NZ615884B2 - N-functionalized imidazole-containing systems and methods of use - Google Patents

Abstract

Disclosed are systems containing non-ionic liquid imidazoles or blends of imidazoles and amines. Disclosed are methods of their preparation and use including the reduction of carbon dioxide and other volatile compounds from gas streams and liquid streams by contacting the natural gas feed stream with the system comprising the imidazole-amines blends. h the system comprising the imidazole-amines blends.

Description

N-FUNCTIONALIZED IMIDAZOLE-CONTAINING SYSTEMS AND METHODS OF USE CROSS-REFERENCE TO PRIORITYAPPLICATION This ation claims the benefit of priority to US. Provisional Application No. 61/468,314, filed March 28, 2011, which is incorporated herein by reference in its entirety.

FIELD The subject matter disclosed herein generally relates to systems containing imidazoles or imidazole-amine blends and s of their preparation. Also, the subject matter described herein generally relates to s of using the systems bed herein to capture and reduce le compounds from gas streams and liquid streams.

BACKGROUND There is a worldwide interest in capturing and sequestering or reusing carbon dioxide (CO2) emissions to stabilize the climate. Aqueous amine processes, widely used throughout the natural gas industly to reduce C02 from gas streams via al reaction, represent the benchmark by which C02 capture technologies are evaluated (NETL, Carbon Sequestration Technology Roadmap and Program Plan (2007); Rochelle, G.T., “Amine Scrubbing for C02 e,” Science, 325: 1652-1654 ). While effective at reducing CO2 from gas streams, amine processes are highly energy ive, with much of the energy penalty attributed to boiling water during amine regeneration. Thus, s amine processes will inherently suffer from large energy penalties. However, new solvents with little or no volatility can provide the desired energy efficiency.

Ionic liquids have received icant attention as solvents for CO2 capture (Bara, J.E., et al., “Guide to CO2 Separations in Imidazolium-based Room- Temperature lonic Liquids,” Ind. Eng. Chem. Res., 48:2739-2751 (2009)). As ionic liquids do not evaporate, they potentially offer greatly improved energy efficiency.

However, the use of ionic liquids for CO2 capture has not been scaled due to limitations of their physical and thermodynamic properties. Issues with ionic liquids consistently cited are very low CO2 loading, high viscosity, and exceedingly high costs (NETL, Existing Plants, Emissions and Capture — Setting C02 Program Goals, DOE/NETL—2009/1366). Inclusion of amine functionalities within the ionic liquid PCT/U52012/030672 (i.e., “task—specific” ionic liquids) or blending ionic liquids with commodity amines such as monoethanolamine (MEA) greatly improves the C02 capacity of the solvent and also reduces the energy requirement (NETL, Existing , Emissions and Capture — Setting C02 Program Goals, DOE/NETL-2009/1366; Camper, D. et al., “Room-Temperature Ionic Liquid — Amine Solutions: Tunable Solvents for Efficient and Reversible Capture of C02,” Ind. Eng. Chem. Res, 47:8496-8498 (2008)). While using ionic liquid—amine blends is promising, alternative volatile solvents that overcome the viscosity and cost limitations of ionic liquids are needed.

SUMMARY In accordance with the purposes of the disclosed materials. compounds, compositions, and methods, as embodied and broadly described herein, the disclosed subject , in one aspect, relates to compounds and compositions and methods for preparing and using such compounds and compositions. In a further aspect, the disclosed subject matter relates to s that can be used for the capture of volatile compounds in industrial and commercial natural gas tion and power generation industries. More specifically, systems for the reduction of volatile compounds are described herein. Thc system comprises an N-functionalizcd imidazolc and can optionally e an amine. The N—functionalized imidazole for use in the disclosed system is non-ionic under neutral conditions (e. g., under conditions Where an acidic proton is not available). In other es, the N—functionalized imidazole is not functionalized on both nitrogen atoms.

Further provided herein are methods for reducing C02, 802, or HZS from a stream (e.g., a gas stream or a liquid stream). The methods include contacting the stream with an ive amount of a system sing an N-functionalized imidazolc and, ally, an amine, wherein the N—functionalizcd imidazolc is non- ionic under neutral conditions.

Methods for sweetening a natural gas feed stream are also provided .

The methods comprise ting the natural gas feed stream With an effective amount of a system as bed herein to form a purified natural gas feed stream and a gas rich system and separating the ed natural gas feed stream from the gas-rich system. The methods can further comprise regenerating the system by, for e, heating or pressurizing the gas rich system.

PCT/U52012/030672 onal ages will be set forth in part in the description that follows, and in part will be s from the description, or may be learned by practice of the aspects described below. The advantages bed below will be realized and attained by means of the elements and combinations particularly d out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are ary and explanatory only and are not restrictive.

DESCRIPTION OF FIGURES The accompanying Figures, which are incorporated in and constitute a part of this specification, illustrate several aspects of the invention and together with the description serve to explain the principles of the ion.

Figure l is a schematic of the gas solubility apparatus.

Figure 2 is a graph depicting the relationship between C02 partial pressure and loading per initial amine molecule in 80:20 (v/v) l-butylimidazole-amine mixtures at °C.

Figure 3 is a graph depicting the relationship between C02 partial pressure and loading in 80:20 (v/v) l—butylimidazolc + N—mcthylcthanolaminc (NMEA) mixtures at temperatures between 25—80 °C.

DETAILED DESCRIPTION The materials, compounds, compositions, articles, and methods described herein may be understood more readily by reference to the following detailed ption of specific aspects of the disclosed subject matter and the Examples included therein.

Before the present materials, nds, compositions, kits, and s are discloscd and described, it is to be understood that thc aspccts dcscribcd bclow are not limited to specific synthetic methods or specific reagents, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

Also, throughout this specification, various publications are referenced. The sures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the alt to which the disclosed matter pertains. The nces sed are also individually PCT/U52012/030672 and specifically incorporated by reference herein for the material contained in them that is discussed in the ce in which the reference is relied upon.

A. l ions In this specification and in the claims that follow, reference will be made to a number of terms, which shall be d to have the following meanings: Ll] Throughout the description and claims of this specification the word “comprise” and other forms of the word, such as “comprising” and “comprises,” means including but not limited to, and is not intended to exclude, for example, other additives, components, integers, or steps.

As used in the description and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

Thus, for example, nce to “a composition” includes mixtures of two or more such compositions, reference to “the compound” includes mixtures of two or more such compounds, and the like.

“Optional” or “optionally” means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are sed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. It is also understood that there are a number of values disclosed herein, and that each value is also herein sed as “about” that particular value in addition to the value . For example, if the value “10” is disclosed, then “about 10” is also disclosed. It is also understood that when a value is sed, then “less than or equal to” the value, “greater than or equal to the value,” and possible ranges between values are also disclosed, as appropriately understood by the skilled n. For e, if the value “10” is disclosed, then “less than or equal to 10” as well as “greater than or equal to 10” is also disclosed. it is also understood that throughout the application data are ed in a number of different formats and that this data represent endpoints and starting PCT/U52012/030672 points and ranges for any combination of the data points. For example, if a particular data point “10” and a particular data point “15” are disclosed, it is tood that greater than, greater than or equal to, less than, less than or equal to, and equal to 10 and 15 are considered disclosed as well as between 10 and 15. It is also understood that each unit between two particular units are also disclosed. For example, if 10 and are disclosed, then ll, l2, l3, and 14 are also disclosed.

By “reduce” or other forms of the word, such as “reducing” or “reduction,” is meant ng of an event or characteristic (e.g., volatile compounds in a stream). lt is understood that this is typically in on to some standard or expected value, in other words it is relative, but that it is not always necessary for the standard or relative value to be referred to. For example, “reduces C02” means reducing the amount of C02 in a stream relative to a standard or a control. As used herein, reduce can e complete l. In the disclosed method, reduction can refer to a 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100% decrease as compared to the standard or a l. It is understood that the terms “sequester,” ‘6capture, 5’ “remove,” and “separation” are used synonymously with the term “reduce.” By “treat” or other forms of the word, such as “treated” or “treatment,” is meant to add or mix two or more compounds, compositions, or materials under appropriate conditions to produce a desired product or effect (e.g., to reduce or eliminate a particular characteristic or event such as C02 reduction). The terms ct” and “react” are used synonymously with the term “treat.” It is understood that throughout this ication the identifiers “first” and “second” are used solely to aid in distinguishing the various components and steps of the disclosed subject matter. The identifiers “first” and “second” are not intended to imply any particular order, amount, preference, or importance to the components or steps d by these terms.

B. Chemical Definitions References in the specification and concluding claims to parts by weight of a particular element or component in a composition denotes the weight relationship between the element or component and any other elements or components in the ition or article for which a pait by weight is expressed. Thus, in a compound ning 2 parts by weight of component X and 5 parts by weight component Y, X PCT/U52012/030672 and Y are present at a weight ratio of 2:5, and are present in such ratio regardless of r additional components are contained in the compound.

A weight percent (wt. %) of a component, unless specifically stated to the contrary, is based on the total weight of the formulation or composition in which the component is included.

The term “i011,” as used herein, refers to any molecule, n of a molecule, cluster of molecules, molecular complex, moiety, or atom that contains a charge (positive, negative, or both at the same time within one molecule, cluster of molecules, molecular complex, or moicty (e.g., Zwitterions)).

The term “anion” is a type of ion and is included within the g of the term “ion.” An “anion” is any molecule, portion of a molecule (e.g., Zwitterion), cluster of molecules, molecular x, moiety, or atom that contains a net negative charge.

The term “cation” is a type of ion and is included within the meaning of the term “ion.” A “cation” is any le, portion of a molecule (e.g., rion), cluster of molecules, molecular complex, moiety, or atom that contains a net positive charge.

The term “non—ionic” as used herein refers to being free of ionic groups or groups that are readily substantially ionized in water. A “non—ionic” compound does not n a charge at neutral pH (e.g., at a pH from 6.7 to 7.3). However, non-ionic nds can be made to have a charge under acidic or basic conditions or by methods known in the art, e.g., protonation, deprotonation, ion, ion, alkylation, acetylation, esterification, deesterification, hydrolysis, etc. Thus, the disclosed “non-ionic” nds can become ionic under conditions where, for example, an acidic proton is available to protonate the compound.

The term “volatile compound” as used herein refers to chemical nds that are capable of vaporizing to a significant amount or that exist as a gas at ambient conditions. The “volatile nds” described herein are found in the streams and have higher vapor pressures than the stream, such as natural gas feeds. Examples of volatile compounds include light gases and acid gases, such as CO2, 02, N2, CH4, H2, hydrocarbons, H28, 802, NO, N02, COS, CS2, and the like.

As used herein, the term “substituted” is contemplated to include all permissible substituents of organic compounds. In a broad aspect, the permissible PCT/U52012/030672 substituents include acyclic and , branched and unbranched, carbocyclic and heterocyclic, and aromatic and nonaromatic tuents of organic compounds.

Illustrative substituents include, for example, those described below. The sible tuents can be one or more and the same or different for appropriate organic compounds. For purposes of this disclosure, the heteroatoms, such as nitrogen, can have hydrogen substituents and/or any permissible substituents of organic compounds described herein which satisfy the ies of the heteroatoms. This disclosure is not intended to be limited in any manner by the permissible substituents of organic nds. Also, the terms “substitution” or “substituted wit ” include the implicit proviso that such substitution is in accordance with permitted valence of the substituted atom and the substituent, and that the substitution s in a stable compound, e.g., a compound that does not spontaneously undergo ormation such as by rearrangement, cyclization, elimination, etc.

“Al,” “AZ,” “A3,” and “A4” are used herein as generic symbols to ent various specific substituents. These symbols can be any substituent, not limited to those disclosed herein, and when they are defined to be certain substituents in one instance, they can, in another instance, be defined as some other substituents.

The term “aliphatic” as used herein refers to a non—aromatic hydrocarbon group and includes branched and unbranched, alkyl, alkenyl, or alkynyl groups.

The term “alkyl” as used herein is a branched or unbranched saturated hydrocarbon group of l to 24 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, eicosyl, tetracosyl, and the like. The alkyl group can also be substituted or unsubstituted. The alkyl group can be substituted with one or more groups including, but not limited to, alkyl, nated alkyl, alkoxy, alkcnyl, alkynyl, aryl, heteroaryl, aldehyde, amino, ylic acid, ester, ether, halide, hydroxy, ketone, nitro, silyl, sulfo—oxo, sulfonyl, e, sulfoxide, or thiol, as described below. hout the specification “alkyl” is generally used to refer to both unsubstituted alkyl groups and substituted alkyl groups; however, substituted alkyl groups are also specifically referred to herein by identifying the specific substituent(s) on the alkyl group. For example, the term “halogenated alkyl” specifically refers to an alkyl group that is substituted with one or more halide, e.g., fluorine, chlorine, PCT/U52012/030672 bromine, or iodine. The term “alkoxyalkyl” specifically refers to an alkyl group that is tuted with one or more alkoxy groups, as described below. The term “alkylamino” cally refers to an alkyl group that is substituted with one or more amino groups, as described below, and the like. When “alkyl” is used in one instance and a specific term such as alcohol” is used in another, it is not meant to imply that the term “alkyl” does not also refer to specific terms such as “alkylalcohol” and the like.

