Carbon monoxide electrolyzer used in conjunction with a reverse water gas shift reactor for the conversion of carbon dioxide to value-added products

Abstract

A method and system for valorizing carbon dioxide is disclosed. The disclosed system includes a reverse water gas shift (RWGS) reactor, a carbon dioxide source connection fluidly connecting a carbon dioxide source to the RWGS reactor, an electrolyzer having an anode region and a cathode region, and a carbon monoxide source connection fluidly connecting the RWGS reactor to the cathode region. The RWGS reactor is configured to use a quantity of carbon dioxide from the carbon dioxide source connection to produce a quantity of carbon monoxide in an RWGS reaction. The electrolyzer is configured to use the electrolyzer, reduction of the quantity of carbon monoxide from the carbon monoxide source connection, and oxidation of an oxidation substrate to produce a quantity of product chemicals including hydrocarbons, organic acids, alcohols, olefins, or N-rich organic compounds.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Patent Application No. 18 / 111,631, filed February 20, 2023, and U.S. Provisional Patent Application No. 63 / 427,800, filed November 23, 2022, both of which are incorporated by reference in their entirety for all purposes. [Background technology]

[0002] Our society urgently needs to reduce the emissions associated with the production of useful fuels and chemicals. Furthermore, there is an urgent need to develop technologies that make carbon dioxide capture or direct valorization more economical. Therefore, technologies that use carbon dioxide feedstocks that would otherwise be released into the atmosphere while simultaneously producing useful fuels and chemicals are of great importance, because both produce useful chemicals without additional emissions, and the economic value of the useful chemicals offsets the costs of carbon dioxide capture and conversion. Summary of the Invention

[0003] The low-carbon production of valuable small molecules (e.g., hydrocarbons, olefins, alcohols, and carboxylic acids) from carbon dioxide is particularly challenging because carbon dioxide is an inert molecule that requires energy input to be reduced to energy-rich small molecules. Carbon dioxide electrolysis is a recent technology route that uses low-carbon electricity to electrolyze carbon dioxide and water to carbon monoxide and other small molecules. However, this process has several drawbacks, many of which are related to the so-called "carbonate problem," which involves the reaction of carbon dioxide with alkali equivalents in the electrolytic cell.

[0004] The carbonate problem leads to excessive energy consumption in carbon dioxide electrolyzers. The energy required to power the electrochemical processes occurring at the cathode and anode of a carbon dioxide electrolyzer is minimized when the electrolyzer is operated in a highly alkaline electrolyte. Operation at a high pH also allows for the use of efficient and abundant metal catalysts for the water oxidation reaction at the electrolyzer anode. However, at steady state, carbon dioxide reacts with alkali equivalents in the electrolyzer (see Equations 1-4 below), consuming alkali equivalents in the electrolyzer and forming bicarbonate and carbonate species, thereby lowering the electrolyzer's operating pH. This leads to a significant increase in the energy required to power the carbon dioxide electrolysis process, and the formation of these anionic species and their salts reduces the electrolyzer's performance and lifetime. CO2+OH - ⇔HCO3 - (1) CO2 + H2O ⇔ H2CO3 (2) HCO3 - +OH - ⇔CO3 2- +H2O (3) HCO3 - +H2O⇔H3O + +CO3 2- (4)

[0005] A low cell pH increases the energy requirements at the anode of a carbon dioxide electrolyzer because non-precious metal anode materials with high activity, selectivity, and stability (e.g., without limitation, those composed of Ni, Co, Mn, Ti, and Fe) require a higher driving force to achieve the same current at low versus high pH. A high cell pH also reduces the cathodic overpotential because dihydrogen generation is more readily achieved at lower pH. A lower electrolyte pH may also increase the proportion of current that produces dihydrogen at the cathode instead of reducing carbon dioxide to more valuable products, potentially altering the product distribution of carbon dioxide reduction products.

[0006] Reactions related to carbonate issues can also lead to corrosion and degradation of carbon dioxide electrolyzer components. For example, as mentioned above, low cell pH can adversely affect electrolyzer membrane performance by reducing transport rates over time. As another example, carbon dioxide reactions to produce carbonate and bicarbonate species can lead to the formation of salt precipitates or high-salt regions, fouling electrolyzer components and significantly reducing performance. At the cathode, these deposits are typically hygroscopic and impede efficient gas and liquid transport across the cathode. This is exacerbated by the fact that the mass diffusivity of carbon dioxide in water is approximately four orders of magnitude lower than its mass diffusivity in the gas phase. As another example, salts formed from the reaction of alkaline media with carbon dioxide gas can also precipitate within membrane pores, impeding efficient ion transport. At the anode, the incorporation of anionic species other than hydroxide can reduce the efficiency of the desired anode reaction by site poisoning and increasing the rate of anode corrosion.

[0007] As outlined above, the carbonate problem results in: 1) a significant reduction in electrolysis efficiency; 2) reduced carbon efficiency, as some of the carbon dioxide is converted to bicarbonate and carbonate and then transported to another section of the system, requiring additional separation costs to capture the carbon dioxide; and 3) a reduced system lifetime, as the carbonate problem causes degradation of the system at steady state. As a result, carbon dioxide electrolysis is associated with high costs, which currently hinder its development on an industrial scale.

[0008] While efficient production of valuable small molecules (e.g., hydrocarbons, olefins, alcohols, and carboxylic acids) from carbon dioxide remains elusive, carbon dioxide is often used to produce synthesis gas (a mixture of dihydrogen and carbon monoxide), which is considered useful as a fuel source with lower emissions compared to alternative hydrocarbons. For example, the reverse water gas shift (RWGS) reaction is used to produce a mixture of carbon monoxide and dihydrogen from carbon dioxide and dihydrogen according to equation (5) shown below. RWGS reactors may also produce other hydrocarbons (e.g., methane). The chemicals produced by the reactor can be described as those generated from the reactor input. The performance of an RWGS reactor can be measured in terms of its selectivity for a particular chemical. For example, an RWGS reactor can have a selectivity defined as the ratio of the amount of carbon monoxide generated to the sum of the amount of carbon monoxide and the amount of methane generated. Using some of the approaches disclosed herein, selectivity can exceed 90%. Water produced during the process is separated from the mixture to produce synthesis gas. Because this reaction is endothermic, it is thermodynamically favored at high temperatures. This reaction is the reverse of the water-gas shift reaction used to produce dihydrogen. The RWGS reactor is fed a mixture of carbon dioxide and dihydrogen at high temperature (100°C-1000°C) and moderate pressure (1-30 bar). The dihydrogen-to-carbon dioxide ratio in the reactor feed is typically on the order of 0.9-2, depending on the desired outlet syngas quality. [ka] The syngas produced from the RWGS reactor can be used directly as a fuel source or to feed various processes (e.g., without limitation, the Fischer-Tropsch process or the Sapatier process, which produces liquid hydrocarbons and methane, respectively). However, unsaturated molecules (e.g., olefins, organic acids, and alcohols) remain difficult to access through these syngas upgrading systems. Other technologies exist for converting carbon dioxide to syngas (e.g., solid oxide electrolysis cells (SOECs)), but have other drawbacks associated with operating at high temperatures (e.g., coking of electrodes (solid carbon deposits that inhibit catalytic action) and mechanical issues associated with operating at high temperatures).

[0009] The problem solved by certain embodiments of the invention disclosed herein is the cost-competitive production of sustainable chemicals (e.g., small olefins, organic acids, and alcohols) from carbon dioxide without suffering from the carbonate problem described above.

[0010] The problem solved by certain embodiments of the invention disclosed herein is the lack of a sustainable source of carbon monoxide to feed a carbon monoxide electrolyzer. Technologies other than RWGS exist for converting carbon dioxide to carbon monoxide, but typically have poor steady-state performance, require high energy input for efficient performance, or require the conversion of fossil carbon feedstocks.

[0011] The problem solved by certain embodiments of the invention disclosed herein is the lack of incentives and high costs to reduce the carbon dioxide emission intensity of processes that produce valuable feedstock chemicals and / or materials. This problem includes the lack of technological solutions for producers operating processes with high greenhouse gas emissions to comply with regulatory requirements while remaining financially sustainable. In principle, the direct carbon dioxide emission intensity of industrial processes with high greenhouse gas emissions (e.g., without limitation, chemical manufacturing, cement manufacturing, and steel manufacturing) can be reduced by capturing and sequestrating carbon dioxide. However, carbon dioxide capture and sequestration fundamentally represents and incurs economic and energy costs. Technologies that can lead to carbon dioxide capture and sequestration while lowering overall costs and provide economic incentives are needed to reduce the greenhouse gas emissions of many industrial processes. The carbon dioxide used by the systems disclosed herein can be a quantity of carbon dioxide captured from an industrial process, which can be one of a steel or metal manufacturing process, a cement manufacturing process, a dihydrogen production process, a partial oxidation process, a biomass processing plant, a biomass gasification plant, a bioethanol production process, a biogas production process, a biowaste incineration process, a hydroformylation process, a power generation process, and a waste incineration process. Carbon dioxide can also be captured from direct air capture.

[0012] Disclosed herein are methods and systems relating to the valorization of carbon dioxide using a RWGS reactor, purification of the output stream, and a novel carbon monoxide electrolyzer. Particular embodiments of the invention disclosed herein utilize a novel system integration that combines the use of a RWGS reactor for the specific production of carbon monoxide with a novel electrolyzer designed for the low-temperature electrolysis of carbon monoxide. This combined process does not suffer from the carbonate problems associated with direct carbon dioxide electrolysis. The combined process enables the sustainable production of useful chemicals that benefit from the advantageous selectivity and compatibility of carbon oxide electrolysis, while suppressing the carbonate problems that have previously hindered the large-scale development of alternative solutions.

[0013] In certain embodiments of the invention disclosed herein, the RWGS reactor takes in a certain amount of carbon dioxide as a feedstock and forms a certain amount of carbon monoxide. The certain amount of carbon monoxide is then fed to the cathode of a carbon monoxide electrolyzer, where it can be used as a reduction substrate for a reduction reaction that pairs with the oxidation reaction at the anode of the carbon monoxide electrolyzer. One or more additive chemicals can be fed to the electrolyzer along with the carbon monoxide. Useful chemicals can be produced by the reduction of carbon monoxide, allowing the tandem reactor comprising the RWGS reactor and the carbon monoxide electrolyzer to serve to add value to carbon dioxide. The properties of the chemicals produced depend on the properties of the electrolyzer and the additive chemicals.

[0014] In certain embodiments of the invention disclosed herein, the RWGS reactor is used in conjunction with a gas separation system to produce a pure carbon monoxide stream, as opposed to its conventional use for the production of an unseparated synthesis gas stream consisting of carbon monoxide, dihydrogen, carbon dioxide, and water. The purified low carbon dioxide, high carbon monoxide content gas stream produced by the RWGS reactor and gas separator is then provided to feed a carbon monoxide electrolyzer as previously described.

[0015] In certain embodiments of the invention disclosed herein, the RWGS reactor is a RWGS plasma-based reactor, and the RWGS reaction involves the generation of a plasma. A major advantage of integrating a plasma-based RWGS reactor with a carbon monoxide electrolyzer is that both process segments of the production line can be operated at low temperatures, allowing for flexible operation and tolerance to intermittencies.

[0016] In certain embodiments of the invention disclosed herein, the RWGS reactor is calibrated to maximize carbon monoxide production relative to other potential outputs of a conventional RWGS reactor. In these embodiments, the reaction conditions of the RWGS process chain are optimized to minimize the amount of dihydrogen produced and maximize the amount of carbon monoxide produced. This embodiment reduces separation costs downstream of the RWGS reactor by maximizing the conversion of inlet dihydrogen into the system to form carbon monoxide.

[0017] In certain embodiments of the invention disclosed herein, a separator (e.g., an acid scrubber) is placed in the production line between the RWGS reactor and the carbon monoxide electrolyzer to remove any remaining carbon dioxide from the RWGS reactor product (e.g., synthesis gas) before it reaches the electrolyzer.

[0018] Certain embodiments of the invention disclosed herein utilize a dihydrogen recycle system that optimizes feedstock utilization and minimizes costs. For example, certain embodiments of the invention disclosed herein utilize a recycle scheme to recycle parasitic dihydrogen from the carbon monoxide electrolyzer as a feedstock for the RWGS reactor. In certain embodiments of the invention disclosed herein, dihydrogen is fed back from one or more points on the tandem reactor to serve as a feedstock for the RWGS reactor. For example, unconverted dihydrogen can be separated from carbon monoxide between the RWGS reactor and the electrolyzer and returned as an input to the RWGS reactor. As another example that can be used alternatively or in combination, the cathode of the electrolyzer can perform a parasitic reduction reaction (in addition to the targeted carbon monoxide reduction reaction) to produce dihydrogen, which can then be returned as an input to the RWGS reactor. These approaches reduce the cost of operating the RWGS reactor because the expensive dihydrogen feedstock is used more efficiently.

[0019] In certain embodiments of the invention disclosed herein, dihydrogen is produced at the output of the RWGS reactor, and some or all of such dihydrogen is separated from the RWGS gas stream and separately valorized. These approaches are advantageous in embodiments where the input and output mass flow rates of the RWGS process chain and the carbon monoxide electrolyzer are mismatched, allowing for continuous operation and minimizing process bottlenecks. In certain embodiments, both dihydrogen recycling and separate valorization of dihydrogen from the RWGS gas stream can occur in a single system. In these embodiments, the ratio of recycled dihydrogen to externally valorized dihydrogen can be adjusted to match the capacity of the carbon monoxide electrolyzer. Furthermore, in such embodiments, a single production line can produce both dihydrogen and useful chemicals (e.g., ethylene) from a power source and a carbon dioxide source, with the net ratio controlled by the dihydrogen recycle rate downstream of the RWGS reactor (e.g., after a combined carbon monoxide and dihydrogen separation unit downstream of the RWGS reactor and before the carbon monoxide electrolyzer).

[0020] As used herein, the term "amount" of a substance (e.g., a quantity of carbon monoxide) is not intended to denote a separate, distinct, refined physical quantity, but rather is intended to refer to a collection of substances in the same sense that a cup of coffee with one tablespoon of milk contains a "quantity" of milk, and that amount is one tablespoon. As used herein, the term "fluid" is used to refer to describe a substance in any physical form, including liquid, gas, supercritical, or a combination of liquid and gas forms.

