(495b) Origins of Enhanced Levoglucosan Yields during the Co-Pyrolysis of Cellulose and High-Density Polyethylene
The widely available forest, crop, and wood resources in the United States have the capability to produce at least one billion dry tons of renewable biomass per year. Cellulose is the largest fraction of biomass and the most abundant biopolymer in the world. Converting cellulose in a biorefinery into value added chemicals or fuels presents a unique opportunity to create cost-effective and sustainable chemical production processes in regions where biomass is widely available. Fast pyrolysis is one of the simplest methods for biomass conversion, but producing value added chemicals via fast pyrolysis is still challenging due to its low selectivity. As a result, traditional application of cellulose pyrolysis is to produce biofuels via a series of small oxygenated molecules followed by upgrading. Levoglucosan (LG) is the primary pyrolysis product of cellulose, with yields as high as 70%. Although the objective of conventional biofuel production has been to minimize its yields, LG has gained recent interest as a value added chemical due to its potential applications in polymer, pharmaceutical, and consumer product industries. In this work, we present a strategy to enhance LG yields during cellulose pyrolysis by incorporating high density polyethylene (HDPE). Our experiments have shown that during cellulose/HDPE co-pyrolysis under low-pressure conditions, LG yields can be enhanced by as much as 26%. Co-pyrolysis experiments with different mixing patterns indicate that the origins of this enhancement could be from the reduction of thermohydrolysis reaction at low pressures and the inhibition of the mass transfer processes, such as evaporation, escape, and ejection, of the small sugar molecules by the addition of HDPE. Our work suggests that the interplay between chemical kinetics and mass transfer can be manipulated to alter the yields of key products during cellulose pyrolysis.