METHODS AND SYSTEMS FOR THE ELECTROCHEMICAL REDUCTION OF CARBON DIOXIDE USING SWITCHABLE POLARITY MATERIALS
20200255958 ยท 2020-08-13
Inventors
- Tedd E. Lister (Bangor, ME, US)
- Eric J. Dufek (Ammon, ID, US)
- AARON D. WILSON (IDAHO FALLS, ID, US)
- Luis A. Diaz Aldana (Idaho Falls, ID, US)
- BIRENDRA ADHIKARI (AMMON, ID, US)
- Ningshengjie Gao (Idaho Falls, ID, US)
Cpc classification
Y02P20/151
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
C25B15/08
CHEMISTRY; METALLURGY
Y02E60/36
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
Y02C20/40
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
C25B11/051
CHEMISTRY; METALLURGY
International classification
Abstract
A method of electrochemically reducing CO.sub.2 comprises introducing a first feed stream comprising H.sub.2O to a positive electrode of an electrolysis cell comprising the positive electrode, a negative electrode, and a proton conducting membrane. A second feed stream comprising a solvent and a non polar form of a switchable polarity material is directed into a CO.sub.2 capture apparatus. A third feed stream comprising CO.sub.2 is directed into the CO.sub.2 capture apparatus to interact with the second feed stream and form a first product stream comprising the solvent and a polar form of the switchable polarity material. The first product stream is introduced to the negative electrode. A potential difference is applied between the positive electrode and the negative electrode to convert the polar form of the switchable polarity material into CO.sub.2 and the non-polar form and to form products from the CO.sub.2 and the solvent. A CO.sub.2 treatment system is also described.
Claims
1. A method of electrochemically reducing CO.sub.2, comprising: introducing a first feed stream comprising H.sub.2O to a positive electrode of an electrolysis cell comprising the positive electrode, a negative electrode, and a proton-conducting membrane between the positive electrode and the negative electrode; directing a second feed stream comprising a solvent and a non-polar form of a switchable polarity material into a CO.sub.2 capture apparatus; directing a third feed stream comprising CO.sub.2 into the CO.sub.2 capture apparatus to interact with the second feed stream and form a first product stream comprising the solvent and a polar form of the switchable polarity material; introducing the first product stream to the negative electrode of the electrolysis cell; and applying a potential difference between the positive electrode and the negative electrode of the electrolysis cell to generate hydrogen ions from the H.sub.2O that diffuse through the proton-conducting membrane to convert the polar form of the switchable polarity material into CO.sub.2 and the non-polar form of the switchable polarity material and to form one or more products from the produced CO.sub.2 and the solvent.
2. The method of claim 1, further comprising: selecting the solvent of the second feed stream to comprise H.sub.2O; and selecting the non-polar form of the switchable polarity material of the second feed stream to comprise one or more of a tertiary amine compound, an amidine compound, and a guanidine compound.
3. The method of claim 2, wherein directing a third feed stream comprising CO.sub.2 into the CO.sub.2 capture apparatus comprises to interact with the second feed stream and form a first product stream comprises reacting the CO.sub.2 of the third feed stream with the H.sub.2O and the one or more of a tertiary amine compound, an amidine compound, and a guanidine compound of the second feed stream to form one or more an aminium bicarbonate, an amidinium bicarbonate, and a guanidinium bicarbonate.
4. The method of claim 1, further comprising selecting the CO.sub.2 capture apparatus to comprise a gas diffusion membrane apparatus.
5. The method of claim 1, further comprising selecting the electrolysis cell to further comprise a porous buffer structure between the proton-conducting membrane and the negative electrode.
6. The method of claim 5, further comprising selecting the porous buffer structure to comprise a polymeric fabric.
7. The method of claim 1, further comprising: selecting the proton-conducting membrane of the electrolysis cell to comprise a suflonated tetrafluoroethylene-based flouropolymer-coplymer material; selecting the positive electrode of the electrolysis cell to comprise one or more of Pt, Ti, and an alloy thereof; and selecting the negative electrode of the electrolysis cell to comprise a metal-coated carbon material.
8. The method of claim 7, wherein selecting the negative electrode of the electrolysis cell to comprise a metal-coated carbon material comprises selecting the negative electrode to comprise reticulated vitreous carbon coated with metallic particles comprising one or more of Ag, Cu, Pb, Sn, Zn, Au.
9. The method of claim 1, further comprising: directing a second product stream comprising the non-polar form of the switchable polarity material and the one or more products away from the electrolysis cell and into a separation apparatus; and separating a gaseous phase of the second product stream from a liquid phase of the second product stream within the separation apparatus, the liquid phase comprising the non-polar form of the switchable polarity material.
10. The method of claim 9, further comprising directing the separated liquid phase of the second product stream into the CO.sub.2 capture apparatus to interact with additional CO.sub.2 in the CO.sub.2 capture apparatus and form an additional amount of the polar form of the switchable polarity material.
11. A method of electrochemically reducing CO.sub.2, comprising: reacting gaseous CO.sub.2 with a mixture of at least one tertiary amine and H.sub.2O to form an aqueous tertiary aminium bicarbonate solution; introducing the aqueous tertiary aminium bicarbonate solution to a negative electrode of an electrolysis cell while introducing additional H.sub.2O to a positive electrode of the electrolysis cell, the electrolysis cell comprising the negative electrode, the positive electrode, a proton-conductive membrane between the negative electrode and the positive electrode, and a buffer structure between the negative electrode and the proton-conductive membrane; and activating the electrolysis cell to convert a portion of the aqueous tertiary aminium bicarbonate solution into a synthesis gas comprising CO and H.sub.2.
12. The method of claim 11, wherein reacting gaseous CO.sub.2 with a mixture of at least one tertiary amine and H.sub.2O to form at aqueous tertiary aminium bicarbonate solution comprising reacting the gaseous CO.sub.2 with 1-cyclohexylpiperidine and liquid H.sub.2O to form an aqueous 1-cyclohexylpiperidinium bicarbonate solution.
13. The method of claim 11, wherein activating the electrolysis cell comprises applying a potential difference between the positive electrode and the negative electrode to generate hydrogen ions from the additional H.sub.2O that diffuse through the proton-conducting membrane and into the aqueous tertiary aminium bicarbonate solution at the negative electrode to form a multi-phase mixture comprising a gaseous phase including the synthesis gas and a liquid phase including the at least one tertiary amine.
14. The method of claim 11, further comprising: separating the synthesis gas from a liquid material comprising 1-cyclohexylpiperidine and liquid H.sub.2O; and reacting the liquid material with additional CO.sub.2 to form an additional aqueous tertiary aminium bicarbonate solution.
15. A CO.sub.2 treatment system, comprising: an H.sub.2O source; a CO.sub.2 source; a source of a non-polar form of a switchable polarity material; a CO.sub.2 capture apparatus downstream of the CO.sub.2 source and the source of the non-polar form of the switchable polarity material, the CO.sub.2 capture apparatus configured to effectuate the formation of a polar form of the switchable polarity material from reactions between CO.sub.2 and the non-polar form of the switchable polarity material; and an electrochemical apparatus downstream of the CO.sub.2 capture apparatus and the H.sub.2O source, the electrochemical apparatus comprising: a housing structure configured and positioned to receive an H.sub.2O stream from the H.sub.2O source into a first region of an internal chamber thereof and to receive another stream comprising the polar form of the switchable polarity material from the CO.sub.2 capture apparatus into a second region of the internal chamber thereof; and an electrolysis cell within the internal chamber of the housing structure, and comprising: a positive electrode adjacent the first region of the internal chamber; a negative electrode adjacent the second region of the internal chamber; and a proton-conducting membrane between the positive electrode and the negative electrode.
16. The CO.sub.2 treatment system of claim 15, wherein the CO.sub.2 source comprises one or more of a hydrocarbon combustion apparatus and a biomass gasification apparatus.
17. The CO.sub.2 treatment system of claim 15, wherein the source of the non-polar form of a switchable polarity material comprises a storage vessel containing one or more of a tertiary amine compound, an amidine compound, and a guanidine compound.
