Electrochemical water-gas shift reactor and method of use

Abstract

Described herein is an electrochemical reactor that includes an ion-conducting membrane, which electrochemically performs a water-gas shift reaction without electrical input, where the electrochemical water-gas shift reaction involves the exchange of ions across the membrane and includes a forward water-gas shift reaction, or a reverse water-gas shift reaction, or both. Also described herein is a reactor that includes a bifunctional layer and a mixed conducting membrane, where the bifunctional layer and the mixed conducting membrane are in contact with each other, and where the bifunctional layer catalyzes the reverse water-gas shift (RWGS) reaction and serves as an anode in the electrochemical reaction.

Description

[Technical Field]

[0001] The present invention relates generally to the water-gas shift reaction, and more particularly to the water-gas shift reaction involving an electrochemical pathway. [Background technology]

[0002] The water-gas shift (WGS) reaction is the reaction of carbon monoxide with water vapor to form carbon dioxide and hydrogen:

number

[0003] Traditionally, the WGS reaction is catalyzed by two categories of catalysts: high-temperature shift (HTS) catalysts and low-temperature shift (LTS) catalysts. HTS catalysts consist of iron oxide stabilized by chromium oxide, while LTS catalysts are copper-based. To date, the WGS equilibrium reaction has been carried out chemically. In contrast to traditional practice, this disclosure describes the unexpected discovery of an electrochemically carried out WGS reaction. An electrochemical reactor and method for carrying out such a reaction are also described. Summary of the Invention

[0004] Described herein are electrochemical reactors that include an ion-conducting membrane, where the reactor electrochemically performs a water-gas shift reaction without electrical input, where the electrochemical water-gas shift reaction involves the exchange of ions across the membrane and includes a forward water-gas shift reaction, a reverse water-gas shift reaction, or both.

[0005] In one embodiment, the reactor comprises a porous electrode comprising a metallic phase and a ceramic phase, wherein the metallic phase is electronically conductive and the ceramic phase is ionically conductive. In one embodiment, the electrodes are separated by a membrane and both are exposed to a reducing environment. In one embodiment, the electrode comprises Ni or NiO and a material selected from the group consisting of YSZ, CGO, SDC, SSZ, LSGM, and combinations thereof.

[0006] In one embodiment, the ion-conducting membrane is impermeable to fluid flow. In one embodiment, the ion-conducting membrane also conducts electrons, and the reactor does not include interconnects. In one embodiment, the membrane comprises CGO. In one embodiment, the membrane comprises CoCGO. In one embodiment, the reactor includes a catalyst that promotes the chemical reverse water gas shift (RWGS) reaction. In one embodiment, the reactor also performs the chemical water gas shift reaction.

[0007] Also described herein is a reactor comprising a bifunctional layer and a mixed conducting membrane, wherein the bifunctional layer and the mixed conducting membrane are in contact with each other, and the bifunctional layer catalyzes the reverse water gas shift (RWGS) reaction and serves as the anode in an electrochemical reaction.

[0008] In one embodiment, the bifunctional layer as an anode is exposed to a reducing environment, and the electrochemical reaction occurring in the bifunctional layer is oxidation. In one embodiment, a current collector is not attached to the bifunctional layer. In one embodiment, the reactor does not include an interconnect, and the reactor does not receive or generate electricity. In one embodiment, the bifunctional layer comprises Ni or NiO and a material selected from the group consisting of YSZ, CGO, SDC, SSZ, LSGM, and combinations thereof.

[0009] In one embodiment, the reactor includes a catalyst that promotes a chemical reverse water gas shift (RWGS) reaction. In one embodiment, the catalyst is a high-temperature RWGS catalyst. In one embodiment, the catalyst is part of a bifunctional layer. In one embodiment, the catalyst is configured to be outside of the bifunctional layer. In one embodiment, the catalyst includes Ni, Cu, Fe, a Pt group metal, or a combination thereof.

[0010] Further aspects and embodiments are provided in the following drawings, detailed description, and claims. Unless otherwise specified, features described herein may be combined, and all such combinations are within the scope of the present disclosure. [Brief explanation of the drawings]

[0011] The following drawings are provided to illustrate certain embodiments described herein. The drawings are merely illustrative and are not intended to limit the scope of the claimed invention, nor are they intended to show every possible feature or embodiment of the claimed invention. The drawings are not necessarily drawn to scale, and in some instances, certain elements of the drawings may be enlarged relative to other elements of the drawings for illustrative purposes.

