Catalytic two-step for better diesel

With petroleum prices soaring, an 80-year-old process that can convert carbon sources like coal and biomass into liquid fuel is taking on a new luster. One reason the Fischer-Tropsch (F-T) diesel-making process hasn't taken off globally is that it yields a complex hydrocarbon brew. A portion of it consists of the fuel "sweet spot:" alkanes in the C₉ to C₂₀ range. It takes refining steps to either remove or rework the components that are smaller and larger than those in that range. Alan S. Goldman of Rutgers University, Maurice Brookhart of the University of North Carolina, Chapel Hill, and coworkers have devised a two-catalyst approach that might help (Science 2006, 312, 258). One catalyst dehydrogenates alkanes, such as hexane, into alkenes. The second catalyst orchestrates metathesis reactions involving the alkenes. Hydrogenation with the first catalyst gives longer, fuel-friendly alkanes. "This could ultimately make the overall process more economical," Goldman says. Charles Benham of Rentech, a Denver-based firm working toward commercial F-T diesel production, has seen plenty of good ideas, but catalyst cost and stability are frequent showstoppers, he says.