WO2023220684A1

WO2023220684A1 - Carbon dioxide and hydrocarbon mixture separation systems and methods of the same

Info

Publication number: WO2023220684A1
Application number: PCT/US2023/066889
Authority: WO
Inventors: Ryan P. LIVELY; Akriti SARSWAT; David S. Sholl
Original assignee: Georgia Tech Research Corporation
Priority date: 2022-05-11
Filing date: 2023-05-11
Publication date: 2023-11-16

Abstract

Disclosed herein are CO₂ and hydrocarbon mixture separation systems and methods comprising reacting CO₂ electrochemically to generate reduction products in an electrochemical reduction reaction, separating the products mixture to obtain one or more products and reject one or more combustion reagents, receiving additional combustion reagents, combusting the one or more combustion reagents and the additional combustion reagents in a complete combustion reaction to obtain one or more combustion products, and recycling the one or more combustion products to the electrochemical reduction reaction.

Description

CARBON DIOXIDE AND HYDROCARBON MIXTURE SEPARATION SYSTEMS AND METHODS OF THE SAME

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 63/340,513, filed on 11 May 2022, and the entire contents and substance of each is incorporated herein by reference in its entirety as if fully set forth below.

FIELD OF THE DISCLOSURE

[0002] The present disclosure relates generally to carbon dioxide and hydrocarbon mixture separation systems and methods. Particularly, embodiments of the present disclosure relate to downstream purification of products from the electrochemical reduction of carbon dioxide via the use of a combustion chamber and an input of fuel such as methane.

BACKGROUND

[0003] The hydrocarbon processing industry is in the midst of a major shift in feedstocks, structure, and products. Aggressive carbon abatement targets and intrinsic efficiency advantages from electric vehicles strongly undercut the advantages of fossil fuels, which are the majority product of this industry. However, the immense value of the existing hydrocarbon infrastructure suggests that fossil feedstocks, processing, and products will be the dominant form for quite some time. Existing fossil-based plants with compatible equipment (e.g., hydrocrackers) will begin the externality- induced transition over to bio- and e-refinery formats to leverage this valuable existing infrastructure and logistical connections. Advanced separations play a role in this transition in several ways. First, advanced separations can partner with existing separation units (e.g., distillation) to extend the time in which fossil-based processing remains competitive under modem externalities (e.g., CO2). Moreover, energy- and capital-efficient separation technologies can mitigate the decrease in returns of energy invested in fossil-based refining due to greenhouse gas emission mandates. While bio- and e-refineries are often thought of as a greenfield for advanced separations technologies (thus bypassing the problem of working, amortized capital in existing plants), in fact, the adaptation of existing fossil-based refineries to renewable feedstocks suggests that the “hybrid” separation system paradigm is likely to be the standard for years to come. Nevertheless, these “green refineries” introduce many new separations challenges that are likely to be poorly addressed by conventional technologies. Finally, decades-old regulatory definitions of fuels will continue to promote distillation-centric refinery designs — flexibility in not only these regulations, but also in end use will pave the way for low energy, low carbon separation techniques.

[0004] Fossil fuels have played an instrumental and important role in rapidly advancing and improving many aspects of the human condition. However, a major change is underway for the various industries that have grown out of our dependency on energy derived from fossil fuels. This sea of change is driven by several factors, but a common driving force for change in all energy-related industries is the consensus that carbon emissions need to be reduced. The Paris Agreement requires a substantial year-over-year decrease in CO2 emissions to limit global surface warming to +2°C above preindustrial levels and current global policies are predicted to result in +2.6-3. 1°C increases. Unfortunately, climate and economic forecasts suggest tremendous damage could be incurred if the latter levels of warming are ultimately realized. Thus, the aggressive reductions in carbon emissions that are required to stay below +2°C can be thought of as one boundary condition that the hydrocarbon processing industry is facing as it moves forward.

[0005] The second major boundary condition is the significant increase in renewable electric power generation in the developed world. The United States Energy Information Administration (EIA) predicts that primary energy generation in the U.S. will come from renewable resources by 2050. This dramatic rise in renewable electricity — coupled with scheduled fossil-based plant closures — has already started the process of decarbonizing the power generation sector. It is expected that the transportation sector — especially personal vehicle transportation — will decarbonize over the next 50 years via increasing utilization of electric vehicles. The rate of this decarbonization will depend on the relative electric vehicle benefits (e.g., energy efficiency of 1 mile per MJ for an electric vehicle versus 0.37 mile per MJ for a standard internal combustion engine personal vehicle) and difficulties of broad adoption of this new technology (e.g., overhauling the grid). Regardless, this decarbonization is more of a question of when and not if, and highlights that a major market for hydrocarbon processors (i.e., fuels for personal vehicles in developed countries) will continue to decline in total volume. Thus, the second boundary condition can be concisely stated as an expected peak demand for fossil fuels in the industrial world.

