Low viscosity metal ion-containing liquids

Abstract

The metal ionic liquid can exhibit a sharply increased viscosity relative to the same ionic liquid that does not contain metal cations. Disclosed are metal ion-containing liquid compositions containing a viscosity modifier that reduces the viscosity. The metal ion-containing liquids are useful in processes and systems designed for removal and recovery of certain components such as ethylene, isobutane, or both in a process stream. Also disclosed herein are processes for the removal and recovery of ethylene from a process stream with improved ethylene removal capability while reducing viscosity without the need to correspondingly reduce the metal cation concentration.

Description

Technical Field

[0001] The present disclosure generally relates to metal-containing ionic liquids having reduced viscosity, methods for removing and recovering ethylene from process streams using metal-containing ionic liquids, complexes for preparing ionic liquids, and related product processing systems for recovering ethylene from process streams using ionic liquids. Background Art

[0002] Metal-containing ionic liquids have been found to be useful for capturing and recovering certain compounds from process streams. For example, systems have been developed that contact metal-containing ionic liquids with process streams to capture ethylene through pi-bond interactions with the metal-containing ionic liquids. Generally, higher metal concentrations are associated with an increased ability of the ionic liquid to chelate ethylene in the process stream (e.g., increased loading). However, increasing the metal cation concentration also dramatically increases the viscosity of the metal-containing ionic liquid relative to a metal-free ionic liquid.

[0003] Increased viscosity can be detrimental. In general, the efficiency of contact of the process stream with the ionic liquid and the ability to transport the ionic liquid throughout the recovery system is often inversely proportional to the viscosity of the metal-containing ionic liquid. Thus, higher viscosity ionic liquid compositions may be more difficult, or even impossible, to implement in an ethylene recovery system than lower viscosity ionic liquid compositions.

[0004] Thus, the present disclosure is generally directed to metal ionic liquid compositions having acceptable viscosities for use in ethylene recovery systems. SUMMARY OF THE INVENTION

[0006] The present invention summary is provided to introduce a series of concepts that will be further described in the detailed description below in a simplified form. The present invention summary is not intended to identify the necessary or essential features of the claimed subject matter. The present invention summary is also not intended to be used to limit the scope of the claimed subject matter.

[0007] Aspects of the present invention relate to compositions comprising: (i) an ionic liquid comprising an ionic liquid cation and an ionic liquid anion; (ii) a metal cation; and (iii) a viscosity modifier. For example, the ionic liquid may be N,N-allylmethylimidazolium bis(trifluoromethanesulfonyl)imide or (1-(2-cyanoethyl))-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, the metal cation may be a copper cation or a silver cation, and the viscosity modifier may be 3,4-dichlorotoluene, sulfolane, N-methylpyrrolidone, caprolactone, propylene carbonate, benzyl butyl phthalate, or any combination thereof.

[0008] According to another aspect of the present invention, a method for reducing the viscosity of a metal-containing ionic liquid may include combining the metal-containing ionic liquid with a viscosity modifier to form a composition having a viscosity less than or equal to 80% of the metal-containing ionic liquid. The method may also include selecting the viscosity modifier based on its boiling point, dipole moment, Hansen solubility properties, or any combination thereof.

[0009] According to another aspect of the present invention, a method for separating ethylene from a process stream is disclosed, and this method may include: (i) contacting a process stream containing ethylene with a metal-containing ionic liquid to form an ethylene-rich metal-containing ionic liquid containing ethylene captured from the process stream; (ii) separating the ethylene-rich metal-containing ionic liquid from the process stream; and (iii) releasing ethylene from the ethylene-rich metal-containing ionic liquid to form an ethylene-depleted metal-containing ionic liquid. The method may produce sufficient overall ethylene recovery capacity to remove 1 mol of ethylene from the process stream per liter of metal-containing ionic liquid contacted with the process stream.

[0010] Also disclosed herein is a novel copper complex, namely bis(trifluoromethanesulfonyl)imide Cu(I).

[0011] The foregoing summary of the invention and the following detailed description all provide examples and are illustrative only. Therefore, the foregoing summary of the invention and the following detailed description should not be considered restrictive. Further, in addition to those features or variations set forth herein, features or variations may also be provided. For example, certain aspects may be directed to various feature combinations and sub-combinations described in the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The following drawings form part of this specification and are included to further illustrate certain aspects of the invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.

[0013] Figure 1 A graph of viscosity as a function of temperature for certain metal ion liquid-containing compositions in Table 2 is presented.

[0014] Figure 2 Presented are graphs of the ethylene solubility of metal-containing ionic liquid A at various ethylene partial pressures with and without the addition of 5 wt % 3,4-dichlorotoluene, normalized to the Cu concentration.

[0015] Although the invention disclosed herein is susceptible to various modifications and alternative forms, only a few specific embodiments have been shown by way of example in the drawings and described in detail below. The drawings and detailed description of these specific embodiments are not intended to limit the breadth or scope of the inventive concept or the appended claims in any way. Instead, the drawings and detailed written description are provided to illustrate the disclosure to those of ordinary skill in the art and enable such persons to make and use the inventive concept.

[0016] definition

[0017] In order to more clearly define the terms used herein, the following definitions are provided. Unless otherwise indicated, the following definitions apply to the present disclosure. If a term is used in the present disclosure but is not specifically defined herein, the definition in IUPAC Compendium of Chemical Terminology, 2nd Edition (1997) may be applied, as long as the definition does not conflict with any other disclosure or definition applied herein, or does not make any claim to which the definition is applied uncertain or invalid. If any definition or usage provided by any document incorporated herein by reference conflicts with the definition or usage provided herein, the definition or usage provided herein shall prevail. Unless otherwise indicated, the Hansen solubility characteristics of the compounds stated herein are taken from the values ​​listed in "Hansen Solubility Parameters: A User's Handbook" (CRC Press, 2007) by Charles M. Hansen.

[0018] Herein, features of the subject matter are described such that within a particular aspect, combinations of different features are contemplated. For each aspect and each feature disclosed herein, all combinations that do not adversely affect the process or method described herein are contemplated, and specific combinations may or may not be explicitly described. In addition, unless explicitly stated otherwise, any aspect or feature disclosed herein may be combined to describe an inventive composition or method consistent with the present disclosure.

[0019] For any particular compound or group disclosed herein, unless otherwise indicated, any name or structure presented (generally or specifically) is intended to encompass all conformational isomers, regioisomers, stereoisomers, and mixtures thereof that may result from a particular set of substituents. It will be appreciated by those skilled in the art that, unless otherwise indicated, a name or structure (generally or specifically) also encompasses all enantiomers, diastereomers, and other optical isomers, if any, in both enantiomeric and racemic forms, as well as mixtures of stereoisomers. For example, a general reference to pentane includes n-pentane, 2-methylbutane, and 2,2-dimethylpropane; and a general reference to butyl includes n-butyl, sec-butyl, isobutyl, and tert-butyl.

[0020] Unless otherwise indicated, the terms "contacting" and "combining" are used herein to describe compositions and methods in which materials or components are contacted or combined together in any order, in any manner, and for any length of time. For example, the materials or components can be blended, mixed, slurried, dissolved, reacted, treated, impregnated, compounded, or otherwise contacted or combined in some other manner or by any suitable method or technique.

[0021] In the present disclosure, although compositions and methods are described in terms of "comprising / including" various components or steps, unless otherwise specified, compositions and methods may also "consist essentially of" or "consist of" the various components or steps. Unless otherwise specified, the terms "a / an" and "the" are intended to include multiple alternatives, such as at least one.

