Multistage absorption and desorption for co 2 separations

Abstract

Electrochemically mediated sorbent-based carbon capture systems have recently gained attention as an alternative to traditional thermally based separations. Realizations of such systems typically require a choice between thermodynamically favorable but practically challenging two-stage systems, which combine activation with capture and deactivation with release, or pragmatic but less energy-efficient stepwise four-stage processes decoupling these steps. In this work, we present a thermodynamic assessment of novel multistage systems, which are shown to combine the practicality of sequential unit operations with the thermodynamic favorability of concerted operations. A generalized thermodynamic assessment shows these systems approach the thermodynamic minimum energy of separation in the limit of many stages for an arbitrary sorbent chemistry. Staged desorption is further shown to decrease dramatically the amount of gas in the cell during deactivation, potentially reducing bubble-driven inefficiencies.

Description

[0001] MULTISTAGE ABSORPTION AND DESORPTION FOR CO2SEPARATIONS

[0002] RELATED APPLICATIONS

[0003] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63 / 707,718 filed October 15, 2024, and entitled “Multistage Absorption and Desorption for Electrochemically Mediated CO2 Separations,” which is incorporated herein by reference in its entirety for all purposes.

[0004] GOVERNMENT SPONSORSHIP

[0005] This invention was made with Government support under DE-AR0001409 awarded by the U.S. Department of Energy. The government has certain rights in the invention.

[0006] TECHNICAL FIELD

[0007] Methods and systems for multistage absorption and desorption for CO2 separations are generally described.

[0008] SUMMARY

[0009] This Summary introduces a selection of concepts in simplified form that are described further below in the Detailed Description. This Summary neither identifies key or essential features, nor limits the scope, of the claimed subject matter.

[0010] One aspect of the disclosure herein is a system and / or method for separating (capturing) CO2 comprising: a. one or more pumps for moving CO2; b. a power supply for the one or more pumps; c. tubing and a valve a feed gas comprising CO2; d. an absorber that captures CO2; e. a multiplicity of electrochemical cells, wherein each electrochemical cell upon exposure to an electrical potential undergoes electrochemical activation and CO2 absorption in stages, followed by sequential deactivation and desorption; wherein activation and absorption are concurrent or sequential, f. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and g. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

[0011] #14499920vl In one embodiment of the disclosed system and / or method, the sequential activation and absorption followed by electrochemical deactivation and CO2 desorption occurs in in four or more stages.

[0012] One aspect of the disclosure herein is a system and / or method for separating (capturing) CO2 comprising: a. one or more pumps for moving CO2; b. a power supply for the one or more pumps; c. tubing and a valve a feed gas comprising CO2; d. an absorber that captures CO2; e. a multiplicity of electrochemical cells, wherein each electrochemical cell upon exposure to an electrical potential undergoes sequential activation and absorption followed by electrochemical deactivation and CO2 desorption in stages; wherein activation and absorption are concurrent or sequential, f. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and g. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

[0013] In one embodiment of the disclosed system and / or method, the sequential activation and absorption followed by electrochemical deactivation and CO2 desorption in stages occurs in four or more stages.

[0014] One aspect of the disclosure herein is a system and / or method for separating (capturing) CO2 comprising: a. one or more pumps for moving CO2; b. a power supply for the one or more pumps; c. tubing and a valve a feed gas comprising CO2; d. an absorber that captures CO2; e. a multiplicity of electrochemical cells, wherein i. one or more electrochemical cell upon exposure to an electrical potential undergoes electrochemical activation and CO2 absorption in stages, followed by sequential deactivation and desorption in stages; and ii. one or more electrochemical cell upon exposure to an electrical potential undergoes sequential activation and absorption followed by electrochemical deactivation and CO2 desorption in stages,

[0015] #14499920vl f. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and g. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

[0016] In one embodiment of the disclosed system and / or method, the feed gas comprises air, flue gas, or an aqueous medium comprising CO2.

[0017] In one embodiment of the disclosed system and / or method, the electrochemical cells comprise an electrochemical sorbent.

[0018] One aspect of the disclosure herein is a system for separating CO2 comprising: a. an absorber that captures CO2; b. a multiplicity of electrochemical cells, wherein each electrochemical cell upon exposure to an electrical potential undergoes electrochemical activation and CO2 absorption in stages, followed by sequential deactivation and desorption; wherein activation and absorption are concurrent or sequential; c. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and d. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

[0019] Another aspect of the disclosure herein is a system for separating CO2 comprising: a. an absorber that captures CO2; b. a multiplicity of electrochemical cells, wherein each electrochemical cell upon exposure to an electrical potential undergoes sequential activation and absorption followed by electrochemical deactivation and CO2 desorption in stages; wherein activation and absorption are concurrent or sequential; c. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and d. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

[0020] Another aspect of the disclosure herein is a system for separating CO2 comprising: a. an absorber that captures CO2; b. a multiplicity of electrochemical cells, wherein i. one or more electrochemical cell upon exposure to an electrical potential undergoes electrochemical activation and CO2 absorption in stages, followed by sequential deactivation and desorption in stages; and

[0021] #14499920vl ii. one or more electrochemical cell upon exposure to an electrical potential undergoes sequential activation and absorption followed by electrochemical deactivation and CO2 desorption in stages, c. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and d. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

[0022] One aspect is a method for separating CO2 comprising: a. providing a feed gas comprising CO2 to an absorber that captures CO2; b. providing the absorbed CO2 to a multiplicity of electrochemical cells, wherein each electrochemical cell upon exposure to an electrical potential undergoes electrochemical activation and C02absorption in stages, followed by sequential deactivation and desorption; wherein activation and absorption are concurrent or sequential; c. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and d. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

[0023] Another aspect is a method for separating CO2 comprising: a. providing a feed gas comprising CO2 to an absorber that captures CO2; b. providing the absorbed CO2 to a multiplicity of electrochemical cells, wherein each electrochemical cell upon exposure to an electrical potential undergoes sequential activation and absorption followed by electrochemical deactivation and CChdesorption in stages; wherein activation and absorption are concurrent or sequential; c. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and d. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

[0024] Another aspect is a method for separating CO2 comprising: a. providing a feed gas comprising CO2 to an absorber that captures CO2; b. providing the absorbed CO2 to a multiplicity of electrochemical cells, wherein

[0025] #14499920vl i. one or more electrochemical cell upon exposure to an electrical potential undergoes electrochemical activation and CChabsorption in stages, followed by sequential deactivation and desorption in stages; and ii. one or more electrochemical cell upon exposure to an electrical potential undergoes sequential activation and absorption followed by electrochemical deactivation and CCbdesorption in stages , c. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and d. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

[0026] The following Detailed Description references the accompanying drawings which form a part this application, and which show, by way of illustration, specific example implementations. Other implementations may be made without departing from the scope of the disclosure.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIGS. 1A-1D show the following: a) Direct cycle for a generic redox-active absorbent operating in aprotic media. A and A- represent the dormant and activated states, respectively, b) Semi-direct cycle operating in protic media. AH represents the activated protonated state, c) Indirect cycle: an electrochemically inert absorbent with a redox-active blocker species. Band B+ represent the dormant and activated states of the blocker, respectively. Inset graphs in a— c show the fraction of redox species active as a function of applied potential E, with the standard potential, EO, marked by a dashed gray line, d) example sorbent used in direct and semi-direct processes.