[0012] [Figure 1] 1 illustrates an electrochemical (EC) reactor or electrochemical gas generator according to one embodiment of the present disclosure. [Figure 2A] 1 illustrates a tubular electrochemical reactor according to one embodiment of the present disclosure. [Figure 2B] FIG. 1 shows a cross-sectional view of a tubular electrochemical reactor according to one embodiment of the present disclosure. [Figure 3] 1 illustrates a hydrogen production system utilizing an EC reactor as described herein, according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0013] overview The disclosure herein describes an electrochemical WGS reactor and method of use. Various components of the reactor, such as electrodes and membranes, are described, along with the components' materials of construction. The following description details various aspects and embodiments of the invention disclosed herein. The specific embodiments are not intended to define the scope of the invention. Rather, the embodiments provide non-limiting examples of various compositions and methods falling within the scope of the claimed invention. This description should be read from the perspective of one of ordinary skill in the art and, therefore, does not necessarily include information known to one of ordinary skill in the art.

[0014] Unless otherwise defined herein, the following terms and phrases have the meanings indicated below. This disclosure may use other terms and phrases not expressly defined herein. Such other terms and phrases shall have the meanings that they would have within the context of this disclosure to one of ordinary skill in the art. In some cases, terms or phrases may be defined in the singular or plural. In such instances, it is understood that any term in the singular may include its plural counterpart, and vice versa, unless expressly stated to the contrary.

[0015] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. For example, reference to a "substituent" encompasses a single substituent, as well as two or more substituents, and so forth. As used herein, "for example," "for instance," "such as," or "including" means introducing an example that further clarifies a more general subject matter. Unless otherwise expressly indicated, such examples are provided solely as an aid in understanding the embodiments set forth in this disclosure and are not intended to be limiting in any way. Furthermore, these terms do not imply any preference of any kind for the disclosed embodiments.

[0016] As used herein, composition and material are used interchangeably unless otherwise specified. Each composition / material may have multiple elements, phases, and components. As used herein, heating refers to the active application of energy to a composition or material.

[0017] As used herein, CGO refers to gadolinium-doped ceria, also known as gadolinia-doped ceria, gadolinium-doped cerium oxide, cerium(IV) oxide, gadolinium-doped GDC, or GCO (formula Gd:CeO). Unless otherwise specified, CGO and GDC are used interchangeably. Syngas (i.e., synthesis gas) in this disclosure refers to a mixture consisting primarily of hydrogen, carbon monoxide, and carbon dioxide.

[0018] As used herein, ceria refers to cerium oxide, also known as ceric oxide, ceric dioxide, or cerium dioxide, and is an oxide of the rare earth metal cerium. Doped ceria refers to ceria doped with other elements, such as samaria-doped ceria (SDC) or gadolinium-doped ceria (GDC or CGO). As used herein, chromite refers to chromium oxide, including all oxidation states of chromium oxide.

[0019] As used herein, a layer or material that is impermeable refers to its impermeability to fluid flow. For example, an impermeable layer or material has a permeability of less than 1 microdarcy, or less than 1 nanodarcy.

[0020] In this disclosure, sintering refers to a process of forming a solid mass of material by heat or pressure, or a combination thereof, without melting the material to the point of liquidization. For example, material particles are heated to agglomerate into a solid or porous mass, and atoms within the material particles diffuse across the particle boundaries, fusing the particles together to form one solid piece.

[0021] Interconnects in electrochemical devices (e.g., fuel cells) are often either metal or ceramic placed between individual cells or repeating units. Their purpose is to connect each cell or repeating unit so that electricity can be distributed or combined. Interconnects are also referred to as bipolar plates in electrochemical devices. As used herein, an interconnect that is an impermeable layer refers to a layer that is impermeable to fluid flow.

[0022] Electrochemistry is the branch of physical chemistry concerned with the relationship between electric potential, as a measurable, quantitative phenomenon, and identifiable chemical changes, where an electric potential is either the result of a particular chemical change or its inverse. These reactions involve electrons moving between electrodes through an electronically conducting phase (typically, but not necessarily, an external electric circuit) separated by an ionically conducting and electronically insulating membrane (or ionic species in solution). When a chemical reaction is affected by a potential difference, such as in electrolysis, or when the electric potential arises from a chemical reaction, such as in a battery or fuel cell, it is called an electrochemical reaction. Unlike chemical reactions, in electrochemical reactions, electrons (and the resulting ions) are not transferred directly between molecules, but rather through the aforementioned electronic and ionic conduction circuits, respectively. This phenomenon distinguishes electrochemical reactions from chemical reactions.

