Renewable solvent mixtures for acid gas separation

Abstract

A solvent system for removing acid gases from a mixed gas stream is provided. A method for removing acid gases from a mixed gas stream using the disclosed solvent system is also provided. The solvent system can be utilized in a gas processing system.

Description

Technical Field

[0001] This invention relates to solvent systems for removing specific components from gas streams, and to apparatus and methods for using such systems. Specifically, the invention provides for the removal of acidic gases such as CO2, SO2, COS, CS2, and NOx. The invention also provides for continuous operation of apparatus and methods using such systems. Furthermore, the methods of the invention can utilize multiple absorption / desorption devices, including gas absorption / desorption and / or phase-enhanced absorption / desorption. Background of the Invention

[0002] Various strategies are being explored to minimize the generation and release of harmful emissions during combustion. One such strategy is the development of technologies for removing specific acidic gases from gas mixtures, such as the exhaust gases from carbon combustion processes. Separating acidic gases like CO2 from gas mixtures has been implemented industrially for over a century, but no method has been used on a large scale (e.g., as required by large industrial power plants). Among the various methods for CO2 separation, existing technologies primarily focus on the application of various solvents, such as BENFIELD. TM Alkali metal carbonates in method (UOP, LLC), ECONAMINE FG PLUS TM The method (Fluor Corporation) in the presence of alcoholamines, and in The method (Lurgi, GmbH) uses alcohols, diols, and ethers, as well as SELEXOL. TM Solvent (The Dow Chemical Company). In a typical solvent-based method, the gas mixture to be treated passes through a liquid solvent that interacts with acidic compounds (e.g., CO2 and SO2) in the gas stream and separates them from the non-acidic components. The liquid becomes enriched with the acidic gas components, which are then removed under a set of different operating conditions, allowing the solvent to be recovered for the removal of other acidic gases.

[0003] Methods for removing acidic gas components from rich solvents involve altering pressure and temperature. Certain solvents are preferred for specific applications, depending on the temperature of the gas mixture and the partial pressure of the acidic gas within it. An exothermic chemical reaction occurs when the solvent interacts with the acidic gas through a chemisorption operation. Reversing this reaction requires at least the amount of energy generated in the preceding reaction to be added back to the rich solvent, not to mention the energy required to bring the rich solvent to a temperature suitable for substantial reversal and to maintain those conditions for the reversal to proceed to a considerable extent. The energy required to obtain purified acidic gas from the rich solvent is part of the cost of the purified product. Specifically, the cost of purifying acidic gases has become a significant obstacle to applying solvent technology to petrochemical fuel combustion power plants for removing acidic gases from flue gas.

[0004] Non-aqueous solvents have been used to remove CO2 from natural gas streams, requiring less energy for regeneration. Single-component physical absorption solvents for CO2 separation, such as Receptol, are also available. TM and They are commercially available, but their performance is poor under humid conditions associated with flue gas and challenging environmental stress conditions. Various studies have combined alkanolamines and amines with alcohols, glycols, and cyclic carbonates to form "mixed solvents," and their reaction mechanisms and kinetics have been investigated in the literature. See Alvarez-Fuster et al., Chem. Eng. Sci. 1981, 36, 1513; Ali et al., Separation and Purification Technology 2000, 18, 163; Usubharatan et al., Energy Procedia 2009, 1, 95; and Park et al., Sep. Sci. Technol. 2005, 40, 1885. Furthermore, a method called "transition phase absorption method" is disclosed, relating to a method for reducing gaseous mixtures, which typically consists of: absorbing acidic gas into an "absorbent phase" composed of nitrogen-containing bases and alcohols with a density less than water, and then transferring the absorbed acidic gas into an aqueous "carrier phase." The aqueous carrier phase can be regenerated in a regenerator. This method claims to save energy by absorbing acidic gas at a faster rate than using only the absorbent phase, and by transferring the acidic gas between multiple phases by gravity in a single column used for absorption and regeneration, thus avoiding the energy required to pump the rich absorbent phase into a separate regenerator.

[0005] Another group of non-aqueous liquids that could be developed to address many of the problems affecting CO2 solvents are room-temperature convertible ionic liquids. These equimolar mixtures of nitrogenous bases and alcohols containing amidines or guanidins are room-temperature nonionic liquids that react with CO2 to form room-temperature ionic liquids. Typically, the conductivity of the equimolar mixture increases by one or two orders of magnitude when CO2 is added. Importantly, these solvents have a higher CO2 loading than some aqueous amines and can be regenerated under milder conditions. While these solvents are promising alternatives, they are not suitable for flue gas applications because of their chemistry with water, which is often the predominant component of flue gas. CO2 can also be captured by forming alkyl carbonates of amidines and guanidins derived from the conjugate bases of deprotonated alcohol components. However, alkyl carbonates typically hydrolyze in water under alkaline conditions to yield bicarbonates.

[0006] Therefore, it would be beneficial to develop a new solvent system that can effectively remove acidic gases from gas streams (especially water-containing gas streams) and can be regenerated at lower temperatures and energy loads than existing solvents used for this purpose. Summary of the Invention

[0007] This invention generally provides a solvent system for removing acidic gases such as CO2 from a gas stream, and a method for using such a solvent system to remove acidic gases. Various solvent systems described herein can possess this capability.

[0008] In one aspect, a solvent system is provided comprising a solution formed from: an ionic liquid consisting of a nucleophilic amine and a protonated nonaqueous liquid, wherein the ionic liquid reacts with an acidic gas to form an ionic solution comprising: 1) carbamates, zwitterionic aminosulfonic acids, sulfates, or combinations thereof; and 2) protonated weak acids. In some such solvent systems, the nucleophilic amine is selected from the group consisting of: primary amines, secondary amines, diamines, triamines, tetraamines, pentamines, cyclic amines, cyclic diamines, amine oligomers, polyamines, alkanolamines, and mixtures thereof. In some such solvent systems, the protonated nonaqueous liquid is a liquid with a pKa of approximately 8-15. For example, the protonated nonaqueous liquid may be selected from the group consisting of: fluorinated alcohols, optionally substituted phenols; nitrogen heterocycles, and mixtures thereof. Exemplary non-aqueous proton-containing liquids include, but are not limited to: 2,2,3,3,4,4,5,5-octafluoropentanol; 2,2,3,3-tetrafluoropropanol; 2,2,3,3,3-pentafluoropropanol; 2,2,3,3,4,4-hexafluorobutanol; 2,2,2-trifluoroethanol; nonafluoro-1-hexanol; 4,4,5,5,6,6,7,7,7-nonafluoroheptanol; 1,1,3,3-hexafluoro-2-phenyl-2-propanol; 4-methoxy 4-Ethoxyphenol; 2-Ethoxyphenol; 4-Propoxyphenol; Imidazole; Benzimidazole; N-Methylimidazole; 1-Trifluoroacetylimidazole; 1,2,3-Triazole; 1,2,4-Triazole; 2-Trifluoromethylpyrazole; 3,5-Bistrifluoromethylpyrazole; 3-Trifluoromethylpyrazole, 2-Fluorophenol, 3-Fluorophenol, 4-Fluorophenol, 2-Trifluoromethylphenol, 3-Trifluoromethylphenol, 4-Trifluoromethylphenol, and mixtures thereof.

[0009] In another aspect, a solvent system is provided, comprising a solution formed from the following substances:

[0010] A mixture of two or more nucleophilic amines and two or more non-aqueous liquids, wherein one or more nucleophilic amines have a structure such that they react with an acidic gas to form one or more of the following substances: carbamates, mixed carbamates, zwitterionic aminosulfonic acids, and sulfates. In some embodiments of such a solvent system, the two or more nucleophilic amines may be alkylfluoroaromatic amines. For example, alkylfluoroaromatic amines may be selected from the group consisting of: 3-fluoro-N-methylbenzylamine, 4-fluoro-N-methylbenzylamine, 2-fluorophenylethylamine, 3-fluorophenylethylamine, and 4-fluorophenylethylamine. In some embodiments, the two or more non-aqueous liquids according to certain embodiments of such a solvent system may be selected from the group consisting of: 2,2,3,3,4,4,5,5-octafluoropentanol, 3,3,4,4,5,5,6,6-hexafluorobutanol, and 4,4,5,5,6,6,7,7,7-nonafluoroheptanol.

[0011] In one aspect, a solvent system is provided comprising a solution formed from: a nucleophilic amine; a nonnucleophilic nitrogenous base; and a nonaqueous liquid, wherein the nucleophilic amine has a structure such that it reacts with an acidic gas to form a carbamate, a mixture of carbamates, aminosulfonic acid, aminosulfonate, or sulfate, and wherein the nonnucleophilic nitrogenous base reacts with the nonaqueous liquid to form a mixture of carbamates, carbonates, or heteroatom analogs of carbonates. In some such solvent systems, the nucleophilic amine is selected from the group consisting of 3-fluoro-N-methylbenzylamine, 4-fluoro-N-methylbenzylamine, 2-fluorophenylethylamine, 3-fluorophenylethylamine, 4-fluorophenylethylamine, and mixtures thereof. In some such solvent systems, the nonnucleophilic nitrogenous base may be a guanidine or a substituted guanidine. The nonaqueous liquid in this type of solvent system may be, for example, a fluorinated alcohol having five or more carbon atoms.

[0012] In another aspect, a solvent system is provided comprising a pure nucleophilic amine having a structure such that it reacts with an acidic gas to form an amine carbamate, a zwitterionic aminosulfonic acid, a sulfate, or a mixture thereof. In one specific embodiment, the nucleophilic amine in such a solvent system is 3-fluoro-N-methylbenzylamine.

[0013] In another aspect, a solvent system is provided comprising a solution formed of one or more nucleophilic amines and one or more non-nucleophilic nitrogenous bases having structures such that they react with an acidic gas to form carbamates, mixed carbamates, aminosulfonic acids, sulfates, or mixtures thereof. In some embodiments, such a solvent system may be such that one or more nucleophilic amines include primary or secondary amines and / or one or more non-nucleophilic nitrogenous bases include tertiary amines, amidines, and / or guanidines (wherein optionally, one or more of the primary, secondary, tertiary, guanidine, and / or amidines can be fluorinated). Examples of primary and secondary amines include, but are not limited to, 3-fluoro-N-methylbenzylamine, 4-fluoro-N-methylbenzylamine, 2-fluorophenylethylamine, 3-fluorophenylethylamine, and 4-fluorophenylethylamine.

[0014] In some embodiments, the nucleophilic amine component in any of these solvent systems may be hydrophobic. When a nonnucleophilic nitrogenous base is present, the nonnucleophilic nitrogenous base may be hydrophobic or substantially immiscible with water. In some embodiments, the solvent systems described herein are generally substantially immiscible with water. For example, in some embodiments, the solvent system has a solubility in water of less than about 10 g or less than about 20 g solvent / 100 mL water. In some embodiments, one or more (including all) components of the solvent systems described herein may be described as hydrophobic, substantially immiscible with water, and / or immiscible with water. The acidic gases that can react with the various solvent systems described herein may vary and may include, for example, CO2, SO2, COS, CS2, NO. x or combinations thereof. In some specific embodiments, the acidic gas includes CO2 or SO2.

