U.S. patent application number 14/748686 was filed with the patent office on 2015-10-22 for hydrogen production.
The applicant listed for this patent is Unique Global Possibilities (Australia) Pty Ltd. Invention is credited to Russell Beckett.
Application Number | 20150299873 14/748686 |
Document ID | / |
Family ID | 49626397 |
Filed Date | 2015-10-22 |
United States Patent
Application |
20150299873 |
Kind Code |
A1 |
Beckett; Russell |
October 22, 2015 |
HYDROGEN PRODUCTION
Abstract
The invention relates to a process for generating hydrogen. In
this process an aqueous liquid is exposed to carbon dioxide and a
current is passed through the aqueous liquid so as to generate
hydrogen.
Inventors: |
Beckett; Russell; (Mollymook
Beach, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Unique Global Possibilities (Australia) Pty Ltd |
Ulladulla |
|
AU |
|
|
Family ID: |
49626397 |
Appl. No.: |
14/748686 |
Filed: |
June 24, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13926408 |
Jun 25, 2013 |
9090978 |
|
|
14748686 |
|
|
|
|
Current U.S.
Class: |
518/704 ;
205/628; 205/637 |
Current CPC
Class: |
C10G 2/50 20130101; C25B
1/10 20130101; C25B 1/04 20130101; C25B 9/10 20130101; B01D 53/62
20130101; B01D 2256/16 20130101; Y02E 60/36 20130101; Y02E 60/50
20130101; B01D 53/22 20130101; Y02E 60/366 20130101; Y02E 60/364
20130101; C07C 1/12 20130101 |
International
Class: |
C25B 1/10 20060101
C25B001/10; C25B 9/10 20060101 C25B009/10; C07C 1/12 20060101
C07C001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 19, 2012 |
AU |
2012904094 |
Claims
1. A process for generating hydrogen, said process comprising the
steps of: a) exposing an aqueous liquid to carbon dioxide at a
pressure of about 2 to about 100 atmospheres; and b) passing a
current through the aqueous liquid so as to generate hydrogen.
2. The process of claim 1 wherein step b) is conducted at a
pressure of about 2 to about 100 atmospheres.
3. The process of claim 1 wherein step a) comprises either passing
a gas containing carbon dioxide through the aqueous liquid or
exposing the surface of the aqueous liquid to a gas containing
carbon dioxide or both.
4. The process of claim 3 wherein the gas is released to the
atmosphere following step a) whereby the process is a process for
reduction of emissions of carbon dioxide into the atmosphere.
5. The process of claim 4 wherein the gas in step a) is a waste gas
from an industrial process.
6. The process of claim 1 wherein step a) comprises exposing the
aqueous liquid to a gas containing carbon dioxide, said carbon
dioxide having a partial pressure in said gas of at least about
0.01 atmospheres.
7. The process of claim 6 wherein the gas comprises at least about
95% carbon dioxide on a volume basis.
8. The process of claim 1 wherein the aqueous liquid comprises an
electrolyte which is not derived from the carbon dioxide.
9. The process of claim 1 wherein the aqueous liquid has no
electrolyte other than an electrolyte derived from splitting of
water by the carbon dioxide.
10. The process of claim 1 wherein the aqueous liquid is at a
temperature of less than about 15.degree. C.
11. The process of claim 1 wherein the current is applied under a
voltage of about 0.1 to about 50V.
12. The process of claim 11 wherein the voltage is less than about
1.3V.
13. The process of claim 1 wherein step b) is conducted at a
voltage of about 0.4 to about 4V, whereby the process produces
oxygen at the anode.
14. The process of claim 13 additionally comprising using the
oxygen in Oxyfuel combustion.
15. The process of claim 1 wherein the current is less than about
20 amps.
16. The process of claim 1 wherein step b) comprises applying a
voltage between a cathode and an anode, wherein the cathode is at
least partially immersed in the aqueous liquid and the anode is in
electrical communication with the aqueous liquid.
17. The process of claim 1 wherein hydrogen evolved in said process
is at least partially purified by passing through a gas separation
membrane.
18. The process of claim 1 additionally comprising: c) reacting the
hydrogen with carbon dioxide so as to produce methane and
water.
19. The process of claim 1 wherein the carbon dioxide is derived
from the combustion of a fossil fuel.
20. The process of claim 1 wherein the process is conducted in an
electrolyser comprising a proton exchange membrane or a polymer
electrolyte membrane (PEM).
21. A method of producing methane and water comprising: a) exposing
an aqueous liquid to carbon dioxide at a pressure of about 2 to
about 100 atmospheres; and b) passing a current through the aqueous
liquid so as to generate hydrogen; and c) reacting the hydrogen
with carbon dioxide so as to produce methane and water.
22. A method for increasing the rate of hydrogen production in
electrolysis of an aqueous solution, said method comprising
exposing the aqueous solution to carbon dioxide prior to and/or
during said electrolysis at a pressure of about 2 to about 100
atmospheres.
23. The method of claim 22 wherein the carbon dioxide is, or is
derived from, and industrial waste gas.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Ser. No.
13/926,408, filed Jun. 25, 2013, which is a United States National
Phase patent application based on Australian application 2012904094
filed Se. 19, 2012. Both applications are incorporated in their
entirety as if fully set forth herein.
FIELD
[0002] The invention relates to improvements in generation of
hydrogen.
BACKGROUND
[0003] USA and Europe and other developed and developing countries
face challenges in the areas of air pollution, public health,
economic growth, energy security and national security as a result
of overdependence on petroleum fuels. In January 2012, the
Californian emissions trading scheme came into effect. This aims to
reduce carbon dioxide emissions from the use of petroleum and other
fossil fuels. In June 2012, the US Court of Appeals upheld the US
Administration's set of clean car and fuel economy standards which
aim to cut new car pollution, and petroleum use, in half by
2025.
[0004] A solution to the above problems is to develop a
non-polluting, more secure and more sustainable transportation and
energy economy utilising hydrogen. Indeed, this is recognised
worldwide. Hydrogen is a high energy source with water as the
non-polluting final combustion product.
[0005] At present, commercial hydrogen production relies mainly on
the steam reformation of methane (natural gas). Over three quarters
of the global production of hydrogen occurs using steam-methane
reformation. In this process, steam and methane at high
temperatures (about 1,000.degree. C.) react to yield synthesis gas
or syngas (a mixture of carbon monoxide and hydrogen). The carbon
monoxide produced can be converted, by a subsequent water gas shift
reaction, to carbon dioxide with the production of more
hydrogen.
[0006] Commercial hydrogen production also occurs via the
gasification of coal. In this process, steam and oxygen at high
temperatures and pressures react with coal to yield syngas. Coal
gasification is the oldest method of hydrogen production in both
Europe and the USA.
[0007] Small commercial amounts of pure hydrogen are produced from
the electrolysis of water. In this process, water is decomposed
into hydrogen and oxygen using an electric current passed between
two electrodes that are immersed in the water. Hydrogen is
collected at the cathode and oxygen is collected at the anode.
