choline acetate and hydrated oxalic acid (ChAc + OxAd);

1: 2 mixture of choline acetate and anhydrous oxalic acid (ChAc + OxA _a );

1: 2 mixture of choline acetate and malonic acid (ChAc + MA);

Fig. 2 a mixture of choline acetate and citric acid (ChAc + CA) in the ratio 2: 1;

1: 1 mixture of choline acetate and formic acid (ChAc + FA);

1: 2 mixture of choline acetate and formic acid (ChAc + FA);

1: 3 mixture of choline acetate and formic acid (ChAc + FA);

Fig. 3 a 1: 1 mixture of choline acetate and acetic acid (ChAc + AA);

1: 2 mixture of choline acetate and acetic acid (ChAc + AA);

mixture: choline acetate and acetic acid (ChAc + AA) in the ratio 1: 3.

Figures 4-14 show graphs of kinematic viscosity as a function of temperature measured for the obtained choline acetate ion mixtures with selected organic compounds, i.e .:

Fig. 4 a 1: 1 mixture of choline acetate and formic acid (ChAc + FA);

Fig. 5 a 1: 2 mixture of choline acetate and formic acid (ChAc + FA);

Fig. 6 a 1: 3 mixture of choline acetate and formic acid (ChAc + FA);

Fig. 7 a 1: 1 mixture of choline acetate and acetic acid (ChAc + AA);

Fig. 8 a 1: 2 mixture of choline acetate and acetic acid (ChAc + AA);

Fig. 9 a 1: 3 mixture of choline acetate and acetic acid (ChAc + AA);

Fig. 10 a mixture of choline acetate and urea (Ch + U) in the ratio 1: 2;

Fig. 11 1: 2 mixture of choline acetate and hydrated oxalic acid (ChAc + OxAd);

Fig. 12 a 1: 2 mixture of choline acetate and anhydrous oxalic acid (ChAc + OxA _a );

Fig. 13 a 1: 2 mixture of choline acetate and malonic acid (ChAc + MA);

Fig. 14 a mixture of choline acetate and citric acid (ChAc + CA) in the ratio 2: 1.

Figures 15-25 show the graphs of conductivity as a function of temperature measured for the obtained choline acetate ion mixtures with selected organic compounds, i.e .:

Fig. 15 mixture: choline acetate and formic acid (ChAc + FA) in a 1: 1 ratio; Fig. 16 mixture: choline acetate and formic acid (ChAc + FA) in a ratio of 1: 2; Fig. 17 mixture: choline acetate and formic acid (ChAc + FA) in a ratio of 1: 3; Fig. 18 mixture: choline acetate and acetic acid (ChAc + AA) in a ratio of 1: 1; Fig. 19 mixture: choline acetate and acetic acid (ChAc + AA) in a ratio of 1: 2; Fig. 20 mixture: choline acetate and acetic acid (ChAc + AA) in a ratio of 1: 3; Fig. 21 mixture: choline acetate and urea (Ch + U) in a ratio of 1: 2; Fig. 22 mixture: choline acetate and hydrated oxalic acid (ChAc + OxAd) in a ratio of 1: 2; Fig. 23 mixture: choline acetate and anhydrous oxalic acid (ChAc + OxA _a ) in a ratio of 1: 2; Fig. 24 mixture: choline acetate and malonic acid (ChAc + MA) in a ratio of 1: 2; Fig. 25 mixture: choline acetate and citric acid (ChAc + CA) in a ratio of 2: 1.

The composition of the above mixtures was determined in the molar ratios of the indicated components.

Detailed Description of the Invention.

Choline salts in mixtures with simple organic compounds and organic acids form ionic systems with a melting point lower than room temperature, which makes it possible to use them as a non-aqueous medium in electrochemical processes. Known non-toxic ionic mixtures containing i.a. Chlorides show high viscosity and low, insufficient conductivity at room temperature, as shown in Table 3.