[0021] As used herein, carbon dioxide valorization refers to the conversion of carbon and oxygen components of carbon dioxide into more economically valuable chemicals (e.g., hydrocarbons, organic acids, alcohols, olefins, and N-rich organic compounds).

[0022] In certain embodiments of the invention disclosed herein, a method is provided that includes collecting a quantity of carbon dioxide, supplying the quantity of carbon dioxide to a reverse water gas shift reactor, producing a quantity of carbon monoxide in a reverse water gas shift reaction using the quantity of carbon dioxide and the reverse water gas shift reactor, supplying the quantity of carbon monoxide to a cathode region of an electrolyzer, and producing a quantity of product chemical using the electrolyzer, reduction of the quantity of carbon monoxide, and oxidation of an oxidation substrate, where the quantity of product chemical is at least one of a quantity of hydrocarbon, a quantity of organic acid, a quantity of alcohol, a quantity of olefin, and a quantity of N-rich organic compound.

[0023] In certain embodiments of the invention disclosed herein, a system is provided. The system includes a reverse water gas shift reactor, a carbon dioxide source connection fluidly connecting a carbon dioxide source to the reverse water gas shift reactor, an electrolytic cell having an anode region and a cathode region, and a carbon monoxide source connection fluidly connecting the reverse water gas shift reactor to the cathode region. The reverse water gas shift reactor is configured to use a certain amount of carbon dioxide from the carbon dioxide source connection to produce a certain amount of carbon monoxide in a reverse water gas shift reaction. The electrolytic cell is configured to use the reduction of the certain amount of carbon monoxide from the carbon monoxide source connection and the oxidation of an oxidation substrate to produce a certain amount of product chemical. The certain amount of product chemical is at least one of a certain amount of hydrocarbon, a certain amount of organic acid, a certain amount of alcohol, a certain amount of olefin, and a certain amount of N-rich organic compound.

[0024] In certain embodiments of the present invention, a system is provided that includes a reverse water gas shift reactor, an electrolytic cell having an anode region and a cathode region, means for supplying a quantity of carbon dioxide to the reverse water gas shift reactor, means for producing a quantity of carbon monoxide in a reverse water gas shift reaction using the quantity of carbon dioxide and the reverse water gas shift reactor, means for supplying the quantity of carbon monoxide to the cathode region of the electrolytic cell, and means for producing a quantity of product chemical using the electrolytic cell, the quantity of carbon monoxide, and the oxidation of an oxidation substrate, where the quantity of product chemical is at least one of a quantity of hydrocarbon, a quantity of organic acid, a quantity of alcohol, a quantity of olefin, and a quantity of N-rich organic compound. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a flow chart for a set of methods for operating tandem reactors for carbon dioxide valorization using the RWGS reaction, according to certain embodiments of the invention disclosed herein. [Figure 2] FIG. 1 is a block diagram of a RWGS reactor according to certain embodiments of the invention disclosed herein. [Figure 3] 1 is a plot of the equilibrium volume percent products of a RWGS reactor at various temperatures in accordance with certain embodiments of the presently disclosed invention. [Figure 4] 1 is a plot of the equilibrium volume percent products of a RWGS reactor with different feed ratios at various temperatures in accordance with certain embodiments of the presently disclosed invention; [Figure 5] FIG. 1 is an exploded block diagram of an electrolytic cell according to certain embodiments of the presently disclosed invention. [Figure 6] FIG. 1 illustrates a first set of electrolytic cell reactions available in accordance with certain embodiments of the presently disclosed invention. [Figure 7] FIG. 1 illustrates a second set of electrolytic cell reactions that can be utilized in accordance with certain embodiments of the presently disclosed invention. [Figure 8] FIG. 1 shows an electrolytic cell using a diaphragm as a separation element according to certain embodiments of the invention disclosed herein. [Figure 9] FIG. 1 is a block diagram of a tandem carbon dioxide valorization reactor with feedback paths for carbon dioxide and dihydrogen according to certain embodiments of the invention disclosed herein. [Figure 10] FIG. 1 is a block diagram of a tandem carbon dioxide valorization reactor with a carbon monoxide concentrator in accordance with certain embodiments of the presently disclosed invention. [Figure 11] FIG. 1 is a block diagram of a tandem carbon dioxide valorization reactor that produces dihydrogen along with other valuable chemical products in accordance with certain embodiments of the invention disclosed herein. [Figure 12] FIG. 1 is a block diagram of a tandem carbon dioxide valorization reactor with a feedback path for carbon monoxide to the electrolyzer and a feedback path for dihydrogen to the RWGS reactor, according to certain embodiments of the presently disclosed invention. [Figure 13] FIG. 1 is a block diagram of a tandem carbon dioxide valorization reactor without a dihydrogen separator, according to certain embodiments of the invention disclosed herein. [Figure 14] FIG. 1 is a block diagram of a tandem carbon dioxide valorization reactor supplying dihydrogen from a RWGS reactor to an electrolyzer anode, according to certain embodiments of the invention disclosed herein. [Figure 15] FIG. 1 is a block diagram of a tandem carbon dioxide valorization reactor in which dihydrogen is supplied to the RWGS reactor from an electrolyzer, and the RWGS reactor does not receive any dihydrogen from another source external to the reactor, according to certain embodiments of the invention disclosed herein. [Figure 16] FIG. 1 is a block diagram of an electrolyzer that receives carbon monoxide mixed with one or more additive chemicals, according to certain embodiments of the invention disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0026] Methods and systems for carbon dioxide valorization using the RWGS reaction according to the above outline are disclosed in detail herein. The methods and systems disclosed in this section are non-limiting embodiments of the present invention, are provided for illustrative purposes only, and should not be used to limit the overall scope of the present invention. It should be understood that the disclosed embodiments may or may not overlap with each other. Thus, portions of one embodiment, or a specific embodiment thereof, may or may not be included within the scope of another embodiment, or a specific embodiment thereof, and vice versa. Different embodiments from different aspects may be combined or implemented separately. Many different combinations and subcombinations of the exemplary embodiments shown within the broad framework of the present invention may be apparent to those skilled in the art but may not be explicitly or specifically described, and should not be construed as being excluded.

[0027] Instead of performing low-temperature carbon dioxide electrolysis to obtain unsaturated chemicals (for example, without limitation, olefins, carboxylic acids, and alcohols), reducing carbon monoxide in an electrolyzer is advantageous in maintaining low overall energy demand. Carbon monoxide is an important intermediate product toward value-added products when carbon dioxide is reduced in an electrolyzer. Unlike carbon dioxide, carbon monoxide is a non-acid gas that does not rapidly react with hydroxide ions to form anionic species. In electrolyzers using alkaline electrolytes and carbon monoxide feed, carbon monoxide can be efficiently reduced by metal electrodes to valuable hydrocarbons, olefins, alcohols, and carboxylic acids. Therefore, electrolyzers fed with carbon monoxide can operate under alkaline conditions, thus lowering the energy usage of the electrolysis process.

[0028] A key technology gap that has prevented the wider adoption of carbon monoxide electrolyzers is the lack of a sustainable carbon monoxide source. One reason that integrating a RWGS reactor with a carbon monoxide electrolyzer has not been obvious is because RWGS reactors are typically configured to produce a mixture of carbon monoxide, carbon dioxide, and water, which can then be fed to thermochemical reaction systems that are insensitive to the presence of the gas mixture (e.g., without limitation, Fischer-Tropsch, methanation, and methanol synthesis processes). In contrast, the performance of a carbon monoxide electrolyzer is highly sensitive to the composition of the electrolyzer gas feed. A RWGS fed with low-carbon dihydrogen and carbon dioxide and a gas separation system can serve as a sustainable carbon monoxide source for the carbon monoxide electrolyzer, enabling low-carbon production of small molecules.

[0029] The aforementioned factors motivate electrolysis of carbon monoxide supplied from RWGS instead of carbon dioxide in an electrolyzer using an alkaline electrolyte. If the carbon monoxide used in the carbon monoxide electrolyzer is ultimately supplied from carbon dioxide and the process is driven by low-emission energy input, the carbon emission benefits are achieved because the condensed-phase product of the carbon monoxide electrolyzer effectively sequester the converted carbon dioxide. Therefore, integrating the carbon monoxide electrolyzer with an upstream carbon dioxide-carbon monoxide conversion system is beneficial. In addition to RWGS, there are several other technological routes for converting carbon dioxide to carbon monoxide. Low-temperature electrolysis of carbon dioxide to carbon monoxide, as previously mentioned, requires high energy and is therefore expensive due to the reaction of carbon dioxide with alkaline equivalents.

[0030] One barrier to the industrial adoption of RWGS reactors is the requirement for dihydrogen as an input, which is typically produced using an energy-intensive process. Recycling dihydrogen from process units downstream of the RWGS reactor back to the RWGS reactor is a less obvious, but important, feature of certain embodiments of the invention disclosed herein to reduce the energy demands of the RWGS reactor and the overall integrated system. Because RWGSs are typically configured by design to produce mixed carbon monoxide and dihydrogen streams, separating the carbon monoxide to high purity and recycling the dihydrogen back to hydrogenate carbon dioxide has not been standard technology. Recycling dihydrogen back within the RWGS process chain can help maximize the utilization of dihydrogen fed into the RWGS process and reduce the amount of dihydrogen that would otherwise have to be fed exogenously.

[0031] A feature of certain embodiments of the invention disclosed herein is the recycling of dihydrogen from the carbon monoxide electrolyzer back into the RWGS process chain, representing an opportunity to recover energy losses associated with the parasitic production of dihydrogen during carbon monoxide electrolysis. This approach can also be used to generate hydrogen for the RWGS process chain during startup, before carbon monoxide is available for the carbon monoxide electrolyzer. The novel carbon monoxide electrolyzer exhibits a faradaic efficiency for dihydrogen production of up to 80%, meaning that, depending on the operating conditions, a significant portion of the supplied power is lost to the reduction of dihydrogen to water or protons. The dihydrogen obtained from carbon monoxide electrolysis can be value-added by separating it from other components of carbon monoxide electrolysis. However, doing so may not be economically viable because the cost of producing dihydrogen using an electrolyzer optimized for carbon monoxide reduction is higher than that of an electrolyzer optimized for dihydrogen production. Furthermore, valorizing dihydrogen to commercial grade may require other downstream capital equipment and processing steps (e.g., compression and transportation) that may be prohibitively expensive for a carbon monoxide electrolysis plant operator to implement. Thus, the energy loss associated with the production of parasitic dihydrogen during carbon monoxide electrolysis can be partially recovered using the RWGS unit, simultaneously reducing the exogenous dihydrogen demand of the RWGS and leading to process synergies.

[0032] In certain embodiments of the present invention, a carbon monoxide electrolysis process downstream in the RWGS process chain can produce enough dihydrogen to feed the RWGS process, reducing the demand for an upstream dihydrogen source. In these embodiments, the carbon monoxide electrolyzer can be operated at a high current density (e.g., 200 mA cm -2RWGS is operated at a high proportion of dihydrogen in its output (>20%) at temperatures above 1000°C (>1200°F), improving the productivity of the integrated process while reducing capital expenditures relative to the size of the carbon monoxide electrolyzer. Furthermore, it reduces the demand of the RWGS on upstream processes that supply dihydrogen (e.g., dedicated dihydrogen electrolyzers or industrial dihydrogen waste streams). Reduced upstream dihydrogen demand also allows for more flexible and cost-effective integration scenarios (e.g., integration with smaller upstream dihydrogen sources, reduced demand for renewable power and associated infrastructure, and minimal capital intensity for project viability). In certain embodiments of the present invention, the carbon monoxide electrolyzer produces enough dihydrogen that no additional dihydrogen is fed into the process chain; all the required dihydrogen is produced by the carbon monoxide electrolyzer and separation unit.

[0033] In a specific embodiment of the present invention, the start-up period of the tandem process chain is carried out without any external dihydrogen input (e.g., the reactor shown in FIG. 15). Within a limited time interval when the process chain is initially activated, the carbon monoxide electrolyzer can be operated without any carbon monoxide gas input and controlled to produce dihydrogen, which can then be recycled into the upstream RWGS reactor, which is fed only with carbon dioxide-rich gas. After this start-up period, the downstream electrolyzer in the RWGS process chain begins converting carbon monoxide to products as it is produced and separated in the RWGS process chain and fed into the electrolyzer. In this specific embodiment, the process chain embodies a novel feedback loop: if the RWGS process chain provides insufficient carbon monoxide to the carbon monoxide electrolyzer, the downstream electrolyzer proceeds to produce a higher proportion of dihydrogen. As the amount of dihydrogen produced in the electrolyzer increases and is then recycled back into the RWGS process chain, the amount of carbon monoxide produced in the RWGS process chain and fed to the electrolyzer increases, and the electrolyzer's conversion of carbon monoxide to products increases. Given the relative sizes of the electrolyzer, RWGS reactor, and associated separation unit, a steady-state carbon monoxide conversion rate can be achieved that is highly dependent on the electrolyzer current density, the system separation efficiency, and the conversion rate in the RWGS process chain. In this particular embodiment, the RWGS process chain, carbon monoxide electrolyzer, and associated separation system must be appropriately sized relative to the overall system to ensure stability. For example, a high current density in the electrolyzer must be forced to ensure sufficient dihydrogen flux to the RWGS process chain.

[0034] A unique advantage of certain embodiments of the invention disclosed herein arises from the fact that the upstream RWGS and gas separation process chain are uniquely suited to accepting and valorizing recycled dihydrogen from a downstream electrolyzer system. For example, excess dihydrogen cannot be introduced into the anode of an O2-transporting SOEC because of the fire and explosion hazards of mixing the inlet dihydrogen with electrogenerated oxygen. Similar safety issues arise in any carbon dioxide to carbon monoxide conversion system that co-produces oxygen or some other substance that can oxidize dihydrogen. In another example, recycling excess dihydrogen from a downstream carbon monoxide electrolyzer back into the cold carbon dioxide-carbon monoxide electrolyzer can reduce the efficiency of the carbon dioxide electrolyzer because it reduces the partial pressure of carbon dioxide entering the electrolyzer at the same total pressure.

