P-1296-PCT
Title
Method and Device for Pure Hydrogen Generation
From Acidic Solution
Background
The present development relates to a method and apparatus for generating
pure hydrogen from an organic acid solution. The method reacts a pure metal with
an organic acid and an oxidizing agent, and generates hydrogen gas having a purity
greater than 99.9%. The hydrogen gas is then removed and the metal is
precipitated as a metal oxide. In subsequent steps, the metal may be reduced back
to zero valency by known methods, such as reaction with a hydrocarbon, and the
organic acid is regenerated. Hydrogen generation is gradual and more consistent
than observed by prior art methods, making the present method suitable for fuel
cell applications.
In recent years, interest has been generated in fuel-cell based engines.
These engines have an energy efficiency that is two to three times higher than
internal combustion engines (50-55% for fuel cell vs. 15-17% for internal
combustion engines). Typically, hydrogen is a supplied directly to a fuel cell to
generate electricity.
Hydrogen, however, does not exist in elemental form in nature. Rather, the
hydrogen must be liberated from hydrogen-containing compounds. This requires
the consumption of energy. For example, water is the most common substance on
earth, covering more than 70% of the earth's surface. Water contains about 11%
hydrogen by weight, but because of the stability of water, in theory, more than
10,000 joules of energy are needed to obtain one liter of hydrogen gas from water.
For commercial operations, hydrogen is commonly derived either from hydrogen-
rich chemicals, such as methanol or dimethyl ether, or from fuels, such as coal,
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natural gas or gasoline. In most cases, liberation of pure hydrogen from the
chemicals and fuels is complex and costly.
In order to make fuel cells attractive for application in consumer products,
the cost for on-board fuel processing will preferably be less than about $10 per
kilowatt. However, using the technology of the prior art, on-board fuel processing
costs nearly ten times more than the target. Thus, there is a need for a lower cost
alternative. Further, it is highly desirable that for portable appliances fueled by
fuel cells, the hydrogen can be generated instantaneously at the moment when the
machine is turned on. Due to activation energy requirements for most chemical
reaction systems, it is very difficult to overcome the start-up issues by conventional
reforming or shift reactions.
Summary of the Invention
The present development is a method for generating pure hydrogen from an
organic acid solution and a portable hydrogen-generating device. A zero-valent
metal is reacted with an organic acid and an oxidizing agent. Hydrogen gas
generated by the reaction is removed and the metal is precipitated as a metal oxide,
In subsequent steps, the metal may be reduced back to zero valency by known
methods, such as reaction with a hydrocarbon, and the organic acid is regenerated.
Hydrogen generation is gradual and more consistent than observed by prior art
methods, making the present method suitable for fuel cell applications. A portable
hydrogen-generating device using the method of generating pure hydrogen from
acidic solution is further disclosed.
Brief Description of the Figures
Figure 1 is a graphical representation of hydrogen production over time
resulting from the method of the present development - reaction of iron and an
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organic acid - versus hydrogen production over time resulting from a prior art
method - reaction of iron and a mineral acid; and
Figure 2 is a drawing of a portable hydrogen-generating device made in
accordance with the present development.
Detailed Description of the Preferred Embodiment
The present invention is a renewable hydrogen generation system. By
reacting an organic acid and metal, hydrogen generation can occur at ambient
temperature, defined herein as temperatures less than about 35°C, and ambient
pressure, or at pressures of about 1 bar. The purity of the hydrogen generated is
greater than 99.9%, and the hydrogen can be generated continuously at an
essentially steady rate.
As shown in Figure 1, when approximately one gram of iron powder is
reacted with from about 100 mL to about 300 mL acid, hydrogen gas is generated.
When the iron powder is reacted with a mineral acid, such as hydrochloric acid, the
initial hydrogen generation is extremely rapid and then the production rate holds
steady. By contrast, when the iron powder is reacted with an organic acid, such as
formic acid or acetic acid, the initial hydrogen production rate is less abrupt with a
gradual increase in hydrogen production. In situations where a hydrogen storage
tank is not available, it is preferable to have a gradual, consistent rate of hydrogen
production. Thus, it is advantageous to have a method for harnessing the hydrogen
produced by these organic acid plus metal reactions.
The method of the present invention is intended for use in a portable
hydrogen-generating device. The method comprises the steps of:
(a) reacting a zero-valent metal with an organic acid, and optionally an
oxidizing agent, thereby forming a metal-O-CO-R complex;
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(b) removing the hydrogen produced by the reaction of the metal and
acid;
(c) regenerating the organic acid by oxidizing the metal-O-CO-R
complex by reacting the complex with an oxidizing agent;
(d) precipitating the metal as a metal oxide; and,
(e) optionally, reacting the metal oxide with a hydrocarbon to reduce
the metal to the zero-valent state.