[0029] FIGS. 2A-2D show the following: Depictions of previously proposed systems; a) depiction of a 4-stage configuration with sequential activation, absorption, deactivation, and desorption b) depiction of 3 stage system with sequential activation and absorption followed by concurrent deactivation and desorption c) depiction of 3 stage system with concurrent activation and absorption followed by sequential deactivation and desorption d) depiction of a two-stage configuration with coupled activation and absorption, and with coupled deactivation and desorption.

[0030] FIGS. 3A-3D show the following: Thermodynamic cycles for CO2 separations with an arbitrary electrochemical sorbent, with the minimum work of separation for a given process represented by the area enclosed. Cycles correspond to the processes depicted in FIGS. 2A-2D. FIG. 3A shows a thermodynamic cycle for a 4-stage configuration with sequential activation,

[0031] #14499920vl absorption, deactivation, and desorption; numbers correspond to states shown in FIG. 2A. FIG 3B shows a thermodynamic cycle for a 3-stage configuration with concerted activation and absorption followed by sequential deactivation and desorption (see FIG. 2B). FIG. 3C shows a thermodynamic cycle for a 3-stage configuration with sequential activation and absorption followed by concerted deactivation and desorption (see FIG. 2C). FIG. 3D shows a thermodynamic cycle for a two-stage configuration with coupled activation and absorption, and with coupled deactivation and desorption (see FIG. 2D).

[0032] FIGS. 4A-4B show the following: Depictions of novel multistage systems; a) is a depiction of a system with electrochemical activation and CO2 absorption in stages, followed by sequential deactivation and desorption; and b) is a depiction of a system with sequential activation and absorption followed by electrochemical deactivation and CO2 desorption in stages.

[0033] FIGS. 5A-5B show the following: Thermodynamic cycles for newly proposed CO2 separations with an arbitrary electrochemical sorbent, with the minimum work of separation with such a process represented by the area enclosed, a) Thermodynamic cycle for a system with electrochemical activation and CO2 absorption in stages, followed by sequential deactivation and desorption; numbers correspond to states in FIG. 4A. b) Thermodynamic cycle for a system with sequential activation and absorption followed by electrochemical deactivation and CO2 desorption in stages; numbers correspond to states in FIG. 4B.

[0034] FIGS. 6A-6B show the following:, a) nominal thermodynamic cycle for a system with sequential activation and absorption followed by electrochemical deactivation and CO2 desorption in four stages b) percentage of deactivation / desorption decoupling penalty reduced as a function of stages.

[0035] FIG. 7 shows the maximum predicted CO2 partial pressure experienced in the cell as a function of the number of desorption stages.

[0036] FIGS. 8A-8H show depictions of previously proposed systems and their corresponding thermodynamic cycles. On all plots, the curved dotted lines denote potentials for constant CO2 loadings over all speciations (CO2,g, CO2,soi, and Q-mCO2) and the horizontal lines denote CO2 isobars. FIG. 8A is a depiction of a 4-stage EMCC system configuration with discrete, sequential activation, absorption, deactivation, and desorption. FIG. 8B shows corresponding thermodynamic cycle for a 4-state system in FIG. 8A with 50% state of charge swing. FIG.8C is a depiction of 3-stage system with concurrent activation and absorption followed by sequential deactivation and desorption. FIG. 8D shows corresponding thermodynamic cycle for a 3-stage system in FIG. 8C with cathodic absorption. FIG 8E is a depiction of 3-stage system with

[0037] #14499920vl sequential activation and absorption followed by concurrent deactivation and desorption. FIG.8F shows corresponding thermodynamic cycle for a 3-stage system with anodic desorption shown in FIG. 8E. FIG. 8G is a depiction of 2-stage system featuring both concurrent activation and absorption and concurrent deactivation and desorption FIG. 8H shows a corresponding thermodynamic cycle for a system with cathodic absorption and anodic desorption shown in FIG. 8G.

[0038] FIGS. 9A-9D depict process diagrams and thermodynamic cycles for newly proposed multistage CO2 separation systems with the minimum process work represented by the area enclosed. Sorbent properties are identical to those assumed in FIGS. 8A-8H. FIG. 9A is a depiction of an EMCC system configuration with activation and absorption split over two stages, followed by discrete deactivation and desorption. FIG. 9B shows corresponding thermodynamic cycle diagram for sequential system with staged absorption shown in FIG. 9A, with the original 4-stage process overlaid as a dotted line. FIG. 9C is a depiction of an EMCC system configuration with sequential activation and absorption followed by deactivation and desorption split over two discrete stages. FIG. 9D shows a corresponding thermodynamic cycle diagram for sequential system with staged desorption shown in FIG. 9C, with the original 4-stage process overlaid as a dotted line.

[0039] FIGS. 10A-10F depict multistage EMCC systems in the limit of many stages. FIG. 10A is a depiction of an EMCC system configuration with activation and absorption split over many counterflowing stages in series, followed by sequential deactivation and desorption. FIG. 10B shows a thermodynamic cycle diagram for sequential system with 10 absorption stages shown in FIG. 10A, with the original 4-stage process overlaid as a dotted line. FIG. 10C is a depiction of an EMCC system configuration with activation and absorption split over many stages with feed gas piped into each in parallel, followed by sequential deactivation and desorption. FIG. 10D shows a thermodynamic cycle diagram for sequential system with 10 absorption stages from parallelized feed gas shown in FIG. 10C, with the original 4-stage process overlaid as a dotted line. FIG. 10E is a depiction of an EMCC system configuration with sequential activation and absorption followed by deactivation and desorption split over many stages. FIG. 10F shows a corresponding thermodynamic cycle diagram for sequential system with desorption split over 10 stages shown in FIG. 10E, with the original 4-stage process overlaid as a dotted line. Parameters in b / d / f are identical to those used in FIGS. 8A-8H.

[0040] FIGS. 11A-11D show performance metrics as a function of the number of sequential gas exchange stages. FIG. 11A shows the process work of staged absorption in series or in parallel with anodic desorption, benchmarked against 3-stage work, ideal work for 50% capture, and

[0041] #14499920vl work of capture from an infinite reservoir. FIG. 1 IB shows the maximum achievable CO2 capture as a function of the number of parallel absorption stages. FIG. 11C shows the reduction in decoupling work penalty 1 Here, absorption is assumed to occur with w4stage~w3stage feed gas piped in series, as it approaches the 2- stage limit for a fair comparison. FIG. 1 ID shows the maximum anodic CO2 partial pressure as a function of the number of desorption stages. Parameters are identical to those in the previous figures except PCo2,raf = 0.015.

