KU Researchers Develop Clean-Burning Synthetic Diesel Fuel

KU researchers developed formulations of the fuel that allowed the elimination of one of the three steps in the Fischer-Tropsch conversion of natural gas to synthetic diesel, said Galen Suppes, associate professor of chemical and petroleum engineering. Without the extra step, the production of synthetic diesel fuel could be more economically feasible.

"Preliminary engine tests indicate that these formulations are probably the best liquid fuel that has ever been recorded for use in a diesel engine," Suppes said. "A few hurdles lie between the point where we are and commercial utilization, but this fuel definitely has possibilities."

KU's fuel application research complements production development by Syntroleum Corp., Tulsa, Okla., to make clean synthetic fuels commercially available on a widespread basis. These fuels could exceed current or proposed environmental standards and still be produced economically. A patent is pending on the formulation developed at KU.

To convert natural gas to a liquid form, heat, steam and a nickel-based catalyst are used to produce a carbon monoxide and hydrogen mixture known as synthesis gas - or syngas. The second step in the process is to produce a liquid fuel from the syngas using the Fischer-Tropsch reaction.

Developed in 1923 by Franz Fischer and Hans Tropsch, Fischer-Tropsch technology was used by Germany in World War II to produce liquid fuels from coal. This allowed Germany to develop a reliable, if expensive, source of diesel fuel within its borders.

Although synthetic fuels have been produced from coal since the war, a costly refining technique has always been needed as a third and final production step after the Fischer-Tropsch synthesis.

According to Suppes, with the KU formulations and other recent production improvements, the third step is unnecessary.

"We believe that the fuel is good enough to use after the second step," he said. "We used the synthetic oil in different formulations in engine tests and identified several that worked very well in an unmodified diesel engine. It worked better than diesel fuel."

"In preferred blends, nitrogen oxide emissions were reduced by 10 percent," Suppes said, "while particulate emissions decreased from 5 percent to 69 percent, depending on the mixture. Blending is important for the best performance."

Syntroleum has already taken steps to certify a number of different alternative fuels, including the one researched by KU. Once certified, these fuels can be produced by any of Syntroleum's licensees. Current licensees include ARCO, Texaco, Kerr-McGee, YPF, Marathon and Enron.

Syntroleum is one of the world's corporate leaders in developing processes to convert natural gas to synthetic liquid fuels. Researchers believe that a synthetic fuel could be economically produced from natural gas that is found in hard-to-reach regions, such as Alaska's North Slope, or that is currently being burned off in various locations around the world.

"The synthetic fuel can be produced from coal, biomass, municipal solid waste and natural gas. And the fuel can be distributed in existing pipelines," Suppes said. "This is a great greenhouse gas solution."