18. The CO.sub.2 treatment system of claim 15, wherein the CO.sub.2 capture apparatus comprises a gas diffusion membrane apparatus.
19. The CO.sub.2 treatment system of claim 15, wherein the electrolysis cell further comprises a porous buffer structure between the proton-conducting membrane and the negative electrode.
20. The CO.sub.2 treatment system of claim 19, wherein the porous buffer structure comprises a polyester fabric.
21. The CO.sub.2 treatment system of claim 15, wherein: the positive electrode comprises one or more of Pt and Ti; the negative electrode comprises an Ag-coated carbon material; and the proton-conducting membrane comprises a suflonated tetrafluoroethylene-based flouropolymer-coplymer membrane.
22. The CO.sub.2 treatment system of claim 15, further comprising a separation apparatus downstream of the electrochemical apparatus and upstream of the CO.sub.2 capture apparatus.
23. The CO.sub.2 treatment system of claim 22, wherein the separation apparatus is configured to separate a gaseous phase of a multi-phase stream received thereby from at least one liquid phase of the multi-phase stream.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0010]
[0011]
[0012]
[0013]
[0014]
DETAILED DESCRIPTION
[0015] Methods and systems for electrochemically reducing CO.sub.2 are disclosed. In some embodiments, a method of electrochemically reducing CO.sub.2 includes reacting CO.sub.2 with a mixture of a solvent (e.g., H.sub.2O) and a non-polar form of at least one switchable polarity material (e.g., a tertiary amine compound, an amidine compound, a guanidine compound) to effectively capture the CO.sub.2 as a bicarbonate ion (HCO.sub.3.sup.) of a polar form of the at least one switchable polarity material (e.g., a tertiary aminium bicarbonate compound, an amidinium bicarbonate compound, a guanidinium bicarbonate compound). A switchable polarity material solution including the polar form of the switchable polarity material and the solvent is directed into an electrochemical apparatus including at least one electrolysis cell therein. The electrolysis cell comprises positive electrode (anode), a negative electrode (cathode), and a proton-conducting membrane between the positive electrode and the negative electrode. The switchable polarity material solution is provided to the negative electrode side of the electrolysis cell while H.sub.2O is provided to the positive electrode side of the electrolysis cell. Electrical current is applied to the H.sub.2O across the positive electrode and the negative electrode of the electrolysis cell to generate O.sub.2 gas, hydrogen ions (H.sup.+) (i.e., protons), and electrons (e.sup.). The generated H.sup.+ permeate across the proton-conducting membrane of the electrolysis cell, and portion of generated H.sup.+ react with polar form of the switchable polarity material at or near the negative electrode to produce CO.sub.2 and the non-polar form of the switchable polarity material. The produced CO.sub.2 and solvent (e.g., H.sub.2O) at or near the negative electrode then undergo electrochemical reduction through reactions with received e.sup. and an additional portion of the generated H.sup.+ to form one or more desirable products (e.g., a synthesis gas (syngas) including carbon monoxide (CO) gas and hydrogen (H.sub.2) gas). A multi-phase mixture including a gaseous phase including one or more gases (e.g., CO, H.sub.2, CO.sub.2), and at least one liquid phase including one or more liquids (e.g., the non-polar form of the switchable polarity material, remaining polar form of the switchable polarity material, remaining liquid solvent) may exit the electrochemical apparatus, and may be directed into a separation device to separate the gaseous phase from the liquid phase. The separated liquid phase may be introduced to additional CO.sub.2 to form an additional amount of the non-polar form of the switchable polarity material, which may be used to repeat the process. The methods, systems, and apparatuses of the disclosure may be more efficient (e.g., increasing material conversion efficiency; reducing equipment, material, and/or energy requirements; etc.), and/or less complicated as compared to conventional methods, conventional systems, and conventional apparatuses for capturing CO.sub.2 and synthesizing desirable materials therefrom.
[0016] The following description provides specific details, such as material compositions and processing conditions (e.g., temperatures, pressures, flow rates, etc.) in order to provide a thorough description of embodiments of the disclosure. However, a person of ordinary skill in the art will understand that the embodiments of the disclosure may be practiced without necessarily employing these specific details. Indeed, the embodiments of the disclosure may be practiced in conjunction with conventional systems and methods employed in the industry. In addition, only those process components and acts necessary to understand the embodiments of the present disclosure are described in detail below. A person of ordinary skill in the art will understand that some process components (e.g., pipelines, line filters, valves, temperature detectors, flow detectors, pressure detectors, and the like) are inherently disclosed herein and that adding various conventional process components and acts would be in accord with the disclosure. In addition, the drawings accompanying the disclosure are for illustrative purposes only, and are not meant to be actual views of any particular material, device, or system.
[0017] As used herein, spatially relative terms, such as beneath, below, lower, bottom, above, upper, top, front, rear, left, right, and the like, may be used for ease of description to describe one element's or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Unless otherwise specified, the spatially relative terms are intended to encompass different orientations of the materials in addition to the orientation depicted in the figures. For example, if materials in the figures are inverted, elements described as below or beneath or under or on bottom of other elements or features would then be oriented above or on top of the other elements or features. Thus, the term below can encompass both an orientation of above and below, depending on the context in which the term is used, which will be evident to one of ordinary skill in the art. The materials may be otherwise oriented (e.g., rotated 90 degrees, inverted, flipped) and the spatially relative descriptors used herein interpreted accordingly.
[0018] As used herein, the singular forms a, an, and the are intended to include the plural forms as well, unless the context clearly indicates otherwise.
[0019] As used herein, and/or includes any and all combinations of one or more of the associated listed items.
[0020] As used herein, the term configured refers to a size, shape, material composition, material distribution, and arrangement of one or more of at least one structure and at least one apparatus facilitating operation of one or more of the structure and the apparatus in a pre-determined way.
[0021] As used herein, the term substantially in reference to a given parameter, property, or condition means and includes to a degree that one of ordinary skill in the art would understand that the given parameter, property, or condition is met with a degree of variance, such as within acceptable manufacturing tolerances. By way of example, depending on the particular parameter, property, or condition that is substantially met, the parameter, property, or condition may be at least 90.0% met, at least 95.0% met, at least 99.0% met, at least 99.9% met, or even 100.0% met.
[0022] As used herein, the term about in reference to a given parameter is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the given parameter).
[0023] As used herein, the term negative electrode means and includes an electrode having a relatively lower electrode potential in an electrochemical cell (i.e., lower than the electrode potential in a positive electrode therein). Conversely, as used herein, the term positive electrode means and includes an electrode having a relatively higher electrode potential in an electrochemical cell (i.e., higher than the electrode potential in a negative electrode therein).
[0024] As used herein the term electrolyte means and includes an ionic conductor, which can be in a solid state, a liquid state, or a gas state (e.g., plasma).
[0025] As used herein, the term compatible means that a material does not undesirably react, decompose, or absorb another material, and also that the material does not undesirably impair the chemical and/or mechanical properties of the another material.
[0026] An embodiment of the disclosure will now be described with reference to
[0027] With continued reference to
[0028] As shown in
[0029] A single (e.g., only one) H.sub.2O stream 124 my exit the H.sub.2O source 102, or multiple (e.g., more than one) H.sub.2O streams 124 may exit the H.sub.2O source 102. If multiple H.sub.2O streams 124 exit the H.sub.2O source 102, each of the multiple H.sub.2O streams 124 may exhibit substantially the same properties (e.g., substantially the same material composition, substantially the same temperature, substantially the same pressure, substantially the same flow rate, etc.), or at least one of the multiple H.sub.2O streams 124 may exhibit one or more different properties (e.g., a different material composition, a different temperature; a different pressure; a different flow rate; etc.) than at least one other of the multiple H.sub.2O streams 124.