[0042] DETAILED DESCRIPTION

[0043] Reference numbers in superscripts herein refer to the corresponding literature listed in the attached REFERENCES which forms a part of this Specification, and the literature is incorporated by reference herein.

[0044] An example implementation is described in the Additional Detail section below.

[0045] Electrochemically mediated sorbent-based carbon capture systems have gained attention as an electrically driven alternative to traditional thermally based separations. Sorbent chemistries vary but follow one of three schemes: direct binding of CO2 to a redoxactive sorbent, semi-direct CO2 absorption via a pH-swing in protic media, or indirect modulation of an electrochemically inactive CO2 sorbent through the use of faradaic blockers. These schemes are summarized in FIGS. 1A-1D.

[0046] For a given electrochemically modulated sorbent (denoted "Q"), electrochemical carbon capture systems operate through four primary reactions: a. Electrochemical: Sorbent activation (Q + e -> Q-) b. Gas Exchange: CO2 absorption (CO2,g -> C02,sol ; Q- + CO2,aq Q-CO2) c. Electrochemical: Sorbent deactivation (Q- CO2 Q + CO2,aq + e-) d. Gas Exchange: CO2 release (C02,sol CO2,g)

[0047] These reactions can either be performed individually as sequential unit operations, or with concerted electrochemical and gas exchange steps (i.e., coupled activation / absorption or deactivation / desorption). Combining these unit operations into a cyclic separation system yields a process with 2, 3, or 4 stages, depicted in FIGS. 2A-2D.

[0048] To evaluate process energetics, diagrams are constructed relating charge to excess thermodynamic potentials as a closed cycle analogous to a heat engine. Extending a derivation performed by Shaw et. al for an arbitrary sorbent, the cycles of two, three, and four stage configurations are shown in FIGS. 4A-4B.

[0049] #14499920vl Four-stage systems use standard absorption columns and flash tanks separate from the electrochemical cell for easier gas handling (FIG. 2A, FIG. 3A); this comes at the expense of a buildup of products in the activation / deactivation cell, resulting in a thermodynamic penalty.

[0050] These penalties can be offset by moving to three-stage system architectures, binding activated sorbent with CO2 upon formation (FIG. 2B, FIG. 3B) or removing CO2 from the system immediately upon release (FIG. 2C, FIG.3C). Accounting only for variations in open circuit potential, the minimum energy of CO2 separation using a particular sorbent is achieved using a two-stage system, with combined activation / absorption and deactivation / desorption occurring in the cell (diagram in FIG. 2D; cycle in FIG. 3D). This configuration can be challenging to achieve in practice, as it necessitates the use of gas diffusion electrodes or hollow fiber membranes. Increases in activation and mass transfer overpotentials with such architectures often outweigh improvements in the minimum thermodynamic work required.

[0051] We propose a novel electrochemically mediated carbon capture system with multiple stages of sequential activation / absorption (FIG. 4A) or deactivation / desorption (FIG. 4B). These processes are intended to enable practical integration with existing designs offered by 4-stage systems while also reducing the thermodynamic penalties associated with deviating from the ideal 2- stage case.

[0052] Energy savings are visualized below in FIGS. 5A-5B, using the same thermodynamic analysis as prior.

[0053] In FIGS. 5A-5B, we evaluate the thermodynamic work associated with a novel multistage system with multiple intermediate absorption steps during sorbent activation or multiple intermediate desorption steps during sorbent deactivation. The area enclosed by these cycles (and therefore the minimum work required) is appreciably smaller than that enclosed by the four- stage system in FIG. 3D; this is quantified for staged desorption as a function of the number of stages in FIG. 6A-6B.

[0054] As shown in FIG. 6B, the penalty associated with shifting from anodic desorption to sequential deactivation and desorption is increasingly offset as the number of desorption stages increases. In the limit of a system with infinitely many stages of both absorption and desorption, the work would be identical to that of an ideal two- stage system. In practice, diminishing returns indicate that beyond a certain finite number of stages, capital costs associated with hardware (flash tanks, absorber columns, pumps, and piping) would outweigh energetic enhancements. Calculations are less straightforward for multistage activation and absorption as the feed gas conditions can vary in co-flow or counterflow, but similar trends hold.

[0055] #14499920vl Beyond thermodynamic enhancements, desorption in stages is particularly relevant as it enables practical enhancements in gas handling. In real cells, accumulation of CO2 during deactivation eventually leads to nucleation and growth of bubbles, which passivate the electrode surface and increase overpotentials. FIG. 7 indicates the maximum partial pressure in the anodic chamber as a function of the number of desorption stages, which is directly related to the accumulation of bubbles and associated overpotentials.

[0056] Sequential activation and absorption and deactivation and desorption as described herein may have other advantages, such as improved thermal management. In some embodiments, absorption of CO2 is exothermic process, which may raise temperatures and / or require cooling, and desorption of CO2 is an endothermic process, which may lower temperatures and / or require heating. It may be beneficial to be able to physically separate the thermal management of absorption stages and desorption stages due to their competing thermodynamics. In some embodiments, the differing energetic properties of absorption and desorption can be synergistic. For example, in some embodiments, absorption stages and desorption stages may each be connected to the electrochemical cell. The electrochemical cell may experience internal heat transfer between the cathodic chamber and the anodic chamber. This may advantageously facilitate heat management of the exothermic (e.g., absorption) and endothermic (e.g., desorption) processes performed in the system.

[0057] It should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific implementations described above. The specific implementations described above are disclosed as examples only.

[0058] REFERENCES

[0059] (1) Massen-Hane, M.; Diederichsen, K. M.; Hatton, T. A. Engineering Redox- Active Electrochemically Mediated Carbon Dioxide Capture Systems. Nature Chemical Engineering 2024 1:1 2024, 1 (1), 35-44. https: / / doi.org / 10.1038 / s44286-023-00003-3.

[0060] (2) Shaw, R. A.; Hatton, T. A. Electrochemical CO2 Capture Thermodynamics. International Journal of Greenhouse Gas Control 2020, 95, 10287, https: / / doi.Org / 10.1016 / i.ijggc.2019.102878.

[0061] ADDITIONAL DETAIL

[0062] ABSTRACT: Electrochemically mediated sorbent-based carbon capture systems have recently gained attention as an alternative to traditional thermally based separations. Realizations of such

[0063] #14499920vl systems typically require a choice between thermodynamically favorable but practically challenging two-stage systems, which combine activation with capture and deactivation with release, or pragmatic but less energy-efficient stepwise four-stage processes decoupling these steps. In this work, we present a thermodynamic assessment of novel multistage systems, which are shown to combine the practicality of sequential unit operations with the thermodynamic favorability of concerted operations. A generalized thermodynamic assessment shows these systems approach the thermodynamic minimum energy of separation in the limit of many stages for an arbitrary sorbent chemistry. Staged desorption is further shown to decrease dramatically the amount of gas in the cell during deactivation, potentially reducing bubble-driven inefficiencies.