[0008] The decomposition of water into hydrogen and oxygen by
electrolysis at standard temperature and pressure is not favourable
thermodynamically. Energy in the form of electricity or heat must
be supplied. The reaction occurring at the anode can be represented
by:
Anode (oxidation)
2H.sub.2O.fwdarw.O.sub.2+4H.sup.++4e.sup.-E=-1.23V
The reaction occurring at the cathode can be represented by:
Cathode (reduction) 4H.sup.++4e.sup.-.fwdarw.2H.sub.2E=0.00V
[0009] Pure water conducts electricity poorly. If an appropriate
electrolyte at an appropriate concentration is added to water, the
electrical conductivity of water increases considerably. Care must
be exercised in the choosing of electrolytes so that competition
does not occur between the electrolyte and water to gain electrons
at the cathode (reduction of cation) and to give up electrons at
the anode (oxidation of anion).
[0010] Other methods of hydrogen production that are less common
include biomass gasification, the carbon black and hydrogen
process, photoelectrolysis, thermal decomposition of water, and
photobiological production.
[0011] The production of hydrogen from methane produces large
amounts of carbon oxides and produces several other pollutants and
toxic by-products. Some impurities, such as carbon monoxide, are
poisonous to humans and can be detrimental to various systems that
require hydrogen--particularly hydrogen fuel cells containing
proton exchange membranes. These impurities have delayed the
utilisation of hydrogen fuel cells in automobiles and public
transport.
[0012] The production of hydrogen from the electrolysis of water
results in the least contaminated hydrogen product. Some pollutants
may arise if electrolytes are added to the water to facilitate the
process or to increase the velocity of the process, or if other
substances are present in the water. Pollutants may arise
particularly at the anode with the oxidation of anions (anode mud,
etc.). Some pollutants may occur at the cathode from reactions with
protons and electrons and substances present in water (carbon
compounds for example). Either damage to, or dissolution of,
electrodes may occur and the replacement of electrodes results in
substantial financial costs. However, in principle, the production
of hydrogen by the electrolysis of water should minimise
considerably the overall production of carbon dioxide, pollutants
and toxic by-products compared to other methods of hydrogen
production.
[0013] Hydrogen can be used as a fuel directly in an internal
combustion engine. Some automobile companies produce automobiles
that can combust either hydrogen or gasoline. Because of its
relative purity, the hydrogen produced by the electrolysis of water
can be utilised also in hydrogen fuel cells. In a hydrogen fuel
cell, as with hydrogen combustion, water is the final product.
Vehicles in cities that operate utilising either hydrogen fuel
cells or hydrogen combustion produce negligible pollutants compared
with vehicles combusting gasoline or methane or other fossil fuels.
The large scale use of hydrogen, produced by electrolysis, either
in fuel cells or in internal combustion engines of vehicles would
diminish city air pollution very significantly.
[0014] In addition, those countries that import oil and petroleum
fuels can utilise hydrogen as a general energy source and become
economically less dependent on oil and petroleum fuel imports.
Amongst a range of other advantages, a hydrogen economy is an
economy that has energy security, and hence, national security.
Hydrogen is not only the cleanest energy available but it has the
highest energy content of all fuels on a weight basis. The energy
content of hydrogen is about three times higher than gasoline,
natural gas, and propane on a weight basis.
[0015] Hydrogen also is an essential component in the production of
ammonia and a range of other compounds. The most important use of
ammonia is as an agricultural fertiliser. Its importance arises
also from its conversion into a wide range of nitrogen containing
compounds. A source of uncontaminated hydrogen and ammonia is vital
for a clean chemical and food industry.
[0016] At present, the cost of producing hydrogen from the
electrolysis of water is many times the cost of producing hydrogen
from methane. This high cost occurs because electrolysis in
practice does not meet efficiencies that are possible in theory.
Overpotentials are needed to overcome interactions at the electrode
surface. Competing side reactions at the electrodes result in
various products and pollutants and less than ideal Faradaic
efficiency. In addition, much energy is lost as heat because of the
difficulty in finding suitable electrodes--particularly anodes. The
cost of hydrogen production from electrolysis is a linear function
of the cost of electricity.
[0017] In the Sabatier reaction, carbon dioxide is converted to
methane in the presence of hydrogen. For the Sabatier reaction to
be economically viable, large amounts of hydrogen need to be
produced at relatively low cost. The reaction has been studied
extensively as a means of converting carbon dioxide emissions, from
fossil fuel combustion, to methane. The methane produced is then
capable of further combustion. NASA intends using the Sabatier
reaction on the space station to produce water for consumption by
astronauts and as a means of utilising atmospheric carbon dioxide
on Mars to produce methane for fuel. Carbon dioxide recycling from
power plants and other industries via the Sabatier reaction is
recognised as a major means of capturing and utilising carbon
dioxide. In this reaction, carbon dioxide and hydrogen react in the
gaseous phase, which avoids expensive carbon dioxide capture,
transport and geologic sequestration. The Sabatier reaction can be
represented by:
CO.sub.2+4H.sub.2.fwdarw.CH.sub.4+2H.sub.2O
[0018] There is a need to decrease the cost of hydrogen production
from the electrolysis of water. There is a need to produce hydrogen
from the electrolysis of water without the production of pollutants
or toxic by-products. There is a need to identify electrolytes or
catalysts to facilitate the electrolytic process or to increase the
rate of the electrolytic process, preferably without producing side
reactions at the electrodes or pollutants or toxic by-products and
without causing damage to electrodes. There is a need to decrease
the power utilised in the electrolysis of water for hydrogen
production. There is a need to decrease the reaction overpotential
for the four electron oxidation of water to oxygen at the anode.
There is a need to identify chemical catalysts and/or electro
catalysts that can be utilised in the electrolysis of water to
maximise the production of hydrogen per unit of electricity.
[0019] It is an object of the present invention to substantially
overcome or at least ameliorate one or more of the above
disadvantages. It is a further object to at least partially satisfy
at least one of the above needs.
SUMMARY OF INVENTION
[0020] In a first aspect of the invention there is provided a
process for generating hydrogen, said process comprising the steps
of: a) exposing an aqueous liquid to carbon dioxide; and b) passing
a current through the aqueous liquid so as to generate
hydrogen.
[0021] The following options may be used in conjunction with the
first aspect, either individually or in any suitable
combination.
[0022] Step a) may comprise either passing a gas containing carbon
dioxide through the aqueous liquid or exposing the surface of the
aqueous liquid to a gas containing carbon dioxide or both. It may
comprise exposing the aqueous liquid, optionally the surface of the
aqueous liquid, to a gas containing carbon dioxide. The gas may
have a higher concentration of carbon dioxide than is present in
ambient air. In the gas, the carbon dioxide may have a partial
pressure in said gas of at least about 0.01 atmospheres. The carbon
dioxide may have a partial pressure in the gas of about 0.01 to
about 100 atmospheres or of at least about 1 atmosphere. The gas
may comprise at least about 95% carbon dioxide on a volume basis.
The invention may comprise the step of providing the carbon
dioxide. This step may involve providing a gas comprising carbon
dioxide at a concentration higher than is present in ambient air,
or at a concentration of at least about 500 ppm, or at least about
1000, 2000, 5000 or 10,000 ppm on a volume basis.
