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System and method for production of synthetic fuel through co2 capture and … — Arizona Board Of Regents On Behalf Of Arizona State University (US20250050273A1)

Arizona Board Of Regents On Behalf Of Arizona State University · Google Patents

Google Patents · Patents · License: Open Access

patent, google patents, intellectual property, US20250050273A1, Arizona Board Of Regents On Behalf Of Arizona State University, Klaus Lackner, en, 2025

ABSTRACT

Abstract

A system for producing gas streams for use in synthetic fuel production through CO2 capture and water splitting is disclosed. The system includes a CO2 capture device configured to receive a CO2-containing stream and including an aqueous alkaline solution. The alkaline solution includes hydroxide and/or carbonate ions. The CO2 capture device generates a carbon-rich solution when the alkaline solution absorbs CO2. The carbon-rich solution includes carbonate and/or bicarbonate ions. The system also includes an electrolyzer fluidically coupled to the CO2 capture device, and defining a volume including an anode region having an anode, and a cathode region having a cathode. The volume includes an electrolyte solution having a pH gradient generated by an electric current, causing the electrolyte solution to be acidic in the anode region and alkaline in the cathode region. The carbon-rich solution is received into the electrolyzer. The electrolyzer generates hydrogen, oxygen, and CO2 streams.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Utility application Ser. No. 17/428,965, entitled âSystem and Method for Production of Synthetic Fuel Through Co2 Capture and Water Splitting,â filed on Aug. 5, 2021, which is a the U.S. National Stage of International Application No. PCT/US2020/016864, entitled âSystem and Method for Production of Synthetic Fuel Through Co2 Capture and Water Splitting,â filed Feb. 5, 2020, which claims priority to and the benefit of U.S. Provisional Patent Application Nos. 62/801,356 entitled âSystem and Method for Production of Synthetic Fuel Through Co2 Capture and Water Splitting,â filed Feb. 5, 2019, the contents of each of which are hereby incorporated by reference in its entirety their entireties.

TECHNICAL FIELD

Embodiments described herein relate generally to systems and methods for producing synthetic fuel via capture of carbon dioxide and water splitting.

BACKGROUND

Although the importance of removing carbon dioxide from the atmosphere has been well established, a number of factors stand as obstacles. The technology is still new, and is often both expensive and fragile. Conventional capture devices also tend to have large initial capital costs in addition to high operating costs. The economic viability of CO 2 capture devices can be improved by reducing the cost of the devices, creating a new revenue stream from high value products produced from the captured CO 2 , or both.

SUMMARY

Embodiments described herein relate generally to systems and methods for the production of gas for synthetic fuel through CO 2 capture and water splitting. The system includes a CO 2 capture device that receives a CO 2 -containing stream and an aqueous alkaline solution. The aqueous alkaline solution includes hydroxide ions and/or carbonate ions and absorbs CO 2 from the CO 2 -containing stream to generate a carbon-rich solution. The carbon-rich solution includes carbonate ions and/or bicarbonate ions. The system further includes an electrolyzer fluidically coupled to the CO 2 capture device. The electrolyzer includes an anode region, a cathode region, and an electrolyte solution. The electrolyzer generates a pH gradient in the electrolyte solution when an electrolyte current is applied to the electrolyzer, such that the electrolyte solution is acidic in the anode region and alkaline in the cathode region. The electrolyzer also receives the carbon-rich solution in an incoming stream and generates hydrogen, oxygen, and CO 2 gas streams.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a system for production of gas streams that can be used to produce synthetic fuel through CO 2 capture and water splitting, according to an embodiment.

FIG. 2 shows an electrolyzer that can be incorporated in a system for production of synthetic fuel through CO 2 capture and water splitting, according to an embodiment.

FIG. 3 shows an electrolyzer that can be incorporated in a system for production of synthetic fuel through CO 2 capture and water splitting, according to an embodiment.

FIG. 4 shows a plot of relative carbonate fractions as a function of pH.

DETAILED DESCRIPTION

Embodiments described herein relate generally to systems and methods for the production of synthetic fuel through CO 2 capture and water splitting. In some embodiments, the system includes a CO 2 capture device and an electrolyzer. A CO 2 -containing gas stream can flow into the CO 2 capture device and contact an alkaline solution that flows into the CO 2 capture device via a separate stream. In the CO 2 capture device, the alkaline solution captures CO 2 after direct or indirect contact with a CO 2 -containing gas stream. Upon capturing the CO 2 , the alkaline solution transforms into a dissolved inorganic carbon (DIC) rich solution (referred to herein also as a carbon-rich solution), which can then flow into the electrolyzer. In some embodiments, the DIC-rich solution can have a higher CO 2 concentration than the CO 2 -containing gas stream. In some embodiments, the DIC-rich solution can have a greater mass flow rate of CO 2 than the CO 2 -containing gas stream. Upon removal of CO 2 from the CO 2 -containing stream, the CO 2 -containing stream transforms into an effluent stream. The exit stream leaves the CO 2 capture device with a lower total flow rate of CO 2 than the total flow rate of CO 2 in the CO 2 -containing stream flowing into the CO 2 capture device. In some embodiments, a water stream can flow into the system to supply make-up water consumed either in the CO 2 capture device or the electrolyzer.