[0015] In another aspect of the invention, a method for removing acidic gases from a gas stream is provided, the method comprising contacting the gas stream containing the acidic gas with any of the solvent systems described herein. In some embodiments, the gas stream containing the acidic gas may include CO2, SO2, COS, CS2, NO. x A mixed gas stream, or a combination thereof. In some embodiments, the solvent system can tolerate up to or equal to about 20% by volume of water without degradation of solvent performance. In some embodiments, the gas stream containing acidic gases includes water, and the water can be collected as a phase separate from the solvent system.

[0016] In some embodiments, the method may further include recovering the acid-rich gaseous solvent and the acid-lean gaseous gas stream. In some embodiments, the method may further include regenerating the acid-rich gaseous solvent by applying heat to form a regenerated solvent containing a lower concentration of acidic gases than present in the acid-rich gaseous solvent. For example, the heat involved in this method may come from a source selected from the group consisting of low-pressure steam, hot flue gas, or combinations thereof. Brief description of the attached figures

[0017] Figure 1 This is a schematic diagram showing various implementations of the solvent system and reaction pathway used for CO2 capture;

[0018] Figure 2 This is a schematic diagram of a reboiler-based system for capturing and regenerating acidic gases from a mixed gas stream, specifically as described in this invention.

[0019] Figure 3 This is a schematic diagram of a system without a reboiler for capturing acidic gases from a mixed gas stream, specifically as described in this invention.

[0020] Figure 4 This is a schematic diagram of a reboiler-assisted system for capturing acidic gases from a mixed gas stream, specifically as described in this invention.

[0021] Figure 5 This is a schematic diagram of a waste heat reboiler system for capturing acidic gases from a mixed gas stream, specifically illustrating the present invention; and

[0022] Figure 6 This is a schematic diagram of a waste heat utilization system for capturing acidic gases from a mixed gas stream, specifically as described in this invention. Invention Details

[0023] The invention will be described more fully herein with reference to the accompanying drawings, which illustrate some, but not all, embodiments of the invention. In fact, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments described herein; rather, these embodiments are provided so that the disclosure of the invention may meet applicable legal requirements. The same numerals denote the same elements. The singular forms “a,” “an,” and “the” used in this specification and claims include plural references unless the context clearly indicates otherwise.

[0024] In one aspect of the invention, a liquid solvent system is provided. The solvent system can be used to separate acidic gases from a gas mixture. The term "acid gas" or "acidic gas" is used to refer to any gaseous component that, when mixed with water, can result in the formation of an acid. Non-limiting examples of acidic gases included in the invention include CO2, SO2, COS, CS2, and NOx. For simplicity, the invention will be described below with particular reference to CO2 and SO2. However, it should be understood that the invention includes methods and systems for removing any acidic gaseous component from a gas stream. In some embodiments, the solvent system is regenerable in that it can release acidic gases from the solvent and can be reused to separate other acidic gases from other gas mixtures. In a specific embodiment, the solvent system is regenerated at a temperature below that typically required for solvents used for this purpose.

[0025] Generally, the solvent systems described herein comprise combinations of one or more reagents of the following types: nitrogenous bases (including nucleophilic amines and non-nucleophilic nitrogenous bases); non-aqueous liquids; protonated non-aqueous liquids; diluents; and / or ionic liquids. In some aspects, the solvent systems described herein comprise mixtures of components from two or more of these types. In some aspects, the solvent systems described herein consist of one or more components from a single type of these reagents. These types of reagents are described in general terms herein. The various types of solvent systems intended to be included in the invention, and the particularly preferred reagents for each solvent system, will be described independently below.

[0026] Generally, nitrogen-containing base components include nucleophilic amines and non-nucleophilic nitrogen-containing bases. A nitrogen-containing base component (i.e., a nucleophilic amine and / or a non-nucleophilic nitrogen-containing base) is a nitrogen-containing base that reacts according to one or more mechanisms provided herein. For example, according to one embodiment provided herein, the nitrogen-containing base can react with CO2 and / or other components of a solvent system. In some embodiments, one or more nitrogen-containing base components (which may be nucleophilic amines and / or non-nucleophilic nitrogen-containing bases) may have the following pKa: about 8-15, about 8-14, about 8-13, about 8-12, about 8-11, or about 8-10. In some embodiments, the pKa of the nitrogen-containing base component is less than about 11. In other embodiments, the pKa of the nitrogen-containing base may be about 12-15, about 12-14, or about 13-15, for example, about 12, 13, 14, or 15.

[0027] In the solvent system described herein, the nitrogen-containing base component (or components thereof) (when present) is preferably selected such that it has low miscibility with water. In a preferred embodiment, the nitrogen-containing base and optionally one or more other components of the solvent system have higher miscibility than water. In some embodiments, one or more nitrogen-containing base components have high solubility in optionally one or more components of the solvent system.

[0028] A nucleophilic amine is an amine with a reactive nitrogen center that is linked to a non-hydrogen nucleus on the relevant process timescale and under the relevant typical process conditions used to process the gas mixture. Nucleophilic amines include, but are not limited to: primary amines, secondary amines, diamines, triamines, tetraamines, pentamines, cyclic amines, cyclic diamines, amine oligomers, polyamines, and alkanolamines.

[0029] A nonnucleophilic nitrogenous base is a nitrogenous base (including but not limited to amines) that, as a Bronsonted base, forms a bond with one or more hydrogen nuclei (protons) under the relevant process timescale and typical process conditions used to process the gas mixture, resulting in a positively charged nitrogen center. Nonnucleophilic nitrogenous bases include tertiary amines, guanidines, and amidines and / or their analogues.

[0030] In some specific embodiments, examples of nitrogen-containing bases that can be used as components of a solvent system may be selected from the group consisting of: 1,4-diazabicyclo-undecyl-7-ene (“DBU”); 1,4-diazabicyclo-2,2,2-octane; piperazine (“PZ”); triethylamine (“TEA”); 1,1,3,3-tetramethylguanidine (“TMG”); 1,8-diazabicyclo-undecyl-7-ene; monoethanolamine (“MEA”); diethylamine (“DEA”); ethylenediamine (“EDA”); 1,3-diaminopropane; 1, 4-Diaminobutane; hexamethylenediamine; 1,7-diaminoheptane; diethanolamine; diisopropylamine (“DIPA”); 4-aminopyridine; pentanylamine; hexylamine; heptylamine; octylamine; nonylamine; decylamine; tert-octylamine; dioctylamine; dihexylamine; 2-ethyl-1-hexylamine; 2-fluorophenylethylamine; 3-fluorophenylethylamine; 3,5-difluorobenzylamine; 3-fluoro-N-methylbenzylamine; 4-fluoro-N-methylbenzylamine; imidazole; benzimidazole; N-methylimidazole; 1-trifluoroethylimidazole; 1,2,3-triazole; 1,2,4-triazole; and mixtures thereof. Other nitrogenous bases that may also be used according to the invention include, for example, those described in U.S. Patent Application Publication No. 2008 / 0058549 by Jessop et al., which is incorporated herein by reference.

[0031] Non-aqueous liquids should be understood as liquids other than water. In some cases, non-aqueous liquids are proton-non-aqueous liquids, which are liquids containing ionizable hydrogen that readily dissociates in the presence of non-nucleophilic amines. Thus, in some embodiments, a non-aqueous liquid (e.g., a proton-non-aqueous liquid) is a “relatively acidic component”, which should be understood as a material whose acidity is greater than that of water, preferably significantly greater than that of water. For example, in some embodiments, a non-aqueous liquid (e.g., a proton-non-aqueous liquid) is a relatively acidic component that may have a pKa of less than about 15, less than about 14, less than about 13, less than about 12, less than about 11, or less than about 10. In some embodiments, the pKa of the relative acidic component is about 8 to about 15, 9 to about 15, about 10 to about 15, about 11 to about 15, about 12 to about 15, about 13 to about 15, about 8 to about 14, about 8 to about 13, about 8 to about 12, or about 8 to about 11, about 9 to about 14, about 9 to about 13, about 9 to about 12, about 9 to about 11, about 10 to about 12, about 10 to about 13, about 10 to about 14, about 11 to about 13, or about 11 to about 14. According to some embodiments of the invention, the relative acidic component of example types that can be used (as a non-aqueous liquid or a proton-based non-aqueous liquid) includes, but is not limited to, the following: fluorinated alcohols; optionally substituted phenols; and nitrogen-containing heterocycles (e.g., pyrazoles and imidazoles). Particularly preferably, the relative acidic component is selected from fluorinated alcohols and optionally substituted phenols.

[0032] In some embodiments, the solvent comprises one or more diluents. A diluent should be understood as a solvent component that does not significantly participate in the reaction with other components in the solvent system. In such embodiments, the types of substances that can be used as diluents include certain non-aqueous liquids (including protonated non-aqueous liquids), as described above. Whether a non-aqueous liquid (including protonated non-aqueous liquids) can be used as a diluent depends on one or more other components of the solvent system in which it is used. Unless otherwise stated, non-aqueous liquids (including protonated non-aqueous liquids) are considered as reactive components of the solvent system described herein. In some embodiments, the diluent is a relatively acidic component. Relatively acidic components of example types that can be used as diluents according to some embodiments of the invention include, but are not limited to, the following: fluorinated alcohols; optionally substituted phenols; and nitrogen heterocycles (e.g., pyrazoles and imidazoles).

[0033] In some embodiments, the diluent may have a pKa of less than about 15, less than about 14, less than about 13, less than about 12, less than about 11, or less than about 10. In some embodiments, the diluent has an alcohol component with a pKa of about 6 to about 15, about 7 to about 15, about 8 to about 15, about 9 to about 15, about 6 to about 14, about 7 to about 14, about 8 to about 13, about 9 to about 13, about 6 to about 12, about 7 to about 12, about 8 to about 12, about 9 to about 12, about 6 to about 11, about 7 to about 11, about 8 to about 11, about 9 to about 11, about 6 to about 10, about 7 to about 10, or about 8 to about 10. In other embodiments, the non-aqueous liquid used as the diluent is not a relatively acidic component, and its pKa does not fall within the above ranges. For example, in some embodiments, the diluent has a pKa greater than about 15.

[0034] In some embodiments, the diluent is preferably a non-aqueous diluent. In some embodiments, the diluent is selected such that it has low miscibility with water. For example, in some embodiments, the solubility of the diluent in water at 25°C is less than or equal to about 10 g / 100 mL (i.e., 10 g solvent / 100 mL water) or about 20 g / 100 mL. In other embodiments, the solubility of the diluent in water at 25°C is less than or equal to about 0.01 g / 100 mL, less than or equal to about 0.1 g / 100 mL, less than or equal to about 0.5 g / 100 mL, less than or equal to about 1 g / 100 mL, less than or equal to about 1.5 g / 100 mL, less than or equal to about 2 g / 100 mL, less than or equal to about 2.5 g / 100 mL, less than or equal to about 3 g / 100 mL, less than or equal to about 4 g / 100 mL, less than or equal to about 5 g / 100 mL, less than or equal to about 6 g / 100 mL, less than or equal to about 7 g / 100 mL, less than or equal to about 8 g / 100 mL, or less than or equal to about 9 g / 100 mL. In some embodiments, the diluent is completely immiscible with water. Solvent systems can be obtained using diluents with low water solubility, exhibiting one or more of the following performance characteristics: they require less energy to regenerate; they can have a high CO2 loading capacity; they can tolerate water in the gas stream; and / or they can be separated from water without significant energy loss.

