Method for the production of ionic liquids

Abstract

Method for the manufacturing of at least one ionic liquid of the general formula [Y]+ [X]-, wherein as starting material R1R2R3N is provided in a first solvent, and wherein an alkylation reagent of the general formula RX, is added under formation of said ionic liquid, and wherein said first solvent is selected such that the alkylation reagent is essentially insoluble in that first solvent.

Description

[0001] TITLE

[0002] METHOD FOR THE PRODUCTION OF IONIC LIQUIDS

[0003] TECHNICAL FIELD

[0004] The present invention relates to a method or synthesis for making ionic liquid systems or at least cations for ionic liquid systems. It furthermore relates to use of corresponding ionic liquids for certain applications and to ionic liquids obtained using that method.

[0005] PRIOR ART

[0006] Ionic liquids (ILs) are defined as compounds completely composed of ions with melting point below 100°C (Lei, Z., Chen, B., Koo, Y.M. and MacFarlane, D.R., 2017. Introduction: ionic liquids. Chemical Reviews, 117(10), pp.6633-6635). Many different combinations of cations and anions may be used in ionic liquids, providing a wide array of physical and chemical properties that can be adapted to various applications.

[0007] Ionic liquids have a wide range of potential applications in industry, including as green solvents for chemical reactions and also for dissolution of organic and inorganic compounds. Ionic liquids have also been identified as promising solvents for dissolution of cellulose and for production of fibers (see e.g. WO-A-03029329, WO-A-2004084627). Catalytic reactions and also electrochemical systems including batteries (Watanabe, M., Thomas, M.L., Zhang, S., Ueno, K., Yasuda, T. and Dokko, K., 2017. Application of ionic liquids to energy storage and conversion materials and devices. Chemical reviews, 117(10), pp.7190-7239), supercapacitors and fuel cells are also areas of increasing demand for ILs. Extraction and purification processes can benefit from the properties of ILs including in the extraction of metals from ores and waste streams and also selective absorption of gases from mixtures (e.g. CO2 sequestration). Additional applications for ILs include as lubricants, antistatic additives, dispersing agents and as thermal fluids (WO-A-2013113461), glueing of polymers (WO-A-2015079028, WO-A-2015158866) and hydrogen storage (WO-A- 2010081657).

[0008] WC-A-2005070896 relates to a method for producing ionic liquids consisting first in reacting an ionic liquid with an alkylate, a hydrogencarbonate, a carbonate, a carboxylate or a hydroxide and, afterwards in neutralising with an acid. The ionic liquids contain a phoshonium and / or ammonium cation and an anion selected from a group comprising halogenides, aryl sulfonates, alkyl sulfonates, sulphates, hydroxysulfates, alkyl sulfates, hydrogencarbonates, carbonates, triflates and carboxylates. The inventive method makes it possible to introduce any desired anion into the ionic liquids.

[0009] WO-A-2008052863 relates to a method for producing 1 ,3-heteroaromatic hydrogen carbonates of formula (Illa) and / or (I lib) and / or 1 ,3-heteroaromatic carbonates of formula (IVa) and / or (IVb). According to the method, 1 ,3-heteroaromatic 2-carboxylates of formula (la) and / or (lb) or mixtures of 1 ,3-heteroaromatic 2-carboxylates and 1 ,3-heteroaromatic alkyl carbonates and / or 1 ,3-heteroaromatic aryl carbonates of formula (Ila) and / or (lib), are hydrolysed with water to form 1 ,3-heteroaromatic hydrogen carbonates and / or 1 ,3- heteroaromatic carbonates. Said hydrolysis is carried out in the absence of Bronsted acids or Bronsted-bases.

[0010] WO-A-2022246381 discloses the synthesis of imidazolium-based poly(ionic liquid)s. Chemical Mechanical Planarization (CMP) slurries comprise abrasives; activator; oxidizing agent; additive comprising imidazolium-based poly(ionic liquid); and water. The use of the synthesized imidazolium-based poly(ionic liquid)s in the CMP slurries reduces dishing and erosion in highly selective tungsten slurries.

[0011] Hussain et al. in Journal of the Taiwan Institute of Chemical Engineers 153(5): 105195, D0l:10.1016 / j.jtice.2023.105195 report, that ionic liquids have received a lot of interest in recent years from scientists and academics due to their distinctive qualities, including low vapor pressure, low toxicity, high thermal stability, and recyclability. Ionic liquids have become a more sustainable substitute for volatile organic solvents. Ionic liquids can be synthesized with tailored properties by combining specific cationic and anionic components. Because of their distinct physiochemical characteristics and advantages, ionic liquids were used in different industrial processes such as organic / inorganic synthesis, biomass conversion, desulfurization, catalysis, electrochemistry, spectroscopy, and energy storage.

[0012] The primary goal of the review is to outline the numerous synthetic routes for various classes of ionic liquids such as imidazolium, phosphonium, sulfonium, pyridinium, ammonium, pyrazolium, triazolium, and protic ionic liquids. Ionic liquids have drawn interest for a variety of oilfield applications because of their stability under challenging reservoir conditions, tunability, and low toxicity. This review primarily concentrates on the numerous oilfield applications including demulsification, drilling, heavy oil recovery, and CO2 capture.

[0013] This review also covers the challenges and drawbacks associated with the synthesis and applications of ionic liquids and provides a reasonable solution and potential ideas to address the challenges.

