Amine solvent-based carbon capture compositions

Abstract

A composition for carbon dioxide (CO2) capture includes 2-aminocyclohexanol, cis-1,2-diaminocyclohexane, meglumine, or combinations thereof. A process of CO.sub.2 capture includes mixing a CO.sub.2-containing gas with the composition. A system includes a component for receiving a gas and the composition, which absorbs CO.sub.2 from the gas. A further composition includes a first amine solvent selected from 2-aminocyclohexanol, cis-1,2-diaminocyclohexane, and meglumine and a second amine solvent independently selected from 2-aminocyclohexanol, cis-1,2-diaminocyclohexane, meglumine, ethyl diethanolamine, dimethylethanolamine, piperidine, 2-amino-2-methyl-1-propanol, and monoethanolamine. A further process includes reacting CO.sub.2 with an amine selected from 2-aminocyclohexanol, cis-1,2-diaminocyclohexane, and meglumine.

Claims

1. A process of point-source carbon dioxide (CO2) capture, comprising: mixing a post-combustion gas with a composition comprising cis-1,2-diaminocyclohexane and at least one amine solvent selected from the group consisting of 2-aminocyclohexanol and meglumine.

2. The process of claim 1, wherein the composition is an aqueous solution with a total amine concentration of about 30%.

3. The process of claim 1, wherein the composition is an aqueous solution of the cis-1,2-diaminocyclohexane and the at least one amine solvent.

4. The process of claim 1, wherein the composition further comprises an additional amine solvent selected from the group consisting of methyl diethanolamine, dimethylethanolamine, piperidine, 2-amino-2-methyl-1-propanol, and monoethanolamine.

5. The process of claim 1, wherein the process further comprises obtaining a CO.sub.2-rich amine solution formed by absorption of CO.sub.2 from the post-combustion gas during the mixing.

6. The process of claim 5, wherein the process further comprises removing the absorbed CO.sub.2 from the CO.sub.2-rich amine solution, and wherein the removing regenerates the composition.

7. The process of claim 6, further comprising mixing new post-combustion gas with the regenerated composition.

8. The process of claim 6, wherein the removing comprises mineralizing the absorbed CO.sub.2.

9. The process of claim 6, wherein the removing comprises treating the CO.sub.2-rich amine solution with pressurized steam.

10. A process of point-source carbon dioxide (CO.sub.2) capture, comprising: reacting the CO.sub.2 with a solution comprising cis-1,2-diaminocyclohexane.

11. The process of claim 10, further comprising removing a product of the reacting to regenerate the cis-1,2-diaminocyclohexane.

12. The process of claim 11, wherein the product comprises a carbonate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The drawings included in the present application are incorporated into, and form part of, the Specification. They illustrate embodiments of the present disclosure and, along with the description, serve to explain the principles of the disclosure. The drawings are only illustrative of certain embodiments and do not limit the disclosure.

(2) FIG. 1 is a flowchart illustrating a process of capturing CO.sub.2, according to some embodiments of the present disclosure.

(3) FIG. 2 is a block diagram illustrating a carbon capture environment, according to some embodiments of the present disclosure.

(4) FIG. 3 is a graph plotting experimentally obtained carbon capture capacities and reaction rates for a set of amine solvents.

DETAILED DESCRIPTION

(5) Embodiments of the present disclosure are generally directed to carbon capture technology and, more specifically, to solvent molecules for capturing and reacting with gaseous carbon dioxide (CO.sub.2). While the present disclosure is not necessarily limited to such applications, various aspects of the disclosure may be appreciated through a discussion of examples using this context.

(6) Techniques for reducing atmospheric CO.sub.2 are essential for the goal of limiting the global temperature rise to 1.5 C. by 2050. Point source capture, zero-emission technologies, such as renewables for energy production, and reduced-emission programs are expected to lower emissions (e.g., by about 800-900 Mt/yr). However, these efforts cannot offset CO.sub.2 from long distance travel/cargo transport and certain heavy industries (expected to account for 15+% emissions annually), nor can they remove already-emitted CO.sub.2 from the atmosphere.

