Doped Barium Niobate Catalyst for Cogeneration of Electricity and Syngas from Methane

Abstract

A syngas production method includes introducing oxygen to a reactor which may include a catalyst. The syngas production method includes introducing methane to the reactor, and forming carbon monoxide and hydrogen by partial oxidation of the methane, and where the catalyst may include a barium niobate-based perovskite structure having a chemical formula of Ba.sub.1x(AE).sub.xNb.sub.1(y+z)(AE).sub.yM.sub.zO.sub.3, where AE is an alkaline earth (AE) element and M is a metal. M may include a transition metal or a rare earth metal. AE may include Mg, Ca, Sr, or a combination thereof. AE may include K, Rb, Cs, or a combination thereof. M may include Fe, Co, Ni, Y, Yb, W, Ta, Pr, or a combination thereof. M may include Sc, Ti, V, Cr, Mn, Cu, Zn, Zr, Mo, La, Ce, Sm, Gd, W or a combination thereof.

Claims

1. A syngas production method, comprising: introducing oxygen to a reactor comprising a catalyst; introducing methane to the reactor; and forming carbon monoxide and hydrogen by partial oxidation of the methane; and wherein: the catalyst comprises a barium niobate-based perovskite structure having a chemical formula of Ba.sub.1x(AE).sub.xNb.sub.1(y+z)(AE).sub.yM.sub.zO.sub.3 wherein AE is an alkaline earth (AE) element and M is a metal.

2. The syngas production method of claim 1, wherein M comprises a transition metal or a rare earth metal.

3. The syngas production method of claim 1, wherein AE comprises Mg, Ca, Sr, or a combination thereof.

4. The syngas production method of claim 1, wherein AE comprises K, Rb, Cs or a combination thereof.

5. The syngas production method of claim 1, wherein M comprises Fe, Co, Ni, Y, Yb, W, Ta, Pr, or a combination thereof.

6. The syngas production method of claim 1, wherein M comprises Sc, Ti, V, Cr, Mn, Cu, Zn, Zr, Mo, La, Ce, Sm, Gd, W or a combination thereof.

7. The syngas production method of claim 1, wherein x is from 0 to about 0.60.

8. The syngas production method of claim 1, wherein y is from 0 to about 0.80.

9. The syngas production method of claim 1, wherein z is from 0 to about 0.80.

10. The syngas production method of claim 1, wherein the barium niobate-based perovskite structure has the chemical formula of BaCa.sub.0.33Nb.sub.0.67xM.sub.xO.sub.3 and BaMg.sub.0.33Nb.sub.0.67xM.sub.xO.sub.3 where M is one or more of Fe, Co, Ni, Y, Yb, or Pr and M is from about x=0 to about x=0.33.

11. The syngas production method of claim 1, wherein the oxygen and methane are introduced into the reactor in a stoichiometric ratio between 1:1 to 1:19.

12. The syngas production method of claim 1, further comprising: combining the catalyst with silicon carbide; and placing the combined catalyst and silicon carbide in the reactor.

13. The syngas production method of claim 1, further comprising supplying the oxygen to a membrane comprising the catalyst.

14. A syngas production method, comprising: feeding methane into a reactor, the reactor comprising a solid oxide fuel cell comprising: an anode comprising a catalyst; a cathode; and an electrolyte positioned between the anode and the cathode; feeding oxygen into the reactor at the cathode; and producing carbon monoxide and hydrogen at the anode; and wherein the methane is fed into the reactor at the anode.

15. The syngas production method of claim 14, wherein the anode further comprises an ionic conductor selected from the group consisting of Gd-Doped Ceria, Sm-Doped Ceria, and a combination thereof.

16. The syngas production method of claim 14, wherein the anode further comprises an electronic conductor selected from the group consisting of Ni, Ag, and a combination thereof.

17. The syngas production method of claim 14, wherein the electrolyte comprises yttria-stabilized zirconia (YSZ), lanthanum strontium gallium magnesium oxide (LSGM), yttria-doped barium zirconate (BZY), or a combination thereof.

18. The syngas production method of claim 14, further comprising producing electricity as an additional product of the production method.

