Patent Application
20240200207
Global warming is primarily caused by the atmospheric build-up of carbon dioxide (CO2). A promising method to lower its atmospheric concentration and provide sustainable substitutes to current feedstocks derived from fossil fuels is to capture it at emitting point sources or directly from the air (through direct air capture). This method then transforms the captured material into valuable chemicals and fuels using a decarbonized source of electricity. The polymer-electrolyte-membrane-based electroreduction technology stands out among the envisioned conversion technologies due to its adaptability (possible usage at a wide range of temperatures and pressures, possible intermittent use) and capacity to generate a wide range of products.
Carbon monoxide (CO), formic acid, ethylene, ethanol, ethane, propanol, propylene, and acetaldehyde are just a few of the compounds that have been reported to be produced by the electroreduction of CO2. Reviews of this technology's potential have been published in multiple places. Also being investigated is the electroreduction of bicarbonate and carbonate ions (HCO3− and CO32−), in which CO2 positively develops in a low (or high) alkalinity aqueous solution. This is particularly relevant because the majority of CO2 collection systems involve interacting CO2 with alkaline aqueous solutions to create molecules like bicarbonate and carbonate that have little additional value by themselves. Finally, CO electroreduction is receiving more and more attention. CO electroreduction has been reported as a potential economically viable way to produce some commodities, such as ethylene, when combined with a first step which ensures the conversion of CO2 into CO (by any means, including but not limited to electroreduction, hydrogenation of CO2, or gasification of carbon containing feedstocks, including but not limited to waste and biomass).
To reimagine commercial chemical processes involving the formation of C—N bonds, electroreduction of CO and N containing reactants such as but not limited to NH3, NO2, and NO3 is also of great interest.
The term COx will be used to refer to CO2, CO, and other oxocarbons in the information that follows. Typically, a COx electrolysis reactor is made up of one or more stacks, each of which is made up of several cells piled on top of one another. Each individual cell in a stack is made up of two half cells that are connected by an ion-conducting medium, such as, but not limited to, a polymer electrolyte membrane. The two half cells are an anodic compartment where water or another reactant is oxidised and a cathodic compartment where at least COx is reduced into a desired product.
A flow field assures electrical contact and the delivery of reactants to a porous and conductive support in each half cell. Each half cell is made up of a flow field that ensures electrical contact as well as the delivery of reactants to a porous and conductive support (such as a gas diffusion layer (GDL) or a porous metal support), the latter of which is in close proximity to a catalyst on the surface of which reactions occur. A membrane-electrode assembly (MEA) is the combination of the central one or more membranes, the two porous supports, and their corresponding catalysts. Conductive polar plates support individual cells physically on each side (either bipolar or monopolar). A bipolar plate secures the series connection between two neighbouring cells by supporting the flow fields of the first and subsequent cells on each of its sides.
For conciseness in the following, a cell will jointly refer to a central catalytic assembly (such as but not limited to an MEA in the case where the ion-conducting media is membrane-based) including the two flow fields and supporting polar plates.
Multiple other electrolysis reactor configurations are possible. Some prior art studies report a circular modular electrolyzer and process to convert carbon dioxide to gaseous products at elevated pressure and with a high conversion rate or provide an example of a rectangular electrolyzer for gaseous carbon dioxide conversion.
There is an urgent need to reduce the emissions related to the production of useful fuels and chemicals in our society. Furthermore, there is an urgent need to develop technologies that make the capture or direct valorization of carbon dioxide more economical. Accordingly, technologies that both generate useful fuels and chemicals, while at the same time using carbon dioxide feedstock that would otherwise have been emitted into the atmosphere, are critically important because they generate useful chemicals without additional emissions and because the economic value of the useful chemicals can offset the cost of carbon dioxide capture and conversion.
A class of technologies that can address the problems outlined in the prior paragraph is oxocarbon electrolyzers. These devices take in an oxocarbon as an input and can produce valuable chemicals by valorizing the oxocarbon. Electrolyzers are reactors that operate using a paired reduction and oxidation reaction. The reduction reaction occurs in a cathode area of the reactor and the oxidation reaction occurs in an anode area of the reactor. The cathode area includes an electrode that can be referred to as the cathode of the electrolyzer. The anode area includes an electrode that can be referred to as the anode of the electrolyzer. The reactions require the activity of a catalyst that is in contact with an electrode. For example, the reduction reaction in a cathode area can occur around a copper catalyst surface where the catalyst is in contact with the cathode. The catalyst in the cathode area can be referred to as a cathode catalyst or reduction catalyst. The catalyst in the anode area can be referred to as an anode catalyst or oxidation catalyst.
