[Bioconversion] Beyond Ethanol: Synthetic fuel offers promising alternative: DMF

Fri Jun 29 19:07:02 EDT 2007

"Don't stop with ethanol" is probably the message of this note on the
development of DMF (2,5-dimethylfuran) .

Tom Miles

>From Science News June 23, 2007, vol 171 No. 25

http://www.sciencenews.org/articles/20070623/fob6.asp

Beyond Ethanol: Synthetic fuel offers promising alternative

Davide Castelvecchi

DMF may not yet be a household name, but thanks to newly improved production
processes, this biofuel may some day prove even better than ethanol as a
sustainable alternative to gasoline. 

Plant-derived biofuels such as ethanol offer renewable-energy alternatives
to fossil fuels. Their use could help reduce carbon emissions and
greenhouse-gas generation. 

Currently, the global leader in biofuel production is Brazil, which focuses
on converting energy-rich sugarcane into ethanol. Meanwhile, corn-to-ethanol
plants, which are less efficient, are popping up across the midwestern
United States. 

Even ethanol from sugarcane, however, is far from ideal. A gallon of ethanol
yields less energy than a gallon of gasoline, resulting in lower automobile
mileage. Moreover, producing ethanol from sugar is slow and inefficient. As
in wine and beer making, ethanol plants use yeast fermentation to brew the
fuel from sugary liquids. Unfortunately, this process can take several days.

Chemists have long known about a synthetic alternative fuel called
2,5-dimethylfuran, or DMF. Like ethanol, DMF can be derived from sugars, but
it has a 40 percent higher energy density, says James Dumesic, a chemical
engineer at the University of Wisconsin-Madison. That means cars could get
at least as many miles per gallon of DMF as they get from gasoline. 

Until now, DMF production has largely been confined to the lab. Typically,
acidic catalysts are used to strip oxygen off either of two types of sugar,
glucose or fructose, producing an intermediate compound known as
5-hydroxymethylfurfural (HMF). Extracting the HMF has been cumbersome,
however. "If you leave it in water, it tends to react with the sugar that's
still there," Dumesic says. 

Now, Dumesic and his colleagues have developed a technology that could
extract HMF efficiently enough to make DMF an attractive alternative to
ethanol. 

The team describes its two-step process in the June 21 Nature. First, the
researchers added salt along with the acidic catalyst to a solution of
sugars in water. They then exposed the watery mix to a second fluid, a
hydrocarbon. The HMF quickly transferred into the hydrocarbon, in which it
dissolved more readily than in water. Crucially, the presence of salt sped
up the process by making the water more hostile to the HMF. 

In the second step, the scientists mixed HMF with hydrogen and a
copper-ruthenium-based catalyst. The hydrogen stripped two more oxygen atoms
off HMF, producing water and DMF. 

It should be relatively easy to apply the new technique on an industrial
scale, says Dumesic. Before DMF can be mass-produced, however, further
research is needed to explore its toxicity and potential environmental
impact, he adds. 

The new process is an "interesting piece of technology," says Lanny Schmidt
of the University of Minnesota in Minneapolis. Using catalysts rather than
fermentation could dramatically speed and simplify the conversion process,
resulting in lower costs, he notes. Conrad Zhang of the Pacific Northwest
National Laboratory in Richland, Wash., calls the technique "an important
step toward a usable, liquid transportation fuel." 