The electrolyzer, in addition to producing hydrogen and oxygen gas streams, can produce a CO 2 stream with relatively high purity. The electrolyzer includes an electrolyte solution. When an electrical current is applied to the electrolyzer, the electrolyte solution has a pH gradient and several ionic concentration gradients. In some embodiments, the electrolyzer can include one or more dividers that partition the electrolyzer into a discrete anode region and a discrete cathode region. In some embodiments, the dividers can partition the electrolyzer into a discrete anode region, a discrete cathode region, and a discrete neutral region between the anode region and the cathode region. The electrolyte acts as an anolyte in the anodic region and a catholyte in the cathodic region. In some embodiments, the composition of the anolyte and the catholyte can be engineered to maximize the pH gradient across the electrolyzer and the yield of gas products from the electrolyzer. The aforementioned DIC-rich solution can flow into the electrolyzer, while the aforementioned alkaline solution can flow out of the electrolyzer. In some embodiments, a carbonate stream can flow out of the electrolyzer for further processing.

The removal of CO 2 from air, engine exhaust, bodies of water, or other sources of CO 2 can aid in combatting climate change. Several systems and processes currently exist for CO 2 capture. Examples include moisture swing apparatus and activated carbon adsorption. Additional examples of apparatus used for CO 2 capture are described in U.S. Pat. No. 8,133,305 entitled, âREMOVAL OF CARBON DIOXIDE FROM AIR,â filed Nov. 5, 2008 (âthe '305 Patentâ), the disclosure of which is incorporated herein by reference in its entirety.

While the capture of CO 2 from various sources provides environmental benefits, CO 2 capture by itself is typically not economically viable. With the use of additional chemical processes, high-value products can be developed from captured CO 2 . However, such chemical processes typically require significant energy input. Energy can be introduced into an electrolyzer to split water into hydrogen and oxygen. By combining a CO 2 capture device or system with an electrolyzer; CO 2 , oxygen, and hydrogen gas streams with high purity can be produced. In some embodiments, the energy introduced into the electrolyzer can be partially or substantially renewable (e.g., solar, wind, geothermal, etc.). The hydrogen stream, and the energy associated with the hydrogen, can effect subsequent reactions and chemical transformations and aid in the development of high-value products. This can improve both the economic and thermodynamic favorability of CO 2 capture systems and processes.

There is a wide range of useful chemicals that can be formed from the hydrogen and CO 2 derived from systems described herein. Examples include, but are not limited to, methane from hydrogen and CO 2 (i.e., the Sabatier reaction: CO 2 +4H 2 âCH 4 +2H 2 O+165 kJ/mol), methanol from hydrogen and CO 2 (i.e., CO 2 +3H 2 âH 3 COH+H 2 O+130.7 kJ/mol), and syngas from hydrogen and CO 2 (i.e., reverse water gas shift: CO 2 +H 2 âCO+H 2 O+2.8 kJ/mol). Other examples of fuels or fuel precursors that may be produced from hydrogen and CO 2 include, but are not limited to, dimethyl-ether, formic acid, ethylene, ethylene oxide, mixtures like gasoline, diesel, kerosene or jet fuel, or other hydrocarbons, alcohols, ethers, ketones, or organic acids. Additional examples of systems and methods used for the conversion of hydrogen and CO 2 into high-value fuel are described in V. N. Ipatieff, and G. S. Monroe, Synthesis of methanol from carbon dioxide and hydrogen over copper-alumina catalysts. Mechanism of reaction, Journal of the American Chemical Society, 67, no. 12 (1945): 2168-2171, Y. Izumi, Recent advances in the photocatalytic conversion of carbon dioxide to fuels with water and/or hydrogen using solar energy and beyond, Coordination Chemistry Reviews, 257, no. 1 (2013): 171-186, and U.S. Pat. No. 8,133,926 entitled, âCONVERSION OF CARBON DIOXIDE TO DIMETHYL ETHER USING BI-REFORMING OF METHANE OR NATURAL GASâ filed Jun. 19, 2008 (âthe '926 Patentâ), the disclosures of which are incorporated herein by reference in their entirety.

As used in this specification, the singular forms âa,â âan,â and âtheâ include plural referents unless the context clearly dictates otherwise. Thus, for example, the term âa memberâ is intended to mean a single member or a combination of members, âa materialâ is intended to mean one or more materials, or a combination thereof.