[0014] Tsanas et al. Fluid Phase Equilibria, Vol. 379, p 148-156, report isobaric vapor-liquid equilibrium measurements of the ethanol / water binary mixture and ethanol / water / ionic liquid ternary mixtures using an ebuliometer at 101.3 and 66.6 kPa. The ionic liquids (ILs) synthesized and examined as entrainers for the ethanol / water azeotropic mixture were 1-butyl-3- methylimidazolium bromide ([BMIM][Br]) and 1-ethyl-3-methylimidazolium bromide ([EM I M][Br]) . For both ILs, the initial concentrations for the ternary mixtures were 5%, 10% and 15% w / w. The entrainers were also tested for their recoverability and biodegradability. Analysis with 1 H NMR proved that the ionic liquids can be recycled and reused while their ability to biodegrade was found to be relatively low.

[0015] CN-A-109734668 discloses a synthetic method of tetrafluoroborate ionic liquid. The method comprises the following steps: enabling a quaternized substrate and alkyl halide to be dispersed in a solvent in a molar ratio of 1 to (1-7), adopting ultraviolet irradiation at 30- 50°C, enabling illumination intensity to be 10-1 ,000W / m2and irradiating for 8-12h to obtain a quaternary ammonium salt solution; enabling the quaternary ammonium salt solution and tetrafluoroborate to be uniformly mixed, adopting the ultraviolet irradiation at 35-45°C, enabling the illumination intensity to be 10-1 ,000W / m2and irradiating for 16-20h to obtain mixed liquor; enabling the mixed liquor to be filtered to obtain filtrate, enabling the filtrate to be heated and concentrated, and removing the solvent to obtain the tetrafluoroborate ionic liquid. The method adopts the modes of ultraviolet irradiation and heating to synthesize the tetrafluoroborate ionic liquid, and the yield and reaction rate are high.

[0016] CN-A-115772082 discloses a method for preparing p-methoxycinnamate by using an imidazole basic ionic liquid as a catalyst, which is applied to the technical field of sunscreening agent synthesis, and the method comprises the following steps of: catalytically synthesizing p-methoxycinnamate by using an aldehyde compound and an acetate compound as raw materials and using the imidazole basic ionic liquid as the catalyst; in a reaction for synthesizing p-methoxycinnamate, the addition amount of a catalyst is 0.1 -0.5 wt% of the total mass of an aldehyde compound and an acetate compound, after the reaction is finished, a crude product is separated through suction filtration, a filtrate water phase is cooled to 20°C or below, the ionic liquid and water are subjected to automatic phase separation, the imidazole ionic liquid is separated for reuse, and the p- methoxycinnamate is obtained. The crude product obtained through separation is washed, distilled and recrystallized, and the final product p-methoxycinnamate is obtained. The ionic liquid adopted in the method is simple in preparation process and low in price, the ionic liquid serving as a catalyst is high in catalytic activity, does not corrode equipment and is short in condensation reaction time, and the ionic liquid can be repeatedly used.

[0017] Betti et al. in Tetrahedron, Vol. 64, Issue 8, p. 1689-1695, https: / / doi.orq / 10.1016 / i.tet.2007.12.009, report that the nucleophilic reactivity of a representative series of anions has been measured in [hmim][CI04] 3i, [hm2im][CIO4] 3'i, and [hmim][PF6] 3I ILs in the reaction with n-alkyl methanesulfonates and compared with that found in common molecular solvents (MeOH, DMSO, PhCI). The reactivity is found to depend on both the imidazolium cation-anion interaction and the specific solvation by water present in the IL, the water playing the main effect, in particular with hydrophilic anions. Removal of the largest quantity of water remarkably increases the ion pair reactivity in the IL up to rate constant value k comparable with those obtained in DMSO and in low polarity media (PhCI).

[0018] SUMMARY OF THE INVENTION

[0019] It is an object of the present invention to provide an improved method for the production of ionic liquids, in particular those suitable for the above-mentioned applications.

[0020] This invention relates to a process to prepare ionic liquids of the general formula [Y]+[X]’ by an alkylation reaction in the presence of a solvent, in particular a polar solvent such as water, via a phase transfer reaction.

[0021] [Y]+in the present context is a quaternary ammonium [RIR2RSRN]+cation or a corresponding quaternized nitrogen heteroaromatic or at least heterounsaturated, preferably heterounsaturated cyclic system (i.e. a cation system of the type [RIR2RN]+, wherein the bond between N and one of Ri and R2 is a double bond and wherein preferably R1 and R2 are directly or indirectly connected to form a ring).

[0022] The residues R1, R2, and if present R3, can be the same or different. The residues R1, R2, and if present R3, can be linear, cyclic, branched, saturated or unsaturated alkyl residues, preferably linear or branched, saturated C1-C18, more preferably C1-C12 alkyl residues, in particular selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl or tert-butyl residues. Also possible for residues R1, R2, and if present R3, are mono- or polycyclic aromatic or heteroaromatic residues. These residues can also be substituted with further functional groups, which can be bound to a carbon atom or a heteroatom. Suitable examples are -OH (hydroxy), =0 (in particular as carbonyl group), -NH2 (amino), - NHR', -NHR'2, -NH (imino), -NR', -COOH (carboxy), -CONH2(carboxamide), -SO3H (sulfo) and -CN (cyano). Functional groups and heteroatoms can also be directly adjacent, so that combinations of a plurality of adjacent atoms, for instance -O- (ether), -S- (thioether), -COO- (ester), -CONH- (secondary amide) or -CONR'- (tertiary amide), are also comprised. R' can be linear, cyclic, branched, saturated or unsaturated alkyl residues, preferably linear or branched, saturated C1-C18, more preferably C1-C12 alkyl residues.