[0035] The following paragraphs describe methods for producing dihydrogen in a carbon monoxide electrolyzer that can be fed into a RWGS process train. Dihydrogen can be produced from water available on the cathode side of the carbon monoxide electrolyzer. Water can be present at the cathode by diffusing from the anolyte across a separator (e.g., a central membrane) or can be introduced in gaseous (as humidity) or liquid form through the carbon monoxide stream. To increase hydrogen production, specific measures can be taken to increase the amount of water on the cathode side of the carbon monoxide electrolyzer. For example, increasing the humidity of the input stream to the cathode region of the carbon monoxide electrolyzer, directly feeding liquid water to the cathode region, or reducing the pressure in the cathode region to promote water ingress from the anode region into the cathode region of the electrolyzer. Dihydrogen can be produced on the cathode side by modifying the current density supplied to the cathode region. After a certain point, excess current becomes available in the cathode region beyond that required to reduce carbon monoxide, and all of the excess current is used to produce dihydrogen. Thus, the current density supplied to the cathode region can be increased or decreased to change the amount of dihydrogen produced therein, and specific steps can be taken to change the amount of carbon monoxide supplied to the cathode region, which will also change the amount of dihydrogen produced therein for a given current density.

[0036] The current density for carbon monoxide conversion in a carbon monoxide electrolyzer is limited by its mass transport from the gas phase to the solid interface of the cathode, as well as the rate at which the cathode can transfer electrons to the surface-bound carbon monoxide. These two factors define the maximum current density at which the electrolyzer can convert carbon monoxide, with any additional current density being diverted to converting water to hydrogen. In certain embodiments of the present invention, a carbon monoxide electrolyzer can be driven toward the production of dihydrogen by changing the current density at which the electrolyzer operates. This increases the voltage required for the electrolyzer. For example, if the maximum current density for carbon monoxide conversion is 200 mA cm -2 If it is observed that-2 When configured to operate at 100 mA / cm², an additional 100 mA / cm² is dedicated to the reduction of water to produce dihydrogen. -2 The mole fraction of hydrogen in the stream increases proportionally with the additional current density.

[0037] In certain embodiments of the present invention, a carbon monoxide electrolyzer can be driven toward dihydrogen production by reducing the molar flow rate of carbon monoxide to the cathode region. This increases the voltage required for the electrolyzer. To maintain a given current density for carbon monoxide conversion, a carbon monoxide electrolyzer requires a certain mass transport rate of carbon monoxide. If the mass transport (determined by a metric such as gas mass flow rate) is reduced below that required to maintain a given current density for carbon monoxide conversion and the carbon monoxide electrolyzer is operated such that the current remains stable, the remainder of the current density is dedicated to the reduction of water to hydrogen. The molar ratio of hydrogen in the stream increases proportionally to the additional current density. Thus, by changing the amount of carbon monoxide supplied to the cathode region, the amount of dihydrogen produced can be changed.

[0038] Heat from both the RWGS process chain (including the heater) and the electrolyzer can be added to reduce the heat demand of the process subunits. A key feature of RWGS is the endothermic nature of the reactions, necessitating the addition of external heating or energy to the system. To reduce the amount of external heat added, the gas stream exiting the RWGS reactor is typically at a high temperature and can be recovered using a heat exchanger to power downstream processes (e.g., gas separation and compression and / or distillation of liquid products). Heat can also be used to preheat the RWGS reactor process gas stream or recycled around the RWGS reactor to provide process insulation. Additionally, heat from the RWGS reactor can be used to power a carbon dioxide capture process upstream of the RWGS process. The electrolyzer can generate significant excess heat due to ohmic losses during operation. Electrolyzer waste heat can be used for processes with lower temperature demands (e.g., distillation and gas separation) or can be added separately from the core RWGS-carbon monoxide electrolyzer process chain for general heating applications.

[0039] When the RWGS reaction is carried out using a reaction system that includes or is driven by plasma, the temperature is generally lower than when the RWGS is driven by externally supplied heat. In a tandem system that includes a plasma-driven RWGS reaction in a plasma-based RWGS reactor and a carbon monoxide electrolyzer, a larger portion of the system's energy input can be obtained from low-carbon electricity. Unlike a high-temperature RWGS reactor, integrating a carbon monoxide electrolyzer with a low-temperature RWGS reactor can improve the system's compatibility with intermittent power input (e.g., from intermittent renewable energy sources) and allows for more flexible operation, as the output of each unit in the process chain is proportional to the input power.

[0040] The synergistic benefits of combining RWGS with carbon monoxide electrolysis are not obvious, in part because the typical thermochemical carbon monoxide upgrading process performed downstream of the RWGS reactor does not produce dihydrogen. For example, in the case of methanol synthesis (Equation 7) or Fischer-Tropsch synthesis, dihydrogen is also consumed as a feedstock in the thermochemical step following RWGS, and dihydrogen is not typically produced by the thermochemical process consuming syngas. Therefore, opportunities to recover energy losses by implementing a parasitic or excess dihydrogen recycle step are limited because both RWGS and methanol synthesis / Fischer-Tropsch synthesis require additional exogenous dihydrogen. In contrast, the parasitic production of dihydrogen in the reduction of carbon monoxide provides a way to reduce the dihydrogen demand of the RWGS reaction and recover the parasitic energy loss of producing dihydrogen in the CO electrolyzer. CO2+H2⇔CO+H2O (6)RWGS 2CO2+3H2⇔CH3OH+H2O (7)MeOH synthesis

[0041] Figure 1 shows a flow chart 100 for a set of methods for carbon dioxide valorization using RWGS reactions, according to certain embodiments of the invention disclosed herein. Figure 1 includes step 101, in which a quantity of carbon dioxide is collected. Carbon dioxide can be a by-product of industrial processes (e.g., power generation, chemical and material production) from which it can be harvested, or it can be obtained from the capture of carbon dioxide from any carbon dioxide emission source. There are several industrial processes that emit large amounts of carbon dioxide into the atmosphere, which can also be used to harvest carbon dioxide in step 101.

[0042] Flowchart 100 continues with step 102, in which a quantity of carbon dioxide collected in step 101 is supplied to the RWGS reactor 110. This step may involve supplying the carbon dioxide from a carbon storage tank through a fluid connection. The fluid connection may include one or more separators to filter out specific chemicals not intended for application in the RWGS reactor. Specific separators may be used to remove hydrocarbon compounds, oxygen- and / or sulfur-containing compounds, phosphorus-containing compounds, and reactive nitrogen-containing compounds. A particle and / or dust filtering system may also be used to remove solid contaminants from the carbon dioxide-containing stream that could adversely affect the performance of the RWGS reactor. The fluid connection may be provided through one or more valves, one or more seals, and / or one or more regulators or additional equipment in a pipe or other connection that couples the carbon dioxide source to the RWGS reactor. The fluid connection may also include valves and conduits that allow carbon dioxide to be mixed with dihydrogen in different ratios to provide an optimal mixture of dihydrogen and carbon dioxide to the RWGS reactor. The fluid connection can be connected to a carbon dioxide source (e.g., a pressurized storage tank or separator connected directly to the output exhaust gas of an industrial process). The fluid connection can also be connected to a dihydrogen source (e.g., a pressurized storage tank). The fluid connection can also include a feedback conduit for obtaining carbon dioxide or dihydrogen from a downstream source in the tandem reactor of which the RWGS reactor 110 is a part, as described below. The dihydrogen source can also be output from a water electrolyzer (e.g., without limitation, an alkaline electrolyzer, a proton exchange membrane-based electrolyzer, an alkali exchange membrane-based electrolyzer, a solid oxide electrolyzer, a hydrocarbon pyrolysis reactor). The dihydrogen source can also be dihydrogen produced by an oil refinery, a dehydrogenation process, a steam reforming plant, and a polymerization process.

[0043] Flowchart 100 continues in step 103 with the production of a quantity of carbon monoxide in a RWGS reaction using the quantity of carbon dioxide provided in step 102 and RWGS reactor 110. The carbon dioxide provided in step 102 can be mixed with dihydrogen before being provided to the RWGS reactor. The RWGS reactor can convert the carbon dioxide and dihydrogen to carbon monoxide, with oxygen atoms being separated from the carbon dioxide and combining with the dihydrogen to form water, leaving behind carbon monoxide. The RWGS reactor can operate by passing the mixture of carbon dioxide and dihydrogen over a catalyst at high temperature (e.g., 100-1200°C) and moderate pressure (e.g., 1-30 bar). The catalyst promotes the reaction between the carbon dioxide and dihydrogen to produce carbon monoxide and water.

[0044] Flowchart 100 continues with step 104, in which a quantity of carbon monoxide produced in step 103 is supplied to a cathode region of electrolyzer 120. The electrolyzer can include a cathode region and an anode region. The cathode region can include a cathode input for receiving a feedstock (e.g., carbon monoxide) for a reduction reaction and a cathode output for removing at least one product of the reduction reaction. The anode region can include an anode input for receiving a feedstock for an oxidation reaction and an anode output for removing at least one product of the oxidation reaction. The electrolyzer can also include a separation layer or region between the cathode and the anode. Supplying carbon monoxide from the RWGS reactor to the electrolyzer can be accomplished using a fluid connection. The fluid connection can be provided through one or more valves, one or more seals, and / or one or more regulators or additional equipment in a pipe or other connection that couples the output of the RWGS reactor to the electrolyzer. The fluid connection can include one or more separators for removing unwanted chemicals from the output of the RWGS reactor. The fluid connections may also include one or more valves and conduits that allow an additive chemical to be supplied to the anode of the electrolyzer along with the carbon monoxide. The fluid connections may also include a feedback conduit for obtaining carbon monoxide from a downstream source in the tandem reactor of which the electrolyzer 120 is a part, as described below.

[0045] The carbon monoxide supply can include collecting all of the carbon monoxide produced by the RWGS reactor or a portion of the amount of carbon monoxide produced by the RWGS reactor. The amount of carbon monoxide can be collected as part of a carbon monoxide-containing stream in which the amount of carbon monoxide is mixed with other chemicals or impurities. Valves, seals, and any other necessary equipment can be configured to route the carbon monoxide first to the electrolyzer and then to a second system. A connection or pipe can be connected to an accumulation tank or set of tanks located between the electrolyzer and the RWGS reactor to accumulate excess carbon monoxide if there is any difference in velocity between the RWGS reactor and the electrolyzer. Such an accumulation tank or set of tanks can also be used to temporarily store carbon monoxide during periods of high power costs when operating the electrolyzer is prohibitively expensive.

[0046] The amount of carbon monoxide can be mixed with additional fluid to form the cathode input fluid, or can be kept pure so that the cathode input fluid is pure carbon monoxide. This step can include transporting a tank of carbon monoxide from the area where it was collected and connecting it to a connection or pipe coupled to the cathode area of ​​the electrolyzer. The step can also include temporarily storing the carbon monoxide in the tank until electricity prices drop, and then supplying the stored carbon monoxide to the electrolyzer when it becomes more economical to do so. This step can alternatively include sending the carbon monoxide directly from the RWGS reactor through a connection or pipe to the electrolyzer in the same industrial facility.

[0047] Both carbon dioxide capture and carbon monoxide delivery can occur within a single facility and can include direct or indirect capture and delivery. In indirect capture, carbon monoxide from the RWGS reaction can be piped to a storage tank and then sealed. The tank can then be transported to a location where the carbon monoxide is utilized or stored on-site for later use. In contrast, direct capture can involve piped carbon monoxide from the RWGS reaction directly from the reactor or other system where the RWGS reaction occurs to the electrolyzer or other system where the carbon monoxide is utilized (e.g., one or more intermediate steps may occur before the carbon monoxide is delivered to the electrolyzer). For example, a dihydrogen production line can be located within the same facility as the electrolyzer 120 and the RWGS reactor 110, and carbon dioxide produced by the dihydrogen production line can be captured and delivered directly to the RWGS reactor 110. In these embodiments, a portion of the dihydrogen produced by the production line can be mixed with carbon dioxide and delivered as a feedstock to the RWGS reactor 110. The carbon monoxide produced by the RWGS reactor 110 can then similarly be fed directly to the electrolyzer 120, or there can be one or more intermediate steps between the RWGS reactor 110 and the electrolyzer 120 to pretreat the carbon monoxide-containing stream before it is fed to the electrolyzer. As another example, the carbon monoxide can be collected indirectly, where the RWGS reactor is fluidly connected to one or more storage tanks that store the carbon monoxide for transport and / or later use. In either case, two or more of the carbon dioxide source, the RWGS reactor, and the electrolyzer can be located within a single industrial facility (e.g., a refinery, biorefinery, chemical plant, industrial laboratory, waste treatment plant, or other facility). In certain embodiments of the present invention, a single industrial process or facility may produce both carbon dioxide and carbon monoxide, with both chemicals separated and then fed into the same tandem reactor, with the carbon dioxide being introduced into the RWGS reactor input and the carbon monoxide being introduced into the fluid connection between the RWGS reactor and the electrolyzer (i.e., by mixing with the carbon monoxide produced by the RWGS reactor).

[0048] Flowchart 100 continues with step 105 of generating a quantity of product chemical using electrolyzer 120 and the reduction of a quantity of carbon monoxide and the oxidation of an oxidation substrate. The oxidation substrate can be water, dihydrogen gas, a halide, an alcohol, an organic waste (e.g., without limitation, glycerol), or any other oxidation substrate. The quantity of product chemical can include at least one of a quantity of hydrocarbon, a quantity of organic acid, a quantity of alcohol, a quantity of olefin, and a quantity of N-rich organic compound. Electrolyzer 120 can generate a quantity of product chemical on either the anode or the cathode. Electrolyzer 120 can be energized to initiate a pair of reduction and oxidation reactions at the cathode and anode, respectfully, to generate a quantity of product chemical.