[0022] The present invention discloses several types of scopes. When disclosing or claiming any type of scope, it is intended to disclose or claim separately every possible number that such scope can reasonably cover, including the endpoints of the scope and any sub-ranges and combinations of sub-ranges covered therein. For example, the ionic liquid composition disclosed herein can have a certain viscosity. The disclosure that the weight percentage of the viscosity modifier in the ionic liquid can be in the range of 3 wt % to 25 wt %, it is intended to narrate that the weight percentage can be any amount within the range, and for example, any range or range combination of 3 wt % to 25 wt % can be included, such as 5 wt % to 10 wt %, 3 wt % to 20 wt %, etc. Similarly, all other scopes disclosed herein should be interpreted in a manner similar to this example.

[0023] Generally, an amount, size, formulation, parameter, range, or other quantity or characteristic is "about" or "approximately", whether or not expressly stated as such. Whether or not modified by the term "about" or "approximately", the claims include equivalents to the quantities or characteristics.

[0024] As used herein, the term "ionic liquid" (or "IL") is given its ordinary meaning in the art and means a liquid, more specifically a molten salt, containing essentially only ions and more specifically only anions and cations, having a melting point of 200°C or less and having high thermal stability and low flammability. Room temperature ionic liquids (RTILs) are ionic liquids that are liquid at standard temperature and pressure, preferably below 100°C. In certain embodiments, the ionic liquid can be represented by the empirical formula A x Qy represents, wherein A is a monoanion or polyanion, Q is a monocation or polycation, x is a number in the range of 1 to about 4, and y is a number in the range of 1 to about 4. The cations associated with ILs are structurally diverse, but generally contain one or more nitrogens as part of the ring structure and can be converted into quaternary amines. Examples of such cations include pyridinium, pyridazinium, pyrimidinium, pyrazinium, imidazolium, pyrazolium, oxazolium, triazolium, thiazolium, piperidinium, pyrrolidinium, quinolinium, and isoquinolinium. The anions associated with the ILs can also be structurally diverse and varied, and can have a significant effect on the solubility of the ILs in different media. For example, ionic liquids containing hydrophobic anions such as hexafluorophosphate or trifluoromethanesulfonimide have very low solubility in water, while ionic liquids containing hydrophilic anions such as chloride or acetate are completely miscible in water. The names of ionic liquids can generally be represented by abbreviations. Alkyl cations are usually named with the letters of the alkyl substituent and the cation placed in a set of brackets, followed by the abbreviation of the anion. Although not explicitly written, it is understood that the cation is positively charged and the anion is negatively charged. For example, [BMIm]OAc represents 1-butyl-3-methylimidazolium acetate, [AMIm]Cl represents 1-allyl-3-methylimidazolium chloride, and [EMIm]OF represents 1-ethyl-3-methylimidazolium formate.

[0025] The term ionic liquid "composition" is used herein to describe a composition comprising an ionic liquid as a major component, and thus may be used for compositions that generally contain more than 50% by weight of ion pairs and exist in liquid form at standard temperature and pressure. Thus, an ionic liquid composition may be understood to generally refer to compositions including, but not limited to, ionic liquids, metal-containing ionic liquids, ethylene-rich metal-containing ionic liquids, ethylene-poor metal-containing ionic liquids, and metal-containing ionic liquids comprising a viscosity modifier.

[0026] Although any methods, devices, and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the typical methods, devices, and materials are described herein.

[0027] All publications and patents mentioned herein are incorporated herein by reference in their entirety for the purpose of describing and disclosing, for example, the constructs and methodologies that are described in the publications and patents, which might be used in connection with the presently described invention. DETAILED DESCRIPTION

[0028] The present invention generally relates to methods of reducing the viscosity of metal-containing ionic liquids and methods of capturing and recovering components of process streams using metal-containing ionic liquids. Disclosed herein are ionic liquid compositions having significantly reduced viscosities by the addition or presence of a viscosity modifier that is compatible with the ionic liquid. The viscosity of the resulting ionic liquid composition can be reduced to less than 200 cP at 40° C. in certain aspects, and can be reduced to 50% or more of the viscosity of a similar ionic liquid composition without the viscosity modifier in certain aspects.

[0029] Generally, the addition of metal cations to ionic liquid compositions is accompanied by a dramatic increase in viscosity. For example, after loading with metal cations at a concentration of 1M to 2M, the viscosity of the ionic liquid can increase by about 10 times. Since the metal cations are believed to be responsible for reversibly retaining ethylene when in contact with the process stream, it is desirable to maximize the concentration of the metal cations. The viscosity modifiers disclosed herein are beneficial components in metal-containing ionic liquid formulations, typically reducing the viscosity by more than 50% with only a slight dilution of the metal cation concentration (e.g., 3-5%).

[0030] Metal ion-containing liquid composition

[0031] Ionic liquid compositions are contemplated herein, particularly as described herein for removing certain components from process streams. In general, ionic liquid compositions may include anions and cations, metal cations, and viscosity modifiers that constitute the ionic liquid. In some aspects, the ionic liquid may account for the majority of the ionic liquid composition, and may comprise at least 50 wt %, at least 60 wt %, at least 75 wt %, at least 90 wt %, or at least 95 wt % of the ionic liquid composition. The ionic liquids contemplated herein may be used as solvents, carriers, or stock solutions for adding and loading metal cations that are complexed or otherwise dispersed in the ionic liquid composition.

[0032] In some aspects, the metal cation can be provided as a metal salt comprising a metal cation and a metal anion and is present in the ionic liquid composition. When the metal cation is loaded into the ionic liquid, the ionic liquid cation can be exchanged with the metal cation, thereby forming a metal complex between the ionic liquid anion and the metal cation. Advantageously, the metal cation can be provided as a salt or complex of the metal cation and the anion identical to the ionic liquid anion. In these aspects, the addition of the metal cation and the formation of the desired metal complex can be performed independently of the preparation of the ionic liquid composition. For example, bis(trifluoromethanesulfonyl)imide Cu(I) is identified and disclosed herein as a specific example of a metal complex suitable for use in ionic liquid compositions.

[0033] In certain aspects, the ionic liquid cation can comprise allylmethylimidazolium, butylethylimidazolium, butylmethylimidazolium, butyldimethylimidazolium, decaethylimidazolium, decamethylimidazolium, diethylimidazolium, dimethylimidazolium, ethyl-2,4-dimethylimidazolium, ethyldimethylimidazolium, ethylimidazolium, ethylmethylimidazolium, ethylpropylimidazolium, ethoxyethylmethylimidazolium, ethoxydimethylimidazolium, hexadecylmethylimidazolium, heptylmethylimidazolium, hexylethylimidazolium, hexylmethylimidazolium, hexyldimethylimidazolium, methoxyethylmethylimidazolium. , methoxypropylmethylimidazolium, methylimidazolium, dimethylimidazolium, methylnonylimidazolium, methylnonylimidazolium, octadecylmethylimidazolium, hydroxyethylmethylimidazolium, hydroxyoctylmethylimidazolium, hydroxypropylmethylimidazolium, octylmethylimidazolium, octyldimethylimidazolium, phenylethylmethylimidazolium, phenylmethylimidazolium, phenyldimethylimidazolium, pentylmethylimidazolium, propylmethylimidazolium, 1-butyl-2-methylpyridinium, 1-butyl-3-methylpyridinium, butylmethylpyridinium, 1-butyl-4-dimethylacetylpyridinium, 1-butyl- 4-Methylpyridinium, 1-ethyl-2-methylpyridinium, 1-ethyl-3-methylpyridinium, 1-ethyl-4-dimethylacetylpyridinium, 1-ethyl-4-methylpyridinium, 1-hexyl-4-dimethylacetylpyridinium, 1-hexyl-4-methylpyridinium, 1-octyl-3-methylpyridinium, 1-octyl-4-methylpyridinium, 1-propyl-3-methylpyridinium, 1-propyl-4-methylpyridinium, butylpyridinium, ethylpyridinium, heptylpyridinium, hexylpyridinium, hydroxypropylpyridinium, octylpyridinium, pentylpyridinium, propylpyridinium, butylpyridinium

[0063] The phosphonium iodide can be selected from the group consisting of phosphonium iodide, ...

