U.S. patent application number 12/212948 was filed with the patent office on 2009-04-23 for methods and apparatus for the synthesis of useful compounds.
This patent application is currently assigned to The University of Connecticut. Invention is credited to Boxun Hu, Victor Stancovski, Steven Lawrence Suib.
Application Number | 20090101516 12/212948 |
Document ID | / |
Family ID | 40377683 |
Filed Date | 2009-04-23 |
United States Patent
Application |
20090101516 |
Kind Code |
A1 |
Suib; Steven Lawrence ; et
al. |
April 23, 2009 |
METHODS AND APPARATUS FOR THE SYNTHESIS OF USEFUL COMPOUNDS
Abstract
The present invention relates to methods and apparatus for
activation of a low reactivity, non-polar chemical compound. In one
example embodiment, the method comprises introducing the low
reactivity chemical compound to a catalyst. At least one of (a) an
oxidizing agent or a reducing agent and (b) a polar compound is
provided to the catalyst and the chemical compound. An alternating
current is applied to the catalyst to produce an activation
reaction in the chemical compound. This activation reaction
produces a useful product. The present invention also relates to a
method for oxidizing aromatic compounds by electrocatalysis to
oxidized products.
Inventors: |
Suib; Steven Lawrence;
(Storrs, CT) ; Hu; Boxun; (Storrs, CT) ;
Stancovski; Victor; (Groton, CT) |
Correspondence
Address: |
CANTOR COLBURN, LLP
20 Church Street, 22nd Floor
Hartford
CT
06103
US
|
Assignee: |
The University of
Connecticut
Farmington
CT
Catelectric Corp.
Hartford
CT
|
Family ID: |
40377683 |
Appl. No.: |
12/212948 |
Filed: |
September 18, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60994854 |
Sep 20, 2007 |
|
|
|
Current U.S.
Class: |
205/338 ;
205/412; 205/456 |
Current CPC
Class: |
H01M 4/8621 20130101;
Y02E 60/50 20130101; C07C 45/36 20130101; H01M 4/9016 20130101;
C07C 45/36 20130101; C07C 49/78 20130101 |
Class at
Publication: |
205/338 ;
205/456; 205/412 |
International
Class: |
C25B 3/02 20060101
C25B003/02 |
Claims
1. A method for oxidizing chemical compounds to oxidized products
by electrocatalysis comprising: i) providing a catalytic cell; ii)
applying a polarized current or voltage to the catalytic cell; iii)
passing a gaseous stream of air or oxygen or a mixture of oxygen;
and one or more inert gases and the compound to be oxidized over
the catalytic cell.
2. A method for oxidizing aromatic compounds to oxidized products
by electrocatalysis comprising the steps of: i) providing a
catalytic cell comprising a cryptomelane-type manganese oxide
octahedral molecular sieve (OMS-2); ii) applying a polarized
current or voltage to the catalytic cell; iii) passing a gaseous
stream of air or oxygen or a mixture of oxygen and one or more
inert gases and the aromatic compound to be oxidized over the
catalytic cell.
3. The method according to claim 2 wherein said catalytic cell
comprises a working electrode comprising a substrate having a
manganese oxide octahedral molecular sieve catalyst (OMS-2)
thereon; a counter electrode and a reference electrode.
4. The method according to claim 3 wherein said OMS-2 contains
nano-metal particles.
5. The method according to claim 4 wherein the metal is chosen from
the group consisting of Ni.sup.2+, Zn.sup.2+, Co.sup.2+, Cu.sup.2+,
Fe.sup.2+, Fe.sup.3+, V.sup.4+, V.sup.5+, Ti.sup.4+, Ti.sup.3+,
Cr.sup.3+, Cr.sup.2+, Co.sup.3+, Cu.sup.1+, Ce.sup.3+, Ce.sup.4+,
La.sup.3+, Na.sup.+, K.sup.+, Ba.sup.2+, Y.sup.3+, Zr.sup.4+,
Li.sup.+, Sr.sup.2+.
6. The method according to claim 2 wherein the OMS-2 containing
nano-metal particles is Pt-OMS-2.
7. The method according to claim 3 wherein the substrate is a
porous material.
8. The method according to claim 7 wherein the porous material has
a pore size of 5-20 mesh.
9. The method according to claim 8 wherein the porous material is
Corning Honeycomb Cordierite.RTM..
10. The method according to claim 7 wherein the porous material is
chosen from the group consisting of yttrium stabilized zirconium,
CeO.sub.2 and HfO.sub.2.
11. The method according to claim 3 wherein the working electrode
comprises silver or platinum gauze supported by an insulated pad,
the working electrode in contact with the substrate having a
cryptomelane-type manganese oxide octahedral molecular sieve
catalyst thereon.
12. The method according to claim 11 wherein the catalyst is
Pt-OMS-2.
13. The method according to claim 11 wherein the counter electrode
is a silver or platinum wire.
14. The method according to claim 11 wherein the reference
electrode is a silver or platinum wire.
15. The method according to claim 2 wherein said catalytic cell is
heated to a temperature of between about 25.degree. and about
900.degree. C.
16. The method according to claim 1 wherein said catalytic cell is
heated to a temperature of between about 100.degree. and about
450.degree. C.
17. The method according to claim 2 wherein the oxidation is
accomplished at a pressure of about 1 atm to about 2 atm.
18. The method according to claim 2 wherein the gaseous stream
further comprises CO.sub.2 and water vapor alone or in
combination.
19. The method according to claim 2 wherein said aromatic compound
is chosen from the group consisting of benzene and its
derivatives.
20. The method according to claim 2 wherein the aromatic compound
is benzene and the oxidized product is acetophenone.
21. A method for oxidizing aromatic compounds to oxidized products
by electrocatalysis comprising the steps of: i) providing a
catalytic cell comprising a metal oxide chosen from the group
consisting of CuO.sub.x, Ni O.sub.x, ZnO and VO.sub.x (wherein x is
an integer from 1-4; ii) applying a polarized current or voltage to
the catalytic cell; iii) passing a gaseous stream of air or oxygen
or a mixture of oxygen and one or more inert gases and the aromatic
compound to be oxidized over the catalytic cell.
22. The method according to claim 21 wherein the catalytic cell is
heated to a temperature of about between about 25.degree. C. and
about 900.degree. C.
23. The method according to claim 21 wherein the oxidation is
accomplished at a pressure of about 1 atm to about 2 atm.
24. The method according to claim 21 wherein the gaseous stream
further comprises CO.sub.2 and water vapor alone or in
combination.
25. The method according to claim 21 wherein the aromatic compound
is a derivative of benzene.
26. The method according to claim 21 wherein the aromatic compound
is benzene and the oxidized product is acetophenone.
Description
[0001] This application claims the benefit of U.S. provisional
patent application No. 60/994,854 filed on Sep. 20, 2007, which is
incorporated herein and made a part hereof by reference for all
purposes as if set forth in its entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to methods and apparatus for
the activation of a low reactivity, non-polar chemical compound.
More specifically, the present invention relates to process for the
synthesis of useful compounds from non-polar compounds such as
carbon dioxide and the like. The present invention also relates to
a method for oxidizing aromatic compounds to oxidized products by
electrocatalysis.
[0003] The chemical reduction of carbon dioxide using molecular
hydrogen is not thermodynamically viable. However, the possibility
to use activated hydrogen-containing compounds for the preparation
of useful products from carbon dioxide is intriguing.