[0049] In certain embodiments of the present invention, the RWGS reactor utilizes one or more catalysts to promote the conversion of carbon dioxide to carbon monoxide. The RWGS reactor can be a single heterogeneous catalyst or a set of heterogeneous catalysts. The RWGS reactor can include active metal and metal oxide-supported catalysts. The active metal oxide catalyst can include at least one of Pt, Pd, Rh, Ru, Au, Fe, Mo, Cu, Co, Cr, In, Ba, Zr, and Ni. The first five of these active metals are effective due to their high hydrogenation activity. However, Cu and Ni are promising for RWGS reactors due to their relatively low cost and high activity and selectivity. However, Cu oxide and Ni oxide catalysts tend to deactivate in RWGS due to agglomeration of Cu and Ni particles at the high temperatures required for RWGS reactor operation. In certain embodiments of the present invention, the RWGS reactor can use an active metal (e.g., without limitation, Pt, Mo, Co, or Fe) supported by a metal oxide support catalyst (e.g., without limitation, CeO, ZrO, or AlO). Other catalysts that can be used in RWGS include transition metal carbides (e.g., MoC and WC) and metal sulfides (e.g., lanthanide sulfides and molybdenum sulfides), and metal phosphides. Other catalyst formulations based on alkali metal carbonates (e.g., KCO, NaCO, CsCO, RbCO) that can be dispersed on mesoporous supports (e.g., carbon, zeolites, SiO, AlO, TiO, and other metal oxides and ceramics) can also convert carbon dioxide to carbon monoxide with high efficiency, lower temperatures, high stability, and resilience to poisons in the feed gas.

[0050] RWGS reactors operating at high temperatures according to certain embodiments of the invention disclosed herein can be classified into two main categories: (1) fixed-bed and (2) fluidized-bed. The primary difference lies in the catalyst geometry and gas superficial velocity. Catalyst geometries include, but are not limited to, pellets, beads, monoliths, foams, and powders. Fixed-bed reactors use catalysts in the form of pellets or beads (1-100 mm), which has the advantage of simplicity. However, they present several limitations in terms of heat transfer. Several hot and cold spots may appear along the reactor, leading to loss of catalytic activity (sintering, coking) and loss of carbon monoxide selectivity (methane production). In fluidized-bed reactors, the catalyst is in the form of a powder (<500 μm) suspended in the gas stream. These reactors improve heat transfer and provide uniform temperatures throughout the catalyst bed. However, the catalyst must be specially formulated to resist attrition, achieve long life, and limit catalyst regeneration. Either fixed-bed or fluidized-bed reactors are based on a stainless steel insulated / heat-traced cylindrical vessel, as shown in Figure 2. The vessel contains a gas distribution system at the bottom of the reactor, followed by the bed section. Several reactor vessels can be arranged in series to increase yield. Additionally, interstage cooling / condensation / reheating steps can be implemented between each reactor. In the case of a fluidized bed, filters and / or cyclones can be installed immediately downstream of the reactor to capture catalyst fines and recirculate them instead. Implementing an electrolyzer downstream of the RWGS reactor may require minor modifications to the RWGS reactor design (e.g., adding a fluid port to integrate a dihydrogen recycle loop).

[0051] FIG. 2 shows a block diagram 200 of a RWGS reactor according to certain embodiments of the invention disclosed herein. Block diagram 200 includes a heat exchanger 201 to which carbon dioxide and dihydrogen feedstocks are supplied. The heated gas is then fed through a gas distribution system 202 to a catalyst fixed-bed or fluidized-bed reactor and insulation 203, as previously described. The reactor output, particularly in the case of a fluidized-bed reactor, is fed to a particle filter or cyclone 204, which can return particles to the reactor. Gas product 205 produced in the reactor and passed through the filter or cyclone 204 is then processed by the heat exchanger 201 and output from the system. Heat makeup 206 is used to compensate for heat losses and the endothermic nature of the reaction. This makeup can be achieved by an electric heater or the combustion of a fuel source. As previously described, in certain embodiments of the invention, the RWGS reactor can be a plasma-based reactor. In such embodiments, the reactor can include a power source (e.g., a high-voltage power supply 207). High voltage power supply 207 is shown in phantom to indicate that it is not required in embodiments that do not utilize a plasma-based reactor.

[0052] To maintain high carbon monoxide selectivity and limit the methane content in the RWGS reactor outlet gas, two solutions are available: maintain the temperature above 700°C to thermodynamically avoid methane production and / or force the RWGS to highly selectively catalyze the production of carbon monoxide instead of methanating carbon dioxide. Figure 3 illustrates this point by showing a line plot of the equilibrium volume percent of the RWGS reactor output stream over various temperatures. Above 700°C, carbon monoxide selectivity to methane is thermodynamically greater than 90%, and above 800°C, greater than 95%. In certain embodiments of the present invention, the RWGS reactor operates between 600 and 1000°C. Diminishing returns in carbon dioxide conversion and energy / process efficiency occur above 1000°C, further imposing constraints on material selection, as, for example, steel reactors can rapidly deteriorate above 1000°C under RWGS conditions. Operating a catalytic RWGS reactor at such high temperatures can lead to coke deposition on the catalyst surface, catalyst sintering, or phase separation (thermal degradation), which in turn increases activity loss and shortens lifespan. Note that the operating pressure does not affect thermodynamic equilibrium. Because the RWGS reaction is slightly endothermic, the inlet gas mixture is typically heated to above 800-900°C to maintain the reactor temperature above 700-850°C. A feed / exhaust heat exchanger (e.g., heat exchanger 201) is installed to recover the majority of the heat and limit heat makeup. This heat makeup is still necessary to compensate for the endothermic nature of the reaction and heat losses. Heat makeup can be achieved using methods such as, but not limited to, an electrical heating system or burning a fuel (e.g., natural gas). To avoid coke and / or methane production and to reduce the energy consumption of the process, some low-temperature reactors (200-600°C) using specific catalyst formulations (e.g., dispersed alkali metal carbonates) can be used to obtain selectivities higher than 80-90%.

[0053] Another solution developed to minimize energy consumption and increase carbon monoxide production is the RWGS Chemical Looping (RWGS-CL) reactor. In the RWGS-CL process, the RWGS reaction is split into two stages: (1) the reduction of carbon dioxide to carbon dioxide and (2) the oxidation of dihydrogen to water. A circulating oxygen carrier material (metal oxide, e.g., FeO 4 / 3 ) can help improve the reaction efficiency by acting as an oxygen carrier, facilitating the acceptance of oxygen from carbon dioxide and the donation of oxygen to dihydrogen. The two-stage reaction can lower the partial pressure of water in the carbon monoxide-enriched stream, shifting the thermodynamic equilibrium toward the production of carbon monoxide.

[0054] Dielectric barrier discharge (DBD) plasma reactors can also be used for RWGS reactions. DBD plasma reactors are an example of a plasma-based RWGS reactor. DBD reactors use metal, metal oxide, or ceramic catalysts and can operate at ambient to moderate temperatures (400 °C) and atmospheric pressure, resulting in high energy efficiency. While reactor configurations for DBD vary, they typically involve flowing carbon dioxide and / or dihydrogen into a gap between two electrodes, where a voltage sufficient to generate a plasma is applied. The reactor temperature, pressure, and composition are controlled to optimize performance. The reaction is activated by the plasma, resulting in the conversion of the input to carbon monoxide, water, and oxygen at the output. Reaction conditions must be controlled to avoid oxygen accumulation within the reactor due to the safety risk of mixing dihydrogen with oxygen, as well as the undesirable consumption of reducing equivalents from the dihydrogen and oxygen.

[0055] The ratio of carbon monoxide to dihydrogen produced by an RWGS system can be adjusted by adjusting the amount of dihydrogen and carbon dioxide fed into the RWGS reactor and adjusting the temperature of the RWGS reactor. In certain embodiments of the invention disclosed herein, it is useful to maximize the amount of carbon monoxide produced relative to dihydrogen, contrary to the operating principles of conventional RWGS reactors used to produce syngas. For example, an inlet composition of 80% carbon dioxide and 20% dihydrogen fed into the RWGS reactor can produce a stream consisting mostly of carbon dioxide and carbon monoxide at high temperatures, with minimal dihydrogen. This is illustrated by comparing Figures 3 and 4, because the plot in Figure 3 is for a 1:1 feed ratio of carbon dioxide to dihydrogen, while the plot in Figure 4 is for a 4:1 feed ratio of carbon dioxide to dihydrogen. The composition in Figure 4 would not normally be accessed by the RWGS reactor because it is configured to produce syngas for hydrogenation reactions, but such a carbon monoxide-rich outlet stream is particularly advantageous for integration with a downstream carbon monoxide electrolyzer.

[0056] Maximizing the amount of carbon monoxide output from the RWGS reactor relative to dihydrogen provides various advantages. For example, by reducing the amount of dihydrogen required as a feedstock for the RWGS reactor, the power input required to operate the entire production line is minimized. Furthermore, in some embodiments, the dihydrogen output from the RWGS reactor can be recycled as an input to the RWGS reactor, but the cost of separating the dihydrogen to do so is significant. Before use as a feedstock in the RWGS system, the outlet gas stream of the carbon monoxide electrolyzer containing dihydrogen is partially purified to remove other gas components (e.g., without limitation, carbon monoxide, carbon dioxide, methane, ethylene, and water). Furthermore, the purified dihydrogen must be recompressed to the pressure required to operate the RWGS reaction, incurring energy costs. Minimizing the amount of dihydrogen produced by the RWGS process reduces this energy cost. Furthermore, in some embodiments, because the carbon monoxide electrolyzer can operate with dihydrogen as an input, minimizing the amount of dihydrogen may eliminate the need for a separation block altogether. Thus, an approach to minimizing dihydrogen output from the RWGS reactor can lower both capital and operating costs.

[0057] Depending on the specific embodiment of the present invention, three main steps can be used downstream of the RWGS reactor to produce pure carbon monoxide for the electrolyzer: (1) Cool and condense the gas to remove the water produced; (2) Remove carbon dioxide (e.g., using an amine scrubbing unit or one of the separation methods described below) and separate the carbon dioxide for recycling upstream of the RWGS reactor; and (3) Remove dihydrogen (e.g., using a membrane module or one of the separation methods described below) and separate the dihydrogen for recycling upstream of the RWGS reactor. The configuration of each of the three steps downstream of the RWGS reactor can be tailored to the electrolyzer performance requirements (e.g., final CO, CO2, HO, CH4, and H2 contents) and minimize the production costs and energy consumption of the overall system.

[0058] Electrolyzers can have a variety of configurations to convert carbon monoxide into valuable chemicals. Electrolyzers can include an anode region and a cathode region. Carbon monoxide can be fed to the anode region. Useful chemicals can be produced in the cathode region, the anode region, or a separation region located between the cathode and anode regions of the electrolyzer. Electrolyzers can be single planar cells. Electrolyzers can be stacks of cells. Cells within the stack can utilize bipolar plates. The bipolar plates can be electrically charged to initiate reactions within the reactor. Electrolyzers can also be filter press cells or tubular cells.

[0059] In certain embodiments of the invention disclosed herein, a dihydrogen or syngas generator is advantageously integrated with a carbon monoxide electrolyzer that includes a cathode region where the reduction of carbon monoxide occurs according to Equation 8 below, and an anode region where an oxidation reaction occurs on an oxidation substrate. The oxidation substrate can be water, dihydrogen, a halide, organic waste, or any other oxidation substrate. For example, the oxidation can involve the oxidation of water or the oxidation of dihydrogen according to Equations 9 and 10 below, respectively. xCO(x+yz)H2O+(2x+y-2z)e - ⇔ C x H y O z +(2x+y-2z)OH - (8) 2H2O⇔4H + +4e - +O2(9) H2⇔2H + +2e - (10) Both carbon monoxide and the oxidized substrate can be mixed with an additive chemical to modify the reactor properties and change the properties of the chemicals produced by the electrolyzer. For example, water and carbon monoxide can be mixed to form the cathode input fluid for the electrolyzer, while an oxidized substrate (e.g., dihydrogen) is fed to a separate connection coupled to the anode input of the electrolyzer. This type of reaction can be useful in tandem reactors according to certain embodiments of the invention disclosed herein because RWGS reactors generally already feed carbon monoxide mixed with water, eliminating the need to separate the water, potentially leading to simpler and less expensive reactor designs and power savings for tandem reactor operation.

[0060] The chemicals produced by the electrolytic cell may vary in different specific embodiments of the invention disclosed herein. Chemicals can be separated using a separation element (e.g., a trap for liquid chemicals on the anode or cathode output of the electrolytic cell, or a separation region between the cathode and anode regions with their own outputs from the electrolytic cell). Product chemicals can be removed from the electrolytic cell in solid or gas form, from the cathode or anode output stream on the cathode or anode output of the electrolytic cell, or from a separate output through a separation layer. Examples of such separation layers are shown below. A single electrolytic cell can simultaneously produce chemicals in both gas and liquid form. Thus, the amount of chemical produced in a step such as step 105 can include at least one of a certain amount of hydrocarbon, a certain amount of organic acid, a certain amount of alcohol, a certain amount of olefin, and a certain amount of N-rich organic compound, where the chemicals are in gas or liquid form. For example, the certain amount of product chemical can include a certain amount of gaseous hydrocarbon and a certain amount of liquid alcohol. As another example, the certain amount of product chemical can include a certain amount of gaseous hydrocarbon and a certain amount of organic acid. In certain embodiments, the primary target products are ethylene (in the gaseous product stream) and acetic acid / acetate (in the liquid product stream), while in other embodiments the primary target product is propanol (in the liquid product stream).

[0061] In certain embodiments of the present invention, dihydrogen for the RWGS reactor may be supplied from a low carbon footprint dihydrogen generation system.

[0062] In certain embodiments of the present invention, dihydrogen for the RWGS reactor can be supplied from a syngas generation system operating on the same stream of carbon dioxide. The syngas generation system can be part of a reactor such as that described in U.S. Patent Application No. 17 / 980,912, filed November 4, 2022, which is incorporated by reference in its entirety for all purposes. The tandem reactor described in that prior application and the tandem reactor described in this application can be located in the same industrial facility to obtain synergistic benefits (e.g., production of dihydrogen for the RWGS reactor and inclusion of two streams of useful chemicals from a single carbon dioxide source).