[0006] The third major boundary condition is the continual increase in access to energy in the developing world. For instance, the U.S. EIA projects that non-OECD countries will consume 60% more energy by 2050 than currently consumed in 2020 and this increase will be a major driver in the expected continued rise in global energy consumption. Improvements in energy access have broad benefits to the affected populations. Perhaps not surprisingly, fossil fuels are the primary form of energy most often being utilized in developing nations. This rapid increase in energy consumption per capita — coupled with greater increases in population than developed countries — will require significant increases in fossil fuel production, as a majorityelectric energy infrastructure will likely not be viable in these regions for decades. It is likely that this will result in global increases in fossil fuel production, although the overall percentage of fossil fuels in the energy supply portfolio may decrease as a result of more renewables.

[0007] Electrochemical reduction of carbon dioxide into value added products is an attractive technology with promise to address some of these challenges. This reaction, however, produces a complex mixture of products which require high input of energy for their purification. What is needed, therefore, is a carefully crafted downstream processing design containing an assortment of traditional separations (like distillation or flash tanks) and non-thermal separations (like adsorption- or membrane-based separations). Embodiments of the present disclosure address this need as well as other needs that will become apparent upon reading the description below in conjunction with the drawings.

BRIEF SUMMARY OF THE DISCLOSURE

[0008] The present disclosure relates generally to carbon dioxide and hydrocarbon separation systems and methods. Particularly, embodiments of the present disclosure relate to downstream purification of products from electrochemical reduction of carbon dioxide via the use of a combustion chamber and an input of fuel such as methane.

[0009] An exemplary embodiment of the present disclosure can provide a separation system comprising: an electrochemical cell comprising a feed line, an oxidation products outlet line, and a reduction products outlet line, the electrochemical cell configured to receive CO2 from the feed line and electrochemically convert the CO2 in a reduction reaction to generate multiple products; a separation unit attached to the reduction products outlet line, the separation unit configured to receive the reduction products generated by the electrochemical cell and separate one or more products from the mixture , and reject one or more combustion reagents; and a combustion chamber attached to the separation unit and comprising a reagent inlet and a recycle line, the combustion chamber configured to receive the one or more combustion reagents rejected by the separation unit, receive additional combustion reagents from the reagent line, and fully combust the one or more combustion reagents in a complete combustion reaction to create one or more combustion products, wherein the one or more combustion products are recycled to the feed line through the recycle line. [0010] In any of the embodiments disclosed herein, the one or more products can comprise C2H4, syngas, ethanol, and acetic acid.

[0011] In any of the embodiments disclosed herein, the one or more combustion reagents can comprise C2H6, CH4, and CO.

[0012] In any of the embodiments disclosed herein, the additional combustion reagents can comprise CH4.

[0013] In any of the embodiments disclosed herein, separation system can produce a net energy of approximately 40 to approximately 80 GJ/tonne of one or more products produced.

[0014] In any of the embodiments disclosed herein, the separation system can produce a net energy of approximately 40 to approximately 80 GJ/tonne of C2H4 produced.

[0015] In any of the embodiments disclosed herein, the electrochemical cell can have a CO2 atom efficiency of 10% to 50%, and the separation system can have an overall CO2 atom efficiency of 80% to 100%.

[0016] In any of the embodiments disclosed herein, the separation unit can comprise a flash tank configured to condense one or more of the condensable products into the liquid phase, the flash tank being attached to one or more distillation columns configured to separate one or more components in the liquid phase.

[0017] In any of the embodiments disclosed herein, the separation unit can comprise one or more adsorbents and one or more membranes configured to separate one or more of the products in the gas phase.

[0018] In any of the embodiments disclosed herein, the one or more distillation columns can produce acetic acid and ethanol in the liquid phase, and the one or more membranes can produce syngas and the one or more adsorbents produce C2H4 in the gas phase.

[0019] In any of the embodiments disclosed herein, the complete combustion reaction in the combustion chamber can be defined as the combustion reaction consuming all available oxygen in the combustion chamber.

[0020] Another embodiment of the present disclosure can provide a separation system comprising: an electrochemical cell comprising a feed line, an oxidation products outlet line, and a reduction products outlet line, the electrochemical cell configured to receive CO2 from the feed line and electrochemically convert the CO2 in a reduction reaction to generate multiple products; a separation unit attached to the reduction products outlet line, the separation unit configured to receive the reduction products generated by the electrochemical cell and separate one or more products from the mixture, and reject one or more combustion reagents; and a combustion chamber attached to the separation unit and comprising a reagent inlet, the combustion chamber configured to receive the one or more combustion reagents rejected by the separation unit, receive additional combustion reagents from the reagent line, and fully combust the one or more combustion reagents in a complete combustion reaction to create one or more combustion products.

