In developing new industrial chemicals, companies undoubtedly should consider their global warming potential. Researchers at Purdue University, West Lafayette, Ind., and the U.S. National Aeronautics and Space Administration's Ames Research Center, Moffett Field, Calif., have developed some insights that can help. They studied a variety of fluorine-containing molecules to determine what increases or decreases their impact on global warming. Such compounds last longer in the atmosphere than carbon dioxide and other major global warming agents and so, even if generated at low volumes, can have a significant cumulative impact.
"We specifically looked at molecules that we felt would have the potential for industrial use as replacements for chlorofluorocarbons," notes Joseph Francisco, a professor of chemistry and earth and atmospheric sciences at Purdue and co-author of a recent paper on the study that appeared in the Proceedings of the National Academy of Sciences. The chemicals included hydrofluorocarbons, perfluorocarbons, hydrofluoroethers, hydrofluoroolefins and sulfur and nitrogen fluorides.
The amount and placement of fluorine proved to be a key factor. Multiple fluorine bonds in a compound made the global warming potential worse. "In other words, don't put them all on one atom. Spread them out," advises Francisco.
"What we're hoping is that these additional requirements for minimizing global warming will be used by industry as design constraints for making materials that have, perhaps, the most green chemistry," he says.
"Our goal has been to provide the community, i.e., chemical engineers and other technologists in the chemical industry, some useful tools to help evaluate one of several considerations that go into developing environmentally benign materials."
"We are planning a follow-up study. We want to start to look at the issue of lifetime of greenhouse gases in the atmosphere, and how specifically various substituent groups influence the lifetime of modified greenhouse gases," Francisco adds.