COx electrolysis reactors are complex and therefore subject to frequent failures and performance degradations. They can be hard to maintain because the access is difficult for human operators in charge of their maintenance. For these reasons above, the operating costs can be high. In the path towards industrialization, there is now a need to maximize reactor performance metrics as well as the capacity factor (i.e., the ratio between the actual rate at which the plant production is operated vs. the maximum production rate). Efforts have been made towards revitalization of catalyst candidates varying both their chemical nature (e.g., metal alloys, single-metal-site catalysts, molecular species, use of additives) and structure (e.g., nanoparticles, dendrites, films). In all cases, efforts have focused on chemically modifying the electrocatalytic systems to increase their performance and stability.
It is also desirable to limit the maintenance costs and reduce the maintenance time of an electrolysis reactor comprising multiple electrolysis cells. There arises a need to find ways to maintain the performance of the electrolyzer for as long as possible before stopping the system for maintenance operation and minimizing the duration of such maintenance operation.
The present disclosure relates to catalysts used in oxocarbon electrolyzers. The oxocarbon electrolyzers utilized in the embodiments disclosed herein are electrolysis reactors that take in an oxocarbon as an input and produce a useful species as an output. The oxocarbon can be carbon dioxide or carbon monoxide. The oxocarbon can be taken from an emissions source such as an industrial process or taken directly from the atmosphere via direct air capture technology. The useful species include sustainable carbon-based feedstocks such as hydrocarbons, organic acids, carboxylates, and alcohols. The useful species can include higher-value products such as acetic acid, ethylene, propanol, and ethanol. These processes therefore both consume greenhouse gases that would otherwise contribute to global warming while at the same time producing sustainable feedstock chemicals that themselves are currently produced from unsustainable fossil fuel resources.
A problem solved by specific embodiments of the inventions disclosed herein is the decline in performance observed in oxocarbon electrolyzers over time due to the deactivation of the catalyst structure when producing useful species from oxocarbon inputs. The exact catalyst structure may become overly reduced, aggregated, or poisoned during electrolyzer operation, which slows or prevents the formation of useful species. Catalysts for these reactions tend to have limited long-term stability, leading to unattractive costs associated with catalyst replacement and electrolyzer maintenance. This in turn sacrifices the economic feasibility of the technology. One example of such a catalyst is copper, which exhibits both high intrinsic selectivity for carbon-oxide conversion and high susceptibility to deactivation.
In specific embodiments of the inventions disclosed herein, a catalyst in an oxocarbon electrolyzer is revitalized through the introduction of a chemical into the electrolyzer either during the operation of the electrolyzer or during a temporary pause in the operation of the electrolyzer. Using these processes, the catalytic performance of the catalyst can be regenerated. The chemical can be an oxidant that is introduced into the cathode side of the electrolyzer to revitalize the reduction catalyst. The oxidant revitalizes the reduction catalyst by oxidizing the reduction catalyst material and altering the morphology of the catalyst to increase its catalytic potential. Further, the oxidant can revitalize the reduction catalyst by oxidizing fouling agents on the catalyst that build up during operation. The introduction of the oxidant prolongs the time over which the desired catalytic selectivity of oxocarbon conversion is maintained. Specific embodiments of the invention disclosed herein can improve the efficiency of oxocarbon electrolyzers in terms of the amount of useful chemicals produced for a given amount of input energy. These improvements are important both from the perspective of accelerating revenue generation and minimizing expenses, as well as from the perspective that it is generally preferable from an environmental standpoint to minimize energy consumption for a given application.
In specific embodiments of the invention, the revitalization process can be conducted in accordance with a fixed schedule or based on a monitored performance of the electrolyzer. For example, a selectivity of the electrolyzer for a specific useful species (e.g., ethylene) can be monitored, and the revitalization process can be conducted based on a determination that the selectivity has dipped below an acceptable level. The revitalization process can then be conducted by shutting down the electrolyzer temporarily and applying an oxidant to the cathode area, or, in embodiments where the oxidant is supplied along with the reduction substrate while the electrolyzer is operational, the revitalization process can then be conducted by increasing a supply of the oxidant to the cathode area without shutting down the electrolyzer.