[0063] A carbon monoxide electrolyzer used in accordance with the present disclosure can include one or more electrocatalytic cells arranged on top of or adjacent to one another to increase the surface area available for reaction. They can be stacked on top of one another, and such stacks can also be paralleled. The cells can be connected in series or in parallel. Many different cell and stack configurations can be used in electrolyzers in accordance with the present disclosure. For illustrative purposes, FIG. 5 shows a diagram of an electrolyzer 500. The methods and systems disclosed herein are generally applicable to electrolyzers capable of receiving a carbon input (e.g., carbon monoxide), and electrolyzer 500 is shown as a non-limiting example of one such electrolyzer.

[0064] FIG. 5 includes a diagram of an electrolyzer 500 in the form of a stack, according to certain embodiments of the invention disclosed herein. The electrolyzer 500 includes end plates (e.g., end plate 502), monopolar plates (e.g., monopolar plate 504), rigid bars (e.g., rigid bar 506), a membrane electrode assembly (MEA) (e.g., MEA 508) or any form of catalytic core, flow fields (e.g., flow field 510), and bipolar plates (e.g., bipolar plate 512). Again, while an example of an MEA is shown, this is merely an example, and electrolyzers with any form of catalytic core can be used according to embodiments disclosed herein. Additionally, the electrolyzer 500 includes an inlet 514 and outlet 516 for the anode flow, as well as an inlet 518 for the cathode flow and an outlet 520 for the cathode flow. The plates (e.g., monopolar plate 504 and bipolar plate 512) can be part of cells within the stack. The laminate may also include gaskets, seals of any shape, insulating layers, and materials not shown in FIG. 5 for clarity.

[0065] In an electrolytic stack, subsequent cells can be physically separated by bipolar plates (BPPs) (e.g., bipolar plate 512 in FIG. 5 ), which can provide mechanical support for each of the electrolytic cells on either side of the BPP. The BPPs ensure electrical series connection between subsequent electrolytic cells and also allow the introduction and removal of reactants and products, respectively. At the ends of the stack, only one side of the plate can contact the terminal cell, which is therefore referred to as a monopolar plate (e.g., monopolar plate 504 in FIG. 5 ). At the ends of the stack, current collectors can allow connection to an external power source, which can also be used, among other elements, for electrical monitoring of the stack. The stack can be assembled within a stack casing, which not only provides mechanical support and compression but also allows the supply and transport of reactant and product streams to and from the stack. The stack casing can include end plates that ensure electrical insulation of the stack and provide inlets and outlets for the reactant and product streams. Alternatively, an insulating plate can be placed between an end plate (e.g., end plate 502) and a monopolar plate (e.g., monopolar plate 504) to ensure stack-to-stack casing electrical insulation, depending on the end plate material.

[0066] The carbon monoxide electrolyzer can take as inputs a cathode input stream (e.g., a carbon monoxide-rich stream) and an anode input stream. The cathode input stream can be provided at an inlet (e.g., inlet 518). The anode input stream can be provided at an inlet (e.g., inlet 514). The cathode and anode streams can flow through the stack from the inlet to the outlet and can be separately distributed to each cathode and anode region through flow channels (e.g., in the flow field 510 of each cell). The anode and cathode streams flow through separate channels on either side of the cell. Alternatively, at least one of the cathode and anode streams can be individually supplied to each cell instead of through a connection across all plates. In this case, each cell has a dedicated fluid inlet and outlet for the cathode and / or anode stream. The nature of the anode stream can be determined by the nature of the targeted oxidation reaction (e.g., without limitation, water oxidation, dihydrogen oxidation, chloride oxidation, halide oxidation, hydrocarbon oxidation, and waste organic oxidation). When powered, the carbon monoxide electrolyzer simultaneously reduces carbon monoxide and oxidizes selected oxidation substrates to produce value-added chemicals (e.g., hydrocarbons, organic acids and / or alcohols, and / or N-containing organic products) in an output cathode stream separated from the anode stream, where the oxidation products are specifically collected. For example, producing chemicals using carbon monoxide and the electrolyzer in step 105 can include providing a quantity of carbon monoxide to a cathode region of the electrolyzer as a cathode input fluid and providing a quantity of water to an anode region of the electrolyzer as an anode input fluid.

[0067] In certain embodiments of the present invention, the anode region can include an anode catalyst layer capable of oxidizing a substance to produce products and protons. The catalyst can include one or more of the following: molecular species, single-metal-site heterogeneous compounds, metal compounds, carbon-based compounds, polymer electrolytes (also known as ionomers), metal-organic frameworks, 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 compounds can be in the form of metal nanoparticles, nanowires, nanopowders, nanoarrays, nanoflakes, nanocubes, dendrites, films, layers, or mesoporous structures. The single-metal-site compounds can include metal-doped carbon-based materials or metal-NC-based compounds. Anode catalyst species used for this purpose can include, without limitation, metals and / or ions of Ir, Co, Cu, Ni, Fe, Pt, Rh, Re, Ru, Pd, Os, Mo, and mixtures and / or alloys thereof. For example, the anode catalyst can be Ni, such that the electrolyzer assembly includes a nickel-based anode. The polymer electrolyte can be selected from the same materials used in the described membranes. The carbon-based compound can include carbon nanofibers, carbon nanotubes, carbon black, graphite, boron-doped diamond powder, diamond nanopowder, boron nitride, or a combination thereof. The additive can be a halide-based compound including F, Br, I, and Cl. The additive can be specifically tailored for hydrophobicity modification, for example, treatment with polytetrafluoroethylene (PTFE), sulfonated tetrafluoroethylene-based fluoropolymer copolymer, or another hydrophobic polymer ionomer additive, or carbon black. The anode catalyst can be selected to tailor electrolyzer performance and net product flow by selecting a catalyst with higher or lower capacity for anodic alcohol oxidation to the corresponding carboxylic acid, aldehyde, or carbon dioxide.

[0068] The anode catalyst may be deposited on a gas diffusion layer, or a porous transport layer, or any other support that facilitates diffusion of gas from the interface of the anode to a purified gas stream separated from the cathode stream. The anode region may also include a gas diffusion layer having one or more separators (e.g., without limitation, membranes, polymeric materials, diaphragms, inorganic materials) on its boundary, as described below.

[0069] In certain embodiments of the present invention, the cathode region can include a catalyst layer capable of reducing a substance (e.g., carbon monoxide) to produce value-added hydrocarbons, alcohols, or organic acids. The catalyst can include one or more of the following: molecular species, single-metal-site heterogeneous compounds, metal compounds, carbon-based compounds, polymer electrolytes (also known 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 compounds can be in the form of metal nanoparticles, nanowires, nanopowders, nanoarrays, nanoflakes, nanocubes, dendrites, films, layers, or mesoporous structures, with particle sizes precisely selected to control performance. The single-metal-site compounds can include metal-doped carbon-based materials or metal-NC-based compounds. The cathode catalyst may be made of a metal or metal ion from a metal (e.g., without limitation, Cu, Ag, Au, Zn, Sn, Bi, Ni, Fe, Co, Pd, Ir, Pt, Mn, Re, Ru, La, Tb, Ce, Dy, or other lanthanides, as well as mixtures and / or alloys thereof). For example, the cathode catalyst may include Cu, such that the electrolytic cell assembly includes a copper-based cathode. The polymer electrolyte may be selected from the same materials used in the described membranes. Carbon-based compounds may include carbon nanofibers, carbon nanotubes, carbon black, graphite, boron-doped diamond powder, diamond nanopowder, boron nitride, or combinations thereof. The additive may be a halide-based compound including F, Br, I, or Cl. The additive may be specially dedicated for hydrophobic modification, for example, PTFE, sulfonated tetrafluoroethylene-based fluoropolymer copolymer, or another hydrophobic polymer ionomer additive, or treatment with carbon black. The cathode may further comprise a catalyst layer on a gas diffusion layer, porous transport layer, or any other support to facilitate diffusion of gases from the stream to the surface of the catalyst and to allow release of non-reacted / product gases.The cathode region can also include a gas diffusion layer having one or more separators (e.g., without limitation, membranes, polymeric materials, diaphragms, and inorganic materials) on its boundaries, as described below. The catalyst and additive loading on the gas diffusion layer can be precisely selected to favor specific performance characteristics (e.g., voltage, conductivity, carbon monoxide mass transport rate, product selectivity, and stability differences).

[0070] In certain embodiments of the invention disclosed herein, the porous support for either the anode region, the cathode region, or both can be selected from carbon-based porous supports or metal-based porous materials or combinations. The carbon-based porous support can be based on carbon fiber, carbon cloth, carbon felt, carbon fabric, carbon paper, molded graphite laminates, etc., or mixtures thereof. The carbon-based porous support can be a gas diffusion layer with or without a microporous layer. Such carbon-based supports can be specifically selected from 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, AvCarbon1209, AvCarb 1185, AvCarb1186, AvCarb 7497, AvCarbT1819, 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, AvCarb EP40T, AvCarb P75T, AvCarb EP55T, AvCarb MGL190, AvCarb MGL280, AvCarb MGL370. The metal-based porous support can be selected from titanium, stainless steel, Ni, Cu, or any other suitable metal and can be in the form of a mesh, frit, foam, or plate of any thickness or porosity.

[0071] In certain embodiments of the present invention, the electrolytic cell can include a separation element for separating certain product chemicals from others. The separation element can be one or more traps on the cathode and / or anode outputs of the electrolytic cell that separate the liquid output from the gaseous output. It can also be more complex systems known to those skilled in the art for efficient product separation. The separation element can be a separation region between the anode and cathode regions configured to separate a certain amount of product chemical from the electrolytic cell. The separation region can be a separation layer. Efficient physical separation between the anode and cathode regions may facilitate easier separation of gases released from each section of the reactor. The separator can be an ion-conducting polymer separator, an ionomer solution coated on an electrode, a diaphragm, a ceramic-containing material, an uncharged separator scaffold, a mixed ceramic organic compound separator, or any other separator. Separation may be achieved through the use of ion exchange membranes (which facilitate the diffusion of either anions (in the anion exchange membrane) or cations (in the cation exchange membrane)), or bipolar membranes (including mixtures of cation and anion exchange membranes), or other types of separators, such as diaphragms, ceramic-containing materials (particularly mixed ceramic / organic compounds), or uncharged separator scaffolds. Anion exchange membranes can include organic polymers with positively charged functional groups (e.g., without limitation, imidazolium, pyridinium, or tertiary amines). This allows the negatively charged hydroxide ions (OH) generated during the reduction of carbon monoxide to be absorbed. -) can easily migrate from the cathode to the anode. The use of this layer also prevents crossover of other gases from the cathode to the separation layer. The cation exchange membrane can include an organic polymer with negatively charged functional groups (e.g., without limitation, sulfonic acid groups). The membrane or uncharged separator can be derived from an insulating material that can be charged by an ion-conducting electrolyte to facilitate charge transfer between the electrodes. The ceramic-containing material can be a pure ceramic or a mixed polymer and ceramic material. Ceramic and polymer blends can reach higher temperatures than purely organic polymers and can utilize the ion exchange function within the polymer to pass charge between the electrodes. The membrane thickness can be precisely selected to control the transport rates of working species (e.g., anions, cations) and neutral species (e.g., alcohols and water).

[0072] In certain embodiments of the present invention, the system can include an electrolyte that facilitates ion transport and provides ions that promote the reaction. In particular, the electrolyte can be a concentrated alkaline solution, such as a solution of a hydroxide-containing salt (e.g., without limitation, potassium, sodium, or cesium hydroxide), at concentrations such as (0.01 molar (M), 0.05M, 0.1M, 0.2M, 0.5M, 1M, 2M, 3M, 4M, 5M, 6M, 7M, 8M, 9M, and 10M). The use of a concentrated alkaline solution reduces the overall energy requirements of the reaction. Alkali metal cations (e.g., Li, Na, K, Cs, Rb) can also be used as countercations. The electrolyte can also include oxidizing substrates other than water or hydroxides, such as dihydrogen, alcohols, glycerol, other organic materials, and other oxidizable raw materials.

[0073] In certain embodiments of the invention disclosed herein, the flow field can include a ladder, single or multiple serpentines, interdigitated patterns, pillars, bioinspired leaf shapes, or mixtures thereof. The electrolysis cell can also include electrodes, as further described in this disclosure. Electrolyzer performance can be tuned by modifying the flow field characteristics, particularly to prevent the accumulation of condensed phases that slow carbon monoxide mass transport and liquid product egress. For example, using more flow field channels of the same area can result in more efficient extraction of liquid product from the cathode compared to a flow field with a lower density of channels.

[0074] Certain embodiments of the invention disclosed herein allow the electrolyzer to be operated at high temperatures and pressures to promote electrolyzer stability and performance by improving carbon monoxide mass transport and product efflux. High temperatures can serve to vaporize liquid products present in the cathode catalyst layer, while high pressure can reduce liquid intrusion and stagnation in the cathode catalyst layer. The electrolyzer can be operated under high pressure in both the anode and cathode compartments, or only in one compartment to precisely manage liquid and gas crossover in the electrolyzer.

[0075] In certain embodiments of the invention disclosed herein, humidification of carbon monoxide upstream of the carbon monoxide electrolyzer is a key parameter in the process chain. Depending on the electrolyzer configuration, humidification of the carbon monoxide gas stream can be important for improving electrolysis efficiency. Several humidification processes can be applied to the carbon monoxide stream, including, but not limited to, (1) steam injection into the gas stream, (2) membrane water / gas contact modules, (3) water-gas bubblers, and (4) other water / gas contact systems (e.g., but not limited to, atomizers and packed columns). For solutions (2), (3), and (4), the moisture content of the gas outlet depends primarily on the system operating conditions (pressure and temperature), contact time, and exchange area between the two phases. In this case, it may be necessary to heat the inlet gas stream and / or the water in contact with the gas to increase the moisture content in the gas stream. Solution (1) includes a steam generation module that can use electricity or fuel gas in a boiler as primary energy. The generated steam is then mixed with the gas stream to control the relative humidity. The gas stream can be preheated to avoid condensation in the mixing area.

[0076] As an alternative method for humidifying the carbon monoxide gas stream and reducing the energy demand for humidifying the carbon monoxide electrolyzer, the water required to humidify the carbon monoxide gas stream can be supplied from the water produced from the RWGS process. This also serves to reduce the energy demand for the CO2 / H2 / CO / H2O separation after the RWGS reactor by allowing more water to be mixed into the carbon monoxide outlet stream of the separator unit.

