U.S. patent application number 17/447903 was filed with the patent office on 2022-03-17 for methods for producing ammonia and related systems.
The applicant listed for this patent is Battelle Energy Alliance, LLC. Invention is credited to Dong Ding, Bin Hua, Meng Li, Wei Wu.
Application Number | 20220081786 17/447903 |
Document ID | / |
Family ID | |
Filed Date | 2022-03-17 |
United States Patent
Application |
20220081786 |
Kind Code |
A1 |
Hua; Bin ; et al. |
March 17, 2022 |
METHODS FOR PRODUCING AMMONIA AND RELATED SYSTEMS
Abstract
A method for producing ammonia comprises introducing a first
feed stream to a positive electrode of an electrochemical cell. The
electrochemical cell comprises the positive electrode, a negative
electrode, and an electrolyte between the positive electrode and
the negative electrode. A second feed stream comprising a nitrogen
source is introduced to the negative electrode and a potential
difference is applied between the positive electrode and the
negative electrode to produce hydrogen ions, a first product stream
comprising carbon monoxide, and a second product stream comprising
ammonia. Additional methods and systems are disclosed.
Inventors: |
Hua; Bin; (Ammon, ID)
; Li; Meng; (Ammon, ID) ; Wu; Wei; (Idaho
Falls, ID) ; Ding; Dong; (Idaho Falls, ID) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Battelle Energy Alliance, LLC |
Idaho Falls |
ID |
US |
|
|
Appl. No.: |
17/447903 |
Filed: |
September 16, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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63078994 |
Sep 16, 2020 |
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International
Class: |
C25B 1/27 20060101
C25B001/27; C25B 9/17 20060101 C25B009/17; C25B 11/077 20060101
C25B011/077; C25B 11/081 20060101 C25B011/081; C25B 1/02 20060101
C25B001/02; C25B 1/23 20060101 C25B001/23 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] This invention was made with government support under
Contract Number DE-AC07-05ID14517 awarded by the United States
Department of Energy. The government has certain rights in the
invention.
Claims
1. A method for producing ammonia comprising: introducing a first
feed stream comprising carbon dioxide to a positive electrode of an
electrochemical cell, the electrochemical cell comprising the
positive electrode, an electrolyte, and a negative electrode;
introducing a second feed stream comprising a nitrogen source to
the negative electrode; and applying a potential difference between
the positive electrode and the negative electrode of the
electrochemical cell to produce hydrogen ions, a first product
stream comprising carbon monoxide, and a second product stream
comprising ammonia.
2. The method of claim 1, wherein introducing a first feed stream
to a positive electrode comprises introducing the first feed stream
comprising the carbon dioxide and one or more alkane.
3. The method of claim 2, wherein introducing a first feed stream
to a positive electrode comprises introducing the first feed stream
comprising carbon dioxide, methane, and another alkane.
4. The method of claim 2, wherein applying a potential difference
between the positive electrode and the negative electrode comprises
producing the first product stream substantially free of carbon
dioxide and the one or more alkane.
5. The method of claim 1, wherein introducing a first feed stream
comprising carbon dioxide to a positive electrode of an
electrochemical cell comprises introducing the first feed stream
substantially free of water.
6. The method of claim 1, wherein introducing a first feed stream
comprising carbon dioxide to a positive electrode comprises
introducing the first feed stream to the positive electrode
comprising an oxidation catalyst, the oxidation catalyst comprising
a perovskite doped with a metal of palladium (Pd), platinum (Pt),
iridium (Ir), ruthenium (Ru), rhodium (Rh), nickel (Ni), cobalt
(Co), or a combination thereof.
7. The method of claim 1, wherein introducing a second feed stream
comprising a nitrogen source to the negative electrode comprises
introducing the second feed stream to the negative electrode
comprising a reduction catalyst, the reduction catalyst comprising
a metal hydroxide catalyst.
8. The method of claim 1, wherein introducing a second feed stream
comprising a nitrogen source to the negative electrode comprises
reducing the gas at a temperature of about 500.degree. C. or
less.
9. The method of claim 1, wherein introducing a second feed stream
comprising a nitrogen source to the negative electrode comprises
introducing the second feed stream comprising nitrogen, nitrogen
monoxide, nitrogen dioxide, or a combination thereof.
10. The method of claim 1, wherein applying a potential difference
between the positive electrode and the negative electrode of the
electrochemical cell to produce a second product stream comprises
diffusing the hydrogen ions through the electrolyte and reacting
the hydrogen ions with the nitrogen source to produce the
ammonia.
11. The method of claim 1, wherein applying a potential difference
between the positive electrode and the negative electrode of the
electrochemical cell to produce hydrogen ions, a first product
stream comprising carbon monoxide, and a second feed stream
comprising ammonia comprises simultaneously producing the carbon
monoxide and the ammonia.
12. The method of claim 1, further comprising introducing a stream
comprising water to the negative electrode.
13. A method for producing ammonia comprising: introducing a first
feed stream comprising methane and carbon dioxide to a positive
electrode of an electrochemical cell, the electrochemical cell
comprising the positive electrode, a negative electrode, and an
electrolyte between the positive electrode and the negative
electrode and the positive electrode comprising an oxidation
catalyst; introducing a second feed stream comprising nitrogen gas
to the negative electrode, the negative electrode comprising a
reduction catalyst; and applying a potential difference between the
positive electrode and the negative electrode to oxidize the
methane and carbon dioxide to produce carbon monoxide and to reduce
the nitrogen gas to produce ammonia.
14. The method of claim 13, wherein introducing a second feed
stream to the negative electrode comprises interacting the second
feed stream with the reduction catalyst comprising a metal
hydroxide integrated into a doped perovskite or supported metal
catalyst.
15. The method of claim 14, wherein introducing a second feed
stream to the negative electrode comprises interacting the second
feed stream with the reduction catalyst comprising a comprising a
metal hydroxide comprising a metal selected from the group of
rhodium (Rh), ruthenium (Ru), palladium (Pd), platinum (Pt),
iridium (Ir), nickel (Ni), cobalt (Co), or a combination
thereof.
16. The method of claim 15, wherein introducing a second feed
stream to the negative electrode comprises introducing the second
feed stream comprising water and one or more of dinitrogen,
nitrogen monoxide, nitrogen dioxide, or a combination thereof.