[0023] Unlike conventional practice, an electrochemical reactor comprising an ion-conducting membrane has been discovered that can perform the water-gas shift reaction electrochemically, which involves the exchange of ions across the membrane and includes a forward water-gas shift reaction, a reverse water-gas shift reaction, or both, which differs from the water-gas shift reaction via a chemical route because the chemical water-gas shift reaction involves the direct binding of reactants.

[0024] In one embodiment, the reactor comprises porous electrodes comprising a metallic phase and a ceramic phase, where the metallic phase is electronically conductive and the ceramic phase is ionically conductive. In various embodiments, the electrodes do not have current collectors attached to them. In various embodiments, the reactor does not contain any current collectors. Clearly, such a reactor is fundamentally different from any electrolyzer or fuel cell. In various embodiments, such a reactor neither receives nor generates electricity.

[0025] In one embodiment, one of the electrodes in the reactor is an anode configured to be exposed to a reducing environment while electrochemically undergoing an oxidation reaction, hi various embodiments, the electrode comprises Ni or NiO and a material selected from the group consisting of YSZ, CGO, SDC, SSZ, LSGM, and combinations thereof.

[0026] The electrochemical water-gas shift reaction occurring in the reactor comprises an electrochemical half-cell reaction, which is as follows:

number

[0027] In various embodiments, the half-cell reaction occurs at a three-phase boundary, which is the intersection of the electronically and ionically conducting phases with the pores. Additionally, the reactor can also perform a chemical water-gas shift reaction.

[0028] In various embodiments, the ion-conducting membrane conducts protons or oxide ions. In various embodiments, the ion-conducting membrane comprises a solid oxide. In various embodiments, the ion-conducting membrane is impermeable to fluid flow. In various embodiments, the ion-conducting membrane also conducts electrons, and the reactor does not include an interconnect.

[0029] Further described herein is a reactor comprising a bifunctional layer and a mixed conducting membrane, the bifunctional layer and the mixed conducting membrane being in contact with each other, the bifunctional layer catalyzing the reverse water gas shift (RWGS) reaction and functioning as an anode in the electrochemical reaction. In one embodiment, the bifunctional layer as an anode is exposed to a reducing environment, and the electrochemical reaction occurring in the bifunctional layer is oxidation. In one embodiment, a current collector is not attached to the bifunctional layer. In one embodiment, the bifunctional layer comprises Ni or NiO and a material selected from the group consisting of YSZ, CGO, SDC, SSZ, LSGM, and combinations thereof.

[0030] Such reactors have a variety of uses. In one embodiment, the reactor is utilized to produce carbon monoxide by hydrogenation of carbon dioxide. In another embodiment, the reactor is used to adjust the syngas composition (i.e., the H2 / CO ratio) by converting H2 to CO or CO to H2. In the following description, hydrogen production is used as an example, but the use of the reactor is not limited to hydrogen production.

[0031] Electrochemical Reactor Unlike conventional practice, an electrochemical reactor has been discovered that includes a mixed conducting membrane, allowing the reactor to electrochemically produce hydrogen from water without electrical input. The electrochemical reaction involves the exchange of oxide ions across the membrane to oxidize a fuel (e.g., carbon monoxide). The mixed conducting membrane also conducts electrons to complete the electrochemical reaction. As such, the reactor does not include interconnects or bipolar plates. Furthermore, the reactor does not generate electricity and is not a fuel cell. In various embodiments, the electrodes do not have current collectors attached to them. In various embodiments, the reactor does not contain any current collectors. Clearly, such a reactor is fundamentally different from any electrolyzer or any fuel cell.

[0032] 1 illustrates an electrochemical reactor or electrochemical (EC) gas generator 100 according to one embodiment of the present disclosure. The electrochemical reactor (or EC gas generator) device 100 includes a first electrode 101, a membrane 103, and a second electrode 102. The first electrode 101 (also referred to as the anode) is configured to receive a fuel 104. The stream 104 is oxygen-free. In this disclosure, oxygen-free means that there is no oxygen present at the first electrode 101, or at least not enough oxygen to inhibit the reaction. The second electrode 102 (also referred to as the cathode) is configured to receive water (e.g., steam), as indicated at 105.