(7) Carbon capture (also referred to herein as CO.sub.2 capture) requires selectively removing CO.sub.2 from a gas stream or atmosphere. Current technology for emission control focuses on post-combustion capture of CO.sub.2 from the output gas streams of point-source generators such as power plants and heavy industry. Several technologies have been developed, including selective membranes, solid sorbents (e.g., zeolites, alkaline salts, and alkaline solutions), and aqueous organic amine solutions. For example, amines can capture CO.sub.2 through chemisorption and conversion to a carbamate or carbonate, which can be released by heating or pressure swing.

(8) Existing chemisorption technologies used for point-of-generation capture of about 5-30% by volume can require 2-4 gigajoules (GJ) per metric ton (t) of CO.sub.2. The regeneration energy needed to release the CO.sub.2 from capture reagents dominates the energy costs. As an example, current amine-scrubbing plants use aqueous amine solutions that capture CO.sub.2 at about 25-40 C. and release the CO.sub.2 at about 100-150 C. with flow rates of thousands of tons per hour, thus requiring heating and cooling of significant quantities of fluid. A key chemical challenge remains to produce new molecules that can capture CO.sub.2 and regenerate/release the captured CO.sub.2 with a minimum energy budget.

(9) In commercial systems for carbon capture using amine solutions, the amine solution is a core operation cost. State-of-the-art amine formulations typically employ blends of amines, which can allow cooperative effects between high capacity/slow reacting amines and low capacity/fast reacting amines. Improvements in either amine type can allow better formulations by increasing capture capacity and rate of capture. However, amines are a vast class of chemicals with many sub-classes and usages, from pharmaceuticals and biological processes to fertilizers and carbon capture. In addition to the requirements for sufficiently high capture capacities and reaction rates, amines selected for CO.sub.2 capture formulations must satisfy safety requirements. For example, amines that can negatively impact health and/or the environment when used on an industrial scale may not be appropriate for CO.sub.2 capture processes. Therefore, identifying amines suitable for carbon capture presents significant challenges.

(10) Various embodiments of the present disclosure may be used to overcome these and other challenges. Solvent-based carbon capture requires a trade-off between the reaction rate at which a reaction with CO.sub.2 can occur (reaction kinetics) and the amount of CO.sub.2 that can be sequestered per molecule of capture solvent (capture capacity). Disclosed herein are carbon capture techniques using amine-based compositions. In some embodiments, the compositions include amine solvent molecules that may have both improved reaction kinetics and carbon capture capacity relative to existing carbon capture formulations (e.g., monoethanolamine (MEA) and other amine solvents and mixtures). In some embodiments, the disclosed carbon capture compositions are used in post-combustion solvent-based carbon capture using thermal swing capture.

(11) In some embodiments, the disclosed CO.sub.2-capture solvents can include cis- and/or trans-2-aminocyclohexanol-collectively, 2-aminocyclohexanol, represented by the following structure:

(12) ##STR00001##
In further embodiments, the disclosed compositions can include cis-1,2-diaminocyclohexane, which has the following structure:

(13) ##STR00002##
In additional embodiments, the disclosed compositions can include meglumine, which has the following structure:

(14) ##STR00003##

(15) The amine solvents may also be in a solution (e.g., an aqueous solution) containing at least one of cis-1,2-diaminocyclohexane, 2-aminocyclohexanol, meglumine. The mixture may optionally include at least one additional primary, secondary, and/or tertiary amine. Primary, secondary, and tertiary amine moieties can be generically represented by

(16) ##STR00004##
and

(17) ##STR00005##
respectively, where each starred bond is to a carbon atom.

(18) Further, the disclosed amine solvents may satisfy safety requirements for use in large-scale CO.sub.2 capture. For example, cis-1,2-diaminocyclohexane, 2-aminocyclohexanol, and meglumine are each predicted to have lower toxicities than MEA, which is commonly used for CO.sub.2 capture. That is, median lethal dose (LD.sub.50) values predicted computationally for each of cis-1,2-diaminocyclohexane, 2-aminocyclohexanol, and meglumine are lower than the LD.sub.50 of MEA.

(19) Referring now to the drawings, in which like numerals represent the same or similar elements, FIG. 1 is a flowchart illustrating a process 100 of capturing CO.sub.2, according to some embodiments of the present disclosure. For illustrative purposes, process 100 is discussed with reference to the carbon capture environment 200 of FIG. 2. However, process 100 may be carried out using any appropriate apparatus and techniques consistent with amine-based CO.sub.2 capture. Various types of apparatus may be used in mediating absorption in process 100 (see below). Techniques for gas-liquid mass transfer known to those of ordinary skill may be employed, and parameters such as flow rates, temperatures, concentrations, residence times, packing or tray types, nozzle design, droplet size (in spray methods) can be tuned.