[0023] The gas may be released to the atmosphere following step a),
optionally following step b), whereby the process is a process for
reduction of emissions of carbon dioxide into the atmosphere. This
reduction may be achieved by dissolving carbon dioxide in water or
by production of bicarbonate at the anode or by reutilizing carbon
dioxide to produce methane. The gas in step a) may be a waste gas
from an industrial process. It may be a waste gas from power
generation.
[0024] The aqueous liquid may comprise an electrolyte which is not
derived from the carbon dioxide. It may comprise an electrolyte
which is not aqueous carbon dioxide, a carbonate salt or a
bicarbonate salt. The aqueous liquid prior to step a) may comprise
an electrolyte. The aqueous liquid may be, or may be obtained from,
potable water, non-potable water, waste water, storm water,
reclaimed water, recycled water, sea water, ocean water, brackish
water, saline water, brine, fresh water, stored water, surface
water ground water or rain., or any combination of two or more of
these.
[0025] The current may be applied under a voltage of about 0.1 to
about 50V, or less than about 1.3V, or less than about 1V.
[0026] Step b) may in some instances be conducted at a voltage of
about 0.4 to about 4V, whereby the process produces oxygen at the
anode. The oxygen produced in this way may be used in Oxyfuel
combustion. The combustion may be combustion of methane, coal or
petroleum or of some other substance. Thus the oxygen may be
combined with, or exposed to, a fuel and said fuel may then be
combusted using Oxyfuel combustion.
[0027] In some embodiments no chlorine is produced. In particular,
the aqueous liquid may comprise chloride ions (e.g. sea water or
saline water) and the current may be passed at low voltages (e.g.
less than 1.5 volts) whereby no chlorine gas is generated at the
anode. The voltage may be sufficiently low that no chlorine is
produced. In further embodiments no halogens (X.sub.2, where X=F,
Cl, Br or I) are produced. This may be due to the low voltage used
or due to the absence of halide ions in the aqueous liquid or
both.
[0028] The current may be less than about 20 amps, or less than
about 1 amp, or less than about 0.01 amp. The current may be
generated by green energy or from a renewable energy source.
Suitable energy sources include photovoltaic cells or wind or tidal
energy.
[0029] The aqueous liquid may have a pH of about 0 to about 9.
[0030] Step b) may comprise applying a voltage between a cathode
and an anode. The cathode may be at least partially immersed in the
aqueous liquid. The anode may be in electrical communication with
the aqueous liquid. In some embodiments both the anode and the
cathode are at least partially immersed in the aqueous liquid. At
least one of the anode and the cathode may comprise a material
selected from the group consisting of platinum, graphite,
palladium, copper, zinc, silver, gold and mixtures thereof.
[0031] The hydrogen evolved in the process may be at least
partially purified. The process may comprise the step of at least
partially purifying the hydrogen generated in the process. The at
least partially purifying may comprise passing the hydrogen through
a gas separation membrane.
[0032] The process may additionally comprise reacting the hydrogen
with carbon dioxide so as to produce methane and water.
[0033] The carbon dioxide used in the process may be derived from
the combustion of a fossil fuel, for example coal, oil or natural
gas. Alternatively it may be obtained from the production of liquid
natural gas.
[0034] The process may be conducted in an electrolyser comprising a
proton exchange membrane or a polymer electrolyte membrane
(PEM).
[0035] In a particular embodiment of the invention there is
provided a process for generating hydrogen, said process comprising
the steps of: a) exposing an aqueous liquid of pH about 0 to about
9 to carbon dioxide; and b) passing a current of less than 1 amp
under a voltage of less than 1.3V through the aqueous liquid so as
to generate hydrogen, wherein step a) comprises either passing a
gas containing carbon dioxide at a partial pressure of at least
0.01 atmospheres, optionally at least 1 atmosphere, through the
aqueous liquid or exposing the surface of the aqueous liquid to a
gas containing carbon dioxide at a partial pressure of at least
0.01 atmospheres, or both.
[0036] In another embodiment there is provided a process for
generating hydrogen, said process comprising the steps of: a)
exposing an aqueous liquid of pH about 0 to about 9 to a gas
comprising carbon dioxide at a level of at least about 1000 ppm;
and b) passing a current of less than 1 amp under a voltage of less
than 1.3V through the aqueous liquid so as to generate hydrogen,
wherein said gas is derived from the combustion of a fossil fuel,
for example coal, oil or natural gas, or is obtained from the
production of liquid natural gas or from power generation. This
embodiment may represent a process for at least partially scrubbing
carbon dioxide from said gas.
[0037] In another embodiment there is provided a process for
generating hydrogen, said process comprising the steps of: a)
exposing an aqueous liquid of pH about 0 to about 9 to a gas
comprising carbon dioxide at a level of at least about 1000 ppm;
and b) passing a current, optionally a current of less than about 1
amp, through the aqueous liquid under a voltage of about 0.4 to
about 4V, so as to generate hydrogen and oxygen separately.
[0038] In a second aspect of the invention there is provided
hydrogen produced by the first aspect of the invention. The
hydrogen may be used for producing methane and water.
[0039] In a third aspect of the invention there is provided use of
hydrogen produced by the first aspect of the invention for
producing methane and water.
[0040] In a fourth aspect of the invention there is provided a
method of producing methane and water comprising making hydrogen by
the process of the first aspect and reacting the hydrogen with
carbon dioxide so as to produce methane and water.
[0041] In a fifth aspect of the invention there is provided a
method for increasing the rate of hydrogen production in
electrolysis of an aqueous solution, said method comprising
exposing the aqueous solution to carbon dioxide prior to and/or
during said electrolysis.
[0042] The method may comprise exposing the aqueous solution to a
gas comprising carbon dioxide. The gas may be a gas having a
greater concentration of carbon dioxide than normal air. It may be
a gas having a partial pressure of carbon dioxide of at least about
0.01 atmospheres, optionally of at least about 0.01 to about 100
atmospheres. It may be a gas having a carbon dioxide concentration
of at least about 10% v/v, optionally of at least about 50% v/v,
optionally of at least about 90% v/v.
[0043] In the method of the fifth aspect, the carbon dioxide may
be, or may be derived from, and industrial waste gas. It may be, or
may be derived from, combustion of a fuel or of a waste product, or
may be, or may be derived from, some other industrial process. In
this case the method may serve to scrub carbon dioxide from the gas
so as to reduce carbon dioxide emissions from the industrial
combustion or process.
[0044] There is also provided a method for increasing the rate of
hydrogen production in electrolysis of an aqueous solution, said
method comprising increasing the concentration of carbon dioxide in
a gas to which the aqueous solution is exposed, said increasing
occurring prior to and/or during said electrolysis.
BRIEF DESCRIPTION OF DRAWINGS
[0045] FIG. 1 is a diagramatic representation of a modified Hoffman
apparatus with platinum electrodes apparatus used in the
Examples.
[0046] FIG. 2 is a diagramatic representation of a modified
Brownlee apparatus with platinum electrodes used in the
Examples.
[0047] FIG. 3 shows photographs of hydrogen gas production from
water with added carbon dioxide 1 atmosphere at low voltage in a
modified Brownlee apparatus (temperature 10.degree. C., <1 volt,
platinum electrodes, pH of water 3.5). The absence of oxygen gas at
the anode should be noted, and the distinct production of hydrogen
gas at the cathode. This indicates that hydrogen production may
occur at low voltage (less than 1.23 volts, the voltage required
for the dissociation of water) from the reduction of protons that
were produced from carbon dioxide molecules dissociating water
molecules rather than the electrolysis of water per se.