17. A system for producing ammonia comprising: an electrochemical
cell comprising: a positive electrode comprising an oxidation
catalyst formulated to produce carbon monoxide; a negative
electrode comprising a reduction catalyst formulated to produce
ammonia; and an electrolyte between the positive electrode and the
negative electrode.
18. The system of claim 17, wherein the positive electrode
comprises a supported metal catalyst.
19. The system of claim 17, wherein the negative electrode
comprises a reduction catalyst comprising a lanthanum-doped ceria
doped with platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium
(Ru), iridium (Ir), or iron (Fe).
20. The system of claim 17, wherein the negative electrode
comprises a metal hydroxide catalyst.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit under 35 U.S.C. .sctn.
119(e) of U.S. Provisional Patent Application Ser. No. 63/078,994,
filed Sep. 16, 2020, the disclosure of which is hereby incorporated
herein in its entirety by this reference.
TECHNICAL FIELD
[0003] Embodiments of the disclosure relate to systems and methods
directed to producing ammonia. The systems and associated methods
are particularly directed towards so-called "green" processes
(i.e., those that do not generate GHGs) for producing ammonia and
related systems.
BACKGROUND
[0004] As the human population has continued to grow, the demand
for fertilizers in the agriculture sector grows to meet demand. As
a result, ammonia production (an important product in fertilizer)
has also increased. Ammonia is synthesized through the Haber-Bosch
(HB) process, wherein nitrogen reacts with hydrogen to produce
ammonia, as follows:
N.sub.2+3H.sub.2.fwdarw.2NH.sub.3 (1)
[0005] A source of hydrogen for the nitrogen reduction reaction
come from hydrogen gas produced via (1) processing alkanes with
steam (i.e., "steam reformation") (eq. 2) or (2) a water shift
reaction (eq. 3), as follows:
CH.sub.4+H.sub.2O.fwdarw.CO+3H.sub.2 (2)
CO+H.sub.2O.fwdarw.CO.sub.2+H.sub.2 (3)
[0006] The steam reformation/water shift reactions and ammonia
synthesis occur in separate chambers in the conventional Haber
Bosch process, and both reactions occur simultaneously. However,
the water shift reaction generates CO.sub.2, a known greenhouse gas
(GHG) that must be captured and removed. The Haber Bosch process is
responsible for 1.4% of the annual global CO.sub.2 emissions and
consumes between 1-3% of global energy production. Additionally,
the steam reformation and water shift reactions require high
temperatures and pressures to produce CO, CO.sub.2, and H.sub.2.
Thus, synthesis of ammonia via the Haber Bosch process comes at the
cost of increasing CO.sub.2 production and large energy inputs,
which can be expensive.
[0007] Some efforts have been made towards electrochemical methods
for synthesizing ammonia to circumvent the need for systems that
can tolerate high pressures and high temperatures to drive the
oxidation and reduction reactions. Additionally, electrochemical
methods for ammonia synthesis have been able to half the CO.sub.2
emissions while consuming only 25% of global energy production
under the conventional HB process. In such electrochemical cells,
the anode catalyzes the oxidation of an alkane (such as methane)
via steam reformation to produce hydrogen ions and electrons (eq.
4):
CH.sub.4+2H.sub.2O.fwdarw.CO.sub.2+8H.sup.++8e.sup.- (4)
[0008] The produced hydrogen ions travel through a proton
conducting ceramic material to the cathode, where nitrogen gas
reduction occurs to form ammonia (as in eq. 1).
[0009] However, such electrochemical methods produce CO.sub.2 even
though the reactions utilize less extreme conditions (i.e., by
implementing different catalysts in the electrochemical cell).
Accordingly, ammonia synthesis is not a truly green process, even
though other GHGs such as CH.sub.4 are consumed in the process.
BRIEF SUMMARY
[0010] A method for producing ammonia is disclosed and comprises
introducing a first feed stream to a positive electrode of an
electrochemical cell. The electrochemical cell comprises the
positive electrode, a negative electrode, and an electrolyte
between the positive electrode and the negative electrode. A second
feed stream comprising a nitrogen source is introduced to the
negative electrode and a potential difference is applied between
the positive electrode and the negative electrode to produce
hydrogen ions, a first product stream comprising carbon monoxide,
and a second product stream comprising ammonia.
[0011] Another method for producing ammonia is disclosed. The
method comprises introducing a first feed stream comprising methane
and carbon dioxide to a positive electrode of an electrochemical
cell. The positive electrode comprises an oxidation catalyst. The
electrochemical cell comprises the positive electrode, a negative
electrode, and an electrolyte between the positive electrode and
the negative electrode. A second feed stream comprising nitrogen
gas is introduced to the negative electrode. The negative electrode
comprises a reduction catalyst. A potential difference is applied
between the positive electrode and the negative electrode to
oxidize the methane and carbon dioxide to produce carbon monoxide
and to reduce the nitrogen gas to produce ammonia.
[0012] A system for producing ammonia is also disclosed and
comprises an electrochemical cell, which comprises a positive
electrode, a negative electrode, and an electrolyte between the
positive electrode and the negative electrode. The positive
electrode comprises an oxidation catalyst formulated to produce
carbon monoxide. The negative electrode comprises a reduction
catalyst formulated to produce ammonia.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic illustration of a system in accordance
with embodiments of the disclosure;
[0014] FIG. 2 is a flow chart of a process of producing ammonia in
accordance with embodiments of the disclosure;
[0015] FIGS. 3A and 3B are SEM images of cross-sections of
electrochemical cells in accordance with embodiments of the
disclosure;
[0016] FIGS. 4A-4E are graphs showing properties of the
electrochemical cell of FIG. 3A; and
[0017] FIG. 5A-5E are graphs showing properties of the
electrochemical cell of FIG. 3B.
DETAILED DESCRIPTION
[0018] Disclosed herein are methods and systems for transforming
greenhouse gases (GHG) into ammonia and other commercially
desirable products. The methods and systems enable the production
of industrially important products, such as ammonia and carbon
monoxide, by utilizing known GHGs, such as carbon dioxide, without
using water (e.g., steam). The methods and systems produce ammonia
while simultaneously consuming carbon dioxide. The methods and
systems provide a so-called "dry reformation process" instead of a
steam reformation process as conventionally used in the Haber-Bosch
process. The carbon dioxide (and other GHGs) are consumed from a
feed stream by utilizing the carbon dioxide as a starting material
without using steam as a starting material. The production of
ammonia and carbon monoxide occurs at a low temperature, such as at
a temperature of less than or equal to about 500.degree. C.
