Sponsored by Dow Chemical and endowed by Rohm and Haas
Biodiesel production was on the rise in the early 2000s, boosting supplies of glycerin, a by-product of making this vegetable-oil-based fuel. Market watchers predicted growing supplies and lower prices for glycerin.
Seeing a potential business opportunity at hand, researcher William J. (Jack) Kruper, a corporate fellow at Dow Chemical, swung into action. He probed the possibilities of using glycerin as a low-cost, renewable feedstock for commodity chemicals and plastics.
He and colleagues at Dow successfully developed and piloted a process for converting glycerin to epichlorohydrin. This chemical is an intermediate in the production of liquid epoxy resins, which are used in the electronics industry. Dow is the largest manufacturer of epichlorohydrin and liquid epoxy resins.
“It turned out to be about the best process on the planet for making epichlorohydrin—provided you can get cheap glycerin,” Kruper says.
Making epichlorohydrin from glycerin has a number of advantages compared with using propylene as a raw material. It is a solventless process that produces far less wastewater than the current process. Therefore, it requires smaller plants and processing vessels—meaning a smaller capital investment (Clean, DOI: 10.1002/clen.200800067).
The process involves reacting glycerin with hydrogen chloride in the presence of a carboxylic acid catalyst at elevated temperature and pressure. Conditions are optimized for regioselectivity, producing 30 to 50 molecules of 1,3-dichloropropanol for every one molecule of 2,3-dichloropropan-1-ol at 98% conversion. The 1,3 isomer is converted to epichlorohydrin about 300 times faster than the 2,3 isomer. In contrast, the conventional propylene-based process favors formation of the less reactive 2,3 isomer.
The key aspect of the glycerin-to-epichlorohydrin conversion is that it allows the water produced as a by-product to stay in the reaction vessel.
“By leaving the water in, the conversion is not equilibrium-limited, and unexpectedly, much lower levels of by-products are formed,” including chlorinated ethers and chloroacetone, Kruper tells C&EN. “The process itself embodies the principles of atom economy.”
In 2008 Dow’s board of directors approved investment in a plant to apply this new technology, which is covered by three U.S. patents, on a commercial scale. But the downturn in the economy has put those plans on the shelf for now, Kruper says.
“We’re still looking into the option of doing this chemistry commercially, and we are active in maintaining and establishing intellectual property,” he adds.
Kruper’s work “combines rigorous scientific habits with a keen understanding of the cost and engineering constraints that differentiate an interesting process from one that is useful,” says Clark R. Landis, a professor of chemistry at the University of Wisconsin, Madison. “Jack has the ability to simultaneously think like both a mechanistic chemist and a chemical engineer.”
Kruper, 58, has worked for three decades at Dow. He earned a B.S. in chemistry from the University of Michigan, Dearborn, and a Ph.D. in organic chemistry from the university’s Ann Arbor campus. He holds 62 U.S. patents and has published 26 peer-reviewed papers.
Kruper will deliver the award address before the ACS Division of Inorganic Chemistry.