[0048] FIG. 4 shows a diagrammatic representation of the
utilisation of hydrogen for the Sabatier reaction in recycling of
carbon dioxide from power plant emissions:
CO.sub.2+4H.sub.2.fwdarw.CH.sub.4+2H.sub.2O.
DESCRIPTION OF EMBODIMENTS
[0049] The present invention provides a process for generating
hydrogen, said process comprising the steps of: a) exposing an
aqueous liquid to carbon dioxide; and b) passing a current through
the aqueous liquid so as to generate hydrogen. The inventor has
surprisingly found that more hydrogen may be produced, and/or
hydrogen may be produced at a greater rate, by hydrolysis of water
in the presence of carbon dioxide than in its absence. More
particularly, an increase in hydrogen production from electrolysis
of water is observed on increasing the concentration of carbon
dioxide and/or of carbon dioxide derived species in the water. In
particular, more hydrogen may be produced with lower power in the
presence of carbon dioxide under pressure than is achievable at
present. The present process therefore may be such that the
hydrogen is produced in greater amount, and/or at a greater rate,
than would be produced using the same conditions of electrolysis
but without the step of exposing the aqueous liquid to carbon
dioxide. It may generate more hydrogen, and/or generate hydrogen at
a greater rate, than standard electrolysis of the aqueous liquid,
all other conditions being equal. The increase in hydrogen
generation and/or in rate may be at least about 5%, or at least
about 10, 15, 20, 25, 50, 75 or 100%. Under some conditions it may
be higher than this, e.g. at least about 1.5 fold, or 2, 3, 4, 5,
10, 20, 50 or 100 fold.
[0050] Step a) may refer to any suitable method for raising the
concentration of carbon dioxide related species (carbon dioxide,
carbonate, bicarbonate) in the aqueous liquid by use of carbon
dioxide gas. Suitable methods include passing a gas containing
carbon dioxide through the aqueous liquid and exposing the surface
of the aqueous liquid to a gas containing carbon dioxide. A further
suitable method is to expose the aqueous liquid to solid carbon
dioxide. As the carbon dioxide sublimes (i.e. transforms from a
solid directly to a gas) within the aqueous liquid, this results in
exposure of the liquid to the sublimed (i.e. gaseous) carbon
dioxide. It also results in cooling of the aqueous liquid, thereby
increasing the solubility of the carbon dioxide in the liquid (as
described elsewhere herein). In this instance, the solid carbon
dioxide may be added in a single amount or may be added
intermittently over time. For example it may be added repeatedly as
soon as the previous amount has completely sublimed and/or
dissolved.
[0051] The step of exposing may be for sufficient time to reach an
equilibrium concentration of carbon dioxide in the aqueous liquid.
This may be for at least 1 minute, or for at least 2, 3, 4, 5 or 10
minutes, or for about 1 to about 10 minutes, or about 1 to 5, 1 to
2 or 5 to 10 minutes, e.g. for about 1, 2, 3, 4, 5, 6, 7, 8, 9 or
10 minutes. In some cases it may be for less than 1 minute, or may
be for more than 10 minutes. The exposing may be ceased before step
b) or may be continued throughout step b) or may be conducted
concurrently or at least partially concurrently with step b).
[0052] The gas containing carbon dioxide may have a higher
concentration of carbon dioxide than that in normal air. It may
comprise between about 0.01 and 100% carbon dioxide on a volume
basis, or about 0.1 to 100, 1 to about 100, 10 to 100, 50 to 100,
80 to 100, 95 to 100, 0.01 to 50, 0.01 to 10, 0.01 to 1, 0.01 to
0.1, 0.1 to 50, 0.1 to 10, 0.1 to 1, 1 to 50, 1 to 10, 10 to 50, 50
to 95 or 80 to 95%, e.g. about 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1,
2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75,
80, 85, 90, 95 or 100% on a volume basis. The partial pressure of
carbon dioxide in the gas may be at least about 0.01 atmospheres,
or at least about 0.02, 0.05, 0.1, 0.2 0.5, 1, 2, 3, 4, 5, 10, 20,
30, 40, 50, 60, 70, 80, 90 or 100 atmospheres, or about 1 to about
100, 10 to 100, 50 to 100, 80 to 100, 95 to 100, 0.01 to 50, 0.01
to 10, 0.01 to 1, 0.01 to 0.1, 0.1 to 50, 0.1 to 10, 0.1 to 1, 1 to
50, 1 to 10, 10 to 50, 50 to 95 or 80 to 95 atmospheres, e.g. about
0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30,
35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100
atmospheres. The total pressure of the gas may be about 1
atmosphere, or may be about 1 to about 100 atmospheres, or about 1
to 50, 1 to 20, 1 to 10, 1 to 5, 2 to 100, 5 to 100, 10 to 100, 50
to 100, 10 to 50 or 10 to 20 atmospheres, e.g. about 1, 2, 3, 4, 5,
10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90 or 100
atmospheres. Step a) may be sufficient to raise the concentration
of carbon dioxide related species (as defined above) in the aqueous
liquid by a factor of at least about 50% or at least about 100%, or
by at least 2, 3, 4, 5, 10, 20, 50, 100, 200, 500 or 1000 fold. It
may be sufficient to raise the concentration of carbon dioxide
related species (as defined above) in the aqueous liquid by the
above stated factor above the equilibrium concentration of carbon
dioxide of the aqueous liquid in contact with normal air. In the
event that the gas containing carbon dioxide is not 100% carbon
dioxide, the carbon dioxide may be mixed with one or more other
gases and/or vapours. These are preferably unreactive under the
conditions of the process. Suitable gases and/or vapours include,
but are not limited to, nitrogen, argon, helium, carbon monoxide
and water vapour.
[0053] In the event that step a) comprises passing the gas through
the aqueous liquid, this may comprise bubbling the gas
therethrough. This may be for example through a frit or other
dispersal device so as to reduce bubble size and/or increase bubble
surface area. This may serve to accelerate equilibration with the
aqueous liquid or to reach saturation of the liquid with carbon
dioxide more rapidly. In some instances the step of passing the gas
through the aqueous liquid may be such that the gas remains remote
from the cathode. This may prevent the gas from mixing with the
hydrogen evolved at the cathode. In some instances, as described
elsewhere herein, the cathode is disposed in a cathode chamber and
the anode in an anode chamber. Where these two chambers are
separated, they must be electrically coupled so as to allow ions to
travel between them. The electrical coupling may be such that it
prevents passage of carbon dioxide gas. In this case the carbon
dioxide containing gas may be passed through the aqueous liquid in
the anode chamber so as to prevent it mixing with the evolved
hydrogen at the cathode.