[0019] The following description provides specific details, such as
material compositions and processing conditions (e.g.,
temperatures, pressures, flow rates, etc.) in order to provide a
thorough description of embodiments of the disclosure. However, a
person of ordinary skill in the art will understand that the
embodiments of the disclosure may be practiced without necessarily
employing these specific details. Indeed, the embodiments of the
disclosure may be practiced in conjunction with conventional
systems and methods employed in the industry. In addition, only
those process components and acts necessary to understand the
embodiments of the disclosure are described in detail below. A
person of ordinary skill in the art will understand that some
process components (e.g., pipelines, line filters, valves,
temperature detectors, flow detectors, pressure detectors, and the
like) are inherently disclosed herein and that adding various
conventional process components and acts would be in accord with
the disclosure. In addition, the drawings accompanying the
disclosure are for illustrative purposes only, and are not meant to
be actual views of any particular material, device, or system.
[0020] As used herein, spatially relative terms, such as "beneath,"
"below," "lower," "bottom," "above," "upper," "top," "front,"
"rear," "left," "right," and the like, may be used for ease of
description to describe one element's or feature's relationship to
another element(s) or feature(s) as illustrated in the figure.
Unless otherwise specified, the spatially relative terms are
intended to encompass different orientations of the materials in
addition to the orientation depicted in the figure. For example, if
materials in the figure are inverted, elements described as "below"
or "beneath" or "under" or "on bottom of" other elements or
features would then be oriented "above" or "on top of" the other
elements or features. Thus, the term "below" can encompass both an
orientation of above and below, depending on the context in which
the term is used, which will be evident to one of ordinary skill in
the art. The materials may be otherwise oriented (e.g., rotated 90
degrees, inverted, flipped) and the spatially relative descriptors
used herein interpreted accordingly.
[0021] As used herein, the singular forms "a," "an," and "the" are
intended to include the plural forms as well, unless the context
clearly indicates otherwise.
[0022] As used herein, "and/or" includes any and all combinations
of one or more of the associated listed items.
[0023] As used herein, the term "hydrocarbon" means and include a
carbon-containing compound that includes at least one carbon (C1)
atom.
[0024] As used herein, the term "configured" refers to a size,
shape, material composition, material distribution, and arrangement
of one or more of at least one system or apparatus facilitating
operation of one or more of the structure and the system or
apparatus in a pre-determined way.
[0025] As used herein, the term "substantially" in reference to a
given parameter, property, or condition means and includes to a
degree that one skilled in the art would understand that the given
parameter, property, or condition is met with a small degree of
variance, such as within acceptable manufacturing tolerances. For
example, a parameter that is substantially met may be at least
about 90% met, at least about 95% met, or even at least about 99%
met.
[0026] As used herein, the terms "about" and "approximately" in
reference to a numerical value for a particular parameter are
inclusive of the numerical value and a degree of variance from the
numerical value that one of ordinary skill in the art would
understand is within acceptable tolerances for the particular
parameter. For example, "about" in reference to a numerical value
may include additional numerical values within a range of from 90.0
percent to 110.0 percent of the numerical value, such as within a
range of from 95.0 percent to 105.0 percent of the numerical value,
within a range of from 97.5 percent to 102.5 percent of the
numerical value, within a range of from 99.0 percent to 101.0
percent of the numerical value, within a range of from 99.5 percent
to 100.5 percent of the numerical value, or within a range of from
99.9 percent to 100.1 percent of the numerical value.
[0027] As used herein, the terms "comprising," "including,"
"containing," "characterized by," and grammatical equivalents
thereof are inclusive or open-ended terms that do not exclude
additional, unrecited elements or method acts, but also include the
more restrictive terms "consisting of" and "consisting essentially
of" and grammatical equivalents thereof.
[0028] As used herein, the term "may" with respect to a material,
structure, feature or method act indicates that such is
contemplated for use in implementation of embodiments of the
disclosure and such term is used in preference to the more
restrictive term "is" so as to avoid any implication that other,
compatible materials, structures, features and methods usable in
combination therewith should or must be excluded.
[0029] As used herein, the terms "catalyst material" and "catalyst"
and their grammatical equivalents each mean and include a material
formulated to promote one or more reactions, resulting in the
formation of a product.
[0030] As used herein, the term "negative electrode" and
grammatical equivalents means and includes an electrode having a
relatively lower electrode potential in an electrochemical cell
(e.g., lower than the electrode potential in a positive electrode
therein).
[0031] Conversely, as used herein, the term "positive electrode"
and grammatical equivalents means and includes an electrode having
a relatively higher electrode potential in an electrochemical cell
(e.g., higher than the electrode potential in a negative electrode
therein).
[0032] As used herein, the term "electrolyte" and grammatical
equivalents means and includes an ionic conductor, which can be in
a solid state, a liquid state, or a gaseous state (e.g.,
plasma).
[0033] As illustrated in FIG. 1, a system 100 according to
embodiments of the disclosure comprises an electrochemical cell
102, which comprises a positive electrode 104 (e.g., an anode), an
electrolyte 106, and a negative electrode 108 (e.g., a cathode),
where the electrolyte 106 is interposed between the positive
electrode 104 and the negative electrode 108. The positive
electrode 104 and the negative electrode 108 are electrically
coupled to a power source 110. The system 100 comprises a first
chamber 112 adjacent to the positive electrode 104, where the
positive electrode 104 comprises an oxidation catalyst 114. The
system 100 further comprises a second chamber 116 adjacent to the
negative electrode 108, where the negative electrode 108 comprises
a reduction catalyst 118. The first chamber 112 is coupled to a
first inlet 120 that is configured to direct a first feed stream
122 into the first chamber 112. The second chamber 116 is coupled
to a second inlet 124 that is configured to direct a second feed
stream 126 into the second chamber 116. The first chamber 112 is
coupled to a first outlet 128 that directs a first product stream
130 away from the first chamber 112. The second chamber 116 is
coupled to a second outlet 132 that directs a second product stream
134 away from the second chamber 116. The first product stream 130
and the second product stream 134 including the desired products
may be collected and recovered. The power source 110 is configured
to apply a potential difference (e.g., voltage) between the
negative electrode 108 and the positive electrode 104 of the
electrochemical cell 102.