This practice is also used for other groups described herein. That is, while a term such as alkyl” refers to both unsubstituted and substituted cycloalkyl moieties, the substituted moieties can, in addition, be specifically identified herein; for e, a particular substituted lkyl can be referred to as, e. g., an “alkylcycloalkyl.” Similarly, a substituted alkoxy can be specifically referred to as, e. g., a “halogenated alkoxy,” a particular tuted alkcnyl can be, e.g., an “alkenylalcohol,” and the like. Again, the practice of using a general term, such as “cycloalkyl,” and a specific term, such as “alkylcycloalkyl,” is not meant to imply that the general term does not also include the specific term.

The term “alkoxy” as used herein is an alkyl group bound through a singlc, terminal ether linkage; that is, an “alkoxy” group can be defined as 70A1 where A1 is alkyl as defined above.

The term “alkenyl” as used herein is a hydrocarbon group of from 2 to 24 carbon atoms with a structural formula containing at least one carbon-carbon double bond. Asymmetric structures such as C=C(A3A4) are intended to include both the E and Z isomers. This can be presumed in stiuctural formulae herein wherein an asymmetric alkene is present, or it can be explicitly indicated by the bond symbol C=C. Thc alkcnyl group can be substituted with one or more groups including, but not limited to, alkyl, halogenated alkyl, alkoxy, alkenyl, alkynyl, aryl, heteroaryl, aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, , nitro, silyl, sulfo-oxo, sulfonyl, sulfone, sulfoxide, or thiol, as described below.

The term yl” as used herein is a hydrocarbon group of 2 to 24 carbon atoms with a ural formula containing at least one carbon-carbon triple bond.

The alkynyl group can be substituted with one or more groups including, but not limited to, alkyl, nated alkyl, alkoxy, alkenyl, alkynyl, aryl, heteroaryl, PCT/U52012/030672 aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, ketone, nitro, silyl, sulfo—oxo, sulfonyl, e, sulfoxide, or thiol, as described below.

The term “aryl” as used herein is a group that contains any carbon-based aromatic group including, but not limited to, benzene, naphthalene, phenyl, biphenyl, phenoxybenzene, and the like. The term “heteroaryl” is defined as a group that contains an aromatic group that has at least one heteroatom incorporated within the ring of the aromatic group. es of heteroatoms include, but are not limited to, en, oxygen, sulfur, and phosphorus. The term “non-heteroaryl,” which is included in the term “aryl,” defines a group that contains an ic group that does not contain a heteroatom. The aryl and heteroaryl groups can be substituted or unsubstituted. The aryl and heteroaryl groups can be substituted with one or more groups including, but not limited to, alkyl, halogenated alkyl, alkoxy, l, alkynyl, aryl, heteroaryl, de, amino, carboxylic acid, ester, ether, halide, hydroxy, , nitro, silyl, sulfo-oxo, sulfonyl, sulfone, sulfoxide, or thiol as described herein. The term “biaryl” is a specific type of aryl group and is included in the definition of aryl. Biaryl refers to two aryl groups that are bound together via a fused ring structure, as in naphthalcnc, or are attached via onc or more carbon-carbon bonds, as in biphenyl.

The term “cycloalkyl” as used herein is a omatic carbon-based ring composed of at least three carbon atoms. Examples of cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, etc. The term “heterocycloalkyl” is a cycloalkyl group as defined above where at least one of the carbon atoms of the ring is tuted with a heteroatom such as, but not limited to, nitrogen, oxygen, sulfur, or phosphorus. The cycloalkyl group and heterocycloalkyl group can bc substitutcd or unsubstitutcd. Thc cycloalkyl group and hctcrocycloalkyl group can be substituted with one or more groups ing, but not limited to, alkyl, alkoxy, alkenyl, alkynyl, aryl, heteroaryl, aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, , nitro, silyl, sulfo—oxo, sulfonyl, sulfone, sulfoxide, or thiol as described .

The term “cycloalkenyl” as used herein is a non—aromatic carbon—based ring composed of at least three carbon atoms and containing at least one double bound, i.e., C=C. Examples of cycloalkenyl groups include, but are not limited to, cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclopentadienyl, cyclohexenyl, PCT/U52012/030672 cyclohexadienyl, and the like. The term “heterocycloalkenyl” is a type of cycloalkenyl group as defined above, and is ed within the meaning of the term alkenyl,” where at least one of the carbon atoms of the ring is substituted with a heteroatom such as, but not limited to, nitrogen, oxygen, sulfur, or phosphorus. The cycloalkenyl group and heterocycloalkenyl group can be substituted or unsubstituted.

The cycloalkenyl group and heterocycloalkenyl group can be substituted with one or more groups including, but not limited to, alkyl, alkoxy, l, alkynyl, aryl, heteroaryl, aldehyde, amino, ylic acid, ester, ether, halide, hydroxy, , nitro, silyl, sulfo-oxo, sulfonyl, sulfone, sulfoxide, or thiol as described herein.

The term “cyclic group” is used herein to refer to either aryl groups, non—aryl groups (i.€., cycloalkyl, heterocycloalkyl, lkenyl, and heterocycloalkenyl groups), or both. Cyclic groups have one or more ring systems that can be substituted or unsubstituted. A cyclic group can contain one or more aryl groups, one or more non-aryl groups, or one or more aryl groups and one or more non—aryl groups.

The term “aldehyde” as used herein is represented by the formula —C(O)H.

Throughout this specification “C(O)” or “CO” is a short hand notation for C=O.

Thc tcrm “amino” as used herein is represented by the formula —NA1A2, where A1 and A2 can each be substitution group as described herein, such as hydrogen, an alkyl, halogenated alkyl, alkenyl, alkynyl, aryl, aryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, or heterocycloalkenyl group described above.

The term “carboxylic acid” as used herein is represented by the formula —C(O)OH. A “carboxylate” or “carboxyl” group as used herein is represented by the a —C(0)o'.

The term “ester” as used herein is represented by the formula iOC(O)A1 or —C(O)OA1, where A1 can be an alkyl, nated alkyl, alkenyl, alkynyl, aryl, heteroaryl, lkyl, cycloalkenyl, heterocycloalkyl, or heterocycloalkenyl group described above.

The term “ether” as used herein is represented by the a A10A2, where A1 and A2 can be, independently, an alkyl, halogenated alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, or heterocycloalkenyl group described above.

The term “ketone” as used herein is represented by the formula A1C(O)A2, Where A1 and A2 can be, independently, an alkyl, halogenated alkyl, alkenyl, alkynyl, 2012/030672 aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, or heterocycloalkenyl group described above.

The term “halide” or “halogen” as used herein refers to the e, chlorine, bromine, and iodine.

The term “hydroxyl” as used herein is represented by the formula —OH.

The term “nitro” as used herein is represented by the a —N02.

The term “silyl” as used herein is represented by the formula —SiA1A2A3, where A1, A2, and A3 can be, independently, hydrogen, alkyl, halogenated alkyl, alkoxy, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, or heterocycloalkenyl group described above.

The term nyl” is used herein to refer to the sulfo-oxo group represented by the formula —S(O)2Al, where A1 can be hydrogen, an alkyl, halogenated alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, cycloalkyl, or cycloalkenyl group described above.

The term “sulfonylamino” or “sulfonamide” as used herein is represented by the formula —S(O)2NH—.

The term “thiol” as used herein is represented by the formula —SH.

The term “thio” as used herein is represented by the formula 787.

“R1,” “R2,” “R3,” “Rn,” etc., where n is some integer, as used herein can, independently, s one or more of the groups listed above. For example, if R1 is a straight chain alkyl group, one of the hydrogen atoms of the alkyl group can optionally be substituted with a hydroxyl group, an alkoxy group, an amine group, an alkyl group, a , and the like. Depending upon the groups that are selected, a first group can be incorporated within second group or, alternatively, the first group can bc pendant (i.e., attached) to the second group. For example, with the phrase “an alkyl group comprising an amino group,” the amino group can be incorporated within the backbone of the alkyl group. Alternatively, the amino group can be attached to the backbone of the alkyl group. The nature of the group(s) that is (are) ed will determine if the first group is embedded or attached to the second group.

It is to be understood that the compounds provided herein can n chiral centers. Such chiral centers can be of either the (R-) or (S—) configuration. The compounds provided herein can either be enantiomerically pure, or be diastereomeric 0r enantiomeric mixtures. 2012/030672 As used herein, substantially pure means sufficiently homogeneous to appear free of readily detectable ties as determined by standard methods of analysis, such as thin layer chromatography (TLC), nuclear magnetic resonance (NMR), gel ophoresis, high performance liquid chromatography (HPLC) and mass spectrometry (MS), gas-chromatography mass spectrometry (GC-MS), and similar, used by those of skill in the art to assess such purity, or sufficiently pure such that further purification would not detectably alter the physical and chemical properties, such as enzymatic and biological activities, of the nce. Both traditional and modern methods for purification of the nds to produce substantially chemically pure compounds are known to those of skill in the art. A substantially chemically pure compound can, however, be a mixture of stereoisomers.

Unless stated to the contrary, a formula with chemical bonds shown only as solid lines and not as wedges or dashed lines contemplates each possible isomer, e. g., each enantiomer, diastereomer, and meso compound, and a mixture of isomers, such as a racemic or scalemic e.

Reference will now be made in detail to c aspects of the disclosed materials, compounds, compositions, es, and methods, examples of which are illustrated in the accompanying Examples.

C. Materials and Compositions N-Funczionalized Imidazoles Systems comprising N-functionalized imidazoles are provided herein. These compounds are useful for reducing volatile compounds, such as carbon dioxide (C02), carbon monoxide (CO), sulfur dioxide (SOZ), hydrogen sulfide (H28), en oxide (NO), nitrogen dioxide (N02), carbonyl sulfide (COS), and carbon disulfide (C82), mcrcaptans, 1-120, 02, H2, N2, C1—C8 hydrocarbons (e.g., e and propane), volatile organic compounds, and mixtures of these and other volatile compounds from gas streams and liquid streams. The tionalized imidazoles are non—ionic compounds under neutral compounds (2'.e., the oles do not contain a charge under neutral conditions). Neutral conditions include conditions where no proton is available to react with the N-functionalized imidazole (z'.e., to ate the N— functionalized imidazole). Protons can be present, but the conditions of the system, including the basicity ofthe N-functionized imidazole, are such that no significant amount of protonation ofthe N-functionalized imidazole , i.e., the conditions PCT/U52012/030672 do not produce imidazolium ion. Neutral conditions for the N—funetionalized imidazoles include conditions where the pH of the system is from about 6.7 to about 7.3. In some examples, the pH of the system can be about 6.7, about 6.8, about 6.9, about 7.0, about 7. 1, about 7.2, about 7.3, or the like, where any of the stated values can form an upper or lower endpoint of a range. The term “neutral conditions” is used herein relative to the specific imidazole, thus this term means conditions n the imidazole is not protonated (i.e., made cationic). For example, the pH of the system can be from about 6.8 to about 7.2, or from about 6.9 to about 7.1. Further, the N-funetionalized imidazoles described herein are not components of an ionic- liquid (2'. e., liquids that contain ions under all conditions).

The N—functionalized oles described herein are represented by Formula H (I) NYN‘ R1 and derivatives thereof.

In Formula I, R1 is substituted or unsubstituted C1_zo alkyl, tuted or unsubstituted €2.20 alkenyl, substituted or unsubstituted €2-20 alkynyl, substituted or unsubstituted C1_20 heteroalkyl, substituted or tituted C2_20 heteroalkenyl, substituted or unsubstituted C2_20 heteroalkynyl, substituted or unsubstituted lkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted thio, substituted or tituted amino, substituted or unsubstituted alkoxyl, substituted or unsubstituted aryloxyl, silyl, siloxyl, or cyano.

Also in Formula 1, R2, R3, and R4 are each independently selected from hydrogen, halogen, hydroxyl, substituted or unsubstituted €1.20 alkyl, substituted or unsubstituted C2_20 l, substituted or unsubstituted €2-20 alkynyl, tuted or unsubstituted C1_2o heteroalkyl, substituted or unsubstituted €2.20 heteroalkenyl, substituted or tituted C240 heteroalkynyl, tuted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or tituted thio, substituted or unsubstituted alkoxyl, substituted or unsubstituted aryloxyl, substituted or unsubstituted amino, cyano, or nitro.