[0054] In a particular embodiment therefore, step a) of the process
comprises exposing the surface of the aqueous liquid to an
atmosphere of about 1 atmosphere, or of about 1 to about 20
atmospheres, of a gas comprising at least about 90% carbon dioxide
on a mole or volume basis. In another particular embodiment, the
process comprises passing a current through an aqueous liquid so as
to generate hydrogen, the surface of said aqueous liquid being
exposed to an atmosphere of about 1 atmosphere, or of about 1 to
about 20 atmospheres, of a gas comprising at least about 90% carbon
dioxide on a mole or volume basis. In a further particular
embodiment, the process comprises passing a current through an
aqueous liquid so as to generate hydrogen, whilst passing a gas
comprising at least about 90% carbon dioxide on a mole or volume
basis through said aqueous liquid. In a further particular
embodiment, the process comprises passing a current through an
aqueous liquid so as to generate hydrogen, the surface of said
aqueous liquid being exposed to an atmosphere having a partial
pressure of carbon dioxide of at least about 0.1 atmospheres, or at
least about 1 atmosphere. In a further particular embodiment, the
process comprises passing a current through an aqueous liquid so as
to generate hydrogen, whilst passing a gas having a partial
pressure of carbon dioxide of at least about 0.1 atmospheres, or at
least about 1 atmosphere, through said aqueous liquid.
[0055] The aqueous liquid may comprise an electrolyte which is not
derived from the carbon dioxide. This additional electrolyte may be
an ionic salt. It may be a sodium salt, a potassium salt, a
magnesium salt, a calcium salt, a chloride salt, a bromide salt, a
sulfate salt, a nitrate salt or any suitable combination of these,
or may be some other type of salt and/or other metallic and/or
non-metallic material. The aqueous liquid may be, or may be
obtained from, sea water or ocean water (typically about 3.5
percent salt), brackish water (typically about 0.05 to 3.5 per cent
salt), saline water (typically about 3.5 to 5 percent salt), or
brine (typically more than 5 per cent salt) or other suitable
aqueous liquid. The concentration of the additional electrolyte may
be about 0.05 to about 10% on a w/v basis in the aqueous liquid, or
may be about 0.05 to 5, 0.05 to 1, 0.05 to 0.5, 0.05 to 0.1, 0.1 to
10, 1 to 10, 5 to 10, 0.1 to 1, 1 to 5, 2 to 5, 1 to 3 or 3 to 5%,
e.g. about 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7,
8, 9 or 10%w/v. In some instances the aqueous liquid has no
electrolyte other than an electrolyte derived from the carbon
dioxide. The aqueous liquid may have no organic solvent mixed
therewith, or may in some instances have a water miscible organic
solvent, e.g. methanol, ethanol etc. Typically the concentration of
the organic solvent, if present, will be less than about 10% v/v,
or less than about 5, 1, 0.5 or 0.1% v/v.
[0056] The aqueous liquid may be agitated, e.g. shaken, stirred,
swirled, sonicated or otherwise agitated during the passing of the
current and/or during the step of exposing the aqueous liquid to
carbon dioxide. This may for example be achieved by means of a
stirrer or sonicator probe within the aqueous liquid. It may be
facilitated by the presence of baffles or other barriers in the
aqueous liquid, i.e. in the chamber in which the aqueous liquid is
located. In one embodiment of the invention, the aqueous liquid is
exposed to carbon dioxide (by any of the various methods described
elsewhere herein) in an exposure chamber and then passes to a
separate electrolysis chamber in which current is passed through
the liquid so as to generate hydrogen. The electrolysis chamber may
be a flow cell whereby the carbon dioxide exposed liquid flows
through either intermittently or continuously. The liquid flowing
out of the electrolysis chamber may be passed to waste or may be
recycled through the exposure chamber where it may be re-exposed to
carbon dioxide. Thus an apparatus for conducting the present
invention may in one embodiment comprise a flow through
electrolysis chamber coupled to an exposure chamber and having an
anode and a cathode therein. A pump may be provided to cause the
liquid to pass from the exposure chamber to the electrolysis
chamber. The apparatus may also have a return line to return the
aqueous liquid from the electrolysis chamber to the exposure
chamber, or may have a waste line to pass the aqueous liquid from
the electrolysis chamber to waste. In this embodiment, the
electrolysis chamber may be as described elsewhere herein. It may
comprise a single chamber having an anode and a cathode therein, or
may comprise electrically coupled separate anode and cathode
chambers. The exposure chamber may comprise a gas bubbler, frit or
other dispersion device for passing a gas containing carbon dioxide
(optionally mixed with one or more other gases, as described
elsewhere herein) through the aqueous liquid, or may comprise a
system for exposing the surface of the aqueous liquid to a gas
containing carbon dioxide, or may comprise both of these.
[0057] The current may be applied under a voltage of about 0.1 to
about 50V, or about 0.1 to 20, 0.1 to 10, 0.1 to 5, 0.1 to 2, 0.1
to 1.3, 0.1 to 1, 0.1 to 0.5, 0.5 to 1, 0.5 to 1.3, 0.5 to 2, 0.5
to 5, 0.5 to 10, 0.5 to 20, 0.4 to 4, 1 to 4, 2 to 4, 1 to 10, 1 to
5, 1 to 2 or 1 to 1.3V, e.g. about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6,
0.7, 0.8, 0.9, 1, 1.1, 1.2, 1,3, 1.4, 1.5, 2, 2.5, 3, 3.5, 4, 4.5,
5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45 or 50V. The applied
voltage may be less than about 50V, or less than about 40, 30, 20,
10, 5, 4, 3, 2, 1.3, 1.23, 1 or 0.5V. It may be sufficiently low
that, if the aqueous liquid contains chloride, no chlorine is
produced at the anode. It may be sufficiently low that no oxygen is
produced at the anode. Alternatively it may be sufficient for
oxygen to be produced at the anode.
[0058] The current may be less than about 20 amps, or less than
about 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3,
2 or 1 amp, or less than about 0.5, 0.2, 0.1, 0.05, 0.02 or 0.01
amp. The current may be about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06,
0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1
amp. The current may be about 1 amp, or about 2, 3, 4, 5, 6, 7. 8,
9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 amps. The current
may be generated by photovoltaic cells or by wind or tidal forces
or by some other renewable or green energy source, e.g. falling
water, co-generation, or energy obtained from biomass, natural gas
or coal.
[0059] The current may be passed through the aqueous liquid at a
power of less than about 100W, or less than about 50, 20, 10, 5, 2,
1.5, 1, 0.5, 0.2 or 0.1 W, or of about 0.01, 0.02, 0.03, 0.04,
0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7,
0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. 15. 20, 25, 30, 35, 40,
45, 50, 60, 70, 80, 90 or 100 W.
[0060] Step b) may in some instances be conducted at a voltage of
about 0.4 to about 4V, so as to produce oxygen at the anode. The
oxygen produced in this way may be used in Oxyfuel combustion.
