A new catalytic process is able to convert lignin — once considered biomass waste — into lucrative chemical products that can be used in fragrances, flavorings or to create high-octane fuel for racecars and jets.
A team of researchers from Purdue University’s Center for Direct Catalytic Conversion of Biomass to Biofuels, or C3Bio, has developed a process that uses a chemical catalyst and heat to spur reactions that convert lignin into valuable chemical commodities.
The process starts with untreated chipped and milled wood from sustainable poplar, eucalyptus or birch trees. A catalyst is added to initiate and speed the desired chemical reactions, but is not consumed by them and can be recycled and used again. A solvent is added to the mix to help dissolve and loosen up the materials. The mixture is contained in a pressurized reactor and heated for several hours. The process breaks up the lignin molecules and results in lignin-free cellulose and a liquid stream that contains two additional chemical products.
The liquid stream contains the solvent, which is easily evaporated and recycled, and two phenols, a class of aromatic hydrocarbon compounds used in perfumes and flavorings. A commonly used artificial vanilla flavoring is currently produced using a phenol that comes from petroleum, says Mahdi Abu-Omar, the R.B. Wetherill Professor of Chemistry and Professor of Chemical Engineering and associate director of C3Bio, who led the team.
The team also developed an additional process that uses another catalyst to convert the two phenol products into high-octane hydrocarbon fuel suitable for use as drop-in gasoline. The fuel produced has a research octane rating greater than100, whereas the average gas we put into our cars has an octane rating in the eighties, he said.
The processes and resulting products are detailed in a paper published online in the Royal Society of Chemistry journal Green Chemistry. The U.S. Department of Energy funded the research.
Lignin has a potential market value of $242 billion if steps are taken to bring it to market, according to a July 2014 report by Lux Research.