[0034] As described above, the ionic liquid anion can be selected based on its compatibility with the metal cation in forming a complex and a certain ability to retain ethylene through intermolecular interactions. In certain aspects, the ionic liquid anion can include a bis(trifluoromethanesulfonyl)imide anion, a bis(fluorosulfonyl)imide anion, a hexafluorophosphate anion, a trifluoromethanesulfonate anion, a dicyanamide anion, a tetrafluoroborate anion, a thiocyanate anion, a nitrate anion, a sulfonate anion, a methylsulfate anion, a methanesulfonate anion, a trifluoroacetate anion, an acetate anion, or a combination thereof.

[0035] The ionic liquid compositions disclosed above may also contain metal cations and may be used to remove ethylene (and other compounds) from process streams. Metal cations suitable for use in ionic liquid compositions are not limited to any particular metal or cation, and may generally be any metal or cation that is miscible with the ionic liquids disclosed herein and that may be used to reversibly retain a desired compound (e.g., ethylene, isobutane) in a metal-containing ionic liquid composition. Suitable metal cations may include, but are not limited to, copper cations, silver cations, and gold cations, and more specifically, Cu(I), Ag(I), and Au(I). Other transition metal cations, heavy metal cations (including, but not limited to, platinum cations, palladium cations, iridium cations, and rhenium cations), alkaline earth metal cations, alkali metal cations may also be considered suitable for the purpose of binding a compound through a π interaction between a given compound and the metal cation.

[0036] In certain aspects, the ionic liquid compositions disclosed herein can be characterized by an ethylene capacity (e.g., ethylene solubility) of at least 1 mol / L, at least 1.1 mol / L, at least 1.2 mol / L, at least 1.5 mol / L, at least 2 mol / L, at least 3 mol / L, or at least 5 mol / L at 0.10 MPa ethylene and standard temperature and pressure.

[0037] In certain aspects, the ethylene capacity of a metal-containing ionic liquid composition can be determined by the amount of metal cations in the composition and the efficiency and strength of the binding interactions between the metal cations and ethylene. As disclosed herein, the amount of metal cations that can be added to the ionic liquid may be limited in practice by the dramatic increase in viscosity observed, particularly when the metal cation concentration exceeds 0.5 M, 1.0 M, 1.5 M, 2 M, 2.5 M, or 3 M. In certain aspects, the ionic liquid composition can have a metal cation concentration of at least 0.5 M, at least 0.75 M, at least 1.0 M, at least 1.5 M, at least 2 M, or at least 2.5 M. For example, a suitable ionic liquid composition can have a metal cation concentration in the range of 0.5 to 2.5 M, 0.75 M to 2.0 M, or 1.0 M to 2.0 M.

[0038] The viscosity modifier can dilute the metal-containing ionic liquid, particularly the metal cation concentration within the ionic liquid. Thus, the ionic liquid compositions disclosed herein can exhibit reduced ethylene solubility (e.g., ethylene capacity) compared to metal-containing ionic liquids without a viscosity modifier. Metal-containing ionic liquid compositions containing relatively small amounts of viscosity modifiers can take advantage by limiting the dilution effect. In certain aspects, the ionic liquid compositions disclosed herein can have an ethylene solubility (e.g., ethylene capacity) of at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 98% of the ethylene solubility (e.g., ethylene capacity) of a composition that does not contain a viscosity modifier and is otherwise identical.

[0039] In the methods disclosed herein, the metal cations and complexes thereof in the metal-containing ionic liquids can impart the desired selectivity to capture and recover specific compounds from process streams. In certain aspects, the metal cations in the ionic liquid compositions can exhibit an affinity for retaining ethylene or isobutane in a selective manner relative to other compounds that may be prevalent in a given process stream. For example, the metal-containing ionic liquid compositions disclosed herein can have (or can be characterized by) a molar selectivity for retaining ethylene relative to ethane in the range of 10:1 to 500:1, 15:1 to 200:1, 25:1 to 150:1, or 100:1 to 200:1.

[0040] Therefore, for the purpose of reversibly retaining ethylene, the ionic liquid composition disclosed herein may also contain ethylene. In certain aspects, the metal ionic liquid composition may contain 0.1 wt% to 5 wt% ethylene, 0.1 wt% to 3 wt% ethylene, 0.5 wt% to 5 wt% ethylene, 0.5 wt% to 3 wt% ethylene, or 1 wt% to 3 wt% ethylene, but is not limited thereto.

[0041] Viscosity modifier

[0042] As discussed above, the viscosity modifiers encompassed herein can be any viscosity modifier suitable for reducing the viscosity of a metal-containing ionic liquid without unacceptably diluting the ethylene capacity of the metal-containing ionic liquid. Thus, the viscosity modifiers disclosed herein can significantly reduce the viscosity increase that typically accompanies an increase in metal cation concentration in an ionic liquid formulation.

[0043] Surprisingly, the ability to reduce the viscosity of the ionic liquid composition is not directly dependent on the viscosity of the viscosity modifier itself. Compounds that exhibit a viscosity reduction equivalent only to that expected based on the amount of viscosity modifier relative to the viscosity of the ionic liquid composition may provide limited value in modifying the viscosity of the metal-containing ionic liquid, at least because the viscosity reduction in this regard may be commensurate with the overall reduction in the concentration of metal cations and the overall effectiveness of the metal-containing ionic liquid to capture ethylene.

[0044] In contrast, the viscosity modifiers encompassed herein may greatly exceed the algebraic expectations of the reduction in viscosity of metal-containing ionic liquids. In certain aspects, a suitable viscosity modifier may be any compound that provides a composition with a viscosity less than or equal to 90%, less than or equal to 80%, less than or equal to 70%, less than or equal to 60%, less than or equal to 50%, or less than or equal to 35% of the original viscosity of the ionic liquid composition. It is noteworthy that under the same conditions, the viscosity modifiers encompassed herein can achieve such a reduction in viscosity even if the amount of viscosity modifier is less than or equal to 25% by weight, less than or equal to 20% by weight, less than or equal to 15% by weight, less than or equal to 10% by weight, less than or equal to 5% by weight, or less than or equal to 3% by weight of the ionic liquid composition. As shown in the following examples, it should be understood that in certain aspects, the viscosity of the ionic liquid composition can be reduced to less than or equal to 50% by adding less than or equal to 10% by weight, less than or equal to 5% by weight, or less than or equal to 3% by weight of certain viscosity modifiers.

[0045] In certain aspects, the viscosity of the ionic liquid composition containing the viscosity modifier at 40° C. can be less than or equal to 1000 cP, less than or equal to 500 cP, less than or equal to 250 cP, less than or equal to 200 cP, or less than or equal to 100 cP. In addition, the viscosity can be reduced by at least 50% relative to the starting viscosity of the ionic liquid composition as described above. Again, this reduction in viscosity can be achieved using a relatively small amount of viscosity modifier, so as not to dilute the metal cation concentration of the ionic liquid composition (and therefore not negatively affect ethylene solubility or ethylene capacity).

[0046] Suitable viscosity modifiers are identified in the examples below, and as shown, may include 3,4-dichlorotoluene, sulfolane, N-methylpyrrolidone, caprolactone, propylene carbonate, benzyl butyl phthalate, and the like, or any combination thereof. Halogenated aromatic compounds and small molecule heterocyclic compounds of similar structure and generally having a molecular weight of less than 400 Da are also contemplated as viscosity modifiers, and in certain aspects may include 1-bromo-2-chloro-4-methylbenzene, 4-bromo-1,2-dichlorobenzene, 4-chlorotoluene, 3-chlorotoluene, trimethylene sulfone, 1-butane sultone, 1-propane sultone, dibutylene sulfone, 2-methyl sulfolane, 3-methyl sulfolane, 2,4-dimethyl sulfolane, 1,3-dihydrobenzothiophene 2,2-dioxide, γ-butyrolactone, cyclohexanone, cycloheptanone, cyclopentanone, 1,3-dioxane-2-one, 1,3-cycloheptanedione, 1,4-dioxane-2-one, tetrahydro-4H-pyran-4-one, caprolactam, ethylene carbonate, and 1,3-oxazepine-2-one.