[0030] With continued reference to
[0031] At least one CO.sub.2 stream 128 including CO.sub.2 (e.g., gaseous CO.sub.2, liquid CO.sub.2) exits the CO.sub.2 source 104, and may be directed into the CO.sub.2 capture apparatus 106. In some embodiments, the CO.sub.2 stream 128 is formed of and includes gaseous CO.sub.2. The CO.sub.2 stream 128 may only include CO.sub.2 (e.g., only gaseous CO.sub.2), or may include CO.sub.2 and one or more other materials (e.g., one or more of N.sub.2; H.sub.2; CO; lower hydrocarbon(s), such as methane, ethane, and/or propane; inert material(s), such as a noble gas; materials to be reacted with CO.sub.2 electrochemical reduction products within the electrochemical apparatus 108 to form desired products; etc.). In some embodiments, the CO.sub.2 stream 128 is substantially free of materials other than CO.sub.2 gas. One or more apparatuses (e.g., heat exchangers, pumps, compressors, expanders, mass flow control devices, etc.) may be employed within the CO.sub.2 treatment system 100 to adjust the one or more of the temperature, pressure, and flow rate of the CO.sub.2 stream 128 delivered into the CO.sub.2 capture apparatus 106.
[0032] A single (e.g., only one) CO.sub.2 stream 128 may be directed into the CO.sub.2 capture apparatus 106, or multiple (e.g., more than one) CO.sub.2 streams 128 may be directed into the CO.sub.2 capture apparatus 106. If multiple CO.sub.2 streams 128 are directed into the CO.sub.2 capture apparatus 106, each of the multiple CO.sub.2 streams 128 may exhibit substantially the same properties (e.g., substantially the same material composition, substantially the same temperature, substantially the same pressure, substantially the same flow rate, etc.), or at least one of the multiple CO.sub.2 streams 128 may exhibit one or more different properties (e.g., a different material composition, a different temperature, a different pressure, a different flow rate, etc.) than at least one other of the multiple CO.sub.2 streams 128.
[0033] Still referring to
[0034] The non-polar form of the SPM may comprise one or more of an amine compound (e.g., a tertiary amine compound), an amidine compound, and a guanidine compound. The general structure of each of an amine compound, an amidine compound, and a guanidine compound is, respectively, shown below:
##STR00001##
[0035] where R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are independently hydrogen; a substituted or unsubstituted alkyl group (i.e., linear, branched, or cyclic) containing from 1 carbon atom to 10 carbon atoms; a substituted or unsubstituted C.sub.nSi.sub.m group where n and m are independently an integer from 0 to 10 and n+m is an integer from 1 to 10; and a substituted or unsubstituted aryl group or heteroaryl group that may contain at least one {Si(R.sup.6).sub.2O} where R.sup.6 is a substituted or unsubstituted alkyl, aryl, heteroaryl, or alkoxy group. If a group is substituted, the substituent may be an alkyl, alkenyl, alkynl, alky halide, aryl, aryl halide, heteroaryl, non-aromatic ring, Si(alkyl).sub.3, Si(alkoxy).sub.3, alkoxy, amino, ester, amide, thioether, alkylcarbonate, or thioester group. Optionally, two or more of the R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 groups may form a ring structure (e.g., an alicylic group, or an aryl group) with each other.
[0036] The non-polar form of the SPM may have a nitrogen atom to carbon atom ratio with a range of from about 1:2 to about 1:15. If the non-polar form of the SPM comprises at least one amine compound, the amine compound may comprise a tertiary amine compound fully saturated at the nitrogen position. R.sup.1, R.sup.2, and R.sup.3 in a tertiary amine compound are each independently a moiety (e.g., a substituted or unsubstituted alkyl group; a substituted or unsubstituted aryl group) other than hydrogen. The amine compound may be linear, cyclic, or branched and may include a single nitrogen atom or multiple nitrogen atoms. The amine compound may be a monoamine compound (i.e., a compound including one amino group) or may a polyamine compound (i.e., a compound including two or more amino groups). In some embodiments, the amine compound has as one nitrogen atom and less than or equal to eleven (11) carbon atoms. Non-limiting examples of suitable amine compounds include 1-cyclohexylpiperidine, cyclohexyldimethylamine, 1-butylpyrrolidine, 1-ethylpiperidine, N,N-diethylcyclohexylamine, triethylamine, N,N-dibutylmethylamine, 2-ethyl-hexyl-N,N-dimethylamine, N-benzyldimethylamine, N,N-dimethyl-2-phenylethanamine, N,N-dimethyl-3-phenylpropanamine, N-methyldipropylamine, N-butyldiethylamine, N-butyldimethylamine, N,N-dimethylpentylamine, N-heptyldimethylamine, N,N-dimethyloctylamine, N,N-dimethylnonanamine, N-decyldimethylamine, and N-hexyldimethylamine. Non-limiting examples of suitable amidine compounds include N,N,N-tripropylbutanamidine, N,N,N-tributylpentanamidine, and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). Non-limiting examples of suitable guanidine compounds include 1,1,3,3-tetramethyl-2-phenylguanidine, 2-(2-fluorophenyl)-1,1,3,3-tetramethylguanidine, 1,1,3,3-tetraethyl-2-hexylguanidine, 2-butyl-1,1,3,3-tetraethylguanidine, and 2-hexyl-1,1,3,3-tetramethylguanidine. Suitable amine compounds, amidine compounds, and guanidine compounds are commercially available from numerous sources, such as from Sigma-Aldrich Company (St. Louis, Mo.). In some embodiments, the non-polar form of the SPM comprises 1-cyclohexylpiperidine, which has the following structure:
##STR00002##
[0037] At least one SPM feed stream 130 including a non-polar form of at least one SPM (e.g., one or more of an amine compound, such as a tertiary amine compound; an amidine compound; and a guanidine compound) exits the SPM source 105, and may be directed into the CO.sub.2 capture apparatus 106. The SPM feed stream 130 may be formed of and include the non-polar form of the SPM, at least one solvent, and, optionally, at least one additive. The solvent and the additive (if any) may be included with the non-polar form of the SPM in the SPM source 105, or may be subsequently combined (e.g., mixed) with the non-polar form of the SPM exiting the SPM source 105. In some embodiments, at least the non-polar form of the SPM and the solvent of the SPM feed stream 130 are obtained together from the SPM source 105.
[0038] The solvent of the SPM feed stream 130 may comprise at least one flowable material (e.g., fluid) that is compatible with the other components (e.g., the non-polar form of the SPM) of the SPM feed stream 130, and that facilitates the conversion of CO.sub.2 of the CO.sub.2 stream 128 and the non-polar form of the SPM of the SPM feed stream 130 into one or more desired products (e.g., aminium salts, such as tertiary aminium salts; amidinium salts; guanidinium salts) in the CO.sub.2 capture apparatus 106, as described in further detail below. As used herein, the term compatible means that a material does not undesirably react, decompose, or absorb another material, and also that the material does not undesirably impair the chemical and/or mechanical properties of the another material. The solvent may comprise a liquid material, a gaseous material, or a combination thereof. In some embodiments, the solvent comprises a liquid material. The solvent may, for example, comprise an aqueous liquid material (e.g., substantially pure liquid H.sub.2O, an aqueous liquid solution including liquid H.sub.2O and one or more other materials). In some embodiments, the solvent comprises substantially pure, liquid H.sub.2O.
[0039] The additive (if any) of the SPM feed stream 130 may comprise one or more materials formulated to assist with the production of one or more desirable products from an SPM product stream 132 subsequently formed in the CO.sub.2 capture apparatus 106 and directed into the electrochemical apparatus 108. By way of non-limiting example, if included in the SPM feed stream 130, the additive may comprise at least one electrolyte that increases the ionic conductivity of the SPM product stream 132. In some embodiments, the additive comprises potassium sulfate (K.sub.2SO.sub.4). In additional embodiments, SPM feed stream 130 is free of materials other than the at least one solvent and the non-polar form of at least one SPM.