[0004] Some catalysts, e.g., transition metal complexes, have been
shown to catalyze the reduction of carbon dioxide via hydride
complexes, in which the origin of the activated hydrogen is water.
Such reactions result usually in a partial reduction of carbon
dioxide to carbon monoxide. However, the possibility of the further
reduction to formaldehyde, methanol and/or methane is potentially
very significant. Such reduction products are particularly
important in chemical manufacture (formaldehyde and methanol), as
well as fuels (methanol and methane). [see, e.g., "Thermodynamic,
Kinetic and Product Considerations in Carbon Dioxide Reactivity",
F. R. Keene, Chapter 1 in monograph "Electrochemical and
Electrocatalytic Reactions of Carbon Dioxide" (B. P. Sullivan, K.
Krist, and H. E. Guard, eds.); Elsevier (Amsterdam), 1993].
[0005] In particular, formaldehyde and its derivatives serve a wide
variety of end uses such as for plastics and coatings. Formaldehyde
is considered one of the world's most important industrial and
research chemicals, owing to the vast number of chemical reactions
it can participate in.
[0006] As formaldehyde polymerizes readily in the presence of
minute amounts of impurities, the commercial forms usually
available comprise:
[0007] the polymer form, which can be reversibly converted to a
monomer by the reaction of heat or an acid:
H--(OCH.sub.2--)--.sub.n--OH
[0008] the cyclic trimeric form, called trioxane; and
[0009] the aqueous solution in which over 99 of formaldehyde is
present as hydrate or a mixture of oxymethylene glycol
oligomers.
[0010] It would be advantageous to provide methods and apparatus
for activation of a low reactivity, non-polar chemical compound. In
particular, it would be advantageous to provide methods and
apparatus for the reduction of carbon dioxide without the need to
use molecular hydrogen. It would be further advantageous to enable
the reduction of carbon dioxide using water or steam as the source
of hydrogen. It would also be advantageous to enable the oxidation
or reduction of aromatic compounds such as benzene and its
derivatives to derivative compounds, such as acetophenone, a
phenol, cyclohexane, or other benzene derivatives. Another
advantageous possibility is to provide the capability of achieving
a further reduction of formaldehyde-derived polymers to higher
molecular mass alcohols and to olefins.
[0011] The methods and apparatus of the present invention provide
the foregoing and other advantages.
SUMMARY OF THE INVENTION
[0012] The present invention relates to methods and apparatus for
activation of a low reactivity, non-polar chemical compound. In one
example embodiment, the method comprises introducing the low
reactivity chemical compound to a catalyst. At least one of (a) an
oxidizing agent or a reducing agent, and (b) a polar compound is
provided to the catalyst and the chemical compound. An alternating
current is applied to the catalyst to produce an activation
reaction in the chemical compound. This activation reaction
produces a useful product.
[0013] The activation reaction may comprise one of a reduction or
an oxidation reaction. The polar compound may comprise one of water
or steam. One of ammonia, nitric oxide, carbon monoxide, methane,
or the like may be added to the water or steam.
[0014] In another example embodiment, the polar compound may
comprise one of water, ammonia, nitric oxide, and carbon monoxide.
Those skilled in the art will appreciate that other polar compounds
may be used with the present invention.
[0015] In a further example embodiment, the chemical compound and
the at least one of the oxidizing agent or the reducing agent and
the polar compound may be introduced into a chamber containing the
catalyst.
[0016] In one example embodiment, the low reactivity chemical
compound may comprise CO.sub.2. In such an embodiment, the useful
product may comprise formaldehyde in at least one of a monomeric
and a polymeric form. In other example embodiments, the useful
product may comprise at least one of an aldehyde, trioxane, ethane,
ethylene, formaldehyde, and paraformaldehyde. The useful products
may contain at least one of carbon, hydrogen, and oxygen. Still
further, the useful products may comprise at least one of an
alcohol compound and an olefin.
[0017] In a further example embodiment, the chemical compound may
comprise an aromatic compound.
[0018] The aromatic compound may comprise benzene or a benzene
derivative. In such an embodiment, a reducing agent such as
hydrogen may be provided to the catalyst and the aromatic compound,
and the useful product may comprise cyclohexane or a benzene
derivative. Alternatively, an oxidizing agent such as oxygen may be
provided to the catalyst and the aromatic compound, and the useful
product may comprise at least one of acetophenone, a phenol, or a
benzene derivative.
[0019] The catalyst may comprise one of a precious metal, a
semi-conducting oxide, a semi-conducting cermet, and a varistor.
Examples of catalysts that may be used with the present invention
include, but are not limited to catalysts comprising platinum,
platinum black, rhodium, rhodium black, palladium, palladium black,
silver, manganese oxide, a manganese oxide derivative, molybdenum
oxide, a molybdenum oxide derivative, iron oxide, an iron oxide
derivative, cerium oxide, a cerium oxide derivative, titanium
oxide, doped titanium oxide and related compounds, cobalt oxide,
rhodium oxide, zinc oxide, and the like.
[0020] In one example embodiment, the catalyst may comprise a
catalyst layer applied to a porous ceramic substrate. The catalyst
layer may be supported by a layer of a solid electrolyte. The solid
electrolyte layer may be one of a continuous layer or a
discontinuous layer. The solid electrolyte may comprise one of
stabilized zirconia (stabilized with, e.g., gadolinium oxide,
samarium oxide, lanthanum oxide, ytterbium oxide, yttrium oxide or
other adequate materials known to those skilled in the art),
Nafion, other hydrogen ion conducting materials, beta aluminas, or
the like
[0021] The alternating current may be applied across a three-phase
boundary at an interface between the catalyst and the solid
electrolyte layer. In order to apply the alternating current to the
catalyst layer, three electrodes may be provided. For example, a
reference electrode may be applied to the solid electrolyte layer,
a counter electrode may be applied between the catalyst and the
solid electrolyte layer, and a working electrode may be applied to
the catalyst layer.
[0022] In a further example embodiment, a polarization impedance of
the supported catalyst layer may be monitored. The polarization
impedance may be controlled by varying the alternating current,
enabling optimization of the activation reaction.
[0023] In addition, a controlled oxygen partial pressure
environment may be provided at a level of the supported catalyst
layer. The partial pressure of the oxygen at a level of the
catalyst layer may be monitored. The monitoring of the partial
pressure of the oxygen may comprise monitoring an interfacial
impedance of the supported catalyst layer. The partial pressure of
oxygen at a level of the catalyst layer may then be determined as a
function of the interfacial impedance. Alternately, the
polarization impedance of the supported catalyst layer may be
monitored, and the partial pressure of oxygen at the level of the
catalyst layer may be determined as a function of the monitored
polarization impedance.
[0024] In addition, a momentary value of the alternating current
may be determined as a function of the monitored polarization
impedance.
[0025] The amount of the at least one of the oxidizing agent, the
reducing agent, and the polar compound provided may be controlled
in order to optimize the activation reaction. Further, a ratio of
an amount of the chemical compound to an amount of the at least one
of the oxidizing agent, the reducing agent, and the polar compound
provided may be controlled in order to optimize the activation
reaction.
[0026] In a further example embodiment, heat may be applied to the
catalyst in order to optimize the activation reaction.
