(452c) Solvent Fractionation of Biomass: Applications of Switchgrass Pretreatment for Biofuels

Interest in recovering cellulose from biomass has grown steadily over the last few years as cellulose can be enzymatically hydrolyzed to sugars and fermented to ethanol. Under the Energy Independence and Security Act of 2007, refiners must produce 16 billion gallons of cellulosic ethanol per year by the year 2022. Switchgrass is a very promising lignocellulosic source for this ethanol. Switchgrass is a versatile and adaptable plant, as it can grow in different weather conditions. It is a perennial and can grow in poor soils that cannot support any food crops. It is not a food source so it will not compete for food crops. We are investigating solvent fractionation (organosolv processing) to isolate the required cellulose from switchgrass. Solvent fractionation is a process of choice for pretreatment because it is suitable for use with several different biomass feedstocks, giving favorable separations, easy isolation of products after fractionation, and offers recovery of each component in a high yield and purity amenable to conversion to other chemicals. Fractionation technology developed at the National Renewable Energy Laboratory is being used at the University of Tennessee for the separation of switchgrass into its primary components. The fractionation employs a mixture of organic solvents and water to separate switchgrass into cellulose, lignin and hemicellulose for the production of fuels and chemicals. Fractionation is carried out by adding biomass, a ternary solvent mixture, and a sulfuric acid catalyst to a 3.5 L, 3? bore, pressurized, Hastelloy flow-through reactor, controlled via LabVIEW and operating at three temperatures: 120 deg C, 140 deg C, and 160 deg C. The recovered solvent is subjected to a phase separation, giving an organic phase containing lignin and an aqueous phase containing hemicellulose. The cellulose fraction is obtained as a solid in an average yield of 38.6% by weight (7 runs). Lignin yield at an average of 6.3% by weight (9 runs) is fairly constant and independent of temperature and pressure. 2D NMR data used to determine structural changes in lignin as a function of separation conditions will be presented.