[0034] While not shown, the system 100 may include one or more
apparatuses (e.g., heat exchangers, pumps, compressors, expanders,
mass flow control devices, etc.) to adjust one or more of
temperature, pressure, and flow rate of the first feed stream 122
and the second feed stream 126 delivered to the positive electrode
104 and to the negative electrode 108, respectively. The flow rates
for the first feed stream 122 and second feed stream 126 may be
adjusted depending on the compositions of the first feed stream 122
and second feed stream 126. The flow rates may range from about 20
ml min.sup.-1 to about 150 ml min.sup.-1. The temperature of the
system 100 may be adjusted from about 25.degree. C. to about
500.degree. C.
[0035] The first feed stream 122 enters the system 100 through the
first inlet 120 and passes into the first chamber 112 and over the
positive electrode 104. The first feed stream 122 includes carbon
dioxide and at least one hydrocarbon. The hydrocarbon may, for
example, be an alkane, such as methane, ethane, propane, other
linear alkane, or a combination thereof. The first feed stream 122
may, therefore, include carbon dioxide and the alkane. The first
feed stream 122 may optionally include hydrogen gas as a source of
hydrogen ions. By way of example only, the first feed stream 122
may include air, biogas, a carbon dioxide-containing feed stream
from an industrial process, or a substantially pure source of
carbon dioxide and the alkane. In certain embodiments the first
feed stream 122 includes carbon dioxide and methane. In certain
embodiments, the first feed stream 122 includes carbon dioxide,
methane, and ethane. The hydrocarbon of the first feed stream 122
provides a source of hydrogen ions (e.g., protons) as a result of
catalytic electrolysis, which are used to reduce (e.g., chemically
reduce) the second feed stream 126 at the negative electrode 108
using the reduction catalyst 118. The carbon dioxide in the first
feed stream 122 may be present in a liquid phase (e.g., CO.sub.2
dissolved in an ionic liquid), a gaseous phase, or a combination
thereof. The first feed stream 122 is substantially free of water,
such as including less than about 5% water or less than about 1%
water.
[0036] The positive electrode 104 may comprise an oxidation
catalyst 114 that is formulated to oxidize starting materials
within the first feed stream 122. In some embodiments, the
oxidation catalyst 114 is on the surface of the positive electrode,
and the oxidation catalyst is capable of interacting with starting
materials in the first feed stream. The oxidation catalyst 114 may
convert the starting materials within the first feed stream into a
first product stream. The positive electrode 104 may be formed of
and include at least one catalyst-doped material compatible with
the material compositions of the electrolyte 106, the first feed
stream 122, the negative electrode 108, and the operating
conditions (e.g., temperature, pressure, current density, etc.) of
the electrochemical cell 102.
[0037] The oxidation catalyst 114 may comprise a single material
(e.g., a single metal) or at least two materials. For example, the
oxidation catalyst 114 may be a supported metal catalyst doped with
a metal. The metal may be palladium (Pd), platinum (Pt), rhodium
(Rh), ruthenium (Ru), iridium (Ir), nickel (Ni), cobalt (Co), or a
combination thereof. The supported metal catalyst may be a
perovskite material, such as BZCYYb, BSNYYb, doped BaCeO.sub.3,
BaZrO.sub.3, Ba.sub.2(YSn)O.sub.5.5, Ba.sub.3(CaNb.sub.2)O.sub.9.
The perovskite material of the oxidation catalyst 114 may be doped
with Ni, Au, Pd, Pt, Ir, Rh, Ru, Co, or a combination thereof. The
oxidation catalyst 114 may be BZCYYb doped with Ni (or Ni--BZCYYb).
The metal support may be PrBaMn.sub.2O.sub.5+.delta. (PBM) material
doped with a metal from the group as described above. In some
embodiments, the positive electrode 104 is PrBaMn2O5+.delta. (PBM)
doped with Pt (or PBM/Pt) as the oxidation catalyst 114. The
oxidation catalyst 114 may also be a metal-doped perovskite, where
the perovskite may be LaAl.sub.0.2Ni.sub.0.8O.sub.3 doped with
iridium (Ir), palladium (Pd), platinum (Pt), rhodium (Rh),
ruthenium (Ru), or a combination thereof. In some embodiments, the
positive electrode 104 comprises Ni--BZCYYb, where surface Ni
species are the oxidation catalyst 114. In additional embodiments,
the positive electrode 104 comprises NiAu--BZCYYb, where the
surface NiAu species are the oxidation catalyst 114.
[0038] In some embodiments, the oxidation catalyst 114 of the
positive electrode 104 converts methane (CH.sub.4) and carbon
dioxide (CO.sub.2) of the first feed stream 122 to carbon monoxide
(CO) according to the following reaction:
CH.sub.4+CO.sub.2.fwdarw.2CO+4H.sup.++4e.sup.- (5)
[0039] In some embodiments, the first feed stream 122 includes
ethane (C.sub.2H.sub.6). When ethane is present, the positive
electrode 104 catalyzes the following reaction:
C.sub.2H.sub.6.fwdarw.C.sub.2H.sub.4+2e.sup.-+2H.sup.+ (6)
[0040] The generated hydrogen ions are transported from the
positive electrode 104 through the electrolyte 106 to the negative
electrode 108. The hydrogen ions may be involved in the
hydrogenation (a reduction reaction) of starting materials in the
second feed stream 126, where the second feed stream 126 is
introduced into a second chamber 116 via second inlet 124 and
passed through the negative electrode 108. The second feed stream
126 may comprise a nitrogen source, such as nitrogen gas (N.sub.2),
nitrous oxide (N.sub.2O), nitrogen monoxide (NO), or a combination
thereof. The second feed stream 126 optionally comprises water. In
some embodiments, the second feed stream 126 comprises one or more
of dinitrogen, nitrogen monoxide, nitrogen dioxide, or a
combination thereof and water. The second feed stream 126 may, for
example, include air, a nitrogen source-containing feed stream from
an industrial process, or a substantially pure nitrogen source. The
hydrogen ions produced from the carbon dioxide in the first feed
stream 122 may be reacted with the nitrogen source of the second
feed stream 126 to produce the ammonia.