The reaction occurs at essentially ambient temperature, defined herein as at
a temperature of less than about 35°C. Further, the reaction occurs at essentially
ambient pressure or at about 1 bar.
The metal may be any metal that can be easily oxidized in the presence of
mild aqueous acid, such as iron, zinc, copper, aluminum, nickel and a combination
thereof. The metal may be in the form of powder, granules or pellets and acidic
aqueous solution. Iron has been found to be particularly effective for the reaction
both in terms of hydrogen yield and with respect to being a relatively low cost
metal source.
The organic acids are selected on the basis of a steady hydrogen production
rate during a period of time and the absence of additional cations or anions in the
solutions. The organic acid may be any RCOOH or HCOOH compound, including
carboxylic acids, formic acid, acetic acid, oxalic acid, and combinations thereof.
The oxidizing agent may be any oxidant that can oxidize the M-O-CO-R
complex with concomitant formation of the free acid HO-CO-R. Such agents
would include, without limitation, hydrogen peroxide, oxygen, ozone, starches and
sugars.
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The present invention further includes a portable hydrogen-generating
device designed around this method. With reference to Figure 2, the device
proposed would include a case (D) housing a first cartridge (A) filled with the
metal, a solution recycle column holding additional solution of organic acid (C)
and, optionally, the oxidizing agent, and an optional a second replacement
cartridge filled with metal (B). The recycle column is plumbed to both cartridges
with valves to allow the recycle column to be inline with the cartridge in use. A
variable speed pump moves the solution between the active reaction cartridge and
the recycle column. When fed to the active reaction cartridge, the organic acid and
oxidizing agent solution is preferably fed across the metal as uniformly as possible,
such as may be accomplished by using a solution distribution plate or a spray
nozzle. The hydrogen gas formed in the active reaction cartridge is vented from
the cartridge and case to any desired location. To minimize the risk of
contamination of the hydrogen gas by mist or other gases, a hydrogen-permeable
membrane is preferably mounted between the metal and the hydrogen vent.
It is noted that although there is significant prior art that teaches hydrogen
generation from the reaction of iron with mineral acids, reactions between iron and
organic acids are less well-known. Further, the present development includes
experimental data showing surprising results - exceptionally high purity and very
good yields for hydrogen production at a steady hydrogen production rate - when
iron metal is reacted with an organic acid.
It is understood that the processing conditions and apparatus designs may
be varied as known to those skilled in the art without exceeding the scope of this
development.
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P-1296-PCT
What is claimed is:
1. A method for generating hydrogen using reactants and regenerating those
reactants comprising the steps of:
(a) reacting a zero-valent metal, preferably selected from the group
consisting of iron, zinc, copper, aluminum, nickel and a
combination thereof and more preferably iron, with an organic acid,
preferably selected from the group consisting of carboxylic acids,
formic acid, acetic acid, oxalic acid, and combinations thereof,
thereby forming a metal-0-CO-R complex;
(b) removing hydrogen produced by the reaction of the metal and acid;
(c) regenerating the organic acid by oxidizing the metal-O-CO-R
complex utilizing an oxidizing agent, preferably selected from the
group consisting of hydrogen peroxide, starches, sugars, oxygen,
ozone and combinations thereof; and,
(d) precipitating the metal as a metal oxide.

2. The method of Claim 1 further including addition of additional oxidizing
agent with the organic acid.
3. The method of Claims 1 or 2 further including reacting the metal oxide
with a hydrocarbon to reduce the metal to a zero-valent state.
4. The method of any of Claims 1-3 further comprising passing the hydrogen
through a hydrogen-permeable membrane.
5. A portable hydrogen-generating device comprising a case housing (i) a first
cartridge filled with a metal, and (ii) a recycle column filled with an
organic acid solution, wherein said recycle column is plumbed to said
cartridge, and wherein a variable speed pump is also connected to the
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P-1296-PCT
device so as to move said acid solution between the first cartridge and the
recycle column.
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6. The device of Claim 5 further including a replacement cartridge filled with
a metal plumbed to said recycle column.
7. The device of any of Claims 5-6 further including at least one valve to
allow said recycle column to be in communication with each of the first
cartridge and the replacement cartridge separately.
8. The device of any of Claims 5-7 wherein said recycle column contains an
oxidizing agent.
9. The device of any of Claims 5-8 further including a means for uniformly
dispersing said organic acid within the first cartridge.
10. The device of any of Claims 5-9 further including a means for venting gas.

The present development is a method for generating pure hydrogen from an
organic acid solution and a zero-valent metal. By reacting the metal with the
organic acid rather than a mineral acid, hydrogen generation occurs at a gradual
and more consistent rate than is observed by prior art methods, making the present
method suitable for fuel cell applications. A portable hydrogen-generating device
using the method of generating pure hydrogen from acidic solution is further
disclosed