Chemical
engineering researchers Wei Fan, Paul Dauenhauer and colleagues report this
week that they’ve discovered a new chemical process to make p-xylene, an
important ingredient of common plastics, at 90 percent yield from
lignocellulosic biomass, the highest yield achieved to date. Details are in the
current issue of Green Chemistry.
As Dauenhauer explains, the chemical
industry currently produces p-xylene from more expensive petroleum, while the
new process will make the same chemical from lower-cost, renewable biomass. He
and colleagues call the process “ultraselective” because of its ability to
achieve 90 percent selectivity for the desired product. “The biomass-derived
p-xylene can be mixed with petroleum-based plastics, and consumers will not be
able to tell the difference. But manufacturers and chemical companies will be
able to operate more sustainably and at lower cost in the future because of this
discovery,” he adds.
Consumers already know the plastics
made from this new process by the triangular recycling label “#1” on plastic
containers. Xylene chemicals are used to produce a plastic called PET
(polyethylene terephthalate), which is currently used in many products
including soda bottles, food packaging, synthetic fibers for clothing and even
automotive parts, Dauenhauer says.
The UMass Amherst team’s discovery
reveals the impact of nano-structured catalyst design on renewable chemical
processes. Led by Fan, they examined a large number of nano-porous catalytic
materials, including zeolites, investigating their capability for producing
p-xylene. A specific material identified as ‘zeolite beta’ was found to be
optimal. “We discovered that the performance of the biomass reaction was
strongly affected by the nanostructure of the catalyst, which we were able to
engineer and achieve 90 percent yield,” Fan says.
Besides Dauenhauer and Fan, the
research team includes Chun-Chih Chang, Sara Green and C. Luke Williams,
doctoral students in chemical engineering at UMass Amherst.