(505c) Revealing Reactions in Cellulose Pyrolysis

Biomass fast pyrolysis is a promising technology for the thermal conversion of biomass to liquid fuels. With less-severe operating temperatures than gasification, fast pyrolysis produces a primarily liquid product, which requires less-costly equipment for processing and storage than a vapor product. Currently, improvements to make this technology more economically attractive are hampered by a lack of understanding of the reaction chemistry. Computational molecular science offers tools to examine fleeting transition states, knowledge of which can aid in rational catalyst and process design. Computation also aids in elucidation of individual mechanisms from a large slate of reactions. In the absence of a mechanistic understanding, pyrolysis models rely on lumped components or a fixed-percent conversion and accurately predict very few individual products. Their validity is limited to feeds and operating conditions very similar to those used to provide the experimental training data for the model. Without product speciation, they have limited usefulness for process optimization to improve yields. This talk will share our recent efforts in revealing cellulose pyrolysis reactions using density functional theory. Specifically, we evaluated several competing theories for the formation of the main product of pure cellulose pyrolysis, levoglucosan, and uncovered a new mechanism that yields results consistent with experiment. We also evaluated several key decomposition reactions of glucose, the cellulose monomer and postulated key intermediate, and how they are perturbed by alkali metal.