The term âsubstantiallyâ when used in connection with âcylindrical,â âlinear,â and/or other geometric relationships is intended to convey that the structure so defined is nominally cylindrical, linear or the like. As one example, a portion of a support member that is described as being âsubstantially linearâ is intended to convey that, although linearity of the portion is desirable, some non-linearity can occur in a âsubstantially linearâ portion. Such non-linearity can result from manufacturing tolerances, or other practical considerations (such as, for example, the pressure or force applied to the support member). Thus, a geometric construction modified by the term âsubstantiallyâ includes such geometric properties within a tolerance of plus or minus 5% of the stated geometric construction. For example, a âsubstantially linearâ portion is a portion that defines an axis or centerline that is within plus or minus 5% of being linear.

As used herein, the term âsetâ and âpluralityâ can refer to multiple features or a singular feature with multiple parts. For example, when referring to a set of electrodes, the set of electrodes can be considered as one electrode with multiple portions, or the set of electrodes can be considered as multiple, distinct electrodes. Additionally, for example, when referring to a plurality of electrochemical cells, the plurality of electrochemical cells can be considered as multiple, distinct electrochemical cells or as one electrochemical cell with multiple portions. Thus, a set of portions or a plurality of portions may include multiple portions that are either continuous or discontinuous from each other. A plurality of particles or a plurality of materials can also be fabricated from multiple items that are produced separately and are later joined together (e.g., via mixing, an adhesive, or any suitable method).

As used in this specification, âdissolved inorganic carbon (DIC)â can include dissolved CO 2 , bicarbonate ions (HCO 3 â ), carbonate ions (CO 3 2â ), and other molecular species that bind CO 2 , HCO 3 â and CO 3 2â in aqueous solution.

FIG. 1 is a schematic illustration of a system 100 for production of synthetic fuel through CO 2 capture and water splitting, according to an embodiment. The system circulates fluids between a CO 2 capture device 110 that absorbs CO 2 and an electrolyzer 120 that electrolyzes DIC-containing water to produce CO 2 , hydrogen, and oxygen.

CROSS-REFERENCE TO RELATED APPLICATIONS

TECHNICAL FIELD

Embodiments described herein relate generally to systems and methods for producing synthetic fuel via capture of carbon dioxide and water splitting.

BACKGROUND

SUMMARY

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a system for production of gas streams that can be used to produce synthetic fuel through CO 2 capture and water splitting, according to an embodiment.

FIG. 2 shows an electrolyzer that can be incorporated in a system for production of synthetic fuel through CO 2 capture and water splitting, according to an embodiment.

FIG. 3 shows an electrolyzer that can be incorporated in a system for production of synthetic fuel through CO 2 capture and water splitting, according to an embodiment.

FIG. 4 shows a plot of relative carbonate fractions as a function of pH.

DETAILED DESCRIPTION

The CO 2 capture device 110 is configured to receive a CO 2 -containing stream 112 through an input 115 , which is then either directly or indirectly exposed to an alkaline solution 114 . In some embodiments, the input 115 may be a conduit or channel, while in others it may be an aperture through which fluid communication between the electrolyzer 120 and capture device 110 is possible. In some embodiments, the CO 2 capture device 110 is fluidically coupled (e.g., via a conduit) to the electrolyzer 120 such that wherein the alkaline solution 114 is received from the electrolyzer 120 through an output 113 of the electrolyzer 120 . In some embodiments, the output 113 may be a conduit or channel, while in others it may be an aperture through which fluid communication between the electrolyzer 120 and capture device 110 is possible. The CO 2 capture device 110 is also fluidically coupled to the electrolyzer 120 via another conduit such that the CO 2 capture device 110 can deliver a DIC- rich solution 116 to the electrolyzer 120 . The CO 2 capture device 110 also expels an exit stream 118 with a lower total amount of CO 2 , when compared to the CO 2 -containing stream 112 . In some embodiments, a water stream 119 can flow into the system 100 (e.g., to the CO 2 capture device 110 , the electrolyzer 120 , or elsewhere) to supply make-up water consumed either in the CO 2 capture device 110 or the electrolyzer 120 .

In some embodiments, the CO 2 capture device 110 can directly expose the CO 2 -containing stream 112 to the alkaline solution 114 . The alkaline solution 114 absorbs substantially all or a portion of the CO 2 from the CO 2 -containing stream 112 . This works to remove CO 2 from the CO 2 -containing stream 112 while simultaneously lowering the pH of the alkaline solution 114 and transforming the alkaline solution 114 into the DIC- rich solution 116 . In some embodiments, the CO 2 capture device 110 can include an intermediary sorbent or sorbent system that contacts the alkaline solution and absorbs CO 2 from the CO 2 -containing stream 112 , such that the alkaline solution 114 does not directly contact the CO 2 -containing stream 112 . In some embodiments, the intermediary sorbent can include activated hydrophobic carbon. In some embodiments, heat can be applied to the intermediary sorbent or sorbent system during CO 2 absorption to facilitate CO 2 transfer.