[0021] In any of the embodiments disclosed herein, the one or more products can comprise C2H4, syngas, ethanol, and acetic acid.

[0022] In any of the embodiments disclosed herein, the one or more combustion reagents can comprise C2H6, CH4, and CO.

[0023] In any of the embodiments disclosed herein, the additional combustion reagents can comprise CH4.

[0024] In any of the embodiments disclosed herein, the separation system can produce a net energy of approximately 40 to approximately 80 GJ/tonne of one or more products produced.

[0025] In any of the embodiments disclosed herein, the separation system can produce a net energy of approximately 40 to approximately 80 GJ/tonne of C2H4 produced.

[0026] In any of the embodiments disclosed herein, the electrochemical cell can have a CO2 atom efficiency of 10% to 50%, and the separation system can have an overall CO2 atom efficiency of 80% to 100%.

[0027] In any of the embodiments disclosed herein, the separation unit can comprise a flash tank configured to condense one or more of the condensable products into the liquid phase, the flash tank being attached to one or more distillation columns configured to separate one or more components in the liquid phase.

[0028] In any of the embodiments disclosed herein, the separation unit can comprise one or more adsorbents and one or more membranes configured to separate one or more of the products in the gas phase.

[0029] In any of the embodiments disclosed herein, the one or more distillation columns can produce acetic acid and ethanol in the liquid phase, and the one or more membranes can produce syngas and the one or more adsorbents produce C2H4 in the gas phase.

[0030] In any of the embodiments disclosed herein, the complete combustion reaction in the combustion chamber can be defined as the combustion reaction consuming all available oxygen in the combustion chamber.

[0031] Another embodiment of the present disclosure can provide a separation method comprising: reacting CO2 electrochemically to generate value added products, the reaction comprising an electrochemical reduction reaction; processing the product mixture to obtain one or more products and reject one or more combustion reagents; receiving additional combustion reagents; combusting the one or more combustion reagents and the additional combustion reagents in a complete combustion reaction to obtain one or more combustion products; and recycling the one or more combustion products to the electrochemical reduction reaction.

[0032] In any of the embodiments disclosed herein, the one or more products can comprise C2H4, syngas, ethanol, and acetic acid.

[0033] In any of the embodiments disclosed herein, the one or more combustion reagents can comprise C2H6, CH4, and CO.

[0034] In any of the embodiments disclosed herein, the additional combustion reagents can comprise CH4.

[0035] In any of the embodiments disclosed herein, the separation method can produce a net energy of approximately 40 to approximately 80 GJ/tonne of one or more products produced. [0036] In any of the embodiments disclosed herein, the separation method can produce a net energy of approximately 40 to approximately 80 GJ/tonne of C2H4 produced.

[0037] In any of the embodiments disclosed herein, the electrochemical reduction reaction can have a CO2 atom efficiency of 10% to 50%, and the separation method can have an overall CO2 atom efficiency of 80% to 100%.

[0038] In any of the embodiments disclosed herein, the separation can comprise condensing one or more of the condensable products into the liquid phase and distilling one or more components in the liquid phase.

[0039] In any of the embodiments disclosed herein, the complete combustion reaction can be defined as the combustion reaction consuming all available oxygen.

[0040] These and other aspects of the present disclosure are described in the Detailed Description below and the accompanying figures. Other aspects and features of embodiments of the present disclosure will become apparent to those of ordinary skill in the art upon reviewing the following description of specific, exemplary embodiments of the present invention in concert with the figures. While features of the present disclosure may be discussed relative to certain embodiments and figures, all embodiments of the present disclosure can include one or more of the features discussed herein. Further, while one or more embodiments may be discussed as having certain advantageous features, one or more of such features may also be used with the various embodiments of the invention discussed herein. In similar fashion, while exemplary embodiments may be discussed below as device, system, or method embodiments, it is to be understood that such exemplary embodiments can be implemented in various devices, systems, and methods of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate multiple embodiments of the presently disclosed subject matter and serve to explain the principles of the presently disclosed subject matter. The drawings are not intended to limit the scope of the presently disclosed subject matter in any manner.

[0042] FIG. 1 is a process flow diagram for a separation system, in accordance with some embodiments of the present disclosure.

[0043] FIG. 2 is another process flow diagram of a portion of a separation system, in accordance with some embodiments of the present disclosure.

