Ipatieff Prize Winner
Notre Dame chemical engineer wins national award for supercritical work

Chemical engineer Joan Brennecke of Granger, Ind., was honored April 3 by the world's largest scientific society for her insights into supercritical fluids, an environmentally friendly medium for such processes as decaffeinating coffee and polymerizing the building blocks of plastics. She received the 2001 Ipatieff Prize from the American Chemical Society at its 221st national meeting in San Diego.

Brennecke, a chemical engineer at the University of Notre Dame, said she studies how supercritical fluids -- heated gases so highly compressed they behave almost like liquids - influence reactions.  "The reason that's interesting is because a couple of them might substitute for some nasty organic solvents," she said. Benzene, methylene chloride and such solvents are useful in making plastic, detergents, pharmaceuticals and other products, but can damage health or the environment.  Industry has used methylene chloride to decaffeinate coffee, for example, but now Kraft Foods Inc. uses supercritical carbon dioxide, which is much more benign, said Brennecke.

But to apply such new techniques in the field, one must understand them first down to their very molecules, she added. One discovery her team has made may help increase the rate of reactions with little expense or effort -- "a freebie, if you will," she said.  Called a local composition effect, reactants actually cluster around each other in supercritical fluids. "Why? It's because the molecules can arrange themselves in their energetically preferred positions," Brennecke said. "Liquids are too dense, so molecules can get in the way. And in regular gases, the molecules are too far apart to find each other easily."

With a chemical engineer for a father, Brennecke said she knew ever since she was young that she wanted to be one too. "When I was a kid, I was always helping him take things apart, figuring out how they worked and putting them back together," she remembered.  Brennecke received her undergraduate degree from the University of Texas, Austin, in 1984 and her Ph.D. from the University of Illinois, Urbana-Champaign, in 1989. She is a member of the ACS industrial and engineering chemistry divisions.