[0027] The present invention also generally includes a method for
activation of a chemical compound. The chemical compound is
introduced to a catalyst. An oxidizing agent or a reducing agent is
provided to the catalyst and the chemical compound. An alternating
current is applied to the catalyst to produce an activation
reaction in the chemical compound. This activation reaction
produces a useful product. For example, the chemical compound may
comprise a polar compound and the oxidizing or reducing agent may
comprise a polar reactant or a nonpolar reactant. Additionally, the
chemical compound may comprise a nonpolar chemical compound and the
oxidizing or reducing agent may comprise a polar reactant or a
nonpolar reactant.
[0028] The present invention also encompasses apparatus for
activation of a low reactivity, non-polar chemical compound which
can be used to carry out the various embodiments of the methods
discussed above. The apparatus may comprise a catalyst, a means for
introducing the low reactivity chemical compound to the catalyst, a
means for providing at least one of (a) an oxidizing agent or a
reducing agent, and (b) a polar compound to the catalyst and the
chemical compound, and means for applying an alternating current to
the catalyst to produce an activation reaction in the chemical
compound, such that the activation reaction produces a useful
product.
[0029] The present invention also relates to a method for oxidizing
chemical compounds to oxidized products by electrocatalysis
comprising: providing a catalytic cell, applying a polarized
current or voltage to the catalytic cell and passing a gaseous
stream of air or oxygen or a mixture of oxygen and one or more
inert gases and the compound to be oxidized over the catalytic
cell.
[0030] The present invention also relates to a method for oxidizing
aromatic compounds to oxidized products by electrocatalysis
comprising the steps of: providing a catalytic cell comprising a
cryptomelane-type manganese oxide octahedral molecular sieve
(OMS-2); applying a polarized current or voltage to the catalytic
cell; and passing a gaseous stream of air or oxygen or a mixture of
oxygen and one or more inert gases and the aromatic compound to be
oxidized over the catalytic cell.
[0031] In one embodiment the catalytic cell comprises a working
electrode comprising a substrate having a manganese oxide
octahedral molecular sieve catalyst (OMS-2) thereon; a counter
electrode and a reference electrode.
[0032] In further embodiment the OMS-2 contains nano-metal
particles.
[0033] In further embodiment the metal contained in the OMS-2
having nano-metal particles is chosen from the group consisting of
Ni.sup.2+, Zn.sup.2+, Co.sup.2+, Cu.sup.2+, Fe.sup.2+, Fe.sup.3+,
V.sup.4+, V.sup.5+, Ti.sup.4+, Ti.sup.3+, Cr.sup.3+, Cr.sup.2+,
Co.sup.3+, Cu.sup.1+, Ce.sup.3+, Ce.sup.4+, La.sup.3+, Na.sup.+,
K.sup.+, Ba.sup.2+, Y.sup.3+, Z.sup.4+, Li.sup.+, Sr.sup.2+.
[0034] In a further embodiment the OMS-2 containing nano-metal
particles is Pt-OMS-2.
[0035] In a further embodiment the substrate having manganese oxide
octahedral molecular sieve catalyst (OMS-2) is a porous material
preferably having a pore size of 5-20 mesh.
[0036] Preferably the porous substrate is Corning Honeycomb
Cordierite.RTM., yttrium stabilized zirconium, CeO.sub.2 or
HfO.sub.2.
[0037] In a further embodiment the catalytic cell comprises a
working electrode comprising silver or platinum gauze supported by
an insulated pad, the working electrode in contact with the
substrate, the substrate having a cryptomelane-type manganese oxide
octahedral molecular sieve catalyst thereon (preferably Pt-OMS-2).
The counter electrode is a silver or platinum wire and the
reference electrode is a silver or platinum wire.
[0038] In a further embodiment the catalytic cell is heated to a
temperature of between about 25.degree. and about 900.degree. C.,
preferably between about 100.degree. and about 450.degree. C.
[0039] In further embodiment the oxidation is accomplished at a
pressure of about 1 atm to about 2 atm.
[0040] In a further embodiment the gaseous stream further comprises
CO.sub.2 and water vapor alone or in combination.
[0041] In a further embodiment the aromatic compound is a
derivative of benzene, preferably the aromatic compound is benzene
and the oxidized product is acetophenone.
[0042] The present invention also relates to a method for oxidizing
aromatic compounds to oxidized product by electrocatalysis
comprising the steps of: providing a catalytic cell comprising a
metal oxide chosen from the group consisting of CuO.sub.x, Ni
O.sub.x, ZnO and VO.sub.x (wherein x is an integer from 1-4;
applying a polarized current or voltage to the catalytic cell; and
passing a gaseous stream of air or oxygen or a mixture of oxygen
and one or more inert gases and the aromatic compound to be
oxidized over the catalytic cell.
[0043] In another embodiment the catalytic cell is heated to a
temperature of about between about 25.degree. C. and about
900.degree. C. preferably between about 100.degree. C. and about
450.degree. C.
[0044] In another embodiment the oxidation is accomplished at a
pressure of about 1 atm to about 2 atm.
[0045] In another embodiment the gaseous stream further comprises
CO.sub.2 and water vapor alone or in combination.
[0046] In another embodiment the aromatic compound is a derivative
of benzene.
[0047] In another embodiment the aromatic compound is benzene and
the oxidized product is acetophenone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0048] The present invention will hereinafter be described in
conjunction with the appended drawing figures, wherein like
reference numerals denote like elements, and:
[0049] FIG. 1 shows an example embodiment of an apparatus in
accordance with the present invention;
[0050] FIG. 2 shows a further example embodiment of an apparatus in
accordance with the present invention;
[0051] FIG. 3 shows an example embodiment of an electrode
arrangement in accordance with the present invention;
[0052] FIG. 4 shows NMR analysis results for the output achieved
with one example embodiment of the present invention;
[0053] FIG. 5 shows NMR analysis results for the output achieved
with a further example embodiment of the present invention;
[0054] FIGS. 6 and 7 show scanning electron microscopy images of
the catalyst assembly at different resolutions, respectively, in
accordance with an example embodiment of the invention;
[0055] FIG. 8 shows an NMR spectrum for the output achieved with a
further example embodiment of the present invention;
[0056] FIG. 9 shows a polarization Bode spectrum from one example
embodiment of the present invention;
[0057] FIG. 10 shows a single frequency EIS (Electrochemical
Impedance Spectroscopy) spectrum from one example embodiment of the
present invention;
[0058] FIG. 11 shows a further example embodiment of an apparatus
in accordance with the present invention;
[0059] FIG. 12 shows GC-MS results of oxidation of benzene;
[0060] FIG. 13 shows MS of peak 3 (Acetophenone) of GCMS of FIG.
12; and
[0061] FIG. 14 shows MS of peak 3 (p-methylacetophenone) of GCMS of
FIG. 12.
DETAILED DESCRIPTION
[0062] The ensuing detailed description provides exemplary
embodiments only, and is not intended to limit the scope,
applicability, or configuration of the invention. Rather, the
ensuing detailed description of the exemplary embodiments will
provide those skilled in the art with an enabling description for
implementing an embodiment of the invention. It should be
understood that various changes may be made in the function and
arrangement of elements without departing from the spirit and scope
of the invention as set forth in the appended claims.