[0077] 6 and 7 show examples of reactions that can be performed by the electrolyzer assemblies described herein. While only a single cell is shown for clarity, these can easily be assembled into multiple cells (e.g., stacks). In the figures, the carbon monoxide electrolyzer includes a cathode comprising a gas diffusion layer and a copper-based catalyst, and the anode comprises a nickel material in any form (e.g., without limitation, foam, mesh, deposition on a conductive porous transport layer (PTL)). In this case, the carbon monoxide reduction products include one or more of the following: ethylene (C2H4), ethanol (C2H5OH), acetic acid (CH3COOH), propylene (C3H6), propanol (C3H8O), oxalic acid (COOH-COOH), acrylic acid (C2H3COOH), and glyoxylic acid (COH-COOH), produced by the following carbon monoxide reduction reaction: In neutral / alkaline conditions, 2CO+6H2O+8e - →CH2CH2+8OH - (11) 2CO+7H2O+8e - →CH3CH2OH+8OH - (12) 2CO+4H2O+4e-→CH3COOH+4OH - (13) 3CO+5H2O+6e - →C2H3COOH+6OH - (14) 3CO+9H2O+12e-→C3H6+12OH - (15) 3CO+10H2O+12e-→C3H8O+12OH - (16) In acidic conditions, 2CO+8H + +8e - →CH2CH2+2H2O (17) 2CO+8H + +8e - →CH3CH2OH+H2O (18) 2CO+4H + +4e - →CH3COOH (19) 3CO+6H+ +6e - →C2H3COOH+H2O (20) 3CO+12H + +12e - →C3H6+3H2O (21) 3CO+12H + +12e - →C3H8O+2H2O (22)

[0078] In certain embodiments, the carbon monoxide stream is mixed with other gaseous or liquid compounds to produce higher value-added products at the cathode. In one such embodiment, an imine, amine, nitrogen oxide, or ammonia is added to react with carbon monoxide or the intermediate products formed during its reduction to form amide bonds or N-rich organic compounds (e.g., amino acids or ureas). Examples of such reactions are as follows: 2CO+3H2O+NH3+4e‐→CH3CONH2+4OH - (Neutral / alkaline conditions) (23) 2CO+4H + +NH3+4e - →CH3CONH2+H2O (acidic conditions) (24)

[0079] In certain embodiments, the oxidation reaction at the anode is selected from the group consisting of reactions that take place in an acidic environment and reactions that take place in an alkaline environment, including, but not limited to, anodic reactions in an acidic environment, such as: 2H2O→O2+4H + +4e - (twenty five) H2→2H + +2e - (26) Cl - →Cl2+2e - (27) Br - →Br2+2e - (28) I - →I2+2e - (29) C3H8O3 (glycerol) → C3H6O3 (glyceraldehyde) +2H + +2e - (30) C3H8O3 (glycerol) + H2O → C3H5O4 - (glycerate) +5H + +4e - (31) C3H8O3 (glycerol) + 3 / 2H2O → 3 / 2C2H3O3 - +13 / 2H + +5e - (32) C3H8O3 (glycerol) + 3H2O → 3HCOO - (formate) +11H + +8e - (33) C3H8O3 (glycerol) + 3H2O → 3 / 2C2O4 2- +14H + +11e - (34) and anodic reactions in neutral / alkaline environments, e.g. 4OH - →O2+2H2O+4e - (35) H2+2OH - →2H2O+2e - (36) Cl - →Cl2+2e - (37) Br - →Br2+2e - (38) I - →I2+2e - (39) C3H8O3(glycerol)+2OH - →C3H6O3 (glyceraldehyde) +2H2O+2e - (40) C3H8O3(glycerol)+5OH - →C3H5O4 - (glycerate) +4H2O+4e- (41) C3H8O3(glycerol)+13 / 2OH - →3 / 2C2H3O3 - +5H2O+5e - (42) C3H8O3(glycerol)+11OH - →3HCOO - (formate) + 8H2O + 8e - (43) C3H8O3(glycerol)+14OH - →3 / 2C2O4 2- +11H2O+11e - (44) C2H5OH+5OH - →CH3COO - +4H2O+4e - (45) C3H7OH+5OH - →CH3CH2COO - +4H2O+4e - (46)

[0080] In certain embodiments of the present invention, the carbon monoxide electrolyzer comprises one or more ion exchange membranes selected from anion exchange membranes (e.g., without limitation, commercially available Ionomr®, Orion®, Sustainion®, Piperion®, ionomer anion exchange membranes), proton exchange membranes (e.g., without limitation, Nafion®, Aquivion®, or commercially available membranes), and bipolar membranes (e.g., without limitation, Fumasep® FBM and Xion®). In certain embodiments of the present invention, the membranes in the anion exchange membranes are prepared using N-containing monomers. In the example reactor 600, the electrolyzer comprises an anion exchange membrane, and hydroxides migrate from the cathode to the anode. The oxidation products, which are dependent on the oxidation substrate, can be any of the aforementioned product chemicals collected from the cathode output. In the example reactor 602, the electrolyzer comprises a cation exchange membrane, and protons migrate from the anode to the cathode. The oxidation product will again depend on the oxidation substrate, but the product collected from the cathode output can be any of the product chemicals previously mentioned.

[0081] In certain embodiments of the present invention, the electrolytic cell can include a separation layer. In the example reactor 601, the carbon monoxide electrolyzer includes a central separation layer through which electrolyte fluid circulates, allowing for collection of the liquid carbon monoxide reduction product moving from the cathode toward the central separation layer. In certain embodiments, the central separation layer is separated from the cathode by an anion exchange membrane or from the anode by a cation exchange membrane, or both membranes are present. In the example reactor 601, both membranes are present. In this example, useful products can be collected from both the liquid stream from the separation layer and the gas stream from the cathode output. For example, carbon monoxide can be used by the electrolyzer to produce one or more of the following: ethylene (C2H4), ethanol (C2H5OH), acetic acid (CH3COOH), propylene (C3H6), propanol (C3H8O). In certain embodiments, the primary target product is ethylene (in the gaseous product stream). In another specific embodiment, the primary target products are ethylene (in the gaseous product stream) and ethanol (in the liquid product stream). In another particular embodiment, the primary target products are ethylene (in the gaseous product stream) and acetic acid / acetate (in the liquid product stream). For example, in reactor 602, a trap is placed at the cathode output to separate the liquid product from the gaseous product so that both can be collected. In these examples, the oxidation occurring at the anode can be water / hydroxide oxidation, dihydrogen oxidation, or chloride oxidation. Notably, in the physical system, the trap is placed on the connection to the cathode outlet (e.g., piping connected to the cathode), and the trap is depicted connected to the cathode region for illustrative purposes only.

[0082] The example shown in FIG. 7 is similar to the example shown in FIG. 6 in terms of the overall reactor theory. However, the approach of FIG. 7 operates without an exchange membrane, instead using a separation layer to achieve a similar effect. Reactor 700 is similar to reactor 600 in that hydroxide ions migrate from the cathode to the anode, and generated products can be collected from the cathode output. Reactor 701 is similar to reactor 601 in that the separation layer contains a liquid electrolyte, and useful products can be collected from both the separation layer output in liquid form and the cathode region output in fluid form. Reactor 702 is similar to reactor 602 in that protons migrate across the separation layer, and useful products can be collected from the cathode output.

[0083] In certain embodiments of the present invention, a porous diaphragm can be used in an electrolytic cell as a separation element to achieve separation. The diaphragm can be saturated with electrolyte, allowing ions to pass between the cathode and anode. Figure 8 shows a reactor 800. In reactor 800, the separation element is a diaphragm that allows ions to pass from the anode to the cathode and / or ions to pass from the cathode to the anode.

[0084] In certain embodiments of the present invention, the carbon monoxide stream is mixed with at least one other chemical (e.g., another gas or liquid compound) to generate higher value-added products at the cathode of the electrolyzer. The carbon monoxide stream can be mixed with such added chemicals as the carbon monoxide is fed to the electrolyzer. In one such embodiment, an imine, amine, nitrogen oxide, or ammonia is added to react with the carbon monoxide or intermediate products formed during its reduction to form an amide bond or nitrogen-rich organic compound (e.g., an amino acid). In another embodiment, an aromatic compound or a fatty acid / aldehyde / alcohol is added to react with the carbon monoxide or intermediate products formed during its reduction to form a hydrocarbon, alcohol, or organic acid. In another embodiment, an aromatic compound or aliphatic olefin or hydrocarbon is added to react with the carbon monoxide or intermediate products formed during its reduction to form a hydrocarbon, alcohol, or organic acid. These reactions can be combined with any of the reactors described above. For example, the oxidation occurring at the anode can be water oxidation, hydroxide oxidation, dihydrogen oxidation, or halide oxidation.

[0085] Figures 9-15 show examples of tandem reactor configurations including a RWGS reactor and electrolyzer in series with various separation units to produce valuable products from carbon dioxide. Figure 9 shows a block diagram 900 of a tandem carbon dioxide valorization reactor with feedback paths for carbon dioxide and dihydrogen, according to certain embodiments of the invention disclosed herein. Figure 10 shows a block diagram 1000 of a tandem carbon dioxide valorization reactor with a carbon monoxide concentrator, according to certain embodiments of the invention disclosed herein. Figure 11 shows a block diagram 1100 of a tandem carbon dioxide valorization reactor that produces a low dihydrogen output and does not use a dihydrogen separator between the RWGS reactor and the carbon monoxide electrolyzer. Figure 12 shows a block diagram 1200 of a tandem carbon dioxide valorization reactor that produces dihydrogen as an output in addition to useful products produced by the carbon monoxide electrolyzer. Figure 13 shows a block diagram 1300 of a tandem carbon dioxide valorization reactor that removes only carbon dioxide, but not dihydrogen, from the RWGS process outlet stream. The mixture of carbon monoxide, dihydrogen, and water is then fed into a carbon monoxide electrolyzer according to certain embodiments of the invention disclosed herein. Figure 14 shows a block diagram 1400 of a tandem carbon dioxide valorization reactor in which dihydrogen from the output of the RWGS reactor is fed to the electrolyzer anode for use as the electrolyzer's oxidation substrate. Figure 15 shows a block diagram 1500 of a tandem carbon dioxide valorization reactor in which all dihydrogen required by the RWGS reactor is supplied from the electrolyzer within the tandem reactor, and no external source of dihydrogen is required.

[0086] The tandem reactor architecture disclosed herein can be designed to operate continuously, with carbon monoxide being produced by the RWGS reactor in time to feed the carbon monoxide electrolyzer. The tandem reactor architecture disclosed herein can be designed to produce output from the RWGS reactor with the ratio of carbon monoxide to dihydrogen being adjusted for the characteristics of the downstream carbon monoxide electrolyzer or can be changed based on conditions in the downstream portion of the overall production line. The control system for the tandem reactor can include safeguards that shut down the reactor or portions thereof upon detection of the presence or absence of certain chemicals in the reactor (e.g., shutting down the electrolyzer to conserve power if not enough carbon monoxide is being produced by the RWGS reactor).

[0087] In certain embodiments of the invention disclosed herein, one or more separators can be positioned on the fluid connections between reactor components. The separators can be designed to separate specific chemicals from the fluid streams at the fluid connections. For example, a quantity of carbon monoxide can be separated from a quantity of carbon dioxide at the output of the RWGS reactor using at least one separator unit, such as in step 911 of flowchart 910, where carbon dioxide separator 903 separates carbon dioxide from the output of the RWGS reactor. The at least one separator in this example can be an acid scrubber, and the electrolyzer can use an alkaline electrolyte.

[0088] In certain embodiments of the present invention, carbon monoxide can be separated from trace chemicals remaining in the output of the RWGS reactor and in the water output by the RWGS reactor. Carbon monoxide can be separated using various approaches, such as membrane separation, cryogenic separation, separation methods based on various physical or chemical properties of the components in the RWGS reactor output, pressure swing adsorption, temperature swing adsorption, vacuum or vacuum pressure swing adsorption-based separation, or absorption-based separation. For example, a separation system can be used on the output of the RWGS reactor to first cool the output to remove impurities, then heat the output fluid to evaporate purified dihydrogen through a membrane that filters out carbon monoxide. Any carbon dioxide or dihydrogen filtered from the output of the RWGS reactor can be fed back to serve as feed to the RWGS reactor. Any parasitic dihydrogen or carbon monoxide filtered from the output of the electrolyzer can be fed back to serve as feed to the RWGS reactor. Any carbon monoxide filtered from the output of the electrolyzer can be fed back to serve as feed to the electrolyzer. Alternatively, any dihydrogen filtered from the output of the electrolyzer's RWGS reactor can be removed from the system as a useful product, along with the chemicals produced by the electrolyzer.

[0089] The carbon monoxide gas mixture to be purified and fed into the carbon monoxide electrolyzer can be saturated with water at a relative humidity as high as 80% to 100% at the pressure and temperature considered, depending on the production process. To avoid water condensation in pipes, gas compressors, and process units, water can be completely or partially removed down to the dew point of a specified temperature. The pipes and process units can be insulated or heat traced (electrically or through a sealed envelope). Several processes for removing water can be used. For example, but not limited to, (1) heat exchangers that use cold refrigerants to condense water, (2) physical absorption units using physical solvents (e.g., but not limited to, methanol, glycols (monoethylene glycol (MEG), diethylene glycol (DEG), triethylene glycol (TEG), tetraethylene glycol (TREG))), (3) membrane-based processes that are selective for water removal, and (4) adsorption filters using absorbents (e.g., but not limited to, activated alumina, zeolites (3A, 4A), and silica gel). Solution (1) cannot lower the gas-water dew point below 0-5°C. Solutions (2), (3), and (4) can lower the gas-water dew point to -10°C to -50°C, which means the water is less than 10 ppm.

