Hydrogen From Renewable Biomass

THE MAGAGINE DEVOTED TO NICKEL AND ITS APPLICATIONS October 2003 Volume 19, Number 1

ORGANIC WASTE FROM CROPS such as this wheat, could someday be used to generate hydrogen.

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A new nickel catalyst could lead to an inexpensive way to produce hydrogen. By Virginia Heffernan

Nickel magazine, October, 2003 -- Chemical engineers at the University of Wisconsin have developed a nickel-based catalyst that could play a role in the evolution of the hydrogen economy.

The Raney-nickel catalyst, named after the scientist who patented the Raney alloy in 1927, can generate hydrogen from common plant sources by converting their byproducts to carbon dioxide (CO₂) and hydrogen gas (H₂).

Platinum can also perform this trick, but the precious metal is costly and often in short supply. Motivated by the demand for a lower-cost alternative, the Wisconsin researchers tested more than 300 catalysts before honing in on Raney-nickel, a nickel-aluminum alloy that is 90% nickel by weight.

But Raney-nickel wasn't perfect. Although the alloy did just as good a job converting sugar water (a glucose-rich organic material derived from ground-up plant matter) to hydrogen as its platinum-aluminum cousin, the reaction at the catalytic surface also produced methane, a greenhouse gas. So the scientists tried adding tin to the mix.

"In order to avoid methane formation, we alloyed the nickel with tin and were able to produce mainly CO₂ and H₂, the desired reaction products," explains James Dumesic, the principal researcher on the project, who explains his findings in the June 27, 2003 issue of Science. "The nickel-tin combination is several orders of magnitude cheaper than precious metals with similar properties."

The discovery is significant because it may provide, for the first time, a cost-efficient means of producing hydrogen for fuel cells using renewable resources. Fuel cells (see accompanying story: How Fuel Cells Work) are a clean and highly efficient alternative to traditional power generators that rely on fossil fuels, but their development and use has been inhibited by cost.

"The new nickel-tin catalyst is cheap enough to compete in the electricity and fuel markets, provided the sugar water feed stock is available at low cost," says Dumesic. "The first applications of this process might be in combination with portable fuel cells to provide power for laptop computers, military equipment, and maybe cars someday."

In these types of applications, batteries would be replaced with cartridges filled with an innocuous liquid such as glycerol.

The catalyst transforms sugar water into hydrogen using a process called aqueous-phase reforming (APR). APR cleaves the C-C, C-H and/or O-H bonds in compounds with a C:O ratio of 1:1 (carbohydrates) to form adsorbed species on the a catalytic surface. In order to be useful for H₂ production, the catalyst must facilitate the C-C bond cleavage while, at the same time, promote the water-gas shift reaction that removes the adsorbed CO species. The modified Raney-nickel catalyst fits the bill.

Other methods of H2 production use steam reforming of fossil fuels, a complicated, three-reactor process that requires temperatures of more than 625°C. The APR process is superior, and perhaps better suited for transportation applications in that it uses a renewable resource and requires only a single reactor at temperatures of 225°C.

The research will continue to be developed and commercialized by Virent Energy Systems, which is building a larger scale reactor to test the process. Wisconsin's Division of Energy, intrigued by the potential for the APR process to convert waste steams from food generators and other businesses into energy, is providing grants to Virent for both business development and R&D.

Virginia Heffernan is a Toronto-based freelance writer.

PHOTO: Tim Pelling

James Dumesic 3014 Engineering Hall 1415 Engineering Drive Madison, Wisconsin 53706 U.S.A. Tel: 1 608 262 1095 Fax: 1 608 262 5434 E-mail: dumesic@engr.wisc.edu Virent Energy Systems 100 Sourth Baldwin Street Suite 206 Madison, Wisconsin 53703-3001 U.S.A. Web site: www.virent.com For other recent Nickel Magazine articles on the use of nickel-containing materials in the energy sector, click here.

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