In some embodiments, the CO 2 -containing stream 112 can include an ambient air stream, CO 2 at higher concentration derived from an ambient air stream, or any other gaseous or liquid stream that contains CO 2 . In some embodiments, the CO 2 -containing stream 112 can include exhaust from an engine or a power plant from a biological process producing CO 2 , as for example from a fermenter, from a calciner, or from CO 2 produced inside buildings by human occupants or animals. Other sources include calciners, industrial processes, etc. For example, in a factory where liquid or gaseous fuels are produced from CO 2 and hydrogen, it may be advantageous to consume some of the liquid or gaseous fuel to deliver electricity when solar electricity is not in sufficient supply. The exhaust gas from such a factory may be processed for recovering all or some of the produced CO 2 so that it can be reconverted to fuel at a later time. In some embodiments, the CO 2 -containing stream 112 can include any combination of the aforementioned sources.

In some embodiments, the CO 2 -containing stream 112 can have a CO 2 concentration significantly lower than the CO 2 concentration of ambient outdoor air. Streams with CO 2 concentrations significantly below those of ambient outdoor air can be processed in order to clean up the streams. In such cases, CO 2 is a byproduct of the cleaning process. An example would be removing CO 2 from air prior to liquefaction. In some embodiments, the CO 2 -containing stream 112 can have a CO 2 concentration significantly greater than the CO 2 concentration of ambient outdoor air. Streams with CO 2 concentrations higher or equal to that of air may be processed for the primary purpose of producing a stream of CO 2 . In some embodiments, the CO 2 -containing stream 112 can have a CO 2 -concentration of at least about 10 ppm, at least about 50 ppm, at least about 100 ppm, at least about 200 ppm, at least about 300 ppm, at least about 400 ppm, at least about 500 ppm, at least about 600 ppm, at least about 700 ppm, at least about 800 ppm, at least about 900 ppm, at least about 0.1 vol %, at least about 0.5 vol %, at least about 1 vol %, at least about 5 vol %, at least about 10 vol %, at least about 20 vol %, at least about 30 vol %, at least about 40 vol %, at least about 50 vol %, at least about 60 vol %, at least about 70 vol %, at least about 80 vol %, at least about 90 vol %, at least about 95 vol %, at least about 96 vol %, at least about 97 vol %, at least about 98 vol %, or at least about 99 vol %. In some embodiments, the CO 2 -containing stream 112 can have a CO 2 concentration of no more than about 100 vol %, no more than about 99 vol %, no more than about 98 vol %, no more than about 97 vol %, no more than about 96 vol %, no more than about 95 vol %, no more than about 90 vol %, no more than about 80 vol %, no more than about 70 vol %, no more than about 60 vol %, no more than about 50 vol %, no more than about 40 vol %, no more than about 30 vol %, no more than about 20 vol %, no more than about 10 vol %, no more than about 5 vol %, no more than about 1 vol %, no more than about 0.5 vol %, no more than about 0.1 vol %, no more than about 900 ppm, no more than about 800 ppm, no more than about 700 ppm, no more than about 600 ppm, no more than about 500 ppm, no more than about 400 ppm, no more than about 300 ppm, no more than about 200 ppm, no more than about 100 ppm, or no more than about 50 ppm. Combinations of the above referenced CO 2 concentration ranges in the CO 2 -containing stream 112 are also possible (e.g., at least about 10 ppm and no more than about 100 vol % or at least about 300 ppm and no more than about 90 vol %), inclusive of all values and ranges therebetween. In some embodiments, the CO 2 -containing stream 112 can have a CO 2 concentration of about 10 ppm, about 50 ppm, about 100 ppm, about 200 ppm, about 300 ppm, about 400 ppm, about 500 ppm, about 600 ppm, about 700 ppm, about 800 ppm, about 900 ppm, about 0.1 vol %, about 0.5 vol %, about 1 vol %, about 5 vol %, about 10 vol %, about 20 vol %, about 30 vol %, about 40 vol %, about 50 vol %, about 60 vol %, about 70 vol %, about 80 vol %, about 90 vol %, about 95 vol %, about 96 vol %, about 97 vol %, about 98 vol %, about 99 vol %, or about 100 vol %.