PCT/U52012/030672 Further in Formula I, adjacent R groups, 126., R1 and R2, R1 and R4, and R2 and R3 can be ed to form a substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted lkenyl, substituted or unsubstituted cycloalkynyl, substituted or unsubstituted heterocycloalkyl, substituted or tituted heterocycloalkenyl, or substituted or unsubstituted heterocycloalkynyl. R2, R3, R4, and R5 can each also be halides, cyano, nitro, and other similar groups.

In some embodiments, the N-functionalized oles represented by a I can be selected fiom an N—alkyl imidazole, an N—alkenyl ole, an N— l imidazole, an N—aryl imidazole, or mixtures thereof. In some examples of a I, R1 can be unsubstituted alkyl as represented by Formula I-A. In other examples of Formula I, R1 can be a heteroalkyl group such as an ethoxylated group as represented by Formula 1-8. In still further examples of Formula I, R1 can be a tuted alkyl group, such as, for example, cyanoalkyl or hydroxyalkyl as represented by Formula I-C and Formula I-D, respectively.

R3 R3 HR2 2 N NHR if”? 34/ #0}ijN .

R R Formula I-A Formula I-B R2 R3 2 Formula I-C Formula l-D In Formula I-A, m is an integer from 0 to 20. In Formulas I-B, I-C, and LB, 11, p, and q, respectively, are independently integers fiom l to 20. In some embodiments, R2, R3, and R4 are each hydrogen.

In some examples of Formula I, R1 can be an alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl, heteroalkynyl, cycloalkyl, heterocycloalkyl, aryl, aryl, thio, amino, alkoxyl, aiyloxyl, or silyl substituted with an imidazole group to form a bis-N—substituted imidazole. For example, Formula I can be represented by Formula I-E as shown below.

PCT/U52012/030672 Formula I-E Tn Formula I—E, L is selected from substituted or tituted C140 alkyl, substituted or unsubstituted C240 alkenyl, substituted or unsubstituted €2.20 alkynyl, substituted or unsubstituted €1.20 heteroalkyl, substituted or unsubstituted €2.20 heteroalkenyl, substituted or unsubstituted C240 heteroalkynyl, substituted or unsubstituted cycloalkyl, tuted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted thio, tuted or tituted amino, substituted or unsubstituted alkoxyl, substituted or unsubstituted aryloxyl, or silyl.

Also in a l-E, R5, R6, and R7 are each independently selected from hydrogen, halogen, hydroxyl, substituted or unsubstituted C140 alkyl, substituted or unsubstituted C240 alkenyi, substituted or unsubstituted €2-20 alkynyl, substituted or tituted Cm) heteroalkyl, substituted or unsubstituted €2.20 heteroalkenyl, substituted or unsubstituted C240 heteroalkynyl, substituted or unsubstituted cycloalkyl, tuted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted thio, substituted or unsubstituted alkoxyl, substituted or tituted aryloxyl, substituted or unsubstituted amino, or cyano. in some examples of Formula l-E, the imidazole is an imidazole dimer. In other words, in some examples of Formula I-E, R2 and R5 are the same substituent, R3 and R6 are the same substituent, and R4 and R7 are the same substituent.

Particular examples of Formula I include the following compounds: No No H VNV VNW NVN\/\0/ Compound I-1 Compound I-2 Compound I-3 /—\ /=\ _ N N \ N\/\/\/ \ N\/\O/ NWNW Y 1 nd 1-4 Compound 1-5 Compound 1-6 2012/030672 Compound I-7 Amines In some embodiments, the N-functionalized imidazole containing systems can further comprise one or more amine compounds. The amine can be a primary amine, a secondary amine, a tertiary amine, a cyclic amine, or a mixture thereof. The amine compounds described herein can be represented by a II: If‘ (11) R3 R2 In a 11, R1, R2, and R3 can each independently be selected from the group consisting of hydrogen, substituted or unsubstituted €1-20 alkyl, substituted or unsubstituted C240 l, substituted or unsubstituted C220 alkynyl, substituted or unsubstituted Cmo heteroalkyl, substituted or unsubstituted C2,2011eteroalkeiiyl, substituted or unsubstituted C240 heteroalkynyl, tuted or unsubstituted eyeloalkyl, substituted or unsubstituted heteroeyeloalkyl, substituted or unsubstituted aryl, substituted or tituted heteroaryl, substituted or unsubstituted thio, substituted or unsubstituted amino, substituted or unsubstituted alkoxyl, substituted or unsubstituted aryloxyl, silyl, l, or eyano.

In some embodiments, the amine can be a primary amine. According to these examples, two of R1, R2, or R3 are hydrogen and the remaining group is other than hydrogen to form a nd according to Formula II-A.

II'N‘II Formula II—A In Formula II-A, R1 is selected from substituted or unsubstituted €1.20 alkyl, substituted or unsubstituted C2.20 alkenyl, substituted or unsubstituted C2_20 alkynyl, substituted or unsubstituted Cmo heteroalkyl, substituted or unsubstituted C2_20 heteroalkenyl, tuted or unsubstituted 02,20 heteroalkynyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted cyeloalkyl, tuted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted thio, substituted or unsubstituted amino, substituted or unsubstituted alkoxyl, or PCT/U52012/030672 substituted or unsubstituted yl. Particular examples of y amines as described herein include monoethanolamine (MEA), diglycolamine (DGA), 2—amino— 2-methylpropanol (AMP), and l-(3 propyl)-imidazole (API).

In some embodiments, the amine can be a secondary amine Where one of R], R2, or R3 is hydrogen and the remaining two groups are other than hydrogen.

Secondary amines as described herein can be represented by Formula “-8.

H’N‘R2 Formula II-B In Formula II-B, R1 and R2 are each independently selected from substituted or unsubstituted C1_20 alkyl, substituted or unsubstituted C2_20 alkenyl, substituted or unsubstituted C2_20 alkynyl, substituted or unsubstituted C1_20 heteroalkyl, substituted or unsubstituted C120 heteroalkenyl, substituted or unsubstituted C240 heteroalkynyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, tuted or unsubstituted aryl, substituted or unsubstituted thio, substituted or tituted amino, substituted or unsubstituted alkoxyl, or substituted or unsubstituted aryloxyl. Particular examples of secondary amines as described herein include ylethanolamine (NMEA), diethanolamine (DEA), and diisopropanolamine (DIPA).

In further embodiments, the amine can be a tertiary amine where each of R1, R2, and R3 are other than hydrogen as represented by Formula II-C.

Ryfils R2 a II-C In Formula II-C, R1, R2, and R3 are each ndently selected from substituted or unsubstituted C140 alkyl, substituted or unsubstituted Cz_20 alkenyl, substituted or unsubstituted C2_20 alkynyl, substituted or unsubstituted C1_20 heteroalkyl, substituted or tituted C2.20 heteroalkenyl, substituted or tituted C2_2o heteroalkynyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted a1yl, substituted or unsubstituted heteroaryl, substituted or unsubstituted thio, substituted or unsubstituted amino, substituted or tituted alkoxyl, or substitutcd or unsubstitutcd aryloxyl.

A particular e of a tertiary amine includes N—methyldiethanolamine (MDEA).

PCT/U52012/030672 The amines for use in the systems bed herein can also include cyclic amines. According to these examples, two of R1, R2, or R3 can combine to form a substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted cycloalkenyl, substituted or unsubstituted cycloalkynyl, substituted or unsubstituted heterocycloalkyl, tuted or unsubstituted heterocycloalkenyl, or substituted or unsubstituted heterocycloalkynyl. The cyclic amines can be represented by Formula II-D.

H’N‘RZR1,)| Formula II-D In Formula II-D, the line connecting R1 and R2 represents a connection (e.g., a single bond or double bond) between R1 and R2 that forms a cyclic structure including R1, N, and R2. Examples of suitable cyclic amines for use in the s described herein e a substituted or unsubstituted zine (P2) and an unsubstituted imidazole.

The amine described herein can contain one amino functional group (2'. e., can bc a monoaminc) or can contain two amino functional groups (i.e., can bc a diaminc), or can contain more than two amino functional groups (i.e., can be a polyamine).

Systems The systems disclosed herein can contain one or more N-functionalized oles and ally, one or more amines. The systems described herein are not ionic liquids. For example, the combination of one or more N-functionalized imidazoles and one or more amines does not result in a low melting salt. Upon addition of an acid gas (e.g., C02, HZS, etc.) the system can contain charge. Further, the systems described herein can be distilled whereas ionic liquids do not have this capability. The systems discloscd hcrcin can be neat (126., can bc composcd of the N— functionalized imidazole and/or amine without any additional solvent) or can be dissolved or dispersed in one or more additional solvents. In some ments, the system is a neat system comprised primarily of one or more N-functionalized imidazoles. Systems sed primarily of the N-functionalized imidazole can contain about 3% or less of impurities (116., the system contains about 97% or higher, about 98% or higher, or about 99% or higher ionalized imidazole based on the weight of the system).

WO 35178 PCT/U52012/030672 In some ments, the system is a neat system composed of a e of one or more N—functionalized imidazoles as described herein and one or more amines as described herein (1'.e., an imidazole—amine blend). The addition to one or more amines to one or more N-functionalized imidazoles s in a system with low volatility, low viscosity, and high C02 capacity. The properties of the system can be altered by changing the ratios of'N-functionalized imidazole and amine present in the system.

The N -functionalized imidazole can comprise 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 89%, 88%, 87%, 86%, 85%, 84%, 83%, 82%, 81%, 80%, 79%, 78%, 77%, 76%, 75%, 74%, 73%, 72%, 71%, 70%, 69%, 68%, 67%, 66%, 65%, 64%, 63%, 62%, 61%, 60%, 59%, 58%, 57%, 56%, 55%, 54%, 53%, 52%, 51%, 50%, 49%, 48%, 47%, 46%, 45%, 44%, 43%, 42%, 41%, 40%, 39%, 38%, 37%, 36%, 35%, 34%, 33%, 32%, 31%, 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1% ofthe system, where any ofthe stated values can form an upper or lower endpoint of a range. In further examples, the N-functionalizcd imidazolc can comprise from 1% to 99%, 10% to 90%, 20% to 80%, % to 70%, 40% to 60%, or 50% of the system. For example, the N—functionalized imidazole can comprise 67% of the system.

Likewise, the amine can comprise 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 89%, 88%, 87%, 86%, 85%, 84%, 83%, 82%, 81%, 80%, 79%, 78%, 77%, 76%, 75%, 74%, 73%, 72%, 71%, 70%, 69%, 68%, 67%, 66%, 65%, 64%, 63%, 62%, 61%, 60%, 59%, 58%, 57%, 56%, 55%, 54%, 53%, 52%, 51%, 50%, 49%, 48%, 47%, 46%, 45%, 44%, 43%, 42%, 41%, 40%, 39%, 38%, 37%, 36%, 35%, 34%, 33%, 32%, 31%, 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1% of the system, where any of the stated values can form an upper or lower endpoint of a range. In further examples, the amine can comprise from 1% to 99%, 10% to 90%, 20% to 80%, 30% to 70%, 40% to 60%, or 50% of the system. For example, the amine can comprise 33% of the system.

In some embodiments, the system can have an N-functionalized imidazole to amineratio of9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, and the like. In other PCT/U52012/030672 embodiments, the system can have an amine to N—functionalized imidazole ratio of 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, and the like.

As described above, the systems described herein can be dissolved or dispersed in one or more additional solvents. For example, the one or more N- functionalized imidazole or the one or more N-functionalized imidazole and one or more amine blend can be mixed with a solvent such as water, tetrahydrofuran (THF), dichloromethane, acetonitrile, e, yl sulfoxide (DMSO), pyridine, dimethylformamide, dioxane, glycol solvents, methanol, ethanol, propanol, butanol, ethyl acetate, methyl ethyl ketone, acetone, and the like to provide a system. In these examples, the N—functionalized imidazole or the N—functionalized imidazole and amine blend can comprise from about 0.1% to about 99.9% of the system. For example, the N—functionalized imidazoles or the N—functionalized imidazole and amine blend can comprise from about 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 89%, 88%, 87%, 86%, 85%, 84%, 83%, 82%, 81%, 80%, 79%, 78%, 77%, 76%, 75%, 74%, 73%, 72%, 71%, 70%, 69%, 68%, 67%, 66%, 65%, 64%, 63%, 62%, 61%, 60%, 59%, 58%, 57%, 56%, 55%, 54%, 53%, 52%, 51%, 50%, 49%, 48%, 47%, 46%, 45%, 44%, 43%, 42%, 41%, 40%, 39%, 38%, 37%, 36%, %, 34%, 33%, 32%, 31%, 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1% of the system, Where any of the stated values can form an upper or lower endpoint of a range. In further examples, the N-functionalized imidazole or the N-functionalized imidazole and amine blend can se from 1% to 99%, 10% to 90%, 20% to 80%, 30% to 70%, 40% to 60%, or 50% of the system.