[0035] Certain specific solvent systems, such as those of the present invention Figure 1As shown and described below. For further discussion of solvent components that can be used in certain solvent systems of the present invention, see, for example, International Application No. PCT / US2011 / 050442 filed September 2, 2011 by Lail et al., and PCT / US2011 / 050452 filed September 3, 2011 by Lail et al., all of which are incorporated herein by reference. In some embodiments, the solvent system described herein is substantially immiscible with water, and its solubility at 25°C is less than or equal to about 10 g solvent / 100 mL water, less than or equal to about 20 g solvent / 100 mL water, less than or equal to about 9 g solvent / 100 mL water, less than or equal to about 8 g solvent / 100 mL water, less than or equal to about 7 g solvent / 100 mL water, less than or equal to about 6 g solvent / 100 mL water, less than or equal to about 5 g solvent / 100 mL water, less than or equal to about 4 g solvent / 100 mL water, less than or equal to about 3 g solvent / 100 mL water, less than or equal to about 2 g solvent / 100 mL water, less than or equal to about 1 g solvent / 100 mL water, less than or equal to about 0.5 g solvent / 100 mL water, less than or equal to about 0.1 g / 100 mL water, or less than or equal to about 0.01 g / 100 mL water. In some embodiments, the solvent system is completely immiscible with water. In some embodiments, solvent systems with low water solubility may exhibit one or more of the following performance characteristics: they require less energy to regenerate; they may have a high CO2 loading capacity; they are tolerant of water in the gas stream; and / or they can be separated from water without significant energy loss. It should be noted that while solvent systems with low water miscibility are preferred, the present invention also includes solvent systems in which one or more components of the solvent system are at least partially miscible with water.

[0036] As described above, the solvent system described herein can be used to remove one or more acidic gases from a gas stream. In some embodiments, the solvent system described herein can be specifically used to capture CO2 from a gas stream. The gas stream can be a mixed gas stream that includes one or more other components besides CO2. When a CO2-containing gas mixture is bubbled into a solution comprising the solvent system of the present invention, one or more components of the solvent system react chemically with the CO2, binding the CO2 into the solution. In some embodiments, the solvent system described herein has a high CO2 loading. For example, the solvent system can be used to capture or remove nitrogenous bases in amounts greater than about 0.05 mol CO2 / mol, greater than about 0.1 mol CO2 / mol, greater than about 0.2 mol CO2 / mol, greater than about 0.3 mol CO2 / mol, greater than about 0.4 mol CO2 / mol, greater than about 0.5 mol CO2 / mol, greater than about 0.6 mol CO2 / mol, greater than about 0.7 mol CO2 / mol, greater than about 0.8 mol CO2 / mol, greater than about 0.9 mol CO2 / mol, or greater than about 1 mol CO2 / mol.

[0037] In some embodiments, any solvent system described herein can tolerate the presence of water. In some embodiments, the solvent system tolerates up to or equal to about 30% by volume of water. For example, in some embodiments, the solvent system tolerates up to or equal to about 25% by volume of water, up to or equal to about 20%, up to or equal to about 15%, up to or equal to about 10%, up to or equal to about 5%, up to or equal to about 2%, or up to or equal to about 1% by volume of water. In some embodiments, tolerating the presence of water means that the solvent performance is minimally or not degraded in the presence of up to the indicated volume of water. In some embodiments, the solvent system maintains or approaches its initial CO2 loading capacity when loaded with up to the indicated volume of water.

[0038] In some embodiments, the solvent system may also contain one or more other components. For example, other components may be added to increase the solubility of the captured CO2 products in the solvent system, thereby preventing precipitation. However, in other embodiments, solid formation may be desirable, and this formation can be enhanced by varying the concentrations of one or more solvent system components.

[0039] In a preferred embodiment, CO2 captured using the solvent system described herein can be released to regenerate the solvent system for reuse. Preferably, the solvent system can be regenerated under mild conditions (e.g., at low temperatures) (or the reaction with CO2 is reversible). In some embodiments, the release of CO2 and the regeneration of the corresponding solvent system are carried out by heating. When a solution containing bound CO2 is heated, the chemical reaction is reversed, releasing CO2 and yielding a concentrated CO2 stream.

[0040] In some embodiments, the present invention relates to solvent systems and methods for removing CO2 from a gas stream. The invention is applicable to any gas stream containing CO2. For example, in specific embodiments, the invention relates to a method for removing CO2 from flue gas from fossil fuel combustion, natural gas mixtures, or CO2-containing breathing gas mixtures from enclosed spaces. The method involves passing a mixed gas stream through a solvent system described herein. In some embodiments, the invention also relates to the regeneration of the solvent system, which releases CO2. Various techniques can be used to regenerate the solvent. These include, but are not limited to: thermal changes, partial pressure changes formed by flashing, stripping, applying vacuum, or combinations thereof, pH changes, or combinations thereof. In some embodiments, the regeneration of the solvent system involves heating the solvent system at a temperature sufficient to release CO2. In some embodiments, the method involves heating the solvent system at temperatures less than or equal to about 200°C, for example, less than or equal to about 185°C, less than or equal to about 150°C, or less than or equal to about 125°C. In a preferred embodiment, the method involves heating the solvent system at temperatures less than or equal to about 100°C, for example, at temperatures less than or equal to about 95°C, less than or equal to about 90°C, less than or equal to about 85°C, less than or equal to about 80°C, less than or equal to about 75°C, or less than or equal to about 70°C. In some embodiments, CO2 may be released at ambient temperature. In some embodiments, CO2 is captured in a non-aqueous phase under conditions where water aggregates into a separate, lower-density phase. This phase, along with the non-aqueous-rich phase to be regenerated, may be fed into a regenerator at a lower temperature than the corresponding individual aqueous-rich phase. This phase may then undergo phase separation from the regenerated lean solvent before being returned to the absorber.

[0041] In some embodiments, 100% or about 100% of the CO2 is removed from the CO2-rich solvent system. However, in some embodiments, less than about 100% of the CO2 is removed from the CO2-rich solvent system. In preferred embodiments, about 50-100% of the captured CO2 is removed from the CO2-rich solvent system, preferably about 75%-100%, about 80%-100%, about 90%-100%, about 95%-about 100%, or about 98%-100%. For example, in some embodiments, at least about 98%, 95%, 90%, 85%, 80%, 75%, 70%, 60%, or 50% of the captured CO2 is removed from the CO2-rich solvent system.

[0042] In some implementations, removing CO2 from a gas mixture that includes H2O in addition to CO2 can cause H2O to accumulate in the solvent system, either as a single-phase solution or as a two-phase solution depending on the reaction conditions. As mentioned above, the presence of H2O in the solvent mixture can be disadvantageous because of undesirable side reactions and because more energy is required during solvent regeneration due to the need to remove water from the solvent. Therefore, the accumulation of H2O in the solvent system can increase the required regeneration energy and reduce the efficiency of the regeneration system.

[0043] In some embodiments, the method of the present invention provides a method that avoids the adverse effects of H2O aggregation in a solvent system. For example, by providing a method for capturing CO2 in a solvent system at a temperature above the saturation temperature of H2O in the gas mixture, the adverse effects of H2O aggregation on the energy requirements for solvent system regeneration can be minimized. Furthermore, in some embodiments, by providing a method for H2O to aggregate into a separate aqueous phase in a solvent system, the adverse effects of H2O aggregation on the energy requirements for solvent system regeneration can be minimized. This method involves using a solvent system that has little or no solubility in water. In such a system, the collected water is treated as a separate phase. The separate aqueous phase can be removed by mechanical rather than thermal methods, such as pouring it off or centrifuging it, minimizing the energy required to maintain an effective CO2 removal system. For example, the solubility of a fatty alcohol in water decreases as the hydrocarbon chain length increases. The same is true for fluorinated alcohols. For example, 2,2,3,3,4,4,5,5-octafluoropentanol (“OFP”) is substantially immiscible with water. Therefore, some solvent systems described herein include suitable components that, when combined with water, form a two-phase liquid solution. In such solvent systems, water can be separated from the solvent system by pouring it off from the fluorinated phase or by centrifuging the aqueous phase layer, without distillation or the use of a membrane. In some embodiments, after removing H₂O, the CO₂-rich solvent system can be regenerated at low temperatures by adding a low-boiling-point diluent to meet the partial pressure requirements. Thus, the solvent system avoids the additional energy losses associated with water distillation. By providing a non-aqueous CO₂ absorption solvent system with low water solubility, this solvent system offers lower energy requirements and milder regeneration conditions compared to aqueous or high-water-affinity CO₂ solvent systems.

[0044] In some embodiments, a system for removing CO2 from a gas stream is provided. A schematic diagram of an example system of the present invention is shown below. Figure 2-6As shown. The CO2 removal system 10 includes an absorber 12 configured to have an inlet for receiving a gas stream. For example, the gas stream may come directly from the combustion chamber of a boiling system in a power plant. The gas stream may or may not pass through a gas cleaning system before entering the CO2 removal system. The absorber can be any chamber including a solvent system for removing CO2, having an inlet and an outlet for the gas stream, and wherein the gas stream and the solvent system can be contacted. In the absorber, CO2 can be transferred from the gas phase to the liquid phase according to the principles described herein. The absorber can be of any type: for example, the absorber may include a spray tower absorber, a packed bed absorber (including countercurrent or crossflow towers), a tray tower absorber (with various tray types, including bubble cap trays, sieve trays, impact trays, and / or float valve trays), a venturi absorber, or a jet absorber. The temperature and pressure in the absorber can be controlled. For example, in one embodiment, the temperature of the absorber can be maintained at or near 50-60°C, and the absorber pressure can be maintained at or near atmospheric pressure. Therefore, the absorber can be equipped with a heating / cooling system and / or a pressurization / vacuum system.

[0045] In the absorber, the gas stream and the solvent system described herein are brought into fluid contact and pass through the solvent system. The solvent system reacts with CO2 present in the gas stream, trapping the CO2 and separating it from the remaining components of the gas, releasing the resulting CO2-free gas stream from the absorber through an outlet. As the mixed gas stream passes through, the solvent system continuously reacts with the incoming CO2 until it becomes "CO2-rich". The absorber is optionally connected to one or more components. For example, the absorber is preferably configured to have means for delivering the solvent to a unit where water can be poured out, centrifuged, or otherwise removed from the system.

[0046] At any stage of the CO2 capture method, the solvent system can be regenerated. Therefore, the system optionally includes a regeneration system 14 to release the captured CO2 by separating the CO2 gas stream, thereby regenerating the solvent system. The regeneration system is configured to receive a “rich” solvent feed from the absorber and, once the CO2 has been separated from the “rich” solvent, return the regenerated solvent to the absorber. The regeneration system may simply include a chamber having a heating unit that heats the solvent system at a temperature sufficient to release the gas, and a release valve that allows CO2 to be discharged from the regeneration system. It may also be a distillation column and have a design substantially the same as that of an absorber column as described above. The regeneration system may optionally be connected to one or more components. For example, the regenerator is preferably configured to have means for conveying the solvent to a unit in which water can be poured out, centrifuged, or otherwise removed from the system.

[0047] Released CO2 can be separated / recovered from the system and output to a storage tank or for other predetermined applications. The regenerated solvent system can easily absorb CO2 from the gas stream and guide it back into the absorber.

[0048] I. Ionic liquids, including nucleophilic amines and proton-containing nonaqueous liquids.