[0063] The present invention is the product of a joint research
agreement between Catelectric Corp. (Catelectric) and The
University of Connecticut and relates to methods and apparatus for
activation of a low reactivity, non-polar chemical compound in
order to produce useful products. In particular, the present
invention relates to methods and apparatus for the preparation of
useful products, such as, e.g., paraformaldehyde, via the
activation (e.g., reduction or oxidation) of carbon dioxide, using
water as the source of hydrogen. However, as will be explained in
detail below, the present invention is not limited to such
reactions and products. The reaction is activated via the DECAN.TM.
process developed by Catelectric. The DECAN.TM. process is
described in Catelectric's U.S. Pat. No. 7,325,392 issued on Feb.
5, 2008 and entitled "Control Systems for Catalytic Processes" and
in Catelectric's pending in U.S. patent application Ser. No.
11/588,113 filed on Oct. 25, 2006 entitled "Methods and Apparatus
for Controlling Catalytic Processes, Including Catalyst
Regeneration and Soot Elimination" (published as 2007/0095673),
both of which are incorporated herein and made a part hereof by
reference.
[0064] The present invention relates to methods and apparatus for
activation of a low reactivity, non-polar chemical compound. FIG. 1
shows an example embodiment of an apparatus 10 for activation of a
low reactivity, non-polar chemical compound. A low reactivity
chemical compound 12 is introduced to a catalyst (e.g., catalyst
layer 14). The catalyst layer 14 may be supported on a support 16.
At least one of (a) an oxidizing agent or a reducing agent 19, and
(b) a polar compound 18 is provided to the catalyst 14 and the
chemical compound 12. An alternating current (e.g., from
current/voltage source 20) is applied to the catalyst 14 to produce
an activation reaction in the chemical compound 12. This activation
reaction produces a useful product. The present invention also
relates to the oxidation of aromatic compounds preferably benzene
and its derivatives by electrocatalysis. The term aromatic compound
refers to an aryl or heteroaryl compound. An aryl compound refers
to a mono, bi or tricyclic aromatic C.sub.6-C.sub.14 carbocycle,
which can be optionally substituted by 1 to 5 substituents.
Examples include but are not limited to benzene, toluene, biphenyl
phenol, xylene, and napthalene. Heteroaryl refers to a
C.sub.2-C.sub.14 mono, bi or tricyclic ring (optionally substituted
with 1-5 substituents, which may be the same or different)
containing 1 to 5 heteroatoms in the ring independently chosen from
O, S, N and NR1 where R1 is C.sub.1-C.sub.6 alkyl or H. Examples
include but are not limited to pyridine, indole thiophene, furan
and isoquinoline. Substituent groups are any substituent with a
molecular weight of about 300 or less. Examples include but are not
limited to halogen, hydroxy, cyano, --C(O)C.sub.1-6
C.sub.1-C.sub.12 alkyl, C.sub.1-C.sub.12 alkenyl or alkynyl, halo
alkyl, C.sub.1-C.sub.12 alkoxy nitro and amino. Compounds which
have substituents added to their core structure are termed
derivatives. For example toluene and acetophenone are derivatives
of benzene.
[0065] It should be appreciated that the term "non-polar chemical
compound" as used herein denotes a chemical compound, which, as a
whole, has a zero permanent dipole moment. For example, by this
definition, CO.sub.2 is considered to be non-polar, even though it
has polar bonds between the individual molecules. Accordingly, the
term "polar compound" as used herein denotes a compound that, as a
whole, has a non-zero dipole moment.
[0066] The activation reaction may comprise one of a reduction or
an oxidation reaction. The polar compound 18 may comprise one of
water or steam. One of ammonia, nitric oxide, carbon monoxide,
methane, or the like may be added to the water or steam.
[0067] In another example embodiment, the polar compound 18 may
comprise one of water, ammonia, nitric oxide, and carbon monoxide.
Those skilled in the art will appreciate that other polar compounds
may be used with the present invention. Further, those skilled in
the art will appreciate that the use of water (or steam) will
facilitate both an oxidation and a reduction reaction.
[0068] In a further example embodiment as shown in FIG. 2, the
chemical compound 12 and the at least one of the oxidizing agent or
the reducing agent 19 and the polar compound 18 may be introduced
into a chamber 22 containing the catalyst 14. The chamber 22 may
comprise a tubular reactor. The alternating current may be
controlled by an electronic control device 24. The chemical
compound 12 (e.g., CO.sub.2) may be introduced to the chamber 22
from a gas tank 11. The polar compound 18 (e.g., water) may be
introduced to the chamber 22 from a peristaltic pump 17. The
oxidizing agent (e.g., oxygen) or the reducing agent (e.g.
hydrogen) 19 may be introduced from tank 21. After passing the
chemical compound 12 and at least one of the oxidizing agent or the
reducing agent 19 and the polar compound 18 through the chamber 22
containing the catalyst 14 and applying the alternating current
thereto, the resulting products of the reaction may be passed
through an ice-water trap 26 and/or a dry ice/liquid nitrogen trap
28 before being separated in a molecular sieve 30 prior to computer
analysis (such as gas chromatography-mass spectrometry (GC-MS),
high performance liquid chromatography-mass spectrometry (HPLC-MS),
nuclear magnetic resonance (NMR) and other analysis techniques) at
analyzer 32.
[0069] In one example embodiment, the low reactivity chemical
compound 12 may comprise CO.sub.2. In such an embodiment, the
useful product may comprise formaldehyde in at least one of a
monomeric and a polymeric form. In other example embodiments, the
useful product may comprise at least one of an aldehyde, trioxane,
ethane, ethylene, formaldehyde, and paraformaldehyde. The useful
products may contain at least one of carbon, hydrogen, and oxygen.
Still further, the useful products may comprise at least one of an
alcohol compound and an olefin. Also, oxygen (O.sub.2) may be a
result of the reaction.
[0070] In a further example embodiment, the chemical compound 12
may comprise an aromatic compound. The aromatic compound may
comprise benzene or a benzene derivative. In such an embodiment,
the reducing agent 19 (such as hydrogen) may be provided to the
catalyst and the aromatic compound, and the useful product may
comprise cyclohexane or a benzene derivative. Alternatively, an
oxidizing agent 19 (such as oxygen) may be provided to the catalyst
and the aromatic compound, and the useful product may comprise at
least one of acetophenone, a phenol, or a benzene derivative.
[0071] The catalyst 14 may comprise one of a precious metal, a
semi-conducting oxide, a semi-conducting cermet, and a varistor.
Examples of catalysts that may be used with the present invention
include, but are not limited to catalysts comprising platinum,
platinum black, rhodium, rhodium black, palladium, palladium black,
silver, manganese oxide, a manganese oxide derivative, molybdenum
oxide, a molybdenum oxide derivative, iron oxide, an iron oxide
derivative, cerium oxide, a cerium oxide derivative, titanium
oxide, doped titanium oxide and related compounds, cobalt oxide,
rhodium oxide, zinc oxide, and the like. Further examples for
catalyst material may generally include oxides of alkali metals,
alkaline earths, lanthanides, actinides, transition metals, and
nonmetals.
[0072] In one example embodiment as shown in FIG. 3, the catalyst
14 may comprise a catalyst layer applied to a support 16 such as
porous ceramic substrate. For example, the catalyst layer 14 may be
supported by a layer 16 of a solid electrolyte. In certain
embodiments, the catalyst 14 may be applied to the solid
electrolyte layer 16, which in turn may be applied onto a separate
support (not shown). The solid electrolyte layer 16 may be one of a
continuous layer or a discontinuous layer. The solid electrolyte 16
may comprise one of stabilized zirconia (stabilized with, e.g.,
gadolinium oxide, samarium oxide, lanthanum oxide, ytterbium oxide,
yttrium oxide or other adequate materials known to those skilled in
the art), Nafion, other hydrogen ion conducting materials, beta
aluminas, or the like. The temperature range of the reactor will be
determined by the specific properties of these materials, known to
those skilled in the art.