The alkaline solution 114 includes alkalizing ions. In some embodiments, the alkalizing ions can include hydroxide ions, carbonate ions, phosphate ions, ammonium ions, polyprotic organic acids, citrate ions, or any other suitable alkalizing ions. In some embodiments, the alkaline solution 114 can be aqueous. In some embodiments, the counter-ion to the alkalizing ions can be an alkali metal (e.g., sodium, potassium, etc.), an alkaline earth metal (e.g., magnesium, calcium, etc.), or any other suitable counter-ion. In some embodiments, the alkaline solution 114 can include dissolved sodium hydroxide, and can absorb CO 2 to form sodium carbonate via chemical equation 1.

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In some embodiments, the alkaline solution 114 can be in contact with a moisture swing sorbent that transfers CO 2 from the CO 2 -containing stream 112 to the alkaline solution 114 . In some embodiments, the CO 2 capture device 110 can apply a moisture swing sorbent to absorb CO 2 in the CO 2 capture device 110 when the alkaline solution 114 is exposed to open air and regenerate the sorbent in the presence of water vapor (e.g., delivered by the alkaline solution 114 ). In some embodiments, the moisture swing sorbent can include a moisture swing active membrane that transports CO 2 from the side of the membrane with the CO 2 -containing stream 112 to the side of the membrane with the alkaline solution 114 . In some embodiments, the CO 2 capture device 110 can employ a hollow fiber filter that is exposed to and absorbs CO 2 from the CO 2 -containing stream 112 . In some embodiments, the alkaline solution 114 can include additives and/or promoters to enhance and/or speed up CO 2 absorption from the CO 2 -containing stream 112 and/or CO 2 desorption from the alkaline solution 114 . See, for example, additive 215 of FIG. 2 . In some embodiments, the alkaline solution 114 can include a sodium carbonate/bicarbonate solution that is enriched with carbonic anhydrase to speed up the liquid gas transfer between the CO 2 -containing stream 112 and the alkaline solution 114 . In some embodiments, the alkaline solution 114 can include a sodium carbonate/bicarbonate solution that is enriched with phosphates to speed up the liquid gas transfer between the CO 2 -containing stream 112 and the alkaline solution 114 . In some embodiments, the alkaline solution 114 can be converted into a bicarbonate-rich solution during CO 2 capture. In some embodiments, the alkaline solution 114 can be converted into a carbonate-rich solution during CO 2 capture.

In some embodiments, the alkaline solution 114 can include dissolved potassium hydroxide. In some embodiments, the alkalizing ions can have a concentration in the alkaline solution 114 of at least about 0.5 mM, at least about 1 mM, at least about 5 mM, at least about 10 mM, at least about 50 mM, at least about 100 mM, at least about 500 mM, at least about 1 M, at least about 2 M, at least about 3 M, at least about 4 M, at least about 5 M, at least about 6 M, at least about 7 M, at least about 8 M, or at least about 9 M. In some embodiments, the alkalizing ions can have a concentration in the alkaline solution 114 of no more than about 10 M, no more than about 9 M, no more than about 8 M, no more than about 7 M, no more than about 6 M, no more than about 5 M, no more than about 4 M, no more than about 3 M, no more than about 2 M, no more than about 1 M, no more than about 500 mM, no more than about 100 mM, no more than about 50 mM, no more than about 10 mM, no more than about 5 mM, or no more than about 1 mM. Combinations of the above-referenced concentrations of alkalizing ions in the alkaline solution 114 are also possible (e.g., at least about 0.5 mM and no more than about 10 M or at least about 1 mM and no more than about 500 mM). In some embodiments, the alkalizing ions can have a concentration in the alkaline solution 114 of about 0.5 mM, about 1 mM, about 5 mM, about 10 mM, about 50 mM, about 100 mM, about 500 mM, about 1 M, about 2 M, about 3 M, about 4 M, about 5 M, about 6 M, about 7 M, about 8 M, about 9 M, or about 10 M.

In some embodiments, the rate of CO 2 transfer between the CO 2 -containing stream 112 and the alkaline solution 114 can be a function of the contact area between the CO 2 -containing stream 112 and the alkaline solution 114 (or the contact area between the CO 2 -containing stream 112 and any intermediary sorbent and the contact area between any intermediary sorbent and the alkaline solution 114 ), the temperature of the CO 2 capture device 110 , the relative flow rates of the alkaline solution 114 and the CO 2 -containing stream 112 , and any other factors that affect CO 2 diffusion and CO 2 uptake. Additionally, CO 2 transfer between the CO 2 -containing stream 112 and the alkaline solution 114 is a function of the pH of the alkaline solution 114 , as a higher pH allows for both higher possible carbon uptake per unit volume of solution and drives a higher reaction rate. In some embodiments, the alkaline solution 114 can include a buffer to maintain a high pH.