[0049] In one aspect of the invention, a solvent system comprising an ionic liquid is provided, wherein the ionic liquid is prepared by combining one or more nucleophilic amines and one or more protonated nonaqueous liquids. The ionic liquid solvent system described herein is a system in which ions (cations and anions) are present in solution. The components typically have suitable pKa values ​​to form an ionic liquid, wherein the nucleophilic amine is a cation. In some embodiments, a solvent system comprising an ionic liquid at ambient temperatures (e.g., about 20°C to about 25°C) is provided. Preferably, the ionic liquid solvent system described herein is reactable with an acidic gas to form an ionic solution comprising: 1) carbamates, zwitterionic aminosulfonic acids, sulfates, or combinations thereof; and 2) protonated weak acids.

[0050] Nucleophilic amines that can be used to form certain example ionic liquid solvent systems of this type can be primary and / or secondary amines having a reactive nitrogen center. Primary amines should be understood as compounds having the general formula NH₂R, where R is a carbon-containing group, including but not limited to C1-C. 20 Alkyl groups. Secondary amines should be understood as compounds having the general formula NHR1R2, wherein R1 and R2 are independently carbon-containing groups, including but not limited to C1-C2. 20 Alkyl group. Optionally, one or more hydrogen atoms on R, R1, and R2 may be substituted with one or more substituents. For example, one or more hydrogen atoms on R, R1, or R2 may be substituted with: optionally substituted C1-C6 alkyl groups, optionally substituted C1-C6 alkoxy groups, optionally substituted C2-C6 alkyl groups, or optionally substituted C2-C6 alkoxy groups. 10 alkenyl; optionally substituted C2-C 10 Alkynyl; optionally substituted alkylaryl; optionally substituted arylalkyl; optionally substituted aryloxy; optionally substituted heteroaryl; optionally substituted heterocyclic; halogen (e.g., Cl, F, Br, and I); hydroxyl; haloalkyl (e.g., CF3, 2-Br-ethyl, CH2F, CH2CF3, and CF2CF3); haloaryl; haloalkylaryl; halobenzyl; optionally substituted amino; optionally substituted alkylamino; optionally substituted arylamino; optionally substituted acyl; CN; NO2; N3; CH2OH; CONH2; C1-C3 alkylthio; sulfate; sulfonic acid; sulfonate (e.g., methanesulfonyl); phosphonic acid; phosphate; phosphonate; mono-, bis-, or triphosphate; triphenylmethyl or monomethoxytriphenylmethyl; CF3S; CF3SO2; or silyl (e.g., trimethylsilyl, dimethyl-tert-butylsilyl, and diphenylmethylsilyl).

[0051] In some embodiments, the primary or secondary amine may be selected from amines functionalized with fluoroalkyl aryl groups. In specific embodiments, the amine may be selected from the group consisting of: 2-fluorophenylethylamine, 3-fluorophenylethylamine, 4-fluorophenylethylamine, 2-fluoro-N-methylbenzylamine, 3-fluoro-N-methylbenzylamine, and 4-fluoro-N-methylbenzylamine, 2-fluorobenzylamine, 3-fluorobenzylamine, 4-fluorobenzylamine, 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecanodecylamine, 2,3-difluorobenzylamine, 2,4-difluorobenzylamine, 2,6-difluorobenzylamine, 3,4-difluorobenzylamine, 3,5-difluorobenzylamine, 2-trifluoromethylbenzylamine, 3-trifluoromethylbenzylamine, 4-trifluoromethylbenzylamine, D-4-fluoro-α-methylbenzylamine, and L-4-fluoro-α-methylbenzylamine.

[0052] In some embodiments, the nucleophilic amine that can be used in such a solvent system may include cyclic amines, diamines, and primary and / or secondary alcoholamines. Cyclic amines are amines in which the nitrogen atom forms part of a ring structure, and may include, but are not limited to: aziridine, aziridine, pyrrolidine, piperidine, piperazine, pyridine, and pyrimidine. Cyclic amines may include one or more rings and may optionally be substituted with one or more substituents as described above. In some embodiments, the nitrogen-containing base may be a diamine. In some embodiments, the nitrogen-containing base may be a primary or secondary alcoholamine. Alcoholamines are also called amino alcohols and include both an alcohol and an amino group. The amino group of an alcoholamine may be any type of amine described herein. In some embodiments, the nucleophilic amine component is preferably hydrophobic.

[0053] Proton-nonaqueous liquids that can be used to form such ionic liquid solvent systems include, for example, fluorinated alcohols; optionally substituted phenols; and nitrogen heterocycles. Some proton-nonaqueous liquids are fluorinated alcohols (e.g., fluorinated alcohols having 5 or more carbon atoms, preferably having a low water content (e.g., < about 10% by weight water)). Fluorinated alcohols usable according to the invention include any compounds having the general formula R-OH, wherein R is an alkyl group (e.g., C1-C1). 10 Alkyl, C1-C8 alkyl, C1-C6 alkyl, C2-C 10 Alkyl, C2-C8 alkyl, C2-C6 alkyl, C3-C 10 Alkyl (C3-C8 alkyl, or C3-C6 alkyl), wherein one or more hydrogen atoms of the alkyl group are substituted with fluorine. In some embodiments, it is considered useful when the number of hydrogen atoms substituted with fluorine is two, three, four, five, six, seven, eight, nine, or greater. In other embodiments, one or more other substituents, including, but not limited to, C1-C6 alkyl, C1-C6 alkoxy, and halogen substituents, may optionally be used to substitute one or more hydrogen atoms of the alkyl group.

[0054] The phenols that can be optionally substituted for use in this invention should be understood to refer to phenols in which one or more hydrogen atoms on the benzene ring may be replaced by substituents. Non-limiting examples of substituents for one or more hydrogen atoms on the benzene ring include C1-C6 alkyl, C1-C6 alkoxy, and halogens. A nitrogen heterocycle should be understood to refer to any cyclic compound (including, but not limited to, imidazole, pyrazole, and triazole) that includes at least one nitrogen atom in its ring structure and is optionally substituted, such that one or more hydrogen atoms on the ring structure may be replaced by substituents. In some embodiments, at least one nitrogen atom in the ring structure includes an acidic hydrogen atom with a pKa value less than about 15 (e.g., about 8-15). Non-limiting examples of substituents for one or more hydrogen atoms on the ring include C1-C6 alkyl, C1-C6 alkoxy, and halogens.

[0055] In a specific embodiment, the proton-nonaqueous liquid may be a relatively acidic component selected from the group consisting of: 2,2,3,3,4,4,5,5-octafluoropentanol (“OFP”); 2,2,3,3-tetrafluoropropanol (“TFP”); 2,2,3,3,3-pentafluoropropanol (“PFP”); 2,2,3,3,4,4-hexafluorobutanol (“HFB”); 2,2,2-trifluoroethanol (“TFE”); nonafluoro-1-hexanol; 4,4,5,5,6,6,7,7,7-nonafluoroheptanol; 1,1,3,3-hexafluoro-2 -Phenylacetyl-2-propanol; 4-methoxyphenol (“4-MeOPh”); 4-ethoxyphenol (“4-EtOPh”); 2-ethoxyphenol; 4-propoxyphenol; imidazole; benzimidazole; N-methylimidazolium; 1-trifluoroethylimidazolium; 1,2,3-triazole; 1,2,4-triazole; 2-trifluoromethylpyrazole; 3,5-bistrifluoromethylpyrazole; 3-trifluoromethylpyrazole, 2-fluorophenol, 3-fluorophenol, 4-fluorophenol, 2-trifluoromethylphenol, 3-trifluoromethylphenol, 4-trifluoromethylphenol, and mixtures thereof. Preferably, the proton-nonaqueous liquid used in the solvent systems described herein may have a low water content (e.g., < about 10% by weight of water) and / or low water solubility. Typically, the proton-nonaqueous liquid used in such solvent systems is the active component of the solvent system (i.e., not merely used as a diluent).

[0056] In the ionic liquid solvent system described herein, the hydrogen nuclei of the protonated nonaqueous liquid are sufficiently ionizable to dissociate from the protonated nonaqueous liquid and react with affinistic bases. By reversibly forming a protonated solvent and creating a link between the nucleophilic amine nitrogen and nonacidic gas nuclei, acidic gas components such as CO2 and SO2 can be formed, for example, carbamates, zwitterions (e.g., zwitterionic aminosulfonic acids), aminosulfonic acid / salts, or combinations thereof, absorbing acidic gas components such as CO2 and SO2 in such ionic liquid solvents. An example solvent system and reaction mechanism are as follows: Figure 1 As shown in A).

[0057] In this type of solvent system, the absorption of the acidic gaseous component is preferably reversible. After the loss of the acidic gaseous component, the protic solvent can again provide protons for the nucleophilic base. The advantage of this solvent system is that it minimizes the loss of nucleophilic amines into vapor, for example because of the low vapor pressure of ionic liquid salts in the absorption column, and, for example, the low vapor pressure of carbamates in the regeneration section.

[0058] II. A mixture containing two or more nucleophilic amines and two or more non-aqueous liquids.

[0059] In another aspect, a solvent system is provided comprising two or more nucleophilic amines mixed in a wide range of component proportions with two or more non-aqueous liquids, and is used to separate an acidic gaseous component from a gas mixture. The two or more nucleophilic amines react with the acidic gaseous component (e.g., CO2 or SO2) to form at least one bond with a nitrogen atom involving a nucleus other than a hydrogen atom. The product formed with CO2 is a carbamate, and may consist of a single amine carbamate structure or a mixture of amine carbamate structures. In some embodiments, the solvent system removes CO2 without significantly forming carbonates or heteroatom analogs of carbonates.

[0060] Nucleophilic amines that can be used to form certain example solvent systems of this type can be primary and / or secondary amines having a reactive nitrogen center. Primary amines should be understood as compounds having the general formula NH₂R, where R is a carbon-containing group, including but not limited to C1-C. 20 Alkyl groups. Secondary amines should be understood as compounds having the general formula NHR1R2, wherein R1 and R2 are independently carbon-containing groups, including but not limited to C1-C2. 20 Alkyl group. Optionally, one or more hydrogen atoms on R, R1, and R2 may be substituted with one or more substituents. For example, one or more hydrogen atoms on R, R1, or R2 may be substituted with: optionally substituted C1-C6 alkyl groups, optionally substituted C1-C6 alkoxy groups, optionally substituted C2-C6 alkyl groups, or optionally substituted C2-C6 alkoxy groups. 10 alkenyl; optionally substituted C2-C 10Alkynyl; optionally substituted alkylaryl; optionally substituted arylalkyl; optionally substituted aryloxy; optionally substituted heteroaryl; optionally substituted heterocyclic; halogen (e.g., Cl, F, Br, and I); hydroxyl; haloalkyl (e.g., CF3, 2-Br-ethyl, CH2F, CH2CF3, and CF2CF3); haloaryl; haloalkylaryl; halobenzyl; optionally substituted amino; optionally substituted alkylamino; optionally substituted arylamino; optionally substituted acyl; CN; NO2; N3; CH2OH; CONH2; C1-C3 alkylthio; sulfate; sulfonic acid; sulfonate (e.g., methanesulfonyl); phosphonic acid; phosphate; phosphonate; mono-, bis-, or triphosphate; triphenylmethyl or monomethoxytriphenylmethyl; CF3S; CF3SO2; or silyl (e.g., trimethylsilyl, dimethyl-tert-butylsilyl, and diphenylmethylsilyl).