[0040] A concentration of the non-polar form of the SPM in the SPM feed stream 130 may be tailored to a desired concentration of a polar form (e.g., hydrophilic form) of the SPM in a SPM product stream 132 to be formed in the CO.sub.2 capture apparatus 106. The SPM feed stream 130 may, for example, include a sufficient concentration of the non-polar form of the SPM to form the SPM product stream 132 having a concentration of the polar form of the SPM within range of from a lowest effective concentration of the polar form of the SPM for downstream use of the SPM product stream 132 in the electrochemical apparatus 108 to a solubility limit of the polar form of the SPM in the SPM product stream 132. A concentration of the non-polar form of the SPM in the SPM feed stream 130 able to facilitate a sufficient concentration of the polar form of the SPM in the SPM product stream 132 for desired downstream use of the SPM product stream 132 in the electrochemical apparatus 108 may at least partially depend on the properties (e.g., material compositions, viscosities, pressures, temperatures, flow rates, etc.) of the SPM feed stream 130 and the CO.sub.2 stream 128, and the properties (e.g., structural configurations, including individual component configurations; material compositions; etc.) of the CO.sub.2 capture apparatus 106 and the electrochemical apparatus 108. As a non-limiting example, a concentration of the non-polar form of the SPM in the SPM feed stream 130 may be within a range of from about 0.1 mol/kg to about 20.0 mol/kg, such as from about 0.5 mol/kg to about 15.0 mol/kg, from about 1.0 mol/kg to about 10.0 mol/kg, or from about 1.0 mol/kg to about 5.0 mol/kg. The concentration of the non-polar form of the SPM entering the CO.sub.2 capture apparatus 106 may be controlled as desired by adjusting one or more of an amount of the non-polar form of the SPM in the SPM feed stream 130, an amount of the solvent in the SPM feed stream 130, and an amount of the additive (if any) in the SPM feed stream 130.
[0041] The SPM feed stream 130 may be substantially homogeneous (e.g., each of the components of the SPM feed stream 130 may be uniformly dispersed throughout the SPM feed stream 130), or may be heterogeneous (e.g., at least one of the components of the SPM feed stream 130 may be non-uniformly dispersed throughout the SPM feed stream 130). In some embodiments, the SPM feed stream 130 is substantially homogeneous.
[0042] A single (e.g., only one) SPM feed stream 130 may be directed into the CO.sub.2 capture apparatus 106, or multiple (e.g., more than one) SPM feed streams 130 may be directed into the CO.sub.2 capture apparatus 106. If a single SPM feed stream 130 is directed into the CO.sub.2 capture apparatus 106, the SPM feed stream 130 may comprise a mixture of materials (e.g., a mixture comprising the non-polar form of the SPM, the solvent, and the additive (if any)). If multiple SPM feed streams 130 are directed into the CO.sub.2 capture apparatus 106, each of the SPM feed streams 130 may exhibit substantially the same properties (e.g., the same material composition, including the same type and amount of each of the non-polar form of the SPM and the solvent; the same temperature; the same pressure; the same flow rate; etc.), or at least one of the SPM feed streams 130 may exhibit one or more different properties (e.g., one or more of a different material composition, such a different type and/or a different amount of one or more of the non-polar form of the SPM and the solvent; a different temperature; a different pressure; a different flow rate; etc.) than at least one other of the SPM feed streams 130. Each of the multiple SPM feed streams 130 may individually comprise a single material (e.g., the non-polar form of the SPM, the solvent, the additive (if any)), each of the multiple SPM feed streams 130 may independently comprise a mixture of materials (e.g., a mixture of the non-polar form of the SPM, the solvent, and the additive (if any)), or at least one of the multiple SPM feed streams 130 may comprise a single material and at least one other of the multiple SPM feed streams 130 may comprise a mixture of materials. At least some of the multiple SPM feed streams 130 may be combined with one another prior to being directed into the CO.sub.2 capture apparatus 106, and/or at least some of the multiple SPM feed streams 130 may be directed into the CO.sub.2 capture apparatus 106 separately (e.g., discretely, individually, etc.) and combined with one another within CO.sub.2 capture apparatus 106. If at least some of the multiple SPM feed streams 130 are separately directed into the CO.sub.2 capture apparatus 106, the multiple SPM feed streams 130 may be directed into the CO.sub.2 capture apparatus 106 simultaneously, non-simultaneously, or a combination thereof. In some embodiments, a single SPM feed stream 130 comprising a mixture of materials (e.g., the non-polar form of the SPM and the solvent) is directed into the CO.sub.2 capture apparatus 106.
[0043] The SPM feed stream 130 and the CO.sub.2 stream 128 may each individually exhibit a temperature, a pressure, and a flow rate facilitating the formation of a predetermined concentration of the polar form of the SPM in the SPM product stream 132 in a predetermined amount of time by way of interactions between components (e.g., the non-polar form of the SPM, the solvent, etc.) of the SPM feed stream 130 and the CO.sub.2 of the CO.sub.2 stream 128 within the CO.sub.2 capture apparatus 106. The temperature(s), pressure(s), and flow rate(s) of the SPM feed stream 130 and the CO.sub.2 stream 128 may facilitate the substantially complete conversion of CO.sub.2 from the CO.sub.2 stream 128, and may be selected relative to one another and at least partially based on the configuration of the CO.sub.2 capture apparatus 106 (e.g., including the sizes, shapes, material compositions, and arrangements of the components thereof). In some embodiments, the temperature(s), pressure(s), and flow rate(s) of the SPM feed stream 130 and the CO.sub.2 stream 128 are controlled (e.g., selected and/or adjusted) to facilitate the formation of an SPM product stream 132 including greater than or equal to about 2.0 mol/kg (e.g., greater than or equal to about 2.5 mol/kg, greater than or equal to about 3.0 mol/kg, greater than or equal to about 3.5 mol/kg, or greater than or equal to about 4.0 mol/kg) of the polar form of the SPM in less than or equal to about 4 hours (e.g., less than or equal to about 3 hours, less than or equal to about 2 hours, less than or equal to about 1 hour, etc.) residence time in the CO.sub.2 capture apparatus 106.
[0044] The temperature(s) of the SPM feed stream 130 and the CO.sub.2 stream 128 may be individually be selected relative to one another, the material compositions of the SPM feed stream 130 and the CO.sub.2 stream 128, and the configuration of the CO.sub.2 capture apparatus 106 (e.g., including component sizes, component shapes, component material compositions, and component arrangements thereof) to control one or more of the viscosity of the SPM feed stream 130, chemical reaction rates during the formation of the polar form of the SPM within the CO.sub.2 capture apparatus 106, the solubility of the CO.sub.2 of the CO.sub.2 stream 128 in the SPM feed stream 130, and the stability of the polar form of the SPM produced within CO.sub.2 capture apparatus 106. The temperature(s) of the SPM feed stream 130 and the CO.sub.2 stream 128 may, for example, be independently selected such that the production of the polar form of the SPM is limited by chemical reaction rate. By way of non-limiting example, temperature(s) of the SPM feed stream 130 and the CO.sub.2 stream 128 may individually be within a range of from about 10 C. to about 40 C., such as from about 10 C. to about 30 C., or from about 20 C. to about 30 C. In some embodiments, each of the SPM feed stream 130 and the CO.sub.2 stream 128 individually exhibit a temperature within a range of from about 20 C. to about 30 C. The SPM feed stream 130 and the CO.sub.2 stream 128 may each individually exhibit a substantially constant (e.g., substantially invariable, substantially unchanging, etc.) temperature over the period of time the SPM feed stream 130 and the CO.sub.2 stream 128 are directed into the CO.sub.2 capture apparatus 106, or one or more of the SPM feed stream 130 and the CO.sub.2 stream 128 may exhibit variable (e.g., non-constant, changing, etc.) temperatures over the period of time the SPM feed stream 130 and the CO.sub.2 stream 128 are directed into the CO.sub.2 capture apparatus 106.
[0045] The SPM feed stream 130 and the CO.sub.2 stream 128 may each individually exhibit any pressure(s) permitting the CO.sub.2 of the CO.sub.2 stream 128 to interact with the components (e.g., the non-polar form to the SPM, the solvent) of SPM feed stream 130 to form the polar form of the SPM. The SPM feed stream 130 and the CO.sub.2 stream 128 may each independently exhibit a substantially constant (e.g., substantially invariable, substantially unchanging, etc.) pressure over the period of time the SPM feed stream 130 and the CO.sub.2 stream 128 are directed into the CO.sub.2 capture apparatus 106, or one or more of the SPM feed stream 130 and the CO.sub.2 stream 128 may exhibit variable (e.g., non-constant, changing, etc.) pressures over the period of time the SPM feed stream 130 and the CO.sub.2 stream 128 are directed into the CO.sub.2 capture apparatus 106. In some embodiments, the pressure of one or more of the SPM feed stream 130 and the CO.sub.2 stream 128 is changed (e.g., increased) over the period of time the SPM feed stream 130 and the CO.sub.2 stream 128 are directed into the CO.sub.2 capture apparatus 106 to account for viscosity changes (e.g., increases in the viscosity of the SPM feed stream 130) within the CO.sub.2 capture apparatus 106 during the production of the polar form of the SPM.