[0047] Viscosity modifiers encompassed herein may also be characterized by physical properties, as shown in Table 1 below. Compounds with relatively high dipoles may be beneficial in helping to miscibility with metal-containing ionic liquids. In some aspects, the viscosity modifier may have a dipole moment in the range of 2D to 6D, 2.5D to 5D, 3D to 5D, or at least 2.5D, at least 3D, at least 3.5D, at least 4D, or at least 5D. Viscosity modifiers with certain ranges of Hansen solubility parameters have also been identified as being beneficial for reducing the viscosity of metal-containing ionic liquid compositions disclosed herein. In some aspects, the viscosity modifier may have a Hansen solubility hydrogen bonding parameter in the range of 2 to 11, a Hansen solubility dispersion parameter in the range of 17 to 21, a Hansen solubility polarity parameter in the range of 9 to 19, or any combination thereof.

[0048] Physical characteristics such as specific boiling point and melting point ranges may also contribute to the suitability of the viscosity modifier. In certain aspects, the viscosity modifier may have a boiling point of at least 125°C, at least 150°C, at least 200°C, or at least 250°C at standard temperature and pressure. The melting point of the viscosity modifier may also be low enough to ensure that the resulting ionic liquid composition remains liquid over a wide range of conditions, and in certain aspects, is less than or equal to 0°C, less than or equal to -20°C, or less than or equal to -50°C.

[0049] Table 1. Physical properties of viscosity modifiers

[0050]

[0051] Methods, related systems and separation methods for reducing the viscosity of metal ion-containing liquids

[0052] Disclosed herein are methods for reducing the viscosity of an ionic liquid, such as reducing the viscosity of an ionic liquid to less than or equal to 95%, less than or equal to 90%, less than or equal to 85%, less than or equal to 80%, less than or equal to 75%, or less than or equal to 60% of the original ionic liquid. In certain aspects, such methods can be applied to any ionic liquid composition or metal-containing ionic liquid disclosed herein.

[0053] As can be seen from the examples of viscosity modifiers below, methods of modifying the viscosity of ionic liquids cannot be achieved simply by adding any miscible compound that itself has a relatively low viscosity. Thus, methods of reducing the viscosity of the ionic liquids or metal-containing ionic liquids disclosed herein may include selecting a viscosity modifier based at least in part on any combination of several parameters related to polarity and solubility, such as dipole moment, Hansen solubility dispersion parameter, Hansen solubility hydrogen bonding parameter, and Hansen solubility polarity parameter. It will also be appreciated by those skilled in the art that the choice of viscosity modifier may also be limited by practical considerations related to the particular intended application of the composition, such as boiling point.

[0054] Of particular relevance to the present disclosure, metal-containing ionic liquids having reduced viscosity can be beneficially used to capture and recover the material from a process stream containing one or more olefins (e.g., ethylene), acid gases, or any other compound that exhibits a reversible binding affinity to the metal-containing ionic liquid. For example, in certain aspects, ethylene can be removed from a process stream containing ethylene to form an ethylene-rich metal-containing ionic liquid. Similarly, isobutane can be removed from a process stream containing isobutane to form an isobutane-rich metal-containing ionic liquid. In certain aspects, the process stream can contain ethylene and / or isobutane, each of which can be removed from the process stream using a metal-containing ionic liquid. In certain aspects, the selection of the viscosity modifier can be performed by identifying a compound having a boiling point of at least 150°C, a dipole moment of at least 2.5D, a Hansen solubility hydrogen bonding parameter in the range of 2 to 11, a Hansen solubility dispersion parameter in the range of 17 to 21, a Hansen solubility polarity parameter in the range of 9 to 19, or any combination thereof.

[0055] The method of reducing the viscosity of an ionic liquid composition can include contacting a selected viscosity modifier (e.g., any suitable viscosity modifier disclosed herein) with an ionic liquid composition (e.g., any metal-containing ionic liquid disclosed herein).

[0056] Metal ion-containing liquids with reduced viscosity can be advantageously used to recover certain gaseous components in process streams, such as those described in U.S. Pat. Nos. 10,227,274 and 9,732,016. For example, U.S. Pat. No. 10,227,274 provides examples of process streams in which it may be advantageous to separate gaseous components from liquid components in the process stream, including, but not limited to, polymerization process streams containing olefins and alkanes; ethane cracking process streams containing ethane and ethylene; natural gas process streams containing natural gas and acid gas; synthesis gas process streams containing synthesis gas and carbon dioxide; biomass gasification process streams containing carbon dioxide; Fischer-Tropsch process streams containing unreacted synthesis gas, methane, olefins, and alkanes; alkane dehydrogenation process streams containing olefins and alkanes; and alcohol dehydration process streams containing olefins, alkanes, and alcohols.

[0057] In certain aspects, the process stream may contain ethylene in an amount ranging from 3 to 70 wt%, 5 to 50 wt%, 10 to 40 wt%, 10 to 25 wt%, but is not limited thereto. Additionally or alternatively, the amount of ethylene in the gaseous process stream may be characterized by the ethylene partial pressure, and in certain aspects, the ethylene partial pressure in the process stream may be in the range of 10 psia to 500 psia, 30 psia to 250 psia, or 20 psia to 200 psia. Disclosed herein is a method for separating ethylene from a process stream using an ionic liquid composition with reduced viscosity, the method may include contacting a process stream containing ethylene with a metal-containing ionic liquid to form an ethylene-rich metal-containing ionic liquid containing ethylene captured from the process stream. The amount of ethylene captured from the process stream by the metal-containing ionic liquid during the contacting step may be affected by the duration and efficiency of the contacting step, the amount of ethylene in the process stream, and the solubility of ethylene in the metal-containing ionic liquid.

[0058] In general, the contacting of the process stream with the metal-containing ionic liquid can be performed in any manner that allows sufficient interaction between the streams to allow the ionic liquid to capture ethylene from the process stream. In certain aspects, the contacting of the process stream with the metal-containing ionic liquid can capture or remove at least 60 wt%, at least 70 wt%, at least 75 wt%, 80 wt%, at least 90 wt%, at least 95 wt%, or at least 99 wt% of the ethylene from the process stream. Multiple contacting steps can be applied to further recover ethylene that is not captured during a single pass.

[0059] In some aspects, the process stream can be a gaseous process stream. In these aspects, the ionic liquid can be applied in the countercurrent direction of the process stream to increase the contact efficiency between the process stream and the ionic liquid, and is incorporated into a separator to perform liquid-gas separation as part of the contact step. In other aspects, the flow rate can be increased to improve the efficiency of the contact step. The increase in the ionic liquid flow rate may be limited at or above a viscosity of 200cP, 400cP or 1000cP. At least in part due to the reduced viscosity of the composition disclosed herein, the ionic liquid can be conveyed (and contacted with the process stream) at a flow rate in the range of 1,000 pounds per hour to 300,000 pounds per hour, 3,000 pounds per hour to 150,000 pounds per hour, or 5,000 pounds per hour to 100,000 pounds per hour. In some aspects, the flow rate of the process stream can be in the range of 10 pounds per hour to 5,000 pounds per hour, or in the range of 100 pounds per hour to 3,000 pounds per hour. Thus, in certain aspects, the mass flow ratio of the flow rate of the metal-containing ion liquid to the flow rate of the process stream can be in the range of 1 to 500, 10 to 300, 25 to 250, 10 to 100, or 10 to 50. Given that the mass flow ratio can be heavily biased toward the metal-containing ion liquid, a factor limiting the scalability of the methods disclosed herein for separating ethylene from process streams can be the flow rate of the metal-containing ion liquid, which in turn can be limited by the viscosity of the metal-containing ion liquid. Surprisingly, the compositions described herein provide a significant reduction in viscosity with only a minimal reduction in metal cation concentration.