[0061] In some embodiments, the primary or secondary amine may be selected from amines functionalized with fluoroalkyl aryl groups. In specific embodiments, the amine may be selected from the group consisting of: 2-fluorophenylethylamine, 3-fluorophenylethylamine, 4-fluorophenylethylamine, 2-fluoro-N-methylbenzylamine, 3-fluoro-N-methylbenzylamine, and 4-fluoro-N-methylbenzylamine, 2-fluorobenzylamine, 3-fluorobenzylamine, 4-fluorobenzylamine, 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecanodecylamine, 2,3-difluorobenzylamine, 2,4-difluorobenzylamine, 2,6-difluorobenzylamine, 3,4-difluorobenzylamine, 3,5-difluorobenzylamine, 2-trifluoromethylbenzylamine, 3-trifluoromethylbenzylamine, 4-trifluoromethylbenzylamine, D-4-fluoro-α-methylbenzylamine, and L-4-fluoro-α-methylbenzylamine.

[0062] In some embodiments, the nucleophilic amine that can be used in such solvent systems may include cyclic amines, diamines, and primary and / or secondary alcoholamines. Cyclic amines are amines in which the nitrogen atom forms part of a ring structure, and may include, but are not limited to: aziridine, aziridine, pyrrolidine, piperidine, piperazine, pyridine, and pyrimidine. Cyclic amines may include one or more rings and may optionally be substituted with one or more substituents as described above. In some embodiments, the nucleophilic amine may be a diamine. In some embodiments, the nucleophilic amine may be a primary or secondary alcoholamine. Alcoholamines are also called amino alcohols and include both an alcohol and an amino group. The amino group of an alcoholamine may be any type of amine described herein.

[0063] Preferably, one or both nucleophilic amines are non-aqueous and / or hydrophobic, and preferably have low water solubility (e.g., < about 10% by weight)). Some example nucleophilic amines that can be used in this type of solvent system include, but are not limited to, alkylfluoroaromatic amines, such as 3-fluoro-N-methylbenzylamine, 4-fluoro-N-methylbenzylamine, 2-fluorophenylethylamine, 3-fluorophenylethylamine, and 4-fluorophenylethylamine.

[0064] The non-aqueous liquids that can be used in this type of solvent system can vary. In some embodiments, it should be noted that one or more of these non-aqueous liquids may be proton-based non-aqueous liquids. Preferably, one or two non-aqueous liquids have low water solubility (e.g., < about 10% by weight) and / or hydrophobicity. In some embodiments, such non-aqueous liquids include fluorinated alcohols. Fluorinated alcohols available according to the invention include any compound having the general formula R-OH, wherein R is an alkyl group (e.g., C1-C1). 10 Alkyl, C1-C8 alkyl, C1-C6 alkyl, C2-C 10 Alkyl, C2-C8 alkyl, C2-C6 alkyl, C3-C 10 Alkyl (C3-C8 alkyl, or C3-C6 alkyl), wherein one or more hydrogen atoms of the alkyl group are substituted with fluorine. In some embodiments, it is considered useful when the number of hydrogen atoms substituted with fluorine is two, three, four, five, six, seven, eight, nine, or greater. In other embodiments, one or more other substituents, including, but not limited to, C1-C6 alkyl groups and halogen substituents, may optionally be used to substitute one or more hydrogen atoms of the alkyl group. Some example non-aqueous liquids include, but are not limited to, 2,2,3,3,4,4,5,5-octafluoropentanol, 3,3,4,4,5,5,6,6-hexafluorobutanol, and 4,4,5,5,6,6,7,7,7-nonafluoroheptanol. In specific embodiments, one or more non-aqueous liquids may be selected from the group consisting of: toluene, p-xylene, 1-methylnaphthalene, 2,4,6-dimethylaminophenol, benzyl alcohol, 2,6-dimethylcyclohexanone, 3,5-dimethylpyridine, cyclohexanone, aniline, pyridine, 2-fluoroacetylphenone, 1-fluorodecane, 2,4-difluorobenzophenone, 2-fluoro-3-trifluoromethylaniline, 2-fluoroaniline, 4-fluoroaniline, 3-trifluoromethylacetophenone, 2-trifluoromethylacetophenone, di(2,2,2-trifluoroethyl)methylphosphate, 4-fluoro-3-(trifluoromethyl)benzaldehyde, and mixtures thereof.

[0065] Other example types of proton-based non-aqueous liquids that can be used with this type of solvent system include, but are not limited to, optionally substituted phenols and nitrogen heterocycles. Optionally substituted phenols that can be used in this invention should be understood to refer to phenols in which one or more hydrogen atoms on the benzene ring may be substituted with substituents. Non-limiting examples of one or more dependent substituents on the benzene ring include C1-C6 alkyl, C1-C6 alkyl, and halogens. Nitrogen heterocycles should be understood to refer to any cyclic compound (including, but not limited to, imidazole, pyrazole, and triazole) that includes at least one nitrogen atom in its ring structure and is optionally substituted, such that one or more hydrogen atoms on the ring structure may be substituted with substituents. In some embodiments, at least one nitrogen atom in the ring structure includes an acidic hydrogen atom with a pKa value less than about 15 (e.g., about 8-15). Non-limiting examples of substituents for one or more hydrogen atoms on the ring include C1-C6 alkyl, C1-C6 alkoxy, and halogens.

[0066] In some specific embodiments, the non-aqueous liquid may be a relatively acidic component selected from the group consisting of: 2,2,3,3,4,4,5,5-octafluoropentanol (“OFP”); 2,2,3,3-tetrafluoropropanol (“TFP”); 2,2,3,3,3-pentafluoropropanol (“PFP”); 2,2,3,3,4,4-hexafluorobutanol (“HFB”); 2,2,2-trifluoroethanol (“TFE”); nonafluoro-1-hexanol; 4,4,5,5,6,6,7,7,7-nonafluoroheptanol; 1,1,3,3-hexafluoro-2 -Phenyl-2-propanol; 4-methoxyphenol (“4-MeOPh”); 4-ethoxyphenol (“4-EtOPh”); 2-ethoxyphenol; 4-propoxyphenol; imidazole; benzimidazole; N-methylimidazolium; 1-trifluoroacetylimidazolium; 1,2,3-triazole; 1,2,4-triazole; 2-trifluoromethylpyrazole; 3,5-bistrifluoromethylpyrazole; 3-trifluoromethylpyrazole, 2-fluorophenol, 3-fluorophenol, 4-fluorophenol, 2-trifluoromethylphenol, 3-trifluoromethylphenol, 4-trifluoromethylphenol, and mixtures thereof.

[0067] An example combination of two nucleophilic amines and two non-aqueous liquids, such as Figure 1As shown in B). In some embodiments, combinations of hydrophobic nucleophilic amines and nonaqueous liquids offer several advantages compared to solvents involving only a single hydrophobic amine and a single nonaqueous liquid (e.g., as described in International Application No. PCT / US2011 / 050452, filed September 3, 2011, by Lail et al., which is incorporated herein by reference). In some embodiments, such mixed solvent systems are more desirable because they allow control over important solvent properties, such as viscosity, heat capacity, heat of reaction, moisture content, and / or prevention of precipitation formation in some non-blended formulations that affect the performance and cost-effectiveness of acid gas removal processes.

[0068] Typically, the non-aqueous liquid used in such solvent systems is the active component of the solvent system (i.e., not merely used as a diluent). Although the solvent systems of the present invention are described as comprising one or more non-aqueous liquids, it should be noted that in relevant embodiments, one or more non-aqueous liquids may be diluents. Therefore, in some embodiments, the present invention also relates to mixtures comprising two or more nucleophilic amines and two or more components selected from non-aqueous liquids and diluents.

[0069] III. A mixture containing nucleophilic amines, non-nucleophilic nitrogenous bases, and non-aqueous liquids.

[0070] In one aspect of the invention, the solvent system may comprise a mixture of one or more nucleophilic amines, one or more non-nucleophilic nitrogenous bases, and one or more non-aqueous liquids. Compared to non-blended formulations, the properties of the solvent in this formulation are altered, and it is preferably used to meet specific process requirements for gas treatment. In this embodiment, the solvent system can reversibly react with carbon dioxide and other acidic gases.

[0071] In some embodiments, the nucleophilic amine that can be used in this type of solvent formulation may be a primary amine and / or a secondary amine having a reactive nitrogen center. Primary amines should be understood as compounds having the general formula NH₂R, where R is a carbon-containing group, including but not limited to C₁-C₂. 20 Alkyl groups. Secondary amines should be understood as compounds having the general formula NHR1R2, wherein R1 and R2 are independently carbon-containing groups, including but not limited to C1-C2. 20 Alkyl group. Optionally, one or more hydrogen atoms on R, R1, and R2 may be substituted with one or more substituents. For example, one or more hydrogen atoms on R, R1, or R2 may be substituted with: optionally substituted C1-C6 alkyl groups, optionally substituted C1-C6 alkoxy groups, optionally substituted C2-C6 alkyl groups, or optionally substituted C2-C6 alkoxy groups. 10 alkenyl; optionally substituted C2-C 10Alkynyl; optionally substituted alkylaryl; optionally substituted arylalkyl; optionally substituted aryloxy; optionally substituted heteroaryl; optionally substituted heterocyclic; halogen (e.g., Cl, F, Br, and I); hydroxyl; haloalkyl (e.g., CF3, 2-Br-ethyl, CH2F, CH2CF3, and CF2CF3); haloaryl; haloalkylaryl; halobenzyl; optionally substituted amino; optionally substituted alkylamino; optionally substituted arylamino; optionally substituted acyl; CN; NO2; N3; CH2OH; CONH2; C1-C3 alkylthio; sulfate; sulfonic acid; sulfonate (e.g., methanesulfonyl); phosphonic acid; phosphate; phosphonate; mono-, bis-, or triphosphate; triphenylmethyl or monomethoxytriphenylmethyl; CF3S; CF3SO2; or silyl (e.g., trimethylsilyl, dimethyl-tert-butylsilyl, and diphenylmethylsilyl).

[0072] In some embodiments, the primary or secondary amine may be selected from amines functionalized with fluoroalkyl aryl groups. In specific embodiments, the amine may be selected from the group consisting of: 2-fluorophenylethylamine, 3-fluorophenylethylamine, 4-fluorophenylethylamine, 2-fluoro-N-methylbenzylamine, 3-fluoro-N-methylbenzylamine, and 4-fluoro-N-methylbenzylamine, 2-fluorobenzylamine, 3-fluorobenzylamine, 4-fluorobenzylamine, 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecanodecylamine, 2,3-difluorobenzylamine, 2,4-difluorobenzylamine, 2,6-difluorobenzylamine, 3,4-difluorobenzylamine, 3,5-difluorobenzylamine, 2-trifluoromethylbenzylamine, 3-trifluoromethylbenzylamine, 4-trifluoromethylbenzylamine, D-4-fluoro-α-methylbenzylamine, and L-4-fluoro-α-methylbenzylamine.

[0073] In some embodiments, the nucleophilic amine that can be used in such solvent systems may include cyclic amines, diamines, and primary and / or secondary alcoholamines. Cyclic amines are amines in which the nitrogen atom forms part of a ring structure, and may include, but are not limited to: aziridine, aziridine, pyrrolidine, piperidine, piperazine, pyridine, and pyrimidine. Cyclic amines may include one or more rings and may optionally be substituted with one or more substituents as described above. In some embodiments, the nucleophilic amine may be a diamine. In some embodiments, the nucleophilic amine may be a primary or secondary alcoholamine. Alcoholamines are also called amino alcohols and include both an alcohol and an amino group. The amino group of an alcoholamine may be any type of amine described herein.