19. A syngas production method, comprising: introducing oxygen to a reactor comprising a catalyst; introducing methane to the reactor; and forming carbon monoxide and hydrogen by partial oxidation of the methane; and wherein the catalyst comprises a barium niobate-based perovskite structure having a chemical formula of Ba.sub.1x(AE).sub.xNb.sub.1(y+z)(AE).sub.yM.sub.zO.sub.3 wherein AE is an alkaline earth (AE) element and M is a metal; and the reactor further comprises a solid oxide fuel cell comprising a cathode, an electrolyte, and an anode comprising the catalyst.

20. The syngas production method of claim 19, wherein the barium niobate-based perovskite structure has the chemical formula of BaCa.sub.0.33Nb.sub.0.67xM.sub.xO.sub.3 and BaMg.sub.0.33Nb.sub.0.67xM.sub.xO.sub.3; and wherein M is one or more of Fe, Co, Ni, Y, Yb, or Pr; M is from about x=0 to about x=0.33; and AE comprises Mg, Ca, Sr, or a combination thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present teachings and together with the description, serve to explain the principles of the disclosure. In the figures:

[0013] FIGS. 1A-1C depict schematics and data related to the use of solid oxide electrolyzer cells utilizing doped BCN as an anode, in accordance with the present disclosure.

[0014] FIG. 2 is a schematic of a process for producing syngas using doped BCN catalysts in a catalytic reactor when exposed to CH.sub.4 and O.sub.2, in order to produce syngas at high oxygen concentrations, in accordance with the present disclosure.

[0015] FIGS. 3A and 3B depict portions of a process utilizing doped BCN perovskites as a catalytic membrane reactor to produce syngas from methane and oxygen, in accordance with the present disclosure.

[0016] It should be noted that some details of the figures have been simplified and are drawn to facilitate understanding of the present teachings rather than to maintain strict structural accuracy, detail, and scale.

DETAILED DESCRIPTION

[0017] Reference will now be made in detail to exemplary embodiments of the present teachings, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same, similar, or like parts.

[0018] Fundamental requirements of effective catalysts for use in electrochemical syngas production processes include chemical stability upon exposure to methane, carbon dioxide, water, and increased oxide ion conductivity and basicity. The present disclosure provides a barium niobate perovskite catalyst for use in effective partial oxidation processes for syngas synthesis. The use of doped BCN family of catalysts in synthesis gas (syngas) generation and electricity processes utilize the combination of oxygen and methane to produce carbon monoxide and hydrogen. In examples, syngas can then be used to manufacture other materials while also producing energy in the system. Synthesis gas, also called syngas, is a gas mixture that contains varying amounts of carbon monoxide and hydrogen generated by the gasification of a carbon-containing fuel.

[0019] The doped BCN family of catalysts can be used to produce syngas by partial oxidation processes, including: [0020] Combining oxygen with methane to produce carbon monoxide (CO) and hydrogen (H.sub.2) gas. [0021] This process is difficult to achieve operation with other materials (specifically catalysts) because the carbon can deposit on the surface of the catalysts, deactivating the catalyst. There is no evidence of this occurring with the doped BCN family of catalysts at conditions relevant for syngas production.

[0022] Use of doped BCN perovskites can be employed as catalyst for partial oxidation of methane to synthesize gas comprised of carbon monoxide or hydrogen. Three methods can be used to produce synthesize gas, including the use of solid oxide electrolyzer cells utilizing doped BCN as an anode, heterogenous catalysis, or the use of doped BCN perovskites as a catalytic membrane reactor.

[0023] Illustrative examples of catalysts described herein can include compounds notated as BCNF, which can include calcium-doped, iron-doped, or yttrium-doped barium niobate in compositions such as BaCa.sub.0.33Nb.sub.0.67O.sub.3(BCN), BaCa.sub.0.33Nb.sub.0.50Fe.sub.0.17O.sub.3(BCNF17), BaCa.sub.0.33Nb.sub.0.42Fe.sub.0.25O.sub.3(BCNF25), BaCa.sub.0.33Nb.sub.0.34Fe.sub.0.33O.sub.3(BCNF33), BaCa.sub.0.33Nb.sub.0.54Y.sub.0.13O.sub.3(BCNY13), BaCa.sub.0.33Nb.sub.0.34Fe.sub.0.2Y.sub.0.13O.sub.3(BCNFY), BaCa.sub.0.33Nb.sub.0.47Y.sub.0.20O.sub.3(BCNY20), BaCa.sub.0.33Nb.sub.0.42Y.sub.0.25O.sub.3(BCNY25), BaCa.sub.0.33Nb.sub.0.34Y.sub.0.33O.sub.3(BCNY33), or magnesium-doped, iron-doped compositions such as BaMg.sub.0.33Nb.sub.0.50Fe.sub.0.17O.sub.3(BMNF17), BaMg.sub.0.33Nb.sub.0.42Fe.sub.0.25O.sub.3(BMNF25), BaMg.sub.0.33Nb.sub.0.34Fe.sub.0.33O.sub.3(BMNF33) or combinations thereof.