In specific embodiments of the invention, a method for operating an oxocarbon electrolysis reactor is provided. The method comprises supplying a cathode area of the oxocarbon electrolysis reactor with an oxocarbon species as a reduction substrate for a reduction reaction, supplying an anode area of the oxocarbon electrolysis reactor with an oxidation substrate for an oxidation reaction, and valorizing the oxocarbon species into a useful species via a valorization process. The valorization process includes the reduction reaction and the oxidation reaction. The method also comprises monitoring a performance of the valorization process in a monitoring process and supplying an oxidant to the cathode area of the oxocarbon electrolysis reactor in a revitalization process conducted in response to a change in the performance of the valorization process as monitored in the monitoring process.
In specific embodiments of the invention, another method for operating an oxocarbon electrolysis reactor is provided. The method comprises supplying a cathode area of the oxocarbon electrolysis reactor with an oxocarbon species as a reduction substrate for a reduction reaction. The reduction reaction uses a catalyst in the cathode area of the oxocarbon electrolysis reactor. The method also comprises supplying an anode area of the oxocarbon electrolysis reactor with an oxidation substrate for an oxidation reaction. The method also comprises valorizing the oxocarbon species into a useful species in a valorization process. The valorization process includes the reduction reaction and the oxidation reaction. The method also comprises supplying an oxidant to the cathode area of the oxocarbon electrolysis reactor, whereby the oxidant revitalizes the catalyst.
In specific embodiments of the invention, another method for operating an oxocarbon electrolysis reactor is provided. The method comprises supplying a cathode area of the oxocarbon electrolysis reactor with an oxocarbon species as a reduction substrate for a reduction reaction, supplying an anode area of the oxocarbon electrolysis reactor with an oxidation substrate for an oxidation reaction, and valorizing the oxocarbon species into a useful species in a valorization process. The valorization process includes the reduction reaction and the oxidation reaction. The method also comprises supplying an oxidant to the cathode area of the oxocarbon electrolysis reactor in a revitalization process. The revitalization process comprises: (i) shutting down the oxocarbon electrolysis reactor: (ii) pressurizing the cathode area to a pressure while the oxidant is in the cathode area; and (iii) supplying the oxidant to the cathode area while the oxocarbon electrolysis reactor is shut down and the cathode area is pressurized to the pressure.
Using specific embodiments of the inventions disclosed herein, the stability of a catalytic reactor can be maintained, through the intermittent or continuous introduction of oxidant, which leads to a superior rate of oxocarbon conversion than an equivalent reactor without the intermittent or continuous introduction of oxidant.
The accompanying drawings illustrate various embodiments of systems, methods, and embodiments of various other aspects of the disclosure. A person with ordinary skills in the art will appreciate that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. It may be that in some examples one element may be designed as multiple elements or that multiple elements may be designed as one element. In some examples, an element shown as an internal component of one element may be implemented as an external component in another and vice versa. Furthermore, elements may not be drawn to scale. Non-limiting and non-exhaustive descriptions are described with reference to the following drawings. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating principles.
Reference will now be made in detail to implementations and embodiments of various aspects and variations of systems and methods described herein. Although several exemplary variations of the systems and methods are described herein, other variations of the systems and methods may include aspects of the systems and methods described herein combined in any suitable manner having combinations of all or some of the aspects described.
Methods and systems related to catalysts used in oxocarbon electrolysis reactors in accordance with the summary above are disclosed in detail herein. The methods and systems disclosed in this section are nonlimiting embodiments of the invention, are provided for explanatory purposes only, and should not be used to constrict the full scope of the invention. It is to be understood that the disclosed embodiments may or may not overlap with each other. Thus, part of one embodiment, or specific embodiments thereof, may or may not fall within the ambit of another, or specific embodiments thereof, and vice versa. Different embodiments from different aspects may be combined or practiced separately. Many different combinations and sub-combinations of the representative embodiments shown within the broad framework of this invention, that may be apparent to those skilled in the art but not explicitly shown or described, should not be construed as precluded.