[0041] The reduction catalyst 118 of the negative electrode 108 is
formed of and includes a material that interacts with and reduces
(e.g., hydrogenates) the one or more components of the second feed
stream 126. When the second feed stream 126 comprises, for example,
dinitrogen (N.sub.2), the reduction catalyst 118 of the negative
electrode 108 catalyzes the following reactions:
N.sub.2+6e.sup.-+6H.sup.+.fwdarw.2NH.sub.3 (7)
2H.sup.++2e.sup.-.fwdarw.H.sub.2 (8)
N.sub.2+3H.sub.2.fwdarw.2NH.sub.3 (9)
The reduction reactions of dinitrogen gas and hydrogen ions to form
ammonia and hydrogen gas, respectively, compete with each other at
the negative electrode 108. In some embodiments the negative
electrode 108 selectively reduces dinitrogen, as illustrated in eq.
7, over reducing hydrogen ions that diffuse to the negative
electrode 108, as illustrated in eq. 8. In some embodiments, the
negative electrode 108 chemically reduces dinitrogen using hydrogen
formed in eq. 8, as illustrated in eq. 9. The reduced nitrogen gas
may be ammonia or hydrazine (for partial reduction).
[0042] The negative electrode 108 may comprise a single material
(e.g., a single metal) or at least two materials (e.g., a
bimetallic material). Similar to the positive electrode 104, the
negative electrode 108 may be formed of and include at least one
catalyst-doped material compatible with the material compositions
of the electrolyte 106, the second product stream 134, the positive
electrode 104, and the operating conditions of the electrochemical
cell 102. The negative electrode 108 may be an alloy, such as an
AgPd alloy or a Ni-based alloy. The negative electrode 108 may, for
example, comprise a cermet material comprising at least one
catalyst material including one or more of a metal, metal alloy, or
at least one perovskite, such as a doped perovskite cermet
material, denoted as M-perovskite, where M may be a metal, such as
a noble metal (Pt, Pd, Rh, Ru, Ir), Fe, Ag, or a combination
thereof, or another material. For example, and not by limitation,
the negative electrode 108 may comprise M-BZCYYb, M-BSNYYv,
M-PrBa.sub.0.5Sr.sub.0.5Co.sub.1.5Fe.sub.0.5O.sub.5+.delta.
(M-PBSCF), M-PrNi.sub.0.5Co.sub.0.5O.sub.3-.delta. (M-PNC),
M-Pr.sub.0.5Ba.sub.0.5Co.sub.xFe.sub.1-x.sup.O.sub.3,
M-BaCe.sub.0.9Y.sub.0.1O.sub.3, M-Pr.sub.0.5Ba.sub.0.5FeO.sub.3,
M-BaCeO.sub.3, M-BaZrO.sub.3, M-Ba.sub.2(YSn)O.sub.5.5,
M-Ba.sub.3(CaNb.sub.2)O.sub.9), an MNi/perovskite (such as
RuNi/perovskite) cermet (MNi-perovskite, such as RuNi-perovskite)
material (e.g., MNi-BZCYYb, MNi-BSNYYb, MNi-PBSCF, MNi-PNC,
MNi-Pr.sub.0.5Ba.sub.0.5Co.sub.xFe.sub.1-xO.sub.3,
MNi-Pr.sub.0.5Ba.sub.0.5FeO.sub.3, MNi-BaCeO.sub.3,
MNi-BaZrO.sub.3, MNi-Ba.sub.2(YSn)O.sub.5.5,
MNi-Ba.sub.3(CaNb.sub.2)O.sub.9), an MCe/perovskite cermet (such as
a RuCe-perovskite) material (e.g., MCe-BZCYYb, MCe-BSNYYb,
MCe-PBSCF, MCe-PNC,
MCe-Pr.sub.0.5Ba.sub.0.5Co.sub.xFe.sub.1-xO.sub.3,
MCe-Pr.sub.0.5Ba.sub.0.5FeO.sub.3, MCe-BaCeO.sub.3,
MCe-BaZrO.sub.3, MCe-Ba.sub.2(YSn)O.sub.5.5,
MCe-Ba.sub.3(CaNb.sub.2)O.sub.9), and an MNiCe/perovskite cermet
(RuNiCe-perovskite) material (e.g., RuNiCe--BZCYYb, RuNiCe--BSNYYb,
RuNiCe--PBSCF, RuNiCe--PNC,
RuNiCe--Pr.sub.0.5Ba.sub.0.5Co.sub.xFe.sub.1-xO.sub.3,
RuNiCe--Pr.sub.0.5Ba.sub.0.5FeO.sub.3, RuNiCe--BaCeO.sub.3,
RuNiCe--BaZrO.sub.3, RuNiCe--Ba.sub.2(YSn)O.sub.5.5,
RuNiCe--Ba.sub.3(CaNb.sub.2)O.sub.9. The negative electrode 108 may
be, for example, a metal-doped ceria, such as lanthanum-doped ceria
(LDC), samarium-doped ceria (SDC), or a combination thereof.
[0043] The reduction catalyst 118 of the negative electrode 108 may
comprise a dopant integrated into the at least one catalyst
material. For example, the dopant of the reduction catalyst 118 may
comprise a metal-doped ceria, such as lanthanum-doped ceria (LDC)
or samarium-doped ceria (SDC). The metal-doped ceria may be further
doped with a metal, such as a noble metal (e.g., Pt, Pd, Rh, Ir,
Ru) or iron (Fe). In some embodiments, the negative electrode 108
is PBSCF and comprises a reduction catalyst 118 that is Ru-doped
LDC (Ru/LDC). The reduction catalyst 118 may further comprise a
metal hydroxide species. In some embodiments, the reduction
catalyst 118 is Ru-doped LDC having a Ru--OH surface species. In
other embodiments, the reduction catalyst may be a potassium- or
aluminum-modified Fe--BaCe.sub.0.9Y.sub.0.1O.sub.3. In some
embodiments, the reduction catalyst 118 comprises single atoms
(e.g., single Ru atoms), nanoclusters (e.g., Ru--NCs), or
nanoparticles (e.g., Ru-NPs).
