Process ups biodiesel efficiency
Technology Research News
fuel produced when cornstarch is converted to sugar, then the sugar converted
to ethanol, takes a fair bit of energy to make. About one third of the energy
required to produce ethanol is used in the conversion step of separating
ethanol from water.
Researchers from the University of Wisconsin at Madison have shown
that it is possible to convert biomass materials like corn into fuel that
could be used in diesel engines in a way that automatically separates the
fuel from water. "This is a new process to produce liquid fuels from biomass,"
said James Dumesic, a professor of chemical and biological engineering at
the University of Wisconsin.
Because no energy is required to separate the fuel from water, the
process has a relatively high overall energy efficiency.
The fuel could eventually be blended with diesel fuel produced from
petroleum sources to reduce oil needs, according to Dumesic. The process
could also eventually produce diesel fuel that does not have to be blended
with petroleum-based fuel, he said.
The researchers' method converts biomass into liquid alkanes within
a self-sustained refinery.
Alkanes are hydrocarbons. The simplest is methane. More complex
alkanes are the main components of gasoline. The new method uses existing
processes to convert biomass to sugar, to convert part of the sugar to hydrogen,
and to convert part of the sugar to carbonyl-containing compounds. Carbonyl
compounds contain oxygen atoms double-bonded to carbon atoms.
The researchers devised a process to convert carbonyl compounds
to a useful fuel. The first step condenses the carbonyl-containing compounds
with acetone to convert them to large, water-soluble organic compounds.
The second step involves a four-phase dehydration-hydrogenation reactor
that converts these compounds into liquid alkanes.
Key to the process is the order in which the conversion takes place.
The bonds between carbon atoms, which are broken to gain energy when fuel
is burned, are formed before the hydrogenation phase.
The alkane fuel contains 90 percent of the energy of the glucose
and hydrogen that the reaction begins with, said Dumesic. "Thus burning
the alkane fuel would give you 90 percent of the energy compared to burning
the glucose and the hydrogen."
The advantage of the researchers' process is that when alkanes are
produced they spontaneously separate from water, said Dumesic. "In contrast
to our process... ethanol must be separated from water by an energy-intensive
distillation step," he said. "For our process, no energy is required to
separate the alkane products from water."
This boosts the overall energy efficiency of the fuel. The ratio
of energy derived from ethanol to the energy required to produce it is 1.1
to 1. The researchers' process has an estimated ratio of 2.2 to 1, according
The current disadvantage of the process is that it takes a lot of
steps. This can be improved, however, said Dumesic. "Now that we have elucidated
the chemical pathways, we believe that we can intensify our process by combining
various steps... by using multi-component catalysts," he said.
The conversion process has the potential to allow domestically-available
biomass to become part of the solution to the United States' current dependence
on fossil fuels, according to Dumesic. "The main obstacle to the more widespread
utilization of our low-cost biomass resources is the absence of low-cost
processing technologies," he said.
The key is building biorefineries that balance the energy. A refinery
balances energy requirements of each process with those of other processes
and the chemical intermediaries of each process are either separated as
final products or used elsewhere in the refinery, said Dumesic.
Dumesic's research colleagues were George Huber, Juben N. Chheda
and Christopher J. Barrett. The work appeared in the June 2, 2005 issue
of Science. The research was funded by the Department of Energy (DOE),
the National Science Foundation (NSF) and Conoco-Phillips.
Funding: Corporate; Government
TRN Categories: Energy; Chemistry
Story Type: News
Related Elements: Technical paper, "Production of Liquid Alkalines
by Aqueous-Phase Processing of Biomass-Derived Carbohydrates," Science,
June 2, 2005
June 15/22, 2005
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