Oxyfuel combustion involves combustion of a fuel in an atmosphere
having an oxygen concentration higher than that of ambient air
rather than in ambient air, e.g. in an oxygen-enriched air
atmosphere. The oxygen in the atmosphere in which the Oxyfuel
combustion is conducted in the present instance may be for example
at least about 30% by volume, or at least about 40, 50, 60, 70, 80,
90, 95, 96, 97, 98 or 99% by volume (excluding any gaseous fuel
present). Thus if a solid fuel is used, the oxygen concentration
may be as described. If however a gaseous or vapour phase fuel is
used, the concentration of oxygen may be as described accounting
for the concentration of the fuel. For example if a gaseous phase
containing 10% by volume methane were used, the concentration of
oxygen may be at least about 27% (i.e. 30% of the remaining 90%
after methane is discounted) by volume. An advantage of Oxyfuel
combustion is that the production of nitrogenous by-products is
suppressed or eliminated. The nitrogen in the atmosphere in which
the Oxyfuel combustion is conducted may be for example less than
about 70% by volume, or less than about 60, 50, 40, 30, 20, 10, 5,
2 or 1%. In order to achieve this, the oxygen may be purified prior
to use in the Oxyfuel combustion. This may be for example by means
of selective condensation of liquid gases followed by
revaporisation, or may be by means of a selective gas membrane or
may be by some other method. The oxygen from the present process,
either after purification or without purification, may be mixed
with a second gas, e.g. air, recycled flue gas etc. before being
used as an atmosphere for the Oxyfuel combustion.
[0061] The aqueous liquid used in the process of the present
invention may have a pH of about 0 to about 9, or about 0 to 8, 0
to 7, 0 to 6, 0 to 5, 0 to 4, 0 to 3, 0 to 2, 0 to 1, 1 to 9, 1 to
7, 1 to 5, 1 to 3, 3 to 9, 3 to 7, 3 to 5, 5 to 7, 7 to 9 or 6 to
8, e.g. about 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9. This pH may be either
as measured prior to step a) or as measured during step b). It may
have a temperature of between 0 and 100.degree. C., or 0 to 50, 0
to 20, 0 to 10, 10 to 100, 20 to 100, 50 to 100, 10 to 20, 20 to 50
or 20 to 30.degree. C., e.g. about 0, 5, 10, 15, 20, 25, 30, 40,
50, 60, 70, 80, 90 or 100.degree. C. It may have a subambient
temperature. It may have a temperature of less than about
25.degree. C., or less than about 20, 15, 10 or 5.degree. C. This
may serve to increase the solubility of the carbon dioxide in the
aqueous liquid. This temperature may apply either during step a) or
step b) or both. The process may comprise cooling the aqueous
liquid. This may be done before and/or during either step a) or
step b) or both. In some instances the cooling may be effected by
means of solid carbon dioxide ("dry ice"). If sufficient solid
carbon dioxide is used, excessive freezing of the aqueous liquid
may occur, resulting in a loss of efficiency of the process. In
such instances, heating may be applied so as to at least partially
remelt the aquous liquid.
[0062] The process, in particular step b) of the process, may be
conducted in any suitable apparatus for electrolysis of an aqueous
liquid. Suitable apparatuses are well known to those skilled in the
art. In one embodiment the apparatus comprises a proton exchange
membrane or a polymer electrolyte membrane (PEM). This membrane may
be used to separate the two half cells of the apparatus.
[0063] Step b) of the process may comprise applying a voltage
between a cathode and an anode. Suitable materials for the two
electrodes include (independently) platinum, graphite, palladium,
copper, zinc, silver, gold and mixtures thereof, however the
skilled worker will readily appreciate that other suitable
electrode materials may also be used. Commonly both electrodes are
at least partially immersed in the aqueous liquid, however in some
instances the anode may be in electrical communication with the
cathode without being immersed in the same body of aqueous liquid,
e.g. by means of an ion bridge. The anode may be immersed in an
aqueous liquid in an anode chamber and the cathode may be immersed
in an aqueous liquid in a cathode chamber. The two aqueous liquids
may each, independently, be as described earlier for "the" aqueous
liquid (in which case they may be the same or may be different), or
one or the other may be as so described and the other may be
different. If the anode chamber is separate from the cathode
chamber, the aqueous liquid in the cathode chamber or in the anode
chamber or in both may be exposed to the carbon dioxide. If
present, the anode chamber and the cathode chamber may be coupled
by means of an ion bridge, an ion permeable membrane or by some
other means for electrically coupling the chambers.
[0064] The hydrogen evolved in the process may be at least
partially purified. This may for example be accomplished by passing
through a gas separation membrane. Suitable membranes include dense
polymer membranes, ceramic membranes, dense metallic membranes
(e.g. Pd-Cu membranes) and porous carbon membranes.
[0065] The process may additionally comprise reacting the hydrogen
with carbon dioxide so as to produce methane and water. This may
for example be accomplished by means of the Sabatier reaction. This
is illustrated diagrammatically in FIG. 4. For the Sabatier
reaction to be economically viable, large amounts of hydrogen need
to be produced at relatively low cost. Carbon dioxide recycling
from power plants and other industries via the Sabatier reaction is
recognised as a major means of capturing and utilising carbon
dioxide. The reaction between carbon dioxide and hydrogen takes
place in the gaseous phase which avoids expensive carbon dioxide
capture, transport and geologic sequestration. The Sabatier
reaction can be represented by:
CO.sub.2+4H.sub.2.fwdarw.CH.sub.4+2H.sub.2O
[0066] The hydrogen may alternatively be used as a fuel, e.g. in
combustion to generate heat energy or in a hydrogen fuel cell.
[0067] An overall industrial scheme therefore may be as follows.
Electrolysis of water according to the process of the present
invention, commonly at low voltage (e.g. below 1.0V), generates
hydrogen, which may be used in the Sabatier reaction (described
above). Water produced in the Sabatier reaction may be recycled to
the electrolysis chamber. Methane produced in the Sabatier reaction
may be combusted, e.g. in an Oxyfuel reaction or simply in normal
atmosphere, to generate energy. The carbon dioxide generated by
this methane combustion may be separated from other combustion
products and used either in the Sabatier reaction or in the
electrolysis chamber (or both). If the electrolysis is conducted at
higher voltage (i.e. above 1.0V), oxygen is generated in addition
to hydrogen. This may be used in the Oxyfuel combustion of the
methane generated from the Sabatier reaction, with the hydrogen
being used as described above.
[0068] Aspects of the invention may therefore include one or more
of the following:
[0069] a. Utilising a range of carbon dioxide pressures, e.g. from
0.01 atmospheres to 100 atmospheres.
[0070] b. Utilising a range of water temperatures, e.g. from 0 to
100.degree. C.
[0071] c. Utilising a range of pH values, e.g. from pH=0 to
pH=9.
[0072] d. Utilising a range of voltages between the electrodes,
e.g. from 0.1 volts to 50 volts.
[0073] e. Utilising a range of electrode materials, e.g. platinum,
graphite, palladium, copper, zinc, silver, gold and other metallic
and non-metallic materials.
[0074] f. Utilising a range of electrolyte solutions or solutes in
water, e.g. sodium chloride and other metal and non-metal
salts.
[0075] g. Utilising sea water or ocean water (3.5 percent salt),
brackish water (0.05 to 3.5 per cent salt), saline water (3.5 to 5
percent salt), or brine (more than 5 percent salt) as an
electrolyte.
[0076] h. Utilising diluted or filtered sea water or ocean water or
brackish water or saline water or brine as an electrolyte.
[0077] i. Utilising a hydrogen separation cell or hydrogen
permeable membrane to obtain the separation of hydrogen, for
collection, from carbon dioxide and other gases.