[0074] Generally, such compounds react and form bonds with non-hydrogen atoms in the acidic gaseous component. These reactions can lead to the formation of, for example, carbamates, mixed carbamates, zwitterions, aminosulfonates, and / or aminosulfonic acids. Preferably, the nucleophilic amine has a low water content (e.g., < about 10% by weight water) and readily forms a separate liquid phase when saturated with water. Example nucleophilic amines that can be used in these types of solvent systems include, but are not limited to, alkylfluoroaromatic amines, such as 3-fluoro-N-methylbenzylamine, 4-fluoro-N-methylbenzylamine, 2-fluorophenylethylamine, 3-fluorophenylethylamine, and 4-fluorophenylethylamine.

[0075] One or more non-nucleophilic nitrogen-containing bases can vary in such solvent systems. In some embodiments, a non-nucleophilic nitrogen-containing base with a low water content (e.g., < about 20% by weight or < about 10% by weight water at 25°C) is used, and which readily forms a separated liquid phase when combined with water. Therefore, preferably, the non-nucleophilic nitrogen-containing base that can be used in such solvent systems can be hydrophobic and / or substantially immiscible with water, wherein "substantially immiscible with water" is the same as described elsewhere in the invention. An example type of non-nucleophilic nitrogen-containing base that can be used in such solvent systems is guanidine or a substituted guanidine (e.g., fluorinated guanidine).

[0076] Guanidine should be understood as a compound having the structure RNC(NR1R2)2, wherein R, R1, and R2 are independently H or carbon-containing groups, including but not limited to C1-C. 20 Alkyl group. Optionally, one or more hydrogen atoms on R, R1, and / or R2 may be substituted with one or more substituents. For example, one or more hydrogen atoms on R, R1, R2, and R3 may be substituted with: optionally substituted C1-C6 alkyl groups, optionally substituted C1-C6 alkoxy groups, optionally substituted C2-C6 alkyl groups, etc. 10 alkenyl; optionally substituted C2-C 10 Alkynyl; optionally substituted alkylaryl; optionally substituted arylalkyl; optionally substituted aryloxy; optionally substituted heteroaryl; optionally substituted heterocyclic; halogen (e.g., Cl, F, Br, and I); hydroxyl; haloalkyl (e.g., CF3, 2-Br-ethyl, CH2F, CH2CF3, and CF2CF3); haloaryl; haloalkylaryl; halobenzyl; optionally substituted amino; optionally substituted alkylamino; optionally substituted arylamino; optionally substituted acyl; CN; NO2; N3; CH2OH; CONH2; C1-C3 alkylthio; sulfate; sulfonic acid; sulfonate (e.g., methanesulfonyl); phosphonic acid; phosphate; phosphonate; mono-, bis-, or triphosphate; triphenylmethyl or monomethoxytriphenylmethyl; CF3S; CF3SO2; or silyl (e.g., trimethylsilyl, dimethyl-tert-butylsilyl, and diphenylmethylsilyl).

[0077] Another group of non-nucleophilic nitrogen-containing bases that can be used in such solvent systems are amidines, including but not limited to carboxamidine / carboximidamide, which should be understood as compounds having the structure RC(=NH)NR1R2, wherein R, R1, and R2 are independently H or carbon-containing groups, including but not limited to C1-C. 20 Alkyl group. Optionally, one or more hydrogen atoms on R, R1, and / or R2 may be substituted with one or more substituents. For example, one or more hydrogen atoms on R, R1, R2, and R3 may be substituted with: optionally substituted C1-C6 alkyl groups, optionally substituted C1-C6 alkoxy groups, optionally substituted C2-C6 alkyl groups, etc. 10 alkenyl; optionally substituted C2-C 10 Alkynyl; optionally substituted alkylaryl; optionally substituted arylalkyl; optionally substituted aryloxy; optionally substituted heteroaryl; optionally substituted heterocyclic; halogen (e.g., Cl, F, Br, and I); hydroxyl; haloalkyl (e.g., CF3, 2-Br-ethyl, CH2F, CH2CF3, and CF2CF3); haloaryl; haloalkylaryl; halobenzyl; optionally substituted amino; optionally substituted alkylamino; optionally substituted arylamino; optionally substituted acyl; CN; NO2; N3; CH2OH; CONH2; C1-C3 alkylthio; sulfate; sulfonic acid; sulfonate (e.g., methanesulfonyl); phosphonic acid; phosphate; phosphonate; mono-, bis-, or triphosphate; triphenylmethyl or monomethoxytriphenylmethyl; CF3S; CF3SO2; or silyl (e.g., trimethylsilyl, dimethyl-tert-butylsilyl, and diphenylmethylsilyl).

[0078] Examples of guanidines and amidines include, but are not limited to: 1,1,3,3-tetramethylguanidine (“TMG”); N-tert-butyl-1,1,3,3-tetramethylguanidine, diphenylguanidine, xylenemethylguanidine, 1,8-diazabicyclo(5.4.0)undecyl-7-ene, 1,1,3-trimethyl-3-(2,2,3,3-tetrafluoropropyl)guanidine; 1,1,3-trimethyl-3-(2,2,3,3,3-pentafluoropropyl)guanidine; 1,3-dimethyl-1,3-bis(2,2,2-trifluoroethyl)guanidine ; 1,3-bis(2,2,3,3-tetrafluoropropyl)guanidine; 1,3-bis(4-fluorophenyl)guanidine; 1,3-bis(3-fluorophenyl)guanidine; 1,3-bis(2-fluorophenyl)guanidine; 2-(2,2,2-trifluoroethyl)-1,4,5,6,-tetrahydroxypyrimidine; 2-(2,2,3,3-tetrafluoropropyl)-1,4,5,6,-tetrahydroxypyrimidine; 3,3,4,4-tetrafluoro-N,N-dimethylbutamidine; 3,3,3-trifluoro-N,N-dimethylpropanediamine, and mixtures thereof. Other non-nucleophilic nitrogenous bases that can also be used as non-nucleophilic nitrogenous base components in such solvent systems include, but are not limited to: tertiary amines (e.g., fluorinated tertiary amines).

[0079] Preferably, the non-aqueous liquid used in the solvent system described herein may have a low water content (e.g., < about 10% by weight of water) and / or low water solubility. Example types of non-aqueous liquids that can be used according to this type of solvent system include, but are not limited to, zeolite catalysts, optionally substituted phenols, and nitrogen heterocycles. Fluorinated alcohols (e.g., fluorinated alcohols having 5 or more carbon atoms, preferably having a low water content (e.g., < about 10% by weight of water)) are particularly preferred according to this specific type of solvent system. Fluorinated alcohols available according to the invention include any compound having the general formula R-OH, wherein R is an alkyl group (e.g., C1-C1). 10 Alkyl, C1-C8 alkyl, C1-C6 alkyl, C2-C 10 Alkyl, C2-C8 alkyl, C2-C6 alkyl, C3-C 10 Alkyl (C3-C8 alkyl, or C3-C6 alkyl), wherein one or more hydrogen atoms of the alkyl group are substituted with fluorine. In some embodiments, it is considered useful when the number of hydrogen atoms substituted with fluorine is two, three, four, five, six, seven, eight, nine, or greater. In other embodiments, one or more other substituents, including, but not limited to, C1-C6 alkyl, C1-C6 alkyl, and halogen substituents, may optionally be used to substitute one or more hydrogen atoms of the alkyl group.

[0080] The phenols that can be optionally substituted for use in this invention should be understood to refer to phenols in which one or more hydrogen atoms on the benzene ring may be replaced by substituents. Non-limiting examples of one or more dependent substituents on the benzene ring include C1-C6 alkyl groups, C1-C6 alkyl groups, and halogens. A nitrogen heterocycle should be understood to refer to any cyclic compound (including, but not limited to, imidazoles, pyrazoles, and triazoles) that includes at least one nitrogen atom in its ring structure and is optionally substituted, such that one or more hydrogen atoms on the ring structure may be replaced by substituents. In some embodiments, at least one nitrogen atom in the ring structure includes an acidic hydrogen atom with a pKa value less than about 15 (e.g., about 8-15). Non-limiting examples of substituents for one or more hydrogen atoms on the ring include C1-C6 alkyl groups, C1-C6 alkoxy groups, and halogens.

[0081] In some specific embodiments, the non-aqueous liquid may be a relatively acidic component selected from the group consisting of: 2,2,3,3,4,4,5,5-octafluoropentanol (“OFP”); 2,2,3,3-tetrafluoropropanol (“TFP”); 2,2,3,3,3-pentafluoropropanol (“PFP”); 2,2,3,3,4,4-hexafluorobutanol (“HFB”); 2,2,2-trifluoroethanol (“TFE”); nonafluoro-1-hexanol; 4,4,5,5,6,6,7,7,7-nonafluoroheptanol; 1,1,3,3-hexafluoro-2 -Phenylacetyl-2-propanol; 4-methoxyphenol (“4-MeOPh”); 4-ethoxyphenol (“4-EtOPh”); 2-ethoxyphenol; 4-propoxyphenol; imidazole; benzimidazole; N-methylimidazolium; 1-trifluoroacetylimidazolium; 1,2,3-triazole; 1,2,4-triazole; 2-trifluoromethylpyrazole; 3,5-bistrifluoromethylpyrazole; 3-trifluoromethylpyrazole, 2-fluorophenol, 3-fluorophenol, 4-fluorophenol, 2-trifluoromethylphenol, 3-trifluoromethylphenol, 4-trifluoromethylphenol, and mixtures thereof. Typically, the non-aqueous liquid used in these solvent systems is the active component of the solvent system (i.e., not merely used as a diluent).

[0082] When reacting with acidic gases such as carbon dioxide, solvents comprising one or more nucleophilic amines, one or more non-nucleophilic nitrogenous bases, and one or more proton-containing non-aqueous liquids will form two products, such as... Figure 1As shown in C). The product formed by the reaction of a nucleophilic amine with carbon dioxide is an amine carbamate. The reaction of a nonnucleophilic nitrogenous base and a proton-containing nonaqueous liquid with carbon dioxide results in the formation of carbonates. Therefore, this solvent system has a higher, for example, CO2 loading compared to a pure nucleophilic amine solvent. Adding an amine to a nonnucleophilic nitrogenous base solution improves the solvent system by significantly reducing the viscosity of the viscous ionic liquid. Adding a nucleophilic amine to a nonnucleophilic nitrogenous base and a proton-containing nonaqueous liquid solvent system improves the separation of water from the nonnucleophilic nitrogenous base. The molar ratio of one or more nucleophilic amines to one or more nonnucleophilic nitrogenous bases can cover a wide range. Similarly, the molar ratio of one or more nucleophilic amines to one or more nonnucleophilic nitrogenous bases to a proton-containing nonaqueous liquid can also cover a wide range.