The systems bed herein are substantially free from volatile c compounds. By substantially frcc is mcant that volatile organic compounds arc t at less than about 3%, 2%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, 0.001%, %, or the like of volatile organic compounds. Further, these systems are characterized by low viscosity in ison with imidazolium- based ionic liquids. For example, the systems described herein are at least 10 times, 9 times, 8 times, 7 times, 6 times, 5 times, 4 times, 3 times, or 2 times less viscous than imidazolium-based ionic liquids. The intrinsic viscosity of the systems described herein can be measured, for example, according to the method described in ASTM D5225-09 using a differential viscometer. For example, the intrinsic viscosity of the PCT/U52012/030672 systems can be measured using a Brookfield DV—II+ Pro Viscometer ed with a ULA (low Viscosity) spindle (Brookfield Engineering Laboratories, Inc.; Middleboro, MA). Further, the intrinsic Viscosities of the s can be measured neat (i. e. , with no additional solvent . In some embodiments, the Viscosities of the s at 24 °C can be less than 20 cP, less than 19 CF, less than 18 CF, less than 17 cP, less than 16 CF, less than 15 CF, less than 14 CF, less than 13 CF, less than 12 CF, less than 11 CF, less than 10 cP, less than 9 CF, less than 8 CF, less than 7 CF, less than 6 CF, less than 5 CR less than 4 cP, less than 3 cP, less than 2 CF, less than 1 CF, less than 0.9 eP, less than 0.8 cP, less than 0.7 cP, less than 0.6 cP, less than 0.5 cP, less than 0.4 cP, less than 0.3 cP, less than 0.2 cP, less than 0.1 CR or the like, where any of the stated values can form an upper or lower nt of a range. In further embodiments, the tionalized imidazoles can have a Viscosity from about 0.1 CF to about 20 cP, about 0.2 CF to about 19 cP, about 0.3 GP to about 18 cP, about 0.4 CF to about 17 cP, about 0.5 CF to about 16 CF, about 0.6 CF to about 15 CF, about 0.7 CF to about 14 CF, about 0.8 cP to about 13 CF, about 0.9 CF to about 12 CF, about 1 CF to about 1 1 CF, about 2 CF to about 10 cP, about 3 CF to about 9 cP, about 4 CF to about 8 GP, or about CF to about 7 CF. For example, at 24 0C, a system comprised of l-ethylimidazole has a Viscosity of about 2.02 eP. In another example, a system comprised of l— butylimidazole has a Viscosity of about 3.38 cP at 24 °C. In a further example, a system comprised of l-hexylimidazole has a Viscosity of about 2.99 cP at 45 °C. Still further, a system comprised of l-octylimidazole has a Viscosity of about 7.77 CP at 25 The N-fimctionalized imidazoles according to Formula I and the amines according to Formula II can be prepared in a variety of ways known to one skilled in the art of organic synthesis or variations thereon as appreciated by those skilled in the art. The compounds described herein can be ed from readily available starting materials. Optimum reaction conditions can vary with the particular reactants or ts used, but such conditions can be determined by one skilled in the art. The use of protection and deproteetion, and the selection of appropriate protecting groups can be determined by one skilled in the art. The chemistry of ting groups can be found, for example, in Wuts and Greene, Protective Groups in Organic Synthesis, 4th Ed, Wiley & Sons, 2006, which is incorporated herein by reference in its entirety.

PCT/U52012/030672 Variations on Formula I and Formula II include the addition, subtraction, or movement of the various constituents as described for each compound. Similarly, when one or more chiral centers are present in a molecule, the chirality of the molecule can be Changed. Additionally, compound synthesis can involve the protection and deprotection of various chemical groups.

The N-functionalized imidazoles and amines or the starting materials and reagents used in preparing the disclosed compounds are either available from commercial suppliers such as Aldrich al Co., (Milwaukee, W1), Acros Organics (Morris Plains, NJ), Fisher ific burgh, PA), Sigma (St. Louis, MO), Pfizer (New York, NY), GlaxoSmithKline (Raleigh, NC), Merck (Whitehouse Station, NJ), Johnson & Johnson (New Brunswick, NJ), Aventis (Bridgewater, NJ), AstraZeneca (Wilmington, DE), Novartis (Basel, Switzerland), Wyeth (Madison, NJ), Bristol-Myers—Squibb (New York, NY), Roche (Basel, rland), Lilly (Indianapolis, IN), Abbott (Abbott Park, IL), Schering Plough worth, NJ), or Boehringer Jngelheim (Ingelheim, Germany), or are prepared by methods known to those skilled in the art following procedures set forth in references such as Fieser and Ficscr’s ts for c Synthesis, Volumcs 1-17 (John Wiley and Sons, 1991); Rodd’s try of Carbon Compounds, Volumes 1—5 and Supplementals (Elsevier Science Publishers, 1989); Organic Reactions, Volumes 1-40 (John Wiley and Sons, 1991); March’s ed c try, (John Wiley and Sons, 4th Edition); and Larock’s hensive Organic Transformations (VCH Publishers Inc., 1989).

Reactions to produce the compounds described herein can be carried out in ts, which can be selected by one of skill in the art of organic synthesis.

Solvents can be substantially nonreactive with the starting materials (reactants), the intcrmcdiatcs, or products under the conditions at which the reactions arc carricd out, i.e., temperature and pressure. Reactions can be carried out in one solvent or a mixture of more than one solvent. Product or intermediate formation can be red according to any suitable method known in the art. For example, product ion can be monitored by spectroscopic means, such as nuclear magnetic resonance spectroscopy (e.g., 1H or C) infrared spectroscopy, spectrophotometry (e.g., UV-visible), or mass spectrometly, or by chromatography such as high performance liquid chromatography (HPLC) or thin layer chromatography.

PCT/U52012/030672 As shown in Scheme 1, the N—substituted imidazoles described by Formula I can be made, for example, by treating commercially available imidazole (1) with a strong base (6.53., sodium hydride or sodium hydroxide) to form the imidazolate sodium salt (2). The imidazolate sodium salt (2) can then be treated with an alkyl halide to form the N—alkylated imidazole (3). Similarly, other organohalides can be used in place of the alkyl halide to provide the corresponding N-organosubstituted imidazoles.

Scheme 1: RX; THF /—\ Base — e reflux — N NH a E“) —> v NVN Na NVNt (1) (2) (3) In addition, the bis-N—substituted imidazoles described by Formula I-E can be made, for example, by treating two equivalents of imidazolium sodium salt (2) with an alkyl de to form compound (4) (see Scheme 2).

SchemeZ: 2 e@fl> f\=\N N/:/\N v V \L/ V Na ref1ux (2) (4) Further, the N-substituted imidazoles according to Formula I can be synthesized according to methods described in US. hed Patent Application Number 2009/0171098, which is orated by reference herein for its teaching of methods of synthesis of N-substituted imidazoles.

The disclosed ole—amine blends can be prepared by methods described herein. Generally, the particular tionalized imidazole(s) and s) used to prepare the systems are selected as described herein. Then, with the particular N- functionalized imidazole(s) and s) in hand, they can be combined, resulting in a system as described herein.

Providing N-functionalized imidazoles and amines used to prepare the systems depends, in one aspect, on the desired properties of the resulting system. As described herein, the disclosed compositions can have multiple desired properties (e.g., low viscosity, low volatility, high C02 capacity, etc.), which, at least in part, come from the properties of the imidazoles and amines used to prepare the systems.

PCT/U52012/030672 Thus, to prepare the disclosed s, one or more N—functionalized imidazoles with desired properties and one or more amines with desired properties are selected and provided. Providing a desired imidazole and amine can be done in any order, depending on the preference and aims of the practitioner. For example, a particular imidazole can be provided and then a particular amine can be provided.

Alternatively, a particular amine can be provided and then a particular imidazole can be provided. Further, the imidazole and amine can be provided simultaneously.

Properties desired to be adjusted based on the selection of the imidazole and the amine can include, for example, the vapor pressure, Viscosity, density, heat capacity, thermal conductivity, and surface tension. For example, in high pressure applications, the systems can be comprised primarily of N—functionalized oles. In low pressure applications, the systems can comprise a combination of the N— functionalized imidazoles and one or more amines. r, the amines used in the systems can be varied based on the pressure level of the application. Primary (1°) amines, such as monoethanolamine (MBA) or diglycolamine (DGA), can be suitable for use in low pressure applications. An example of a low pressure application includes post—combustion C02 capture from power plants. Secondary (2°) , such as N—methylethanolamine (NMBA) or piperazine (PZ), or ally hindered 2O amines, such as diisopropranolamine (DIPA), can be suitable for use in moderate to high pressure applications. An example of a moderate to high pressure ation is the l of C02 from natural gas.

D. iMethods of Using the Systems The systems described herein can be used to reduce volatile compounds from s (e.g., gas streams or liquid streams) as described in US. Published Patent Application Number 2009/0291874, which is incorporated by reference herein for its s and ques of volatile compound ion. As used , volatile compounds can include to undesirable gaseous components found in a source and having a lar weight lower than 150 g/mol. For example, the volatile compounds can have a molecular weight lower than 140 g/mol, 130 g/mol, 120 g/mol, llO g/mol, 100 g/mol, 90 g/mol, 80 g/mol, 70 g/mol, 60 g/mol, 50 g/mol, 40 g/mol, 30 g/mol, 20 g/mol, or the like, where any of the stated values can form an upper or lower endpoint of a range. Examples of volatile compounds include C02, CO, COS, PCT/U52012/030672 H28, 802, NO, N20, mercaptans, H20, 02, H2, N2, C1—C3 hydrocarbons (e.g., methane and propane), volatile organic compounds, and mixtures of these.

The method for reducing a volatile nd from a stream can include contacting the stream with an effective amount of a system as bed herein. In some ments, the system is comprised primarily of an tionalized imidazole. in other ments, the system contains an N—functionalized imidazole and an amine. For example, volatile compounds from a gas stream (e.g., a natural gas stream or a flue gas ) can be reduced according to this method.

Further described herein is a method for sweetening a natural gas feed stream.

The method includes contacting the natural gas feed stream with an effective amount of a system as described herein to form a ed natural gas feed stream and a gas- rich system. Optionally, the l gas feed stream can be contacted with a second system as described herein. The contacting of the natural gas feed stream with the second system can be performed simultaneously as the contacting with the first system (i.e., the gas feed stream can be contacted with both the first and second system) or can be performed sequentially (126., the gas feed stream can be contacted with the second system after the gas feed stream has been contacted with the first system). The purified natural gas feed stream can then be separated from the gas—rich system. In some embodiments, the volatile compounds are reduced from the gas-rich system to regenerate the system. The system can be regenerated by heating or pressurizing the gas-rich system.

The es below are intended to further illustrate n aspects of the methods and compositions described , and are not intended to limit the scope of the claims.

EXAMPLES The ing examples are set forth below to illustrate the methods and results according to the disclosed subject matter. These examples are not intended to be inclusive of all aspects of the subject matter disclosed herein, but rather to illustrate entative methods and results. These examples are not intended to exclude equivalents and variations of the present invention which are apparent to one skilled in the art.

Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.) but some errors and deviations should be accounted for.

PCT/U52012/030672 Unless indicated otherwise, parts are parts by weight, temperature is in °C or is at ambient temperature, and pressure is at or near atmospheric. There are numerous variations and combinations of on conditions, e.g., component concentrations, temperatures, pressures and other reaction ranges and conditions that can be used to optimize the product purity and yield obtained from the described process. Only reasonable and routine experimentation will be required to optimize such process ions.

Example I : Materials l—methylimidazole (1) was ed from Sigma-Aldrich (Milwaukee, WI USA) and used without further purification. 1—n—alkylimidazoles (2 — 10) were synthesized from sodium imidazolate (Nalm) and a corresponding alkyl bromide as described in Bara et al., “Versatile and le Method for Producing N— Functionalized Imidazoles,” Ind. Eng. Chem. Res, 50(24); 13614-13619 (2011) and in US. Published Patent Application Number 2009/0171098, which are incorporated by reference herein in their entireties for their ng of N—functionalized imidazoles and synthesis thereof. Research Grade C02 and CH4 were purchased from AirGas (Radnor, PA USA). e 2: y Measurements y values for each l-n-alkylimidazole were obtained using a Mettler Toledo DM45 DeltaRange density meter, which operates via electromagnetically d oscillation of a glass U-form tube, with automatic compensation for variations in atmospheric pressure. The density meter can measure liquid samples within the range of 0 — 3 g/cm3 with a minimal sample size of 1.2 cm3. The accuracy of the y meter measurements is ::0.00005 g’cm3 for all operating temperatures.