The electrolyzers used in accordance with the approaches disclosed herein can have various architectures. The electrolyzer can include an anode area and a cathode area. The anode area and the cathode area can each either be aqueous phase reactor areas or gaseous phase reactor areas. An oxocarbon can be provided to the cathode area of the reactor as a reduction substrate in liquid or gaseous form. Useful species can be produced in the cathode area, in the anode area, or in a separating area located between the cathode area and the anode area of the electrolyzer. The rate at which the reaction occurs can be dependent upon the performance of one or more catalysts in the reactor. The catalysts can be anode catalysts, cathode catalysts, or both. The electrolyzer can be a single planar electrolyzer. The electrolyzer can be a stack of cells. The cells in the stack can utilize bipolar plates. The bipolar plates can be charged to initiate reactions within the reactor. The electrolyzer can also be a filter press electrolyzer or a tubular electrolyzer.
The electrolyzers used in accordance with this disclosure can comprise one or more electrocatalytic cells positioned on top or next to one another to increase the surface available for the reaction. They can be stacked on top of one another, and such stacks can also be parallelized. These cells may be connected in series or in parallel. Many different cell and stack configurations can be used for the electrolyzers in accordance with this disclosure.
In an electrolysis stack, subsequent cells can be physically separated by bipolar plates (BPPs), such as bipolar plate 112 in
The oxocarbon electrolyzers can take as an input, a cathodic input stream (e.g., a stream enriched in carbon monoxide or carbon dioxide), and an anode input stream. In such cases, the reduction substrate is carbon monoxide or carbon dioxide. The cathodic input stream can be provided to an inlet such as inlet 118. The anodic input stream can be provided to an inlet such as inlet 114. The cathodic stream and anodic stream can flow through the stack from the inlets to the outlets and be distributed through the flow channels, such as those in flow field 110 of each cell to each cathodic and anode area separately. The anodic stream and cathodic stream would flow through separate channels on either side of the cell. Alternatively, at least one of the cathodic and anodic streams may be provided to each cell individually instead of through a connection crossing all the plates. In this case, each cell has a dedicated fluid inlet and outlet for this cathodic and/or anodic stream. The nature of the anodic stream can be determined by the nature of the targeted oxidation reaction (such as, but not limited to, water oxidation, dihydrogen oxidation, chloride oxidation, halide oxidation, hydrocarbon oxidation, and waste organic oxidation). For example, the generating of chemicals using carbon monoxide and the electrolyzer could involve supplying the volume of carbon monoxide to a cathode area of the electrolyzer as a cathodic input fluid and supplying a volume of water to an anode area of the electrolyzer as an anodic input fluid. When electrically powered, the carbon monoxide electrolyzer carries out the concomitant reduction of carbon monoxide and oxidation of the chosen oxidation substrate to produce useful species such as hydrocarbons, organic acids and/or alcohols, and/or N-containing organic products in the anodic stream.
When operating, the oxocarbon electrolysis reactor 200 can be fed a stream of humidified carbon oxide gas humified by the humidifier 203 to the cathode area 201 side of the oxocarbon electrolysis reactor 200, and an aqueous stream is fed to the anode area 202. In alternative embodiments, the humidifier is removed, and the reactor receives a stream of oxocarbon without an appreciable amount of water vapor. A voltage is applied across the reactor that facilitates the carbon-oxide reduction reaction at the cathode area 201 and complimentary oxidation reaction at the anode area 202, this is referred to as the operation mode in
Introduction of the oxidant to the cathode area leads to the reactivation of the cathode area 301 catalyst. This reactivation occurs throughout a predetermined amount of time in which the oxidant is introduced (e.g., 10 minutes). In specific embodiments of the invention, the oxidant is supplied in a concentration of at least 0.01 M for at least 5 minutes. Following this reactivation, the electrolyzer is reverted to operation mode, where the catalytic activity resumes a level similar to that at the beginning of the electrolyzer operation.
In another embodiment of the invention, the oxidant is fed constantly alongside the oxocarbon in a proportion at which the reductive catalyst maintains its selectivity of oxocarbon conversion to the desired products. This avoids the need to remove the voltage of the electrolyzer and the need for an explicit reactivation stage. As a result, the reactor can produce useful products continuously, and no time is wasted transitioning the reactor through different modes of operation.
In one example, an oxocarbon electrolysis reactor 400 is composed of a cathode area 401 comprising a gas-diffusion layer and a copper-based carbon-oxide-reduction catalyst. The anode area 402 comprises a catalyst with at least one of Ir, Co, Cu, Ni, Fe, Pt, Rh, Re, Ru, Pd, Os, and Mo supported by a porous metal-based support of any shape (such as but not limited to a foam, a mesh, or a conductive PTL). The metal of the metal-based support could be titanium-based, nickel-based, or be based on any other metal mentioned herein for this purpose. In this case, the reduction products include one or more of the following: ethylene (C2H4), ethanol (C2H5OH), acetic acid (C2H3COOH), propylene (C3H6), propanol (C3H8O).
