A team of researchers from Purdue University's Center for Direct Catalytic Conversion of Biomass to Biofuels (C3Bio) has developed a new catalytic process that converts biomass waste into chemical products that can be used in fragrances, flavorings or to create high-octane fuel for racecars and jets, Phys.org reports.
The process uses a chemical catalyst and heat to spur reactions that convert lignin—a durable and complex molecule that gives the plant cell wall its rigid structure—into valuable chemical commodities.
Plant biomass is made up primarily of lignin and cellulose—in ethanol production, enzymes are used to break down the biomass and release sugars, and yeast feed on the sugars to create ethanol. Lignin acts as a physical barrier that makes it difficult to extract sugars from biomass and acts as a chemical barrier that poisons the enzymes. That is why many refining processes include pretreatment steps to break down and remove lignin.
The Purdue team developed a process that begins with untreated chipped and milled wood from sustainable poplar, eucalyptus or birch trees. A catalyst is added to start and speed the desired chemical reactions, but is not consumed by them and can be recycled and reused. A solvent is added to the mixture to help dissolve and loosen up the materials, which 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.
The researchers 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 than 100—to put this into context, the average gas we put into our cars has an octane rating in the eighties.
Earlier this year, a report by Frost & Sullivan said lignin could be used as early as 2017 to address high-value opportunities, including serving as a substitute for phenol or as a component in polyurethane formulation. In particular, this research explores four promising lignin applications: BTX, phenol, carbon fiber and vanillin. The development of public and private R&D projects in this field could make lignin-based phenolic monomers or carbon fiber a reality by 2020.
In October, Chemists at the University of Birmingham announced they had found a new way to make nanostructured carbon using the waste product sawdust. By cooking sawdust with a thin coating of iron at 700 degrees centigrade, the researchers found they can create carbon with a structure made up of several tiny tubes. These tubes are one thousand times smaller than an average human hair.