[0044] The positive electrode 104 and the negative electrode 108
may individually exhibit any desired dimensions (e.g., length,
width, thickness) and any desired shape (e.g., a cubic shape,
cuboidal shape, a tubular shape, a tubular spiral shape, a
spherical shape, a semi-spherical shape, a cylindrical shape, a
semi-cylindrical shape, a conical shape, a triangular prismatic
shape, a truncated version of one or more of the foregoing, and
irregular shape) as are known in the art. For example, the
dimensions and the shapes of the positive electrode 104 and the
negative electrode 108 may be selected relative to the dimensions
and the shape of the electrolyte 106 such that the electrolyte 106
substantially intervenes between opposing surfaces of the positive
electrode 104 and the negative electrode 108. The material
compositions of the positive electrode 104 and the negative
electrode 108 may be selected relative to one another, relative to
the electrolyte 106, the components of the first feed stream 122,
and/or the components of the second feed stream 126. The oxidation
catalyst 114 and the reduction catalyst 118 may be incorporated
into the positive electrode 104 and the negative electrode 108 by
conventional techniques.
[0045] The electrolyte 106 comprises at least one electrolyte
material exhibiting ionic conductivity, such as H.sup.+
conductivity. In some embodiments, the electrolyte 106 is a proton
exchange membrane (PEM). The electrolyte 106 enables H.sup.+ to
move from the positive electrode 104 to the negative electrode 108.
The thickness of the electrolyte 106 should comprise a thickness to
effectively transfer H.sup.+ but not so thick as to require a large
over potential to sustain H.sup.+ transport. For instance, when the
thickness of the positive electrode 104 and the negative electrode
108 may be substantially the same, the thickness of the electrolyte
106 is at least the sum of the thicknesses of the positive
electrode 104 and the negative electrode 108. In some embodiments,
the thickness of the electrolyte 106 is substantially the same as
one of the positive electrode 104 or the negative electrode 108. In
some embodiments, the positive electrode 104 is of sufficient
thickness to provide mechanical support for the system 100, and the
thickness of the electrolyte 106 is about 10 .mu.m.
[0046] The electrolyte 106 may be formed of a material that
exhibits an ionic conductivity of greater than or equal to about
10.sup.-2 S/cm (e.g., within a range of from about 10.sup.-2 S/cm
to about 1 S/cm) at one or more temperatures within a range of from
about 150.degree. C. to about 650.degree. C. (e.g., from about
300.degree. C. to about 500.degree. C.). In addition, the
electrolyte 106 may be formulated to remain substantially adhered
(e.g., laminated) to the positive electrode 104 and the negative
electrode 108 at relatively high current densities, such as at
current densities greater than or equal to about 0.1 amperes per
square centimeter (A/cm.sup.2) (e.g., greater than or equal to
about 0.5 A/cm.sup.2, greater than or equal to about 1.0
A/cm.sup.2, greater than or equal to about 2.0 A/cm.sup.2, etc.).
For example, the electrolyte 106 may comprise one or more of a
solid acid material, a polybenzimidazole (PBI) material (e.g., a
doped PBI material), and a BZCYYb material (e.g.,
BaZr.sub.0.1Ce.sub.0.7Y.sub.0.1Yb.sub.0.1O.sub.3-.delta. or a doped
variant). The material composition of the electrolyte 106 may
provide the electrolyte 106 with enhanced ionic conductivity at a
temperature within the range of from about 150.degree. C. to about
650.degree. C. as compared to conventional electrolytes (e.g.,
membranes employing conventional electrolyte materials, such as
yttria-stabilized zirconia (YSZ)) of conventional electrochemical
cells.
[0047] The electrolyte 106 comprises a perovskite material (e.g., a
BZCYYb, a BSNYYb, a doped BaCeO.sub.3, a doped
BaZrO.sub.3.Ba.sub.2(YSn)O.sub.5.5, Ba.sub.3(CaNb.sub.2)O.sub.9,
etc.) having an operational temperature within a range of from
about 350.degree. C. to about 650.degree. C., the negative
electrode 108 may comprise a catalyst-doped perovskite material
compatible with the perovskite material of the electrolyte 106.
[0048] In some embodiments, the electrolyte 106 is formed of and
includes at least one perovskite material having an operational
temperature (e.g., a temperature at which the H.sup.+ conductivity
of the perovskite material is greater than or equal to about
10.sup.-2 S/cm, such as within a range of from about 10.sup.-2 S/cm
to about 10.sup.-1 S/cm) within a range of from about 350.degree.
C. to about 650.degree. C. In some embodiments, the perovskite
material is a proton conducting ceramic. As a non-limiting example,
the electrolyte 106 may comprise one or more of a yttrium- and
ytterbium-doped barium-zirconate-cerate (BZCYYb), a yttrium- and
ytterbium-doped barium-strontium-niobate (BSNYYb), doped
barium-cerate (BaCeO.sub.3) (e.g., yttrium-doped BaCeO.sub.3
(BCY)), doped barium-zirconate (BaZrO.sub.3) (e.g., yttrium-doped
BaCeO.sub.3 (BZY)), barium-yttrium-stannate
(Ba.sub.2(YSn)O.sub.5.5); and barium-calcium-niobate
(Ba.sub.3(CaNb.sub.2)O.sub.9). In some embodiments, the electrolyte
106 comprises BZCYYb (e.g.,
BaZr.sub.0.1Ce.sub.0.7Y.sub.0.1Yb.sub.0.1O.sub.3-.delta. and
BaZr.sub.0.4Ce.sub.0.4Y.sub.0.1Yb.sub.0.1O.sub.3-.delta.).
[0049] The system 100 may be equipped with heating apparatuses that
maintain substantially the same temperature across the system 100.
The temperature within the system 100 may be maintained at about
500.degree. C. or less. In some embodiments, the system 100
operates at a temperature of about 400.degree. C. or less.
[0050] While FIG. 1 illustrates the system 100 as including a
single electrochemical cell 102, the system 100 may be used in
series or in parallel with other systems to maximize production
(i.e., scale-up) of ammonia simultaneous with consumption of carbon
dioxide.
[0051] Embodiments of the disclosure will now be described with
reference to FIG. 2, which is a flow chart illustrating a method
200 for producing ammonia. The method 200 is used to convert carbon
dioxide into ammonia and other commercially desirable products,
such as carbon monoxide. The method 200 produces ammonia while
simultaneously consuming carbon dioxide. As shown in act 202 the
process comprises introducing (e.g., providing) the first feed
stream 122 to the positive electrode 104 of the electrochemical
cell 102 (see FIG. 1), which includes the positive electrode 104,
the negative electrode 108, and the electrolyte 106 as described
above. The method 200 may include introducing (e.g., providing) the
second feed stream 126 to the negative electrode 108, as shown in
act 204. As shown in act 206, a potential difference is applied
between the positive electrode 104 and the negative electrode 108
of the electrochemical cell 102 to produce hydrogen ions, and the
hydrogen ions diffuse through the electrochemical cell 102.