[0033] In one embodiment, the device 100 is configured to receive a stream 104 containing a fuel (e.g., ammonia or syngas) and produce CO and / or HO (106) at a first electrode (101). In various embodiments, the fuel includes H, CO, syngas, ammonia, or a combination thereof. In one embodiment, the device 100 is also configured to receive water or steam (105) and produce hydrogen (107) at a second electrode (102). In some cases, the second electrode receives a mixture of steam and hydrogen. Water is considered the oxidant in this scenario because it provides the oxidizing ions (transported through the membrane) necessary to oxidize the fuel (e.g., H) at the opposite electrode. Thus, the first electrode 101 is undergoing an oxidation reaction in a reducing environment, and the second electrode 102 is undergoing a reduction reaction in a reducing environment. In various embodiments, 103 represents an oxide-ion conducting membrane. In one embodiment, the oxide-ion conducting membrane 103 also conducts electrons. Thus, the membrane is of mixed conductivity.

[0034] In one embodiment, the first electrode 101 and the second electrode 102 comprise Ni-YSZ or NiO-YSZ. In various embodiments, the electrodes 101 and 102 comprise Ni or NiO and a material selected from the group consisting of YSZ, CGO, SDC, SSZ, LSGM, and combinations thereof. Alternatively, the hydrocarbon-containing gas is reformed before contacting the membrane 103 / electrode 101. The reformer is configured to perform steam reforming, dry reforming, or a combination thereof. The reformed gas is suitable as the feed stream 104.

[0035] In various embodiments, the device does not include a current collector. In one embodiment, the device does not include interconnects. No electricity is required; such a device is not an electrolyzer. This is a major advantage of the EC reactor of the present disclosure. The membrane 103 is configured to conduct electrons and is therefore mixed conductive, i.e., both electronically and ionically conductive. In one embodiment, the membrane 103 conducts oxide ions and electrons. In one embodiment, the electrodes 101, 102 and the membrane 103 are tubular (see, e.g., Figures 2A and 2B). In one embodiment, the electrodes 101, 102 and the membrane 103 are planar. In these embodiments, the electrochemical reactions at the anode and cathode occur spontaneously without the need for an applied potential / electricity to the reactor.

[0036] In one embodiment, an electrochemical reactor (or EC gas generator) is a device including a first electrode, a second electrode, and a membrane between the electrodes, where the first electrode and the second electrode include a metallic phase that does not contain platinum group metals during use of the device, and the membrane is oxide-ion conductive. In an embodiment, the first electrode is configured to receive a fuel. In one embodiment, the fuel includes ammonia, or hydrogen, or carbon monoxide, or a combination thereof. In an embodiment, the second electrode is configured to receive water and hydrogen and is configured to reduce water to hydrogen. In various embodiments, such reduction occurs electrochemically without electrical input.

[0037] In one embodiment, the film comprises an electronically conductive phase containing doped lanthanum chromite or an electronically conductive metal, or a combination thereof, and the film comprises an ionically conductive phase containing a material selected from the group consisting of gadolinium-doped ceria (CGO), samarium-doped ceria (SDC), yttria-stabilized zirconia (YSZ), lanthanum strontium gallate magnesite (LSGM), scandia-stabilized zirconia (SSZ), Sc- and Ce-doped zirconia, and combinations thereof. In one embodiment, the doped lanthanum chromite comprises strontium-doped lanthanum chromite, iron-doped lanthanum chromite, strontium- and iron-doped lanthanum chromite, lanthanum calcium chromite, or a combination thereof, and the conductive metal comprises Ni, Cu, Ag, Au, Pt, Rh, or a combination thereof.

[0038] In one embodiment, the film comprises gadolinium-doped ceria, samarium-doped ceria, a sintering aid, or a combination thereof. In various embodiments, the sintering aid comprises a divalent or trivalent transition metal ion or a combination thereof. In one embodiment, the metal ion is an oxide. In one embodiment, the transition metal comprises Co, Mn, Fe, Cu, or a combination thereof. In one embodiment, the film comprises CGO. In one embodiment, the film comprises cobalt-doped CGO (CoCGO). In one embodiment, the film consists essentially of CGO. In one embodiment, the film consists essentially of CoCGO. In one embodiment, the film consists of CoCGO. In one embodiment, the reactor does not include interconnects.