[0023] In case of heteroaromatic or at least heterounsaturated systems, the bond between the heteroatom and one of R1 and R2 is a double bond, and preferably a double bond to a carbon atom, and preferably R1 and R2 are directly or indirectly connected to form a ring. In case of heteroaromatic systems, R1 and R2 are directly or indirectly connected to form at least one aromatic ring, preferably a 5 or 6 member aromatic ring, at least said heteroatom, preferably with at least two heteroatoms, which can be directly adjacent or spaced by at least one carbon atom, most preferably said two heteroatoms are both selected as N. For the case of heteroaromatic or heterounsaturated cyclic systems, Ri and R2 are directly or indirectly connected to form a ring and R1 and R2 are selected as substituted or unsubstituted N (so e.g. -NH2-, =N-, -NRX-, or the like, wherein Rxare defined as below) or substituted or unsubstituted C, so e.g. -CH2-, =CH-, =CRX-, -CR , or the like, wherein Rxare defined as below.

[0024] R can be the same or different as any of R1, R2, and if present R3. The residue R can be a linear, cyclic, branched, saturated or unsaturated alkyl residue, preferably a linear or branched, saturated C1-C18, more preferably C1-C12 alkyl residue, in particular selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl or tert-butyl residues. Also possible for residue R are mono- or polycyclic aromatic or heteroaromatic residues. The residue R as defined above can also be substituted with further functional groups functional groups which can be bound to a carbon atom or a heteroatom. Suitable examples are -OH (hydroxy), =0 (in particular as carbonyl group), -NH2 (amino), -NHR', - NHR'2, -NH (imino), -NR', -COOH (carboxy), -CONH2 (carboxamide), -SO3H (sulfo) and - CN (cyano). Functional groups and heteroatoms can also be directly adjacent, so that combinations of a plurality of adjacent atoms, for instance -O- (ether), -S- (thioether), -COO- (ester), -CONH- (secondary amide) or -CONR'- (tertiary amide), are also comprised. R' can be linear, cyclic, branched, saturated or unsaturated alkyl residues, preferably linear or branched, saturated C1-C18, more preferably C1-C12 alkyl residues.

[0025] Possible systems for [Y]+are illustrated below (for the cyclic systems R1 and R2 as defined above are not specifically indicated in these representations if part of the ring; (examples, no complete summary):

[0026]

[0027] Rxin these illustrations can be each, independently of one another, hydrogen, a sulfo group or a carbon-comprising organic, saturated or unsaturated, acyclic or cyclic, aliphatic, aromatic or araliphatic radical which has from 1 to 20 carbon atoms and may be unsubstituted or be interrupted or substituted by from 1 to 5 heteroatoms or functional groups, where the radicals Rxwhich are bound to a carbon atom (and not to a heteroatom) can additionally be halogen or a functional group as defined further above; or two adjacent radicals from the group consisting of Rxmay together also form a divalent, carbon- comprising organic, saturated or unsaturated, acyclic or cyclic, aliphatic, aromatic or araliphatic radical which has from 1 to 30 carbon atoms and may be unsubstituted or be interrupted or substituted by from 1 to 5 heteroatoms or functional groups.

[0028] Further possible are derivatives of these residues substituted with further functional groups, and wherein Ri, R2, R3, R may also be linked to one another (multi-bond residue).

[0029] Z is selected as N, and [Y]+is an ammonium cation [RIR2RN]+in the form of a preferably heterounsaturated cyclic system. Preferably the ammonium cation comprises one ring and 1 , 2 or 3 nitrogen atoms in the ring, and further preferably the ammonium cation is an aromatic compound with one ring and 1 , 2 or 3 nitrogen atoms.

[0030] [X]’ can be a halide including chloride, bromide, iodide, sulfate, phosphate, p- toluenesulfonate, alkylsulfonate, trifluoromethanesulfonate, trifluoroacetate anion, or a combination thereof or any other anion, resulting from a classical quaternization reaction of a corresponding linear or cyclic amine NR1R2R3 analogous nitrogen heteroaromatics.

[0031] Ionic liquids are ionic salts with a melting point below 100°C. Ideally, the salts are also liquid at room temperature while maintaining a relatively low viscosity.

[0032] According to the prior art, ionic liquids should be prepared in water-free in particular according to WO-A-2005070896 and must be very pure for the different applications as described in the above-mentioned prior art.

[0033] A typical example for the prior art preparation of ionic liquids for the example of [EMIM]Br involves acetonitrile and the crude product needs to be worked up as [EMIM]CI. The final product must be dried over P2O5. Such a synthesis path has major disadvantages. This includes the strong exothermicity of the reaction as well as the time-consuming purification of the product before further use is possible. The reaction with bromoalkanes is the fastest but also the most energetic. This means that special care must be taken for large scale reactions, not only for the safety but the high heat can also lead to discoloration of the product and therefore impurities. Also, the cleaning process is tedious as it involves multiple recrystallizations. In addition to that the solvent has to be removed from the system. This means there is always a vacuum distillation required to completely remove solvents.

[0034] The present invention was therefore based on the task of eliminating the before mentioned disadvantages, while a high purity product, easy cleanup and immediate processing is secured.

[0035] Accordingly, a new process was invented to prepare ionic liquids of the general formula [Y]+[X]’ by an alkylation reaction, in particular in the presence of water, via a phase transfer reaction. This reaction is carried out using e.g. a corresponding linear or cyclic amine NR1R2R3 or analogous nitrogen heteroaromatics and a alkylation agent such as RX where X can be a chloride, bromide, iodide, sulfate, phosphate, p-toluenesulfonate, alkylsulfonate, trifluoromethanesulfonate, trifluoroacetate anion or any other anion, resulting from a classical quaternization reaction of a corresponding linear or cyclic amine NR1R2R3 or analogous nitrogen heteroaromatics. The residues Ri, R2, R3, R are defined as above. An example for this reaction is given below for the example of linear or cyclic amines NR1R2R3.

