Joan F. Brennecke’s research interests — supercritical fluid technology and thermodynamics — are not the stuff of everyday conversation, but their implications could make a lot of manufacturing processes safer for workers and more benign to the environment. “In general,” she says, “what I work on is looking for substitutes for the normal solvents used in industry.”
She’s talking about things like benzene, perchloroethylene, acetone and hexane, commonly used in applications ranging from dry cleaning to decaffeinating coffee and extracting soybean oil out of soybeans. Their drawback is a high degree of volatility — some are flammable, some have been linked to increased cancer rates, most are oxidized in the atmosphere to form carbon dioxide, adding a greenhouse gas linked to global warming. Working with solvents, says Brennecke, “even if you’re careful you’re still going to end up with some of them escaping into the atmosphere where people will breath them. So there’s a big push for alternatives.”
Paradoxically, one of the alternatives this professor of chemical engineering has been exploring in her laboratory is carbon dioxide — not ordinary CO2, however, but supercritical carbon dioxide, a state where the CO2 is a single phase compressible fluid. Using this material as a solvent, she says, “is environmentally benign. We’re not adding any carbon dioxide to the atmosphere; we’re just taking it from the atmosphere and using it in a process. There’s no net accumulation of CO2.”
A related focus of Brennecke’s research is ionic liquids — salts that are liquid at room temperature and don’t vaporize. In a recent article in Nature, Brennecke called these liquids potentially good solvents, but noted: “Once the reaction is complete, we need to get the chemical product out of the ionic liquid in pure form.” That’s a problem she has been investigating with graduate students and colleagues at Notre Dame and researchers at the University of Pittsburgh.
“Now we’re saying,” says Brennecke of this research, “that we can design ionic liquids so they’ll give us the separation properties we want. This is a very important advance.”
A member of Notre Dame’s faculty since 1989, Brennecke has been honored with a National Science Foundation Presidential Young Investigator Award. She’s also the recipient of a Special Presidential Award from Notre Dame for her classroom teaching, graduate student mentoring, research and service efforts to the University and the chemical engineering profession.