[0039] FIG. 2A illustrates (not to scale) a tubular electrochemical (EC) reactor or EC gas generator 200 according to one embodiment of the present disclosure. The tubular generator 200 includes an inner tubular structure 202, an outer tubular structure 204, and a membrane 206 disposed between the inner tubular structure 202 and the outer tubular structure 204, respectively. The tubular generator 200 further includes a void space 208 for fluid passage. FIG. 2B illustrates (not to scale) a cross-sectional view of the tubular generator 200 according to one embodiment of the present disclosure. The tubular generator 200 includes a first inner tubular structure 202, a second outer tubular structure 204, and a membrane 206 disposed between the inner tubular structure 202 and the outer tubular structure 204. The tubular generator 200 further includes a void space 208 for fluid passage.

[0040] In one embodiment, the electrodes and membrane are tubular, the first electrode being outermost and the second electrode being innermost, the second electrode being configured to receive water and hydrogen. In one embodiment, the electrodes and membrane are tubular, the first electrode being innermost and the second electrode being outermost, the second electrode being configured to receive water and hydrogen. In one embodiment, the electrodes and membrane are tubular.

[0041] In one embodiment, the reactor includes a catalyst that promotes the chemical reverse water gas shift (RWGS) reaction. In one embodiment, the catalyst is a high-temperature RWGS catalyst. In one embodiment, the catalyst is part of the anode in the reactor. In one embodiment, the catalyst is configured to be external to the anode. For example, Ni-Al2O3 pellets as such a catalyst are placed in the reactor surrounding the tubes, as shown in Figures 2A and 2B. In one embodiment, the catalyst includes Ni, Cu, Fe, a Pt group metal, or a combination thereof. In one embodiment, the catalyst includes Pt, Cu, Rh, Ru, Fe, Ni, or a combination thereof.

[0042] Hydrogen production system and method The method disclosed herein includes providing a device including a first electrode, a second electrode, and a membrane between the electrodes, introducing a first stream to the first electrode, introducing a second stream to the second electrode, and extracting hydrogen from the second electrode, wherein the first electrode and the second electrode comprise a metallic phase that does not contain a platinum group metal during use of the device. In one embodiment, the membrane is oxide-ion conductive.

[0043] In one embodiment, the device is operated at a temperature of 500°C or greater, or 600°C or greater, or 700°C or greater, or 750°C or greater, or 800°C or greater, or 850°C or greater, or 900°C or greater, or 950°C or greater, or 1000°C or greater. In various embodiments, the pressure difference between the first electrode and the second electrode is 2 psi or less, or 1.5 psi or less, or 1 psi or less. In one embodiment, the first stream enters the device at a pressure of 10 psi or less, or 5 psi or less, or 3 psi or less. In one embodiment, the second stream enters the device at a pressure of 10 psi or less, or 5 psi or less, or 3 psi or less.

[0044] In one embodiment, the first stream comprises a fuel. In one embodiment, the fuel comprises a hydrocarbon, hydrogen, carbon monoxide, ammonia, or a combination thereof. In one embodiment, the first stream is introduced directly to the first electrode, or the second stream is introduced directly to the second electrode, or both. In one embodiment, the method includes providing a reformer or catalytic partial oxidation (CPOX) reactor upstream of the first electrode, wherein the first stream passes through the reformer or CPOX reactor before being introduced to the first electrode, and the first electrode comprises Ni or NiO. In one embodiment, the reformer is a steam reformer or an autothermal reformer.

[0045] In one embodiment, the first stream comprises a fuel. In one embodiment, the fuel comprises a hydrocarbon, or hydrogen, or carbon monoxide, or ammonia, or a combination thereof. In one embodiment, the second stream consists of water and hydrogen. In one embodiment, the first stream comprises carbon monoxide and no significant amounts of hydrogen, hydrocarbons, or water. In such cases, no upstream reformer is required. In this disclosure, no significant amounts of hydrogen, hydrocarbons, or water means that the volume content of hydrogen, hydrocarbons, or water is 5% or less, or 3% or less, or 2% or less, or 1% or less, or 0.5% or less, or 0.1% or less, or 0.05% or less.

