Ethanol yields hydrogen
Technology Research News
Fuel cells that convert the chemical bonds
between hydrogen atoms to energy are about three times more efficient
than combustion engines that burn hydrocarbons. And fuel cells powered
with pure hydrogen carry out the conversion cleanly.
The trick is finding a cost-effective way to produce hydrogen
without polluting the environment.
Researchers from the University of Minnesota and the University
of Patras in Greece have devised a way to extract hydrogen directly from
ethanol, which would make for a renewable energy cycle. Ethanol is produced
by converting biomass like cornstarch to sugar, then fermenting it.
The researchers' method is relatively simple, and an ethanol-to-hydrogen
converter designed for home use would be not much larger than a coffee
mug, according to Lanny Schmidt, a professor of chemical engineering and
materials science at the University of Minnesota.
Historically, there have been two major stumbling blocks to using
ethanol as a source for hydrogen. Ethanol is fairly flammable, and the
process of extracting hydrogen from ethanol destroys the catalyst traditionally
used to extract hydrogen from hydrocarbons like oil.
The University of Minnesota researchers were looking to find a
good way to convert ethanol because it packs a lot of energy -- 80 percent
that of gasoline -- and is a renewable fuel source. "We tried ethanol,"
said Schmidt. "And it didn't work for two years."
The researchers eventually solved the flammability problem by
using an automotive fuel injector, said Schmidt. "It rapidly vaporizes
ethanol water and mixes [it] with air and does this so fast that there's
no time for flames to start," he said.
They solved the catalyst problem accidentally, said Schmidt. At
first the researchers were using the same rhodium catalyst they'd had
success with in extracting hydrogen from diesel fuel and natural gas.
This, "forms carbon on the surface and otherwise makes a mess out of things,"
which destroyed the catalyst within a few hours, said Schmidt. "We...
discovered serendipitously that rhodium-ceria as the catalyst had a long
life," he said. The researchers are still investigating exactly why the
new catalyst works so much better.
The gasoline sold by many service stations around the country
is really a mix of ethanol and gasoline, but fuel ethanol must be refined
so that it contains no water. The researchers' method not only allows
for water to be mixed with ethanol, it extracts some of the hydrogen from
the water as well, said Schmidt. This makes producing ethanol for hydrogen
potentially cheaper. Ethanol is currently more expensive than gasoline,
but the two fuels are in the same realm -- wholesale prices are about
$1.10 a gallon versus 70 cents for gasoline, he said.
The researchers' method is relatively simple. "You feed ethanol
plus water into the top of a reactor," said Schmidt. The fuel injector
vaporizes the fuel and sprays the drops onto a hot surface to make a mixture
of mostly ethanol with a little air and water, which hits a catalyst that's
glowing bright orange from the heat of the chemical reaction. "That makes
hydrogen form very quickly... and that feeds into the fuel cell," he said.
The reactor could be any size depending on the application, said
Schmidt. A reactor large enough to extract hydrogen for a washing machine-sized
fuel cell designed to power a house could be made as small as a coffee
mug, said Schmidt.
The method could be used in practical applications now, said Schmidt.
"We'll have the technical capability to switch to a significant extent
away from fossil fuels toward renewable fuels, but whether we do... is
a political question and an economic question," he said. "It's not cheaper
than natural gas or coal... but it's cleaner, and renewable."
Although extracting hydrogen from ethanol produces carbon dioxide,
the carbon dioxide is reclaimed by the next year's crop, making for a
renewable energy cycle. "If you use biomass as your source of energy instead
of fossil fuels, carbon dioxide gets sequestered back into next year's
crop," said Schmidt.
Eventually waste products like wood chips, grass clippings and
crop wastes could be used to make lower-cost ethanol, said Schmidt. How
far down the road this is depends on "when we want to switch to renewable
fuels," he said. "Technically we could do it in 10 years."
Schmidt's research colleagues were Gregg A. Deluga and James R.
Salge at the University of Minnesota, and Xenephon E. Verykios at the
University of Patras in Greece. The work appeared in the February 13,
2004 issue of Science. The research was funded by the National
Science Foundation (NSF), the Department of Energy (DOE), and the Initiative
for Renewable Energy and the Environment at the University of Minnesota.
Timeline: Now, 10 years
Funding: Government, University
TRN Categories: Energy
Story Type: News
Related Elements: Technical paper, "Renewable Hydrogen from
Ethanol by Autothermal Reforming," Science, February 13, 2004
February 25/March 3, 2004
Ethanol yields hydrogen
Biochip makes droplet
Model keeps virtual
Simple optics make
Hot tip boosts
Nanowires spot DNA
up object orientation
makes liquid crystal
Research News Roundup
Research Watch blog
View from the High Ground Q&A
How It Works
News | Blog
Buy an ad link