[0024] FIGS. 1A-1C depict schematics and data related to the use of solid oxide electrolyzer cells utilizing doped BCN as an anode, in accordance with the present disclosure. A solid oxide fuel cell 100, in FIG. 1A, used for electrochemical syngas production includes a cathode 102, an electrolyte 104 and an anode 106. In examples, the anode 106 includes a material selected from the BCN family of catalysts as described herein. Doped BCN perovskites are used as anode 106 material in solid oxide electrolyzer cells 100 (SOEC) utilizing methane as a fuel can produce syngas while simultaneously producing energy. Oxygen enters the fuel cell 100 at the cathode 102 and permeates through the electrolyte 104 layer to the surface of the anode 106 and reacts with methane in contact with the anode 106 comprising one or more doped BCN perovskite catalysts that results in the formation of syngas. The cathode can be prepared by mixing doped BCN perovskites with gadolinium (Gd) doped ceria (GDC) for improving oxide ion conductivity. Cyclic voltammetry results in combination with mass spectroscopic analysis in an SOEC setup, as shown in FIG. 1B and FIG. 1C, indicate the preferential production of syngas (CO and H.sub.2) at potentials close to open circuit values (1.0 V) while at very high overpotentials (0.25 to 0.5V) produces combination of products such as CO, CO.sub.2, H.sub.2, C.sub.2H.sub.4, and H.sub.2O. The results shown in FIGS. 1B and 1C indicate that doped BCN materials, such as BCNF33 and others described herein, can be utilized to produce syngas and energy simultaneously from methane in an SOEC setup. This ability of BCNF perovskites and other catalysts described herein make them ideal candidates for coproduction of syngas and electricity. Highly electrolyzing conditions where energy is inputted leads to overoxidation products such as CO.sub.2, H.sub.2O along with ethylene and CO. However, the ability to produce syngas at close to OCV make BCNF perovskites ideally suited for syngas and electricity coproduction. Supplying oxygen through a solid oxide fuel cell possesses an advantage of being an exergonic reaction, one which can generate electrical energy as an additional byproduct. A particular advantage of this use of solid oxide electrolyzer cells includes the option of producing additional energy as byproduct.

[0025] In examples of a syngas production method, the steps of the production method can be conducted using a reactor including a solid oxide fuel cell having an anode comprising a catalyst, a cathode, and an electrolyte positioned between the anode and the cathode. The steps of syngas production can include feeding methane into a reactor at the anode, feeding oxygen into the reactor at the cathode, and producing carbon monoxide and hydrogen at the anode. In examples, the anode can also include an ionic conductor selected from the group consisting of gadolinium-doped ceria, or Gd-Doped Ceria, samarium-doped ceria, or Sm-Doped Ceria, or a combination thereof. In other examples, the anode can further include an electronic conductor such as nickel (Ni), silver (Ag), or a combination thereof. Exemplary electrolytes for such a system of syngas production can include an electrolyte composed of yttria-stabilized zirconia (YSZ), lanthanum strontium gallium magnesium oxide (LSGM), yttria-doped barium zirconate (BZY), or a combination thereof. In the example of a solid oxide fuel cell being used in syngas production, the method can also produce electricity as an additional product of the production method.