[0044] FIG. 3 is a chart of energy consumption for a CO2 and hydrocarbon mixture separation system, in accordance with some embodiments of the present disclosure.

[0045] FIG. 4 is a flowchart of a method for CO2 and hydrocarbon mixture separation, in accordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

[0046] Performing CO2 reduction reactions (CO2RR) using aqueous phase electrochemistry with the cathodic and anodic sides of a cell separated by an anion exchange membrane (AEM) can be used with the disclosed systems and methods. CO2RR involves reducing carbon dioxide at a cathode using electrical energy: x CO₂ + m H₂O + n e~ -> C_xH_yO_z + n OH~ (1).

[0047] These reactions are often accompanied by production of hydrogen:

2 H⁺ + 2 e~ H₂ (2).

[0048] These cathodic reactions are accompanied by oxidation of water at the anode:

2 H₂O -> 4 H⁺ + 4 e~ + O₂ (3).

[0049] This series of reactions present an opportunity to convert CO2 from post combustion capture, direct air capture, or other sources to useful products via renewable energy and is therefore a potential basis for future for e-refineries. There are many catalytic features of CO2RR that affect the efficiency of this process. These features include developing catalysts with improved selectivity for specific products of interest (for example, carbon monoxide, formic acid, methane or C2+ hydrocarbons), improving Faradaic efficiencies and increasing reactant conversion.

[0050] Despite the benefits of the CO2RR, the downstream processing of the reaction products remains difficult. This situation has led to several challenges and has largely resulted in the overall process efficiency of CO2RR being overlooked. First, practical electrochemical cells produce a mixture of products at the cathode, often with low yields, requiring additional processing steps before high purity reaction products are available. This observation implies that downstream processing must be considered in any attempt to assess the energy efficiency of CO2RR processes. Second, only a fraction of the CO2 at the cathode reacts, so some fraction of the CO2 entering the reactor remains unused. Third, alkaline conditions must be maintained on the cathodic side of a CO2RR cell to suppress hydrogen evolution. In this alkaline environment, CO2 reacts with OH" ions to produce HCO3" and CO3²". These ions migrate to the anodic side via AEMs to maintain electroneutrality. In the acidic environment of the anode, HCO3" and CO3²"convert back to CO2. In electrochemical cells reducing CO2 to C2 hydrocarbons, 75% of the CO2 entering the cell ultimately migrates to the anode, strongly limiting the single pass conversion of the cell. This feature of CO2RR processes seems almost entirely unappreciated.

[0051] The observations above imply that in existing CO2RR processes the proportion of CO2 entering the reactor that forms desired products is often 10% or less. From an atom efficiency perspective, the observation that a majority of the reactant of interest leaves the process in an unreacted state is a glaring inefficiency. From a cost perspective, capturing CO2 from point sources or via DAC will inevitably cost money, so emitting much of the resulting CO2 from a conversion reactor without any effort to capture its value seems unwise.

[0052] Disclosed herein are separation strategies that can enable dramatic efficiency increases in CO2RR. Most importantly, the present disclosure includes concepts associated with recycling of downstream CO2 into the electrochemical CO2RR process. The concept of recycling partially reacted products into a reactor is a key concept in chemical process development, but remarkably it does not seem to have been considered in the development of CO2RR processes. An important implication of considering processes that include reactant recycling is that the single pass efficiency of the reactor, a focus of the existing CO2RR process, is only one of many variables controlling the overall process efficiency and that maximizing single pass conversion is unlikely to be the best overall strategy. [0053] In addition to considering process schemes with CO2 recycling, disclosed herein are separation systems and methods based on separations that are expected to be more energy efficient than standard separation systems. In particular, the present disclosure includes the use of adsorption- and membrane-based separations. In addition to offering a way to reduce the energy intensity of the separations, these choices are readily scalable. Moreover, they are well suited to laboratory implementation on the scale at which much of the research on CO2RR is being performed.

[0054] Although certain embodiments of the disclosure are explained in detail, it is to be understood that other embodiments are contemplated. Accordingly, it is not intended that the disclosure is limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. Other embodiments of the disclosure are capable of being practiced or carried out in various ways. Also, in describing the embodiments, specific terminology will be resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art and includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.

[0055] Herein, the use of terms such as “having,” “has,” “including,” or “includes” are open- ended and are intended to have the same meaning as terms such as “comprising” or “comprises” and not preclude the presence of other structure, material, or acts. Similarly, though the use of terms such as “can” or “may” are intended to be open-ended and to reflect that structure, material, or acts are not necessary, the failure to use such terms is not intended to reflect that structure, material, or acts are essential. To the extent that structure, material, or acts are presently considered to be essential, they are identified as such.