Table 3. Characteristics of selected mixtures of choline chloride with urea, oxalic acid and malonic acid, respectively. (d) density; (η) dynamic viscosity; (σ) conductivity, (-) no value in the literature. [J. Chem. Eng. Data, 597 (2014) 2221; Chem. Soc. Rev., 41 (2012) 7108; Phys. Chem. Chem. Phys., 13 (2011) 21383; ACS Sustainable Chem. Eng., 2 (2014) 2416; J. Am. Chem. Soc., 126 (2004) 9142]

Symbol Molar ratio d [g-on- *] at 25 * 0 η | mPa> s] at 25 * C o [mS-cm ^-1 ] ChCI + U 1: 2 1,250 750 0.199 (at 40 * C | ChCI + OxA 1: 1 1,260 8953 4.98 (at 30 * C) WANT + MA 1: 1 1,230 1389 0.742 (at 25 * C) WANT + MA 1: 2 1,250 1124 -

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In order to ensure the non-toxicity of the liquid ionic system according to the invention, it was decided to use choline acetate, which is neutral for humans, since both choline and acetic acid are compounds found in the human body.

Choline acetate is not often used in chemical and biochemical laboratories mainly due to the relatively high price compared to choline chloride and the difficulty of purifying choline acetate in the vacuum drying process. Although this compound is commercially available, it is relatively poorly studied physicochemically.

In search of the optimal composition of the liquid mixture based on choline acetate, light low-toxic, bi-neutral organic compounds were selected: formic acid, acetic acid, urea, hydrated oxalic acid, anhydrous oxalic acid, malonic acid and citric acid. Any toxic or bio-incompatible compounds were excluded from the study, even if their use could potentially lower the viscosity of the mixture or increase its ionic conductivity. The basic physicochemical properties of the components used in the preparation of ionic mixtures (melting point, density) are presented in Table 4.

Table 4. Characteristics of the components of the mixtures according to the invention. (Mp) melting point; (d) density; (-) no value in literature.

The naive of the component and its symbol tt d [rem ¹ ] Choline chloride [ChCl] 302-305 1.024 (25 * C) Choline acetate [ChAc] 80-85 - Formic acid [FA] 8.3 1,220 (20Χ) Acetic acid [AA] 17 1.045 (25Χ) Urea [UJ 132-135 1.335 (25XJ Oxalic acid (dihydrate) [OxAd] 98-100 1,650 (20Χ) Oxalic acid (anhydrous) [ΟχΑ,] 189.5 1,900 (25Χ) Malonic acid [MA] 132-135 1.619 (25Χ) Citric acid (monohydrate) [CA] 156 1.542 (25Χ)

Choline acetate ionic mixtures (ChAc) with selected organic components (formic acid FA, acetic acid AA, urea U, hydrated oxalic acid OxAd, anhydrous oxalic acid OxA _a , malonic acid MA, citric acid CA) were prepared in various molar ratios. Preparation of liquid ionic mixtures based on choline acetate is uncomplicated and consists in mixing the components and heating the obtained mixture to approx. 65-70 ° C for less than 60 minutes. This procedure is much simpler and faster compared to the procedures for the preparation of analogous mixtures based on choline chloride, which require more time (even several hours) due to the slow mixing process of the mixture components resulting from the high viscosity of the ionic liquid formed.

Detailed recipes for the preparation of ionic mixtures according to the invention are presented in Examples 1-12, and the appearance of the mixtures obtained is summarized in Table 5. The compositions of the mixtures have been experimentally developed to minimize their viscosity. It was observed that too high a choline acetate content led to too viscous liquids (e.g. Example 11). It was observed that a liquid ionic mixture was formed in less than 60 minutes when solid choline acetate was mixed with the remaining organic components of the mixtures.

The ionic conductivity of the obtained ionic mixtures based on choline acetate was investigated. Surprisingly, it was found that these mixtures exhibit significantly higher ionic conductivity and lower viscosity (Table 6) compared to similar mixtures based on choline chloride (Table 3).

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Table 5. Characterization of the appearance of the obtained mixtures of choline acetate with urea, oxalic acid, malonic acid, citric acid, formic acid and acetic acid, respectively. T = 25 ° C.