Densities of l-n-alkylimidazoles were recorded over a temperature range of 20 — 80°C at 10°C increments, for a total of seven density ements per compound. The unit was washed between every run with deionized H20, followed by an acetone rinse, and then dried by air flow. The density reading of the clean, empty cell was verified to be consistent with that of air at 20°C (0.00120 g/cm3) before continuing to the next sample.

PCT/U52012/030672 The measured density values for l—n—alkylimidazoles over the temperature range of 20 — 80°C are presented in Table 1.

Table 1 Density (g/em") l-n- Temperature (°C) alkylimidazole 70 80 1.03525 1.02644 1.01760 1.00871 0.99979 0.99083 0.98178 2—Ethyl 0.99448 0.98581 0.97712 0.96843 0.95969 0.95089 0.94208 3—Propy1 0 0.96456 4 0.94789 0.93952 0.93111 0.92267 4 —Butyl 0.95137 0.94338 0.93540 0.92740 0.91938 0.91132 0.90320 — Pentyl 0.93887 0.93111 0.92334 6 0.90776 0.89994 0.89208 6 — Hexyl 0.92990 0.92226 0.91463 0.90698 0.89932 0.89166 0.88395 7 — Octyl 4 9 0.89706 0.88983 0.88259 0.87531 0.86801 8 —Decyl 0.90145 0.89437 0.88729 2 0.87315 0.86608 0.85900 9 — Dodecyl 0.89474 0.88776 0.88083 0.87390 0.86699 0.86008 0.85315 deeyl 0.88940 0.88255 0.87574 0.86895 0.86218 0.85541 0.84862 Ll] With the exception of l-methylimidazole in the range of 20 — 50°C, all of the measured ies for l-n—alkylimidazoles were less than 1.00000 g/cm3. For each nd, density was observed to se linearly with increasing temperature, and across the entire group of l—n—alkylimidazoles, density decreased with increasing length of the n—alkyl substituent.

Example 3: Viscosity Measurements Viscosity data were obtained using a Brookfield DV—H+ Pro viscometer. The viscosity measurement is based on a torque value and shear rate of a certain sized spindle in t with a pre—determined amount of fluid. The “ULA” spindle and jacketed sample cell was used for these relatively low ity liquids (< 25 CP), which required a minimal sample size of approximately 16 cm3. The viscometer accuracy is ::l% of the reading for torque measurement with a repeatability of ::0.2% of the reading. The ity of each l—n—alkylimidazole was measured at ten temperatures within the range of 20 — 80°C. The temperature of the jacketed sample Chamber was controlled via the Brookfield P circulating bath, which has an operating range of -20 — 200°C and a temperature stability of :: 001°C. The sample 2012/030672 cell was cleaned between every run by rinsing with deionized water and acetone, followed by air . The viscometer was re—zeroed between runs.

The measured viscosity values for l-n-alkylimidazoles over the temperature range of 20 — 80°C are presented in Table 2.

Table 2 Viscosity (cP) l-n- Temperature (°C) alkylimidazole 1 — Methyl 1.17 2 — Ethyl 1.22 3 — Propyl 1.23 4 — Butyl 1.42 — Pentyl 1.43 6—chyl 4.38 3.82 2.67 2.18 1.82 1.55 7 — Octyl 6.56 5.63 3.76 3.00 2.44 2.04 8 — Decyl 9 — Dodecyl 12.36 10.34 — 16.60 13.72 Tetradeeyl As can be seen in Table 2, almost all of the measured viscosities for the ten 1— n-alkylimidazole compounds were < 10 CP, and only 1—tetradecylimidazole exhibited a viscosity > 20 cP below 30°C. For each compound, viscosity was observed to decrease in a non-linear fashion with sing temperature. Viscosity was strongly correlated to length of the n-alkyl substitucnt, with an order of magnitude difference between the least viscous and most viscous compounds at 20°C, though reducing to about 3.5x difference at the highest temperature.

Example 4: C02 Solubility Measurements The lity of C02 in each of the l-n-alkylimidazoles was measured using a custom built tus (Figure 1) based on an approach ped for the natural gas industly (see Bara et 61]., Acc. Chem. Res. 2010, 43, 152 — 159).

The cell body was constructed from a 2.5" OD (6.35 cm OD) sanitary fitting butt-welded to a ponding bottom cap. 1/4" (0.635 cm) VCR and 1/8" (0.3175 cm) tube fittings were welded to the top cap, and a PTFE gasket and spring-loaded PCT/U52012/030672 clamp were used to seal the vessel. The sanitary fittings, gaskets, and clamps were purchased from McMaster—Carr. Swagelok fittings were sed from Alabama Fluid Systems Technologies (Pelham, AL). Machine work was performed by Engineering Technical Services at the University of a. Welding was performed by McAbee Construction (Tuscaloosa, AL).

Experiments were conducted at ambient temperature (25 :: 05°C) and the temperature controlled via air circulation. Approximately 40 mL of a 1—11- alkylimidazole compound of interest was added to the cell and the weight of solvent recorded using a Mettler Toledo XS6OOZS Precision Balance, with a repeatability of 8 mg. The volume of solvent was calculated using the density values measured as described above. A 1.75 inch (4.445 cm) wide stir bar was added to ensure thorough contact between the gas and liquid phases. The vessel was then sealed and the residual air d via vacuum until the system pressure was less than about 5 torr as measured by an MKS on pressure transducer (accuracy of :: 0.5% of the reading) and displayed on a MKS PDR2000A annel l Power Supply/Readout. The transducer was also aced with LabView (National Instrumcnts) for digital data acquisition and visual monitoring of system temperature and pressure. The sealed apparatus was then weighed to provide a tare weight prior to adding CO2, the mentation re-connected and then unit secured above a stir plate.

CO2 was added to the cell at pressures between 3 — 7 atm, and the brium re and weight of added CO2 were recorded. Confirmation that equilibrium had been reached was determined via a stable re reading (:: 2 torr) over 10 minutes on both the readout and from the data acquisition software. Because the solvent viscosity was low, and the vessel could be stirred, equilibrium was typically achieved in < 30 min.

A C02 pressure of 3 atm was chosen as a starting point so as to ensure a sufficient mass of CO2 had been added to be far outside the error of the e.

About 350 — 400 mg of C02 per atmosphere of CO2 pressure were absorbed in 40 mL of solvent. The moles of CO2 (nco2) added to the vessel were calculated from the mass increase and the molecular weight of C02 (44.01 g/mol). The moles of C02 in the vapor phase (nvco2) were calculated by subtracting the volume of the stir bar and solvent from that of the empty cell, and applying the ideal gas law (Eqn. 1 ).

PCT/U52012/030672 vapor (V ell _ Vtz'rbar _c s solvent) 2 ”:70: RTvapor (1) The moles of C02 in the liquid phase (n‘CO2) were taken to be the moles in the vapor phase subtracted from the total moles of CO2 added to the cell (Eqn. 2). l v ”C02 — ”CO, _nco2_ (Z) The error in repeatability using this apparatus and technique was found to be :: 4%, which is in line with the error of similar equipment previously described for making similar gas solubility measurements on lLs. See, for example, Bara et al, Acc.

Chem. Res. 2010, 43, 152 — 159; Armand et al., Nat. Mater. 2009, 8, 621-629; and MCCabe el al., Unit Operations ofChemical Engineering, 6th Ed.; MCGraw-Hill: , 2001.

It was d that the solvent density was nt upon addition of C02 (i.e., no expansion). The solubility of CO2 in each l-n-alkylimidazole was found to be linear in the pressure range examined, and Henry’s Law constants (H(atm)) were calculated from the following relationship (Eqn. 3): P(atm) - (nlco2 + nmd ) H(atm) = (3) nCOZ Volumetric solubility (S) was calculated as standard cubic eters (em3(STP)) of CO2 ved per cm3 of l-n-alkylimidazole (em3 imid) per atmosphere of pressure, according to Eqn. 4: cm3 (STP) n90, .22414 molCO2 S = (4) imid P(atm) Solubility data for CO2 in l-n-alkylimidazoles at low pressures and 25 :: 05°C in terms ofHenry’s constants (H(atm)) and volumetric lity (S) are presented in Table 3.

Table 3 l-n-alkylimidazole H002 (atm) S (cm3 (STP) cm'3 atm'l) 1 — Methyl 109 :: 2 2.71 :: 0.04 2 — Ethyl 97.9 :: 0.6 2.49 :: 0.07 3 — Propyl 4 — Butyl — Pentyl 6 — Hexyl 7 — Octyl 2012/030672 8 — Decyl 53.6 :: 0.7 1.99 :: 0.06 9 — Dodecyl — Tctradccyl 48.6 :: 1.7 1.77 :: 0.04 Uncertainties represent ::1 standard ion from the mean.

Example 5: Comparison ity & Viscosity For 1-n—alkylimidazoles, density is influenced by the length of the n-alkyl chain and temperature. Both increasing temperature and increasing side chain length are observed to decrease density. Trends similar to 1-n-alkylimidazoles are also observed for families of [Cnmim] [X] ILs (e. g., [C211’1111’1][BF4], [C4mim][BF4], [C6mim][BF4]), however IL density is also strongly influenced by the nature of the anion, across a family with identical cations such as ][BF4], [C4mim] [P176], [C4mim][OTf], etc. While densities of 1—n—alkylimidazoles were observed to only vary about 15% between the least and most dense species at a given temperature, densities of ILs can vary more widely. For example, a 30% difference is ed in the densities of [C4mim][Tf2N] (r = 1.44 g/cm3) and ][dca] (r = 1.06 g/cm3) at 298 K. Even greater spreads are possible with smaller cations such as [szim] or anions with greater fluorination such as bis(perfluoroethylsulfonyl)imide ([beti]). All [Cnmim] [X] ILs are about 10% or more dense than their l-n-alkylimidazole analogues at the same tcmpcraturc.

The differences in ies n l—n—alkylimidazoles and [Cnmim] [X] ILs might influence certain process design considerations (e.g., head pressure in a vessel, increased mass flow rate), the magnitude of the difference (10 — 50%) is relatively small and within range of many common organic compounds. Common chlorinated organic solvents (e.g., chloroform) are nearly as dense as the most dense ILs, while ated compounds (e.g., bromoform) can be at least twice as dense as most [Cnmim] [X] ILs.

While the change in density associated with transitioning from a neutral l-n- alkylimidazole to a [Cnmim] [X] IL is relatively small, a penalty is exacted on the solvent viscosity. Viscosity increases by an order of magnitude or more when transitioning from the neutral 1-n-alkylimidazole to the [Cnmim] [X] IL. For 1-n- alkylimidazoles, Viscosity was observed to increase with increasing chain length and decreasing ature. A similar trend holds for across a family of [Cnmim] ILs with the same anion, [X]. However, viscosity ences between ILs with the same PCT/U52012/030672 [Cnmim] cation and different anion s can be quite large, spanning almost an order of magnitude.

Example 6: I-N-Alkylimidazoles as Co-solventsfor Post-Combustion C02 Capture In order to determine if l-n-alkylimidazoles could be used as solvents/agents for low pressure C02 capture applications, the uptake of C02 in an mixture of l- butylimidazole (37.37 g, 158.2 mmol) and monoethanolamine (MEA) (9.968 g, 163.2 mmol) (overall mixture about 80:20 vol/vol) was determined using the same apparatus as described in Example 4, and a ly modified experimental ure.

Initially, a stream of CO2 at about 1000 torr of CO2 was fed to the cell for several minutes. The valve was then closed and the pressure in the cell was observed to decay until an brium pressure of 606 torr was achieved. After obtaining the mass of the cell and applying Eqn. 1, it was found that 118 mmol (5.20 g) of CO2 were absorbed by the liquid phase.

An initial attempt to determine the exact reaction mechanism(s) responsible for the excess absorption of CO2 was carried out using 1H NMR spectroscopy. 1H NMR spectra were obtained in d6—DMSO as well as with no deuterated solvent.

Proton signals originally in the range of 5 ppm whcn the t had absorbed less than 100% of its theoretical capacity were observed to shift downfield to the range of 6.5-7.0 ppm when the solvent had absorbed more than 100% of its tical CO2 capacity. The chemical shifts were also r downfield than were reported when CO2 was captured by MBA in an [C6mim][Tf2N], which was limited to 0.50 mol C02 / mol MEA due to precipitation of the MEA-carbamate t. For the l— butylimidazole—MEA solvent mixture, a broad peak was observed even further downfleld between 8.5—8.75 ppm, when no deuterated solvent was included in the NMR sample, which is likcly indicative of H+ cxchangc bctwccn 1-butylimidazolc and MBA. These data te that 1—butylimidazole can have a participatory role in chemical reactions to capture C02 in the presence of an amine.

