Oil is the fuel of modern life. Made up of long hydrocarbon chains, it can be broken down into a slew of useful substances and products. Other fossil resources-- coal and natural gas--are made up of much shorter chains and it has proved difficult to rearrange their carbon and hydrogen atoms to make fuels such as diesel. Now chemists have used a combination of catalysts to produce more useful hydrocarbons from short-chain molecules, potentially opening the door to an alternative-fuel future.
In a paper published today in Science, chemists Alan Goldman of Rutgers University and Maurice Brookhart of the University of North Carolina describe the new work. They first used an iridium-based molecule to snatch hydrogen away from its carbon. Without the hydrogen to bond with, the carbon instead linked up with its fellow carbon atoms. Next the chemists added a second catalyst--one of the so-called Schrock-type catalysts, which merited last year's Nobel Prize in Chemistry--to redistribute the carbon chains into longer, heavier molecules. The original iridium catalyst then released the captured hydrogen, which promptly attached to the longer and heavier carbon chain, turning it into a useful hydrocarbon. Thus, freed of its hydrogen cargo, the iridium molecule was free to search out more short-chain molecules and start the process all over again.
"We take all these undesirable medium-weight substances and convert them to the useful higher- and lower-weight products," Goldman says. The process could be used to help turn coal, leftover oil refinery products or even plants into diesel fuel and other functional hydrocarbons.
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But the technique still requires considerable refinement before it can be used effectively, Brookhart cautions. For one thing, longer lasting Schrock-type catalysts must be developed. The scientists also want to hone the process so that it creates only useable hydrocarbons, rather than the range of variants it currently produces. "We [also] need to be able to demonstrate that instead of getting a couple of thousand turnovers, we can get many millions," he says.
Still, the novel technique seems to work more effectively than its predecessors. "We're not the first to accomplish this, but we've got a very nice, potentially useful system here," Brookhart concludes. And it just might prove a critical step in transforming the world's oil addiction.