[0060] The method for removing ethylene from a process stream may also include separating the ethylene-rich metal-containing ionic liquid from the process stream, and generally can be performed by allowing the uncaptured portion of the process stream to flow out of a separator separately from the ethylene-rich metal-containing ionic liquid. After separation from the process stream, the ethylene-rich metal-containing ionic liquid will be subjected to certain conditions so that the captured ethylene is released to form ethylene and ethylene-poor metal-containing ionic liquid. The ethylene-poor metal-containing ionic liquid can be considered to be a regenerated form of the metal-containing ionic liquid and is suitable for returning (or recycling) to the separator to capture another amount of ethylene from the process stream in a continuous process.

[0061] The conditions of the contacting step and the releasing step are not limited to any particular set of conditions other than conditions suitable for capturing and releasing ethylene from the metal ion-containing liquid and not interfering with the purity or quality of the process stream. In certain aspects, the contacting of the process stream with the metal ion-containing liquid can be carried out at a contact temperature in the range of -10°C to 100°C, 5°C to 50°C, or 20°C to 40°C. The process stream and the metal ion-containing liquid can be contacted at a contact pressure in the range of 50 psia to 500 psia or 100 psia to 250 psia. The disclosed methods are limited to these specific temperature and pressure ranges.

[0062] Therefore, the method for separating ethylene from a process stream may also include releasing ethylene from an ethylene-rich metal-containing ionic liquid to form an ethylene-depleted metal-containing ionic liquid and ethylene, and physically separating ethylene from the ethylene-depleted metal-containing ionic liquid. In certain aspects, this may be achieved by allowing ethylene to leave the regenerator in gaseous form from an outlet at an upper portion of the regenerator, while simultaneously withdrawing the ethylene-depleted metal-containing ionic liquid (e.g., regenerated metal-containing ionic liquid) from the regenerator from an outlet at a lower portion of the regenerator.

[0063] Similar to the contacting step, the release of ethylene can be carried out under conditions suitable for affecting the release of ethylene, and there is no particular limitation. In some aspects, the release of ethylene from the ethylene-rich metal ion liquid can include a release temperature (e.g., recovery temperature) in the range of 50°C to 500°C, 60°C to 450°C, 100°C to 300°C, or 100°C to 200°C. In some aspects, the release of ethylene from the ethylene-rich metal ion liquid can be carried out at a release pressure (e.g., recovery pressure) in the range of 5psia to 50psia or 10 to 25psia. In some aspects, the release of ethylene from the ethylene-rich metal ion liquid includes releasing at least 90% by weight, at least 95% by weight, at least 98% by weight, or at least 99% by weight of the captured ethylene from the ethylene-rich metal ion liquid.

[0064] Method disclosed herein can also include reclaiming the ethylene released. In some aspects, the ethylene released from the metal ion liquid rich in ethylene can be almost all recovered, or alternatively, at least 90 % by weight, at least 95 % by weight, at least 98 % by weight or at least 99 % by weight of the ethylene released can be recovered. The ethylene released with a purity of at least 90 % by weight, at least 95 % by weight, at least 98 % by weight or at least 99 % by weight can also be recovered.

[0065] Systems suitable for performing the above methods are not limited to any particular system, and generally can be any system capable of transferring ionic liquids, contacting process streams with ionic liquids, and maintaining appropriate conditions (e.g., temperature, pressure) during the separation process. For example, U.S. Patent No. 10,227,274 describes a system including a separator and a regenerator, wherein the ionic liquid is continuously transported between the separator and the regenerator; such systems and devices can be used to perform the methods described herein. Specifically, a system for contacting a process stream with a metal-containing ionic liquid is disclosed, the system being configured to flow a gaseous process stream through a first inlet into a separation tank and to a first outlet located above the first inlet, and to flow a metal-containing ionic liquid into the separation tank via a second inlet located above the first inlet and to a second outlet located below the second inlet.

[0066] Example

[0067] The present invention is further illustrated by the following examples, which should not be construed as limiting the scope of the present invention in any way. After reading the description herein, those of ordinary skill in the art can conceive of various other aspects, modifications and their equivalents without departing from the spirit of the present invention or the scope of the appended claims.

[0068] Metal-containing ionic liquids were prepared to examine their viscosity and compared with compositions containing metal-containing ionic liquids and any of several potential viscosity modifiers. The preparation of the ionic liquids is described in detail below. The viscosity (m) measurements disclosed herein were measured using an automatic rolling ball viscometer (Anton-Paar (Graz, Austria), model Lovis 2000M / Me), which has a LOVIS 1.8 mm capillary and a steel ball with a diameter of 1.5 mm, and the instrument's specified measurement accuracy is 0.5%. The experimental data for each sample was measured over a temperature range of 20°C to 60°C, with increments of 5°C or 10°C, as shown in the data table below. The viscosity measurements were made at a measuring angle of 70°.

[0069] Ionic liquid A. 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([allylmim][NTf 2 ]).

[0070] 1-Methylimidazole (16.0g, 195mmol) was dissolved in toluene (18mL). 1-allyl bromide (24.8g, 205mmol) was added to the solution and heated to 75 ° C for 7 hours. The solid was washed with ethyl acetate / hexane and purified using acetonitrile and ethyl acetate to remove impurities to obtain 1-allyl-3-methylimidazolium bromide (36.8g, 181mmol) (93% yield) as a white solid. 1-allyl-3-methylimidazolium bromide (40.0g, 197mmol) was dissolved in water (100mL), followed by addition of bis(trifluoromethylsulfonyl)imide lithium (59.4g, 207mmol). It was stirred for 5 hours and extracted with dichloromethane (25mL×3). 1-Allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide salt (71.5 g, 177 mmol) was obtained as a clear viscous liquid (90% yield).

[0071] Ionic liquid B. Prepared according to the method of Dyson et al. in Journal of the American Chemical Society 2004, 126, 48, 15876-15882 [emimCN][NTf 2 ], which is incorporated herein by reference.

[0072] After obtaining the above ionic liquids, metal-containing ionic liquid compositions A and B were obtained by adding metal cations in the form of metal salt bis(trifluoromethanesulfonate)imide Cu(I)bisacetonitrile to the ionic liquids. The acetonitrile was then removed by heating the metal salt under vacuum as shown below.

[0073] Cu I (NTf 2 )(MeCN) 2 Synthesis of Lithium bis(trifluoromethylsulfonyl)imide (1 eq) was suspended in sulfuric acid (7 eq) and heated to 80 ° C for 12 hours. Using a short column and with the receiving bottle immersed in a liquid nitrogen bath, the reaction mixture was vacuum distilled at 90 ° C to obtain bis(trifluoromethylsulfonyl)imidic acid (92% yield) as a white solid. Dissolve bis(trifluoromethylsulfonyl)imidic acid in water (2 eq), then add copper (II) oxide (1 eq) and stir overnight. Filter out excess copper oxide, and remove the solvent in vacuo at 40 ° C to obtain di-bis(trifluoromethylsulfonyl)imide copper (II) [Cu II (NTf 2 ) 2The blue solid was dissolved in anhydrous acetonitrile (1M solution) and stirred with 0.5 equivalent of copper (0) powder for 1 day, the solution became colorless. The solvent was removed in vacuo and treated under nitrogen to obtain the product as a white solid.