[0056] By “comprising” or “containing” or “including” is meant that at least the named compound, element, particle, or method step is present in the composition or article or method, but does not exclude the presence of other compounds, materials, particles, method steps, even if the other such compounds, material, particles, method steps have the same function as what is named.

[0057] It is also to be understood that the mention of one or more method steps does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified.

[0058] The components described hereinafter as making up various elements of the disclosure are intended to be illustrative and not restrictive. Many suitable components that would perform the same or similar functions as the components described herein are intended to be embraced within the scope of the disclosure. Such other components not described herein can include, but are not limited to, for example, similar components that are developed after development of the presently disclosed subject matter.

[0059] Reference will now be made in detail to exemplary embodiments of the disclosed technology, examples of which are illustrated in the accompanying drawings and disclosed herein. Wherever convenient, the same references numbers will be used throughout the drawings to refer to the same or like parts.

[0060] FIG. 1 shows the overall schematic of the separation system 100 disclosed herein. An aim of the separation system 100 is to separate the mixture of products exiting the cathode in the electrochemical cell 110 to ultimately obtain ethylene, syngas, acetic acid, and ethanol as pure products in the separation unit 120 while recycling carbon dioxide back to the electrochemical cell 110. The remaining unseparated mixture contains methane, carbon monoxide, and ethane. Instead of further separating these gases in the separation unit 120, the proposed process uses them as combustion fuel in the combustion chamber 130 to obtain energy for the separation processes in the separation unit 120.

[0061] The anode mixture can contain oxygen along with water and “crossover” CO2, which as mentioned above accounts for the majority of CO2 fed into the reactor. This mixture can be first fed to a flash tank to remove water. Separating CO2 and O2 can be an extremely energy intensive operation to the point that simply venting this CCT-ladcn mixture would be desirable in the past. Instead of applying an energy-intensive separation to this CO2/O2 mixture, the presently disclosed separation system 100 can instead use this mixture as oxyfuel for combustion of the unseparated hydrocarbon mixture from the cathodic products. Stoichiometrically, the amount of oxygen produced at the anode can be greater than the amount of oxygen required for this combustion process. The disclosed systems and methods therefore can add additional methane to the combustion chamber 130 to ensure that all oxygen entering the combustion chamber 130 is consumed. This combustion not only eliminates an energy- intensive separation but can also generate enough energy to drive the separation processes and, in principle, some excess energy that could be used for upstream direct air capture of carbon dioxide. CO2 and H2O produced as a result of the combustion can be recycled back to the electrochemical cell 110.

[0062] No CO2 remains in the streams exiting the process in FIG. 1. The atom efficiency for the CO2RR reactor considered here is at best 10% (e.g., the single-pass conversion). The addition of the downstream separations and CO2 recycle in the disclosed systems and methods can increase this atom efficiency by approximately an order of magnitude to nearly 100% overall conversion of CO2. The process can use CH4 combustion as part of the downstream processes, but this combustion does not lead to net CO2 emissions because all CO2 in the process can be converted to products.

[0063] In some examples, the atom efficiency of the CO2RR (e.g., the single-pass conversion) can be from 10% to 50% (e.g., from 10% to 45%, from 10% to 40%, from 10% to 35%, from 10% to 30%, from 10% to 25%, from 10% to 20%, from 15% to 50%, from 20% to 50%, from 25% to 50%, from 30% to 50%, from 35% to 50%, or from 40% to 50%). Similarly, the atom efficiency for the entire separation system 100 can be from 80% to 100% (e.g., from 81% to 100%, from 82% to 100%, from 83% to 100%, from 84% to 100%, from 85% to 100%, from 86% to 100%, from 87% to 100%, from 88% to 100%, from 89% to 100%, or from 90% to 100%).

[0064] An example of a separation unit 120 containing separation operations used in the present disclosure are illustrated in FIG 2 by way of illustration and not limitation. The cathodic products can be separated into gaseous and liquid streams using a flash tank 210. The gas mixtures comprising of C2H4, C2H6, CH4, CO, H2 and CO2 can then be separated by a combination of adsorption 230 and membrane 240 separations. The mixture can first be passed over molecular sieves to ensure that any trace water in the effluent gas stream from the flash tank 210 is removed. The mixture can then be passed through one or more adsorbents 230. The one or more adsorbents 230 can include a first adsorbent, which can be configured to selectively adsorb C2H4 and CO2. For instance, the first adsorbent can comprise the zeolite CaX. The mixture of C2H6, CH4, CO and H2 obtained above can then be passed through one or more membranes 240. For example, the one or more membranes 240 can include a hydrogen selective polymeric membrane, such as cellulose acetate or polyimide to obtain syngas.

