(413d) Fuels From Biomass Via Supercritical Fluid Processes

Biomass, whether energy crops or residues from agriculture, is a renewable source of energy. Modern society uses liquid and gaseous fuels as energy carriers, so biomass conversion to these fuels is an integral part of a sustainable energy future. Solvothermal processes, which involve the simultaneous action of a solvent and elevated temperature, perhaps along with a catalyst, can do this necessary conversion. This presentation will describe our recent work in converting biomass to gases and bio-oils and the subsequent upgrading of the bio-oil to liquid hydrocarbons. We examined the gasification of biomass in supercritical water, the liquefaction of biomass in near-critical water, and the esterification of oleic acid in supercritical ethanol. Cellulose and lignin were converted to gases rich in H2 and CH4. Both the gas yield and its composition were sensitive to changes in the gasification temperature, the biomass loading, and the water density. Additionally, metal catalysts can be used to obtain further control of the rate and selectivity of the gasification reaction. Hydrothermal liquefaction of microalgae generated a bio-oil that contained molecules in the size range needed for liquid transportation fuels. Catalytic conversion of these molecules can improve the quality of the renewable liquid fuel. Esterification of free fatty acids by alcohols is one step in an envisioned catalyst-free process for biodiesel production from triglycerides. The esterification proceeds smoothly in supercritical ethanol, and we examined the effects of the process variables on the kinetics and ester yields. The processes noted above are but three that illustrate the usefulness of supercritical fluids for biomass processing. In each of these systems, the fluid (water or ethanol) serves not only as the solvent but also as a key reactant in the process.