[0090] The systems utilized to perform the aforementioned separation steps and processes can take a variety of forms. Separation systems can perform one or more of multiple separation / purification steps, including any technology available for the targeted purification / separation. Separation systems can include separation units based on membrane technology (e.g., without limitation, dense polymer membranes, ultrafiltration and nanofiltration membranes, facilitated transport membranes, metal membranes, hollow fiber pervaporation membranes), cryogenic technology, adsorption technology (e.g., without limitation, physical adsorption and chemical adsorption), and absorption technology (e.g., physical adsorption and chemical adsorption), operating technologies such as, without limitation, vacuum pressure swing, temperature swing, pressure swing, dry pressure swing, combined pressure and temperature swing, and electrical swing. Chemical adsorbents that can be used include, without limitation, amine-based adsorbents (amine-grafted or impregnated solids), metal oxides, metal salts, double salts, and hydrotalcites. Physical adsorbents that can be used include, but are not limited to, materials such as carbon-based materials, mesoporous silica, zeolites, zeolitic imidazolate frameworks (ZIFs), metal-organic frameworks (MOFs), and mixed adsorbents.

[0091] To remove carbon dioxide or other acid gases from a gas mixture using the techniques detailed above, the carbon dioxide concentration must be below a certain desired threshold, depending on the process conditions. This acid gas removal process may require a combination of technologies or multiple stages of separator units to more completely remove the acid gases from the gas mixture. For example, to reduce the carbon dioxide concentration to less than 1% in a carbon monoxide-rich gas stream from a carbon monoxide generation process, one or more pressure swing adsorption subunits, absorption subunits, or membrane separation subunits may be combined in series or parallel to ensure a high degree of acid gas removal, depending on the required process conditions.

[0092] Hydrogen sulfide is a well-known contaminant from RWGS gas streams. It can be removed from the gas stream using a variety of specific absorbents in fixed-bed beds through which the gas stream flows before further downstream processing. Most commonly, activated carbon impregnated with specific species (e.g., without limitation, potassium iodide, potassium permanganate, and metal oxides (e.g., without limitation, CuO, FeO, MgO)) is used. The impregnation of these specific species promotes the oxidation of hydrogen sulfide to elemental sulfur, which accumulates on the absorbent surface. Adsorption capacities can be as high as 80-100% w / w. Once the filter is saturated, the absorbent must be replaced. Other processes, such as chemical absorption, can also be implemented to remove hydrogen sulfide.

[0093] Chemical absorption techniques for removing acid gases (e.g., carbon dioxide and hydrogen sulfide) from RWGS streams can include those that rely on reversible complexation with soluble metal complexes or those that use alkali and / or amine-containing solutions that use base-equivalent chemistry to capture the acid gases. Most commonly, chemical and physical absorption process units for separating carbon dioxide from gas streams consist of two main devices: (1) an absorber tower and (2) a regenerator tower. In the absorber tower, inlet gas is fed to the bottom, and liquid is fed countercurrently to the top. Column internals include, but are not limited to, structured packing, random packing, trays, gas and liquid distributors, and liquid sprayers designed to maximize the exchange area between the liquid and gas phases. Absorption columns can operate at 10 to 80 °C and 1 to 80 bar, depending on the solvent used. The packed solvent exits the bottom of the absorber tower, is then pumped, and preheated before entering the regenerator tower. The regeneration column can be a stripping column or a distillation column, including a reboiler and a condenser. The absorbed carbon dioxide is released at the top of the column by increasing the temperature and / or decreasing the pressure. The regeneration column operates at 80-150°C and 1-10 bar. The lean solvent is then pumped and cooled before entering the absorption column, completing the loop. The chemical-based solvent can be, but is not limited to, methylethanolamine (MEA), dimethylethanolamine (DEA), methyldiethanolamine (MDEA), piperazine (PZ), soda (NaOH), KOH, and solvent blends. The physical solvent can be dimethyl ether (DME), methanol, or solvent blends.

[0094] Swing adsorption techniques can be used to physically or chemically adsorb species in a fluid line and separate them from other gases. These techniques use an adsorbent selective for one or more of the molecules in the fluid line, achieving separation through the following steps: first, adsorption of one species while all other species pass through the adsorbent; second, regeneration, using an increase in temperature or / and a decrease in pressure to extract the adsorbed species from the adsorbent. Multiple swing adsorption separators (typically 2-10) can be operated in parallel to enable continuous separation and minimize specific power consumption. Adsorbents can operate by chemical or physical mechanisms. Chemical adsorbents that can be used include, but are not limited to, amine-based adsorbents (amine-grafted or impregnated solids), metal oxides, metal salts, double salts, and hydrotalcites. Physical adsorbents that can be used include, but are not limited to, materials such as activated carbon, carbon molecular sieves, mesoporous silica, zeolites, zeolitic imidazolate structures (ZIFs), metal-organic frameworks (MOFs), or mixed adsorbents. Depending on the nature of the adsorbent, the number of different absorbent layers, and the operating conditions, the swing adsorption process can be applied to, without limitation, carbon dioxide removal, oxygen removal, carbon monoxide and dihydrogen separation, nitrogen removal, volatile organic chemical removal, methane and carbon monoxide separation, gas drying, and combinations of the aforementioned applications.

[0095] Membrane separation uses an extended surface containing polymer species to transport / restrict specific species in a fluid line. Separators can contain multiple layers of membrane surfaces to achieve effective separation. On a commercial scale, membranes can be arranged in, without limitation, hollow fiber or spiral-wound modules. Separation is achieved through favorable chemical interactions between the membrane and the substance to be removed from the fluid line, or through pore sizes tailored to exclude larger molecules in the fluid. Different gas species end up on either the permeate side, meaning passage through the membrane layer leading to a pressure drop, or the retentate side. The driving force for separation can be a pressure gradient or / and a concentration gradient between the permeate and retentate sides. These processes may require several independent stages of compressors and membrane units to achieve complete purification of the fluid line and maximum recovery of the desired species. Depending on the membrane material, number of membrane stages, and operating conditions, membrane separation can be applied to, without limitation, carbon dioxide removal, oxygen removal, nitrogen removal, dihydrogen and carbon monoxide separation, olefin removal, gas drying, and combinations of the aforementioned applications.

[0096] Downstream of the RWGS reactor and separation / purification unit, the CO2-rich gas can be compressed before being introduced into the electrolyzer. Compressor technology can be, without limitation, centrifugal or positive displacement. Positive displacement technologies include, without limitation, membrane compressors, screw compressors, and reciprocating compressors. The choice of technology depends on the gas flow rate and the required outlet pressure. Knowing that the maximum compression ratio through a compressor is typically 3, one to five compression stages may be required to reach the required pressure, and an interstage cooling step is then required.

[0097] While the system shown in Figure 9 includes two separation systems and a single electrolytic cell, many different variations are possible. For example, a single or multiple separation systems can be connected in series to separate chemicals (e.g., carbon dioxide) from reaching the input of the electrolytic cell. The separation can be at ever-increasing purity levels, and one or more of the multiple separation systems can be coupled to a single electrolytic cell to provide carbon monoxide. As another example, multiple such separation systems can be coupled to a set of electrolytic cells configured to receive cathode inputs having different levels of carbon monoxide amounts or concentrations.

[0098] The tandem reactor of block diagram 900 includes a RWGS reactor 901 and three separators, in sequence, that sequentially remove water, carbon dioxide, and dihydrogen. As shown, separator 902 separates the water produced by the RWGS reactor 901, carbon dioxide separator 903 separates trace carbon dioxide from the output of the RWGS reactor 901, and dihydrogen separator 904 performs step 911 of flowchart 910, separating a certain amount of carbon monoxide and a certain amount of dihydrogen from the output of the RWGS reactor 901. Separator 902 functions by cooling the gas and draining the condensed water that forms. The dihydrogen separator and carbon dioxide separator units can utilize, without limitation, swing adsorption, absorption, membrane-based, or cryogenic processes. The dihydrogen separator and carbon dioxide removal units can be in any order. As illustrated, flowchart 910 continues with step 912, in which a quantity of dihydrogen is supplied as a feed from at least one separator unit (i.e., dihydrogen separator 904) to the RWGS reactor 901. The water in this example is discarded for other uses in the illustrated approach, but in other approaches it can be used as a feed to the carbon monoxide electrolyzer 905 and does not need to be separated from the carbon monoxide. The carbon dioxide in this example is also fed back for use as a feed to the RWGS reactor 901. Thus, the carbon dioxide separator 903 serves the dual purpose of not only avoiding contamination in the carbon monoxide electrolyzer but also ensuring that no carbon dioxide is released by the system.

[0099] FIG. 10 includes a block diagram 1000. In block diagram 1000, a gas mixture containing dihydrogen and carbon dioxide is fed to the RWGS reactor 901. The resulting gas mixture contains dihydrogen, carbon monoxide, carbon dioxide, and water. Most of the water vapor is removed by cooling the gas and draining the condensed water formed in the separator 902. The carbon monoxide is then extracted from the other gases by a dedicated unit. This unit can be, without limitation, an absorption unit using a liquid solvent (e.g., CO-SORB process reactor 1001) or a PSA (pressure swing adsorption) unit (e.g., CO-PSA) using a specific adsorbent (e.g., impregnated with copper species). The separated stream containing carbon dioxide and dihydrogen is recycled upstream of the RWGS reactor. The purified carbon monoxide is then sent to an electrolyzer (e.g., carbon monoxide electrolyzer 905) to produce any valuable product (e.g., ethylene, ethanol, or acetic acid, among others). This type of process can be directed to obtaining high carbon monoxide purity for the downstream electrolyzer. A small portion of the carbon monoxide is recycled to the RWGS reactor along with the concentrated dihydrogen and carbon dioxide streams.

[0100] 11 shows a block diagram 1100 having similar components to that of block diagram 900. However, in block diagram 1100, the dihydrogen coming from dihydrogen separation unit 1104 is not fed back to RWGS reactor 901, but instead is directly value-added / sold as a pure product in another process. The process carried out by the tandem reactor according to block diagram 1100 exhibits the great advantage of being able to simultaneously produce both dihydrogen and useful products (e.g., ethylene).

[0101] The approaches of FIGS. 11 and 9 can be combined in a single embodiment, allowing a single reactor to alternatively directly valorize or recycle dihydrogen separate from the output of the RWGS reactor. These approaches are advantageous in embodiments where the input and output mass flow rates of the RWGS process chain and the carbon monoxide electrolyzer are not matched, allowing continuous operation and minimizing process bottlenecks. In certain embodiments, by separately valorizing dihydrogen from the RWGS, the ratio of recycled dihydrogen to externally valorized dihydrogen can be matched with the capacity of the carbon monoxide electrolyzer. Furthermore, in such embodiments, a single production line can produce both dihydrogen and useful chemicals (e.g., ethylene) from a power source and a carbon dioxide source, with the net ratio controlled by the dihydrogen recycle rate downstream of the RWGS reactor (e.g., after the dihydrogen separation unit 1104 downstream of the RWGS reactor 901 and before the carbon monoxide electrolyzer 905).

[0102] FIG. 12 shows block diagram 1200 having similar components to that of block diagram 900. However, in block diagram 1200, separator unit 1201 at the output of carbon monoxide electrolyzer 905 separates the carbon monoxide and sends it back as feed to carbon monoxide electrolyzer 905, and also separates water and dihydrogen, leaving useful products produced by the carbon monoxide electrolyzer. The useful products may be in liquid form and can be separated from the dihydrogen and monoxide by the phase difference between gas and liquid. Water can be separated using a process similar to that described with reference to separator 902 above. Separator unit 1201 can be any of a swing adsorption process, an absorption process, a membrane-based process, a cryogenic process, or a liquid / gas separation vessel. The useful products can be any of those described throughout this disclosure.

[0103] FIG. 12 also includes a flowchart 1210. The flowchart 1210 includes step 1211 for separating dihydrogen from the output of a carbon monoxide electrolyzer (e.g., carbon monoxide electrolyzer 905) and step 1212 for supplying a quantity of dihydrogen from the anode region of the electrolyzer as a feedstock to the RWGS reactor. This dihydrogen is produced as a result of the reduction of water and / or protons during the electrolysis of carbon monoxide and is mixed with the outlet gas stream of the carbon monoxide electrolyzer. At the outlet of the carbon monoxide electrolyzer, a gas stream consisting of unconverted carbon monoxide, undesired dihydrogen, ethylene gas, and / or other hydrocarbons is produced. In certain embodiments of the present invention, the dihydrogen content in the gas stream is so small that it may be uneconomical to invest in the downstream infrastructure required to condition the undesired dihydrogen for further processing or sale, and therefore this approach (in which dihydrogen is still utilized) offers significant advantages. The oxidation substrate in the carbon monoxide electrolyzer 905 can be either water or dihydrogen.

[0104] 13 includes a block diagram 1300 having elements similar to those of block diagram 900, except that there is no separator to separate the carbon monoxide from the dihydrogen produced by the RWGS reactor. In certain embodiments of the invention, this approach is useful in that there is no capital expenditure for such a separator and no energy requirements associated with operating such a separator. In these embodiments, the RWGS reactor 1301 can be configured to produce an output stream having a high selectivity for carbon monoxide over dihydrogen, minimizing the amount of unrecovered dihydrogen.

[0105] FIG. 14 includes a block diagram 1400 having elements similar to those in block diagram 900. FIG. 14 also includes a flowchart 1410 of a set of methods that can be used in accordance with certain embodiments of the invention disclosed herein. Block diagram 1400 differs from FIG. 13 in that dihydrogen separated by dihydrogen separator 1404 is fed to the anode of carbon monoxide electrolyzer 1405 to serve as the oxidation substrate for the reactor. In these embodiments, dihydrogen is oxidized at the anode instead of an alternative oxidation substrate (e.g., water). Thus, flowchart 1410 includes step 1411 of separating a quantity of dihydrogen. The dihydrogen can be a quantity of carbon monoxide, along with a quantity of dihydrogen produced by the RWGS reactor, as illustrated. While the dihydrogen is shown separated just before the carbon monoxide electrolyzer, it can be separated at any point along the production line. Flowchart 1410 further includes step 1412 of feeding a quantity of dihydrogen to the anode of the electrolyzer to serve as the oxidation substrate.