[0036] NR1R2R3+ R X - — * [NRIR2R3R ]+[X]’

[0037] The reaction is usually carried out and / or started at a reaction temperature of at least 30°C or at least 40°C or at least 45°C or in the range of 30°C to 100°Cor 30°C to 55°C depending on the properties of the reactants.

[0038] The solvent in which the alkylation reagent is insoluble, is preferably chosen as water. So water is preferably used in the reaction and prevents a one-phase mixture between all reaction components and therefore an uncontrolled heating up of the reaction. This happens because in this two-phase system the alkylation only occurs on the phase boundary. Therefore, the reaction is at least partly inhibited but at the same time, it is not needed to cool the mixture to prevent excessive heating and therefore denaturation of the reactants / product. This leads to a lot faster reaction time because the reaction is controllable during the whole process. Starting parameters are controlled by stirring speed and / or water amount and / or starting temperature. During the synthesis it can be actively controlled via stirring speed and temperature. Using these options the conversion rate on the phase boundary can be easily adjusted before and during the synthesis and that is why the alkylation can be easily controlled and be executed optimally even in large scale industrial sizes.

[0039] Kinetic experiments show that using the proposed approach the alkylation is 100% completed after 3h e.g. for C4MIM and 4h for C5MIM by the usage of water at 50°C while the reaction execution is improved.

[0040] Preheating of the reaction mixture to 30°C or 40°C or 50°C or higher (within the specified ranges) before adding the alkylation agent is possible, or heating while or after adding the alkylation agent. Also possible is the complete addition of the alkylation agent at once (heat is released over a longer time frame because of the two phase system (controlled by temperature, water content and stirring speed) and therefore the system doesn’t reach the critical temperature (denaturation of reactants / product) as easily as when using a 1 -phase system = higher yield, shorter reaction time) and at least partial heating of the mixture by the excess heat.

[0041] Active control over the reaction at all times is possible via the stirring speed and / or the water amount and / or the reaction temperature control.

[0042] This is especially important for large scale batches, so for reaction volumes larger than 20 mol product.

[0043] Typically, the reaction is carried out for a time span of 60-250 min, preferably 120-200 min at the given temperature to lead to a conversion to the IL of at least 95% or at least 99,9% (measured by NMR).

[0044] Normally 0.5% to 70%, preferably 2% to 50%, more preferably 5% to 25% water is used relative to the amount (by weight) of ionic liquid formed. It is also possible to work with smaller amounts of water, but this increases the exothermicity per time. Preferably the water makes up at most 30% relative to the amount (by weight) of ionic liquid formed. Alternatively higher amounts of water can be used but may lead to a reduction in the space-time yield. The only purification step needed is the removal of the alkylation agent, which can be done by evaporation or liquid-liquid extraction or filtration. After that the water can be removed and the product completely dried if needed. However, for ion exchange processes the ionic liquid (IL) dissolved in water can directly be used without further cleanup.

[0045] With this invention several key advantages can be realized to remove or minimize disadvantages of the conventional prior art synthesis processes of ionic liquids of the formula [Y]+ [X]’:

[0046] • Using water instead of organic solvents gives control of the reaction. This leads to a control of the conversion rate and the released heat over time of the strong exothermic alkylation reaction before and after it is started. This improved control is based on the fact that the alkylation agents are insoluble in water. Therefore, the alkylation takes place only between the liquid-liquid phase boundary of the alkylating agent and the water phase. By adjusting the agitation speed in the reaction vessel, the temperature, the amount of excess of one educt, and the ratio of water to the compound to be alkylated derivate it is possible to achieve excellent control of the alkylation reaction kinetics. The reaction velocity can be reduced nearly to zero when there is no agitation in the reaction vessel and / or the water content is too high. This can also be used to interrupt the reaction at any given time to prevent uncontrolled reaction conditions.

[0047] Also by the usage of the two-phase system, the reaction execution can be optimized. This means the reaction takes place as fast as possible without being able to reach the degeneration point (this is conventionally achieved by carefully dropping in alkylation agents and / or cooling, which is a lot harder to control).

[0048] • By controlling the reaction kinetics, the released reaction heat can also be controlled very well in upscaling experiments. This eliminates a major disadvantage of the previous synthesis of uncontrolled release of the reaction enthalpy. The present invention is therefore advantageous for reducing the hazard profile of the process while reaction speed still fast / faster.

[0049] • Compared to the prior art process as given in WO-A-2008052863, this synthesis approach is more selective (approx. 100%) and also achieves a higher conversion rate (99-100%).

[0050] • Compared to the process as given in WO-A-2008052863 this synthesis approach does not release any CO2.

[0051] • Compared to the process as given in WO-A-2008052863 this synthesis does not need any high-pressure equipment and works at more moderate temperatures (<100°C).

[0052] • Conventional synthesis processes, such as the process as given in WO-A- 2008052863, described in the prior art rely on organic solvents (e.g. methanol, ethanol, acrylonitrile) to maintain a homogeneous reaction environment. By using water as the solvent medium in a liquid-liquid two phase system, in addition to the benefits of the kinetics and enthalpy control described above, there are significant advantages in eliminating organic solvents from scale-up processing including reduced flammability hazard and reduced process complexity (e.g. eliminates need for high pressure vessels).