[0073] The alternating current may be applied across a three-phase
boundary at an interface between the catalyst 14 and the solid
electrolyte layer 16 via the electronic control device 24. In order
to apply the alternating current to the catalyst layer 14, three
electrodes may be provided. For example, a reference electrode 40
may be applied to the solid electrolyte layer 16, a counter
electrode 42 may be applied to the solid electrolyte layer 16, and
a working electrode 44 may be applied to the catalyst layer 14.
[0074] In a further example embodiment, a polarization impedance of
the supported catalyst layer 14 may be monitored. In order to
monitor the polarization impedance, the electronic control device
24 may include means for determining the applied current and
voltage. The determination of the polarization impedance from the
sensed current is explained in detail in Catelectric's U.S. Pat.
No. 7,352,392 incorporated by reference in its entirety. The
polarization impedance may be controlled by varying the alternating
current from electronic control device 24, enabling optimization of
the activation reaction.
[0075] In addition, a controlled oxygen partial pressure
environment may be provided at a level of the supported catalyst
layer. The oxygen may be produced from the solid electrolyte layer
16 under the voltage applied between the working electrode 44 and
the reference electrode 40, and is a function of the DECAN.TM.
process. Alternately, the oxygen may be provided from tank 21 (FIG.
2). The partial pressure of the oxygen at a level of the catalyst
layer 14 may be monitored. The determining of the partial pressure
of oxygen may also be achieved via the electronic control device 24
as a function of a voltage measurement. For example, a monitoring
of the partial pressure of the oxygen may comprise monitoring an
interfacial impedance of the supported catalyst layer 14. The
partial pressure of oxygen at a level of the catalyst layer 14 may
then be determined as a function of the interfacial impedance.
Alternately, the polarization impedance of the supported catalyst
layer 14 may be monitored as discussed above, and the partial
pressure of oxygen at the level of the catalyst layer 14 may be
determined as a function of the monitored polarization impedance
(e.g., achieved via the electronic control device 24).
[0076] In addition, a momentary value of the alternating current
may be determined by the electronic control device 24 as a function
of the monitored polarization impedance.
[0077] The amount of the oxidizing agent or the reducing agent 19
and/or the polar compound 18 provided may be controlled in order to
optimize the activation reaction. Further, a ratio of an amount of
the chemical compound 12 to an amount of the oxidizing agent or the
reducing agent 19 and/or the polar compound 18 provided may be
controlled in order to optimize the activation reaction.
[0078] In a further example embodiment, heat may be applied to the
catalyst in order to optimize the activation reaction. Heat may be
applied via heating element 34, which is controlled by temperature
control unit 36 (FIG. 2). Oxygen 19 may be applied from an oxygen
source (e.g., tank 21) or may be generated by controlling the
voltage applied to the solid electrolyte layer, as discussed
above.
[0079] The present invention also generally includes a method for
the activation of a chemical compound. The chemical compound 12 is
introduced to a catalyst 14. An oxidizing agent or a reducing agent
19 is provided to the catalyst 14 and the chemical compound 12. An
alternating current is applied to the catalyst 14 to produce an
activation reaction in the chemical compound 12. This activation
reaction produces a useful product. For example, the chemical
compound may comprise a polar compound 12 and the oxidizing or
reducing agent 19 may comprise a polar reactant (e.g., water or
steam) or a non-polar reactant (oxygen or hydrogen). Additionally,
the chemical compound may comprise a non-polar chemical compound 12
(as discussed above) and the oxidizing or reducing agent 19 may
comprise a polar reactant (e.g., water or steam) or a non-polar
reactant (oxygen or hydrogen). For example, one polar compound like
methanol could react with another polar compound like ethanol to
form products of value, or one non-polar compound like benzene
could react with another nonpolar compound like methane.
[0080] As shown in FIG. 11, the present invention also relates to
methods and apparatus for oxidizing chemical compounds (e.g.,
aromatic compounds 112) by electrocatalysis comprising: providing a
catalytic cell 14, applying a polarized current or voltage to the
catalytic cell from a current/voltage source 20, and passing an
oxidizing agent 19 (such as a gaseous stream of air, oxygen, or a
mixture of oxygen and one or more inert gases) and the compound to
be oxidized 112 over the catalytic cell 14.
[0081] The catalytic cell 14 may comprise a cryptomelane-type
manganese oxide octahedral molecular sieve (OMS-2).
[0082] In one embodiment, the catalytic cell 14 comprises a working
electrode 44 comprising a substrate having a manganese oxide
octahedral molecular sieve catalyst (OMS-2) thereon, a counter
electrode 42 and a reference electrode 40.
[0083] In further embodiment the OMS-2 catalyst 14 contains
nano-metal particles.
[0084] In further embodiment the metal contained in the OMS-2
catalyst 14 having nano-metal particles is chosen from the group
consisting of Ni.sup.2+, Zn.sup.2+, Co.sup.2+, Cu.sup.2+,
Fe.sup.2+, Fe.sup.3+, V.sup.4+, V.sup.5+, Ti.sup.4+, Ti.sup.3+,
Cr.sup.3+, Cr.sup.2+, Co.sup.3+, Cu.sup.1+, Ce.sup.3+, Ce.sup.4+,
La.sup.3+, Na.sup.+, K.sup.+, Ba.sup.2+, Y.sup.3+, Zr.sup.4+,
Li.sup.+, Sr.sup.2+.
[0085] In a further embodiment the OMS-2 catalyst 14 containing
nano-metal particles is Pt-OMS-2.
[0086] In a further embodiment the substrate (support 16) having
manganese oxide octahedral molecular sieve catalyst (OMS-2) 14 is a
porous a porous material preferably having a pore size of 5-20
mesh.
[0087] Preferably the porous substrate 16 is Corning Honeycomb
Cordierite.RTM. yttrium stabilized zirconium, CeO.sub.2 or
HfO.sub.2.
[0088] In a further embodiment the catalytic cell 14 comprises a
working electrode 44 comprising silver or platinum gauze supported
by an insulated pad, the working electrode 44 in contact with the
substrate 16, said substrate 16 having a cryptomelane-type
manganese oxide octahedral molecular sieve catalyst 14 thereon
(e.g., Pt-OMS-2). The counter electrode 42 is a silver or platinum
wire and the reference electrode 40 is a silver or platinum wire.
In a further embodiment the catalytic cell is heated to a
temperature of between about 25.degree. and about 900.degree. C.,
preferably between about 100.degree. and about 450.degree. C.
(e.g., via heating element 34 of FIG. 2).
[0089] In further embodiment the oxidation is accomplished at a
pressure of about 1 atm to about 2 atm.
[0090] In a further embodiment the gaseous stream further comprises
CO.sub.2 and water vapor alone or in combination.
[0091] In a further embodiment the aromatic compound 112 is a
derivative of benzene, preferably the aromatic compound is benzene
and the oxidized product is acetophenone.
