About 40 percent of all the carbon dioxide pollution produced in the United States today comes
from the coal-fired power plants that make half the nation's electricity. Currently, power
companies aren't required to remove CO2 from their smokestacks. If they were, conventional
technology would add about 30 percent to your electric bill.
Clearly, a cheaper solution to the greenhouse gas problem is needed, and some Notre
Dame chemical engineers believe salts may be the answer. Not the kind you sprinkle on french
fries, but "molten salts," also known as ionic liquids. These manmade chemical salts are fluid at
room temperature.
Ed Maginn, Joan Brennecke and William Schneider, Notre Dame chemical and
biomolecular engineering professors, first recognized their potential a few years ago while
studying the compounds for possible use as nontoxic, "green" industrial solvents. In the course
of that work, the Notre Dame researchers found that nitrogen, a large component of power plant
emissions, is insoluble in an ionic liquid. "And that was when we first got the idea they might be
a useful tool for doing gas separations," Brennecke says.
Subsequent work revealed that ionic liquids do indeed have the ability to soak up a good
deal of CO2. The basic idea in most carbon dioxide reduction schemes is to separate CO2 from
the flue gas and then sequester it by pumping it down and out of the atmosphere into deep saline
aquifers in old, played-out oil well fields.
Ionic liquids have the potential to be more economical than such reduction methods
because they work at higher temperatures and are less corrosive to plumbing. With the
conventional water-based technology, power plant gases must first be cooled before they are
passed through the capturing chemicals. This method also reacts with sulfur dioxide, corroding
pipes.
Currently, the Notre Dame research team is working to fine-tune the amount of energy
needed to release the CO2. from the ionic liquid and to optimize its capacity to carry the gas.
DTE, the Detroit power company; Babcock & Wilcox, a power plant construction firm; and
Air Products, a gas separation firm, are partners in the research.
(October 2007)
