The multitude of competing reactions enabled near 500 °C and occurring on the timescale of seconds have stymied experimental efforts seeking to uncover the fundamental chemistry governing biomass fast pyrolysis. This lack of understanding hinders our ability to predict the product yield and composition from different feeds and reaction conditions, which, in turn, impedes the design and optimization of commercial processes. Computational chemistry tools such as density functional theory provide approaches for investigating complex reaction networks, allowing us to model elementary reaction steps, compare competing proposals of reaction mechanism, and examine fleeting transition states, knowledge of which can aid in rational catalyst design. We have focused on reactions central to cellulose fast pyrolysis, including the evaluation of 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 have also evaluated several key decomposition reactions of glucose, the cellulose monomer and postulated key intermediate, and how they are perturbed by alkali metal ions naturally present in biomass. The results of these studies have been used in building the first mechanistic model of cellulose pyrolysis, which offers predictions of detailed product speciation that closely match experimental results, and thus provides valuable aid in the advancement of this renewable energy technology.

Charting elementary steps in the cellulose pyrolysis reaction network

249th National Meeting (2015)

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