[0064] Introduction:

[0065] As atmospheric carbon dioxide (CO2) concentrations continue to increase beyond pre-industrial levels, there is a pressing urgency to develop economical, energy-efficient, and scalable CO2 separation technologies, both to decarbonize industrial activities and to remediate legacy emissions.1Traditional sorbent-based CO2 capture systems are driven by using variations in temperature or pressure to swing CO2 sorption capacity, enabling uptake from a mixed gas feed and release into a pure CO2 outlet stream.2Electrochemically mediated carbon capture (EMCC) systems have recently gained attention as electrically driven alternatives to these traditional thermally based separations. EMCC systems employ applied electrical potentials to swing sorbent capacity, potentially enabling more favorable energetics, integration with renewable energy sources, and more modular, flexible scaling.3A broad array of different chemistries and system designs have been proposed in literature. Aqueous EMCC systems often leverage water dissociation to uptake CO2 in alkaline conditions and to release it under neutral or acidic conditions. These pH variations can be driven by electrolytic cation exchange, bipolar membrane electrodialysis,4or by electrochemical looping of gaseous H25or O2.6Another family of EMCC technologies leverages dissolved redox-active species to drive CO2 uptake and release, either directly through CO2 binding at an activated site or semi-directly through alkalinity modulation in protic media.3 7 10The most widely studied examples are those of quinone compounds, which upon electrochemical reduction can either form a CCb-adduct or act as a proton acceptor depending on molecular properties and the solvent employed.11Closely related are ‘indirect’ chemistries where CCk-binding sorbents are modulated by redox-active blocking species. The most developed implementation of such a system is electrochemically mediated amine regeneration by copper ion modulation, where carbamates will decompose to release CO2

[0066] #14499920vl upon Cu2+complexation.12 20This work concerns system designs for the latter cases of redoxactive sorbents and blockers in solution.

[0067] Systems employing redox-active sorbents and blockers operate through a series of electrochemical (activation / deactivation) and gas exchange (absorption / desorption) processes. The most straightforward embodiment is a four-stage system with each process carried out sequentially, employing a two-compartment electrochemical cell for electrochemical modulation and conventional absorption columns and flash tanks to facilitate gas exchange. Energetic savings are theoretically possible by combining activation with absorption or deactivation with desorption to consume products as they form, binding CO2 to activated free sorbent in the cathodic chamber or removing free CO2 from the anodic chamber.21 23Such concerted systems have been demonstrated at the laboratory scale through the use of gas diffusion electrodes and in-cell hollow fibers.24While further engineering and development are needed, initial results suggest that in many cases the projected thermodynamic enhancements achievable through concerted operations can be overshadowed by losses due to transport overpotentials and back diffusion of CO2, and the scalability of such systems is uncertain due to kinetic limitations.25This motivates the development of multistage EMCC systems, which we show in this work have the potential to achieve some of the energetic savings of concerted systems without sacrificing the flexibility and scalability of sequential systems. In this work, we recap thermodynamic assessments of these existing systems, and then extend established frameworks to analyze novel multistage systems employing multiple discrete gas exchange and electrochemical steps. We conclude with a high-level discussion of practical benefits and drawbacks of multistage systems.

[0068] Background:

[0069] For a given electrochemically modulated sorbent (denoted “2”) with m active sites each requiring one electron to be modulated, a corresponding EMCC system will operate through four primary reactions: i. Electrochemical: Sorbent activation (Q + me’ — Qm) ii. Gas Exchange: CO2 absorption (CCh.g -^CCb soi ; Q + mCCh.soi — > Q- mCCE) iii. Electrochemical: Sorbent deactivation (Q-mCO2 — Q + mC02,aq+ me ) iv. Gas Exchange: CO2 release (CO2.SO1 — > CO2,g)

[0070] #14499920vl Unbound CO2 in the system can either be gaseous (CC .g ) or dissolved in solvent CCh.soi), and up to m CO2 molecules can be bound to the activated sorbent Q-mCC )'. These reactions can either be performed individually as sequential unit operations, or with concerted electrochemical and gas exchange steps (i.e. concurrent activation / absorption or deactivation / desorption). Combining these unit operations into a cyclic separation system yields a process with 4, 3, and 2 stages, respectively, as depicted in FIGS. 8A-8H.

[0071] FIGS. 8A-8H show depictions of previously proposed systems and their corresponding thermodynamic cycles. On all plots, the curved dotted lines denote potentials for constant CO2 loadings (e.g., over all speciations (CO2,g, CCh.soi, andQ-mCO2)) and the horizontal lines denote CO2 isobars. FIG. 8A is a depiction of a 4-stage EMCC system configuration with discrete, sequential activation, absorption, deactivation, and desorption. FIG. 8B shows corresponding thermodynamic cycle for a 4-state system in FIG. 8A with 50% state of charge swing. FIG.8C) is a depiction of 3-stage system with concurrent activation and absorption followed by sequential deactivation and desorption. FIG. 8D shows corresponding thermodynamic cycle for a 3-stage system in FIG. 8C with cathodic absorption. FIG 8E is a depiction of 3-stage system with sequential activation and absorption followed by concurrent deactivation and desorption. FIG. 8F shows corresponding thermodynamic cycle for a 3-stage system with anodic desorption shown in FIG. 8E. FIG. 8G is a depiction of 2-stage system featuring both concurrent activation and absorption and concurrent deactivation and desorption FIG. 8H shows a corresponding thermodynamic cycle for a system with cathodic absorption and anodic desorption shown in FIG. 8G. Cycles are evaluated using nominal values from Shaw:21T=323K, KC02= 500, kh>CO2=0.05, m=l, and Pco2,feed= 0-15 for all; PCo2,eff = 0.075 for the cases with cathodic absorption. States l / 2 / 3a correspond to the positions during reduction / ab sorption and oxidation / desorption where the sorbent is sufficiently activated / deactivated to initiate gas exchange, and would be physically located within the electrochemical cell.

[0072] The minimum process work for a given chemistry and system configuration can be modelled using the framework developed by Shaw and Hatton.21We consider an arbitrary dormant sorbent, Q, at atmospheric pressure Po, with m active sites, total concentration Qo, binding constant and Henry’s constant kh CO=kfl'c°2P° which is '2 mQo co exposed to a CO2 partial pressure P(:o.}= — Deviation from the reference potential can be 2 Po expressed as:

[0073] #14499920vlcCO- 0 —

[0074] The normalized CO2 concentration ) is related to PC0.2and to the state of charge

[0075] ((Z = m(CQm- = mQoxQ m— ) by the following expression:

[0076] The thermodynamic state of the system can be captured on an EDev— a diagram such as that shown in FIG. 8B, which shows curved lines of constant CO2 concentration accounting for all speciations, and horizontal lines capturing the actual partial pressure of the CO2 within the solution. Three simple thermodynamic pathways exist for the different operations:

[0077] 1. Follow constant xC02(alter the state of charge in a closed system)

[0078] 2. Exchange gas (vertical line between CO2 isobars)