In some embodiments, the alkaline solution 114 can have a pH of at least about 10, at least about 10.5 at least about 11, at least about 11.5, at least about 12, at least about 12.5, at least about 13, at least about 13.5, at least about 14. In some embodiments, the alkaline solution 114 can have a pH of no more than about 15, no more than about 14.5, no more than about 14, no more than about 13.5, no more than about 13, no more than about 12.5, no more than about 12, no more than about 11.5, no more than about 11, or no more than about 10.5. Combinations of the above-referenced pH-values for the alkaline solution 114 are also possible (e.g., at least about 10 and no more than about 15 or at least about 12 and no more than about 13), inclusive of all values and ranges therebetween. In some embodiments, the alkaline solution 114 can have a pH of about 10, about 10.5, about 11, about 11.5, about 12, about 12.5, about 13, about 13.5, or about 14.

In some embodiments, the alkaline solution 114 can include DIC, in the form of carbonate and/or bicarbonate. In some embodiments, the alkaline solution 114 can be free or substantially free of DIC. In some embodiments, DIC concentration can be defined as the number of moles of carbon per liter of solution. In some embodiments, the alkaline solution 114 can have a DIC concentration of at least about 0.1 mM, at least about 0.5 mM, at least about 1 mM, at least about 5 mM, at least about 10 mM, at least about 50 mM, at least about 100 mM, at least about 500 mM, at least about 1 M, or at least about 2 M. In some embodiments, the alkaline solution 114 can have a DIC concentration can be no more than about 3 M, no more than about 2 M, no more than about 1 M, no more than about 500 mM, no more than about 100 mM, no more than about 50 mM, no more than about 10 mM, no more than about 5 mM, no more than about 1 mM, or no more than about 0.5 mM. Combinations of the above-referenced concentrations DIC concentration in the alkaline solution 114 are also possible (e.g., at least about 0.1 mM and no more than about 3 M or at least about 1 mM and no more than about 500 mM). In some embodiments, the alkaline solution 114 can have a DIC concentration of about 0.1 mM, about 0.5 mM, about 1 mM, about 5 mM, about 10 mM, about 50 mM, about 100 mM, about 500 mM, or about 1 M, about 2 M, or about 3 M.

As described above, the DIC- rich solution 116 results from the absorption of CO 2 by the alkaline solution 114 upon exposure to the CO 2 -containing stream. In some embodiments, the DIC- rich solution 116 can have a pH of at least about 8, at least about 8.5, at least about 9, at least about 9.5, at least about 10, at least about 10.5, at least about 11, at least about 11.5, at least about 12, at least about 12.5, at least about 13, or at least about 13.5. In some embodiments, the DIC- rich solution 116 can have a pH of no more than about 14, no more than about 13.5, no more than about 13, no more than about 12.5, no more than about 12, no more than about 11.5, no more than about 11, no more than about 10.5, no more than about 10, no more than about 9.5, no more than about 9, or no more than about 8.5. Combinations of the above-referenced pH-values for the DIC- rich solution 116 are also possible (e.g., at least about 8 and no more than about 14 or at least about 10 and no more than about 13), inclusive of all values and ranges therebetween. In some embodiments, the DIC- rich solution 116 can have a pH of about 8, about 8.5, about 9, about 9.5, about 10, about 10.5, about 11, about 11.5, about 12, about 12.5, about 13, about 13.5, or about 14.

In some embodiments, the DIC- rich solution 116 can include carbonate ions, bicarbonate ions, or any other suitable DIC species. In some embodiments, the counter-ion to the DIC species in the DIC- rich solution 116 can include one or more alkali metals (e.g., sodium, potassium, etc.), one or more alkaline earth metals (e.g., magnesium, calcium, etc.), or any other suitable counter-ion. In some embodiments, the DIC- rich solution 116 can be produced or obtained from outside the system 100 . In some embodiments, the DIC- rich solution 116 can be stored in a tank for later introduction into the electrolyzer 120 under more advantageous conditions (e.g., when intermittent electrical power is available to power the electrolyzer 120 ).

In some embodiments, the DIC species can have a concentration in the DIC- rich solution 116 of at least about 0.1 mM, at least about 0.5 mM, at least about 1 mM, at least about 5 mM, at least about 10 mM, at least about 50 mM, at least about 100 mM, at least about 500 mM, at least about 1 M, or at least about 2 M. In some embodiments, the DIC species can have a concentration in the DIC- rich solution 116 of no more than about 3 M, no more than about 2 M, no more than about 1 M, no more than about 500 mM, no more than about 100 mM, no more than about 50 mM, no more than about 10 mM, no more than about 5 mM, no more than about 1 mM, or no more than about 0.5 mM. Combinations of the above-referenced concentrations of DIC species in the DIC- rich solution 116 are also possible (e.g., at least about 0.1 mM and no more than about 3 M or at least about 1 mM and no more than about 500 mM), inclusive of all values and ranges therebetween. In some embodiments, the DIC species can have a concentration in the DIC- rich solution 116 of about 0.1 mM, about 0.5 mM, about 1 mM, about 5 mM, about 10 mM, about 50 mM, about 100 mM, about 500 mM, or about 1 M, about 2 M, or about 3 M.

