|
|
|
Green coal? Process converts coal into diesel fuel Coal-to-Diesel could reduced foreign dependence on oil University of North Carolina at Chapel Hill April 14, 2006 Making alternative fuel becomes more efficient with dual-catalyst system: UNC-Rutgers study CHAPEL HILL – As the United States’ oil reserves dwindle, some say the nation will have to rely on synthetic petroleum fuel made from its large stores of coal. "Two percent of the United States’ energy reserves is in oil, 3 percent is in gas, and 95 percent is in coal," said Dr. Maurice Brookhart, W.R. Kenan Jr. professor of chemistry in UNC’s College of Arts and Sciences. "Many people in the energy sector think that when oil starts to run out, coal will be a source of transportation fuel for some time before we perfect the science behind solar and hydrogen-based energy. Producing diesel fuels from coal is especially attractive since diesel engines are more efficient than gasoline engines." The Fischer-Tropsch method of making synthetic liquid fuels from coal and other carbon sources has been used since the 1920s. Today, Fischer-Tropsch fuels power most large vehicles in South Africa, and American companies have expressed interest in these fuels, which emit fewer particulates and less carbon monoxide than conventional diesel fuels. Such fuels have been termed "green diesel." The cost of making Fischer-Tropsch fuels has been considered prohibitive. "But right now, with oil this expensive, I think it will soon become a competitive process to make liquid fuels," said Brookhart, an author of the study, which is published Friday (April 14) in the journal Science. Dr. Alan S. Goldman, professor of chemistry and chemical biology at Rutgers, is the lead author of the study. The Fischer-Tropsch reaction creates hydrocarbon compounds called alkanes. Methane and ethane are examples of alkanes. Some of the alkanes created by Fischer-Tropsch are desirable for use as fuel, but others have low molecular weights that make them unsuitable.
"It’s accomplished by a dual-catalyst system that allows us to take low molecular weight alkanes with between four and nine carbons in the chain and boost their weights up to a range appropriate for diesel fuel (10 to 19 carbons)," he added. Brookhart said that in the dual-catalyst system, "one catalyst removes hydrogen, converting the alkane to a new material that contains carbon-carbon double bonds." Those double bonds make the new material more reactive, he added. Then a second catalyst "scrambles" the carbon bonds, creating compounds with higher molecular weights. The first catalyst then returns the hydrogen atoms to the rearranged compounds, yielding alkanes that are usable as fuel. Currently, a process termed hydrocracking is used to break down hydrocarbons with molecular weights too high for fuel use into lower molecular weight materials, but the process is not very selective. "The catalyst system we used can combine very low molecular weight and very high molecular weight alkanes to produce alkanes in the diesel fuel range and, thus, may also prove useful for recovering value from high molecular weight materials," Brookhart said. The other authors of the study, in addition to Brookhart and Goldman, are Rutgers postdoctoral research associate Dr. Ritu Ahuja; postdoctoral research associate Dr. Amy H. Roy and research assistant Dr. Zheng Huang, both of UNC’s department of chemistry; and Dr. William Schinski, a chemist with Chevron Research and Technology Company. The research was sponsored by a grant from the National Science Foundation Center for the Activation and Transformation of Strong Bonds (CATSB), of which Brookhart and Goldman are members. The center, based at the University of Washington, is one of the first "chemical bonding centers" funded by the NSF to encourage groups of scientists to work together to tackle major problems in chemistry to benefit society. Its work focuses on finding new ways to transform strong chemical bonds, in hopes of creating environmentally friendly ways to synthesize materials on a large scale. RELATED ARTICLE Clean coal could fight climate change A new chemical process for removing impurities from coal could lead to significant reductions in carbon dioxide emissions from coal-fired power stations say researchers sponsored by the Engineering and Physical Sciences Research Council, Britain's main agency for funding research in engineering and the physical sciences. The text of this document is a modified news release from the University of North Carolina at Chapel Hill. The photo and photo caption are from mongabay.com. News index | RSS | Add to MyYahoo! Advertisements: Organic Apparel from Patagonia | Insect-repelling clothing |
MONGABAY.COM
T-SHIRTS 
CALENDARS 
CANVAS BAGS 
|
|
|