The viscosity of the CO2-rich solvent was measured immediately after the experiment was completed and the liquid phase rapidly transferred to the viscometer.

The viscosity of the C02—rich solution was initially ed as about 100 cP at 25°C, though the value drifted lower to 85 cP over several minutes, presumably due to loss of CO2 from the on product(s).

PCT/U52012/030672 The results for the l—butylimidazole—MEA mixture indicate that the mixtures of kylimidazoles can be used as effective solvents/agents for low pressure C02 capture that provide high C02 capacity and relatively low ities for the CO2-rich phase, especially when compared to TSIL compounds. Carbamate-imidazolium salt products can be considered as a type of reversible IL that exists as a t formed between CO2, an amine and a l-n—alkylimidazole.

Example 7: C02 and CH4 Solubility iMeasurements Solubilities of C02 and CH4 in l-n—alkylimidazoles were measured as described above in Example 2. Experiments were conducted at temperatures of 30, 45, 60, and 75 °C (as lled by an oil bath) for both C02 and CH4 measurements.

An l charge of gas was fed at 30 °C until the pressure equilibrated at about 5 atm, which was selected as the target pressure. Solubility values for all temperatures were then calculated from this known mass of gas in the system and the change in pressure upon heating (see, e. g, Finotello et al, “Room-temperature ionic liquids: Temperature dependence of gas solubility selectivity,” Ind. Eng. Chem. Res, 47:3453-3459 (2008), which is incorporated herein for its teaching of gas solubility measurements and calculations). The vapor pressure of the l-n-alkylimidazole compound can be assumed as negligible under the experimental temperature and pressure conditions, as it is low (about 5 mmHg maximum and typically <1 Torr) and very small (about 0.1%) compared to the partial pressure of the gas (see, e.g., Emel’yanenko et (1]., “Building Blocks for ionic liquids: Vapor pressures and vaporization enthalpies of l-(n—alkyl)-imidazoles,” J. Chem. Thermodyn., 43:1500- 1505 (201 l); Verevkin et al, “Thermodynamics of Ionic Liquids sors: l- Methylimidazole,” J. Phys. Chem. B, 11524404-4411 (2011)). The respective errors associated with Henry's Constants (H) and volumetric lity (S) were ated based upon ation of error of the experimental parameters (i.e., re, temperature, volumes, mass, etc.), in which all errors associated with the instrumentation were quantified. In this method, both the moles of gas dissolved in the liquid and the molecular weight of the gas are factors to consider in determining the magnitude of the uncertainty. As CO2 is both more soluble and of a greater molecular weight than CH4, measurements for CO2 exhibit an order of magnitude smaller error than those for CH4, with typical mental errors of l -2 and 10—15%, respectively. The errors for CO2 solubility are consistent with those described above. 2012/030672 Henry’s constants (HJ- (atm)) and volumetric solubilities (8,) of C02 and CH4 in l—n—alkylimidazoles at temperatures between 30 and 75 °C are presented in Table 4.

Table 4 co2 CH4 1_n_ alkyllmldazole ) :t“ Scozb it, 1:31;” in SCH4b in 1 7 Meth l 2 245 0.04 1920 270 0.14 0.02 __0.13 0.02 0.12 0.02 0.11 0.02 2 7 Ethyl 0.19 0.02 0.16 0.02 0.14 0.02 0.13 0.02 3 7 Butyl 0.27 0.02 0.25 0.02 0.24 0.02 0.23 0.02 4 7 Hexyl 0.30 0.02 0.26 0.02 0.24 0.02 0.23 0.02 7 Octyl 0.20 0.02 m”0140. 16 0.02 0.02 mm013 0.02 6 7Dec 1 9 0.02 0 16 0.02 75 27 0.77 0.02 779 120 0. 12 0.02 “Error represents one standard deviation ' S [=]](_cm gas (STP))(cm solvent) atm .

Table 4 reveals that, at any given temperature, l-methylimidazole exhibited the highest solubility of C02 and lowest lity of CH4 per volume. 1- Hexylimidazole displayed the st volumetric solubility of CH4 under the same conditions. The solubility of both gases in each of the l-n—alkylimidazoles decreased with increasing temperature. As a point of reference, molar solubility data are also presented in Table l as Henry’s constants, and indicate that CO; is most soluble in l- octylimidazole and l-decylimidazole, while still indicating that CH4 is most soluble in l—hexylimidazole. However, the greater C02 solubility indicated by the smaller Henry’s constants for larger l—n-alkylimidazoles is primarily due to the >2 times increase in molecular weight between l—methylimidazole and l—octylimidazole (i.e., larger molar volume). Thus, the volumetric solubility data are useful in forming direct comparisons to conventional ts, ILs, and polymers (Bara el (1]., “Guide to C02 Separations in lmidazolium—Based emperature lonic Liquids,” Ind. Eng.

PCT/U52012/030672 Chem. Res, 48:2739—2751 (2009); Lin et al, “Materials selection guidelines for membranes that remove CO2 from gas mixtures,” J. Mol. , 739:57—74 (2005)).

The solubility data in Table 4 indicate that ylimidazole also has the greatest working capacity of the l-n—alkylimidazole solvents in terms of an absorption—regeneration process for CO2 removal from CH4 using a physical solvent.

The about 60% decrease in CO2 solubility between 30 and 75 °C indicates that CO2 can easily be desorbed from the solvent under moderate heating and/or mild vacuum.

With sing chain s in l-n-alkylimidazoles, it was observed that CH4 solubility (SCH4) increased from l—methylimidazole to l-hexylimidazole, yet declined in l—octylimidazole and l—decylimidazole. Although the overall solvent environments are much less polar in limidazole and l—decylimidazole than in l- ethylimidazole, these solvents exhibit similar levels of CH4 uptake. These trends indicate that greater arbon content does not necessarily favor CH4 dissolution in this family of molecules, as increasing chain length must eventually limit the available space for CH4 to dissolve.

Example 8: Comparison ofI-methylimidazole to commercialphysical solvent ses and ionic liquids A general ple d to selecting solvents for acid gas removal is that polar groups s, nitriles, etc.) favor CO2 dissolution and CO2/CH4 separation (see Bara et al, “Guide to CO2 Separations in Imidazolium—Based Room-Temperature Ionic Liquids,” Ind. Eng. Chem. Res, 48:2739-2751 (2009); Lin et al, “Materials selection ines for membranes that remove CO2 from gas mixtures,” J. iMol.

Struck, 739: 57-74 (2005)). Thus, polar c solvents (e. g., DMPEG, MeOH, etc.) are typically used for natural gas sweetening and other acid gas removal applications.

Howcvcr, a variety of factors are considered for a physical solvcnt to bc uscd in a commercially viable process, including low volatility, low viscosity, stability, and availability in bulk at favorable costs. Furthermore, no one physical solvent is appropriate for every gas treating application, due to the differences in the gas streams to be treated and/or the requisite purity of the product gas. Four of the most utilized physical solvents are dimethyl ethers of poly(ethylene glycol) (DMPEG), propylene ate (PC), N-methylpyrrolidone (NMP), and methanol (MeOH), each with its own capabilities and tions. A number of factors relating to solvent properties PCT/U52012/030672 and the composition of the gas to be treated also play roles in determining solvent selection.

For e, DMPEG is effective at achieving selective separation of H28 from CO2, but has a higher viscosity than other physical solvents, which s mass transfer rates, especially if operated below 25 °C. PC is not typically recommended for use when high concentrations of H28 are present, as it becomes unstable during regeneration (about 93 OC). Of the solvents considered here, NMP has the highest selectivity for H2S/ C02, but is more volatile than DMPEG or PC. At t conditions, MeOH is quite le, but when chilled to subzero temperatures (as low as about —70.5 °C), MeOH becomes ive at near complete removal of C02, H28, and other contaminants. ng MeOH (or any physical solvent) increases acid gas loadings, but does so at the cost of the power supply for eration and potential increases in solvent viscosity. However, these operating expenses can be offset via reduced solvent circulation rates (process footprint), which results in lower capital expenses. Also, as the solubility of CH4 changes much less with temperature than does C02 (or other acid gases), selectivity enhancements can be achieved through chilling. While C02 and H28 are typically the impurities present in the greatest proportions, other minor species such as carbonyl sulfide (COS), carbon disulfide (C82), and mercaptans (RSH) can also be removed. Another consideration in solvent selection and process design is the absorption and loss of larger hydrocarbons, which can accumulate in the solvent. Thus, process designs can be quite different for each of these solvents ing on both solvent physical ties and the number of unit operations required.

Table 5 presents the physical properties most relevant to process operation for the four physical ts discussed, as well as l-methylimidazolc. ionic liquids (lLs) have also been included in this comparison. All physical properties are at 25°C, unless otherwise noted.

Table 5 DMPEG PC NMP MeOH l-methyl- Ionic liquids imidazole Viscosity (0P) 5.8 . . ~25-1000 Specific gravity (kg m3) 1030 1000-1500 Molecular weight (g mol’l) 280 ~200—500 PCT/U52012/030672 Vapor pressure (mmHg) 0.00073 0.085 0.40 125 0.37 0.000001 Freezing point -28 Variable Boiling point (760 mmHg) 275 /A Max. ing temp. (°C) 175 Dependsa co2 solubility (ft3 USgal '1) 0.485 CO2/CH4 15 H2S/CO2 8.82 H2O miscible? Yes Partial Yes Yes Yes Varies “bp” = boiling point; a Property depends b Estimated C Solubility on stability; value; selectivity data at -25°C for MeOH.

Table 5 illustrates that l—methylimidazole is most similar to NMP in terms of physical properties. Both NMP and l-methylimidazole are about 50% less viscous than PC and about 70% less viscous than DMPEG. While l—methylimidazole has about 20% lower CO2 solubility than NMP and DMPEG, it has a higher CO2/ CH4 selectivity than DMPEG and NMP. The potential for higher 2 selectivity also exists in l-methylimidazole based on y to the 4 and H2S/CO2 ratios ed for NMP, and the presence of a basic, nitrogen center which has allowed its use as an acid scavenger, and should allow reversible acid-base interactions with the acidic prot0n(s) of H28. Table 5 trates that l-methylimidazole is useful for IGCC or pre-combustion CO2 capture based on its selectivity for H2S/CO2.

Example 9: C02 Capture by Imidazoles andAmines The utility of imidazoles for CO2 capture applications was examined by studying mixtures of limidazole with other amine-based compounds, including NMEA, APT, AMP, piperazine, imidazole, and DIPA. Experiments were carried out, as bed above and in Shannon et al., rties of alkylimidazoles as solvents for CO2 capture and comparisons to imidazolium-based ionic s,” Ind. Eng.

Chem. Res, 50:8665-8677 (20] l), at ambient temperature (25°C) and at CO2 partial pressures between 5—225 kPa. The relationships between CO2 absorbed and pressure for various limidazolc + amine combinations are presented in Figure 2.

With the exception of l—butylimidazole + imidazole, all combinations exhibited chemical reactions with CO2 as evidenced by a sharp increase in loading of CO2 at partial pressures about 10 kPa. In the case of piperazine, which was only sparingly soluble in l-butylimidazole, high levels of CO2 uptake were still achieved PCT/U52012/030672 via rapid on of C02 with the well—mixed slurry. Piperazine was nearly stoichiometrically saturated with CO2 in a 1:1 ratio prior to any appreciable pressure measurement could be obtained from the equipment. The slope of the line presented (nearly parallel to that of the mixture containing imidazole, which enced no chemical reaction at all) is thus indicative of CO2 physical lity in l- butylimidazole, as all of the piperazine has already been reacted with CO2.

At loadings below about 0.35 mol COz/mol amine, omethylpropanol (AMP) remained soluble in l-butylimidazole and displayed a sharp increase in CO; absorbed at partial res about 10 kPa. However, above this loading, AMP- carbamate precipitated from solution and the relationship between loading and pressure became more representative of a physical solvent. Precipitation ofAMP upon reaction with CO2 is commonly ed in organic solvents where carbamate formation is favored, but not in aqueous solutions where carbonate formation is the preferred mechanism.

NMEA did not precipitate from solution upon absorption of CO2, and ted the most favorable loading profile. At a partial pressure of 50 kPa, the l- butylimidazolc + NMEA mixture achieved a loading of 0.75 mol CO2 / mol NMEA.

In non—aqueous solvent ning 2° amines, it would be expected that a level of 0.50mol CO2 / mol amine could be achieved, with additional physical solubility ing at increasing pressure. However, physical solubility in the 1-butylimidazole solvent at these relatively low CO2 partial pressures could only t for a fraction (<20%) of the CO2 absorbed in excess of the 0.50 mol CO2/mol NMEA iometric al reaction limit. By comparison of the slope of the data for l— butylimidazolebimidazole, it appears that the combination of l-butylimidazole + NMEA crcatcs a synergistic cffcct on C02 uptakc.