[0046] The flow rate(s) of the SPM feed stream 130 and the CO.sub.2 stream 128 may be individually be selected relative to one another, the material compositions of the SPM feed stream 130 and the CO.sub.2 stream 128, and the configuration of the CO.sub.2 capture apparatus 106 to control residence time within the CO.sub.2 capture apparatus 106 as well as the concentration of the polar form of the SPM produced within the CO.sub.2 capture apparatus 106. By way of non-limiting example, the SPM feed stream 130 and the CO.sub.2 stream 128 may each individually exhibit a flow rate greater than or equal to about 100 milliliters per minute (ml/min), such as a flow rate within a range of from about 100 ml/min to about 10000 ml/min, from about 200 ml/min to about 5000 ml/min, from about 300 ml/min to about 1000 ml/min, or from about 500 ml/min to about 1000 ml/min. The SPM feed stream 130 and the CO.sub.2 stream 128 may each individually exhibit a substantially constant (e.g., substantially invariable, substantially unchanging, etc.) flow rate over the period of time the SPM feed stream 130 and the CO.sub.2 stream 128 are directed into the CO.sub.2 capture apparatus 106, or one or more of the SPM feed stream 130 and the CO.sub.2 stream 128 may exhibit variable (e.g., non-constant, changing, etc.) flow rates over the period of time the SPM feed stream 130 and the CO.sub.2 stream 128 are directed into the CO.sub.2 capture apparatus 106. In some embodiments, the flow rate of at least the SPM feed stream 130 is substantially constant of the period of time the SPM feed stream 130 and the CO.sub.2 stream 128 are directed into the CO.sub.2 capture apparatus 106.
[0047] With continued reference to
[0048] In embodiments wherein the SPM feed stream 130 directed into the CO.sub.2 capture apparatus 106 includes at least one amine compound (e.g., at least one tertiary amine compound), CO.sub.2 from the CO.sub.2 stream 128 facilitates the formation of at least one aminium salt. As used herein, the term aminium salt means and includes an aminium cation and an anionic counterion and has a neutral charge. By way of non-limiting example, if the CO.sub.2 stream 128 includes CO.sub.2 and the SPM feed stream 130 includes at least one amine compound and H.sub.2O, CO.sub.2 of the CO.sub.2 stream 128 reacts with the amine compound and the H.sub.2O of the SPM feed stream 130 to form an aminium bicarbonate (e.g., a tertiary aminium bicarbonate) according to the following reversible reaction:
##STR00003##
[0049] where R.sup.1, R.sup.2, and R.sup.3 are as defined above; and where X is a substituted or unsubstituted alkyl, alkenyl, alkynyl, aryl, silyl, or siloxyl, and is linear, branched, or cyclic. Accordingly, the CO.sub.2 from the CO.sub.2 stream 128 becomes effectively captured as the bicarbonate ion (HCO.sub.3.sup.) of the produced aminium bicarbonate.
[0050] In embodiments wherein the SPM feed stream 130 includes at least one amidine compound, CO.sub.2 from the CO.sub.2 stream 128 facilitates the formation of at least one amidinium salt. As used herein, the term amidinium salt means and includes an amidinium cation and an anionic counterion and has a neutral charge. As a non-limiting example, if the CO.sub.2 stream 128 includes CO.sub.2 and the SPM feed stream 130 includes at least one amidine compound and H.sub.2O, CO.sub.2 of the CO.sub.2 stream 128 reacts with the amidine compound and the H.sub.2O of the SPM feed stream 130 to form an amidinium bicarbonate according to the following reversible reaction:
##STR00004##
[0051] where R.sup.1, R.sup.2, R.sup.3, R.sup.4, and X are as defined above. Accordingly, the CO.sub.2 from the CO.sub.2 stream 128 becomes effectively captured as the HCO.sub.3.sup. of the produced amidinium bicarbonate.
[0052] In embodiments wherein the SPM feed stream 130 includes at least one guanidine compound, CO.sub.2 from the CO.sub.2 stream 128 facilitates the formation of at least one guanidinium salt. As used herein, the term guanidinium salt means and includes a guanidinium cation and an anionic counterion and has a neutral charge. As a non-limiting example, if the CO.sub.2 stream 128 includes CO.sub.2 and the SPM feed stream 130 includes at least one guanidine compound and H.sub.2O, CO.sub.2 of the CO.sub.2 stream 128 reacts with the guanidine compound and the H.sub.2O of the SPM feed stream 130 to form a guanidinium bicarbonate according to the following reversible reaction:
##STR00005##
[0053] where R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, and X are as defined above. Accordingly, the CO.sub.2 from the CO.sub.2 stream 128 becomes effectively captured as the HCO.sub.3.sup. of the produced guanidinium bicarbonate.
[0054] In some embodiments, the CO.sub.2 stream 128 includes CO.sub.2 and the SPM feed stream 130 includes 1-cyclohexylpiperidine and H.sub.2O, and the CO.sub.2 of the CO.sub.2 stream 128 reacts with the 1-cyclohexylpiperidine and the H.sub.2O of the SPM feed stream 130 to form 1-cyclohexylpiperidinium bicarbonate according to the following reversible reaction:
##STR00006##
[0055] Accordingly, the CO.sub.2 from the CO.sub.2 stream 128 becomes effectively captured as the HCO.sub.3.sup. of the produced 1-cyclohexylpiperidinium bicarbonate.
[0056] With continued reference to
[0057] A single (e.g., only one) SPM product stream 132 may be directed into the electrochemical apparatus 108, or multiple (e.g., more than one) SPM product streams 132 may be directed into the electrochemical apparatus 108. If multiple SPM product streams 132 are directed into the electrochemical apparatus 108, each of the multiple SPM product streams 132 may exhibit substantially the same properties (e.g., substantially the same material composition, substantially the same temperature, substantially the same pressure, substantially the same flow rate, etc.), or at least one of the multiple SPM product streams 132 may exhibit one or more different properties (e.g., a different material composition, a different temperature, a different pressure, a different flow rate, etc.) than at least one other of the SPM product streams 132.
[0058] With continued reference to
[0059] The housing structure 112 may at least partially define at least one internal chamber 136 at least partially (e.g., substantially) surrounding the electrolysis cell 114. The electrolysis cell 114 may serve as a boundary between a first region 138 (e.g., an anodic region) of the internal chamber 136 configured and positioned to receive the H.sub.2O stream 124 and to direct the O.sub.2 stream 126 from the electrochemical apparatus 108, and a second region 140 (e.g., a cathodic region) of the internal chamber 136 configured and positioned receive the SPM product stream 132 and to direct the reaction product stream 134 from the electrochemical apparatus 108.
[0060] As shown in
[0061] The proton-conducting membrane 120 may be formed of and include at least one electrolyte material exhibiting desired ionic conductivity (e.g., H.sup.+ conductivity) at the operating temperature of the electrolysis cell 114, such an ionic conductivity greater than or equal to about 10.sup.3 S/cm (e.g., greater than or equal to about 10'S/cm) at a temperature greater than or equal to about 25 C. (e.g., within a range of from about 25 C. to about 650 C.). In addition, the electrolyte material may be formulated to remain substantially adhered to the positive electrode 116 and the negative electrode 118 at relatively high current densities, such as at current densities greater than or equal to about 0.1 amperes per square centimeter (A/cm.sup.2) (e.g., greater than or equal to about 0.5 A/cm.sup.2, greater than or equal to about 1.0 A/cm.sup.2, greater than or equal to about 2.0 A/cm.sup.2, etc.). For example, the proton-conducting membrane 120 may comprise a suflonated tetrafluoroethylene-based flouropolymer-coplymer material. Suitable suflonated tetrafluoroethylene-based flouropolymer-coplymer membranes are commercially available from numerous sources, such as from DuPont (Wilmington, Del.) under the NAFION trade name. In some embodiments, the proton-conducting membrane 120 comprises a NAFION 117 perflourinated membrane.