When operating, the oxocarbon electrolysis reactor 400 is fed a stream of humidified carbon oxide gas humified by the humidifier 403 along with an oxidant on the cathode area 401 side of the oxocarbon electrolysis reactor 400, and an aqueous stream is fed to the anode area 402. A voltage is applied across the reactor that facilitates the carbon-oxide reduction reaction at the cathode area 401 and complimentary oxidation reaction at the anode area 402, this is referred to as the operation mode. Continuous analysis of the product stream of the cathode area 201 is carried out, which confirms the production of the desired species, for example, ethylene. A gas separator 404 is employed at the outlet, such as but not limited to, a pressure swing adsorption column or a membrane-based separator, to remove the unreacted carbon oxide from the ethylene. The unreacted carbon oxide can then be fed back to the cathode area 401 inlet. At the anode area 402, produced oxygen from the oxidation of water is separated from water through a gas-liquid separator 405.
When operating, the oxocarbon electrolysis reactor 500 is fed at the cathode area 501 with a stream of humidified carbon-oxide gas, humified by a humidifier 503 along with a portion of oxidant from the anode area 502, and an aqueous stream is fed to the anode area 502. A voltage is applied across the oxocarbon electrolysis reactor 500 that facilitates the carbon-oxide reduction reaction at the cathode area 501 and a complimentary oxidation reaction at the anode area 502. A gas separator 504 is employed at the outlet, such as but not limited to, a pressure swing adsorption column or a membrane-based separator, to remove the unreacted carbon oxide from the ethylene. The unreacted carbon oxide can then be fed back to the cathode inlet. At the anode area 502, produced oxygen from the oxidation is separated from water through a gas-liquid separator 505.
In another embodiment of the invention, if the oxidant is a liquid, such as a dilute solution containing hydrogen peroxide or nitric acid, then the oxidant is injected into the electrolyzer in place of the carbon-oxide containing fluid line where it can serve as an oxidant-as disclosed in step 605b.
Further, the revitalization of the electrolysis reactor process can be based on if the oxidant is supplied when the reactor is operational or when the reactor is temporarily stopped. In some embodiments, where the reactor is temporarily stopped, the process can include shutting down the oxocarbon electrolysis reactor in a step 605ca, then supplying the oxidant to the cathode area in a step 605cb. Further, the process can include pressurizing the cathode area 605cc to a pressure while the oxidant is in the cathode area. In specific embodiments, the pressure can be at least 1.1 bar to produce an improvement in the revitalization of the catalyst. In some embodiments, where the reactor is not stopped, the process can occur while the reactor is operational in a step 605d, the application of the oxidant can be continuous as in step 605da or variable as in step 605db.
The variable application of the oxidant can be conducted in various ways. The oxidant can be applied in a binary on/off manner at different times or in a continuous stream along with the reduction substrate with variable conditions such as the amount of oxidant supplied, temperature of the cathode area, or pressure of the cathode area. The variations can be conducted in an open loop manner in accordance with a fixed schedule or in a close loop manner in response to a measured parameter of operation.
If the process is intermittent as in step 605db1 (either in terms of the oxidant only being supplied during a temporary break or the intensity of a continuously supplied stream varying), the period between applications, or the intensity of applications can be adjustable. Further, the oxidant can be supplied as part of a default shutdown or startup procedure 605db2, or a combination of both 605db3. For example, apply a small amount of oxidant could be applied continuously during operation and then a heavier application could be applied during a temporary stop.
Further, the revitalization can be performed based on a fixed schedule for the application of oxidant or by monitoring the fouling of the catalyst at the cathode. When the adjustment is based on a fixed schedule, it is termed as open loop control as in step 605e. The intensity of a continuous stream can be adjusted based on a fixed schedule. The periodicity of a periodically applied stream can also be adjusted based on a fixed schedule. The parameters for the oxidant supply such as the temperature and pressure can also be adjusted based on a fixed schedule.