[0046] In various embodiments, the first stream comprises 50% or more CO by volume, or 60% or more CO by volume, or 70% or more CO by volume, or 80% or more CO by volume, or 90% or more CO by volume. In one embodiment, the first stream comprises CO. In one embodiment, the first stream comprises syngas (CO and H). In one embodiment, the first stream comprises an inert gas, such as argon or nitrogen. In one embodiment, the second stream consists of water and hydrogen.

[0047] In one embodiment, the method includes using the extracted hydrogen in one of a Fischer-Tropsch (FT) reaction, a dry reforming reaction, a nickel-catalyzed Sabatier reaction, a Bosch reaction, a reverse water gas shift reaction, an electrochemical reaction to produce electricity, ammonia production, fertilizer production, an electrochemical compressor for hydrogen storage, a hydrogen vehicle, or a hydrogenation reaction, or a combination thereof.

[0048] In one embodiment, the first stream and the second stream do not contact each other within the device. In various embodiments, the reduction of water to hydrogen is performed electrochemically without electrical input. In one embodiment, the first stream does not contact hydrogen. In one embodiment, the first stream and the second stream are separated by a membrane within the device.

[0049] In one embodiment, the fuel comprises a hydrocarbon, or hydrogen, or carbon monoxide, or ammonia, or a combination thereof. In one embodiment, the second stream comprises hydrogen. In one embodiment, the first stream comprises a fuel. In one embodiment, the fuel consists of carbon monoxide. In one embodiment, the first stream consists of carbon monoxide and carbon dioxide. In one embodiment, the second stream consists of water and hydrogen. In one embodiment, the second stream consists of steam and hydrogen.

[0050] As shown in FIG. 3, a hydrogen production system is illustrated. The system includes a catalytic partial oxidation (CPOX) reactor 310, a steam generator 330, and an electrochemical (EC) reactor 320. The CPOX reactor product stream 323 is introduced into the EC reactor, and the steam generator provides steam 321 to the EC reactor. The product stream 323 and the steam 321 do not contact each other within the EC reactor. The CPOX reactor product stream 323 is used as fuel in the EC reactor 320. The CPOX reactor 310 receives a stream 311 containing hydrocarbons (e.g., methane, ethane, propane, gasoline, jet fuel, etc.) and oxidizes the hydrocarbons to produce syngas, CO, water, etc. The EC reactor can efficiently perform the intended reaction in the presence of gases such as nitrogen, argon, and carbon dioxide, eliminating the need for gas separation between the CPOX reactor and the EC reactor. This also allows the CPOX reactor to utilize air as an oxidant. Of course, purified oxygen can always be used in a CPOX reactor, but using air directly can result in significant savings in both capital and operating costs.

[0051] The EC reactor 320 produces a first product stream 324 containing CO and CO2 and a second product stream 322 containing H2 and HO, with the two product streams not contacting each other. In some cases, at least a portion (325) of the first product stream 324 is recycled to a steam generator to provide heat and generate steam from water. In some cases, a portion of the second product stream 322 is recycled to the EC reactor (cathode side, not shown in FIG. 3). In various embodiments, the EC reactor 320 includes an ion-conducting membrane that, together with an anode, enables the reactor to perform an electrochemical water-gas shift reaction, which involves the exchange of ions across the membrane and includes a forward water-gas shift reaction, a reverse water-gas shift reaction, or both. The anode also enables the reactor to perform a chemical water-gas shift reaction.

[0052] Thus, hydrogen is produced by the following method, which includes introducing a hydrocarbon into a catalytic partial oxidation (CPOX) reactor to produce a product stream, and providing the product stream and steam to an electrochemical (EC) reactor, where the product stream and steam do not contact each other within the EC reactor. The EC reactor includes an ion-conducting membrane, and the reactor is capable of electrochemically performing a water-gas shift reaction, which involves the exchange of ions across the membrane and includes a forward water-gas shift reaction, a reverse water-gas shift reaction, or both. Furthermore, the membrane separates the product stream from the steam. In various embodiments, the pressure difference between the product stream side and the steam side is 2 psi or less, or 1.5 psi or less, or 1 psi or less.