[0078] Carbon dioxide dissolves to some extent in water at normal
atmospheric pressure. At a gas pressure of one atmosphere (Standard
Temperature and Pressure Dry--STPD) approximately 1.5 litres of
carbon dioxide gas dissolves in 1 litre of cold water at 5.degree.
C. and 0.5 litres of carbon dioxide gas dissolves in 1 litre of
warm water at 30.degree. C. Accordingly, the concentration of
carbon dioxide (optionally of carbon dioxide plus bicarbonate ion
plus carbonate ion) during step b) of the present process may be at
least about 0.1 litres (equivalent of carbon dioxide for carbonate
and bicarbonate) per litre of water, or at least about 0.2, 0.3,
0.4, 0.5, 0.75, 1, 1.25 or 1.5 litres per litre of water, or about
0.1 to about 1.5, 0.1 to 1, 0.1 to 0.5, 0.5 to 1.5, 1 to 1.5 or 0.5
to 1 litres per litre of water, e.g. about 0.1, 0.2, 0.3, 0.4, 0.5,
0.75, 1, 1.25 or 1.5 litres per litre of water, depending on the
temperature of the water. The inventor has found that under
increasing pressure the concentration of carbon dioxide increases
in water.
[0079] Water is a polar molecule with a dipole moment of 1.85
Debyes. Carbon dioxide does not possess a dipole moment but has a
polarizability of 2.63 x 10.sup.-24 cm.sup.3. Carbon dioxide can be
seen as a linear resonance. When carbon dioxide is dissolved in
water, the slight negative charge on the oxygen atom of the water
molecule attracts the slight positive charge on the carbon atom of
carbon dioxide. It is thought that the product of this interaction
is a proton (H.sup.+) and a bicarbonate ion (HCO.sub.3.sup.-).
[0080] The inventor has found that under increasing pressure and/or
increasing carbon dioxide concentration, the concentrations of
protons and bicarbonate ions increase. It is possible to achieve a
proton and bicarbonate ion concentration of more than 10.sup.-1
moles per litre by further increasing the contact between carbon
dioxide molecules and water molecules either by further increasing
pressure or by utilising appropriate mixing and mechanical baffles.
That is, it is possible to reach a pH value less than pH=1. In
biology and human physiology, the enzyme carbonic anhydrase
produces sufficient proton concentrations from carbon dioxide and
water to achieve pH values between pH 2 and pH 4 in various body
organs and cell organelles (for example, the stomach and
intracellular lysosomes). Commercial carbonation of drinks
utilising pressure can obtain pH values of pH=2 to pH=3. The carbon
dioxide dissolved in rain water results in a pH value of pH=5 to
pH=6 depending on temperature.
[0081] The inventor considers that the bicarbonate ion produced by
carbon dioxide in water can be considered as carbon dioxide
hydroxide, CO.sub.2.OH.sup.-. That is, carbon dioxide in water can
be viewed as an hydroxide ion carrier. The hydroxide ion per se is
a relatively good electron donor but has slight reducing power. The
oxidation of hydroxide ions can be represented by:
4H.sup.-.fwdarw.O.sub.2+2H.sub.2O+4e.sup.-E=-0.40 V
[0082] When carbon dioxide in water is utilised to facilitate the
electrolysis of water, the following reactions are considered to
occur:
TABLE-US-00001 Cathode (reduction) 4H.sup.+ + 4e.sup.- .fwdarw.
2H.sub.2 Anode (oxidation) 4OH.sup.- .fwdarw. O.sub.2 + 2H.sub.2O +
4e.sup.- 4HCO.sub.3.sup.- .fwdarw. 4OH.sup.- + 4CO.sub.2 2H.sub.2O
.fwdarw. O.sub.2 + 4H.sup.+ + 4e.sup.-
[0083] In this scheme, hydrogen gas is produced at the cathode and
oxygen gas is produced at the anode. Carbon dioxide gas is released
from bicarbonate ions at the anode.
[0084] At low voltages, particularly at voltages below 1.23V,
protons that are reduced to hydrogen at the cathode are thought to
derive originally from the splitting of water by carbon dioxide as
represented schematically above.
[0085] Thus a solution of carbon dioxide in water can be regarded
as a catalyst or facilitator for the electrolysis of water. Carbon
dioxide in water produces protons and bicarbonate ions in
reasonable quantities under appropriate conditions of temperature
and pressure. As a consequence, carbon dioxide in water decreases
the power required for hydrogen production by electrolysis relative
to standard electrolysis (where Power=Current.times.Voltage).
Carbon dioxide decreases electrical resistance relative to standard
electrolysis and this can be viewed as decreasing the reaction
overpotential at the anode.
[0086] The carbon dioxide utilised to facilitate the electrolysis
of water to produce hydrogen gas can be derived from the combustion
of fossil fuels such as coal, oil and natural gas. The hydrogen gas
produced from the electrolysis of water can be used in the Sabatier
reaction to produce methane.
[0087] The enzyme carbonic anhydrase is the fastest biological
enzyme known. Depending on the isoenzyme, each molecule of carbonic
anhydrase is able to catalyse (hydrate) between 10,000 and
1,000,000 molecules of carbon dioxide per second. This enzyme speed
becomes important at all levels of cell and organ physiology; from
mitochondria to the lungs and kidneys. The proton concentration
gradient that can arise from the action of carbonic anhydrase
enzyme is transduced often into other forms of energy such as ATP
concentrations and sodium and potassium gradients.
[0088] The inventor has hypothesised that the thermodynamics of
carbon dioxide hydration per se may be as important as the kinetics
of the carbonic anhydrase enzyme reaction. It therefore followed
that one should concentrate carbon dioxide as much as possible in
water in order to turn the resultant protons into hydrogen gas by
electrolysis. The present specification illustrates this
invention.
[0089] The above explanation of the invention is illustrated
quantitatively in Example 1, Table 1.2, provided later in this
specification. Thus at low potential (around 1 to 1.3 volts) the
quantity of hydrogen produced is increased several hundred fold
when carbon dioxide is added to water under pressure (1
atmosphere). All other results in other Examples substantiate this
result.
[0090] Initially, experiments were conducted with sensitive
analytical techniques such as gas chromatography, mass spectrometry
and high-pressure liquid chromatography. These techniques were able
to distinguish between hydrogen gas, methane, carbon monoxide,
formic acid and oxalic acid. All these compounds are known, to a
greater or lesser extent, to be the result of carbon dioxide in
water reacting with hydrogen gas in the presence of electrons.
[0091] Later experiments were conducted using specific hydrogen
detectors that are used in industry to detect hydrogen leaks in
high pressure pipes. Three different hydrogen detectors were
utilised. The disadvantage of these detectors is that they had to
be calibrated by the manufacturer on a routine basis and they could
not detect gases or compounds apart from hydrogen, methane and
propane (when appropriately calibrated). One detector (the
Sensit.RTM. HXG-3) was calibrated for hydrogen but also may have
detected some methane. This detector was used initially to obtain
results which were then repeated by other detectors. Mostly the
detectors worked well in a linear manner up to about 10,000 ppm
hydrogen.