[0062] The proton-conducting membrane 120 may be substantially homogeneous or may be substantially heterogeneous. As used herein, the term homogeneous means amounts of a material do not vary throughout different portions (e.g., different lateral portions, different longitudinal portions) of a structure. Conversely, as used herein, the term heterogeneous means amounts of a material vary throughout different portions of a structure. Amounts of the material may vary stepwise (e.g., change abruptly), or may vary continuously (e.g., change progressively, such as linearly, parabolically) throughout different portions of the structure. In some embodiments, the proton-conducting membrane 120 is substantially homogeneous. In additional embodiments, the proton-conducting membrane 120 is heterogeneous. The proton-conducting membrane 120 may, for example, be formed of and include a stack of at least two (e.g., at least three, at least four, etc.) different materials. As a non-limiting example, the proton-conducting membrane 120 may comprise a stack of at least two (e.g., at least three, at least four, etc.) different suflonated tetrafluoroethylene-based flouropolymer-coplymer materials.
[0063] The proton-conducting membrane 120 may exhibit any desired dimensions (e.g., length, width, thickness) and any desired shape (e.g., a cubic shape, cuboidal shape, a tubular shape, a tubular spiral shape, a spherical shape, a semi-spherical shape, a cylindrical shape, a semi-cylindrical shape, a conical shape, a triangular prismatic shape, a truncated version of one or more of the foregoing, and irregular shape). The dimensions and the shape of the proton-conducting membrane 120 may be selected such that the proton-conducting membrane 120 substantially intervenes between opposing surfaces of the positive electrode 116 and the negative electrode 118, and exhibits an H.sup.+ conductivity greater than or equal to about 10.sup.3 S/cm at a temperature greater than or equal to about 25 C. A thickness of the proton-conducting membrane 120 may be within a range of from about 5 micrometers (m) to about 1000 m, and may at least partially depend on the material composition of the proton-conducting membrane 120.
[0064] The positive electrode 116 and the negative electrode 118 may individually be formed of and include at least one material compatible with the material composition of the proton-conducting membrane 120 and the operating conditions (e.g., temperature, pressure, current density, etc.) of the electrolysis cell 114, and facilitating the formation of the reaction product stream 134 and the O.sub.2 stream 126 from the H.sub.2O stream 124 and the SPM product stream 132. Accordingly, the material compositions of the positive electrode 116 and the negative electrode 118 may be selected relative to one another, the material composition of the proton-conducting membrane 120, and the operating conditions of the electrolysis cell 114.
[0065] As a non-limiting example, if the proton-conducting membrane 120 comprises a suflonated tetrafluoroethylene-based flouropolymer-coplymer material, the positive electrode 116 may comprise one or more of metal and an alloy compatible with the suflonated tetrafluoroethylene-based flouropolymer-coplymer material; and the negative electrode 118 of the proton-conducting membrane 120 may comprise one or more of metal, an alloy, a metal coated material, an alloy coated material compatible with the suflonated tetrafluoroethylene-based flouropolymer-coplymer material. In some embodiments, the proton-conducting membrane 120 comprises a suflonated tetrafluoroethylene-based flouropolymer-coplymer material; the positive electrode 116 comprises one or more of platinum (Pt), titanium (Ti), an alloy thereof, or a combination thereof; and the negative electrode 118 comprises a metal-coated carbon material, such as carbon material (e.g., reticulated vitreous carbon) coated with one or more of silver (Ag), copper (Cu), gold (Au), tin (Sn), lead (Pb), and zinc (Zn). The metal coating the carbon material may comprise a plurality of metallic (e.g., pure metal, alloy) particles (e.g., discrete metallic particles). The metallic particles may be nano-sized (e.g., exhibiting an average particle size less than 1 micrometer (m), such as less than or equal to 750 nanometers, less than or equal to 500 nanometers, or less than or equal to 250 nm), micro-sized (e.g., exhibiting an average particle size greater than or equal 1 m, such as within a range of from about 1 m to about 50 m, within a range of about 1 m to about 25 m, within a range of about 1 m to about 10 m, or within a range of about 1 m to about 5 m). In some embodiments, the metal-coated carbon material comprises reticulated vitreous carbon coated with Ag particles having an average particle size within a range of from about 1 micrometer (m) to about 5 m).
[0066] Optionally, one or more of the positive electrode 116 and the negative electrode 118 may include at least one additional catalyst material thereon, thereover, and/or therein. As used herein, the terms catalyst material and catalyst each mean and include a material formulated to promote one or more reactions, resulting in the formation of a product. For example, an additional catalyst material may be included on, over, and/or within the material of the positive electrode 116 to accelerate reaction rates within the positive electrode 116 to produce gaseous O.sub.2, H.sup.+, and e.sup. from H.sub.2O of the H.sub.2O stream 124. In some embodiments, a PrNiFe oxide is provided on, over, and/or within the positive electrode 116 to accelerate oxygen evolution reaction (OER) rates therein. As another example, a catalyst material may be included on, over, and/or within the material of the negative electrode 118 to accelerate reaction rates within the negative electrode 118 to produce a desired product from H.sup.+, e.sup., and one or more of CO.sub.2, CO.sub.2 electrochemical reduction product(s), and reaction product(s) of CO.sub.2 and/or CO.sub.2 electrochemical reduction product(s) and one or more other materials. In some embodiments, Cu is provided on, over, and/or within the negative electrode 118 to accelerate reaction rates at the negative electrode 118. In additional embodiments, nano-sized (e.g., having a cross-sectional width or diameter less than about one (1) m, such as less than or equal to about 100 nanometers (nm), less than or equal to about 20 nm, or less than or equal to about 10 nm) particles (e.g., Cu particles) are provided on, over, and/or within the negative electrode 118 to promote reaction rates therein.
[0067] The positive electrode 116 and the negative electrode 118 may individually exhibit any desired dimensions (e.g., length, width, thickness) and any desired shape (e.g., a cubic shape, cuboidal shape, a tubular shape, a tubular spiral shape, a spherical shape, a semi-spherical shape, a cylindrical shape, a semi-cylindrical shape, a conical shape, a triangular prismatic shape, a truncated version of one or more of the foregoing, and irregular shape). The dimensions and the shapes of the positive electrode 116 and the negative electrode 118 may be selected relative to the dimensions and the shape of the proton-conducting membrane 120 such that the proton-conducting membrane 120 substantially intervenes between opposing surfaces of the positive electrode 116 and the negative electrode 118. Thicknesses of the positive electrode 116 and the negative electrode 118 may individually be within a range of from about 10 m to about 1000 m.
[0068] As shown in
[0069] The electrolysis cell 114, including the positive electrode 116, the proton-conducting membrane 120, and the negative electrode 118 thereof, may be formed through conventional processes (e.g., rolling process, milling processes, shaping processes, pressing processes, consolidation processes, etc.), which are not described in detail herein. The electrolysis cell 114 may be mono-faced or bi-faced and may have a prismatic, folded, wound, cylindrical, or jelly rolled configuration. The electrolysis cell 114 may be placed within the housing structure 112 to form the electrochemical apparatus 108, and may be electrically connected to the power source 122.