Mixture Molar ratio Appearance ChAc + FA 1: 1 transparent, colorless liquid ChAc + FA 1: 2 transparent, colorless liquid ChAc + FA 1: 3 transparent, colorless liquid ChAc + AA 1: 1 transparent, colorless liquid ChAc + AA 1: 2 transparent, colorless liquid ChAc + AA 1: 3 transparent, colorless liquid ChAc + U 1: 2 transparent, colorless, viscous liquid ChAc + OxAd 1: 2 transparent, colorless liquid ChAc + ΟχΑ. 1: 2 transparent, colorless liquid ChAc + MA 1: 2 transparent, colorless, viscous liquid, gas bubbles are released ChAc + CA 1: 2 very sticky substance ChAc + CA 2: 1 transparent, colorless, viscous liquid

It was observed that among the mixtures in a molar ratio of 1: 2, the mixtures of choline acetate with formic acid (Ch + FA: 21.46 mPa s, 9.93 mS cm) showed particularly good parameters (low viscosity and high conductivity) at 25 ° C. ¹ ), acetic acid (Ch + AA: 55.31 mPa s, 3.28 mS cm ¹ ) and dihydrate oxalic acid (Ch + OxAd: 43.13 mPa s, 7.51 mS cm ¹ ), distinguishes them from known mixtures containing the choline cation. It was also observed that in the case of mixtures of choline acetate with formic acid and acetic acid, the ionic conductivity increased significantly with a decrease in the content of choline acetate (Table 5). It should be noted that even with a low content of choline acetate (25%, molar ratio 1: 3), these mixtures show higher ionic conductivity at room temperature (Ch + FA: 15.80 mS cm ¹ ; Ch + AA: 4.86 mS cm · ¹ ) than pure formic acid (FA: 5.50 mScm · ¹ at 18 ° C) and acetic acid (AA: 0.32 mS cm · ¹ at 18 ° C), as well as choline acetate itself, which in is a solid at room temperature.

It was also observed that the water content in ionic mixtures, even those obtained from substrates containing traces of it, is higher than it results from the sum of its content in these substrates. Water is formed in a system containing choline acetate as a result of a slow esterification reaction, analogous to mixtures based on choline chloride [ACS Sustainable Chem. Eng., 7 (2019) 11521]. It turns out, however, that the low, but noticeable, water content can significantly improve the parameters such as viscosity and conductivity of the ionic mixture, which was illustrated by the conductivity of the system of choline acetate with oxalic acid. The ionic conductivity of the mixture increases significantly from the value of 0.48 mS cm · ¹ at the water content of approx. 3% by weight. in the system obtained from anhydrous oxalic acid (Ch + OxA _a ), to approx. 7.51 mS cm · ¹ for the system obtained from oxalic acid dihydrate (Ch + OxAd) containing approx. 12 wt. water.

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Table 6. Characteristics of the obtained mixtures of choline acetate with urea, oxalic acid, malonic acid, citric acid, formic acid and acetic acid, respectively, (d) density; (η) dynamic viscosity; (σ) conductivity, (wh2o) - water content, (~) approximate value, due to gas bubbles.

Mixture Molar ratio d [g-cm ³ ] q [mPas] o [mS-cm ¹ ] 25'C SO'C 25 * C 5O * C 25'C 50'C 25 * C ChAc + FA 1: 1 1.106 1.090 50.04 21.38 5.48 8.76 1.58 ChAc * FA 1: 2 1,120 1.105 21.46 10.41 9.93 15.82 1.81 ChAc * FA 1: 3 1.130 1.111 12.37 6.28 15.80 19.22 1.68 ChAc * AA 1: 1 1.090 1.072 126.96 42.24 1.89 3.65 0.54 ChAc * AA 1: 2 1.085 1.074 55.31 21.60 3.28 4.96 1.09 ChAc * AA 1: 3 1.083 1.061 32.20 13.35 4.86 7.82 0.57 ChAc * U 1: 2 1.176 1.164 1444.72 206.17 0.24 1.36 0.98 ChAc + OxAd 1: 2 1.249 1.229 43.13 15.34 7.51 21.80 12.10 ChAc * OxA> 1: 2 1.296 1.286 1464.51 272.92 0.48 1.30 3.68 I want * MA 1: 2 * 1.165 -1.155 -437.15 -107.63 -0.79 -2.23 2.17 ChAc * CA 2: 1 1,211 1.198 2654.66 629.19 0.19 0.50 4.42