EXAMPLES
[0092] Experiments were conducted utilising various carbon dioxide
concentrations in water to facilitate the production of hydrogen
gas by electrolysis. Carbon dioxide concentrations in water
decreased the pH value of the water, i.e. carbon dioxide
concentrations increased proton concentrations. The utilisation of
carbon dioxide in water resulted in very significant increases in
the production of hydrogen per unit of electricity relative to the
absence of carbon dioxide.
[0093] Experiments were conducted using various carbon dioxide
concentrations in sea water, saline waters and electrolyte
solutions to facilitate the production of hydrogen gas. The
utilisation of carbon dioxide in sea water, saline waters and
electrolyte solutions resulted in very significant increases in the
production of hydrogen per unit of electricity relative to the
absence of carbon dioxide.
[0094] Experiments were conducted utilising a range of carbon
dioxide concentrations in water, sea water and saline waters by
altering pressure and temperature. Increasing the pressure of
carbon dioxide in all waters increased the production of hydrogen
very significantly. Decreasing temperature increased carbon dioxide
solubility and increasing temperature increased carbon dioxide and
water reactivity. In both cases, the production of hydrogen was
increased significantly in all waters.
[0095] Experiments were conducted utilising carbon dioxide
concentrations in water, sea water and saline waters with a range
of low voltages and electrode materials. Significant hydrogen
production was obtained in all waters at low voltages (less than
1.23V) utilising a range of electrode materials.
Example 1
Hydrogen Production From Water Under 1 Atmosphere CO.sub.2 at
Different Voltages
[0096] This experiment was conducted at various voltages as shown
in Tables 1.1 and 1.2, using current of less than 0.01 amps in a
modified Brownlee or modified Hoffman apparatus (see FIGS. 1 and 2)
with minimal platinum electrode surface area. Hydrogen gas was
measured quantitatively as ppm hydrogen gas at 10 minutes following
commencement of current flow.
TABLE-US-00002 TABLE 1.1 No voltage: control background reading
(range over 10 measurements) NO VOLTAGE WATER HYDROGEN PPM WATER
WITHOUT 0 to 10 CO.sub.2 ADDED WATER WITH CO.sub.2 50 to 100 ADDED
1 ATMOSPHERE
[0097] The inventor hypothesises on the basis of the above data
that the carbon dioxide used in the present experiments contained
low levels of hydrogen. In order to control for this, the above
data were subtracted from the data obtained when voltage was
applied so as to determine the excess hydrogen evolved as a result
of the electrolysis.
TABLE-US-00003 TABLE 1.2 Reading minus control background reading
at 10 minutes (mean of 10 measurements) WATER WITH CO.sub.2 WATER
WITHOUT ADDED CO.sub.2 ADDED 1 ATMOSPHERE VOLTAGE Cathode Cathode
(<0.01 amps) Hydrogen ppm Hydrogen ppm 1 volt 0 400 1.3 volts 10
530 5 volts 50 1,450 10 volts 320 2,550 20 volts 1,080 3,970 30
volts 2,980 4,960
[0098] The increase in hydrogen production from water with CO.sub.2
added was significant compared to water without CO.sub.2. Some
methane may have been produced at the cathode. Oxygen was produced
at the anode above 1.0 volt.
Example 2
Low Voltage Relative Hydrogen Production From Sea Water at CO.sub.2
at 1 Atmosphere
[0099] This experiment was conducted using various low voltages and
current <0.01 amps. Hydrogen gas was measured quantitatively as
ppm hydrogen gas in modified Brownlee and modified Hoffman
apparatus at 3 minutes after commencement of current flow. Minimal
platinum electrode surface area was used.
TABLE-US-00004 TABLE 2.1 No voltage Control background reading
(range over 10 measurements) NO VOLTAGE SEA WATER HYDROGEN PPM Sea
water without 0 to 10 CO.sub.2 added Sea water with CO.sub.2 50 to
100 added 1 atmosphere
TABLE-US-00005 TABLE 2.2 Reading minus control background reading
at 3 minutes (mean of 10 measurements) SEA WATER SEA WATER WITH
WITHOUT CO.sub.2 ADDED CO.sub.2 ADDED 1 ATMOSPHERE VOLTAGE Cathode
Cathode (<0.01 amps) Hydrogen ppm Hydrogen ppm 0.2 volt 280
1,490 0.4 volt 490 2,070 0.6 volt 1,400 5,540 0.8 volt 2,200 5,800
1.0 volt 3,050 5,900
[0100] Increased hydrogen production at low voltages from sea water
with CO.sub.2 added was significant compared to sea water without
CO.sub.2. The hydrogen produced from sea water without added
CO.sub.2 may derive either from the inherent CO.sub.2 present in
sea water that originates from the atmosphere or from the reduction
of cations to metals at the cathode which subsequently split water
molecules.
Example 3
Low Voltage Relative Hydrogen Production From Electrolyte Solution
at CO.sub.2 1 Atmosphere
[0101] This experiment was conducted using 1.0M sodium chloride as
electrolyte at various low voltages and current <0.01 amps.
Hydrogen gas was measured quantitatively as ppm hydrogen gas in
modified Brownlee and modified Hoffman apparatus at 3 minutes after
commencement of current flow. Minimal platinum electrode surface
area was used.
TABLE-US-00006 TABLE 3.1 No voltage Control background reading
(range over 10 measurements) ELECTROLYTE NO VOLTAGE SOLUTION
HYDROGEN PPM Electrolyte 0 to 10 solution without CO.sub.2 added
Electrolyte solution 50 to 100 with CO.sub.2 added 1 atmosphere
TABLE-US-00007 TABLE 3.2 Reading minus control background reading
at 3 minutes (mean of 10 measurements) ELECTROLYTE ELECTROLYTE
SOLUTION SOLUTION WITH CO.sub.2 WITHOUT CO.sub.2 ADDED 1 ADDED
ATMOSPHERE VOLTAGE Cathode Cathode (<0.01 amps) Hydrogen ppm
Hydrogen ppm 0.2 volt 190 900 0.4 volt 450 1,800 0.6 volt 800 2,700
0.8 volt 1,400 4,300 1.0 volt 2,100 6,200 5.0 volts 7,800 11,300
(0.02 amps)
[0102] Increased hydrogen production at low voltages from
electrolyte solution with CO.sub.2 added was significant compared
to electrolyte solution without CO.sub.2. The hydrogen production
from electrolyte solution without CO.sub.2 added may derive from
the reduction of cations to metals at the cathode which
subsequently split water molecules. Some methane may have been
produced at the cathode. Oxygen was produced at the anode above 1.0
volt.
Example 4
Relative Hydrogen Production From Water at Various CO.sub.2
Pressures
[0103] This experiment was conducted at voltage 5V and current
<0.01 amps. Hydrogen gas was measured quantitatively as ppm
hydrogen gas in modified Brownlee and modified Hoffman apparatus at
10 minutes. Minimal platinum electrode surface area was used.
TABLE-US-00008 TABLE 4.1 Hydrogen production at 10 minutes (mean of
10 measurements) WATER WITH CO.sub.2 ADDED CO.sub.2 Cathode
ATMOSPHERES Hydrogen ppm 1 1,400 2 2,100 3 3,300 5 4,300 10 6,800
20 8,200
[0104] Increased hydrogen production with increased CO.sub.2
pressures was significant. Oxygen was produced at the anode.
* * * * *