[0070] During use and operation of the electrochemical apparatus 108, the H.sub.2O stream 124 received in the first region 138 of the internal chamber 136 of the housing structure 112 interacts with the positive electrode 116 of the electrolysis cell 114, while the SPM product stream 132 received in the second region 140 of the internal chamber 136 of the housing structure 112 interacts with the negative electrode 118 of the electrolysis cell 114. A potential difference (e.g., voltage) is applied between the positive electrode 116 and the negative electrode 118 of the electrolysis cell 114 by the power source 122 so that as the H.sub.2O of the H.sub.2O stream 124 interacts with the positive electrode 116, H atoms of the gaseous H.sub.2O release their electrons (e) to generate O.sub.2 gas (O.sub.2(g)), H.sup.+, and e.sup. according to the following equation:
2H.sub.2O.fwdarw.O.sub.2(g)+4H.sup.++4e.sup.(4)
[0071] The generated H.sup.+ permeate (e.g., diffuse) across the proton-conducting membrane 120 to the negative electrode 118, the generated e are directed to the power source 122 through external circuitry, and the generated O.sub.2(g) exits the electrochemical apparatus 108 as the O.sub.2 stream 126. At the negative electrode 118, the generated H.sup.+ interacts with the bicarbonate ion (HCO.sub.3.sup.) of the polar form of the SPM (e.g., the HCO.sub.3.sup. of the aminium salt, the bicarbonate ion of the amidinium salt, the bicarbonate ion of the guanidinium salt) to produce CO.sub.2 and H.sub.2O according to the following equation:
HCO.sub.3.sup.+H.sup.+.fwdarw.CO.sub.2+H.sub.2O(5)
[0072] At the negative electrode 118, produced CO.sub.2 may react with H.sub.2O and e.sup. received from the power source 122 to produce CO and hydroxyl ions (OH.sup.), and H.sub.2O may react with e.sup. received from the power source 122 to produce H.sub.2 gas and OH.sup., according to the following equations, respectively:
CO.sub.2+H.sub.2O+2e.sup..fwdarw.CO.sub.(g)+2OH.sup.(6)
2H.sub.2O+2e.sup..fwdarw.H.sub.2(g)+2OH.sup.(7)
[0073] Thus, a synthesis gas (syngas) including CO.sub.(g) and H.sub.2(g) may be produced within the second region 140 of the internal chamber 136 of the housing structure 112. Furthermore, produced OH.sup. may interact with remaining cation (e.g., aminium cation, amidinium cation, guanidinium cation) of the polar form of the SPM (e.g., the aminium salt, the amidinium salt, guanidinium salt) to re-produce the non-polar form of the SPM (e.g., the amine compound, the amidine compound, the guanidine compound) and H.sub.2O, according to one or more of the following equations:
##STR00007##
[0074] where R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and X are as defined above.
[0075] Optionally, depending at least on the diffusivity (e.g., diffusion rate) of the generated H.sup.+ through the proton-conducting membrane 120, CO.sub.2 produced at the negative electrode 118 of the electrolysis cell 114 may be reacted with generated H.sup.+ exiting the proton-conducting membrane 120 and e.sup. received from the power source 122 to form one or more products other than CO. By way of non-limiting example, produced CO.sub.2 may be reacted with generated H.sup.+ and received e.sup. to produce one or more of formic acid (CH.sub.2O.sub.2), methane (CH.sub.4), and ethylene (C.sub.2H.sub.4) according to the following equations, respectively:
CO.sub.2+2H.sup.++2e.sup..fwdarw.CH.sub.2O.sub.2,(11)
CO.sub.2+8H.sup.++8e.sup..fwdarw.CH.sub.4+2H.sub.2O,(12)
CO.sub.2+12H.sup.++12e.sup..fwdarw.C.sub.2H.sub.4+4H.sub.2O.(13)
[0076] In addition, optionally, products formed from reactions between produced CO.sub.2, generated H.sup.+, and received e.sup. at the negative electrode 118 may be reacted with additional generated H.sup.+ and additional received e.sup. to form one or more additional products. As a non-limiting example, CH.sub.2O.sub.2 produced at the negative electrode 118 according to the reaction of Equation (11) above may be reacted with additional generated H.sup.+ and additional received e.sup. to produce formaldehyde (CH.sub.2O) according to the following equation:
##STR00008##
[0077] As another non-limiting example, CH.sub.2O produced at the negative electrode 118 according to the reaction of Equation (14) above may be reacted with yet additional generated H.sup.+ and yet additional received e.sup. to produce methanol (CH.sub.3OH) according to the following equation:
CH.sub.2O+2H.sup.++2e.sup..fwdarw.CH.sub.3OH(15)
[0078] Although the electrochemical apparatus 108 is depicted as including a single (i.e., only one) electrolysis cell 114 in
[0079] In addition, although the CO.sub.2 treatment system 100 is depicted as including a single (i.e., only one) electrochemical apparatus 108 in
[0080] With continued reference to
[0081] A single (e.g., only one) reaction product stream 134 may be directed into the separation apparatus 110, or multiple (e.g., more than one) reaction product streams 134 may be directed into the separation apparatus 110. If multiple reaction product streams 134 are directed into the separation apparatus 110, each of the multiple reaction product streams 134 may exhibit substantially the same properties (e.g., substantially the same material composition, substantially the same temperature, substantially the same pressure, substantially the same flow rate, etc.), or at least one of the multiple reaction product streams 134 may exhibit one or more different properties (e.g., a different material composition, a different temperature, a different pressure, a different flow rate, etc.) than at least one other of the reaction product streams 134.
[0082] The separation apparatus 110 may comprise at least one device or apparatus configured and operated to separate (e.g., remove) a liquid phase of the reaction product stream 134 from a gaseous phase of the reaction product stream 134. In some embodiments, the separation apparatus 110 comprises at least one distillation column. As shown in
[0083] The gaseous product stream 142 exiting the separation apparatus 110 may include one or more gaseous products formed through the electrochemical reduction of one or more of CO.sub.2, CO.sub.2 electrochemical reduction products, and H.sub.2O in the electrochemical apparatus 108. By way of non-limiting example, the gaseous product stream 142 may include one or more of CO gas, H.sub.2 gas, CH.sub.4 gas, C.sub.2H.sub.4 gas, and CH.sub.2O gas. The gaseous product stream 142 may also include one or more other gaseous materials, such as one or more of gaseous H.sub.2O, gaseous CO.sub.2, and at least one inert gas (e.g., N.sub.2 gas, a noble gas). In some embodiments, the gaseous product stream 142 comprises a syngas including a mixture of CO gas and H.sub.2 gas. The syngas may also include one or more of CO.sub.2 and CH.sub.4. By way of non-limiting example, the gaseous product stream 142 may comprise a syngas including from about 10 wt % CO to about 30 wt % CO, from about 60 wt % H.sub.2 to about 80 wt % H.sub.2, from about 0 wt % CO.sub.2 to about 15 wt % CO.sub.2, and from about 0 wt % CH.sub.4 to about 5 wt % CH.sub.4. The gaseous product stream 142 may be utilized, further processed, and/or disposed of as desired.
[0084] The liquid product stream 144 exiting the separation apparatus 110 may include the non-polar form of at least one SPM (e.g., one or more of a tertiary amine, an amidine, and a guanidine), liquid H.sub.2O, and, optionally, one or more liquid products (e.g., CH.sub.2O.sub.2, CH.sub.3OH) formed through the electrochemical reduction of one or more of CO.sub.2 and CO.sub.2 reduction products in the electrochemical apparatus 108. In some embodiments, the gaseous product stream 142 comprises a mixture of liquid H.sub.2O and one or more of a tertiary amine compound, an amidine compound, and a guanidine compound. As shown in
[0085] The methods, systems (e.g., the CO.sub.2 treatment system 100), and apparatuses (e.g., the CO.sub.2 capture apparatus 106; the electrochemical apparatus 108, including the electrolysis cell 114 thereof) of the disclosure facilitate simple and efficient capture, transport, and conversion of CO.sub.2 into one or more desirable products. The methods, systems, and apparatuses of the disclosure reduce one or more of the time, costs, and energy (e.g., thermal energy, electrical energy, etc.) required to capture and transport CO.sub.2 (e.g., CO.sub.2 gas) and to synthesize one or more desirable products from CO.sub.2 relative to conventional methods, systems, and apparatuses. Accordingly, the methods, systems, and apparatuses of the disclosure may be more efficient, durable, and reliable that conventional methods, conventional systems, and conventional apparatuses of capturing and transporting CO.sub.2 and of synthesizing one or more desirable products from CO.sub.2.
[0086] The following examples serve to explain embodiments of the disclosure in more detail. These examples are not to be construed as being exhaustive or exclusive as to the scope of the disclosure.
