New process making green diesel

University of Wisconsin-Madison College of Engineering researchers are making a diesel-like liquid fuel from carbohydrates commonly found in plants.

A four-phase catalytic reactor in which corn and other biomass-derived carbohydrates can be converted to sulfur-free liquid alkanes is resulting in an ideal additive for diesel transportation fuel, as detailed by graduate students George Huber, Juben Chheda, Chris Barrett and Steenbock Professor James Dumesic in the June 3 issue of the journal Science, Chemical and Biological Engineering.

"It's a very efficient process," Huber says. "The fuel produced contains 90 percent of the energy found in the carbohydrate and hydrogen feed. If you look at a carbohydrate source such as corn, our new process has the potential to creates twice the energy as is created in using corn to make ethanol."

Ethanol production creates 1.1 units of energy for every unit of energy consumed because about 67 percent of the energy required to make ethanol is consumed in fermenting and distilling corn. Ethanol production creates 1.1 units of energy for every unit of energy consumed.

In the UW-Madison process, the desired alkanes spontaneously separate from water, meaning no additional heating or distillation is required. So 2.2 units of energy are created for every unit of energy consumed in energy production.

"The fuel we're making stores a considerable amount of hydrogen," says Dumesic. "Each molecule of hydrogen is used to convert each carbon atom in the carbohydrate reactant to an alkane. It's a very high yield. We don't lose a lot of carbon. The carbon acts as an effective energy carrier for transportation vehicles. It's not unlike the way our own bodies use carbohydrates to store energy."

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