When the application of oxidant is based on monitoring performance, it is termed as closed-loop control as in step 605f. The parameters of the process are adjusted based on monitoring performance, wherein at least one of the selectivity of the reactor to the valuable products (e.g., given X mol of input fluid, you were able to obtain Y mol of the valuable product); efficiency of the reactor (e.g., given X mol of input fluid you used 1,000 kWh); a voltage or current of individual cells; and a voltage or current through an entire reactor. These values or a proxy for these values may need to be calculated in real-time to control the loop. The monitoring process can comprise monitoring an electrical parameter of the oxocarbon electrolysis reactor. The performance of the electrolysis reactor can be derived from the electrical parameter (e.g., an increase in cell voltage can be used to derive a decrease in selectivity). Detecting a decrease in performance can serve as a trigger for a revitalization process to occur. When the device is temporarily stopped, there are variations in the amount of time to wait for the amount of oxidant to supply and variations in pressure further, when the device is operational, there is an increase or decrease in the instantaneous amount of oxidant supplied and it is required to control period between applications.
In specific embodiments, an excess of oxidant over the required amount will decrease the performance of the valorisation process being conducted by the reactor. As such, a control system can be used to filter decreases in performance that are correlated to oxidant supply from decreases in performance that are uncorrelated to oxidant supply. In response to this determination, the control system can increase oxidant supply for uncorrelated decrease in performance and decrease oxidant supply for correlated decreases in performance.
In variant embodiments, there are different phases (e.g., gaseous or liquid) for different areas of the electrolyzer such that the oxidant needs to be provided in different ways. For example, electrolyzers can have different phases in different areas: the cathode area can be gaseous (input fluid (e.g., humidified carbon monoxide is delivered as a gas); and the anode area can be aqueous (input fluid (e.g., water) is delivered as a liquid). The opposite is an option as well as dual aqueous and dual gaseous forms.
Further, as shown in
In
In specific embodiments of the invention, methods, and systems related to catalysts used in oxocarbon electrolysis reactors in accordance with the summary above are disclosed in detail herein. The methods and systems disclosed in this section are non-limiting embodiments of the invention, are provided for explanatory purposes only, and should not be used to constrict the full scope of the invention. It is to be understood that the disclosed embodiments may or may not overlap with each other. Thus, part of one embodiment, or specific embodiments thereof, may or may not fall within the ambit of another, or specific embodiments thereof, and vice versa. Different embodiments from different aspects may be combined or practiced separately. Many different combinations and sub-combinations of the representative embodiments shown within the broad framework of this invention, that may be apparent to those skilled in the art but not explicitly shown or described, should not be construed as precluded.
In specific embodiments of the invention, the anode area could comprise an anodic catalyst layer able to oxidize a substance to produce a product and protons. The catalyst can comprise one or more of: molecular species, single-metal-site heterogeneous compounds, metal compounds, carbon-based compounds, polymer electrolytes (also referred to as ionomers), metal-organic frameworks, metal-doped covalent organic framework or any other additives. The molecular species can be selected from metal porphyrins, metal phthalocyanines or metal bipyridine complexes. The metal compound can be under the form of metal nanoparticles, nanowires, nano powder, nanoarrays, nanoflakes, nanocubes, dendrites, films, layers or mesoporous structures. The single-metal-site compounds can comprise a metal-doped carbon-based material or a metal-N—C-based compound. Anodic catalyst species used for this purpose could include, but are not limited to, metals and/or ions of: Ir, Co, Cu, Ni, Fe, Pt, Rh, Re, Ru, Pd, Os, Mo and mixture and/or alloys thereof. For example, the anodic catalyst could be Ni such that the electrolyzer assembly included a nickel-based anode. The polymer electrolyte can be selected out of the same materials as the one used for the described membranes. The carbon-based compounds can comprise carbon nanofibers, carbon nanotubes, carbon black, graphite, boron-doped diamond powder, diamond nanopowder, boron nitride or a combination thereof. The additives can be halide-based compounds including F, Br, I, and Cl. The additives can be specifically dedicated to modifying hydrophobicity such as treatment with polytetrafluoroethylene (PTFE), Nafion or another hydrophobic polymeric ionomer additive, or carbon black. The anodic catalyst may be chosen to tune the performance and net product stream of the electrolyzer by choosing catalysts that are more or less capable of anodic alcohol oxidation to the corresponding carboxylic acid, aldehyde, or carbon dioxide.
The anodic catalyst may be deposited onto a gas diffusion layer or a porous transport layer or any other support that facilitates the diffusion of gas from the interface of the anode to a purified gas stream separated from the cathodic stream. The anode area could also include a gas diffusion layer with one or more separators such as but not limited to membranes, polymeric materials, diaphragm, inorganic material on its borders as described below.