[0106] In certain embodiments of the present invention, the carbon monoxide supplied to the carbon monoxide electrolyzer in the tandem reactor can be combined with an additive chemical. FIG. 16 includes a block diagram 1600 having similar components as FIGS. 9 and 12 . However, a mixer 1601 is added that can be used in step 1611 from flowchart 1610 to mix the additive chemical with the carbon monoxide from the output of the RWGS reactor. After mixing the additive chemical with the carbon monoxide, the resulting product can be applied to the carbon monoxide electrolyzer. This can be done in step 1612, which includes applying a quantity of additive chemical and carbon monoxide to the cathode region of the carbon monoxide electrolyzer. In certain embodiments, the quantity of at least one additive chemical includes water, and the water is from the RWGS reactor, eliminating the need for mixer 1601 because the carbon monoxide is already mixed with the water vapor. In an alternative embodiment, the quantity of additive chemical can include a chemical applied externally to the system and first introduced at mixer 1601. The additive chemical can be one of an imine, an amine, a nitrogen oxide, and ammonia. The amount of added chemical may be an amount of an amino acid.

[0107] In certain embodiments, the same electrolyzer, or part of the same tandem reactor, can be used with alternative functional units to produce different chemicals at different times. For example, an electrolyzer can be used as part of a system that removes carbon monoxide from a syngas generation process to produce high-purity dihydrogen. Then, after producing the dihydrogen, the same electrolyzer can be used with an RWGS reactor to add value to the carbon dioxide, and the already purified dihydrogen can be used as a feedstock for the RWGS reactor. Alternatively, different electrolyzers can be used for each operation, and the same carbon dioxide source can be routed between tandem reactors containing two different electrolyzers at different times.

[0108] Certain embodiments of the present invention may include a means for supplying a controlled amount of carbon dioxide to the reverse water gas shift reactor. The means may include fluid connections including any one of valves, seals, pumps, conduits, pressure regulators, and associated electronic or mechanical controls that can release a controlled, controlled amount of carbon dioxide fluid into the reverse water gas shift reactor. For example, the means may be the components that control the supply of carbon dioxide into the RWGS reactor 901 described above.

[0109] Certain embodiments of the present invention may include means for producing a fixed amount of carbon monoxide in a RWGS reaction using a fixed amount of carbon dioxide and a RWGS reactor. These means may include actuators and associated control hardware, firmware, or software that introduce a desired mixture of dihydrogen and carbon dioxide into the RWGS reactor, heat the RWGS reactor to a desired temperature, pressurize the RWGS reactor to a desired pressure, and remove the produced carbon monoxide and water from the reactor. The means may include one or more catalysts for the RWGS reactor, as described above. The means may include actuators and associated control hardware, firmware, or software that can accept carbon dioxide or dihydrogen fed back from a tandem carbon dioxide enhancement reactor to the RWGS reactor 901.

[0110] Certain embodiments of the present invention may include a means for supplying a controlled amount of carbon monoxide to the cathode region of the electrolyzer. The means may include fluid connections including any one of valves, seals, pumps, conduits, pressure regulators, and associated electronic or mechanical controls that allow a controlled, controlled amount of carbon monoxide fluid to enter the cathode region of the electrolyzer. The means may include a separator in the form of a fluid trap to remove liquid entering the electrolyzer. For example, the means may be the component that controls the supply of carbon monoxide into the carbon monoxide electrolyzer 905 described above.

[0111] Certain embodiments of the present invention may include a means for producing a fixed amount of product chemical using an electrolytic cell and the reduction of a fixed amount of carbon monoxide and the oxidation of an oxidized substrate. The means may include fluid connections, including any one of valves, seals, pumps, conduits, pressure regulators, and associated electronic or mechanical controls, that allow controlled, fixed amounts of reduced substrate, oxidized substrate, and any electrolyte or added chemicals to enter the cathode and anode regions of the electrolytic cell. The means may include similar fluid connections and components for removing controlled, fixed amounts of reduced products, oxidized substrate, and electrolyte, and produced chemicals from the cathode and anode regions of the electrolytic cell. The means may also include one or more catalysts within the anode and / or cathode regions and may include a separation layer or region between the anode and cathode regions. As previously mentioned, the separation region may also include fluid inputs and fluid outputs.

[0112] While this specification has been described in detail with respect to specific embodiments of the present invention, it will be understood that those skilled in the art, upon understanding the foregoing, will readily appreciate modifications, variations, and equivalents to these embodiments. The disclosure of quantities of chemicals in this disclosure is not intended to refer to physically isolated quantities, as a quantity of dihydrogen can exist in a single physical quantity with a quantity of carbon dioxide in the form of a quantity of synthesis gas. While the examples in this disclosure apply generally to industrial chemical processes, the same approach is applicable to chemical processes of any scale and scope. Furthermore, while the examples in this disclosure apply generally to feeding carbon monoxide to an electrolytic cell, the approach disclosed herein is more broadly applicable to feeding any member of the oxocarbon family to an electrolytic cell for the purpose of producing useful chemicals. These and other modifications and variations to the present invention can 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.

Claims

1. 1. A method (100) comprising: feeding (102) a quantity of carbon dioxide to a reverse water gas shift reactor (110, 901); producing (103) a quantity of carbon monoxide in a reverse water gas shift reaction using the quantity of carbon dioxide and the reverse water gas shift reactor (110, 901); separating (911) the quantity of carbon monoxide and a second quantity of carbon dioxide from the output of the reverse water gas shift reactor (110, 901) using a separator; After the quantity of carbon monoxide and the quantity of carbon dioxide have been separated, supplying (102) the quantity of carbon monoxide to a cathode region of an electrolyzer (120, 500); generating (103) a quantity of product chemical using the electrolytic cell (120, 500), the reduction of the quantity of carbon monoxide, and the oxidation of an oxidation substrate; The method (100), wherein the quantity of product chemical is at least one of a quantity of hydrocarbon, a quantity of organic acid, a quantity of alcohol, a quantity of olefin, and a quantity of N-rich organic compound.

2. supplying (912) a quantity of dihydrogen as a feedstock to the reverse water gas shift reactor (110, 901) from the cathode region of the electrolyzer (120, 500); 10. The method (100) of claim 1, wherein the amount of dihydrogen is controlled based on at least one of: (i) a decrease in the amount of carbon monoxide supplied to the electrolyzer (120, 500) by the reverse water gas shift reactor (110, 901); and (ii) an increase in the current density forced in the electrolyzer (120, 500).

3. 10. The method (100) of claim 1, further comprising supplying (912) a quantity of dihydrogen as a feedstock to the reverse water gas shift reactor (110, 901) from the cathode region of the electrolyzer (120, 500).

4. Separating (911) the quantity of carbon monoxide and the quantity of dihydrogen from the output of the reverse water gas shift reactor (110, 901) using at least one separator unit (1201); 10. The method (100) of claim 1, further comprising: supplying (912) the quantity of dihydrogen from the at least one separator unit (1201) to the reverse water gas shift reactor (110, 901) as a feedstock.

5. The method (100) of claim 1, wherein the electrolytic cell (120, 500) uses an alkaline electrolyte.

6. The reverse water gas shift reactor (110, 901) uses a set of heterogeneous catalysts, the reverse water gas shift reactor (110, 901) has a selectivity for carbon monoxide of greater than 90%; 10. The method (100) of claim 1, wherein the selectivity is defined as the ratio of the amount of carbon monoxide produced to the sum of the amount of carbon monoxide produced and the amount of methane produced.

7. The method (100) of claim 1, wherein the reverse water gas shift reactor (110, 901) is operated at 200 to 600°C.

8. The method (100) of claim 1, wherein the reverse water gas shift reactor (110, 901) is operated at 600 to 1000°C.

9. The method (100) of claim 1, wherein the reverse water gas shift reactor (110, 901) is a plasma-based reverse water gas shift reactor (110, 901).

10. 10. The method of claim 1, wherein the electrolyzer comprises an ion exchange membrane between the cathode and anode regions of the electrolyzer, the cathode region comprising a copper-based catalyst.

11. further comprising supplying (102) a quantity of dihydrogen to the anode of the electrolytic cell (120, 500) to serve as the oxidation substrate; 10. The method (100) of claim 1, wherein the quantity of dihydrogen is from the reverse water gas shift reactor (110, 901) along with the quantity of carbon monoxide.

12. further comprising: mixing (1611) the quantity of carbon monoxide with a quantity of at least one additive chemical; 10. The method (100) of claim 1, wherein the quantity of carbon monoxide is mixed with the quantity of at least one additive chemical when the quantity of carbon monoxide is provided to the electrolyzer (120, 500).

13. the quantity of at least one added chemical comprises water; 13. The method (100) of claim 12, wherein at least a portion of the water is from the reverse water gas shift reactor (110, 901).

14. the amount of added chemical is one of an imine, an amine, a nitrogen oxide, and ammonia; 13. The method (100) of claim 12, wherein the amount of product chemical is an amount of an amino acid.

15. 1. A system comprising: a reverse water gas shift reactor (110, 901); a carbon dioxide source connection fluidly connecting a carbon dioxide source to the reverse water gas shift reactor (110, 901); an electrolytic cell (120, 500) having an anode region and a cathode region; a carbon monoxide source connection fluidly connecting the reverse water gas shift reactor (110, 901) to the cathode region; the reverse water gas shift reactor (110, 901) is configured to use a quantity of carbon dioxide from the carbon dioxide source connection to produce a quantity of carbon monoxide in a reverse water gas shift reaction (103); the electrolyzer (120, 500) is configured to generate (103) a quantity of product chemical using the reduction of the quantity of carbon monoxide from the carbon monoxide source connection and the oxidation of an oxidation substrate; The system wherein the quantity of product chemicals is at least one of a quantity of hydrocarbons, a quantity of organic acids, a quantity of alcohols, a quantity of olefins, and a quantity of N-rich organic compounds.

16. further comprising a dihydrogen connection fluidly connecting the cathode region of the electrolyzer (120, 500) to the reverse water gas shift reactor (110, 901); 15. The system (200) of claim 14, wherein the dihydrogen connection is configured to supply a quantity of dihydrogen as a feedstock to the reverse water gas shift reactor (110, 901) from the cathode region of the electrolyzer (120, 500).

17. a separator unit (1201) on said carbon monoxide source connection; a dihydrogen connection fluidly connecting the separator unit (1201) to the reverse water gas shift reactor (110, 901); 15. The system (200) of claim 14, wherein the dihydrogen connection is configured to supply (912) the quantity of dihydrogen gas from the separator unit (1201) to the reverse water gas shift reactor (110, 901) as a feedstock.

18. further comprising a separator unit (1201) on at least one of said carbon monoxide source connections, said at least one separator unit (1201) comprising an acid scrubber; The system (200) of claim 14, wherein the electrolytic cell (120, 500) uses an alkaline electrolyte.

19. The reverse water gas shift reactor (110, 901) uses a set of heterogeneous catalysts, the reverse water gas shift reactor (110, 901) has a selectivity for carbon monoxide of greater than 90%; 15. The system (200) of claim 14, wherein the selectivity is defined as the ratio of the amount of carbon monoxide produced to the sum of the amount of carbon monoxide produced and the amount of methane produced.

20. The system (200) of claim 14, wherein the reverse water gas shift reactor (110, 901) is configured to operate at 200 to 600°C.

21. The system (200) of claim 14, wherein the reverse water gas shift reactor (110, 901) is configured to operate at 600 to 1000°C.

22. 15. The system (200) of claim 14, wherein the reverse water gas shift reactor (110, 901) is a plasma-based reverse water gas shift reactor (110, 901).

23. the electrolytic cell (120, 500) comprises an ion exchange membrane between the cathode and anode regions of the electrolytic cell (120, 500); The system (200) of claim 15, wherein the cathode region comprises a copper-based catalyst.

24. 16. The system of claim 15, wherein the electrolytic cell includes at least one separation element selected from an ion-conducting polymer separator, a polymer separator, a diaphragm, a ceramic-containing material, a non-charged separator scaffold, and a mixed ceramic organic compound separator.

25. the quantity of carbon dioxide is extracted from an industrial process; 16. The system (200) of claim 15, wherein the industrial process is one of a steel or metal manufacturing process, a cement manufacturing process, a dihydrogen production process, a partial oxidation process, a biomass processing plant, a biomass gasification plant, a bioethanol production process, a biogas production process, a biowaste incineration process, a hydroformylation process, a power generation process, and a waste incineration process.

26. a storage vessel for concentrating the quantity of carbon dioxide before feeding the quantity of carbon dioxide to the reverse water gas shift reactor; 16. The system (200) of claim 15, wherein the amount of carbon dioxide is captured using direct air capture.

27. said quantity of carbon monoxide being mixed with a quantity of at least one additive chemical; 16. The system (200) of claim 15, wherein the quantity of carbon monoxide is mixed with the quantity of at least one additive chemical when the quantity of carbon monoxide is supplied to the electrolyzer (120, 500).

28. the quantity of at least one added chemical comprises water; 27. The system (200) of claim 26, wherein the water is from the reverse water gas shift reactor (110, 901).

29. the amount of added chemical is one of an imine, an amine, a nitrogen oxide, and ammonia; 27. The system (200) of claim 26, wherein the amount of product chemical is an amount of an amino acid.

30. further comprising an anode input to said electrolytic cell (120, 500); the anode input is fluidly connected to a dihydrogen source connection configured to receive a quantity of dihydrogen to be used as an oxidation substrate; 16. The system (200) of claim 15, wherein the quantity of dihydrogen is produced by the reverse water gas shift reactor (110, 901) along with the quantity of carbon monoxide.

31. 1. A system comprising: a reverse water gas shift reactor (110, 901); an electrolytic cell (120, 500) having an anode region and a cathode region; means for supplying (102) a quantity of carbon dioxide to said reverse water gas shift reactor (110, 901); means for producing (103) a quantity of carbon monoxide in a reverse water gas shift reaction using the quantity of carbon dioxide and the reverse water gas shift reactor (110, 901); means for supplying (102) said quantity of carbon monoxide to a cathode region of an electrolyzer (120, 500); and means for producing (103) a quantity of product chemical using the electrolytic cell (120, 500) and the reduction of the quantity of carbon monoxide and the oxidation of an oxidation substrate; The system wherein the quantity of product chemicals is at least one of a quantity of hydrocarbons, a quantity of organic acids, a quantity of alcohols, a quantity of olefins, and a quantity of N-rich organic compounds.

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