[0026] FIG. 2 is a schematic of a process for producing syngas using doped BCN catalysts in a catalytic reactor when exposed to CH.sub.4 and O.sub.2, in order to produce syngas at high oxygen concentrations, in accordance with the present disclosure. The OCM catalytic reactor 200 shown in FIG. 2 includes a furnace 202 encompassing an inlet 204 where oxygen, methane, and other reactants are introduced into the reactor 200. Inside the reactor 200 is a BCN catalyst 206 on a silicon carbide support material surrounded by quartz wool 208 held within an alumina tube. After reaction, the outlet 210 removes carbon monoxide and hydrogen as well as other products of the syngas synthesis. In examples of the heterogenous catalysis in a catalytic furnace reactor 200, the outlet can feed further into a gas chromatograph and/or mass spectrometer or other analytical measurement system for product and production efficiency analysis. In addition to silica (SiO.sub.2), several other oxide and non-oxide supports can be used to enhance the thermal stability, dispersion, and redox behavior of the doped barium calcium niobate (BCN) catalyst. Materials such as Alumina (Al2O3), Magnesia (MgO), Silica (SiO2, Titania (TiO2) can all be used as support. As alternatives to quartz wool, glass wool, alumina fiber wool, ceramic fiber mats, silica-alumina fibers, kaowool (an aluminosilicate fiber), and porous zirconia or SiC felt can also be used. The wool material is mainly used as a mechanical support to hold the catalyst powder in place. It also helps in transporting the reactants and products in and out of the reactor while preventing catalyst escaping. In the heterogeneous catalysis process oxygen is introduced into a feed stream with methane at the appropriate stoichiometric ratios. CH.sub.4+O.sub.2.fwdarw.CO+H.sub.2. Syngas is produced with heterogeneous oxidation and partial oxidation of methane. In addition, the partial oxidation, heterogeneous catalysis, setup is similar to the OCM setup but will use oxygen at a high concentration. The catalyst for this purpose can also have metal nanoparticles deposited on top of BCN perovskites to improve process efficiency.

[0027] FIGS. 3A and 3B depict portions of a process utilizing doped BCN perovskites as a catalytic membrane reactor to produce syngas from methane and oxygen, in accordance with the present disclosure. A portion of a reactor 300 is shown for purposes of clarity, where a membrane 302 including doped BCN perovskite is utilized to produce syngas from an input of oxygen and methane. In a dual membrane reactor 304, a first dense ion conducting membrane 306, typically comprised at least in part of one or more well-known and effective oxide ion conductors, such as YSZ, LSGM, BaZr.sub.0.8Y.sub.0.2O.sub.3 (BZY), and BaCe.sub.0.9Gd.sub.0.2O.sub.3 (BCG), or combinations thereof, is shown adjacent to a porous doped BCN perovskite membrane 308, which could also include a coated membrane where the coating on the membrane includes porous doped BCN perovskite materials. These show examples where dense oxide ion conducting membranes coated with highly porous doped BCN perovskite can be utilized to produce syngas or ethylene and hydrogen.

[0028] The BCNF family of catalysts used in these processes is advantageous because they do not show evidence of catalyst deactivation in these partial oxidation technologies, which is normally a common problem. BCNF catalyst material properties also do not undergo a large structural change of the material when cycled between very reducing and very oxidizing conditions or high and low temperature ranges. In the reversible reactions between oxidation and reduction, it maintains its composition and crystal structure. From an economic standpoint this is advantageous, as it provides natural gas producers a process to generate syngas right on site, where syngas can subsequently be readily transformed into higher hydrocarbons or alcohols.

[0029] The present disclosure provides the use of the BCNF family of catalysts in syngas generation and electricity production process. The process uses the combination of oxygen and methane to produce carbon monoxide and hydrogen. In examples, Syngas can then be used to manufacture other materials while also producing energy in the system. Synthesis gas (also called syngas) is a gas mixture that contains varying amounts of carbon monoxide and hydrogen generated by the gasification of a carbon-containing fuel.