In specific embodiments of the invention, the cathode area could comprise a catalyst layer able to reduce a substance (e.g., carbon monoxide) to generate value-added hydrocarbons/alcohols/organic acids. The catalyst can comprise one or more: molecular species, single-metal-site heterogeneous compounds, metal compounds, carbon-based compounds, polymer electrolytes (also referred to as ionomers), metal-organic frameworks, or metal-doped covalent organic frameworks or any other additives. The molecular species can be selected from metal porphyrins, metal phthalocyanines or metal bipyridine complexes. The metal compound can be under the form of metal nanoparticles, nanowires, nano powder, nanoarrays, nanoflakes, nanocubes, dendrites, films, layers or mesoporous structures, with precisely chosen particle sizes to control performance. The single-metal-site compounds can comprise a metal-doped carbon-based material or a metal-N—C-based compound. The cathode catalyst may be made of a metal or metal ion from metals selected from a group consisting of: Cu, Ag, Au, Zn, Sn, Bi, Ni, Fe, Co, Pd, Ir, Pt, Mn, Re, Ru, La, Tb, Ce, Dy or other metals, lanthanides, and mixture and/or alloys thereof. For example, the cathodic catalyst could comprise Cu such that the electrolyzer assembly included a copper-based cathode. The polymer electrolyte can be selected out of the same materials as the one used for the described membranes. The carbon-based compounds can comprise carbon nanofibers, carbon nanotubes, carbon black, graphite, boron-doped diamond powder, diamond nanopowder, boron nitride or a combination thereof. The additives can be halide-based compounds including F, Br, I, Cl. The additives can be specifically dedicated to modifying hydrophobicity such as treatment with PTFE, Nafion or another hydrophobic polymeric ionomer additive, or carbon black. The cathode may further comprise a catalyst layer on a gas diffusion layer, a porous transport layer, or any other support, which encourages the diffusion of the gas from a stream to the surface of the catalyst, as well as allowing the release of non-reacted/product gases. The cathode area could also include a gas diffusion layer with one or more separators such as, but not limited to, membranes, polymeric materials, diaphragms, and inorganic materials on its borders as described below. The loading of catalyst and additives on the gas diffusion layer can be precisely chosen to favor certain performance characteristics, such as differences in voltage, conductivity, carbon monoxide mass transport rate, product selectivity, and stability.
In specific embodiments of the invention, the porous support for either the anode area, the cathode area, or both, can be selected from carbon-based porous supports or metal-based porous material or a combination. The carbon-based porous support can be based on carbon fibers, carbon cloth, carbon felt, carbon fabric, carbon paper, molded graphite laminates and the like or a mixture thereof. The carbon-based porous support can be a gas diffusion layer with or without microporous layer. Such carbon-based support can be in particular chosen in the among the following list: Sigracet 39AA, Sigracet 39BC, Sigracet 39BB, Sigracet 39BA, Sigracet 36AA, Sigracet 36BB, Sigracet 35BC, Sigracet 35BA, Sigracet 29BA, Sigracet 28BB, Sigracet 28AA, Sigracet 28BC, Sigracet 25BC, Sigracet 22BB, Sigracet 35BI, Toray papers, Toray THP-H-030, Toray TGP-H-060, Toray TGP-H-090, Toray TGP-H-120, Freudenberg H23C6, Freudenberg H15C13, Freudenberg H15C14, Freudenberg H14C10, Freudenberg H14CX483, Freudenberg H14CX653, Freudenberg H23C2, Freudenberg H23CX653, Freudenberg H24CX483, Freudenberg H23C6, Freudenberg H23C8, Freudenberg H24C5, Freudenberg H23C3, Avcarb MB-30, Avcarb GDS5130, Avcarb GDS2130, Avcarb GDS3250, Avcarb GDS3260, Avcarb GDS2230, Avcarb GDS2240, Avcarb GDS2255, Avcarb GDS2185, AvCar 1071, AvCarb 1698, AvCarbon 1209, AvCarb 1185, AvCarb1186, AvCarb 7497, AvCarb T1819, AvCarb T1820, AvCarb T1824, AvCarbon 1071, AvCarb 1698, AvCarb 1209, AvCarb 1185, AvCarb 1186, AvCarb 1186, AvCarb T1819, AvCarb T1820, AvCarb T1824, AvCarb EP40, AvCarb P75, AvCarb EP55, AvCarbon EP40T, AvCarb P75T, AvCarb EP55T, AvCarb MGL190, AvCarb MGL280, AvCarbMGL370. The metal-based porous support can be selected from titanium, stainless steel, Ni, Cu or any other suitable metal and can be under the form of mesh, frit, foam or plate of any thickness or porosity.
