Corn Yields Another Useful Product: Polypropylene Glycol

Randy Cortright and James Dumesic, chemical engineers at the University of Wisconsin-Madison, have invented a catalytic process for converting the corn-derived compound, lactic acid, into the chemical polypropylene glycol. More than 450 tons of polypropylene glycol are used in the United States annually.

Unlike current processes for manufacturing polypropylene glycol, which make use of petroleum-based starting materials, this advance taps into a low cost, renewable resource available in surplus right now. The U.S. Department of Agriculture estimates that over a billion bushels of corn went unused last year.

"This [technology] provides a sustainable method of producing important chemicals," Cortright says. It also promises to reduce reliance on imported oil and open new markets for U.S.-grown corn.

A chain of processes links corn to polypropylene glycol. It begins with fermentation of the corn-derived sugar glucose into lactic acid, followed by separation and purification of the acid. Cortright and Dumesic's method completes the critical last step by using a copper catalyst in the presence of hydrogen gas to chemically transform lactic acid into polypropylene glycol.

The approach is more cost-efficient than past methods, Cortright says. "We're using a relatively inexpensive metal, running the reaction at lower [hydrogen] pressure and we get 100 percent conversion," of the lactic acid, with fewer unwanted byproducts like alcohols.

Cortright and Dumesic's research builds upon the work of Homer Adkins, a UW-Madison chemistry professor from 1919-49. At a time when most chemicals were produced from agricultural products rather than oil, Cortright says, Adkins was the first to use copper catalysts to turn lactic acid into propylene glycol. "It feels like we've come full circle," Cortright says, "We enhanced the technology, but the basic ideas were known 70 years ago."