The developed mixtures of choline acetate with oxalic acid (Ch + OxAd), formic acid (Ch + FM) and acetic acid (Ch + AA) in a ratio of 1: 2 also show a satisfactory potential window of 1.05 V, 2.45 V and 2.60 V, which makes it possible to carry out measurements and electrochemical tests using these mixtures as a medium. This stability is slightly lower than that of known ionic liquids based on other choline salts, but still satisfactory.

Table 7. Electrochemical properties of the obtained mixtures of choline acetate with urea, oxalic acid, malonic acid, citric acid, formic acid and acetic acid, respectively. The potentials were determined against the Ag | AgCl (10 mmol / dm3 ⁾ silver chloride electrode in [C2py] (Tf2N] ionic liquid.

Mtesianlna Molar ratio EsM E * M Potential window [V] ChAc + FA 1: 2 -1.65 0.80 2.45 ChAc + AA 1: 2 -1.65 0.95 2.60 ChAc * U 1: 2 -1.60 -0.30 1.30 ChAc * OxAj 1: 2 -1.10 -0.05 1.05 I want * MA 1: 2 -1.15 -0.50 1.65 ChAc * CA 2: 1 -1.40 0.00 1.40

A series of multi-component ionic mixtures containing choline acetate and a mixture of two or three additional organic components were also prepared, from among the components selected earlier, one of these components having a dominant content (90 mol%), and the admixture of the remaining components did not exceed 10 mol%. The obtained multi-component mixtures had properties substantially similar to those of two-component mixtures containing the same additional organic component as the dominant component in the multi-component mixtures.

The developed mixtures according to the invention show stability at room temperature, which is sufficient for conducting electrochemical experiments lasting even hours. Due to the progressive esterification reaction causing the increase of the water content in the ionic mixture, it is recommended, however, to prepare ionic mixtures each time before the experiment, in order to ensure the repeatability of the measurement conditions.

The ionic mixtures according to the invention can be used as test medium for electrochemical processes, for example for the separation of metals or their oxides. Due to the small

Due to the water content, moderate viscosity and high ionic conductivity, it is also possible to conduct electrophoresis of organic compounds therein. Additionally, they can serve as media during the electrochemical characterization of systems unstable in aqueous solutions. It is also expected that the presence of organic acids will inhibit the growth of microorganisms, and thus the indicated mixtures will show preservative properties.

The ionic mixtures according to the invention are highly bio-neutral for humans, as all their components are present in the human body and are non-toxic. Moreover, the ionic mixtures according to the invention are highly biodegradable since they contain organic compounds consisting only of elements such as carbon, hydrogen, oxygen and nitrogen.

The invention will now be described in the following examples with reference to the drawing and the tables presented above.

Example 1 7.14 g of choline acetate and 1.64 cm ³ of formic acid (molar ratio 1: 1) were introduced into a glass vessel with a capacity of 20 cm ³ (molar ratio 1: 1), stirred at room temperature, obtaining a colorless, transparent liquid after 30 minutes. . The characteristics of the components are presented in Table 4, and the parameters of the obtained mixture in Tables 5-6 and Figures 2, 4, 15.

Example 2 7.12 g of choline acetate and 3.28 cm ³ of formic acid (molar ratio 1: 2) were introduced into a glass vessel with a capacity of 20 cm ³ (molar ratio 1: 2), stirred at room temperature, obtaining a colorless, transparent liquid after 30 minutes. . The characteristics of the components are shown in Table 4, and the parameters of the obtained mixture in Tables 5-7 and Figures 2, 5, 16.