[0053] The ionic liquid of the general formula [Y]+[X]’ can also be converted to other ionic liquids by swapping the compound [X]’ e.g. in an anion exchange process for another desired anion. Often OH' is chosen, as [Y]+OH' can be reacted further to a large number of ionic liquids with other anions such as acetate or amino acids.

[0054] Generally speaking, the present invention relates to a method for the manufacturing of at least one ionic liquid of the general formula [Y]+[X]', wherein as starting material R1R2R3Z is provided in a first solvent, and wherein an alkylation reagent of the general formula RX, is added under formation of said ionic liquid, and wherein said first solvent is selected such that the alkylation reagent is essentially insoluble in that first solvent.

[0055] Here

[0056] Z is selected as N;

[0057] X is selected from the group consisting of chloride, bromide, iodide, sulfate, phosphate, p- toluenesulfonate, alkylsulfonate, trifluoromethanesulfonate, trifluoroacetate anion;

[0058] [Y]+is an ammonium cation [RIR2RSRN]+, or a corresponding nitrogen heteroaromatic or at least heterounsaturated, preferably heterounsaturated cyclic, system, in which case R3 is not present and the bond between the heteroatom and one of R1 and R2 is a double bond;

[0059] R1 , R2, if present R3, and R are selected as above or in particular as linear, cyclic, branched, saturated or unsaturated, substituted or unsubstituted alkyl residues, or mono- or polycyclic, substituted or unsubstituted, aromatic or heteroaromatic residues, and wherein for the case of heteroaromatic or heterounsaturated cyclic systems, R1 and R2 are directly or indirectly connected to form a ring and Ri and R2 are selected as substituted or unsubstituted N or substituted or unsubstituted C.

[0060] R1R2R3Z is preferably selected as 1 -Methylimidazole, 1 -Ethylimidazole, Triethylamine, 1- Methylpiperidine, 1-Methyl-pyrrolidine, Pyridine or a combination thereof.

[0061] According to a first preferred embodiment, the alkylation reagent is added in a second solvent, wherein said second solvent is essentially immiscible with said first solvent.

[0062] Preferably, the alkylation reagent has a solubility in said first solvent which is lower than 5 g / 100ml preferably lower than 3 g / 100ml, most preferably lower than 2 g / 100ml in each case measured at a temperature of 25°C.

[0063] Said first solvent is preferably water or a mixture of water with another polar solvent selected from the group consisting of alkanol, including ethanol, methanol, propanol, acetonitrile, or a combination thereof, wherein the proportion of water by weight is preferably more than 50%.

[0064] Most preferably, said first solvent is exclusively water.

[0065] In the alkylation reagent of the general formula RX, R is normally as above or in particular selected as a linear, saturated unsubstituted alkyl residue, preferably having 1-18 or 1-8 carbon atoms, most preferably selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tertbutyl, in particular from methyl, ethyl, propyl, or isopropyl.

[0066] X is normally selected as Cl, Br or I.

[0067] As starting material R1R2N is preferably provided in a first solvent, preferably selected as water, R1 and R2 are connected to form a five-member aromatic ring with two nitrogen atoms.

[0068] The starting material is preferably selected as imidazole, preferably as methyl imidazole or ethyl imidazole.

[0069] Before, while or after adding the alkylation reagent the starting material R1R2R3Z or R1R2Z provided in a first solvent or the mixture can be allowed to heat up or actively heated to a temperature of at least 40°C or at least 45°C, up to 100°C preferably for at least one hour, optionally followed by boiling, preferably under reflux, preferably for at least one hour, Before adding the alkylation reagent the starting material in the first solvent can be cooled, preferably below room temperature, the alkylation reagent can be added, and the mixture maintained under cooling for a time span of at least 30 minutes, preferably of at least 1 hour, and subsequently the mixture can be heated above room temperature, preferably at least 40°C, followed by boiling, preferably under reflux, preferably for at least one hour.

[0070] The resulting ionic liquid can be converted by exchanging the anion [X]’ to one selected from the group consisting of acetate, hydroxide, BF4' (tetrafluoroborate) [NTf2]' (bis(trifluoromethylsulfonyl)amide), [DCA]' (dicyanamide), or a combination thereof. For exchanging the anion [X]’ the ionic liquid can be passed through an ion exchange column to convert to a hydroxide, and adding the final anion to the solution followed by removal of water.

[0071] Furthermore the present invention relates to an ionic liquid obtained by a method as given above. Such a system typically has a water content in the range of 1-500 ppm depending on the drying conditions which are used.

[0072] Also, the present invention relates to specific uses of such systems.

[0073] This in particular for chemical reactions, for dissolution of organic and inorganic compounds including dissolving cellulose (including for the production of cellulose yarns from cellulose material), for catalytic reactions, in electrochemical systems, for extraction and purification processes, as lubricant, antistatic additive, dispersing agent, thermal fluid, glueing.

[0074] Further embodiments of the invention are laid down in the dependent claims.

[0075] BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings, Fig. 1 shows the formation of [C4MIM][Br] as a function of time;

[0077] Fig. 2 shows the formation of [CsMIM][Br] as a function of time.

[0078] DESCRIPTION OF PREFERRED EMBODIMENTS

[0079] Preferred embodiments of the invention are described in the following with reference to the experimental evidence, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same.

