Revealing Cellulose Pyrolysis Chemistry

Title: Revealing Cellulose Pyrolysis Chemistry

Authors: Alex D. Paulsen, Matthew S. Mettler, Dionisios G. Vlachos & Paul J. Dauenhauer

Abstract: Fast pyrolysis converts solid biomass to a liquid bio-oil which can be further upgraded to fuels or chemicals. This multi-step process consists of solid, liquid, gas and catalytic chemistries which must be studied independently in order to maximize insight. This work develops a kinetically-limited experimental technique for studying biomass pyrolysis and shows that glucose and cellodextrins do not behave similarly to cellulose while α-cyclodextrin does. The effect of temperature on cellulose pyrolysis products is also examined.

Additionally, we investigate secondary pyrolysis pathways within molten biomass using isotopically-labeled starting materials. Through the use of ¹³C-labeled sugars, we show that levoglucosan breaks down within the molten phase to form pyrans, light (C₂-C₃) oxygenates, and other anhydrosugars. The mechanisms of these reactions is unknown; however, we have shown using deuterated carbohydrates that levoglucosan decomposition products exhibit a distinct relationship between extent of elimination reactions and hydrogen exchange during reaction.  This demonstrates that hydrogen, which likely serves as a Brønsted catalyst within molten cellulose, plays a role in the decomposition of levoglucosan during cellulose pyrolysis.