DIPA, a bulky, hindered 2° amine also exhibited absorption behavior similar to NMEA, but with less overall loading as the amine group is less accessible to CO2 to form the carbamate.

Interestingly, API (an amine-imidazole hybrid) achieved a loading of 0.50 mol CO2/mol —NH2 group below 10 kPa, yet exhibited only physical solubility for CO2 at increasing pressures. Based 011 a possible H+ transfer mechanism, this behavior indicates that the carbamate formed between 2 molecules of API is not ible to l-butylimidazole to promote levels of CO2 uptake similar to ts containing W0 2012/135178 PCT/U52012/030672 NMEA, or as in the case of AMP, lo amines with bulky side groups are less likely ates to y achieve loadings >0.50 per molecule of amine. With the exception of zine, which was a heterogeneous mixture, small alkanolamines, such as NMEA and MBA, can achieve the greatest CO2 uptake in imidazole-based For NMEA, APT, and DlPA viscosities of the CO2-rich mixtures at the maximum CO2 loading were measured immediately after the experiments were completed. The results are summarized in Table 6.

Table 6 Compound Type Viscosity (cP) of COz-rich solution 25 OC N—methylethanolamine 2° alkanolamine 28—3 1 (NMEA) l-(3-aminopropyl)— Imidazole - lo amine 41 imidazole (APT) hybrid Diisopropanolamine (DIPA) Hindered 2° 27—32 alkanolaminc Interestingly, all of the ch solvents had viscosities in the range of 30—40 cP, which represents an 8—10x increase from the viscosity of neat l-butylimidazole at °C. The l-butylimidazole + NMEA viscosity in the highly CO2-rich state was only aboutl/3 that of a mixture containing l-butylimidazole + MBA at a similar loading.

Although viscosity increases with CO2 absorption, the values ed are still less than most conventional ILs which cannot achieve high levels of CO2 loading under these partial pressures and other reactive & ible ILs (see, e. g., Bara et (1]., “Guide to C02 separations in imidazolium—based room-temperature ionic s,” Ind. Eng. Chem. Res., 48: 2739-2751 (2009); Gardas el al., “A group contribution 2O method for viscosity estimation of ionic liquids,” Fluid Phase Equilibr., 266: 1 (2008)). Additionally, this viscosity range is approaching that of some aqueous amine solvcnts proposed for post—combustion C02 capture ations as well as solutions y commercially applied in the natural gas industry. Initial results indicate that further reductions in viscosity can be achieved with N—functionalized imidazoles with shorten pendant alkyl chains (e. g., l—methylimidazole, l,2—dimethylimidazole, etc).

Based on the performance of the l-butylimidazole + NMEA mixture at ambient temperature, the temperature dependence of loading was characterized in order to generate baseline data for both absmption and desorption in imidazolepamine PCT/U52012/030672 mixtures. Figure 3 presents these data across the range of 25780°C at pressures >10 kPa. For typical flue gas ions (40°C, 2 psia CO2), the l—butylimidazole + NMEA solvent es loadings approaching 0.50 mol CO2/mol amine. As can be seen in Figure 3, CO2 solubility decreases with increasing temperature for a given pressure. The l-butylimidazole + NMEA mixture exhibits a working capacity of about0.40 mol CO2/mol NMEA at a constant pressure when the temperature is increased from 40 °C to 80 °C. These data, combined with the relatively low viscosity in the CO2-rich state, indicate that imidazole + amine solvents are capable of both the e and release of CO2 within a conventional absorber—stripper process.

As a wide variety of imidazole and amine derivatives might be used in s concentrations to formulate solvent mixtures CO2 capture, this particular combination of l-butylimidazole + NMEA (80:20 vol:vol) is only a representative example. Both the structures of the imidazole and amine components are likely to ce both physical and chemical properties of the resultant t mixture.

Example I0: Imidazoles as Agentsfor S02 Removal midazoles can also be used to reversibly absorb S02 via both al and chemical interactions. This feature presents sting possibilities as alkylimidazoles could be used as both a chemical and physical solvent to recover $02 from flue gas.

To demonstrate absorption of 802 in an alkylimidazole solvent, an experiment was carried out in a well-ventilated fume hood. A handheld SO2 sensor was also employed to ensure exposure of personnel to $02 was minimized. l-Hexylimidazole (5.00 g, 32.8 mmol) was stirred in a SOmL round bottom flask contained within a room—temperature water bath. Low pressure S02 (aboutl psig) was bubbled into the solvent, and the total on volume was observed to expand rapidly with a single liquid phase present. After 5 minutes of exposure to the bubbling SO2 stream, the mass of the flask contents was observed to increase by 2.46 g, indicating that 38.4 mmol or 1.17 mol SO2/mol limidazole were t in the flask. After the flow of the S02 stream ceased, the contents of the flask were swept with a stream ofN2 for several hours at room temperature. After this time, the liquid phase had transformed to a transparent, viscous gel, containing about0.5 mol SO2/mol l-hexylimidazole as determined by the residual mass ofthe flask contents. The S02 lost is likely the portion that was physically dissolved, thus indicating that 802 reacts with PCT/U52012/030672 alkylimidazoles in a 1:2 ratio. The chemically—bound 802 could be released by heating the sample at >100°C while under N2 sweep. No irreversible degradation of the l-hexylimidazole was observed via 1H NMR.

While l-hexylimidazole was chosen for convenience of its very low volatility, this reaction could have been carried out with any alkylimidazole compound. Thus, it is likely that the properties of the reaction product (229., viscosity and solid/liquid/gel state) between SO; and imidazoles will likely depend on the length of the alkyl chain as well as any additional functionalization at the C(2), C(4), and/or C(S) positions.

Functionalization of the carbon positions can also e the ability to tune the equilibrium of the chemical on or control desorption temperature.

As with the l-butylimidazole + NMEA e for C02 capture, the example of l-hexylimidazole is not optimized. However, N—functionalized imidazoles t new opportunities for reversible SOZ capture from flue gas in the electric power industry. Reversible SOz capture is of interest as current “scrubbing” logies rely on the reaction of 802 + CaSO3 (Ca803, with Ca303 then oxidized to CaSO4 and commonly sold for use as drywall). Direct recovery of $02 eliminates process engineering issues with the handling of solids in flue gas desulfurization, while aneously allowing for the production of higher value sulfur products such as H2804.

Additional opportunities exist in ng imidazoles for HZS l through an acid-base reaction similar to that exhibited by anhydrous amines. As the pKa of the first proton dissociation for H23 is about 7.0, l,2-dialkylimidazoles and 1,2,4- triaklyimidazoles are capable of near quantitative deprotonation of H28 to form an imidazolium bisulfide salt.

The compounds and methods of the appended claims are not limited in scope by the specific compounds and methods described herein, which are intended as illustrations of a few s of the claims and any compounds and methods that are functionally equivalent are within the scope of this disclosure. Various modifications of the compounds and methods in addition to those shown and described herein are intended to fall within the scope of the appended claims. r, while only certain entative compounds, s, and aspects of these compounds and methods are specifically described, other compounds and methods and combinations of various features of the compounds and methods are intended to fall within the scope of the PCT/U52012/030672 appended claims, even if not cally recited. Thus a combination of steps, elements, ents, or constituents can be explicitly mentioned herein; however, all other combinations of steps, elements, components, and constituents are included, even though not explicitly stated.

Claims (81)

What is claimed

1. A method for reducing carbon dioxide from a stream, comprising: contacting the stream with a solvent system comprising an N-functionalized imidazole and an amine to capture the carbon dioxide, wherein the N-functionalized imidazole is non-ionic under neutral conditions and the N- functionalized imidazole and amine comprises more than 97% by weight of the solvent system.

2. The method of claim 1, wherein the N-functionalized imidazole is an N-alkyl imidazole, an N-alkenyl imidazole, an N-alkynyl imidazole, an N-aryl imidazole, or mixtures thereof.

3. The method of claim 1 or 2, wherein the N-functionalized ole has the following ure: R3 R2 N N R1 , wherein R1 is substituted or unsubstituted C1-20 alkyl, tuted or unsubstituted C2-20 alkenyl, substituted or unsubstituted C2-20 alkynyl, substituted or unsubstituted C1-20 heteroalkyl, tuted or unsubstituted C2-20 heteroalkenyl, tuted or unsubstituted C2-20 heteroalkynyl, substituted or unsubstituted cycloalkyl, substituted or tituted heterocycloalkyl, substituted or unsubstituted aryl, substituted or tituted heteroaryl, substituted or unsubstituted thio, substituted or unsubstituted amino, substituted or unsubstituted alkoxyl, substituted or unsubstituted aryloxyl, silyl, siloxyl, cyano, or nitro; and R2, R3, and R4 are each independently selected from hydrogen, halogen, hydroxyl, tuted or unsubstituted C1-20 alkyl, tuted or unsubstituted C2-20 l, substituted or unsubstituted C2-20 alkynyl, substituted or unsubstituted C1-20 heteroalkyl, substituted or unsubstituted C2-20 heteroalkenyl, tuted or unsubstituted C2-20 heteroalkynyl, substituted or unsubstituted cycloalkyl, substituted or tituted heterocycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted thio, substituted or unsubstituted alkoxyl, substituted or unsubstituted aryloxyl, substituted or unsubstituted amino, cyano, or nitro; wherein substituted comprises substitution with one or more substituents chosen from alkyl, heteroalkyl, alkoxy, alkenyl, heteroalkenyl, alkynyl, aklynyl, aryl, heteroaryl, aryloxyl, aldehyde, amino, ylic acid, cyano, ester, ether, halide, hydroxy, ketone, nitro, silyl, sulfo-oxo, sulfonyl, sulfone, sulfoxide, or thiol.

4. The method of any of claims 1-3, wherein the amine is ed from the group consisting of primary amines, secondary amines, ry amines, cyclic amines, and mixtures thereof.

5. The method of any of claims 1-4, wherein the amine has the following structure: R3 R2, wherein R1, R2, and R3 are each independently selected from the group consisting of hydrogen, substituted or unsubstituted C1-20 alkyl, substituted or unsubstituted C2-20 l, substituted or unsubstituted C2-20 alkynyl, substituted or unsubstituted C1-20 heteroalkyl, substituted or unsubstituted C2-20 heteroalkenyl, substituted or unsubstituted C2-20 heteroalkynyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, tuted or unsubstituted aryl, substituted or tituted aryl, substituted or unsubstituted thio, substituted or unsubstituted amino, substituted or tituted alkoxyl, substituted or unsubstituted aryloxyl, silyl, siloxyl, cyano, or nitro; wherein substituted can comprise substitution with one or more tuents chosen from alkyl, heteroalkyl, alkoxy, alkenyl, heteroalkenyl, alkynyl, heteroaklynyl, aryl, heteroaryl, aryloxyl, aldehyde, amino, carboxylic acid, cyano, ester, ether, , hydroxy, ketone, nitro, silyl, sulfo-oxo, sulfonyl, sulfone, sulfoxide, or thiol.

6. The method of claim 4, wherein the y amine is selected from the group consisting of monoethanolamine, diglycolamine, 2-aminomethylpropanol, and mixtures thereof.

7. The method of claim 4, wherein the secondary amine is selected from the group consisting of diethanolamine, diisopropanolamine, and mixtures thereof.

8. The method of claim 4, wherein the tertiary amine is N-methyldiethanolamine.

9. The method of claim 4, wherein the cyclic amine is substituted or unsubstituted piperazine.

10. The method of any of claims 1-9, wherein the amine is a monoamine, a diamine, or a polyamine.

11. The method of any of claims 1-10, wherein the N-functionalized imidazole comprises at least 10% by weight of the solvent system.

12. The method of any of claims 1-11, n the N-functionalized imidazole comprises at least 25% by weight of the solvent system.

13. The method of any of claims 1-12, wherein the N-functionalized imidazole comprises at least 50% by weight of the solvent system.

14. The method of any of claims 1-13, wherein the amine comprises at least 10% by weight of the solvent system.

15. The method of any of claims 1-14, wherein the amine comprises at least 25% by weight of the solvent system.

16. The method of any of claims 1-15, wherein the amine comprises at least 50% by weight of the t system.

17. The method of any of claims 1-16, wherein the N-functionalized imidazole and the amine are present in a ratio from 9:1 to 1:9.

18. The method of any of claims 1-17, wherein the N-functionalized imidazole and the amine are present in a ratio of 2:1.