[0079] 3. Follow constant PC02(alter the state of charge while exchanging gas with a reservoir, along a horizontal CO2 isobar)

[0080] In the case of cathodic absorption, both xC02and PC02vary with the state of charge, so an additional mass balance equation is required to track the partial pressure at a state xi, Pi) as CO2 is absorbed from PCo2,feed down to PCo2,eff incounterflow:

[0081] The equivalent mass balance equation for co-flow can be found in Clarke et al;23thermodynamically, the requisite minimum process work is identical for co-flow and counterflow cathodic absorption configurations, but the sorbent working capacity is higher in the counterflow case presented here. To evaluate minimum process energetics neglecting finite electrode overpotentials, we can construct cycle diagrams from these pathways relating state of charge variation to excess thermodynamic potentials as a closed cycle analogous to a heat engine. Numerically, the work can be calculated as:

[0082] Here, J7denotes Faraday’s constant. Cycles of two, three, and four stage configurations are shown in FIG. 8B, FIG. 8D, FIG. 8F, and FIG. 8H. It can be observed visually that the work of separation can be reduced through combined electrochemical and gas exchange unit operations, as the shaded region shrinks as the number of stages decreases. For the example parameters roughly corresponding to capture from 15% CO2 flue gas with an amine solution, the minimum process works are 18, 10.1, 13.8, and 5.9 kJ / mol CO2 for 4-stage, 3-stage with cathodic absorption, 3-stage with anodic desorption, and 2 stage systems respectively. The

[0083] #14499920vl thermodynamic minimum work of concentrating CO2 to 1 bar for a given PCo2,feedan(J Pco2,eff can be calculated as:26

[0084] For the chosen parameters, Wmin=5.9 kJ / mol, corresponding precisely to the 2-stage work shaded in FIG. 8H as the processes la— >2 and 2a— >1 are both thermodynamically reversible. In the 2- stage case, state paths la— >2 and 2a— >1 are thermodynamically reversible, whereas 1— >1 a and 2^2a are thermodynamically irreversible; the irreversibility of processes 1— >1 a and 2^2a are the source of this minimum process work requirement.

[0085] Thermodynamics of Multistage EMCC Systems

[0086] To reduce the thermodynamic penalty associated with decoupling electrochemical and gas exchange reactions, we can divide these processes into multiple stages, as shown in FIGS. 9A-9D.

[0087] FIGS. 9A-9D depict process diagrams and thermodynamic cycles for newly proposed multistage CO2 separation systems with the minimum process work represented by the area enclosed. Sorbent properties are identical to those assumed in FIGS. 8A-8H. FIG. 9A is a depiction of an EMCC system configuration with activation and absorption split over two stages, followed by discrete deactivation and desorption. FIG. 9B shows corresponding thermodynamic cycle diagram for sequential system with staged absorption shown in FIG. 9A, with the original 4-stage process overlaid as a dotted line. FIG. 9C is a depiction of an EMCC system configuration with sequential activation and absorption followed by deactivation and desorption split over two discrete stages. FIG. 9D shows a corresponding thermodynamic cycle diagram for sequential system with staged desorption shown in FIG. 9C, with the original 4-stage process overlaid as a dotted line. Parameters in b and d are identical to those used in FIGS. 8A-8H.

[0088] Staged absorption can be achieved in multiple ways: a feed gas stream can be divided over multiple absorption columns with varying sorbent states of charge, as in FIGS. 10C-10D, or a counterflowing gas feed stream and liquid stream can be intermittently contacted, as shown in FIGS. 9A-9B and FIGS. 10A-10B. In the case of split feed gas streams, process energetics are agnostic to the effluent pressure; as in 4-stage systems, counterflowing sorbent will equilibrate to the inlet feed gas partial pressure, and the capture fraction is primarily a consideration for absorber column sizing and associated capital expenses. The latter case of a single gas stream

[0089] #14499920vl with intermittent activation and absorption requires mass balances across the stages, as in the case of cathodic absorption. By contrast, implementing staged desorption is straightforward, as accumulated gaseous CO2 in the anode is simply flashed down to a fixed outlet pressure periodically during deactivation, as shown in FIGS 2C-2D. Both staged absorption and desorption are shown to reduce the process work, with savings graphically indicated by the unshaded areas between the work curves and the dotted line denoting a 4-stage process. In this example, the four-stage work (18 kJ / mol) is reduced to 16.3 kJ / mol by an additional absorption stage, or to 16.7 kJ / mol by an additional desorption stage. Further insights can be drawn by extrapolating to the limiting case of many stages, depicted in FIGS. 10A-10F.

[0090] FIGS. 10A-10F depict multistage EMCC systems in the limit of many stages. FIG. 10A is a depiction of an EMCC system configuration with activation and absorption split over many counterflowing stages in series, followed by sequential deactivation and desorption. FIG. 10B shows a thermodynamic cycle diagram for sequential system with 10 absorption stages shown in FIG. 10A, with the original 4-stage process overlaid as a dotted line. FIG. 10C is a depiction of an EMCC system configuration with activation and absorption split over many stages with feed gas piped into each in parallel, followed by sequential deactivation and desorption. FIG. 10D shows a thermodynamic cycle diagram for sequential system with 10 absorption stages from parallelized feed gas shown in FIG. 10C, with the original 4-stage process overlaid as a dotted line. FIG. 10E is a depiction of an EMCC system configuration with sequential activation and absorption followed by deactivation and desorption split over many stages. FIG. 10F shows a corresponding thermodynamic cycle diagram for sequential system with desorption split over 10 stages shown in FIG. 10E, with the original 4-stage process overlaid as a dotted line. Parameters in b / d / f are identical to those used in FIGS. 8A-8H.

[0091] In the limit of many feed gas contacting stages in series, the activation / absorption process begins to resemble that of cathodic absorption, depicted in FIGS. 10A-10B. In this limit, the alternative staged absorption system configuration where feed gas is parallelized into each absorber column begins to diverge, instead approaching absorption at constant CO2 partial pressure (FIGS. 10C-10D). As progressively more desorption stages are introduced, the curves for discretized deactivation / desorption begin to approach the anodic desorption limit, shown in FIGS. 10E-10F. It is important to note that while staged systems can lower the thermodynamic penalty of decoupling electrochemical and gas exchange reactions, these processes are fundamentally different from concerted pathways as they are thermodynamically irreversible. This is observed in FIG. 11A below, as the asymptotic energy consumption of staged absorption

[0092] #14499920vl (FIGS. 10A-10B) or staged desorption (FIGS. 10E-10F) approaches but does not fully reach that of a concerted process.

[0093] FIGS. 11A-1 ID show performance metrics as a function of the number of sequential gas exchange stages. FIG. 11A shows the process work of staged absorption in series or in parallel with anodic desorption, benchmarked against 3-stage work, ideal work for 50% capture, and work of capture from an infinite reservoir. FIG. 1 IB shows the maximum achievable CO2 capture as a function of the number of parallel absorption stages. FIG. 11C shows the reduction in decoupling work penalty 1 Here, absorption is assumed to occur with w4stage~w3stage feed gas piped in series, as it approaches the 2- stage limit for a fair comparison. FIG. 1 ID shows the maximum anodic CO2 partial pressure as a function of the number of desorption stages. Parameters are identical to those in the previous figures except PCo2,raf = 0.015.