[0065] The other output from the first adsorbent bed can be a mixture of C2H4 and CO2. This mixture can be fed into a second adsorbent bed with the aim of separating the two components. For example, the second adsorbent bed can comprise Metal Organic Frameworks (MOFs) with unsaturated metal sites as they can use 7r electron interactions to selectively adsorb ethylene. Single component isotherms of C2H4 and CO2 at room temperature for open metal site MOFs from the M2(m-dobdc) (M = Fe, Mn, Ni, Mg, Co) series can be used to select the second adsorbent bed. For example, Ni2(m-dobdc) can be used as the second adsorbent. Mn2(m-dobdc) and Fe2(m-dobdc) MOFs can also be used in the second adsorbent bed but may require inert atmospheres for synthesis and storage, which make them less ideal for practical use.

[0066] The aqueous mixture of condensable products leaving the cathode-side flash tank 210 in FIG. 2 can be separated to obtain useful fractions via one or more distillation columns 220. These columns can produce acetic acid and azeotropic mixture of alcohols (for instance, mostly ethanol) as byproducts.

[0067] Mass and energy balances for the resulting process can be performed using the ASPEN HYSYS software. Operating temperatures for the flash tanks can be, for example, -14, 4 and 3.6 °C for the flash tanks for cathodic gas mixture, anodic gas mixture and post combustion mixture, respectively. The adsorbents were chosen as described above. Single component isotherms for C2H4, C2H6, CO2, CO and CH4 for CaX and Ni2(m-dobdc) can be digitized and fitted to a Dual Site Langmuir-Freundlich Isotherm equation . Ideal Adsorbed Solution Theory can be employed to obtain estimate gas adsorption isotherms for all mixtures. The heats of adsorption can be used to estimate of energy requirements for regeneration of adsorbents. Heats of adsorption can provide minimum thermodynamic estimate of the process. As disclosed herein, the actual energy required can be 1.5 times this thermodynamic minimum. The choice of membrane can determine the ratio of H2 and CO in the syngas produced by the disclosed systems and methods. One example can include a cellulose acetate membrane with a H2/CO separation factor of 21 and operating at an upstream pressure of 35 bar at 35 °C. The distillation columns can be used to achieve > 99% purity of acetic acid and an azeotropic mixture of alcohols (-90% alcohol). The energy produced from the combustion chamber 130 can be calculated using the heats of combustion values for the gases.

[0068] FIG. 3shows the energy consumed by each separation process described in the examples above. Among the four separations in the process, adsorption can consume the most energy, followed by distillation, membrane separation, and flash tanks. Even though a separation of the cathodic gaseous mixture by adsorption can consume -34.5 GJ/tonne of C2H4 produced, this energy can be significantly lower than the energy input required by a combination of amine absorption, tri-ethylene glycol dehydration and cryogenic distillation for the same purification, which is about 68.9 GJ/tonne C2H4. Combusting the components that do not exit the process as purified products can produces 27.67 GJ/tonne C2H4 less than is required for the separations. A key part of the disclosed systems and methods is the use of CH4 combustion to avoid an energy-intensive separation of CO2 and O2. The amount of CH4 consumed for this purpose can be driven by the stoichiometry of the process, and it can be seen in FIG. 3 that as a result the overall process can produce excess energy of approximately 40 to approximately 80 (e.g., 52.38) GJ/tonne C2H4. This excess energy could of course be used in a number of ways. One attractive use of this excess energy is the capture of CO2 from the air to supply CO2 to the e-refinery (CO2 from the combustion system is insufficient; an external CO2 source is still needed). [0069] For instance, the separation system 100 can produce a net energy of approximately 40 GJ/tonne to approximately 80 GJ/tonne (e.g., from 40 GJ/tonne to 75 GJ/tonne, from 40 GJ/tonne to 70 GJ/tonne, from 40 GJ/tonne to 65 GJ/tonne, from 40 GJ/tonne to 60 GJ/tonne, from 40 GJ/tonne to 55 GJ/tonne, from 45 GJ/tonne to 55 GJ/tonne, from 50 GJ/tonne to 55 GJ/tonne, from 45 GJ/tonne to 80 GJ/tonne, from 50 GJ/tonne to 80 GJ/tonne, from 55 GJ/tonne to 80 GJ/tonne, from 60 GJ/tonne to 80 GJ/tonne, from 65 GJ/tonne to 80 GJ/tonne, or from 70 GJ/tonne to 80 GJ/tonne) based on the tonnes of product produces, such as based on the tonnes of C2H4 produced.