Applying the potential difference between the positive electrode
104 and the negative electrode 108 produces the first product
stream 130, where the first product stream 130 comprises carbon
monoxide. Additionally, applying the potential difference between
the positive electrode 104 and the negative electrode 108 produces
the second product stream 134, where the second product stream 134
comprises ammonia. The reactions within the system 100 may occur at
a temperature of about 500.degree. C. In some other embodiments,
the act 206 occurs at a temperature of about 400.degree. C.
[0052] As described above, the first feed stream 122 comprises
carbon dioxide. In some embodiments, the first feed stream 122
comprises carbon dioxide and one or more alkane. In some
embodiments, the first feed stream 122 comprises carbon dioxide and
methane. In other embodiments, the first feed stream 122 comprises
carbon dioxide, methane, and another alkane, such as ethane. In
some embodiments, the first feed stream 122 comprises carbon
dioxide and one or more alkane and is substantially free of
water.
[0053] As described above, the second feed stream 126 comprises
dinitrogen, nitrogen monoxide, nitrogen dioxide, or a combination
thereof. In some embodiments, the second feed stream 126 comprises
one or more of dinitrogen, nitrogen monoxide, nitrogen dioxide, and
water. In other embodiments, the act 204 of introducing the second
feed stream 126 over the negative electrode 108 comprises passing
the second feed stream 126 over a Ru-LDC catalyst over a PBSCF
material. In yet other embodiments, passing the second feed stream
126 over a Ru-LDC reduction catalyst 118 over a PBSCF material
comprises interacting the second feed stream 126 with a metal
hydroxide catalyst, such as Ru--OH/LDC.
[0054] As described above, applying the potential difference
between the positive electrode 104 and the negative electrode 108
of the electrochemical cell produces the first product stream 130
comprising carbon monoxide over the positive electrode 104. In some
embodiments, producing the first product stream 130 comprising
carbon monoxide further comprises forming the first product stream
130 that is substantially free of carbon dioxide. If the first feed
stream 122 comprises carbon dioxide and at least one hydrocarbon,
then the first product stream 130 is substantially free of carbon
dioxide and the at least one hydrocarbon, such as containing less
than about 10% of carbon dioxide and the at least one hydrocarbon.
In some embodiments, the first product stream 130 may comprise less
than about 5% of carbon dioxide and the at least one
hydrocarbon.
[0055] As described above, applying a potential difference between
the positive electrode 104 and the negative electrode 108 of the
electrochemical cell produces the second product stream 134. The
applied potential difference produces hydrogen ions that diffuse
through the cell and to the negative electrode 108. At the negative
electrode 108, the hydrogen ions react with the nitrogen source of
the second feed stream 126 to produce ammonia in the second product
stream 134. In other words, the second product stream 134 may
comprise ammonia, as produced from the reduction of dinitrogen,
nitrogen monoxide, nitrogen dioxide, or a combination thereof. In
some embodiments, the second product stream 134 may also comprise
hydrazine (the partially hydrogenated product). In some
embodiments, applying a potential difference between the positive
electrode 104 and the negative electrode 108 simultaneously
produces carbon monoxide and ammonia.
[0056] The first product stream 130 and the second product stream
134 including the desired products may be collected and recovered.
The first product stream 130 contains CO, which may be used as a
starting material (e.g., a feed stock) to produce a commodity
product. The commodity product may include, but is not limited to,
acetic acid, formic acid, formaldehyde, methanol, a formate, a
methylated amine, an alcohol other than methanol, a carboxylic
acid, a formamide, an aldehyde, a polycarbonate or other
commercially valuable compound or product. Similarly, the ammonia
of the second product stream 134 may be used as fertilizer, a fuel,
or other commercially valuable compound or product.
[0057] The system 100 containing the electrochemical cell 102 and
the methods according to embodiments of the disclosure are
advantageous over conventional systems for synthesizing ammonia.
Under the conventional HB configurations and electrochemical
methods, carbon dioxide is necessarily produced as a product of
steam reformation. In contrast, in the methods according to
embodiments of the disclosure, the carbon dioxide is converted into
carbon monoxide, while simultaneously producing ammonia. Therefore,
carbon dioxide is consumed rather than produced. The methods
according to embodiments of the disclosure also do not utilize
water (as steam) to drive oxidation. Concomitant oxidation of the
alkane over the positive electrode provides hydrogen ions and
electrons for ammonia synthesis over the negative electrode.
Additionally, the method according to embodiments of the disclosure
may be advantageous over conventional methods because the system
may be operated at intermediate temperatures, such as from about
300.degree. C. to about 500.degree. C. Therefore, the system 100
and method 200 may be utilized in on-site CO.sub.2 conversion and
ammonia synthesis within a single system. Additionally, because
CO.sub.2 is consumed in the process of ammonia synthesis, a carbon
dioxide capture act is not needed.
[0058] The following examples serve to explain embodiments of the
disclosure in more detail. These examples are not to be construed
as being exhaustive or exclusive as to the scope of this
disclosure.
Example 1
[0059] An electrochemical cell, such as the electrochemical cell
102 in FIG. 1, was formed and used to convert nitrogen gas to
ammonia. The electrochemical cell 300A shown in FIG. 3A included a
Ni--BZCYYb anode, a BZCYYb electrolyte, and a doped
PrBa.sub.0.5Sr.sub.0.5CoFeO.sub.5+.delta. (PBSCF) cathode. The
electrochemical cell 300B shown in FIG. 3B included a
PrBaMn.sub.2O.sub.5+.delta.+Pt (PBM/Pt) anode, a doped PBSCF
cathode, and a BZ.sub.4CYYb--S electrode.
[0060] The electrochemical cell 300A was tested for conversion of
nitrogen gas to ammonia using three differently doped cathodes: (1)
ruthenium doped PBSCF (P/Ru), (2) ruthenium doped PBSCF integrated
into a lanthanum doped ceria (LDC) lattice (P/LDCRu-D), and (3)
another ruthenium doped PBSCF integrated into a lanthanum doped
ceria (LDC) lattice (P/LDCRu-W). P/LDCRu-D was produced by exposing
the cathode material to dry air (i.e., substantially free of
moisture). P/LDCRu-W was produced by exposing the cathode material
to ambient air, which was presumed to contain water.