[0092] In a further embodiment the catalytic cell 14 may comprise a
metal oxide chosen from the group consisting of CuO.sub.x, Ni
O.sub.x, ZnO and VO.sub.x (wherein x is an integer from 1-4).
[0093] In another embodiment the catalytic cell 14 is heated to a
temperature of about between about 25.degree. C. and about
900.degree. C. preferably between about 100.degree. C. and about
450.degree. C.
[0094] In another embodiment the oxidation is accomplished at a
pressure of about 1 atm to about 2 atm.
[0095] In another embodiment the gaseous stream further comprises
CO.sub.2 and water vapor alone or in combination.
[0096] In another embodiment the aromatic compound 112 is benzene
and the oxidized product is acetophenone.
[0097] The examples below illustrate example embodiments of a
process for the reduction of carbon dioxide using water as the
source of hydrogen in accordance with the present invention. The
examples below were carried out using the apparatus described above
in connection with FIG. 2. However, it should be appreciated by
those skilled in the art that the inventive process is not limited
by the following examples and may be implemented for the reduction
of other molecules, e.g., higher molecular mass alcohols to olefins
and other compounds.
EXAMPLE 1
[0098] a. Substrates: Commercial Calcia Fully Stabilized Zirconia
(FSZ) porous ceramics from Vesuvius Hi-Tech Ceramics was used as
the solid electrolyte layer 16. [0099] b. Deposition of the
catalyst: Liquid-Phase Chemical Vapor Deposition (LP-CVD) was used
for coating of the catalyst layer 14 (platinum). Pt(acac).sub.2
(Strem Chemicals Inc.) was used as the platinum precursor. The
temperature of the precursor was set at 120-150 C, while the
temperature of the FSZ (calcia) was set at 400-500 C. Argon was
used as the carrier gas. The carrier gas flow rate of the precursor
was 500-1000 sccm/min, and the carrier gas was heated to 100-150 C
before being introduced into the CVD synthesis tube. Oxygen was
used as an oxidant. The oxygen flow rate was set at 80-200 sccm/cm.
The total pressure of the CVD reactor was controlled at 5-20 KPa.
The platinum deposition time was 1-4 hours. [0100] c. Assembling of
three electrodes: Three electrodes were deposited on the FSZ
(calcia) ceramic catalyst as described above in connection with
FIG. 3. The three electrodes each comprise 0.25 mm platinum wires
(Alfa Aesar). The three platinum wires were assembled on the FSZ
(calcia) using platinum paste (from Engelhard/BASF) and then
treated in air at 900.degree. C. The reference electrode 40 was
directly connected to the support 16 without contact with the
platinum layer 14. The counter electrode 42 was assembled before
the deposition of the catalyst layer 14 of LP-CVD of platinum, and
is in contact with the FSZ support layer 16. The working electrode
44 was deposited on the platinum LP-CVD catalyst layer 14. After
assembling the three electrodes, the catalyst assembly with three
electrodes was placed in a quartz tube and reduced in 8%
hydrogen/helium mixed gas at 600-800.degree. C. for 4-6 hours.
[0101] d. Catalytic reaction--reactor and reaction parameters: The
supported Pt-FSZ catalyst assembly, with the three electrodes, was
placed in a quartz tube reactor (e.g., tubular reactor 22 of FIG.
2). The reactor was purged of air and was thereafter operated at
slightly positive pressure of about 5-14 psig. The tube reactor
temperature was set at 600 to 950.degree. C.
[0102] It should be noted that the present invention is not limited
to the foregoing description. For example, the temperature may be
as low as room temperature or higher than 950.degree. C.; the solid
electrolyte can be Nafion, and the catalyst can be platinum black.
Other materials for use as the solid electrolyte or catalyst will
be apparent to those skilled in the art.
[0103] Further, the solid electrolyte layer 16 can be deposited on
a support 16 comprising an inert ceramic substrate (e.g.,
cordierite catalyst supports provided by Corning Inc. or St. Gobain
Co) via any of the appropriate methods known to those skilled in
the art. Similarly, the catalyst 14 can be deposited on the solid
electrolyte layer 16 via any of the appropriate methods known to
those skilled in the art.
[0104] In addition, the implementation of the process does not
require a continuity of the solid electrolyte layer 16 or of the
catalyst layer 14. What is necessary is a preponderance of grain
boundaries where the catalyst 14 is in contact with the solid
electrolyte 16 and sufficient open porosity to allow for the access
of the reacting phases to the catalytically active interfaces.
[0105] Carbon dioxide (CO.sub.2) used was zero grade gas from
Airgas. Water used was de-ionized water. Water was injected by a
peristaltic pump 17, and evaporated by a heated ceramic tube.
CO.sub.2 was used as the carrier gas provided from tank 11. The
molar ratio of CO.sub.2 to water was set at 10 to 1 or 5 to 1. The
flow of CO.sub.2 was monitored by a mass flow meter and was varied
between 200 scc/minute and 1600 scc/minute. It should be noted that
the water/CO.sub.2 ratio can take any values within the interval
1/1000 to 1000/1, and even outside this range.
[0106] The system was polarized (via the electronic control device
24 and three electrodes 40, 42, and 44) with a pulsed current at
about 1 kHz at average voltages ranging from 0.03 to 0.1 V rms. The
current passed averaged between 0.03 and 0.13 mA. This process is
described in detail in U.S. patent application Ser. No. 11/588,113
mentioned above.
[0107] Eight runs of polarization were applied, each lasting about
15 minutes.
[0108] An unexpected result of this process was that a substantial
amount of a white powder was formed, which was collected at the
cold areas of the reactor 22, as well as in the water trap 26 and
liquid nitrogen trap 28. The gas phase was analyzed by gas
chromatography (e.g., analyzer 32) with thermal and flame
ionization detectors.
[0109] The powder was dispersed in the water samples collected by
the traps, which were then analyzed by Nuclear magnetic resonance
spectroscopy (NMR) and High-Pressure Liquid Chromatography (HPLC).
With the reactor temperature set at 900.degree. C. data collected
was consistent with the presence in these samples of
paraformaldehyde and small amounts of trioxane. The result of the
NMR analysis is shown in FIG. 4.
EXAMPLE 2
[0110] The catalyst 14 used in this example was the same as that
for example 1. The temperature of the quartz tube reactor was set
at 600.degree. C. The main product identified by NMR was
paraformaldehyde, as shown in FIG. 5.
EXAMPLE 3
[0111] a. Substrates: Commercial Calcia Fully Stabilized Zirconia
(FSZ) porous ceramics from Vesuvius Hi-Tech Ceramics was used as
the solid electrolyte layer 16. [0112] b. Deposition of the
catalyst: A catalyst layer 14 of octahedral manganese oxide OMS-2
was prepared as follows: 5.6 g K.sub.2SO.sub.4, 8.81 g
K.sub.2S.sub.2O.sub.8 and 3.77 g MnSO.sub.4 and 70 ml DI water were
added into a 125 ml autoclave and put into a 4748 Parr acid
digestion bomb for 96 hours; the temperature was maintained at
250.degree. C. The solid was washed repeatedly with de-ionized
water. The suspension was filtered and stirred overnight at
85.degree. C. into a beaker with 300 ml de-ionized water. The
suspension was coated on the Vesuvius porous ceramic body and was
dried at 120.degree. C. for 12 hours. [0113] c. Assembly of
electrodes: Three platinum electrodes were positioned as described
in Example 1. Platinum paste (Engelhard BASF) was applied to
assemble the electrodes. Then the catalytic assembly was reduced in
6% Hydrogen/helium mixed gas for 2 hours at 150-300.degree. C.