The exit stream 118 is an effluent stream from the CO 2 capture device 110 . The CO 2 from the CO 2 -containing stream 112 is either partially or completely removed in the CO 2 capture device 110 and the CO 2 -containing stream 112 transforms into the exit stream 118 (i.e., the exit stream 118 is substantially the same as the CO 2 -containing stream 112 without the removed CO 2 ). In some embodiments, the exit stream 118 can be a gas stream. In some embodiments, the exit stream 118 can be a liquid stream. In some embodiments, the exit stream 118 can include liquid and gas. In some embodiments, the exit stream 118 can include dissolved solids. The total flow rate of CO 2 exiting the CO 2 capture device 110 is less than the total flow rate of CO 2 entering the CO 2 capture device 110 .

In some embodiments, the exit stream 118 can have a CO 2 concentration of no more than about 100 vol %, no more than about 95 vol %, no more than about 90 vol %, no more than about 80 vol %, no more than about 70 vol %, no more than about 60 vol %, no more than about 50 vol %, no more than about 40 vol %, no more than about 30 vol %, no more than about 20 vol %, no more than about 10 vol %, no more than about 5 vol %, no more than about 1 vol %, no more than about 0.5 vol %, no more than about 0.1 vol %, no more than about 900 ppm, no more than about 800 ppm, no more than about 700 ppm, no more than about 600 ppm, no more than about 500 ppm, no more than about 400 ppm, no more than about 300 ppm, no more than about 200 ppm, no more than about 100 ppm, no more than about 50 ppm, no more than about 10 ppm, no more than about 5 ppm, or no more than about 1 ppm, inclusive of all values and ranges therebetween. In some embodiments, the exit stream 118 can be free or substantially free of CO 2 .

In some embodiments, the water stream 119 delivers make-up water to the system 100 . This make-up water can replenish water to the system 100 that is split in the electrolyzer 120 . As shown, the water stream 119 is fluidically coupled to the CO 2 capture device 110 . In some embodiments, the water stream 119 can be fluidically coupled to the electrolyzer 120 . In some embodiments, water can be removed from the system 100 when excess water is present in the system 100 . In some embodiments, water vapor can be removed from the CO 2 -containing stream 112 .

In some embodiments, the water stream 119 can be subject to additional processing before delivering water to the system 100 . In some embodiments, contaminants can be either partially removed or substantially removed from the water stream 119 prior to the delivery of water to the system 100 . These contaminants can include chlorides, nitrates, sulfates, and any other undesirable components, includes such that may poison the electrode catalysts. The processing of the water stream 119 can ultimately yield greater purity levels in the production streams (i.e., the hydrogen stream, the oxygen stream, the CO 2 stream, and/or the carbonate stream). The additional processing can include reverse osmosis, filtration, membrane treatment, distillation, or any other suitable process or combination of processes.

In some embodiments, the flow rate of the alkaline solution 114 , the DIC- rich solution 116 and/or the water stream 119 can be at least about 1 mL/min, at least about 5 mL/min, at least about 10 mL/min, at least about 50 mL/min, at least about 100 mL/min, at least about 200 mL/min, at least about 300 mL/min, at least about 400 mL/min, at least about 500 mL/min, at least about 600 mL/min, at least about 700 mL/min, at least about 800 mL/min, at least about 900 mL/min, at least about 1 L/min, at least about 5 L/min, at least about 10 L/min, at least about 50 L/min, at least about 100 L/min, at least about 200 L/min, at least about 300 L/min, at least about 400 L/min, at least about

CLAIMS

Claims ( 30 )

1 .- 31 . (canceled)

32 . A system for producing gas streams for use in synthetic fuel production through CO 2 capture and water splitting, comprising:

a CO 2 capture apparatus containing an aqueous alkaline solution absorbing CO 2 from air received into the CO 2 capture apparatus; an electrolyzer fluidically coupled to the CO 2 capture apparatus, the electrolyzer comprising an output, a volume including an anode region having an anode, and a cathode region having a cathode, the volume comprising an electrolyte solution having a pH gradient generated by the application of an electric current between the anode and the cathode, causing the electrolyte solution in the anode region to have a pH less than about 6, and the electrolyte in the cathode region to have a pH greater than about 5; and a conduit placing the CO 2 capture device in fluid communication with the volume of the electrolyzer through a distributor disposed between the anode region and the neutral region, the distributor having a plurality of holes facing toward the neutral region and away from the anode region, wherein the carbon-rich solution is received into the electrolyzer; and wherein an alkaline-rich solution is removed from the cathode region of the electrolyzer through the output.