[0030] This process is difficult to achieve with other materials, particularly catalysts, because the carbon can deposit on the surface of the catalysts, deactivating the catalyst. There is no evidence of this occurring with the BCNF family of catalysts. The BCNF family of catalysts used in these processes is advantageous because they do not show evidence of catalyst deactivation in these partial oxidation technologies. BCNF catalyst material properties also do not undergo a large structural change of the material when cycled between very reducing and very oxidizing conditions or high and low temperature ranges. In the reversible reactions between oxidation and reduction, it maintains its composition and crystal structure. In examples of membrane properties using BCNF catalysts, the BCN catalyst can be coated onto another membrane. The formation of another membrane adds an extra, second layer that provides a support material, while the inner layer includes the BCN and the two layers may provide a synergistic effect on catalysis. From an economic standpoint, the use of the BCNF family of catalysts can prove advantaged, as its use and the use of the processes described herein provide natural gas producers a process to generate syngas right on site, where syngas can subsequently be readily transformed into higher hydrocarbons or alcohols.

[0031] In examples of the syngas production method or methods described in the present disclosure, the procedure includes introducing oxygen to a reactor comprising a catalyst, introducing methane to the reactor, and forming carbon monoxide and hydrogen by partial oxidation of the methane, and wherein the catalyst comprises a barium niobate-based perovskite structure having the chemical formula of Ba.sub.1x(AE).sub.xNb.sub.1(y+z)(AE).sub.yM.sub.zO.sub.3 wherein AE is an alkaline earth (AE) element and M is a metal. The syngas production method can include producing electricity as an additional product of the production method when SOEC was utilized, and also introducing the oxygen and methane into the reactor in a stoichiometric ratio in a heterogeneous partial oxidation of methane reactor. The methane to oxygen ratio can be between 1:1 to 19:1 respectively. The reactor can include a solid oxide fuel cell comprising a cathode, an electrolyte, and an anode comprising the catalyst, or can include the practice of combining the catalyst with silicon carbide and placing the combined catalyst and silicon carbide in the reactor.

[0032] In examples of the catalyst, the M, or metal can include a transition metal or a rare earth metal, such as, for example, Fe, Co, Ni, Y, Yb, W, Ta, Pr, Sc, Ti, V, Cr, Mn, Cu, Zn, Zr, Mo, La, Ce, Sm, Gd, W, or a combination thereof. The metal M can be structurally doped, exsolved on to the catalyst surface as subnano, nano, or micron sized particles, or deposited on the surface of the catalyst separately. In examples of the catalyst, the AE or alkaline earth element can include Mg, Ca, Sr, or a combination thereof, or K, Rb, Cs or a combination thereof. In examples, x is from 0 to about 0.60, y is from 0 to about 0.80, or z is from 0 to about 0.80. Specific examples of the barium niobate-based perovskite structure can include those having the chemical formula of BaCa.sub.0.33Nb.sub.0.67xM.sub.xO.sub.3 and BaMg.sub.0.33Nb.sub.0.67xM.sub.xO.sub.3 where M is one or more of Fe, Co, Ni, Y, Yb, or Pr and M is from about x=0 to about x=0.33.

[0033] While the present teachings have been illustrated with respect to one or more implementations, alterations and/or modifications may be made to the illustrated examples without departing from the spirit and scope of the appended claims. For example, it may be appreciated that while the process is described as a series of acts or events, the present teachings are not limited by the ordering of such acts or events. Some acts may occur in different orders and/or concurrently with other acts or events apart from those described herein. Also, not all process stages may be required to implement a methodology in accordance with one or more aspects or embodiments of the present teachings. It may be appreciated that structural objects and/or processing stages may be added, or existing structural objects and/or processing stages may be removed or modified. Further, one or more of the acts depicted herein may be carried out in one or more separate acts and/or phases. Furthermore, to the extent that the terms including, includes, having, has, with, or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term comprising. The term at least one of is used to mean one or more of the listed items may be selected. Further, in the discussion and claims herein, the term on used with respect to two materials, one on the other, means at least some contact between the materials, while over means the materials are in proximity, but possibly with one or more additional intervening materials such that contact is possible but not required. Neither on nor over implies any directionality as used herein. The term conformal describes a coating material in which angles of the underlying material are preserved by the conformal material. The term about indicates that the value listed may be somewhat altered, as long as the alteration does not result in nonconformance of the process or structure to the illustrated embodiment. The terms couple, coupled, connect, connection, connected, in connection with, and connecting refer to in direct connection with or in connection with via one or more intermediate elements or members. Finally, the terms exemplary or illustrative indicate the description is used as an example, rather than implying that it is an ideal. Other embodiments of the present teachings may be apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the present teachings being indicated by the following claims.