[0074] Metal ion liquid composition A (1.5M Cu I (NTf 2 ) / [allylmim][NTf 2 ]) Synthesis: Cu I (NTf 2 )(MeCN) 2 (4.26 g) was dissolved in 10 g of the ionic liquid A ([allylmim][NTf 2 The resulting solution was stirred and heated at 140°C under vacuum for 10 days to obtain a high viscosity orange fluid. 1 H NMR showed that there was a small amount of residual acetonitrile. After 5 days, a large amount of acetonitrile still remained in the solution.

[0075] Metal ion liquid composition B (MCIL-B; 1.5M Cu I (NTf 2 ) / [emimCN][NTf 2 ]) and metal ionic liquid composition C (MCIL-C; 0.75M Cu I (NTf 2 ) / [emi mCN][NTf 2 The synthesis of MCIL-A was as described above for MCIL-A by combining appropriate metal salts and ionic liquids in appropriate relative amounts.

[0076] The viscosity of the metal ion-containing liquid comprising the viscosity modifier is reduced.

[0077] The compounds listed in Table 2 were evaluated as viscosity modifiers in metal-containing ionic liquids. In general, metal-containing ionic liquids AC (MCIL-A to MCIL-C) prepared as above were mixed with the compounds listed in Tables 2-4 in amounts of 5-15 wt %, and the effect on viscosity was measured. First, the miscibility of each compound was assessed, and samples that did not produce a completely dissolved solution were not further tested. For example, as shown with MCIL-A, neither 1,2,4,5-tetrachlorobenzene nor high concentrations of 3,4-dichlorotoluene were miscible, as reported in Table 2 below.

[0078] In addition, the viscosity of certain ionic liquid compositions was qualitatively measured by placing a sample of each composition horizontally and observing the horizontal displacement of the composition. The results showed that compositions with a greater horizontal displacement than the pure composition had reduced viscosity. Compositions that showed significant horizontal displacement or excellent miscibility were again quantitatively examined and examined at higher concentrations of viscosity modifier.

[0079] As shown in Table 2 below, propylene carbonate, 3,4-dichlorotoluene, and sulfolane all exhibit significant viscosity reduction at concentrations of only 5 wt%, particularly at temperatures between 20°C and 40°C. For example, 3,4-dichlorotoluene exhibits a viscosity reduction of more than 50% at 25°C relative to pure MCIL-A, while it only comprises 5 wt% of the ionic liquid composition. Sulfolane also exhibits a significant reduction effect and also has excellent miscibility with MCIL-A at up to 15 wt%. As shown in Table 2, item 4, the addition of 15 wt% sulfolane as a viscosity modifier to the ionic liquid composition results in a viscosity reduction of more than 66% at 25°C relative to pure MCIL-A. These trends maintain a significant reduction in viscosity even at higher temperatures, as demonstrated by the reduction of the viscosity of the resulting ionic liquid composition to less than 200 cP at 40°C with the addition of sulfolane, 3,4-dichlorotoluene, or propylene carbonate. Figure 1 Data associated with each entry in Table 2 are shown, where quantitative data are provided.

[0080] As shown in Tables 3 and 4, respectively, an unexpected reduction in viscosity was also observed with the addition of viscosity modifiers to MCIL-B and MCIL-C. Although the viscosity of neat MCIL-B at 25°C is about ten times higher than that of MCIL-A, and the miscibility of viscosity modifiers in MCIL-B / C is also generally lower, the addition of viscosity modifiers generally results in a significant reduction in the viscosity of each sample in which the viscosity modifier is miscible compared to neat MCIL (Comparative Examples 3-4). As can be seen from Examples 12 and 15, the addition of 5 wt% viscosity modifiers is still able to significantly reduce the viscosity of neat MCIL-B, from about 34,000 cP to less than 10,000 cP in both examples (22% and 27% of the viscosity of MCIL-B, respectively). Example 13 (5 wt% 3,4-dichlorotoluene) also shows a reduced viscosity relative to MCIL-B. Although the reduction is not as great as that seen in Examples 12 and 15, the addition of 3,4-dichlorotoluene still reduces the viscosity to 80% of Comparative Example 3.

[0081] It is noteworthy that the viscosity of MCIL-B is unusually high due to the relatively high concentration of metal cations in the metal-containing ionic liquid (1.5 M Cu). Without being bound by theory, it is believed that it may be unusually difficult to reduce the viscosity of a metal-containing ionic liquid having a high viscosity to above a certain threshold (e.g., 10,000 cP, 20,000 cP, 30,000 cP, or 50,000 cP). For example, the viscosity of Example 14 containing 5 wt % benzyl butyl phthalate was almost unchanged (about 3%) relative to the viscosity of pure MCIL-B.

[0082] It was also observed that the viscosity modifier was added to MCIL-C, which is a metal ion liquid with a lower metal cation concentration (0.75 M) than MCIL-B (1.5 M) and therefore a lower viscosity. As shown in the data of Examples 16 and 17 in Table 4 below, propylene carbonate and caprolactone each behaved similarly, significantly reducing viscosity. However, 3,4-dichlorotoluene was not miscible with MCIL-C, unlike MCIL-B, which had a higher metal cation concentration. Surprisingly, benzyl butyl phthalate also behaved significantly differently in MCIL-C and caused a viscosity reduction comparable to that of Examples 16 and 17, whereas benzyl butyl phthalate had little effect on viscosity in MCIL-B.

[0083] Effect of viscosity modifiers on ethylene solubility

[0084] The ethylene solubility of MCIL-A with and without the addition of 5 wt% 3,4-dichlorotoluene was measured at several ethylene partial pressures in the range of 0-0.20 MPa ethylene and the results are shown graphically in Figure 2 Adding 3,4-dichlorotoluene reduced the metal concentration from 1.5M to 1.43M, such as Figure 2 As shown. Considering that the ethylene solubility in each sample remained roughly the same after the metal concentration decreased, only a slight decrease in the ethylene solubility of the sample containing 5 wt% 3,4-dichlorotoluene was observed. This confirms that the mechanism by which the metal-containing ionic liquids A and B acquire the ability to reversibly capture ethylene is largely independent of the mechanism that causes the viscosity reduction. Therefore, the viscosity modifier disclosed herein can be added to the metal-containing ionic liquid without worrying about a significant decrease in the ethylene solubility of the metal-containing ionic liquid.

[0085] Table 2. Viscosity (unit: cP) of metal ion liquid A and viscosity modifier at different temperatures (unit: °C).

[0086]

[0087] Table 3. Viscosity (unit: cP) of metal ion liquid B and viscosity modifier at different temperatures (unit: °C).

[0088] Example Ionic Liquids / Viscosity Modifiers weight% Viscosity: 25℃ Comparative Example 3 Pure MCIL B N / A 34,000 12 Propylene carbonate 5 7,495 13 3,4-Dichlorotoluene 5 28,000 14 Benzyl butyl phthalate 5 34,900 15 Caprolactone 5 9,433

[0089] Table 4. Viscosity (unit: cP) of metal ion liquid C and viscosity modifier at different temperatures (unit: °C).

[0090]

[0091] aspect

[0092] The present invention has been described above with reference to many aspects and specific embodiments. Based on the above detailed description, many variations will occur to those skilled in the art. All such obvious variations are within the full intended scope of the appended claims. Other aspects of the present invention may include, but are not limited to, the following aspects (these aspects are described as "comprising", but alternatively, may be "essentially composed of" or "consisting of"):

[0093] Aspect 1. A composition comprising:

[0094] i) an ionic liquid comprising an ionic liquid cation and an ionic liquid anion;

[0095] ii) a metal cation; and

[0096] iii) Viscosity modifiers.