[0094] FIG. 11A shows the work of processes with anodic desorption and varying absorption schemes- a standard 3-stage configuration, 50% capture via many stages with gas piped in series, many stages with gas piped in parallel, and 2-stage cathodic absorption. In the limit of many stages, process work for series fed multistage absorption asymptotically approaches the thermodynamic minimum work of separation, equal to that of a 2-stage system. In contrast, the process work of staged absorbers fed in parallel approaches that of capture from an inexhaustible reservoir of CO226:

[0095] In the parallel fed case, the achievable capture fraction decreases with increasing stage count, as seen in FIG. 1 IB. While this effect is relatively insignificant for low numbers of stages, there is a meaningful drop-off at higher stage counts. Thermodynamically, the process work of staged absorption from feed gas distributed in parallel is favorable compared to that of series absorption so long as the desired capture fraction is achievable. FIG. 11C compares the decoupling penalty offsets achievable with staged absorption (in series) and staged desorption. For a given number of gas exchange steps, multistage desorption provides a greater relative thermodynamic enhancement, but both processes asymptotically approach the work of a concerted process in the limit of many stages.

[0096] Practical Considerations

[0097] Beyond thermodynamics, significant practical benefits can be offered by staged processes, with staged desorption in particular alleviating challenges in gas handling. Gas- induced inefficiencies can be significant in electrochemical cells, as bubbles substantially limit

[0098] #14499920vl achievable current densities by blocking active area and increasing ohmic losses.27,28Specific to EMCC systems, the stoichiometric ratios inherent to sorbents dictate that gas volumes generated per unit of circulating electrolyte volume are often significantly higher than those in more conventional chlor-alkali or water electrolysis cells.3,29FIG. 11D implies that splitting desorption over multiple stages can significantly reduce the volume of gas buildup in the electrochemical cell.

[0099] Benefits of implementation at scale are ultimately determined by a tradeoff between increased capital costs of gas exchange equipment and enhancements in cell performance enabling smaller stacks and / or improved energetics. Previous technoeconomic assessments suggest that staged desorption in particular could be beneficial in this regard - Wang et al. projected that flash tanks would make up less than 1% of the total capital expenses of equipping a power plant with an EMAR carbon capture system, so costs of additional stages would mainly be embodied in additional pumps (totaling 9% of the retrofit CAPEX).30Technoeconomic tradeoffs associated with varying absorption schemes are more challenging to evaluate at a high level, as absorber towers are highly sensitive to kinetics and transport,25,31and the total system cost is much more sensitive to changes due to the higher associated CAPEX values. The absorption column CAPEX is likely to increase with a staged configuration, as the driving force for absorption is reduced. A rate-based model analogous to that used for intercooled thermal amine absorption towers would be needed to quantify the tradeoff.32Wang et al. projected that absorbers and blowers make up 9% and 5% of the retrofit CAPEX, respectively, and additional pumps would also be required.30In either case, it is likely that only a few additional stages would be desirable before enhancements in cell performance are outweighed by increases in gas handling capital expenses.

[0100] Conclusions and Outlook

[0101] In this work, we presented multistage absorption / desorption schemes as a means to reduce the thermodynamic penalties associated with decoupling electrochemical reactions from gas exchange processes in electrochemically mediated carbon capture systems. Extending the framework established by Shaw and Hatton.,21we quantified the thermodynamic energy savings achievable through multistage gas exchange schemes, indicating that the decoupling penalties can be meaningfully offset. Beyond thermodynamic considerations, staged desorption is suggested as a promising means of reducing bubble-driven inefficiencies in systems at scale. EMCC systems with multiple gas exchange stages can be challenging to demonstrate at the labscale due to experimental complexity and need for comparatively high gas throughputs, but such

[0102] #14499920vl configurations are likely to become more relevant as EMCC systems are developed at industrial scales.

[0103] Acknowledgements

[0104] This work was supported under ARPA-E Grant DE-AR0001409

[0105] References

[0106] (1) IPCC Working Group II. IPCC AR6 Working Group II: Summary for Policymakers: Climate Change 2022, Impacts, Adaptation And Vulnerability. Implementing a US Carbon Tax: Challenges and Debates 2022.

[0107] (2) Halliday, C.; Hatton, T. A. Sorbents for the Capture of CO 2 and Other Acid Gases: A Review. Industrial & Engineering Chemistry Research 2021, 60 (26), 9313-9346. https: / / doi.org / 10.1021 / acs.iecr.lc00597.

[0108] (3) Massen-Hane, M.; Diederichsen, K. M.; Hatton, T. A. Engineering Redox-Active Electrochemically Mediated Carbon Dioxide Capture Systems. Nature Chemical Engineering 2024 1:1 2024, 1 (1), 35-44. https: / / doi.org / 10.1038 / s44286-023-00003-3.

[0109] (4) Eisaman, M. D.; Alvarado, L.; Lamer, D.; Wang, P.; Garg, B.; Littau, K. A. CO2 Separation Using Bipolar Membrane Electrodialysis. Energy and Environmental Science 2011, 4 (4), 1319-1328. https: / / doi.org / 10.1039 / c0ee00303d.

[0110] (5) Jiang, W.; Liu, W.; Wang, Y.; Zhao, Z.; Li, Q.; Wu, Y.; Liu, T.; Xie, H.

[0111] Electrochemically Regenerated Amine for CO2 Capture Driven by a Proton-Coupled Electron Transfer Reaction. Industrial and Engineering Chemistry Research 2022, 61 (36), 13578-13588. https: / / doi.org / 10.1021 / acs.iecr.2c01047.

[0112] (6) Zhu, P.; Wu, Z. Y.; Elgazzar, A.; Dong, C.; Wi, T. U.; Chen, F. Y.; Xia, Y.; Feng, Y.; Shakouri, M.; Kim, J. Y. (Timothy); Fang, Z.; Hatton, T. A.; Wang, H. Continuous Carbon Capture in an Electrochemical Solid-Electrolyte Reactor. Nature 2023, 618 (7967), 959-966. https: / / doi.org / 10.1038 / s41586-023-06060-l.

[0113] (7) Zito, A. M.; Clarke, L. E.; Barlow, J. M.; Bim, D.; Zhang, Z.; Ripley, K. M.; Li, C. J.; Kummeth, A.; Leonard, M. E.; Alexandrova, A. N.; Brushed, F. R.; Yang, J. Y. Electrochemical Carbon Dioxide Capture and Concentration. Chemical Reviews. 2023, pp 8069-8098. https: / / doi.org / 10.1021 / acs.chemrev.2c00681.