[0080] Example 1 : [EMIM1 [Brl / [EMIM1 [OAd

[0081] In a 1-liter flask with reflux condenser, 50 g (0.61 mol) 1 -methylimidazole (Carl Roth GmbH, 99%) and approx. 11 ,64 ml water (dest.) were added and cooled in an ice bath. Then 71 ,01 g (0.65 mol, 107 %) of ethyl bromide (Carl Roth GmbH, 99.5%) was added. The mixture was stirred ca. 16 hours in the ice bath. After that the solution was heated to ca. 40 °C (65°C water bath) and was boiled under reflux for another 4h to ensure full conversion. The water was removed with a rotary evaporator at 50 mbar. The oil bath was successively heated to 80 °C. The final drying was done with an oil pump for 2-4 hours to obtain [EMIM][Br] with below mentioned properties.

[0082] Yield NMR 100%; substance recovered [EMIM][Br]: 99,7 %

[0083] Water content: 200 - 300 ppm (If a lower water content is desired the product can be dried at 1 mbar over P2O5) NMR (DMSO-d6):1H: [EMIM][Br] 1.38 (t,3JH-H = 0.025 ppm, 3H); 3.87 (s, 3H); 4.22 (q,3JH- H = 0.023 ppm, 2H); 7.79 (t,3JH-H = 0.005 ppm, 1 H); 7.89 (t,3JH-H = 0.005 ppm, 1 H); 9.39 (s, 1 H); Water: 3.47 2H

[0084] This experimental procedure allows a direct comparison to classical reactions to synthesize ionic liquids. With NMR analysis we noticed that the reaction was very slow while cooling with the ice bath since we are using water. It is necessary, if no solvent is present or the solvent dissolves all reactants into one phase, to ensure that the reaction does not generate too much reaction heat and that the product and the reactants therefore are not destroyed. It is, however, still very fast once it is heated while the reaction kinetics and therefore heatbuildup can be completely controlled when water is used.

[0085] 19,2 g of [EMIM] [Br] (0,1 mol) is dissolved in 76,8 g (300 wt.%) water inside of a beaker. The mixture was then passed through an ion exchange column filled with Amberlite IRA- 402 OH' form (DuPont) and converted into [EMIM] [OH] (3% - 8% solution in water). To the [EMIM] [OH] solution acetic acid was added in equimolar ratio. After this the water was evaporated to receive the final product. [EMIM] [OAc] could be further dried using P2O5. Yield [EMIM][OAc]: 97,7%

[0086] Water content: 2%

[0087] NMR (DMSO-d6):1H: [EMIM][OAc] 1.41 (t,3JH-H = 0.025 ppm, 3H); 1.60 (s, 3H); 3.86 (s, 3H); 4.19 (q,3JH-H = 0.023 ppm, 2H); 7.72 (t,3JH-H = 0.005 ppm, 1 H); 7.81 (t,3JH-H = 0.005 ppm, 1 H); 9.53 (s, 1 H).

[0088] Example 2: [DMIM] [I]

[0089] In a 1-liter flask with reflux condenser, 18.32 g (0.22 mol) 1 -methylimidazole (Carl Roth GmbH, 99%) and 5 ml (10 wt.% compared to product mass) water (dest.) were added and cooled in an ice bath. Then 34.07 g (0.24 mol, 107 %) of lodinemethane (Carl Roth GmbH, 99%) was added. The mixture was stirred ca. 16 hours in the ice bath. After that the solution was heated to ca. 40 °C (65°C water bath) and was boiled under reflux for another 4h to ensure full conversion. Then the water was removed with a rotary evaporator at 50 mbar. The oil bath was successively heated to 80 °C. The final drying was done with an oil pump for 2-4 hours to obtain [DMIM][I] with below mentioned properties.

[0090] Yield NMR: 100% substance recovered [DMIM][I]: 99,5 %

[0091] Water content: 200 - 300 ppm (If a lower water content is desired the product can be dried at 1 mbar over P2O5)

[0092] NMR (DMSO-d6):1H: [DMIM][I] 3.85 (s, 6H); 7.70 (d,3JH-H = 0.001 ppm, 1 H); 9.09 (s, 1 H);

[0093] Water: 3.41 (s, 2H)

[0094] Example 3: [DEIM1 [Brl

[0095] In a 1-liter flask with reflux condenser, 46.87 g (0.49 mol) 1 -ethylimidazole (Carl Roth GmbH, 99%) and 10 ml (10 wt.% compared to product mass) water (dest.) were added and cooled in an ice bath. Then 57.135 g (0.52 mol, 107 %) of Bromoethane (Carl Roth GmbH, 98%) was added. The mixture was stirred ca. 16 hours in the ice bath. After that the solution was heated to ca. 40 °C (65°C water bath) and was boiled under reflux for another 4h to ensure full conversion. Then the water was removed with a rotary evaporator at 50 mbar. The oil bath was successively heated to 80 °C. The final drying was done with an oil pump for 2-4 hours to obtain [DEIM][Br] with below mentioned properties.

[0096] Yield NMR: 100% substance recovered [DEIM][Br]: 100,1 %

[0097] Water content: 0,5% - 1 % (If a lower water content is desired the product can be dried at 1 mbar over P2O5)

[0098] NMR (DMSO-d6):1H: [DEIM][Br] 1.40 (t,3JH-H = 0.025 ppm, 6H); 4.23 (q,3JH-H = 0.026 ppm, 4H); 7.93 (d,3JH-H = 0 ppm, 2H); 9.55 (s, 1 H); Water: 3.46 (s, 2H)

[0099] These two experiments 2 and 3 show similar results as example 1. The kinetics are very slow when a ice bath is used. Therefore, with water present as solvent a much more advanced reaction handling can be used.

[0100] This handling is shown in the kinetics experiments for [C4MIM][Br] and [CsMIM][Br] as well as in the examples further below given in the kinetic experiment description.

