Patent Application
20060266159
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, 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.
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.
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
The method of the present invention is intended for use in a portable hydrogen-generating device. The method comprises the steps of:
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.
The present invention further includes a portable hydrogen-generating device designed around this method. With reference to
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.
This application claims priority to U.S. Provisional Patent application 60/684,459 filed on May 25, 2005, which is incorporated herein in its entirety by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60684459 | May 2005 | US |