[0097] Aspect 2. The composition of aspect 1, wherein the ionic liquid cation comprises allylmethylimidazolium, butylethylimidazolium, butylmethylimidazolium, butyldimethylimidazolium, decaethylimidazolium, decamethylimidazolium, diethylimidazolium, dimethylimidazolium, ethyl-2,4-dimethylimidazolium, ethyldimethylimidazolium, ethylimidazolium, ethylmethylimidazolium, ethylpropylimidazolium, ethoxyethylmethylimidazolium, ethoxydimethylimidazolium, hexadecylmethylimidazolium, heptylmethylimidazolium, hexylethylimidazolium, hexylmethylimidazolium, hexyldimethylimidazolium, methylimidazolium Oxyethylmethylimidazolium, methoxypropylmethylimidazolium, methylimidazolium, dimethylimidazolium, methylnonylimidazolium, methylnonylimidazolium, octadecylmethylimidazolium, hydroxyethylmethylimidazolium, hydroxyoctylmethylimidazolium, hydroxypropylmethylimidazolium, octylmethylimidazolium, octyldimethylimidazolium, phenylethylmethylimidazolium, phenylmethylimidazolium, phenyldimethylimidazolium, pentylmethylimidazolium, propylmethylimidazolium, 1-butyl-2-methylpyridinium, 1-butyl-3-methylpyridinium, butylmethylpyridinium, 1-butyl-4-dimethylacetylpyridinium , 1-butyl-4-methylpyridinium, 1-ethyl-2-methylpyridinium, 1-ethyl-3-methylpyridinium, 1-ethyl-4-dimethylacetylpyridinium, 1-ethyl-4-methylpyridinium, 1-hexyl-4-dimethylacetylpyridinium, 1-hexyl-4-methylpyridinium, 1-octyl-3-methylpyridinium, 1-octyl-4-methylpyridinium, 1-propyl-3-methylpyridinium, 1-propyl-4-methylpyridinium, butylpyridinium, ethylpyridinium, heptylpyridinium, hexylpyridinium, hydroxypropylpyridinium, octylpyridinium, pentylpyridinium, propylpyridinium methylammonium, dimethylammonium, tetramethylammonium, ethylammonium, diethylammonium, tetraethylammonium, tetraheptylammonium, tetrahexylammonium, methylammonium, dimethylammonium, tetramethylammonium, ammonium, butyldimethylethanolammonium, dimethylethanolammonium, ethanolammonium, ethyldimethylethanolammonium, tetrapentylammonium, tetrapropylammonium, tetrabutylphosphonium, tributyloctylphosphonium, or a combination thereof.

[0098] Aspect 3. A composition as described in aspect 1 or 2, wherein the ionic liquid anion comprises a bis(trifluoromethanesulfonyl)imide anion, a bis(fluorosulfonyl)imide anion, a hexafluorophosphate, a trifluoromethanesulfonate, a dicyanamide anion, a tetrafluoroborate, a thiocyanate, a nitrate, a sulfonate, a methylsulfate, a methanesulfonate, a trifluoroacetate, an acetate, or a combination thereof.

[0099] Aspect 4. The composition according to any one of aspects 1 to 3, wherein:

[0100] The ionic liquid cation is allylmethylimidazolium, ethylmethylimidazolium, (1-(2-cyanoethyl))-3-methylimidazolium, propenylmethylimidazolium, propargylmethylimidazolium, butylmethylimidazolium, butylmethylpyridinium, or a combination thereof; and

[0101] The ionic liquid anion is a bis(trifluoromethanesulfonyl)imide anion, hexafluorophosphate, trifluoromethanesulfonate, dicyanamide anion, tetrafluoroborate, thiocyanate, nitrate, sulfonate, methylsulfate or a combination thereof.

[0102] Aspect 5. The composition according to any one of aspects 1 to 4, wherein:

[0103] The ionic liquid cation is (1-(2-cyanoethyl))-3-methylimidazolium or N,N-allylmethylimidazolium; and

[0104] The ionic liquid anion is a bis(trifluoromethanesulfonyl)imide anion.

[0105] Aspect 6. The composition of any one of aspects 1-5, wherein the metal cation is a copper cation or a silver cation.

[0106] Aspect 7. The composition of any one of aspects 1-6, wherein the metal cation is provided in the form of a metal salt.

[0107] Aspect 8. The composition of any one of aspects 1-7, wherein the metal salt is copper(I)bis(trifluoromethanesulfonyl)imide.

[0108] Aspect 9. The composition of any one of aspects 1-8, wherein the composition has a metal cation concentration in the range of 1M to 2M.

[0109] Aspect 10. The composition of any one of aspects 1-9, wherein the amount of the viscosity modifier is in the range of 3 wt % to 25 wt % of the ionic liquid.

[0110] Aspect 11. The composition of aspect 10, wherein the amount of the viscosity modifier is less than or equal to 10 wt % of the ionic liquid.

[0111] Aspect 12. The composition according to any one of aspects 1 to 11, wherein the viscosity modifier has:

[0112] A dipole moment of at least 2.5D;

[0113] Hansen solubility hydrogen bonding parameters in the range of 2 to 11;

[0114] Hansen solubility dispersion parameters in the range of 17 to 21;

[0115] Hansen solubility polarity parameters in the range of 9 to 19;

[0116] A boiling point of at least 150°C at standard temperature and pressure;

[0117] or any combination thereof.

[0118] Aspect 13. The composition of any one of aspects 1 to 12, wherein the viscosity modifier comprises 3,4-dichlorotoluene, sulfolane, N-methylpyrrolidone, caprolactone, propylene carbonate, benzyl butyl phthalate, or any combination thereof.

[0119] Aspect 14. The composition of any one of aspects 1-13, wherein the viscosity of the composition is less than or equal to 80% (eg, less than or equal to 70%) of an otherwise identical composition without the viscosity modifier.

[0120] Aspect 15. The composition of any one of aspects 1-14, wherein the composition has a viscosity at 40° C. of less than or equal to 500 cP (or less than or equal to 200 cP).

[0121] Aspect 16. The composition of any one of aspects 1-15, wherein the composition has an ethylene capacity of at least 1 mol / L at 0.10 MPa ethylene.

[0122] Aspect 17. The composition of any of aspects 1-16, wherein the ethylene capacity of the composition is at least 75% of an otherwise identical composition without the viscosity modifier.

[0123] Aspect 18. The composition of any of aspects 1-17, wherein the ethylene capacity of the composition is at least 90% of an otherwise identical composition without the viscosity modifier.

[0124] Aspect 19. The composition of any of aspects 1-18, wherein the composition has an ethylene:ethane molar selectivity of 15:1 to 200:1 (or 25:1 to 150:1).

[0125] Aspect 20. The composition of any one of aspects 1-19, further comprising ethylene.

[0126] Aspect 21. The composition of aspect 20, comprising 0.1 wt% to 3 wt% ethylene, based on the weight of the composition.

[0127] Aspect 22. A method for reducing the viscosity of an ionic liquid, the method comprising combining the ionic liquid with a viscosity modifier to form a composition having a viscosity less than or equal to 80% of the ionic liquid (eg, the composition of any one of aspects 1-19).

[0128] Aspect 23. A method for separating ethylene from a process stream, the method comprising:

[0129] contacting the process stream comprising ethylene with a metal ionic liquid (e.g., the composition of any one of aspects 1-19) to form an ethylene-rich metal ionic liquid (e.g., the composition of aspect 20 or 21) comprising ethylene captured from the process stream;

[0130] separating an ethylene-rich metal ion-containing liquid from the process stream;

[0131] Ethylene is released from the ethylene-rich metal ion-containing liquid to form an ethylene-depleted metal ion-containing liquid.

[0132] Aspect 24. The method of aspect 23, wherein the process stream is a gaseous process stream.

[0133] Aspect 25. The method of aspect 23 or 24, wherein contacting the process stream with the metal-containing ionic liquid comprises flowing the metal-containing ionic liquid at a metal-containing ionic liquid flow rate in a range of 1,000 pounds per hour to 300,000 pounds per hour.