In specific embodiments of the invention, the electrolyzer can include a separating element to separate specific generated chemicals from others. The separating element can be one or more traps on the cathodic and/or anodic outputs of the electrolyzer which separates liquid outputs from gaseous outputs. It can also be more complex systems known by those skilled in the art for the purpose of efficient product separation. The separating element can be a separating area between the anode area and the cathode area configured to separate the volume of generated chemicals from the electrolyzer. The separating area can be a separating layer. Efficient physical separation of the anode area and cathode area may allow easier separation of the gases released from each section of the reactor. The separator can be an ion-conducting polymeric separator, a non-ion conducting polymeric separators, a non-ionically charged polymer, a non-ionically charged separator, an ionomer solution coated onto the electrodes, a diaphragm, a ceramic-containing material, a non-charged separator scaffold, a mixed ceramic-organic compound separator, or any other separator. Separation may occur through the use of ion-exchange membranes, which favor the diffusion of either anions (in an anion-exchange membrane) or cations (in a cation-exchange membrane), or a bipolar membrane (including a mixture of cation- and anion-exchange membranes) or other types of separators, such as diaphragms, ceramic-containing materials (in particular mixed ceramic/organic compounds), or non-charged separator scaffolds. Anion-exchange membrane can comprise an organic polymer with positively charged functionality, such as, but not limited to, imidazolium, pyridinium or tertiary amines. This allows facile migration of negatively charged hydroxide ions (OH−) produced during carbon monoxide reduction from the cathode to the anode. The use of this layer also prevents the crossover of other gases from the cathode to the separating layer. Cation-exchange membranes can comprise an organic polymer with negatively charged functionality such as, but not limited to, sulfonate groups. Diaphragms or non-charged separators can be materials derived from insulating materials which may be charged with an ion-conducting electrolyte to facilitate charge transfer between electrodes. Ceramic-containing materials may be a purely ceramic or mixed polymer and ceramic material. Ceramic-polymer mixes can reach higher temperatures than purely organic polymers and may take advantage of ion-exchange functionality in the polymer to pass charge between electrodes. The thickness of the membranes can be chosen precisely to control the transport rates of species such as anions, cations, and neutral species such as alcohols and water during operation.
In specific embodiments of the invention, the system can include an electrolyte that will facilitate the transportation of ions and provide ions that promote the reactions. In particular, the electrolyte may be a concentrated alkaline solution such as a solution of hydroxide-containing salt such as but not limited to potassium, sodium or cesium hydroxide with concentrations such as (0.01 molarity (M), 0.05 M, 0.1 M, 0.2 M, 0.5 M, 1 M, 2 M, 3 M, 4 M, 5 M, 6 M, 7 M, 8 M, 9 M and 10 M). The use of concentrated alkaline solution brings down the energy requirement of the overall reaction. Alkali metal cations (such as Li, Na, K, Cs, Rb) may be used as counter-cations. This electrolyte may contain oxidation substrates other than water or hydroxide, such as dihydrogen, alcohols, glycerol, other organic materials, and other oxidizable feedstocks.
While the specification has been described in detail with respect to specific embodiments of the inventions disclosed herein, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily conceive of alterations to, variations of, and equivalents to these embodiments. Although examples in the disclosure were generally applied to an electrolyzer generating ethylene, the same approaches are applicable to electrolyzers generating any useful chemical or otherwise sequestering or valorizing oxocarbons. Furthermore, while the examples in this disclosure were generally applied to the delivery of carbon monoxide to an electrolyzer, approaches disclosed herein are more broadly applicable to the delivery of any member of the oxocarbon family to an electrolyzer to generate useful chemicals therefrom. These and other modifications and variations to the present invention may be practiced by those skilled in the art, without departing from the scope of the present invention, which is more particularly set forth in the appended claims.
This application claims the benefit of U.S. Provisional Pat. App. No. 63/433,738 filed Dec. 19, 2022, which is incorporated by reference herein in its entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 63433738 | Dec 2022 | US |