Example 3 3.54 g of choline acetate and 2.46 cm ³ of formic acid (molar ratio 1: 3) were introduced into a glass vessel with a capacity of 20 cm ³ (molar ratio 1: 3), mixed at room temperature, obtaining a colorless, transparent liquid after 30 minutes. . The characteristics of the components are shown in Table 4, and the parameters of the mixture obtained in Tables 5-6 and Figures 2, 6, 17.

Example 4 5.40 g of choline acetate and 1.91 cm ³ of acetic acid (molar ratio 1: 1) were introduced into a glass vessel with a capacity of 20 cm ³ (molar ratio 1: 1), then stirred at room temperature, and then heated for 7 minutes at the temperature. 60 ° C to obtain a colorless, transparent liquid. The characteristics of the components are presented in Table 4, and the parameters of the obtained mixture in Tables 5-6 and Figures 3, 7, 18.

Example 5 5.40 g of choline acetate and 3.81 cm ³ of acetic acid (molar ratio 1: 2) were introduced into a glass vessel with a capacity of 20 cm ³ (molar ratio 1: 2), stirred at room temperature, obtaining a colorless, transparent liquid after 50 minutes. . The characteristics of the components are shown in Table 4, and the parameters of the obtained mixture in Tables 5-7 and Figures 3, 8, 19.

Example 6 3.56 g of choline acetate and 3.83 cm ³ of acetic acid (molar ratio 1: 3) were introduced into a glass vessel with a capacity of 20 cm ³ (molar ratio 1: 3), stirred at room temperature, obtaining a colorless, transparent liquid after 50 minutes. . The characteristics of the components are shown in Table 4, and the parameters of the obtained mixture in Tables 5-6 and Figures 3, 9, 20.

Example 7 6.75 g of choline acetate and 5.00 g of urea (molar ratio 1: 2) were introduced into a glass vessel with a capacity of 20 cm ³ , mixed at room temperature, and then heated for 25 minutes at 65 ° C. C until a homogeneous, clear liquid is obtained. Then the system was cooled to room temperature, obtaining a colorless, transparent, viscous liquid. The characteristics of the components are shown in Table 4, and the parameters of the obtained mixture in Tables 5-7 and Figures 1, 10, 21.

Example 8 3.90 g of choline acetate and 6.00 g of hydrated oxalic acid (molar ratio 1: 2) were introduced into a glass vessel with a capacity of 20 cm ³ , and stirred at room temperature. Then, the system was heated for 10 min at 65 ° C until a uniform, clear liquid was obtained, and then the system was cooled to room temperature, obtaining a colorless, transparent liquid. The characteristics of the components are shown in Table 4, and the parameters of the resulting mixture in Tables 5-7 and Figures 1, 11, 22.

Example 9 5.46 g of choline acetate and 6.00 g of anhydrous oxalic acid (molar ratio 1: 2) were introduced into a glass vessel with a capacity of 20 cm ³ , and stirred at room temperature. Then the system was heated for 60 min at the temperature of 60 ° C until a uniform, clear liquid was obtained, and then the system was cooled to room temperature, obtaining a colorless, transparent, viscous liquid. The characteristics of the components are shown in Table 4, and the parameters of the resulting mixture in Tables 5-6 and Figures 1, 12, 23.

Example 10. 4.68 g of choline acetate and 6.00 g of malonic acid (molar ratio 1: 2) were introduced into a glass vessel with a capacity of 20 cm ³ , stirred at room temperature,

The mixture was then heated for 40 min at 65 ° C until a uniform, clear liquid was obtained. Then the system was cooled to room temperature, obtaining a colorless, transparent, viscous liquid. The characteristics of the components are presented in Table 4, and the parameters of the obtained mixture in Tables 5-7 and Figures 1, 13, 24.

Example 11 1..95 g of choline acetate and 5.00 g of citric acid (monohydrate) (1: 2 molar ratio) were introduced into a glass vessel with a capacity of 20 cm ³ , stirred at room temperature and then heated for 60 min. at 65 ° C, then for 60 min at 70 ° C. A very sticky, heterogeneous substance was obtained, which was not further tested.