(20) FIG. 2 is a block diagram illustrating a simplified carbon capture environment 200, according to some embodiments of the present disclosure.

(21) An amine composition 205 that includes at least one solvent selected from 2-aminocyclohexanol, cis-1,2-diaminocyclohexane, and meglumine is provided. This is illustrated at operation 110. In some embodiments, the amine composition 205 is an aqueous solution of at least one of the amine solvent(s) cis-1,2-diaminocyclohexane, 2-aminocyclohexanol, and meglumine. The amine composition 205 may be an aqueous solution of the amine solvent(s) with about 5-40% amine (e.g., 5-30% or 20-40% amine). Herein, concentrations (% amine) refer to weight percent (% w/w) unless otherwise noted. by weight (w/w) may be used as well. In some embodiments, the amine composition 205 may be an aqueous solution of about 33% cis-1,2-diaminocyclohexane, 2-aminocyclohexanol, and/or meglumine. The amine composition 205 may optionally include at least one additional primary, secondary, and/or tertiary amine. In some embodiments, the amine composition 205 is an aqueous solution with a total amine solvent concentration of about 5-40%, 5-30%, 20-40%, or any other appropriate solvent concentration.

(22) Amines that can be blended with 1,2-diaminocyclohexane, 2-aminocyclohexanol, and/or meglumine in the amine composition 205 may include methyl diethanolamine (MDEA), dimethylethanolamine (DMEA), piperidine, 2-amino-2-methyl-1-propanol, MEA, or any other suitable amine. For example, the amine composition 205 may include a mixture of about 1-20% 1,2-diaminocyclohexane, 2-aminocyclohexanol, and/or meglumine combined with about 99-80% MDEA or DMEA. In some embodiments, the amine composition 205 includes about 5-40% of the mixture in an aqueous solution.

(23) The amine composition 205 can be mixed with a CO.sub.2-containing gas (feed gas 210). This is illustrated at operation 120. For example, the feed gas 210 can be directed into an absorption component 220 containing the amine composition 205. When the feed gas 210 enters the absorption component 220, the CO.sub.2 can be absorbed by the amine solvent molecules of the amine composition 205. For example, the amine solvents can act as activators in a post-combustion scrubbing formulation consistent with formulations known in the art.

(24) The absorption component 220 may be a trayed adsorption column. In these instances, the feed gas 210 may be continuously introduced at the bottom of the column while a CO.sub.2-absorbing liquid (the amine composition 205) is introduced at the top of the column. As the gas and liquid phases mix in the column, the gas can percolate on trays positioned in the column to allow sufficient residence time for gas absorption into the liquid phase. The gas remaining (treated gas) after CO.sub.2 is absorbed from the feed gas 210 can then be collected at the top of the column, and the CO.sub.2-containing amine composition 205 (enriched amine) can be collected at the bottom of the column for further downstream processing. Downstream processing is discussed in greater detail below with respect to operation 130.

(25) In some embodiments, the absorption component 220 may be a spray tower or a spray dryer. In a spray tower, the amine composition 205 can be sprayed from the top of the tower into the feed gas 210. When a spray dryer is used, a controlled mist of the amine composition 205 can be introduced into a tower or column concurrently with the feed gas 210. In the spray dryer, both the amine composition 205 and the feed gas 210 may be heated to ensure evaporation of the liquid phase. In either the spray tower or the spray dryer, the enriched amine can then be collected (e.g., at the bottom of the tower/column) for further downstream processing.

(26) The captured CO.sub.2 can be transferred and/or stored as CO.sub.2 or a product of CO.sub.2 activation. This is illustrated at operation 130. At operation 130, the amine composition 205 may be regenerated upon transfer of the captured CO.sub.2. FIG. 2 illustrates captured CO.sub.2 being released from a regeneration component (regenerator) 230 as a CO.sub.2 product. In some embodiments, the CO.sub.2 product is gaseous or liquid carbon dioxide. In these instances, operation 130 may include heating and/or changing the pressure of the enriched amine, causing the CO.sub.2 to be released from the solution and collected. For example, the enriched amine can be pumped to the regenerator 230 (e.g., a stripping column), which applies pressurized steam to release the captured CO.sub.2 from the enriched amine and regenerate the amine solution (lean amine), which is then returned to the absorption component 220.