[0114] (8) Gurkan, B.; Su, X.; Klemm, A.; Kim, Y.; Mallikarjun Sharada, S.; Rodriguez-Katakura, A.; Kron, K. J. Perspective and Challenges in Electrochemical Approaches for Reactive CO2 Separations. iScience. 2021, p 103422. https: / / doi.Org / 10.1016 / j.isci.2021.103422.

[0115] #14499920vl (9) Renfrew, S. E.; Starr, D. E.; Strasser, P. Electrochemical Approaches toward CO2 Capture and Concentration. ACS Catalysis 2020, 10 (21), 13058-13074. https: / / doi.org / 10.1021 / acscatal.0c03639.

[0116] (10) Seo, H.; Nitzsche, M. P.; Hatton, T. A. Redox-Mediated PH Swing Systems for Electrochemical Carbon Capture. Acc Chem Res 2023, 56 (22), 3153-3164. https: / / doi.org / 10.1021 / ACS.ACCOUNTS.3C00430 / ASSET / IMAGES / LARGE / AR3C00 430_0006.JPEG.

[0117] (11) Barlow, J. M.; Clarke, L. E.; Zhang, Z.; Bim, D.; Ripley, K. M.; Zito, A.; Brushed, F. R.; Alexandrova, A. N.; Yang, J. Y. Molecular Design of Redox Carriers for Electrochemical CO2 Capture and Concentration. Chemical Society Reviews. 2022, pp 8415-8433. https: / / doi.org / 10.1039 / d2cs00367h.

[0118] (12) Wang, M.; Herzog, H. J.; Hatton, T. A. CO 2 Capture Using Electrochemically Mediated Amine Regeneration. Ind Eng Chem Res 2020, 59 (15), 7087-7096. https: / / doi.org / 10.1021 / acs.iecr.9b05307.

[0119] (13) Stern, M. C.; Hatton, T. A. Bench-Scale Demonstration of CO2 Capture with Electrochemically-Mediated Amine Regeneration. RSC Adv 2014, 4 (12), 5906. http s : / / doi. org / 10.1039 / c3ra46774k.

[0120] (14) Wang, M. Flue Gas CO2 Capture Using Electrochemically Mediated Amine Regeneration. PhD Dissertation, Massachusetts Institute of Technology, Cambridge, MA, 2020.

[0121] (15) Stern, M. C.; Simeon, F.; Herzog, H.; Hatton, T. A. Post-Combustion Carbon Dioxide Capture Using Electrochemically Mediated Amine Regeneration. Energy Environ Sci 2013, 6 (8), 2505. https: / / doi.org / 10.1039 / c3ee41165f.

[0122] (16) Wang, M.; Hariharan, S.; Shaw, R. A.; Hatton, T. A. Energetics of Electrochemically Mediated Amine Regeneration Process for Flue Gas CO2 Capture. International Journal of Greenhouse Gas Control 2019, 82, 48-58. https: / / doi.org / 10.1016 / jdjggc.2018.12.028.

[0123] (17) Wang, M.; Rahimi, M.; Kumar, A.; Hariharan, S.; Choi, W.; Hatton, T. A. Flue Gas CO2 Capture via Electrochemically Mediated Amine Regeneration: System Design and Performance. Appl Energy 2019, 255, 113879. https: / / doi.Org / 10.1016 / j.apenergy.2019.113879.

[0124] (18) Wang, M.; Hatton, T. A. Flue Gas CO 2 Capture via Electrochemically Mediated Amine Regeneration: Desorption Unit Design and Analysis. Ind Eng Chem Res 2020, 59 (21), 10120-10129. https: / / doi.org / 10.1021 / acs.iecr.0c00790.

[0125] (19) Rahimi, M.; Diederichsen, K. M.; Ozbek, N.; Wang, M.; Choi, W.; Hatton, T. A. An Electrochemically Mediated Amine Regeneration Process with a Mixed Absorbent for

[0126] #14499920vl Postcombustion CO 2 Capture. Environ Sci Technol 2020, 54 (14), 8999-9007. https: / / doi.org / 10.1021 / acs.est.0c02595.

[0127] (20) Rahimi, M.; Zucchelli, F.; Puccini, M.; Alan Hatton, T. Improved CO 2 Capture Performance of Electrochemically Mediated Amine Regeneration Processes with Ionic Surfactant Additives. ACS Appl Energy Mater 2020, 5 (11), 10823-10830. https: / / doi.org / 10.1021 / acsaem.0c01859.

[0128] (21) Shaw, R. A.; Hatton, T. A. Electrochemical CO2 Capture Thermodynamics. International Journal of Greenhouse Gas Control 2020, 95, 102878. https: / / doi.org / 10.1016 / jdjggc.2019.102878.

[0129] (22) Stern, M. C.; Simeon, F.; Hammer, T.; Landes, H.; Herzog, H. J.; Hatton, T. A. Electrochemically Mediated Separation for Carbon Capture. In Energy Procedia', 2011; Vol. 4. https: / / doi.Org / 10.1016 / j.egypro.2011.01.130.

[0130] (23) Clarke, L. E.; Leonard, M. E.; Hatton, T. A.; Brushed, F. R. Thermodynamic Modeling of CO 2 Separation Systems with Soluble, Redox- Active Capture Species. Ind Eng Chem Res 2022, 61 (29), 10531-10546. https: / / doi.org / 10.1021 / acs.iecr.lc04185.

[0131] (24) Diederichsen, K. M.; DeWitt, S. J. A.; Hatton, T. A. Electrochemically Facilitated Transport of CO2 between Gas Diffusion Electrodes in Flat and Hollow Fiber Geometries. A CS ES and T Engineering 2023, 3 (7), 1001-1012. https: / / doi.org / 10.1021 / acsestengg.3c00030.

[0132] (25) Boualavong, J.; Gorski, C. A. Kinetic Drawbacks of Combining Electrochemical CO2 Sorbent Reactivation with CO2 Absorption. Ind Eng Chem Res 2023, 62 (46), 19784- 19800. https: / / doi.org / 10.1021 / ACS.IECR.3C02204 / SUPPL_FILE / IE3C02204_SI_001.PDF.

[0133] (26) Lackner, K. S. The Thermodynamics of Direct Air Capture of Carbon Dioxide. Energy 2013, 50 (1), 38-46. https: / / doi.Org / 10.1016 / j.energy.2012.09.012.

[0134] (27) Angulo, A.; van der Linde, P.; Gardeniers, H.; Modestino, M.; Fernandez Rivas, D. Influence of Bubbles on the Energy Conversion Efficiency of Electrochemical Reactors. Joule. 2020, pp 555-579. https: / / doi.Org / 10.1016 / j.joule.2020.01.005.

[0135] (28) He, Y.; Cui, Y.; Zhao, Z.; Chen, Y.; Shang, W.; Tan, P. Strategies for Bubble Removal in Electrochemical Systems. Energy Reviews. 2023. https: / / doi.Org / 10.1016 / j.enrev.2023.100015.