EXAMPLES
Example 1Sample System Configuration and Operation
[0087] 1-Cyclohexylpiperidine (CHP) was tested for the capture and electrochemical reduction of CO.sub.2 gas. Deionized H.sub.2O and CHP were used for the capture of CO.sub.2 in a gas diffusion membrane apparatus permitting the continuous production of 1-cyclohexylpiperidinium bicarbonate (CHPH.sub.2CO.sub.3) solutions. A CO.sub.2 gas stream and a SPM feed stream including water and CHP were introduced to one another in the gas diffusion membrane apparatus with gas and liquids fed in opposite sides of a gas diffusion membrane. The gas diffusion membrane provided a mass transfer area permitting the diffusion of CO.sub.2 molecules through the gas diffusion membrane and into a SPM feed stream. The produced CHPH.sub.2CO.sub.3 solution was recirculated in the gas diffusion membrane apparatus until a homogenous SPM product stream comprising an aqueous 3.0 M CHPH.sub.2CO.sub.3 solution was achieved. CO.sub.2 gas capture was performed at room temperature. Concentrations of the produced CHPH.sub.2CO.sub.3 were measured using an Agilent 7890 GC equipped with a 7693 auto-sampler and a flame ionization detector (FID).
[0088] Electrochemical reduction of captured CO.sub.2 in the SPM feed stream (in the form of CHPH.sub.2CO.sub.3) was performed in a 10 cm.sup.2 electrolysis cell station (electrochemical apparatus) manufactured by Fuel Cell technology, Inc. (Albuquerque, N. Mex.) customized with titanium (Ti) plate current collectors (end plates) and connected to a BK Precision 1739 DC power supply. The electrolysis cell station included an electrolysis cell comprising a NAFION 117 proton exchange membrane (PEM); a positive electrode (anode) formed of platinum (Pt)-plated, sintered Ti on a first side of the NAFION 117 PEM; an ultra-thin (178 m) polyester fabric on a second, opposing side of the NAFION 117 PEM; and a negative electrode (cathode) formed of a catalyst coated, reticulated vitreous carbon (RVC) foam (80 nominal number of pores per inch (2.54 cm) of foam, 10 cm.sup.2, 1.5 mm thick) on the ultra-thin polyester fabric. To prepare the catalyst coating of the negative electrode, silver (Ag) powder (1 m to 3 m average particle size, Alfa Aesar) was mixed in a solution including 2-propanol, NAFION perfluorinated resin solution (5%, Aldrich), and polytetrafluorethylene (PTFE) preparation (60%, Aldrich), to reach a final catalyst composition of 80 wt % Ag, 10 wt % Nafion, and 10 wt % PTFE. The negative electrode had a total Ag loading of 25 mg cm.
[0089] A Master Flex C/L peristaltic pump was used to recirculate anolyte (aqueous 1M H.sub.2SO.sub.4 solution) in a first (anode) chamber of the electrolysis cell station through a serpentine flow pattern engraved in a Ti current collector. In a second (cathode) chamber of the electrolysis cell station, a cathode current collector was modified by removing the flow channels and replacing them with a hollow compartment that could fit the negative electrode. 15 mL of catholyte comprising the produced CHPH.sub.2CO.sub.3 solution of the homogenous SPM product stream was recirculated to flood the second chamber, and was directed into a recirculation reservoir that served as a phase separator, using a bench-top Cole Parmer gear pump system. All of the CO.sub.2 added to the electrolysis cell station came from CHPH.sub.2CO.sub.3 solution of the homogenous SPM product stream, and no additional CO.sub.2 gas was added directly to the electrolysis cell station and/or to the CHPH.sub.2CO.sub.3 solution during operation. Once a desired current was applied, the negative electrode (cathode) side of the electrolysis cell station was allowed to self-pressurize by the gases produced at in the second chamber. The pressure on the negative electrode side was manually controlled using a needle valve and the gases were collected in a Restek Multilayer bag, for gas chromatography (GC) analysis. Electrochemical reduction experiments were performed at different current densities from 25 to 100 mA cm, back pressures of 0, 137.9, and 275.9 KPa (0, 20, and 40 psig), and constant temperature of 25 C. Gases produced during the electrochemical reduction of CO.sub.2 were analyzed in a Hewlett Packard 5890 GC equipped with two TCD detectors and two columns. A molecular sieve 5A and argon as gas carrier were used for the detection and quantification of CO, while a capillary column 2C D-poraPLOTU and helium gas carrier were used for the detection and quantification of CO.sub.2. Finally, the volume of collected gas was measured using a Hamilton, Co. model s-1000 syringe. From the product analysis, syngas compositions, faradaic efficiencies (FE), and CO.sub.2 conversions were determined.
Example 2CO.SUB.2 .Conversion at Different Back Pressures and Constant Current Density
[0090] CO.sub.2 conversion tests based on the sample system configuration described in Example 1 were performed at constant current density of 100 mA cm over 30 min at 0 KPa (0 psig) and 137.9 KPa (20 psig) negative electrode (cathode) side back pressure. Analysis of the produced gases demonstrated the presence of CO and an H.sub.2 as products of CHPH.sub.2CO.sub.3 solution electrolysis, as well as the presence of CO.sub.2 released from the CHPH.sub.2CO.sub.3 solution. A reaction product stream exiting the electrolysis cell station exhibited a liquid portion and a gaseous portion. In the liquid portion, two liquid phases were observed. A top liquid phase comprised CHP, and a bottom liquid phase comprised an aqueous solution including unreacted CHPH.sub.2CO.sub.3. In the gaseous portion, H.sub.2 gas was the primary component, and low CO Faradaic efficiencies (FE) of 1.1% and 2.9% were observed at 0 KPa (0 psig) and 137.9 KPa (20 psig), respectively. Higher amounts of CO.sub.2 were released when no back pressure was applied. The results suggest a beneficial effect on the back pressure possibly re-dissolving unreacted CO.sub.2, hence increasing the efficiency for CO production. During the operation the cell potential varied from ca 5.5 V to 4.5 V. The high cell potential (electrode polarization induced by the low ionic conductivity) was then attributed to be one of the main causes.
Example 3CO.SUB.2 .Conversion at Different Current Densities and Constant Back Pressure
[0091] CO.sub.2 conversion tests based on the system configuration described in Example 1 were performed using 137.9 KPa (20 psig) back pressure and current densities from 26 to 104 mA cm.
Example 4Syngas Faraday Efficiencies and CO.SUB.2 .Conversion at Different Current Densities and Different Back Pressures
[0092] Faraday Efficiencies (FE) of syngas produced using the system configuration described in Example 1 were determined at current densities and different back pressures. The results are shown in
[0093] In addition, employing an assumption that the only products formed during the electrolysis of the CHPH.sub.2CO.sub.3 solution were CO and H.sub.2, CO.sub.2 conversions were calculated based on the amount of CO.sub.2 released from the CHPH.sub.2CO.sub.3 solution during the test (unreacted CO.sub.2+CO.sub.2 converted to CO). The results are shown on
Example 5Syngas Composition and CO.SUB.2 .Conversion Over Time
[0094] A transient performance analysis was performed to evaluate the performance of the system configuration described in Example 1 and the characteristics of syngas produced thereby over an extended period of time (105 min). For this purpose, the system was run at 100 mA cm, 275.9 KPa (40 psig), and 25 C., collecting samples every 15 minutes for GC analysis. The CHPH.sub.2CO.sub.3 solution was kept on recyrculation and without external additions of fresh solution. The results are shown in
[0095] The results depicted in
[0096] In addition, as shown in
Example 6Effect of Supporting Electrolyte Additive on the Ionic Conductivity of a CHPH.SUB.2.CO.SUB.3 .Solution
[0097] The effect of the addition of a supporting electrolyte on the ionic conductivity of a CHPH.sub.2CO.sub.3 solution was investigated. K.sub.2SO.sub.4 was tested. Diluted CHPH.sub.2CO.sub.3 solutions with 0.2 M K.sub.2SO.sub.4 were prepared, and ionic conductivity was measured. The results are shown in
[0098] While the disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, the disclosure is not limited to the particular forms disclosed. Rather, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the following appended claims and their legal equivalent. For example, elements and features disclosed in relation to one embodiment may be combined with elements and features disclosed in relation to other embodiments of the disclosure.