19. The method of any of claims 1-18, wherein the solvent system is substantially free from volatile compounds.

20. The method of any of claims 1-19, wherein the ity of the N-functionalized imidazole is less than 10 cP at 24°C.

21. The method of any of claims 1-19, wherein the viscosity of the N-functionalized imidazole is less than 8 cP at 24°C.

22. The method of any of claims 1-19, wherein the viscosity of the N-functionalized imidazole is less than 5 cP at 24°C.

23. A method for removing volatile nd from a stream, comprising: contacting the stream with a solvent system comprising an N-functionalized imidazole, wherein the N-functionalized imidazole is non-ionic under neutral ions and is from about 20% to about 80% by weight of the solvent system, and wherein the volatile compound comprises carbon dioxide, carbon monoxide, sulfur dioxide, en sulfide, thiols, nitrogen oxide, nitrogen dioxide, carbonyl sulfide, carbon disulfide, or any e f.

24. The method of claim 23, wherein the N-functionalized imidazole is an l imidazole, an N-alkenyl imidazole, an N-alkynyl imidazole, an N-aryl imidazole, or mixtures thereof.

25. The method of claim 23 or 24, wherein the N-functionalized imidazole has the following structure: R3 R2 N N R1 , wherein R1 is substituted or unsubstituted C1-20 alkyl, substituted or unsubstituted C2-20 alkenyl, substituted or unsubstituted C2-20 alkynyl, substituted or unsubstituted C1-20 heteroalkyl, substituted or unsubstituted C2-20 alkenyl, substituted or tituted C2-20 heteroalkynyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted thio, substituted or unsubstituted amino, substituted or unsubstituted alkoxyl, substituted or tituted aryloxyl, silyl, siloxyl, cyano, or nitro; and R2, R3, and R4 are each independently selected from hydrogen, halogen, hydroxyl, substituted or unsubstituted C1-20 alkyl, substituted or unsubstituted C2-20 alkenyl, substituted or unsubstituted C2-20 alkynyl, tuted or unsubstituted C1-20 heteroalkyl, substituted or unsubstituted C2-20 alkenyl, substituted or unsubstituted C2-20 heteroalkynyl, substituted or unsubstituted cycloalkyl, substituted or tituted heterocycloalkyl, tuted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted thio, substituted or unsubstituted alkoxyl, substituted or unsubstituted yl, substituted or unsubstituted amino, cyano, or nitro; n substituted comprises substitution with one or more substituents chosen from alkyl, heteroalkyl, alkoxy, alkenyl, heteroalkenyl, alkynyl, heteroaklynyl, aryl, heteroaryl, aryloxyl, aldehyde, amino, ylic acid, cyano, ester, ether, halide, hydroxy, ketone, nitro, silyl, sulfo-oxo, sulfonyl, sulfone, sulfoxide, or thiol.

26. The method of any of claims 23-25, wherein the solvent system further comprises an amine.

27. The method of claim 26, n the amine is ed from the group consisting of primary amines, secondary amines, tertiary , cyclic amines, [[or]]and mixtures thereof.

28. The method of claim 26 or 27, wherein the amine has the following structure: R3 R2, wherein R1, R2, and R3 are each independently selected from the group consisting of en, substituted or unsubstituted C1-20 alkyl, substituted or unsubstituted C2-20 alkenyl, substituted or unsubstituted C2-20 alkynyl, substituted or unsubstituted C1-20 heteroalkyl, substituted or tituted C2-20 heteroalkenyl, substituted or unsubstituted C2-20 heteroalkynyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or tituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted thio, substituted or unsubstituted amino, substituted or unsubstituted alkoxyl, substituted or unsubstituted yl, silyl, siloxyl, cyano, or nitro; wherein substituted comprises substitution with one or more substituents chosen from alkyl, heteroalkyl, alkoxy, alkenyl, heteroalkenyl, alkynyl, heteroaklynyl, aryl, heteroaryl, aryloxyl, aldehyde, amino, carboxylic acid, cyano, ester, ether, halide, hydroxy, ketone, nitro, silyl, sulfo-oxo, sulfonyl, sulfone, sulfoxide, or thiol.

29. The method of claim 27, wherein the primary amine is selected from the group ting of monoethanolamine, diglycolamine, 2-aminomethylpropanol, and mixtures thereof.

30. The method of claim 27, wherein the secondary amine is selected from the group consisting of nolamine, ropanolamine, and mixtures thereof.

31. The method of claim 27, wherein the tertiary amine is yldiethanolamine.

32. The method of claim 27, wherein the cyclic amine is substituted or unsubstituted piperazine.

33. The method of any of claims 26-32, wherein the amine is a monoamine, a diamine, or a polyamine.

34. The method of any of claims 23-33, wherein the amine is selected from the group consisting of N-methylethanolamine, monoethanolamine, diglycolamine, diethanolamine, N- methyldiethanolamine, and mixtures f

35. The method of any of claims 23-34, wherein the N-functionalized imidazole comprises at least 25% by weight of the solvent system.

36. The method of any of claims 23-35, wherein the N-functionalized imidazole comprises at least 50% by weight of the solvent system.

37. The method of any of claims 23-36, wherein the amine comprises at least 10% by weight of the solvent system.

38. The method of any of claims 23-37, wherein the amine comprises at least 25% by weight of the solvent system.

39. The method of any of claims 23-38, wherein the amine comprises at least 50% by weight of the solvent system.

40. The method of any of claims 23-39, wherein the N-functionalized imidazole and the amine are present in a ratio from 9:1 to 1:9.

41. The method of any of claims 23-40, wherein the N-functionalized imidazole and the amine are present in a ratio of 2:1.

42. The method of any of claims 23-41, wherein the solvent system is substantially free from le compounds.

43. The method of any of claims 23-42, wherein the viscosity of the N-functionalized imidazole is less than 10 cP at 24°C.

44. The method of any of claims 23-42, wherein the viscosity of the N-functionalized imidazole is less than 8 cP at 24°C.

45. The method of any of claims 23-42, wherein the viscosity of the tionalized imidazole is less than 5 cP at 24°C.

46. The method of any of claims 1-45, wherein the stream is a gas stream or a liquid stream.

47. The method of claim 46, wherein the gas stream is a natural gas stream, a synthesis gas stream, or a flue gas stream.

48. A method for sweetening a natural gas feed stream, comprising: contacting the natural gas feed stream with a solvent system comprising an N- functionalized imidazole, wherein the N-functionalized ole is non-ionic under neutral conditions and comprises at least 50% by weight of the solvent system, to form a ed natural gas feed stream and a gas-rich system; and separating the purified natural gas feed stream from the gas-rich system.

49. The method of claim 48, n the t system r comprises an amine.

50. The method of claim 49 or 50, further comprising contacting the natural gas feed stream with a second t system comprising an N-functionalized imidazole, wherein the N- functionalized imidazole is non-ionic under neutral conditions.

51. The method of claim 51, wherein the second solvent system further comprises an amine.

52. The method of any of claims 48-51, further comprising regenerating the solvent system.

53. The method of claim 52, wherein the solvent system is regenerated by heating the h system.

54. The method of claim 52, wherein the solvent system is regenerated by depressurizing the gas-rich system.

55. A solvent system for capturing volatile compounds, comprising: at least 50% by weight of an N-functionalized imidazole, wherein the N-functionalized imidazole is non-ionic under neutral ions; and the volatile compound selected from the group consisting of carbon e, hydrogen sulfide, sulfur dioxide, nitrogen oxide, nitrogen dioxide, carbonyl sulfide, carbon disulfide, and mixtures thereof.

56. The system of claim 55, further comprising an amine.

57. The solvent system of claim 55 or 56, wherein the viscosity of the solvent system is less than 20 cP at 24oC.

58. The solvent sstem of any of claims 55-57, n the N-functionalized imidazole is with shorten pendent alkyl chains.

59. The t system of any of claims 55-58, wherein the N-functionalized imidazole is selected from the group consisting of 1,2-dimethyl, 1-n- methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl, tetradecyl imidazole, and combinations thereof.

60. The solvent system of any of claims 55-59, wherein the N-functionalized imidazole is 1,2-dimethyl imidazole.

61. The solvent system of any of claims 55-60, wherein the N-functionalized imidazole and the amine are t in a weight ratio from 9:1 to 1:1.

62. The t system of any of claims 55-61, wherein the tionalized imidazole and amine comprises more than 97% by weight of the solvent system,

63. The solvent system of any of claims 60-62, wherein the N-functionalized imidazole is 1- butylimidazole and the amine is N-methylethanolamine (NMEA).

64. A solvent system for capturing a volatile compound from a stream, comprising: from about 20% to about 80% by weight of an N-functionalized imidazole, wherein the N- onalized imidazole is non-ionic under neutral conditions; and an amine.

65. The t system of claim 64, wherein the N-functionalized imidazole comprises from about 30% to about 70% by weight of the solvent system.

66. The solvent system of claim 64 or 65, wherein the N-functionalized imidazole has the following structure: R3 R2 N N R1 R1 is substituted or unsubstituted C1-20 alkyl, substituted or unsubstituted C2-20 alkenyl, substituted or unsubstituted C2-20 alkynyl, substituted or unsubstituted C1-20 heteroalkyl, substituted or unsubstituted C2-20 heteroalkenyl, substituted or unsubstituted C2-20 heteroalkynyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or tituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted thio, substituted or unsubstituted amino, substituted or tituted alkoxyl, substituted or unsubstituted aryloxyl, silyl, siloxyl, cyano, or nitro; and R2, R3, and R4 are each independently selected from en, halogen, hydroxyl, substituted or unsubstituted C1-20 alkyl, substituted or unsubstituted C2-20 alkenyl, substituted or unsubstituted C2-20 alkynyl, substituted or unsubstituted C1-20 alkyl, substituted or unsubstituted C2-20 heteroalkenyl, substituted or unsubstituted C2-20 alkynyl, substituted or tituted cycloalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or tituted thio, substituted or unsubstituted alkoxyl, substituted or unsubstituted aryloxyl, substituted or unsubstituted amino, cyano, or nitro; wherein substituted comprises tution with one or more substituents chosen from alkyl, heteroalkyl, alkoxy, l, heteroalkenyl, alkynyl, heteroaklynyl, aryl, heteroaryl, aryloxyl, de, amino, carboxylic acid, cyano, ester, ether, halide, hydroxy, ketone, nitro, silyl, sulfo-oxo, sulfonyl, sulfone, sulfoxide, or thiol.

67. The solvent system of any of claims 64-66, wherein the amine has the following structure: R3 R2 R1, R2, and R3 are each independently ed from the group consisting of hydrogen, substituted or unsubstituted C1-20 alkyl, substituted or unsubstituted C2-20 alkenyl, substituted or tituted C2-20 l, substituted or unsubstituted C1-20 heteroalkyl, substituted or unsubstituted C2-20 heteroalkenyl, tuted or unsubstituted C2-20 alkynyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted thio, substituted or unsubstituted amino, substituted or unsubstituted alkoxyl, substituted or unsubstituted aryloxyl, silyl, siloxyl, cyano, or nitro; wherein substituted comprises substitution with one or more substituents chosen from alkyl, heteroalkyl, alkoxy, alkenyl, heteroalkenyl, alkynyl, heteroaklynyl, aryl, heteroaryl, aryloxyl, aldehyde, amino, carboxylic acid, cyano, ester, ether, halide, hydroxy, ketone, nitro, silyl, oxo, sulfonyl, sulfone, sulfoxide, or thiol.

68. The solvent system of any of claims 64-67, wherein the amine is monoethanolamine, N- methylethanolamine, diglycolamine, diethanolamine, or N-methyldiethanolamine.

69. The solvent system of any of claims 64-67, n the amine is 2-amino methylpropanol.

70. The solvent system of any of claims 64-67, wherein the amine is diisopropanolamine.

71. The solvent system of any of claims 64-67, wherein the amine is substituted or unsubstituted piperazine.

72. The solvent system of any of claims 64-71, wherein the N-functionalized imidazole and the amine are present in the solvent system in a weight ratio from 9:1 to 1:9.

73. The solvent system of any of claims 64-71, further comprising water.

74. The method of any of claims 1-22, wherein the amine is selected from the group consisting of N-methylethanolamine, monoethanolamine, and es thereof.

75. The method of claim 23-47, wherein the N-functionalized imidazole comprises from about 30% to about 70% by weight of the solvent .

76. The method of claim 46, wherein the liquid stream is a liquid hydrocarbon stream.

77. The method of any of claims 23-47 or 76, further comprising regenerating the t system by heating, ng vacuum or any combination thereof to regenerate the solvent

78. The method of any of claims 23-47 or 76-77, wherein the solvent system further comprises water.

79. The method of any of claims 23-47 or 75-78, wherein the volatile compound comprises carbon e.

80. The method of any of claims 1-22, 74 or 79, wherein the carbon dioxide is captured through the formation of a carbamate-imidazolium salt between the carbon dixode and the N- functionalized imidazole and amine.

81. The method of claim 64, wherein the carbamate-imidazolium salt releases carbon dioxide upon heating and forms a regenerated solvent system.