Example 12 7.75 g of choline acetate and 5.00 g of citric acid (monohydrate) (2: 1 molar ratio) were introduced into a 20 cm ³ glass vessel, stirred at room temperature and then heated for 60 min. at 65 ° C, and then for 60 min at 70 ° C until a uniform, clear liquid is obtained. The system was cooled to room temperature, obtaining a colorless, transparent, viscous liquid. The characteristics of the components are shown in Table 4, and the parameters of the obtained mixture in Tables 5-7 and Figures 2, 14, 25.

Example 13 The procedure of Examples 1-12 was followed, with the only difference that in place of the pure additional organic component, mixtures of this component with one of the remaining additional organic components were added in a 9: 1 molar ratio. The resulting liquid ionic mixtures exhibited characteristics substantially consistent with those of the mixtures of the corresponding Examples 1-12.

Example 14 The procedure of Examples 1-12 was followed, except that in place of the pure additional organic component, mixtures of this component were added with any of the remaining additional organic components in a molar ratio of 18: 1: 1. The resulting liquid ionic mixtures exhibited characteristics substantially consistent with those of the mixtures of the corresponding Examples 1-13.

Abbreviations used

ChCI - choline chloride (cholinechloride)

ChBr - choline bromide (cholinebromide)

Chl - choline iodide

ChAc - choline acetate

FA - formic acid

AA - acetic acid

U - urea

OxAd - oxalic acid dihydrate

OxAa - oxalic acid anhydrous

MA - malonic acid

CA - citric acid

[N (HO-Et) H3] [CHO2] - 2-Hydroxyethylammonium formate

[C2Mim] [AcO] - 1-Ethyl-3-methylimidazolium acetate

[C2Mim] [BF4] - 1-Ethyl-3-methylimidazolium tetrafluoroborate

[EtNH3] [NO3] - Ethylammonium nitrate

[PrC2MIM] [BF4] - 1,2-Dimethyl-3-propylimidazolium bis (trifluoromethylsulfonyl) imide

[HO-C2Mim] [BF4] - 1- (2-Hydroxyethyl) -3-methylimidazolium tetrafluoroborate

[C4Mim] [PF6] - 1-Butyl-3-methylimidazolium hexafluorophosphate

[C4Mim] [BF4] -1-Butyl-3-methyIimidazolium tetrafluoroborate

[C4Mim] [SCN] - 1-Butyl-3-methylimidazolium thiocyanate

[C4Mim] [TCM] - 1-Butyl-3-methylimidazolium tricyanomethanide

[C4Mim] [TfO] - 1-Butyl-3-methylimidazolium triflate

[C10Mim] [Cl] - 1-Decyl-3-methylimidazolium chloride

[C10Mim] [TfO] - 1-Decyl-3-methylimidazoliunn triflate

[C18Mim] [Cl] - 1-Methyl-3-octylimidazolium chloride

Claims (6)

PL 240 103 B1 Patent claims 1. Ionic mixture containing choline cations and an admixture of an organic component, characterized by the fact that it is liquid at room temperature and contains only non-toxic, bi-neutral and biodegradable components, i.e. choline acetate and an additional organic component, i.e. formic acid, acetic acid, urea, oxalic acid, malonic acid, citric acid, or mixtures thereof. 2. The ionic mixture according to claim 1 The method of claim 1, characterized in that the choline acetate content in the mixture is less than 75 mol%, preferably less than 50 mol%. 3. The ionic mixture according to claim 1 2. The process of claim 1, wherein the water content of the mixture is greater than 0.5 mol%. 4. The ionic mixture of claim 1 The method of claim 1, characterized in that the content of the additional organic component in the mixture is more than 25 mol%, preferably more than 50 mol%. 5. The ionic mixture of claim 1 A composition according to claim 1, characterized in that it contains more than one additional organic component, and their total content in the mixture is more than 25 mol%, preferably more than 50 mol%. 6. The use of the ionic mixture as defined in claims 1-5 as a medium in electrochemical measurements and tests, preferably as a medium for the precipitation of metals or metal oxides, as a medium for electrophoresis of organic compounds, as a medium during the electrochemical characterization of unstable systems in aqueous solutions.