[0136] (29) Liu, Y.; Lucas, E.; Sullivan, I.; Li, X.; Xiang, C. Challenges and Opportunities in Continuous Flow Processes for Electrochemically Mediated Carbon Capture. iScience 2022, 25 (10), 105153. https: / / doi.org / 10.1016 / jdsci.2022.105153.

[0137] #14499920vl (30) Wang, M.; Shaw, R.; Gencer, E.; Hatton, T. A. Technoeconomic Analysis of the Electrochemically Mediated Amine Regeneration CO 2 Capture Process. Ind Eng Chem Res 2020, 59 (31), 14085-14095. https: / / doi.org / 10.1021 / acs.iecr.0c02166.

[0138] (31) Ripley, K. M.; Brushed, F. R. Modeling and Comparative Analysis of CO2 Absorption Columns in Electrochemical and Thermochemical Carbon Capture Systems. Ind Eng

[0139] Chem Res 2024. https: / / doi.org / 10.1021 / ACS.IECR.4C01523.

[0140] (32) Hemmati, A.; Rashidi, H. Optimization of Industrial Intercooled Post-Combustion CO2 Absorber by Applying Rate- Base Model and Response Surface Methodology (RSM). Process Safety and Environmental Protection 2019, 121, 77-86. https: / / doi.Org / 10.1016 / J.PSEP.2018.10.00

[0141] #14499920vl

Claims

CLAIMSWhat is claimed is:

1. A system and / or method for separating (capturing) CO2 comprising a. one or more pumps for moving CO2; b. a power supply for the one or more pumps; c. tubing and a valve d. a feed gas comprising CO2; e. an absorber that captures CO2; f. a multiplicity of electrochemical cells, wherein each electrochemical cell upon exposure to an electrical potential undergoes electrochemical activation and CO2 absorption in stages, followed by sequential deactivation and desorption; wherein activation and absorption are concurrent or sequential; g. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and h. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

2. The system of claim 1, wherein sequential activation and absorption followed by electrochemical deactivation and CO2 desorption occurs in four or more stages.

3. A system and / or method for separating (capturing) CO2 comprising a. one or more pumps for moving CO2; b. a power supply for the one or more pumps; c. tubing and a valve; d. a feed gas comprising CO2; e. an absorber that captures CO2; f. a multiplicity of electrochemical cells, wherein each electrochemical cell upon exposure to an electrical potential undergoes sequential activation and absorption followed by electrochemical deactivation and CO2 desorption in stages; wherein activation and absorption are concurrent or sequential; g. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and#14499920vlh. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

4. The system of claim 3, wherein sequential activation and absorption followed by electrochemical deactivation and CO2 desorption in stages occurs in four or more stages.

5. A system and / or method for separating (capturing) CO2 comprising a. one or more pumps for moving CO2; b. a power supply for the one or more pumps; c. tubing and a valve; d. a feed gas comprising CO2; e. an absorber that captures CO2; f. a multiplicity of electrochemical cells, wherein i. one or more electrochemical cell upon exposure to an electrical potential undergoes electrochemical activation and CO2 absorption in stages, followed by sequential deactivation and desorption in stages; and ii. one or more electrochemical cell upon exposure to an electrical potential undergoes sequential activation and absorption followed by electrochemical deactivation and CO2 desorption in stages , g. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and h. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

6. The system of any one of claims 1-5, wherein the feed gas comprises air, flue gas, or an aqueous medium comprising CO2.

7. The system of any one of claims 1-6, wherein the electrochemical cells comprise an electrochemical sorbent.

8. A system for separating CO2 comprising: a. an absorber that captures CO2; b. a multiplicity of electrochemical cells, wherein each electrochemical cell upon exposure to an electrical potential undergoes electrochemical activation and CO2#14499920vlabsorption in stages, followed by sequential deactivation and desorption; wherein activation and absorption are concurrent or sequential; c. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and d. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

9. The system of claim 8, wherein sequential activation and absorption followed by electrochemical deactivation and CO2 desorption occurs in four or more stages.

10. A system for separating CO2 comprising a. an absorber that captures CO2; b. a multiplicity of electrochemical cells, wherein each electrochemical cell upon exposure to an electrical potential undergoes sequential activation and absorption followed by electrochemical deactivation and CO2 desorption in stages; wherein activation and absorption are concurrent or sequential; c. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and d. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

11. The system of claim 10, wherein sequential activation and absorption followed by electrochemical deactivation and CO2 desorption in stages occurs in four or more stages.

12. A system for separating CO2 comprising a. an absorber that captures CO2; b. a multiplicity of electrochemical cells, wherein i. one or more electrochemical cell upon exposure to an electrical potential undergoes electrochemical activation and CO2 absorption in stages, followed by sequential deactivation and desorption in stages; and ii. one or more electrochemical cell upon exposure to an electrical potential undergoes sequential activation and absorption followed by electrochemical deactivation and CO2 desorption in stages ,#14499920vlc. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and d. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

13. The system of any one of claims 8-12, further comprising a feed gas comprising air, flue gas, or an aqueous medium comprising CO2.

14. The system of any one of claims 8-13, wherein the electrochemical cells comprise an electrochemical sorbent.

15. A method for separating CO2, comprising: a. providing a feed gas comprising CO2 to an absorber that captures CO2; b. providing the absorbed CO2 to a multiplicity of electrochemical cells, wherein each electrochemical cell upon exposure to an electrical potential undergoes electrochemical activation and CO2 absorption in stages, followed by sequential deactivation and desorption; wherein activation and absorption are concurrent or sequential; c. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and d. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

16. The method of claim 15, wherein sequential activation and absorption followed by electrochemical deactivation and CO2 desorption occurs in four or more stages.

17. A method for separating CO2, comprising: a. providing a feed gas comprising CO2 to an absorber that captures CO2; b. providing the absorbed CO2 to a multiplicity of electrochemical cells, wherein each electrochemical cell upon exposure to an electrical potential undergoes sequential activation and absorption followed by electrochemical deactivation and CO2 desorption in stages; wherein activation and absorption are concurrent or sequential; c. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and#14499920vld. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

18. The method of claim 17, wherein sequential activation and absorption followed by electrochemical deactivation and CO2 desorption in stages occurs in four or more stages.

19. A method for separating CO2 comprising a. providing a feed gas comprising CO2 to an absorber that captures CO2; b. providing the absorbed CO2 to a multiplicity of electrochemical cells, wherein i. one or more electrochemical cell upon exposure to an electrical potential undergoes electrochemical activation and CChabsorption in stages, followed by sequential deactivation and desorption in stages; and ii. one or more electrochemical cell upon exposure to an electrical potential undergoes sequential activation and absorption followed by electrochemical deactivation and CCbdesorption in stages, c. a cathode and an anode for controlling electrochemical potential of the electrochemical cells; and d. a power supply for creating an electrical current between an anode and a cathode of the electrochemical cell.

20. The method of any one of claims 15-19, further comprising a feed gas comprising air, flue gas, or an aqueous medium comprising CO2.

21. The method of any one of claims 15-20, wherein the electrochemical cells comprise an electrochemical sorbent.#14499920vl

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