Researchers Find New Metal Combination
by Paul Recer, Associated Press
WASHINGTON -- Organic wastes such as paper mill sludge or cheese whey can be converted into hydrogen using an inexpensive metal catalyst, researchers say, in a process that could boost efforts to replace oil and gas fuels.
Researchers at the University of Wisconsin tested more than 300 metal combinations before finding that a mix of nickel, tin, and aluminum could separate hydrogen from a mixture rich in glucose, a sugar common in many organic wastes. A report on the study appears Friday in the journal Science.
Glenn L. Schrader, a National Science Foundation chemical engineer who supervises grants for hydrogen research projects, said the catalyst could be a significant advance in efforts to develop a hydrogen-based energy system.
"We really need to develop fuel cells that use metals cheaper than platinum, and this work provides a very promising lead," he said.
Many experts believe that hydrogen eventually will replace oil and gas as the energy that drives industry and transportation. Hydrogen burns cleanly, and there is an almost unlimited supply. A major technical problem has been finding a cheap way to separate hydrogen from other compounds and to store the fuel efficiently and safely.
The most likely immediate application of hydrogen would be in fuel cells, which combine hydrogen and oxygen to make electricity, heat, and water.
James Dumesic, a professor of chemical engineering at the University of Wisconsin and lead author of the study, said the combination metal catalyst worked as efficiently in laboratory tests as a much more expense platinum catalyst and at a lower temperature and pressure.
Platinum is known to be excellent for chemically separating hydrogen, but the rare metal costs about $8,000 a pound, many times more than the tin, nickel, and aluminum used in the Wisconsin device, experts said. Dumesic said the hydrogen catalyst is, in effect, a pressure cooker filled with pellets made of nickel, tin, and aluminum. A stream of raw stock rich in glucose is heated to 437 degrees and introduced into the device. The glucose reacts with the metal pellets, and hydrogen and carbon dioxide separate from the mix.
"The hydrogen and carbon dioxide kind of bubble up," said Dumesic. The gas is piped away and then cooled.
Dumesic said the hydrogen-carbon dioxide mix could be used as a fuel in some applications, or the CO2 could be separated out using a second, simpler process.
Catalysts made of nickel and aluminum produce hydrogen but also produce methane, an unwanted pollutant. By adding more tin to the combination, the production of methane was halted, while the production of hydrogen was increased, Dumesic said.
Dumesic said the Wisconsin device, using the combination of common metals, could reduce the catalyst cost by 10 to 100 times.
In theory, the catalyst could use any organic waste flow rich in glucose as a feed stock. Dumesic said he and his associates are now developing a system that would produce about one kilowatt of power. He said if the pilot plant works as expected, then the first application may be at dairy processing plant, such as a cheese factory, where dairy wastes could be used as the feed stock. Waste from pulp mill, corn processing plants, or food processing factories could be a source of hydrogen, said Dumesic.
The combination metal catalyst has been patented and is controlled by the Wisconsin Alumni Research Foundation. Dumesic said he is co-founder of a company that has been licensed to use the patent in developing energy systems. He said he has a personal financial interest in the success of the effort.
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