(27) In further embodiments, the CO.sub.2 product may be a reaction product formed by activation of the captured CO.sub.2. For example, CO.sub.2 can be activated by the amine solvent molecules and reacted to form carbonate or carbamate products. These products may be minerals, organic molecules, polymers, etc. For example, the CO.sub.2 product may be a mineral formed by reacting the absorbed/activated CO.sub.2 with a metal halide (MX or MX.sub.2), such as a metal chloride where M is sodium, potassium, magnesium, calcium, etc. This can result in mineralization of the CO.sub.2, wherein a bicarbonate (MHCO.sub.3) or carbonate (MCO.sub.3) is formed by the reaction. For example, sodium bicarbonate (NHCO.sub.3) can form when MX is NaCl, calcium carbonate (CaCO.sub.2) can form when MX.sub.2 is CaCl.sub.2.Math.2H.sub.2O, and magnesium carbonate (MgCO.sub.3) can form when MX.sub.2 is MgCl.sub.2. The solid (bi)carbonate can be removed from the solution by filtration, resulting in the regenerated composition 205 (lean amine).

(28) In some embodiments, the regenerated amine composition 205 formed at operation 130 can be reused to capture CO.sub.2 from new feed gas 210. In these instances, process 100 can return to operation 120 after regeneration at operation 130. Additional cycles of operations 120 and 130 may be carried out as well, e.g., where feed gas 210 is continuously introduced at operation 120. In other embodiments, process 100 may end after operation 130.

(29) FIG. 3 is a graph 300 illustrating experimentally obtained carbon capture capacities (moles CO.sub.2/mole amine) and corresponding reaction rates (per second) of a set of amines. The graph 300 plots experimental results obtained by monitoring a set of reactions between CO.sub.2 and ninety-nine different amines, including MEA, 2-aminocyclohexanol, cis-1,2-diaminocyclohexane, and meglumine.

(30) The measurement principle illustrated in FIG. 2 is that CO.sub.2 lost in an exhaust stream (e.g., feed gas 110) is absorbed in an amine solution (e.g., amine composition 205). Quantification of the gas content as a function of time t and integration affords the amount of CO.sub.2 absorbed and, therefore, capture capacity a (moles CO.sub.2/mole amine) of the amine. In theory, an optimal capture capacity a is 0.5 per amine group. Therefore, an ideal carbon capture solvent may sit at the top right of this graph 200 (e.g., by capturing more than one CO.sub.2 molecule per molecule of amine (A>0.5) at a fast rate). The mean capture capacity of the 99 points plotted in FIG. 2 is =0.43. The distribution of the plotted capture capacities is multimodal, with populations centered around =0.0, 0.27, and 0.49, as well as a low-sampled population at =1.0.

(31) The data shown in FIG. 2 was obtained by testing the ninety-nine aqueous amine solutions for CO.sub.2 absorption based on infrared (IR) absorbance. The amine solutions were each prepared by dissolving the amine in water at a concentration of about 30% amine, by weight (w/w), as this concentration is typical in currently deployed industrial offerings. Nominally 200 L samples of the amine solutions were held at about 40 C. using a 200 mL water bath, this temperature chosen to fit that of a typical industrial CO.sub.2 absorption unit. An approximately 10 SCCM (standard cubic centimeters per minute, equivalent to 1.67.Math.10.sup.7 m.sup.3.Math.s.sup.1), gas stream was bubbled into each amine solution and the exhaust gas analyzed for CO.sub.2 at the 4.3 m absorption band. Run times for the monitored reactions varied from 5-120 minutes.

(32) A 3.9 m reference band was used to account for slight attenuation due to humidity and signal drift. The absorption signal was calibrated against atmosphere (414 ppm CO.sub.2), CO.sub.2 balance nitrogen calibration gas (9.96% CO.sub.2, by volume, or 10% v/v), and substantially pure CO.sub.2 gas, as a function of flow rate q=2-40 SCCM. Aqueous MEA (30% w/w) was used as a calibrant as it has a well-established capture capacity a 0.50. The estimated measurement apparatus delay time was 0.16 min, and control experiments with water alone measured a background absorption of 20 mol CO.sub.2.