[0134] Aspect 26. The method of any one of aspects 23-25, wherein the process stream has a process stream flow rate in the range of 10 pounds per hour to 3,000 pounds per hour.

[0135] Aspect 27. The method of aspect 26, wherein the mass flow ratio of the flow rate of the metal ion-containing liquid to the flow rate of the process stream is in the range of 10 to 300 (eg, 10 to 100).

[0136] Aspect 28. The method of any one of aspects 23-27, wherein contacting the process stream with the metal-ion-containing liquid comprises flowing the metal-ion-containing liquid countercurrently with respect to the process stream.

[0137] Aspect 29. The method of any one of aspects 23-28, wherein contacting the process stream with the metal ion-containing liquid comprises:

[0138] allowing a gaseous process stream to flow into a knockout drum through a first inlet and to a first outlet located above the first inlet; and

[0139] The metal ion-containing liquid is allowed to flow into the separation tank through a second inlet located above the first inlet, and to flow to a second outlet located below the second inlet.

[0140] Aspect 30. The method of any one of aspects 23-29, comprising contacting the process stream with the metal ion-containing liquid at a contact temperature in the range of 5°C to 50°C (or 20°C to 40°C).

[0141] Aspect 31. The method of any one of aspects 23-30, comprising contacting the process stream with the metal ion-containing liquid at a contact pressure in the range of 100 psia to 250 psia.

[0142] Aspect 32. A method as described in any of Aspects 23-31, wherein the process stream is contacted with the metal-ionic liquid so that the metal-ionic liquid captures ethylene in the process stream (e.g., at least 80 wt%, at least 90 wt%, at least 95 wt% of the ethylene in the process stream).

[0143] Aspect 33. The method of aspect 32, wherein releasing ethylene from the ethylene-rich metal-ion-containing liquid comprises releasing at least 90 wt % (e.g., at least 95 wt %, at least 98 wt %, at least 99 wt %) of the ethylene in the ethylene-rich metal-ion-containing liquid.

[0144] Aspect 34. The method of aspect 33, further comprising recovering the released ethylene (e.g., at least 90 wt%, at least 95 wt%, at least 98 wt% of the released ethylene).

[0145] Aspect 35. The method of aspect 34, wherein the recovered ethylene has a purity of at least 90 wt % (e.g., at least 95 wt %, at least 98 wt %).

[0146] Aspect 36. The method of any one of aspects 23-35, wherein releasing ethylene from the ethylene-rich metal ion-containing liquid comprises heating the ethylene-rich metal ion-containing liquid to a recovery temperature in the range of 60°C to 450°C.

[0147] Aspect 37. The method of any one of aspects 23-36, wherein releasing ethylene from the ethylene-rich metal ion-containing liquid comprises a recovery pressure in the range of 5 psia to 50 psia.

[0148] Aspect 38. The method of any one of aspects 23-37, wherein the process stream further comprises isobutane.

[0149] Aspect 39. The method of any one of aspects 23-38, wherein the ethylene-rich metal ion-containing liquid comprises isobutane.

[0150] Aspect 40. The method of any one of aspects 23-39, wherein the process stream comprises an ethylene amount in the range of 5 to 50 wt%, a partial pressure in the range of 20 to 200 psia, or both.

[0151] Aspect 41. The method according to any one of aspects 23 to 40, further comprising returning the ethylene-depleted metal ion-containing liquid to contact the process stream.

[0152] Aspect 42. Copper(I)bis(trifluoromethanesulfonyl)imide.

[0153] Aspect 43. A composition comprising copper(I)bis(trifluoromethanesulfonyl)imide.

[0154] Aspect 44. The composition of aspect 43, further comprising a viscosity modifier.

[0155] Aspect 45. The composition of aspect 44, further comprising ethylene.

Claims

1. A composition comprising: i) an ionic liquid comprising an ionic liquid cation and an ionic liquid anion; ii) a metal cation; and iii) Viscosity modifiers.

2. The composition of claim 1, wherein the ionic liquid cation is allylmethylimidazolium, ethylmethylimidazolium, (1-(2-cyanoethyl))-3-methylimidazolium, propenylmethylimidazolium, propargylmethylimidazolium, butylmethylimidazolium, butylmethylpyridinium, or a combination thereof.

3. The composition of claim 1, wherein the ionic liquid anion comprises a bis(trifluoromethanesulfonyl)imide anion, a bis(fluorosulfonyl)imide anion, a hexafluorophosphate, a trifluoromethanesulfonate, a dicyanamide anion, a tetrafluoroborate, a thiocyanate, a nitrate, a sulfonate, a methylsulfate, a methanesulfonate, a trifluoroacetate, an acetate, or a combination thereof.

4. The composition of claim 1, wherein: The ionic liquid cation is (1-(2-cyanoethyl))-3-methylimidazolium or N,N-allylmethylimidazolium; and The ionic liquid anion is a bis(trifluoromethanesulfonyl)imide anion.

5. The composition of claim 1, wherein the metal cation is a copper cation or a silver cation.

6. The composition of claim 1, wherein the composition has a metal cation concentration in the range of 0.5M to 2M.

7. The composition of claim 1, wherein the amount of the viscosity modifier ranges from 3 wt% to 20 wt% of the ionic liquid.

8. The composition of claim 1, wherein the viscosity modifier has: A dipole moment of at least 2.5D; Hansen solubility hydrogen bonding parameters in the range of 2 to 11; Hansen solubility dispersion parameters in the range of 17 to 21; Hansen solubility polarity parameters in the range of 9 to 19; A boiling point of at least 150°C at standard temperature and pressure; or any combination thereof.

9. The composition of claim 1, wherein the viscosity modifier has: Hansen solubility hydrogen bonding parameters in the range of 4 to 9; Hansen solubility dispersion parameters in the range of 17 to 21; and Hansen solubility polarity parameters in the range of 11 to 19.

10. The composition of claim 1, wherein the viscosity modifier comprises 3,4-dichlorotoluene, sulfolane, N-methylpyrrolidone, caprolactone, propylene carbonate, benzyl butyl phthalate, or any combination thereof.

11. The composition of claim 1, wherein the composition has a viscosity less than or equal to 80% of an otherwise identical composition lacking the viscosity modifier.

12. The composition of claim 1, wherein the composition has a viscosity of less than or equal to 500 cP at 40°C.

13. The composition of claim 1, wherein the composition has an ethylene capacity of at least 1 mol / L at 0.10 MPa ethylene.

14. The composition of claim 1, wherein the ethylene capacity of the composition is at least 90% of an otherwise identical composition lacking the viscosity modifier.

15. The composition of claim 1, wherein the composition has an ethylene:ethane molar selectivity of 15:1 to 200:

1.

16. The composition of claim 1 further comprising ethylene.

17. A method for reducing the viscosity of a metal-containing ionic liquid, the method comprising combining the metal-containing ionic liquid with a viscosity modifier to form the composition of claim 1, the composition having a viscosity less than or equal to 80% of the metal-containing ionic liquid.

18. A method for separating ethylene from a process stream, the method comprising: contacting the process stream comprising ethylene with the metal-ionic liquid-containing composition of claim 1 to form an ethylene-rich metal-ionic liquid comprising ethylene captured from the process stream; separating an ethylene-rich cationic composition from the process stream; releasing ethylene from the ethylene-rich metal ion-containing liquid to form an ethylene-poor metal ion-containing liquid; The overall ethylene recovery capacity of the process is at least 1 mol of ethylene recovered from the process stream per liter of the metal ion liquid composition contacted with the process stream.

19. Copper(I)bis(trifluoromethanesulfonyl)imide.

20. A composition comprising copper(I)bis(trifluoromethanesulfonyl)imide and a viscosity modifier.

21. The composition of claim 20, further comprising ethylene.

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