Biomass can provide a drop-in replacement for gasoline, report researchers at the University of California, Davis. The team has developed a three-step catalytic process using levulinic acid as feedstock. "It's a cheap and practical starting point that can be produced from raw biomass with high yield," says Mark Mascal, a professor of chemistry at the school.
"What's exciting is that there are lots of processes to make linear hydrocarbons, but until now nobody has been able to make branched hydrocarbons with volatility in the gasoline range," he adds.
In the process, first the levulinic acid is dehydrated to angelica lactone using a heterogeneous acid catalyst, montmorillonite clay (K10). This then is treated with catalytic K2CO3 to produce angelica lactone dimer. Finally, the dimer undergoes hydrodeoxygenation at relatively mild conditions using robust platinum- or iridium-based catalysts to give branched C7–C10 hydrocarbons. Overall yield for the three steps reaches up to 76%, note the researchers. More details appear in a recent article in Angewandte Chemie.
Considering that biomass conversion to levulinic acid can exceed 80%, the "field-to-tank" yield for drop-in gasoline potentially could surpass 60%, they believe.
At this point, the researchers want others to take over development. "We do not have the equipment to adapt the process to a flow reactor, or to go to the demonstration scale (kilograms) or beyond," notes Mascal. "The challenge that remains is effective scaling and process development. In the hands of expert engineers, we feel that a highly competitive biomass-to-gasoline technology can be developed."
Availability of the catalysts isn't an issue, says Mascal. "K10 and K2CO3 are cheap, readily available, and are both probably recyclable. The metal catalysts are sold on large scales to industry, so no problem there."
Output of biomass-based levulinic acid seems poised to take off. A number of companies already are planning to commercialize processes to make levulinic acid from agricultural wastes and other biomass. For instance, Biofine, Framingham, Mass., has been operating a demonstration plant in Gorham, Maine, since 2007 (see: "Cellulosics Conversion Gets a Boost"), and Segetis, Golden Valley, Minn., successfully started up a pilot plant last October.