[0114] The as-prepared catalytic assembly was placed in a tube
quartz reactor (tubular reactor 22) and connected with the
electronic control device 24. The tube quartz reactor 22 was sealed
and isolated with an air environment. CO.sub.2 (zero grade from Air
gas) was introduced from tank 11 and controlled with a flow meter.
Water was injected with a pre-calibrated peristaltic pump 17. Water
was heated by a ceramic tube at above 130.degree. C. Then the
reactor 22 was purged with CO.sub.2.
[0115] The system was set at slightly higher atmosphere pressure
(for example 5 kpa). The electronic control device 24 supplied
polarized current or voltage to the catalytic assembly via
electrodes 40, 42, and 44. The tube reactor was set at
250-450.degree. C.
[0116] The products were analyzed by NMR and GC techniques.
[0117] The Pt-OMS-2 catalyst 14 was tested in the
CO.sub.2--H.sub.2O system starting from 250.degree. C. and up to
450.degree. C. When the reaction started at 250.degree. C., it was
slow. After 4 hours, the sample was analyzed from the first ice
water trap 26 by NMR. The resultant NMR patterns did not show any
product. The concentration of products may have been out of the
limit or the product yield was very low. The second test was done
at 300.degree. C. The resultant NMR proton patterns showed a low
concentration of paraformaldehyde (about 0.5-1.0% in molar). In
particular, the NMR results showed a weak peak of paraformaldehyde
at this temperature. The third test was done at 400.degree. C. The
resultant NMR patterns from the ice water trap 26 and the NMR
patterns of the dry ice trap 28 showed stronger peaks of
paraformaldehyde at this temperature. The concentration of
paraformaldehyde was about 1.0-1.5% in molar. The fourth test was
done at 450.degree. C. The resultant NMR proton patterns show
higher concentrations of paraformaldehyde at this temperature. The
concentration of paraformaldehyde was about 3.0-5.0% in molar.
[0118] For the above four tests, the CO.sub.2 flow rate used was
200 sccm, and the water injection rate was 9.16 ml/min. The flow
rate of CO.sub.2/H.sub.2O was 2.37.
[0119] Based on the above results, the CO.sub.2 conversion rate at
different temperatures is shown in Table 1 below.
TABLE-US-00001 TABLE 1 Conversion rate of carbon dioxide in the
reactions at different temperatures Temperature (.degree. C.)
Conversion Rate (%) 250 Low 300 0.5-1.0% 400 1.0-1.5% 450
3.0-5.0%
EXAMPLE 4
[0120] Synthesis of ZnO Catalyst: A low-pressure chemical vapor
deposition (LPCVD) technique was used to deposit a catalyst layer
14 of ZnO on a calcium fully stabilized zirconia (FSZ) support 16.
The Zn precursor was Zn(CHCOO).sub.2(98+%, Aldrich). The
temperature of the FSZ template was set at 300.degree. C. The
temperature of precursor was set at 160.degree. C. The deposition
pressure was controlled at 3 kPa. The sample was coated two times.
In the second run, the position of the sample was reversed (front
to back and top bottom of reactor) to get better uniformity of
coating. Each coating time was 4 hours. The total CVD coating time
was 8 hours. After LPCVD, the sample was heated with a ramp rate at
5.degree. C./min and calcined at 600.degree. C. for 12 hours in
air.
[0121] Reactor and Electrodes: Three electrodes were assembled on
the ZnO-coated FSZ support as described above in connection with
FIG. 3. After the ZnO coated FSZ catalyst assembly was calcined, an
area of 25 mm2 at the end was pretreated with 5M HCL to remove ZnO.
A Platinum reference electrode 40 was assembled at this area. At
another end of the cylinder sample, the same method as above was
used to remove the ZnO layer, and a platinum wire was connected
with the FSZ support layer 16 directly as the counter electrode 42.
The working electrode 44 was attached to the ZnO catalyst layer 14.
Platinum paste (6082 from BASF) was applied to enable the platinum
electrodes to have good contact with the catalyst assembly.
[0122] After the electrodes were assembled, the resistance between
the electrodes was measured with a Digital Multimeter (HDM350). The
results are shown in Table 2 below.
TABLE-US-00002 TABLE 2 Resistance between electrodes at different
temperatures Resistance between Resistance between Resistance
between working electrode working electrode counter electrode and
reference and counter and reference Temp. electrode electrode
electrode 200.degree. C. 20M 135K >20M 500.degree. C. 10.5M
19.6K 10.1M 600.degree. C. 1.06M 5.85K 0.55M
[0123] The CO.sub.2 flow from tank 11 was measured with a flowmeter
(OMEGA FL-3504G). Water injection was measured by a calibrated
peristaltic pump 17 (Watson Marlow Sci400). Water was dropped on
heated ceramic frit (>130.degree. C.) and evaporated in a T
tube. Then water was introduced into the reactor with the CO.sub.2
carrier gas. ZnO-FSZ catalyst assembly was placed into a 2-inch
quartz tube reactor (e.g., tubular reactor 22). The reactor 22 was
heated to 600-700.degree. C. with a tube furnace (Thermolyne 21100)
or via heating element 34. The ZnO-FSZ catalyst assembly was
connected with the three electrodes to the electronic control
device 24 and polarized by a voltage or a current controlled by the
electronic control device 24. The outflow products were cooled by
an ice-water trap 26 and a dry ice trap 28. The gas from the
reactor was dried by a molecular sieve column 30, then the gas
composition was analyzed with an analyzer 32 (e.g., a gas
chromatograph (SRI 8610C)).
[0124] A voltage of -2.5 V to 2.5V was applied for the polarization
tests for with a potentiostatic EIS mode or single frequency mode.
The temperature of CO.sub.2 and H.sub.2O was set at 600 and
700.degree. C. The flow rate of CO.sub.2 was between 200-500 sccm.
The ratio of CO.sub.2/H.sub.2O was set at 1:1 and 1:3 respectively.
With different polarization, each EIS spectrum was taken by a Gamry
Reference 600.
[0125] The ZnO coated FSZ assembly was investigated by scanning
electron microscopy (SEM). The morphology of the ZnO catalyst layer
14 is shown in FIG. 6 (.times.50000) and FIG. 7 (.times.100000).
Based on SEM images, the morphologies suggest that the ZnO catalyst
layer 14 is continuous and the ZnO particle size is about 20-50
nm.
[0126] The products of CO.sub.2 and H.sub.2O activation were
separated into two phases: liquid phase and gas phase. Liquid phase
products were characterized by NMR and gas phases were analyzed
with an SRI 8610C gas chromatograph. Other techniques such as
HPLC-MS and GC-MS may also be employed. FIG. 8 is a proton NMR
spectrum of the synthesized products. The CO.sub.2 flow rate was
set at 320-450 sccm; water was injected with a flow rate of 10
mL/hour (or 207 sccm/min). The CO.sub.2/H.sub.2O molar ratio was
1.6-2.2. Based on the results shown in FIG. 8, one major product
was synthesized. The NMR chemical shift is between 4.75 to 5.20
ppm. Small amounts of formaldehyde were present at a chemical shift
of 8.25 ppm.