[0101] Example 4: 1-ethyl-1-methyl-pyrrolidinium bromide

[0102] 10,96 g 1-methylpyrrolidine (97%, Sigma-Aldrich, 0,125 mol) and 1 ,34 g water (5% in relation to mass of final product) are placed into a flask and heated to 50°C. After the mixture reached the desired temperature 14,9g bromoethane (98%, Thermo-Scientific, 0,134 mol; 7% excess) is added into the flask at one. The reaction is carried out for 3 hours until the mixing and heating is stopped. The final product is recovered using the rotatory evaporator. The temperature of the reaction mixture is not rising a lot, after the bromoethane is added as the water prevents a one-phase mixture and therefore an uncontrolled reaction.

[0103] Yield NMR: 100%, substance recovered 99,24%. NMR: 1 H NMR (500 MHz, DMSO) 5 3.56 - 3.44 (m, 6H), 3.01 (s, 3H), 2.06 (d, J = 5.4 Hz, 4H), 1.24 (tt, J = 7.3, 2.0 Hz, 3H). 2.5 dmso.

[0104] Example 5: 1-ethyl-pyridinium bromide

[0105] 10 g pyridine (99%, Carl Roth GmbH, 0,125 mol) and 1 ,28 g water (5% in relation to mass of final product) are placed into a flask and heated to 50°C. After the mixture reached the desired temperature 14,9g bromoethane (98%, Thermo-Scientific, 0,134 mol; 7% excess) is added into the flask at once. The reaction is carried out for 3 hours until the mixing and heating is stopped. The final product is recovered using the rotatory evaporator.

[0106] Yield NMR: 100%, substance recovered 98,33%.

[0107] NMR:1 H NMR (500 MHz, DMSO) 5 9.24 - 9.18 (m, 2H), 8.62 (tt, J = 7.7, 1.4 Hz, 1 H), 8.18 (t, J = 7.2 Hz, 2H), 4.69 (q, J = 7.3 Hz, 2H), 1.54 (t, J = 7.3 Hz, 3H). 3.51 water; 2.5 dmso.

[0108] Example 6: Tetraethylammonium bromide

[0109] 12,65 g triethylamine (99,5%, Carl Roth GmbH, 0,125 mol) and 1 ,3 g water (5% in relation to mass of final product) are placed into a flask and heated to 50°C. After the mixture reached the desired temperature 14,9g bromoethane (98%, Thermo-Scientific, 0,134 mol; 7% excess) is added into the flask at once. The reaction is carried out for 3 hours until the mixing and heating is stopped. The final product is recovered using the rotatory evaporator. Yield NMR: 100%, substance recovered 99,5%.

[0110] NMR: 1 H NMR (500 MHz, DMSO) 5 3.20 (q, J = 7.3 Hz, 8H), 1.13 (t, 12H). 3.64 water; 2.5 dmso.

[0111] Kinetic experiment description

[0112] For all kinetic experiments a 3 necked 250 ml flask with reflux condenser on top was placed inside a water bath. The starting material and water are then added to the flask and preheated to the desired temperature. Once the system reaches the temperature the alkylation agent is completely added at once to start the reaction. Samples are collected from the water phase every hour and measured via NMR to track the conversion of the starting material to the final product. Since the alkylation agent does not mix itself with the water phase the reaction is stopped the moment a sample is collected. This ensures accurate measurements via NMR.

[0113] All kinetic experiments used the same equipment and parameters:

[0114] Target product amount: 0,125 mol

[0115] Flask: 250 ml, 3 necked, reflux condenser on top

[0116] Magnetic stirrer: Rpm: 750

[0117] Water bath: 900 ml crystallization dish

[0118] Detailed kinetic experiment descriptions:

[0119] Kinetic experiment 1-butyl-3-methyl-imidazolium bromide [C4MIM][Br]

[0120] 10,38 g 1-methylimidazolium (99%) (0,125 mol) and 1 ,37 g water (5% related to mass of the final product) were added into a 250 ml flask with a reflux condenser on top and placed inside a water bath. The mixture was stirred at 750 rpm and heated to 50 °C. Once the temperature was reached, 18,75 g 1 -bromobutane (0,134 mol; 7% excess) was added to start the reaction. Samples were collected every hour from the water phase. To collect the sample, the stirring was stopped for 30 seconds to 1 minute to allow the phases to completely separate. All samples were analysed via NMR to track the conversion.

[0121] Results:

[0122] The NMR results show a fast conversion of the 1-methylimidazolium into the final product within 3 hours. After this time no 1-methylimidazolium or any by-products can be detected inside the NMR samples. The conversion is depicted in Fig. 1 and Tab. 1 below:

[0123] Table 1 : 1-butyl-3-methyl-imidazolium bromide:

[0124] Kinetic experiment 1-pentyl-3-methyl-imidazolium bromide FCsMIMITBrl

[0125] Into a three necked 250 ml flask with a reflux condenser on top 10,37 g 1-methylimidazolium (99%) (0,125 mol) and 1 ,47 g water (5% related to mass of the final product) are added. The flask is placed in a water bath and the mixture is stirred at 750 rpm. Once the system reaches 50 °C 20,65 g 1 -bromopentane 0,134 mol; 7% excess) is completely added to the flask to start the conversion. NMR samples are collected every hour to track the reaction progress.