33 . (canceled)

34 . The system of claim 32 , wherein the conduit is a first conduit, further comprising a second conduit, the second conduit placing the CO 2 capture apparatus in fluid communication with the volume of the electrolyzer.

35 . The system of claim 32 , wherein the electrolyzer further comprises a neutral region between the anode region and cathode region, the neutral region having a pH between about 6 and about 13.

36 . The system of claim 35 , further comprising a conduit, the conduit placing the CO2 capture apparatus in fluid communication with the neutral region.

37 - 40 . (canceled)

41 . The system of claim 32 , wherein the electrolyzer produces oxygen gas in the electrolyzer and an oxygen product stream exits the electrolyzer.

42 . The system of claim 41 , the electrolyzer further comprising an anodic head space above at least the anode region, wherein the oxygen product stream exits the electrolyzer via the anodic head space.

43 .- 44 . (canceled)

45 . An electrolyzer, comprising:

a volume having a cathode region, an anode region, and a neutral region between the cathode region and the anode region; an electrolyte solution inside the volume having a pH gradient when an electric current is applied to the electrolyzer such that the electrolyte solution has a pH of less than about 6 in the anode region, a pH of greater than about 5 in the cathode region, and a pH of between about 6 and about 13 in the neutral region; an output in the cathode region configured to remove an alkaline-rich solution from the electrolyzer; and an input configured to supply a carbon-rich solution to the electrolyzer, wherein the input is fluidically coupled to a distributor disposed between the anode region and the neutral region, the distributor having a plurality of holes facing toward the neutral region and away from the anode region.

46 . The electrolyzer of claim 45 , wherein the alkaline-rich solution comprises hydroxide ions and/or carbonate ions.

47 . The electrolyzer of claim 45 , wherein the carbon-rich solution comprises carbonate ions and/or bicarbonate ions.

48 .- 52 . (canceled)

53 . The electrolyzer of claim 45 , further comprising a cathodic head space over at least part of the cathode region, wherein the electrolyzer produces CO2 gas in the neutral region, and a CO2 gas stream exits the electrolyzer via the cathodic head space, wherein the electrolyzer produces hydrogen gas in the cathode region and a hydrogen product stream exits the electrolyzer via the cathodic head space.

54 . (canceled)

55 . The electrolyzer of claim 45 , further comprising an anodic head space over at least part of the anode region, wherein the electrolyzer produces oxygen gas in the anode region, and an oxygen product stream exits the electrolyzer via the anodic head space.

56 . The electrolyzer of claim 55 , wherein the anodic head space has a pressure of between about 1 bar absolute and about 3 bar absolute.

57 . The electrolyzer of claim 45 , wherein the electrolyte of the anode region comprises dissolved sulfate ions, suflite ions, and/or phosphate ions.

58 . The electrolyzer of claim 45 , wherein the input is fluidically coupled to a distributor disposed between the anode region and the neutral region.

59 . The electrolyzer of claim 58 , wherein the distributor has a plurality of holes facing toward the neutral region and away from the cathode region.

60 . An electrolyzer, comprising:

a cathode region including a cathode; an anode region including an anode; a neutral region; an output in the cathode region configured to remove an aqueous alkaline solution from the electrolyzer; and an input in the neutral region configured to supply a DIC-rich solution to the electrolyzer, wherein the cathode generates hydrogen gas, the anode generates oxygen gas, and CO 2 gas is generated in the neutral region, wherein the input is fluidically coupled to a distributor disposed between the anode region and the neutral region, the distributor having a plurality of holes facing toward the neutral region and away from the anode region.

61 .- 64 . (canceled)

65 . The electrolyzer of claim 60 , further comprising a divider separating the anode region from the neutral region, the divider comprising at least one of a porous membrane, a mesh material, or a porous material.

66 . The electrolyzer of claim 65 , wherein the divider includes a flow straightener configured to establish a horizontal flow and prevent back mixing.

67 .- 68 . (canceled)

69 . The electrolyzer of claim 68 , wherein a hydrogen product stream exits the electrolyzer via the cathodic head space, and wherein the cathodic head space has a pressure of between about 1 bar absolute and about 3 bar absolute.

70 .- 71 . (canceled)

72 . The electrolyzer of claim 60 , wherein the electrolyte of the anode region comprises dissolved sulfate ions.

73 .- 83 . (canceled)

US18/805,064

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System and method for production of synthetic fuel through co2 capture and water splitting

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System and method for production of synthetic fuel through co2 capture and water splitting

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System and method for production of synthetic fuel through co2 capture and water splitting

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System and method for production of synthetic fuel through CO2 capture and water splitting

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System and method for production of synthetic fuel through co2 capture and … — Arizona Board Of Regents On Behalf Of Arizona State University (US20250050273A1)

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