[0127] The polarization voltage was set at -1.2 V to -1.5 V. The
typical polarization bode spectrum is shown in FIG. 9. The "A" line
is without polarization and the "B" line is with -1.2 V
polarizations. In the polarization condition, the Zmod decreased.
For example, Zmod decreased from 3.825 k.OMEGA. to 3.573 k.OMEGA.
at a frequency of 500 kHz. These data suggest that the reaction is
fast when the catalytic cell was polarized.
[0128] FIG. 10 is a single frequency EIS spectrum. With the fixed
frequency of 500 KHz, the Zmod was shown to change with time. This
change reflected the dynamic reactions at the surface of the
catalytic assembly. The comparison tests showed that if alternating
negative and positive polarizations were used, the Zmod would
decrease after negative polarization, which increases the reaction
rate.
[0129] Gas chromatography (GC) online analysis of the products of
the reaction found new broad peaks at 14.5-20.5 min. These peaks
were assigned to ethylene and ethane.
EXAMPLE 5
[0130] a) Synthesis of the OMS-2 Catalyst
[0131] K.sub.2S.sub.2O.sub.8, K.sub.2SO.sub.4, and MnSO.sub.4 were
mixed with 70 ml Deionized (DI) water in a 125 ml autoclave. The
autoclave with above suspension was heated at 250.degree. C. for
3-4 days. Then as-synthesized product was wash with DI water for
several times to remove inorganic ions. The pulp-like OMS-2 was
then put into a beaker with 200-300 ml DI water.
[0132] Other doped catalysts have different recipes. Co, Cu, Fe,
and Ce doped OMS-2 could be synthesized using hydrothermal
methods.
[0133] b) Substrate
[0134] Porous materials were used as the substrate for (Support 16)
loading OMS-2 coating (catalyst 14) at the surface. Corning
Honeycomb cordierite was used as the substrate. Its pore sizes are
5-20 mesh. Other porous substrates such as yttrium stabilized
zirconium could be used.
[0135] c) Assembly of Three Electrodes
[0136] Counter electrode 42 and reference electrode 40 were
assembled first before coating a layer of OMS-2 manganese oxide
(catalyst 14). Silver or platinum wires were used as electrode.
Silver conductive paste was applied to fix the wires on the
substrate 16. After assembled electrodes, the sample was put in an
oven for curing at 80.degree. C. for 6 hours. Then it was calcined
at 600.degree. C. for 8 hours.
[0137] The other working electrode 44 was assembled by using silver
or platinum gauze. The gauze was supported by an insulated pad. The
pad was contacted with the substrate.
[0138] d) Loading OMS-2 Catalyst on the Substrate
[0139] 10-mesh cordierite honeycomb is used as the substrate
16.
[0140] The pulp-like OMS-2 was stirred and heated to 80-90.degree.
C. for 6 hours in a beaker. OMS-2 pulp-like slurry was dropped to
the substrate. By using the evacuation apparatus (FIG. 2), OMS-2
was uniformly coated on the substrate 16 to provide catalyst layer
14.
[0141] The working electrode 44 was modified by using droplets of
pulp-like OMS. The reference electrode 40 was cleaned by removing
OMS-2. The OMS-2 coated substrate was dried at 120.degree. C. for
overnight.
[0142] e) Chemical Vapor Deposition of Platinum on OMS-2
[0143] The as-coated OMS-2 sample was put into a quartz tube
(tubular reactor 22). The tube was heated in a tube furnace at
300-450.degree. C. Pt(acac).sub.2 (Stream Chemicals Inc.) was used
as the precursor and oxygen was used as oxidant (oxidizing agent
19). Argon was used as the carrier gas and preheated to
100-150.degree. C. The pressure in the tube was set at 5-20 kPa.
The carrier gas flow was set at 500-1000 sccm and oxygen flow was
set at 50-200 sccm. The LP-CVD time was 1-3 hours.
EXAMPLE 6
Electrocatalytic Oxidation of Benzene
[0144] a) Reaction Setup
[0145] Air was used as carrier gas and oxidant 19. The flow rate
was controlled by a Mass flow controller or a rotameter. The
concentration of benzene could be diluted by addition of air and
other gases. By putting the benzene bubbler in a warm water bath,
the concentration of benzene 112 will be increased.
[0146] The system was set at slightly higher than atmospheric
pressure (for example 5 kpa). The current/voltage source 20
supplied polarized current or voltage to the catalytic cell 14. The
tube reactor temperature was set at 100-450.degree. C. controlled
by heating element 34 of FIG. 2.
[0147] The products were analyzed by NMR, GC-MS, and GC at analyzer
32. GCMS data for the oxidation of benzene is provided at FIGS.
12-14.
[0148] b) Polarization Methods
[0149] OMS-2 is a mixed valent manganese oxide. Mn has high mixed
oxidation states of valence 3.sup.+ and 4.sup.+. Oxygen ion is easy
to move between the vacancies of the lattice. When a small DC
current was applied to the sample at a certain frequency, the
impedance of the sample changed more than 10 percent. Oxygen ions
could be continuously driven to the surface by positive current (or
DC voltage). These oxygen ions could react with benzene.
[0150] Method 1: Apply a small current on the interface of the
catalysts.
[0151] Galvanostatic EIS graph showed that the reaction was
promoted by using a small current.
[0152] Method 2: Apply a positive or negative voltage on the
interface of the catalysts.
[0153] The foregoing examples are meant to illustrate the function
and applicability of the present invention without limiting its
scope. Those skilled in the art will appreciate that the present
invention has numerous applications and that the parameters,
materials, chemical compounds, and other variables mentioned in the
examples above can be varied or changed depending on the
application and desired result.
[0154] From the foregoing examples those skilled in the art will
appreciate that the present invention encompasses methods,
processes, and apparatus for the activation of the reaction between
low-reactivity, non-polar molecules (such as CO.sub.2) with polar
molecules/species (such as water or steam), leading to products
useful in the production of polymers, in organic synthesis
reactions. For example, in accordance with the present invention a
process is provided which leads to the activation of the reaction
of carbon dioxide (and of other similar low-reactivity, non-polar
molecules) with polar compounds (such as water, steam, or others)
in a heterogeneous catalytic reaction. For example, the present
invention may be used to activate the following reactions (among
others):
[0155] CO.sub.2+H.sub.2O
[0156] CO.sub.2+H.sub.2O+CH.sub.4
[0157] CO.sub.2+NO
[0158] CO.sub.2+NO+CH.sub.4
[0159] CO.sub.2+NH.sub.3
[0160] C.sub.6H.sub.6+H.sub.2O
[0161] C.sub.6H.sub.6+C.sub.6H.sub.6+CH.sub.4
[0162] C.sub.6H.sub.6+H.sub.2O+CH.sub.4
[0163] C.sub.6H.sub.6+CH.sub.3OH and similar compounds
[0164] C.sub.6H.sub.6+NO
[0165] C.sub.6H.sub.6+NH.sub.3
[0166] Those skilled in the art will appreciate that the foregoing
list of reactions is not intended to be limiting, and that the
present invention may be used to facilitate other reactions, as
discussed in detail above.
[0167] It should now be appreciated that the present invention
provides advantageous methods and apparatus for the activation of
carbon dioxide and other low-reactivity molecules.
[0168] Although the invention has been described in connection with
various illustrated embodiments, numerous modifications and
adaptations may be made thereto without departing from the spirit
and scope of the invention as set forth in the claims.
* * * * *