(33) Analysis of the time progression of the 4.3 m CO.sub.2 absorption signal afforded information on the relative speeds of the CO.sub.2 capture reactions. For slow-reacting samples, the kinetics of the reaction could be followed through a majority of the run and, therefore, the initial observed rate could be quantified by fitting/extrapolating back to t=0. For fast-reacting amines, including MEA, the CO.sub.2 absorbance rate was faster than the feed rate (flow rate q), leading to a period of saturation in the signal wherein substantially all of the CO.sub.2 gas was absorbed by the amine and, thus, could not be measured in the gas stream. In these instances, the initial observed rate could not be extrapolated and was substituted with a breakthrough time to, which was defined as the time the signal stayed in saturation before signal roll off. The breakthrough time to can roughly be considered a surrogate for reaction time because the fast-reacting amines typically have short transitions from saturation to baseline (e.g., no CO.sub.2 absorption), leaving most of the CO.sub.2 absorption occurring during saturation.

(34) The results measured for 2-aminocyclohexanol, cis-1,2-diaminocyclohexane, and meglumine are indicated by arrows from the structures to corresponding data points on the graph 200 in FIG. 1. The measured CO.sub.2 capture capacities (CO.sub.2 Capacity in moles CO.sub.2/mole amine) and reaction rates (s.sup.1) are also shown in Table 1. Additionally, for reference, the results observed with MEA are shown in Table 1. As shown in Table 1, each of the disclosed carbon capture amine solvents demonstrated a larger CO.sub.2 capture capacity, and faster rate of reaction with CO.sub.2, than MEA.

(35) TABLE-US-00001 TABLE 1 Amine CO.sub.2 Capacity Reaction Rate Monoethanolamine (MEA) 0.55 0.13 2-Aminocyclohexanol 0.75 0.35 Meglumine 0.71 0.20 cis-1,2-Diaminocyclohexane 0.56 1.69

(36) Various embodiments of the present disclosure are described herein with reference to the related drawings, where like numbers refer to the same component. Alternative embodiments can be devised without departing from the scope of the present disclosure. It is noted that various connections and positional relationships (e.g., over, below, adjacent, etc.) are set forth between elements in the following description and in the drawings. These connections and/or positional relationships, unless specified otherwise, can be direct or indirect, and the present disclosure is not intended to be limiting in this respect. Accordingly, a coupling of entities can refer to either a direct or an indirect coupling, and a positional relationship between entities can be a direct or indirect positional relationship. As an example of an indirect positional relationship, references in the present description to forming layer A over layer B include situations in which one or more intermediate layers (e.g., layer C) is between layer A and layer B as long as the relevant characteristics and functionalities of layer A and layer B are not substantially changed by the intermediate layer(s).

(37) The following definitions and abbreviations are to be used for the interpretation of the claims and the specification. As used herein, the terms comprises, comprising, includes, including, has, having, contains or containing, or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, a mixture, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but can include other elements not expressly listed or inherent to such composition, mixture, process, method, article, or apparatus. Further, the word providing as used herein can refer to various actions such as creating, purchasing, obtaining, synthesizing, making available, etc. or combinations thereof.

(38) As used herein, the articles a and an preceding an element or component are intended to be nonrestrictive regarding the number of instances (i.e., occurrences) of the element or component. Therefore, a or an should be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously meant to be singular.

(39) As used herein, the terms invention or present invention are non-limiting terms and not intended to refer to any single aspect of the particular invention but encompass all possible aspects as described in the specification and the claims.

(40) Unless otherwise noted, ranges (e.g., time, concentration, temperature, etc.) indicated herein include both endpoints and all numbers between the endpoints. Unless specified otherwise, the use of a tilde () or terms such as about, substantially, approximately, slightly less than, and variations thereof are intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, about can include a range of +8% or 5%, or 2% of a given value, range of values, or endpoints of one or more ranges of values. Unless otherwise indicated, the use of terms such as these in connection with a range applies to both ends of the range (e.g., approximately 1-5 g should be interpreted as approximately 1 g-approximately 5 g) and, in connection with a list of ranges, applies to each range in the list (e.g., about 1-5 g, 5-10 g, etc. should be interpreted as about 1 g-about 5 g, about 5 g-about 10 g, etc.).

