Presidential Green Chemistry Challenge: 2006 Academic Award

Professor Galen J. Suppes of the University of Missouri-Columbia

Biobased Propylene Glycol and Monomers from Natural Glycerin

Innovation and Benefits: Professor Suppes developed an inexpensive method to convert waste glycerin, a byproduct of biodiesel fuel production, into propylene glycol, which can replace ethylene glycol in automotive antifreeze. This high-value use of the glycerin byproduct can keep production costs down and help biodiesel become a cost-effective, viable alternative fuel, thereby reducing emissions and conserving fossil fuels.

Summary of Technology: Glycerin is a coproduct of biodiesel production. The U.S. biodiesel industry is expected to introduce one billion pounds of additional glycerin into a market that is currently only 600 million pounds. The economics of biodiesel depend heavily on using its glycerin coproduct. A high-value use for glycerin could reduce the cost of biodiesel by as much as 40¢ per gallon. There is simply not enough demand for glycerin, however, to make use of all the waste glycerin expected.

One solution is to convert the glycerin to propylene glycol. Approximately 2.4 billion pounds of propylene glycol are currently made each year, almost exclusively from petroleum-based propylene oxide. Propylene glycol is a less toxic alternative to ethylene glycol in antifreeze, but is currently more expensive and, as a result, has a very small market share. Professor Galen J. Suppes has developed a catalytic process that efficiently converts crude glycerin to propylene glycol.

Professor Suppes's system couples a new copper-chromite catalyst with a reactive distillation. This system has a number of advantages over previous systems that perform this conversion. The new process uses a lower temperature and lower pressure than do previous systems (428 °F versus 500 °F and <145 psi versus >2,170 psi), converts glycerin to propylene glycol more efficiently, and produces less byproduct than do similar catalysts. Propylene glycol made from glycerin by Professor Suppes's method is also significantly cheaper than propylene glycol made from petroleum.

Another solution is to convert glycerin to acetol (i.e., 1-hydroxy-2-propanone or hydroxyacetone), a well-known intermediate and monomer used to make polyols. When made from petroleum, acetol costs approximately $5 per pound, prohibiting its wide use. Professor Suppes's technology can be used to make acetol from glycerin at a cost of approximately 50¢ per pound, opening up even more potential applications and markets for products made from glycerin.

Professor Suppes initiated this project in June 2003. The first commercial facility, with a capacity of 50 million pounds per year, is under construction and is expected to be in operation by October 2006.

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