Oxides of calcium and magnesium are acknowledged natural catalysts within high temperature renewable energy systems including gasification, combustion and pyrolysis of lignocellulosic biomass[1]. However, probing the kinetics, reaction pathways and mechanisms promoted by these natural catalytic materials remains a fundamental challenge in catalysis for energy applications. Cellulose is known to react through a short-lived (10-100 ms) liquid intermediate during pyrolysis[2], which determines the product distribution in cellulose pyrolysis. Using a novel reactor design, we find that levoglucosan undergoes secondary reactions within the liquid intermediate to form pyrans, anhydrosugars, and light (C2-C3) oxygenates. The mechanisms of these reactions are unknown; however, we have shown the relationship between levoglucosan decomposition and hydrogen transfer within the liquid intermediate by using deuterated carbohydrates.[5] It is likely that hydrogen serves as a Brønsted catalyst for the decomposition of levoglucosan within molten cellulose. We utilize a novel thin-film pyrolysis reactor technique to investigate the effect of temperature on kinetically-limited, isothermal cellulose pyrolysis yields over a range of reaction temperatures (350 - 550 °C).[3] The presence of aldehyde groups in bio-oil leads to polymerization, which makes bio-oil unstable at storage conditions[4]. We promoted this chemistry by impregnating cellulose with a carbon-supported metal catalyst to reduce the aldehyde content of bio-oil while maintaining the overall bio-oil yield. Finally, the kinetics of impregnated alkaline earth metals were measured and compared with uncatalyzed reactions to furanic compounds, thus providing the first kinetic measurements of catalytic turnover in high temperature biopolymer degradation. [1] M.S. Mettler, D.G. Vlachos, P.J. Dauenhauer, “Top Ten Fundamental Challenges of Biomass Pyrolysis,” Energy & Environmental Science 2012, 5, 7797-7809. [2] Dauenhauer, P. J.; Colby, J. L.; Balonek, C. M.; Suszynski, W. J.; Schmidt, L. D., Reactive boiling of cellulose for integrated catalysis through an intermediate liquid. Green Chemistry 2009, 11, (10), 1555-1561. [3] Paulsen, A. D., Mettler, M. S., Vlachos, D. G., & Dauenhauer, P. J., Energy & Fuels 2013 [4] A.D. Paulsen, D.G. Vlachos, P.J. Dauenhauer, "Tuning Cellulose Pyrolysis Chemistry: Selective Decarbonylation via Catalyst-Impregnated Pyrolysis," M.S. Mettler, Catalysis Science & Technology 2014, 4, 3822-3825

Probing the surface kinetics of high temperature, millisecond reactions

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.