(41) As discussed above, CPIs and other compounds herein include R groups (e.g., R, R, and Rx, where x is an integer), which can be any appropriate organic substituent known to persons of ordinary skill. In some embodiments, the R groups can include substituted or unsubstituted aliphatic groups. As used herein, the term aliphatic encompasses the terms alkyl, alkenyl, and alkynyl.

(42) As used herein, an alkyl group refers to a saturated aliphatic hydrocarbon group containing from 1 to 20 (e.g., 2 to 18, 2 to 8, 2 to 6, or 2 to 4) carbon atoms. An alkyl group can be straight, branched, cyclic, or any combination thereof. Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-heptyl, or 2-ethylhexyl. An alkyl group can be substituted with one or more substituents or can be multicyclic as set forth below. Unless specified otherwise, the term alkyl, as well as derivative terms such as alkoxy and thioalkyl, as used herein, include within their scope, straight chain, branched chain, and cyclic moieties.

(43) As used herein, an alkenyl group refers to an aliphatic carbon group that contains from 2 to 20 (e.g., 2 to 18, 2 to 8, 2 to 6, or 2 to 4) carbon atoms and at least one double bond. Like an alkyl group, an alkenyl group can be straight, branched, or cyclic, or any combination thereof. Examples of an alkenyl group include, but are not limited to, allyl, isopropenyl, 2-butenyl, and 2-hexenyl. An alkenyl group can be substituted with one or more substituents as set forth below.

(44) As used herein, an alkynyl group refers to an aliphatic carbon group that contains from 2 to 20 (e.g., 2 to 18, 2 to 8, 2 to 6, or 2 to 4) carbon atoms and has at least one triple bond. Like an alkyl group, an alkynyl group can be straight, branched, or cyclic, or any combination thereof. Examples of an alkynyl group include, but are not limited to, propargyl and butynyl. An alkynyl group can be substituted with one or more substituents as set forth below.

(45) The term alkylthio includes straight-chain alkylthio, branched-chain alkylthio, cycloalkylthio, cyclic alkylthio, heteroatom-unsubstituted alkylthio, heteroatom-substituted alkylthio, heteroatom-unsubstituted Cn-alkylthio, and heteroatom-substituted Cn-alkylthio. In some embodiments, lower alkylthios are contemplated.

(46) The term haloalkyl refers to alkyl groups substituted with from one up to the maximum possible number of halogen atoms. The terms haloalkoxy and halothioalkyl refer to alkoxy and thioalkyl groups substituted with from one up to five halogen atoms.

(47) As described herein, compounds of the present disclosure can optionally be substituted with one or more substituents, such as are illustrated generally above, or as exemplified by particular classes, subclasses, and species of the present disclosure. Each substituent of a specific group may further be substituted with one to three of, for example, halogen, cyano, sulfonyl, sulfinyl, carbonyl, oxoalkoxy, hydroxy, amino, nitro, aryl, haloalkyl, and alkyl. For instance, an alkyl group can be substituted with alkyl sulfonyl and the alkyl sulfonyl can be optionally substituted with one to three of halogen, cyano, sulfonyl, sulfinyl, carbonyl, oxoalkoxy, hydroxy, amino, nitro, aryl, haloalkyl, and alkyl.

(48) In general, the term substituted refers to the replacement of hydrogen radicals in a given structure with the radical of a specified substituent. Specific substituents are described above in the definitions and below in the description of compounds and examples thereof. Unless otherwise indicated, an optionally substituted group can have a substituent at each substitutable position of the group, and when more than one position in any given structure can be substituted with more than one substituent selected from a specified group, the substituent can be either the same or different at every position. A ring substituent, such as a hetero cycloalkyl, can be bound to another ring, such as a cycloalkyl, to form a spiro-bicyclic ring system, e.g., both rings share one common atom. As one of ordinary skill in the art will recognize, combinations of substituents envisioned by this present disclosure are those combinations that result in the formation of stable or chemically feasible compounds.

(49) Modifications or derivatives of the disclosed compounds are contemplated as being useful with the methods and compositions of the present disclosure. Derivatives may be prepared, and the properties of such derivatives may be assayed for their desired properties by any method known to those of skill in the art. In certain aspects, derivative refers to a chemically modified compound that still retains the desired effects of the compound prior to the chemical modification.

(50) The descriptions of the various embodiments of the present disclosure have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments described. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments described herein.