[0070] FIG. 4 illustrates a CO2 and hydrocarbon mixture separation method 400. Although the method is described with respect to the CO2 and hydrocarbon mixture separation system 100, it is understood that some or all of the separation method 400 can be performed by other systems or components not shown.

[0071] As shown, the method 400 can comprise reacting 410 CO2 to generate condensable products. The reaction can include an electrochemical reduction reaction. The reaction can occur in the electrochemical cell 110. The reaction 410 can reduce CO2 as described above in Equations 1-3. Unreacted reagents can be recycled to facilitate further reaction. The method 400 can then continue on to block 420.

[0072] In block 420, the method 400 can comprise separating 420 the reduction products. The separation can obtain products and reject combustion reagents. The obtained products can be further processed and/or sold. As described above with respect to the separation unit 120, the separation can include a flash tank, one or more distillation columns, one or more adsorbents, and/or one or more membranes. The obtained products can include, but are not limited to, acetic acid, ethanol, syngas, and C2H4. The method 400 can then continue on to block 430.

[0073] In block 430, the method 400 can comprise receiving 430 additional combustion reagents. A combustion reaction can include the reaction of a combustion reagent with oxygen. The combustion reagents can be received in the combustion chamber 130. In block 440, the method 400 can include combusting 440 the combustion reagents in a complete combustion reaction. Without wishing to be bound by any particular scientific theory, in a complete combustion, CO2 and H2O are the only products, and no hydrocarbon is left remaining. Combustion products can include CO2 (or CO) and H2O. The method 400 can then continue on to block 450.

[0074] In block 450, the method 400 can comprise recycling 450 the combustion products to the reduction reaction. As would be appreciated, the combustion products can include CO2 (or CO) and H2O, which can be used in the electrochemical reduction reaction in block 410. The method 400 can terminate after block 540. However, the method 400 can also include and proceed on to other method steps described herein but not shown.

[0075] Certain embodiments and implementations of the disclosed technology are described above with reference to block and flow diagrams of systems and methods and/or computer program products according to example embodiments or implementations of the disclosed technology. It will be understood that one or more blocks of the block diagrams and flow diagrams, and combinations of blocks in the block diagrams and flow diagrams, respectively, can be implemented by computer-executable program instructions. Likewise, some blocks of the block diagrams and flow diagrams may not necessarily need to be performed in the order presented, may be repeated, or may not necessarily need to be performed at all, according to some embodiments or implementations of the disclosed technology.

[0076] While the present disclosure has been described in connection with a plurality of exemplary aspects, as illustrated in the various figures and discussed above, it is understood that other similar aspects can be used, or modifications and additions can be made to the described aspects for performing the same function of the present disclosure without deviating therefrom. For example, in various aspects of the disclosure, methods and compositions were described according to aspects of the presently disclosed subject matter. However, other equivalent methods or composition to these described aspects are also contemplated by the teachings herein. Therefore, the present disclosure should not be limited to any single aspect, but rather construed in breadth and scope in accordance with the appended claims.

Claims

CLAIMS What is claimed is:

1. A separation system comprising: an electrochemical cell comprising a feed line, an oxidation products outlet line, and a reduction products outlet line, the electrochemical cell configured to receive CO2 from the feed line and electrochemically convert the CO2 in a reduction reaction to generate a product mixture; a separation unit attached to the condensable products outlet line, the separation unit configured to receive the reduction products generated by the electrochemical cell and separate one or more value-added products from the product mixture, and reject one or more combustion reagents; and a combustion chamber attached to the separation unit and comprising a reagent inlet and a recycle line, the combustion chamber configured to receive the one or more combustion reagents rejected by the separation unit, receive additional combustion reagents from the reagent line, and fully combust the one or more combustion reagents in a complete combustion reaction to create one or more combustion products, wherein the one or more combustion products are recycled to the feed line through the recycle line.

2. The separation system of Claim 1, wherein the one or more products comprise C2H4, syngas, ethanol, and acetic acid.

3. The separation system of Claim 1, wherein the one or more combustion reagents comprise C₂H₆, CH₄, and CO.

4. The separation system of any of Claims 1-3, wherein the additional combustion reagents comprise CH4.

5. The separation system of any of Claims 1-4, wherein the separation system produces a net energy of approximately 40 to approximately 80 GJ/tonne of one or more products produced.

6. The separation system of any of Claims 3-5, wherein the separation system produces a net energy of approximately 40 to approximately 80 GJ/tonne of C2H4 produced.

7. The separation system of any of Claims 1-6, wherein the electrochemical cell has a CO2 atom efficiency of 10% to 50%, and the separation system has an overall CO2 atom efficiency of 80% to 100%.