[0053] In various embodiments, the CPOX reactor utilizes air as the oxidant. In various embodiments, the CPOX reactor product stream enters the EC reactor directly without gas separation. In various embodiments, the EC reactor oxidizes the CPOX reactor product stream in a reducing environment to produce a first product stream comprising CO and CO, and the EC reactor electrochemically reduces steam to hydrogen without electrical input to produce a second product stream comprising H and HO. In various embodiments, a membrane separates the first and second product streams. In various embodiments, at least a portion of the first product stream is utilized to generate steam from water. In various embodiments, at least a portion of the second product stream is recycled to enter the EC reactor.

[0054] The steam generator produces steam from water. In one embodiment, the steam entering the electrochemical reactor has a temperature of 600° C. or greater, or 700° C. or greater, or 800° C. or greater, or 850° C. or greater, or 900° C. or greater, or 950° C. or greater, or 1000° C. or greater, or 1100° C. or greater. In one embodiment, the steam entering the electrochemical reactor has a pressure of 10 psi or less, or 5 psi or less, or 3 psi or less.

[0055] It should be understood that this disclosure describes exemplary embodiments for implementing different features, structures, or functions of the present invention. While exemplary embodiments of components, arrangements, and configurations are described to simplify the disclosure, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the present invention. The embodiments presented herein may be combined unless otherwise specified. Such combinations do not depart from the scope of the present disclosure.

[0056] Furthermore, certain terms are used throughout the description and claims to refer to particular components or steps. As one skilled in the art will appreciate, various entities may refer to the same component or process step by different names, and thus, the naming conventions for elements described herein are not intended to limit the scope of the invention. Furthermore, the terminology and naming conventions used herein are not intended to distinguish between components, features, and / or steps that differ in name but function.

[0057] While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and description. It should be understood, however, that the drawings and detailed description are not intended to limit the disclosure to the particular forms disclosed, but on the contrary, are intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure.

Claims

1. An electrochemical reactor, comprising: a porous anode; a porous cathode; a membrane separating the anode and the cathode; the membrane has ionic and electronic conductivity; the cathode comprises Ni or NiO and a material selected from the group consisting of YSZ, CGO, SDC, SSZ, LSGM, and combinations thereof; The reactor performs a water-gas shift reaction electrochemically without electrical input, the electrochemical water-gas shift reaction involving an exchange of ions across the membrane, and including a forward water-gas shift reaction, a reverse water-gas shift reaction, or both.

2. A reactor as described in claim 1, wherein each of the anode and the cathode comprises a metal phase and a ceramic phase, the metal phase being electronically conductive and the ceramic phase being ionically conductive.

3. 10. The reactor of claim 1, wherein the anode and the cathode are both exposed to a reducing environment.

4. 10. The reactor of claim 1, wherein the anode comprises Ni or NiO and a material selected from the group consisting of YSZ, CGO, SDC, SSZ, LSGM, and combinations thereof.

5. A reactor as described in claim 1, wherein the reactor does not include any interconnections.

6. 10. The reactor of claim 1, wherein the membrane comprises CGO.

7. 10. The reactor of claim 1, wherein the membrane comprises CoCGO.

8. 10. The reactor of claim 1, comprising a catalyst that promotes a chemical reverse water gas shift (RWGS) reaction.

9. 10. The reactor of claim 1, wherein the reactor also performs a chemical water-gas shift reaction.

10. A two-functional layer; a cathode; a mixed conducting membrane separating the bifunctional layer and the cathode; the cathode comprises Ni or NiO and a material selected from the group consisting of YSZ, CGO, SDC, SSZ, LSGM, and combinations thereof; A reactor wherein the bifunctional layer and the mixed conducting membrane are in contact with each other, and the bifunctional layer catalyzes the reverse water gas shift (RWGS) reaction and functions as an anode in an electrochemical reaction.

11. 11. The reactor of claim 10, wherein the bifunctional layer as the anode and the cathode are simultaneously exposed to a reducing environment.

12. 11. The reactor of claim 10, wherein a current collector is not attached to the bifunctional layer.

13. 11. The reactor of claim 10, wherein the reactor does not include any interconnects and the reactor does not receive or generate electricity.

14. 11. The reactor of claim 10, wherein the bifunctional layer comprises Ni or NiO and a material selected from the group consisting of YSZ, CGO, SDC, SSZ, LSGM, and combinations thereof.

15. 11. The reactor of claim 10, comprising a catalyst that promotes a chemical reverse water gas shift (RWGS) reaction.

Images