[0061] 4A-4E are graphs illustrating properties of the
electrochemical cells 300A (FIG. 3A), where FIG. 4A illustrates
total current generated from the electrochemical cells. FIG. 4B is
a graph illustrating a comparison of the faradaic efficiencies
(FEs) of the electrochemical cells. FIG. 4C is a graph illustrating
a comparison of current generated by the electrochemical cells.
FIG. 4D is a bar graph illustrating a comparison of the production
rate (PR) of the electrochemical cells. FIG. 4E is a graph
illustrating the current density (solid line) and faradaic
efficiency (empty pentagons) of the electrochemical cell over
time.
[0062] Total current densities of the electrochemical cell 300A
with P/Ru, P/LDCRu-D, and P/LDCRu-W cathodes for the conversion of
N.sub.2 into NH.sub.3 are shown in FIG. 4A and were measured by
conventional techniques. H.sub.2 gas was used as the proton source
over the anode and flowed at a rate of 60 mL min.sup.-1. At the
cathode, N.sub.2 was flowed at a rate of 20 mL min.sup.-1. The use
of P/Ru as the cathode did not produce an appreciable amount of
ammonia, as illustrated by a lower total current density
(J.sub.total). The use of the P/LDCRu-D and P/LDCRu-W cathodes
produced more NH.sub.3 than the P/Ru catalyst. The faradaic
efficiency (FE) of the electrochemical cell 300A using the
different cathode catalysts (P/Ru, P/LDCRu-D, and P/LDCRu-W) are
illustrated in FIGS. 4B and 4C and were measured by conventional
techniques. The FE of the different cathode catalysts of the
electrochemical cells varied as a function of the potential bias
(E.sub.bias), with the P/LDCRu-W catalyst showing the best FE of
23.1% for ammonia production at a E.sub.bias of .about.0.6V from a
N.sub.2 stream over the cathode and a H.sub.2 stream over the
anode. The temperature of the chamber was about 400.degree. C.
Without being bound by any theory, the active catalytic species of
the P/LDCRu-W electrode was proposed to be a surface Ru--OH
species.
[0063] The production rate (PR) was determined for each of the
different cathode catalysts, as illustrated in FIG. 4D. The cathode
catalysts were able to convert N.sub.2 using hydrogen ions
generated from H.sub.2 at the anode to produce ammonia at the
cathode. The PR was found to change as a function of E.sub.bias.
The highest observed PR was measured to be 2.191 mol h.sup.-1
m.sup.-2.
[0064] The stability of the electrochemical cell having a P/LDCRu-W
cathode, Ni--BSCYYb anode, and BZCYYb electrolyte was tested over
the course of 550 hours while measuring the total current generated
(solid lines) and the FE for ammonia production (dots) over that
time frame, as illustrated in FIG. 4E. The E.sub.bias was set to
0.6V and kept constant over the time frame. The temperature was set
to 400.degree. C. and also kept constant over the time frame.
Example 2
[0065] An electrochemical cell having a PBM/Pt anode, a P/LDCRu-W
cathode, and a BZCYYb--S electrolyte was tested for ammonia
production, as illustrated in FIGS. 5A through 5E. FIG. 5A-5E are
graphs illustrating properties of the electrochemical cell (FIG.
3B), where FIG. 5A is a graph illustrating a comparison of current
generated by the electrochemical cells. FIG. 5B is a graph
illustrating the faradaic efficiency (FE) and production rate (PR)
of the electrochemical cells. FIG. 5C is a graph illustrating a
comparison of current generated by the electrochemical cells. FIG.
5D is a graph illustrating the faradaic efficiency and production
rate of the electrochemical cells. FIG. 5E is a graph illustrating
the current density (solid line) and faradaic efficiency (empty
pentagons) of the electrochemical cell over time.
[0066] A feed stream of a 1:1 CO.sub.2:CH.sub.4 mixture was
introduced over the anode at a flow rate of about 60 mL min.sup.-1,
and a feed stream of N.sub.2 gas was introduced over the cathode.
The total current density (dark squares) of the electrochemical
cell and the current density generated attributable to the
formation of ammonia (light circles) are shown in FIG. 5A.
[0067] The faradaic efficiency (FE, dark squares) and the
production rate (PR, light circles) of the electrochemical cell are
illustrated in FIG. 5B. As the potential bias increased, the FE of
the electrochemical cell reached a maximum around 0.6 V and slowly
decreased. As the potential bias increased, the PR of the
electrochemical cell increased.
[0068] When using C.sub.2H.sub.6 in the feed stream to the anode
and N.sub.2 in the feed stream to the cathode, the total current
density of the electrochemical cell and the current generated due
to ammonia increased as a function of increasing E.sub.bias, as
illustrated in FIG. 5C. The FE and PR for ammonia production of the
electrochemical cell under these conditions is illustrated in FIG.
5D. The FE reached a maximum around 0.6V, while the PR of the cell
continued to increase as a function of increasing E.sub.bias.
[0069] The stability of the electrochemical cell over 30 hours,
while switching the potential bias and feed stream contents over
the anode, is shown in FIG. 5E. N.sub.2 gas was flowed over the
cathode. The total current generated throughout the time frame is
shown in solid lines, and the FE for NH.sub.3 production is shown
in empty pentagons. Over the time frame, switching the potential
bias and feed stream (i.e., the proton source) among H.sub.2,
C.sub.2H.sub.6, and CO.sub.2:CH.sub.4 did not appear to appreciably
decrease the total current generated in the electrochemical cell.
These conditions did not appear to change the FE for NH.sub.3
production over the same time frame, indicating that the
electrochemical cell was stable and capable of tandem dry reforming
(oxidation of a hydrogen source and carbon dioxide) and ammonia
production.
[0070] While the disclosure is susceptible to various modifications
and alternative forms, specific embodiments have been shown by way
of example in the drawings and have been described in detail
herein. However, the disclosure is not limited to the particular
forms disclosed. Rather, the disclosure is to cover all
modifications, equivalents, and alternatives falling within the
scope of the following appended claims and their legal equivalent.
For example, elements and features disclosed in relation to one
embodiment may be combined with elements and features disclosed in
relation to other embodiments of the disclosure.
* * * * *