8. The separation system of any of Claims 1-7, wherein the separation unit comprises a flash tank configured to condense one or more of the condensable products into the liquid phase, the flash tank being attached to one or more distillation columns configured to separate one or more components in the liquid phase.

9. The separation system of any of Claims 1-8, wherein the separation unit comprises one or more adsorbents and one or more membranes configured to separate one or more of the product mixture in the gas phase.

10. The separation system of any of Claims 8-9, wherein the one or more distillation columns produce acetic acid and ethanol in the liquid phase, and the one or more membranes produce syngas and the one or more adsorbents produce C2H4 in the gas phase.

11. The separation system of any of Claims 1-10, wherein the complete combustion reaction in the combustion chamber is defined as the combustion reaction consuming all available oxygen in the combustion chamber.

12. A separation system comprising: an electrochemical cell comprising a feed line, an oxidation products outlet line, and a reduction products outlet line, the electrochemical cell configured to receive CO2 from the feed line and electrochemically convert the CO2 in a reduction reaction to generate a product mixture; a separation unit attached to the reduction products outlet line, the separation unit configured to receive the product mixture generated by the electrochemical cell and separate one or more value-added products from the product mixture, and reject one or more combustion reagents; and a combustion chamber attached to the separation unit and comprising a reagent inlet, the combustion chamber configured to receive the one or more combustion reagents rejected by the separation unit, receive additional combustion reagents from the reagent line, and fully combust the one or more combustion reagents in a complete combustion reaction to create one or more combustion products.

13. The separation system of Claim 12, wherein the one or more products comprise C2H4, syngas, ethanol, and acetic acid.

14. The separation system of Claim 12, wherein the one or more combustion reagents comprise C2H6, CH4, and CO.

15. The separation system of any of Claims 12-14, wherein the additional combustion reagents comprise CH4.

16. The separation system of any of Claims 12-15, wherein the separation system produces a net energy of approximately 40 to approximately 80 GJ/tonne of one or more products produced.

17. The separation system of any of Claims 14-16, wherein the separation system produces a net energy of approximately 40 to approximately 80 GJ/tonne of C2H4 produced.

18. The separation system of any of Claims 12-17, wherein the electrochemical cell has a CO2 atom efficiency of 10% to 40%, and the separation system has an overall CO2 atom efficiency of 80% to 100%.

19. The separation system of any of Claims 12-18, wherein the separation unit comprises a flash tank configured to condense one or more of the condensable products into the liquid phase, the flash tank being attached to one or more distillation columns configured to separate one or more components in the liquid phase.

20. The separation system of any of Claims 12-19, wherein the separation unit comprises one or more adsorbents and one or more membranes configured to adsorb one or more of the reduction products in the gas phase.

21. The separation system of any of Claims 19-20, wherein the one or more distillation columns produce acetic acid and ethanol in the liquid phase, and one or more membranes produce syngas and the one or more adsorbents C2H4 in the gas phase.

22. The separation system of any of Claims 12-21, wherein the complete combustion reaction in the combustion chamber is defined as the combustion reaction consuming all available oxygen in the combustion chamber.

23. A separation method comprising: reacting CO2 electrochemically to generate condensable products, the reaction comprising an electrochemical reduction reaction; separating the product mixture to obtain one or more products and reject one or more combustion reagents; receiving additional combustion reagents; combusting the one or more combustion reagents and the additional combustion reagents in a complete combustion reaction to obtain one or more combustion products; and recycling the one or more combustion products to the electrochemical reduction reaction.

24. The separation method of Claim 23, wherein the one or more products comprise C2H4, syngas, ethanol, and acetic acid.

25. The separation method of Claim 23, wherein the one or more combustion reagents comprise C2H6, CH4, and CO.

26. The separation method of any of Claims 23-25, wherein the additional combustion reagents comprise CH4.

27. The separation method of any of Claims 23-26, wherein the CO2 reduction reaction method produces a net energy of approximately 40 to approximately 80 GJ/tonne of one or more products produced.

28. The separation method of any of Claims 25-27, wherein the separation method produces a net energy of approximately 40 to approximately 80 GJ/tonne of C2H4 produced.

29. The separation method of any of Claims 23-28, wherein the electrochemical reduction reaction has a CO2 atom efficiency of 10% to 50%, and the separation method has an overall CO2 atom efficiency of 80% to 100%.

30. The separation method of any of Claims 23-29, wherein the separating comprises condensing one or more of the condensable products into the liquid phase and distilling one or more components in the liquid phase.

31. The CO2 reduction reaction method of any of Claims 23-30, wherein the complete combustion reaction is defined as the combustion reaction consuming all available oxygen.