[0126] Results:

[0127] The NMR data shows a full conversion of the 1-methylimidazolium into 1-pentyl-3-methyl- imidazolium bromide within 5 hours. After this time no 1-mehtylimidazolium or any byproducts can be detected inside the NMR samples. The conversion is depicted in Fig. 2 and Tab. 2 below:

[0128] Table 2: 1-pentyl-3-methyl-imidazolium bromide:

[0129] LIST OF REFERENCE SIGNS

[0130] C4MIM 1-butyl-3-methyl-imidazolium bromide

[0131] C5MIM 1-pentyl-3-methyl-imidazolium bromide

[0132] DEIM 1 ,3-Diethylimidazolium

[0133] DMIM 1 ,3-Dimethylimidazolium

[0134] DMSO Dimethyl sulfoxide

[0135] EMIM 1-Ethyl-3-methylimidazolium

[0136] IL ionic liquid

Claims

CLAIMS1. Method for the manufacturing of at least one ionic liquid of the general formula [Y]+[X]’, wherein as starting material R1R2R3Z is provided in a first solvent, and wherein an alkylation reagent of the general formula RX, is added under formation of said ionic liquid at a reaction temperature of at least 30°C, and wherein said first solvent is selected such that the alkylation reagent is essentially insoluble in that first solvent whereinZ is selected from the group consisting as N;X is selected from the group consisting of chloride, bromide, iodide, sulfate, phosphate, p-toluenesulfonate, alkylsulfonate, trifluoromethanesulfonate, trifluoroacetate anion;[Y]+is an ammonium cation [RIR2RSRN]+, or a corresponding nitrogen heteroaromatic or at least heterounsaturated, preferably heterounsaturated cyclic, system, in which case R3 is not present and the bond between the heteroatom and one of R1 and R2 is a double bond;R1, R2, if present R3, and R are selected as linear, cyclic, branched, saturated or unsaturated, substituted or unsubstituted alkyl residues, or mono- or polycyclic, substituted or unsubstituted, aromatic or heteroaromatic residues, and wherein for the case of heteroaromatic or heterounsaturated cyclic systems, R1 and R2 are directly or indirectly connected to form a ring and R1 and R2 are selected as substituted or unsubstituted N or substituted or unsubstituted C.

2. Method according to the preceding claim, wherein the alkylation reagent is added in a second solvent, wherein said second solvent is essentially immiscible with said first solvent.

3. Method according to any of the preceding claims, wherein the alkylation reagent has a solubility in said first solvent which is lower than 5 g / 100ml preferably lower than 3 g / 100ml, most preferably lower than 2 g / 100ml in each case measured at a temperature of 25°C.

4. Method according to any of the preceding claims, wherein said first solventis water or a mixture of water with another polar solvent selected from the group consisting of alkanol, including ethanol, methanol, propanol, acetonitrile, or a combination thereof, wherein preferably the proportion of water by weight is more than 50%, and wherein preferably said first solvent is exclusively water.

5. Method according to any of the preceding claims, wherein in the alkylation reagent of the general formula RX, R is selected as a linear or branched, saturated unsubstituted alkyl residue, including functionalized alkyl residues, preferably having 1-18 or 1-8 carbon atoms, most preferably selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tertbutyl.

6. Method according to the preceding claim, wherein X is selected as Cl, Br or I.

7. Method excluding to any of the preceding claims, wherein [Y]+is an ammonium cation [RIR2RN]+in the form of a preferably heterounsaturated cyclic system, wherein preferably the ammonium cation comprises one ring and 1 , 2 or 3 nitrogen atoms in the ring, wherein further preferably the ammonium cation is an aromatic compound with one ring and 1 , 2 or 3 nitrogen atoms.

8. Method according to any of the preceding claims, in particular claim 6, wherein as starting material R1R2N or R1R2R3N is provided in a first solvent, preferably selected as water, wherein preferably as starting material R1R2N is used and R1 and R2 are connected to form a five-member aromatic ring with two nitrogen atoms.

9. Method according to claim 8, wherein the starting material is selected as imidazole or a derivative or substituted, in particular C1-C8 alkyl substituted, forms thereof, preferably as methyl imidazole or ethyl imidazole.

10. Method according to any of the preceding claims, wherein before, while or after adding the alkylation reagent the starting material R1R2R3Z or R1R2Z provided in a first solvent or the mixture is allowed to heat up or actively heated to a temperature of at least 40°C or at least 45°C, up to 100°C, preferably for at least one hour, optionally followed by boiling, preferably under reflux, preferably for at least one hour, or wherein, before adding the alkylation reagent the starting material in the first solvent is cooled, preferably below room temperature, the alkylation reagent is added, andthe mixture maintained under cooling for a time span of at least 30 minutes, preferably of at least 1 hour, and subsequently the mixture is heated above room temperature or to a temperature of at least 40°C, followed by boiling, preferably under reflux, preferably for at least one hour.11 . Method according to any of the preceding claims, wherein the resulting ionic liquid is converted by exchanging the anion [X]’ to one selected from the group consisting of acetate, hydroxide, BF4' (tetrafluoroborate), [NTf2]' (bis(trifluoromethylsulfonyl)amid), [DCA]- (dicyanamide), or a combination thereof.

12. Method according to the preceding claim, wherein for exchanging the anion [X]’ the ionic liquid is passed through an ion exchange column to convert to a hydroxide, and adding the final anion to the solution followed by removal of water.

13. Ionic liquid obtained by a method according to any of the preceding claims.

14. Ionic liquid according to the preceding claim having a water content in the range of 1-500 ppm or 10-500 ppm.

15. Use of an ionic liquid according to any of the preceding claims as a solvent for chemical reactions, for dissolution of organic and inorganic compounds including dissolving cellulose, including for the production of cellulose yarns from (recycling) cellulose material, for catalytic reactions, in electrochemical systems, for extraction and purification processes, as lubricant, antistatic additive, dispersing agent, thermal fluid, glueing.

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