(70b) Intrinsic Chemistry of Biomass Pyrolysis for Biofuels: Primary and Secondary Reactions of Cellulose Decomposition

The next generation of biomass pyrolysis models must be capable of predicting the molecular-level chemistry occurring during the fast pyrolysis process.  The first step in developing molecular prediction requires elucidating the primary and secondary reactions of biopolymers such as cellulose during pyrolysis. Experimental evidence has indicated that the reactive intermediates for carbohydrates, lignin, and lignocellulose at temperatures exceeding 500 °C exist within a short-lived intermediate liquid which subsequently evaporates to vapors and gases.  We utilize a novel ‘thin-film pyrolysis’ technique to elucidate the primary and secondary reaction pathways of cellulose to volatile products including anhydrosugars, pyrans, furans, and light oxygenates.  The distribution of products from carbohydrate polymers is shown to depend upon the chain length, with longer chains producing more anhydrosugars such as levoglucosan.  Finally, the secondary, condensed-phase pathways of levoglucosan are revealed using isotopically-labeled samples to depend upon the residence time within molten cellulose.  Combination of these results provides the first insight into the chemical pathways which dictate the composition of bio-oil.