[0083] IV. Pure, hydrophobic nucleophilic amine

[0084] In another aspect of the invention, a pure, hydrophobic non-aqueous solvent may be provided. Specifically, the pure solvent according to the invention may consist of a single nucleophilic amine. As used herein, the term "pure" means the absence of other co-solvents in the solvent system, may mean the absence or presence of other liquids in the solvent system (e.g., including cases where the solvent system includes a small amount of undesirable water, e.g., < about 10% by weight), or may mean the absence of other reactive components in the solvent system (i.e., those that can react with the hydrophobic nucleophilic amine, an acidic gas, or both). In some embodiments, the pure hydrophobic nucleophilic amine may comprise a mixture of hydrophobic nucleophilic amines, but preferably comprises a single hydrophobic nucleophilic amine component. In some embodiments, the "pure" hydrophobic nucleophilic amine solvent system consists of a pure hydrophobic nucleophilic amine and an acidic gas. The pure hydrophobic nucleophilic amine can react with acidic gases such as CO2 and SO2 to form amine carbamates, zwitterionic aminosulfonic acids, and / or sulfates, and in some embodiments, no additional diluent is required to prevent precipitation.

[0085] An example of a hydrophobic nucleophilic amine suitable for this purpose is 3-fluoro-N-methylbenzylamine, such as... Figure 1 As shown in D). However, the present invention is not intended to be limiting, and other hydrophobic nucleophilic amines that can react in this manner are also intended to be included in the present invention.

[0086] For example, in some embodiments, the hydrophobic nucleophilic amine that can be used to form certain example pure solvent systems of this type can be a primary amine and / or a secondary amine having a reactive nitrogen center. Primary amines should be understood as compounds having the general formula NH₂R, where R is a carbon-containing group, including but not limited to C₁-C₂. 20 Alkyl groups. Secondary amines should be understood as compounds having the general formula NHR1R2, wherein R1 and R2 are independently carbon-containing groups, including but not limited to C1-C2.20 Alkyl group. Optionally, one or more hydrogen atoms on R, R1, and R2 may be substituted with one or more substituents. For example, one or more hydrogen atoms on R, R1, or R2 may be substituted with: optionally substituted C1-C6 alkyl groups, optionally substituted C1-C6 alkoxy groups, optionally substituted C2-C6 alkyl groups, or optionally substituted C2-C6 alkoxy groups. 10 alkenyl; optionally substituted C2-C 10 Alkynyl; optionally substituted alkylaryl; optionally substituted arylalkyl; optionally substituted aryloxy; optionally substituted heteroaryl; optionally substituted heterocyclic; halogen (e.g., Cl, F, Br, and I); hydroxyl; haloalkyl (e.g., CF3, 2-Br-ethyl, CH2F, CH2CF3, and CF2CF3); haloaryl; haloalkylaryl; halobenzyl; optionally substituted amino; optionally substituted alkylamino; optionally substituted arylamino; optionally substituted acyl; CN; NO2; N3; CH2OH; CONH2; C1-C3 alkylthio; sulfate; sulfonic acid; sulfonate (e.g., methanesulfonyl); phosphonic acid; phosphate; phosphonate; mono-, bis-, or triphosphate; triphenylmethyl or monomethoxytriphenylmethyl; CF3S; CF3SO2; or silyl (e.g., trimethylsilyl, dimethyl-tert-butylsilyl, and diphenylmethylsilyl).

[0087] In some embodiments, the primary or secondary amine may be selected from amines functionalized with fluoroalkyl aryl groups. In specific embodiments, the amine may be selected from the group consisting of: 2-fluorophenylethylamine, 3-fluorophenylethylamine, 4-fluorophenylethylamine, 2-fluoro-N-methylbenzylamine, 3-fluoro-N-methylbenzylamine, and 4-fluoro-N-methylbenzylamine, 2-fluorobenzylamine, 3-fluorobenzylamine, 4-fluorobenzylamine, 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecanodecylamine, 2,3-difluorobenzylamine, 2,4-difluorobenzylamine, 2,6-difluorobenzylamine, 3,4-difluorobenzylamine, 3,5-difluorobenzylamine, 2-trifluoromethylbenzylamine, 3-trifluoromethylbenzylamine, 4-trifluoromethylbenzylamine, D-4-fluoro-α-methylbenzylamine, and L-4-fluoro-α-methylbenzylamine.

[0088] In some embodiments, the hydrophobic nucleophilic amines that can be used in such solvent systems may include cyclic amines, diamines, and primary and / or secondary alcoholamines. Cyclic amines are amines in which the nitrogen atom forms part of a ring structure and may include, but are not limited to, aziridine, aziridine, pyrrolidine, piperidine, piperazine, pyridine, and pyrimidine. Cyclic amines may include one or more rings and may optionally be substituted with one or more substituents as described above. In some embodiments, the nucleophilic amine may be a diamine. In some embodiments, the nucleophilic amine may be a primary or secondary alcoholamine. Alcoholamines are also called amino alcohols and include both an alcohol and an amino group. The amino group of an alcoholamine may be any type of amine described herein. It should be noted that, in order to be used as a pure hydrophobic amine solvent, some nucleophilic amines (e.g., cyclic amines) are preferably functionalized with a fluorinated group.

[0089] Preferably, the pure hydrophobic nucleophilic amine has a low water content (e.g., < about 10% by weight) and forms a separate liquid phase with water. Using a pure hydrophobic amine solvent offers several advantages for non-aqueous solvent processes for acid gas removal. First, the low heat capacity of the pure amine solvent significantly reduces the sensible heat requirement of the solvent. Furthermore, processing water in contact with the solvent is simplified because the number of components in the solvent mixture is reduced. A relatively small group of secondary amines does not require diluents to avoid precipitation formation during reaction with acid gases (pure nucleophilic amines). Many of these relatively few secondary amines are unsuitable for processing industrially produced gas streams containing acid gases because they are immiscible with water. Since many gas streams containing acid gases (e.g., combustion flue gas, cement kiln gas, natural gas, syngas, etc.) may include high concentrations of water (typically about 2-30% by volume), a water-miscible pure secondary amine strips the water from the gas stream, thereby forming a mixture with water. To avoid the formation of such a mixture, a pure secondary amine with very low water miscibility is preferably selected. As a result, in this implementation, the solvent for the acid gas removal process can be considered to consist of a single component, or mainly a single component.

[0090] V. A mixture including nucleophilic amines and non-nucleophilic nitrogenous bases

[0091] In another aspect of the invention, a combination of one or more nucleophilic amines and one or more non-nucleophilic nitrogenous bases can be used to separate acidic gaseous components (such as carbon dioxide) from a gas mixture. In some embodiments, such solvent systems do not contain diluents (e.g., providing a "pure" mixture of one or more nucleophilic amines and one or more non-nucleophilic nitrogenous bases). However, embodiments with one or more added diluents are also included within this type of solvent system. Preferably, the solvent system comprising nucleophilic amines and non-nucleophilic nitrogenous bases comprises a mixture of hydrophobic nucleophilic amines and hydrophobic non-nucleophilic nitrogenous bases, with a total water content of less than 10% by weight.

[0092] Nucleophilic amines that can be used to form certain example solvent systems of this type can be primary and / or secondary amines having a reactive nitrogen center. Primary amines should be understood as compounds having the general formula NH₂R, where R is a carbon-containing group, including but not limited to C1-C. 20 Alkyl groups. Secondary amines should be understood as compounds having the general formula NHR1R2, wherein R1 and R2 are independently carbon-containing groups, including but not limited to C1-C2. 20 Alkyl group. Optionally, one or more hydrogen atoms on R, R1, and R2 may be substituted with one or more substituents. For example, one or more hydrogen atoms on R, R1, or R2 may be substituted with: optionally substituted C1-C6 alkyl groups, optionally substituted C1-C6 alkoxy groups, optionally substituted C2-C6 alkyl groups, or optionally substituted C2-C6 alkoxy groups. 10 alkenyl; optionally substituted C2-C 10 Alkynyl; optionally substituted alkylaryl; optionally substituted arylalkyl; optionally substituted aryloxy; optionally substituted heteroaryl; optionally substituted heterocyclic; halogen (e.g., Cl, F, Br, and I); hydroxyl; haloalkyl (e.g., CF3, 2-Br-ethyl, CH2F, CH2CF3, and CF2CF3); haloaryl; haloalkylaryl; halobenzyl; optionally substituted amino; optionally substituted alkylamino; optionally substituted arylamino; optionally substituted acyl; CN; NO2; N3; CH2OH; CONH2; C1-C3 alkylthio; sulfate; sulfonic acid; sulfonate (e.g., methanesulfonyl); phosphonic acid; phosphate; phosphonate; mono-, bis-, or triphosphate; triphenylmethyl or monomethoxytriphenylmethyl; CF3S; CF3SO2; or silyl (e.g., trimethylsilyl, dimethyl-tert-butylsilyl, and diphenylmethylsilyl).

[0093] In some embodiments, the primary or secondary amine may be selected from amines functionalized with fluoroalkyl aryl groups. In specific embodiments, the amine may be selected from the group consisting of: 2-fluorophenylethylamine, 3-fluorophenylethylamine, 4-fluorophenylethylamine, 2-fluoro-N-methylbenzylamine, 3-fluoro-N-methylbenzylamine, and 4-fluoro-N-methylbenzylamine, 2-fluorobenzylamine, 3-fluorobenzylamine, 4-fluorobenzylamine, 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecanodecylamine, 2,3-difluorobenzylamine, 2,4-difluorobenzylamine, 2,6-difluorobenzylamine, 3,4-difluorobenzylamine, 3,5-difluorobenzylamine, 2-trifluoromethylbenzylamine, 3-trifluoromethylbenzylamine, 4-trifluoromethylbenzylamine, D-4-fluoro-α-methylbenzylamine, and L-4-fluoro-α-methylbenzylamine.

[0094] In some embodiments, the nucleophilic amine that can be used in such a solvent system may include cyclic amines, diamines, and primary and / or secondary alcoholamines. Cyclic amines are amines in which the nitrogen atom forms part of a ring structure, and may include, but are not limited to: aziridine, aziridine, pyrrolidine, piperidine, piperazine, pyridine, and pyrimidine. Cyclic amines may include one or more rings and may optionally be substituted with one or more substituents as described above. In some embodiments, the nitrogen-containing base may be a diamine. In some embodiments, the nitrogen-containing base may be a primary or secondary alcoholamine. Alcoholamines are also called amino alcohols and include both an alcohol and an amino group. The amino group of an alcoholamine may be any type of amine described herein.

[0095] One or more non-nucleophilic nitrogen-containing bases can vary in such solvent systems. In some embodiments, a non-nucleophilic nitrogen-containing base with a low water content (e.g., < about 20% by weight or < about 10% by weight water at 25°C) is used, and which readily forms a separate liquid phase when combined with water. Therefore, preferably, the non-nucleophilic nitrogen-containing base that can be used in such solvent systems can be hydrophobic and / or substantially immiscible with water, wherein “substantially immiscible with water” is the same as described elsewhere in the invention. Example types of non-nucleophilic nitrogen-containing bases that can be used in this type of solvent system are guanidine or substituted guanidine (e.g., fluorinated guanidine), amidine (e.g., fluorinated amidine), or tertiary amine (e.g., fluorinated tertiary amine).

[0096] Guanidine should be understood as a compound having the general formula RNC(NR1R2)2, wherein R, R1, and R2 are independently H or carbon-containing groups, including but not limited to C1-C. 20 Alkyl group. Optionally, one or more hydrogen atoms on R, R1, and / or R2 may be substituted with one or more substituents. For example, one or more hydrogen atoms on R, R1, R2, and R3 may be substituted with: optionally substituted C1-C6 alkyl groups, optionally substituted C1-C6 alkoxy groups, optionally substituted C2-C6 alkyl groups, etc. 10 alkenyl; optionally substituted C2-C 10Alkynyl; optionally substituted alkylaryl; optionally substituted arylalkyl; optionally substituted aryloxy; optionally substituted heteroaryl; optionally substituted heterocyclic; halogen (e.g., Cl, F, Br, and I); hydroxyl; haloalkyl (e.g., CF3, 2-Br-ethyl, CH2F, CH2CF3, and CF2CF3); haloaryl; haloalkylaryl; halobenzyl; optionally substituted amino; optionally substituted alkylamino; optionally substituted arylamino; optionally substituted acyl; CN; NO2; N3; CH2OH; CONH2; C1-C3 alkylthio; sulfate; sulfonic acid; sulfonate (e.g., methanesulfonyl); phosphonic acid; phosphate; phosphonate; mono-, bis-, or triphosphate; triphenylmethyl or monomethoxytriphenylmethyl; CF3S; CF3SO2; or silyl (e.g., trimethylsilyl, dimethyl-tert-butylsilyl, and diphenylmethylsilyl).

[0097] Amidons, including but not limited to carboxamidine / carboximidamide, should be understood as compounds having the structure RC(=NH)NR1R2, wherein R, R1, and R2 are independently H or carbon-containing groups, including but not limited to C1-C. 20 Alkyl group. Optionally, one or more hydrogen atoms on R, R1, and / or R2 may be substituted with one or more substituents. For example, one or more hydrogen atoms on R, R1, R2, and R3 may be substituted with: optionally substituted C1-C6 alkyl groups, optionally substituted C1-C6 alkoxy groups, optionally substituted C2-C6 alkyl groups, etc. 10 alkenyl; optionally substituted C2-C 10 Alkynyl; optionally substituted alkylaryl; optionally substituted arylalkyl; optionally substituted aryloxy; optionally substituted heteroaryl; optionally substituted heterocyclic; halogen (e.g., Cl, F, Br, and I); hydroxyl; haloalkyl (e.g., CF3, 2-Br-ethyl, CH2F, CH2CF3, and CF2CF3); haloaryl; haloalkylaryl; halobenzyl; optionally substituted amino; optionally substituted alkylamino; optionally substituted arylamino; optionally substituted acyl; CN; NO2; N3; CH2OH; CONH2; C1-C3 alkylthio; sulfate; sulfonic acid; sulfonate (e.g., methanesulfonyl); phosphonic acid; phosphate; phosphonate; mono-, bis-, or triphosphate; triphenylmethyl or monomethoxytriphenylmethyl; CF3S; CF3SO2; or silyl (e.g., trimethylsilyl, dimethyl-tert-butylsilyl, and diphenylmethylsilyl).

[0098] Examples of guanidines and amidines include, but are not limited to: 1,1,3,3-tetramethylguanidine (“TMG”); N-tert-butyl-1,1,3,3-tetramethylguanidine, diphenylguanidine, xylenemethylguanidine, 1,8-diazabicyclo(5.4.0)undecyl-7-ene, 1,1,3-trimethyl-3-(2,2,3,3-tetrafluoropropyl)guanidine; 1,1,3-trimethyl-3-(2,2,3,3,3-pentafluoropropyl)guanidine; 1,3-dimethyl-1,3-bis(2,2,2-trifluoroethyl)guanidine ; 1,3-bis(2,2,3,3-tetrafluoropropyl)guanidine; 1,3-bis(4-fluorophenyl)guanidine; 1,3-bis(3-fluorophenyl)guanidine; 1,3-bis(2-fluorophenyl)guanidine; 2-(2,2,2-trifluoroethyl)-1,4,5,6,-tetrahydroxypyrimidine; 2-(2,2,3,3-tetrafluoropropyl)-1,4,5,6,-tetrahydroxypyrimidine; 3,3,4,4-tetrafluoro-N,N-dimethylbutamidine; 3,3,3-trifluoro-N,N-dimethylpropanediamine, and mixtures thereof.

[0099] Tertiary amines should be understood as compounds having the general formula NR1R2R3, wherein R1, R2, and R3 are independently carbon-containing groups, including but not limited to C1-C. 20 Alkyl group. Optionally, one or more hydrogen atoms on R, R1, R2, and R3 may be substituted with one or more substituents. For example, one or more hydrogen atoms on R, R1, R2, and R3 may be substituted with: optionally substituted C1-C6 alkyl groups, optionally substituted C1-C6 alkoxy groups, optionally substituted C2-C6 alkyl groups, etc. 10 alkenyl; optionally substituted C2-C 10 Alkynyl; optionally substituted alkylaryl; optionally substituted arylalkyl; optionally substituted aryloxy; optionally substituted heteroaryl; optionally substituted heterocyclic; halogen (e.g., Cl, F, Br, and I); hydroxyl; haloalkyl (e.g., CF3, 2-Br-ethyl, CH2F, CH2CF3, and CF2CF3); haloaryl; haloalkylaryl; halobenzyl; optionally substituted amino; optionally substituted alkylamino; optionally substituted arylamino; optionally substituted acyl; CN; NO2; N3; CH2OH; CONH2; C1-C3 alkylthio; sulfate; sulfonic acid; sulfonate (e.g., methanesulfonyl); phosphonic acid; phosphate; phosphonate; mono-, bis-, triphosphate; triphenylmethyl or monomethoxytriphenylmethyl; CF3S; CF3SO2; or silyl (e.g., trimethylsilyl, dimethyl-tert-butylsilyl, and diphenylmethylsilyl).

[0100] Some example formulations include, but are not limited to: one or more primary and / or secondary amines, including alkyl fluoroaromatic amines such as 3-fluoro-N-methylbenzylamine, 4-fluoro-N-methylbenzylamine, 2-fluorophenylethylamine, 3-fluorophenylethylamine, and 4-fluorophenylethylamine, which are used in combination with one or more tertiary amines (e.g., fluorinated alcohol tertiary amines), guanidines (e.g., fluorinated guanidines), and / or amidines (e.g., fluorinated amidines).

[0101] In some specific embodiments, this type of solvent system may consist of secondary amines and guanidines, such as... Figure 1 As shown in E). In some embodiments, the prepared solvent (i.e., a mixture comprising one or more nucleophilic amines and one or more non-nucleophilic nitrogen-containing bases) reacts with carbon dioxide to form carbamates (e.g., mixed carbamates). In the reaction product, the nucleophilic amine component forms a carbon-nitrogen bond with CO2 (or another acidic gas), and the non-nucleophilic amine component forms a bond with a hydrogen nucleus (proton). The structure of the formed product is a mixed amine carbamate. The molar ratio of one or more non-nucleophilic amines to one or more nucleophilic amines can cover a wide range. The mixture of nucleophilic and non-nucleophilic bases can improve the kinetics of carbon dioxide absorption and increase the CO2 loading at a given temperature (carbon dioxide vapor-liquid equilibrium) due to the improved thermokinetics. Compared to the conventional use of a single nucleophilic amine to capture CO2 from solution, the mixed solvent in some embodiments absorbs more CO2 at slightly higher temperatures, making the solvent preferably used for CO2 separation from the gas stream within certain temperature ranges.

[0102] Based on the above description and related figures, those skilled in the art will conceive of many modifications and other embodiments of the present invention. Therefore, it should be understood that the present invention is not limited to the specific embodiments described herein, and the various modifications and other embodiments described above are included within the scope defined by the appended claims. Although specific terminology is used in this invention, these terms are used in a general and descriptive sense only and are not intended to limit the invention.

Claims

1. A solvent system comprising a solution formed by a combination of a first nucleophilic amine and the following substances: a) a second nucleophilic amine and two or more non-aqueous liquids, wherein, The solvent system is an ionic liquid, and the nucleophilic amine is an alkylfluoroaromatic amine that reacts with an acidic gas to form one or more of the following substances: carbamates, mixed carbamates, zwitterionic aminosulfonic acids, and sulfates; or b) Nonnucleophilic nitrogenous bases; and proton-nonaqueous liquids, wherein the nonnucleophilic nitrogenous bases and proton-nonaqueous liquids react with an acidic gas to form carbonates or heteroatom analogs of carbonates, and / or a first nucleophilic amine reacts with an acidic gas to form mixed carbamates; or c) One or more non-nucleophilic nitrogen-containing bases, wherein the solvent system reacts with an acidic gas to form a carbamate, a mixture of carbamates, aminosulfonic acid, sulfate, or a combination thereof, wherein the solvent system is free of diluent.

2. The solvent system of claim 1, wherein, The first nucleophilic amine is hydrophobic.

3. The solvent system of claim 1, wherein, The first nucleophilic amine is combined with b) or c), and wherein the non-nucleophilic nitrogenous base is hydrophobic or substantially immiscible with water.

4. The solvent system of claim 1, wherein, The solvent system is essentially immiscible with water.

5. The solvent system of claim 1, wherein, The solvent system has a solubility in water of less than 20 g solvent / 100 mL water.

6. The solvent system of claim 1, wherein, The acid gas includes CO2, SO2, COS, CS2, NO x , or combinations thereof.

7. The solvent system of claim 1, wherein, The acidic gas includes CO2 or SO2.

8. The solvent system of claim 1, wherein, said first nucleophilic amine is combined with b) and wherein said nucleophilic amine is selected from the group consisting of 3-fluoro- N - methylbenzylamine, 4-fluoro- N - methylbenzylamine, 2-fluoro-phenethylamine, 3-fluoro-phenethylamine, 4-fluoro-phenethylamine, and mixtures thereof.

9. The solvent system of claim 1, wherein, The first nucleophilic amine is combined with b), and wherein the non-nucleophilic nitrogenous base is a guanidine or a substituted guanidine.

10. The solvent system as claimed in claim 1, characterized in that, The first nucleophilic amine is combined with b), and wherein the proton-nonaqueous liquid is a fluorinated alcohol having 5 or more carbon atoms.

11. The solvent system of claim 1, wherein, The first nucleophilic amine is combined with c), wherein the first nucleophilic amine comprises a primary or secondary amine, and one or more non-nucleophilic nitrogenous bases comprise tertiary amines, amidines, and / or guanidines.

12. The solvent system of claim 11, wherein, One or more of the primary amine, secondary amine, tertiary amine, guanidine, and amidine are fluorinated.

13. The solvent system of claim 11, wherein, said primary or secondary amine is selected from the group consisting of 3-fluoro- N - methylbenzylamine, 4-fluoro- N - methylbenzylamine, 2-fluorophenethylamine, 3-fluorophenethylamine and 4- fluorophenethylamine.

14. The solvent system of claim 1, wherein, The first nucleophilic amine is combined with c), and the solvent system further comprises one or more other nucleophilic amines.

15. The solvent system of claim 1, wherein, The alkylfluoroaromatic amines are selected from the group consisting of: 3-fluoro- N -Methylbenzylamine, 4-fluoro- N -Methylbenzylamine, 2-fluorophenylethylamine, 3-fluorophenylethylamine and 4-fluorophenylethylamine.

16. The solvent system of claim 1, wherein, The two or more non-aqueous liquids are selected from the group consisting of: 2,2,3,3,4,4,5,5-octafluoropentanol, 3,3,4,4,5,5,6,6-hexafluorobutanol and 4,4,5,5,6,6,7,7,7-nonafluoroheptanol.

17. The solvent system of claim 1, wherein, The first nucleophilic amine is combined with a), and the solvent system further comprises one or more other nucleophilic amines.

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